JPH06202073A - Active matrix liquid crystal display device - Google Patents

Abstract

(57) [Summary] [Objective] To obtain an active matrix type liquid crystal display device having features such as low cost, good viewing angle characteristics, good display characteristics and easy multi-gradation display. [Structure] m × n matrix-shaped pixels, active elements in the pixels, and driving means for applying a predetermined voltage waveform,
The pixel has a predetermined structure capable of applying an electric field parallel to the surface of the substrate and controlling the alignment state of liquid crystal molecules by the potential difference between the potential of the signal wiring during scanning and the potential of the adjacent scanning wiring to modulate light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low cost active matrix type liquid crystal display device having good display characteristics, good mass productivity and a driving method thereof.

[0002]

2. Description of the Related Art In a conventional active matrix type liquid crystal display device, transparent electrodes, which are formed on the interface between two substrates and face each other, are used as electrodes for driving a liquid crystal layer. This is because a twisted nematic display method is adopted, which operates by making the direction of the electric field applied to the liquid crystal substantially perpendicular to the substrate interface. On the other hand, as a method for setting the direction of the electric field applied to the liquid crystal to be substantially parallel to the substrate interface, a method using a comb-shaped electrode pair is disclosed in, for example, Japanese Patent Laid-Open No. 12052/1991.
Proposed by Issue 8.

[0003]

However, in the prior art using the twisted nematic display system described above, it is necessary to use a vacuum-type manufacturing facility such as sputtering in order to form a transparent electrode typified by ITO. , The equipment cost was huge. Also, the use of vacuum-based manufacturing equipment causes a reduction in throughput, which significantly increases manufacturing costs. Further, in general, the transparent electrode has irregularities of about several tens of nm on its surface, which makes it difficult to process a fine active element such as a thin film transistor. Further, the convex portion of the transparent electrode often separates and mixes into other portions such as the electrode, which causes a dot-shaped or linear-shaped display defect, which is one of the factors that lower the yield. For these reasons, it has been impossible to stably provide a low-cost liquid crystal display device that meets market needs. Further, the above-mentioned conventional techniques have many problems in terms of image quality. In particular, the luminance changes significantly when the viewing angle direction is changed, making it difficult to display halftone. Furthermore, in the conventional structure, since the common electrode is required, a process for forming the common electrode is required, which lowers the yield and the throughput. Further, in the conventional configuration, the generation of the DC component due to the operation of the active element hinders the driving of the liquid crystal that requires pure AC driving, which causes image quality defects such as luminance inclination, flicker, and afterimage. The variation in the characteristics of (3) caused uneven brightness.

Further, in the conventional publicly known technology for applying an electric field to the liquid crystal in a direction substantially parallel to the substrate interface, no technology for driving the liquid crystal using an active matrix has been devised.

The present invention solves these problems at the same time. The first object of the present invention is, at the low cost, high contrast without a transparent electrode and mass production with a low yield of a high yield. An object is to provide an active matrix type liquid crystal display device. Secondly, it is to provide an active matrix type liquid crystal display device having good viewing angle characteristics and easy multi-gradation display. Thirdly, it is to provide an active matrix type liquid crystal display device free from image quality defects such as luminance inclination, flicker, afterimage and unevenness. Further, in addition to these objects, a fourth object is to provide an active matrix type liquid crystal display device capable of lowering a signal voltage, low power consumption, and an inexpensive LSI having a low breakdown voltage.

[0006]

To achieve the above object, the present invention provides, as a first device, a pair of substrates, at least one of which is transparent, and a liquid crystal composition layer sandwiched between the substrates. M scan wirings and n signal wirings arranged on one side of the substrate, m × n matrix-shaped pixels,
In a liquid crystal display device including an active element and a capacitive element arranged in the pixel, and a driving unit that applies a predetermined voltage waveform to the scanning wiring and the signal wiring, in the pixel, among the signal wiring One signal wiring I and one scanning wiring II among the scanning wirings are arranged, and an electric field mainly applied to the liquid crystal composition layer in parallel to the substrate surface is applied to the pixel, and , The potential difference between the potential V1 of the signal wiring I and the potential V2 of the scanning wiring II at the time of scanning | V1-V2
With |, the liquid crystal display device is configured to have a predetermined structure capable of controlling the alignment state of liquid crystal molecules and modulating light.

As a second device including the first device, an active element A connected to the signal wiring I and an active element B connected to the scanning wiring II are provided in the pixel.
And a pixel electrode connected to the active element A and a counter electrode connected to the active element B, and the electric field between the pixel electrode and the counter electrode is mainly an electric field parallel to the substrate surface. A liquid crystal display device characterized by having a certain predetermined structure.

As a third device including the first device, the pixel includes an active element A connected to the signal line I, and a pixel electrode connected to the active element A.
An active element B connected to the scan line II, a counter electrode connected to the active element B, and a capacitive element between the pixel electrode and the counter electrode are provided. The liquid crystal display device is configured to have a predetermined structure in which an electric field between them is mainly an electric field parallel to the surface of the substrate.

As a fourth device, a pair of substrates, at least one of which is transparent, a liquid crystal composition layer sandwiched between the substrates, m scanning wirings and n arranged on one of the substrates.
Book signal wiring, m × n matrix-shaped pixels, active elements and capacitive elements arranged in the pixels,
A liquid crystal having a predetermined structure for applying a predetermined voltage waveform to the scanning wiring and the signal wiring, and for applying an electric field mainly parallel to the substrate surface to the liquid crystal composition layer. In the display device, the predetermined structure is
A liquid crystal display device is constituted by an electrode having a comb shape having one or more elongated protrusions.

As a fifth device including the second device, an active element A in which the pixel is connected to the signal wiring is provided.
And an active element B connected to the scan line II,
A pixel electrode connected to the active element A and a counter electrode connected to the active element B are provided, and an electric field between the pixel electrode and the counter electrode is mainly an electric field parallel to the substrate surface. In a liquid crystal display device having a structure,
Driving means for applying the potential 1 to the pixel electrode through the signal wiring and driving means for applying the potential 2 to the counter electrode through the scanning wiring II are provided in synchronism with the voltage pulse I used for selecting the scanning wiring I. It is equipped.

As a sixth device including the fifth device, the positive and negative polarities of the potential 2 applied to the counter electrode cause a voltage difference when an electric field is applied to the liquid crystal composition layer (white display of the liquid crystal display device is performed. The liquid crystal display device is characterized in that it is greater than or equal to the voltage difference between the voltage V _W ) and the voltage V _{BLK for} displaying black in the liquid crystal display device.

As a seventh device including the first device, the plurality of pixels selected by the scan wiring I are adjacent to the first scan wiring II adjacent to the scan wiring I or the scan wiring I. The active element B connected to the other scan wiring III, the active element A connected to the signal wiring, the pixel electrode connected to the active element A, and the counter electrode connected to the active element B. The liquid crystal display device has a predetermined structure in which the electric field between the pixel electrode and the counter electrode is mainly an electric field parallel to the substrate surface.

An eighth device including the seventh device is characterized in that the active element B of the adjacent pixel is connected to the scan wiring II or the scan wiring III arranged before and after the scan wiring I. It is a display device.

As a ninth device including the seventh or eighth device, a plurality of the pixels selected by the scanning wiring I have the first scanning wiring II adjacent to the scanning wiring I or the scanning wiring II. An active element B connected to another scan wiring III adjacent to I, an active element A connected to the signal wiring, a pixel electrode connected to the active element A, and an active element B connected to the active element B. In a liquid crystal display device having a counter electrode and having a predetermined structure in which the electric field between the pixel electrode and the counter electrode is mainly an electric field parallel to the substrate surface, the scan line I is selected during the selection period of the scan line I. A voltage having a potential difference which is greater than or equal to the voltage difference between (the voltage V _{W for} displaying white on the liquid crystal display device) and (the voltage V _{BLK for} displaying black on the liquid crystal display device) on the scanning line II or the scanning line III before and after pulse With applied, in which a liquid crystal display device characterized by applying a predetermined voltage to the electric field direction to be applied to adjacent pixels are opposite directions to each other to the signal line.

As a tenth device including the first device, a pair of substrates, at least one of which is transparent, a liquid crystal composition layer sandwiched between the substrates, and m provided on one of the substrates.
Scanning lines and n signal lines, m × n pixels in a matrix, active elements and first capacitive elements arranged in the pixels, and a predetermined voltage waveform with the scanning lines and the In a liquid crystal display device including a driving unit that applies a signal to a signal line, the pixel includes an active element A connected to the signal line and a scan line II adjacent to the scan line I via a second capacitive element. Connected to the active element B, a pixel electrode connected to the active element A, and a counter electrode connected to the active element B. The electric field between the pixel electrode and the counter electrode is mainly The liquid crystal display device has a predetermined structure that is an electric field parallel to the substrate surface.

[0016]

Next, the operation of the present invention will be described with reference to FIG.

17 (a) and 17 (b) are side sectional views showing the operation of the liquid crystal in the liquid crystal panel of the present invention.
Represents the front view. In FIG. 17, the active element is omitted. Further, in the present invention, a plurality of pixels are formed by forming a striped electrode, but only one pixel portion is shown here. FIG. 17 (a) shows a cross section of the cell when no voltage is applied.
A front view at that time is shown in FIG. Linear electrodes 201 and 202 are formed on the inner side of a pair of transparent substrates 203, and an alignment control film 204 is applied and aligned on the linear electrodes 201 and 202. A liquid crystal composition is sandwiched between the pair of transparent substrates 203. The rod-shaped liquid crystal molecules 205 have a slight angle with respect to the longitudinal direction of the striped electrode when no electric field is applied, that is, 45 ° ≦ | an angle formed by the liquid crystal molecule major axis (optical axis) direction near the interface with respect to the electric field direction. <90 degrees,
Are oriented so that The alignment direction of liquid crystal molecules on the upper and lower interfaces will be described here by taking parallel as an example. The dielectric anisotropy of the liquid crystal composition is assumed to be positive. Next, the electric field 20
When 7 is applied, the liquid crystal molecules change their directions in the direction of the electric field as shown in FIGS. 17 (b) and 17 (d). By arranging the polarization transmission axis of the polarizing plate 206 at a predetermined angle 209, the light transmittance can be changed by applying an electric field. Thus, according to the present invention, it is possible to provide a display that gives a contrast ratio of transmitted light without a transparent electrode.

As a concrete structure for imparting a contrast ratio, a mode utilizing a state in which the liquid crystal molecule orientations on the upper and lower substrates are substantially parallel (an interference color due to a birefringence phase difference is utilized, it is called a birefringence mode here). ) And a liquid crystal molecule alignment direction on the upper and lower substrates intersect and the molecular arrangement in the cell is twisted (the rotation of the polarization plane in the liquid crystal composition layer is used. There is a sex mode). In the birefringence mode, the direction of the molecular long axis (optical axis) is changed in the plane while the direction of the molecular long axis (optical axis) is almost parallel to the substrate interface by applying a voltage, and the angle formed by the axis of the polarizing plate set to a predetermined angle is changed. Change the transmittance. Even in the optical rotation mode, similarly, only the orientation in the long axis direction of the molecule is changed by applying a voltage,
In this case, the change in optical activity due to the unravel of the streak is used. Further, in the display mode of the present invention, the long axis of the liquid crystal molecule is always substantially parallel to the substrate and does not stand up, and therefore the change in brightness when the viewing angle direction is changed is small, so there is no viewing angle dependency and the viewing angle The characteristics are greatly improved.
In this display mode, the dark state is not obtained by making the birefringence phase difference almost zero by applying a voltage as in the conventional case, but the angle formed by the long axis of the liquid crystal molecule and the axis of the polarizing plate (absorption or transmission axis) is It changes and is fundamentally different. In the case of raising the liquid crystal molecule long axis perpendicularly to the substrate interface as in the conventional TN type, the viewing angle direction in which the birefringence phase difference becomes 0 is only the front direction, that is, the direction perpendicular to the substrate interface, and even if slightly inclined. Birefringence phase difference appears. Light leaks in the normally open type,
It causes a decrease in contrast ratio and inversion of gradation level.

Further, in the display mode of the present invention, the transmittance changes mainly due to the electric field 207 parallel to the substrate surface, and the electric field 20
The intensity E of 7 depends on the distance d between the electrodes 201 and 202. Therefore, the variation in the distance d between the electrode 201 and the electrode 202 causes variation in brightness, which is a problem. Therefore, high alignment accuracy of the electrodes 201 and 202 is required. Since the alignment accuracy for laminating two substrates is two to three times worse than the alignment accuracy of the photomask, the electrodes 201 and 202 must be formed on the same substrate. However, the electrode 201
Alternatively, when one of the electrodes 202 is formed as a common electrode on the same substrate as the substrate on which the thin film transistor element is formed,
There is a concern that the wiring and the crossing area between the wirings increase, the short-circuit defects with the scanning wirings and the signal wirings increase, and the yield decreases. In the structure of the liquid crystal display device of the present invention, since the common electrode does not need to be drawn out from the panel for each column by applying the common electrode potential from the scanning wiring, the number of wiring is not increased, the yield is improved, and the transparent electrode is used. In addition to not using, it becomes possible to provide a liquid crystal display device at a lower cost.

Furthermore, in the driving method of the present invention, since the two thin film transistor elements are used for driving, mutual characteristics can be canceled, image quality defects such as luminance gradient, flicker, and afterimage can be eliminated, and display characteristics are good. . Further, although a voltage for applying a common potential is superimposed on the scanning wiring, a conventional method for applying a voltage by sample-holding a video signal or a method for converting a digital image data into a voltage and applying the same to the signal wiring. You can follow it.

[0021]

EXAMPLES The present invention will be specifically described with reference to examples.

[Example 1] The substrate has a thickness of 1.1 mm.
Two glass substrates whose surfaces have been polished by are used. Dielectric anisotropy Δε is positive between these substrates and its value is 4.5,
A nematic liquid crystal composition having a birefringence Δn of 0.072 (589 nm, 20 ° C.) is sandwiched. Although a liquid crystal having a positive dielectric anisotropy Δε is used here, a negative liquid crystal may be used. The polyimide orientation control film applied on the substrate surface is rubbed to obtain a pretilt angle of 3.5 degrees. The rubbing directions on the upper and lower interfaces were substantially parallel to each other, and the angle formed with the direction of the applied electric field was 85 degrees. The gap between the upper and lower substrates was 4.5 μm when the spherical polymer beads were dispersed and sandwiched between the substrates and the liquid crystal was sealed. Therefore, Δn · d is 0.324 μm. The panel was sandwiched between two polarizing plates, and the polarization transmission axis of one polarizing plate was made substantially parallel (85 °) to the rubbing direction, and the other was orthogonal (−5 °) to it. As a result, normally closed characteristics were obtained.

A pixel as shown in FIG. 1 was formed on one insulating substrate. The equivalent circuit of the pixel is as shown in FIG. Also,
A sectional view taken along the line AA of FIG. 1 is shown in FIG. 3, a sectional view taken along the line BB is shown in FIG.
A sectional view taken along the line CC is shown in FIG. The display device has 40 (× 3) pixels with a pixel pitch of 80 μm in the horizontal direction and 240 μm in the vertical direction.
The arrangement is x30 (that is, m = 120 and n = 30), but a high-definition display device of about 2000 × 2000 pixels can be applied. The scanning wirings 3 and 4 were formed in the horizontal direction, were made orthogonal to the scanning wiring, and the signal wirings 1 and 2 were formed in the vertical direction. Further, in the pixel, a thin film transistor element 5a using amorphous silicon 8a having an inverted stagger structure as shown in the AA cross-sectional view of FIG. 3 and 8b not shown and 5b not shown are formed. In the present embodiment, an amorphous silicon thin film transistor element is formed and used, but in addition, a polysilicon thin film transistor element, a MOS type transistor on a silicon wafer, an organic TFT or M
A two-terminal element such as an IM (Metal-Insulator-Metal) diode (strictly not an active element, but an active element in the present invention) may be used. As shown in FIG. 1, a signal voltage corresponding to an image is applied to the drain electrode 9a of the thin film transistor element 5a (in the actual driving state, it may act as a source, but in the present embodiment, it is applied to the signal wiring and the gate wiring of the next stage. The connected electrode is defined as the drain electrode, and the electrode connected to the pixel electrode or serving as the pixel electrode is defined as the source electrode), and a signal is applied via the source electrode 7a and the through hole 21. Electrode 2
Connected to 3. The voltage of the counter electrode 24, which gives a potential difference from the signal electrode 23, is applied from the scanning electrode 4 at the next stage to the through hole 2
2 and the drain electrode 9b of the thin film transistor element 5b,
It was given through the source electrode 7b. Also, as shown in FIG.
The capacitive element 6 was formed using the signal electrode 23, the counter electrode 24, and the gate insulating film 11. Here, the capacitive element 6 is provided to hold the potential of the source electrode at a constant potential by absorbing noise due to the signal. In this way, two thin film transistor elements are provided in one pixel, and as shown in FIG. 4, the signal electrode 23 and the counter electrode 24 are provided.
The electric field direction E between them has a component mainly parallel or horizontal to the substrate surface. Here, two thin film transistor elements are used, but a redundant configuration may be adopted by using three or more thin film transistor elements. Similarly, the capacitive element is 2
One or more may be used. Here, the orientation of the liquid crystal molecules in the liquid crystal layer is controlled by the potential difference between the two electrodes, that is, the signal electrode 23 and the counter electrode 24. Light is transmitted between the signal electrode 23 and the counter electrode 24, is incident on the liquid crystal layer 17, and is modulated, so that the pixel electrode (for example, I
It is not necessary to provide a transparent electrode such as TO) in particular, because of the sectional structure of the conventional active matrix type liquid crystal display device,
It is possible to eliminate the two transparent electrode layers, and by forming the transparent electrode layer in the same layer as the signal wiring, it is possible to significantly shorten the process. Further, generally, the alignment accuracy of the photomask is significantly higher than the alignment accuracy between two glass substrates facing each other. Therefore, although these constituent elements can be arranged separately on both substrates, it is preferable to form them on one substrate. Here, the signal electrode 23
Since the alignment between the counter electrode 24 and the counter electrode 24 is performed only by the photomask, the variation in the electric field E applied to the liquid crystal layer is suppressed to a small level. Furthermore, since both source electrodes are formed in the same layer, the variation in the distance d between the signal electrode 23 and the counter electrode 24 can be suppressed to 5% or less. Also,
The scanning wirings 3 and 4 also functioned as gate electrodes and were formed of a tantalum thin film. The signal wirings 1 and 2 also serve as drain electrodes, and were formed of a titanium thin film at the same time as the source electrodes 7a and 7b. Scan wiring 3, 4 and signal wiring 1, 2.
There is no particular restriction on the material, and chromium, aluminum, or the like may be used, but considering corrosion at the connection terminal portion with the drive LSI, a metal that is highly resistant to corrosion is desirable. Further, since it is desirable for the scanning wirings 3 and 4 to be a metal having a low electric resistance, the scanning wirings may be composed of two or more metal layers. As for the number of signal wirings and scanning wirings, assuming that the number of pixels is m × n, the same number of signal wirings as in the conventional configuration are m, and the scanning wiring of the next stage applies a voltage to the source electrode 7b of the thin film transistor element 5b. Since one extra piece is required, the number is n + 1. Furthermore, on the thin film transistor elements 5a and 5b,
A protective film 12 was formed of silicon nitride so as to protect the thin film transistor element. In addition, a striped R, G, B three-color filter 13 is provided on a substrate (hereinafter, referred to as a counter substrate) opposite to a substrate having a thin film transistor element. The filter 13 is unnecessary. A transparent resin 14 for flattening the surface is laminated on the color filter 13. An epoxy resin was used as the material of the transparent resin 14. Further, a polyimide-based orientation control film 16 was applied on the transparent resin 14 and the substrate having the thin film transistor element. As the orientation control film on the flattening film 14, the surface may be directly rubbed without forming another film. In this case, this epoxy resin has both functions of flattening and controlling the alignment of liquid crystal molecules. This eliminates the step of applying the alignment film, and makes the manufacturing easier and shorter.
Generally, in the TN type which is the conventional method, the characteristics required for the orientation control film are diverse, and it is necessary to satisfy all of them, so that it is limited to some materials such as polyimide. A particularly important characteristic is the tilt angle. However, the display mode of the present invention does not require a large tilt angle, and therefore,
The choice of materials is significantly improved. Similarly, the protective film 12 for protecting the thin film transistor may be made of epoxy resin and subjected to rubbing treatment. Further, in order to eliminate the decrease in contrast due to the influence of the defective alignment region, the light shielding film 15 was formed on the glass substrate using chromium. Further, it is more preferable that the light shielding film 15 is formed of an organic polymer. This is because, as a result, no electrically conductive substance is present on the counter substrate. In the configuration of the present embodiment, even if a conductive foreign substance is mixed in during the manufacturing process, there is no possibility of contact between electrodes via the counter substrate, and the defective rate due to this is suppressed to zero. Therefore, the margin of cleanliness such as alignment film formation, rubbing, and liquid crystal encapsulation process is widened, and the manufacturing process can be simplified. Furthermore, the light shielding film 15
When is formed of an organic polymer containing a black pigment, it is possible to prevent glare due to reflection of external light and a decrease in contrast. Further, by laying out the light shielding film 15 in a stripe shape, a printing process can be used. As a result, the manufacturing process can be further simplified and the cost can be reduced.

As shown in FIG. 6, a TCP (Tape) including drive LSIs 163 and 164 in the above liquid crystal display panel.
Carrier Package) was connected and driven. It is desirable that the signal-side drive LSI 64 be divided into an odd-numbered column and an even-numbered column and be connected to the upper and lower sides of the display panel because the connection pitch becomes wider and the connection becomes easier.

Next, the driving method will be described. FIG. 7 shows the waveform of the voltage applied to each electrode. Line-sequential driving in which signals are written is performed for each row. Gate voltage 31: Vgi is a selection pulse 4 that selects one row of TFTs to turn them on
1: Vgoni and a counter voltage pulse 51: Vgci for applying the potential Vc to the counter electrode one row before. The counter voltage pulse 52: Vgci + 1 of the i + 1th row is applied almost in synchronization with the selection pulse 41: Vgoni of the gate line of the ith row. Therefore, the selection pulse 4 is applied to the gate voltage 31 of the i-th gate line.
When 1 is applied, the thin film transistor elements 5a and 5b are turned on, and the signal voltage 61: Vds and the counter voltage pulse 52: Vgci + 1 on the i + 1th row are applied to the signal wiring 1 and the gate wiring 4 through the respective thin film transistor elements 5a and 5b. The data is written in the storage capacitor 17 and the liquid crystal element 6 connected to. When the writing period (1H) of the row ends, the gate voltage 31: Vgi falls to the off level, the thin film transistor elements 5a and 5b are turned off, and the written voltage is held. When 31 falls to the off level, the thin film transistor element 5
The voltage shifts 76 and 77 due to the coupling noise due to the parasitic capacitances a and 5b occur, and are held at that voltage. Here, the voltage applied to the liquid crystal is the voltage between the source voltages 71 and 61 of the thin film transistor elements 5a and 5b.
8 is applied, and the voltage 78 determines the brightness (transmittance) of the pixel.

In this embodiment, since there is no transparent electrode, the manufacturing process can be simplified, the yield can be improved, and the cost can be remarkably reduced. In particular, the equipment and process for forming the transparent electrode are not required, and the cost for manufacturing can be reduced because the investment cost for manufacturing equipment is greatly reduced and the number of processes is reduced.
In addition, since a special common electrode for applying a voltage to the counter electrode is not required by applying a potential to the counter electrode from the next-stage scanning wiring, the step of forming the common electrode can be reduced, and no electrodes are provided on the counter substrate. No longer needed. As a result, the contact failure with the common electrode becomes zero, the yield can be improved, and the cost can be reduced.

FIG. 8 shows the electro-optical characteristics showing the relationship between the voltage applied to the liquid crystal and the brightness in this embodiment. The contrast ratio is 150 or more when driven by 7V, and the difference in the curves when the viewing angle is changed to the left and right and up and down is extremely small compared to the conventional method (shown in Comparative Example 1), and the display characteristics change almost even when the viewing angle is changed. I didn't. In addition, the liquid crystal alignment was good, and no domain with poor alignment was generated.

Further, in the conventional driving method, when the thin film transistor element is switched from the on state to the off state, the DC component of the liquid crystal applied voltage generated by the voltage shifts 76 and 77 received through the parasitic capacitance of the thin film transistor element is the present embodiment. Does not occur because the two thin film transistor elements cancel each other. Therefore, without correcting the DC component that was conventionally corrected by the common electrode,
Since the liquid crystal can be driven by alternating current, flicker did not occur. Similarly, an afterimage due to a DC component could not be confirmed, and the brightness gradient was not noticeable. Furthermore, when a two-terminal element such as an MIM diode is used, image quality defects such as uneven brightness due to variations in the threshold value of the element are similarly canceled by the two elements, so uneven brightness is eliminated.

Comparative Example A conventional twisted nematic (TN) type is used as a comparative example. Since the transparent electrode is provided as compared with the first embodiment, the structure is complicated and the manufacturing process is long. As the nematic liquid crystal composition, one having the same dielectric anisotropy Δε as in Example 1 and a positive value of 4.5 and a refractive index anisotropy Δn of 0.072 (589 nm, 20 ° C.) was used. The gap was 7.3 μm and the twist angle was 90 degrees. Therefore, Δn · d is 0.526 μm.

The electro-optical characteristics are shown in FIG. The curve changed drastically in the viewing direction. In addition, an alignment defect domain in which the alignment direction of liquid crystal molecules was different from that in the peripheral portion was generated in the vicinity of the gap structure in the adjacent portion of the thin film transistor. Furthermore, in the common electrode, the DC component cannot be canceled, and flicker, an afterimage, and a brightness gradient occur.

[Embodiment 2] FIG.
Pixels such as This embodiment is a pixel equivalent circuit,
Since the vertical structure of the pixel and the driving method are the same as those in FIGS. 2 to 5 and 7 of the first embodiment, description thereof will be omitted.

As shown in FIG. 10, this embodiment is different in that the pixel electrode 23 and the counter electrode 24 have a comb structure. If the distance between both electrodes to which the electric field E is applied is long, the electric field is not effectively applied to the liquid crystal, and the threshold voltage of the liquid crystal rises.
By forming both electrodes 23 and 24 in a comb structure and arranging them so that they mesh with each other, the inter-electrode distance could be reduced to about 1/3 of that in the first embodiment. As a result, the electric field applied to the liquid crystal was tripled, and as a result, both the threshold voltage and the response time were shortened as compared with the first embodiment.
When the voltage at which the brightness changes by 10% of the total change amount (defined as V ₁₀ ) is defined as the threshold voltage, what is 9.5 V in the first embodiment is 5.8 V. became. Further, the response time is such that the on-off switching is performed between a voltage of 0 V and a voltage (defined as V ₉₀ ) at which the brightness changes by 90% of the total change amount, and the response time (t _ON +
When t _OFF ) was measured, what was 650 ms in Example 1 was shortened to 140 ms. Here, t _ON ,
90% of the total amount of dynamic brightness change for t _OFF
It represents the time until it changes.

As described above, in this embodiment, in addition to the effects of the first and second embodiments, both the threshold voltage and the response time are shortened as compared with the first embodiment.

[Third Embodiment] The configuration of this embodiment is the same as that of the first embodiment except for the following requirements.

FIG. 11 is a plan view of a pixel of this embodiment, and FIG.
Shows the equivalent circuit diagram. The drain electrode of the thin film transistor element 5 a that applies a potential to the counter electrode 24 was connected to the scanning wiring 4 in the next stage via the capacitive element 101. In addition, by configuring the capacitive element 6 connected between the signal electrode 23 and the counter electrode 24 for the purpose of removing noise due to a signal by connecting two capacitive elements 6a and 6b in series, the first and second exemplary embodiments can be obtained. We were able to remove all the required through holes. This eliminates the need for processing such as patterning and drilling in the interlayer insulating film in pixels that require fine processing, eliminating short-circuiting or connection failure between different layers due to defective insulating film processing, and creating a through-hole area unrelated to display. It is possible to realize a high quality liquid crystal display device by improving the aperture ratio due to the reduction.

When a potential is applied to the counter electrode 24 by capacitive coupling, as shown in FIG.
The potential of the counter electrode 24 is determined by the ratio of 1 to the liquid crystal capacitance 17 and the combined capacitance of the capacitance elements 6a and 6b. Signal electrode 23
, Vds, the voltage of the scanning wiring of the next stage is Vgc, the voltage of the counter electrode 24 is Vc, the liquid crystal capacitance 17 and the capacitive element 6
The capacitance values of a and 6b are C17, C6a and C6, respectively.
b, where the combined capacitance value of these is C102 and the capacitance value of the capacitive element 101 is C101, the signal electrode 23 and the counter electrode 24
Since the liquid crystal capacity between is very small,

[0037]

[Equation 1]

The voltage applied to the liquid crystal is

[0039]

[Equation 2]

It becomes

Therefore, the capacitance value C101 of the capacitive element 101
Is sufficiently larger than the composite capacitance C102, a sufficient voltage can be applied to drive the liquid crystal, and even if the voltage is 2 to 3 times, the voltage amplitude of the scanning wiring in the next stage is 25 to 33%.
The display characteristics are not affected at all by only increasing the size.

According to the present embodiment, since the voltage of the counter electrode is applied by capacitive coupling, processing such as patterning and drilling in the interlayer insulating film becomes unnecessary, and the area unrelated to the display can be reduced, and the aperture ratio can be improved. It is possible to realize a high-quality liquid crystal display device with few defects due to defective insulation film processing.

[Embodiment 4] The configuration of this embodiment is the same as that of the embodiment 1 except for the following requirements.

The drive waveform is shown in FIG. The pixel configuration and the equivalent circuit are the same as those in FIGS. 1 and 2, but the gate voltage is 3
2: Counter voltage pulse 52: Vgci + 1 of 1 out of Vgi + 1
The feature is that the polarity is inverted centering on Vcc for each row. The liquid crystal voltage 62 is the signal voltage 61 and the counter voltage 52: Vgci.
Since the differential voltage is +1, the polarity of the counter voltage pulse 52 of the gate at the next stage of the selected row is inverted for each row, and the write polarity of the liquid crystal is determined with the counter voltage pulse as a reference. Thus, low voltage driving can be realized. The amplitude of the signal voltage can be minimized by appropriately selecting the voltage amplitude of the counter voltage 52 and making the center values of the signal voltage and the counter voltage substantially equal. In this embodiment, by selecting the driving conditions in this way, it is possible to reduce the voltage of the signal side driving element and reduce the flicker by reversing the polarity every row. Therefore, in addition to the high image quality display, the liquid crystal display by the low voltage is displayed. The power consumption of the entire device and the cost of the driving element are reduced, and a highly portable personal computer or multifunctional terminal device can be realized.

[Embodiment 5] The construction of this embodiment is the same as that of Embodiment 4 except for the following requirements.

FIG. 14 shows a pixel plan view of 2 rows by 2 columns of this embodiment, FIG. 15 shows an equivalent circuit diagram, and FIG. 16 shows its drive waveform. The entire display device is constructed by repeating this pixel arrangement. The basic structure of the pixel is the same as that of the first embodiment shown in FIG. 1, but the connection with the scanning wiring for applying the potential of the counter electrode 24 is connected to the upper and lower scanning wirings 4a and 4b for each column, and the driving method is used. Based on the low voltage driving of the fourth embodiment, two types of counter voltages, which are applied to the upper and lower scanning wirings 4a and 4b by reversing the polarity for each row in the fourth embodiment, are applied to one column. The feature is that it is applied every time.

According to the present embodiment, it is possible to invert the writing polarity to the liquid crystal for each column, so that the horizontal linear noise (horizontal smear) which is likely to occur when a pattern such as a window is displayed. It is possible to prevent the crosstalk current by canceling the crosstalk current by writing a signal voltage of opposite polarity on the gate wiring, and at the same time, it is possible to reduce the signal voltage. Further, by reversing the polarity for each row, smear in the vertical direction can be prevented at the same time, and high image quality and low voltage driving can be realized.

According to the present embodiment, even if the load on the gate wiring is increased to some extent, the crosstalk current can be canceled by writing a signal voltage of reverse polarity on the gate wiring. Even in a high-definition display device, a high-quality display device without smear can be realized with low power consumption.

[0049]

As described in detail above, according to the present invention,
The pixel electrode does not need to be transparent, an opaque metal electrode having high conductivity can be used, and a low-priced active matrix liquid crystal display device that can be mass-produced with a low yield by a high yield can be obtained. In addition, since it is not necessary to form a common electrode on the counter substrate side, it is possible to reduce the steps involved in forming the common electrode or eliminate the yield loss associated with the formation of the common electrode. A matrix type liquid crystal display device can be obtained. Further, it is possible to obtain an active matrix type liquid crystal display device having good viewing angle characteristics and easy multi-gradation display. Furthermore, by utilizing the difference between the signal voltage and the counter voltage,
By using two thin film transistor elements for one pixel, it is possible to cancel the voltage fluctuation relating to the characteristics of the thin film transistor element, and obtain a high image quality active matrix type liquid crystal display device without image quality defects such as luminance gradient, afterimage and flicker. Further, an active matrix type liquid crystal display device of low voltage and low power consumption can be obtained at the same time.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a pixel portion according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an equivalent circuit of the pixel configuration of the first embodiment.

FIG. 3 is a diagram showing a cross-sectional view taken along line A of the pixel configuration of the first embodiment.

FIG. 4 is a diagram showing a cross-sectional view taken along line B of the pixel configuration according to the first exemplary embodiment.

FIG. 5 is a diagram showing a cross-sectional view taken along the line C of the pixel configuration of the first embodiment.

FIG. 6 is a schematic view of a liquid crystal display device of the present invention.

FIG. 7 is a diagram showing a voltage waveform applied to each electrode of the first embodiment.

FIG. 8 is a diagram showing the viewing angle dependence of the liquid crystal display device of the present invention.

FIG. 9 is a diagram showing the viewing angle dependence of a conventional liquid crystal display device.

FIG. 10 is a diagram showing a configuration of a pixel portion according to a second embodiment of the present invention.

FIG. 11 is a diagram showing a configuration of a pixel portion according to a third embodiment of the present invention.

FIG. 12 is a diagram showing an equivalent circuit according to a third embodiment of the present invention.

FIG. 13 is a diagram showing drive waveforms according to the fourth embodiment of the present invention.

FIG. 14 is a diagram showing a configuration of a pixel portion according to a fifth embodiment of the present invention.

FIG. 15 is a diagram showing an equivalent circuit of a fifth embodiment of the present invention.

FIG. 16 is a diagram showing drive waveforms according to the fifth embodiment of the present invention.

FIG. 17 is a diagram showing a liquid crystal operation in the liquid crystal display device of the present invention.

[Explanation of symbols]

1 ... jth column signal wiring, 2 ... (j + 1) th column signal wiring, 3 ... i row scanning wiring, 4 ... (i-1) row scanning wiring, 5a ... one thin film transistor element, 5b ... the other thin film transistor element, 6a ... the one capacitor element, 6b
One capacitance element, 7a ... Source electrode of one thin film transistor element, 7a ... Source electrode of the other thin film transistor element, 8a, 8b ... Amorphous silicon, 9 ... Liquid crystal layer, 11 ... Gate insulating film, 12 ... Protective film, 13 ... color filter, 14 ... flattening film, 15 ... light shielding layer, 16 ... alignment film, 61 ... source voltage waveform of the other thin film transistor element, 71 ... source voltage waveform of one thin film transistor element, 76, 77 ... voltage shift, 78 … Liquid crystal applied voltage,
161 ... Substrate having thin film transistor element, 162 ...
Counter substrate, 163 ... Scan side drive LSI, 164 ... Signal side drive LSI, 165 ... Control circuit.

Claims (9)

[Claims] 1. A pair of substrates, at least one of which is transparent, a liquid crystal composition layer sandwiched between the substrates, m scanning wirings and n signal wirings disposed on one of the substrates, m
A liquid crystal display device comprising: × n matrix-shaped pixels, active elements and capacitive elements arranged in the pixels, and driving means for applying a predetermined voltage waveform to the scanning wiring and the signal wiring, An electric field mainly applied to the liquid crystal composition layer in parallel to the substrate surface is applied to the pixel, and either one of the potential V1 of the signal line at the time of scanning and the scan line I adjacent to the scan line I is scanned. A predetermined structure capable of controlling the alignment state of liquid crystal molecules and modulating light by applying a potential difference | V1-V2 | of the potential V2 of the wiring II between substantially parallel electrodes provided in the pixel. Liquid crystal display device. 2. The pixel includes an active element A connected to the signal wiring, an active element B connected to the scanning wiring II, a pixel electrode connected to the active element A, and the active element B. 2. The liquid crystal display device according to claim 1, further comprising a counter electrode connected to the pixel electrode, and a predetermined structure in which an electric field between the pixel electrode and the counter electrode is mainly an electric field parallel to the substrate surface. . 3. The pixel includes an active element A connected to the signal line, a pixel electrode connected to the active element A, an active element B connected to the scan line II, and the active element B. A predetermined structure in which a counter electrode connected to the counter electrode and a capacitor element between the pixel electrode and the counter electrode are provided, and an electric field between the pixel electrode and the counter electrode is mainly an electric field parallel to the substrate surface. The liquid crystal display device according to claim 1, further comprising: 4. A pair of substrates, at least one of which is transparent, a liquid crystal composition layer sandwiched between the substrates, m scanning wirings and n signal wirings disposed on one of the substrates, m
The liquid crystal composition layer includes: × n pixels in a matrix, active elements and capacitive elements arranged in the pixels, and driving means for applying a predetermined voltage waveform to the scanning wiring and the signal wiring. On the other hand, in a liquid crystal display device characterized by having a predetermined structure for mainly applying an electric field parallel to the substrate surface, the predetermined structure is composed of an electrode having a comb shape having one or more elongated protrusions. And a liquid crystal display device. 5. The pixel has an active element A connected to the signal line, an active element B connected to the scan line II, a pixel electrode connected to the active element A, and the active element B. A liquid crystal display device having a predetermined structure in which an electric field between the pixel electrode and the counter electrode is mainly an electric field parallel to the substrate surface. 7. A driving means for applying a potential 1 to the pixel electrode through the signal wiring and a driving means for applying a potential 2 to the counter electrode through the scanning wiring II substantially in synchronism with the voltage pulse I. 2. The liquid crystal display device according to item 2. 6. The positive and negative electric potentials 2 given to the counter electrode.
Is, when an electric field is applied to the liquid crystal composition layer is greater than or equal to the potential difference between the (voltage VW to white display of the liquid crystal display device) (voltage V _BLK to the black display of the liquid crystal display device) of the potential difference The liquid crystal display device according to claim 5, wherein 7. A plurality of the pixels selected by the scan line I are connected to the first scan line II adjacent to the scan line I or another scan line III adjacent to the scan line I. An active element B, an active element A connected to the signal line, a pixel electrode connected to the active element A, and a counter electrode 2 connected to the active element B are provided, and the pixel electrode and the counter electrode 2 are connected to each other. The liquid crystal display device according to claim 1, wherein the liquid crystal display device has a predetermined structure in which an electric field between the electrodes is mainly an electric field parallel to the surface of the substrate. 8. A plurality of the pixels selected by the scan wiring I, wherein the plurality of pixels are adjacent to the scan wiring I.
II or an active element B connected to another scan wiring III adjacent to the scan wiring I, an active element A connected to the signal wiring, a pixel electrode connected to the active element A, and the active element In a liquid crystal display device having a predetermined structure in which an electric field between the pixel electrode and the counter electrode is an electric field mainly parallel to the substrate surface, the liquid crystal display device has a counter electrode connected to B, By selectively applying two types of voltage pulses having a predetermined potential difference to a plurality of opposing electrodes through the scanning line II or the scanning line III before and after the scanning line I, two kinds of electric fields in opposite directions are generated in the liquid crystal composition. The liquid crystal display device according to claim 7, wherein the liquid crystal display device is selectively applied to an object. 9. A pair of substrates, at least one of which is transparent, a liquid crystal composition layer sandwiched between the substrates, m scanning wirings and n signal wirings disposed on one of the substrates. m
A liquid crystal display including × n pixels in a matrix, active elements and first capacitive elements arranged in the pixels, and driving means for applying a predetermined voltage waveform to the scanning wiring and the signal wiring. In the device, the pixel includes an active element A connected to the signal wiring, an active element B connected to a scanning wiring II adjacent to the scanning wiring I via a second capacitive element, and an active element A. A predetermined structure in which the electric field between the pixel electrode and the counter electrode is mainly an electric field parallel to the substrate surface. The liquid crystal display device according to claim 1.