JPH0437726A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To offer the liquid crystal display device which is uniform in contrast among respective parts of its screen and has superior display quality by forming a common electrode which is divided into plural areas nearly corresponding to the thickness of a liquid crystal layer and connecting the respective areas to mutually different external driving circuits. CONSTITUTION:In this active matrix liquid crystal display, the common electrodes 4a, 4b, and 4c arranged on a front glass substrate 1 are divided corresponding to variation in the thickness (cell interval) of the liquid crystal layer between the respective areas and a rear glass substrate 2, and the respec tive areas of the divided common electrodes are connected to the external driving circuits through mutually different connection terminals 7a, 7b, and 7c. Therefore, the respective areas of the common electrodes can be applied with mutually different voltages corresponding to the cell intervals, so even when the cell intervals are irregular, a difference in contrast between respective parts of the screen, specially, between the center part and end edge part of the screen is reducible and the superior display quality is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to liquid-black display devices, and more particularly to active matrix liquid crystal displays.

[Prior Art] FIG. 2 is a cross-sectional view schematically showing a configuration example of a conventional active matrix liquid crystal display, and FIG. 3 is a plan view schematically showing an example of electrode arrangement of a conventional active matrix liquid crystal display. It is a diagram. Hereinafter, a conventional active liquid crystal display will be described, mainly based on FIG. 2 and with reference to FIG. 3 as necessary. Therefore, unless otherwise specified, the following explanation is based on the second
This is a description regarding the figure. However, Figures 2 and 3 are
Since this is a conceptual diagram, the number of electrodes or thin film transistors is the same in both diagrams, and does not necessarily match the number of liquid crystal display devices used in practical use.

Traditional active matrix liquid crystal displays
As shown in the figure, a liquid crystal layer 27 is sandwiched between a front glass substrate 22 bonded together by a sealing layer 21, a rear glass substrate 25 provided with a thin film transistor 23 and a pixel electrode 24, and a spacer 26.

A common electrode 28 made of a transparent electrode material such as ITO and facing the pixel electrode 23 is provided on the front glass substrate 22, a black matrix 29 is provided on the common electrode 28, and a black matrix 29 is provided on the black matrix 29. Alignment film 3
0 is provided.

On the other hand, the front glass substrate 2 of the back glass substrate 23
2, a plurality of data line electrodes 31 and scanning electrodes 32 (see FIG. 3) are formed in a stripe shape orthogonal to each other, and a thin film transistor 23 is provided at the intersection of the two electrodes. It is being Further, a pixel electrode 24 is provided between the two electrodes, and the pixel electrode 24
is connected to the thin film transistor 23. An insulating film 33 is provided on the thin film transistor 23 and the pixel electrode 24 to protect the surfaces of the thin film transistor 23 and the pixel electrode 24, and an alignment film 33 is provided on the insulating film 33.
4 are provided.

The common electrode 28 is connected to a connection terminal 36 provided on the rear glass substrate 23 for connecting to an external drive circuit by a conductive adhesive (for example, silver paste) 35 buried inside the sealing layer 21. ing.

In the conventional active matrix liquid crystal display having the above configuration, the pixel electrode 24 and the common electrode 28
Since display is performed by applying a voltage between the two electrodes to change the arrangement state of the liquid crystal between the two electrodes, the display is held between the front glass substrate 22 and the rear glass substrate 23 in order to make the contrast of each part of the screen uniform. The thickness of the liquid crystal layer 25 (
It is desirable to keep the cell spacing constant. Therefore,
The front glass substrate 22 and the back glass substrate 23 are usually 3
A liquid crystal layer 27 is sandwiched between a spacer 26 which is a molded body made of glass fiber, ceramic or resin and has a spherical or cylindrical shape having a substantially uniform diameter in the range of ~10 μm, and the cell interval defined by the diameter of the spacer 26 is set. Designed to hold.

Furthermore, in the conventional active matrix liquid crystal display described above, the common electrode 28 is formed on the entire surface of the front substrate 22 without being divided, and a single voltage is supplied to the common electrode 28 from an external drive circuit through the connection terminal 36. The structure is such that

[Problems to be Solved by the Invention] However, in the conventional active matrix liquid crystal display described above, the glass substrate is deformed due to heat in the process of forming thin film transistors, so it is difficult to maintain a constant cell spacing using spacers alone. However, there is a problem in that there is a difference in cell spacing between the center and edge of the screen. In the conventional active matrix liquid crystal display mentioned above, a single voltage is applied between the common electrode and the pixel electrode, so if the cell spacing is not uniform, the contrast of the entire screen will be uneven and the display quality will be affected. This tendency tends to decrease as the display screen becomes larger.

Therefore, the present invention has been made to solve the problems of the prior art as described above, and its purpose is to:
It is an object of the present invention to provide a liquid crystal display device with uniform contrast in each part of the screen and excellent display quality.

[Means for Solving the Problems] A liquid crystal display device according to the present invention includes a first substrate provided with a thin film transistor and a pixel electrode, and a second substrate provided with a common electrode facing the pixel electrode. , a liquid crystal display device comprising a liquid crystal layer provided between the first and second substrates, wherein the common electrode is formed divided into a plurality of regions approximately corresponding to the thickness of the liquid crystal layer;
The above-mentioned regions are each connected to different external drive circuits.

[Function] In the liquid crystal display device of the present invention, the common electrode is formed by being divided into a plurality of regions corresponding to the thickness (cell spacing) of the liquid crystal layer, and each region of the common electrode has a different external Connected to the drive circuit. Therefore, by supplying a voltage adjusted according to the cell spacing corresponding to each area to each area of the common electrode, the difference in contrast between each part of the screen, especially the center and edge areas of the screen, can be corrected. .

[Example] The present invention will be explained below based on illustrated embodiments.

FIG. 1 is a plan view schematically showing the electrode arrangement of an embodiment of an active matrix liquid crystal display according to the present invention.

The active matrix liquid crystal display of this example is
As shown in FIG. 1, a front glass substrate 1 and a rear glass substrate 2 are bonded together by a sealing layer 3, and a liquid crystal layer (not shown) is provided between the front glass substrate 1 and the rear glass substrate 2. There is. The front glass substrate 1 and the back glass substrate 2 may be configured to sandwich the liquid crystal layer via a spacer or the like.

Common electrodes 4a, 4b, and 4C made of a transparent electrode material such as ITO are provided on the front glass substrate 2, and each of the common electrodes 4a and 4b is connected to a different external drive circuit. portions 41a and 41b of
are integrally formed.

On the other hand, on the surface of the rear glass substrate 2 facing the front glass substrate 1, a plurality of data line electrodes 5 and scanning electrodes 6 are formed in a stripe shape orthogonal to each other. Thin film transistor (not shown)
is provided.

Further, a pixel electrode (not shown) is provided between the two electrodes, and the pixel electrode is connected to a thin film transistor. Further, on the surface of the rear glass substrate 2 facing the front glass substrate 1, a connection terminal 7a to an external drive circuit is provided.
, 7b and 7C are provided.

In the active matrix liquid crystal display of this embodiment, the common electrodes 4a, 4b, and 4C provided on the front glass substrate 1 are arranged so that the thickness of the liquid crystal layer (cell The common electrode is divided so as to correspond to a change in the distance between the common electrodes 7a, 7b, and 7, and each area of the divided common electrode is divided into different connection terminals 7a, 7b, and 7.
It is characterized in that it is connected to an external drive circuit by C.

In general, active matrix liquid crystal displays
Due to the heat generated during the process of forming thin film transistors, the center of the glass substrate tends to be deformed into a convex or concave shape. Therefore, it is preferable that the common electrode is divided so that the voltage can be applied in two to three steps from the center of the screen to the edge. Therefore, in this embodiment, the common electrode is formed in three broad stages, 4a, 4b, and 4C, from the center of the screen to the edge. The common electrodes 4a, 4b and 4
It is sufficient that each region c approximately corresponds to the cell interval, and a portion belonging to each region, for example, the connecting portions 41a, 41
It is not necessary to correspond to the cell spacing, such as b. Moreover, the communication portion between the above-mentioned - region and the corresponding connection terminal may be formed so as to cross a part of the other region.

The common electrodes 4a and 4b located in the center of the screen among the respective regions of the common electrode are connected to the connecting portions 41a and 41, respectively.
b, and the outermost common electrode 4C is provided on the rear glass substrate 2 without a connecting part via a conductive adhesive (for example, silver paste) 8 buried inside the sealing layer 3. Connecting terminal 7a to external drive circuit
, 7b and 7C. The connection using the conductive adhesive 8 can be made in the same manner as in the lower conventional example.

It is preferable that the common electrodes 4a, 4b, and 4C are formed close enough to each other so that the display is not cut off in each area of the screen, and the interval between each area (including the connecting portion) is in the range of 10 to 30 μm. It is preferable that it be made of

In the active matrix liquid crystal display of this embodiment, the counter electrodes 4a, 4b, and 4C each have Vcoml±.
It is driven by applying AC pulse voltages of V1, V com2±■2, and V com3±■3. When the glass substrate or its central part is convex, that is, when the cell spacing or the central part of the screen is thick, the above voltage is as follows: Vcoml±Vl>Vcom2±V2>Vco
Make it m3±v3. Since the voltages can be adjusted independently according to the size of the cell interval to which each region of the common electrode corresponds, it is possible to avoid complicating the external drive circuit.

The active matrix liquid crystal display of this example is
By driving as described above, even if the cell spacing is uneven, it is possible to reduce the difference in contrast between various parts of the screen, especially between the center and edge parts of the screen.

In this embodiment, the common electrode is divided into four regions so that eight levels of voltage can be applied, but it may be broadly divided into two regions so that two levels of voltage can be applied.

Further, in this embodiment, the common electrodes 4a and 4b are formed in an elliptical shape, but the opposing electrodes 4a and 4b may have a rectangular shape as shown in FIG. 4, or may have other shapes such as a circular shape. It may be. In FIG. 4, the same components as in FIG. 3 are denoted by the same reference numerals, and detailed explanations will be omitted.

The active matrix liquid crystal display of this embodiment is similar to the conventional active matrix liquid crystal display except that the common electrode is formed by dividing it as described above, and each area of the common electrode is connected to a different connection terminal. It can be manufactured in the same way as a display.

The common electrodes 4a, 4b, and 4C are formed by forming a transparent electrode material such as ITO on the front glass substrate 1 by sputtering or vapor deposition to a thickness of about 0.1 μm, and then The transparent electrode film may be formed into a pattern divided into predetermined regions by photolithography and etching.

[Effects of the Invention] As described in detail above, according to the liquid crystal display device of the present invention, the common electrode is formed by being divided into a plurality of regions approximately corresponding to the cell spacing, and each region of the common electrode Different voltages can be applied to each cell depending on the cell spacing.

Therefore, in the liquid crystal display device of the present invention, even when the cell spacing is uneven, it is possible to reduce the difference in contrast between each part of the screen, especially between the center and edge parts of the screen, and to obtain excellent display quality. be able to.

[Brief explanation of the drawing]

FIG. 1 is a plan view schematically showing the electrode arrangement of an embodiment of an active matrix liquid crystal display according to the present invention, and FIG. 2 is a sectional view schematically showing a configuration example of a conventional active matrix liquid crystal display. 3 is a step plan view schematically showing the electrode arrangement of a conventional active matrix liquid crystal display, and FIG. 4 is a schematic diagram showing another aspect of the electrode arrangement of an embodiment of the active matrix liquid crystal display according to the present invention. FIG. 4 a, 4 b, 4 c=-common electrode, 41a, 4
1b -- one connection part, 5a, 5b, 5c... connection terminal.

Claims (1)

[Scope of Claims] A first substrate provided with a thin film transistor and a pixel electrode, a second substrate provided with a common electrode facing the pixel electrode, and a device provided between the first and second substrates. In a liquid crystal display device comprising a liquid crystal layer, the common electrode is divided into a plurality of regions approximately corresponding to the thickness of the liquid crystal layer, and each region is connected to a different external drive circuit. A liquid crystal display device characterized by: