JPS62116921A - Liquid crystal display - Google Patents

Abstract

PURPOSE:To improve display picture quality by setting the position of a thin film transistor (TR) and the direction of orientation of liquid crystal so that a display defect part due to the inversion of orientation of molecules of liquid crystal and the thin film TR overlap each other. CONSTITUTION:A display electrode 3, the thin film TR 4, and an oriented film 5 are provided on the top surface of a lower substrate 1 and a polarizing plate 6 is provided on the reverse surface. A common electrode 7 and an oriented film 8 which are formed on the reverse surface are provided to an upper substrate 2 and a polarizing plate 9 is provided on the top surface. Liquid crystal 10 is interposed between the oriented films 5 and 8 of the substrates 1 and 2. Drain electrodes 11 are formed among longitudinal arrays of electrodes 3 across an insulating film 15, gate electrodes 12 are formed directly on the substrate 1 among lateral arrays, and TRs 4 are formed between gate electrodes 12 and the display electrodes 3 nearby intersections of electrodes 11 and 12. The orientation direction of the oriented films 5 and 8 is so set that a defect display part 3a due to an edge domain is formed on a TR 4. Thus, the area of a normal display part on a display electrode is not reduced and the picture quality is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a field-effect type device that prevents display defects caused by so-called edge domains, which are the reversal phenomenon of liquid crystal molecular alignment that occurs at positions overlapping the edge portions of display electrodes. The present invention relates to a liquid crystal display device.

[Technology background]

In general, in this type of liquid crystal display device, for example, as shown in FIG. ,
An alignment film 24, a common electrode 25, and an alignment film 26 are laminated on the upper substrate 22, and the alignment films 24, 2
A liquid crystal 27 (for example, twisted nematic liquid crystal) is interposed between the liquid crystals 6 and 6.

The upper and lower alignment films 24 and 26 are both made of organic polymer material and formed to a predetermined thickness, and during the curing process, they are rubbed with a cloth in directions perpendicular to each other to increase the alignment force for liquid crystal molecules. As a result, the spindle-shaped liquid crystal molecules are oriented 90 degrees horizontally near the lower substrate 21 and horizontally 90 degrees near the upper substrate 22, as shown in FIG.
The orientation is maintained in a state where the orientation is changed.

Then, when a voltage is selectively applied between the upper and lower common electrodes 25 and the display electrode 23, the liquid crystal molecules located between the display electrode 23 and the common electrode 25 to which the voltage has been applied It is designed to rise in the direction of the direction of the light, and to control the transmission or blocking of light.

By the way, in such a liquid crystal display device, the liquid crystal molecules located between the display electrode 23 to which a voltage is applied and the common electrode 25 and corresponding to one corner of the display electrode 23 are the fifth This is a so-called process in which the orientation of liquid crystal molecules is reversed as shown in Figure (C).

It is known that the cytomain phenomenon occurs and a defective display area 23a is generated at one corner of the display electrode 23 as shown in FIG. 5(d).

[Prior Art] As a method for improving the defective portion 23a in the display state due to such a rainbow domain phenomenon, the defective portion 23a as described above is
A method has been proposed in which the display electrode is cut out at the portion where a is formed (Japanese Patent Laid-Open No. 59-202433).

[Problem that the invention seeks to solve]

However, the above-described method has the problem that the aperture ratio of the liquid crystal display device decreases, and a decrease in image contrast is unavoidable.

[Means for solving problems]

The present invention has been made in view of the above circumstances, and an object of the present invention is to use thin film transistors configured as switching elements for signals to display electrodes made of Si.
It is composed of a quality silicon layer made of materials such as Al, U, etc., and gate electrodes, source electrodes, drain electrodes, etc. made of materials such as Al, U, etc., and focusing on the fact that it is opaque itself,
By setting the defective display area due to edge domains to be formed overlapping the thin film transistor, the area occupied by the defective display area on the display electrode can be reduced as much as possible by utilizing the existence of the inherently opaque thin film transistor. An object of the present invention is to provide a liquid crystal display device in which the display image quality can be improved.

In the liquid crystal display device according to the present invention, in an active matrix type liquid crystal display device using thin film transistors as switching elements, the thin film transistor overlaps with a display defective portion due to a molecular orientation reversal phenomenon of the liquid crystal occurring on the display electrode. The present invention is characterized in that the position of the thin film transistor with respect to the display electrode and the direction of alignment treatment with respect to the liquid crystal are set relative to each other.

(Examples) The present invention will be specifically described below based on drawings showing examples thereof. FIG. 1 is a cross-sectional structural diagram of a liquid crystal display device according to the present invention, and FIG. 2 is a schematic plan view seen from the nn line direction of FIG. A transparent glass substrate is shown. On the lower board l,
A display electrode 3 formed of an ITO film or the like, a thin film transistor 4, and an orientation 1415 are disposed on the upper surface, and a polarizing plate 6 is disposed on the lower surface.
is provided, and on the other hand, ITOg is provided on the lower surface of the lower upper side 2.
A common electrode 7 formed of ill, etc., and its orientation are laminated, a polarizing plate 9 is provided on the upper surface, and a liquid crystal IO is interposed between the orientation y15.8 of the upper and lower substrates 1 and 2. There is.

The display electrodes on the substrate 1 are arranged in a grid pattern with slight gaps in the vertical and horizontal directions, and drain electrodes 11 are arranged between the columns of the display electrodes 3 with insulators 115 in between.
Furthermore, a gate electrode 12 is formed directly on the substrate 1 between the rows, and a thin film transistor 4, which is a switching element, is formed near the intersection of the drain electrode 11 and the gate electrode 12, and between each display electrode 3. It is formed.

As is clear from FIG. 1, in the S-film transistor 4, a silicon layer 13 to be quality is laminated on the tongue portion 12a extending from the gate electrode 2 with an insulating film 15 in between, and a silicon layer 13 to be quality is formed on the silicon layer 13 to be quality. , the drain electrode 11 and the source electrode 14 are laminated so as not to be in contact with each other,
The aforementioned display electrode 3 is formed on the source electrode 13 with one corner thereof overlapping, and the gate electrode 12 is scanned line-sequentially, and all the thin film transistors on the negative gate electrode are temporarily turned on. A signal is supplied from a signal circuit (not shown) to each signal storage capacitor via the drain electrode 11, and the supplied signal continues to excite the liquid crystal until the next frame is scanned.

For orientation 1*5.8, the organic polymer film is approximately 1000A.
They are formed to a certain thickness, and are oriented in directions perpendicular to each other by rubbing with a cloth during the curing process. The orientation processing direction is set so that the defective display portion 3a due to the edge domain is formed on the #l*l-transistor 4, more precisely on the display electrode 3 and on the source electrode l4 constituting the thin film transistor 4. Orientation 1m formed on the lower substrate 1! 5 is aligned in the direction shown by the broken line in FIG. 2, and the alignment film 8 formed on the upper substrate 1 is aligned in the direction shown by the solid line in FIG.

A defective display portion appearing at one corner of the display electrode 3 due to the edge domain has a certain relationship with the direction of alignment treatment in the alignment films 5 and 8, as shown in FIG. Figure 3 (
A) to (D) are explanatory diagrams showing the relationship between the alignment processing direction and the defective display area occurrence position when liquid crystal molecules exhibit left-shifting property, and the alignment processing direction for the lower alignment 1115 is indicated by a broken line on the left; Also the upper orientation y! The direction of the alignment process for 8 is shown by a solid line, and the defective display portion 3a produced on the display electrode 3 is shown on the right side.

As is clear from this, in the case of a left-shifting liquid crystal, when the lower side is aligned downward to the right and the upper side is aligned upward to the right as shown in FIG. Further, as shown in FIG. 3(b), when the lower side is oriented downward to the left and the upper side is oriented downward to the right, the defective display area 3a will occur at the upper right corner, and as shown in FIG. 3(c). As shown in FIG. 3(d), when the lower side is aligned upward to the right and the upper side is aligned downward to the left, the defective display area 3a occurs at the lower right corner, and as shown in FIG. 3(d), the lower side is aligned upward to the right. , it can be seen that when the lower side is oriented upward to the left, the defective display portion 3a occurs at the lower left corner.

The central part of FIG. 3 (a) to (d) is the optimal visual direction, and the directions are respectively 6 o'clock, 9 o'clock, 12 o'clock, and 3 o'clock with respect to the vertical line at the center of the display electrode 3. A slightly inclined position is the optimal viewing direction.

From this, when the thin film transistor 4 is arranged at the lower left corner of each display electrode 3 as shown in FIG.
As shown in Figure (d), it can be seen that the orientation treatment on the lower side can be performed upward to the right, and the orientation treatment on the upper side can be performed downward to the left.

FIG. 4 is a schematic plan view showing another embodiment of the device of the present invention, in which the thin film transistor 4 is positioned at the lower left corner with respect to the display electrode 3, and the defective display portion 3a is also positioned so as to overlap with this position. . In the case shown in FIG. 2, the optimal viewing direction is the 3 o'clock direction as shown in FIG. 3 (d). Therefore, for example, if the 6 o'clock direction is the optimal viewing direction for a liquid crystal display as a universal viewing direction,
As shown in Figure 3 (a), the lower orientation process is done downward to the right.
The upper side may be oriented upwardly to the right. In this case, since the defective display portion 3a due to the edge domain occurs at the lower left corner of the display electrode 3, it is only necessary to design the thin film transistor 4 so that it is located here.

[Effect] As described above, in the device of the present invention, since the defective display portion due to the edge domain phenomenon is formed at a position overlapping the thin film transistor, the area of the normal display portion occupied by the display electrode is not reduced. Moreover, the present invention has excellent effects, such as making it possible to eliminate most of the defective display area from the field of view and displaying without reducing the numerical aperture.

[Brief explanation of drawings]

Figure 1 is a cross-sectional structural diagram of the device of the present invention, and Figure 2 is
3 (a) to 3 (d) are explanatory diagrams showing the relationship between the alignment treatment direction and the edge domain position for the alignment film, and FIG. 4 shows another embodiment of the present invention. The schematic plan views shown in FIGS. 5(a) to 5(d) are explanatory diagrams showing the relationship between the alignment direction of liquid crystal and the edge domain. 1, 2... Substrate 3... Display electrode 4... N film transistor 5... Alignment film 6... Polarizing plate 7.
・・Common electrode 8・Alignment film 9・Polarizing plate 10・
...Liquid crystal 11...Drain electrode 12...Gate electrode 13...Silicon film to be quality 14...Source electrode Patent Applicant: Sanyo Electric Co., Ltd. Representative Patent Attorney Noboru Kono↓ 1 Illustration 2 Evil and true 3 Zuhata 512]

Claims (1)

[Claims] 1. In an active matrix liquid crystal display device using thin film transistors as switching elements,
A liquid crystal characterized in that the position of the thin film transistor with respect to the display electrode and the alignment treatment direction with respect to the liquid crystal are set relative to each other so that a display defect caused by a molecular orientation reversal phenomenon of the liquid crystal occurring on the display electrode and the thin film transistor overlap with each other. Display device.