JPH02184823A - Active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To form the additive capacity to be connected in parallel with the capacity of a liquid crystal cell without complicating production processes by adopting the disposition in which one end of picture element electrodes and one end of the adjacent scan bus lines facing thereto are formed as comb-tooth patterns and the comb-tooth parts of both are meshed with each other so as to face each other in parallel. CONSTITUTION:The opposite parts of both the respective picture element electrodes E and the adjacent scan bus lines SB' are formed as the comb-tooth-shaped 11, 12 patterns and are disposed to face each other in parallel in such a manner that the projecting parts on one side are positioned in the recesses of the other. The length of the opposite sides of the picture element electrodes E and the scan bus lines SB' is extremely long at this time and since both are in proximity to each other, a large capacity is formed between the picture element and the adjacent scan bus line SB'. The greater part between one frame of all the scan bus lines is in a non-selection state and since the potential at the time of the non-selection is constant, the capacity acts as the additive capacity C3 connected in parallel to the liquid crystal cell capacity CLC. The additive capacity C3 is formed in this way by the simplified production processes.

Description

[Detailed Description of the Invention] [Summary] Regarding an active matrix liquid crystal display device that can achieve high image quality and high reliability, an additional capacitance connected in parallel with the capacitance of a liquid crystal cell can be added without complicating the manufacturing process. A plurality of pixel electrodes and switching elements associated with each pixel electrode are arranged in a matrix, and a plurality of pixel electrodes and a switching element corresponding to each pixel electrode are arranged in a matrix, and a switch is provided for selecting the row corresponding to each row of the pixel electrode. In an active matrix configuration in which a scan canvas line is provided, one end of each pixel electrode and an example end of the scan canvas line corresponding to an adjacent row opposite thereto are both formed into a comb tooth pattern, and the tooth portions of both combs are formed into a comb tooth pattern. The configuration is an interlocking arrangement.

[Industrial application field]

The present invention relates to an active matrix liquid crystal display device that can achieve high image quality and high reliability.

Liquid crystal display devices have the characteristics of low power consumption, light weight, and easy color display, so they are widely used in TVs and TVs.
A: Active matrix type liquid crystal display devices driven by thin film transistors, which have a large capacity and can provide clear gradation displays, are gaining a wide market as flat display devices for terminal equipment, etc., and are currently in widespread use, with some of them being put into practical use. Development and research is progressing to further improve image quality and reliability. However, at present, due to temperature rise or contamination during manufacturing, the resistance of the liquid crystal decreases and the display quality deteriorates. Therefore, there is a strong demand for a liquid crystal display device in which the display quality does not deteriorate even if the liquid crystal resistance decreases.

[Conventional technology]

A conventional active matrix liquid crystal display device uses thin film transistors (TPTs) as shown in the equivalent circuit diagram of FIG.
)1 is used as a switching element, and when selected, data voltage is written to the liquid crystal cell LC, and when not selected, the capacitance of the liquid crystal cell (hereinafter simply referred to as cell capacitance) etc.
The potential is maintained by

The resistance component of this liquid crystal cell (this is called liquid crystal resistance) R
When tc decreases, the time constant determined by its product with the cell capacity I CL C decreases, causing a problem in that the voltage applied to the liquid crystal cell LC decreases significantly due to leakage, resulting in a decrease in brightness.

[Problems to be Solved by the Invention] Therefore, as shown in FIGS. 4(a) and 4(b), a part of the pixel electrode E and the scan canvas line SB" in the adjacent row are made to face each other with the insulating film 2 in between. It has been devised that an electrostatic capacitance is formed by connecting this as an additional capacitance C8 in parallel to the cell capacitance ffi Ct c.(b) in the same figure is a cross section taken along the line B-B in (a). It is a diagram.

FIG. 5 shows an equivalent circuit when the additional capacitor C5 is provided as shown in FIGS. 4(a) and 4(b) above.

By doing this, the capacitance component increases to the sum of the cell capacitance CtC and the additional capacitance C8, so that the time constant RLCX
(CLC+Cs) becomes large, and the liquid crystal resistance RLC
Even if the voltage decreases to some extent, the decrease in voltage applied to the liquid crystal cell LC due to leakage is suppressed, and the adverse effect on display is reduced.

However, in this structure, since each pixel electrode E overlaps the adjacent scan canvas line SB', there is a problem that the manufacturing process is complicated and the manufacturing yield is lowered.

Therefore, an object of the present invention is to enable formation of an additional capacitor connected in parallel with the capacitor of a liquid crystal cell without complicating the manufacturing process.

[Means to solve the problem]

In the present invention, one end of a pixel electrode and one end of an adjacent scan canvas line opposite thereto are both formed into a comb tooth-like pattern, and the two comb tooth portions are interlocked and arranged to face each other in parallel. did.

[For production]

With the above configuration, the length of the opposing sides of the pixel electrode and the adjacent scan canvas line becomes extremely long. Since the two are close to each other, a large capacitance is formed between the pixel electrode and the adjacent scan canvas line. Most of the scan canvas lines are in a non-selected state during one frame, and the potential when non-selected is constant, so the above capacitance is an additional capacitor connected in parallel to the liquid crystal cell volume Mt Ct c. Works as C5.

To form the additional capacitor 1cs of the present invention, it is only necessary to partially change the mask pattern used in the step of patterning the pixel electrode and scan canvas line, and there is no need to change the manufacturing process itself. Therefore, when implementing the present invention, the additional capacitor C8 can be easily formed without any problems in the manufacturing process.

Therefore, in the present invention, even if the resistance of the liquid crystal decreases, the change in brightness is negligible, and it is possible to prevent the image quality of the liquid crystal display device from deteriorating. There are no crossing parts, and the manufacturing yield is improved from this point of view as well.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a diagram showing one pixel of this embodiment, where the pixel electrode E is the thin film transistor 1 that drives the pixel, and the control electrode (
Gate electrode) G to scan canvas line SB, and two controlled electrodes (drain electrode).

One side 3 of the source electrodes is connected to the data bus line DB, and the other side 4 is connected to the pixel electrode.

A large number of pixels configured in this manner are arranged in a matrix on one glass substrate (not shown) to constitute a TPT substrate.

A liquid crystal display panel is constructed by sandwiching liquid crystal between the TPT substrate and another glass substrate (counter substrate) placed opposite to each other.

A counter electrode made of a transparent electrode is formed on the counter substrate. Therefore, each pixel electrode E faces a counter electrode with the liquid crystal interposed therebetween, forming a parallel plate capacitor. This capacitance forms the liquid crystal cell volume Ietc.

In addition to the above-mentioned conventional structure, in this embodiment, each pixel electrode E and the adjacent scan canvas line SB have a comb tooth-like pattern in their opposing parts, and the convex part on the - side is located in the concave part on the other side. The combs are arranged so that they face each other parallel to each other, and the tooth patterns of both combs are interlocked with each other.

By arranging the comb tooth parts lL12 to face each other in parallel, the pixel type iE and the adjacent scan canvas line S
The distance between B' and B' is extremely large, and
A large capacitance can be formed in this portion.

By the way, the length of the tooth part 11.12 of the comb is about 10
0μm9 When both the width and the interval are approximately 2μm, and the size of the pixel electrode is approximately 300μm x 300μm, approximately 0
．． An additional capacitance C5 of 5 pF can be obtained.

When an additional capacitance C3 of about 0.5 pF is provided in this way, as shown by curve A in Fig. 2, compared to the case where only the cell capacitance CLc is about 0.4 pF [curve B in the same figure]. Therefore, the effective voltage applied to the liquid crystal cell, that is, the effective value of the voltage between the pixel electrode E and the counter electrode within one frame increases significantly. Note that the horizontal axis in the figure represents the resistivity [Ωcm] of the liquid crystal, and the vertical axis represents the ratio of the effective voltage applied to the liquid crystal to the data voltage.

In this manner, in this embodiment, even if the resistivity of the liquid crystal decreases, the effective value decreases less, and therefore the brightness decreases less, thereby reducing deterioration in image quality. Moreover, when manufacturing the active matrix liquid crystal display device of this example,
It is only necessary to partially change the mask pattern used in the manufacturing process, and there is no need to change the manufacturing process itself. Therefore, there is no difficulty in manufacturing this embodiment. Furthermore, in this embodiment, since there is no overlap between the pass line and the pixel electrode, there is no occurrence of defects such as short circuits due to differences in level, and these factors combine to improve manufacturing yield and reliability.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the configuration of one embodiment of the present invention, Fig. 2 is an explanatory diagram of the effect of the above embodiment, Fig. 3 is an equivalent circuit diagram for one pixel of a conventional liquid crystal cell, Fig. 4 (a), (b) is an explanatory diagram of the structure of the conventional additional capacitor, No. 5
The figure is an equivalent circuit diagram when additional capacitance is provided. In the figure, 1 is a thin film transistor, E is a pixel electrode, and S
B is a scan canvas line, SB' is an adjacent scan canvas line, DB is a data bus line, CLC is a liquid crystal cell capacitance, C3 is an additional capacitance, and RLc is a liquid crystal resistance. [Effects of the Invention] As described above, according to the present invention, an additional capacitor can be formed through a simplified manufacturing process, and it is possible to prevent deterioration of image quality and improve manufacturing yield and reliability. Gate 1 [Unexploded at 6, Ichitutei Reisei to Qiancho drunkenness Figure 1 RLe: 涛品马性cLc: 3f(+Shikiru oomumu/157 to T!-1 R) Figure 4

Claims (1)

[Claims] A plurality of pixel electrodes (E) and switching elements (1) associated with each pixel electrode are arranged in a matrix, and a switching element (1) corresponding to each row of the pixel electrode (E) is arranged in a matrix. In an active matrix configuration in which scan canvas lines (SB, SB') are provided for selecting the pixels, one end of each pixel electrode (E) and one scan canvas line (SB') corresponding to the adjacent row facing thereto. Both side edges have a comb tooth pattern, and both comb teeth (11, 12)
An active matrix liquid crystal display device characterized by an arrangement in which the two are interlocked with each other.