JPH04338729A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain a uniform display in a screen by varying the channel length and channel width of thin film transistors(TFT), formed on an insulating substrate, in the display screen. CONSTITUTION:When liquid crystal 4 is driven, the life should be prevented from becoming short by inverting the polarity of an applied voltage at a constant period without fail. The polarity is inverted in each one-vertical-scanning period. Even when the TFTs(thin film transistor) 2 formed on the insulating substrate 1 are off, charges accumulated in display electrodes 3 slightly leak to data electric conductors 7 through the TFTs 2. The amount of leaking charges is smaller and smaller as the channel length is longer and longer and the channel width is narrower and narrower. For the purpose, the channel length and channel width of the TFTs 2 are varied in the display screen. Consequently, the leakage of charges from the display electrodes 3 to the data electric conductors 7 can be equalized.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improving the display performance of a liquid crystal display device using thin film transistors (hereinafter abbreviated as TFTs) formed on an insulating substrate.

0002

2. Description of the Related Art In a conventional active matrix type liquid crystal display device using TFTs, a plurality of TFTs arranged in a matrix within a display screen all have the same channel length and the same channel width.

0003

[Problem to be Solved by the Invention] In the above-mentioned conventional technology, the plurality of TFTs arranged in a matrix within the display screen had the same channel length and the same channel width, so uneven brightness occurred within the screen. .

An object of the present invention is to realize uniform display within the screen.

[0005]

The above object is achieved by changing at least one of the channel length and channel width of a plurality of TFTs arranged on an insulating substrate within a display screen.

[0006]

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

FIG. 1 is an equivalent circuit diagram showing an active matrix substrate of a liquid crystal display device according to the present invention. 1 is an insulating substrate, 2 is a TFT, 3 is a display electrode, 4 is a liquid crystal, 5 is a transparent counter electrode, 6 is an address wiring, and 7 is a data wiring. A gate pulse voltage is sequentially applied to the address wiring 6 to excite the TFT 2 to a conductive state for each row. The signal voltage is supplied to the data line 7 in synchronization with the gate pulse voltage, and the TFT
2 to the display electrode 3. When the gate pulse voltage moves to the next row, the TFT 2 becomes non-conductive, and the data line 7 and the display electrode 3 are insulated. Therefore, the signal voltage stored in the capacitor between the display electrode 3 and the transparent counter electrode 5 is held until the next scan. The liquid crystal 4 is driven quasi-statically by the voltage between the display electrode 3 and the transparent counter electrode 5.

When driving a liquid crystal, the polarity of the applied voltage must be reversed at regular intervals to prevent shortening of its life. This polarity reversal is often performed every vertical scanning period. Even when the TFT 2 is in a non-conductive state, the charge stored in the display electrode 3 leaks to the data line 7 via the TFT 2 to some extent. The amount of leakage increases as the potential difference between the display electrode 3 and the data wiring 7 increases. When reversing the polarity of the display signal voltage every vertical scanning period, the time from when the display signal voltage is written to the display electrode 3 to when the polarity of the display signal voltage of the data wiring 7 is reversed toward the lower part of the display screen. is short. Therefore, the lower the display screen, the more the display electrode 3
The period during which the potential difference between the data line 7 and the data line 7 is large is long. For this reason, when the TFT 2 has the same channel length and the same channel width within the display screen as in the conventional technology, the amount of charge leaking from the display electrode 3 to the data wiring 7 becomes larger toward the lower part of the display screen. This results in uneven brightness at the top and bottom of the screen.

FIG. 2(a) is a plan view showing the configuration of the main part of the upper part of the active matrix substrate of the present invention, and FIG. 2(b) is an embodiment of the plan view showing the structure of the main part of the bottom part of the active matrix substrate. be. 8 is a contact hole. TF
The longer the channel length and the smaller the channel width, the smaller the amount of charge leaking through T2. Since at least one of the channel length and channel width of the TFT 2 is changed within the display screen in this way, the amount of charge leaking from the display electrode 3 to the data wiring 7 can be made the same, and a uniform display can be obtained within the screen. made possible.

0010

[Effects of the Invention] As described above, the present invention changes at least one of the channel length and channel width of a thin film transistor formed on an insulating substrate within a display screen, so that a uniform display can be obtained within the screen. made possible.

[Brief explanation of drawings]

FIG. 1 is an equivalent circuit diagram showing an active matrix substrate according to an embodiment of the present invention.

FIGS. 2(a) and 2(b) are plan views showing the configuration of the main parts thereof.

[Explanation of symbols]

1 Insulating substrate 2 Thin film transistor 3 Display electrode 4.LCD 5 Transparent counter electrode 6 Address wiring 7 Data wiring 8 Contact hole

Claims (1)

[Claims] Claim 1: An insulating substrate, a plurality of address wirings and data wirings arranged intersecting each other on the substrate, and gate electrodes formed at the intersections of each address wiring and data wiring as the address wirings. In a display drive circuit board having a plurality of thin film transistors each having a source electrode connected to a data wiring, and a plurality of display electrodes respectively connected to a drain electrode of these thin film transistors, the channel length and the channel width of the thin film transistor are A liquid crystal display device characterized in that at least one of the elements is changed within a display screen.