JPH04366819A - Active matrix liquid crystal display device - Google Patents

Abstract

PURPOSE:To obviate the impression of an unnecessary voltage to the liquid crystal on TFT(thin-film transistor) parts by selectively removing the counter electrode existing in the parts right above the TFTs. CONSTITUTION:Red, green and blue color filters 3 and light shielding parts 4 are provided on a color film side glass substrate 2 and the transparent counter electrode 5 is constituted on the surface thereof to constitute a coor filter substrate. The TFTs 7 and picture element electrodes 8 are provided on a TFT side glass substrate 9 to constitute a TFT substrate. These two substrates are disposed to face each other and the liquid crystal 6 is inserted between the substrates. The structure 5b in which the counter electrode 5a exists on the picture element electrodes 8 and does not exist on the TFTs 7 by selectively etching away this electrode is adopted. Since the application of the voltage to the liquid crystal 6 on the TFTs 7 is thereby prevented, the concentration of the movable charges, such as alkali ions, contained in the producing members to the TFTs 7 is averted.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix liquid crystal display (LCD), and more particularly to an electrode structure on a color filter side of a liquid crystal having high stability and reliability.

0002

2. Description of the Related Art Conventionally, this type of active matrix LCD has red, green, and blue color filters 3 and a light shielding section 4 provided on a glass substrate 2 on the color filter side, as shown in FIG. It has a structure in which a color filter substrate on which a transparent counter electrode 5 is provided, a TFT substrate on which a TFT 7 and a pixel electrode 8 are provided on a TFT side glass substrate 9 are opposed to each other, and a liquid crystal 6 is sandwiched between them. Here, red, green, and blue color filters 3 are designed to be positioned directly above each pixel electrode 8 with a liquid crystal sandwiched therebetween. TFT7
Alternatively, although not shown in the figure, a light shielding section 4 is located directly above the wiring section and the like. A voltage is applied between the counter electrode 5 and the pixel electrode 8 to align the liquid crystal and perform display.

0003

[Problems to be Solved by the Invention] In the conventional active matrix LCD described above, since the counter electrode 5 covers the entire surface of the liquid crystal 6, voltage is also applied to the TFT 7 or the liquid crystal 6 on the wiring part. . Therefore, if the voltage of the counter electrode is Vc, the gate voltage of TFT is VG, and the drain voltage is VD, then VC -VG, VC -V
A voltage drop caused by the potential difference D2 also occurs in the liquid crystal 6 above the TFT 7, and mobile charges such as alkali ions are accumulated on the surface of the TFT 7, degrading reliability. In a normal n-channel, inverted staggered TFT, since Vc - VG is often positive in terms of timing, the back channel Si is n-inverted, which causes TFT leakage current and leads to defects such as display unevenness and contrast. There are drawbacks.

As a countermeasure against this problem, a silicon nitride film or a silicon oxynitride film is formed as a surface protection film on the back channel side of the conventional TFT 7, so that mobile charges can be directly transferred to the TFT.
It is made so that it does not reach the back channel side of FTSi. However, it cannot be ignored that the mobile charges accumulated at the interface between the liquid crystal and the surface protective film induce charges on the Si back channel side due to the surface protective film capacitance>liquid crystal capacitance. Moreover, in the case of silicon oxynitride, the Beria effect on mobile charges itself is insufficient.

[0005]

[Means for Solving the Problems] The present invention provides an active matrix liquid crystal display device in which a color filter substrate and a thin film transistor substrate are opposed to each other with a liquid crystal interposed therebetween, in which at least the portion of the counter electrode on the color filter side facing the thin film transistor is selected. It is characterized by being completely removed.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings. FIG. 1 is a sectional view of a first embodiment of the present invention, and FIG. 2 is a plan view thereof. A counter electrode 5a is located on the pixel electrode 8 as in the conventional art. On the other hand, the TFT 7 is selectively etched away to form a structure 5b in which no counter electrode is located.

As described above, in this embodiment, since the counter electrode on the TFT is removed, no voltage is applied to the liquid crystal on the TFT. Therefore, it is possible to avoid movable charges such as alkali ions contained in the manufacturing member from concentrating on the TFT. Furthermore, the effect can be further improved by cooperating with the surface protective film coating on the TFT back channel.

FIG. 3 is a plan view of a second embodiment of the invention. In this embodiment, the portion 5c of the counter electrode where the portion directly above the TFT is selectively etched away is the drain wiring 10.
The gate wiring 11 including the TFT peripheral portion is also removed. Therefore, in this embodiment, no voltage is applied to the liquid crystal not only in the TFT portion but also in the TFT peripheral portion, further guaranteeing high reliability.

[0009]

As described above, the present invention eliminates unnecessary voltage from being applied to the liquid crystal above the TFT by selectively removing the counter electrode located directly above the TFT. For this reason, alkali ions such as Na+ or H+ contained in the manufacturing process or manufacturing parts
It is possible to prevent movable charges such as the like from concentrating locally on the TFT section.

Since the area of the portion of the counter electrode that is selectively removed is more than an order of magnitude smaller than the total area, variations in the voltage VC of the counter electrode depending on location due to an increase in resistance can be ignored.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an active matrix LCD according to a first embodiment of the present invention.

FIG. 2 is a plan view of the first embodiment of the invention.

FIG. 3 is a plan view of a second embodiment of the invention.

FIG. 4 is a cross-sectional view of a conventional active matrix LCD.

[Explanation of symbols]

1 Polarizing plate 2 Color filter side glass substrate 3 Color filter 4 Light shielding part 5 of the color filter Counter electrode 5a Counter electrode 5b, 5 with the right upper part of TFT removed
c Counter electrode where the right upper part of TFT is removed 6 Liquid crystal 7 Thin film transistor (TFT) 8 Pixel electrode 9 TFT side glass substrate 10 Drain wiring 11 Gate wiring

Claims (1)

[Claims] 1. In an active matrix liquid crystal display device in which a color filter substrate and a thin film transistor substrate are opposed to each other with a liquid crystal interposed therebetween, at least a portion of the counter electrode on the color filter side facing the thin film transistor is selectively removed. Active matrix liquid crystal display device.