JP2667586B2 - Active matrix driven liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly to an active matrix liquid crystal display using thin film transistors (TFTs).

[0002]

2. Description of the Related Art Recent active matrix drive type liquid crystal displays have made remarkable progress and are being actively applied to laptop personal computers and the like due to features such as high image quality and high definition. The active matrix drive type liquid crystal display includes an active matrix substrate and a counter electrode substrate, and a TFT is provided on the active matrix substrate.
A driving element array such as a thin film transistor (thin film transistor) and a counter electrode are formed on the counter electrode substrate over the entire display region.

FIG. 5 is a plan view of a conventional active matrix substrate, and FIG. 6 is a sectional view of a part thereof (AA 'in FIG. 5). 5 and 6, 1 is a glass substrate, 3 is a data line, 4 is a gate bus, 5 is a TFT, 6 is a pixel electrode, and 7 is a pixel electrode.
Is passivation, and 10 is an alignment film. FIG. 7 is a plan view of a conventional counter electrode substrate, and FIG. 8 is a partial cross-sectional view (AA 'of FIG. 7). In FIG. 7, a figure surrounded by a line is an opening of the black mask 8. In FIG. 8, reference numeral 2 denotes a glass substrate, a black mask 8 made of a metal thin film such as chromium (Cr) is formed on a part of the surface, and ITO (Indi) is formed on the entire display region.
um Tin Oxide) and an alignment film 10 are formed.

An active matrix drive type liquid crystal display is formed by bonding the two substrates and injecting a liquid crystal between the two substrates. FIG. 9 is a plan view of a conventional active matrix drive type liquid crystal display, and FIG. 10 is a cross-sectional view of a part thereof (AA ′ in FIG. 9). As shown in FIGS. 9 and 10, the data lines 3 on the active matrix substrate, the wiring region of the gate bus 4, and the TFT 5 region are shielded from light by the black mask 8 on the counter electrode substrate.

There are two purposes for providing the black mask 8. One is to shield the TFT channel region from light and suppress the photoelectric effect due to incident light from the counter substrate side. And the other is the reference (1) A.LIEN "IDRC EU
RODISPLAY'90 DIGEST P248-251 ", (2) T. ONOZAWA
"JJAP 1990 Vol.29 No.10 P1853-1855", (3)
Eiichi Takahashi et al. “16th LCD Panel Meeting Material P212-21
3 "and (4) a region in which liquid crystal molecules operate due to an electric field between the data line 3, the gate bus 4, and the counter electrode 9 (see FIG. 9). And shaded portions in FIG. 10). For example, TN (twisted nematic)
In the case of the method, since the light transmittance in this area cannot be controlled,
If this area is not shielded from light by a black mask, display quality such as contrast will deteriorate.

Here, the point that the liquid crystal molecules operate due to the electric field between the data line 3, the gate bus 4, and the counter electrode 9 will be described. FIG. 11 is a distribution diagram of lines of electric force between a data line, a pixel electrode, and a counter electrode in a conventional active matrix drive type liquid crystal display. As shown, the data line 3 to the counter electrode 9 and the pixel electrode 6
The lines of electric force are distributed. In particular, since the distance between the data line 3 and the counter electrode 9 is short, the electric field therebetween is strong, and the horizontal component of the electric field affects the liquid crystal molecules. Leakage occurred, and a disclination line due to reverse tilt was generated on the pixel electrode 6. Then, in References (1) and (2), the electric field distribution is obtained by simulation to find the position where the disclination occurs. Reference (3) requires an experiment to determine that the tilt angle is related to this phenomenon.

[0007]

However, these documents do not specify a specific countermeasure, and the countermeasure described in Reference (4) has a drawback that the clear viewing direction changes. . Further, when the viewing angle is large (when the liquid crystal display is viewed obliquely), the black mask 8 is provided to overlap the pixel electrode 6 to some extent in order to achieve the above object. According to the references (1) and (2), this overlap amount needs to be at least about 20 microns. However, as the definition of the liquid crystal display increases, the aperture ratio of the black mask 8 decreases. Therefore, there is a problem in that the smaller the overlap amount is, the more desirable it is.

Further, a reverse tilt disclination line generated by an electric field distribution between the data line 3, the gate bus 4, the pixel electrode 6 and the counter electrode 9 is shown in FIG.
As shown in (1), since the light is generated by entering into the pixel region at the corner of the pixel electrode, it reaches the black mask opening beyond the overlap amount, and the display quality is degraded. If these areas are shielded from light by a black mask, the effect of disclination is removed, but there is a problem that the display luminance further decreases due to a further decrease in the aperture ratio.

An object of the present invention is to provide an active matrix drive type liquid crystal display in which the aperture ratio of a black mask is increased without solving the above-mentioned conventional problems and without impairing the high display quality of the active matrix drive type liquid crystal display. Aim.

[0010]

In order to solve the above problems, the present invention provides an active matrix comprising an active matrix substrate, a counter electrode substrate, and a twisted nematic liquid crystal disposed between the two substrates. In a drive-type liquid crystal display, a counter electrode provided on a counter electrode substrate is an aggregate of stripe electrodes having substantially the same width and facing a pixel electrode provided on an active matrix substrate. An aggregate electrically connected to each other outside, and no counter electrode is disposed in a counter region on a counter electrode substrate facing a data line provided on an active matrix substrate, and a black pigment is dispersed in at least the counter region. A black mask formed of the photosensitive resin described above is provided.

[0011]

According to the present invention, since the active matrix drive type liquid crystal display is constructed as described above, the electric field intensity is reduced in the region beside the data line, and unnecessary movement of the liquid crystal molecules beside the data line is reduced. . This prevents light leakage and disclination lines in the pixel electrodes.

Further, according to the present invention, a black mask formed of a photosensitive resin in which a black pigment is dispersed suppresses unnecessary movement of liquid crystal molecules beside data lines and prevents light leakage.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a plan view of an active matrix drive type liquid crystal display according to an embodiment of the present invention,
FIG. 2 is a sectional view taken along the line AA '. The features of the present invention reside in the shape of the counter electrode 9 and the material of the black mask 8 on the counter electrode substrate.

That is, the counter electrode 9 (hatched portion) is an aggregate of stripe electrodes which are parallel to the data lines 3 and face the pixel electrodes 6 and have substantially the same width. These stripe electrodes are all electrically connected outside the display area. The counter electrode 9 was formed by a known photolithographic etching technique. The black mask 8 was formed using a photosensitive resin (manufactured by Fuji Hunt) in which a black pigment was dispersed.

Then, a TN (twisted nematic) mode NB (normally black) mode liquid crystal display was formed using this counter electrode substrate and the same active matrix substrate as the conventional one. The cell interval is 5 μm, the thickness of the data line 3 is 1 μm, the distance between the data line 3 and the pixel electrode 6 is 10 μm, and the distance between the gate bus 4 and the pixel electrode 6 is 10 μm.
μm, and the amount of overlap between the pixel electrode 6 and the black mask 8 was 5 μm.

FIG. 3 is a distribution diagram of electric lines of force between data lines, pixel electrodes, and counter electrodes in an active matrix drive type liquid crystal display according to an embodiment of the present invention. As shown in the drawing, in the present embodiment, the black mask 8 is formed of resin (insulator), and since there is no counter electrode in the counter region on the counter electrode substrate facing the data line, the data line In the region next to No. 3, the electric field intensity was reduced, and the influence on the liquid crystal molecules was reduced as compared with the conventional case.

FIG. 4 is a characteristic diagram of light leakage measured in the liquid crystal displays of the active matrix driving type according to the embodiment of the present invention and the conventional example. As shown in the figure, when the effective voltage of the data bus increases and exceeds 60% (corresponding to the saturation voltage), the transmittance (light leakage) sharply increases in the prior art. Has hardly changed.

Also, in the embodiment of the present invention, no disclination line due to the reverse state was generated in the pixel area. The embodiment of the present invention was more effective as the number of TFTs connected to one data line turned on increased. Furthermore, the pixel electrode 6 of the black mask 8
Good display quality and viewing angle characteristics were obtained even when the amount of overlap with 0 was set to 0.

It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

In the embodiment of the present invention, the case of monochrome display is described. However, the same effect is obtained when a color filter is provided on the counter electrode substrate 2 to perform color display.

[0021]

As described above in detail, according to the present invention, an active matrix substrate, a counter electrode substrate,
In an active matrix drive type liquid crystal display including a twisted nematic type liquid crystal arranged between the both substrates, a counter electrode arranged on a counter electrode substrate is opposed to a pixel electrode arranged on the active matrix substrate. An aggregate of stripe electrodes having substantially the same width, and an aggregate in which each stripe electrode is electrically connected to each other outside the display area, and a counter electrode on a counter electrode substrate facing a data line disposed on an active matrix substrate. Since the counter electrode is not disposed in the region and a black mask formed of a photosensitive resin in which a black pigment is dispersed is disposed at least in the counter region, the electric field intensity in the region beside the data line is reduced. Since unnecessary movement of liquid crystal molecules is suppressed, light leakage occurs and a disclination line occurs in the pixel electrode. No longer.

Further, since the black mask is formed of an insulating material to suppress unnecessary movement of liquid crystal molecules beside the data lines, the black mask opening is made larger than before and the amount of overlap with the pixel electrode is reduced. Even then, it is possible to obtain good viewing angle characteristics.

[Brief description of the drawings]

FIG. 1 is a plan view of an active matrix driving type liquid crystal display according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of an active matrix drive type liquid crystal display according to an embodiment of the present invention.

FIG. 3 is a distribution diagram of lines of electric force between data lines, pixel electrodes, and counter electrodes in an active matrix driving type liquid crystal display according to an embodiment of the present invention.

FIG. 4 is a characteristic diagram of light leakage measured in an active matrix drive type liquid crystal display according to an embodiment of the present invention and a conventional example.

FIG. 5 is a plan view of a conventional active matrix substrate.

FIG. 6 is a partial cross-sectional view of a conventional active matrix substrate.

FIG. 7 is a plan view of a conventional counter electrode substrate.

FIG. 8 is a partial cross-sectional view of a conventional counter electrode substrate.

FIG. 9 is a plan view of a conventional active matrix drive type liquid crystal display.

FIG. 10 is a partial sectional view of a conventional active matrix drive type liquid crystal display.

FIG. 11 is a distribution diagram of lines of electric force between data lines, pixel electrodes, and counter electrodes in a conventional active matrix drive type liquid crystal display.

FIG. 12 is an explanatory diagram of a reverse tilt decrement line in a conventional active matrix drive type liquid crystal display.

[Explanation of symbols]

 1, 2 glass substrate 3 data line 4 gate bus 5 thin film transistor 6 pixel electrode 7 passivation 8 black mask 9 counter electrode 10 alignment film 11 disclination line

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tsutomu Nomoto 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (56) References JP-A-64-25133 (JP, A) JP-A Showa 60-262137 (JP, A) Japanese Patent Laid-Open No. 3-4214 (JP, A) Actually Opening 2-136233 (JP, U)

Claims (1)

(57) [Claims] 1. An active matrix substrate, a counter electrode substrate, and a twisted nematic disposed between the substrates.
In the active matrix drive type liquid crystal display that includes a mold LCD, active matrix and opposing electrode disposed opposite electrode on a substrate
And pixel electrodes and counter disposed Rikusu substrate and about the same
An assembly of stripe electrodes of one width and each stripe electrode
And electrically connecting the assembly to one another in the display area outside the, A
Active disposed in a matrix on a substrate data lines and the counter
The counter electrode is not arranged in the opposing region on the opposing electrode substrate and
A photosensitive resin in which a black pigment is dispersed in at least the opposed region.
An active matrix drive type liquid crystal display, comprising a black mask formed of a fat .