JPS63266427A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To improve the quality of a display part having the same color to that of a background, without an irregularity in color due to a faulty gap between each a substrate by providing with a dummy electrode which does not impress signal voltage, in the titled element, thereby making a display part and a display electrode forming part. in the same state. CONSTITUTION:The striped display electrode 13 is composed from a transparent electrically conductive material such as ITO, etc., and is formed on an upper substrate 11, and the sealing part 17 is formed on an outer circumference of said substrate 11. The dummy electrode 25 is provided between the electrode 13 and the part 17, and the part between the display part 19 and the part 17 makes in the same state to that of the display part 19 by the dummy electrode 25. In the case that the dummy electrode 25 and the display electrode are formed at the same time, said electrodes can be made in the same material and film thickness, but, the signal voltage does not impresses to the dummy electrode. In the lower substrate 21, the dummy electrode 27 is formed between the display electrode 23 and the sealing part 17 in the same manner as the upper substrate 11. Thus, the irregularity in color due to the faulty gap between the substrates is lessened, thereby improved the quality of the display part.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dot matrix type liquid crystal display device using a plastic film substrate, and particularly to a liquid crystal display device with a large area and high duty driving.

In a conventional liquid crystal display device using a plastic film as a substrate, in a large-area, high-duty panel, if the resistance of the ITO electrode is high, the drive signal will be attenuated, causing color unevenness in contrast.

However, in the case of a plastic substrate, there are restrictions on the substrate heating temperature when forming an ITO film, and the resistance of ITO formed on a plastic substrate by a low-temperature sputtering method is about 200 Ω/mouth at a film thickness of 200 mm.

On the other hand, high-duty panels (e.g. display area 240
x 150mm, 640 x 400dots),
Since an ITO electrode with a resistance of 60 Ω/Ω or less is required, I
The thickness of TO is required to be 1000 Å or more.

However, when the film thickness of the ITO electrode increases, color unevenness occurs between the display electrode forming area and the non-forming area, especially between the display electrode and the sealing area, which is caused by 5TN (Super Twisted
This is noticeable in nematic type liquid crystal display elements.

An STN type liquid crystal display element is a pair of substrates having electrodes, which are sandwiched at a predetermined interval (liquid crystal layer thickness) so that liquid crystal molecules having positive dielectric anisotropy are aligned approximately horizontally with respect to the substrates when no voltage is applied. , the liquid crystal molecules are configured to have a twisted structure in the thickness direction of the liquid crystal layer between the open substrates,
The twist angle is larger than a normal TN element, for example 180
degree or more, preferably 180 to 250 degrees. This element is used with polarizers placed on both sides. Since STN type liquid crystal display elements perform display using coloring due to birefringence, control of the cell gap is particularly important.

FIG. 3 is a plan view showing a configuration example of a conventional STN type liquid crystal display element, and FIG. 4 is an enlarged view of section A thereof. An upper substrate 11 and a lower substrate 21 made of plastic film are separated and faced to each other with their outer peripheries sealed by a seal portion 15, and a liquid crystal is sealed in this gap. Furthermore, bead-shaped gap agents are sprinkled between the substrates in order to maintain a uniform cell gap. Upper substrate 11. Display electrodes 12.23 made of ITO are formed on the lower substrate 21, and the area where the display electrodes 13.23 of both substrates intersect is the display section 19.
becomes. Note that the display electrodes 13 and 23 are shown only on both sides thereof, and the middle portion is omitted.

Both substrates 11.21 are made of polyethylene terephthalate (
PET) film was used to form an ITO electrode with a film thickness of 1000 mm, display area 240 x 150 mm, 640 mm
When a 200@twist STN type liquid crystal display element with X 400 dots is manufactured, color unevenness occurs between the display portion and the seal portion indicated by 29 (X X X . . . ) in the figure.

this is ■The difference in level in that area.

■Difference in surface tension of liquid crystal between ITO and PET surfaces.

Possible reasons include concentration of gap agents, and it is thought that this may occur singly or as a synergistic effect.

SUMMARY OF THE INVENTION The present invention aims to prevent color unevenness and improve contrast in a plastic film substrate liquid crystal display element.

1. The liquid crystal display element of the present invention has display electrodes formed on the opposing surfaces of two opposing plastic film substrates. A liquid crystal display element having a dot matrix electrode structure in which liquid crystal is sealed is characterized in that a dummy electrode to which no signal voltage is applied is formed on the surface facing the substrate of the liquid crystal sealed part around five display electrodes.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is a plan view showing an upper substrate 11 used in the present invention. On the upper substrate 11, striped display electrodes 13 made of a transparent conductive material such as ITO are formed.

Further, a seal portion 17 is formed on the outer periphery of the upper substrate 11 . A dummy electrode 25 is formed between the display electrode 13 and the seal portion 17. The dummy electrode 25 is used to maintain the same state between the display section 19 and between the display section 19 and the seal section 15, and no signal voltage is applied thereto. Since the dummy electrode 25 is formed at the same time as the first display electrode 13, it can be made of the same material and have the same thickness as the first display electrode 13. It is desirable that the dummy electrode 25 not be formed on the seal portion 15. This is because the sealant generally used for liquid crystal display elements is an epoxy adhesive, and the adhesive force when used to bond ITO films together is significantly inferior to the adhesive force between PET films.

FIG. 2 is a plan view showing the lower substrate 21, in which a surface electrode 23 is formed similarly to the upper substrate, and a seal portion 15 is formed on the outer periphery. The dummy electrode 27 is the display electrode 2
3 and the seal portion 17.

In FIG. 1 and FIG. 2, the seal portion 15 is shown on both the upper substrate 11 and the lower substrate 21 to indicate the formation position of the dummy electrode, but in reality, the seal portion 15 is shown on the upper substrate 11 and the lower substrate 21, respectively. Display electrodes 13.23 and dummy electrodes 25.27 are formed, adhesive is printed on either side to form a seal portion 17, and a gap agent is spread between the open substrates so that the striped display electrodes are perpendicular to each other. Both boards 11
．． 21 to create an empty cell, and attach the liquid crystal inlet 9
Liquid crystal is injected and sealed. Display electrode 1 on upper substrate 11
3 and the display electrode 23 of the lower substrate 21 becomes the display section 19 of the liquid crystal display element. Since the dummy electrodes 25 and 27 are formed between the display part 19 and the seal part 15, the gap situation in this part is the same as that of the display part, and the same color as the background color of the display part is obtained, which significantly improves the display quality. Improved.

In the above description, a case has been described in which a dummy electrode is provided between the seal portion and the display portion, but the dummy electrode may be provided in any other portion as long as it is not electrically connected to the display electrode.

According to the present invention, in a dot matrix type liquid crystal display device using a plastic film substrate, by providing a dummy electrode to which no signal voltage is applied, it is possible to create a state similar to that of the display electrode forming part. , color unevenness due to poor gap between substrates is eliminated, the same color as the background color of one display area is obtained, and display quality is significantly improved.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an upper substrate used in an embodiment of the present invention, and FIG. 2 is a plan view showing a lower substrate. FIG. 3 is a plan view showing a conventional STN type liquid crystal display element;
FIG. 4 is an enlarged view of section A. 11... Upper substrate 13... Display electrode 15...
-Seal part 17...Liquid crystal injection port 19...Display part 21...Lower substrate 23...Display electrode
25.27...Dummy electrode 29...Uneven color Figure 1, Figure 2t! 1

Claims (1)

[Claims] 1. A dot matrix electrode structure type in which display electrodes are formed on the opposing surfaces of two opposing plastic film substrates, the substrates are spaced apart and facing each other, the outer periphery is sealed, and liquid crystal is sealed in the gap between the substrates. 1. A liquid crystal display element comprising: a dummy electrode to which no signal voltage is applied; a dummy electrode to which no signal voltage is applied is formed on a surface of a liquid crystal enclosure surrounding a display electrode facing a substrate.