JPS6326631A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To eliminate the cause of a gap defective by adhering the peripheral parts of both main opposite surfaces of 1st and 2nd substrates, holding liquid crystal in the gap formed between both substrates, and forming dummy wiring irrelevant to electric connections penetrating the adhesion part on the 1st substrate. CONSTITUTION:The substrate 1 needs to be sealed with the 2nd substrate which is arranged opposite it by the adhesion part 7 and a specific number of dummy wires 8 which do not function electrically are installed at the adhesion part and its internal area where no connection wire is present so as to uniform the distribution of the surface recesses and projections. Namely, the dummy wiring 8 is only formed simultaneously a bus and connection wiring and also arranged at the corner parts of the 1st substrate 1 which are a part of a display substrate; and neither of wires 4 and 6 for connections is formed at this part. Further, the dummy wiring 8 may be formed among wires 4 which have wide intervals, i.e., rough distribution density. The wiring 6 is the same.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a display device (liquid crystal display device).

A conventional liquid crystal display device generally has one electrode portion formed on one main surface of a first substrate, and the other electrode formed on one main surface of a second substrate.
The main surfaces of both substrates are made to face each other, and the peripheral portions of the substrates are bonded together, and the liquid crystal is held in a space formed by both substrates and the bonding portion. In order to maintain this space (gap) at a predetermined design value, glass fibers or spherical substances of a specific diameter are used as spacers and dispersed between both substrates.

Problems to be Solved by the Invention In recent years, as the performance of liquid crystal display devices has improved, control of the thickness of the liquid crystal layer has become an extremely important issue. That is, even when using a conventional twisted nematic (TN) type liquid crystal, a multi-gap type full color liquid crystal display device has been put into practical use in order to improve display quality. In this case, the liquid crystal layer thickness becomes an important parameter that determines display quality. Also, in the supertwist structure, controlling the optical path length in the liquid crystal is equally important. The thickness of this liquid crystal layer (hereinafter referred to as the gap) must be controlled uniformly over the entire display area of the display device.
If gap unevenness exists even partially, the display becomes uneven and the display quality deteriorates. Therefore, maintaining a uniform gap over the entire display area is an extremely important issue industrially.

If the two substrates have completely flat surfaces, the dispersed spacer material of a specific diameter will receive an equal force from both substrates, and the gap will be defined by the diameter of the material. However, the main surface of the substrate for a liquid crystal display device is not strictly flat because display electrodes and other structures are formed therein.

In particular, the surface of a substrate on which active elements such as thin film transistors (TPTs) and diodes are formed usually has display irregularities of approximately several thousand amps to 1 μm. In such a case, the gap may be filled only by a specific diameter of the material (
, is determined by the height and specific diameter of the convex portion on the substrate surface.

On the other hand, the unevenness on the substrate surface is not necessarily uniformly distributed over the entire area of the substrate. In particular, in the area where the bidirectional surfaces of both substrates are bonded, there is usually an area where wiring for supplying power to the display element is formed, but this wiring is not necessarily evenly distributed, and there are certain areas where the wiring is formed. In some areas, there may be dense wiring, and in other areas, there may be no wiring at all. In such a case, the gap becomes large near an area where wiring is dense, and the gap becomes small near an area where there is no wiring.

Therefore, it has often appeared that gap non-uniformity occurs particularly in the peripheral area of the display device.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides that when using a substrate with unevenness formed on one main surface, the unevenness should be formed almost uniformly in the region related to gap formation. (In particular, the power supply line that crosses the adhesive part is unnecessary only in the design of the power supply function, and even in areas where it is not originally necessary to install it, for example, create an uneven shape using dummy wiring made of the same material as the power supply line. Prevent uneven gaps from occurring.

Since the working uneven shape is uniformly formed on the main surface, it is possible to uniformly form the gap defined by the height of the convex portion and the spacer diameter over the entire area of the display substrate.

Embodiment FIG. 1 shows a partially enlarged view of a liquid crystal display device according to an embodiment of the present invention. In this embodiment, for example, amorphous silicon (
a-3i) Thin film transistor (TPT) and display electrode
It has an image display section 2 formed with 40 rows x 372 columns, and each TP
T (not shown) is 240 gate busbars 2A, 372
It is formed at the intersection of the source bus lines 2B of the book. Each gate busbar 2A is connected to a connection terminal portion 3 with a gate drive circuit wired outside the substrate via a connection wiring portion (4) to the gate busbar. Similarly, the signal bus (source bus) 2B is connected to a connection terminal portion 5 with a signal voltage supply circuit installed outside the board via a connection wiring portion 6 to the signal bus.

On the other hand, the substrate 1 needs to be sealed to a second substrate (not shown in FIG. 1) disposed opposite to the substrate 1 with the adhesive part 7 (the area between the dashed-dotted lines in FIG. 1). A predetermined number of dummy wires 8, which do not function electrically at all, are installed inside the bonding portion and the adhesive portion in areas where no connection wires are present, in order to equalize the distribution of surface irregularities.

That is, the dummy wiring 8 only needs to be formed at the same time as the bus bar and the connection wiring.
．． 6 is not formed.

Note that the dummy wiring 8 may be formed between the wirings 4 in a portion where the distance between the wirings 4 is wide, that is, the distribution density is sparse. This also applies to the wiring 6.

FIG. 2(a) shows a connection wiring section in the liquid crystal display device of the present invention, and FIG. 2(b) shows a part other than the connection wiring section, that is, a part of the upper right corner in FIG. 10 is a second transparent substrate, 1
1 is a liquid crystal, 12 is a peripheral adhesive, and the TFT 1 color filter and the like are omitted. That is, according to the present invention, it is possible to maintain the gaps 11 and 12 approximately equal.

In a liquid crystal display device formed by combining the first substrate 1 on which the dummy wiring 8 is installed and the second substrate (color filter substrate in the case of color display), for example, gaps 5 to 6 are formed.
In the case of μ, it was possible to maintain a uniform gap (with a variation of ±0.1 μ11) up to a part of the upper right corner of the display section 2 in FIG.

However, from the substrate shown in Fig. 1, the first
In a liquid crystal display device in which the above substrate and the second substrate were combined, the gap at the upper right corner was clearly reduced by about 0.8 μm, degrading the display quality. The degree of this gap reduction was comparable to the degree of unevenness of the connection wiring portion 4.6. In other words, 0.8 μm thick AI wiring was used in 4.6, but
The gap was partially reduced by about 0.8 μm, which significantly deteriorated the display quality.

Effects of the Invention As described above, including the above embodiments, according to the present invention, it is possible to maintain a uniform thickness of the liquid crystal layer over the entire display area of a liquid crystal display device. Particularly in twisted nematic type and super twisted type liquid crystal display devices, particularly ferroelectric liquid crystal display devices, in which the wavelength of light in the liquid crystal is important, non-uniformity of the gap has a serious adverse effect on display quality. For example, the super twist type requires a gap accuracy of less than a predetermined value of ±0.2 μm, and only display devices with a gap difference greater than this must be considered defective. Furthermore, in a multi-gap type full color display device using twisted nematics, although the tolerance for gap errors is somewhat larger, it is of course desirable to control the gap error to around a predetermined value. A display device having a local gap reduction region of 0.8 μm, which occurs when the dummy wiring is removed, is inevitably a defective product.

As described above, according to the present invention, it is possible to eliminate the causes of gap defects with an extremely simple structure, and it is possible to produce liquid crystal display devices with extremely good display quality with a stable yield. It becomes possible.

Further, in the embodiment, the dummy wiring (a) is formed in a linear shape, but it is possible to provide the same function by using a dotted shape or other shape.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged plan view of one principal surface of one substrate of a liquid crystal display device according to an embodiment of the present invention, and FIG. 2 is a partially sectional view of the same device. 1.10...Substrate, 2...Image display section, 3,5...
- Connection terminal part, 4, 6... Connection wiring part, 7... Adhesive part, 8... Dummy wiring. Name of agent: Patent attorney Toshio Nakao and one other person Figure 1

Claims (2)

[Claims] (1) A display electrode and a bus bar for supplying voltage to the display electrode are formed on one main surface of the first substrate, and an electrode facing the display electrode is formed on one main surface of the second substrate. and
Both main surfaces of the first and second substrates are made to face each other and peripheral portions of the two main surfaces are bonded, and a gap is provided between the two substrates, and the liquid crystal is held in this gap, and the first A liquid crystal display device, characterized in that, at least in a bonded portion on a substrate, a dummy wiring unrelated to the electrical connection passing through the bonded portion is formed. (2) The liquid crystal display device according to claim 1, wherein dummy wiring is formed at the corners of the first and second substrates.