JPH02306221A - Active matlix type electrooptical device - Google Patents

Abstract

PURPOSE:To improve the in-plane uniformity of an action characteristic by changing the area of a switching element according to a distance from a driving circuit. CONSTITUTION:The area of the switching element part, in which a picture element electrode 5 overlaps with a row electrode 4, is made comparatively small at a point C close to a driving circuit connecting part 3 and made succes sively large as it goes away from points B and A and the connecting part 3. As it goes away from the connecting part 3, a voltage given to the switching element by the line resistances of the row electrode and column electrode is made relatively low, and a current to flow in the element is increased to the contrary by the degree to increase the area of the switching element. Both effects offset each other, a charge quantity to flow into a picture element is made approximately fixed, and respective picture elements on a substrate show approximately fixed action characteristics to the voltage impressed from the connecting part 3. Thus, the in-surface uniformity of the action characteristics can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active matrix electro-optical device using a liquid crystal and a switching element, which is used in large image displays, computer terminals, optical shutters, and the like.

[1 Summary of the Invention] The present invention provides an active matrix electro-optical device in which 1M switching elements are formed on a substrate, by changing the area of the switching elements depending on the distance from the drive circuit, thereby improving the operational characteristics. This is to improve internal uniformity.

[Conventional technology]

Liquid crystal display devices, which first appeared as displays in clocks and calculators, have come to be used as electro-optic bags in a wide range of fields, including applications other than displays, such as computer terminals and optical shutters, as image quality has improved and they have become larger. It's here. In particular, active matrix electro-optical devices, in which switching elements are built into each pixel on the substrate surface, offer excellent display' (, Y
Future development is expected due to its nature. The active matrix type electro-optical device is MIM (Metal-1ns
ulator-Metal) and MS I (Me L
two-terminal type and three-terminal type TPT (Th t n-F i 1m-
Transistors).

A plan view of an MSI panel, which is a typical two-terminal active matrix type optical device, is shown in Figure 2 (al), an enlarged plan view is shown in Figure 2 (bl), and a cross section of the D-D' portion of (bl) is shown in Figure 2 (al). An enlarged view is shown in Figure 2 (C1). Figure 2 (at, (
bl.

[In el, 1 is the upper substrate, 2 is the lower substrate, 3 is the drive circuit connection part, 4 is the row electrode, 5 is the pixel electrode, 6 is the nonlinear film,
7 is a column electrode, and 8 is a liquid crystal. However, for convenience of explanation, bl shows only the state of the lower substrate surface, and the upper substrate is omitted. It has a structure in which an electrically nonlinear electrode 1126 such as SiNx is sandwiched between the row electrode 4 and the pixel electrode 5, and the entire structure constitutes a switching element. If the number of row electrodes 4 is m and the number of column electrodes 7 is n, an active matrix electro-optical device with m×n pixels is obtained. An outline of the manufacturing process of the electro-optical device shown in FIG. 2 will be described below.

(1) An ITO film is formed on a glass substrate that will become the lower substrate 2 by sputtering or vapor deposition, and patterned to form the pixel electrode 5.

(2) Furthermore, a SiNx film and a metal layer that will become the row electrodes 4 are formed thereon and patterned to form switching elements.

(3) I on the other glass substrate that will become the upper substrate 1
TO is formed into a film and patterned into stripes to form column electrodes 7.

(4) Both glass substrates are bonded together so that the row electrodes 4 and column electrodes 7 are perpendicular to each other, and the pixel electrodes 5 and column electrodes 7 are opposite to each other.

f51 Liquid crystal 8 is sealed between both substrates.

(61 Connect the drive circuit to the drive circuit connection section 3.

Specifically, the connection of the drive circuit is to extend the row electrode 4 and the column electrode 7 to the drive circuit connection part 3 shown in FIG.
ed-Circuit) COF (Cip-On-FPC)
) Connect using methods such as COG (Cip-On-Grass).

Next, the operation will be explained. The nonlinear film 6 has a property that its resistance is high at low voltages, but its resistance decreases as the voltage increases. Therefore, when an ON voltage is applied to the liquid crystal 8, the nonlinear film 6 becomes conductive and charges can be written into the pixel electrode 5, but when an OFF voltage is applied, the nonlinear element 6 becomes almost an insulator and no charge is stored. retains the electric charge. By controlling the voltage applied to the liquid crystal 8 using a switching element, good contrast and viewing angle characteristics can be obtained in 7x7x driving as well as in static driving.

[Problem to be solved by the invention]

However, the conventional active matrix electro-optical device has a problem in that its operating characteristics vary depending on the location on the substrate. FIG. 3 shows an example of the operating characteristics of a conventional active matrix electro-optical device. In Figure 3, the vertical axis is the transmittance of the electro-optical device, the horizontal axis is the applied voltage,
◎ indicates the operating characteristics corresponding to each point on the substrate shown in FIG. 2 (al).

As can be seen from Fig. 3, the transmittance at the point near the drive circuit connection part 3 changes at a relatively low voltage, whereas
◎ and the voltage that changes as it moves away from the connection part 3 becomes higher. This is mainly due to the resistance of the row electrodes 4 and column electrodes 7, and as the distance from the circuit connection section 3 increases, the voltage actually applied to the element decreases, and as a result, the amount of charge accumulated in the pixel also decreases. It's for a reason. The higher the resistance of the electrode, the stronger the above tendency.

If the purpose of this electro-optical device is to simply switch between an ON state and an OFF state, there will be no problem, and it is sufficient to apply a voltage [F] in the ON state and a voltage 2 in the OFF state. However, in applications such as display devices, it is often necessary to represent intermediate transmittance states. In this case, the above-mentioned difference in operating characteristics depending on location becomes a big problem. For example, when a voltage ◎ is applied, a difference in transmittance of △R occurs between the points and the points ■, resulting in apparent display unevenness.

As a countermeasure to this problem, measures have been taken to reduce the abrasive resistance by replacing the electrode material 4 with one that has as low a resistance as possible, or by increasing the film thickness of each electrode, but as the electro-optical device becomes larger, none of these methods will work. There is a limit.

The present invention has been made to solve the above problems.

[Means to solve the problem]

The present invention provides an active matrix electro-optical device in which a plurality of switching elements are formed on a substrate.
By changing the area of the switching element depending on the distance from the drive circuit connection part, the operating characteristics can be improved. is made uniform at each point indoors.

[Effect]

As the area of the switching element increases, the cross-sectional area for current also increases, and therefore the amount of charge flowing through the element also increases. By taking advantage of this phenomenon and increasing the area of the switching element as it moves away from the circuit connection, it is possible to cancel out the effect of the applied voltage decreasing due to the resistance of the electrodes and keep the current r:Ir11 flowing into each pixel constant. . That is, the operating characteristics of each pixel can be made substantially the same at each point within the substrate.

〔Example〕

The present invention will be described in detail below according to Examples.

A plan view of the active matrix electro-optical device of the present invention is shown in Fig. 1 (al), and an enlarged view of the pixel in the
1, an enlarged view of the pixels in the 0th part is shown in FIG. 1 (C1), and an enlarged view of the pixels in the 0th part is shown in FIG. 1Fdl.

ibl, (C1, (d+, 1 is the upper substrate, 2 is the lower substrate, 3 is the drive circuit connection part, 4 is the row electrode, and 5 is the pixel electrode. The pixel electrode formed on the surface of the lower substrate 2 SiNx is sandwiched between 5 and row electrodes 4 to form a switching element.Column electrodes (omitted in FIG. 1) are formed in stripes on the upper substrate 1 in a direction perpendicular to the row electrodes 4. A liquid crystal is sealed in between.As described above, the basic structure and manufacturing process are exactly the same as the electro-optical device shown in FIG. 2 described above.

The active matrix electro-optical device shown in FIG. 1 differs from conventional devices in that the area of the overlapping portion of the row electrode 4 and pixel electrode 5, that is, the area of the switching element portion, differs depending on the location. . At point ◎, which is close to the drive circuit connection part 3, the area of the switching element part is relatively small, whereas at points ■ and ■, the area of the switching element part increases continuously as you move away from the drive circuit connection part 3. . As explained in the operation section, the voltage applied to the switching element due to the line resistance of the row and column electrodes becomes relatively lower as the distance from the drive circuit connection part 3 increases, but this is due to the increase in the area of the switching element. Conversely, the current flowing through the element increases by 21iL. As both of these effects cancel each other out, the amount of charge flowing into the pixel through the switching element becomes almost constant.
Each pixel on the substrate surface exhibits substantially constant operating characteristics with respect to the voltage applied from the drive circuit connection portion.

The rate of change in the area of the switching element can be determined by calculation from the resistances (a) of the row electrodes 4 and column electrodes 7, but in reality the applied voltage varies depending on the ratio of capacitance between the switching element and the liquid crystal layer. It is necessary to perform some preliminary experiments before designing the element area.The active matrix electro-optical device shown in Fig. 1 was fabricated and the relationship between voltage and transmittance as shown in Fig. 3 was obtained. When measured at each point on g4H, it was found that there was almost no variation in characteristics depending on location) and good in-plane uniformity was observed. Further, even if the area of the switching elements is changed for each area or for each plurality of switching elements depending on the distance from the drive circuit connection part, a display state better than that of the conventional one can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain an active matrix electro-optical device that has extremely good in-plane uniformity without variations in operating characteristics with respect to applied voltage even when it is large-sized.

[Brief explanation of the drawing]

FIG. 1 +al is a plan view of the active matrix electro-optical device of the present invention, FIG. Figure (d) is an enlarged view of the pixel section of the C part of ta+, Figure 2 (tal) is a plan view of a conventional active matrix type electro-optic device, Figure 2 (bl is a plan view of a conventional active matrix type electro-optic FIG. 2(C) is an enlarged plan view of the device; FIG. 2(C) is an enlarged cross-sectional view of the DD' portion of (bl); FIG.・Upper board 2...Lower board 3...Drive circuit connection part 4...Row electrode 5...Pixel?i1 pole
6... Nonlinear film 7... Column electrode 8...
・Liquid crystal and above Applicant Seiko Electronics Industries Co., Ltd. Agent Patent Attorney Takayuki Hayashi Top view of Kanmei Sukemoto's active matrix 7-type electromagnetic device Figure 1 (
'd) IQ) exA sound p's a basic diagram IQ
I no B Iku no Gasaku Maki Oguchi M I 121(b)
[l m(C)(0) c
Figure 1 (d) Half-view of the president's office with conventional active matrix type housing. Hayamen Sojinzu No. 21Z (b)

Claims (4)

[Claims] (1) In an active matrix electro-optical device in which a liquid crystal is sealed between two substrates and a plurality of switching elements are formed on the inner surface of at least one of the substrates, the area of the switching elements is different at each location on the substrate. An active matrix electro-optical device characterized by: (2) The area of the switching element closest to the drive circuit is the smallest, the area of the switching element gradually increases as the distance from the drive circuit increases, and the area of the switching element farthest from the drive circuit is the largest. An active matrix electro-optical device according to claim 1, configured as follows. (3) The switching element is SiN_x, SiO_x
2. The active matrix electro-optical device according to claim 1, which is a nonlinear element constructed using a film having electrically nonlinear characteristics, such as SiC_x. (4) An active matrix electro-optical device in which a plurality of switching elements are formed, in which the area of the switching elements differs from region to region depending on the distance from the drive circuit connection portion.