JPS60192920A - Display device - Google Patents

Abstract

PURPOSE:To realize high-grade gradation display by using an active matrix display device using a two-terminal switching element that enables gradation display by lighting areas. CONSTITUTION:Data lines are classified for each area of sub-picture elements, and data lines D11, D12 are connected to sub-picture element A1, data lines D21, D22 are connected to sub-picture elements A2, data lines D41, 42 are connected to sub-picture elements A4, and data lines D81, D82 are connected to sub- picture elements A8. Instead of arranging sub-picture elements parallelly, they may be arranged in four quadrants, making connection to data lines one by one, and collecting every two scanning lines together. This gives better positional mixability of gradation. By selecting the optimum data signal amplitude for every area of sub-picture element, i.e. for every picture element capacity, effective voltage applied to each sub-picture element can be made uniform and large among sub-picture elements when lighting and non-lighting.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to the improvement of an active matrix display device using a two-terminal type switching element, and more specifically, the present invention relates to an improvement of an active matrix display device using a two-terminal type switching element. The present invention relates to the configuration of an active matrix display device using type switching elements.

[Background of the invention]

In recent years, so-called active matrix display devices in which switching elements are directly connected to unit pixels have been actively developed. This method is described, for example, in the following paper (B. J. Lecbner et al.
Proc, IEEE, 59.1.566-1579 (1
971) '1, and a three-terminal switching element such as a thin film transistor (TPT) or a two-terminal switching element such as a diode or a nonlinear resistance element (NLR) is used. In particular, the two-terminal type is easier to manufacture than the three-terminal type, and an active matrix that combines a two-terminal switching element and a liquid crystal display element is the most promising as a high-density flat display.

Regarding liquid crystal display elements, effective voltage gradation and area gradation have been proposed as gradation display using liquid crystal display elements. Effective voltage gradation is a method of changing brightness by modulating the effective voltage applied to a unit pixel, and is commonly used because it is easy to configure. In the 1- or intermediate-gradation area, the brightness changes depending on the viewing direction, and there is a drawback that the gradation inversion occurs depending on the angle. Therefore, there are problems with active matrices that combine two-terminal switching elements and liquid crystal display elements.

Next, talking about the area gradation method, the area gradation method is detailed in the previous application (Japanese Patent Application No. 165422-1981).
This is a method of displaying gradations by digitally turning on and off a plurality of sub-pixels with different areas and combining them, making it possible to display gradations with a wide viewing angle and high contrast. Therefore, although a display using an active matrix area modulation method using two-terminal switching elements is desired, the reality is that it has not been put to practical use.

[Conventional technology and problems]

Figures 1 to 3 show general diagrams of display devices;
To explain the prior art with reference to FIG. 3, FIG. 1 is a plan view of an active matrix display device in which a nonlinear element is used as a two-terminal switching element. S
, -S2+... are scanning lines, D, +D2+...
... is a data line, NL (i-j) is a nonlinear element, C
(i-j) is a unit pixel formed by a display element such as a liquid crystal.

FIG. 2 (al is a series connection circuit diagram of the unit pixel C in FIG. 1 and the nonlinear element NL, and FIG. 2 (bl is an equivalent circuit diagram of FIG. 2 (a). CNL is the nonlinear element capacitance, RNL is the nonlinear resistance of the nonlinear element, and CLc is the pixel capacitance.

RLc is the leak resistance of the pixel. The aforementioned Lechne
The paper by R et al. deals with the ideal conditions in which CNL is 0-R+ and c is infinite (but in reality this does not happen and causes a problem in driving. In particular, the capacitance ratio CNL/CLc is important and the conventional In the driving method of
t, A6 IEEE ED, 28736-739). However, in the previous application (Japanese Patent Application No. 58-147047), it was shown that it is possible to achieve CNL/CLC=2 by optimizing the drive. The basis of this optimal driving method is to set the data voltage amplitude () to the threshold voltage Vtb of the nonlinear element (
CNL/Ct, c+1)・Vo.

Therefore, if the pixel capacitances CLc are distributed within the display device, uniform display becomes difficult.

FIG. 3 is a plan view of 4 unit pixels in 2 rows and 2 columns when the area coverage modulation method is used. The unit pixel is composed of four sub-pixels A]=A2=A4 and A8 having different areas.

The area ratio of each sub-pixel is set to 1:2:4:8, and 16 levels of gradation from 0 to 15 are controlled by 4-bit information by combinations of lighting and non-lighting of the 4 sub-pixels. On the other hand, the pixel capacitance is distributed depending on the area. For example, in the example shown in FIG. 3, the capacitance ratio between subpixels is widely distributed as 1:2:4:8. In the example of FIG. 3, the data line DI.

D3 has sub-pixels A1 and A2 - data lines D2 and D4VC
Since sub-pixels A4 and A8 are connected, it is not possible to drive all pixels with the optimum data amplitude.

[Purpose of the invention]

An object of the present invention is to solve the drawbacks of the prior art and provide an active matrix display device using a two-terminal switching element that enables gray scale display depending on the lighting area, thereby achieving high quality gray scale display. It is something.

[Embodiments of the invention]

FIG. 4 is a plan view of four unit pixels in two rows and two columns according to an embodiment of the present invention. A feature of the present invention is that data lines are classified according to the area of subpixels. For example, data lines Dll, D1
2 is for subpixel A1, and data lines D21 and D22 are for subpixel A.
2, data lines D41 and D42 are connected to sub-pixel A4, and data lines D81-D82 are connected to sub-pixel A8.

FIG. 5 is a plan view of another embodiment θ) of 2 rows, 2 columns, and 4 unit pixels of the present invention. The difference from the embodiment shown in FIG. 4 is that, whereas in FIG. 4, the sub-pixels were arranged in parallel, they are arranged in four quadrants, and the connection to the data line is made one by one, and the scanning The lines are at the points where every two lines are grouped together. Compared to the parallel arrangement, the positional mixing of gradations is better. Furthermore, in this embodiment, a nonlinear element NL, which is a two-terminal switching element, is connected to a data line, and a data signal is supplied to the subpixel via the switching element. In this way, it is free to place the switching element between the sub-pixel and the scanning line or between the sub-pixel and the data line.

By using independent data lines according to the area of the sub-pixel as in the embodiment shown in FIG. 4 or FIG.

It is possible to select the optimum data signal amplitude for each pixel area, that is, for each pixel capacitance CLC. For example, if all switching element capacitances CNL are equal, subpixels A1, A2, A1A
3 each capacitance as CLCI, 2CLC1-data line D11,
A drive waveform diagram of data signals D21 and D41-D81 is shown. Sl and S2 are examples of scanning transmission. By driving in this manner, the effective voltage applied to each sub-pixel can be made uniform and large between each sub-pixel in both lighting and non-lighting.

FIG. 7 is an isometric circuit of a unit pixel portion of an active matrix using a rectifying element instead of a nonlinear element as a two-terminal switching element in the embodiments of FIGS. 4 and 5. FIG. 62 and 63 are rectifying elements, 64 is a pixel, S is a scanning electrode + DA + D8 is a data electrode. Even in this configuration, the ratio between the rectifying element capacitances CNL and CLc is important as in the nonlinear element, and the ratios are different. Therefore, this embodiment is extremely effective for driving with the same voltage.

As the display element used in the present invention, not only liquid crystal but also electrochromic, electroluminescent, and other elements may be used.

Further, in the embodiment described above, all independent data lines were used for each subpixel area, but the data lines may be grouped together for each subpixel having a similar area, and data signals with different data widths may be applied to each group.

〔Effect of the invention〕

As described above, the present invention enables area gradation display using an active matrix using a two-terminal switching element that is cheaper than a three-terminal type and can be arranged in a large area and at high density. Particularly effective.

[Brief explanation of the drawing]

Fig. 1 is a plan view of an active matrix display device using a nonlinear element as a two-terminal switching element, Fig. 2(a) is a circuit diagram of the series connection of the unit pixel and nonlinear element in Fig. ) is an equivalent circuit diagram of Fig. 2(a), Fig. 3 is a plan view of 4 unit pixels in 2 rows and 2 columns by the area coverage method, and Fig. 4 is an equivalent circuit diagram of Fig. 2(a).
The figure is a plan view of 2 rows, 2 columns, and 4 unit pixels in one embodiment of the present invention, FIG. 5 is a plan view of 2 rows, 2 columns, and 4 unit pixels in another embodiment of the present invention, and FIG. 4 and 5, and FIG. 7 is a unit pixel section when a rectifying element is used instead of the nonlinear element as the two-terminal switching element in the embodiment shown in FIGS. 4 and 5. FIG. NL...Nonlinear element, 62.63...Rectifying element, A1, A2. A4. A8... Subpixel. CNL...1 two-terminal switching element capacitance, CLC
...Pixel capacitance - D i ], DI 2. D21 D22, D41, D
42, D81. D82...Data line. Figure 1 Figure 2 Figure 3 Figure 4 Figure 7

Claims (4)

[Claims] (1) In a display device that has a plurality of unit pixels each consisting of a plurality of subpixels that are driven by a two-terminal switching element and have different areas, and that displays gradations by a combination of lit subpixels, the subpixel is a display device characterized in that data signals are supplied from a plurality of data lines classified according to area. (2) The display device according to claim 1, wherein the maximum amplitude of the data signal applied to the data lines differs between each data line depending on the area of the sub-pixel. (3) The display device according to claim 1, wherein the data line is directly connected to each subpixel. (4) The display device according to claim 1, wherein the data line is connected to each subpixel via a two-terminal switching element.