JPH04301624A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To increase a total capacity, to suppress the decrease in the voltage of a liquid crystal due to charges leaking through floating capacity when the external voltage is not applied and to prevent a display irregularity and a flicker from being generated by forming additional capacity in parallel to the liquid crystal. CONSTITUTION:Two-terminal elements 1 and pixel electrodes 2 are arranged in matrix arrays on a transparent insulating substrate 10, scanning lines 9 are arranged in the column direction of the pixel electrodes 2, and a liquid crystal layer 12 is put in a counter transparent electrode 11 formed in the row direction of the pixel electrodes 2 to constitute the liquid crystal display device. A black matrix layer 5 is formed on the additional capacity electrode 13 connected to the pixel electrodes 2 and counter transparent electrode substrate 11, color filter layers 6-8 of red, blue, and green are superposed thereupon, and a counter additional capacity electrode 14 is connected to the counter transparent electrode 3. In this manufacture process, a thin film insulating layer 16 with a high dielectric constant is formed on the counter additional capacity to form an additional capacitance. Namely, the additional capacitance is provided in parallel to the liquid crystal capacity to increase the total capacity.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a two-terminal element type liquid crystal display device (hereinafter referred to as a two-terminal-LCD device) used for a liquid crystal display, etc.
It is abbreviated as. ).

0002

2. Description of the Related Art Currently, image display devices for liquid crystal televisions are broadly classified into simple matrix type and active matrix type.

In the simple matrix method, a plurality of liquid crystal pixels are arranged in a matrix and connected between strip electrode groups (row electrode group and column electrode group) arranged at right angles. During this time, a predetermined voltage is applied by a drive circuit to operate the liquid crystal. This method has the advantage of being able to realize a system at a low cost due to its simple structure, but it cannot be used for displaying images on LCD televisions because crosstalk occurs in each LCD pixel, resulting in low pixel contrast. Ta.

On the other hand, in the active matrix method, a switch is provided for each liquid crystal pixel to maintain the voltage, and even if the liquid crystal display device is time-divisionally driven, the liquid crystal pixel cannot maintain the voltage at the time of selection. Therefore, it is possible to increase the display capacity, and the image quality characteristics such as contrast are good.
It is possible to realize image display on a liquid crystal television. However, the active matrix method has disadvantages in that it has a complicated structure, resulting in poor product yield and high manufacturing costs. For example, in a TFT type switch that uses a thin film field effect transistor as a switch, it is difficult to increase the yield of the product because five or more photomasks are used in the manufacturing process to stack five or more layers of thin films.

[0005] Due to the above-mentioned circumstances, it is desired to realize a liquid crystal display device that has good image quality characteristics such as contrast, has a simple structure, and is low in cost. Element-type liquid crystal display devices are attracting attention.

One pixel of a two-terminal LCD has a pixel electrode and two terminals.
It consists of terminal elements (printed varistors, etc.). Further, colorization is performed by a micro color filter provided for each pixel. That is, as shown in FIG. 5, blue (B), green (G), and red (R) filters are fabricated on each pixel electrode by a dyeing method, a pigment dispersion method, a printing method, or the like. Here, the order of forming each color of R, G, and B is not limited.

In recent years, high-definition liquid crystal display devices with a large amount of image information have been actively developed. As the definition becomes higher, the number of pixels increases, and as a result, the area of each pixel decreases. Therefore, the liquid crystal capacitance decreases and the ability to store charge decreases. Further, as described above, the area of each pixel becomes smaller due to higher definition, but it is difficult to reduce the area occupied by a two-terminal element manufactured by printing or the like to match the reduction in pixel area. FIG. 9 shows an electrical equivalent circuit of one pixel of liquid crystal, two-terminal elements (varistors, etc.), and stray capacitance.

The stray capacitance Cvar between the two-terminal element, the pixel, and the scanning electrode is not negligibly small compared to the pixel capacitance Clc of the liquid crystal. Therefore, a large amount of charge leaks through the stray capacitance, and the charge stored in the liquid crystal cannot be stored until the next charging time. Therefore, it is difficult to display images. Furthermore, even if the image can be displayed, display unevenness and flicker may occur, which poses a problem.

FIGS. 7 and 8 show a general two-terminal LCD. As shown in FIG. 7, a scanning line electrode 9 and a pixel electrode 2 are provided on a lower transparent insulating substrate 10 at a predetermined distance d, and these scanning line electrodes 9 and pixel electrodes 2 are connected to a two-terminal element 1. It is connected with Then, an alignment film 18 is provided on top of these. On the other hand, the upper opposing transparent insulating substrate 11
On the insulating overcoat film 17, a counter transparent electrode 3 is provided in a stripe pattern, and an alignment film 19 is provided thereon. The transparent insulating substrate 10 and the counter transparent insulating substrate 11, which were separately produced in this way, are stacked with their respective alignment films facing each other and the distance D maintained by a spacer. Liquid crystal is injected into the gap to produce a two-terminal LCD. In FIG. 8, the stray capacitance generated between the opposing transparent electrode and the scanning line is shown by Css.

0010

As described above, in the conventional two-terminal LCD structure, it is difficult to achieve high definition due to the charge retention ability of the liquid crystal.

An object of the present invention is to increase the overall capacitance by forming an additional capacitor in parallel with the liquid crystal, thereby suppressing the decrease in voltage of the liquid crystal caused by the charge leaking through the stray capacitance when no voltage is applied, and thereby suppressing display unevenness and flickering. It lies in eliminating it.

0012

[Means for Solving the Problems] The present invention has been made in view of the above problems, and as shown in the electrical equivalent circuit of FIG. 6, an additional capacitor Cs is provided in parallel with the liquid crystal capacitor Clc. That is, in the actual manufacturing process, two-terminal elements and pixel electrodes are arranged in a matrix array on a transparent insulating substrate, scanning lines are arranged in the column direction of the pixel electrodes, and a line between the transparent insulating substrate and the pixel electrodes is arranged. In a liquid crystal display device in which a liquid crystal layer is sandwiched between opposing transparent electrode substrates formed in stripes in the row direction, a black matrix layer is formed on the additional capacitance electrode connected to the pixel electrode and the opposing transparent conductive substrate, and a black matrix layer is formed on the additional capacitance electrode connected to the pixel electrode, and Three layers of red, blue, and green color filter layers are stacked on top of each other, and a counter additional capacitor electrode is connected to the counter transparent electrode.
The above problem has been solved by a liquid crystal display device characterized in that a thin film insulating layer with a high dielectric constant is formed on the opposing additional capacitor to serve as an additional capacitor.

[0013]

[Function] The additional capacitance can be made in the same manufacturing process as the color filter. That is, a black matrix layer is formed on the transparent conductive substrate facing the additional capacitance electrode connected to the pixel electrode, and three color filter layers of red, blue, and green are layered on top of the black matrix layer, and the counter addition capacitance electrode is placed on top of it. An additional capacitor can be produced by connecting to a transparent electrode and forming a thin film insulating layer with a high dielectric constant on the opposing additional capacitor.

[0014]

[Example] [Example 1] Below, Fig. 1, Fig. 2 and Fig. 10
(a) to (f), Fig. 11 (a) to (f), Fig. 12 (a)
An embodiment of the present invention will be described in (f) to (f) along with its manufacturing process. Each pixel has one color, and each pixel forms a red, green, and blue color filter. For example, FIG. 10 shows a pixel in which a blue color filter is formed. Similarly, FIG. 11 shows a pixel in which a green color filter is formed. Similarly, FIG. 12 shows a pixel in which a red color filter is formed. Here, the order of colors is not limited in this patent.

As shown in FIG. 2, a pixel electrode 2, a scanning line electrode 9, a two-terminal element (varistor) 1, and a pixel electrode 2
An additional capacitance electrode 13 connected to is formed on a transparent insulating substrate 10. On the other hand, as shown in FIGS. 2 and 10, a black matrix layer 5 made of pigment is formed on the opposing transparent insulating substrate 11 other than the pixel electrodes 2 (see FIG. 10(a)). Next, first, blue color filter layers 4 and 6 are formed on the pixel electrode portion and the additional capacitance electrode portion containing that color (see FIG. 10(b)). Next, green color filter layers 4 and 7 are formed on the pixel electrode section and the additional capacitance electrode section where that color is included (see Fig. 11).
c) see).

Further, red color filter layers 4 and 8 are formed on the pixel electrode section and the additional capacitance electrode section containing the red color (FIG. 1).
2(d)). Then, the pixel part is a single color filter layer, but the additional capacitance electrode part has a black matrix layer and three layers of blue, green, and red color filters, forming a pattern with a total film thickness of four layers. Formation (Figure 1
0, see FIGS. 11 and 12(d)). On top of that, I
TO film is formed by sputtering with good coverage (Fig. 10, Fig. 11,
(see FIG. 12(e)), and the opposing transparent electrode 3 and the opposing additional capacitor electrode 14 are electrically connected.

In addition, it has a high dielectric constant (relative permittivity=about 25)
A high dielectric constant capacitance layer 16 made of tantalum pentoxide of
, see FIGS. 11 and 12(f)). Here, in order to avoid an increase in the wiring resistance of the counter electrode, the connection metal counter electrode 1
5 (see FIG. 1) is formed on a black matrix, and is not formed on a color filter layer.

Thereafter, a TN type liquid crystal was injected between the transparent insulating substrate 10 and the opposing transparent insulating substrate 11 (see FIG. 2) to form a liquid crystal layer 12, thereby producing a two-terminal LCD. The capacitance is inversely proportional to the electrode spacing d, and proportional to the area and dielectric constant. Therefore, by reducing the thickness d of the dielectric layer and using a dielectric material with a high dielectric constant, a high additional capacitance can be formed even with a small area.

Two-terminal LCD obtained as above
Even if the capacitance of the pixel is small and the ability to hold charges is at risk, by providing an additional capacitor in parallel with the liquid crystal, the ability to hold charges can be improved and it is possible to suppress a decrease in pixel voltage. Furthermore, since the high dielectric constant capacitor layer 16 can be thinned at the same time as the color filter manufacturing process, it is possible to reduce the complexity of the process associated with manufacturing the additional capacitor.

[Embodiment 2] An embodiment of the present invention is shown in FIGS. 3 and 4. When the size occupied by the two-terminal element is smaller than the pixel area, the additional capacitance can be provided at a position aligned with the two-terminal element as shown in FIG. All manufacturing steps are the same as in Example 1 above.

[0021]

As explained above, according to the present invention, the ratio of stray capacitance to pixel capacitance can be reduced and the charge retention ability can be improved, so that it is possible to suppress a decrease in pixel voltage. As a result, display unevenness and flicker can be reduced.

[0022]

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the configuration of one pixel of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a portion indicated by AA' in the diagram of FIG. 1;

FIG. 3 is a plan view showing the configuration of one pixel of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view of the portion indicated by AA' in FIG. 3 of the second embodiment.

FIG. 5 is an explanatory diagram showing the arrangement of red, blue, and green micro color filters.

FIG. 6 is an electrical equivalent circuit diagram of one pixel of the two-terminal LCD of the present invention.

FIG. 7 is a plan view showing the configuration of one pixel of a conventional two-terminal LCD.

8 is a sectional view of a portion indicated by AA' in the diagram of FIG. 7. FIG.

FIG. 9 is an electrical equivalent circuit diagram of one pixel of a conventional two-terminal LCD.

FIG. 10 is an explanatory diagram of one pixel provided with a blue color filter in the manufacturing process of the present invention.

FIG. 11 is an explanatory diagram of one pixel provided with a green color filter in the manufacturing process of the present invention.

FIG. 12 is an explanatory diagram of one pixel provided with a red color filter in the manufacturing process of the present invention.

[Explanation of symbols]

1 2-terminal element (varistor, etc.) 2 Pixel electrode 3 Opposing transparent electrode 4 Color filter layer (pixel electrode part) 5 Black matrix layer 6 Color filter layer (additional capacitance electrode part) 7 Color filter layer (additional capacitance electrode part) 8 Color filter layer (additional capacitance electrode part) 9 Scanning line electrode 10 Transparent insulating substrate 11 Opposed transparent insulating substrate 12 Liquid crystal layer 13 Additional capacitance electrode 14 Opposed additional capacitance electrode 15 Metal counter electrode for connection 16 High dielectric constant capacitance layer 17 Insulation overcoat film 18 alignment film 19 alignment film

Claims (2)

[Claims] 1. Two-terminal elements and pixel electrodes are arranged in a matrix array on a transparent insulating substrate, scanning lines are arranged in the column direction of the pixel electrodes, and scanning lines are arranged in the row direction of the transparent insulating substrate and the pixel electrodes. In a liquid crystal display device in which a liquid crystal layer is sandwiched between opposing transparent electrode substrates formed on stripes, a thin film insulation with a high dielectric constant is provided between an additional capacitor electrode connected to the pixel electrode and a counter additional capacitor electrode connected to the opposite transparent electrode. A liquid crystal display device characterized by forming an additional capacitor made of a film. 2. In claim 1, a black matrix layer is formed on the facing transparent conductive substrate, and three color filter layers of red, blue, and green are layered on top of the black matrix layer, and a facing additional capacitance electrode is placed on top of the black matrix layer as the facing transparent electrode. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is formed by connecting.