JP2669289B2 - Active matrix type liquid crystal device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, an active matrix
Liquid crystal device . More specifically, the present invention relates to an active matrix type liquid crystal device in which display-like noise generated due to driving of a liquid crystal which must not respond on a signal electrode is hardly seen. As is well known, most liquid crystal devices are called a current effect (for example, a dynamic scattering effect) or a field effect (for example, a twisted nematic effect, hereinafter TN) between a pair of electrodes facing each other. ) Is displayed. Therefore, the manufacturer of the liquid crystal device may design the shape of the portion where the pair of opposing electrodes overlap to a desired display shape. However, static drive or multiplex drive with a large duty ratio (that is, low time division) causes no problem, but the duty ratio is small or one unit (a pixel) of the display portion is small and crowded. In some multiplex drive or active matrix drive liquid crystal devices , signal electrodes that are not necessarily pixel components may overlap with the counter electrode. At this time, the liquid crystal existing between the signal electrode and the counter electrode is driven by the above-described current effect or electric field effect, and turns on. This is a noise on the display because the lighting is not intended by the designer. [0004] In particular, this drawback is a serious problem in active matrices, which have recently attracted attention due to their good display quality. This is because the pixels of the active matrix are driven substantially statically, so that it is not necessary to form the counter electrode 1 in a shape matching the pixel electrode 2 as shown in FIG. 1, and the entire surface of the solid electrode is low in cost and high in yield. The structure is possible, but this is because the overlapping portion 4 with the signal electrode 3 is generated as described above. Here, if this liquid crystal device is a normally white type TN (it turns black when a voltage is applied and turns on),
The overlapping portion 4 is turned on according to the signal flowing through the signal electrode 3, and a blackish display is seen. In FIG. 1, 5 is a transparent substrate and 6 is a liquid crystal layer. It will be described in detail how the noise on the display looks on the screen. For example, as shown in FIG. 2A, a normally white TN liquid crystal of an active dot matrix is used.
Assume that the device projects a black image 7 in the center of the screen. At this time, the pixels of the portion 8 are the same as the pixels of the portion 9 and display white. Since the signal shown in FIG. 2B is flowing through the signal electrode 10 in the portion 9 of FIG. 9, the signal electrode in this portion looks white. However, as shown in FIG. 2C, the signal 15 for displaying the black image 7 is flowing through the signal electrode 11 in the portion 8 so that the signal electrode 11 is lightened in black depending on the effective voltage of this signal. . The signal electrode is generally much thinner than the pixel electrode, but since the number is large, the entire screen looks light black as shown by 8 in FIG. 2A when the part is lit. This is visible as noise on the display, as the 8 part must look white like the 9 part. [0008] If the liquid crystal device is a normally black type, the portion that must be black appears gray, contrary to the above. In addition, TN using a color polarizing plate, color G
If it is H (guest host), its display color is not light but black. SUMMARY OF THE INVENTION An object of the present invention is to make it difficult to see a display that causes noise on the signal electrodes as described above. In the active matrix type liquid crystal device of the present invention, liquid crystal is sealed between a pair of substrates, and a plurality of pixel electrodes and a plurality of signals are provided on the first substrate. In a normally white type active matrix type liquid crystal device in which an electrode, a switching element connected to the signal electrode and the pixel electrode are formed, and a counter electrode is formed on the second substrate facing each other, It is characterized in that an opaque black-looking metal layer is formed on the signal electrode. Next, the present invention will be described specifically with reference to examples. All the embodiments will be described with an active matrix normally white TN liquid crystal device . Reference Example 1 FIG. 3 shows a first reference example. In this embodiment , an opaque colored film 12 is formed on the signal electrode 3 by applying a dye or a pigment by vapor deposition, sputtering, electrodeposition, printing, dyeing, or the like. Since the color of the film 12 is a normally white type, the color at the time of lighting is set to be black, for black-and-white display, or red for mono-color display, for example, white-red display. With such a structure, since the signal electrode 3 is always colored, it is the same as a constantly lit state.
No matter how the signal flows and the liquid crystal 4 on the signal electrode 3 responds, it becomes difficult to see it. In the case of a normally black type liquid crystal device , if the film 12 is set to a color when it is not lit, it is always colored as in the normally white type, and the signal flows to the signal electrode 3. However, it does not become whitish and the noise becomes less visible. Reference Example 2 FIG. 4 shows a second reference example. In this reference example, the signal electrode 1
4 itself is a metal thin film. Metal types are Al and C
Various types such as r, Cr + Au, Ni, and Ta can be considered. Instead of the metal thin film, a thin film of amorphous silicon or polysilicon which is a material of an active matrix thin film transistor (TFT) may be used. Means for applying a thin film of metal or silicon include vapor deposition, sputtering, plating and the like. Also in this reference example, the thin film of metal or silicon forming the signal electrode itself is opaque and looks dark, so that in the case of a black-and-white liquid crystal device, the signal electrode 3 is always colored. This is the same as the lighting state, and the noise on the display becomes inconspicuous regardless of the response state of the liquid crystal 4 on the signal electrode 3. Embodiment 1 FIG. 5 shows an embodiment of the present invention. This embodiment is structurally the same as the first embodiment, but uses the same metal thin film as the second embodiment as the film 12. As a result, as in the case of the first reference example, the effect is that the signal electrode 3 always appears black and is colored, so that the noise on the display does not occur regardless of the response state of the liquid crystal 4 on the signal electrode 3. Becomes inconspicuous. When a metal is used as in this embodiment, an effect more than initially expected is obtained. That is, if it is a metal thin film, the resistance value of the signal electrode 3 becomes small and the signal electrode 3 can be made thin. If narrow the signal electrode 3, issue
The noise on the display becomes less noticeable and the LCD
The aperture ratio of the device can be improved. Reference Example 3 FIG. 6 is a third reference example . The film 12 is formed on a portion of the counter electrode 1 facing the signal electrode 3. The material of the film 12 is a dye, a pigment, a metal, silicon, or the like. The effect is the same as that of the first embodiment and the first and second embodiments. Ma
Further, when a metal is used, there is also an effect that the sheet resistance of the counter electrode 1 becomes small. Reference Example 4 FIG. 7B is a fourth reference example . This reference example is a case of a liquid crystal device that performs full-color display by using dot-shaped or stripe-shaped color filters. As shown in FIG. 7A, the normal color filter has a colored layer 1 only on each pixel.
Form 3 This is applied to the signal electrode 3 as shown in FIG.
If the adjacent colored layers 13 are made to overlap each other at a portion opposed to, this portion is not completely black, but becomes a considerably darker and less saturated color. Even with this structure, the problematic display noise becomes less visible. According to this reference example , in the case of a liquid crystal device having a color filter, only the size of the colored layer 13 needs to be changed, so that the object can be achieved without increasing the number of steps, and the cost does not increase. is there. The three types of hatching of the colored layer 13 indicate the difference between red, green and blue. Reference Example-Others Further, although not shown in the drawings, some other reference examples will be described. The positions of the film 12 and the signal electrode 3 in FIGS. 3 and FIG.
The positions of the film 12 and the counter electrode 1 in FIG.
An example is conceivable in which the counter electrode 1 is formed on the counter electrode 1, or the colored layer 13 and the counter electrode 1 in FIG. . In addition, an example in which a metal, silicon, a dye, or a pigment is applied to a portion of the upper and lower transparent substrates 5 facing the signal electrode on the outside by vapor deposition, sputtering, printing, or the like can be considered. Although the embodiment has been described with respect to the normally white type TN liquid crystal device of the active dot matrix,
The present invention can be similarly applied to a liquid crystal device of a simple matrix type, a normally black type, and a GH or dynamic scattering mode. As described above, in the active matrix type liquid crystal device of the present invention, liquid crystal is sealed between a pair of substrates, and a plurality of pixel electrodes and a plurality of pixel electrodes are provided on the first substrate. A normally white active matrix liquid crystal device in which a signal electrode, a switching element connected to the signal electrode and the pixel electrode are formed, and a counter electrode is formed on a second substrate facing the signal electrode. By forming an opaque black-looking metal layer on the signal electrode, the liquid crystal responds to the signal flowing through the signal electrode in a normally white type active matrix liquid crystal device.
In a state where a display other than the intended display occurs, it can be made inconspicuous. In addition, since an opaque black-looking metal layer is formed on the signal electrode, the resistance of the signal electrode can be reduced and the signal electrode can be made thin, so that the response of the liquid crystal in the signal electrode portion can be reduced. And the aperture ratio of the liquid crystal device can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing a conventional liquid crystal device. FIG. 2 is a diagram showing how a display noise appears in a conventional liquid crystal device. FIG. 3 is a cross-sectional view showing a first reference example. FIG. 4 is a sectional view showing a second reference example. FIG. 5 is a sectional view showing an embodiment of the present invention. FIG. 6 is a sectional view showing a third reference example. FIG. 7 is a sectional view showing a fourth reference example. [Explanation of symbols] 1 counter electrode 2 pixel electrode 3 signal electrode 4 liquid crystal layer 5 at the overlapping portion of the signal electrode and the counter electrode 5 transparent electrode 6 liquid crystal layer 7 black image 8 display noise screen 9 normal screen 10, 11 signal Electrode 12 Opaque film 13 Colored layer of color filter 14 Opaque signal electrode 15 Signal waveform showing a black image Signal waveform showing a portion of 16

Claims (1)

(57) [Claims] A liquid crystal is sealed between a pair of substrates, and a plurality of pixel electrodes, a plurality of signal electrodes, and a switching element connected to the signal electrodes and the pixel electrodes are formed on the first substrate. A counter electrode was formed on the second substrate
A normally white type active matrix type liquid crystal device, wherein an opaque metal layer that appears black is formed on the signal electrode.