The present invention relates to a color liquid-crystal display unit having color filters disposed in a liquid-crystal element.
FIGS. 1A and 1B show an example of a conventional color liquid-crystal display unit of the same general type to which the invention pertains, of which FIG. 1A is plan view showing a main portion of the display unit, FIG. 1B is a sectional view taken along a line A-A' in FIG. 1A, and FIG. 1C is a sectional view taken along a line B-B' in FIG. 1A. In these drawings, a liquid-crystal display element 9 is provided in which a plurality of belt-like scanning electrodes 3 and a plurality of belt-like signal electrodes 4, each made of a transparent conductive film, are arranged on respective opposite surfaces of an upper substrate 1 and a lower substrate 2, each made of a light-transmissible glass plate, such that the scanning electrodes 2 and the signal electrodes intersect perpendicularly to each other. Rubbing-treated liquid-crystal orientation films 5 are formed on the surfaces of the scanning electrodes 3 and the signal electrodes 4, respectively. Tri-color filters 6R, 6G, and 6B, for example, of red, green, and blue colors are formed on the signal electrodes 4 succeedingly at a fixed repetition interval. The upper and lower substrates 1 and 2 are separated by a predetermined gap and are sealed at the their peripheral portions by a sealing material 7 including spacers to thereby form an enclosure in which a TN (twisted nematic) liquid crystal 8 is enclosed. Further, a pair of upper and lower polarization plates 10 and 11 with their polarizing axes or light-absorbing axes arranged parallel to each other are adhesively attached to the upper and lower substrates 1 and 2 at their outer surfaces. A color liquid-crystal display unit is thereby formed.
In the thus-arranged color liquid-crystal display unit, when, for example, red color is to be displayed, a predetermined voltage is applied across the signal electrode provided with the red filter thereon and the opposing signal electrode to thereby change the optical property of the TN liquid crystal 8 to allow the light incident on a liquid-crystal portion corresponding to the red filter 6R to pass so that a pattern of red can be seen from the front side of the upper substrate 1. A green display pattern and a blue display pattern can be similarly produced. White display can be effected by applying a predetermined voltage simultaneously across the signal electrodes and the scanning electrodes corresponding to the red filter 6R, the green filter 6G, and the blue filter 6B, respectively. Thus, combinations of color filters of various colors enables a variety of color displays.
In the thus-arranged color liquid-crystal display unit, however, the color filters 6R, 6G, and 6B form patterns elongated in one direction, as shown in FIG. 1A, and hence there has been a problem in that since a color picture displayed on a display screen is composed of a longitudinally elongated dot arrangement, the resolution and clarity of the picture are often insufficient and a desired color mixing effect cannot be obtained.
In order to solve such a problem, for example, in the case where four-color display of red, green, yellow, and black is carried out through additive mixture of color stimuli by use of two color filters 6R and 6G of red and green as shown in FIG. 2, there has been proposed a color liquid-crystal display unit in which the ratio of the areas of the electrode patterns of adjacent signal electrodes 4 are made different from each other. In such an arrangement, because the red and green filter 6R and 6G differ from each other in area ratio, the displayed color picture does not have the longitudinally elongated dot arrangement, and the unit size of one color in the two-color display is substantially the same as that of the other color, resulting in a balanced display and a desired color mixing effect. On the other hand, however, there has been a problem in that as the number of the signal electrodes 4 is increased, the number of electrode lead-out terminals is increased and the interval between adjacent terminals must be reduced. Thus, electrical connection with a driving circuit substrate becomes difficult, resulting in a lowering of the reliability of the device.