LIQUID CRYSTAL DISPLAY DEVICE

Abstract: Color filters are provided on electrodes (a-g). The color filters and the electrodes (a-g) are constituted by disposing a single strip electrode and filter in parallel and in the same direction. A glare protection filter (12) is so provided as to be proximate to the front surface of the color filter. The glare protection filter (12) includes minute louvers (14) thereinto in parallel to each other. The direction of the louvers (14) of the filter (12) is perpendicular to that of the electrodes (a-g).

Description: FIELD OF THE INVENTION The present invention relates to a liquid crystal display device which is capable of variegating its display figures as referred to in the generic part of the main claim. BACKGROUND OF THE INVENTION There is a growing demand for electronic meters that utilize a fluorescent display tube, a light emitting diode or a liquid crystal rather than conventional mechanical meters. For instance, a liquid crystal display device is disclosed in JP-A-59 94 739. In the prior art, electrodes and color filters provided on each electrode are formed by arranging a series of many strip electrodes and filters in parallel and in the same direction for displaying a dotted image, and a polarizing film plate is provided on the front surface of the filters for preventing chromatic aberration of the filters. When a variable color type liquid crystal display device is used for displaying a numeral or a letter of alphabet, electrodes and color filters are constituted by disposing a single strip electrode and filter in parallel and in the same direction. In a car, these electronic display meters, however, have a defect, namely the light reflects on the windshield thereby forming an image on the line of driver's vision. This is commonly referred to as an "interference imaging phenomenon" which interferes with the driver's view of the road. As a countermeasure against the "interference imaging phenomenon" there has been proposed a method of providing a glare protection filter on the surface of a meter, which has already been disclosed in FIG.4 of page 79 of NIKKEI MECHANICAL published on May 6, 1985. However, when a glare protection is applied to a conventional variable color type liquid crystal display device used for indicating a numeral, interference streaks are produced in the direction in which the louvers of the filter are formed, thereby interfering with the driver's view of the road. SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device that prevents an "interference imaging phenomenon" and further a decline of visual recognizability, which decline is caused by the aforementioned interference streaks. The foregoing object of the present invention is achieved in accordance with the features of the independent claim. Dependent claims are directed on preferred embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing a fundamental structure of a liquid crystal display device according to the present invention. Figs. 2(a) to 2(c) inclusive are views each showing arrangements of color filters and strip electrodes which are formed on a liquid crystal display element of the liquid crystal display device shown in Fig. 1. Fig. 3 shows a detailed configuration containing one electrode and one filter of the liquid crystal display device according to the present invention. Fig. 4 shows a construction of a glare protection filter applied to the present invention and a function thereof. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Fig. 1, there are shown a liquid crystal display element 10 which is an essential feature of a liquid crystal display device according to the present invention and a glare protection filter 12 which is to be disposed on the front surface thereof. In the Figure only the numeral 8 appears on the surface of the liquid crystal display element 10 for simplifying the description. It is commonly known that seven display segments a to g inclusive are provided on the surface of the liquid crystal display element 10 for the purpose of indicating numerals, letters of the alphabet or the like. The numerals and letters of the alphabet are variegated for display, this requiring such a step that the respective display segments are constituted by a plurality of minutely stripped color filters which are respectively disposed thereon. These color filters are capable of making display colors variable, the arrangement being such that each of the color filters is tinted in, for example, red, green and blue per row, and the forementioned numerals or letters of the alphabet are exhibited in desired colors according to combinations of pre-determined electric potentials. As regards disposition of the respective stripped electrodes, two methods can be considered. Namely, these stripped electrodes are, as shown in Fig. 2A, arranged in the longitudinal direction of the segments; and the other method is such that the respective segments are, as illustrated in Figs. 2B and 2C, uniformly disposed in a lateral direction or a perpendicular direction regardless of the longitudinal direction thereof. With an experiment, the structure shown in Fig. 2A has, however, proved to be defective. To be specific, if the stripped electrodes are incorporated in the transparent type liquid crystal display device and are then combined with a glare protection filter 12 inclusive of louvers 14 disposed in the lateral direction as shown in Fig. 1, interference streaks are produced between the louvers 14 and the segments a , d and g thereby to deteriorate its visual recognizability. On the basis of such a fact, the plurality of stripped electrodes which form the respective display segments a to g inclusive are set in a single direction, whereas the glare protection filters which are to be disposed thereon are provided in such a manner that the louvers thereof are so aligned as to be perpendicular to the direction in which to dispose the stripped electrodes. To wit, it can be seen in Fig. 1 that the vertically stripped segments identical with those shown in Fig. 2C are to be combined with the glare protection filter 12 including the laterally stripped louvers 14 which are perpendicular thereto. However, if the display segments are constituted by the laterally stripped electrodes as shown in Fig. 2B, it will be obvious that a glare protection filter having perpendicularly stripped louvers is inevitably utilized, this being the reverse of the former. In the second place, a structure in which to apply the present invention to a transparent liquid crystal display device will hereinafter be described with reference to Fig. 3. As depicted in Fig. 3, a light-diffusion transparent plate 20 is provided on the rear surface of the liquid crystal display element 10 equipped with the display segments respectively consisting of a plurality of laterally or perpendicularly stripped electrodes; and further a fluorescent lamp 30 is provided on the rear surface of the light-diffusion transparent plate 20. The light emitted from the fluorescent lamp 30 reflects on a reflection plate 40 which is so provided as to surround the hemispherical surface of the lamp 30. A part of the reflected light is directly incident upon the light-diffusion transparent plate 20 where the light is diffused such as to entirely and evenly disperse behind the liquid crystal display element 10. By virtue of the thus scattered light, the numerals or the like formed on the liquid crystal display plate 10 are selectively displayed. In such a case, it is feasible to exhibit them in desired colors by making use of color combinations of color filters. The glare protection filter 12 is so provided as to be proximate to the front surface of the color liquid crystal display element 10. Fig. 4 depicts a function of this glare protection filter 12 with respect to the display element. The glare protection filter 12 is enclosed in a transparent box which is surrounded by six transparent plates. The glare protection filter 12 includes a plurality of minute louvers 14 incorporated thereinto in parallel to each other. The width of each electrode is narrower than the opening between the louvers. The viewing angle of the display device is adjusted within a range by adjusting the angular position of the louvers 14. With this arrangement, provided that the glare protection filter 12 is applied to, for instance, a vehicle display device or the like which is to be installed on the dashboard of an automobile, it is possible to prevent undesirable image formation in the driver's line of vision, viz., the so-called interference imaging phenomenon referable to the fact that the display light reflects on the windshield of the automobile. In the case of equipping an automobile or the like with the aforementioned filter, it is desirable that the glare protection filter is disposed such as to turn the louvers thereof to the lateral direction, this arrangement hindering the interference imaging phenomenon most effectively. As described above, the stripped electrodes which constitute the display segments of the liquid crystal display element 10 are arranged to be perpendicular to the louvers 14 of the glare protection filter 12, this making it possible to prevent the creation of interference streaks which may be attributable to the parallel disposition of the louvers 14.

Claims: A liquid crystal display device comprising a liquid crystal display element (10) including display segments (a-g) formed thereon which are constituted by a plurality of transparent minute strip electrodes and minute colour filters, said strip electrodes and said colour filters being disposed in parallel and extending in the same direction, and further comprising a glare protection filter (12) including minute louvers (14) parallel to each other and being proximate to the front surface of said liquid crystal display element (10), characterized in that said glare protection filter (12) is disposed in such a manner that the direction of said louvers (14) is perpendicular to the direction of said strip electrodes. A liquid crystal display device as set forth in claim 1, wherein, in display position, said louvers (14) extend in a horizontal direction, whereas said strip electrodes are aligned in a vertical direction. A liquid crystal display device as set forth in claims 1 or 2, wherein said louvers (14) are enclosed in a transparent box which consists of six transparent plates. A liquid crystal display device as set forth in any of claims 1 to 3, wherein means are provided for adjusting the angular position of said louvers (14). A liquid crystal display device as set forth in claim 1, wherein the width of each electrode is narrower than the opening between the louvers (14).

Inventors: HIROSHI, ITO, MASARU, KUGO
Applicants: HITACHI AUTOMOTIVE ENGINEERING CO., LTD., HITACHI, LTD.
Application year: 1986
Main classification: G02F1
IPC codes: G02F1, G09F9