Color Display Device

Abstract

A color display device includes a substrate which forms a partition wall for defining a vacuum space, a plurality of cathode protrusions effecting field emission are formed on the substrate, and a transparent insulator which forms the vacuum space along with the substrate. A plurality of phosphor dots are formed on the surface of the transparent insulator on the side of the vacuum space, are arranged in opposition to the electron sources and have mutually different colors of light emission. Anodes are arranged between the electron sources and the phosphor dots which cause electrons to be generated from the electron sources by field emission, and a transparent electrode is disposed between the phosphor dots and the transparent insulator. Apertures are provided in the anodes through which the electrons pass, whereby the electrons are released from the cathode projections by selectively applying voltages to the anodes, so as to impinge on the phosphor dots of desired color.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a color display device for providing a color display of letters, numerals, etc., and more particularly to a device which adequately selects for each letter, numeral, etc., a desired color from a plurality of colors to produce selected color display letters, numerals, etc.

2. Description of the Prior Art

As means for effecting letter display, there has heretofore been provided a device, such as the Nixie tube, which produces light emission attendant on gaseous discharge, a device which produces light emission of a fluorescent material based on the impingement of an electron beam with the material, a device which produces electroluminescence, a device which produces changes in the intensity of reflected light due to electric fields applied to a liquid crystal, and a device which produces light emission of a luminescent diode attendant on current injection. In all of these devices, however, the light emission has been in a single color. There has not yet been realized a device capable of altering the color of letters. This has resulted from the fact that gas within a closed envelope cannot be simply exchanged and that multicolored elements for the light emission cannot be arranged in a minute area. It is apparent that, since the prior-art various display devices cannot arbitrarily select a plurality of display colors in this manner, the indicating function cannot help but be insufficient.

If a plurality of colors are selected for the display, the indicating function will be enhanced. For example, if the display color is changed in accordance with the transfer of codes or with the relation in magnitude to a suitably set threshold value in the indication of numerals, or with the contents of words such as "caution" by red and "preparation" by green, then the meaning of the display can be more sufficiently impressed on an observer.

SUMMARY OF THE INVENTION

In view of the desireability of such a feature, the present invention has as its principle object the provision of a display device for letters, numerals, etc., which is capable of multicolored indication.

In order to accomplish such an object, according to the present invention, field emission type electron sources are employed as cathodes; phosphor dots are arranged in opposition to the electron sources which emit differed colored light from one another when bombarded and caused to luminesce by electrons released from the electron sources, and the cathodes opposite to those of the phosphor dots which are of the same color of light emission are electrically connected to form a single constituent element in the form of letters, numerals, etc., by the use of the phosphor dots of the same luminescent color.

The present invention will be described in detail hereunder with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1a is a cross-sectional view and FIG. 1b is a fragmentary view partly in section of an embodiment of the present invention; and

FIG. 2 is a detail view of the construction of essential portions for explaining the operation of another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1a and 1b are views showing an embodiment of the present invention; wherein, FIG. 1a is a sectional view of the structure of the embodiment, and FIG. 1b illustrates the construction of the embodiment as assembled. Reference numeral 1 designates a substrate which also serves as a partition wall for defining a vacuum space 12. Each of the cathodes 2 formed on the substrate 1 has a projection which is sufficiently sharp at its tip to generate electrons by field emission. An anode 3 serves to draw out field emission electron currents from the respective cathodes. Numeral 4 indicates an insulator for supporting the anode 3 and for providing the necessary electrical insulation between the cathodes and the anode. Shown at 4' are apertures which are provided in the anode 3 in opposition to the respective cathode projections. An insulator 5 functions to define the vacuum space in which the electron beams which have passed through the apertures 4' are accelerated. A transparent partition wall 6 functions to define the vacuum space, and is made of an insulator. Numeral 7 denotes phosphor dots of various colors applied on that surface of the transparent partition wall 6 which is located on the side of the vacuum space 12. A transparent electrode 7' is formed between the phosphor dots 7 and the transparent partition wall 6.

With such a construction, a voltage which is positive or the anode side is applied between the cathodes 2 and the anode 3 (the power source being omitted from the drawing in this figure), to impress an electric field of sufficient intensity on the tips of the projections of the cathodes 2 to cause emission. Thus, field emission currents are generated from the pointed ends of the projections of the cathodes. When the material of the cathodes is, for example, tungsten, molybdenum or the like, the field emission arises at an electric field strength of approximately 10.sup.7 (volts/cm). Therefore, assuming that the radius of curvature of the tip of each cathode projection is 1,000 (A), a voltage of 100 (V) or so may be applied between the cathode 2 and the anode 3.

Subsequently, the electron beams from the cathode projections pass through the corresponding apertures 4' which are provided in the anode 3. Thereafter, they are accelerated by an accelerating voltage (whose power source is not shown) applied between the anode 3 and the surface with the phosphor dots 7 applied thereon, namely, the transparent electrode 7'. After thus acquiring energy enough to stimulate the phosphor 7 so as to bring it into luminescence, the electron beams impinge on the corresponding phosphor dots opposite to the cathode projections and cause them to emit light. Of course, the space in which the electron beams permeate may be kept at a low pressure in this case.

Further, according to the present invention, the cathodes opposing the phosphor dots of the same color of light emission are electrically connected in the respective patterns of the letters, numerals, etc., to make groups of cathodes, so that they may be simultaneously operable. Thus, a single constituent element of letters, numerals, etc., is formed in conjunction with groups of phosphor dots having the same luminescent color. Display colors can accordingly be selected in dependence on the colors of the groups of phosphor dots which oppose the cathode groups that are operated. More specifically, the anode corresponding to the single constituent element of letters, numerals, etc., formed by each respective cathode group is electrically connected so that an electric field may be applicable at the same time to the group of cathode projections belonging to the particular constituent element of letter, numerals, etc., as will be explained in conjunction with FIG. 2. In this way, the selective operation of the letter elements is made possible in dependence on which letter elements the anodes applied with the voltages correspond to.

For example, as seen in FIG. 1b, three cathode groups of similar configuration are associated with each anode 3 so that each letter, numeral, etc., formed by a cathode group may effect illumination of respective groups of phosphor dots arranged in a corresponding pattern providing illumination in one of three select colors depending upon which cathode group associated with a given anode is energized.

FIG. 2 is a diagram for explaining the operation of the selection of the display color and the selection of the letter element as stated above. The figure typically illustrates the structure of the cathodes as well as an anode of one constituent element of letters, numerals, or the like, and the electrical connection therefor. In FIG. 2, numeral 2 indicates the cathode projections, among which projections 2 - 1 and 2 - 4 are opposite phosphor dots having the same luminescent color. Similarly, a set of the projecting cathodes 2 - 2 and 2 - 5 are opposite phosphor dots having the same color of light emission, which is different from the color of the light emission, the phosphor dots opposite the protruding cathodes 2 - 1 and 2 - 4.

The cathode projections 2 - 3 and 2 - 6 are similarly opposite to phosphor dots which are of the same luminescent color to each other, but which differ from the aforesaid two sets of phosphor dots.

As shown in the figure, the perspective cathode projections of the sets, namely, projections 2 - 1 and 2 - 4, projections 2 - 2 and 2 - 5 and projections 2 - 3 and 2 - 6 are electrically connected in common, and the respective sets are selected by means of a switch 9. Since, in the case of FIG. 2, only the single element is representatively shown, the anode 3 is common to the cathodes.

While the switch 9 is for the selection of the display color, a switch 10 serves to select the particular element. The switch 10 is adapted to close a single contact, or a plurality of contacts at the same time. As apparent from the foregoing explanation, the voltage of a power source 11 is selectively applied between the anode 3 selected by the switch 10 and the group of cathode projections selected by the switch 9. In consequence, letters or numerals represented by the combination of the respective constituent elements of the letters or numerals as prescribed by the selection of the contacts of the switch 10 are displayed in the color selected by the switch 9.

The above description has been made of a mere example of structure. By way of example, it is, of course, possible to reverse the relation of the electric connections between the anodes and the cathodes as for the selections of the elements and colors of the letters, numerals or the like, or to additionally provide control electrodes for the intensity modulation of the electron beams.

As described above in detail, in accordance with the present invention, the multicolored indication of letters, characters, numerals, etc., which has hitherto been impossible is easily attained. In particular, if the modern technique of integrated circuits in the production of semiconductor devices is applied to the present invention, the cathode protrusions can be manufactured with sufficient density, for example, at intervals of several tens (.mu.m). Thus, changes in the position of a light emitting portion as attendant on the selections of the display colors can be made sufficiently small. In addition, owing to an increase in the number of letter or character elements, letters or characters can be indicated in their natural form, and even complicated letters or characters can be displayed. Furthermore, owing to the utilization of the field emission type electron sources, the time response for lighting and extinction becomes extremely quick, and it is also realized to reduce required power and to prolong life.

Claims

What is claimed is:

1. A color display device comprising an insulating substrate, a transparent insulator defining a vacuum space along with said substrate, a plurality of groups of field emission type electron sources formed in respective patterns on said substrate and serving as cathodes, a plurality of groups of phosphor dots applied on the surface of said transparent insulator on the inside of said vacuum space in positions to oppose said electron sources and having predetermined colors of light emission, means to commonly connect said electron sources of each group into a number of constituent elements forming patterns of identical configuration equal to the number of colors of phosphor dots so that those of said phosphor dots opposing each group of electron sources and which have the same color of light emission oppose one constituent element of said group of electron sources forming a respective pattern, anodes arranged respectively between each opposing group of phosphor dots and electron sources in order to draw out electrons from the commonly connected cathodes by field emission, apertures provided in said anodes in a manner to oppose said electron sources, a transparent electrode provided between said transparent insulator and said phosphor dots, first selector means to selectively connect said commonly connected cathodes to energizing potential, and second selector means to selectively connect said anodes to energizing potential, whereby said electrons drawn out from said cathodes by voltages applied between said cathodes and anodes by said first and second selector means are accelerated by a voltage impressed on said transparent electrode and impinge on said phosphor dots of the same color of light emission.

2. A color display device as defined in claim 1 wherein said electron sources are interconnected so that said constituent elements corresponding to each pattern are reproduced in number equal to the number of different colors of phosphor dots provided.

3. A color display device as defined in claim 1 wherein said anodes have the configuration of the pattern formed by the constituent elements with which they are operatively associated.

4. A color display device as defined in claim 1 further including means for applying an accelerating voltage to said transparent electrode to create an accelerating field between said anodes and said phosphor dots.