TRANSPARENT PLANAR SWITCH STRUCTURE AND SWITCH UNIT

FIELD OF THE INVENTION

The present invention relates to a switch with a special transparent structure visible from the front, particularly to the structure of a transparent switch used in the composite switch comprising a display system and touch switch, the requirement for which is showing a rapid increase with the increased use of the display systems.

DESCRIPTION OF THE PRIOR ART

Currently, touch switches are being widely used in a variety of instruments for cash registers, desk-top calculators, automobiles, etc. Their structure is made up of layers of character plate, pressure-sensitive conductive rubber or rubber cushions and electrode plates and most of the character plates are printed on one side of the film or rubber sheet. These switches are rapidly becoming popular taking the place of the conventional switch panels in which individual push-button switches are arranged in parallel.

The present invention is intended to provide a switch structure and a switching device the technology of which is unimaginably more advanced than that of conventional switches; specifically, this invention uses a display system, which exhibits characters, pictures, positions, etc., using electric signals instead of the conventional dial on which a given content has been indicated, thus a switch structure having highly dense displays and switch functions can be provided using a composite device comprising a display and touch switch which may.be turned on at a specified position according to the displayed signals.

SUMMARY OF THE INVENTION

The present invention (1) : relates to a transparent sheet switch structure consisting of two electrodes and an anisotropic conductor sandwiched between them, the anisotropic conductor and at least one of the electrodes being transparent and an insulator being present between the electrodes; and (2): the present invention provides, as an inside arrangement of the switch structure, a switch device having transparent sheet switch structure, constructed on the display side of the sheet display, said transparent sheet switch structure having a transparent anisotropic conductor and an insulator sandwiched between the transparent electrodes placed face to face each other.

Adoption of such a technical configuration has made a highly sophisticated use of a switch possible, that is, integration of the display and the switch. Furthermore, to function display content of the switch structure, a display other than on the surface to be touched, for example, the indication of the display can be used as it is or it can be displayed on the electrode placed on the back side of said switch structure. Thus, the present invention is permanently free from the loss or stains of the displayed symbols.

The present invention is a transparent touch switch formed on the top of a multiple liquid crystal display capable of displaying several types of data in the same area, using electric input signals instead of the conventional dial display which is incapable of doing so. This has the advantage of reducing the number of switch elements required to a fraction of what conventionally would be 'required, thus considerably expanding the latitude of its application.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1 to 4 show examples of the transparent sheet switch structure according to the present invention. Figure 2 shows the simultaneous combination of the switch structure and display system.

DETAILED DESCRIPTION OF THE INVENTION

The electrode as referred to in the present invention consists of an electrically-conductive layer on the surface of a substrate such as an electrically-insulating film or plate. Usually a metal is used as the conductive layer.

For the substrate materials for the above-mentioned electrically-insulating film or plate, polyesters such as polyethyleneterephthalate, polycarbonate, polymethylmethacrylate, polystyrene and ABS resin. Also, resins such as polyvinylchloride, polyethylene, polypropylene, polyamide, cellulose acetate, polyimide and polysulfone show relatively good results. To produce optimal surface conditions, it is recommended that the above-mentioned resin coatings or adhesives are applied to the various substrates or the surfaces of these substrates are treated with a corona discharge or a flame.

Metals used to form the conductive layer on the substrate can be any conducting metal including Cr, Co, Al, Cu, Zn, Sn, Mn, Mo, Ni, Pt, Pd, Au, Ag, Rh and In, as well as their alloys and oxides. In particular, Al, Cu, Sn, Pt, Pd, Au, Ag, Rh and In, as well as Al-Cu alloy and metal oxides such as indium oxide and tin oxide are preferred from a transparency viewpoint. To provide such a metal on the substrate as a conductive layer, construction in the form of the metal foil or plating layer may be acceptable, but an extremely thin conductive metal layer is preferable in view of transparency and adherence, which can be applied, for example, by vacuum deposition, sputtering, or ion plating. The vacuum metallizing may be done by such methods as ordinary resistance heating, induction heating, electron- beam heating and laser heating. Sputtering may employ any of the various known methods such as cathode sputtering, high frequency sputtering and plasma sputtering. The transparency of such a metal membrane deposited electrode may be sufficient if the display on the back side can easily be read with the naked eye. The above-mentioned method, however, can result in an optical transparency of not less than 30 %, preferably not

less than 50 %, or even not less than 60 %. Moreover, an excellent conductivity with the surface resistivity of less than 10⁸ / square and even 10⁶ / square or less can be attained. The metal membrane mentioned above is further etched to form the electrode.

The electrodes of the present invention are of two types: the front electrode requires both pressure sensitive functioning capability and transparency, while the back electrode needs neither requirement. The front type may be applied to the back or a plate electrode having excellent transparency may be used on the back side. The use of a transparent electrode on the back side makes possible the display switch structure to be arranged to permit reading of the displayed indications, thus the latitude of the application can be expanded.

For the anisotropic conductor used for the present invention, a composite material consisting of transparent plastic or elastic materials, in which conductive filaments are oriented, is used.

For the transparent plastic material, the electrical insulator forming the above-mentioned electrode is used, while for the transparent elastic material, any transparent elastic material such as silicone rubber, polyurethane, etc., may be used but silicone rubber is preferred for its durable and stable qualities.

The above-mentioned conductive filaments may be stainless steel fibers, carbon fibers or molybdenum fibers. However, particles mixed with resin may also be used to create the conductive paths. For such particles, iron, nickel, stainless steel, silver or silver-coated glass beads may be used.

In order to form an anisotropic conductor, the conductive filaments must be embedded in the depth direction and be electrically non-conducting in the surface direction. The anisotropic conductor consisting of conductive particles may be of a type in which the particles are dispersed uniformly, and will undergo compression in the depth direction, thus being conductive only in the depth direction. To enhance the transparency, it is preferable to concentrate the particles over a specific area magnetically, and thus to minimize the particle content of the anisotropic conductor.

Since the conductive filament or particle path tends to reduce the transparency when the density is too high, such density must be determined considering the size of the electrode to be connected. In the case of a 1 mm thick transparent resin oriented with filaments of about 10 in diameter, no more than about 10 filaments/mm2 are usually preferable.

For example, the anisotropic sheet conductor using a 1 mm thick transparent silicone rubber containing-stainless steel fibers about 10 in diameter, oriented in the depth direction at a ratio of about 5 filaments per/mm2, gives a total optical transparency of not less than 90 %. Since the filaments embedded especially after bending take advantage of the filaments' spring effect, they are preferable in terms of durability of the switch.

For the electrical insulator materials used in the present invention, either plastic or elastic substances . applied to the above-mentioned electrode and anisotropic conductor are used. Other electrically insulating substances, moreover, may be used. The electrical insulator may be integral with the electrode or with the anisotropic conductor, or may be independent of these. In any case, it must effectively insulate the two electrodes when no compression is applied. The use of an electrical insulator having transparency is preferable for the present invention.

The transparent sheet switch structure of the present invention is composed of the sheet electrodes and the anisotropic conductor as illustrated in Figures 1 to 4 or may be any combination of these.

• Figure 1 shows a embodiment of the present invention, when front side is provided with an electrode assembly 1 composed of transparent electrode 4 and transparent electrically-insulating film 5, anisotropic conductor 2 having a transparent elastomer in which the conductive filaments 7 are embedded orientatively in the.depth direction as well as electric insulator 6 integrally constructed on the surface, and electrode 8, while the back side is equipped with a circuit board 3 which is the back transparent electrode assembly on which symbols or pictographs are printed. The arrow indicates the direction the pressure is applied to actuate the switch. Figure 1 shows the mechanism by which the insulating rubber layer 6 containing anisotropic conductor 2 is compressed such that conductive filaments 7 are brought into contact with transparent electrode 4 to be conductive, thereby making the switching action possible.
• Figure 2 shows another embodiment of the present invention in which insulating rubber 6 used for the switch action is applied only onto certain parts of transparent electrode assembly 1. 6 need not be transparent but must give the effect of transparency when applied over the entire surface. Anisotropic conductor 2 differs from that in Figure 1 in that since no electrically insulating layer is provided to its surface. 3 is the same type of transparent electrode assembly in which the same transparent electrode 4 as 1 is formed. 10 is the liquid crystal display.
• Figure 3 shows a configuration composed of the structures in Figures 1 and 2, in which the same anisotropic conductor 2 as in Figure 2 is used and electrical insulator 6 is provided between anisotropic conductor 2 and electrode assembly 1. The switch action is the same as in-Figure 1.
• Figure 4 shows a structure which is different from those of the previous three examples. Electrical insulator 6 is provided along both sides of anisotropic conductor 2 and a gap is left between front and back electrodes 1 and 3 as insulation. This is similar to the structure as shown in Figure 2 in that a gap is formed.

_. To keep electrode assembly 1 and anisotropic conductor 2 insulated when no conduction is occurring, an electrically-stable and insulating inert gas such as air or nitrogen may be used. In this instance, a sealed space is provided between electrode 1 and anisotropic conductor 2, in which such a gas is enclosed at a higher level of pressure than ambient. Application of a required pressure will produce a conductive state.

Although in Figures 1 to 4 the shapes of the present invention are illustrated only as a flat cross section they are not restricted or limited thereto. They may possess a curved surface such as that of a CRT (Cathode Ray Tube). Any shapes are acceptable provided electrodes 1 and 3 are arranged face to face with a given accuracy and anisotropic conductor 2 is in conformity with the shape without causing any trouble in functioning.

Various methods are available for outputting the switch signal. When either or both electrodes 1 and 3 are subdivided, the area which has become conductive can be directly detected by numbering the subdivided electrode beforehand. Also, when a current coming from electrode 1 flows to electrode 3 through an area which has become conductive, filament electrodes are provided on both sides in the x and y directions which are the surface direction of electrode 3. Thus, the position in such direction can be detected from the ratio or the values of the current flowing through each filament electrode. In this method, the electrode portions of electrodes 1 and 3 are not required to be subdivided but may be continuous. Furthermore, the position becoming conductive can be detected by setting resistance values in the surface directions of the electrodes of electrode assemblies 1 and 3 at different levels, by coducting current from the ends of electrode assemblies 1 and 3 and by measuring the conduction resistance to the opposite end of the other electrode. Similarly, the position can be detected by maintaining a constant current and measuring the voltage.

It is preferable to apply a resin coating to the operating side of the transparent films used in the present invention so as to improve the durability. In addition, the display referred to as 9 may be, in addition to of a liquid crystal display element method, of other methods using a luminous diode, an electroluminescent device, etc.

A typical method for producing the transparent sheet switch structure in the present invention is described below.

First, transparent electrodes were made by sputtering palladium metal over biaxially oriented

polyethyleneterephthalate film (Thickness: 100 micron; Light transmittance at a wave length of 550m : 89 %) by the d.c dipolar sputtering method. Sputtering was made using a chromium-plated rotary roll electrode (Diameter: 200 mm; Length: 200mm) as the anode, while for the cathode, a semicircular palladium metal plate nearly paralleled to the electrode roll anode as the target. The palladium plate was 200 mm in length, in the machine direction, and 200 mm in width. Palladium metal was precipitated and deposited by sputtering after the polyester film was continuously transferred along the periphery of the said electrode roll anode whose inside has been so designed as to be properly cooled by water, etc.

Various conditions for sputtering, such as spacing (10 to 40 mm) between the cathode and anode, discharge current, degree of vacuum, composition of enclosed gases (mainly argon), temperature of substrate and position of the screen for collecting electron, were finely adjusted according to the thickness of palladium film varying in close proportion to the transfer speed of the film. The film obtained is best suited to produce the transparent electrode having a transparent palladium film on its one side.

- Next, for the process for making the anisotropic conductor for the present invention, for instance, the original matrix liquid consisting of the above-mentioned plastic or elastic material to which conductive filaments are added and oriented magnetically, can be cured. For example, the sheet-like anisotropic conductor is easily made as follows: the above-mentioned short metal fibers used as the conductive filaments are added to the original liquid consisting of a plastic resin or elastic resin having a viscosity of not more than 5000 poise, preferably not more than 1000 poise; the resulting mixture is inserted into a metal mold which will be heated if necessary, and a magnetic field with a strength of not less than 200 gauss or not less than 1000 gauss if necessary, is applied to create magnetic lines of force through the mold; the short metal fibers are oriented in the vertical direction (sheet depth direction) along the magnetic lines of force; and the resin is cured with the magnetic field applied. This also can produce random arrangements of the short metal fibers in the anisotropic conductor and pattern arrangements by changing the distribution of the magnetic field.

Also, this can be accomplished by setting with the matrix resin the filament group that has a continuous supporting section at the end and is placed at intervals and in parallel each other in the central section, then removing the continuous section at the end and slicing to the predetermined thickness. The process for making the anisotropic conductor having insulating layers on one side or on both sides may involve applying a coating on the conductor or setting the original matrix liquid layer after placing in a frame. There is also a high productivity process which involves applying a coating of silicone rubber or similar by screen printing on the anisotropic conductor or the opposite side of the transparent film or similar having transparent electrode.

Thus-obtained transparent electrodes, anisotropic conductor and electrical insulator are cut to the desired sizes and laminated as shown in Figures 1 to 4, thus the transparent sheet switch structure for the present invention is formed. In the structures shown in Figure 1 and Figure 3, each layer may be brought into contact with each other with no gaps, thus further improving the transparency. In Figures 2 and 4, however, the transparency tends to be lower due to the gaps that must be provided. Layers for display, patterns or characters may be provided on the back side electrode or the display surface itself may be utilized. In either case, because it is constructed with transparent materials, the symbols are visible, and further there is no fear of the symbols becoming displaced or blurred since each is protected by the other transparent parts. Moreover, high efficiency can be attained since the operation by watching only one switch panel is possible.

Described below is combination of the transparent sheet switch structure in the present invention and; say, a liquid crystal display or similar. Microcomputer terminal input and output devices are usually operated by switching the input and output device arranged separately while watching the display. However, direct mounting of the over-all transparent sheet switch structure of the present invention on the display device can result in that direct switch operation becomes possible according to the signals displayed electrically and thus not only high density can be achieved, but also prevention of operating errors as well as display of signals to be switched becomes possible.

That is to say, because instructions by words are not used, and the positions to be switched can be specified directly, the operation of a switch panel having many contacts can be carried out simply by pushing the appropriate switch in accordance with the specified information. In addition there are no operating errors since it is possible to watch a switch while pushing it.