JPH02297822A - Push button keypad - Google Patents

Abstract

PURPOSE: To provide a thin type key pad with an electrostatic shield device to be easily installed by forming, on a surface of base means, a corresponding pattern in conductive area so that it moves to contact the corresponding conductive area and bridge a contact element when button area is pushed. CONSTITUTION: A flexible thin film element 3 is made from a transparent polyestel sheet. On one side, an electrostatic screen 4 containing a horizontal conductor strip 5 forming a grid and a grid pattern of a vertical conductor strip 6 is provided. On the other side of the thin film element 3, a corresponding array of a contact 8 which is combined and open circuited is provided on the surface of the thin film element. When push button area is pushed down, the corresponding contact area, which is open circuited on a flexible thin film is pushed against a short circuited pad to be bridged in the contact which is combined and open circuited. Accordingly, a thin film type pad with an electrostatic shield device to be easily and effectively installed can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a first
a corresponding open contact area formed by the combined conductive fingers such that when the button is pressed the shorting pad completes the circuit through its associated combined contact area. Concerning a thin film keypad covering an array.

BACKGROUND OF THE INVENTION When such keypads are used as inputs for sensitive electronic devices such as microprocessors or other logic devices, problems arise due to the static charge generated on the person using the keypad. It is known that this occurs. This charge is capacitively coupled to the microprocessor's input circuitry and can cause it to lock up.

SUMMARY OF THE INVENTION In order to counteract the above-mentioned problems, it is known to provide an electrostatic screen device in the form of a grid of conductors surrounding but insulated from the pushbutton leads. Such screens are difficult to provide and their effectiveness is limited due to the required large spacing between the conductors of the grid.

It is an object of the present invention to provide a thin film keeper having an electrostatic shielding device that is effective and easy to install.

SUMMARY OF THE INVENTION The technical concept of the present invention is to provide a rigid support element with a shorting pad that connects the open contact element on one side of the flexible membrane to the opposite side of the flexible membrane. Provide an electrostatic screen.

In accordance with the invention there is provided a thin film keypad comprising a laminate structure of a rigid flat base means of insulating material, a flexible flat cover element and an intermediate flexible sheet of insulating material. Said intermediate flexible sheet is provided with a conductive suclean layer covering at least part of its surface on one side in contact with said cover element, and has a contact element open-circuited on the other side facing said base means. A pattern can be set. When a corresponding button area of the array of button areas on the cover element is pressed, a corresponding open contact element is moved into contact with a corresponding conductive area to bridge the contact element. , a corresponding pattern of electrically conductive areas spaced from the open contact element is provided on the surface of the base means opposite thereto.

EXAMPLE Referring to FIG. 1, the top cover element 1 is formed from a thin flexible sheet of polyester material;
Limit the array of button portions 2.

The button part is revealed by a colored part that contrasts with the color of the remaining part of the sheet. Each button portion is provided with a small central protrusion (not shown) for the tactile position of the button.

Referring to FIGS. 2, 3 and 4, the flexible thin film element 3 is formed from a sheet of transparent polyester material. On one side shown in FIG.
．． An electrostatic screen 4 is provided which includes a grid pattern of horizontal conductor strips 5 and vertical conductor strips 6 forming a grid of less than 5C square. On the opposite side of the thin film element 3 (FIG. 3) a corresponding array of interlocking and open contacts 8 is provided on the surface of the thin film element. The conductive tracks connected to the various contacts are terminated in leads 9. It will be appreciated that the electrostatic screen may be of any suitable type and may also be a continuous layer.

Referring to FIG. 5, the rigid support element 10 is formed from a sheet of ABS material and is provided with an array of shorting pads 11 of conductive material corresponding to the array of open contacts 8. Each shorting pad 11 is placed in a recess 12 with a depth of about 0.1 square inch. Each recess is connected to its mating recess by an air channel 13. These air channels allow compressed air to be released by actuation of a button.

By placing the shorting pad in the recess, no spacer element is required between the support element 10 and the flexible membrane 3, but an arrangement that includes both a spacer element and a recess and
It will be appreciated that arrangements in which the recess is omitted and spacer elements are used are also envisioned in the present invention. Furthermore, the support element IO may be part of the surface of a case of an electronic device, for example a case of a telephone.

Referring to FIG. 6, the various elements described above are assembled in a stacked arrangement to form a keypad. Adhesive layer 1
3 and 14 are respectively between the cover element l and the thin film element 3;
and placed between the thin film element 3 and the support element IO. The adhesive layer is first provided with a pattern of cut-outs corresponding to the array of open contact areas and shorting pads.

The assembled keypad is typically about 31 mm thick.

In operation, when the button portion is pressed down, the corresponding open contact area on the flexible membrane is pressed against the bridging □ corresponding shorting pad of the combined open contact.

Although the invention has been described with reference to a number of specific configurations, it will be understood that equivalents may be readily substituted without departing from the scope of the invention.

[Brief explanation of drawings]

FIG. 1 shows the top cover element of the keypad device of the invention. FIG. 2 shows the electrostatic shielding device on one side of the flexible thin film element of the keypad device. FIG. 3 shows an array of open contacts on the other side of the thin film device shown in FIG. FIG. 4 shows a transparent view of a flexible thin film showing the matching of the electrostatic shield and the array of open contacts. FIG. 5 shows a rigid support element of the keypad device. FIG. 6 shows a side view, enlarged for clarity, of the assembled laminar arrangement of the various elements shown in FIGS. 1-5. 1... Cover element, 2... Button portion, 3... Thin film element, 4... Electrostatic screen, 8... Open contact, lO... Support element, 11... Short circuit pad.

Claims (11)

[Claims] (1) A thin film keypad comprising a lamination device of a rigid flat base means of insulating material, a flexible flat cover element, and an intermediate flexible sheet of insulating material, wherein said intermediate flexible sheet a sheet is provided with a conductive screen layer covering at least part of its surface on one side in contact with the cover element and with a pattern of open contact elements on the other side facing the base means; such that when a corresponding button area of the array of button areas on the cover element is pressed, a corresponding open contact element moves into contact with a corresponding conductive area, bridging said contact element; A thin film keypad, wherein a corresponding pattern of electrically conductive areas spaced from the open contact element is provided on the surface of the base means opposite thereto. 2. The keypad of claim 1, wherein said conductive screen layer is in the form of an open grid pattern. 3. The keypad of claim 1, wherein said conductive screen layer is in the form of a continuous layer. 4. A keypad according to claim 1, wherein each conductive region is provided at the bottom of a recess formed in said surface of said base means. 5. The keypad of claim 4, wherein the recesses are interconnected by channels. 6. A keypad as claimed in claim 1, in which a spacer element is inserted between the intermediate flexible sheet and the flat base means. (7) the laminating device is held together by two layers of adhesive material inserted between the base means and the flexible sheet and between the flexible sheet and the cover element, respectively; Claims 1 to 6, wherein the layer has a pattern of cut-out portions corresponding to the areas.
The keypad according to any one of the following. 8. A keypad according to claim 1, wherein said flat base means is part of a surface of an electronic device. (9) The keypad of claim 8, wherein the electronic device is a telephone. 10. The keypad of claim 1, wherein the array of button areas is defined by graphics. 11. The keypad of claim 1, wherein each button area includes a central protrusion for tactile positioning.