Browse Prior Art Database

Liquid Crystal Display and Touch Panel Keyboard Input

IP.com Disclosure Number: IPCOM000053157D
Original Publication Date: 1981-Sep-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 3 page(s) / 64K

Publishing Venue

IBM

Related People

Harris, RH: AUTHOR [+2]

Abstract

This device eliminates the need for using a transparent touch panel input over a liquid crystal display (LCD) in order to create an overall input and display device. It uses the normal top electrode in the liquid crystal display device itself in a unique manner to provide the keyboard or input device function. As shown in Fig. 1, a plan view of a single character segment area on an L:CD display, typical character segments 2 may be energized by circuits (not shown) to create the image desired in the L:CD display format. The cross-sectional view in Fig. 2 shows the overall construction.

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Liquid Crystal Display and Touch Panel Keyboard Input

This device eliminates the need for using a transparent touch panel input over a liquid crystal display (LCD) in order to create an overall input and display device. It uses the normal top electrode in the liquid crystal display device itself in a unique manner to provide the keyboard or input device function. As shown in Fig. 1, a plan view of a single character segment area on an L:CD display, typical character segments 2 may be energized by circuits (not shown) to create the image desired in the L:CD display format. The cross-sectional view in Fig. 2 shows the overall construction.

Substrate 1, which may be the silicon or glass substrate on which the L:CD drive circuits are placed, bears the metalized drive elements for the display 2. A separator or insulator 3 lies on the top surface of substrate 1. The overlying glass cover or top electrode-bearing member 4 carries the normal L:CD electrode
5. The electrode 5 has been divided in this device into three areas labeled 5A through 5C. The top surface of the cover glass 4 bears an additional transparent electrode touch pad 6. Each of the pads is a transparent indium-tin oxide compound that is electrically conductive and transparent. These materials are well known in the art for this function.

The three areas of the top electrode in the LCD device labeled 5A, 5B and 5C are normally conjoined as a single electrode. They are separated in this invention and are utilized during an input touch-mode sensing phase as keyboard drive and sense elements of the capacitive type. The sense mode can be electrically interleaved with the display mode and occur at such a rapid rate that there is no flicker or dimming of the display. Electrical means for periodically driving the key input electrode and sensing whether or not a signal is present on the coupling or sensing electrode is not shown, but may be embodied with the display control electronics and operate interleaved with the driving of the display character elements.

The electrical analogy is shown in Fig. 3. The transparent touc...