Liquid crystal display

• US 5,159,323 A
• Filed: 06/06/1989
• Issued: 10/27/1992
• Est. Priority Date: 02/19/1987
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Mase, Akira, Yamazaki, Shunpei
• Primary Examiner(s): Weldon, Ulysses
• Assistant Examiner(s): Liang, Regina
• Application Number:
  US07/361,954
• Time in Patent Office: 1,239 Days
• Field of Search: 340/712, 340/706, 341/33, 341/34, 341/784.1
• US Class Current: 345/104
• CPC Class Codes: G01L 1/16 using properties of piezoelectric devices
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/047 using sets of wires, e.g. crossed wires

Abstract

A liquid crystal display is provided having pressure detection ability. An information input can be implemented by directly touching the display which has presented an image. The pressure detection is performed by means of the liquid crystal material which is also provided for use in a displaying operation. In the method of operation, the displaying and pressure operations are carried out alternately.

Claims

1. A liquid crystal display comprising:

a pair of substrates at least one of which is transparent;

an electrode arrangement formed on the inside surfaces of said substrates in order to define a plurality of pixels;

a liquid crystal material having a piezoelectric effect disposed between said substrates;

a means for supplying driving signals to said electrode arrangement in order to construct an image on said display;

a means for detecting the voltage generated across said liquid crystal material between said substrates due to pressure applied thereto; and

a means for controlling said driving means and detecting means in order that the displaying operation by means of said supplying means and the detection operation by means of said detecting means are performed alternately.

2. The display of claim 1 wherein said electrode arrangement comprises a plurality of first parallel conductive strips formed on one of said substrates and a plurality of second parallel conductive strips, said first and second strips being arranged orthgonally in order to form a matrix.

3. The display of claim 2 wherein said supplying means comprising an oscillator which supplies addressing signals to said first strips and a driver which supplies input signals to said second strips in synchronization with said addressing signals.

4. The display of claim 3 wherein said detecting means comprises a switching circuit which sequentially grounds one of said first strips whereas the others of said first strips are opened, and a shift register which stores the voltage levels of said second strips in synchronization with said switching circuit.

5. The display of claim 1 wherein the pressure detection operation scanning through the display area is effected after the display operation of several frames.

6. The display of claim 1 wherein said electrode arrangement is scanned with said driving signals n times (where n>

2) and subsequently scanned with voltage detection signals one time.

7. The display of claim 1 wherein said liquid crystal material comprises a ferroelectric liquid crystal.

8. A method for operating a liquid crystal display device comprising a pair of substrates with a gap therebetween filled with a liquid crystal layer having a piezoelectric effect and an electrode arrangement defining a plurality of picture elements in said liquid crystal layer, said method comprising the steps of:

first scanning said picture elements with signals for displaying a visual image in said device;

second scanning said picture elements with signals subsequent to said first scanning for sensing a voltage generated by said liquid crystal layer at each picture element in response to a pressure applied thereto; and

repeating said first and second scanning steps.

9. The method of claim 8 wherein said liquid crystal layer comprises a ferroelectric liquid crystal layer.

10. A liquid crystal device comprising:

a pair of substrates, at least one of which is transparent, each having an inside and an outside;

row and column electrode strips respectively formed on the insides of said substrates;

a liquid crystal layer having a piezoelectric effect disposed between said substrates;

means for scanning said row electrode strips with address signals;

means for supplying said column electrode strips with data signals in synchronization with said address signals;

means for detecting a voltage generated across said liquid crystal layer in response to a pressure applied thereto, said means comprising a means for scanning said row electrode strips with ground level signals, a plurality of AND gates where each of said column electrode strips is connected to one of two inputs of said AND gates respectively, a means for applying a voltage to the other one of said two inputs of said AND gates and a means for detecting outputs of said AND gates; and

a controller for driving said means for scanning said row electrode strips, said means for supplying said column electrode strips and said means for detecting a voltage in order that a display operation and a pressure detection of said liquid crystal device are performed alternatively.

11. The device of claim 10 wherein said liquid crystal layer comprises a ferroelectric liquid crystal.