Method of using a liquid crystal display device as a data input device

• US 4,224,615 A
• Filed: 09/14/1978
• Issued: 09/23/1980
• Est. Priority Date: 09/14/1978
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Penz, Perry A.
• Primary Examiner(s): Trafton, David L.
• Application Number:
  US05/942,226
• Time in Patent Office: 740 Days
• Field of Search: 340/365 C, 340/712, 350/334
• US Class Current: 345/174
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G02F 1/134327 Segmented, e.g. alpha numeric display
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0447 Position sensing using the local deformation of sensor cells
• CPC Class Codes: G09G 3/18 using liquid crystals
• CPC Class Codes: H01H 2219/012 programmable
• CPC Class Codes: H03K 17/962 Capacitive touch switches

Abstract

A liquid crystal display (LCD) device may be used as a device for receiving data from a human operator, that is, an LCD device may be used as a keyboard for receiving data from a human operator. The LCD device preferably has a rear substrate, a transparent front plate, a plurality of segments formed on the substrate and on the plate, liquid crystal material disposed between the cover and the substrate and the plate, and means for sealing the liquid crystal material between the substrate and the plate. The front plate material, which may be glass, plastic or other transparent materials, has sufficient flexibility to deflect toward the substrate in response to the application of pressure by the human operator. The application of pressure occurs, for instance, when the human operator depresses selected areas of the LCD device in much the same manner as when a human operator applies pressure to a keyboard to input information. Selected segments of the LCD device are preferably actuated to define one or more areas on the device where the operator may input information and the segments disposed in the regions of the one or more areas are sensed for a change in capacitance between the segments disposed on the substrate and the segments disposed on the front plate, the change in capacitance occurring when the operator applies pressure to the plate and deflects it toward the substrate.

Claims

1. A method of inputting information to a liquid crystal display device, said device having a plurality of segments suitable for outputting information and a flexible front substrate, said method comprising:

activating selected segments of the liquid crystal display device to define selected areas where a human operator may input information to the liquid crystal display device by depressing the flexible front substrate thereof;

inputting information to the liquid crystal display device by selectively depressing a portion of the flexible front substrate associated with a particular activated selected area to change the impedance between at least one segment pair in the particular activated selected area corresponding to the depressed portion of the flexible front substrate;

sensing the impedance between at least one segment pair in each of the activated selected areas; and

determining the particular activated selected area corresponding to the portion of the flexible front substrate as selectively depressed by sensing an impedance change between at least one segment pair in the particular activated selected area corresponding to the depressed portion of the flexible front substrate.

2. A method of inputting information to a liquid crystal display device, wherein said liquid crystal display device includes a plurality of segments suitable for outputting information, a body of liquid crystal material to which the plurality of segments are exposed, and a flexible front substrate overlying the body of liquid crystal material, said method comprising:

inputting information to the liquid crystal display device by selectively depressing a portion of the flexible front substrate against the body of liquid crystal material for changing the impedance between at least one segment pair in the area corresponding to the depressed portion of the flexible front substrate.

3. A method as set forth in claim 2, further including sensing the impedance between a plurality of segment pairs in respective areas of the liquid crystal display device;

and

determining the particular selected area corresponding to the portion of the flexible front substrate as selectively depressed by sensing an impedance change between at least one segment pair in the particular area corresponding to the depressed portion of the flexible front substrate.

4. A method as set forth in claim 3, further including initially activating selected segments of the liquid crystal display device to define selected areas where information may be input to the liquid crystal display device prior to the inputting of information to the liquid crystal display device;

and

thereafter inputting information to the liquid crystal display device by the selective depression of a portion of the flexible front substrate associated with a particular activated selected area.

5. A method as set forth in claim 4, wherein the selective depression of a portion of the flexible front substrate is limited as to extent by the underlying body of liquid crystal material to prevent contact of the depressed portion of the flexible front substrate with an opposed interior surface of a component of the liquid crystal display device.

6. A method as set forth in claim 4, further including selecting at least one segment pair in each of the activated selected areas for impedance sensing in which the at least one segment pair selected in each of the activated selected areas is a pair in a non-activated state for the purpose of displaying information.

7. A method as set forth in claim 4, wherein the liquid crystal display device includes a plurality of character display positions, and a plurality of multi-bit digital codes, each of which defines the segments to be actuated and non-actuated in one of said character display positions, and further including:

selecting particular ones of said character display positions to be the activated selected areas.

8. A liquid crystal display device capable of receiving input information for affecting a visual output display comprising:

a housing including a flexible front substrate and a rear wall in spaced substantially parallel relation thereto;

conductive segments formed on at least one of said front substrate and said rear wall and adapted to display information;

a body of liquid crystal material contained within said housing and disposed between said front substrate and said rear wall;

said flexible front substrate having sufficient flexibility to deflect toward said rear wall in response to the application of finger tip pressure by a human operator; and

a portion of said flexible front substrate being depressible toward said rear wall in response to the application of downward pressure by a finger tip of a human operator to reduce the thickness of the liquid crystal material disposed between the depressed portion of said front substrate and said rear wall for inputting information to the liquid crystal display by changing the impedance associated with the conductive segment in the area corresponding to the depressed portion of the flexible front substrate.

9. A liquid crystal display device as set forth in claim 8, wherein said rear wall of said housing is a relatively rigid rear substrate of less flexibility than said front substrate.

10. A liquid crystal display device as set forth in claim 9, wherein said conductive segments are provided on each of said front and rear substrates in opposed relationship with respect to each other and in contact with the body of liquid crystal material disposed between said front and rear substrates.

11. A liquid crystal display device as set forth in claim 10, further including impedance-sensing circuit means operatively coupled to said conductive segments for sensing a change in the impedance between at least one pair of said conductive segments in response to the selective depression of a portion of the flexible front substrate corresponding to the area in which said at least one pair of said conductive segments is positioned.

12. A liquid crystal display device as set forth in claim 11, wherein said impedance-sensing circuit means is integrated with said conductive segments on said rear substrate.

13. A liquid crystal display device as set forth in claim 8, wherein any portion of said flexible front substrate which is depressed is limited as to the extent of its movement toward said rear wall to remain in spaced relation with respect to said rear wall, but with a reduced thickness of the liquid crystal material being disposed therebetween.