Touch-panel input device

• US 6,356,259 B1
• Filed: 07/13/1999
• Issued: 03/12/2002
• Est. Priority Date: 07/15/1998
• Status: Expired due to Term

• Current Assignee: SMK Corporation
• Original Assignee: SMK Corporation
• Inventors: Tanaka, Hiroshi, Maeda, Toshifumi
• Primary Examiner(s): Saras, Steven
• Assistant Examiner(s): Bell, Paul A
• Application Number:
  US09/352,219
• Time in Patent Office: 973 Days
• Field of Search: 345/173, 345/174, 345/104, 178/18.01, 178/18.03, 178/18.05, 178/18.06, 178/18.07, 341/20, 341/34, 156/99, 156/104, 156/107, 156/295, 156/350, 156/292, 522/95, 522/96, 522/98, 522/100, 522/103, 522/170, 296/22
• US Class Current: 345/173
• CPC Class Codes: B32B 17/10018 comprising only one glass sheet
• CPC Class Codes: B32B 17/10174 Coatings of a metallic or dielectric material on a constituent layer of glass or polymer
• CPC Class Codes: B32B 17/10302 Edge sealing
• CPC Class Codes: B32B 17/10917 between two pre-positioned glass layers
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact
• CPC Class Codes: H01H 13/703 characterised by spacers between contact carrying layers
• CPC Class Codes: H01H 2209/038 transparent
• CPC Class Codes: H01H 2209/06 transparent
• CPC Class Codes: H01H 2209/082 transparent
• CPC Class Codes: H01H 2211/002 Fluid or inflatable keyboards
• CPC Class Codes: Y10T 29/49105 Switch making

Abstract

Two transparent conductive panels are separated by a perimeter of elastic adhesive that forms a sealed gap in which transparent insulative fluid is interposed. The fluid has a refraction index close to that of the panels to improve light transmittance through the device. The small width of the gap improves response time and prevents formation of a vacuum in the gap. The panels are connected to a position detection circuit that determines coordinate position of an applied pressure point. Spacers in the gap reduce the chance of accidental large-area contact which would result in an erroneous position command. The elasticity of the adhesive and the small gap width provide better temperature variation tolerance in addition to improved consistency and reliability of operation.

Claims

1. A touch-panel input device comprising:

at least first and second transparent plates having faces opposed to one another and substantially parallel;

a portion of said opposing faces of said at least first and second transparent plates being transparent electrically conductive surfaces with uniform surface resistance;

an elastic adhesive disposed around a perimeter of said conductive surfaces, whereby said opposing faces are bonded together and separated by a sealed gap having a uniform width;

a transparent insulative fluid interposed in said sealed gap, said fluid having a refraction index close to that of said transparent plates;

at least one of said at least first and second transparent plates capable of resiliently flexing toward an other of said transparent plates, whereby an electrical relationship is changed between said conductive surfaces; and

said relationship is related to a coordinate position on said device.

2. A touch-panel input device according to claim 1, wherein:

said relationship is a voltage drop across a resistance provided by an electrical connection; and

said voltage drop is related to said coordinate position on said device by a proportional relationship.

3. A touch-panel input device according to claim 1, wherein said width of said gap is in the range of from 5 to 50 microns.

4. A touch-panel input device according to claim 1, wherein said adhesive is composed substantially of solids.

5. A touch-panel input device according to claim 1, wherein said transparent insulative fluid has a viscosity with a surface tension within said gap that overcomes a weight of said fluid, thereby preventing formation of a vacuum cavity in said gap when an orientation of said device is changed.

6. A touch-panel input device according to claim 1, wherein said elastic adhesive is ultraviolet light curable and provides pressure sensitive bonding.

7. A touch-panel input device according to claim 6, wherein said width of said gap is in the range of from 5 to 40 microns.

8. A touch-panel input device according to claim 1, wherein said elastic adhesive is thermosetting curable and provides pressure sensitive bonding.

9. A touch-panel input device according to claim 1, wherein said transparent conductive surfaces are transparent conductive layers disposed on said transparent plates with uniform thickness.

10. A touch-panel input device according to claim 9, wherein said transparent conductive layers are composed of Indium Titanium Oxide (ITO).

11. A touch-panel input device according to claim 9, further including:

transparent electrical connection leads on opposing ends of each of said transparent conductive layers;

an external connector;

said leads connected to said external connector; and

said external connector effective to provide electrical connection to each of said leads from a device external to said touch-panel input device.

12. A touch-panel input device according to claim 11, wherein:

each of said transparent conductive layers includes a plurality of parallel strips; and

said pluralities on said opposing faces being substantially perpendicular to each other.

13. A touch-panel input device according to claim 11, wherein said external connector is electrically connected to an external device having a circuit effective to measure a selected voltage drop along a path through said conductive surfaces to determine a coordinate position indicated by said electrical connection between said transparent conductive surfaces.

14. A touch-panel input device according to claim 13, wherein:

said circuit includes a DC voltage source;

a controller for controlling input/output and switches;

a first switch connected in series between said voltage source and a first lead on said flexible transparent conductive surface;

a second switch connected in series between said voltage source and a first lead on said rigid transparent conductive surface;

a third switch connected in series between a second lead on said flexible transparent conductive surface and ground;

a fourth switch connected in series between a second lead on said rigid transparent conductive surface and ground;

an input of an analog to digital converter connected through a fifth switch to said second leads on said conductive surfaces;

said controller receiving an output of said analog to digital controller; and

said controller effective to control said switches to measure a first voltage across a first resistor network formed by contact between said transparent conductive surfaces and to measure a second voltage across a second resistor network formed by said contact, thereby effective to determine a coordinate position of said contact.

15. A touch-panel input device according to claim 9, further including:

a transparent barrier layer between said fixed transparent plate and said transparent conductive layer disposed on said fixed transparent plate; and

said barrier layer effective to prevent contamination of said fluid.

16. A touch-panel input device according to claim 1, further including:

regularly spaced insulative protrusions disposed on at least one of said opposing surfaces of said at least first and second transparent plates; and

said protrusions effective to slightly increase and evenly distribute pressure applied to said flexible transparent plates necessary to change said electrical relationship between said conductive surfaces.

17. A touch-panel input device according to claim 16, wherein a height of said protrusions is substantially less than said width of said gap.

18. A touch-panel input device according to claim 16, wherein said protrusions are 5 microns in height or less.

19. A touch-panel input device according to claim 16, further including:

a conductive powder dispersed in said fluid;

said powder having particles with a diameter slightly less than a height of said protrusions; and

said powder effective to decrease the amount of pressure per unit of surface area applied to said flexible transparent plate necessary to change said electrical relationship between said conductive surfaces.

20. A touch-panel input device according to claim 1, wherein said elastic adhesive is sufficiently elastic to permit said electrical relationship to change by application of external pressure near said perimeter without loss of resiliency or adversely affecting said sealed gap.

21. A touch-panel input device according to claim 1, wherein said elastic adhesive exhibits elasticity sufficient to permit said flexible transparent plate to move resiliently in a direction parallel to said rigid transparent plate.

22. A method for constructing a touch-panel input device comprising steps of:

forming transparent conductive layers with conductive leads on portions of at least two transparent plates;

disposing a curable reactive adhesive on a perimeter of one of said conductive layers;

curing said reactive adhesive to form an elastic pressure sensitive adhesive with a specified height above said transparent plate;

applying a conductive bonding agent to an external connector;

positioning said external connector in a region outside of a space defined by said adhesive and in contact with said conductive leads;

pressing said transparent plates together with said conductive layers being opposed thereby bonding said transparent plates together and forming a sealed gap between said conductive layers; and

interposing an insulative transparent fluid in said gap, said fluid having a refraction index near that of said transparent plates.

23. A method for constructing a touch-panel input device according to claim 22, further including connecting said external connector to a position detection circuit.

24. A method for constructing a touch-panel input device according to claim 22, further including a step of depositing insulative protrusions at regularly spaced intervals on at least one of said at least two transparent plates.

25. A method for constructing a touch-panel input device according to claim 24, further including a step of dispersing a conductive powder in said insulative transparent fluid.

26. A touch-panel input device comprising:

at least first and second transparent plates having faces opposed to one another and substantially parallel;

transparent electrically conductive layers disposed on each of said opposing faces, said conductive layers having substantially uniform surface resistance and transparent electrical connection leads disposed on opposing ends of said conductive layers;

pairs of said connection leads of said conductive layers defining a coordinate axis;

regularly spaced insulative protrusions on at least one of said conductive layers effective to slightly increase and evenly distribute pressure applied to said transparent plates needed to cause contact between said conductive layers;

an elastic adhesive disposed around a perimeter of said conductive layers, whereby said opposing faces are bonded together and separated by a sealed gap having a substantially uniform width;

transparent insulative fluid interposed in said sealed gap, said fluid having a refraction index close to that of said transparent plates; and

an external connector connected to said leads.

27. A touch-panel input device according to claim 26 further comprising:

a position detection circuit connected to said external connector;

at least one of said transparent plates capable of resiliently flexing to change an electrical relationship between said conductive layers; and

said change in said relationship being measurable by said circuit effective to determine a point on said coordinate axis where said change in said relationship occurs.

28. A touch-panel input device according to claim 26, further including a conductive powder dispersed in said insulative fluid effective to decrease applied pressure needed to form said electrical connection.

29. A touch-panel input device according to claim 26, further including:

a transparent barrier layer between one of said conductive layers and said transparent plates; and

a transparent hard coat layer on an external surface of another of said transparent plates.