Wear resistant improved tablet for a digitizer

• US 5,466,895 A
• Filed: 01/07/1994
• Issued: 11/14/1995
• Est. Priority Date: 01/07/1994
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: MicroTouch Systems, Inc. (3M Company)
• Inventors: Logan, James D.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Shankar, Vijay
• Application Number:
  US08/178,500
• Time in Patent Office: 676 Days
• Field of Search: 178/18, 178/19, 345/173, 345/179, 345/177, 345/180
• US Class Current: 178/18.05
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

An improved tablet for a digitizer including a stylus and a tablet for digitizi An 5 Vt pV:stylus position on the tablet as a function of the stylus current distribution over the tablet includes a first resistive coating on the face of the tablet for conducting stylus current to a plurality of current sensors about the periphery of the tablet; and one or more additional resistive coatings covering the first resistive coating and connected electrically in parallel with the first resistive coating for providing an additional wearing layer to protect and prolong the life of the first reactive coating, the additional resistive coatings having resistance values higher than the first resistive coating.

Claims

1. An improved tablet for a digitizer including a stylus for digitizing stylus position on the improved tablet as a function of the stylus current distribution over the improved tablet comprising:

a first resistive coating on the face of the improved tablet for conducting stylus current to a plurality of current sensors about the periphery of the improved tablet; and

a second resistive coating, covering said first resistive coating and connected electrically in parallel with said first resistive coating, for providing an additional wearing layer to protect and prolong the life of said first resistive coating, said second resistive coating having a resistance value higher than said first resistive coating.

2. The improved tablet of claim 1 in which the resistance of said second resistive coating is at least double that of said first resistive coating.

3. The improved tablet of claim 1 in which the resistance of said second resistive coating is an order of magnitude greater than that of said first resistive coating.

4. The improved tablet of claim 1 in which the resistance of said second resistive coating is one hundred times greater than that of said first resistive coating.

5. The improved tablet of claim 1 in which said second resistive coating is approximately as thick as said first resistive coating.

6. The improved tablet of claim 1 in which said second resistive coating is thicker than said first resistive coating.

7. The improved tablet of claim 1 in which said second resistive coating is thinner than said first resistive coating.

8. The improved tablet of claim 1 in which said second resistive coating is a removable sheet.

9. An improved tablet for a digitizer including a stylus for digitizing stylus position on the improved tablet as a function of the stylus current distribution over the improved tablet comprising:

a first resistive coating on the face of the improved tablet for conducting stylus current to a plurality of current sensors about the periphery of the improved tablet; and

a plurality of additional resistive coatings connected electrically in parallel with each other and with said first resistive coating, each said additional resistive coatings covering the next previous coating beginning with said first resistive coating for providing additional wearing layers to protect and prolong the life of said first resistive coating, each of said additional resistive coatings having a different resistance which is higher than that of said first resistive coating.

10. The improved tablet of claim 9 in which the resistance of said additional resistive coatings is at least double that of said first resistive coating.

11. The improved tablet of claim 9 in which the resistance of said additional resistive coatings is an order of magnitude greater than that of said first resistive coating.

12. The improved tablet of claim 9 in which the resistance of said additional resistive coatings is one hundred times greater than that of said first resistive coating.

13. The improved tablet of claim 9 in which said additional resistive coatings are approximately as thick as said first resistive coating.

14. The improved tablet of claim 9 in which said additional resistive coatings are thicker than said first resistive coating.

15. The improved tablet of claim 9 in which said additional resistive coatings are thinner than said first resistive coating.

16. An improved digitizer, comprising:

a substrate;

a first resistive coating on the substrate for conducting stylus current; and

a second resistive coating on said first resistive coating, said second resistive coating connected electrically in parallel with said first resistive coating, for providing an additional wearing layer to protect and prolong the life of said first resistive coating, said second resistive coating having a resistance value higher than said first resistive coating.