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Erasable Thermal Writing for Displays and Terminals

IP.com Disclosure Number: IPCOM000078118D
Original Publication Date: 1972-Nov-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Zappe, HH: AUTHOR

Abstract

As shown in Fig. 1, a clear sheet of plastic has a roughened side and is backed by a dark sheet of paper impregnated with wax. Light which strikes the plastic sheet is scattered by the rough side and diffuses back, giving the sheet a slightly greyish appearance. If the dark wax paper is brought into close contact with the plastic, light will not be diffused back and the plastic will appear dark at the area of contact. Erasing is obtained by rupturing the contact between the plastic and the wax paper.

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Erasable Thermal Writing for Displays and Terminals

As shown in Fig. 1, a clear sheet of plastic has a roughened side and is backed by a dark sheet of paper impregnated with wax. Light which strikes the plastic sheet is scattered by the rough side and diffuses back, giving the sheet a slightly greyish appearance. If the dark wax paper is brought into close contact with the plastic, light will not be diffused back and the plastic will appear dark at the area of contact. Erasing is obtained by rupturing the contact between the plastic and the wax paper.

Thermal writing is used to melt the wax in well-defined areas. Wire heating elements are located close to the dark wax paper and current through these wires causes localized melting of the wax. As shown in Fig. 2, the array of heating elements can have a variety of forms. Such an array can be used to provide outlines of numbers and letters, such as the number 7 which is indicated in dashed lines in Fig. 2.

Each heating filament is connected to a current driver which generates a short current pulse in it, if it is selected by a decoder containing the information to be written. The sheet of plastic and the wax paper are placed on top of this writing head, and optical contact with the dark paper is achieved through melting of the wax in well-defined areas. Mechanical rupture between the plastic sheet and the wax paper provides erasure.

The use of thermal writing means that the wax need not be very soft. A compound with...