Feldmuhle Aktiengesellschaft

Kurt Ramlow

Kurt Riecke

Guido Dessauer

Franz Wirnitzer

A recording sheet consisting mainly of fibrous material is capable of displaying a colored image when contacted under pressure with substantially colorless crystal violet lactone and similar dye precursors if at least 3% of the fibrous material is constituted by uniformly distributed asbestos fibers. Sheets having adequate strength for carbonless copying should not contain more than 30% asbestos fibers. Stronger colors are obtained if the sheet further contains a mixture of .gamma.-alumina and .gamma.-alumina precursors in an amount of 2% to 20% of the weight of the fibrous material, the mixture containing 1% to 30% water volatile at 1000.degree. C, and being converted substantially entirely to .gamma.-alumina when heated from 300.degree. to 1000.degree. C.

Recording material containing asbestos

A mixture of .gamma.-alumina and its precursors containing 1 to 30% water volatile at 1000.degree. C converts normally colorless dye materials such as crystal violet lactone, malachite green lactone, benzoyl leuco methylene blue and N-phenylleukauramine to the corresponding colored dyes upon contact, and improves the results achieved with recording material consisting essentially of a fibrous web and a pigment composition secured to the fibers of the web if the mixture amounts to at least 10% of the weight of the pigment composition. Particularly strong and stable colors are produced if the fibrous web is coated with a pigment composition prepared from an aqueous dispersion of the mixture and other pigments on which a basic compound is deposited from a water-soluble zinc salt by means of hydroxyl ions.

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Schafflund, Germany

Kurt Ramlow