| 摘要 |
1,215,247. Magnetic printing. E.I. DU PONT DE NEMOURS & CO. 12 Nov., 1968 [13 Nov., 1967], No. 53653/68. Heading B6C. [Also in Divisions C7 and H1] A thermomagnetic recording member comprises a film transparent to an exposing radia tion (i.e. transmitting 10-90%) containing a plurality of discrete indented areas arranged in a substantially regular pattern and containing discrete magnetic elements, the elements being provided with a coating of reflective material capable of shielding them from exposing radiation incident upon the coating in a direction normal to the plane of the film. The elements are capable of being magnetized to a hard state such that (BH) max = 0À08-8À0 x 10<SP>6</SP> gaussoersteds, B r = 500-21,500 gauss, He = 40- 6000 oersteds, and Curie point less than 1200‹ C. Specified reflective coatings are Au, Ag, Cu, Al, Cr, Ni, Fe, Ir, Pt, In, Sb, TiO 2 and MgO 2 . The magnetic material may be a ferrite or an alloy, and the transparent film a synthetic polymer. One recording member (Fig. 1) comprises a visible-light transparent film 1 bearing indentations filled with magnetic material 2 and coated with reflective material 4. Incident radiation 7 passes through the member to document 5 bearing portions 6 of different reflectivity. The structures may be made by coating with reflective material a film bearing impressed indentations removing by abrasion the reflective material lying within the indentations, and filling the coated indentations with particulate magnetic material in a binder. Examples describe the production of recording members consisting of (1) CrO 2 magnetic elements coated with silver and embedded in a polycarbonate film; (2) CrO 2 elements coated with TiO 2 in a cellulose acetate film. |
