Method for formation of invisible marking and method for reading of invisible marking
AssigneesKansai Paint Co., Ltd., Fujikura Ltd., Matsuo Sangyo Co., Ltd.
InventorsTsutomu Maruyama, Atsushi Akiyama, Kazuo Sanada, Sadao Chigira, Masanobu Hidaka
Life of this patent
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Abstract
Information is printed on the surface of a substrate with a marking ink containing a mixture of an indium-tin mixed oxide and at least one compound selected from the group consisting of alumina, barium sulfate, silicon dioxide and calcium carbonate, to prepare an invisible marking-printed material; and infrared rays of 2-10 .mu.m wavelength are applied onto the invisible marking-printed material to measure the infrared absorptivities of the invisible marking area and other area of said material and identify the information signified by the invisible marking.
Claims18
A method for formation of invisible marking, which comprises printing information on the surface of a substrate with a marking ink containing a mixture of an indium-tin mixed oxide and at least one compound selected from the group consisting of alumina, barium sulfate, silicon dioxide and calcium carbonate.
A marking ink containing a mixture of an indium-tin mixed oxide and at least one compound selected from the group consisting of alumina, barium sulfate, silicon dioxide and calcium carbonate.
Dependencies are inferred from the claim text.