An information carrying sheet of securities, identification cards and the like which is provided with an illegal copying preventive image pattern in which the existence of an illegal copying preventive image pattern is hardly discriminated by the naked eye. An illegal copying preventive image pattern which prevents an unnecessary exposure by combining a plurality of patterns having an absorption in different regions used in the sheet and incorporating a dummy pattern, and which is difficult to perform falsifying/altering/counterfeiting action; and an ink composition which is used for the image pattern, and has a high IR absorption. Whether copying is acceptable or not can be promptly judged with a less memory capacity to shorten copying processing time, and falsifying/altering/counterfeiting action can be securely prevented in such a manner that the application of an illegal copying preventive processing is not noticed easily by a third party.