Particles emitting fluorescence by irradiation of infrared ray and forgery preventing paper using the same

摘要

An infrared fluorescent particles emitting fluorescence upon irradiation with infrared rays, and anti-falsification paper in which the particles are contained and the particles emitting fluorescence at a specific hue can be clearly recognized visually upon irradiation with infrared rays are provided. The infrared fluorescent particles comprise granules of a powdery material and a coating layer of a water-insoluble infrared fluorescent pigment emitting fluorescence upon irradiation with infrared rays formed on the surface of the granule. Water resistance can be imparted to the particles by using a resin having reactive groups capable of reacting with hydroxyl groups of the powdery material in combination as a binder upon coating, or by incorporating an anionic binder or a cationic binder in the granules and incorporating a cationic material or an anionic material in the coating layer. When a water-insoluble ultraviolet fluorescent pigment emitting fluorescence upon irradiation with ultraviolet rays is mixed with the infrared fluorescent pigment and used together, particles in which the infrared fluorescent pigment emits fluorescence upon irradiation with infrared rays and the ultraviolet fluorescent pigment emits fluorescence upon irradiation with ultraviolet rays can be obtained. By inclusion of the infrared fluorescent particles in paper, anti-falsification paper excellent in the anti-falsification effect can be obtained.