Abstract: The label printing apparatus has a structure including: a label feed means for successively feeding plural labels, each having an information printing area including a heat-sensitive color developing ink layer, to predetermined printing positions; a laser printing device which is provided with a sensor and a light source, said sensor serving to discriminate between presence and absence of the label in the predetermined printing position and to output a label detection signal, said light source serving to release a laser beam, and which receives the label detection signal directly from the sensor, prints information on the label by means of the laser beam when the presence of the label on the predetermined printing position is confirmed by the label detection signal, and outputs a shot signal; and a controller to discriminate whether the output interval between the shot signals is within a given period of time or not and to output an error signal when the output interval between the shot signals is not within

Abstract: A non-destructive laser marking method including irradiating laser light on a thermosensitive color-forming layer formed by printing with a printing ink containing a leuco dye as a color former and an acidic substance as a color developer, and at least one background color formation inhibitor selected from the group consisting of a water-soluble amino acid, an ammonium salt of an inorganic acid, a pH buffer, and water. Laser marking can be achieved with low energy and at high speed while minimizing background color formation to provide a high-contrast color image.

Abstract: A resin composition for laser-marking which comprises at least one inorganic compound selected from the group consisting of anhydrous metal borate salt, an anhydrous metal phosphate salt, a phosphoric acid-containing glass, basic zinc carbonate and basic magnesium carbonate, and a resin; and a method for laser-marking the surface of an object composed of the said resin composition by applying laser beams onto the surface.

Abstract: A laser-marking composition characterized by containing a non-black inorganic lead compound and a resin and a laser-marking method characterized by marking the surface of an object comprising said composition by exposure to laser beams having wavelengths falling in the far infrared regions.