Abstract: The present invention provides a polyolefin resin-based marking composition capable of developing a vivid color in dark brown to black on irradiation with laser beams, moldings of the composition, and a laser marking method. The marking composition comprises a polyolefin resin-based marking composition containing from 0.005% by weight to less than 0.5% by weight of a silicon compound based on the polyolefin resin.

Abstract: A marking composition comprising an energy ray curing resin, a leuco dye and a color developer both of which are low in solubility in toluene, which composition is capable of forming a vivid black color on irradiation with laser beams, and a laser marking method for forming a clear-cut black-colored mark by using the above composition.

Abstract: The present invention relates to a marking composition capable of developing a vivid white color upon the application of laser beams, which composition comprises a polyolefin resin having no fluidity at a temperature of 50.degree. C. and at least one inorganic material selected from talc, calcium carbonate and aluminum hydroxide, wherein the inorganic material is blended in a ratio of 1-300 w/w % based upon the polyolefin resin. The invention also provides the resin moldings obtained by molding the marking compositions.

Abstract: This invention relates to a laser marking method which comprises heating a base article having on its surface a thin film of a laser marking composition containing a color former and a color developer having a melting point of 200.degree. C. or above, and then applying laser light to the thin film. The method of this invention is capable of no-break marking with vivid color development by application of laser light, without causing discoloration of the ground even under a condition of 120.degree. C. or above.

Abstract: This invention relates to a laser marking method which comprises coating a laser marking composition containing as essential components a color former, a color developer and an inorganic compound having the absorption peak on the infrared absorption spectrum in the region of 900-1,000 cm.sup.-1 on a substrate to form a color developing layer, and irradiating laser light to the color developing layer; the laser marking composition; and articles having a color developing layer made of the laser marking composition. The method of this invention is capable of forming a mark with vivid color development even when the color developing layer is a thin film of less than 5 .mu.m in thickness or when marking is carried out at high speed.