Method of laser marking

• US 4,861,620 A
• Filed: 10/22/1987
• Issued: 08/29/1989
• Est. Priority Date: 11/14/1986
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Sakaki, Masaaki, Azuma, Kenkoku
• Primary Examiner(s): LUSIGNAN, MICHAEL R
• Application Number:
  US07/111,320
• Time in Patent Office: 677 Days
• Field of Search: 427/53.1, 346/1.1, 346/108, 430/962, 430/348, 430/349, 430/363, 430/365, 430/945, 430/964
• US Class Current: 427/556
• CPC Class Codes: B41M 5/26 Thermography B41M5/20, B41M5/24 take precedence; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used B23K takes precedence; thermographic or photothermographic systems using noble metal compounds G03C1/494
• CPC Class Codes: B41M 5/28 using thermochromic compounds or layers containing liquid crystals, microcapsules, bleachable dyes or heat- decomposable compounds, e.g. gas- liberating B41M5/38271 takes precedence
• CPC Class Codes: B41M 5/34 Multicolour thermography
• CPC Class Codes: B44C 1/005 by altering locally the surface material surface treatment to obtain special artistic surface effects or finishes B44D5/00
• CPC Class Codes: B44F 1/08 characterised by colour effects
• CPC Class Codes: B44F 1/10 Changing, amusing, or secret pictures
• CPC Class Codes: C09K 9/00 Tenebrescent materials, i.e. materials for which the range of wavelengths for energy absorption is changed as a result of excitation by some form of energy
• CPC Class Codes: C09K 9/02 Organic tenebrescent materials
• CPC Class Codes: Y10S 430/146 Laser beam

Abstract

A pigment layer is provided on a surface of an article on which a marking is to be formed and is irradiated with patterned laser light to change internal molecular structure of pigment to thereby change its color. The marking can be multicolored by a suitable selection of pigment and laser energy density.

Claims

1. A method of marking an article surface comprising the steps of

coating the article surface with pigment or mixing the pigment into the material of the article, wherein said pigment is capable of changing its original color to another color at or higher than a predetermined temperature, and

irradiating portions of the pigment coating with a marking laser light, whereby the irradiated portions are marked by the another color,

wherein said pigment is a combination of a plurality of different pigments providing different colors at different temperatures, respectively, and said marking laser is a mixture of a corresponding number of laser beams having different energy densities necessary to heat said article surface to said different temperatures, respectively, whereby said irradiated portions of said article surface are marked with said different colors.

2. The method as claimed in claim 1, wherein said pigment contains material capable of changing its original color to another color by a change of its internal molecular structure caused by heat given by said laser light.

3. The method as claimed in claim 2, wherein said pigment is selected from a group consisting of Hg compound, cobalt compound, potassium cobaltienitride, copper compound, nickel compound, lead compound, iron compound, vanadium compound and any mixture thereof.

4. The method as claimed in claim 1, wherein said portions of said pigment layer are irradiated with laser light of different energy density, respectively.