Claims
- 1. A composite plastic part of thermoplastic materials having good adhesion and compatability with one another and similar contraction behavior and having material properties altered by a laser beam, the composite plastic part having a thermoplastic surface layer with a layer thickness of from 0.1 to 2 mm, a light transmission value .tau. of greater than 0.8 and more particularly greater than 0.9 at a wavelength of from 1000 to 20,000 um, and an internal thermoplastic material region below the surface layer with a light absorption value to a depth of 2 mm of greater than 80% of incident laser beams, internal thermoplastic material region containing a subsequently laser induced change therein.
- 2. A composite plastic part as in claim 1 wherein the internal thermoplastic material region contains metallic inclusions.
- 3. A composite plastic part as in claim 1 wherein the internal thermoplastic material region consists of polyacrylonitrile.
- 4. A composite plastic part as in claim 1 wherein the subsequently laser induced change in the internal thermoplastic material region is in the form of a carbonized electrically conductive path.
- 5. A composite plastic part as in claim 3 wherein the subsequently laser induced change in the internal thermoplastic material region is in the form of a carbonized electrically conductive path.
- 6. A composite plastic part as in claim 1 wherein one thermoplastic material is cellulose acetate and the other thermoplastic material is at least one of acrylonitrile-butadiene-styrene, cellulose acetate and ethylene vinyl acetate.
- 7. A composite plastic part as in claim 1 wherein one thermoplastic material is polycarbonate and the other thermoplastic material is at least one of polycarbonate and acrylonitrile-butadiene-styrene.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 3411797 |
Mar 1984 |
DEX |
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SUMMARY OF THE INVENTION
This application is a division of application Ser. No. 716,757 filed Mar. 27, 1985 pending.
This invention relates to a plastics part and to a laser process for altering material properties, more particularly for marking a plastics part beneath its surface.
Visible or invisible marking is necessary for certain plastics parts to identify their function so that they may be operated accordingly (for example, keys) or electronically scanned.
Tampo-printing, screen printing and transfer printing are all known processes in which the identifications are applied by printing.
The disadvantage of these processes lies in the fact that the identification can become unreadable through mechanical damage (scratches), abrasion and chemical influences and, as a result, no longer fulfills its function. In addition, the imprint is particularly difficult to apply to curved or textured surfaces. Tooling and block costs are particularly high in the case of unit production.
Plastics parts in which the identification is produced by two-colour injection moulding are also known. This process is very expensive because separate complicated tools are required for each colour. Tooling costs are high. Changing the identification involves considerable effort so that this process is only suitable for high-volume production.
Laser beam processes in which the idenification is burnt onto the surface of the plastics part are also known. These processes are attended by the disadvantage that the rough surface has to be coated with a transparent lacquer on account of the danger of contamination and the unpleasant feel, and this is a very involved operation in the case of mass-produced parts and therefore very expensive.
An object of the present invention is to provide a flexible, fast process with suitable plastics parts by which it is possible to obtain a permanent change in material properties, more particularly marking with characters, which can be detected at any time by selected means (magnet, light, electricity) and which cannot be subsequently influenced by chemical or mechanical damage or by deliberate manipulation (tamper-proof).
According to the invention, this object is achieved in that at least one laser beam passes through the surface zone of a first plastic material nearly with virtually no losses of energy, in order subsequently to produce by absorption of the laser beam in a following, inaccessible region of plastic material new, permanent detectable material properties.
It is surprising to the expert to combine several layers having different absorption coefficients, for example, by the two-component process, in such a way that a laser beam passes through the upper, predominantly transparent region of plastics material without major energy losses (.ltoreq.10) and hence without affecting this material, and the shortest path is then absorbed by the material, particularly plastics material, in a following region not directly accessible from outside, to such an extent that the heat generated in that region brings about a change in colour and transformation of the molecular structure or destruction (cut) of the material. Using a program-guided laser beam, it is possible by this process quickly and economically to obtain a clearly defined marking which can be read back at any time. The outer plastics material, which may be transparent to the eye or opaque to electronic reading, acts as a wave window of which the smooth outer surface protects the internally situated marking against mechanical or chemical damage and contamination. The marking cannot be subsequently altered without destruction. In addition, interruptions may be specifically produced, in particular, in a reflecting layer, the arrangement of which; may be subsequently read by digital means.
US Referenced Citations (4)
Divisions (1)
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Number |
Date |
Country |
| Parent |
716757 |
Mar 1985 |
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Patent Grant
4822973
