Method and apparatus for producing a relief pattern with a microscopic structure, in particular having an optical diffraction effect

• US 4,761,253 A
• Filed: 01/29/1987
• Issued: 08/02/1988
• Est. Priority Date: 07/06/1984
• Status: Expired due to Term

• Current Assignee: OVD Kinegram AG (Leonhard KURZ Stiftung & Company KG)
• Original Assignee: LGZ Landis & Gyr Zug AG (Landis+Gyr Group AG)
• Inventors: Antes, Gregor
• Primary Examiner(s): Lowe, James
• Application Number:
  US07/014,096
• Time in Patent Office: 551 Days
• Field of Search: 264/1.3, 264/2.7, 264/284, 264/293, 264/1.4, 264/1.7, 264/25, 264/40.1, 425/174.4, 425/385, 425/150
• US Class Current: 264/1.31
• CPC Class Codes: B29C 2035/0838 using laser
• CPC Class Codes: B29C 59/02 by mechanical means, e.g. pressing B29C59/007 takes precedence; embossing expanded porous articles B29C44/5627
• CPC Class Codes: B29K 2101/12 Thermoplastic materials
• CPC Class Codes: B29L 2011/00 Optical elements, e.g. lenses, prisms
• CPC Class Codes: B29L 2017/003 Records or discs
• CPC Class Codes: G03H 1/0236 Form or shape of the hologram when not registered to the substrate, e.g. trimming the hologram to alphanumerical shape substrates bearing a hologram G03H1/0272
• CPC Class Codes: G03H 1/0244 Surface relief holograms replicating hologram without interference recording G03H1/0276
• CPC Class Codes: G03H 1/028 by embossing
• CPC Class Codes: G03H 2001/0497 Dot matrix holograms
• CPC Class Codes: G03H 2224/06 Thermal or photo-thermal means infra red source G03H2222/16
• CPC Class Codes: G03H 2260/61 Producing material deformation
• CPC Class Codes: G06K 1/126 by photographic or thermographic registration recording apparatus for measuring instruments G01D15/00
• CPC Class Codes: G06K 19/16 the marking being a hologram or diffraction grating

Abstract

A method and apparatus for embossing a pattern having a microscopic relief structure, such as, for example, an optical diffraction grating, onto a layer of thermoplastic material is disclosed. A small circular region of a flexible embossing die is pressed against the thermoplastic layer by means of a punch. A fraction of the corresponding small circular region of the thermoplastic layer is then heated from the rear by a beam of radiant energy. The process may be repeated at all points on the thermoplastic layer where the pattern is desired.

Claims

1. A method of embossing a pattern, having a microscopic relief structure of the type which produces an optical diffraction effect, onto the surface of a layer of thermoplastic material comprising the steps of:

a. placing a flexible embossing die, in the form of a foil, bearing a microscopic relief structure to be reproduced in the thermoplastic layer, in closely-spaced but not touching relationship with said layer of thermoplastic material;

b. applying an embossing pressure to a small, substantially circular region, of said flexible embossing die, whereby said region of said flexible embossing die is brought into embossing contact with a correspondingly small, substantially circular region of said thermoplastic layer;

c. placing a radiant source of thermal energy so that said thermoplastic layer is between said flexible embossing die and said radiant source of thermal energy;

d. focussing said thermal energy onto a focal spot in the region of said thermoplastic layer which is in embossing contact with said flexible embossing die, thereby causing said region of said thermoplastic layer to heat up and soften;

e. interrupting said thermal energy, whereby said small substantially circular region of said thermoplastic layer is allowed to cool and harden, thereby fixing said microscopic relief structure in said small, substantially circular region of said thermoplastic layer;

f. removing said embossing pressure from said small, substantially circular region of said flexible embossing die, whereby embossing contact with said small substantially circular region of said thermoplastic layer is ended; and

g. repeating above steps as many times and in as many regions of said thermoplastic layer as is required to form the desired pattern.

2. The method as recited in claim 1, wherein said embossing pressure is applied only in the region of said focal spot.

3. The method as recited in claim 2, wherein said embossing pressure is applied in said region of said focal spot by means of a punch having a convex surface.

4. A method according to claim 1 wherein interconnected strip-like regions, of said microscopic relief structure of said flexible embossing die, are formed in said thermoplastic layer by continuously displacing said flexible embossing die and said thermoplastic layer relative to said focal spot.

5. A method as recited in claim 1, wherein said thermoplastic layer is repositioned, relative to said focal spot when said beams of thermal energy are interrupted and when said embossing pressure is removed.

6. A method according to claim 5 wherein said flexible embossing die is turned or replaced, during said repositioning.

7. A method according to claim 1 wherein a pattern original is scanned by means of an optical-electronic scanning device, and synchronously with respect thereto said flexible embossing die and said thermoplastic layer are displaced relative to said focal spot and said radiant source is controlled in dependence on the output signal of said scanning device.

8. A method of embossing a pattern, having a microscopic relief structure of the type which produces an optical diffraction effect, onto the surface of a substrate covered with a layer of radiant energy absorbing thermoplastic material comprising the steps of:

(a) placing a flexible embossing die, in the form of a foil, bearing a microscopic relief structure to be reproduced in the thermoplastic layer, in closely-spaced but not touching relationship with said layer of thermoplastic material;

(b) applying pressure to said embossing die, whereby said flexible embossing die is brought into contact with said thermoplastic layer and an elastic deformation occurs;

(c) placing a radiant source of thermal energy so that said thermoplastic layer is between said flexible embossing die and said radiant source of thermal energy;

(d) focussing said thermal energy through said transparent pressure plate and substrate in a small region of said radiation absorbent thermoplastic layer which is in contact with said flexible embossing die, thereby causing said region of said thermoplastic layer to heat up, soften and to be plastically deformed;

(e) interrupting said thermal energy, whereby said small region of said thermoplastic layer is allowed to cool and harden, thereby fixing said microscopic relief structure in the form of an approximately circular surface region of said thermoplastic layer;

(f) removing pressure from said flexible embossing die, whereby contact with said small substantially circular region of said thermoplastic layer is ended; and

(g) repeating steps d and e as many times and in as many regions of said thermoplastic layer as is required to form the desired pattern.

9. A method according to claim 8, wherein interconnected strip-like regions of said microscopic relief structure of said flexible embossing die are formed in said thermoplastic layer by continuously displacing said flexible embossing die and said thermoplastic layer relative to said focal spot.

10. A method according to claim 8, wherein said thermoplastic layer is displaced in a stepwise manner relative to said focal spot when said beams of thermal energy are interrupted and when said pressure is removed.

11. A method according to claim 10, wherein said flexible embossing die is turned or replaced during said stepwise displacement.

12. A method according to claim 8, wherein a pattern original is scanned by means an optical-electronic scanning device, and synchronously with respect thereto said flexible embossing die and said thermoplastic layer are displaced relative to said focal spot and said radiation energy beam source is controlled according to the output signal of said scanning device.

13. An apparatus for embossing a pattern having a microscopic relief structure of the type which produces an optical diffraction effect, onto the surface of a substrate covered with a layer of radiant energy absorbing thermoplastic material, said apparatus comprising a flat, rigid and optically transparent pressure plate capable of supporting said substrate and said radiant energy absorbing thermoplastic layer, a flexible embossing die spaced apart from said pressure plate for receiving said substrate, said embossing die being capable of being placed on said thermoplastic layer of said substrate, but not in embossing contact with said thermoplastic layer, a punch located on the other side of said flexible embossing die from said substrate, a radiant energy beam source located on the other side of said pressure plate from said substrate, focussing means located between said radiant energy beam source and said pressure plate capable of producing a focal spot of said beam source on said substrate, said focal spot heating a circular surface element of said thermoplastic layer on said substrate, said punch having a convex surface and being capable of being positioned so as to produce through said embossing die an embossing pressure only in the region of said focal spot onto said thermoplastic layer, said embossing die and said substrate with said thermoplastic layer being capable of being displaced, in a plane parallel to said thermoplastic layer, relative to said focal spot and said punch.

14. An apparatus according to claim 13 wherein said punch includes a ballholder defining a cylindrical chamber and a ball which is capable of a freely rolling movement in said cylindrical chamber, of projecting partly out of said chamber and of acting as a piston in said chamber, the ballholder being capable of guiding the ball towards the embossing die, of exerting a force upon the embossing die and of building up the embossing pressure by the air pressure built up in said chamber behind the ball by means of a controlled inflow of compressed air and of the leakage of air between the ball and the wall of said chamber.

15. The apparatus of claim 13, wherein said apparatus further comprises

an optical electrical scanning device, and

displacement means for guiding asid scanning device over a pattern original for synchronously displacing said embossing die and said thermoplastic layer relative to said focal spot and said punch,

said scanning device having an electrical output connected to a control input of said beam source.

16. An apparatus for embossing a pattern having microscopic relief structure of the type which produces an optical diffraction effect onto the surface of a substrate covered with radiant energy absorbing thermoplastic material, said apparatus comprising a flat, rigid optically transparent pressure plate capable of supporting said substrate with a radiant-energy absorbing thermoplastic layer, a flexible embossing die spaced apart from said pressure plate by said substrate and capable of being positioned on said thermoplastic layer of said substrate, a punch located on the other side of said flexible embossing die from said substrate being capable of pressing the flexible embossing die onto said thermoplastic layer so that only an elastic deformation on the surface of said thermoplastic layer occurs, a radiation energy beam source located on the other side of said pressure plate from said substrate, focussing means located between said radiation-energy beam source and said pressure plate capable of concentrating the energy of said beam source in a focal spot through the pressure plate on through said substrate in said thermoplastic layer and heating a small region of thermoplastic layer on said substrate so that said thermoplastic layer softens and yields to said embossing die under the pressure of said punch by a plastic deformation, whereby the embossing occurs only in the region of said focal spot, said flexible embossing die and said substrate with said thermoplastic layer capable of being displaced in a plane parallel to said thermoplastic layer relative to said focal spot and said punch.