Method for the selective closing of the pores of the surface of thermo-plastic porous material

• US 5,858,298 A
• Filed: 07/23/1997
• Issued: 01/12/1999
• Est. Priority Date: 01/24/1995
• Status: Expired due to Term

• Current Assignee: Millennium Marking Company (Trodat Trotec Holding GmbH)
• Original Assignee: Leo-henn Humal
• Inventors: Humal, Leo-Henn
• Primary Examiner(s): Tentoni, Leo B.
• Application Number:
  US08/875,311
• Time in Patent Office: 538 Days
• Field of Search: 264/321, 264/413
• US Class Current: 264/413
• CPC Class Codes: B23K 26/18 using absorbing layers on the workpiece, e.g. for marking or protecting purposes
• CPC Class Codes: B29C 2035/0838 using laser
• CPC Class Codes: B29C 35/0894 provided with masks or diaphragms
• CPC Class Codes: B29C 44/5636 with the addition of heat
• 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 2105/04 cellular or porous
• CPC Class Codes: B41C 1/055 Thermographic processes for producing printing formes , e.g. with a thermal print headB41C1/02 takes precedence; fabrication of relief or intaglio plates by ablative recording with a laser beam B41C1/05; production of lithographic forms B41C1/10; producing of screen printing forms or stencils B41C1/14

Abstract

A method for closing of the pores of selected areas of the surface of thermo-plastic porous material (7), comprising heating of selected areas of the surface of the porous material (7) by light radiation. Simultaneously, the surface of the porous material (7) is compressed by a transparent smooth body (11). According to the embodiment (I), the surface of the porous material (7) is scanned over by one of the several focused light beams, that are switched on and off. According to the embodiment (II), between the porous material (6) and the smooth transparent body (11), a transparent means containing a light-absorbing pattern (9) of surface elements with pores being left open is placed, whereas the distance between the light-absorbing surface (10) and the surface (7) of the porous material (6) is at least 0.02 mm, or, according to embodiment (III), it is a means with low light-absorption (14) containing a light-absorbing pattern (15) of the surface elements with pores to be closed, that is in good thermal contact with the surface (7) of the porous material (6), and a light of high intensity is conducted through the transparent smooth body (11).

Claims

1. A method for closing pores located in selected areas of the surface of a thermo-plastic porous material, comprising the steps of heating said selected areas by light radiation and compressing said surface using a smooth transparent body simultaneous with said heating.

2. The method according to claim 1, wherein said surface is scanned by at least one focused light beam which is switched on while scanning said selected areas and which is switched off at the areas of said surface with pores to be left open and wherein the power and the scanning speed and the number of repeated scans of said at least one light beam are chosen so that the heat produced by said radiation is absorbed by said surface to melt said surface so that the pressure applied by said smooth transparent body closes pores located in said selected areas of said surface.

3. The method according to claim 1, wherein a transparent means containing a light-absorbing pattern covering areas of said surface having pores to be left open is placed between said smooth transparent body and said porous material such that said light-absorbing pattern is at least 0.02 mm from said surface and wherein light of high intensity is conducted through said smooth transparent body with a power density at said surface and an exposure time chosen so that the areas of said surface not covered by said light-absorbing pattern melt under said exposure so that the pressure applied by said smooth transparent body closes the pores in said uncovered areas of said surface and wherein the light that has been absorbed by said light absorbing pattern is not sufficient to melt the areas of said surface covered by said light absorbing pattern such as to cause the pores located in said covered areas of said surface to close.

4. The method according to claim 1, wherein a means of low light absorption which contains a light-absorbing pattern that covers said selected areas of said surface is placed between said smooth transparent body and said porous material such that said light absorbing pattern is in thermal contact with said surface and wherein light of high intensity is conducted through said smooth transparent body with a power density at said surface and an exposure time chosen so that the areas of said surface covered by said light-absorbing pattern melt under said exposure so that the pressure applied by said smooth transparent body closes the pores in said covered areas of said surface and wherein the light that falls onto the uncovered areas of said surface is not sufficient to cause the pores in said uncovered areas of said surface to close.