MULTI-STEP ETCHING PROJECTION SYSTEM

• US 3,726,732 A
• Filed: 07/09/1970
• Issued: 04/10/1973
• Est. Priority Date: 07/09/1970
• Status: Expired due to Term

• Current Assignee: New Franklin Mint
• Original Assignee: James J. Keegan III, Robert W. Richardson
• Inventors: Richardson, Robert W., Keegan, James J. III
• Primary Examiner(s): Powell, William A.
• Application Number:
  US05/053,358
• Time in Patent Office: 1,006 Days
• Field of Search: 156/7,8,11,18,345 96/36,36.3 72/359
• US Class Current: 430/347
• CPC Class Codes: C23F 1/02 Local etching
• CPC Class Codes: G03F 7/2022 Multi-step exposure, e.g. hybrid; backside exposure; blanket exposure, e.g. for image reversal; edge exposure, e.g. for edge bead removal; corrective exposure

Abstract

An optical projection system employing ultraviolet light for step projection and repeat projection of imagery to the surface of a photoresist coated coining die so that the die may be etched to various levels in registration with other projections. This permits photofabrication of dies of various sizes from a single series of step and repeat photographic negatives, each of which is in photographic registration to each other and to the respective etched surface of the coining die being fabricated. Filtered light permits visual examination of the projected imagery prior to exposure of the photoresist surface on the die. Enlargements and reductions are also possible with suitable lens systems.

Claims

2. A method in accordance with claim 1 wherein said step of projecting a second image includes projecting the second image so that it at least partially overlies the first cavity.

3. A method in accordance with claim 1 including using a tool steel as the metal from which the die is made, and using an acid to etch the cavities.

4. A method in accordance with claim 1 including the step of coining coins by use of said etched die face.

5. A method in accordance with claim 1 wherein application of the photoresist material includes pouring it onto the die face while the die face rotates about a vertical axis.

6. A method in accordance with claim 1 including baking the photoresist material on the die face before each exposure, to reduce sensitivity of the photographic resist.