Printing – Bed-and-platen machines – Inker
Patent
1998-02-02
1998-10-06
Funk, Stephen R.
Printing
Bed-and-platen machines
Inker
101327, 101364, B41F 140
Patent
active
058161589
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATION
This application is a 371 of PCT/US97/18173, filed Oct. 7, 1997, which claims the benefit of U.S. provisional application Ser. No. 60/027,303, filed Oct. 10, 1996, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention resides in a process for transferring dots, lines, or geometric designs of liquid print material from a bath of the material to a flat or curved surface.
2. Description of the Prior Art
Included among the wide variety of commercially used printing processes are rotogravure, reverse roller coating, the transfer of dots or lines by use of dispensing methods or intinction, and the transfer of dots or lines by dipping a needle or an engraved stamp into a liquid ink or plastic. Printing processes that are used routinely in the electronics industry include screen printing, stenciling, and tampo printing.
In the electronics industry, printing processes are used for applying marking inks, structural adhesives and die attach materials to various different substrates. These substances are applied in the form of pastes or dispensable liquids that typically contain a carrier solvent to achieve the desired viscosity. When carrier solvents are used, a problem commonly encountered is the fouling of the transfer stamp or print medium when the solvent evaporates. This problem is particularly acute when conductive materials such as silver particles are included in the print material, or when the print material is a solder paste that contains lead or zinc particles or a solder or frit glass compound that contains lead oxide.
SUMMARY OF THE INVENTION
This invention eliminates the adverse effects of solvent evaporation by immersing the stamp or engraved print design (referred to in the electronics industry as a "die" or a "stamping die") in a bath of the material to be printed, with the raised (negative) design pattern facing upward. The bath contains the print material in liquid form at a viscosity that will permit drainage at a controlled rate. Once the die is immersed in the bath, the print is made by vertically displacing the raised negative from the liquid level to expose the wet raised negative. With the wet raised negative still facing upward, the part or surface to be printed is then placed in contact with the wet raised negative to transfer the print material in accordance with the raised negative pattern. Exposure of the wet raised negative can be done by lowering the liquid level of the bath or by holding the liquid level stationary while raising the die itself. Movement of the die in a highly controlled fashion can be achieved by mounting the die on a mechanical stage or device to physically raise the die out of the liquid in mechanized fashion. Exposure of the wet die surface can also be achieved by a combination of both a movable die and a movable liquid level.
These and other features and advantages of the invention and its preferred embodiments will become apparent from the description that follows.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of an apparatus for an inverted stamping process in accordance with this invention.
FIGS. 2a, 2b, 2c, 2d, and 2e are vertical cross section views, each showing two cross sections taken at right angles to each other, of a print material bath and a surface to be printed, the five figures depicting five stages of a process in accordance with this invention.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
The design to be printed in accordance with this invention can be any configuration with sharply defined boundaries, including designs that are ornamental, functional, or a combination of both. The invention is applicable to designs printed on continuous surfaces or discontinuous surfaces, and the design can cover part of the surface or the entire surface.
The raised negative will be configured to produce the design when the negative is contacted with the surface that the design is to be printed on. Fo
REFERENCES:
patent: 2700629 (1955-01-01), Townsend
patent: 2905085 (1959-09-01), Mercer et al.
patent: 3140655 (1964-07-01), Lally
patent: 3741764 (1973-06-01), Weglin
patent: 5095817 (1992-03-01), Takamura
patent: 5127330 (1992-07-01), Okazaki et al.
M.B. Rossman, "Hot-Melt Printing Technologies," Tappi Journal (Apr. 1992) 75(4): 111-115.
Funk Stephen R.
RJR Polymers, Inc.
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