Plastic and nonmetallic article shaping or treating: processes – Pore forming in situ – Including surface treatment of porous body
Reexamination Certificate
1998-12-29
2001-01-30
Dixon, Merrick (Department: 1774)
Plastic and nonmetallic article shaping or treating: processes
Pore forming in situ
Including surface treatment of porous body
C264S050000, C264S046500, C264S045800, C264S288800, C430S300000, C430S307000, C430S330000
Reexamination Certificate
active
06180036
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of image plates. More specifically, this invention relates to an image plate formed from a pre-inked thermoplastic medium which is inked prior to processing with an imaging device. Disclosed herein is a pre-inked open-celled thermoplastic material for use with thermal imaging techniques as well as a method of use and manufacture of the pre-inked thermoplastic material.
BACKGROUND OF THE INVENTION
In recent years, the field of manufacturing or producing printing plates such as rubber stamps has experienced rapid advancement, especially in the methods used to fabricate the stamps. Resinous relief printing plates, planographic printing plates, and intaglio printing plates all formed using photosensitive resins now enjoy widespread use. In addition, a number of methods are known for forming printing plates using stencil images. These methods generally involve the use of a thermal printer or a wire dot printer to form a stencil image on a sheet, which is then utilized as a printing plate. These are but a few of the common techniques for forming images on a printing plate or stamp. As disclosed in the related art, the principal areas of stamp manufacturing focus principally on three areas and combinations or modifications thereof which can be classified as molding, etching, and thermal imaging.
In recent years, the art has focused on photosensitive polymers which are selectively exposed to photo rays and harden upon exposure. In a typical manufacturing process utilizing photosensitive polymers, the image to be duplicated on the stamp is prepared or generated using a computer software program, typesetting, or another selected method. The designed image or art is generated using these methods. After the art is camera ready, a photograph is taken and a negative is made. The negative is then placed over a photopolymer plate, after which an ultraviolet light is impinged upon the negative. The ultraviolet light cures the polymer to which it is exposed and any uncured resin is washed away in a washout unit. At this point the photopolymer plate is placed in contact with ink in order to act as a carrier of the ink. It is known that the steps in preparing the artwork in camera ready format, making the negative, and washing away uncured photopolymer, account for more than half the materials and two-thirds of the labor used in manufacturing the stamps. It is also known that these materials are typically thrown away after the particular stamp is made because they are useless for anything but identical stamp preparation. Further, it is known that the process of curing the photopolymer plate using ultraviolet light is both expensive and may have a negative impact on the environment.
Another method involves a complicated process for producing either a metal printing plate or a photosensitive resinous printing plate. In addition, the use of a press machine or heated roller is required for this process. Further, positioning the embossing plate properly on a plate prior to pressing can be challenging to even those highly skilled in the art, and deviation from the proper position can readily occur.
U.S. Pat. No. 5,665,524, which is hereby incorporated herein in its entirety by reference, describes a printing plate which is formed from an open celled thermoplastic medium wherein the open cells are sealed upon exposing to energy rays. The methods described in this reference generally require the use of a negative to block photorays which results in a portion of the photosensitive thermoplastic medium remaining open, unfused or unsealed (these terms refer interchangeably to the fact that thermoplastic foam retains open-cell characteristics) by blocking the energy rays, and a separate portion which is fused or sealed (impermeable to ink) by exposure to the energy rays. The exposed portion forms a background of the image to be formed on the stamp. The background portion prevents the transfer of ink from the thermoplastic foam to the receiving medium, i.e. paper, in these regions. As is common in the related art and as is specifically discussed in this reference, it is not until the image is formed on the sheet that the sheet is exposed to or soaked in ink to absorb the ink which is to be transferred to a print medium. Some of the common reasons associated with inking the plate after the image is formed is to substantially eliminate unwanted effusion or release of the ink. Additionally, adverse conditions may result (i.e., heat dispersion) as a result of heat transfer characteristics of the ink. These and other adverse consequences are recited in U.S. Pat. No. 5,460,757 which is hereby incorporated herein in its entirety by reference. This reference is directed to a gel or colloidal dispersion of uncured or unformed polymer and ink constituents.
SUMMARY OF THE INVENTION
The present invention primarily focuses on the manufacture and use of printing plates comprised of open-celled images on sheets of thermoplastic resins. More specifically, the invention focuses on the use of post-cured or pre-formed thermoplastic resin in the form of sheets, which are then processed via imaging processes known in the art, including thermography and photo flash imaging to form an image of open-cells on a printing plate. In this regard, the related art is deficient in teaching the use of a thermoplastic sheet medium which may be inked prior to forming the images thereon. Although forming a pre-ink stamp is known in the art, the pre-ink material is either in liquid form or gel form. The present invention is directed to a preformed or hardened thermoplastic recording material or thermoplastic sheet which contains an ink constituent at a predetermined concentration to be used in an imaging process whereby open-cells of the thermoplastic medium are heated and sealed in predetermined areas and other areas of open-cells are not heated and left open so that they can transfer an ink constituent contained within the thermoplastic sheet to material to be printed on. When the thermal imaging process is used, selected portions of the thermoplastic medium are heated and sealed, that is, the open cells of the thermoplastic medium are closed, and this results in the formation of a background image or non-image on the thermoplastic medium which is substantially impermeable to the ink constituent and an image portion. When mounted in a hand stamper, the thermoplastic medium effuses ink when pressure is applied.
The present invention provides numerous benefits over the related art. Eliminating the necessity of inking the printing plate after the image is formed reduces the mess normally present when using such ink pads. Additionally, by inking at the optimal saturation levels of the thermoplastic material, the pre-inked thermoplastic material can be used in standard thermal head printers without concern for unwanted effusion of the ink out of the foam during the processing of the thermoplastic material. Also, even minimally pre-inking the thermoplastic material allows for better “wicking” of the ink. This condition improves the capillary action of the thermoplastic material. As a result, if the printing plate or thermoplastic material is more fully inked after the image is formed, the capillary action is much faster and thus the absorption of the ink occurs in a much more timely manner.
These and other features of the invention will be more fully appreciated with reference to the figures and the disclosure to follow:
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Moss Russell
Venkataraman Ravi
Dixon Merrick
Identity Group, Inc.
Reed Smith Shaw & McClay LLP
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