Coating processes – Direct application of electrical – magnetic – wave – or... – Electrostatic charge – field – or force utilized
Patent
1992-04-09
1993-06-15
Pianalto, Bernard
Coating processes
Direct application of electrical, magnetic, wave, or...
Electrostatic charge, field, or force utilized
427180, 427261, 427288, 427375, 427386, 427391, 427411, 427470, 427559, B05D 306
Patent
active
052196224
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the formation of indicia on sheets of material, for example alphanumeric indicia, designs or both.
European patent application serial No. 237,258, the disclosure of which is incorporated herein by reference, describes a marker assembly having a support layer and a porous coating of a latent curable material that is capable of receiving printed indicia and which can subsequently be cured to render the indicia substantially indelible. The porous coating may be in particulate or filamentary form or both, but preferably is in particulate form, having particles of weight average particle size of not more than 100 micrometers, more preferably not more than 50 micrometers and especially not more than 25 micrometers, the preferred coatings having a particle size of less than 10 micrometers. The preferred materials for use as the coatings are ones in which the latency of the curing reaction is achieved by processing the reactive components of the coating into separate particles and mixing the particles together to form the coating, so that the particles will exist separately from one another until they are heated whereupon they will fuse and react. The marker assembly is preferably heated to a temperature of 150.degree. to 170.degree. C. for a period of up to 7 minutes in order to cause the particles to melt and coalesce in order that the components may react. As mentioned in the above patent specification, whether or not the indicia are substantially indelible will depend, among other things on the ink that is used to form the indicia and in particular on whether it is absorbed or rejected by the curable marker coating material in to uncured state, only those inks that are absorbed by the marker coating being considered appropriate for use with that marker.
Although it is possible to form very good and permanent graphics and alphanumeric indicia on these markers, this is achieved by the use of a personal computer with appropriate printer and software, which can be relatively expensive, especially if such cables are required only on an occasional basis.
We have now found, however, that a significant degree of permanency or indelibility of indicia can be achieved by forming them on a curable porous surface such as described above by means of an electrostatic copying process. Thus, according to the present invention, there is provided a method of forming a sheet of material with indicia thereon, which comprises applying indicia to the sheet by an electrostatic copying process in which a toner powder is deposited on the sheet and is then heated to fuse the toner, the sheet of material comprising a flexible support layer that is provided with a porous coating of a latent curable material that is in particulate and/or filamentary form.
Surprisingly, the indicia formed according to the invention are significantly more indelible than electrostatically copied indicia on other surfaces such as paper and the like, notwithstanting the fact that the fused toner used in the electrostatic copying process is not absorbed substantially by the curable material but instead tends to remain on the surface of it. The material is significantly more resistant to abrasion than electrostatically copied images on other common materials such as paper, both when dry and when in the presence of a variety of solvents. Furthermore, we have found that the quality of the formed indicia is improved if it is subjected to no further heating step after the toner has been caused to fuse: If the sheet of material is subjected to the normal heating or "permatising" step it is possible for surface imperfections to be generated in the printed areas. Thus, the total length of time for which heat is applied will usually be not more than 2 and especially not more than 1 second, so that the total heat applied to the sheet of material is insufficient to cure the material or to melt the particles or filaments although some sintering of the particles may occur.
The sheet of material should be flexible in order to enable it to be passed t
REFERENCES:
patent: 3130064 (1964-04-01), Insalaco
patent: 3906138 (1975-09-01), Evensen
patent: 4245025 (1981-01-01), Kato et al.
Burkard Herbert G.
Novack Sheri M.
Pianalto Bernard
Raychem GmbH
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