Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Magnetic imaging
Reexamination Certificate
2000-10-25
2003-01-21
Chapman, Mark A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Magnetic imaging
C430S097000, C430S111400
Reexamination Certificate
active
06509128
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the imagewise printing, particularly electrophotographic printing, of adhesives, and particularly acrylate-based adhesives, that have latent adhesive properties, particularly latent pressure sensitive adhesive properties.
BACKGROUND
Pattern coating of adhesives is of significant importance in the assembly industry. For example, pattern coating of adhesives is needed in the application of border adhesives in medical electrodes, laminating adhesives in membrane switches, attachment adhesives in electronic packaging and electronic. circuit boards.
Pattern coating of adhesives is generally a more economical alternative to the use of film adhesives, which involves die-cutting and a significant amount of manual handling to apply the adhesive to the part. Printable adhesives are available in a number of formats, ranging from solvent-borne, water-borne to UV-curable reactive monomer/oligomers. All of these materials require a drying or curing step, which would be desirable to eliminate. Also, between coating operations the equipment needs thorough clean-up, often involving solvents, which would also be desirable to eliminate. Hot-melt screen printing is yet another alternative to pattern coating of adhesives. Not only is the hot-melt handling a safety concern, but the melt Theological behavior of the adhesives can be a roadblock to successful implementation. Thus, what is needed is a more economical and efficient means of pattern coating adhesives.
One such way can include the use of electrostatic means, magnetic means, or both. One particular such example involves the use of electrophotography. A general discussion of color electrophotography is presented in “Electrophotography”, by R. M. Schaffert, Focal Press, London & New York, 1975, pages 178-190. In general, in electrophotography, copies or printed materials are obtained by forming an electrostatic latent image utilizing a photoconductive material (i.e., photoconductor). The photoconductor is entirely charged with a charging device and then exposed in an imagewise fashion to light to form an electrostatic latent image thereon. The electrostatic latent image is subsequently developed with a dry toner to form a toner image on the photoconductor. The toner image (i.e., the “real” image) is transferred onto an image receiving material such as a paper sheet. This can occur by direct or indirect means. The toner image transferred on the image receiving material is then fixed upon application of heat, pressure, solvent vapor, or a combination thereof. The toner that is not transferred and is left on the photoconductor is removed by various means if necessary, and then the above process is repeated.
Dry toners for use in such image forming methods typically include a binder resin and a colorant, and optionally include a charge controlling agent, a fixing agent, and a releasing agent. The properties requisite for these dry toners include good fixing ability, charging ability, fluidity, stability to environmental changes, and mechanical strength.
In general, the particle size of such dry toners is in a range from a few microns (i.e., micrometers) to about 30 microns. These particle sizes can be obtained by pulverizing the toners or by polymerization techniques. However, the majority of such polymers used in toners have not been shown to have adhesive properties sufficient to hold substrates together.
Limited uses of electrophotography of adhesive toners have been demonstrated, however. For example, U.S. Pat. No. 5,361,089 (Bearss et al.) discloses the imagewise electrographic printing of adhesive toners onto imaged color toners to enhance subsequent transfer of the toner image to a substrate; however, the composition of the adhesive toners is not disclosed. Also, U.S. Pat. No. 5,599,618 (Callahan, Jr. et al.) discloses the application of core-shell pressure sensitive adhesive particles via electrostatic means, magnetic means, or both. Such core-shell pressure sensitive adhesive particles include a nontacky outer shell and a pressure sensitive adhesive core that is exposed upon activation of the particles, for example, by application of pressure.
Other adhesives capable of being imagewise printed, as well as other means of imagewise printing adhesives, and methods of making such adhesives are still needed.
SUMMARY OF THE INVENTION
The present invention is directed to latent adhesive toners, methods of making such adhesive toners, and imagewise printing processes, particularly electrophotographic printing processes, of such latent adhesive toners. The latent adhesive toners typically include dry particles (e.g., powders) having latent adhesive properties, optionally dispersed in a liquid carrier. Preferably, there is no liquid carrier thereby making the printing process a 100% solids operation. Typically, for 100% solids operations clean-up is simpler, switching between adhesives is simpler, and precautions in the handling of the adhesives is simpler, only requiring the handling of powders. This makes preferred processes of the present invention an excellent fit for short run operations.
The resolution of the printed image is mostly limited by the quality of the powder utilized. Using the adhesive toners described herein, high resolution can indeed be obtained. The print pattern is readily altered by simply changing the image on the photo-receptor which can be done within seconds using a pattern stored in a computer. New patterns can be computer designed within minutes. The development of the adhesive properties can be done in line with printing and does not require any manual handling of the material.
Such imagewise printed adhesives are useful in the manufacture of medical electrodes, membrane switches, electronic packaging, electronic circuit boards, graphic articles, retroreflective articles, labels, note pads, etc.
In one embodiment of the invention, there is provided a method of applying an adhesive to a substrate in an imagewise fashion. The method includes: providing a substrate having a latent adhesive image thereon; and applying a plasticizing agent to activate the latent adhesive image to form an adhesive image. Preferably, providing a substrate having a latent adhesive image thereon includes providing a substrate; applying a latent adhesive toner in an imagewise fashion to the substrate; and fusing the latent adhesive toner to the first substrate to form a latent adhesive image.
The plasticizing agent can be applied before, during, or after the latent adhesive toner is applied as long as precautions are taken to prevent activation of the latent adhesive until the desired time. For example, a plasticizing agent can be applied in a solid form or in an encapsulated form and heat applied to melt the plasticizing agent and cause it to activate the latent adhesive.
In another embodiment, there is provided a method of adhering substrates together using an adhesive printed in an imagewise fashion. The method includes: applying a latent adhesive toner in an imagewise fashion to a first substrate, wherein the latent adhesive toner comprises single-composition latent adhesive particles; fusing the latent adhesive toner to the first substrate to form a latent adhesive image; activating the latent adhesive image to form an adhesive image; and applying a second substrate to the adhesive image disposed on the first substrate. Preferably, the latent adhesive toner includes latent adhesive particles of an acrylic, urethane, phenolic, polyimide, cyanate ester, or epoxy. In another embodiment, the latent adhesive toner includes particles of a latent adhesive acrylic polymer with crystalline side chains. In yet another embodiment, the latent adhesive toner includes latent adhesive particles of an epoxy-acrylic or epoxy-polyester structural or semi-structural adhesive. In still another embodiment, the latent adhesive toner includes latent adhesive particles of a polyester or polyamide adhesive.
In yet another embodiment, there is provided a method of adhering substrates together using an adhesive pri
Everaerts Albert I.
Nguyen Lang N.
3M Innovative Properties Company
Chapman Mark A.
Pribnow Scott R.
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