Photocopying – Projection printing and copying cameras – With developing
Reissue Patent
1996-05-01
2001-07-03
Braun, Fred L. (Department: 2852)
Photocopying
Projection printing and copying cameras
With developing
C355S032000, C396S581000
Reissue Patent
active
RE037257
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an imaging system and more particularly to an office based system which is suitable for making photocopies. In accordance with the invention, images are formed by image-wise exposing a composition comprising a chromogenic material and photosensitive encapsulate to actinic radiation and rupturing the capsules in the presence of a developer whereby a patterned reaction between the chromogenic material and developer is obtained which produces an image. This application specifically addresses transfer systems in which the capsules are ruptured in contact with a developer sheet to which chromogenic material is transferred for the patterned image-forming reaction.
Imaging systems based on photosensitive encapsulates are known. Berman, U.S. Pat. No. 3,219,446 discloses a transfer imaging process in which azo-blue-“B” black dye is encapsulated with a cross-linkable polymer or a polymerizable monomer as a fluid-droplet containing film or a fluid droplet containing microcapsules. As described, the Berman imaging system is a transfer system which relies upon selectively transferring the encapsulated dye to a copy sheet in correspondence with the image. Imaging is accomplished by image-wise exposing a layer of the encapsulate to electromagnetic radiation to cross-link the polymer, causing the liquid in the exposed capsules to assume a rigid condition and not transfer to a copy sheet. Dye transfer is limited to the unexposed areas of the encapsulate containing layer.
Phillips, U.S. Pat. No. 3,700,439 discloses a photocopy process wherein Michler's ketone is encapsulated in a conventional manner and provided as a layer on a support. Michler's ketone itself is not a color former, but patterned irradiation of the ketone containing capsules produces a latent image of colorless, acid-colorable, dye precursor from the ketone such that upon contact with an acid developer such as acid clay a visible image is obtained. Phillips discloses both a system wherein the exposed imaging sheet is calendered face-to-face with an acid-coated receiving sheet to form images and a system wherein the acid developer is on the same surface as the capsule coating so that after rupturing the capsules on the imaging sheet there is development without transfer.
Berman et al, U.S. Pat. No. 3,072,481 discloses another type of encapsulated light sensitive element which utilizes a light-sensitive material which is readily converted to a colored form when carried in a liquid vehicle but which is insensitive to light when solid. By encapsulating such a material with a volatile solvent, image-wise exposing a layer of the encapsulate and rupturing the capsules to evaporate the solvent, an image is obtained and fixed.
Forris, U.S. Pat. No. 3,001,873, discloses a more complex system wherein the walls of capsules containing a solid dye are photosensitized such that patterned exposure renders the capsules unswellable. By wetting the sheet to swell the unexposed capsules and heating, the dye is immobilized in the unexposed areas. Thereafter, by rupturing the capsules in contact with a receiving sheet there is an image-wise transfer of the dye from the exposed areas only.
While image-forming techniques such as these have been known, for various reasons, they have not matured into commercial photocopy systems. Furthermore, the potential of these systems to afford a low cost imaging system has not been realized.
SUMMARY OF THE INVENTION
Thus, a principal object of the present invention is to provide an imaging system in which images are formed by image-wise exposing a photosensitive encapsulate to actinic radiation and rupturing the capsules in the presence of a developer such that there is a patterned reaction of a chromogenic material, present in the encapsulate or co-deposited on a support with the encapsulate, and the developer which yields an image of the original.
Another object of the present invention is to provide an imaging system based on a photosensitive encapsulate which provides images with high resolution and good tonal qualities.
Still another object of the present invention is to provide a dry photocopy system which is affordable and does not require expensive and sophisticated machinery for exposure and processing.
A specific object of the present invention is to provide a transfer imaging system in which an image-wise exposed imaging sheet bearing the photo-sensitive encapsulate is placed in contact with a developer or copy sheet and the capsules are ruptured such that chromogenic material pattern-wise transfers to the developer sheet and reacts to form an image.
Another object of the present invention is to provide an imaging system which is useful in transmission and reflected light imaging and hence can be utilized in photocopying printed documents and other materials.
Another object of the present invention is to provide an imaging sheet carrying a photosensitive encapsulate wherein the encapsulate comprises a chromogenic material and a photosensitive composition.
Another more particular object of the present invention is to provide an imaging paper which is sensitive to blue light (380 to 480 nm), and which incorporates a fugitive yellow dye such that said system can be handled in room light for sufficiently short periods of time to load said paper in an exposure apparatus.
A still further object of the present invention is to provide an imaging process wherein images are formed by exposing a layer of a photosensitive encapsulate preferably containing a chromogenic material to actinic radiation, and rupturing the capsule in the presence of a developer.
These and other objects are attained in the present invention which in a specific embodiment relates to a transfer imaging system basically having:
an imaging sheet having a first substrate,
a chromogenic material,
a photosensitive composition,
a coating containing said chromogenic material and said photosensitive composition on one surface of said first substrate,
said photosensitive composition being encapsulated in pressure rupturable capsules, as an internal phase, and
a developer sheet comprising a second substrate and a developer material which is capable of reacting with the chromogenic material to for a an image on one surface of said second substrate upon transfer of said chromogenic material thereto.
Herein, the term “encapsulated” refers to both so-called resin dispersion or open phase systems in which the internal phase containing the chromogenic material is dispersed as droplets throughout a dispersing medium and systems in which the capsule is formed with a discrete capsular wall, the latter encapsulation typically being in the form of microcapsules. “Pressure rupturable capsules” are, accordingly, considered to exist in either of these “encapsulated” systems. Furthermore, while the capsules are described herein as “pressure rupturable” means other than pressure may be used to rupture them.
In accordance with the present invention images are formed by exposing a coated composition containing the chromogenic material and the encapsulated photosensitive composition to actinic radiation and rupturing the capsules in the presence of a developer. The invention system is designed such that when these steps are carried out, the image-forming reaction between the chromogenic material and the developer discriminately occurs in the exposed or unexposed areas and produces a detectable image. In the case of a transfer imaging system, this is accomplished by image-wise photochemically controlling whether the chromogenic material can transfer from the imaging sheet to the developer sheet. By “image-wise” it is meant that upon exposure and transfer the chromogenic material and the developer react to form a positive or negative image of the original.
In accordance with the principal embodiment of the invention, the chromogenic material is encapsulated with a photosensitive composition. In general, the photosensitive composition can be described as one having a viscosity which changes upon expos
Braun Fred L.
Cycolor, Inc.
Thompson Hine & Flory LLP
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