Incremental printing of symbolic information – Ink jet – Medium and processing means
Reexamination Certificate
1998-05-15
2001-02-27
Braun, Fred L (Department: 2852)
Incremental printing of symbolic information
Ink jet
Medium and processing means
Reexamination Certificate
active
06193366
ABSTRACT:
FIELD OF INVENTION
The present invention is related to a method for printing gradient images using phase change ink with discrete drop size. More specifically, the present invention is related to an apparatus and method for printing an image with a high gradient and excellent resolution without substantial compromises in physical stability of the image.
BACKGROUND OF THE INVENTION
Many methods have been proposed for the generation of gradient images from discrete dots of ink.
Combinations of different density solvent based inks in an ink jet printing method have been shown to be a suitable approach to the generation of high gradient images from a discrete number of inks. U.S. Pat. Nos. 4,727,436; 4,860,026; 5,142,374; 4,713,746; and 4,713,701 all teach variations on methods and apparatus for combining inks. Suitable gradients are available using these and other techniques. Even with suitable gradients the image quality is still unsuitable due to image dot spreading which occurs as a result of the carrier solvent, such as water or an organic, and the ink diffusing into the media. Another major disadvantage of solvent based ink jet systems is the solvent which must be absorbed by the media or evaporated after printing. Evaporation of the solvent is environmentally unsatisfactory particularly when non-aqueous solvents are employed. It has been a long standing goal of skilled artisans to decrease the amount of ink used to form an image which, in-turn, decreases the image dot spread and lowers cost.
Phase change ink printing provides some advantages over solvent based ink jet systems. Specifically, there is no solvent since the phase change ink is a solid at room temperature and a liquid at coating temperatures. One disadvantage of phase change ink printing is the inability to easily vary drop size on demand. Discrete drop sizes limit the gradient levels available with conventional phase change ink printing methods due to the lack of continuously variable ink density levels. Phase change ink printing does allow for the placement of multiple dots at a given position which increases the contrast available to some extent. When multiple dots are applied image resolution and image durability deteriorate due to the appearance of ink islands occurring as a result of the stacking of solid ink. Phase change inks and printing techniques are described, for instance, in U.S. Pat. Nos. 5,372,852 and 5,276,468 and in European Patent Applications 0 566 259 and 0 604 025.
It would be highly advantageous to combine the dry printing capabilities of phase change ink printing with the ink combining methods of solvent based ink jet printing to achieve a superior print with high resolution and contrast. Efforts towards this goal have been thwarted and the method has been considered to be abandoned by skilled artisans due to the loss of resolution and poor image durability resulting from the ink islands.
The present invention provides a method for eliminating the problems associated with combining phase change inks of different densities. The resulting image exhibits excellent gradation without discontinuities and provides a superior method of printing.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a printing system which provides an image with the appearance of continuous gradients from discrete ink drops.
It is another object of the present invention to provide an imaging system which is durable and less susceptible to physical deterioration resulting from abrasion.
It is yet another object of the present invention to provide an imaging system which does not require the absorption, or evaporation of solvents.
These and other advantages, as will be apparent, are provided in an apparatus for recording a gradient image on transparent media comprising: at least one solid phase change ink; a solid null image element; a heating system capable of melting the solid phase change ink to form a molten phase change ink and capable of melting the solid null image element to form a molten null image element; a printing head capable of receiving the molten phase change ink and the molten null image element and depositing them in an imagewise pattern onto a transfer surface; a transfer surface capable of receiving the imagewise pattern; a cooling mechanism for cooling the molten phase change ink and the molten null image element in the imagewise pattern to form a malleable phase change ink and a malleable null image element in the imagewise pattern on the transfer surface; a media; a transfer mechanism capable of transferring said malleable phase change ink and said malleable null image element in said imagewise pattern on said transfer surface to said media.
A particularly preferred embodiment is provided in an apparatus for recording a gradient image on media comprising: a set of solid phase change inks comprising: a first solid phase change ink with an optical density defined by the formula:
P
1
≦N
a
·n·m·P
n
+D;
a second solid phase change ink with an optical density (P
2
) defined by the formula:
P
2
≦N
a
·n·m·P
n
+N
1
·n·m·P
1
+D;
and a third imaging ink has an optical density (P
3
) defined by the formula:
P
3
≦N
a
·n·m·P
n
+N
1
·n·m·P
1
+N
2
·n·m·P
2
+D;
a solid null image element; a heating system capable of melting the set of solid phase change inks to form a set of molten phase change inks and melting the solid null image element to form a molten null image element; a printing head capable of receiving the set of molten phase change inks and the molten null image element and depositing the set of molten phase change inks and the molten null image element in a molten imagewise pattern; a transfer surface capable of receiving the molten imagewise pattern from the printing head; a cooling mechanism for cooling said molten imagewise pattern to form a malleable imagewise pattern on the transfer surface; a media; and a transfer mechanism capable of transferring the malleable imagewise pattern to the media.
Another preferred embodiment is provided in an apparatus for recording a gradient image on media comprising: a set of solid phase change inks comprising: a first solid phase change ink with an optical density of at least 0.08 to no more than 0.40 for a 19 &mgr;m thick drop; a second solid phase change ink has an optical density of more than 0.40 to no more than 0.90 for a 19 &mgr;m thick drop; a third imaging ink has an optical density of at least 1.2 to 5.0 for a 19 &mgr;m thick drop; a solid null image element wherein said null image element has an optical density of less than 0.15 for a 19 &mgr;m thick drop; a heating system capable of melting said set of solid phase change inks to form a set of molten phase change inks and melting said solid null image element to form a molten null image element; a printing head capable of receiving said set of molten phase change inks and said molten null image element and depositing said set of molten phase change inks and said molten null image element in a molten imagewise pattern; a transfer surface capable of receiving said molten imagewise pattern from said printing head; a cooling mechanism for cooling said molten imagewise pattern to form a malleable imagewise pattern on said transfer surface; a media; and a transfer mechanism capable of transferring said malleable imagewise pattern on said transfer surface to said media.
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Apple Bernard Allen
Jaeger C. Wayne
Kroon Stephen M.
Thomas, Jr. Jule William
Agfa Gevaert N.V.
Braun Fred L
Guy, Jr. Joseph T.
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