Printing – Printing members – Blanks and processes
Reexamination Certificate
2000-05-02
2001-06-05
Yan, Ren (Department: 2854)
Printing
Printing members
Blanks and processes
C219S121690, C430S307000
Reexamination Certificate
active
06240844
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to the field of gravure coating, and in particular, to controlling gravure cylinder engraving. More specifically, the invention relates to a method for specifying an electromechanical cylinder engraving for coatings containing particles in order to provide improved imaging quality.
BACKGROUND OF THE INVENTION
Gravure cylinders are used for coating liquid compositions on moving supports. The amount of liquid deposited by the gravure cylinder is a function of the recessed cells on the surface of the cylinder. A typical design used in an engraving for the gravure cylinder has been reliance on a large inventory of finished cylinders having different engraved cell patterns, sizes and shapes. The proper lay down of the liquid coating composition is determined empirically, by either trying a number of cylinders, or using cylinders that worked previously. Although somewhat successful, the shortcomings of this method are the reliance upon empirical experimentation and the ability of a single source engraver service to make it “like another cylinder.” The engraver would empirically change the cell depth to increase or decrease fluid deposit lay down with a minimum concern for cell geometry effect on coating quality.
U.S. Pat. No. 5,426,588, hereby incorporated herein by reference, discloses a process of electromechanical engraving and a method for specifying cell geometry and engraving process setup conditions based on a cell volume model. In accordance with the aforementioned method, a skilled artisan can specify to an engraver the proper parameters needed to engrave a cylinder that will produce the desired coating coverage. Using these guidelines it is possible to specify an engraving process that will yield good coating quality for formulations which do not contain particulate material, such as beads. However, when gravure coatings containing particulate materials are used in low gloss printing applications, the method described in U.S. Pat. No. 5,426,588 is not sufficient to predict acceptable coating or imaging performance.
A particular problem with coating formulations containing particles, such as beads, which are dispersed but not dissolved in the formulation is that the particles can interact with the engraving process in such a manner that the expected good coating quality is not achieved. One such coating formulation is disclosed in Japanese Kokai [1997]-323482. According to this Japanese Kokai, the use of imaging-protecting layers that contain thermally expandable micro-capsules for “easy matting” of the image surface are described. When micro-capsules such as these are used a more severe problem can occur in gravure coated image protecting layers where an objectionable image artifact can be observed based on an interference pattern which results when the light source orientation and the coating direction of the protecting layer coincide. This artifact can be eliminated and the gloss position can be improved by specifically defining the engraving dimensions for the gravure cylinder with respect to the particle size range being used in the formulation.
Therefore, there exists a need in the art for a modified method for specifying engraving parameters which takes into account the specific size range of the beads or particles that are in the coating formulation.
SUMMARY OF THE INVENTION
It is, therefore, an object of the invention to provide a method for specifying engraving using a coating composition containing particulate matter.
Another object of the invention is to provide a modified method for specifying the engraving such that the ratio of particulate size in the formulation to channel depth in the engraving is defined.
The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the present invention, a method of engraving a gravure cylinder having a circumference (C) for coating a liquid composition on a substrate, said liquid composition containing a concentration of particles having a predetermined particle diameter, said method comprising the steps of:
(a) determining a coverage VA, of the liquid composition on the substrate;
(b) selecting a stylus angle &thgr;;
(c) selecting a compression angle &agr;;
(d) specifying a first ratio (D
B
/D
o
) of said predetermined particle diameter D
B
to an engraving channel depth D
o
;
(e) calculating said engraving channel depth D
o
based on said first ratio (D
B
/D
o
) and said predetermined particle diameter D
B
.
(f) specifying a second ratio (W
w
/W
o
) of a wall width W
w
to cell width W
o
;
(g) calculating a channel width W
c
according to equation
W
c
=[2 tan &thgr;/2]
D
o
(h) calculating the cell width W
o
according to the equation
VA
=[1122.5/(tan &thgr;/2)]*[3
W
o
2
+2
W
o
W
c
+3
W
c
2
]*[({square root over (2)})/
X]
wherein
X=W
o
+W
c
+2
W
w
;
(i) calculating the wall width W
w
based on the second ratio; and,
(j) engraving the gravure cylinder according to &thgr;, &agr;, W
c
, W
w
, and W
o
.
The present invention has numerous important advantages over the prior art including: it enables the optimization of image gloss level; and, it produces an image free of light interference artifacts.
REFERENCES:
patent: 4841611 (1989-06-01), Kusaba et al.
patent: 4939994 (1990-07-01), Puleston
patent: 5126531 (1992-06-01), Majima et al.
patent: 5426588 (1995-06-01), Walters et al.
patent: 5427026 (1995-06-01), Kuwahara
patent: 9323482 (1997-12-01), None
Flosenzier Linda S.
Hastreiter, Jr. Jacob J.
Bailey, Sr. Clyde E.
Eastman Kodak Company
Yan Ren
LandOfFree
Method for specifying engraving of a gravure cylinder for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for specifying engraving of a gravure cylinder for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for specifying engraving of a gravure cylinder for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2470052