Radiation imagery chemistry: process – composition – or product th – Transfer procedure between image and image layer – image... – Imagewise heating – element or image receiving layers...
Reexamination Certificate
2000-05-04
2001-02-20
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Transfer procedure between image and image layer, image...
Imagewise heating, element or image receiving layers...
C430S200000, C430S273100, C430S933000, C430S964000
Reexamination Certificate
active
06190827
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to use of a laser donor element and process for producing a laser-induced white transfer image.
BACKGROUND OF THE INVENTION
There is great interest in the generation of images using thermal transfer technology, particularly in the generation of images via near-infrared laser devices. In general, most of these systems rely on the conversion of light to heat energy by an IR absorber, and the subsequent transfer of colorant or other imaging material from the exposed areas to a receiver. The images derived may be monochrome, or by repetition of the process with various colored donors, a multi-colored image can be produced on a common receiver, useful for generating color proofs. The process can also be used to transfer other materials to a receiver, such as IR absorbing materials, UV absorbing materials, polymeric binders or other useful imaging materials. This process is described, for example, in U.S. Pat. No. 5,126,760 which discloses the use of an IR absorber to effect sublimation or diffusion of a colorant from a donor element to a receiver layer.
U.S. Pat. No. 5,278,023 discloses a propellant-containing thermal transfer donor element which is used to mass transfer colorants to a receiver element. However, there is a problem with this element in that during laser imaging, a portion of the infrared-absorbing material transfers to the receiving element and causes color contamination.
U.S. Pat. No. 5,171,650 a discloses a laser thermal donor element which uses ablation transfer mechanism to transfer a colorant to a receiver element. However, again there is a problem with this element in that during laser imaging, a portion of the infrared-absorbing material transfers to the receiving element and causes color contamination.
It is an object of this invention is to provide a laser donor element that is capable of transferring images without color contamination by other components contained within the donor element.
It is another object of this invention is to provide a rapid and efficient process for the transfer of a white pigment to a receiver which has improved whiteness.
SUMMARY OF THE INVENTION
These and other objects are obtained by this invention which relates to a laser donor element comprising a transparent support having thereon the following layers in the order recited:
a) a hydrophilic layer;
b) a propellant layer comprising a gas-producing polymer being capable of forming a gas upon heating by the laser and an infrared-absorbing material, the propellant layer having been coated using a polar solvent having an E
t
value of between about 0.3 and 1.0; and
c) a colorant transfer layer comprising a white pigment and an optical brightener dispersed in a binder.
Another embodiment of the invention relates to a process of producing a laser-induced transfer image comprising:
I) imagewise-heating, by means of a laser, the laser donor element described above, and
II) transferring the laser-induced image to a receiving element.
By use of the invention, color contamination caused by unwanted transfer of infrared-absorbing material is minimized and improved whiteness is obtained.
DETAILED DESCRIPTION OF THE INVENTION
Any transparent material can be used as the support for the colorant-donor element employed in the invention provided it is dimensionally stable and can withstand the heat of the laser. Such materials include polyesters such as poly(ethylene terephthalate) or poly(ethylene naphthalate); polyamides; polycarbonates; cellulose esters such as cellulose acetate; fluorine polymers such as poly(vinylidene fluoride) or poly(tetrafluoroethylene-co-hexafluoropropylene); polyethers such as polyoxymethylene; polyacetals; polyolefins such as polystyrene, polyethylene, polypropylene or methylpentene polymers; and polyimides such as polyimide-amides and polyether-imides. The support generally has a thickness of from about 5 to about 200 &mgr;m. It may also be coated with a subbing layer, if desired, such as those materials described in U.S. Pat. Nos. 4,695,288 or 4,737,486. It may also be coated with any of the anti-static and/or slip layers well known to those in the imaging art.
The hydrophilic layer used in the invention may be, for example, gelatin, polyvinyl alcohol, polyvinyl acetate, methyl cellulose, hydroxypropyl methyl cellulose, polyvinylpyrrolidone, sulfonated polystyrenes, polyacrylamides, etc . The hydrophilic layer may be about 0.1 to about 100 &mgr;m in thickness, preferably between about 0.25 and about 50 &mgr;m thick. In a preferred embodiment, the hydrophilic layer is gelatin.
The gas-producing polymers employed in the propellant layer of the invention include self oxidizing binders, such as nitrocellulose, energetic polymers as described in U.S. Pat. No. 5,308,737, thermally decomposable polycarbonates as described in U.S. Pat. No. 5,156,938, and low ceiling temperature polymers as described in U.S. Pat. No. 5,576,144. In a preferred embodiment of the invention, the gas-producing polymer comprises a vinyl polymer having recurring units of the following formula:
wherein:
R
1
and R
2
each independently represents a ketal group; an acetal group; a thioketal group; a thioacetal group; or an unsaturated group containing a double or triple bond between any two atoms, one of which is the atom of attachment to the polymer chain; such as cyano, carbonyl, isocyanate, azide, sulfonyl, nitro, phosphoric, phosphonyl, acetylenic, ethylenic, substituted or unsubstituted aryl or heteroaryl; or
R
1
and R
2
, as defined above, may be joined together to form a ring.
In a preferred embodiment of the invention, R
1
and R
2
each independently represents —C(═X)R
3
where X is O, S, NR, or N
+
(R)
2
; R
3
is R, OR, O
−
M
+
, OCOOR, SR, NHCOR, NHCON(R)
2
, N(R)
2
, N
+
(R)
3
, or (N)
3
; M
+
is an alkali or ammonium moiety; and R is hydrogen, halogen, or a substituted or unsubstituted alkyl or cycloalkyl group; or X and R
3
may be joined together to form a ring.
In another preferred embodiment of the invention, the vinyl polymer has repeating units derived from alkyl cyanoacrylates or amides, or methylene diacrylates or diamides. In still another preferred embodiment, the vinyl polymer is a poly(alkyl cyanoacrylate) such as poly(methyl cyanoacrylate), poly(ethyl cyanoacrylate), poly(propyl cyanoacrylate), poly(butyl cyanoacrylate), poly(ethylhexyl cyanoacrylate), or poly(methoxyethyl cyanoacrylate).
The average molecular weights of the vinyl polymers described above may be between 1,000 and 1,000,000. Particularly good results have been obtained with polymers having a molecular weight between 2,000 and 500,000 weight average (polystyrene equivalent by size exclusion chromatography).
The vinyl polymers described above may also be copolymerized with other monomers. For example, the vinyl polymer may comprise copolymers of at least 50 wt. %, preferably more than 75 wt. %, of repeating units as described above along with other vinyl monomers such as acrylates and methacrylates, acrylamides and methacrylamides, vinyl ethers, vinyl alkyl esters, maleic anhydrides, maleimides, itaconic acid and esters, fumaric acid and esters, etc.
Examples of vinyl polymers useful in the invention include the following:
Compound
R
1
R
2
1
—C≡N
—COOCH
3
2
—C≡N
—COOC
2
H
5
3
—C≡N
—COOC
3
H
7
4
—C≡N
—COOC
4
H
9
5
—C≡N
—COOH
6
—C≡N
—C≡N
7
—C≡N
—COOCH
2
CH(CH
2
CH
3
)C
4
H
9
8
—C≡N
—COOCH
2
CH
2
OCH
3
9
—C≡N
—COOCH
2
CH
2
OCH
2
CH
3
10
—C≡N
—CONHCH
3
11
—C≡N
—CON(CH
3
)
2
12
—COOCH
3
—COOCH
3
13
—CONHCH
3
—CONHCH
3
14
—C≡N
(—COOCH
3
)
70
(—COOC
2
H
5
)
30
As described above, the propellant layer contains a polar solvent having a polarity constant, E
t
, value of between about 0.3 and 1.0, as described in Reichardt, C., Angew. Chem. Int. Ed. Eng., 4, 29, 1965. In a preferred embodiment of the invention, the polar solvent is pyridine, acetophenone, dichloromethane, 3-methyl-2-butanone, hexamethylphosphoric acid triamide, morpholine, tetramethylurea, 2-pe
Cole Harold E.
Eastman Kodak Company
Schilling Richard L.
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