Radiation imagery chemistry: process – composition – or product th – Diazo reproduction – process – composition – or product – Composition or product which contains radiation sensitive...
Reexamination Certificate
2001-09-05
2003-07-15
Chu, John S. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Diazo reproduction, process, composition, or product
Composition or product which contains radiation sensitive...
C430S271100, C430S302000, C101S451000, C101S456000, C101S465000, C101S467000
Reexamination Certificate
active
06593055
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to lithographic printing. More particularly, this invention relates to multi-layer thermally imageable elements, useful as lithographic printing plate precursors, that can be thermally imaged and processed with aqueous alkaline developers.
BACKGROUND OF THE INVENTION
In lithographic printing, ink receptive regions, known as image areas, are generated on a hydrophilic surface. When the surface is moistened with water and ink is applied, the hydrophilic regions retain the water and repel the ink, and the ink receptive regions accept the ink and repel the water. The ink is transferred to the surface of a material upon which the image is to be reproduced. Typically, the ink is first transferred to an intermediate blanket, which in turn transfers the ink to the surface of the material upon which the image is to be reproduced.
Imageable elements useful as lithographic printing plates, also called printing plate precursors, typically comprise an imageable layer applied over the surface of a hydrophilic substrate. The imageable layer includes one or more radiation-sensitive components, which may be dispersed in a suitable binder. Alternatively, the radiation-sensitive component can also be the binder material.
Thermally imageable elements useful as lithographic printing plate precursors, which obviate the need for exposure through a negative, are becoming increasingly important in the printing industry. After imagewise thermal exposure, the rate of removal of the exposed regions by a developer is greater than the rate of removal of the unexposed regions so that the exposed regions are removed by the developer to form an image. Such systems are disclosed in, for example, Parsons, WO 97/39894 and U.S. application Ser. No. 08/981,620; Nagasaka, EP 0 823 327; Miyake, EP 0 909 627; West, WO 98/42507 and U.S. application Ser. No. 08/821,844; and Nguyen, WO 99/11458, and U.S. application Ser. No. 08/922,190.
Although advances have been made in the preparation of heat-sensitive elements for the production of lithographic printing plates, there remains a need for such elements having improved sensitivity to infrared laser imaging devices.
SUMMARY OF THE INVENTION
The invention is a thermally imageable element having improved sensitivity to infrared laser imaging devices. The element comprises:
(a) a hydrophilic substrate;
(b) an absorber layer; and
(c) a top layer;
wherein:
the top layer comprises a first polymeric material;
the top layer is ink receptive and insoluble in an aqueous alkaline developer;
the top layer and the absorber layer are each removable by the aqueous alkaline developer following thermal exposure; and
the absorber layer consists essentially of a photothermal conversion material or a mixture of photothermal conversion materials and, optionally, a surfactant or a mixture of surfactants.
In one embodiment of the invention, an underlayer comprising a second polymeric material is between the support and the absorber layer.
In another aspect, the invention is a method for producing an image useful as a lithographic printing plate. The method comprises imaging the thermally imageable element and developing it with an aqueous alkaline developer. In another aspect, the invention is a method of printing using the printing plate and an aqueous fountain solution.
DETAILED DESCRIPTION OF THE INVENTION
This invention is a thermally imageable element. The element comprises a hydrophilic substrate, an absorber layer, and a top layer. The absorber layer contains a photothermal conversion material. The element may also comprise an underlayer between the substrate and the absorber layer. Unless the context indicates otherwise, in the specification and claims, the terms “first polymeric material,” “second polymeric material,” “photothermal conversion material,” “dissolution inhibitor,” and similar terms also refer to mixtures of such materials.
Hydrophilic Substrate
The hydrophilic substrate, i.e., the substrate that comprises at least one hydrophilic surface, comprises a support, which may be any material conventionally used to prepare imageable elements useful as lithographic printing plates. The support is preferably strong, stable and flexible. It should resist dimensional change under conditions of use so that color records will register in a full-color image. Typically, it can be any self-supporting material, including, for example, polymeric films such as polyethylene terephthalate film, ceramics, metals, or stiff papers, or a lamination of any of these materials. Metal supports include aluminum, zinc, titanium, and alloys thereof.
The surface of the aluminum support may be treated by techniques known in the art, including physical graining, electrochemical graining, chemical graining, and anodizing. The substrate should be of sufficient thickness to sustain the wear from printing and be thin enough to wrap around a printing form, typically from about 100 to about 600 &mgr;m.
Typically, the substrate comprises an interayer between the aluminum support and the imageable layer. The interlayer may be formed by treatment of the support with, for example, silicate, dextrine, hexafluorosilicic acid, phosphate/fluoride, polyvinyl phosphonic acid (PVPA) or polyvinyl phosphonic acid copolymers.
Absorber Layer
The absorber layer absorbs radiation, preferably radiation in the range of about 800 nm to 1200 nm, the range of radiation commonly used for imaging thermally imageable elements. An absorber, sometimes referred to as “a photothermal conversion material,” is present in the absorber layer. Photothermal conversion materials absorb radiation and convert it to heat. Photothermal conversion materials may absorb ultraviolet, visible, and/or infrared radiation and convert it to heat.
The photothermal conversion material may be either a dye or pigment, such as a dye or pigment of the squarylium, merocyanine, indolizine, pyrylium, or metal diothiolene class. Examples of absorbing pigments are Projet 900, Projet 860 and Projet 830 (all available from the Zeneca Corporation). Carbon black pigments may also be used. Because of their wide absorption bands, carbon. black-based plates can be used with multiple infrared imaging devices having a wide range of peak emission wavelengths.
Dyes, especially dyes that are soluble in the aqueous alkaline developer, are preferred to prevent sludging of the developer by insoluble material. The dye may be chosen, for example, from indoaniline dyes, oxonol dyes, porphyrin derivatives, anthraquinone dyes, merostyryl dyes, pyrylium compounds, and sqarylium derivatives. Absorbing dyes are disclosed in numerous disclosures and patent applications in the field, for example, Nagasaka, EP 0,823,327; Van Damme, EP 0,908,397; DeBoer, U.S. Pat. No. 4,973,572; Jandrue, U.S. Pat. No. 5,244,771; and Chapman, U.S. Pat. No. 5,401,618. Examples of useful absorbing dyes include, ADS-830 WS and ADS-1064 (both available from American Dye Source, Montreal, Canada), EC2117 (available from FEW, Wolfen, Germany),. Cyasorb IR 99 and Cyasorb IR 165 (both available from Glendale Protective Technology), Epolite IV-62B and Epolite III-178 (both available from the Epoline), PINA-780 (available from the Allied Signal Corporation), SpectraIR 830A and SpectraIR 840A (both available from Spectra Colors).
The absorber layer consists essentially of the photothermal conversion material or a mixture of photothermal conversion materials and, optionally, a surfactant, such as a polyethoxylated dimethylpolysiloxane copolymer, or a mixture of surfactants. In particular, the absorber layer is substantially free of binders, such as those used as the first polymeric material and the second polymeric material. The surfactant may be present to help disperse the photothermal conversion material in a coating solvent.
The thickness of the absorber layer is generally sufficient to absorb at least 90%, preferably at least 99%, of the imaging radiation. As is well known to those skilled in the art, the amount of absorber required to absorb a particular amount of radi
Patel Jayanti
Shimazu Ken-Ichi
Chu John S.
Kodak Polychrome Graphics LLC
RatnerPrestia
LandOfFree
Multi-layer thermally imageable element does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multi-layer thermally imageable element, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multi-layer thermally imageable element will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3093320