Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-01-27
2002-03-19
Jagannathan, Vasu (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S099000, C524S548000, C252S299010
Reexamination Certificate
active
06359056
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a printing plate, a method of making a printing plate, and a method of printing using such a plate to form a desired image on a medium. More particularly, the printing plate of this invention employs a printing plate substrate and a fluid composition comprising an acidic polymeric compound and a second compound comprising a pyridyl group, which adhere to a substrate. The fluid composition is applied by ink jetting to the substrate, providing a printing plate that is ready-to-use on a press without having to develop it.
BACKGROUND OF THE INVENTION
The offset lithographic printing process has long used a developed planographic printing plate having oleophilic image areas and hydrophilic non-image areas. The plate is commonly dampened before or during inking with an oil-based ink composition. The dampening process utilizes a fountain solution such as those described in U.S. Pat. Nos. 3,877,372, 4,278,467 and 4,854,969. When water is applied to the plate, the water will form a film on the non-image hydrophilic areas, but will contract into tiny droplets on the oleophilic image areas. When a roller carrying an oil-based ink composition is passed over the dampened plate, it will not ink the non-image areas that are covered by the aqueous film, but will emulsify the water droplets on the water repellant image areas, which will then take up ink. The resulting ink image is transferred, or “offset,” onto a rubber blanket, which is then used to print onto a medium such as paper.
It has been proposed to apply “direct” ink jet printing techniques to lithographic printing. For example, European Patent Publication No. 503,621 discloses a direct method to make lithographic plates by jetting a photocurable ink onto the plate substrate, and then exposing the plate to ultraviolet radiation to harden the image area. An oil-based ink may then be transferred to the image area for printing onto a printing medium. But, neither the resolution of ink drops jetted onto the substrate, nor the durability of the lithographic printing plate with respect to printing runlength was disclosed.
It has also been proposed to apply the direct ink jet printing techniques without the additional steps of chemical development of the plate. This approach advantageously results in lower production costs and a more environmentally acceptable printing process. However, in such techniques it is difficult to control the spreading of the droplets of ink jetted fluid that forms the oleophilic ink-accepting regions on the printing plate substrate. Such droplet “dot spreading” causes lower resolution of printed images and reduced image quality. For example, European Patent Application No. 0591,916 A2 discloses a water-based ink having a polymer containing anhydride groups which are thermally cross-linked on the substrate with a hydroxy-functional polymer. This formulation is applied by jetting the formulation, which is at room temperature, onto a room temperature substrate. However, this formulation does not achieve good control of dot spreading.
U.S. Pat. No. 4,833,486 discloses the apparatus and process for imaging a plate with a “hot melt” type of ink jet printer. The image is produced by jetting at high temperature a “phase change” type of ink which solidifies when it hits the cooler substrate. The ink becomes instantaneously solid rather than remaining a liquid or gel which is thereafter cured to form a solid. However, such an ink does not provide good resistance to press run due to the wax-type nature of the ink formulation.
U.S. Pat. Nos. 5,492,559 and 5,551,973 describe an ink jet formulation based on an aqueous phase, an oil phase, an oil soluble dye, and a surfactant, wherein the ink exhibits a liquid crystalline gel phase at one temperature and a liquid microemulsion phase at a higher temperature. However, no component of the composition, standing alone, exhibits liquid crystalline behavior. Further, it is not disclosed that the composition can be ink jetted to make a printing plate with an imaged, ink-receptive layer.
Thus, it would be advantageous to employ a printing plate capable of extended press run length which does not require chemical development.
It is one object of this invention to provide such a fluid composition and printing plate. It is another object of this invention to provide a method of preparing such a printing plate. It is yet another object of this invention to provide a method of using such a printing plate. The printing plate of this invention may advantageously be prepared without a chemical development step typically required. The printing plate of this invention is also capable of extended press run length.
SUMMARY OF THE INVENTION
The fluid composition of this invention is suitable for ink jetting upon a substrate and comprises an acidic polymeric compound combined with a second compound comprising a pyridyl group, the mixture being dissolved in a diglyme or glycolic solution and ink jetted. Alternatively, the mixture may be hot melt ink jetted onto the substrate.
The printing plate of this invention is prepared by: (a) providing a substrate; and (b) applying by ink jetting to the substrate a fluid composition as described. Optionally, a surfactant is applied to at least one surface of the substrate to prepare a “printing plate precursor” upon which the fluid composition is image-wise ink jetted. In a preferred embodiment, the precursor plate surfactant is a fluorosurfactant.
In preferred embodiments, acidic polymeric compounds suitable for this invention are poly(acrylic acid)s, poly(methacrylic acid)s, poly(maleic acid)s, poly(fumaric acid)s, poly(styrene-co-acrylic acid)s, poly(styrene-co-maleic acid)s, poly(styrene-co-fumaric acid)s, and mixtures or derivatives thereof. In a particularly preferred embodiment, the acidic polymeric compound is a poly(acrylic acid) and the second compound is a pyridyl liquid crystal.
The printing plate of this invention is capable of extended press run length and advantageously avoids the need of chemical development.
DETAILED DESCRIPTION OF THE INVENTION
To achieve extended printing runs with printing plates the oleophilic material must adhere well to the substrate. Adhesion of the oleophilic material may be controlled in at least two ways. First, the oleophilic material should have a chemical interaction with the substrate that provides a type of chemical binding and promotes adhesion. For example, the chemical composition of the oleophilic material can be varied to promote its adhesion to the substrate. Also, the composition of the substrate can be varied to increase binding of the oleophilic material. Further, high cohesive strength of the oleophilic material helps to bind it to itself on the substrate, thus improving its adhesion. Cohesive strength of the oleophilic material is enhanced by providing a means for chemical interaction or association between the molecules of the oleophilic material.
The second way that adhesion of the oleophilic material may be controlled is by providing a substrate in which microscopic topology allows the oleophilic material to interlock mechanically with the substrate when dry or hardened. Mechanical interlocking can be affected by roughening the surface of the substrate. Thus, by controlling these variables, a printing plate can be made with increased adhesion of the oleophilic material, and correspondingly longer printing run operation.
In the invention described here, the oleophilic material is placed on the substrate by ink jetting a fluid composition comprising an acidic polymeric compound and a second compound comprising a pyridyl group. Optionally, by pretreating the substrate surface with a surfactant to lower its surface tension, the spreading of droplets of fluid composition is reduced. Thus, by these and other features inherent in the composition and method described here, excellent printing resolution can be obtained, as well as long-lasting adhesion of the dried oleophilic material to the substrate.
The printing plate of this invention encompasses lithograp
Aurenty Patrice M.
Grant Alexander
Lindsey Mark J.
Stone Edward
Baker & Botts L.L.P.
Jagannathan Vasu
Kodak Polychrome Graphics LLC
Shosho Callie
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