Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
2000-05-01
2001-01-23
Truong, Duc (Department: 1711)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C428S424200, C428S491000, C428S511000, C428S913000, C427S407100, C427S408000, C427S411000, C427S316000, C427S318000, C101S453000, C101S463100, C101S470000, C528S422000, C528S206000, C528S208000, C528S210000, C528S212000, C528S216000, C528S218000, C528S219000, C430S118600, C430S126200, C430S127000
Reexamination Certificate
active
06177182
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to novel coating materials for direct digital imaging by laser. More specifically the novel coating materials are thermally reactive near infrared absorption polymers designed for use with near infrared laser imaging devices. This invention further extends to the preparation and methods of use of the novel materials. The invention is particularly useful in the preparation of lithographic printing plates for computer-to-plate and digital-offset-press technologies. The invention extends to photoresist applications, to rapid prototyping of printed circuit boards and to chemical sensor development.
BACKGROUND OF THE INVENTION
The printing and graphic arts industries require printing plates coated with substances which are suitable for direct digital imaging by laser. The graphic image stored and created on computers can be output to a near infrared laser digital imaging device which will “draw” the image on the printing plate coating by eliciting a localized transformation of the coating. This method has the distinct advantage of not requiring a wet development step. The printing plate can act as a positive or a negative depending on the laser effect on the coating.
In the case of the present invention, the coating is oleophilic (attracts ink) and the undercoating is hydrophilic. Depending on where the laser image is drawn on the coating, the printing plate may be made to act as a positive or negative plate. Indeed, exposure to laser radiation renders the coating locally hydrophilic which causes it to wash away with water based inks and fountain solutions.
Various near infrared absorption polymers have been proposed in the prior art. However, these polymers face the various drawbacks outlined below.
U.S. Pat. No. 5,362,812 discloses reactive polymeric dyes comprising an azlactone moiety for use in photoresist systems and color proofing media. These materials contain visible light absorption chromophoric moiety and acrylate functional groups, which undergo cross-linking reactions via free radical initiating upon exposure to ultraviolet light. However, these materials cannot be used for lithographic printing plate due to an absence of absorption in the near infrared region.
U.S. Pat. No. 4,666,819 and 4,680,375 teach the preparation of polymers containing cyanine dyes in the polymer backbone for optical recording. These materials are sufficiently stable so as not to be chemically changed upon exposure to near infrared laser light and are not useful in lithographic printing.
U.S. Pat. No. 5,824,768 also teaches to the preparation of polymeric dyes for optical recording. More particularly these dyes are used as coatings in recordable CDs. These materials do not undergo chemical changes upon exposure to near infrared laser light and are not useful.
EP 0652483A1 teaches the preparation of lithographic printing plates, which by virtue of a coating composition can be imaged by near infrared laser light and which do not require wet chemical development. The coating composition contains near infrared absorption dyes, thermal acid generators and polymers having pendant hydrophobic groups such as t-alkyl carboxylates, t-alkyl carbonates, benzyl carboxylates and alkoxyalkyl esters. Upon exposure to near infrared laser light, the exposed area becomes hydrophilic, therefore repelling water based inks. The unexposed areas remain hydrophobic and become the image areas. This type of coating composition however requires high laser power to image and is sensitive to handling.
U.S. Pat. No. 5,569,573 also teaches the preparation of lithographic printing plates, which can be imaged with near infrared laser light and do not require wet chemical development. The laser imaging layer comprises microencapsulated oleophilic materials in hydrophilic binder resins capable of forming a three dimensional network with the microcapsulated oleophilic materials upon exposure to near infrared laser light to becomes image area. This type of coating is difficult to prepare and requires high laser power to achieve imaging.
EP 0 770 495 A1 teaches to prepare lithographic printing plates, which can be imaged with near infrared laser light. The unexposed areas are removed on press with ink and fountain solution. The imaging layer comprises near infrared absorption materials, polymer binders and thermoplastic particles capable of coalescing under heat. This type of coating offers poor substrate adhesion and consequently fail to provide sufficient run length on press.
Thus there remains a need for new polymer coating compositions which overcome the drawbacks of the prior art coatings. The goals are to achieve coating compositions combining the advantages of long-life printing plates, absence of phase separation of the different ingredients in the coating formulation, easily manufactured and inexpensive coating formulations, precisely imagable coatings providing high image resolutions.
SUMMARY OF THE INVENTION
The present invention relates to the preparation of thermally reactive near infrared absorption polymers and to their use in lithographic printing plates for computer-to-plate and digital-offset-press technologies. More particularly, this invention relates to thermally reactive near infrared absorption polymers having repeating units according to Formula I:
Wherein
E represents the near infrared absorption segment, which exhibits strong absorption bands between 780 and 1200 nm.
F represents the processing segment, which provides excellent film forming properties and solubility in aqueous solutions having pH between 2.0 and 14.0
G represents the thermally reactive segment, which undergoes chemical or physical reactions with or without catalysts upon exposure to near infrared laser light.
a, b and c represent the molar ratios, which vary from 0.01 to 1.00
and wherein the molecular weight is greater than about 5,000.
The present invention also relates to the use of thermally reactive near infrared absorption polymers for making lithographic printing plates, which can be digitally imaged with solid state diode lasers and do not require wet chemical developing process. More particularly, the lithographic printing plates of the present invention comprise an imaging layer containing thermally reactive near infrared absorption polymers of the present invention, optional binder resins and film forming additives applied to a heat insulating hydrophilic layer coated on any suitable substrate such as papers, plastics or aluminum.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that this detailed description, while indicating preferred embodiments of the invention, is given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.
DETAILED DESCRIPTION OF THE INVENTION
The thermally reactive near infrared absorption polymers of this present invention may be described accordingly to Formula II to V:
Wherein
F represents a processing unit, which is selected from alkyl acrylate, alkyl methacrylate, hydroxy alkyl acrylate, hydroxy alkyl methacrylate, methyl acrylic acid, methyl methacrylic acid, hydroxy phenyl, hydroxy styrene, sulfoalkyl acrylic acid, sulfoalkyl methacrylic acid, sulfoalkyl acrylic acid metal salts, sulfoalkyl methacrylic acid metal salts, vinyl pyridine, vinyl alkyl pyridium salts, dialkylamino acrylate, and dialkylamino methacrylate.
G represents a thermally reactive unit, which is selected from hydroxy akyl acryalate, hydroxy alkyl methacrylate, hydroxy styrene, amino styrene, N-alkoxymethyl acrylamide, N-alkoxymethyl methacrylamide, glycidyl alkyl acrylate, and glycidyl alkyl methacrylate.
X represents an anionic counter ion selected from bromide, chloride, iodide, tosylate, triflate, trifluoromethane carbonate, dodecyl benzosylfonate and tetrafluoroborate.
M represents oxygen, sulfur, dialkyl amine.
m represents number of repeating uni
American Dye Source, Inc.
Goudreau Gage Dubuc
Truong Duc
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