Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2000-10-26
2003-02-25
Hamilton, Cynthia (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S270100, C430S271100, C430S944000
Reexamination Certificate
active
06524767
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the use of metal compounds in imagable articles. In particular the invention relates to the use of thermally decomposable metal compounds in imagable coatings on electronic parts, lithographic printing plates and their precursors.
BACKGROUND OF THE INVENTION
Conventionally, lithographic printing plates and electronic parts, such as printed circuit boards (PCBs), which have image areas consisting of elemental metal, (herein after referred to as “metal image lithographic printing plates” or “metal image electronic parts”) have been prepared using multi-stage subtractive or additive techniques.
Conventional metal image lithographic printing plates are generally bimetal plates consisting of a metal image on a substrate of, for example, aluminium or stainless steel. Usually a continuous layer of metal is deposited onto the substrate and the resultant layer is then etched to leave the desired image. This process is a subtractive process, and the metal used to layer the plate is generally copper, which can then be etched with suitable chemical etchants such as ferric chloride.
An example of an additive process which has been used to create metal image lithographic plates, consists of depositing a metal through a stencil onto a substrate to form the desired image, for example by precipitating a metal from a corresponding metal salt solution.
In both additive and subtractive processes used to prepare metal image lithographic printing plates, the resultant metal image areas are oleophilic, or ink-accepting, whereas the background substrate is hydrophilic or ink-repelling.
EP 407 081 A discloses a method of producing a metal image lithographic printing plate by applying a copper salt or copper compound to a substrate and then irradiating the desired image areas with controlled electromagnetic radiation to decompose the copper salt or copper compound and deposit an image of metallic copper on the substrate. The remaining non-imaged areas of copper salt or copper compound are then conveniently washed off.
Copper is also used extensively in the electronics industry as an interconnect material, because of its high conductivity and resistance to electromigration. The direct writing of copper onto substrates for use in printed circuit boards is well known. The methods used to deposit copper onto the substrate are similar to the subtractive and additive methods used in the production of lithoplates employing direct metal writing.
WO93/03197 discloses a method for the production of electronic parts employing laser-induced direct copper writing. Direct writing refers to the formation of image areas consisting of element metal by the direct deposition of the elemental metal onto the image areas of a substrate, without the need for additive or substantive processed described above. Direct writing removes the need for etching processes or the use of masks or stencils. In WO 93/03197 a solution of copper formate and a crystallisation inhibiting compound, such as glycerol, citric acid or malic acid, are deposited as a thin film onto a substrate, dried and image-wise exposed to a heat source to decompose the copper formate image-wise. The non-imaged areas are then removed to leave behind deposits of elemental copper on the images areas. Using a crystallisation inhibiting compound provides films that do not crystallise during drying and can then be exposed image-wise to laser light. Lasers disclosed in WO93/03197 as suitable for use in direct copper writing include Nd: YAG, Ar
+
, CO
2
and excimer lasers.
Conventional direct metal writing techniques suffer from the fact that the efficiency and speed of decomposition of the metal compound is limited by the efficiency of the metal compound in absorbing laser light sufficient to decompose the compound to elemental metal. This deficiency results in higher imaging power being needed in order to decompose the metal salt or compound to element metal in a useful time period.
In WO93/03197 the amount of laser energy needed to obtain acceptable copper images by direct writing of copper formate is in the region of 2500 J cm
−2
.
The present invention provides a new heat sensitive system suitable for employing in the direct metal writing of imagable articles such as printing plates and electronic parts, which overcomes the difficulties presented in the conventional systems described above.
SUMMARY OF THE INVENTION
The inclusion of a radiation absorbing compound in a coating comprising a metal salt has been found to substantially reduce the energy needed to decompose the metal compound to elemental metal in a direct writing process.
In accordance with the present invention there is provided an imagable article comprising a thermally imagable coating on a substrate, the coating comprising a radiation absorbing compound and a metal compound which is thermally decomposable, to form a metal.
DETAILED DESCRIPTION OF THE INVENTION
The coating may comprise a composition including the radiation absorbing compound and thermally decomposable metal compound in admixture. The coating may further comprise one or more polymers useful as a film-forming compound and/or binding agent.
Suitable polymers useful as film-forming agents and/or binding agents in the present invention include gum arabic, carboxymethylcellulose or other water-soluble celluloses, dextrins, alginates, polyvinyl pyrrolidone, polyvinyl alcohol, hydrolysed polyvinyl methyl ether-maleic anhydride copolymers, and mixtures thereof.
Preferably the polymer comprises a polymer having hydroxyl groups.
Particularly useful polymers having hydroxyl groups in this invention are condensation reaction products between appropriate phenols, for example phenol itself, C-alkyl substituted phenols (including cresols, xylenols, p-tert-butyl-phenol, p-phenylphenol and nonyl phenols), diphenols e.g. bisphenol-A (2,2-bis(4-hydroxyphenyl)propane), and appropriate aldehydes, for example formaldehyde, chloral, acetaldehyde and furfuraldehyde and/or ketones, for example acetone. Dependent on the preparation route for the condensation a range of phenolic materials with varying structures and properties can be formed. Particularly useful in this invention are novolac resins, resole resins and novolac/resole resin mixtures. Most preferred are novolac resins. The type of catalyst and the molar ratio of the reactants used in the preparation of phenolic resins determines their molecular structure and therefore the physical properties of the resin. An aldehyde: phenol ratio between 0.5:1 and 1: 1, preferably 0.5:1 to 0.8:1 and an acid catalyst is used to prepare novolac resins.
Examples of suitable novolac resins have the following general structure
wherein the ratio of n:m is in the range of 1:20 to 20:1, and preferably 1:3 to 3:1. In one preferred embodiment, n=m. In certain embodiments, n or m may be zero.
Other polymers suitable for inclusion in the composition, notably in admixture with a phenolic, preferably novolac, resin include: a polymer or copolymer of styrene, a polymer or copolymer of hydroxystyrene, notably of 4-hydroxystyrene or 3-methyl-4-hydroxyystyrene, a polymer or copolymer of an alkoxystyrene, notably of 4-methoxystyrene, a polymer or copolymer of acrylic acid, a polymer or copolymer of methacrylic acid, a polymer or copolymer of acrylonitrile, a polymer or copolymer of acrylamide, a polymer or copolymer of vinyl alcohol, an acrylate polymer or copolymer, a polymer or copolymer of methacrylamide, a sulfonamido or imido polymer or copolymer, a polymer or copolymer of maleiimide or of alkylmaleiimide or of dialkylmaleiimide, or a polymer or copolymer of maleic anhydride (including partially hydrolysed forms).
Other suitable polymers useful as film-forming compounds and/or binding agents include poly(methyl methacrylate), epoxy resins, polyamides, solid acrylic resins, and copolymers thereof.
The coating may be dissolved in a solvent and applied to the substrate in liquid form, from which the solvent is preferably removed by evaporation.
Alternatively, the c
Kitson Anthony Paul
Monk Alan Stanley Victor
Ray Kevin Barry
Faegre & Benson LLP
Hamilton Cynthia
Kodak Polychrome Graphics LLC
LandOfFree
Use of metal compounds in imagable articles does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Use of metal compounds in imagable articles, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Use of metal compounds in imagable articles will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3174232