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
1999-11-19
2001-10-09
Baxter, Janet (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
C430S005000, C430S302000, C430S311000, C430S320000
Reexamination Certificate
active
06300038
ABSTRACT:
FIELD OF THE INVENTION
The present specification relates to articles having positive working heat imagable coatings, for example precursors which are imaged and developed in the production of lithographic printing plates and electronic parts. The invention relates further to the manufacture of such precursors, and to their use in making articles such as lithographic printing plates, electronic parts and masks.
BACKGROUND OF THE INVENTION
A generally used type of lithographic printing plate precursor has a radiation sensitive coating applied to an aluminum substrate. A positive working precursor has a radiation sensitive coating, which after imagewise exposure to radiation of a suitable wavelength becomes more soluble in the exposed areas than in the non-exposed areas, in a developer. Only the remaining, image, area of the coating is ink-receptive.
The differentiation between image and non-image areas is made in the exposure process where a film is applied to the printing plate precursor with a vacuum to ensure good contact. The printing plate precursor is then exposed to a radiation source; conventionally this has been a UV radiation source. In the case where a positive printing plate precursor is used, the area of the film that corresponds to the image in the printing plate precursor is opaque so that no light will strike the printing plate precursor, whereas the area on the film that corresponds to the non-image area is clear and permits the transmission of light to the coating which becomes more soluble and is removed on development.
In the manufacture of electronic parts such as printed circuits, after exposure to radiation and development, the resist pattern is used as a mask for forming the patterns onto the underlying electronic elements—for example by etching an underlying copper foil. Due to the high resolution demands and the requirements of high resistance to etching techniques, positive-working systems are widely used. In particular, in the main there have been used alkali developable positive working resists mainly composed of alkali-soluble novolac resins.
The types of electronic parts whose manufacture may use a resist include printed wiring boards (PWBs), thick- and thin-film circuits, comprising passive elements such as resistors, capacitors and inductors; multichip devices (MDCs); and integrated circuits (ICs). These are all classified as printed circuits.
Imagable compositions may also be applied to plastics films in order to form masks. The required pattern is formed on the mask, which is then used as a screen in a later processing step, in forming a pattern on, for example, a printing plate or electronic part precursor.
Common to virtually all commercial applications of positive working systems employing UV radiation over several decades have been compositions comprising alkali soluble phenolic resins and naphthoquinone diazide (NQD) derivatives. The NQD derivatives have been simple NQD compounds used in admixture with resins, or NQD resin esters in which the photoactive NQD moiety has been chemically attached to the resin itself, for example by esterification of the resin with an NQD sulphonyl chloride.
As demands on the performance of UV sensitive positive working coatings have increased so NQD technology has become limiting. In addition, digital and laser imaging technology is making new demands on coatings.
We have devised new positive working heat sensitive systems, to meet the new demands. Our new systems and methods are the subject of our patent applications WO 97/39894, WO 99/01796, WO 99/01795, WO 99/08879, WO 99/21715, WO 99/21725 and WO 99/11458 which are hereby incorporated by reference in their entirety. Heat is delivered to the coatings described by conduction, using a heated body such as a stylus, or by charged particle radiation, or, preferably, by means of infra-red radiation, the coatings then containing suitable infra-red absorbers.
Our new systems are very effective and are in production, and proving very successful in the marketplace, but it would be desirable to improve them further, by making their coatings more resistant to the effects of movement; for example within the manufacturing plant; during transportation from the manufacturing plant to a customer's site; and within the customer's site. One example of a source of problems in the customer's site is at the image setter. This will often have linear conveying equipment to convey a precursor into and out of the image setter, and this can leave markings in the travel direction, and/or it may have lifting equipment which can leave markings caused by elastomeric lifting disks.
It is an object of the invention to provide articles having coatings which may be imaged by heat, the articles having good resistance to the effects of movement, especially caused by mechanical handling equipment, notably such equipment used by printers and printed circuit board manufacturers.
SUMMARY OF THE INVENTION
We have devised technology which offers improvement of our new systems mentioned above, such that their coatings continue to show good develop ability, with heated areas dissolving in aqueous developers and with unheated areas remaining insoluble in such developers, but wherein the coatings have improved mechanical properties.
In accordance with a first aspect of the invention there is provided a positive working heat imagable lithographic precursor comprising a substrate and a polymeric coating thereon, wherein all of the polymeric coating thereon is in a single layer applied to the substrate by application of an organic solvent containing the polymeric material of the polymeric coating, and removal of the organic solvent, wherein the coating comprises a polymeric matrix material and polymeric particles therein, wherein the polymeric matrix material is soluble in an organic solvent and the polymeric particles are insoluble in the organic solvent, the coating having the property that when imagewise heated and then subjected to an aqueous developer, heated regions of the coating are selectively removed by the aqueous developer leaving behind unheated regions.
In accordance with a second aspect of the invention there is provided a positive working heat imagable lithographic precursor comprising a substrate and a polymeric coating thereon, wherein the polymeric coating thereon is provided in more than one layer, wherein one layer of the coating, not being the outer layer, is formed by application of an organic solvent containing the polymeric material of that layer, and removal of the organic solvent, wherein that layer comprises a polymeric matrix material and polymeric particles therein, wherein the polymeric matrix material is soluble in an organic solvent and the polymeric particles are insoluble in the organic solvent, the coating having the property that when imagewise heated and then subjected to an aqueous developer, heated regions of the coating are selectively removed by the aqueous developer leaving behind unheated regions.
Preferably the polymeric particles are such that the coating containing them has improved mechanical properties, compared with a corresponding coating with no such particles (that is, in which the weight proportion which would have been constituted by the polymeric particles is instead constituted by the same weight of matrix material). Preferably the coating containing polymeric particles has improved resistance to mechanical handling equipment used in the manufacture and/or use of lithographic plate precursors and/or plates.
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patent:
Parsons Gareth Rhodri
Riches John David
Shimazu Ken
Baker & Botts L.L.P.
Baxter Janet
Gilmore Barbara
Kodak Polychrome Graphics LLC
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