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
2000-04-25
2003-05-06
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
C430S281100, C430S286100, C430S302000, C430S303000, C430S311000, C430S325000, C430S326000, C430S348000, C430S944000, C430S945000, C430S964000
Reexamination Certificate
active
06558869
ABSTRACT:
This invention relates to the formation of a resist pattern in the preparation of, for example, a planographic, especially a lithographic, printing member or electronic parts such as printed circuits, or masks. Particularly, although not exclusively, there is described a precursor for preparing a resist pattern; a method of preparing a said precursor; a method of preparing a resist pattern; a formulation; a kit; and a printing member.
Lithographic processes involve establishing image (printing) and non-image (non-printing) areas on a substrate, substantially on a common plane. When such processes are used in printing industries, non-image areas and image areas are arranged to have different affinities for printing ink. For example, non-image areas may be generally hydrophilic or oleophobic and image areas may be oleophilic.
A conventional lithographic printing member precursor has a light sensitive coating over an aluminium support. Negative working lithographic printing member precursors have a radiation sensitive coating which when imagewise exposed to light hardens in the exposed areas. On development, the non-exposed areas of the coating are removed leaving the image. On the other hand, positive working lithographic printing member precursors have a radiation sensitive coating which, after imagewise exposure to light, has exposed areas which are more soluble in a developer than non-exposed areas. This light induced solubility differential is called photosolubilisation. A large number of commercially available positive working printing member precursors coated with quinone diazides together with a phenolic coated with quinone diazides together with a phenolic resin work by photosolubilisation to produce an image. In both cases the image area on the printing member itself is ink-receptive or oleophilic and the non-image area or background is water receptive or hydrophilic.
In addition to quinone diazides/phenolic resins, conventional positive working light sensitive compositions may include minor amounts of additives which are arranged to cause small changes in selected properties of the compositions. For example, additives are known for improving the quality and/or uniformity of a process for coating light sensitive compositions on a support; for improving resistance of compositions to white light fogging or to processing chemicals (e.g. isopropyl alcohol, UV ink, plate cleaner etc); and for improving ink adhesion to a form surface at the start of printing. Any effect such additives may have on the solubility of the compositions is small and/or incidental.
Recent developments in the field of lithographic printing form precursors have resulted in radiation-sensitive compositions useful for the preparation of direct laser addressable printing form precursors. Digital imaging information can be used to image the printing form precursor without the need to utilise an imaging master such as a photographic transparency.
U.S. Pat. No. 5,491,046 (Kodak) describes a laser addressable printing member precursor which, it is stated, can be utilised as a direct positive working system. The patent describes a radiation induced decomposition of a latent Bronsted acid to increase the solubility of a resin matrix on imagewise exposure.
In general, the quinone diazide/phenolic resin conventional positive working light sensitive precursors described above comprise a composition which is inherently generally very insoluble in alkaline developers. Thus, non-exposed areas have a relatively low tendency to dissolve in developer during development, yet UV exposure still renders the exposed areas developer soluble. However, heat sensitive positive working precursors generally have quite different chemistries and may comprise a composition which has a much higher solubility in alkaline developers. As a result, the solubility differential between exposed and non-exposed areas in laser addressable precursors is much narrower than for conventional precursors. Consequently, development of laser addressable precursors must be carried out under strictly controlled conditions, whereas conventional precursors can be developed under a relatively wide range of conditions.
To the Applicant's knowledge, the only commercially available printing member precursor which uses an IR laser to affect the relative solubilities of exposed and non-exposed areas to provide a printing member is a negative working precursor of a type described in U.S. Pat. No. 5,491,046, referred to above. No laser addressable positive working precursors (described in U.S. Pat. No. 5,491,046 or elsewhere) are commercially available. One of the reasons for this may be due to the narrow solubility differentials between exposed and non-exposed areas in the positive working compositions proposed. However, the aforementioned patent neither addresses, solves or provides any insight or comment into the problem of the relatively narrow solubility differential between imaged and non-imaged areas of heat sensitive positive working radiation sensitive compositions. It is an object of the present invention to address this problem.
The types of electronic parts whose manufacture may use a radiation sensitive composition include printed wiring boards (PWBs), thick-and thin-film circuits, comprising passive elements such as resistors, capacitors and inductors; multichip devices (MDCs); integrated circuits (ICs); and active semiconductor devices. The electronic parts may suitably comprise conductors, for example copper board; semiconductors, for example silicon or germanium; and insulators, for example silica as a surface layer with silicon beneath, with the silica being selectively etched away to expose portions of the silicon beneath (a step in the manufacture of e.g. field effect transistors). In relation to masks, a required pattern may be formed in the coating on the mask precursor, for example a plastics film, which is then used in a later processing step, in forming a pattern on, for example, a printing or electronic part substrate.
The invention is based on the discovery that certain additives which have little or no effect on the solubility differential between imaged and non-imaged areas in conventional light sensitive printing member precursors have a surprisingly large and advantageous effect on the solubility differential between imaged and non-imaged areas of heat-sensitive positive radiation sensitive compositions.
According to a first aspect of the present invention, there is provided a precursor for preparing a resist pattern by heat mode imaging, the precursor comprising a heat sensitive composition, the solubility of which in an aqueous developer is arranged to increase in heated areas, and a means for increasing the resistance of non-heated areas of the heat sensitive composition to dissolution in an aqueous developer (hereinafter the “developer resistance means”), wherein said developer resistance means comprises one or more compounds selected from the groups comprising:
(A) compounds which include a poly(alkylene oxide) unit;
(B) siloxanes; and
(C) esters, ethers and amides of polyhydric alcohols.
Developer resistance means of the type described have been found, surprisingly, to provide a relatively large increase in the resistance of non-heated areas to developer compared to the resistance when no developer resistance means is present. For example, there may be at least a 50% increase in the time taken for a first heat sensitive composition containing a said developer resistance means to completely dissolve in a developer (e.g. a typical commercially available positive lithographic plate developer) compared to the time taken for complete dissolution of a heat sensitive composition which does not contain said developer resistance means but is in all other respects identical to said first heat sensitive composition. In some embodiments, the increase may be greater than 65% or even greater than 80%. Preferably developer resistance means of the present invention do not have acid labile groups. Preferably the composition does not pro
Bayes Stuart
Bennett Peter Andrew Reath
Hearson John Andrew
Hoare Richard David
Kitson Anthony Paul
Baxter Janet
Faegre & Benson LLP
Gilliam Barbara
Kodak Polychrome Graphics LLC
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