Polymeric compounds

Details Polymeric compounds Polymeric compounds

2000-12-01

2002-11-05

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

C430S283100, C524S530000, C524S553000, C525S205000, C525S282000

Reexamination Certificate

active

06475698

ABSTRACT:

This invention relates to polymeric compounds and particularly, although not exclusively, relates to polymeric compounds which incorporate an N-substituted cyclic imide moiety. Compounds of the invention may be used in radiation sensitive layers of printing members, especially lithographic printing plates or in radiation sensitive layers used in the manufacture of electronic parts such as printed circuits.
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. In “wet” lithographic printing, a dampening or fountain (water-based) liquid is applied initially to a plate prior to application of ink so that it adheres to the non-image areas and repels oil-based inks therefrom. In “dry” printing, ink is repelled from non-image areas due to their release property.
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 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 for use in “wet” printing or oleophobic for use in “dry” printing.
Recent developments in the field of lithographic printing member precursors have included the use of radiation sensitive compositions which can be imaged directly using a laser. Advantageously, digital imaging information can be used to image the precursor without the need to use an imaging master such as a photographic transparency. Examples of such compositions are provided in PCT Publication No. WO97/39894.
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.
Additives have been used to address problems associated with radiation sensitive coatings of UV printing plates. UV printing plates are plates which utilise an ink (“UV ink”) containing an ultraviolet absorber.
UV printing plates must use radiation sensitive compositions which are not substantially susceptible to attack by UV inks or any press chemicals associated with UV inks. For example, such compositions should be substantially insoluble in UV inks and substantially insoluble in solvents, often glycol ethers, used to clean the plates during a print run or after one print run and prior to another. Conventional quinone diazide/phenolic resin based radiation sensitive compositions are highly soluble in glycol ether solvents and, accordingly, cannot be used for UV printing plates.
Another problem that needs to be addressed in relation to many types of radiation sensitive compositions is that of ensuring that they are not substantially soluble in the founts (or dampening liquids) which are used to wet the hydrophilic areas of the plates. Traditionally founts are largely comprised of water and a small amount of alcohol. More recently, such founts have been replaced, in some situations, with formulations comprising alternative additives to water in order to remove inflammable alcohol solvents from press room environments. Additives that have been used include surfactants and other non-volatile solvents which can be more aggressive towards the compositions. Conventional radiation sensitive compositions are relatively susceptible to attack by the replacement founts and, accordingly, steps must be taken to reduce such susceptibility by using additives and/or different resins in the compositions.
Various additives and/or novel resins have been proposed for addressing the above described problems. However, often the additives/resins proposed are made by complicated and/or difficult and/or unversatile chemistry which limits their commercial application.
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).
This invention is based upon the discovery of a novel process for preparing polymeric compounds and novel compounds per se. The process is simple and highly versatile in allowing polymeric compounds to be produced having a wide range of desirable properties.
Thus, the object of the present invention is to provide a process and/or compounds which may be advantageous over the prior art.
According to a first aspect of the invention, there is provided a lithographic printing member precursor which includes a polymeric compound, suitably in a first layer of the printing member, having the structural unit
wherein R
1
represents an optionally-substituted cyclic or alkyl group and x represents 0 or 1.
According to a second aspect of the invention, there is provided a process for the preparation of a polymeric compound which process includes preparing a polymeric compound having the structural unit I described above by treating a polymeric compound having the structural unit
with an amine of formula R
1
NH
2
and optionally derivatising said compound having the structural unit I, wherein, in units I and II, R
1
represents an optionally-substituted cyclic or alkyl group and x represents 0 or 1.
It has been found that the identity of the unit I affects the solubility of polymeric compounds incorporating the unit to a significant degree. Advantageously, the process can be used to produce compounds having varying degrees of solubility in solvents used in lithographic, especially UV, printing. Thus, according to a third aspect, the invention provides a process for the preparation of a polymeric compound which process includes preparing a polymeric compound having the structural unit I as described above for a printing member precursor, especially a lithographic printing member precursor, the process including the step of selecting an amine of formula R
1
NH
2
as described above to give when reacted with a polymeric compound have a structural unit II as described above, and optionally derivatised, the desired resistance to a solvent used in printing; treating said compound having the structural unit II with said amine to yield a compound having the structural unit I; and optionally derivatising said compound having the structural unit I.
Unless otherwise stated in this specification, an alkyl or alkenyl group (whether alone or as part of another functional group, for example an alkoxy group) may be linear or branched and may have up to 20, suitably up to 16, preferably up to 12, more preferably up to 8, especially up to 4 carbon atoms.
Unless otherwise stated in this specification, a cyclic group m

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