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
2001-12-10
2004-09-14
Gilliam, Barbara (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
C430S964000, C101S453000
Reexamination Certificate
active
06790588
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The invention relates to amino acid and amides and their use in imagable articles. In particular the invention relates to amino acid or amide-containing compositions and to their use in heat-sensitive film-forming coatings for imagable articles.
2. Background to the Invention
Imagable articles, such as lithographic printing form precursors, electronic part precursors and mask precursors, conventionally comprise a substrate onto which is coated a film-forming radiation-sensitive composition. After image-wise exposure of the precursor to radiation of suitable wavelength, and development of the imaged precursor, an imaged article is produced.
Negative working imagable article precursors have a radiation sensitive coating, which, when imagewise exposed to radiation of a suitable wavelength, hardens in the exposed areas. On development, the non-exposed areas of the coated composition area removed, leaving the image.
The coatings are normally laid down as solutions in organic solvents, which are removed by evaporation. Conventionally, ultra-violet or visible radiation has been employed to image compositions sensitive to radiation of those wavelengths. Recently infra-red (IR) radiation has become of interest.
In many proposals the compositions contain IR absorbers which convert IR radiation to heat, and it is the heat which is the direct cause of the hardening in the negative-working compositions. A heated body delivering heat conductively to corresponding compositions not containing IR absorbers can likewise effect a solubility change. A suitable IR radiation source is an IR laser digitally controlled to produce the required pattern of heated areas. Thus, these compositions are suitable for advanced “Computer-to-Plate” (CTP) techniques. Some compositions, which are not additionally sensitive to ultra-violet or visible radiation offer the advantage, over traditional photosensitive recording compositions, that they do not need to be handled in a dark room, or under ultra-violet safelighting conditions, but can simply be handled in ordinary light.
There are many examples of negative working compositions which are sensitive to IR radiation, and which are used in coatings on imagable articles. Many such negative working compositions utilise acid-polymerisable monomers in conjunction with a radiation absorbing compound and a compound capable of generating an acid upon heating.
U.S. Pat. No. 4,961,960 discloses photo-curable coating compositions comprising a photo-curable monomer or polymer, and a compound having a blocked isocyanate group and at least one ethylenically unsaturated group. These coatings are cured by exposure to ultra-violet light.
U.S. Pat. No. 4,997,745 discloses photopolymerisable compositions comprising a trihalomethyl-s-triazine compound, a photosensitiser in the form of an IR dye and a polymerisable compound having at least one ethylenically unsaturated group.
EP 854,388 discloses a negative-working image record material containing a polymer having a heterocyclic group containing an unsaturated bond therein, a cross-linking agent that cross-links with the aid of an acid, and a compound that generates an acid on exposure to light or heat.
U.S. Pat. No. 5,372,907 discloses a radiation sensitive composition adapted to be sensitive to both ultra-violet and infra-red radiation and capable of functioning in either a positive- or negative-working manner, the composition comprising a resole resin, a novolac resin, a latent Bronsted acid and an infra-red absorber. The solubility of the composition in aqueous alkaline developing solution is both reduced in exposed areas and increased in unexposed area by imagewise exposure to radiation and heating.
EP 903,225 discloses a light sensitive composition comprising an acid generating compound, an infra-red absorbing compound, either a compound which is decomposable by acid or a compound having a group which is cross-linkable by an acid, and a polymer obtained from a polymerisable composition comprising an ethylenically unsaturated monomer.
The prior compositions display disadvantages in use as coatings for imagable articles. Some of the prior art compositions in which polymerisation occurs suffer from the fact that there is no efficient termination stage during polymerisation, which can lead to inconsistencies in the molecular weight distribution of the polymer on the substrate of the imagable article, and hence inconsistent image and non-image areas. Other monomers used in prior art compositions are prohibitively expensive or have difficult synthetic pathways.
It is therefore an object of the present invention to provide a negative-working radiation sensitive composition which overcomes at least some of the disadvantages displayed by the prior art.
The applicants have surprisingly found that the use of amino acid and amides, in conjunction with a compound capable of generating an acid on heating, and preferably with an IR absorbing compound, provides a negative-working composition which has an efficient termination stage during polymerisation and which is cheap and easy to manufacture. Furthermore amino acids and amides may be incorporated as pendent groups on polymeric substances suitable for use in negative-working compositions.
SUMMARY OF THE INVENTION
According to the present invention there is provided an imagable article comprising a thermally imagable coating on a substrate, the coating comprising a compound capable of generating an acid upon heating, and an amino acid or amide compound or moiety capable of polymerizing when said compound generates an acid on heating.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides an imagable article comprising a thermally imagable coating on a substrate, the coating comprising a compound capable of generating an acid upon heating, and an amino acid or amide compound or moiety capable of polymerizing when said compound generates an acid on heating. Preferably the coating further comprises a compound capable of absorbing radiation and converting it to heat.
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.
Preferably the coating comprises a composition including the amino acid or amide and the acid generating compound in admixture. More preferably the coating comprises a composition including the amino acid or amide, the acid generating compound and the radiation absorbing compound in admixture.
Alternatively the coating may comprise at least two layers and the radiation absorbing compound is provided in a separate layer to the amino acid or amide and the acid generating compound.
In one embodiment of the invention the radiation absorbing compound may be provided in an underlayer of the coating and the amino acid or amide and the acid generating compound are provided in an overlayer of the coating, the underlayer being applied to the substrate first, and the overlayer being applied on top of the underlayer.
Suitable amino acids include linear amino acid having the general formula (I) below:
HOOC—(CH
2
)
n
—NH
2
(I)
where n is 1 to 20, preferably 1 to 12.
Particularly useful amino acids of formula (J) include 6-aminocaproic acid and 12-aminododecanoic acid.
Preferably the amide is a cyclic amide.
Suitable cyclic amides include lactams of general formula (II) below, and their derivatives:
where n is 2 to 10, preferably 3 to 6.
Particularly suitable lactams of formula (II) include caprolactam and valerolactam. Preferably the caprolactam is &dgr;-caprolactam, and the valerolactam is &egr;-valerolactam.
Suitable lactam derivatives include vinyl lactams.
Other suitable cyclic amides include 2-azacyclotridecanone, or 4-azatricycloundecan-5-one.
Suitably the amino acid or amide constitutes at least 50% of the total weight of the coating, preferably at least 60%, more preferably at least 70% and most preferably at least 80% of the total weight of the coating.
Suitably the amino acid or amide constitutes no more than 95%
Howard Denise
Turner Gregory
Faegre & Benson LLP
Gilliam Barbara
Kodak Polychrome Graphics LLC
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