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
1996-01-11
2001-12-04
Dote, Janis L. (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S282100, C430S288100, C430S306000, C430S910000, C522S110000, C522S137000, C522S148000
Reexamination Certificate
active
06326126
ABSTRACT:
The invention relates to a photocurable negative-working mixture and a recording material which is obtained therefrom and which is suitable for the production of elastic relief printing plates, planographic printing plates and resist materials.
Mixtures of the generic type mentioned are known and usually contain an elastomeric binder, a free-radical-polymerizable compound and a polymerization initiator which can be activated by actinic radiation. Such mixtures, which are described, for example, in DE-A 22 15 090 (=GB-A 1 366 769) use as binders thermoplastic block copolymers composed of non-elastomeric and elastomeric blocks, the exposed printing form being developed to produce a relief image by organic solvents.
Although DE-A 27 25 730 (=U.S. Pat. No. 4,042,386), DE-A 30 03 011 (=ZA 80/506), DE-A 33 22 994 (=U.S. Pat. No. 4,554,240) and EP-A 0 130 828 describe recording materials developable in aqueous media and based on partially hydrolyzed polyvinyl acetate derivatives, the water resistance of such systems is low, with the result that use with water-dilutable printing inks is impossible. DE-A 30 12 841 (=U.S. Pat. No. 4,272,608) and DE-A 35 43 646 (=U.S. Pat. No. 4,916,045) EP-A 0 277 418, 0 261 910, 0 183 552, 0 251 228 and 0 273 393, and also GB-A 2 179 360, U.S. Pat. Nos. 4,517,279 and 4,446,220 therefore propose recording materials based on diene elastomers containing carboxyl groups. If the proportion of carboxyl groups is kept low in such systems, developability in aqueous media can only be achieved with difficulty and it is necessary to add a high proportion of polar monomers or auxiliaries, which result, in turn, in high cold-flow of the unexposed material. Although an increase in the carboxyl group content results in an improved developability in aqueous media, the rubber-elastic properties of these materials deteriorate for system reasons. In addition, the resistance to water-containing printing inks decreases.
In addition to the desire for environmentally friendly development of the relief layers, an improvement in the specific characteristics within the printing process is desirable. For example, if non-absorbent printing materials such as sheets of polyester, aluminum, PVC or PVDC are to be imprinted, an adequate ink coverage and ink drying speed can be achieved only by the presence of so-called “accelerators”. These are usually organic solvents such as ethyl acetate, propyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone etc., which can accelerate the drying process by rapid evaporation and, in addition, may have adhesion-promoting activity. The known “photopolymer” relief printing forms are, however, insufficiently resistant to such solvents, i.e. strong swelling of the relief layer reduces the reproduction quality and prevents a high printing run. DE-A 38 03 457 (=U.S. Pat. No. 4,994,344) describes sheet-like photo-sensitive recording materials which have beneficial swelling properties in relation to the accelerators mentioned. The binders used in such systems are so-called EPM and EPDM elastomers. Because of their saturated polymer main chain, these materials are largely nonpolar, with the result that compatibility problems frequently arise in the production of photopolymerizable recording materials. In this connection, this frequently deficient compatibility with olefinically unsaturated monomers, polymerization initiators, dyes, plasticizers and other additives results, as a rule, in products having inadequate processability and also poor mechanical and reproduction quality. As described, for example, in DE-A 39 05 947 (=U.S. Pat. No. 5,147,757) to improve the properties, it is necessary to incorporate so-called “compatibilizers”, which, although they reduce the compatibility problem in such materials, which are described as blends, are, as a rule, unsuitable, or have to be described as extremely troublesome, in optically transparent systems owing to the formation of discreet phases.
Printing forms such as those described in DE-A 22 15 090 require ozone resistance. Ozone is produced, for example, during the imagewise exposure of the photopolymerizable elastomeric layer, in particular if UV light is used, but also when using the exposed and developed printing forms in a printing operation. Especially in the latter case, particularly high ozone concentrations occur, in particular if flexible packaging materials such as paper or plastics have to be imprinted. Since appreciable amounts of ozone are produced during corona treatment and corona treatment is most effective if it is carried out immediately prior to the printing process, the printing form comes into contact with ozone produced by this process to an appreciable extent. The susceptibility of the developed printing forms to ozone is increased still further because, in most cases, the printing form is post-treated with halogen or UV-C-radiation, which is necessary to reduce its tackiness.
In DE-A 22 15 090, waxes, certain thioureas, various polymers etc. are added to the photopolymer mixture to increase the ozone resistance. The disadvantage of this procedure is that the additives mentioned are often insufficient to ensure the required resistance to ozone, or if the active concentration of these additives is increased, the photopolymerizable mixture exhibits turbidities to such an extent that a perfect exposure can no longer be achieved. Other patents describe methods of post-treating the developed and treated printing form with, for example, Ni or Zn dialkyldithiocarbamates (EP-A 0 137 331), liquid polyethers (DE-A 35 12 632=U.S. Pat. No. 4,680,251) or polyamide solutions (DE-A 34 15 044=U.S. Pat. No. 4,640,877). Apart from the additional operational step, relief printing forms treated in this way frequently exhibit initial crack formations after a short exposure to air containing ozone.
The object of the invention was to propose binders for photosensitive elastomeric mixtures which, while retaining the thermoplastically elastic properties, can be tailored to suit the printing application.
Surprisingly, it has now been possible to achieve this object by using symmetrical or asymmetrical block copolymers having a segment composition adapted to the particular application purpose as binders.
The invention relates to a photocurable elastomeric mixture which contains:
a) an amphiphilic elastomeric binder or a mixture of such binders,
b) a free-radical-polymerizable compound which is compatible with the binder and which has at least one terminally ethylenically unsaturated group and a boiling point at normal pressure of over about 100° C. and
c) a compound or a combination of compounds which is capable of initiating the polymerization of compound (b) on exposure to actinic light
and the binder is made up of the segments A, B and C, where
A is a hydrophobic, soft block having a glass transition temperature T
g
of below about −30° C.,
B is a hydrophobic hard block having a glass transition temperature T
g
of over about +30° C.,
C is a polar block which is made up of vinyl monomers and/or heterocyclic compounds which can be polymerized by anionic ring opening or a combination thereof.
These block copolymers may be built up in variety of ways, depending on which and how many of these segments the copolymer contains and how said segments are linked to one another. These block copolymers may, for example, have the following structures: A-B-C, A-B-A-C, or C-A-B-A-C. It is furthermore possible to build up the block C of various sub-blocks, by copolymerization of various monomers.
Suitable monomers for the block polymers A are conjugated dienes such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-3-ethyl-1,3-butadiene, 3-methyl-1,3-pentadiene, 2-methyl-3-ethyl-1,3-pentadiene, 2-ethyl-1,3-pentadiene, 1,3-hexadiene, 2-methyl-1,3-hexadiene, 1,3-heptadiene, 1,3-octadiene, 3,4-dimethyl-1,3-hexadiene and 2-phenyl-1,3-butadiene. The use of mixtures of suitable dienes or the use of other anionic
AGFA-GEVAERT
Dote Janis L.
Foley & Lardner
LandOfFree
Photocurable elastomeric mixture and recording material... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Photocurable elastomeric mixture and recording material..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Photocurable elastomeric mixture and recording material... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2597795