Radiation imagery chemistry: process – composition – or product th – Diazo reproduction – process – composition – or product – Composition or product which contains radiation sensitive...
Reexamination Certificate
2002-04-11
2003-07-22
Chu, John S. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Diazo reproduction, process, composition, or product
Composition or product which contains radiation sensitive...
C430S157000, C430S176000, C430S302000, C525S056000, C525S061000
Reexamination Certificate
active
06596456
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to binders and radiation-sensitive compositions comprising said binders and, Inter alia, are excellently suitable for the production of lithographic plates.
BACKGROUND OF THE INVENTION
Currently, photosensitive compositions usable particularly for high-performance lithographic plates must fulfill high requirements.
In order to improve the properties of photosensitive compositions and thus also of the corresponding lithographic plates, essentially two different ways are taken. One of them deals with the improvement of the properties of the photosensitive components in the compositions (frequently negative diazo resins, photo polymers etc.), the other one with the search for novel polymeric compounds (“binders”), which are to control the physical properties of the photosensitive layers. In particular the latter way is decisive for lithographic plates because the behavior in the developing and printing processes (such as developability, ink receptivity, scratch resistance, consistency in the number of prints produced) is decisively influenced by the polymeric binders. Also shelf life and photosensitivity of the materials are strongly influenced by such polymeric compounds.
The polymeric binders, therefore, exhibit various structural elements for satisfying the extensive requirements, which may have different effects on individual properties. For instance, hydrophilic structural elements such as carboxyl groups, hydroxyl groups and the like generally promote the developability of the photosensitive compositions in aqueous alkaline developers and partly ensure sufficient adhesion to polar substrates. Hydrophobic structural elements, on the other hand, reduce the capability of being developed in the above-mentioned developers, but ensure the good ink receptivity used in the printing process, which is indispensable in lithographic plates.
Due to the broad range of requirements regarding the polymeric binders, there have been extensive studies for many years on the synthesis and optimization of the use of these substances for photosensitive compositions, cf. e.g. H. Baumann and H.-J. Timpe: “Chemical Aspects of Offset Printing” in
J. prakt. Chem./Chemiker-Zeitung
[Journal for chemists] 336 (1994) pages 377-389.
Negative photosensitive compositions for lithographic plates can be divided into the following two main groups:
a) Systems where the binder forms a network together with a photosensitive component due to exposure to light. Such photosensitive components are e.g. diazo resins; reactive photolysis products thereof react for example with OH groups of the binder. A disadvantage of these systems is their low print run stability.
b) Systems containing binders with photoreactive groups, which can be crosslinked by exposure to light (in many cases by the additional use of a sensitizer). These systems allow the production of plates with high print run stability.
The following applications and patents deal with systems of item b) above: U.S. Pat. No. 2,690,966 discloses cinnamic acid esters of polyvinyl alcohol useful in photomechanical resist compositions. GB-B-1274017 describes lithographic printing plates comprising a layer containing polyvinylacetal; the polyvinylacetal contains at least 10 wt.-% polyvinyl alcohol units which are partially esterified with cinnamic acid. These printing plates are, however, only developable with developers having a high solvent content which is disadvantageous for environmental reasons.
In U.S. Pat. No. 2,861,058 radiation-sensitive polymers are claimed where polyvinylalcohol is esterified with cinnamic acid and further acids and contains free carboxyl groups in the side chain of the polymer. Printing plate precursors comprising such a polymer are, however, insufficient in photospeed.
In EP-A-0 092 901 polyvinyl acetals modified by chalcon groups are claimed. The length of run of plates made with these polymers and the photospeed are, however, insufficient nowadays.
U.S. Pat. No. 3,030,208 and U.S. Pat. No. 3,622,320 disclose polymers which contain cinnamoyl groups in the main chain of polyester resins. The developing of radiation-sensitive elements containing such polymers requires the use of developers with high solvent content; furthermore, there is a high tendency to form sludge in the developing machine.
In U.S. Pat. No. 3,929,489, and U.S. Pat. No. 4,419,437 polymers are claimed which contain cinnamoyl groups in the main chain of polyester resins and further contain disulfone amino groups. The developability and length of run of plates obtained therewith, however, do not meet the high requirements nowadays.
In U.S. Pat. No. 2,787,546 acetal polymers are disclosed containing in one side chain both cinnamate and carboxylic group functionalities. However, plates comprising such polymers suffer from the disadvantage of insufficient photospeed.
SUMMARY OF THE INVENTION
It is thus the object of the present invention to provide polymers for radiation-sensitive compositions which, in addition to their high photospeed and resolution, ensure a high durability on the press and also a low tendency to form sludge in the developing processor during developing and which, furthermore, do not require developers with a high content of organic solvents.
These objects are achieved by means of the cinnamic acid groups containing acetal polymers comprising units A-D and optionally E, wherein A is present in an amount of about 25 to 55 mol % and is of the formula
B is present in an amount of about 0.5 to 25 mol % and is of the formula
wherein R
1
is selected from the group consisting of alkyl, aryl and aralkyl,
C is present in an amount of about 0.5 to 40 mol % and is of the formula
wherein X is an aliphatic or aromatic spacer group, and Ac is an acidic group selected from the group consisting of —COOH, —SO
3
H or —SO
2
NR
9
R
10
with R
9
and R
10
independently being selected from hydrogen and alkyl; and when X is phenylene, Ac can also be OH,
D is present in an amount of about 20 to 70 mol % and is of the formula
wherein Ci is selected from the group consisting of Ci-1, Ci-2, Ci-3 and Ci-4 which are represented by the following formulae
wherein:
k, m and n are integers independently selected from 0 to 5, R
3
, R
4
and R
7
are independently selected from the group consisting of alkyl, alkoxy, —COOR
8
,
—NR
9
R
10
, —NH—CO—CH
3
, halogen and cyano,
R
8
is selected from hydrogen and alkyl;
R
9
and R
10
are independently selected from hydrogen and alkyl,
R
5
is selected from the group consisting of hydrogen, alkyl, aryl and aralkyl;
R
6
is selected from the group consisting of alkyl, aryl and aralkyl and
Y is selected from the group consisting of alkylene, arylene and arylenealkylene; and
E is present in an amount of about 0 to 50 mol % and is of the formula
wherein R
2
is selected from the group consisting of alkyl, aryl and aralkyl groups.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to photosensitive compositions comprising:
(i) a polymeric binder and
(ii) optionally at least one other component selected from the group consisting of photosensitizers for photocyclo addition, diazo resins, colorants, exposure indicators, surfactants, stabilizing acids and plasticizers
characterized in that the binder comprises units A, B, C, D and optionally E wherein A is present in an amount of about 25 to 55 mol % and is of the formula
B is present in an amount of about 0.5 to 25 mol % and is of the formula
wherein R
1
is selected from the group consisting of alkyl, aryl and aralkyl
C is present in an amount of about 0.5 to 40 mol % and is of the formula
wherein X is an aliphatic or aromatic spacer group, and Ac is an acidic group selected from the group consisting of —COOH, —SO
3
H or —SO
2
NR
9
R
10
with R
9
and R
10
independently being selected from hydrogen and alkyl; and when X is phenylene, Ac can also be OH,
D is present in an amount of about 20 to 70 mol % and is of the formula
wherein Ci is selected from the group consisting of Ci-1, Ci-2, Ci-3 and Ci-4 which are
Baumann Harald
Flugel Michael
Kottmair Eduard
Chu John S.
Kodak Polychrome Graphics LLC
RatnerPrestia
LandOfFree
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