Radiation-sensitive mixture comprising IR-absorbing, anionic...

Details Radiation-sensitive mixture comprising IR-absorbing, anionic... Radiation-sensitive mixture comprising IR-absorbing, anionic...

1999-07-29

2001-05-29

Le, Hoa Van (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

C430S270100, C430S302000

Reexamination Certificate

active

06238838

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a positive-working, radiation-sensitive mixture which contains an organic polymeric binder which is insoluble in water but soluble in aqueous alkaline solution and an IR-absorbing dye or pigment. It also relates to a recording material comprising a substrate and a layer of this mixture and a process for the production of lithographic printing plates from the recording material. The layer has high sensitivity in the IR range so that the recording material is suitable for direct thermal image production by the computer-to-plate CTP method.
2. Description of the Related Art
The use of dyes and pigments as IR absorbers in radiation-sensitive mixtures is generally known in the art. For example, the recording material according to WO 96/20429 comprises a layer with IR-absorbing carbon black pigments, 1,2-naphthoquinone-2-diazidosulfonic esters or -carboxylic esters and a phenol resin. The 1,2-naphthoquinone-2-diazidosulfonic acid or -carboxylic acid can also be directly esterified with the hydroxyl groups of the phenol resin. The layer is first exposed uniformly to UV radiation and then imagewise to IR laser beams. As a result of the action of the IR radiation, specific parts of the layer rendered soluble by the UV radiation become insoluble again. This is therefore a negative-working system. The processing of the material is thus relatively complicated.
EP-A 0 784 233 likewise describes a negative-working mixture which contains a) novolak and/or polyvinylphenol, b) amino compounds for curing the component a), c) a cyanine and/or polymethine dye which absorbs in the near IR range and d) photochemical acid formers.
The non-prior published Patent Application DE 197 39 302 describes a positive-working, IR-sensitive mixture which comprises a binder which is insoluble in water but soluble, at least swellable in aqueous alkali and carbon black particles dispersed in said binder. The carbon black particles are the radiation-sensitive component essential for imagewise differentiation.
WO 97/39894 describes layers which contain dissolution-inhibiting additives. The additives reduce the solubility of the layer in the unexposed parts in aqueous alkaline developers. These additives are, in particular, cationic compounds, especially dyes and cationic IR absorbers, such as quinolinecyanine dyes, benzothiazolecyanine dyes or merocyanines, in addition to various pigments. However, if these layers are heated to 50 to 100° C. for from 5 to 20 s, the additives lose their inhibiting effect, and the layer becomes soluble in aqueous alkaline solutions.
The positive-working mixture disclosed in EP-A 0 823 327 contains cyanine, polymethine, squarylium, croconium, pyrylium or thiopyrylium dyes as IR absorbers. Most of these dyes are cationic and have an inhibiting effect. In addition, many of them are halogen-containing. Under unfavorable conditions, environmentally harmful decomposition products may form therefrom. However, some dyes having a betaine structure and an anionic dye (compound S-9 on page 7) are also disclosed. After drying of the layer, however, this anionic dye, owing to its large number of sulfonate groups, generally causes crystallization or precipitation of components of the layer, which leads to substantially poorer properties of the IR-sensitive layer and also results in a poor appearance of the layer.
The disadvantage of the layer compositions generally known in the art is that the increase in solubility which is achieved by the post-bake is reversible after storage at room temperature. Thus, if a printing plate is not further processed immediately after baking (e.g. using a heating oven), the development properties change. Thus, reproduction problems during the processing of the recording materials may also result. In addition, many cationic additives are halogen-containing, so that environmentally harmful decomposition products may form under unfavorable conditions.
SUMMARY OF THE INVENTION
It is one object of the invention to provide a radiation-sensitive mixture and a recording material comprising the same.
These and other objects can be achieved by a positive-working, radiation-sensitive mixture comprising: an organic, polymeric binder which is insoluble in water but soluble or at least swellable in aqueous alkaline solution and at least one IR-absorbing dye, wherein the IR-absorbing dye is an anionic cyanine dye of the formula I
wherein
n is 2 or 3,
R
1
to R
8
independently of one another, are a hydrogen or halogen atom, a sulfonate, carboxylate, phosphonate, hydroxyl, (C
1
-C
4
)alkoxy, nitro, amino, (C
1
-C
4
)alkylamino or di(C
1
-C
4
)alkylamino group or a (C
6
-C
10
)aryl group which in turn may be substituted by one or more halogen atoms and/or one or more sulfonate, carboxylate, phosphonate, hydroxyl, (C
1
-C
4
)alkoxy, nitro, amino, (C
1
-C
4
)alkylamino and/or di(C
1
-C
4
)alkylamino groups,
R
9
and R
10
independently of one another, are a straight-chain or branched (C
1
-C
6
)alkyl, a (C
7
-C
16
)aralkyl or a (C
6
-C
10
)aryl group, each of which in turn may be substituted by one or more halogen atoms and/or one or more sulfonate, carboxylate, phosphonate, hydroxyl, (C
1
-C
4
)alkoxy, nitro, amino, (C
1
-C
4
)alkylamino and/or di(C
1
-C
4
)alkylamino groups,
Z
1
and Z
2
independently of one another, are a sulfur atom, a di(C
1
-C
4
)-alkylmethylene group or an ethene-1,2-diyl group and
X
+
is a cation,
with the proviso that the dye contains from 2 to 4 sulfonate, carboxylate and/or phosphonate groups but altogether not more than two sulfonate groups.
Additional objects, features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects, features and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A preferred recording material of the present invention contains neither diazonium compounds nor heat-curable or acid-curable amino compounds, nor any silver halide compounds and, apart from imagewise exposure and development, requires no additional operation, such as post-bake or postexposure. The recording material should be virtually insensitive to daylight.
Z
1
and Z
2
are preferably isopropylidene groups, i.e., groups of the formula —C(CH
3
)
2
—.
Preferred cations include alkali metal and alkaline earth metal cations, especially sodium and potassium ions, as well as ammonium ions, or mono-, di-, tri- or tetraalkylammonium ions.
Dyes having symmetrical structure, i.e., those in which the (partly) aromatic radicals in the formula (I) are substituted in the same manner, are preferred. They are also generally easier to synthesize. Thus, dyes which contain two sulfonate groups are particularly advantageous. The dyes of the formula (I) surprisingly have absolutely no solubility-inhibiting effect on the mixture or a layer produced therefrom.
The (C
1
-C
4
)alkoxy group is preferably a methoxy or ethoxy group, while the (C
7
-C
16
)aralkyl group is preferably a benzyl group. The halogen atoms are generally chlorine, bromine or iodine atoms, although any halogen can be used. In a first preferred embodiment, R
9
and R
10
are each a group of the formula —[CH
2
]
n
—SO
3
—, in which n is an integer from 1 to 6. In a further preferred embodiment, one of the groups R
1
to R
4
or R
5
to R
8
is in each case a sulfonate group. As already mentioned, other substituents from among the stated ones, in particular carboxylate or phosphonate groups, may be present in addition to or in place of the sulfonate groups. If amino, (C
1
-C
4
)alkylamino or di(C
1
-C
4
)alkylamino groups are present in the cyanine dye of the formula I, the number thereof is at least 2 less than that of the carboxylate, sulfonate and/or phosphonate groups, so that the dye remains anionic.
In the mixture according to

Affiliated with

Also associated with

Rating

Radiation-sensitive mixture comprising IR-absorbing, anionic... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Radiation-sensitive mixture comprising IR-absorbing, anionic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radiation-sensitive mixture comprising IR-absorbing, anionic... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2457746