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
2001-10-09
2003-11-25
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
C430S271100, C430S273100, C430S302000, C430S327000, C430S348000, C430S495100, C430S496000, C430S944000, C430S945000, C430S964000
Reexamination Certificate
active
06653046
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a coating liquid for forming an infrared sensitive layer removable by an infrared laser, which coating liquid is used for the formation of a flexographic printing plate suitable for a plate making process comprising directly drawing an image of digitized information by an infrared laser without use of a negative film, and also relates to a process for obtaining a seamless photosensitive resin sleeve printing plate, which comprises using said coating liquid.
BACKGROUND ART
As disclosed in JP-A-55-48744 and JP-A 5-134410, it is general that a usual flexographic printing plate is formed in a manner such that a photosensitive elastomer composition is used and subjected to image-exposure through a negative film, and an unexposed portion is washed away. When used for printing, the thus obtained printing plate is affixed to a cylinder of a printer, and on this occasion, there is required much time for an operation to affix it to an accurately determined position, and therefore, it is desired to simplify or, if possible, omit the operation.
For this purpose, it is practiced that a printing plate is processed into a sleeve form prior to the image-exposure. In this case, however, when a pattern continuing without interruption is required to be printed, it has been required that a naturally board like photosensitive resin be wound around a sleeve or the like and thereafter a seam potion in the plate be treated to disappear.
As a process for obtaining a seamless printing plate of a sleeve form, there has been applied a process according to which a board like photosensitive resin is wound around a sleeve or the like, a liquid resin similar thereto or a photosensitive elastomer composition is dissolved in a solvent to be used as an adhesive agent for bonding the seam, and a protuberance produced on the seam portion is, for example, shaved to make it seamless. However, there are required skill and a long time for completing such an operation, and moreover it is difficult to make the seam completely disappear, and therefore, it has been desired to develop a process for simply obtaining a completely seamless plate.
As a process for obtaining a completely seamless plate of a sleeve form, there has been applied a process according to which a board like photosensitive resin is wounded around a sleeve, followed by heating at a temperature not lower than a softening temperature of said photosensitive resin to make the seam disappear, and successively followed by polishing the surface thereof with a grinder, thereby obtaining a highly accurate seamless photosensitive resin layer. According to the process, it has been made possible to obtain a highly accurate seamless photosensitive resin layer of a sleeve form. However, there has never been obtained a seamless printing plate, because when a negative film is bonded with the above-mentioned photosensitive resin layer of a sleeve form, followed by exposure, ends of the negative film overlap each other, and as a result, a figure different in level appears on that portion of the resulting printing plate.
In recent years, as disclosed in JP-A-8-305030 and JP-A-9-166875, there has been developed a process according to which an infrared sensitive layer, which is removable by an infrared laser and which has a property of screening non-infrared rays, is provided on the surface of a photosensitive resin, and a mask is formed by image-drawing with an infrared laser, followed by successive image-exposure through the mask, development and drying, whereby a printing plate can be obtained.
Using such technology, it has been also attempted that a seamless infrared sensitive layer is provided on a seamless photosensitive resin layer, and a mask is formed using an infrared laser, followed by image-exposure through the mask, development and drying to obtain a seamless printing plate.
In this case, in order to provide the infrared sensitive layer, which is removable by an infrared laser and which has a property of screening non-infrared rays, on the photosensitive resin layer, there is applied a process comprising coating a solution containing a component capable of constituting the infrared sensitive layer.
However, the photosensitive resin surface polished with a grinder has roughness, and therefore, there has been left a problem such that faults such as pinholes easily occur when an infrared sensitive coating liquid is coated on said surface. Further, there has been left a problem such that ink coverage on printing becomes inferior due to the roughness.
When the infrared sensitive composition disclosed in the above-mentioned literatures is used as its solution, it is frequent that an organic solvent such as toluene is used as a solvent. Therefore, there has been also left a problem such that in the case where a ring coater is used for the coating formation of the infrared sensitive layer on the photosensitive resin layer, a squeegee rubber of the ring coater is subjected to great swell-deformation by the action of the solvent, and as a result, it is forced to renew the squeegee rubber at every coating.
Moreover, the solvent as disclosed in the above-mentioned literatures deteriorates a work environment and accompanies the risk of a fire and an explosion, and therefore a high safety solvent has been desired.
Accordingly, it has been desired to develop a coating liquid, which is capable of forming an infrared sensitive layer without occurrence of faults such as pinholes even on the photosensitive resin having a rough surface caused by polishing with a grinder, and which is little in its effect on the swell-deformation of rubber and high in safety, and also to develop a process for obtaining a seamless photosensitive resin sleeve printing plate superior in its ink coverage.
DISCLOSURE OF INVENTION
The present invention provides a process for obtaining a seamless photosensitive resin sleeve printing plate, according to which problems of the prior art as mentioned above can be solved. That is, the present invention provides a process for obtaining a seamless photosensitive sleeve printing plate that is superior in its ink coverage, according to which an infrared sensitive layer can be formed without any fault such as pinholes even on a photosensitive resin surface having a roughness caused by polishing with a grinder, repeat use of a squeegee rubber can be made possible in the case of carrying out a coating with a ring coater as a means for coating an infrared sensitive coating liquid, a work environment in a coating step of providing an infrared sensitive layer can be improved, the risk of an ignition explosion can be reduced, and moreover a roughness of a photosensitive resin surface caused by polishing with a grinder can be mitigated
The present inventors have undertaken extensive studies to solve the above-mentioned problems, and as a result, it has been found that when a liquid obtained by dissolving or dispersing a binder polymer soluble in a solvent defined below, an infrared absorbing substance and, if desired, a non-infrared opaque substance in a solvent, which comprises an ester solvent represented by a general formula (A), is used as an infrared sensitive coating liquid, it thereby solves the above-mentioned problems, and as a result, the present invention has been accomplished.
R
1
COOR
2
(A)
In the formula, R
1
is CH
3
or C
2
H
5
, and R
2
is an alkyl group represented by —C
n
H
2n+1
, wherein n is an integer of 6 to 10, a substituted or unsubstituted cycloalkyl group represented by —C
6
H
10
X, wherein X is H or an alkyl group having 1 to 4 carbon atoms, an aralkyl group represented by —C
n
H
2n
Ar, wherein Ar is an aromatic group and n is 1 or 2, or an alkoxypolyoxyalkylenyl group represented by —(C
n
H
2n
O)
a
C
m
H
2m+1
, wherein n is an integer of 2 to 6, m is an integer of 1 to 4, and a is 1 or 2, provided that a/(na+m)≦¼.
That is, the present invention provides a coating liquid for providing an infrared sensitive layer on the surface of a photosensitive resin, whi
Kozaki Shuji
Tabata Shusaku
Asahi Kasei Kabushiki Kaisha
Baxter Janet
Gilliam Barbara
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