Radiation imagery chemistry: process – composition – or product th – Microcapsule – process – composition – or product
Reexamination Certificate
2000-08-09
2002-10-15
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Microcapsule, process, composition, or product
C430S348000, C430S270110
Reexamination Certificate
active
06465146
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a radiation-sensitive lithographic printing plate precursor. More particularly, the present invention relates to a positive-working polarity conversion type unprocessed printing plate precursor.
BACKGROUND OF THE INVENTION
In general, a lithographic printing plate precursor comprises a lipophilic image area which receives an ink during printing process and a hydrophilic non-image area which receives a dampening water. As a precursor from which such a lithographic printing plate is prepared there has heretofore been widely known a PS plate comprising a lipophilic photosensitive resin layer provided on a hydrophilic support. In order to make a printing plate from such a PS plate, a method may be normally used which comprises exposing the PS plate to light through a lithographic film having an image recorded thereon, and then dissolving the non-image area away from the PS plate with a developer. In accordance with this method, a desired printing plate can be obtained.
The foregoing conventional method for making a printing plate from PS plate is disadvantageous in that it requires a development step to dissolve the non-image area away from the PS plate. Accordingly, the conventional plate making method faces an assignment of eliminating or simplifying the additional wet processing step. In particular, the whole industry's recent great concern is the disposal of waste liquid discharged from the wet processing step from the standpoint of global environment. Thus, there is an ever growing demand for improvement in these requirements.
As one of simple plate-making methods meeting these requirements there has been proposed a plate-making method which performs image formation on a printing plate precursor free from development using a heat energy developed by photo-heat conversion. Since high output solid lasers such as semiconductor laser and YAG laser have been available at low price, a photo-heat conversion type plate-making method using such a laser as an image-recording means has recently been considered favorable. In this type of plate-making method, a high power density exposure using a high output laser causes a large amount of optical energy to be concentrated onto an area to be exposed for an instantaneous period of time, making it possible to effectively convert optical energy to heat energy by which a thermal change such as chemical change, phase change and state or structure change then takes place. The change is utilized to record an image. In other words, image data is inputted in the form of optical energy, but image recording is carried out by reaction using a heat energy. In general, such a recording process utilizing heat developed by high power density exposure is called heat mode recording, and the conversion of optical energy to heat energy is called photo-heat conversion.
Known examples of the use of an infrared laser-sensitive positive-working lithographic printing plate precursor containing an infrared absorber include one involving the combined use of an acid-decomposable carboxylic acid ester and an infrared absorbing dye as disclosed in JP-A-7-186562 (The term “JP-A” as used herein means an “unexamined published Japanese patent application”) and one involving the combined use of an ablation polymer and an infrared absorbing dye as disclosed in U.S. Pat. No. 5,605,780. Examples of the use of an infrared laser-sensitive negative-working lithographic printing plate precursor include one involving the combined use of a resol resin as a heat-crosslinkable resin, an acid generator and an infrared absorber as disclosed in JP-A-56-69193, JP-A-7-20629 and JP-A-7-271029.
However, these proposed lithographic printing plate precursors leave something to be desired in sensitivity from the practical standpoint of view and thus have been required to have an enhanced sensitivity. Further, many of these infrared absorbers to be incorporated in these lithographic printing plate precursors occasionally undergo decomposition to become hydrophobic themselves after photo-heat conversion. The resulting decomposition product can be left behind as a film on the exposed area or can form a tailing-like solid phase in the dampening water during printing, causing scumming.
There are two representative examples of conventional positive-working polarity conversion type unprocessed printing plate which have been under the research and development to solve the foregoing defects. One of the two representative examples is a positive-working unprocessed printing plate comprising a polymer having a group which changes from hydrophobic to hydrophilic when acted upon by heat such as alkoxyalkylester group as disclosed in EP 652483. The other is a positive-working unprocessed printing plate comprising a silica gel-containing sol-gel crosslinked sulfonate compound. Both the two groups provide elimination of the foregoing defects. However, these proposals leave something to be desired in the prevention of scumming on the non-image area, which is one of important requirements for printing quality.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a radiation-sensitive lithographic printing plate precursor which allows direct plate making from digital data from computers, etc. using an infrared laser. It is another object of the present invention to provide a radiation-sensitive lithographic printing plate precursor which exhibits a sufficient sensitivity and causes no scumming on printed matters.
It is a further object of the present invention to provide a radiation-sensitive lithographic printing plate precursor which requires no special processing such as wet development and rubbing after image writing. In particular, it is a further object of the present invention to provide a radiation-sensitive lithographic printing plate precursor which allows direct plate making from digital data by recording using a solid laser, semiconductor laser or the like which emits infrared rays.
It is a still further object of the present invention to provide a positive-working radiation-sensitive lithographic printing plate precursor which exhibits a long press life and can give printed matters free from scumming on image area.
The inventor found that scumming on printed matters is greatly attributed to thermal decomposition of a photo-heat conversion compound such as infrared absorbent. The inventor then found that scumming on printed matters can be prevented by incorporating a photo-heat conversion compound in the polarity conversion layer in the form of photo-heat conversion compound-encapsulated particulate metal oxide having a photo-heat conversion compound encapsulated in a protective material structure such as particulate silica gel rather than in direct form. It was thus found that the encapsulation in a protective material structure makes the photo-heat conversion compound less decomposable and hydrophobicized when irradiated with laser beam, enhancing the hydrophilicity of the area irradiated with light and hence improving the scumming resistance of the non-image area. Further, studies were made of printing plate precursor embodying these findings. As a result, it was found that the combination of the foregoing photo-heat conversion compound-encapsulated particulate metal oxide with a specific polymer compound makes it possible to enhance the effect of prolonging press life and inhibiting scumming on printed matters, which is an object of the present invention.
In other words, the present invention is intended for a radiation-sensitive lithographic printing plate precursor comprising a photo-heat conversion agent incorporated therein, wherein the photo-heat conversion agent is a particulate metal oxide comprising an organic photo-heat conversion compound encapsulated therein.
The present invention is intended also for a radiation-sensitive lithographic printing plate precursor having a sensitive layer comprising at least a binder and a photo-heat conversion agent incorporated therein provided on a support, whe
Baxter Janet
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Gilliam Barbara
LandOfFree
Radiation-sensitive lithographic printing plate precursor 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 lithographic printing plate precursor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radiation-sensitive lithographic printing plate precursor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2986441