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
2001-01-10
2004-02-03
Ashton, Rosemary (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
C430S273100, C430S138000, C101S453000
Reexamination Certificate
active
06686125
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a lithographic printing plate precursor which requires no development and is excellent in press life. More specifically, the present invention relates to a lithographic printing plate precursor capable of plate-making by heat mode image-recording, also capable of image-recording by scanning exposure based on digital signals, and capable of mounting on a printing machine for plate-making and printing with requiring no development.
BACKGROUND OF THE INVENTION
A lithographic printing plate generally comprises a lipophilic image area which receives an ink and a hydrophilic non-image area which receives fountain solution during printing. As such a lithographic printing plate precursor, a PS plate (presensitized plate) comprising a hydrophilic support having provided thereon a lipophilic photosensitive resin layer has so far been widely used.
On the other hand, digitized techniques of electronically processing, accumulating and outputting image data by using a computer have prevailed, and various image output systems corresponding to these digitized techniques have been put to practical use. As one example of such techniques, a computer-to-plate technique directly making a printing plate is attracting public attention, which comprises a step of scanning exposing a printing plate precursor with high convergent radiant rays such as laser beams carrying digitized image data without using a lith film. With such a tendency, it has become an important technical subject to obtain the printing plate precursor well adapted to this purpose.
Solid state lasers having high output, e.g., a semiconductor laser and a YAG laser are inexpensively available in recent years. As a result, as a producing method of a printing plate by scanning exposure which is easy to be incorporated in a digitized technique, a plate-making method using these lasers as an image-recording means is promising.
In conventional plate-making methods, image-recording is performed by imagewise exposing a photosensitive printing plate precursor in low to middle intensity to cause the change of imagewise physical properties on the surface of the precursor by a photochemical reaction. On the other hand, in a method of using the exposure of high power density by a high output laser, a large quantity of light energy is irradiated on an exposure region convergently during a momentary exposure time, the light energy is efficiently converted to heat energy to cause a chemical change, a phase change, or a thermal change such as the change of form and structure due to the heat, and that change is utilized in image-recording. That is, image data are inputted by light energy such as laser beams, but image-recording is performed by the reaction due to heat energy. This recording system making use of heat generation by high power density exposure is generally called heat mode recording and converting light energy to heat energy is called light-to-heat conversion.
A big advantage of a plate-making method utilizing a heat mode recording means is that a material is not sensitive to light of general intensity level, such as room illumination, and the image recorded by high intensity exposure does not necessitate fixation. That is, when a heat mode material is used in image-recording, the material is safe to room light before exposure and fixation of the image after exposure is not essential.
Accordingly, if heat mode recording is utilized, it is expected that it will be possible to obtain a lithographic printing plate precursor which is easily developed to a computer-to-plate system.
As one preferred plate-making method of lithographic printing plate on the basis of heat mode recording, a method has been suggested which comprises the steps of providing a hydrophobic image-recording layer on a hydrophilic substrate, imagewise exposing the hydrophobic layer by heat mode exposure to change the solubility and dispersibility of the hydrophobic layer, and, if necessary, removing the non-image area by wet development.
As an example of such a printing plate precursor, there is disclosed in JP-B-46-27919 (the term “JP-B” as used herein means an “examined Japanese patent publication”) a method for obtaining a printing plate by heat mode recording a printing plate precursor comprising a hydrophilic support having provided thereon a recording layer showing a so-called positive function, i.e., a recording layer having a function whose solubility is improved by heat, specifically a recording layer having a specific composition such as saccharides and melamine-formaldehyde resins. Since the disclosed simple plate-making techniques of heat mode recording including the above method are in general not sufficient in heat sensitivity, the sensitivity is extremely insufficient for heat mode scanning exposure. Hence the discrimination of hydrophobicity/hydrophilicity of the irradiated area and the non-irradiated area, i.e., the discrimination of the image area and the non-image area, is small, which has been the restriction in practical use. If the discrimination is insufficient, plate-making according to the on-press development system is substantially difficult.
As the means to solve that problem, methods to remove the image layer at the irradiated area by heat splashing due to the work of heat by high output laser beam irradiation (called abrasion) are disclosed, e.g., in WO 98/40212, WO 98/34796 and JP-A-6-199064 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), specifically lithographic printing plate precursors capable of plate-making without performing development which comprises a substrate having thereon plural layers comprising a hydrophilic layer containing transition metallic oxide colloid as the upper layer and a lipophilic image-recording layer as the lower layer are disclosed. The discriminability of the irradiated area and the non-irradiated area where heat splashing has been completely performed is certainly large according to these methods, but there arise other problems that the printing machine (i.e., the printing press) is stained by the splashed matter, the stain on the printing plate surface impairs the operation of the printer and printing quality, in addition, the heat of the irradiated light often does not reach the deep part of the image-recording layer, as a result, the bottom part of the image-recording layer close to the support is not splashed and remains, i.e., the phenomenon called a residual film is brought about. Substantial discriminability cannot be exhibited due to the residual film, which leads to the reduction of printing quality.
As is the situation, as a method not accompanied by such drawbacks, there are disclosed simple plate-making methods making use of the change of the degree of hydrophilicity/hydrophobicity of the surface by heat, i.e., the change of polarity, not according to abrasion even when an image is formed by heat mode light irradiation. For example, methods comprising the steps of the addition of a thermoplastic polymer such as hydrophobic wax and polymer latex to a hydrophilic layer and hydrophobitization by phase separation to the surface by heat are disclosed in JP-B-44-22957, JP-A-58-199153 and U.S. Pat. No. 3,168,864. These techniques suggest a direction of the improving means of discriminability. However, since these disclosed techniques are insufficient in discriminability and there is apprehension about staining of printed matter due to, in particular, insufficient hydrophilicity, the improvement is desired.
Sufficient discrimination of an image area and a non-image area is a fundamental important characteristic directly linked with the improvement of printing quality, such as printing stain prevention and inking property, and press life, accordingly, the development of a plate-making method having high discriminating property and easiness of print-making operation, in particular, a plate-making method having high discriminating property and high sensitivity, requiring no development process, capable of
Fukino Kiyotaka
Hoshi Satoshi
Ishimaru Shingo
Ogawa Keizo
Waki Kouichi
Ashton Rosemary
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Gilliam Barbara
LandOfFree
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 Lithographic printing plate precursor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lithographic printing plate precursor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3315619