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
2001-04-18
2004-03-16
Hamilton, Cynthia (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
C430S947000
Reexamination Certificate
active
06706462
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a photosensitive image-recording material containing a novel photoinitiator, in particular a photoinitiator which is high sensitive and excellent in stability. More specifically, the present invention relates to a photosensitive image-recording material which is excellent as the material for a lithographic printing plate precursor capable of plate-making by scanning exposure on the basis of digital signals.
BACKGROUND OF THE INVENTION
A PS plate comprising a hydrophilic support having provided thereon a lipophilic photosensitive resin layer has so far been widely used as a lithographic printing plate, and a desired printing plate has been obtained by mask exposure (surface exposure) via a lith film and then dissolving and removing a non-image domain.
Digitized techniques of electronically processing, accumulating and outputting image data using a computer have prevailed in recent years, and various image output systems corresponding to these digitized techniques have been put to practical use. As a result, a computer-to-plate (CTP) technique directly making a printing plate which comprises the step of scanning digitized image data with a highly directional light such as a laser beam without using a lith film is desired. With such a trend, it has become an important technical subject to obtain a printing plate precursor well adapted to this purpose.
As one means to obtain a lithographic printing plate capable of such scanning exposure, the constitution in which a high speed photopolymerizable composition is used as the ink-receptive photosensitive resin layer (hereinafter referred to as “photosensitive layer”) provided on a hydrophilic support has so far been proposed and such printing plate is now on the market. The printing plate precursor having this constitution is easy to perform development process and, further, has desired properties as the printing plate and printing properties, e.g., excellent in resolution, adhesion of ink, press life, and smearing prevention.
The photopolymerizable composition fundamentally comprises an ethylenically unsaturated compound, a photopolymerization initiator and a binder resin. The photopolymerization initiator absorbs light to generate an active radical, causes addition polymerization of the ethylenically unsaturated compound and the photosensitive layer is insolubilized, thereby an image is formed. The greatest part of the conventional proposals concerning photopolymerizable compositions capable of scanning exposure have been those disclosing the use of a photopolymerization initiator having high photosensitivity, e.g., those described in Bruce M. Monroe et al.,
Chemical Review,
93,435 (1993) and R. S. Davidson,
Journal of Photochemistry and Biology A: Chemistry,
73.81 (1993).
However, since a photosensitive lithographic printing plate corresponding to CTP is markedly high speed as compared with conventional PS plates to be exposed via a lith film, a photoreaction is liable to occur even under a safelight, thereby a trouble of fog due to light is easily generated. Therefore, handling of a photosensitive lithographic printing plate under a safelight is restricted such that a safelight must be changed to a darker light and the greatest possible care should be taken to the light leaking in from the outside. For solving this problem of fog due to light, JP-B-7-60268 (the term “JP-B” as used herein means an “examined Japanese patent publication”) proposes a technique of providing a protective layer containing a colorant having absorption spectrum near the emission spectrum of a safelight.
However, since the oxygen cutoff effect of the protective layer is reduced according to this method, the lowering of sensitivity is caused with a high speed printing plate.
Besides, it is difficult to select a colorant having appropriate absorption spectrum and the problem of fog cannot be solved without causing the reduction of sensitivity. In particular, a lithographic printing plate corresponding to CTP containing a titanocene photoinitiator (Japanese Patent Application Nos. 11-61559 and 11-221480) is high speed and useful on one hand but a trouble of fog due to light under safelight is liable to occur on the other hand.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a photosensitive image-recording material which is excellent in safelight aptitude without reducing sensitivity, in particular, to provide a photosensitive image-recording material which is excellent as the material for a lithographic printing plate precursor capable of plate-making by scanning exposure on the basis of digital signals.
In a first aspect, the present invention relates to a photosensitive image-recording material which comprises a support having provided thereon a photosensitive layer and an oxygen-cutoff layer in this order from the support, wherein a colored layer for cutting off lights other than the light of the wavelength of the exposure light source is provided between the photosensitive layer and the oxygen-cutoff layer or as the outermost layer on the oxygen-cutoff layer.
As a result of eager investigation to solve the above problem, the present inventors have found that it becomes possible to maintain an oxygen cutoff property, prevent sensitivity from being reduced, and contain a filter dye in high concentration by the provision of a colored layer containing a filter dye besides an oxygen cutoff layer, as a result, a photosensitive image-recording material more excellent in safelight aptitude can be obtained. Thus, the present invention has been accomplished.
In a second aspect, the present invention relates to a photosensitive image-recording material which comprises a support having provided thereon a photosensitive layer, and a protective layer containing a colorant having a main absorption spectrum in a wavelength region of an emission spectrum of a safelight, wherein the photosensitive layer contains at least a titanocene photoinitiator, and the absorption spectrum of the colorant in the protective layer shows the optical density (OD) of 1.0 or more in the wavelength region of from 520 to 540 nm, and the optical density (OD) of 0.3 or less in the wavelength region of 500 nm or less of the exposure light source.
As a result of eager investigation to solve the above problem, the present inventors have found that the cause of the light fog under safelight when a titanocene photoinitiator is used results from the secondary absorption of the photoinitiator (near 450 to 550 nm), and a photosensitive image-recording material excellent in safelight aptitude can be obtained without reducing sensitivity by adding a colorant having absorption spectrum of sufficient optical density (OD) near the secondary absorption and having no or little absorption in exposure wavelength (500 nm or less) to a protective layer. Thus, the present invention has been accomplished.
Moreover, in the photosensitive image-recording material according to the second aspect of the present invention, light fog can be effectively avoided and it becomes possible to handle the material under a brighter safelight than those so far been used by making both of the absorption spectrum of a sensitizing dye and the wavelength of an exposure light source shorter than the emission spectrum of a safelight. The generation of light fog under a safelight due to a titanocene compound highly sensitized by a sensitizing dye is effectually avoidable by making the absorption spectrum of a sensitizing dye sufficiently shorter than the emission spectrum of a safelight so that both spectra do not overlap or hardly overlap with each other.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below.
The photosensitive image-recording material according to the present invention comprises a support having provided thereon (A) an oxygen-cutoff layer (it is also referred to as a protective layer), (B) a photosensitive layer, and, optionally, (C) a colored layer. These components will be specifically describe
Koizumi Shigeo
Kunita Kazuto
Murota Yasubumi
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Hamilton Cynthia
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