Incremental printing of symbolic information – Ink jet – Medium and processing means
Reexamination Certificate
2002-08-20
2004-03-09
Stephens, Juanita (Department: 2861)
Incremental printing of symbolic information
Ink jet
Medium and processing means
C428S040200
Reexamination Certificate
active
06702437
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat mode-compatible negative image recording material on which an image is formable due to heat mode exposure using an infrared laser, and in particular to a negative image recording material that can form a planographic printing plate that has excellent printing resistance and in which the strength of an image portion is high.
2. Description of the Related Art
The development of lasers in recent years has been remarkable. In particular, high-output, compact solid-state lasers and semiconductor lasers having an emission range in the near infrared to infrared range (referred to as infrared lasers below) are being developed. These infrared lasers are extremely useful as an exposure light source at the time a printing plate is formed directly on the basis of digital data from a computer or the like.
Negative planographic printing plates exposable to an infrared laser use, as a recording layer, a negative image recording material that includes an infrared absorbent, a polymerization initiator that generates radicals by light or heat, and a polymerizable compound. Usually, the negative image recording material utilizes a recording system where the radicals generated by light or heat act as an initiator to trigger a polymerization reaction of the polymerizable compound, whereby the recording layer of the exposed region is cured to form an image portion.
Negative image forming materials have poor image formability in comparison with positive image forming materials, in which dissolution of the recording layer is caused by the energy from infrared laser irradiation. For this reason, negative image forming materials are generally heated prior to being developed in order to promote curing reaction by polymerization to form a stronger image portion.
As printing plates using a recording layer that utilize such an image forming mechanism, printing plates are known that use, as a recording layer (photosensitive layer), a photo- or heat-polymerizable composition, as disclosed in Japanese Patent Application Laid-Open (JP-A) Nos. 8-108621 and 9-34110. Although these recording layers have excellent high sensitive image formability, there are problems in that adhesion between the recording layer and the substrate is low and printing resistance is poor when a substrate that has been made hydrophilic is used as the support.
The use of high-output infrared lasers for exposure is also being studied in order to improve sensitivity, but there is a problem in that the optical system may be polluted due to ablation of the recording layer at the time of laser scanning.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a negative image recording material that can form a planographic printing plate that has excellent printing resistance and storage stability, in which the strength of an image portion is high, and in which an unwanted curing reaction arising during ordinary storage is suppressed.
As a result of extensive study, the present inventors found that, by selecting a polymer compound having an unsaturated bond in a side chain and a specific glass transition temperature as an alkali-soluble polymer compound used in an image recording material, excellent recording becomes possible in which the strength of an image portion is high.
Namely, a negative image recording material of the invention comprises: (A) a specific polymer compound that has at least one carbon—carbon double bond in a side chain thereof and a glass transition temperature of 80° C. or more, and is soluble in an aqueous alkaline solution; (B) a light-heat converting agent; and (C) a compound that generates radicals by heat mode exposure using light of a wavelength absorbable by the light-heat converting agent.
The negative image recording material may further comprise (D) a radical-polymerizable compound.
Although the mechanism resulting in the working of the invention is not entirely clear, it is thought that an image having excellent strength can be obtained because the glass transition temperature of the compound itself is at least 80° C., which is a comparatively high temperature, as a result of using, as the polymer compound soluble in an aqueous alkaline solution, a polymer compound that has at least one carbon—carbon double bond in a side chain thereof and a glass transition temperature of at least 80° C. Usually, a chemical reaction occurs more easily and excellent image formability is obtained with a fluidic material (i.e., a material that is flexible), with respect to materials that utilize a chemical reaction such as a polymerization reaction and a crosslinking reaction to form an image as in the case of negative image forming materials. However, the fact that the chemical reaction occurs easily conversely results in a reduction in stability. For instance, film remains at unexposed regions due to an undesired chemical reaction arising even under ordinary indoor and outdoor storage temperature conditions, and the non-image portion becomes easily contaminated when the material is used as a planographic printing plate. The polymer compound used in the invention has a reactive double bond, but because its glass transition temperature is high, the recording layer itself formed from this material also has a high glass transition temperature. A strong and rigid layer is formed that is not fluidic under ordinary indoor and outdoor storage temperature conditions. Under such conditions, the unexposed region has the characteristic of excellent stability, and the exposed region is heated by heat mode exposure to a temperature that is higher than the glass transition temperature, whereby the recording layer is instantaneously melted and becomes fluidic, a chemical reaction is triggered, curing is effected rapidly, and an image is formed. By using the specific alkali-soluble polymer compound of the invention in this manner, it is possible to obtain an image recording material that has both excellent storage stability and excellent image formability and, when this recording material is applied to the recording layer of a planographic printing plate, to obtain a printing plate that has excellent printing resistance and excellent storage stability.
In the invention, “heat mode-compatible” means that recording is possible by heat mode exposure. The definition of heat mode exposure in the invention will now be described in detail below. As described by Hans-Joachim Timpe in IS&Ts NIP 15: International Conference on Digital Printing Technologies, Orlando, Fla., (1999), p. 209, it is known that there are roughly two modes of processes by which an image is formed through a chemical change or a physical change resulting from light-excitation of a light-absorbing substance (e.g., a dye) in a photosensitive material. One mode is the so-called photon mode, in which the optically excited light-absorbing substance is inactivated by a photochemical interaction (e.g., energy transfer and electron transfer) with another reactive substance in the photosensitive material and the activated reactive substance triggers a chemical or physical change necessary to form an image. The other mode is the so-called heat mode, in which the optically excited light-absorbing material generates heat and is inactivated a reactive substance uses this heat to trigger a chemical or physical change necessary to form an image. Besides these modes, there are also special modes such as ablation, in which the substances are explosively scattered due to local concentration of light energy, and multiple photon absorption, in which a large number of photons are absorbed at once. However, description of these modes will be omitted here.
Exposure processes utilizing the respective modes described above are called photon mode exposure and heat mode exposure. The technical difference between photon mode exposure and heat mode exposure is whether or not the energy amount of the numerous photons to be exposed can be summed up and used with respect to the energy amount of th
Fujimaki Kazuhiro
Sorori Tadahiro
Fuji Photo Film Co. , Ltd.
Stephens Juanita
LandOfFree
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