Radiation imagery chemistry: process – composition – or product th – Transfer procedure between image and image layer – image... – Imagewise heating – element or image receiving layers...
Reexamination Certificate
1998-02-20
2002-07-23
Angebranndt, Martin (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Transfer procedure between image and image layer, image...
Imagewise heating, element or image receiving layers...
C430S201000, C430S945000, C430S961000, C430S269000, C503S227000, C156S239000
Reexamination Certificate
active
06423464
ABSTRACT:
The present invention relates to a laser ablative recording material, and more particularly to an ablative recording material having a low temperature heat decomposable polymer used in an overcoat layer.
Recently, a thermal transfer system forming an image by imparting an electric signal to a thermal print head has become more popular. A method of forming an image by the use of a laser in place of the thermal print head was on the other hand developed, and is expected to become more popular along with the tendency toward a higher laser output.
A recording material for laser recording contains a material having a strong absorption in the laser wavelength region, and this absorbing material converts optical energy into thermal energy, and brings about effects similar to those available by the use of a thermal print head. Use of a laser, unlike the use of a thermal print head, permits heating without contact with a recording material, thus providing an advantage of the image surface free from flaws. Because of the possibility to stop down a laser beam, there is provided another advantage of improving image resolution.
A method for forming an image using a high-output laser known as the dye ablation has recently been developed. Japanese Unexamined Patent Publications Nos. 7-164,755, 7-149,063, and 7-149,065 (corresponding to U.S. Pat. No. 5,330,876, U.S. Pat. No. 5,401,618 and U.S. Pat. No. 5,459,017) disclose recording materials applicable in this method, and Japanese Unexamined Patent Publications Nos. 8-48,053 and 8-72,400 (corresponding to U.S. Pat. Nos. 5,521,629 and 5,574,493) disclose imaging apparatuses used in this method. Image recording based on the ablation method is accomplished by irradiating a laser from a coloring agent layer side onto a recording material having a coloring agent layer comprising a coloring agent, a material having absorption in the laser wavelength region (infrared-absorbing material) and a binder formed on a support. On the spot to which the laser beam has been irradiated, a sharp local change takes place in the coloring agent layer under the effect of energy from the laser, and this drives away the material from the layer. According to the aforesaid patent publications, this local change is not a perfectly physical change such as melting, evaporation or sublimation, but a kind of chemical change such as bond-breaking, and is believed to be a complete, not partial, removal of the coloring agent.
These recording materials used in the dye ablation imaging method have been pointed out as being inferior in scratch resistance to conventional silver halide photographic materials, and their improvements have been demanded. In this view, a method has been provided which improves scratch resistance by laying an overcoat layer containing polytetrafluoroethylene beads on an image forming layer (Japanese Unexamined Patent Publication No. 8-108,622).
However, this method has a certain effect in improving scratch resistance, but has posed the problem of lowering the efficiency of ablation.
Usefulness of the dye ablation imaging method largely depends upon the efficiency of removing the imaging dye upon laser exposure. As a scale representing this efficiency, the minimum density value (Dmin) of the laser exposed area is employed. A lower Dmin points to a higher dye removing efficiency. Thus, it has been desired to provide a laser ablative recording material having high scratch resistance and a low Dmin.
The present invention aims to provide a novel laser ablative recording material which has solved the problem facing a known laser ablative recording material. That is, an object of the invention is to provide a laser ablative recording material having satisfactory scratch resistance, a low Dmin and a high ablation efficiency. Another object of the invention is to provide an image-formed laser ablative record which ensures a high storage stability of an image formed through imagewise heating and easy handling with little image discoloration caused by, for example, fingerprints. Other objects of the invention would be easily understood from the entire description of this specification by a person skilled in the art.
We, the inventors, have conducted extensive studies in an attempt to attain the foregoing objects. As a result, we have found that a recording medium with a low Dmin and a high ablation efficiency can be provided by incorporating a low temperature heat decomposable polymer into an overcoat layer. This finding has led us to accomplish the present invention.
That is, the invention provides a laser ablative recording material having at least one coloring agent layer and at least one overcoat layer on a surface of a support, wherein at least one of the overcoat layers contains a non-self-oxidizing, low temperature heat decomposable polymer which, when heated at a rate of 10° C./min, starting at room temperature, decreases in weight by 50% or more before reaching 300° C.
According to a preferred embodiment of the invention, at least one of the overcoat layers contains a non-self-oxidizing, low temperature heat decomposable polymer which, when heated at a rate of 10° C./min, starting at room temperature, decreases in weight by 50% or more at a temperature in the range of from 100 to 300° C. The content of the low temperature heat decomposable polymer is preferably 0.1 to 5 g/m
2
.
According to another preferred embodiment of the invention, at least one of the overcoat layers contains polytetrafluoroethylene beads. Particularly preferably, at least one of the overcoat layers contains 0.005 to 5.0 g/M
2
of polytetrafluoroethylene beads having a particle size of 0.1 to 20 &mgr;m.
According to still another preferred embodiment of the invention, the coefficient of dynamic friction of the overcoat layer is 0.15 or less, more preferably 0.10 or less.
According to a further preferred embodiment of the invention, the coloring agent layer contains a pigment or inorganic fine particles. Particularly preferably, the coloring agent layer contains carbon black.
According to a still further preferred embodiment of the invention, the coloring agent layer contains cellulose nitrate or nitric ester of carboxyalkyl cellulose. Preferably, the nitric ester of carboxyalkyl cellulose has a degree of nitric ester group substitution per glucose anhydride unit within the range of from 0.2 to 2.2, and has a degree of carboxyalkyl ether group substitution per glucose anhydride unit of 0.05 to 1.5.
According to an additional preferred embodiment of the invention, the ablation recording material has at least one intermediate layer between the support and the coloring agent layer. The intermediate layer preferably contains a material having absorption in the laser wavelength region.
According to a further additional preferred embodiment of the invention, the ablation recording material has a back layer on the surface of the support on the opposite side to the coloring agent layer. Preferably, the Beck smoothness of the outermost layer surface of the back layer is 4,000 seconds or less.
The laser ablative recording material preferably has a minimum recording density (Dmin) after laser irradiation of 0.11 or less.
The invention also provides a laser ablative image-formed record prepared by irradiating a laser onto the laser ablative recording material of the invention. Particularly preferred is a laser ablative image-formed record prepared by providing a withstanding layer on a surface on the coloring agent layer side after laser irradiation.
Now, the laser ablative recording material and the laser ablative image-formed record of the invention will be described in detail below.
For the overcoat layer of the laser ablative recording material of the invention, a low temperature heat decomposable polymer is used as a polymeric binder. This low temperature heat decomposable polymer has to be a non-self-oxidizing polymer which, when heated at a rate of 10° C./min, starting at room temperature, decreases in weight by 50% or more before reaching 300° C. Preferred is a non-self-oxidizing polymer
Ito Tadashi
Kubo Kazuro
Angebranndt Martin
Fuji Photo Film Co. , Ltd.
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