Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making printing plates
Reexamination Certificate
2000-09-22
2002-07-30
Chu, John S. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making printing plates
C430S157000, C430S162000, C430S165000, C430S175000, C430S192000, C430S303000, C430S945000, C430S281100
Reexamination Certificate
active
06426173
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a planographic printing plate employed in the field of offset printing, and more specifically, to a preparation method for the printing plate that employs a novel light source with a conventional planographic printing original plate. This application claims priority from and is based on PCT application No. PCT/JP00/00312 filed on Jan. 24, 2000, which in turn claims priority from patent applications filed in Japan (Japanese Patent Application No. 11-14190 filed on Jan. 22, 1999 and No. 2000-12261 filed on Jan. 24, 2000), the contents of which are incorporated herein by reference.
2. Background Information
In the conventionally employed method for preparing the planographic printing plates that are used in offset printing, a film on which an image is already formed is adhered to a conventional planographic printing original plate in which at least one photosensitive layer has been provided on a substrate. The image is then transferred onto the conventional planographic printing original plate by flood exposure with active rays. The printing plate is then obtained following wet developing, post-treating and drying steps. A mercury lamp, metal halide lamp, xenon lamp, chemical lamp, or carbon arc lamp may be cited as examples of the light source of active rays that are employed here. The photosensitive layer of the conventional planographic printing original plate is designed to be sensitive to 300~450 nm light, corresponding to the output wavelength of these light sources. However, the sensitivity of the photosensitive layer in the conventional planographic printing original plate is extremely low as compared to other photosensitive materials such as silver film and the like. Accordingly, irradiation with active rays may require from a few seconds to several minutes using flood exposure. Accordingly, there had not been a means for directly drawing digital information to this type of conventionally known planographic printing original plate.
Image information has been shifting from analog to digital data in recent years, however, accompanying developments in the information industry. In response to this trend, new technology has been developed to draw the digital information from a computer directly on to a planographic printing original plate, and then carry out a post-treatment to make a printing plate. This new technology includes high sensitivity PS plates that employ an argon gas laser (488/514 nm) or the second harmonic (532 nm) of a YAG solid-state semiconductor laser, i.e., a green laser, as a high density energy light source. Specific
product examples include the LA-2 and LY-2 manufactured by Mitsubishi Chemical Corp., and the Brillia LP-N made by Fuji Photo Film Co., Ltd. Examples of relevant references include Japanese Patent Application, First Publication No. 7-325391; Japanese Patent Application, First Publication No. 8-240908; Japanese Patent Application, First Publication No. 8-248639, and Japanese Patent Application, First Publication No. 8-248640, among others.
Specific examples of thermal planographic printing original plates that employ various types of solid state semiconductor lasers having an excitation wavelength in the range of 800~1200 nm, i.e., infrared lasers, as a high density energy light source include the DITP and Electra DC by Kodak Polychrome Graphics Company Ltd., the LT-1 and LT-G by Mitsubishi Chemical Corp., and the LH-PI and LH-NI by Fuji Photo Film Co., Ltd. Relevant references include Japanese Patent Application, First Publication No. 7-20629; Japanese Patent Application, First Publication No. 7-271029; Japanese Patent Application, First Publication No. 8-220752; Japanese Patent Application, First Publication No. 8-234426; Japanese Patent Application, First Publication No. 9-171254; Japanese Patent Application, First Publication No. 9-197668; Japanese Patent Application, First Publication No. 9-211863; Japanese Patent Application, First Publication No. 9-211865; Japanese Patent Application, First Publication No. 9-221652; Japanese Patent Application, First Publication No. 9-222731; Japanese Patent Application, First Publication No. 9-304931, among others.
In the preparation method for a planographic printing original plate using these high density energy light sources, drawing of the image is accomplished by contracting the light beam so that the diameter of the surface irradiated with the high density energy light in a lens or other such optical system is reduced to several to 20 micrometers, and then scanning the light beam over the planographic printing original plate based on the digital information. The irradiating time per spot is from several milliseconds to 20-30 nanoseconds. The energy on the plate surface ranges from 100 mJ/cm
2
to several 100 mJ/cm
2
. Following drawing of the image, the steps of wet developing, post-treating and drying are carried out in the same way as in the case of a conventional planographic printing original plate employing the light source of active rays, to obtain the printing plate.
Planographic printing original plates that use high density energy light source employ different techniques and materials from those used in conventional planographic printing original plates that use the light source of active rays. Namely, in order to use high density energy light source, these planographic printing original plates employ such materials as pigments or dyes with an absorption region at 450 nm or more as a substance that generates heat upon absorbing light corresponding to the excitation wavelength of such high density energy light, and such techniques as adding acid generator or measures against high intensity law failure. For this reason, it is not possible to draw an image using a high density energy light source in the range of 300~450 nm to a planographic printing original plate that employs such high density energy light source in the range of 450 nm or more.
Japanese Patent Application, First Publication No. 8-194317 discloses a technique for directly drawing digital information to a conventional planographic printing original plate using an argon ion laser that has a wavelength in the range of 320~400 nm as the high density energy light.
However, these types of gas lasers are problematic with respect to stability. In addition, practical use of such lasers is difficult due to the requirement for a large cooling device. Such gas lasers are also expensive, and therefore have not been economical.
Japanese Patent Application, First Publication No. 10-293405 discloses a technique for directly drawing digital information to a conventional planographic printing original plate using second harmonic laser light with an output wavelength in the range of 400~450 nm that is obtained from a semiconductor laser that has a fundamental wavelength of 800~900 nm.
Japanese Patent Application, First Publication No. 10-301296 discloses a technique for directly drawing digital information to a conventional planographic printing original plate using second harmonic laser light with an output wavelength in the range of 370~480 nm that is obtained from a semiconductor laser having a fundamental wavelength of 740~960 nm.
Japanese Patent Application, First Publication No. 10-319602 discloses a technique for directly drawing digital information to a conventional planographic printing original plate using second or third harmonic laser light with an output wavelength of 400 nm or more that is obtained from a semiconductor laser.
Japanese Patent Application, First Publication No. 11-15144 discloses a technique for directly drawing digital information to a conventional planographic printing original plate using second harmonic laser light with an output wavelength in the range of 370~480 nm that is obtained from a semiconductor laser having a fundamental wavelength of 740~960 nm.
Lasers in the 370 nm~480 nm wavelength region are not capable of transmitting power that consistently reproduces the image with high resolution. For this reason, in the
Kojima Yasuhiko
Oe Koji
Shimizu Shinji
BakerBotts L.L.P.
Chu John S.
Kodak Polychrome Graphics LLC
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