Plate-making method of printing plate

#The present invention relates to a plate-making method of a printing plate. More particularly, it relates to a plate-making method using a printing plate precursor for a lithographic printing plate or a letterpress printing plate, which can be used in a so-called direct plate-making method wherein a printing plate is directly prepared based on digital signal, for example, from a computer using various kinds of lasers, and a developer in combination.

#A solid laser, semiconductor laser and gas laser having a large output and a small size, which radiate an ultraviolet ray, visible light or infrared ray having a wavelength of from 300 to 1,200 nm, have become easily available, and these lasers are very advantageous for a recording light source used in the direct plate-making based on digital signal, for example, from a computer.

#Various investigations on recording materials sensitive to such laser beams have been made. Representative examples of the recording material include first recording materials capable of being recorded with an infrared laser having a wavelength of not less than 760 nm, for example, positive working recording materials as described in U.S. Pat. No. 4,708,925 and negative working recording materials of acid catalyst crosslinking type described in JP-A-8-276558 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), and second recording materials responsive to an ultraviolet ray or visible light laser having a wavelength of from 300 to 700 nm, for example, negative working recording materials of radical polymerization type as described in U.S. Pat. No. 2,850,445 and JP-B-44-20189 (the term “JP-B” as used herein means an “examined Japanese patent publication”).

#In a flask were charged 0.75 mols of 1,6-hexanediol diacrylate (manufactured by Nakamura Chemical Co., Ltd.), 1.0 mol of a 37% aqueous solution of formaldehyde and 100 ml of tetrahydrofuran. Then, 0.135 mols of DABCO was added to the mixture, followed by reacting with stirring for 24 hours. To the reaction mixture was added a mixture of 40 ml of 1 N hydrochloric acid and 200 ml of water, and the mixture was extracted with ethyl acetate. The extract was dried over magnesium sulfate and filtered. The filtrate was concentrated under a reduced pressure, separated by silica gel chromatography (hexane/ethyl acetate=9/1) and concentrated under a reduced pressure to obtain Compound C-1 in a yield of 20%. The structure of the compound was confirmed by NMR, MASS and IR.

#In a flask were charged 1.0 mol of Compound A-1, 100 ml of ethyl acetate, 1.0 mol of pyridine and 0.1 mol of DMAP (4-dimethylaminopyridine). Then, 0.5 mols of butanediol dichloride was dropwise added to the mixture under cooling with ice over a period of one hour, and the temperature of mixture was returned to room temperature, followed by stilling for 3 hours. To the reaction mixture was added 200 ml of water, and the ethyl acetate layer was extracted. The extract was dried over magnesium sulfate and filtered. The filtrate was sufficiently concentrated under a reduced pressure to obtain Compound D-7 in a yield of 80%. The structure of the compound was confirmed by NMR, MASS and IR.

#In a flask were charged 0.375 mols of pentaerythritol tetraacrylate (manufactured by Nakamura Chemical Co., Ltd.), 1.0 mol of a 37% aqueous solution of formaldehyde and 100 ml of tetrahydrofuran. Then, 0.135 mols of DABCO was added to the mixture, followed by reacting with stirring for 24 hours. To the reaction mixture was added a mixture of 40 ml of 1 N hydrochloric acid and 200 ml of water, and the mixture was extracted with ethyl acetate. The extract was dried over magnesium sulfate and filtered. The filtrate was concentrated under a reduced pressure, separated by silica gel chromatography (hexane/ethyl acetate=9/1) and concentrated under a reduced pressure to obtain Compound E-4 in a yield of 10%. The structure of the compound was confirmed by NMR, MASS and IR.