Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Patent
1995-05-17
1998-02-10
Hamilton, Cynthia
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
522 92, 522 96, G03F 7027
Patent
active
057167575
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a liquid photosensitive resin composition used for forming a printing plate having an increased impact resilience for printing on a corrugated board. Such a printing plate has been strongly desired in the field of corrugated board printing.
BACKGROUND ART
As a printing plate material for corrugated board printing, there has been used a rubber, a solid photosensitive resin and a liquid photosensitive resin. The liquid photosensitive resin is often used as a printing material plate for corrugated board printing because of the economic advantage that an unhardened resin can be recovered and reused, and the feature that it provides a good working environment since the development is done with aqueous washout solution.
A liquid photosensitive resin composition used for forming a printing plate to print on a corrugated board generally comprises a prepolymer having an ethylenically unsaturated double bond, an ethylenically unsaturated compound and a photopolymerization initiator. A printing plate used for corrugated board printing is produced by imagewise exposing the liquid photosensitive resin composition to an actinic ray (photo-curing) and then conducting a developing process, a post-exposure process and a drying process.
One of the important physical properties required for a printing plate used for corrugated board printing is impact resilience. Japanese Patent Examined Publication No. 35481/1978 (An improved photosensitive composition for use in forming a flexographic printing plate) discloses that because a corrugated board has a rough and corrugated surface, a flexographic printing plate used for corrugated board printing having a low hardness (Shore A) of 35 to 45 degrees, an excellent strength and an excellent impact resilience is advantageous.
European Patent Unexamined Publication No. 263366 (A photoresin printing plate for use in printing a corrugated board) discloses the following. When corrugated board printing is conducted by using a photosensitive resin plate having a low hardness, paper dust or the like present on the surface of a corrugated board supplied to a printing machine often adheres to the surface of the printing plate. Because paper dust or the like, once adhered, can not be easily released from the surface of the printing plate, it is necessary to interrupt the operation of the printing machine in order to clean the printing plate. Therefore the photosensitive resin plate having a low hardness has a big practical problem that the productivity or the yield of the prints is inevitably lowered. In order to solve this problem, it is necessary to both reduce the surface tack of the printing plate and increase the impact resilience of the printing plate.
As mentioned above, a printing plate having a higher impact resilience is desirable in printing a corrugated board. As conditions of a liquid photosensitive resin composition to provide a printing plate having a higher impact resilience, the foregoing European Patent Unexamined Publication No. 263366 discloses that (1) (i) it is preferable to reduce the density of ester bonds, amide bonds and urethane bonds of the prepolymer contained in the liquid photosensitive resin composition because the presence of these bonds in the prepolymer has a tendency to reduce the impact resilience of the resultant photosensitive resin printing plate. Moreover (ii) when an unsaturated polyurethane is used as the prepolymer, a polyetherpolyol is advantageous as a polyol segment and (iii) particularly, the above unsaturated polyurethane prepolymer having 20% by weight or more of polytetramethylene glycol as the polyol segment provides a photosensitive resin printing plate having a higher impact resilience. Further, it teaches that (2) as the ethylenically unsaturated compound contained in the liquid photosensitive resin composition, an acrylate provides a photosensitive resin printing plate having a higher impact resilience than a methacrylate. However, a printing plate having superior impact resilience is s
REFERENCES:
patent: 4298630 (1981-11-01), Kapuscinski et al.
patent: 4854666 (1989-08-01), Kohara et al.
patent: 4932750 (1990-06-01), Ansel et al.
patent: 5288571 (1994-02-01), Nakamura et al.
Sakata Norihiko
Tabata Shusaku
Ueno Yoko
Asahi Kasei Kogyo Kabushiki Kaisha
Hamilton Cynthia
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