Method of making subtractive offset printing plate

Details Method of making subtractive offset printing plate Method of making subtractive offset printing plate

1993-04-23

1995-07-25

Bowers, Jr., Charles L.

Radiation imagery chemistry: process, composition, or product th

Diazo reproduction, process, composition, or product

430300, 430325, 430326, 430331, 354317, 354319, G03F 726, G03F 730

Patent

active

054361052

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a method of making a subtractive offset printing plate. More particularly, it relates to a method of making a subtractive offset printing plate, which may well be developed even with an automatic developing machine for additive offset printing plate.


PRIOR ART

An additive offset printing plate is advantageous in general as the base plate may be manufactured inexpensively. At present, it is used essentially in the field of printing newspapers. Such an additive offset printing plate which has heretofore been utilized generally in printing needs lacquering on the image area so as to reinforce the area. For this, a developer to be used for making additive offset printing plates contains a component of removing the non-image area of the plate and a lacquer component of reinforcing the image area of the same, and the content of organic compounds therein reaches 50% by weight. Regarding the physical properties of the developer, it is highly more viscous rather than an aqueous solution and is near to a paint. For developing a printing plate, a relatively small amount of such a developer is applied to the surface of the plate and the non-image area of the plate is removed by strongly rubbing it with a brush. On the other hand, a developer for making a subtractive offset, printing plate which does not need lacquering or the like reinforcement of the image area is an alkaline aqueous solution having a content of organic compounds of being 10% by weight or less. Regarding the physical properties of the developer, it is near to water. For developing a subtractive offset printing plate, a relatively large amount of such a developer is applied to the surface of the printing plate almost without rubbing the surface with a brush, whereupon the non-image area is dissolved out into the developer and removed from the plate.


PROBLEMS TO BE SOLVED BY THE INVENTION

As mentioned above, the developer for making additive offset printing plates has a higher concentration of organic compounds therein than that for making subtractive offset printing plates. Therefore, treatment for discharging the waste of the used developer involves an environmental problem.
As one means of solving the problem, it may be considered to substitute the additive developing machine by a subtractive one. However, in newspaper printing companies and others, automatic and continuous printing plate making lines for exposure, developing, punching and folding of additive offset printing plates have already been equipped so as to efficiently make printing plates in a short period of time. It is not easy to substitute such expensive printing plate making lines by subtractive offset printing plate making lines.
As another means of solving the problem, it may easily be considered to feed a subtractive developer to the additive developing machine for developing subtractive printing plates. However, as mentioned above, there are noticeable differences in the composition of the photosensitive layer between the additive and subtractive printing plates, in the composition of the developer to be used between them and in the brush pressure to the developing machine between them. Therefore, even though a conventional subtractive developer and a subtractive printing plate are applied, so as to develop the subtractive printing plate, to the additive developing machine as manufactured only for use in making additive printing plate with an additive developer, satisfactory printing plates could not be made.
The present invention has been made in consideration of the preceding situation. The present inventor earnestly investigated in order to provide a method of making a subtractive offset printing plate by applying a subtractive printing plate and a subtractive developer which has few environmental problems to an additive developing machine where printing plates are developed by brushing development so as to make satisfactory printing plates and, as a result, has found that the intended object may be attained by the

REFERENCES:
patent: 3682078 (1972-08-01), Parker et al.
patent: 4186006 (1980-01-01), Kobayashi et al.

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