Printing – Printing members – Rolling contact
Reexamination Certificate
1998-08-10
2001-01-23
Funk, Stephen R. (Department: 2854)
Printing
Printing members
Rolling contact
C101S382100
Reexamination Certificate
active
06176182
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a block copy material for a lithographic printing plate material, a lithographic press and a lithographic printing method.
BACKGROUND OF THE INVENTION
Generally, in printing machines for lithography, printing plates are wrapped around plate cylinders and mechanically fixed thereto, and in this state, printing is carried out.
However, lithographic printing plates using materials other than easily treatable metals (for example, plastic films and paper) as substrates have a disadvantage in dimensional stability. For example, they have the problem that the plates are partially strained by the friction between blanket cylinders and the plates, resulting in deterioration of the printing dimension and printing accuracy.
In the case of the plates in which the substrates as described are used, therefore, the use thereof has hitherto been limited to easy methods in which the register accuracy of printed matter is not required and a small number of sheets are printed, and they have not been used as such in high-grade multicolor accurate printing and full-scale printing using large-sized printing machines.
In order to solve such a problem, JP-A-63-109090 proposes a method of directly adhering a plate material to a plate cylinder or a block copy plate for adjusting touch pressure between a printing plate and a blanket cylinder by use of, for example, an acrylic or rubber adhesive double coated sheet or spray adhesive.
In such a method, however, the problem newly arises that fine adjustment of the position of the printing plate on the plate cylinder is impossible, or that the workability of plate discharge and the like after printing is extremely deteriorated, because the printing plate is firmly adhered to the plate cylinder.
Further, JP-B-7-425 proposes a method of providing a plate cylinder of a printing machine with a specified silicone rubber film to improve the printing accuracy.
According to this method, however, the silicone rubber film is not separated from the printing machine, so that, for example, it is difficult to simply remove it as the conventional block copy materials for the adjustment, and when printing plates different in thickness are used in the same printing machine, it becomes necessary to replace a block copy material for the adjustment to the plate thickness thereof. This method therefore has the problem that the workability of this replacement is extremely deteriorated.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a block copy material for a lithographic printing plate material, a lithographic press and a lithographic printing method which can avoid the deterioration of the printing dimension and printing accuracy caused by strain partially developed in printing, and can solve the problem of the above-mentioned conventional methods, the deterioration of the workability in printing.
Such an object can be attained by any one of the following (1) to (4):
(1) A block copy material for a lithographic printing plate material comprising a sheet-like substrate, on at least one side of which a plurality of minute projections are distributively formed, wherein the density of minute projections having a height of more than 40 &mgr;m is 20 projections/cm
2
or less on surface average, and the density of minute projections having a height of 3 &mgr;m or more is 25 projections/cm
2
or more on surface average;
(2) A lithographic printing method comprising carrying out printing by using a plate cylinder provided with the block copy material for the lithographic printing plate material of the above (1) so that the side on which the minute projections are formed face toward the lithographic printing plate material side;
(3) A lithographic press having a plate cylinder, wherein said plate cylinder has a surface on which a plurality of minute projections are formed, the density of projections having a height of more than 40 &mgr;m is 20 projections/cm
2
or less on surface average, and the density of minute projections having a height of 3 &mgr;m or more is 25 projections/cm
2
or more on surface average; and
(4) A lithographic printing method comprising carrying out printing by using the plate cylinder for lithography of the above (3) around which a lithographic printing plate is wrapped.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, using the block copy material for the lithographic printing plate material on at least one side of which the plurality of minute projections are formed or the plate cylinder for lithography having the surface on which the plurality of minute projections are formed, the frictional resistance with the lithographic printing plate material opposes the force applied to the lithographic printing plate material in printing to suppress the strain (elongation) caused by this force. Moreover, in the block copy material for the lithographic printing plate material or the plate cylinder, the strain of the lithographic printing plate material is not suppressed by the conventional adhesive force, so that the printing plate material is easily removed.
Accordingly, the block copy material for the lithographic printing plate material and the plate cylinder of the present invention prevents the strain of the printing plate with no sacrifice in workability.
Specific constitution of the present invention is described below in detail.
When the block copy material having the constitution of the above (1) is used, the printing machine which can be used in the present invention may be any, as long as it comprises at least an ink supply device for forming an ink film having a definite thickness on a surface of a form roller, a plate cylinder fitted with a printing plate by fixing a head portion of a printing plate comprising an image area receiving ink and a nonimage area to which no ink is adhered, and by forcedly pulling an edge portion of the plate as required, and an impression cylinder for urging a material to be printed toward the above-mentioned plate cylinder to perform printing. An example thereof is an offset printing press in which a blanket cylinder which is pressed on the above-mentioned plate cylinder to transfer an image and urges the image toward the material to be printed to conduct printing is attached between the above-mentioned plate cylinder and impression cylinder of the printing machine.
Then, the block copy material for prevention of the strain (elongation) of the lithographic printing plate in the present invention is described.
The block copy material of the invention (1) is a sheet-like member having an area approximately similar to that of the lithographic printing plate material, and the plurality of minute projections are distributively formed on at least one side thereof. The height of the minute projections is preferably 1 to 50 &mgr;m. The density of projections having a height of more than 40 &mgr;m is preferably 20 projections/cm
2
or less on surface average, and particularly preferably 0, and the density of projections having a height of 3 &mgr;m or more is preferably 25 projections/cm
2
or more, and particularly preferably 400 projections/cm
2
or more. When the distribution of minute projections is within the above-mentioned range, the force for suppressing the strain of the lithographic printing plate material in printing effectively acts. Although there is no particular upper limit to the number of the distributed minute projections having a height of 3 &mgr;m or more, it is considered to be about 10,000 projections/cm
2
.
The shape of the above-mentioned minute projections is not particularly required, but they are usually in rod or needle form.
According to one method for forming the minute projections of the present invention, minute particles are dispersed in a binder to prepare a dispersion, which is applied onto a surface of the sheet-like substrate and dried.
The average particle size of the minute particles used is preferably about 2 to about 50 &mgr;m.
The above-mentioned minute particles may be either organic materials or i
Nakayama Takao
Naniwa Mutsumi
Sera Hidefumi
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Funk Stephen R.
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