Patent Application
20120111266
This application claims priority to Japanese Patent Application No. 2010-248912 filed on Nov. 5, 2010, which is incorporated herein by reference in its entirety.
The present invention relates to an automatic plate processor which includes a protective gum solution coating apparatus which coats a developed lithographic printing plate precursor with a protective gum solution while conveying it by rolls after rinsing.
Among lithographic printing plate precursors which are to be treated using alkali developing solutions, lithographic printing plate precursors which are comprised of hydrophilic supports on which are provided image forming layers which contain compositions which change in solubility with respect to the alkali developing solutions due to chemical rays or heat are known. These are exposed by bringing silver salt mask films on which images have been recorded in advance into close contact with the photosensitive surfaces of the lithographic printing plate precursors.
On the other hand, along with the advances in computer image processing, lithographic printing plate precursors for direct photosensitive or thermosensitive platemaking which are formed with images directly by laser beams or thermal heads etc. from digital image information without output to silver salt mask films have come under the spotlight.
If these lithographic printing plate precursors are image-wise exposed to light or heat, cured area corresponding to the image area in the final printed matter or area dissolvable by the treatment solution corresponding to the non-image area will be formed. The non-image part regions are dissolved away by an alkali treatment solution.
Usually, these lithographic printing plate precursors are developed by automatic plate processors. In the final step of development (or the gum section), a plate surface protective agent (also called a “desensitizing solution” or “protective gum solution”) is coated over the plate surface of the printing plate precursor on which the image is formed. By using the protective gum solution to cover the entire plate surface, the hydrophilicity of the support surface at the non-image regions is maintained. Further, contamination of the plate surface due to fingermarks or deposition of grease, dust, etc. at the time of storage in the period until platemaking and printing and at the time of handling at the time of mounting to a printing press is prevented. Further, the scratch resistant strength is improved.
In general, at the final step of development (or the gum section), the developed lithographic printing plate precursor passes through a pair of upstream side rollers (pair of conveyor rollers), then the protective gum solution is sprayed on an upper roller and/or lower roller of a pair of downstream side rollers of the gum section (hereinafter referred to as the “pair of gum rollers”) using a gum solution sprayer at the lithographic printing plate precursor. When the lithographic printing plate precursor passes through the pair of gum rollers, the lithographic printing plate precursor is uniformly coated by the protective gum solution. After that, the lithographic printing plate precursor on which the protective gum solution is coated is sent to a drying step.
To uniformly coat the protective gum solution on the lithographic printing plate precursor, in the past, various measures have been taken in the protective gum solution coating step at the protective gum solution coating apparatus or plate processor. For example, Japanese Utility Model Publication (A) No. 62-185065 describes to solve the problem of the insufficient coating of the desensitizing agent at the end faces of a printing plate, in particular the front end face when viewed in plate feed direction, by a plate desensitizing apparatus characterized by moving an upper plate feed roller to the plate feed direction with respect to a lower plate feed roller among the pair of plate feed rollers of a desensitizing solution feed apparatus which feeds a desensitizing solution.
Japanese Utility Model Publication (A) No. 2-112430 describes to prevent a gum solution from flowing back to the pair of conveyor rollers by a plate desensitizing apparatus characterized by making a slant angle of the pair of gum solution coating rollers further larger in the plate feed direction than the slant angle of the pair of conveyor rollers set right before them.
Further, in the past, when developing a lithographic printing plate precursor, the problem arose of a considerable amount of the protective gum solution remaining on the plate surface at the rear end part of the coated printing plate precursor after passing through the gum solution coating apparatus. This residual gum solution sometimes was not sufficiently dried at the drying step and caused stacked printing plates to stick together (blocking) when storing printing plate precursors stacked up after the drying step.
Japanese Patent Publication (A) No. 7-244371 describes to eliminate the protective gum solution remaining at the rear end part of a printing plate by a lithographic printing plate platemaking apparatus which uses as the material of the coating surfaces of the protective gum solution coating rolls at the protective gum solution processing part a hydrophilic material with a porosity of 70% or more so as to absorb the excess gum solution. However, with this apparatus, causing the gum solution to be absorbed requires control of the pressure of the coating rolls. Further, it is necessary to squeeze out the protective gum solution which the coating rolls have absorbed after the end of the work so as to restore the gum solution absorption ability.
This present invention provides a protective gum solution coating apparatus which coats a developed lithographic printing plate precursor with a protective gum solution while conveying it by rolls and an automatic plate processor including such a coating apparatus wherein, without using special surface-treated protective gum solution coating rolls, no residual gum solution is caused on the plate surface of the rear end part of the printing plate on which the protective gum solution is coated and therefore a simple protective gum solution coating apparatus is provided.
As a result of in-depth studies to solve the above problem, the inventors discovered that by changing the position and diameter of the upper roller in a pair of downstream side rollers (pair of gum rollers) of a gum section of a protective gum solution coating apparatus for coating a protective gum solution, unexpectedly no residual gum solution is formed on the plate surface at the rear end part of the printing plate precursor, and thereby completed the present invention.
That is, the present invention provides a protective gum solution coating apparatus for coating a protective gum solution on a lithographic printing plate precursor comprising a pair of upstream side rollers in a gum section, a pair of downstream side rollers in the gum section, and a protective gum solution feeding device, wherein, in a plane orthogonal to the axes of the rollers,
when a contact point between a common tangent of a lower roller of said pair of upstream side rollers and a lower roller of said pair of downstream side rollers and the lower roller of said pair of downstream side rollers is CP,
an upper roller of said pair of downstream side rollers inclines to a direction opposite to a direction where the lithographic printing plate precursor progresses so that an angle “a” between a line which links the centers of the lower roller and the upper roller of said pair of downstream side rollers and a line which links the center of the lower roller of said pair of downstream side rollers and said contact point CP becomes 0<a≦5 degrees.
As one aspect of the present invention, an automatic plate processor which has such a protective gum solution coating apparatus built into it may be mentioned.
a) is a view showing the state where protective gum solution remains at the rear end part of a lithographic printing plate precursor, while (b) is a view showing the state of the pool of the protective gum solution which causes the protective gum solution to remain.
The present invention will be explained below with reference to
In the following drawings, the protective gum solution coating apparatus of the present invention will be explained relating to an aspect where it is built into an automatic plate processor for a lithographic printing plate precursor, but this does not limit the protective gum solution coating apparatus of the present invention in any way. An aspect where it is included in a development system as an independent processor is of course also one aspect of the present invention.
The protective gum solution coating section 13 (part surrounded by broken line) has a pair of upstream side rollers (hereinafter also referred to as “a pair of conveyor rollers”) 15a and 15b, a pair of downstream side rollers (pair of gum rollers) 16a and 16b, and a pair of protective gum solution feeding devices 17. In
The protective gum solution coating section of the prior art usually has the upper gum roller 16b of the gum roller pair with a diameter D2 the same as the diameter D1 of the lower gum roller 16a. Further, a line connecting a center C2 of the upper gum roller 16b and a center C1 of the lower gum roller 16a perpendicularly intersects the common tangent along the path line of the lower conveyor roller 15a and the lower gum roller 16a at the contact point CP with the lower gum roller. The contact point CP is not the point where the pair of gum rollers 16a and 16b contact. As explained later, if the upper gum roller is inclined, the point where the pair of gum rollers contact moves. In this figure, the path line is straight between the upstream conveyor rollers and the gum rollers and is superposed on the tangent. The line connecting the centers C1 and C2 of the pair of gum rollers 16a and 16b perpendicularly intersects the path line.
The protective gum solution is sprayed by the gum sprayers 17a and 17b on to the plate surface of the lithographic printing plate precursor. The protective gum solution which was sprayed from the gum sprayers 17a and 17b pools on the plate surface of the lithographic printing plate precursor. While the precursor is conveyed between the pair of gum rollers 16a and 16b, the pool is spread by the pair of gum rollers and the solution is uniformly coated on the surface of the printing plate precursor. After that, the lithographic printing plate precursor on which the protective gum solution has been coated leaves the pair of gum rollers and is sent to the drying section.
a) shows the state of the lithographic printing plate precursor 30 on which the protective gum solution has been coated right after leaving a pair of gum rollers 16a and 16b of a protective gum solution coating section of the prior art. “A” shows the direction of progress of the plate (plate feed). As will be understood from this figure, the lithographic printing plate precursor is coated with the protective gum solution as a uniform layer 31, but a pool 32 of protective gum solution is observed remaining in a considerable amount on the plate surface of the rear end part of the printing plate precursor. If this remaining pool of protective gum solution is sent to the subsequent drying section, the problem arises that it will not be sufficiently dried. If such printing plates are stacked, the stacked plates will stick together (blocking).
b) shows the state when leaving a pair of gum rollers 16a and 16b of the protective gum solution coating section of the prior art. After being sprayed by the protective gum solution by the gum sprayers 17a and 17b, the lithographic printing plate precursor passes through the pair of gum rollers. When the lithographic printing plate precursor separates from the pair of gum rollers, the upper gum roller 16b, the lower gum roller 16a, and the rear end part of the lithographic printing plate precursor form a closed space S. This space S contains the protective gum solution. When the lithographic printing plate precursor is further conveyed and the rear end part of the lithographic printing plate precursor separates from the pair of gum rollers 16a and 16b whereby the closed space S is opened, the protective gum solution which was inside the closed space S is believed to spring up on the plate surface of the rear end part of the plate causing the residual pool of gum solution 32.
Explaining the position of the upper gum roller in detail, at the protective gum solution coating section of the prior art shown in
The slant angle “a” is 0<a≦5 degrees in range. In this range, it was learned that the amount of the pool of protective gum solution remaining on the plate surface at the rear end part of the plate precursor is reduced. Even if over 5 degrees, the amount of the residual gum solution decreases, but a pool of the protective gum solution tended to be observed remaining at the back surface of the plate surface of the rear end part of the plate precursor.
The following examples are provided for illustrating the working of the present invention. It is not intended by any means to limit the present invention to these examples.
In Example Nos. 1 to 8, an automatic plate processor, that is, a P-940X Plate Processor (made by Kodak), is used to process a 0.24 mm×1030 mm×790 mm lithographic printing plate precursor. An outline of the configuration of the P-940X Plate Processor and the processing conditions are as follows:
Gum solution: SWF1 (water 1:1.5 dilution), made by Kodak
Gum processing temperature/processing speed: room temperature/1,332 mm/min
Drying temperature: 50° C. to 55° C.
Tact time: 50 seconds
Example Nos. 1, 3, and 4 have a diameter D1 of the lower gum roller the same as the diameter D3 of the upper gum roller. The slant angle “a” of the upper gum roller position is zero. These show examples of the prior art (comparative examples).
Evaluation Method
The dried state of the center part of the plate surface of the lithographic printing plate precursor emerging from the drying unit, the state of occurrence of pools of gum at the rear end part of the plate surface, and the state of blocking when stacking processed lithographic printing plate were evaluated.
The results are shown in Table 1. Note that the dried state of the center part of the plate surface was sufficient in each of Example Nos. 1 to 8.
State of Occurrence of Residual Stationary Gum at Rear End Part of Surface (Length in Direction of Progression of Plate)
At the rear end part of the plate surface, the part with a greater thickness of the gum compared with the center part of the plate surface was defined as the residual pool of gum. The length of that part in the direction of progression of the plate was measured and the results were judged as follows:
Good: Length of residual pool of gum of less than 0.1 mm
Fair: Length of residual pool of gum of 0.1 mm to 1 mm
Poor: Length of residual pool of gum of over 1 mm
Blocking when Stacked (when Stacking 20 Plates)
To examine the state of blocking when stacking processed lithographic printing plates, the presence of any blocking was observed when stacking 20 processed lithographic printing plate - more than the usual embodiment (stacking five to 10 plates). The results were evaluated as follows:
A: No blocking
B: Blocking observed at one to two plates from bottom of stack. (However, no blocking when stacking five to 10 plates in ordinary use).
C: Blocking observed at one to four plates from bottom of stack. (However, no blocking when stacking five to 10 plates in ordinary use).
D: Blocking observed at one to five plates from bottom of stack. Blocking seen to occasionally occur even when stacking five to 10 plates in ordinary use.
In Example Nos. 1, 3, and 4 (comparative examples), blocking was seen in one to five plates from the bottom of the stack (blocking was sometimes seen even when stacking five to 10 plates as in normal use). By making the angle of the position of the upper gum roller tilt to the opposite side from the direction of progression, blocking could be completely suppressed when stacking five to 10 plates as in normal use. Further, if making the diameter of the upper gum roller larger than the diameter of the lower gum roller as well, blocking when stacking five to 10 plates as in normal use was suppressed. The effect of suppression of blocking by the slant angle of the position of the upper gum roller was larger. When both the requirements of the slant angle “a” of the position of the upper gum roller and the diameter of the upper roller are satisfied, even if stacking more than double the usual number (stacking 20), no blocking could be observed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-248912 | Nov 2010 | JP | national |
