JP3676865B2 - Method for preparing flexographic printing plate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a flexographic printing plate excellent in plate making and printing properties.
[0002]
[Prior art]
Conventionally, a flexographic printing method is generally used for printing on corrugated cardboard, multilayer film, liner paper, film, and the like. In the flexographic printing method, a relief printing material made of a flexible elastic material typified by a rubber plate is usually used. When an image of such relief printing material is transferred to a printing material, the printed image is printed by printing pressure. There is a problem that fatness tends to occur.
[0003]
For the purpose of solving such a problem of fatness, conventionally, JP-A-57-210341, JP-A-61-84289, JP-A-62-229127, and JP-A-2-56554 have been disclosed. An elastic foam body made of a foamed plastic sheet or a foamed rubber sheet having continuous and / or single fine air bubbles is joined to the relief plate itself as disclosed, and printing is performed using an integrated printing plate. Is doing.
[0004]
However, an elastic foam body made of a foamed plastic sheet or a foamed rubber sheet having air bubbles is easily eroded by ink used in printing, a plate cleaning agent, or the like. In the case of having a skin layer on the surface of the elastic foam body, the degree is light, but since the cut end surface has no skin layer, the end surface of the elastic foam body is infiltrated with ink or a cleaning agent, and the end surface is It swells and increases its thickness, which causes the printing surface to become dirty or the edge of the plate to peel off, causing a printing trouble.
[0005]
In order to prevent this problem, conventionally, a caulking material represented by silicon sealant or the like has been applied to the end face of the elastic foam body.
[0006]
[Problems to be solved by the invention]
However, in the method using the caulking material, it takes time and skill to apply the caulking material in order to reliably block the air bubbles opened at the end face of the elastic foam body, and the caulking material is hardened. In the case of several hours to a long time until it can be used, it takes one night, so that the printing plate cannot be used immediately. Moreover, since the silicon sealant normally used as a caulking material is relatively expensive, there is also a problem that it is inferior in economic efficiency.
[0007]
An object of the present invention is to solve such problems of the prior art, and is a flexographic printing plate in which an elastic foam body is joined and integrated with a relief plate material, which has excellent platemaking and printing properties, and As a method for reliably closing the air bubbles opened at the end face of the elastic foam body, it is possible to provide a method that requires only a short time, does not require skill in the work, and does not use expensive materials.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems, a method for producing a flexographic printing plate according to the present invention includes a flexographic printing plate in which an elastic foam body having fine bubbles is bonded to a surface opposite to a relief forming side of a photosensitive resin layer. In the production method, a step of cutting and removing an edge portion of a printing plate unnecessary for use in printing, and heating an end face of the elastic foam body generated in the cutting and removing step to a temperature equal to or higher than a softening temperature of the elastic foam body. The method further includes a step of closing the bubbles opened at the end face.
[0010]
The method for heating the end face of the elastic foam body in the method for producing a flexographic printing plate of the present invention includes a method in which a heating element such as a soldering iron is brought into contact with the end face, a method using a high-frequency welder, heat-compressed air and combustion The method etc. which spray gas on the said end surface are mentioned. The heating temperature is not less than the softening temperature of the elastic foam body, preferably not less than the melting temperature.
[0011]
Various thermal analysis techniques are generally used to measure the softening temperature of the elastic foam body, and examples thereof include a dynamic thermomechanical measurement method (DYNAMIC THERMOMECHANO-METRY; DMTA UK, manufactured by Polymer Laboratories).
As the photosensitive resin composition constituting the photosensitive resin layer, the property before photocuring may be either liquid or solid, and the resin properties after photocuring can be used as a flexographic printing plate. Good. Examples of such a photosensitive resin composition include JP-B-60-7261, JP-A-63-088555, JP-B-51-37320, JP-B-53-37762, and JP-B-59-22219. And those described in Japanese Patent Publications.
[0012]
Examples of the elastic foam include polyolefin having continuous and / or single fine bubbles, polyurethane, ethylene propylene rubber, etc., having a density of 0.1 to 0.6 g / cm ³ and a Shore-A hardness of 10 to 60 degrees. Although it is suitable, it is not particularly limited as long as it satisfies an elastic characteristic or the like that does not hinder actual printing characteristics. Such elastic foams are described in, for example, JP-A 57-210341, JP-A 59-212298, JP-A 61-84289, JP-A 62-22912, and the like. Are listed.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described.
FIG. 1 is a cross-sectional configuration diagram illustrating a flexographic printing plate according to an embodiment of the present invention. As can be seen from this figure, the flexographic printing plate 10 has an adhesive layer 2, an elastic foam layer 3, an adhesive layer 4, and a photosensitive resin layer 5 laminated on a support 1 in this order. The bubbles on the end surface 31 of the layer 3 are closed with the material forming the elastic foam body.
[0014]
In the flexographic printing plate 10, the air bubbles on the end face 31 of the elastic foam layer 3 are closed, so that ink used in printing, a cleaning agent for the plate, and the like hardly penetrate into the elastic foam layer 3. As a result, the end face does not swell and the thickness does not increase, and printing troubles such as smearing the print face and peeling off the end of the plate are unlikely to occur.
In addition, for example, the bubbles on the end surface 31 may be blocked by bringing a heating element such as a soldering iron into contact with the end surface 31, performing high-frequency heating with a high-frequency welder, or blowing heat-compressed air or combustion gas onto the end surface 31. And since it is made by heating the said end surface 31 above the softening point temperature or melting temperature of the said elastic foam body, special skill is not required and it can work in a short time. In addition, such blockage of bubbles by heat treatment is economical because expensive materials are not used as in the prior art.
[0015]
The heat treatment may be performed on the exposed plate on which the relief is formed by plate making or on the unexposed plate before the relief is formed. Further, the penetration of the developing solvent into the elastic foam layer 3 in the development process of the plate making for producing the relief can be suppressed. When it is not necessary to cut the edge of the elastic foam layer 3 after joining with the photosensitive resin layer 5, the heating is performed on the end face 31 of the elastic foam layer 3 before joining with the photosensitive resin layer 5. Processing may be performed.
[0016]
Hereinafter, embodiments of the present invention will be described in detail with reference to specific examples.
[0017]
[Example 1]
The flexographic printing plate 10 has a total thickness of 2.85 mm, the support 1 is made of a polyester film having a thickness of 0.1 mm, and the adhesive layers 2 and 4 are made of a urethane adhesive having a thickness of 0.05 mm. The elastic foam layer 3 is made of urethane foam (elastic foam body) having a thickness of 1.15 mm and a density of 0.38 g / cm ^3. The photosensitive resin layer 5 has a thickness of 1.50 mm and a relief height of 0.1. It consists of an 8 mm letterpress material.
[0018]
The photosensitive resin layer 5 uses a solid photocurable resin AFPXAR-928 (trade name; manufactured by Asahi Kasei Kogyo Co., Ltd.) having a thickness of 1.50 mm as a photosensitive resin, and has a protective film. The cover film on the side not to be peeled is peeled off and pressure bonded to the elastic foam layer 3 via a urethane adhesive, and then a predetermined plate making process is performed to form a relief.
[0019]
Further, the flexographic printing plate 10 is subjected to a process of heating the end face 31 of the elastic foam layer 3 to 250 ° C. with a soldering iron after the plate making process, after cutting and removing an unnecessary edge part with scissors. As a result, a large number of bubble openings that were present at the time of cutting were closed.
In addition, when the softening temperature of the elastic foam body used here was measured in air | atmosphere by DMTA (Polymer Laboratories, UK), it has confirmed that it was 185-190 degreeC.
[0020]
This flexographic printing plate 10 and the flexographic printing plate 11 of FIG. 2 in which heat treatment was not performed on the end face 31 of the elastic foam layer 3 after the cutting (the end face 31 of the elastic foam layer 3 has a large number of bubble openings). And printing on a film with a solvent ink while performing a wiping treatment with a solvent in the middle.
As a result, in the flexographic printing plate 10 in which the end face 31 of the elastic foam layer 3 was subjected to the heat treatment, printing for 3 hours was completed, but in the flexographic printing plate 11 that was not subjected to the heat treatment, the printing time was less than one hour. Since the edges were soiled, the printing was not completed, and the plate had to be replaced before printing.
[0021]
[Example 2]
When the flexographic printing plate having the same configuration as that of the flexographic printing plate 10 of Example 1 is manufactured in the same procedure, the heat treatment temperature of the end face 31 of the elastic foam layer 3 is changed, and the bubbles are blocked by the heat treatment temperature. I examined the difference.
The heat treatment was performed by applying the tip of a temperature-adjusted soldering iron with temperature adjustment (manufactured by Hakuko Co., Ltd .; HAKKO 926) to the end face 31 of the elastic foam layer 3. At this time, the surface temperature of the tip portion of the soldering iron applied to the end surface 31 was measured with a surface thermometer (Anritsu Meter Co., Ltd .; Anritsu Thermometer Type E).
[0022]
When the set temperature of the soldering iron is 250 ° C. (measured temperature at the time of use of the tip portion is 180 ° C.), there is almost no change in the end face 31 of the elastic foam body even if the contact is continued for 2 minutes (that is, the end face is opened) Air bubbles were not occluded). When the set temperature was 275 ° C. (the actual measured temperature was 200 ° C.), blocking of the bubbles opened at the end face 31 of the elastic foam body was observed by applying for 1 minute. When the set temperature was 325 ° C. (the measured temperature was 230 ° C.), the air bubbles opened at the end face 31 of the elastic foam body were closed very easily (just by applying for about several seconds).
[0023]
Using these flexographic printing plates produced by the same method as in Example 1 except that the heat treatment temperature was different, printing was performed on the same film with the same solvent ink and plate wiping solvent as in Example 1, The one that was processed at the actual measurement temperature of 180 ° C was stained on the printed surface within one hour as the unprocessed one, while the one that was processed at the same actual temperature of 200 ° C was the one that was processed at 230 ° C for two hours. Was able to withstand printing for more than 3 hours.
[0026]
【The invention's effect】
As described above , according to the method for producing a flexographic printing plate of the present invention, the end face processing operation of the elastic foam body can be easily performed in a short time without any special skill. Further, this method is economical because it does not use expensive materials as in the prior art.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram illustrating a flexographic printing plate according to an embodiment of the present invention.
FIG. 2 is a cross-sectional configuration diagram showing a flexographic printing plate of a comparative example of the present invention.
[Explanation of symbols]
3 Elastic foam layer 5 Photosensitive resin layer 31 End face

Claims (1)

In the method for producing a flexographic printing plate in which an elastic foam body having fine bubbles is bonded to the surface opposite to the relief forming side of the photosensitive resin layer,
Cutting and removing edges of the printing plate that are unnecessary for use in printing;
A flexographic printing plate comprising: a step of closing air bubbles opened at the end face by heating an end face of the elastic foam produced in the cutting and removing step to a temperature equal to or higher than a softening temperature of the elastic foam body . Manufacturing method .

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