JP2007225883A - Processing apparatus for computer-to-plate (ctp) printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a processing apparatus for a CTP printing plate that gives no adverse influence on an automatic platemaking machine caused by an elution defect portion on an end face of a photosensitive material due to pressure fog upon developing, even in a CTP printing plate requiring a chamfering process, and that can carry out stable development for a long period of time without depositing dirt on the surface of a conveyer roll. <P>SOLUTION: The processing apparatus has functions of, while conveying a CTP printing plate which is to be directly exposed to laser light as a light source and the end face of which is chamfered, as nipped by rolls, immersing the plate in at least a developing solution to elute and remove a non-image part and rinsing the plate with water, wherein the rinsing process includes a shower means which diffuses water at a discharge angle of 45 or more in a direction orthogonal to the conveying direction of the CTP printing plate at a discharge pressure of 0.1 to 0.5 MPa and a flow rate ranging from 1 to 10 L/min. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a processing device for a lithographic printing plate, particularly a lithographic printing plate that is directly exposed using a laser beam as a light source.

  In recent years, direct plate-making systems using various lasers such as ultraviolet, visible, and infrared (computer-to-plate, acronyms are also called CTP systems for directly making computer-generated image information) are available. It has been put into practical use and is widely used in the field of general commercial printing. This direct plate making system is advantageous in comparison with conventional plate making systems using film in terms of speed, cost, stability, etc. by digitizing the system, and is becoming mainstream in today's general commercial printing market.

  Due to these advantages, the direct plate making system is spreading not only in the general commercial printing market but also in the newspaper printing market. In newspaper printing, printing conditions are severer than general commercial printing because of its large number of copies and high printing speed, and high printing durability is required for printing plates. For this reason, negative type photopolymerizable photosensitive materials capable of forming an image with higher strength by a crosslinking reaction than positive type photosensitive materials have been used in conventional film plate making systems. For this reason, a lithographic printing plate having high image strength was indispensable for introducing a direct plate-making system into the newspaper printing market.

  Conventional film-making systems using negative photosensitive materials cause a cross-linking reaction of the photosensitive layer by prolonged contact exposure with a very high energy light source such as a mercury lamp. The image obtained was very strong. In the direct plate making system, since exposure processing is performed with lower exposure energy than these light sources, it was initially difficult to form an image with the same intensity, but in recent years, various photosensitivities have been developed to improve the image intensity. Materials have been developed. In particular, high-power semiconductor lasers that emit light in the infrared region of 750 nm or more are becoming more compact and higher-powered and are very useful as exposure light sources for direct plate-making systems. In the plate making system, the development of photosensitive materials has made remarkable progress, and various proposals have been made.

  For example, the photosensitive material described in JP-A-7-20629 is characterized in that it contains a resole resin, a novolak resin, a latent Bronsted acid, and an infrared absorber, and can be used for both positive and negative plates. The version is described. JP-A-2000-089452 discloses a cross-linkable compound having a unique structure, and a binder is a polymer having an aromatic hydrocarbon ring directly bonded to a hydroxy group or an alkoxy group in a side chain or main chain, In addition, a negative image recording material containing a compound that generates an acid by heat and an infrared absorber is described. JP-A-2001-272778 discloses a photosensitive material comprising a borate complex salt, a trihaloalkyl-substituted compound, and a sensitizing dye having absorption in a wavelength range from near infrared light to infrared light. Are listed.

  However, in the lithographic printing plate (hereinafter referred to as CTP printing plate) corresponding to these direct plate making, there has been a problem that has not been seen in the general commercial printing field in the newspaper printing field. It is pressure fogging by chamfering of the end face.

  Unlike general commercial printing, newspaper printing often requires frequent replacement of printing plates. Therefore, it is common to place multiple printing plates on a single plate cylinder and perform printing while replacing printing plates as necessary. . However, when a plurality of printing plates are printed side by side on a single plate cylinder, the border between adjacent printing plates appears linearly on the printed paper surface due to ink on the cut surface of the printing plate, so-called frame contamination. It becomes a printing failure called. In order to prevent this printing failure, the CTP printing plate used for newspaper printing is generally chamfered on the CTP printing plate in the manufacturing process.

  The chamfering process referred to in the present invention is a process of chamfering the end face of the CTP printing plate. When the CTP printing plate is cut to a required size by a cutting finishing machine such as a flying shear, a rotary shear, or a guillotine, the clearance of the blade This means that the edge of the surface on which the photosensitive layer is applied is scraped off while having an oblique linear shape or a curvature. FIG. 2 shows a schematic cross-sectional view of a CTP printing plate that has been chamfered. In FIG. 2, b represents a CTP printing plate support, and a represents a photosensitive layer. Moreover, c shows the side part formed by the chamfering process. Further, A represents the horizontal length from the end face of the support removed by the chamfering process, and B represents the vertical length from the photosensitive layer surface of the part removed by the chamfering process. The values of A and B are not particularly limited, but are generally 50 μm to 200 μm.

  When this chamfering process is performed, the photosensitive layer is locally subjected to a large pressure by the blade of the cutting and finishing machine, and the photosensitive layer is strongly pressed against the support. The pressed photosensitive layer may be embedded in the support, or the components in the photosensitive layer may be altered by pressure, resulting in a change in dissolution during development. This is particularly noticeable in the case of a CTP printing plate having higher sensitivity than the PS plate. As a result, an elution defect portion is generated on the end surface of the CTP printing plate, and a phenomenon called pressure fogging sometimes occurs. In addition, the photosensitive layer may wrap around the side surface of the support during the chamfering process, and elution of the wrapped photosensitive layer will be delayed during the development process, and it will not peel off from the side surface of the support and will remain on the plate as a poorly eluted portion. There were cases where it remained. These poorly eluted portions appeared as residual films in various forms such as needles, thin layers, and grains on the end face of the developed CTP printing plate, causing a plate making failure.

  Further, since the elution by the developing solution is weaker than that at the rear end at the top of the processing, the occurrence is remarkable. The reason why the elution property of the head part becomes weak is that, in the method of immersing in the developer, it is not horizontally transported but is transported in a curved shape to the developer reservoir, so that it is separated from the developer reservoir upward. This is because the liquid breakage is improved and the development is completed earlier than the rear end. On the contrary, the rear end portion will be supplied more abundantly after being drawn into the air from the developer storage portion by the excess liquid from the squeeze roll, so that a difference occurs.

  If this poorly eluted portion cannot be completely removed by the developing unit of the plate-making processing device, it is sandwiched by the transport roll of the water washing unit in the next process, but in the case of a developer immersion type, it is detached from the solution and transported. When the printing plate is directed upward, it first hits the upper roll and then nips, so if there is an elution failure part at the processing head part of the printing plate, the elution failure part strongly against the part where the printing plate head contacts Sometimes peeled off by impact and transferred. In this case, the ink is accumulated on the roll as the number of plate-making plates increases, and gradually retransfers to the surface of the printing plate to be processed thereafter. In some cases, the printing plate quality deteriorates due to printing stains. Moreover, the dirt adhering to the plate surface may be re-transferred to the transport roll in the process after the washing section, which has been a cause of deteriorating the maintainability of the plate making apparatus as a whole.

Many immersion development type processing apparatuses have been proposed so far (for example, the processing apparatuses described in Patent Documents 1 and 2), both of which are caused by transfer dirt due to the residual film on the end face and dirt on the washing unit transport roll. No corresponding one has been proposed.
Japanese Patent Laid-Open No. 8-248642 JP 2000-298357 A

  Accordingly, the problem of the present invention is that even in a CTP printing plate that requires chamfering processing, there is no adverse effect on the automatic plate making machine due to the poor elution of the end face of the photosensitive material due to pressure fog at the time of development, and the surface of the transport roll is stained. Is to provide a CTP printing plate processing apparatus capable of performing a stable development process over a long period of time without sticking.

It has been found that the above object of the present invention can be achieved by the CTP printing plate processing apparatus described below.
1. A CTP printing plate having an image forming layer on a metal support, which is directly exposed using a laser beam as a light source and whose end face is chamfered, is immersed in at least a developing solution while being conveyed by nipping the roll, and is non-image part. In the processing apparatus that performs the water washing treatment after elution and removal, the water washing treatment is carried out in the transport direction of the CTP printing plate in the processing equipment in the range of the discharge pressure of 0.1 to 0.5 MPa and the flow rate of 1 to 10 L / min. A CTP printing plate processing apparatus comprising shower means for diffusing at an ejection angle of 45 degrees or more in an orthogonal direction.

  According to the present invention, even if the chamfering process applied to newspaper printing is performed, there is no elution failure of the end face portion of the photosensitive layer due to pressure fog or the like, and an excellent effect can be obtained that can obtain a printing plate in which no frame smear occurs even in printing. can get.

  As a result of intensive studies by the inventor, the CTP printing plate is transported in the processing apparatus in the range of a discharge pressure of 0.1 to 0.5 MPa and a flow rate of 1 to 10 L / min with respect to the above problems. It was found that a plate making apparatus having shower means that diffuses at a discharge angle of 45 degrees or more in a direction orthogonal to the direction is extremely useful.

  The development processing apparatus according to the present invention will be described below with reference to FIG. FIG. 1 is a sectional view of an automatic processor showing an example of the present invention. The CTP printing plate 100 subjected to the exposure processing in FIG. 1 is inserted into an automatic developing machine with the photosensitive layer surface facing upward, and is conveyed into the development processing unit by the conveying rolls 1 and 2, and is kept at a constant temperature via the conveying auxiliary rolls 3 and 4. And dipped in a temperature-controlled developer.

  The photosensitive layer of the CTP printing plate immersed in the developer is in a state in which the unexposed part, which is a non-image part, is swollen by the developer and is easily eluted, while the submerged transport rolls 3 and 4 and the transport auxiliary roll 5, 6 to the scraping section. Elution is promoted by rubbing the swollen non-image area by the scraping roll 7. On the other hand, the image area where the crosslinking reaction has occurred by exposure hardly swells in the developer and remains as an image.

  Next, the CTP printing plate on which the image is formed by elution of the non-image portion is squeezed with the developer squeeze rolls 9 and 10 to squeeze the excess developer on the plate surface, and is transported to the water washing processing unit which is the next step. The surface of the CTP printing plate 100 is washed with the washing water discharged from the shower means 14 while being conveyed by the washing washing rolls 11 and 12 in the washing treatment section. The shower means 14 includes a gear pump (not shown), a pressure resistant pipe 142, and a plurality of discharge nozzles 143 attached to the pressure resistant pipe 142. The washing water is discharged and diffused from the discharge nozzle 143 in a direction perpendicular to the transport direction of the CTP printing plate, and the plurality of discharge nozzles 143 overlaps a part of the discharge range, and the injection amount with respect to the CTP printing plate surface Is sprayed so as to be uniform. Due to the high discharge pressure, the photosensitive layer residue due to elution failure of the plate surface non-image portion and the transferred material from the roll are removed, and the plate surface is cleaned. Further, since the washing water transporting rolls 11 and 12 are installed so that a part of the washing water sprayed thereon is hit, even if a part of the photosensitive layer adheres as dirt, the separation is promoted, and the width of the water washing transportation roll 11 is increased. It is cleaned over the entire direction.

  Thereafter, the water washing liquid is squeezed by the water washing conveyance rolls 16 and 17 and conveyed to a gum processing unit (not shown). In the gum processing section, a gum solution is applied to form a protective film on the surface of the CTP printing plate, and finally, drying is performed in the drying processing section.

  The structure of the shower means that is a feature of the present invention will be described in detail. The shower means includes a pump capable of pressurizing at least 0.1 MPa, a pressure-resistant piping capable of withstanding a pressure of 0.5 MPa, and a discharge nozzle capable of diffusing 45 degrees or more as a discharge angle. As a pump to be used, a positive displacement pump such as a gear pump or a diaphragm pump is preferable because of excellent liquid feeding property in a pressurized state. Among them, a gear pump is preferable because it can obtain a relatively high flow rate and has no pulsation. Moreover, the discharge pressure in this invention is a pressure just before discharging, and can be measured by installing a water pressure gauge in the discharge nozzle part of the shower means. FIG. 3 is a schematic view seen from the CTP plate conveying direction showing the discharge state of the shower means. Any discharge nozzle may be used as long as it is attached to a pressure-resistant pipe and the discharge angle is 45 degrees or more. When the discharge angle is 45 degrees or less, there is a tendency for the discharge pressure and amount at the discharge center to increase, and the portion may be affected in a streak pattern on the corresponding printing plate. . The number of discharge nozzles and the intervals between them can be appropriately set according to the width of the CTP plate to be processed and the distance from the tip of the discharge nozzle to the plate surface. If the distance from the tip of the discharge nozzle to the printing plate is too close, the effective area becomes narrow, so it is preferably 20 mm or more.

  The discharge nozzle will be described in more detail. FIG. 4 is a plan view and a schematic cross-sectional view of the ejection portion of the discharge nozzle. As the injection port, a notch groove in the diametrical direction is formed on the outlet side of the through hole having a diameter of 0.1 to 1 mm, so that the discharged water is jetted in a substantially flat shape along the notch groove. Those are preferred. By directing the notch groove in a direction perpendicular to the conveying direction of the CTP printing plate, the washing water is diffused and jetted in the processing width direction of the CTP printing plate. Further, the discharge angle can be set by adjusting the depth and length of the cutout groove. In the present invention, the discharge angle may be set to 45 degrees or more. Although the discharge angle depends on the processing width, the distance to the plate surface, and the external dimensions of the apparatus, the wide angle is preferable because the effective area for injection onto the plate surface is widened and the number of nozzles can be set small.

  Next, the discharge pressure and flow rate of flush water discharged from the nozzle will be described. In general, the plate surface cleaning effect is better as a stronger force is applied to the plate surface, and higher discharge pressure is preferable. Conventionally, an impeller-type liquid feed pump classified into a turbo type that can obtain a flow rate with a simple structure has been used in a washing section of a processing apparatus for a planographic printing plate. In this case, if the discharge pressure is increased, the flow rate will inevitably increase and the amount of washing water that remains on the plate surface in the washing treatment section will increase, so the momentum of the newly discharged washing water becomes a film on the plate surface. Suppressed by flushing water. Further, when the flow rate is further increased, the adverse effect of flush water scattered around and the amount of flush water stored for treatment increase, resulting in a large apparatus, increased waste liquid, and many disadvantages. On the other hand, with an impeller-type liquid feed pump, liquid feed becomes unstable when the outlet is throttled and pressurized, and the discharge pressure does not increase even if the pump capacity is increased. For this reason, as a result of investigating using the pump which can carry out pressurized liquid feeding, it discovered that the flow rate of 1-10 L / min was optimal with the discharge pressure of 0.1-0.5 MPa. If the discharge pressure is high, the cleaning effect increases proportionally, but it may affect the print reproducibility, especially for high-definition images of 200 lines / inch or higher and image portions formed by FM screening. This is because inconveniences such as a jam may occur due to the influence on the conveyance. If the flow rate range is wide, there are problems and adverse effects as described above.

  Next, the CTP printing plate used in the present invention will be described. The CTP printing plate used in the present invention is a lithographic printing plate comprising a polymerizable compound having at least one ethylenically unsaturated bond capable of photopolymerization and a photopolymerization initiator, and is a conventionally known CTP printing A plate can be used. In particular, a chamfering treatment used for newspaper printing is sufficiently effective. In addition, the CTP plate used for newspaper printing is more sensitive than the PS plate, and the occurrence of pressure fog due to the chamfering process becomes more prominent, so that it can be used more effectively. Examples of these printing plates include lithographic printing plates characterized by containing a resole resin, a novolak resin, a latent Bronsted acid and an infrared absorber described in JP-A-7-20629, and JP-A 2000-2000. The compound having crosslinkability described in Japanese Patent No. 089452 has a unique structure, and the binder is a polymer having an aromatic hydrocarbon ring directly bonded to a hydroxy group or an alkoxy group in a side chain or main chain, and an acid is generated by heat. A lithographic printing plate containing a generated compound and an infrared absorber, a borate complex salt described in JP-A-2001-272778, a trihaloalkyl-substituted compound, and an increase having absorption in a wavelength range from near infrared light to infrared light region. Examples thereof include a lithographic printing plate characterized by containing a dye-sensitive dye. In particular, the photosensitive layer of a lithographic printing plate has a copolymer of a monomer having a polymerizable double bond in the side chain and a carboxyl group-containing monomer as a polymerizable polymer, and lithographic printing having an organic boron salt as a photopolymerization initiator The plate can be applied effectively because it is more sensitive.

  The developer used in the present invention will be described. Any alkaline aqueous solution can be used as long as it is an alkaline liquid having a pH of 8 or higher and can be dissolved in a CTP printing plate to be used in a predetermined time. Examples of the alkali agent include inorganic alkalis such as sodium hydroxide and potassium hydroxide, organic alkali agents such as monomethylamine, dimethylamine and trimethylamine, and alkali metal silica such as sodium silicate, potassium silicate and lithium silicate. Examples thereof include acid salts and ammonium silicate. These can be used alone or in combination of two or more. Further, anionic, cationic, nonionic and amphoteric surfactants can be added singly or in combination in consideration of elution adjustment and detergency after dissolution.

  A printing plate developed with a developer having such a composition is then post-treated with a washing water, a rinse solution containing a surfactant, a finisher mainly composed of gum arabic or starch derivatives, or a protective gum solution. Applied. In the post-treatment of the printing plate of the present invention, these treatments can be used in various combinations. For example, development → water washing → rinsing liquid treatment containing surfactant or development → water washing → finisher liquid treatment is a rinse liquid or finisher. Less liquid fatigue is preferable. Furthermore, a countercurrent multistage process using a rinse liquid or a finisher liquid is also a preferred embodiment. These post-processing are generally performed using an automatic developing machine including a developing unit and a post-processing unit. As the post-treatment liquid, a method of spraying from a spray nozzle or a method of conveying through a treatment tank filled with the treatment liquid is used. A method is also known in which a fixed amount of a small amount of washing water is supplied to the plate surface after development, and the waste liquid is reused as dilution water for the developer stock solution. In such automatic processing, each processing solution can be processed while being replenished with the respective replenishing solution according to the processing amount and operating time. In addition, a so-called disposable processing method in which treatment is performed with a substantially unused post-treatment liquid can also be applied.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples as well as the effects.

  The automatic plate making machine in the present embodiment will be described below with reference to FIG. FIG. 1 is a schematic sectional view of a developing portion of an automatic plate making machine showing an example of the present invention. The CTP printing plate 100 subjected to the exposure processing in FIG. 1 is inserted into an automatic developing machine with the photosensitive layer surface facing upward, and is conveyed into the development processing unit by the conveying rolls 1 and 2, and is kept at a constant temperature via the conveying auxiliary rolls 3 and 4. And dipped in a temperature-controlled developer.

  The photosensitive layer of the CTP printing plate immersed in the developing solution is conveyed to the scraping unit by the submerged conveying rolls 5 and 6 while the unexposed portion which is a non-image portion is swollen by the developing solution and is easily eluted. Is done. Elution is promoted by rubbing the swollen non-image area by the scraping roll 7. On the other hand, the image area where the crosslinking reaction has occurred by exposure hardly swells in the developer and remains as an image.

  Next, the CTP printing plate on which the image is formed by elution of the non-image portion is squeezed with the developer squeeze rolls 9 and 10 to squeeze the excess developer on the plate surface, and is transported to the water washing processing unit which is the next step. The surface of the CTP printing plate 100 is washed with the washing water discharged from the shower means 14 while being conveyed by the washing washing rolls 11 and 12 in the washing treatment section. The shower means 14 includes a gear pump (not shown), a pressure resistant pipe 142, and a plurality of discharge nozzles 143 attached to the pressure resistant pipe 142. The discharge pressure is set to 0.3 MPa, the flow rate is set to 8 L / min, and the discharge angle is set to 115 degrees. The washing water is discharged and diffused from the discharge nozzle 143 in a direction perpendicular to the transport direction of the CTP printing plate, and the plurality of discharge nozzles 143 overlaps a part of the discharge range, and the injection amount with respect to the CTP printing plate surface Is sprayed so as to be uniform. Due to the high discharge pressure, the photosensitive layer residue due to elution failure of the plate surface non-image portion and the transferred material from the roll are removed, and the plate surface is cleaned. Further, since the washing water transporting rolls 11 and 12 are installed so that a part of the washing water sprayed thereon is hit, even if a part of the photosensitive layer adheres as dirt, the separation is promoted, and the width of the water washing transportation roll 11 is increased. It is cleaned over the entire direction.

  Thereafter, the water washing liquid is squeezed by the water washing conveyance rolls 16 and 17 and conveyed to a gum processing unit (not shown). In the gum processing section, a gum solution is applied to form a protective film on the surface of the CTP printing plate, and finally, drying is performed in the drying processing section.

  A commercially available CTP printing plate for newspaper printing (PD-News 300 manufactured by Mitsubishi Paper Industries, 1100 mm × 398 mm) was chamfered using a commercially available shearing machine (M-1245 manufactured by Amada). At this time, by adjusting the clearance of the blade edge, a CTP printing plate of the following chamfered processed product 1 and a non-chamfered processed product 2 substantially not having a chamfered processing portion was prepared. The end face shape of the chamfered product 1 was 50 μm in the horizontal direction from the end face of the support, which is A in FIG. 2, and 50 μm in the vertical direction from the surface of the photosensitive layer, which was B in FIG. .

For the CTP printing plates 1 and 2 produced as described above, laser irradiation was performed at a drum rotation speed of 1000 rpm using an external drum type plate setter (PT-R4000 manufactured by Dainippon Screen Mfg. Co., Ltd.) equipped with an 830 nm semiconductor laser. The exposure process was carried out with the energy fixed at 50 mJ / cm ² , and then the development process was carried out with the automatic plate making machine.

  With the above automatic plate making machine, each of the chamfered processed product 1 and the non-chamfered processed product 2 was processed continuously for 500 plates, and the plate surface was observed from the first plate-making product to the 500th plate-making product. No abnormalities were observed, and good prints were obtained even after printing. In addition, the washing transport roll 11 after completion of the plate making showed no particular adhesion of dirt. Next, the shower means 14 of the washing section is removed, and instead, a shower pipe is prepared by opening a through hole with a diameter of 2 mm at a pitch of 10 mm in a SUS304 pipe having an inner diameter of 12 mm within the range of the processing width, and an impeller pump is used. When the continuous plate-making process is performed in the same manner as described above with the flow rate set to 30 L / min, the chamfered processed product 1 is not reflected in the printed matter, but the portion of the plate surface that gradually contacts the processing head from the 300th plate is transferred. Was confirmed. Furthermore, the washing washing rolls 11 and 12 in the washing unit and the rolls in the gum treatment unit were so dirty that it took time to clean.

  As an application example of the present invention, it can be used as an automatic developing device for a CTP printing plate for the newspaper printing field.

1 is a schematic cross-sectional view of an automatic plate making machine showing an example of the present invention. It is the cross-sectional schematic of the CTP printing plate which performed the chamfering process concerning this invention. It is the schematic seen from the CTP plate conveyance direction which shows the discharge state of the shower means of the washing process of the automatic plate-making machine which shows an example of this invention. It is the injection part plane and cross-sectional schematic diagram of the discharge nozzle of the shower means of the washing process of the automatic plate making machine which shows an example of this invention.

Explanation of symbols

a CTP printing plate photosensitive layer b CTP printing plate support c Side surface formed by chamfering process A Horizontal length from the end surface of the support removed by the chamfering process B Part of the part removed by the chamfering process Length in the vertical direction from the surface of the photosensitive layer 100 CTP printing plate 101 CTP printing plate head portion 1, 2 transport roll 3, 4 transport auxiliary roll 5, 6 submerged transport roll 7 scraping roll 8 guide plate 9, 10 development aperture Roll 11, 12 Flushing roll 14 Shower means 142 Pressure-resistant piping 143 Discharge nozzle 15 Flushing shower pipe 16, 17 Flushing roll

Claims (1)

  A CTP printing plate having an image forming layer on a metal support, which is directly exposed using a laser beam as a light source and whose end face is chamfered, is immersed in at least a developing solution while being conveyed by nipping the roll, and is non-image part. In the processing apparatus that performs the water washing treatment after elution and removal, the water washing treatment is carried out in the transport direction of the CTP printing plate in the processing equipment in the range of the discharge pressure of 0.1 to 0.5 MPa and the flow rate of 1 to 10 L / min. A CTP printing plate processing apparatus comprising shower means for diffusing at an ejection angle of 45 degrees or more in an orthogonal direction.

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