JP2016173454A - Photosensitive resin relief printing plate precursor and production method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photosensitive resin relief printing plate precursor or a photosensitive flexographic printing plate precursor, in which a side face of a plate end is coated with a coating material that blocks chemical rays by a safe and easy method.SOLUTION: The photosensitive resin relief printing plate precursor or the photosensitive flexographic printing plate precursor has a layer where laser drawing can be performed, and is characterized in that: a side face edge of the printing plate precursor is coated with a coating material; the coating material comprises at least one UV ray absorbing material, a film-forming polymer, and a solvent or a solvent mixture; and the film-forming polymer is a water-soluble polymer.SELECTED DRAWING: None

Description

  The present invention relates to a photosensitive resin relief plate precursor or a photosensitive flexographic printing plate precursor whose side surfaces are coated with a light shielding material, and a method for producing the same.

  The photosensitive printing plate is used for producing a resin relief plate or a flexographic printing plate, and is a printing method generally used for mass printing. In these printings, it is used for various printed materials such as paper, paperboard material, cardboard, film, foil, two-piece cans and cylindrical materials found in plastic containers. The resin relief printing plate or flexographic printing plate has a relief shape in which the image portion is a convex portion and the non-image portion is a concave portion, and a desired image is printed by transferring the ink to the printing medium via the convex portion.

  In general, a photosensitive resin relief plate or a photosensitive flexographic plate is a multilayer body comprising a support, one or more photocurable layers, a slip coat layer, and a cover film in this order.

  The support literally supports the plate and consists of a transparent or opaque plastic film or a metal plate such as steel.

  The photocurable layer can contain a known photosensitive resin, monomer, initiator, reactive or non-reactive diluent, filler, dye, surfactant, and the like. Photo-curing refers to polymerization, cross-linking or other curing reactions in response to actinic radiation, and unexposed areas are selectively separated and removed from exposed (cured) areas to form a three-dimensional relief pattern of the cured product. A solid composition that can be formed. Suitable photocurable materials include resins or elastomeric compounds, at least one ethylenically unsaturated compound, and a photoinitiator. The photocurable material is generally cured by crosslinking in at least a certain actinic wavelength region. In this specification, actinic radiation is 250 to 450 nm, more preferably 300 to 400 nm, and still more preferably 320 to 380 nm, particularly in the ultraviolet light wavelength region. One suitable source of actinic radiation is an ultraviolet lamp, although other sources are generally known to those skilled in the art.

  The slip coat layer is a thin layer for protecting the photosensitive resin and improving the handleability of the photosensitive resin. In the conventional plate making process, the slip coat layer remains on the photocured layer when the cover film is peeled off, the negative film is placed on the slip coat layer, and the photocured layer is selectively exposed by exposure through the negative film. And relief can be formed by separating and removing the unexposed portions, commonly referred to as “analog” versions. On the other hand, in the type of plate called “CTP (Computer To Plate)”, a layer containing an infrared absorbing material typified by carbon black (hereinafter referred to as a mask layer) is arranged on the photocurable layer. In addition, by selectively ablating the mask layer with a dedicated laser drawing machine using infrared light as a light source, it is possible to create a state similar to placing a negative film (hereinafter, this process is referred to as a drawing process) By exposing through the mask layer after drawing, the photo-cured layer can be selectively cured, and relief can be formed by separating and removing the unexposed parts, and the plate-making efficiency including preparation of negative film is an analog version. It is said that it is very high compared with. The laser drawing machine includes a cylindrical cylinder on which a plate with the mask layer on the outside is to be mounted, and draws the mask layer by scanning the laser light source in the direction perpendicular to the rotation direction while rotating the cylinder. There are many types.

  In the case of the analog version, since it is necessary to install a negative film, the exposure process is generally carried out by installing a plate on a flat table and using an actinic light source disposed on the negative film placed on the plate surface. Since the size of the plate is often slightly larger than the size of the negative film due to the stability of the arrangement, the outer peripheral portion of the plate is not shielded by the negative film, and an unnecessary cured portion is formed in the exposure process. For this reason, it is possible to prevent the formation of the unnecessary hardened portion by arranging an appropriate actinic light-shielding member in a form along the plate edge. In addition to the unavoidable problem of a significant decrease, the exposed portion that should be the relief portion approaches the vicinity of the plate edge depending on the image to be formed. That itself is difficult. In this case, a separate process of removing the unnecessary hardened portion formed at the plate edge in the exposure process by cutting is necessary, and there is a problem that the efficiency of the plate making process is significantly reduced.

  On the other hand, in the case of the CTP plate, since the mask layer is previously laminated on the photocured layer as described above, in principle, the actinic radiation at the time of exposure is shielded from the portions ablated by the infrared laser to become unexposed portions. Therefore, it is washed out by the developer in the developing process and can be a recess. However, since the mask layer is not disposed on the side portion of the photocurable layer at the end portion of the plate, the photocurable layer is exposed to actinic radiation, and as a result, an unnecessary cured portion is formed on the outer peripheral portion of the plate end portion. As a result, the same work as that of the analog version is often required as a result, and the plate-making efficiency is remarkably lowered in that respect.

  In recent years, the laser drawing machine is equipped with an actinic light source represented by LED-UV for exposing a photosensitive resin in addition to a laser light source for removing a mask layer. It is possible to improve the plate making efficiency because it can be carried out with one device at a time, but the same is true for exposure of actinic radiation to the plate edge, and the plate is placed on a flat table. Therefore, it is difficult to dispose the light shielding member at the end of the plate.Therefore, as in the case of the analog plate, there is a problem that a process of cutting and removing unnecessary hardened portions at the end of the plate after exposure occurs inevitably. Still remains.

  In order to solve the above problem, for example, Patent Document 1 discloses that there is no need for a plate edge by exposure by coating a film side surface with a film-forming polymer soluble in an organic solvent, a UV absorber, and a solution containing an organic solvent as a main component. Although a method for suppressing photocuring is disclosed, the method involves drying of an organic solvent, so that safety is required and a solvent recovery or incineration facility for preventing air pollution is required. There is a problem. In addition, the coating process on the plate edge has a problem that a large amount of labor is required because of the large number of plates. Therefore, a safe and simple coating method on the side of the plate has been desired.

Japanese Patent No. 4125411

  An object of the present invention is to provide a photosensitive resin relief printing plate precursor or a photosensitive flexographic printing plate precursor, which is coated with a coating material that shields actinic radiation on the side surface of the plate edge by a safe and simple method.

  As a result of intensive studies to achieve the above object, the present inventors have made the binder polymer of the coating material on the side surface of the plate edge a water-soluble polymer, and further coated the same size plate by laminating a plurality of plates of the same size. The inventors have found that it is possible to provide a plate in which the side surface of the plate edge is coated safely and simply by coating the side surface at a time, and the present invention has been completed.

That is, the configuration of the present invention is as follows.
(1) A photosensitive resin relief printing plate precursor or a photosensitive flexographic printing plate precursor having a laser-drawable layer, wherein a side edge of the printing plate precursor is coated with a coating material, and the coating material is at least 1 A printing plate precursor comprising a kind of ultraviolet absorbing material, a film-forming polymer, and a solvent or solvent mixture, wherein the film-forming polymer is a water-soluble polymer.
(2) The printing plate precursor as described in (1), wherein the film-forming polymer is polyvinyl alcohol or partially saponified polyvinyl alcohol having a saponification degree of 50 mol% or more and 95 mol% or less and a polymerization degree of 400 or more and 800 or less.
(3) The printing according to (1) or (2), wherein the polymer in the relief forming layer of the photosensitive resin relief printing plate precursor or the photosensitive flexographic printing plate contains polyvinyl alcohol or partially saponified polyvinyl alcohol Version original edition.
(4) The printing plate precursor according to any one of (1) to (3), wherein a plurality of the printing plate precursors cut to the same size are stacked to form a laminate, and the coating material is applied to the side surface. A method for producing a printing plate precursor comprising coating

  According to the present invention, it is possible to obtain a photosensitive resin relief printing plate precursor or a photosensitive flexographic printing plate precursor in which the plate edge is not exposed to actinic radiation at the time of exposure, and formation of unnecessary cured portions is suppressed. This is expected to greatly improve the plate-making efficiency.

  Hereinafter, the present invention will be described focusing on preferred embodiments.

  The coating liquid for coating the plate edge in the present invention will be described. In the coating material used in the present invention, the binder polymer is a water-soluble polymer. By using a water-soluble polymer, the solvent of the coating solution can be changed to water, and there is no danger of ignition during coating, and even a contractor without special equipment can easily perform coating. The type of the water-soluble polymer is not limited as long as the effect of the present invention is not impaired, but from the viewpoint of coating properties described later, polyvinyl alcohol or partially saponified polyvinyl alcohol is preferable, and film strength after coating and drying is ensured. From this viewpoint, the saponification degree is preferably 70 mol% or more and 95 mol% or less.

  The ultraviolet absorbing material can be shared with the film-forming polymer, and various materials that absorb light having a wavelength in the 250 to 400 nm region of the ultraviolet spectrum can be arbitrarily used. Typical examples include, for example, benzophenol derivatives such as 2,2'-dihydroxy-4,4'-dimethoxybenzophenol, benzotriazole or benzotriazole derivatives, p-aminobenzoic acid, menthyl anthranilate, octyl salicylate. Organic compounds such as oxybenzene, triethanolamine salicylate, phenylbenzimidazole sulfonate, inorganic compounds such as titanium dioxide, zinc oxide, and carbon black can be used.

  Further, the present coating material is made from a thickener, preservative, stabilizer, viscosity modifier, surfactant, pigment dispersant, rheology modifier, pH adjuster, polymer and combinations thereof within a range not impairing the effects of the present invention. One or more additives selected from the group consisting of may be used.

  The plate edge coating method of the present invention is preferably carried out by stacking plates instead of one by one for improving efficiency, and a known method such as spray spraying or roller coating of the coating material can be used.

  The film-forming polymer and the ultraviolet absorbing material are used in an amount capable of preventing edge curing during exposure of the drawn plate. Also, in the above coating method, since the stacked plates are separated from each other after the coating material is applied and dried, if the film strength is too strong, the film itself is peeled off from the end of the plate due to the stress when the connected film is separated. Care must be taken, and from this viewpoint, the degree of polymerization of polyvinyl alcohol is preferably from 400 to 800.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

[Preparation of evaluation printing plate precursor]
A printing plate for evaluating the effects of the present invention was produced by the following method.

  100 sheets of polyvinyl alcohol-based water developing resin letterpress CTP plate “DWF95HX4” (thickness: 0.95 mm, size: 5 cm short side × 30 cm long side) manufactured by Toray Industries, Inc., each having a mask layer were prepared.

[Method of applying coating liquid to the side of the plate]
100 CTP plates described above were stacked and fixed with a tape or the like so that the plates were not separated from each other, thereby forming a solid rectangular parallelepiped. Of the side surfaces of the plate, the surface including the long side (30 cm x 9.5 cm) is placed so as to face the horizontal base, and the opposite surface (30 cm x 9.5 cm) is the horizontal top surface. Formed. A coating solution was applied to this surface with a # 12 bar coater and dried in an oven at 50 ° C. for 5 minutes to form a coating film on the side of the plate.

[Separability of the coating film on the side of the plate]
The coated surfaces of the plate side surfaces obtained by coating and drying 100 sheets collectively by the above method were separated from each other, and the fixability of the film on the plate side surface at that time was confirmed. ○, if the coating film was separated and fixed on the side of each plate, the film was disturbed in such a way that a thread was pulled during the separation, and x if the coating film was partly or largely peeled off from the side of the plate .

[Evaluation of coating film properties]
This evaluation was performed by applying a # 12 bar coater to a 100 μm thick polyester film obtained by corona-treating the coating liquid of the present invention instead of coating on the side of the plate and drying it in an oven at 50 ° C. for 10 minutes. . After drying, the appearance was observed to confirm the presence or absence of uncoated parts such as clear shading and omission, and the OD value was measured using a concentration meter “TR-927” manufactured by Macbeth. If the OD value was 3.0 or more, it was rated as ◯, and if it was less than 3.0, it was marked as x.

[Viscosity evaluation of coating liquid]
For the viscosity measurement, a B-type viscometer (model: BL, manufactured by Tokyo Keiki Co., Ltd.) was used, the evaluation liquid was kept at 25 ° C., and the rotor was No. 2. The number of rotations of the rotor was measured at 60 rpm. The viscosity at 25 ° C. was measured using a B-type viscometer.

[Evaluation of the quality of coating film formation by the presence or absence of curing of the plate edge]
Evaluation was performed by performing plate making under the following conditions on a plate having a coating film on the side surface of the plate by the method described above.

  (I) Drawing process: The drawing machine did not carry out the laser drawing process of the mask layer for the purpose of evaluating the presence or absence of an unnecessary hardened portion by exposure to ultraviolet rays at the edge of the plate.

  (Ii) Exposure process: The exposure was performed for 5 minutes with an exposure machine “AQF-A1” (registered trademark) manufactured by DANTEX equipped with an 80 W lamp “10R” manufactured by Philips.

  (Iii) Development step: Development was performed at a water temperature of 30 ° C. for 200 seconds using a batch type developing machine “Tomiflex A3” (registered trademark) manufactured by Tomihiro Sangyo Co., Ltd.

  (IV) Drying step: The printing plate was dried at 50 ° C. for 10 minutes.

  (V) Judgment of presence / absence of curing of plate edge: If the side surface of the plate is not exposed to light by the coating film, the entire surface of the plate becomes an uncured portion, and the photocurable layer is completely removed in the development process leaving the support. If it was, it was evaluated as ◯, and if a cured part was formed at the end of the plate, it was rated as x.

"Example 1"
A coating solution on the side of the plate was prepared by the following method and evaluated.

  Water is added to polyvinyl alcohol powder “PVA-205” (saponification degree: 86.5 to 90 mol%, average polymerization degree: 500) manufactured by Kuraray Co., Ltd., and the temperature is raised to 90 ° C. and maintained for 2 hours. A 30% aqueous solution of alcohol was prepared. To 200 g of the 30% aqueous solution of polyvinyl alcohol, 180 g of water and 40 g of ethanol were further added and mixed uniformly. To this polyvinyl alcohol solution, 180 g of a sulfonic acid-treated carbon black aqueous dispersion “CAB-O-JET200” (solid content concentration 20%) manufactured by Cabot Corporation was added and mixed uniformly.

  When the coating solution thus prepared was applied and dried with a # 12 bar coater, a uniform film without omission was formed, and the OD value was 3.5 to 3.7. The viscosity of the coating liquid was 90 mPa · s. It was visually confirmed that the film after application and drying of the bar coater on the side surface of the plate on which the coating solution was stacked was suitably separated without being stretched and fixed on the side surface of the plate when the plates were separated from each other. Further, when this plate was made, no hardening phenomenon occurred at the edge of the plate, and all was washed away in the development process.

[Example 2]
A coating solution was prepared in the same manner as in Example 1 except that polyvinyl alcohol in Example 1 was changed to “PVA-405” (saponification degree: 80 to 83 mol%, average polymerization degree: 500) manufactured by Kuraray Co., Ltd. And evaluated. When the coating solution was applied and dried with a # 12 bar coater, a uniform film with no omission was formed, and the OD value was 3.4 to 3.7. The viscosity of the coating liquid was 70 mPa · s. The film after application and drying of the bar coater on the side surface of the plate on which the coating liquid was stacked was suitably separated without being stretched and fixed on the side surface of the plate when the plates were separated from each other. Further, when this plate was made, no hardening phenomenon occurred at the edge of the plate, and all was washed away in the development process.

"Comparative Example 1"
A coating solution was prepared in the same manner as in Example 1 except that polyvinyl alcohol in Example 1 was changed to “PVA-203” (saponification degree: 86.5 to 90 mol%, average polymerization degree: 300) manufactured by Kuraray Co., Ltd. Fabricated and evaluated. The viscosity of this coating solution was 30 mPa · s. Fine cracks were observed in part of the coated and dried film, and the OD value of the area including the cracked part was less than 2.0. When this plate was coated on the side of the plate and the plate was made, there was no problem with the separation of the film when the plates were pulled apart from each other, but a hardened part was formed at a part of the plate edge after plate making, and the light shielding effect of the plate side It was speculated that was not enough.

"Comparative Example 2"
The coating liquid was prepared in the same manner as in Example 1 except that the polyvinyl alcohol in Example 1 was changed to “PVA210” (saponification degree: 87 to 89 mol%, average polymerization degree: 1000) manufactured by Kuraray Co., Ltd. Fabricated and evaluated. The viscosity of this coating liquid was 350 mPa · s. Unevenness was observed in the film after coating and drying, and the OD value was 3.1 to 3.7. When this liquid was coated on the side of the plate and the plate was made, the film was stretched when the plates were pulled apart from each other, and only a part of the plate was wrinkled from the side of the plate. When a plate containing this part was made, it was speculated that a hardened part was formed at the plate end of the part, and the light shielding effect on the side of the plate was not sufficient.

  Table 1 shows the evaluation results of Examples 1-2 and Comparative Examples 1-2.

  From the results of Table 1, by providing a photosensitive resin relief printing plate precursor or a photosensitive flexographic printing plate precursor coated with a coating material that shields actinic radiation on the side surface of the plate edge by a safe and simple method, CTP It was confirmed that unnecessary curing of the edge due to exposure that hinders plate making efficiency of the plate can be suppressed.

Claims (4)

A photosensitive resin relief printing plate precursor or a photosensitive flexographic printing plate precursor having a laser-drawable layer, wherein a side surface of the printing plate precursor is coated with a coating material, and the coating material absorbs at least one ultraviolet ray. A printing plate precursor comprising a material, a film-forming polymer, and a solvent or solvent mixture, wherein the film-forming polymer is a water-soluble polymer. The printing plate precursor according to claim 1, wherein the film-forming polymer is polyvinyl alcohol or partially saponified polyvinyl alcohol having a saponification degree of 70 mol% or more and 95 mol% or less and a polymerization degree of 400 or more and 800 or less. The printing plate precursor according to claim 1 or 2, wherein the polymer component in the relief forming layer of the photosensitive resin relief printing plate precursor or the photosensitive flexographic printing plate precursor contains polyvinyl alcohol or partially saponified polyvinyl alcohol. The method for producing a printing plate precursor according to any one of claims 1 to 3, wherein a plurality of the printing plate precursors cut to the same size are stacked to form a laminated body, and then the coating material is coated on a side surface. A method for producing a printing plate precursor, comprising: