Method for manufacturing printing plate

Abstract

Disclosed is a method for manufacturing a printing plate, the method including: a superposing step for sequentially superposing, on a first hard plate 11 which is located at a lower position, a negative film 1 which has a microcell pattern, a liquid photosensitive resin composition layer 2, a support 3, and a second hard plate 12 which is located at an upper position; and a light exposure step for curing the photosensitive resin composition layer 2 by irradiating active rays from the first hard plate 11 side and the second hard plate 12 side. In the superposing step, the photosensitive resin composition layer 2 is directly superposed on the negative film 1, and the solubility parameter SpA of the photosensitive resin composition that constitutes the photosensitive resin composition layer 2 and the solubility parameter SpB of the negative film have a relationship of the following formula (I).　(I): |SpA - SpB| ≥ 2.0

Description

Printing plate manufacturing method

[0001] The present invention relates to a method for making a printing plate.

[0002] In recent years, flexographic printing using flexographic printing plates has been widely used as a method for printing on various media such as cardboard, paper, film, etc. Various methods for manufacturing flexographic printing plates have been proposed (see, for example, Patent Document 1).

[0003] Patent Document 1 discloses the following method for producing a flexographic printing plate. First, a negative film with a desired pattern and a transparent protective film are laminated on a lower hard plate. A liquid photosensitive resin composition layer is laminated on the transparent protective film. A support is laminated if necessary, and an upper hard plate is laminated. The photosensitive resin composition layer sandwiched between the lower and upper laminate plates is adjusted to a desired uniform thickness. Next, the photosensitive resin composition layer is exposed to ultraviolet light (back exposure) from the upper hard plate corresponding to the upper hard plate. Then, ultraviolet light is irradiated through the negative film and the transparent protective film from the uncured photosensitive resin composition layer side opposite the UV-exposed side, i.e., the lower hard plate corresponding to the lower hard plate, through relief exposure to obtain a flexographic printing plate blank. The photosensitive resin composition in the unexposed areas of the flexographic printing plate blank is then developed by, for example, washing away, to form a relief image, thereby obtaining a flexographic printing plate.

[0004] The method for producing a flexographic printing plate using the liquid photosensitive resin composition as described above allows the photosensitive resin composition in the unexposed areas to be recovered, thereby achieving both a reduction in the amount of photosensitive resin composition to be disposed of and a reduction in the cost of producing flexographic printing plates, and is therefore widely used as a method for producing flexographic printing plates that is highly environmentally adaptable.

[0005] On the other hand, "solid density" is known as an indicator of the appearance of a printed matter using a flexographic printing plate. Generally, a higher solid density is preferable, and a technique for forming "microcells" on the surface of a flexographic printing plate to improve the solid density is known (see, for example, Patent Document 2).

[0006] Recently, computer-to-plate (CTP) technology has become known as a method for producing flexographic printing plates. In this CTP technology, an ablation layer capable of being ablated by infrared light is formed on a photosensitive resin composition layer, and the ablation layer is then removed in a desired shape by irradiating it with an infrared laser, forming an actinic ray-transmitting portion corresponding to a negative. Next, the photosensitive resin composition layer is irradiated with ultraviolet light using the ablation layer as a mask, causing the photosensitive resin composition to react in the same shape as the actinic ray-transmitting portion formed in the ablation layer, thereby performing relief exposure. Finally, the unnecessary ablation layer and the unexposed portions of the photosensitive resin composition are developed and removed to produce a flexographic printing plate. However, the above-described method for producing flexographic printing plates is designed to provide high adhesion between the ablation layer and the photosensitive resin composition from the standpoint of practicality, which poses a problem in that it is difficult to isolate and recover the photosensitive resin composition in the unexposed portions after relief exposure. Furthermore, the elution and migration of the ablation layer into the photosensitive resin composition cannot be completely suppressed, making it difficult to isolate and recover the photosensitive resin composition in the unexposed areas, and there is also the problem that there is room for improvement in terms of ensuring the quality of the flexographic printing plate. Here, "elution" refers to the components constituting the ablation layer being individually mixed into the photosensitive resin composition, and "migration" refers to the ablation layer peeling off from the substrate while maintaining its film shape and being mixed into the photosensitive resin composition.

[0007] As a solution to the problems caused by adhesion, elution, and migration of the ablation layer to the photosensitive resin composition, a method has been proposed in which an infrared laser is irradiated onto a flexographic printing plate precursor having a photosensitive resin composition layer, a film layer, and an optical density changing layer corresponding to the ablation layer on a predetermined support to form an image mask (see, for example, Patent Document 3). Also, as a technology for forming an article having a relief image using a predetermined removable film, a method has been proposed in which an image-forming film containing an image-forming material is imagewise exposed to imaging radiation to obtain an image-formed film, the image-formed film is laminated onto an image-forming article containing a photosensitive material and a release layer, curing radiation is irradiated through the image-formed film, the image-formed film is removed from the image-formed article, and the image-formed article is then developed to form a relief image (see, for example, Patent Document 4). In these methods, ultraviolet light is irradiated from above the image mask to perform overall exposure, and then the image mask is peeled off and removed together with the film layer or release layer, and then development is performed to obtain a flexographic printing plate. These methods have the advantage that the image mask is removed before development, thereby preventing adhesion to, elution from, and migration of the photosensitive resin composition layer.

[0008] Japanese Patent Publication No. 2005-301071 Japanese Patent Publication No. 2021-525661 International Publication No. 01 / 18605 Japanese Patent No. 4971311

[0009] However, the methods for producing flexographic printing plates proposed in Patent Documents 1, 3, and 4 have the problem that the film layer or release layer between the photosensitive resin composition layer and the negative film or image mask makes it easy for ultraviolet light to bend or scatter, resulting in reduced image reproducibility. In particular, as described above, when microcells are formed on the surface of a flexographic printing plate to increase the solid density of the printed matter, the bending and scattering of ultraviolet light by the film layer or release layer deteriorates the formation of microcells, resulting in reduced quality of the final printing plate. On the other hand, if no film layer or release layer is provided between the photosensitive resin composition layer and the negative film or image mask, the adhesive strength between the photosensitive resin composition layer and the negative film or image mask becomes excessive, resulting in the problem of elution and migration between the layers.

[0010] In view of the above-mentioned problems of the conventional art, the present invention aims to provide a method for producing a printing plate that suppresses the elution and migration of a negative film into a photosensitive resin composition layer, is capable of forming microcells, and produces a printing plate with high solid density and excellent image reproducibility.

[0011] As a result of extensive research aimed at solving the above-mentioned problems, the present inventors have found that the above-mentioned problems of the conventional art can be solved by directly laminating a liquid photosensitive resin composition layer on a negative film and then performing pattern exposure, and by specifying the absolute value of the difference between the solubility parameter of the photosensitive resin composition and the solubility parameter of the negative film to be a predetermined value or more, and have thus completed the present invention.

[0012] [1] A method for producing a printing plate, comprising: a laminating step of laminating, on a first hard plate located below, a negative film having a microcell pattern, a liquid photosensitive resin composition layer, a support, and a second hard plate located above, in that order; and an exposure step of irradiating the photosensitive resin composition layer with actinic light from the side of the first and second hard plates to cure the photosensitive resin composition layer, wherein in the laminating step, the photosensitive resin composition layer is directly laminated on the negative film, and a solubility parameter SpA of the photosensitive resin composition constituting the photosensitive resin composition layer and a solubility parameter SpB of the negative film satisfy the relationship represented by the following formula (I): |SpA - SpB| ≧ 2.0 (I) [2] A method for producing a printing plate according to [1] above, further comprising, as a step prior to the laminating step, a drawing step of forming a microcell pattern on the negative film, wherein the drawing step uses at least one method selected from the group consisting of an ablation method, a thermal method, an inkjet method, and a silver halide method. [3] The method for producing a printing plate according to [1] or [2] above, wherein the solubility parameter SpA of the photosensitive resin composition constituting the photosensitive resin composition layer is 10.0 or more and 14.0 or less. [4] The method for producing a printing plate according to any one of [1] to [3] above, wherein the solubility parameter SpB of the negative film is greater than 14.0. [5] The method for producing a printing plate according to any one of [1] to [3] above, wherein the solubility parameter SpB of the negative film is less than 10.0. [6] The method for producing a printing plate according to any one of [1] to [5] above, wherein the negative film contains a resin having a structural unit represented by the following general formula (II):

[0013]

[0014] In formula (II), R １ and R ２ each independently represents a non-polar group, R ３ and R ４ each independently represents a hydrogen atom or a nonpolar group.

[0015] [7] In the formula (II), R and R are each independently any one selected from the group consisting of an alkyl group, an alkenyl group, and an alkynyl group, ３ and R ４ [8] The method for producing a printing plate according to [6] above, wherein R is independently any one selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, and an alkynyl group. １ and R ２ are each independently an alkyl group; R ３ and R ４are each independently a hydrogen atom or an alkyl group. [9] The method for producing a printing plate according to any one of [6] to [8] above, wherein the resin having a structural unit represented by general formula (II) further contains a structural unit derived from a monovinyl-substituted aromatic hydrocarbon.

[10] The method for producing a printing plate according to any one of [1] to [9] above, wherein the negative film contains at least one selected from the group consisting of polyurethane, polylactic acid, polycarbonate, polyester, polyamide, polybutyral, polyvinyl alcohol, poly(meth)acrylate, and modified or partially saponified products thereof.

[11] The method for producing a printing plate according to any one of [1] to

[10] above, further comprising, after the exposure step, a development step of removing unexposed areas of the photosensitive resin composition layer, and a recovery step of recovering the unexposed areas removed in the development step and using the unexposed areas as a photosensitive resin composition for producing a new printing plate.

[12] A method for producing a printing plate, comprising: a laminating step of sequentially laminating, on a first hard plate located below, a negative film having a microcell pattern, a liquid photosensitive resin composition layer, a support, and a second hard plate located above; and an exposure step of irradiating the photosensitive resin composition layer with actinic light from the side of the first hard plate and the second hard plate to cure the photosensitive resin composition layer, wherein, in the laminating step, the photosensitive resin composition layer is directly laminated on the negative film, and the solubility parameter SpB of the negative film is 13.0 or more.

[13] A method for producing a printing plate, comprising: a laminating step of sequentially laminating, on a first hard plate located below, a negative film having a microcell pattern, a liquid photosensitive resin composition layer, a support, and a second hard plate located above; and an exposure step of irradiating the photosensitive resin composition layer with actinic light from the side of the first hard plate and the second hard plate to cure the photosensitive resin composition layer, wherein, in the laminating step, the photosensitive resin composition layer is directly laminated on the negative film, and the solubility parameter SpB of the negative film is 9.0 or less.

[0016] According to the present invention, a method for producing a printing plate can be provided that suppresses the elution and migration of a negative film into a photosensitive resin composition layer, is capable of forming microcells, and produces a printing plate with high solid density and excellent image reproducibility.

[0017] 1 is a schematic diagram illustrating a method for producing a flexographic printing plate according to the present invention; FIG. 2 is a schematic cross-sectional view of an example of a negative film used in the method for producing a printing plate according to the present invention;

[0018] Hereinafter, a mode for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. Note that the following present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out by appropriately modifying it within the scope of its gist.

[0019] [Method for Manufacturing a Printing Plate] The method for manufacturing a printing plate of this embodiment includes a lamination step of sequentially laminating a negative film having a microcell pattern, a liquid photosensitive resin composition layer, a support, and a second hard plate located above on a first hard plate located below, and an exposure step of irradiating the photosensitive resin composition layer with actinic light from the side of the first and second hard plates to cure the photosensitive resin composition layer. In the lamination step, the photosensitive resin composition layer is directly laminated on the negative film. The solubility parameter SpA of the photosensitive resin composition constituting the photosensitive resin composition layer and the solubility parameter SpB of the negative film have the relationship represented by the following formula (I): |SpA - SpB| ≧ 2.0 (I)

[0020] According to the method for producing a printing plate of this embodiment, it is possible to suppress the elution and migration of a negative film into a photosensitive resin composition layer, and it is also possible to form microcells, thereby obtaining a flexographic printing plate that has a high solid density and excellent image reproducibility.

[0021] (Lamination Step) FIG. 1 shows a schematic cross-sectional view illustrating the method for producing a printing plate according to this embodiment. In the lamination step, a negative film 1 having a predetermined pattern 1a for forming the desired printing pattern in the final printing plate and a predetermined microcell pattern 1b for forming microcells, a liquid photosensitive resin composition layer 2, a support 3, and a second hard plate 12 located above are sequentially laminated on a first hard plate 11 located below. A back-exposure negative film 4 having a pattern 4a for forming a shelf layer during back exposure may be provided between the photosensitive resin composition layer 2 and the second hard plate 12. In the lamination step of the method for producing a printing plate according to this embodiment, the liquid photosensitive resin composition layer 2 is directly laminated on the negative film 1 without an intervening cover film or the like. This prevents bending and scattering of exposure light during the exposure step, resulting in high image reproducibility.

[0022] <Hard Plate> The first hard plate 11 and the second hard plate 12 used in the method for producing a printing plate of this embodiment may be an ultraviolet-transmitting glass plate or the like that is known for use in producing flexographic printing plates.

[0023] <Negative Film> The negative film 1 used in the method for producing a printing plate of this embodiment has a predetermined printing pattern 1a for forming a desired relief, and a predetermined microcell pattern 1b for forming microcells.

[0024] [Microcell Pattern] Increasing the surface area of ​​a relief printing plate is an effective method for improving solid density in a printing plate. A technique for forming microcells on the surface of a printing plate is known, which aims to improve solid density by uniformly and densely coating the printing plate with ink. For example, various microcell patterns have been used, such as those disclosed in JP-A-2021-525661. Specifically, the surface area of ​​the printing plate surface can be increased by providing microcells of various shapes, such as dots, grids, halftone dots, and lines, in a finely textured pattern on the printing plate surface. Microcell patterns can be used not only in solid areas to improve the solid density of the printed ink, but also for text, line drawings, halftones, or any other image element that achieves improved ink transfer characteristics. While microcell patterns are typically not visible in the final print, they form a surface structure that results in improved ink spread.

[0025] In the printing plate manufacturing method of this embodiment, a drawing step of forming a predetermined microcell pattern on the negative film 1 is preferably included as a pre-step of the lamination step. The microcell pattern is preferably applied to a printing area of ​​any size and formed in the desired area so that a uniform solid area can be printed. The drawing step of forming the microcell pattern can be performed by, but is not limited to, an ablation method, a thermal method, an inkjet method, a silver halide method, or the like. Specifically, when the negative film 1 has an ablation layer on a predetermined substrate, the ablation layer can be irradiated with infrared light to perform drawing processing. The drawing method is not particularly limited, and can be performed using a known irradiation unit. The ablation layer is irradiated with an infrared laser to decompose the resin in the irradiated area, thereby drawing and processing the pattern. This results in an ablation layer with a pattern drawn and processed. Examples of infrared lasers include an ND / YAG laser (e.g., 1064 nm) or a diode laser (e.g., 830 nm). Laser systems suitable for CTP platemaking technology are commercially available, and for example, a diode laser system CDI Spark (ESKO GRAPHICS) can be used. This laser system includes a rotating cylindrical drum that holds a negative film, an IR laser irradiation device, and a layout computer, and image information is sent directly from the layout computer to the laser device.

[0026] Because the negative film 1 has the microcell pattern 1b, the printing plate obtained by the printing plate manufacturing method of this embodiment has, for example, a relief surface having a pattern 2a including microcells 2b, which are multiple minute irregularities having a predetermined area and height and formed from the negative film 1. In the printing plate manufacturing method of this embodiment, by using a negative film 1 having the microcell pattern 1b, it is possible to improve the solid density.

[0027] [Relationship between Solubility Parameters] In the printing plate manufacturing method of this embodiment, the solubility parameter SpA of the photosensitive resin composition constituting the photosensitive resin composition layer described below and the solubility parameter SpB of the negative film satisfy the relationship represented by the following formula (I): |SpA - SpB| ≥ 2.0 (I) That is, the absolute value of the difference between SpA and SpB is 2.0 or greater. Preferably, it is 2.1 or greater, and more preferably, it is 2.2 or greater. Both cases are possible in which SpB is greater than SpA and in which SpB is smaller than SpA. By ensuring that the absolute value of the difference between SpA and SpB is 2.0 or greater, elution and migration of the negative film into the photosensitive resin composition can be effectively suppressed, even when the negative film and the liquid photosensitive resin composition are directly laminated. The upper limit of the absolute value of the difference between SpA and SpB is determined by the selected materials for the negative film and the photosensitive resin composition layer, and from a practical standpoint, it is 13.0 or less.

[0028] As described above, in this embodiment, since elution and migration of the negative film into the photosensitive resin composition layer can be suppressed, isolation and recovery of the photosensitive resin composition in the unexposed areas can be facilitated, and the quality of the printing plate can be improved. Furthermore, since elution and migration of the negative film into the photosensitive resin composition layer can be suppressed, there is no need to provide a specific film layer between the negative film and the photosensitive resin composition layer, and the bending and scattering of ultraviolet light that would be caused by providing such a film layer can be prevented, thereby achieving excellent image reproducibility. In particular, in the printing plate manufacturing method of this embodiment, since the negative film has a microcell pattern, it is possible to avoid providing a specific film layer between the negative film and the photosensitive resin composition layer, which is extremely effective from the viewpoints of improving the formability of microcells and the quality of the final printing plate obtained.

[0029] Generally, the solubility parameter (Sp value) is defined by the following formula (1): Sp value (δ) = (ΔE / V) 1 / 2 [(cal / cm ３ ) 1 / 2]...(1) where V is the molar volume of the organic solvent, and ΔE is the cohesive energy (evaporation energy). The molar volume and cohesive energy of the organic solvent can be determined from known values, for example, from the literature "POLYMER ENGINEERING AND SCIENCE, Vol. 14, 147-154, 1974."

[0030] On the other hand, when the above parameters are not known, they can be measured using a technique called turbidity point titration. Specifically, first, a sample with an unknown SP value is dissolved in a good solvent with a known SP value, and a poor solvent with an SP value lower than that of the good solvent is added dropwise to the solution, and the volume of the poor solvent at which the solute begins to precipitate is measured. Next, a newly prepared sample with an unknown SP value is dissolved in a good solvent with a known SP value, and a poor solvent with an SP value higher than that of the good solvent is added dropwise to the solution, and the volume of the poor solvent at which the solute begins to precipitate is measured. The SP value (δ) can be calculated by applying the volumes of the respective poor solvents calculated here to the following formula (2): SP value (δ) = (V ml 1 / 2 ・δ ml +V mh 1 / 2 ・δ mh ) / (V ml 1 / 2 +V mh 1 / 2 ) ... (2) where V ml is the volume of the poor solvent with a low SP value, V mh is the volume of the poor solvent with a high SP value, δ ml is the SP value of the poor solvent with a low SP value, δ mh is the SP value of a poor solvent with a high SP value. All of the SP values ​​described in the examples below are values ​​actually measured by the turbidity point titration method.

[0031] The absolute value of the difference between the solubility parameter (SpB) of the negative film used in this embodiment and the solubility parameter (SpA) of the photosensitive resin composition can be controlled within the above-mentioned numerical range by selecting a combination of the negative film and the photosensitive resin composition having appropriate solubility parameters. Specifically, by selecting at least one resin having a structural unit represented by the general formula (II) described below as the material for the negative film, polyurethane, polylactic acid, polycarbonate, polyester, polyamide, polybutyral, polyvinyl alcohol, poly(meth)acrylate, and modified or partially saponified products thereof, and by selecting a photosensitive material containing the polymer (b-1), ethylenically unsaturated compound (b-2), and photopolymerization initiator (b-3) described below as the material for the photosensitive resin composition, the absolute value of the difference from the solubility parameter (SpA) of the photosensitive resin composition can be controlled to 2.0 or more.

[0032] In calculating the SP value, the following good solvents and poor solvents and their respective SP values ​​can be used. Good solvent: Toluene (SP value: 8.9 [(cal / cm 3 ) 1 / 2 ]) p-xylene (SP value: 8.7 [(cal / cm 3 ) 1 / 2 ]) Butyl acetate (SP value: 8.5 [(cal / cm 3 ) 1 / 2 ]) ethyl acetate (SP value: 9.1 [(cal / cm 3 ) 1 / 2 ]) Acetone (SP value: 9.8 [(cal / cm 3 ) 1 / 2 ]) Poor solvent: n-hexane (SP value: 7.2 [(cal / cm 3 ) 1 / 2 ]) Ethanol (SP value: 12.9 [(cal / cm 3 ) 1 / 2 ]) Water (SP value: 23.4 [(cal / cm 3 ) 1 / 2 ])

[0033] The solubility parameter SpA of the photosensitive resin composition constituting the photosensitive resin composition layer described below is usually determined by the material used as the photosensitive resin composition for producing a flexographic printing plate. From a practical standpoint, the solubility parameter SpA of the photosensitive resin composition is preferably 10.0 or more and 14.0 or less. Therefore, from the standpoint of increasing the absolute value of the difference in solubility parameters between the photosensitive resin composition and the negative film and suppressing elution and migration of the negative film into the photosensitive resin composition, when the solubility parameter SpB of the negative film is greater than the SpA, SpB is preferably 13.0 or more, more preferably 13.5 or more, even more preferably 14.0 or more, and even more preferably greater than 14.0. When the SpB is greater than the SpA, the material of the negative film is preferably, but not limited to, at least one selected from the group consisting of polyurethane, polylactic acid, polycarbonate, polyester, polyamide, polybutyral, polyvinyl alcohol, poly(meth)acrylate, and modified or partially saponified products thereof. Polyurethane and / or polybutyral are particularly preferred. When the SpB is greater than the SpA, the material constituting the blackening layer of the negative film tends to be highly polarized, improving the strength of the blackening layer and the adhesion to the hard plate in contact with the negative film, and thus the blackening layer tends to have better scratch resistance and solvent resistance.

[0034] By setting the solubility parameter SpB of the negative film to 13.0 or more, the absolute value of the difference between the solubility parameter SpA and the solubility parameter SpB of the photosensitive resin composition can be controlled to 2.0 or more, since the solubility parameter SpA of the photosensitive resin composition can be determined by the materials usually used as the photosensitive resin composition for producing flexographic printing plates. This makes it possible to suppress elution and migration of the negative film into the photosensitive resin composition layer.

[0035] On the other hand, when the solubility parameter SpB of the negative film is smaller than the SpA, SpB is preferably less than 10.0, more preferably 9.5 or less, and even more preferably 9.0 or less. When the SpB is smaller than the SpA, the material of the negative film is preferably, but not limited to, those conventionally used in the production of flexographic printing plates, such as thermoplastic elastomer block copolymers, fully or partially hydrolyzed polyvinyl esters, partially hydrolyzed polyvinyl acetates, polyvinyl alcohol derivatives, partially hydrolyzed vinyl acetate / alkylene oxide graft copolymers or polyvinyl alcohols subsequently acrylated by a polymer-analogous reaction, polybutadienes, polyamides, and mixtures thereof. Thermoplastic elastomer block copolymers include those containing at least one block containing alkenyl aromatic monomer units and at least one block containing 1,3-diene monomer units. Examples of alkenyl aromatic compounds forming the alkenyl aromatic monomer units include styrene, α-methylstyrene, and vinyltoluene. As the 1,3-dienes, for example, butadiene and isoprene are preferred from the viewpoints of reducing the steric hindrance of the vinyl groups, increasing the photocrosslinking efficiency, and preventing the ablation layer from eluting into the printing original plate after exposure. The solubility parameter SpB of the negative film can be controlled within the above-mentioned numerical range by appropriately selecting the resin material constituting the negative film. Specifically, the solubility parameter SpB can be controlled to be high by selecting a resin material with high polarity, and can be controlled to be low by selecting a resin material with low polarity.

[0036] By setting the solubility parameter SpB of the negative film to 9.0 or less, the absolute value of the difference between SpA and SpB can be controlled to 2.0 or more, since the solubility parameter SpA of the photosensitive resin composition can be determined by the materials usually used as the photosensitive resin composition for producing flexographic printing plates. This makes it possible to suppress elution and migration of the negative film into the photosensitive resin composition layer.

[0037] <Negative Film of First Form> In the method for producing a printing plate of this embodiment, a negative film having a configuration including a substrate and an ablation layer laminated on the substrate can be used (hereinafter, this type of negative film may be referred to as a negative film of the first form). In the negative film of the first form, the solubility parameter SpB of the negative film refers to the solubility parameter of the ablation layer. The negative film of the first form preferably contains a resin having a structural unit represented by the following general formula (II). More specifically, the negative film preferably has a substrate and an ablation layer laminated on the substrate, and the ablation layer contains a resin having a structural unit represented by the following general formula (II). The negative film used in the method for producing a printing plate of this embodiment is not limited to the negative film of the first form.

[0038]

[0039] In the formula (II), R １ and R ２ each independently represents a non-polar group, R ３ and R ４ each independently represents a hydrogen atom or a nonpolar group.

[0040] Figure 2 shows a schematic cross-sectional view of an example of a negative film used in the method for producing a printing plate of this embodiment. The negative film shown in Figure 2 is composed of a substrate 21 and an ablation layer 22 that functions as a mask when forming the desired relief pattern and microcell pattern of the printing plate. The negative film will be described in detail below.

[0041] [Substrate] The negative film shown in FIG. 2 has a substrate 21 and an ablation layer 22 laminated on the substrate 21. The ablation layer 22 is imaged, thereby serving as a negative film for forming a relief and microcells in the printing plate manufacturing process described below. The quality of the relief and microcells, particularly image reproducibility, is significantly affected by the negative film through which ultraviolet light passes during exposure. Generally, the thicker the negative film, the greater the bending and scattering of ultraviolet light within the negative film, which tends to result in poorer image reproducibility. Since the thickness of the substrate 21 shown in FIG. 2 accounts for the majority of the overall thickness of the negative film, a thinner substrate 21 is preferable from the perspective of printing plate quality. Meanwhile, it is also important that the negative film have a certain degree of rigidity and dimensional stability. If the negative film easily deforms, this can lead to deformation or damage to the image formed on the negative film in processes prior to relief exposure, resulting in poor image reproducibility. However, if the negative film has too high rigidity, it may be incompatible with the equipment used in the manufacturing process for the intended printing plate, or excessive stress may be concentrated on the ablation layer during handling, resulting in irreversible damage such as scratches or wrinkles. From the above-mentioned perspectives, the thickness of the substrate 21 is preferably 10 μm or more and less than 100 μm. This numerical range allows for a negative film with excellent image reproducibility and appropriate rigidity to be obtained. Furthermore, a thickness of 20 μm or more is preferred, and 40 μm or more is more preferred. A thickness of 10 μm or more of the substrate 21 provides sufficient strength and rigidity for practical use, thereby preventing image deformation and damage during the manufacturing process for the printing plate. Furthermore, from the perspective of ensuring appropriate flexibility and good handleability during the manufacturing process for the printing plate, the thickness of the substrate 21 is preferably less than 100 μm, more preferably 90 μm or less, and even more preferably 70 μm or less.

[0042] Furthermore, from the viewpoints of dimensional stability, transparency, and adhesion to the ablation layer 22, the substrate 21 preferably contains a resin having a polyester or polyolefin skeleton. Here, the resin contained in the substrate 21 may be a mixture or copolymer of polyester and a resin having a polyolefin skeleton. Examples of polyester include, but are not limited to, polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Examples of resins having a polyolefin skeleton include, but are not limited to, polyethylene, polypropylene, and resins copolymerized therewith. Furthermore, from the viewpoint of image reproducibility, the substrate 21 is more preferably made of a resin having a polyester or polyolefin skeleton, and even more preferably made of a resin having a polyolefin skeleton. This is because resins having a polyolefin skeleton have high oxygen permeability. Here, oxygen permeability is one of the physical properties of a film, and is the oxygen permeability of 1 m of film under conditions of 1 atm (1 atmosphere). ２ It represents the amount of oxygen passing through the body per day. The unit is cm ３ / m ２ - 24h atm. The higher the value, the easier it is to pass, and the lower the value, the harder it is to pass.

[0043] In the manufacturing process of a printing plate, when a photosensitive resin composition layer is cured by ultraviolet irradiation, the curing of the photosensitive resin composition proceeds by radical polymerization. If oxygen is present during this radical polymerization, the radical-generating compound reacts with the oxygen, inhibiting the polymerization reaction. In other words, by reducing the amount of oxygen present during exposure of the photosensitive resin composition layer, the degree of polymerization can be improved, thereby enhancing the image reproducibility of the final flexographic printing plate. Here, if the substrate 21 of the negative film laminated on the photosensitive resin composition layer has high oxygen permeability, oxygen remaining on the surface and / or inside of the photosensitive resin composition layer upon ultraviolet irradiation can easily diffuse to the outside, thereby suppressing the effect of oxygen inhibiting the polymerization reaction. In the negative film, the substrate 21 may be used in an untreated state, or may be subjected to a predetermined surface treatment as necessary, or may be provided with functions such as antistatic treatment. Examples of surface treatments include corona treatment and matte finish.

[0044] [Ablation Layer] The negative film shown in FIG. 2 has an ablation layer 22 laminated on a substrate 21. The ablation layer 22 contains a predetermined resin, is ablatable with an infrared laser, and functions as a light-shielding layer for rays other than infrared. To prevent components contained in the ablation layer 22 from leaching into the photosensitive resin composition layer or migrating to the photosensitive resin composition of the ablation layer 2, it is effective to improve the adhesion between the substrate 21 and the ablation layer 22 or reduce the compatibility between the ablation layer 22 and the photosensitive resin composition layer. In particular, in this embodiment, the absolute value of the difference between the solubility parameter SpA of the photosensitive resin composition and the solubility parameter of the negative film, i.e., the solubility parameter SpB of the ablation layer constituting the negative film, is specified to be 2.0 or greater. This effectively prevents the ablation layer from leaching into and migrating to the photosensitive resin composition layer, even when the ablation layer of the negative film is directly laminated to the photosensitive resin composition.

[0045] The ablation layer 22 contains a resin, an infrared-absorbing material, and a non-infrared shielding material such as ultraviolet light. From the viewpoint of improving the adhesion between the substrate 21 and the ablation layer 22, it is important to strengthen the interaction between the layers. Examples of methods for strengthening the interaction between the layers include improving chemical interaction and improving physical interaction. Examples of methods for improving chemical interaction include imparting similar molecular structures to the constituent materials of both the substrate 21 and the ablation layer 22. Examples of methods for improving physical interaction include improving the flexibility of the ablation layer 22 or imparting appropriate flexibility to the ablation layer 22 in order to suppress peeling when the film is bent. Another effective method for improving chemical interaction is to impart similar molecular structures to the constituent materials of both the substrate 21 and the ablation layer 22, thereby maintaining the adhesion between the layers and ensuring high ablation efficiency with an infrared laser. Furthermore, from the viewpoint of reducing the compatibility between the ablation layer 22 and the photosensitive resin composition layer, it is effective to select an appropriate resin material for the ablation layer 22. From the above viewpoints, it is preferable that the ablation layer 22 of the negative film used in the method for producing a printing plate of this embodiment contains a resin having a structural unit represented by the following general formula (II), which contains a quaternary carbon atom to which two nonpolar groups are bonded. Note that the resin may contain other structural units as necessary.

[0046] In this specification, the term "monomer" refers to a compound before polymerization, and the term "structural unit" refers to a predetermined repeating unit formed by polymerizing a monomer.

[0047]

[0048] In formula (II), R １ and R ２ each independently represents a non-polar group, R ３ and R ４ each independently represents a hydrogen atom or a nonpolar group.

[0049] As described above, the ablation layer 22 of the negative film used in the printing plate manufacturing method of this embodiment preferably contains a resin having a structural unit represented by general formula (II). When the resin contained in the ablation layer 22 has a polar group in its main chain, strong intermolecular non-covalent bonds are formed, improving the strength of the ablation layer 22. On the other hand, the structure available for interaction with the constituent materials of the substrate 21 is reduced, tending to reduce adhesion between the substrate 21 and the ablation layer 22. Furthermore, the rigidity of the ablation layer 22 becomes too high, causing stress generated by bending or stretching to concentrate between the layers, making interfacial peeling more likely. Furthermore, when the resin contained in the ablation layer 22 has a polar group in its side chain, this tends to be undesirable from the perspective of laser ablation efficiency, as described below. To ensure laser ablation efficiency, it is important that the resin contained in the ablation layer 22 be easily depolymerized. "Depolymerization" is the reverse reaction of polymerization, in which a polymer breaks down into monomers. Irradiation with an infrared laser causes the ablation layer 22 to instantaneously reach high temperatures of several hundred degrees. During this process, the main chain in the resin decomposes, rapidly reducing its molecular weight and removing it from the ablation layer 22. However, resins that are difficult to depolymerize tend to undergo only side chain decomposition during ablation, without scission of the main chain. As a result, the resin remains in the ablation layer 22 even after irradiation with an infrared laser. Resins obtained by condensation polymerization are known to form ring structures during decomposition, followed by scission of the main chain. In other words, infrared ablation, which is a short-term heat treatment, is less likely to result in a decrease in molecular weight, and ablation layers containing resins obtained by such condensation polymerization tend to have poor ablation efficiency. From the above perspective, it is important that the ablation layer 22 contains a resin that is easily depolymerized. It is generally known that main chain cleavage is likely to initiate from thermally unstable portions present in the polymer, such as branches. However, if the side chain corresponding to the branch is polar, side chain decomposition tends to occur predominantly, making main chain scission less likely, which is undesirable. Therefore, it is preferable that the resin contained in the ablation layer 22 have side chains with nonpolar groups.Furthermore, the contribution of intramolecular or intermolecular chain transfer cannot be ignored when main chain cleavage progresses. Therefore, it is preferable that the polymer does not have tertiary hydrogen atoms that are easily abstracted by chain transfer. In other words, it is preferable that the portion corresponding to the symmetrical plane of the branching is also a nonpolar group. Furthermore, it is important that the side chain is a nonpolar group from the viewpoint of achieving rubber-like elasticity. This results in a soft portion of the elastomer, improving the flexibility of the ablation layer 22. From the above viewpoints, in a negative film, the content of the resin having the structural unit represented by the general formula (II) in the ablation layer is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more.

[0050] The non-polar group in the general formula (II) is preferably any one of an alkyl group, an aryl group, a cycloalkyl group, a phenyl group, an alkenyl group, an aralkyl group, a cycloalkenyl group, an alkynyl group, a silyl group, and a siloxanyl group. Note that the non-polar group does not contain a hydrogen atom. In particular, from the viewpoint of improving the flexibility of the ablation layer 22 and ensuring adhesion to the substrate 21, R １ and R ２ are each independently any one selected from the group consisting of an alkyl group, an alkenyl group, and an alkynyl group, and are further preferably an alkyl group in terms of low polarity.

[0051] Examples of monomers that can form the structural unit represented by general formula (II) include, but are not limited to, isobutylene, 2-methyl-2-butene, 2,3-dimethyl-2-butene, and those in which the methyl group is replaced with another alkyl group such as an ethyl group, and modified products thereof; α-methylstyrene, cis-(1-methyl-1-propenyl)benzene, trans-(1-methyl-1-propenyl)benzene, and those in which the methyl group is replaced with another alkyl group such as an ethyl group, and modified products thereof; and 1,1-diphenylethylene.

[0052] In the general formula (II), R ３ and R ４R each independently represents a hydrogen atom or a non-polar group. ３ and R ４ are each independently preferably any one selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, and an alkynyl group, and more preferably a hydrogen atom or an alkyl group. ３ and R ４ are all hydrogen atoms, the depolymerization properties of the resin are further improved, which is more preferable.

[0053] The structural unit represented by the general formula (II) constituting the resin may be of one type alone or of two or more types. For example, the resin may contain, as the structural unit (II), R １ and R ２ is an alkyl group; and R １ and R ２ The compound may have a structural unit in which one of the groups is an alkyl group and the other is a phenyl group. By having both an alkyl group and a phenyl group, the properties of both groups can be obtained.

[0054] The resin contained in the ablation layer 22 preferably further contains a structural unit derived from a monovinyl-substituted aromatic hydrocarbon in addition to the structural unit represented by general formula (II). The monovinyl aromatic hydrocarbon may be chemically bonded to the structural unit represented by general formula (II) or may be added as a separate resin. However, from the viewpoint of dispersibility and the resulting uniformity of laser processing, it is preferable that the structural unit derived from the monovinyl-substituted aromatic hydrocarbon be chemically bonded to the structural unit represented by general formula (II) to form a copolymer. When the resin used in the ablation layer contains a structural unit derived from a monovinyl-substituted aromatic hydrocarbon, the adhesion between the ablation layer 22 and the substrate 21 is improved and the rigidity of the negative film tends to be improved. Compounds used to form the structural unit derived from a monovinyl aromatic hydrocarbon include, but are not limited to, monomers such as styrene, t-butylstyrene, N,N-dimethyl-p-aminoethylstyrene, N,N-diethyl-p-aminoethylstyrene, vinylpyridine, p-methylstyrene, and tertiary butylstyrene. Styrene is particularly preferred from the viewpoint of being able to mold a negative film smoothly at a relatively low temperature. The structural unit derived from the monovinyl-substituted aromatic hydrocarbon may be of one type alone or of two or more types.

[0055] The ablation layer 22 may contain an infrared-absorbing material for ablation processing. Examples of infrared-absorbing materials include elements or compounds that typically have strong absorption in the 750 to 2000 nm range. Examples of infrared-absorbing materials include, but are not limited to, inorganic pigments such as carbon black, graphite, copper chromite, and chromium oxide; and dyes such as polyphthalocyanine compounds, cyanine dyes, and metal thiolate dyes. The smaller the particle size, the higher the sensitivity to infrared lasers. Carbon black, in particular, can be used over a wide particle size range of 13 to 85 nm and is therefore preferred as an infrared-absorbing material. Carbon black can also function as a shielding material, as described below. These infrared-absorbing materials are added in a range that provides sufficient sensitivity for ablation with the laser beam used.

[0056] The ablation layer 22 may contain a non-infrared shielding material, such as a material that reflects or absorbs ultraviolet light, to function as a mask. Examples of the non-infrared shielding material include, but are not limited to, ultraviolet absorbers, carbon black, and graphite.

[0057] The ablation layer 22 should be thicker to ensure UV shielding properties during the exposure process described below, but thinner to enhance ablation properties. From the above perspectives, the thickness of the ablation layer 22 is preferably 0.1 μm or more and 20 μm or less, more preferably 0.5 μm or more and 15 μm or less, and even more preferably 1.0 μm or more and 10 μm or less. To ensure the non-infrared shielding effect of the ablation layer 22, the ablation layer 22 preferably has an optical density of 2 or more, and more preferably an optical density of 3 or more. The optical density can be measured using a D200-II transmission densitometer (manufactured by GretagMacbeth). The optical density is measured by ISO visual standards, and the light to be measured has a wavelength range of approximately 400 to 750 nm.

[0058] <Method for Manufacturing Negative Film of First Form> The method for manufacturing the negative film of the first form described above is not limited to the following. For example, when carbon black is used as both an infrared absorbing material and a non-infrared blocking material, a solution of a resin having a structural unit represented by the general formula (II) described above is first prepared using a predetermined solvent, and carbon black and a dispersant are added to the solution to disperse the carbon black in the resin solution, thereby obtaining a solution or dispersion for forming the ablation layer 22. The solution or dispersion for forming the ablation layer is then coated onto a predetermined substrate 21. Effective methods for dispersing carbon black in the resin solution include a combination of forced stirring using a stirring blade and stirring using ultrasonic waves or various mills. Alternatively, a method of pre-kneading the resin, carbon black, and dispersant using an extruder or kneader and then dissolving them in a solvent is also effective for achieving good carbon black dispersibility. Another method is to forcibly disperse carbon black in a resin in the form of a latex dispersion.

[0059] The solvent used to prepare the solution, dispersion, or the like for forming the ablation layer 22 can be appropriately selected taking into consideration the solubility of the resin and infrared absorber used. A single solvent may be used, or two or more solvents may be mixed. Furthermore, for example, mixing a solvent with a relatively low boiling point with a solvent with a high boiling point can control the evaporation rate of the solvent, thereby improving the film quality of the ablation layer 22. Examples of solvents for forming the ablation layer 22 include, but are not limited to, toluene, xylene, cyclohexane, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, amyl acetate, methyl ethyl ketone, acetone, cyclohexanone, ethylene glycol, propylene glycol, ethanol, water, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, dimethylacetamide, dimethylformamide, n-propyl alcohol, i-propyl alcohol, 1,4-dioxane, tetrahydrofuran, diethyl ether, n-hexane, n-heptane, n-pentane, acetonitrile, and analogs thereof.

[0060] <Negative Film of Second Embodiment> In the method for producing a printing plate of this embodiment, a negative film having a UV printing polymer layer of a desired pattern on a predetermined UV printing substrate can be used.

[0061] [UV Printing Substrate] The UV printing substrate is not limited to the following, but may be, for example, a transparent material selected from the group consisting of polyethylene terephthalate, polycarbonate, and polyethylene naphthalate. The thickness of the UV printing substrate is preferably 10 μm or more and less than 100 μm. This numerical range allows for the production of a negative film with excellent image reproducibility and appropriate rigidity. Furthermore, a thickness of 20 μm or more is preferred, and 40 μm or more is more preferred. A thickness of 10 μm or more of the UV printing substrate provides sufficient strength and rigidity for practical use, thereby preventing image deformation and damage during the printing plate production process. Furthermore, from the viewpoint of ensuring appropriate flexibility and good handleability during the printing plate production process, the thickness of the UV printing substrate is preferably less than 100 μm, more preferably 90 μm or less, and even more preferably 70 μm or less.

[0062] [UV Printed Polymer Layer] The UV ink may contain one or more photoinitiators, monomers, binders, and pigment materials. The pigment materials may include a four-color system including cyan, magenta, yellow, and black. The UV ink is preferably cured by exposure to at least one UV light source with a wavelength output ranging from approximately 365 nm to approximately 405 nm. The UV printed polymer layer has a predetermined pattern similar to that of a negative film, and after exposure and curing, contains a polymer formed from the monomers. Examples of the polymer include, but are not limited to, at least one selected from the group consisting of polyurethane, polylactic acid, polycarbonate, polyester, polyamide, polybutyral, polyvinyl alcohol, poly(meth)acrylate, and modified or partially saponified versions of these. In order to suppress the elution of components contained in the UV printing polymer layer into the photosensitive resin composition layer or the migration of the UV printing polymer layer into the photosensitive resin composition, it is effective to improve the adhesion between the UV printing substrate and the UV printing polymer layer or to reduce the compatibility between the UV printing polymer layer and the photosensitive resin composition layer. In particular, in this embodiment, the absolute value of the difference between the solubility parameter SpA of the photosensitive resin composition and the solubility parameter SpB of the negative film, i.e., the UV printing polymer layer, is specified to be 2.0 or more. This allows for effective suppression of elution and migration of the UV printing polymer layer into the photosensitive resin composition layer, even when directly laminated with the photosensitive resin composition.

[0063] <Method for manufacturing negative film of second form> The negative film of the second form can be obtained by dispersing a UV ink in a desired pattern on the UV printing substrate using, for example, an inkjet printer, and curing the UV ink with an actinic radiation source to crosslink and cure the UV ink, thereby forming a UV printing polymer layer in the desired pattern.

[0064] <Photosensitive Resin Composition Layer> In the printing plate manufacturing method of this embodiment, a liquid photosensitive resin composition layer is directly laminated onto the negative film described above. Liquid photosensitive resin compositions have high fluidity and can easily change shape. Therefore, when laminating onto the negative film, the photosensitive resin composition is formed into a film of a consistent thickness inside a dedicated device (platemaking machine). For example, as shown in FIG. 1 , negative film 1 is placed on a UV-transmitting first hard plate 11, and the liquid photosensitive resin composition is poured onto it. A support 3 is then laminated onto the negative film 1 to achieve a consistent plate thickness. A back exposure negative film 4 and a second hard plate 12 are then pressed down on top of the negative film 1 to form the photosensitive resin composition layer 2. In the process of forming the photosensitive resin composition layer 2, after placing the negative film 1 on the first hard plate 11, it is preferable to vacuum the negative film 1 to securely fix the negative film 1 and remove oxygen-inhibiting factors. The vacuuming mechanism is not particularly limited, but examples include a method of vacuuming using a pump through a groove provided around the periphery of the first hard plate 11. If the negative film 1 lacks rigidity, wrinkles may develop in the negative film 1 during the vacuuming process, and in severe cases, the wrinkles may remain and cannot be removed. These wrinkles may be transferred to the relief surface after curing, significantly reducing image reproducibility. Furthermore, if the negative film 1 lacks dimensional stability, the drawn pattern may be deformed, similarly reducing image reproducibility. On the other hand, if the negative film 1 has too high rigidity, it may not completely conform to the lower glass during vacuuming, leaving gaps and air trapped within. This may result in increased oxygen inhibition and adversely affect image reproducibility. Furthermore, stress generated by deformation of the highly elastic negative film 1 may concentrate in the ablation layer, resulting in wrinkles and pinholes. In other words, it is extremely important that the negative film 1 have an appropriate range of rigidity.

[0065] The photosensitive resin composition layer preferably contains, for example, the polymer (b-1), ethylenically unsaturated compound (b-2), and photopolymerization initiator (b-3) described below. These can be used selectively as appropriate. Furthermore, the photosensitive resin composition layer may further contain auxiliary additive components as needed. The solubility parameter SpA of the photosensitive resin composition constituting the photosensitive resin composition layer is typically determined by the materials used as photosensitive resin compositions for producing flexographic printing plates. From a practical standpoint, the solubility parameter SpA of the photosensitive resin composition is 10.0 or more and 14.0 or less. Each component of the photosensitive resin composition layer will be described in detail below.

[0066] [Polymer (b-1)] The polymer (b-1) may be a linear, branched, or dendritic polymer, and may be a homopolymer or a copolymer. The copolymer may be a random copolymer, an alternating copolymer, or a block copolymer. Examples of the polymer (b-1) include those conventionally used in the production of flexographic printing plates, such as fully or partially hydrolyzed polyvinyl esters, partially hydrolyzed polyvinyl acetates, polyvinyl alcohol derivatives, partially hydrolyzed vinyl acetate / alkylene oxide graft copolymers, or polyvinyl alcohols subsequently acrylated by a polymer-analogous reaction, polybutadienes, polyamides, and mixtures thereof. In addition to the above, thermoplastic elastomeric block copolymers may also be used. Examples of thermoplastic elastomeric block copolymers include those containing at least one block containing alkenyl aromatic monomer units and at least one block containing 1,3-diene monomer units. Examples of alkenyl aromatic compounds forming the alkenyl aromatic monomer units include styrene, α-methylstyrene, and vinyltoluene. As the 1,3-dienes, for example, butadiene and isoprene are preferred from the viewpoints of reducing the steric hindrance of the vinyl group, increasing the photocrosslinking efficiency, and preventing the ablation layer from eluting into the printing original plate after exposure.

[0067] Furthermore, the polymer (b-1) preferably contains a compound having a carbonyl group. Using a compound having a highly polar carbonyl group as the polymer (b-1) can reduce compatibility with the resin having a nonpolar group in the ablation layer, which tends to suppress elution of the ablation layer into the photosensitive resin composition layer. Examples of the polymer (b-1) include, but are not limited to, polyester, polyamide, and polyurethane. It is more preferable for the polymer (b-1) to contain polyurethane in order to prevent damage to the relief surface due to the load applied when peeling the film for flexographic printing plate production after the exposure step. Furthermore, in order to improve the mechanical properties of the flexographic printing plate finally obtained by photocrosslinking, it is preferable for the polyurethane to have a (meth)acrylic group at its terminal group. The photosensitive resin composition layer used in the method for producing a printing plate of this embodiment preferably has a solubility parameter SpA controlled to 10.0 or more and 14.0 or less from a practical standpoint, and preferably contains 60% by mass or more of polyurethane in order to suppress elution of the ablation layer into the photosensitive resin composition layer. In this configuration, the negative film preferably contains 20% by mass or more and less than 60% by mass of polyurethane and / or polybutyral, which can effectively prevent the ablation layer from leaching into the photosensitive resin composition layer.

[0068] Examples of methods for producing polyurethanes having (meth)acrylic groups at their terminals include reacting a diol having repeating units in its molecule with a diisocyanate to form a polyurethane having isocyanate groups at its terminals of a given molecular weight, and then reacting the polyurethane with a compound containing active hydrogen and a (meth)acrylic group in its molecule. Another method involves reacting a diol having repeating units in its molecule with a diisocyanate to form a polyurethane having isocyanate groups at its terminals of a given molecular weight, and then reacting the polyurethane with a compound containing a hydroxyl group and a (meth)acrylic group in its molecule. The polyurethane structure obtained by the above-described production method is a structure formed by reacting a diol having repeating units in its molecule with a diisocyanate. Hereinafter, the "polyurethane having (meth)acrylic groups at its terminals" produced by the above-described method will be referred to as an "unsaturated prepolymer."

[0069] The "diol having a repeating unit in the molecule" used in producing the unsaturated prepolymer is not limited to the following, but examples thereof include polyester diols composed of dicarboxylic acids and diols, polyether diols, polyether polyester copolymer diols, 1,2-polybutadiene compounds having terminal hydroxyl groups, etc. The diols having a repeating unit in the molecule may be used alone or in combination of two or more.

[0070] Examples of dicarboxylic acids constituting the polyester diol include, but are not limited to, succinic acid, glutaric acid, adipic acid, pimenic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, terephthalic acid, isophthalic acid, and 1,5-naphthalenedicarboxylic acid. Examples of diols constituting the polyester diol include, but are not limited to, 1,4-butanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, neopentyldiol, 1,6-hexanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, and diethylene glycol (dioxyethylenediol).

[0071] Examples of the polyether diol include, but are not limited to, polyoxyethylene diol, polyoxypropylene diol, polyoxytetramethylene diol, polyoxy 1,2-butylene diol, polyoxyethylene / polyoxypropylene random copolymer diol, polyoxyethylene / polyoxypropylene block copolymer diol, polyoxyethylene / polyoxytetramethylene random copolymer diol, and polyoxyethylene / polyoxytetramethylene block copolymer diol.

[0072] The polyether polyester copolymer diol is not limited to the following, but examples thereof include copolymers having a structure in which repeating units forming the molecular chain of the above-mentioned polyether diol and repeating units forming the molecular chain of the above-mentioned polyester diol are linked in block or random fashion.

[0073] The 1,2-polybutadiene compound having terminal hydroxyl groups may be a hydrogenated compound. Examples of the 1,2-polybutadiene compound having terminal hydroxyl groups include, but are not limited to, hydrogenated poly-1-butene and hydrogenated 1,2-polybutadiene. The number of terminal hydroxyl groups is not particularly limited, but from the viewpoint of preventing damage to the relief surface due to the load when the printing plate production film is peeled off after exposure, the number of terminal hydroxyl groups per molecule is preferably 1.2 or more, more preferably 1.5 or more, and even more preferably 2.0 or less.

[0074] Examples of the diisocyanate include, but are not limited to, tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, and norbornene diisocyanate. One type of diisocyanate may be used alone, or two or more types may be used in combination.

[0075] [Ethylenically Unsaturated Compound (b-2)] As described above, the photosensitive resin composition layer preferably contains an ethylenically unsaturated compound (b-2). The ethylenically unsaturated compound (b-2) is a compound having a radically polymerizable unsaturated double bond. Examples of the ethylenically unsaturated compound (b-2) include, but are not limited to, olefins such as ethylene, propylene, vinyltoluene, styrene, and divinylbenzene; acetylenes; (meth)acrylic acid and / or its derivatives; haloolefins; unsaturated nitriles such as acrylonitrile; unsaturated amides and derivatives thereof such as acrylamide and methacrylamide; unsaturated dicarboxylic acids and derivatives thereof such as maleic anhydride, maleic acid, and fumaric acid; vinyl acetates; N-vinylpyrrolidone; N-vinylcarbazole; and N-substituted maleimide compounds. Examples of the derivatives include, but are not limited to, alicyclic compounds having a cycloalkyl group, a bicycloalkyl group, a cycloalkenyl group, a bicycloalkenyl group, or the like; aromatic compounds having a benzyl group, a phenyl group, a phenoxy group, or a naphthalene skeleton, an anthracene skeleton, a biphenyl skeleton, a phenanthrene skeleton, a fluorene skeleton, or the like; compounds having an alkyl group, a halogenated alkyl group, an alkoxyalkyl group, a hydroxyalkyl group, an aminoalkyl group, a glycidyl group, or the like; ester compounds with polyhydric alcohols such as alkylene glycol, polyoxyalkylene glycol, polyalkylene glycol, and trimethylolpropane; and compounds having a polysiloxane structure such as polydimethylsiloxane and polydiethylsiloxane.

[0076] The ethylenically unsaturated compound (b-2) may also be a heteroaromatic compound containing elements such as nitrogen and sulfur.

[0077] Examples of the (meth)acrylic acid and / or derivatives thereof include, but are not limited to, diacrylates and dimethacrylates of alkanediols such as hexanediol and nonanediol; diacrylates and dimethacrylates of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, and butylene glycol; trimethylolpropane tri(meth)acrylate; dimethyloltricyclodecane di(meth)acrylate; isobornyl(meth)acrylate; phenoxypolyethylene glycol (meth)acrylate; pentaerythritol tetra(meth)acrylate, etc. These may be used alone or in combination of two or more.

[0078] From the viewpoint of preventing damage to the relief surface due to the load when peeling off the negative film after exposure, it is preferable to use at least one kind of (meth)acrylate as the ethylenically unsaturated compound (b-2), and it is more preferable to use at least one kind of bifunctional (meth)acrylate.

[0079] [Photopolymerization initiator (b-3)] The photosensitive resin composition layer preferably contains a photopolymerization initiator (b-3). The photopolymerization initiator (b-3) is a compound that absorbs light energy and generates radicals, and examples of the photopolymerization initiator include a degradable photopolymerization initiator, a hydrogen abstraction photopolymerization initiator, and a compound having a moiety that functions as a hydrogen abstraction photopolymerization initiator and a moiety that functions as a degradable photopolymerization initiator in the same molecule.

[0080] Examples of such photopolymerization initiator (b-3) include, but are not limited to, benzophenone, 4,4-bis(diethylamino)benzophenone, 3,3',4,4'-benzophenonetetracarboxylic anhydride, 3,3',4,4'-tetramethoxybenzophenone, and other benzophenones; anthraquinones, such as t-butylanthraquinone and 2-ethylanthraquinone; thioxanthones, such as 2,4-diethylthioxanthone, isopropylthioxanthone, and 2,4-dichlorothioxanthone; Michler's ketone; diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, 2-methyl-1-( acetophenones such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone, trichloroacetophenone, etc.; benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, etc.; acylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, etc.; methylbenzoyl formate; 1,7-bisacridinylheptane; 9-phenylacridine; azo compounds such as azobisisobutyronitrile, diazonium compounds, and tetrazene compounds. These may be used alone or in combination of two or more.

[0081] From the viewpoint of preventing damage to the relief surface due to the load when peeling off the negative film after exposure, the content of the photopolymerization initiator (b-3) in the photosensitive resin composition layer is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 5% by mass or less, and even more preferably 0.3% by mass or more and 5% by mass or less, when the total amount of the photosensitive resin composition layer is taken as 100% by mass.

[0082] [Auxiliary Additive Components] Examples of auxiliary additive components include, but are not limited to, plasticizers, thermal polymerization inhibitors, antioxidants, light stabilizers, ultraviolet absorbers, dyes and pigments.

[0083] Examples of plasticizers include, but are not limited to, liquid dienes such as liquid polybutadiene, liquid polyisoprene, modified liquid polybutadiene, modified liquid polyisoprene, liquid acrylonitrile-butadiene copolymer, and liquid styrene-butadiene copolymer; hydrocarbon oils such as naphthenic oil and paraffin oil; conjugated diene rubbers mainly composed of liquid dienes such as liquid acrylonitrile-butadiene copolymer and liquid styrene-butadiene copolymer; polystyrenes having a number average molecular weight of 2000 or less; and ester-based plasticizers such as sebacate esters and phthalate esters. These plasticizers may have a hydroxyl group or a carboxyl group. These plasticizers may also be provided with a photopolymerizable reactive group such as a (meth)acryloyl group. The plasticizers may be used alone or in combination. In this specification, the term "liquid" refers to a state that can easily flow and deform and solidify into the deformed shape upon cooling. From the viewpoint of preventing damage to the ablation layer when the negative film is peeled off after exposure and preventing elution into the photosensitive resin composition layer, the content of the plasticizer in the photosensitive resin composition layer is preferably 0% by mass or more and 30% by mass or less, more preferably 8% by mass or more and 30% by mass or less, and even more preferably 8% by mass or more and 25% by mass or less, when the total amount of the photosensitive resin composition layer is taken as 100% by mass.

[0084] The thermal polymerization inhibitor and antioxidant can be one commonly used in the fields of resin materials or rubber materials, such as a phenolic material. Examples of the phenolic thermal polymerization inhibitor and antioxidant include, but are not limited to, vitamin E, tetrakis-(methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate)methane, 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 3,9-bis-{1,1-dimethyl-2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}-2,4,8,10-tetraoxaspiro(5,5)undecane, and 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate. Other examples of the thermal polymerization inhibitor and antioxidant include phosphine-based materials such as triphenyl phosphite. The thermal polymerization inhibitor and antioxidant may be used alone or in combination of two or more.

[0085] Light stabilizers and UV absorbers include, but are not limited to, known benzophenone compounds, salicylate compounds, acrylonitrile compounds, metal complex salt compounds, and hindered amine compounds. Furthermore, the dyes and pigments listed below may be used as UV absorbers. Examples of such light stabilizers and UV absorbers include, but are not limited to, 2-ethoxy-2'-ethyloxalic acid bisanilide, 2,2'-dihydroxy-4-methoxybenzophenone, bis(1,2,2,6,6-pentamethyl-4-piperidyl)-decanedioate, and 1,2,3-benzotriazole. Dyes and pigments are effective as coloring means for improving visibility. Examples of dyes include, but are not limited to, water-soluble basic dyes, acid dyes, and direct dyes, as well as water-insoluble sulfur dyes, oil-soluble dyes, and disperse dyes. Anthraquinone dyes, indigoid dyes, and azo dyes are particularly preferred. Examples of pigments include, but are not limited to, natural pigments, synthetic inorganic pigments, synthetic organic pigments, etc. Examples of synthetic organic pigments include azo pigments, triphenylmethane pigments, quinoline pigments, anthraquinone pigments, and phthalocyanine pigments.

[0086] The photosensitive resin composition constituting the photosensitive resin composition layer can be produced by mixing the above-mentioned materials, i.e., the polymer (b-1), the ethylenically unsaturated compound (b-2), the photopolymerization initiator (b-3), and, if necessary, auxiliary additive components.

[0087] <Support> In the printing plate manufacturing method of this embodiment, as shown in FIG. 1 , a support 3 is laminated on the liquid photosensitive resin composition layer 2 described above. Examples of the support include, but are not limited to, polyester film, polyamide film, polyacrylonitrile film, and polyvinyl chloride film. Among these, polyester film is preferred as the support. Examples of polyesters used for the support include, but are not limited to, polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. The thickness of the support is not particularly limited, but is preferably 50 to 300 μm. Furthermore, a predetermined adhesive layer may be provided on the support to enhance the adhesive strength between the support and the liquid photosensitive resin composition layer described below. Examples of the adhesive layer include, but are not limited to, the adhesive layers described in WO 2004 / 104701, JP 3094647, and JP 2634429.

[0088] (Exposure Step) In the method for producing a printing plate of this embodiment, after the lamination step described above, an exposure step is performed in which actinic rays are irradiated from the first hard plate 11 and second hard plate 12 to cure the photosensitive resin composition layer 2, as shown in FIG. 1 . In the exposure from the first hard plate 11 side, the photosensitive resin composition layer 2 is irradiated with actinic rays, for example, ultraviolet rays, using a negative film 1 on which a desired printing pattern and a microcell pattern have been drawn as a mask, thereby performing pattern exposure. During this exposure, the light passing through the negative film 1 promotes the curing reaction of the photosensitive resin composition layer 2, and the printing pattern 1a and microcell pattern 1b formed on the negative film 1 are transferred to the photosensitive resin composition layer 2 with their concave and convex shapes reversed, thereby obtaining a pattern-exposed photosensitive resin composition layer. In the method for producing a printing plate of this embodiment, the negative film 1 is positioned so that the surface on which the pattern has been drawn is in direct contact with the liquid photosensitive resin composition layer 2, in order to reduce the effects of bending and scattering of the actinic rays irradiated to the photosensitive resin composition layer. When exposing from the second hard plate 12 side, if necessary, a back exposure negative film 4 having a desired pattern for forming a shelf layer is used as a mask to irradiate the photosensitive resin composition layer with active light to form a shelf layer 5. For example, when preparing a flexographic printing plate (thickness 4 mm or more) used for corrugated board printing, it is preferable to form a base shelf layer 5 on the upper second hard plate 12 side to compensate for the strength of the relief against the printing pressure during printing. Back exposure may be performed from the second hard plate 12 side without using the back exposure negative film 4, to deposit a uniform thin cured resin layer (back deposition layer) over the entire surface. Both the back deposition layer and the shelf layer are formed by curing the photosensitive resin composition layer on the side opposite the side on which the printing pattern is formed. When the entire photosensitive resin composition layer on the support side is cured, a back deposition layer is formed, and when the photosensitive resin composition layer is partially cured according to the position of the printing pattern, a shelf layer is formed. The method of irradiating with actinic rays is not particularly limited, and can be carried out using a known irradiation unit. The wavelength of the ultraviolet rays to be irradiated is preferably 150 to 500 nm, more preferably 300 to 400 nm.Examples of light sources that can be used include, but are not limited to, low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, zirconium lamps, carbon arc lamps, and ultraviolet fluorescent lamps.

[0089] (Developing Step) In the method for producing a printing plate according to this embodiment, after the exposure step, a developing step is carried out in which the unexposed portions of the photosensitive resin composition layer are removed. The method for removing the unexposed portions is not particularly limited, and conventionally known methods can be applied. Specific methods include, for example, exposing the photosensitive resin composition layer 2 and then washing away the unexposed portions with a solvent for solvent development or a cleaning solution for water development, or contacting the unexposed portions with a predetermined absorbing layer capable of absorbing the unexposed portions and removing the absorbing layer to remove the unexposed portions. Note that, as a pre-removal step, the unexposed portions may be removed in advance using a spatula or roll. Thereafter, a post-exposure treatment is performed as necessary to obtain a printing plate.

[0090] (Step of recovering photosensitive resin composition from unexposed portions) The printing plate manufacturing method of this embodiment preferably further includes a recovery step in which the unexposed portions removed in the development step are recovered and converted into a photosensitive resin composition for use in manufacturing a new printing plate. The recovered photosensitive resin composition can be reused as a photosensitive resin composition in manufacturing a new printing plate. Using the recovered photosensitive resin composition reduces waste and also reduces material costs. On the other hand, if a large amount of the ablation layer elutes and / or migrates into the recovered photosensitive resin composition, various problems such as scattering of actinic light may occur in the printing plate manufacturing process using the recovered photosensitive resin composition, which may impair the quality of the final printing plate. According to the printing plate manufacturing method of this embodiment, elution and / or migration of the ablation layer into the photosensitive resin composition layer can be suppressed in the final printing plate, allowing for the recovery of a photosensitive resin composition with quality comparable to that of an unused plate at a high yield. Therefore, quality, such as improved white-out depth, can be maintained even in new printing plates manufactured using the recovered photosensitive resin composition. Specifically, the method for producing a printing plate according to this embodiment has the following advantages (1) to (4).

[0091] (1) It is possible to suppress the elution and migration of negative film into the photosensitive resin composition layer. (2) It is possible to form microcells, and to produce a printing plate with high solid density and excellent image reproducibility. (3) It is possible to remove and recover unexposed photosensitive resin composition with reduced deterioration and contamination, thereby preventing deterioration of the photosensitive resin composition and allowing high-quality photosensitive resin composition to be reused with a high yield. (4) In the development process, it is possible to suppress the incorporation of impurities into the unexposed photosensitive resin composition, so a wide range of development methods can be selected.

[0092] Hereinafter, the present embodiment will be described in more detail with reference to specific examples and comparative examples, but the present invention is not limited to the following examples in any way.

[0093] In the examples and comparative examples described below, flexographic printing plates were prepared, and the elution and migration of the negative film into the photosensitive resin composition and the solid density of the flexographic printing plates were evaluated.

[0094] [Production of Negative Films for Manufacture of Flexographic Printing Plates] Negative films 1 to 5 for manufacture of flexographic printing plates were produced as follows.

[0095] (Preparation of Negative Film 1) <Preparation of Resin 1 for Negative Film 1> After replacing the atmosphere inside a 2-L separable flask polymerization vessel with nitrogen, 456.1 mL of n-hexane (dried over molecular sieves) and 656.5 mL of butyl chloride (dried over molecular sieves) were added using a syringe, and the polymerization vessel was cooled by immersing it in a dry ice / methanol bath at -70°C. A Teflon (registered trademark) liquid transfer tube was then connected to a pressure-resistant glass liquefier / collection tube equipped with a three-way stopcock containing 161.1 g (2871 mmol) of isobutylene monomer, and the isobutylene monomer was transferred into the polymerization vessel under nitrogen pressure. 0.647 g (2.8 mmol) of p-dicumyl chloride and 1.22 g (14 mmol) of N,N-dimethylacetamide were then added. Next, 8.67 mL (79.1 mmol) of titanium tetrachloride was added to initiate polymerization. After stirring at the same temperature for 1.5 hours from the start of polymerization, approximately 1 mL of the polymerization solution was extracted for sampling. Subsequently, a mixed solution of 77.9 g (748 mmol) of styrene monomer, 23.9 mL of n-hexane, and 34.3 mL of butyl chloride, which had been cooled to -70°C in advance, was added to the polymerization vessel. 45 minutes after the addition of the mixed solution, approximately 40 mL of methanol was added to terminate the reaction, yielding a reaction solution. After distilling off the solvent and other components from the reaction solution, the solution was dissolved in toluene and washed twice with water. Furthermore, the toluene solution was added to a large amount of methanol to precipitate a polymer, and the resulting polymer was vacuum-dried at 60°C for 24 hours to obtain Resin 1. The styrene content was １ The content was determined to be 30% by mass by H-NMR.

[0096] <Production of Flexographic Printing Plate Production Film 1> 6.5 parts by mass of the resin 1 prepared as described above, 54.0 parts by mass of toluene, and 36.0 parts by mass of cyclohexanone were mixed to dissolve the resin 1 in the solvent. Subsequently, 3.5 parts by mass of carbon black (Mitsubishi Chemical Corporation, #1000) was further added, and the mixture was mixed in a bead mill for 4 hours to obtain a carbon black dispersion. The carbon black dispersion obtained as described above was coated onto a 50 μm-thick polypropylene substrate (Toyobo Co., Ltd., Pylen P3162) so that the film thickness after drying was 2.5 μm, and the coating was dried at 90° C. for 2 minutes to obtain a flexographic printing plate production film 1, which is a laminate of an ablation layer and a substrate.

[0097] <Laser drawing on film 1 for producing flexographic printing plates> Film 1 for producing flexographic printing plates was placed in a CDI Crystal 5080 manufactured by ESKO, and laser drawing was performed on the ablation layer with an MCWSI pattern under conditions of a resolution of 4000 dpi and a laser intensity of 2.4 J, thereby obtaining negative film 1 on which a printing pattern having a microcell pattern was formed.

[0098] (Preparation of Negative Film 2) Laser ablation was performed without using a microcell pattern, and other conditions were the same as those for Negative Film 1, to obtain Negative Film 2 having a solid pattern. In Table 1 below, this is indicated as "Solid No. MC."

[0099] (Preparation of Negative Film 3) <Preparation of Film 2 for Flexographic Printing Plate Production> 6.5 parts by mass of butyral resin (PVB resin, Mobital B30H manufactured by Kuraray Co., Ltd.), 54.0 parts by mass of ethanol, and 36.0 parts by mass of 1-butanol were mixed, and Mobital B30H was dissolved in the solvent. Subsequently, 3.5 parts by mass of carbon black (#1000 manufactured by Mitsubishi Chemical Corporation) was further added, and the mixture was mixed in a bead mill for 4 hours to obtain a carbon black dispersion. The carbon black dispersion obtained as described above was coated onto a 50 μm-thick polypropylene substrate (Pylen P3162 manufactured by Toyobo Co., Ltd.) so that the film thickness after drying was 2.5 μm, and the coating was dried at 90° C. for 2 minutes to obtain Film 2 for flexographic printing plate production, which is a laminate of an ablation layer and a substrate.

[0100] <Laser drawing on film 2 for producing a flexographic printing plate> The film 2 for producing a flexographic printing plate was placed in a CDI Crystal 5080 manufactured by ESKO, and laser drawing was performed on the ablation layer with an MCWSI pattern at a resolution of 4000 dpi and a laser intensity of 3.4 J, thereby obtaining a negative film 3 on which a printing pattern having a microcell pattern was formed.

[0101] (Preparation of Negative Film 4) Laser ablation was performed without using a microcell pattern, and other conditions were the same as those for Negative Film 3, to obtain Negative Film 4 having a solid pattern. In Table 1 below, this is indicated as "Solid No. MC".

[0102] (Preparation of Negative Film 5) An NX film (FLEXCEL NX Thermal Imaging Layer, manufactured by Milacron Co.) was placed in a Flexcel Wide-C imager manufactured by Kodak Corporation, and laser drawing was performed with a Digicap Standard pattern at a resolution of 2400 dpi.

[0103] [Photosensitive Resin Composition] The following photosensitive resin compositions were used for producing flexographic printing plates. Photosensitive Resin Composition 1 produced as follows: Photosensitive Resin Composition 2 produced as follows:

[0104] (Preparation of Polymers for Photosensitive Resin Composition) To prepare a photosensitive resin composition, first, polymers 1 and 2 were prepared as polymer (b-1).

[0105] (Polymer 1) As the diol, 1200 g of poly(3-methyl-1,5-pentanediol adipate)diol ("Kuraray Co., Ltd." "Clapol P3010"), 800 g of polyoxyethylene (EO)-oxypropylene (PO) block copolymer diol ("Sanyo Chemical Industries, Ltd." "Sannyx PL2100"), and 0.03 g of dibutyltin dilaurate were added and stirred at 40 ° C until homogeneous, to obtain a mixture. To the obtained mixture, 137 g of tolylene diisocyanate ("Coronate T80" manufactured by Tosoh Corporation) was added and stirred until homogeneous, to obtain a mixture. When homogeneous, the mixture was heated to 80 ° C and then reacted for 4 to 5 hours to prepare a prepolymer precursor having isocyanate groups at both ends. To the obtained prepolymer precursor, 387 g of poly(oxypropylene) glycol monomethacrylate ("Blemmer PP" manufactured by NOF Corporation) was added as a (meth)acrylation agent, and the mixture was allowed to react for 2 hours to obtain a reaction product. A portion of the obtained reaction product was taken out and subjected to IR spectroscopy to confirm the disappearance of the isocyanate group. Polymer 1 was obtained in this manner.

[0106] (Polymer 2) As the diol, 1300 g of polyoxyethylene (EO)-oxypropylene (PO) block copolymer diol (Sanyo Chemical Industries, Ltd. "Sannyx PL2100"), 750 g of 2,4-diethyl-1,5-pentanediol-adipic acid polycondensate (Toyokuni Oil Mills Co., Ltd. "HS2N-521A"), and 0.02 g of dibutyltin dilaurate were added and stirred at 40 ° C. until homogeneous, to obtain a mixture. To the obtained mixture, 145 g of tolylene diisocyanate (Tosoh Corporation "Coronate T80") was added and stirred until homogeneous, to obtain a mixture. When homogeneous, the mixture was heated to 80 ° C. and then reacted for 4 to 5 hours to prepare a prepolymer precursor having isocyanate groups at both ends. To the obtained prepolymer precursor, 370 g of polyoxypropylene monoacrylate ("PPM" manufactured by NOF Corporation) was added as a (meth)acrylation agent, and the mixture was allowed to react for 2 hours to obtain a reaction product. A portion of the obtained reaction product was taken out and subjected to IR spectroscopy to confirm the disappearance of the isocyanate group. Polymer 2 was obtained in this manner.

[0107] (Preparation of Photosensitive Resin Composition) Photosensitive resin compositions were prepared using polymers 1 and 2 obtained as described above. The photosensitive resin composition constituting the photosensitive resin composition layer was produced by mixing polymer 1, polymer 2, the ethylenically unsaturated compound (b-2), the photopolymerization initiator (b-3), and auxiliary additive components prepared as described above. Photosensitive resin composition 1 was prepared using polymer 1, and photosensitive resin composition 2 was prepared using polymer 2, as described below.

[0108] <Photosensitive resin composition 1> 68.2 parts by mass of the above-described polymer 1, 21.8 parts by mass of diethylene glycol (2-ethylhexyl) ether acrylate ("Aronix M-120" manufactured by Toagosei Co., Ltd.) as an ethylenically unsaturated compound (b-2), 1.1 parts by mass of trimethylolpropane trimethacrylate ("NK Ester TMPT" manufactured by Shin-Nakamura Chemical Co., Ltd.) as a (b-2) component, 6.3 parts by mass of dibutyl sebacate ("DBS" manufactured by Toyokuni Oil Mills Co., Ltd.) as a plasticizer, and 2,2-dimethoxy-2-phenylacetophenone ("IRGACURE" manufactured by Ciba Specialty Chemicals) as a photopolymerization initiator (b-3). 1.0 part by mass of an antioxidant ("IONOL" manufactured by Oxalis Chemicals Co., Ltd.) and 1.6 parts by mass of 2,6-di-t-butyl-p-cresol ("IONOL" manufactured by Oxalis Chemicals Co., Ltd.) were added to the resulting mixture, and the mixture was stirred and mixed in a heated state at 60°C to obtain a photosensitive resin composition.

[0109] <Photosensitive resin composition 2> 65.6 parts by mass of the above-mentioned polymer 2, 20.2 parts by mass of 2-(diethylamino)ethyl methacrylate ("Acryester DE" manufactured by Mitsubishi Chemical Corporation) as the ethylenically unsaturated compound (b-2), 7.0 parts by mass of butoxydiethylene glycol methacrylate ("Light Ester AK-8" manufactured by Kyoeisha Chemical Co., Ltd.) as the (b-2) component, 5.8 parts by mass of dibutyl sebacate ("DBS" manufactured by Toyokuni Oil Mills Co., Ltd.) as a plasticizer, 1.2 parts by mass of benzophenone ("Benzophenone" manufactured by Daikifan Co., Ltd.) as a photopolymerization initiator (b-3), and 1.8 parts by mass of bis(1,2,2,6,6-pentamethyl-4-piperidyl) = decanedioate ("HS Ester 765" manufactured by Toyokuni Oil Mills Co., Ltd.) as an antioxidant were added, and the mixture was stirred and mixed at a heated state of 60 ° C. to obtain a photosensitive resin composition 2.

[0110] [Physical Properties of Negative Film and Photosensitive Resin Composition] (Sp Value (SpB) of Negative Film and Sp Value (SpA) of Photosensitive Resin Composition) The Sp value (SpB) of the negative film and the SP value (SpA) of the photosensitive resin composition were measured by turbidity point titration. A measurement sample was dissolved in a good solvent with a known SP value, and a poor solvent with a lower SP value than the good solvent was added dropwise to the solution, and the volume of the poor solvent at which the solute began to precipitate was measured. Next, a newly prepared sample with an unknown SP value was dissolved in a good solvent with a known SP value, and a poor solvent with a higher SP value than the good solvent was added dropwise to the solution, and the volume of the poor solvent at which the solute began to precipitate was measured. The SP value (δ) was calculated by applying the volumes of the respective poor solvents calculated here to the following formula (2): SP value (δ) = (V ml 1 / 2 ・δ ml +V mh 1 / 2 ・δ mh ) / (V ml 1 / 2 +V mh 1 / 2 ) ... (2) where V ml is the volume of the poor solvent with a low SP value, V mh is the volume of the poor solvent with a high SP value, δ ml is the SP value of the poor solvent with a low SP value, δ mh is the SP value of a poor solvent with a high SP value. Calculations were made using the following good solvents and poor solvents and their respective SP values. Good solvent: Toluene (SP value: 8.9 [(cal / cm 3 ) 1 / 2 ]) p-xylene (SP value: 8.7 [(cal / cm 3 ) 1 / 2 ]) Butyl acetate (SP value: 8.5 [(cal / cm 3 ) 1 / 2 ]) ethyl acetate (SP value: 9.1 [(cal / cm 3 ) 1 / 2 ]) Acetone (SP value: 9.8 [(cal / cm 3 ) 1 / 2 ]) Poor solvent: n-hexane (SP value: 7.2 [(cal / cm 3 ) 1 / 2 ]) Ethanol (SP value: 12.9 [(cal / cm 3) 1 / 2 ]) Water (SP value: 23.4 [(cal / cm 3 ) 1 / 2 ])

[0111] [Evaluation of Characteristics in Printing Plate Production] (Solid Density) The solid density of the printed matter was measured and evaluated. Indigo ink was printed on a transparent PET film using the flexographic printing plates prepared in the Examples and Comparative Examples described below. The pressure settings from the anilox roll to the flexographic printing plate and from the flexographic printing plate to the transparent film, the printing press hardware, tools, software, and operating configuration, as well as the handling, cleaning, surface treatment, and mounting of the flexographic printing plate and the transparent PET film were all performed under standard industrial production printing conditions. The printing press was an AI-3 flexographic printing press manufactured by Iyo Machinery Manufacturing Co., Ltd., running at 100 m / min. The ink used was Hydric FCF739 (manufactured by Dainichiseika Color & Chemicals Co., Ltd.) with a viscosity of 12 seconds measured using a Zahn cup #4. The transparent PET film used was a 330 mm wide, 12 μm thick transparent PET film R8150 Cycle Clean (manufactured by Toyobo Co., Ltd.). The anilox roll was an Apex 860 lpi 5.1 cc roll, and the liquid plate was attached using Lohmann's DuploFlex 5.2+ tape. Next, the reflectance of the printed matter was measured, and the solid density was calculated. The reflectance was measured using the eXact Standard, a standard measurement performed using a reflection optical density meter (a meter commonly used in the graphic arts field). The solid density was measured under the following conditions: color-related values: no filter, density-related values: no filter, and density color: cyan. A solid density of 1.40 or higher was evaluated as being good for practical use.

[0112] (Evaluation of Dissolution and Migration of Negative Film into Photosensitive Resin Composition Layer) Dissolution and migration of negative film into the photosensitive resin composition layer of the flexographic printing plates produced in the Examples and Comparative Examples described below were evaluated by the following method. Each negative film was placed in a vial filled with the photosensitive resin composition, left to stand overnight in a thermostatic chamber at 30°C, and evaluated according to the following evaluation criteria. If the evaluation was A to B, it was determined that the plate could be used without any problems in practical use. <Evaluation Criteria> A: No separation of the ablation layer was observed, and there was no contamination of the photosensitive resin composition. Furthermore, it could not be removed by rubbing with a medicine spoon. B: No separation or contamination of the negative film was observed unless force was applied with a medicine spoon or the like, but the ablation layer was separated when rubbing with a medicine spoon. C: Separation of the ablation layer and contamination of the photosensitive resin composition were observed.

[0113] [Production of printing plate] (Example 1) Using the above-mentioned photosensitive resin composition 1 and negative film 1 as the photosensitive resin composition, a flexographic printing plate was produced by sequentially going through the molding / exposure step, the development step, the post-exposure step, and the drying step as described below.

[0114] <(1) Forming and Exposure Steps> Forming and exposure were performed using an "ALF-213E platemaking machine" manufactured by Asahi Kasei Corporation according to steps (A1) to (A3). (A1): Negative film 1 after image drawing was placed on a UV-transmitting lower glass plate such that the ablation layer after image drawing was located on the opposite side of the lower glass plate across the substrate. Thereafter, the step of laminating a cover film on the ablation layer (hereinafter, this step will be referred to as the "insertion step") was not performed, and the negative film 1 was fixed by vacuuming with a pump through a groove provided around the periphery of the lower glass plate. A liquid photosensitive resin composition was poured onto the negative film 1, and a base film serving as a support was laminated to the negative film 1 via a spacer so that the resulting plate had a uniform thickness. A negative film for back exposure was placed on the base film, and then pressed down with a UV-transmitting glass plate (upper glass plate) to form a photosensitive resin composition layer. (A2): After molding the photosensitive resin composition layer, back exposure was performed by irradiating the photosensitive resin composition layer from the upper glass plate side through the base film with actinic rays (light rays having a wavelength distribution of 300 nm or more) from an ultraviolet fluorescent lamp or the like as an actinic light source. (A3): After the back exposure step, a relief formation exposure step was performed in which the photosensitive resin composition layer was irradiated from the lower glass plate side through the image-drawn negative film 1 with actinic rays similar to those from the upper side to form an image, thereby obtaining a flexographic printing original plate.

[0115] As described above, a photosensitive resin composition layer was formed in (A1). The photosensitive resin composition layer was then exposed in (A2) and (A3) to obtain a flexographic printing original plate having a plate thickness of 1.7 mm and a relief depth of 0.6 mm. Here, the relief depth is the plate thickness minus the height of the shelf layer, i.e., a conventional term expressing the depth of the printing image relief. To adjust the relief depth, the back exposure amount was appropriately adjusted. The relief exposure amount was 600 mJ / cm. ２ The exposure conditions were as follows:

[0116] <(2) Development Step> After the image was drawn, the negative film 1 was peeled from the flexographic printing plate, and the unexposed resin was recovered and removed from the flexographic printing plate using a rubber spatula. Then, an aqueous solution containing 2% by mass of Asahi Kasei Corporation's "APR (registered trademark) Cleaner Type W-10" (main component: anionic surfactant), 0.5% by mass of Asahi Kasei Corporation's "APR (registered trademark) Surface Treatment Agent Type A-10" (main component: nonionic surfactant, benzophenone), and 0.3% by mass of Asahi Kasei Corporation's "Antifoaming Agent SH-4" (silicone mixture) was prepared as a developer in an "AL-400W type developer" (drum rotation spray type, drum rotation speed: 20 rpm, spray pressure: 0.15 Pa). The developer was developed at a liquid temperature of 40°C for 10 minutes. After development, the developer was washed with tap water to remove any bubbles from the developer.

[0117] <(3) Post-exposure step> Post-exposure was carried out by an underwater exposure method using an "AL-200UP type post-exposure machine" manufactured by Asahi Kasei Corporation, which is equipped with both an ultraviolet fluorescent lamp and a germicidal lamp. The exposure doses irradiated from each light source were as follows on the surface of the photosensitive resin composition: ultraviolet fluorescent lamp: 2000 mJ / cm ２ , Germicidal lamp: 2000mJ / cm ２ The exposure was carried out for an exposure time of .

[0118] <(4) Drying Step> Using "ALF-DRYER" manufactured by Asahi Kasei Corporation, the post-exposed plate was dried for about 30 minutes until all moisture on the surface was removed, thereby obtaining a flexographic printing plate of Example 1.

[0119] (Example 2) Negative film 3 was used. Other conditions were the same as those in the above (Example 1), and a flexographic printing plate was produced.

[0120] Example 3 A flexographic printing plate was produced using the photosensitive resin composition 2 described above, except that the other conditions were the same as those in Example 1.

[0121] (Example 4) Negative film 3 was used. As the photosensitive resin composition, the above-mentioned photosensitive resin composition 2 was used. Other conditions were the same as those in the above-mentioned (Example 1), and a flexographic printing plate was produced.

[0122] Comparative Example 1 Negative film 2 was used. Other conditions were the same as those in Example 1, and a flexographic printing plate was produced.

[0123] Comparative Example 2 A flexographic printing plate was produced under the same conditions as in Example 1 except for the insertion step of laminating a cover film (CF-92 manufactured by Asahi Kasei Corporation) on the ablation layer.

[0124] Comparative Example 3 A flexographic printing plate was produced using Negative Film 5. Other conditions were the same as those in Example 1.

[0125] (Comparative Example 4) Negative film 5 was used. An insertion step of laminating a cover film (CF-92 manufactured by Asahi Kasei Corporation) on the ablation layer was carried out. Other conditions were the same as those in Example 1, and a flexographic printing plate was produced.

[0126] Comparative Example 5 A flexographic printing plate was produced using Negative Film 4. Other conditions were the same as those in Example 1.

[0127] (Comparative Example 6) Negative film 3 was used. An insertion step of laminating a cover film (CF-92 manufactured by Asahi Kasei Corporation) on the ablation layer was performed. Other conditions were the same as those in Example 1, and a flexographic printing plate was produced.

[0128] Comparative Example 7 Negative film 2 was used. As the photosensitive resin composition, the above-described photosensitive resin composition 2 was used. Other conditions were the same as those in Example 1, and a flexographic printing plate was produced.

[0129] Comparative Example 8 Negative film 5 was used. As the photosensitive resin composition, the photosensitive resin composition 2 was used. Other conditions were the same as those in Example 1, and a flexographic printing plate was produced.

[0130] As shown in Table 1, in the examples, there was no elution or migration of the ablation layer into the photosensitive resin composition, and flexographic printing plates with high solid density were obtained.

[0131] This application is based on a Japanese patent application (Patent Application No. 2023-220270) filed with the Japan Patent Office on December 27, 2023, the contents of which are incorporated herein by reference.

[0132] The present invention has wide industrial applicability in the general commercial printing field.

[0133] REFERENCE SIGNS LIST 1 negative film 1a print pattern 1b microcell pattern 2 photosensitive resin composition layer 2b microcell 2a pattern 3 support 4 negative film for back exposure 4a shelf layer forming pattern 5 shelf layer 11 first hard plate 12 second hard plate 21 substrate 22 ablation layer

Claims

1. A method for manufacturing a printing plate, comprising: a lamination step of sequentially laminating a negative film having a microcell pattern, a liquid photosensitive resin composition layer, a support, and a second rigid plate located above on a first rigid plate located below; and an exposure step of irradiating actinic rays from the sides of the first rigid plate and the second rigid plate to cure the photosensitive resin composition layer, wherein in the lamination step, the photosensitive resin composition layer is directly laminated on the negative film, and the solubility parameter SpA of the photosensitive resin composition constituting the photosensitive resin composition layer and the solubility parameter SpB of the negative film have the relationship of the following formula (I): |SpA - SpB| ≥ 2.0... (I) 2. As a pre-step of the lamination step, the method for manufacturing a printing plate according to claim 1, comprising a drawing step of forming a microcell pattern on the negative film, and in the drawing step, at least one selected from the group consisting of an ablation method, a thermal method, an inkjet method, and a silver salt method is used.

3. The method for manufacturing a printing plate according to claim 1, wherein the solubility parameter SpA of the photosensitive resin composition constituting the photosensitive resin composition layer is 10.0 or more and 14.0 or less.

4. The method for manufacturing a printing plate according to claim 1, wherein the solubility parameter SpB of the negative film is greater than 14.

0.

5. The method for manufacturing a printing plate according to claim 1, wherein the solubility parameter SpB of the negative film is less than 10.

0.

6. The method for producing a printing plate according to claim 1, wherein the negative film contains a resin having a structural unit represented by the following general formula (II). (In the formula (II), R １ and R ２ each independently represent a nonpolar group, and R ３ and R ４ each independently represent a hydrogen atom or a nonpolar group.) 7. In the formula (II), R1 and R2 are each independently any one selected from the group consisting of an alkyl group, an alkenyl group, and an alkynyl group, and R ３ and R ４ are each independently any one selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, and an alkynyl group. The method for producing a printed version according to claim 6.

8. In the formula (II), R １ and R ２ are each independently an alkyl group, and R ３ and R ４ are each independently a hydrogen atom or an alkyl group. The method for producing a printed version according to claim 6.

9. The method for manufacturing a printing plate according to claim 6, wherein the resin having a structural unit represented by the general formula (II) further contains a structural unit derived from a monovinyl-substituted aromatic hydrocarbon.

10. The method for manufacturing a printing plate according to claim 1, wherein the negative film contains at least one selected from the group consisting of polyurethane, polylactic acid, polycarbonate, polyester, polyamide, polybutyral, polyvinyl alcohol, poly(meth)acrylate, and modified products or partially saponified products thereof.

11. After the exposure step, the method for manufacturing a printing plate according to claim 1, further comprising a developing step of removing the unexposed portion of the photosensitive resin composition layer, and a recovery step of recovering the unexposed portion removed in the developing step and using it as a photosensitive resin composition for manufacturing a new printing plate.

12. A method for manufacturing a printing plate, comprising: a lamination step of sequentially laminating a negative film having a microcell pattern, a liquid photosensitive resin composition layer, a support, and a second rigid plate located above on a first rigid plate located below; and an exposure step of irradiating the photosensitive resin composition layer with actinic rays from the sides of the first rigid plate and the second rigid plate to cure the photosensitive resin composition layer, wherein in the lamination step, the photosensitive resin composition layer is directly laminated on the negative film, and the solubility parameter SpB of the negative film is 13.0 or more.

13. A method for manufacturing a printing plate, comprising: a lamination step of sequentially laminating a negative film having a microcell pattern, a liquid photosensitive resin composition layer, a support, and a second rigid plate located above on a first rigid plate located below; and an exposure step of irradiating the photosensitive resin composition layer with actinic rays from the sides of the first rigid plate and the second rigid plate to cure the photosensitive resin composition layer, wherein in the lamination step, the photosensitive resin composition layer is directly laminated on the negative film, and the solubility parameter SpB of the negative film is 9.0 or less.