Method for manufacturing a printing plate

Abstract

A method for manufacturing a printing plate includes: a lamination process in which a negative film (1) having a micro-unit pattern, a liquid photosensitive resin composition layer (2), a support (3), and a second rigid plate (12) located above are sequentially laminated on a first rigid plate (11) located below; and an exposure process in which active light is irradiated from the first rigid plate (11) and the second rigid plate (12) to cure the photosensitive resin composition layer (2). In the lamination process, the photosensitive resin composition layer (2) is directly laminated on the negative film (1), and the solubility parameter SpA of the photosensitive resin composition constituting the photosensitive resin composition layer (2) and the solubility parameter SpB of the negative film have the following relationship (I): |SpA-SpB|≥2.0 …(I).

Description

Technical Field

[0001] This invention relates to a method for manufacturing printing plates. Background Technology

[0002] In recent years, flexographic printing, based on flexographic printing plates, has been widely used as a method for printing on various media such as corrugated paper, paper, and film.

[0003] Various manufacturing methods have been proposed for flexographic printing plates (see, for example, Patent Document 1).

[0004] Patent Document 1 discloses the following method as a method for manufacturing flexographic printing plates.

[0005] First, a negative film with a desired pattern and a transparent protective film are stacked on a rigid plate located below. A liquid photosensitive resin composition layer is then stacked on the transparent protective film. A support is then stacked as needed, and a rigid plate located above is further stacked. The photosensitive resin composition layer sandwiched between the lower and upper stacked plates is controlled to a desired uniform thickness.

[0006] Next, the photosensitive resin composition layer is exposed to ultraviolet light (back exposure) from the upper rigid plate side, which corresponds to the upper rigid plate. The photosensitive resin composition layer in its uncured state, which is the opposite side of the ultraviolet-exposed surface, i.e. the lower rigid plate side, which corresponds to the lower rigid plate, is exposed to ultraviolet light through the negative film and the transparent protective film to perform relief exposure, thereby obtaining a flexible printing master.

[0007] Then, by cleaning and removing the photosensitive resin composition from the unexposed areas of the flexographic printing plate, a relief image is formed, thereby obtaining the flexographic printing plate.

[0008] The method for manufacturing flexographic printing plates using liquid photosensitive resin compositions as described above can recycle the photosensitive resin composition of unexposed portions, thereby reducing both the amount of waste photosensitive resin composition and the manufacturing cost of flexographic printing plates. Therefore, it is widely used as a manufacturing method for flexographic printing plates with high environmental adaptability.

[0009] On the other hand, "solid density" is a known indicator of the appearance of printed matter obtained using a flexographic printing plate. Generally, a higher solid density is preferred, and to improve the solid density, techniques for forming "microcells" on the surface of the flexographic printing plate are known (see, for example, Patent Document 2).

[0010] In addition, in recent years, CTP (Computer To Plate) technology has been known as a method for manufacturing flexographic printing plates.

[0011] In the CTP technology, an ablation layer that can be ablated using infrared light is pre-formed on the photosensitive resin composition layer. By irradiating it with an infrared laser, the ablation layer is removed into the desired shape, forming a portion that transmits light equivalent to a negative light source. Next, using the ablation layer as a mask, ultraviolet light is irradiated onto the photosensitive resin composition layer, causing the photosensitive resin composition to react to the same shape as the portion of the photosensitive resin composition that transmits light, resulting in relief exposure. Finally, the unwanted ablation layer and the unexposed portions of the photosensitive resin composition are developed and removed to create a flexographic printing plate.

[0012] However, in the flexographic printing plate manufacturing method described above, from the viewpoint of ensuring practicality, the design aims to increase the adhesion between the ablation layer and the photosensitive resin composition. Therefore, it presents a problem where it is difficult to separate and recover the photosensitive resin composition from the unexposed areas after embossing exposure. Furthermore, it also has the problem that the dissolution and transfer of the ablation layer into the photosensitive resin composition cannot be sufficiently suppressed, making it difficult not only to separate and recover the photosensitive resin composition from the unexposed areas, but also leaving room for improvement from the viewpoint of ensuring the quality of the flexographic printing plate.

[0013] Here, "dissolution" refers to the components constituting the ablation layer being mixed into the photosensitive resin composition, and "transfer" refers to the ablation layer being peeled off from the substrate while maintaining the film shape and mixed into the photosensitive resin composition.

[0014] As a countermeasure to the problems caused by the adhesion, dissolution, and transfer of the photosensitive resin composition by the aforementioned ablation layer, a method has been proposed for forming an image mask by irradiating a flexible printing master having an optical density variation layer equivalent to the photosensitive resin composition layer, the film layer, and the ablation layer on a specified support with infrared laser light (see, for example, Patent Document 3). Furthermore, as a technique related to a method for forming an article with an embossed image using a specified removable film, a method has been proposed as follows: an image-forming film containing an image-forming material is image-exposed using image-forming radiation to obtain an image-forming film; the image-forming film is laminated onto an image-forming article containing a photosensitive material and a release layer; the image-forming film is irradiated with curing radiation to remove it from the image-forming article; and then the image-forming article is developed to form an embossed image (see, for example, Patent Document 4).

[0015] In these methods, the entire image mask is exposed to ultraviolet light, and then the image mask is peeled off along with the thin film layer or release layer. Development is then performed to obtain a flexographic printing plate. Because the image mask is removed before development, these methods have the advantage of suppressing adhesion, dissolution, and transfer of the photosensitive resin composition layer.

[0016] Existing technical documents

[0017] Patent documents

[0018] Patent Document 1: Japanese Patent Application Publication No. 2005-301071

[0019] Patent Document 2: Japanese Patent Publication No. 2021-525661

[0020] Patent Document 3: International Publication No. 01 / 18605

[0021] Patent Document 4: Japanese Patent No. 4971311 Summary of the Invention

[0022] The problem the invention aims to solve

[0023] However, the manufacturing methods for flexographic printing plates proposed in Patent Documents 1, 3, and 4 have the following problems: ultraviolet light is easily bent and scattered due to the thin film layer or release layer located between the photosensitive resin composition layer and the negative or image mask, resulting in reduced image reproducibility. In particular, as described above, when micro-units are formed on the surface of the flexographic printing plate to increase the solidity of the printed matter, the formation of micro-units deteriorates due to the bending and scattering of ultraviolet light caused by the thin film layer or release layer, leading to a decrease in the quality of the final printing plate.

[0024] On the other hand, if no thin film layer or release layer is provided between the photosensitive resin composition layer and the negative or image mask, there is a problem that the adhesion between the photosensitive resin composition layer and the negative or image mask becomes too strong, and it is impossible to avoid interlayer dissolution or transfer.

[0025] Therefore, in view of the problems of the prior art, the present invention aims to provide a method for manufacturing a printing plate that suppresses the dissolution and transfer of the negative to the photosensitive resin composition layer and is able to form micro-units, for manufacturing a printing plate with high solidity and excellent image reproducibility.

[0026] Solution for solving the problem

[0027] In order to solve the above-mentioned problems, the inventors have repeatedly conducted in-depth research and found that by directly stacking a liquid photosensitive resin composition layer with a negative film and exposing the pattern, and by determining 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 above a specified value, the problems of the prior art can be solved, and thus the present invention is completed.

[0028] That is, the present invention is as follows. [1]

[0030] A method for manufacturing a printing plate, comprising the following steps:

[0031] In the lamination process, a negative film with a micro-unit pattern, a liquid photosensitive resin composition layer, a support, and a second rigid plate located above are sequentially laminated on a first rigid plate located below; and

[0032] In the exposure process, active light is irradiated from the first and second rigid plate sides to cure the photosensitive resin composition layer.

[0033] In the lamination process, the photosensitive resin composition layer is directly laminated onto the negative film.

[0034] 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 following relationship: (I)

[0035] |SpA-SpB|≥2.0 …(I). [2]

[0037] According to the printing plate manufacturing method described above [1], a drawing step for forming a micro-unit pattern on the negative is included as a pre-step step of the lamination process.

[0038] In the drawing process, at least one of the following methods is used: ablation, thermal method, inkjet method, and silver halide method. [3]

[0040] According to the printing plate manufacturing method described in [1] or [2] above, 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]

[0042] The method for manufacturing a printing plate according to any one of [1] to [3] above, wherein the solubility parameter SpB of the negative is greater than 14.0. [5]

[0044] The method for manufacturing a printing plate according to any one of [1] to [3] above, wherein the solubility parameter SpB of the negative is less than 10.0. [6]

[0046] The method for manufacturing a printing plate according to any one of [1] to [5] above, wherein the negative comprises a resin having a structural unit shown in the following general formula (II).

[0047]

[0048] In formula (II), R1 and R2 independently represent nonpolar groups, and R3 and R4 independently represent hydrogen atoms or nonpolar groups. [7]

[0050] According to the printing plate manufacturing method described above [6], in formula (II), R1 and R2 are each independently selected from the group consisting of alkyl, alkenyl and alkynyl groups.

[0051] R3 and R4 are each independently selected from the group consisting of hydrogen atoms, alkyl groups, alkenyl groups, and alkynyl groups. [8]

[0053] According to the printing plate manufacturing method described in [6] or [7] above, wherein in the formula (II), R1 and R2 are each independently alkyl, and R3 and R4 are each independently hydrogen atoms or alkyl. [9]

[0055] The method for manufacturing a printing plate according to any one of [6] to [8] above, wherein the resin having the structural unit shown in general formula (II) further comprises a structural unit derived from a monovinyl substituted aromatic hydrocarbon.

[10]

[0057] The method for manufacturing 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 their modifiers or partial saponifications.

[11]

[0059] The method for manufacturing a printing plate according to any one of [1] to

[10] above includes a developing step after the exposure step, in which the unexposed portion of the photosensitive resin composition layer is removed.

[0060] It also includes a recycling process for recovering the unexposed portions removed in the developing process and producing a new photosensitive resin composition for printing plate manufacturing.

[12]

[0062] A method for manufacturing a printing plate, comprising the following steps:

[0063] In the lamination process, a negative film with a micro-unit pattern, a liquid photosensitive resin composition layer, a support, and a second rigid plate located above are sequentially laminated on a first rigid plate located below; and

[0064] In the exposure process, active light is irradiated from the first and second rigid plate sides to cure the photosensitive resin composition layer.

[0065] In the lamination process, the photosensitive resin composition layer is directly laminated onto the negative film.

[0066] The solubility parameter SpB of the negative film is 13.0 or higher.

[13]

[0068] A method for manufacturing a printing plate, comprising the following steps:

[0069] In the lamination process, a negative film with a micro-unit pattern, a liquid photosensitive resin composition layer, a support, and a second rigid plate located above are sequentially laminated on a first rigid plate located below; and

[0070] In the exposure process, active light is irradiated from the first and second rigid plate sides to cure the photosensitive resin composition layer.

[0071] In the lamination process, the photosensitive resin composition layer is directly laminated onto the negative film.

[0072] The solubility parameter SpB of the negative film is below 9.0.

[0073] The effects of the invention

[0074] According to the present invention, a method for manufacturing a printing plate is provided, which inhibits the dissolution and transfer of the negative film to the photosensitive resin composition layer and is able to form micro-units, thereby obtaining a printing plate with high solidity and excellent image reproducibility. Attached Figure Description

[0075] Figure 1 This diagram illustrates a schematic configuration of the method for manufacturing the flexographic printing plate of the present invention.

[0076] Figure 2 A schematic cross-sectional view showing an example of the negative used in the method for manufacturing the printing plate of the present invention. Detailed Implementation

[0077] Hereinafter, the method for carrying out the present invention (hereinafter referred to as "this embodiment") will be described in detail.

[0078] Furthermore, the following embodiments are illustrative of the present invention and are not intended to limit the present invention to the following content.

[0079] This invention can be implemented with appropriate modifications without departing from its spirit.

[0080] [Methods for manufacturing printing plates]

[0081] The method for manufacturing the printing plate in this embodiment includes the following steps:

[0082] The lamination process involves sequentially laminating a negative film with a micro-unit pattern, a liquid photosensitive resin composition layer, a support, and a second rigid plate located above on a first rigid plate located below; and the exposure process involves irradiating the photosensitive resin composition layer with active light from the first rigid plate and the second rigid plate side to cure the photosensitive resin composition layer.

[0083] In the lamination process, the photosensitive resin composition layer is directly laminated onto the negative film.

[0084] 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 following relationship (I).

[0085] |SpA-SpB|≥2.0 …(I)

[0086] According to the printing plate manufacturing method of this embodiment, the dissolution and transfer of the negative to the photosensitive resin composition layer can be suppressed and micro-units can be formed, resulting in a flexible printing plate with high solidity and excellent image reproducibility.

[0087] (Layering process)

[0088] Figure 1 The diagram shows a schematic cross-sectional view illustrating the method for manufacturing a printing plate for explaining this embodiment.

[0089] In the lamination process, a negative sheet 1, a liquid photosensitive resin composition layer 2, a support 3, and a second rigid plate 12 located above are sequentially laminated on a first rigid plate 11 located below. The negative sheet 1 has a prescribed pattern 1a for forming a desired printed pattern in the final printing plate and a prescribed micro-unit pattern 1b for forming micro-units.

[0090] Alternatively, a negative film 4 for back exposure, having a pattern 4a for forming a shelf layer in back exposure, may be provided between the photosensitive resin composition layer 2 and the second rigid plate 12.

[0091] In the printing plate manufacturing method of this embodiment, during the lamination process, the liquid photosensitive resin composition layer 2 is directly laminated onto the negative film 1 without passing through a cover film or the like. This prevents the bending and scattering of exposure light during the exposure process, resulting in high image reproducibility.

[0092] <Hardboard>

[0093] The first rigid plate 11 and the second rigid plate 12 used in the printing plate manufacturing method of this embodiment can be made of ultraviolet-transmitting glass plates or the like, which are known for their use in the manufacture of flexible printing plates.

[0094] Negative Film

[0095] The negative 1 used in the printing plate manufacturing method of this embodiment has a prescribed printing pattern 1a for forming a desired relief and a prescribed micro-unit pattern 1b for forming micro-units.

[0096] [Micro-unit pattern]

[0097] Increasing the surface area of ​​a letterpress printing plate is an effective method for improving the density of ink in a printing plate. To increase the density of ink by uniformly and densely coating the printing plate, techniques for forming micro-units on the surface of the printing plate are known. For example, various micro-unit patterns disclosed in Japanese Patent Application Publication No. 2021-525661 are used. Specifically, by setting micro-units of various shapes, such as dots, grids, halftone dots, and lines, into finely textured, uneven shapes on the surface of the printing plate, the surface area of ​​the printing plate can be increased.

[0098] Furthermore, micro-cell patterns can be used not only for solid areas to increase the solidity of the printed ink, but also for strings, line drawings, halftones, and all kinds of image elements used to improve ink transfer properties. Micro-cell patterns are typically not visually discernible in the final print, resulting in a surface structure that improves ink spread.

[0099] In the printing plate manufacturing method of this embodiment, as a pre-process of the lamination process, a drawing process is preferably included to form a predetermined micro-unit pattern on the negative film 1. The micro-unit pattern is applicable to printing areas of any size, and is preferably formed in the desired area in a manner that enables the printing of a uniform solid area.

[0100] The patterning process for forming micro-unit patterns is not limited to the following; it can be performed, for example, by ablation, thermal methods, inkjet printing, and silver halide methods. Specifically, when the negative 1 has an ablation layer on a specified substrate, the ablation layer can be irradiated with infrared light to perform the patterning process. The patterning method is not particularly limited, and a known irradiation unit can be used. Infrared laser light is irradiated onto the ablation layer to decompose the resin in the irradiated portion, thus patterning is performed. This yields an ablation layer with a patterned pattern.

[0101] Examples of infrared lasers include ND / YAG lasers (e.g., 1064nm) or diode lasers (e.g., 830nm). Laser systems suitable for CTP (Continuous Photolithography) technology are commercially available; for example, the CDISpark diode laser system (ESKO GRAPHICS) can be used. This laser system includes a rotating cylindrical drum holding the negative, an IR laser irradiation device, and a plotting computer, from which image information is sent directly to the laser device.

[0102] By giving the negative 1 a micro-unit pattern 1b, the printing plate obtained by the printing plate manufacturing method of this embodiment, for example a relief plate, has a pattern 2a containing micro-units 2b on its surface, which are multiple micro-bumps and depressions with a specified area and height formed from the negative 1.

[0103] In the printing plate manufacturing method of this embodiment, the solidity can be increased by using a negative film 1 having a micro-unit pattern 1b.

[0104] [Relationship between solubility parameters]

[0105] 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 later has the following relationship with the solubility parameter SpB of the negative film: (I).

[0106] |SpA-SpB|≥2.0 …(I)

[0107] That is, the absolute value of the difference between SpA and SpB is 2.0 or more. Preferably, it is 2.1 or more, and more preferably 2.2 or more. It is possible for SpB to be larger than SpA or for SpB to be smaller than SpA.

[0108] By ensuring that the absolute value of the difference between SpA and SpB is greater than 2.0, even when negatives are directly laminated with liquid photosensitive resin compositions, the dissolution and transfer of negatives into the photosensitive resin compositions can be effectively suppressed.

[0109] Furthermore, the upper limit of the absolute value of the difference between SpA and SpB is determined by the materials of the selected negative and photosensitive resin composition layer, and from a practical point of view, it is 13.0 or less.

[0110] As described above, in this embodiment, the dissolution and transfer of the negative to the photosensitive resin composition layer can be suppressed, thus making it easier to separate and recover the photosensitive resin composition in the unexposed areas. In addition, the quality of the printing plate can be improved.

[0111] Furthermore, since the dissolution and transfer of the negative to the photosensitive resin composition layer can be suppressed, it is not necessary to provide a predetermined thin film layer between the negative and the photosensitive resin composition layer. This prevents the bending and scattering of ultraviolet light caused by the provision of such a thin film layer, thereby achieving excellent image reproduction. In particular, in the printing plate manufacturing method of this embodiment, since the negative has a micro-unit pattern, it is possible to eliminate the need for a predetermined thin film layer between the negative and the photosensitive resin composition layer. This is extremely effective from the viewpoint of improving the formation of micro-units and the quality of the final printing plate.

[0112] Generally, the solubility parameter (Sp value) is defined as shown in equation (1) below.

[0113] Sp value (δ) = (ΔE / V) 1 / 2 [(cal / cm 3 ) 1 / 2 …(1)

[0114] Here, V is the molar volume of the organic solvent, and ΔE is the cohesive energy (evaporation energy).

[0115] The molar volume and cohesive energy of organic solvents can be determined from known values, for example, as in the literature “POLYMER ENGINEERING AND SCIENCE, Vol. 14, 147-154, 1974”.

[0116] On the other hand, when the above parameters are not publicly known, they can be measured using a method known as turbid point titration.

[0117] Specifically, firstly, for a solution obtained by dissolving a sample with an unknown SP value in a good solvent with a known SP value, a poor solvent with an SP value lower than that of the good solvent is gradually added dropwise, and the volume of the poor solvent at which the solute begins to precipitate is measured. Next, for a newly prepared solution obtained by dissolving a sample with an unknown SP value in a good solvent with a known SP value, a poor solvent with an SP value higher than that of the good solvent is gradually added dropwise, and the volume of the poor solvent at which the solute begins to precipitate is measured. By applying the volumes of various poor solvents determined here to the following equation (2), the SP value (δ) can be calculated.

[0118] SP value (δ) = (V ml 1 / 2 ·δ ml +V mh 1 / 2 ·δ mh ) / (V ml 1 / 2 +V mh 1 / 2 …(2)

[0119] Here, V ml It is the volume of poor solvents with low SP values, V mh It is the volume of poor solvents with high SP values, δ ml The SP value of a poor solvent with a low SP value is δ. mh It is the SP value of a poor solvent with a high SP value.

[0120] All SP values ​​described in the following examples are values ​​measured by the above-described turbidity point titration method.

[0121] As for the aforementioned negative film and photosensitive resin composition, by selecting substances having suitable solubility parameters in combination, 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 aforementioned numerical range.

[0122] Specifically, by selecting a resin having the structural unit shown in general formula (II) as described below, at least one selected from polyurethane, polylactic acid, polycarbonate, polyester, polyamide, polybutyral, polyvinyl alcohol, poly(meth)acrylate, and their modifiers or partial saponifications as the material of the negative film, and selecting a photosensitive material containing the polymer (b-1), olefinic unsaturated compound (b-2), and photopolymerization initiator (b-3) as the material of the photosensitive resin composition, it is possible to control the absolute value of the difference between the solubility parameter (SpA) of the photosensitive resin composition and that of the negative film to be greater than 2.0.

[0123] In addition, the following good and bad solvents, and their respective SP values, can be used in the calculation of the SP values ​​above.

[0124] Good solvent:

[0125] Toluene (SP value: 8.9 [(cal / cm³)) 3 ) 1 / 2 ])

[0126] p-Xylene (SP value: 8.7 [(cal / cm)]) 3 ) 1 / 2 ])

[0127] Butyl acetate (SP value: 8.5 [(cal / cm)) 3 ) 1 / 2 ])

[0128] Ethyl acetate (SP value: 9.1 [(cal / cm))) 3 ) 1 / 2 ])

[0129] Acetone (SP value: 9.8 [(cal / cm)]) 3 ) 1 / 2 ])

[0130] Unsuitable solvents:

[0131] n-Hexane (SP value: 7.2 [(cal / cm)) 3 ) 1 / 2 ])

[0132] Ethanol (SP value: 12.9 [(cal / cm³)) 3 ) 1 / 2 ])

[0133] Water (SP value: 23.4 [(cal / cm³)) 3 ) 1 / 2 ])

[0134] The solubility parameter SpA of the photosensitive resin composition constituting the photosensitive resin composition layer described later is generally determined by the material used in the photosensitive resin composition for manufacturing flexographic printing plates. From a practical point of view, the solubility parameter SpA of the photosensitive resin composition is preferably 10.0 or more and 14.0 or less. Therefore, from the viewpoint of increasing the absolute value of the difference between the solubility parameters of the photosensitive resin composition and the negative film, and suppressing the dissolution and transfer of the photosensitive resin composition by the negative film, when the solubility parameter SpB of the negative film is greater than SpA, SpB is preferably 13.0 or more, more preferably 13.5 or more, further preferably 14.0 or more, and even more preferably greater than 14.0.

[0135] When SpB is greater than SpA, the material of the negative is not limited to the following materials, for example, at least one selected from the group consisting of polyurethane, polylactic acid, polycarbonate, polyester, polyamide, polybutyral, polyvinyl alcohol, poly(meth)acrylate, and their modified or partially saponified forms are preferred materials. Polyurethane and / or polybutyral are particularly preferred.

[0136] When SpB is greater than SpA, the material constituting the blackening layer as the negative tends to be highly polarized, and the strength of the blackening layer and its adhesion to the rigid plate in contact with the negative are improved. Therefore, the blackening layer tends to have better damage resistance and solvent resistance.

[0137] By setting the solubility parameter SpB of the negative to 13.0 or higher, the solubility parameter SpA of the photosensitive resin composition can generally be determined based on the material used in the photosensitive resin composition for flexographic printing plate manufacturing. Therefore, the absolute value of the difference between SpA and SpB can be controlled to 2.0 or higher. This suppresses the dissolution and transfer of the negative to the photosensitive resin composition layer.

[0138] On the other hand, when the solubility parameter SpB of the negative is less than that of SpA, SpB is preferably less than 10.0, more preferably 9.5 or less, and even more preferably 9.0 or less.

[0139] When SpB is less than SpA, the material of the negative is not limited to the following materials, for example: thermoplastic elastomer block copolymers, fully or partially hydrolyzed polyethylene esters, partially hydrolyzed polyvinyl acetate, polyvinyl alcohol derivatives, partially hydrolyzed vinyl acetate / alkylene oxide graft copolymers, or polyvinyl alcohol, polybutadiene, polyamides and mixtures thereof that have been acryliced ​​through a polymer-like reaction are preferred materials in the manufacture of flexographic printing plates.

[0140] As thermoplastic elastomer block copolymers, examples include block copolymers containing at least one block comprising an alkenyl aromatic monomer unit and at least one block comprising a 1,3-diene monomer unit.

[0141] Examples of alkenyl aromatic compounds that form alkenyl aromatic monomer units include styrene, α-methylstyrene, or vinyltoluene. As for 1,3-dienes, butadiene and isoprene are preferred, for example, from the viewpoint of reducing the stereohindrance of vinyl groups, improving photocrosslinking efficiency, and preventing the ablation layer from dissolving into the exposed printing plate.

[0142] The solubility parameter SpB of the negative film can be controlled to the aforementioned range by appropriately selecting the resin material constituting the negative film. Specifically, a higher solubility parameter SpB can be achieved by selecting a resin material with high polarity, and a lower solubility parameter SpB can be achieved by selecting a resin material with low polarity.

[0143] By setting the solubility parameter SpB of the negative to 9.0 or below, the solubility parameter SpA of the photosensitive resin composition can generally be determined based on the material used in the photosensitive resin composition for flexographic printing plate manufacturing. Therefore, the absolute value of the difference between SpA and SpB can be controlled to be 2.0 or above. This suppresses the dissolution and transfer of the negative to the photosensitive resin composition layer.

[0144] <First-method negative>

[0145] In the printing plate manufacturing method of this embodiment, a negative film can be used as the negative film, which has a substrate and an ablation layer laminated on the substrate (hereinafter, the negative film of this type is sometimes referred to as the negative film of the first type).

[0146] It should be noted that in the negative of the first method, the solubility parameter SpB of the negative refers to the solubility parameter of the ablation layer.

[0147] The negative of the first embodiment preferably comprises a resin having structural units shown in general formula (II). More specifically, it is preferred that the negative has a substrate and an ablation layer laminated on the substrate, wherein the ablation layer comprises a resin having structural units shown in general formula (II).

[0148] It should be noted that the negative used in the printing plate manufacturing method of this embodiment is not limited to the negative of the first method.

[0149]

[0150] In the above formula (II), R1 and R2 independently represent nonpolar groups, and R3 and R4 independently represent hydrogen atoms or nonpolar groups.

[0151] Figure 2 A schematic cross-sectional view showing an example of the negative used in the printing plate manufacturing method of this embodiment.

[0152] Figure 2 In the negative shown, a substrate 21 and an ablation layer 22 are stacked. The ablation layer 22 functions as a mask when forming the embossed pattern and micro-unit pattern of the target printing plate.

[0153] The following is a detailed explanation of negative film.

[0154] [Substrate]

[0155] Figure 2 The negative shown has a substrate 21 and an ablation layer 22 stacked on the substrate 21, and the ablation layer 22 is image-depicted, thereby serving as a negative for forming reliefs and micro-units in the printing plate manufacturing process described later.

[0156] The quality of relief and microcells, especially image reproducibility, is greatly affected by the negative's ultraviolet light transmission during exposure. Generally, the greater the thickness of the negative, the greater the bending or scattering of ultraviolet light within it, and the lower the image reproducibility tends to be. Regarding the overall thickness of the negative, Figure 2 The thickness of the substrate 21 shown accounts for most of the thickness; therefore, from the viewpoint of printing plate quality, it is preferable that the thickness of the substrate 21 is small.

[0157] On the other hand, a certain degree of rigidity and dimensional stability of the negative is also important. If the negative is easily deformed, deformation and damage to the image formed on the negative will be induced during the processes before relief exposure, resulting in a tendency for reduced image reproducibility. However, if the rigidity of the negative is too high, there is a tendency for poor compatibility with the equipment during the manufacturing process of the printing plate, or for excessive stress concentration in the ablation layer during processing, causing irreversible damage such as damage and wrinkles.

[0158] Based on the above viewpoints, the thickness of the substrate 21 is preferably 10 μm or more and less than 100 μm. Within this range, a negative film with excellent image reproducibility and moderate rigidity can be obtained. Furthermore, 20 μm or more is preferred, and 40 μm or more is more preferable. By making the thickness of the substrate 21 10 μm or more, sufficient strength and rigidity for practical use can be obtained, suppressing image deformation and damage during the printing plate manufacturing process. Additionally, from the viewpoint of ensuring moderate flexibility and good operability during the printing plate manufacturing process, 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.

[0159] Furthermore, from the viewpoints of dimensional stability, transparency, and adhesion to the ablation layer 22, the substrate 21 preferably comprises polyester or a resin having a polyolefin backbone. Here, the resin contained in the substrate 21 may be a mixture of polyester and a resin having a polyolefin backbone, or it may be a copolymer.

[0160] As a polyester, it is not limited to the following, for example, polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, etc.

[0161] Resins having a polyolefin backbone are not limited to the following, for example, polyethylene, polypropylene, and resins copolymerized from them.

[0162] Furthermore, from the viewpoint of image reproducibility, the substrate 21 is more preferably composed of polyester or a resin with a polyolefin backbone, and even more preferably composed of a resin with a polyolefin backbone. This is because resins with a polyolefin backbone have high oxygen permeability. Here, oxygen permeability is one of the physical properties of the film, representing the oxygen permeability per 1m of film under conditions of 1 atm (1 atmosphere). 2 The amount of oxygen that permeates through the membrane in one day. The unit is cm. 3 / m 2 •24h·atm, the higher the value, the easier it is to pass through; the lower the value, the more difficult it is to pass through.

[0163] In the printing plate manufacturing process, when the photosensitive resin composition layer is cured by ultraviolet irradiation, the curing of the photosensitive resin composition is carried out by free radical polymerization. If oxygen is present during this free radical polymerization, the free radical-generated compounds react with oxygen and hinder the polymerization reaction. That is, by reducing the amount of oxygen present during exposure of the photosensitive resin composition layer, the degree of polymerization can be increased, thereby improving 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 the photosensitive resin composition layer during ultraviolet irradiation can easily diffuse to the outside, suppressing the effect of oxygen-induced polymerization reaction hindrance.

[0164] In negative film, substrate 21 can be used in an untreated state, or it can undergo a specified surface treatment as needed. Alternatively, a substrate with functions such as antistatic treatment can be used. Examples of surface treatments include corona treatment and matte finishing.

[0165] [Ablation layer]

[0166] Figure 2 The negative shown has an ablation layer 22 stacked on the substrate 21.

[0167] The ablation layer 22 contains a specified resin, can be removed using an infrared laser, and functions as a light shielding layer other than infrared light.

[0168] To suppress the leaching of components contained in the ablation layer 22 into the photosensitive resin composition layer and the transfer of the ablation layer 2 into the photosensitive resin composition, it is effective to improve the adhesion between the substrate 21 and the ablation layer 22, or to 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 SpB of the negative film, i.e., the solubility parameter SpB of the ablation layer constituting the negative film, is determined to be 2.0 or higher. Therefore, even if the ablation layer of the negative film and the photosensitive resin composition are directly laminated, the leaching and transfer of the ablation layer into the photosensitive resin composition layer can be effectively suppressed.

[0169] The ablation layer 22 contains resin, infrared absorbing materials, and non-infrared shielding materials such as ultraviolet rays.

[0170] From the viewpoint of improving the adhesion between the substrate 21 and the ablation layer 22, strengthening the interlayer interaction is important. Methods for strengthening such interlayer interaction include, for example, methods that enhance chemical interactions and methods that enhance physical interactions.

[0171] As a method to improve chemical interactions, one example is to impart a molecular structure similar to that of the constituent materials of both the substrate 21 and the ablation layer 22. As a method to improve physical interactions, one example is to increase the flexibility of the ablation layer 22 or impart moderate softness to suppress peeling during film bending. Furthermore, to improve chemical interactions, it is also effective to impart a molecular structure similar to that of the constituent materials of both the substrate 21 and the ablation layer 22, maintaining interlayer adhesion while ensuring high removal efficiency of the ablation layer 22 under infrared laser light.

[0172] 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 material as the resin material in the ablation layer 22.

[0173] Based on the above viewpoint, in the negative film used in the printing plate manufacturing method of this embodiment, the ablation layer 22 preferably comprises a resin having a structural unit containing quaternary carbon atoms bonded to two nonpolar groups, as shown in the following general formula (II).

[0174] It should be noted that the resin may have other structural units as needed.

[0175] In addition, in this specification, "monomer" refers to the compound before polymerization, and "structural unit" refers to a specified repeating unit formed by monomer polymerization.

[0176] [Chemical Formula 3]

[0177]

[0178] In formula (II), R1 and R2 independently represent nonpolar groups, and R3 and R4 independently represent hydrogen atoms or nonpolar groups.

[0179] As described above, the ablation layer 22 of the negative used in the printing plate manufacturing method of this embodiment preferably contains a resin having structural units shown in general formula (II).

[0180] When the main chain of the resin contained in the ablation layer 22 has polar groups, non-covalent bonds are firmly formed between molecules, increasing the strength of the ablation layer 22. On the other hand, there is a tendency for the structure for interaction with the constituent raw materials of the substrate 21 to decrease, and for the adhesion between the substrate 21 and the ablation layer 22 to decrease. In addition, there is a tendency for the rigidity of the ablation layer 22 to become too high, for stress generated by bending or stretching to concentrate between layers, and for interfacial delamination to easily occur.

[0181] Furthermore, when the side chains of the resin contained in the ablation layer 22 have polar groups, as described below, there is a tendency for it to be undesirable from the viewpoint of laser ablation efficiency of the ablation layer 22.

[0182] To ensure efficient laser ablation, it is important that the resin contained in the ablation layer 22 is easily depolymerized. "Depolymerization" refers to the reverse reaction of polymerization, which is the reaction in which the polymer decomposes into monomers.

[0183] By irradiating the ablation layer 22 with an infrared laser, the temperature instantly reaches several hundred degrees Celsius. At this point, the main chain of the resin decomposes, the molecular weight drops sharply, and it is removed from the ablation layer 22. However, resins that are difficult to depolymerize tend to undergo only side chain decomposition without main chain breakage during ablation. Therefore, resin remains in the ablation layer 22 after irradiation with an infrared laser. It is known that resins obtained through condensation polymerization form ring structures upon decomposition, leading to main chain breakage. That is, in infrared ablation, which is a short-time heat treatment, the molecular weight is difficult to reduce, and ablation layers containing resins obtained through this condensation polymerization tend to have poor removal efficiency.

[0184] 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 tends to begin from thermally unstable portions present in polymers such as branches. However, if the side chains, which are equivalent to branches, are polar, then the decomposition of the side chains tends to dominate, making it difficult for the main chain to break, which is therefore undesirable.

[0185] Therefore, the resin contained in the ablation layer 22 preferably has nonpolar side chains. Furthermore, the contribution of intramolecular or intermolecular chain transfer cannot be ignored when the main chain undergoes cracking. Therefore, it is preferable to avoid having tertiary hydrogens that are easily removed due to chain transfer. That is, the portion corresponding to the symmetry plane of the branch is also preferably a nonpolar group.

[0186] Furthermore, from the viewpoint of achieving rubber-like elasticity, it is also important that the side chains are nonpolar groups. This makes them the softer part of the elastomer, thus improving the flexibility of the ablation layer 22.

[0187] Based on the above viewpoint, in the negative, the content of resin having the structural unit shown in the above 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.

[0188] The nonpolar group in the above general formula (II) is preferably any one of alkyl, aryl, cycloalkyl, phenyl, alkenyl, aralkyl, cycloalkenyl, alkynyl, silyl, and siloxane. Furthermore, the nonpolar group does not contain hydrogen atoms.

[0189] In particular, from the viewpoint of improving the flexibility of the ablation layer 22 and ensuring its adhesion to the substrate 21, in the above general formula (II), it is more preferable that R1 and R2 are each independently selected from any group consisting of alkyl, alkenyl and alkynyl groups, and from the viewpoint of low polarity, alkyl is even more preferred.

[0190] The monomer capable of forming the structural unit shown in general formula (II) above is not limited to the following monomers, for example isobutene, 2-methyl-2-butene, 2,3-dimethyl-2-butene, and monomers obtained by replacing their methyl groups with other alkyl groups such as ethyl groups, and their modified forms; α-methylstyrene, cis-(1-methyl-1-propenyl)benzene, trans-(1-methyl-1-propenyl)benzene, and monomers obtained by replacing their methyl groups with other alkyl groups such as ethyl groups, and their modified forms; 1,1-diphenylethylene, etc.

[0191] In the above general formula (II), R3 and R4 independently represent hydrogen atoms or nonpolar groups, respectively.

[0192] R3 and R4 are each preferably selected independently from any group consisting of hydrogen atoms, alkyl groups, alkenyl groups, and alkynyl groups, and more preferably hydrogen atoms or alkyl groups. If both R3 and R4 are hydrogen atoms, the depolymerization property of the resin is further improved, and therefore it is further preferred.

[0193] Furthermore, the structural unit represented by the general formula (II) constituting the above-mentioned resin can be a single type or two or more types. For example, regarding the above-mentioned resin, structural unit (II) can have: a structural unit where R1 and R2 are alkyl groups, and a structural unit where one of R1 and R2 is an alkyl group and the other is a phenyl group. By having both alkyl and phenyl groups, the properties of two groups can be obtained.

[0194] The resin contained in the ablation layer 22 preferably contains structural units derived from monovinyl substituted aromatic hydrocarbons in addition to the structural units shown in the general formula (II) above.

[0195] Monovinyl aromatic hydrocarbons can be chemically bonded to the structural units shown in the above general formula (II) or added as different resins. However, from the viewpoint of dispersibility and laser processing uniformity, it is preferable to form copolymers by chemically bonding structural units derived from monovinyl substituted aromatic hydrocarbons to the structural units shown in the above general formula (II).

[0196] By incorporating structural units derived from monovinyl substituted aromatic hydrocarbons into the resin used in the ablation layer, there is a tendency to improve the adhesion between the ablation layer 22 and the substrate 21, and to increase the rigidity of the negative.

[0197] The compounds used to form structural units derived from monovinyl aromatic hydrocarbons are not limited to the following, but may include monomers such as styrene, tert-butylstyrene, N,N-dimethyl-p-aminoethylstyrene, N,N-diethyl-p-aminoethylstyrene, vinylpyridine, p-methylstyrene, and tert-butylstyrene. Styrene is particularly preferred from the viewpoint of being able to smoothly form negatives at lower temperatures.

[0198] The structural units derived from monovinyl substituted aromatic hydrocarbons can be of only one type or more than two types.

[0199] The ablation layer 22 may contain infrared absorbing materials for the purpose of ablation processing.

[0200] As infrared absorbing substances, monomers or compounds that have strong absorption in the range of 750~2000nm can usually be listed.

[0201] Infrared absorbing materials are not limited to the following substances, but may include inorganic pigments such as carbon black, graphite, copper chromite, and chromium oxide; and pigments such as polyphthalocyanine compounds, anthocyanins, and metal thiols. Smaller particle sizes result in higher sensitivity to infrared lasers, but carbon black, in particular, is preferred as an infrared absorbing material because it can be used in a wide particle size range of 13–85 nm. Furthermore, carbon black can also function as a shielding material. These infrared absorbing materials are added within a range that imparts sensitivity suitable for cutting using the laser light employed.

[0202] The ablation layer 22 acts as a mask, and therefore can contain non-infrared shielding materials such as ultraviolet rays. Materials that reflect or absorb ultraviolet light can be used as non-infrared shielding materials.

[0203] As a shielding material, it is not limited to the following substances, such as ultraviolet absorbers, carbon black and graphite.

[0204] From the viewpoint of ensuring the shielding of ultraviolet rays during the subsequent exposure process, it is preferable that the ablation layer 22 be thicker; from the viewpoint of improving ablation performance, it is preferable that it be thinner.

[0205] Based on the above viewpoint, 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.

[0206] As a non-infrared shielding effect of the ablation layer 22, it is preferable that the optical concentration of the ablation layer 22 is 2 or more, and more preferably that the optical concentration is 3 or more.

[0207] Optical density can be measured using a D200-II transmission density meter (manufactured by GretagMacbeth). Furthermore, optical density is also known as ISO visual density, and the light being measured is in the wavelength range of approximately 400–750 nm.

[0208] <First Method for Manufacturing Negative Film>

[0209] The method for manufacturing the negative of the first method described above is not limited to the following methods, but can include, for example, the following method: When both the infrared absorbing material and the non-infrared shielding material are carbon black, firstly, a solution of a resin having the structural unit shown in the above general formula (II) is prepared using a specified solvent. 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. Then, the ablation layer is manufactured by coating the solution or dispersion for forming the ablation layer onto a specified substrate 21.

[0210] As a method for dispersing carbon black in the above-mentioned resin solution, forced stirring based on stirring blades and stirring using ultrasound or various mills are effective methods. Alternatively, to obtain good dispersibility of carbon black, it is also effective to pre-mix the resin, carbon black, and dispersant using an extruder or kneader before dissolving them in a solvent. In addition, methods for forcibly dispersing carbon black in resin in the state of a latex dispersion can also be cited.

[0211] The solvent used in the preparation of the solution, dispersion, etc., for forming the ablation layer 22 can be appropriately selected considering the solubility of the resin and infrared absorber used. Only one solvent can be used, or two or more solvents can be mixed.

[0212] In addition, the quality of the ablation layer 22 can also be improved by mixing solvents with lower boiling points and solvents with higher boiling points to control the evaporation rate of the solvents.

[0213] The solvent used to form the ablation layer 22 is not limited to the following solvents, such as toluene, xylene, cyclohexane, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, pentyl acetate, methyl ethyl ketone, acetone, cyclohexanone, ethylene glycol, propylene glycol, ethanol, water, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, dimethylacetamide, dimethylformamide, n-propanol, isopropanol, 1,4-dioxane, tetrahydrofuran, diethyl ether, n-hexane, n-heptane, n-pentane, and acetonitrile, and their analogues.

[0214] <Second Method Negative>

[0215] In the printing plate manufacturing method of this embodiment, a negative film consisting of a UV printing polymer layer having a desired pattern on a specified UV printing substrate can be used as the negative film.

[0216] UV printing substrate

[0217] The UV printing substrate described above is not limited to the following; for example, a substrate containing a transparent material selected from the group consisting of polyethylene terephthalate, polycarbonate, and polyethylene naphthalate can be used.

[0218] The thickness of the aforementioned UV printing substrate is preferably 10 μm or more and less than 100 μm. Within this range, a negative film with excellent image reproducibility and moderate rigidity can be obtained. Furthermore, 20 μm or more is preferred, and 40 μm or more is more preferable. By ensuring the thickness of the UV printing substrate is 10 μm or more, sufficient strength and rigidity for practical use can be obtained, suppressing image deformation and damage during the printing plate manufacturing process. Additionally, from the viewpoint of ensuring moderate flexibility and good operability during the printing plate manufacturing 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.

[0219] [UV-printed polymer layer]

[0220] As the aforementioned UV ink, a UV ink containing one or more photoinitiators, monomers, binders, and pigments can be used. As the aforementioned pigments, materials containing four color systems, including cyan, magenta, yellow, and black, can be listed. The aforementioned UV ink is preferably cured by exposure to a UV light source with a wavelength output in the range of about 365 nm to about 405 nm.

[0221] The UV-printed polymer layer has a specified pattern in the negative and, after exposure and curing, contains a polymer that is a monomer.

[0222] The polymers mentioned above are not limited to those listed below, but may include at least one selected from the group consisting of polyurethane, polylactic acid, polycarbonate, polyester, polyamide, polybutyral, polyvinyl alcohol, poly(meth)acrylate, and their modifiers or partial saponifications.

[0223] To suppress the leaching of components from the UV-printed polymer layer into the photosensitive resin composition layer and the transfer of components from the UV-printed polymer layer into the photosensitive resin composition layer, it is effective to either improve the adhesion between the UV-printed substrate and the UV-printed polymer layer, or reduce the compatibility between the UV-printed 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-printed polymer layer, is set to 2.0 or higher. Therefore, even when directly laminated with the photosensitive resin composition, the leaching and transfer of components from the UV-printed polymer layer into the photosensitive resin composition layer can be effectively suppressed.

[0224] <Second Method for Manufacturing Negative Film>

[0225] The negative of the second method is obtained by the following operation: using, for example, an inkjet printer, dispersing UV ink in a desired pattern on the UV printing substrate, curing the UV ink using a chemical radiation source, causing the UV ink to crosslink and cure, and forming a UV printing polymer layer in the desired pattern, thereby obtaining the negative.

[0226] <Photosensitive Resin Composition Layer>

[0227] In the printing plate manufacturing method of this embodiment, a liquid photosensitive resin composition layer is directly laminated on the negative film.

[0228] Liquid photosensitive resin compositions have high fluidity and can easily change shape. Therefore, when laminated onto a negative, the photosensitive resin composition is formed into a film of a specified thickness inside a dedicated device (plate-making machine).

[0229] For example, such as Figure 1 As shown, a negative film 1 is placed on a first rigid plate 11 that is transmissive to ultraviolet light, and a liquid photosensitive resin composition flows on it. The support 3 is then attached to the negative film 4 for back exposure and a second rigid plate 12 to form a photosensitive resin composition layer 2.

[0230] In the process of forming the photosensitive resin composition layer 2, after the negative film 1 is placed on the first rigid plate 11, and the negative film 1 is reliably fixed, it is preferable to evacuate the negative film 1 to remove oxygen-blocking factors. The mechanism of evacuation is not particularly limited; for example, a method of evacuating by using a pump to create a vacuum in a groove provided around the first rigid plate 11 can be cited.

[0231] If the rigidity of the negative film 1 is insufficient, wrinkles will form on the negative film 1 during the vacuuming process. Under heavy conditions, these wrinkles cannot be removed and remain. These wrinkles, when transferred to the cured embossed surface, may significantly reduce image reproducibility. Furthermore, if the dimensional stability of the negative film 1 is insufficient, the pattern drawn on it will be deformed, which also contributes to reduced image reproducibility.

[0232] On the other hand, if the rigidity of the aforementioned negative 1 is too high, it cannot completely follow the lower glass during vacuuming, leaving gaps and residual air. As a result, the effect of oxygen obstruction increases, potentially adversely affecting image reproducibility. Furthermore, stress generated by the deformation of the highly elastic negative 1 may concentrate in the ablation layer, causing wrinkles and pinholes. Therefore, it is extremely important that the negative 1 has an appropriate range of rigidity.

[0233] The photosensitive resin composition layer preferably contains, for example, the polymer (b-1), olefinic unsaturated compound (b-2), and photopolymerization initiator (b-3) described later. They can be used selectively as appropriate.

[0234] In addition, the photosensitive resin composition layer may contain further auxiliary additives as needed.

[0235] The solubility parameter SpA of the photosensitive resin composition constituting the photosensitive resin composition layer is usually determined by the material used in the photosensitive resin composition for manufacturing flexographic printing plates. From a practical point of view, the solubility parameter SpA of the photosensitive resin composition is 10.0 or higher and 14.0 or lower.

[0236] The components of the photosensitive resin composition layer are described in detail below.

[0237] [Polymer(b-1)]

[0238] The polymer (b-1) mentioned above can be any of the following: linear, branched, or dendritic polymers; it can be a homopolymer or a copolymer. The copolymer mentioned above can be a random copolymer, an alternating copolymer, or a block copolymer.

[0239] Examples of the polymers mentioned above (b-1) include, for example, fully or partially hydrolyzed polyethylene ester, partially hydrolyzed polyvinyl acetate, polyvinyl alcohol derivatives, partially hydrolyzed vinyl acetate / olefin graft copolymers, or polyvinyl alcohol, polybutadiene, polyamides and mixtures thereof that have been subsequently acryliced ​​through a polymer-like reaction and are conventionally used in the manufacture of flexographic printing plates.

[0240] In addition to the above, thermoplastic elastomer block copolymers can also be used, for example.

[0241] Examples of thermoplastic elastomer block copolymers include block copolymers containing at least one block comprising an alkenyl aromatic monomer unit and at least one block comprising a 1,3-diene monomer unit. Examples of alkenyl aromatic compounds forming the alkenyl aromatic monomer unit include styrene, α-methylstyrene, or vinyltoluene. As for the 1,3-diene, butadiene or isoprene are preferred, for example, from the viewpoint of reducing the stereohindrance of vinyl groups, improving photocrosslinking efficiency, and preventing the ablation layer from dissolving into the exposed printing plate.

[0242] Furthermore, the polymer (b-1) preferably contains a compound having a carbonyl group. As the polymer (b-1), by using a compound having a highly polar carbonyl group, it has the ability to reduce its compatibility with the resin having nonpolar groups in the ablation layer and to suppress the tendency of the ablation layer to dissolve into the photosensitive resin composition layer.

[0243] The polymer (b-1) described above is not limited to the following, and examples include polyester, polyamide, and polyurethane. From the viewpoint of preventing damage to the embossed surface caused by the load when peeling off the film used for manufacturing the flexible printing plate after the exposure process, polyurethane is more preferably included. Furthermore, from the viewpoint of improving the mechanical properties of the flexible printing plate finally obtained by photocrosslinking, the polyurethane preferably has (meth)acrylic groups at the end groups.

[0244] From a practical point of view, the solubility parameter SpA of the photosensitive resin composition layer used in the printing plate manufacturing method of this embodiment is preferably controlled to be 10.0 or more and 14.0 or less. From the viewpoint of suppressing the dissolution of the ablation layer into the photosensitive resin composition layer, it is preferable to contain 60% by mass or more of polyurethane. It should be noted that in this configuration, the negative film preferably contains 20% by mass or more and less than 60% by mass of polyurethane and / or polybutyral. As a result, the dissolution of the ablation layer into the photosensitive resin composition layer can be effectively suppressed.

[0245] One method for manufacturing polyurethane with (meth)acrylic acid groups at the ends includes: reacting a diol having repeating units within the molecule with a diisocyanate to form a polyurethane with isocyanate groups at the ends, resulting in a polyurethane of any molecular weight; and then reacting the polyurethane with a compound containing active hydrogen and (meth)acrylic acid groups. Another method includes: reacting a diol having repeating units within the molecule with a diisocyanate to form a polyurethane with isocyanate groups at the ends, resulting in a polyurethane of any molecular weight; and then reacting the polyurethane with a compound containing hydroxyl and (meth)acrylic acid groups.

[0246] The polyurethane structure obtained by the above manufacturing method is formed by reacting diols with diisocyanates that have repeating units within the molecule.

[0247] Hereinafter, the "polyurethane having (meth)acrylic groups at the end" manufactured by the above method will be referred to as an "unsaturated prepolymer".

[0248] The "diol having repeating units within the molecule" used to manufacture the above-mentioned unsaturated prepolymers is not limited to the following, but may include, for example, polyester diols formed from dicarboxylic acids and diols; polyether diols; polyether polyester copolyols; 1,2-polybutadiene compounds having terminal hydroxyl groups, etc. One type of diol having repeating units within the molecule may be used alone, or two or more may be used in combination.

[0249] The dicarboxylic acids constituting the above-mentioned polyester diols are not limited to the following, and examples include succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, maleic acid, terephthalic acid, isophthalic acid, and 1,5-naphthalenedicarboxylic acid.

[0250] The diols constituting the aforementioned polyester diols are not limited to the following, but may include, for example, 1,4-butanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, neopentanediol, 1,6-hexanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, and diethylene glycol (dioxyethylenediol).

[0251] The polyether diols mentioned above are not limited to the following, and examples include polyoxyethylene diol, polyoxypropylene diol, polyoxytetramethylene diol, polyoxy-1,2-butene diol, polyoxyethylene / polyoxypropylene random copolymer diol, polyoxyethylene / polyoxypropylene block copolymer diol, polyoxyethylene / polyoxytetramethylene random copolymer diol, and polyoxyethylene / polyoxytetramethylene block copolymer diol.

[0252] The polyether polyester copolydiol described above is not limited to the following, for example, a copolymer having a structure in which repeating units of the molecular chain forming the polyether diol and repeating units of the molecular chain forming the polyester diol are block- or randomly connected.

[0253] The aforementioned 1,2-polybutadiene compound with terminal hydroxyl groups can be a hydrogenated compound. The 1,2-polybutadiene compound with terminal hydroxyl groups is not limited to the following; examples include hydrides of poly-1-butene and hydrides of 1,2-polybutadiene. The number of terminal hydroxyl groups is not particularly limited, but from the viewpoint of preventing damage to the embossed surface caused by the load during the peeling of the film used in printing plate manufacturing after exposure, the number of hydroxyl groups per molecule is preferably 1.2 or more, more preferably 1.5 or more, and even more preferably 2.0 or less.

[0254] The diisocyanates mentioned above are not limited to the following, and examples include toluene diisocyanate, phenyl diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, and norbornene diisocyanate.

[0255] Diisocyanates can be used alone or in combination of two or more.

[0256] [Alkene unsaturated compound (b-2)]

[0257] As described above, the photosensitive resin composition layer preferably contains an olefinic unsaturated compound (b-2). The olefinic unsaturated compound (b-2) refers to a compound having unsaturated double bonds capable of undergoing free radical polymerization.

[0258] As an olefinic unsaturated compound (b-2), it is not limited to the following, but may include, for example, alkenes such as ethylene, propylene, vinyltoluene, styrene, and divinylbenzene; acetylenes; (meth)acrylic acid and / or its derivatives; halogenated alkenes; unsaturated nitriles such as acrylonitrile; unsaturated amides such as acrylamide and methacrylamide and their derivatives; unsaturated dicarboxylic acids such as maleic anhydride, maleic acid, and fumaric acid and their derivatives; vinyl acetates; N-vinylpyrrolidone; N-vinylcarbazole; N-substituted maleimide compounds, etc.

[0259] As for the aforementioned derivatives, they are not limited to the following, but may include, for example: alicyclic compounds having cycloalkyl, bicycloalkyl, cycloalkenyl, bicycloalkenyl, etc.; aromatic compounds having benzyl, phenyl, phenoxy, or naphthalene skeleton, anthracene skeleton, biphenyl skeleton, phenanthrene skeleton, fluorene skeleton, etc.; compounds having alkyl, haloalkyl, alkoxyalkyl, hydroxyalkyl, aminoalkyl, glycidyl, etc.; ester compounds of polyols such as alkylene glycol, polyoxyalkylene glycol, polyalkylene glycol, trimethylolpropane, etc.; and compounds having a polysiloxane structure such as polydimethylsiloxane, polydiethylsiloxane, etc.

[0260] In addition, the olefinic unsaturated compound (b-2) can be a heteroaromatic compound containing elements such as nitrogen and sulfur.

[0261] As for the above-mentioned (meth)acrylic acid and / or its derivatives, they are not limited to the following, for example, diacrylates and dimethacrylates of alkyl diols such as hexanediol and nonanediol; diacrylates and dimethacrylates of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, and butanediol; trimethylolpropane tri(meth)acrylate; dimethyloltricyclodecane di(meth)acrylate; isobornyl (meth)acrylate; phenoxy polyethylene glycol (meth)acrylate; pentaerythritol tetra(meth)acrylate, etc.

[0262] These compounds can be used alone or in combination of two or more.

[0263] From the viewpoint of preventing damage to the relief surface caused by the load when peeling off the negative after exposure, at least one type of (meth)acrylate is preferably used as the olefinic unsaturated compound (b-2), and more preferably at least one type of difunctional (meth)acrylate.

[0264] [Photopolymerization initiator (b-3)]

[0265] The photosensitive resin composition layer preferably contains a photopolymerization initiator (b-3).

[0266] Photopolymerization initiators (b-3) are compounds that absorb light energy and generate free radicals. Examples include cleavage-type photopolymerization initiators, hydrogen-abstraction-type photopolymerization initiators, and compounds that have sites within the same molecule that function as hydrogen-abstraction-type photopolymerization initiators and sites that function as cleavage-type photopolymerization initiators.

[0267] As such photopolymerization initiators (b-3), they are not limited to the following, for example, benzophenone, 4,4-bis(diethylamino)benzophenone, 3,3',4,4'-benzophenone tetracarboxylic anhydride, 3,3',4,4'-tetramethoxybenzophenone and other benzophenones; anthraquinones such as tert-butylanthraquinone, 2-ethylanthraquinone and other anthraquinones; thioxanthones such as 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone and other thioxanthones; michidone; diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, benzoylayldimethyl ketal, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propane Acetophenones such as 1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, and trichloroacetophenone; benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; acylphosphine oxides such as 2,4,6-trimethylbenzoyl diphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; methyl benzoylformate; 1,7-bisacridylheptane; 9-phenylacridinium; azo compounds such as azobisisobutyronitrile, diazo compounds, and tetrazene compounds.

[0268] These compounds can be used alone or in combination of two or more.

[0269] Regarding the content of photopolymerization initiator (b-3) in the photosensitive resin composition layer, from the viewpoint of preventing damage to the embossed surface caused by the load when peeling off the negative after exposure, when the total amount of the photosensitive resin composition layer is set to 100% by mass, it 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.

[0270] [Additional Ingredients]

[0271] As auxiliary additives, they are not limited to the following, such as plasticizers, anti-heat polymerization agents, antioxidants, light stabilizers, ultraviolet absorbers, dyes / pigments, etc.

[0272] As a plasticizer, it is not limited to the following, for example, liquid polybutadiene, liquid polyisoprene, modified liquid polybutadiene, modified liquid polyisoprene, liquid acrylonitrile-butadiene copolymer, liquid styrene-butadiene copolymer and other liquid dienes; hydrocarbon oils such as cycloalkane oil and paraffin oil; conjugated diene rubbers with liquid dienes as the main body such as liquid acrylonitrile-butadiene copolymer and liquid styrene-butadiene copolymer; polystyrene with a number average molecular weight of less than 2000; ester plasticizers such as sebacic acid ester and phthalic acid ester.

[0273] These plasticizers can contain hydroxyl or carboxyl groups. Additionally, these plasticizers can be endowed with photopolymerizable reactive groups such as (meth)acryloyl groups. The aforementioned plasticizers can be used alone or in combination of two or more.

[0274] It should be noted that, in this specification, "liquid" refers to a state in which the liquid can easily flow and deform and can solidify into a deformable shape upon cooling.

[0275] Regarding the content of plasticizer in the photosensitive resin composition layer, from the viewpoint of preventing damage to the ablation layer when peeling off the negative after exposure and dissolution into the photosensitive resin composition layer, when the total amount of the photosensitive resin composition layer is set to 100% by mass, it 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.

[0276] As an anti-heat polymerization agent and antioxidant, it can be used in substances commonly used in the field of resin materials or rubber materials, such as phenolic materials.

[0277] Regarding phenolic materials used as anti-heat polymerization agents and antioxidants, the following are not limited to: vitamin E, tetra-(methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate)methane, 2,5-di-tert-butylhydroquinone, 2,6-di-tert-butyl-p-cresol, 3,9-bis-{1,1-dimethyl-2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}-2,4,8,10-tetraoxaspiro(5,5)undecane, 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, etc.

[0278] Other anti-heat polymerization agents and antioxidants include, for example, phosphine-based materials such as triphenyl phosphite.

[0279] Anti-heat polymerization agents and antioxidants can be used alone or in combination of two or more.

[0280] As a light stabilizer and ultraviolet absorber, it is not limited to the following substances, such as well-known benzophenone compounds, salicylate compounds, acrylonitrile compounds, metal complex salt compounds, and hindered amine compounds.

[0281] Alternatively, the dyes / pigments shown below can also be used as ultraviolet absorbers.

[0282] Such light stabilizers and ultraviolet absorbers are not limited to the following substances, for example, 2-ethoxy-2'-ethyloxalyl diphenylamine, 2,2'-dihydroxy-4-methoxybenzophenone, bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-sebacate, 1,2,3-benzotriazole, etc.

[0283] Dyes / pigments are effective as a coloring method to improve visibility.

[0284] As dyes, the following are not limited to: water-soluble basic dyes, acid dyes, direct dyes, etc.; and water-insoluble sulfur dyes, oil-soluble dyes, disperse dyes, etc. Anthraquinone dyes, indigo dyes, and azo dyes are particularly preferred.

[0285] As a pigment, it is not limited to the following pigments, but may include natural pigments, synthetic inorganic pigments, and synthetic organic pigments. Examples of synthetic organic pigments include azo pigments, triphenylmethane pigments, quinoline pigments, anthraquinone pigments, and phthalocyanine pigments.

[0286] The photosensitive resin composition constituting the photosensitive resin composition layer can be manufactured by mixing the above-mentioned materials, namely polymer (b-1), olefinic unsaturated compound (b-2), photopolymerization initiator (b-3), and auxiliary additives as needed.

[0287] <Support>

[0288] In the method for manufacturing the printing plate in this embodiment, such as Figure 1 As shown, a support 3 is laminated on the liquid photosensitive resin composition layer 2.

[0289] The support material is not limited to the following, but may include, for example, polyester film, polyamide film, polyacrylonitrile film and polyvinyl chloride film.

[0290] Polyester film is preferred as the support.

[0291] Polyesters used as supports are not limited to the following, for example, polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate.

[0292] The thickness of the support is not particularly limited, but is preferably 50~300μm.

[0293] Furthermore, to improve the adhesion between the support and the aforementioned liquid photosensitive resin composition layer (described later), a specified adhesive layer may be provided on the support. There are no particular limitations on the adhesive layer; examples include those described in International Patent Publication No. 2004 / 104701, Japanese Patent No. 3094647, and Japanese Patent No. 2634429.

[0294] (Exposure process)

[0295] In the printing plate manufacturing method of this embodiment, after the above-described lamination process, as follows: Figure 1 As shown, an exposure process is performed in which active light is irradiated from the first rigid plate 11 and the second rigid plate 12 to cure the photosensitive resin composition layer 2.

[0296] In the exposure from the first rigid plate 11 side, a negative 1 with the desired printed pattern and micro-unit pattern is used as a mask, and the photosensitive resin composition layer 2 is irradiated with active light, such as ultraviolet light, to expose the pattern. At this time, the light passing through the negative 1 promotes the curing reaction of the photosensitive resin composition layer 2, causing the printed pattern 1a and micro-unit pattern 1b formed on the negative 1 to be reversed and transferred to the photosensitive resin composition layer 2, resulting in a pattern-exposed photosensitive resin composition layer.

[0297] In the printing plate manufacturing method of this embodiment, from the viewpoint of reducing the effects of bending and scattering of active light irradiated onto the photosensitive resin composition layer, the plate is configured such that the pattern-drawing side of the negative 1 is in direct contact with the liquid photosensitive resin composition layer 2.

[0298] During exposure from the second rigid plate 12 side, as needed, a negative film 4 with a desired pattern for forming the shelf layer is used as a mask for back exposure, and active light is irradiated onto the aforementioned photosensitive resin composition layer to form the shelf layer 5. For example, in the case of manufacturing a flexographic printing plate (thickness of 4 mm or more) for corrugated paper printing, in order to compensate for the relief strength in relation to the printing pressure during printing, it is preferable to form the shelf layer 5 as a base on the upper second rigid plate 12 side.

[0299] Alternatively, instead of using the negative film 4 for back exposure, a back exposure can be performed in which a uniform and thin cured resin layer (back precipitation layer) is precipitated from the side of the second rigid plate 12 across the entire surface.

[0300] Both the back-side deposition layer and the shelf layer are formed by curing the photosensitive resin composition layer on the side opposite to the side where the printed pattern is formed. When the photosensitive resin composition layer on the entire support side is cured, it becomes the back-side deposition layer; when the photosensitive resin composition layer is partially cured according to the position of the printed pattern, it becomes the shelf layer.

[0301] There are no particular limitations on the irradiation method for the active light, and a known irradiation unit can be used. The wavelength of the irradiated ultraviolet light is preferably 150-500 nm, more preferably 300-400 nm.

[0302] As a light source, it is not limited to the following, for example, 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 can be used.

[0303] (Developing process)

[0304] In the printing plate manufacturing method of this embodiment, after the exposure step, a development step is performed to remove the unexposed portion of the photosensitive resin composition layer.

[0305] There are no particular limitations on the method for removing the unexposed portion; previously known methods can be applied.

[0306] Specific methods include, for example, exposing the photosensitive resin composition layer 2 to light exposure, and then rinsing the unexposed areas with a solvent or a water-based cleaning solution; or contacting the unexposed areas with a predetermined absorbent layer to remove the absorbent layer, thereby removing the unexposed areas. Alternatively, as a pre-removal step, a doctor blade or roller can be used to remove the unexposed areas beforehand. Then, a post-exposure treatment is performed as needed to obtain the printing plate.

[0307] (Recycling process of the photosensitive resin composition in the unexposed portion)

[0308] In the printing plate manufacturing method of this embodiment, a recycling step is preferably included, in which the unexposed portions removed in the developing step are recycled to produce a new photosensitive resin composition for printing plate manufacturing. The recycled photosensitive resin composition can be reused as a photosensitive resin composition in the manufacture of a new printing plate.

[0309] By using recycled photosensitive resin compositions, waste can be reduced and material costs can also be lowered.

[0310] On the other hand, if a large amount of ablation layer dissolves and / or transfers into the recycled photosensitive resin composition, various adverse conditions such as scattering of active light may occur in the printing plate manufacturing process using the recycled photosensitive resin composition, potentially damaging the quality of the final printing plate.

[0311] According to the printing plate manufacturing method of this embodiment, in the final obtained printing plate, the dissolution and / or transfer of the ablation layer to the photosensitive resin composition layer can be suppressed, thus enabling the recovery of the photosensitive resin composition with a high yield and quality no less than that of the unused version. Therefore, even in new printing plates manufactured using the recovered photosensitive resin composition, the improved hollow depth can be maintained.

[0312] In detail, the printing plate manufacturing method of this embodiment has the following effects (1) to (4).

[0313] (1) It can inhibit the dissolution and transfer of the negative to the photosensitive resin composition layer.

[0314] (2) It can form micro-units and manufacture solid printing plates with high density and excellent image reproducibility.

[0315] (3) It can remove and recycle unexposed photosensitive resin compositions that have deteriorated and have reduced contamination, thereby preventing the deterioration of the photosensitive resin compositions and enabling the high-quality photosensitive resin compositions to be reused in high yield.

[0316] (4) In the developing process, it is possible to suppress the mixing of impurities into the unexposed photosensitive resin composition, thus enabling the selection of a wide range of developing methods.

[0317] Example

[0318] The following are specific embodiments and comparative examples to illustrate this implementation in more detail, but the present invention is not limited to any of the following embodiments.

[0319] In the examples and comparative examples described later, flexographic printing plates were prepared, and the dissolution and transfer of the negative film into the photosensitive resin composition, as well as the solidity of the flexographic printing plate were evaluated.

[0320] Manufacturing of negatives for flexographic printing plates

[0321] As described below, negative films 1 to 5 are used to manufacture flexographic printing plates.

[0322] (The making of negative 1)

[0323] <Manufacturing of Resin 1 for Negative Film 1>

[0324] After purging the polymerization vessel in a 2L separable flask with nitrogen, 456.1 mL of hexane (dried with molecular sieves) and 656.5 mL of chlorobutane (dried with molecular sieves) were added using a syringe. The polymerization vessel was then cooled in a dry ice / methanol bath at -70°C. Next, a Teflon delivery tube was connected to a pressure-resistant glass liquefaction collection tube with a three-way stopcock containing 161.1 g (2871 mmol) of isobutylene monomer, and isobutylene monomer was introduced into the polymerization vessel under nitrogen pressure. Then, 0.647 g (2.8 mmol) of p-dicumyl chloride and 1.22 g (14 mmol) of N,N-dimethylacetamide were added. Following this, 8.67 mL (79.1 mmol) of titanium tetrachloride was added, and polymerization began.

[0325] After stirring at the same temperature for 1.5 hours from the start of polymerization, about 1 mL of the polymerization solution was taken for sampling.

[0326] Next, a mixture of 77.9 g (748 mmol) of styrene monomer, 23.9 mL of n-hexane, and 34.3 mL of chlorobutane, pre-cooled to -70 °C, was added to the polymerization vessel. Forty-five minutes after the addition of the mixture, approximately 40 mL of methanol was added to complete the reaction, yielding the reaction solution.

[0327] After removing the solvent from the reaction solution by distillation, the polymer was dissolved in toluene and washed twice with water. Then, the toluene solution was added to a large amount of methanol to precipitate the polymer. The resulting polymer was then vacuum-dried at 60°C for 24 hours to obtain resin 1.

[0328] pass 1 The styrene content was determined by H-NMR and the result was 30% by mass.

[0329] <Manufacturing of Film 1 for Flexible Printing Plate Manufacturing>

[0330] Mix 6.5 parts by weight of resin 1, 54.0 parts by weight of toluene, and 36.0 parts by weight of cyclohexanone prepared as described above, and dissolve resin 1 in the solvent.

[0331] Then, 3.5 parts by weight of carbon black (Mitsubishi Chemical Corporation, #1000) were added and mixed in a bead mill for 4 hours to obtain a carbon black dispersion.

[0332] The carbon black dispersion obtained as described above was coated onto a 50 μm thick polypropylene substrate (Toyobo Co., Ltd. PYLEN P3162), resulting in a dried film thickness of 2.5 μm. The film was then dried at 90°C for 2 minutes to obtain a flexible printing plate manufacturing film 1, which serves as a laminate of an ablation layer and a substrate.

[0333] <Laser drawing of film 1 for flexographic printing plate manufacturing>

[0334] A thin film 1 for flexographic printing plate manufacturing is placed on a CDICrystal 5080 manufactured by ESKO Corporation. Under the conditions of 4000 dpi resolution and 2.4 J laser intensity, MCWSI pattern is laser-drawn on the ablation layer to obtain a negative film 1 with a printed pattern having micro-unit patterns.

[0335] (The production of Negative Film 2)

[0336] Laser ablation was performed without using micro-unit patterns, and all other conditions were set the same as those for negative 1 described above, resulting in negative 2 with a solid pattern. In Table 1 below, it is marked as "solid No MC".

[0337] (The production of Negative 3)

[0338] <Manufacturing of Film 2 for Flexible Printing Plate Manufacturing>

[0339] 6.5 parts by weight of butyral resin (PVB resin, Mowital B30H manufactured by Kuraray), 54.0 parts by weight of ethanol and 36.0 parts by weight of 1-butanol were mixed to dissolve Mowital B30H in the solvent.

[0340] Then, 3.5 parts by weight of carbon black (Mitsubishi Chemical Corporation, #1000) were added and mixed in a bead mill for 4 hours to obtain a carbon black dispersion.

[0341] The carbon black dispersion obtained as described above was coated onto a 50 μm thick polypropylene substrate (Toyobo Co., Ltd. PYLEN P3162), resulting in a dried film thickness of 2.5 μm. The film was then dried at 90°C for 2 minutes to obtain a flexible printing plate manufacturing film 2, which serves as a laminate of the ablation layer and the substrate.

[0342] <Laser drawing of film 2 for flexographic printing plate manufacturing>

[0343] A thin film 2 for flexographic printing plate manufacturing is placed on a CDICrystal 5080 manufactured by ESKO Corporation. Under the conditions of 4000dpi resolution and 3.4J laser intensity, MCWSI pattern is used to laser-draw on the ablation layer to obtain a negative film 3 with a printed pattern having micro-unit patterns.

[0344] (The production of negative 4)

[0345] Laser ablation was performed without using micro-unit patterns, and other conditions were set the same as those for negative 3 described above, resulting in negative 4 with a solid pattern. In Table 1 below, it is marked as "solid No MC".

[0346] (The production of negative 5)

[0347] The NX film (Milacron, FLEXCEL NX Thermal Imaging Layer) was placed on a Kodak Flexcel Wide-C imager and laser-drawn at a resolution of 2400 dpi using Digicap's Standard pattern.

[0348] [Photosensitive Resin Composition]

[0349] The following photosensitive resin composition is used as a photosensitive resin composition for manufacturing flexographic printing plates.

[0350] Photosensitive resin composition 1 manufactured as described below

[0351] Photosensitive resin composition 2 manufactured as described below

[0352] (Preparation of polymers for photosensitive resin compositions)

[0353] In order to prepare a photosensitive resin composition, polymer 1 and polymer 2 are first prepared as polymer (b-1).

[0354] (Polymer 1)

[0355] As a diol, 1200g of poly(3-methyl-1,5-pentanediol adipate) diol (Kuraray Corporation "KURAPOLP3010"), 800g of polyoxyethylene (EO)-oxypropylene (PO) block copolymer diol (Sanyo Chemical Industry Co., Ltd. "SANNIXPL2100"), and 0.03g of dibutyltin dilaurate were added and stirred at 40°C until homogeneous to obtain a mixture.

[0356] Add 137g of toluene diisocyanate (CORONATE T80 manufactured by Tosoh Corporation) to the obtained mixture and stir until homogeneous to obtain the mixture.

[0357] After achieving homogeneity, the mixture is heated to 80°C and reacted for 4-5 hours to prepare a prepolymer precursor with isocyanate groups at both ends.

[0358] 387g of poly(oxypropylene) glycol monomethacrylate ("BLEMMER PP" manufactured by Nippon Oil Company) was added to the obtained prepolymer precursor as a (meth)acrylating agent, and the reaction was carried out for 2 hours to obtain the reaction product.

[0359] A portion of the obtained reaction product was taken out and subjected to IR spectrophotometry to confirm the disappearance of the isocyanate group.

[0360] The polymer 1 described above was obtained as above.

[0361] (Polymer 2)

[0362] As a diol, 1300g of polyoxyethylene (EO)-oxypropylene (PO) block copolymer diol (SANNIX PL2100 manufactured by Sanyo Chemical Industries Co., Ltd.), 750g of 2,4-diethyl-1,5-pentanediol-adipic acid condensate (HS2N-521A manufactured by Toyok Oil Co., Ltd.), and 0.02g of dibutyltin dilaurate were added and stirred at 40°C until homogeneous to obtain a mixture.

[0363] Add 145g of toluene diisocyanate (CORONATE T80 manufactured by Tosoh Corporation) to the obtained mixture and stir until homogeneous to obtain the mixture.

[0364] After achieving homogeneity, the mixture is heated to 80°C and allowed to react for 4-5 hours to prepare a prepolymer precursor with isocyanate groups at both ends.

[0365] 370g of polyoxypropylene monoacrylate (Nippon Oil Company's "PPM") was added to the obtained prepolymer precursor as a (meth)acrylating agent, and the reaction was carried out for 2 hours to obtain the reaction product.

[0366] A portion of the obtained reaction product was taken out and subjected to IR spectrophotometry to confirm the disappearance of the isocyanate group.

[0367] The polymer 2 described above was obtained as described above.

[0368] (Preparation of photosensitive resin composition)

[0369] A photosensitive resin composition was prepared using polymers 1 and 2 obtained as described above.

[0370] The photosensitive resin composition constituting the photosensitive resin composition layer is manufactured by mixing polymer 1, polymer 2, olefinic unsaturated compound (b-2), photopolymerization initiator (b-3), and auxiliary additives prepared as described above.

[0371] Photosensitive resin composition 1 is prepared by using the polymer 1 described above, and photosensitive resin composition 2 is prepared by using the polymer 2 described above as follows.

[0372] <Photosensitive Resin Composition 1>

[0373] The above polymer 1 was added in the following proportions: 68.2 parts by weight; diethylene glycol (2-ethylhexyl) ether acrylate (Aronix M-120 manufactured by Toa Synthetic Co., Ltd.) as an olefinic unsaturated compound (b-2); 1.1 parts by weight of trimethylolpropane trimethacrylate (NK ESTER TMPT manufactured by Shin-Nakamura Chemical Co., Ltd.) as component (b-2); 6.3 parts by weight of dibutyl sebacate (DBS manufactured by Toyokuni Oil Co., Ltd.) as a plasticizer; 1.0 part by weight of 2,2-dimethoxy-2-phenylacetophenone (IRGACURE 651 manufactured by Ciba Specialty Chemicals Co., Ltd.) as a photopolymerization initiator (b-3); and 1.6 parts by weight of 2,6-di-tert-butyl-p-cresol (IONOL manufactured by Oxalis Chemicals Co., Ltd.) as an antioxidant. The mixture was stirred and mixed at 60°C to obtain a photosensitive resin composition.

[0374] <Photosensitive Resin Composition 2>

[0375] 65.6 parts by weight of the above polymer 2, 20.2 parts by weight of 2-(diethylamino)ethyl methacrylate ("ACRYESTER DE" manufactured by Mitsubishi Chemical Co., Ltd.) as an olefinic unsaturated compound (b-2), 7.0 parts by weight of butoxydiethylene glycol methacrylate ("LIGHT ESTER AK-8" manufactured by Kyoeisha Chemical Co., Ltd.) as component (b-2), 5.8 parts by weight of dibutyl sebacate ("DBS" manufactured by Toyokuni Oil Co., Ltd.) as a plasticizer, 1.2 parts by weight of benzophenone ("benzophenone" manufactured by Daiki Fine Co., Ltd.) as a photopolymerization initiator (b-3), and 1.8 parts by weight of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate ("HS ESTER 765" manufactured by Toyokuni Oil Co., Ltd.) as an antioxidant were added and stirred at 60°C to obtain photosensitive resin composition 2.

[0376] [Physical properties of negative film and photosensitive resin composition]

[0377] (Sp value of negative film (SpB) and Sp value of photosensitive resin composition (SpA))

[0378] The Sp value (SpB) of the negative and the Sp value (SpA) of the photosensitive resin composition were determined by turbidity point titration.

[0379] For a solution obtained by dissolving the sample to be measured in a good solvent with a known SP value, a poor solvent with a lower SP value than the good solvent is gradually added dropwise, and the volume of the poor solvent at which the solute begins to precipitate is measured. Next, for a newly prepared solution obtained by dissolving a sample with an unknown SP value in a good solvent with a known SP value, a poor solvent with a higher SP value than the aforementioned good solvent is gradually added dropwise, and the volume of the poor solvent at which the solute begins to precipitate is measured. The SP value (δ) is determined by applying the volumes of various poor solvents obtained here to the following equation (2).

[0380] SP value (δ) = (V ml 1 / 2 ·δ ml +V mh 1 / 2 ·δ mh ) / (V ml 1 / 2 +V mh 1 / 2 …(2)

[0381] Here, V ml It is the volume of poor solvents with low SP values, V mh It is the volume of poor solvents with high SP values, δ ml The SP value of a poor solvent with a low SP value is δ. mh It is the SP value of a poor solvent with a high SP value.

[0382] The following calculations were performed using good and bad solvents, and their respective SP values.

[0383] Good solvent:

[0384] Toluene (SP value: 8.9 [(cal / cm³)) 3 ) 1 / 2 ])

[0385] p-Xylene (SP value: 8.7 [(cal / cm)]) 3 ) 1 / 2 ])

[0386] Butyl acetate (SP value: 8.5 [(cal / cm)) 3 ) 1 / 2 ])

[0387] Ethyl acetate (SP value: 9.1 [(cal / cm))) 3 ) 1 / 2 ])

[0388] Acetone (SP value: 9.8 [(cal / cm)]) 3 ) 1 / 2 ])

[0389] Unsuitable solvents:

[0390] n-Hexane (SP value: 7.2 [(cal / cm)) 3 ) 1 / 2 ])

[0391] Ethanol (SP value: 12.9 [(cal / cm³)) 3 ) 1 / 2 ])

[0392] Water (SP value: 23.4 [(cal / cm³)) 3 ) 1 / 2 ])

[0393] [Characteristics Evaluation in Printing Plate Manufacturing]

[0394] (Solid Concentration)

[0395] The solidity of the printed material is measured and evaluated.

[0396] Blue ink was printed on a transparent PET film using the flexible printing plates prepared in the embodiments and comparative examples described later.

[0397] The pressure applied by the anilox roller to the flexographic printing plate, the printing pressure setting from the flexographic printing plate to the transparent film, the printing machine hardware, tools, software, motion configuration, and the processing, cleaning, surface treatment, and installation of the flexographic printing plate and the transparent PET film are all carried out under standard industrial production printing conditions.

[0398] The printing press was an AI-3 flexographic printing press manufactured by Iyo Machinery Co., Ltd. with a speed of 100 m / min, and the ink was Hydric FCF739 (manufactured by Daihatsu Seika Co., Ltd.) with a viscosity of 12 seconds as measured using a Zahn Cup #4.

[0399] The transparent PET film used is R8150 CircleClean (manufactured by Toyobo Co., Ltd.), which has a width of 330 mm and a thickness of 12 μm.

[0400] As the anilox roller, an Apex 860 LPI 5.1 cc was used, and the liquid plate was mounted using DuploFlex 5.2+ tape manufactured by Lohmann.

[0401] Next, the reflectivity of the printed material was measured, and the solidity was calculated.

[0402] Reflectance is measured using the eXact Standard, which measures reflectance optical density using a reflectance density meter (an instrument commonly used in the graphic arts field). Solid density is measured under the following conditions: color correlation value: no filter; density correlation value: no filter; density color: Cyan.

[0403] If the solid concentration is above 1.40, it is rated as good in practical use.

[0404] (Evaluation of the dissolution and transfer of negative film to the photosensitive resin composition layer)

[0405] The leaching and transfer of the negative of the flexographic printing plate prepared in the following examples and comparative examples to the photosensitive resin composition layer were evaluated using the following method.

[0406] Place each negative film in a vial filled with the photosensitive resin composition, and let it stand overnight in a constant temperature chamber at 30°C. Evaluate the film according to the following evaluation criteria. If the evaluation is A to B, it is determined that the film can be used without any practical problems.

[0407] <Evaluation Criteria>

[0408] A: No free ablation layer was observed, nor was there any contamination from the photosensitive resin composition. Furthermore, it could not be scraped off even with a spatula.

[0409] B: As long as no force is applied using a spatula or similar object, there will be no separation or contamination of the negative. However, if the ablation layer is scraped with a spatula, it will become separated.

[0410] C: Contamination of the ablation layer with free, photosensitive resin composition was confirmed.

[0411] [Printing process]

[0412] (Example 1)

[0413] Using the above-mentioned photosensitive resin composition 1 and negative film 1 as the photosensitive resin composition, a flexographic printing plate is produced by sequentially passing through a molding / exposure process, a developing process, a post-exposure process, and a drying process as described below.

[0414] <(1) Molding / Exposure Process>

[0415] Using the Asahi Kasei Corporation's "ALF-213E plate-making machine", the forming and exposure are performed through (A1)~(A3).

[0416] (A1):

[0417] The negative 1, after image depiction, is placed on the ultraviolet-transmitting lower glass plate with the ablation layer of image depiction separated from the substrate. Then, without performing the process of laminating a film on the ablation layer (hereinafter referred to as the insertion process), the negative 1 is fixed by vacuuming using a pump through a groove provided around the lower glass.

[0418] A liquid photosensitive resin composition is flowed on the negative 1, and a base film is bonded to the negative 1 with spacers to form a support, so that the base film is of a specified thickness. A negative film for back exposure is loaded on the base film, and then a layer of photosensitive resin composition is formed by pressing it on the negative film with an ultraviolet-transmitting glass plate (upper glass plate).

[0419] (A2):

[0420] After the photosensitive resin composition layer is formed, the back side is exposed by irradiating the base film with active light (light with a wavelength distribution above 300nm) using an active light source such as an ultraviolet fluorescent lamp through the upper glass plate side.

[0421] (A3):

[0422] After the back exposure process, the same active light as the upper one is irradiated from the lower glass plate side through the negative 1 after the image is drawn, and the relief forming exposure process for image formation is performed to obtain the flexible printing master.

[0423] As described above, a photosensitive resin composition layer is formed in (A1).

[0424] Next, in steps (A2) and (A3) above, the photosensitive resin composition layer is exposed to obtain a flexible printing master with a thickness of 1.7 mm and an embossing depth of 0.6 mm. Here, embossing depth refers to the length obtained by subtracting the height of the shelf layer from the plate thickness, which is a common term used to describe the depth of the embossed printed image.

[0425] To adjust the depth of the relief, adjust the exposure on the back side accordingly.

[0426] Regarding the relief exposure, at 600mJ / cm 2 The exposure conditions were carried out.

[0427] <(2) Developing process>

[0428] After the negative 1 with the image drawn was peeled off from the flexographic printing plate, the unexposed resin was removed from the flexographic printing plate using a rubber squeegee. Then, in an Asahi Kasei Corporation "AL-400W type developer" (cylindrical rotary spray type, cylinder speed: 20 rpm, spray pressure: 0.15 Pa), an aqueous solution containing 2% by mass of Asahi Kasei Corporation "APR (registered trademark) cleaning agent W-10 type" (main agent: anionic surfactant) capable of emulsifying the photosensitive resin composition, 0.5% by mass of Asahi Kasei Corporation "APR (registered trademark) surface treatment agent A-10 type" (main agent: nonionic surfactant, benzophenone), and 0.3% by mass of Asahi Kasei Corporation "defoamer SH-4" (organosilicon mixture) was prepared as the developing solution. The developing process was carried out at a liquid temperature of 40°C and a developing time of 10 minutes.

[0429] After development, rinse with tap water until the foam caused by the developer disappears.

[0430] <(3) Post-exposure process>

[0431] The Asahi Kasei Corporation's "AL-200UP Post-Exposure Machine," equipped with both ultraviolet fluorescent lamps and germicidal lamps, is used for post-exposure via underwater exposure.

[0432] The exposure levels from various light sources on the surface of the photosensitive resin composition become ultraviolet fluorescent lamps: 2000 mJ / cm². 2 Germicidal lamp: 2000mJ / cm 2 Exposure time is determined by the exposure period.

[0433] <(4) Drying process>

[0434] Using the "ALF-DRYER" manufactured by Asahi Kasei Corporation, the post-exposed plate was dried for about 30 minutes until the moisture on its surface disappeared, thus obtaining the flexible printing plate of Example 1.

[0435] (Example 2)

[0436] Use negative 3.

[0437] Other conditions are the same as those described above (Example 1), and a flexographic printing plate is made.

[0438] (Example 3)

[0439] The photosensitive resin composition 2 is used as the photosensitive resin composition.

[0440] Other conditions are the same as those described above (Example 1), and a flexographic printing plate is made.

[0441] (Example 4)

[0442] Use negative 3.

[0443] The photosensitive resin composition 2 is used as the photosensitive resin composition.

[0444] Other conditions are the same as those described above (Example 1), and a flexographic printing plate is made.

[0445] (Comparative Example 1)

[0446] Use negative 2.

[0447] Other conditions are the same as those described above (Example 1), and a flexographic printing plate is made.

[0448] (Comparative Example 2)

[0449] An insertion process is performed on which a thin film (CF-92 manufactured by Asahi Kasei Corporation) is laminated onto the ablation layer.

[0450] Other conditions are the same as those described above (Example 1), and a flexographic printing plate is made.

[0451] (Comparative Example 3)

[0452] Use negative 5.

[0453] Other conditions are the same as those described above (Example 1), and a flexographic printing plate is made.

[0454] (Comparative Example 4)

[0455] Use negative 5.

[0456] An insertion process is performed on which a thin film (CF-92 manufactured by Asahi Kasei Corporation) is laminated onto the ablation layer.

[0457] Other conditions are the same as those described above (Example 1), and a flexographic printing plate is made.

[0458] (Comparative Example 5)

[0459] Use negative 4.

[0460] Other conditions are the same as those described above (Example 1), and a flexographic printing plate is made.

[0461] (Comparative Example 6)

[0462] Use negative 3.

[0463] An insertion process is performed on which a thin film (CF-92 manufactured by Asahi Kasei Corporation) is laminated onto the ablation layer.

[0464] Other conditions are the same as those described above (Example 1), and a flexographic printing plate is made.

[0465] (Comparative Example 7)

[0466] Use negative 2.

[0467] The photosensitive resin composition 2 is used as the photosensitive resin composition.

[0468] Other conditions are the same as those described above (Example 1), and a flexographic printing plate is made.

[0469] (Comparative Example 8)

[0470] Use negative 5.

[0471] The photosensitive resin composition 2 is used as the photosensitive resin composition.

[0472] Other conditions are the same as those described above (Example 1), and a flexographic printing plate is made.

[0473] [Table 1]

[0474]

[0475] As shown in Table 1, in the embodiments, no ablation layer was used for the dissolution and transfer of the photosensitive resin composition, resulting in a flexographic printing plate with a high solid concentration.

[0476] This application is based on Japanese Patent Application No. 2023-220270, filed with the Japan Patent Office on December 27, 2023, the contents of which are incorporated herein by reference.

[0477] Industrial availability

[0478] This invention has industrial applicability in a wide range of general commercial printing fields.

[0479] Explanation of reference numerals in the attached figures

[0480] 1 Negative

[0481] 1a Printed pattern

[0482] 1b Micro-unit Pattern

[0483] 2. Photosensitive resin composition layer

[0484] 2b microcell

[0485] Pattern 2a

[0486] 3. Support

[0487] 4. Negative film for back exposure

[0488] 4a Pattern for forming shelf layers

[0489] 5 shelf layers

[0490] 11 First Hardboard

[0491] 12 Second hardboard

[0492] 21 Substrate

[0493] 22 Ablation layer

Claims

1. A method for manufacturing a printing plate, comprising the following steps: In the lamination process, a negative film with a micro-unit pattern, a liquid photosensitive resin composition layer, a support, and a second rigid plate located above are sequentially laminated on a first rigid plate located below; and In the exposure process, active light is irradiated from the first and second rigid plate sides to cure the photosensitive resin composition layer. In the lamination process, the photosensitive resin composition layer is directly laminated onto 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 following relationship: (I) |SpA-SpB|≥2.0 …(I).

2. The method for manufacturing a printing plate according to claim 1, wherein, As a preceding step in the lamination process, a drawing step is included to form a micro-unit pattern on the negative film. In the drawing process, at least one of the following methods is used: ablation, thermal method, inkjet method, and silver halide method.

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 is less than 10.

0.

6. The method for manufacturing a printing plate according to claim 1, wherein, The negative film comprises a resin having structural units represented by the following general formula (II), In formula (II), R1 and R2 independently represent nonpolar groups, and R3 and R4 independently represent hydrogen atoms or nonpolar groups.

7. The method for manufacturing a printing plate according to claim 6, wherein, In formula (II), R1 and R2 are each independently selected from the group consisting of alkyl, alkenyl, and alkynyl groups. R3 and R4 are each independently selected from the group consisting of hydrogen atoms, alkyl groups, alkenyl groups, and alkynyl groups.

8. The method for manufacturing a printing plate according to claim 6, wherein, In formula (II), R1 and R2 are each independently an alkyl group, and R3 and R4 are each independently a hydrogen atom or an alkyl group.

9. The method for manufacturing a printing plate according to claim 6, wherein, The resin having the structural unit shown in general formula (II) also contains structural units derived from monovinyl substituted aromatic hydrocarbons.

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 their modifiers or partial saponifications.

11. The method for manufacturing a printing plate according to claim 1, wherein, Following the exposure step, a developing step is performed to remove the unexposed portions of the photosensitive resin composition layer. It also includes a recycling process for recovering the unexposed portions removed in the developing process and producing a new photosensitive resin composition for printing plate manufacturing.

12. A method for manufacturing a printing plate, comprising the following steps: In the lamination process, a negative film with a micro-unit pattern, a liquid photosensitive resin composition layer, a support, and a second rigid plate located above are sequentially laminated on a first rigid plate located below; and In the exposure process, active light is irradiated from the first and second rigid plate sides to cure the photosensitive resin composition layer. In the lamination process, the photosensitive resin composition layer is directly laminated onto the negative film. The solubility parameter SpB of the negative film is 13.0 or higher.

13. A method for manufacturing a printing plate, comprising the following steps: In the lamination process, a negative film with a micro-unit pattern, a liquid photosensitive resin composition layer, a support, and a second rigid plate located above are sequentially laminated on a first rigid plate located below; and In the exposure process, active light is irradiated from the first and second rigid plate sides to cure the photosensitive resin composition layer. In the lamination process, the photosensitive resin composition layer is directly laminated onto the negative film. The solubility parameter SpB of the negative film is below 9.0.

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