Flexographic printing plate manufacturing method

Abstract

The present invention provides a flexographic printing plate production method for achieving both desired recess depth and reproducibility of independent dots by increasing a hardened area around the respective independent dots and resolving the problem of insufficient depth of the recesses. This flexographic printing plate production method comprises: an exposure step for subjecting a flexographic original plate, which is at least sequentially equipped with a support, a photosensitive layer, and a mask portion having an image formed thereon, to irradiation with energy rays via the mask portion to expose the photosensitive layer; and a development step for removing unexposed portions of the photosensitive layer. The exposure step comprises a step for performing irradiation with energy rays in a state in which the mask portion and a film-like optical element are located, in this sequence from the photosensitive layer side, between an energy ray source and the photosensitive layer. The film-like optical element is an element that converges incoming energy rays to enhance directivity of the energy rays and emits the energy rays onto the mask portion.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a flexographic printing plate using a film-like optical element during exposure. [Background technology]

[0002] Flexographic printing is a printing method in which ink is applied to raised portions of a printing plate using an anilox roll or the like and then transferred to a substrate. Flexographic printing plates used in flexographic printing include, for example, flexographic printing plate precursors having a photosensitive layer that have been imagewise exposed and developed. Various methods are known for manufacturing flexographic printing plates. For example, Patent Document 1 describes a method for manufacturing a flexographic printing plate.

[0003] In Patent Document 1, ultraviolet light is irradiated from the substrate side of the flexographic printing plate precursor (back exposure) to form a relief image in the photosensitive layer of the flexographic printing plate precursor. The ultraviolet light can be irradiated by a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a xenon lamp, a carbon arc lamp, a chemical lamp, an LED (Light Emitting Diode), or the like, which is capable of irradiating light with a wavelength of 300 to 400 nm. When an analogue flexographic printing plate precursor is used, the protective film is peeled off and a negative film on which an image has been formed is placed in close contact with the exposed anti-adhesive layer. On the other hand, when an LAM (laser ablation mask) flexographic printing plate precursor is used, the protective film is peeled off and the exposed infrared ablation layer is irradiated with an infrared laser to form a desired image. Next, the photosensitive layer is hardened by irradiating ultraviolet light from above the negative film or infrared ablation layer (main exposure). The irradiated portions of the photosensitive layer are hardened by ultraviolet light. The photosensitive layer covered with the negative film or infrared ablation layer has hardened portions irradiated with ultraviolet light and unhardened portions not irradiated with ultraviolet light. The unhardened portions of the photosensitive layer are then removed in a developer to form a relief image. The printing plate material is then removed from the developer and dried, or heated and brought into contact with a nonwoven fabric, where the unhardened portions are transferred to the nonwoven fabric and removed. If necessary, the entire printing plate material is irradiated with ultraviolet light (post-exposure). This produces a flexographic printing plate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 130784 Summary of the Invention [Problem to be solved by the invention]

[0005] In the method for manufacturing a flexographic printing plate disclosed in Patent Document 1, scattered light is used for exposing a flexographic printing plate precursor. When scattered light is used for exposure, halation hardens the photosensitive layer of the flexographic printing plate precursor, resulting in insufficient recess depth. Furthermore, when collimated light is used for exposure, the hardened area around the isolated dots in the photosensitive layer becomes smaller, and the isolated dots tend to disappear during development. As a result, the reproducibility of the isolated dots on the flexographic printing plate deteriorates. An object of the present invention is to provide a method for manufacturing a flexographic printing plate that achieves both sufficient recess depth and reproducibility of the isolated small dots by increasing the hardened region around the isolated small dots and eliminating the need for insufficient recess depth. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, one aspect of the present invention provides a method for producing a flexographic printing plate, which includes an exposure step in which a flexographic printing plate precursor having at least a support, a photosensitive layer, and a mask portion on which an image is formed, in this order, is irradiated with energy rays through the mask portion to expose the photosensitive layer, and a development step in which the unexposed portion of the photosensitive layer is removed, wherein the exposure step includes a step of irradiating with energy rays from the photosensitive layer side in a state in which the mask portion and a film-like optical element are present in this order between the energy ray source and the photosensitive layer, and the film-like optical element is an element that converges the incident energy rays, increases the directivity, and emits them toward the mask portion.

[0007] The energy rays are preferably ultraviolet light. The film-like optical element is preferably a prism sheet or a lenticular lens. The film-like optical element is preferably made of glass. The film-like optical element is preferably made of resin. [Effects of the Invention]

[0008] According to the present invention, a flexographic printing plate can be obtained that achieves both a good recess depth and good reproducibility of isolated small dots. [Brief explanation of the drawings]

[0009] [Figure 1] 1A to 1C are schematic diagrams illustrating an example of a method for producing a flexographic printing plate according to an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic cross-sectional view illustrating an example of a flexographic printing plate precursor used in a method for producing a flexographic printing plate according to an embodiment of the present invention. [Figure 3] FIG. 2 is a schematic cross-sectional view showing another example of a flexographic printing plate precursor used in the method for producing a flexographic printing plate according to an embodiment of the present invention. [Figure 4] 1A to 1C are schematic cross-sectional views illustrating a method for manufacturing a mask portion of an example of a flexographic printing plate precursor used in a method for manufacturing a flexographic printing plate according to an embodiment of the present invention. [Figure 5]FIG. 1 is a schematic cross-sectional view showing a mask portion of an example of a flexographic printing plate precursor used in a method for producing a flexographic printing plate according to an embodiment of the present invention. [Figure 6] FIG. 4 is a schematic cross-sectional view showing a state before a mask portion is formed on another example of a flexographic printing plate precursor used in the method for producing a flexographic printing plate according to an embodiment of the present invention. [Figure 7] FIG. 1 is a schematic cross-sectional view showing the depth of recesses when scattered light is used for exposing a flexographic printing plate precursor. [Figure 8] FIG. 1 is a schematic cross-sectional view showing an isolated small dot when scattered light is used for exposing a flexographic printing plate precursor. [Figure 9] FIG. 10 is a schematic cross-sectional view showing the depth of recesses when completely collimated light is used to expose a flexographic printing plate precursor. [Figure 10] FIG. 1 is a schematic cross-sectional view showing an isolated small dot when fully collimated light is used to expose a flexographic printing plate precursor. [Figure 11] 3A to 3C are schematic cross-sectional views showing the depth of recesses formed by a method for producing a flexographic printing plate according to an embodiment of the present invention. [Figure 12] 1 is a schematic cross-sectional view showing an isolated small dot formed by a method for producing a flexographic printing plate according to an embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the method for producing a flexographic printing plate of the present invention will be described in detail based on the preferred embodiment shown in the accompanying drawings. It should be noted that the drawings described below are illustrative for explaining the present invention, and the present invention is not limited to the drawings shown below. In the following, the range of values ​​indicated by "~" includes the values ​​written on both sides. For example, when ε is the value ε α ~number ε β That is, the range of ε is the number ε α and the number ε β The range includes ε α ≦ε≦ε β is. Unless otherwise specified, angles such as "parallel" and "perpendicular" include a generally acceptable error range in the relevant technical field. Each component may be used alone or in combination of two or more. When two or more components are used in combination, the content of the components refers to the total content unless otherwise specified. In addition, "(meth)acrylic" is a notation that represents "acrylic" or "methacrylic", "(meth)acrylate" is a notation that represents "acrylate" or "methacrylate", and "(meth)acryloyl" is a notation that represents "acryloyl" or "methacryloyl".

[0011] [Flexographic printing plate manufacturing method] FIG. 1 is a schematic diagram showing an example of a method for producing a flexographic printing plate according to an embodiment of the present invention. As shown in FIG. 1, the method for producing a flexographic printing plate uses a flexographic printing plate precursor 10 having at least a support 20, a photosensitive layer 22, and a mask portion 24 on which an image is formed, in that order. The method for producing a flexographic printing plate includes an exposure step of irradiating the above-mentioned flexographic printing plate precursor 10 with energy rays through the mask portion 24, and a development step of removing the unexposed portions of the photosensitive layer 22.

[0012] (Exposure process) In the exposure step, the mask portion 24 and the film-like optical element 14 are present in this order from the photosensitive layer 22 side between the energy ray source 12 and the photosensitive layer 22, and energy rays Le are irradiated from the mask portion 24 side. The film optical element 14 is an element that converges the incident energy rays Le to enhance their directivity and emits light with adjusted directivity. When scattered light is incident on the film optical element 14, the film optical element 14 emits light that has a larger amount of parallel components than the scattered light as output light. This allows exposure to be performed using light that has a larger amount of collimated light components. The light emitted by the film optical element 14, i.e., the light used for exposure, is light whose directivity has been adjusted as described above. The light emitted by the film optical element 14 contains a collimated light component, but may also contain scattered light, and the emitted light is not limited to collimated light.

[0013] As shown in FIG. 1, a film-like optical element 14 is disposed on a mask portion 24 of a flexographic printing plate precursor 10, and an energy ray source 12 is disposed on the film-like optical element 14. The flexographic printing plate precursor 10 is made into a flexographic printing plate through an exposure step and a development step. The flexographic printing plate has an image area and a non-image area. The flexographic printing plate precursor 10 will be described later.

[0014] [Energy ray source] The energy ray source 12 irradiates energy rays Le for exposing the photosensitive layer 22 of the flexographic printing plate precursor 10. As the energy ray source 12, a ray source according to the energy ray Le to be irradiated is appropriately used. The energy rays Le are preferably ultraviolet light because a system can be constructed relatively inexpensively. Ultraviolet light has a wavelength of, for example, 100 to 400 nm. When the energy rays Le are ultraviolet light, a light source that irradiates ultraviolet light is used as the energy ray source 12. For example, the energy ray source 12 that irradiates ultraviolet light can typically be a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a xenon lamp, a carbon arc lamp, a chemical lamp, or an LED, all of which are capable of irradiating light with a wavelength of 300 to 400 nm. Furthermore, a reflecting mirror may be used to effectively utilize the light components reflected by the film optical element 14. In this case, it is preferable that the energy ray source be disposed between the reflecting mirror and the film optical element 14. In the exposure step, since the film-like optical element 14 is used, scattered light can be used for the energy rays Le, and there is no need to control the directivity of the energy rays Le, such as by making them parallel.

[0015] (Film-type optical element) The film-like optical element 14 allows the energy rays Le irradiated from the energy ray source 12 to pass through the mask portion 24 and irradiate the photosensitive layer 22 with the energy rays Le via the mask portion 24 . The film optical element 14 has a film shape and is an element that changes the characteristics of light when light passes through it from one surface to the other. As described above, the film optical element 14 is an element that converges the incident energy rays Le, increases the directivity, and emits the energy rays Le. Therefore, when scattered light is incident on the film optical element 14, the scattered light is converged, the directivity is increased, and the light is made appropriately parallel, and is emitted as light close to collimated light. The energy beam Le can be converged using, but not limited to, a prism or a lens, for example, by refracting light. Directivity refers to the spread of light. High directivity means that light does not spread. An example of highly directional light is laser light. The collimated light is light that is incident in a direction perpendicular to the surface of the flexographic printing plate precursor 10 .

[0016] The film optical element 14 is preferably one that has the property of increasing the directivity of the scattered light to a directivity close to that of collimated light when the scattered light passes through as the energy ray Le. In other words, the film optical element 14 is preferably one that has the property of changing the directivity of the incident light to a directivity close to that of parallel light. It is preferable that the film optical element 14 has the property of not absorbing the energy rays Le. This allows the energy rays Le to be used effectively for exposure.

[0017] Specifically, the film-like optical element 14 is preferably a prism sheet, a lenticular lens, or the like, because of its ability to enhance the directivity of incident energy rays. The prism sheet is a parallel prism plate in which a plurality of prisms extending in one direction are arranged on a plane with their extending directions aligned. A lenticular lens is a flat surface on which cylindrical lenses are arranged. The film optical element 14 may be a single element or multiple elements. The number of film optical elements 14 is determined appropriately depending on the characteristics of the light emitted from the film optical element 14. For example, in the case of a prism sheet, two prism sheets can be stacked with the prisms extending in directions perpendicular to each other. In the case of a lenticular lens, two lenticular lenses can be stacked with the cylindrical lenses extending in directions perpendicular to each other.

[0018] The film-like optical element 14 is made of, for example, glass. As the glass, glass used in manufacturing microlens arrays and the like can be appropriately used, and optical glass, quartz glass, or the like can be used. It is preferable that the glass has the property of not absorbing light in the wavelength range of the energy beam Le used for exposure. This allows the energy beam Le to be used effectively for exposure. When the film optical element 14 is made of resin, the film optical element 14 is formed by, for example, thermal polymerization or melt molding. When the film-like optical element 14 made of resin is formed by thermal polymerization, it is preferable that the resin be one that is polymerized by addition polymerization, and for example, acrylic resin, polyvinyl chloride, polyacrylonitrile, polystyrene, or ABS resin (a general term for copolymer synthetic resins of acrylonitrile, butadiene, and styrene), etc. can be used. When the film-like optical element 14 made of resin is formed by melt molding, there are no particular limitations on the polymerization method for the resin, but for example, acrylic resin, polyvinyl chloride, polycarbonate, polyethylene terephthalate, polyacrylonitrile, polystyrene, polypropylene, or ABS resin can be used. The thermally polymerized resin and melt-molded resin that form the film-like optical element 14 preferably have the property of not absorbing light in the wavelength range of the energy beam Le used for exposure, thereby enabling the energy beam Le to be used effectively for exposure.

[0019] The film optical element 14 can also be formed from a resin that is cured with ultraviolet light using an initiator that has absorption in the ultraviolet wavelength range different from the wavelength range of the energy rays Le. Resins that are UV-cured using an initiator that has absorption in the ultraviolet wavelength range different from the wavelength range of the energy rays Le include, for example, acrylic resin, polyvinyl chloride, polyacrylonitrile, polystyrene, ABS resin, and the like.

[0020] (Configuration of flexographic printing plate precursor) Figure 2 is a schematic cross-sectional view showing one example of a flexographic printing plate precursor used in the method for producing a flexographic printing plate according to an embodiment of the present invention, and Figure 3 is a schematic cross-sectional view showing another example of a flexographic printing plate precursor used in the method for producing a flexographic printing plate according to an embodiment of the present invention. In Figures 2 and 3, the same components as those in the flexographic printing plate precursor 10 shown in Figure 1 are designated by the same reference numerals, and detailed description thereof will be omitted. Note that, in the present invention, the configuration of the flexographic printing plate precursor is not limited to that shown below. The flexographic printing plate precursor 10a shown in Figure 2 is an example of an analog flexographic printing plate precursor. The flexographic printing plate precursor 10a is in a form to be subjected to exposure and has a mask portion 24. In the flexographic printing plate precursor 10a, a pattern representing an image is formed in the mask portion 24. In other words, the image is formed in the mask portion 24. The flexographic printing plate precursor 10a has an adhesive layer 21 and a photosensitive layer 22 disposed in this order on a support 20. An infrared ablation layer 32, an adhesive layer 34, and a carrier sheet 35 disposed in this order on a surface 22a of the photosensitive layer 22. The infrared ablation layer 32, the adhesive layer 34, and the carrier sheet 35 on the surface 22a of the photosensitive layer 22 form a mask portion 24.

[0021] The infrared ablation layer 32 is a layer that can remove portions irradiated with an infrared laser, and also has the function of blocking the transmission of ultraviolet light at a practical level. A pattern representing an image is formed in the infrared ablation layer 32, and the infrared ablation layer 32 has openings 33 based on the pattern. The mask portion 24 on which the image is formed has the infrared ablation layer 32 having openings 33 based on the pattern representing the image. Note that the infrared ablation layer 32 may be replaced with a negative film. In the flexographic printing plate precursor 10a, the film-like optical element 14 is placed on the surface 35a of the carrier sheet 35 and exposed. The adhesive layer 21 and the adhesive layer 34 are, for example, an optically transparent adhesive (OCA). The carrier sheet 35 is, for example, a PET (polyethylene terephthalate) film.

[0022] The flexographic printing plate precursor 10b shown in Figure 3 is an example of a flexographic printing plate precursor of the LAM system. The flexographic printing plate precursor 10b is in a form to be subjected to exposure and has a mask portion 24. In the flexographic printing plate precursor 10b, a pattern representing an image is formed in the mask portion 24. That is, the image is formed in the mask portion 24. The flexographic printing plate precursor 10b has an adhesive layer 21 and a photosensitive layer 22 disposed in this order on a support 20. An infrared ablation layer 32 is disposed on a surface 22a of the photosensitive layer 22. The infrared ablation layer 32 on the surface 22a of the photosensitive layer 22 constitutes a mask portion 24. The infrared ablation layer 32 has a pattern representing an image formed thereon, and the infrared ablation layer 32 has openings 33 based on the pattern representing the image.

[0023] The pattern of the mask portion 24 of the flexographic printing plate precursor 10a shown in FIG. 2 is formed, for example, as follows. As shown in Fig. 4, a laminate 25 in which an adhesive layer 34 and an infrared ablation layer 32 are laminated in this order on a carrier sheet 35 is subjected to pattern exposure using infrared rays from the side of the infrared ablation layer 32. This results in a mask portion 24 in which openings 33 based on a pattern representing an image are formed in the infrared ablation layer 32, as shown in Fig. 5. The surface 32a of the infrared ablation layer 32 of the mask portion 24 shown in Fig. 5 is bonded to the surface 22a of the photosensitive layer 22 shown in Fig. 2, thereby obtaining a flexographic printing plate precursor 10a to be subjected to the exposure step shown in Fig. 2. Here, Fig. 4 is a schematic cross-sectional view showing a method for manufacturing a mask portion of an example of a flexographic printing plate precursor used in the method for manufacturing a flexographic printing plate according to an embodiment of the present invention, and Fig. 5 is a schematic cross-sectional view showing a mask portion of an example of a flexographic printing plate precursor used in the method for manufacturing a flexographic printing plate according to an embodiment of the present invention. In Fig. 4 and Fig. 5, the same components as those in the flexographic printing plate precursor 10a shown in Fig. 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

[0024] The flexographic printing plate precursor 10b shown in Fig. 3 is provided with a protective sheet 37 before exposure, as shown in Fig. 6. During exposure, the protective sheet 37 is peeled off, and the infrared ablation layer 32 is pattern-exposed using infrared rays from the infrared ablation layer 32 side. This results in a mask portion 24 in which openings 33 based on the pattern representing the image are formed in the infrared ablation layer 32, as shown in Fig. 3. The protective sheet 37 is, for example, a PET film. Here, Fig. 6 is a schematic cross-sectional view showing the state before the formation of the mask portion of another example of a flexographic printing plate precursor used in the method for manufacturing a flexographic printing plate according to an embodiment of the present invention. In Fig. 6, the same components as those in the flexographic printing plate precursor 10b shown in Fig. 3 are designated by the same reference numerals, and detailed description thereof will be omitted.

[0025] (Development process) By the exposure step, the exposed areas of the photosensitive layer 22 are hardened and exist as hardened areas, while the unexposed areas are not hardened and exist as unhardened areas. After the development step, the exposed areas become image areas, and the unexposed areas become non-image areas. In the development process, the unexposed areas of the photosensitive layer are removed in a developer to obtain the exposed areas, i.e., the image areas. The developer used is an organic solvent or a water-based developer (aqueous developer). Aqueous developers are water to which surfactants and pH (hydrogen ion exponent) adjusters, etc., are added as needed. For example, the unexposed areas of the photosensitive layer are removed by washing them out using a spray-type developing device or a brush-type washer. The flexographic printing plate precursor is then removed from the developer and dried. For the development process, thermal development can be used, in which the uncured part is transferred to the nonwoven fabric by applying heat after contact with the nonwoven fabric. Since thermal development does not use a developer, drying is not required. Next, the entire dried flexographic printing plate precursor is irradiated with ultraviolet light (post-exposure) as needed, thereby obtaining a flexographic printing plate having image areas and non-image areas. It should be noted that a flexographic printing plate precursor developed using a water-based developer is prone to scattering light, and therefore, as described above, it is more preferable to use a film-like optical element 14 in the exposure step.

[0026] (recess depth and independent small points) The recess depth and the isolated small dots in the exposure process will be described below. Fig. 7 is a schematic cross-sectional view showing the recess depth when scattered light is used to expose a flexographic printing plate precursor, and Fig. 8 is a schematic cross-sectional view showing an isolated small dot when scattered light is used to expose a flexographic printing plate precursor. Fig. 9 is a schematic cross-sectional view showing the recess depth when fully collimated light is used to expose a flexographic printing plate precursor, and Fig. 10 is a schematic cross-sectional view showing an isolated small dot when fully collimated light is used to expose a flexographic printing plate precursor. In Figs. 7 to 10, the same components as those in the flexographic printing plate precursor 10 shown in Fig. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. When scattered light is used in the exposure process, halation reduces the bottom area of ​​the unexposed portion 23b below the infrared ablation layer 32 in the photosensitive layer 22, as shown in FIG. 7, and the recess depth becomes insufficient. 8, in the opening 33 corresponding to the isolated small dot, the exposed portion 23a below the opening 33 in the photosensitive layer 22 becomes larger due to halation, and the isolated small dot is unlikely to disappear from the exposed portion 23a during development. However, if scattered light is used in the exposure process, the recess depth becomes insufficient.

[0027] When completely collimated light is used in the exposure process, the unexposed portion 23b below the infrared ablation layer 32 in the photosensitive layer 22 becomes larger, as shown in FIG. 9, and a recess depth is obtained. Furthermore, when fully collimated light is used, the bottom area of ​​the exposed portion 23a below the opening 33 in the photosensitive layer 22, which corresponds to the isolated small dot as shown in Figure 10, becomes smaller, and the exposed portion 23a is likely to disappear as an isolated small dot during development. As a result, the reproducibility of the isolated small dot on the flexographic printing plate deteriorates. Note that fully collimated light is light that is composed of collimated light and contains almost no scattered light.

[0028] Fig. 11 is a schematic cross-sectional view showing the recess depth obtained by the method for producing a flexographic printing plate according to an embodiment of the present invention, and Fig. 12 is a schematic cross-sectional view showing an isolated small dot obtained by the method for producing a flexographic printing plate according to an embodiment of the present invention. In Fig. 11 and Fig. 12, the same components as those in the flexographic printing plate precursor 10 shown in Fig. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. In the exposure step, a film optical element 14 is used. By using the film optical element 14, for example, when ultraviolet light in a scattered light state is used for exposure, the ultraviolet light incident on the film optical element 14 is converged relative to the mask portion 24, increasing its directivity, and the photosensitive layer 22 is exposed to the light with adjusted directivity. As a result, as shown in Fig. 11, in the photosensitive layer 22, exposed portions 23a are formed below the openings 33 in the infrared ablation layer 32, and unexposed portions 23b are formed below the infrared ablation layer 32. The exposed portions 23a become cured portions, and the unexposed portions 23b become uncured portions. The development process removes the unexposed portions 23b of the photosensitive layer 22, leaving the exposed portions 23a. Because the energy rays Le used for exposure are light with adjusted directionality, halation is suppressed compared to when scattered light is used, and a recess depth sufficient for practical use can be obtained.

[0029] 12, in the case of an opening 33 corresponding to an isolated small dot, an exposed portion 23a is formed in the photosensitive layer 22 below the opening 33, and an unexposed portion 23b is formed below the infrared ablation layer 32. The unexposed portion 23b of the photosensitive layer 22 is removed in the development process, leaving the exposed portion 23a. Because the energy beam Le used for exposure is light with adjusted directionality, the exposed portion 23a is less likely to lose its isolated small dot form during development compared to when fully collimated light is used, and as a result, the reproducibility of the isolated small dots on the flexographic printing plate is better than when fully collimated light is used. In this way, the method for manufacturing a flexographic printing plate can eliminate the insufficient recess depth and increase the exposed area by exposing the area around the isolated small dots, i.e., by increasing the hardened area, thereby achieving both recess depth and reproducibility of the isolated small dots.

[0030] The flexographic printing plate precursor will be described in more detail below. Note that, in the present invention, the flexographic printing plate precursor is not limited to those shown below. [Flexographic printing plate precursor] A flexographic printing plate precursor (hereinafter also referred to as a "printing plate precursor") contains a binder, a monomer, and a photopolymerization initiator.

[0031] First, the photosensitive layer of the printing plate precursor will be described below.

[0032] [Photosensitive layer] The photosensitive layer of the printing plate precursor (hereinafter also referred to as "photosensitive layer") contains a binder, a monomer, and a photopolymerization initiator. Each component contained in the photosensitive layer will be described below.

[0033] <Binder> The binder contained in the photosensitive layer is not particularly limited, and examples thereof include thermoplastic polymers. The thermoplastic polymer is not particularly limited as long as it is a polymer that exhibits thermoplasticity, and specific examples thereof include polystyrene resin, polyester resin, polyamide resin, polysulfone resin, polyethersulfone resin, polyimide resin, acrylic resin, acetal resin, epoxy resin, polycarbonate resin, rubber, thermoplastic elastomer, etc. These may be used alone or in combination of two or more. Among these, rubber and thermoplastic elastomers are preferred, rubber is more preferred, and diene rubber is even more preferred, because they make it easier to form a soft and flexible film.

[0034] The rubber is preferably a non-flowable rubber, which does not have flowability, in order to ensure the elasticity of the flexographic printing plate precursor. Specific examples include butadiene rubber (BR), nitrile rubber (NBR), acrylic rubber, epichlorohydrin rubber, urethane rubber, isoprene rubber, styrene-isoprene rubber, styrene-butadiene rubber (SBR), ethylene-propylene copolymer, chlorinated polyethylene, etc. These may be used alone or in combination of two or more. Among these, at least one rubber selected from the group consisting of butadiene rubber (BR), styrene-butadiene rubber (SBR), and nitrile rubber (NBR) is preferred from the viewpoint of better water developability, drying properties, and image reproducibility, and butadiene rubber and styrene-butadiene rubber are more preferred from the viewpoint of water-based ink resistance.

[0035] Examples of the thermoplastic elastomer include PB (polybutadiene-based thermoplastic elastomer), polyisoprene-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, and acrylic-based thermoplastic elastomer. Specific examples include SB (polystyrene-polybutadiene), SBS (polystyrene-polybutadiene-polystyrene), SIS (polystyrene-polyisoprene-polystyrene), SEBS (polystyrene-polyethylene / polybutylene-polystyrene), ABS (acrylonitrile butadiene styrene copolymer), ACM (acrylic acid ester rubber), ACS (acrylonitrile-chlorinated polyethylene styrene copolymer), acrylonitrile styrene copolymer, syndiotactic 1,2-polybutadiene, polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate, etc. Among these, PB, SBS, and SIS are particularly preferred because of their improved water developability and from the viewpoints of drying properties and image reproducibility.

[0036] The content of the binder is preferably from 1 to 50% by mass, more preferably from 5 to 40% by mass, and even more preferably from 7 to 30% by mass, based on the total mass of the solid content of the photosensitive layer.

[0037] <Monomer> As described above, the photosensitive layer of the present invention contains a monomer. The monomer is not particularly limited, but monofunctional monomers, bifunctional monomers, or monomers having higher functional groups may be used alone or in combination, because this will result in better effects of the present invention.

[0038] (monofunctional monomer) The monofunctional monomer is preferably a compound having one ethylenically unsaturated group, because this provides better effects of the present invention, etc. Specific examples of the ethylenically unsaturated group are as described above.

[0039] Examples of compounds having one ethylenically unsaturated group include: N-vinyl compounds such as N-vinylformamide; (meth)acrylamide compounds such as (meth)acrylamide, N-methylol (meth)acrylamide, diacetone (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, (meth)acryloylmorpholine, and (meth)acrylamide; 2-Hydroxyethyl (meth)acrylate, Butoxyethyl (meth)acrylate, Carbitol (meth)acrylate, Cyclohexyl (meth)acrylate, Tetrahydrofurfuryl (meth)acrylate, Benzyl (meth)acrylate, Tridecyl (meth)acrylate, 2-Phenoxyethyl (meth)acrylate, Glycidyl (meth)acrylate, Isobornyl (meth)acrylate, Dicyclopentenyl (meth)acrylate, Dicyclopentenyloxyethyl (meth)acrylate, Dicyclopentanyl (meth)acrylate, 2-Hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl phthalate, Methoxy-Polyethylene Glycol (meth)acrylate, 2-(meth)acryloyloxyethyl (meth)acrylate compounds such as ethyl-2-hydroxyethyl phthalate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethoxylated phenyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, nonylphenol EO adduct (meth)acrylate, phenoxy-polyethylene glycol (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalate, lactone-modified (meth)acrylate, stearyl (meth)acrylate, isoamyl (meth)acrylate, isomyristyl (meth)acrylate, isostearyl (meth)acrylate, and cyclic trimethylolpropane formal (meth)acrylate; Methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, t-butyl vinyl ether, n-octadecyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, dodecyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, cyclohexylmethyl vinyl ether, 4-methylcyclohexylmethyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether Monovinyl ether compounds such as ethoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl ether, tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexylmethyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether, chloroethoxyethyl vinyl ether, phenylethyl vinyl ether, phenoxypolyethylene glycol vinyl ether, cyclohexanedimethanol monovinyl ether, and isopropenyl ether-O-propylene carbonate; The following are examples: EO stands for ethylene oxide.

[0040] The content of the monofunctional monomer in the photosensitive layer of the present invention is preferably 0.1 to 30% by mass, and more preferably 1 to 10% by mass, based on the total solid content of the photosensitive layer of the present invention, for reasons such as better effects of the present invention.

[0041] (Difunctional Monomer) The bifunctional monomer is preferably a compound having two ethylenically unsaturated groups, because this provides better effects of the present invention. Examples of the ethylenically unsaturated group include radically polymerizable groups including an acryloyl group, a methacryloyl group, a vinyl group, a styryl group, and an allyl group. Among these, an acryloyl group, a methacryloyl group, and C(O)OCH=CH are preferred, and an acryloyl group and a methacryloyl group are more preferred.

[0042] Examples of compounds having two ethylenically unsaturated groups include: glycol di(meth)acrylate compounds such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetrapropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, ethoxylated neopentyl glycol di(meth)acrylate, and propoxylated neopentyl glycol di(meth)acrylate; divinyl ether compounds such as ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, and cyclohexanedimethanol divinyl ether; Bisphenol A di(meth)acrylate compounds such as bisphenol A diglycidyl ether (meth)acrylic acid adduct, modified bisphenol A di(meth)acrylate, bisphenol A PO adduct di(meth)acrylate, and bisphenol A EO adduct di(meth)acrylate; In addition, PO represents propylene oxide and EO represents ethylene oxide.

[0043] The content of the bifunctional monomer in the photosensitive layer of the present invention is preferably 0.1 to 30% by mass based on the total solid content of the photosensitive layer of the present invention, because the effects of the present invention are more excellent.

[0044] <Photopolymerization initiator> The photosensitive layer of the present invention preferably contains a photopolymerization initiator because the effects of the present invention are more excellent. The photopolymerization initiator is not particularly limited, and examples thereof include alkylphenones, acetophenones, benzoin ethers, benzophenones, thioxanthones, anthraquinones, benzils, and biacetyls. More specific examples include benzyl dimethyl ketal, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, methyl-o-benzoylbenzoate, and 1-hydroxycyclohexyl phenyl ketone.

[0045] In view of sensitivity and the like, the content of the photopolymerization initiator in the photosensitive layer of the present invention is preferably 0.3 to 15 mass %, more preferably 0.5 to 10 mass %, based on the total solid content of the photosensitive layer of the present invention.

[0046] <Water dispersible particles> The photosensitive layer may contain water-dispersible particles to enable development with an aqueous developer. The water-dispersible particles are not particularly limited, but are preferably polymers because they have better water-dispersibility, and the resulting flexographic printing plate has better printing durability, handleability, and trailing-end ink-receiving property, better development reproducibility and solid quality, and a wider printing pressure latitude. Hereinafter, "having better water-dispersibility, and the resulting flexographic printing plate has better printing durability, handleability, and trailing-end ink-receiving property, better development reproducibility and solid quality, and a wider printing pressure latitude" will also be referred to as "having better effects as a flexographic printing plate precursor." Specific examples of the polymers mentioned above include diene polymers (for example, polybutadiene, natural rubber, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methyl methacrylate-butadiene copolymer, polychloroprene, polyisoprene), polyurethane, vinylpyridine polymer, butyl polymer, thiokol polymer, acrylate polymer, and polymers obtained by copolymerizing these polymers with other components such as acrylic acid and methacrylic acid, and these may be used alone or in combination of two or more. The above polymer is preferably a diene polymer, more preferably polybutadiene, because it provides better effects as a flexographic printing plate precursor. The above-mentioned polymer preferably does not have reactive functional groups (for example, (meth)acryloyloxy groups) at both ends.

[0047] The above-mentioned polymer is preferably a polymer obtained by removing water from a water-dispersed latex, because this provides better effects as a flexographic printing plate precursor, etc. Specific examples of the above-mentioned water-dispersed latex include the water-dispersed latexes of the specific examples of the polymers mentioned above.

[0048] The content of the water-dispersible particles in the photosensitive layer is preferably 5 to 80 mass %, more preferably 10 to 50 mass %, and even more preferably 20 to 40 mass %, relative to the total solid content of the photosensitive layer, for reasons such as better effects as a flexographic printing plate precursor.

[0049] (plasticizer) The photosensitive layer may contain a plasticizer to further improve flexibility.

[0050] Specific examples of the plasticizer include liquid rubber, oil, polyester, and phosphoric acid compounds. Specific examples of liquid rubber include liquid polybutadiene, liquid polyisoprene, and those modified with maleic acid or an epoxy group. Specific examples of oils include paraffin, naphthene, and aromatics. Specific examples of polyesters include adipic acid polyesters. Specific examples of phosphoric acid compounds include phosphate esters.

[0051] The content of the plasticizer in the photosensitive layer is preferably 0.1 to 40% by mass, and more preferably 5 to 30% by mass, based on the total solid content of the photosensitive layer, for the reason that flexibility is further improved.

[0052] (surfactant) The photosensitive layer may contain a surfactant in order to further improve water developability. Examples of the surfactant include cationic surfactants, anionic surfactants, and nonionic surfactants. Among these, anionic surfactants are preferred because they provide superior effects as a flexographic printing plate precursor.

[0053] Specific examples of the anionic surfactant include: aliphatic carboxylates such as sodium laurate and sodium oleate; higher alcohol sulfates such as sodium lauryl sulfate, sodium cetyl sulfate, and sodium oleyl sulfate; Polyoxyethylene alkyl ether sulfates such as sodium polyoxyethylene lauryl ether sulfate; Polyoxyethylene alkyl allyl ether sulfates such as sodium polyoxyethylene octylphenyl ether sulfate and sodium polyoxyethylene nonylphenyl ether sulfate; alkyl sulfonates such as alkyl diphenyl ether disulfonates, sodium dodecyl sulfonate, and sodium dialkyl sulfosuccinate; alkyl aryl sulfonates such as alkyl disulfonates, sodium dodecylbenzenesulfonate, sodium dibutylnaphthalenesulfonate, and sodium triisopropylnaphthalenesulfonate; higher alcohol phosphate ester salts such as disodium lauryl phosphate monoester and sodium lauryl phosphate diester; Polyoxyethylene alkyl ether phosphate ester salts such as polyoxyethylene lauryl ether phosphate monoester disodium and polyoxyethylene lauryl ether phosphate diester sodium; These may be used alone or in combination of two or more.

[0054] Among these, sulfonic acid surfactants such as alkyl sulfonates and alkyl aryl sulfonates are preferred because they provide better water developability.

[0055] The content of the surfactant in the photosensitive layer is preferably 0.1 to 20% by mass, more preferably 1 to 10% by mass, based on the total solid content of the photosensitive layer, from the viewpoint of developability or drying property after development.

[0056] (thermal polymerization inhibitor) A thermal polymerization inhibitor (stabilizer) may be added to the photosensitive layer from the viewpoint of improving the thermal stability during kneading and the storage stability. Examples of the thermal polymerization inhibitor include phenols, hydroquinones, and catechols.

[0057] The content of the thermal polymerization inhibitor in the photosensitive layer is preferably 0.001 to 5% by mass relative to the total solid content of the photosensitive layer, because this provides better effects as a flexographic printing plate precursor.

[0058] (Other additives) To the photosensitive layer, additives such as ultraviolet absorbers, dyes, pigments, antifoaming agents, and fragrances may be added as appropriate to improve various properties, as long as the effects of the flexographic printing plate precursor are not impaired.

[0059] <Method for producing photosensitive layer> The method for producing the photosensitive layer is not particularly limited, and examples thereof include a method in which a composition (photosensitive resin composition) containing the above-mentioned components is prepared and then coated on a support or the like.

[0060] [Preferred embodiment] The printing plate precursor is preferably a so-called analog type printing plate precursor in which a negative film (on which an image has already been formed) is brought into close contact with the photosensitive layer during use, or a LAM type printing plate precursor included in the so-called CTP (Computer to Plate) type in which an infrared ablation layer is previously brought into close contact with the photosensitive layer, because these have better effects as a flexographic printing plate precursor.

[0061] For reasons such as superior effects as a flexographic printing plate precursor, an analog printing plate precursor preferably comprises a support on which an adhesive layer made of an adhesive or the like that bonds the support and the photosensitive layer, a photosensitive layer, an anti-adhesion layer that prevents the surface of the photosensitive layer from sticking, and a protective film that prevents scratches on the photosensitive layer before use are laminated in this order. When using an analog printing plate precursor, the protective film is peeled off and a negative film on which an image has been formed is placed in close contact with the exposed anti-adhesion layer. Examples of the above-mentioned support include the following.

[0062] [Support] The material used for the support of the flexographic printing plate precursor of the present invention is not particularly limited, but materials with high dimensional stability are preferably used, and examples thereof include metals such as steel, stainless steel, and aluminum; polyesters (e.g., PET (polyethylene terephthalate), PBT (polybutylene terephthalate), and PEN (polyethylene naphthalate)), PI (polyimide), polyamide, LCP (liquid crystal polymer), and PAN (polyacrylonitrile); plastic resins such as polyvinyl chloride; synthetic rubbers such as styrene-butadiene rubber; plastic resins (e.g., epoxy resins or phenolic resins) reinforced with glass fibers; cloth, and paper. From the viewpoints of dimensional stability and availability, the support is preferably a polymer film or cloth, more preferably a polymer film. The form of the support is determined by whether the polymer layer is in the form of a sheet or a sleeve.

[0063] As the cloth, a plain or twill woven fabric made of natural fibers such as cotton, linen, silk, or wool, or a synthetic fiber such as acetate, vinylon, vinylidene, polyvinyl chloride, acrylic, polypropylene, polyethylene, polyurethane, fluorine-based filament, polychlor, rayon, nylon, polyamide, or polyester, or various knitted or nonwoven fabrics can be used. Examples of polymer films include films formed from various polymers such as polyester (e.g., PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PEN (polyethylene naphthalate)), PI (polyimide), polyamide, LCP (liquid crystal polymer), PAN (polyacrylonitrile); plastic resins such as polyvinyl chloride; synthetic rubbers such as styrene-butadiene rubber; and plastic resins reinforced with glass fibers (epoxy resins, phenolic resins, etc.). Among these, polyester films are preferred from the viewpoint of dimensional stability, etc. Examples of the polyester film include PET film, PBT film, and PEN film, but from the viewpoint of dimensional stability, PET (polyethylene terephthalate) film is preferred.

[0064] The thickness of the support is not particularly limited, but from the viewpoint of dimensional stability and handleability, it is preferably 5 to 3000 μm, more preferably 50 to 2000 μm, and even more preferably 100 to 1000 μm.

[0065] An analog printing plate precursor can be produced, for example, by applying an adhesive to one side of a support in advance, applying an anti-tack agent to one side of a protective film in advance, sandwiching the above-mentioned photosensitive resin composition between the support to which the adhesive has been applied in advance and the protective film to which the anti-tack agent has been applied in advance, and pressing the resulting photosensitive layer to a predetermined thickness.

[0066] A LAM-type printing plate precursor differs from an analog-type printing plate precursor in that it has an infrared ablation layer between the photosensitive layer and the protective film, but otherwise has the same configuration as an analog-type printing plate precursor. That is, it consists of an adhesive layer, a photosensitive layer, an infrared ablation layer, and a protective film laminated in this order on a support. When using a LAM-type printing plate precursor, the protective film is peeled off to expose the infrared ablation layer.

[0067] The infrared ablation layer is a layer that can remove the portion irradiated with an infrared laser, and itself has the function of blocking the transmission of ultraviolet light at a practical level, and can function as a negative or positive by forming an image on it.

[0068] The infrared ablation layer is mainly composed of a resin or rubber binder, an infrared absorbing material, an ultraviolet absorbing material, a plasticizer, etc. The infrared ablation layer can be produced, for example, by dissolving the above-mentioned materials in a solvent, applying the solution to a substrate, and then drying to remove the solvent.

[0069] A printing plate precursor for the LAM system can be produced, for example, by applying an adhesive to one side of a support in advance, applying an infrared ablation layer to one side of a protective film in advance, sandwiching the above-mentioned photosensitive resin composition between the support to which the adhesive has been applied in advance and the protective film to which the infrared ablation layer has been applied in advance, and pressing the resulting photosensitive layer to a predetermined thickness.

[0070] In any printing plate precursor, the thickness of the photosensitive layer is preferably within the range of 0.01 to 10 mm, for reasons such as better effects as a flexographic printing plate precursor. If the thickness of the photosensitive layer is 0.01 mm or more, a sufficient relief depth can be ensured. The relief depth refers to the difference in height between the printing area (relief surface) and the non-printing area (back surface) of the flexographic printing plate.

[0071] [Infrared ablation layer] The infrared ablation layer of the flexographic printing plate precursor is a mask that covers the surface of the photosensitive layer. The infrared ablation layer is a portion that can be removed by an infrared laser, and the portion that is not removed blocks (absorbs) ultraviolet light, masking it so that the photosensitive layer underneath is not irradiated with ultraviolet light. Such an infrared ablation layer can be formed using a resin composition containing a binder and an infrared absorbing substance.

[0072] <Binder> The binder is, for example, a resin or rubber as described above. The resin is preferably a (meth)acrylic resin. The rubber is preferably butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), or styrene butadiene rubber (SBR), and more preferably acrylonitrile butadiene rubber (NBR).

[0073] <Infrared absorbing material> The infrared absorbing substance contained in the resin composition is not particularly limited as long as it is a substance that can absorb infrared rays and convert them into heat. Specific examples of infrared absorbing substances include black pigments (e.g., carbon black, aniline black, cyanine black, etc.), green pigments (e.g., phthalocyanine, naphthalocyanine, etc.), rhodamine dyes, naphthoquinone dyes, polymethine dyes, diimonium salts, azoimonium dyes, chalcogen dyes, carbon graphite, iron powder, diamine metal complexes, dithiol metal complexes, phenolthiol metal complexes, mercaptophenol metal complexes, aryl aluminum metal salts, inorganic compounds containing crystal water, copper sulfate, metal oxides (e.g., cobalt oxide, tungsten oxide, etc.), and metal powders (e.g., bismuth, tin, tellurium, aluminum, etc.). Among these, carbon black, carbon graphite, etc. are preferred from the viewpoint of having ultraviolet absorbing properties.

[0074] The infrared ablation layer may contain various additives in addition to the binder and infrared absorbing material as described above. Such additives include surfactants, plasticizers, ultraviolet absorbing substances, release agents, dyes, pigments, antifoaming agents, perfumes, and the like. The method for producing the infrared ablation layer is not particularly limited, but examples thereof include a method in which a resin composition containing the above-mentioned components is prepared and then coated on the above-mentioned intermediate layer. The thickness of the infrared ablation layer is preferably 0.1 to 6 μm, and more preferably 0.5 to 3 μm.

[0075] [Flexographic printing plate] The flexographic printing plate is obtained by the above-described method for producing a flexographic printing plate. The flexographic printing plate has an image area and a non-image area. Note that the flexographic printing plate is not limited to the one shown below. Here, the image area is an image area obtained by imagewise exposing the photosensitive layer of the flexographic printing plate precursor to light and developing it. The printing plate is preferably obtained by the following method, because it has better printing durability, handling properties, and ink-receiving properties at the rear end portion.

[0076] To form an image area in the photosensitive layer of a flexographic printing plate precursor, first, the support side of the flexographic printing plate precursor is irradiated with ultraviolet light (back exposure).

[0077] When an analogue printing plate precursor is used, the protective film is peeled off and a negative film with a pre-formed image is placed on the exposed anti-adhesive layer, whereas when an LAM printing plate precursor is used, the protective film is peeled off and the exposed infrared ablation layer is irradiated with an infrared laser to form a pattern representing the desired image.

[0078] Next, the photosensitive layer is cured by irradiating ultraviolet light from above the negative film or the infrared ablation layer (main exposure). The main exposure corresponds to the above-mentioned exposure step. For example, when the photosensitive layer is irradiated with ultraviolet light, the irradiated exposed portion is cured. In a photosensitive layer covered with a negative film or an infrared ablation layer, exposed portions irradiated with ultraviolet light and unexposed portions not irradiated with ultraviolet light are generated. The exposed portions are cured portions, and the unexposed portions are uncured portions.

[0079] The unexposed, i.e., unhardened, areas of the photosensitive layer are then removed in a developer, leaving the exposed areas of the photosensitive layer, thereby providing image and non-image areas. The developer used is an aqueous developer (aqueous developer). The aqueous developer is composed of water to which a surfactant or a pH adjuster, etc., has been added as needed. The uncured portions of the photosensitive layer can be removed by washing them out using, for example, a spray-type developing device or a brush-type washer.

[0080] The printing plate material is then removed from the developer and dried, and then, if necessary, the dried printing plate material is irradiated with ultraviolet light (post-exposure), thereby obtaining a flexographic printing plate.

[0081] The present invention is basically configured as described above. Although the method for producing a flexographic printing plate of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various improvements and modifications may be made without departing from the spirit and scope of the present invention. [Example]

[0082] The features of the present invention will be explained in more detail below with reference to examples. The materials, reagents, amounts and proportions of substances, and procedures shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following examples. In this example, the reproduction of recess depth and isolated small dots was evaluated for the following Examples 1 to 6 and Comparative Examples 1 and 2. The evaluation results of the reproduction of recess depth and isolated small dots are shown in the following Table 1. The reproduction of recess depth and isolated small dots will be explained below.

[0083] Recess Depth The recess depth of the obtained flexographic printing plate was evaluated as follows. The surface of the solid image area of ​​the flexographic printing plate was confocal measured at 0.1 μm height intervals using a hybrid laser microscope OPTELICS (registered trademark) HYBRID (manufactured by Lasertec Corporation) and a 50x Apo objective lens (high numerical aperture (NA)), to obtain three-dimensional data. The recess depth between the centers of the dots was measured from the above-mentioned observation image. The measured recess depth was evaluated based on the following evaluation criteria. (Evaluation criteria) A: Recess depth is 60 μm or more B: Recess depth is 50 μm or more and less than 60 μm C: Recess depth is less than 50 μm

[0084] [Reproduction of independent dots] The obtained flexographic printing plates were evaluated for reproduction of isolated small dots as follows. The flexographic printing plates were observed with a magnifying glass to confirm reproduction of each of the 50 μm and 100 μm small independent dots. The reproduction of the isolated small dots was evaluated based on the observed independent dots and the following evaluation criteria. (Evaluation criteria) A: Reproduces 100μm and 50μm small dots B: Reproduces 100 μm small dots, does not reproduce 50 μm small dots C: 100μm small dots and 50μm small dots are not reproduced

[0085] Next, a description will be given of Examples 1 to 6 and Comparative Examples 1 and 2. Examples 1 to 6 and Comparative Examples 1 and 2 are also shown in Table 1 below.

[0086] Example 1 [Manufacture of flexographic printing plates] (Back exposure process) The flexographic printing plate precursor used was FLENEX FW-L2 (thickness: 1.14 mm) manufactured by Fujifilm Global Graphic Systems. Using an exposure device with 15 40W chemical lamps arranged in a row, the exposure dose of the flexographic printing plate precursor was 256mJ / cm from a position 15cm away from the support side of the flexographic printing plate precursor. 2 The image was exposed so that the image was as follows (back exposure).

[0087] (Negative pattern formation process) After the back exposure, the protective film of the flexographic printing plate precursor was peeled off, and a negative pattern was formed on the infrared ablation layer using an exposure device. The negative pattern included a 50% halftone dot area, a solid image area, and patterns corresponding to 100 μm dots and 50 μm dots. The exposure device used was an exposure device with an arrangement of 15 40 W chemical lamps. The exposure device irradiates ultraviolet light as an energy beam, and the ultraviolet light is in a scattered light state.

[0088] (Main exposure process) Two film-like optical elements 1 were placed on top of the flexographic printing plate precursor on which a negative pattern had been formed, with the concave and convex surfaces facing the flexographic printing plate precursor. The film-like optical elements 1 were prism sheets. The two film-like optical elements 1 were stacked so that the prism extension directions were perpendicular to each other, and were placed between the above-mentioned exposure device used as an energy ray source and the flexographic printing plate precursor, with the surface on which the prisms of each prism sheet were arranged facing the opposite side to the light incident side. Using the above-mentioned exposure device as an energy ray source, the exposure dose of the flexographic printing plate precursor was 2880 mJ / cm 2 from a position 15 cm away from the infrared ablation layer side via two film-like optical elements 1. 2 The film was exposed so that the image was as follows (main exposure).

[0089] (Development process) After the main exposure, the film was developed for 10 minutes using a brush-type washer (liquid temperature 50°C) containing an aqueous developer containing 0.5% detergent (additive-free dishwashing soap, manufactured by Miyoshi Soap Co., Ltd.), and then dried using hot air at 60°C until all moisture was removed.

[0090] (Post-exposure process) After drying, without placing the film-like optical element 1, the exposure device was used to expose the film to an exposure dose of 2000 mJ / cm 2 from a position 15 cm away from the photosensitive layer side. 2 In this way, a flexographic printing plate was obtained.

[0091] [Film-like optical element 1] LPV90-0.1 (grade without UV absorber: prism plate with a pitch of 0.1 mm, prism angle of 90 degrees) manufactured by Nippon Tokushu Kogaku Jushi Co., Ltd. was used as the film-like optical element 1. As described above, the film-like optical element 1 is a prism sheet manufactured by melt molding.

[0092] <Example 2> In Example 2, a flexographic printing plate was produced in the same manner as in Example 1, except that Film Optical Element 2 was used. [Film-like optical element 2] LL0.1-0.05 (grade without UV absorber: linear lenticular lens with a pitch of 0.1 mm, cylindrical lens radius of 0.05 mm) manufactured by Nippon Tokushu Kogaku Jushi Co., Ltd. was used as the film-like optical element 2. The film-like optical element 2 was manufactured by melt molding.

[0093] Example 3 In Example 3, a flexographic printing plate was produced in the same manner as in Example 1, except that film-like optical element 3 was used. [Film-like optical element 3] As the film-like optical element 3, a quartz glass prism sheet was used, which was produced by mold pressing using a mold with a pitch of 0.1 mm, a prism angle of 90 degrees, and a total thickness of 2 mm.

[0094] Example 4 In Example 4, a flexographic printing plate was produced in the same manner as in Example 1, except that film-like optical element 4 was used. [Film-like optical element 4] For the film-like optical element 4, 199 parts by mass of methyl methacrylate manufactured by Tokyo Chemical Industry Co., Ltd. was added to 1 part by mass of benzoyl peroxide manufactured by Tokyo Chemical Industry Co., Ltd., and the mixture was reacted with stirring at a temperature of 90°C until a viscosity of 0.1 Pascal seconds (1 poise) was reached, followed by rapid cooling using dry ice and methanol. The resulting liquid was poured into the same mold as the film-like optical element 3 of Example 3 described above, and heated at a temperature of 90°C for 20 hours and then at 110°C for 2 hours to obtain a prism sheet. The film-like optical element 4 was formed by thermal polymerization.

[0095] <Example 5> In Example 5, a flexographic printing plate was produced in the same manner as in Example 1, except that film-like optical element 5 was used. [Film-like optical element 5] To prepare the film-like optical element 5, 356.25 parts by mass of A-NOD-N1,9-nonanediol diacrylate manufactured by Shin-Nakamura Chemical Co., Ltd. was added to 1-hydroxycyclohexyl phenyl ketone manufactured by Tokyo Chemical Industry Co., Ltd., and the mixture was stirred and poured into a mold similar to that of the film-like optical element 3 of Example 3 described above, and then covered with a glass plate. A metal halide lamp UVL-1500M2 manufactured by Ushio Inc. was used to apply 450 mJ / cm from the glass plate side. 2 The prism sheet was obtained by irradiating and curing the ultraviolet light under the conditions below: The film-like optical element 5 was formed by ultra-short wave UV polymerization. Example 6 In Example 6, an LED area exposure device (UVA500 × 500) manufactured by Micro Square Corporation was used as the energy ray source, and the exposure dose of the flexographic printing plate precursor was 2880 mJ / cm from a position 5 cm away from the infrared ablation layer side through two film-like optical elements 1. 2 A flexographic printing plate was produced in the same manner as in Example 1, except that the two film-like optical elements 1 were exposed so that the prism extension directions were perpendicular to each other, as in Example 1, and were placed between the above-mentioned LED area exposure device used as an energy ray source and the flexographic printing plate precursor so that the surface on which the prisms of each prism sheet were arranged was opposite to the light incident side.

[0096] <Comparative Example 1> In Comparative Example 1, a flexographic printing plate was produced in the same manner as in Example 1, except that no film-like optical element was used. In Comparative Example 1, exposure was performed using scattered light. In addition, since Comparative Example 1 did not use a film-like optical element, "-" is entered in the columns for the name, material, shape and manufacturing method of the film-like optical element in Table 1 below. <Comparative Example 2> In Comparative Example 2, a flexographic printing plate was produced in the same manner as in Example 1, except that no film-like optical element was used and the exposure device was UVE-365-4040 manufactured by Quantum Ushikata Co., Ltd. In Comparative Example 2, exposure was performed using fully collimated light. In addition, since Comparative Example 2 did not use a film-like optical element, "-" is entered in the columns for the name, material, shape and manufacturing method of the film-like optical element in Table 1 below.

[0097] [Table 1]

[0098] As shown in Table 1, in comparison with Comparative Examples 1 and 2, Examples 1 to 6 achieved both a greater recess depth and better reproduction of isolated small dots. In Comparative Example 1, since no film-like optical element was used, the depth of the recesses was insufficient due to halation caused by scattered light. In Comparative Example 2, since no film-like optical element was used, the reproduction of isolated small dots was poor due to completely collimated light. From Examples 1 to 6, in Examples 1 to 4 and 6, the transmission of exposure light through the film-like optical elements 1 to 4 was sufficient, and the reproduction of recess depths and isolated small dots was excellent. [Explanation of symbols]

[0099] 10, 10a, 10b Flexographic printing plate precursor 12 Energy ray source 14 Film-like optical elements 20 Support 21 Adhesive layer 22 Photosensitive layer 22a, 32a surface 23a Exposure section 23b Unexposed area 24 Mask section 25 Laminate 32 Infrared ablation layer 33 Aperture 34 Adhesive layer 35 Carrier Sheet 35a surface 37 Protective Sheet Le energy ray

Claims

1. an exposure step of irradiating a flexographic printing plate precursor having at least a support, a photosensitive layer, and a mask portion on which an image is formed, in this order, with energy rays through the mask portion to expose the photosensitive layer; a development step of removing unexposed areas of the photosensitive layer, the exposure step includes a step of irradiating the photosensitive layer with the energy rays in a state in which the mask portion and the film-like optical element are present in this order from the photosensitive layer side between an energy ray source and the photosensitive layer, The method for manufacturing a flexographic printing plate, wherein the film-like optical element is an element that converges the incident energy beam, increases the directivity of the beam, and emits the beam to the mask portion.

2. A method for manufacturing a flexographic printing plate as described in claim 1, wherein the flexographic printing plate precursor is a LAM type printing plate precursor.

3. The flexographic printing plate precursor is an analog printing plate precursor, the mask portion has a negative film adhered to the photosensitive layer, and the negative film has a pattern representing an image formed thereon; The method for producing a flexographic printing plate according to claim 1 , wherein the exposure step exposes the photosensitive layer in a state where the negative film is in close contact with the photosensitive layer.

4. The method for producing a flexographic printing plate according to any one of claims 1 to 3, wherein the energy rays are ultraviolet light.

5. The method for producing a flexographic printing plate according to any one of claims 1 to 3, wherein the film-like optical element is a prism sheet or a lenticular lens.

6. The method for producing a flexographic printing plate according to any one of claims 1 to 3, wherein the film-like optical element is made of glass.

7. The method for producing a flexographic printing plate according to any one of claims 1 to 3, wherein the film-like optical element is formed from a resin.

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