Development medium, thermal development method, and thermal development system

Abstract

A heat developing medium for flexographic heat development, wherein the porosity is 35% to 95% and the elastic recovery is 40% to 99%.

Description

[Technical Field]

[0001] The present invention relates to a development medium, a thermal development method, and a thermal development system. [Background technology]

[0002] In recent years, flexographic printing has been widely used as a method for printing on flexible packaging such as paper, film, etc. Examples of printing plates for relief printing, typified by flexographic printing, include photosensitive resin plates having a photosensitive resin composition layer on a support. Examples of methods for producing a flexographic printing plate from a photosensitive resin plate include the following methods. First, the photosensitive resin composition layer is exposed to ultraviolet light (called back exposure) over the entire surface through the support, forming a uniform photocured layer. Next, relief exposure is performed from the backside, i.e., the uncured photosensitive resin composition layer side opposite the UV-exposed side, to obtain a flexographic printing plate precursor. Next, relief exposure is performed. Examples of relief exposure methods include a method of UV exposure through a transparent image carrier such as a negative film that selectively transmits UV light, and a method of UV exposure through a thin layer in which a digital image has been ablated with an infrared laser to form UV-transmitting areas. The photosensitive resin composition in the unexposed areas of the flexographic printing plate precursor is then removed with a developer, or the like, to form a relief image, thereby obtaining a flexographic printing plate.

[0003] On the other hand, due to the recent increase in environmental awareness, a solvent-free development process that does not use organic solvents as a developer is being considered. Among these, the thermal development method, in which a flexographic printing plate after relief exposure is heated to melt the non-exposed areas and the melted non-exposed areas are removed using a non-woven fabric or the like, is attracting attention because it allows for solvent-free development.

[0004] As a technology relating to the thermal development method, for example, Patent Document 1 proposes a dry development process, which has the advantages of not generating organic solvent waste or contaminated wastewater by-products in the washing and removal process, and not requiring long drying times after development. Patent Document 2 also proposes a nonwoven fabric made of polyester that can more effectively remove the photosensitive resin composition from unexposed areas. On the other hand, the thermal development method has the problem that the surface roughness of the flexographic printing plate finally obtained is rougher than that of the conventional solvent development method, and that the nonwoven fabric used during development, etc., remains on the surface, which is likely to cause problems such as ink entanglement. In view of such problems, Patent Document 3 proposes a technique for controlling the surface roughness of the plate during thermal development. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3117749 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-109606 [Patent Document 3] Patent No. 5827746 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the techniques disclosed in Patent Documents 1 and 2 have problems in that the removability of the photosensitive resin composition in the unexposed areas is still insufficient, and a nonwoven fabric or the like having an area about 10 times that of the original printing plate is required for thermal development. Therefore, from the viewpoint of reducing waste, there is room for further improvement. Furthermore, in the technology proposed in Patent Document 3, the surface roughness of the flexographic printing plate is controlled, but there is still room for improvement in terms of the ink entanglement mentioned above.

[0007] In view of the above-mentioned problems of the conventional art, an object of the present invention is to provide a development medium for flexographic thermal development, which is used to obtain a flexographic printing plate having excellent removability of the photosensitive resin composition in the unexposed areas when a thermal development method is used. Another object of the present invention is to provide a thermal development system that improves ink entanglement when a thermal development method is used. [Means for solving the problem]

[0008] As a result of extensive research into solving the above problems, the inventors discovered that the above problems can be solved by using a development medium with a specified porosity and elastic recovery rate in a thermal development process, and thus completed the present invention. That is, the present invention is as follows.

[0009] [1] 1. A development medium for flexographic thermal development, comprising: The porosity is 35% or more and 95% or less, A development medium having an elastic recovery of 40% or more and 99% or less. [2] The development medium according to [1] above, wherein the elastic recovery rate is 65% or more and 99% or less. [3] The development medium according to [1] or [2] above, wherein the Gakushin abrasion fluff grade is between 4.0 and 5.0. [4] The development medium according to any one of [1] to [3] above, wherein the pore size is 1.0 μm or more and 50.0 μm or less. [5] The development medium according to any one of [1] to [4] above, wherein the fiber length is 50 mm or more. [6] The development medium according to any one of [1] to [5] above, which contains a polyester resin and / or a polyester copolymer. [7] The development medium according to any one of [1] to [6] above, comprising a fiber layer having a fiber diameter of 0.1 μm or more and 5.0 μm or less. [8] The development medium according to any one of [1] to [7], which comprises at least two fiber layers each having a fiber diameter of 5.0 μm or more and 30.0 μm or less, and which comprises a fiber layer having a fiber diameter of 0.1 μm or more and 5.0 μm or less as an intermediate layer between the fiber layers having a fiber diameter of 5.0 μm or more and 30.0 μm or less. [9] Weight is 10g / m 2 More than 60g / m 2 The development medium according to any one of [1] to [8] above,

[10] The development medium according to any one of [1] to [9] above, having a thickness of 15 μm or more and 300 μm or less.

[11] A thermal development method using a thermal development system for a flexographic printing plate precursor, comprising: The thermal development system for the flexographic printing original plate includes a melting section that melts the non-exposed area of ​​the photosensitive resin composition, an absorbing and removing section that has an absorbing layer, and , and The development medium according to any one of [1] to

[10] above, wherein the absorbing layer is bringing an absorbing layer into contact with the non-exposed portion to absorb and remove the non-exposed portion; Thermal development method.

[12] 1. A flexographic printing plate thermal development system comprising: a melting portion that melts the non-exposed portion of the photosensitive resin composition; an absorbing / removing section that brings an absorbing layer into contact with the non-exposed section and absorbs and removes the non-exposed section; , and The absorbing layer is the development medium according to any one of [1] to

[10] above. Thermal development system.

[13] The thermal development system according to

[12] above, wherein the photosensitive resin composition contains 60% or more of components having a weight average molecular weight (Mw) of 70,000 or more as measured by GPC.

[14] The thermal development system according to

[12] or

[13] , wherein the amount of components having a weight average molecular weight (Mw) of 70,000 or more as measured by GPC in the photosensitive resin composition is 60% or more and 80% or less. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a development medium for flexographic thermal development that is excellent in the removability of the photosensitive resin composition in the unexposed areas, and a thermal development system and a thermal development method that can obtain a flexographic printing plate with reduced ink entanglement. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following describes in detail an embodiment of the present invention (hereinafter referred to as "the present embodiment"); however, the present embodiment is an example for explaining the present invention and is not intended to limit the present invention to the following content. The present invention can be implemented by appropriately modifying it within the scope of the gist thereof.

[0012] [Developing medium for flexographic thermal development] The development medium for flexographic thermal development of this embodiment has a porosity of 35% to 95% and an elastic recovery rate of 40% to 99%. The development medium for flexographic thermal development of this embodiment is used to remove unexposed areas of a photosensitive resin composition from a flexographic printing plate precursor after pattern exposure in the manufacturing process of a flexographic printing plate. Specifically, after pattern exposure, the non-exposed areas of the photosensitive resin composition of the flexographic printing plate precursor are heated and melted, and then the non-exposed areas are absorbed and removed by the development medium of this embodiment. The development medium of this embodiment provides an excellent effect in terms of removing the photosensitive resin composition from the unexposed areas. Examples of development media for flexographic thermal development include woven fabrics, knitted fabrics, net-like materials, and nonwoven fabrics made of organic polymer fibers, as well as porous membranes and films produced by phase separation and stretching of resins, among which nonwoven fabrics are preferred from the viewpoint of achieving both developability and durability.

[0013] In this specification, the term "nonwoven fabric" refers to a web made by bonding or intertwining fibers with each other through thermal, mechanical, or chemical action.

[0014] (porosity) The porosity of the developing medium of this embodiment is 35% or more and 95% or less, preferably 40% or more and 90% or less, and more preferably 45% or more and 85% or less. If the porosity is 35% or more, a large amount of the photosensitive resin composition can be wiped off, and if it is 95% or less, sufficient strength can be obtained for practical use when handling the developing medium. The porosity of the development medium can be measured by the method described in the examples below. The porosity of the developing medium can be controlled within the above range by adjusting the thermal bonding conditions of the fibers that make up the developing medium. In other words, the overall porosity can be controlled by adjusting the thickness of the developing medium through temperature, pressure, and line speed.

[0015] (Elastic recovery rate) The development medium of this embodiment has an elastic recovery rate of 40% or more and 99% or less. The compressibility of the development medium correlates with the contact area between the development medium and the non-exposed photosensitive resin composition when pressed against the substrate, significantly affecting wiping performance. Among the compressibility characteristics, the elastic recovery rate is a factor directly linked to the absorption performance of the development medium. During development, pressure is applied between the development medium and the flexographic printing plate, causing the development medium to deform. Subsequently, when the pressure during development is released, the internal porosity of the development medium recovers, allowing the development medium to absorb the soft photosensitive resin composition in the non-exposed areas, thereby achieving wiping performance. In other words, a high elastic recovery rate of the development medium results in a large amount of void recovery upon unloading, leading to improved photosensitive resin composition support. In this sense, a development medium with an elastic recovery rate of 40% or higher can achieve sufficient void recovery. If the content is 99% or less, the photosensitive resin composition layer can be sufficiently absorbed. The elastic recovery rate of the development medium is preferably 46% or more, more preferably 65% ​​or more, and even more preferably 70% or more. Also, it is preferably 98% or less, more preferably 97% or less, and even more preferably 95% or less. The upper and lower limits of these numerical ranges can be combined arbitrarily. The elastic recovery rate of the development medium of this embodiment can be measured by the method described in the Examples section below. The elastic recovery rate of the development medium can be controlled within the above-mentioned range by controlling the temperature of the fabric when it enters the press roll in the thermal bonding step of the fibers constituting the development medium. The method for adjusting the fabric temperature is not particularly limited, but examples include a method of effectively utilizing the heat dissipation from the heated press roll using a heat insulating plate, and a method of preheating the development medium with a preheating roll.

[0016] The Gakushin abrasion fluff rating of the development medium of this embodiment is preferably 4.0 or higher, more preferably 4.2 or higher, and even more preferably 4.5 or higher. If the Gakushin abrasion fluff rating of the development medium is 4.0 or higher, fiber debris is less likely to fall off during wiping, making it less likely that fiber debris will remain on the surface. The upper limit for the Gakushin abrasion fluff rating is 5.0. The Gakushin abrasion fluff rating of the development medium is an index of abrasion resistance and can be measured by the method described in the examples below. The abrasion fluff grade of the development medium can be controlled within the above range by adjusting the thermal bonding conditions of the fibers that make up the development medium, specifically by adjusting the temperature, pressure, line speed, etc. of the press roll.

[0017] (opening diameter) The pore size of the development medium of this embodiment is preferably 1.0 μm or more and 50.0 μm or less, more preferably 2.0 μm or more and 30 μm or less, and even more preferably 3.0 μm or more and 20.0 μm or less. The pore size of the development medium affects the amount of photosensitive resin composition that can be held in the internal void structure during use. If the pore size of the development medium is 1.0 μm or more, sufficient gaps can be formed between adjacent threads, while if it is 50.0 μm or less, a dense fiber network can be sufficiently formed, which tends to ensure the retention of the photosensitive resin composition. The pore size of the development medium can be measured by the method described in the examples below. The pore size of the developing medium can be controlled within the above range by adjusting the fiber diameter and basis weight of the constituent fibers.

[0018] (fiber length) The fiber length of the development medium of this embodiment is preferably 50 mm or more, more preferably 100 mm or more, and even more preferably 200 mm or more. If the fiber length of the developing medium is 50 mm or more, fewer fibers fall off during wiping, leaving fewer fibers unwiped, and the tensile strength of the developing medium is also increased. The fiber length of the development medium can be measured, for example, by optical or electron microscopy.

[0019] (material) The material of the development medium of this embodiment may be a thermoplastic resin. Examples of the thermoplastic resin include polyester resins and / or polyester copolymers, polyamide resins, and resins using cellulose derivatives. Since the non-exposed portion of the photosensitive resin composition layer is wiped off with the developing medium while being heated, the developing medium preferably has heat resistance, and if the developing medium contains the above-mentioned resin, this heat resistance is fully satisfied. Furthermore, from the viewpoint of affinity with the photosensitive resin composition, the developing medium of this embodiment more preferably contains a polyester resin and / or a polyester copolymer.

[0020] Examples of polyester resins include, but are not limited to, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate, and polybutylene naphthalate.

[0021] (fiber layer) The development medium of this embodiment preferably includes an ultrafine fiber layer (I layer) having a fiber diameter of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 4.5 μm, and even more preferably 0.3 μm to 4.0 μm. The development medium of this embodiment contains the ultrafine fiber layer as described above, which enables the formation of a dense network structure and dramatically improves the carrying capacity of the photosensitive resin composition. This carrying capacity also contributes to suppressing strike-through of the wiped photosensitive resin composition, enabling stable production of flexographic printing plates. If the fiber diameter of the ultrafine fiber layer is 0.1 μm or more, a dense network structure is easily formed, and if it is 5.0 μm or less, an appropriate inter-fiber distance is easily maintained. The fiber diameter of the development medium can be measured by the method described in the examples below. The fiber diameter of the development medium can be controlled within the above range by, for example, adjusting the fiber drawing conditions. Specifically, in the case of a spunbond method, a preferred method is to adjust the drawing conditions of the draw jet.

[0022] (Layered structure of fiber layers) The development medium of this embodiment preferably includes at least two fiber layers (II layers) having a fiber diameter of 5.0 μm or more and 30.0 μm or less, and includes an ultrafine fiber layer (I layer) having a fiber diameter of 0.1 μm or more and 5.0 μm or less as an intermediate layer between the fiber layers (II layers) having a fiber diameter of 5.0 μm or more and 30.0 μm or less. The developing medium having the laminated structure has a layer having a thick fiber diameter disposed on the surface, and the uneven shape of the thick fibers present on the surface of the developing medium has a scraping effect when the resin comes into contact with the layer, improving wiping performance. In addition, the wiped photosensitive resin composition passes through the highly porous thick fiber layer and can be retained in the ultrafine fiber layer, achieving a long number of repeated uses.

[0023] (Metsuke) The basis weight of the development medium in this embodiment is 10 g / m 2 More than 60g / m 2 It is preferable that the content is 15 g / m or less, and more preferably 15 g / m 2 More than 65g / m 2 More preferably, 20 g / m or less 2 More than 60g / m 2 The following is the result. The weight of the developing medium is 10g / m 2If the strength is 60 g / m or more, a strength sufficient to perform a roll-to-roll process in the absorption and removal step of the non-exposed portion of the photosensitive resin composition layer can be obtained, and 2 If the thickness is less than this, sufficient flexibility is obtained, and the effect of easily pressing the adhesive layer against the photosensitive resin composition layer and wiping it off is obtained. The basis weight of the development medium can be measured by the method described in the examples below. The basis weight of the developing medium can be controlled within the above numerical range by adjusting the discharge amount and the line speed.

[0024] (Thickness) The thickness of the development medium of this embodiment is preferably 15 μm or more and 400 μm or less, more preferably 20 μm or more and 300 μm or less, and even more preferably 30 μm or more and 200 μm or less. If the thickness of the development medium is 15 μm or more, it has sufficient strength to enable a roll-to-roll process to be carried out in the absorption and removal step of the non-exposed portions of the photosensitive resin composition layer, and if it is 400 μm or less, it has sufficient flexibility to be easily pressed against the photosensitive resin composition layer and wiped off.

[0025] (thermocompression bonding) The development medium of this embodiment may be thermocompression bonded. In this case, the thermocompression bonding ratio (the area of ​​the pressure-bonded portion relative to the area of ​​the development medium) is preferably 5% to 20%, more preferably 11% to 17%.

[0026] (Development medium manufacturing method) The manufacturing method of the development medium of this embodiment is not limited. The fiber layer (II layer) is preferably manufactured by a spunbonding method, a dry method, a wet method, or the like. The fibers for the fiber layer (II layer) may be thermoplastic resin fibers, or the like. The ultrafine fiber layer (I layer) composed of ultrafine fibers with a fiber diameter of 0.1 μm to 5.0 μm can be manufactured by, for example, a dry method, a wet method, or the like using ultrafine fibers, or by electrospinning, melt-blown method, force spinning, or the like. From the viewpoint of easily and densely forming the ultrafine fiber layer (I layer) composed of ultrafine fibers, the ultrafine fiber layer (I layer) is particularly preferably formed by a melt-blown method. The fibers may also be split or fibrillated by beating, partial dissolution, or the like before being used to manufacture a nonwoven fabric.

[0027] Methods for forming a development medium having the above-mentioned ultrafine fiber layer (layer I) and fiber layer (layer II) include, for example, a method of integrating them by thermal bonding, a method of three-dimensionally entangling them by spraying a high-speed water stream, and a method of integrating them using a particulate or fibrous adhesive. Examples of integration methods by thermal bonding include integration by thermal embossing (thermal embossing roll method) and integration by high-temperature hot air (air-through method). Integration by thermal bonding is preferred from the viewpoint that a laminated development medium can be formed without using a binder. Integration by thermal bonding can be carried out, for example, by bonding using a press roll (flat roll or embossing roll) at a temperature 50 to 120° C. lower than the melting point of the synthetic resin and a linear pressure of 100 to 1000 N / cm. By applying a linear pressure of 100 N / cm or more in the thermal bonding step, sufficient bonding is achieved and sufficient strength is exhibited, while by applying a linear pressure of 1000 N / cm or less, large deformation of the fibers can be prevented, and an increase in apparent density and a decrease in porosity can be prevented, thereby effectively achieving the effects of the present invention. Furthermore, this integration can be achieved by controlling the fabric temperature as it enters the press roll during the thermal bonding process, thereby controlling the subsequent compression characteristics of the development medium. The fabric temperature before pressing refers to the temperature of the support 50 cm upstream from the roll nip point. For example, in the case of polyester materials, specifically, setting the fabric temperature before pressing in the range of 40 to 120°C makes it possible to obtain the elastic recovery rate and compressibility of the development medium described above. By setting the fabric temperature high in advance, the crystallinity of the yarn is promoted in advance, thereby ensuring the minimum amorphous content required for yarn-to-yarn bonding while suppressing excessive compression at the contact points, resulting in a support with a high elastic recovery rate. There are no particular limitations on the method for adjusting the fabric temperature within the above range, but examples include using a heat-retaining plate to effectively utilize the heat dissipation from the heated press roll or preheating the nonwoven fabric with a preheating roll.

[0028] The most preferred method for producing the development medium of this embodiment, for example when the development medium is a nonwoven fabric, is to sequentially produce a spunbond nonwoven fabric layer, a meltblown nonwoven fabric layer and / or a spunbond nonwoven fabric layer, stack them, and press them together with an embossing roll or a heat press roll. This method is preferable when the objective is to obtain a uniform nonwoven fabric with a low basis weight, because it allows the laminated nonwoven fabric to be formed from the same material and can be produced on a continuous, integrated production line. Specifically, one or more spunbond nonwoven fabric layers are spun on a conveyor using a thermoplastic resin, and one or more ultrafine fiber nonwoven fabric layers with a fiber diameter of 0.1 to 5 μm are then sprayed onto the spunbond nonwoven fabric layers using a melt-blown method using a thermoplastic resin. Then, one or more layers of nonwoven fabric composed of thermoplastic resin fibers are laminated using a thermoplastic resin. Next, these layers are preferably integrated by calendering using a metal roll to press the layers together. Examples of calendering include a method in which the nonwoven fabric layers are pressed together using a heated roll. This method can be carried out on a continuous, integrated production line, and is therefore suitable for obtaining a uniform nonwoven fabric with a low basis weight. The thermal bonding step can be carried out, for example, at a temperature 50°C to 120°C lower than the melting point of the thermoplastic resin, and at a linear pressure of 100 to 1000 N / cm. A linear pressure in the calendering process within the above range is preferred from the viewpoint of improving the strength and porosity of the nonwoven fabric. The heated roll used in the calendering process may be a roll with an uneven surface, such as an embossed or satin-finish pattern, or may be a smooth flat roll. The surface pattern of the uneven roll is not limited, and may include an embossed pattern, satin-finish pattern, rectangular pattern, line pattern, etc., as long as it can bond the fibers together by heat.

[0029] [Thermal Development System] The thermal development system of this embodiment includes a melting section that melts the non-exposed areas of the photosensitive resin composition of the flexographic printing plate precursor, and an absorbing / removing section that brings an absorbing layer into contact with the non-exposed areas and absorbs and removes the non-exposed areas. The absorbing layer is the development medium of this embodiment described above.

[0030] In the thermal development system of this embodiment, the unexposed portions of the photosensitive resin composition of the flexographic printing plate precursor after pattern exposure are removed. The non-exposed portion of the photosensitive resin composition is heated and melted by the melting portion, and then the non-exposed portion is absorbed and removed by the adsorption removing portion. With the above-described configuration, the thermal development system of this embodiment can provide a flexographic printing plate with reduced ink entanglement.

[0031] (Flexographic printing plate used in thermal development systems) As described above, the thermal development system of this embodiment melts and absorbs and removes the unexposed areas of a photosensitive resin composition layer of a flexographic printing original plate having a photosensitive resin composition layer that has been subjected to pattern exposure. Before pattern exposure of the photosensitive resin composition layer, the flexographic printing original plate has a configuration including at least a support (a) and a photosensitive resin composition layer (b) laminated on the support (a). In this specification, such a configuration may be referred to as a "photosensitive resin construct for a flexographic printing plate." That is, as will be described later, a photosensitive resin construct for a flexographic printing plate is subjected to pattern exposure to form a flexographic printing plate precursor, and the non-exposed areas of the flexographic printing plate precursor are melted and removed to obtain a flexographic printing plate.

[0032] <Support (a)> The support (a) is not limited to the following, but examples thereof include polyester films, polyamide films, polyacrylonitrile films, and polyvinyl chloride films. Among these, polyester film is preferred as the support (a). The polyester used for the support (a) is not limited to the following, but examples thereof include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. The thickness of the support (a) is not particularly limited, but is preferably 50 to 300 μm. Furthermore, for the purpose of increasing the adhesive strength between the support (a) and the photosensitive resin composition layer (b) described later, an adhesive layer may be provided on the support (a). Examples of the adhesive layer include, but are not limited to, the adhesive layers described in WO 2004 / 104701.

[0033] <Photosensitive resin composition layer (b)> The photosensitive resin construct for a flexographic printing plate has a photosensitive resin composition layer (b) on a support (a). The photosensitive resin composition layer (b) may be laminated directly on the support (a) or may be laminated indirectly via the adhesive layer or the like. In the photosensitive resin composition layer (b), the amount of components having a weight average molecular weight (Mw) of 70,000 or more as measured by gel permeation chromatography (GPC) is preferably 60% or more. The amount of the component measured by GPC can be calculated from the area ratio of the measurement curve when measuring the tetrahydrofuran (THF) soluble content of the photosensitive resin composition layer (b). The presence of 60% or more of components with a weight-average molecular weight (Mw) of 70,000 or more means the presence of a large amount of highly elastic polymers. This allows the polymers constituting the photosensitive resin composition layer to restore their original shape even when the photosensitive resin composition layer comes into contact with the absorbing layer, i.e., the development medium of this embodiment, to absorb and remove the unexposed areas during thermal development, as described below. This prevents the smoothness after development from being impaired, resulting in excellent surface smoothness. Furthermore, the above-described configuration ensures excellent surface elasticity of the flexographic printing plate during printing. Furthermore, adhesion of the development medium during thermal development can be prevented. Even if the development medium does adhere, accumulation of the development medium on the surface of the flexographic printing plate during the printing process can be prevented, thereby improving ink entanglement. The amount of components having a weight average molecular weight (Mw) of 70,000 or more is preferably 60% or more and 80% or less. By keeping the amount of components with a weight-average molecular weight (Mw) of 70,000 or more to 80% or less, the product has excellent wiping properties and excellent surface roughness after development, resulting in excellent effects by improving ink entanglement. The amount of components having a weight average molecular weight (Mw) of 70,000 or more is more preferably 63 to 78%, and even more preferably 65 to 75%. Within this range, the improvement in ink entanglement is particularly remarkable. The amount of the component having a weight-average molecular weight (Mw) of 70,000 or more can be controlled by adjusting the blending amount of the constituent material having a weight-average molecular weight of 70,000 or more among the constituent materials used in forming the photosensitive resin composition layer (b). For example, it can be controlled by changing the content of the thermoplastic elastomer (b-1) described below.

[0034] The photosensitive resin composition layer (b) contains, for example, a thermoplastic elastomer (b-1), and preferably contains an ethylenically unsaturated compound (b-2) and a photopolymerization initiator (b-3), and may further contain a liquid diene. The photosensitive resin composition layer (b) may further contain auxiliary additive components as needed. Each component will be described in detail below.

[0035] [Thermoplastic elastomer (b-1)] Examples of the thermoplastic elastomer (b-1) include, but are not limited to, copolymers having a structural unit derived from a monovinyl-substituted aromatic hydrocarbon and a structural unit derived from a conjugated diene. The thermoplastic elastomer (b-1) may further have a structural unit derived from another monomer. The use of such a thermoplastic elastomer tends to provide a flexographic printing plate with excellent elasticity, further reducing adhesion of the development medium during thermal development.

[0036] The thermoplastic elastomer (b-1) may be a random copolymer or a block copolymer, but is preferably a block copolymer having a polymer block of a monovinyl-substituted aromatic hydrocarbon and a polymer block of a conjugated diene. The use of such a thermoplastic elastomer tends to further improve the printing durability of the flexographic printing plate.

[0037] Examples of the monovinyl-substituted aromatic hydrocarbon constituting the thermoplastic elastomer (b-1) include, but are not limited to, styrene, t-butylstyrene, 1,1-diphenylethylene, N,N-dimethyl-p-aminoethylstyrene, N,N-diethyl-p-aminoethylstyrene, vinylpyridine, p-methylstyrene, p-methoxystyrene, tertiary butylstyrene, α-methylstyrene, and 1,1-diphenylethylene. These may be used alone or in combination of two or more. Among these, styrene is preferred from the viewpoints of enabling the photosensitive resin composition layer (b) to be smoothly molded at a relatively low temperature and improving the surface smoothness.

[0038] Conjugated dienes constituting the thermoplastic elastomer (b-1) include, but are not limited to, butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, and chloroprene. These may be used alone or in combination of two or more. Among these, butadiene is preferred from the viewpoint of improving ink entanglement on the flexographic printing plate.

[0039] From the viewpoint of improving ink entanglement, the weight-average molecular weight (Mw) of the thermoplastic elastomer (b-1) is preferably 50,000 to 300,000, and more preferably 70,000 to 200,000. The weight-average molecular weight can be measured by gel permeation chromatography (GPC) and is expressed in terms of polystyrene equivalent molecular weight.

[0040] When the thermoplastic elastomer (b-1) is a block copolymer having a polymer block made of a monovinyl-substituted aromatic hydrocarbon and a polymer block made of a conjugated diene, examples of the thermoplastic elastomer (b-1) include linear block copolymers represented by the following general formula group (I) and / or linear block copolymers or radial block copolymers represented by the following general formula group (II):

[0041] General formula group (I): (AB) n , A-(BA) n , A-(BA) n -B, B-(AB) n General formula group (II): [(AB) k ] m -X, [(AB) k -A] m -X, [(BA) k ] m -X, [(BA) k -B] m -X

[0042] In the general formula groups (I) and (II), A represents a polymer block made of a monovinyl-substituted aromatic hydrocarbon. B represents a polymer block made of a conjugated diene. X represents a residue of a coupling agent such as silicon tetrachloride, tin tetrachloride, epoxidized soybean oil, a polyhalogenated hydrocarbon compound, a carboxylic acid ester compound, a polyvinyl compound, a bisphenol-type epoxy compound, an alkoxysilane compound, a halogenated silane compound, or an ester-based compound, or a residue of a polymerization initiator such as a polyfunctional organolithium compound. In the general formula groups (I) and (II), n, k and m each represent an integer of 1 or more, for example, 1 to 5.

[0043] The content of conjugated dienes and monovinyl-substituted aromatic hydrocarbons in the thermoplastic elastomer (b-1) was measured by a nuclear magnetic resonance spectrometer ( 1 H-NMR) can be used to measure the 1 Measurements can be performed using a JNM-LA400 (manufactured by JEOL, trade name) as the H-NMR measuring instrument, deuterated chloroform as the solvent, a sample concentration of 50 mg / mL, an observation frequency of 400 MHz, TMS (tetramethylsilane) as the chemical shift standard, a pulse delay of 2.904 seconds, 64 scans, a pulse width of 45°, and a measurement temperature of 25°C.

[0044] In the thermoplastic elastomer (b-1), the copolymerization ratio (mass ratio) of the monovinyl-substituted aromatic hydrocarbon to the conjugated diene is preferably monovinyl-substituted aromatic hydrocarbon / conjugated diene=10 / 80 to 90 / 20, more preferably 10 / 90 to 85 / 15, and even more preferably 10 / 90 to 60 / 40, from the viewpoints of printing durability and surface smoothness of the flexographic printing plate. In the above ratio (mass ratio), if the proportion of the monovinyl-substituted aromatic hydrocarbon is 10 or more, sufficient hardness can be obtained in the photosensitive resin composition layer (b), and appropriate printing can be performed with normal printing pressure. In addition, if the proportion of the monovinyl-substituted aromatic hydrocarbon is 90 or less in the above ratio (mass ratio), appropriate hardness can be obtained in the photosensitive resin composition layer (b), and ink can be sufficiently transferred to the printing object in the printing process.

[0045] If necessary, other functional groups may be introduced into the thermoplastic elastomer (b-1), or the thermoplastic elastomer (b-1) may be chemically modified by hydrogenation or the like, or may be copolymerized with other components.

[0046] From the viewpoint of improving ink entanglement in the flexographic printing plate, the content of the thermoplastic elastomer (b-1) in the photosensitive resin composition layer (b) is preferably 60% by mass or more, more preferably 60 to 80% by mass, even more preferably 65 to 80% by mass, and even more preferably 65 to 75% by mass, when the total amount of the photosensitive resin composition layer (b) is taken as 100% by mass.

[0047] <Ethylenically unsaturated compound (b-2)> As described above, the photosensitive resin composition layer (b) preferably contains an ethylenically unsaturated compound (b-2). The ethylenically unsaturated compound (b-2) is a compound having a radically polymerizable unsaturated double bond.

[0048] Examples of such ethylenically unsaturated compounds (b-2) include, but are not limited to, olefins such as ethylene, propylene, vinyltoluene, styrene, and divinylbenzene; acetylenes; (meth)acrylic acid and / or derivatives thereof; haloolefins; unsaturated nitriles such as acrylonitrile; unsaturated amides and derivatives thereof such as acrylamide and methacrylamide; unsaturated dicarboxylic acids and derivatives thereof such as maleic anhydride, maleic acid, and fumaric acid; vinyl acetates; N-vinylpyrrolidone; N-vinylcarbazole; and N-substituted maleimide compounds. Among these, (meth)acrylic acid and / or its derivatives are preferred from the viewpoint of ultraviolet curability and printing durability of the cured photosensitive resin composition layer (b).

[0049] Examples of the derivatives include, but are not limited to, alicyclic compounds having a cycloalkyl group, a bicycloalkyl group, a cycloalkenyl group, a bicycloalkenyl group, or the like; aromatic compounds having a benzyl group, a phenyl group, a phenoxy group, or a naphthalene skeleton, an anthracene skeleton, a biphenyl skeleton, a phenanthrene skeleton, a fluorene skeleton, or the like; compounds having an alkyl group, a halogenated alkyl group, an alkoxyalkyl group, a hydroxyalkyl group, an aminoalkyl group, a glycidyl group, or the like; ester compounds with polyhydric alcohols such as alkylene glycol, polyoxyalkylene glycol, polyalkylene glycol, and trimethylolpropane; and compounds having a polysiloxane structure such as polydimethylsiloxane and polydiethylsiloxane.

[0050] The ethylenically unsaturated compound (b-2) may also be a heteroaromatic compound containing elements such as nitrogen and sulfur.

[0051] Examples of the (meth)acrylic acid and / or derivatives thereof include, but are not limited to, diacrylates and dimethacrylates of alkanediols such as hexanediol and nonanediol; diacrylates and dimethacrylates of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, and butylene glycol; trimethylolpropane tri(meth)acrylate; dimethyloltricyclodecane di(meth)acrylate; isobornyl(meth)acrylate; phenoxypolyethylene glycol (meth)acrylate; pentaerythritol tetra(meth)acrylate, etc. These may be used alone or in combination of two or more.

[0052] From the viewpoint of the mechanical strength of the flexographic printing plate, it is preferable to use at least one type of (meth)acrylate as the ethylenically unsaturated compound (b-2), and it is more preferable to use at least one type of bifunctional (meth)acrylate.

[0053] The number average molecular weight (Mn) of the ethylenically unsaturated compound (b-2) is preferably 100 or more from the viewpoint of improving the non-volatility of the ethylenically unsaturated compound (b-2) during production and storage of the photosensitive resin constituent for flexographic printing plates, and is preferably less than 1,000 from the viewpoint of compatibility with other components, and more preferably 200 or more and 800 or less.

[0054] From the viewpoint of improving ink entanglement in the flexographic printing plate, the content of the ethylenically unsaturated compound (b-2) in the photosensitive resin composition layer (b) is preferably 2% by mass to 30% by mass, more preferably 2% by mass to 25% by mass, and even more preferably 2% by mass to 20% by mass, when the total amount of the photosensitive resin composition layer (b) is taken as 100% by mass.

[0055] [Photopolymerization initiator (b-3)] The photosensitive resin composition layer (b) preferably contains a photopolymerization initiator (b-3). The photopolymerization initiator (b-3) is a compound that absorbs light energy and generates radicals, and examples thereof include a degradable photopolymerization initiator, a hydrogen abstraction photopolymerization initiator, and a compound having a moiety that functions as a hydrogen abstraction photopolymerization initiator and a moiety that functions as a degradable photopolymerization initiator in the same molecule.

[0056] Examples of such photopolymerization initiator (b-3) include, but are not limited to, benzophenone, 4,4-bis(diethylamino)benzophenone, 3,3',4,4'-benzophenonetetracarboxylic anhydride, 3,3',4,4'-tetramethoxybenzophenone, and other benzophenones; anthraquinones, such as t-butylanthraquinone and 2-ethylanthraquinone; thioxanthones, such as 2,4-diethylthioxanthone, isopropylthioxanthone, and 2,4-dichlorothioxanthone; Michler's ketone; diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, 2-methyl-1-( acetophenones such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone, trichloroacetophenone, etc.; benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, etc.; acylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, etc.; methylbenzoyl formate; 1,7-bisacridinylheptane; 9-phenylacridine; and azo compounds such as azobisisobutyronitrile, diazonium compounds, and tetrazene compounds. These may be used alone or in combination of two or more. Among these, from the viewpoint of printing durability of the flexographic printing plate, compounds having a carbonyl group are preferred, and aromatic carbonyl compounds such as benzophenones and thioxanthones are more preferred.

[0057] From the viewpoint of improving ink adhesion of the flexographic printing plate, the content of the photopolymerization initiator (b-3) in the photosensitive resin composition layer (b) is preferably 0.1 to 10 mass%, more preferably 0.1 to 5 mass%, and even more preferably 0.5 to 5 mass%, when the total amount of the photosensitive resin composition layer (b) is taken as 100 mass%.

[0058] [Liquid diene] The photosensitive resin composition layer (b) preferably contains a liquid diene. A liquid diene is a compound having a liquid carbon-carbon double bond. In this specification, the term "liquid" in "liquid diene" refers to a property that allows it to easily flow and deform and to solidify into the deformed shape upon cooling. This term corresponds to an elastomer that has the property of deforming instantly in response to the application of an external force and recovering its original shape in a short time when the external force is removed.

[0059] Examples of liquid dienes include, but are not limited to, liquid polybutadiene, liquid polyisoprene, modified liquid polybutadiene, modified liquid polyisoprene, liquid acrylonitrile-butadiene copolymer, and liquid styrene-butadiene copolymer. The liquid diene is a copolymer containing 50% by mass or more of a diene component. Among these, liquid polybutadiene is preferred from the viewpoint of the mechanical properties of the flexographic printing plate.

[0060] Furthermore, the 1,2-vinyl bond content of the liquid diene, preferably liquid polybutadiene, is preferably 1% or more and 80% or less, more preferably 5% or more and 70% or less, and even more preferably 5% or more and 65% or less, from the viewpoint of ensuring appropriate hardness of the photosensitive resin constituent for flexographic printing plates and the flexographic printing plates using the same. Here, the "1,2-vinyl bond content" refers to the proportion of conjugated diene monomers incorporated via 1,2-bonds among those incorporated via 1,2-bonds, 3,4-bonds, and 1,4-bonds. The 1,2-vinyl bond content can be determined from the peak ratio in the proton NMR (magnetic resonance spectrum) of the liquid polybutadiene.

[0061] In addition, 1,2-polybutadiene, which is a liquid polybutadiene having a 1,2-vinyl bond, has a vinyl double bond in the side chain, and therefore has high reactivity in radical polymerization, and is preferable from the viewpoint of increasing the hardness of the photosensitive resin composition layer (b). Furthermore, liquid polybutadiene is usually a mixture of 1,2-polybutadiene having a 1,2-vinyl bond and 1,4-polybutadiene having a 1,4-vinyl bond. In order to improve the flexibility of a photosensitive resin constituent for a flexographic printing plate and a flexographic printing plate using the same, it is effective to include 1,4-polybutadiene in the liquid diene.

[0062] There are two types of 1,4-polybutadiene: cis-type and trans-type. Both cis-type and trans-type 1,4-polybutadiene have a vinyl group, which is a double bond, inside, so they have low reactivity in radical polymerization and can ultimately be used to produce flexible resins.

[0063] When a mixture of liquid polybutadienes having different 1,2-vinyl bond contents is used, the average value thereof is used as the 1,2-vinyl bond content. From the viewpoint of easily adjusting the reactivity of the photosensitive resin composition layer (b), it is preferable to mix a liquid polybutadiene having a 1,2-vinyl bond content of 10% or less with a liquid polybutadiene having a 1,2-vinyl bond content of 80% or more to adjust the total 1,2-vinyl bond content. From the same viewpoint as above, it is more preferable to mix a liquid polybutadiene having a 1,2-vinyl bond content of 5% or less with a liquid polybutadiene having a 1,2-vinyl bond content of 80% or more to adjust the total 1,2-vinyl bond content.

[0064] Furthermore, the number average molecular weight of the liquid diene is not particularly limited as long as it is liquid at 20°C. However, from the viewpoint of the printing durability and handling of a flexographic printing plate obtained using the photosensitive resin construct for a flexographic printing plate, it is preferably 500 or more and 60,000 or less, more preferably 500 or more and 50,000 or less, and even more preferably 800 or more and 50,000 or less.

[0065] From the viewpoint of improving ink adhesion of the flexographic printing plate, the content of the liquid diene in the photosensitive resin composition layer (b) is preferably 10 to 30 mass%, more preferably 15 to 30 mass%, and even more preferably 20 to 30 mass%, when the total amount of the photosensitive resin composition layer (b) is taken as 100 mass%.

[0066] [Auxiliary additive ingredients] Examples of auxiliary additive components include, but are not limited to, polar group-containing polymers, plasticizers other than liquid dienes, thermal polymerization inhibitors other than stabilizers, antioxidants, ultraviolet absorbers, dyes and pigments, etc.

[0067] Examples of polar group-containing polymers include, but are not limited to, water-soluble or water-dispersible copolymers having polar groups such as hydrophilic groups such as carboxyl groups, amino groups, hydroxyl groups, phosphoric acid groups, and sulfonic acid groups, and salts thereof. More specific examples include carboxyl group-containing acrylonitrile-butadiene rubber, carboxyl group-containing styrene-butadiene rubber, carboxyl group-containing aliphatic conjugated diene polymers, emulsion polymers of ethylenically unsaturated compounds having phosphoric acid groups or carboxyl groups, sulfonic acid group-containing polyurethanes, and carboxyl group-containing butadiene latexes. These polar group-containing polymers may be used alone or in combination of two or more. Among these, carboxyl group-containing butadiene latex is preferred from the viewpoint of obtaining high resolution in a flexographic printing plate.

[0068] Examples of plasticizers other than liquid dienes include, but are not limited to, hydrocarbon oils such as naphthenic oil and paraffin oil; liquid diene-based conjugated diene rubbers such as liquid acrylonitrile-butadiene copolymer and liquid styrene-butadiene copolymer; polystyrene having a number average molecular weight of 2000 or less; and ester-based plasticizers such as sebacate esters and phthalate esters. These other plasticizers may have a hydroxyl group or a carboxyl group. Furthermore, these other plasticizers may have a photopolymerizable reactive group such as a (meth)acryloyl group. The other plasticizers may be used alone or in combination of two or more.

[0069] As the thermal polymerization inhibitor and antioxidant, those commonly used in the field of resin materials or rubber materials can be used, specifically, phenol-based materials. Examples of such phenolic materials include, but are not limited to, vitamin E, tetrakis-(methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate)methane, 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, etc. The thermal polymerization inhibitors and antioxidants may be used alone or in combination of two or more.

[0070] Examples of UV absorbers include, but are not limited to, known benzophenone compounds, salicylate compounds, acrylonitrile compounds, metal complex compounds, and hindered amine compounds. The dyes and pigments listed below may also be used as UV absorbers. Examples of such ultraviolet absorbers include, but are not limited to, 2-ethoxy-2'-ethyloxalic acid bisanilide, 2,2'-dihydroxy-4-methoxybenzophenone, and the like.

[0071] Dyes and pigments are effective as coloring means for improving visibility. Examples of dyes include, but are not limited to, water-soluble basic dyes, acid dyes, direct dyes, etc., and water-insoluble sulfide dyes, oil-soluble dyes, disperse dyes, etc. In particular, anthraquinone dyes, indigoid dyes, and azo dyes are preferred, and azo oil-soluble dyes, etc. are more preferred. Examples of pigments include, but are not limited to, natural pigments, synthetic inorganic pigments, synthetic organic pigments, etc. Examples of synthetic organic pigments include azo pigments, triphenylmethane pigments, quinoline pigments, anthraquinone pigments, and phthalocyanine pigments.

[0072] The total amount of the auxiliary additive components is preferably 0 to 10% by mass, more preferably 0 to 5% by mass, and even more preferably 0 to 3% by mass, when the total amount of the photosensitive resin composition layer (b) is taken as 100% by mass.

[0073] Use of a flexographic thermal development system and thermal development method in the manufacturing process of flexographic printing plates A method for producing a flexographic printing plate includes the following steps: first, using the photosensitive resin construct for a flexographic printing plate described above, irradiating the support side with ultraviolet light (first step); in the case of digital platemaking, irradiating the infrared ablation layer with infrared light to form a pattern; in the case of analog platemaking, attaching a negative to the photosensitive resin layer (second step); using the infrared ablation layer or the negative on which the pattern has been formed as a mask, irradiating the photosensitive resin composition layer with ultraviolet light to form a pattern; and, in the fourth step, removing the unexposed portions of the photosensitive resin composition layer. The flexographic thermal development system of this embodiment is used in the fourth step. Thereafter, a post-exposure treatment step is carried out as necessary, and a flexographic printing plate (relief printing plate) is obtained from the cured product of the photosensitive resin composition layer. From the viewpoint of imparting releasability, the surface of the flexographic printing plate may be brought into contact with a liquid containing a silicone compound and / or a fluorine compound.

[0074] (First step) In the first step, the method of irradiating the photosensitive resin composition layer (b) with ultraviolet light from the support (a) side is not particularly limited, and can be carried out using a known irradiation unit. The wavelength of the ultraviolet light irradiated in this case is preferably 150 to 500 nm, more preferably 300 to 400 nm. Examples of ultraviolet light sources that can be used include, but are not limited to, low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, zirconium lamps, carbon arc lamps, and ultraviolet fluorescent lamps. The first step may be carried out before or after the second step described below.

[0075] (Second step) In the second step, the method for irradiating the infrared ablation layer with infrared rays to form a pattern is not particularly limited, and can be performed using a known irradiation unit. Note that the infrared ablation layer can be irradiated with infrared rays from the infrared ablation layer side. When the photosensitive resin composition for flexographic printing plates described above has a cover film, the cover film is first peeled off before infrared irradiation. The infrared ablation layer is then irradiated with infrared light in a pattern to decompose the resin in the irradiated areas and draw a pattern. This allows a mask for the infrared ablation layer to be formed on the photosensitive resin composition layer. In the second step, suitable infrared lasers include, for example, ND / YAG lasers (e.g., 1064 nm) or diode lasers (e.g., 830 nm). Laser systems suitable for CTP platemaking technology are commercially available; for example, the diode laser system CDI Spark (ESKO GRAPHICS) can be used. This laser system includes a rotating cylindrical drum that holds the structure, an IR laser irradiation device, and a layout computer, and image information is sent directly from the layout computer to the laser device. In analogue plate making, a mask can be similarly formed by using a negative film.

[0076] (Third step) In the third step, the photosensitive resin composition layer is irradiated with ultraviolet light using the infrared ablation layer or negative film on which the pattern has been drawn as a mask, thereby performing pattern exposure. During this process, the ultraviolet light passing through the mask promotes the curing reaction of the photosensitive resin composition layer, and the pattern formed on the infrared ablation layer or negative film is transferred to the photosensitive resin composition layer with the concave and convex portions reversed. The ultraviolet light irradiation may be performed by continuous partial irradiation or by full-surface irradiation. The third step can be carried out while the photosensitive resin construct for a flexographic printing plate is attached to a laser cylinder, but in general, the photosensitive resin construct for a flexographic printing plate is removed from the laser device and irradiated with ultraviolet light using a conventional irradiation unit, which can be the same as the unit exemplified for ultraviolet light irradiation in the first step.

[0077] (Fourth step) The fourth step is a step of removing the unexposed areas of the photosensitive resin composition layer. In the fourth step (development step), the removal method is a thermal development method. In the melting section of the thermal development system of this embodiment, the photosensitive resin construct for flexographic printing plates after the third step is heated to 40°C to 200°C, and the photosensitive resin composition that is masked by the infrared ablation layer or negative film and has not been irradiated with ultraviolet light, i.e., the unexposed area, is melted. The photosensitive resin composition layer is heated by the melting section of the thermal development system of this embodiment. The melting portion may be any known one that has the function of heating the photosensitive resin composition layer. For example, it may be a heating means incorporated in a roll on which a photosensitive resin construct for a flexographic printing plate is placed, or a heating means installed outside the roll. For example, an infrared lamp that irradiates the photosensitive resin composition layer with infrared rays may be used. Next, the non-exposed portion that has melted as described above is absorbed and removed by the absorption and removal unit of the thermal development system of this embodiment. The adsorption / removal section has an absorption layer, and the absorption layer is brought into contact with the non-exposed section to absorb and remove the non-exposed section. The absorbing layer is the developing medium of the present embodiment described above, and it is preferable to use a nonwoven fabric as the developing medium. Thereafter, a flexographic printing plate is produced by optionally post-exposing the plate. When an intermediate layer is present between the infrared ablation layer and the photosensitive resin composition layer, the intermediate layer may be removed simultaneously in the development step. [Example]

[0078] The present invention will be described in more detail below with reference to specific examples and comparative examples, but the present invention is not limited to the following examples in any way. Hereinafter, unless otherwise specified, the length direction of the development medium is the MD (machine direction), and the width direction is the direction perpendicular to the length direction within the plane of the development medium.

[0079] [Physical properties and characteristics of development media for flexographic thermal development] The physical properties and characteristics of the development medium for flexographic thermal development are described below. ((1) Weight) Using nonwoven fabric as the development medium, test pieces of 20 cm long x 25 cm wide nonwoven fabric were taken in accordance with the method specified in JIS L-1906, at three locations per meter in the width direction and three locations per meter in the length direction of the nonwoven fabric sample, for a total of nine locations per meter x 1 m. The mass of the test pieces was measured, and the average value was converted into a mass per unit area to determine the basis weight.

[0080] ((2) Thickness) Using nonwoven fabric as the development medium, the thickness of a test piece of nonwoven fabric (1 m wide x 0.15 m long) was measured at 10 points per 1 m width under a load of 9.8 kPa (load area: 1 cmφ) according to the method specified in JIS L-1906, and the average value was calculated.

[0081] ((3) Apparent density) The basis weight (g / m2) measured as described above (1) 2 ) and the thickness (mm) measured in (2) above, and adjust the units to obtain the following formula: Apparent density = (basis weight) / (thickness) The apparent density of the nonwoven fabric was calculated using the above formula. The apparent density value was used to calculate the void ratio described below.

[0082] ((4) Porosity) The apparent density (g / cm) calculated as in (3) above 3 ) to obtain the following formula: Porosity = {1-(apparent density) / (density of resin that makes up nonwoven fabric)} / 100 The porosity of the nonwoven fabric was calculated from the above.

[0083] ((5) Fiber diameter) The nonwoven fabric used as the development medium was cut to a size of 10 cm x 10 cm, and the top and bottom surfaces were pressed with iron plates at 60°C at a pressure of 0.30 MPa for 90 seconds. Platinum was then vapor-deposited. Using an SEM device (JSM-6510 manufactured by JEOL Ltd.), the platinum-deposited nonwoven fabric was photographed under conditions of an accelerating voltage of 15 kV and a working distance of 21 mm. The magnification was 10,000x for yarns with a weight-average fiber diameter of less than 0.5 μm, 6,000x for yarns with a weight-average fiber diameter of 0.5 μm to 1.5 μm, and 4,000x for yarns with a weight-average fiber diameter of 1.5 μm or more. The field of view at each magnification was 12.7 μm x 9.3 μm at 10,000x, 21.1 μm x 15.9 μm at 6,000x, and 31.7 μm x 23.9 μm at 4,000x. More than 100 fibers were randomly photographed, and the diameters of all fibers were measured. However, fibers fused together in the length direction were excluded from the measurement. The weight average fiber diameter (Dw) when Ni fibers with a fiber diameter Di were present was calculated using the following formula, and the weight average fiber diameter (μm) thus obtained was taken as the fiber diameter of the nonwoven fabric. Dw=ΣWi·Di=Σ(Ni·Di 2 ) / (Ni·Di) (Wherein, Wi = weight fraction of fiber diameter Di = Ni·Di / ΣNi·Di) In Table 1, when multiple numerical values ​​for fiber diameter are listed, each indicates the fiber diameter of each layer in the laminate structure.

[0084] ((6) Opening diameter) The pore size of the nonwoven fabric, which is the development medium, was measured using a Perm Porometer (model: CFP-1200AEX) manufactured by PMI. For the measurements, Silwick manufactured by PMI was used as the immersion liquid, and the sample was immersed in the immersion liquid and thoroughly degassed before the measurements were performed. This measuring device uses a nonwoven fabric as a filter, and with the filter as a measurement sample, the filter is immersed in a liquid with a known surface tension. All of the pores in the filter are covered with a film of liquid, and pressure is applied to the filter. The pore size of the pores is calculated from the pressure at which the liquid film breaks and the surface tension of the liquid. The following formula was used for the calculation. d=C·r / P (In the formula, d (unit: μm) is the pore size of the filter, r (unit: N / m) is the surface tension of the liquid, P (unit: Pa) is the pressure at which the liquid film of that pore size breaks, and C is a constant.) Using the above formula, the flow rate (wet flow rate) was measured when the pressure P applied to a filter immersed in liquid was continuously changed from low to high pressure. At the initial pressure, the liquid film in even the largest pores is not destroyed, so the flow rate is 0. As the pressure is increased, the liquid film in the largest pores is destroyed, generating a flow rate (bubble point). As the pressure is further increased, the flow rate increases with each pressure. The flow rate at the pressure when the liquid film in the smallest pore is destroyed is the same as the flow rate in a dry state (dry flow rate). In the measurement method using this measuring device, the cumulative filter flow rate (unit: %) is calculated by dividing the wet flow rate at a certain pressure by the dry flow rate at the same pressure. The pore size of the liquid film that breaks at the pressure where the cumulative filter flow rate becomes 50% is called the mean flow pore size, and this mean flow pore size is taken as the opening size. Using the above measurement method, measurements were made at three points for each sample, and the pore diameter was calculated as the average value.

[0085] ((7) Elastic recovery rate) The elastic recovery rate of the nonwoven fabric, which is the development medium, was measured using a Shimadzu MCT-50 microcompression tester. The test conditions were a load-unload mode in which a load was applied to the sample up to the maximum test force and then unloaded down to the minimum test force, and measurements were taken. The minimum test force was set to 0.05 mN, and the maximum test force was set to the test force when the nonwoven fabric thickness d was deformed by 10% in compression mode. The elastic recovery was calculated as follows: Elastic recovery rate (%) = L2 / (L1-L2) x 100 L1: Difference in displacement between maximum and minimum test forces in load mode L2: Difference in displacement between maximum and minimum test forces in unloading mode

[0086] ((8) Gakushin Abrasion Fluff (Abrasion Resistance)) Five test pieces (approximately 30 cm wide x 3 cm long) were taken in the width direction, spaced 20 cm apart from the center of the test pieces, and the Gakushin abrasion fluff of the nonwoven fabric used as the development medium was measured using a friction tester Type II (Gakushin type) as described in JIS L-0849, Testing method for color fastness to friction. The test piece was attached to the test table and the friction element so that the measurement surface was in contact with each other, and rubbed back and forth 30 times. After rubbing, the appearance of the nonwoven fabric was inspected and evaluated according to the following criteria. Grade 5: No change on the surface of the nonwoven fabric. Grade 4: There is no pilling on the surface of the nonwoven fabric, but individual threads stand out on the surface, making the surface slightly rough. Grade 3: There is pilling less than 0.5 cm in length, or fluff is floating all over the surface. Grade 2: There is pilling of 1 cm or more in length, or cotton-like material is floating on the friction surface, or the friction surface is worn down. Grade 1: Part of the nonwoven fabric is torn.

[0087] (9) Removability of the Photosensitive Resin Composition in the Unexposed Area The following photosensitive resin composition plate was used. (I) Solvent-developable, non-exposed photosensitive resin composition plate AFP-TOP (registered trademark, manufactured by Asahi Kasei Corporation) A letterpress printing original plate with a support made of polyester film and a thin, flexible film layer made of a photosensitive resin composition primarily composed of styrene-butadiene block copolymer, containing polymerizable monomer components, photopolymerization initiators, plasticizers, and thermal polymerization inhibitors. It is 1.7 mm thick. (II) Water-developable, non-exposed photosensitive resin composition plate AWP-DEF (registered trademark, manufactured by Asahi Kasei Corporation) A letterpress printing original plate with a support made of polyester film and a thin, flexible film layer containing a photosensitive resin composition primarily composed of styrene-butadiene block copolymer, hydrophilic polymer, polymerizable monomer component, photopolymerization initiator, plasticizer, and thermal polymerization inhibitor. It is 1.7 mm thick. (I) and (II) were each cut into a size of 30 cm x 30 cm, the cover film was peeled off, and the pieces were placed in an Esko CDI SPARK2530. Laser drawing was performed at a laser intensity of 3.8 J to form an exposed area of ​​10 cm x 10 cm in the center. On an "AFP-1216E" exposure machine (manufactured by Asahi Kasei Corporation, product name), a lower ultraviolet lamp (manufactured by PHILIPS, product name UV lamp TL80W / 10R) was used to first expose the printing plate from the support side to 600 mJ / cm so that the relief depth of the printing plate was 0.5 mm. 2 The entire surface was exposed. Next, the upper lamp (PHILIPS UV lamp TL80W / 10R, product name) was used to irradiate the cover film with 8000mJ / cm 2 The exposure intensity was measured using a UV illuminance meter MO-2 manufactured by Oak Manufacturing Co., Ltd. (product name: UV-35 filter). The exposed flexographic printing plate was fixed to a 35 cm diameter metal roll driven by a motor using double-sided adhesive tape. A nonwoven fabric for thermal development, which was a development medium, was placed so as to be able to pass between a plurality of heatable metal rolls each having a diameter of 5 cm. An infrared lamp for heating the photosensitive resin composition layer was fixed on the metal roll holding the flexographic printing plate precursor. The infrared lamp was turned on, and the metal roll heated to 170°C was slowly rotated (about 2 rpm) by a motor. 5 The nonwoven fabric was brought into contact with the surface of the photosensitive resin composition layer of the flexographic printing plate precursor at a contact pressure of 100 Pa and then passed through. The cycle was repeated until the relief depth, that is, the difference in level between the exposed and unexposed areas, reached 0.5 mm. The removability was evaluated based on the number of cycles required to wipe off the non-exposed area. The fewer the number of cycles, the better the removal. In the following evaluation criteria, if the rating was 3 or higher, it was determined that a waste reduction effect could be expected. <Evaluation criteria> 4: After wiping 10 times or less, the relief depth, i.e., the difference in level between the exposed and unexposed areas, became 0.5 mm. 3: Ten wipes were not sufficient, but 12 wipes or less reduced the relief depth, i.e., the difference in level between the exposed and unexposed areas, to 0.5 mm. 2: Twelve wipes were not sufficient, but 14 or fewer wipes reduced the relief depth, i.e., the difference in level between the exposed and unexposed areas, to 0.5 mm. 1: After wiping 15 times or more, the relief depth, i.e., the difference in level between the exposed and unexposed areas, became 0.5 mm.

[0088] [Production of nonwoven fabric for flexographic thermal development] (Examples 1 (1a, 1b), 2 to 3, 6) The resin material shown in Table 1 below was extruded from a spunbond spinneret (V-shaped nozzle) at a spinning temperature of 290°C, and the filaments were symmetrically cooled from both sides by a cooling device directly below the spinneret (air speed of 0.5 m / s for both sides), and drawn by a draw jet to obtain continuous filaments (fiber diameter 16 μm). The fibers were spread and dispersed, and deposited on a web conveyor to form a web. In Table 1 below, "PET / CoPET" is a sheath-core structure fiber made of polyethylene terephthalate and a polyethylene terephthalate copolymer, "PET" is polyethylene terephthalate, and "Ny" is nylon 6. Furthermore, the webs were integrated using a calendar roll (roll temperature 220° C., linear pressure 500 N / cm). The "flat" type of calendar roll is a calendar roll for flattening, which applies pressure to the entire surface. The "emboss" type is a calendar roll for embossing, which applies pressure to only a portion of the nonwoven fabric surface using an uneven roll. The thermal compression rate is the ratio of the area of ​​the compressed portion to the area of ​​the nonwoven fabric, and is expressed in %. The position of the heat retaining plate of the heating roll was adjusted so that the fabric temperature before pressing, which is important for controlling the elastic recovery rate, would be the temperature shown in Table 1 below. Other manufacturing conditions than those mentioned above, and the physical properties and evaluation results of the nonwoven fabric for flexographic thermal development produced are shown in Table 1 below.

[0089] (Examples 4 and 5 (5a and 5b)) Polyethylene terephthalate (PET) was extruded from a spinneret (V-shaped nozzle) for the spunbonding method at a spinning temperature of 290°C, and the filaments were cooled symmetrically from both sides by a cooling device directly below the spinneret (air speed of 0.5 m / s for both sides). The filaments were then drawn by a draw jet to obtain continuous filaments (fiber diameter 16 μm). The filaments were then spread and dispersed, and deposited on a web conveyor to form a web. Next, a PET solution was used to form an ultrafine fiber nonwoven fabric layer (layer I) by melt-blown spinning at a spinning temperature of 290°C and sprayed onto the web. The distance from the melt-blown nozzle to the web was 300 mm, and the suction force at the collection surface directly below the melt-blown nozzle was set to 0.2 kPa and the wind speed to 7 m / sec. This resulted in the formation of an ultrafine fiber nonwoven fabric layer with a fiber diameter of 3 μm. Furthermore, a continuous filament web (fiber diameter 16 μm) produced by the same spunbonding method as above was laminated thereon to obtain a laminated web. Furthermore, the laminated web was integrated using a calender roll (roll temperature 220° C., linear pressure 500 N / cm). The position of the heat insulating plate of the heating roll was adjusted so that the fabric temperature before pressing, which is important for controlling the compression characteristics, would be the temperature shown in Table 1 below. Table 1 shows the manufacturing conditions other than those mentioned above, the physical properties of the nonwoven fabric for flexographic thermal development produced, and the evaluation results.

[0090] (Comparative example 1 (1a, 1b), 2) The resin material was nylon (Comparative Example 1) or polyethylene terephthalate (Comparative Example 2), and the temperature of the nonwoven fabric before calendaring was set to the ambient temperature of 24 to 25°C. Other conditions were the same as in Example 1, and a nonwoven fabric for flexographic thermal development was produced. The physical properties and evaluation results of the produced nonwoven fabric for flexographic thermal development are shown in Table 1 below.

[0091] In Table 1, it is assumed that the same nonwoven fabric for flexographic thermal development is used in (Examples 1a and 1b), (Examples 5a and 5b), and (Comparative Examples 1a and 1b). The "-" in the heat-pressing rate indicates that the calender roll type is flat, and therefore heat-pressing is performed on the entire surface of the nonwoven fabric.

[0092] [Table 1]

[0093] [Manufacture and evaluation of flexographic printing plates] In the following examples and comparative examples, flexographic printing plates were produced using a thermal development system and evaluated.

[0094] Laminates 1 to 6 each comprising a support and a photosensitive resin composition layer were produced as follows. ((1) Production of Laminate of Support and Photosensitive Resin Composition Layer) <Production Example 1 of Laminate 1 of Support and Photosensitive Resin Composition Layer> A photosensitive resin composition was prepared by kneading 70 parts by mass of Tufprene A (styrene-butadiene-styrene block copolymer manufactured by Asahi Kasei Corporation), 21 parts by mass of B-2000 (liquid polybutadiene manufactured by Nippon Petrochemical Co., Ltd.), 7 parts by mass of 1,9-nonanediol diacrylate, 2 parts by mass of 2,2-dimethoxy-2-phenylacetophenone, and 0.3 parts by mass of 2,6-di-t-butyl-p-cresol in a pressure kneader. Next, the photosensitive resin composition was loaded into an extrusion molding machine, and a support (polyethylene terephthalate film) was laminated to one side of the photosensitive resin composition layer extruded from the T-shaped die, and a release film (Diafoil MRV100, manufactured by Mitsubishi Chemical Corporation) was laminated to the side of the photosensitive resin composition layer opposite the support laminate side, thereby obtaining a laminate 1 of the support and the photosensitive resin composition layer. The photosensitive resin composition layer was subjected to molecular weight distribution measurement by GPC. By calculating the area of ​​the molecular weight distribution curve for components with a weight average molecular weight (Mw) of 70,000 or more, it was found that the amount of components with Mw of 70,000 or more was 74.3%.

[0095] <Production Examples 2 to 5 of Laminates of Support and Photosensitive Resin Composition Layer> Laminates 2 to 5 of a support and a photosensitive resin composition layer were obtained in the same manner as the above-mentioned Laminate 1, except that the amounts (parts by mass) of Tufprene A and B-2000 were changed as shown in the following Table 2. Table 2 shows the physical properties.

[0096] <Production Example of Laminate 6 of Support and Photosensitive Resin Composition Layer> A pressure-resistant reactor equipped with a stirrer and a temperature-controlling jacket was initially charged with 125 parts by mass of water and 2 parts by mass of ammonium salt of α-sulfo(1-nonylphenoxy)methyl-2-(2-propenyloxy)ethoxy-poly(oxy-1,2-ethanediyl) "ADEKA REASOAP" (manufactured by Asahi Denka Kogyo Co., Ltd.) as a reactive emulsifier, and the internal temperature was raised to 80°C. 10 parts by mass of styrene, 60 parts by mass of butadiene, 23 parts by mass of butyl acrylate, 5 parts by mass of methacrylic acid, and An oily mixture of a monomer mixture consisting of 2 parts by mass of acrylic acid and 2 parts by mass of t-dodecyl mercaptan and an aqueous solution consisting of 28 parts by mass of water, 1.2 parts by mass of sodium peroxodisulfate, 0.2 parts by mass of sodium hydroxide, and 2 parts by mass of the ammonium salt of α-sulfo(1-nonylphenoxy)methyl-2-(2-propenyloxy)ethoxy-poly(oxy-1,2-ethanediyl) were added at a constant flow rate over 5 hours, and over 6 hours, respectively. The temperature was then maintained at 80°C for 1 hour to complete the polymerization reaction, and a copolymer latex was obtained, which was then cooled. Furthermore, the pH of the produced copolymer latex was adjusted to 7 with sodium hydroxide, and then unreacted monomers were removed by steam stripping. The mixture was then filtered through a 200-mesh wire screen, and finally the solid content of the filtrate was adjusted to 40% by mass, thereby obtaining an aqueous dispersion of the hydrophilic copolymer. The resulting aqueous dispersion of the hydrophilic copolymer was dried up in a vacuum dryer at 50° C. to remove water, thereby obtaining a hydrophilic copolymer. A photosensitive resin composition was prepared by kneading 10 parts by mass of the hydrophilic copolymer, 65 parts by mass of Tufprene A (styrene-butadiene-styrene block copolymer manufactured by Asahi Kasei), 16 parts by mass of B-2000 (liquid polybutadiene manufactured by Nippon Petrochemical Co., Ltd.), 7 parts by mass of 1,9-nonanediol diacrylate, 2 parts by mass of 2,2-dimethoxy-2-phenylacetophenone, and 0.3 parts by mass of 2,6-di-t-butyl-p-cresol in a pressure kneader. Next, the photosensitive resin composition was placed in an extrusion molding machine, and a support (polyethylene terephthalate film) was laminated to one side of the photosensitive resin composition layer extruded from a T-die, and a release film (Diafoil MRV100, manufactured by Mitsubishi Chemical Corporation) was laminated to the side of the photosensitive resin composition layer opposite the support laminate side, thereby obtaining a laminate 6 of the support and the photosensitive resin composition layer. Table 2 shows the physical properties.

[0097] [Table 2]

[0098] ((2) Manufacturing of infrared ablation layer laminate) <Production Example of Infrared Ablation Layer Laminate> 7.8 parts by mass of Tufprene 315 (Asahi Kasei, styrene-butadiene block copolymer), 70.4 parts by mass of toluene, and 17.6 parts by mass of propylene glycol 1-monomethyl ether 2-acetate (PMA) were mixed to dissolve the Tufprene 315 in the solvent. Then, 4.2 parts by mass of carbon black (Mitsubishi Chemical, #30) was added, and the mixture was mixed for 4 hours using a bead mill to obtain a carbon black dispersion. The carbon black dispersion obtained as described above was coated onto a 100 μm-thick PET film serving as a cover film so that the film thickness after drying would be 2.5 μm, and the coating was dried at 90°C for 2 minutes to obtain an infrared ablation layer laminate, which is a laminate of an infrared ablation layer and a cover film.

[0099] ((3) Production of Printing Plates Using Thermal Development Systems of Examples 101 to 110 and Comparative Examples 101 to 103) [Example 101] The release film was peeled off from the laminate of the support and the photosensitive resin composition layer, and the infrared ablation layer laminate was laminated in an environment of 25°C and 40% humidity so that the infrared ablation layer was in contact with the photosensitive resin composition layer. The laminate was then placed on a hot plate set to 120°C so that the cover film surface was in contact with the heating part of the hot plate, and heat was applied for 1 minute to obtain photosensitive resin structure 1 for flexographic printing plates of Example 101. The bar film was peeled off from the photosensitive resin construct 1 for flexographic printing plates prepared as described above, and the apparatus was placed on an Esko CDI SPARK2530, and a halftone dot image (AM100, 133, 150, 175, 200 lines) was drawn using a laser intensity of 3.8J. On an "AFP-1216E" exposure machine (manufactured by Asahi Kasei Corporation, product name), a lower ultraviolet lamp (manufactured by PHILIPS, product name UV lamp TL80W / 10R) was used to first expose the printing plate from the support side to 600 mJ / cm so that the relief depth of the printing plate was 0.5 mm. 2 The entire surface was exposed. Next, the upper lamp (PHILIPS UV lamp TL80W / 10R, product name) was used to irradiate the cover film with 8000mJ / cm 2 The exposure intensity was measured using a UV illuminance meter MO-2 manufactured by Oak Manufacturing Co., Ltd. (product name: UV-35 filter). The exposed flexographic printing plate was fixed to a 35 cm diameter metal roll driven by a motor using double-sided adhesive tape. As a development medium for thermal development, the nonwoven fabric of Example 5 (common to 5a and 5b) shown in Table 1 was placed so as to be able to pass between a plurality of heatable metal rolls each having a diameter of 5 cm. An infrared lamp for heating the photosensitive resin composition layer relatively quickly was fixed on the metal roll holding the flexographic printing plate precursor. The infrared lamp was turned on, and the metal roll heated to 170°C was slowly rotated (about 2 rpm) by a motor. 5 The nonwoven fabric was brought into contact with the photosensitive resin composition surface of the printing plate blank at a contact pressure of 100 Pa and passed through. The roll holding the printing plate was cycled 14 times to remove the uncured portions of the photosensitive resin composition layer.

[0100] [Examples 102 to 110] and [Comparative Examples 101 to 103] The type of laminate of the support and the photosensitive resin composition layer was selected from 1 to 6 in Table 2 and changed. In addition, the type of nonwoven fabric used as a development medium for thermal development was selected from those shown in Table 1 and changed to those shown in Table 3 below. In addition, since Examples 1a, 1b, Examples 5a, 5b, and Comparative Examples 1a, 1b all use the same nonwoven fabric, they are referred to as Example 1, Example 5, and Comparative Example 1, respectively. Other conditions were the same as in Example 101, and a flexographic printing plate was produced.

[0101] [Evaluation of the print version] <Evaluation of ink entanglement> An AI-3 type flexographic printing machine (manufactured by Iyo Kikai) was used, and OPP film was used as the printing substrate. The solvent ink used was Process X Cyan (trade name, manufactured by Toyo Ink Mfg. Co., Ltd.). The ink was adjusted by adding a solvent to a viscosity of 15 seconds using a Zahn Cup #4 manufactured by Rigo Co., Ltd., and used as the printing ink. The anilox roll was 800 lpi (cell volume 3.8 cm). 3 / m 2 ), and 3M1020 (trade name, manufactured by Sumitomo 3M Limited) was used for the cushion tape, and 100 m was printed at a printing speed of 100 m / min. At this time, in order to accelerate the ink entanglement evaluation, the pressure of the anilox roll was increased by 0.02 mm from the appropriate value in order to supply an excess amount of ink to the flexographic printing plate, and the printing pressure was also increased by 0.15 mm from the appropriate value in order to increase the deformation of the relief surface and accelerate the ink entanglement. After printing 100 m, the anilox roll was separated from the flexographic printing plate. Then, 10 m of printing was carried out with the flexographic printing plate not in contact with the anilox roll, and excess ink was removed from the surface of the flexographic printing plate. The printing press was then stopped and the remaining ink in the halftone dot areas of the flexographic printing plate was evaluated. The halftone dots to be evaluated were 10 locations in total, with halftone dot areas of 3 and 30% set at AM100, 133, 150, 175, and 200 lines placed within the image. The spaces between the halftone dots (recesses) on the resulting flexographic printing plate after printing were observed with a magnifying glass. The evaluation criteria for the observation results are shown below. In the following evaluation criteria, a rating of 3 or higher was evaluated as being suitable for practical use without any problems.

[0102] <Evaluation criteria> 5: No ink entanglement was observed among the 10 halftone dots. 4: Of the 10 halftone dots, there were 1 to 2 halftone dots where the ink entangled over 10% or more of the image area. 3: Of the 10 halftone dots, there were 1 to 2 halftone dots where ink was mixed over 30% or more of the image area. 2: Of the ten halftone dots, 3 to 5 had ink entangled over 30% or more of the image area. 1: Of the 10 halftone dots, there were 6 or more halftone dots with ink entangled over 30% or more of the image area.

[0103] [Table 3]

[0104] This application is based on a Japanese patent application (Patent Application No. 2021-068920) filed with the Japan Patent Office on April 15, 2021, and a Japanese patent application (Patent Application No. 2021-068918) filed with the Japan Patent Office on April 15, 2021, the contents of which are incorporated herein by reference. [Industrial Applicability]

[0105] The development medium and heat development system for flexographic thermal development of the present invention have wide industrial applicability in the general commercial printing field.

Claims

1. 1. A development medium for flexographic thermal development, comprising: The porosity is 35% or more and 95% or less, The elastic recovery rate is 40% or more and 99% or less, It is a nonwoven fabric, A development medium comprising a polyester resin and / or a polyester copolymer.

2. 2. The development medium of claim 1, wherein the elastic recovery is 46% or more and 99% or less.

3. 2. The development medium of claim 1, wherein the elastic recovery is 65% or more and 99% or less.

4. The Gakushin abrasion fluff grade is between 4.0 and 5.

0. The development medium of claim 1 .

5. The pore diameter is 1.0 μm or more and 50.0 μm or less, A development medium according to any one of claims 1 to 4.

6. The fiber length is 50 mm or more. A development medium according to any one of claims 1 to 5.

7. A fiber layer having a fiber diameter of 0.1 μm or more and 5.0 μm or less, A development medium according to any one of claims 1 to 6.

8. At least two fiber layers each having a fiber diameter of 5.0 μm or more and 30.0 μm or less are included, a fiber layer having a fiber diameter of 0.1 μm or more and 5.0 μm or less as an intermediate layer between the fiber layers having a fiber diameter of 5.0 μm or more and 30.0 μm or less; A development medium according to any one of claims 1 to 7.

9. Weight per unit area is 10g / m 2 60g / m or more 2 That is, A development medium according to any one of claims 1 to 8.

10. The thickness is 15 μm or more and 300 μm or less. A development medium according to any one of claims 1 to 9.

11. A thermal development method using a thermal development system for a flexographic printing plate precursor, comprising: The thermal development system for the flexographic printing original plate includes a melting section that melts the non-exposed area of ​​the photosensitive resin composition, an absorbing and removing section that has an absorbing layer, and , and The absorbent layer is a development medium according to any one of claims 1 to 10, bringing an absorbing layer into contact with the non-exposed portion to absorb and remove the non-exposed portion; Thermal development method.

12. 1. A flexographic printing plate thermal development system comprising: a melting portion that melts the non-exposed portion of the photosensitive resin composition; an absorbing / removing section that brings an absorbing layer into contact with the non-exposed section and absorbs and removes the non-exposed section; , and The absorbent layer is a development medium according to any one of claims 1 to 10. Thermal development system.

13. The photosensitive resin composition comprises The amount of components having a weight average molecular weight (Mw) of 70,000 or more as measured by GPC is 60% or more.

13. The thermal development system of claim 12.

14. The photosensitive resin composition comprises the amount of components having a weight average molecular weight (Mw) of 70,000 or more as measured by GPC is 60% or more and 80% or less; 14. The thermal development system according to claim 12 or 13.

Images