Developing brush, developing device, method for manufacturing flexographic printing plate, and method for developing photosensitive resin flexographic printing original plate

Abstract

The purpose of the present invention is to provide a developing brush, a developing device, a method for manufacturing a flexographic printing plate, and a method for developing a photosensitive resin flexographic printing original plate, which satisfy desired developing speed and image reproducibility and have long performance duration. A developing brush (1) which rubs against a photosensitive resin flexographic printing original plate (2) in order to remove an uncured portion of a photosensitive resin from the photosensitive resin flexographic printing original plate (2) and develop the photosensitive resin flexographic printing original plate (2) is characterized in that the brush has a plurality of bristles implanted on a base material (22), each of the plurality of bristles has a diameter of 80-250 [mu] m, and the brush (1) is provided with a plurality of brush teeth. The bristle density, expressed as the ratio of the cross-sectional area of the plurality of bristles to the area of the surface of the base material into which the plurality of bristles are implanted, is 22-37%.

Description

Technical Field

[0001] The present invention relates to a developing brush, a developing device, a method for manufacturing a flexible printing plate and a method for developing a photosensitive resin flexible printing original plate. Background Art

[0002] As a method for producing a printing plate by forming projections and depressions on a photosensitive resin layer stacked on the surface of a support, the following method is known: a photosensitive resin layer formed using a photosensitive composition is exposed to ultraviolet light via an original image film or the like, the image portion is selectively cured, and the uncured portion is removed using a developer (for example, refer to Patent Document 1).

[0003] There is a demand for improving the development speed and image reproducibility in the development method, and a brush development method, a spray development method, and a method combining brush development and spray development (for example, see Patent Document 2) are being studied. [Prior art literature] [Patent Document]

[0004] Patent Document 1: Japanese Patent Application Publication No. 6-83072 Patent Document 2: JP Patent Publication No. 2010-117623 Summary of the invention [Problems to be Solved by the Invention]

[0005] However, none of these prior arts have studied the duration of their performance.

[0006] The present invention has been completed in view of the above circumstances, and its purpose is to provide a developing brush, a developing device, a method for manufacturing a flexographic printing plate, and a method for developing a photosensitive resin flexographic printing plate that can satisfy all of the following three elements in a high-dimensional manner, that is, satisfy the desired development speed and image reproducibility, and have a long duration of performance (hereinafter, also referred to as brush life). [Methods for solving the problem]

[0007] The present inventors have conducted intensive research and found that the above-mentioned problems can be solved by the following means, thereby achieving the present invention. That is, the present invention may include the following inventions. [1] A developing brush, characterized in that it is a brush that is rubbed against a photosensitive resin flexographic printing plate in order to remove uncured portions of a photosensitive resin from the photosensitive resin flexographic printing plate for development. The brush has a plurality of bristles embedded in a substrate. Each of the plurality of bristles has a diameter of 80 to 250 μm, and a bristle density expressed as a ratio of a cross-sectional area of ​​the plurality of bristles to an area of ​​a surface of the base material on which the plurality of bristles are implanted is 22% to 37%. [2] The developing brush according to [1], wherein the length of each of the plurality of bristles from the end portion on the side not implanted in the substrate to the substrate is 10 mm to 25 mm. [3] The developing brush according to [1], characterized in that the material of the plurality of bristles is polyester resin and / or polyamide resin and / or olefin resin. [4] A developing device, comprising: using the developing brush described in any one of [1] to [3] to remove the uncured portion from the photosensitive resin flexographic printing original plate. [5] The developing device according to [4], wherein a brush pressure of the developing brush during development of the photosensitive resin flexographic printing original plate is 0.5 to 5 mm. [6] A method for manufacturing a flexible printing plate, characterized in that the flexible printing plate is manufactured by rubbing a brush against a photosensitive resin flexible printing plate to remove uncured portions of the photosensitive resin from the photosensitive resin flexible printing plate, wherein the brush is a brush having a plurality of bristles implanted in a substrate, each of the plurality of bristles having a diameter of 80 to 250 μm, and a bristle density expressed as a ratio of the cross-sectional area of ​​the plurality of bristles to the area of ​​the surface of the substrate on which the plurality of bristles are implanted, being greater than 22% and less than 37%. [7] A method for developing a photosensitive resin flexible printing plate, characterized in that the following development is performed: by rubbing a brush against the photosensitive resin flexible printing plate, the uncured portion of the photosensitive resin is removed from the photosensitive resin flexible printing plate, the brush is a brush having a plurality of bristles implanted in a substrate, the plurality of bristles each having a diameter of 80 to 250 μm, and a bristle density expressed as a ratio of the cross-sectional area of ​​the plurality of bristles to the area of ​​the surface of the substrate on which the plurality of bristles are implanted is greater than 22% and less than 37%. [Effects of the invention]

[0008] According to the present invention, a developing brush, a developing device, a method for producing a flexographic printing plate, and a method for developing a photosensitive resin flexographic printing plate can be provided which can satisfy desired developing speed and image reproducibility and have a long brush life and can maintain the performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] [ Figure 1 ] is a diagram showing an example of the structure of an intermittent developing machine for developing a photosensitive resin plate having a brush involved in the first embodiment. [ Figure 2 ] is a diagram showing an example of the structure of an online developing machine for developing a photosensitive resin plate having a brush involved in the first embodiment. [ Figure 3 ] is a diagram showing an example of the structure of the brush involved in the first embodiment as a basic pattern. [ Figure 4 ] is a diagram for explaining the length of the bristles of the brush involved in the first embodiment. [ Figure 5 ] is a diagram for explaining the bristle density of the brush involved in the first embodiment. [ Figure 6 ] is a diagram showing another example of the structure of the brush involved in the first embodiment as a staggered pattern. [ Figure 7 ] is a diagram showing another example of the structure of the brush involved in the first embodiment as a deformed staggered pattern. [reference numerals] 100: Intermittent developer 1: Developer brush 2: Photosensitive resin plate 3: Developing brush motor 4: Locator 5: Developer 6: Development tank 7: Circulation pump 8: Filter 200: Online developer 9: Pre-wash 10: Conveyor pin 11: Rinse brush 12: Air Knife 13: Conveyor chain 14: Developer receiver 15: Flushing liquid piping 16: Filter pump 17: Concentrate tank 18: Developer tank 19: Developer pump 20: Bristle Bundle 21: Brush holes 22: Base material DETAILED DESCRIPTION

[0010] Hereinafter, the various embodiments of the present application will be described with reference to the accompanying drawings. The following embodiments are merely preferred application examples, and the application scope of the technology involved in the present application is not limited to these. In this specification, for the sake of simplicity of reference, components having the same function may be represented by the same reference numerals, but these components do not necessarily refer to the same components.

[0011] <Developer> Figure 1 An example of the structure of an intermittent developer 100 having a developing brush (hereinafter, also referred to as a brush) 1 according to the first embodiment is shown. The intermittent developer 100 uses the brush 1 to develop a photosensitive resin plate 2. The photosensitive resin plate before development may also be referred to as a photosensitive resin original plate. The intermittent developer 100 includes, for example, a developing brush motor 3, a setter 4, a developing tank 6 storing a developer 5, a circulation pump 7, and a filter 8.

[0012] The intermittent developer 100 fixes the photosensitive resin plate 2 to the positioner 4, and makes the brush 1 and the photosensitive resin plate 2 relatively rub against each other in the developer 5, thereby developing the photosensitive resin plate 2, that is, removing the uncured part of the photosensitive resin in the photosensitive resin plate 2. As a result of the development, a printing plate is manufactured from the photosensitive resin plate 2. The rubbing movement can be performed while applying the developer 5 instead of performing it in the developer 5. The rubbing movement is achieved by rotating and / or translating the brush 1 and / or the positioner 4. Figure 1 , an example of a case where the positioner 4 is caused to perform rotational motion and / or translational motion by the developing brush motor 3 is shown. In the intermittent developing machine 100, the following intermittent form is adopted: after the photosensitive resin plate 2 is developed for a predetermined time, it is taken out from the positioner 4, a new photosensitive resin plate 2 is fixed, and the next development is performed. During the development, the portion of the photosensitive resin of the photosensitive resin plate 2 that has not been cured in the exposure process of the previous process is removed. Figure 1 The example of a typical intermittent developer is shown, but the structure of the intermittent developer that can use the brush 1 according to the first embodiment is not limited to Figure 1 The structure shown. Since the photosensitive resin dispersed in the developer 5 does not separate and the resin concentration in the developer 5 can be homogenized, it is preferred that the developer 5 is always circulated in the circulation pump 7. Since the debris floating in the developer 5 can be removed, it is further preferred that the developer 5 circulated by the circulation pump 7 passes through the filter 8. The debris refers to the debris that is peeled off from the plate due to insufficient curing of the photosensitive resin after exposure, and the debris obtained by the developer 5 drying in the platemaking machine.

[0013] Figure 2 An example of the structure of an inline developer 200 having the brush 1 according to the first embodiment is shown. The inline developer 200 also uses the brush 1 to develop the photosensitive resin plate 2. The inline developer 200 includes, for example, a filter 8, a pre-washing brush 9, a conveying pin 10, a flushing brush 11, an air knife 12, a conveying chain 13, a developer receiver 14, a flushing liquid pipe 15, a filter pump 16, a concentration tank 17, a developer tank 18 storing a developer 5, and a developer pump 19.

[0014] Similar to the intermittent developer 100, the inline developer 200 also develops the photosensitive resin plate 2 by relatively frictionally moving the brush 1 and the photosensitive resin plate 2 in the presence of the developer 5. Unlike the intermittent developer, the inline developer 200 is a developing device characterized by being able to continuously develop the photosensitive resin plate 2. Figure 2 The example of a typical inline developer is shown, but the structure of the inline developer that can use the brush 1 according to the first embodiment is not limited to Figure 2 The structure shown. A plurality of holes are formed at the end of the photosensitive resin plate 2 and the holes are inserted into the pins of the conveying pin 10, thereby fixing the photosensitive resin plate 2 to the conveying pin 10. The online developer 200 conveys the conveying chain 13 by hooking the conveying pin 10 on the conveying chain 13 of the developer, thereby conveying the photosensitive resin plate 2 from the front end to the rear of the online developer 200. In the online developer 200, a pre-washing brush 9, a developing brush 1, a rinsing brush 11, and an air knife 12 are sequentially arranged from the front end to the rear. In addition, an exposure device may be arranged in front and behind.

[0015] The pre-washing brush 9 is in the shape of a roller, and the mask layer on the surface of the photosensitive resin plate 2 is removed by the rotation of the roller. The mask layer includes, for example, a protective layer and an infrared photosensitive layer. The developing brush 1 is used to develop the photosensitive resin plate 2. Specifically, the brush 1 and the photosensitive resin plate 2 are rubbed relative to each other in the developer 5 while the photosensitive resin plate 2 is transported at a predetermined speed, thereby developing the photosensitive resin plate 2. The rubbing movement can be performed while applying the developer 5 instead of performing it in the developer 5. The rubbing movement is achieved by rotating and / or translating the brush 1. Regarding the rubbing movement, in addition to rotating and / or translating the brush 1, or by translating the transport pin 10 instead of rotating and / or translating the brush 1, the rubbing movement can be achieved. During the development, the portion of the photosensitive resin of the photosensitive resin plate 2 that has not been cured in the exposure process of the previous process is removed. The developer 5 used in the development is stored in the developing tank 18. The developer circulated from the development tank 18 by the developer pump 19 is used when removing the mask layer with the pre-washing brush and / or performing development with the development brush 1 .

[0016] The washing brush 11 is in the shape of a roller, and by rotating the roller, it rubs the photosensitive resin plate 2, sprays a developer having a lower resin concentration than the developer 5 used in the development, a new developer or water, and removes the debris remaining on the plate. The air knife 12 blows the supplied air finely, blows the moisture of the photosensitive resin plate 2 to the front side of the conveying direction, and drains the moisture. The filter 8 is a cross-flow filter membrane, and the diameter of the membrane is, for example, 0.05 to 10 μm. A part of the developer 5 accumulated in the developer tank 18 used in the development is moved to the concentration tank 17, and the developer in the concentration tank 17 is moved by the filter pump 16, passes through the filter 8, and the filtrate is moved to the washing liquid pipe 15, and the developer with a high resin concentration is returned to the concentration tank 17 for circulation. By using such a precise filter membrane, the developer 5 used in the development is made into the developer used in the washing brush 11. Compared with the case of using a new developer, the use of the developer generated in this way is excellent in that the amount of development waste liquid generated can be reduced. When using water to remove debris in the rinse brush 11 , a structure is used in which water is drained without mixing with the developer 5 .

[0017] The case where the conveying pin 10 is used in conveying the photosensitive resin plate 2 is shown as an example, but as an online developer having the brush 1 involved in the first embodiment, in addition to the above, there can be used: a conveyor type having a conveyor belt that can fix the photosensitive resin plate 2; and a setting machine type in which the photosensitive resin plate 2 is attached and fixed to a setting machine plate, and the setting machine plate is conveyed by a clamping roller or a chain, etc. There is a rigid structure on the back of the photosensitive resin plate 2, and the transfer method is not particularly specified as long as the photosensitive resin plate 2 can be transferred from the front to the rear of the developing device.

[0018] <Developer Brush> Figure 3 FIG. 1 is an example of the structure of the brush 1 according to the first embodiment. The following description is made using the following two axial directions parallel to the surface of the base material of the brush 1 on which the bristles are planted. Figure 1 The depth direction is called the X-axis direction. If it is an online device, the direction perpendicular to the plate transfer direction can be called the X-axis direction. In addition, if it is an intermittent device, Figure 1 The left and right direction is called the Y-axis direction. If it is an online device, the plate transfer direction can be called the Y-axis direction.

[0019] The brush 1 includes a plurality of bristle bundles 20 and a base material (hereinafter, also referred to as a brush base material) 22. The brush 1 is made, for example, by regularly arranging a plurality of brush holes 21 on the base material 22 and planting bristles of a certain bristle bundle 20 in each hole 21. There are various methods for planting bristles, representative of which are a mechanical method of planting bristles by using a thin metal wire to drive the folded bristles into the base material 22, a manual sewing method of pulling the folded bristles from the inside of the hole with a thread or a metal wire to fix them, and an ultrasonic method of directly driving the bristle bundle 20 into the hole of the base material 22 and fixing them by ultrasonic welding. The brush 1 can be made by any method.

[0020] The material of the bristles of the bristle bundle 20 is, for example, usually a resin monofilament, and the most suitable is a polyester resin and / or a polyamide resin and / or an olefin resin. For example, filaments made of animal hair such as vinyl chloride, acrylic, fluorine fiber, horse hair or pig hair, plant fiber such as hemp or palm, and metal such as copper or brass can be used. The cross-sectional shape of the bristles cut by a surface parallel to the surface of the substrate 22 where the bristles are planted is usually circular, but bristles of various shapes such as elliptical, triangular, square, and star-shaped can also be used.

[0021] The diameter of the bristle is measured by measuring the diameter of the cross section. In the case where the shape of the cross section is not circular, in this specification, the diameter of a circle with the same area as the area of ​​the cross section may be referred to as the diameter of the bristle. The diameter is preferably 80 to 250 μm, more preferably 90 to 240 μm, more preferably 110 to 220 μm, and further preferably 150 to 180 μm. For example, the lower the diameter is below the above lower limit, the slower the development speed becomes, and / or the easier it is for the bristles to open; the higher the diameter is above the above upper limit, the faster the development speed becomes, and on the other hand, the poorer the fine image reproducibility. Based on this viewpoint, the preferred range of bristle diameter is designed. As the diameter, a range with any two values ​​selected from 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm, 210μm, 220μm, 230μm, 240μm and 250μm as the lower limit and upper limit can be selected.

[0022] Figure 3 In the example of FIG. 1 , a plurality of brush holes 21 are arranged on a substrate 22 in a certain regular pattern, which is referred to as a basic pattern in this specification. Figure 3As shown, the basic pattern is a pattern in which brush holes 21 are opened at equal intervals in the horizontal direction of the brush 1. More specifically, it is described as follows. In the substrate 22, a plurality of brush holes 21 are arranged at equal intervals in the X-axis direction, for example. In addition, in the substrate 22, such a plurality of brush holes 21 are arranged at equal intervals in the Y-axis direction. That is, the basic pattern has a pattern of brush holes 21 based on a repeating unit of a spacing of a certain length in the X-axis direction (hereinafter, it may also be referred to as the brush hole X spacing) and a spacing of a certain length in the Y-axis direction (hereinafter, it may also be referred to as the brush hole Y spacing). Figure 3 In the example, the brush hole X spacing is a, and the brush hole Y spacing is b.

[0023] Figure 4 This is a diagram for explaining the length L of the bristles of the bristle bundle 20 according to the brush 1 according to the first embodiment (hereinafter, may also be referred to as the bristle length). The bristle length L is the length from the front end of the bristle to the surface of the side of the substrate 22 where the bristles are planted. The bristle length L can be used as long as it is 3 mm or more and 50 mm or less, preferably 7 mm or more and 30 mm or less, more preferably 10 mm or more and 25 mm or less, and more preferably 12 mm or more and 20 mm or less. For example, the lower the bristle length L is than the above lower limit, the faster the developing speed becomes, on the other hand, the easier the bristles are to open, and / or the poorer the fine image reproducibility; the higher the bristle length L is than the above upper limit, the slower the developing speed becomes. Based on this viewpoint, the preferred range of the bristle length is designed. As the bristle length L, any two values ​​selected from 3 mm, 7 mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, 25 mm, 30 mm and 50 mm can be selected as the range of the lower limit and the upper limit.

[0024] The diameter of the brush hole 21 (hereinafter, may also be referred to as the brush hole diameter) d refers to the diameter of the brush hole 21 provided in the brush base material 22, and is measured by measuring the diameter of the completed bristle bundle 20. The shape of the brush hole 21 is usually circular, but various shapes such as ellipse, triangle, square, star, etc. may be adopted. In the measurement of the diameter of the brush hole 21, if the shape of the brush hole 21 is not circular, in this specification, the diameter of a circle having the same area as the area of ​​the brush hole 21 may be referred to as the diameter of the brush hole 21.

[0025] The brush substrate 22 can be made of any material as long as it will not be deformed by the developer, and is usually made of vinyl chloride, Duracon, nylon, polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, FRP, wood, metal, etc. The shape of the substrate 22 can be considered to be a quadrangular prism, a cylindrical prism, a triangular prism, etc., but any shape is acceptable as long as the brush's bristle-planting surface is flat. The thickness T of the substrate 22 is not particularly limited, and a thickness within a range that does not cause practical problems is selected. The thickness T is usually less than 30 mm in most cases.

[0026] Figure 5 This is a diagram for explaining the bristle density of the brush 1 according to the first embodiment. Figure 5 In the Figure 3 The repeating unit of the basic pattern shown in . The bristle density is expressed as the ratio of the cross-sectional area of ​​the bristles to the surface area of ​​the brush substrate 22 on which the bristles are embedded. More specifically, the bristle density in this specification is Figure 5 The ratio of the unit brush area S2 occupied by the brush holes 21 in the area S1 to the unit area S1 of the brush base material 22 is shown. The formula is as follows.

Formula 1

[0027] about Figure 3 and Figure 4 The unit area can be calculated by a×b. Since the unit area contains 4 shapes of 1 / 4 of a certain brush hole 21, the unit brush area is the area of ​​1 brush hole 21, which can be calculated by 1 / 4πd 2 calculate.

[0028] Above, refer to Figure 3 , Figure 4 as well as Figure 5 , the case where a plurality of brush holes 21 are provided in the base material 22 in a basic pattern has been described. This embodiment is not limited to this. Figure 6 and Figure 7 Each shows another example of the structure of the brush 1 according to the first embodiment. Figure 5 In the example of FIG. 5 , a plurality of brush holes 21 are arranged in a staggered pattern in a substrate 22 . Figure 6 In the example of FIG. 1 , a plurality of brush holes 21 are arranged in a substrate 22 in a deformed staggered pattern.

[0029] Figure 6 An example of an interlaced pattern is Figure 6 As shown, it is a pattern that staggers the angle of the basic pattern. More specifically, Figure 6 An example staggered pattern is to Figure 4 The basic pattern of the example is obtained by rotating the angle θ (hereinafter also referred to as the brush hole pitch angle) with the direction perpendicular to the X-axis and the Y-axis as the rotation axis. The angle θ is greater than 0 degrees and less than 90 degrees. When θ = 0 degrees, it is equivalent to the basic pattern. Therefore, the shape of the repeating unit of the staggered pattern is the same as Figure 5 The repeating units of the basic patterns shown are the same. Therefore, the unit area and unit brush area of ​​the staggered pattern are respectively Figure 5 The unit area S1 and unit brush area S2 of the example are calculated similarly.

[0030] Figure 7 An example of a deformed staggered pattern is shown in Figure 7 As shown in FIG. 1 , it is a pattern obtained by overlapping two basic patterns. More specifically, the deformed staggered pattern is composed of Figure 7 The basic pattern Pa composed of the brush holes 21 represented by the blank and the basic pattern Pb composed of the brush holes 21 represented by the oblique lines are overlapped. The basic patterns Pa and Pb are each composed of the same brush hole X spacing a and brush hole Y spacing b. On the other hand, the basic patterns Pa and Pb are offset by a certain displacement in the X-axis direction (hereinafter, also referred to as the overlapping spacing X displacement) and by a certain displacement in the Y-axis direction (hereinafter, also referred to as the overlapping spacing Y displacement). Figure 7 In the example, the overlap spacing X is shifted by δa, and the overlap spacing Y is shifted by δb. δa and δb can be any number such as 0<δa<1 / 2a, 0<δb<1 / 2b, etc. It should be noted that the case where δa=1 / 2a and δb=1 / 2b is equivalent to the staggered pattern. Therefore, the unit brush area of ​​the deformed staggered pattern contains two brush holes 21, and the unit area is equal to Figure 5 The unit area S1 of the example is calculated similarly. On the other hand, the unit brush area can be used Figure 5 Example: 2 times the unit brush area S2 = 1 / 2πd 2 calculate.

[0031] In connection with the developing brush 1 described above, the brush pressure during development of the photosensitive resin original plate will be described. The brush pressure is expressed as the distance that the front end of the bristles of the brush 1 is compressed in a direction perpendicular to the bristle planting surface of the substrate 22, from the state where the front end of the bristles of the brush 1 is not subjected to pressure to the state where the front end of the bristles of the brush 1 is subjected to pressure. More specifically, when it is assumed that the bristles of the brush 1 during development in the developer are not bent from the surface of the substrate, the brush pressure is the displacement of the position of the tip of the bristle tip that penetrates the photosensitive resin original plate and the position of the surface of the photosensitive resin original plate measured based on the structure of the developer. The brush pressure is preferably 0.5 to 5 mm, and it can be used as long as it is above 0 mm and below the bristle length L. If the brush pressure is less than 0.5 mm, there will be places where the brush cannot contact evenly, so it is not practical. If the brush pressure is greater than 5 mm, the reproducibility of fine images is reduced, and the opening of the brush is promoted. Based on this viewpoint, a preferred range of brush pressure can be set.

[0032] <Photosensitive resin original plate> As described below, a photosensitive resin original plate used for flexographic printing is also referred to as a photosensitive resin flexographic printing original plate, or simply as a flexographic printing original plate. A plate developed from such an original plate is also referred to as a flexographic printing plate. The flexographic printing plate is a flexographic printing plate in which a photosensitive resin layer obtained from a photosensitive resin composition is disposed on a support, and is preferably a water-developable flexographic printing plate using an aqueous developer as an eluent. The water-developable photosensitive resin composition contains a synthetic rubber polymer, a photopolymerizable unsaturated monomer compound, and a photopolymerization initiator. The development method is effective when the photosensitive resin layer contains a water-dispersible synthetic rubber polymer, and the effect remains the same even if it contains a water-insoluble synthetic rubber polymer. In addition, the photosensitive resin composition may contain a water-soluble or hydrophilic polymer component.

[0033] As the support used for the printing original plate, a material having flexibility and excellent dimensional stability is preferred, and examples thereof include a support made of metal such as steel, aluminum, copper, nickel, and a film made of a thermoplastic resin such as a polyethylene terephthalate film, a polyethylene naphthalate film, a polybutylene terephthalate film, or a polycarbonate film. Among them, a polyethylene terephthalate film having excellent dimensional stability and sufficiently high viscoelasticity is particularly preferred.

[0034] The water-dispersible synthetic rubber polymer used in the photosensitive resin composition is used to impart appropriate rubber elasticity to the photosensitive resin layer. As the synthetic rubber polymer, a rubber component known in the past can be used. In order to impart rubber elasticity, the water-dispersible synthetic rubber polymer is preferably solid at room temperature. In addition, as specific examples of water-dispersible synthetic rubber polymers, polybutadiene, polychloroprene, polyacrylonitrile-butadiene, polyacrylic acid, epichlorohydrin, polyurethane, polyisoprene, polystyrene-isoprene copolymer, polystyrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, ethylene-propylene copolymer, butyl polymer, chlorinated polyethylene, etc. can be cited, and polymers obtained by copolymerizing other components such as acrylic acid or methacrylic acid in these polymers can be cited. Among the water-dispersible synthetic rubber polymers, it is preferred to have a water-dispersible synthetic rubber polymer with a butadiene skeleton and / or a styrene skeleton from the perspective of developability and physical properties. As a water-dispersible synthetic rubber polymer, a water-dispersible latex is preferred. The water-dispersible latex can be a latex having a cross-linked structure in the molecule represented by the degree of gelation. As the latex having a crosslinked structure in the molecule, a hydrophobic polymer obtained from a water-dispersed latex having a weight average gelation degree of 20 to 80% is preferred. They can be used alone or in combination of two or more. The water-dispersed latex refers to a latex in which rubber polymer particles are dispersed in water to form a stable suspension. By removing water from the water-dispersed latex, a polymer is obtained.

[0035] The photosensitive resin composition for flexographic printing original plate may contain a water-insoluble synthetic rubber polymer within a range that does not adversely affect the performance. As such a water-insoluble elastomer, elastomers such as polybutadiene, polychloroprene, polyacrylonitrile-butadiene, polyurethane, polyisoprene, polystyrene-isoprene copolymer, and polystyrene-butadiene copolymer can be cited. Among them, by containing a water-insoluble elastomer, physical properties and water resistance are improved, so it is preferred.

[0036] The photosensitive resin composition for a flexographic printing plate may contain a water-soluble or water-dispersible polymer in addition to the water-dispersible synthetic rubber polymer. Examples of the water-soluble or water-dispersible polymer include water-soluble polyamides and water-dispersible polyamides in which a hydrophilic group is introduced into the polyamide, partially saponified polyvinyl acetate and its derivatives, and anionic acrylic polymers.

[0037] In the photosensitive resin composition for flexographic printing original plate, since the water-dispersible synthetic rubber polymer is dispersed in the developer, the polymer concentration in the developer does not increase sharply. In addition, since the synthetic rubber polymer is water-dispersible, it is suitable for waste liquid treatment by centrifugal separation.

[0038] The photopolymerizable unsaturated monomer compound used in the photosensitive resin composition is contained for curing by ultraviolet crosslinking. The photopolymerizable unsaturated monomer compound may be a compound having only one ethylenically unsaturated bond, or may be a compound having two or more ethylenically unsaturated bonds. The photopolymerizable unsaturated monomer compound may contain an oligomer introduced with a photopolymerizable group, or a polymer introduced with a photopolymerizable group. From the perspective of compatibility with the synthetic rubber copolymer, the photopolymerizable unsaturated monomer compound preferably contains a compound having a common skeleton with the synthetic rubber copolymer. These photopolymerizable unsaturated monomer compounds are not limited to the case where only one is used, and can also be used in combination.

[0039] Specific examples of the ethylenically unsaturated compound having only one ethylenically unsaturated bond include (meth)acrylates having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, and β-hydroxy-β'-(meth)acryloyloxyethyl phthalate; alkyl (meth)acrylates such as propyl (meth)acrylate, butyl (meth)acrylate, isopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate; phenoxyalkyl (meth)acrylates such as phenoxyethyl acrylate and nonylphenoxyethyl (meth)acrylate; and alkoxyalkylene glycol (meth)acrylates such as ethoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, and methoxydipropylene glycol (meth)acrylate.

[0040] Specific examples of the ethylenically unsaturated compound having two or more ethylenically unsaturated bonds include alkyl di(meth)acrylates such as 1,9-nonanediol di(meth)acrylate, polyethylene glycol di(meth)acrylates such as diethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylates such as dipropylene glycol di(meth)acrylate, polyvalent (meth)acrylates of polyhydric alcohols such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and glycerol tri(meth)acrylate, polyvalent (meth)acrylates obtained by addition reaction of unsaturated carboxylic acid with ethylene glycol diglycidyl ether, polyvalent (meth)acrylates obtained by addition reaction of unsaturated epoxy compounds such as glycidyl (meth)acrylate with carboxylic acid or amine, and polyvalent (meth)acrylamides such as methylenebis(meth)acrylamide.

[0041] As the photopolymerization initiator, any photopolymerization initiator can be used as long as it can polymerize polymerizable unsaturated groups by light irradiation, and it is particularly preferred to use a photopolymerization initiator that has the function of generating free radicals by light absorption, self-decomposition or hydrogen abstraction. Specifically, for example, benzoin alkyl ethers, benzophenones, anthraquinones, benzyls, acetophenones, diacetyl, etc. can be used. In addition, the photopolymerization initiator can be not only one type, but also a combination of two or more types.

[0042] The developer used in the present disclosure is an aqueous developer containing water as a main component, and is used to remove the water-dispersible uncured portion in the photosensitive resin. Preferred aqueous developers include the following aqueous developers.

[0043] The aqueous developer may be water alone, or may be an aqueous solution to which a water-soluble development accelerator is added. Examples of the development accelerator include surfactants, acids, alkalis, salts, etc. From the perspective of development speed, it is preferred to add a water-soluble development accelerator. As the development accelerator, commercially available soaps or lotions may be used.

[0044] Examples of the surfactant include cationic surfactants, anionic surfactants, and nonionic surfactants. Specifically, examples include the above-mentioned various surfactants.

[0045] Examples of the acid include inorganic acids such as sulfuric acid, nitric acid, and phosphoric acid, and organic acids such as formic acid, acetic acid, oxalic acid, succinic acid, citric acid, maleic acid, and p-toluenesulfonic acid. Examples of the base include lithium hydroxide, sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0046] The development accelerator used in the present disclosure may be a surfactant, an acid, an alkali, and a salt in combination, and the optimal formulation of the development accelerator may be determined according to the components of the photosensitive resin composition.

[0047] The aqueous developer may contain a water-soluble organic solvent in addition to water. Examples of such an organic solvent include methanol, ethanol, isopropyl alcohol, cellosolve, glycerin, ethylene glycol, and polyethylene glycol.

[0048] In order to suppress the generation of bubbles, a defoaming agent may be added. Any defoaming agent may be water-soluble, and examples of the defoaming agent include higher alcohols, fatty acid derivatives, silicon dioxide, alumite, silicone, and the like. Example

[0049] Hereinafter, although an Example is demonstrated concretely, the technique of this application is not limited to these Examples.

[0050] <Preparation of Photosensitive Resin Master Plate> (1) Preparation of photosensitive resin composition Photosensitive resin composition A': 91 parts by weight of butadiene latex (LX111NF manufactured by Zeon Japan, solid content concentration: 55%) as latex, 15 parts by weight of oligomeric butadiene acrylate (ABU-4 manufactured by Kyoeisha Chemical Co., Ltd.: molecular weight 2700) as a photopolymerizable compound, 10 parts by weight of lauryl methacrylate (LMA manufactured by U-Pica Co., Ltd.), 10 parts by weight of trimethylolpropane trimethacrylate (Sanshin Chemical Co., Ltd., Sanester TMP) 10 parts by mass, benzyl dimethyl ketal (2,2-dimethoxy-2-phenylacetophenone, manufactured by Tokyo Chemical Industry Co., Ltd.) as a photopolymerization initiator 1 part by mass, PFT-4 (a polymer having a molecular weight of about 20,000 and a solid content concentration of 25%) manufactured by Kyoeisha Chemical Industry as a hydrophilic polymer 20 parts by mass, hydroquinone monomethyl ether (4-methoxyphenol, manufactured by Tokyo Chemical Industry Co., Ltd.) as a polymerization inhibitor 0.1 parts by mass, liquid butadiene (B-3000, manufactured by Nippon Soda Co., Ltd.) as a plasticizer 9 parts by mass, and toluene (Toluene, manufactured by Tokyo Chemical Industry Co., Ltd.) 5 parts by mass were mixed in a container, then kneaded at 105° C. using a pressure kneader, and then toluene and water were distilled off under reduced pressure to obtain a photosensitive resin composition A′.

[0051] Photosensitive resin composition B': 31 parts by mass of Nipol LX111NF (manufactured by Zeon Co., Ltd., Japan) as a solid component of water-dispersible latex, 10 parts by mass of polybutadiene terminal diacrylate (manufactured by Osaka Organic Chemical Co., Ltd., BAC-45), and 10 parts by mass of acrylic monomer (1,9-nonanediol dimethacrylate) were mixed, and the water was evaporated for 2 hours in a dryer heated to 120°C to obtain a mixture of a polymer obtained from the water-dispersible latex and a photopolymerizable monomer. The mixture, 6 parts by mass of butadiene rubber (manufactured by Zeon Co., Ltd., Nipol BR1220), 7 parts by mass of a surfactant (4 parts by mass in terms of solid content), and 10 parts by mass of a plasticizer were kneaded in a kneader for 45 minutes. Then, 0.2 parts by mass of a thermal polymerization inhibitor and 1 part by mass of a photopolymerization initiator were added to the kneader and kneaded for 5 minutes to obtain a photosensitive resin composition B'.

[0052] Photosensitive resin composition C': 100 parts by mass of carboxyl-modified methyl methacrylate-butadiene latex (MR174 manufactured by Nippon A&L Co., Ltd., solid content concentration 50%) as a latex having a carboxyl group, 15 parts by mass of oligomeric butadiene acrylate (ABU-3 manufactured by Kyoeisha Chemical: molecular weight 2700) as a photopolymerizable compound, 10 parts by mass of lauryl methacrylate, 10 parts by mass of trimethylolpropane trimethacrylate, 1 part by mass of benzyl dimethyl ketal as a photopolymerization initiator, 20 parts by mass of PFT-3 manufactured by Kyoeisha Chemical (a polymer having a molecular weight of about 20,000 having a polyurethane urea structure, solid content concentration 25%) as a hydrophilic polymer, 0.1 parts by mass of hydroquinone monomethyl ether as a polymerization inhibitor, 9 parts by mass of liquid butadiene as a plasticizer, and 5 parts by mass of toluene were mixed in a container, and then kneaded at 105° C. using a pressure kneader, and then toluene and water were distilled off under reduced pressure to obtain a photosensitive resin composition C′.

[0053] Photosensitive resin composition D': 71 parts by mass of styrene-butadiene latex (C4850 manufactured by Zeon Japan, solid content concentration 70%) as a latex of a polystyrene-butadiene copolymer, 15 parts by mass of oligobutadiene acrylate (ABU-3 manufactured by Kyoeisha Chemical: molecular weight 2700) as a photopolymerizable compound, 10 parts by mass of lauryl methacrylate, 10 parts by mass of trimethylolpropane trimethacrylate, 1 part by mass of benzyl dimethyl ketal as a photopolymerization initiator, 20 parts by mass of PFT-3 manufactured by Kyoeisha Chemical (a polymer having a molecular weight of about 20,000 and a polyurethane urea structure, solid content concentration 25%) as a hydrophilic polymer, 0.1 parts by mass of hydroquinone monomethyl ether as a polymerization inhibitor, 9 parts by mass of liquid butadiene as a plasticizer, and 5 parts by mass of toluene were mixed in a container, and then kneaded at 105° C. using a pressure kneader, and then toluene and water were distilled off under reduced pressure to obtain a photosensitive resin composition D′.

[0054] (2) Preparation of protective layer coating solution A protective layer coating liquid is prepared by dissolving low-saponification polyvinyl alcohol (PVA405, manufactured by Kuraray Co., Ltd.), a plasticizer (SANFLEX SE270, manufactured by Sanyo Chemical Industries, Ltd., aliphatic polyol polyether polyol, solid content concentration 85%) and NBR latex (SX1503A, manufactured by Zeon Co., Ltd., solid content concentration 42%) in a water / isopropyl alcohol mixture at a solid content weight ratio of 35 / 35 / 30.

[0055] (3) Preparation of infrared photosensitive layer coating liquid A carbon black dispersion (AMBK-8, manufactured by Orient Chemical Industry Co., Ltd.) and a copolymerized polyamide (PA223, manufactured by Toyobo Co., Ltd.) were dissolved in a methanol / ethanol / isopropanol mixed solution at a solid content weight ratio of 63 / 37 to prepare an infrared photosensitive layer coating solution.

[0056] (4) Preparation of laminated film Y The infrared photosensitive layer coating liquid was applied to a 100 μm PET film with a release treatment on both sides using a suitable type of bar coater, and dried at 120° C. for 5 minutes to laminate an infrared photosensitive layer with a film thickness of 1.5 μm on the PET film. The optical density at this time was 2.3. The optical density was measured by a black and white transmission densitometer DM-520 (Dainippon Screen Manufacturing Co., Ltd.). Next, a protective layer coating liquid is applied on the infrared photosensitive layer using a suitable type of rod coater and dried at 120°C for 5 minutes to obtain a laminated film Y in which a 1.5 μm thick infrared photosensitive layer and a 0.5 μm thick protective layer are sequentially laminated on a PET film.

[0057] (5) Preparation of photosensitive resin original plates A, B, C, D respectively composed of photosensitive resin compositions A', B', C', D' and laminated film Y The above-mentioned photosensitive resin composition A' is arranged on a 125μm PET film coated with a copolyester-based adhesive, and a laminate film Y is stacked thereon. The lamination is performed at 100°C using a hot press to obtain a photosensitive resin original plate (flexographic printing original plate) A consisting of a PET support, an adhesive layer, a photosensitive resin layer, a protective layer, an infrared photosensitive layer, and a release-treated PET protective film (cover film). The total thickness of the plate is 1.14mm. The photosensitive resin composition A' is changed to photosensitive resin compositions B', C', and D', respectively, and the same treatment as the photosensitive resin composition A' is performed to prepare photosensitive resin original plates (flexographic printing original plates) B to D.

[0058] <Method for preparing developer> Sodium oleate (NONSOUL ON-1N manufactured by NOF Corporation) was measured so as to account for 1% of the total developer solution, and dissolved in tap water to prepare 10 L of an aqueous developer solution.

[0059] <Development Test Method> The brush produced by the method described below is set in an intermittent developing device so that the brush pressure is 2 mm. The photosensitive resin original plate with the covering film peeled off is fixed in the setting machine with double-sided tape. The entire amount of the prepared developer is put into the developing tank of the intermittent developing device so that the water depth at the head of the brush is 10 mm. The temperature of the developer is adjusted to 40°C with a heater. The circulation pump always operates at a flow rate of 5 L / min during the addition of the developer, and a 30-mesh cartridge filter is used as a filter. The developing brush motor rotates the setting machine at a radius of 20 mm at 60 rpm.

[0060] <Method for measuring development time> The developer prepared by the above-mentioned development test method is covered with a lid, and the setting machine is rotated to develop the photosensitive resin original plate. The end point of the development is determined by visually confirming whether the adhesive layer on the PET support is exposed in more than half of the entire area. After 5 minutes from the start of the setting machine rotation, the lid is opened to confirm the state of the photosensitive resin plate, and then every 1 minute.

[0061] <1% dot reproducibility measurement method> Using an exposure device of 900mm×1200mm size with 30 60W Philips 10R fluorescent lamps arranged, the 125μm PET support side of the photosensitive resin original was exposed for 20 seconds, and ultraviolet rays were irradiated to form a base. The cover film was peeled off from the photosensitive resin original, and the photosensitive resin original was set on CDI4835 (with online UV) manufactured by ESKO. Next, a square evaluation image pattern consisting of 9 squares arranged at 30mm intervals, 3 vertical and horizontal flat screens composed of 1% dots of 150L PI mesh angle 45 degrees, was drawn on the infrared photosensitive layer. The photosensitive resin original was exposed to ultraviolet rays. Using the photosensitive resin original, development was performed using the above-mentioned development test method, only for the time calculated by the above-mentioned development time measurement method. The plate was taken out, the dot image was confirmed with a magnifying glass, and the reproducibility of the tone image was observed and evaluated. Regarding the evaluation criteria, the case where all dots of the 9 tone images are reproduced is defined as 100%, the case where dot defects are observed in any one of the tone images is defined as 90%, the case where dot defects are observed in two tone images is defined as 80%, and in descending order, the case where all dots of the 9 tone images are observed is defined as 10%, and the case where dot defects are significantly observed is defined as 0%.

[0062] <Evaluation method of brush opening> The brush produced by the method described below is set in an intermittent developing device so that the brush pressure is 5 mm. A 2 mm thick NBR plate is fixed to the setting machine with double-sided tape. The entire amount of the prepared developer is put into the developing tank of the intermittent developing device so that the water depth at the head of the brush is 10 mm. The temperature of the developer is adjusted to 50°C with a heater. The developing brush motor rotates the setting machine at a radius of 20 mm at 60 rpm. The intermittent developing machine is covered with a lid and rotated for a total of 1000 hours. After the brush is worn, the brush is taken out. If the opening of the hair tip is less than 4 mm, it is ○, if the opening of the hair tip is more than 4 mm and less than 7 mm, it is △, and if the opening of the hair tip is more than 7 mm, it is ×.

[0063] <Evaluation method of resin clogging> The unexposed photosensitive resin original is attached to the setting machine and developed by the above-mentioned development test method, using only the time obtained by the above-mentioned development time measurement method. After developing 10 sheets in a rapid and continuous manner, the brush is taken out of the developing tank and the bristles are observed. If resin residue can be confirmed to be attached between the bristles, it is evaluated as ×, if resin residue can be observed but is in a state where it is easy to fall off, it is evaluated as △, and if no resin residue is confirmed, it is evaluated as ○.

[0064] [Example 1] On a vinyl chloride board of 300mm long × 210mm wide × 10mm thick, nylon 6, i.e. nylon 120T 0.170W manufactured by Toray Monofilament Co., Ltd., was used as bristles, and the bristles were implanted in a basic pattern with a brush hole diameter of 2mm, a brush hole X spacing of 3.3mm, and a brush hole Y spacing of 3.4mm outside the circumference of the vinyl chloride board. The bristle length was cut into 17mm to make a brush. In this brush, the bristle density was calculated to be 28%. By setting the brush on a developer, each evaluation was carried out using the above method. As shown in Table 1, the evaluation results show that the development speed (expressed by the development time), fine image reproducibility (expressed by 1% dot reproducibility), and brush life (expressed by brush opening and resin clogging) are all at a high level.

[0065] [Other embodiments] As Examples 2 to 14, the results of experiments conducted in the same manner as in Example 1 are described. Detailed conditions and results are summarized in Table 1. Nylon 6 shown in Table 1 used nylon 120T manufactured by Toray Filament Co., Ltd., the same as in Example 1. Nylon 610 used nylon 200T manufactured by Toray Filament Co., Ltd., PBT used Polyseter PBT monofilament manufactured by KRPlastic Industriesco., LTD., PP used Polyseter Polypropylene monofilament manufactured by KRPlastic Industriesco., LTD., and nylon 66 used Nylone 66 monofilament manufactured by KRPlastic Industriesco., LTD.

[0066] [Table 1]

[0067] As shown in Table 1, it can be seen that the performances such as the development speed corresponding to the development time, 1% dot reproducibility, and brush life (brush opening, resin clogging) in any example are each at a high level or an acceptable level. More specifically, it is as follows.

[0068] In Examples 2 and 3, the bristle diameter in Example 1 is changed from 170 μm. In either case of the bristle diameter being 90 μm and 240 μm, the development speed, 1% dot reproducibility, and brush life are all at high levels. In Examples 4 and 5, the bristle length in Example 1 is changed from 17 mm. In either case of the bristle length being 11 mm and 24 mm, the development speed, 1% dot reproducibility, and brush life are all at high levels. In Examples 6 and 7, the brush hole diameter and / or the brush hole X spacing and the brush hole Y spacing in Example 1 are changed so that the bristle density is changed from 28%. In either case of the bristle density being 23% and 33%, the development speed, 1% dot reproducibility, and brush life are all at high levels.

[0069] In Example 8, the bristle length in Example 1 was set from 17 mm to 8 mm, which is shorter than in Example 4. In this case, the bristles were easily opened compared to other examples, and the 1% dot reproducibility was low, but these were acceptable levels. In Example 9, the bristle length in Example 1 was set from 17 mm to 27 mm, which was longer than in Example 5. In this case, the development time was long compared to other examples, but this was an acceptable level.

[0070] In Examples 10, 11, 12 and 13, the brush bristle material in Example 1 was changed to nylon 6. When the brush bristle material was any of nylon 610, nylon 66, PBT and PP, the development speed, 1% dot reproducibility and brush life were all at high levels. In Examples 14, 15 and 16, the photosensitive resin original plate used in Example 1 was changed to photosensitive resin original plate A. When any of photosensitive resin original plates B, C and D were used, the development speed, 1% dot reproducibility and brush life were all at high levels.

[0071] In Example 17, the brush hole X pitch and brush hole Y pitch in Example 2 were changed so that the bristle density was changed from 28% to 23%. In this case, the development time was longer than that in Example 2, but this was an acceptable level. In Example 18, the brush hole diameter, brush hole X pitch and brush hole Y pitch in Example 3 were changed so that the bristle density was changed from 28% to 33%. In this case, the development time was further shortened compared with Example 3, but on the other hand, the 1% dot reproducibility was reduced, but this was an acceptable level.

[0072] [Comparative Example] As Comparative Examples 1 to 6, the results of experiments performed in the same manner as in Example 1 will be described. Detailed conditions and results are summarized in Table 2.

[0073] [Table 2]

[0074] In Comparative Example 1, the bristle diameter in Example 1 is set from 170 μm to 70 μm, which is smaller than that in Example 2. In this case, the performance of the development of the photosensitive resin original A is deteriorated in that the development time is longer than that in the example. In addition, although it is within the allowable range, the brush is also easy to open. In Comparative Example 2, the bristle diameter in Example 1 is set from 170 μm to 295 μm, which is larger than that in Example 3. In this case, the development time is shortened, and on the other hand, the performance is deteriorated compared with the example in that the value of 1% dot reproducibility is lowered. In Comparative Example 3, the brush hole X spacing and the brush hole Y spacing in Example 1 are changed so that the bristle density is changed from 28% to smaller than that in Example 6. In this case, the bristle density is 20%, and the performance of the development of the photosensitive resin original A is deteriorated in that the development time is longer than that in the example. In Comparative Example 4, the brush hole diameter, brush hole X pitch, and brush hole Y pitch in Example 1 were changed so that the bristle density was increased from 28% to be greater than that in Example 7. In this case, the bristle density was 39%, and the development time was shortened, but on the other hand, the performance was inferior to that of the example in that resin clogging was easily caused.

Claims

1. A developing brush, characterized in that: The brush is a brush that is rubbed against the photosensitive resin flexographic printing plate in order to remove the uncured portion of the photosensitive resin from the photosensitive resin flexographic printing plate for development. The brush has a plurality of bristles embedded in a substrate. Each of the plurality of bristles has a diameter of 80 to 250 μm, and a bristle density expressed as a ratio of a cross-sectional area of ​​the plurality of bristles to an area of ​​a surface of the base material on which the plurality of bristles are implanted is 22% to 37%.

2. The developing brush according to claim 1, characterized in that: The length of each of the plurality of bristles from the end portion on the side not implanted in the base to the base is 10 mm or more and 25 mm or less.

3. The developing brush according to claim 1, characterized in that: The material of the plurality of bristles is polyester resin and / or polyamide resin and / or olefin resin. 4 . A developing device, comprising removing the uncured portion from the photosensitive resin flexographic printing original plate using the developing brush according to claim 1 .

5. The developing device according to claim 4, characterized in that: The brush pressure of the developing brush during development of the photosensitive resin flexographic printing original plate is 0.5 to 5 mm.

6. A method for manufacturing a flexible printing plate, characterized in that: A flexible printing plate is manufactured by rubbing a brush against a photosensitive resin flexible printing plate to remove uncured portions of the photosensitive resin from the photosensitive resin flexible printing plate. The brush has a plurality of bristles implanted in a substrate, each of the plurality of bristles having a diameter of 80 to 250 μm, and a bristle density expressed as a ratio of the cross-sectional area of ​​the plurality of bristles to the area of ​​the surface of the substrate on which the plurality of bristles are implanted, which is greater than 22% and less than 37%.

7. A method for developing a photosensitive resin flexographic printing plate, characterized in that: The following development is performed: by rubbing a brush against the photosensitive resin flexible printing original, the uncured portion of the photosensitive resin is removed from the photosensitive resin flexible printing original, the brush is a brush having a plurality of bristles implanted on a substrate, each of the plurality of bristles has a diameter of 80 to 250 μm, and the bristle density expressed as the ratio of the cross-sectional area of ​​the plurality of bristles to the area of ​​the surface of the substrate on which the plurality of bristles are implanted is greater than 22% and less than 37%.

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