Developing brush, developing apparatus, method for manufacturing a flexographic printing plate, and method for developing a photosensitive resin flexographic printing plate.

Abstract

The purpose of the present invention is to provide a development brush, a development device, a flexographic printing plate production method and a light-sensitive resin flexographic printing original plate development method with which a desired development speed and image reproducibility are satisfied and the performance thereof is sustained for a long period. Provided is a development brush 1 which, for the purpose of development in which uncured parts of a light-sensitive resin are removed from a light-sensitive resin flexographic printing original plate 2, is rubbed against the light-sensitive resin flexographic printing original plate, said development brush being characterised in that: the brush has a plurality of brush bristles implanted on a base material 22; the plurality of brush bristles each have a diameter of 80-250 μm; and a brush bristle density, which is indicated by the ratio of the cross-sectional area of the plurality of brush bristles to the area of the surface of the base material on which the plurality of brush 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 flexographic printing plate, and a method for developing a photosensitive resin flexographic printing original plate.

Background Art

[0002] As a method for producing a printing plate by forming irregularities on a photosensitive resin layer laminated on the surface of a support, a photosensitive resin layer formed using a photosensitive composition is exposed to ultraviolet rays through an original film or the like, and the image portion is selectively cured, and the uncured portion is removed with a developer. This method is well known (see, for example, Patent Document 1).

[0003] Regarding the developing method, there is a desire to improve the developing speed and image reproducibility, and a brush developing method, a spray developing method, and a method combining brush and spray developing (see, for example, Patent Document 2) have been studied.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in these conventional techniques, no consideration has been given to the period during which their performance lasts.

[0006] The present invention has been made in view of these circumstances, and aims to provide a developing brush, a developing apparatus, a method for manufacturing a flexographic printing plate, and a method for developing a photosensitive resin flexographic printing plate that can satisfy all three of the following elements at a high level, namely, that the desired developing speed and image reproducibility are satisfied and the period during which the performance is maintained (hereinafter may also be called brush life) is long. [Means for solving the problem]

[0007] As a result of diligent research, the inventors of this invention have found that the above problems can be solved by the means described below, and have arrived at the present invention. That is, the present invention may include the following inventions. [1] A brush rubbed against a photosensitive resin flexographic printing plate for developing purposes, to remove uncured portions of the photosensitive resin from the photosensitive resin flexographic printing plate, The brush has a plurality of brush bristles embedded on a substrate, A developing brush characterized in that each of the plurality of brush bristles has a diameter of 80 to 250 μm, and the brush bristle density, expressed as the ratio of the cross-sectional area of ​​the plurality of brush bristles to the area of ​​the surface of the substrate on which the plurality of brush bristles are implanted, is 22% to 37%. [2] The developing brush according to [1], characterized in that the length from the end of each of the plurality of brush bristles that is not embedded in the substrate to the substrate is 10 mm or more and 25 mm or less. [3] The developing brush according to [1], characterized in that the material of the plurality of brush bristles is polyester resin and / or polyamide resin and / or olefin resin. A developing apparatus that removes the uncured portion from the photosensitive resin flexographic printing plate using a developing brush described in any of [4], [1], to [3]. [5] The developing apparatus according to [4], characterized in that the brush pressure for the developing brush during development of the photosensitive resin flexographic printing plate is 0.5 to 5 mm. [6] A method for manufacturing a flexographic printing plate, characterized in that a brush having a plurality of brush bristles embedded on a substrate, each of the plurality of brush bristles having a diameter of 80 to 250 μm, and a brush bristle density expressed as the ratio of the cross-sectional area of ​​the plurality of brush bristles to the area of ​​the surface on which the plurality of brush bristles are embedded on the substrate, is 22% to 37%, and the brush is rubbed against a photosensitive resin flexographic printing plate to remove the uncured portion of the photosensitive resin from the photosensitive resin flexographic printing plate. [7] A method for developing a photosensitive resin flexographic printing plate, characterized by rubbing the brush, which has a plurality of brush bristles embedded on a substrate, each of which has a diameter of 80 to 250 μm, and having a brush bristle density expressed as the ratio of the cross-sectional area of ​​the plurality of brush bristles to the area of ​​the surface on which the plurality of brush bristles are embedded on the substrate, with the brush, which has a brush bristle density expressed as the ratio of the cross-sectional area of ​​the plurality of brush bristles to the area of ​​the surface on which the plurality of brush bristles are embedded, with a photosensitive resin flexographic printing plate, and thereby developing the photosensitive resin flexographic printing plate to remove the uncured portion of the photosensitive resin. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a developing brush, a developing apparatus, a method for manufacturing a flexographic printing plate, and a method for developing a photosensitive resin flexographic printing plate, which satisfy the desired development speed and image reproducibility and have a long brush life that sustains that performance. [Brief explanation of the drawing]

[0009] [Figure 1] A diagram showing an example of the configuration of a batch-type developing machine used for developing photosensitive resin plates, having a brush according to the first embodiment. [Figure 2] A diagram showing an example of the configuration of an in-line developing machine used for developing photosensitive resin plates, having a brush according to the first embodiment. [Figure 3] A diagram showing an example of the brush configuration according to the first embodiment as a basic pattern. [Figure 4] A diagram illustrating the length of the brush bristles of the brush according to the first embodiment. [Figure 5]A diagram illustrating the bristle density of a brush according to the first embodiment. [Figure 6] A figure showing another example of the brush configuration according to the first embodiment, as a staggered pattern. [Figure 7] A figure showing yet another example of the brush configuration according to the first embodiment, as a modified staggered pattern. [Modes for carrying out the invention]

[0010] The embodiments of this application will be described below with reference to the drawings. The embodiments described below are merely preferred examples of application, and the scope of the technology relating to this application is not limited to these. In this specification, for the sake of brevity of reference, components having equivalent functions may be denoted by the same reference numerals, but these components do not necessarily refer to the same thing.

[0011] <Developing machine> Figure 1 shows an example of the configuration of a batch-type developing machine 100 having a developing brush (hereinafter also simply referred to as a brush) 1 according to the first embodiment. The batch-type developing machine 100 develops a photosensitive resin plate 2 using the brush 1. The photosensitive resin plate before development may also be referred to as a photosensitive resin master plate. The batch-type developing machine 100 includes, for example, a developing brush motor 3, a setter 4, a developing tank 6 in which developing solution 5 is stored, a circulation pump 7, and a filter 8.

[0012] The batch developing machine 100 fixes the photosensitive resin plate 2 to the setter 4, and develops the photosensitive resin plate 2 by relatively rubbing the brush 1 and the photosensitive resin plate 2 in the developing solution 5, that is, removes the uncured part of the photosensitive resin in the photosensitive resin plate 2. As a result of this development, a printing plate is manufactured from the photosensitive resin plate 2. Instead of being performed in the developing solution 5, the rubbing motion may be performed while the developing solution 5 is being applied. The rubbing motion is realized by rotating and / or translating the brush 1 and / or the setter 4. FIG. 1 shows an example in which the setter 4 is rotated and / or translated by the developing brush motor 3. In the batch developing machine 100, a batch format is adopted in which the photosensitive resin plate 2 is developed for a predetermined time, removed from the setter 4, a new photosensitive resin plate 2 is fixed, and the next development is performed. In development, the portion of the photosensitive resin of the photosensitive resin plate 2 that was not cured in the exposure process of the previous process is removed. Although FIG. 1 shows an example of a typical batch developing machine, the configuration of the batch developing machine in which the brush 1 according to the first embodiment can be used is not limited to that shown in FIG. 1. It is desirable to keep the developing solution 5 constantly circulating with the circulation pump 7 because the photosensitive resin dispersed in the developing solution 5 does not separate and the resin concentration in the developing solution 5 can be homogenized. It is even more desirable to pass the developing solution 5 circulated by the circulation pump 7 through the filter 8 because debris floating in the developing solution 5 can be removed. Debris refers to those in which the photosensitive resin is exposed and cured but the curing is insufficient and peeled off from the plate, and those in which the developing solution 5 has dried in the plate making machine.

[0013] FIG. 2 shows an example of the configuration of an in-line developing machine 200 having the brush 1 according to the first embodiment. The in-line developing machine 200 also develops the photosensitive resin plate 2 using the brush 1. The in-line developing machine 200 includes, for example, a filter 8, a pre-wash brush 9, a conveying pin bar 10, a rinse brush 11, an air knife 12, a conveying chain 13, a developing solution receiver 14, a rinse solution pipe 15, a filter pump 16, a concentration tank 17, a developing solution tank 18 in which the developing solution 5 is stored, and a developing solution pump 19.

[0014] Similar to the batch-type developer 100, the inline developer 200 develops the photosensitive resin plate 2 by rubbing the brush 1 and the photosensitive resin plate 2 together in the presence of the developer 5. Unlike the batch-type developer, the inline developer 200 is characterized by its ability to continuously develop the photosensitive resin plate 2. Figure 2 shows a typical example of an inline developer, but the configuration of the inline developer in which the brush 1 according to the first embodiment can be used is not limited to that shown in Figure 2. The photosensitive resin plate 2 is fixed to the transport pin bar 10 by making multiple holes in the edge of the photosensitive resin plate 2 and inserting these holes into the pins of the transport pin bar 10. The transport pin bar 10 is hooked onto the transport chain 13 of the developer, and the transport chain 13 is transported, thereby transporting the photosensitive resin plate 2 from the front to the back of the inline developer 200. In the inline developing machine 200, a pre-wash brush 9, a developing brush 1, a rinse brush 11, and an air knife 12 are arranged in order from the front to the rear. Exposure devices may also be provided at the front and rear.

[0015] The pre-wash brush 9 is in a roll shape, and the mask layer on the surface layer of the photosensitive resin plate 2 is removed by the rotation of the roll. The mask layer includes, for example, a protective layer and an infrared-sensitive layer. The developing brush 1 is for developing the photosensitive resin plate 2. Specifically, the photosensitive resin plate 2 is developed by transporting the photosensitive resin plate 2 at a predetermined speed while relatively rubbing the brush 1 and the photosensitive resin plate 2 in the developing solution 5. Instead of being performed in the developing solution 5, the rubbing motion may be performed while the developing solution 5 is being applied. The rubbing motion is realized by rotating and / or translating the brush 1. The rubbing motion may be realized by translating the conveying pin bar 10 in addition to or instead of rotating and / or translating the brush 1. In development, the unhardened portions of the photosensitive resin of the photosensitive resin plate 2 in the previous exposure process are removed. The developing solution 5 used in development is stored in the developing tank 18. The developing solution circulated from the developing tank 18 by the developing solution pump 19 is used for removing the mask layer by the pre-wash brush and / or for development using the developing brush 1.

[0016] The rinse brush 11 is roll-shaped and, as the roll rotates, rubs the photosensitive resin plate 2, removing debris remaining on the plate while applying a developer with a lower resin concentration than the developer 5 used for development, new developer, or water. The air knife 12 blows a thin stream of supplied air, blowing moisture off the photosensitive resin plate 2 towards the front in the transport direction to remove the water. The filter 8 is a cross-flow type filtration membrane, with a diameter of, for example, 0.05 to 10 μm. A portion of the developer 5 used for development and stored in the development tank 18 is moved to the concentration tank 17, and the developer in the concentration tank 17 is moved by the filter pump 16 and passes through the filter 8. The filtrate moves to the rinse solution piping 15, and the developer with a higher resin concentration returns to the concentration tank 17, where it is circulated. By using such a precise filtration membrane, the developer used by the rinse brush 11 is made from the developer 5 used for development. Using the developer solution generated in this way is advantageous because it reduces the amount of developer waste compared to using a fresh developer solution. When water is used to remove debris with the rinse brush 11, a mechanism is used to drain the water so that it does not mix with the developer solution 5.

[0017] While an example was shown in which a transport pin bar 10 is used to transport the photosensitive resin plate 2, other in-line developing machines having the brush 1 according to the first embodiment may also be used, such as a belt conveyor type equipped with a belt conveyor capable of fixing the photosensitive resin plate 2, and a setter type in which the photosensitive resin plate 2 is attached to and fixed to a setter plate and the setter plate is transported by a nip roll or chain. As long as there is a rigid structure on the back of the photosensitive resin plate 2 and the photosensitive resin plate 2 can be transported from the front to the back of the developing machine, the transport method is not particularly specified.

[0018] <Developing Brush> Figure 3 shows an example of the configuration of the brush 1 according to the first embodiment. Hereinafter, the explanation will use the following two axial directions parallel to the surface on which the brush bristles are planted on the base material of the brush 1. In a batch-type apparatus, the depth direction in Figure 1 may be referred to as the X-axis direction, and in an in-line apparatus, the direction perpendicular to the plate transfer direction may be referred to as the X-axis direction. Furthermore, in a batch-type apparatus, the left-right direction in Figure 1 may be referred to as the Y-axis direction, and in an in-line apparatus, the plate transfer direction may be referred to as the Y-axis direction.

[0019] Brush 1 comprises multiple bundles of brush bristles 20 and a base material (hereinafter also referred to as brush base material) 22. Brush 1 is manufactured, for example, by providing multiple regularly spaced brush holes 21 in the base material 22 and planting the bristles of a certain bundle of brush bristles 20 in each of the holes 21. There are various methods for planting the bristles, including the machine-insertion method in which folded bristles are driven into the base material 22 with a thin metal wire, the hand-sewing method in which folded bristles are pulled and fixed from the back of the hole with thread or wire, and the ultrasonic method in which the bundles of brush bristles 20 are driven directly into the holes of the base material 22 and fixed by ultrasonic fusion. Brush 1 may be manufactured using any of these methods.

[0020] As for the material of the brush bristles of the brush bristle bundle 20, for example, resin monofilaments, such as polyester resin and / or polyamide resin and / or olefin resin, are generally the most suitable. However, vinyl chloride, acrylic, fluorocarbon fibers, animal hair such as horsehair or pig hair, plant fibers such as hemp or palm, and metal filaments such as copper or brass can also be used. The cross-sectional shape of the brush bristles, measured from a plane parallel to the surface on which the brush bristles are planted on the base material 22, is generally circular, but brush bristles of various shapes such as elliptical, triangular, square, and star-shaped are also usable.

[0021] The diameter of the brush bristles is measured by measuring the diameter of the cross-section. If the shape of the cross-section is not circular, the diameter of a circle with the same area as the cross-section may be referred to as the diameter of the brush bristles in this specification. The diameter is preferably 80 to 250 μm, more preferably 90 to 240 μm, more preferably 110 to 220 μm, and even more preferably 150 to 180 μm. For example, the lower the diameter, the slower the development speed and / or the more easily the brush bristles spread out, while the higher the diameter, the faster the development speed, but the worse the reproduction of fine images. A preferred range for the diameter of the brush bristles has been designed with this in mind. The diameter can be selected within a range where any two values ​​chosen from 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm, 210μm, 220μm, 230μm, 240μm, and 250μm are used as the lower and upper limits.

[0022] In the example shown in Figure 3, multiple brush holes 21 are provided on the base material 22 in a certain regular pattern, and in this specification, this pattern is referred to as the basic pattern. The basic pattern is a pattern in which brush holes 21 are opened at equal intervals in the horizontal direction of the brush 1, as shown in Figure 3. More specifically, it is as follows: Multiple brush holes 21 are provided on the base material 22 at equal intervals in the X-axis direction, for example. Furthermore, multiple such brush holes 21 are provided on the base material 22 at equal intervals in the Y-axis direction. That is, the basic pattern has a pattern of brush holes 21 in repeating units with a pitch of a certain length in the X-axis direction (hereinafter also referred to as the brush hole X pitch) and a pitch of a certain length in the Y-axis direction (hereinafter also referred to as the brush hole Y pitch). In the example shown in Figure 3, the brush hole X pitch is a and the brush hole Y pitch is b.

[0023] Figure 4 is a diagram illustrating the length L of the brush bristles (hereinafter also referred to as the brush bristle length) of the brush bristle bundle 20 according to the brush 1 according to the first embodiment. The brush bristle length L is the length from the tip of the brush bristles to the surface of the substrate 22 on the side where the brush bristles are planted. The brush bristle length L can be used if it is between 3 mm and 50 mm, preferably between 7 mm and 30 mm, more preferably between 10 mm and 25 mm, and even more preferably between 12 mm and 20 mm. For example, the lower the brush bristle length L is, the faster the development speed becomes, but the brush bristles tend to spread out more easily and / or the fine image reproduction quality deteriorates, while the higher the brush bristle length L is, the slower the development speed becomes. A preferred range for the brush bristle length is designed with this in mind. As for the brush bristle length L, it is possible to select a range such that 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 are used as the lower and upper limits.

[0024] The diameter d of the brush hole 21 (hereinafter also referred to as the brush hole diameter) 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 brush bristle bundle 20. The shape of the brush hole 21 is generally circular, but it can take various shapes such as ellipse, triangle, square, or star. In measuring 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 with 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 base material 22 can be any material that is not affected or deformed by the developing solution, and is generally made of polyvinyl chloride, Delrin, nylon, polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, FRP, wood, or metal. The shape of the base material 22 can be a rectangular prism, cylinder, or triangular prism, but any shape is acceptable as long as the surface on which the bristles are attached is flat. There are no particular restrictions on the thickness T of the base material 22, and a thickness within a range that does not pose practical problems should be selected. Generally, the thickness T is often set to 30 mm or less.

[0026] Figure 5 is a diagram illustrating the bristle density of brush 1 according to the first embodiment. Figure 5 shows the repeating units of the basic pattern shown in Figure 3. The bristle density is expressed as the ratio of the cross-sectional area of ​​the bristle to the area of ​​the surface on which the bristle is embedded within the brush substrate 22. More specifically, the bristle density as used herein is the ratio of the unit brush area S2 occupied by the bristle holes 21 within a unit area S1 of the brush substrate 22, as shown in Figure 5. The calculation formula is as follows:

number

[0027] The brush bristle density will be explained using the examples in Figures 3 and 4. The unit area can be calculated as a × b. Since the unit area includes four shapes that are 1 / 4 of a certain brush hole 21, the unit brush area is the area of ​​one brush hole 21, which is 1 / 4πd. 2 It can be calculated using this method.

[0028] The above describes the case in which multiple brush holes 21 are provided in the substrate 22 in the basic pattern with reference to Figures 3, 4, and 5. This embodiment is not limited thereto. Figures 6 and 7 show other examples of the configuration of the brush 1 according to the first embodiment. In the example of Figure 5, multiple brush holes 21 are provided on the substrate 22 in a staggered pattern. In the example of Figure 6, multiple brush holes 21 are provided on the substrate 22 in a modified staggered pattern.

[0029] The staggered pattern in the example in Figure 6 is a pattern obtained by shifting the angle of the basic pattern, as shown in Figure 6. More specifically, the staggered pattern in the example in Figure 6 is obtained by rotating the basic pattern in the example in Figure 4 by an angle θ (which may also be called the brush hole pitch angle) around a rotation axis perpendicular to the X and Y axes. The angle θ is greater than 0 degrees and less than 90 degrees. When θ = 0 degrees, it corresponds to the basic pattern. Therefore, the repeating unit of the staggered pattern has the same shape as the repeating unit of the basic pattern shown in Figure 5. Accordingly, the unit area and unit brush area of ​​the staggered pattern are calculated in the same way as the unit area S1 and unit brush area S2 in the example in Figure 5, respectively.

[0030] The modified staggered pattern in the example shown in Figure 7 is a pattern formed by the overlapping of two basic patterns, as shown in Figure 7. More specifically, this modified staggered pattern is formed by the overlap of a basic pattern Pa, which consists of brush holes 21 shown in white in Figure 7, and a basic pattern Pb, which consists of brush holes 21 shown in diagonal lines. Basic patterns Pa and Pb each consist of the same brush hole X pitch a and brush hole Y pitch b. On the other hand, basic patterns Pa and Pb are shifted by a certain displacement in the X-axis direction (hereinafter also referred to as overlap pitch X displacement) and a certain displacement in the Y-axis direction (hereinafter also referred to as overlap pitch Y displacement). In the example in Figure 7, the overlap pitch X displacement is δa and the overlap pitch Y displacement is δb. δa and δb can take any numbers such that 0 < δa < 1 / 2a and 0 < δb < 1 / 2b, respectively. Note that when δa = 1 / 2a and δb = 1 / 2b, it corresponds to a staggered pattern. Therefore, the unit area of ​​the modified staggered pattern includes the unit brush area of ​​2 brush holes 21 minutes apart, and this unit area is calculated in the same way as the unit area S1 in the example of Figure 5, while this unit brush area is twice the unit brush area S2 in the example of Figure 5, which is 1 / 2πd. 2 It can be calculated using this method.

[0031] In relation to the developing brush 1 described above, the brush pressure used when developing a photosensitive resin original will now be explained. Brush pressure is expressed as the distance from which the tips of the bristles of brush 1 are compressed in a direction perpendicular to the surface on which the bristles are planted on the substrate 22, starting from a state where the tips of the bristles of brush 1 are not under pressure, to a state where the tips of the bristles of brush 1 are under pressure. More specifically, brush pressure is measured from the structure of the developing machine by determining the displacement between the position where the tip surface of the bristles should be located after penetrating the photosensitive resin master and the position on the surface of the photosensitive resin master, assuming that the bristles of brush 1 are not bent from the substrate surface during development. A brush pressure of 0.5 to 5 mm is suitable, and it is usable as long as it is 0 mm or more and the bristle length is L or less. If the brush pressure is less than 0.5 mm, areas will occur where the brush does not make uniform contact, making it impractical. If the brush pressure exceeds 5 mm, the fine image reproduction quality will decrease and the bristles will spread out. From these perspectives, a preferred range for brush pressure can be set.

[0032] <Photosensitive resin master plate> As explained below, a photosensitive resin plate for flexographic printing is also called a photosensitive resin flexographic printing plate, or simply a flexographic printing plate. The resulting plate from development of such a plate is also called a flexographic printing plate. A flexographic printing plate is a flexographic printing plate having a photosensitive resin layer obtained from a photosensitive resin composition provided on a support, and a water-developable flexographic printing plate using an aqueous developer as the wash solution is preferred. The water-developable photosensitive resin composition contains a synthetic rubber polymer, a photopolymerizable unsaturated monomer compound, and a photopolymerization initiator. The developing method is effective when the photosensitive resin layer contains a water-dispersible synthetic rubber polymer, and the effect does not change even if it also contains a water-insoluble synthetic rubber polymer. In addition, the photosensitive resin composition may contain water-soluble or hydrophilic polymer components.

[0033] As a support material for printing plates, a flexible material with excellent dimensional stability is preferred. Examples include metal supports such as steel, aluminum, copper, and nickel, and thermoplastic resin films such as polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, or polycarbonate film. Among these, polyethylene terephthalate film, which has excellent dimensional stability and sufficiently high viscoelasticity, is particularly preferred.

[0034] Water-dispersible synthetic rubber polymers used in photosensitive resin compositions are used to impart appropriate rubber elasticity to the photosensitive resin layer, and conventionally known rubber components can be used as such synthetic rubber polymers. It is preferable that the water-dispersible synthetic rubber polymer be solid at room temperature to impart rubber elasticity. Specific examples of water-dispersible synthetic rubber polymers include polybutadiene, polychloroprene, polyacrylonitrile-butadiene, polyacrylic, epichlorohydrin, polyurethane, polyisoprene, polystyrene-isoprene copolymer, polystyrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, ethylene-propylene copolymer, butyl polymer, and chlorinated polyethylene. Polymers obtained by copolymerizing these polymers with other components such as acrylic acid or methacrylic acid can also be cited. Among water-dispersible synthetic rubber polymers, water-dispersible synthetic rubber polymers having a butadiene skeleton and / or a styrene skeleton are preferred in terms of developability and physical properties. Water-dispersible latex is preferred as the water-dispersible synthetic rubber polymer. The water-dispersed latex may be a latex having a cross-linked structure within the molecule, as expressed by its degree of gelation. Preferably, the latex with a cross-linked structure within the molecule is a hydrophobic polymer obtained from a water-dispersed latex with a weight-average degree of gelation of 20-80%. These may be used individually or in combination of two or more types. Water-dispersed latex is a stable suspension in which fine particles of rubber polymer are dispersed in water. A polymer is obtained by removing water from this water-dispersed latex.

[0035] The photosensitive resin composition for flexographic printing plates may contain a water-insoluble synthetic rubber polymer to the extent that it does not adversely affect performance. Examples of such water-insoluble elastic materials include polybutadiene, polychloroprene, polyacrylonitrile-butadiene, polyurethane, polyisoprene, polystyrene-isoprene copolymer, and polystyrene-butadiene copolymer. Among these, the inclusion of a water-insoluble elastic material is preferred because it improves physical properties and water resistance.

[0036] The photosensitive resin composition for flexographic printing plates may contain water-soluble or water-dispersible polymers in addition to water-dispersible synthetic rubber polymers. Examples of water-soluble or water-dispersible polymers include water-soluble polyamides and water-dispersible polyamides obtained by introducing hydrophilic groups into polyamides, partially saponified polyvinyl acetate and its derivatives, and anionic acrylic polymers.

[0037] In photosensitive resin compositions for flexographic printing plates, a water-dispersible synthetic rubber polymer is dispersed in the developer solution, so the polymer concentration in the developer solution does not increase rapidly. Furthermore, because the synthetic rubber polymer is water-dispersible, it is suitable for wastewater treatment by centrifugal separation.

[0038] The photopolymerizable unsaturated monomer compounds used in the photosensitive resin composition are included to enable crosslinking and curing by ultraviolet light. The photopolymerizable unsaturated monomer compounds may be compounds having only one ethylenically unsaturated bond, or compounds having two or more ethylenically unsaturated bonds. The photopolymerizable unsaturated monomer compounds may also include oligomers with introduced photopolymerizable groups or polymers with introduced photopolymerizable groups. From the standpoint of compatibility with synthetic rubber copolymers, it is preferable to include photopolymerizable unsaturated monomer compounds that share a common skeleton with the synthetic rubber copolymer. These photopolymerizable unsaturated monomer compounds are not limited to being used individually, but may be used in combination.

[0039] Examples of ethylenically unsaturated compounds having only one ethylenically unsaturated bond include hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, β-hydroxy-β'-(meth)acryloyloxyethyl phthalate, propyl (meth)acrylate, butyl (meth)acrylate, isoamyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate. Examples include alkyl(meth)acrylates such as methylhexyl(meth)acrylate, lauryl(meth)acrylate, and stearyl(meth)acrylate; phenoxyalkyl(meth)acrylates such as phenoxyethyl(meth)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] Examples of ethylenically unsaturated compounds having two or more ethylenically unsaturated bonds include alkyl diol 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, polymethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, glycerol tri(meth)acrylate, and other polyhydric alcohol polyhydric (meth)acrylates, polyhydric (meth)acrylates obtained by the addition reaction of an unsaturated carboxylic acid to ethylene glycol diglycidyl ether, polyhydric (meth)acrylates obtained by the addition reaction of an unsaturated epoxy compound such as glycidyl (meth)acrylate with a carboxylic acid or amine, and polyhydric (meth)acrylamides such as methylenebis(meth)acrylamide.

[0041] Any photopolymerization initiator that can polymerize polymerizable unsaturated groups upon light irradiation can be used, but those that have the function of generating radicals through self-decomposition or hydrogen abstraction upon light absorption are particularly preferred. Specifically, for example, benzoin alkyl ethers, benzophenones, anthraquinones, benzyls, acetophenones, and diacetyls can be used. Furthermore, not only one type of photopolymerization initiator but also two or more types may be used in combination.

[0042] The developer used in this disclosure is an aqueous developer mainly composed of water, and is used to remove water-dispersible uncured portions of the photosensitive resin. Preferred aqueous developers include the following:

[0043] The aqueous developer may consist of water alone, or it may be an aqueous solution to which a water-soluble development accelerator has been added. Examples of development accelerators include surfactants, acids, bases, and salts. From the standpoint of development speed, it is preferable to add a water-soluble development accelerator. Commercially available soap or detergent may be used as the development accelerator.

[0044] Examples of surfactants include cationic surfactants, anionic surfactants, and nonionic surfactants. More specifically, the various surfactants mentioned above are examples.

[0045] Examples of acids 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 bases include lithium hydroxide, sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0046] The development accelerator used in this disclosure may be a combination of surfactants, acids, bases, and salts, and the optimal formulation of the development accelerator should be determined according to the components of the photosensitive resin composition.

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

[0048] Furthermore, an antifoaming agent may be added to suppress foam generation. Any water-soluble antifoaming agent will suffice, and examples of antifoaming agent components include higher alcohols, fatty acid derivatives, silica, anodized aluminum, and silicone. [Examples]

[0049] The following describes specific examples, but the technology relating to this application is not limited to these examples.

[0050] <Preparation of photosensitive resin master plates> (1) Preparation of photosensitive resin composition Photosensitive resin composition A´: The latex consists of 91 parts by mass of butadiene latex (manufactured by Nippon Zeon, LX111NF, solid content 55%), 15 parts by mass of oligobutadiene acrylate (manufactured by Kyoeisha Chemical, ABU-4: molecular weight 2700) as a photopolymerizable compound, 10 parts by mass of lauryl methacrylate (manufactured by Nippon Yupika Co., Ltd., LMA), and trimethylolpropane trimethacrylate (manufactured by Sanshin Chemical Industry Co., Ltd., Sunester). 10 parts by mass of TMP, 1 part by mass of benzyldimethyl ketal (manufactured by Tokyo Chemical Industry Co., Ltd., 2,2-Dimethoxy-2-phenylacetophenone) as a photopolymerization initiator, 20 parts by mass of PFT-4 (a polymer with a urethane urea structure and a molecular weight of approximately 20,000, solid content concentration 25%) manufactured by Kyoeisha Chemical as a hydrophilic polymer, 0.1 parts by mass of hydroquinone monomethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd., 4-Methoxyphenol) as a polymerization inhibitor, and 9 parts by mass of liquid butadiene (manufactured by Nippon Soda Co., Ltd., B-3000) as a plasticizer were mixed in a container with 5 parts by mass of toluene (manufactured by Tokyo Chemical Industry Co., Ltd., Toluene), then kneaded at 105°C using a pressurized kneader, and then the toluene and water were removed by vacuum distillation to obtain photosensitive resin composition A'.

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

[0052] Photosensitive resin composition C´: As a carboxyl group-containing latex, 100 parts by mass of carboxy-modified methyl methacrylate-butadiene latex (manufactured by Nippon A&L, MR174, solid content concentration 50%) was mixed with 5 parts by mass of toluene in a container. Then, the mixture was kneaded at 105°C using a pressurized kneader, and subsequently, the toluene and water were removed by vacuum distillation to obtain photosensitive resin composition C'.

[0053] Photosensitive resin composition D´: As a polystyrene-butadiene copolymer latex, 71 parts by mass of styrene-butadiene latex (manufactured by Nippon Zeon, C4850, solids content 70%), 15 parts by mass of oligobutadiene acrylate (manufactured by Kyoeisha Chemical, ABU-3: 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 benzyldimethyl ketal as a photopolymerization initiator, 20 parts by mass of PFT-3 (manufactured by Kyoeisha Chemical, a polymer with a urethane urea structure and a molecular weight of approximately 20,000, solids content 25%) as a hydrophilic polymer, 0.1 parts by mass of hydroquinone monomethyl ether as a polymerization inhibitor, and 9 parts by mass of liquid butadiene as a plasticizer were mixed in a container with 5 parts by mass of toluene, kneaded at 105°C using a pressurized kneader, and then the toluene and water were removed by vacuum distillation to obtain photosensitive resin composition D'.

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

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

[0056] (4) Fabrication of laminated film Y An infrared-sensitive layer coating solution was applied to a 100 μm PET film that had been treated with a release agent on both sides using an appropriate type of bar coater, and dried at 120°C for 5 minutes to laminate an infrared-sensitive layer with a thickness of 1.5 μm onto the PET film. The optical density at this time was 2.3. This optical density was measured using a monochrome transmission densitometer DM-520 (Dainippon Screen Mfg. Co., Ltd.). Next, a protective coating liquid was applied onto the infrared-sensitive layer using an appropriate type of bar coater, and dried at 120°C for 5 minutes to obtain a laminated film Y in which an infrared-sensitive layer with a thickness of 1.5 μm and a protective layer with a thickness of 0.5 μm were laminated in that order on a PET film.

[0057] (5) Preparation of photosensitive resin masters A, B, C, D, each consisting of photosensitive resin compositions A', B', C', D' and laminated film Y. A photosensitive resin composition A' was placed on a 125 μm PET film coated with a copolymer polyester adhesive, and a laminate film Y was placed on top of it. Lamination was performed at 100°C using a heat press to obtain a photosensitive resin master plate (flexographic printing master plate) A consisting of a PET support, adhesive layer, photosensitive resin layer, protective layer, infrared-sensitive layer, and release-treated PET protective film (cover film). The total thickness of the plate was 1.14 mm. Photosensitive resin composition A' was changed to photosensitive resin compositions B', C', and D' respectively, and the same processing as for photosensitive resin composition A' was performed to prepare photosensitive resin master plates (flexographic printing master plates) B to D.

[0058] <Method for preparing developing solution> Sodium oleate (Non-Sal ON-1N, manufactured by NOF Corporation) was measured and dissolved in tap water to make up 1% of the total developer solution, and 10 liters of aqueous developer solution were prepared.

[0059] <How to perform a development test> The brushes, generated using the method described below, were installed in a batch-type developing apparatus with a brush pressure of 2 mm. A photosensitive resin master plate, with the cover film removed, was fixed to the setter with double-sided tape. The entire volume of the prepared developer was poured into the developing tank of the batch-type developing apparatus, so that the brush heads were at a water depth of 10 mm. The temperature of the developer was adjusted to 40°C using a heater. The circulation pump ran continuously at a flow rate of 5 L / min while the developer was present, and a 30-mesh cartridge filter was used as a filter. The developing brush motor rotated the setter at a radius of 20 mm at 60 rpm.

[0060] <Method for measuring development time> The developing machine, prepared using the method described above, was covered, and the setter was rotated to develop the photosensitive resin plate. The end point of development was determined by visually checking whether the adhesive layer on the PET support was exposed over more than half of the total area. The cover was opened 5 minutes after the setter started rotating to check the condition of the photosensitive resin plate, and thereafter it was checked every minute.

[0061] <Method for measuring 1% halftone reproducibility> Using an exposure apparatus measuring 900mm x 1200mm with 30 60W Philips 10R fluorescent lamps arranged in a row, the above-mentioned photosensitive resin master plate was exposed to ultraviolet light for 20 seconds from the 125μm PET support side to form a base. After that, the cover film was peeled off the photosensitive resin master plate, and the photosensitive resin master plate was set in an ESKO CDI4835 (with inline UV). Next, a square evaluation image pattern consisting of nine 20mm x 20mm flat halftones, each 30mm apart, was drawn on the infrared-sensitive layer, and at the same time, the photosensitive resin master plate was exposed to ultraviolet light. Using this photosensitive resin master plate, development was carried out for the time determined by the development time measurement method described above, using the development test method described above. The plate was removed, the halftone image was checked with a magnifying glass, and the reproducibility of the flat halftone image was evaluated. The evaluation criteria were defined as follows: 100% if all halftone dots in all nine flat screen images were reproduced, 90% if any halftone dots were missing in one of the flat screen images, 80% if two halftone dots were missing, and so on, decreasing to 10% if all nine flat screen images had missing halftone dots, and 0% if there were significant halftone dot defects.

[0062] <Method for evaluating brush spread> The brushes produced using the method described below were installed in a batch-type developing machine with a brush pressure of 5 mm. A 2 mm thick NBR plate was fixed to the setter with double-sided tape. The entire volume of the prepared developer was poured into the developing tank of the batch-type developing machine, and the brush heads were positioned so that the water depth was 10 mm. The temperature of the developer was adjusted to 50°C using a heater. The developing brush motor rotated the setter at a radius of 20 mm at 60 rpm. After closing the lid of the batch-type developing machine and running the rotational motion for a total of 1000 hours to wear down the brushes, the brushes were removed and judged as follows: ○ if the bristle spread was less than 4 mm, △ if it was between 4 mm and 7 mm, and × if it was 7 mm or more.

[0063] <Method for evaluating resin clogging> An unexposed photosensitive resin plate was attached to the setter and developed for the time determined by the development time measurement method described above, using the development test method described above. After developing 10 plates consecutively in the same manner, the brush was removed from the developing tank and the brush bristles were observed. If resin residue was observed between the brush bristles, it was marked as ×; if resin residue was visible but easily washed away, it was marked as △; and if no resin residue was observed, it was marked as ○.

[0064] [Example 1] A brush was created by planting nylon 6 (Nylon 120T 0.170W) manufactured by Toray Monofilament Co., Ltd. as brush bristles on a 300mm long, 210mm wide, and 10mm thick PVC board. The bristles were planted in a basic pattern with a brush hole diameter of 2mm, brush hole X pitch of 3.3mm, and brush hole Y pitch of 3.4mm, excluding the 5mm perimeter of the PVC board. The brush bristles were then trimmed to a length of 17mm. The calculated brush bristles density was 28%. This brush was then installed in a developing machine, and the evaluations described above were performed. The evaluation results are shown in Table 1, and it was found that the performance in terms of development speed (expressed as development time), fine image reproduction (expressed as 1% halftone reproduction), and brush life (expressed as brush opening and resin clogging) were all at a high level.

[0065] [Other examples] Examples 2 to 14 describe the results of experiments conducted using the same method as in Example 1. Detailed conditions and results are summarized in Table 1. The nylon 6 shown in Table 1 is the same nylon 120T manufactured by Toray Monofilament Co., Ltd. as in Example 1. Nylon 610 is nylon 200T manufactured by Toray Monofilament Co., Ltd., PBT is Polyseter PBT monofilament manufactured by KRPlastic Industries co., LTD., PP is Polyseter Polypropylene monofilament manufactured by KRPlastic Industries co., LTD., and nylon 66 is Nylone 66 monofilament manufactured by KRPlastic Industries co., LTD.

[0066] [Table 1]

[0067] As shown in Table 1, in each example, the development speed corresponding to the development time, 1% halftone reproducibility, and brush life (brush opening, resin clogging) were found to be at a high or acceptable level. More specifically, the results are as follows:

[0068] Examples 2 and 3 are variations of Example 1, where the brush bristle diameter is changed from 170 μm. In both cases, with brush bristle diameters of 90 μm and 240 μm, development speed, 1% halftone reproducibility, and brush life are all at high levels. Examples 4 and 5 are variations of Example 1, where the brush bristle length is changed from 17 mm. In both cases, with brush bristle lengths of 11 mm and 24 mm, development speed, 1% halftone reproducibility, and brush life are all at high levels. Examples 6 and 7 are variations of Example 1, where the brush bristle density is changed from 28%, and / or the brush hole X pitch and brush hole Y pitch are changed. In both cases, with brush bristle densities of 23% and 33%, development speed, 1% halftone reproducibility, and brush life are all at high levels.

[0069] Example 8 is a modification of Example 1 in which the brush bristle length was changed from 17 mm to 8 mm, which is shorter than that of Example 4. In this case, compared to the other examples, the brush bristles tend to spread out more easily and the 1% halftone dot reproducibility is lower, but these are at an acceptable level. Example 9 is a modification of Example 1 in which the brush bristle length was changed from 17 mm to 27 mm, which is longer than that of Example 5. In this case, compared to the other examples, the development time is longer, but this is at an acceptable level.

[0070] Examples 10, 11, 12, and 13 are variations of Example 1 in which the brush bristle material is changed from nylon 6. In all cases where the brush bristle material is nylon 610, nylon 66, PBT, or PP, the development speed, 1% halftone reproduction, and brush life are all at a high level. Examples 14, 15, and 16 are variations of Example 1 in which the photosensitive resin master used is changed from photosensitive resin master A. In all cases where photosensitive resin masters B, C, or D are used, the development speed, 1% halftone reproduction, and brush life are all at a high level.

[0071] Example 17 is a modification of Example 2 in which the brush bristle density is changed from 28% to 23%, and the brush hole X pitch and brush hole Y pitch are modified. In this case, the development time is longer compared to Example 2, but this is at an acceptable level. Example 18 is a modification of Example 3 in which the brush bristle density is changed from 28% to 33%, and the brush hole diameter, as well as the brush hole X pitch and brush hole Y pitch are modified. In this case, the development time is even shorter compared to Example 3, while the 1% halftone reproducibility is lower, but this is at an acceptable level.

[0072] [Comparative Example] Comparative Examples 1 to 6 describe the results of experiments conducted using the same method as in Example 1. Detailed conditions and results are summarized in Table 2.

[0073] [Table 2]

[0074] Comparative Example 1 is an example in which the diameter of the brush bristles in Example 1 is reduced from 170 μm to 70 μm, which is even smaller than in Example 2. In this case, the performance is inferior to the Example in that the development time for developing the photosensitive resin master A is longer. Also, although within an acceptable range, the brush tends to spread out more easily. Comparative Example 2 is an example in which the diameter of the brush bristles in Example 1 is reduced from 170 μm to 295 μm, which is even larger than in Example 3. In this case, the development time is shorter, but the performance is inferior to the Example in that the 1% halftone reproducibility value is lower. Comparative Example 3 is an example in which the brush hole X pitch and brush hole Y pitch are increased so that the brush bristle density is reduced from 28% to even smaller than in Example 6. In this case, the brush bristle density is 20%, and the performance is inferior to the Example in that the development time for developing the photosensitive resin master A is longer. Comparative Example 4 is a modified version of Example 1 in which the brush bristle density is increased from 28% to even greater than that of Example 7, by changing the brush hole diameter, as well as the brush hole X pitch and brush hole Y pitch. In this case, the brush bristle density is 39%, which shortens the development time, but is inferior to the example in that resin clogging is more likely to occur. [Explanation of Symbols]

[0075] 100-batch developing machine 1. Developing brush 2 Photosensitive resin plate 3. Developing brush motor 4 Setters 5. Developer 6 Developer tank 7. Circulation pump 8 filters 200 In-line Developing Machines 9 Pre-wash brush 10 Transport pin bars 11. Rinse brush 12 Air Knives 13 Conveyor chain 14. Developer container 15. Rinse fluid piping 16. Filter pump 17 Concentration Tank 18 Developer tank 19. Developer pump 20 brush bristle bundles 21 brush holes 22 Base material

Claims

1. When developing a photosensitive resin flexographic printing plate using an aqueous developer containing at least one surfactant selected from the group consisting of cationic surfactants, anionic surfactants, and nonionic surfactants, the brush is rubbed against the photosensitive resin flexographic printing plate, The above development is a development in which a brush pressure is applied to the tip of the brush from a state where no pressure is being applied to the tip of the brush, such that the distance the tip of the brush is compressed in a vertical direction is 0.5 to 5 mm. The brush has a plurality of bristles regularly planted on a substrate, each of the plurality of bristles having 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 planted, is 22% to 37%. A developing brush characterized in that the length from the end of each of the plurality of brush bristles that is not embedded in the substrate to the substrate is 10 mm or more and 25 mm or less.

2. The developing brush according to claim 1, characterized in that the material of the plurality of brush bristles is polyester resin and / or polyamide resin and / or olefin resin.

3. A developing apparatus for removing the uncured portion from the photosensitive resin flexographic printing plate using the developing brush described in claim 1 or 2.

4. A method for manufacturing a flexographic printing plate, characterized in that a developing brush according to claim 1 or 2 is rubbed against a photosensitive resin flexographic printing plate to remove the uncured portion of the photosensitive resin from the photosensitive resin flexographic printing plate and thereby manufacture a flexographic printing plate.

5. A method for developing a photosensitive resin flexographic printing plate, characterized in that development is performed by rubbing the developing brush described in Claim 1 or 2 against the photosensitive resin flexographic printing plate to remove the uncured portion of the photosensitive resin from the photosensitive resin flexographic printing plate.

Images