Flexographic printing plate manufacturing method

Abstract

To provide a method for manufacturing a flexographic printing plate that can produce printed materials with high print density and suppressed dot gain. [Solution] A method for manufacturing a flexographic printing plate having a substrate and a relief containing 20% ​​by mass or more of thermoplastic resin, wherein the relief has halftone areas and / or solid areas with a halftone area ratio of 90% or more and halftone areas with a halftone area ratio of less than 25%, wherein the relief is formed on the substrate such that the elastic modulus Ea measured by the force volume method of the relief (a) of the halftone areas and / or solid areas with a halftone area ratio of 90% or more and the elastic modulus Eb measured by the force volume method of the relief (b) of the halftone areas with a halftone area ratio of less than 25% satisfy Ea > Eb.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a flexographic printing plate.

Background Art

[0002] Flexographic printing is widely used in paper containers, labels, flexible packaging applications, electronics applications, etc. by taking advantage of its flexibility. Flexographic printing is a printing method in which ink is adhered to the upper surface of the convex relief of a flexographic printing plate, and the relief is pressed against a printing object, thereby transferring the ink from the relief to the printing object.

[0003] As a method for forming the relief of a flexographic printing plate used in flexographic printing, for example, ultraviolet rays are irradiated through an image mask or an original film on the photosensitive resin layer of a photosensitive flexographic printing plate original to selectively photocure the image portion, and the uncured portion is removed with a developer. Also, there are methods such as directly engraving the resin layer of the flexographic printing plate original in an image pattern using a laser.

[0004] Since a flexographic printing plate has a flexible relief, during printing, the relief is deformed, and a phenomenon (dot gain) occurs where the dots printed are thicker than the dot size of the plate material. It is known that the dot gain becomes more prominent as the dots become smaller. On the other hand, although the dot gain of microdots can be reduced by lowering the pressing pressure during printing, streaks are likely to occur in the solid portions. Therefore, as a flexographic printing plate that can achieve both reduction of dot gain of microdots and sufficient ink uptake in the solid portions, a flexographic printing plate obtained from a flexographic printing plate original in which at least a support, a photosensitive resin layer, and a thermal mask layer are sequentially laminated, characterized in that the complex elastic modulus of the dots is 30 to 80 MPa and the complex elastic modulus of the solid portions is 5 to 15 MPa (for example, see Patent Document 1) has been proposed.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] International Publication No. 2021 / 39106 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, even with the technology described in Patent Document 1, it was still difficult to achieve both high print density and suppression of dot gain. The inventors focused on the fact that in gravure printing, the amount of ink supplied is adjusted according to the image by the diameter and depth of the holes provided in the gravure printing plate, whereas in flexographic printing, ink is supplied by a uniform porous anilox roll, so the same ink thickness is supplied regardless of the image. In other words, if an anilox roll with a small anilox capacity is selected, the amount of ink supplied will be small, so although dot gain of minute halftone dots is suppressed, the print density tends to be insufficient. On the other hand, if an anilox roll with a large anilox capacity is selected, the print density will be sufficient, but dot gain of minute halftone dots tends to occur easily.

[0007] Therefore, the present invention aims to provide a method for manufacturing a flexographic printing plate that can produce printed materials with high print density and suppressed dot gain. [Means for solving the problem]

[0008] To solve the above problems, the present invention mainly has the following configuration. A method for manufacturing a flexographic printing plate, having a relief containing 20% ​​by mass or more of a substrate and thermoplastic resin, wherein the relief comprises a halftone area ratio of 90% or more and a solid area, and a halftone area ratio of less than 25%, wherein the relief is formed on the substrate such that the elastic modulus Ea of the relief (a) of the halftone area ratio of 90% or more, measured by the force volume method, and the elastic modulus Eb of the relief (b) of the halftone area ratio of less than 25%, measured by the force volume method, satisfy Ea > Eb. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a method for manufacturing a flexographic printing plate that can produce printed materials with high print density and suppressed dot gain. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic cross-sectional view showing one embodiment of a flexographic printing plate according to the present invention. [Figure 2] This is a schematic cross-sectional view showing another embodiment of the flexographic printing plate in the present invention. [Figure 3] This is a schematic cross-sectional view showing another embodiment of the flexographic printing plate in the present invention. [Figure 4] This is a schematic cross-sectional view showing another embodiment of the flexographic printing plate in the present invention. [Modes for carrying out the invention]

[0011] The present invention will be described in detail below. In this invention, "greater than or equal to" means the same as or greater than the numerical value shown. Also, "less than or equal to" means the same as or less than the numerical value shown. Furthermore, "(meth)acryloyl group" is a general term for acryloyl groups and methacryloyl groups.

[0012] The flexographic printing plate in this invention has a substrate and a relief containing 20% ​​by mass or more of thermoplastic resin. The substrate has the function of supporting the relief in the flexographic printing plate. The relief has halftone areas and / or solid areas with a halftone area ratio of 90% or more, and halftone areas with a halftone area ratio of less than 25%. High printing density is required in the halftone areas and / or solid areas with a halftone area ratio of 90% or more, and suppression of dot gain is required in the halftone areas with a halftone area ratio of less than 25%. As described above, since flexographic printing supplies ink by a uniform porous anilox roll, the ink is supplied with the same ink thickness regardless of the image. Then, due to the pressure (printing pressure) during printing, the ink on the relief is pushed to the edge of the relief, causing dot gain. Therefore, in flexographic printing using anilox rolls, in order to maintain a high printing density in halftone areas and / or solid areas with a halftone area ratio of 90% or more, and to suppress dot gain in halftone areas with a halftone area ratio of less than 25%, the elastic modulus of the surface of the relief (a) (hereinafter sometimes abbreviated as "relief (a)") of the halftone areas and / or solid areas with a halftone area ratio of 90% or more is made greater than that of the relief (b) (hereinafter sometimes abbreviated as "relief (b)") of the halftone areas with a halftone area ratio of less than 25%, that is, the relief is formed such that the elastic modulus Ea of relief (a) measured by the force volume method and the elastic modulus Eb of relief (b) measured by the force volume method satisfy Ea > Eb.

[0013] Here, the elastic moduli Ea and Eb are those measured by the force-volume method using an atomic force microscope (AFM). The force-volume method allows for the measurement of surface elastic moduli in minute regions measurable by AFM, eliminating the influence of underlying layers, and enabling direct evaluation of the tops of each relief in a flexographic printing plate. Details of the measurement principle and method are described in known literature (e.g., Journal of Polymer Science, 2012, No. 69, pp. 435-442).

[0014] Relief (a) increases the elastic modulus Ea to increase the print density of halftone areas and / or solid areas with a halftone area ratio of 90% or more, and makes it easier to transfer ink to the printed material when printing pressure is applied. On the other hand, halftone dots with a halftone area ratio of less than 25% are, for example, minute halftone dots of 72 μm or less at a screen ruling of 200 lpi. Relief (b) corresponding to these areas has a lower elastic modulus Eb, making it more susceptible to shape changes in response to printing pressure than relief (a), and its height is lower, so that the printing pressure can be partially reduced to suppress dot gain.

[0015] The modulus of elasticity Ea is preferably 20 MPa or higher from the viewpoint of facilitating ink transfer from the relief (a) to the printed material and thereby increasing the print density. On the other hand, the modulus of elasticity Ea is preferably 200 MPa or lower, and more preferably 100 MPa or lower, from the viewpoint of facilitating ink transfer from the anilox roll to the relief and thereby increasing the print density.

[0016] An elastic modulus Eb of 3 MPa or higher is preferable from the viewpoint of facilitating ink transfer from the relief (b) to the printed material and thereby increasing print density. On the other hand, an elastic modulus Eb of less than 20 MPa is preferable from the viewpoint of further suppressing dot gain by reducing the printing pressure.

[0017] From the viewpoint of further enhancing the aforementioned effects, the difference between the elastic modulus Ea and the elastic modulus Eb is preferably 10 MPa or more, and more preferably 15 MPa or more. On the other hand, the difference between the elastic modulus Ea and the elastic modulus Eb is preferably 30 MPa or less, and more preferably 25 MPa or less.

[0018] The elastic modulus Ea and the elastic modulus Eb are values measured by the force-volume method using an atomic force microscope (AFM) as described above, and can be measured using, for example, a scanning probe microscope NanoScope V Dimension Icon manufactured by Bruker. Specifically, the flexographic printing plate is cut into a 1 cm square and fixed to a silicon wafer. Among the reliefs (a) and (b) of the printing plate, for three randomly selected locations from the following measurement locations respectively, under the following conditions, the elastic modulus of the scanning range at the top (outermost layer) of each relief is measured to obtain the most frequent value, and the average value of the three locations is taken as the elastic modulus. Probe: silicon cantilever Scanning mode: force-volume (contact mode) Scanning range: 3 μm square [[ID=z7]] Measurement environment: room temperature, in air. Measurement location of relief (a): solid part, if there is no solid part, the relief of the halftone part with the largest halftone area ratio Measurement location of relief (b): relief of the halftone part with the smallest halftone area ratio

[0019] In the method for manufacturing a flexographic printing plate of the present invention, from the viewpoint of more effectively adjusting the influence of the printing pressure on the relief surface according to the pattern, it is preferable that the height Ha of the relief (a) and the height Hb of the relief (b) satisfy Ha > Hb. By making Ha larger than Hb, the printing pressure of the relief (a) can be increased more to increase the printing density, and the printing pressure of the relief (b) can be made lower to more suppress the dot gain. Here, the height of the relief refers to the height from the bottom surface of the relief to the printing surface. Here, the bottom surface of the relief refers to the interface with the substrate when the relief is on the substrate, and the interface with the floor layer when the relief is on the floor layer.

[0020] From the viewpoint of selectively applying a higher printing pressure to the relief (a) and increasing the printing density more, the difference between the heights Ha and Hb is preferably 10 μm or more, and more preferably 20 μm or more. On the other hand, from the viewpoint of applying an appropriate printing pressure to the relief (b) and enhancing the reproducibility of the dots of the halftone, the difference between Ha and Hb is preferably 50 μm or less, and more preferably 40 μm or less.

[0021] The relief heights Ha and Hb are preferably between 200 μm and 700 μm.

[0022] The relief heights Ha and Hb are determined, for example, by using a white-light confocal microscope ("OPTELICS®" HYBRID+, manufactured by Lasertec Corporation) to measure the height from the bottom of the relief to the printed surface at three randomly selected locations from the following measurement points on relief (a) and relief (b) of the printing plate, under the following conditions, and the average value of the three measurements is taken as the height. However, if a randomly selected location from the halftone area does not include the printed surface of the relief, the height to the nearest printed surface is measured. Objective lens: 20X (Working distance: 1.65mm, Numerical aperture: 0.80) Light source: Xenon lamp Operation mode: Surface shape Relief (a) Measurement location: Solid area; however, if there is no solid area, the relief of the halftone dot area with the largest halftone dot area ratio is measured. Relief (b) Measurement location: The relief of the halftone dot area with the smallest halftone dot area ratio.

[0023] Figure 1 shows a schematic cross-sectional view illustrating one embodiment of a flexographic printing plate according to the present invention. The substrate (1) has a relief (a) of height Ha and a relief (b) of height Hb.

[0024] The relief contains a thermoplastic resin. The inclusion of a thermoplastic resin provides rubber elasticity suitable for receiving ink and transferring it to the printed material. From the viewpoint of improving the print resistance of the flexographic printing plate, thermoplastic elastomers such as isoprene rubber, butadiene rubber, styrene-butadiene copolymer rubber, acrylonitrile rubber, chloroprene rubber, ethylene propylene diene rubber, acrylic rubber, silicone rubber, and urethane rubber are preferred as the thermoplastic resin. Two or more of these may be included. These thermoplastic resins can be solid or liquid at room temperature and pressure, and can be selected according to the molding method described later. For example, for heating and melting methods such as fused deposition modeling, a solid at room temperature and pressure is preferred, while for methods that mix with other liquid components and spray, such as stereolithography, a liquid at room temperature and pressure is preferred.

[0025] From the viewpoint of improving the print durability of the flexographic printing plate, the thermoplastic resin content in the relief should be 20% by mass or more, and preferably 30% by mass or more.

[0026] The relief preferably further contains an acrylic crosslinked material, which allows the elastic modulus to be adjusted to a desired range. For example, the elastic modulus can be increased by increasing the crosslinking density of the acrylic crosslinked material. In addition, the elastic modulus can also be increased by selecting the structure of the acrylic crosslinked material. For this reason, it is more preferable that relief (a) contains an acrylic crosslinked material. Here, an acrylic crosslinked material refers to a compound having a (meth)acryloyl group that has formed a crosslinked structure by a radical reaction or the like. Examples of compounds having a (meth)acryloyl group include those exemplified as monofunctional acrylate monomers and bifunctional or more functional acrylate monomers in Japanese Patent Application Publication No. 2017 / 75222.

[0027] The content of the acrylic crosslinked material in the relief can be selected according to the desired elastic modulus of the relief, and 10 to 60% by mass is preferred.

[0028] The substrate is preferably one that has excellent dimensional stability against heat and physical stress, such as plastic sheets made of polyester or polyolefin, or metal plates made of steel, stainless steel, or aluminum.

[0029] From the viewpoint of handling and flexibility, the substrate thickness is preferably 50 μm to 300 μm.

[0030] The substrate may be treated to improve adhesion between the substrate and the relief or floor layer described later. Methods for improving adhesion include, for example, mechanical treatment such as sandblasting, physical treatment such as corona discharge, and chemical treatment such as coating. Among these, providing an easy-adhesion layer by coating is preferable from the viewpoint of adhesion.

[0031] In the method for manufacturing a flexographic printing plate according to the present invention, it is preferable to further form a floor layer containing ethylene propylene diene rubber and / or chloroprene rubber between the substrate and the relief. Since such a floor layer is highly flexible, it can impart rubber elasticity to the relief. Furthermore, by forming a floor layer that does not require patterning, the height of the relief layer can be reduced, and the time required for manufacturing the flexographic printing plate can be shortened.

[0032] From the viewpoint of suppressing a reduction in rubber elasticity, it is preferable that the floor layer is substantially free of acrylic crosslinks. Here, "substantially free of acrylic crosslinks" means that the acrylic crosslink content in the floor layer is 0.1% by mass or less.

[0033] Figure 2 shows a schematic cross-sectional view illustrating another embodiment of the flexographic printing plate according to the present invention. It has a substrate (1) on which a floor layer (3) is located, and on the floor layer (3) there are reliefs (a) of height Ha and reliefs (b) of height Hb.

[0034] In the method for manufacturing a flexographic printing plate of the present invention, it is preferable to form a relief by printing at least a thermoplastic resin on a substrate or floor layer using a 3D printer, from the viewpoint of controlling the material, elastic modulus, and height of the thermoplastic resin that forms the relief for any image. From the viewpoint of shortening the time required to manufacture the flexographic printing plate, it is preferable to form the relief by printing at least a thermoplastic resin on the floor layer using a 3D printer.

[0035] 3D printing methods include fused deposition modeling (FDM), stereolithography (SLA), material jetting, powder bed bonding, powder bed fusion, and optical 3D printing.

[0036] When forming a relief using a filamentous molding material, fused deposition modeling (FDM) is preferred. The filamentous molding material can be obtained, for example, by melting the aforementioned thermoplastic resin and, if necessary, a material containing an acrylic crosslinker and other components, and extruding it from a spinning nozzle.

[0037] When forming a relief using powdered molding material, powder bonding and powder bed fusion bonding methods are preferred. Powdered molding material and filamentous molding material can be obtained, for example, by cutting filamentous molding material to any length and turning it into a powder.

[0038] When forming a relief using a photocurable liquid molding material, optical stereolithography is preferred. A photocurable liquid molding material can be obtained, for example, by mixing liquid (meth)acrylates, liquid rubber or rubber particles, and a photopolymerization initiator.

[0039] In another aspect of the method for manufacturing a flexographic printing plate according to the present invention, it is preferable to form a top layer containing a thermoplastic resin on the relief of a halftone dot area and / or solid area with a halftone dot area ratio of 90% or more of a flexographic printing plate precursor having at least a relief on a substrate, thereby forming the relief (a). By forming a top layer on the relief of a halftone dot area and / or solid area with a halftone dot area ratio of 90% or more of a conventional flexographic printing plate (referred to as a "flexographic printing plate precursor") using a material with a higher modulus of elasticity than the relief constituent material of the flexographic printing plate precursor, the modulus of elasticity of the relief can be easily made Ea > Eb using an existing flexographic printing plate precursor. Furthermore, since the height of the relief (a) is increased by the top layer, the height of the relief can be made Ha > Hb.

[0040] Figures 3-4 show schematic cross-sectional views illustrating another embodiment of the flexographic printing plate in the present invention. The flexographic printing plate shown in Figure 3 has a substrate (1) on which reliefs (5a) and (5b) derived from the flexographic printing plate precursor are located. The outermost layer (4) is located on the reliefs (5a) of the halftone areas and / or solid areas with a halftone area ratio of 90% or more, and the reliefs (5a) derived from the flexographic printing plate precursor and the outermost layer (4) become a relief (a) of height Ha. On the other hand, in the halftone areas with a halftone area ratio of less than 25%, the reliefs (5b) derived from the flexographic printing plate precursor remain as a relief (b) of height Hb. The flexographic printing plate shown in Figure 4 has a floor layer (3) on the substrate (1), and the floor layer (3) has reliefs (5a) and (5b) derived from the flexographic printing plate precursor. The outermost layer (4) is located on the relief (5a) of the halftone area and / or solid area with a halftone area ratio of 90% or more, and the relief (5a) derived from the flexographic printing plate precursor and the outermost layer (4) become a relief (a) of height Ha. On the other hand, in the halftone area with a halftone area ratio of less than 25%, the relief (5b) derived from the flexographic printing plate precursor becomes a relief (b) of height Hb.

[0041] Examples of flexographic printing plate precursors include those obtained by exposing and developing commercially available flexographic printing plates. Examples of flexographic printing plates include the "CYREL®" series (DuPont), the AWP series (Asahi Kasei Corporation), FLEXILIGHT CBU (Macdermid), FLEXCEL NX (Miraclon), and DF114YSE (Toray Industries, Inc.). [Examples]

[0042] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these.

[0043] [Evaluation of flexographic printing] The flexographic printing plates produced in the examples and comparative examples were evaluated as described in (1) and (2), respectively.

[0044] (1) Elastic modulus of the relief The flexographic printing plates manufactured in each example and comparative example were cut into 1 cm squares and fixed to a silicon wafer. For relief (a) of the printing plate, three locations were randomly selected from the solid area, and for relief (b), three locations were randomly selected from the 20% halftone area. The elastic modulus of the scanning range of the top (outermost layer) of each relief was measured using a Bruker NanoScope V Dimension Icon scanning probe microscope under the following conditions, and the mode was determined. The average of the three locations was taken as the elastic modulus Ea and Eb. Probe: Silicone cantilever Scanning mode: Force volume (contact mode) Scanning range: 3 μm square Measurement environment: Room temperature, in ambient air.

[0045] (2) Relief height For each example and comparative example, of the flexographic printing plates manufactured, the height from the bottom of the relief to the printed surface was measured using a white confocal microscope ("OPTELICS®" HYBRID+, manufactured by Lasertec Corporation) at three randomly selected locations from the solid area as relief (a) and three randomly selected locations from the 20% halftone area as relief (b), under the following conditions. The average of the three locations was taken as the height. However, if a randomly selected location from the halftone area did not include the printed surface of the relief, the height to the nearest printed surface was measured. Objective lens: 20X (Working distance: 1.65mm, Numerical aperture: 0.80) Light source: Xenon lamp Operation mode: Surface shape.

[0046] [Evaluation of printed materials] The flexographic printing plates manufactured in the examples and comparative examples were attached to the plate cylinder of a flexographic printing press (EF340, manufactured by MPS Corporation) using cushion tape (tesa "softprint®" 73526 (manufactured by TESA Corporation)). The screen ruling was 470 lcm, and the cell capacity was 3.2 cm². 3 / m 2 Using an anilox roll (manufactured by Apec), black ink of UV-curing flexographic ink "FLASH DRY®" FL (manufactured by ARTIENCE Co., Ltd.) was supplied to the printing plate, and printing was performed at a speed of 100 m / min on a 25 μm thick PET film ("Lumirror®" T25 (Toray Industries, Inc.)). The printing pressure was fixed at a pressure 20 μm higher than the pressure at which blurring of the halftone dot area at a halftone dot ratio of 20% disappeared. After printing 100 m, the printed material was taken and evaluated according to (3) and (4), respectively.

[0047] (3)Print density For the solid areas of printed materials, the print density was measured at five randomly selected locations using the "X-Rite®" eXact (Advance) spectrophotometer (manufactured by Xrite Corporation), and the average value of the five locations was calculated. A print density of 1.9 or higher was judged as excellent, 1.7 to 1.9 as good, and below 1.7 as poor.

[0048] (4) Dot Gain For the 20% halftone area of ​​printed materials, the dot gain value was measured at five randomly selected locations using the "X-Rite®" eXact (Advance) spectrophotometer (manufactured by Xrite), and the average value of the five locations was calculated. A dot gain value within the range of 10±4% was judged to indicate good tonal representation, within the range of 10±1% to indicate excellent, and outside the range of 10±4% to indicate poor.

[0049] The materials used for relief formation in each example and comparative example are as follows: Material 1: BIOMED Flex 80A (FORMLABS): Acrylic rubber, contains acrylic crosslinking when formed into relief. Material 2: Silicone 40A (FORMLABS): Silicone rubber, without acrylic crosslinking when formed into a relief. Material 3: FLEXIBLE 80A RESIN (FORMLABS): Acrylic rubber containing acrylic crosslinks when formed into relief.

[0050] (Example 1) A 188 μm thick PET film with an easy-adhesion layer ("Panacrea®" ACM188, manufactured by Panac Co., Ltd.) was printed and UV-cured using a 3D printer "STRATASYS®" J35Pro (STRATASYS Inc.) with a solid color area and a halftone area with a 20% halftone dot ratio, each measuring 10 mm x 10 mm. Thermoplastic resin 1 was used for the relief (a) corresponding to the solid color area, and thermoplastic resin 2 was used for the relief (b) corresponding to the halftone area with a 20% halftone dot ratio, to obtain a flexographic printing plate containing reliefs (a) and (b). The obtained flexographic printing plates were evaluated using the method described above. The evaluation results are shown in Table 1.

[0051] (Examples 2-4) A flexographic printing plate was obtained in the same manner as in Example 1, except that the height Ha of relief (a) and the height Hb of relief (b) were changed as shown in Table 1. The results of evaluating the obtained flexographic printing plate using the method described above are shown in Table 1.

[0052] (Examples 5-6) A flexographic printing plate was obtained in the same manner as in Example 3, except that the materials for relief (a) and relief (b) were changed as shown in Table 1. The results of evaluating the obtained flexographic printing plate using the method described above are shown in Table 1.

[0053] (Example 7) A floor layer was formed on a substrate by sandwiching ethylene propylene diene rubber (Mitsui EPT 3045, Mitsui Chemicals, Inc.) between a 188 μm thick PET film with an easy-adhesion layer ("Panacrea®" ACM188, manufactured by Panac Co., Ltd.) and an anti-tack film (PET film coated with a release agent), so that the total thickness was 0.7 mm, and heating at 150°C for 20 minutes. A test pattern containing a solid area and a halftone area with a halftone dot ratio of 20%, each measuring 10 mm x 10 mm, was printed and UV-cured on the exposed floor layer using a 3D printer "STRATASYS®" J35Pro (STRATASYS Inc.). Material 1 was used for the relief (a) corresponding to the solid area, and material 2 was used for the relief (b) corresponding to the halftone area with a halftone dot ratio of 20%, to obtain a flexographic printing plate containing relief (a) and relief (b). Table 1 shows the results of evaluating the obtained flexographic printing plates using the method described above.

[0054] (Comparative Example 1) A commercially available flexographic printing plate (DF114HR2, manufactured by Toray Industries, Inc.) was subjected to back exposure using an ultraviolet exposure machine (JE-A2-SS, manufactured by JDELK SEIKI) from the substrate side, so that the cured pattern height would be approximately 0.6 mm. Next, the cover film was peeled off, and the PET substrate was mounted on an external drum-type platesetter (CDI SPARK2530, manufactured by ESCO Graphics Co., Ltd.) equipped with a fiber laser that emits light in the infrared range, with the substrate side in contact with the drum. A test pattern including a solid area and a halftone area with a dot ratio of 20%, each measuring 10 mm x 10 mm, was output at 2.4 J / cm². 2 The image mask was formed from the thermal mask layer by drawing with a laser. Then, under atmospheric conditions, a main exposure was performed for 10 minutes using an ultraviolet exposure machine, similar to the back exposure. After that, development was performed at 40°C for 5 minutes using a cleaning machine (JOW-A3-P, manufactured by JDELK SEIKI Co., Ltd.) with a 1% by mass aqueous developer from Nissan Soap, followed by drying in a 60°C oven for 10 minutes. Next, an integrated light intensity of 12,000 mJ / cm² was applied using a high-intensity chemical lamp TL-K 40W / 10R. 2 Post-exposure was performed to achieve a certain degree of exposure, and a flexographic printing plate containing 20% ​​by mass or more of thermoplastic resin in the relief was obtained. The results of evaluating the obtained flexographic printing plate using the method described above are shown in Table 1.

[0055] (Example 8) Using the flexographic printing plate obtained in Comparative Example 1 as a flexographic printing plate precursor, material 3 was printed and UV-cured only in the areas corresponding to the solid areas using a 3D printer "STRATASYS®" J35Pro (STRATASYS Inc.) to form the outermost layer and create relief (a). A flexographic printing plate was obtained. The results of evaluating the obtained flexographic printing plate using the method described above are shown in Table 1.

[0056] [Table 1] [Explanation of symbols]

[0057] (1) Circuit board (2a) Relief (a) (2b) Relief (b) (3) Floor Layer (4) Top layer (5a) Relief of flexographic printing plate precursor (5b) Relief of flexographic printing plate precursor

Claims

1. A method for manufacturing a flexographic printing plate, having a relief containing 20% ​​by mass or more of a substrate and thermoplastic resin, wherein the relief has halftone areas and / or solid areas with a halftone area ratio of 90% or more and halftone areas with a halftone area ratio of less than 25%, wherein the relief is formed on the substrate such that the elastic modulus Ea measured by the force volume method for the relief (a) of the halftone areas and / or solid areas with a halftone area ratio of 90% or more and the elastic modulus Eb measured by the force volume method for the relief (b) of the halftone areas with a halftone area ratio of less than 25% satisfy Ea > Eb.

2. A method for manufacturing a flexographic printing plate according to claim 1, wherein the elastic modulus Ea is 20 MPa or more and 200 MPa or less, and the elastic modulus Eb is 3 MPa or more and less than 20 MPa.

3. The method for producing a flexographic printing plate according to claim 1 or 2, wherein the thermoplastic resin includes isoprene rubber, butadiene rubber, styrene-butadiene copolymer rubber, acrylonitrile rubber, chloroprene rubber, ethylene propylene diene rubber, acrylic rubber, silicone rubber and / or urethane rubber.

4. A method for manufacturing a flexographic printing plate according to any one of claims 1 to 3, wherein the height Ha of the relief (a) of the halftone area portion and / or solid area portion with a halftone area ratio of 90% or more and the height Hb of the relief (b) of the halftone area portion with a halftone area ratio of less than 25% satisfy Ha > Hb.

5. The method for manufacturing a flexographic printing plate according to claim 4, wherein the difference between the heights Ha and Hb is 10 μm or more and 50 μm or less.

6. A method for manufacturing a flexographic printing plate according to any one of claims 1 to 5, wherein the relief further comprises an acrylic crosslinked body.

7. A method for manufacturing a flexographic printing plate according to any one of claims 1 to 6, further comprising forming a floor layer containing ethylene propylene diene rubber and / or chloroprene rubber between the substrate and the relief.

8. The method for manufacturing a flexographic printing plate according to claim 7, wherein the floor layer substantially does not contain an acrylic crosslinked body.

9. A method for manufacturing a flexographic printing plate according to any one of claims 1 to 6, comprising forming a relief on a substrate by printing at least a thermoplastic resin using a 3D printer.

10. A method for manufacturing a flexographic printing plate according to claim 7 or 8, comprising forming a relief on a floor layer by printing at least a thermoplastic resin using a 3D printer.

11. A method for manufacturing a flexographic printing plate according to any one of claims 1 to 10, wherein a top layer containing a thermoplastic resin is formed on the relief of a flexographic printing plate precursor having at least relief on a substrate, in which the relief consists of a halftone area ratio of 90% or more and / or a solid area, to form the relief (a).

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