JP2022152366A - Manufacturing method of photosensitive resin printing plate for flexographic printing - Google Patents

Abstract

To provide a method capable of stably manufacturing a photosensitive resin printing plate for flexographic printing that does not generate problems concerning reproducibility of a square thin line and a depth of a fine recess even when many sheets are manufactured over a long period.SOLUTION: A method of manufacturing ten or more sheets of photosensitive resin printing plates for flexographic printing over eight hours by steps including a mask layer forming step, an image exposure step through a mask layer, a removing step of an uncured portion and a drying step, by using a flexographic printing original plate provided with at least a support, a photosensitive resin layer, and a heat-sensitive mask layer in this order, wherein a time from completion of the image exposure step of all manufactured printing plates to a start of the removing step of uncured portion is set to within two hours.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a method for producing a photosensitive resin printing plate for flexographic printing, and more particularly to a method for preventing deterioration in quality of printed matter caused by swelling of the printing plate that occurs during long-term production.

Flexographic printing is a printing method in which ink is applied to convex portions of a plate material, and the ink is transferred from the plate material to the base material by pressing the plate material against the base material. Since the plate material used in flexographic printing is relatively flexible and can follow various shapes, it is possible to print on a wide range of substrates. Examples of substrates include packaging films, label paper, beverage cartons, paper containers, envelopes, corrugated cardboards, etc. Among them, flexographic printing is exclusively used for substrates with rough surfaces. In addition, flexographic printing can use water-based or alcohol-based inks with low VOC emissions, and is a printing method with high environmental adaptability.

A printing plate used in flexographic printing is generally made from a photosensitive resin original printing plate in which a photosensitive resin composition layer is provided on a polyester film as a support.

As a method of obtaining a printing plate from a photosensitive resin original printing plate, the following method is generally performed.
First, the entire surface is exposed to ultraviolet rays (back exposure) through a polyester film, which is a support of the photosensitive resin printing original plate, to form a photocurable layer having a uniform cushioning property. Next, after removing the protective film, an image pattern is formed on the heat-sensitive mask layer with an infrared laser, and the photosensitive resin composition layer is irradiated with actinic rays through the image pattern of the heat-sensitive mask layer to expose the photosensitive resin composition layer to light. Harden. Thereafter, the unexposed portions (uncured portions) are developed with a developer to obtain a printing plate having the desired relief image formed thereon. If necessary, finishing treatment such as detack treatment is subsequently performed to obtain a photosensitive resin printing plate.

In recent years, flexographic printing is required to have unprecedented high print quality. The quality of flexographic printing has improved to a certain extent by increasing the precision of printing presses and anilox rolls, but to further improve the quality of flexographic printing, it is necessary to improve the performance of printing plates.

For example, in order to produce a printing plate that can faithfully reproduce fine lines, it is conceivable to increase the relief exposure dose and increase the reaction with actinic rays. This is not desirable because it causes

On the other hand, in Patent Document 1, the exposure distribution of actinic rays in the exposure surface (minimum value of irradiation intensity of actinic rays/maximum value of irradiation intensity of actinic rays) is 80% or more. It is disclosed that the quality of the plate is stabilized and the plate making efficiency is improved. In addition, in Patent Document 2, in the drying treatment step of the developer in the method for manufacturing a photosensitive resin plate for printing plates, the difference between the maximum temperature and the minimum temperature of the temperature distribution in the drying treatment range is set to 20° C. or less to form a relief. It is disclosed to stabilize the depth and the thickness of the printing plate.

However, when a large number of conventional photosensitive resin plate manufacturing methods, including the methods of Patent Documents 1 and 2, are manufactured over a long period of time, the resulting printing plate has poor reproducibility of rectangular fine lines and fine recesses. In many cases, there were problems with the depth of the data, and it was not possible to stably obtain sharp prints that were faithful to the data.

Japanese Patent Application Laid-Open No. 2018-116110 JP 2018-185421 A

The present invention was made in order to solve the problems of the prior art, and the object thereof is to solve problems related to the reproducibility of rectangular thin lines and the depth of fine recesses even when a large number of printing plates are manufactured over a long period of time. To provide a method for stably producing a photosensitive resin printing plate for flexographic printing which does not cause

As a result of intensive studies to achieve the above object, the inventors of the present invention have found that, in the conventional manufacturing method, in the case of short-time small-quantity production, development is performed without leaving a time interval after exposure, but development takes a long time. In the case of manufacturing a large number of sheets, the exposure process is performed sequentially, and after the exposure is completed, development is performed collectively, or after the exposure process, other parallel work is performed, and then development is performed collectively. It was found that the time from exposure to development was long in some cases. They have also found that such a printing plate requiring a long time from exposure to development has problems with respect to the reproducibility of rectangular fine lines and the depth of fine recesses.

Furthermore, in order to eliminate such a cause, the present inventor limited the time from exposure to development of all the printing plates manufactured within a specific time. The inventors have found that stable printing can be obtained, and have completed the present invention.

The present invention has been completed based on such findings, and has the following configurations (1) to (5).
(1) At least, using a flexographic printing original plate provided with a support, a photosensitive resin layer and a heat-sensitive mask layer in this order, a mask layer forming step, an image exposure step through the mask layer, and an uncured portion are removed. A method for producing 10 or more photosensitive resin printing plates for flexographic printing over a period of 8 hours or more by a step including a removing step and a drying step, wherein the uncured portion of all the printing plates produced from the end of the imagewise exposure step A method characterized in that the time until the start of the removal step is within 2 hours.
(2) The method according to (1), wherein the photosensitive resin layer contains 10 to 40% by mass of a component that is liquid at 10 to 30°C.
(3) The method according to (1), wherein the photosensitive resin layer contains an intramolecularly crosslinked hydrophilic polymer having an intramolecular hydrophilic group.
(4) The method according to any one of (1) to (3), wherein the step of removing uncured portions includes a step of developing with a developer containing 70% by mass or more of water.
(5) The original plate for flexographic printing has an oxygen barrier layer between the photosensitive resin layer and the heat-sensitive mask layer, and the oxygen barrier layer contains a polymer having a hydrophilic group in its molecule. The method according to any one of (1) to (4).

According to the method of the present invention, it is possible to provide a photosensitive resin printing plate for flexographic printing that is excellent in the reproducibility of rectangular fine lines and the depth of fine recesses even if a large number of printing plates are produced over a long period of time. As a result, it is possible to stably obtain clear printing that is faithful to the data.

FIG. 1 shows how a rectangular thin line on a printing plate is distorted.

The method of the present invention will be specifically described below, but the present invention is not limited thereto.

In the method for producing a photosensitive resin printing plate for flexographic printing of the present invention, a mask layer is formed using a flexographic printing original plate in which at least a support, a photosensitive resin composition layer and a heat-sensitive mask layer are provided in this order. A method for producing 10 or more photosensitive resin printing plates for flexographic printing over a period of 8 hours or more by steps including a step, an image exposure step through a mask layer, a step of removing uncured portions, and a drying step, wherein the The time from the end of the image exposure process for all printing plates to the start of the process of removing uncured portions is limited to within 2 hours.

The support used in the original plate for flexographic printing is preferably a material that is flexible but has excellent dimensional stability. Thermoplastic supports such as phthalate film, polybutylene terephthalate film, or polycarbonate film can be used. Among these, a polyethylene terephthalate film having excellent dimensional stability and sufficiently high viscoelasticity is particularly preferred. The thickness of the support is desirably 50 to 350 μm, preferably 100 to 250 μm, from the viewpoints of mechanical properties, shape stabilization, handleability during printing plate making, and the like. Moreover, if necessary, an adhesive may be provided between the support and the photosensitive resin layer in order to improve the adhesion between them.

Conventionally known photosensitive resin compositions can be used as the photosensitive resin composition for forming the photosensitive resin layer used in the original plate for flexographic printing. A photopolymerizable unsaturated compound, and (c) a photopolymerization initiator, and if necessary, a plasticizer, a hydrophilic polymer, an ultraviolet absorber, a surface tension modifier, a thermal polymerization inhibitor, a dye, a pigment, a fragrance, or Those containing additives such as antioxidants are preferred.

The photosensitive resin composition preferably contains 10 to 40% by mass of components that are liquid at 10 to 30°C. Liquid components in the photosensitive resin composition include photopolymerizable unsaturated compounds and plasticizers. In particular, when the content of the photopolymerizable unsaturated compound that contributes to photocuring is within the above range, the effects of the present invention can be exhibited.

(a) As the polymer obtained by polymerizing a conjugated diene, conventionally known synthetic high molecular compounds used for printing original plates can be used. Specifically, a polymer obtained by polymerizing a conjugated diene-based hydrocarbon, or a copolymer obtained by copolymerizing a conjugated diene-based hydrocarbon and a monoolefin-based unsaturated compound may be mentioned. For example, butadiene polymer, isoprene polymer, chloroprene polymer, styrene-butadiene copolymer, styrene-butadiene-styrene copolymer, styrene-isoprene copolymer, styrene-isoprene-styrene copolymer, styrene-chloroprene copolymer Polymer, acrylonitrile-butadiene copolymer, acrylonitrile-isoprene copolymer, methyl methacrylate-butadiene copolymer, methyl methacrylate-isoprene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-isoprene-styrene copolymer A polymer etc. are mentioned. It is also possible to copolymerize methacrylic acid and acrylic acid. Among these, butadiene polymers are preferably used from the viewpoint of properties as a flexographic printing plate, ie impact resilience of the plate surface, strength and elongation physical properties, resin plate hardness, shape stability when not exposed to light, and availability. The polymer obtained by polymerizing the conjugated diene is preferably a particulate latex from the viewpoint of imparting high resolution to the printing plate. These polymers may be used individually by 1 type, and may use 2 or more types together. The proportion of component (a) in the photosensitive resin composition forming the photosensitive resin layer is preferably in the range of 40 to 70 mass %.

(b) As the photopolymerizable unsaturated compound, conventionally known compounds used in printing plates can be used. It is a compound containing one or more photopolymerizable unsaturated groups in the molecule. Examples of such compounds include polyvalent acrylates and polyvalent methacrylates such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, pentaerythritol diacrylate, pentaerythritol triacrylate and glycerol dimethacrylate, and ethylene glycol diglycidyl ether. , Trimethylolpropane triglycidyl ether and other polyvalent glycidyl ethers, polyvalent acrylates and polyvalent methacrylates obtained by the addition reaction of compounds with ethylenically unsaturated bonds and active hydrogen, such as unsaturated carboxylic acids and unsaturated alcohols. , addition reaction products of unsaturated epoxy compounds such as glycidyl acrylate and compounds having active hydrogen such as carboxylic acids and amines, unsaturated polyesters, unsaturated polyurethanes, and the like. These monomers can be used alone or in combination of two or more. Among them, it is preferable to include (i) a (meth)acrylate compound having a number average molecular weight of 100 or more and 600 or less (hereinafter also simply referred to as a low molecular weight (meth)acrylate compound) (i), and in addition, a number average molecular weight of more than 600 and 20 ,000 or less (hereinafter simply referred to as a (meth)acrylate compound of high molecular weight) (ii). Here, the low-molecular-weight (meth)acrylate compound is crosslinked and cured by a photopolymerization initiator to form a dense crosslinked network, and the high-molecular-weight (meth)acrylate compound is crosslinked and cured by the photopolymerization initiator. It forms a loosely crosslinked network. The former more preferably has a number average molecular weight of 200 or more and 500 or less, and the latter more preferably has a number average molecular weight of 2000 or more and 10000 or less. As described above, by blending not only the low-molecular-weight (meth)acrylate compound but also the high-molecular-weight (meth)acrylate compound, the reproducibility of independent points and the durability during printing are not impaired. This is probably because the high-molecular-weight (meth)acrylate compound contained in a certain proportion increases the toughness of the plate. The proportion of component (b) in the photosensitive resin composition forming the photosensitive resin layer is preferably in the range of 10 to 50 mass %.

(c) Examples of photopolymerization initiators include benzophenones, benzoins, acetophenones, benzyls, benzoin alkyl ethers, benzyl alkyl ketals, anthraquinones, and thioxanthones. Specifically, benzophenone, chlorobenzophenone, benzoin, acetophenone, benzyl, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl dimethyl ketal, benzyl diethyl ketal, benzyl diisopropyl ketal, anthraquinone, 2-ethylanthraquinone , 2-methylanthraquinone, 2-allylanthraquinone, 2-chloroanthraquinone, thioxanthone, 2-chlorothioxanthone and the like. These may be used individually by 1 type, and may be used in combination of 2 or more types. The proportion of component (c) in the photosensitive resin composition is preferably in the range of 0.1 to 10 mass %.

The plasticizer imparts flexibility to the photosensitive resin layer (B), and examples of plasticizers include liquid rubber, oil, polyester, and phosphoric acid compounds. The content of the plasticizer in the photosensitive resin composition is preferably 3 to 15% by mass.

The hydrophilic polymer enhances the developability of the photosensitive resin layer with an aqueous developer. When the flexographic printing original plate of the present invention is water-developable, it preferably contains a hydrophilic polymer. Examples of hydrophilic compounds include acrylic polymers, urethane polymers, polyamide polymers having hydrophilic groups such as carboxylic acid, carboxylate, sulfonic acid, sulfonate, hydroxyl group, amino group, phosphoric acid group, ethylene oxide, and propylene oxide. Coalescing, polyester polymers. The content of the hydrophilic compound in the photosensitive resin composition is preferably 1 to 15% by mass.

The surface tension modifier adjusts the surface tension of the printing plate, and by adjusting the surface tension of the printing plate, it is possible to adjust ink transferability and ink clogging on the printing plate. Examples of surface tension modifiers include paraffin oil, long-chain alkyl compounds, surfactants, fatty acid amides, silicone oils, modified silicone oils, fluorine compounds, and modified fluorine compounds. The content of the surface tension modifier in the photosensitive resin composition is preferably 0.1 to 2% by mass.

The UV absorber increases the exposure latitude of the photosensitive resin layer. and coumarin-based and furan-based compounds. The content of the ultraviolet absorber in the photosensitive resin composition is preferably 0.005 to 0.1% by mass.

The flexographic printing plate precursor of the present invention preferably has an oxygen barrier layer between the photosensitive resin layer and the heat-sensitive mask layer. By providing the oxygen barrier layer, inhibition of oxygen polymerization during main exposure is suppressed, and a sufficient curing reaction occurs in both halftone dot portions and solid portions. As a result, the halftone dot portion forms a flat top suitable for printing. The flat top improves the print dot gain of fine halftone dots. In addition, the surface of the solid portion is smoothed, and the ink transfer on the solid portion is improved. Known polymers can be used as the oxygen barrier layer.

When the flexographic printing original plate of the present invention is water-developable, the oxygen barrier layer preferably contains a film-forming polymer having a hydrophilic group in the molecule. Examples of hydrophilic groups include, but are not limited to, hydrophilic groups such as carboxyl groups, amino groups, hydroxyl groups, phosphoric acid groups and sulfonic acid groups, and hydrophilic groups such as salts thereof. Specific polymers include polyvinyl alcohol, partially saponified vinyl acetate, alkyl cellulose, cellulosic polymers, and polyamides. These polymers are not limited to the use of one type, and two or more types of polymers can be used in combination. Polyvinyl alcohol, partially saponified vinyl acetate, and polyamide are preferred polymers in terms of oxygen barrier properties. Image reproducibility can be suitably controlled by selecting these polymers.

The oxygen barrier layer can also be formed by blending a polymer having low oxygen barrier properties with a polymer having favorable oxygen barrier properties. Polymers with low oxygen barrier properties include polymers with low crystallinity, such as low saponification vinyl acetate, polymers obtained by polymerizing conjugated diene hydrocarbons, low crystallinity nylons, and polyurethanes. As for the form of the polymer, it may be particulate in terms of dispersibility in the polymer. The oxygen barrier layer may contain additives in addition to the polymer. Additives include plasticizers, UV absorbers and stabilizers.

The layer thickness of the oxygen barrier layer is preferably 0.2 to 3.0 μm, more preferably 0.2 to 1.5 μm. If the layer thickness is less than the above range, the oxygen barrier property of the oxygen barrier layer is insufficient, and the printing plate surface of the relief may be roughened. If the above range is exceeded, fine line reproducibility may be poor.

Next, a method for producing a photosensitive resin printing plate for flexographic printing using the original plate for flexographic printing will be described. The method of the present invention uses the flexographic printing original plate described above, and performs photosensitive resin printing for flexographic printing through steps including a mask layer forming step, an image exposure step through the mask layer, an uncured portion removing step, and a drying step. A method of manufacturing 10 or more plates over 8 hours or more, characterized in that the time from the end of the image exposure process to the start of the uncured portion removal process for all the printing plates manufactured is within 2 hours. do. The production time of the printing plate may be 10 hours or more, further 12 hours or more, and the number of printing plates produced at that time may be 20 or more, 30 or more, or 40. can be more than

In the method of the present invention, it is preferable to irradiate actinic rays through the support (back exposure) to form a photocurable layer. Specifically, it is preferable to perform exposure through the support to photo-cure the photosensitive resin layer to provide a uniform photo-cured layer.

In the mask layer forming step, a mask layer for forming an image for a printing plate is formed by ablating the thermal mask layer with an infrared laser. As the heat-sensitive mask layer, a known one can be used. For example, carbon black, which is a material having a function of absorbing infrared laser and converting it into heat and a function of blocking ultraviolet light, its dispersed binder, and film formation. It is preferably composed of a possible binder polymer. The dispersing binder and the film-forming binder polymer can also be used together. Further, as optional components other than these, a pigment dispersant, a filler, a surfactant, a coating aid, or the like can be contained within a range that does not impair the effects of the present invention.

The thermal mask layer is preferably water-developable. Specific heat-sensitive mask layers include a heat-sensitive mask layer combining a polar group-containing polyamide and a butyral resin (Japanese Patent No. 4200510), a polymer having the same structure as the polymer in the photosensitive resin layer, and an acrylic resin. A heat-sensitive mask layer (Patent No. 5710961), a heat-sensitive mask layer containing an anionic polymer and a polymer having an ester bond in the side chain and a degree of saponification of 0% or more and 90% or less (Patent No. 5525074). .

Examples of suitable infrared lasers include ND/YAG lasers (1064 nm) or diode lasers (eg 830 nm). Laser systems suitable for computer engraving techniques are commercially available, for example CDI (Esco Graphics) can be used. The laser system includes a rotating cylindrical drum that holds the printing master, an infrared laser illumination device, and a layout computer, with image information transferred directly from the layout computer to the laser device.

In the image exposure step through the mask layer, ultraviolet light having an emission peak at a wavelength of 330 to 380 nm can be used as actinic light. Low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, zirconium lamps, carbon arc lamps, ultraviolet fluorescent lamps, LEDs, and the like can be used as the light source.

The step of removing the uncured portion is a step called development, and is a step of removing portions other than the image portion used as the printing plate. It is preferable that the developer contains water as a main component from the viewpoint of handleability. A developer containing water as a main component is a developer containing 70% by mass or more of water, preferably a developer containing 90% by mass or more of water. The developer preferably contains a surfactant, a pH adjuster, and the like.

The drying step is a step of drying with hot air to completely remove water droplets such as developer remaining on the plate surface of the printing plate after the step of removing the uncured portion. The drying method is not particularly limited, but for example, a method can be employed in which the printing plate whose uncured portion has been removed is placed in a predetermined space, and air heated by a heater is fed into the space and circulated.

The method of the present invention is characterized in that the time from the end of the imagewise exposure step to the start of the step of removing uncured portions for all printing plates to be produced is within 2 hours, preferably within 100 minutes. By limiting the time from exposure to development of all printing plates manufactured in this way within a specific time, printed matter with excellent reproducibility of rectangular fine lines and depth of fine recesses can be obtained.

When manufacturing a large number of printing plates over a long period of time, the conventional method takes a long time from exposure to development. In that case, liquid components (such as cross-linking monomers) migrate from the unexposed area to the exposed area during the time until development starts, and the exposed area expands. , and the depth of fine recesses on the printing plate was shallow. As a result, data-faithful and clear prints could not be obtained using such a printing plate. In the method of the present invention, since the time from exposure to development is shortened to within a specific time, swelling of the exposed area due to migration of the liquid components is completely eliminated, and data can be obtained using any of these printing plates. Faithful and clear printing can now be performed stably.

The effect of the method of the present invention is illustrated by the following examples, but the present invention is not limited to these. In addition, the evaluation in the examples was performed by the following methods.

(1) Distortion of rectangular thin lines A printing plate is produced using a test image having a square consisting of thin lines with a side length of 50 mm and a width of 50 μm, and the length of one side of the test image of the printing plate is measured at four points. and calculated the average value. Furthermore, this average value of 30 printing plates was further averaged and calculated. The closer this value is to 50 mm, the smaller the distortion and the better the fine line reproduction of the printing plate.

(2) Depth of Fine Recess Using a test image having a slit (recess) with a width of 50 μm, a printing plate was produced, and the depth of the recess was measured. The measurement was performed using VK9510 manufactured by Keyence Corporation, and the deepest point in the recess with a width of 50 μm was defined as the depth. Depth was taken as the mean value of measurements of 30 printing plates. The greater the depth, the clearer the printing plate that can be printed.

Preparation of photosensitive resin composition (A) As a polymer obtained by polymerizing a conjugated diene, butadiene latex (Nipol LX111NF, non-volatile content 55%, manufactured by Nippon Zeon Co., Ltd.) 86 parts by mass, and acrylonitrile-butadiene latex (Nipol SX1503) , non-volatile content 42%, Nippon Zeon Co., Ltd.) 24 parts by mass, polybutadiene-terminated acrylate (BAC45, Osaka Organic Chemical Industry Co., Ltd.) 15 parts by mass having a number average molecular weight of 10000 as an ethylenically unsaturated compound, and 10 parts by weight of trimethylolpropane trimethacrylate (light ester TMP, manufactured by Kyoeisha Chemical Co., Ltd.) having a number average molecular weight of 338, 3 parts by weight of benzyl dimethyl ketal as a photopolymerization initiator, and a hydrophilic polymer (PFT- 4, non-volatile content 25%, Kyoeisha Chemical Co., Ltd.) 20 parts by mass, butadiene oligomer (Nippon Soda Co., Ltd. B2000) 9.9 parts by mass, heat stabilizer (4-methoxyphenol) 0.1 parts by mass, A dope was prepared by mixing 0.01 part by mass of an ultraviolet absorber (TINUVIN 326) in a container. The dope was put into a pressure kneader and the solvent was removed under reduced pressure at 80° C. to obtain a photosensitive resin composition (A).

Preparation of photosensitive resin composition (B) In the photosensitive resin composition (A), the acrylonitrile-butadiene latex was changed to a styrene-butadiene block copolymer [Kraton D-KX405], mixed in the same manner, and then the solvent was removed under reduced pressure. Then, a photosensitive resin composition (B) was obtained.

(Example 1)
Carbon black dispersion (Orient Chemical Industry Co., Ltd., AMBK-8), copolyamide (PA223, Toyobo Co., Ltd.), propylene glycol, and methanol were mixed at a mass ratio of 45/5/5/45. , to obtain a heat-sensitive mask layer coating solution. After applying release treatment to both sides of a PET film (E5000, thickness 100 μm, manufactured by Toyobo Co., Ltd.), the heat-sensitive mask layer coating solution is applied with a bar coater so that the thickness of the coating film after drying is 2 μm. and dried at 120° C. for 5 minutes to obtain a film laminate (I). The optical density was 2.3. The optical density was measured with a black-and-white transmission densitometer DM-520 (Dainippon Screen Mfg. Co., Ltd.). The above photosensitive resin composition (A) is placed on a PET film support (Toyobo Co., Ltd., E5000, thickness 125 μm) coated with a copolymer polyester adhesive, and the film laminate ( II) were superimposed. A heat press was used to laminate at 100° C. to obtain a flexographic printing original plate comprising a PET support, an adhesive layer, a photosensitive resin layer, an oxygen barrier layer, a heat-sensitive mask layer and a cover film. The total plate thickness was 1.14 mm.

Back exposure was performed for 10 seconds from the PET support side of the flexographic printing original plate. Subsequently, the cover film was peeled off. This plate was wrapped around a CDI4530 manufactured by Esko Graphic Co., Ltd., and ablation was performed at a resolution of 4000 dpi with a square test image for measuring the distortion of the rectangular thin wire and a slit test image for measuring the depth of the fine recess. . Subsequently, after adjusting the temperature and humidity in the exposure machine, the plate was taken out from the CDI, placed on the exposure machine stand, and subjected to image exposure for 9 minutes. 10 minutes after the completion of exposure, the exposed printing plate was exposed to a developing machine (Stuck System, 1% laundry soap solution, 40°C) adjusted to a temperature of 23°C and a relative humidity of 50%. Removal (development) of the uncured portion was carried out for 8 minutes, and water droplets on the plate surface were completely removed with a watering rod. After that, it was dried in a dryer at 60°C for 10 minutes. Subsequently, post-exposure was performed for 7 minutes, and finally irradiation with a germicidal lamp was performed for 5 minutes to obtain a resin printing plate for flexographic printing. A Philips TL-K 60W/10R lamp (peak wavelength 370 nm, illuminance at 350 nm is 10.5 mW/cm ² ) was used for back exposure, main exposure, and post-exposure, and a germicidal lamp GL-40 manufactured by Panasonic ( A peak wavelength of 250 nm and an illumination intensity of 4.5 mW/cm ² at 250 nm were used. A total of 30 resin printing plates for flexographic printing were obtained over 10 hours in the same process.

(Examples 2-4)
A resin printing plate for flexographic printing was obtained in the same manner as in Example 1, except that the time from the completion of exposure to the start of removal of the uncured portion was changed as shown in Table 1.

(Example 5)
A resin printing plate for flexographic printing was obtained in the same manner as in Example 1, except that the photosensitive resin composition (A) was changed to the photosensitive resin composition (B).

(Comparative example 1)
A resin printing plate for flexographic printing was obtained in the same manner as in Example 1, except that the time from the completion of exposure to the start of removal of the uncured portion was changed as shown in Table 1.

(Comparative example 2)
A resin printing plate for flexographic printing was obtained in the same manner as in Comparative Example 1, except that the photosensitive resin composition (A) was changed to the photosensitive resin composition (B).

Table 1 shows the evaluation results of the printing plates of Examples 1-5 and Comparative Examples 1-2.

As can be seen from Table 1, in the resin printing plates for flexographic printing of Examples 1 to 5, the time from the end of the image exposure step to the start of the step of removing the uncured portion is suppressed within the range defined by the present invention. Therefore, the printing plate does not swell, and the performance evaluations are all good. On the other hand, in the resin printing plates for flexographic printing of Comparative Examples 1 and 2, since the time was set longer than the range specified in the present invention, an exposed portion of the liquid component was generated, resulting in swelling of the printing plate, which resulted in poor performance evaluation. All items are inferior.

According to the method of the present invention, even when manufacturing a large number of printing plates over a long period of time, it is possible to stably manufacture flexographic printing plates with excellent reproducibility of fine fine line linearity and large depth of fine recesses. can do. Therefore, the method of the present invention is extremely useful in the art.

Claims (5)

Using a flexographic printing original plate comprising at least a support, a photosensitive resin layer, and a heat-sensitive mask layer in this order, a mask layer forming step, an image exposure step through the mask layer, an uncured portion removing step, and A method of manufacturing 10 or more photosensitive resin printing plates for flexographic printing over a period of 8 hours or more by a process including a drying process, wherein the process of removing uncured portions from the end of the image exposure process for all the printing plates manufactured is completed. A method characterized in that the time to start is set within 2 hours. 2. The method according to claim 1, wherein the photosensitive resin layer contains 10 to 40% by weight of a liquid component at 10 to 30.degree. 2. The method according to claim 1, wherein the photosensitive resin layer contains an intramolecularly crosslinked hydrophilic polymer having an intramolecular hydrophilic group. 4. The method according to any one of claims 1 to 3, wherein the step of removing the uncured portion includes a step of developing with a developer containing 70% by mass or more of water. 4. The original plate for flexographic printing has an oxygen barrier layer between the photosensitive resin layer and the heat-sensitive mask layer, and the oxygen barrier layer contains a polymer having a hydrophilic group in its molecule. 5. The method according to any one of 1 to 4.

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