JP6494484B2 - Flexographic printing plate precursor - Google Patents

Description

  The present invention relates to a flexographic printing plate precursor, and more particularly to a flexographic printing plate precursor suitable as a master for forming a relief plate by laser engraving.

  Conventionally, letterpress printing, intaglio printing, or planographic printing has been performed on printing materials such as packaging materials, labels, and magazines using printing plates. Among these, letterpress printing is performed using letterpress. This relief printing plate includes a flexographic printing plate that can be applied to various types of printing bodies because the material is soft.

  As a method of forming a relief from an original plate of a flexographic printing plate, a predetermined image is exposed by exposing a predetermined image on a photosensitive resin layer, and a cured portion is embossed, and a predetermined image is embossed by laser engraving on a crosslinked resin layer. There is a way to make it. Examples of the flexographic printing plate precursor used for forming a relief plate by the laser engraving method include those described in Patent Document 1.

Japanese Patent Laying-Open No. 2015-30121

  While high-definition printed matter is demanded, the flexographic printing plate precursor used for letterpress formation by the laser engraving method has problems in engraving speed and engraving unevenness.

  The problem to be solved by the present invention is to provide a flexographic printing plate precursor which is excellent in engraving speed and suppresses uneven engraving in a flexographic printing plate precursor capable of laser engraving.

In order to solve the above problems, a flexographic printing plate precursor according to the present invention has an elastic layer on the surface of a support, and the elastic layer is a crosslinked composition containing the following (a) to (c): The gist is that it consists of a body.
(A) Rubber polymer (b) Crosslinker (c) Acetylene black having a hydrochloric acid absorption of 15.0 ml / 5 g or more

The (a) preferably contains an ethylene-propylene-diene copolymer. The (b) is preferably a peroxide. The bulk density of (c) is preferably 0.10 g / cm ³ or less. The (a) preferably further contains 1,2-polybutadiene.

  According to the flexographic printing plate precursor according to the present invention, the elastic layer contains acetylene black. Since acetylene black has high crystallinity and excellent thermal stability, it can generate heat up to a relatively high temperature. Thereby, since a combustion rate improves, it is excellent in engraving speed. Moreover, the dispersibility of acetylene black improves because the hydrochloric acid absorption amount of acetylene black shall be 15.0 ml / 5g or more. Thereby, uneven engraving is suppressed.

When (a) contains an ethylene-propylene-diene copolymer, swelling due to ink is further suppressed. When (b) is a peroxide, the crosslinking density is improved and the durability is excellent. When the bulk density of (c) is 0.10 g / cm ³ or less, the dispersibility of acetylene black is further improved. When (a) further contains 1,2-polybutadiene, the dispersibility of acetylene black is further improved.

1 is a cross-sectional view of a flexographic printing plate precursor according to an embodiment of the present invention.

  Next, the present invention will be described in detail.

  FIG. 1 is a cross-sectional view of a flexographic printing plate precursor according to an embodiment of the present invention. As shown in FIG. 1, the flexographic printing plate precursor 10 according to an embodiment includes a support 12, an adhesive layer 14, and an elastic body layer 16. On the surface of the support 12, an adhesive layer 14 and an elastic body layer 16 are laminated in this order. The adhesive layer 14 is provided in contact with the support 12, and the elastic body layer 16 is provided in contact with the adhesive layer 14. The adhesive layer 14 adheres the elastic body layer 16 to the support 12, and if the elastic body layer 16 is directly formed on the surface of the support 12, the adhesive layer 14 can be satisfactorily adhered. Is not necessary.

  The support 12 supports a layer such as the elastic body layer 16 laminated thereon. Although it does not specifically limit as the support body 12, For example, a resin film is mentioned. Examples of the resin film include a polyester film such as a PET film because of excellent dimensional stability. The thickness of the support 12 is not particularly limited, but from the viewpoint of obtaining a sufficient strength to support a layer such as the elastic body layer 16 laminated thereon, for example, 50 to 300 μm. Should be within the range.

  The adhesive layer 14 contains an adhesive component. Although it does not specifically limit as an adhesive agent component, Since it is excellent in the adhesiveness with the support body 12 and the elastic body layer 16, a polyester-type adhesive agent is mentioned. The binder resin of the polyester adhesive is made of a polyester resin. The thickness of the adhesive layer 14 is not particularly limited, but may be in the range of 1 to 100 μm because of excellent adhesion. Further, the surface of the support 12 may be subjected to a surface treatment (plasma treatment, UV treatment, EB treatment, corona treatment, etc.) for imparting an active group.

The elastic body layer 16 consists of a crosslinked body of a composition containing the following (a) to (c).
(A) Rubber polymer (b) Crosslinker (c) Acetylene black having a hydrochloric acid absorption of 15.0 ml / 5 g or more

  (A) As rubber polymer, polybutadiene (BR), polyisoprene (IR), styrene-butadiene random copolymer (SBR), styrene-butadiene block copolymer (SBS), styrene-isoprene block copolymer (SIS) ), Ethylene-propylene-diene copolymer (EPDM), butyl rubber (IIR), nitrile rubber (NBR), chlorosulfonated polyethylene (CSM), urethane rubber (PUR), fluoro rubber (DuPont Elastomer "Viton", etc.) ), Polysulfide polymers (such as “Thiocol” manufactured by Toray Industries, Inc.), and partially hydrogenated products thereof. Examples of the polybutadiene (BR) include 1,2-polybutadiene (1,2-BR) and 1,4-polybutadiene (1,4-BR). 1,2-polybutadiene is syndiotactic 1,2-polybutadiene.

  (A) Each said rubber polymer illustrated as a rubber polymer may be used individually by 1 type as a (a) rubber polymer, and may be used in combination of 2 or more type. Among these, since it is excellent in ink resistance (swelling by ink is suppressed), (a) as a rubber polymer, ethylene-propylene-diene copolymer (EPDM), polybutadiene (BR), butyl rubber (IIR), It is preferable to include one or more nitrile rubbers (NBR). In particular, an ethylene-propylene-diene copolymer (EPDM) is preferably included. In addition, from the viewpoint of excellent ink resistance (suppression of swelling due to ink) and improvement in dispersibility of (c), (a) as a rubber polymer, ethylene-propylene-diene copolymer (EPDM) and 1 , 2-polybutadiene is preferably included. 1,2-polybutadiene can stabilize the viscosity of a polymer containing an ethylene-propylene-diene copolymer (EPDM) during kneading, thereby stabilizing the kneading shear and stabilizing dispersibility. Engraving unevenness is suppressed.

  (A) When an ethylene-propylene-diene copolymer (EPDM) is included as a rubber polymer, the content thereof is within the range of 50 to 100% by mass with respect to the entire polymer component including (a) the rubber polymer. Preferably there is. More preferably, it exists in the range of 75-95 mass%.

  (B) A crosslinking agent is a crosslinking agent which bridge | crosslinks (a) rubber polymer. (B) As a crosslinking agent, sulfur, a peroxide, a hydrosilyl compound, thiourea, etc. are mentioned. Among these, a peroxide is preferable from the viewpoint of the crosslinking density and the like.

  The peroxide is not particularly limited. What is necessary is just to select suitably in consideration of the balance of thermal stability and thermal decomposability. Specific examples of the peroxide include di-n-propyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, bis (2-ethylhexyl) peroxydicarbonate, and tert-butyl peroxyneo. Decanoate, tert-butylperoxyneoheptanoate, bis (3,5,5-trimethyl-1-oxohexyl) peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate , Tert-hexylperoxy-2-ethylhexanate, tert-butylperoxy-2-ethylhexanate, dibenzoyl peroxide, 1,1-di (tert-butylperoxy) -2-methylcyclohexane, 1, 1-di (tert-butylperoxy) cyclohexane, tert Hexyl peroxyisopropyl monocarbonate, tert-butyl peroxylaurate, tert-butyl peroxyisopropyl monocarbonate, tert-hexyl peroxybenzoate, tert-butyl peroxyacetate, n-butyl-4,4-di (tert- Butylperoxy) valerate, di (2-tert-butylperoxyisopropyl) benzoate, dicumyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, tert-butylcumyl peroxide , Di-tert-butyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane-3, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl high B peroxide, cumene hydroperoxide, etc. tert- butyl hydroperoxide and the like. Although content of a peroxide is not specifically limited, (a) 0.1-10 mass parts etc. should just be with respect to 100 mass parts of polymer components containing a rubber polymer.

  (C) is an energy absorber for facilitating laser engraving and is an infrared absorbing material. (C) consists of acetylene black. Compared to other carbon blacks, acetylene black has few impurities and high crystallinity. For this reason, since it is excellent in thermal stability, it can generate heat up to a relatively high temperature. Thereby, since a combustion rate improves, it is excellent in engraving speed. (C) is acetylene black having a hydrochloric acid absorption amount of 15.0 ml / 5 g or more. Thereby, since the dispersibility of acetylene black improves, an engraving nonuniformity is suppressed. Since acetylene black having a high hydrochloric acid absorption capacity can absorb a larger amount of hydrochloric acid, it is presumed that the surface is negatively charged electronically. As a result, the acetylene blacks repel each other due to electrical action, and are easily broken by the shearing force of kneading (becomes easy to disperse), and re-aggregation after dispersion is also suppressed by the electrical action. It is estimated that it will improve. Therefore, when (c) is acetylene black having a hydrochloric acid absorption amount of 15.0 ml / 5 g or more, the engraving speed is excellent and engraving unevenness is suppressed.

  The amount of acetylene black absorbed by hydrochloric acid is preferably 20.0 ml / 5 g or more, more preferably 25.0 ml / 5 g or more, from the viewpoint of further improving dispersibility. The hydrochloric acid absorption amount of acetylene black is measured according to JIS K1469 (2003).

(C) also preferably has a bulk density of 0.10 g / cm ³ or less. Since the bulk density is small, dispersibility is further improved and unevenness of engraving is suppressed. The bulk density of this respect, (c) is more preferably 0.08 g / cm ³ or less, further preferably 0.05 g / cm ³ or less. On the other hand, the lower limit of the bulk density of (c) is not particularly limited, but is 0.01 g / cm ³ or more from the standpoint of scattering during kneading. The bulk density of (c) is measured according to JIS K6219-2.

  The content of (c) is preferably in the range of 5 to 40 parts by mass with respect to 100 parts by mass of the polymer component including (a) the rubber polymer. More preferably, it exists in the range of 10-25 mass parts. Engraving is easy when the content of (c) is 5 parts by mass or more with respect to 100 parts by mass of the polymer component. When the content of (c) is 40 parts by mass or less with respect to 100 parts by mass of the polymer component, the engraving speed is excellent.

  In the composition, in addition to the above (a) to (c), other additives may be included. Examples of such other additives include processing aids, fillers, plasticizers, co-crosslinking agents, and anti-aging agents. Examples of the processing aid include fatty acid zinc, fatty acid ester, and organosilicone. Examples of the filler include calcium carbonate, silica, and clay.

  The kind of the plasticizer is not particularly limited, and examples thereof include paraffinic oil, naphthene oil, aroma oil, ester, ether, ester ether, liquid polybutadiene, liquid polyisoprene, and polyisobutene. It is preferable that content of a plasticizer exists in the range of 1-100 mass parts with respect to 100 mass parts of polymer components from a viewpoint of workability or handling.

  The kind of co-crosslinking agent is not particularly limited, and examples thereof include (meth) acrylic monomers, (meth) acrylic oligomers, (meth) acrylic modified polymers, (meth) acrylic metal salts, and bismaleimides. It is preferable that content of a co-crosslinking agent exists in the range of 1-30 mass parts with respect to 100 mass parts of polymer components from viewpoints, such as hardness.

  The type of the antioxidant is not particularly limited, and examples thereof include amines, phenols, benzimidazoles, nickel dithiocarbamate, phosphoric acid, and organic thioacids. From the viewpoint of storage stability and bleed, it is preferably in the range of 0.1 to 5 parts by mass with respect to 100 parts by mass of the polymer component.

  Although the thickness of the elastic body layer 16 is not specifically limited, It is preferable to exist in the range of 0.5-5 mm from a viewpoint of productivity.

  The flexographic printing plate precursor 10 has a surface of the support 12 that is a precursor layer before cross-linking for obtaining the elastic layer 16 by, for example, extruding the above composition on the surface of the support 12 through the adhesive layer 14. It can be obtained by forming and crosslinking this precursor layer.

According to the flexographic printing plate precursor 10 having the above-described configuration, the elastic layer 16 contains acetylene black. Since acetylene black has high crystallinity and excellent thermal stability, it can generate heat up to a relatively high temperature. Thereby, since a combustion rate improves, it is excellent in engraving speed. Further, since the hydrochloric acid absorption amount of acetylene black is 15.0 ml / 5 g or more, the dispersibility of acetylene black is improved. Thereby, uneven engraving is suppressed. At this time, the dispersibility of acetylene black improves more because the bulk density of (c) is 0.10 g / cm < ³ > or less. Moreover, the dispersibility of acetylene black becomes more stable because (a) contains 1,2-polybutadiene together with an ethylene-propylene-diene copolymer (EPDM).

  The obtained flexographic printing plate precursor 10 is subjected to laser engraving on the elastic layer 16 to form a relief image. Since engraving residue adheres to the surface after laser engraving, it is preferable to wash the engraving residue with a cleaning liquid such as water and then dry it. Thereby, a flexographic printing plate having a predetermined relief image is obtained.

  The laser used for laser engraving is not particularly limited, and a known laser can be used. Examples of the laser include a carbon dioxide laser, a semiconductor laser, and a YAG laser.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

<Preparation of composition for elastic layer>
Each component was mix | blended so that it might become a mixing | blending composition (mass part) of Table 1, and the composition for elastic body layers was prepared by knead | mixing in a kneader at 100 degreeC.

Each component used is as follows.
・ EPDM: “Esprene 305” manufactured by Sumitomo Chemical Co., Ltd.
1,2-BR <1>: Syndiotactic 1,2-polybutadiene, “RB810” manufactured by JSR
1,2-BR <2>: Syndiotactic 1,2-polybutadiene, “RB820” manufactured by JSR
・ Ethylene-butene copolymer: “ENGAGEHM7447, melting point 35 ° C.” manufactured by DOW
・ Plasticizer: “Diana Process Oil PW-380” manufactured by Idemitsu Kosan Co., Ltd.
Carbon <1>: Acetylene black (hydrochloric acid liquid absorption 25.8 ml / 5 g, bulk density 0.05 g / ml), Denka Black FX-35 manufactured by Denki Kagaku Kogyo
Carbon <2>: Acetylene black (hydrochloric acid absorption 16.8 ml / 5 g, bulk density 0.04 g / ml), “Denka black powder” manufactured by Denki Kagaku Kogyo
Carbon <3>: Acetylene black (hydrochloric acid absorption amount 10.4 ml / 5 g, bulk density 0.15 g / ml), “Denka Black HS-100” manufactured by Denki Kagaku Kogyo
Carbon <4>: Acetylene black (hydrochloric acid absorption 14.0 ml / 5 g, bulk density 0.25 g / ml), “Denka Black granular product” manufactured by Denki Kagaku Kogyo
・ Carbon <5>: Furnace black (bulk density 0.38g / ml), "Seast 3" made by Tokai Carbon
・ Peroxide: NOF "Perbutyl P"
The amount of hydrochloric acid absorbed by each carbon is a value measured according to JIS K1469 (2003). Moreover, the bulk density of each carbon is the value measured based on JISK6219-2.

<Preparation of flexographic printing plate precursor>
A 125 μm thick PET film was used as the support. An adhesive layer coating solution containing a polyester resin solution (“Byron 30SS” manufactured by Toyobo Co., Ltd., solid content: 30% by mass) is applied by bar coating on the surface of the support so that the thickness after drying becomes 10 μm And then dried at 120 ° C. for 10 minutes to form an adhesive layer on the support. Next, the precursor layer is extruded on the surface of the adhesive layer formed on the support at 100 ° C. at a rate of 100 mm / min with a thickness of 1 mm, a width of 50 mm, and a length of 100 mm. Formed. Next, a precursor layer was sandwiched between iron plates provided with a 1 mm spacer, and a heat crosslinking treatment was performed in an oven at 170 ° C. for 30 minutes to prepare a flexographic printing plate precursor having an elastic layer thickness of 1 mm.

  About the produced flexographic printing plate precursor, a flexographic printing plate on which a predetermined relief image was formed was produced using a laser engraving machine, and the engraving speed and engraving unevenness were evaluated. In addition, the kneadability of the elastic layer composition was evaluated. Evaluation methods and evaluation criteria are shown below. Table 1 shows the composition and evaluation results of the elastic layer composition.

<Engraving speed>
The prepared flexographic printing plate precursor was engraved once with an average output of 34 W and 50 mm / s using LP-S502 (YAG laser with a wavelength of 1064 nm) manufactured by Panasonic Device Sunx Co., Ltd., and engraved white lines. The white line of the engraved printing plate was cut in a direction perpendicular to the line, and the engraving depth was measured with a microscope from the cross section. The case where the engraving depth was 100 μm or more was designated as “◯”, and the case where the engraving depth was less than 100 μm was designated as “X”.

<Uneven sculpture>
The produced flexographic printing plate precursor was engraved once with an average output of 34 W and 50 mm / s using LP-S502 (YAG laser with a wavelength of 1064 nm) manufactured by Panasonic Device Sunx Co., Ltd., and engraved white lines. The white line of the engraved printing plate was cut in a direction perpendicular to the line, and the engraving depth was measured at five points with a microscope from the cross section. The case where the median engraving depth is within ± 10% is indicated by “◯”, and the case outside the range is indicated by “X”. Furthermore, when the unevenness of engraving is good, the case where the median depth of engraving is within ± 5% is designated as “◎”.

  In Comparative Example 3, the carbon of the elastic layer is furnace black, which is inferior in engraving speed. In Comparative Examples 1 and 2, the carbon of the elastic layer is acetylene black, but its hydrochloric acid absorption is as low as less than 15.0 ml / 5 g, and engraving unevenness is large. On the other hand, in the examples, the carbon of the elastic layer is acetylene black, the hydrochloric acid absorption amount is as high as 15.0 ml / 5 g, the engraving speed is excellent, and the engraving unevenness is small. Therefore, the elastic layer carbon is acetylene black, and its hydrochloric acid absorption is as high as 15.0 ml / 5g or more, so that the flexographic printing plate precursor capable of laser engraving has excellent engraving speed and suppresses engraving unevenness. I understand that In addition, from the comparison in the examples, it can be seen that by including 1,2-BR in addition to EPDM, kneading shear is stabilized, dispersibility is stabilized, and engraving unevenness is further suppressed.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10 Flexographic printing plate precursor 12 Support body 14 Adhesive layer 16 Elastic body layer

Claims (5)

Having an elastic layer on the surface of the support,
The flexographic printing plate precursor, wherein the elastic layer is composed of a crosslinked product of a composition containing the following (a) to (c).
(A) Rubber polymer (b) Crosslinker (c) Acetylene black having a hydrochloric acid absorption of 15.0 ml / 5 g or more   The flexographic printing plate precursor according to claim 1, wherein (a) comprises an ethylene-propylene-diene copolymer.   The flexographic printing plate precursor according to claim 1 or 2, wherein (b) is a peroxide. 4. The flexographic printing plate precursor according to claim 1, wherein the bulk density of (c) is 0.10 g / cm ³ or less. 5. The flexographic printing plate precursor according to any one of claims 1 to 4, wherein (a) further contains 1,2-polybutadiene.

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