JP2015123714A - Resin composition for laser-engraving, original plate for laser-engravable flexographic printing plate and method for producing the same, and platemaking method for flexographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition for laser-engraving, which can afford a flexographic printing plate excellent in rinsability of engraving scraps, image quality, and ink transferability, and to provide an original plate for a laser-engravable flexographic printing plate.SOLUTION: Provided is a resin composition for laser-engraving, comprising: a component A of a binder polymer having an ethylenic unsaturated bond at least at one portion selected from the group consisting of an inside of a main chain, a terminal of the main chain, and a side chain; a component B of a polymerization initiator; and a component C of a blowing agent. The component A is a plastomer selected from the group consisting of a polymer having a polybutadiene structure, a polymer having a polyisoprene structure, and urethane (meth)acrylate, and a content of the component A is 50 mass% or more relative to a total mass of the composition. Also provided is an original plate for a laser-engravable flexographic printing plate, having a crosslinked relief formation layer obtained by foaming and crosslinking a layer comprising the resin composition for laser-engraving.

Description

  The present invention relates to a resin composition for laser engraving, a laser engraving-type flexographic printing plate precursor and a method for producing the same, and a method for making a flexographic printing plate.

Many so-called “direct engraving CTP methods” have been proposed in which a relief forming layer is directly engraved with a laser to make a plate. In this method, the flexographic original plate is directly irradiated with a laser, and thermal decomposition and volatilization are caused in the relief forming layer by photothermal conversion to form a recess. Unlike the relief formation using the original film, the direct engraving CTP method can freely control the relief shape. For this reason, when an image such as a letter is formed, the area is engraved deeper than other areas, or the fine halftone dot image is engraved with a shoulder in consideration of resistance to printing pressure. Is also possible. In general, a high-power carbon dioxide laser is used as a laser for this method. In the case of a carbon dioxide laser, all organic compounds can absorb irradiation energy and convert it into heat. On the other hand, inexpensive and small semiconductor lasers have been developed. However, since these are visible and near infrared light, it is necessary to absorb the laser light and convert it into heat.
As conventional flexographic printing plates, for example, those described in Patent Documents 1 to 3 are known.

JP-T-2007-520379 Japanese Patent Laid-Open No. 2002-3665 JP 2002-103539 A

The problem to be solved by the present invention is a laser engraving-type flexographic printing plate precursor capable of obtaining a flexographic printing plate excellent in engraving residue rinsing properties and excellent in image quality and ink transferability, a method for producing the same, and flexographic printing It is to provide a plate making method.
Another problem to be solved by the present invention is to provide a resin composition for laser engraving that is suitably used for such a printing plate precursor.

The above-mentioned problems of the present invention have been solved by the means described in <1>, <8>, <9>, <16> or <18> below. It is described below together with <2> to <7>, <10> to <15> and <17> which are preferred embodiments.
<1> (Component A) a binder polymer having an ethylenically unsaturated bond in at least one portion selected from the group consisting of the inside of the main chain, the main chain terminal and the side chain, (Component B) a polymerization initiator, and (Component C) A plastomer selected from the group consisting of a foaming agent, wherein component A is a polymer having a polybutadiene structure, a polymer having a polyisoprene structure, and urethane (meth) acrylate, and the content of component A is A resin composition for laser engraving, which is 50% by mass or more based on the total mass of the composition;
<2> The resin composition for laser engraving according to <1>, wherein Component A is polybutadiene, polyisoprene, or a copolymer obtained by copolymerizing at least butadiene and / or isoprene,
<3> The resin composition for laser engraving according to <1> or <2>, wherein component A is polybutadiene or polyisoprene,
<4> The resin composition for laser engraving according to any one of <1> to <3>, wherein Component B is an organic peroxide,
<5> The resin composition for laser engraving according to any one of <1> to <4>, wherein Component C is a chemical foaming agent,
<6> (Component D) The resin composition for laser engraving according to any one of <1> to <5>, further containing a polymerizable compound,
<7> (Component E) The resin composition for laser engraving according to any one of <1> to <6>, further containing a photothermal conversion agent,
<8> Laser engraving-type flexographic printing plate precursor having a crosslinked relief-forming layer obtained by foaming and cross-linking a layer made of the resin composition for laser engraving according to any one of <1> to <7>,
<9> (Component A) a binder polymer having an ethylenically unsaturated bond in at least one portion selected from the group consisting of the inside of the main chain, the main chain terminal and the side chain, (Component B) a polymerization initiator, and (Component C) A plastomer selected from the group consisting of a foaming agent, wherein component A is a polymer having a polybutadiene structure, a polymer having a polyisoprene structure, and urethane (meth) acrylate, and the content of component A is A laser engraving-type flexographic printing plate precursor comprising a crosslinked relief-forming layer obtained by foaming and cross-linking a layer composed of a resin composition for laser engraving that is 50% by mass or more based on the total mass of the composition;
<10> The laser engraving-type flexographic printing plate precursor according to <9>, wherein component A is polybutadiene, polyisoprene, or a copolymer obtained by copolymerizing at least butadiene and / or isoprene,
<11> Component A is polybutadiene or polyisoprene, the laser engraving-type flexographic printing plate precursor according to <9> or <10>,
<12> Component B is an organic peroxide, the laser engraving-type flexographic printing plate precursor according to any one of <9> to <11>,
<13> Component C is a chemical foaming agent or a physical foaming agent, the laser engraving-type flexographic printing plate precursor according to any one of <9> to <12>,
<14> The laser engraving-type flexographic printing plate precursor according to any one of <9> to <12>, wherein the resin composition for laser engraving further contains (Component D) a polymerizable compound,
<15> The laser engraving-type flexographic printing plate precursor according to any one of <9> to <14>, wherein the resin composition for laser engraving further contains (Component E) a photothermal conversion agent,
<16> (Component A) a binder polymer having an ethylenically unsaturated bond in at least one portion selected from the group consisting of the inside of the main chain, the main chain terminal and the side chain, (Component B) a polymerization initiator, and (Component C) A plastomer selected from the group consisting of a foaming agent, wherein component A is a polymer having a polybutadiene structure, a polymer having a polyisoprene structure, and urethane (meth) acrylate, and the content of component A is A step of forming a layer composed of a resin composition for laser engraving of 50% by mass or more based on the total mass of the composition, and a crosslinked relief forming layer obtained by foaming and crosslinking the layer composed of the resin composition for laser engraving <8>-<15> including the process to form, The manufacturing method of the laser-engraving type flexographic printing plate precursor as described in any one of the above,
<17> The method for producing a laser engraving-type flexographic printing plate precursor according to <16>, wherein the foaming and crosslinking are simultaneously performed at least partially.
<18> A step of preparing the laser engraving-type flexographic printing plate precursor according to any one of <8> to <15>, and a engraving step of laser engraving the crosslinked relief forming layer to form a relief layer Including flexographic printing plate making method.

ADVANTAGE OF THE INVENTION According to this invention, the laser-engraving type | mold flexographic printing plate precursor which can obtain the flexographic printing plate which was excellent in the rinse property of engraving residue, and was excellent in image quality and ink transfer property, its manufacturing method, and the plate-making method of a flexographic printing plate Could be provided.
Moreover, according to this invention, the resin composition for laser engravings used suitably for such a printing plate precursor could be provided.

Hereinafter, the contents of the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.
In the present invention, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.
In the present invention, “(Component A) a binder polymer having an ethylenically unsaturated bond in at least one portion selected from the group consisting of the inside of the main chain, the main chain terminal and the side chain” and the like are simply referred to as “Component A”. Also called etc.
Furthermore, in the description of the group (atomic group) in this specification, the description which does not describe substitution and unsubstituted includes the thing which has a substituent with the thing which does not have a substituent. For example, the “alkyl group” includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group).
In the present invention, “parts by mass” and “% by mass” are synonymous with “parts by weight” and “% by weight”, respectively.
Moreover, in this invention, the combination of a preferable aspect is a more preferable aspect.

(Resin composition for laser engraving)
The resin composition for laser engraving of the present invention (hereinafter also simply referred to as “resin composition” or “composition”) is at least selected from the group consisting of (Component A) the inside of the main chain, the main chain terminal, and the side chain. Binder polymer having ethylenically unsaturated bond in one part, (Component B) Polymerization initiator, and (Component C) Foaming agent, Component A is a polymer having a polybutadiene structure, Polymer having a polyisoprene structure And a plastomer selected from the group consisting of urethane (meth) acrylates, wherein the content of component A is 50% by mass or more based on the total mass of the composition.
The resin composition for laser engraving of the present invention preferably has foamability and crosslinkability.

As a result of intensive studies by the present inventors, the resin composition for laser engraving contains component A to component C, so that the engraving residue generated at the time of laser engraving is excellent, and the image quality and ink transfer of the resulting flexographic printing plate are excellent. It has been found that a resin composition for laser engraving having excellent properties can be provided.
Although the detailed mechanism is unknown, (Component A) For a resin composition comprising a binder polymer having an ethylenically unsaturated bond in at least one portion selected from the group consisting of the inside of the main chain, the end of the main chain and the side chain , (Component B) A polymerization initiator and (Component C) a foaming agent can cause foaming and crosslinking to form a relief layer having air bubbles in a specific resin structure, and the surface of the relief layer is also derived from air bubbles. It is estimated that the ink transfer property is improved.
In addition, the present inventor has the contradictory relationship that the relief layer of the flexographic printing plate has a high Young's modulus and high image quality, but the ink transfer property is deteriorated, and if the low Young's modulus is too low, the ink transfer property is high but the image quality is deteriorated. I found it. However, in the present invention, due to the above effects, the ink transfer property can be sufficiently ensured, and the bubbles give flexibility, the matrix portion other than the bubbles has a specific structure, and has a high Young's modulus and also has flexibility due to the bubbles. It is presumed that the ink transfer property and the image quality can be compatible because of the relief layer. In addition, when hollow particles having a shell as described in Patent Document 1 are used, both the ink transferability and the image quality are inferior, but it is estimated that the recesses and the relief layer are not sufficiently flexible. The
Further, although the detailed mechanism is unknown, the flexographic printing plate obtained by using the resin composition for laser engraving of the present invention has a relief layer having bubbles in a specific resin structure. It is considered that the amount generated is small and the rinse property is excellent.

In the present specification, regarding the description of the flexographic printing plate precursor, the component A and the component B are contained, and the surface is a flat layer as an image forming layer to be subjected to laser engraving and is an uncrosslinked crosslinkable layer Is called a relief forming layer, a layer obtained by crosslinking the relief forming layer is called a crosslinked relief forming layer, and a layer in which irregularities are formed on the surface by laser engraving is called a relief layer. In addition, when using a physical foaming agent as component C, after forming a relief forming layer or a crosslinked relief forming layer, you may make it contain in a relief forming layer or a crosslinked relief forming layer by impregnation.
Hereinafter, the components contained in the resin composition for laser engraving of the present invention will be described.

(Component A) Binder polymer having an ethylenically unsaturated bond in at least one portion selected from the group consisting of the inside of the main chain, the main chain terminal, and the side chain The resin composition for laser engraving of the present invention comprises (Component A) main A binder polymer having an ethylenically unsaturated bond in at least one portion selected from the group consisting of the inside of the chain, the main chain end, and the side chain, wherein the component A is a polymer having a polybutadiene structure, a polymer having a polyisoprene structure, And a plastomer selected from the group consisting of urethane (meth) acrylates, and the content of component A is 50% by mass or more based on the total mass of the composition.
Component A is preferably a water-insoluble binder polymer.

Component A has an ethylenically unsaturated bond in at least one portion selected from the group consisting of the inside of the main chain, the main chain end and the side chain, and at least one selected from the group consisting of the inside of the main chain and the main chain end The portion preferably has an ethylenically unsaturated bond, and more preferably has at least one portion inside the main chain having an ethylenically unsaturated bond.
In the present invention, “main chain” represents a relatively long bond chain in the molecule of the polymer compound constituting the resin, and “side chain” represents a carbon chain branched from the main chain. The side chain may contain a hetero atom.
The ethylenically unsaturated group that component A may have is not particularly limited, but is preferably an ethylenically unsaturated bond derived from butadiene or isoprene, or a (meth) acryl group, Alternatively, an ethylenically unsaturated bond derived from isoprene or a (meth) acryloxy group is more preferable, and an ethylenically unsaturated bond derived from butadiene or isoprene is still more preferable.
Moreover, as an ethylenically unsaturated bond derived from butadiene or isoprene, an ethylenically unsaturated bond inside the main chain formed by 1,4-addition, a side formed by 1,2-addition or 3,4-addition The ethylenically unsaturated bonds of the chain and ethylenically unsaturated compounds in which these ethylenically unsaturated bonds are regioisomerized may be used, but component A is formed by 1,4-addition of butadiene or isoprene. Further, it preferably has an ethylenically unsaturated bond inside the main chain.

  Component A is a plastomer selected from the group consisting of a polymer having a polybutadiene structure, a polymer having a polyisoprene structure, and a urethane (meth) acrylate, and component A is a polybutadiene, polyisoprene, butadiene and / or isoprene. It is preferable that the copolymer is at least a copolymer and a plastomer selected from the group consisting of urethane (meth) acrylates. From polybutadiene, polyisoprene, and a copolymer obtained by copolymerizing at least butadiene and / or isoprene. More preferably, the plastomer selected from the group consisting of polybutadiene and polyisoprene is more preferable, the plastomer selected from the group consisting of polybutadiene and polyisoprene. Preferred. In the above embodiment, a flexographic printing plate excellent in printing durability and ink transfer property is obtained, and the engraving residue rinsing property is excellent.

Component A is a plastomer at 20 ° C.
When an elastomer such as rubber or thermoplastic elastomer is used as component A, strength and flexibility cannot be achieved at the same time, and since there is no fluidity when performing crosslinking, sufficient crosslinking cannot be performed. It is inferior to printing durability and image quality, and sculpture residue rinse.
In the present invention, “plastomer” means that it is easily deformed by heating and deformed by cooling, as described in “New edition polymer dictionary” edited by the Society of Polymer Science, Japan (Asakura Shoten, published in 1988). It means a polymer having the property that it can be solidified into a shaped shape. Plastomer is a term for an elastomer (having the property of instantly deforming according to the external force when an external force is applied and restoring the original shape in a short time when the external force is removed). It does not show such elastic deformation and easily plastically deforms.
In the present invention, when the original size is 100%, the plastomer can be deformed to 200% with a small external force at room temperature (20 ° C.) and does not return to 130% or less even when the external force is removed. Means things. The small external force specifically refers to an external force having a tensile strength of 1 to 100 MPa. More specifically, based on the tensile permanent strain test of JIS K 6262-1997, the distance between the marked lines before tension of the dumbbell-shaped No. 4 test piece specified in JIS K 6251-1993 in the tensile test at 20 ° C. is 2 It can be stretched without breaking twice, and after holding for 60 minutes when stretched to twice the distance between the marked lines before tension, the tensile permanent strain is 30% or more after 5 minutes excluding the tensile external force Means a polymer. In the present invention, all of the test pieces are JIS K 6262 except that the test piece is made into a dumbbell shape defined in JIS K 6251, the holding time is 60 minutes, and the temperature of the test chamber is 20 ° C. According to the 1997 tensile set test method.

In the case of a polymer that cannot be measured as described above, that is, in a tensile test, a polymer that does not return to its original shape even if a tensile external force is not applied, or a polymer that breaks by applying a small external force at the time of measurement corresponds to a plastomer. To do. For example, a polymer that is liquid at 20 ° C. is a plastomer.
Furthermore, the plastomer may be judged from the glass transition temperature (Tg) of the polymer being less than 20 ° C. In the case of a polymer having two or more Tg, all Tg is less than 20 ° C. The Tg of the polymer can be measured by a differential scanning calorimetry (DSC) method.

A polymer having a polybutadiene structure or a polymer having a polyisoprene structure may be a butadiene or isoprene homopolymer or a copolymer obtained by copolymerizing butadiene and / or isoprene. It may be a polymer.
In addition, a polymer having a polybutadiene structure or a polymer having a polyisoprene structure may be a polymer having a main chain mainly composed of isoprene or butadiene as a monomer unit, and a part thereof is hydrogenated to be converted to a saturated bond. It may be. In addition, the main chain or the terminal of the polymer may be modified with an amide, a carboxy group, a hydroxy group, a (meth) acryloyl group or the like, or may be epoxidized.
The copolymerizable monomer is not particularly limited, and examples thereof include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, acrylamide, methacrylamide, and meta. Examples include vinyl acrylamide, acrylic acid ester, methacrylic acid ester, acrylic acid, and methacrylic acid.

Specific examples of the copolymer obtained by copolymerizing at least butadiene and / or isoprene include styrene-butadiene copolymer, styrene-isoprene polymer, acrylonitrile-butadiene copolymer, acrylonitrile-isoprene copolymer, acrylate ester- Butadiene copolymer, acrylic ester-isoprene copolymer, acrylic ester-chloroprene copolymer, acrylonitrile-butadiene-styrene copolymer, styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer Copolymer, terminal (meth) acrylate modified polybutadiene, terminal (meth) acrylate modified polyisoprene, terminal (meth) acrylate modified hydrogenated polybutadiene, terminal (meth) acrylate modified hydrogenated polyisoprene, etc. And the like.
The polymer having a polybutadiene structure and the polymer having a polyisoprene structure may be produced by emulsion polymerization or may be produced by solution polymerization.

In the present invention, the polymer having a polybutadiene structure and the polymer having a polyisoprene structure have a proportion of monomer units derived from aliphatic hydrocarbons (isoprene, butadiene, or hydrogenated products thereof) in the main chain of 80 mol%. The above is preferable. It is preferable for the proportion of monomer units derived from aliphatic hydrocarbons in the main chain to be 80 mol% or more because the rinsing properties are good. The content of the monomer unit derived from the aliphatic hydrocarbon is more preferably 90 mol% or more of the total monomer units constituting the main chain of the component A, still more preferably 95 mol%, and more preferably 99 mol% or more. It is particularly preferred.
That is, for example, in the polymer having a polyisoprene structure, the ratio of the monomer units derived from the hydrogenated product of isoprene and isoprene is preferably 80 mol% or more in total, more preferably 90 mol% or more, More preferably, it is 95 mol% or more, and it is especially preferable that it is 99 mol% or more.
Similarly, in the polymer having a polybutadiene structure, the proportion of monomer units derived from the hydrogenated product of butadiene and butadiene is preferably 80 mol% or more in total, more preferably 90 mol% or more, and 95 mol%. More preferably, it is more preferably 99 mol% or more.
Further, when isoprene or butadiene copolymer is used as Component A, it is preferable that the monomer units derived from isoprene, butadiene and their hydrogenated substances are contained in a total of 80 mol% or more, preferably 90 mol% or more. More preferably, it is more preferably 95 mol% or more, and particularly preferably 99 mol% or more.

Isoprene is known to polymerize by 1,2-, 3,4-, or 1,4-addition, depending on the catalyst and reaction conditions, but the present invention is not limited to polyisoprene polymerized by any of the above additions. Good. Among these, from the viewpoint of obtaining a desired Mooney viscosity, it is preferable to contain cis-1,4-polyisoprene as a main component. The content of cis-1,4-polyisoprene is preferably 50% by mass or more, more preferably 65% by mass or more, still more preferably 80% by mass or more, and 90% by mass. The above is particularly preferable.
Moreover, as a polyisoprene, the commercially available polyisoprene can also be used, for example, a NIPOL IR series (made by Nippon Zeon Co., Ltd.) is illustrated.

Butadiene is known to be polymerized by 1,2- or 1,4-addition depending on the catalyst and reaction conditions, but the present invention may be polybutadiene polymerized by any of the above additions. Among these, it is more preferable that 1,4-polybutadiene is a main component from the viewpoint of obtaining a desired Mooney viscosity.
The content of 1,4-polybutadiene is preferably 50% by mass or more, more preferably 65% by mass or more, further preferably 80% by mass or more, and 90% by mass or more. It is particularly preferred.
In addition, the content of the cis body and the trans body is not particularly limited, and may be appropriately selected within a desired viscosity or Mooney viscosity range. From the viewpoint of developing rubber elasticity after crosslinking and foaming, the cis body is preferable, The content of cis-1,4-polybutadiene is preferably 50% by mass or more, more preferably 65% by mass or more, further preferably 80% by mass or more, and 90% by mass or more. Is particularly preferred.
A commercially available product may be used as the polybutadiene, and examples thereof include the NIPOL BR series (manufactured by ZEON Corporation), the UBEPOL BR series (manufactured by Ube Industries, Ltd.), and the like.

Examples of the liquid polybutadiene include commercially available products such as Claprene LBR-305 (manufactured by Kuraray Co., Ltd.) and Ricon (manufactured by Sartomer).
Examples of the liquid polyisoprene include Claprene LIR-30 and LIR-50 (manufactured by Kuraray Co., Ltd.).
Examples of the polyisoprene having a (meth) acrylate group include methacrylate-introduced polyisoprene (Kuraprene US-203, UC-102, manufactured by Kuraray Co., Ltd.).
Moreover, as a polybutadiene which has an ethylenically unsaturated group at the terminal, (meth) acrylate group introduction | transduction polybutadiene (NISSO-PB TEAI-1000, EA-3000, Nippon Soda Co., Ltd. product) is mentioned, for example.

Among these, as the polymer having a polybutadiene structure and the polymer having a polyisoprene structure, polyisoprene, polybutadiene, styrene-isoprene-styrene block copolymer, or styrene-butadiene-styrene block copolymer is more preferable. Polyisoprene or polybutadiene is particularly preferable.
Component A is preferably polybutadiene or polyisoprene, and particularly preferably polybutadiene, from the viewpoints of printing durability of flexographic printing plates, rinsing properties of engraving residue, and handling.

  Urethane (meth) acrylate is a polyurethane resin having a (meth) acryloxy group in the main chain, main chain terminal or side chain, and includes aliphatic urethane (meth) acrylate and aromatic urethane (meth) acrylate. It is done. For details, refer to the oligomer handbook (supervised by Junji Furukawa, Chemical Daily Co., Ltd.).

  The urethane (meth) acrylate preferably has at least one bond selected from the group consisting of a carbonate bond and an ester bond in the molecule. When the urethane (meth) acrylate has the above bond, resistance of the printing plate to an ink cleaning agent containing an ester solvent used in printing or an ink cleaning agent containing a hydrocarbon solvent is improved.

Examples of the diol compound having a carbonate bond used for the production of a polyurethane resin having a hydroxyl group include fats such as 4,6-polyalkylene carbonate diol, 8,9-polyalkylene carbonate diol, and 5,6-polyalkylene carbonate diol. Group polycarbonate diol and the like. Further, polycarbonate diol having an aromatic ring may be used.
The terminal hydroxyl groups of these compounds are tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, tetramethylxylene diisocyanate, xylene diisocyanate, naphthalene diisocyanate, trimethylhexamethylene diisocyanate, p-phenylene diisocyanate, cyclohexylene. Diisocyanate compounds such as diisocyanate, lysine diisocyanate, triphenylmethane diisocyanate, triphenylmethane triisocyanate, 1-methylbenzene-2,4,6-triisocyanate, naphthalene-1,3,7-triisocyanate, biphenyl-2,4 , 4'-Triisocyanate A urethane bond can be introduced by a condensation reaction of a polyisocyanate compound such as a cyanate compound.

  Urethane (meth) acrylates are commercially available products such as, for example, the UV-3200, UV-3000B, UV-3700B, UV-3210EA, UV-2000B, and UV-3630ID80 (manufactured by Nippon Synthetic Chemical Co., Ltd.). , EBECRYL230, EBECRYL9227EA (above, Daicel Cytec Co., Ltd.), Hicorp AU series AU-3040, AU-3050, AU-3090, AU-3110, AU-3120 (above, manufactured by Tokushi Co., Ltd.) be able to.

As another method for obtaining urethane (meth) acrylate and the like, there is also a method of producing a polyurethane by polyaddition reaction of the aforementioned polyisocyanate compound and a diol compound having a (meth) acryloxy group.
Preferred examples of the diol compound having a (meth) acryloxy group used in this case include Blemma-GLM manufactured by NOF Corporation, DA-212, DA-212 of "Denacol Acrylate" series manufactured by Nagase ChemteX Corporation. -250, DA-721, DA-722, DA-911M, DA-920, DA-931, DM-201, DM-811, DM-832, DM-851 and the like.

The molecular weight of component A is a weight average molecular weight (GPC, polystyrene equivalent), preferably 1,000 or more, more preferably 3,000 or more, and still more preferably 10,000 or more, 25 Is particularly preferably 8,000 or more, and most preferably 80,000 or more. The molecular weight of component A is preferably 3,000,000 or less, more preferably 2,000,000 or less, and 1,500,000 or less in terms of weight average molecular weight (GPC, polystyrene conversion). More preferably. Within the above range, processing of the resin composition for laser engraving is easy, and the printing durability of the resulting flexographic printing plate is excellent.
In the present invention, the weight average molecular weight and the number average molecular weight are measured by a gel permeation chromatography method (GPC) method and are calculated by standard polystyrene. Specifically, for example, GPC uses HLC-8220GPC (manufactured by Tosoh Corporation), and TSKgeL SuperHZM-H, TSKgeL SuperHZ4000, TSKgeL SuperHZ2000 (4.6 mm ID × 15 cm, manufactured by Tosoh Corporation) are used as columns. Three are used and THF (tetrahydrofuran) is used as an eluent. As conditions, the sample concentration is 0.35% by mass, the flow rate is 0.35 ml / min, the sample injection amount is 10 μl, the measurement temperature is 40 ° C., and an IR detector is used. In addition, the calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, It is prepared from 8 samples of “A-2500”, “A-1000”, “n-propylbenzene”.

In the present invention, the Mooney viscosity of Component A is not particularly limited, but is preferably 90 or less, more preferably 70 or less, and 60 or less, from the viewpoint of solvent solubility and ease of handling during mixing. More preferably. Further, the lower limit value of the Mooney viscosity is not particularly limited, and for example, the component A may be in a liquid or syrupy state.
In the present invention, the Mooney viscosity is a value measured in accordance with JIS 6300-1. Specifically, a cylindrical space is formed between dies capable of temperature control to form a sample chamber, a rotor is disposed in the center of the sample chamber, and a sample to be measured is filled into the sample chamber. While maintaining the temperature at a predetermined temperature, the rotor is rotated at a specified rotational speed, and the rotor counter torque generated by the viscous resistance of the molten sample is detected by a load cell. The Mooney viscosity value used in the present invention is an L-shaped rotor, the preheating time is 1 minute, the rotor rotation time is 4 minutes, and the Mooney viscosity of the rubber sample is rotated at 100 ° C. with a preheating period of 1 minute. The Mooney viscosity (ML _{1 + 4} ) after 4 minutes is shown.

  Content of component A is 50 mass% or more with respect to the total mass of the resin composition for laser engravings, preferably 50 to 95 mass%, more preferably 55 to 90 mass%, 65 More preferably, it is -90 mass%, and it is especially preferable that it is 70-85 mass%. When the content of Component A is in the above range, a relief layer having excellent engraving residue rinsing properties and excellent ink transfer properties can be obtained.

The resin composition for laser engraving of the present invention may contain a binder polymer (resin component) other than Component A. Examples of binder polymers other than Component A include non-elastomers described in JP2011-136455A, unsaturated group-containing polymers described in JP2010-208326A, and JP2012-45801A. The binder polymers described in paragraphs 0009 to 0030 are exemplified.
When the resin composition for laser engraving of the present invention contains other binder polymer in addition to Component A, it is preferably 30% by mass or less based on the total mass of the resin composition for laser engraving, and is 10% by mass. More preferably, it is more preferably 5% by mass or less, particularly preferably 2% by mass or less, and most preferably 0% by mass, that is, not containing. Within the above range, a relief layer having excellent engraving residue rinsing properties and excellent ink transfer properties can be obtained.
As the binder polymer other than Component A, an ethylene-propylene-diene copolymer can be exemplified, and an ethylene-propylene-5-ethylidene-2-norbornene copolymer can be exemplified more preferably.

(Component B) Polymerization Initiator The resin composition for laser engraving of the present invention contains (Component B) a polymerization initiator.
As the polymerization initiator, those known to those skilled in the art can be used without limitation. Hereinafter, although the radical polymerization initiator which is a preferable polymerization initiator is explained in full detail, this invention is not restrict | limited by these description.
As the polymerization initiator, a radical polymerization initiator is preferable.
Moreover, as a polymerization initiator, it is preferable that it is a thermal polymerization initiator, and it is more preferable that it is a thermal radical polymerization initiator.

  In the present invention, preferred polymerization initiators include (a) aromatic ketones, (b) onium salt compounds, (c) organic peroxides, (d) thio compounds, (e) hexaarylbiimidazole compounds, f) ketoxime ester compounds, (g) borate compounds, (h) azinium compounds, (i) metallocene compounds, (j) active ester compounds, (k) compounds having a carbon halogen bond, (l) azo compounds, etc. Can be mentioned. Specific examples of the above (a) to (l) are given below, but the present invention is not limited to these.

  In the present invention, from the viewpoints of engraving sensitivity and a good relief edge shape when applied to the relief forming layer of a flexographic printing plate precursor, (c) an organic peroxide and ( l) Azo compounds are more preferred, and (c) organic peroxides are particularly preferred.

(A) aromatic ketones, (b) onium salt compounds, (d) thio compounds, (e) hexaarylbiimidazole compounds, (f) ketoxime ester compounds, (g) borate compounds, (h) azinium compounds , (I) a metallocene compound, (j) an active ester compound, and (k) a compound having a carbon halogen bond, the compounds listed in paragraphs 0074 to 0118 of JP-A-2008-63554 are preferably used. Can do.
In addition, (c) the organic peroxide and (l) the azo compound are preferably the following compounds.

(C) Organic peroxide Preferred as a polymerization initiator that can be used in the present invention (c) As an organic peroxide, 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone, 3,3 ′, 4,4′-tetra (t-amylperoxycarbonyl) benzophenone, 3,3 ′, 4,4′-tetra (t-hexylperoxycarbonyl) benzophenone, 3,3 ′, 4,4 '-Tetra (t-octylperoxycarbonyl) benzophenone, 3,3', 4,4'-tetra (cumylperoxycarbonyl) benzophenone, 3,3 ', 4,4'-tetra (p-isopropylcumylperoxy) Carbonyl) benzophenone, di-t-butyldiperoxyisophthalate, di-t-butyldiperoxyisophthalate, t-butylperoxybenzoate, t-butylperoxy-3-methylbenzoate, t-butylperoxylaurate, t-butylperoxypivalate, t-butylperoxy-2-ethylhexanoate, t-butylperoxy-3,5, 5-trimethylhexanoate, t-butylperoxyneoheptanoate, t-butylperoxyneodecanoate, t-butylperoxyacetate, α, α'-di (t-butylperoxy) diisopropylbenzene, Peroxide esters such as t-butylcumyl peroxide, di-t-butyl peroxide, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate are preferred.

(L) Azo-based compound Preferred as a polymerization initiator that can be used in the present invention (l) As the azo-based compound, 2,2′-azobisisobutyronitrile, 2,2′-azobispropionitrile, 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2 ′ -Azobis (4-methoxy-2,4-dimethylvaleronitrile), 4,4'-azobis (4-cyanovaleric acid), dimethyl 2,2'-azobisisobutyrate, 2,2'-azobis (2-methylpropion) Amidooxime), 2,2′-azobis [2- (2-imidazolin-2-yl) propane], 2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2 -Hydro Cyethyl] propionamide}, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis (N-butyl-2-methylpropionamide), 2,2 '-Azobis (N-cyclohexyl-2-methylpropionamide), 2,2'-azobis [N- (2-propenyl) -2-methylpropionamide], 2,2'-azobis (2,4,4- Trimethylpentane) and the like.

  In the present invention, the above-mentioned (c) organic peroxide is particularly preferable as a polymerization initiator in the present invention from the viewpoint of crosslinkability of the film (relief forming layer) and improvement of engraving sensitivity.

From the viewpoint of engraving sensitivity, an embodiment in which this (c) organic peroxide and a later-described (component E) photothermal conversion agent are combined is particularly preferable.
This is because when an organic peroxide is used to cure the relief forming layer by thermal crosslinking, unreacted organic peroxide that does not participate in radical generation remains, but the remaining organic peroxide is self-reactive. Works as an additive and decomposes exothermically during laser engraving. As a result, it is presumed that the engraving sensitivity is increased because the heat generated is added to the irradiated laser energy.
In addition, although explained in full detail in description of a photothermal conversion agent, this effect is remarkable when using carbon black as a photothermal conversion agent. This is because heat generated from carbon black is transferred to (c) organic peroxide, and as a result, heat is generated not only from carbon black but also from organic peroxide. This is because energy generation occurs synergistically.

In the present invention, Component B may be used alone or in combination of two or more.
The content of Component B contained in the resin composition for laser engraving of the present invention is preferably 0.01% by mass or more and 0.1% by mass or more with respect to the total mass of the resin composition. It is more preferable that the content is 0.5% by mass or more. The upper limit of the content of component B is not particularly limited, but is preferably 30% by mass or less, more preferably 20% by mass or less, and more preferably 10% by mass or less from the viewpoint of the blending amount of other components. More preferably. When the content is in the above range, a flexographic printing plate excellent in printing durability and ink transfer property can be obtained, and the engraving residue rinsing property is excellent.

(Component C) Foaming Agent The resin composition required for laser engraving of the present invention contains (Component C) a foaming agent.
As the foaming agent, a known foaming agent can be used, which may be a chemical foaming agent or a physical foaming agent, but from the viewpoint of handleability and storage stability as a resin composition, Preferably there is.
The chemical foaming agent may be an inorganic compound or an organic compound, or two or more kinds may be used in combination.
Examples of organic chemical foaming agents include nitrosamine compounds such as dinitrosopentamethylenetetramine (DPT), azo compounds such as azodicarbonamide (ADCA), 4,4′-oxybisbenzenesulfonyl hydrazide (OBSH), and hydrazodicarbon. And hydrazine compounds such as amide (HDCA).
Examples of the inorganic chemical foaming agent include bicarbonates such as sodium bicarbonate, carbonates, combinations of bicarbonates and organic acid salts, and the like.
Among these, organic chemical foaming agents are preferable, nitrosamine compounds, azo compounds and hydrazine compounds are more preferable, azo compounds are further preferable, and azodicarbonamide is particularly preferable.
As the azo compound used as the foaming agent, a compound in which the radical generated upon decomposition is a radical having a low polymerization initiating ability such as an amino radical (.NH ₂ ) is preferable.
Examples of the physical foaming agent include inert gases such as nitrogen and carbon dioxide, and volatile organic compounds. Among them, it is preferable to use an inert gas, and it is preferable to use supercritical carbon dioxide, nitrogen, or a mixture thereof.

When using a chemical foaming agent, it is preferable to mix with a resin composition to produce a relief-forming layer or a crosslinked relief-forming layer and foam it by heat.
When a physical foaming agent is used, it may be mixed with the resin composition under normal pressure or under pressure to produce a relief-forming layer or a crosslinked relief-forming layer and foamed, or a relief-forming layer or a crosslinked relief is formed. Layers may be made and impregnated with a physical foaming agent to foam.
In addition, it is particularly preferable to perform foaming and crosslinking with a polymerization initiator at least partially simultaneously after the relief forming layer is produced.
Although there is no restriction | limiting in particular as a foaming method, Specifically, methods, such as a batch foaming method, a press foaming method, a normal pressure foaming method, a normal pressure secondary foaming method, are mentioned.
As the foaming agent and foaming method, the foaming agent and foaming method described in JP-A No. 11-106543, “Basic edition of new edition rubber technology”, edited by Japan Rubber Association can be referred to.

The combination of the polymerization initiator and the foaming agent in the resin composition for laser engraving of the present invention is preferably a combination in which generation of a polymerization initiating species from the polymerization initiator and decomposition of the foaming agent occur at the same temperature.
The combination of the polymerization initiator and the foaming agent in the resin composition for laser engraving of the present invention is preferably a combination of an organic peroxide as the polymerization initiator and an organic foaming agent as the foaming agent. More preferably a combination of an organic peroxide as an initiator and a nitrosamine compound, an azo compound or a hydrazine compound as a foaming agent, an organic peroxide as a polymerization initiator, and a nitrosamine compound or an azo compound as a foaming agent A combination of organic peroxide as a polymerization initiator and dinitrosopentamethylenetetramine or azodicarbonamide as a foaming agent is particularly preferable. With the above embodiment, it is easy to at least partially simultaneously foam and crosslink the relief forming layer, and a flexographic printing plate that is superior in image quality and ink transferability can be obtained. Excellent.
Further, in addition to the organic peroxide and the organic foaming agent, it is preferable to further combine a (component F) foaming aid described later.

Only one type of foaming agent may be used, or two or more types may be used in combination, or a chemical foaming agent and a physical foaming agent may be used in combination.
The content of Component C contained in the resin composition for laser engraving of the present invention is preferably 0.1 to 30% by mass, and 0.5 to 20% by mass with respect to the total mass of the resin composition. Is more preferably 1 to 15% by mass, and particularly preferably 2 to 10% by mass. When the content is in the above range, a flexographic printing plate excellent in image quality and ink transferability is obtained, and engraving sensitivity and engraving residue rinsing properties are excellent.

(Component D) Polymerizable Compound The resin composition for laser engraving of the present invention preferably further contains (Component D) a polymerizable compound in order to promote the formation of a crosslinked structure. By containing component D, formation of a crosslinked structure is promoted, and the resulting flexographic printing plate is excellent in printing durability.
Component D is a polymerizable compound other than Component A.
Furthermore, Component D is preferably a compound having a molecular weight of less than 3,000, more preferably a compound having a molecular weight of less than 2,000, and still more preferably a compound having a molecular weight of less than 1,000.
Component D is preferably a radically polymerizable compound, and is preferably an ethylenically unsaturated compound.

The polymerizable compound that can be used in the present invention is preferably a polyfunctional polymerizable compound, and more preferably a polyfunctional ethylenically unsaturated compound. In the above embodiment, the resin composition is excellent in curability, and a flexographic printing plate having excellent printing durability can be obtained.
The polyfunctional ethylenically unsaturated compound that can be used in the present invention preferably has a molecular weight (or weight average molecular weight) of less than 2,000.
The polyfunctional ethylenically unsaturated compound is a compound having two or more ethylenically unsaturated groups. A polyfunctional ethylenically unsaturated compound may be used individually by 1 type, and may use 2 or more types together.
Moreover, the compound group which belongs to an ethylenically unsaturated compound is widely known in this industry field, and can use these without a restriction | limiting in particular in this invention. These have chemical forms such as monomers, prepolymers, i.e. dimers, trimers and oligomers, or copolymers thereof, and mixtures thereof.
A polyfunctional monomer is preferably used as the polyfunctional ethylenically unsaturated compound. The molecular weight of these polyfunctional monomers (when having a molecular weight distribution, the weight average molecular weight) is preferably 200 or more and less than 2,000, more preferably 200 to 1,000, and 200 to 700. More preferably it is.

As the polyfunctional monomer, a compound having 2 to 20 terminal ethylenically unsaturated groups is preferable.
Examples of the polyfunctional monomer include unsaturated carboxylic acids (for example, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, etc.), esters and amides thereof. Esters of saturated carboxylic acids and aliphatic polyhydric alcohol compounds, and amides of unsaturated carboxylic acids and aliphatic polyvalent amine compounds are used. Also, unsaturated carboxylic acid esters having nucleophilic substituents such as hydroxyl groups and amino groups, amides and polyfunctional isocyanates, addition reaction products of epoxies, dehydration condensation reaction products of polyfunctional carboxylic acids Etc. are also preferably used. Further, unsaturated carboxylic acid esters having an electrophilic substituent such as isocyanato group, epoxy group, etc., addition reaction products of amides with monofunctional or polyfunctional alcohols, amines, halogen groups, tosyloxy A substitution reaction product of an unsaturated carboxylic acid ester or amide with a monofunctional or polyfunctional alcohol or amine having a leaving substituent such as a group is also suitable. As another example, a compound group in which a vinyl compound, an allyl compound, an unsaturated phosphonic acid, styrene, or the like is substituted for the above unsaturated carboxylic acid can be used.

  The ethylenically unsaturated group contained in the polyfunctional monomer is preferably an acrylate, methacrylate, vinyl compound, or allyl compound residue from the viewpoint of reactivity, and particularly preferably acrylate or methacrylate.

  Specific examples of the monomer of an ester of an aliphatic polyhydric alcohol compound and an unsaturated carboxylic acid include acrylic acid esters such as ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, 1, 3 -Butanediol diacrylate, tetramethylene glycol diacrylate, propylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1 , 4-Cyclohexanediol diacrylate, tetraethylene glycol diacrylate, polytetramethyl Glycol diacrylate, 1,8-octanediol diacrylate, 1,9-nonanediol diacrylate, 1,10-decanediol diacrylate, tricyclodecane dimethanol diacrylate, trimethylolpropane triacrylate, trimethylolpropane triacrylate (Acryloyloxypropyl) ether, ditrimethylolpropane tetraacrylate, trimethylolethane triacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol diacrylate, dipentaerythritol hexaacrylate, sorbitol triacrylate, Sorbitol tetraacrylate, sorbitol pentaacrylate Sorbitol hexaacrylate, tri (acryloyloxyethyl) isocyanurate, polyester acrylate oligomer.

  Methacrylic acid esters include tetramethylene glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, propylene glycol dimethacrylate, dipropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, polypropylene Glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, 1,3-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,8-octanediol dimethacrylate, 1 , 9-Nonanediol dimethacryl 1,10-decanediol dimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol dimethacrylate, dipentaerythritol hexamethacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate, bis [p -(3-Methacryloxy-2-hydroxypropoxy) phenyl] dimethylmethane, bis [p- (methacryloxyethoxy) phenyl] dimethylmethane and the like.

Examples of other esters include aliphatic alcohol esters described in JP-B-46-27926, JP-B-51-47334, JP-A-57-196231, JP-A-59-5240, Those having an aromatic skeleton described in JP-A-59-5241 and JP-A-2-226149 and those containing an amino group described in JP-A-1-165613 are also preferably used.
The ester monomers can also be used as a mixture.

Specific examples of amide monomers of aliphatic polyvalent amine compounds and unsaturated carboxylic acids include methylene bisacrylamide, methylene bismethacrylamide, 1,6-hexamethylene bis-acrylamide, 1,6-hexamethylene bis. Examples include methacrylamide, diethylenetriamine trisacrylamide, xylylene bisacrylamide, and xylylene bismethacrylamide.
Examples of other preferable amide monomers include those having a cyclohexylene structure described in JP-B No. 54-21726.

In addition, urethane-based addition polymerizable compounds produced by using an addition reaction of isocyanate and hydroxyl group are also suitable, and specific examples thereof include, for example, one molecule described in JP-B-48-41708. A vinylurethane compound containing two or more polymerizable vinyl groups in one molecule obtained by adding a vinyl monomer containing a hydroxyl group represented by the following formula (i) to a polyisocyanate compound having two or more isocyanate groups. Etc.
_{CH 2 = C (R) COOCH} 2 CH (R ') OH (i)
(However, R and R ′ each represent H or CH _3. )

Further, urethane acrylates such as those described in JP-A-51-37193, JP-B-2-32293, JP-B-2-16765, JP-B-58-49860, JP-B-56-17654 Urethane compounds having an ethylene oxide skeleton described in JP-B-62-39417 and JP-B-62-39418 are also suitable.
Further, by using addition-polymerizable compounds having an amino structure in the molecule described in JP-A-63-277653, JP-A-63-260909, and JP-A-1-105238, short A resin composition that cures over time can be obtained.

  Other examples include reacting polyester acrylates, epoxy resins and (meth) acrylic acid as described in JP-A-48-64183, JP-B-49-43191 and JP-B-52-30490. And polyfunctional acrylates and methacrylates such as epoxy acrylates. Further, specific unsaturated compounds described in JP-B-46-43946, JP-B-1-40337, JP-B-1-40336, and vinylphosphonic acid compounds described in JP-A-2-25493 are also included. be able to. In some cases, a structure containing a perfluoroalkyl group described in JP-A-61-22048 is preferably used. Furthermore, the Japan Adhesion Association magazine vol. 20, no. 7, pages 300 to 308 (1984), which are introduced as photocurable monomers and oligomers, can also be used.

Monofunctional polymerizable compounds having only one ethylenically unsaturated group include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid and their salts, ethylenically unsaturated Group-containing anhydrides, (meth) acrylates, (meth) acrylamides, (meth) acrylonitriles, styrenes, various unsaturated polyester resins, unsaturated polyether resins, unsaturated polyamide resins, unsaturated urethanes Examples thereof include polymerizable compounds such as resins.
In addition, an addition reaction product of an unsaturated carboxylic acid ester or amide having an nucleophilic substituent such as a hydroxyl group, an amino group or a mercapto group and an isocyanate or an epoxy, and a monofunctional or polyfunctional carboxylic acid A dehydration condensation reaction product or the like is also preferably used.

Furthermore, addition reaction products of unsaturated carboxylic acid esters or amides having an electrophilic substituent such as an isocyanato group or an epoxy group with alcohols, amines or thiols, and further elimination of a halogeno group or a tosyloxy group. A substitution reaction product of an unsaturated carboxylic acid ester or amide having a releasing substituent with alcohols, amines or thiols is also suitable.
As another example, it is also possible to use a group of compounds substituted with unsaturated phosphonic acid, styrene, vinyl ether or the like instead of the unsaturated carboxylic acid.
There is no restriction | limiting in particular as a polymeric compound, In addition to the compound illustrated above, well-known various compounds can be used, For example, you may use the compound etc. which are described in Unexamined-Japanese-Patent No. 2009-204962.

Furthermore, as monofunctional ethylenically unsaturated compounds, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, butoxyethyl (Meth) acrylate, carbitol (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, N-methylol (meth) acrylamide, (meth) acrylic acid derivatives such as epoxy (meth) acrylate, N-vinylpyrrolidone N-vinyl compounds such as N-vinylcaprolactam and derivatives of allyl compounds such as allyl glycidyl ether, diallyl phthalate and triallyl trimellitate are preferably used.
Among these, as a polyfunctional ethylenically unsaturated compound, a monofunctional (meth) acrylate compound (monofunctional (meth) acrylic acid ester) is preferable.

Among these, component D is preferably acrylate (acrylic ester compound) or methacrylate (methacrylic ester compound), and particularly preferably an ester of an aliphatic polyhydric alcohol and acrylic acid or methacrylic acid. . Component C preferably has 2 to 20 (meth) acryloyloxy groups in a molecule, more preferably 2 to 8, more preferably 2 to 6, and more preferably 2 to 4. Particularly preferred.
Among these, component D includes hexanediol di (meth) acrylate, decanediol di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, pentaerythritol tetra (meth) acrylate, and dipentaerythritol hexa (meth). ) It is preferred to contain at least one compound selected from the group consisting of acrylates.

The content of the component D contained in the resin composition for laser engraving is preferably 1 to 50% by mass, more preferably 3 to 40% by mass, and 5 to 30% by mass with respect to the total mass of the resin composition. Further preferred. Within the above range, the relief forming layer comprising the resin composition for laser engraving is excellent in printing durability.
Further, from the viewpoint of improving the printing durability and suppressing the amount of engraving residue, the content of the component D contained in the resin composition for laser engraving is 10 to 50 mass relative to the total mass of the resin composition. % Is preferred.

(Component E) Photothermal Conversion Agent The resin composition for laser engraving of the present invention preferably further contains (Component E) a photothermal conversion agent. That is, it is considered that the photothermal conversion agent in the present invention promotes thermal decomposition of a cured product during laser engraving by absorbing laser light and generating heat. For this reason, it is preferable to select a photothermal conversion agent that absorbs light having a laser wavelength used for engraving.

A laser engraving type flexographic printing plate precursor produced using the resin composition for laser engraving of the present invention is irradiated with a laser (YAG laser, semiconductor laser, fiber laser, surface emitting laser, etc.) emitting infrared rays of 700 to 1,300 nm. As the photothermal conversion agent, it is preferable to use a compound having a maximum absorption wavelength at 700 to 1,300 nm.
Various dyes or pigments are used as the photothermal conversion agent in the present invention.

  Among the photothermal conversion agents, as the dye, commercially available dyes and known ones described in documents such as “Dye Handbook” (edited by the Society for Synthetic Organic Chemistry, published in 1970) can be used. Specific examples include those having a maximum absorption wavelength at 700 to 1,300 nm, such as azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, diimmonium compounds, and quinoneimine dyes. Preferred are dyes such as methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, metal thiolate complexes. Dyes preferably used in the present invention include cyanine dyes such as heptamethine cyanine dyes, oxonol dyes such as pentamethine oxonol dyes, phthalocyanine dyes, and paragraphs 0124 to 0137 of JP-A-2008-63554. Mention may be made of dyes.

Among the photothermal conversion agents used in the present invention, commercially available pigments and color index (CI) manuals, “latest pigment manuals” (edited by the Japan Pigment Technical Association, published in 1977), “latest pigment application” The pigments described in “Technology” (CMC Publishing, 1986) and “Printing Ink Technology” CMC Publishing, 1984) can be used. Examples of the pigment include pigments described in paragraphs 0122 to 0125 of JP-A-2009-178869.
Of these pigments, carbon black is preferred.

  As long as the dispersibility in the composition is stable, carbon black can be used regardless of the classification according to ASTM or the use (for example, for color, for rubber, for dry battery, etc.). Carbon black includes, for example, furnace black, thermal black, channel black, lamp black, acetylene black and the like. In order to facilitate dispersion, black colorants such as carbon black can be used as color chips or color pastes previously dispersed in nitrocellulose or a binder, if necessary. Such chips and pastes can be easily obtained as commercial products. Examples of carbon black include those described in paragraphs 0130 to 0134 of JP2009-178869A.

Only 1 type may be used for the photothermal conversion agent in the resin composition of this invention, and it may use 2 or more types together.
The content of the photothermal conversion agent in the resin composition for laser engraving varies greatly depending on the molecular extinction coefficient inherent to the molecule, but is preferably 0.01 to 30% by mass with respect to the total mass of the resin composition. 0.05 to 20% by mass is more preferable, and 0.1 to 10% by mass is particularly preferable.

(Component F) Foaming aid The resin composition for laser engraving of the present invention preferably further comprises (Component F) a foaming aid. By using the foaming aid, the decomposition temperature of the foaming agent, the size of the bubbles, etc. can be easily adjusted.
As the foaming aid, known ones can be used, and depending on the type of foaming agent used and / or the polymerization initiation species generation temperature (decomposition temperature) of the polymerization initiator used, the type and amount used are appropriate. Should be selected.
As foaming aids, urea compounds such as urea and urea derivatives, zinc compounds (zinc oxide), zinc compounds such as zinc carbonate and zinc stearate, organic acid compounds such as salicylic acid, phthalic acid, stearic acid and oxalic acid, Examples include triethanolamine and titanium white.
Among them, it is preferable to use a urea compound, a zinc compound, and / or an organic acid compound, more preferably to use a urea compound, and to use a urea compound, a zinc compound, and an organic acid compound in combination. Is more preferable.

Only one foaming aid may be used, or two or more foaming aids may be used in combination.
The content of the foaming aid contained in the resin composition for laser engraving of the present invention is preferably 0.1 to 20% by mass, and 0.5 to 15% by mass with respect to the total mass of the resin composition. %, More preferably 1 to 10% by mass, still more preferably 2 to 10% by mass. When the content is in the above range, a flexographic printing plate excellent in image quality and ink transferability is obtained, and engraving sensitivity and engraving residue rinsing properties are excellent.

  Hereinafter, in addition to Component A to Component F, various components that can be contained in the resin composition for laser engraving of the present invention will be described.

<Solvent>
In preparing the resin composition for laser engraving of the present invention, a solvent may be used, but it is preferably not used.
As the solvent, an organic solvent is preferably used.
Preferred specific examples of the aprotic organic solvent include acetonitrile, tetrahydrofuran, dioxane, toluene, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl isobutyl ketone, ethyl acetate, butyl acetate, ethyl lactate, N, N-dimethylacetamide, N -Methylpyrrolidone, dimethyl sulfoxide are mentioned.
Preferable specific examples of the protic organic solvent include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 1-methoxy-2-propanol, ethylene glycol, diethylene glycol, and 1,3-propanediol.
Among these, propylene glycol monomethyl ether acetate is particularly preferable.
The content of the solvent in the resin composition for laser engraving of the present invention is preferably 10% by mass or less, more preferably 1% by mass or less, based on the total mass of the resin composition. It is more preferable that the content is not more than mass%, and it is particularly preferable that the content is not contained.

<Other additives>
In the resin composition for laser engraving of the present invention, various known additives can be appropriately blended as long as the effects of the present invention are not impaired. Examples include plasticizers, fillers, waxes, process oils, metal oxides, antiozonants, antiaging agents, polymerization inhibitors, colorants, etc., and these may be used alone. Two or more kinds may be used in combination.

(Laser engraving type flexographic printing plate precursor and its manufacturing method)
The first embodiment of the laser engraving-type flexographic printing plate precursor of the present invention has a relief forming layer made of the resin composition for laser engraving of the present invention.
The second embodiment of the laser engraving-type flexographic printing plate precursor of the present invention has a crosslinked relief forming layer obtained by foaming and cross-linking a layer made of the resin composition for laser engraving of the present invention.
In the present invention, the “laser engraving type flexographic printing plate precursor” means the state before the foamed and crosslinkable relief-forming layer made of the resin composition for laser engraving is foamed and crosslinked, and light and / or It refers to either or both of the foamed and crosslinked state by heat.
In the present invention, the “relief-forming layer” refers to a layer in a state before being foamed and crosslinked, that is, a layer formed of the resin composition for laser engraving of the present invention, and is dried as necessary. May be.
A “flexographic printing plate” is produced by laser engraving a printing plate precursor having a crosslinked relief forming layer.
In the present invention, the “crosslinked relief forming layer” refers to a layer obtained by foaming and crosslinking the relief forming layer. The foaming and crosslinking can be performed by heat and / or light. Moreover, the said bridge | crosslinking will not be specifically limited if it is reaction by which a resin composition is hardened, The crosslinked structure by reaction of the component A and the component B etc. can be illustrated. The foaming is foaming due to Component C, and the obtained crosslinked relief forming layer has bubbles.
In the present invention, the “relief layer” refers to a layer engraved with a laser in a flexographic printing plate, that is, the crosslinked relief forming layer after laser engraving.

The laser engraving-type flexographic printing plate precursor of the present invention comprises a relief-forming layer comprising a resin composition for laser engraving containing the above components, and a layer comprising a resin composition for laser engraving containing the above components. It has a crosslinked relief forming layer that is foamed and crosslinked. The relief forming layer and the crosslinked relief forming layer are preferably provided on the support.
If necessary, the laser engraving-type flexographic printing plate precursor further comprises an adhesive layer between the support and the relief forming layer or the crosslinked relief forming layer, and a slip coat layer and a protective film on the relief forming layer or the crosslinked relief forming layer. You may have.

<Relief forming layer>
The relief forming layer is a layer made of the resin composition for laser engraving of the present invention, and is preferably a thermally crosslinkable layer.

  The flexographic printing plate produced by the laser engraving-type flexographic printing plate precursor includes a flexographic printing plate precursor having a crosslinked relief forming layer obtained by foaming and crosslinking the relief forming layer, and then forming a crosslinked relief forming layer (hard relief forming layer). ) Is preferably engraved by laser engraving to form a relief layer to produce a flexographic printing plate. By crosslinking the relief forming layer, abrasion of the relief layer during printing can be prevented, and a flexographic printing plate having a relief layer having a sharp shape after laser engraving can be obtained.

The relief forming layer can be formed by molding a resin composition for laser engraving having the above components for the relief forming layer into a sheet shape or a sleeve shape. The relief forming layer is usually provided on a support which will be described later. However, the relief forming layer can be directly formed on the surface of a member such as a cylinder provided in an apparatus for plate making and printing, or can be arranged and fixed there. It does not necessarily require a support.
Hereinafter, the case where the relief forming layer is formed into a sheet shape will be mainly described as an example.

<Support>
The material used for the support of the laser engraving type flexographic printing plate precursor is not particularly limited, but a material having high dimensional stability is preferably used. For example, a metal such as steel, stainless steel, aluminum, polyester (for example, PET (polyethylene terephthalate)) , Plastic resins such as PBT (polybutylene terephthalate), PAN (polyacrylonitrile)) and polyvinyl chloride, synthetic rubbers such as styrene-butadiene rubber, and plastic resins reinforced with glass fibers (such as epoxy resins and phenol resins) It is done. As the support, a PET film or a steel substrate is preferably used. The form of the support is determined depending on whether the relief forming layer is a sheet or a sleeve.

<Adhesive layer>
When the relief forming layer is formed on the support, an adhesive layer may be provided between the two for the purpose of enhancing the adhesive strength between the layers.
As a material (adhesive) that can be used for the adhesive layer, for example, I.I. Those described in the edition of Skeist, “Handbook of Adhesives”, the second edition (1977) can be used.

<Protective film, slip coat layer>
For the purpose of preventing scratches or dents on the surface of the relief forming layer or the surface of the crosslinked relief forming layer, a protective film may be provided on the surface of the relief forming layer or the surface of the crosslinked relief forming layer. The thickness of the protective film is preferably 25 to 500 μm, more preferably 50 to 200 μm. As the protective film, for example, a polyester film such as PET, or a polyolefin film such as PE (polyethylene) or PP (polypropylene) can be used. The surface of the film may be matted. The protective film is preferably peelable.

  When the protective film cannot be peeled or when it is difficult to adhere to the relief forming layer, a slip coat layer may be provided between both layers. The material used for the slip coat layer is composed mainly of a resin that is soluble or dispersible in water, such as polyvinyl alcohol, polyvinyl acetate, partially saponified polyvinyl alcohol, hydroxyalkyl cellulose, alkyl cellulose, and polyamide resin, and that is less sticky. It is preferable to do.

The method for producing the laser engraving-type flexographic printing plate precursor is not particularly limited. For example, a resin composition for laser engraving is prepared, and the solvent is removed from the coating solution composition for laser engraving as necessary. Then, a method of melt extrusion on a support can be mentioned. Alternatively, the resin composition for laser engraving may be cast on a support and dried in an oven to remove the solvent from the resin composition.
Among them, the method for producing a laser engraving type flexographic printing plate precursor according to the present invention includes a step of forming a layer made of the resin composition for laser engraving of the present invention, and foaming and cross-linking the layer made of the resin composition for laser engraving. It is preferable that the production method includes a step of forming a crosslinked relief forming layer.

Thereafter, a protective film may be laminated on the relief forming layer as necessary. Lamination can be performed by pressure-bonding the protective film and the relief forming layer with a heated calendar roll or the like, or by bringing the protective film into close contact with the relief forming layer impregnated with a small amount of solvent on the surface.
When using a protective film, you may take the method of laminating | stacking a relief forming layer on a protective film first, and laminating a support body then.
When providing an adhesive layer, it can respond by using the support body which apply | coated the adhesive layer. When providing a slip coat layer, it can respond by using the protective film which apply | coated the slip coat layer.

<Layer formation process>
The method for producing a laser engraving-type flexographic printing plate precursor of the present invention preferably includes a layer forming step of forming a relief forming layer comprising the resin composition for laser engraving of the present invention.
As a method for forming a relief forming layer, the resin composition for laser engraving of the present invention is prepared, a method of extruding rubber on a support, and a resin composition for laser engraving of the present invention are prepared, if necessary, After removing the solvent from the resin composition for laser engraving, a method of melt extrusion on a support, preparing the resin composition for laser engraving of the present invention, and applying the resin composition for laser engraving of the present invention on the support A method in which the solvent is removed by casting and drying in an oven is preferable.
The resin composition for laser engraving is, for example, a method of mixing component A to component C, further arbitrarily mixing component D or the like, or mixing component A and component B, and optionally further mixing component D or the like sequentially. Then, the resin composition is prepared, component C is mixed or impregnated later, component A to component C, and optional components are dissolved or dispersed in an appropriate solvent, and then component D is optionally mixed However, a method that does not use a solvent is preferable. Since most of the solvent component is preferably removed at the stage of producing the flexographic printing plate precursor, the solvent is a low-molecular alcohol that easily volatilizes (for example, methanol, ethanol, n-propanol, isopropanol, propylene glycol monomethyl ether). It is preferable to keep the total amount of solvent added as small as possible by adjusting the temperature.

  The thickness of the (crosslinking) relief forming layer in the laser engraving-type flexographic printing plate precursor is preferably 0.05 mm or more and 10 mm or less, more preferably 0.05 mm or more and 7 mm or less, and more preferably 0.05 mm or more and 3 mm or less before and after crosslinking. Further preferred.

<Crosslinking process>
The method for producing a laser engraving-type flexographic printing plate precursor according to the present invention is a production method including a crosslinking step in which a layer made of a resin composition for laser engraving is foamed and crosslinked to form a crosslinked relief forming layer.
In the crosslinking step, foaming and crosslinking are performed by heat, or foaming is performed by heat, and crosslinking is preferably performed by light, and foaming and crosslinking is more preferably performed by heat.
In addition, foaming and crosslinking in the crosslinking step may be performed simultaneously or separately, but after performing crosslinking, it is preferable to perform foaming, or at least partially perform foaming and crosslinking simultaneously, More preferably, foaming and crosslinking are performed at least partially simultaneously. In the case where the foaming and the crosslinking are performed at least partially simultaneously by heat, a method of performing at a temperature at which both the thermal polymerization initiator and the foaming agent contained are decomposed can be mentioned. Moreover, when performing foaming by heat and crosslinking by light at least partly simultaneously, there is a method of irradiating light with which the photopolymerization initiator decomposes while heating to a temperature at which the foaming agent decomposes.
The heating temperature in the crosslinking step can be arbitrarily set according to the decomposition temperature of the polymerization initiator and the foaming agent, but is preferably 90 ° C to 250 ° C, more preferably 100 ° C to 180 ° C. 100 ° C. to 160 ° C. is more preferable, and 120 ° C. to 160 ° C. is particularly preferable. In the above embodiment, foaming and crosslinking by heat can be easily performed simultaneously.
Examples of the heating means in the crosslinking step include a method of heating the printing plate precursor in a hot air oven or a far infrared oven for a predetermined time, or a method of contacting a heated roll for a predetermined time.

  In general, the light irradiation in the crosslinking step is performed on the entire surface of the relief forming layer. Examples of light (also referred to as “active light”) include visible light, ultraviolet light, and electron beam, with ultraviolet light being most preferred. If the substrate side for immobilizing the relief forming layer, such as the support of the relief forming layer, is the back side, the surface may only be irradiated with light, but the support should be a transparent film that transmits actinic rays. For example, it is preferable to irradiate light from the back side. When the protective film exists, the irradiation from the surface may be performed while the protective film is provided, or may be performed after the protective film is peeled off. Since polymerization inhibition may occur in the presence of oxygen, irradiation with actinic rays may be performed after the relief forming layer is covered with a polyvinyl chloride sheet and evacuated.

The crosslinked relief forming layer obtained through the crosslinking step has bubbles inside and on the surface by foaming.
The cells in the crosslinked relief forming layer may have a closed cell structure or an open cell structure, but from the viewpoint of printing durability and image quality, a closed cell structure is preferable.
The volume foaming ratio of the relief forming layer, the crosslinked relief forming layer or the relief layer in the present invention is preferably 10 to 200%, more preferably 50 to 180%, from the viewpoint of printing durability and image quality. 70 to 140% is more preferable.
The volume foaming ratio may be measured by measuring the volume change before and after foaming, or may be calculated from the total volume of the bubble portions in the crosslinked relief forming layer or relief layer after foaming.
The volume average diameter of the bubbles in the crosslinked relief forming layer is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and still more preferably 1 to 10 μm. Within the above range, the ink transfer property and the image quality are excellent.
Examples of the method for measuring the volume average diameter of the bubbles in the crosslinked relief forming layer include a method of observing and measuring a cross section of the crosslinked relief forming layer with an optical or electron microscope, a method of calculating the image by photographing the above cross section, image processing, and the like. Can be mentioned.

Also, in the crosslinking step, both sides of the relief forming layer are sandwiched between a support or a substrate such as a support and a heating device surface from the viewpoint of adjusting the foaming rate of the resulting crosslinked relief forming layer and smoothness. You may foam in a state. In addition, from the viewpoint of adjusting the foaming rate and smoothness of the resulting crosslinked relief forming layer, foaming in the sandwiched state is preferably performed in a state where pressure is applied from at least one surface.
Further, after the crosslinking step, the support may be peeled from the crosslinked relief forming layer, and from the viewpoint of strength and smoothness, after peeling the support provided during the crosslinking step from the crosslinked relief forming layer, It is preferable to provide another support on the surface of the cross-linked relief forming layer on the side opposite to the surface on which the support is provided or provided.

(Flexographic printing plate and plate making method)
The plate making method of the flexographic printing plate of the present invention preferably includes a preparation step of preparing the flexographic printing plate precursor of the present invention and an engraving step of laser engraving the flexographic printing plate precursor having the crosslinked relief forming layer.
The flexographic printing plate of the present invention is a flexographic printing plate having a relief layer obtained by foaming and cross-linking a layer comprising the resin composition for laser engraving of the present invention and laser engraving, and the flexographic printing plate of the present invention. The flexographic printing plate made by the plate making method is preferably used.
As the preparation step in the plate making method of the flexographic printing plate of the present invention, the layer forming step and the crosslinking step are preferably mentioned. It is synonymous and the preferable range is also the same.

<Engraving process>
The plate making method of the flexographic printing plate of the present invention includes an engraving step of laser engraving the flexographic printing plate precursor having the crosslinked relief forming layer.
The engraving step is a step of forming a relief layer by laser engraving the crosslinked relief forming layer crosslinked in the crosslinking step. Specifically, it is preferable to form a relief layer by engraving a crosslinked crosslinked relief forming layer by irradiating a laser beam corresponding to a desired image. Moreover, the process of controlling a laser head with a computer based on the digital data of a desired image, and carrying out scanning irradiation with respect to a bridge | crosslinking relief forming layer is mentioned preferably.
In this engraving process, an infrared laser is preferably used. When irradiated with an infrared laser, the molecules in the crosslinked relief forming layer undergo molecular vibrations and generate heat. When a high-power laser such as a carbon dioxide laser or YAG laser is used as an infrared laser, a large amount of heat is generated in the laser irradiation part, and molecules in the crosslinked relief forming layer are selectively cut by molecular cutting or ionization. That is, engraving is performed. The advantage of laser engraving is that since the engraving depth can be set arbitrarily, the structure can be controlled three-dimensionally. For example, a portion that prints fine halftone dots can be engraved shallowly or with a shoulder so that the relief does not fall down due to printing pressure, and a portion of a groove that prints fine punched characters is engraved deeply As a result, the ink is less likely to be buried in the groove, and it is possible to suppress the crushing of the extracted characters.
In particular, when engraving with an infrared laser corresponding to the absorption wavelength of the photothermal conversion agent, the crosslinked relief forming layer can be selectively removed with higher sensitivity, and a relief layer having a sharp image can be obtained.

As the infrared laser used in the engraving process, a carbon dioxide laser (CO ₂ laser) or a semiconductor laser is preferable from the viewpoints of productivity and cost. In particular, a semiconductor infrared laser with a fiber (FC-LD) is preferably used. In general, a semiconductor laser can be downsized with high efficiency and low cost of laser oscillation compared to a CO ₂ laser. Moreover, since it is small, it is easy to form an array. Furthermore, the beam shape can be controlled by processing the fiber.
The semiconductor laser preferably has a wavelength of 700 to 1,300 nm, more preferably 800 to 1,200 nm, still more preferably 860 to 1,200 nm, and particularly preferably 900 to 1,100 nm.

Moreover, since the semiconductor laser with a fiber can output a laser beam efficiently by attaching an optical fiber, it is effective for the engraving process in the present invention. Furthermore, the beam shape can be controlled by processing the fiber. For example, the beam profile can have a top hat shape, and energy can be stably given to the plate surface. Details of the semiconductor laser are described in “Laser Handbook 2nd Edition” edited by Laser Society, “Practical Laser Technology” edited by IEICE.
Also, a plate making apparatus equipped with a fiber-coupled semiconductor laser that can be suitably used in a method for making a flexographic printing plate using the flexographic printing plate precursor of the present invention is disclosed in JP 2009-172658 A and JP 2009-214334 A. It is described in detail in the official gazette and can be used for making a flexographic printing plate according to the present invention.

In the method for making a flexographic printing plate of the present invention, after the engraving step, the following rinsing step, drying step, and / or post-crosslinking step may be included as necessary.
Rinsing step: a step of rinsing the engraved surface of the relief layer surface after engraving with water or a liquid containing water as a main component.
Drying step: a step of drying the engraved relief layer.
Post-crosslinking step: a step of imparting energy to the relief layer after engraving and further crosslinking the relief layer.
Since the engraving residue is attached to the engraving surface after the above steps, a rinsing step of rinsing the engraving residue by rinsing the engraving surface with water or a liquid containing water as a main component may be added. As a means of rinsing, there is a method of washing with tap water, a method of spraying high-pressure water, and a known batch type or conveying type brush type washing machine as a photosensitive resin relief printing machine. For example, when the engraving residue cannot be removed, a rinsing liquid to which soap or a surfactant is added may be used.
When the rinsing process for rinsing the engraving surface is performed, it is preferable to add a drying process for drying the engraved relief forming layer and volatilizing the rinsing liquid.
Furthermore, you may add the post-crosslinking process which further bridge | crosslinks a relief forming layer as needed. By performing the post-crosslinking step, which is an additional cross-linking step, the relief formed by engraving can be further strengthened.

The rinsing liquid that can be used in the present invention is preferably a rinsing liquid having a pH of 8 to 14. In the above embodiment, the rinsing property of engraving residue generated during laser engraving is excellent.
Further, the pH of the rinsing solution that can be used in the present invention is more preferably 9 or more, further preferably 10 or more, and particularly preferably 11 or more. The pH of the rinse liquid is more preferably 13.5 or less, and further preferably 13.2 or less. When it is within the above range, handling is easy and the rinse property of engraving residue generated during laser engraving is excellent.
What is necessary is just to adjust pH using an acid and / or a base suitably in order to make a rinse liquid into said pH range, and the acid and base to be used are not specifically limited. From the viewpoint of cost and the like, the base is preferably an alkali metal or alkaline earth metal hydroxide.
The rinsing liquid that can be used in the present invention is preferably an aqueous rinsing liquid containing water as a main component.
Moreover, the rinse liquid may contain water miscible solvents, such as alcohol, acetone, tetrahydrofuran, etc. as solvents other than water.

It is preferable that the rinse liquid contains a surfactant.
As the surfactant that can be used in the present invention, a carboxybetaine compound, a sulfobetaine compound, a phosphobetaine compound, an amine oxide compound, or from the viewpoint of reducing engraving residue removal and influence on the flexographic printing plate Preferred are betaine compounds (amphoteric surfactants) such as phosphine oxide compounds.

Examples of the surfactant include known anionic surfactants, cationic surfactants, and nonionic surfactants. Furthermore, fluorine-based and silicone-based nonionic surfactants can be used in the same manner.
Surfactant may be used individually by 1 type, or may use 2 or more types together.
Although the usage-amount of surfactant does not need to specifically limit, it is preferable that it is 0.01-20 mass% with respect to the total mass of a rinse liquid, and it is more preferable that it is 0.05-10 mass%.

As described above, a flexographic printing plate having a relief layer on the surface of an arbitrary substrate such as a support can be obtained.
The thickness of the relief layer of the flexographic printing plate is preferably 0.05 mm or more and 10 mm or less, more preferably 0.05 mm or more and 7 mm, from the viewpoint of satisfying various printability such as abrasion resistance and ink transferability. Hereinafter, it is particularly preferably 0.05 mm or more and 3 mm or less.

Moreover, it is preferable that the Shore A hardness of the relief layer which a flexographic printing plate has is 50 degree or more and 90 degrees or less. When the Shore A hardness of the relief layer is 50 ° or more, even if the fine halftone dots formed by engraving are subjected to the strong printing pressure of the relief printing press, they do not collapse and can be printed normally. In addition, when the Shore A hardness of the relief layer is 90 ° or less, it is possible to prevent faint printing in a solid portion even in flexographic printing with a kiss touch.
In addition, the Shore A hardness in this specification is a numerical value obtained by indenting and deforming an indenter (called a push needle or an indenter) on a surface to be measured at 25 ° C., and measuring the deformation amount (indentation depth). This is a value measured with a durometer (spring type rubber hardness meter).

  The flexographic printing plate of the present invention is particularly suitable for printing with water-based ink by a flexographic printing machine, but printing is possible with any of water-based ink, oil-based ink and UV ink by a relief printing press. In addition, printing with UV ink by a flexographic printing machine is also possible. The flexographic printing plate of the present invention has excellent rinsing properties, no engraving residue remains, and the obtained relief layer is excellent in elasticity, so that it has excellent water-based ink transfer properties and printing durability, and a relief layer over a long period of time. Thus, printing can be carried out without concern for plastic deformation or deterioration of printing durability.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited to these examples. In the following description, “part” means “part by mass” unless otherwise specified, and “%” means “% by mass”. Moreover, the unit of each numerical value in Table 1 mentioned later is a mass part.
In addition, the number average molecular weight (Mn) and the weight average molecular weight (Mw) of the polymer in an Example have shown the value measured by GPC method unless there is particular notice.

Details of the components used in each example and comparative example are as follows.
<Binder polymer>
UV-3000B: Urethane acrylate having an acryloxy group at the end of the main chain (Mw: 18,000, Tg: -39 ° C., Nikko Synthetic Chemical Co., Ltd., Murasakiko UV-3000B, a liquid polymer, which is a plastomer)
UV-3630ID80: Urethane acrylate having an acryloxy group at the end of the main chain (purple UV-3630ID80 manufactured by Nippon Synthetic Chemical Co., Ltd., because it is a liquid polymer)
IR2200L: polyisoprene (Mooney viscosity (ML _{1 + 4} , 100 ° C.): 70, Mw: 1,350,000, Mn: 472,000, Tg: about −60 ° C., tensile set: 53%, Ube Industries, Ltd. (NIPOL IR2200L)
BR150L: polybutadiene (Mooney viscosity (ML _{1 + 4} , 100 ° C.): 43, Mw: 467,000, Mn: 243,000, Tg: about −103 ° C., tensile permanent strain: 63%, manufactured by Ube Industries, Ltd. UBEPOL BR150L)
LBR305: Liquid polybutadiene (Mn: 26,000, Mw: 28,000, Kuraray Co., Ltd. LBR-305, a liquid polymer, which is a plastomer)
EPDM505: ethylene-propylene-5-ethylidene-2-norbornene copolymer (binder polymer not corresponding to component A, Mooney viscosity (ML _{1 + 4} , 125 ° C.): 59, Esprene EPDM505 manufactured by Sumitomo Chemical Co., Ltd.)
D1102: Styrene-butadiene-styrene block copolymer (SBS resin, binder polymer not corresponding to component A, Mw: 100,000, tensile set: 0%, Kraton D1102 manufactured by Kraton)

<Polymerization initiator>
PCD-40: Dicumyl peroxide (organic peroxide, Park Mill D-40 manufactured by NOF Corporation, containing 40% dicumyl peroxide, 10 hour half-life temperature: 116.4 ° C.)
Irgacure 651: photopolymerization initiator, 2-phenyl-2,2-dimethoxyacetophenone (IRGACURE 651, manufactured by Ciba Geigy)

<Foaming agent>
・ ADCA (Azodicarbonamide, manufactured by Tokyo Chemical Industry Co., Ltd.)
・ DPT (Dinitrosopentamethylenetetramine, manufactured by Tokyo Chemical Industry Co., Ltd.)
<Foaming aid>
・ Urea (Wako Pure Chemical Industries, Ltd.)
・ Zinc oxide (Wako Pure Chemical Industries, Ltd.)
・ Stearic acid (Wako Pure Chemical Industries, Ltd.)

<Polymerizable compound>
HDDA: hexanediol diacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.)
<Photothermal conversion agent>
# 45L: Carbon black # 45L (Mitsubishi Chemical Corporation, particle size: 24 nm, specific surface area: 125 m ² / g, DBP oil absorption: 45 ml / 100 g)
<Additives>
・ Expancel DU930-170 (thermal expansion microcapsule, particle size 28-38 μm, manufactured by Nippon Philite Co., Ltd.)

(Examples 1-7)
<Preparation of laser engraving type flexographic printing plate precursor>
Laboplast mill (Toyo Seiki Seisakusho Co., Ltd.) was prepared by removing the foaming agent, urea, zinc oxide, stearic acid and the polymerization initiator from the composition described in Table 1 described later. Kneaded at 60 ° C. for 20 minutes. Thereafter, a foaming agent, urea, zinc oxide, stearic acid and a polymerization initiator were added, and further kneaded (80 ° C. for 5 minutes) to obtain a resin composition for laser engraving. The obtained resin composition is formed into a sheet having a thickness of 1 mm by a rubber extruder, and this is put into a heating furnace and heated at 140 ° C. for 80 minutes to be crosslinked and foamed, thereby laser engraving flexographic printing I got the original version.

<Preparation of flexographic printing plate>
The crosslinked resin composition layer (crosslinked relief forming layer) was engraved with the following two types of lasers.
As a carbon dioxide laser engraving machine, engraving by laser irradiation was performed using a high-quality CO ₂ laser marker ML-9100 series (manufactured by Keyence Corporation). Using a carbon dioxide laser engraving machine, a 1 cm square solid part was raster engraved under the conditions of output: 12 W, head speed: 200 mm / second, pitch setting: 2,400 DPI.
As a semiconductor laser engraving machine, a laser recording apparatus equipped with a fiber-coupled semiconductor laser (FC-LD) SDL-6390 (JDSU, wavelength 915 nm) having a maximum output of 8.0 W was used. A 1 cm square solid part was raster engraved with a semiconductor laser engraving machine under conditions of laser output: 7.5 W, head speed: 409 mm / second, pitch setting: 2,400 DPI.
The engraving machine used is shown in Table 2. “FC-LD” means that a semiconductor laser engraving machine was used, and “CO ₂ ” means that a carbon dioxide laser engraving machine was used.

(Example 8)
Laboplast mill (Toyo Seiki Seisakusho Co., Ltd.) was prepared by removing the foaming agent, urea, zinc oxide, stearic acid and the polymerization initiator from the composition described in Table 1 described later. Kneaded at 60 ° C. for 20 minutes. Thereafter, a foaming agent, urea, zinc oxide, stearic acid and a polymerization initiator were added, and further kneaded (80 ° C. for 5 minutes) to obtain a resin composition for laser engraving. The obtained resin composition is molded into a sheet having a thickness of 1 mm with a rubber extruder, and then subjected to ultraviolet exposure while being heated at 100 ° C. for 80 minutes with an ultraviolet (UV) exposure machine installed on a heating plate. This was crosslinked and foamed to obtain a laser engraving-type flexographic printing plate precursor.
The obtained laser engraving type flexographic printing plate precursor was laser engraved in the same manner as in Example 1 to obtain a flexographic printing plate.

(Comparative Examples 1-3)
Laser engraving-type flexographic printing plate precursors were prepared by the same procedure as in Example 1 except that the materials and compositions described in Tables 1 and 2 described below were used and foaming was not performed.
The obtained laser engraving type flexographic printing plate precursor was laser engraved in the same manner as in Example 1 to obtain a flexographic printing plate.

-Evaluation of laser engraving-type flexographic printing plate precursors and flexographic printing plates-
The performance evaluation of the laser engraving-type flexographic printing plate precursor or the flexographic printing plate obtained in the examples and comparative examples was performed according to the following items. The evaluation results are also shown in Table 2.

<Engraving sensitivity evaluation>
The “engraved depth” of the relief layer obtained by laser engraving the crosslinked relief forming layer of the flexographic printing plate precursor was measured as follows. Here, “sculpture depth” refers to the difference between the engraved position (height) and the unengraved position (height) when the cross section of the relief layer is observed. The “engraving depth” in this example was measured by observing the cross section of the relief layer with an ultra-deep color 3D shape measuring microscope VK9510 (manufactured by Keyence Corporation). A large engraving depth means high engraving sensitivity.

<Evaluation of the amount of engraving residue remaining on the plate>
The laser engraved plate was subjected to relative evaluation by observing the presence or absence of residue on the surface of the relief layer with an optical microscope.

<Rinse evaluation>
The laser-engraved plate was immersed in water, and the engraved part was rubbed 10 times with a toothbrush (Lion Corporation, Clinica Habrush Flat). Then, the presence or absence of debris on the surface of the relief layer was confirmed with an optical microscope. The case where there was no residue was designated as A, the case where there was almost no residue as B, and the residue with a slight residue remaining as C.

<Evaluation of ink transfer properties>
The obtained flexographic printing plate is set in a printing press (ITM-4 type, manufactured by Iyo Machinery Co., Ltd.), and water-based ink Aqua SPZ16 Beni (manufactured by Toyo Ink Manufacturing Co., Ltd.) is used without being diluted. Then, printing was continued using full-color form M70 (manufactured by Nippon Paper Industries Co., Ltd., thickness: 100 μm) as printing paper, and highlights of 1 to 10% were confirmed with printed matter.
The degree of ink adhesion in the solid part on the printed matter at 1,000 m from the start of printing was compared visually.
The evaluation criteria are A, density, which has no density unevenness, and is uniform and slightly glossy (a glossiness is an indicator that the ink has been transferred by an appropriate thickness (amount)). A uniform sample with no unevenness was designated as B, a sample with totally unevenness was designated as D, and a sample with partially uneven density was designated as C. An evaluation of B or higher is a level with no practical problem.

<Image quality evaluation>
Three engraving relief images of 130, 150, and 175 lpi were prepared on a printing plate with FC-LD, UV ink printing (UV ink flexo 500CF, manufactured by T & K TOKA Corporation) was performed for 10 km, and the printed matter at 10 km Was observed with an optical microscope, and the limit number of lines that could reproduce a sculpture image (number of lines) as a printed material was taken as the image quality of the example. For example, three engraving relief images of 130, 150, and 175 lpi have been created, but the printed material can be reproduced beautifully up to 130 lpi and 150 lpi, but if 175 lpi cannot be reproduced as engraved relief, the image quality evaluation is 150 lpi.

<Print durability>
The obtained flexographic printing plate was set on a printing machine (ITM-4 type, manufactured by Iyo Machinery Co., Ltd.). As the ink, solvent ink (XS-716 507 primary color indigo (manufactured by DIC Graphics Co., Ltd.)) was used. Printing was continued using full-color foam M70 (manufactured by Nippon Paper Industries Co., Ltd., thickness: 100 μm) as printing paper, and highlights of 1 to 10% were confirmed with printed matter. Printing was performed when a halftone dot that was not printed occurred, and the length (km) of the paper printed before the printing was used as an index. The larger the value, the better the printing durability.

Claims (18)

(Component A) a binder polymer having an ethylenically unsaturated bond in at least one portion selected from the group consisting of the inside of the main chain, the end of the main chain and the side chain,
(Component B) a polymerization initiator, and
(Component C) contains a foaming agent,
Component A is a plastomer selected from the group consisting of a polymer having a polybutadiene structure, a polymer having a polyisoprene structure, and a urethane (meth) acrylate,
Content of component A is 50 mass% or more with respect to the total mass of a composition, The resin composition for laser engravings characterized by the above-mentioned.   The resin composition for laser engraving according to claim 1, wherein component A is polybutadiene, polyisoprene, or a copolymer obtained by copolymerizing at least butadiene and / or isoprene.   The resin composition for laser engraving according to claim 1 or 2, wherein Component A is polybutadiene or polyisoprene.   The resin composition for laser engraving according to any one of claims 1 to 3, wherein Component B is an organic peroxide.   The resin composition for laser engraving according to any one of claims 1 to 4, wherein Component C is a chemical foaming agent.   The resin composition for laser engraving according to claim 1, further comprising (Component D) a polymerizable compound.   The resin composition for laser engraving according to claim 1, further comprising (Component E) a photothermal conversion agent.   A laser engraving-type flexographic printing plate precursor having a crosslinked relief-forming layer obtained by foaming and cross-linking a layer made of the resin composition for laser engraving according to claim 1. (Component A) Binder polymer having an ethylenically unsaturated bond in at least one portion selected from the group consisting of the inside of the main chain, the main chain terminal and the side chain, (Component B) a polymerization initiator, and (Component C) foaming The component A is a plastomer selected from the group consisting of a polymer having a polybutadiene structure, a polymer having a polyisoprene structure, and a urethane (meth) acrylate, and the content of the component A is A laser engraving-type flexographic printing plate precursor comprising a crosslinked relief-forming layer obtained by foaming and cross-linking a layer composed of a resin composition for laser engraving that is 50% by mass or more based on the total mass.   The laser engraving flexographic printing plate precursor according to claim 9, wherein Component A is polybutadiene, polyisoprene, or a copolymer obtained by copolymerizing at least butadiene and / or isoprene.   The laser engraving-type flexographic printing plate precursor according to claim 9 or 10, wherein Component A is polybutadiene or polyisoprene.   The laser engraving-type flexographic printing plate precursor according to any one of claims 9 to 11, wherein Component B is an organic peroxide.   The laser engraving-type flexographic printing plate precursor according to any one of claims 9 to 12, wherein Component C is a chemical foaming agent or a physical foaming agent.   The laser engraving-type flexographic printing plate precursor according to any one of claims 9 to 13, wherein the resin composition for laser engraving further comprises (Component D) a polymerizable compound.   The laser engraving-type flexographic printing plate precursor according to any one of Claims 9 to 14, wherein the resin composition for laser engraving further contains (Component E) a photothermal conversion agent. (Component A) Binder polymer having an ethylenically unsaturated bond in at least one portion selected from the group consisting of the inside of the main chain, the main chain terminal and the side chain, (Component B) a polymerization initiator, and (Component C) foaming The component A is a plastomer selected from the group consisting of a polymer having a polybutadiene structure, a polymer having a polyisoprene structure, and a urethane (meth) acrylate, and the content of the component A is A step of forming a layer composed of a resin composition for laser engraving that is 50% by mass or more based on the total mass; and
The method for producing a laser engraving-type flexographic printing plate precursor according to any one of claims 8 to 15, comprising a step of foaming and crosslinking a layer made of the resin composition for laser engraving to form a crosslinked relief forming layer.   The method for producing a laser engraving-type flexographic printing plate precursor according to claim 16, wherein the foaming and crosslinking are performed at least partially simultaneously. Preparing the laser engraving-type flexographic printing plate precursor according to any one of claims 8 to 15, and
A method for making a flexographic printing plate, comprising engraving a step of laser engraving the crosslinked relief forming layer to form a relief layer.