WO2015115599A1

WO2015115599A1 - Resin composition for laser engraving, flexographic printing original plate for laser engraving, method for producing flexographic printing original plate for laser engraving, flexographic printing plate, and plate making method for flexographic printing plate

Info

Publication number: WO2015115599A1
Application number: PCT/JP2015/052671
Authority: WO
Inventors: 和博 ▲濱▼田
Original assignee: 富士フイルム株式会社
Priority date: 2014-01-31
Filing date: 2015-01-30
Publication date: 2015-08-06

Abstract

The present invention addresses the problem of providing: a resin composition for laser engraving, which is capable of providing a flexographic printing plate that exhibits excellent sheet processability, ink resistance and printing durability; a flexographic printing original plate for laser engraving, which uses this resin composition for laser engraving; a method for producing this flexographic printing original plate for laser engraving; a plate making method for a flexographic printing plate, which uses this flexographic printing original plate; and a flexographic printing plate which is obtained by this plate making method. A resin composition for laser engraving according to the present invention is characterized by containing a polymer that has a monomer unit derived from a conjugated diene hydrocarbon (component (A)) and a transpolyisoprene and/or a polyoctenylene (component (B)) in an amount of 1 part by mass or more per 100 parts by mass of the component (A). This resin composition for laser engraving is also characterized in that the component (A) and the component (B) are different polymers.

Description

Resin composition for laser engraving, flexographic printing plate precursor for laser engraving and method for producing the same, and flexographic printing plate and method for making the same

The present invention relates to a resin composition for laser engraving, a flexographic printing plate precursor for laser engraving, a method for producing a flexographic printing plate precursor for laser engraving, a flexographic printing plate, 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 printing plate precursor is directly irradiated with a laser to cause thermal decomposition and volatilization by photothermal conversion, thereby forming recesses. 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. As a laser used in this method, a high output carbon dioxide laser is often used. 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 plate precursors for laser engraving, for example, those described in Patent Documents 1 and 2 are known.

Patent Document 1 describes a laser processing composition containing (A1) 100 parts by mass of a thermoplastic elastomer and (B) 0.1 to 50 parts by mass of silica particles.
U.S. Pat. No. 6,089,075 includes an elastomeric relief-forming laser platenable thermally and / or photochemically crosslinkable layer provided on a dimensionally stable flexible support. Syndiotactic 1,2-polybutadiene having a content of ˜100% 1,2-crosslinked butadiene units, a crystallinity of 5˜30%, and an average molecular weight of 20,000˜300,000 g / mol as a binder in an amount of 5% by weight or more. A laser-engravable flexographic printing element characterized in that it is described.

JP 2006-206872 A JP-T-2004-523401

The problem to be solved by the present invention is to use a resin composition for laser engraving, which can obtain a flexographic printing plate excellent in sheet processability, ink resistance and printing durability, and the resin composition for laser engraving. It is intended to provide a flexographic printing plate precursor for laser engraving and a production method thereof, a flexographic printing plate making method using the flexographic printing plate precursor, and a flexographic printing plate obtained by the plate making method.

The above-described problems of the present invention have been solved by the following means <1>, <16>, <17>, <19>, <23>, <25> and <26>. They are listed together with <2> to <15>, <18>, <20> to <22> and <24>, which are preferred embodiments.
<1> Component A is a polymer having a monomer unit derived from a conjugated diene hydrocarbon, and Component B is trans polyisoprene and / or polyoctenylene in an amount of 1 part by mass or more based on 100 parts by mass of component A (preferably 3 parts by mass or more, more preferably 5 parts by mass or more, preferably 300 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 80 parts by mass or less, particularly preferably 50 parts by mass or less, and most preferably 35 parts by mass. And a resin composition for laser engraving, wherein component A is a polymer different from component B,
<2> The resin composition for laser engraving according to <1>, wherein the SP value of component A is 9 or less (more preferably 8.0 to 9.0, more preferably 8.0 to 8.5),
<3> The resin composition for laser engraving according to <1> or <2>, wherein the component A contains a monomer unit derived from butadiene and / or isoprene.
<4> The proportion of monomer units derived from butadiene, isoprene or hydrogenated products thereof contained in Component A is 30 mol% or more in total (more preferably 50 mol% or more, more preferably 80 mol% or more). The resin composition for laser engraving according to any one of <1> to <3>,
<5> Component A has a weight average molecular weight of 10,000 or more (more preferably 10,000 to 2,000,000, still more preferably 30,000 to 1,800,000, particularly preferably 50,000 to 1,500,000), <1> to <4>, the resin composition for laser engraving according to any one of
<6> The resin composition for laser engraving according to any one of <1> to <5>, wherein Component A is a plastomer or a thermoplastic elastomer,
<7> The resin composition for laser engraving according to any one of <1> to <6>, further containing a crosslinking agent as component C.
<8> The resin composition for laser engraving according to <7>, wherein Component C is an organic peroxide,
<9> The resin composition for laser engraving according to any one of <1> to <8>, further containing a photothermal conversion agent as component D
<10> The resin composition for laser engraving according to any one of <1> to <9>, further comprising factice as component E
<11> The resin composition for laser engraving contains 0 to 5% by mass of a solvent (more preferably 0 to 3% by mass, and more preferably 0% by mass). <1> to the resin composition for laser engraving according to any one of <10>,
<12> Component A is composed of polybutadiene, partially hydrogenated polybutadiene, terminal-modified polybutadiene, polyisoprene, partially hydrogenated polyisoprene, terminal-modified polyisoprene, SBR, SBS, ABS, SIS, and isoprene / butadiene copolymer. Selected from the group (more preferably, polybutadiene, partially hydrogenated polybutadiene, hydroxyl-terminated polybutadiene, glycidyl ether-modified polybutadiene, polyisoprene, partially hydrogenated polyisoprene, hydroxyl-terminated polyisoprene, glycidyl ether-modified polyisoprene, SBS, and Selected from the group consisting of SIS, more preferably selected from the group consisting of polybutadiene, partially hydrogenated polybutadiene, polyisoprene, partially hydrogenated polyisoprene, SBS, and SIS. Preferably, the laser is selected from the group consisting of polybutadiene, polyisoprene, SBS, and SIS, and most preferably polybutadiene and / or polyisoprene), <1> to <11> Engraving resin composition,
<13> The total content of component A is 10 to 90% by mass (more preferably 20 to 85% by mass, still more preferably 30 to 80% by mass) based on the total mass of the solid content of the resin composition for laser engraving. The resin composition for laser engraving according to any one of <1> to <12>,
<14> The resin composition for laser engraving according to any one of <1> to <13>, wherein Component B is polyoctenylene,
<15> The total content of component B is 1 to 60% by mass (more preferably 3 to 40% by mass, still more preferably 5 to 25% by mass) based on the total mass of the solid content of the resin composition for laser engraving. The resin composition for laser engraving according to any one of <1> to <14>,
<16> A flexographic printing plate precursor for laser engraving, comprising a relief forming layer comprising the resin composition for laser engraving according to any one of <1> to <15> on a support,
<17> Laser engraving provided on a support with a crosslinked relief forming layer obtained by crosslinking the relief forming layer comprising the resin composition for laser engraving according to any one of <1> to <15> with heat and / or light For flexographic printing plate,
<18> A flexographic printing plate precursor for laser engraving according to <17>, comprising a crosslinked relief-forming layer crosslinked by heat,
<19> A layer forming step of forming a relief forming layer comprising the resin composition for laser engraving according to any one of <1> to <15>, and the relief forming layer is crosslinked by heat and / or light And a crosslinking step for obtaining a flexographic printing plate precursor having a crosslinked relief forming layer, a method for producing a flexographic printing plate precursor for laser engraving,
<20> The step of forming the layer includes a step of kneading the resin composition for laser engraving according to any one of <1> to <15>, and a step of molding the obtained kneaded material into a sheet shape. A method for producing a flexographic printing plate precursor for laser engraving according to <19>,
<21> The method for producing a flexographic printing plate precursor for laser engraving according to <20>, wherein the step of forming into a sheet is a step of forming into a sheet by hot pressing or extrusion,
<22> The method for producing a flexographic printing plate precursor for laser engraving according to any one of <19> to <21>, wherein in the crosslinking step, the relief forming layer is crosslinked by heat,
<23> A step of preparing the flexographic printing plate precursor for laser engraving according to any one of <16> to <18>, and an engraving for forming a relief layer by laser engraving the flexographic printing plate precursor for laser engraving A process for making a flexographic printing plate, comprising:
<24> The method for making a flexographic printing plate according to <23>, further comprising a rinsing step of rinsing the relief layer surface with an aqueous rinsing liquid after the engraving step,
<25> Flexographic printing plate made by the plate making method according to <23> or <24>,
<26> Use of the resin composition for laser engraving according to any one of <1> to <15> for a relief forming layer of a printing plate precursor for laser engraving.

According to the present invention, a resin composition for laser engraving capable of obtaining a flexographic printing plate having excellent sheet processability and excellent ink resistance and printing durability, and a flexo for laser engraving using the above resin composition for laser engraving. A printing plate precursor and a method for producing the same, a method for making a flexographic printing plate using the flexographic printing plate precursor, and a flexographic printing plate obtained by the plate making method can 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, the description of “lower limit to upper limit” representing the numerical range represents “lower limit or higher and lower limit or lower”, and the description of “upper limit to lower limit” represents “lower limit or higher and lower limit or higher”. That is, it represents a numerical range including an upper limit and a lower limit. In the present invention, “a polymer having a monomer unit derived from a conjugated diene hydrocarbon” or the like is also simply referred to as “component A” or the like.
Further, “parts by mass” and “% by mass” have the same meanings as “parts by weight” and “% by weight”, respectively.
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).
A combination of preferred embodiments in the following description is a more preferred embodiment.
In addition, in this specification, regarding the description of the flexographic printing plate and the flexographic printing plate precursor, the component A and the component B are contained, the surface is a flat layer as an image forming layer to be subjected to laser engraving, and is uncrosslinked A crosslinkable layer is referred to as a relief forming layer, a layer obtained by crosslinking the relief forming layer is referred to as a crosslinked relief forming layer, and a layer in which irregularities are formed on the surface by laser engraving is referred to as a relief layer.

1. Resin composition for laser engraving The resin composition for laser engraving of the present invention (hereinafter also simply referred to as “resin composition”) comprises, as component A, a polymer having a monomer unit derived from a conjugated diene hydrocarbon. Component B contains trans polyisoprene and / or polyoctenylene in an amount of 1 part by mass or more based on 100 parts by mass of Component A, and Component A is a polymer different from Component B.
As a result of intensive studies by the inventor, the resin composition for laser engraving contains component A and component B, whereby a flexographic printing plate having excellent sheet processability and excellent ink resistance and printing durability can be obtained. It has been found that a resin composition for laser engraving can be provided.
Here, being excellent in sheet workability means that there is little deformation or shrinkage when the resin composition for laser engraving is processed into a sheet shape.
Although the detailed mechanism is unknown, when component B is kneaded with component A, it is presumed that a phase-separated structure is appropriately formed and shrinkage after kneading of component A is suppressed. Thereby, it is thought that sheet workability is greatly improved. In addition, it is speculated that the improvement in strength due to the crystal portion of component B is one cause of the improvement in workability.
Hereinafter, essential or optional components of the resin composition of the present invention will be described.

Component A: Polymer Having Monomer Unit Derived from Conjugated Diene Hydrocarbon The resin composition of the present invention contains, as Component A, a polymer having a monomer unit derived from a conjugated diene hydrocarbon. Component A is a polymer different from Component B described later. That is, it is a polymer having monomer units derived from conjugated diene hydrocarbons excluding transisoprene and polyoctenylene.
In the present invention, the polymer refers to a compound having a molecular weight (when having a molecular weight distribution, a weight average molecular weight) of 3,000 or more.
Component A has at least a monomer unit derived from a conjugated diene hydrocarbon. In Component A, the proportion of monomer units derived from the conjugated diene hydrocarbon is preferably 10 mol% or more in total, more preferably 30 mol% or more, and further preferably 50 mol% or more. Preferably, it is particularly preferably 70 mol% or more.

As component A, a polymer obtained by polymerizing a conjugated diene hydrocarbon, a copolymer obtained by polymerizing a conjugated diene hydrocarbon and another unsaturated compound, preferably a monoolefin unsaturated compound, etc. Is preferred. In addition, the above-mentioned polymer and copolymer may be modified, for example, a reactive group such as a (meth) acryloyl group may be introduced at the terminal, and a part of the internal olefin is hydrogen. It may be added. In the following description, polybutadiene in which part of the internal olefin is hydrogenated is also referred to as “partially hydrogenated polybutadiene”, and similarly, polyisoprene in which part of the internal olefin is hydrogenated is also referred to as “partially hydrogenated polyisoprene”. . Furthermore, the copolymer may be a random copolymer, a block copolymer, or a graft copolymer, and is not particularly limited.
The conjugated diene hydrocarbon is a hydrocarbon having a conjugated diene with a double bond separated by one single bond, and a part of it may be substituted by another atom. Examples of the other atom include a halogen atom, and specific examples include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, a chlorine atom is preferably exemplified as the substituent.

Specific examples of the conjugated diene hydrocarbon include 1,3-butadiene, isoprene, chloroprene and the like. These compounds are used alone or in combination of two or more.
Specific examples of the monoolefin unsaturated compound include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, isobutene, (meth) acrylonitrile, vinyl chloride, vinylidene chloride, (meth ) Acrylamide, (meth) acrylamide vinyl acetate, (meth) acrylic acid ester, (meth) acrylic acid and the like.

The polymer obtained by polymerizing the conjugated diene hydrocarbon or the copolymer obtained by polymerizing the conjugated diene hydrocarbon and the monoolefin unsaturated compound is not particularly limited, and specifically, Butadiene polymer, isoprene polymer, chloroprene polymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-chloroprene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-isoprene copolymer, acrylonitrile-chloroprene Copolymer, Acrylic ester-isoprene copolymer, Acrylic ester-chloroprene copolymer, Copolymer of methacrylic acid ester and conjugated diene, Acrylonitrile-butadiene-styrene copolymer, Styrene-isoprene-styrene block copolymer Polymer, steel Down - butadiene - styrene block copolymer, isobutene - isoprene copolymer (butyl rubber) and the like.
These polymers may be emulsion-polymerized or solution-polymerized.

<Polymer having monomer units derived from butadiene and / or isoprene>
In the present invention, component A is preferably a polymer having monomer units derived from butadiene and / or isoprene.
Specifically, polybutadiene, partially hydrogenated polybutadiene, terminal-modified polybutadiene, polyisoprene, partially hydrogenated polyisoprene, terminal-modified polyisoprene, SBR (styrene butadiene rubber), SBS (styrene-butadiene-styrene triblock copolymer) , ABS (acrylonitrile-butadiene-styrene copolymer), SIS (styrene-isoprene-styrene triblock copolymer), isoprene / butadiene copolymer, and the like.
The terminal modification means that the main chain or side chain terminal is modified with an amide group, a carboxy group, a hydroxy group, a (meth) acryloyl group, a glycidyl group, or the like.
Among these, polybutadiene, partially hydrogenated polybutadiene, hydroxyl-terminated polybutadiene, glycidyl ether-modified polybutadiene, polyisoprene, partially hydrogenated polyisoprene, hydroxyl-terminated polyisoprene, glycidyl ether-modified polyisoprene, SBS, and SIS are preferable. Polybutadiene, partially hydrogenated polybutadiene, polyisoprene, partially hydrogenated polyisoprene, SBS and SIS are more preferred, polybutadiene, polyisoprene, SBS and SIS are more preferred, and polybutadiene and polyisoprene are particularly preferred.

In Component A, the proportion of monomer units derived from butadiene, isoprene or hydrogenated product thereof is preferably 30 mol% or more in total, more preferably 50 mol% or more, and more preferably 80 mol% or more. More preferably it is.

Isoprene is known to polymerize by 1,2-, 3,4-, or 1,4-addition depending on the catalyst and reaction conditions. In the present invention, isoprene is polymerized by any of the above additions. Isoprene may be used. Among these, from the viewpoint of obtaining desired elasticity, it is preferable to contain cis-1,4-polyisoprene as a main component. When component A is polyisoprene, the content of cis-1,4-polyisoprene is preferably 50% by mass or more, more preferably 65% by mass or more, and 80% by mass or more. More preferably, it is particularly preferably 90% by mass or more.
Further, as the polyisoprene, natural rubber may be used, and commercially available polyisoprene may be used, and examples thereof include the NIPOL IR series (manufactured by Nippon Zeon Co., Ltd.).

Butadiene is known to be polymerized by 1,2- or 1,4-addition depending on the catalyst and reaction conditions. In the present invention, polybutadiene polymerized by any of the above additions may be used. Among these, from the viewpoint of obtaining desired elasticity, it is more preferable that 1,4-polybutadiene is a main component.
When component A is polybutadiene, the content of 1,4-polybutadiene is preferably 50% by mass or more, more preferably 65% by mass or more, and further preferably 80% by mass or more. It is preferably 90% by mass or more.
The content of the cis body and the trans body is not particularly limited, but from the viewpoint of developing rubber elasticity, the cis body is preferable, and the content of cis-1,4-polybutadiene is preferably 50% by mass or more. , 65% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more.
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.

Component A is preferably a polymer having a main chain mainly composed of isoprene or butadiene as a monomer unit, and a part thereof may be hydrogenated to be converted into a saturated bond. 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.
Among these, as the component A, polybutadiene, polyisoprene, and isoprene / butadiene copolymer are preferably exemplified from the viewpoint of solubility in a solvent and handling, polybutadiene and polyisoprene are more preferable, and polybutadiene is further preferable.

Component A has an ethylenically unsaturated group based on at least a conjugated diene hydrocarbon. In addition to this, the component A may have an ethylenically unsaturated group at the main chain terminal or side chain as described above.

Component A is preferably a plastomer or a thermoplastic elastomer. When component A is a plastomer or a thermoplastic elastomer, a flexographic printing plate precursor for laser engraving and a flexographic printing plate excellent in flexibility and rubber elasticity can be obtained, which is preferable.
Here, in the present invention, “plastomer” means that it is easily fluidly deformed by heating, as described in “New edition polymer dictionary” edited by the Society of Polymer Science, Japan (Asakura Shoten, published in 1988), and It means a polymer having the property that it can be solidified into a deformed shape by cooling. 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, the plastomer can be deformed to 200% with a small external force at room temperature (20 ° C.) when the original size is 100%, 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 is determined by the tensile test at 20 ° C. 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 except JIS K 6251 are dumbbell-shaped as specified 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.
In the above test, the elastomer can be stretched without breaking to twice the distance between the marked lines before tension, and is 60 when stretched to twice the distance between the marked lines before tension. It means a polymer having a tensile set of less than 30% after 5 minutes after holding for 5 minutes and excluding tensile external force. “Thermoplastic elastomer” means an elastomer that can be repeatedly softened by heating and cured by cooling.
Among these, component A is more preferably a plastomer. When the component A is a plastomer, the sheet processability is more excellent.

Furthermore, in this invention, it is preferable from a viewpoint of a softness | flexibility and rubber elasticity expression that the component A has a glass transition temperature (Tg) of 20 degrees C or less.
The glass transition temperature of component A is measured according to JIS K7121-1987 using a differential scanning calorimeter (DSC).
In addition, when the component A has a glass transition temperature of 2 or more, at least one is preferably 20 ° C. or lower, and all glass transition temperatures are more preferably 20 ° C. or lower. In particular, when Component A is a plastomer, when Component A has a glass transition temperature of 2 or higher, all glass transition temperatures are 20 ° C. or lower.

The weight average molecular weight of component A is 3,000 or more, preferably 10,000 or more, more preferably 10,000 to 2,000,000, still more preferably 30,000 to 1.8 million, and 50,000 to 1,500,000. It is particularly preferred that When the weight average molecular weight is 10,000 or more, the form retainability as a single resin is excellent, and when it is 2 million or less, a resin composition for laser engraving is prepared from the viewpoint of viscosity and compatibility with other components. It is suitable for.
In the present invention, the weight average molecular weight is measured by a gel permeation chromatography (GPC) method and is determined by conversion with 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. 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” and “n-propylbenzene”.

In the present invention, the component A preferably has an SP value of 9.0 or less. The SP value is also called a solubility parameter or solubility coefficient, and is a measure of the miscibility between liquids.
An SP value of 9.0 or less is preferable because resistance to solvent ink and UV ink is improved and printing durability is improved.
The SP value is more preferably from 8.0 to 9.0, and even more preferably from 8.0 to 8.5.
The SP value is calculated based on the Okitsu method described in Journal of the Japan Adhesion Society 29 (3) 1993, 204-211.

In the present invention, Component A may be used alone or in combination of two or more.
The total content of component A in the resin composition for laser engraving of the present invention is preferably 10 to 90% by mass, more preferably 20 to 85% by mass, based on the total solid content of the resin composition for laser engraving. More preferably, it is 80% by mass. When the content of component A is 10% by mass or more, printing durability sufficient to use the obtained flexographic printing plate as a printing plate can be obtained, and when it is 90% by mass or less, other components are contained. There is no shortage, and even when a flexographic printing plate is used, flexibility sufficient for use as a printing plate can be obtained.
In addition, "solid content total mass" means the total mass remove | excluding volatile components, such as a solvent, from the resin composition for laser engravings.

Component B: trans polyisoprene and / or polyoctenylene The resin composition for laser engraving of the present invention contains, as component B, at least 1 part by mass of trans polyisoprene and / or polyoctenylene with respect to 100 parts by mass of component A.
As component B, trans polyisoprene or polyoctenylene may be used alone, or both may be used in combination. Moreover, 1 mass part or more of component B is contained with respect to 100 mass parts of component A. Here, when trans polyisoprene and polyoctenylene are used in combination as Component B, the total amount of both may be 1 part by mass or more with respect to 100 parts by mass of Component A. When the content of Component B is less than 1 part by mass, the sheet processability is inferior.
The content of Component B in the resin composition for laser engraving of the present invention is 1 part by mass or more, preferably 3 parts by mass or more, and more preferably 5 parts by mass or more with respect to 100 parts by mass of Component A. preferable. Further, it is preferably 300 parts by mass or less, more preferably 150 parts by mass or less, further preferably 80 parts by mass or less, particularly preferably 50 parts by mass or less, and 35 parts by mass or less. Most preferably it is. It is preferable for the content of component B to be in the above range since sheet workability and printing durability are excellent.

Trans polyisoprene and polyoctenylene are both crystalline resins and have a melting point (Tm).
Component B is preferably a resin having a crystallinity of 5% or more. Here, the crystallinity means the ratio of the mass of the crystalline portion of the polymer solid to the total mass. When the degree of crystallinity is 5% or more, a resin composition for laser engraving that is more excellent in processability can be obtained.
The degree of crystallinity of Component B is more preferably 5 to 70%, further preferably 5 to 50%, and particularly preferably 10 to 50%.
Component A is preferably a resin having a crystallinity of less than 5%. The crystallinity of component A is more preferably 3% or less, further preferably 1% or less, and a resin having no crystal part, that is, the crystallinity is particularly 0%. preferable.
The crystallinity is measured by the density gradient method described in JIS-K7112-1999, and converted from the theoretical crystal density and the theoretical amorphous density, and calculated from the density; amorphous by X-ray diffraction Any method can be used such as a method of calculating using a halo; a method of calculating using a calorific value measured by a differential scanning calorimeter (DSC) and a calorie of melting of a complete crystal;

Trans polyisoprene is trans-1,4-polyisoprene. As a natural rubber, transpolyisoprene is a main component of gutta-percha and balata, which are rubber-like resins obtained from red iron family trees and their sap. In recent years, it has been produced by solution polymerization of isoprene using a Ziegler type catalyst.
The weight average molecular weight of trans polyisoprene is preferably 10,000 to 2,000,000, more preferably 20,000 to 1,000,000, and 25,000 to 500,000. Is more preferable. When the weight average molecular weight of transpolyisoprene is within the above range, a polymer having a high degree of crystallinity can be obtained, and the sheet processability can be improved.
Commercially available products may be used as transpolyisoprene, and examples thereof include Kuraray transpolyisoprene TP-301 (manufactured by Kuraray Co., Ltd.).

Polyoctenylene can be obtained by polymerizing cyclooctene by metathesis polymerization using 1,3-butanediene as a starting material. In the polymerization by the metathesis reaction, the double bond of cyclooctene is retained, and polyoctenylene regularly has a structure having a double bond for every 8 carbons. Depending on the molecular weight, it is a mixture of macrocycles and linear ones, but it is presumed that when the molecular weight is about several thousand to 10,000, it has a cyclic structure, and beyond that, it is linear.
The weight average molecular weight of polyoctenylene is preferably 5,000 to 2,000,000, more preferably 10,000 to 1,000,000, and further preferably 25,000 to 300,000. preferable. When the weight average molecular weight of polyoctenylene is within the above range, a polymer having a high degree of crystallinity can be obtained, and the sheet processability can be improved.
As the polyoctenylene, a commercially available product may be used. For example, Bestenamer 8012 (manufactured by Evonik) is exemplified.

The resin composition for laser engraving of the present invention contains trans polyisoprene and / or polyoctenylene as component B. Trans polyisoprene or polyoctenylene may be used alone, trans polyisoprene having different molecular weight or crystallinity, or polyoctenylene may be used in combination, and trans polyisoprene and polyoctenylene may be used in combination. It is not limited. Among these, it is preferable to use trans polyisoprene or polyoctenylene, and it is particularly preferable to use polyoctenylene.
The total content of component B in the resin composition for laser engraving of the present invention is preferably from 1 to 60 mass%, more preferably from 3 to 40 mass%, based on the total solid content of the resin composition for laser engraving. More preferred is 25% by mass. By making the content of component B 1% by mass or more, processability is excellent. Further, when the content is 60% by mass or less, other components are not deficient, and printing durability sufficient for use as a printing plate can be obtained even when a flexographic printing plate is used.

In the present invention, the resin composition for laser engraving may contain a polymer component other than Component A and Component B, and the content thereof is 0 to 5% by mass relative to the total mass of the solid content of the resin composition. It is preferably 0 to 3% by mass, more preferably 0 to 1% by mass, and most preferably not contained.

Component C: Crosslinking Agent The resin composition for laser engraving of the present invention may contain a crosslinking agent as Component C in order to promote the formation of a crosslinked structure.
As the cross-linking agent of the present invention, any compound that promotes cross-linking of internal olefins of component A and component B can be used without limitation among those skilled in the art, but is known as a radical polymerization initiator. It is preferable to use the compound of. Moreover, although both a thermal polymerization initiator and a photoinitiator can be used, it is preferable to use a thermal polymerization initiator. Although described in detail below, the present invention is not limited by these descriptions.

In the present invention, preferred crosslinking agents include: a: aromatic ketones, b: onium salt compounds, c: organic peroxides, d: thio compounds, e: hexaarylbiimidazole compounds, f: ketoxime ester compounds, g: borate compound, h: azinium compound, i: metallocene compound, j: active ester compound, k: compound having carbon halogen bond, l: azo compound, and the like. As the above a to l, compounds described in paragraphs 0074 to 0118 of JP-A-2008-63554 can be preferably used. Specific examples of the above a to l are given below, but the present invention is not limited thereto.

In the present invention, a: aromatic ketones, c: organic peroxide, and l: from the viewpoints of engraving sensitivity and good relief edge shape when applied to the relief forming layer of a flexographic printing plate precursor. Azo compounds are more preferred, a: aromatic ketones and c: organic peroxides are more preferred, and c: organic peroxides are particularly preferred.
Further, as a: aromatic ketones, c: organic peroxides, and l: azo compounds, the following compounds are preferable.

a: Aromatic ketones Preferred as a crosslinking agent that can be used in the present invention a: Aromatic ketones include benzophenone, 4,4′-bis (dimethylamino) benzophenone, 4,4′-bis (diethylamino) benzophenone 4,4'-dichlorobenzophenone, 1-hydroxycyclohexyl phenyl ketone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1, 2-tolyl-2-dimethylamino-1- ( Benzophenones or acetophenones such as 4-morpholinophenyl) butanone-1,2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-1-propane are preferred, and acetophenone is more preferred.

c: Organic peroxide Preferred as a crosslinking agent that can be used in the present invention c: As the 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-isopropylcumylperoxycarbonyl) benzophenone Di-t-butyldiperoxyisophthalate, t-butylperoxybenzoate, t-butylperoxy-3-methylbenzoate, t- Butyl peroxylaurate, t-butyl peroxypivalate, t-butyl peroxy-2-ethylhexanoate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxyneo Peroxyesters such as heptanoate, t-butylperoxyneodecanoate, t-butylperoxyacetate, α, α'-di (t-butylperoxy) diisopropylbenzene, t-butylcumyl peroxide Di-t-butyl peroxide, dicumyl peroxide, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy-2-ethylhexyl monocarbonate are preferred, and dicumyl peroxide, α, α'-di (t -Butylperoxy) diisopropylbenzene is more preferred, dicumyl Peroxide is more preferred.
Moreover, the product marketed can also be used as an organic peroxide, and perbutyl E and park mill D40 (above, NOF Corporation make) are illustrated.

l: Azo-based compound Preferred as a crosslinking agent that can be used in the present invention: l: Azo-based compounds include 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-methylpropionamide oxime) 2,2′-azobis [2- (2-imidazolin-2-yl) propane], 2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl ] 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-trimethyl) Pentane) and the like.

In addition, as said crosslinking agent in this invention, said c: organic peroxide is preferable from a viewpoint of the crosslinkability of a resin composition, and also as an unexpected effect, it is especially preferable from a viewpoint of engraving sensitivity improvement.

In this invention, a crosslinking agent may be used individually by 1 type, and may use 2 or more types together.
In the present invention, the content of component C in the resin composition for laser engraving is preferably 0.1 to 10% by mass, and preferably 0.5 to 5% by mass with respect to the total solid content of the resin composition. %, More preferably 0.8 to 3% by mass.

Component D: Photothermal Conversion Agent The resin composition for laser engraving of the present invention preferably further contains a photothermal conversion agent as Component D, and the photothermal conversion agent can absorb light having a wavelength of 700 to 1,300 nm. It is more preferable. 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.

In the case of laser engraving the crosslinked relief forming layer in the flexographic printing plate precursor for laser engraving of the present invention using a laser (YAG laser, semiconductor laser, fiber laser, surface emitting laser, etc.) emitting infrared rays of 700 to 1,300 nm as a light source As the photothermal conversion agent, a compound having a maximum absorption wavelength at 700 to 1,300 nm is preferably used.
Various dyes or pigments are used as the photothermal conversion agent that can be used 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 in the range of 700 to 1,300 nm. Azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, diimmonium compounds, quinone imines And dyes such as dyes, 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 pigments include black pigments, yellow pigments, orange pigments, brown pigments, red pigments, purple pigments, blue pigments, green pigments, fluorescent pigments, metal powder pigments, and other polymer-bonded dyes. Specifically, insoluble azo pigments, azo lake pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, anthraquinone pigments, perylene and perinone pigments, thioindigo pigments, quinacridone pigments, dioxazine pigments, isoindolinone pigments In addition, quinophthalone pigments, dyed lake pigments, azine pigments, nitroso pigments, nitro pigments, natural pigments, fluorescent pigments, inorganic pigments and the like can be used. Among these pigments, a black pigment is preferable, and examples thereof include carbon black and titanium black. From the viewpoint of availability, carbon black is preferable.

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.
In the present invention, carbon black having a relatively low specific surface area and relatively low dibutyl phthalate (DBP) absorption and fine carbon black having a large specific surface area can be used. Examples of suitable carbon black include Printex (registered trademark) U, Printex (registered trademark) A, or Specialschwarz (registered trademark) 4 (manufactured by Degussa), # 45L (manufactured by Mitsubishi Chemical Corporation).

The carbon black that can be used in the present invention preferably has a DBP oil absorption of less than 150 ml / 100 g. It is more preferably 100 ml / 100 g or less, and further preferably 70 ml / 100 g or less.
Carbon black is a conductive carbon black having a BET specific surface area of at least 100 m ² / g from the viewpoint of improving engraving sensitivity by efficiently transferring heat generated by photothermal conversion to surrounding polymers. preferable.

The above-described carbon black may be acidic or basic carbon black. The carbon black is preferably basic carbon black. Of course, mixtures of different binders can also be used.

When carbon black is used as the photothermal conversion agent, thermal crosslinking is preferred from the viewpoint of film curability rather than photocrosslinking utilizing UV light or the like, and the above-mentioned preferred combination component (component C) crosslinking agent. It is more preferable to use it in combination with an organic peroxide, because the engraving sensitivity is extremely high.
In the resin composition for laser engraving of the present invention, a polymerization initiator (more preferably a thermal polymerization initiator) as a crosslinking agent and a photothermal conversion agent capable of absorbing light having a wavelength of 700 to 1,300 nm are used in combination. It is particularly preferable to use an organic peroxide as component C and carbon black as component D in combination. In the above embodiment, during laser engraving, the polymerization initiator (preferably thermal polymerization initiator) remaining in the crosslinked relief forming layer is decomposed by the heat generated from the photothermal conversion agent, and component A and the like are decomposed. This can be further promoted and the engraving sensitivity can be improved.

In the resin composition for laser engraving of the present invention, only one type of component D may be used, or two or more types may be used in combination.
The content of component D: photothermal conversion agent in the resin composition for laser engraving of the present invention varies greatly depending on the molecular extinction coefficient inherent to the molecule, but is 2 to 2 with respect to the total solid mass of the resin composition. 60 mass% is preferable, 5-30 mass% is more preferable, and 5-20 mass% is still more preferable.

Component E: Factis The resin composition for laser engraving of the present invention preferably contains Component E: Factis.
As for factice, only 1 type may be used and 2 or more types may be used together.
Here, the factis refers to a rubber-like substance obtained by reacting oil and fat with a crosslinking agent. Note that the factis is also called a sub-rubber-substate, as will be described later.
Examples of the fats and oils include vegetable oils, fish oils, mineral oils (eg, naphthenic mineral oils), synthetic esters, modified alkyd resins, and the like. Among these, vegetable oils are preferred. Examples of vegetable oils include rapeseed oil (rapeseed white squeezed oil, rapeseed industrial oil), refined rapeseed oil, hydrogenated rapeseed oil, soybean oil, and the like. As a crosslinking agent used for manufacture of factice, sulfur, sulfur chloride, an organic peroxide, isocyanate, etc. are mentioned, for example, Sulfur and sulfur chloride are preferable, and sulfur is more preferable.

From the viewpoint of sustaining the anti-aging effect, the factis is preferably at least one selected from the group consisting of a sulfur factis and a sulfur chloride factice.
From the standpoint of migration control, the factis is at least selected from the group consisting of (a) a sulfur factice having an acetone extract of 10 to 50%, and (b) a sulfur chloride factice having an acetone extract of 1 to 10%. More preferably, it is one.
Here, “acetone extract (%)” is a value calculated as follows.
About 0.5 g of the factice sample is wrapped in filter paper or placed in a cylindrical filter paper and placed in the siphon cup of the Kunefrel extractor. Moreover, 50 mL of acetone is put into the extraction flask. Extraction is performed while heating. After 15 minutes of preheating, the heating is adjusted so that the acetone in the siphon cup falls about every 3 minutes. The extraction time is 3 hours continuously. After the extraction is completed, the recovery cup is attached to the extraction device instead of the siphon cup, the extract is recovered, and after acetone is distilled off, it is immediately dried on an air bath at 105 ± 2 ° C. for about 30 minutes. After standing to cool, the mass of the extract is measured, and the acetone extract (%) is calculated by the following formula.
Acetone extract (%) = 100 × mass of extract (g) / sample mass (g)

From the viewpoint of crosslinking speed and rubber physical properties, the factis is more preferably a sulfur factice or a sulfur chloride factice with an acetone extract of 1 to 50%, and a sulfur chloride factice with an acetone extract of 2 to 7%. It is particularly preferred.
Examples of commercially available Factis products are “Golden Factis” series, “Black Sub” series, “Neo Factis” series, “White Sub” series, “Ame Sub” series, “Sulfur-free Factis” manufactured by Tenma Sub Chemical Co., Ltd. (Powder type) "series products, among which" Golden factis "series products (eg Golden T)," Black Sub "series products (eg Black Sub A, Black Sub 30, Black sub 21), “Neo factis” series products (eg Neo N), “White sub” series products (eg white sub S, white sub 1) are preferred, “Golden factis” series, “Neo factis” series “White Sub” series products are more preferred, and “White Sub” series products are even more preferred. Moreover, what solidified the product of "Sulfur-free factice (liquid type)" series made by Tenma Sub Chemical Co., Ltd. with a crosslinking agent may be used as the solid factice.

The addition amount of factice is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, and still more preferably 15 to 35% by mass with respect to the total mass of the solid content of the resin composition for laser engraving.

Component F: Solvent The resin composition for laser engraving of the present invention may contain a solvent as Component F.
The solvent used in preparing the resin composition for laser engraving of the present invention is preferably mainly an aprotic organic solvent from the viewpoint of solubility of each component. More specifically, aprotic organic solvent / protic organic solvent is preferably used at 100/0 to 50/50 (mass ratio), and preferably used at 100/0 to 70/30 (mass ratio). More preferably, it is more preferably used at 100/0 to 90/10 (mass ratio).
Preferred 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 and dimethyl sulfoxide.
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 preferable.

In the present invention, from the viewpoint that it is preferable to knead and mold the resin composition for laser engraving, the resin composition for laser engraving preferably contains no solvent or the content of the solvent is 10% by mass or less ( Hereinafter, “not contained” or that the content is 10% by mass or less is described as “contained from 0 to 10% by mass”.) This is preferable because a flexographic printing plate precursor for laser engraving can be produced without going through a solvent removal step. The content of the solvent is more preferably 0 to 5% by mass, still more preferably 0 to 3% by mass, and particularly preferably 0% by mass.

<Other additives>
In the resin composition for laser engraving of the present invention, additives other than the above components A to E can be appropriately blended as long as the effects of the present invention are not impaired. Examples include waxes, process oils, organic acids, metal oxides, fragrances, antiozonants, antioxidants, thermal polymerization inhibitors, colorants, etc., and these may be used alone. Two or more kinds may be used in combination.

[Process oil]
When process oil is used, for example, aromatic process oil, naphthenic process oil, and paraffinic process oil can be mentioned. The addition amount is preferably 1 to 70 parts by mass with respect to 100 parts by mass of component A.

[Organic acid, metal oxide]
The organic acid can be used as an auxiliary agent for vulcanization acceleration in combination with a conventional vulcanizing agent as a metal salt. Examples of the organic acid include stearic acid, oleic acid, and myristic acid. Examples of the metal source used in combination include metal oxides such as zinc oxide (zinc white) and magnesium oxide. In these vulcanization processes, organic acids and metal oxides form metal salts in the rubber, and the activation of vulcanizing agents such as sulfur is promoted. The addition amount of the metal oxide for forming such a metal salt in the system is preferably 0.1 to 10 parts by mass, more preferably 2 to 10 parts by mass with respect to 100 parts by mass of Component A.
The addition amount of the organic acid is preferably 0.1 to 5 parts by mass, more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of Component A.

[Fragrance]
The resin composition for laser engraving of the present invention preferably contains a fragrance in order to reduce odor. The fragrance is effective for reducing the odor during the production of the flexographic printing plate precursor and during laser engraving.
By containing the fragrance | flavor, the resin composition for laser engravings of this invention can mask the solvent odor which volatilizes when drying the liquid resin composition apply | coated during manufacture. Further, it is possible to mask unpleasant odors such as amine odor, ketone odor, aldehyde odor, and burnt odor on resin nose generated during laser engraving.
As the fragrance, reference is made to paragraphs 0081 to 0088 of JP 2011-245818 A.

The content of the fragrance is preferably 0.003 to 1.5% by mass, more preferably 0.005 to 1.0% by mass, based on the total mass of the solid content of the resin composition. Within the above range, the masking effect can be sufficiently exhibited, the fragrance of the fragrance is moderate, the working environment is improved, and the engraving sensitivity is excellent.

To the resin composition for laser engraving of the present invention, nitrocellulose or a highly heat conductive material may be added as an additive for improving engraving sensitivity.
Since nitrocellulose is a self-reactive compound, it generates heat during laser engraving and assists in the thermal decomposition of coexisting binder polymers. As a result, it is estimated that the engraving sensitivity is improved.
The highly heat conductive material is added for the purpose of assisting heat transfer, and examples of the heat conductive material include inorganic compounds such as metal particles and organic compounds such as a conductive polymer. As the metal particles, the conductive polymer is preferably a gold fine particle, silver fine particle, or copper fine particle having a particle size of micrometer order to several nanometer order. Particularly preferred is a conjugated polymer, and specific examples include polyaniline and polythiophene. It is done.
Moreover, the sensitivity at the time of photocuring the resin composition for laser engraving can be further improved by using a co-sensitizer.
Furthermore, it is preferable to add a small amount of a thermal polymerization inhibitor in order to prevent unnecessary thermal polymerization of the polymerizable compound during the production or storage of the composition.
Colorants such as dyes or pigments may be added for the purpose of coloring the resin composition for laser engraving. Thereby, properties such as the visibility of the image portion and the suitability of the image density measuring device can be improved.

In this invention, it is preferable that the resin composition for laser engraving does not contain a polymerizable monomer and a polymerizable oligomer. By containing a polymerizable monomer or polymerizable oligomer, the viscosity of the resin composition for laser engraving decreases, and shrinkage due to polymerization may occur, so that the sheet processability may be deteriorated.
Here, in the present invention, the polymerizable monomer means a compound having at least one polymerizable group, preferably a radical polymerizable group in the molecule, and having a molecular weight of less than 1,000. The polymerizable oligomer is a compound having at least one polymerizable group, preferably a radical polymerizable group in the molecule, and means a compound having a molecular weight of 1,000 or more and less than 3,000.
The content of the polymerizable monomer and polymerizable oligomer is preferably 0 to 5% by mass, more preferably 0 to 3% by mass, and more preferably 0 to 3% by mass with respect to the solid content of the resin composition for laser engraving. The content is more preferably 1% by mass, and it is particularly preferably not contained, that is, 0% by mass.

2. Flexographic printing plate precursor for laser engraving and manufacturing method thereof (flexographic printing plate precursor for laser engraving)
The first embodiment of the flexographic printing plate precursor for laser engraving in the present invention has a relief forming layer comprising the resin composition for laser engraving of the present invention.
Further, the second embodiment of the flexographic printing plate precursor for laser engraving in the present invention has a crosslinked relief forming layer obtained by crosslinking the relief forming layer made of the resin composition for laser engraving of the present invention.
In the present invention, “a flexographic printing plate precursor for laser engraving” means a state in which a relief-forming layer having a crosslinkability made of a resin composition for laser engraving is in a state before being crosslinked and cured by light or heat. Both or either one.
In the present invention, the “relief-forming layer” refers to a layer in a state before being crosslinked, that is, a layer made of the resin composition for laser engraving of the present invention, and may be dried if necessary. Good.
In the present invention, the “crosslinked relief forming layer” refers to a layer obtained by crosslinking the relief forming layer. The crosslinking can be performed by heat and / or light. In addition, the crosslinking is not particularly limited as long as the resin composition is cured, and is a concept including a crosslinked structure by a reaction between components A, a reaction between components B, and a reaction between components A and B, Any cross-linked structure may be used.
A “flexographic printing plate” is produced by laser engraving a printing plate precursor having a crosslinked relief forming layer.
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 resin composition for laser engraving of the present invention can be widely used for applications other than forming a relief forming layer of a flexographic printing plate precursor subjected to laser engraving without any particular limitation. For example, not only the relief forming layer of the printing plate precursor that forms the convex relief described in detail below by laser engraving, but also other material shapes that form irregularities and openings on the surface, such as intaglio, stencil, stamp, etc. It can be applied to the formation of various printing plates and various molded articles on which necessary images are formed by laser engraving.
The resin composition of the present invention is preferably used to form a relief-forming layer on a suitable support to form a flexographic printing plate precursor for laser engraving.

The flexographic printing plate precursor for laser engraving in the present invention has a relief forming layer made of a resin composition for laser engraving containing the above components. The (crosslinked) relief forming layer is preferably provided on the support.
The flexographic printing plate precursor for laser engraving further has an adhesive layer between the support and the (crosslinked) relief forming layer, if necessary, and a slip coat layer and a protective film on the (crosslinked) relief forming layer. May be.

<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 precursor using the flexographic printing plate precursor for laser engraving includes a flexographic printing plate precursor having a crosslinked relief forming layer by crosslinking the relief forming layer, and then a crosslinked relief forming layer (hard relief forming layer). A mode in which a relief layer is formed by laser engraving to produce a flexographic printing plate is preferred. 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 flexographic printing plate precursor for laser engraving is not particularly limited, but materials having high dimensional stability are preferably used. For example, metals 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.
Examples of materials (adhesives) that can be used for the adhesive layer include: 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 is not peelable or, on the contrary, 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.

(Method for manufacturing flexographic printing plate precursor for laser engraving)
The method for producing the flexographic printing plate precursor for laser engraving is not particularly limited. For example, a resin composition for laser engraving is prepared, and the solvent is removed from the resin composition for laser engraving as necessary. Later, the method of extruding on a support body and the method of pressing are 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 flexographic printing plate precursor for laser engraving in the present invention includes a layer forming step for forming a relief forming layer comprising the resin composition for laser engraving of the present invention, and heat and / or light on the relief forming layer. It is preferable that the production method includes a crosslinking step of obtaining a flexographic printing plate precursor having a crosslinked relief-forming layer crosslinked by the above.

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 a protective film is used, a method of first laminating a relief forming layer on the protective film and then laminating the support may be employed.
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 flexographic printing plate precursor for laser engraving in 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 the relief forming layer, the resin composition for laser engraving of the present invention is prepared, and if necessary, after removing the solvent from the resin composition for laser engraving, the method of extruding onto the support, There is a method using a press or a method in which the resin composition for laser engraving of the present invention is prepared, the resin composition for laser engraving of the present invention is cast on a support, and this is dried in an oven to remove the solvent. Preferred examples can be given.

In the present invention, the layer forming step preferably includes a step of kneading the resin composition for laser engraving of the present invention and a step of molding the obtained kneaded product into a sheet shape. For the step of forming into a sheet, any of extrusion, pressing, calendaring, etc. may be used. Examples of the extrusion process include rubber extrusion and melt extrusion, and examples of the press process include hot press. Among these, the step of forming into a sheet shape is preferably extrusion or pressing, and more preferably formed into a sheet shape by extrusion or hot pressing.
Here, when forming into a sheet form by hot pressing (hot pressing), the processing temperature is preferably 20 ° C. to 130 ° C., more preferably 40 ° C. to 100 ° C., and 50 ° C. to 80 ° C. More preferably.
When forming into a sheet by extrusion, the processing temperature is preferably 40 ° C. to 130 ° C., more preferably 50 ° C. to 100 ° C., and further preferably 60 ° C. to 80 ° C.

The resin composition for laser engraving is preferably prepared, for example, by kneading components A and B and optional components C to E and other components.
In kneading, considering the crosslinking reaction by component C, component C is preferably added after kneading other components such as component A, component B and component D.
Alternatively, components A and B, and optional components C to E and other components may be dissolved or dispersed in a suitable solvent, and then these solutions may be mixed. Since most of the solvent components are preferably removed at the stage of producing the flexographic printing plate precursor, the solvent is a low-molecular alcohol that easily volatilizes (eg, 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 (crosslinked) relief forming layer in the flexographic printing plate precursor for laser engraving is preferably from 0.05 mm to 10 mm, more preferably from 0.05 mm to 7 mm, and more preferably from 0.05 mm to 3 mm before and after crosslinking. Further preferred.

<Crosslinking process>
The method for producing a flexographic printing plate precursor for laser engraving in the present invention may be a production method including a crosslinking step of obtaining a flexographic printing plate precursor having a crosslinked relief forming layer obtained by crosslinking the relief forming layer with heat and / or light. Preferably, the production method includes a crosslinking step for obtaining a flexographic printing plate precursor having a crosslinked relief-forming layer obtained by crosslinking the relief-forming layer with heat.
In this step, polymerization inhibition may occur in the presence of oxygen. Therefore, crosslinking may be performed in a state in which at least the central part of the surface of the relief forming layer is covered with a material capable of blocking air. Moreover, it is preferable to bridge | crosslink in the state which sealed the relief formation layer with the material which can interrupt | block air.
In addition, the surface of the relief forming layer may be cross-linked in direct contact with air, or the relief forming layer may be cross-linked in a vacuumed state with a sheet of a material capable of blocking air such as vinyl chloride. .
By heating the flexographic printing plate precursor for laser engraving, the relief forming layer can be crosslinked (thermal crosslinking step). As a heating means for crosslinking by heat, a printing plate precursor is heated for a predetermined time in a hot air oven or a far-infrared oven, a method of contacting a heated roll for a predetermined time, or pressing while heating with a hot press machine. The method (hot press) is mentioned.
By crosslinking the relief forming layer, there is an advantage that the relief formed first after laser engraving becomes sharp, and second, the adhesiveness of engraving residue generated during laser engraving is suppressed.

Moreover, in order to form bridge | crosslinking using a photoinitiator etc. as a crosslinking agent, you may perform bridge | crosslinking by light.
When the relief-forming layer contains a photopolymerization initiator, the relief-forming layer is crosslinked by irradiating the relief-forming layer with light that triggers the photopolymerization initiator (also referred to as “active light”). Can do.
The light irradiation is generally performed on the entire surface of the relief forming layer. Examples of light include visible light, ultraviolet light, and electron beam, but ultraviolet light is the most common. 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, actinic rays may be irradiated after the relief forming layer is covered with a vinyl chloride sheet and evacuated.

3. Flexographic printing plate and plate making method thereof The method of making a flexographic printing plate in the present invention comprises the steps of preparing the flexographic printing plate precursor for laser engraving in the present invention, and the engraving step of laser engraving the flexographic printing plate precursor for laser engraving It is preferable to contain.
The flexographic printing plate in the present invention is obtained by making a plate by the above-described flexographic printing plate making method.

<Engraving process>
The method for making a flexographic printing plate in the present invention preferably 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 the engraving depth can be set arbitrarily, so that the structure can be controlled three-dimensionally. For example, the 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 the portion of the 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 Electronic Communication Society, and the like.
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 a flexographic printing plate precursor according to the present invention is disclosed in JP 2009-172658 A and JP 2009-214334 A. Which can be used for making a flexographic printing plate according to the present invention.

<Other processes>
In the plate making method of the flexographic printing plate in the present invention, the following rinsing step, drying step, and / or post-crosslinking step may be included as necessary after the engraving step.
Rinsing step: a step of rinsing the engraved surface of the relief layer after engraving with an aqueous rinse solution.
Drying step: A step of drying the relief layer after the rinsing step.
Post-crosslinking step: a step of imparting energy to the relief layer after engraving and further crosslinking the relief layer.
Since the engraving residue has adhered to the engraving surface after the above steps, a rinse step is added to rinse the engraving residue by rinsing the engraving surface with an aqueous rinsing liquid (hereinafter also simply referred to as “rinsing liquid”). May be. The aqueous rinse liquid is water or a liquid containing water as a main component. 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 pH of the rinsing solution that can be used in the present invention is preferably 9 or more, more preferably 10 or more, and still more preferably 11 or more. The pH of the rinsing liquid is preferably 14 or less, more preferably 13.5 or less, still more preferably 13.2 or less, and particularly preferably 12.5 or less. Handling is easy in the said range.
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.
The rinsing liquid that can be used in the present invention preferably contains water as a main component.
Moreover, the rinse liquid may contain water miscible solvents, such as alcohol, acetone, tetrahydrofuran, as solvents other than water.

It is preferable that the rinse liquid contains a surfactant.
As a surfactant that can be used in the present invention, a carboxybetaine compound, a sulfobetaine compound, a phosphobetaine compound, an amine oxide compound, or a viewpoint of reducing engraving residue removal and the 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.
The amount of the surfactant used is not particularly limited, but is preferably 0.01 to 20% by mass, and more preferably 0.05 to 10% by mass with respect to the total mass of the rinsing liquid.

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.
The Shore A hardness in this specification is quantified by measuring the amount of deformation (indentation depth) by indenting and deforming an indenter (called a push needle or indenter) on the surface to be measured at 25 ° C. It 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, but the present invention is not limited to these examples. Unless otherwise specified, “parts” and “%” represent “parts by mass” and “mass%”. In addition, the number average molecular weight (Mn) and the weight average molecular weight (Mw) of the compounds in the examples are the values measured by gel permeation chromatography (GPC) method (eluent: tetrahydrofuran) unless otherwise specified. Yes.

The details of Component A to Component E used in each Example and Comparative Example are as follows.
(Component A) Polymer having monomer units derived from conjugated diene hydrocarbon A-1: UBEPOL BR 130B (manufactured by Ube Industries), polybutadiene, Mw = 340,000, plastomer A-2: UBEPOL BR 150 (manufactured by Ube Industries, Ltd.), polybutadiene, Mw = 470,000, plastomer A-3: UBEPOL BR 150L (manufactured by Ube Industries, Ltd.), polybutadiene, Mw = 500,000, plastomer A-4: Nipol IR2200 (Nippon Zeon Co., Ltd., polyisoprene, Mw = 1,500,000, plastomer A-5: Kraton D1102 (manufactured by Kraton), styrene-butadiene block copolymer, Mw = 80,000, thermoplastic elastomer A -6: Kraton D1161 (Kraton Styrene-butadiene block copolymer, Mw = 120,000, thermoplastic elastomer A-7: Denkachloroprene M-40 (manufactured by Denki Kagaku Kogyo Co., Ltd.), chloroprene rubber, thermoplastic elastomer A-8 (comparison) Example): Purple light UV-3000B (manufactured by Nippon Synthetic Chemical Co., Ltd.), urethane acrylate, Mw = 18,000, thermoplastic elastomer A-1 to A-8 have a crystallinity of less than 1%.

(Component B) trans polyisoprene and / or polyoctenylene B-1: TP-301 (manufactured by Kuraray Co., Ltd.), trans-1,4-polyisoprene, melting point 67 ° C., trans bond 99%, crystallinity 36%, Weight average molecular weight 250,000
B-2: Bestenamer 8012 (manufactured by Evonik), polyoctenylene, melting point 54 ° C., crystallinity 33%, weight average molecular weight 90,000
B-3 (comparative example): BR810 (manufactured by JSR Corporation), syndiotactic 1,2-polybutadiene, crystallinity 18%, weight average molecular weight 180,000

(Component C) Crosslinking agent PCD-40: Park mill D40 (manufactured by NOF Corporation), dicumyl peroxide, purity 40%

(Component D) Photothermal conversion agent # 45L: Mitsubishi carbon black # 45L (manufactured by Mitsubishi Chemical Corporation), carbon black, arithmetic average particle diameter 24 nm, DBP oil absorption 45 ml / 100 g, pH 8, BET specific surface area (JIS K 6217) 125 m ² / g

(Component E) Factis White Sub 1: Acetone extract; 2 to 5%, Sulfur Chloride Factis made from refined rapeseed oil, manufactured by Tenma Sub Chemical Co., Ltd. Black Sub 21: Acetone extract 19 to 27%, mainly vegetable oil Sulfur factice used as raw material, manufactured by Tenma Sub Chemical Co., Ltd.

(Examples 1 to 29 and Comparative Examples 1 to 13)
1. Preparation of resin composition for laser engraving Predetermined amounts of Component A, Component B, Component D and Component E listed in Tables 1 and 2 were added to a Banbury mixer and kneaded at 80 ° C. and 100 rpm for 10 minutes. Thereafter, 0.1 to 5 wt% of Component C was added to the above mixture and kneaded at 10 rpm for 10 minutes to obtain a kneaded product (resin composition for laser engraving) of a crosslinkable relief forming layer. In the table, the description of “-” means that the corresponding component is not contained.

2. Preparation of flexographic printing plate precursor for laser engraving-1 (Making a kneaded sheet)
The kneaded material obtained above and a spacer having a predetermined film thickness (0.8 mm) were placed in a hot press machine and pressed at 60 ° C. and 15 MPa for 1 minute to prepare an uncrosslinked sheet. The obtained sheet was subjected to a shrinkage test for workability evaluation.

3. Preparation of flexographic printing plate precursor for laser engraving -2
The uncrosslinked sheet obtained as described above and a spacer having a predetermined film thickness were placed in a hot press machine and crosslinked by pressing at 160 ° C. and 15 MPa for 20 minutes to obtain a flexographic printing plate precursor for laser engraving.

(Evaluation methods)
<Sheet workability>
An uncrosslinked kneaded product and a spacer having a predetermined film thickness were placed in a hot press machine, and a sheet was produced by pressing at 60 ° C. and 15 MPa for 1 minute. The obtained sheet was taken out, and the workability was evaluated by calculating the shrinkage after 5 minutes.
The evaluation criteria are as follows. If the evaluation result is 1 to 3, there is no practical problem.
1: Shrinkage rate of less than 5% 2: Shrinkage rate of 5% or more and less than 10% 3: Shrinkage rate of 10% or more and less than 20% 4: Shrinkage rate of 20% or more and less than 30% 5: Shrinkage rate of 30% or more

<Ink resistance: Swell ratio measurement>
The flexographic printing plate precursor was cut into about 1 cm square and placed in a sample bottle. Thereto was added 2 mL of solvent ink (UV flexo indigo PHA, manufactured by T & K TOKA, SP value 9.2 to 11.1), and the mixture was allowed to stand at 20 ° C. After 24 hours, the flexographic printing plate precursor was taken out, the mass after wiping the surface was measured, and the swelling ratio was calculated by the following equation.
Swelling ratio (mass%) = (mass after immersion) / (mass before immersion) × 100
This value is preferably as close to 100 wt%.
The evaluation criteria are as follows. If the evaluation result is 1, there is no practical problem.
1: Less than 105 mass% swelling ratio 2: 105 mass% or more swelling ratio

<Print durability>
Log (tan δ / ε) was adopted as an index of printing durability.
Here, tan δ is a value at 50 ° C. and 1 Hz, and ε is elongation at break [%] / 100.
When the printing durability index is less than -1.6, the printing durability is 40 km or more with respect to the solvent ink. The evaluation criteria are as follows. If the evaluation standard is 1 or 2, there is no practical problem.
1: Log (tan δ / ε) is less than −2.0 2: Log (tan δ / ε) is −2.0 or more and less than −1.6 3: Log (tan δ / ε) is −1.6 or more

Claims

As component A, a polymer having a monomer unit derived from a conjugated diene hydrocarbon,
Component B contains trans polyisoprene and / or polyoctenylene in an amount of 1 part by mass or more based on 100 parts by mass of Component A,
Component A is a polymer different from Component B, A resin composition for laser engraving.
The resin composition for laser engraving according to claim 1, wherein the component A has an SP value of 9 or less.
The resin composition for laser engraving according to claim 1 or 2, wherein Component A contains a monomer unit derived from butadiene and / or isoprene.
The resin composition for laser engraving according to any one of claims 1 to 3, wherein Component A has a weight average molecular weight of 10,000 or more.
The resin composition for laser engraving according to any one of claims 1 to 4, wherein Component A is a plastomer or a thermoplastic elastomer.
6. The resin composition for laser engraving according to claim 1, further comprising a crosslinking agent as Component C.
The resin composition for laser engraving according to claim 6, wherein Component C is an organic peroxide.
The resin composition for laser engraving according to any one of claims 1 to 7, further comprising a photothermal conversion agent as Component D.
9. The resin composition for laser engraving according to any one of claims 1 to 8, further comprising factice as component E.
10. The resin composition for laser engraving according to any one of claims 1 to 9, wherein the resin composition for laser engraving contains 0 to 5% by mass of a solvent.
A flexographic printing plate precursor for laser engraving, comprising a relief forming layer comprising the resin composition for laser engraving according to any one of claims 1 to 10 on a support.
A flexographic printing plate precursor for laser engraving, comprising a crosslinked relief forming layer obtained by crosslinking the relief forming layer comprising the resin composition for laser engraving according to any one of claims 1 to 10 by heat and / or light on a support. .
The flexographic printing plate precursor for laser engraving according to claim 12, comprising a crosslinked relief forming layer crosslinked by heat.
A layer forming step of forming a relief forming layer comprising the resin composition for laser engraving according to any one of claims 1 to 10, and
A method for producing a flexographic printing plate precursor for laser engraving, comprising a crosslinking step of obtaining a flexographic printing plate precursor having a crosslinked relief forming layer by crosslinking the relief forming layer with heat and / or light.
The layer forming step includes a step of kneading the resin composition for laser engraving according to any one of claims 1 to 10, and a step of molding the obtained kneaded product into a sheet shape. A method for producing a flexographic printing plate precursor for laser engraving as described in 1 above.
The method for producing a flexographic printing plate precursor for laser engraving according to claim 15, wherein the step of forming into a sheet is a step of forming into a sheet by hot pressing or extrusion.
The method for producing a flexographic printing plate precursor for laser engraving according to any one of claims 14 to 16, wherein in the crosslinking step, the relief forming layer is crosslinked by heat.
Preparing a flexographic printing plate precursor for laser engraving according to any one of claims 11 to 13, and
A method for making a flexographic printing plate, comprising: an engraving step of laser engraving a flexographic printing plate precursor for laser engraving to form a relief layer.
The plate making method of a flexographic printing plate according to claim 18, further comprising a rinsing step of rinsing the relief layer surface with an aqueous rinsing liquid after the engraving step.
A flexographic printing plate made by the plate making method according to claim 18 or 19.