WO2015194427A1 - Flexographic printing plate precursor for laser engraving use and method for production thereof, and flexographic printing plate and method for production thereof - Google Patents

Abstract

The present invention addresses the problem of providing: a flexographic printing plate precursor for laser engraving use, from which a printing plate that has a dot image area improved in a printing pressure latitude can be produced; a method for producing the flexographic printing plate precursor; a flexographic printing plate; and a method for producing the flexographic printing plate. The flexographic printing plate precursor for laser engraving use according to the present invention comprises a first crosslinked relief-forming layer which is arranged on the laser-engraving surface side of the flexographic printing plate precursor and a second crosslinked relief-forming layer which is adjacent to the first crosslinked relief-forming layer, wherein the ratio of the Martens' hardness of the first crosslinked relief-forming layer to that of the second crosslinked relief-forming layer is 1.1 or more, the first crosslinked relief-forming layer has a thickness of 10 to 300 μm, the second crosslinked relief-forming layer has a thickness of 500 to 1600 μm, the first crosslinked relief-forming layer contains a binder polymer and a light-to-heat conversion material, and the second crosslinked relief-forming layer is a layer which is produced by forming a relief-forming layer using a resin composition containing a diene polymer and a thermal crosslinking agent and then causing crosslinking in the relief-forming layer.

Description

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 flexographic printing plate precursor for laser engraving and a manufacturing method thereof, and a flexographic printing plate and a plate making method thereof.

Flexographic printing is a printing method in which an ink is applied to a convex portion on a printing plate using an anilox roll or the like and transferred to a printing object.
Usually, a flexographic printing plate uses an elastic resin layer (relief layer). In the flexographic printing plate precursor, for the purpose of ensuring the strength of the printing plate, a crosslinked relief forming layer is formed by subjecting a resin layer (relief forming layer) before crosslinking to a crosslinking treatment. For the crosslinking treatment, a method of irradiating the resin layer with active rays such as ultraviolet rays and electron beams (photocrosslinking), a vulcanization method, and a method using an organic peroxide (thermal crosslinking) are performed.

In recent years, a method for making a plate (patterning) of a crosslinked relief forming layer by scanning exposure has been studied.
For example, a so-called “direct engraving CTP (Computer To Plate) method” in which a cross-linked relief forming layer is directly engraved with a laser to make a plate has been proposed.
The direct engraving CTP method has an advantage that the relief shape can be freely controlled by literally engraving with a laser to form a relief asperity. 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 such a flexographic printing plate precursor for laser engraving, for example, in Patent Document 1, “a printing original plate for laser engraving for forming a printing plate by image formation by laser light irradiation, having a printing layer, Resin obtained by photoreacting a photosensitive resin composition in which the print layer mainly contains a non-photoreactive synthetic rubber or / and natural rubber, an ethylenically unsaturated compound, and a photopolymerization initiator A printing original plate for laser engraving comprising a composition ”is described.

Patent Document 2 discloses that “a conductive support and a resin layer formed on the surface of the conductive support are included, and the resin layer heats the conductive support by high frequency induction. By this, the printing original plate formed by the thermosetting resin composition arrange | positioned on the surface of the said electroconductive support body being heated and hardened from the surface side which contact | connects the said electroconductive support body. " Are listed.

JP 11-338139 A JP 2011-020363 A

The inventor examined the printing plate precursor for laser engraving described in Patent Documents 1 and 2, and in the halftone image portion, the pressure between the printing plate and the printing medium during printing (hereinafter referred to as “printing pressure”). It was clarified that the tolerance of concentration fluctuations (hereinafter referred to as “printing pressure latitude”) due to.

Therefore, the present invention has an object to provide a flexographic printing plate precursor for laser engraving capable of widening the printing pressure latitude in the halftone image portion of the printing plate and a method for producing the same, and a flexographic printing plate and a method for producing the same. And

As a result of earnestly examining the above-mentioned problems, the present inventor has provided at least two cross-linked relief forming layers having a predetermined thickness and satisfying a specific hardness ratio in a flexographic printing plate precursor for laser engraving. The present inventors have found that the printing pressure latitude in the halftone image portion can be widened, and have reached the present invention.
That is, the present inventor has found that the above problem can be solved by the following configuration.

[1] A flexographic printing plate precursor for laser engraving having at least two crosslinked relief forming layers,
The first crosslinked relief forming layer disposed on the surface side subjected to laser engraving and the second crosslinked relief forming layer adjacent to the first crosslinked relief forming layer, and the Martens hardness B of the second crosslinked relief forming layer The ratio of the Martens hardness A of the first crosslinked relief forming layer to 1.1 is 1.1 or more,
The thickness of the first crosslinked relief forming layer is 10 to 300 μm;
The thickness of the second crosslinked relief forming layer is 500 to 1600 μm;
The first crosslinked relief forming layer contains a binder polymer and a photothermal conversion material,
The flexographic printing plate precursor for laser engraving, wherein the second crosslinked relief-forming layer is a layer formed by forming a relief-forming layer using a resin composition containing a diene polymer and a thermal crosslinking agent and then crosslinking by heat.
[2] The flexographic printing plate precursor for laser engraving according to [1], wherein the thermal crosslinking agent is at least one selected from the group consisting of an organic peroxide and a sulfur compound.
[3] The flexographic printing plate precursor for laser engraving according to [1] or [2], wherein the resin composition further contains a polymerizable compound.
[4] The flexographic printing plate precursor for laser engraving according to any one of [1] to [3], wherein the binder polymer is a crystalline polymer.
[5] The laser according to any one of [1] to [4], wherein the diene polymer is at least one polymer selected from the group consisting of polyisoprene, polybutadiene, and ethylene-propylene-diene copolymer. Flexographic printing plate precursor for engraving.
[6] A first layer forming step of forming a first relief forming layer using a resin composition containing a binder polymer and a photothermal conversion material;
A second layer forming step of forming a second relief forming layer using a resin composition containing a diene polymer and a thermal crosslinking agent;
The first relief forming layer and the second relief forming layer are brought into contact with each other by heat, and the first crosslinked relief forming layer in which the first relief forming layer is crosslinked and the second crosslinked relief in which the second relief forming layer is crosslinked. A crosslinking step of forming at least two crosslinked relief forming layers adjacent to the forming layer,
The ratio of the Martens hardness A of the first crosslinked relief forming layer disposed on the surface side subjected to laser engraving to the Martens hardness B of the second crosslinked relief forming layer adjacent to the first crosslinked relief forming layer is 1.1. That's it,
The thickness of the first crosslinked relief forming layer is 10 to 300 μm;
A method for producing a flexographic printing plate precursor for laser engraving, wherein the second crosslinked relief forming layer has a thickness of 500 to 1600 μm.
[7] Engraving for forming a relief layer by applying laser engraving to the crosslinked relief forming layer of the flexographic printing plate precursor for laser engraving produced by the method for producing a flexographic printing plate precursor for laser engraving described in [6] A method for making a flexographic printing plate, comprising a step.
[8] A flexographic printing plate having a relief layer made by the plate making method of a flexographic printing plate according to [7].

According to the present invention, it is possible to provide a flexographic printing plate precursor for laser engraving which can widen the printing pressure latitude in the halftone image portion of the printing plate and a method for producing the same, as well as a flexographic printing plate and a method for making the same. .

Hereinafter, the present invention will be described in detail.
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.
Further, “parts by mass” and “% by mass” are synonymous with “parts by weight” and “% by weight”, respectively.

Here, regarding the description of the flexographic printing plate and the flexographic printing plate precursor, an uncrosslinked crosslinkable layer is referred to as a “relief forming layer”, and a layer obtained by crosslinking the relief forming layer is referred to as a “crosslinked relief forming layer”. A layer in which irregularities are formed on the surface by laser engraving is referred to as a “relief layer”.
The crosslinking is performed by heat. The crosslinking is not particularly limited as long as the resin composition is cured, and is a concept including a crosslinked structure by reaction between diene polymers. For example, a binder polymer or a diene polymer described below may be used. A crosslinked structure may be formed by reacting with the above components.
Further, a flexographic printing plate is produced by laser engraving a printing plate precursor having a crosslinked relief forming layer and rinsing as required.

[Flexographic printing plate precursor for laser engraving]
The flexographic printing plate precursor for laser engraving of the present invention (hereinafter abbreviated as “printing plate precursor of the present invention”) is a flexographic printing plate precursor for laser engraving having at least two cross-linked relief forming layers. And a second crosslinked relief forming layer adjacent to the first crosslinked relief forming layer, wherein the second crosslinked relief forming layer has a second strength against the Martens hardness B. The ratio of Martens hardness A (hardness A / hardness B) of one crosslinked relief forming layer is 1.1 or more.
In the present invention, the thickness of the first crosslinked relief forming layer is 10 to 300 μm, and the thickness of the second crosslinked relief forming layer is 500 to 1600 μm.
The first crosslinked relief forming layer contains a binder polymer and a photothermal conversion material, and the second crosslinked relief forming layer is formed from a resin composition containing a diene polymer and a thermal crosslinking agent. It is a layer formed by heat and then crosslinked.

According to the present invention, as described above, in the flexographic printing plate precursor for laser engraving, the halftone image of the printing plate is provided by providing at least two crosslinked relief forming layers having a predetermined thickness and satisfying a specific hardness ratio. The printing pressure latitude in the part can be widened.
Although the detailed mechanism is unknown, it is guessed as follows.
That is, in the printing plate on which an image is formed by laser engraving using the printing plate precursor of the present invention, the surface of the halftone dot image portion is harder than the inside, and therefore the printing effect is caused by the cushioning effect inside the halftone dot image portion. This is considered to be because the deformation was reduced and the density fluctuation was suppressed.
Hereinafter, the first crosslinked relief forming layer and the second crosslinked relief forming layer of the printing plate precursor of the present invention, and the resin composition and forming method for forming them will be described in detail.

[First cross-linked relief forming layer]
The first crosslinked relief forming layer of the printing plate precursor of the present invention is a layer that contains a binder polymer and a photothermal conversion material and is disposed on the surface side on which laser engraving is applied.
Here, the “layer disposed on the surface side subjected to laser engraving” refers to the case where it has an optional crosslinked relief forming layer other than the first crosslinked relief forming layer and the second crosslinked relief forming layer described later, A layer having the outermost surface on which laser engraving is performed during image formation.

The Martens hardness A of the first crosslinked relief forming layer is a hardness satisfying a ratio (hardness A / hardness B) of 1.1 or more with respect to the Martens hardness B of the second crosslinked relief forming layer adjacent to the first crosslinked relief forming layer. Although there is no particular limitation as long as it is, it is preferably 1 to 15 N / mm ² , more preferably 3 to 8 N / mm ² .
Here, the Martens hardness in the first crosslinked relief forming layer and the second crosslinked relief forming layer is a hardness measured at an indentation depth of 1 μm by a nanoindentation method according to ISO 14577-1 (instrumented indentation hardness). Say.
Specifically, the Martens hardness A of the first crosslinked relief forming layer is measured by pressing an indenter perpendicularly to the surface of the flexographic printing plate precursor under the following conditions.
Further, the Martens hardness B of the second crosslinked relief forming layer is as follows with respect to the central portion in the thickness direction of the second crosslinked relief forming layer in the obtained section by cutting a section perpendicular to the surface of the flexographic printing plate precursor. It was measured by pressing the indenter vertically under the conditions.
For example, it can be measured using an ultra micro hardness meter (DUH-201S, manufactured by Shimadzu Corporation).
<Measurement conditions>
・ Indenter: Vickers indenter (a quadrangular pyramid diamond indenter with an indenter angle of 136 °)
・ Push-in speed: 0.83mN / sec
・ Indentation depth: 1μm
・ Measurement temperature: 25 ℃

The thickness of the first crosslinked relief forming layer is not particularly limited as long as it is 10 to 300 μm. However, it is preferably 20 to 150 μm because the printing pressure latitude in the halftone image portion of the printing plate can be further increased. 20 to 70 μm is more preferable.

As described above, the first crosslinked relief forming layer contains a binder polymer and a photothermal conversion material.
In addition, as shown in the manufacturing method of the flexographic printing plate precursor of the present invention to be described later, the first crosslinked relief forming layer is, for example, a resin composition (hereinafter referred to as “binder polymer”, a photothermal conversion material, and an optional additive). , Also referred to as “first resin composition”), in a molten state, applied onto an arbitrary support and cooled to form a relief forming layer (hereinafter referred to as “first relief forming layer”). Later, it can be formed by heating and crosslinking.
Hereinafter, the binder polymer, the photothermal conversion material, and optional additives contained in the first resin composition will be described in detail.

<Binder polymer>
Although it does not restrict | limit especially as a binder polymer, A thermoplastic polymer, a diene polymer, etc. are mentioned.
A thermoplastic polymer will not be specifically limited if it is a polymer which shows thermoplasticity.
Examples of such thermoplastic polymers include polystyrene resins, polyester resins, polyamide resins, polysulfone resins, polyethersulfone resins, polyimide resins, hydrophilic polymers containing hydroxyethylene units, acrylic resins, acetal resins, epoxy resins, and polycarbonates. Resins, rubbers, thermoplastic elastomers and the like can be mentioned.
Among these, from the viewpoint of laser engraving sensitivity, a polymer including a partial structure that is thermally decomposed by exposure or heating is preferable. Preferred examples of such polymers include those described in paragraph [0038] of JP-A-2008-163081.
In addition, when the purpose is to form a soft and flexible film, a soft resin or a thermoplastic elastomer is preferable. Preferred examples of such resins and polymers include those described in paragraphs [0039] to [0040] of JP-A-2008-163081.
Furthermore, it is also preferable to use a hydrophilic or alcoholic polymer from the viewpoint of easy preparation of the first resin composition and improvement of resistance to oil-based ink in the printing plate to be produced. As the hydrophilic polymer, those described in paragraph [0041] of JP-A-2008-163081 can be used.

In addition, when used for the purpose of curing by heating or exposure and improving the strength, a polymer having an ethylenically unsaturated bond in the molecule is preferably used.
Examples of such a polymer that includes an ethylenically unsaturated bond in the main chain include SB (polystyrene-polybutadiene), SBS (polystyrene-polybutadiene-polystyrene), SIS (polystyrene-polyisoprene-polystyrene), SEBS ( Polystyrene-polyethylene / polybutylene-polystyrene) and the like.
In addition, as a polymer having an ethylenically unsaturated bond in the side chain, an ethylenically unsaturated group such as an allyl group, an acryloyl group, a methacryloyl group, a styryl group, or a vinyl ether group is included in the side chain of the binder polymer skeleton described later. It is obtained by introducing. The method for introducing an ethylenically unsaturated group into the side chain of the binder polymer is as follows: (1) copolymerizing a structural unit having a polymerizable group precursor formed by bonding a protective group to a polymerizable group to remove the protective group. (2) A polymer compound having a plurality of reactive groups such as a hydroxyl group, an amino group, an epoxy group, and a carboxyl group, and a group that reacts with these reactive groups and an ethylenic group. Known methods such as a method of introducing a compound having an unsaturated group by a polymer reaction can be employed. According to these methods, the amount of ethylenically unsaturated groups introduced into the polymer compound can be controlled.
The binder polymer is preferably a binder polymer having a reactive functional group such as a hydroxyl group, a silanol group, or a hydrolyzable silyl group. Specific examples thereof include vinyl copolymers (such as polyvinyl alcohol and polyvinyl acetal). And vinyl monomers (copolymers and derivatives thereof) and acrylic resins (copolymers and derivatives of acrylic monomers such as hydroxyethyl (meth) acrylate).

On the other hand, examples of the diene polymer include those exemplified as a diene polymer contained as an essential component in a resin composition (hereinafter referred to as “second resin composition”) that forms a second crosslinked relief forming layer described later. It is done.
Among these diene polymers, a liquid polymer (for example, liquid butadiene rubber) having a melting point of 23 ° C. or lower can be suitably used from the viewpoint of improving the film forming property of the first crosslinked relief forming layer.
Here, the melting point is 20 mg of a thermoplastic polymer before heating in a differential scanning calorimetry (DSC) pan, and the temperature is from 30 ° C. to 300 ° C. at 10 ° C./min in a nitrogen stream. It is the starting temperature of the endothermic peak observed when the temperature is raised.

Among such binder polymers, a crystalline polymer is preferable from the viewpoint of ease of forming a relief layer and hardness.
Here, a crystalline polymer means a polymer in which a crystalline region in which long chain molecules are regularly arranged in a molecular structure and an amorphous region that is not regularly arranged are mixed. It refers to a polymer having a crystallinity of 25% or more and 1% by volume or more, which is a ratio of the sex region.
Here, the degree of crystallinity refers to an endothermic peak (ΔH (J) due to crystal melting while changing the temperature at a temperature rising rate of 20 ° C./min in a range from 25 ° C. to 200 ° C. in a nitrogen atmosphere using a differential scanning calorimeter. / G)). Based on the measured ΔH, the ultimate crystallinity (%) is calculated by the following formula.
Crystallinity (%) = {ΔH / a} × 100
In the above formula, “a” is the heat of crystal melting when the crystalline region component is crystallized 100% (for example, 94 J / g for polylactic acid, polyethylene (HDPE) 293 ( J / g)).

Specific examples of such a crystalline polymer include SB (polystyrene-polybutadiene), SBS (polystyrene-polybutadiene-polystyrene), SIS (polystyrene-polyisoprene-polystyrene), and SEBS (polystyrene-polyethylene / polybutylene-). Polystyrene), ABS (acrylonitrile butadiene styrene copolymer), ACM (acrylic ester rubber), ACS (acrylonitrile chlorinated polyethylene styrene copolymer), amorphous polyalphaolefin, atactic polypropylene, acrylonitrile styrene copolymer, Cellulose acetate butyrate, cellulose acetate propionate, cellulose acetate butyrate, ethylene vinyl acetate copolymer, ethyl vinyl ether, poly Acrylic acid, polypropylene, polybutadiene, polyisoprene, polyoctenylene, trans - polyisoprene, polyvinyl butyral, ethylene -α- olefin copolymers, propylene -α- olefin copolymers, and the like 1,3-pentadiene polymers.
Of these, SBS, SIS, SEBS, polypropylene, polybutadiene, polyisoprene, polyoctenylene, trans-polyisoprene, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer are preferable, and among them, polyoctenylene is particularly preferable.

Further, among such binder polymers, if the first resin composition is softened during thermal crosslinking, the thermal crosslinking agent of the second resin composition moves to the first resin composition, and the first resin A polymer having a melting point of 50 to 200 ° C. is preferable, and a polymer having a melting point of 50 to 150 ° C. is more preferable because the composition is more easily crosslinked.

<Photothermal conversion material>
The photothermal conversion material is considered to be a component that promotes thermal decomposition of a cured product during laser engraving by absorbing laser light and generating heat.
Therefore, it is preferable to select a photothermal conversion material that absorbs light having a laser wavelength used for engraving.
For example, when the printing plate precursor of the present invention is used for laser engraving using a laser emitting a 700 to 1,300 nm infrared ray (YAG (Yttrium Alminium Garnet) laser, semiconductor laser, fiber laser, surface emitting laser, etc.) as a light source, As the photothermal conversion material, a compound having a maximum absorption wavelength at 700 to 1,300 nm is preferably used.
Various dyes or pigments are used as such a photothermal conversion material.

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

Among the photothermal conversion materials used in the present invention, commercially available pigments and color index (CI) manuals, “Latest Pigment Handbook” (edited by the Japan Pigment Technical Association, 1977), “Latest Pigment Application” The pigments described in “Technology” (CMC Publishing, 1986) and “Printing Ink Technology” CMC Publishing, 1984) can be used. Examples of the pigment include pigments described in paragraphs 0122 to 0125 of JP2009-178869A.
Among these pigments, carbon black described later is preferable.

(Carbon black)
Specific examples of carbon black include furnace black, thermal black, channel black, lamp black, acetylene black, and the like. These may be used alone or in combination of two or more. Good.
These carbon blacks can be used as color chips or color pastes that are dispersed in nitrocellulose or a binder in advance using a dispersant as needed to facilitate dispersion. To powder.

In the present invention, the average particle size of carbon black is preferably 13 nm or more and 50 nm or less, because the viscosity and workability of the first resin composition are good and the printing durability is good. It is more preferably 40 nm or less and particularly preferably 15 nm or more and 31 nm or less.
Here, the average particle diameter in carbon black is the number average particle diameter, and is measured by a transmission electron microscope.

The nitrogen adsorption specific surface area (hereinafter also abbreviated as “N ₂ SA”) of carbon black is preferably 25 m ² / g or more and 180 m ² / g or less. N ₂ SA of the carbon black used is more preferably 30 m ² / g to 160 m ² / g, and particularly preferably 40 m ² / g to 150 m ² / g.
Here, N ₂ SA in carbon black is obtained according to JIS K6217-2: 2001.

As the carbon black, carbon black for rubber can be used. Specific examples thereof include SAF, SAF-HS, ISAF, ISAF-LS, ISAF-HS, IISAF, IISAF-HS, IISAF-HS, HAF, HAF-HS, HAF-LS, LI-HAF, FEF, FEF-HS, MAF, MAF-HS, T-NS, and the like may be used. These may be used alone or in combination of two or more. May be.
Specifically, commercially available carbon black shown below can be used, but is not limited thereto. In the parentheses, an average particle diameter (nm) and a nitrogen adsorption specific surface area (m ² / g) are sequentially shown.

The carbon black of Asahi Carbon Co., Ltd., for example, Asahi ^{♯78 (22nm, 124m 2 / g} ), Asahi ^{♯80 (22nm, 115m 2 / g} ), Asahi ^{♯70 (28nm, 77m 2 / g} ), Asahi ^{♯70L (27nm, 84m 2 / g} ), Asahi ^{F-200 (38nm, 51m 2} / g), Asahi ^{♯66 (44nm, 43m 2 / g} ), Asahi ^{♯65 (44nm, 42m 2 / g} ), Asahi ♯ 60HN (40 nm, 48 m ² / g), Asahi # 60H (41 nm, 45 m ² / g), Asahi # 60U (43 nm, 43 m ² / g), Asahi # 60 (45 nm, 40 m ² / g), Asahi AX-015 (19 nm, 145 m ² / g) and the like.
The carbon black of Nippon Carbon Co., Ltd., for ^{example, ♯300IH (19nm, 120m 2 /} g), ♯300 (24nm, 117m 2 / g), ♯200IS (26nm, 95m 2 / g), ♯200 ^{(29nm, 75m 2 / g)} , ♯200L (29nm, 81m 2 / g), ♯200IN (31nm, 71m 2 / g), ♯10 (40nm, 49m 2 / g), ♯10K (39nm, 48m 2 / g), ♯10S (42nm, 53m 2 / g), ♯100 (44nm, include 41m ² / g) and the like.
The carbon black of Tokai Carbon Co., Ltd., for example, SEAST ^{9H (18nm, 142m 2 / g} ), SEAST ^{9 (19nm, 142m 2 / g} ), Seast ^{7HM: N234 (19nm, 126m 2} / g), SEAST 6 (22 nm, 119 m ² / g), seast 600 (23 nm, 106 m ² / g), seast 5H (22 nm, 99 m ² / g), seast KH: N339 (24 nm, 93 m ² / g), seast 3H (27 nm, 82 m ² / g), Seest NH: N351 (29 nm, 74 m ² / g), Seest 3 (28 nm, 79 m ² / g), Seest N (29 nm, 74 m ² / g), Seest 300 (28 nm, 84 m ² / g) , Seast ^{116HM (38nm, 56m 2 / g} ), Seast ^{116 (38nm, 49m 2 / g} ), shea Strike ^{FM (50nm, 42m 2 / g} ), Seast ^{SO (43nm, 42m 2 / g} ) , and the like.
Examples of carbon black manufactured by Mitsubishi Chemical Corporation include Diablack A (19 nm, 142 m ² / g), Dia Black N234 (22 nm, 123 m ² / g), Dia Black I (23 nm, 114 m ² / g), Dia Black LI (23 nm, 107 m ² / g), Dia Black II (24 nm, 98 m ² / g), Dia Black N339 (26 nm, 96 m ² / g), Dia Black SH (31 nm, 78 m ² / g), Dia Black H (31 nm, 79 m ² / g), Dia Black LH (31 nm, 84 m ² / g), Dia Black HA (32 nm, 74 m ² / g), Dia Black N550M (43 nm, 47 m ² / g), Dia Black E (48 nm 41 m ² / g) and the like.

As the carbon black, color carbon black can be used. Specific examples thereof include commercially available carbon blacks shown below, but are not limited thereto. In the parentheses, an average particle diameter (nm) and a nitrogen adsorption specific surface area (m ² / g) are sequentially shown.

Examples of the carbon black manufactured by Mitsubishi Chemical Corporation, for ^{example, ♯1000 (18nm, 180m 2 /} g), MCF88 (18nm, 180m 2 / g), MA600 (20nm, 140m 2 / g), ♯750B (22nm, 124m ^{2 / g), ♯650B (22nm} , 124m 2 / g), ♯52 (27nm, 88m 2 / g), ♯47 (23nm, 132m 2 / g), ♯45 (24nm, 120m 2 / g), ♯ 45L (24 nm, 125 m ² / g), # 44 (24 nm, 110 m ² / g), # 40 (24 nm, 115 m ² / g), # 33 (30 nm, 85 m ² / g), # 32 (30 nm, 83 m ²⁾ / g), ♯30 (30nm, 74m 2 / g), ♯25 (47nm, 55m 2 / g), ♯20 (50nm, 45m 2 / g), ♯95 (40nm, 55m 2 g), ♯85 (40nm, 60m 2 / g), ♯260 (40nm, 70m 2 / g), MA77 (23nm, 130m 2 / g), MA7 (24nm, 115m 2 / g), MA8 (24nm, 120m ² / g), MA11 (29 nm, 92 m ² / g), MA100 (24 nm, 110 m ² / g), MA100R (24 nm, 110 m ² / g), MA100S (24 nm, 110 m ² / g), MA230 (30 nm, 74 m ² / g), MA14 (40 nm, 56 m ² / g) and the like.

In the present invention, the content of the photothermal conversion material (particularly carbon black) is 1 to 30 masses per 100 mass parts of the binder polymer because the sensitivity at the time of laser engraving is good and the ink inking property is also good. Part is preferable, and 5 to 20 parts by mass is more preferable.

<Optional additives>
The first crosslinked relief forming layer may contain, for example, a polymerizable compound, a filler other than carbon black, and the like as an optional additive other than the binder polymer and the photothermal conversion material.

(Polymerizable compound)
As a polymeric compound, the thing similar to the polymeric compound contained as an arbitrary component in the 2nd resin composition mentioned later can be used.
Further, the content in the case of containing an optional polymerizable compound is preferably 0.1 to 30% by mass, more preferably 1 to 20% by mass with respect to the total mass of the first resin composition. preferable.

(Other fillers)
Other fillers may be organic or inorganic, but are made of silica, calcium carbonate, mica, talc, and metal stearate from the viewpoint of better processability and cost and strength of the cured film. It is preferable to use at least one selected from the group, and it is particularly preferable to use silica and / or calcium carbonate.

(Other additives)
Various known additives can be appropriately added to the first resin composition as long as the effects of the present invention are not impaired. Examples include cross-linking aids, silane coupling agents, waxes, process oils, metal oxides, antiozonants, anti-aging agents, polymerization inhibitors, colorants, etc., and these can be used alone. Alternatively, two or more kinds may be used in combination.

[Second cross-linked relief forming layer]
The second crosslinked relief forming layer of the printing plate precursor of the present invention is a layer adjacent to the first crosslinked relief forming layer, and comprises a resin composition (second resin composition) containing a diene polymer and a thermal crosslinking agent. It is a layer that is crosslinked by heat after forming a relief forming layer.
Here, the “layer adjacent to the first crosslinked relief forming layer” refers to a layer that is in direct contact with the outermost layer (first crosslinked relief forming layer) on which laser engraving is performed during image formation. Say.

The Martens hardness B of the second crosslinked relief forming layer is not particularly limited as long as the ratio (hardness A / hardness B) with the Martens hardness A of the adjacent first crosslinked relief forming layer satisfies 1.1 or more, 1 to 15 N / mm ² is preferable, and 1 to 3 N / mm ² is more preferable.

The thickness of the second crosslinked relief forming layer is not particularly limited as long as it is 500 to 1600 μm, but it has sufficient cushioning properties against printing pressure, and from the viewpoint of imparting unevenness necessary for forming a non-image part. 700 to 900 μm or 1400 to 1600 μm is preferable.

As described above, the second crosslinked relief forming layer is referred to as a relief forming layer (hereinafter referred to as “second relief forming layer”) using a resin composition (second resin composition) containing a diene polymer and a thermal crosslinking agent. ), And then crosslinked by heat.
Hereinafter, the diene polymer, the thermal crosslinking agent, and optional additives contained in the second resin composition will be described in detail.

<Diene polymer>
The diene polymer contained in the second resin composition is not particularly limited, and a conventionally known diene polymer can be used without limitation.
Specific examples of the diene polymer include polyisoprene, polybutadiene, ethylene-propylene-diene copolymer (EPDM), acrylonitrile-butadiene copolymer, styrene-butadiene copolymer (SBR), and styrene- Examples include isoprene copolymers, styrene-isoprene-butadiene copolymers, polystyrene-polybutadiene-polystyrene block copolymers (SBS), and these may be used alone or in combination of two or more. Good.
Of these, at least one polymer selected from the group consisting of polyisoprene, polybutadiene, and ethylene-propylene-diene copolymer is preferable from the viewpoint of easy removal of residue on the plate generated during engraving. .

In the present invention, polyisoprene or polybutadiene may be a polymer whose main chain is mainly composed of isoprene or butadiene as monomer units, and a part thereof may be hydrogenated to be converted to a saturated bond. Further, the main chain or the terminal of the polymer may be modified with an amino group, an isocyanato group, a carboxy group, a hydroxy group, a (meth) acryloyl group or the like, or may be epoxidized.
In the present specification, the (meth) acryloyl group means an acryloyl group or a methacryloyl group.

In the present invention, the proportion of monomer units derived from aliphatic hydrocarbons (isoprene, butadiene, or hydrogenated products thereof) in the main chain of polyisoprene or polybutadiene may be 80 mol% or more. preferable.
It is preferable that the proportion of monomer units derived from aliphatic hydrocarbons in the main chain is 80 mol% or more, since the engraving residue rinse property is good.
The content of the monomer unit derived from the aliphatic hydrocarbon is more preferably 90 mol% or more of the total monomer units constituting the main chain of the diene polymer, more preferably 95 mol%, and more preferably 99 mol% or more. It is particularly preferred.
In the present invention, “main chain” represents a relatively long bond chain in the molecule of the polymer compound constituting the resin, and “side chain” represents a carbon chain branched from the main chain. The side chain may contain a hetero atom.
That is, for example, in polyisoprene, the proportion of monomer units derived from isoprene and the hydrogenated product of isoprene is preferably 80 mol% or more in total, more preferably 90 mol% or more, and more preferably 95 mol% or more. More preferably, it is 99 mol% or more.
Similarly, in polybutadiene, the proportion of monomer units derived from butadiene and a hydrogenated product of butadiene is preferably 80 mol% or more in total, more preferably 90 mol% or more, and 95 mol% or more. Is more preferable, and 99 mol% or more is particularly preferable.
Further, when an isoprene / butadiene copolymer is used as the diene-based polymer, it is preferable that the monomer units derived from isoprene, butadiene and hydrogenated products thereof are contained in a total of 80 mol% or more, and 90 mol% or more. It is more preferably contained, more preferably 95 mol% or more, and particularly preferably 99 mol% or more.

Isoprene is known to be polymerized by 1,2-, 3,4- or 1,4-addition depending on the catalyst and reaction conditions. Good. Among these, from the viewpoint of obtaining a desired Mooney viscosity, it is preferable to contain cis-1,4-polyisoprene as a main component. The content of cis-1,4-polyisoprene is preferably 50% by mass or more, more preferably 65% by mass or more, still more preferably 80% by mass or more, and 90% by mass. The above is particularly preferable.
As polyisoprene, natural rubber may be used, and commercially available polyisoprene can also be used. For example, the NIPOL IR series (manufactured by Nippon Zeon Co., Ltd.) is exemplified.

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

On the other hand, the ethylene-propylene-diene copolymer (EPDM) is preferably a polymer having a Mooney viscosity ML _{1 + 4} (100 ° C.) of 25 to 90. The Mooney viscosity ML _{1 + 4} (100 ° C.) is a value measured in accordance with ASTM D 1646.
EPDM is preferably a polymer having an ethylene content of 40 to 70% by mass, and is preferably a polymer having a diene content of 1 to 20% by mass.
Examples of the diene component of EPDM include dicyclopentadiene (DCPD), 5-ethylidene-2-norbornene, and 1,4 hexadiene.

In the present invention, the diene polymer preferably has a weight average molecular weight of 200,000 or more, from 300,000 to 2,000,000, from the viewpoint of the tensile strength of the relief forming layer formed into a sheet by a calender roll. More preferred is 300,000 to 1,500,000, still more preferred is 300,000 to 700,000.
Here, the weight average molecular weight is measured by a gel permeation chromatography method (GPC), and is calculated in terms of standard polystyrene. Specifically, for example, GPC uses HLC-8220GPC (manufactured by Tosoh Corporation), and 3 columns of TSKgeL Super HZM-H, TSKgeL SuperHZ4000, TSKgeL SuperHZ2000 (4.6 mm ID × 15 cm) manufactured by Tosoh Corporation. In this use, 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 Mooney viscosity of the diene polymer is preferably 20 or more, more preferably 25 or more, and still more preferably 35 or more, from the viewpoint of printing durability.
Similarly, the Mooney viscosity of the diene polymer is preferably 90 or less, more preferably 70 or less, and still more preferably 60 or less, from the standpoint of solvent solubility and ease of handling during mixing.
Here, the Mooney viscosity is a value measured according to JIS K6300-1. Specifically, a cylindrical space is formed between dies capable of temperature control to form a sample chamber, a rotor is disposed in the center of the sample chamber, and a sample to be measured is filled into the sample chamber. While maintaining the temperature at a predetermined temperature, the rotor is rotated at a specified rotational speed, and the rotor counter torque generated by the viscous resistance of the molten sample is detected by a load cell. The Mooney viscosity value used in the present invention indicates the Mooney viscosity (ML1 + 4) after 4 minutes by rotating the rotor using an L-shaped rotor at a preheating period of 1 minute at 100 ° C.

The content of the diene polymer in the second resin composition is preferably 5 to 90% by mass, more preferably 15 to 85% by mass, and more preferably 30 to 80% by mass with respect to the total solid content. More preferably. It is preferable for the content of the diene polymer to be in the above range since a relief layer having excellent engraving residue rinsing properties and ink transfer properties can be obtained.

<Thermal crosslinking agent>
The thermal crosslinking agent contained in the second resin composition is not particularly limited, and a conventionally known thermal crosslinking agent (so-called vulcanizing agent) can be used without limitation.
Here, the thermal cross-linking agent refers to a compound that advances a cross-linking reaction by the action of heat rather than light, and examples thereof include organic peroxides, sulfur-based compounds, isocyanate-based cross-linking agents, and epoxy resins.
Among these, a thermal cross-linking agent that generates radicals and proceeds with cross-linking is preferable because of its high reaction rate (cross-linking reaction). Specifically, it is composed of an organic peroxide and a sulfur-based compound described later. It is preferably at least one selected from the group.

(Organic peroxide)
Specific examples of the organic peroxide include dicumyl peroxide (10-hour half-life temperature: 116 ° C.), α, α′-di (t-butylperoxy) diisopropylbenzene (10-hour half-life temperature: 119 ° C.), 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (10-hour half-life temperature: 118 ° C.), etc., and these may be used alone. More than one species may be used in combination.

In the present invention, the form of the organic peroxide can be used as it is, but from the viewpoint of handling (danger, workability, etc.), the raw material is converted into an inorganic filler such as calcium carbonate. Diluted products with a concentration of 40 wt% (non-dangerous materials, powder), and master batch type diluted products for the purpose of preventing dusting during kneading and improving dispersibility in polymers can be more preferably used. .
For example, Park Mill D (manufactured by NOF Corporation), Perkadox BC-FF (manufactured by Kayaku Akzo Corporation), Luperox DC (manufactured by Arkema Yoshitomi Corporation), Perbutyl P (manufactured by NOF Corporation), Parka Docks 14 (manufactured by Kayaku Akzo Co., Ltd.), Lupelox F (manufactured by Arkema Yoshitomi Co., Ltd.), Lupelox F90P (manufactured by Arkema Yoshitomi Co., Ltd.), Perhexa 25B (manufactured by NOF Corporation), Kayahexa AD (manufactured by Kayaku Akzo Corporation) ), Lupelox 101 (manufactured by Arkema Yoshitomi Co., Ltd.) or the like can be used, but is not limited thereto.
Examples of the diluted product include, for example, Park Mill D-40 (manufactured by NOF Corporation: diluted inert filler), Park Mill D-40MB (manufactured by NOF Corporation: diluted silica / polymer, etc.), Kayak Mill D- 40C (manufactured by Kayaku Akzo Co., Ltd .: calcium carbonate diluted product), Kayak Mill D-40MB-S (manufactured by Kayaku Akzo Co., Ltd .: rubber master batch), Kayaku Mill D-40MB (manufactured by Kayaku Akzo Co., Ltd .: rubber master batch) Perbutyl P-40 (manufactured by NOF Corporation: diluted inert filler), PERBUTYL P-40MB (manufactured by NOF Corporation: silica / polymer and other diluted products), Perkadox 14/40 (Kayaku Akzo Corporation) Manufactured by: calcium carbonate diluted product), Parka dox 14-40C (manufactured by Kayaku Akzo Co., Ltd .: calcium carbonate diluted product), Luperox F40 (Arkemakichi) Co., Ltd.), Perhexa 25B-40 (manufactured by NOF Corporation: Silica and other diluted products), Kayahexa AD-40C (manufactured by Kayaku Akzo Co., Ltd .: calcium silicate diluted product), Trigonox 101-40MB (Kayaku Akzo Stock) (Manufactured by company: rubber master batch), Lupelox 101XL (manufactured by Arkema Yoshitomi Co., Ltd.) and the like can be used, but are not limited thereto.

(Sulfur compounds)
Examples of sulfur compounds include sulfur (elemental sulfur), sulfur chloride, sulfur dichloride, mercapto compounds, sulfide compounds, disulfide compounds, polysulfide compounds, thiuram compounds, thiocarbamic acid compounds, polyfunctional mercapto compounds, and the like. Among these, sulfur, sulfur chloride, sulfur dichloride, disulfide compounds, thiuram compounds, thiocarbamic acid compounds, and polyfunctional mercapto compounds are preferred.

Specific examples of such sulfur compounds include sulfur, sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, tetramethylthiuram disulfide, selenium dimethyldithiocarbamate, pentaerythritol tetrakis (3-mercaptobutyrate), pentaerythritol. Examples thereof include tetrakisthiopropionate, tris (3-mercaptobutyloxyethyl) isocyanurate, dipentaerythritol hexakisthiopropionate, and the like.
Of these, sulfur, alkylphenol disulfide, and pentaerythritol tetrakis (3-mercaptobutyrate) are preferred, and alkylphenyl disulfide and pentaerythritol tetrakis (3-mercaptobutyrate) are more preferred.

In the present invention, the content of the thermal crosslinking agent is 100 masses of the diene polymer contained in the second resin composition from the viewpoint of adjusting the degree of crosslinking of the relief forming layer after crosslinking, that is, the hardness of the crosslinked relief forming layer. The amount is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 3 parts by mass with respect to parts.

<Optional additives>
The second resin composition may contain, for example, a polymerizable compound, a polymerization initiator, a photothermal conversion material, and the like as optional additives other than the diene polymer and the thermal crosslinking agent.

(Polymerizable compound)
The polymerizable compound is preferably, for example, a compound having an ethylenically unsaturated bond (hereinafter referred to as “ethylenically unsaturated compound”).

The ethylenically unsaturated compound may be a monofunctional ethylenically unsaturated compound or a polyfunctional ethylenically unsaturated compound, but is preferably a polyfunctional ethylenically unsaturated compound. Specifically, the polyfunctional ethylenically unsaturated compound is preferably a compound having 2 to 20 terminal ethylenically unsaturated groups. Such a compound group is widely known in this industrial field, and in the present invention, these can be used without particular limitation.

The ethylenically unsaturated compound is an ethylenically unsaturated compound other than the above-described diene polymer, and is preferably a compound having a molecular weight of less than 1,000.
Examples of compounds derived from an ethylenically unsaturated group in a polyfunctional ethylenically unsaturated compound include unsaturated carboxylic acids (eg, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, etc.) Examples include esters and amides. Preferably, esters of unsaturated carboxylic acids and aliphatic polyhydric alcohol compounds, and amides of unsaturated carboxylic acids and aliphatic polyvalent amine compounds are used.
In addition, unsaturated carboxylic acid esters having nucleophilic substituents such as hydroxy groups and amino groups, amides and polyfunctional isocyanates, addition reaction products of epoxies, and dehydration condensation reaction products of polyfunctional carboxylic acids Etc. are also preferably used.
In addition, an unsaturated carboxylic acid ester having an electrophilic substituent such as an isocyanato group or an epoxy group, an amide and a monofunctional or polyfunctional alcohol, an addition reaction product of an amine, a halogen group, a tosyloxy group, A substituted reaction product of unsaturated carboxylic acid ester, amide and monofunctional or polyfunctional alcohols or amines having a leaving substituent such as the above is also suitable.
As another example, a compound group in which a vinyl compound, an allyl compound, an unsaturated phosphonic acid, styrene, or the like is substituted for the above unsaturated carboxylic acid can be used.

As the ethylenically unsaturated group compound that can be contained in the second resin composition, an acrylate compound, a methacrylate compound, a vinyl compound, and an allyl compound are preferable from the viewpoint of reactivity.

Examples of allyl compounds include polyethylene glycol diallyl ether, 1,4-cyclohexane diallyl ether, 1,4-diethylcyclohexyl diallyl ether, 1,8-octane diallyl ether, trimethylol propane diallyl ether, trimethylol ethane triallyl ether, pentaerythritol. Triaryl ether, pentaerythritol tetraallyl ether, dipentaerythritol pentaallyl ether, dipentaerythritol hexaallyl ether, diallyl phthalate, diallyl terephthalate, diallyl isophthalate, triallyl isocyanurate, triallyl cyanurate, triallyl phosphate, etc. It is done.
Among these, as the allyl compound, triallyl isocyanurate and triallyl cyanurate are particularly preferable.

Specific examples of the ester monomer of an aliphatic polyhydric alcohol compound and an unsaturated carboxylic acid include acrylic acid esters such as ethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butanediol diacrylate, and tetramethylene glycol. Diacrylate, propylene glycol diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane tri (acryloyloxypropyl) ether, trimethylolethane triacrylate, hexanediol diacrylate, 1,4-cyclohexanediol diacrylate , Tetraethylene glycol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate , Pentaerythritol tetraacrylate, dipentaerythritol diacrylate, dipentaerythritol hexaacrylate, sorbitol triacrylate, sorbitol tetraacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate, tri (acryloyloxyethyl) isocyanurate, polyester acrylate oligomer, etc. It is done.

Methacrylic acid esters include tetramethylene glycol dimethacrylate, triethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, Hexanediol dimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol dimethacrylate, dipentaerythritol hexamethacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate, bis [p- (3-methacryloxy- 2-hydroxyp Epoxy) phenyl] dimethyl methane, bis [p- (methacryloxyethoxy) phenyl] dimethyl methane, and the like.

Itaconic acid esters include ethylene glycol diitaconate, propylene glycol diitaconate, 1,3-butanediol diitaconate, 1,4-butanediol diitaconate, tetramethylene glycol diitaconate, pentaerythritol diitaconate Sorbitol tetritaconate and the like.

Examples of crotonic acid esters include ethylene glycol dicrotonate, tetramethylene glycol dicrotonate, pentaerythritol dicrotonate, and sorbitol tetracrotonate.

Examples of isocrotonic acid esters include ethylene glycol diisocrotonate, pentaerythritol diisocrotonate, and sorbitol tetraisocrotonate.

Examples of maleic acid esters include ethylene glycol dimaleate, triethylene glycol dimaleate, pentaerythritol dimaleate, and sorbitol tetramaleate.

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

Specific examples of amide monomers of an aliphatic polyvalent amine compound and an unsaturated carboxylic acid include methylene bisacrylamide, methylene bismethacrylamide, 1,6-hexamethylene bisacrylamide, 1,6-hexamethylene bismethacrylate. Examples include amide, diethylenetriamine trisacrylamide, xylylene bisacrylamide, and xylylene bismethacrylamide.

Examples of other preferable amide monomers include those having a cyclohexylene structure described in JP-B No. 54-21726.

In addition, urethane-based addition polymerizable compounds produced by using an addition reaction of isocyanate and hydroxyl group are also suitable. Specific examples thereof include, for example, one molecule described in JP-B-48-41708. A vinyl urethane compound containing two or more polymerizable vinyl groups in one molecule obtained by adding a vinyl monomer containing a hydroxyl group represented by the following formula (i) to a polyisocyanate compound having two or more isocyanato groups. Etc.

_{CH 2 = C (R) COOCH} 2 CH (R ') OH (i)
(However, R and R ′ each represent H or CH _3. )

Further, urethane acrylates such as those described in JP-A-51-37193, JP-B-2-32293, JP-B-2-16765, JP-B-58-49860, JP-B-56-17654 Urethane compounds having an ethylene oxide skeleton described in JP-B-62-39417 and JP-B-62-39418 are also suitable.

Further, by using addition polymerizable compounds having an amino structure in the molecule described in JP-A-63-277653, JP-A-63-260909, and JP-A-1-105238, a short time can be obtained. A cured composition can be obtained.

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

Examples of the vinyl compound include butanediol-1,4-divinyl ether, ethylene glycol divinyl ether, 1,2-propanediol divinyl ether, 1,3-propanediol divinyl ether, 1,3-butanediol divinyl ether, 1,4 -Butanediol divinyl ether, neopentyl glycol divinyl ether, trimethylolpropane trivinyl ether, trimethylol ethane trivinyl ether, hexanediol divinyl ether, tetraethylene glycol divinyl ether, pentaerythritol divinyl ether, pentaerythritol trivinyl ether, pentaerythritol tetravinyl ether, Sorbitol tetravinyl ether, sorbitol pentavinyl ether, ethylene glycol Rudiethylene vinyl ether, ethylene glycol dipropylene vinyl ether, trimethylolpropane triethylene vinyl ether, trimethylolpropane diethylene vinyl ether, pentaerythritol diethylene vinyl ether, pentaerythritol triethylene vinyl ether, pentaerythritol tetraethylene vinyl ether, 1,1,1-tris [4- (2-vinyloxyethoxy) phenyl] ethane, bisphenol A divinyloxyethyl ether, divinyl adipate and the like.

The said polymeric compound may contain individually by 1 type, or may contain 2 or more types.
When the polymerizable compound is contained, the content is preferably 0.1 to 30% by mass, and more preferably 1 to 20% by mass with respect to the total mass of the second resin composition.

(Polymerization initiator)
When the 2nd resin composition contains the polymeric compound (especially ethylenically unsaturated compound) mentioned above, it is preferable to use a polymerization initiator together.
A conventionally well-known polymerization initiator can be used for the said polymerization initiator without a restriction | limiting.
The polymerization initiator may be a radical polymerization initiator or a cationic polymerization initiator, but is preferably a radical polymerization initiator.
The polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator, but is preferably a thermal polymerization initiator.

(Photothermal conversion material)
As a photothermal conversion material, the same thing as the photothermal conversion material contained as an essential component in the 1st resin composition mentioned above (especially carbon black) can be used.
Further, the content in the case of containing an arbitrary photothermal conversion material is preferably 0.1 to 30 parts by mass with respect to 100 parts by mass of the diene polymer contained in the second resin composition, and 2 to 5 parts by mass. More preferably, it is a part.

(Other additives)
Various known additives can be appropriately blended with the second resin composition as long as the effects of the present invention are not impaired. Examples include crosslinking aids, silane coupling agents, fillers other than carbon black, waxes, process oils, metal oxides, antiozonants, antioxidants, polymerization inhibitors, colorants, and the like. A seed may be used independently and two or more sorts may be used together.

[Support]
The printing plate precursor of the present invention may have a support for supporting the first or second crosslinked relief forming layer, if necessary.
The material used for the support is not particularly limited, but those having high dimensional stability are preferably used. For example, metals such as steel, stainless steel, and aluminum; polyester (for example, PET (polyethylene terephthalate), PBT (polybutylene terephthalate)) , PAN (polyacrylonitrile)), polyvinyl chloride and other plastic resins; styrene-butadiene rubber and other synthetic rubbers; plastic fibers reinforced with glass fibers (such as epoxy resins and phenolic resins); and the like.
As the support, PET film, PEN film, PI film, PA film, fluororesin film, and silicone resin film are preferably used.

(Adhesive layer)
When forming the 1st or 2nd bridge | crosslinking relief forming layer on a support body, you may provide an adhesive layer between both in order to strengthen the adhesive force of an interlayer.
Examples of the material (adhesive) that can be used for the adhesive layer include I.I. Those described in the edition of Skeist, “Handbook of Adhesives”, the second edition (1977) can be used.
When providing an adhesive layer, it can respond by using the support body which apply | coated the adhesive layer.

[Method of manufacturing flexographic printing plate precursor for laser engraving]
The method for producing a flexographic printing plate precursor for laser engraving of the present invention (hereinafter also abbreviated as “method for producing a printing plate precursor of the present invention”) is a production method for producing the printing plate precursor of the present invention described above, A first layer forming step of forming a first relief forming layer using a resin composition (first resin composition) containing a binder polymer and a photothermal conversion material, and a resin composition containing a diene polymer and a thermal crosslinking agent The second layer forming step of forming the second relief forming layer using the (second resin composition), the first relief forming layer and the second relief forming layer are brought into contact with each other by heat, A crosslinking step of forming at least two crosslinked relief forming layers adjacent to each other, the first crosslinked relief forming layer crosslinked by the relief forming layer and the second crosslinked relief forming layer crosslinked by the second relief forming layer.
The first layer forming step and the second layer forming step (hereinafter collectively referred to as “layer forming step”) and the crosslinking step will be described in detail below.

[Layer formation process]
The method for producing a printing plate precursor according to the present invention includes a first layer forming step of forming a first relief forming layer using the first resin composition described above, and a second relief forming using the second resin composition described above. A second layer forming step of forming a layer.
As a formation method of a 1st relief forming layer and a 2nd relief forming layer, the method etc. which shape | mold each resin composition (kneaded material) prepared by kneading | mixing in a sheet form etc. are mentioned, for example.
Here, the preparation method of each resin composition is not particularly limited, each component described above, for example, a single-screw extruder, a multi-screw extruder, a Banbury mixer, an intermix mixer, a kneader or other closed kneader, Examples of the method include kneading using a non-sealing (open type) kneader such as a mixing roll (open roll).
Moreover, the sheet | seat shaping | molding mentioned in full detail below may be implemented in the state which provided the prepared resin composition on a support body, and may be implemented in the state without a support body. In the present invention, the first relief forming layer is preferably provided on the support because the thickness of the first crosslinked relief forming layer after crosslinking is as thin as 10 to 300 μm, and the second relief forming layer is preferably formed after crosslinking. Since the thickness of the second crosslinked relief forming layer is as thick as 500 to 1600 μm, it may be carried out without a support.

<Sheet molding>
Sheet molding for molding each prepared resin composition into a sheet will be described.
As a method of forming the first resin composition into a sheet, for example, a method in which the first resin composition is heated and melted and applied on a support, and then the coating film is cooled and solidified. Examples of the method include preparing a solution in which the first resin composition is dissolved in an organic solvent, applying the solution on the support, and drying and solidifying the coating film.
Further, when the first relief forming layer is formed by molding the first resin composition into a sheet shape, the thickness of the first relief forming layer is 10 to 300 μm after the crosslinking. From the viewpoint, it is preferably 10 to 300 μm.

Moreover, as a method of shape | molding 2nd resin composition in a sheet form, the method etc. which carry out rolling shaping | molding by calendering are mentioned, for example. The calender roll can be a calender roll having a combination of a plurality of rolls from one set of rolls (a pair of upper and lower two rolls), and the roll can be used depending on the film thickness accuracy required for the product. The number and roll interval (clearance) can be set. The number of rolls is two or more and can be appropriately selected according to the purpose. Moreover, the shape of the roll can be set in various shapes depending on how the rolls are combined. For example, in the case of a combination of four rolls, the I type in which the four are arranged vertically, the S type, and the inverted L type. Various arrangements such as Z-type and oblique Z-type can be taken. The roll interval is usually set so that the initial roll interval is larger than the target film thickness, and gradually decreased, and the final roll interval is set so that the final sheet thickness becomes the target film thickness.
In addition, when the second resin composition is formed into a sheet by calendering to form the second relief forming layer, the thickness of the second relief forming layer is 500 to 500 mm after the crosslinking. From the standpoint of 1600 μm, the last roll interval is preferably set in the range of 500 to 1600 μm.

[Crosslinking process]
In the method for producing a printing plate precursor according to the present invention, the first relief forming layer and the second relief forming layer are cross-linked by heat in a contact state, and the first relief forming layer and the first cross-linked relief forming layer are cross-linked. A crosslinking step of forming at least two crosslinked relief forming layers adjacent to the second crosslinked relief forming layer crosslinked by the two relief forming layers;
Since the thermal crosslinking agent in the second relief forming layer moves into the first relief forming layer by crosslinking with heat in such a contact state, the first crosslinked relief having a thin thickness of 10 to 300 μm is formed. Layers can be formed (crosslinked).
That is, since the thickness of the first crosslinked relief forming layer is 10 to 300 μm, as described above, the first relief forming layer is applied by a method in which the first resin composition is heated and melted and applied onto the support. However, in this method, the thermal crosslinking agent in the adjacent second relief forming layer is used as the first relief forming layer in the present invention. It is used for cross-linking.

Examples of such crosslinking include a method of heating while pressing in a state where the first relief forming layer and the second relief forming layer are bonded together.
Here, the pressing pressure is preferably from 1 MPa to 20 MPa, more preferably from 3 MPa to 12 MPa, from the viewpoint of suppressing in-plane variation of the film thickness in a state where the first relief forming layer and the second relief forming layer are bonded together. .
The heating temperature is preferably from 100 ° C. to 200 ° C., more preferably from 120 ° C. to 190 ° C., and particularly preferably from 140 ° C. to 180 ° C. from the viewpoints of the strength (printing durability), rinse properties and surface tack of the cured film. .
The heating time is preferably 1 minute to 100 minutes, more preferably 3 minutes to 60 minutes, and particularly preferably 5 minutes to 30 minutes.
As a general guideline for the heating temperature and heating time, if heating is performed at a temperature at which the half-life of the thermal crosslinking agent is 1 minute, the heating time is 5 to 10 minutes.

Examples of the thermal crosslinking equipment include, but are not limited to, a hot-air heating furnace, a heating press machine (single-wafer heating press machine, continuous press conveyor), a heating roll, and the like. When cross-linking after cutting to a desired size with a cutter before the cross-linking step, a single-wafer type heat press is used.

[How to make flexographic printing plates]
The plate making method of the flexographic printing plate of the present invention is a sculpture in which a relief layer is formed by performing laser engraving on the crosslinked relief forming layer of the flexographic printing plate precursor for laser engraving obtained by the method for producing a printing plate precursor of the present invention. It is a plate making method which has a process.
Moreover, it is preferable that the plate making method of the flexographic printing plate of the present invention has a rinsing step of rinsing the surface of the relief layer with an alkaline aqueous solution after the engraving step to obtain a flexographic printing plate.
The engraving process and the rinsing process will be described in detail below.

[Engraving process]
The plate making method of the flexographic printing plate according to the present invention includes at least two crosslinked reliefs in which a first crosslinked relief forming layer obtained by crosslinking a first relief forming layer and a second crosslinked relief forming layer obtained by crosslinking a second relief forming layer are adjacent to each other. An engraving step of laser engraving the formation layer;
Here, 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”, Electronic Communication Society, etc.
Also, a plate making apparatus equipped with a fiber-coupled semiconductor laser that can be suitably used in a method for making a flexographic printing plate using the flexographic printing plate precursor of the present invention is disclosed in JP 2009-172658 A and JP 2009-214334 A. It is described in detail in the official gazette and can be used for making a flexographic printing plate according to the present invention.

[Rinse process]
The plate making method of the flexographic printing plate of the present invention preferably has a rinsing step of rinsing the surface of the relief layer with an alkaline aqueous solution after the engraving step.
The plate making method of the flexographic printing plate of the present invention has a rinsing step, so that the engraving residue adhering and remaining on the surface of the relief layer can be washed away and removed.
As a rinsing method, a method of immersing in an alkaline aqueous solution, a method of rotating a rinsing solution while immersing in an alkaline aqueous solution, a method of sliding an engraving plate with a brush, a method of spraying an alkaline aqueous solution, a developing machine for a photosensitive resin relief plate In a known batch type or conveying type brush type washing machine, there are methods such as brushing the engraved surface mainly in the presence of an alkaline aqueous solution. If the engraving residue cannot be removed, use soap or a surfactant. An added rinse solution may be used.

The pH of the rinsing liquid (alkaline aqueous solution) that can be used in the present invention is preferably 10.0 or more, more preferably 12 or more, and still more preferably 13 or more. Moreover, it is preferable that the pH of the rinse liquid is 14 or less. It is excellent in rinse property as it is 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, etc. 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, amphoteric 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.

The plate making method of the flexographic printing plate of the present invention may further include a drying step and / or a post-crosslinking step as necessary.
Drying step: a step of drying the engraved relief layer.
Post-crosslinking step: a step of imparting energy to the relief layer after engraving and further crosslinking the relief layer.
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 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.

[Flexographic printing plate]
The flexographic printing plate of the present invention is a flexographic printing plate having a relief layer made by the method of making a flexographic printing plate of the present invention.
Here, the thickness of the relief layer of the flexographic printing plate is preferably from 0.05 mm to 10 mm, more preferably from the viewpoint of satisfying various printability such as wear resistance and ink transferability. It is from 05 mm to 7 mm, particularly preferably from 0.05 mm to 3 mm.

Moreover, it is preferable that the Shore A hardness of the relief layer which a flexographic printing plate has is 50 or more and 90 or less. When the Shore A hardness of the relief layer is 50 or more, the fine halftone dots formed by engraving will not collapse and collapse even when subjected to the strong printing pressure of the relief printing press, and normal printing can be performed. 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 conforms to ISO868: 2003, and at 25 ° C., an indenter (called a push needle or an indenter) is pushed into the surface of the object to be measured, and the amount of deformation (indentation depth). Is a value measured by a durometer (spring type rubber hardness tester) which measures and digitizes.

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

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

In Table 1 below, details of the components used in each Example and Comparative Example are as follows.

[First cross-linked relief forming layer]
<Binder polymer>
SBS (30/70): Styrenic thermoplastic elastomer [ASAPRENE (registered trademark, hereinafter the same) T-411, weight average molecular weight: 430,000, manufactured by Asahi Kasei Chemicals Corporation]
SBS (46/54): Styrenic thermoplastic elastomer [ASAPRENE 303, weight average molecular weight: 170,000, manufactured by Asahi Kasei Chemicals Corporation]
SBS (40/60): Styrenic thermoplastic elastomer [Tufprene (registered trademark, the same applies hereinafter) 125, weight average molecular weight: 100,000, manufactured by Asahi Kasei Chemicals Corporation]
Crystalline polyoctenamer: Bestenamer 8012 (weight average molecular weight: 100,000, manufactured by Huls)
-Ethylene-α-olefin copolymer: Tafmer DF840 (weight average molecular weight: 150,000, manufactured by Mitsui Chemicals)
Polypropylene: El Modu S901 (weight average molecular weight: 170,000, manufactured by Idemitsu Kosan Co., Ltd.)

<Photothermal conversion material>
CB: carbon black (# 45L, average particle size: 24 nm, specific surface area: 125 m ² / g, manufactured by Mitsubishi Chemical Corporation)

<Other ingredients>
-Liquid BR: diene polymer (liquid butadiene rubber, LBR305, weight average molecular weight: 30,000, manufactured by Kuraray Co., Ltd.)
HDDA: polymerizable compound (1,6-hexanediol diacrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd.)

[Second cross-linked relief forming layer]
<Diene polymer>
-BR: Butadiene rubber (BR150L, weight average molecular weight: 470,000, manufactured by Ube Industries)
EPDM: ethylene-propylene-diene copolymer (EP24, weight average molecular weight: 500,000 or more, manufactured by JSR)
IR: Isoprene rubber (IR2200L, manufactured by Ube Industries)
SBS (30/70): Styrenic thermoplastic elastomer [Asaprene T-411, weight average molecular weight: 430,000, manufactured by Asahi Kasei Chemicals Corporation]

<Thermal crosslinking agent>
Park mill D: organic peroxide [dicumyl peroxide (40% by mass), manufactured by NOF Corporation]

<Other ingredients>
HDDA: polymerizable compound (1,6-hexanediol diacrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd.)

[Examples 1 to 35]
<Preparation of first resin composition>
Using an MS-type compact pressure kneader (manufactured by Moriyama Co., Ltd.), the binder polymer, photothermal conversion material and other components shown in Table 1 below were kneaded for 10 minutes at the blending amounts (grams) shown in the same table, and the first relief A first resin composition for the forming layer was prepared. In Table 1 below, “-” as the blending amount indicates that the corresponding component is not blended.

<Preparation of second resin composition>
Using an MS-type compact pressure kneader (Moriyama Co., Ltd.), the diene polymer, photothermal conversion material, thermal crosslinking agent and other components shown in Table 1 below were kneaded for 10 minutes at the blending amounts (grams) shown in the same table. A second resin composition for the second relief forming layer was prepared.

<Preparation of first relief forming layer>
The first resin composition obtained above was melted at 150 ° C., applied on a PET substrate so that the thickness after crosslinking was as shown in Table 1 below, and cooled at 25 ° C. for 20 minutes, One relief forming layer was formed. The thickness in Table 1 below is the thickness of the “first crosslinked relief forming layer” after crosslinking, but no change in thickness was observed before and after crosslinking.

<Preparation of second relief forming layer>
The second resin composition obtained above is pressed while sandwiching a spacer and heated at 80 ° C. for 5 minutes so that the thickness after crosslinking is the thickness shown in Table 1 below. A certain second relief forming layer was obtained. The thickness in Table 1 below is the thickness of the “second crosslinked relief forming layer” after crosslinking, but no change in thickness was observed before and after crosslinking.

<Preparation of flexographic printing plate precursor>
The first relief forming layer formed on the PET substrate is attached to the second relief forming layer, and the thickness after crosslinking is the thickness of the first relief forming layer and the second relief forming layer shown in Table 1 below, respectively. The substrate was hot-pressed at 160 ° C. for 20 minutes to obtain a flexographic printing plate precursor having a first crosslinked relief forming layer and a second crosslinked relief forming layer.

[Comparative Example 1]
A flexographic printing plate precursor was produced in the same manner as in Example 1 except that the first relief forming layer was not formed. That is, the flexographic printing plate precursor produced in Comparative Example 1 is an embodiment in which the crosslinked relief forming layer is one layer as in Patent Documents 1 and 2.

[Measurement of Martens hardness]
About each produced flexographic printing plate precursor, the Martens hardness of the 1st crosslinked relief forming layer and the 2nd crosslinked relief forming layer was measured. The evaluation method of Martens hardness is as described above. Table 1 below shows the Martens hardness of the Martens hardness of the first crosslinked relief forming layer and the second crosslinked relief forming layer.

[Printing pressure latitude]
For the relief forming layer after crosslinking of the obtained flexographic printing plate precursor for laser engraving, a semiconductor laser engraving machine (FC-LD) SDL-6390 with a maximum output of 8.0 W (manufactured by JDSU, wavelength) Using a laser recording apparatus equipped with 915 nm), 2% halftone dots were engraved under the conditions of laser output: 7.5 W, head speed: 409 mm / second, pitch setting: 2,400 DPI, and then sodium bicarbonate 1 A flexographic printing plate was prepared by rinsing with an aqueous solution containing mass%.
The obtained flexographic printing plate was set in a flexographic printing machine (ITM-4 type, manufactured by Iyo Machinery Co., Ltd.). As the printing ink, solvent ink (XS-716 507, primary color indigo (manufactured by DIC Graphics Corporation)) was used. Printing was performed using full-color foam M70 (manufactured by Nippon Paper Industries Co., Ltd., thickness: 100 μm) as printing paper.
In the above flexographic printing press, the distance between the plate cylinder and the thick cylinder can be controlled with a dial, so the distance is adjusted and the reflection density of 2% halftone dot is measured by a densitometer (Macbeth RD-19I manufactured by Gretag). It measured by measurement. The printing pressure (indentation amount) at which the solid was printed uniformly was used as the reference (0 μm).
Table 1 below shows the difference (value) between the halftone dot reflection density under the indentation amount of 20 μm and the halftone dot reflection density under the indentation amount of 120 μm. A smaller value means a wider printing pressure latitude.

As shown in Table 1, it was found that when the first crosslinked relief forming layer was not provided, in other words, when there was no hardness difference in the crosslinked relief forming layer, the printing pressure latitude was narrowed (Comparative Example 1).
On the other hand, in the case where a first crosslinked relief forming layer and a second crosslinked relief forming layer having a predetermined thickness are provided and the ratio of these Martens hardnesses satisfies a specific relationship, in the halftone image portion of the printing plate It was found that the printing pressure latitude can be widened (Examples 1 to 35).
In particular, the results of Examples 1 to 6 indicate that when the binder polymer contained in the first crosslinked relief forming layer is a crystalline polymer, the difference in reflection density is the smallest and the printing pressure latitude is wider ( Example 6).
In addition, it was found from the comparison between Example 4 and Example 34 that the resin composition forming the second crosslinked relief forming layer contains a polymerizable compound, so that the printing pressure latitude becomes wider.
Further, from comparison between Example 4 and Example 35, it was found that the resin composition that forms the second crosslinked relief forming layer uses polybutadiene as the diene polymer, so that the printing pressure latitude is wider. .

Claims (8)

1. A flexographic printing plate precursor for laser engraving having at least two crosslinked relief forming layers,
   The first crosslinked relief forming layer disposed on the surface side subjected to laser engraving, and the second crosslinked relief forming layer adjacent to the first crosslinked relief forming layer, the Martens of the second crosslinked relief forming layer The ratio of the Martens hardness A of the first crosslinked relief forming layer to the hardness B is 1.1 or more,
   The first crosslinked relief forming layer has a thickness of 10 to 300 μm;
   The second crosslinked relief forming layer has a thickness of 500 to 1600 μm;
   The first crosslinked relief forming layer contains a binder polymer and a photothermal conversion material,
   The flexographic printing plate precursor for laser engraving, wherein the second crosslinked relief-forming layer is a layer that is crosslinked by heat after forming a relief-forming layer using a resin composition containing a diene polymer and a thermal crosslinking agent.
2. The flexographic printing plate precursor for laser engraving according to claim 1, wherein the thermal crosslinking agent is at least one selected from the group consisting of organic peroxides and sulfur-based compounds.
3. The flexographic printing plate precursor for laser engraving according to claim 1 or 2, wherein the resin composition further contains a polymerizable compound.
4. The flexographic printing plate precursor for laser engraving according to any one of claims 1 to 3, wherein the binder polymer is a crystalline polymer.
5. The laser engraving according to any one of claims 1 to 4, wherein the diene polymer is at least one polymer selected from the group consisting of polyisoprene, polybutadiene, and ethylene-propylene-diene copolymers. Flexographic printing plate precursor.
6. A first layer forming step of forming a first relief forming layer using a resin composition containing a binder polymer and a photothermal conversion material;
   A second layer forming step of forming a second relief forming layer using a resin composition containing a diene polymer and a thermal crosslinking agent;
   The first relief forming layer and the second relief forming layer are crosslinked by heat in a state where the first relief forming layer and the second relief forming layer are in contact with each other, and the first crosslinked relief forming layer and the second relief forming layer are crosslinked by the first relief forming layer. A crosslinking step of forming at least two crosslinked relief forming layers adjacent to the second crosslinked relief forming layer;
   The ratio of the Martens hardness A of the first crosslinked relief forming layer disposed on the surface side subjected to laser engraving to the Martens hardness B of the second crosslinked relief forming layer adjacent to the first crosslinked relief forming layer, 1.1 or more,
   The first crosslinked relief forming layer has a thickness of 10 to 300 μm;
   A method for producing a flexographic printing plate precursor for laser engraving, wherein the second crosslinked relief forming layer has a thickness of 500 to 1600 μm.
7. It has the engraving process which gives a laser engraving with respect to the bridge | crosslinking relief forming layer of the flexographic printing plate precursor for laser engraving produced with the manufacturing method of the flexographic printing plate precursor for laser engraving according to claim 6, and forms a relief layer , Plate making method of flexographic printing plate.
8. A flexographic printing plate having a relief layer made by the plate making method of a flexographic printing plate according to claim 7.