JP2019109444A - Method for producing photosensitive resin plate for flexographic printing - Google Patents

Abstract

To provide a method for producing a photosensitive resin plate for flexographic printing that gives a flexographic printing plate that (1) reduces distortion in ink transfer in printed matter and (2) has excellent durability in repeated bonding in printing (particularly, prevents cracking).SOLUTION: A method for producing a photosensitive resin plate for flexographic printing has a step of producing a printing original plate having a support, and a photosensitive resin layer put on the support. The photosensitive resin layer has at least one elastomer binder (A), at least one ethylene unsaturated copolymerizable monomer (B), at least one hydrocarbon compound (C), and at least one photopolymerizable initiator (D). A dissolution rate of the photosensitive resin layer dissolved with a hydrocarbon-containing cleaning solvent (E) is 0.09-0.6 mm/min.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a photosensitive resin plate for flexographic printing.

  For example, as described in Patent Documents 1 and 2, a photosensitive resin composition used for producing a photosensitive resin plate for flexographic printing comprises a thermoplastic elastomer, a photopolymerizable unsaturated monomer, a plasticizer, and Those containing a photopolymerization initiator are common.

  As a composition for flexographic printing plate, a polyester film or the like is used as a support, a layer containing the above-mentioned photosensitive resin composition (a photosensitive resin layer is laminated thereon, and if necessary, a contact with a negative film is made In order to smooth the surface, it is generally constructed by further laminating a slip layer or a protective layer, or an ultraviolet shielding layer containing an infrared sensitive material that can be removed by an infrared laser, on the above layer.

  In order to make a flexographic printing plate from such a photosensitive composition for flexographic printing plate, first, the entire surface is exposed to ultraviolet light (back exposure) through the support to provide a thin uniform cured layer, and then through the negative film or Image exposure (relief exposure) is performed on the surface of the photosensitive resin layer directly from above the ultraviolet shielding layer, and the unexposed area is washed away with a developing solvent or after heat melting and absorption removal by an absorption layer, post-processing exposure It is generally manufactured by

  In general printing using a photosensitive resin plate for flexographic printing, an ink containing an ester solvent or the like is supplied to the surface of the convex portion of the resin plate having irregularities using an ink supply roll or the like, and then the resin plate is It is made to contact the to-be-printed body, and the ink of the convex part surface is transferred to a to-be-printed body, and is performed.

  In such flexographic printing, when the shape (resolution) faithful to the negative film can not be obtained or the ester solvent resistance is not obtained, the printing plate is broken or swollen during printing for a long time, and the original pattern is not formed. Parts may be printed.

  Various plasticizers have been proposed for such photosensitive resin compositions. For example, in Patent Document 3, a liquid polyisoprene having a large amount of unsaturated bonds in a molecule having a molecular weight of 25,000 or more is used as a plasticizer for improving solvent resistance. As a control, a naphthenic oil having a low refractive index is used as a hydrocarbon-based plasticizer in Example 1. In Examples 1 to 9, as a hydrocarbon-based plasticizer, styrene-based oligomers having a large amount of unsaturated bonds are used.

  In addition, in Patent Document 4, in order to improve the ink resistance containing an ester solvent etc., the elastomer resin has a weight average molecular weight of 2000 or less, an unsaturated bond amount of 0.5 mol / 100 g or less, and a refractive index at 20 ° C. of 1 . 497 or more of a hydrogenated terpene resin, a photopolymerizable unsaturated monomer, a photopolymerization initiator, and, if necessary, a photosensitive resin containing a dye, a pigment, a polymerization inhibitor, an antioxidant and a photodegradation inhibitor Compositions have been proposed. By way of example, the examples show a photosensitive resin composition comprising a styrene isoprene styrene block copolymer, a hydrogenated terpene resin, two photopolymerizable monomers, and a benzyldimethyl ketal as a photopolymerization initiator. There is.

JP, 2000-155418, A JP 02-108632 A Unexamined-Japanese-Patent No. 04-342258 JP 10-288838 A JP, 2006-3570, A JP, 2007-148322, A

  However, in these photosensitive resin compositions, the cohesion between molecules is enhanced for the purpose of improving the solvent resistance, and therefore, there is a tendency for the molecules to be easily oriented locally at the time of flexographic printing plate formation. Therefore, when the printing plate is pressed against the printing cylinder at the time of printing, the degree of deformation between the MD direction and the TD direction changes, and ink transfer can not be performed precisely as designed. In addition, since the tensile properties of the MD direction and the TD direction differ due to the orientation of the plate, when the plate is repeatedly attached to the impression cylinder and removed, there is a problem that a minute crack occurs in the plate.

  The present invention provides (1) less distortion of ink transfer in printed matter, and (2) excellent flexing resistance at the time of repeated application during printing (in particular, generation of cracks is suppressed), to obtain a flexographic printing plate It is an object of the present invention to provide a method for producing a photosensitive resin plate for flexographic printing that can be used.

  As a result of intensive studies to solve the above problems, the present inventors manufacture a flexographic printing original plate having a support as shown below and a specific photosensitive resin layer laminated on the support. It has been found that it is possible to obtain a flexographic printing plate which is less in distortion of ink transfer in printed matter and excellent in durability at the time of repeated application in printing by using a manufacturing method having the following steps. It reached.

  That is, the factor which can obtain the flexographic printing plate which has few distortions of the ink transfer in printed matter, and was excellent in the durability at the time of printing and sticking is considered as follows. However, the factor is not limited to this. The elastomeric binder (A) contained in the photosensitive resin layer is bonded to the ethylenically unsaturated copolymerizable monomer (B) by cleavage of the photopolymerizable initiator (D) at the time of exposure to generate radicals. It becomes insoluble in the developing solution. The hardness, durability, and orientation of the resin after exposure are affected by the intermolecular distance between the elastomeric binder (A) and the ethylenically unsaturated copolymerizable monomer (B). The hydrocarbon compound (C), which is important in the present invention, can enter between the elastomeric binders (A) to reduce the intermolecular distance between the elastomers, thereby reducing the cohesion of the elastomeric binders (A). Can. After exposure and development of the photosensitive resin, a part of the hydrocarbon compound (C) is dissolved in the developer and removed, so that a slight void is formed between the elastomeric binder (A), and the orientation of the resin is reduced. can do.

  Further, the removability of the hydrocarbon compound (C) contained in the photosensitive resin layer is influenced by the solubility of the hydrocarbon compound (C) in the hydrocarbon-containing cleaning solvent (E). And the intermolecular force of the hydrocarbon compound (C). If the solubility of the uncured resin in the developer is too high, the voids of the resin after exposure and development become large, and the resin becomes brittle. In addition, when the solubility of the uncured resin in the developer is too low, voids in the resin after exposure and development become small, and the orientation can not be sufficiently reduced.

  Thus, as a result of intensive studies, the inventors of the present invention have found that the orientation of the resin in the photosensitive resin layer after curing is controlled by controlling the dissolution rate of the unexposed photosensitive resin layer in the developer. It has been found that it is controlled to reduce distortion of ink transfer of printed matter, and to suppress cracking that occurs during repeated application during printing.

In addition, when the photosensitive resin layer contains a hydrocarbon compound (C) having a solubility parameter of 18 MPa ^1/2 or less, it has been found that the ink transfer distortion and the cracks of the plate are more remarkably suppressed. . The solubility parameter of the hydrocarbon-containing cleaning solvent (E) used in the present invention is closer to the solubility parameter of the hydrocarbon compound (C) than the solubility parameter of the elastomeric binder (A). The hydrocarbon compound (C) is considered to be more soluble in the hydrocarbon-containing washing solvent (E) than A), and is considered to affect the formation of voids in the resin.

  The improvement of print quality by controlling the developing speed at the time of plate making is a surprising finding, and there has been no case reported so far.

That is, the present invention is as follows.
[1]
A production method comprising the steps of producing a photosensitive resin plate for flexographic printing comprising a support and a photosensitive resin layer laminated on the support,
The photosensitive resin layer is
At least one elastomeric binder (A),
At least one or more ethylenically unsaturated copolymerizable monomers (B),
At least one or more hydrocarbon compounds (C),
A flexographic printing plate precursor comprising: at least one photopolymerization initiator (D);
The dissolution rate of the photosensitive resin layer dissolved by the hydrocarbon-containing cleaning solvent (E) is 0.09 to 0.6 mm / min.
The manufacturing method of the photosensitive resin plate for flexographic printings.
[2]
The photosensitive resin layer contains a hydrocarbon compound (C) having a solubility parameter of 18 MPa ^1/2 or less.
The manufacturing method of the photosensitive resin for flexographic printing as described in [1].
[3]
The hydrocarbon compound (C) contains paraffin oil,
The manufacturing method of the photosensitive resin for flexographic printing as described in [1] or [2].
[4]
The hydrocarbon compound (C),
The density at 15 ° C. is 0.7 to 1.0 g / cm ² ,
The kinematic viscosity at 40 ° C. is 100 mm ² / s or less,
The weight average molecular weight is 1,000 or less,
The hydrocarbon compound (C) contains a plasticizer having a naphthene ratio in the hydrocarbon compound (C) of 5.0 to 60 mol%.
The manufacturing method of the photosensitive resin for flexographic printings in any one of [1]-[3].
[5]
The photosensitive resin layer contains an elastomeric binder (A) in an amount of less than 60% by mass, based on the total amount of the photosensitive resin layer.
The manufacturing method of the photosensitive resin for flexographic printings in any one of [1]-[4].

  According to the method for producing a photosensitive resin plate for flexographic printing according to the present invention, it is possible to obtain a flexographic printing plate which is less in distortion of ink transfer in printed matter and excellent in durability at the time of repeated application during printing.

  Hereinafter, although a mode for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail, the present invention is not limited to this, and various modifications can be made within the scope of the present invention. Is possible.

[Method of producing photosensitive resin plate for flexographic printing]
The method for producing a photosensitive resin plate for flexographic printing according to the present embodiment is a flexographic printing plate precursor having a support and a photosensitive resin layer laminated on the support (hereinafter, “a construction for flexographic printing plate”) Also has a process of manufacturing. In addition, the photosensitive resin layer of the present embodiment includes at least one or more types of elastomeric binders (A) (hereinafter, also simply referred to as “(A)”) and at least one or more types of ethylenically unsaturated copolymerizable monomers (B) (hereinafter also referred to simply as "(B)"), at least one or more hydrocarbon compounds (C) (hereinafter referred to simply as "(C)"), and at least one or more types of light And a polymerizable initiator (D) (hereinafter, also simply referred to as "(D)"). Furthermore, in the flexographic printing original plate of the present embodiment, the dissolution rate of the photosensitive resin layer dissolved by the hydrocarbon-containing washing solvent (E) (hereinafter also referred to as “developing solvent” or “(E)”) is It is 0.09-0.6 mm / min.

(Support)
The support of the present embodiment is not particularly limited as long as it can support the photosensitive resin layer. As the support, for example, a polyester film is suitably used, and particularly preferably polyethylene terephthalate is mentioned.

(Photosensitive resin layer)
The photosensitive resin layer of the present embodiment is laminated on a support. The photosensitive resin layer can be obtained, for example, by sheet-forming the photosensitive resin composition constituting the photosensitive resin layer, bringing it into close contact with a support by roll lamination, and performing heat pressing after lamination. Moreover, according to such a method, the photosensitive resin layer further excellent in thickness accuracy can be obtained.

  The flexographic printing plate construction of the present embodiment can be prepared by various methods using a support, a photosensitive resin composition which is a raw material of a photosensitive resin layer, and the like. For example, the raw material of the photosensitive resin composition is dissolved in a suitable solvent such as chloroform, tetrachloroethylene, methyl ethyl ketone, toluene or the like and mixed, and cast into a mold to evaporate the solvent, and the plate is used as it is It can be Moreover, although it can knead | mix with a calender roll, a press, etc. after kneading | mixing with a kneader, a roll mill, or a screw extruder without using a solvent, it can be shape | molded to a desired thickness. It is not limited to what is obtained by the preparation method.

  Since the composition for flexographic printing plate usually has tackiness, it is a photosensitive resin in order to improve the contact with a negative film to be overlaid thereon during platemaking, or to enable reuse of the negative film. A solvent-soluble thin flexible protective layer (see, for example, Japanese Patent Publication No. 5-13305) may be further provided on the surface of the layer. Further, instead of the flexible protective layer, an ultraviolet shielding layer containing an infrared sensitive material may be provided, and the ultraviolet shielding layer itself may be used as a negative by direct drawing with an infrared laser. In either case, when the unexposed area of the photosensitive resin layer is washed out after the exposure is completed, the thin flexible protective layer or the ultraviolet shielding layer is also removed simultaneously.

  As a solvent-soluble thin flexible protective layer, for example, a layer of polyamide, partially saponified polyvinyl acetate, cellulose ester or the like which is soluble in the washing solution is to be provided on the surface of the photosensitive resin layer, This may be dissolved in an appropriate solvent and the solution coated directly on the photosensitive resin layer. Alternatively, the film may be coated (protective film) on a film of polyester, polypropylene or the like, and then this protective film may be laminated or pressed onto the photosensitive resin layer to transfer the protective film.

  The protective layer is obtained by sheet-forming the photosensitive resin composition constituting the photosensitive resin layer, bringing the photosensitive resin composition into close contact with the protective film by roll lamination, and heat pressing after lamination, as in the case of the support.

<Elastomer binder (A)>
The elastomeric binder (A) of the present embodiment means a polymer which can be plasticized at high temperature to be molded, and exhibits a property as a rubber elastic body at normal temperature. Among the elastomeric binders (A), thermoplastic block copolymers having aromaticity are preferable from the viewpoint of shortening of plate making time and image reproducibility of a printing plate.

  The thermoplastic block copolymer having aromaticity means a copolymer having at least a polymer block mainly composed of a vinyl aromatic hydrocarbon and a polymer block mainly composed of a conjugated diene. In the present specification, the term "main body" means that the content is 70% by mass or more.

  The vinyl aromatic hydrocarbon is not particularly limited, and examples thereof include styrene, P-methylstyrene, tertiary butylstyrene, α-methylstyrene, 1,1-diphenylethylene and the like, among them from the viewpoint of availability And styrene are preferred. One of these may be used alone, or two or more of these may be used in combination.

  The content of the vinyl aromatic hydrocarbon is preferably 13% by mass, from the viewpoint of the cold flow resistance of the uncured resin composition, with respect to the total amount (100% by mass) of the thermoplastic block copolymer having aromaticity. %, And from the viewpoint of solvent resistance, preferably 28% by mass or less, more preferably 14% by mass to 25% by mass, and still more preferably 15% by mass to 25% by mass.

  The conjugated diene is not particularly limited, and examples thereof include butadiene and isoprene and / or a hydrogenated product thereof. One of these may be used alone, or two or more of these may be used in combination. The hydrogenation of the conjugated diene may be carried out after forming a thermoplastic block copolymer having aromaticity.

  Among them, butadiene and / or a hydrogenated product thereof is preferable from the viewpoints of reducing the tackiness of the surface, the abrasion resistance of the printing plate, and the haze resistance.

  The vinyl content in the conjugated diene block is preferably 5.0% by mass to 40% by mass from the viewpoint of the scuff resistance.

  The structure of the thermoplastic block copolymer having aromaticity may be linear or radial of 3 to 6 branches from the viewpoint of easiness of production.

  The thermoplastic block copolymer having an aromatic group contains 10% by mass or more of a diblock having a vinyl aromatic hydrocarbon block and a conjugated diene block from the viewpoint of the flexibility of the printing plate and the scuff resistance. It is preferable to do.

  The elastomeric binder (A) may further contain a block mainly composed of ethylene or propylene, if necessary.

  The weight average molecular weight of the elastomeric binder (A) is not particularly limited, but it is preferable that the balance between molding processability and solid retention of the photosensitive resin to be obtained be excellent, and polystyrene conversion using gel permeation chromatography (GPC) The standard polystyrene equivalent is preferably 8 to 400,000.

  The content of the elastomeric binder (A) is preferably 20% by mass or more based on the total amount (100% by mass) of the photosensitive resin layer, from the viewpoint of the cold flow resistance and the scuff resistance of the uncured resin composition. And from the viewpoint of flexibility, preferably 90% by mass or less, more preferably 30% by mass or more, more preferably 75% by mass or less, still more preferably 40% by mass or more, further preferably Is less than 60% by mass.

  If necessary, the photosensitive resin layer can contain 20% by mass or less of an elastomer (other elastomer) other than the elastomeric binder (A). As another elastomer, polyolefin, polyester, polyurethane etc. are mentioned, for example.

<Ethylene unsaturated copolymerizable monomer (B)>
The ethylenically unsaturated copolymerizable monomer (B) of the present embodiment is not particularly limited, and, for example, esters such as acrylic acid, methacrylic acid, fumaric acid, and maleic acid; derivatives of acrylamide and methacrylamide; allyl ester, Styrene and its derivatives; N-substituted maleimide compounds and the like can be mentioned.

  Specific examples of the ethylenically unsaturated copolymerizable monomer (B) include diacrylates and dimethacrylates of alkanediols such as hexanediol and nonanediol; ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, butylene Diacrylates and dimethacrylates of glycols; trimethylolpropane tri (meth) acrylate, dimethylol tricyclodecane di (meth) acrylate, isoboronyl (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate, pentaerythritol tetra (meth) acrylate N, N'-hexamethylene bisacrylamide and methacrylamide, styrene, vinyl toluene, divinyl benzene, dia Lil phthalate, triallyl cyanurate, fumaric acid diethyl ester, fumaric acid dibutyl ester, fumaric acid dioctyl ester, fumaric acid distearyl ester, fumaric acid butyl octyl ester, fumaric acid diphenyl ester, fumaric acid dibenzyl ester, maleic acid dibutyl ester And maleic acid dioctyl ester, fumaric acid bis (3-phenylpropyl) ester, fumaric acid dilauryl ester, fumaric acid dibehenyl ester, N-lauryl maleimide and the like. One of these may be used alone, or two or more of these may be used in combination.

  When the content of the ethylenically unsaturated copolymerizable monomer (B) is equal to or more than a predetermined lower limit relative to the total amount (100% by mass) of the photosensitive resin layer, the formation of fine points and characters is deteriorated. In order to suppress the decrease in cold flow resistance when the photosensitive resin layer before exposure is laminated and the decrease in the flexibility of the printing plate by suppressing and not exceeding the predetermined upper limit value, preferably 1. It is 0-20 mass%.

  From the viewpoint of ester solvent resistance, the ethylenically unsaturated copolymerizable monomer (B) is preferably a photopolymerizable unsaturated monomer having a bifunctional or higher polyfunctional (meth) acrylate, preferably 3.0 mass% to It contains 15% by mass, more preferably 5.0 to 15% by mass. Furthermore, it is more preferable that the ethylenically unsaturated copolymerizable monomer (B) contains both a polyfunctional acrylate and a polyfunctional methacrylate.

<Hydrocarbon compound (C)>
Although it does not specifically limit as a hydrocarbon compound (C) of this embodiment, For example, it is resin which consists of substance and carbon and hydrogen, and a paraffin hydrocarbon, an olefin hydrocarbon, a naphthene hydrocarbon etc. are mentioned, for example. One of these may be used alone, or two or more of these may be used in combination.

Paraffinic hydrocarbons are saturated chain compounds of the molecular formula C _n H _{2n + 2} , and include unbranched normal paraffins and branched isoparaffins.

The olefinic hydrocarbon is a chain hydrocarbon having a double bond, and when there is one double bond, it is represented by a general formula of C _n H _{2 n} .

A naphthenic hydrocarbon is a hydrocarbon containing at least one saturated ring (naphthenic ring) in one molecule, and is represented by the general formula of C _n H _{2 n} . Naphthenic hydrocarbons present in crude oil and petroleum products are those in which two or three naphthene rings are connected, those condensed with an aromatic ring, and further, various paraffin side chains are attached to the naphthenic ring and the condensed ring. There are things etc.

The hydrocarbon compound (C) preferably has a low density, dynamic viscosity, weight average molecular weight, and naphthene ratio from the viewpoint of developability of the photosensitive resin layer, and has a density from the viewpoint of elution of the resin into a developer. The higher the dynamic viscosity, the weight average molecular weight, and the naphthene ratio, the better. Therefore, the density of the hydrocarbon compound (C) at 15 ° C. is 0.7 to 1.0 g / cm ² , the kinematic viscosity at 40 ° C. is 100 mm ² / s or less, and the weight average molecular weight is 1,000 The hydrocarbon compound (C) preferably has a naphthene ratio in the hydrocarbon compound (C) of 5.0 to 60 mol%, and a density at 15 ° C. of 0.8 to 0.9 g. / Cm ² , the kinematic viscosity at 40 ° C. is 70 mm ² / s or less, the weight average molecular weight is 600 or less, and the hydrocarbon compound (C) is a naphthene occupied in the hydrocarbon compound (C) More preferably, the ratio is 10 to 50 mol%.

  The density at 15 ° C. can be measured, for example, by the method described in JIS Z8804.

  The kinematic viscosity at 40 ° C. can be measured, for example, by a Ubbelode viscometer described in JIS Z8803.

  The said weight average molecular weight is the value calculated | required from polystyrene conversion which used gel permeation chromatography (GPC). Specifically, it was analyzed and calculated using an RI detector of HLC-8020 (GPC manufactured by Tosoh Corporation, trade name "Column TSK-GEL-GMHXL").

  The naphthene ratio in the above-mentioned hydrocarbon compound (C) can be measured by NMR or the like.

(Solubility parameter)
The solubility parameter is a substance-specific parameter introduced to estimate the affinity of the solvent and the solute, and the combination of the solvent and the solute having the closer solubility parameter can provide good solubility. The solubility parameter is known as Hildebrand, Hansen et al., And the solubility parameter in this specification refers to the Hildebrand solubility parameter. The details of the Hildebrand solubility parameter are described in "POLYMER HANDBOOK" (Fourth Edition, pp. 675-714, Joh Wiley & Sons, Inc. 1999) and the like.

Solubility parameter of the hydrocarbon compound (C) is preferably at 18 MPa ^1/2 or less, more preferably 17.5MPa ^1/2 or less, more preferably 17 MPa ^1/2 or less. When the solubility parameter is in the above range, the developability tends to be excellent.

  The content of the hydrocarbon compound (C) is preferably 5.0% by mass or more to suppress local orientation with respect to the total amount (100% by mass) of the photosensitive resin layer, and a micro image Preferably, it is 50% by mass or less in terms of the formability of Moreover, More preferably, it is 10 mass% or more, More preferably, it is 35 mass% or less, More preferably, it is 20 mass% or more, More preferably, it is 30 mass% or less.

<Photoinitiator (D)>
The photopolymerization initiator (D) of the present embodiment means a compound that absorbs light energy and generates a radical. Moreover, although various well-known things can be used for a photoinitiator (D), It is suitable to use various organic carbonyl compounds, especially an aromatic carbonyl compound.

  Specific examples of the photopolymerization initiator (D) include, for example, benzophenone, 4,4-bis (diethylamino) benzophenone, t-butylanthraquinone, 2-ethylanthraquinone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4 Thioxanthones such as dichlorothioxanthone; diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, Acetophenones such as 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone Benzoin methine Benzoin ethers such as ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether; 2,4,6-trimethylbenzoyl diphenyl phosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentyl phosphine Oxides, acyl phosphine oxides such as bis (2,4,6-trimethyl benzoyl) -phenyl phosphine oxide; methyl benzoyl formate; 1,7-bisacridinyl heptane; 9-phenyl acridine and the like. One of these may be used alone, or two or more of these may be used in combination.

  The content of the photopolymerization initiator (D) is not less than a predetermined lower limit value with respect to the total amount (100% by mass) of the photosensitive resin layer, thereby suppressing a decrease in the formability of fine points and characters. By being less than a predetermined upper limit value, in order to suppress the transmittance | permeability fall of active light, such as an ultraviolet-ray, Preferably it is 1.0-5.0 mass%, More preferably, 1.5 mass% -4.0 It is mass%.

<Conjugated diene rubber>
The photosensitive resin layer of the present embodiment can further contain a conjugated diene rubber.

  Conjugated diene rubbers are obtained from dienes. As the diene, isoprene and / or butadiene are preferable in terms of availability, and butadiene is more preferable from the viewpoint of cake resistance.

  Specific examples of conjugated diene rubbers include polybutadiene and polyisoprene. Moreover, B-2000 (brand name by Nippon Soda Co., Ltd.) is mentioned as a commercial item. One of these may be used alone, or two or more of these may be used in combination.

  The vinyl content in the conjugated diene rubber is preferably as high as possible from the viewpoint of the formation of minute images and resistance to scuffing, preferably 50 mol% or more, more preferably 70 mol% or more, and still more preferably 75 mol% It is above. The vinyl content in the conjugated diene rubber can be determined from proton NMR (nuclear magnetic resonance spectrum).

  The weight average molecular weight (Mw) of the conjugated diene rubber is preferably lower from the viewpoint of handleability and compatibility of the photosensitive resin composition, and higher from the viewpoint of scuff resistance, preferably 1000 to 50000, More preferably, it is 2000-30000, More preferably, it is 3000-20000. The weight average molecular weight of the conjugated diene rubber can be measured by gel permeation chromatography (GPC) as in the measurement of the weight average molecular weight of the component (C).

  The content of the conjugated diene rubber is preferably 3.0% by mass or more from the viewpoint of the image reproducibility, the scuff resistance, and the flexibility with respect to the total amount (100% by mass) of the photosensitive resin layer, and the printing plate From the viewpoint of the solid maintenance property of the photosensitive composition for use, the content is preferably 40% by mass or less, more preferably 5.0 to 30% by mass, and still more preferably 7.0 to 20% by mass

  The photosensitive resin layer of the present embodiment may further contain various auxiliary additive components, for example, a plasticizer, a thermal polymerization inhibitor, an ultraviolet light absorber, an antihalation agent, a light stabilizer, an antioxidant and the like, as desired. Can.

[Flexographic printing plate]
The flexographic printing plate of the present embodiment is prepared from the flexographic printing plate (photosensitive composition for flexographic printing plate) described above. As a general method of making a flexographic printing plate from a photosensitive composition for flexographic printing plate, first, the entire surface is exposed to ultraviolet light through the support (back exposure), a thin uniform cured layer is provided, and then through a negative film, Alternatively, image exposure (relief exposure) is performed on the surface of the photosensitive resin layer directly from above the ultraviolet shielding layer, and the unexposed area is washed away with a developing solvent, or after heat melting and absorption and removal by an absorption layer, post-processing exposure Manufactured by doing. Here, a "hardened layer" means the layer hardened | cured, for example by receiving the irradiation of an ultraviolet-ray among photosensitive resin layers.

  The Shore A hardness of the printing plate (thickness: 3.94 mm) of the present embodiment is preferably 50 ° or less, more preferably 45 ° or less from the viewpoint of suppressing transfer unevenness of the ink generated at the time of corrugated board printing. And more preferably 40 ° or less. After leaving a 3.94 mm thick flexographic printing plate in a constant temperature and humidity chamber at a temperature of 23 ° C. and a relative humidity of 50% for 1 day, a JIS constant pressure load device GS-710 (a durometer manufactured by Techlock Co., Ltd., durometer GS-719G ASTM) It can measure using: D2240A, JIS: K6253A, ISO: 7619A). The value after 15 seconds of load (mass 1 kg) on a solid surface is taken as Shore-A hardness.

  As image exposure for changing the surface tension of the surface of a printing plate, after exposing the ultraviolet-ray of a 200-300 nm wavelength range, you may expose with the ultraviolet ray of a 310-400 nm wavelength range.

  Either of the exposure from the negative film side (relief exposure) and the exposure from the support side (back exposure) may be performed first, or both may be performed simultaneously.

  Examples of the exposure light source include high pressure mercury lamps, ultraviolet fluorescent lamps, carbon arc lamps, xenon lamps, and diode lamps.

  Cleaning out of the unexposed area by the developing solvent is performed by jet from a nozzle or by brushing with a brush.

  As the post-treatment exposure, a method of irradiating the surface with light having a wavelength of 300 nm or less is generally used. If necessary, light larger than 300 nm may be used in combination.

<Hydrocarbon-containing cleaning solvent (E)>
The hydrocarbon-containing cleaning solvent (E) (developing solvent) of the present embodiment is used as a cleaning solvent for the photosensitive resin layer. Moreover, it is used also as a developing solvent used for developing an unexposed part. Examples of the hydrocarbon-containing cleaning solvent (E) include esters such as heptyl acetate and 3-methoxybutyl acetate; petroleum fractions, hydrocarbons such as toluene and decalin; chlorinated organic solvents such as tetrachlorethylene; propanol And alcohols such as butanol and pentanol, and mixtures of two or more thereof. In particular, a mixed solvent of decalin, tetrachlorethylene and propanol is preferable.

(Dissolution rate)
The dissolution rate in this embodiment is the dissolution rate of the photosensitive resin layer, but may be the dissolution rate of flexo printing plate or flexo printing plate (of photosensitive resin layer), 0.09 to 0.6 mm / Min, preferably 0.1 to 0.4 mm / min, more preferably 0.15 to 0.3 mm / min. When the dissolution rate is in the above-mentioned range, it is possible to obtain a flexographic printing plate which is less in distortion of ink transfer in printed matter and is excellent in durability at the time of repeated sticking at the time of printing. In order to obtain a printing plate precursor having a dissolution rate in the above range, for example, the ratio of the chlorine-based organic solvent of the hydrocarbon-containing washing solvent (E) may be changed. The dissolution rate is determined by dividing the thickness of the unexposed area of the photosensitive resin layer, which decreases after development with the hydrocarbon-containing washing solvent (E), by the time taken for washing out with the developing solvent in plate making of flexographic printing plate Be Specifically, it is determined by the method described in the examples described later.

  Hereinafter, the present embodiment will be described in more detail based on examples, but the present embodiments are not limited to the following examples. First, measurement methods and evaluation criteria of each physical property and evaluation will be described below.

(Synthesis of elastomeric binder (A))
After thoroughly replacing the 10 L stainless steel reactor equipped with a jacket and a stirrer with nitrogen, 6,500 g of cyclohexane, 1.2 g of tetrahydrofuran, and 300 g of styrene were charged, and the contents were set to about 55 ° C. by passing warm water through the jacket. After this, n-butyllithium cyclohexane solution (pure 0.96 g) was added to initiate polymerization of styrene. Three minutes after almost complete polymerization of styrene, 700 g of butadiene (1,3-butadiene) is added to continue polymerization, and butadiene is almost completely polymerized to reach a maximum temperature of about 90 ° C., and 4 minutes after Then, 1.25 g of dibromoethane as a coupling agent was added to cause a coupling reaction. Immediately after the styrene was charged, the system was continuously stirred by a stirrer during this time to obtain a solution of a block copolymer.

  The solution of the obtained block copolymer is withdrawn, 10 g of water is added, and after stirring, 3.0 g of n-octadecyl-3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate, The solvent was removed by steam-stripping the solution obtained by adding 1.5 g of 2,4-bis (n-octylthiomethyl) -O-cresol to obtain a water-containing crumb. Subsequently, it was dehydrated and dried by a heat roll to obtain a sample of SBS-A (elastomeric binder (A)).

(Preparation of Photosensitive Resin Composition and Photosensitive Composition)
The photosensitive resin composition was manufactured by charging the following raw materials into a kneader (Powrex Co., Ltd., FM-MW-3 type) and mixing at 140 ° C. for 60 minutes.

  50 parts by mass of SBS-A (sample obtained above) which is a block copolymer of styrene-butadiene as the elastomeric binder (A), 1,9-nonanediol as the ethylenically unsaturated covalent monomer (B) 6 parts by mass of acrylate, 20 parts by mass of dodecane as hydrocarbon compound (C), 2 parts by mass of 2,2-dimethoxy-phenylacetophenone as photopolymerization initiator (D), and conjugated diene compounds as other components The photosensitive resin composition 1 was obtained by kneading 15 parts by mass of liquid polybutadiene B-2000 (product name, manufactured by Nippon Soda Co., Ltd.) under the above conditions. It knead | mixed similarly by the composition shown to following Table 1, and obtained photosensitive resin composition 2-10.

The resulting photosensitive resin composition is sandwiched between a 125 μm thick polyester film support coated with an adhesive containing a thermoplastic elastomer and a 100 μm polyester cover sheet having a 4 μm thick polyamide layer. A photosensitive structure for a flexographic printing plate was molded by using a 4 mm spacer and a pressure of 200 kg / cm ² for 4 minutes at 130 ° C. in a press.

(Manufacture of printing plates for characterization)
In the photosensitive composition for flexographic printing plate as described above, the cover sheet is peeled off, a negative film is adhered on the photosensitive resin layer, and the lower part on an "AFP-1216E" exposure machine (trade name of Asahi Kasei Co., Ltd.). First, using the side ultraviolet lamp (UV lamp TL80W / 10R manufactured by PHILIPS, trade name), the entire surface was exposed at 600 mJ / cm ² from the support side so that the relief depth of the printing plate was 1.6 mm.

Subsequently, ultraviolet light of 8000 mJ / cm ² was irradiated from the black layer side with an upper lamp (UV lamp TL80W / 10R manufactured by PHILIPS, trade name). In addition, the exposure intensity | strength at this time was measured by UV luminometer MO-2 type | mold machine (Oak Manufacturing Co., Ltd. make, brand name, UV-35 filter) made by Oak Works.

  Next, development is carried out at a liquid temperature of 30 ° C. at a speed of 80 mm / min using an “AFP-1321P” developing machine (trade name of Asahi Kasei Co., Ltd.) using the washing solvent (E) as a developer, and 2 hours at 60 ° C. It was allowed to dry.

Thereafter, as post-exposure processing, using AFP-1216LF (trade name, manufactured by Asahi Kasei Co., Ltd.) and using a germicidal lamp having a central wavelength of 254 nm (trade name, manufactured by Toshiba Corporation, GL-30, trade name) It was exposed to 1000 mJ / cm ² to the entire rESIN plate surface. The post-exposure amount by the germicidal lamp here is calculated from the illuminance measured using the UV-25 filter of the "UV-MO2" machine.

(Dissolution rate)
The plate thickness difference between the exposed area and the unexposed area after development of the photosensitive composition for a flexographic printing plate of each photosensitive resin composition obtained above is measured, and divided by the development time, and the dissolution rate [mm / min] I asked for. The results are shown in Table 1.

(Solubility parameter)
When each hydrocarbon compound (C) used for the photosensitive resin composition is composed of a plurality of materials, the solubility parameter of each material is multiplied by the mass ratio to the total mass of the layer (A) of that material The sum was used as the solubility parameter of the layer (A) to determine the solubility parameter [MPa ^1/2 ]. The results are shown in Table 1.

The details of the materials in Table 1 are as follows.
[Elastomer binder (A)]
SBS-A (Styrene-Butadiene Copolymer)
[Ethylene Unsaturated Copolymerizable Monomer (B)]
1,9-nonanediol acrylate [hydrocarbon compound (C)]
Dodecane Smoyle 350P (liquid paraffin, manufactured by Matsumura Oil Co., Ltd.)
Paraffin oil tetraethylene glycol [photopolymerization initiator (D)]
2,2-Dimethoxy-1,2-diphenylethaneethane-1-one [conjugated diene compound]
B-2000 (product name of Nippon Soda Co., Ltd.)
[Other resin components]
[Washing solution]
Tetrachlorethylene / propanol / decalin ratio A: 70/15/15
Ratio B: 85/10/5
Ratio C: 30/40/30
Ratio D: 98/1/1

  “*” In Table 1 is an estimated value from a representative structure, and more specifically, the numerical range is defined from the similar structure of the main components of Smoyl 350P and paraffin oil from Hildebrand solubility parameter described in POLYMER HANDBOOK And the estimated value.

(Ink transfer distortion)
A printing test was performed on a flexographic printing machine using the obtained 3.94 mm-thick printing plate. The pattern of the negative film used for making the printing plate has two line numbers of 40 lpi and 60 lpi and halftone dots of 20%, 30%, 40%, 50%, 60% (each size 10 cm x 75 cm) respectively Is printed. As ink using Wasser Super Z Plus 3L (Osaka Printing Ink Mfg. Co., Ltd., trade name), using B-stage sheet (core 160 g), 250 lpi anilox roll as printing material at printing speed of 60 sheets / minute After printing 10 sheets, 5 printed matters of each halftone dot of the printed matter were observed with a microscope, and distortion of the ink transfer was evaluated according to the following evaluation criteria. The results are shown in Table 2.
(Evaluation criteria)
:: The 5-point average of the ratio of the horizontal length to the vertical of the ink transfer portion is 0.9 to 1.1
Δ: 5-point average of the ratio of the horizontal length to the vertical length of the ink transfer portion is 0.8 to 0.9 or 1.1 to 1.2
X: 5-point average of the ratio of the horizontal length to the vertical length of the ink transfer portion is less than 0.8 or 1.2 or more

(Plate crack resistance)
A 1 cm × 5 cm size, 3.94 mm thick printing plate is exposed at 600 mJ / cm 2 and immersed in 20 wt% ethyl acetate-isopropyl alcohol solution for 4 hours, the support is removed, and both ends of the printing plate are tensile tester It was stretched to 10 cm using and the crack condition of the plate surface was visually observed. Table 2 shows the results of evaluating the plate crack resistance using the following evaluation criteria.
(Evaluation criteria)
○: no cracks on the surface of the plate 無 し: no breakage of resin, cracks on the surface of the plate ×: breakage of resin

Claims (5)

A production method comprising the steps of producing a flexographic printing original plate having a support and a photosensitive resin layer laminated on the support,
The photosensitive resin layer is
At least one elastomeric binder (A),
At least one or more ethylenically unsaturated copolymerizable monomers (B),
At least one or more hydrocarbon compounds (C),
Containing at least one photopolymerization initiator (D),
The dissolution rate of the photosensitive resin layer dissolved by the hydrocarbon-containing cleaning solvent (E) is 0.09 to 0.6 mm / min.
The manufacturing method of the photosensitive resin plate for flexographic printings. The photosensitive resin layer contains a hydrocarbon compound (C) having a solubility parameter of 18 MPa ^1/2 or less.
The manufacturing method of the photosensitive resin for flexographic printings of Claim 1. The hydrocarbon compound (C) contains paraffin oil,
The method for producing a photosensitive resin for flexographic printing according to claim 1. The hydrocarbon compound (C),
The density at 15 ° C. is 0.7 to 1.0 g / cm ² ,
The kinematic viscosity at 40 ° C. is 100 mm ² / s or less,
The weight average molecular weight is 1,000 or less,
The hydrocarbon compound (C) contains a plasticizer having a naphthene ratio in the hydrocarbon compound (C) of 5.0 to 60 mol%.
The manufacturing method of the photosensitive resin for flexographic printing as described in any one of Claims 1-3. The photosensitive resin layer contains an elastomeric binder (A) in an amount of less than 60% by mass, based on the total amount of the photosensitive resin layer.
The manufacturing method of the photosensitive resin for flexographic printing as described in any one of Claims 1-4.