JP2017181781A - Photosensitive resin composition for ctp flexographic printing plate precursor and printing plate precursor obtained from the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-performance CTP photosensitive flexographic printing plate precursor that suppresses thinning in printing due to a build-up of a relief edge, which is a problem specific to a CTP plate, and that has sufficient printing durability, and a photosensitive resin composition for the plate precursor.SOLUTION: The photosensitive resin composition comprises at least (A) a block copolymer comprising a styrene derivative and a conjugate diene, (B) a photopolymerizable unsaturated compound, and (C) a photopolymerization initiator. The (B) photopolymerizable unsaturated compound comprises (B-1) a photopolymerizable monomer containing no hydroxyl group and (B-2) a hydroxyl group-containing photopolymerizable monomer having a pentaerythritol skeleton, a dipentaerythritol skeleton or a glycerin skeleton and having a weight average molecular weight of 200 to 1500; and the content of the (B-2) hydroxyl group-containing photopolymerizable monomer in the (B) photopolymerizable unsaturated compound is 1 to 20 mass%.SELECTED DRAWING: None

Description

  The present invention relates to a photosensitive resin composition used for producing a flexographic printing plate by a computer to plate technology.

  In recent years, in the field of flexographic printing, CTP technology known as digital image forming technology has become very common. The CTP technique is a method for obtaining a relief uneven pattern by directly outputting information processed on a computer onto a printing plate. This technique eliminates the need for a negative film manufacturing process, thereby reducing costs and the time required to create the negative.

  As a CTP photosensitive flexographic printing original plate, a water-developable photosensitive flexographic printing original plate in which a protective layer (barrier layer) is provided on a photosensitive resin layer and a thermal mask layer is further provided thereon has been proposed. (Patent Document 1). Patent Document 1 can provide a photosensitive flexographic printing original plate having excellent laser ablation properties, but causes printing blur at the relief edge, which was not a problem with the negative method. In the first place, the ablation layer provided for CTP is easily deformed compared to the negative film. For this reason, it has the fault that the shape of a relief top part deform | transforms easily. For this reason, in printing, unevenness of ink transfer (print blur) due to the rising of the edge portion is likely to occur.

  Moreover, the photosensitive resin composition for CTP photosensitive flexographic printing original plate of patent document 1 has the fault that mechanical strength is insufficient and printing durability at the time of printing is insufficient, and the improvement was calculated | required.

  As described above, the CTP flexographic printing original plate using the conventional water-developable photosensitive resin composition is all about the laser ablation performance, water developability, printing durability, and the solution of printing blur caused by the relief top shape change. It wasn't to satisfy.

  In order to cope with such a problem, the present inventor has proposed to use a specific hydroxyl group-containing photopolymerizable monomer as a crosslinking component of the photosensitive resin composition (see Patent Document 2). However, Patent Document 2 is intended exclusively for a photosensitive resin composition mainly composed of a water-dispersed latex. In the photosensitive resin composition mainly composed of a specific rubber, laser ablation performance, water developability However, no consideration is given to solving printing blur due to printing durability and relief top shape change.

Japanese Patent No. 4332865 WO2013 / 146586

  The present invention was devised in view of the current state of the prior art, and the object thereof is to develop the conventional developability in a CTP water-developable flexographic plate containing a specific type of rubber in a photosensitive resin composition.・ High-performance CTP photosensitive flexographic printing plate and photosensitive resin for suppressing printing shading due to bulging of the relief edge, which is a problem unique to the CTP plate, while maintaining image reproducibility and satisfying printing durability It is to provide a composition.

  As a result of intensive investigations to achieve such an object, the present inventors have used a specific hydroxyl group-containing photopolymerizable monomer in a specific amount as a crosslinking component of the photosensitive resin layer in the printing original plate, thereby obtaining a desired amount. The inventors have found that an effect can be obtained and have completed the present invention.

That is, the present invention has the following configurations (1) to (3).
(1) A photosensitive resin composition comprising at least (A) a block copolymer comprising a styrene derivative and a conjugated diene, (B) a photopolymerizable unsaturated compound, and (C) a photopolymerization initiator, The photopolymerizable unsaturated compound is (B-1) a hydroxyl group-free photopolymerizable monomer, (B-2) a hydroxyl group-containing photopolymerization having a weight average molecular weight of 200 to 1500 having a pentaerythritol skeleton, a dipentaerythritol skeleton or a glycerin skeleton. And (B-2) a photopolymerizable unsaturated compound containing (B-2) a hydroxyl group-containing photopolymerizable monomer in an amount of 1 to 20% by mass. Resin composition.
(2) (B-2) In (1), the concentration of the hydroxyl group derived from the hydroxyl group-containing photopolymerizable monomer in the photosensitive resin composition is 0.01 to 0.13 equivalent mol / kg. The photosensitive resin composition for CTP flexographic printing original plates as described.
(3) A CTP flexographic printing original plate, wherein a thermal mask layer is provided on the surface of the photosensitive resin layer comprising the photosensitive resin composition according to (1) or (2) via a barrier layer.

  Since the photosensitive resin composition of the present invention contains a specific hydroxyl group-containing photopolymerizable monomer in a specific amount in the photopolymerizable unsaturated compound to be used, cupping, cover film peelability, heat sensitive mask layer resistance Further, it is possible to provide a CTP photosensitive flexographic printing original plate excellent in mechanical strength and developability. In particular, the photosensitive resin composition of the present invention has a remarkable effect when used in a CTP flexographic printing original plate in which a barrier layer is provided between the photosensitive resin layer and the thermal mask layer.

  Hereinafter, the photosensitive resin composition for CTP flexographic printing original plate of the present invention and the CTP flexographic printing original plate obtained therefrom will be described.

  The photosensitive resin composition for CTP flexographic printing plate precursor of the present invention contains at least (A) a block copolymer comprising a styrene derivative and a conjugated diene, (B) a photopolymerizable unsaturated compound, and (C) a photopolymerization initiator. In particular, the (B) photopolymerizable unsaturated compound is characterized in that a specific (B-2) hydroxyl group-containing photopolymerizable monomer is used in a specific amount.

  (A) A block copolymer composed of a styrene derivative and a conjugated diene is a block copolymer having at least a polymer block composed mainly of structural units derived from styrene and a polymer block composed of structural units derived from conjugated diene. . The block copolymer composed of a styrene derivative and a conjugated diene contains 10 to 25% by mass, preferably 15 to 25% by mass of a structural unit derived from styrene, and 90 to 75% by mass, preferably 85, of a structural unit derived from a conjugated diene. Contains ~ 75% by mass. The block copolymer comprising a styrene derivative and a conjugated diene may contain structural units derived from styrene monomers other than styrene. Examples of styrene monomers other than styrene include α-methyl styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, pt-butyl styrene, 2,4-dimethyl styrene, vinyl naphthalene, and vinyl anthracene. Can be mentioned. On the other hand, examples of the conjugated diene in the polymer block composed of a structural unit derived from a conjugated diene include butadiene, isoprene, chloroprene, 2,3-dimethylbutadiene, 1,3-pentadiene, 1,3-hexadiene, and the like. Isoprene is preferred. The above monomers and conjugated dienes may be used singly or in combination of two or more. Specific examples of the styrene block copolymer include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), acrylonitrile-butadiene-styrene copolymer (ABS), and the like. Is mentioned. As these commercially available products, for example, “Clayton D” (trade name) manufactured by Clayton Polymer Co., Ltd., “Toughprene” (trade name) and “Asaprene T” (trade name) manufactured by Asahi Kasei Chemicals Corporation, and JSR Corporation “JSR TR” (trade name) and “JSR SIS” (trade name), “Quintac” (trade name) manufactured by Nippon Zeon Co., Ltd., and the like. Among these, a styrene-butadiene-styrene block copolymer (SBS) excellent in wear resistance and mechanical properties is preferable.

  It is preferable that the compounding quantity of (A) component in the photosensitive resin composition is 70-85 mass%. If it is less than 70% by mass, the flexibility as a printing plate is insufficient, and if it exceeds 85% by mass, the strength of the printing plate may be deteriorated.

  The (B) photopolymerizable unsaturated compound comprises (B-1) a hydroxyl group-free photopolymerizable monomer and (B-2) a hydroxyl group-containing photopolymerizable monomer. It is preferable that the compounding quantity of (B) component in the photosensitive resin composition is 7-15 mass%. If it is less than 7% by mass, the image reproducibility of the printing plate is deteriorated, and if it exceeds 15% by mass, the hardness of the printing plate may be too high.

  (B-1) The hydroxyl group-free photopolymerizable monomer is an ethylenically unsaturated hydrocarbon compound having no hydroxyl group in the molecule. The component (B-1) can be added within a range that does not impair the effects of the present invention in order to increase the crosslinking density of the printing plate surface. The hydroxyl group-free photopolymerizable monomer is preferably a compound having a molecular weight of 100 to 500 and having at least two ethylenically unsaturated groups at the terminal or side chain. Specifically, ethylene glycol di (meta ) Acrylate, diethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, trimethylolpropane tri (Meth) acrylate, glycerin di (meth) acrylate, triethylene glycol di (meth) acrylate, 1,3-butanediol dimethacrylate, neopentyl glycol di (meth) acrylate, 1,10-decanediol dimethacrylate, pentaerythritol Tetra Acrylate, polytetramethylene glycol di (meth) acrylate and the like, in particular 1,6-hexanediol di (meth) acrylate and 1,9-nonanediol di (meth) acrylate.

  (B-2) The hydroxyl group-containing photopolymerizable monomer is an ethylenically unsaturated hydrocarbon compound having at least one hydroxyl group in the molecule. As a structure, it has at least one skeleton among a pentaerythritol skeleton, a dipentaerythritol skeleton, or a glycerin skeleton, and has a hydroxyl group derived from the skeleton in the molecule. A dihydric alcohol such as ethylene glycol or propylene glycol may be added to these skeletons. The concentration of the hydroxyl group derived from the hydroxyl group-containing photopolymerizable monomer in the photosensitive resin composition is preferably 0.01 to 0.2 equivalent mol / kg. The lower limit of the concentration of the hydroxyl group derived from the hydroxyl group-containing photopolymerizable monomer in the photosensitive resin composition is more preferably 0.05 equivalent mol / kg, still more preferably 0.1 mol / kg. The upper limit of the concentration of the hydroxyl group derived from the hydroxyl group-containing photopolymerizable monomer in the photosensitive resin composition is more preferably 0.15 equivalent mol / kg, still more preferably 0.13 mol / kg. If the hydroxyl group concentration is less than the above range, cupping may occur, and if it exceeds the above range, the cover film may not be peeled off. Moreover, the weight average molecular weight of a hydroxyl-containing photopolymerizable monomer is 200-1500, 200-1000 are preferable and 210-900 are more preferable. If the weight average molecular weight of the hydroxyl group-containing photopolymerizable monomer is less than the above range, the photosensitive resin component may be easily migrated, and if it exceeds the above range, the cupping suppressing effect may not be exhibited. This (B-2) component swells the structure of the photosensitive resin plate surface layer such as the heat-sensitive mask layer and the barrier layer, and the photosensitive resin component oozes out from the non-dewed back portion to the exposed portion during the main exposure. , Have a role to prevent from dissolving and increasing the tackiness of the release part.

  (B-2) Specific examples of the hydroxyl group-containing photopolymerizable monomer include pentaerythritol (poly) acrylate, ethoxylated pentaerythritol (poly) acrylate, propoxylated pentaerythritol (poly) acrylate, and (poly) glycidyl ether penta. Erythritol (poly) acrylate, dipentaerythritol (poly) acrylate, ethoxylated dipentaerythritol (poly) acrylate, propoxylated dipentaerythritol (poly) acrylate, polyglycidyl ether dipentaerythritol (poly) acrylate, glycidyl phthalate (poly) ) Acrylate, polyglycidyl phthalate (poly) acrylate, glycidyl hexahydrophthalate (poly) acrylate, polyglycidyl hexahydrophthalate ( I) acrylate, trimethylolpropane glycidyl (poly) acrylate, trimethylolpropane polyglycidyl (poly) acrylate, ethoxylated glycidyl (di) acrylate, propoxylated glycidyl (di) acrylate, polyglycidyl (poly) acrylate, And / or methacrylate. (B) The compounding quantity of (B-2) component in a photopolymerizable unsaturated compound is 1-20 mass%, Preferably it is 1.5-19 mass%. If the blending amount of the component (B-2) is less than the above range, the effect of suppressing cupping may be inferior, and printing blur may occur. If the amount exceeds the above range, the heat-sensitive mask layer resistance may be inferior.

  (C) A photoinitiator will not be specifically limited if it can superpose | polymerize a polymerizable carbon-carbon unsaturated group with light. Especially, what has the function to produce | generate a radical by self-decomposition or hydrogen abstraction by light absorption is used preferably. Examples include benzoin alkyl ethers, benzophenones, anthraquinones, benzyls, acetophenones, diacetyls and the like. 0.1-10 mass% is preferable, and, as for the compounding quantity of (C) component in the photosensitive resin composition, More preferably, it is 0.2-5 mass%. When the blending amount of the component (C) is less than the above range, the above polymerization effect is not sufficiently obtained, and when it exceeds the above range, the transparency of the resin is impaired and a sharp relief may not be obtained.

  In the photosensitive resin composition of the present invention, an anti-aggregation agent, a plasticizer, a polymerization inhibitor, an ultraviolet absorber, a dye, a pigment, an antifoam are used for the purpose of improving various properties within the range not impairing the effects of the present invention. Other components, such as an agent and a fragrance | flavor, can be added suitably.

  The photosensitive resin composition of the present invention is for use in a photosensitive resin layer of a CTP flexographic printing original plate. The CTP flexographic printing original plate of the present invention comprises at least a support, a photosensitive resin layer, a barrier layer, and a thermal mask layer.

  The support used in the original plate of the present invention is flexible but is preferably a material having excellent dimensional stability. For example, a metal support such as steel, aluminum, copper, nickel, polyethylene terephthalate film, polyethylene Mention may be made of thermoplastic resin supports such as phthalate films, polybutylene terephthalate films, or polycarbonate films. Among these, a polyethylene terephthalate film having excellent dimensional stability and sufficiently high viscoelasticity is particularly preferable. The thickness of the support is from 50 to 350 μm, preferably from 100 to 250 μm, from the viewpoint of mechanical properties, shape stability, or handleability during plate making. Moreover, in order to improve the adhesiveness of a support body and the photosensitive resin layer, you may provide an adhesive agent between them as needed.

  The barrier layer used in the original plate of the present invention is provided in order to prevent mass transfer between the photosensitive resin layer and the heat-sensitive mask layer and polymerization inhibition due to oxygen in the photosensitive resin layer. According to the present invention, by providing such a barrier layer, there is also an effect that the top shape of the relief can be a flat dot. The barrier layer is not particularly limited as long as it is a polymer that can block oxygen or reduce oxygen permeability, and can be constituted by using any polymer that is soluble or insoluble in water. it can. Examples of the polymer constituting the barrier layer include polyamides, partially saponified vinyl acetate, polyvinyl alcohol, polyvinyl pyrrolidone, alkyl celluloses such as methyl cellulose, polyacrylic acid, polyethylene oxide, cellulose polymers (particularly hydroxypropyl cellulose, hydroxyethyl cellulose, nitro Cellulose), cellulose acetate butyrate, polybutyral, butyl rubber, NBR rubber, acrylic rubber, styrene-butadiene rubber, latex, and soluble polyester. These polymers are not limited to one type of use, and two or more types of polymers can be used in combination. The barrier layer preferably has a higher thermal decomposition temperature than the thermal mask layer. This is because if the thermal decomposition temperature of the barrier layer is lower than that of the thermal mask layer, the barrier layer may also be thermally decomposed during the ablation of the thermal mask layer.

  The thickness of the barrier layer is preferably 0.2 μm to 3.0 μm, more preferably 0.2 m to 1.5 μm. If it is less than the above lower limit, the oxygen barrier property is insufficient and the relief plate surface may be roughened. If the above upper limit is exceeded, there is a risk that fine line reproduction failure will occur.

  The heat-sensitive mask layer used in the original plate of the present invention is composed of carbon black, which is a material having a function of absorbing infrared laser and converting it into heat, and a function of blocking ultraviolet light, and a dispersion binder thereof. Further, as an optional component other than these, a pigment dispersant, a filler, a surfactant, a coating aid or the like can be contained within a range that does not impair the effects of the present invention.

  The thermal mask layer preferably has an optical density of 2.0 or more with respect to actinic radiation, more preferably an optical density of 2.0 to 4.0, and particularly preferably an optical density of 2.2 to 3.5. It is.

  The layer thickness of the heat sensitive mask layer is preferably 0.5 to 2.5 μm, and more preferably 1.0 to 2.0 μm. If it is more than the said minimum, a high coating technique is not required but an optical density more than fixed can be obtained. Moreover, if it is below the said upper limit, high energy is not required for evaporation of a thermal mask layer, and it is advantageous in cost.

  It is preferable to protect the printing original plate by providing a peelable flexible cover film on the heat sensitive mask layer. Suitable examples of the peelable flexible cover film include a polyethylene terephthalate film, a polyethylene naphthalate film, and a polybutylene terephthalate film. However, such a protective film is not absolutely necessary.

  As a method for producing a printing plate from the printing original plate of the present invention, when a protective film is present, the protective film is first removed from the photosensitive printing plate. Thereafter, the thermal mask layer is irradiated imagewise with an IR laser to form a mask on the photosensitive resin layer. Examples of suitable IR lasers include ND / YAG laser (1064 nm) or diode laser (eg, 830 nm). Laser systems suitable for computer plate making technology are commercially available, and for example, CDI SpArk (Esco Graphics) can be used. This laser system includes a rotating cylindrical drum that holds a printing original, an IR laser irradiation device, and a layout computer, and image information is directly transferred from the layout computer to the laser device.

  After the image information is written on the heat-sensitive mask layer, the photosensitive printing original plate is irradiated with actinic rays through the mask. This can be done with the plate attached to the laser cylinder, but removing the plate from the laser device and irradiating with a conventional flat irradiation unit is advantageous in that it can cope with non-standard plate sizes. It is general. As the actinic ray, ultraviolet rays having a wavelength of 150 to 500 nm, particularly 300 to 400 nm can be used. As the light source, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a metal halide lamp, a xenon lamp, a zirconium lamp, a carbon arc lamp, an ultraviolet fluorescent lamp, or the like can be used. Thereafter, the irradiated plate is developed to obtain a printing plate. The development step can be performed with a conventional development unit.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.

Example 1:
<Creation of thermal mask layer>
Preparation of Dispersion Binder As a dispersion binder, a butyral resin and a tertiary amine group-containing polyamide were prepared. As the butyral resin, BM-5 manufactured by Sekisui Chemical Co., Ltd. was used. As the tertiary amine group-containing polyamide, one synthesized as follows was used.

Synthesis of tertiary amine group-containing polyamide Autoclaving 50 parts by weight of ε-caprolactam, 40 parts by weight of N, N, -di (γ-aminopropyl) piperazine adipate, 10 parts by weight of 3-bisaminomethylcyclohexane adipate and 100 parts by weight of water The solution was charged into the interior, purged with nitrogen, sealed and gradually heated. From the time when the internal pressure reached 10 kg / m ³ , water was distilled off until the pressure could not be maintained, returned to normal pressure in about 2 hours, and then reacted at normal pressure for 1 hour. The maximum polymerization reaction temperature was 255 ° C. As a result, a tertiary amine group-containing polyamide having a melting point of 137 ° C. and a specific viscosity of 1.96 was obtained.

Preparation of thermal mask layer coating liquid Butyral resin and tertiary amine group-containing polyamide as a dispersion binder are dissolved in a solvent at a mass ratio of 1: 1, and an amount of carbon black equivalent to the dispersion binder is dispersed therein to form a dispersion liquid. Was prepared as a heat-sensitive mask layer coating solution. The solvent used was a mixed solution of methanol and ethanol in a weight ratio of 70:30.

Preparation of heat-sensitive mask layer A PET film support (Toyobo Co., Ltd., E5000, thickness 100 μm) subjected to mold release treatment on both sides is coated with a heat-sensitive mask layer coating solution so that the layer thickness becomes 1.5 μm. Coating was performed using an appropriately selected bar coater, and drying was performed at 120 ° C. for 5 minutes to prepare a heat-sensitive mask layer [film laminate (I)].

Preparation of Barrier Layer As a polymer constituting the barrier layer, low saponification degree polyvinyl alcohol (KH20, manufactured by Nihon Gosei Co., Ltd.) and plasticizer (Sunflex SE270, manufactured by Sanyo Chemical Industries, aliphatic polyhydric alcohol polyether polyol) , Solid content concentration 85%) was mixed at a mass ratio of 70/30 to obtain a barrier layer coating solution. On the heat-sensitive mask layer of the film laminate (I) provided with the heat-sensitive mask layer, a barrier layer coating solution was applied with a bar coater so that the thickness of the coating film after drying was 2.0 μm, The film laminate (II) was obtained by drying for 5 minutes.

<Preparation of flexographic printing plate>
(A) 80 parts by mass of a polystyrene-polybutadiene-polystyrene block copolymer as a block copolymer comprising a styrene derivative and a conjugated diene, (B-1) 1,6-hexamethylenediol diacrylate as a hydroxyl-free photopolymerizable monomer 6 parts by mass, 3 parts by mass of 1,6-hexamethylenediol dimethacrylate, (B-2) 2 parts by mass of pentaerythritol triacrylate as a hydroxyl group-containing photopolymerizable monomer, and (C) benzyldimethyl ketal as a photopolymerization initiator. 5 parts by weight, 5.9 parts by weight of naphthenic oil (Shelfex 371) as a plasticizer, 1.5 parts by weight of 2,6-di-tert-butyl-p-cresol and 0.1 part by weight of hydroquinone monomethyl ether as a stabilizer Part of the mixture using a twin screw extruder at a resin temperature of 160-17. Extruded at 0 ° C. and discharged from a slot die. The molten resin discharged from the die is a heat-sensitive mask layer on a lower calender roll fed with a 125 μm polyethylene terephthalate film coated with a polyester urethane adhesive layer and a 125 μm polyethylene terephthalate film coated with a release layer. The flexographic printing original plate having a total thickness of 1.7 mm was manufactured by passing it between upper calendar rolls to which a cover film provided with a film was fed.

<Creation of evaluation relief>
The flexographic printing original plate was subjected to back exposure using an ultraviolet lamp (10R manufactured by PHILIPS) at 350 nm and an illuminance of 8.0 w / m ² , and the cover film was peeled off. Next, an image containing fine lines having a line width of at least 300 μm was ablated on the thermal mask layer of the flexographic printing plate using an IR laser irradiation machine. Thereafter, main exposure was performed with the same ultraviolet lamp, and development was performed with a developing device. As the developer, a solvent for flexographic development was used. Subsequently, the solvent on the developed plate surface is removed, dried at 65 ° C. for 2 hours, subjected to post-exposure for 5 minutes using the same ultraviolet lamp, and then subjected to surface treatment by irradiation with a germicidal lamp for 5 minutes. An evaluation relief was obtained.

  Each performance evaluation was performed by the measuring method shown below.

<Copping evaluation>
The evaluation relief created by the above method was fixed to a metal board using a magnet, and a 300 μm fine line of the evaluation relief was photographed in 3D with a KEIENCE ultra-deep color 3D shape measurement microscope (VK-9500). The distance (μm) from the lowest point to the highest point of the 300 μm fine wire top was taken as the cupping value. The cupping value indicates that the lower the value, the better.

<Cover film peelability evaluation>
For the cover film peelability, the flexographic printing original plate prepared by the above method was left as it was under light-shielding conditions for 24 hours, and then the cover film could be peeled off, and the cover film could not be peeled off.

<Heat sensitive mask layer (coat layer) resistance evaluation>
(B) Evaluation of heat-sensitive mask layer (coat layer) resistance to photopolymerizable unsaturated compound was carried out by using a barrier layer (polyvinyl alcohol) and a heat-sensitive mask layer (butyral resin and tertiary amine group) on a polyethylene terephthalate film having a thickness of 125 μm. A gauze containing (B) a photopolymerizable unsaturated compound was affixed to the surface of the cover film coated with polyamide dispersed in carbon black. After 10 minutes, remove the gauze containing (B) the photopolymerizable unsaturated compound, rub the coated surface with new gauze, and mark that where the coat peels off at that time as x, and after 24 hours (B) photopolymerizable unsaturated The gauze containing the compound was removed, and the coated surface was rubbed with a new gauze. In addition, the thing applicable to x and △ was set to x, and the thing which does not correspond to x and △ was set as ◯.

Examples 2-8
In Examples 2 to 8 and Comparative Examples 1 to 3, a photosensitive resin composition and a flexographic printing original plate were prepared and evaluated in the same manner as in Example 1 except that only the components and the blending ratio thereof were changed as shown in Table 1. did. In addition, the mixture ratio of each component in Table 1 is shown by the mass part. Details of the photosensitive resin composition and evaluation results are shown in Table 1.

  As is clear from the results in Table 1, Examples 1 to 8 which are within the scope of the present invention are all good in cupping, cover film peelability, and thermal mask layer (coat layer) resistance. In contrast, Comparative Example 1 in which the molecular weight of the (B-2) hydroxyl group-containing photopolymerizable monomer is too small is inferior in the cover film peelability. (B-2) The comparative example 2 which does not use the hydroxyl-containing photopolymerizable monomer is inferior to cupping. (B-2) The comparative example 3 with too much content of a hydroxyl-containing photopolymerizable monomer is inferior to heat-sensitive mask layer tolerance.

  The flexographic printing plate using the photosensitive resin composition of the present invention is excellent in image reproducibility and developability, and also prevents printing scum by minimizing the bulge of the relief edge, and also has printing durability. Since it is satisfied, it can be effectively used as a CTP photosensitive flexographic printing original plate.

Claims (3)

  A photosensitive resin composition comprising at least (A) a block copolymer comprising a styrene derivative and a conjugated diene, (B) a photopolymerizable unsaturated compound, and (C) a photopolymerization initiator, and (B) photopolymerizable. The unsaturated compound is (B-1) a hydroxyl group-free photopolymerizable monomer, (B-2) a hydroxyl group-containing photopolymerizable monomer having a weight average molecular weight of 200 to 1500 having a pentaerythritol skeleton, a dipentaerythritol skeleton, or a glycerin skeleton. And (B) the content of the photopolymerizable monomer containing (B-2) hydroxyl group in the photopolymerizable unsaturated compound is 1 to 20% by mass. .   (B-2) The CTP according to claim 1, wherein the concentration of the hydroxyl group derived from the hydroxyl group-containing photopolymerizable monomer in the photosensitive resin composition is 0.01 to 0.13 equivalent mol / kg. Photosensitive resin composition for flexographic printing original plate.   A CTP flexographic printing original plate, wherein a thermal mask layer is provided on the surface of a photosensitive resin layer comprising the photosensitive resin composition according to claim 1 or 2 via a barrier layer.