JP2001005173A - Water-developable photosensitive flexographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water-developable photosensitive flexographic printing plate excellent in image reproducibility and having a small dot gain and good printing performance by making the ratio of the dynamic hardness of the surface of a dot part having a specified density or below to the dynamic hardness of the surface of a solid part having 100% density a specified value or above. SOLUTION: In this water-developable photosensitive flexographic printing plate, the ratio (A/B) of the dynamic hardness A of the surface of a dot part having >=50% density to the dynamic hardness B of the surface of a solid part having 100% density is >=1.1. In the case of A/B>=1.1, ink on the solid part is satisfactorily transferred under low printing pressure, the dot part is sharply printed without crushing and well-balanced printed matter is obtained. In the case of A/B<1.1, the dot part collapses in printing and clear printed matter can not be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a water-developing type photosensitive flexographic printing plate having excellent image reproducibility.

[0002]

2. Description of the Related Art Hitherto, flexographic printing has been generally used widely because it uses water-based inks and low-viscosity inks containing alcohol, and is therefore environmentally friendly. Moreover, the printing machine is simple and the productivity is high. However, image reproducibility is inferior to letterpress printing, lithographic printing, gravure printing or the like using oil-based ink, and improvement of the image reproducibility is desired.

A printing plate used for flexographic printing is made of a material having rubber elasticity and has a thickness of 1 m.
It is characterized by being as thick as m to 7 mm. For this reason, in printing, when a printing plate contacts an object to be printed and transfers ink, there is a problem that the printing plate is deformed and a so-called dot gain that a printed image becomes larger than an original image occurs. Further, since the printing plate has a thickness greater than that of a relief printing plate or a planographic printing plate using oil-based ink, light required for forming an image is not sufficiently transmitted to the inside. Therefore, there is a problem that image reproducibility is not good.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a flexographic printing plate having excellent image reproducibility in flexographic printing and low dot gain and good printability.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have achieved high image reproducibility by making a difference between the surface and the internal dynamic hardness of the printing plate. And a photosensitive flexographic printing plate having the same. That is, the present invention provides a water-developing type photosensitive flexographic printing plate in which the ratio (A) / (D) of the dynamic hardness (A) of the halftone dot surface having a density of 50% or less to the dynamic hardness (B) of the solid portion surface having a density of 100%. B) is 1.1
A water-developable photosensitive flexographic printing plate characterized by the above.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The dynamic hardness of a halftone dot surface having a concentration of 50% or less in the present invention is a dynamic hardness at a depth of 0 to 10 μm from the outermost surface of a halftone dot having a concentration of 50% or less. Is concentration 10
0% means the dynamic hardness at a depth of 0 to 10 μm from the outermost surface of the solid portion. The dynamic hardness in the present invention is expressed by Shimadzu Review Vol. 50, No. 3 (1993.12) 321.
Shimadzu Dynamic Ultra-Micro Hardness Tester D, which provides information on the strength characteristics of the sample surface as described in
This is the hardness measured by UH201.

In the present invention, the ratio (A) / (B) of the dynamic hardness (A) of the halftone dot surface having a concentration of 50% or less to the surface hardness (B) of the solid portion having a concentration of 100% is 1.1 or more. In printing, the solid portion ink is well transferred at a low printing pressure, and at the same time, the dot portion is clearly printed without being destroyed, so that a well-balanced printed matter is obtained as a whole. On the other hand, the ratio (A) / (B) of the dynamic hardness is 1.
If it is less than 1, the halftone dot portion is destroyed in printing, and a clear printed matter cannot be obtained, which is not preferable.

In the present invention, the method of setting the ratio (A) / (B) of the dynamic hardness (A) of the halftone dot surface to the dynamic hardness (B) of the solid portion surface at 1.1 or more is based on the distribution of the plate composition. As an example, the phase structure in the state takes a so-called sea-island type phase-separated structure, and gives a difference in hardness using a difference in solubility of the cross-linking component in each sea-island component.
It is not limited to this.

In forming the sea-island type phase structure, when the constituent composition is a non-crosslinked body, for example, the document “Polymer Alloy”: edited by The Society of Polymer Science, Tokyo Chemical Dojin P22 (198)
As described in 1), a composition having a relatively low viscosity and being easily flowable has a sea phase structure. When the structural composition is a non-crosslinked body and a crosslinked body, the crosslinked body does not dissolve in the non-crosslinked body, so that the non-crosslinked body having low viscosity and fluidity also has a sea phase structure. In the sea-island structure, the outermost surface of the printing plate has a sea component as a main component, and the sea component composition can be localized. In the present invention, it is considered that the sensitivity is increased due to the high crosslink density of the outermost surface of the printing plate, and higher image reproducibility can be obtained as compared with a conventional flexographic printing plate.

As described above, the photosensitive flexographic printing plate having a sea-island structure in the present invention may be constituted by a non-crosslinked body and a crosslinked body, or may be constituted by phase separation of the non-crosslinked body. In the following, a case composed of a non-crosslinked body and a crosslinked body will be described. Examples of the cross-linkable particulate hydrophilic or water-swellable elastomer include partial internal cross-links obtained by radical emulsion polymerization disclosed in JP-A-1-300246. The partially internally crosslinked copolymer is composed of 40 to 95 mol% of an aliphatic conjugated diene monomer and 0.1 to 10 mol% of a compound having at least two addition-polymerizable groups.
Is obtained by radical emulsion polymerization of a monomer mixture containing Examples of the aliphatic conjugated diene monomer as the copolymer component include butadiene, isoprene,
Dimethyl butadiene, chloroprene and the like can be mentioned.
Examples of the α, β-ethylenically unsaturated carboxylic acid include acrylic acid, maleic acid, fumaric acid, tetraconic acid, protonic acid and the like. Examples of the compound having at least two groups capable of addition polymerization include trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, divinylbenzene, ethylene glycol di (meth) acrylate, pentaerythritol tetra ( (Meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and the like. Note that α,
The carboxyl group of the β-ethylenically unsaturated carboxylic acid may be salified by a basic nitrogen atom-containing compound, and preferred basic nitrogen atom compounds include N, N-dimethylaminopropyl (meth) acrylamide, N, N
-Dimethylaminoethyl (meth) acrylamide, N,
N-dimethylaminoethyl-N '-(meth) acryloylcarbamate, N, N-dimethylaminoethoxyethanol, N, N-dimethylaminoethoxyethyl (meth) acrylate and the like can be mentioned.

Another example of a cross-linked particulate hydrophilic or water-swellable elastomer is disclosed in JP-A No. 2-17 / 1990.
Core-shell microgel binders disclosed in Japanese Patent No. 5702 and the like. As used herein, a core-shell microgel binder is a particle having two regions: a core having a crosslinking of 10% or less, and an outer crosslinkable non-crosslinkable shell made of an acid-modified copolymer. It is. Monomers forming the core include methyl methacrylate, ethyl acrylate, methacrylic acid, butyl methacrylate, ethyl methacrylate, glycidyl methacrylate, styrene and allyl methacrylate, and butanediol acrylate and ethylene glycol dimethacrylate as crosslinkers. Acrylate, tetramethylene glycol diacrylate, trimethylolpropane triacrylate, tetramethylene glycol dimethacrylate and the like can be mentioned. On the other hand, as the copolymer modified with an acid forming a shell, n-butyl acrylate modified with methacrylic acid is preferable. The core-shell microgel binder is usually produced by emulsion polymerization using these monomers.

In addition to the above, examples of crosslinked or non-crosslinked particulate hydrophilic or water-swellable elastomers include latexes described in JP-A-6-289610. This latex can be obtained by emulsion polymerization of a monomer mixture comprising a monoolefinic unsaturated monomer and an unsaturated monomer having a hydrophilic functional group. Monoolefinically unsaturated monomers include methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, dodecyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, cyanoethyl acrylate, hydroxyethyl acrylate, Acrylic esters such as hydroxypropyl acrylate, and methacrylic esters thereof are exemplified.
Other monoolefinically unsaturated monomers include styrene, acrylonitrile, vinyl chloride, ethylidene norbornene, propenyl norbornene, dicyclopentadiene and the like. In some cases, a conjugated diene-based monomer such as 1,3-butadiene, isoprene, chloroprene, or 1,3-pentadiene may be used, or a polyfunctional vinyl compound may be introduced for crosslinking. Examples of the hydrophilic functional group include a carboxyl group, a phosphoric acid group, a phosphoric acid ester group, a sulfonic acid group, and a hydrohistyl group, and a phosphoric acid ester group is more preferable from the viewpoint of washability.

The unsaturated monomers containing a phosphate group include ethylene (meth) acrylate, trimethylene (meth) acrylate, propylene (meth) acrylate, and tetramethylene (meth) phosphate.
Acrylate, (bis) ethylene phosphate (meth) acrylate, (bis) trimethylene phosphate (meth) acrylate, (bis) tetramethylene (meth) acrylate, diethylene glycol (meth) acrylate phosphate, (bis) triphosphate Ethylene glycol (meth) acrylate, phosphoric acid (bis) polyethylene glycol (meth) acrylate, and the like are included.

The case of the present invention comprising a non-crosslinked body and a crosslinked body will be described below. Examples of the non-crosslinked type particulate hydrophilic or water-swellable elastomer include a phase mainly composed of a hydrophobic polymer and a phase mainly composed of a hydrophilic polymer described in JP-A-3-72353. Can be mentioned. As the hydrophobic polymer constituting the particles, a polymer obtained by polymerizing a conjugated diene-based hydrocarbon, or a copolymer obtained by polymerizing a conjugated diene-based hydrocarbon and a monoolefin-based unsaturated compound, a conjugated diene-based Examples include polymers that do not contain hydrocarbons. Examples of the hydrophilic polymer mainly forming a phase surrounding the particles include a polymer having a hydrophilic group such as a hydroxyl group, a carboxyl group, an amino group, a sulfonic acid group and / or a polyethylene glycol chain.

A polymer obtained by polymerizing the conjugated diene-based hydrocarbon forming a phase mainly composed of a hydrophobic polymer;
Examples of the copolymer obtained by polymerizing a conjugated diene-based hydrocarbon and a monoolefin-based unsaturated compound include butadiene polymer, isoprene polymer, chloroprene polymer, styrene-butadiene copolymer, and styrene-isoprene copolymer. Polymer, styrene-chloroprene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-isoprene copolymer, methyl methacrylate-butadiene copolymer, methyl methacrylate-isoprene copolymer, methyl methacrylate-chloroprene copolymer Methyl acrylate-butadiene copolymer, methyl acrylate-isoprene copolymer, methyl acrylate-chloroprene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-chloroprene-styrene copolymer, and the like. That.

Examples of the polymer which does not contain a conjugated diene-based hydrocarbon forming a phase mainly composed of a hydrophobic polymer include elastomers containing a specific amount of chlorine and non-conjugated diene-based hydrocarbons. Specifically, epichlorohydrin polymer, epichlorohydrin-ethylene oxide copolymer, epichlorohydrin-propylene oxide copolymer and / or epichlorohydrin rubber which is a copolymer of these with acrylic glycidyl ether [Epichroma, Goodvich manufactured by Osaka Soda Industry Co., Ltd.] HYDR manufactured by
IN, Nippon Zeon Corporation GECHRON, Zeospan, Hevcules
HERCLOR manufactured by Co., Ltd.), chlorinated polyethylene [Eraslen manufactured by Showa Denko KK, Daisorac manufactured by Osaka Soda Kogyo KK, HORTALITZ manufactured by Hoechst KK, Dow Chemical Co., Ltd.
Manufactured by Dow CPE. These hydrophobic polymers may be used alone or in combination of two or more, and the content in the composition is preferably from 20% by weight to 80% by weight. When the content is 20% by weight or less, the handleability is remarkably impaired, and when the content is 80% by weight or more, the water developability is impaired. A particularly preferred content is 30% by weight or more and 70% by weight or less.

Specific examples of the hydrophilic polymer which forms a phase containing a hydrophilic polymer as a main component include polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, water-soluble polyurethane, water-soluble polyurea urethane, water-soluble polyester, and water-soluble polyester. Epoxy compounds, carboxyl group-containing acrylonitrile-butadiene copolymer, carboxyl group-containing styrene-butadiene copolymer, carboxyl group-containing polybutadiene, polyacrylamide, sodium polyacrylate, carboxyl group polyurea urethane, polyamic acid, etc. can be used, but are not limited thereto. Not necessarily. In the case of the composition, it is preferable to form a continuous phase and a dispersed phase by separating the components while mixing and mixing the components. From the viewpoint, from 1% by weight to 40% by weight, preferably from 2% by weight to 30% by weight, particularly preferably from 3% by weight to 2% by weight.
0% by weight or less.

Although the particulate hydrophilic or water-swellable elastomer has been described above by type, the content of the water-swellable elastomer in the whole composition is preferably from 20% by weight to 80% by weight. And more preferably 30% by weight or more and 70% by weight or less. If the amount is less than 20% by weight, problems arise in developing properties, shape retention characteristics, etc.
Exceeding 0% by weight is not preferable because a problem occurs in water resistance.

In the present invention, in order to increase the crosslink density of the printing plate surface, it is preferable to add a specific amount of the specific ethylenically unsaturated compound. The specific ethylenically unsaturated compound in the present invention is a compound having a molecular weight of 500 or less and having at least two or more ethylenically unsaturated groups at a terminal or a side chain. Such specific ethylenically unsaturated compounds include ethylene glycol di (meth) acrylate,
Diethylene glycol di (meth) acrylate, 1,4
-Butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, glycerin di (meth) acrylate, triethylene glycol di (meth) acrylate, PEG # 200 di (Meth) acrylate,
PEG # 400 di (meth) acrylate, 1,3-butanediol dimethacrylate, neopentyl glycol di (meth) acrylate, 1,10-decanediol dimethacrylate, ethylene oxide adduct of bisphenol A di (meth) acrylate, ethylene Oxide-modified trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, 1,9-nonanediol di (meth) acrylate, light ester P-2M [manufactured by Kyoeisha Chemical Co., Ltd.],
Examples include triacrylate of 3-mol ethylene oxide adduct of pentaerythritol, oligopropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, and the like, and particularly preferred are alkylene glycol-based and alkylene ether-based crosslinking agents.

Since such a specific ethylenically unsaturated compound has a small molecular weight, it tends to be distributed in a sea component having a low viscosity and a relatively high fluidity in the sea-island structure of the printing plate described above. As a result, the specific ethylenically unsaturated compound is greater on the printing plate surface where the amount of the sea component is large than on the inside of the printing plate, and the crosslinking density is higher than on the inside of the printing plate. As a result, a difference in the dynamic hardness between the plate surface and the inside, which is a feature of the present invention, is generated. At the same time, the sensitivity of the entire photosensitive layer constituting the printing plate is dramatically increased because the content of the specific ethylenically unsaturated compound is large on the printing plate surface, which is a feature of the present invention.
It is possible to achieve a high level of image reproducibility that cannot be realized by a conventional flexographic printing plate.

In order for the above-mentioned specific ethylenically unsaturated compound to be distributed on the printing plate surface, the content thereof is in the range of 0.5% by weight to 10% by weight, especially 1 to 10% by weight in the printing plate photosensitive layer. Preferably it is at 9% by weight. When the content is larger than this range, the dynamic hardness of the solid portion surface becomes large, and it is necessary to apply a printing pressure in order to perform good solid portion printing in printing, and in that case, halftone dots are crushed and a clear printed matter cannot be obtained. . On the other hand, if the content is less than this range, the crosslinking density on the printing plate surface becomes small, and the printing plate surface is undesirably deformed in printing.

In the present invention, the above-mentioned specific ethylenically unsaturated compound may be used in combination with a compound having a molecular weight of 1,000 or more and having an ethylenically unsaturated group at a terminal or a side chain. Such a device is disclosed in, for example, JP-A-1-2198.
No. 33, oligobutadiene (meth) acrylate, oligostyrene butadiene (meth) acrylate, oligonitrile butadiene (meth)
Acrylate, oligoisoprene (meth) acrylate, oligobutadiene urethane (meth) acrylate,
Examples include, but are not limited to, oligostyrene butadiene (meth) acrylate and oligobutadienamide (meth) acrylate. Such a compound having an ethylenically unsaturated group having a molecular weight of 1,000 or more may be used as a mixture with the above-mentioned specific ethylenically unsaturated compound at an arbitrary ratio.

Examples of the initiator used in the present invention include benzophenones, acetophenones, α-diketones,
Examples include acyloins, acyloin ethers, benzylalkyl ketals, polynuclear quinones, thioxanthones, acylphosphines, and the like.Specifically, benzophenone, chlorobenzophenone, acetophenone, benzyl, diacetyl, benzoin, bivaloin, benzoinmethyl Ether, benzoin ethyl ether, benzyl diethyl ketal, benzyl diisopropyl ketal,
Examples include anthraquinone, 1,4-naphthoquinone, 2-chloroanthraquinone, thioxanthone, 2-chlorothioxanthone, and acylphosphine oxide.
These may be used alone or in combination.
It is preferred to be incorporated in a 10% by weight composition. 0.
If it is less than 01% by weight, it cannot function as an initiator, and if it exceeds 10% by weight, the function of an internal filter becomes strong and the internal curing becomes insufficient. More preferably, it is 0.5 to 5% by weight.

As the method for producing the water-developable photosensitive flexographic printing plate precursor in the present invention, a usual method can be adopted. For example, the photosensitive resin composition is prepared by mixing the photosensitive resin composition with a polyethylene terephthalate film coated with an adhesive layer. It can be manufactured by sandwiching between a polyethylene terephthalate film coated with a slip coat layer made of a water-soluble resin, heating and pressing.

The outline of an example of a method for producing a water-developable photosensitive flexographic printing plate according to the present invention has been described above. Next, the developing step will be described in more detail. After applying an inspection negative and irradiating ultraviolet rays under appropriate exposure conditions, a non-image portion is removed using a developer to obtain a photosensitive resin printing plate of the present invention.
The developer has a pH of 5.0 containing general water for daily use.
9.0 is optimal, and other alkaline compounds,
It may contain a surfactant, a water-soluble organic solvent, and in some cases, an organic acid. In addition, as the above-mentioned surfactant,
Sodium alkylnaphthalenesulfonate, sodium alkylbenzenesulfonate, sodium alkylbenzenesulfonate, and the like are most suitable, and anionic surfactants, nonionic surfactants, and amphoteric surfactants can also be used.
Further, the temperature of the developer is preferably 25 to 50 ° C.

The photosensitive flexographic printing plate of the present invention can be obtained by performing ordinary drying for removing water adhering to the surface of the printing plate after the development, and performing post-exposure in the same manner as in a normal printing plate. In this case, as shown in FIG. 2, a halftone dot having a density of 50% or less and a density of 10% or less where the projections of the printing plate independently exist.
The 0% solid image differs in post-exposure by the area of the continuous phase in which the particular ethylenically unsaturated compound is directly exposed to light. That is, the area of the continuous phase which is cured by post-exposure to reinforce the printing plate surface per unit area of printing is larger in the halftone dot image than in the solid portion image.
For this reason, the dynamic hardness of the halftone printing plate surface of the present invention is larger than the dynamic hardness of the solid portion surface. As a result, it is considered that a flexographic printing plate capable of performing clear printing which is a feature of the present invention can be obtained.

On the other hand, a halftone dot having a density of 50% or less has a convex portion which becomes an image discontinuously and independently of an adjacent convex portion. For this reason, there is an exposed portion and a non-exposed portion, and the probability that a termination reaction of the photoradical reaction is generated is small. On the other hand, in a solid portion having a density of 100%, there is no boundary between an exposed portion and a non-exposed portion, and a convex portion exists continuously.
For this reason, the solid portion has a smaller photocuring degree because the probability of the termination reaction of the photoradical reaction being generated is larger than the halftone dot portion. The photosensitive resin composition of the present invention is characterized in that the specific ethylenically unsaturated compound is localized in the continuous phase, so that the difference in photocuring degree between the halftone dot portion and the solid portion is large, so that the dynamic hardness on each surface is large. It seems that the image is clearly reproduced.

[0028]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The term “parts” means “parts by weight” and was evaluated by the following measurement methods in each evaluation. 1) Dynamic hardness measurement conditions Model: Dynamic ultra-micro hardness tester manufactured by Shimadzu Corporation Test mode: Test for soft material (mode 3) Load: 2.5 gf 2) Dynamic hardness measurement sample and measurement ・ Plate thickness 1.70mm photosensitive flexographic original plate
Halftone dot 200 lines-1% to 95%, minimum independent point diameter 100 μm, minimum independent line width 30 μm, minimum extraction
Inspection negative including width 100μm, minimum convex character 1 point, minimum extracted character 1 point, solid image, step guide
At a gap of 300 μm slit width is at least 3
A flexographic printing plate was obtained by post-exposure curing after a minimum exposure amount of a surface exposure time of 0 μm or more and at which 1% of 200 lines of halftone dots were reproduced, an appropriate developing step and a drying step. Halftone dots of 150 lines 5% and density of 10
Measure the dynamic hardness of the outermost surface of each printing plate with 0% solid part.

Example 1 29.0 parts of polytetramethylene glycol (G-850 manufactured by Hodogaya Chemical Co., Ltd.) 62.0 parts of dimethylolpropionic acid (Fujii Yoshitsusho) and 119.0 parts of hexamethylene diisocyanate (Nippon Polyurethane) And a solution prepared by dissolving 5.0 parts of n-butyltin dilaurate in 300.0 parts of tetrahydrofuran.
Put the flask in a 6-liter flask while stirring.
The mixture was heated to 5 ° C., and the reaction was continued for 3 hours. Further, 26.0 parts of hydroxyethyl methacrylate was added, and the reaction was continued for 2 hours while heating to 65 ° C. Acrylonitrile containing terminal amino group, butadiene oligomer (Hycar AT
A solution prepared by dissolving 184.0 parts of BNX 1300 × 16 Ube Industries, Ltd. in 270.0 parts of tetrahydrofuran was added to the above one-liter flask with stirring at room temperature. The obtained polymer solution was dried under reduced pressure to remove tetrahydrofuran, thereby obtaining a hydrophilic polymer [I].

10.5 parts of the above hydrophilic polymer, nitrile butadiene rubber (acrylonitrile 35%) (NIPUL-10
42 Nippon Bion Co., Ltd. 33 parts, butadiene rubber (JSR BR
OLLL) 22 parts, oligobutadiene acrylate (PB-
A Kyoeisha Chemical Co., Ltd., 29 parts, 1.6 parts of hexanediol dimethacrylate, 3 parts of dimethylbenzyl ketal as photoinitiator, 0.1 part of hydroquinone monomethyl ether, 40 parts of toluene, 10 parts of water And kneaded at 105 ° C., and then toluene and water were distilled off under reduced pressure. The resulting photosensitive resin composition was coated to a thickness of 12
A film in which a polyester-based adhesive layer is coated on a 5 μm polyethylene terephthalate film, and a film in which an anti-adhesion layer (containing polyvinyl alcohol, propylene glycol, and a surfactant) is coated on the same polyethylene terephthalate film (an adhesive layer, (So that the anti-adhesion layer is in contact with the photosensitive resin composition) at 105 ° C. and 100 kg / cm ² with a heat press.
1.7mm thick by heating and pressurizing at a pressure of 1 minute
Was prepared. The cover film of the obtained original plate was peeled off, and an inspection negative including a halftone dot 200 line -1% to 95%, a minimum independent point diameter of 100 μm, a minimum convex character, one point, a minimum extracted character one point solid image, and a step guide was prepared. 17. Illuminance at 365 mm light
5w / m ² (Anderson A Vreeland lamp FR20
Using T12-BL-9-BP), back exposure and front exposure were performed to remove the negative film, and developed for 12 minutes in neutral water at 40 ° C. containing 4% by weight of sodium alkylnaphthalenesulfonate. Dried for 20 minutes. Further, exposure was performed from the table to obtain a printing plate.

The obtained printing plate has a relief depth of 0.8.
mm, halftone dot 200 line 1% to 95%, minimum independent point diameter 100 μm, minimum independent line width 30 μm, minimum outgoing line width 1
Image reproducibility that cannot be realized with a conventional flexographic printing plate reproducing 00 μm, 1 point of minimum convex characters, and 1 point of minimum extracted characters was obtained. Table 1 shows the dynamic hardness of the halftone dots and solid portions of the obtained printing plate and their ratios. Table 1
As is clearer, it can be seen that when printing is performed with aqueous ink using the obtained printing plate, a printed matter that faithfully reproduces the negative original image is obtained.

Example 2 The procedure of Example 1 was repeated except that 3 parts of dipentaerythritol hexaacrylate was used instead of 3 parts of 1.6 hexanediol dimethacrylate. Was obtained.

Example 3 In Example 1, cis isoprene rubber (manufactured by IR-10 Kuraray Co., Ltd.) was used instead of 33 parts of nitrile butadiene rubber.
The same procedure as in Example 1 was performed except that 33 parts were used, and the same results as in Example 1 were obtained.

Example 4 Isoprene rubber (IR-310 Shell Japan Co., Ltd.)
21 parts, polybutadiene rubber (JSR BROLL Nippon Synthetic Rubber Co., Ltd.) 10.5 parts, nitrile butadiene rubber (JSR230S Nippon Synthetic Rubber Co., Ltd.) 4.5 parts, liquid isoprene rubber (LIR-410 Kuraray Co., Ltd.) 5 .0
Parts, polybutadiene acrylate (PBA-Kyoeisha Chemical Co., Ltd. 30 parts, hydrophilic polymer [I] 10.5 parts,
5 parts of 6-hexanediol dimethacrylate, 2.0 parts of benzyldimethyl ketal and 0.1 part of hydroquinone monomethyl ether were mixed and evaluated in the same manner as in Example 1. As a result, the same results as in Example 1 were obtained.

Example 5 45 parts of chlorinated polyethylene (Daisolac H-135 Daiso Co., Ltd.) and butadiene rubber (JSR BROLL)
Nippon Synthetic Rubber Co., Ltd. 14 parts, butadiene oligoacrylate (PB-A Kyoeisha Chemical Co., Ltd. 25 parts, 1,6 hexanediol dimethacrylate 2.5 parts, dipentaerythritol hexaacrylate 2.5 parts), hydrophilic 10.5 parts of the reactive polymer I, 2 parts of benzyldimethyl ketal, and 0.3 part of hydroquinone monomethyl ether were mixed and evaluated in the same manner as in Example 1. As a result, the same results as in Example 1 were obtained.

Example 6 40 parts of a random copolymer containing a phosphate ester group (monomer composition: 65% of butadiene, 4% of methyl acrylate, 20% of ethylene phosphate, 10% of styrene, 1% of divinylbenzene), polystyrene 27 parts of a polybutadiene-polystyrene type block copolymer, 25 parts of liquid polybutadiene (Nisso-PBB1000), 1 part of benzyldimethyl ketal, and 7 parts of 1,6 hexanediol dimethacrylate are melt-kneaded using a heating kneader, and the photosensitive resin composition is obtained. I got something. When the obtained photosensitive resin composition was evaluated in the same manner as in Example 1, the same results as in Example 1 were obtained.

Example 7 A carboxyl group-containing core-shell cyclogel (core: 2-ethylhexyl acrylate-89) was used in Example 6 instead of 40 parts of the phosphate group-containing random copolymer.
Part, allyl acrylate + 1 part, copolymer of 8 parts of 1,4 butanediol, shell: n-butyl acrylate 80
Parts, methacrylic acid 20 parts copolymer, and the reaction ratio of the core and the shell was 2/1), except that 40 parts were used. The same results as in Example 6 were obtained.

Comparative Example 1 Evaluation was made in the same manner as in Example 1 except that 1,6 hexanediol dimethacrylate was used.
50 lines 3% to 95% Minimum independent point diameter 200 μm, minimum independent line width 5 μm, minimum line width 150 μm Minimum convex character 3
Only the image reproducibility of 4 points and the minimum extracted characters was obtained. Table 1 shows the dynamic hardness of the printing plate halftone dots and the solid portions and their ratios.

[0039]

[Table 1]

[0040]

As is clear from the above description, the water-developable photosensitive flexographic printing plate of the present invention achieves high image reproducibility that cannot be achieved by conventional flexographic printing and contributes to the industry. It is big.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toru Wada 2-1-1 Katata, Otsu-shi, Shiga F-term in Toyobo Co., Ltd. Research Laboratory (reference) 2H025 AA04 AB02 AC01 AD01 BC34 BC36 CA05 CB11 DA05 DA19 DA35 EA04 EA08 FA07 FA17 FA30 2H096 AA03 BA05 CA12 CA16 EA02 EA15 GA08 HA03

Claims (1)

[Claims] 1. A water-developable photosensitive flexographic printing plate,
Water wherein the ratio (A) / (B) of the dynamic hardness (A) of the halftone dot surface having a concentration of 50% or less to the dynamic hardness (B) of the solid portion surface having a concentration of 100% is 1.1 or more. Developable photosensitive flexographic printing plate.