JP2001337446A - Flexographic printing plate and water developable photosensitive original plate for flexographic printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexographic printing plate manufactured from a water developable photosensitive original plate for flexographic printing, excellent in image reproducibility and having a small dot gain and good printing property. SOLUTION: In the flexographic printing plate obtained by subjecting the water developable photosensitive original plate with at least a base and a photosensitive layer to exposure and water development, the relative dielectric constant (A) of the photosensitive layer before exposure is 4-10, the relative dielectric constant (B) of the photosensitive layer after exposure is 2-7 and the ratio of (A) to (B) is >1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexographic printing plate and a water-developable photosensitive original plate for flexographic printing.

[0002]

2. Description of the Related Art Conventionally, flexographic printing is preferable in terms of environmental hygiene because aqueous inks and low-viscosity inks containing alcohol are used as printing inks, and a simple printing machine and high productivity are required. Is widely used in general. The printing plate used for such flexographic printing is prepared by exposing and developing the photosensitive layer of the printing original plate.However, due to problems such as safety, in recent years, a water-developing printing original plate has been required. I have.

However, since the printing plate used for such flexographic printing is made of a material having rubber elasticity, when the printing plate comes into contact with a printing medium and transfers ink,
There is a problem in that the printing plate is deformed and the printed image becomes larger than the original image, that is, a so-called dot gain occurs. The flexographic printing plate has a thickness (typically 1).
mm to 7 mm) is thicker than letterpress printing plates, lithographic printing plates, gravure printing, etc. using oil-based ink, so that the light necessary for forming an image does not sufficiently penetrate into the inside. Image reproducibility is poor.

[0004]

Accordingly, the present invention is directed to a flexographic printing plate produced from a water-developable photosensitive original plate for flexographic printing, which has excellent image reproducibility, small dot gain and good printability. The purpose is to provide. Still another object is to provide a water-developable photosensitive original plate for flexographic printing used for the flexographic printing plate.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, the relative permittivity of the photosensitive layer before or after exposure is shown below. The inventors have found that the object can be achieved, and have completed the present invention.

That is, the present invention relates to a flexographic printing plate obtained by exposing and water developing a water-developable photosensitive original plate for flexographic printing having at least a support and a photosensitive layer.
A flexographic printing plate, wherein the photosensitive layer before exposure has a relative dielectric constant (A) of 4 to 10.

The present invention has found that the relative dielectric constant (A) of the photosensitive layer before exposure is related to hydrophilicity, that is, the ease of penetration of the unexposed photosensitive layer into a water developing solution. By setting the dielectric constant (A) within the above range, the water developability of the unexposed photosensitive layer is ensured, and the image reproducibility of the printing plate is realized. When the relative dielectric constant (A) is less than 4, the hydrophilicity is low, and the unexposed photosensitive layer has insufficient water developability. From such a viewpoint, the relative dielectric constant (A) is preferably 5 or more. On the other hand, when the relative dielectric constant (A) exceeds 10, the hydrophilicity becomes too high, and the printing plate swells in a flexographic ink containing a highly polar solvent such as water, alcohol, and esters, and high image reproducibility is obtained. I can't get it. From this viewpoint, the relative dielectric constant (A) is preferably set to 7 or less.

The present invention also relates to a flexographic printing plate obtained by exposing and water developing a water-developable photosensitive original plate for flexographic printing having at least a support and a photosensitive layer. B) is a flexographic printing plate, wherein B is 2 to 7.

In the present invention, the relative permittivity (B) of the photosensitive layer after exposure indicates the balance between hydrophilicity and hydrophobicity of the printing plate, that is, the transferability of the printing plate to flexographic ink and the resistance to ink swelling. Finding something related to image reproducibility,
By setting the relative dielectric constant (B) within the above range, water developability of the unexposed photosensitive layer is ensured, and high image reproducibility is realized. When the relative dielectric constant (B) is less than 2,
The wettability of the printing plate to a flexographic ink containing a highly polar solvent such as water, alcohol, esters and the like becomes poor, and ink repelling occurs to make the printed matter unclear. From this viewpoint, the relative dielectric constant (B) is preferably set to 4 or more. On the other hand, when the relative dielectric constant (B) exceeds 7, the hydrophilicity of the printing plate becomes too high, and the printing plate swells in a flexographic ink containing a highly polar solvent such as water, alcohol, esters, etc. Image reproducibility cannot be obtained. From this viewpoint, the relative dielectric constant (B) is preferably set to 6 or less.

[0010] The present invention also relates to a flexographic printing plate obtained by exposing and water developing a water-developable photosensitive original plate for flexographic printing having at least a support and a photosensitive layer. A) and a flexographic printing plate, wherein the relative permittivity (B) of the photosensitive layer after exposure is (A) / (B)> 1.

In the present invention, the relative dielectric constant (A) of the photosensitive layer before the exposure is changed by a photoreaction by exposure, and the relative dielectric constant (B) after the exposure is higher than the relative dielectric constant (A) before the exposure. When it is smaller, that is, when (A) / (B)> 1, the hydrophilic property is secured by the relative dielectric constant (A) to enable water development of the unexposed portion of the photosensitive layer, It has been found that high surface image reproducibility excellent in ink swelling resistance can be realized by securing hydrophobicity by the dielectric constant (B). From such a viewpoint, the ratio of the relative permittivity is preferably set to 1.01 or more. The upper limit of (A) / (B) is preferably 2 or less.

As described above, the present invention relates to the relative permittivity (A) of the photosensitive layer before exposure, the relative permittivity (B) after exposure, and the ratio of these relative permittivity (A) and (B). Although the specific ranges related to the relative dielectric constants (A) and (B) may be combined, the specific ranges may be combined.
Even when (A) / (B)> 1, it is preferable that the relative dielectric constant (A) satisfies 4 to 10 and the relative dielectric constant (B) satisfies 2 to 7.

Further, the present invention relates to a water-developable photosensitive resin original plate for flexographic printing, having at least a support and a photosensitive layer, used for the flexographic printing plate.

By exposing and developing such a water-developable photosensitive original plate for flexographic printing, the flexographic printing plate is obtained.

The relative dielectric constant is, for example, the magnitude of the electrostatic energy stored in a unit volume under a unit electric field, as described in the document “Electrical and Electronic Functional Materials” (Ohm). It is a quantity representing the degree and is obtained by the following equation.

Relative permittivity (ε ') = (Cx / Co) Cx: capacitance of measured object Co: geometric capacitance

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The flexographic printing plate of the present invention is obtained by exposing and water developing a water-developable photosensitive original plate for flexographic printing having at least a support and a photosensitive layer. The exposed photosensitive layer in the printing plate has water developability, that is, hydrophilicity, and the exposed photosensitive layer in the printing plate has flexo ink resistance, that is, water resistance, alcohol resistance, cosolvent ink resistance and appropriate water resistance that can realize high surface image reproducibility. Flexo ink receiving transferability is required.

For forming such a photosensitive layer, for example,
A photosensitive resin composition containing a hydrophobic component for expressing flexographic ink resistance, a hydrophilic component for expressing water developability, and a photopolymerizable ethylenically unsaturated compound for imparting photosensitivity is provided. Used. Since the components of these photosensitive resin compositions are not the same in chemical structure,
In the photosensitive layer, a so-called sea-island type phase separation structure is formed. In the case of forming a sea-island type phase-separated 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 Doujin P22 (1
As described in 981), a composition having a relatively low viscosity and being easily flowable has a sea phase structure. Further, when the structural composition is a non-crosslinked body and a crosslinked body, the crosslinked body does not dissolve in the noncrosslinked body, so that the noncrosslinked body having low viscosity and fluidity also has a sea phase structure.

The presence of the hydrophobic component, the hydrophilic component, and the ethylenically unsaturated compound in the photosensitive layer is controlled so that the relative permittivity of the entire photosensitive layer is in a specific range.
It forms a phase-separated structure that exhibits proper water developability in the original plate, good flexographic ink resistance in the printing plate, and excellent print image reproducibility. The relative permittivity of the photosensitive resin can be controlled by the balance of the existing state of the hydrophilic component and other components and the content ratio.

The hydrophobic component contained in the photosensitive resin composition may be a non-crosslinked hydrophobic polymer. Specifically, a polymer obtained by polymerizing a conjugated diene-based hydrocarbon, a copolymer obtained by polymerizing a conjugated diene-based hydrocarbon and a monoolefin-based unsaturated compound, and a polymer containing no conjugated diene-based hydrocarbon are used. Coalescence and the like. These hydrophobic components may be used alone or in combination of two or more.

Specific examples of the polymer containing a conjugated diene hydrocarbon include butadiene polymer, isoprene polymer, chloroprene polymer, styrene-butadiene copolymer, styrene-isoprene copolymer, and styrene-chloroprene copolymer. , Acrylonitrile-butadiene copolymer, acrylonitrile-isoprene copolymer, methyl methacrylate-isoprene copolymer, methyl methacrylate-chloroprene copolymer, methyl acrylate-butadiene copolymer, methyl acrylate-chloroprene copolymer Acrylonitrile-butadiene-styrene copolymer, acrylonitrile-chloroprene-styrene copolymer and the like.

Examples of the polymer containing no conjugated diene-based hydrocarbon include an elastomer containing a specific amount of chlorine and a polymer of a non-conjugated diene-based hydrocarbon. Specifically, epichlorohydrin-propylene oxide copolymer is used. Polymers, epichlorohydrin rubber which is a copolymer of these and acrylic glycidyl ether [Osaka Soda Kogyo Co., Ltd.
Manufactured by: trade name Epichromer, manufactured by Goodrich Co., Ltd .:
Product name HYDRIN, manufactured by Zeon Corporation: Product name CE
CHRON, Zeospan, Hercules, Inc .:
Trade name HERCLOR], chlorinated polyethylene [Showa Denko KK: trade name Eraslen, Osaka Soda Industry Co., Ltd.]
Manufactured by: Daisorak, manufactured by Hoechst Corporation: H
ORTALITZ, Dow Chemical Co., Ltd.
Manufactured by Dow CPE).

The hydrophilic component contained in the photosensitive resin composition includes a non-crosslinked hydrophilic polymer and a crosslinked hydrophilic polymer.

Examples of the crosslinked hydrophilic polymer (also referred to as a crosslinked type of particulate hydrophilic or water-swellable elastomer) include partial internal crosslinks obtained by radical emulsion polymerization described in JP-A-1-300246. Examples are given. The partially internally crosslinked copolymer is obtained by radical emulsion polymerization of a monomer mixture containing 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. Obtained by

Examples of the aliphatic conjugated diene monomer as the copolymer component include butadiene, isoprene, dimethylbutadiene, chloroprene and the like. Examples of the compound having at least two addition-polymerizable groups include:
Trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, divinylbenzene, ethyne glycol di (meth) acrylate, pentaerythritol tetra (meth) acrylate, 1,4-butanediol di (meth) acrylate,
1,6-hexadiol di (meth) acrylate and the like can be mentioned.

The monomer mixture may contain an α, β-ethylenically unsaturated carboxylic acid, and examples thereof include acrylic acid, maleic acid, fumaric acid, tetraconic acid, and protonic acid. The carboxyl group of the α, β-ethylenically unsaturated carboxylic acid may be salified by an alkali metal or a compound containing a basic nitrogen atom. Preferred basic nitrogen atom compounds include N,
N-dimethylaminopropyl (meth) acrylamide,
N, N-dimethylaminoethyl (meth) acramide,
N, N-dimethylaminoethyl-N ′-(meth) acryloylcarbamate, N, N-dimethylaminoethoxyethanol, N, N-dimethylaminoethoxyethyl (meth) acrylate, and the like.

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. The core-shell microgel binder as used herein has two regions: a core having a crosslinking of 10% by weight or less, and an aqueous-processable non-crosslinking outer shell made of an acid-modified copolymer. Particles. Monomers that form the core include methyl methacrylate, ethyl acrylate, methacrylic acid, butyl methacrylate, ethyl methacrylate, glycidyl methacrylate, styrene and allyl methacrylate, and butanediol diacrylate, ethylene glycol dimethacrylate, and tetramethylene glycol as crosslinkers. Examples include diacrylate, trimethylolpropane triacrylate, tetramethylene glycol dimethacrylate, and the like. On the other hand, as the copolymer modified with an acid that forms a shell, n-butyl acrylate modified with methacrylic acid is preferable. The core-shell microgel binder is produced by usual 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, Examples thereof include acrylates such as hydroxypropyl acrylate and methacrylates thereof.
Other monoolefinically unsaturated monomers include styrene, acrylonitrile, vinyl chloride, ethylidene norbornene, propenyl norbornene, dicyclopentadiene and the like. In some cases, a conjugated diene 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 of the unsaturated monomer having a hydrophilic functional group include a carboxyl group, a phosphoric acid group, a phosphoric ester group, a sulfonic acid group, and a hydroxyl group. Phosphate groups are preferred.

Examples of the above-mentioned unsaturated monomer containing a phosphate group include ethylene phosphate (meth) acrylate, trimethylene phosphate (meth) acrylate, propylene phosphate (meth) acrylate, and tetramethylene phosphate (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.

Other examples of the hydrophilic polymer include polymers 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. More specifically, polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, water-soluble polyurethane, water-soluble polyurea urethane, water-soluble polyester, water-soluble epoxy compound, carboxyl group-containing acrylonitrile-butadiene copolymer, carboxyl group-containing styrene-butadiene copolymer And carboxyl group-containing polybutadiene, polyacrylamide, sodium polyacrylate, carboxyl group polyurea urethane, polyamic acid, and the like, but are not limited to the polymers described in JP-A-3-72353. .

The photopolymerizable ethylenically unsaturated compound contained in the photosensitive resin composition of the present invention includes, specifically,
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 is preferably used. Such specific ethylenically unsaturated compounds include, for example, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol (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, bisphenol A ethylene oxide adduct di (meth) A) acrylate, ethylene oxide-modified trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, 1,9-nonanediol di (meth) acrylate, light ester P-2M [Kyoeisha Chemical ( Co., Ltd., trade name], triacrylate of 3 mol ethylene oxide adduct of pentaerythritol,
Oligopropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate and the like can be mentioned. Of these, alkylene glycol-based and alkylene ether-based ones are particularly preferred.

The specific ethylenically unsaturated compound includes lauryl methacrylate, N- (3-dimethylaminopropyl) (meth) acrylamide, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, ethyl (meth) acrylate. ) Acrylate,
A compound having one ethylenically unsaturated group such as propyl (meth) acrylate can also be used.

In the present invention, in addition to the above-mentioned specific ethylenically unsaturated compound, a compound having a molecular weight of 1,000 or more and containing one or two or more ethylenically unsaturated groups at terminals or side chains is used. You may use together. Such compounds include oligobutadiene (meth) acrylate, oligostyrenebutadiene (meth) acrylate, oligonitrile butadiene (meth) acrylate, and oligoisoprene (meth) acrylate as described in JP-A-1-219833. , Oligobutadiene urethane (meth) acrylate, oligobutadiamide (meth) acrylate, and the like, but are not limited thereto. Such a molecular weight is 1
The compound having an ethylenically unsaturated group of not less than 000 may be used in an arbitrary ratio with the specific ethylenically unsaturated compound as long as the relative dielectric constants (A) and (B) of the photosensitive layer fall within the above ranges. You may mix and use.

The photosensitive resin composition contains a photopolymerization initiator in addition to the pre-hydrophobic component, the hydrophilic component and the ethylenically unsaturated compound. Examples of photopolymerization initiators include benzophenones, acetophenones, α-diketones, acyloins, acyloin ethers, benzylalkyl ketals, polynuclear quinones, thioxanthones,
Acylphosphines and the like, specifically, benzophenone, chlorbenzophenone, acetophenone, benzyl, diacetyl, benzoin, bivaloin, benzoin methyl ether, benzoin ethyl ether, benzyl diethyl ketal, benzyl diisopropyl ketal, anthraquinone, Examples thereof include 1,4-naphthoquinone, 2-chloroanthraquinone, thioxanthone, 2-chlorothioxanthone, and acylphosphine oxide. These may be used alone or in combination.

The relative permittivity of the photosensitive resin composition can be adjusted by adjusting the mixing ratio of the above-mentioned hydrophobic component, hydrophilic component and ethylenically unsaturated compound. The relative dielectric constant (A) of the photosensitive layer before exposure and the relative dielectric constant (B) after exposure of the photosensitive layer can be controlled by the compounding ratio of the compound so as to be within the above range.

The mixing ratio of the photosensitive resin composition is, specifically, 2 to 70% by weight of the hydrophilic component and 20 to 70% by weight of the hydrophobic component.
80% by weight, 1 to 70% by weight of ethylenically unsaturated compound
It is preferable to mix them such that More preferably,
3-50% by weight of a hydrophilic component and 25-70% of a hydrophobic component
% By weight, and 3 to 60% by weight of the ethylenically unsaturated compound.

When the content of the hydrophilic polymer in the composition is less than 2% by weight, problems occur in water developability and shape retention, and when it exceeds 70% by weight, problems occur in water resistance.

When the content of the hydrophobic polymer in the composition is 20
When the content is less than 10% by weight, the handleability is impaired, and
If the amount is more than 10% by weight, water developability is impaired.

When the content of the ethylenically unsaturated compound in the composition is less than 1% by weight, photopolymerizability becomes insufficient,
If it exceeds 70% by weight, the hardness becomes high and the flexibility becomes insufficient.

The photopolymerization initiator is desirably added to the photosensitive resin composition in an amount of 0.01 to 10% by weight from the viewpoint of photopolymerization initiation ability. In addition, the photosensitive resin composition of the present invention, in addition to the composition, a thermal polymerization inhibitor, a plasticizer,
Dyes and various additives thereof may be blended.

The water-developable photosensitive original plate for flexographic printing of the present invention can be produced according to a usual method. For example, the photosensitive resin composition is sandwiched between a polyethylene terephthalate film (support) coated with an adhesive layer and a polyethylene terephthalate film coated with a slip coat layer mainly composed of a water-soluble resin, and heated and pressed. To form a photosensitive layer on a support. The thickness of the support and the thickness of the photosensitive layer may be the same as those in the related art, and can be appropriately determined.

As a method for preparing a printing plate from the water-developable photosensitive original plate for flexographic printing, first, a photosensitive layer of the printing original plate is exposed to an inspection negative and irradiated with ultraviolet rays under appropriate exposure conditions. The photosensitive printing plate is obtained by removing the non-image area using the liquid. As the developer, water having a pH of 5.0 to 9.0 containing general water for daily use is most suitable. The developer may further contain an alkaline compound, a surfactant, a water-soluble organic solvent, and in some cases, an organic acid. As the above-mentioned surfactant, sodium alkylnaphthalenesulfonate, sodium alkylbenzenesulfonate and the like are most suitable. In addition, anionic surfactants, nonionic surfactants, and amphoteric surfactants can be used. Further, the developer is preferably used at a temperature of about 25 to 50 ° C.

[0044]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In each example, “parts” means “parts by weight”, and the relative permittivity is a value obtained by a measurement method described below.

(1) Measurement Conditions of Relative Dielectric Constant A sample piece obtained by cutting a photosensitive original plate or a printing plate into a 6 cm square was set on a TRS-10T type dielectric loss measuring device (manufactured by Ando Electric Co., Ltd.), and the frequency was measured. The dielectric loss of each sample piece was measured at 1 kz.

Example 1 (1) Preparation of hydrophilic polymer 29.0 parts of polytetramethylene glycol (trade name: PTG-80, manufactured by Hodogaya Chemical Co., Ltd.), dimethylolpropionic acid (produced by Yoshitsuka Fujii) 0 part, 119.0 parts of hexamethylene didiisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd.) and 5.0 parts of n-butyltin dilaurate dissolved in 300 parts of tetrahydrofuran are placed in a 1-liter flask equipped with a stirrer and stirred. The flask was heated to 65 ° C. while continuing the reaction, and the reaction was continued for 3 hours. Further, 26.0 parts of hydroxyethyl methacrylate was added and the mixture was added at 65 ° C.
The reaction was continued for 2 hours while heating. A solution prepared by dissolving 184.0 parts of acrylonitrile-butadiene oligomer having a terminal amino group (trade name: Hycar ATBNX 1300 × 16 Ube Industries) in 270.0 parts of tetrahydrofuran in a separate container at room temperature in the above 1 liter flask Add under stirring. The obtained polymer solution was dried under reduced pressure to remove tetrahydrofuran, and then treated with lithium hydroxide and magnesium acetate to neutralize the carboxyl groups contained in the polymer to obtain a hydrophilic polymer {1}.

(2) Preparation of photosensitive resin composition The hydrophilic polymer {1} 10.5 as a hydrophilic component
Part, nitrile butadiene rubber (acrylonitrile 35%) as a hydrophobic component (trade name: NIPOL-1042,
33 parts of Nippon Bion Co., Ltd.) and butadiene rubber (J
22 parts by SR: trade name BROLL), 29 parts by weight of oligobutadiene acrylate (trade name: PB-A, Kyoeisha Chemical Co., Ltd.) as an ethylenically unsaturated compound, and 1,6
-3 parts of hexanediol dimethacrylate, 2 parts of dimethylbenzyl ketal as a photopolymerization initiator, and 0.1 part of hydroquinone monomethyl ether,
Parts and 10 parts of water were kneaded at 105 ° C. using a heating kneader, and then toluene and water were distilled off under reduced pressure to prepare a photosensitive resin composition.

(3) Preparation of Photosensitive Master The obtained photosensitive resin composition was coated on a 125 μm-thick polyethylene terephthalate film coated with a polyester-based adhesive layer. (Contains polyvinyl alcohol, propylene glycol, and surfactant)
(So that the adhesive layer and the anti-adhesion layer are in contact with the photosensitive resin composition), and heated and pressed at 105 ° C. under a pressure of 100 kg / cm ² for 1 minute with a heat press to obtain a thickness of 1 mm. A 0.7 mm photosensitive original plate was prepared. The cover film of the obtained master was peeled off, and the relative dielectric constant (A) of the photosensitive layer was measured. The results are shown in Table 1.

(4) Production of printing plate Halftone dot 200 line -1% to 95%, minimum independent point diameter 100
μm, minimum convex character 1 point, minimum extracted character 1 point,
Inspection negatives including solid images and step guides, 36
Illuminance of about 17.5 w / m ^{2 at} 5 nm light (Ander
Son A Vreland Co., Lamp FR20T
12-BL-9-BP), back exposure and front exposure were performed, the negative film was removed, and the residue was exposed to neutral water at 40 ° C. containing 4% by weight of sodium alkylnaphthalenesulfonate.
Developed for 2 minutes and dried for 60 minutes for 20 minutes. Further, exposure was performed from the table to obtain a printing plate.

The obtained printing plate had a relief depth of 0.8.
mm, 1% to 95% halftone dot, 100 μm minimum independent point diameter, 30 μm minimum independent line width, 100 μm minimum line width, 1 point minimum convex character, 1 point minimum conventional character Image reproducibility that could not be achieved with the printing plate was obtained.

Table 1 shows the relative dielectric constant (B) and print image reproducibility of the obtained printing plate.

The circle of 200% 1% of the halftone dot has a diameter of 1 /
This means that an image having a dot size of 200 inches and a dot area (dense) of 1% has been printed.

As is evident from Table 1, when printing was carried out with the obtained printing plate using an aqueous ink, a printed matter faithfully reproducing the negative original was obtained.

Example 2 In the preparation of the photosensitive resin composition (2) of Example 1,
Except that 3 parts of dipentaerythritol hexaacrylate was used instead of 3 parts of 1,6-hexanediol dimethacrylate, the relative dielectric constant (A) of the unexposed photosensitive layer and the obtained dielectric constant were obtained in the same manner as in Example 1. The relative permittivity (B) of the printing plate thus obtained was measured, and print image reproduction was evaluated. Table 1 shows the results
Shown in

Example 3 In the preparation of the photosensitive resin composition (2) of Example 1, 33 parts of cis isoprene rubber (trade name: IR-10, manufactured by Kuraray Co., Ltd.) was used instead of 33 parts of nitrile butadiene rubber. The relative dielectric constant (A) of the unexposed photosensitive layer and the relative dielectric constant (B) of the obtained printing plate were measured in the same manner as in Example 1 except for using, and the reproduction of a printed image was evaluated. Table 1 shows the results
Shown in

Example 4 In the preparation of the photosensitive resin composition (2) of Example 1, isoprene rubber (trade name: IR-31) was used as the hydrophobic component.
0, manufactured by Shell Japan Co., Ltd.), 18 parts of polybutadiene rubber (trade name: JSR BRO2LL, manufactured by Nippon Synthetic Rubber Co., Ltd.), 12 parts, nitrile butadiene rubber (trade name:
6 parts of JSR230S, manufactured by Nippon Synthetic Rubber Co., Ltd. and 5.0 parts of liquid isoprene rubber (trade name: LIR-410, manufactured by Kuraray Co., Ltd.); , Kyoeisha Chemical Co., Ltd.) 30 parts, 1,6-hexanediol dimethacrylate 5 parts, hydrophilic polymer {1} 10.5 parts prepared in Example 1 (1) as a hydrophilic component, photopolymerization initiator 2.0 parts of benzyldimethyl ketal and 0.1 part of hydroquinone monomethyl ether as
0 ° C, 105 ° C using a heating kneader together with 10 parts of water
And then distilling off toluene and water under reduced pressure to prepare a photosensitive resin composition in the same manner as in Example 1 except that the relative dielectric constant (A) of the unexposed photosensitive layer and the obtained printing were obtained. The relative dielectric constant (B) of the plate was measured, and print image reproduction was evaluated. Table 1 shows the results.

Example 5 In the preparation of the photosensitive resin composition (2) of Example 1, 40 parts of chlorinated polyethylene (trade name: Daisolac H-135, manufactured by Daiso Co., Ltd.) and butadiene rubber ( Trade name: 14 parts of JSR BRO2LL, manufactured by Nippon Synthetic Rubber Co., Ltd., 30 parts of butadiene oligoacrylate (trade name: PB-A, manufactured by Kyoeisha Chemical Co., Ltd.) as an ethylenically unsaturated compound, 1,6-hexanediol 2.5 parts of dimethacrylate and 2.5 parts of dipentaerythritol hexaacrylate, hydrophilic polymer {1} 10.5 prepared in Example 1 (1) as a hydrophilic component
Part, benzyl dimetal ketal 2 as photopolymerization initiator
Part, and further, 0.3 part of hydroquinone monomethyl ether was kneaded at 105 ° C. using a heating kneader together with 40 parts of toluene and 10 parts of water, and then toluene and water were distilled off under reduced pressure to prepare a photosensitive resin composition. In the same manner as in Example 1, the relative permittivity (A) of the unexposed photosensitive layer and the relative permittivity (B) of the obtained printing plate were measured, and print image reproduction was evaluated. Table 1 shows the results.

Example 6 In the preparation of the photosensitive resin composition (2) of Example 1, a phosphate ester group-containing random copolymer (monomer composition = butanediene 65%, methyl acrylate 4%, 45 parts of ethylene phosphate 20%, styrene 10%, divinylbenzene 1%), 27 parts of a polystyrene-polybutadiene-polystyrene type block copolymer and 20 parts of liquid polybutadiene (Nisso-PB-B1000) as hydrophobic components, ethylenic 7 parts of 1,6-hexanediol dimethacrylate as an unsaturated compound, benzyl dimethyl ketal 1 as a photopolymerization initiator
Parts, 40 parts of toluene, 10 parts of water, and kneaded at 105 ° C. using a heating kneader, and then toluene and water were distilled off under reduced pressure to prepare a photosensitive resin composition. The relative dielectric constant (A) of the unexposed photosensitive layer and the relative dielectric constant (B) of the obtained printing plate were measured, and the reproduction of a printed image was evaluated. Table 1 shows the results.

Example 7 A carboxyl group-containing core-shell microgel (core: 2-ethylhexyl acrylate 8) was used in Example 6 in place of 45 parts of the phosphate ester group-containing random copolymer.
9 parts, allyl acrylate 1 part, 1,4-butanediol 8 parts copolymer, shell: n-butyl acrylate 8
Preparation of (2) photosensitive resin composition of Example 1 according to Example 6, except that 0 parts, a copolymer of 20 parts of methacrylic acid, and a reaction ratio of the core and the shell were 2/1) and 40 parts were used. In the same manner as in Example 1, the relative permittivity (A) of the unexposed photosensitive layer and the relative permittivity (B) of the obtained printing plate were measured, and the printed image reproduction was evaluated. Table 1 shows the results.

Example 8 In the preparation of the photosensitive resin composition (2) of Example 1, 40 parts of a polybutadiene-maleic anhydride copolymer as a hydrophilic component, 50 parts of a styrene butadiene-isoprene block polymer as a hydrophobic component, 1,10-dodecanol dimethacrylate 2 as an ethylenically unsaturated compound
Parts, 3 parts of polyethylene glycol monomethacrylate and 3 parts of bisphenol A-dihydroxyethyl acrylate, 1 part of benzyldimethyl ketanol as a photopolymerization initiator, 40 parts of toluene, and 10 parts of water, and kneaded at 105 ° C. using a heating kneader, Thereafter, toluene and water were distilled off under reduced pressure to prepare a photosensitive resin composition in the same manner as in Example 1 except that the relative dielectric constant (A) of the unexposed photosensitive layer and the relative dielectric constant of the obtained printing plate were changed. The rate (B) was measured, and print image reproduction was evaluated. Table 1 shows the results.

[0061]

[Table 1] Comparative Examples 1 to 8 The relative dielectric constant of the unexposed photosensitive layer (A) was changed in the same manner as in Examples 1 to 8, except that the amount of the hydrophilic component used was changed as shown in Table 2. ) And the relative permittivity (B) of the obtained printing plate were measured, and the printing image reproduction was evaluated. Table 2 shows the results. The numbers of Comparative Examples 1 to 8 are the same as those of Examples 1 to 8.
8 respectively.

[0062]

[Table 2] In the comparative example, the relative dielectric constants (A), (B) and (A) /
(B) is out of the predetermined range of the present invention. The reproducibility of the printed image was poor, and printing was impossible.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Satoshi Imahashi 2-1-1 Katata, Otsu-shi, Shiga F-term in Toyobo Co., Ltd. Research Laboratory (reference) 2H096 AA02 EA02 GA08 LA17

Claims (4)

[Claims] 1. A flexographic printing plate obtained by exposing and water-developing a water-developable photosensitive original plate for flexographic printing having at least a support and a photosensitive layer, has a relative dielectric constant (A) of 4 before exposure. 10. A flexographic printing plate, characterized in that: 2. A flexographic printing plate obtained by exposing and water developing a water-developable photosensitive original plate for flexographic printing having at least a support and a photosensitive layer, has a relative dielectric constant (B) of 2 after exposure. Flexographic printing plate, characterized in that: 3. A flexographic printing plate obtained by exposing and water developing a water-developable photosensitive original plate for flexographic printing having at least a support and a photosensitive layer, and the relative dielectric constant (A) of the photosensitive layer before exposure and exposure. The relative permittivity (B) of the subsequent photosensitive layer is
A flexographic printing plate, wherein (A) / (B)> 1. 4. A water-developable photosensitive original plate for flexographic printing, comprising at least a support and a photosensitive layer, which is used for the flexographic printing plate according to claim 1.