JP2998513B2 - Photosensitive resin composition and photosensitive flexographic printing plate containing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a water-developable photosensitive resin composition and a photosensitive flexographic printing plate containing the same. More particularly, the present invention relates to a photosensitive resin composition having excellent transparency and a photosensitive flexographic printing plate containing the same and having a high resolution and a good relief image.

[0002]

2. Description of the Related Art Flexographic printing includes cardboard, wrapping paper,
It is used for printing flexible packaging packages such as packaging films. Since the surface of the printing medium is not always smooth, a printing plate having low hardness and high resilience capable of following the surface of the printing medium is used to perform uniform ink transfer. Conventionally, rubber plates have been used as such flexographic printing plates. There are hand-carved and molded rubber versions. The hand-engraved rubber plate is literally a sculpture plate with a chisel, and has the drawback that it requires a high degree of skill in plate making and is not suitable for general use. Also, for the molded rubber plate, first create a metal original plate, then create a master mold that molds it, then melt the unvulcanized rubber, pour it into the master mold, cure it and create a printing plate, Finally, there is a disadvantage that the plate making process is complicated and the plate making time is long, such as adjusting the plate thickness by polishing.

In recent years, photosensitive resin plates have been used instead of rubber plates having the above-mentioned disadvantages. The plate making process of the photosensitive resin plate is simple, exposing, developing, drying and post-exposure, and does not require a high level of skill, and the plate making time is short.
However, the developing solution for the photosensitive resin plate is generally halogenated solvents such as trichloroethylene and tetrachloroethylene, and these halogenated solvents have a bad effect on the human body and the global environment. Since 1996, it can no longer be used. Under such circumstances, a photosensitive resin plate developable with water has been desired.

Accordingly, the present inventors have conducted research and found that a cationic reactive microgel having a polymerizable unsaturated double bond introduced quantitatively into the particle surface (disclosed in JP-A-2-263805). It has been found that the photosensitive flexographic printing plate contained can be developed only with water and has water resistance compatible with water-based inks. However, there are drawbacks that the resolution of the plate is insufficient, and even if the resolution is excellent, the latitude is narrow and a sufficient relief height cannot be obtained. Latitude refers to the permissible range of the appropriate table exposure that can simultaneously express the highlight and shadow areas, and the relief height is the vertical distance from the bottom of the image to the surface of the image area, and the height of the relief from the bottom of the image to the surface of the non-image area. This is the distance obtained by subtracting the vertical distance, and usually 1 mm or more is desired.

[0005] If the relief height is low, the ink is transferred to the non-image area, and a good printed matter cannot be obtained. Usually, the relief height is controlled by exposure conditions. That is, although the exposure is performed from both the front and back sides, the relief exposure height can be increased by reducing the back exposure amount and increasing the front exposure amount accordingly. However, at this time, if the table exposure exceeds the allowable range of the appropriate table exposure, the concave points constituting the shadow portion cannot be expressed, and the resolution is reduced. Therefore, in order to increase the relief height while keeping the resolution high, the latitude must be widened.

[0006]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies to develop a photosensitive resin composition having water developability, water resistance, low hardness and high rebound resilience. It has been found that both water developability and water resistance can be achieved by using a reactive microgel in which the components are unevenly distributed on the surface of the fine particles, fixed by covalent bonds, and further provided with reactivity. Furthermore, the respective refractive indices of a compound having an α, β-polymerizable unsaturated double bond compounded mainly for the purpose of increasing the strength and a rubber or thermoplastic elastomer compounded mainly for the purpose of reducing the hardness and increasing the rebound resilience. Has been found to be suitable for the purpose of the photosensitive resin composition having a specific range, and the present invention has been completed. The present inventors have also found that a photosensitive flexographic printing plate containing the photosensitive resin composition has a wide latitude.

[0007]

That is, according to the present invention, the difference between the refractive index of the reactive microgel (1) and that of the above-mentioned (1) in the measurement at 25 ° C. and the sodium D line is within ± 0.04. A compound (2) having a certain α, β-polymerizable unsaturated double bond and a rubber or a heat exchanger having a refractive index difference within ± 0.04 from that of the above (1) in the measurement of sodium D line at 25 ° C. Provided is a photosensitive resin composition containing a plastic elastomer (3) and a photosensitive flexographic printing plate containing the same.

Hereinafter, the present invention will be described in detail. The main cause of narrowing the latitude is light scattering in the photosensitive resin composition, and curing by the scattered light causes filling of fine concave points and thickening of convex points. The cause of light scattering is that the photosensitive resin composition is optically non-uniform,
That is, the reason is that the refractive index is non-uniform inside the photosensitive resin composition. Therefore, in order to prevent the scattering of light, it is necessary to use a component having excellent compatibility to disperse each component well to about 1/10 or less of the wavelength of the light source to form a pseudo-uniform structure, or to use a refractive index. Must be used. Since the photosensitive resin composition of the present invention contains a reactive microgel, it has an essentially non-uniform structure, and the latter method must be used to prevent light scattering. In this case, the refractive index of each component does not need to be completely the same, and a practically sufficient latitude can be obtained if the difference in the refractive index is within ± 0.04 in the measurement at 25 ° C. and the sodium D line. it can.

The reactive microgel (1) mainly has a function of developing water developability without impairing water resistance, and is obtained, for example, as follows. That is, a compound (a) having an α, β-polymerizable unsaturated double bond is prepared by using a reactive emulsifier (b) containing an α, β-polymerizable unsaturated double bond and a tertiary ammonium salt. The microgel (A) obtained by emulsion polymerization or suspension polymerization is reacted with a compound (B) having an epoxy group and an α, β-polymerizable unsaturated double bond that reacts with a tertiary ammonium salt. .

Among the compounds (a) having an α, β-polymerizable unsaturated double bond, low molecular weight monomers include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and hexyl (meth) acrylate. acrylates, C ₁ -C ₂₀ alkyl esters of (meth) acrylic acid and lauryl (meth) acrylate and allyl acrylate (meth) C ₂ -C ₈ alkenyl esters of acrylic acid: and allyl oxyethyl acrylate (meth) C ₃ -C ₁₉ alkenyloxyalkyl esters of acrylic acid: Styrene-based monomers such as styrene, α-methylstyrene, o-chlorostyrene, vinyltoluene, divinylbenzene, etc .: Hydroxyacrylates: Nitrile-containing monomers such as acrylonitrile and butyronitrile : Vinyl acetate, vinyl carbazo Le, trimethylolpropane tri (meth) acrylate, glycol di (meth) acrylate, alkyl di (meth) acrylate, butadiene, and the like.

The oligomers and polymers include acryloyl-modified polybutadiene: hydroxyl-containing reactive oligomers such as polybutadiene polyol, polyolefin polyol, polyether polyol, acrylic polyol, and polyester polyol, such as toluene diisocyanate and isophorone diisocyanate. Compounds obtained by extending the chain with a diisocyanate compound and reacting a terminal isocyanate group with an α, β-polymerizable compound having a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, polycondensation of a diol and a dicarboxylic acid ,
Alternatively, the carboxylic acid terminal of the polyester obtained by ring-opening polycondensation of caprolactone is 2-hydroxy (meth)
Examples include compounds reacted with a compound having a hydroxyl group and a (meth) acryloyl group such as acrylate and pentaerythritol tri (meth) acrylate.

These compounds are appropriately selected according to the desired physical properties, and can be used alone or in combination of two or more. In particular, regarding the refractive index, if a high refractive index is desired, for example, a monomer containing a halogen group or a benzene ring such as styrene, o-chlorostyrene and vinylcarbazole can be used in combination, and conversely, a low refractive index can be used. If a refractive index is desired, acrylonitrile, ethyl (meth) acrylate, butyl (meth) acrylate, or the like can be used in combination.

The refractive index of the reactive microgel depends on its constituents, ie, the compound (a) having an α, β-polymerizable unsaturated double bond, the α, β-polymerizable unsaturated double bond, Reactive emulsifier containing tertiary ammonium salt (b)
The compound (B) having an epoxy group and an α, β-polymerizable unsaturated double bond is multiplied by the volume fraction of each component, and the sum of the values is the sum of the refractive index increment due to polymerization. . The increase in refractive index due to polymerization is generally 2-7%.

Α, β-polymerizable unsaturated double bond and tertiary
Examples of the reactive emulsifier (b) containing a tertiary ammonium salt include monomers having a tertiary ammonium group such as N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate. Glycidyl is added to a part of the tertiary ammonium salt obtained by copolymerizing the monomer and the compound having an α, β-polymerizable unsaturated double bond exemplified in (a) and neutralizing with an acid. An emulsifier obtained by reacting a compound having an epoxy group and an α, β-polymerizable unsaturated double bond such as (meth) acrylate can be used. Also, (a)
The refractive index can be adjusted using a method similar to that described above.

Immobilizing the emulsifier on the microgel surface using a reactive emulsifier has the following meaning. That is, to increase the thermodynamic stability of the reactive microgel in water, to prevent fusion between the particles in the drying of the reactive microgel described below, and more importantly, the photosensitivity of the present invention. The advantage is that in the preservation of the flexographic printing plate precursor, the emulsifier is prevented from dissipating from the surface of the microgel due to macro Brownian motion, whereby water developability can be maintained without deterioration over time.

The reactive emulsifier (b) is used in an amount of 0.1 to 300% by weight based on the compound (a) having an α, β-polymerizable unsaturated double bond, and preferably 3 to 50% by weight from the viewpoint of water resistance. Can be For the purpose of assisting emulsification, a cationic or nonionic surfactant may be used in combination with the reactive emulsifier (b) as long as physical properties such as water resistance are not impaired.

The polymerization is carried out in an aqueous medium. At this time, a lower alcohol or an acid may be added for the purpose of controlling the surface tension or pH of the medium. Combining a compound (a) having an α, β-polymerizable unsaturated double bond with a reactive emulsifier (b) containing an α, β-polymerizable unsaturated double bond and a tertiary ammonium salt and a surfactant The solid content is preferably 10 to 50% by weight, and preferably 15 to 35% by weight from the viewpoint of productivity and stability of polymerization. The polymerization temperature varies depending on the initiator used, but is usually 40 to 95 ° C., preferably 50 to 95 ° C. because the polymerization is carried out in an aqueous medium.
85 ° C. The polymerization time also depends on the initiator used and the polymerization temperature, and is preferably within 8 hours in consideration of productivity, but is not limited thereto.

As the initiator, a water-soluble initiator is used for emulsion polymerization, and an oil-soluble initiator is used for suspension polymerization. Both may be used in combination. Whether emulsion polymerization or suspension polymerization is performed is mainly related to the particle size of the microgel to be obtained.If the polymerization is of the same composition, emulsion polymerization is smaller than suspension polymerization. Can be The particle size also depends on the stirring speed and stirring efficiency during polymerization, the type of emulsifier, and the amount of emulsifier. The particle size of the microgel obtained by the above method is usually 0.02 to 30 μm as measured by a light diffraction method or a photon correlation method.

Particle size affects developability, water resistance and resolution. The relationship between the particle size and the total surface area when the total volume is constant is shown.If the particle size is increased by a factor of 1 / x, the total surface area becomes x times. Particle size 1
When / x is set, the coating density of (b) with respect to (a) on the particle surface is 1 / x. If the coating density is too low, water developability will not be exhibited. Further, when the ratio of the amount of (b) to the amount of (a) is increased for the purpose of increasing the coating density, the water resistance deteriorates accordingly. Therefore, in order to achieve both water developability and water resistance, it is preferable to increase the coating density with a small amount of (b), and for that purpose, a larger particle size is advantageous. However, if the particle size is too large, the resolution of the plate is impaired. In consideration of the above, the particle size is preferably 0.1 to 10 μm.

The tertiary ammonium salt present on the surface of the microgel (A) thus obtained is reacted with a compound (B) having an epoxy group and an α, β-polymerizable unsaturated double bond, and An α, β-polymerizable unsaturated double bond is introduced into the surface of (A). As the compound (B), for example, glycidyl (meth) acrylate, N-glycidyl (meth) acrylamide, glycidyl allyl ether, 1,2-
Epoxy compounds having a polymerizable unsaturated double bond such as epoxy-5-hexene are exemplified. These compounds (B)
Is appropriately selected according to desired physical properties, and can be used alone or in combination of two or more.

The compound (B) can be introduced at a free ratio of 1 to 100 mol% with respect to the tertiary ammonium base on the surface of the microgel particles. With this introduction, the water resistance is further improved and the strength is also enhanced. However, since excessive introduction increases the hardness, the introduction amount should be determined in consideration of the balance of the entire photosensitive resin composition. The reaction is completed by mixing the compound (B) with the microgel (A) emulsion at a temperature of 40 to 95 ° C, preferably 65 to 85 ° C for about 2 to 6 hours.

The reactive microgel thus obtained (1)
Can be dried by a conventional method. For example, filtration, hot air drying, spray drying, freeze drying, drying by vacuum drying, etc., reactive microgel (1)
Can be isolated.

A compound having an α, β-polymerizable unsaturated double bond (2) having a refractive index difference of ± 0.04 or less from the reactive microgel (1) at 25 ° C. at the sodium D line. )
Is mainly responsible for enhancing the strength, (1) constituting the compound having an α, β-polymerizable unsaturated double bond (a) of the same compounds as those exemplified in (1), Are selected alone or in combination of two or more. At this time, (2)
It need not be exactly the same as (a). However, (2), even after curing, (1)
It is desirable that the difference between the refractive index and the refractive index is within ± 0.04.
If the difference between the refractive indices of (1) and (2) exceeds ± 0.04, the latitude becomes narrow due to light scattering, so that it is impossible to achieve both high resolution and high relief height.

Rubber or thermoplastic elastomer (3) having a difference in refractive index from the reactive microgel (1) within ± 0.04 in the measurement at 25 ° C. and the sodium D line mainly has a reduced hardness and rebound. Has a function of improving elasticity, for example, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, nitrile rubber, butyl rubber, chloroprene rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, acrylic rubber, urethane rubber, Among ethylene-vinyl acetate rubbers and the like, those having a difference in refractive index from (1) within ± 0.04 are selected and used alone or in combination of two or more.
If the difference between the refractive indices of (1) and (3) exceeds ± 0.04, the latitude becomes narrow due to light scattering, so that it is impossible to achieve both high resolution and high relief height.

It is preferable that (2) and (3) are compatible with each other, and that the difference between the refractive indices of (2) and (3) is also within ± 0.04.

The reactive microgel (1), the compound (2) having an α, β-polymerizable unsaturated double bond whose difference in refractive index from the above (1) is within ± 0.04, and the above (1) Rubber or thermoplastic elastomer whose difference in refractive index is within ± 0.04
The mixing ratio of (3) is such that (1) is 20 to 90% by weight, (2) is 1 to 50% by weight, and (3) is based on the total solid content of the photosensitive resin composition.
5 to 78% by weight. If (1) is less than 20% by weight, water developability is not exhibited, and if it exceeds 90% by weight, water resistance is poor. If (2) is less than 1% by weight, the strength is low, and if it exceeds 50% by weight, the hardness becomes too high. If (3) is less than 5% by weight, there is no effect on lowering the hardness, and if it exceeds 78% by weight, the amount of the hardening component is small and the strength is weak.

Curing of the photosensitive resin composition of the present invention is started by irradiating radiation, but in the case of ultraviolet irradiation, a photopolymerization initiator is required. 2 for UV
A light source having a wavelength range of 00 to 400 nm is effective, and examples of the light source used include a low-pressure mercury lamp, a high-pressure mercury lamp, a chemical lamp, a germicidal lamp, and a deuterium lamp.

Examples of the photopolymerization initiator include benzoin, α-methylbenzoin, α-benzylbenzoin,
α-methylol benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzophenone, chlorobenzophenone, acetophenone, acetoin, benzyl, benzyl dimethyl ketal, benzyl diethyl ketal, benzyl isopropyl ketal,
Anthraquinone, 2-chloroanthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-amylanthraquinone, 2-nitroanthraquinone, anthraquinone-1-aldehyde, benzoyl peroxide, lauryl peroxide, diphenyl disulfide, dibenzoyl disulfide, diacetyl disulfide , 2-methylcaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptobenzimidazole, thioxanthone, 2-chlorothioxanthone, azobisisobutyronitrile and the like. These may be used alone or in combination of two or more.

The compounding amount of the photopolymerization initiator is 0.1 to 10% by weight based on the total solid content of the photosensitive resin composition. 0.1% by weight
If it is less than 11% by weight, the photocuring is slow, and if it exceeds 11% by weight, the effect of increasing the amount of light is not recognized due to its own light-shielding effect, and the photocuring in the deep part is delayed.

The photosensitive resin composition of the present invention may further comprise a polymerization inhibitor, an antioxidant, an antiozonant, a sensitizer, a compatibilizer, a plasticizer, a colorant, a stabilizer, Additives such as a lubricant, an antifoaming agent, a conductive material, a magnetic substance, a flame retardant, a preservative, and a desiccant can be contained in a range that does not impair the original performance.

There is no particular limitation on the processing and molding method for obtaining a raw plate of a photosensitive flexographic printing plate from the above ingredients, but usually, the ingredients are two rolls, a kneader,
The mixture is kneaded using a plast mill, extruder or the like, and the kneaded material is formed into a sheet having a thickness of about 1 to 8 mm by pressure molding or extrusion molding, and an adhesive layer and a transparent film such as a polyethylene terephthalate film are formed on each side of the sheet. A base film composed of a support, a water-soluble release layer such as polyvinyl alcohol, and a cover film composed of a transparent support such as a polyethylene terephthalate film are pressed to obtain a raw plate.

Next, the back surface of the raw plate is irradiated with ultraviolet rays to perform back exposure, the cover film is peeled off, a negative film is adhered, and the ultraviolet rays are irradiated to cure the image area. Then, the non-image portion not exposed is washed away with water, dried, and the dried product is post-exposed to obtain a printing plate.

[0033]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" and "%" mean "parts by weight" and "% by weight", respectively. The particle size of the reactive microgel was measured using an optical diffraction particle size distribution meter (“SALD-1100” manufactured by Shimadzu Corporation). The refractive index was measured using an Abbe refractometer (“Abe refractometer 2T” manufactured by Atago) at 25 ° C. with a sodium D line.

(Synthesis Example of Reactive Emulsifier) A separable flask was charged with 360 parts of lauryl methacrylate, 150 parts of N, N-dimethylaminoethyl methacrylate, and 320 parts of butanol, and stirred with an anchor-type stirring blade at 200 rpm. After heating to 80 ° C. in a nitrogen atmosphere, 4 parts of 2,2′-azobis (isobutyronitrile) (hereinafter abbreviated as AIBN) was added to initiate polymerization. 4 hours after the start of polymerization, 1 part of AIBN was further added and the mixture was kept for 2 hours. Then, air was bubbled back to the atmosphere, 60 parts of acetic acid and 14 parts of glycidyl methacrylate were added, and the mixture was kept for 2 hours. Was completed. According to GPC measurement, the number average molecular weight of the obtained reactive emulsifier was about 200
00. (Synthesis example of non-reactive emulsifier) The same as the synthesis example of the reactive emulsifier, except that glycidyl methacrylate was not added.

(Synthesis example 1 of reactive microgel) 192 parts of 2-ethylhexyl acrylate, 48 parts of 1,6-hexanediol diacrylate, 40 of a reactive emulsifier (solid content 59%)
Parts, 24 parts of polyoxyethylene nonylphenyl ether (Emulgen 950, manufactured by Kao Corporation), 1.2 parts of AIBN, and 496 parts of ion-exchanged water are placed in a separable flask, and stirred with an anchor-type stirring blade at a speed of 300 revolutions per minute. The temperature was raised to 80 ° C. in an atmosphere to initiate polymerization. Two hours after the start of the polymerization, 2,2′-azobis (2-amidinopropane) dihydrochloride
AAPD (abbreviated as AAPD) was added, and the mixture was kept for 3 hours. After bubbling air, the mixture was returned to an air atmosphere, 2.4 parts of glycidyl methacrylate was added, and the mixture was kept for 2 hours to complete the polymerization. The particle size of the resulting reactive microgel is about 2 μm. The obtained water dispersion was dried in an oven at 60 ° C. to a moisture content of 0.1% or less to obtain a dried product. The dried product was pressed under the conditions of 50 ° C. and 150 kg / cm ² for 15 minutes to form a 1.5 mm-thick sheet. The refractive index of the sheet was 1.475.

(Synthesis example 2 of reactive microgel) 168 parts of 2-ethylhexyl acrylate, 48 parts of 1,6-hexanediol diacrylate, 24 parts of styrene, 40 parts of a reactive emulsifier (solid content 59%), "Emulgen 950 24 copies, AIBN 1.2
And 496 parts of ion-exchanged water were placed in a separable flask, stirred at 300 rpm / min with an anchor-type stirring blade, and heated to 80 ° C. in a nitrogen atmosphere to initiate polymerization. Two hours after the start of the polymerization, 12 parts of a 10% AAPD aqueous solution was added, and the mixture was maintained for 3 hours.
Air was bubbled back into the air atmosphere, 2.4 parts of glycidyl methacrylate was added, and the mixture was kept for 2 hours to complete the polymerization. The particle size of the obtained reactive microgel is about 1
μm. When the refractive index was measured in the same manner as in Synthesis Example 1, it was 1.491.

(Synthesis Example 3 of Reactive Microgel) Both ends acrylic-modified polybutadiene (“R45A” manufactured by Idemitsu Petrochemical Co., Ltd.)
CR-LC ”, number average molecular weight 3000-4000) 100 parts, reactive emulsifier (solid content 59%) 17 parts,“ Emulgen 950 ”10 parts, acetic acid 2 parts, ion exchange water 200 parts are charged into a separable flask, The mixture was stirred with an anchor-type stirring blade at a speed of 300 rpm, heated to 80 ° C. in a nitrogen atmosphere, and then 8 parts of a 10% AAPD aqueous solution was added to initiate polymerization. Two hours after the start of the polymerization, 2 parts of a 10% AAPD aqueous solution was further added, and the mixture was maintained for 3 hours. Then, air was bubbled back to an air atmosphere, and glycidyl methacrylate was added.
Was added and the mixture was held for 2 hours to complete the polymerization. The particle size of the resulting reactive microgel is about 4 μm. When the refractive index was measured in the same manner as in Synthesis Example 1, it was 1.538.

(Synthesis Example 1 of Non-Reactive Microgel) The same as Synthesis Example 1 of the reactive microgel except that a non-reactive emulsifier is used in place of the reactive emulsifier and glycidyl methacrylate is not added. (Synthesis example 2 of non-reactive microgel) It is the same as the synthesis example 3 of the reactive microgel except that a non-reactive emulsifier is used instead of the reactive emulsifier and glycidyl methacrylate is not added.

Example 1 50 parts of the dried product of Synthesis Example 1 of a reactive microgel, 20 parts of a urethane acrylate elastomer ("UV49", refractive index 1.491, manufactured by Sanyo Chemical Industries, Ltd.), and acrylic rubber (manufactured by Zeon Corporation) AR51 ", refractive index 1.471)
30 parts and 0.1 part of benzyldimethyl ketal were kneaded with two rolls. (Example 2) The same as Example 1 except that a urethane acrylate elastomer ("UT1829" manufactured by Nippon Synthetic Chemical Industry Co., Ltd., refractive index 1.484) was used instead of "UV49".

Example 3 50 parts of the dried product of Synthesis Example 2 of reactive microgel, 10 parts of 1,6-hexanediol diacrylate (refractive index: 1.478), hydrogenated styrene-isoprene-styrene rubber (Mitsubishi Yuka "Lavalon SE6301C", refractive index 1.492) 40 parts, benzyl dimethyl ketal 0.1 part 2
It was kneaded with this roll. (Example 4) Dried product 50 of Synthesis Example 3 of reactive microgel
Parts, 20 parts of urethane acrylate elastomer (Hayakawa Rubber "LN56", refractive index 1.526), 20 parts of isoprene rubber (Nippon Synthetic Rubber "IR2200", refractive index 1.520) 30 parts, and benzyl dimethyl ketal 0.1 part in two rolls And kneaded.

(Example 5) 50 parts of the dried product of Synthesis Example 3 of reactive microgel, 20 parts of urethane acrylate elastomer ("LN22", refractive index 1.533, manufactured by Hayakawa Rubber Co., Ltd.), and butadiene rubber (manufactured by Nippon Synthetic Rubber Co., Ltd.) BR02L '', refractive index 1.52
2) 30 parts and 0.1 part of benzyldimethyl ketal were kneaded with two rolls. (Example 6) Dried product 50 of Synthesis Example 1 of reactive microgel
Parts, "UV49" 20 parts, "AR51" 30 parts, benzyldimethyl ketal 0.1 part, thermal polymerization inhibitor ot-butylphenol 0.01
Part was kneaded with two rolls. (Example 7) Dried product 50 of Synthesis Example 3 of reactive microgel
Parts, `` LN22 '' 20 parts, `` BR02L '' 30 parts, benzyldimethyl ketal 0.1 part, thermal polymerization inhibitor ot-butylphenol 0.
01 parts were kneaded with two rolls.

(Comparative Example 1) Instead of "AR51", "BR02L
Is the same as in Example 1 except that "" is used. (Comparative Example 2) The same as Example 1 except that "LN22" was used instead of "UV49". (Comparative Example 3) Dried product 50 of Synthesis Example 1 of reactive microgel
Parts, 20 parts of "LN22", 30 parts of "BR02L", and 0.1 part of benzyldimethyl ketal were kneaded with two rolls.

(Comparative Example 4) Instead of "IR2200", use "AR5
Example 4 is the same as Example 4 except that “1” was used. (Comparative Example 5) The same as Example 4 except that "UV49" was used instead of "LN56". (Comparative Example 6) Dried product 50 of Synthesis Example 3 of reactive microgel
Parts, 20 parts of "UV49", 30 parts of "AR51" and 0.1 part of benzyldimethyl ketal were kneaded with two rolls.

Comparative Example 7 Synthesis Example 1 of Non-Reactive Microgel Instead of the Dried Product of Synthesis Example 1 of Reactive Microgel
Example 6 is the same as Example 6 except that the dried product is used. (Comparative Example 8) The same as Example 7 except that the dried product of Synthesis Example 2 of the non-reactive microgel was used instead of the dried product of Synthesis Example 3 of the reactive microgel.

(Sheet formation) Examples 1 to 7 and Comparative Example 1
The kneaded material obtained in Steps (1) to (8) was sandwiched between a 100 μm-thick polyethylene terephthalate film coated with polyvinyl alcohol of about 1 μm on one side and a 100 μm-thick polyethylene terephthalate film coated with nothing.
Pressure molding was performed at 100 ° C. and 100 kgf / cm ² for 15 minutes to obtain a raw plate having a thickness of 2 mm.

(Evaluation of Physical Properties) Examples 1 to 5, Comparative Examples 1 to 6
The raw plate was evaluated for developability and latitude. However, the developability was evaluated by the development speed, and the latitude was evaluated by the depth of the fine concave after image formation. In addition, the raw plate is exposed to the whole surface to obtain a cured product, which has water resistance, hardness, strength,
The rebound resilience was evaluated. However, the water resistance was evaluated by the water swelling rate. Table 1 shows the results. Each measurement condition is as follows.

Development speed (μm / min): Development was performed with tap water at 25 ° C. using a developing machine (“Tsuki M Relief Pet A4” manufactured by Shueido Printing Equipment Co., Ltd.). Depth of concave point (μm): Back exposure is performed so that the relief height is 1 mm, 3%, 48 lines / cm minimum highlight exposure is performed. After development, the concave point of 200 μm diameter The depth was measured with an optical microscope. However, the exposure light source is 360
A chemical lamp having a peak at nm ("FL20SBL-360" manufactured by Mitsubishi Electric OSRAM) was used.

The water swelling ratio, hardness, strength, and rebound resilience were measured using the above-mentioned chemical lamp on the front and back surfaces of the raw plate.
Exposure at mJ was performed and used as a sample. Water swelling ratio (%): A sample having a size of 10 × 40 × 2 (mm) was immersed in ion-exchanged water at 25 ° C. for 24 hours and determined by the following equation. ((Weight after immersion in water for 24 hours) / (weight before immersion) -1)
× 100 Hardness (JIS-A): According to JIS-K6301. Breaking strength (kgf / cm ² ): Measured at a sample size of 10 × 40 × 2 (mm) and a tensile speed of 50 mm / min. Rebound resilience (%): According to JIS-K6301.

[0049]

[Table 1]

With respect to the raw plates of Examples 6 to 7 and Comparative Examples 7 to 8, the development speed, the water swelling ratio, and the development speed after storage at 40 ° C. for one month were measured. Table 2 shows the results.

[Table 2]

[0051]

The photosensitive resin composition of the present invention has stable water developability and water resistance over time by containing a reactive microgel, and realizes low hardness and high rebound resilience. are doing. Further, since the difference in the refractive index between the reactive microgel and other components is small, the photosensitive flexographic printing plate containing the same has a wide latitude and can achieve both high resolution and high relief height.

Continuation of front page (56) References JP-A-5-178946 (JP, A) JP-A-5-204139 (JP, A) JP-A-3-75750 (JP, A) JP-A-5-45874 (JP) JP-A-6-194833 (JP, A) JP-A-6-51511 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03F 7/027 G03F 7/032

Claims (3)

(57) [Claims] The difference between the refractive index of the reactive microgel (1) and that of the reactive microgel (1) is ± 0.
Compound (2) having an α, β-polymerizable unsaturated double bond of not more than 04, and the difference in refractive index from that of (1) in the measurement with sodium D line at 25 ° C. is within ± 0.04. A photosensitive resin composition comprising a rubber or a thermoplastic elastomer (3). 2. A reactive microgel (1) comprising a compound (a) having an α, β-polymerizable unsaturated double bond and an α, β-polymerizable unsaturated double bond and a tertiary ammonium salt. A microgel (A) obtained by emulsion polymerization or suspension polymerization using a reactive emulsifier (b) containing a compound (B) having an epoxy group and an α, β-polymerizable unsaturated double bond. The photosensitive resin composition according to claim 1, wherein 3. A photosensitive flexographic printing plate comprising the photosensitive resin composition according to claim 1 or 2.