JPS5921541B2 - Photosensitive resin composition for printing plates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photosensitive resin composition for printing plates.

An object of the present invention is to provide a resin composition for flexo stamp B1 which is required to have low hardness and high strength. As is well known, rubber plates have traditionally been used in flexographic printing, which is used to print packaging materials such as film, cardboard, and kraft paper, but recently there has been a demand for simplification and labor-saving of the plate-making process. Along with this, there is a rapidly increasing momentum to use photosensitive resins in place of rubber plates.

For example, it has been proposed to apply a urethane-modified acrylate resin obtained by introducing polyether or polyester between double bonds to a photosensitive resin composition for flexographic printing plates (JP-A-49-109105, Kosho 50-3
4964 etc.). However, although the printing plates obtained by these methods satisfy the hardness (Shore A40 to 80) normally required for flexographic printing, they are insufficient in strength, resulting in the printing plates tearing or lacking relief. It has the following drawbacks, and has the problem that it is either impractical or suitable only for limited printing purposes.

In view of these points, the present inventors have conducted extensive research to obtain a low hardness and high strength resin for printing plates, especially a photosensitive resin suitable for flexographic printing plates, and as a result, they have developed a urethane-modified acrylate resin. In urethane modified acrylate,
Two active hydrogen groups in the molecule that can react with isocyanate groups
Polyalkylene glycol A as a compound having more than
It has been found that by using aromatic oligoester B, a photosensitive resin composition for printing plates with extremely excellent performance that can be developed with an aqueous solvent can be obtained.

In addition, the present inventors have also discovered that by using polytetramethylene glycol as a part of polyalkylene glycol A, a photosensitive resin composition for printing plates with extremely excellent physical properties can be obtained, and the present invention has been achieved. That is, the present invention provides a photosensitive resin composition comprising urethane-modified acrylate I, a copolymerizable monomer, and a photosensitizer, in which urethane-modified acrylate 1 is composed of polyalkylene glycol A having a molecular weight of 400 to 5000 and a molecular weight of 200 to 20.
Consisting of an aromatic oligoester B having an acid value of 20 or less and a molecular weight of 200 to 2000, having an acid component consisting of an aromatic polybasic acid of 0.00 and an alcohol component consisting of a polyhydric alcohol, with a molar ratio of A/B of 4/1. A compound having two or more active hydrogen groups in the molecule that can react with an isocyanate group and having an A/B weight ratio of 1.0 or more, an organic diisocyanate, and an alcoholic hydroxyl group-containing acrylate. A compound obtained by reacting a compound and/or an alcoholic hydroxyl group-containing methacrylate compound, which has an acryloyloxy group and/or a methacryloyloxy group at the end of the molecule, and an ether bond, an ester bond, and a urethane bond in the molecule. This is a photosensitive resin composition for printing plates characterized by the following.

Further, in the present invention, polyalkylene glycol A has a molecular weight of 50.
0-3000 polytetramethylene glycol 20-8
This is a photosensitive resin composition for a printing plate characterized by comprising 0 mol% and 80 to 20 mol% of another polyalkylene glycol having a molecular weight of 400 to 5,000. The urethane-modified acrylate resin of the present invention uses polyalkylene glycol A and aromatic oligoester B as compounds having two or more active hydrogen groups capable of reacting with isocyanate groups. It not only provides strength and elongation that cannot be obtained by using polyalkylene glycol alone or in combination, but also has excellent properties such as washout properties and ink resistance, which are essential for photosensitive resin compositions for printing plates.

Further, by using a portion of polytetramethylene glycol, a composition can be obtained which has much better strength, especially tear strength, than can be obtained by using other alkylene glycols such as polypropylene glycol or polyethylene glycol alone. The urethane-modified acrylate resin in the present invention refers to a copolymerizable acrylate resin having at least two acryloyloxy groups and/or methacryloyloxy groups at the end of the molecule and at least four urethane bonds within the molecule. It is a curable resin that is blended with polymer.

The above-mentioned urethane-modified acrylate is obtained by reacting a compound having two or more active hydrogen groups in the molecule that can react with an isocyanate group with an organic diisocyanate and an acrylate compound containing an alcoholic hydroxyl group. Urethane-modified acrylate I used in the present invention uses polyalkylene glycol A and aromatic oligoester B as compounds having two or more active hydrogen groups in the molecule that can react with isocyanate groups.

Polyalkyne V used in the present invention. Glycol A includes polyethylene glycol with a molecular weight of 400 to 5,000, polypropylene glycol with a molecular weight of 400 to 5,000, polytetramethylene glycol with a molecular weight of 500 to 3,000, ethylene glycol-propylene glycol protein copolymer with a molecular weight of 500 to 5,000, and polypropylene glycol with a molecular weight of 500 to 5,000.
Ethylene glycol-tetramethylene glycol copolymer with a molecular weight of 400 to 3,000, a propylene oxide or/and ethylene oxide adduct of glycerin with a molecular weight of 400 to 3,000, a propylene oxide or/and ethylene oxide adduct of pentaerythritol with a molecular weight of 400 to 3,000, a molecular weight of 400 to 3,000 Propylene oxide or/and ethylene oxide adduct of trimethylolpropane, bismae with a molecular weight of 400 to 2000. Examples include propylene oxide and/or ethylene oxide adducts of Nord A, and propylene oxide and/or ethylene oxide adducts of hydrogenated bisphenol A having a molecular weight of 400 to 2,000.

In addition, if necessary, ethylene glycol, propylene glycol, 1,3-pronoquinediol, diethylene glycol, dipropylene glycol, neopentyl glycol, dichloroneobentyl glycol, dibromoneopentyl glycol, 1,4-butanediol, 1,
4-butenediol, 2,2,4-trimethyl-1,3
-pentanediol, 1,6-hexanediol, 1,
It is also possible to use one part of a low molecular weight polyhydric alcohol such as 4-cyclohexanedimethanol, 1,4-cyclohexanediol, glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol.
In particular, it is preferable to partially use polytetramethylene glycol with a molecular weight of 500 to 3000 and other polyalkylene glycol, and the proportion of polytetramethylene glycol with a molecular weight of 500 to 3000 in polyalkylene glycol A is 20 to 80 mol%. The proportion of other polyalkylene glycols is preferably 80 to 20 mol%. The aromatic oligoester B used in the present invention has an acid value of 20 or less and a molecular weight of 20, which has an acid component consisting of an aromatic polybasic acid and an alcohol component consisting of a polyhydric alcohol.
It is an oligoester of 0 to 2000.

Examples of aromatic polybasic acids include orthophthalic acid, isophthalic acid, terephthalic acid, phthalic anhydride, and naphthalene dicarboxylic acid, with terephthalic acid and its derivatives being particularly preferred. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, diethylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, dipropylene glycol, neopentyl glycol, and 1,4-butene. diol,
1,6-hexanediol, 2,2,4-trimethyl-
1,3-pentanediol, dichloroneopentyl glycol, dibromoneopentyl glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, glycerin, trimethylolpropane , pentaerythritol, etc. Aromatic oligoester B can be produced by, for example, direct esterification of an aromatic polybasic acid and a polyhydric alcohol, or by transesterification of an aromatic polybasic acid derivative, such as an aromatic polybasic acid ester and a polyhydric alcohol. There are methods such as depolymerizing a high molecular weight aromatic polyester, such as polyethylene terephthalate or polybutylene terephthalate, with a polyhydric alcohol, and known catalysts can be used as necessary during production.

The aromatic oligoester B used in the present invention needs to have an acid value of 20 or less and a molecular weight of 200 to 2,000.

When the acid value exceeds 20, the solubility deteriorates, the transparency of the urethane-modified acrylate resin is lost, and the molecular weight exceeds 20.
If it exceeds 00, the viscosity of the urethane-modified acrylate resin becomes extremely high, causing problems such as difficulty in handling. Examples of the organic diisocyanate compounds used in the present invention include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, metaphenylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, bis(isocyanatemethyl)cyclohexane, and isoboron. There are diisocyanates, and these organic diisocyanate compounds are used alone or in combination.

In order to obtain urethane-modified acrylate I used in the present invention, first, polyalkylene glycol A and aromatic oligoester B are reacted with an organic diisocyanate compound to obtain a urethane prepolymer containing terminal isocyanate groups, and then this terminal isocyanate group-containing urethane prepolymer is obtained. A urethane-modified acrylate is obtained by reacting a urethane prepolymer with an alcoholic hydroxyl group-containing acrylate or methacrylate.

The method for producing the urethane prepolymer containing terminal isocyanate groups is as follows: (1) Polyalkylene glycol A, aromatic oligoester B, and an organic diisocyanate compound are mixed in a ratio of (OH group + COOH group)/NCO group <l (equivalent ratio). or (2) react polyalkylene glycol A (or aromatic oligoester B and organic diisocyanate compound (OH group + COOH group)/NCO
The aromatic oligoester B (or polyoxyalkylene glycol A) is added to the reaction product obtained by reacting with the group <1 (equivalent ratio) to the remaining isocyanate group (OH group +
There is a method in which the reaction is carried out at a ratio of COOH group)/NCO group x 1 (equivalent ratio).

Polyalkylene glycol A$? The reaction ratio between the aromatic oligoester B and the organic diisocyanate compound is (0H group+COOH group)/NCO group (equivalence ratio), preferably 0.3 to 0.8.

Further, the molar ratio of polyalkylene glycol A to aromatic oligoester B is 4/l to 1/4, preferably 3
/l to 1/2, and the weight ratio is A/B 1,
Preferably A/B<0.6. A/B is 4 in molar ratio
If it exceeds /1, the effect of the aromatic oligoester will not be expressed and only a printing plate with low strength will be obtained. Furthermore, if the A/B molar ratio is less than 1/4 and the weight ratio is less than 1.0, the viscosity of the urethane-modified acrylate resin increases, making it difficult to handle, and it is also extremely difficult to wash out unexposed areas with a water-based solvent. becomes. The above reaction is carried out without a solvent or using a solvent inert to isocyanate groups such as styrene, vinyltoluene, ethyl acrylate, methyl methacrylate, penseltoluene, methylene chloride and the like.

The reaction temperature is preferably 20 to 120°C, particularly 50 to 100°C. If necessary, a catalyst such as an organic tin compound or an organic amine can also be used. Examples of the alcoholic hydroxyl group-containing acrylate or methacrylate that can react with the terminal isocyanate group-containing urethane prepolymer include ethylene glycol mono(meth)acrylate, propylene glycol mono(meth)acrylate, and 1,3-pro'-diol mono(meth)acrylate. Acrylate, 1,3-butanediol mono(meth)acrylate, 1,4-butanediol mono(meth)acrylate, 1,6-hexanediol mono(meth)acrylate, diethylene glycol mono(meth)acrylate,
Dihydric alcohol mono(meth)acrylates such as dipropylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, trimethylolethane mono(meth)acrylate, trimethylolproban mono( Mono(meth)acrylates and di(meth)acrylates of trihydric alcohols such as meth)acrylate, trimethylolethane di(meth)acrylate, trimethylolprobane di(meth)acrylate, glycerin mono(meth)acrylate, glycerin di(meth)acrylate, etc. meth)acrylate, or pentaerythritol di(meth)acrylate, pentaerythritol tri(
Examples include di(meth)acrylates and tri(meth)acrylates of polyhydric alcohols having a valence of four or more, such as meth)acrylates.

The reaction ratio between the terminal isocyanate group-containing urethane polymer and the alcoholic hydroxyl group-containing acrylate or methacrylate is 0H group/NCO group≧1 (equivalent ratio), preferably 1.05 to 1.8.

The reaction is preferably carried out in the solvent used in the first stage reaction or without a solvent, and the reaction temperature is preferably 80°C or lower. In order to inhibit thermal polymerization in the above reaction, it is desirable to use a known thermal polymerization inhibitor such as hydroquinone, hydroquinone monomethyl ether, t-butylcatechol, p-benzoquinone, or phenothiazine. The molecular weight of the urethane-modified acrylate I obtained by the above reaction is 1,500 to 10,000, preferably 3,000 to 8
It is 000.

When the molecular weight is less than 1,500, it is difficult to obtain a rubber elastic body with high hardness, and when the molecular weight exceeds 10,000, the strength and photosensitivity decrease significantly. Examples of copolymerizable monomers include styrene, vinyltoluene, chlorostyrene, t-butylstyrene, α-methylstyrene, dipinylbenzene, acrylic acid, methacrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n -Propyl (meth)acrylate, IBO
-Propyl (meth)acrylate, n-butyl (meth)
Acrylate, IsO-butyl (meth)acrylate,
Scc-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, lauryl (meth)acrylate, n-tridecyl ( meth) acrylate, stearyl (
meth)acrylate, ethylene glycol mono(meth)
Acrylate, propylene glycol mono(meth)acrylate, diethylene glycol mono(meth)acrylate, dipropylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate with a molecular weight of 200 to 1000, polypropylene glycol mono(meth)acrylate with a molecular weight of 200 to 1000 acrylate,
Polyethylene glycol monomethyl ether mono(meth)acrylate with a molecular weight of 200 to 1000, molecular weight 20
0-1000 polypropylene glycol monomethyl ether mono(meth)acrylate, molecular weight 200-10
00 polyethylene glycol monoethyl ether mono(meth)acrylate, polypropylene glycol monoethyl ether mono(meth)acrylate with molecular weight 200-1000
Acrylate, n-butoxyethyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-phenoxypropyl (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, allyl ( meth)acrylate, benzyl(meth)acrylate, tripromophenyl(meth)acrylate, 2,
3-dichloropropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, N
, N-diethylaminoethyl (meth)acrylate, N
, N-dimethylaminoethyl (meth)acrylate, N
-t-butylaminoethyl (meth)acrylate, acrylamide, N,N-dimethylacrylamide, N,N
-Diethyl acrylamide, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,3-pro-kundiol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, meth)acrylate, 1,6-hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, glycerin di(meth)acrylate, glycerin tri(meth)acrylate, trimethylolpropane tri (meta)
Examples include acrylate, trimethylolethane tri(meth)acrylate, ethylene bisacrylamide, diallyl phthalate, triallyl cyanurate, diethyl fumarate, dibutyl fumarate, and vinyl acetate, and are selected depending on the purpose. Photosensitizers used in the present invention include: benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin-1s0-propylether, benzoin-n-butyl ether, diacetyl, benzyl, benzophenone, acetophenone, butyroin, trioin, fluorescein. , eosin, erythrosin, α-mercaptobenzothiazole, 2-mercaptobenzoxazole, diphenyl disulfide, dibenzyl disulfide, tetramethylthiuram monosulfide, tetramethylthiuram disulfide, 1-naphthalenesulfonyl Chloride, 9,10-anthraquinone,
Examples include 1,4-naphthoquinone.

The photosensitive resin composition for printing plates of the present invention is obtained by blending urethane-modified acrylate I with copolymerizable monomer I and a photosensitizer. The mixing ratio of urethane-modified acrylate I and these copolymerizable monomers is 90:5 to 20:8 by weight.
0, preferably 80:20 to 40:60.

The content of the photosensitizer is preferably 0.1 to 10% by weight, particularly 0.5 to 5% by weight, based on the total weight of urethane-modified acrylate I and copolymerizable monomer. The photosensitive resin composition for printing plates of the present invention may include soluble polyamide, soluble polyester, soluble polyurethane, methacrylic acid-methacrylic acid ester copolymer, polyvinyl acetate, polyvinyl alcohol, polybutadiene, within a range that does not impair its properties. , maleated polybutadiene, styrene-butadiene copolymer, butadiene-acrylonitrile copolymer, ethylene monovinyl acetate copolymer, cellulose acetate phthalate, and other organic polymer compounds can also be blended.

The light source used for curing the photosensitive resin composition for printing plates of the present invention must be appropriately selected depending on the type of photosensitizer, the type of resin composition, etc., and examples include sunlight, low-pressure mercury lamps, etc. , high-pressure mercury lamps, carbon arc lamps, xenon lamps, tungsten lamps, etc.

The photosensitive resin composition for printing plates of the present invention is prepared by exposing a suitable negative film to light using the above light source to form a relief image, and washing the unexposed areas using a suitable solvent. A printing plate can be obtained by printing out.

As such a solvent, an aqueous solvent such as an alkaline aqueous solution, a neutral detergent aqueous solution, or an alcohol/water mixed solution can be used. Of course, it is also possible to use organic solvents such as acetone and tetrachloroethylene, but this
Needless to say, it is preferable to use an aqueous solvent since it causes problems such as air pollution. As mentioned above, the photosensitive resin composition for printing plates of the present invention (1) can be developed with an aqueous solvent, (2) has low hardness and high strength, especially excellent tear strength, and (3) has excellent moisture resistance. It has many advantages such as being able to be plated and having excellent 4J ink resistance, and is a photosensitive resin composition particularly suitable for flexographic printing plates that require rubber elasticity. The resin composition of the present invention takes advantage of the above characteristics and can be used, for example, in paints, adhesives,
Needless to say, it can also be applied to vibration isolating materials, damping materials, coating agents, impregnating materials, and other uses.

Next, Examples will be given to further specifically explain the present invention.

The mechanical properties of the cured products in the examples were measured according to JIS K63Ol, using a No. 3 tampel test piece for the tensile test and a B type (right angle type) test piece for the tear test at 23°C. Synthesis Example 1 In a reaction vessel equipped with a thermometer, a reflux condenser, and a stirrer,
Polypropylene glycol +2000 (molecular weight 1968
) 394t (0.2 mol), terephthalic acid-dipropylene glycol oligoester (acid value 2.8, molecular weight 39
0) 39t (0.1 mol) and 70f (0.4 mol) of 2,4-tolylene diisocyanate were charged and reacted at 80°C for 4 hours using 0.21 dibutyltin dilaurate as a catalyst to form a urethane blend containing terminal isocyanate groups. I got Polymer One.

Next, 0.05f of hydroquinone, 0.05f of phenothiazine
．． 29 t (0.22 mol) of ethylene glycol monomethacrylate containing 0.2 t was charged and reacted at 80° C. for 3 hours to obtain urethane-modified acrylate A.
Similarly, urethane-modified acrylates B to I were produced using compounds having active hydrogen groups shown in Table 1.

Example 1 Urethane-modified acrylate A-17 obtained in Synthesis Example 1
Styrene 121, ethylene glycol monomethacrylate 97, n-butyl acrylate 97, and benzoin methyl ether 2t were added (and dissolved) to 01 to prepare a photosensitive resin composition.

After injecting the obtained photosensitive resin composition between two quartz plates sandwiching a 3m771 silicone spacer, a 20CT
A 140 W mercury lamp was irradiated for 30 minutes from a distance of II to obtain a cured product. The mechanical properties of the obtained cured product are shown in Table 2. The above photosensitive resin composition (sample A or G) using urethane-modified acrylate A or G was covered with a polyester film, poured onto a glass plate sandwiching a 3 mm thick rubber spacer, and a negative film was applied to the photosensitive resin composition (sample A or G). Irradiate the film with a 140W mercury lamp from a distance of 30CTII for 1 minute from the opposite side, then irradiate it from the negative film side for 4 minutes, and then apply Nonion L-6 (NOF Corporation) to the end-exposed area.
The table below shows the results of brushing cleaning with a 3% aqueous solution (washout property) and the ink resistance when the flexographic printing plate of the obtained relief image was lined with a 4m7B thick rubber plate and printed on cardboard. Shown below. Synthesis Example 2 Add polypropylene glycol + to the same reaction vessel as Synthesis Example 1.
1000 (molecular weight 1057) 317f (0.3 mol),
After charging 104 t (0.6 mol) of 2,4-tolylene diisocyanate and reacting with 0.3 f of dibutyltin dilaurate as a catalyst at 80°C for 2 hours, terephthalic acid monodipropylene glycol oligoester (acid value 1. 2,
A urethane prepolymer containing terminal isocyanate groups was obtained by charging 118V (0.2 mol) with a molecular weight of 590 and reacting at 80° C. for 3 hours.

Next, hydroquinone 0.041, phenothiazine 0
．． Ethylene glycol monomethacrylate 29V (0.22 mol) containing 02f1 was added and reacted at 80°C for 3 hours to obtain urethane-modified acrylate J. Similarly, adipic acid-propylene glycol oligoester, which is an aliphatic oligoester (acid value 2.8, molecular weight 640
) 128r (0.2 mol) to obtain urethane-modified acrylate K. Example 2 Urethane modified acrylate J, K7 obtained in Synthesis Example 2
A copolymerizable monomer and a photosensitizer were added and dissolved in Of, in the proportions shown in Table 3 to form a photosensitive resin composition (J-1 to J-3, K
-1 to 3) were obtained.

Obtained photosensitive resin compositions (J-1 to 3, K-1 to 3)
Table 4 shows the mechanical properties of the cured product obtained by curing it in exactly the same manner as in Example 1.

In Table 4, although the composition of the present invention shows a slightly higher value in terms of hardness, it is clear that the tensile strength is more than twice as high as that of the composition of the present invention, and is extremely excellent in elongation and tear strength. Synthesis Example 1 In a reaction vessel equipped with a thermometer, a reflux condenser, and a stirrer,
Polypropylene glycol +2000 (molecular weight 1968
)945t (0.48 mol), styrene, 220t,.
n-butoxyethyl acrylate 165rV hydroquinone 0.151, phenothiazine 0.08f, 2,4-
After charging 167 t (0.96 mol) of tolylene diisocyanate and adding 0.34 f of dibutyltin dilaurate and reacting at 80°C for 2 hours, terephthalic acid-dipropylene glycol oligoester (acid value 2.8, molecular weight 39) was added.
0) 125t (0.32 mol) was added and the reaction was further carried out for 3 hours to obtain a solution of a urethane prepolymer containing terminal isocyanate groups.

Then, ethylene glycol mometaacrylate 211
V was added and reacted for 3 hours to obtain a urethane-modified acrylate resin liquid. Example 3 To 200 tons of the urethane-modified acrylate resin liquid obtained in Synthesis Example 3, 1.0 f of ethylene glycol dimethacrylate and 3.6 f of benzoin-1s0-propyl ether were added and dissolved to obtain a photosensitive resin composition L.

Photosensitive resin composition L was cured in the same manner as in Example 1, and its mechanical properties were as follows. Hardness (Shore A)
42 Tensile strength (engineering) 5
3 Tensile modulus (Kg/Crli) 17 elongation
9.9 Example 4 The photosensitive resin composition L obtained in Example 3 was covered with a polyester film and placed on a glass plate sandwiching a rubber spacer with a thickness of 3 WLm. After pouring the film, place a negative film on it and irradiate it with a 140W mercury lamp from a distance of 30c1r1 for 1 minute from the opposite side of the negative film, then irradiate it for 4 minutes from the negative film side, then apply a nonion L-6 (manufactured by NOF Corporation) to the last exposed part. )3(f
l) After brushing and cleaning with an aqueous solution, a flexographic printing plate with a clear relief image was obtained.

When this was backed with a 4 mm thick rubber plate and printed on cardboard, the ink transfer properties were good and the printing durability was over 500,000 copies. Comparative Example 1 In Synthesis Example 1, terephthalic acid-ethylene glycol oligoester (acid value 25.
2. Molecular weight: 385) A urethane-modified acrylate was obtained in exactly the same manner as in Synthesis Example 1 except that 38.5t was used, but the obtained urethane-modified acrylate was cloudy.

Furthermore, when styrene 121, n-butoxyethyl acrylate 91, and lauryl methacrylate 9V were added to this urethane-modified acrylate 701 and mixed, the resin liquid became cloudy and could not be put to practical use. This is because the acid value of the aromatic oligoester exceeded 20, resulting in extremely low solubility. Comparative Example 2 Polypropylene glycol was added to the same reaction vessel as Synthesis Example 1.
+2000 (molecular weight 1968) 197f (0.1 mol)
, terephthalic acid-dipropylene glycol oligoester (acid value 1.2, molecular weight 590) 236f (0.4 mol), benzene 200f, 2,4-tolylene diisocyanate 104f (0.6 mol) were prepared, and dibutyltin dilaurate was prepared. After adding 0.2f and reacting for 4 hours, 0.047V of hydroquinone, 0.02V of phenothiazine, and 29V of ethylene glycol monomethacrylate were added, and the reaction was further continued for 3 hours.

Benzene in the resulting reaction solution was completely distilled off at 80° C. under reduced pressure using a rotary evaporator to obtain a highly viscous liquid urethane-modified acrylate as a residue. The obtained urethane-modified acrylate 70f was mixed with styrene 12V5.
Ethylene glycol monomethacrylate 9t,. Although it was dissolved in n-butoxyethyl methacrylate 9f, the viscosity was extremely high at 560 voids at 25°C, and the defoaming property was poor, making handling extremely difficult. This is because the content of aromatic oligoester is larger than that of polyether.
That is, it shows that the viscosity was extremely high because the A/B ratio by weight was less than 1.0.

Synthesis Example 4 Add polypropylene glycol + 2000 (molecular weight 1968) to a reaction vessel equipped with a thermometer, reflux condenser, and stirrer.
197t (0.1 mol), polytetramethylene glycol≠2000 (molecular weight 1934) 193t (0.1 mol), terephthalic acid-dipropylene glycol oligoester (acid value 2.8, molecular weight 390) 39V (0.1 mol) ), 2,4-tolylene diisocyanate 70f (0.4
mol) and reacted for 4 hours at 80° C. using 0.2 f of dibutyltin dilaurate as a catalyst to obtain a urethane prepolymer containing terminal isocyanate groups.

Next, 0.05t of hydroquinone and 0.05t of phenothiazine were added.
29 t (0.22 mol) of ethylene glycol monomethacrylate containing 027 was charged, and 3
Urethane-modified acrylate M was obtained by reacting for a period of time. Similarly, urethane-modified acrylate NR was produced using the compounds having active hydrogen groups shown in Table 5. Example 5 Urethane-modified acrylate obtained in Synthesis Example 4 (M-R
) 70t, styrene 12f, ethylene glycol monomethacrylate 9V. A photosensitive resin composition was prepared by adding and dissolving n-butyl acrylate 9f and benzoin methyl ether 2r.

3 m of the photosensitive resin composition obtained above (sample M-R)
20 CI after injecting between two quartz plates sandwiching silicon spacers of 11! 30 with a 140W mercury lamp from a distance of l.
A cured product was obtained by exposure for a minute. Table 6 shows the mechanical properties of the obtained cured product. Synthesis Example 5 Reaction vessel K equipped with a thermometer, reflux condenser, and stirrer,
Polypropylene glycol ◆2000 (molecular weight 1968
) 708f (0.36 mol), polytetramethylene glycol ≠ 2000 (molecular weight 1934) 232V (0.1
2 mol), styrene 220f, . n-ptoquine ethyl methacrylate 165t, hydroquinone 0.15f,
After charging 0.08f of phenothiazine, 167t (0.96 mol) of 2,4-tolylene diisocyanate and adding 0.34t of dibutyltin dilaurate and reacting at 80°C for 2 hours, terephthalic acid-dipropylene glycol oligoester ( Acid value 2.8, molecular weight 390) 125f(0
．． 32 mol) was added and the reaction was further carried out for 3 hours to obtain a solution of a urethane prepolymer containing terminal isocyanate groups.

Then ethylene glycol monomethacrylate 211f
was added and reacted for 3 hours to obtain a urethane-modified acrylate resin liquid. Example 6 Urethane modified acrylate resin liquid obtained in Synthesis Example 5 200
For f, benzoin-1s0-propyl ether 6t
was added and dissolved to obtain a photosensitive resin composition S.

When the obtained photosensitive resin composition S was cured in the same manner as in Example 5, the mechanical properties were as follows. Hardness (Shore A) 43 Tensile strength (Kg) 59 Tensile modulus (Kg/c!11) 19 Elongation (To)
330 tear strength (kg)
11.0 Example 7 The photosensitive resin composition S obtained in Example 6 was covered with a polyester film, poured onto a glass plate sandwiching a rubber spacer with a thickness of 311 mm, and a negative film was applied.
20CI of 0W mercury lamp! After irradiating the film for 2 minutes from a distance of 200 m, and then irradiating it for 5 minutes from the negative film side, the unexposed areas were brushed and cleaned with a 3% aqueous solution of Nonion L-6 (manufactured by NOF Corporation), resulting in a clear relief image. A flexo printing plate was obtained.

When this was backed with a 4-thickness rubber plate and printed on cardboard, the ink transfer properties were good and the printing life was over 600,000 copies. Comparative Example 3 In the same reaction vessel as Synthesis Example 4, polytetramethylene glycol≠2000 (molecular weight 1934) 387f (0.2 mol), terephthalic acid-dipropylene glycol oligoester (acid value 2.8, molecular weight 390) 3.9t (0.1 mol), 2,4-tolylene diisocyanate 70V (0.
After reacting at 80°C for 4 hours using 0.2 t of dibutyltin dilaurate as a catalyst, ethylene glycol monomethacrylate 291 containing 0.05 f of hydroquinone and 0.02 f of phenothiazine was charged.
A urethane-modified acrylate was obtained by similarly reacting at 80° C. for 3 hours.

A photosensitive resin composition was prepared and cured using the obtained urethane-modified acrylate in exactly the same manner as in Example 5. Hardness (Shore A) 55 Tensile strength (K9 eyebrow) 65 Tensile modulus (K9A→) 39 Elongation (a) The tear strength (kg) was 260 and the tear strength (kg) was 17, but the viscosity of the resin was 381 poise at 25°C, making it difficult to handle.

On the other hand, the viscosity of Sample M of Example 5 was as low as 67 poise at 25° C., which was an appropriate viscosity for a liquid photosensitive resin.

Claims (1)

[Claims] 1. Urethane-modified acrylate I, copolymerizable monomer II
and a photosensitizer, the urethane-modified acrylate I has a molecular weight of 400 to 500.
0 polyalkylene glycol A and an aromatic oligoester B having an acid value of 20 or less and a molecular weight of 200 to 2000, which has an acid component composed of an aromatic polybasic acid and an alcohol component composed of a polyhydric alcohol, and A/B is molar. 4 in ratio
/1 to 1/4, and the weight ratio of A/B is 1.
A molecule obtained by reacting a compound having two or more active hydrogen groups in the molecule that can react with 0 or more isocyanate groups, an organic diisocyanate, and an alcoholic hydroxyl group-containing acrylate compound and/or an alcoholic hydroxyl group-containing methacrylate compound. 1. A photosensitive resin composition for printing plates, which is a compound having an acryloyloxy group and/or a methacryloyloxy group at a terminal, and an ether bond, an ester bond, and a urethane bond in the molecule. 2 Polyalkylene glycol A with a molecular weight of 400 to 5,000 in Claim 1 is 20 to 80 mol% of polytetramethylene glycol with a molecular weight of 500 to 3,000 and 80% of other polyalkylene glycols with a molecular weight of 400 to 5,000.
A photosensitive resin composition for a printing plate, characterized in that the composition comprises ~20 mol%.