Support for Liquid Photosensitive Resin

A polyester-polyurethane resin having a molecular weight of about 40,000 obtained by chain-extending polyethylene adipate having a hydroxyl group at both ends and having an average molecular weight of 1300 was dissolved in a mixed solvent consisting of ethyl acetate and methyl ethyl ketone to form a 35% solution. This polyester-polyurethane resin had an end blocking agent added to its termini, and had a hydroxyl value of not more than 2. Ten parts of a 75% ethyl acetate solution of an adduct of trimethylol propane and TDI (Coronate L-75, isocyanate group content 13.4%, the product of Nippon Polyurethane Company) was added to 100 parts of the resulting 35% solution. Then, an oil-soluble yellow dye (color index No. 11390) was added to the mixture in an amount of 2% based on the resin content. A solvent was further added to form a solution having a solids content of 15%. The solution was thoroughly stirred in a ball mill until its viscosity became 20 poises. The coating solution was then coated by a bar coater uniformly on the surface of a 0.15 mm thick aluminum plate degreased with trichloroethylene.

Immediately then, the coated base plate was placed in a hot air dryer held at 100.degree. C., and dried for about 2 minutes to drive off the solvent. The coated layer had an average thickness of about 8 microns. At this time, the surface of the coated layer was almost free from tackiness, and could come into contact with other materials without blocking.

When the resulting product was allowed to stand for 5 days in a dry room held at 40.degree. C., the coated layer was sufficiently cross-linked and was hardly swollen with ethyl acetate.

For comparison, 30 parts of Coronate L-75 (the molar ratio of hydroxyl to isocyanate being about 1) was added to 100 parts of a 40% ethyl acetate solution of the same polyethylene adipate as used above (hydroxyl value 87), and 0.2%, based on the resin content, of a tertiary amine catalyst was added to form a coating solution. The solution was coated on the same base plate, and dried under the same conditions. The coating was very tacky, and its handling was extremely inconvenient unless a releasing paper is laminated thereon. When the coating was heated for 40 hours at 80.degree. C., the surface became non-tacky, and cross-linking proceeded sufficiently.

A semi-transparent liquid photosensitive composition consisting of 35 parts of methyl cellulose, 65 parts of triethylene glycol diacrylate, 3 parts of anthraquinone, and 0.03 part of hydroquinone was uniformly coated on each of the two plates obtained above to a thickness of 0.7 mm. Immediately then, the plate obtained was exposed to ultraviolet rays through a negative film adhered intimately to the photosensitive resin layer via a 12 micron thick polypropylene sheet. At this time, the temperature of the surface of the film was 35.degree. C.

Those portions of the resin layer which were not polymerized by exposure were washed out with water to prepare a printing plate. Furthermore, the printing plate was sufficiently exposed to solidify the reliefs completely. The solidified portions were in the form of a square having each side measuring 10 mm and a height of 0.7 mm and a rectangle having a size of 10 mm .times. 20 mm. The test pieces obtained were each wound around a cylinder having a radius of curvature of 45, 20, 16, 12, 9, and 6.5 mm respectively at 20.degree. C., and the state of separation of the relief portions was observed. The minimum radius with which the separation occurred is shown in Table 1 for each of the test pieces.

In the comparison, separation occurred between the adhesive layer and the resin layer, and the printing plate could not be used.

Polybutylene adipate having a molecular weight of 1500 was chain-extended with TDI, and the chain was terminated with monoalcohol to form polyester-polyurethane having a molecular weight of about 20,000 and a hydroxyl value of about 1. To a solution of 50 parts of the polyester-polyurethane in 350 parts of ethyl acetate were added 8.5 parts of Coronate L-75, and 3 parts of the same yellow dye as used in Example 1, and the mixture was thoroughly stirred.

On the other hand, for comparison, 100 parts of a commercially available copolyester resin (Vylon No. 300, Toyo Spinning Company, a highly polymerized saturated polyester having a hydroxyl value of 7 and prepared from terephthalic acid, sebacic acid and ethylene glycol), 50 parts of a vinyl chloride/vinyl acetate copolymer (Vinylite VYHH, vinyl acetate content 13%, Union Carbide Corporation), 10 parts of Coronate L-75, 5 parts of an organic yellow pigment and 400 parts of a mixed solvent consisting of methyl ethyl ketone and toluene were thoroughly mixed.

A biaxially oriented polyethylene terephthalate film having a thickness of 125 microns was prepared, and each of the adhesive solutions prepared above was coated on it, and immediately, dried with hot air at 120.degree. C. for 1 minutes to drive off the solvent. The amount of coating was about 10 gr/m.sup.2 in each case. At this time, the surface of the coated film was non-tacky. When the coated film was allowed to stand for several days in a dry room held at 20.degree. C., the cross-linking of the adhesive layer proceeded, and the cross-linked layer could not be dissolved in solvent.

A photosensitive resin was prepared from 57 parts of a polyester (prepared by using 8 mols of fumaric acid, 2 mols of trimellitic acid anhydride and 9 mols of diethylene glycol) 6 parts of acrylamide, 20 parts of tetraethylene glycol dimethacrylate, 16 parts of nonaethylene glycol dimethacrylate, 1 part of benzoin methyl ether and 0.01 part of hydroquinone.

The resulting photosensitive resin solution was coated to a thickness of 0.7 mm on each of the films coated with the adhesive layer. A thin polyester cover film and a negative film were superimposed on the surface of the resulting resin layer, and the plate was exposed for 5 minutes through the negative film maintained at 60.degree. C., using a 450 W high pressure mercury lamp. After exposure, the uncured portions were washed out with a 0.5% aqueous solution of sodium carbonate, and the plate was then further exposed to solidify the reliefs completely.

The resulting printing plates were subjected to the same separation test as in Example 1, and the results obtained are shown in Table 2.

Separation, mostly between the base film and the adhesive layer, occurred very simply in the printing plate obtained in the comparison, and the separation.

A liquid photosensitive resin composition was prepared from 30 parts of a methyl methacrylate/methacrylic acid (70:30), 30 parts of triethylene glycol diacrylate, 30 parts of trimethylol propane trimethacrylate, 10 parts of polyethylene glycol having a molecular weight of 100,000 and 2 parts of benzoin ethyl ether. The composition was uniformly coated on each of the same base plates having the adhesive layers as prepared in Example 2 and Comparative Example 2 to a thickness of 0.5 mm, and the plate was exposed imagewise for 5 minutes in the same way as in Example 2. Then, the unexposed portions were washed out with a 1% aqueous solution of sodium hydroxide at 40.degree. C.

In the comparison, the small halftone-dot reliefs separated from the base plate during 3 minutes' washing, and the plate could not be used.

In the plate obtained in the example, relief images could be reproduced in perfect condition, and after post-exposure, the printing plate could endure printing of 200,000 copies.

Polycaprolactone (PANDEX M-103ES, the tradename for the product of Dainippon Ink and Chemicals, Inc.) having an average molecular weight of 2000 and having a hydroxyl group at both ends was chain-extended with a mixture of TDI and MDT (1:1 mol ratio) to form polyester-polyurethane having an average molecular weight of 20,000. 50 parts of the resulting polyester-polyurethane, 10 parts of a 75% ethyl acetate solution of an addition product of trimethylol propane and xylylene diisocyanate (TAKENATE D-110-N, the tradename for the product of Takeda Pharmaceutical Co., Ltd.), 0.1 part of triethylene diamine, 3 parts of a yellow pigment, and 300 parts of a mixed solvent consisting of methyl ethyl ketone and toluene were mixed to form an adhesive solution. The resulting adhesive solution was coated on a polyethylene terephthalate film having a thickness of 100 microns.

For comparison, 50 parts of Desmophen-800 (a polyhydroxy compound having a hydroxyl value of 290 and prepared from adipic acid, phthalic acid, triol), 20 parts of Desmophen 1700 (polyhydroxy polyester having a hydroxyl value of 40), 70 parts of Coronate L-75, 5 parts of a yellow pigment, and 300 parts of a mixed solvent consisting of ethylene glycol acetate, butyl acetate, ethyl acetate and toluene were well mixed to form a polyurethane coating solution.

The resulting solution was coated on the same base film as used above to a thickness of about 10 microns using a bar coater.

Immediately, each of the coated base films was dried for 2 minutes at 120.degree. C. to drive off the solvent, and by a customary method, curing was further performed at 50.degree. C. for several days. The adhesive layers were cross-linked, and could not be redissolved in solvent. However, the film used in the comparison was markedly warped, and lent itself to troublesome handling.

Using the same unsaturated polyester-type photosensitive resin as used in Example 2, the same relief images as in Example 2 were formed on each of the films obtained, and the resulting printing plates were subjected to the same separation test as in Example 1. The results obtained were substantially the same as those shown in Table 1.

Polybutylene adipate having an average molecular weight of 1,500 and a hydroxyl group at both ends was chainextended with IDI to form a polyester-polyurethane resin having a molecular weight of about 40,000 and a hydroxyl value of less than 1. The resin was dissolved in a mixed solvent consisting of ethyl acetate and methyl ethyl ketone to form a 35% solution. 100 parts of the resulting 35% solution, 8 parts of 2-hydroxyethyl methacrylate, 2%, based on the resin content, of an oil-soluble yellow dye (color index 11390), and a solvent were mixed in a ball mill. Finally, 10 parts of a 75% ethyl acetate solution of an adduct of trimethylol propane and TDI (Coronate L-75, isocyanate content 13.4%, the product of Nippon Polyurethane Co., Ltd.) was added. When the viscosity of the resulting solution became 20 poises, the solution was coated uniformly on a biaxially oriented polyethylene terephthalate film having a thickness of 0.125 mm using a bar coater. Immediately then, the coated film was dried for about 2 minutes in a hot air dryer at 100.degree. C. to drive off the solvent. The coated layer had a thickness of about 10 microns. At this time, the surface of the adhesive layer was almost non-tacky, and could be freely contacted with other substances without blocking. When the coated film was allowed to stand for 3 days in a dry room held at 20.degree. C., the coated layer was sufficiently cross-linked, and it was found that the cross-linked layer was scarcely swollen with ethyl acetate.

For comparison, a base plate with an adhesive layer was prepared in the same way as above except that 2-hydroxyethyl methacrylate was not used, and the amount of the Coronate L-75 was reduced to 7 parts. The adhesive layer of the comparison plate was also in the sufficiently cross-linked state.

A photosensitive resin composition as used in Example 2 was coated on each of the above base plates containing adhesive layers, to a thickness of 0.7 mm. A thin polyester cover film and a negative film were superimposed on the surface of the resulting resin layer, and the plate was exposed for 5 minutes through the negative film maintained at 60.degree. C., using a 450 W high pressure mercury lamp. After exposure, the uncured portions were washed out with a 0.5% aqueous solution of sodium carbonate, and then, the plate was post-exposed for another 5 minutes to solidify the reliefs completely. The solidified reliefs were of a rectangular shape having a size of 10 mm .times. 20 mm, and of a line-relief having a width of 0.06 mm.

The resulting printing plates were wound around a cylinder having a radius of curvature of 4 mm, 6.5 mm, 9 mm, 12 mm, and 16 mm respectively, and the state of separation of the relief portion was observed. The minimum radius with which the separation occurred in each of the plates is shown in Table 3.

Separation occurred over a substantial portion between the adhesive layer and the resin layer in the line-reliefs of the comparison plate, but in the example, the separation was only partial.

A photosensitive resin solution was prepared from 30 parts of a methyl methacrylate/methacrylic acid copolymer (70:30), 30 parts of triethylene glycol diacrylate, 30 parts of trimethylol propane methacrylate, 10 parts of polyethylene glycol having a molecular weight of 100,000, 2 parts of benzoin ethyl ether and 0.03 part of methoxyhydroquinone. The solution was unfiromly coated to a thickness of 0.5 mm on each of the same base plates having adhesive layers as used in Example 5 and Comparative Example 5. The coated plate was exposed imagewise for 5 minutes in the same way as in Example 5, and the unexposed areas were washed out with a 0.3% aqueous solution of sodium hydroxide at 40.degree. C.

In the comparison, the line-reliefs having a size of 0.06 mm were somewhat separated, and were completely removed by a washing operation using a washing oil which was performed during printing. On the other hand, the printing plate obtained in the example could withstand printing of 300,000 copies.

Polyethylene butylene adipate having a molecular weight of 2,000 was chain-extended with a mixture of equal amounts of TDI and MDT, and the chain was blocked with monoalcohol to form polyester-polyurethane having a molecular weight of about 20,000 and a hydroxyl value of about 2. 100 parts of a 35% ethyl acetate solution of this resin was mixed with 5 parts of pentaerythritol trimethacrylate and 4 parts of an organic yellow pigment. The mixture was diluted with ethyl acetate, and completely stirred in a ball mill. Furthermore, 10 parts of Coronate L was added, and the mixture was diluted with ethyl acetate to form a 15% solution.

For comparison, an adhesive solution was prepared from 100 parts of a commercially available copolyester resin (Vylon No. 300 of Toyo Spinning Co., Ltd., a highly polymerized saturated polyester resin having a hydroxyl value of 7 and prepared from terephthalic acid, isophthalic acid, sebacic acid and ethylene glycol), 50 parts of a vinyl chloride/vinyl acetate copolymer (Vinylite VYHH, vinyl acetate content 13%, the product of Union Carbide Corporation), 15 parts of Coronate L-75, 7 parts of pentaerythritol trimethacrylate, some amount of an organic yellow pigment, and 400 parts of a mixed solvent consisting of methyl ethyl ketone and toluene.

Each of the above adhesive solutions was coated on a 100 .mu. thick polyethylene terephthalate film using a bar coater, and then dried for 2 minutes with hot air at 120.degree. C. to drive off the solvent. The thickness of the coating was about 8 microns. At this time, the surface of the coated layer was non-tacky. When it was cured for several days at 40.degree. C., the adhesive layer was cross-linked, and the cross-linked layer could not be re-dissolved in solvent.

Relief images were obtained in the same way as in Example 5 using the same unsaturated polyester-type photosensitive resin.

In the comparison, the line-reliefs having a width of 0.06 was separated during the 3-minute development procedure, and rectangular relief images of 10 .times. 20 mm were separated from the base film by a slight curving with a radius of curvature of more than 45 mm.

On the other hand, in the example, the line-reliefs of 0.06 mm was completely bonded to the adhesive layer, and the printing plate could endure printing of more than 300,000 copies in a printing test using a small-sized relief printing press.

The same adhesive composition as used in Comparative Example 7 was coated to a thickness of 5 microns on a polyethylene terephthalate film having a thickness of 100 microns, and cured for 10 minutes at 80.degree. C. Furthermore, it was allowed to stand for several days at room temperature, and then a top coating solution was applied to it. The top coating solution was prepared by dissolving a composition consisting of 100 parts of the same polyester-polyurethane resin as used in Example 5, 50 parts of a 1:1 mixture of pentaerythritol tetraacrylate and pentaerythritol triacrylate, 25 parts of Coronate L and 2 parts of bonzoyl peroxide in a mixed solvent consisting of ethyl acetate and toluene. The coated layer had a thickness of about 5 microns. The coated layer was cured at 100.degree. C. and 120.degree. C. for about 5 minutes and at 130.degree. C. for 2 minutes.

The top coat changed to an almost non-tacky state, but warping of the film occurred with the coated surface being inside. In addition, wavy corrugations occurred at random at many places of the film, and the resulting coated film could not be used.

Polyethylene butylene adipate having a molecular weight of 1600 (ODX-451, tradename for the product of Dainippon Ink Chemicals, Inc., hydroxyl value 72.5, both ends being hydroxyl groups) was completely dehydrated, and reacted with stirring with 2 molar times of toluylene diisocyanate which had been purified by distillation, at 100.degree. C. for 3 hours. After the terminal hydroxyl groups were completely reacted, the product was cooled, and dissolved in a suitable amount of dimethyl formamide. The prepolymer solution was added dropwise with vigorous stirring to a dimethyl formamide solution of .beta.-alanine hydrazide (NH.sub.2.sup.. CH.sub.2.sup.. CH.sub.2.sup.. CONHNH.sub.2). The viscosity increased gradually, and finally, a polyester-polyurethaneurea solution having a viscosity of 800 poises and a solids concentration of 30% was formed. After stabilizing the remaining isocyanate groups completely with diethyl amine, 100 parts of the polyester-polyurethaneurea resin solution was mixed with 10 parts of Coronate L-75 and 3 parts of Hansa Yellow. The resulting solution was diluted with ethyl acetate to a concentration of 10%.

The resulting solution was coated on a uniform polyethylene terephthalate film having a thickness of 125 microns using a bar coater. The thickness of the coating was 5 microns. Then, the coated film was dried with hot air to drive off the solvent completely. At this time, the surface of the coating was almost non-tacky. Then, the coated film was cured for about 5 days in an oven at 50.degree. C. The isocyanate groups in the coating were completely consumed, and the coated layer was cross-linked.

The same unsaturated polyester-type liquid photosensitive resin as used in Example 2 was coated on the resulting base plate, and a printing plate was prepared from the coated plate in the same way as in Example 1.

When the resulting printing plate was subjected to a slight stress, the polyurethaneurea adhesive layer was separated from the polyethylene terephthalate base film, and the relief images were easily removed. Thus, the printing plate could not be used for actual printing.

It is seen from this comparison that when a polyester-polyurethaneurea resin is used instead of the polyester-polyurethane resin, a satisfactory adhesive layer cannot be formed.

An unsaturated polyester liquid photosensitive resin was prepared by mixing 60 parts of an unsaturated polyester (acid value about 100; obtained by condensing 1 mol of trimellitic anhydride, 6 mols of fumaric acid, 3 mols of adipic acid and 9 mols of diethylene glycol at an elevated temperature in a customary manner), 6 parts of methacrylamide, 6 parts of tetraethyleneglycol dimethacrylate, 12 parts of nonaethyleneglycol dimethacrylate, 16 parts of 2-acetoxyethylmethacrylate, 0.7 part of benzoin ethyl ether, and 0.003 part of N-nitrosodiphenylamine.

On the other hand, the same lacquer consisting mainly of polyester-polyurethane resin as used in Example 7 was coated on one sand-blasted surface of a polyethylene terephthalate film having a thickness of 125 microns. The amount of the lacquer coated was about 10 gr/m.sup.2 calculated as solids content. The solvent was immediately removed off by hot air, and the coated film was heated at 130.degree. C. for about 3 minutes. At this time, the coating was substantially non-tacky. The curing was further continued at 40.degree. C. for about 10 days to complete the cross-linkage.

The resulting base plate was coated with the above photosensitive resin to a thickness of about 0.7 mm, and exposed imagewise for 4 minutes from the distance of about 10 cm using eight 20 W chemical fluorescent lamps. Then, the unexposed areas were washed out with a dilute aqueous solution of sodium carbonate. It was found that the image was faithfully reproduced and adhered strongly to the based plate. In particular, isolated dots having a diameter of 200 microns or fine line-reliefs with a width of 50 microns were also completely bonded to the base plate. The resulting printing plate was subjected to post-exposure for 6 minutes, and dried. The resulting printing plate was mounted on a rotary press using an adhesive tape, and printing was continued at high speed (about 100 m/min.). The plate was in perfect condition even after producing 500,000 printed copies.