US 3733200 A
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y 15, 1973 SHUNJI TAKAISHI ET AL 3,733,200
PRINTING PLATE Filed Feb. 12 1971 INVENTORS flflu/vf/ 72/4449 Y 4 6424 fiira United States Patent 3,733,200 PRINTING PLATE Shunji Takaishi, Tokyo, and Akira Kato, Yokohama, Japan, assignors to Hydron Chemical Co., Ltd., Tokyo, and Kansai Paint Co., Osaka, Japan Filed Feb. 12, 1971, Ser. No. 114,887 Claims priority, application Japan, Feb. 19, 1970, 45/ 13,759 Int. Cl. G03c 1/94 US. Cl. 96-86 R 12 Claims ABSTRACT OF THE DISCLOSURE A printing plate is constituted a basic plate, a layer of water insoluble hydrophilic acrylate or methacrylate polymers over the plate and a photo-sensitive layer over the layer.
The present invention relates to a printing plate. More particularly, it relates to a printing plate having a photosensitive layer on the surface of water insoluble hydro philic acrylic resins layer.
The most conventional printing plates are aluminium plates having sanded or chemically treated surface on which e.g. gelatin, polyvinyl alcohol or albumins are applied together with one of photosensitive materials such as chromates and diazo compounds and finally those plates are dried, and exposed through a negative photo-film over the plate, developed and treated again. The photo-sensitively cured parts of lines and pictures absorb ink well due to the lipophilic property. On the other hand, the surface of the aluminium plate exposed by developing absorbs water and repels ink. In the process of offset printing by using such plates, the exposed surface of the aluminium plate gradually wears thin by eternal friction together with cured parts and lines. In some cases, worn out lines and pictures are fixed and reinforced by lacquerlike materials. The surface of the aluminium plate, especially its sanded surface tends to wear out sometimes more easily than the photo-sensitive cured layer. When the surface wears out, the defaced plate results in indistinct pictures with less hydrophilic function, and finally it becomes impossible to print. Furthermore, water supply to the sanded aluminium surface has to be appropriate in order to obtain clear pictures and skilled work is required to the adjustment of water supply.
An object of the present invention is to provide a novel printing plate.
Another object of the present invention is to provide a printing plate having an extremely great printing durability.
A further object of the present invention is to provide an improved starting printing plate bringing about a simplification of the make-up operation.
Still further objects and entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The printing plate according to the present invention comprises a basic plate, a layer of water insoluble hydro philic acrylate or methacrylate polymers (hydrophilic acrylic resins) over the plate and a photo-sensitive layer over the layer.
As a basic plate used in the starting printing plate of the present invention, there are employed metallic plates such as steel plate, tin plate, zinc plate, stainless steel plate, etc., plastic sheets such as polyethylene terephthalate sheet, polystyrene sheet, acetyl cellulose sheet, hydrophilic acrylic resin sheets, etc. and papers.
It is indispensable that the hydrophilic acrylic resins which form hydrophilic layers are water insoluble. And the hydrophilic acrylic resins should be capable of absorbing at least 20% of its weight of water and preferably do not absorb more than about of its weight of water.
Preferably the hydrophilic monomer employed in the hydrophilic acrylic resins is a hydroxy lower alkyl acrylate or methacrylate or hydroxy lower alkoxy lower alkyl acrylate or methacrylate, e.g. 2-hydroxyethyl acrylate, 2- hydroxyethyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, dipropylene glycol monomethacrylate and dipropylene glycol monoacrylate. The most preferred monomers are the hydroxyalkyl acrylates and methacrylates, particularly Z-hydroxyethyl methacrylate.
There can also be employed polymers of acrylamide, methacrylamide, N-alkyl substituted acrylamide and methacrylamide such as N-propylacrylamide, N -isopropyl acrylamide, N-isopropyl methacrylamide, N-propyl methacrylamide, N-butyl acrylamide, N-methyl acrylamide and N-methyl methacrylamide, diacetone acrylamide, N-(2-hydroxyethyl) acrylamide and N- (Z-hydroxyethyl) methacrylamide.
Likewise, there can be employed copolymers of these monomers with each other or with other copolymerizable monomers. In fact, if the hydrophilic monomer gives a product which is water soluble, e.g. polyacrylamide, it is necessary to employ a copolymerizable monomer to render it only water swellable rather than water soluble. The copolymerizable monomer can be used in an amount of 0.05 to 50%. Preferably, comonomers include methyl acrylate, ethyl acrylate, isopropyl acrylate, propyl acrylate, butyl acrylate, sec. butyl acrylate, pentyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, sec. butyl methacrylate, pentyl methacrylate, lower alkoxyethyl acrylates and methacrylates, e.g. methoxyethyl acrylate, methoxyethyl methacrylate, ethoxyethyl acrylate and ethoxyethyl methacrylate, triethylene glycol acrylate, triethylene glycol methacrylate, glycerol monoacrylate and glycerol monomethacrylate.
There can also be used unsaturated amines, p-aminostyrene, oaminostyrene, 2-amino 4 vinyltoluene, alkylamino alkyl acrylates and methacrylates, e.g. diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, t-butylaminoethyl acrylate, t-butylaminoethyl methacrylate, piperidinoethyl acrylate, piperidinoethyl methacrylate, morpholinoethyl acrylate, morpholinoethyl methacrylate, 2-vinylpyridine, 3-vinylpyridine, 4-viny1- pyridine, Z-ethyl-S-vinylpyridine, dimethylamino propyl acrylate, dimethylamino propyl methacrylate, dipropylaminoethyl acrylate, dipropylaminoethyl methacrylate. di-n-butylaminoethyl acrylate, di n butylaminoethyl methacrylate, di-sec. butylaminoethyl acrylate, di-sec. butylaminoethyl methacrylate, dimethylaminoethyl vinyl ether, diethylaminoethyl vinyl sulfide, diethylaminoethyl vinyl ether, aminoethyl vinyl ether, aminoethyl vinyl sulfide, monomethylaminoethyl vinyl sulfide, monomethyl aminoethyl vinyl ether, N-(gamma-monomethylamino) propyl acrylamide, N (betamonomethylamino) ethyl acrylamide, N- (beta-monomethylamino) ethyl methacrylamide, 10-amin0decyl vinyl ether, 8-aminooctyl vinyl ether, S-aminopentyl vinyl ether, 3-aminopropyl vinyl ether, 4aminobutyl vinyl ether, Z-aminobutyl vinyl ether, monoethylaminoethyl methacrylate, N-(3,5,5-trimethylhexyl) aminoethyl vinyl ether, N-cyclohexylaminoethyl vinyl ether, 2-(1,1,3,3-tetramethylbutylamino) ethyl methacrylate, N-t-butylarninoethyl vinyl ether, N-methylamino-ethyl vinyl ether, N-Z-ethylhexylaminoethyl vinyl ether, N-t-butylaminoethylvinyl ether, N-t-octylaminoethyl vinyl ether, Z-pyrrolidinoethyl acrylate, 2-pyrrolidinoethyl methacrylate, 3-dimethylaminoethyl)-2-hydroxypropyl acrylate, 3- (dimethylaminoethyl -2-hydroxypropyl methacylate, Z-aminoethyl acrylate, 2-aminoethyl methacrylate. The presently preferred amino compounds are alkylaminoethyl acrylates and methacrylates, most preferably t-butyl aminoethyl methacrylate.
Preferably, the cross-linking agent is present in an amount of 0.1 to 2.5%, most preferably not over 2.0%, although from 0.05 to 15% or even 20%, of crosslinking agents can be used. Of course, care should be taken that cross-linking agents are not used in an amount which renders the product incapable of absorbing at least 20% of water.
Typical examples of cross-linking agents include ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,2- butylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, propyl ene glycol diacrylate, propylene glycol dimethacrylate, diethylene glycol dimethacrylate, di-propylene glycol dimethacrylate, diethylene glycol diacrylate, dipropylene glycol diacrylate, divinyl benzene, divinyl toluene, diallyl tartarate, allyl pyruvate, allyl maleate, divinyl tartrate, triallyl melamine, N,N' methylene bis acrylamide, .glycerine trimethacrylate, diallyl maleate, divinyl ether, diallyl monoethylene glycol citrate, ethylene glycol vinyl allyl citrate, allyl vinyl maleate, diallyl itaconate, ethylene glycol diester of itaconic acid, divinyl sulfone, h'exahydro-1,3,5-triacryltriazine, triallyl phosphite, diallyl ester of benzene phosphonic acid, polyester of maleic anhydride with triethylene glycol, polyallyl glucose, e.g. triallyl glucose, polyallyl sucrose, e.g. pentaallyl sucrose, sucrose diacrylate, glucose dimethacrylate, pentaerythritol tetraacrylate, sorbitol dimethacrylate, diallyl aconitate, divinyl citraconate, diallyl fumarate.
There can be included ethylenically unsaturated acids or salts thereof such as acrylic acid, cinnamic acid, crotonic acid, methacrylic acid, itaconic acid, aconitic acid, maleic acid, fumaric acid, mesaconic acid and citraconic acid. Also, as previously indicated there can be used partial esters such as mono 2-hydroxypropyl itaconate, mono 2-hydroxyethyl itaconate, mono Z-hydroxyethyl citraconate, mono 2-hydroxypropyl aconitate, mono 2-hydroxyethyl maleate, mono 2-hydroxypropyl fumarate, monomethyl itaconate, monoethyl itaconate, mono methyl Cellosolve ester of itaconic acid (methyl Cellosolve is the monomethyl ether of diethylene glycol), mono methyl Cellosolve ester of maleic acid.
The polymers can be prepared as casting syrups, as aqueous dispersions, by aqueous suspension polymerization or as solutions in organic solvents such as ethyl alcohol, methyl alcohol, propyl alcohol, isopropyl alcohol, formamide, dimethyl sulfoxide or other appropriate solvent.
Polymerization can be carried out at 20 to 150 C., frequently 35 to 90 C. and can be completed after applying. The polymerization can be carried out employing a free radical catalyst in the range of 0.05 to 1% of the polymerizable monomers. Typical catalyst include tbutyl peroctoate, benozyl peroxide, isopropyl percarbonate, 2,4-dichlorobenzoyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide and dicumyl peroxide. Irradiation, e.g. by ultraviolet light or gamma rays, also can be employed to catalyze the polymerization.
The hydrophilic polymer is used as a solution, as a casting syrup or as a sheet, coated on the surface of basic plate by means of painting, casting, adhering and the like with or without using adhesives, and forms a water insoluble hydrophilic resin layer. The thickness of the hydrophilic resin layer is generally 5 to 300 microns, preferably 10 to 50 microns. Thus, by providing a water insoluble hydrophilic layer on the suface of the basic plate, there can be attained good results in respect of dimension stability of the hydrophilic layer or printing plate, its installation on the printing machine and the like. As the hydrophilic resin is transparent, when a transparent plastic sheet is used as a basic plate, it becomes wholly transparent. Therefore, it is very advantageous, because the registering at the multi color printing is easier.
Further, there can be incorporated with the hydrophilic resin to provide a layer having increased mechanical strength as well as adherence to the basic plate by oxidizing type curing agents such as sodium, potassium or ammonium chromate or dichromate, aminoplast resins such as melamine resin, benzoguanamine resin or acetoguanamine resin, acid anhydrides such as maleic anhydride, citraconic anhydride, succinic anhydride, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride and the like, polyamines such as ethylene diamine, propylene diamine, diethylene triamine, tetraethylene pentamine, piperazine, m-xylylene diamine, p-xylylene diamine, m-phenylene diamine, p-phenylene diamine, benzidine, diaminodiphenyl methane, diaminodiphenyl sulfone, 3,3-dichloro-4,4-diphenyl methane diamine, naphthalene diamine and the like. The amount of the curing agents to the hydrophilic resin is generally less than 2% by weight, preferably 0.1 to 0.5% by weight.
However, mechanical strength of the hydrophilic resin layer increases by addition of the curing agents, while the hydrophilic property sometimes decreases. In such a case, it is preferable to add fine divided powdered materials to the hydrophilic resin. By such addition sufficient hydrophilic property for a printing plate is attained. As such powdered materials, there are fine divided powdered inorganic materials such as, e.g., silica, alumina, magnesia, zirconia, barium sulfate, acid actinated clay, talc and diatomaceous earth. Preferable materials are silica and alumina. The amount of the powdered materials to the hydrophilic resin is less than 5% by weight, preferably 0.5 to 2% by weight.
As the compound which forms a photo-sensitive layer according to the present invention, there are used photocurable compositions composed of vinyl monomers, photosensitizers and resins such as unsaturated polyester resin, alkyd resin, acrylurethane resin, silicone modified acrylic resin, polybutadiene and cellulose; light-sensitive polymers modified by compounds such as diazo compounds, azide compounds, organo sulfur compounds and cinnamic acid compounds; and compositions composed of dichromates and gelatin, polyvinyl alcohol or albumin. Considering the printing capacity and resolving power, acrylurethane resin is especially superior to the others.
The above mentioned polymeric materials are dissolved in organic solvents having the property of swelling or partially dissolving the hydrophilic layer, e.g., alcohols, ketones and esters, and are applied to the surface of the hydrophilic resin layer by coating and drying. In such a case, the surface of the hydrophilic resin layer swells or partially dissolves and mixes with photo-sensitive compounds, and both layers are adhered together. Thus obtained printing plate is exposed using a negative film over it, developed, washed by water and dried, and if necessary absorbed in water. Then it is equipped to the otfset printing machine and used in the offset printing. It gives us excellent results. When the hydrophilic layer is relatively thicker, water supply by fountain roller may be extremely little.
In the present invention, we use a water insoluble hydrophilic resin coated metallic plate, plastic sheet, paper and the like instead of the conventional aluminium plate. Therefore, if abrasion of the hydrophilic resin layer occurs, lithographic printability is not completely prevented where the hydrophilic layer exists. Thus printing capacity and its durability is greatly increased. For example, though we could only print less than 20,000 sheets of paper by using the conventional aluminium plate, which had been sanded and then coated with albumin, it is a surprising effect that We can print more than 100,000 sheets of paper by using the printing plate according to the present invention.
Further effect of the present invention is that only a little supply of water is sufiicient for the lithographic printing. That is to say, the hydrophilic resin layer which absorbed water releases water slowly and constantly, and it is possible to print with only a little water supply. Thus no excessive water is transferred to the printing paper and printing precision increases remarkably without any stretch in the size of paper. These features also contribute to make the printing operation easy as no skilled control is required in the water supply.
As mentionad above, the printing palte having a photosensitive layer on the hydrophilic resin layer has very excellent advantages in comparison with a conventional printing plate having a photo-sensitive layer on the aluminium plate directly, and is very useful in respect to increasing printing durability and printing precision, and bringing about simple printing operation.
The invention will be understood best in connection with drawing wherein:
FIG. 1 shows a partial sectional view of the printing plate according to the invention; and
FIG. 2 shows a partial sectional view of the printing plate after exposing and developing.
Referring more specifically to the drawing, the starting printing plate is constituted of a basic plate 1, a layer 2 of water insoluble hydrophilic acrylic resins over the plate 1 and a photo-sensitive layer 3 over the layer 2. The thickness of the layers 2 and 3 are greatly exaggerated for illustrative purposes.
Unless otherwise indicated in the specification and claims all parts and percentages are by weight.
EXAMPLE 1 400 parts of polyethyleneglycol-400 Was added to 360 parts of tolylene diisocyanates, reacted by heating at a temperature of 140 C. for 30 minutes and cooled, then there were added 260 parts of 2-hydroxyethyl methacrylate and 0.21 part of p-benzoquinone to the reactant and reacted at a temperature of 40 C. for 24 hours to obtain the unsaturated acrylurethane resin (I). The resin (I), was a very viscous liquid at room temperature. The photosensitive resin composition was obtained by mixing 50 parts of resin (I) with 50 parts of commercial cellulose phthalate, 1 part of benzoin ethylether and 100 parts of acetone.
EXAMPLE 2 The solution consisting of 2-hydroxyethyl methacrylate 79.6%, ethyleneglycol dimethacrylate 0.3%, glycerol 20% and diethyl percarbonate 0.1% was poured into the space between two glass plates adjusted by spacer in order to maintain 0.15 mm. of space carefully so as to not form bubbles. The composition was polymerized maintaining a temperature of 65 C. for 20 minutes, then the transparent sheet obtained by removing the plates was washed by distilled water and the glycerol extracted out, and further dried at a room of 40% of relative humidity at a temperature of 25 C. for 24 hours to obtain a hydrophilic resin sheet. The sheet was adhered to the aluminium plate having 0.15 mm. of thickness using epoxy resin polyamide resin mixed adhesive. The other side of the resin sheet was coated uniformly with photo-sensitive resin composition obtained in Example 1 so that the thickness of drying film was about 2 microns, and dried to obtain the printing plate.
After the negative film was put on the printing plate,
6 the plate was set in the vacuum printing frame and exposed by a high pressure mercury lamp at a distance of 35 cm. for one minute, then it was developed by 1% ethanolamine aqueous solution, washed by water and dried to obtain the lithography for printing. Otfset printing was carried out by using the lithography, and very excellent printing effects having good distinction and measure accuracy were obtained. Also it was able to print more than 100,000 sheets of paper per plate, and the control of water supply was easier than that with the conventional method.
EXAMPLE 3 Hydrophilic monomer solution of Example 2 was coated on the aluminium plate having 0.15 mm. of thickness which was previously coated with epoxy resin-polyamide resin mixed primer so as to be 10 microns thickness, so that the thickness of the hydrophilic resin was about 0.2 mm, and polymerized under nitrogen atmosphere by similar condition as Example 2. Then the photography for printing was prepared and offset printing was carried out, similar good results as Example 2 were obtained.
EXAMPLE 4 A hydrophilic resin sheet obtained by Example 2 was adhered on the surface of polyethylene terephthalate sheet having 0.2 mm. of thickness by means of epoxy adhesive and the other surface of the resin sheet was coated with diazo compound Fuji Super-Resist: trademark of (Fuji Chemicals Co., Ltd.) as thin as 3 microns, exposed through negative fihn and treated as prescribed to obtain a printing plate. Offset printing with four colors was carried out using the printing plate, and the good results of Example 2 were obtained. Also registering of each plate was carried out easily and rapidly, because of its transparency.
EXAMPLE 5 1,000 grams of xylene, grams of 2-hydroxyethyl methacrylate and 0.33 gram of isopropyl percarbonate were charged to a flask equipped with an agitator and heating mantle. The flask was rapidly agitated at 100 C. under a nitrogen atmosphere. After 15 minutes the slurry was filtered hot to isolate the polymer. The polymer powder was reslurried in 300 ml. of xylene, filtered and dried. A 98% yield of 2 to 5 micron particle size alcohol soluble powder was obtained. 100 grams of the polymer powder was dissolved in 200 ml. of methanol, then added 0.2 gram of epoxy resin and 1.5 grams of fine divided silica powder and dispersed homogeneously. The thus obtained solution was coated on epoxy resin-polyamide resin mixed primer coating which was previously coated on a steel plate having a 0.15 mm. thickness so as to be 10 microns thick so that the dried thickness of layer was 20 microns and dried. Then the lithography for printing was prepared and offset printing was carried out, similar good results to those in Example 2 were obtained. Mechanical strength of the hydrophilic resin layer was good.
EXAMPLE 6 EXAMPLE 7 A casting syrup was made from 100 grams of 2-hydroxyethyl methacrylate, 0.2 gram of ethyleneglycol dimethacrylate and 0.4 gram of t-butyl peroctoate. 0.2 gram of potassium dichromate and 2 grams of fine divided silica powder were added into the syrup and dispersed homogeneously. The syrup was coated on an aluminium plate so that the dried thickness was 25 microns. Then the lithography for printing was prepared and offset printing was carried out, similar good results to those of Example 2 were obtained. Mechanical strength of the hydrophilic resin layer was very good.
EXAMPLE 8 7.5 liters of ethanol, 100 grams of t-butylaminoethyl methacrylate, 150 grams of N-isopropyl acrylamide and 2.25 kilo-grams of 2-hydroxyethyl methacrylate (containing 0.3% of ethyleneglycol dimethacrylate) together with 10 grams of t-butyl peroctoate were charged into a vessel and the solution heated at 85 C. for 7 hours to effect polymerization to a 90% conversion level. 0.25 gram of maleic anhydride and 1 gram of fine divided silica powder were added into the polymer solution thus obtained, and dispersed homogeneously. The solution was coated on an aluminium plate so that the dried thickness was 35 microns. Then the lithography for printing was prepared and offset printing was carried out, similar good results to those in Example 2 were obtained. Mechanical strength of the hydrophilic resin layer was very good.
What is claimed is:
1. A printing plate comprising a basic plate, a layer of water insoluble hydrophilic acrylate or methacrylate polymer selected from the group consisting of a polymer of a hydrophilic hydroxy lower alkyl acrylate, hydroxy lower alkyl methacrylate, hydroxy lower alkoxy lower alkyl acrylate and hydroxy lower alkoxy lower alkyl methacrylate over said plate and a photosensitive layer over said hydrophilic polymer layer.
2. A printing plate according to claim 1 wherein the Water insoluble polymer comprises a polymer selected from the group consisting of a polymer of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate.
3. A printing plate according to claim 2 wherein the polymer is a linear polymer.
4. A printing plate according to claim 3 wherein the polymer is a homopolymer.
5. A printing plate according to claim 2 wherein the polymer is a copolymer of said acrylate or methacrylate with a minor amount up to 15% of a cross-linking agent.
6. A printing plate according to claim 1 wherein the water insoluble hydrophilic polymer layer includes a curing agent in an amount up to 2% by weight.
7 A printing plate according to claim 6 wherein the water insoluble hydrophilic polymer layer includes finely divided powdered inorganic material.
8. A printing plate according to claim 7 wherein the Water insoluble polymer comprises a polymer selected from the group consisting of a polymer of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate.
9. A printing plate according to claim 8 wherein the polymer is a linear polymer.
10. A printing plate according to claim 8 wherein the polymer is a copolymer of said acrylate or methacrylate with a minor amount up to 15 of a cross-linking agent.
11. A printing plate according to claim 7 wherein the fine divided powdered inorganic material is powdered silica.
12. A printing plate according to claim 7 wherein the fine divided powdered inorganic material is powdered alumina.
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