US 3829319 A
Description (OCR text may contain errors)
United States Patent 3,829,319 WETTING LIQUID COMPOSITION FOR OFFSET MASTER PLATE Shigeyoshi Suzuki and Norio Kobayashi, Kyoto, and
Kazuo Shimizu, Tokyo, Japan, assignors to Mitsubishi.
U.S. Cl. 106-2 4 Claims ABSTRACT OF THE DISCLOSURE The printability of an offset master plate can be markedly improved by using a wetting liquid composition comprising (A) at least one of transparent and water insoluble fine particles having a particle size of not more than 0.1 such as colloidal silica and alumina, (B) at least one of alkali metal salts such as sulfates, halides and nitrates of K and Na, (C) at least one of low molecular polyhydrie alcohols and polyalkylene oxides having a molecular weight of not more than 1000 such as polyethylene glycol, propylene glycol, diethylene glycol and hexylene glycol and (D) at least one of weak organic acids such as citric acid, succinic acid, tartaric acid, adipic acid, ascorbic acid and propionic acid. Said composition preferably has a pH value of about 4.0-5.6.
The present invention relates to a wetting liquid composition for improving the printability of an offset master plate and more particularly to a wetting liquid composition effective for wetting a presensitized master plate, an offset master plate which utilizes silver salt diffusion transfer system (disclosed, e.g., in Japanese Patent Publication No. 14330/ 67 and Japanese Patent Application No. 72039/67 corresponding to U.S.S.N. 71623) or a silver salt offset master plate such as photolithographic plate containing the developer as disclosed in U.S. Pat. 3,146,- 104.
It is well known that the action of wetting liquid in offset printing operation is to impart a uniform ink repellency to non-image areas (hydrophilic areas which do not accept ink) on a master plate, whereby smooth operation can be attained and clear printed matter can be obtained.
However, as often experienced by printing operations, the conventional wetting liquid is sometimes insufficient to obtain constant printed matters even by suitable wetting operation.
Furthermore, the conventional wetting liquids in which various chemical agents coexist have had difiiculties in stability in storage and moreover have had difficulty in obtaining clear printed matters. In addition, stain of ground color is readily caused due to unnecessary adhesion of ink to non-image areas of the printed matter. This is considered to occur due to kind of ink, condition of atmosphere (temperature or humidity of room), the number of wettings, etc.
On the other hand, printing operation for long period of time causes emulsification of wetting liquid by the action of oil components in ink. This emulsification prevents adhesion of ink to image areas to cause breaking of the image areas or stains of non-image areas with ink. The wetting effect and the emulsification phenomenon have close relation with each other and generally the Wetting liquids which have great wetting effect tends to cause emulsification and those which cause no emulsification show substantially no wetting effect. Therefore, it is a requirement for obtaining wetting liquids having good durability to suitably keep the balance between the two phenomena.
3,829,319 Patented Aug. 13, 1974 It has been recognized that the conventionally used wetting liquids which comprise one or more of hydrophilic materials such as CMC, gum arabic, sodium alginate, glycol compounds and metal salts of nitric acid, phosphoric acid, etc. are not suitable in the long period printing. Moreover, the state of many of these wetting liquids are extremely changeable due to kind of plates, kind of inks and dispersion of printing conditions and are not practicable. For example, when printing is conducted with use of an offset master plate which utilizes silver salt diffusion transfer system and which is obtained by undercoating a polyester film with hydrophilic subbing layer and then coated thereon a surface layer which contains nuclei for physical development which are fine particles of heavy metals or sulfides thereof and up to 30% by weight of said nuclei of a high molecular weight compound (see U.S.S.N. 71632), the emulsification is especially apt to occur and if the emulsification is controlled, the balance with the wetting effect is lost to cause stain of the printed matters.
In an attempt to eliminate the above defects, various stabilizers, dispersants and activators have been added, but such addition rather gives an effect on the aggregationprecipitation action and buffering action.
As the results of the inventors extensive researches on the above-mentioned defects and undesirable phenomena in offset printing, it has been found that a wetting liquid composition containing four components comprising (A) at least one of transparent and water insoluble fine particles having a particle size of not more than 0.1,u, especially sol of oxide or hydroxide of a metal belonging to Group III-IV of short form of the periodic table such as colloidal silica, alumina, etc., (B) at least one of organic or inorganic salts of alkali metals, especially anhydrides such as sulfates, halides, nitrates of K and Na. in some instance, those containing water of crystallization, (C) at least one of low molecular polyhydric alcohols and polyalkylene oxides having a molecular weight of not more than 1000 such as polyethylene glycol, propylene glycol, pentaerythritol, glycerol, etc. and (D) at least one of weak organic acids usually employed by one skilled in the art for accelerating printability and maintaining pH at suitable value, such as citric acid, succinic acid, tartaric acid, adipic acid, ascorbic acid, propionic acid, etc. has remarkably high stability and can extremely improve the printability of offset master plates. The polyalkylene oxides having a molecular weight of not more than 1000" means the commercially available polyalkylene oxides.
The above components (A) preferably have a particle size of no more than 0.1;, more preferably 0.00l0.5g. The reason therefore is that when it becomes aqueous dispersion, it must be transparent and must not lose water retention effect and that it must have compatibility with other components. In this case, it seems that as the result of ionic bond and covalent bond with alkali metal salt, these produce a stable dispersion.
It is most suitable to adjust the pH value after wetting to about 4.0-5.6. This adjustment is effected with said weak acids or salts thereof (e.g., sodium acetate, borax, sodium citrate).
Therefore, pH value outside said pH range causes conspicuous reduction of the printability and unstability of the liquid. Of course, said liquid is in the form of aqueous dispersion.
In this case, the limitation of the amount of the components is necessary and the fine particle component is preferably about 0.1-1%, especially about 0.5% as solid matter. The alkali metal salt component is preferably 3-8 times, especially 4-6 times the amount of said fine particles. The polyol compound is preferably about 5-10% ice although the amount depends upon control of viscosity and stability. The component weak organic acid may be used in an amount necessary for adjustment of pH and preferably 0.1-l% by weight of the wetting composition.
Thus prepared liquid is diluted to about 10-20 times. The degree of this dilution depends upon kind of plates, kind of ink and circumstance of printing (kind of printing machine, external weather conditions) and cannot be limited in a definite range. However, in the composition of the present invention, the degree of dilution of less than 10 times tends to cause emulsification phenomena while that of more than 20 times results in difliculty in wetting.
Furthermore, taking the discrimination and appearance of the liquid into consideration, coloring agents such as cobalt chloride, manganese chloride, phthalocyanine pigments, malachite green, ultramarine, etc. may be added in a slight amount.
Besides, if necessary, hydrophilic materials such as CMC, gum arabic, sodium alginate, vinyl-pyrrolidone, vinylimidazole, methyl vinyl ether, maleic anhydride, etc. which are wetting components experimentally employed by one skilled in the art, water miscible organic solvents such as methanol, dimethylformamide, dioxane, etc. and ion-containing compound disclosed in Japanese Patent Publication No. 10910/61 and US. Pat. 3.490,906 may also be added.
The present invention will be illustrated in the following Examples.
EXAMPLE 1 Part by weight Water 820 Succinic acid 6 Borax 8.4 Sodium sulfate (anhydrous) 25 Cobalt chloride (hexahydrate) 2.5 Ethylene glycol 100 Colloidal silica (20% liquid) 28 PH:4.8-
The liquid comprising the above components was diluted with water in an amount of 10 times that of the components to obtain a wetting liquid. A master plate was manufactured as follows: A polyester film base was under-coated in a thickness of 100p. and immersed in a sol prepared from the following formulation.
Palladium sulfide sol (I+IIIIII) PdCl g H01 ml 40 Water ml 1000 Na s g 8.6 Polyethylene glycol ml 30 Alkyl ether ml 10 Water Y ml 1000 III Methylvinyl ether-maleic anhydride copolymer To thus obtained offset master was transferred an image from a negative sheet by the silver salt diffusion transfer process and then the offset master plate was wetted with said wetting liquid and used for printing by the commercially available offset printing machine (printing conditions: room temperature=25 C. and relative humidity=70% 4 COMPARATIVE EXAMPLE 1 The conventional wetting liquid comprising the following components was diluted with water to 10 times.
NH H PO 10 Ni(NO 6H O v 15 CMC 4 Glycerin Water to be made 1000 ml.
COMPARATIVE EXAMPLE 2 The wetting liquid of Example 1 from which sodium sulfate and colloidal silica were omitted or replaced by sodium tertiary phosphate was used.
Comparative example Stability=Degree of clearance of the liquid after allowing to stand 7 days at constant; temperature and humidity.
Emulsitication state=Degree of clearance of the liquid and state of wetting roller after about 1 hour from beginning of printing.
Stain of ground co1or=Degree of stain of 50th, 100th, 300th, 500th and 1,000th printed matter.
(The wetting state was the same.)
The wetting effect according to the present invention was not greatly affected by difference in kind of ink and in conditions and substantially maintained the results of the above table.
EXAMPLE 2 Substantially the same effects as those of Example 1 were obtained by substituting alumina sol for colloidal silica and a mixture of 60 g. of polyethylene glycol and 20 g. of ethylene glycol for ethylene glycol in Example 1.
EXAMPLE 3 G. 4-Phenyl catechol 5 Dibutyl phthalate 50 The above components were dispersed in 300 g. of 10% gelatin solution and the resultant dispersion was dispersed in a dispersion medium comprising 25 cc. of 8% saponin solution and 180 cc. of water by colloid mill to obtain a developer dispersion. Furthermore, an aqueous dispersion having the following formulation was prepared.
G. The resultant developer dispersion Aqueous gelatin solution (10%) 400 Aqueous saponin solution (15%) 50 Formalin liquid (2%) 5 Water 425 The resultant aqueous dispersion was coated on a paper substrate to which polyethylene was laminated (coating amount: about 7 g./m. After fixation of said layer, a photosensitive liquid comprising the following components was further coated on said layer in an amount of 15 g./m.
AgCl emulsion (silver concentration 3.2 mol G. percent) 600 Aqueous saponin solution (15% 40 Formalin liquid (2%) 7 Water 830 The following fogged photosensitive liquid chemically fogged at higher than 40 C. for about 40 minutes was further coated on said layer in an amount of about 7 g./m.
G. AgCl emulsion (silver concentration 3.2 mol percent) 360 Water 200 NaOH A N 24 Formalin liquid (2%) 5 H S0 (2N) 3.5 Aqueous saponin solution (15%) Formalin liquid (2%) 2 Water 955 (Liquids I and II were mixed to obtain a coating liquid.)
Thus obtained olfset master plate was exposed through a line drawing original and treated with an aqueous solution of Na CO (4%) for about 20 sec. and furthermore with a 2% CH COOH stop solution for 1 minute. Then, this was passed through a 1% aqueous solution of phosphoric acid to obtain a master plate.
Olfset printing was conducted in the same manner as in Example 1 with use of the same wetting liquid to obtain the similar results as those in Example 1.
What is claimed is:
1. A wetting liquid composition for an offset master plate, said composition having a pH of about 4.0-5.6 and containing (A) transparent and water insoluble fine particles having a particle size of not more than 0.1g selected from the group consisting of colloidal silica and alumina, (B) a member of the group consisting of potassiurn and sodium sulfates, halides and nitrates, (C) a member of the group consisting of low molecular weight polyhydric alcohols and polyalkylene oxides having a molecular weight of not more than 1000, and (D) at least one weak organic acid, the amount of component (A) being about 0.1-l%, that of component (B) being about 3-8 times that of component (A), that of component (C) being about 5-10% and that of component (D) being about 0.110% by weight of the wetting liquid compo sition.
2. A wetting liquid composition according to claim 1 wherein (C) is a member of the group consisting of polyethylene glycol, propylene glycol, pentaerythritol, glycerol, diethylene glycol and hexylene glycol.
3. A wetting liquid composition according to claim 2, wherein (D) is selected from the group consisting of citric acid, succinic acid, tartaric acid, adipic acid, ascorbic acid and propionic acid.
4. A wetting liquid composition according to claim 1, wherein (B) is sodium sulfate.
References Cited UNITED STATES PATENTS 3,028,804 4/1962 Neugebauer et al. 101-451 3,522,062 7/1970 Shimizu et a1 1062 3,547,632 12/1970 Nadeau 101-451 3,696,746 10/1972 Harper 106-2 DAVID KLEIN, Primary Examiner US. Cl. X.R. 10l--451