US3364858A - Method for the preparation of an offset printing master - Google Patents

Description

United States Patent 3,364,858 METHSD F61 THE PREPARATION OF AN SFFSET PRlNTlNG MAfiTER Yoshio Kojima, Toshimi Kishida, Masaaki Yoshiolra, and lsanru Fushiki, Tokyo, Japan, assignors to Konishiroku Photo Industry (10., Ltd, Tokyo, Japan, a corporation of Japan N0 Drawing. Filed Sept. 9, 1964, Ser. No. 395,283 Claims priority, application Japan, Sept. 20, 1963, 38/513,228 2 Claims. (Cl. 101-467) ABSTRACT 6F THE DISCLOSURE A hydrophilic sheet such as paper bearing photographic or printed matter, is placed in contact with sheet of heatsensitive material and then subjected to infrared radiation. This causes the heat-sensitive material in contact with and corresponding to the photographic or printed matter to fuse and to form a tacky image to which a hydrophobic polymer powder is applied and then fixed as by treatment with solvent vapor or heat, to form an olfset printing master.

This invention relates to a method for the preparation of an offset printing master, and more particularly, to the preparation of an offset master by fixation of a hydrophobic polymer material on the infrared-absorbing image portion of a sheet bearing an image on a hydrophilic surface by the co-action of a heat-sensitive material also present on the said image portion.

In accordance with a method of the present invention, there is prepared a sheet bearing a hydrophilic surface with an infrared-absorbing image, e.g., photographic, printed or hand-written figures or letters, on which sheet a normally solid heat-sensitive material which can fuse, with or without decomposition, at a temperature as high as 50-150 C., leaving a fluidized mass having dustadhering property is placed on the said image area.

This master unit is then subjected to infrared radiation thereby to form on the image portion such a fluidized mass as mentioned above. To the fluidized mass, a finely powdered composition mainly comprising a hydrophobic polymer material is applied, and then fixation is effected in an appropriate manner depending on the property of the hydrophobic polymer material, thereby to produce an offset printng master. If desired, after-treatment is made so that the hydrophilic property of the sheet surface may be improved.

The preparation of an offset printing master of the enlarged size from a photographic film by using an offset master paper is heretofore known in the art. However, this is disadvantageous because of its requirement for an expensive apparatus and for complicated procedures.

The disadvantages of the prior art can be overcome by the present invention. That is to say, the present invention enables us to prepare an offset printing master not only from a paper or the like containing hand-written or printed images, but also from a photographic print containing a photographic picture obtained by enlargement from a microfilm or from a sheet containing a photographic picture obtained by a silver diffusion transfer process, without necessitating the use of any expensive apparatus or complicated procedures. The offset printing master obtained by the present invention is of the lithographic type with a slightly projected image portion, so that it is quite ink-receptive and allows of sharp printing.

It is accordingly one object of the present invention to provide a simple and economical method for the preparation of an offset printing master by utilization of a supercooling phenomenon.

Another object of the invention is to provide a method for the preparation of an offset printing master from an original by direct application of a heat-sensitive material thereto in which method irnagewise fusion of a heat-sensitive material and the subsequent fixation are effected.

Still another object is to provide a method for the preparation of an offset printing master from an original by indirect application of a heat-sensitive material theretoin which method imagewise fusion and transfer of a heatsensitive material and the subsequent fixation are effected.

Still another object of the invention is to provide a method for the preparation of an offset printing master in which image formation with a heat-sensitive material and the subsequent fusion and fixation are effected.

Other objects, features, capabilities and advantages of the present invention will be apparent from the description and claims which follow.

Now the present invention will be explained hereinbelow:

The heat-sensitive materials which can be placed on the image portion of original are such materials which are normally solid and availably maintained in the supercooled liquid or semi-solid state when they are fused with or without decomposition by heating and then cooled down to a temperature below their melting or decomposing point. Suitable heat-sensitive materials are those of highly dust-adhering property in their supercooled state and sometimes they should preferably have a tendency to be vaporized at a temperature above their melting or decomposing point.

A likelihood of a heat-sensitive material to provide high dust-adhesion may not only depend on the melting or decomposing point of the said material, but also it may be influenced by the inherent physical properties (e.g., dimensional structure of molecules, viscosity and surface tension of the fused mass), purity, particle size of the material as well as the condition at which the material is heated or cooled. A period over which the material can provide high dust-adhesion also varies depending on any of the afore-mentioned factors, and it will usually be within the range of from several minutes to several hours. Some of the heat-sensitive materials which will be specified later would be able to exhibit dust-adhering property even over two days.

Various factors on which the durability (or stability) of the supercooled state of a heat-sensitive material depends have been studied, and one of the important factors is found to be the particle size of a heat-sensitive material. For example, benzotriazole or benzotriazole-acetanilide combination can provide a greatly increased life time of their supercooled state in response to the decrease of the particle size. (The term, a combination, used herein means that it is not a simple mixture of the specified components and obtained by fusing, solidifying and then pulverizing the said simple mixture). At a certain limit of particle size, the life time of the heat-sensitive material is increased unexpectedly, and it is indicated that if the material has a particle size below the critical limit, the supercooled state can be maintained as long as several days. It is further assumed that a suitable combination of two substances, even if each of the said substances has no good stability of the supercooled state, would be highly improved in its supercooling stability.

Generally speaking, a heat-sensitive material useful in the practice of the invention has a particle size ranging from 1 micron to microns, depending on the type and nature of the said material.

Suitable heat-sensitive materials may be either inorganic or organic substances, and various ones are useful for this invention. Typical inorganic materials which melt with out decomposition or melt with vaporization include simple substances like sulfur and compounds like the halides of a non-metal, e.g., antimony and phosphorus. Typical-organic materials include fructose, glucose, maltose or the like sugars; acids and their salts, such as benzoic acid, cinnamic acid, maleic anhydride, sebacic acid, malic acid, phthalic anhydride, potassium sodium tartrate, ammonium citrate, etc.; acid amides, such as acetanilide, phenacetin, acetylsemicarbazide and urea. Other organic substances have also been found to be suitable herein, which include sodium diethylthiocarbamate, iodoform, p-dimethylamino-benzaldehyde, methylhydroquinone, resorcine, l-phenyl-3-pyrazolidine, benzotriazole, dimedone, B-naphthol, sorbitol, etc. Use of a heat-sensitive material which is normally solid and decomposes by heating also is possible. The fluidized mass resulted from such heat-decomposable material will comprise, in addition to the supercooled melt of the original material, the supercooled comelt of the decomposition products which may be the normally solid material and the normally oily or semisolid material. Typical materials which will leave a liquid decomposate with decomposition by heating are hydrazine sulfite, p-toluenesulfonylhydrazide, diphenyl-4,4-diazide, etc.

The heat-sensitive material mentioned above should be used in such a state that it is placed on the image area of an original from which an offset printing master isto be produced. In one embodiment of the present invention, a heat-sensitive material is distributed directly onto the image-bearing surface of an orginal by lightly rubbing said surface several times with an absorbent cotton, a felt, a cloth or the like containing the fine powder of the heatsensitive material which has been pulverized to the particle size of ll microns. An alternative method for forming a heat-sensitive layer directly on an original comprises dissolving a heat-sensitive material into a volatile solvent, spraying the resulted solution in an aerosol form onto the image-bearing surface of an original or coating said solution onto the image-bearing surface of an original with a brush, a cloth, a felt, an absorbent cotton or the like as impregnated with said solution and then drying the original. In the latter case, it is important to be careful that ink of the letters or figures on the surface of an original if it is hand-written or printed should not be dissolved to blot on the surface. Further alternatively, the heat-sensitive material may be either incorporated into a paper stock or sized over the surface of papers, in order to produce an offset printing master paper having an internal or top layer of the heat-sensitive material. Still further, when a heat-sensitive material which is not decomposed by heat and which is considerably vaporizable, e.g., sulfur, is employed, it is possible to have such heatsensitive material deposit thereon as a thin, uniform heatsensitive layer in vacuo.

In another embodiment of the present invention, the above heat-sensitive material may be used in a layer on a suitable support other than an original. In other words, a specific heat-sensitive sheet comprising a transparent support and thereon a layer of the heat-sensitive material is used in this embodiment. In order to prepare such a heat-sensitive sheet as referred to above, the following typical procedures will be in order: The heatsensitive material, together with the small amount of a binder, is prepared as a solution or dispersion which is then applied or sprayed onto the surface of a transparent support which suitably is a tracing paper, a cellophane or a plastic film. Alternatively, a heat-sensitive material being as fine as 1-100 microns in particle size can be rubbed onto the said surface to produce a useful heat-sensitive sheet. The heat-sensitive sheet thus prepared is brought into contact with the image-bearing surface of an original, and then the composite is irradiated with infrared ray from the side of the said heat-sensitive sheet, so as to effect imagewise fusion and subsequent transfer of the heatsensitive material onto the image portion of the original which is then further processed to have an offset printing master. 7 a

In still another embodiment of the present invention, imagewise application of a heat-sensitive material is effected directly onto a paper which can be suitably processed to produce an offset printing master. The characteristic of this embodiment is that image formation with and distribution of a heat-sensitive material on a sheet can be carried out at one time. In this preferable emf.

bodiment, for example, letters or figures or other images are printed or drawn with an ink containing a heat-sensitive material on a suitable paper. Handwriting, type-writing or printing can be employed at option. The printed or drawn paper is then processed by infrared irradiation and fixing to produce an offset printing master.

In the practice of the present invention, an original treated with the heat-sensitive material is subjected to infrared radiation, whereby the heat-sensitive material corresponding to the image portion is fused with or without decomposition and it remains as the fluidized mass having dust-adhering property for a significant period even when it is cooled to room temperature. The image-bearing surface of the original is then treated with the finely powdered hydrophobic polymer material so as to have the polymer material adhere on the image portion only of the original, and after an excess of the hydrophobic polymer material is removed from the non-image portion, fixation is made over the whole surface of the original. Alternatively, an untreated original is brought into contact with a heat-sensitive sheet on which a heat-sensitive material is present as a top layer and then the composite is subjected to infrared radiation, whereby the heatsensitive material corresponding to the image portion is fused and transferred from the sheet to the image portion of the original. After separation of the sheet from the original, a fluidized mass having dust-adhering property on the image portion of the original is treated with a hydrophobic polymer material so as to effect selective adhesion of the material onto the image portion of the" original. Fixation is conducted in the same manner as above.

In carrying out infrared irradiation for the process of the present invention, it is convenient to use a quartz infrared lamp as a heat source. Exposure should preferably be as short as possible in order to have an effective utilization of heat uptaken by the image portion of an original, while avoiding heat loss due to transport to the non-image portion and this may be accomplished by employing a heat source having a high output. In general, when a quartz infrared lamp of 30-100 watts/cm. output is used, appropriate infrared radiation can be made at the distance of 1 cm. from the radiation source for 0.05 to 1.0 sec. A Thermofax copying machine (manufactured by Minnesota Mining & Mfg. Co., USA.) may be conveniently used for this purpose.

A hydrophobic polymer material usable in this invention should be such that it can melt or soften at a comparatively low temperature or can be easily dissolved in an organic solvent. Preferably, the hydrophobic polymer material is used in the form of a fine powder having the particle size of 5-100 microns. Suitable polymer materials are polystyrene resin (for example, Piccolastic B75 and Piccolastic Dl00, both of which are commercially manufactured and sold by Pennsylvania Industrial and Chemical Co.), styrene-butadiene copolyrner resin (for example, Pliolite S4, Pliolite S5 and Pliolite S6, all of which are commercially manufactured and sold by Goodyear Tire & Rubber Co.), polyindenecournarone resin (for example, Cumar P-10 and Cumar P25, both of which are commercially manufactured and sold by Allied Chemical Corp.) and the like resins. Usually a toner usable for electrostatic photographic processes can be employed for the instant purpose. By using a colored pigment in combination with the polymer material, it is possible to visually ascertain the degree of adhesion of the polymer material.

Fixation of the hydrophobic polymer material can be carried out by either one of heating or solvent treatment, depending on the type of the said polymer material. If a heat-fusible resin is used as the hydrophobic polymer material, heating up to the softening point of the resin (usually 50200 C.) is sufiicient. Where a solventsoluble resin is used as the hydrophobic polymer material, the image-bearing surface to be fixed is exposed to solvent vapor until the resin particles adhering on the image portion is converted to an aggregated mass. As apparent for those skilled in the art, it is understood that the solvent used here should be a non-solvent for printing ink.

The original thus treated now has two portions, i.e., the image portion which is hydrophobic and the noniruage portion which is not hydrophobic, and so it is ready for use as an offset printing master. However, if the nonimage portion of the master is still insufiicient in hydrophilic or oleophobic property, it is advantageous to treat the said master with an etching solution which suitably is an aqueous solution of a hydrophilic polymer substance, e.g., gum arabic, sodium carboxymethyl cellulose, etc., or an alkaline solution, for example, containing sodium hydroxide or sodium carbonate, or the mixture of these two solutions, thereby improving the hydrophilic or oleophobic property of the non-image area of the master. Usually for a commercially available photographic paper, such hydrophilic treatment is necessary or appropriate.

The following examples describe certain ways in which the principle of the invention has been applied, but are not to be construed as limiting its scope.

Example 1 Water (50 C.) 1 cc 750 Metol (Monomethyl p-aminophenol sulfate) g 2 Anhydrous sodium sulfite g 40 Hydroquinone .n g 8 Sodium carbonate (monohydrate) g 47 Potassium bromide g 2 Water to make 1 1 After completion of the development, the print is processed in the usual manner, i.e., by short stop, fixing, rinsing for 10 minutes and then drying. The print thus obtained is used as an original.

Commercially available sulfur powder is rubbed over the image-bearing surface of the original by means of a buffing roller. Then, the original is subjected to infrared radiation using a 2,300 kw-output quartz infrared lamp of 50 cm. long at the distance of 1 cm. from said original at the relative speed of 12 cm./sec. Thereafter, Konifax toner PP (an electrostatic photographic toner commercially manufactured and sold by Konishiroku Photo Industry Co., Ltd.) is dusted over the original trereby to have the toner adhere on the image portion. The toner on the non-image portion is removed by the action of compressed air. Then, fixation of the image portion is made by irradiation from the said quartz infrared lamp at the relative speed of 5 cm./sec., thereby to converting the image portion to oleophilic.

The non-image portion of the original thus treated has insufiicient hydrophilic property and may be stained with ink. In order to avoid this, surface treatment of the original is preferably made with an etching solution containing 0.5 g. sodium hydroxide and 0.05 g. sodium carboxymethyl cellulose in 100 cc. of Water. The original is now ready for use as an offset printing master.

Example 2 In this example, an offset printing master is prepared by applying a heat-sensitive material onto only the image portion of matter printed on an art paper with an infrared-absorbing ink through imagewise transfer of the heat-sensitive material from a heat-sensitive sheet, and then fixing thereon a hydrophobic polymer material.

The heat-sensitive sheet used is prepared by strongly rubbing the finely powdered benzotriazoleacetanilide (:25 by weight) combination with the particle size of 1-100 microns over a tracing paper by means of a buffing roller, the said combination being obtained by mixing and fusing the specified components and then pulverizing the fused mass.

The image-bearing surface of an original is brought into contact with the heat-sensitive surface of the heatsensitive sheet, and then the resulted composite is subjected to infrared radiation from the side of the heatsensitive sheet in the same manner as in Example 1. After irradiation with infrared ray, the original is separated from the heat-sensitive sheet and then dusted with finely powdered Piccolastic D-75 so as to have it adhere on the image portion of said original. Fixation is elfected by using trichloroethylene vapor. Now the original is ready for use as an offset printing master.

Example 3 On a photographic paper having a light-sensitive silver chlorobromide emulsion layer, a protective coating is provided by using the following formulation:

Gelatin g 1.6 p-Toluenesulfonylhydrazide (heat-sensitive material) tg Water cc The photographic paper with the protective coating is printed and processed by development, fixation and rinsing in the same manner as in Example 1, thereby to obtain an original. Then, the original is subjected to infrared irradiation with a quartz infrared lamp (same as that of Example 1) at the distance of 1 cm. at the speed of 15 cm./sec. The original is treated with finely powdered Piccolastic D-75 in order to make the image portion lipophilic and then immersed for 2 minutes for an etching solution of 0.2 g. of sodium hydroxide and 0.02 g. of sodium carboxymethyl-cellulose in 100 cc. of water in order to improve the lipophobic nature of the non-image portion. The original thus treated is ready for use as an offset printing master.

Example 4 Typewriting is made on a commercially available offset master paper with a typewriting ribbon impregnated with an ink of the following formulation:

G. Mineral oil 108 Carbon black 3O Oleic acid 20 Oil-soluble coloring matter 5 Sebacic acid 3 Benzotriazole 1 75 portions.

What We claim is:

1. A method for the preparation of an offset printing master which comprises typewriting on paper having a hydrophilic surface with an infrared absorbing ink containing powdered material which melts at 50 to 150 C. and has a particle size Within the range of 1 to 100 microns, then irradiating the resulting type-written paper, with infrared irradiation and then dusting it with hydrophobic polymeric material having a particle size of 1 to 100 microns whereby said polymeric material adheres to the type areas and fixing the adhered polymeric material to form the hydrophobic image portions of the printing master.

2. The method for the preparation of an ofiset printing master of claim 1 wherein the powdered material contained in the ink is sebacic acid and benzotriazole and the hydrophobic polymeric material is cournarone-indene resin.

References Cited UNITED STATES PATENTS 2,503,758 4/1950 Murray 101149.4 3,132,963 5/1964 Jarvis 101-149.4 3,196,029 7/1965 Lind 101-149.4 X 3,260,612 7/1966 Dulmage et a1. 101-149.2 X

DAVID KLEIN, Primary Examiner.