JPH08108662A - Developing ink for lithographic printing plate - Google Patents

Abstract

PURPOSE: To obtain developing ink for imparting a visible image with a superior stability with time and without occurrence of filling up by a method wherein the ink is made of an emulsion of an aqueous-phase component containing water, an acid component, and a water-soluble soybean polysaccharide and an oil-phase component containing a volatile solvent incompatible with water and a coloring agent. CONSTITUTION: Developing ink for lithographic printing plate at least contains a) water, b) an acid component, and c) a water-soluble soybean polysaccharide as 1) an aqueous-phase component as well as d) a volatile solvent incompatible with water and e) a coloring agent as an oil-phase component. The ink also contains (3) other components, as required, i.e., f) an alkali metal salt or an ammonium salt, g) a lipophilic polymer compound soluble in the volatile solvent of the g) component, h) an emulsifying agent, i) sensitizing agent, j) a wetting agent, k) an antiseptic agent, and l) a thickening substance, such as silicon fine powder, talc, and zeolite. This developing ink can be effectively used for any lithographic printing plate, but has an excellent effect esp. in the application to a lithographic printing plate obtained by subjecting a presensitized plate of a photosensitive printing plate with an aluminum substrate to an image exposure and a development.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing ink for a lithographic printing plate, and more particularly to an emulsion type developing ink for a lithographic printing plate.

[0002]

2. Description of the Related Art Lithographic printing is a printing method that makes good use of the property that water and oil are essentially immiscible. The printing plate surface receives water and repels areas that repel oil-based ink and water. Then, the former is called a non-image area and the latter is called an image area. The lithographic printing plate may be treated with a composition called a developing ink in order to easily maintain and increase the oil sensitivity of the image obtained after development and facilitate plate inspection. More specifically, this developing ink composition for a lithographic printing plate makes it easy to visually distinguish the image area and the non-image area of the lithographic printing plate, facilitates correction (erasure) of unnecessary image areas, and is a lipophilic substance. Applied to the lithographic printing plate for the purpose of adhering the image area to the image area to increase the acceptability of the printing ink and further to protect the image area in various operations such as gumming performed thereafter. Is.

In recent years, as the developing ink, a type of ink in which an oil phase containing a colorant and an aqueous phase containing an acidic component are emulsified is used. However, when such an emulsion type developing ink composition is applied to a halftone dot image formed on a lithographic printing plate, so-called kalami (i.e., a lipophilic substance contained in the developing ink composition, Adhesion occurs so as to bridge between adjacent halftone dots or to cover a small non-image area surrounded by the image area.). Further, the developing ink itself had an insufficient point in terms of stability with time (that is, the property that the performance immediately after production is maintained even after a long time has passed).

[0004]

That is, the object of the present invention is to solve the above-mentioned problems of the prior art,
It is an object of the present invention to provide a developing ink that does not cause karami. Another object of the present invention is to provide a developing ink having excellent stability over time. Another object of the present invention is to provide a developing ink that gives a visible image that faithfully reproduces the image area of a lithographic printing plate. Yet another object of the present invention is to provide a developing ink which can be applied onto a lithographic printing plate with a simple tool.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted various studies to achieve the above-mentioned objects, and as a result, a water-soluble soybean polysaccharide has been found to be an emulsion-type protective colloid for emulsion-type developing inks for lithographic printing. It has been found that the action is made extremely large, whereby a stable fine emulsion can be obtained, and the above object of the present invention is achieved. That is, the present invention is an emulsion of water, an aqueous phase component containing an acidic component and a water-soluble soybean polysaccharide, and an oil phase component containing a water-immiscible volatile solvent and a colorant, A characteristic developing ink for lithographic printing plates.

The developing ink for lithographic printing plate of the present invention will be described in detail below. The developing ink for a lithographic printing plate of the present invention contains at least the following components (a) to (e). Water phase component (a) Water (b) Acid component (c) Water-soluble soybean polysaccharide Oil phase component (d) Water-immiscible volatile solvent (e) Colorant The components (f) to (l) can be included. Others (f) Alkali metal salt or ammonium salt, (g) Lipophilic polymer compound dissolved in volatile solvent of component (d), (h) Emulsifier, (i) Sensitizer, (j)
Wetting agents, (k) preservatives, (l) silicon fine powder, talc, thickening substances such as zeolite.

In the present invention, (a) an acidic component (b) which is soluble in water as a constituent component used in the above aqueous phase, for example, a mineral acid such as phosphoric acid, metaphosphoric acid, sulfuric acid, nitric acid, citric acid, Organic acids such as malic acid, glacial acetic acid, lactic acid, oxalic acid, phytic acid, malonic acid, tartaric acid, hydroxyacetic acid and gluconic acid are useful. Further, the alcal earth metal salts and ammonium salts of these mineral acids and organic acids can be preferably used. You may use together at least 1 type, or 2 or more types, such as a mineral acid, an organic acid, and these salts. The preferred pH range of the developing ink composition of the present invention obtained by adding the acidic component (b) is 1 to 5, and the most preferred range is 2 to 4.
Is. Among the above-exemplified compounds, phosphoric acid, metaphosphoric acid, and phytic acid are particularly preferable because they have a function of adjusting the pH and also have an effect of preventing stains on the non-image area.

The water-soluble soybean polysaccharide (c) that can be used in the present invention is a polysaccharide (a kind of hemicellulose) obtained by extracting raw soybean with water. Preferably, the constituent sugars include rhamnose, fucose, arabinose, xylose, galactose, glucose, and uronic acid, and the viscosity in a 0.1 M sodium nitrate solution is measured using a standard vullan (available from Showa Denko KK). The average molecular weight measured by the limiting viscosity method is 50,000 to 1,000,000, and the specific illuminance (25 ° C)
Is 15 or more, is a water-soluble polysaccharide that is water-soluble, has adhesive properties, and has film-forming properties. The water-soluble soybean polysaccharide that can be used in the present invention preferably has a viscosity of a 10 wt% aqueous solution in the range of 5 to 100 cP. The content of soybean polysaccharide as an emulsion-stabilizing protective colloid in the developing ink composition for a lithographic printing plate of the present invention is preferably 0.3 to 50% by weight, more preferably 1 to 40% by weight. As commercially available products, Soya Five-LN-1 (manufactured by Fuji Oil Co., Ltd.),
Soya Five-S-LN-1 (manufactured by Fuji Oil Co., Ltd.) and the like can be mentioned. As a method for producing such a water-soluble soybean polysaccharide, any method may be used.
It can be manufactured by the method as described in Example 1 described in Japanese Patent No. 32701.

One aspect of a method for producing a water-soluble soybean polysaccharide will be described. The production method is as follows: Water is added to raw okara obtained in the isolated soybean protein production process in an amount of 2 times by weight, and the pH is adjusted with hydrochloric acid.
Is adjusted to 4.5 and hydrolyzed at 120 ° C. for 1.5 hours,
After cooling, centrifugation (10000 g × 30 minutes) was performed to separate the supernatant into a precipitate, and the precipitate was washed with an equal weight of water and centrifuged to combine the supernatant with the above supernatant. If necessary, a method of obtaining a water-soluble polysaccharide by drying a liquid obtained by treating with an activated carbon column can be mentioned.

These soybean polysaccharides are dissolved in water or warm water and used as a uniform aqueous solution. In the present invention, soybean polysaccharide may be used in combination with other starch or modified starch such as dextrin. Further, another water-soluble polymer compound may be added. For example, gum arabic, fibrin derivatives (for example, carboxymethyl cellulose, carboxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, etc.) and modified products thereof, polyvinyl alcohol and its derivatives, polyvinylpyrrolidone, polyacrylamide and its copolymers, vinyl methyl ether. / Maleic anhydride copolymer, vinyl acetate / maleic anhydride copolymer, styrene / maleic anhydride copolymer and the like.

In the present invention, an alkali metal salt or ammonium salt which is the compound (f) can be preferably added to the aqueous phase component. The compound has a function of making the non-image area of the lithographic printing plate hydrophilic and preventing the oil phase of the developing ink from remaining in the non-image area, and the effect of being contained in the oil phase component in the non-image area during washing with water. It has the effect of facilitating the removal of oily components. Examples of the alkali metal salt or ammonium salt which gives particularly excellent effects include water-soluble alkali metal salts and ammonium salts of acids such as acetic acid, molybdic acid, boric acid, nitric acid, sulfuric acid, phosphoric acid and polyphosphoric acid. Is ammonium acetate, sodium acetate,
Potassium acetate, sodium molybdate, potassium molybdate, sodium borate, ammonium borate, lithium nitrate, sodium nitrate, potassium nitrate, sodium phosphate monobasic, sodium phosphate dibasic, sodium phosphate tribasic, potassium phosphate monobasic, potassium phosphate dibasic, Examples thereof include potassium triphosphate, ammonium triphosphate, sodium polyphosphate, and the like. Among the above, particularly preferred are potassium acetate, sodium borate, ammonium borate, potassium nitrate, sodium molybdate, potassium molybdate, and potassium sulfate. The compound of the component (d) can be used alone or in combination of two or more kinds, and is 0.1 to the total weight of the developing ink composition of the present invention.
It is used in the range of 10 to 10% by weight, preferably 0.2 to 5% by weight.

Next, the oil phase in the developing ink of the present invention will be described. As the volatile solvent of the component (d) used in the present invention, those which are immiscible with water can be used,
More preferably, it is selected from those which do not adversely affect the image area of the lithographic printing plate and have low toxicity. Preferred specific examples of such a volatile solvent include turpentine oil, xylene, toluene, n-heptane, solvent naphtha, petroleum fractions such as kerosene and mineral spirits, and hydrocarbon solvents having a boiling point of about 120 to 250 ° C. These can be used alone or in combination of two or more. Also, with these hydrocarbon volatile solvents,
For example, cyclohexanone, ketones such as methyl ethyl ketone, glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monophenyl ether,
For example, ethers such as phenyl glycol, esters such as butyl acetate and amyl acetate, alcohols such as benzyl alcohol and amyl alcohol,
For example, halogenated hydrocarbons such as ethylene chloride and trichloroethylene can be used in combination, whereby the resin of the component (g) can be easily dissolved, or the water phase and the oil phase can be easily emulsified. Like The solvent of the component (d) is 3 to 30% by weight, more preferably 5 to 25% by weight, based on the total weight of the developing ink composition of the present invention.
Used in the range of. In addition, the latter solvent (that is,
A solvent used in combination with a hydrocarbon solvent. ) Is 5% by weight or less based on the total weight of the solvent of component (d), and more preferably 2 to
It is used in such a range that it occupies 3% by weight.

The colorant of the component (e) used in the present invention is used after the oil phase contained in the developing ink of the present invention adheres to the image area of the lithographic printing plate and the solvent of the component (a) evaporates. , Used to provide visual contrast with non-image areas and can be selected from a wide range of dyes and pigments. Carbon black can be mentioned as a preferable example. The colorant as the component (e) is contained in the oil phase in a range that gives a desired concentration, but is preferably 0.3 to 10% by weight, more preferably based on the total weight of the developing ink composition of the present invention. Is used in the range of 1 to 7% by weight. If necessary, the oily dye may be used in combination with blue or black.

The lipophilic polymer as the component (g) can be preferably added to the oil phase in the present invention. As the lipophilic polymer as the component (g), any lipophilic polymer which can be dissolved in the solvent as the component (d) can be used. In particular, those used as a lithographic printing plate ink vehicle can be preferably used. As an example, rosin, for example, maleica rosin (rosin / maleic anhydride adduct), modified rosin such as hydrous rosin, for example, petroleum resin such as gilsonite, epoxy resin, polyvinyl formal, polyvinyl butyral, etc. can be used. A particularly useful binder is petroleum resin. The resin of component (g) can be used alone or in combination of two or more kinds, and the amount thereof is 0.1 to 10% by weight, more preferably the total amount of the developing ink composition of the present invention. It is in the range of 0.3 to 5% by weight.

The emulsifier (surfactant) of component (h) preferably used in the oil phase in the present invention is used to emulsify the aqueous phase and oil phase of the developing ink of the present invention to obtain a stable emulsion. However, it can be said to be a component that substantially constitutes the oil phase. Such a surfactant is its HLB
Those having a value in the range of 1 to 8 are preferable. Such surfactants include, for example, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers,
Polyoxyethylene polystyryl phenyl ether, polyoxyethylene polyoxypropylene alkyl ether, glycerin fatty acid partial ester, sorbitan fatty acid partial ester, pentaerythritol fatty acid partial ester, propylene glycol monofatty acid ester,
Sucrose fatty acid partial ester, polyoxyethylene sorbitan fatty acid partial ester, polyoxyethylene sorbitol fatty acid partial ester, polyethylene glycol fatty acid ester, polyglycerin fatty acid partial ester, polyoxyethylenated castor oil, polyoxyethylene glycerin fatty acid partial Examples include esters, fatty acid diethanolamides, N, N-bis-2-hydroxyalkylamines, polyoxyethylene alkylamines, triethanolamine fatty acid esters, trialkylamine oxides, and the like. Among them, polyoxyethylene alkyl phenyl ethers, polyoxyethylene-
Polyoxypropylene block polymers and the like are preferably used. Of these, sorbitan fatty acid esters are particularly excellent. Specific examples include sorbitan monolaurate, sorbitan monopalmirate, sorbitan monostearate and the like.

Further, in the present invention, it is preferable to use an anionic surfactant together, because a suitable emulsion can be obtained. Examples of the anionic surfactant include fatty acid salts, abietic acid salts, hydroxyalkanesulfonic acid salts, alkanesulfonic acid salts, dialkylsulfosuccinic acid salts, linear alkylbenzenesulfonic acid salts,
Branched chain alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkylphenoxy polyoxyethylene propyl sulfonates, polyoxyethylene alkyl sulfophenyl ether salts, N-methyl-N
-Sodium oleyl taurine, N-alkylsulfosuccinic acid monoamide disodium salt, petroleum sulfonate, sulfated castor oil, sulfated tallow oil, sulfate ester salt of fatty acid alkyl ester, alkyl sulfate ester salt, polyoxyethylene alkyl ether sulfate Ester salts, fatty acid monoglyceride sulfuric acid ester salts, polyoxyethylene alkylphenyl ether sulfuric acid ester salts, polyoxyethylene styryl phenyl ether sulfuric acid ester salts, alkyl phosphoric acid ester salts, polyoxyethylene alkyl ether phosphoric acid ester salts, polyoxyethylene alkylphenyl ether phosphoric acid Ester salts, partially saponified products of styrene-maleic anhydride copolymer, partially saponified products of olefin-maleic anhydride copolymer, naphthalene Hong formalin condensates and the like. When two or more of the above-mentioned surfactants are used in combination rather than one, they function as an emulsifier. In the present invention,
The surfactant is used in the range of 0.1 to 5% by weight based on the total weight of the developing ink composition of the present invention.

Further, the oil phase in the present invention comprises the component (i)
An oil-sensitizing agent can also be added. For example, plasticizers such as dihexyl phthalate, dioctyl phthalate, and dibutyl phthalate, fats and oils such as beef tallow, oleic acid, lauric acid, valeric acid, nonyl acid, capric acid, mysteric acid, and palmitic acid having 5 to 25 carbon atoms. Organic carboxylic acids and the like can be contained alone or in combination of two or more. These compounds have an effect of preventing the image area of the printing plate from being adversely affected by the developing ink composition of the present invention. Therefore, when the developing ink composition of the present invention is applied to a lithographic printing plate having an image region which is particularly susceptible to adverse effects, it is preferable to contain the above compound. These compounds are contained in an amount of 0.05 to 8% by weight, preferably 0.1 to 8% by weight, based on the total weight of the developing ink composition of the present invention.
It can be used in the range of 5% by weight. In addition to the above components, ethylene glycol, propylene glycol, triethylene glycol, butylene glycol, hexylene glycol, diethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, diglycerin and the like are preferably used as the wetting agent for component (j). These wetting agents may be used alone or in combination of two or more. Generally, it is preferred to use the wetting agent in an amount of 1 to 25% by weight. Further, the component (k) used in the present invention
As the preservative, for example, phenol or its derivative, formalin, imidazole derivative, sodium dehydroacetate, 4-isothiazolin-3-one derivative, benzisothiazolin-3-one, benztriazole derivative, amidinganidin derivative, quaternary ammonium salt, pyridine , Quinoline, guanidine and other derivatives, diazine,
Examples thereof include triazole derivatives, oxazoles, oxazine derivatives and the like. The preferred addition amount is bacteria, mold, yeast, etc., which is an amount that exerts a stable effect, and bacteria,
Although it varies depending on the types of mold and yeast, it is preferably in the range of 0.01 to 4% by weight with respect to the developing ink at the time of use, and two or more preservatives so as to be effective against various molds and sterilization. Is preferably used in combination. Further, fine powder of silicon, talc, zeolite or the like can be added as the component (l) viscosity modifier used in the present invention.

Next, a typical method for preparing the developing ink of the present invention will be described. To prepare the aqueous phase, first, the water-soluble soybean polysaccharide as the component (c) and other necessary water-soluble polymers are dissolved in water (a). After dissolution, the acidic component of (b) and, if necessary, the alkali metal salt or ammonium salt of component (f) are dissolved, and then a pH adjuster is added as necessary to prepare an aqueous phase of the developing ink composition of the present invention. To be done. Separately, the lipophilic polymer compound of the component (g) is dissolved in the volatile solvent of the component (d) of the oil phase, and the colorant of the component (e) and the emulsifier of the (h) are added thereto, and then a ball mill, a roll mill, Mix well using a colloid mill to prepare an oil phase. While stirring the aqueous phase with a stirrer, the oil phase was added dropwise thereto to obtain a dispersion, which was further emulsified with a homogenizer, and thus the developing ink of the present invention was obtained.

The developing ink of the present invention can be effectively used for lithographic printing plates obtained by any method, but in particular, a photosensitive printing plate presensitized plate having an aluminum plate as a support is used. ,
Abbreviated as PS version. When a) is used for a lithographic printing plate obtained by imagewise exposing and developing, a particularly excellent effect is obtained. Preferred such PS plates are, for example, from a mixture of shellac with a diazo resin (a salt of a condensate of p-diazodiphenylamine and formaldehyde) as described in GB 1,350,521. A photosensitive layer provided on an aluminum plate, a diazo resin as described in British Patent Nos. 1,460,978 and 1,505,739, and a hydroxyethyl methacrylate unit or hydroxy. Negative PS plates, such as those having a light-sensitive layer comprising a mixture with a polymer having ethyl acrylate units as the main repeating unit on an aluminum plate, and JP-A-50-12.
A positive PS plate in which a photosensitive layer made of a mixture of an o-quinonediazide photosensitive material and a novolac type phenolic resin as described in Japanese Patent No. 5806 is provided on an aluminum plate is included. Further, a PS plate having a photosensitive layer of a photocrosslinkable photopolymer as specifically shown in U.S. Pat. No. 3,860,426 on an aluminum plate, U.S. Pat. No. 4,072,528. No. and No. 4,072,
PS plate having a photosensitive layer of a photopolymerizable photopolymer composition as described in each specification of 527 provided on an aluminum plate, British Patent Nos. 1,235,281 and 1,495,861. A PS plate having a light-sensitive layer made of a mixture of an azide and a water-soluble polymer as described in each of the above-mentioned specifications on an aluminum plate is also preferable.

Next, an example of use of the developing ink of the present invention when using a PS plate will be described. Image exposure of PS plate first
Then, development is performed to prepare a lithographic printing plate. The planographic printing plate is washed with water, squeezed with water on the plate surface, an appropriate amount of the developing ink of the present invention is poured on the plate surface, and the developing ink is rubbed with a sponge or the like so as to coat the entire surface of the plate. As a result, the oil phase of the developing ink uniformly adheres only to the image area on the plate surface, the solvent of the oil phase evaporates, and the image area is visualized. Next, the plate surface is washed with water to complete the processing step with the developing ink. After that, if necessary, erase unnecessary image areas formed on the plate surface, and if printing is not started immediately, for example, apply an aqueous solution of gum arabic to protect the non-image areas and store the planographic printing plate. To be done. On the other hand, when printing is started immediately, the developing ink adhering to the image area is removed by using the solvent of the component (a) or the like, and thereafter printing is started according to a normal procedure.

The developing ink of the present invention has the following features. (1) There is no occurrence of karami. In particular, a shadow portion area on the lithographic printing plate corresponding to a portion of the printed matter having a high image density (in this area, the area of the non-image area per unit area is much smaller than that of the image area, and the color is easily generated).
It has excellent performance in that there is no occurrence of karami. (2) Even when stored for a long time, the aqueous phase and the oil phase are not separated, the performance is not deteriorated, and the storage stability with time is excellent. (3) A visible image that faithfully reproduces the image area on the planographic printing plate is provided. Therefore, it is advantageous in examining the quality of the finished planographic printing plate by enlarging and observing the shadow portion of the planographic printing plate with a magnifying glass or the like. (4) When applied to the planographic printing plate, it can be applied by using a sponge or the like, so that the operation is easy and the work efficiency is increased. (5) It has no adverse effect on both the image area and the non-image area of the planographic printing plate. For example, the ability to accept printing ink in the image area is not reduced, and the non-image area is not easily stained with the printing ink.

[0022]

The present invention will be described in more detail based on the following examples, but the scope of the present invention is not limited thereto. In addition, "part" shall mean a "weight part." Example 1 Petroleum resin (Petrosin # 8 manufactured by Mitsui Petrochemical Co., Ltd.) was added to a mixed solvent of 155 parts of turpentine oil and 30 parts of cyclohexanone.
0) 10 parts were dissolved. To this solution, sorbitan monostearate (trade name: Span 60, manufactured by Kao Atlas Co., Ltd.)
15 parts and sorbitan monooleate (brand name nonion op
-80, Nippon Oil & Fats Co., Ltd. 5 parts was melt | dissolved, it put into the container made from a porcelain, 20 parts of asphalt powder and 15 parts of carbon black were then added, and it was made to disperse | distribute with the ball mill for 20 to 24 hours, and the oil phase was obtained. Separately, as an aqueous phase, water-soluble soybean polysaccharide (Soya Five-LN-manufactured by Fuji Oil Co., Ltd.) was added to 66.0 parts of water.
1: Analytical value galactose 43.6%, arabinose 2
2.5%, galacturonic acid 2.2%, residual protein 7%)
3.0 parts were dissolved, 4 parts glycerin were mixed, and 1 part phosphoric acid (85% by weight), 0.5 part sodium monophosphate and 0.5 part ammonium acetate were dissolved. Further, 0.4 part of a 4-isothiazoline derivative was dissolved as a preservative to obtain an aqueous phase. While stirring the aqueous phase (total amount) with a stirrer, 25 parts of the completely dispersed dispersion oil phase was slowly added dropwise to disperse the mixture, which was then passed through a homogenizer to form an emulsion, which was used as the developing ink composition (1) of the present invention. made.

The positive photosensitive lithographic printing plate described in Example 1 of JP-A-50-125806 (Japanese Patent Application No. 49-33264) is shaded by the method described in Example 1. The image with fine halftone dots was exposed, developed, and washed with water. A small amount of the above-mentioned developing ink composition was applied onto the image of this lithographic printing plate, and this was applied by spreading it over the entire surface of the plate with a sponge. Then, when the plate was washed with water, the developing ink composition in the non-image area was washed out, and the oil phase of the developing ink composition adhered only to the image area, and a black image was formed on a white background of aluminum. When the obtained image was observed with a magnifying glass, the original image was faithfully reproduced without the occurrence of coloration even in the halftone dot image portion.
This plate was coated with a 14 ° Be aqueous gum arabic solution, buff dried, and stored for 1 month. The plate after storage was washed with water to remove gum arabic, and then the developing ink adhering to the image area was removed with a solvent naphtha. Then, the plate was mounted on a printing machine and printed. A printed matter was obtained. The developing ink composition (1) was used after being stored in a hermetically sealed container for 1 year, and the same result as above was obtained. Comparative Example 1 A developing ink composition was prepared in the same manner as in Example 1 except that the water-soluble soybean polysaccharide was replaced with gum arabic. The developing ink composition of Example 1 and the developing ink composition of Comparative Example 1 were visually evaluated in a transparent sealed container for emulsion stability over time. In Comparative Example 1, liquid separation occurred within 1 week. It can be seen that in Example 1 of the present invention, it does not separate even after storage for one month, and the stability with time is good.

Example 2 A developing ink composition was prepared in the same manner as in Example 1 except that both solutions having the following formulations were used to obtain a developing ink composition (2) of the present invention. Oil phase Turpentine oil 7.0 parts Toluene 8.0 parts Sorbitan monostearate (Span-60, manufactured by Kao Atlas Co., Ltd.) 2.0 parts Sorbitan tristearate (Span-65, manufactured by Kao Atlas Co., Ltd.) 0 .3 parts Petroleum resin (Petrosin # 120, manufactured by Mitsui Petrochemical Co., Ltd.) 1.5 parts Rosin 0.5 parts Asphalt powder 1.0 parts Carbon black 2.2 parts

Water Phase Water 60.0 parts Glycerin 5.0 parts Soyafive S-LN-1 (soybean polysaccharide) (manufactured by Fuji Oil Co., Ltd.) 5.0 parts Arabic gum 2.0 parts Phosphoric acid (85% ) 3.0 parts Sodium hexametaphosphate 2.5 parts This developing ink composition (2) was used in a lithographic printing plate obtained in the same manner as in Example 1, and it was completely the same as in Example 1. Similar good results were obtained.

Example 3 A developing ink composition was prepared in the same manner as in Example 1 except that both solutions having the following formulations were used to obtain a developing ink composition (3) of the present invention. Oil phase Solvent naphtha 15 parts Ethylene glycol monophenyl ether 3 parts Sorbitan monostearate (Solgen-50, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) 1.5 parts Sorbitan monooleate (Solgen-80, Dai-ichi Kogyo Seiyaku Co., Ltd.) 0.3 parts Petrosin # 80 (see Example 1) 1.5 parts Hydrogenated rosin modified resin (Hakoline) 0.5 parts Asphalt powder 1.0 parts Carbon black 3.0 parts Lauric acid 0.2 parts

Water Phase Water 59.9 parts Glycerin 8.0 parts Soyafive LN-1 (soybean polysaccharide) (manufactured by Fuji Oil Co., Ltd.) 4.0 parts Phosphoric acid (85% by weight) 3.0 parts Potassium nitrate 0 0.3 parts Sodium molybdate 0.3 parts JP-A-50-118802 (Japanese Patent Application No. 49-239)
No. 40), the negative-working photosensitive lithographic printing plate described in Example 1 was imagewise exposed and developed by the method described in Example 1. When the composition (3) was used, the same result as in the case of Example 1 was obtained. The developer ink composition (3) stored for 1 year was tested in the same manner as in Example 1, but no change in performance was observed, and good results were obtained as in Example 1.

Example 4 A developing ink composition was prepared in the same manner as in Example 1 except that both solutions having the following formulations were used to obtain a developing ink composition (4) of the present invention. Oil phase n-heptane 14.5 parts Cyclohexanone 3 parts Dioctyl phthalate 2 parts Sorbitan monostearate (Solgen-50, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) 2 parts sorbitan sesquioleate (Nonion op-83, NOF Corporation) 0.2 parts Petroleum resin (Petrosin # 80, manufactured by Mitsui Petrochemical Co., Ltd.) 1.8 parts Carbon black 3.0 parts Valeric acid 0.5 parts

Water Phase Water 62.0 parts Soya Five LN-1 (Fuji Oil Co., Ltd., soybean polysaccharide) 1.5 parts Polyvinyl alcohol (GH-17, Nippon Gosei Co., Ltd.) 0.5 part Glycerin 5.0 parts Phosphoric acid (85% by weight) 3.0 parts Sodium sulfate 0.5 parts Potassium molybdate 0.5 parts To the same lithographic printing plate as used in Example 3, the above-mentioned developing ink composition ( When 4) was used, good results were obtained as in the case of Example 1.

[0030]

The developing ink of the present invention has the following effects. (1) There is no occurrence of karami. In particular, a shadow portion area on the lithographic printing plate corresponding to a portion of the printed matter having a high image density (in this area, the area of the non-image area per unit area is much smaller than that of the image area, and the color is easily generated).
It has excellent performance in that there is no occurrence of karami. (2) Even if it is stored for a long time, the aqueous phase and the oil phase do not separate, the performance does not deteriorate, and it has excellent stability over time. (3) A visible image that faithfully reproduces the image area on the planographic printing plate is provided. Therefore, it is advantageous in examining the quality of the finished planographic printing plate by enlarging and observing the shadow portion of the planographic printing plate with a magnifying glass or the like. (4) When applied to a lithographic printing plate, it can be applied using a sponge, so the operation is simple and the work efficiency is increased. (5) It has no adverse effect on both the image area and the non-image area of the planographic printing plate. For example, the ability to accept printing ink in the image area is not reduced, and the non-image area is not easily stained with the printing ink.

Claims (1)

[Claims] 1. An emulsion of an aqueous phase component containing water, an acidic component and a water-soluble soybean polysaccharide, and an oil phase component containing a volatile solvent immiscible with water and a colorant. Development ink for lithographic printing plates.