US3785983A - Method of producing a liquid developer for use in the electronic photography - Google Patents

Abstract

A METHOD OF PRODUCING A LIQUID DEVELOPER FOR USE IN THE ELECTRONIC PHOTOGRAPHY, WHICH METHOD COMPRISES SAPONIFYING AND UNSATURATED FATTY ACIDS SUCH AS AN OLEIC ACID, A LINOLIC ACID, A LINOLENIC ACID OR THE LIKE SO AS TO MAKE A SOAP, DISPERSING A PIGMENT SUCH AS A CARBON BLACK OR THE LIKE IN AN AQUEOUS SOLUTION OF SAID SOAP, SUBSTITUTING THE ALKALINE METALLIC IONS OF SAID SOAP ON THE PIGMENT PARTICLE SURFACE WITH METALLIC IONS HAVING A VALANCE OF 2 OR MORE TO HAVE THEM PRECIPITATED, TREATING THIS PRECIPITATE TY WASHING THE DRYING IT AFTER TAKING IT OUT THEREFROM SO AS TO PRODUCE DRY POWDER OF SAID PIGMENT, AND DISPERSING SAID PIGMENT POWDER IN AN ALIPHATIC PETROLEUM HYDROCARBON.

Description

Jam. 15, 1974 MAS U ETAL 3,785,983

METHOD OF PRODUCING A LIQUID DEVELOPER FOR USE IN THE ELECTRONIC PHOTOGRAPHY Filed Dec. 1, 1971 Q LLl D. O i a 0-5 6 SURFACE ELECTRIC CHARGE DENSITY t (AT THE TIME WHEN THE CAPACITY OF a AN ELECTROSTATIC RECORDING 5 X PAPER USED IS 500 Pf) 0 6 l ldcouLoma z 0 so I00 I50 200 v SURFACE POTENTIAL United States Patent 3 785 983 METHOD OF PRoDUcIN A LI UID DEVELOPER FOR USE IN THE ELECTRONIC PHOTOGRAPHY Masayoshi Inoue, Koji Nagai, and Shigeo Kitaguchi,

3,785,983. Patented Jan. 15,1974

if an electrostatic latent image with a high potential, for instance, of nearly 1000 volts could be formed on the photosensitive substance thereof, when it is transferred onto a transfer sheet by the latent image transfer process,

the potential of the transferred electrostatic image is desg g fi ai gfi gg g Mmolta Camera Kabushlkl creased to the level of one-tenth thereof, that is, usually Filed a 5 Sen No. 203,543 it is lowered to the low potential of the order from 60 Claims priority, application Japan, Dec. 2, 1970, volts to 150 45/105,938 I Consequently, If a liquid developer for use In the de- Im, C G03 9/04 10 velopment of an electrostatic image having a high poten- US. Cl. 252-621 7 Claims tial of the degree from 250 volts to 400 volts formed on a photosensitive sheet is put to use against an electrostatic having such a low potential. as described above in ABSTRACT on THE DISCLOSURE Image I the same way as performed In a conventional copying A method of Pwducmg a llquld develflpef for use In the machine of the lectrofux type, the density of the picture ekfctmnlc P p y whichmeihod mpri s saponiimage obtained therefrom is too weak to put the picture y e and'unsatllfated y aclds $161138 an 0161c 361d, 3 in the practical use. Accordingly desired to use for a translmohc a m acld r the h s as to make fer sheet in a copying machine of the electrostatic latent a ap filspefsll'lg a p Such a carbon fi image transfer type has been a liquid developer which is the llke an aqueouS Solutlon 0f Sald 1 substltutlng appropriate for developing electrostatic charges of a low alkalflne g 5 saidhsoap 0n lp g P potential and endowed with an excellent electric charge 1c e sur ace wit meta 1c lOl'lS aving a va ance o 2 or responsivity more them Precipitated, treating this precipitate While, in order to obtain a stable developer liquid by y Washlng and drying it after l g it Out therefronrso making use of this carbon black, a dispersing agent and a Rrodllce y P d of salfi plgvmellt, and dlsperslng polarity control agent are ordinarily put to use together 581d Plgmtint Powder 111 an allphatlc Petroleum Y therewith, and a surface active agent is therefore added cafbonthereto frequently, however, the carbon black and organic pigments which are usually discriminated therefrom are, BACKGROUND OF THE INVENTION as well known, poor as compared with inorganic pigments The resent invention relates to a method of roducstablllty of h dlsiperswlly as Well as m the ing a li quid developer for use in the electronic photoblllty of their l It 15 consldered that cause of graphy, said developer being excellent in the dispersivity thls factlreildes mg gg 2 poroslly of i and the electric charge responsivity, by treating the sur- Farbon b ac 3 e i e i acwe ,fii face of pigment particles such as carbon black, more par- 18 not only a Sor.e on 6 E t on ac ticularly, to a method of the production of a liquid dealso adsorbed the manor oflts a q t that veloper which is excellently qualified for the development Owmg to the chemlcal reacnon between lmpjmues on of an electronic photograph in which formed in a low l of carbon black and Surface l l potential electrostatic image such as an electrostatic 225; ifigfig by the reactlon are dlssolved Into the 123 3 gigg on a transfer Sheet by the electrostatic 40 It is therefore necessary In order to Improve the dis- A liquid developre for use in the electronic photoil of the carbon black Particles and to have them graphy is as Well known of a high dielectric property and stabilized that the surface thereof 18 adequately treated. composed of a colloidal dispersoid with coloring fine ig F t be i f g meal? l g p grains dispersed in an organic liquid of a low dielectric car on l 1S lmpregna W1 ma y constant, and the toner particle thereof is comprised of a Property either lmeadable wlth the.dlspersmg medlum.or' core of the coloring fine grain and an extremely thin adpufiafle therewlth W as capable of bgmg. i sorption layer formed on the surface of the core by the electrically Wlthm the dlsparsmg l F adsorption of additives such as a resin and the like to be carbon g i fi by s ashdescnbgd functional as a charging control agent, a dispersing agent a mg a e amoln} e ec me w j n and a fixing agent for the purpose of providing the OF the carbon black can be stabillilzed as well as addrtilve ganic liquid with the chargeability, the dispersivity and S fg q g :fi g R i the fixability. The particularly important property as the b1 f g g g t i i liquid developer, as described above, resides in that the ac l ma 6 S o as e 9. g i 1c or dispersion of the coloring particles is stable and the l attain the object of l prfasent mventlon that. a chars charged polarity of the particles is uniform and that the mg coplrol agent a dlspersmg agent and a fixing-agent amount of the electric charge there to is capable of being as addltlves are allowedto 2 anyway adsorbed'umform' magnified in the case of the Carlson type and of being ly on the carbon black particles, and that the amount of lessened in the case of the electrostatic latent image trans- Qharges 18 W adlusted I fer type as well as capable of being kept Stable at all It is in general difiicult to quantitat vely treat the times amount of electric charges of toner particles, however, In case Where a carbon black is put to use as the if it is considered on the basis of the analysis whichjis coloring fine grains, it has ben remarkably diflicult that a heretofore cameid It can be assllmed l the-Tide? stable liquid developer for use in the electronic photovlalopment flincllon for an eiectmstatlc. latent Image graphy is produced by dispersing the carbon black with vlrtue 9 hquld deyeloper 1S substzfmtlally Va prose-S519" fine grains in a dielectric liquid, because that the oil abneutral? the .elecmc charge formmg the electrostatlc sorptive property of the carbon black is remarkable on W Image Wlth the.ele.cmc charges of the toner account of its porosity, and that the chemical property @168 111 the loper liquid. I v I of fine grains of the carbon black is varied depending on Based the conslderatlon i b q P the production method thereof and according to the quist and hls company have studied the variation affected ameter of each grain. to the property of a toner by the: relation between the 7 amount of electric charges of an electrostatic latent image; I;

Moreover, in an electronic photograph copying mae.

on the surface of a photosensitive sheet and the developchine of the electrostatic latent image transfer type, even ment density, and as the result, they assumed the variation of the development density in relation to the amount of the electric charges of an electrostatic latent image as the following equation:

where D=Development density,

q=Amount of electric charges on a photosensitive sheet, r=Dia meter of a toner particle,

n=Number of electric charges per one toner.

Regardless of the trustworthiness of the equation above about its quantitative treatment, it can be fully accepted from the viewpoint of its qualitative treatment. According to the equation, it can be understood that in order to improve the response with respect to any variation of the amount of electric charges, it can be attained by increasing the value of dD/dq, namely, it can be attained It is therefore an object of the present invention to provide a method of the production of a liquid developer for use in the electronic photography, which developer is endowed with the excellent dispersivity and with the uniform electric charging polarity, as well as with a stable amount of its electric charges.

It is still another object of the present invention to provide a method of the production of a liquid developer for use in the electronic photography, in which developer a carbon black is made use of as a pigment, and which is provided with an excellent electric charge responsitivity appropriate to the development of an electrostatic image having such a low potential of around 100 volts as the photosensitive sheet described hereinbefore.

All of the features and the aforementioned objects of the present invention can be more apparently understood by reading the detailed description and claims with reference to an accompanying drawing concerning to the present invention which will be more illustrated hereinbelow.

'BRIEF DESCRIPTION OF THE DRAWING The meredrawing, FIG. 1, is a graphic diagram showing the development characteristics of the relationship between the surface potential of an electrostatic latent image and the development density at which said electrostatic latent imageis developed by virtue of a developer liquid.

DETAILED DESCRIPTION OF THE INVENTION The present invention is disclosed on the basis of the viewpoint as described hereinabove. More specifically, the disclosure utilizes the fact that a carbon black is of the pH value of less than 8 in its aqueous solutions almost all of which are acidic, and that it is remarkably dispersible in an aqueous solution of an alkaline soap, and the carbon black is accordingly treated with a metallic salt the carbon particles are substituted by 2 kinds of metallic ions having a valence of 2 or more so as to produce the so called metallic soap. Since the carbon particles treated as described above are precipitated in the solution, the precipitated particles are taken out therefrom, washed with clean water and then dried out.

The carbon black treated as above is further mixed with a dielectric macromolecular material added thereto, said material being of a property kneadable and puifable with the dispersing liquid, or else the surface thereof is coated with said mixture, and thereafter it is dispersed in the dielectric, aliphatic petroleum hydrocarbon.

By processing as described above, the dispersion thereof can be easily carried out and remarkably stabilized so that its polarity of electric charges is uniform and stable, accordingly obtained is a colloidal developer for use in the electronic photography, said developer being of the positive polarity and having an excellent electric charge responsivity.

In the aforementioned process, the quantity of the unsaturated fatty acid to be added with respect to the carbon black is not necessarily the more the better, and its appropriate amount is less than 20% of the oil absorptive quantity of the carbon black. And the unsaturated fatty acids appropriate to put to use therefore are oleic acid, linolic acid, linolenic acid and the like. Further, said unsaturated fatty acid may be incorporated with an oil carrier material to present an oil composition wherein the total amount of the fatty acid included is more than 50% of the composition. Suitable oils include vegetable oils such as linseed oil, tung oil, perilla oil, sesame oil, soybean oil, etc., or animal oils such as lard, or the like. In addition, the materials having a valent state of 2 or more for producing metallic salts with the unsaturated fatty acids as shown above are appropriately selected frlpm among Ba, Ca, Mg, Al, Pb, Zn, Ni, Co, and the li e.

The diagram shown in FIG. 1 is the measured result of the values of dD/dq for the developer liquid obtained by the producing method in accordance with the present invention as described hereinabove, and the values are compared therein with those measured for some prior developer liquid being sold in the market.

FIG. 1 illustrates the development density characteristics showing the relationship between the surface potential of an electrostatic transfer sheet charged by means of a corona discharge unit and the development density on said transfer sheet after the sheet has been developed by various developer liquid for a period of one minute. The curve A is the development density shown by a developer liquid which is perhaps sold in any market and is represented by the general use developer of the Mitsubishi Seishi Co., Ltd. If a transfer sheet of which the charged surface potential is around volts is developed by said developer liquid, the development density obtained thereby is, as seen in FIG. 1, very weak and its value is less than 1.0, resulting that it can not be put to use in a practical development of a transfer sheet having a low surface potential.

The curve B shows the development density characteristics of a developer liquid which is rarely sold in the market and represented by the linework use developer liquid of the Mitsubishi Seishi Co., Ltd. This developer liquid shows the best electric charge responsivity among those of every developer liquids presently sold in the market, and therefore it may be possibly put to use for the low potential too. However, any developer liquid is generally capable of maintaining its continuous developing operation under the intermittent supply of a condensed toner, and if the developer liquid is continuously kept in its developing operation like this, its development density is gradually degraded down to the degree of about one-half as much as the initial density thereof at the time when nearly 700 sheets have been developed, therefore,

it is hard to say that this developer can be satisfactorily put to use for the low potential.

The curve C shows the development density characteristics of the developer liquid in accordance with the present invention, and the electric charge responsivity thereof is remarkably improved in comparison with those described above, therefore, this developer liquid is endowed with various advantageous properties which will be described hereinafter as the embodiments thereof shown in the Examples No. 11 through No. 15.

The following examples are the embodiments in accordance with the present invention, said examples individually including an excellent developer liquid having good dispersivity and stability.

EXAMPLE NO. 1

An oleic acid of 20 g. is saponified with a caustic soda (NaOI-I) of 8 g. so as to completely produce a soap, thereafter said soap is taken out therefrom and added with clean water up to its volume of 500 cc., then it is heated to be fully dissolved until it is made upinto an aqueous soap. Added into this aqueous soap is 40 g. of the Carbon Black No. 80 (trade name by Asahi Carbon Co., Ltd. the oil absorption rate=125 cc./100 g.) which is then dispersed by the supersonic process until the carbon black particles are completely dispersed therein. While the dispersed liquid of the carbon black is being agitated, a solution including 40 g. of an aluminum sulfate [Al (SO 'l6-18H O] is added thereinto so as to allow the mixture to be doubly decomposed to produce an aluminum soap. The precipitation obtained thereby is taken out therefrom by means of a centrifugal separator, and fully washed with water, thereafter it is dried at a temperature of 120 C. for a period of 6 hours to completely remove the moisture therefrom.

The 0.5 g. part of the powder thus obtained is thereafter dispersed by the supersonic process in the Isopar G (trade name by the Esso Standard Petroleum Co.) with its volume of 500 cc., a novel developer liquid being thus obtained.

By means of an ordinary process, a latent image was made up on a negatively charged Z110 photosensitive sheet by illuminating a positive image thereonto, which image was then developed with this developer liquid, thereby obtained was a good, black, positive image which could be easily fixed by drying it with heated air of 100 C.

After leaving this developer liquid for a week as it was, it was again put to use in the identical development with the previous process, thereby obtained was a good, lblack, positive image which was completely in the same condition as before, additionally, the dispersivity of the developer liquid was still kept in a good condition where the precipitation was rarely found out therefrom.

EXAMPLE NO. 2

With the exception that a linolic acid was put to use instead of the oleic acid in the Example No. 1, the completely identical procedure therewith was followed in this example, too. By making use of the developer liquid obtained thereby, the developing operation was carried out in the same way as the Example No. 1, accordingly obtained was a good, black, position image which was endowed with a good fixability. After leaving this developer liquid *for a week as it Was, it was again put to use in the developing process in the same manner as the Example No. 1, thereby obtained was an identically (good, black, positive image, and the dispersivity of the developer liquid was still kept in a good condition where the precipitation was rarely found out therefrom.

EXAMPLE NO. 3

With the exception that a linolenic acid was put to use instead of the oleic acid in the Example No. 1, the completely identical treatment therewith was carried out in this example too. By making use of the developer liquid thus obtained, the developing operation was carried out just like as in the Example 'No. 1, thereby obtained was a good, black, positive image, of which the fixability was also good. After leaving this developer liquid for a week as it was, it was again put to use in the developing process just like as in the Example No. 1, thereby obtained was an identically good, black, positive image, and the dispersivity of the developer liquid was still kept in a good condition where the precipitation could he rarely found out therefrom.

EXAMPL'E NO. 4

With the exception that a solution including a zinc chloride (ZnCl of 20 g. weight was put to use instead of the aluminum sulfate [Al (SO -16-18H O] in the Example No. 1, the completely identical treatment therewith was carried out. By making use of the developer thus obtained, the developing operation was accomplished in the same way as done in the Example No. 1, thereby obtained was a good, black, positive image. After leaving this developer liquid for one week as it was, it was again put to use in the developing process in the same way as in the Example No. l, accordingly obtained was an identically good, black, positive image, and the dispersivity of the developer liquid was somewhat inferior to that in the case of the Example No. 1, but kept in a good condition where the precipitation could he rarely found out therefrom.

EXAMPLE N0. 5

With the exception that a solution including a stannous chloride (SnCI -ZH O) of 35 g. weight was put to use instead of the aluminum sulfate [Al (SO l6-18H O] in the Example No. 1, the completely identical treatment therewith was carried out in this example, too. By making use of the developer liquid obtained thereby, the developing operation was carried out in the same way as done in the Example No. 1, thereby obtained was a good, black, positive image. After leaving this developer liquid for one week as it was, it was again put to use in the developing process in the same way as in the Example No. 1, accordingly obtained was an identically good, black, positive image, and the dispersivity of the developer liquid was somewhat inferior to that in the case of the 'Example No. 1, but kept in a good condition where the precipitation could he rarely found out therefrom.

EXAMPLE NO. 6

With the exception that a linseed oil containing its unsaturated fatty acid of the range from 84% to was put to use instead of the oleic acid in the Example No.1, and that a mixture of a sodium hydroxide (NaOH) of 5 g. weight and a sodium carbonate (Na CO of 5 g. weight was put to use instead of the caustic soda NaOH) of 8 g. weight in the Example 1, the completely identical treatment therewith was carried out. By making use of the developer liquid thus obtained, the developing operation was carried out in the same way as done in the Example No. 1, thereby obtained was a good, black, positive image which was endowed with the good fixability.'After leaving this developer liquid for one week as it was, it was again put to use in the developing process just like as done in the Example No. 1, accordingly obtained was an identically good, black, positive image, and the dispersivity of the developer liquid was still kept in a good condition where the precipitation coud be rarely found out therefrom.

EXAMPLE NO. 7

With the exception that a tung oil containing its unsaturated fatty acid of the range from 93% to 98% was put to use instead of the oleic acid] in the Example No. 1, and that a mixture of a caustic soda (NaOH) of 5% weight and a sodium carbonate (Na CO 'of 5% weight was put to use instead of the caustic soda (NaOH) of 8 g.

weight in the Example No. 1, the completely identical treatment therewith was carried out. By making use of this developer liquid obtained thereby, the developing operation was carried out ust like as in the Example No. 1, accordingly obtained was a good, black, positive image of which the fixability was good too. After leaving this developer liquid .for one week as it was, it was again put to use in the developing process in the same manner as in the Example No. 1, thereby obtained was an identically good, black positive image, and the dispersivity of the developer liquid was still kept in a good condition where the precipitation could be rarely found out therefrom.

EXAMPLE NO. 8

With the exception that a Victorian Blue of 0.2 g. weight was added and fully dispersed prior to the addition of an aqueous solution of the aluminum sulfate in the Example No. 1 and thereafter the aqueous solution of the aluminum sulfate [Al (SO -16-18H O] was added thereto, the completely identical treatment therewith was carried out. By making use of this developer liquid obtained thereby, the developing operation was carried out just like as done in the Example No. 1, accordingly obtained was a good positive image having been colored with a black containing one kind of weak blue, and its fixability was good too. After leaving the developer liquid for one week as it was, it was again put to use in the developing process in the same manner as in the Example No. 1, thereby obtained was an identically good positive image having been colored with a black containing one kind of weak blue, and the dispersivity of the developer liquid was still kept in a good condition where the precipitation could be rarely found out therefrom.

EXAMPLE NO. 9

A 10 g. weight of the powder obtained in the Example No. 1 and 10 g. weight of an ethyl cellulose are together dissolved in a xylene of 50 cc. and mixed completely by means of a high speed mixer. On the other hand, a solid type paraffin of 10 g. weight is heated and dissolved in the Isopar G of 100 cc., and this solution is added little by little into the previously produced mixture, while the mixture is agitated, and it is fully mixed therewith. The Isopar G is then added into this mixed solution so as to make up a condensed developer liquid until its total volume is brought up to 500 cc. A novel developer liquid is produced by diluting this condensed developer liquid of 10 cc. with the Isopar G down to 1 1. By making use of this developed liquid, the developing operation was carried out in the same way as in the Example No. 1, thereby obtained was a good, black, positive picture image of which the image density was stronger than that of the Example No. 1. In addition, the dispersivity of the developer liquid was outstandingly stable too.

EXAMPLE NO. 10

A 10 g. weight of the powder obtained in the Example No. 1 and a g. weight of an alkyd resin (can be procured under the trade name Aroplaz made by the Nisshoku Aro Chemical Co.) are together dissolved in a xylene of 50 cc. and mixed completely by means of a high speed mixer, and thereafter the mixture is treated in the same way as done in the Example No. 9. 7

By making use of the developer liquid obtained by the process as above, a developing operation was carried out in the same manner as in the Example No. 1, thereby obtained was a good, black, positive picture image, and the dispersivity of the developer liquid was remarkably stable, too.

Hereinbelow shown as the Example No. 11 through No. 15 are each an embodiment of the developed liquid in accordance with the present invention for use in the development of a latent image transfer sheet, said developer liquid being endowed with the excellent electric charge responsitivity.

EXAMPLE NO. 11

An oleic acid of 25 cc. is saponified with a caustic potash (KOH) until they make up a soap completely, thereafter, the soap is taken out therefrom and added with clean water until its volume is brought up to 1000 cc., then the mixture is heated to permit the soap to be completely dissolved therein, an aqueous soap solution being thus obtained. Into this soap solution, a g. weight of the Carbon Black No. 80 (trade name by the Asahi Carbon Co., the oil absorption rate=1.70 cc./g.) is added and dispersed therein by the supersonic dispersion means or by the ball mill means, until the carbon black particles are perfectly dispersed. In the next, the carbon black dispersed liquid is put in a homomixer, and while it is being agitated therein by a high revolution thereof, a mixed solution of a barium acetate of 9.2 g. weight and a calcium acetate of 12.8 g. weight is added thereinto so as to produce a precipitate therein.

The precipitate is taken out therefrom by filtering off, and fully washed out with clean water, thereafter it is vacuum dried at the temperature of about C. so as to completely remove moisture therefrom.

A 30 g. weight of the treated carbon powder obtained by the process aforementioned is mixed with a 12 g. weight of an alkyd resin (can be procured under the trade name Aroplaz No. 6008 by its manufacturer of the Nisshoke Aro Chemical Co., Ltd), a 20 g. weight of a toluene and a 40 g. weight of Isopar H (trade name by its manufacturer of the Esso Standard Petroleum Co.), and this mixture is perfectly dispersed by the ball mill means for a period of about 24 hours.

The mixture thus obtained is again dispersed in Isopar L (trade name by its manufacturer of the Esso Standard PetroleumCo.) of 400 cc. by means of a homomixer so as to make up a condensed toner liquid. By diluting this condensed toner liquid of 20 cc. with 1000 cc. of Isopar G (trade name by its manufacturer the Esso Standard Petroleum Co.), a novel developer liquid is obtained.

The electric charge polarity of this developer liquid is remarkably stable, and the development characteristics provided therewith is as shown by the curve C in FIG. 1, therefore, when it is compared with the characteristics, as

shown by the curves A and B in FIG. 1, of the developers sold in the market, its electric charge responsivity against electric charges of around 100 volts is far better than the latter, accordingly capable of attaining is the object of the present invention whichaims to develop a transfer sheet onto which an electrostatic latent image has been transferred.

When transfer sheets each having an electrostatic image formed thereon with its surface potential of volts were actually developed by making use of the developer liquid as described above, even though more than 2000 sheets were thereby developed, the development density was not degraded by intermittently supplying the condensed toner liquid thereto, so that a nice developing operation could be continuously carried into effect.

EXAMPLE NO. 12

An oleic acid of 12.5 cc. is saponified with a caustic potash (KOH) of 3 g. weight so as to produce a soap-like substance, which is then diluted with clean water of cc. to produce an aqueous soap solution, thereafter, a 90 g. weight of a carbon black having the trade name of Statex B-12 (manufactured by the Columbia Carbon Co., the oil absorption rate=0.85 cc./g.) is added thereinto and dispersed by the supersonic means, thereafter, while the mixture is agitated by means of a homomixer in a high revolution thereof, a mixed aqueous solution of a barium acetate of 4.6 g. weight and a calcium acetate of 6.4 g. weight is added thereinto to have them precipitated, the precipitate is then separated therefrom by filtering off, and

washed out with clean water, thereafter it is dried in a vacuum at the temperature of 55 C. A novel developer liquid obtained by treating the thus produced powder in the same way as described in the Example No. 11 is endowed with the stable electric charge polarity identical with the developer liquid shown in the Example No. 11, and the development characteristic thereof is also approximately identical with that of the Example No. 11.

EXAMPLE NO. 13

With the exception that a 90 g. weight of Carbon Black No. 60 (trade name by its manufacturer of the Asahi Carbon Co., the oil absorption rate=1.65 cc./g.) was put to use instead of Statex B-12 in the Example No. 12, the completely identical treatment with that of the case in the Example No. 12 was carried out, and a novel developer liquid was thereby obtained. By making use of this developer liquid, the development characteristics as shown in FIG. 1 was measured and resulted that the highest density thereof was 1.46 which was somewhat lower than that of the curve C in FIG. 1, but that the inclination thereof was almost approximate to that of the curve C.

EXAMPLE NO. 14

With the exception that a magnesium acetate of 2.9 g. weight was put to use instead of the barium acetate, the completely identical treatment was carried out and a novel developer liquid was obtained. The development characteristics of this developer liquid was almost approximate to that of the Example No. 12.

EXAMPLE NO. 15

With the exception that a linolic acid of 15.5 cc. was put to use instead of the oleic acid in the Example No. 12, the completely identical treatment was carried out and a novel developer liquid was obtained. The development characteristics of this developer liquid was almost approximate to that of the Example No. 12.

As shown in the example described hereinabove, any developer liquid produced in accordance with the present invention for use in the development of electronic photographs is endowed with an excellent dispersivity and stability, as well as the electric charge characteristics thereof is remarkably stable and the electric charge responsitivity in the development characteristics thereof is also good, consequently, it is functionally effective in that it is capable of developing an electrostatic image speedily, so as to obtain a picture image of which the contrast is good and half tones are reproduced with fidelity, even though the surface potential of said image is comparatively low as that of an electrostatic image transferred electrostatically onto not only a transfer sheet but also a photosensitive sheet of the Carlson type.

What is claimed is:

1. A method for producing a developer useful for de veloping latent electrostatic images, said method com prising:

providing a saponifiable fatty acid material including at least about 50%, based on the total quantity of said material, of a saponifiable, unsaturated fatty acid,

the remainder of said material, if any, comprising an oil carrier for said fatty acid;

subjecting said matreial to saponification whereby to produce a soap from said unsaturated fatty acid; admixing said soap with water to produce an aqueous solution thereof;

dispersing particles of pigment material useful in connection with the production of electrostatic images in said aqueous soap solution;

thereafter, at a time while said pigment particles re main dispersed in said soap solution, replacing the alkaline metallic ions of the soap with higher valent metallic ions having a valence state of two or more to thereby produce a modified. oapy substance, said higher valent ions being capable of causing the precipitation of said modified soap after said replacement has taken place whereby said modified soapy substance is precipitated as it is produced to thereby present a precipitated phase of pigment particles coated with and in intimate admixture with said modified soapy substance;

separating said precipitated phase from the remainder of the reaction system; and

drying said precipitated phase to present a dry poW- der; and dispersing said dry powder in an aliphatic petroleum hydrocarbon.

2. A method as set forth in claim 1 wherein a dyestuff is incorporated into said aqueous soap solution prior to said replacement of said alkaline metallic ions with said higher valent ions.

3. A method as set forth in claim 1 wherein a dielectric macromolecular material is incorporated into said precipitated phase.

4. A method as set forth in claim 3 wherein said dry powder and said dielectric macromolecular material are dispersed in an aliphatic petroleum. hydrocarbon.

5. A method a set forth in claim 1 wherein said pigment material comprises carbon black.

6. A method as set forth in claim 5 wherein the quantity of soap in said aqueous soap solution is less than 20 percent of the amount thereof which said dispersed particles of carbon black are capable of absorbing.

7. A method as set forth in claim 1 wherein the soap in said aqueous soap solution is sorbed by said pigment particles prior to the production of said modified soapy substance.

References Cited UNITED STATES PATENTS 3,542,682 11/1970 Mutafiis 25262.1 3,438,904 4/1969 Wagner 25262.1 3,301,698 1/1967 Fauser et all 25262.1 3,253,913 5/1966 Smith et al. 252-62.1 327,813 10/1885 Mitchell et al. 117-DIG. 3

OTHER REFERENCES Ellis, Printing Inks, 1940, pp. 114-115.

J. TRAVIS BROWN, Primary Examiner J. P. BRAMMER, Assistant Examiner UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3, 785, 983

DATED 1 Januany 15, mm

'NVENTOR(S I Masayoshi e, Koji Nagai and Shigeo Kitagucki It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 9, after "45/105,938" add--and application Japan, September 20, 1971, 46/72,532

Signed and Scaled this Twenty-eighth Day Of March I978 [SEAL] .4 nest:

RUTH C. MASON LUTRELLE F. PARKER Arresting Officer Acting Commissioner of Parents and Trademarks

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