GB1583998A - Developing agent for electrographic printing process - Google Patents

Abstract

The developer can be used for developing electrostatic latent images in electrographic printing processes, contains at least 2 different toners of different colour and has a flow capacity of 80 DEG or less, expressed as the angle of repose. It can contain at least one additive which is an alkaline earth metal oxide and/or a triazine compound of the formula (1) or (2) <IMAGE> in which the symbols are as defined in Claim 13. The angle of repose which is important for the properties of the developer is preferably 20 to 60 DEG . The developer also contains a finely particulate carrier, in particular iron powder, in such quantities that the carrier particles can build up on average a coating at most three layers thick on toner particles.

Description

(54) DEVELOPING AGENT FOR ELECTROGRAPHIC PRINTING PROCESS (71) We, KANEBO LIMITED, a Company organised and existing under the laws of Japan, of 3-26, Tsutsumidori 3-chome, Sumida-ku, Tokyo, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a developing agent suitable for use in electrographic printing processes.

Recently, the electrographic technique has been used in continuous printing processes. In this technique, electrostatic images are formed on an electrographic recording element and developed with a developing toner by an electrographic method such as xerography, an electrostatic printing method such as xeroprinting, or an electrostatic gravure printing or TESI method. The developed images on the recording element are transferred from the recording element directly or through a printing medium onto a paper or fabric substrate and the transferred images are fixed on the substrate.

Recent advances in electrographic printing have resulted in the development of a multi-colour printing process in place of the conventional one-colour printing process. In multi-colour printing, the desired colour is formed by superimposing images of cyan, magenta and yellow toners and, if necessary, a black toner.

However, this method produces a limited range of hues and has the disadvantage that a small alteration in the amount of a coloured toner results in a large unevenness or alteration in the colour of the visible images. Further, the superimposition of the component colour images sometimes causes poor image sharpness. Especially in the continuous printing of paper or fabric, it is required that all of the printed images have a sharp outline and are evenly coloured but, in conventional printing methods, it is difficult to meet these requirements.

One concept for satisfying these requirements is to use individual toners having the desired colour. However, the necessary number of colours may be very large and the preliminary preparation of the toners is then costly and complicated.

Accordingly, this concept is not practical.

Another concept for the printing process is to provide the desired colour toner by mixing two or more component colour toners, as disclosed in British Patent Specification No. 1,529,887. In this concept, all the desired colour toners can be prepared by mixing suitable relative amounts of two or more toners selected from at most several tens of differently coloured toners. Accordingly, this process is relatively simple and economical, and is not limited in respect of the hue of the images to be printed. However, it has become clear that, in this process, the hue of the printed images tends to alter during a long continuous printing process due tofluctuation in the mixing ratio of the component toners, owing to the fact that the toners in a toner mixture are adsorbed imagewise on a substrate or master sheet at different rates.It is therefore desirable to provide a toner mixture in which all toners can transfer imagewise in a predetermined mixing ratio to the substrate or master sheet.

According to the present invention, a developing agent suitable for use in an electrographic printing process comprises a mixture of separate particles of (i) a first toner; (ii) a second toner, coloured differently from the first toner; and (iii) an additive selected from alkaline earth metal oxides and triazines of the formula

wherein one or two of X, Y and Z are halogen and the other two or one, respectively, are selected from NR1(CH2)rnQ -NR-CH2-COOM

in which m is an integer from 1 to 5, Q is SO3M, COOM or POOM, M is hydrogen or an alkali metal, R is C2~18 alkyl, R' is hydrogen or methyl, R2 is hydrogen or hydroxy and q is one when Q is COOM or POOM or one, 2 or 3 when Q is SO3M; the mixture having a fluidity, measured as angle of repose (as hereinafter defined), of from 20 to 60 degrees.

The angle of repose is determined by charging a wide-mouth bottle having a diameter of 6 cm and a height of 11 cm with a toner to 60 /" by volume of the inside space of the bottle. The bottle is closed, and then laid down on a flat horizontal surface which causes the toner in the bottle to form a horizontal upper surface. The bottle is then slowly rolled along the horizontal surface so as to form an angle between the upper surface of the toner and the horizontal. The angle between the upper surface and the horizontal at which the toner particles located on the upper surface portion start to slide down, represents the angle of repose of the component particle.

The first toner used in the present invention can be colourless, consisting solely of a polymeric particle-forming material. The second or both toners may comprise a mixture of a polymeric particle-forming material and a colouring matter. The polymeric material may comprise one polymer or a mixture of two or more polymers. The colouring matter may be a single colouring substance or a mixture of two or more- colouring substances, for example, dyes or pigments. Each toner may additionally contain one or more additives such as, for example, agents for regulating the electrical property of the component toner, fillers, anti-oxidants, ultra-violet ray-absorbing agents, magnetic substances and photoconductive materials.

The polymeric particle-forming material usable for the present invention can be selected from polymeric materials capable of being charged when the polymeric material is placed under friction with another solid or liquid-material or under a corona-charge. Such polymeric materials include olefin polymers, for example, polyethylene and polypropylene; vinyl polymers, for example, polyvinyl chloride, polyvinylidene chloride and polyvinyl acetate; styrene-type polymers, for example, polystyrene, polyalkylstyrene and polyamin0;styfehe; acrylic polymers, for example, polymethylmethacrylate; cellulose polyrntrs, for example, cellulose acetate; polyesters, for example, polyethylene terephthalate; mixtures of two or more of the above-mentioned polymers; copolymers of two or more monomers of the above-mentioned polymers; and modified polymers of the above-mentioned polymers and copolymers. The polymeric material may be water-soluble or insoluble. Water-soluble polymers can be utilized for the toners of the present invention, depending on the use of the toner.

The colouring matters usable for the present invention can be selected from colouring materials capable of colouring paper or fabric, for example, disperse dyes, acid dyes, basic dyes, reactive dyes, direct dyes, metallized dyes, oil-soluble colouring materials, and organic and inorganic pigments.

The toners usable for the present invention may be produced by any conventional process for forming fine particles. For example, the toners can be produced by dissolving the polymeric material alone, or a mixture of the polymeric material and the colouring matter, in a solvent; adding the solution to a liquid which is miscible with the solvent but is a non-solvent for the polymeric material and any colouring matter therein, causing coagulation of the polymeric material and any colouring matter in the form of fine particles; and collecting and drying the particles. The solution may alternatively be sprayed into a drying atmosphere to form the toner. In another method, the polymeric material and any colouring matter is melted and kneaded, and after solidifying, the kneaded mixture is finely pulverized.The thus-prepared toner may be coated with an agent for regulating the electrical property of the toner. For this purpose, the component toner is treated with powdered regulating agent or a solution or dispersion of the regulating agent.

The toner may also be produced in-a conventional process for producing microcapsules.

The toners usable for the present invention preferably have an average particle size of 100 ,u or smaller, more preferably 40 , or smaller. It is also preferable that the difference in the average particle size between the toner is 20 y or less.

Further, it is preferable that the absolute value of the difference in the static charge between the toners is not more than 5x 10-5, more preferably not more than 3x 10-5, and most preferably not more than l.5x 10-5, coulomb/g. The term "static charge" of a toner,.as used herein, refers to the amount of static electricity in coulomb/g generated on the component toner by friction between the toner particles and carrier particles, such as powdered iron particles or glass beads, or dispersed solid particles in a liquid carrier, or by corona-discharge applied to the toner, when the toner alone is used for developing electrostatic latent images.

The static charge of the toner is determined in the following manner: A mixture of a toner and a particulate carrier material is charged in a Faraday-cage having an end formed by a metallic net, and the toner is discharged through the metallic net end from the cage by being blown with compressed air or being sucked with a vacuum pump. After the discharge, the amount of static electricity and the weight of the toner removed from the cage are measured to determine the static charge in coulomb/g of the toner.

It is preferable that each toner has an absolute static charge of not more than lOxlO-5 coulomb/g.

When the fluidities of the toners, in terms of angle of repose, are very different, the times in which the toners respectively reach a saturated value of static charge during the developing operation are different, even if the saturated values of static charges of the toners are similar. This time difference results in a difference -in migrating rate between the toners and in a difference in developing time between the toners. Accordingly, it is preferable that a toner having a relatively high fluidity and a relatively low static charge is mixed with a toner having a relatively low fluidity and a relatively high static charge.

The developing agent of the invention may be admixed with a particulate carrier material, such as particulate iron or glass beads, at a mixing ratio in terms of covering rate of 399% or less with respect to total surface area of the carrier particles. The term "covering rate" used herein refers to a mixing ratio of relatively small size toner particles to relatively large size carrier particles, which is determined in such a manner that: when all the outer surfaces of the carrier particles are completely covered with the toner particles arranged in a single layer having no empty area, the covering rate is 100%; when all the outer surfaces of the carrier particles are completely covered with the toner particles arranged in a double layer having no empty area, the covering rate is 200; and when all the outer surfaces of the carrier particles are completely covered with the toner particles arranged in a triple layer having no empty area, the covering rate is 300%.

The covering rate of the toner particles with respect to the carrier particles is relative to the value of the static charge to be generated on the toner particles by contact or friction between the carrier particles and the toner particles. For example, in the case where electrostatic latent images are developed with the developing agent of the present invention in accordance with a magnetic brush method, the covering rate should be considered in relation to the developing surface speed of a developing device and the surface speed of a photosensitive layer.

When the toner mixture is admixed with the carrier material, the covering rate is preferably not more than 300%. A covering rate larger than 300% may result in undesirable staining of the background of the developed images on the substrate or master sheet.

When the carrier material is powdered iron, the iron preferably has an average particle size of 50 to 500 microns.

The additive used in this invention comprises one or more alkaline earth metal oxides or one or more triazines of the formula given above. Examples of suitable alkaline earth metal oxides are magnesium oxide, calcium oxide, strontium oxide and barium oxide; they are usually used in an amount of from 0.01 to 5.0% by weight based on the weight of the toners. The most preferred alkaline earth metal oxide for use in the present invention is magnesium oxide, preferably in an amount of from 0.05 to 3.0%, more preferably 0.1 to 2.0%, by weight based on the weight of the toners. It is preferred that the alkaline earth metal oxide has a particle size of not more than 5 y.

The triazine compounds for use in this invention can be prepared by reacting a halogenated cyanuric compound with an aminomethanecarbocyclic acid, a Nalkylaminomethanecarboxylic acid, a sulfonic acid, carboxylic acid or phosphoric acid compound, or an alkali metal salt thereof.

The above-mentioned aminomethanecarboxylic acids can be prepared by reacting an amine or Cm~,8 alkylamine with monochloroacetic acid or an alkali metal salt thereof in the presence of an alkali at a temperature of 30 to 70"C for 1 to 3 hours.

The sulfonic acid compound may be selected from taurine(aminoethane sulfonic acid), methyltaurine, anilinesulfonic acid, phenolsulfonic acid, toluidinesulfonic acid, toluidinedisulfonic acid, anilinedisulfonic acid, naphthionic acid, 1 - naphthylamine - 3,6 - disulfonic acid, 1 - naphthylamine - 3,6,8 - trisulfonic acid, 1 - amino - 8 - naphthol - 3,6 - disulfonic acid, 1 - naphthylamine - 3,7 - disulfonic acid, 2 - naphthylamine - 3,7 - disulfonic acid, 1 - aminonaphthalene - 7 - sulfonic acid, 1 - amino - naphthalene - 8 - sulfo.nic acid, amino - 2 - naphthol - 3,6 - disulfonic acid, 2 - amino - 8 - naphthol disulfonic acid, RM acid, M-acid, 2 - amino - 5 - naphthol - 7 - sulfonic acid and 2 - naphthylamine - 1 - sulfonic acid.The sulfonic acid compound may be used in the form of its alkali metal salt.

The carboxylic acid compound may be selected from glycine(aminoacetic acid), phenylglycine, aminobenzoic acids, aminobutyric acids, aminocaproic acids, aminopropionic acids and aminophthalic acids. The carboxylic acid compound may be in the form of its alkali metal salt.

The phosphoric acid compound may be selected from aminomethanephosphonic acid, hydroxymethanephosphonic acid, aminoethylphosphonic acid, aminobutylphosphonic acid and anilinephosphonic acid. The phosphoric acid compound may be in the form of its alkali metal salt.

In the production of a triazine compound in which two of X, Y and Z are other than hydrogen and are different, the corresponding halogenated cyanuric compound is subjected to a first reaction with a reactant compound corresponding to one of the radicals, and then to a second reaction with another reactant compound corresponding to the other radical. Generally, the first reaction is carried out at a temperature of 0 to 50C and the second reaction is effected at a temperature of 20 to 400 C. The first and second reactions may be carried out in an aqueous medium, an organic solvent medium or a mixture of aqueous and organic solvents. The reaction results in the product of a hydrohalide which can be neutralized by adding an alkali to the reaction medium. The organic solvent may be selected from acetone, methyl ethyl ketone, and dioxane.The alkali for neutralizing the halogenated hydrogen in the reaction medium can be selected from sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium acetate, calcium hydroxide, magnesium hydroxide, barium hydroxide, and sodium bicarbonate. The most preferable alkali is sodium carbonate, because this compound has a buffer effect for the reaction and can allow the reaction to be carried out at a suitable reaction rate.

Typical triazine compounds usable for the present invention are the eight compounds (1-VIlI) illustrated on page 3 of British Patent Specification No.

1,529,887, and the dibromo and bromo compounds corresponding to the illustrated compounds of formulae II and IV, respectively. The most preferred triazines for use in this invention are 2 - chloro - 4,6 - bis(p - sulfoanilino) - 1,3,5 - triazine disodium salt (III), 2- chloro - 4,6 - bis(p - sulfophenoxy) - 1,3,5 - triazine disodium salt and 2,4 - dichloro - 6 - (p - sulfoanilino) - 1,3,5 - triazine sodium salt (I).

The following two Preparations illustrate how suitable triazines may be prepared.

Preparation 1 A solution of cyanuric chloride was prepared by dissolving 18.5 g (0.1 mole) of cyanuric chloride in 40 ml of acetone. 100 g of ice-water were added while vigorously agitating the solution. The cyanuric chloride was finely dispersed in the mixture of water and acetone. The dispersion was externally cooled to 0 to 50C. A 50% aqueous solution of 18.8 g (0.1 mole) of N-octylglycine was added dropwise into the dispersion while maintaining the temperature of the reaction mixture at 0 to 50C and. eoncurrently maintaining the pH of the reaction mixture at 8 to 9 by adding dropwise a 2 N aqueous solution of sodium carbonate. The reaction operation was continued for 2 hours while stirring the reaction mixture.Thereafter, the reaction mixture was adjusted to a pH of 7, by adding the sodium carbonate solution, and then heated to a temperature of 35"C. At this temperature, a 10% aqueous solution of 17.3 g (0.1 mole) of sulfanilic acid was added to the reaction mixture over a period of one hour, while maintaining the reaction mixture at a pH of 5 to 7; the reaction mixture was then stirred for an additional one hour. Finally, the pH of the reaction mixture was adjusted to 6. The resultant reaction mixture was kept for one night in the presence of sodium acetate, so as to allow the reaction product to precipitate from the reaction mixture. The precipitation was separated by filtering. The above precipitation operation was repeated a further two times.

The precipitation was washed with methyl alcohol and dried under a reduced pressure. The product was 42 g (92%) of white powder.

It was confirmed that the product was a triazine compound of formula IV.

Preparation 2 A four-neck flask having a capacity of 1 liter, and provided with a stirrer, a cooling pipe, a thermometer and a funnel for charging dropwise a reactant solution, was charged with 150 ml of distilled water and the water was cooled to a temperature of 5"C or lower. A solution of 55.2 g (0.3 mole) of cyanuric chloride in 200 ml of acetone was charged into the flask while vigorously agitating the water, so as to prepare a dispersion of the cyanuric chloride. Next, a 30% aqueous solution of 58.5 g (0.3 mole) of the sodium salt of sulfanilic acid was added dropwise to the dispersion from the funnel. After the addition of the solution was completed, the reaction mixture was regulated to a pH of 8 to 9 by adding an aqueous solution of sodium hydroxide, and the reaction mixture was kept under the above-mentioned condition to complete the reaction.

Next, the reaction mixture was heated to a temperature of 40"C and a 30% aqueous solution of 58.5 g (0.3 mole) of the sodium salt of sulfanilic acid was added to the reaction mixture over a period of one hour. The reaction mixture was thereafter adjusted to a pH of 7 by adding the sodium hydroxide aqueous solution, and then kept under these conditions for one hour to complete the reaction. The product was separated from the reaction mixture by the same method as in Preparation 1, washed with methyl alcohol three times and then dried under reduced pressure. 145 g of white powder were obtained. The yield was 96%.

It was confirmed that the product was a triazine compound of formula III.

The triazine compounds usable for the present invention preferably have a particle size of 10 y or less. In the developing agent of the present invention, the triazine compound is preferably used in an amount of 0.05 to 5%, more preferably 0.1 to 3%, by weight based on the weight of the toners.

The developing agent of the present invention can be utilized for developing electrographic latent images. The latent images may be formed by any conventional electrographic methods, for example, xerography, electrofax, electrostatic printing or electrostatic recording. The development can be effected by any conventional developing method such as, for example, the magnetic brush, cascade, impression or fur brush method. The developed visible images can be transferred onto a substrate consisting of paper, fabric or film. The substrate may be made of sheet or fabric consisting of a natural fibres such as cotton, wool and silk; regenerated cellulose fibres such as viscose and cuprammonium rayon, and cellulose acetate fibres; and synthetic fibres such as polyester, polyacrylic, polyamide and polyolefin fibres. Mixtures of two or more of such fibres may be used.The fabric may be in the form of a woven fabric, knitted fabric, non-woven fabric or composite fabric of two or more of the above-mentioned fabrics. The substrate to be printed may be a natural or artificial leather, a film of regenerated cellulose or a synthetic polymer, or a metallic plate or foil. The film may be laminated on a metallic plate or foil. The transferring of the developed images can be effected by any conventional transferring method such as, for example, the corona discharge, bias or repulsion transferring method, which are effected by utilizing electric force; a method utilizing magnetic force; methods utilizing adhesive force; and methods utilizing adsorption force.

The transferred developed images on the substrate are fixed by any conventional fixing method such as, for example, heating or steaming or the solvent vapour method. For example, in the case where the colouring matter in the developing agent is a dye for the substrate, the dye in the developing agent can be fixed to the substrate by the conventional fixing method for the dye, and the polymeric material in the developing agent may be removed from the substrate, if necessary, by dissolving it in a solvent. When the dye sublimes at a high temperature, the developed images can be transferred onto a fabric- or leather only by heating the developed images. Accordingly, such dyes are convenient for a continuous printing process.

The developing agents of the present invention have various advantages. Thus in a prolonged continuous printing process, it is generally possible to obtain developed images having a higher evenness in hue and quality than has been possible previously and it is more easy to obtain the desired hue in the developed images. Also the invention prevents or at least reduces the formation of undesirable stain, in the form of fog or specks, in the non-image area of the substrate, and the staining of the back surface of the substrate, which may be caused by the toners being passed through the substrate. Further, the additives can prevent or at least reduce lumping of the toner particles during long storage periods, or during the preparation of the toner mixture from the individual toners.

The following Examples 1 to 18 illustrate the invention; Examples A to F are comparative. The term "parts" refers to parts by weight. The results of the Examples were evaluated in the following manner.

1. Determination of Mixing Ratio of Component Toners in Developed -Images The developed images were formed on a master sheet and then transferred from the master sheet onto a substrate consisting of paper or fabric. A testing specimen having an area of 5 cmx5 cm was sampled from the substrate having the developed images. The developed images on the testing specimen were dissolved in a predetermined amount, for example, 50 ml, of an organic solvent, for example, trichloroethylene or perchloroethylene. The solution of the developed images was subjected to a spectrophotomeric test in which the absorbance of each dye in the solution was measured at the largest peak in the absorption band of the dye.

Separately, the absorbances of the dyes in a number of solutions, each containing a predetermined concentration of the dye, were measured at the largest peak in the absorption band of the dye. A graph showing the relationship between the absorbances and the concentrations of the dye was obtained. The concentration of the dye in the solution of the developed images was determined from the aboveobtained relationship.

In the measurement of the absorbances of two dyes, in the case where the largest peak of the adsorption band of one dye overlapped the adsorption band of the other dye, the correct value of the absorbance of the one dye was determined by reducing the absorbance value of the other dye from the measured value which was the sum of the absorbance values of the one dye and the other dye.

2. Determination of Fluctuation in Mixing Ratio of Component Toners in Developed Images During a Continuous Printing. Process This fluctuation was indicated in terms of the difference between the mixingratio of the toners in the developing agent at the start of the continuous printing process and the average of the mixing ratios of the toners in the developed images, the sampled testing specimens. The difference was determined in the following manner.

Provided that toner A contains a% of a colouring matter (1) and toner B contains b% of another colouring matter (2), and the toners A and B are mixed in a mixing ratio by weight of :,B to prepare a toner mixture, the concentrations of the colouring matters (I) and (2) in the toner mixture are, respectively: 100 aa/(aa+b) and 100 bp(aa+bp).

The concentration of the colouring matters in the toner mixture was represented in terms of the larger of the concentrations of colouring matters (1) and (2). This concentration was represented by R.

The concentrations of the colouring matters (1) and (2) in the developed images sampled at the last printing operation of every 500 continuous printing operations were determined by the method described in item 1, above. The concentration of the colouring matters in the sampled developed images was represented in terms of the larger of the concentrations of colouring matters (1) and (2). This concentration was represented by rj.

The difference between the concentrations of the colouring matters in the developing agent at the start of the continuous printing process and the average concentration of the colouring matters in the developed images on the sampled testing specimens is:

3. Standard Deviation of the Concentration of the Colouring Matters in the Developed Images The standard deviation was calculated from:

wherein

The stability of chromaticity of thedeveloped images are represented by the standard deviation of the mixing ratio of the component toners in the developed images.

4. Evenness in Hue of Developed Images.

The evenness in hue of developed images continuously printed onto a large length of 10000 meters of a substrate, were classified by naked eye observation of ten experts in accordance with the following classification standard.

Class 1 extremely uneven 2 considerably uneven 3 slightly uneven 4 negligibly uneven 5 completely even The evenness is represented by an average of the results of the ten experts' evaluations.

5. Staining of Non-Image Area of Substrate With Developing Agent The degree of staining of the non-image area of the substrate with a developing agent was classified by naked-eye observation of ten experts in accordance with the following classification standard.

Class 1 highly stained 2 stained 3 slightly stained 4 negligibly stained 5 completely unstained -Examples 1 to 5 and A A yellow toner having an angle of repose of 83 degrees was prepared by mixing 85 parts of polyester resin and 15 parts of C.I. 12790 (C.I. Disperse Yellow 5), heating the mixture at a temperature of 1700C while kneading the mixture, cooling to solidify the mixture, and finely milling and screening the milled mixture so as to collect yellow toner particles having a size of 30 y or smaller. A blue toner having an angle of repose of 75 degrees was prepared in accordance with the same method except that 15 parts of C.I. 60767 (C.I. Disperse Blue 27) were used instead of the C.I. 12790.

Six developing agents were prepared by mixing equal weights of the yellow and blue toners with various amounts (as shown in Table I) of a heavy magnesium oxide (2 to 4 ml/g) having a particle size of about 2 4, except that magnesium oxide was omitted in Example A. Each developing agent was admixed with particulate iron at a covering rate of 110%.

Electrostatic latent images were formed on a photosensitive element consisting of an aluminium substrate, a photoconductive layer consisting of cadmium sulfide, and a polyethylene terephthalate insulating film. The latent images were developed with each of the given developing agents. The developed images were transferred onto a surface of a polyester fabric, and the transferred images were heated with steam at 1300C for 30 minutes to fix the images on the fabric, washed with trichloroethylene and dried. The properties of the developed agents are shown in Table I.

Examples 6 and B A blue toner having an angle of repose of 75 degrees was prepared from 95 parts of polystyrene and 5 parts of C.I. 61200 (C.I. Reactive Blue 19) by the same method as described for Examples 1 to 5. Separately, a colourless toner having an angle of repose of 82 degrees was prepared in the same manner except that no blue colouring matter was used.

Two developing agents were prepared by mixing 33-1/3 parts by weight of the blue toner, 66-2/3 parts by weight of the colourless toner and 0.5 parts by weight of a light magnesium oxide (8 to 10 ml/g) powder, except that magnesium oxide was omitted in Example B. Each developing agent was mixed with a particulate iron carrier at a covering rate of 90%.

Electrostatic latent images were formed on a xero-printing master sheet and developed with each developing agent. The developed images were transferred onto a cotton fabric which had been pretreated with an aqueous solution of sodium hydroxide, and the transferred images were fixed on the cotton fabric by being heated with steam at 1200C for 10 minutes.

The properties of the developed agents are shown in Table I.

Examples 7 to 9 and C A yellow toner having an angle of repose of 72 degrees was prepared by the same method as described for Examples 1 to 5, except that 80 parts of polystyrene and 20 parts of C.I. 11855 (C.I. Disperse Yellow 3) were employed. Separately, a red toner having an angle of repose of 81 degrees was prepared by the same process except that 90 parts of polystyrene and 10 parts of C.I. 11210 (C.I. Disperse Red 17) were used.

Four developing agents were prepared by mixing 10 parts by weight of the yellow toner, 90 parts by weight of the red toner and 0.5 parts by weight of various alkaline earth metal oxides (as shown in Table I) having a particle size of 3 p or smaller, except that no oxide was added in Example C. Each developing agent was mixed with a particulate iron carrier at a covering rate of 100%. The printing procedures described for Examples 1 to 5 were then carried out using these developing agents.

The results are shown in Table I, in which hMgO and 1MgO mean heavy and light magnesium oxide, respectively, the amount of the additive is in parts byweight per 100 parts by weight of the toners, the "mixing variation" is the fluctuation of the mixing ratio of the toners, and the "standard deviation" is that in the mixing ratio of the toners.

TABLE I Repose Mixing Standard Hue Non-image Amounts Angle variation deviation evenness staining Example Additive (parts) ( ) (%) (%) (class) (class) hMgO 3.0 30 0.9 0.56 4.5 4.8 2 hMgO 2.0 37 0.6 0.27 4.7 4.6 3 hMgO 1.0 45 0.3 0.09 4.8 4.7 4 hMgO 0.9 52 0.5 0.29 4.7 4.5 5 hMgO 0.05 59 1.4 0.81 4.5 4.4 A - - 82 1.7 1.52 2.3 2.8 6 1MgO 0.5 55 0.3 4.4 4.2 B - - 81 1.2 2.6 2.7 7 hMgO 0.5 54 0.6 0.38 4.6 4.5 8 CaO 0.5 57 1.0 0.50 4.2 4.1 9 BaO 0.5 59 1.2 0.64 4.1 4.1 C - - 81 2.5 2.07 2.5 2.3 Examples 10 to 14 and D A yellow toner having an angle of repose of 64 degrees was prepared in'the same manner as described for Examples 1- to 5, except that 80 parts of an alkylaminostyrene polymer and 20 parts of C.I. 12790 (C.I. Disperse Yellow 5) were used. A red toner having an angle of repose of 82 degrees was separately prepared using the same process except that 90 parts of the alkylaminostyrene and 10 parts of C.I. 60755 (C.I. Disperse Red 4) were used.

Six developing agents were prepared by mixing 10 parts by weight of the yellow toner, 90 parts by weight of the red toner and various amounts (as shown in Table II) of 2 - chloro - 4,6 - bis(p - sulfoanilino) - 1,3,5 - triazine disodium salt having a particle size of 5 p or smaller, except that the triazine was omitted in Example D. Each developing agent was mixed with a particulate iron carrier at a covering rate of 120%.

Electrostatic latent images were formed on a zinc oxide photosensitive layer and developed with each of the above developing agents. The developed images were transferred onto a polyester fabric and the transferred images were heated with steam at 1800C for 3 minutes. The printing operations were applied to 10,000 meters of-the polyester fabric. The results are shown in Table II.

Examples 15- to 17 and E A blue toner having an angle of repose of 80 degrees was produced from 85 parts of polyester and 15 parts of C.I. 61505 (C.I. Disperse Blue 3) by the same process as described for Examples 10 to 14. Separattly, a yellow toner having an angle of repose of 76 degrees was produced from 85 parts of the polyester and 15 parts of C.I. 26090 (C.I. Disperse Yellow 7) in the same manner.

Four developing agents were prepared by mixing 50 parts by weight of the blue toner, 50 parts by weight of the yellow toner, and 0.5 parts by weight of various triazines (as shown in Table II) having a particle size of 10 p or less. Each developing agent was mixed with a particulate iron carrier at a covering rate of 1.50%.

Electrostatic latent images were formed on a three-layer photosensitive element consisting of an aluminium substrate, a CdS photoconductive layer and a polyethylene terephthalate film, and developed with each of the above developing agents. The developed images were printed onto 10,000 meters of a polyester fabric in the same manner as described for Examples 10 to 14.

The results of the printing processes are shown in Table II.

Examples 18 and F A blue toner having an angle of repose of 81 degrees was produced in the same manner as described for Examples 10 to 14, except that in place of the yellow disperse dye, a reactive dye, C.I. 61200 (C.I. Reactive Blue 19), was employed.

Separately, a red toner having an angle of repose of 76 degrees was produced by the same method, except that a reactive red dye, C.I. 18159 (C.I. Reactive Red 3), was employed in place of the disperse red dye. Two developing agents were prepared by mixing 60 parts by weight of the blue toner, 40 parts by weight of the red toner and 3 parts of 2 - chloro - 4,6 - bis(p - sulfophenoxy) - 1,3,5 - triazine disodium salt, except that the triazine was omitted in Example F.

Electrostatic latent images formed on a xeroprinting master sheet were developed with each developing agent and the developed images were continuously printed on 10,000 meters of a cotton fabric which had been mercerised.

The results of the printing processes are shown in Table II, in which the nature of the triazine is indicated by reference to the appropriate formula in British Patent Specification No. 1,529,887 and 2 - chloro - 4,6 - bis(p - sulfophenoxy) - 1,3,5 triazine disodium salt is represented as CBIS.

Repose Mixing Standard Hue Non-image Amounts angle variation deviation evenness staining Example Additive (parts) (O) (%) (%) (class) (class) 10 III 5.0 33 1.0 0.64 4.2 4.1 11 III 3.0 41 0.6 0.32 4.5 4.4 12 III 1.0 46 0.4 0.18 4.6 4.5 13 III 0.1 52 0.3 0.16 4.5 4.3 14 III 0.01 59 1.0 0.78 4.1 4.2 D - - 83 1.6 1.69 2.7 3.0 15 I 0.5 53 0.8 0.39 4.2 4.3 16 III 0.5 51 0.5 0.21 4.5 4.4 17 VII 0.5 54 - 0.9 0.37 4.3 4.3 E - 81 3.3 1.90 2.8 2.9 18 CBIS 3 57 0.5 0.51 4.3 4.1 F - - 82 0.2 1.97 2.9 2.6 WHAT WE CLAIM IS: 1.A developing agent, suitable for use in an electrographic printing process, which comprises a mixture of separate particles of (i) a first toner; (ii) a second toner, coloured differently from the first toner; and (iii) an additive selective from alkaline earth metal oxides and triazines of the formula

wherein one or two of X, Y and Z are halogen and the other two or one, respectively, are selected from NR1(CH2)rnQ -NR-CH2-COOM

in which m is an integer of from 1 to 5, Q is SO3M, COOM or POOM, M is hydrogen or an alkali metal, R is C2~,8 alkyl, R' is hydrogen or methyl, R2 is hydrogen or hydroxy and q is one when Q is COOM or POOM or one, 2 or 3 when Q is SO3M; the mixture having a fluidity, measured as angle of repose (as hereinbefore defined), of from 20 to 60 degrees.

2. A developing agent as claimed in Claim 1 in which each toner has an absolute static charge of no more than 10-4 coulomb/g.

3. A developing agent as claimed in Claim 1 or Claim 2 in which the absolute difference in electrostatic charge between the toners is not more than 5xl0-5 coulomb/g.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (22)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   and 3 parts of 2 - chloro - 4,6 - bis(p - sulfophenoxy) - 1,3,5 - triazine disodium salt, except that the triazine was omitted in Example F.

   Electrostatic latent images formed on a xeroprinting master sheet were developed with each developing agent and the developed images were continuously printed on 10,000 meters of a cotton fabric which had been mercerised.

   The results of the printing processes are shown in Table II, in which the nature of the triazine is indicated by reference to the appropriate formula in British Patent Specification No. 1,529,887 and 2 - chloro - 4,6 - bis(p - sulfophenoxy) - 1,3,5 triazine disodium salt is represented as CBIS.

   Repose Mixing Standard Hue Non-image Amounts angle variation deviation evenness staining Example Additive (parts) (O) (%) (%) (class) (class)

   10 III 5.0 33 1.0 0.64 4.2 4.1

   11 III 3.0 41 0.6 0.32 4.5 4.4

   12 III 1.0 46 0.4 0.18 4.6 4.5

   13 III 0.1 52 0.3 0.16 4.5 4.3

   14 III 0.01 59 1.0 0.78 4.1 4.2 D - - 83 1.6 1.69 2.7 3.0

   15 I 0.5 53 0.8 0.39 4.2 4.3

   16 III 0.5 51 0.5 0.21 4.5 4.4

   17 VII 0.5 54 - 0.9 0.37 4.3 4.3 E - 81 3.3 1.90 2.8 2.9

   18 CBIS 3 57 0.5 0.51 4.3 4.1 F - - 82 0.2 1.97 2.9 2.6 WHAT WE CLAIM IS: 1.A developing agent, suitable for use in an electrographic printing process, which comprises a mixture of separate particles of (i) a first toner; (ii) a second toner, coloured differently from the first toner; and (iii) an additive selective from alkaline earth metal oxides and triazines of the formula

   wherein one or two of X, Y and Z are halogen and the other two or one, respectively, are selected from NR1(CH2)rnQ -NR-CH2-COOM

   in which m is an integer of from 1 to 5, Q is SO3M, COOM or POOM, M is hydrogen or an alkali metal, R is C2~,8 alkyl, R' is hydrogen or methyl, R2 is hydrogen or hydroxy and q is one when Q is COOM or POOM or one, 2 or 3 when Q is SO3M; the mixture having a fluidity, measured as angle of repose (as hereinbefore defined), of from 20 to 60 degrees.
2. 2. A developing agent as claimed in Claim 1 in which each toner has an absolute static charge of no more than 10-4 coulomb/g.
3. 3. A developing agent as claimed in Claim 1 or Claim 2 in which the absolute difference in electrostatic charge between the toners is not more than 5xl0-5 coulomb/g.
4. 4. A developing agent as claimed in Claim 3 in which the absolute difference in

   electrostatic charge is not more than 3x10-5 coulomb/g.
5. 5. A developing agent as claimed in Claim 4 in which the absolute difference in electrostatic charge is not more than 1.5x10-5 coulomb/g.
6. 6. A developing agent as claimed in any preceding claim in which each toner has an average particle size of not more than 100 p.
7. 7. A developing agent as claimed in Claim 6 in which the average particle size of each toner is not more than 40 p.
8. 8. A developing agent as claimed in any preceding claim in which the difference in the average particle size between the toners is not more than 20 p.
9. 9. A developing agent as claimed in any preceding claim in which the mixture additionally comprises particles of a carrier material.
10. 10. A developing agent as claimed in Claim 9 in which the carrier material is iron having an average particle size of 50 to 500 p.
11. 11. A developing agent as claimed in Claim 9 or Claim 10 in which there is not more than 3 times as much of the toners as of the carrier material, in terms of covering rate (as hereinbefore defined).
12. 12. A developing agent as claimed in any preceding cairn in which the additive is an alkaline earth metal oxide.
13. 13. A developing agent as claimed in Claim 12 which comprises from 0.01 to 5% by weight of the alkaline metal oxide, based on the weight of the toners.
14. 14. A developing agent as claimed in Claim 12 or Claim 13 in which the alkaline earth metal oxide is magnesium oxide.
15. 15. A developing agent as claimed in Claim 14 which comprises from 0.05 to 3% by weight of magnesium oxide, based on the weight of the toners.
16. 16. A developing agent as claimed in Claim 15 which comprises from 0.1 to 2% by weight of magnesium oxide, based on the weight of the toners.
17. 17. A developing agent as claimed in Claim 12 substantially as described in any of Examples 1 to 9.
18. 18. A developing agent as claimed in any of Claims 1 to 11 in which the additive is a triazine as defined in Claim 1.
19. 19. A developing agent as claimed in Claim 18 which comprises from 0.05 to 5.0% by weight of the triazine, based on the weight of the toners.
20. 20. A developing agent as claimed in Claim 19 which comprises from 0.1 to 3.0% by weight of the triazine, based on the weight of the toners.
21. 21. A developing agent as claimed in any of Claims 18 to 20 in which the triazine is selected from 2 - chloro - 4,6 - bis(p - sulfoanilino) - 1,3,5 - triazine disodium salt, 2 - chloro - 4,6 - bis(p - sulfophenoxy) - 1,3,5 - triazine disodium salt and 2,4 - dichloro - 6 - (p - sulfoanilino) - 1,3,5 - triazine sodium salt.
22. 22. A developing agent according to Claim 18 substantially as described in any of Examples 10 to 18.