FR2756942A1 - Electrophotographic toner giving good colour density on transfer to tile or glazed porcelain - Google Patents

Abstract

Toner composition consists of a binder resin and a finely-divided colourant comprising an oxide pigment and a flux. Also claimed are: (a) an electrophotographic copying process for transferring a toner image to a transfer sheet; (b) the transfer sheet with toner image; (c) a method of forming an image on a heat-resistant solid surface by transfer from this sheet and sintering; (d) the article obtained in (c); and (e) a method of producing the toner. The toner is produced by: (i) heating a first mixture of several metal compounds to 1000-1300 deg C to form a metal oxide pigment of the required colour; (ii) grinding the pigment; (iii) heating a second mixture of several metal compounds to 1000-1300 deg C to form a flux; (iv) grinding the flux; (v) mixing the pigment with the flux; (vi) sintering the mixture at 750-800 deg C; (vii) grinding the sintered mixture; (viii) kneading the mixture with a thermoplastic resin binder; and (ix) grinding the kneaded mixture. A metal oxide pigment is used, which contains numerous metal components with two-dimensional distribution when analysed with an electron probe microanalyser. The pigment is coated with a flux, which especially has a specific electrical resistance greater than that of the pigment. The flux especially is lead oxide. It is transparent after sintering and especially has the same colour as the pigment. The composition has an average particle diameter of 5-20 mu m, and is yellow, magenta, cyan or black in colour. The image is covered with thermoplastic resin, glass or substances that can be converted to glass.

Description

 The present invention relates to a developer composition for developing a latent electrostatic image on a sheet. The invention also relates to the use of the sheet bearing the image of the developer for the formation of a monochrome or color sintered design on a solid surface, for example of a glazed tile or porcelain.

Heretofore, a screen printing process has been used to form similar designs on several tiles or the like of porcelain. The document
JP-A-H8-119 668 provides a method in which an electrophotographic operation is used in place of screen printing, and describes a developer which contains a binder and a pigment suitable for the ceramic technique. The developer is used for developing a latent electrostatic image formed on a transfer sheet. The developer image transfer sheet is then applied to a surface of a ceramic body and is heated to fix the design to this surface. The document
JP-A-H8-119 668 suggests the use of the pigment in the form of a mixture with a vitreous material, such as a glass of borosilicate. Such a mixture is produced by mixing one or more metal oxide pigments with a vitreous material, the mixture then being melted at 900 ° C., before cooling and polishing.

The developer which is proposed in the document
JP-A-H8-119 668 poses a problem, however, because a drawing having a high image density cannot be obtained and because the color of the image is not uniform.

 A subject of the present invention is therefore the production of a developer which contains a metal oxide pigment which is useful for forming a pattern on a solid surface, for example of a ceramic, and which has a satisfactory density of color, even when the amount of pigment is low.

 Another subject of the invention is the production of a developer having a high development yield so that a latent electrostatic image of a transfer sheet can be effectively developed so that it forms a developer image of high density.

 The present invention also relates to the production of a developer of the aforementioned type with which a clean monochrome or color drawing can be produced with good reproducibility properties on a solid surface, for example of a ceramic.

 To this end, the invention relates to a developer composition which contains a finely divided coloring agent and a binder resin, the coloring agent containing a pigment of a composite oxide and a flux.

 In another aspect, the invention relates to a developer composition which contains a finely divided coloring agent and a binder resin, the coloring agent containing a flux, and a metal oxide pigment which itself contains several metallic ingredients, and wherein the metallic ingredients have the same two-dimensional distribution when analyzed by an electronic probe microanalyzer.

 The invention also relates to an image forming method which comprises applying electrophotographic treatment to a transfer sheet by using the above-mentioned developer composition, for forming a developer image on the transfer sheet. .

 The invention also relates to a sheet material which comprises a transfer sheet having an image formed by the above developer composition.

 The invention also relates to a method of forming a pattern on a solid and heat-resistant surface, comprising applying the above-mentioned image carrier sheet to the surface, and sintering the applied surface.

The invention further relates to a method for producing a developer, which comprises the following steps:
heating a mixture of several metallic compounds at a temperature of 1,000 to 1,300 "C to form a metallic oxide pigment having a desired color,
grinding the pigment
mixing the pigment with a flux,
sintering the mixture of pigment and flux at a temperature of 750 to 800 OC,
then grinding the sintered mixture,
then kneading the ground sintered mixture with a binder of a thermoplastic resin, and
grinding the kneaded mixture.

 Other objects, characteristics and advantages of the present invention will be better understood on reading the detailed description of preferred examples of implementation of the invention.

 The developer according to the present invention contains a binder resin and a finely divided coloring agent which comprises a composite oxide pigment and a flux.

 The composite oxide pigment is not a simple mixture of several metal oxides, but rather a metal oxide which contains several metals which interact with each other. A composite oxide pigment made up of two metallic ingredients is known as double oxide. Whether or not a metal oxide pigment containing several metal ingredients is a composite oxide pigment can be determined by analysis with an electronic probe microanalyzer. When the metallic ingredients of the pigment have the same two-dimensional distribution, the pigment is considered to be a composite oxide pigment.

 The composite oxide pigment can be obtained by heating a mixture of several metallic compounds at a temperature of 1,000 to 1,300 OC to form a metallic oxide pigment having a desired color. The metal oxide pigment is then cooled, solidified and ground to give a composite oxide pigment. The composite oxide pigment preferably has a volume average particle diameter which does not exceed 100 µm, when measured by a method employing a laser light scattering type particle size measuring apparatus, in which the sample to be measured is subjected to ultrasound in water containing a surfactant.

 It has been found that the composite oxide pigment gives a higher color density than a dye formed by a simple mixture of the corresponding metal compounds. More specifically, a desirable color concentration can be achieved even with a small amount of pigment. It is desirable that the satisfactory color density is obtained with an amount of pigment less than or equal to 9.45.10-4 g / cm2 in the case of a yellow pigment, to 9.45.10-4 g / cm2 in the case of '' a magenta pigment, at 7.35.10-4 g / cm2 in the case of a cyan pigment, and at 7.35.10-4 g / cm2 in the case of a black pigment.

Examples of suitable composite oxide pigments are as follows
(1) a yellow pigment obtained from antimony pentoxide (Sb205), ferric oxide (Fe203) and minium (pub304)
(2) a cyan pigment obtained from cobalt oxide (CoO), zinc white (ZnO) and chromium oxide (Cr203),
(3) a black pigment obtained from cobalt oxide (CoO), manganese oxide (MnO2), chromium oxide (Cr2O3) and ferric oxide (Fe2Q3), and
(4) a magenta pigment obtained from gold (Au), ferrous oxide (FeO) and tin oxide (SnO).

 The composite oxide pigment is combined with a flux for the formation of the coloring agent. It is preferable that the pigment is covered with the flux so that leakage of electrostatic charges during the development stage is avoided.

 It is also preferable that the flux has an electrical resistivity greater than that of the composite oxide pigment. In general, the electrical resistivity of the flux is between 106 and 1016 Q.cm, while that of the pigment is between 105 and 108 R.cm.

 The flux is used to bond the developer image to a solid surface to be colored such as a ceramic surface, after sintering. An enamel material usually used in the field of ceramic technology can advantageously be used as a flux.

 The flux may, for example, be a feldspar, for example a potassium, sodium or lithium feldspar, a natural mineral material such as kaolin, alumina, a silica rock, quartz, titanium oxide, silica, chamotte, limestone, talc, magnesia, dolomite, mineral ash or a mixture thereof, an alkali or alkaline earth hydroxide, such as lithium hydroxide, an alkali or alkaline earth carbonate, such as lithium carbonate, an alkali or alkaline earth chloride, aluminum chloride, boric acid, an alkali or alkaline earth salt of boric acid, an alkali or alkaline earth salt of metaboric acid, an alkaline or alkaline earth salt of phosphoric acid, an alkaline or alkaline earth salt of pyrophosphoric acid, an alkaline or alkaline earth salt of silicic acid, an alkaline or alkaline earth salt of acid metasilicate, zirconium silicate, bone ash, borax, metavanad ate of ammonium, a metal oxide such as tungsten oxide, vanadium pentoxide, tin oxide, zirconium oxide, cerium oxide, molybdenum oxide or oxide of lead, a metal fluoride such as calcium or aluminum fluoride, a glass or a mixture thereof.

 It is preferable that the flux contains a lead compound because it improves the adhesiveness and film-forming properties. It is also preferable that the fondant is transparent when it is sintered for reasons of clarity of the images. It is also preferable that the fondant has the same color tone as the pigment after sintering. The expression "same color tone" used in the present specification refers for example to the relationship between red and pink, between egg yolk and lemon yellow, or between dark blue and sky blue. In this case, the flux has no detrimental effect on the color tone of the pigment when the developer image is fixed.

 The flux and the composite oxide pigment are formed by sintering a mixture of the pigment with the flux at a temperature which is preferably from 750 to 800 ° C., then by grinding the sintered mixture to obtain the coloring agent. finely divided. In this case, it is preferable that the flux is heat treated at a temperature of 1000 to 1300 OC before being mixed with the pigment, to prevent loss of color of the composite metal oxide pigment during sintering. The weight ratio of the composite oxide pigment to the flux is preferably 0.1 / 3. The coloring agent preferably has an average diameter of 1 to 10 µm.

 The agent is used for the preparation of the developer intended for an electrophotographic operation, in the form of a mixture with a binder resin and any other suitable known adjuvant or, if necessary, it can be used as it is for screen printing, inkjet printing and continuous jet printing. When used in the form of a developer, the finely divided coloring agent, which contains the above-mentioned flux and pigment, is mixed in any known manner with a binder. For example, a mixture of the coloring agent and the binder is kneaded at a temperature higher than the melting temperature of the binder. The kneaded mixture is then solidified and ground into particles intended to give a developer according to the invention. The developer preferably has an average particle diameter of between 5 and 20 ssm. The amount of the coloring agent in the developer is preferably between 5 and 60 k by weight.

 The binder can be any thermoplastic resin usually used in the field of developers for electrophotography, for example a polyester, polystyrene, polyethylene, polyamide, epoxy, epoxypolyol, terpene resin or a mixture of such resins. Examples of suitable thermoplastic resins are polystyrene, copolymers of styrene and methyl acrylate, copolymers of styrene and ethyl acrylate and copolymers of styrene, acrylic acid and n-acrylate. butyl.

 The developer preferably contains a commonly used charge control agent. Examples of such suitable positive charge adjusting agents are nigrosine dyes, quaternary ammonium salts, dyes containing Cr, dyes containing Zn, dyes containing Fe, dyes of chelate of molybdic acid and fluorinated modified quaternary ammonium salts. The amount of the charge control agent is generally between 0.1 and 10 parts by weight and preferably between 2 and 6 parts by weight per 100 parts by weight of the binder resin.

 The developer according to the present invention may also contain one or more adjuvants if necessary.

Examples of adjuvants are zinc stearate, hydrophobic silica, aluminum stearate and titanium oxide.

 The developer according to the present invention can be used as a one-component development system in which the developer is used by itself for the development of a latent electrostatic image, or in the form of a two-component development system in which the developer is used with particles of a carrier for the development of a latent electrostatic image. The carrier can be (a) magnetic particles, for example of metals, compounds and alloys of iron, cobalt and nickel, (b) glass beads, or (c) composite particles formed of magnetic particles above or above glass beads each coated with a layer of a resin. Examples of a resin which is suitable for forming the resin coating are a fluorinated hydrocarbon polymer, polyvinyl chloride, polyvinylidene chloride, a phenolic resin, polyvinyl acetal and a silicone resin. In the two-component type system, the developer is used in an amount of between 1 and 20 parts by weight and preferably between 8 and 12 parts by weight per 100 parts by weight of the carrier.

 The developer according to the present invention is used for the formation of a desired monochrome or color design on a continuous surface which resists heat.

The pattern can be formed by directly developing a developer image on the solid surface, the developed developer image then being heated so that it is attached to the solid surface. Alternatively, the design may be formed by a method comprising developing a developer image on a transfer sheet, then applying the sheet carrying the image to the solid surface and heating the sheet so that the image is attached to the solid surface. As the first direct method requires a specific machine for developing the developer image, the second indirect method is preferably used.

 In the indirect method, a commercially available monochrome or color copier can be used for developing a desired developer image on a transfer sheet. The transfer sheet may consist of a substrate, for example of paper, of a resin film or of a glass film, on which is deposited an adhesive layer, for example of a water-soluble adhesive, such as dextrin or polyvinyl alcohol. The developer image is formed on the adhesive layer. Commercially available transfer sheets, of the type used for screen printing and suitable for the ceramic technique, can be used as such in the context of the present invention.

 The surface of the transfer sheet which carries the image preferably receives a deposit of a solution or dispersion which contains a water-insoluble thermoplastic resin, a glass powder or a fondant powder, since the design, after calcination , has better sharpness. The transfer sheet is then immersed in water and separated in the form of the substrate and the surface layer having the developer image.

 The surface layer carrying the image thus separated from the substrate is applied to an article having a heat-resistant surface, for example a tile, an enameled ceramic (for example a glass-ceramic material, an earthenware or a porcelain), a refractory glass , a metal or a metal coated with porcelain enamel.

 It is preferable that the heat resistant solid surface has a high whiteness which gives a clear colored pattern. Preferably, the whiteness of the solid surface is such that the reflectance of light at a wavelength between 450 and 800 nm is at least equal to 93 W and preferably to 98 W. In addition, it is preferable that the solid surface has a low surface roughness, that is to say that the average surface roughness Rz determined at two points by the pulp test method No. 5-7 of the Japanese standard TAPPI is preferably lower or equal to 5 ssm and very advantageously less than or equal to 1 ssm.

 It is also preferable that the solid surface be coated with a fusible mineral substance, such as glass, enamel or flux, so that the adhesion of the developer design to the solid surface is better. Such a coating preferably has a thickness of 1 to 20 Hm and very advantageously of 3 to 10 μm. Alternatively, the fusible mineral can be incorporated into the solid surface if desired.

 The solid surface on which the surface layer bearing the image is applied is then sintered between 800 and 850 OC for 1 to 10 h in an oven of any known type, for example an electric oven, a microwave oven or a dielectric oven , to obtain the final product having a monochrome or color design. Where appropriate, sintering is carried out by adjusting the oxidation and reduction conditions.

 The examples which follow illustrate the present invention more fully. The parts are indicated by weight.

Preparation of a fondant
A mixture of metal oxides composed of 80 parts of Al203, 370 parts of SiO2, 50 parts of Na2O and 500 parts of PbO (mixture designated hereinafter simply as Al203 / SiO2 / Na2O / PbO of 80/370/50 / 500) was ground in a bocard mill and then mixed with a "Henschel" mixer. The mixture was then heat treated at 1,200 ° C. to obtain a fondant (hereinafter called "fondant A"). A sample (10 g) of flux A was placed in a cylindrical electrode chamber of a 4329 high resistance meter (manufactured by
YHP Inc.) and was measured for the determination of volume resistivity under a load of 5 g. The measurement was made on five samples and the resistivity values were used for the formation of the mean. It was found that the flux A had a resistivity of 1.69.109 Q.cm.

Preparation of coloring agents (A) Black composite oxide pigment
A mixture of metal oxides Cr203 / MnO / Fe203 / CoO of 110/270/112/508 was ground with a bocard mill and then mixed in a "Henschel" mixer. The mixture was then subjected to a heat treatment at 1100 ° C. to obtain a composite oxide pigment (hereinafter called pigment A).

 Pigment A (300 parts) was then mixed with 500 parts of flux A with a "Henschel" mixer and the mixture was calcined at 750 ° C. and then ground to obtain a coloring agent (hereinafter called coloring agent) AT).

(B) Yellow composite oxide pigment
A mixture of metallic oxides Fe203 / Sb205 / Pb304 of 10/190/800 was ground with a bocard mill and then mixed by a "Henschel" mixer. The mixture was then heat treated at 1100 ° C. to obtain a composite oxide pigment (hereinafter called pigment B).

 Pigment B (300 parts) was then mixed with 500 parts of flux A using a "Henschel" mixer, and the mixture was calcined at 750 ° C. and then ground to obtain a coloring agent ( hereinafter called coloring agent B).

(C) Magenta composite oxide pigment
A mixture of metallic oxides Fe203 / SiO / CuO / Au2O of 160/40/40/760 was ground in a bocard mill and then mixed with a "Henschel" mixer. The mixture was then heat treated at 1100 ° C. to obtain a composite oxide pigment (hereinafter called pigment C).

 Pigment C (300 parts) was then mixed with 500 parts of flux A with a "Henschel" mixer and the mixture was calcined at 750 ° C. and ground to obtain a coloring agent (hereinafter called coloring agent) VS).

(D) Cyan composite oxide pigment
A mixture of metal oxides Cr203 / Fe203 / Co203 / ZnO of 170/10/690/130 was ground with a bocard mill and then mixed by a "Henschel" mixer. The mixture was then subjected to a heat treatment at 1100 ° C. to obtain a composite oxide pigment (hereinafter called pigment D).

 Pigment D (300 parts) was then mixed with 500 parts of flux A with a "Henschel" mixer and the mixture was calcined at 750 ° C. and ground to obtain a coloring agent (hereinafter called coloring agent) D).

(E) Black oxide pigment E
A mixture of metal oxides Cr203 / MnO / Fe203 / CoO of 110/270/112/508 was ground with a bocard mill and then mixed using a "Henschel" mixer to obtain a pigment. oxide (hereinafter called pigment E).

 Pigment E (300 parts) was then mixed with 500 parts of flux A with a "Henschel" mixer, and the mixture was calcined at 900 ° C. and ground to obtain a coloring agent (hereinafter called agent) dye E).

(F) Black oxide pigment F
Cr2O3 (300 parts) was mixed with 500 parts of flux A with a "Henschel" mixer and the mixture was calcined at 900 ° C. and then ground to obtain a first mixture. MnO (300 parts) was then mixed with 500 parts of flux A with a "Henschel" mixer and the mixture was calcined at 900 OC and then ground to obtain a second mixture. Fe203 (300 parts) was mixed with 500 parts of flux A with a "Henschel" mixer and the mixture was calcined at 900 "C and ground to obtain a third mixture. CoO (300 parts) was mixed to 500 parts of flux A with a "Henschel" mixer and the mixture was calcined at 900 ° C. and ground to obtain a fourth mixture. The four mixtures were then mixed to obtain a coloring agent F having a Cr203 / MnO / Fe203 / CoO weight ratio of 110/270/112/508.

Physical properties of AF pigments and AF coloring agents
AF pigments were each subjected to a volume resistivity measurement and it was found to be between 1.56.106 Q.cm and 5.89.108 Q.cm. Analysis using a SEM scanning electron microscope (magnification 2000) of the coloring agents A to F showed that the pigments A to F were covered with flux A.

 The coloring agents A to F were analyzed by an electronic probe radiographic microanalyzer ("EPMA-8705" manufactured by Shimadzu Seisakusho Co. Ltd.) by the following method.

 A sample was irradiated with an electron beam (beam diameter 1 µm) and the characteristic X-rays created were analyzed spectrometrically to determine the respective elements constituting the coloring agent. The colors are transferred for the respective elements as a function of the image of the SEM scanning electron microscope (magnification 2000). The area of the diagram on the color image for each of the elements is measured. The surface (S1, S2, ... Sn) of the design of each of the elements constituting the pigment is compared to the surface (S) of an element chosen from among the elements (for example Tb) of the flux. When all the surfaces S1 to Sn are in the range 0.9 S to 1.1 S, the distribution of the elements constituting the pigment is considered to be the same.

The results showed that the coloring agents A to
D gave the same distribution. The distribution of the elements constituting the pigments of the coloring agents E and
F was assessed as not being the same.

Vehicle preparation
Silicone resin ("KR50" manufactured
by Shinetsu Kagaku Inc.) 100 parts
Carbon black ("BP2000" manufactured
by Cabott Inc.) 3 parts
Toluene 100 parts
The above composition was mixed with a mixer for 30 min to form a dispersion.

The latter was loaded into a fluidized bed type coating device with 1000 parts of ferrite particles having an average particle diameter of 100 µm.

The ferrite particles thus coated were dried to obtain a carrier A.

Developer and Developer Agent Preparation
230 parts of each of the coloring agents A to F, 100 parts of an epoxy resin (Tg = 60 OC) and 4 parts of zinc salicylate ("Bontron S84" manufactured by Orient
Chemical Inc.) were mixed using a mixer and the mixture was kneaded with a two-cylinder mixer.

The kneaded mixture was rolled, solidified, crushed and sieved to obtain a developer (developers A to F) having a volume average particle diameter indicated in table 1. Each of the developers A to F was mixed at 0 , 5% by weight of hydrophobic silica ("R972" manufactured by
Japan Aerosil Inc.) using a blender. The resulting mixture (90 parts) was then mixed with 910 parts of the carrier A in a ball mill for 30 min with development agents A to F.

Table 1
Particular diameter
Development Agent Medium Milk Developer
developer (clam)
Development Agent A Developer A 9.3
Development agent B Developer B 9.5
Development agent C Developer C 9.7
Development Agent D Developer D 9.3
Drawing formation on a tile
A copy image was formed on a commercially available transfer sheet ("OK Series" sheet for ceramic technique screen printing, manufactured by Nitto
Shiko Inc., in the form of a laminate composed of a surface layer, an adhesive layer and a substrate) using each of the developers A to F loaded into a copier ("Imagio 530" manufactured by Ricoh Company Ltd.) under the following conditions processing speed 120 m / s charging voltage -650 V exposure voltage -100 V development space 0.6 mm scraping space 0.45 mm linear speed ratio 1, 5 (compared to
photoconductor) alternative development polarization (1 kV between
peaks) + continuous (-500 V) transfer polarization on 1400 V
1300 V transfer polarization belt
paper
The developer image surface of the transfer sheet was coated with a layer of polystyrene and then immersed in water to remove the substrate. The substrate layer was applied to a tile ("RS252 / 1001" manufactured by Inax
Inc.), and the whole was sintered at 800 ° C. for 5 h to obtain a desired tile having a design corresponding to the developer image. The density of the image of the design on the tile formed using each of the development agents A to F is indicated in Table 2.

Table 2
Developer Density of image
At 1.57
B 1.12
C 1.09
D 1.07
E * 0.82
F * 0.52
*: comparative example
The invention can be implemented in other forms without departing from the scope of the invention.

 Of course, various modifications can be made by those skilled in the art to the methods, compositions, materials and articles which have just been described solely by way of non-limiting example without departing from the scope of the invention.

Claims (17)

 1. Developer composition, characterized in that it contains a finely divided coloring agent and a binder resin, the coloring agent containing a composite oxide pigment and a flux.  2. Developer composition, characterized in that it comprises a finely divided coloring agent and a binder resin, the coloring agent containing a flux and a metal oxide pigment which contains several metallic ingredients, the metallic ingredients having the same two-dimensional distribution during analysis by an electronic probe microanalyzer.  3. Composition according to one of claims 1 and 2, characterized in that the pigment is covered with the flux.  4. Composition according to one of claims 1 and 2, characterized in that the flux has an electrical resistivity greater than that of the pigment.  5. Composition according to one of claims 1 and 2, characterized in that the flux contains lead oxide.  6. Composition according to one of claims 1 and 2, characterized in that the flux is transparent when it has been sintered.  7. Composition according to one of claims 1 and 2, characterized in that the flux and the pigment have the same color tone.  8. Composition according to one of claims 1 and 2, characterized in that the amount of the pigment is between 0.1 and 3 parts by weight per part by weight of the flux.  9. Composition according to one of claims 1 and 2, characterized in that it has an average particle diameter of between 5 and 20 µm.  10. Composition according to one of claims 1 and 2, characterized in that it has a color chosen from the colors yellow, magenta, cyan and black.  11. An image forming method, characterized in that it comprises the application of an electrophotographic operation to a transfer sheet using a developer composition according to claim 1, for the formation of an image of the developer on the report sheet.  12. The method of claim 11, characterized in that it further comprises covering the image formed on the transfer sheet with a layer of a material chosen from the group consisting of thermoplastic resins, glass and vitrifiable substances.  13. Sheet material, comprising an image carrying sheet formed by a developer composition according to claim 1.  14. Sheet material according to claim 13, characterized in that it further comprises a layer which covers the image and which is formed from a material chosen from the group which consists of thermoplastic resins, glass and vitrifiable substances.  15. A method of forming a pattern on a solid heat resistant surface, characterized in that it comprises applying an image support sheet according to claim 13 to said surface, and sintering the surface after application.  16. Article, characterized in that it is obtained by implementing the method according to claim 15.  17. Method for manufacturing a developer, characterized in that it comprises the following steps  heating a first mixture containing several metallic compounds at a temperature between 1,000 and 1,300 OC for the formation of a metallic oxide pigment having a desired color,  grinding the pigment,  heating a second mixture of several metallic compounds at a temperature between 1,000 and 1,300 OC for the formation of a flux,  the crushing of the flux,  mixing the pigment with the flux,  sintering the mixture of the pigment with the flux at a temperature between 750 and 800 OC,  grinding the sintered mixture,  kneading the ground sintered mixture with a binder of thermoplastic resin, and  grinding the kneaded mixture.