GB2059618A - Developer for electrostatic latent images - Google Patents

Abstract

An electrostatographic developer composition including a carrier material and a toner, the toner comprising a resin and a mixture of at least two colorants selected from cyan, magenta and yellow. The resin may be a styrene/n-butyl methacrylate copolymer. The cyan colorant may be copper tetra-4- octadecylsulfono-mido) phthalocyanine, the magenta colorant may be 2,9-dimethyl substituted quinacridone, and/or the yellow colorant may be diarylide yellow 3,3-dichlorobenzidene aceto acetanilide. The developer composition is useful for developing color images in an electrophotographic imaging system.

Description

SPECIFICATION Electrostatog ra phic developer composition This invention relates to an electrostatographic developer composition which is particularly useful in color electrophotography.

The formation and development of images in an electrophotographic system, and more specifically a xerographic system is well known as described, for example, in U.S. Patent 2,297,691. In such systems, several methods are used for applying the electroscopic particles or toner to the latent electrostatic image to be developed, such methods including cascade development, U.S. Patent 2,618,552; magnetic brush development, U.S. Patent 2,874,063; powder cloud development, U.S. Patent 2,221,776; touchdown development, U.S. Patent 3,166,432 and the like. Generally, the toners used in these types of systems result in the production of black images.

Recently there have been developed processes and materials for use in the formation of color images. Electrophotographic color systems are generally based on trichromatic color synthesis, such as the substractive color formation types. Accordingly, in electrophotographic color systems, toner or developing particles of at least three different colors are employed to synthesize any desired color. Generally, at least three color separation images are formed and the combined images register with each other to form a colored reproduction of a full colored original. In color xerography as described, for example, in Dessauer U.S. Patent 2,962,374, at least three latent electrostatic images are formed by exposing a xerographic plate to different optical color separation images.Each of the latent electrostatic images is developed with a different color toner and subsequently the three toner images are combined to form the final full color image. This combination of three color toner images is generally made on a copy sheet such as paper to which the toner images are permanently affixed. One of the most common techniques for fixing these toner images to the paper copy sheet is by employing a resin toner which includes a colorant, and heat fixing the toner images to this copy sheet. Images may also be fixed by other techniques such as, for example, subjecting them to a solvent vapor.

In one known process an electrostatic latent image is exposed through a green filter to an imagewise projection of a color image to form an electrostatic latent image on the photoreceptor. This electrostatic latent image is then developed with the complementary magenta color toner to form a magenta colored image corresponding to said electrostatic latent image and transferred in register to an image receiving member. The photoreceptor is then electrostatically charged uniformly in the dark and exposed through a red filter to an imagewise projection of a color image in register with said magenta developed image to form a second electrostatic latent image which second image is developed with the complementary cyan-colored toner and likewise transferred in register.The photoconductor is again electrostatically uniformly charged in the dark and then exposed through a blue filter to an imagewise projection of a color image in register with said magenta and cyan developed images to form a third electrostatic latent image which is then developed with the complementary yellow toner and again transferred in register. The sequence of exposures through colored filters in this multiple development process may be performed in any suitable sequence other than the green, red and blue mentioned.

In these systems one important aspect resides in registration of the color toner image on the copy sheet, that is, the cyan, magenta, and yellow image should be in registration on the receiving member.

Generally, each developer used comprises a toner of resin colored mixture in combination with an appropriate carrier. The toners used must possess the appropriate color and continue to function under machine conditions which expose the developer to impaction and humidity among other undesirable factors. A three color system that has been well known and used in the past includes pigments of suitable cyan, magenta and yellow materials. One of the problems associated with the prior art processes is that it is necessary to use multiple passes, that is, three steps in development with three different colors, which can become cumbersome, uneconomical and slow.Other disadvantages of the prior art processes include the requirements that, (1) the photoreceptor be panchromatic, (2) the development response of each of the three toner developers be constant with usage, and (3) the transfer of the three different developed images be constant.

Also it is known in the prior art that the three color layers can be coated one on top of the other, the first layer being the magenta layer, the second being the cyan layer and the third being the yellow layer. Each substractive color transmits two thirds of the spectrum and absorbs one third. The combination of cyan, magenta and yellow layers appears black, while the combination of magenta and yellow layers appears red, the combination of magenta and cyan layers appears blue and the combination of yellow and cyan layers appears green.

According to the present invention there is provided an electrostatographic developer composition including a carrier material and a toner, the toner comprising a resin, and a mixture of at least two colorants selected from cyan, magenta and yellow.

The amounts of ingredients used in the blended toner can vary substantially, such amounts depending on the shade of color desired. Essentially thus any quantity, including the same amounts, or different amounts of cyan, magenta, and yellow materials can be used depending on the shade of color desired. Accordingly, while there is no real preference as to the amounts of colorant used illustrative examples include the following: Approximate Parts of Parts of Parts of Desired Color Cyan Magenta Yellow Shade By Weight By Weight By Weight 1. Yellowish Green 1 0 7 2. Orange 0 1 7 3. Green 1 0 2 4. Blue Green 2 0 1 5. Chocolate Brown 1 2 2 6. Red O 1 1 7. Blue 3 1 0 8. Red 0 2 1 9. Orange (Light) 0 1 2 10.Blue 1 1 0 The percentage of pigment, or colorant, and resin present in the toner can vary depending on many factors including the shade of toner desired, generally, however, from about 1 percent to about 20 percent by weight, and preferably 5 to 1 2 percent by weight of colorant is present, and from about 80 percent to about 99 percent by weight, and preferably from 88 percent to 95 percent by weight of resin is present. It is not intended to be limited to the above amounts as greater and lesser amounts of colorants can be used such amounts effecting only the shade of color to be obtained.

The appropriate amounts of cyan, magenta, and yellow toners can be combined by any suitable method including for example simple known mixing and stirring methods. One specific method employed for combining these materials involves the use of a twin shell mixing-blending apparatus at rotation rates of from about 30 to about 50 revolutions per minute, followed by filtering the resultant blend using a 44 micron sieve for the purpose of eliminating agglomerates. It is important to note that the method by which the materials are blended is not critical, however, though complete mixing is desired so as to result in the production of a homogeneous mixture. In addition to twin shell mixing other types of mixing methods may be employed, including for example paint shaker mixing; Mumson mixing and the like.

Illustrative examples of magenta materials which may be used in the toner include 2,9dimethyl substituted quinacridone, an anthraquinone dye identified in the Colour Index as Ct 60710, Cl Dispersed Red 15, a diazo dye identified in the Colour Index as Cl 26050, Cl Solvent Red 19, and the like.

Illustrative examples of cyan materials that may be used in the toner include copper tetra-4 (octadecylsulfonomido) phthalocyanine, an X-copper phthalocyanine pigment listed in the Colour Index as Cl 74160, CI Pigment Blue 15, an indanthrene blue identified in the Colour Index as Cl 69810, Special Blue X-2137, and the like.

Illustrative examples of yellow materials that may be used in the toner include diarylide yellow 3,3-dichlorobenzidene aceto-acetanilide, a monoazo dye identified in the Colour Index as CI 12700, Cl Solvent Yellow 16, a nitrophenylaminesulfonamide identified in the Colour Index as Foron Yellow SE-GLF, Cl Dispersed Yellow 33, and the like.

Several single suitable carrier materials can be employed including but not limited to sodium chloride, ammonium chloride, granular zinc, silicon dioxide, methyl methacrylate nickel, glass, steel, iron ferrite and the like. Coated carrier materials may also be used, including for example the above mentioned carriers coated with organic materials such as fluorinated polymers, including polyvinylidene fluoride. Many of the carriers that can be used are described in U.S.

Patents 2,618,441, 2,638,416, 3,591,503, 3,533,835, and 3,526,533. Also nickel berry carriers as described in U.S. Patents 3,847,604 and 3,767,598 can be employed, these carriers being nodular carrier beads of nickel characterized by surfaces of recurring recesses and protrusions providing particles with a relatively large external area. It is important that the carrier that is selected establishes the appropriate triboelectric relationship with the resin that is used, which resin is described in detail hereinafter, in order to enable it to function effectively in an eiectrophotographic imaging mode. Generally, the carrier ranges in size from about 35 microns in diameter to about 250 microns and preferably from about 80 microns to about 1 50 microns.

The amount of carrier present can vary depending on many factors, including for example the mass density of the carrier; generally, however, about 0.5 percent to about 5 percent by weight, and preferably 1 percent to 3 percent by weight of carrier is present in the developer mixture.

The blended cyan, magenta, and yellow materials may be combined with any suitable electrophotographic resin including but not limited to thermoplastics like olefin polymers such as polyethylene and polypropylene; polymers derived from dienes such as polybutadiene, polyisobutylene, and polychloropyrene, vinyl and vinylidene polymers such as polystyrene, styrene butylmethacrylate copolymers, styrene-acrylonitrile copolymers, acrylonitrile-butadiene styrene terpolymers, polymethylmethacrylate, polyacrylates, polyvinyl alcohol, polyvinyl chloride polyvinyl carboazole, polyvinyl ethers, and polyvinyl ketones, fluorocarbon polymers such as polytetrafluoroethylene and polyvinylidene fluoride; heterochain thermoplastics such as polyamides, polyester, polyurethanes, polypeptides, casein, polyglycols, polysulfides, and polycarbonates; and cellulosic copolymers such as regenerated cellulose, cellulose acetate and cellulose nitrate.

Generally resins containing a relatively high percentage of styrene are preferred, such as homopolymers of styrene or styrene homologs of copolymers of styrene, with other monomeric groups containing a single methylene group attached to a carbon atom by double bond.

The developer composition of the present invention may be used with any suitable inorganic or organic photoconductor. Typical inorganic photoconductor materials include but are not limited to sulfur, selenium, zinc sulfide, zinc oxide, zinc cadmium sulfide, zinc magnesium oxide, cadmium selenide, zinc silicate, calcium-strontium sulfide, cadmium sulfide, indium trisulfide, gallium triselenide, arsenic disulfide, arsenic trisulfide, arsenic triselenide, antimony trisulfide, cadmium sulfoselenide and mixtures thereof.Typical organic photoconductors include but are not limited to triphenylamine; 2,4-bis(4,4'-diethyl-amino-phenyl)- 1 , 3,4-oxadiazol; N-isopropylcarbazole triphenylpyrrol; 1 .2,5,6-tetraaza-N-isopropyl-carbazole triphenylpyrrol; 4,5-diphenylimidazolidinone; 4,5-diphenylimidazolidinethione; 4-5-bis-(4'-amino-phenyl)-imidazolidione; 1,5-dicyanonaphthalene; 1 ,4-dicyanonaphthalene; aminophthalodinitrile; nitrophthallodinitrile; 1,2,5,6 tetraazacyclooctatetranene-(2,4,6,8); 2-mercapto-benzathiazole; 2-phenyl-4-diphenylidene-oxazo- lone; 6-hydroxy-2, 3-di(p-methoxyphenyl)-benzofurane; 4-dimethyl-aminobenzylidene-benzhydrazide; 3-benzylidene-amino-carbazole; polyvinyl carbazole; (2-nitrobenzylidene)-p-bromo-aniline; 2,3-diphenyl quinazoline; 1,2,4-triazine; 1,5-diphenyl-3 methyl-pyrazoline; 2-(4'-dimethylaminophenyl)-benzoxazole; 3-aminocarbazole; phthalocyanines; trinitrofluoronone polyvinyl carbazole; charge transfer complexes and mixtures thereof.

Typical methods of charging a photoconductor include corona, charge deposition resulting from air breakdown in the gap commonly referred to as TESI, or charging in vacuum with an electron gun.

Any suitable method of exposure of the charged photoconductor may be employed. Typical methods of exposure include; reflex, contact, holographic techniques, non-lens slit scanning systems, and optical projection systems involving lens imaging of opaque reflective subjects as well as transparent film originals.

Any suitable method of development of the resulting electrostatic latent image may be employed. Typical development systems include: cascade development and magnetic brush development.

Any suitable method of fixing the developed image may be employed. Typical methods of fixing include: heat-pressure fusing, combination radiant, conductive and convention fusing, such as oven fusing, cold pressure fixing, solvent fusing, and a combination of heat, pressure and solvent fusing.

The above mentioned developers were found to perform exceptionally well when used for the production of color xerographic printes from an original. There was no degradation of the triboelectric properties of the developer, nor unacceptable imaging due to impaction, and other problems associated with prior art developers. In one embodiment the developer of the present invention is provided from a developer housing in an automatic color electrophotographic imaging machine. A photoconductive member is then charged, selectively exposed to light of the primary colors, or one of the primary colors, developed with the developer of the present invention, transferred to a suitable substrate, such as paper, and then fused.

The developers of the present invention are especially useful in flat color copying systems.

The term flat color is well known in the art, thus for example in the printing industry, flat color copying is accomplished by effecting multiple passes of the output print, through a printing press. Each pass of the print results in the production of a different color. Gradations of value or darkness, and chroma, or saturation are obtained by halftoning techniques, however, gradations of hue during a single pass do not result. Accordingly, the colors on the output print are usually of a uniform shade, and of a uniform darkness, and the number of hues represent the number of passes, by the output document through the press.

The invention will now be described in detail with respect to specific preferred embodiments thereof, it being understood that these examples are intended to be illustrative only and the invention is not intended to be limited to the materials, conditions, process parameters, etc.

recited herein. All parts and percentages are by weight unless otherwise indicated.

EXAMPLE I There was prepared a brownish colored toner blend by mixing together at room temperature 2 parts by weight of the magenta toner material, 2,9-dimethyl substituted quinacridone, 1 part by weight of the cyan toner material copper tetra-4-(octadecylsulfonomido) phthalocyanine, and 2 parts by weight of the yellow toner material diarylide yellow 3,3-dichlorobenzidene aceto acetanilide in a twin shell apparatus having a rotation rate of about 45 revolutions per minute the mixing being accomplished for a period of about 1/2 hours.

The magenta, cyan, and yellow toners are prepared by melt blending 90 parts by weight of a styrene-n-butyl methacrylate copolymer resin, (58/42) and 10 parts by weight respectively of, the magenta material, a 2,9-dimethyl substituted quinacridone, the cyan toner material copper tetra-4-(octadecylsulfonomido) phthalocyanine, and the yellow material, diarylide yellow 3,3dichlorobenzidene aceto acetonilide.

The resultant brownish colored toner blend 97 parts by weight is mixed with 3 parts by weight of a steel carrier. The resultant developer is then employed in a commercial automatic xerographic machine apparatus, and excellent color copies of high resolution rsult after a single development sequence.

The developer produced can also be used in a magnetic brush developer system, which system is positioned around the selenium photoreceptor. The photoreceptor is charged to a positive potential of + 100 volts, and exposed to an image. The latent electrostatic image formed on the photoreceptor is developed with the above developer by engaging the developer housing into development configuration with the photoreceptor. The image on the photoreceptor is then transferred to a receiver sheet in register. The photoreceptor is cleaned of the residual toner and is then ready for a subsequent exposure. The receiver sheet containing the cyan, magenta and yellow toner is then heat fused.

The above process was repeated numerous times, and 75,000 color prints of good contrast, color, and quality were produced.

EXAMPLE II The procedure of Example I was repeated with the exception that a yellow-green shade toner is produced by mixing together zero parts by weight of 2,9-dimethylquinacridone, 1 part by weight of copper tetra-4-(octadecylsulfonomido) phthalocyanine and 7 parts by weight of the diarylide yellow 3,3-dichlorobenzidene aceto acetanilide. A developer was prepared in accordance with Example 1, with the exception that a nickel berry carrier was used in place of the steel carrier.When this developer was used in a commercial automatic xerographic color machine, or with the magnetic brush developer system of Example I, substantially similar results were obtained, that is, excellent color copies of high resultion after a single development sequence; and color prints of good contrast, color, and quality were produced when a magnetic brush developer system was used.

EXAMPLE III The procedure of Example I was repeated with the exception that a green colored toner blend is prepared by mixing together zero parts by weight of 2,9-dimethylquinacridone, 1 part by weight of copper tetra-4-(octadecylsulfonomido) phthalocyanine and 2 parts by weight of diarylide yellow 3,3-dichlorobenzidene aceto acetanilide. A developer material was prepared in accordance with Example II. Substantially similar results were obtained when the developer was used in a commercial automatic xerographic color machine, or with the magnetic brush developer system of Example I.

Claims (7)

1. An electrostatographic developer composition including a carrier material and a toner, the toner comprising a resin, and a mixture of at least two colorants selected from cyan, magenta and yellow.

2. A developer composition in accordance with Claim 1 wherein the resin is a styrene/nbutyl methacrylate copolymer, the cyan colorant is copper tetra-4-(octadecylsulfonomido) phthalocyanine, the magenta colorant is a 2,9-dimethyl substituted quinacridone, and the yellow colorant is a diarylide yellow 3,3-dichiorobenzidene aceto acetanilide, wherein from 1 percent to 20 percent by weight of colorant is present, and from 80 percent to 99 percent by weight of resin is present.

3. A developer composition in accordance with claim 1 or claim 2 wherein the toner includes one part by weight of cyan colorant, and seven parts by weight of yellow colorant.

4. A developer composition in accordance with claim 1 or claim 2, wherein the toner includes two parts by weight of cyan colorant, one part by weight of yellow colorant.

5. A developer composition in accordance with claim 1 or claim 2 wherein the toner includes three parts by weight of cyan colorant and one part by weight of magenta colorant.

6. An electrostatographic developer composition substantially as hereinbefore described.

7. A method of electrostatography including forming an electrostatic latent image, and developing the latent image by means of the developer composition of any one of claims 1 to 6.