the following examples further define , describe and compare methods of preparing the developer materials of the present invention and of utilizing them to develop electrostatic latent images . parts and percentages are by weight unless otherwise indicated . a coated developer mixture was prepared as follows . a toner composition was prepared consisting about 10 percent carbon black commercially available from cities service co . and known as raven 420 , about 0 . 5 percent of nigrosine ssb commercially available from american cyanamid company , and about 89 . 5 percent of a 65 / 35 styrene - n - butyl methacrylate copolymer resin by melt blending followed by mechanical attrition . three parts by weight of this toner composition was mixed with about 100 parts by weight of carrier particles . the carrier particles comprised about 98 . 4 parts of sponge iron carrier cores ( available from hoeganaes corporation , riverton , new jersey , under the tradename ancor eh 80 / 150 ) having an average particle diameter of about 150 microns . a coating coposition comprising about 10 percent solids of polyvinyl chloride and trifluorochloroethylene prepared from a material commercially available as fpc 461 from firestone plastics company , pottstown , pa ., dissolved in methyl ethyl ketone is applied to the carrier cores as to provide them with a coating weight of about 1 . 6 percent . the coating composition was applied to the carrier cores via solution coating employing a spray dryer . the developer mixture was placed in a glass jar and roll mixed at a linear speed of about 90 feet per minute for the time indicated in the following table . the triboelectric charge of the toner was measured by blowing off the toner from the carrier in a faraday cage . ______________________________________ toner tribo μc / groll mixing time ( microcoulombs per gram ) ______________________________________10 min . 171 hr . 24______________________________________ from the above results , it is seen that this developer mixture is slow charging in that it is still charging after 1 hour of mixing time . a developer mixture was prepared as follows . a toner composition was prepared comprising about 6 percent regal 330 carbon black commercially available from cabot corporation , about 0 . 5 percent of cetyl pyridinium chloride commercially available from hexcel company , lodi , new jersey , and about 93 . 5 percent of styrene - n - butyl methacrylate ( 65 / 35 ) copolymer resin by melt blending followed by mechanical attrition . the carrier particles comprised atomized iron carrier cores ( available from hoeganaes corporation , riverton , new jersey , under the tradename ancor steel 80 / 150 ) having an average particle diameter of about 150 microns . the carrier cores were mixed for about 10 minutes with about 0 . 4 parts of powdered perfluoroalkoxy tetrafluoroethylene having an average particle diameter of about 10 microns . the dry mixture was then heated to a temperature of about 650 ° f . and held at that temperature for about 20 minutes then rapidly cooled to room temperature by means of a fluidizing bath . about 97 parts by weight of the coated carrier particles was mixed with about 3 parts by weight of toner particles . the triboelectric charge of the toner after various mixing times as measured in example i was as follows : ______________________________________ toner tribo μc / groll mixing time ( microcoulombs per gram ) ______________________________________ 10 min . 441 hr . 35______________________________________ the toner was fast charging against the carrier and the tribo was stable after the long mixing period . a developer mixture was prepared as follows . a toner composition was prepared comprising about 6 percent regal 330 carbon black commercially available from cabot corporation , about 2 percent of cetyl pyridinium chloride commercially available from hexcel company , lodi , new jersey , and about 92 percent of styrene - n - butyl methacrylate ( 65 / 35 ) copolymer resin by melt blending followed by mechanical attrition . the carrier particles comprised atomized iron carrier cores ( available from hoeganaes corporation , riverton , new jersey , under the tradename ancor steel 80 / 150 ) having an average particle diameter of about 150 microns . the carrier cores were mixed for about 10 minutes with about 0 . 4 parts of powdered perfluoroalkoxy tetrafluoroethylene having an average particle diameter of about 10 microns . the dry mixture was then heated to a temperature of about 650 ° f . and held at that temperature for about 20 minutes then rapidly cooled to room temperature by means of a fluidizing bath . about 97 parts by weight of the coated carrier particles was mixed with about 3 parts by weight of toner particles . the triboelectric charge of the toner after various mixing times as measured in example i was as follows : ______________________________________ toner tribo μc / groll mixing time ( microcoulombs per gram ) ______________________________________ 10 min . 381 hr . 34______________________________________ the toner was fast charging against the carrier and the tribo was stable after the long mixing period . the developer mixture was employed in an electrostatographic device to develop an electrostatic latent image provided from a negatively charged photoreceptor to obtain prints having a 1 . 1 solid area density . print image toner background density was found to be about 0 . 003 after making about 2 , 000 copies and the triboelectric charge on the toner material was about 18 microcoulombs per gram of toner material . a developer mixture was prepared as follows . the toner composition was that employed in example iii . the carrier particles comprised about 99 . 85 parts of atomized iron carrier cores ( available from hoeganaes corporation , riverton , new jersey , under the tradename ancor steel 80 / 150 ) having an average particle diameter of about 150 microns and a surface iron oxide content of about 0 . 7 percent . the carrier cores were mixed for about 10 minutes with about 0 . 15 parts of powdered polyvinylidene fluoride ( available from pennwalt corporation , king of prussia , pa ., under the tradename kynar 301f ) having an average particle diameter of about 0 . 35 micron . the dry mixture was then heated to a temperature of about 510 ° f . for about 60 minutes and cooled to room temperature . about 97 parts by weight of the coated carrier particles was mixed with about 3 parts by weight of the toner particles . the triboelectric charge of the toner after various mixing times as measured in example i was as follows : ______________________________________ toner tribo μc / groll mixing time ( microcoulombs per gram ) ______________________________________10 min . 581 hr . 453 hr . 335 hr . 26______________________________________ the toner was fast charging against this carrier and tribo was stable after long mixing times . the developer mixture was employed in an electrostatographic device to develop an electrostatic latent image provided from a negatively charged photoreceptor to obtain prints having a 1 . 1 solid area density . print image toner background density was found to be about 0 . 003 after making about 2 , 000 copies and the triboelectric charge on the toner material was about 29 microcoulombs per gram of toner material . a fresh sample of developer mixture was aged for about 24 hours by exposure to an atmosphere having a temperature of about 23 ° c . and 20 %, and 80 % relative humidity , respectively . the developer mixture was then roll - mixed in a glass jar at a linear speed of about 90 feet per minute for about 4 hours . the triboelectric charge of the toner was then measured and triboelectric products calculated . the triboelectric product is the value obtained by multiplying the triboelectric charge in microcoulombs per gram of toner by the toner concentration . the triboelectric product of the sample aged at 20 % relative humidity was about 123 and of the sample aged at 80 % relative humidity was about 111 . the percentage decrease in triboelectric product between the developer mixture aged at 20 % relative humidity and that aged at 80 % humidity was only about 10 % resulting in a humidity insensitive developer material . a developer mixture was prepared as follows . a toner composition was prepared comprising about 6 percent regal 330 carbon black , about 1 . 5 percent cetyl pyridinium chloride , and about 92 . 5 percent styrene - n - butyl methacrylate 65 / 35 copolymer by melt blending followed by mechanical attrition . the toner was classified to remove particles having diameters below 5 microns . the carrier particles comprised about 98 . 4 parts of sponge iron carrier cores ( available from hoeganaes corporation , riverton , new jersey , under the tradename ancor eh 80 / 150 ) having an average particle diameter of about 150 microns . a coating composition comprising about 10 percent solids of polyvinyl chloride and trifluorochloroethylene prepared from a material commercially available as fpc 461 from firestone plastics company , pottstown , pa ., dissolved in methyl ethyl ketone is applied to the carrier cores as to provide them with a coating weight of about 1 . 6 percent . the coating composition was applied to the carrier cores via solution coating employing a vibratub ( available from vibraslide , inc ., binghamton , new york ). about 97 parts by weight of the coated carrier particles was mixed with about 3 parts by weight of the toner particles having an average diameter of about 12 microns . the triboelectric charge of the toner after various mixing times as measured in example i was as follows : ______________________________________ toner tribo μc / groll mixing time ( microcoulombs per gram ) ______________________________________ 10 min . 261 hr . 20______________________________________ the toner was fast charging against this carrier and tribo was stable after the long mixing time . the developer was tested in a fixture using a photoreceptor charged negatively . prints of excellent quality and low background were obtained . the developer mixture was employed in an electrostatographic device to develop an electrostatic latent image provided from a negatively charged photoreceptor to obtain prints having a 1 . 1 solid area density . print image toner background density was found to be about 0 . 002 after making about 2 , 000 copies and the triboelectric charge on the toner material was about 22 microcoulombs per gram of toner material . a developer mixture was prepared as follows . a toner composition was prepared comprising about 6 percent regal 330 carbon black , about 1 percent of cetyl pyridinium chloride , and about 93 percent styrene - n - butyl methacrylate 65 / 35 copolymer resin by melt blending followed by mechanical attrition . the carrier particles employed were essentially the same as those of example iii . about 97 parts of the carrier particles was mixed with about 3 parts of the toner particles . the triboelectric charge of the toner after various mixing times as measured in example i was as follows : ______________________________________ toner tribo μc / gramroll mixing time ( microcoulombs per gram ) ______________________________________ 10 min . 421 hr . 35______________________________________ the toner was fast charging against the carrier and the tribo was stable . a developer mixture was prepared as follows . a toner composition was prepared comprising about 10 percent raven 420 carbon black , about 3 percent of cetyl pyridinium chloride , and about 87 percent styrene - n - butyl methacrylate 65 / 35 copolymer resin by melt blending followed by mechanical attrition . the carrier particles comprised about 99 . 85 parts of atomized iron carrier cores ( available from hoeganaes corporation , riverton , new jersey , under the tradename ancor steel 80 / 150 ) having an average particle diameter of about 150 microns and a surface iron oxide content of about 0 . 6 %. the carrier cores were mixed for about 10 minutes with about 0 . 15 parts of powdered polyvinylidene fluoride ( available from pennwalt corporation , king of prussia , pa ., under the tradename kynar 201 ) having an average particle diameter of about 0 . 35 micron . the dry mixture was then heated to a temperature of about 510 ° f . for about 60 minutes and cooled to room temperature . about 97 parts of weight of the coated carrier particles was mixed with about 3 parts by weight of the toner particles . the triboelectric charge of the toner after various mixing times as measured in example i was as follows : ______________________________________ toner tribo μc / gramroll mixing time ( microcoulombs per gram ) ______________________________________ 10 min . 351 hr . 29 24 hr . 25______________________________________ the toner was fast charging against the carrier and the tribo was stable . a developer mixture was prepared as follows . a toner composition was prepared comprising about 6 percent by weight of regal 330 carbon black commercially available from cabot corporation , about 92 percent of a 65 / 35 copolymer resin of styrene - n - butyl methacrylate , and about 2 percent by weight of n , n dimethyl n - cetyl hydrazinium chloride by melt blending followed by mechanical attrition . the toner was classified to remove particles having average diameters below 5 microns , and 3 parts of the classified toner were blended with about 97 parts of the carrier particles of example vii to form a developer mixture . the developer was used in a device containing a polyvinylcarbazole photoreceptor that was charged negatively , and good quality prints were obtained with high optical density and low background . admix experiments indicated the developer had very fast charging characteristics and very narrow charge distribution . the carbon black dispersion and particle to particle uniformity were excellent as determined by transmission electron microscope techniques . the triboelectric charge of the toner was measured by blowing off the toner from the carrier in a faraday cage as in example i . ______________________________________ toner tribo μc / groll mixing time ( microcoulombs per gram ) ______________________________________ 10 min . 491 hr . 47______________________________________ the developer mixture was employed in an electrostatographic device to develop an electrostatic latent image provided from a negatively charged photoreceptor to obtain prints having a 1 . 1 solid area density . print image toner background density was found to be about 0 . 008 after making about 600 copies and the triboelectric charge on the toner material was about 37 microcoulombs per gram of toner material . a developer mixture was prepared as follows . a toner composition was prepared comprising about 6 percent by weight of regal 330 carbon black commercially available from cabot corporation , about 92 percent of a 65 / 35 copolymer resin of styrene - n - butyl methacrylate , and about 2 percent by weight of n , n dimethyl n - cetyl hydrazinium paratoluene sulphonate by melt blending followed by mechanical attrition . the toner was classified to remove particles having average diameters below 5 microns , and 3 parts of the classified toner were blended with about 97 parts of the carrier particles of example iv to form a developer mixture . the developer was used in a device containing a polyvinylcarbazole photoreceptor that was charged negatively , and good quality prints were obtained with high optical density and low background . admix experiments indicated the developer had very fast charging characteristics and very narrow charge distribution . the carbon black dispersion and particle to particle uniformity were excellent as determined by transmission electron microscope techniques . the triboelectric charge of the toner was measured by blowing off the toner from the carrier in a faraday cage as in example i . ______________________________________ toner tribo μc / groll mixing time ( microcoulombs per gram ) ______________________________________ 10 min . 431 hr . 37______________________________________ a toner comprised of about 10 percent raven 420 carbon black commercially available from cities service co ., about 2 percent n , n - dimethyl n - lauryl hydrazinium bromide , and about 88 percent of a 65 / 35 copolymer resin of styrene - n - butyl methacrylate was prepared by melt blending followed by mechanical attrition . the toner was classified to remove particles having a diameter of less than 5 microns . three parts of the resulting classified toner and about 100 parts of the carrier of example iii were blended into a developer . the developer was tested in a device as described in example i . good quality prints of high solid area density and very low background density were obtained . a developer mixture was prepared as follows . a toner composition was prepared comprising about 6 percent regal 330 carbon black commercially available from cabot corporation , about 2 percent of cetyl pyridinium bromide commercially available from hexcel company , lodi , new jersey , and about 92 percent of styrene - n - butyl methacrylate ( 65 / 35 ) copolymer resin by melt blending followed by mechanical attrition . the carrier particles comprised about 99 . 85 parts of atomized iron carrier cores ( available from hoeganaes corporation , riverton , new jersey , under the tradename ancor steel 80 / 150 ) having an average particle diameter of about 150 microns . the carrier cores were mixed for about 10 minutes with about 0 . 15 parts of powdered polyvinyidene fluoride ( available from pennwalt corporation , king of prussia , pa ., under the tradename kynar 201 ) having an average particle diameter of about 0 . 35 micron . the dry mixture was then heated to a temperature of about 510 ° f . and held at that temperature for about 60 minutes then cooled to room temperature . about 97 parts by weight of the coated carrier particles was mixed with about 3 parts by weight of toner particles . the triboelectric charge of the toner after various mixing times as measured in example i was as follows : ______________________________________ toner tribo μ / groll mixing time ( microcoulombs per gram ) ______________________________________ 10 min . 411 hr . 35______________________________________ the toner was fast charging against the carrier and the tribo was stable after the long mixing period . the toner also had a narrow charge distribution . the developer mixture was tested in a fixture using a negatively charged photoreceptor . excellent prints of high solid area density and low background density were obtained . a fresh sample of developer mixture was aged for about 24 hours by exposure to an atmosphere having a temperature of about 23 ° c . and 20 %, and 80 % relative humidity , respectively . the developer mixture was then roll - mixed in a glass jar at a linear speed of about 90 feet per minute for about 4 hours . the triboelectric charge of the toner was then measured and triboelectric products calculated . the triboelectric product is the value obtained by multiplying the triboelectric charge in microcoulombs per gram of toner by the toner concentration . the triboelectric product of the sample aged at 20 % relative humidity was about 116 and of the sample aged at 80 % relative humidity was about 99 . the percentage decrease in triboelectric product between the developer mixture aged at 20 % relative humdity and that aged at 80 % relative humidity was only about 15 % resulting in a humidity insensitive developer material . a develper mixture was prepared as follows . a toner composition was prepared comprising about 6 percent regal 330 carbon black , about 2 percent cetyl pyridinium chloride , and about 92 percent styrene - n - butyl methacrylate 53 / 42 copolymer by melt blending followed by mechanical attrition . the toner was classified to remove particles having diameters below 5 microns . about 97 parts by weight of the carrier particles of example iv was mixed with about 3 parts by weight of the toner particles having an average diameter of about 12 microns . the triboelectric charge of the toner after various mixing times as measured in example i was as follows : ______________________________________ toner tribo μc / groll mixing time ( microcoulombs per gram ) ______________________________________ 10 min . 501 hr . 46______________________________________ the toner was fast charging against this carrier and tribo was stable after the long mixing time . the developer was tested in a fixture using a photoreceptor charged negatively . prints of excellent quality and low background were obtained . although specific materials and conditions are set forth in the foregoing examples , these are merely intended as illustrations of the present invention . various other suitable thermoplastic toner resin components , additives , colorants , and developmen processes such as those listed above may be substituted for those in the examples with similar results . other materials may also be added to the toner or carrier to sensitize , synergize or otherwise improve the fusing properties or other desirable properties of the system . other modifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure . these are intended to be included within the scope of this invention .