Liquid developer compositions with block copolymers

Abstract: A liquid developer comprised of a liquid, thermoplastic resin particles, a nonpolar liquid soluble charge director comprised of an ionic or zwitterionic quaternary ammonium block copolymer ammonium block copolymer, and wherein the number average molecular weight thereof of said charge director is from about 70,000 to about 200,000.

Description: This invention is generally directed to liquid developer compositions and, in particular, to liquid developers containing ionic or zwitterionic ammonium block copolymers. Liquid developers are known from EP-A-0426052, wherein a negative electrostatic liquid developer is disclosed which consists of a nonpolar liquid having a Kauri-butanol value of less than 30, present in a major amount; thermoplastic resin particles having an average by area particle size of less than 10 µm; and an AB diblock copolymer charge director. The B block is a polymer with a number average molecular weight in the range of about 2,000 to 50,000, and the A block is a quaternized trialkyl amino polymer having a number average molecular weight in the range of about 200 to 10,000. The number average degree of polymerization ratio of the B block to the A block is in the range of 10 to 2 to 100 to 20. It is the object of the present invention to provide liquid developers capable of high particle charging and fast toner charging rates. This object is achieved by a liquid developer comprised of a liquid, thermoplastic resin particles, a nonpolar liquid soluble charge director comprised of an ionic or zwitterionic ammonium block copolymer, and wherein the number average molecular weight thereof of said charge director is from about 70,000 to about 200,000. Preferably, the developer is a negatively charged developer comprised of a nonpolar liquid and further comprising a charge adjuvant and a pigment. It is also preferred that the developer is an electrostatographic developer comprised of a nonopolar liquid having a Kauri-butanol value of from about 5 to about 30 and present in a major amount of from about 50 percent to about 95 weight percent; thermoplastic resin particles and pigment particles; a nonpolar liquid soluble polymeric charge director comprised of an ionic or zwitterionic ammonium block copolymer; and a charge adjuvant; and wherein the number average molecular weight thereof of said charge director is from about 80,000 to about 150,000. Preferably, the charge director has a molecular weight of from about 80,000 to about 120,000, and there results a developer with high developer particle charge and low conductivity. It is also preferred that the high developer toner charge provides particle mobilities that range from about 2.0 x 10 -10 m 2 /Vs to about 5 x 10 -10 m 2 /Vs as measured by the Matect ESA and/or the low conductivity of said developer, at 1 percent developer solids in NORPAR 15™, is from about 1 pS/cm. It is also preferred that the resin particles are comprised of a copolymer of ethylene and an α-β-ethylenically unsaturated acid selected from the group consisting of acrylic acid and methacrylic acid, or mixtures thereof; or that the resin particles are comprised of a styrene polymer, an acrylate polymer, a methacrylate polymer, a polyester, or mixtures thereof; or wherein the resin particles are comprised of a copolymer of ethylene and vinyl acetate, polypropylene, polyethylene, and acrylic polymers, or mixtures thereof; or that the resin particles are comprised of a copolymer of ethylene, and acrylic or methacrylic acid, an alkyl ester of acrylic or methacrylic acid wherein alkyl contains from 1 to about 5 carbon atoms or a copolymer of ethylene, and methacrylic acid with a melt index at 190°C of 500. Preferably, the nonpolar liquid is present in an amount of from 85 percent to 99.9 percent by weight based on the total weight of the developer solids of resin, pigment, and charge adjuvant which is present in an amount of from about 0.1 percent to about 15 percent by weight; and the nonpolar liquid soluble polymer charge director is present in an amount of from about 0.5 percent to about 100 percent of the developer solids comprised of resin, pigment, and charge adjuvant; and/or the charge adjuvant is present in an amount of 0.1 to 40 percent by weight based on the total weight of developer solids. It is further preferred that the liquid is an aliphatic hydrocarbon having a mixture of branched hydrocarbons with from about 12 to about 16 carbon atoms; or having a mixture of normal hydrocarbons with from about 12 to about 16 carbon atoms. Preferably, the charge director is of the formula wherein R is hydrogen, alkyl, aryl, or alkylaryl; R 1 is a conjugate oxygen containing acid anion derived from carbon, sulfur, or phosphorus; Z is carbon, sulfur, phosphorus or a substituted phosphorous PR; m is 1 or 2 doubly bonded oxygen atoms; n is 0 or 1 hydroxyl groups; R' is a alkyl, aryl, cycloalkyl, cycloalkylenyl, cycloalkylalkyl, cycloalkylaryl or alkylaryl; R" is alkyl, aryl, cycloalkyl, cycloalkylalkyl, cycloalkylaryl or alkylaryl; R"' is alkyl, aryl, cycloalkyl, cycloalkylalkyl, cycloalkylaryl or akylaryl of 4 to 20 carbons; X is alkylene or arylalkylene; Y is alkylene or arylalkylene; aM a + a'M a is about 3,500 to 120,000 and bM b is 28,000 to 190,000 wherein a, a' and b are the number average degree of polymerization (DP) and M a , M a' and M b are the corresponding repeat unit molecular weights. The present invention also provides an imaging method which comprises forming an electrostatic latent image followed by the development thereof with the liquid developer of the invention. One aspect of the present invention is to provide a liquid developer with high particle charges and low conductivities. In various embodiments the present invention relates to liquid developers with charge directors derived from the alkylation or protonation of poly-2-ethylhexylmethacrylate-co-N',N'dimethylamino-2-ethylmethacrylate (EHMA-DMAEMA) A-8 diblock copolymers which form inverse micelles with the ammonium ionic or polar end of the block copolymer directed or faced inward and the nonpolar EHMA tail pointing in a direction outward toward the hydrophobic hydrocarbon vehicle selected for the liquid developer, and wherein the number average molecular weight, determined, for example, from by dividing the number of moles of monoinitiator into the number of grams of acrylic monomer being initiated by the charged molar quantity of monoinitiator, of the charge director is from about 70,000 to about 200,000, preferably from about 80,000 to about 150,000, and more preferably about 85,000 to 100,000. With the aforementioned molecular weights, there are enabled liquid developers with a number of advantages such as high particle charge with low conductivities. The low conductivities result primarily from the larger micelles which originate from the high molecular weight charge director. The large micelle reduces the conductivity, it is believed, in, for example, the following manner: 1) the electrophoretic mobility is reduced as the size of the micelle increases due to viscous drag; and 2) as the size of the micelle increases, the number of micelles decreases at the same total mass loading of the charge director, resulting in a decrease in the micelle charge density. For example, the effect of charge director molecular weight on the electrophoretic mobility, size, and charge density of micelles formed from the AB diblock ammonium charge directors is illustrated in the following Table. Charge Director Molecular Weight (M n ) Conductivity of 0.1% (by weight) Charge Director in NORPAR 15 (pS/cm) Charged Micelle Electrophoretic Mobility (10 -6 cm 2 /Vs) Micelle Charge Density of 0.1% (by weight) Charge Director (µC/cm 3 ) Very Low (2K) 43 11 3.5 Low (4K) 43 5.4 5.1 Medium (25K) 6 2.5 1.9 Medium (50K) 2 2.2 1.0 High (93K) 0.6 1.5 0.5 Furthermore, it has been determined that these high molecular weight charge directors result in low conductivity liquid toner dispersions with high particle charge. For example it has been found that a developer charged with a 93,519 molecular weight AB diblock EHMA-DMAEMA·HBr enables particles with a mobility greater than 4×10 -10 m 2 /Vs measured, for example, by the ESA method disclosed herein, and a conductivity of a 1 percent developer solids liquid toner dispersion measured with a Scientifica AC conductivity meter disclosed herein of about less then 4 ps/centimeter. The corresponding liquid toner dispersion charged with a 4,000 molecular weight AB diblock EHMA-DMAEMA·HBr enables particles with a mobility of less than 3.5×10 -10 m 2 /Vs and a conductivity greater than 8 pS/cm. The developers of the present invention can be selected for a number of known imaging and printing systems, such as xerographic processes, wherein latent images are rendered visible with the liquid developer illustrated herein. The image quality, solid area coverage and resolution for developed images usually require sufficient toner particle electrophoretic mobility. In one embodiment the invention provides a negatively charged liquid developer wherein there are selected as charge directors ionic and/or zwitterionic ammonium AB diblock copolymers and which copolymer has an important weight average molecular weight of from about 70,000 to about 200,000. Examples of acceptable conductivity and mobility ranges for developers charged with the high molecular weight charge directors of this invention are illustrated herein. Conductivities measured at ambient temperature (21 to 23°C) for developers containing one percent toner solids are considered high in the 10 to 20 pS/cm range and very high at greater than 20 pS/cm. Optimum conductivities are less than about 5 pS/cm and preferably less than about 3 pS/cm. As conductivities increase above the optimum range, excess ions can compete with toner particles of the same charge for development of the latent image giving rise to low developed mass resulting in low print density images. In addition to having an optimum conductivity of less than 10 pS/cm, the liquid toner or developer of this invention also possesses a mobility of at least -2 × 10 -10 m 2 /Vs and preferably greater than -3 × 10 -10 m 2 /Vs in embodiments. The invention provides a liquid developer wherein developed image defects, such as smearing, loss of resolution and loss of density, are eliminated or minimized. In another embodiment the invention provides low conductivity liquid developers which will be effective in an image-on-image xerographic printing process where an image is developed on a latent image bearing member in the xerographic process, and then that image bearing member is passed through the xerographic charging, imagewise discharging, and development steps to develop a multilayered image. The subseqent development steps can be with liquid toner dispersions of colors different than the first or previous development resulting in a multicolored image which can be transferred from the now multiimage bearing member to a substrate. Also, in another embodiment of the present invention there are provided negatively charged liquid developers with certain high molecular weight ionic and/or zwitterionic ammonium AB diblock copolymer charge directors, which are superior in embodiments to, for example, low molecular weight ammonium block copolymers since, for example, they result in higher negative toner particle charge and lower conductivity. For example, it has been found that a developer charged with a 93,519 molecular weight AB diblock EHMA-DMAEMA.HBr obtains particles with a mobility greater than 4 × 10 -10 m 2 /Vs (measured by the ESA technique disclosed herein) and a conductivity (of a 1 percent developer solids liquid toner dispersion measured with a Scientifica AC conductivity meter disclosed herein) of about less then 4 pS/cm. The corresponding liquid toner dispersion charged with 3,945 molecular weight AB diblock EHMA-DMAEMA.HBr obtains particles with a mobility less than 3.5 × 10 -10 m 2 /Vs and a conductivity greater than 8 pS/cm. Also, in another embodiment of the present invention there are provided negatively charged liquid developers with certain high molecular weight ionic and/or zwitterionic ammonium AB diblock copolymer charge directors, which are superior in embodiments to, for example, low molecular weight ionic and/or zwitterionic ammonium AB diblock copolymers since, for example, they result in higher negative particle charge and lower conductivity. Another embodiment of the present invention resides in the provision of negatively charged liquid toners with high molecular weight ionic and/or zwitterionic ammonium block copolymers, and wherein in embodiments enhancement of the negative charge of NUCREL® based toners, especially cyan and magenta toners, is enhanced. In embodiments, the present invention is directed to liquid developers comprised of a toner resin, pigment, charge additive and a charge director comprised of a high molecular weight ionic and/or zwitterionic ammonium block copolymer. In embodiments, the aforementioned charge director contains a polar quaternary ammonium A block and a second B block, constituent or component that is nonpolar thereby enabling hydrocarbon solubility, and which AB diblock copolymers can be obtained from group transfer polymerization, and a subsequent polymer modification reaction of the group transfer prepared AB diblock copolymer in which the ionic or zwitterionic site is introduced into the polar A block, and wherein the number average molecular weight of the charge director is from about 70,000 to about 200,000, and preferably from 80,000 to 150,000, and more preferably from 85,000 to 100,000. In embodiments, the present invention relates to the provision of liquid developers with certain charge directors. Also, in embodiments, the present invention is directed to liquid developers comprised of a toner resin, pigment, and a charge director comprised of a high molecular weight ionic and/or zwitterionic ammonium AB diblock copolymer. In embodiments, the aforementioned charge director contains an ionic or zwitterionic ammonium group and a constituent or component that is nonpolar thereby enabling hydrocarbon solubility, and which block copolymers can be obtained by group transfer polymerization. Embodiments of the present invention relate to a developer comprised of a liquid, thermoplastic resin particles, and a nonpolar liquid soluble ammonium block copolymer charge director; and a liquid electrostatographic developer comprised of (A) a nonpolar liquid having a Kauri-butanol value of from about 5 to about 30, and present in a major amount of from about 50 percent to about 95 weight percent; (B) thermoplastic resin particles having an average volume particle diameter of from about 5 to about 30 microns and pigment; (C) a nonpolar liquid soluble high molecular weight ionic or zwitterionic ammonium block copolymer; and (D) optionally, but preferably a charge adjuvant. In one embodiment a liquid developer is provided wherein the number average molecular weight of said charge director is from about 85,000 to about 100,000. In another embodiment the charge director is selected from the group consisting of poly[2-trimethylammoniumethyl methacrylate bromide co-2-ethylhexyl methacrylate], poly[2-triethylammoniumethyl methacrylate hydroxide co-2-ethylhexyl methacrylate], poly[2-trimethylammoniumethyl methacrylate chloride co-2-ethylhexyl methacrylate], poly[2-trimethylammoniumethyl methacrylate fluoride co-2-ethylhexyl acrylate], poly[2-trimethylammoniumethyl acrylate p-toluenesulfonate co-2-ethylhexyl methacrylate], poly[2-trimethylammoniumethyl acrylate nitrate co-2-ethylhexyl acrylate], poly[2-triethylammoniumethyl methacrylate phosphate co-2-ethylhexyl acrylate], poly[2-triethylammoniumethyl acrylate bromide co-2-ethylhexyl acrylate], poly[2-trimethylammoniumethyl methacrylate hydroxide co-2-ethylhexyl acrylate], poly[2-trimethylammoniumethyl acrylate hydroxideco-2-ethylhexyl acrylate], poly[2-trimethylammoniumethyl methacrylate hydroxide co-N,N-dibutyl methacrylamide], poly[2-triethylammoniumethyl methacrylate chloride co-N,N-dibutyl methacrylamide], poly[2-trimethylammoniumethyl methacrylate bromide co-N,N-dibutylacrylamide], poly[2-triethylammoniumethyl methacrylatehydroxide co-N,N-dibutylacrylamide], poly[2-dimethylammoniumethyl methacrylate bromide co-2-ethylhexyl methacrylate], poly[2-dimethylammoniumethyl methacrylate tosylate co-2-ethylhexyl methacrylate], poly[2-dimethylammoniumethyl methacrylate chloride co-2-ethylhexyl methacrylate], poly[2-dimethylammoniumethyl methacrylate bromide co-2-ethylhexylacrylate], poly[2-dimethylammoniumethyl acrylate bromide co-2-ethylhexyl methacrylate], poly[2-dimethylammoniumethyl acrylate bromide co-2-ethylhexyl acrylate], poly[2-dimethylammoniumethyl methacrylate tosylate co-2-ethylhexyl acrylate, poly[2-dimethylammoniumethyl acrylate tosylate co-2-ethylhexyl acrylate], poly[2-dimethylammoniumethyl methacrylate chloride co-2-ethylhexyl acrylate], poly[2-dimethylammoniumethyl acrylate chloride co-2-ethylhexyl acrylate], poly[2-dimethylammoniumethyl methacrylate bromide co-N,N-dibutyl methacrylamide], poly[2-dimethylammoniumethyl methacrylate tosylate co-N,N-dibutyl methacrylamide], poly[2-dimethylammoniumethyl methacrylate bromide co-N,N-dibutylacrylamide], and poly[2-dimethylammoniumethyl methacrylate tosylate co-N,N-dibutylacrylamide]. In another embodiment the charge director block copolymer is an AB diblock wherein said A block is a polar A block with a positively charged ammonium nitrogen and said B block is a nonpolar B block that functions to effectively dissolve said block copolymer in said nonpolar liquid, and wherein said A block has a number average molecular weight of from about 3,500 to about 120,000 and said B block has a number average molecular weight range of from about 28,000 to about 190,000. In another embodiment the zwitterionic diblock copolymer charge director is selected from a group consisting of poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-methylenecarboxylate-N-ammoniumethyl methacrylate), poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-propylenesulfonate-N-ammoniumethyl methacrylate), poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-propylenephosphonate-N-ammoniumethyl methacrylate), poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-propylenephosphinate-N-ammoniumethyl methacrylate), poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-propylenesulfinate-N-ammoniumethyl methacrylate), poly(2-ethylhexyl methacrylate-co-N,N-diethyl-N-methylenecarboxylate-N- ammoniumethyl methacrylate), poly(2-ethylhexyl methacrylate-co-N,N-diethyl-N-propylenesulfonate-N-ammoniumethyl methacrylate), poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-butylenephosphonate-N-ammoniumethyl methacrylate), poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-decamethylenephosphonate-N-ammoniumethyl methacrylate), poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-decamethylenephosphinate-N-ammoniumethyl methacrylate), poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-butylenecarboxylate-N-ammoniumethyl methacrylate), poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-ethyleneoxyethylenecarboxylate-N-ammoniumethyl methacrylate), poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-ethyleneoxyethylenesulfonate-N-ammoniumethyl methacrylate), poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-ethyleneoxyethylenephosphonate-N-ammoniumethyl methacrylate), poly(N,N-dibutylmethacrylamido-co-N,N-dimethyl-N-methylenecarboxylate-N-ammoniumethyl methacrylate), poly(N,N-dibutylmethacrylamido-co-N,N-dimethyl-N-propylenesulfonate-N-ammoniumethyl methacrylate), poly(N,N-dibutylmethacrylamido-co-N,N-dimethyl-N-propylenephosphonate-N-ammoniumethyl methacrylate), poly(N,N-dibutylmethacrylamido-co-N,N-dimethyl-N-propylenephosphinate-N-ammoniumethyl methacrylate), and poly(N,N-dibutylmethacrylamido-co-N,N-dimethyl-N-propylenesulfinate-N-ammoniumethyl methacrylate). In all of the above examples, the corresponding acrylate copolymer, instead of the methacrylate copolymer, could also be employed as suitable nonpolar liquid soluble zwitterionic AB diblock copolymer charge directors. Additional suitable examples of nonpolar liquid soluble zwitterionic AB diblock copolymer charge directors include poly(4-vinylpyridinium-N-methylenecarboxylate-co-2-ethylhexyl methacrylate), poly(4-vinylpyridinium-N-propylenesulfonate-co-2-ethylhexyl methacrylate), poly(4-vinylpyridinium-N-propylenephosphonate-co-2-ethylhexyl methacrylate), poly(4-vinylpyridinium-N-propylenephosphinate-co-2-ethylhexyl methacrylate), poly(4-vinylpyridinium-N-propylenesulfinate-co-2-ethylhexyl methacrylate), poly(4-vinylpyridinium-N-ethyleneoxyethylenecarboxylate-co-2-ethylhexyl methacrylate), poly(4-vinylpyridinium-N-ethyleneoxyethylenesulfonate-co-2-ethylhexyl methacrylate), poly(4-vinylpyridinium-N-ethyleneoxyethylenephosphonate-co-2-ethylhexyl methacrylate), and poly[4-vinylpyridinum-N-methyl enecarboxylate-co-p-tertbutylstyrene). In another embodiment the A block comprises from about 60 to about 5 mole percent and said B block comprises from about 40 to about 95 mole percent. In another embodiment the charge director is selected in an amount of from about 1 percent to about 20 percent by weight based on the weight of developer solids, which solids are comprised of thermoplastic resin, charge adjuvant, and pigment. In another embodiment a mobility of from a negative 1.24 to a negative 4.40 × 10 -10 m 2 /Vs, and wherein the conductivity is from 1 to 4 pS/cm. In another embodiment a mobility of from a negative 4.40×10 -10 m 2 /Vs, and wherein the conductivity is from 1 to 4 pS/cm. In another embodiment the charge director is the AB diblock copolymer poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide (A block)], and said charge adjuvant is hydroxy bis[3,5-tertiary butyl salicyclic]aluminate monohydrate. Suitable charge directors of the present invention can be represented by the formula wherein R is hydrogen, alkyl, aryl, or alkylary; R' is ethyl or methyl; R" is alkyl, aryl, cycloalkyl, cycloalkylalkyl, cycloalkylaryl or alkylaryl with or without heteroatoms; R"' is alkyl, aryl, cycloalkyl, cycloalkylalkyl, cycloalkylaryl or alkylaryl of 4 to 20 carbons with or without heteroatoms; X is alkylene or arylalkylene of, for example, about 2 to 10 carbons with or without heteroatoms; Y is hydrogen, alkyl of 1 to about 25 carbon atoms, alkylaryl and aryl from 6 to about 30 carbon atoms with or without heteroatoms; Z- is an anion such as bromide, hydroxide, chloride, nitrate, p-toluenesulfonate, sulfate, phosphate, fluoride, dodecylsulfonate, dodecylbenzenesulfonate, acetate, trifluroracetate, chloroacetate, stearate, and the like; aM a + a'M a' is about 3,500 to 120,000 and bM b is 28,000 to 190,000 wherein a, a' and b are the number average degree of polymerization (DP) and M a , M a' and M b are the corresponding repeat unit molecular weights. Alkyl includes groups with 1 to about 25 carbon atoms; aryl includes groups with from 6 to about 24 carbon atoms; and alkylene can include groups with from 1 to about 25 carbon atoms. Examples of specific diblock copolymer charge directors with an M n of from about 70,000 to about 200,000 include poly[2-trimethylammoniumethyl methacrylate bromide co-2-ethylhexyl methacrylate], poly[2-triethylammoniumethyl methacrylate hydroxide co-2-ethylhexyl methacrylate], poly[2-trimethylammoniumethyl methacrylate chloride co-2-ethylhexyl methacrylate], poly[2-trimethylammoniumethyl methacrylate fluoride co-2-ethylhexyl acrylate], poly[2-trimethylammoniumethyl acrylate p-toluenesulfonate co-2-ethylhexyl methacrylate], poly[2-trimethylammoniumethyl acrylate nitrate co-2-ethylhexyl acrylate], poly[2-triethylammoniumethyl methacrylate phosphate co-2-ethylhexyl acrylate], poly[2-triethylammoniumethyl acrylate bromide co-2-ethylhexyl acrylate], poly[2-trimethylammoniumethyl methacrylate hydroxide co-2-ethylhexyl acrylate], poly[2-trimethylammoniumethyl acrylate hydroxideco-2-ethylhexyl acrylate], poly[2-trimethylammoniumethyl methacrylate hydroxide co-N,N-dibutyl methacrylamide], poly[2-triethylammoniumethyl methacrylate chloride co-N,N-dibutyl methacrylamide], poly[2-trimethylammoniumethyl methacrylate bromide co-N,N-dibutylacrylamide], poly[2-triethylammoniumethyl methacrylatehydroxide co-N,N-dibutylacrylamide], poly[2-dimethylammoniumethyl methacrylate bromide co-2-ethylhexyl methacrylate], poly[2-dimethylammoniumethyl methacrylate tosylate co-2-ethylhexyl methacrylatel, poly[2-dimethylammoniumethyl methacrylate chloride co-2-ethylhexyl methacrylate], poly[2-dimethylammoniumethyl methacrylate bromide co-2-ethylhexyl acrylate], poly[2-dimethylammoniumethyl acrylate bromide co-2-ethylhexyl methacrylate], poly[2-dimethylammoniumethyl acrylate bromide co-2-ethylhexyl acrylate], poly[2-dimethylammoniumethyl methacrylate tosylate co-2-ethylhexyl acrylate, poly[2-dimethylammoniumethyl acrylate tosylate co-2-ethylhexyl acrylate], poly[2-dimethylammoniumethyl methacrylate chloride co-2-ethylhexyl acrylate], poly[2-dimethylammoniumethyl acrylate chloride co-2-ethylhexyl acrylate], poly[2-dimethylammoniumethyl methacrylate bromide co-N,N-dibutyl methacrylamide], poly[2-dimethylammoniumethyl methacrylate tosylate co-N,N-dibutyl methacrylamide], poly[2-dimethylammoniumethyl methacrylate bromide co-N,N-dibutylacrylamide], and poly[2-dimethylammoniumethyl methacrylate tosylate co-N,N-dibutylacrylamide]. Other examples of suitable diblock copolymer charge directors include poly[4-vinyl-N,N-dimethylanilinium bromide co-2-ethylhexyl methacrylate], poly[4-vinyl-N,N-dimethylanilinium tosylate co-2-ethylhexyl methacrylate], poly[ethylenimmonium bromide co-2-ethylhexyl methacrylate], and poly[propylenimmonium bromide co-2-ethylhexyl methacrylate]. Further examples of diblock copolymer charge directors include poly[4-vinyl-N,N-trimethylanilinium bromide co-2-ethylhexyl methacrylate], poly[4-vinyl-N,N-triethylanilinium chloride co-2-ethylhexyl methacrylate], poly[quaternary ethylenimmonium fluoride co-2-ethylhexyl methacrylate], poly[quaternary propylenimmonium hydroxide co-2-ethylhexyl methacrylate], and polyvinyl-N-ethyl-pyridinium nitrate-co-p-dodecylstyrene. Preferred ammonium AB diblock copolymer charge directors of this invention contain a polar A block with a positively charged ammonium nitrogen and a nonpolar B block which has sufficient aliphatic content to enable the block copolymer to more effectively dissolve in a nonpolar liquid having a Kauri-butanol value of less than about 30. The A block has, for example, a number average molecular weight range of from about 3,500 to about 120,000 and the B block has a number average molecular weight range of from about 28,000 to about 190,000. In another embodiment, the AB ammonium diblock charge director is comprised of A and B blocks, wherein the A block is an alkyl, aryl or alkylaryl amine containing polymer wherein the alkyl, aryl, or alkylaryl moiety which can be substituted or unsubstituted. Useful A blocks are polymers prepared from at least one monomer selected from the group consisting of 1) CH 2 = CRCO 2 R 1 wherein R is hydrogen, alkyl, aryl, or alkylaryl of 1 to 20 carbons and R 1 is alkyl of 1 to 20 carbons where the terminal end of R 1 is of the general formula -N(R 2 ) 3 X- where N is nitrogen, R 2 is alkyl, cycloalkyl, aryl, or alkylaryl of 1 to 20 carbons, X- is an anion such as OH-, Cl-, Br-, p-toluene sulfonate, dodecylsulfonate, nitrate, phosphate, and the like; and 2) 2, 3, or 4-vinylpyridinium salt wherein the ring carbon atoms not substituted with the vinyl group are substituted with R 2 and the ring nitrogen is substituted with R as defined above. Other suitable nonpolar liquid soluble charge director compound examples selected for the developers of the present invention in various effective amounts, such as from about 0.5 to about 100 weight percent of developer solids, which is also represented as 5 milligrams to 1,000 milligrams of charge director solids to 1 gram of developer solids, and preferably 1 percent to 20 percent by weight relative to developer solids, which is also referred to as 10 milligrams to 200 milligrams of charge director solids to 1 gram of developer solids, include zwitterionic AB diblock copolymers represented by the following formula wherein R is hydrogen, alkyl, aryl, or alkylaryl; R 1 is a conjugate oxygen containing acid anion derived from carbon, sulfur, or phosphorous; Z is carbon (C), sulfur (S), phosphorous (P), or substituted phosphorous (P-R with R defined as above); m is 1 or 2 doubly bonded oxygen atoms; n is 0 or 1 hydroxyl groups; R' is alkyl, aryl, cycloalkyl, cycloalkylenyl cycloalkylalkyl, cycloalkylaryl or alkylaryl with or without heteroatoms; R'' is alkyl, aryl, cycloalkyl, cycloalkylalkyl, cycloalkylaryl or alkylaryl with or without heteroatoms; R''' is alkyl, aryl, cycloalkyl, cycloalkylalkyl, cycloalkylaryl or alkylaryl of 4 to 20 carbons with or without heteroatoms; X is alkylene or arylalkylene of, for example, about 2 to 10 carbons with or without heteroatoms; Y is alkylene or arylalkylene of 1 to 10 carbons with or without heteroatoms; aM a + a'M a' is about 3,500 to 120,000 and bMb is 28,000 to 190,000 wherein a, a' and b are the number average degree of polymerization (DP) and M a , M a' and M b are the corresponding repeat unit molecular weights. Alkyl includes groups with 1 to about 25 carbon atoms; aryl includes groups with from 6 to about 24 carbon atoms; and alkylene can include groups with from 1 to about 25 carbon atoms. The preferred repeat unit content of the polar A block is 60 to 5 mole percent and is more preferably at 40 to 10 mole percent, and the preferred repeat unit content of the nonpolar B block is 40 to 95 mole percent and is more preferably at 60 to 90 mole percent. Amine nitrogen alkylation to form the zwitterionic ammonium polar A block repeat unit wherein both cationic and anionic sites are covalently bonded within the same polar repeat unit should be at least 80 mole percent and preferably at least 90 mole percent for satisfactory charge director performance. The polar A block may be comprised entirely of either of the polar blocks illustrated herein or it may be complex wherein the optional polar A block repeat unit may be 0.1 to 99.9 mole percent of all the polar A block repeat units present. The complex polar A block may be segmented, tapered or random when it contains more than one repeat unit. In another embodiment, the AB zwitterionic ammonium diblock charge director is comprised of A and 8 blocks as described hereinafter. The polar A block is an alkyl, aryl or alkylaryl amine containing polymer wherein the alkyl, aryl, or alkylaryl moiety can be substituted or unsubstituted and be cyclic or noncyclic. Useful A blocks are polymers prepared from at least one monomer selected from the group consisting of 1) CH 2 = CRCO 2 R 1 wherein R is hydrogen, alkyl, aryl, or alkylaryl, and R 1 is a conjugate acid monoanion wherein m = 0 to 2 and n = 0 to 2, and Z is carbon, sulfur, or phosphorus. The charge director can be selected for the liquid developers in various effective amounts, such as for example from about 0.5 percent to 100 percent by weight relative to developer solids and preferably 1 percent to 20 percent by weight relative to developer solids. Developer solids includes toner resin, pigment, and optional charge adjuvant. Without pigment, the developer may be selected for the generation of a resist, or a printing plate and the like. Examples of liquid carriers or vehicles selected for the developers of the present invention include a liquid with viscosity of from about 0,005 to about 5 g/cm x s (about 0.5 to about 500 centipoise), and preferably from about 0.01 to about 0.2 g/cm x s (about 1 to about 20 centipoise), and a resistivity greater than or equal to 5 x 10 9 ohm/centimeters, such as 10 13 ohm/centimeters or more. Preferably, the liquid selected in embodiments is a branched chain aliphatic hydrocarbon. A nonpolar liquid of the ISOPAR® series available from the Exxon Corporation may also be used for the developers of the present invention. These hydrocarbon liquids are considered narrow portions of isoparaffinic hydrocarbon fractions with extremely high levels of purity. For example, the boiling range of ISOPAR G® is between about 157°C and about 176°C; ISOPAR H® is between about 176°C and about 191°C; ISOPAR K® is between about 177°C and about 197°C; ISOPAR L® is between about 188°C and about 206°C; ISOPAR M® is between about 207°C and about 254°C; and ISOPAR V® is between about 254.4°C and about 329.4°C. ISOPAR L® has a mid-boiling point of approximately 194°C. ISOPAR M® has an auto ignition temperature of 338°C. ISOPAR G® has a flash point of 40°C as determined by the tag closed cup method; ISOPAR H® has a flash point of 53°C as determined by the ASTM D-56 method; ISOPAR L® has a flash point of 61°C as determined by the ASTM D-56 method; and ISOPAR M® has a flash point of 80°C as determined by the ASTM D-56 method. The liquids selected are known and should have an electrical volume resistivity in excess of 10 9 ohm-centimeters and a dielectric constant below or equal to 3.0. Moreover, the vapor pressure at 25°C should be less than or equal to 1.33 kPa (10 Torr) in embodiments. While the ISOPAR® series liquids are the preferred nonpolar liquids in embodiments for use as dispersants in the liquid developers of the present invention, the important characteristics of viscosity and resistivity can be achieved, it is believed, with other suitable liquids. Specifically, the NORPAR® series available from Exxon Corporation, the SOLTROL® series available from the Phillips Petroleum Company, and the SHELLSOL® series available from the Shell Oil Company can be selected. Other useful liquid include mineral oils such as the SUPURLA® series available from the Amoco Oil Company. The amount of the liquid employed in the developer of the present invention is from about 90 to about 99.9 percent, and preferably from about 95 to about 99 percent by weight of the total developer dispersion. The total solids content of the developers is, for example, 0.1 to 10 percent by weight, preferably 0.3 to 3 percent, and more preferably 0.5 to 2.0 percent by weight. Various suitable thermoplastic toner resins can be selected for the liquid developers of the present invention in effective amounts of, for example, in the range of 99 percent to 40 percent of developer solids, and preferably 95 percent to 70 percent of developer solids; developer solids includes the thermoplastic resin, optional pigment and charge control agent and any other component that comprises the particles. Examples of such resins include ethylene vinyl acetate (EVA) copolymers (ELVAX® resins, E.I. DuPont de Nemours and Company, Wilmington, Del.); copolymers of ethylene and an α-β-ethylenically unsaturated acid selected from the group consisting of acrylic acid and methacrylic acid; copolymers of ethylene (80 to 99.9 percent), acrylic or methacrylic acid (20 to 0.1 percent)/alkyl (C 1 to C 5 ) ester of methacrylic or acrylic acid (0.1 to 20 percent); polyethylene; polystyrene; isotactic polypropylene (crystalline); ethylene ethyl acrylate series sold under the trademark BAKELITE® DPD 6169, DPDA 6182 Natural (Union Carbide Corporation); ethylene vinyl acetate resins, for example DQDA 6832 Natural 7 (Union Carbide Corporation); SURLYN® ionomer resin (E.I. DuPont de Nemours and Company); or blends thereof; polyesters; polyvinyl toluene; polyamides; styrene/butadiene copolymers; epoxy resins; acrylic resins, such as a copolymer of acrylic or methacrylic acid; and at least one alkyl ester of acrylic or methacrylic acid wherein alkyl is from 1 to about 20 carbon atoms like methyl methacrylate (50 to 90 percent)/methacrylic acid (0 to 20 percent)/ethylhexyl acrylate (10 to 50 percent); and other acrylic resins including ELVACITE® acrylic resins (E.I. DuPont de Nemours and Company); or blends thereof. Preferred copolymers are the copolymer of ethylene and an α-β-ethylenically unsaturated acid of either acrylic acid or methacrylic acid. In a preferred embodiment, NUCREL® like NUCREL® 599, NUCREL® 699, or NUCREL® 960 can be selected as the thermoplastic resin. The liquid developer of the present invention may optionally contain a colorant dispersed in the resin particles. Colorants, such as pigments or dyes and mixtures thereof, are preferably present to render the latent image visible. The colorant may be present in the resin particles in an effective amount of, for example, from about 0.1 to about 60 percent, and preferably from about 1 to about 30 percent by weight based on the total weight of solids contained in the developer. The amount of colorant used may vary depending on the use of the developer. Examples of colorants include pigments like carbon blacks like REGAL 330®, cyan, magenta, yellow, blue, green, brown and mixtures thereof; pigments as illustrated in US-A-5,223,368. To increase the toner particle charge and, accordingly, increase the mobility and transfer latitude of the toner particles, charge adjuvants can be added to the toner. For example, adjuvants, such as metallic soaps like aluminum or magnesium stearate or octoate, fine particle size oxides, such as oxides of silica, alumina, titania, and the like, paratoluene sulfonic acid, and polyphosphoric acid may be added. Negative charge adjuvants can increase the negative charge of the toner particle, while the positive charge adjuvants can increase the positive charge of the toner particles. The adjuvants or charge additives can be comprised of the metal catechol and aluminum hydroxyacid complexes illustrated in US-A-5,306,591 and US-A-5,308,731, and which additives in combination with the charge directors of the present invention have the following advantages over the aforementioned prior art charge additives: improved toner charging characteristics, namely an increase in particle charge, as measured by ESA mobility, from -1.4×10 -10 m 2 /Vs to -2.3×10 -10 m 2 /Vs, that results in improved image development and transfer, from 80 percent to 93 percent, to allow improved solid area coverage from transferred image reflectance density of 1.2 to 1.3. The adjuvants can be added to the toner particles in an amount of from about 0.1 percent to about 15 percent of the total developer solids and preferably from about 1 percent to about 5 percent of the total weight of solids contained in the developer. The charge on the toner particles alone may be measured in terms of particle mobility using a high field measurement device. Particle mobility is a measure of the velocity of a toner particle in a liquid developer divided by the size of the electric field within which the liquid developer is employed. The greater the charge on a toner particle, the faster it moves through the electrical field of the development zone. The movement of the particle is required for image development and background cleaning. Toner particle mobility can be measured using the electroacoustics effect, the application of an electric field, and the measurement of sound, reference US-A-4,497,208. The liquid electrostatic developer of the present invention can be prepared by a variety of known processes such as, for example, mixing in a nonpolar liquid the thermoplastic resin, nonpolar liquid charging additive and colorant in a manner that the resulting mixture contains, for example, about 15 to about 30 percent by weight of solids; heating the mixture to a temperature from about 70°C to about 130°C until a uniform dispersion is formed; adding an additional amount of nonpolar liquid sufficient to decrease the total solids concentration of the developer to about 10 to 20 percent by weight; cooling the dispersion to about 10°C to about 50°C; adding the charge adjuvant compound to the dispersion; and diluting the dispersion, followed by mixing with the charge director. EXAMPLE I CYAN LIQUID TONER PREPARATION: One hundred and seventy-nine and five tenths (179.5) grams of NUCREL 599®, a copolymer of ethylene and methacrylic acid with a melt index at 190°C of 500 dg/minute, available from E.I. DuPont de Nemours & Company, Wilmington, DE, 45.4 grams of the cyan pigment PV FAST BLUE™, 2.30 grams of the charge adjuvant hydroxy bis[3,5-tertiary butyl salicylic] aluminate monohydrate prepared by the ambient temperature synthesis described in Example V, and 307.4 grams of NORPAR 15®, carbon chain of 15 average, available from Exxon Corporation, were added to a Union Process 1S attritor (Union Process Company, Akron, Ohio) charged with 0.1875 inch (4.76 millimeters) diameter carbon steel balls. The mixture was milled in the attritor which was heated with running steam through the attritor jacket at 85 to 96°C for 2 hours and cooled by running water through the attritor jacket to 26°C. An additional 980.1 grams of NORPAR 15® were added, and ground in the attritor for an additional 4.5 hours. An additional 1,550.7 grams NORPAR 15® were added and the mixture was separated by the use of a metal grate from the steel balls yielding a liquid toner concentrate of 7.21 percent solids wherein solids include resin, charge adjuvant, and pigment and 92.59 percent NORPAR 15®. The particle diameter was 1.58 µm average by area as measured with a Horiba Cappa 700. CONTROL 1 LOW MOLECULAR WEIGHT BASE POLYMER (Charged M n of 3,945): There was selected a sequential Group Transfer Polymerization (GTP) of 2-ethylhexyl methacrylate (EHMA) and 2-dimethylaminoethyl methacrylate (DMAEMA) to prepare the low molecular weight AB diblock base polymer, poly [2-ethylhexyl methacrylate (B block)-co-N,N-dimethylamino-N-ethyl methacrylate (A block)]. This low molecular weight AB diblock base polymer was then used to prepare the low molecular weight protonated ammonium bromide AB diblock copolymer charge director, poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide (A block)], described in Control 8. To a 5 liter round bottom flask equipped with a magnetic stirring football, an Argon inlet and outlet and a neutral alumina column was charged, through the alumina column later to be replaced by a rubber septum, which alumina column along with the reactor was maintained under a positive Argon flow and sealed from the atmosphere, 1,245 grams (6.28 mole) of freshly distilled 2-dimethylaminoethyl methacrylate monomer and 1,500 milliliters of freshly distilled (from sodium benzophenone) tetrahydrofuran (THF) solvent. Then, 78.0 milliliters (0.384 mole) of initiator, methyl trimethylsilyl dimethylketene acetal, were syringed into the reactor. The acetal was originally vacuum distilled and a middle fraction was collected and stored (under Argon) for polymerization initiation purposes. Then, 0.033 milliliter of a 0.3 molar solution of tetrabutylammonium acetate (catalyst) in the same dry tetrahydrofuran was syringed into the polymerization vessel. About 1 hour after the mild exotherm peaked, there were added 270 grams (1.72 mole) of freshly distilled 2-dimethylaminoethyl methacrylate monomer through the alumina column, and the solution was magnetically stirred for 18 hours at ambient temperature. Then, the tetrahydrofuran solvent was stripped with a rotoevaporator (4 hours at 75.3 to 8.0 kPa (40 to 60 millimeters Hg) at 50°C to 60°C) and sufficient toluene solvent was added to the solid residue to complete the solvent exchange and to give a 50.86 weight percent toluene solution of the low molecular weight base polymer. The residual solid was generally stirred with toluene for about 16 to 18 hours at ambient temperature to obtain solution. This toluene solution was used to prepare the low molecular weight protonated ammonium bromide charge director described in Control 8. The above charges of initiator and monomers provide an M n and average degree of polymerization (DP) for each block. For the EHMA nonpolar B block, the charged M n is 3,242 and the DP is 16.35, and for the DMAEMA polar A block, the charged M n is 703 and the DP is 4.47. The charged total AB diblock M n is, therefore, 3,945. 1 H-NMR analysis was obtained on a fraction of a 1 to 2 gram sample of this low molecular weight base polymer solid isolated by rotoevaporating the toluene solvent at the same rotoevaporation conditions described above. 1 H-NMR analysis of a 17.6 percent (g/dl) CDCl 3 solution of the copolymer indicated 77.8 mole percent (81.55 weight percent) EHMA and 22.2 mole percent (18.45 weight percent) DMAEMA. Nonaqueous titration of the tertiary aliphatic amine group in each DMAEMA repeat unit of the polar A block of this low molecular weight base polymer indicated a composition very similar to that of the 1 H-NMR analysis 78.26 mole percent (81.95 weight percent) EHMA by difference and 21.74 mole percent (18.05 weight percent) DMAEMA by direct titration. The average DMAEMA content (18.25 weight percent) from both analyses in this low molecular weight base polymer was used in Control 8 to calculate the required amount of 48 percent hydrobromic acid required to make the charge director. The charged M n is obtained by dividing the number of moles of monoinitiator, methyl trimethylsilyl dimethylketene acetal, into the number of grams of non-active hydrogen containing acrylic monomer (A) being initiated by the charged molar quantity of monoinitiator. After the polymerization is completed (that is about 1 hour after the mild exotherm begins to subside), the polymer reaches its charged M n assuming that there were no initiator quenching impurities present. Initiator quenching impurities are active hydrogen containing molecules, most frequently oxygen nucleophiles such as alcohols and water, including atmospheric moisture. Active hydrogen materials in GTP means any material which contains a nucleophilic center capable of forming a covalent bond at tetravalent silicon. These impurities are removed by distillation of monomers and solvents from suitable drying agents and by baking out glassware to remove water from the glass. EXAMPLE II HIGH MOLECULAR WEIGHT BASE POLYMER (Charged M n of 93519): There was selected a sequential Group Transfer Polymerization (GTP) of 2-ethylhexyl methacrylate (EHMA) and 2-dimethylaminoethyl methacrylate (DMAEMA) to prepare the high molecular weight AB diblock base polymer, poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethylamino-N-ethyl methacrylate (A block)]. This high molecular weight AB diblock base polymer was then used to prepare the high molecular weight protonated ammonium bromide AB diblock copolymer charge director, poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide (A block)], described in Example III. To a 100 milliliter round bottom flask equipped with a magnetic stirring football, an Argon inlet and outlet, and a neutral alumina column was charged through the alumina column, later to be replaced by a rubber septum; which alumina column along with the reactor was maintained under a positive Argon flow and sealed from the atmosphere, 20 milliliters of freshly distilled (from sodium benzophenone) tetrahydrofuran (THF) solvent, 9.00 grams (0.0572 mole) of freshly distilled 2-dimethylaminoethyl methacrylate monomer and an additional 8 milliliters of the same THF to rinse down the column. Then 0.2 milliliter of a 0.033 molar solution of tetrabutylammonium acetate (catalyst) in the same dry tetrahydrofuran was syringed into the polymerization vessel. Thereafter, 0.11 milliliter (0.00054 mole) of initiator, methyl trimethylsilyl dimethylketene acetal, was syringed into the reactor. The acetal was originally vacuum distilled and a middle fraction was collected and stored (under Argon) for polymerization initiation purposes. About one hour after the addition of the ketene acetal initiator, the mild exotherm began to subside. After an additional hour, the contents of the 100 milliliters reactor were transferred with a dry syringe into a second reactor (500 milliliter round bottom flask similarly equipped as the first reactor) which second reactor contained 41.5 grams (0.2093 mole) of freshly distilled 2-ethylhexyl methacrylate monomer and 50 milliliters of freshly distilled tetrahydrofuran solvent also at ambient temperature. The combined reactor contents were allowed to stir for 18 hours at ambient temperature. Thereafter, the tetrahydrofuran solvent was stripped with a rotoevaporator (1 hour at 5.3 to 8.0 kPa (40 to 60 millimeters Hg) at 50 to 60°C) and sufficient toluene solvent was added to the solid residue to complete the solvent exchange and to give a 48.14 weight percent toluene solution of the high molecular weight base polymer. The residual solid was generally stirred with toluene for about 16 to 18 hours at ambient temperature to obtain solution. This toluene solution was used to prepare the high molecular weight protonated ammonium bromide charge director described in Example III. The above charges of initiator and monomers provide an M n and average degree of polymerization (DP) for each block. For the EHMA nonpolar B block, the charged M n is 76,852 and the DP is 387.5 and for the DMAEMA polar A block, the charged M n is 16,667 and the DP is 106. The charged total AB diblock M n is therefore 93,519. 1 H-NMR analysis was obtained on a fraction of a 1 to 2 gram sample of this high molecular weight base polymer solid isolated by rotoevaporating the toluene solvent at the same rotoevaporation conditions described above. 1 H-NMR analysis of a 7.6 percent (g/dl) CDCl 3 solution of the copolymer indicated 79.5 mole percent (83.0 weight percent) EHMA and 20.5 mole percent (17.0 weight percent) DMAEMA. CONTROL 2 VERY LOW MOLECULAR WEIGHT BASE POLYMER (Charged M n of 1973): There was selected a sequential Group Transfer Polymerization (GTP) of 2-ethylhexyl methacrylate (EHMA) and 2-dimethylaminoethyl methacrylate (DMAEMA) to prepare the low molecular weight AB diblock base polymer, poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethylamino-N-ethyl methacrylate (A block)]. This low molecular weight AB diblock base polymer was then used to prepare the very low molecular weight protonated ammonium bromide AB diblock copolymer charge director, poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide (A block)], described in Control 6. To a 2 liter 3-neck round bottom flask equipped with a magnetic stirring football, an Argon inlet and outlet and a neutral alumina (150 grams) column were charged, through the alumina column later to be replaced by a rubber septum, which alumina column along with the reactor was maintained under a positive Argon flow and sealed from the atmosphere, 415 grams (2.093 mole) of freshly distilled 2-ethylhexyl methacrylate (EHMA) monomer. Next, 500 milliliters of freshly distilled tetrahydrofuran solvent, distilled from sodium benzophenone, were rinsed through the same alumina column into the polymerization vessel. Subsequently, the GTP initiator, 52 milliliters of methyl trimethylsilyl dimethylketene acetal (44.62 grams; 0.25595 mole) were syringed into the polymerization vessel. The acetal was originally vacuum distilled and a middle fraction was collected and stored (under Argon) for polymerization initiation purposes. After stirring for about 5 minutes at ambient temperature under a gentle Argon flow, 0.50 milliliter of a 0.3 molar solution of tetrabutylammonium acetate (catalyst) in the same dry tetrahydrofuran was syringed into the polymerization vessel. About 0.5 hour after the mild exotherm peaked, there were added 90 grams (0.57246 mole) of freshly distilled 2-dimethylaminoethyl methacrylate monomer through the alumina column and then an additional 0.5 milliliter of 0.3 molar solution of tetrabutylammonium acetate (catalyst). The solution was magnetically stirred for 18 hours at ambient temperature. Then the tetrahydrofuran solvent was stripped with a rotoevaporator (4 hours at 5.3 to 8.0 kPa (40 to 60 millimeters Hg) at 50 to 60°C) and sufficient toluene solvent was added to the solid residue to complete the solvent exchange and to give a 50.63 weight percent toluene solution of the very low molecular weight base polymer. The residual solid was generally stirred with toluene for about 16 to 18 hours at ambient temperature to obtain solution. This toluene solution was used to prepare the very low molecular weight protonated ammonium bromide charge director described in Control 6. The above charges of initiator and monomers provide an M n and average degree of polymerization (DP) for each block. For the EHMA nonpolar B block, the charged M n is 1,621 and the DP is 8.18 and for the DMAEMA polar A block, the charged M n is 352 and the DP is 2.24. The charged total AB diblock M n is therefore 1,973. 1 H-NMR analysis was obtained on a fraction of a 1 to 2 gram sample of this low molecular weight base polymer solid isolated by rotoevaporating the toluene solvent at the same rotoevaporation conditions described above. 1 H-NMR analysis of a 21.2 percent (g/dl) CDCl 3 solution of the copolymer indicated 84.0 mole percent (86.88 weight percent) EHMA and 16.0 mole percent (13.12 weight percent) DMAEMA. Nonaqueous titration of the tertiary aliphatic amine group in each DMAEMA repeat unit of the polar A block of this low molecular weight base polymer indicated a composition very similar to that of the 1 H-NMR analysis: 84.76 mole percent (87.52 weight percent) EHMA by difference and 15.24 mole percent (12.48 weight percent) DMAEMA by direct titration. The nonaqueous titration composition was based on the finding of 0.786 milliequivalent of amine per gram of solid base polymer. The weight percent DMAEMA repeat units (12.48 weight percent) from the nonaqueous titration in this very low molecular weight base polymer was used in Control 6 to calculate the required amount of 48 percent hydrobromic acid required to make the charge director. CONTROL 3 LOW TO MID-MOLECULAR WEIGHT BASE POLYMER (Charged M n of 23315): There was selected a sequential Group Transfer Polymerization (GTP) of 2-ethylhexyl methacrylate (EHMA) and 2-dimethylaminoethyl methacrylate (DMAEMA) to prepare the low-mid molecular weight AB diblock base polymer, poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethylamino-N-ethyl methacrylate (A block)]. This low-mid molecular weight AB diblock base polymer was then used to prepare the low-mid molecular weight protonated ammonium bromide AB diblock copolymer charge director, poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide (A block)]. To a 100 milliliter round bottom flask equipped with a magnetic stirring football, an Argon inlet and outlet, and a neutral alumina column was charged, through the alumina column, later to be replaced by a rubber septum; which alumina column along with the reactor was maintained under a positive Argon flow and sealed from the atmosphere, 20 milliliters of freshly distilled (from sodium benzophenone) tetrahydrofuran (THF) solvent, 9.00 grams (0.0572 mole) of freshly distilled 2-dimethylaminoethyl methacrylate monomer and an additional 8 milliliters of the same THF to rinse down the column. Then, 0.2 milliliter of a 0.033 molar solution of tetrabutylammonium acetate (catalyst) in the same dry tetrahydrofuran was syringed into the polymerization vessel. Then 0.44 milliliter (0.002166 mole) of initiator, methyl trimethylsilyl dimethylketene acetal, was syringed into the reactor. The acetal was originally vacuum distilled, and a middle fraction was collected and stored (under Argon) for polymerization initiation purposes. About one hour after the addition of the ketene acetal initiator, the mild exotherm began to subside. After an additional 0.5 to 1.0 hour, the contents of the 100 milliliter reactor were transferred with a dry syringe into a second reactor (500 milliliter round bottom flask similarly equipped as the first reactor) which second reactor contained 41.5 grams (0.2093 mole) of freshly distilled 2-ethylhexyl methacrylate monomer and 50 milliliters of freshly distilled tetrahydrofuran solvent also at ambient temperature. The combined reactor contents were allowed to stir for 18 hours at ambient temperature. The tetrahydrofuran solvent was then stripped with a rotoevaporator (1 hour at 5.3 to 8.0 kPa (40 to 60 millimeters Hg) at 50 to 60°C) and sufficient toluene solvent was added to the solid residue to complete the solvent exchange and to give a 53.16 weight percent toluene solution of the low-mid molecular weight base polymer. The residual solid was generally stirred with toluene for about 16 to 18 hours at ambient temperature to obtain solution. This toluene solution was used to prepare the low-mid molecular weight protonated ammonium bromide charge director described in Control 5. The above charges of initiator and monomers provide an M n and average degree of polymerization (DP) for each block. For the EHMA nonpolar B block, the charged M n is 19,160 and the DP is 96.6, and for the DMAEMA polar A block, the charged M n is 4,155 and the DP is 26.4. The charged total AB diblock M n is therefore 23,315. A 1 H-NMR analysis was performed on a fraction of a 1 to 2 gram sample of this low-mid molecular weight base polymer solid isolated by rotoevaporating the toluene solvent at the same rotoevaporation conditions described above. 1 H-NMR analysis of about a 15.0 percent (g/dl) CDCl 3 solution of the copolymer indicated 76.9 mole percent (80.76 weight percent) EHMA and 23.1 mole percent (19.24 weight percent) DMAEMA. The weight percent DMAEMA in this low-mid molecular weight base polymer was used in Control 5 to calculate the required amount of 48 percent hydrobromic acid required to make the charge director. CONTROL 4 MID-MOLECULAR WEIGHT BASE POLYMER (Charged M n of 46640): There was selected a sequential Group Transfer Polymerization (GTP) of 2-ethylhexyl methacrylate (EHMA) and 2-dimethylaminoethyl methacrylate (DMAEMA) to prepare the mid molecular weight AB diblock base polymer, poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethylamino-N-ethyl methacrylate (A block)]. This mid-molecular weight AB diblock base polymer was then used to prepare the mid-molecular weight protonated ammonium bromide AB diblock copolymer charge director, poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide (A block)], described in Control 7. To a 100 milliliter round bottom flask equipped with a magnetic stirring football, an Argon inlet, and outlet and a neutral alumina column were charged, through the alumina column, later to be replaced by a rubber septum; which alumina column along with the reactor was maintained under a positive Argon flow and sealed from the atmosphere, 20 milliliters of freshly distilled (from sodium benzophenone) tetrahydrofuran (THF) solvent, 9.00 grams (0.0572 mole) of freshly distilled 2-dimethylaminoethyl methacrylate monomer and an additional 8 milliliters of the same THF to rinse down the column. Then, 0.2 milliliter of a 0.033 molar solution of tetrabutylammonium acetate (catalyst) in the same dry tetrahydrofuran was syringed into the polymerization vessel. Then, 0.22 milliliter (0.001083 mole) of initiator, methyl trimethylsilyl dimethylketene acetal, was syringed into the reactor. The acetal was originally vacuum distilled and a middle fraction was collected and stored (under Argon) for polymerization initiation purposes. About one hour after the addition of the ketene acetal initiator, the mild exotherm began to subside. After an additional hour, the contents of the 100 milliliters reactor were transferred with a dry syringe into a second reactor (500 milliliter round bottom flask similarly equipped as the first reactor) which second reactor contained 41.5 grams (0.2093 mole) of freshly distilled 2-ethylhexyl methacrylate monomer and 50 milliliters of freshly distilled tetrahydrofuran solvent also at ambient temperature. The combined reactor contents were allowed to stir for 18 hours at ambient temperature. Then, the tetrahydrofuran solvent was stripped with a rotoevaporator (1 hour at 5.3 to 8.0 kPa (40 to 60 millimeters Hg) at 50 to 60°C) and sufficient toluene solvent was added to the solid residue to complete the solvent exchange and to give a 48.14 weight percent toluene solution of the mid-molecular weight base polymer. The residual solid was generally stirred with toluene for about 16 to 18 hours at ambient temperature to obtain solution. This toluene solution was used to prepare the mid-molecular weight protonated ammonium bromide charge director described in Control 7. The above charges of initiator and monomers provide an M n and average degree of polymerization (DP) for each block. For the EHMA nonpolar B block, the charged M n is 38,325, and the DP is 193.3 and for the DMAEMA polar A block, the charged M n is 8,311 and the DP is 52.9. The charged total AB diblock M n is therefore 46,636. A nonaqueous titration was performed on a fraction of a 1 to 2 gram sample of this mid-molecular weight base polymer solid isolated by rotoevaporating the toluene solvent at the same rotoevaporation conditions described above Nonaqueous titration indicated the presence of 80.22 mole percent (83.65 weight percent) of EHMA and 19.78 mole percent (16.35 weight percent) of DMAEMA. The nonaqueous titration composition was based on the finding of 1.040 millequivalents of amine per gram of solid base polymer. The weight percent DMAEMA in this mid-molecular weight base polymer was used in Control 7 to calculate the required amount of 48 percent hydrobromic acid required to make the charge director. CONTROL 5 LOW TO MID-MOLECULAR WEIGHT CHARGE DIRECTOR: Preparation of the low mid-molecular weight protonated ammonium bromide AB diblock copolymer charge director, poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide (A block)], from low mid-molecular weight base polymer (charged M n of 23,315), poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethylamino-N-ethyl methacrylate (A block)], prepared in Control 3 and aqueous hydrogen bromide. To a 250 milliliter Erlenmeyer flask were added 20.00 grams of a 53.16 weight percent toluene solution of the low mid-molecular weight AB diblock copolymer (10.63 grams of copolymer and 9.37 grams of toluene) prepared in Control 3 as poly(2-ethylhexyl methacrylate-co-N,N-dimethylamino-N-ethyl methacrylate). The AB diblock copolymer is comprised of 19.24 weight percent of 2-dimethylaminoethyl methacrylate (DMAEMA) repeat units and 80.76 weight percent of 2-ethylhexyl methacrylate (EHMA) repeat units. The 10.63 grams of AB diblock copolymer contains 2.05 grams (0.013039 mole) of DMAEMA repeat units. To this magnetically stirred AB diblock copolymer toluene solution at about 22°C were added an additional 42.34 grams of toluene, 4.10 grams of methanol, and 2.15 grams (0.01278 mole of HBr) of 48 percent aqueous hydrobromic acid (Aldrich). The charged solids level is 17.0 weight percent assuming a quantitative conversion of the targeted 98 mole percent DMAEMA repeat units present in the low mid-molecular weight base polymer to the H8r salt. This solution was magnetically stirred for 16 to 18 hours at ambient temperature to give a slightly viscous low mid-molecular weight protonated ammonium bromide AB diblock copolymer charge director solution. To this charge director solution were added 201.97 grams of NORPAR 15® to give a 5 weight percent (based on the corresponding starting weight of the AB diblock copolymer from Control 3) charge director solution after toluene and methanol rotoevaporation. Toluene and methanol were rotoevaporated at 55 to 60°C for about 1.0 hour at 5.3 to 8.0 kPA (40 to 60 millimeters Hg). The 5 weight percent NORPAR 15® solution of poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide) had a conductivity of 170 pS/cm and was used to charge liquid toner. CONTROL 6 VERY LOW MOLECULAR WEIGHT CHARGE DIRECTOR: Preparation of the very low molecular weight protonated ammonium bromide AB diblock copolymer charge director, poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide (A block)], from the very low molecular weight base polymer (charged M n of 1,973), poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethylamino-N-ethyl methacrylate (A block)], prepared in Control 2 and aqueous hydrogen bromide. To a 250 milliliter Erlenmeyer flask were added 20.00 grams of a 50.63 weight percent toluene solution of the very low molecular weight AB diblock copolymer (10.13 grams of copolymer and 9.87 grams of toluene) prepared in Control 2 as poly(2-ethylhexyl methacrylate-co-N,N-dimethylamino-N-ethyl methacrylate). The AB diblock copolymer was comprised of 12.48 weight percent of 2-dimethylaminoethyl methacrylate (DMAEMA) repeat units and 87.52 weight percent of 2-ethylhexyl methacrylate (EHMA) repeat units. The 10.13 grams of AB diblock copolymer contained 1.26 grams (0.00801 mole) of DMAEMA repeat units. To this magnetically stirred AB diblock copolymer toluene solution at about 2°C were added an additional 38.20 grams of toluene, 3.82 grams methanol, and 1.33 grams (0.00785 mole of HBr) of 48 percent aqueous hydrobromic acid (Aldrich). The charged solids level was 17.0 weight percent assuming a quantitative conversion of the targeted 98 mole percent of DMAEMA repeat units present in the very low molecular weight base polymer to the HBr salt. This solution was magnetically stirred for 16 to 18 hours at ambient temperature to give the very low molecular weight non-viscous solution of protonated ammonium bromide AB diblock charge director solution. The solution was then diluted with NORPAR 15® (192.47 grams) to give a 5 weight percent (based on the corresponding starting weight of the AB diblock copolymer from Control 2) charge director solution after toluene and methanol rotoevaporation. Toluene and methanol were rotoevaporated at 55 to 60°C for 1 hour at 5.3 to 6.7 kPa (40 to 50 millimeters Hg). The 5 weight percent NORPAR 15® solution of poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide) had a conductivity of 2,850 pS/cm and was used to charge liquid toner. CONTROL 7 MID-MOLECULAR WEIGHT CHARGE DIRECTOR: Preparation of the mid-molecular weight protonated ammonium bromide AB diblock copolymer charge director, poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide (A block)], from mid-molecular weight base polymer (charged M n of 46,636), poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethylamino-N-ethyl methacrylate (A block)], prepared in Control 4 and aqueous hydrogen bromide. To a 125 milliliter Erlenmeyer flask were added 20.00 grams of a 46.21 weight percent toluene solution of the mid-molecular weight AB diblock copolymer (9.24 grams of copolymer and 10.76 grams of toluene) prepared from poly(2-ethylhexyl methacrylate-co-N,N-dimethylamino-N-ethyl methacrylate) described in Control 4. The AB diblock copolymer was comprised of 16.35 weight percent of 2-dimethylaminoethyl methacrylate (DMAEMA) repeat units and 83.65 weight percent of 2-ethylhexyl methacrylate (EHMA) repeat units. The 9.24 grams of AS diblock copolymer contained 1.51 grams (0.0096 mole) of DMAEMA repeat units. To this magnetically stirred AB diblock copolymer toluene solution at about 22°C were added an additional 47.53 grams of toluene, 4.62 grams of methanol, and 1.59 grams (0.0094 mole of HBr) of 48 percent aqueous hydrobromic acid (Aldrich). The charged solids level was 13.6 weight percent assuming a quantitative conversion of the targeted 98 mole percent of DMAEMA repeat units present in the mid molecular weight base polymer to the HBr salt. This solution was magnetically stirred for 21 hours at ambient temperature to give a viscous mid-molecular weight protonated ammonium bromide AB diblock copolymer charge director solution. To 36.87 grams of this charge director solution (one-half of the total weight of the charge director solution) were added 87.78 grams of NORPAR 15® to give a 5 weight percent (based on one-half the corresponding starting weight of the AB diblock copolymer from Control 4) charge director solution after toluene and methanol rotoevaporation. Toluene and methanol were rotoevaporated at 50 to 55°C for 2.5 hours at 10.0 to 10.6 kPa (75 to 80 millimeters Hg). The 5 weight percent NORPAR 15® solution of poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide) had a conductivity of 57 pS/cm and was used to charge liquid toner. CONTROL 8 LOW MOLECULAR WEIGHT CHARGE DIRECTOR: Preparation of the low molecular weight protonated ammonium bromide AB diblock copolymer charge director, poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide (A block)], from low molecular weight base polymer (charged M n of 3,945), poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethylamino-N-ethyl methacrylate (A block)], prepared in Control 1 and aqueous hydrogen bromide. To a 4.0 liter Erlenmeyer flask were added 637.1 grams of a 50.86 weight percent toluene solution of the low molecular weight AB diblock copolymer (324.0 grams of copolymer and 313.1 grams of toluene) prepared from poly(2-ethylhexyl methacrylate-co-N,N-dimethylamino-N-ethyl methacrylate) described in Control 1. The AB diblock copolymer was comprised of 18.25 weight percent of 2-dimethylaminoethyl methacrylate (DMAEMA) repeat units and 81.75 weight percent of 2-ethylhexyl methacrylate (EHMA) repeat units. The 324.0 grams of AB diblock copolymer contained 59.1 grams (0.376 mole) of DMAEMA repeat units. To this magnetically stirred AB diblock copolymer toluene solution at about 20°C were added an additional 324.0 grams of toluene, 50.5 grams of methanol, and 62.1 grams (0.368 mole of HBr) of 48 percent aqueous hydrobromic acid (Aldrich). The charged solids level was 32.95 weight percent, assuming a quantitative conversion of the targeted 98 mole percent DMAEMA repeat units present in the low molecular weight base polymer, to the HBr salt. This solution was magnetically stirred for about 66 hours at ambient temperature to give a low molecular weight protonated ammonium bromide AB diblock charge director solution of increased viscosity versus the solution of reactants at time zero. The moderately viscous solution was then diluted with NORPAR 15® (6,156.6 grams) to give a 5 weight percent (based on the corresponding starting weight of the AB diblock copolymer from Control 1) charge director solution after toluene and methanol rotoevaporation. Toluene and methanol were rotoevaporated in 0.5 liter batches at 50 to 60°C for 1.0 to 1.5 hours at 5.3 to 8.0 kPa (40 to 60 millimeters Hg). The 5 weight percent NORPAR 15® solution batches of poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide) had conductivities in the range of 1,970 to 2.110 pS/cm and were used to charge liquid toner. EXAMPLE III HIGH MOLECULAR WEIGHT CHARGE DIRECTOR: Preparation of the high molecular weight protonated ammonium bromide AB diblock copolymer charge director, poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide (A block)], from high molecular weight base polymer (charged M n of 93,519), poly[2-ethylhexyl methacrylate (8 block)-co-N,N-dimethylamino-N-ethyl methacrylate (A block)], prepared in Example II and aqueous hydrogen bromide. To a 250 milliliter Erlenmeyer flask were added 20.00 grams of a 48.14 weight percent toluene solution of the high molecular weight AB diblock copolymer (9.63 grams of copolymer and 10.37 grams of toluene) prepared from poly(2-ethylhexyl methacrylate-co-N,N-dimethylamino-N-ethyl methacrylate) described in Example II. The AB diblock copolymer was comprised of 17.0 weight percent of 2-dimethylaminoethyl methacrylate (DMAEMA) repeat units and 83.0 weight percent of 2-ethylhexyl methacrylate (EHMA) repeat units. The 9.63 grams of AB diblock copolymer contained 1.64 grams (0.0104 mole) of DMAEMA repeat units. To this magnetically stirred AB diblock copolymer toluene solution at about 20°C were added an additional 50.31 grams of toluene, 4.81 grams of methanol, and 0.82 gram (0.0102 mole of HBr) of 48 percent aqueous hydrobromic acid (Aldrich). The charged solids level was 13.6 weight percent, assuming a quantitative conversion of the targeted 98 mole percent DMAEMA repeat units present in the high molecular weight base polymer, to the HBr salt. This solution was magnetically stirred for 16 to 18 hours at ambient temperature to give a very viscous but still magnetically stirrable high molecular weight protonated ammonium bromide AB diblock charge director solution. The viscous solution was then diluted with NORPAR 15® (182.97 grams) to give a 5 weight percent (based on the corresponding starting weight of the AB diblock copolymer from Example II) charge director solution after toluene and methanol rotoevaporation. Toluene and methanol were rotoevaporated at 60 to 65°C for 1 hour at 5.3 to 6.7 kPa (40 to 50 millimeters Hg). The 5 weight percent of NORPAR 15® solution of poly(2-ethylhexyl methacrylate-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide) had a conductivity of only 5.0 pS/cm and was used to charge liquid toner. CONTROL 9 CYAN LIQUID DEVELOPERS CHARGED WITH THE LOW MOLECULAR WEIGHT PROTONATED AMMONIUM BROMIDE AB DIBLOCK COPOLYMER CHARGE DIRECTOR: Cyan liquid toner dispersions were prepared by selecting 27.74 grams of liquid toner concentrate (7.21 percent solids in NORPAR 15®) from Example I and adding to it sufficient NORPAR 15® and 5 percent low molecular weight (charged M n of 3,945) protonated ammonium bromide AB diblock charge director, poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide (A block)], from Control 8 to provide 1 percent solids wherein solids include resin, charge adjuvant, and pigment liquid toner dispersions containing 10, 30, 50, 70, and 90 milligrams or 1, 3, 5, 7 and 9 percent charge director per gram of toner solids (Controls 9A to 9E). The 5 percent low molecular weight protonated ammonium bromide AB diblock charge director was prepared from the low molecular weight base polymer of Control 1. After 1, 7, 14, and 21 days of equilibration, mobility and conductivity were measured for these 1 percent liquid toners to determine the toner charging rate and level. These values were compared to mobility and conductivity values obtained for the 1 percent cyan liquid toners described in Example IV containing the high molecular weight protonated ammonium bromide AB diblock charge director. Table 1 in Example IV contains 200 gram formulations for both sets of cyan liquid toners or developers charged with the low and high molecular weight protonated ammonium bromide AB diblock copolymer charge directors. Table 2 in Example IV contains the corresponding mobility and conductivity values for both sets of cyan liquid toners or developers. EXAMPLE IV CYAN LIQUID DEVELOPERS CHARGED WITH THE HIGH MOLECULAR WEIGHT PROTONATED AMMONIUM BROMIDE AB DIBLOCK COPOLYMER CHARGE DIRECTOR: Cyan liquid toner dispersions were prepared by selecting 27.74 grams of liquid toner concentrate (7.21 percent solids in NORPAR 15®) from Example I and adding to it sufficient NORPAR 15® and 5 percent high molecular weight (charged M n of 93,519) protonated ammonium bromide AB diblock charge director, poly[2-ethylhexyl methacrylate (B block)-co-N,N-dimethyl-N-ethyl methacrylate ammonium bromide (A block)], from Example III to provide 1 percent solids wherein solids include resin, charge adjuvant, and pigment liquid toner dispersions containing 30, 60, 94, 120, and 150 milligrams or 3, 6, 9, 4, 12 and 15 percent charge director per gram of toner solids (Examples IVA to IVE). The 5 percent high molecular weight protonated ammonium bromide AB diblock charge director was prepared from the high molecular weight base polymer of Example II. After 1, 3, 7, and 13 days of equilibration, mobility and conductivity were measured for these 1 percent liquid toners to determine the toner charging rate and level. These values were compared to mobility and conductivity values obtained for the 1 percent cyan liquid toners described in Control 9. Graph 1 contains 200 gram formulations for both sets of cyan developers charged with the low and high molecular weight protonated ammonium bromide AB diblock copolymer charge directors. Table 2 contains the corresponding mobility and conductivity values for both sets of cyan liquid toners or developers. At all charge director concentrations studied, Graph 1 illustrates the consistently lower conductivities obtained after 13 days for cyan developers, prepared from the cyan liquid toner concentrate described in Example I, charged with the high M n AB diblock protonated ammonium bromide (salt) copolymer charge director of the present invention, prepared in Example III from the high molecular weight base polymer described in Example II versus cyan developers, also prepared from the cyan liquid toner concentrate described in Example I, charged with the corresponding low M n AB diblock protonated ammonium bromide (salt) copolymer charge director after 14 days, and prepared in Control 8 from the low molecular weight base polymer described in Control 1. Graph 2 illustrates that cyan developers charged with increasing amounts of the high molecular weight AB diblock protonated ammonium bromide (salt) copolymer charge director level off at mobilities equal to or greater than 4.0 m 2 /Vs after 13 days without any significant further increase in developer conductivity, whereas the corresponding developers charged with increasing amounts of the low molecular weight AB diblock protonated ammonium bromide (salt) copolymer charge director plateau at mobilities equal to or less than 3.5 m 2 /Vs with steadily increasing conductivity. Low ink conductivities are considered necessary for optimum image density and resolution thus making developers charged with high molecular weight AB diblock protonated ammonium bromide copolymer charge directors advantageous over developers charged with the corresponding low molecular weight AB diblock protonated ammonium bromide copolymer charge directors. Graph 3 illustrates that high molecular weight AB diblock protonated ammonium bromide copolymer charge director advantage, versus the low molecular weight variety, because the option of charging toner particles to higher charging levels with higher concentrations of charge director results for the high molecular weight charge director. Cyan Liquid Developer Formulations Charged with Low and High Molecular Weight Protonated Ammonium Bromide AB Diblock Copolymer Charge Directors Developer ID: Control or Example No. Grams Toner Concen- trate From Example I Grams Added NORPAR 15 Grams Added 5% Charge Director (CD) in NORPAR 15 CD Preparation Example No. & CD Level in mg CD/g Toner Solids Control 9A 171.86 0.40 Control 8: 10/1 Low MW Example TVA 27.74 171.06 1.20 Example III: 30/1 High MW Control 9B 171.06 1.20 Control 8: 30/1 Low MW Example IV B 27.74 169.86 2.40 Example III: 60/1 High MW Control 9C 170.26 2.00 Control 8: 50/1 Low MW Example IVC 27.74 168.66 3.74 Example III: 94/1 High MW Control 9D 169.46 2.80 Control 8: 70/1 Low MW Example IVD 27.74 167.46 4.80 Example III: 120/1 High MW Control 9E 168.66 3.60 Control 8: 90/1 Low MW Example IVE 27.74 166.26 6.00 Example III: 150/1 High MW Mobility and Conductivity Results for Cyan Liquid Developers Charged with Low and High Molecular Weight Protonated Ammonium Bromide AB Diblock Copolymer Charge Directors Developer ID: Control or Example No. Aging: Time in Days CD Level: mg CD/g Toner Solids Mobility: 10 -10 m 2 /Vs Cond.: pS/cm COMMENTS Control 9A 1 10/1 Low -2.25 4 Moderate Charging & Low Conductivity 7 MWAB -1.89 4 14 Diblock -1.63 3 21 Copolymer -1.68 3 Control 9B 1 30/1 Low -3.00 11 High Charging & Moderate Conductivity 7 MW AB -3.36 10 14 Diblock -3.45 9 21 Copolymer -3.47 10 Control 9C 1 50/1 Low -3.04 18 High Charging & High Conductivity 7 MW AB -3.19 17 14 Diblock -3.29 16 21 Copolymer -3.54 17 Control 9D 1 70/1 Low -3.16 26 High Charging & Very High Conductivity 7 MW AB -3.40 25 14 Diblock -3.08 22 21 Copolymer -3.58 24 Control 9E 1 90/1 Low -3.19 33 High Charging & Very High Conductivity 7 MW AB -3.38 33 14 Diblock -3.08 30 21 Copolymer -3.49 33 Example IVA 1 30/1 High -1.87 2 Low Charging & Very Low Conductivity 3 MW AB -1.72 2 7 Diblock -1.24 1 13 Copolymer -1.38 1 Example IVB 1 60/1 High -2.97 2 High Charging & Low Conductivity 3 MW AB -3.31 3 7 Diblock -2.77 2 13 Copolymer -3.38 3 Example IVC 1 94/1 High -3.30 3 Very High Charging & Low Conductivity 3 MWAB -3.94 3 7 Diblock -3.75 3 13 Copolymer -3.97 4 Example IVD 1 120/1 High -3.60 3 Very High Charging & Low Conductivity 3 MWAB -4.02 4 7 Diblock -3.89 4 13 Copolymer -4.33 4 Example IVE 1 150/1 High -3.67 3 Extremely High Charging & Low Conductivity 3 MWAB -4.14 4 7 Diblock -4.40 4 13 Copolymer -4.24 3 EXAMPLE VI SERIES-CAPACITOR TECHNIQUE: The electrical properties of liquid developers can be reviewed using a series-capacitor method, which is a well-established method for determining the dielectric relaxation time in partially conductive materials as, for example, might be found in "leaky" capacitors. Two series-capacitors can be used. One is comprised of a dielectric layer (MYLAR®) which corresponds to the photoreceptor, the other is comprised of a layer of liquid (ink). Although a constant bias voltage is maintained across the two capacitors, the voltage across the ink layer decays as the charged particles within it move. Measurement of the external currents allows the observation of the decay of voltage across the ink layer. Depending on the composition of the ink layer, this reflects the motion of charged species, in real time, as in the various, actual LID (Liquid Immersion Development) processes. Application of a codeveloped theoretical analysis, together with a knowledge of the dielectric thicknesses of the MYLAR® and ink layers, the applied bias voltage and the observed current, provides information about the mobilities and densities of the charged species which in general are found to be time and field-dependent. Three liquid developers of Example I were tested, all at 2 percent solids in NORPAR 15®. Example VIA was charged with low molecular charge director of Control 8 (48 milligrams of charge director per gram of ink solids); Example VIB was charged with medium molecular charge director of Control 7 (100 milligrams of charge director per gram of toner solids); and Example VIC was charged with high molecular weight charge director of Example III (100 milligrams of charge director per gram of toner solids). The results are provided in Table 3. EXAMPLE CHARGE DIRECTOR TIME (SEC) CURRENT (MICRO AMPS) VIA Control 8 1 × 10 -4 150 VIA Control 8 3 × 10 -4 200 VIA Control 8 6 × 10 -4 150 VIB Control 7 1 × 10 -4 3 VIB Control 7 3 × 10 -4 12 VIB Control 7 6 × 10 -4 30 VIC Example III 1 × 10 -4 1 VIC Example III 3 × 10 -4 5 VIC Example III 6 × 10 -4 15 Charge Director Molecular Weight (M n ) Conductivity of 0.1 % (by weight) Charge Director in NORPAR 15 (pS/cm) Charged Micelle Electrophoretic Mobility (10 -6 cm 2 /Vs) Micelle Charge Density of 0.1 % (by weight) Charge Director (µC/cm 3 ) Control 6 43 11 3.5 Control 8 43 5.4 5.1 Control 5 6 2.5 1.9 Control 7 2 2.2 1.0 Example III 0.6 1.5 0.5

Claims: A liquid developer comprised of a liquid, thermoplastic resin particles, a nonpolar liquid soluble charge director comprised of an ionic or zwitterionic ammonium block copolymer, and wherein the number average molecular weight thereof of said charge director is from about 70,000 to about 200,000. The developer according to claim 1, wherein the developer is a negatively charged developer comprised of a nonpolar liquid, and further comprising a charge adjuvant and a pigment. The developer according to claim 1, wherein the developer is a electrostatographic developer comprised of (A) a nonpolar liquid having a Kauri-butanol value of from about 5 to about 30 and present in a major amount of from about 50 percent to about 95 weight percent; (B) thermoplastic resin particles and pigment particles; (C) a nonpolar liquid soluble polymeric charge director comprised of an ionic or zwitterionic ammonium block copolymer; and (D) a charge adjuvant; and wherein the number average molecular weight thereof of said charge directcr is from about 80,000 to about 150,000. The developer in accordance with claim 3 wherein the charge director is of the formula wherein R is hydrogen, alkyl, aryl, or alkylaryl; R' is ethyl or methyl; R" is alkyl, aryl, cycloalkyl, cycloalkylalkyl cycloalkylaryl or alkylaryl witn or without heteroatoms; R''' is alkyl, aryl, cycloalkyl, cycloalkylalkyl, cycloalkylaryl or alkylaryl of 4 to 20 carbons with or without heteroatoms; X is alkylene or arylalkylene with or without heteroatoms; Y is hydrogen, alkyl of 1 to about 25 carbon atoms, alkylaryl ,and aryl from 6 to about 30 carbon atoms with or without hetercatoms; Z- is the anion bromide, hydroxide, chloride, nitrate, p-toluenesulfonate, sulfate, phosphate, fluoride, dodecylsulfonate, dodecylbenzenesulfonate, acetate, trifluoroacetate, chloroaceate, or stearate; aM a + a'M a' is about 3,500 to 120,000 and bM b is 28,000 to 190,000 wherein a, a' and b are the number average degree of polymerization (DP) and M a , M a' and M b are the corresponding repeat unit molecular weights. The developer in accordance with claim 2, wherein said charge director has a molecular weight of from about 80,000 to about 120,000, and there results a developer with high developer particle charge and low conductivity. The developer in accordance with claim 5, wherein the high developer toner charge provides particle mobilities that range from about 2.0 x 10 -10 m 2 /Vs to about 5 x 10 -10 m 2 /Vs as measured by the Matec ESA and/or the low conductivity of said developer, at 1 percent developer solids in NORPAR 15™, is from about 1 pS/cm. The developer in accordance with any one of claims 1 to 6, wherein the resin particles are comprised of a copolymer of ethylene and an α, β-ethylenically unsaturated acid selected from the group consisting of acrylic acid and methacrylic acid, or mixtures thereof; or wherein the resin particles are comprised of a styrene polymer, an acrylate polymer, a methacrylate polymer, a polyester, or mixtures thereof; or wherein the resin particles are comprised of a copolymer of ethylene and vinyl acetate, polypropylene, polyethylene, and acrylic polymers, or mixtures thereof; or wherein the resin particles are comprised of a copolymer of ethylene, and acrylic or methacrylic acid, an alkyl ester of acrylic or methacrylic acid wherein alkyl contains from 1 to about 5 carbon atoms or a copolymer of ethylene, and methacrylic acid with a melt index at 190°C of 500. The developer in accordance with claim 3 wherein component (A) is present in an amount of from 85 percent to 99.9 percent by weight based on the total weight of the developer solids of resin, pigment, and charge adjuvant which is present in an amount of from about 0.1 percent to about IS percent by weight; and component (C) is present in an amount of from about 0.5 percent to about 100 percent of the developer solids comprised of resin, pigment, and charge adjuvant; and/or wherein component (D) is present in an amount of 0.1 to 40 percent by weight based on the total weight of developer solids. The developer in accordance with claim 2 wherein the liquid is an aliphatic hydrocarbon having a mixture of branched hydrocarbons with from about 12 to about 16 carbon atoms; or having a mixture of normal hydrocarbons with from about 12 to about 16 carbon atoms. The developer in accordance with claim 3 wherein the charge director is of the formula wherein R is hydrogen, alkyl, aryl, or alkylaryl; R 1 is a conjugate oxygen containing acid anion derived from carbon, sulfur, or phosphorus; Z is carbon, sulfur, phosphorus or a substituted phosphorous PR; m is 1 or 2 doubly bonded oxygen atoms; n is 0 or 1 hydroxyl groups; R' is alkyl, aryl, cycloalkyl, cycloalkylenyl cycloalkylalkyl, cycloalkylaryl or alkylaryl; R" is alkyl, aryl, cycloalkyl, cycloalkylalkyl, cycloalkylaryl or alkylaryl; R"' is alkyl, aryl, cycloalkyl, cycloalkylalkyl, cycloalkylaryl or alkylaryl of 4 to 20 carbons; X is alkylene or arylalkylene; Y is alkylene or arylalkylene; aM a + a'M a' is about 3,500 to 120,000 and bM b is 28,000 to 190,000 wherein a, a' and b are the number average degree of polymerization (DP) and M a , M a' and M b are the corresponding repeat unit molecular weights. An imaging method which comprises forming an electrostatic latent image followed by the development thereof with the liquid developer as claimed in any of claims 1 to 9.

Inventors: ABKOWITZ MARTIN A, ANTONIADIS HOMER, CHEN INAN, LARSON JAMES R, MORT JOSEPH, SPIEWAK JOHN W, ABKOWITZ, MARTIN A., ANTONIADIS, HOMER, CHEN, INAN, LARSON, JAMES R., MORT, JOSEPH, SPIEWAK, JOHN W.
Applicants: XEROX CORP, XEROX CORPORATION
Application year: 1995
Main classification: G03G9
IPC codes: G03G9