FR2472214A1 - LIQUID NEGATIVE REVELATOR COMPOSITION FOR ELECTROSTATIC COPY DRAWING - Google Patents

Abstract

THE INVENTION DESCRIBES A LIQUID NEGATIVE DEVELOPER COMPOSITION WITH IMPROVED EXHAUST CHARACTERISTICS. THE DEVELOPER INCLUDES AN ORGANIC VEHICLE CONTAINING PARTICLES OF A LATEX FORM MAINLY OF A POLYMER OF ACRYLATE OR ALKYL METHACRYLATE CC, A PIGMENT, AN ELECTRIC CHARGE REGULATOR CONSISTING OF A COPOLYMER OF A VINYL ETHER AND OF ' ALKYL CC AND VINYL CHLORIDE, AND ACRYLIC POLYMER GEL TO STABILIZE DISPERSION. THIS DEVELOPER CAN BE USED IN CONVENTIONAL ELECTROSTATIC REPRODUCTION EQUIPMENT TO PRODUCE MORE THAN 20,000 COPIES OF AN ACCEPTABLE IMAGE DENSITY.

Description

The present invention relates to developer compositions for printing

  electrostatically, as well as an improved method of image formation using these compositions. More particularly, the invention relates to liquid compositions of negative developers having a better

  their stability and a longer service life.

  The conventional liquid developers for use in

  electrostatic copiers consist of a liquid vehicle

  of non-polar organic matter with a low dielectric constant

  that and a high resistivity and that contains a colored matter

  comprising solid particulate resinous fixative and a pigment or pigment system. The developer has

  also an electric charge regulator and one or more

  substances intended to prolong the period of

  composition and to maintain the various constituents

  solids in the form of a homogeneously dispersed phase.

  When a substrate or element supporting an electronic image

  latent static is brought into contact with the developer composition, charge-bearing developer components are preferentially attracted to the latent image having an opposite charge and are then attached, typically by applying heat to evaporate

  the vehicle, in order to produce a permanent visible image.

  In a perfect developer composition, the fixer and the pigment must be intimately associated and have a small uniform particle size and a uniform charge. This would give a uniform exhaustion of the coloring matter as the successive development of the images and a uniform density of the copies successively

  produced. In practice, this ideal property of composi-

  developer has proved difficult to achieve.

  The static charge conferred on the solid particles of such

  composition by the charge controller is typically

  the chemical properties of this regulator, the particles

  the coloring matter and the specific contact surface of the particles. Thus, relatively small differences in particle size or particle size give particles of variable intensity charge.

2 2472214

  in use, the large particles of the composition disappear

  fall by preferential exhaustion. As a result,

  density of the image of successively produced copies

  nude since a given area of the latent image formed on the substrate, which has a certain charge, attracts a substantially constant charge but is associated with a lower mass of the dyestuff. Likewise, since the liquid developer compositions mainly contain in-vehicle electrical charge regulators of the composition and the charge regulator runs out less quickly than the fixer and the pigment, the net charge of the particles remaining in the revealing varies from

  complicated way, as the production of the succes-

  cessives, resulting in variations in the density

image copies.

  The prior art teaches various approaches to try to solve this problem, but none has been fully

  successful. Current copiers are equipped with

  positive ones for monitoring the density of liquid developer particles. When the particle density falls below a chosen level, developer concentrate and / or vehicle is added to the suspension used for development to adjust the particle density to better levels. However, the image density of the successively developed copies decreases, however, since the proportion of large particles exhibiting

  optimum charge decreases in the developer being used.

  tion. When the density of the image of the copies falls

  below an acceptable level, additional quantities

  Relatively large amounts of the vehicle are added to the developer-forming mixture in use, typically being done by a machine operating manager or a service representative. This results in a clear decrease in density

  particles read by the detector, resulting in the introduction of

  producing a relatively large amount of concentrated dyestuff. Thus, there has been a marked increase in the proportion of particles with ideal charge

3 2472214 1

  in the composition of the developer and the image density of the copies produced thereafter, but without being able to reach the level achieved by fresh developer. When producing additional copies, the developer gradually wears out again, and there is a repeat of the fragmentary fill cycle followed by a sharp increase in image density when adding a supplement

  of vehicle. After several cycles of this kind, and typically

  after the printing of at least about 10,000 copies, the developer no longer gives copies of an image density

  acceptable and can not be sufficiently improved.

  This requires the removal of the spent developer and its replacement.

  placement by a completely new batch.

  To graphically illustrate this phenomenon, we can represent the density of the image as a function of the number of copies produced. Such a graph, which appears in the appended figures, shows a progressive decrease in

  density of the image as the depletion

  of the developer, despite the progressive replacement of

  the coloring matter, then a clear increase in the den-

  image after the addition of a large amount of developer, and several repetition of the cycle at de-lower densities of the image until this density of the image

become unacceptable.

  The present invention provides a composition of

  revealing having better exhaustion characteristics.

  The use of this developer in electronic copying machines

  conventional static using negative liquid developer provides more than 20,000 copies before the developer needs to be replaced. This property of the developer of the present invention can be attributed to the inclusion, in the composition, of a new charge regulator associated with a particular class of resinous latex, which gives a

  composition comprising particles having a distribution

  more uniform bution of the load with respect to the mass. The electric charge regulator is substantially insoluble in the vehicle and is intimately associated, by forces

  second-rate resinous latex and pigment. Preferably

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  the non-aqueous suspension is maintained in a homogeneous state using a resinous gel designed to

  solubility properties placing it at the limit of the solu-

  and insolubility in the vehicle at the temperature of use. Gel, like the electric charge controller, is designed to be compatible and to be intimate

  associated with latex. In one aspect, the invention proposes a new

  new developer composition, with better characteristics

  exhaustion characteristics, for an electronically

  static. In another aspect, the invention proposes a

  perfected to form images using this

developer composition.

  In its broadest aspect, the developer composition of the invention comprises a liquid organic carrier whose resistivity is greater than 10 9 ohm-cm and whose dielectric constant is less than 3. Particles of a coloring material are dispersed in the vehicle. The particles comprise a mixture of a pigment, an electric charge regulator and a resinous latex, the intimate combination of all these components resulting from their treatment in a ball mill. The latex comprises,

  as an essential ingredient, a vinyl polymer or copolymer

  is insoluble in the vehicle and has a proportion

  of monomer units corresponding to the formula

X

0CH2 -C

  Where X is H or CH3 and Y is C n 2n + 1;

(o l, n <6).

  The electric charge regulator is or comprises a copolymer formed from 10 to 50 parts of a lower alkyl (C2 to C6) vinyl ether-vinyl ether and from 50 to 90 parts of a vinyl chloride. The negative static charge is mainly imparted to the copolymer by vinyl chloride

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  part of the electric charge controller. The ability of this charge controller to remain intimately associated with the vinyl resin polymer fixer insoluble in

  the vehicle is mainly conferred on this regulator by the group

  pe lower alkyl attached to the copolymer via

the ether-oxide bond.

  In preferred embodiments, the revelation

  includes a gel for stabilizing the dispersion and which comprises or consists of a vinyl polymer

  located at the limit of solubility in the vehicle. This poly-

  mother contains a major proportion of monomeric units of formula X

CCH - C 7

C 0

0 -;

  wherein X is H or CH 3 and -r is C n H 2n + (o 8 e n È 20) .Each of the preferred components of the pair formed by the latex and the gel consists essentially of

  in an intimate mixture of a first vinyl polymer containing

  C1-C6 acrylate or methacrylate and one

  second vinyl monomer containing acrylate or methacrylate

  C8-C20 crylate The latex contains a major proportion of the first polymer and a minor proportion of the second, so that it remains insoluble in the vehicle. For example, the weight ratio between the first and second polymers constituting the latex may be of the order of 3: 1. The gel contains a major proportion of the second polymer and a minor proportion of the first, so that it remains at the limit of solubility in the vehicle and swells when it is brought into contact with this vehicle. For example, the gel may comprise about 85 parts by weight of the second

  polymer and 15 parts by weight of the first polymer.

  The latex may comprise a homopolymer of an acrylate

  or C1-C6 alkyl methacrylate or a copolymer or terpolymer comprising one or more of the lower alkyl acrylates or methacrylates with each other

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  or with various other vinyl monomers. Similarly, the gel may comprise a homopolymer of a C8 - C20 methacrylate or methacrylate or a copolymer of these monomeric units.

  with each other or with various other vinyl monomers

  containing substituents for imparting to the polymer solubility properties in the

desired range.

  The preferred electric charge regulator is a copolymer of vinyl ether and butyl on the one hand, and vinyl chloride on the other hand and the preferred ratio of comonomers is about 25 parts by weight vinyl ether for about 75 parts by weight of the vinyl chloride. The molecular weight of polymer has

  not a fundamental importance. We can get the best

  desired compositions of the composition using copolymers

  whose molecular weight is between 10,000 and 150,000.

  Excellent results have been obtained with a copolymer having a median molecular weight of about 70,000. Applicants believe that the chemical nature of the electric charge regulator is a very important aspect of the invention. For example, copolymers of vinyl ether and butyl, on the one hand, and methyl methacrylate, on the other, as well as copolymers of vinyl chloride, on the one hand, and acetate vinyl, on the other hand, have failed to give identical developers the same, the desired properties of exhaustion that is obtained by the implementation of the regulator of

  electric charge according to the invention.

  The preferred electric charge controller is dis-

  available on a large scale under the trademark "Laroflex-MP 35" sold by BASF Uyandotte Corporation. This copolymer is synthesized in the form of a latex which is then subjected to spray drying. During the

  synthesis, anionic surfactants serve as stabilizers

  dispersion. These agents become inevitable-

  associated with the copolymer by both physical mixing and covalent bonding with it. The presence of these surfactants does not affect the usefulness of the copolymer as

7 247221 (4 I

  electric charge regulator, but it is thought that they contribute

  on the contrary, to the ability of the material to confer

negative charge to developers.

  The present invention therefore aims to provide - a negative developer liquid composition to be used for electrostatic prints and which has better depletion properties, i.e. a smaller decrease in the density of the image successive copies, in comparison with the developers of the prior art; a developer composition which is relatively simple to manufacture and which is stable both in use and during its storage; and

  - an electric charge regulator for

  liquid negative developer positions, this regulator being insoluble in the vehicle of the composition and giving a developer having a high content of particles having

  an optimal load and thus presenting a slower

  the density of the image as you obtain a

  large number of copies using this developer.

  These aims and features of the invention, as well as

  others, will emerge from the following description of

  a few preferred embodiments, made with reference to the accompanying drawings, in which: FIG. 1 is a graph showing the density of the image (in arbitrary units on the ordinate) as a function of

  the number of copies obtained. This graph illustrates the

  nomene of the gradual decrease in the density of the image as a function of the increase in the total number of copies (in abscissas) obtained using a given bath or batch of developer. We also see, as indicated above,

  the improvement in the density of the image that immediately follows

  each addition of vehicle (A); and FIG. 2 is a graph showing the density of the image (in arbitrary units, on the ordinate) as a function of the number of copies obtained (on the abscissa). This graph

  compares the depletion properties of

  according to the invention (I) with the depletion properties

8 2472214 1

  of conventional developers (C) available commercially. The shaded area corresponds to a level of image density that has become

unacceptable.

  Broadly speaking, the present invention achieves the various objectives which it has set itself by providing a liquid negative developer consisting essentially of a vehicle, a pigment or a pigment system and a resinous latex as well as

  that an electric charge regulator designed to be

  in the vehicle and to have an important affinity

  aunt for each other. Eventually, instead of sta-

  Conventional dispersion buffers normally used in such developer compositions, this developer may also comprise a gel comprising a resinous material lying at the limit of solubility in the vehicle at the

  temperature of use and also showing

nity for the latex.

  Useful vehicles to be part of the

  position of the invention are solvents or systems of sol-

  non-polar types of the type conventionally used in liquid developers of the prior art. The vehicle will have

  a resistivity greater than about 109 ohm-cm and a

  dielectric aunt less than about 3. As is well known by experts in this field, this vehicle will be characterized by an evaporation rate suitable for rapid evaporation, for example in two seconds, from the substrate.

  subject to development in the event of exposure to temperatures

  lower than those causing the charcoal of the paper. This vehicle will preferably not contain aromatic liquids or other excessively toxic or corrosive constituents. Similarly, as is well known, the vehicle must have a viscosity low enough to allow rapid migration of particles that are attracted to the image

  electrostatic charge and which is to be developed

  per. Typically, the viscosity of the vehicle will be between

  about 0.5 and 2.5 centipoise at room temperature.

  Non-limiting examples of suitable vehicles

  include substantially petroleum fractions

  are relatively inexpensive and commercially available such as those sold by Humble Oil and Refining Company under the trademarks "ISOPAR G", "ISOPAR H",

247221 4 I

  "ISOPAR K" and "ISOPAR L". These materials include various hydrocarbon mixtures corresponding approximately to

C8 - C16.

  The pigment or pigment system used in the composition of the invention is also classi fi ed.

  if that. The preferred method for imparting color to

  ticles of the so-called coloring matter consists in using an end

  solid particulate pigment combined with one or more

  which associate with the resin constituents of the particles

  the. Carbon black particles of

  meter less than one micrometer, but we can also use

  use powdery metals or metal oxides. Various dyes known to be able to impart color to acrylic and / or vinyl resins can be used in combination with the particulate pigment. The presently preferred pigment system for forming the composition of the invention comprises "Printex 1404", which is a carbon black sold by Degussa Inc. and having an average particle size of 0.029 microns, plus alkaline blue (from BASF Wyandotte) and

  phthalocyanine green (from Herculese Inc.).

  The latex forming part of the developer composition comprises a vinyl polymer or copolymer, insoluble in the vehicle and which is preferably mixed with other insoluble materials in the vehicle, such as wood resins or rosins and wax and preferably

  also mixed with smaller amounts of soluble resins

  in the vehicle. An extremely important constituent of the latex is a polymer containing alkyl esters

  C1 - C6 acrylic or methacrylic acid. In general

  ral, the solubility of the polymer in the vehicle increases

  with the increase of the length of the chain of the ester.

  Methyl acrylate and methacrylate units are therefore preferred.

  of methyl. However, as long as the polymer contains a

  major portion of these acrylic or methacrylic motifs,

  other vinylic motifs can be incorporated into the poly-

  mother, in addition to those specified above, without seriously

  the properties of the developer. Non-limiting examples

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  monomers which can be copolymerized or terpolymerized with these esters include vinyl acetate, acrylate and

  hydroxyethyl methacrylate, acrylate and methacrylate

  hydroxypropylate, acrylate and glycidyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide,

  mide, methacrylamide, acrylic anhydride or methacrylate

  monomethyl maleate, monomethyl fumarate, monoethyl maleate, monoethyl fumarate, styrene, vinyltoluene, acid and maleic anhydride,

  as well as crotonic acid and anhydride. We can also

  C7-C20 alkyl acrylates or methacrylates are preferred. A preferred latex comprises a copolymer of methacrylic acid and methacrylate.

  methyl. The molecular weight of the polymer does not have an important

  The presently preferred latex consists of an intimate mixture of 3 parts of a vehicle-insoluble copolymer and a part of a vehicle-soluble unopolymer which are held together by second order forces. The insoluble component in the vehicle comprises 130 parts of methyl methacrylate copolymerized with a part

  of methacrylic acid. The soluble component in the vehicle

  It comprises 20 parts of copolymeric lauryl methacrylate

  with 5 parts of glycidyl methacrylate. Materials of this type are available on a commercial scale

  and can be obtained synthetically by conventional techniques.

  with radical-initiating catalysts

  free radicals, such as benzoyl peroxide and azo-bis-isobutyro-

nitrile.

  The electric charge regulator of the composi-

  The composition comprises a copolymer of 10 to 50 parts of a vinyl ether-lower alkyl (C2-C6) ether and 50 to 90 parts of vinyl chloride. It is believed that the ability of the copolymer to impart a negative charge to the coloring material is to be attributed to the chlorinated component of this copolymer. It is believed that the lower alkyl group attached to the polymer chain via an ether-oxide bond is capable of conferring on this

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  polymer its ability to remain in close association with

  the latex. In general, as the molecular weight

  As the alkoxy side chain of the copolymer increases, the affinity of this copolymer for the vehicle increases and its affinity for the latex decreases correspondingly. The electric charge regulator is preferably included in the composition so as to constitute from about 5 to 10

  the total weight of that composition, excluding the vehicle

  cule. An important feature of the invention is that

  the electric charge regulator is essentially

  luble in the vehicle and remains in close association with

  the latex. It is thought that this property, associated with its

  remarkable study to confer a negative burden on the

  resinous killers of the developer composition, explains the best depletion properties and the lowest rate of decrease in image density characterizing the compositions of the invention. In general, the fraction of vinyl ether-ether which must be included in the copolymer in order to obtain the advantages of the invention is all the lower as the side chain of the alkoxy type is longer.

  in the specified range. Thus, we can see that the

  solid latex and electric charge regulator co-operate to provide new

  developer compositions of the invention.

  The electric charge regulator currently

  preferred comprises a copolymer of 25 parts of the ether

  vinyl oxide and isobutyl and 75 parts of chloride

  of vinyl. This copolymer is commercially available.

  at BASF Wyandotte Corporation under the brand name

  "LAROFLEX-MP 35". "LAROFLEX-MP 35" is obtained from ether-vinyl oxide and isobutyl on the one hand, and monochloroethane, on the other hand, by a synthesis using interfacial polymerization resulting in the

  forming a latex which is then spray-dried.

  The copolymerization is conducted in the presence of anionic surfactants which mix with the resin. Attempts to remove the surfactants have led to the conclusion that at least a fraction of the surfactant contained is bound

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  covalently to the copolymer. Typically, the surfactant used is a mixture of saturated and unsaturated aliphatic hydrocarbon chains containing 10 to 30 carbon atoms.

  and having as substituents several sulfonate groups.

  These alkali metal sulfonate oils are only present in trace amounts and do not interfere with the properties of the electric charge controller. It is believed that the presence of anionic surfactants mixed with the polymer or covalently bonded thereto may enhance its ability

to confer a negative charge.

  A highly preferred but optional component of the developer composition is a polymeric gel that stabilizes the dispersion of the solid particles. The gel is intended to be both compatible with the vinyl component of the

  latex and to be at the limit of solubility and

  solubility in the non-polar organic vehicle. This gel

  takes as essential constituent a polymer or a

  lymere containing a major proportion of monomeric units selected from C8 - C20 esters of acrylic or methacrylic acid. This developer component has a molecular weight of from about 103 to about 106 and swells by mixing with nonpolar organic vehicles of the type described above. Such C 8 -C 20 alkyl esters can be homopolymerized or copolymerized with each other.

  others or with various other monomers of the vinyl type.

  Non-limiting examples of suitable comonomers

  take insoluble monomers in the vehicle as

  lower alkyl esters of acrylic or methacrylic acid

  Crylic, provided that the monomer level is low enough to ensure solvation of the resultant copolymer in the vehicle. Other useful compounds include methacrylate or glycidyl acrylate, crotonic, maleic, atropic, fumaric, itaconic and / or citraconic acids,

  acrylic, methacrylic or maleic anhydrides, acrylonitrile

  nitrile, methacrylonitrile, acrylamide, methacrylate and hydroxyethyl acrylate, methacrylate and acrylate

  hydroxypropyl, methacrylate and dimethyl acrylate

  amino-methyl, allyl alcohol, cinnamic acid,

247221 "1

  methallylic alcohol, propargyl alcohol, as well as

  maleate and monomethyl and / or dimethyl fumarate.

  A preferred way of producing a non-dispersion

  stable aqueous solution consists in using a mixture, in different proportions, of two identical copolymers in order to pro-

  both the gel and the vinyl component of the latex.

* For example, a methacrylate copolymer can be

  lauryl crysate and glycidyl methacrylate at one

  mixing and processing in a ball mill with a copolymer of methacrylic acid and methyl methacrylate, in a ratio of 1 to 3, to produce a vehicle-insoluble latex whose components are held together by second order forces. This latex is added to the developer with a gel comprising, for example, 85 parts of a copolymer of lauryl methacrylate and glycidyl methacrylate and 15 parts of a copolymer of methyl methacrylate and methacrylic acid which is

  the limit of solubility in the vehicle.

  The developer compositions are produced by

  killing the separate synthesis of gel and latex and then

  both these components to a treatment in a ball mill in mixture with the other components of the developer, to form an intimate mixture whose average particle size is between 0.2 and 0.3 micrometers. Thus, to manufacture the resinous components, a multipolymer is produced from, for example, lauryl methacrylate and methacrylate.

  of glycidyl in an "Isopar" solvent using a catalyst.

  a suitable polymer, then a second polymer is formed, for example from methacrylic acid and methyl methacrylate, in the same reaction medium as that of obtaining the first polymer or in a separate reaction medium . In this way, both the gel and the latex can be produced since, by controlling the relative amounts of the lauryl methacrylate copolymer and the methyl methacrylate copolymer, the resulting intimate mixture of copolymers can be made insoluble in the vehicle. Isopar "or at the limit of solubility in this vehicle. Thus, a portion of the lauryl methacrylate copolymer can be blended with three parts of the methyl methacrylate copolymer to form a particulate latex insoluble in

  "Isopar"; a part of the methacrylate copolymer can be mixed

  methyl crylate with about six parts of the lauryl methacrylate copolymer to form a polymer gel at

  limit of solubility in the vehicle "Isopar". The quantities

  relative quantities of the polymers constituting the mixture can vary widely provided that the content of the C1-C6 alkyl acrylate or methacrylate latex is such that the polymer

  resulting mixture, or any mixture used, is

  in the vehicle, and provided that the content of the C8-C12 alkyl acrylate or methacrylate gel is such that the resulting polymer, or any mixture used,

  is at the limit of the solubility in the vehicle.

  Using a ball mill, these constituents are then milled in the vehicle with the electric charge regulator (copolymer of an ether-vinyl oxide and lower alkyl, on the one hand, and chloride of vinyl, on the other hand), the pigment system and preferably the resin and wax, for a sufficient time, typically at 40 hours, for the production of a homogeneous mixture of all constituents having a particle size lying around 0.2-0.3 micrometer and a distribution

  particles between about 0.1 and 1.5 micrometers.

  The presently preferred proportions for the ingredients are indicated in the following non-limiting examples, which

  allow to better understand-the invention.

Example 1

  Preparation of soluble multipolymer precursors A) 800 g of lauryl methacrylate and 3.54 g of benzoyl peroxide are added to 1.3 l of "Isopar G" in a 5 liter flask at a temperature below 800 ° C and allowed to react during 6 hours in a nitrogen atmosphere to form a homopolymer of lauryl methacrylate. The overall concentration of the reaction product is about 40% and

  achieves a polymer conversion rate of about 95% o.

  B) The procedure is repeated (A) except that one

  also introduced into the reaction flask 40 g of metha-

  glycidyl crylate. Thus, a 20: 1 copolymer of the

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  poly (lauryl-glycidyl) methacrylate type. Less than

  % of the monomers added originally remain unaltered.

  (C) Procedure B) is repeated and after six hours of reaction, the reaction medium is allowed to reach the decomposition temperature of benzoyl peroxide at 80 ° C. methacrylic acid and 0.54 g of hydroquinone and the solution is maintained at about 93 C for 12 to 15 hours

  to close a small amount of a hydroquinone / acyl complex

of methacrylic.

  D) The procedure C) is repeated, except that the 40 g of methacrylic acid is replaced by 20 g of acrylic acid. A 20: 1 poly (lauryl-glycidyl) methacrylate copolymer and a hydroquinone and acrylic acid complex are produced. The polymer yield is of the order of

more than 90%.

  E) Procedure (C) is repeated except that one

  replaces 40 g of methacrylic acid with 10 g of

  tonic. A 20: 1 poly (lauryl-glycidyl) methacrylate copolymer and a hydroquinone and crotonic acid complex are produced. The polymer yield is of the order

more than 900%.

  F) Procedure C) is repeated, except that the 40 g of methacrylic acid is replaced by 20 g of acid.

  methacrylic. A 20: 1 copolymer of the methacrylic type is produced.

  poly (lauryl-glycidyl) crylate and a complex of hydro-

quinone and methacrylic acid.

Example 2

  Preparation of a gel G) 40 g of methacrylic acid and 0.5 g of hydroquinone are introduced into 1 liter of "Isopar G" and kept at about C for about 10 hours. Lauryl methacrylate, 18 g of methyl methacrylate and 0.5 g of benzoyl peroxide are then added to the reaction flask to initiate polymerization. We continue the polymerization during

  five hours to obtain a ternary polymer of methacrylate

  of lauryl methacrylate and methyl methacrylate.

  The solution / dispersion of the ternary (or tertiary) polymer is added

  polymer) to about 100 g of soluble precursor A and

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  treated in a ball mill to obtain a gel essential-

  homogeneous at the limit of solubility in "Isopar G".

  H) The procedure G) is repeated, except that the precursor A is replaced by 100 g of the soluble precursor B. After 10 hours of treatment in a ball mill, an essentially homogeneous gel is obtained and at the limit of

solubility in "Isopar G".

  I) 102 g (dry weight) of the precursor solution are mixed

  C with 18 g of methyl methacrylate, 0.3 g of benzoyl peroxide and 900 ml of "Isopar G", and reacted in

  a 2-liter flask in a nitrogen atmosphere for 5 hours.

  A gel is formed which is at the limit of the solubility in "Isopar G" at room temperature. We can not detect

  virtually no free monomer in the reaction flask

tion.

  J) The procedure (I) is repeated, except that the precursor C is replaced by 100 g of the precursor D. A gel whose properties are similar to those of the gel is obtained.

described in I).

  1) The procedure I) is repeated, except that precursor C is replaced by 100 g of precursor E. A gel whose properties are similar to those of gel is obtained.

described in I).

  L) To 36 g of methyl methacrylate and 0.3 g of benzoyl peroxide in 900 ml of "Isopar G" is added 84 g (dry weight) of a precursor similar to precursor C, except that added only 10 g of methacrylic acid after

  the polymerization of the lauryl and glycidyl copolymer.

  The mixture is maintained in a nitrogen atmosphere for 5 hours

  at a temperature below 80 ° C.

  which can be found in the reaction balloon less

  about 4% unaltered polymer.

  M) 90 g (dry weight) of precursor F are added to

  g of methyl methacrylate and 0.3 g of benzyl peroxide

  zoyle in 900 ml of "Isopar G". We keep the mixture in

  nitrogen atmosphere for 5 hours at a lower temperature than

  than about 80 C. We obtain, at a rate of transformation

  about 93%, a viscous but less gelled polymer.

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EXAMPLE 3

Preparation of a latex

  N) is reacted for 50 g (dry weight) of

  slider F, 150 g of methyl methacrylate and 0.75 g of benzoyl peroxide in sufficient "Isopar G" for

  obtain a concentration of 20% of the product of the reaction.

  An insoluble latex is formed in "Isopar". We can find

  in the reaction solution less than about 20% mono-

unaltered mothers.

  O) Procedure N) is repeated, except that 40 g (dry weight) of precursor F is used instead of the 50 g indicated in procedure N); 160 g of methyl methacrylate are used instead of 150 g, and 0.8 g of benzoyl peroxide is used instead of 0.75 g. The reaction results in the formation of a latex obtained at a rate of

90% transformation.

  P) Procedure N) is repeated except that 25 g (dry weight) instead of 50 g of precursor F, g is used instead of 150 g of methyl methacrylate and 0.9 g instead of 0 g. 75 g of benzoyl peroxide. The result of the reaction is the formation of a fine latex obtained with a

94.5% conversion.

Example 4

  Preparation of the developer The developer is prepared by adding the following ingredients to "Isopar G" in order to obtain a dispersion containing 20 to 25% of solid particles:

TABLE I

  Ingredient Percent Weighted Latex N, O or P 20-30% Electric Charge Regulator 5-10% Wax 5-15% Wood Resin 5-15% 5 Pigment 20-30% Gel G, H, 1, J, K, L or M 10-25% Here is the weight percentage of the solid particles of a preferred composition: 247221 f I

TABLE 2

  Ingredient Weight% Latex 20-30% Gel 15-25% "Laroflex MP35" (1) 10% Wax (2) 10% Wood Resin (3) 10% Pigment (4) 25%

  (1) Copolymer of 25% of the ether-vinyl oxide and iso

  butyl and 75% vinyl chloride; average weight

  median area: 70,000-80,000; distribution: between

300,000 and 10,000.

  (2) Paraffin wax (3) From Hercules Chemical Co. (4) 19 parts of carbon black, 2 parts of alkaline blue,

4 parts of phthalocyanine green.

  The dispersion is then placed in a ball mill with a capacity of 6 liters, comprising

  steel, and grinding is carried out for 20 to 40 hours.

  It is then diluted with "Isopar G" to the appropriate developer concentration and grinding is continued for an additional hour. The average particle size of the compositions is around 0.2 to 0.3 microns and the particle size distribution between 0.1 and

About 1.5 microns.

Example 5

  Developer compositions prepared according to the procedures described above by way of example have been extensively tested in commercially available copier equipment using a negative liquid developer. The developers produced according to the invention were found to be capable of continuous operation without replacement up to at least 20,000 copies. On the contrary, negative liquid developers on the market should be replaced after 10,000 to 15,000

  copies to allow an acceptable image density to be

table.

2472214 I

  The attached figure 2 shows curves indicating

  the density of the image of the copies produced (in arbitrary units

  tracts, ordinate) as a function of the number of copies for liquid negative developers currently available (curve C) and for the developers of the present invention (I). As noted above, the shaded area indicates a

unacceptable image density.

Comparative Example 6

  Formulations of colored matter have been prepared

  substantially the same as those indicated above.

  except that the electric charge regulator (copolymer of an ether-vinyl oxide and lower alkyl),

  and vinyl chloride) has been replaced by a different polymer.

  ferent. When using a multipolymer derived from lauryl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate and vinyl ether-isobutyl ether in place of the electrical charge regulator of the invention provides a developer which is amphoteric in nature with 60% negative charge and 40% positive charge. When using a multipolymer derived from vinyl chloride, vinyl alcohol and vinyl acetate, in place of the electric charge regulator of the invention, an amphoteric developer having 75% a charge is obtained. negative and 25% positive charge. Similarly, if the electric charge regulator according to the invention is replaced by a copolymer of vinyl chloride and vinyl acetate, a developer is obtained which exhibits

amphoteric properties.

  It goes without saying that, without departing from the

  vention, many changes can be made

  to the compositions described above.

247221 4 i

Claims (12)

  1. Liquid negative developer composition,   having better exhaustion properties and which is des-   The invention relates to the development of a latent electrostatic image on the surface of an image bearing member, said composition comprising a pigment, an electric charge regulator and particles of a thermoplastic resin.   which are all in dispersion in an organic liquid vehicle   whose resistivity is greater than 109 ohm-cm and whose dielectric constant is less than 3, this composition being characterized in that the particles of the resin, the pigment and the electric charge regulator constitute an intimate mixture formed by: a uinyl polymer latex, which is insoluble in the vehicle and which comprises a major proportion of monomeric units corresponding to the formula: x I fH2 - C - C = 0 0 - Y   (in which X is H or CH 3 and Y is C n H 2n + 1, where 1 n c 6); pigment; and a charge controller   electrical system intended to confer a negative charge on the   position and which comprises a copolymer of 10 to 50 parts of a vinyl ether and lower alkyl (C2-C6)   and from 50 to 90 parts of a vinyl chloride.   2. Developer composition according to the claim   1, characterized in that, to stabilize the dispersion,   it comprises a gel comprising a vinyl polymer   which swells in the presence of the vehicle and   major proportion of monomeric units corresponding to the mule: X úC H - c _ -2 C = O 0 -; 247221? 1   (where X is H or CH3, and Z is CnH2n + l. o 8 c n 20.   3. Developer composition according to the claim   2, characterized in that the latex and the gel each consist essentially of an intimate mixture of a first vinyl polymer containing monomer units corresponding to the formula: X FCH2 - C - C = O 0 - Y   (wherein X is H or CH 3 and Y is C n H 2n + 1, o 1 - n 6) and a second vinyl polymer containing monomer units having the formula: X I H2- HC -O   C = OO-1 (wherein X is H or CH3, and Z is CnH2n + 1,   o 8 n <20); and in that the latex contains a proportion   primary polymer so as to remain insoluble in the vehicle, and in that the gel contains a major proportion of the second polymer so as to swell in the presence of the vehicle.   4. Developer composition according to the claim   3, characterized in that the latex comprises about 3 parts by weight of the first polymer for about 1 part by weight of the second polymer.   5. Developer composition according to claim   cation 3, characterized in that the gel comprises about   parts by weight of the second polymer for about 15 parts by weight of the first polymer.   6. Developer composition according to claim   cation 3, characterized in that the first polymer is a copolymer of methacrylic acid and methyl methacrylate and in that the second polymer is a copolymer of   lauryl methacrylate and glycidyl methacrylate.   7. Developer composition according to the claim   1, characterized by the fact that the electric charge regulator   It comprises a copolymer of butyl ether-vinyl ether and vinyl chloride.   8.Developer composition according to the claim   1, characterized in that the electric charge regulator comprises a copolymer of about 25 parts by weight of a vinyl ether-lower alkyl ether for   about 75 parts by weight of vinyl chloride.   9. Developer composition according to the claim   2, characterized in that it also comprises a wax and wood resin.   10. Developer composition according to the claim   9, characterized in that it comprises, dispersed in the vehicle Ingredient Parts by weight Latex 20-30 Pigment 20-30 Regulator of electric charge 5-10 Wax 5-15 Wood resin 5-15 Gel 10-25   11. Developer composition according to claim   cation 9, characterized in that it comprises, dispersed in the vehicle: Ingredient Parts by weight Latex 20-30 Pigment 25 Polymer of ether-vinyl oxide and isobutyl and vinyl chloride 10 Paraffin wax 10 Wood Resin 10 Gel 15-25 A liquid negative developer composition having improved depletion properties for developing a latent electrostatic image on the surface of an image bearing member, which composition comprises   a pigment, an electric charge regulator and parti-   of a thermoplastic resin dispersed in a vehicle   organic liquid whose resistivity is greater than 109 ohm-cm and whose dielectric constant is less than 3, the composition being characterized in that the particles   of the resin, the pigment and the electric charge regulator   an intimate mixture formed by: a vehicle-insoluble, vinyl polymer latex having a major proportion of monomeric units having the formula: X (X) = ## STR2 ## or CH3; and Y represents CnH2n + o 1 n 4 6) the pigment; and   an electric charge regulator designed to   providing a negative charge to the composition which comprises a copolymer of 10 to 50 parts of a butyl ether-vinyl ether and 50 to 90 parts of a vinyl chloride; and in that the composition also comprises a gel for stabilizing the dispersion and which comprises a vinyl polymer   which swells in the presence of the vehicle and which includes a proportion   major formation of monomeric units corresponding to formula X 7CH2 - C   C = O O -; (wherein X is H or CH3, and Z is CnH2n + 1, o 8 n 4 20).