CA1073726A - Developer composition containing styrene alkyl acrylate or methacrylate polymer with chemically altered aromatic groups - Google Patents
Developer composition containing styrene alkyl acrylate or methacrylate polymer with chemically altered aromatic groupsInfo
- Publication number
- CA1073726A CA1073726A CA230,774A CA230774A CA1073726A CA 1073726 A CA1073726 A CA 1073726A CA 230774 A CA230774 A CA 230774A CA 1073726 A CA1073726 A CA 1073726A
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- Prior art keywords
- toner
- developer composition
- carrier
- polymer
- accordance
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Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G9/00—Developers
- G03G9/08—Developers with toner particles
- G03G9/087—Binders for toner particles
- G03G9/08702—Binders for toner particles comprising macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- G03G9/08706—Polymers of alkenyl-aromatic compounds
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G9/00—Developers
- G03G9/08—Developers with toner particles
- G03G9/087—Binders for toner particles
- G03G9/08784—Macromolecular material not specially provided for in a single one of groups G03G9/08702 - G03G9/08775
- G03G9/08791—Macromolecular material not specially provided for in a single one of groups G03G9/08702 - G03G9/08775 characterised by the presence of specified groups or side chains
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- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- General Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Developing Agents For Electrophotography (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Electrostatographic developer compositions for use in developing electrostatic latent images wherein the triboelectric charging potential of functional polymers employed in the carrier materials are controlled through chemical alteration of aromatic constituents such as by nitration/oxidation, halogenation, acylation, alkyl substi-tution, and the like. The controlled variation of the triboelectric behavior of functional polymers provides a means of attaining optimum triboelectric responses in development systems.
Electrostatographic developer compositions for use in developing electrostatic latent images wherein the triboelectric charging potential of functional polymers employed in the carrier materials are controlled through chemical alteration of aromatic constituents such as by nitration/oxidation, halogenation, acylation, alkyl substi-tution, and the like. The controlled variation of the triboelectric behavior of functional polymers provides a means of attaining optimum triboelectric responses in development systems.
Description
B KGRO~ND OF THE INVENTION
This invention relates in general to imaging systems and more particularly to improved electrostatographic developer mixtures for use in such systems.
The formation and development of images on the surface of photoconductive materials by electrostatographic means is known. The basic electrostatQgraphic process, as taught by C. F. Carlson in U.S. Patent 2,297,691, issued November 6, 1942 involves placing a uniform electrostatic charge on a photoconductive insulating layer, exposing the layer to a light and shadow image to dissipate the charge on the areas of the layer exposed to the light, and developing the resultant electrostatic latent image by depositing on the image a finely-divided electroscopic material referred to in the art as "toner". The toner is attracted to those areas of the layer which retain a charge, thereby forming a toner image corresponding to the electrostatic latent image. This "powder" image may then be transferred, usually electro-statically, to a support surface such as paper. The transferred image may subsequently be permanently affixed to a support surface by heat or other suitable affixing means, such as solvent or overcoating treatment may be used instead.
Many methods are known for applying the electroscopic particles to the latent image to be developed. One development method, as disclosed by E. N. Wise in U. S. Patent 2,618,582, ;i issued November 18, 1952 is known as "cascade" development. In this method, developer material comprising relatively large carrier particles having finely-divided toner particles electrostatically clinging to the surface of the carrier particles is conveyed to and rolled or cascaded across the surface bearing the electrostatic latent image. The charged ,
This invention relates in general to imaging systems and more particularly to improved electrostatographic developer mixtures for use in such systems.
The formation and development of images on the surface of photoconductive materials by electrostatographic means is known. The basic electrostatQgraphic process, as taught by C. F. Carlson in U.S. Patent 2,297,691, issued November 6, 1942 involves placing a uniform electrostatic charge on a photoconductive insulating layer, exposing the layer to a light and shadow image to dissipate the charge on the areas of the layer exposed to the light, and developing the resultant electrostatic latent image by depositing on the image a finely-divided electroscopic material referred to in the art as "toner". The toner is attracted to those areas of the layer which retain a charge, thereby forming a toner image corresponding to the electrostatic latent image. This "powder" image may then be transferred, usually electro-statically, to a support surface such as paper. The transferred image may subsequently be permanently affixed to a support surface by heat or other suitable affixing means, such as solvent or overcoating treatment may be used instead.
Many methods are known for applying the electroscopic particles to the latent image to be developed. One development method, as disclosed by E. N. Wise in U. S. Patent 2,618,582, ;i issued November 18, 1952 is known as "cascade" development. In this method, developer material comprising relatively large carrier particles having finely-divided toner particles electrostatically clinging to the surface of the carrier particles is conveyed to and rolled or cascaded across the surface bearing the electrostatic latent image. The charged ,
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portions o~ the surface have a charge of the same polarity as/ but stronger than, the carrier particles. Toner and carrier particles having opposi~e polarities are selected so that the toner particles cling to the carrier particles. In order to develop a ne~atively charged electrostatic latent image, a toner and carrier combination are selected in which the toner is triboelectrically positive in relation to the ; toner. Conversely, to develop a positively charged electro-static latent image, a toner and carrier combination wherein the toner is triboelectrically negative in relation to the carrier is used. The triboelectric relationship between the toner and carrier depends on the relative positions of the materials in the "triboelectric series". In this series, materials are arranged in ascending ordQr of their ability to take on a positive charge. Each material is positive with respect to any material classified below it in the series; and, negative with respect to any material above it in the series. As the developer mixture cascades or rolls across the image-bearing surface, the toner particles are electrostatically attracted from the carrier to the charged portions of the image-bearing surface, whereas they are not ; electrostatically attracted to the uncharged or background portions of the image which they contact. The carrier particles and unused toner particles are then recycled. The cascade ~.
development process is extremely good for the development of line copy images, and is the most widely used commercial ; `~
electrostatographic development technique. A general purpose office copying machine incorporating this technique is described in U.S. Patent 3,099,943 to Eichorn et al ~ssued ~ugust 8, 1963.
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Another technique for developing electrostatic latent images is the "magnetic brush" process as disclosed for example, in U. S. Patent 2,874,063 to Princeton issued February 17, 1959. In this process, a developer material containing toner and magnetic carrier particles is attracted ~o and is carried by a magnet. The magnetlc field causes alignment of the magnetic particles in a brush-like configuration when this magnetic brush is brought into contact with an electrostatic latent image-bearing surface, the-toner particles are attracted from the carrier particles of the brush to the charged areas of the image-bearing surface but ` not to the uncharged areas. Since the charged areas have an imagewise configuration, the toner material clings to ` the surface in imagewise configuration, thus developing the latent image.
Another method for developing electrostatic latent images is disclosed in U.S. Patent 3,503,776 issued March 31, 1970 to R. W. Gundlach. In this method, images are formed by transporting an electrostatic latent image-bearing surface in a generally ascending arcuate path, and contacting only the image in a contact zone with a bath of developer material transported in a concave chamber adjacent the lower path of the imaging surface. The contact zone extends from about the lowermost point of the arcuate path to the uppermost point of the arcuate path. As the imaging surface is trans-ported along its arcuate path, frictional contact between the developer and the imaging surface in the contact zone circulates the developer in the bath and brings developer - material into developing configuration with the imaged surface.
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Many other methods/ such as the "touchdown"
development method disclosed`by C. R. Mayo in U. S. Patent 2,895,847, issued July 21, 1959 are known for applying electroscopic particles to the electrostatic latent image to be developed. The development process, as described above, together with numerous modifications, are well-known to the art through various patents and publications and through the widespread availability and utilization of electrostatographic imaging equipment.
; 10 In automatic reproduction equipment, it is conventional ~, ` . ' ';', ~ ~ .
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to employ as -the imaging pla-te o-~ a photoconductor on a ccnduc-tive subs-trate in the form o~ a cylindrical drum or a flexible belt which is continuous]y rotated through a cycle of sequential operations including charging, exposing, developing, transferring and cleaning. The developer chamber is charged wlth a developer mixture comprising carrier particles and enough toner particles for hundreds of reproduction cycles. Generally, the freshly charged developer mixtures contain between about 1.5 and 5% toner particles based upon the weight of the developer.
This initial concentration provides sufficient toner for many reproduction cycles without causing undesirably high background toner deposition.
While ordinarily capable of producing good quality images, conventional developing systems suffer serious defi-ciencies in certain areas. In the reproduction of high contrast copies such as letters, tracings and the like, it is desirable to select the electroscopic powder and carrier materials so that their mutual electrification is relatively large; the degree of such electrification being governed in most cases by the distance between their relative ~ositions in the tribo-electric series. However, when otherwise compatible electro-scopic powder and carrier materials are removed from each other in the triboelectric series by too grea-t a distance, the result-ing images are very faint because the attractive forces between -the carrier and toner particles compete with the attractive forces between the electrostatic latent image and the toner particles. Although the image density described in the immediately preceding sentence may be improved by increasing toner concentration in the developer mixture, undesirably high background toner deposition as well as increased toner irnpaction - ~ , ' i , ~(~737'~6 and agglomeration is encountered when the developer mixture i5 overtGned. The initial electros-tatographic plate charge may be inereased -to improve the density of the deposited powder image, but the plate charge would ordinarily have to be excessively high in order to attract the electroscopic powder away from ~;
the carrier partic]es. Excessivly high eleetrostatographic plate charges ar-e not only undesirable because of the high power consumption necessary to maintain the electrostatographic plate at high potentials, but also because the high po-tential causes the carrier particles tG adhere to the eleetros-tatographic ~ -~
plate surface rather than mer-ely roll across and off the electro-statographic plate surface. Print dele-tion and massive carry-over of carrier particles often occur when carrier particles adhere to reusable electrostatographie imaging surfaees. Massive earrier earry-over problems are partieularly acute when the developer is employed in solid area coverage machines where exeessive quantities of toner particles are removed from carrier particles thereby leaving many carrier particles substantially bare of toner particles. Further, adherenee of earrier partieles to reusable eleetrostatographie imaging surfaees promotes -the formation of undesirable scratches cn the surfaces during image transfer and surface cleaning operations.
It is therefore apparent that many materials which otherwise have suitable properties for employment as carrier partieles are unsuitable beeause they possess too high or too ~- ;
low a triboeleetrie value. In addition, uniform triboelectric surfaee characteristics of many carrier surfaces are difficul-t to achieve with mass production techniques. Quality images are, in some instances, almost impossible to oktain in high speed automatic machines when carriers having non-uniform ., , ': ' ~ ' ' -.
3L~73'7Z~i triboelectric proper-ties are employed. Although it may be possible to alter the triboelec-tric vlaue of an insulating carrier material by blending the carrier material with another insula-t`ing material having a triboelec-tric value remote from the triboelectric value o-f -the original carrier material, relatively large quantities of additional material is necessary to alter the triboelectric value of the original carrier material. The addition of large quantities of material tG the original carrier material to change the triboelectric properties thereof requires a major manufacturing opera-tion and often undesirably alters the original physical characteristics of the carrier material. Further, it is highly desirable to control the triboelectric properties of carrier surfaces to accommodate the use of desirable toner compositions while retaining the other desirable physical characteristics of the , carrier. The alteration of the triboelectric properties o-f a carrier by applying a surface coating thereon is a particularly desirable technique. With this technique, not only is it possible to control the triboelectric properties of a carrier made from ;
materials having desirable physical characteristics, it is also possible to employ materials previously not suitable as a carrier. :;
Thus, for example, acarrier having desirable physical properties with the exception of hardness, can be coated with a material having desirable hardness as well as other physical properties, rendering the resultant product more useful as a carrier. How- -~
ever, since most carrier coating ma-terials are deficient in one or more of the above areas, there is a continuing need for improved electrostatographic carrier and developer composition and methods for forming the same.
Further, it is apparent from the description presented ::
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above as well as in other development techniques, that the toner is subjected to severe mechanical attrition which tends to break down the par-ticles into undesirable dust fines. The formation of fines is retarded when the toner contains a tough, high molecular weigh-t resin which is capable of with-standing the shear and impact forces imparted to the toner in the machine. Unfortunately, many high molecular weight materials cannot be employed in high speed automatic machines because they cannot be rapidly fused during a powder image -heat fixing step. On the other- hand, low molecular weight resins which are easily heat fused at relatively low temper-atures are usually undesirable because these materials tend to form thick films on reusable photoconductor surfaces. ;
These films -tend to cause image degradation and contribute to machine maintenance down time. Many low molecular weight resins decompose when subjec-ted to fusing conditions in high speed copying and duplicating machines. In addition, low molecular weight resins tend to form tacky images on the copy sheet which are easily smudged and often offset to other adjacent sheets. Additionally, low molecular weight resins are often extremely difficult or even impossible to comminute in conventional $rindingapparatus. Also, the toner materials must be capable of accepting a charge of -the correct polarity when broughtinto rubbing contact with the surface of carrier materials in cascade or touchdown development systems.
Additionally, many toner materials cannot satisfactorily be transferred by conventianal electrostatographic development systems from reusable imaging surfaces in automatic copying and duplicating machines. Since mos-t polymeric -toner materials are deficient in one or more of -the above areas, there is a lV73~Zfi continuing need for improved toners and developers.
In accordance with one aspect of this invention there is provided an electrostatographic developer composition ~or use in developing electrostatic latent images on a recording surface, the developer composition being comprised of a toner material and a carrier material; the toner material having an average particle diameter of less than about 30 microns and consisting essentially of a colorant and a polymer having aromatic moieties selected from the group consisting of styrene alkyl methacrylates and styrene alkyl acrylates;
the carrier material containing carrier particles having an ::
average particle diameter of between 50 microns and about 1,000 microns, each of the carrier particles comprising a core surrounded by an outex coating in the amount of from 0.1 percent to about 10 percent by weight based on the weight of the carrier particles, the outex- coating consisting ; essentially of a functionalized polymer selected from`the group consisting of styrene alkyl methacrylates and styrene .
alkyl acrylates, the polymer ~or both the toner and the ~ 20 carrier being.obtained.by the systematic chemical alteration of the aromatic moieties of the polymer by nitration, halo- :-genation, acylation, or alkyl substitution to thereby provide toner and carrier particles characterized as having closely controlled triboelectric charging properties.
By way of added explanation, in accordance with an aspect of this invention chemical alteration of the tribo-electric charging potential of functional polymers employed ~ .
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as toner and carrier materials is controlled. The controlled ~, variation of the triboelectric behavior of functional polymers provides a means of attaining optimum triboelectric responses :
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~L~73~26 of electrostatograph:ic developer- materials for specifically defined applica-tions. Ihus? in accordance with this invention, monomeric and/or polymeric materials are systematically chemically modified to provide structural effects which yield structure~triboelectric property relationships among various substituted aromatic moieties such as nitroaromatics, haloaromatics, aromatic ethers, and alkylaromatics. These relationships have been found to be extremely helpful in designing new carrier and toner materials. By -this invention, the triboelectric charging proper-ties of toner-carrier pairs are controlled to enable optimum triboelectric relationships `
in developer compositions. ;
It is noted that, by itself, no material has a tribo- ;
electric charge. The magnitude of a triboelectric charge depends upon both the toner and the carrier material. Thus, replace-ment of one of the components to optimize triboelectric charg-ing properties is generally necessary to provide the desired triboelectric response. By so doing, greater latitude is avail~ -~
able for specific electrostatographic applications. In accord-ance with this invention, it has been found that by varying the degree of chemical modification of polymeric materials for use as toner or carrier materials, the triboelectric properties ~
of developer materials can be controlled in a continuous manner. `
In electrostatographic developrnent of selenium photo-conductor latent images, polymers which tend to take on a rela-tively high positive charge are generally satisfactory for use `
as carrier coating materials and polymers which tend to take on a relatively high negative charge are generally satisfactory for use as toner materials. In electrostatographic developement of other photoconductor latent images, for examp]e, zinc oxide, :, - . , : ~ :,. . . :
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phthalocyanine, cadmium sulfide, polyvinylcarbazole-trinitroflurenone. The reverse is true regarding charging properties of carriers and toner. In accordance with this invention, the triboelectric properties of developer materials are correlated with their structural composition and thereby predictably controlled. Since the distance between a given toner-carrier pair on a trihoelectric charging scale determines the ; triboelectric charge between them, their relative positions determine the sign of the triboelectric charge. Those materials low on the scale prefer to adopt a positive charge and those materials high on the scale prefer to adopt a negative charge.
Appropriate toner-carrier pairs can be selected based on their triboelectric charging or triboelectric series relationship to satisfy a particular acceptable triboelectric charging range re-quirement for a given electrostatographic machine developer housing.
It has been found that triboelectric behavior is a function of molecular structure which now allows the controlled and progressive modification of the triboelectric charging prop-erties of developer compositions so as to obtain optimum tribo-electric charging properties between -toner and carrier pairs.
Thus, by this invention, adjustment of the triboelectric charging properties of electrostatographic developer materials need not be in stepwise fashion but may be accomplished in a continuous manner prcviding a high degree of "fine tuning" of triboelectric properties f-or developer materials.
; In accordance with this invention, the triboelectric charging properties of monomeric and polymeric compounds may be modified by systematic chemical alteration of aromatic moieties of monomers and polymers. Such alteration of a aromatic function-:.
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--1 1-- , ~ ~737Z6 ality may be accomplished by methods Icnown -to the art, such as, halogenation using the reaction of the aromatic polymer with elemental bromine, alkylation or acylation using the well known Friedel-Crafts reaction with alkyl halides and Lewis Acids, or nitration, using nitric/sulfuric acids, special reagents, such as cupric nitrate/acetic anhydride. Aromatic reactions on polymers can not always be driven to completion and frequently side reaction do occur. Under certain nitration conditions, for example, it has been found that oxidation accompanies nitration as manifested by the presence of hydroxyl moieties. Such side-reactions are, however, quite reproducible and, thus, their influence on -the triboelectric behavior of the resultan-t species can also be reproduced with a high degree of precision. The functional groups introduced by these processes may additionally be employed for varied purposes including covalent bonding to dyes having functional groups, the addition of triboelectric charge modifiers, and bonding to substrates. Extensions of these uses are numerous and obvious to the artisan.
Thus, -in accordance with this invention, there is provided a method for the preparation of developer materials having controlled triboelectric properties for electrostato-graphic applications. The principle of this invention may be practiced with any monomer, polymer, or copolymer containing -an aromatic functionality. Therefore, this invention enables the controlled alteration of the triboelectric properties of materials having optimum physical properties to provide developer materials (both toner and carrier) having improved triboelectric properties for electrostatographic use while ~;
retaining their desirable physical properties.
It has been found that the -triboelectric charge ac-quired by -the nitrated aromatics is much more negative than the non-nitra-ted polymer material. It is further noted that a standard nitration procedure usually yields a polymer which does not charge as negatively as a nitrated/oxidized material even though the degree of nitration is comparable. Thus it appears that the oxidation also increases the extent of negative triboelectric charging property of polymeric materials. For example, it has been fou~d that nitration of a styrene-n-butylmethacrylate copolymer material yields a polymer whose triboelectric charging potential enables its use as a carrier material with various toners above it in the triboelectric series including those that are usually referred -to as "reversal"
carriers.
The degree of nitration of nitration-oxidation can be controlled either stoichiometrically or kinetically so as to ; ;
optimize salient physical and triboelectric properties. Typi-cally, any suitable nitration process may be employed to provide the chemically modified carrier materials of this invention.
Typical nitration processes include the use of a mild, non-hydrolytic process employing reagents such as cupric nitra-te and acetic anhydride, for example, when polymers are hydro-lytically unstable under usual nitration conditions. Under conditions using cupric ni-trate/acetic anhydride, oxidation accompanies nitration. Thus, in one step a high work function material with functional groups can be prepared. The use of`
such functional moieties enables the further addition of tribo-electric charging moieties to the polymer.
Therefore, by this invention, desirable electros-tato graphic properties are intrinsic to the polymer material and need not depend upon external addi-tives. The prediction and . .
11~737Z6 control of triboelectric characteristics for imaging materials is now possible by this invention.
It has also been found that introduction of other -electron withdrawing groups such as halogen, chlormethyl or acyl, into the aromatic moieties of polymers such as polystyrene and styrene-n~butyl methacrylate copolymers causes an increase in their propensity for negative triboelectric charging. Con-versely, introduction of electron releasing moieties such as me-thyl, t-butyl, alkoxy, and alkylthio increases their propen-sity for positive charging. Thus the triboelectric properties of polymers containing aromatic moieties may be selectively ~ ~-altered by chemical modification. The chemical modification encompasses the attachment of functionality to the aromatic nucleus. It is also possible to change the triboelectric charging propensity of aromatic polymers by multi-step chemical modification, however, the preferred approaches are one-step transforma-tion such as nitration, hydroxylation, halogenation, sulfonation, alkylation, and acylation. An alternative to ~-~
reactions of polymers in many applications is the polymerization of aromatic monomers bearing the desired substituent. The aforementioned techniques may be applied to many polymers ~ ~ ;
' including those disclosed above and their derivatives as well as polyesters, styrene-alkyl methacrylates, styrene-alkyl acrylates, terephthalate polyesters, and phenolformaldehyde polymers.
The chemical modification of such ma-terials enables the alteration of materials have optimum physical properties in such a way as to improve their triboelectric properties for electro-statographic use. This invention may serve as a guide for the ., .
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~0737Z6 preparation of developer compositions having "finely-tuned"
triboelectric charging properties, and the capacity for continuous control of such properties -through variation in extent of reRction may be employed for such purpose.
In regard to triboelectric response, it is to be noted that materials such as those derived by nitration of styrene-methacrylate copolymers provide excellent carriers or carrier coatings, especially in view of their crosslinkability. For example, by the use of such materials, toners that previously exhibited unacceptable triboelectric response with conventional ~;
carrier now function properly. Thus, the coating of carrier cores, for example, metallic beads, with suitably function-alized polymers containing a crosslinking agent provides carrier materials which in addition to improved toughness, the triboelectric properties thereof may be continuously varied by means of controlling the amount of the crosslinking agent in the coating composition.
The coating of metallic carriers with functionalized polymers and crosslinking these materials, for example, via reaction of pendant hydroxyl with a crosslinking agent such as diisocyanate provides a means of continuous control of the triboelectric properties of the coated carriers. It has been found that as the degree of conversion increases, the capacity for positive triboelectric charging decreases. In addition, the degree of conversion can be controlled stoichiometrically. `-Further, various typcs of crosslinking agents which are reactive toward hydroxyl may be employed. In addition, various amine or sulfhydroxyl containing polymers have been found to exhibit similar effects.
Any suitable carrier material or carrier coating ~3'~2~
material may be chemically modified in accordance with this invention to control the triboelectric properties. Typical materials include styrene-acrylate-organosilicon terpolymers, polyvinyls and polyvinylidenes such as polystyrene, polymethy-lstyrene polyesters such as polyethylene terephthalate;
polyurethanes; polysulfides, polycarbonates; thermosetting resins including phenolic resins such as phenol-formaldehyde, phenol-furfural and resorcinol formaldehyde; amino resins such as melamineformaldehyde; polyester resins; epoxy resins;
and the like. Many of the foregoing and other typical carrier coating materials are described by L. E. Walkup in U. S.
Patent 2,618,551 issued November 18, 1952; B. B. Jacknow et al in U. S. Patent 3,526,533 issued August 1, 1970; and R. J. Hagenbach et al in U. S. Patents 3,533,835 issued ; November 13, 1970 and 3,658,500 issued August 25, 1972. ~ ~;
Any suitable electrostatographic carrier coating thick-ness may be employed. However, a carrier coating having a thick-ness at least sufficient to form a thin continuous film on the ` carrier particle is prefQrred because the carrier coating will then possess sufficient thickness to resist abrasion and pre-vent pinholes which adversely affect the triboelectric pro-perties of th~ coated carrier particles. Generally, for cascade and magnetic brush development, the carrier coating may comprise from about 0.1 percent to about 10.0 percent by weight based on the weight of the coated carrier particles.
Preferably, the carrier coating should comprise ~rom about 0.1 percent to about 1.0 percent by weight based on the weight of the coated carrier partic]es because maximum durability, toner impaction resistance, and copy quality are achieved.
To achieve further variation in the properties of the coated carrier particles, well-known additives such as plasticizers, reactive and non-reactive polymersl dyes, pigments, wetting agents and mixtures thereof may be mixed with the coating materials.
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An ultimate coated carrier particle having an average diameter between about 50 microns and about 1,000 microns is ` preferred in cascade systems because the carrier particle then possesses suf~icient density and inertia to avoid adherence to the electrostatic image during the cascade development process. ~dherence of carrier particles to an electrostato-graphic drum is undesirable because of the ~ormation of deep scratches on the drum surface during the image transfer and drum cleaning steps, particularly where cleaning is accomplishedby a web cleaner such as the web disclosed by W. P. Graff, Jr., et al in U. S. Patent 3,186,838 issued June 1, 1965.
` Any suitable well known coated or uncoated electro-statographic carrier bead material may be employed as the core of the beads of this invention. Typical carrier core matèrials ; include sodium chloride, ammonium chloride, aluminum potassium chloride, Rochelle salt, sodium nitrate, potassium chlorate, granular zircon, granular silicon, methyl methacrylate, glass, silicon dioxide, flintshot, iron, steel, ferrite, nickel, Carborundum, and mixtures thereof.
Typical resins that may be modified in accordance with this invention for use as toners include those having a melting point of at least about 110F such as, for example, i vinyl resins including homopolymers or a copolymers cf two or more vinyl monomers. Typical monomeric units which may be employed to form vinyl polymers includeO styrene, p-chlorostyrene; vinyl naphthalene; ethylenically unsaturated mono-olefins such as ethylene, propylene, butylene, isobutylene and the like; vinyl esters such as vinyl chloride, vinyl b~omide, vinyl ~luoride, vinyl acetate, vinyl propionate, vinyl ~enzoate, vinyl butyrate, and the like; esters o~
alphamethylene aliphatic monocarboxylic * trade mar~
i ~0737Z6 acids such as me-thyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n -octyl acrylate, 2-chloro-ethyl acrylate, phenyl acrylate, methylalpha-chloroacrylate, methyl methacryla-te, ethyl me-thacrylate, butyl methacrylate and the like; acrylonitrile, methacrylonitrile, acrylamide, vinyl ethers such as vinyl methyl ether, vinyl isobutyl ether, vinyl ethyl ether, and the like; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone and the like; vinylidene halides such as vinylidene chloride, vinylidene chlorofluoride and the like; and N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidene and the like; and mixtures thereof. Generally, suitable vinyl resins employed in the toner have a weight average molecular weight between about 3,000 to about 500,000. The resins may be formed by the polymerization of mixtures of two or more of these unsaturated monomers. The expression "addition polymerization" is intended to include known polymerization techniques such as free radical, anionic and cationic polymer-ization processes.
The combination of the resin component and colorant whether the resin component is a homopolymer, copolymer, or blend, should have a blocking temperature of at least about 110F and a melt viscosity of less than about 2.5 x 10 poise at temperatures up to about 450 F. When the toner is charac- .
-terized by a blocking temperature less than about 110 F, the toner particles tend to agglomerate during storage and machine operation and also form undesirable films on the surface of reusable photoreceptors which adversely affect image quality.
` Any suitable pigment or dye rnay be ernployed as the colorant for the toner particles. Toner colorants are well~
'' ~' ' 10~737~26 known and include, ror example, carbon black, nigrosine dye, aniline blue, Calco Oil Blue, chrome yellow, ultra marine blue, duPont Oil Red, Quinoline Yellow, mekhylene blue chloride, phthalocyanine blue, Malachite Green Oxalate, lamp black, Rose Bengal and mixture thereof. The pigment or dye should be present in the toner in a sufficient quantity to render it highly colored so that it will form a clearly visible image on a recording member. Thus, for examp]e, where conventional electrostatographic copies of typed documents are desired, the toner may comprise a b1ack pigment such as carbon black or a black dye such as Amaplast Black dye, available frGm the National Aniline Products, Inc. Generally, the pigment is employed in an amount from about 1 percent to about 20 percent by weight based on the total weight of the colored toner. If the toner colorant employed is a dye, substantially smaller quantitiesof colorant may be used. However, since a number of the above pigments used in electrostatographic toner compo-sitions may affect both the glass transition and fusion temp-eratures of the toner compositions of this invention, their concentration preferably should not exceed about 10 percent by weight of the colored toner.
The toner compositions of the present invention may be prepared by any well-known toner mixing and comminution technique. For example, the ingredients may be thorough~y mixed by blending, mixing and milling the components and thereafter micropulverizing the resulting mixture. Another well-known technique for forming toner particles is to spray-dry a ball-milled toner composition comprising a colorant, a resin, and a solvent.
When the toner materials of this invention are to .
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be employed in a cascade development process, the toner should have an average particle size less than about 30 microns and preferably between about 4 and about 20 microns for optimum results. For use in powder cloud development methods, particle diameters of slightly less than 1 micron are preferred.
In the preparation of developer materials in accordance with this invention, either a toner material having specifically designed properties, a carrier material having specifically designed properties or both may be used. If only a carrier in 10 accordance with this invention is used, any suitable well-known toner material may be employed. Typical toner materials include gum copal, gum sandarac, rosin, cumaroneindene resin, asphaltum~
gilsonite, phenolformaldehyde resins, rosin modified phenolfor-maldehyde resins, methacrylic resins, polystyrene resins, poly-propylene resins, epoxy resins, polyethylene resins, polyester resins, and mixtures thereof. The particular toner material to be employed obviously depends upon the separation of the toner ~ ;
particles from the coated carrier in the triboelectric series and should be sufficient to cause the toner particles to elec- ?
20 trostatically cling to the carrier surface. Among the patents describing electroscopic toner compositions are U. S. Patent 2,659,670 issued November 17, 1953 to Copley; U. S. Patent 2,753,308 issued July 3, 1956 to Landrigan; U. S. Patent
~ . . . . . . .
~V~3'~
portions o~ the surface have a charge of the same polarity as/ but stronger than, the carrier particles. Toner and carrier particles having opposi~e polarities are selected so that the toner particles cling to the carrier particles. In order to develop a ne~atively charged electrostatic latent image, a toner and carrier combination are selected in which the toner is triboelectrically positive in relation to the ; toner. Conversely, to develop a positively charged electro-static latent image, a toner and carrier combination wherein the toner is triboelectrically negative in relation to the carrier is used. The triboelectric relationship between the toner and carrier depends on the relative positions of the materials in the "triboelectric series". In this series, materials are arranged in ascending ordQr of their ability to take on a positive charge. Each material is positive with respect to any material classified below it in the series; and, negative with respect to any material above it in the series. As the developer mixture cascades or rolls across the image-bearing surface, the toner particles are electrostatically attracted from the carrier to the charged portions of the image-bearing surface, whereas they are not ; electrostatically attracted to the uncharged or background portions of the image which they contact. The carrier particles and unused toner particles are then recycled. The cascade ~.
development process is extremely good for the development of line copy images, and is the most widely used commercial ; `~
electrostatographic development technique. A general purpose office copying machine incorporating this technique is described in U.S. Patent 3,099,943 to Eichorn et al ~ssued ~ugust 8, 1963.
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Another technique for developing electrostatic latent images is the "magnetic brush" process as disclosed for example, in U. S. Patent 2,874,063 to Princeton issued February 17, 1959. In this process, a developer material containing toner and magnetic carrier particles is attracted ~o and is carried by a magnet. The magnetlc field causes alignment of the magnetic particles in a brush-like configuration when this magnetic brush is brought into contact with an electrostatic latent image-bearing surface, the-toner particles are attracted from the carrier particles of the brush to the charged areas of the image-bearing surface but ` not to the uncharged areas. Since the charged areas have an imagewise configuration, the toner material clings to ` the surface in imagewise configuration, thus developing the latent image.
Another method for developing electrostatic latent images is disclosed in U.S. Patent 3,503,776 issued March 31, 1970 to R. W. Gundlach. In this method, images are formed by transporting an electrostatic latent image-bearing surface in a generally ascending arcuate path, and contacting only the image in a contact zone with a bath of developer material transported in a concave chamber adjacent the lower path of the imaging surface. The contact zone extends from about the lowermost point of the arcuate path to the uppermost point of the arcuate path. As the imaging surface is trans-ported along its arcuate path, frictional contact between the developer and the imaging surface in the contact zone circulates the developer in the bath and brings developer - material into developing configuration with the imaged surface.
~ - 4 ~
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Many other methods/ such as the "touchdown"
development method disclosed`by C. R. Mayo in U. S. Patent 2,895,847, issued July 21, 1959 are known for applying electroscopic particles to the electrostatic latent image to be developed. The development process, as described above, together with numerous modifications, are well-known to the art through various patents and publications and through the widespread availability and utilization of electrostatographic imaging equipment.
; 10 In automatic reproduction equipment, it is conventional ~, ` . ' ';', ~ ~ .
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to employ as -the imaging pla-te o-~ a photoconductor on a ccnduc-tive subs-trate in the form o~ a cylindrical drum or a flexible belt which is continuous]y rotated through a cycle of sequential operations including charging, exposing, developing, transferring and cleaning. The developer chamber is charged wlth a developer mixture comprising carrier particles and enough toner particles for hundreds of reproduction cycles. Generally, the freshly charged developer mixtures contain between about 1.5 and 5% toner particles based upon the weight of the developer.
This initial concentration provides sufficient toner for many reproduction cycles without causing undesirably high background toner deposition.
While ordinarily capable of producing good quality images, conventional developing systems suffer serious defi-ciencies in certain areas. In the reproduction of high contrast copies such as letters, tracings and the like, it is desirable to select the electroscopic powder and carrier materials so that their mutual electrification is relatively large; the degree of such electrification being governed in most cases by the distance between their relative ~ositions in the tribo-electric series. However, when otherwise compatible electro-scopic powder and carrier materials are removed from each other in the triboelectric series by too grea-t a distance, the result-ing images are very faint because the attractive forces between -the carrier and toner particles compete with the attractive forces between the electrostatic latent image and the toner particles. Although the image density described in the immediately preceding sentence may be improved by increasing toner concentration in the developer mixture, undesirably high background toner deposition as well as increased toner irnpaction - ~ , ' i , ~(~737'~6 and agglomeration is encountered when the developer mixture i5 overtGned. The initial electros-tatographic plate charge may be inereased -to improve the density of the deposited powder image, but the plate charge would ordinarily have to be excessively high in order to attract the electroscopic powder away from ~;
the carrier partic]es. Excessivly high eleetrostatographic plate charges ar-e not only undesirable because of the high power consumption necessary to maintain the electrostatographic plate at high potentials, but also because the high po-tential causes the carrier particles tG adhere to the eleetros-tatographic ~ -~
plate surface rather than mer-ely roll across and off the electro-statographic plate surface. Print dele-tion and massive carry-over of carrier particles often occur when carrier particles adhere to reusable electrostatographie imaging surfaees. Massive earrier earry-over problems are partieularly acute when the developer is employed in solid area coverage machines where exeessive quantities of toner particles are removed from carrier particles thereby leaving many carrier particles substantially bare of toner particles. Further, adherenee of earrier partieles to reusable eleetrostatographie imaging surfaees promotes -the formation of undesirable scratches cn the surfaces during image transfer and surface cleaning operations.
It is therefore apparent that many materials which otherwise have suitable properties for employment as carrier partieles are unsuitable beeause they possess too high or too ~- ;
low a triboeleetrie value. In addition, uniform triboelectric surfaee characteristics of many carrier surfaces are difficul-t to achieve with mass production techniques. Quality images are, in some instances, almost impossible to oktain in high speed automatic machines when carriers having non-uniform ., , ': ' ~ ' ' -.
3L~73'7Z~i triboelectric proper-ties are employed. Although it may be possible to alter the triboelec-tric vlaue of an insulating carrier material by blending the carrier material with another insula-t`ing material having a triboelec-tric value remote from the triboelectric value o-f -the original carrier material, relatively large quantities of additional material is necessary to alter the triboelectric value of the original carrier material. The addition of large quantities of material tG the original carrier material to change the triboelectric properties thereof requires a major manufacturing opera-tion and often undesirably alters the original physical characteristics of the carrier material. Further, it is highly desirable to control the triboelectric properties of carrier surfaces to accommodate the use of desirable toner compositions while retaining the other desirable physical characteristics of the , carrier. The alteration of the triboelectric properties o-f a carrier by applying a surface coating thereon is a particularly desirable technique. With this technique, not only is it possible to control the triboelectric properties of a carrier made from ;
materials having desirable physical characteristics, it is also possible to employ materials previously not suitable as a carrier. :;
Thus, for example, acarrier having desirable physical properties with the exception of hardness, can be coated with a material having desirable hardness as well as other physical properties, rendering the resultant product more useful as a carrier. How- -~
ever, since most carrier coating ma-terials are deficient in one or more of the above areas, there is a continuing need for improved electrostatographic carrier and developer composition and methods for forming the same.
Further, it is apparent from the description presented ::
_7 3L~737Z~ :
above as well as in other development techniques, that the toner is subjected to severe mechanical attrition which tends to break down the par-ticles into undesirable dust fines. The formation of fines is retarded when the toner contains a tough, high molecular weigh-t resin which is capable of with-standing the shear and impact forces imparted to the toner in the machine. Unfortunately, many high molecular weight materials cannot be employed in high speed automatic machines because they cannot be rapidly fused during a powder image -heat fixing step. On the other- hand, low molecular weight resins which are easily heat fused at relatively low temper-atures are usually undesirable because these materials tend to form thick films on reusable photoconductor surfaces. ;
These films -tend to cause image degradation and contribute to machine maintenance down time. Many low molecular weight resins decompose when subjec-ted to fusing conditions in high speed copying and duplicating machines. In addition, low molecular weight resins tend to form tacky images on the copy sheet which are easily smudged and often offset to other adjacent sheets. Additionally, low molecular weight resins are often extremely difficult or even impossible to comminute in conventional $rindingapparatus. Also, the toner materials must be capable of accepting a charge of -the correct polarity when broughtinto rubbing contact with the surface of carrier materials in cascade or touchdown development systems.
Additionally, many toner materials cannot satisfactorily be transferred by conventianal electrostatographic development systems from reusable imaging surfaces in automatic copying and duplicating machines. Since mos-t polymeric -toner materials are deficient in one or more of -the above areas, there is a lV73~Zfi continuing need for improved toners and developers.
In accordance with one aspect of this invention there is provided an electrostatographic developer composition ~or use in developing electrostatic latent images on a recording surface, the developer composition being comprised of a toner material and a carrier material; the toner material having an average particle diameter of less than about 30 microns and consisting essentially of a colorant and a polymer having aromatic moieties selected from the group consisting of styrene alkyl methacrylates and styrene alkyl acrylates;
the carrier material containing carrier particles having an ::
average particle diameter of between 50 microns and about 1,000 microns, each of the carrier particles comprising a core surrounded by an outex coating in the amount of from 0.1 percent to about 10 percent by weight based on the weight of the carrier particles, the outex- coating consisting ; essentially of a functionalized polymer selected from`the group consisting of styrene alkyl methacrylates and styrene .
alkyl acrylates, the polymer ~or both the toner and the ~ 20 carrier being.obtained.by the systematic chemical alteration of the aromatic moieties of the polymer by nitration, halo- :-genation, acylation, or alkyl substitution to thereby provide toner and carrier particles characterized as having closely controlled triboelectric charging properties.
By way of added explanation, in accordance with an aspect of this invention chemical alteration of the tribo-electric charging potential of functional polymers employed ~ .
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as toner and carrier materials is controlled. The controlled ~, variation of the triboelectric behavior of functional polymers provides a means of attaining optimum triboelectric responses :
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~L~73~26 of electrostatograph:ic developer- materials for specifically defined applica-tions. Ihus? in accordance with this invention, monomeric and/or polymeric materials are systematically chemically modified to provide structural effects which yield structure~triboelectric property relationships among various substituted aromatic moieties such as nitroaromatics, haloaromatics, aromatic ethers, and alkylaromatics. These relationships have been found to be extremely helpful in designing new carrier and toner materials. By -this invention, the triboelectric charging proper-ties of toner-carrier pairs are controlled to enable optimum triboelectric relationships `
in developer compositions. ;
It is noted that, by itself, no material has a tribo- ;
electric charge. The magnitude of a triboelectric charge depends upon both the toner and the carrier material. Thus, replace-ment of one of the components to optimize triboelectric charg-ing properties is generally necessary to provide the desired triboelectric response. By so doing, greater latitude is avail~ -~
able for specific electrostatographic applications. In accord-ance with this invention, it has been found that by varying the degree of chemical modification of polymeric materials for use as toner or carrier materials, the triboelectric properties ~
of developer materials can be controlled in a continuous manner. `
In electrostatographic developrnent of selenium photo-conductor latent images, polymers which tend to take on a rela-tively high positive charge are generally satisfactory for use `
as carrier coating materials and polymers which tend to take on a relatively high negative charge are generally satisfactory for use as toner materials. In electrostatographic developement of other photoconductor latent images, for examp]e, zinc oxide, :, - . , : ~ :,. . . :
~737Z~
phthalocyanine, cadmium sulfide, polyvinylcarbazole-trinitroflurenone. The reverse is true regarding charging properties of carriers and toner. In accordance with this invention, the triboelectric properties of developer materials are correlated with their structural composition and thereby predictably controlled. Since the distance between a given toner-carrier pair on a trihoelectric charging scale determines the ; triboelectric charge between them, their relative positions determine the sign of the triboelectric charge. Those materials low on the scale prefer to adopt a positive charge and those materials high on the scale prefer to adopt a negative charge.
Appropriate toner-carrier pairs can be selected based on their triboelectric charging or triboelectric series relationship to satisfy a particular acceptable triboelectric charging range re-quirement for a given electrostatographic machine developer housing.
It has been found that triboelectric behavior is a function of molecular structure which now allows the controlled and progressive modification of the triboelectric charging prop-erties of developer compositions so as to obtain optimum tribo-electric charging properties between -toner and carrier pairs.
Thus, by this invention, adjustment of the triboelectric charging properties of electrostatographic developer materials need not be in stepwise fashion but may be accomplished in a continuous manner prcviding a high degree of "fine tuning" of triboelectric properties f-or developer materials.
; In accordance with this invention, the triboelectric charging properties of monomeric and polymeric compounds may be modified by systematic chemical alteration of aromatic moieties of monomers and polymers. Such alteration of a aromatic function-:.
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--1 1-- , ~ ~737Z6 ality may be accomplished by methods Icnown -to the art, such as, halogenation using the reaction of the aromatic polymer with elemental bromine, alkylation or acylation using the well known Friedel-Crafts reaction with alkyl halides and Lewis Acids, or nitration, using nitric/sulfuric acids, special reagents, such as cupric nitrate/acetic anhydride. Aromatic reactions on polymers can not always be driven to completion and frequently side reaction do occur. Under certain nitration conditions, for example, it has been found that oxidation accompanies nitration as manifested by the presence of hydroxyl moieties. Such side-reactions are, however, quite reproducible and, thus, their influence on -the triboelectric behavior of the resultan-t species can also be reproduced with a high degree of precision. The functional groups introduced by these processes may additionally be employed for varied purposes including covalent bonding to dyes having functional groups, the addition of triboelectric charge modifiers, and bonding to substrates. Extensions of these uses are numerous and obvious to the artisan.
Thus, -in accordance with this invention, there is provided a method for the preparation of developer materials having controlled triboelectric properties for electrostato-graphic applications. The principle of this invention may be practiced with any monomer, polymer, or copolymer containing -an aromatic functionality. Therefore, this invention enables the controlled alteration of the triboelectric properties of materials having optimum physical properties to provide developer materials (both toner and carrier) having improved triboelectric properties for electrostatographic use while ~;
retaining their desirable physical properties.
It has been found that the -triboelectric charge ac-quired by -the nitrated aromatics is much more negative than the non-nitra-ted polymer material. It is further noted that a standard nitration procedure usually yields a polymer which does not charge as negatively as a nitrated/oxidized material even though the degree of nitration is comparable. Thus it appears that the oxidation also increases the extent of negative triboelectric charging property of polymeric materials. For example, it has been fou~d that nitration of a styrene-n-butylmethacrylate copolymer material yields a polymer whose triboelectric charging potential enables its use as a carrier material with various toners above it in the triboelectric series including those that are usually referred -to as "reversal"
carriers.
The degree of nitration of nitration-oxidation can be controlled either stoichiometrically or kinetically so as to ; ;
optimize salient physical and triboelectric properties. Typi-cally, any suitable nitration process may be employed to provide the chemically modified carrier materials of this invention.
Typical nitration processes include the use of a mild, non-hydrolytic process employing reagents such as cupric nitra-te and acetic anhydride, for example, when polymers are hydro-lytically unstable under usual nitration conditions. Under conditions using cupric ni-trate/acetic anhydride, oxidation accompanies nitration. Thus, in one step a high work function material with functional groups can be prepared. The use of`
such functional moieties enables the further addition of tribo-electric charging moieties to the polymer.
Therefore, by this invention, desirable electros-tato graphic properties are intrinsic to the polymer material and need not depend upon external addi-tives. The prediction and . .
11~737Z6 control of triboelectric characteristics for imaging materials is now possible by this invention.
It has also been found that introduction of other -electron withdrawing groups such as halogen, chlormethyl or acyl, into the aromatic moieties of polymers such as polystyrene and styrene-n~butyl methacrylate copolymers causes an increase in their propensity for negative triboelectric charging. Con-versely, introduction of electron releasing moieties such as me-thyl, t-butyl, alkoxy, and alkylthio increases their propen-sity for positive charging. Thus the triboelectric properties of polymers containing aromatic moieties may be selectively ~ ~-altered by chemical modification. The chemical modification encompasses the attachment of functionality to the aromatic nucleus. It is also possible to change the triboelectric charging propensity of aromatic polymers by multi-step chemical modification, however, the preferred approaches are one-step transforma-tion such as nitration, hydroxylation, halogenation, sulfonation, alkylation, and acylation. An alternative to ~-~
reactions of polymers in many applications is the polymerization of aromatic monomers bearing the desired substituent. The aforementioned techniques may be applied to many polymers ~ ~ ;
' including those disclosed above and their derivatives as well as polyesters, styrene-alkyl methacrylates, styrene-alkyl acrylates, terephthalate polyesters, and phenolformaldehyde polymers.
The chemical modification of such ma-terials enables the alteration of materials have optimum physical properties in such a way as to improve their triboelectric properties for electro-statographic use. This invention may serve as a guide for the ., .
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~:
~0737Z6 preparation of developer compositions having "finely-tuned"
triboelectric charging properties, and the capacity for continuous control of such properties -through variation in extent of reRction may be employed for such purpose.
In regard to triboelectric response, it is to be noted that materials such as those derived by nitration of styrene-methacrylate copolymers provide excellent carriers or carrier coatings, especially in view of their crosslinkability. For example, by the use of such materials, toners that previously exhibited unacceptable triboelectric response with conventional ~;
carrier now function properly. Thus, the coating of carrier cores, for example, metallic beads, with suitably function-alized polymers containing a crosslinking agent provides carrier materials which in addition to improved toughness, the triboelectric properties thereof may be continuously varied by means of controlling the amount of the crosslinking agent in the coating composition.
The coating of metallic carriers with functionalized polymers and crosslinking these materials, for example, via reaction of pendant hydroxyl with a crosslinking agent such as diisocyanate provides a means of continuous control of the triboelectric properties of the coated carriers. It has been found that as the degree of conversion increases, the capacity for positive triboelectric charging decreases. In addition, the degree of conversion can be controlled stoichiometrically. `-Further, various typcs of crosslinking agents which are reactive toward hydroxyl may be employed. In addition, various amine or sulfhydroxyl containing polymers have been found to exhibit similar effects.
Any suitable carrier material or carrier coating ~3'~2~
material may be chemically modified in accordance with this invention to control the triboelectric properties. Typical materials include styrene-acrylate-organosilicon terpolymers, polyvinyls and polyvinylidenes such as polystyrene, polymethy-lstyrene polyesters such as polyethylene terephthalate;
polyurethanes; polysulfides, polycarbonates; thermosetting resins including phenolic resins such as phenol-formaldehyde, phenol-furfural and resorcinol formaldehyde; amino resins such as melamineformaldehyde; polyester resins; epoxy resins;
and the like. Many of the foregoing and other typical carrier coating materials are described by L. E. Walkup in U. S.
Patent 2,618,551 issued November 18, 1952; B. B. Jacknow et al in U. S. Patent 3,526,533 issued August 1, 1970; and R. J. Hagenbach et al in U. S. Patents 3,533,835 issued ; November 13, 1970 and 3,658,500 issued August 25, 1972. ~ ~;
Any suitable electrostatographic carrier coating thick-ness may be employed. However, a carrier coating having a thick-ness at least sufficient to form a thin continuous film on the ` carrier particle is prefQrred because the carrier coating will then possess sufficient thickness to resist abrasion and pre-vent pinholes which adversely affect the triboelectric pro-perties of th~ coated carrier particles. Generally, for cascade and magnetic brush development, the carrier coating may comprise from about 0.1 percent to about 10.0 percent by weight based on the weight of the coated carrier particles.
Preferably, the carrier coating should comprise ~rom about 0.1 percent to about 1.0 percent by weight based on the weight of the coated carrier partic]es because maximum durability, toner impaction resistance, and copy quality are achieved.
To achieve further variation in the properties of the coated carrier particles, well-known additives such as plasticizers, reactive and non-reactive polymersl dyes, pigments, wetting agents and mixtures thereof may be mixed with the coating materials.
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An ultimate coated carrier particle having an average diameter between about 50 microns and about 1,000 microns is ` preferred in cascade systems because the carrier particle then possesses suf~icient density and inertia to avoid adherence to the electrostatic image during the cascade development process. ~dherence of carrier particles to an electrostato-graphic drum is undesirable because of the ~ormation of deep scratches on the drum surface during the image transfer and drum cleaning steps, particularly where cleaning is accomplishedby a web cleaner such as the web disclosed by W. P. Graff, Jr., et al in U. S. Patent 3,186,838 issued June 1, 1965.
` Any suitable well known coated or uncoated electro-statographic carrier bead material may be employed as the core of the beads of this invention. Typical carrier core matèrials ; include sodium chloride, ammonium chloride, aluminum potassium chloride, Rochelle salt, sodium nitrate, potassium chlorate, granular zircon, granular silicon, methyl methacrylate, glass, silicon dioxide, flintshot, iron, steel, ferrite, nickel, Carborundum, and mixtures thereof.
Typical resins that may be modified in accordance with this invention for use as toners include those having a melting point of at least about 110F such as, for example, i vinyl resins including homopolymers or a copolymers cf two or more vinyl monomers. Typical monomeric units which may be employed to form vinyl polymers includeO styrene, p-chlorostyrene; vinyl naphthalene; ethylenically unsaturated mono-olefins such as ethylene, propylene, butylene, isobutylene and the like; vinyl esters such as vinyl chloride, vinyl b~omide, vinyl ~luoride, vinyl acetate, vinyl propionate, vinyl ~enzoate, vinyl butyrate, and the like; esters o~
alphamethylene aliphatic monocarboxylic * trade mar~
i ~0737Z6 acids such as me-thyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n -octyl acrylate, 2-chloro-ethyl acrylate, phenyl acrylate, methylalpha-chloroacrylate, methyl methacryla-te, ethyl me-thacrylate, butyl methacrylate and the like; acrylonitrile, methacrylonitrile, acrylamide, vinyl ethers such as vinyl methyl ether, vinyl isobutyl ether, vinyl ethyl ether, and the like; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone and the like; vinylidene halides such as vinylidene chloride, vinylidene chlorofluoride and the like; and N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidene and the like; and mixtures thereof. Generally, suitable vinyl resins employed in the toner have a weight average molecular weight between about 3,000 to about 500,000. The resins may be formed by the polymerization of mixtures of two or more of these unsaturated monomers. The expression "addition polymerization" is intended to include known polymerization techniques such as free radical, anionic and cationic polymer-ization processes.
The combination of the resin component and colorant whether the resin component is a homopolymer, copolymer, or blend, should have a blocking temperature of at least about 110F and a melt viscosity of less than about 2.5 x 10 poise at temperatures up to about 450 F. When the toner is charac- .
-terized by a blocking temperature less than about 110 F, the toner particles tend to agglomerate during storage and machine operation and also form undesirable films on the surface of reusable photoreceptors which adversely affect image quality.
` Any suitable pigment or dye rnay be ernployed as the colorant for the toner particles. Toner colorants are well~
'' ~' ' 10~737~26 known and include, ror example, carbon black, nigrosine dye, aniline blue, Calco Oil Blue, chrome yellow, ultra marine blue, duPont Oil Red, Quinoline Yellow, mekhylene blue chloride, phthalocyanine blue, Malachite Green Oxalate, lamp black, Rose Bengal and mixture thereof. The pigment or dye should be present in the toner in a sufficient quantity to render it highly colored so that it will form a clearly visible image on a recording member. Thus, for examp]e, where conventional electrostatographic copies of typed documents are desired, the toner may comprise a b1ack pigment such as carbon black or a black dye such as Amaplast Black dye, available frGm the National Aniline Products, Inc. Generally, the pigment is employed in an amount from about 1 percent to about 20 percent by weight based on the total weight of the colored toner. If the toner colorant employed is a dye, substantially smaller quantitiesof colorant may be used. However, since a number of the above pigments used in electrostatographic toner compo-sitions may affect both the glass transition and fusion temp-eratures of the toner compositions of this invention, their concentration preferably should not exceed about 10 percent by weight of the colored toner.
The toner compositions of the present invention may be prepared by any well-known toner mixing and comminution technique. For example, the ingredients may be thorough~y mixed by blending, mixing and milling the components and thereafter micropulverizing the resulting mixture. Another well-known technique for forming toner particles is to spray-dry a ball-milled toner composition comprising a colorant, a resin, and a solvent.
When the toner materials of this invention are to .
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be employed in a cascade development process, the toner should have an average particle size less than about 30 microns and preferably between about 4 and about 20 microns for optimum results. For use in powder cloud development methods, particle diameters of slightly less than 1 micron are preferred.
In the preparation of developer materials in accordance with this invention, either a toner material having specifically designed properties, a carrier material having specifically designed properties or both may be used. If only a carrier in 10 accordance with this invention is used, any suitable well-known toner material may be employed. Typical toner materials include gum copal, gum sandarac, rosin, cumaroneindene resin, asphaltum~
gilsonite, phenolformaldehyde resins, rosin modified phenolfor-maldehyde resins, methacrylic resins, polystyrene resins, poly-propylene resins, epoxy resins, polyethylene resins, polyester resins, and mixtures thereof. The particular toner material to be employed obviously depends upon the separation of the toner ~ ;
particles from the coated carrier in the triboelectric series and should be sufficient to cause the toner particles to elec- ?
20 trostatically cling to the carrier surface. Among the patents describing electroscopic toner compositions are U. S. Patent 2,659,670 issued November 17, 1953 to Copley; U. S. Patent 2,753,308 issued July 3, 1956 to Landrigan; U. S. Patent
3,079,342 issued February 26, 1963 to Insalaco; U. S~ Patent Reissue 25,136 issued March 13, 1962 to Carlson and U. S. Patent 2,788,288 issued April 9, 1957 to ~heinfrank et al. These toners generally hav0 an average particle diameter between about 1 and 30 microns.
If only a toner in accordance with this invention is 30 used~ any suitable coated or uncoated carrier material well-known in the art may be used in combination therewith. The carrier particles comprise any suitable solid materials, provided that - 1~737Z6 the carrier particles acquire a charge having an opposite polarity to that of the toner particles when brought in close contact with the toner particles so that the toner particles adhere to and surround the carrier particles. When a positive reproduction of the electrostatic images is desired, the carrier particle is selected so that the toner particles acquire a charge having a polarity opposite to that of the electro-sta-tic image. Al-ternatively, if a reversal reproduction of the elec-trostatic image is desired the carrier is selected so that the toner particles acquire a charge having the same polarity as that of the electrostatic image. Thus -the materials for the carrier particles are selected in accordance with their triboelectric properties in respect to the elec-troscopic toner so that when mixed or brought into mutual contact, one component of the developer is charged positively if the other component is below the first component in the triboelectric series and negatively if the other component is above the first component in a triboelectric series. By proper selection of carrier materials in accordance with their triboelectric effects, the polarities of their charge, when mixed, are such that the electroscopic toner particles adhere to and are coated on the surfaces of carrier particles and also adhere to that portion of the electrostatic image- ~
bearing surface having a grea-ter attraction for the toner ~ -than the carrier particles. Typical carriers include sodium chloride, ammonium chloride, aluminum potassium chloride, Rochelle salt, sodium nitrate, aluminum nitrate, potassium chlorate, granular zircon, granular silicon, methyl methacry-late, glass, silicon dioxide, nickel, steel, iron ferrites, and the like. The carriers may be employed with or without -21~
:, ' ,, .~ :
iO~3~2~, a coating. Many of the foregoing and other typical carriers ; are described by L. E. Walkup et al in U. S. Patent 2,638,416 and E. N. Wise in U. S. Patent 2,618,552 issued November 18, lg52. An ultimate coated carrier particle diameter between about 50 microns to about 1,000 microns is preferred because the carrier particles then possess sufficient density and inertia to avoid adherence to the electrostatic images during the cascade development process. Adherence of carrier beads to electrostatographic drums is undesirable because of the formation of deep scratches on the surface during the imaging transfer and drum cleaning steps, particularly where cleaning is accomplished by a web cleaner such as the web disclosed by W. P. Graff, Jr., et al in U. S. Patent 3,186,838 issued June 1, 1965. Also print deletion occurs when carrier beads adhere to electrostatographic imaging surfaces. Generally speaking, ` ~ ?
satisfactory results are obtained when about 1 part toner is `~
used with about 10 to 200 parts by weight of carrier.
The developer compositions of the instant invention may be employed to develop electrostatic laten~ images on any 20 suitable electrostatic latent image-bearing surface including -~
conventional photoconductive surfaces. Well-known photo-- conductive materials include vitreous selenium, organic or in-organic photoconductors embedded in a non-photoconductive matrix~ i organic or inorganic photoconductors embedded in a photoconduc-tive matrix or the like. Representative patents in which photoconductive materials are disclosed include U. S. Patent 2,903,542 issued September 8, 1959 to ~llrich, U. S. Patent 2,970,906 issued February 7, 1961 to Bixby, U. S. Patent 3l121,006 issued February 11, 1964 to Middleton, U. S. Patent .
3,121,007 issued February 11, 1964 to Middleton, and UO S~
Patent 3,151,982 issued November 6, 1964 to Corrsin.
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~73t726 DESCRIPTION Ol~ PREFERRED EMBODIMENTS
The ~ollowing examples ~urther de~ine, describe, and compare methods of preparing the developer materials o~ the present invention and of utilizing them to develop electro-static latent images. Parts and percentages are by weight unless otherwise indicated.
In the following, the relative triboelectric va~ues generated by contact of carrier beads with toner particles is measured by means of a cascade device. The device comprises a gounded metal plate set at an arbitrary but constant angle of elevation to horizontal, for example, 30 degrees, and a cup at the bottom of the incline. The cup is not attached to the incline and is thus not grounded; it is attached to an electrometer. The material to be tested is coated onto a metallic sheet, such as aluminum, and this is attached to the incline Then beads of the desired carri*r material are cascaded down the film and into the electrometer cup, where the charge acquired by the beads is measured. From this quantity and the weight of the beads the charge to mass ratio is calculated. This quantity is a direct measure of the triboelectric charging capacity of the polymeric film. The measurement is done at constant relative humidity and -temper-ature. Since triboelectric measurements are relative, the measurements should, for comparative purposes, be conducted under substantially identical conditions.
EXAMPLE I
Correlation of molecular structure and tribo-elec-tric behavior in polymeric systems is of practical importance when considering toner candidates and such is demonstrated herein. Thus, a polymeric system based on a :
- , .
~07~7~i polystyrene series, chosen for accessibili-ty and simplicit~, having the generic structure:
wherein X may be ~I, t-C4Hg, Br, CH2Cl, N02, and C~l3was studied. Po]y(p-nitrostyrene), where X = N02, was synthesized from polystyrene by nitration; poly(p bromostyrene), where X = Br, was prepared from polystyrene by using bromine/thallium acetate; poly(p-chloromethylstyrene), where X = CH2Cl9 was prepared by polymerization of the corresponding monomer; and poly~p-methylstyrene), where X = CH3was formed from the polystyrene, X = CH2Cl by reductive dehalogenation with lithium aluminum hydride. Films of the polymers were cast onto aluminum sheets from tetrahydrofuran solution except that poly(p-nitrostyrene) was cast from dimethylformamide.
The films were dried for about fifteen hours in vacuo at about 60C and then transferred without exposure to moist ~, air to a dry box maintained at zero relative humidity. Zinc carrier beads were similarly dried for about fifteen hours in vacuo at about 120C and transferred. Cascade triboelectric measurements were conducted using an angle of about 30 C, a drop height of about 1 cm, and a film length of about nine inches. The humidity was raised to successive constant ~ , levels by use of saturated salt solutions. The films and carrier beads were equilibrated at each relative humidity condition for about twenty hours prior to triboelectric charging measurement. The results indicate that with :- :
increased electron withdrawing power of the substituent -there is an accompanying increase in the amount of negative charge ~ -: ' : . . . . ~ .
1~737;:2~
generated on the film. In the present examples the electron withdrawing power of -the substituents increases in the following order: t - C4Hg ~CH3 ~H ~CH2Cl <Br ~N02. Though both carrier beads and films may be affected by moisture, the slope of a line at a given relative humidity is a function only of the materials since the same carrier is used for each film. These results indicate a practical means of predicting the relative triboelectric behavior of polymers which are substituted in the aromatic moiety, such as pre-dictably increasing the negative charging property of the polymer. While the triboelectric charging property of mix-tures and copolymers is not generally linear with composition it is a linear function of the extent of reac-tion for chemical modifications as shown in the following table.
Zinc Carrier Bead Charge In _ X Nano-Coulombs/gram at ~3% Relative Humidity t-C4H9 +0.13 CH3 +0.19 H +0.30 CH2Cl +0.70 -~r +1.1 2 +4-7 ' EXAMPLE II
To a solution of about 40 ml of concentrated nitric acid and about 40 ml of concentrated sulfuric acid were added with stirring about 62.5 grams of a styrene-n-butyl methacrylate copolymer (2.54:1.00 mole ratio) at such a rate that the tempera-ture did not exceed 30 C. The mixture was then allowed to stand for about 2 hours, then poured into water and fil-trated.
. . - . .
; J ' ~ " . '. '` `` ' '' ` ' ' ~;373~Z6 The solid was washed wi-th water, dissolvecl in tetrahydrof`uran and reprecipitated by dropwise addi-tion to water. This latter step was repeated several times and then the solid was vacuum dried. Elemental analysis showed about 42 percent nitration of available phenyl groups. Films were cast from solution onto aluminum plates and thorougly dried. 250 micron steel beads acquired a charge of -~0.1 nano-coulombs/gram when cascaded down this film. The starting copolymer causes these beads to acquire about -0.29 nano-coulombs per gram. Therefore, nitration of the polymer markedly increases its negative charging capacity.
EXAMPLE III
To a mixture of about 14.7 g of styrene-n-butyl meth-acrylate copolymer (2.54:1.00 mole ratio) is about 250 ml -of acetic anhydride was added with stirring about 53.0g of Cu(N03)2. 3H20 at such a rate that the temperature did not exceed 70 C. The mixture was heated momentarily on a steam bath and then kept at about 70 C for about 1.5 hours. The mixture was poured into water and filtered. ~he solid was washed with i water and saturated sodium bicarbonate. It was dissolved in `~
tetrahydrofuran and precipitated into an aqueous solution of ethylenedinitrilotetraacetic acid disodium salt. It was then ~
successively precipitated from tetrahydrofuran solution into `
aqueous sodium bicarbonate and several times into water. It was then dried in vacuo. Elemental analysis indicated that ;
about 42 percent of the available phenyl groups were nitrated, ~;
while about 50 percent of the phenyl groups were oxidized. A
film was cast from solution onto an aluminum plate and dried thorough-ly Against this film 250 micron steel beads acquired a charge of about +2 nano-coulombs per gram. Steel beads (250 microrl) coated with chlorinated polypropylene, which is very '1.~737Z6 near the bottom of -the triboelectric series and hence with most materials causes these beads to acquire very large negative charges, e.g., with the starting styrene-n-butyl methacrylate (2.54:1.00 mole ratio) copolymer about -2.2 nano-coulombs per gram, take on a charge of abou-t +0.~ nano-coulombs per gram.
Thus, the nitrated/oxidized polymer acquires a much higher nega-tive charge than the nitrated polymer and is even lower in the triboelectric series than chlorinated polypropylene.
EXAMPLE IV
A mixture o-f' about 35.5 grams of styrene-n-butyl methacrylate copolymer (2.54:1.00 mole ratio), about 9.06 grams of thallic acetate sesquihydrate and about 200 ml carbon tetrachloride was stirred for about 18 hours at about 25 . Then about 38.8 grams of bromine was added over about 1.5 hours with stirring. The mixture was stirred for about 6 hours and then heated under reflux for about 12 hours. The mixture was then poured into methanol and filtered. The dried polymer was precipitated from tetrahydrofuran successively with aqueous sodium bisulfite, twice from aqueous sodium bicarbonate, twice from water and once from methanol and dried in vacuo. Elemental analysis showed the presence of about 1.1 bromine atoms per phenyl gro~p. A film was cast from solution onto an aluminum plate and thoroughly dried. Using the cascade device 250 micron steel beads acquired a charge of about +0.95 nano-coulombs per gram vs this film. With the parent copolymer, 250 micron steel beads acquire a charge of about -0.29 nano-coulombs per gram. Thus, the .
bromination of the polymer substantially increases its propen-sity for negative charging.
Although specific components, proportions and pro-cedures have been stated in the above description of the ~ . .
.
~737;2 ~
preferrecl embodiments of -the novel -toner compositions, other suitable components, proportions and procedures as listed above may be used with similar results. Further, other materials and procuedures may be employed to synergize, enhance or other-wise modify the novel system.
Other modifications and ramifications of the present invention will appear to those skilled in the art upon the reading of this disclosure. These are intended to be included within the scope of this invention. ~ , .' ~ . .
'. . , :
. ' ~ ' ::: . - : -
If only a toner in accordance with this invention is 30 used~ any suitable coated or uncoated carrier material well-known in the art may be used in combination therewith. The carrier particles comprise any suitable solid materials, provided that - 1~737Z6 the carrier particles acquire a charge having an opposite polarity to that of the toner particles when brought in close contact with the toner particles so that the toner particles adhere to and surround the carrier particles. When a positive reproduction of the electrostatic images is desired, the carrier particle is selected so that the toner particles acquire a charge having a polarity opposite to that of the electro-sta-tic image. Al-ternatively, if a reversal reproduction of the elec-trostatic image is desired the carrier is selected so that the toner particles acquire a charge having the same polarity as that of the electrostatic image. Thus -the materials for the carrier particles are selected in accordance with their triboelectric properties in respect to the elec-troscopic toner so that when mixed or brought into mutual contact, one component of the developer is charged positively if the other component is below the first component in the triboelectric series and negatively if the other component is above the first component in a triboelectric series. By proper selection of carrier materials in accordance with their triboelectric effects, the polarities of their charge, when mixed, are such that the electroscopic toner particles adhere to and are coated on the surfaces of carrier particles and also adhere to that portion of the electrostatic image- ~
bearing surface having a grea-ter attraction for the toner ~ -than the carrier particles. Typical carriers include sodium chloride, ammonium chloride, aluminum potassium chloride, Rochelle salt, sodium nitrate, aluminum nitrate, potassium chlorate, granular zircon, granular silicon, methyl methacry-late, glass, silicon dioxide, nickel, steel, iron ferrites, and the like. The carriers may be employed with or without -21~
:, ' ,, .~ :
iO~3~2~, a coating. Many of the foregoing and other typical carriers ; are described by L. E. Walkup et al in U. S. Patent 2,638,416 and E. N. Wise in U. S. Patent 2,618,552 issued November 18, lg52. An ultimate coated carrier particle diameter between about 50 microns to about 1,000 microns is preferred because the carrier particles then possess sufficient density and inertia to avoid adherence to the electrostatic images during the cascade development process. Adherence of carrier beads to electrostatographic drums is undesirable because of the formation of deep scratches on the surface during the imaging transfer and drum cleaning steps, particularly where cleaning is accomplished by a web cleaner such as the web disclosed by W. P. Graff, Jr., et al in U. S. Patent 3,186,838 issued June 1, 1965. Also print deletion occurs when carrier beads adhere to electrostatographic imaging surfaces. Generally speaking, ` ~ ?
satisfactory results are obtained when about 1 part toner is `~
used with about 10 to 200 parts by weight of carrier.
The developer compositions of the instant invention may be employed to develop electrostatic laten~ images on any 20 suitable electrostatic latent image-bearing surface including -~
conventional photoconductive surfaces. Well-known photo-- conductive materials include vitreous selenium, organic or in-organic photoconductors embedded in a non-photoconductive matrix~ i organic or inorganic photoconductors embedded in a photoconduc-tive matrix or the like. Representative patents in which photoconductive materials are disclosed include U. S. Patent 2,903,542 issued September 8, 1959 to ~llrich, U. S. Patent 2,970,906 issued February 7, 1961 to Bixby, U. S. Patent 3l121,006 issued February 11, 1964 to Middleton, U. S. Patent .
3,121,007 issued February 11, 1964 to Middleton, and UO S~
Patent 3,151,982 issued November 6, 1964 to Corrsin.
. : ~
., . ; . .
~73t726 DESCRIPTION Ol~ PREFERRED EMBODIMENTS
The ~ollowing examples ~urther de~ine, describe, and compare methods of preparing the developer materials o~ the present invention and of utilizing them to develop electro-static latent images. Parts and percentages are by weight unless otherwise indicated.
In the following, the relative triboelectric va~ues generated by contact of carrier beads with toner particles is measured by means of a cascade device. The device comprises a gounded metal plate set at an arbitrary but constant angle of elevation to horizontal, for example, 30 degrees, and a cup at the bottom of the incline. The cup is not attached to the incline and is thus not grounded; it is attached to an electrometer. The material to be tested is coated onto a metallic sheet, such as aluminum, and this is attached to the incline Then beads of the desired carri*r material are cascaded down the film and into the electrometer cup, where the charge acquired by the beads is measured. From this quantity and the weight of the beads the charge to mass ratio is calculated. This quantity is a direct measure of the triboelectric charging capacity of the polymeric film. The measurement is done at constant relative humidity and -temper-ature. Since triboelectric measurements are relative, the measurements should, for comparative purposes, be conducted under substantially identical conditions.
EXAMPLE I
Correlation of molecular structure and tribo-elec-tric behavior in polymeric systems is of practical importance when considering toner candidates and such is demonstrated herein. Thus, a polymeric system based on a :
- , .
~07~7~i polystyrene series, chosen for accessibili-ty and simplicit~, having the generic structure:
wherein X may be ~I, t-C4Hg, Br, CH2Cl, N02, and C~l3was studied. Po]y(p-nitrostyrene), where X = N02, was synthesized from polystyrene by nitration; poly(p bromostyrene), where X = Br, was prepared from polystyrene by using bromine/thallium acetate; poly(p-chloromethylstyrene), where X = CH2Cl9 was prepared by polymerization of the corresponding monomer; and poly~p-methylstyrene), where X = CH3was formed from the polystyrene, X = CH2Cl by reductive dehalogenation with lithium aluminum hydride. Films of the polymers were cast onto aluminum sheets from tetrahydrofuran solution except that poly(p-nitrostyrene) was cast from dimethylformamide.
The films were dried for about fifteen hours in vacuo at about 60C and then transferred without exposure to moist ~, air to a dry box maintained at zero relative humidity. Zinc carrier beads were similarly dried for about fifteen hours in vacuo at about 120C and transferred. Cascade triboelectric measurements were conducted using an angle of about 30 C, a drop height of about 1 cm, and a film length of about nine inches. The humidity was raised to successive constant ~ , levels by use of saturated salt solutions. The films and carrier beads were equilibrated at each relative humidity condition for about twenty hours prior to triboelectric charging measurement. The results indicate that with :- :
increased electron withdrawing power of the substituent -there is an accompanying increase in the amount of negative charge ~ -: ' : . . . . ~ .
1~737;:2~
generated on the film. In the present examples the electron withdrawing power of -the substituents increases in the following order: t - C4Hg ~CH3 ~H ~CH2Cl <Br ~N02. Though both carrier beads and films may be affected by moisture, the slope of a line at a given relative humidity is a function only of the materials since the same carrier is used for each film. These results indicate a practical means of predicting the relative triboelectric behavior of polymers which are substituted in the aromatic moiety, such as pre-dictably increasing the negative charging property of the polymer. While the triboelectric charging property of mix-tures and copolymers is not generally linear with composition it is a linear function of the extent of reac-tion for chemical modifications as shown in the following table.
Zinc Carrier Bead Charge In _ X Nano-Coulombs/gram at ~3% Relative Humidity t-C4H9 +0.13 CH3 +0.19 H +0.30 CH2Cl +0.70 -~r +1.1 2 +4-7 ' EXAMPLE II
To a solution of about 40 ml of concentrated nitric acid and about 40 ml of concentrated sulfuric acid were added with stirring about 62.5 grams of a styrene-n-butyl methacrylate copolymer (2.54:1.00 mole ratio) at such a rate that the tempera-ture did not exceed 30 C. The mixture was then allowed to stand for about 2 hours, then poured into water and fil-trated.
. . - . .
; J ' ~ " . '. '` `` ' '' ` ' ' ~;373~Z6 The solid was washed wi-th water, dissolvecl in tetrahydrof`uran and reprecipitated by dropwise addi-tion to water. This latter step was repeated several times and then the solid was vacuum dried. Elemental analysis showed about 42 percent nitration of available phenyl groups. Films were cast from solution onto aluminum plates and thorougly dried. 250 micron steel beads acquired a charge of -~0.1 nano-coulombs/gram when cascaded down this film. The starting copolymer causes these beads to acquire about -0.29 nano-coulombs per gram. Therefore, nitration of the polymer markedly increases its negative charging capacity.
EXAMPLE III
To a mixture of about 14.7 g of styrene-n-butyl meth-acrylate copolymer (2.54:1.00 mole ratio) is about 250 ml -of acetic anhydride was added with stirring about 53.0g of Cu(N03)2. 3H20 at such a rate that the temperature did not exceed 70 C. The mixture was heated momentarily on a steam bath and then kept at about 70 C for about 1.5 hours. The mixture was poured into water and filtered. ~he solid was washed with i water and saturated sodium bicarbonate. It was dissolved in `~
tetrahydrofuran and precipitated into an aqueous solution of ethylenedinitrilotetraacetic acid disodium salt. It was then ~
successively precipitated from tetrahydrofuran solution into `
aqueous sodium bicarbonate and several times into water. It was then dried in vacuo. Elemental analysis indicated that ;
about 42 percent of the available phenyl groups were nitrated, ~;
while about 50 percent of the phenyl groups were oxidized. A
film was cast from solution onto an aluminum plate and dried thorough-ly Against this film 250 micron steel beads acquired a charge of about +2 nano-coulombs per gram. Steel beads (250 microrl) coated with chlorinated polypropylene, which is very '1.~737Z6 near the bottom of -the triboelectric series and hence with most materials causes these beads to acquire very large negative charges, e.g., with the starting styrene-n-butyl methacrylate (2.54:1.00 mole ratio) copolymer about -2.2 nano-coulombs per gram, take on a charge of abou-t +0.~ nano-coulombs per gram.
Thus, the nitrated/oxidized polymer acquires a much higher nega-tive charge than the nitrated polymer and is even lower in the triboelectric series than chlorinated polypropylene.
EXAMPLE IV
A mixture o-f' about 35.5 grams of styrene-n-butyl methacrylate copolymer (2.54:1.00 mole ratio), about 9.06 grams of thallic acetate sesquihydrate and about 200 ml carbon tetrachloride was stirred for about 18 hours at about 25 . Then about 38.8 grams of bromine was added over about 1.5 hours with stirring. The mixture was stirred for about 6 hours and then heated under reflux for about 12 hours. The mixture was then poured into methanol and filtered. The dried polymer was precipitated from tetrahydrofuran successively with aqueous sodium bisulfite, twice from aqueous sodium bicarbonate, twice from water and once from methanol and dried in vacuo. Elemental analysis showed the presence of about 1.1 bromine atoms per phenyl gro~p. A film was cast from solution onto an aluminum plate and thoroughly dried. Using the cascade device 250 micron steel beads acquired a charge of about +0.95 nano-coulombs per gram vs this film. With the parent copolymer, 250 micron steel beads acquire a charge of about -0.29 nano-coulombs per gram. Thus, the .
bromination of the polymer substantially increases its propen-sity for negative charging.
Although specific components, proportions and pro-cedures have been stated in the above description of the ~ . .
.
~737;2 ~
preferrecl embodiments of -the novel -toner compositions, other suitable components, proportions and procedures as listed above may be used with similar results. Further, other materials and procuedures may be employed to synergize, enhance or other-wise modify the novel system.
Other modifications and ramifications of the present invention will appear to those skilled in the art upon the reading of this disclosure. These are intended to be included within the scope of this invention. ~ , .' ~ . .
'. . , :
. ' ~ ' ::: . - : -
Claims (18)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electrostatographic developer composition for use in developing electrostatic latent images on a recording surface, the developer composition being comprised of a toner material and a carrier material; the toner material having an average particle diameter of less than about 30 microns and consisting essentially of a colorant and a polymer having aromatic moieties selected from the group consisting of styrene alkyl methacrylates and styrene alkyl acrylates;
the carrier material containing carrier particles having an average particle diameter of between 50 microns and about 1,000 microns, each of the carrier particles comprising a core surrounded by an outer coating in the amount of from 0.1 percent to about 10 percent by weight based on the weight of the carrier particles, the outer coating consisting essentially of a functionalized polymer selected from the group consisting of styrene alkyl methacrylates and styrene alkyl acrylates, the polymer for both the toner and the carrier being obtained by the systematic chemical alteration of the aromatic moieties of the polymer by nitration, halo-genation, acylation, or alkyl substitution to thereby provide toner and carrier particles characterized as having closely controlled triboelectric charging properties.
the carrier material containing carrier particles having an average particle diameter of between 50 microns and about 1,000 microns, each of the carrier particles comprising a core surrounded by an outer coating in the amount of from 0.1 percent to about 10 percent by weight based on the weight of the carrier particles, the outer coating consisting essentially of a functionalized polymer selected from the group consisting of styrene alkyl methacrylates and styrene alkyl acrylates, the polymer for both the toner and the carrier being obtained by the systematic chemical alteration of the aromatic moieties of the polymer by nitration, halo-genation, acylation, or alkyl substitution to thereby provide toner and carrier particles characterized as having closely controlled triboelectric charging properties.
2. An electrostatographic developer composition according to claim 1 wherein the styrene portion of the polymer of said carrier material has the generic structure where X may be t-C4H9, Br, CH2C1, NO2 and CH3.
3. An electrostatographic developer composition according to claim 1 wherein the styrene portion of the polymer of said toner material has the generic structure where X may be H, t-C4H9, Br, CH2Cl, NO2, and CH3.
4. An electrostatographic developer composition in accordance with claim 1 or 2 wherein said systematic chemical alteration of the aromatic moieties of said polymer of said carrier material has been controlled stoichiometrically so as to provide carrier particles having closely controlled triboelectric properties.
5. An electrostatographic developer composition in accordance with claim 1 or 2 wherein said systematic chemical alteration of the aromatic moieties of said polymer of said carrier material has been controlled kinetically so as to provide carrier particles having closely controlled tribo-electric properties.
6. An electrostatographic developer composition in accordance with claim 1 wherein said polymer contains electron releasing groups in said aromatic moieties.
7. An electrostatographic developer composition in accordance with claim 1 or 2 wherein said core is metallic.
8. An electrostatographic developer composition in accordance with claim 1 or 3 wherein said polymer of said toner material consists essentially of a vinyl resin having a melting point of at least about 110°F.
9. An electrostatographic developer composition in accordance with claim 1 or 3 wherein said polymer of said toner material consists essentially of a vinyl resin having a melting point of at least about 110°F, said vinyl resin having a weight average molecular weight between about 3,000 to about 500,000.
10. An electrostatographic developer composition in accordance with claim 1 or 3 wherein said toner particles have a blocking temperature of at least about 110°F and a melt viscosity of less than about 2.5 x 10-4 poise at temperatures of up to about 450°F.
11. An electrostatographic developer composition in accordance with claim 1 or 3 wherein said colorant is selected from the group consisting of pigments and dyes.
12. An electrostatographic developer composition in accordance with claim 1 or 3 wherein said colorant is present in said toner particles in an amount of from about 1 percent to about 20 percent by weight based on the weight of said toner particles.
13. An electrostatographic developer composition in accordance with claim 1 or 3 wherein said systematic chemical alteration of the aromatic moieties of said polymer of said toner particles has been controlled stoichiometrically.
14. An electrostatographic developer composition in accordance with claim 1 or 3 wherein said systematic chemical alteration of the aromatic moieties of said polymer of said toner particles has been controlled kinetically.
15. An electrostatographic developer composition in accordance with claim 1 wherein said polymer of said toner particles contains electron withdrawing groups in said aromatic moieties.
16. An electrostatographic developer composition in accordance with claim 1 or 3 wherein said polymer of said toner particles consists essentially of styrene-n-butyl methacrylate.
17. An electrostatographic developer composition in accordance with claim 6 wherein said electron releasing groups are selected from the group consisting of methyl, t-butyl, alkoxy and alkylthio.
18. An electrostatographic developer composition in accordance with claim 15 wherein said electron withdrawing groups are selected from the group consisting of halogen, chloromethyl and acyl.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US50077874A | 1974-08-26 | 1974-08-26 | |
| US50077174A | 1974-08-26 | 1974-08-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1073726A true CA1073726A (en) | 1980-03-18 |
Family
ID=27053635
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA230,774A Expired CA1073726A (en) | 1974-08-26 | 1975-07-04 | Developer composition containing styrene alkyl acrylate or methacrylate polymer with chemically altered aromatic groups |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5146948A (en) |
| CA (1) | CA1073726A (en) |
| DE (1) | DE2529993A1 (en) |
| FR (1) | FR2283469A1 (en) |
| GB (1) | GB1525704A (en) |
| NL (1) | NL7510081A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7749672B2 (en) | 2006-12-21 | 2010-07-06 | Xerox Corporation | Polyester toner compositions |
-
1975
- 1975-07-04 CA CA230,774A patent/CA1073726A/en not_active Expired
- 1975-07-04 DE DE19752529993 patent/DE2529993A1/en not_active Withdrawn
- 1975-08-19 JP JP50100587A patent/JPS5146948A/ja active Pending
- 1975-08-22 GB GB3494675A patent/GB1525704A/en not_active Expired
- 1975-08-26 NL NL7510081A patent/NL7510081A/en not_active Application Discontinuation
- 1975-08-26 FR FR7526290A patent/FR2283469A1/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| FR2283469A1 (en) | 1976-03-26 |
| JPS5146948A (en) | 1976-04-22 |
| NL7510081A (en) | 1976-03-01 |
| DE2529993A1 (en) | 1976-03-11 |
| GB1525704A (en) | 1978-09-20 |
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