CA1077325A - Toner and/or carrier consisting of polymer with silylated, active hydrogen containing constituents - Google Patents
Toner and/or carrier consisting of polymer with silylated, active hydrogen containing constituentsInfo
- Publication number
- CA1077325A CA1077325A CA230,992A CA230992A CA1077325A CA 1077325 A CA1077325 A CA 1077325A CA 230992 A CA230992 A CA 230992A CA 1077325 A CA1077325 A CA 1077325A
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- CA
- Canada
- Prior art keywords
- carrier
- toner
- polymer
- particles
- accordance
- Prior art date
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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
-
- 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
- G03G9/10—Developers with toner particles characterised by carrier particles
- G03G9/113—Developers with toner particles characterised by carrier particles having coatings applied thereto
- G03G9/1132—Macromolecular components of coatings
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- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- General Physics & Mathematics (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 active hydrogen containing materials by silylation. The controlled variation of the triboelectric behavior of functional polymers by silylation provides a means of attaining optimum triboelectric responses in develop-ment 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 active hydrogen containing materials by silylation. The controlled variation of the triboelectric behavior of functional polymers by silylation provides a means of attaining optimum triboelectric responses in develop-ment systems.
Description
1~77;~;~5 BACI~ OUND OF '~ INvrJNr[lIoN
This invention relates in general to imaging systems and more par~icularly to im~roved elec~rostatoyraphic developer mixtures ~or use in such systems.
The formation and development of imayes on the surface of photoconductive materials by electrostatograpl~ic means is known. The basic elec-trostatographic process, as taught by C. F. Carlson in U. S. Patent 2,297,691, involves placing a uniform electrostatic charge on a photoconductive insulating layer, exposing the layer to a light and shadow image to dissi-pate the charge on the areas of the layer e~posed to the light, and developing the resultant electrostatic latent image by depositing on the image a finely-divided elec-troscopic 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. ~. Wise in U~ S. Patent 2,618,582, is known as "easeade" development. In this method, developer material comprising relatively large carrier particles having finely-dividecl toner particles electrostatically elinging to the surfaee of the carrier partieles in eonveyed to and rolled or eascaded across the surface bearing the electrostatic latent image. The charged portions of the surfaee have a eharge of the same polarity as, but stronger than, the earrier particles.
--2-- ~ `?
~0'77~'~5 Toncr and carrier particles havincJ opposi~e polarities are selec-ted so that -the toner par~iclcs electros~a~ically cliny to the carrier particlcs. In order to develop a ne~ativel~
charged electros-tatic latent image, a toner and carrier com~
bination are selected in which -the toner is triboelectrically positive in relation to the toner. Conversely, to develop a positively charged electrostatic 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 ascerlding order 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 eascades 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 earrier 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 eommercial electrostatographic development technique.-~ A
general purpose office copying machine incorporating this technique is described in U. S. Patent 3,099,943.
Another technique for developing electrostatic latent images is the "magnetic brush" process as disclosed for e~ample, in U. S. Patent 2,874,063. In this process, a developer material ... ...
' ~ , , ' -3~5 COn~aillillCJ tOllC'~ and ma~JnctiC carrier particles is a-ttracted to an~ is carricd by a magnet. The magne-tlc Eield causcs align-ment o~ the mac3netic particles in the brush-like con~iguration when this ma~netic brush is brought into contact with an electrostatic laten-t imaqe-bearing surface, the toner particles are attracted from the carrier particles oE the brush to the charged areas of the image-bearing sur~ace but no-t 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 electrosta-tic latent images is disclosed in U. S. Patent 3,503,776 issued 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 sur-face. 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 transported along its arcuate pa-th, frictional contact between the developer and the imaging sur-face in the contact zone circulates the developer in the bath and brings developer material into developing configuration with the imaged surface.
Many other methods, such as the "touchdown" develop-ment method disclosed by C. R. Mayo in UO S. Patent 2,895,847, are known for applying electroscopic particles to the electro-static 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 1(~77;~25 a~d throu~Jh the widcsprc~d availabili-ty and u~lliza-tion of el~ctrost~togxaphic im~ing equipment.
In au-tomatic reproduction equipment, it is conventional to employ as the imaging plate a photoconductor on a conductive substrate in the form of a c~lindrical drum or a flexible belt ich is continuously rotated through a cycle of sequential oper-ations including charging, exposing, developing, transferring and cleaning. The developer chamber i9 charged with 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 defici-encies 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 electriflcation being governed in most cases by the distance between their relative positions in the tribo-electric series. ~owever, when otherwise compatible electro-scopic powder and carrier materials are removed from each other in the triboelectric series by too great a distance, the resulting 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 , . . .
:~L(3'7732~i in ~he immediately precedin~3 sentcnce may be improved by increasing toner concen-tration in the cleveloper mixture, unde-sirably high bac~round toner deposition as well as increased toner impaction and agglomeration is encountered when the developer mixture is over-toned. The initial electrostato-graphic plate charge may be increased 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 particles.
Excessively high electrostatographic plate charges are not only undesirable because of the high power consumption necessary to maintain the electrostatographic plate at high potentials, but also because the high potential causes the carrier particles to adhere to the electrostatographic plate surface rather than merely roll across and off the electrostatographic plate surface. Print deletion and massive carry-over of carrier particles often occur when carrier particles adhere to reusable electrostatographic imaging surfaces. Massive carrier carry-over problems are particu-larly acute when the developer is employed in solid area coverage machines where excessive quan-tities of toner particles are removed from carrier particles thereby leaving many carrier particles substantially bare of toner particles. Further, adherence o~
carrier particles to reusable electrostatographic imaging surfaces promotes the formation of undesirable scratches on 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 particles are unsuitable because they possess too high a tribo-electric value in addition uniform triboelectric surface characteristics of many carrier surfaces are di~ficult to achieve with Mass production techniques. Quality :::
~V 7 73~
images are, in some installces, allnost :impossible to obtain in high speed automatic maci~ines when carriers having non-uniform triboelectric properties are employed. Although it may be possible to alter the triboelectric value of an insulating carrier material by blending the carrier material with another insulating material having a triboelectric value remote from the triboelectric value of the original carrier material, relatively larger quantities of additional material are necessary to alter the tri~
boelectric value of the original carrier material. The addition of large quantities of material to the original carrier material to change the triboelectric properties thereof requires a major manufacturing operation and often undesirably alters the original physical characteristics of the carrier material. Further, it is highly desirable to control the triboelec-tric properties of carrier surfaces to accommodate the use of desirable toner compositions while retaining the other desirable physical charac-teristics of the carrier. The alteration o-f the triboelectric properties of 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 pos-sible to employ materials previously not suitable as a carrier. Thus, for example, a carrier 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. However, since most carrier coating materials are deficient in one or more of the above areas, there is a continuing need for improved electrostatographic carrier and developer compositions and methods for forming the same.
. . _ . . .
~773ZS
I~ is also apparc~ ~rom the description presented above as well as in other development techniques, that the toner is subjected to severe mechanical attrition which tends to break down the particles into undesirable dus-t fines. The formation of fines is retarded when the toner contains a tough, high molecular weight resin which is capable of withstanding the shear and impact forces imparted to the toner in the machine.
Unfortunately, many high molecular weight materials cannot be employed in high spced automatic machines because they cannot be rapidly fused during a powder image haat fixing step. On the other hand, low molecular weight resins which are easily heat fused at relatively low temperatures are usually undesir-able because these materialstend to form thick films on reusable photoconductor surfaces. These films tend to cause image de-gradation and contribute to machine maintenance down time.
Many low molecular weight resins decompose when subjected 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 of-ten offset to other adjacent sheets. Additionally, low molecular weight resins are often extremely difficult or even impossible to comminute in conventional grinding apparatus. Also, ihe toner materials must bè capable of accepting a charge of the correct polarity when brought into rubbing contact with the surface of carrier materials in cascade or touchdown development systems. Additionally, many toner materials cannot satisfactor-ily be transferred by conventional electrostatographic develop-ment systems from reusable imaging surfaces in automatic copy-ing and duplicating machines. Since most polymeric toner materials are deficient in one or more of the above areas, there is a continuing need for improved toners and developers.
.. . .
:
~l(37~73~5 n accordance with one aspect of this invention there is provided an electrostatographic developer composition for use in developing electros-tatic latent images on a recording surface, said developer composition comprising carrier particles and toner particles, characterized in that at least either the carrier or toner is a functionalized polymer obtained by the systematic chemical alteration of the active hydrogen contain-ing constituents of said polymer by silylation to provide particles having controlled triboelectric charging properties.
In accordance with another aspect of this invention there is provided an electrostatographic imaging process comprising the steps of providing an electrostatographic imaging member having a recording surface, forming an electro-static latent image on said recording surface, and contacting said electrostatic latent image with a developer mixture - comprising finely-divided toner particles electrostatically clinging to the surface of carrier particles having an average particle diameter of between about 50 microns and about 1,000 microns, at least one of either the toner or the carrier com-prising a functionalized polymer obtained by the systematic chemical alteration of the active hydrogen containing constitu-ents of said polymer by silylation to provide particles charac-terized as having controlled triboelectric charging properties, whereby at least a portion of said finely-divided toner particles are attracted to and deposited on said recording sur-face in conformance with said electrostatic latent image.
_g_ -' ' ~ - ~ '. , ~(37~73~5 By way of added explanation, in accordance with an dspect of this invention, chemical alteration of the tribo-electric charging potential of functional polymers employed as toner materials and carrier coating materials is controlled. The controlled vaxiation of the tribo-electric behavior of functional polymexs provides a means of attaining optimum triboelectric responses of electrostatographic developer materials for specifically defined applications. Thus, 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 active hydrogen containing materials such as alcohols, acids, phenols mercaptans, amines, amides, imines and the corresponding silyl derivatives. These relationships have been found to be extremely helpful in designing new toners and carrier materials. Ey this invention, the triboelectric charging properties of toner-carrier pairs are controlled to enable optimum triboelectric relationships in developer compositionsO
It is to be noted that, by itself, no material has a triboelectric charge. The magnitude of a triboelectric charge depends upon both the toner and the carrier material. Thus, replacement of one of the components to optimize triboelectric charging properties is generally necessary to provide the desired triboelectric response. By so doing, greater latitude is available for specific electrostatographic applications. In accordance with this invention, it has been found that by varying the degree of ~L~773~
chcmical moclification of pol~mcrlc matcrials Eor use as toner materials and/or carrier coating materials, either stoichiometrically or kinetically, the triboelectrie propcrties oE developer materials can be controlled in a continuous manner.
In electrostatographic development of selenium photo-conductor latent images, polymers which tend to take on a relatively high positive eharge are gencrally satisfaetory for use as carrier eoating materials and polymers whieh tend to take on a relatively high negative eharge are generally satisfaetory for use as toner materials;in electrostatographic development of other photoeonductor latent images, for example, zine oxide, phthalocyanine, cadmium sulfide and polyvinylearbazole-trinitroflurenone, the opposite is true. 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 triboeleetrie eharging seale determines the triboelectrie eharge between them, their relative positions determine the sign of the triboeleetrie eharge. Those materials low on the scale prefer to adopt a positive eharge and those materials high on the scale prefer to adopt a negative charge. Appropriate toner-carrier pairs ean be seleeted based on their triboeleetrie eharging or triboeleetric series relationship to satisfy a particular acceptable triboelectrie eharging range requirement for a given electrostatographic machine developer housing.
It has been found that triboelectrie behavior is a funetion of molecular strueture whieh now allows the controlled and progressive modification of the triboelectrie eharging properties of ~oner and carrier compositions so as to obtain optimum triboelectric eharging properties between toner and earrier pairs.
. ;.
::;
773'~
Thus, by this invelltion, adjustment o~ the tri~oelectric charging properties of electrostatographic developer rnatcrials need not be in stepwise fashion but may be accomplished in a continuous manner providing a high degree of "fine tuning" of triboelectric properties for developer materials.
In accordance with this invention, the triboelectric charging properties of monomeric and polymeric compounds may be modified by systematic chemical modification by means of silylation.
This chemical process leads to changes in the triboelectric behavior of active hydrogen containiny materials. The process also allows for controlled variation of triboelectric behavior of carrier materials in a continuous fashion. Thus, silylation of hydroxyl moieties of polymeric materials is a means of obtaining such effect.
Generally speaking, the passing of a silylating reagent in a stream of inert gas through a solid bed of hydroxylic material accomplishes silylation. The depth or amount of silylation will depend, to some extent, on the permeability of the silylation reagent through solid.
For some toner and carrier material applications, surface reaction may be sufficient. In addition, solution silylation of the solid may be practiced. Silylation reactions in solution will generally lead to more homogeneous reaction which may be advantageous for some toner and/or carrier applications. In either case, the degree of silylation may be controlled either stoichiome-trically or kinetically, making available a continuous range of toner and carrier materials having controlled various triboelectric properties. Further, this invention is not limited to the silylation of hydroxyl moieties of polymer materials, but extends as well to the silylation of other active hydrogen containing compounds such as alcohols, carboxylic acids, phenols, mercaptans, amines, amides, imines, selenols, thiophenols, and the like. Thus, this invention provides a means of 1C3'7'73~5 ef~c~ing mon.i~ored si.li.con a~di~ions to pol~neric materials by the addition of organic silicon moieties to effect desired an~
controlled triboelectric properties thereto. The si.Licon units may be introduced either as terminal g.roups or as block copolymer components. Therefore, this method affords a means for systemati-cally varying the triboelectric charging relationship of toner-carrier developer compositions by either surface treatment of the materials or by chemical modification of toner and/or carrler materials prior to their fabrication to provide controlled tribo-electric behavior of such materials.
It has been further found that for aliphatic hydroxyls, silylation causes the material to accept more negative tribo-electric charge. Thus, for either a particular toner or carrier material candidate, the desired negative triboelectric charge will be improved. Some of the advantages here include the facile reaction of solid hydroxylic substrates with gaseous silylation reagents which occurs readily. In addition, the conversion of hydroxyl moieties of silyl ether moieties may be controlled in a continuous fashion thus allowing the "fine tuning" of triboelectric properties of developer compositions. For materials containing aromatic hydroxyls, silylation causes the material to accept more positive, that is less negative, charge in triboelectric charging.
Thus, silylation will decrease the negative charge on toners or carrier materials of such structure. Thus, the invention may be employed to increase or decrease the net triboelectric charge to the requisite level for toner-carrier pairs.
In general, any method such as for preparing silyl ethers is wi~hin the scope of this invention. Any suitable silylating agent may be employed to obtain the functionalized carrier materials of this invention. Typical silylating agents include dimethlamino-, ~L~'773;~5 trimcthylsil~ne, trimetllyL- and dimeth~l cl~lorosi:lalles and polysiloxane~ witll reactive terminal moie~ies.
Further, ~he use of dilunctional silylating agents may lead to crosslinkirlg which in some app~ications particularly carriers and carrier co~tings would be advantageous.
The chemical modifica~ion oE such materials enables the alteration of materials having optimum physical properties in such a way as to improve their triboelectric properties for electrostatographic use. This invention may serve as a guide for the preparation of developer compositions having "finely-tuned" triboelectric charging properties, and the capacity for continuous control of such properties through variation in extent of reaction may be employed for such purpose.
In regard to triboelectric response, particularly with regard to carrier materials, it is to be noted that materials such as those derived ~y silylation of styrene-methacrylate co-polymers provide excellent carrier coatings, especially in view of their crosslinkability. By the use of such materials, toners that previously provided unacceptable triboelectric response with conventional carriers now function properly. Thus, the coating of carrier cores, for example, metallic beads, with functionaliæed polymers containing a crosslinking agent provides carrier materials which in addition to improved toughness, the triboelectric pro-perties 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 hydroxy or amino functionalized polymers and crosslinking these materials via re-action of the pendant hydroxyl or amino moieties with a crosslinking agent such as a di~unctional silylating agent provides a means of continuous control of the trikoelectric properties of the coated ' :1(33'7~7;~5 carriers. In ~cklition, tile use oE diEunctional silylating ayents leads t:o crosslillkincJ whicll is advanta~eous as to the abrasion~
resisl:ant properties of th~ carrier coating material. It has been found that as the degree of conversion increases, the capacity for positive triboelectric charging deereases. In addition, the degree of eonversion can be controlled stoichiometrically. ~hus various hydro~yl or amino containing polymers exhibit similar effects. It is to be noted that it is not necessary for the polymer material to be crosslinked to observe a change in the triboelectric charging properties since the change in triboelectrie eharging is not due to molecular weight change. Monofunctional reagents have been found to bring about similar changes. When a earrier coating material of such structure is silylated, it will eause a given toner material to acquire a lower negative charge then the same unsilylated coated carrier.
Any suitable carrier coating material may be chemically modified in accordance with this invention to control the trlbo-electrie properties of the coated carrier. Typical carrier coating materials include styrene-acrylate-organosilicon terpolymers, polyvinyl alcohol, polyvinyl butyral, polyamides such as poly-eaprolactam and polyhexamethylene adipamide; polyurethanes; thermo-setting resins including phenolic resins such as phenol-iorma:Ldehyde, phenol-furfural and resorcinol formaldehyde; amino resins such as urea-formaldehyde and melamineformaldehyde; polymeric acids, alcohols;
and the like. Many of the foregoing and other typical carrier eoating materials are described by L. E. Walkup in U. S. Patent
This invention relates in general to imaging systems and more par~icularly to im~roved elec~rostatoyraphic developer mixtures ~or use in such systems.
The formation and development of imayes on the surface of photoconductive materials by electrostatograpl~ic means is known. The basic elec-trostatographic process, as taught by C. F. Carlson in U. S. Patent 2,297,691, involves placing a uniform electrostatic charge on a photoconductive insulating layer, exposing the layer to a light and shadow image to dissi-pate the charge on the areas of the layer e~posed to the light, and developing the resultant electrostatic latent image by depositing on the image a finely-divided elec-troscopic 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. ~. Wise in U~ S. Patent 2,618,582, is known as "easeade" development. In this method, developer material comprising relatively large carrier particles having finely-dividecl toner particles electrostatically elinging to the surfaee of the carrier partieles in eonveyed to and rolled or eascaded across the surface bearing the electrostatic latent image. The charged portions of the surfaee have a eharge of the same polarity as, but stronger than, the earrier particles.
--2-- ~ `?
~0'77~'~5 Toncr and carrier particles havincJ opposi~e polarities are selec-ted so that -the toner par~iclcs electros~a~ically cliny to the carrier particlcs. In order to develop a ne~ativel~
charged electros-tatic latent image, a toner and carrier com~
bination are selected in which -the toner is triboelectrically positive in relation to the toner. Conversely, to develop a positively charged electrostatic 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 ascerlding order 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 eascades 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 earrier 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 eommercial electrostatographic development technique.-~ A
general purpose office copying machine incorporating this technique is described in U. S. Patent 3,099,943.
Another technique for developing electrostatic latent images is the "magnetic brush" process as disclosed for e~ample, in U. S. Patent 2,874,063. In this process, a developer material ... ...
' ~ , , ' -3~5 COn~aillillCJ tOllC'~ and ma~JnctiC carrier particles is a-ttracted to an~ is carricd by a magnet. The magne-tlc Eield causcs align-ment o~ the mac3netic particles in the brush-like con~iguration when this ma~netic brush is brought into contact with an electrostatic laten-t imaqe-bearing surface, the toner particles are attracted from the carrier particles oE the brush to the charged areas of the image-bearing sur~ace but no-t 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 electrosta-tic latent images is disclosed in U. S. Patent 3,503,776 issued 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 sur-face. 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 transported along its arcuate pa-th, frictional contact between the developer and the imaging sur-face in the contact zone circulates the developer in the bath and brings developer material into developing configuration with the imaged surface.
Many other methods, such as the "touchdown" develop-ment method disclosed by C. R. Mayo in UO S. Patent 2,895,847, are known for applying electroscopic particles to the electro-static 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 1(~77;~25 a~d throu~Jh the widcsprc~d availabili-ty and u~lliza-tion of el~ctrost~togxaphic im~ing equipment.
In au-tomatic reproduction equipment, it is conventional to employ as the imaging plate a photoconductor on a conductive substrate in the form of a c~lindrical drum or a flexible belt ich is continuously rotated through a cycle of sequential oper-ations including charging, exposing, developing, transferring and cleaning. The developer chamber i9 charged with 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 defici-encies 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 electriflcation being governed in most cases by the distance between their relative positions in the tribo-electric series. ~owever, when otherwise compatible electro-scopic powder and carrier materials are removed from each other in the triboelectric series by too great a distance, the resulting 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 , . . .
:~L(3'7732~i in ~he immediately precedin~3 sentcnce may be improved by increasing toner concen-tration in the cleveloper mixture, unde-sirably high bac~round toner deposition as well as increased toner impaction and agglomeration is encountered when the developer mixture is over-toned. The initial electrostato-graphic plate charge may be increased 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 particles.
Excessively high electrostatographic plate charges are not only undesirable because of the high power consumption necessary to maintain the electrostatographic plate at high potentials, but also because the high potential causes the carrier particles to adhere to the electrostatographic plate surface rather than merely roll across and off the electrostatographic plate surface. Print deletion and massive carry-over of carrier particles often occur when carrier particles adhere to reusable electrostatographic imaging surfaces. Massive carrier carry-over problems are particu-larly acute when the developer is employed in solid area coverage machines where excessive quan-tities of toner particles are removed from carrier particles thereby leaving many carrier particles substantially bare of toner particles. Further, adherence o~
carrier particles to reusable electrostatographic imaging surfaces promotes the formation of undesirable scratches on 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 particles are unsuitable because they possess too high a tribo-electric value in addition uniform triboelectric surface characteristics of many carrier surfaces are di~ficult to achieve with Mass production techniques. Quality :::
~V 7 73~
images are, in some installces, allnost :impossible to obtain in high speed automatic maci~ines when carriers having non-uniform triboelectric properties are employed. Although it may be possible to alter the triboelectric value of an insulating carrier material by blending the carrier material with another insulating material having a triboelectric value remote from the triboelectric value of the original carrier material, relatively larger quantities of additional material are necessary to alter the tri~
boelectric value of the original carrier material. The addition of large quantities of material to the original carrier material to change the triboelectric properties thereof requires a major manufacturing operation and often undesirably alters the original physical characteristics of the carrier material. Further, it is highly desirable to control the triboelec-tric properties of carrier surfaces to accommodate the use of desirable toner compositions while retaining the other desirable physical charac-teristics of the carrier. The alteration o-f the triboelectric properties of 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 pos-sible to employ materials previously not suitable as a carrier. Thus, for example, a carrier 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. However, since most carrier coating materials are deficient in one or more of the above areas, there is a continuing need for improved electrostatographic carrier and developer compositions and methods for forming the same.
. . _ . . .
~773ZS
I~ is also apparc~ ~rom the description presented above as well as in other development techniques, that the toner is subjected to severe mechanical attrition which tends to break down the particles into undesirable dus-t fines. The formation of fines is retarded when the toner contains a tough, high molecular weight resin which is capable of withstanding the shear and impact forces imparted to the toner in the machine.
Unfortunately, many high molecular weight materials cannot be employed in high spced automatic machines because they cannot be rapidly fused during a powder image haat fixing step. On the other hand, low molecular weight resins which are easily heat fused at relatively low temperatures are usually undesir-able because these materialstend to form thick films on reusable photoconductor surfaces. These films tend to cause image de-gradation and contribute to machine maintenance down time.
Many low molecular weight resins decompose when subjected 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 of-ten offset to other adjacent sheets. Additionally, low molecular weight resins are often extremely difficult or even impossible to comminute in conventional grinding apparatus. Also, ihe toner materials must bè capable of accepting a charge of the correct polarity when brought into rubbing contact with the surface of carrier materials in cascade or touchdown development systems. Additionally, many toner materials cannot satisfactor-ily be transferred by conventional electrostatographic develop-ment systems from reusable imaging surfaces in automatic copy-ing and duplicating machines. Since most polymeric toner materials are deficient in one or more of the above areas, there is a continuing need for improved toners and developers.
.. . .
:
~l(37~73~5 n accordance with one aspect of this invention there is provided an electrostatographic developer composition for use in developing electros-tatic latent images on a recording surface, said developer composition comprising carrier particles and toner particles, characterized in that at least either the carrier or toner is a functionalized polymer obtained by the systematic chemical alteration of the active hydrogen contain-ing constituents of said polymer by silylation to provide particles having controlled triboelectric charging properties.
In accordance with another aspect of this invention there is provided an electrostatographic imaging process comprising the steps of providing an electrostatographic imaging member having a recording surface, forming an electro-static latent image on said recording surface, and contacting said electrostatic latent image with a developer mixture - comprising finely-divided toner particles electrostatically clinging to the surface of carrier particles having an average particle diameter of between about 50 microns and about 1,000 microns, at least one of either the toner or the carrier com-prising a functionalized polymer obtained by the systematic chemical alteration of the active hydrogen containing constitu-ents of said polymer by silylation to provide particles charac-terized as having controlled triboelectric charging properties, whereby at least a portion of said finely-divided toner particles are attracted to and deposited on said recording sur-face in conformance with said electrostatic latent image.
_g_ -' ' ~ - ~ '. , ~(37~73~5 By way of added explanation, in accordance with an dspect of this invention, chemical alteration of the tribo-electric charging potential of functional polymers employed as toner materials and carrier coating materials is controlled. The controlled vaxiation of the tribo-electric behavior of functional polymexs provides a means of attaining optimum triboelectric responses of electrostatographic developer materials for specifically defined applications. Thus, 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 active hydrogen containing materials such as alcohols, acids, phenols mercaptans, amines, amides, imines and the corresponding silyl derivatives. These relationships have been found to be extremely helpful in designing new toners and carrier materials. Ey this invention, the triboelectric charging properties of toner-carrier pairs are controlled to enable optimum triboelectric relationships in developer compositionsO
It is to be noted that, by itself, no material has a triboelectric charge. The magnitude of a triboelectric charge depends upon both the toner and the carrier material. Thus, replacement of one of the components to optimize triboelectric charging properties is generally necessary to provide the desired triboelectric response. By so doing, greater latitude is available for specific electrostatographic applications. In accordance with this invention, it has been found that by varying the degree of ~L~773~
chcmical moclification of pol~mcrlc matcrials Eor use as toner materials and/or carrier coating materials, either stoichiometrically or kinetically, the triboelectrie propcrties oE developer materials can be controlled in a continuous manner.
In electrostatographic development of selenium photo-conductor latent images, polymers which tend to take on a relatively high positive eharge are gencrally satisfaetory for use as carrier eoating materials and polymers whieh tend to take on a relatively high negative eharge are generally satisfaetory for use as toner materials;in electrostatographic development of other photoeonductor latent images, for example, zine oxide, phthalocyanine, cadmium sulfide and polyvinylearbazole-trinitroflurenone, the opposite is true. 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 triboeleetrie eharging seale determines the triboelectrie eharge between them, their relative positions determine the sign of the triboeleetrie eharge. Those materials low on the scale prefer to adopt a positive eharge and those materials high on the scale prefer to adopt a negative charge. Appropriate toner-carrier pairs ean be seleeted based on their triboeleetrie eharging or triboeleetric series relationship to satisfy a particular acceptable triboelectrie eharging range requirement for a given electrostatographic machine developer housing.
It has been found that triboelectrie behavior is a funetion of molecular strueture whieh now allows the controlled and progressive modification of the triboelectrie eharging properties of ~oner and carrier compositions so as to obtain optimum triboelectric eharging properties between toner and earrier pairs.
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773'~
Thus, by this invelltion, adjustment o~ the tri~oelectric charging properties of electrostatographic developer rnatcrials need not be in stepwise fashion but may be accomplished in a continuous manner providing a high degree of "fine tuning" of triboelectric properties for developer materials.
In accordance with this invention, the triboelectric charging properties of monomeric and polymeric compounds may be modified by systematic chemical modification by means of silylation.
This chemical process leads to changes in the triboelectric behavior of active hydrogen containiny materials. The process also allows for controlled variation of triboelectric behavior of carrier materials in a continuous fashion. Thus, silylation of hydroxyl moieties of polymeric materials is a means of obtaining such effect.
Generally speaking, the passing of a silylating reagent in a stream of inert gas through a solid bed of hydroxylic material accomplishes silylation. The depth or amount of silylation will depend, to some extent, on the permeability of the silylation reagent through solid.
For some toner and carrier material applications, surface reaction may be sufficient. In addition, solution silylation of the solid may be practiced. Silylation reactions in solution will generally lead to more homogeneous reaction which may be advantageous for some toner and/or carrier applications. In either case, the degree of silylation may be controlled either stoichiome-trically or kinetically, making available a continuous range of toner and carrier materials having controlled various triboelectric properties. Further, this invention is not limited to the silylation of hydroxyl moieties of polymer materials, but extends as well to the silylation of other active hydrogen containing compounds such as alcohols, carboxylic acids, phenols, mercaptans, amines, amides, imines, selenols, thiophenols, and the like. Thus, this invention provides a means of 1C3'7'73~5 ef~c~ing mon.i~ored si.li.con a~di~ions to pol~neric materials by the addition of organic silicon moieties to effect desired an~
controlled triboelectric properties thereto. The si.Licon units may be introduced either as terminal g.roups or as block copolymer components. Therefore, this method affords a means for systemati-cally varying the triboelectric charging relationship of toner-carrier developer compositions by either surface treatment of the materials or by chemical modification of toner and/or carrler materials prior to their fabrication to provide controlled tribo-electric behavior of such materials.
It has been further found that for aliphatic hydroxyls, silylation causes the material to accept more negative tribo-electric charge. Thus, for either a particular toner or carrier material candidate, the desired negative triboelectric charge will be improved. Some of the advantages here include the facile reaction of solid hydroxylic substrates with gaseous silylation reagents which occurs readily. In addition, the conversion of hydroxyl moieties of silyl ether moieties may be controlled in a continuous fashion thus allowing the "fine tuning" of triboelectric properties of developer compositions. For materials containing aromatic hydroxyls, silylation causes the material to accept more positive, that is less negative, charge in triboelectric charging.
Thus, silylation will decrease the negative charge on toners or carrier materials of such structure. Thus, the invention may be employed to increase or decrease the net triboelectric charge to the requisite level for toner-carrier pairs.
In general, any method such as for preparing silyl ethers is wi~hin the scope of this invention. Any suitable silylating agent may be employed to obtain the functionalized carrier materials of this invention. Typical silylating agents include dimethlamino-, ~L~'773;~5 trimcthylsil~ne, trimetllyL- and dimeth~l cl~lorosi:lalles and polysiloxane~ witll reactive terminal moie~ies.
Further, ~he use of dilunctional silylating agents may lead to crosslinkirlg which in some app~ications particularly carriers and carrier co~tings would be advantageous.
The chemical modifica~ion oE such materials enables the alteration of materials having optimum physical properties in such a way as to improve their triboelectric properties for electrostatographic use. This invention may serve as a guide for the preparation of developer compositions having "finely-tuned" triboelectric charging properties, and the capacity for continuous control of such properties through variation in extent of reaction may be employed for such purpose.
In regard to triboelectric response, particularly with regard to carrier materials, it is to be noted that materials such as those derived ~y silylation of styrene-methacrylate co-polymers provide excellent carrier coatings, especially in view of their crosslinkability. By the use of such materials, toners that previously provided unacceptable triboelectric response with conventional carriers now function properly. Thus, the coating of carrier cores, for example, metallic beads, with functionaliæed polymers containing a crosslinking agent provides carrier materials which in addition to improved toughness, the triboelectric pro-perties 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 hydroxy or amino functionalized polymers and crosslinking these materials via re-action of the pendant hydroxyl or amino moieties with a crosslinking agent such as a di~unctional silylating agent provides a means of continuous control of the trikoelectric properties of the coated ' :1(33'7~7;~5 carriers. In ~cklition, tile use oE diEunctional silylating ayents leads t:o crosslillkincJ whicll is advanta~eous as to the abrasion~
resisl:ant properties of th~ carrier coating material. It has been found that as the degree of conversion increases, the capacity for positive triboelectric charging deereases. In addition, the degree of eonversion can be controlled stoichiometrically. ~hus various hydro~yl or amino containing polymers exhibit similar effects. It is to be noted that it is not necessary for the polymer material to be crosslinked to observe a change in the triboelectric charging properties since the change in triboelectrie eharging is not due to molecular weight change. Monofunctional reagents have been found to bring about similar changes. When a earrier coating material of such structure is silylated, it will eause a given toner material to acquire a lower negative charge then the same unsilylated coated carrier.
Any suitable carrier coating material may be chemically modified in accordance with this invention to control the trlbo-electrie properties of the coated carrier. Typical carrier coating materials include styrene-acrylate-organosilicon terpolymers, polyvinyl alcohol, polyvinyl butyral, polyamides such as poly-eaprolactam and polyhexamethylene adipamide; polyurethanes; thermo-setting resins including phenolic resins such as phenol-iorma:Ldehyde, phenol-furfural and resorcinol formaldehyde; amino resins such as urea-formaldehyde and melamineformaldehyde; polymeric acids, alcohols;
and the like. Many of the foregoing and other typical carrier eoating materials are described by L. E. Walkup in U. S. Patent
2,618,551; B. B. Jaeknow et al in U. S. Patent 3,526,533; and R. J.
Hagenbach et al in U. S. Patents 3,533,835 and 3,658,500.
Any suitable eleetrostatographic carrier coating thickness may be emp~oyecl. However, a earrier coating having a thickness at ~_.
10~73Z5 lea;t suf~iciellt to ~orm a Lhill c~ntinuous film on thc carrier particle is preerrecl because ~he carr;er COatinCJ will then possess sufEicient thickness to resist abrasion and prevent pin-holes which adversely afect the triboelectric properties of the coatecl carri~r 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 ~n the weight of the coated carrier particles. Preferably, the carrier coating should comprise from about 0~1 percent to about 1.0 percent by weight based on the weight of the coated carrier particles 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 polymers, dyes, pigments, wetting agents and mixtures thereof may be mixed with the coating materials. An ultimate coated carrier particle having an average diameter between about 50 microns and about l,000 microns is preferred in cascade systems because the carrier particle then possess sufficient density -and inertia to avoid adherence to the electrostatic image during the cascade development process. Adherence of carrier particles to an electrostatographic drum is undesirable because of the formation of deep scratches on the drum surface during the image transfer and drum cleaning steps, particularly w~lere 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.
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 materials include sodium chloride, ammonium chloride, aluminum potassium chloriae, Rochelle salt, sodium nitrate, potassium chlorate, ~ranular zircon, granular silicon, mekhyl methacrylate, glass, silicon dioxide, ~lintshot, iron, steel, ferrite, nickel, Carborundum, and mixtures thereof.
Any suitable well-known toner material may be employed with the coated carriers of this invention as well as the toner materials prepared in accordance with this invention. Typical toner materials include gum copal, gum sandarac, rosin, cumaroneindene resin, asphaltum, gilsonite, phenolformaldehyde resins, rosin modified phenolformaldehyde resins, methacrylic resins, polystyrene resins, polypropylene resins, epoxy resins, polyethylene resins, polyester resins, and mixtures thereof. The particular toner material to be employed obviously depends upon the separatlon of the toner particles from the coated carrier in the triboelectric series and should be sufficient to cause the toner particles to electrostatically cling to the carrier surface. Among the patents describing electroscopic toner com-positions are U. S. Patent 2,659,670 to Copley; U. S. Patent 2,753,308 to Landrigan; U. S. Patent 3,079,342 to Insalaco; U. S.
Patent Reissue 25,136 to Carlson and U. S. Patent 2,788,288 to Rheinfrank et al. These toners generally have an average particle diameter between about 1 and 30 microns.
Any suitable photoconductive materials may be used together with the developer materials such as those disclosed in U. S. Patents 2,803,542 to Ullrich, U. S. Patent 2,970,906 to Bixby, U. S. Patent ~,121,006 to Middleton, U. S. Patent 3,121,007 to Middleton, and U. S. Patent 3,151,982 to Corrsin.
~ he surprisingly better results obtained with the electrostatographic coated carriers of this invention may be due to many factoxs. For example, the coated carriers of this invention possess smooth outer surfaces which are highly resistant to cracking, ~L~773Z5 cllippincJ, an~l fl~lkir~g. In c~scade clevelopmen~ syxtems, tlle smooth suriace en~ances tlle rolling action oE the carrier particles across the electrostatographic surfaces and reduce5 the tendency of carrier particles to adhere to tlle electrostatographic imaging surfaces.
When these coated carriers are employed in electrostatographic development systems, carrier liEe is unexpectedly extended particularly with respect to toner impaction resistance. Additionally the carrier coating materials of this invention appear to contribute to the stability of the triboelectric properties of the coated carrier over a wide relative humidity range. Because of their triboelectric properties, these carrier materials may be employed in reversal development of positively charged images. Further, the coa-ted carriers of this invention provide more uniform triboelectric characteristics than current carriers when employed in electrostato-graphic development systems. In addition, the coated carriers of this invention provide exceptionally good life performance, durability, copy ~uality, quality maintenance, less carrier bead sticking and agglomeration, and also provide improved abrasion resistance thereby minimizing carrier chipping and fla~ing. Further, the coated carriers of this invention provide triboelectric values such that they can be used with a wide variety of presently available toners in present electrostatographic processes, and retain a predictable triboelectric value. Thus the improved coated carrier particles of this invention have desirable properties which permit their wide use in presently available electrostatographic systems.
With regard particularly to the toner compositions of this invention, any suitable vinyl resin having a melting point of at least about llO~F may be employed. 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 ~77~25 ~he polymeriza~ion o~ mi~ures o~ two or more of these~ unsaturated monomers. ~le c~pression "addition polymerization" is intended to include known polymerization techniques such as free radical, anionic and cationic polymerization processes.
The combination o~ 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 4 poise at temperatures up to about 450F. ~hen the toner is characterized by a bloc~ing temperature less than about 110F, 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 ~uality.
Any suitable pigment or dye may be employed as the colorant for the toner particles. Toner colorants are well-known and include, for examp]e, carbon black, nigrosine dye, aniline blue, Calco Oil Blue, chrome yellow, ultra marine blue, duPont Oil Red, ~uinoline Yellow, methylene blue chloride, phthalocyanine blue, Malachite Green Oxalate, lamp black, Rose Bengal and mixtures 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 me~ber. Thus, for example, where conventional electrostatographic copies of typed documents are desired, the toner may comprise a b]ack pigment such as carbon black or a blac~ dye such as Amaplast Black dye, available from 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 colorantemployed is a dye, substantially smaller quantities of colorant may be used. However, since a number of the above .
Hagenbach et al in U. S. Patents 3,533,835 and 3,658,500.
Any suitable eleetrostatographic carrier coating thickness may be emp~oyecl. However, a earrier coating having a thickness at ~_.
10~73Z5 lea;t suf~iciellt to ~orm a Lhill c~ntinuous film on thc carrier particle is preerrecl because ~he carr;er COatinCJ will then possess sufEicient thickness to resist abrasion and prevent pin-holes which adversely afect the triboelectric properties of the coatecl carri~r 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 ~n the weight of the coated carrier particles. Preferably, the carrier coating should comprise from about 0~1 percent to about 1.0 percent by weight based on the weight of the coated carrier particles 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 polymers, dyes, pigments, wetting agents and mixtures thereof may be mixed with the coating materials. An ultimate coated carrier particle having an average diameter between about 50 microns and about l,000 microns is preferred in cascade systems because the carrier particle then possess sufficient density -and inertia to avoid adherence to the electrostatic image during the cascade development process. Adherence of carrier particles to an electrostatographic drum is undesirable because of the formation of deep scratches on the drum surface during the image transfer and drum cleaning steps, particularly w~lere 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.
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 materials include sodium chloride, ammonium chloride, aluminum potassium chloriae, Rochelle salt, sodium nitrate, potassium chlorate, ~ranular zircon, granular silicon, mekhyl methacrylate, glass, silicon dioxide, ~lintshot, iron, steel, ferrite, nickel, Carborundum, and mixtures thereof.
Any suitable well-known toner material may be employed with the coated carriers of this invention as well as the toner materials prepared in accordance with this invention. Typical toner materials include gum copal, gum sandarac, rosin, cumaroneindene resin, asphaltum, gilsonite, phenolformaldehyde resins, rosin modified phenolformaldehyde resins, methacrylic resins, polystyrene resins, polypropylene resins, epoxy resins, polyethylene resins, polyester resins, and mixtures thereof. The particular toner material to be employed obviously depends upon the separatlon of the toner particles from the coated carrier in the triboelectric series and should be sufficient to cause the toner particles to electrostatically cling to the carrier surface. Among the patents describing electroscopic toner com-positions are U. S. Patent 2,659,670 to Copley; U. S. Patent 2,753,308 to Landrigan; U. S. Patent 3,079,342 to Insalaco; U. S.
Patent Reissue 25,136 to Carlson and U. S. Patent 2,788,288 to Rheinfrank et al. These toners generally have an average particle diameter between about 1 and 30 microns.
Any suitable photoconductive materials may be used together with the developer materials such as those disclosed in U. S. Patents 2,803,542 to Ullrich, U. S. Patent 2,970,906 to Bixby, U. S. Patent ~,121,006 to Middleton, U. S. Patent 3,121,007 to Middleton, and U. S. Patent 3,151,982 to Corrsin.
~ he surprisingly better results obtained with the electrostatographic coated carriers of this invention may be due to many factoxs. For example, the coated carriers of this invention possess smooth outer surfaces which are highly resistant to cracking, ~L~773Z5 cllippincJ, an~l fl~lkir~g. In c~scade clevelopmen~ syxtems, tlle smooth suriace en~ances tlle rolling action oE the carrier particles across the electrostatographic surfaces and reduce5 the tendency of carrier particles to adhere to tlle electrostatographic imaging surfaces.
When these coated carriers are employed in electrostatographic development systems, carrier liEe is unexpectedly extended particularly with respect to toner impaction resistance. Additionally the carrier coating materials of this invention appear to contribute to the stability of the triboelectric properties of the coated carrier over a wide relative humidity range. Because of their triboelectric properties, these carrier materials may be employed in reversal development of positively charged images. Further, the coa-ted carriers of this invention provide more uniform triboelectric characteristics than current carriers when employed in electrostato-graphic development systems. In addition, the coated carriers of this invention provide exceptionally good life performance, durability, copy ~uality, quality maintenance, less carrier bead sticking and agglomeration, and also provide improved abrasion resistance thereby minimizing carrier chipping and fla~ing. Further, the coated carriers of this invention provide triboelectric values such that they can be used with a wide variety of presently available toners in present electrostatographic processes, and retain a predictable triboelectric value. Thus the improved coated carrier particles of this invention have desirable properties which permit their wide use in presently available electrostatographic systems.
With regard particularly to the toner compositions of this invention, any suitable vinyl resin having a melting point of at least about llO~F may be employed. 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 ~77~25 ~he polymeriza~ion o~ mi~ures o~ two or more of these~ unsaturated monomers. ~le c~pression "addition polymerization" is intended to include known polymerization techniques such as free radical, anionic and cationic polymerization processes.
The combination o~ 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 4 poise at temperatures up to about 450F. ~hen the toner is characterized by a bloc~ing temperature less than about 110F, 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 ~uality.
Any suitable pigment or dye may be employed as the colorant for the toner particles. Toner colorants are well-known and include, for examp]e, carbon black, nigrosine dye, aniline blue, Calco Oil Blue, chrome yellow, ultra marine blue, duPont Oil Red, ~uinoline Yellow, methylene blue chloride, phthalocyanine blue, Malachite Green Oxalate, lamp black, Rose Bengal and mixtures 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 me~ber. Thus, for example, where conventional electrostatographic copies of typed documents are desired, the toner may comprise a b]ack pigment such as carbon black or a blac~ dye such as Amaplast Black dye, available from 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 colorantemployed is a dye, substantially smaller quantities of colorant may be used. However, since a number of the above .
3~
pic~rnen~s usccl il~ elec'~:r~s~cl~oy~c~ ic toner compositions may a~fect both tlle glass ~ran~ition and fusion temperatures o~
the toner compositions of ~his inven~ion, their concentratlon preferably should not e~ceed about 10 percent by weight of the colored toner.
The toner compositions of the present invention may be prepared by any we]l-known toner mixing and comminution technique. For example, the ingredients may be thoroughly 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 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 addition to the carrier particles prepared in accord-ance with this invention, any suitable coated and uncoated carrier materials well-known in the art may be used. The carrier particles comprise any suitable solid materials, provided that the carrier particles acquire a charge having an opposite pol-arity to that of the toner particles when brought in close con-tact with the toner particles so that the toner particles adhere to and surround the carrier particles. When a positive repro-duction of the electrostatic images is desired, the carrier par-ticle is selected so that the toner particles acquire a charge havin~ a polarity opposite to that of the electrostatic image.
~ 773'~5 ~]'~ernatively, if a ~eversal reproduc~ion of the eleetrostatie image is desired, the carrler is selected so tha~ the toner particles acquire a charge having the same polarity as that of the electrostatic image. ~lus the materials or the earrier partieles are selected in accordanee with their triboeleetric properties in respeet to the eleetroscopie toner so that when mixed or brought into mutual eontaet, one component of the developer is charyed positively if the other component is below the first eomponent in the triboelectric series and negatively if the other component is above the first component in a triboelectric series. By proper seleetion of earrier materials in aeeordanee with their triboeleetrie effeets, the polarities of their eharge, when mixed, are such that the eleetroscopic toner partieles adhere to and are eoated on the surfaees of earrier particles and also adhere to that portion of the electrostatic image-bearing surfaee having a greater attraetion for the toner than the earrier partieles.
D~:SCRIPTION OF PREFERRED EMBODIMENTS
The following examples, other than the control examples, further define, describe and compare preferred methods of preparing and utilizing the toner materials and coated earriers of the present invention in eleetrostatographie applieations. Parts and percentages are by weight unless other-wise indicated~
In the following, the relative triboelectrie values generated by contact of earrier beads with toner particles is measured b~ means of a caseade deviee. The deviee eomprises a grounded metal plate set at an arbitrary but eonstant angle of elevation to horizontal, for example, 30 degrees and a eup at the bottom of the ineline. The eup is not attaehed to the ineline and is thus not grounded; it is attaehed to an eleetrometer.
J
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~L~773~5 ~ e material ~o bc te~ c~d is coated onto a metallic sheet, sucll as alulninum, and this is attached to the incline. I'hen beads of tlle desirecl 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 ~uantity is a direct measure of the triboelectric charging capacity of the polymeric film. The measurement is done at constant relative humidity and temperature Since triboelectric measurements are relative, the measurements should, Eor comparative purposes, be conducted under substantially identical conditions.
EXAMPLE I
About 82.3 grams of carrier beads having a particle size of about 600 microns comprising flintshot coated with ethyl cellulose were dried in vacuo for about 17 hours. In a cascade triboelectric measurement as discussed above, these beads were found to acquire a net charge of about +0.57 nanocoulombs per gram versus a film of a styrene-n-butyl methacrylate copolymer having a 2.54:1.00 mole ratio respectively.
EXAMPLE II
About 10.0 ml. of dimethylaminetrimethylsilane was passed on a stream of dry nitrogen through about 82.3 grams of carrier beads having a particle size of about 600 microns comprising flintshot coated wlth ethyl cellulose disposed iIl a 1 x 6 inch cylindrical bed over a period of about 25 minutes.
After drying in vacuo for about 17 hours, in a cascade tribo-electric measurement under substantially the same conditions as in Example I, the treated carrier beads were found to acquire a net charge of about +0.14 nanocoulombs per gram versus a film of a styrene-n-butyl methacrylate copolymer '' ,. ~.
.
7732~;
ha~ing a 2.~ 1.()0 molc ra~io as in Examl~le I. 'l'hus, it was found that t~le triboelectric charcJing capacity oE the sil~la~ed carrier beads is more negative after sil~lation thereof.
EXAMPLE I~I
About S.0 ml. of dimethylaminotrimethylsilane was passed on a stream of dry nitrogen through about 60.0 grams of carrier beads having a particle size of about 250 microns coated with the aminolyzed polymer of a styrene-n-butyl methacrylate copolymer containing hydroxyl moieties for about 90 minutes. The aminolyzed polymer was prepared by ester group aminolysis of the styrene-n-butyl methacrylate copolymer having a 2.54:1.00 mole ratio with an aminoalcohol resulting in formation of hydroxyalkyl amide functions. Thus a mixture of about 117.5 arams (0.289 mole of ester functions based on elemental analysis) of the styrene-n-butyl methacrylate, about 41.0 grams (0.350 mole) of a 6-aminohexanol, and about 39.3 grams (0.350 mole) of 1,4-diazabicyclo (2,2,2) octante was stirred under dry nitrogen at about 180C (oil bath temperature 205C) using an ambient air-cooled condenser to allow excape of the n-butanol produced. The polymer was minolyzed to the extent of about 25 mole percent. The polymer was purified by dissolving in tetrahydrofuran and then 10% HCl was added. The li~uid phase was decanted from the gummy polymer. This procedure was repeated twice, followed by a fourth and fifth was using 5% methanolic HCl. The polymer was taken up in tetrahydrofuran and precipitated by dropwise addition with rapid stirring to 10% HCl. After homogenization in a blender and filtration, the process was repeated. The polymer in tetrahydrofuran solution was then precipitated in like manner from deionized water, and this process repeated. After a final precipitation . .
773~5 from me~llLInol, t:he polymer was dried in vacuo. Gen~rally, the polymer samplc was clissolv~d in about five times its weigh~ oE tetrahydrofuran. Volumes of the precipitatiny solu-tions were 6-]0 times those of the polymertetrahydrofuran solution. 250 micron steel beads were coated with about 0.28 percent of the polymer by evaporation of solvent tetra-hydrofuran from a tumbling mixture of the beads in a solution of the polymer.
A portion of these coated beads, about 60.0 grams, was placed in a 1 inch diameter column and 5 ml. of dimethylamino-trimethylsilane was passed over the beads on a stream of dry nitrogen over a 90 minute period.
After drying in vacuo for about 17 hours, in a cascade triboelectric measurement under substantially the same conditions as in Example I, the silylated coated carrier beads were found to acquire a net charge of about +0.19 nanocoulombs per gram versus a film of a styrene-n-butyl methacrylate copolymer having a 2.54:1.00 mole ratio.
Unsilylated carrier beads coated with the aminolyzed polymer acquired a net charge of about +0O94 nanocoulombs per gram.
The carrier bead coating upon silylation was found to have a lower capacity for positive triboelectric charging.
Although specific components t proportions and procudures have been stated in the above description of the preferred embodiments of the novel carrier compositions, other suitable components, proportions and procedures as listed above may be used with similar results. Further, other materials and procedures may be employed to synergize, enhance or otherwise modify the novel system.
Other modifications and ramifications of the present :1~'7'7~5 inventiol~ w:ill a~l)c,lr to tllosc: skilled in the axt upon the readillg o:F t]lis clisclosure. These are intended to be includecl within the scope of this invention.
,
pic~rnen~s usccl il~ elec'~:r~s~cl~oy~c~ ic toner compositions may a~fect both tlle glass ~ran~ition and fusion temperatures o~
the toner compositions of ~his inven~ion, their concentratlon preferably should not e~ceed about 10 percent by weight of the colored toner.
The toner compositions of the present invention may be prepared by any we]l-known toner mixing and comminution technique. For example, the ingredients may be thoroughly 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 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 addition to the carrier particles prepared in accord-ance with this invention, any suitable coated and uncoated carrier materials well-known in the art may be used. The carrier particles comprise any suitable solid materials, provided that the carrier particles acquire a charge having an opposite pol-arity to that of the toner particles when brought in close con-tact with the toner particles so that the toner particles adhere to and surround the carrier particles. When a positive repro-duction of the electrostatic images is desired, the carrier par-ticle is selected so that the toner particles acquire a charge havin~ a polarity opposite to that of the electrostatic image.
~ 773'~5 ~]'~ernatively, if a ~eversal reproduc~ion of the eleetrostatie image is desired, the carrler is selected so tha~ the toner particles acquire a charge having the same polarity as that of the electrostatic image. ~lus the materials or the earrier partieles are selected in accordanee with their triboeleetric properties in respeet to the eleetroscopie toner so that when mixed or brought into mutual eontaet, one component of the developer is charyed positively if the other component is below the first eomponent in the triboelectric series and negatively if the other component is above the first component in a triboelectric series. By proper seleetion of earrier materials in aeeordanee with their triboeleetrie effeets, the polarities of their eharge, when mixed, are such that the eleetroscopic toner partieles adhere to and are eoated on the surfaees of earrier particles and also adhere to that portion of the electrostatic image-bearing surfaee having a greater attraetion for the toner than the earrier partieles.
D~:SCRIPTION OF PREFERRED EMBODIMENTS
The following examples, other than the control examples, further define, describe and compare preferred methods of preparing and utilizing the toner materials and coated earriers of the present invention in eleetrostatographie applieations. Parts and percentages are by weight unless other-wise indicated~
In the following, the relative triboelectrie values generated by contact of earrier beads with toner particles is measured b~ means of a caseade deviee. The deviee eomprises a grounded metal plate set at an arbitrary but eonstant angle of elevation to horizontal, for example, 30 degrees and a eup at the bottom of the ineline. The eup is not attaehed to the ineline and is thus not grounded; it is attaehed to an eleetrometer.
J
. . .
. . . : -.. . .
~L~773~5 ~ e material ~o bc te~ c~d is coated onto a metallic sheet, sucll as alulninum, and this is attached to the incline. I'hen beads of tlle desirecl 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 ~uantity is a direct measure of the triboelectric charging capacity of the polymeric film. The measurement is done at constant relative humidity and temperature Since triboelectric measurements are relative, the measurements should, Eor comparative purposes, be conducted under substantially identical conditions.
EXAMPLE I
About 82.3 grams of carrier beads having a particle size of about 600 microns comprising flintshot coated with ethyl cellulose were dried in vacuo for about 17 hours. In a cascade triboelectric measurement as discussed above, these beads were found to acquire a net charge of about +0.57 nanocoulombs per gram versus a film of a styrene-n-butyl methacrylate copolymer having a 2.54:1.00 mole ratio respectively.
EXAMPLE II
About 10.0 ml. of dimethylaminetrimethylsilane was passed on a stream of dry nitrogen through about 82.3 grams of carrier beads having a particle size of about 600 microns comprising flintshot coated wlth ethyl cellulose disposed iIl a 1 x 6 inch cylindrical bed over a period of about 25 minutes.
After drying in vacuo for about 17 hours, in a cascade tribo-electric measurement under substantially the same conditions as in Example I, the treated carrier beads were found to acquire a net charge of about +0.14 nanocoulombs per gram versus a film of a styrene-n-butyl methacrylate copolymer '' ,. ~.
.
7732~;
ha~ing a 2.~ 1.()0 molc ra~io as in Examl~le I. 'l'hus, it was found that t~le triboelectric charcJing capacity oE the sil~la~ed carrier beads is more negative after sil~lation thereof.
EXAMPLE I~I
About S.0 ml. of dimethylaminotrimethylsilane was passed on a stream of dry nitrogen through about 60.0 grams of carrier beads having a particle size of about 250 microns coated with the aminolyzed polymer of a styrene-n-butyl methacrylate copolymer containing hydroxyl moieties for about 90 minutes. The aminolyzed polymer was prepared by ester group aminolysis of the styrene-n-butyl methacrylate copolymer having a 2.54:1.00 mole ratio with an aminoalcohol resulting in formation of hydroxyalkyl amide functions. Thus a mixture of about 117.5 arams (0.289 mole of ester functions based on elemental analysis) of the styrene-n-butyl methacrylate, about 41.0 grams (0.350 mole) of a 6-aminohexanol, and about 39.3 grams (0.350 mole) of 1,4-diazabicyclo (2,2,2) octante was stirred under dry nitrogen at about 180C (oil bath temperature 205C) using an ambient air-cooled condenser to allow excape of the n-butanol produced. The polymer was minolyzed to the extent of about 25 mole percent. The polymer was purified by dissolving in tetrahydrofuran and then 10% HCl was added. The li~uid phase was decanted from the gummy polymer. This procedure was repeated twice, followed by a fourth and fifth was using 5% methanolic HCl. The polymer was taken up in tetrahydrofuran and precipitated by dropwise addition with rapid stirring to 10% HCl. After homogenization in a blender and filtration, the process was repeated. The polymer in tetrahydrofuran solution was then precipitated in like manner from deionized water, and this process repeated. After a final precipitation . .
773~5 from me~llLInol, t:he polymer was dried in vacuo. Gen~rally, the polymer samplc was clissolv~d in about five times its weigh~ oE tetrahydrofuran. Volumes of the precipitatiny solu-tions were 6-]0 times those of the polymertetrahydrofuran solution. 250 micron steel beads were coated with about 0.28 percent of the polymer by evaporation of solvent tetra-hydrofuran from a tumbling mixture of the beads in a solution of the polymer.
A portion of these coated beads, about 60.0 grams, was placed in a 1 inch diameter column and 5 ml. of dimethylamino-trimethylsilane was passed over the beads on a stream of dry nitrogen over a 90 minute period.
After drying in vacuo for about 17 hours, in a cascade triboelectric measurement under substantially the same conditions as in Example I, the silylated coated carrier beads were found to acquire a net charge of about +0.19 nanocoulombs per gram versus a film of a styrene-n-butyl methacrylate copolymer having a 2.54:1.00 mole ratio.
Unsilylated carrier beads coated with the aminolyzed polymer acquired a net charge of about +0O94 nanocoulombs per gram.
The carrier bead coating upon silylation was found to have a lower capacity for positive triboelectric charging.
Although specific components t proportions and procudures have been stated in the above description of the preferred embodiments of the novel carrier compositions, other suitable components, proportions and procedures as listed above may be used with similar results. Further, other materials and procedures may be employed to synergize, enhance or otherwise modify the novel system.
Other modifications and ramifications of the present :1~'7'7~5 inventiol~ w:ill a~l)c,lr to tllosc: skilled in the axt upon the readillg o:F t]lis clisclosure. These are intended to be includecl within the scope of this invention.
,
Claims (14)
1. An electrostatographic developer composition for use in developing electrostatic latent images on a recording surface, said developer composition comprising carrier particles and toner particles, characterized in that at least either the carrier or toner is a functionalized polymer obtained by the systematic chemical alteration of the active hydrogen containing constituents of said polymer by silylation to provide particles having controlled tribo-electric charging properties.
2. An electrostatographic developer composition in accordance with Claim 1 characterized in that said carrier composition comprises carrier particles having an average particle diameter of between about 50 microns and about 1,000 microns, each of said carrier particles comprising a core surrounded by an outer coating of a functionalized polymer obtained by systematic chemical alteration of the active hydrogen containing constituents of said polymer by silylation to provide carrier particles characterized as having controlled triboelectric charging properties.
3. An electrostatographic developer composition in accordance with Claim 2 wherein said coating comprises from about 0.1 percent to about 10.0 percent by weight based on the weight of said carrier particles.
4. An electrostatographic developer composition in accordance with Claim 1 wherein said polymer comprises styrene-alkyl methacrylate.
5. An electrostatographic developer composition in accordance with Claim 1 wherein said systematic chemical alteration of said polymer has been controlled stoichio-metrically so as to provide closely controlled triboelectric properties.
6. An electrostatographic developer composition in accordance with Claim 1 wherein said systematic chemical alteration of said polymer has been controlled kinetically so as to provide closely controlled triboelectric properties.
7. An electrostatographic developer composition in accordance with Claim 1 wherein said polymer is the product of silylation with at least one silylating agent selected from the group consisting of dimethylaminotrimethylsilane, dimethyl chlorosilane, trimethylchlorosilane, and polysiloxanes with reactive terminal moieties.
8. An electrostatographic developer composition in accordance with Claim 2 wherein silylation is brought about by a difunctional silylating agent and the product is crosslinked.
9. An electrostatographic developer composition in accordance with Claim 1 characterized in that said toner composition comprises finely-divided toner particles having an average particle diameter or less than about 30 microns, said toner particles comprising a colorant and a functional polymer obtained by systematic chemical alteration of the active hydrogen containing constituents of said polymer by silylation to provide toner particles characterized as having controlled triboelectric charging properties.
10. An electrostatographic developer composition in accordance with Claim 9 wherein said polymer comprises a vinyl resin having a melting point of at least 110°F.
11. An electrostatographic developer composition in accordance with Claim 10 wherein said vinyl resin has a weight average molecular weight between about 3,000 to about 500,000.
12. An electrostatographic developer composition in accordance with Claim 9 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.
13. An electrostatographic developer composition in accordance with Claim 9 wherein said polymer contains electron withdrawing groups.
14. An electrostatographic imaging process comprising the steps of providing an electrostatographic imaging member having a recording surface, forming an electrostatic latent image on said recording surface, and contacting said elec-trostatic latent image with a developer mixture comprising finely-divided toner particles electrostatically clinging to the surface of carrier particles having an average particle diameter of between about 50 microns and about 1,000 microns, at least one of either the toner or the carrier comprising a functionalized polymer obtained by the systematic chemical alteration of the active hydrogen containing constituents of said polymer by silylation to provide particles characterized as having controlled triboelectric charging properties, whereby at least a portion of said finely-divided toner particles are attracted to and deposited on said recording surface in conformance with said electrostatic latent image.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/500,768 US4070186A (en) | 1974-08-26 | 1974-08-26 | Tribo modified toner materials via silylation and electrostatographic imaging process |
| US05/500,775 US4043929A (en) | 1974-08-26 | 1974-08-26 | Electrostatographic carrier composition |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1077325A true CA1077325A (en) | 1980-05-13 |
Family
ID=27053631
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA230,992A Expired CA1077325A (en) | 1974-08-26 | 1975-07-08 | Toner and/or carrier consisting of polymer with silylated, active hydrogen containing constituents |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA1077325A (en) |
| GB (1) | GB1525705A (en) |
| NL (1) | NL7510082A (en) |
-
1975
- 1975-07-08 CA CA230,992A patent/CA1077325A/en not_active Expired
- 1975-08-22 GB GB3494775A patent/GB1525705A/en not_active Expired
- 1975-08-26 NL NL7510082A patent/NL7510082A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| NL7510082A (en) | 1976-03-01 |
| GB1525705A (en) | 1978-09-20 |
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