Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G15/00—Apparatus for electrographic processes using a charge pattern
  • G03G15/02—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G15/00—Apparatus for electrographic processes using a charge pattern
  • G03G15/02—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices
  • G03G15/0208—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices by contact, friction or induction, e.g. liquid charging apparatus
  • G03G15/0216—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices by contact, friction or induction, e.g. liquid charging apparatus by bringing a charging member into contact with the member to be charged, e.g. roller, brush chargers
  • G03G15/0233—Structure, details of the charging member, e.g. chemical composition, surface properties
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G15/00—Apparatus for electrographic processes using a charge pattern
  • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
  • G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
  • G03G15/0806—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer on a donor element, e.g. belt, roller
  • G03G15/0808—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer on a donor element, e.g. belt, roller characterised by the developer supplying means, e.g. structure of developer supply roller
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G15/00—Apparatus for electrographic processes using a charge pattern
  • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
  • G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
  • G03G15/0806—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer on a donor element, e.g. belt, roller
  • G03G15/0818—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer on a donor element, e.g. belt, roller characterised by the structure of the donor member, e.g. surface properties
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G15/00—Apparatus for electrographic processes using a charge pattern
  • G03G15/14—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base
  • G03G15/16—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer
  • G03G15/1665—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer by introducing the second base in the nip formed by the recording member and at least one transfer member, e.g. in combination with bias or heat
  • G03G15/167—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer by introducing the second base in the nip formed by the recording member and at least one transfer member, e.g. in combination with bias or heat at least one of the recording member or the transfer member being rotatable during the transfer
  • G03G15/1685—Structure, details of the transfer member, e.g. chemical composition
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G2215/00—Apparatus for electrophotographic processes
  • G03G2215/08—Details of powder developing device not concerning the development directly
  • G03G2215/0855—Materials and manufacturing of the developing device
  • G03G2215/0858—Donor member
  • G03G2215/0861—Particular composition or materials
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G2215/00—Apparatus for electrophotographic processes
  • G03G2215/08—Details of powder developing device not concerning the development directly
  • G03G2215/0855—Materials and manufacturing of the developing device
  • G03G2215/0866—Metering member

Definitions

• the invention relates to a composition of adjustable electrical conductivity.
• the invention further relates to a conductive article in which, around a conductive sleeve, a covering layer formed with the use of the composition is present, and to a method for fabricating such an article, comprising the application of a layer of the composition to a conductive sleeve.
• Conductive articles of this type are generally used in electrophotographic and xerographic printing and copying equipment, faxes and other office equipment, for example as a charge transfer roller for the purpose of electrostatically charging a photosensitive-sensitive drum, as a developing roller for developing an electrostatic latent image on the surface of said drum to produce a visible toner image, as an image transfer roller for transferring the toner image to a copy, or as a doctor blade for controlling the thickness of a toner layer.
• the inside can likewise be coated with a conductive covering layer.
• the rollers, blades or plates can either be in continuous contact with a cooperating element, for example a photosensitive drum, or there may be a small gap between the article and the cooperating element.
• a cooperating element for example a photosensitive drum
• the roller generally consists of a conductive core, often a metal rod, around which a likewise conductive resilient sleeve is fitted.
• Said sleeve consists of a resilient material which is indented when the roller is pressed against a cooperating roller or face to which charge is to be applied or from which it is to be removed. To supply the charge that is to be transferred, a voltage is applied to the roller.
• the electrical resistance of the roller needs to be within certain limits.
• a covering layer is usually applied to the sleeve, which imparts a desired resistance to the roller as a whole.
• the electrical resistance of core and sleeve, which is connected in series with the resistance of the covering layer, is preferably selected to be sufficiently small for the covering layer in fact to define the total resistance.
• the resistance of the roller is measured as the resistance between the location where the roller, during operation, is brought into contact with the voltage to be applied, as a rule the roller shaft, and a point of the outer circumference of the roller.
• the sleeve may also consist of a non-resilient material, and the sleeves can, for example, also be composed of metal. This is the rule, for example, in the case of magnetic developing rollers. In that case too a covering layer is present which defines the ultimate electrical resistance of the roller.
• What has been said hereinabove about rollers also applies to doctor blades and plates insofar as the mutual relationship of the various layers is concerned.
• at least one layer, the sleeve, having a high conductivity is present with a covering layer applied thereto which defines the ultimate electrical conductivity. Any differences reside in their shape and design. These, however, do not form part of the present invention and are known per se in the art in question. Where a roller is referred to hereinafter, the disclosure, always allowing for any differences in design, equally applies to doctor blades and flat or curved plates .
• the said covering layers are formed, as a rule, from a composition comprising a nonconductive binder and a conductive material finely dispersed therein.
• US Patent No. 5597652 discloses a composition for a covering layer of a conductive roller, which consists of nylon, urethane or rubber as a binder and metal oxides or carbon black as a conductive material.
• the resistance of a covering layer formed from that composition depends on the ratio of binder to conductive material.
• a drawback of this known composition is the poor adjustability of the electrical resistance of a covering layer made using the composition.
• the resistance of the known composition is found to adopt, depending on the concentration of the conductive material, two values with in between, starting from a certain concentration which is referred to as the percolation threshold, a steep transition section. The one extreme is defined by the resistance of the binder which, as a rule, is very high.
• the other extreme is defined by the resistance of the conductive material which, from a certain concentration in the binder onwards, forms conductive paths therein.
• the difference between the two extremes, determined from the resistivity, to be defined hereinafter in more detail, of the material can be very large and often amounts to a factor of from 10 8 to 10 11 .
• those values of the resistance of the covering layer of conductive articles, for example rollers in electrophotographic equipment, for example of a charge transfer roller, which are suitable for practical use are situated precisely between these two extremes and thus in the steep transition section. This makes it particularly difficult for a covering layer having a suitable, desired electrical resistance to be fabricated reproducibly from the known composition.
• the resistance of a covering layer could also be affected by its thickness.
• the thickness of a covering layer is likewise restricted to certain narrow limits. On the one hand, shorting via pinholes or flashovers must be prevented, which imposes a lower limit on the thickness.
• the covering layer On the other hand, certainly in the case of rollers which must be indentable, the covering layer must be sufficiently flexible to be able to follow the indentation of the resilient sleeve without becoming detached or rupturing, which imposes an upper limit on the thickness. Variations in thickness will therefore, in most cases, provide no option or only limited options to influence the resistance of the covering layer.
• composition consisting of an intrisically conductive polymer and an electrically inert film-forming polymer.
• the resistance of this composition changes much more evenly as the concentration of the conductive material changes, in this case the intrisically conductive polymer.
• the composition according to the invention does not exhibit the steep transition section between high and low electrical resistance.
• a roller is known in which the coating layer consists of conductive particles in a binder resin and having a 10% elongation load of not more than 700 gf on a 1 cm wide section.
• the conductive particles also conductive polymers are mentioned. Any teaching that the specific combination according to the invention of conductive polymers with a filmforming resin, in contrast to the other possible combinations, results in coating layers having a controllable electric resistivity showing no steep percolation threshold is absent in this reference
• EP-A-594,366 discloses a coating layer mandatorily containing, in addition to an (optional) polymer binder and charge injection enabling particles (e.g. conductive polymers), charge transport molecules of a specific type.
• the last component is not present in the composition of the present invention in which the conductive properties are only due to the presence of the intrinsic conductive polymer.
• the film-forming polymer acts as a binder within which the intrinsically conductive polymer is dispersed to provide the conductive characteristics.
• the film-forming polymer is electrically inert, which means that it essentialy does not contribute to the transport of electric charge through the coating layer.
• Suitable intrinsically conductive polymers for use in the composition according to the invention include, for example, polyacetylene, polyphenylene, poly (para-phenylene-vinylene) , polypyrrole, polyfuran, polythiophene, polyaniline and conductive substituted forms of these polymers and mixtures of two or more of the said compounds. Highly suitable are polypyrrole, polythiophene and conductive substituted forms of these polymers and mixtures of two or more of the said compounds.
• the intrinsically conductive polymer can be present as such in the composition according to the invention, but may also be bound to a suitable substrate.
• compositions are those in which the conductive polymer, per se or on a substrate, and the organic polymer are present in disperse form in a dispersant.
• a dispersion is any mixture of a dispersant with a conductive and/or film-forming polymer dispersed therein in sufficiently fine form for the intended application, for example a dispersion, a suspension or even a solution.
• Suitable as a film-forming polymer for use as a binder in the composition are organic polymers which are able to form a film.
• organic polymers which are able to form a film.
• examples of these include poly (vinylidene chloride), polymethacrylates, polyurethanes, poly (vinyl acetate) and poly (vinyl alcohol) .
• Preferred are polymers which, for example as a latex, can be converted into a dispersion in a dispersant, preferably water, and which, during and/or after removal of the dispersant, are able to form a film.
• Highly suitable are polyurethane resins, which have a high degree of wear resistance and are often highly flexible.
• a film is a continuous layer which is essentially impermeable for constituents from the underlying sleeve.
• film-forming polymers which form a film of sufficient flexibility, for example having a reversible elastic elongation of at least 50%.
• Film-forming polymers should also be understood as including precursors thereof, for example monomers, oligomers or prepolymers which are able to polymerize to form a film or, for example, two- component systems whose components are able to react, for example cross-link, to form a polymeric film.
• the film-forming polymer is used, as a rule, in the form of a solution or dispersion, on environmental grounds preferably in the form of an aqueous solution or dispersion.
• a conductive polymer should likewise be dispersible in this dispersion.
• the invention also relates to a method for fabricating a conductive article, in particular a roller, a doctor blade or a flat or curved plate, which comprises at least a conductive sleeve and a covering layer, wherein the covering layer is formed by the application, to the sleeve, of a mixture of a conductive polymer and a film-forming polymer.
• the application of a covering layer to the conductive sleeve in order to fabricate a conductive roller, doctor blade or plate can be effected by methods known per se .
• a highly suitable approach is to blend the intrinsically conductive polymer with a dispersion of the film-forming polymer.
• the dispersed mixture can then be applied to the sleeve of the article by means of techniques known per se for this purpose. Examples of such techniques include dip- coating, flow-coating, air spraying or airless spraying, onto an electrostatically charged surface if required, and roller application or brush application.
• the choice of a specific technique is determined by economic factors, but also, to a considerable extent, by the requirement that the covering layer be applicable in the desired thickness and with the smallest possible scatter in thickness.
• it is feasible to apply a plurality of thin layers for example by dip-coating in a relatively low-viscosity composition or by electrostatic spraying.
• dip-coating in a relatively more viscous composition is a suitable technique.
• the layer applied is treated in such a way that it changes into a film. This may involve, for example, the mere removal of the solvent, but also curing at elevated temperature in the presence of a cross-linker.
• Adhesion of the film formed to the sleeve can be promoted by the addition of primers known per se for this purpose.
• the covering layer can be applied, in the case of the sleeve consisting of rubber, to a sleeve whose material has not yet been completely vulcanized. After application of the covering layer, complete vulcanization of the sleeve material is then effected. It was found that this has a beneficial effect on the adhesion of the covering layer to the sleeve.
• the sleeve surface can be subjected to a corona treatment in order to improve adhesion.
• the composition to be admixed, for example, with flow improvers, thickeners and surface tension-reducing agents.
• the uniformity of the film formed may also be affected by the surface roughness of the sleeve. Said surface roughness is preferably below 15 ⁇ m. Greater roughnesses give rise to unevenesses in the covering layer, which adversely affect the quality of, for example, copies made with the aid of an article provided with the covering layer, in particular with the aid of a roller.
• the surface roughness is at most 10 ⁇ m and at least 3 ⁇ m.
• Covering layers of lesser roughness are so smooth that the cohesion in the dispersion applied to a sleeve may become greater than the adhesion between dispersion and sleeve material . This may give rise to contraction of the dispersion applied and consequently to non-uniform thickness of the covering layer.
• the invention further relates to a conductive article, in particular a roller, doctor blade or a flat or curved plate, these at least comprising a conductive sleeve and a covering layer which contains an intrinsically conductive polymer in a polymer film.
• an article of this type is found to have good electric conductivity and high wear resistance.
• the presence of the covering layer is found to have no adverse effect on the indentability of the sleeve, if required.
• the article has a long service life in a copier or printer and can be used to produce excellent copies or printouts.
• the covering layer proves able to withstand indentation of the article when in contact with rollers or other surfaces cooperating therewith.
• the centre section of an indentable conductive roller is often, but not necessarily, made of metal.
• At least a sleeve section consists of a resilient, in particular indentable material, for example a natural or synthetic rubber, a thermoplastic polymer or thermoplastic vulcanizate or a microcellular rubber. Examples which are highly suitable for use in the article according to the invention include, for example, EPDM and SBR.
• This material is conductive, as a rule by having a conductive material dispersed therein.
• the conductive material used is commonly carbon black, but other materials known and customary for this purpose can likewise be used in the sleeve of the article according to the invention, if the sleeve consists of a material which has been made conductive, for example rubber.
• the electrical resistance of the sleeve which has been made conductive is between 100 and 10,000 ⁇ , as a rule, the resistance of a metal core which may or may not be present being negligibly small in comparison.
• Conductive articles for example rollers, which do not come into contact with a cooperating roller or some other element can be made entirely of metal and then have a negligible electrical resistance.
• non- ferrous metals for example aluminium
• non-magnetic materials for example suitable types of stainless steel.
• Such rollers and their design and composition are known per se .
• the resistance of the covering layer should be between 10 5 and 10 7 ⁇ when a voltage of between 100 and 900 V is applied and is preferably virtually constant in the said voltage range and more preferably varies by less than 1 decade, and even less than 0.5 decades, over the entire voltage range.
• the thickness of the covering layer should be such that shorting is prevented. In practice, a thickness of 20 ⁇ m has proved sufficient for this purpose. Preferably, the thickness is greater than 50 ⁇ m and more preferably greater than 80 ⁇ m. In view of the possibly desirable resilient characteristics, a thickness less than 400 ⁇ m is desirable. Preferably, the thickness is less than 200 ⁇ m and more preferably less than 150 ⁇ m.
• the demands to be met regarding the resistance of the covering layer and the thickness thereof define the desired resistivity p in ⁇ .m of the covering layer material. The resistivity is determined by two electrodes having a surface area A being positioned on the material to be measured at a distance 1 from one another and by the resistance R being determined from the current measured when a voltage is applied. The restivities are calculated as:
• Suitable covering layer materials have a restivity of between 2 x 10 5 and 10 7 ⁇ .m, or 2 x 10 7 and 10 9 ⁇ .cm.
• the roller is composed of a steel core having a diameter of 6.0 mm, surrounded by a sleeve of a styrene-butadiene rubber having a hardness of 30 Shore A and 20 wt of a conductive black (DENKA BLACK from Denki KK) dispersed therein.
• compositions for applying a conductive covering layer were fabricated as follows.
• An aqueous dispersion of a mixture of poly (ethylenedioxythiophene) and poly (styrenesulphonate) (Baytron P from Bayer, conductive-polymer content in the dispersion 1.3 wt%) was adjusted to a pH of 7.5, with the aid of 5 wt% ammonia, and then added to an aqueous dispersion of a polyurethane as a binder (Permutex EX-55-038 from Stahl Holland, polyurethane content in the dispersion 40 wt%) and is dispersed therein by stirring.
• the composition was applied to the outer circumference of the roller, by means of dip-coating repeated a number of times, to achieve a total thickness of between 80 and 100 ⁇ m. Each separate layer was dried at room temperature. After the desired thickness had been reached, the roller was kept at 80°C for 1 hour in order to harden the composition.
• each of the compositions was used to prepare three rollers.
• the resistance was determined at 800V, measured between one end of the metal core and a point on the sleeve circumference.
• Figure 1 the mean resistance of the rollers for each percentage of intrinsically conductive polymer is plotted against said percentage.
• the continuous line represents a least-squares fit of the experimental points. As can be seen, the resistance gradually changes with an increase in the percentage of intrinsically conductive polymer, so that a desired resistance can be set with good accuracy by adjusting the percentage of intrinsically conductive polymer in the composition.
• compositions for applying a conductive covering layer were prepared by an aqueous dispersion of a polyurethane (Permutex RA-1035 from Stahl Holland, polyurethane content in the dispersion 40 wt%) being added to an aqueous dispersion of polypyrrole-coated polyurethane particles (Conquest XP-1000 from DSM Solutech, percentage of conductive polymer + substrate in the dispersion 20 wt%) and being dispersed therein by stirring.
• the weight ratios of the two dispersions in the composition and the conductive-polymer content in the composition were as shown in Table 2. Table 2
• composition is applied, by means of dip-coating repeated a number of times, to the sleeve of the roller to produce a thickness of a 85-100 ⁇ m.
• each separate layer was dried at room temperature. After the desired thickness had been reached, the roller was kept at 80 °C for 1 hour in order to harden the composition.
• each of the compositions was used to prepare three rollers.
• the resistance is determined at 800V, measured between one end of the metal core and a point on the sleeve circumference.
• Figure 2 the mean resistance of the rollers for each percentage of intrinsically conductive polymer is plotted against said percentage.
• the continuous line represents a least-squares fit of the experimental points. As can be seen, the resistance changes relatively slowly with an increase in the percentage of intrinsically conductive polymer, so that a desired resistance can be set with good accuracy by adjusting the percentage of intrinsically conductive polymer in the composition.
• Example III In the manner described in Example I, six rollers were provided with a conductive covering layer. In so doing, the composition from Example I having a concentration of 2.17% was used for a first set of three rollers, and a corresponding composition was used for the second set of three rollers, except that the binder used is the urethane resin Impranil 85UD from Bayer .
• Eight rollers were produced by means of the method according to Example I, using a dispersion of Baytron P (Bayer) and Impranil 85 UD (Bayer) having a conductive-polymer content in the final covering layer of 2.17 wt%.
• the thickness of the covering layer was between 85 and 97 ⁇ m.
• the resistance was determined along the longitudinal direction of the rollers at distances of 1 cm each time.
• the mean values of the resistance and the standard deviation as a function of the position on the roller are shown in Figure 4. The mean resistance is found to be virtually constant over the entire sleeve surface, and the scatter likewise remains well within the limits to be stipulated for use of the rollers in electrophotographic and xerographic equipment.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Dry Development In Electrophotography (AREA)
• Rolls And Other Rotary Bodies (AREA)
• Laminated Bodies (AREA)
• Electrophotography Configuration And Component (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)
• Surgical Instruments (AREA)
• Liquid Crystal (AREA)

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Citations (4)

• 1999
  • 1999-07-03 NL NL1012507A patent/NL1012507C2/nl not_active IP Right Cessation
• 2000
  • 2000-06-29 JP JP2001508650A patent/JP2003504668A/ja active Pending
  • 2000-06-29 DE DE60019926T patent/DE60019926T2/de not_active Expired - Lifetime
  • 2000-06-29 KR KR1020017016260A patent/KR100766151B1/ko not_active Expired - Lifetime
  • 2000-06-29 EP EP00946517A patent/EP1192508B1/en not_active Expired - Lifetime
  • 2000-06-29 WO PCT/NL2000/000457 patent/WO2001002911A1/en not_active Ceased
  • 2000-06-29 AT AT00946517T patent/ATE294966T1/de not_active IP Right Cessation
  • 2000-07-04 TW TW089113244A patent/TWI256530B/zh not_active IP Right Cessation

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