Electrical Properties of Conductive Two-Component Xerographic Developer

Xerographic development with a conductive two-component magnetic brush depends on the electrical properties of a developer mixture consisting of insulative toner particles and conductive carrier beads. The electric field driving toner deposition onto an image receiver is affected by the carrier bead conductivity, toner concentration, magnetic field strength, developer thickness, and developer agitation due to the relative motion between the developer and image receiver. To elucidate the dependence of the electrical properties on these parameters, the measurements on an electroded cell of developer under conditions simulating magnetic brush development systems are described. The measurements provide insight into the solid area and line development process with conductive xerographic developer.     

A Model for Magnetic Brush Development in Xerographic Machines

A physical model for magnetic brush development of toner in xerographic machines is described. Deposition and scavenging rates are derived from electrostatic and adhesive force balances on toner particles. Ordinary differential equations (ODE) are derived for toner number densities as a function of toner charge, toner diameter, and position in the development nip. A numerical technique is described for solving these ODE's based on the method of moments. Model predictions of developed mass per unit area, average developed charge per unit mass, and average developed size as a function of development potential for solid areas are compared with experimental data.     

A new nonlevitated mode of traveling wave toner transport

A new mode of transporting charged particles with traveling electrostatic waves is described; it is distinguishable from the curtain mode of S. Masuda (1971,OP1972) and the hopping mode of J.R. Melcher et al. (1989). Structures specifically designed to produce running waves of sufficient strength to move typical xerographic toner synchronously and in sliding contact along a surface without altering their charge are described. Experimental results that strongly indicate that the desired synchronous motion is achieved are presented, but the toner appears to move as tiny clouds rather than in sliding contact with the transport structure. The transport thus appears akin to the synchronous hopping mode of Melcher. However, evidence is presented that indicates the cloud-like character is due to surface scattering rather than lift by the wave, as in the case of hopping. Measurements of mass transport rate that characterize the present mode of transport are presented along with representative development characteristics that illustrate the potential of traveling wave transport as a sensitive scavengeless development process     

Production of thin, uniform toner layers through use of a contactblade with mono-component development systems

The authors focus on the effects of contaminants on the uniformity of the toner layers resulting from the direct observation of the toner flow and metering phenomena. The authors have improved earlier observation methods to observe directly and analyze the toner transportation and toner behavior in the layer thickness control area. Using the improved method, they have experimented with the various kinds of toner transportations and layer thickness control systems. They concentrated on disruption of toner layers by contaminant infiltration and found that static toner and friction force against the toner on the developing sleeve are most important in preventing a contaminant from entering the metering area. Based on these results, they found a highly stable layer-forming method, called the contact blade method. which minimizes the effects of infiltration by contaminants     

Copy Quality Improvement Through Selective Transfer

A method called Selective Transfer may reduce or eliminate background in xerographic copies. Background, or toner deposited in nonimage areas, has always been a problem in xerography. Adjusting development parameters can help keep background at relatively low levels, but the emphasis on higher speeds and solid area development in the newer machines puts practical limits on background reduction. Previous efforts to reduce background have concentrated on two general techniques: 1) nondevelopment of background, and 2) processes for selective fusing combined with abrasive cleanup.     

A Theoretical Study of the Mechanics of a Xerographic Cleaning Blade

The use of a polymeric blade is common in removing the residual toner from the imaging surface in xerography. The cleaning action of such a blade is influenced by its local deformation in the contacting region. A nonlinear beam theory approach is presented for studying the deformation of a xerographic cleaning blade. Both the straight and tip regions of the blade are examined. The parameters studied include the normal load, the ratio of tangential and normal forces (the coefficient of friction , ?), the blade tip angle, blade inclination angle, Young's modulus, Poisson's ratio, blade length, and thickness. The effect of these parameters on the size of the contacting region is presented. The critical ratio ?c and the critical inclination angle which determine blade curl-under and curl-up are discussed. The maximum blade inclination angle which governs the tip stability is predicted. Cleaning performance criteria for planning and local curl-unders are developed in terms of the pressure in the contacting region. Agreement of the analytical findings with the available experimental data is good.     

A finite-element analysis of the electrostatic force on a uniformlycharged dielectric sphere resting on a dielectric-coated electrode in adetaching electric field

In the electrophotographic process, charged toner particles are transferred from one surface to another with an electric field. To enable electric field transfer of toner, the externally applied field strength must be greater than a threshold value, so that the Coulomb force can overcome the toner adhesion force at the supporting surface. In this paper, the threshold field strength to detach a charged dielectric particle is determined efficiently by using the Galerkin finite-element method to simultaneously solve the Laplace equation for the field distribution and an overall constraint equation for the force balance. This computational method also enables calculation of the electrostatic adhesion force and is applicable to various particle-electrode configurations. For illustrative purposes, however, we consider the axisymmetric problem of electric field detachment of a dielectric sphere with uniform surface charge resting on a planar dielectric-coated electrode. The analysis is particularly focused on the dependence of the electrostatic force upon the dielectric overcoating thickness and spacing between parallel plate electrodes. The electrostatic force on a uniformly charged particle in contact with a surface is found to be influenced significantly by the thickness of dielectric overcoating and the spacing between electrodes when either becomes less than five times the particle radius     

Xerographic properties of a-Se:Te photoconductors

It is shown that the dark decay of the electrostatic surface potential on a corona-charged a-Se:Te alloy photoreceptor occurs via electric field-enhanced xerographic depletion discharge (FEXDD) in which Poole-Frenkel-assisted thermal emission of holes from deep mobility-gap states and their subsequent sweep out generates a negative bulk space charge. The theoretical model development is applied to explain the observed experimental dark discharge data over a wide range of charging (initial) voltages. It is shown that although the time required for the surface potential to decay to its half value t_1/2 initially increases with the charging voltage V₀ at the highest charging voltage, t_1/2 actually decreases with V₀. Results obtained from cycled-up xerographic experiments on single and double-layer photoreceptors are also reviewed and discussed in conjunction with transient photoconductivity experiments     

Study of the conditions of irradiating laser for removal of toner from used paper

Though it is said that the paperless age arrived with the spread of personal computers, the amount of office paper used shows no tendency to decrease. In general, used paper is recovered and recycled in order to preserve the environment. But labor and expense are required for the recovery of used paper and the recycled paper is lower in quality. If we could reuse used paper repeatedly without these disadvantages, for example, by using copying machines that could print again by removing the toner on used paper, it would be very convenient and ecological. We therefore studied the removal of toner from used paper by the laser ablation technique. As an optical source, an SHG‐YAG laser was chosen. The energy density of irradiation with an SHG‐YAG laser for the removal of toner from used paper was examined. At an energy density of approximately 12 mJ/mm², which was the average value, the toner was removed sufficiently to allow reuse of the paper. The conditions of the laser irradiation, specifically the laser scanning speed and the number of irradiations, were studied. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(1): 8–14, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21214     

The current status of heavy-duty open gear drive lubrication

Since the enactment of environmental regulations in North America and other regions of the world affecting the use of chlorinated solvents, and the disposal of used lubricants, the practice of lubricating heavy-duty open gear motor drives has been in a state of evolution. One result of these changes is the proliferation of new lubricants professing to be environmentally more acceptable. This, in turn, has burdened gear manufacturers with the need to sanction the use of lubricants which exhibit nontraditional physical and performance characteristics. In many cases this has led to confusion at the end-user level. Another result has been the rationalization by lubricant suppliers and gear manufacturers that the physical and performance differences between the older, more traditional products, and these next generation products, demands re-education at the end-user level. At a minimum, lubricant usage, the monitoring of drive performance, and overall drive maintenance practices must be addressed. This paper attempts to draw a more clear picture of the current state of heavy duty open gear drive lubrication, realizing this remains somewhat a topic of great debate     

Xerographic development using single-component nonmagnetic toner

No magnetic material is necessary for this system. A thin layer of nonmagnetic toner is formed on the surface of a metal roller by means of an elastic plate which is pressed against the roller. The toner particles are charged triboelectrically by friction with the metal plate. The toner layer is attached to the roller by electrostatic force, and is carried around to the photosensitive drum. The latent image is developed with the noncontact development technique. The insulative toner developed for this system has a superior triboelectric characteristic. A model for toner charging is shown. The numerical calculations based on the model agree well with the experimental results. The model suggests that the metal plate controls the toner charge     

Model for a mono-component development process using edgeenhancement effects of floating electrodes [electrophotography]

The contributions of the electrostatic and magnetic fields to the development characteristics of a monocomponent development system are analyzed. This development system uses a special development roller which comprises a development sleeve and a magnetic roller rotating at high speed. The analysis indicates that the magnetic field has a significant effect only on the toner particles which are charged below a certain level. The effect of the magnetic field on the toner particles, which are normally charged above a predetermined level, is negligible. The analysis of the magnetic field indicates that the presently used magnet roller, which rotates at high speed, can be replaced by a micropitch magnet roller, which rotates at low speed. The analysis also indicates that if the quality of the electric charge on the toner particles can be controlled, and that a nonmagnetic toner can also be used in the present development system     

润滑剂对温压成型Fe_(78)Si_(9)B_(13)非晶磁粉芯性能的影响

以机械破碎的Fe78Si9B13非晶粉末为原料制备非晶磁粉芯,研究硬脂酸锌和硬脂酸锂这两种润滑剂的添加量对磁粉芯性能的影响。结果表明,在120℃、800MPa温压成型条件下,对应相同的润滑剂添加量,以硬脂酸锌为润滑剂制备的磁粉芯其综合磁性能优于以硬脂酸锂为润滑剂制备的磁粉芯。随着硬脂酸锌添加量的增多,磁粉芯的密度ρ先增大后减小,当添加量为1.5wt%时,达到最大值,热处理前为4.98g/cm3;相应的有效磁导率μe也达到最大,50kHz时μe可达47.8,磁损耗Ps也最低。     

Encapsulated Toners in Xerography and their Shell Fracture Mechanics

The effect of various elastic and physical parameters on the strength of the shell in encapsulated toner is examined. The contact problem of a toner particle and a pressure roller is discussed, and the mechanism of shell fracture from the viewpoint of Hertz's impact theory is reviewed. The magnitudes of the impact force, the fracturing force, and the paper damaging stress are estimated. Within the framework of linear elasticity theory, general expressions for the stresses induced in the shell and core have been derived for both solid and liquid cores. Particular cases have been computed and presented in normalized graphical form on a unit loading basis. The shell strength depends strongly on the geometrical and elastic properties of the core and shell materials, specifically on the shell thickness, the ratio of the core and shell shear moduli, and the tensile strength of the shell material. The modes of toner fracture and the significant effects of the elastic properties of the paper on the crushing force of the particles is discussed. It is shown that the breaking of the particles is facilitated by a harder surfaced paper.     

A Field-Limited Theory of Cascade Development

Recently reported model experiments of Knapp [1] on electroded cascade development provide an excellent set. of data for testing presumptive development models since so many of the experimental parameters are available. A development model is presented that is based on the assumption that in the dynamic process of cascade development the instantaneous force binding a toner to a carrier is proportional to q, the charge on the toner, rather than to q2. This is in contrast to the q2 force dependence observed in equilibrated mixtures. The mechanism of toner detachment is impact-assisted electric-field stripping. Statistical distributions for toner radius, surface charge density, and impact velocity are introduced. The results are compared with Knapp's experiments and with a recent theoretical model of Maitra, Scher, and Knapp (MSK). In contrast to MSK, although the specific form of the distributions is important for the conclusions, the particular parameters of the distributions have little effect. The statistics do not smear the physics.     

Electrophotographic Properties of an Organic Photoconductor and a Triboelectric Magnetic Toner for a New Diode Laser Printer

The electrophotographic properties of a newly developed organic photoconductor and triboelectric magnetic toner were investigated for a nonimpact printer with a diode laser. The photoconductor was composed of a metal-free phthalocyanine layer and an oxazole-derivative-doped polymer layer. The photoconductor had a charge acceptance of -1000 V and a light sensitivity of more than 0.1 m2/mJ at 780 nm. The magnetic toner had a resistivity as high as 1014 ? cm and could accept triboelectric charge of -3.5 ?C/g. Chrome dye was employed for a negative charge control agent to affect the sign and magnitude of triboelectric charge on toner particles. Using the developed organic photoconductor and triboelectric magnetic toner, good quality prints on plain paper were obtained with the new diode laser printer. Toner mass density deposited on the photoconductor was improved by more than 20 percent as compared with that of conventionally used conductive or high-resistance magnetic toners. It was found that the triboelectric magnetic toner had a very high transfer efficiency of as large as 80 percent, even on plain paper.     

La-Ca-Sr-Co系高性能干压各向异性永磁铁氧体的研制

以北矿BMS-12预烧料为基料,首先通过湿压工艺确定出适宜的二次添加剂添加量,在此基础上采用干压法制备各向异性永磁铁氧体材料,分析黏合剂、润滑剂用量及磁粉粒度对磁体性能的影响。实验结果表明,樟脑黏合剂和硬脂酸钙润滑剂的适宜添加量分别为0.6wt%、0.8wt%。在0.85~1.00μm的粉料粒度范围内都可以获得较高的剩磁和矫顽力。得到的典型干压磁体性能:Br=421m T,Hcb=296k A/m,Hcj=360k A/m,(BH)max=33.2k J/m3,达到TDK的FB5D性能水平。La-Ca-Sr-Co系干压磁体具有比传统锶永磁铁氧体湿压磁体更高的剩磁和内禀矫顽力。     

600MW超临界机组的成膜胺停运保护

以成膜胺在600 MW超临界机组大修停运保护中的应用为例,介绍超临界机组成膜胺保养法的工艺、过程和效果。检查发现成膜胺在热力设备内表面形成了有效的憎水性保护膜,机组再次启动后,蒸汽品质合格时间大大缩短,证明600 MW超临界机组的停运保护采用成膜胺法能达到理想的保护效果。     

Optical Xerography

After a review of standard xerography, it is shown that optical techniques can be used to perform all the xerographic functions (charging, exposure, transfer, fusing and cleaning) except development. ``Photoelectric charging' and ``induction charging' are described in detail, and the complicated and subtle phenomena which occur at the photoconductor interfaces are clarified. ``Persistent internal polarization (PIP)' is also discussed, and the role of the photoconductor interfaces and the bulk traps in the photoconductor are clarified. The spectral considerations necessary to optimize machine performance are discussed in terms of the crucial components (lamps, documents, optics and photoconductors). The new concept of ``optical transfer' and the use of light to aid in ``cleaning' are described. The use of radiation to perform xerographic fusing is described for both ``flash' fusing and ``radiant' fusing. The essential concepts necessary for achieving ``selective fusing' are discussed.