PARAMETERS INFLUENCING TONER CHARGING CHARACTERISTICS IN ELECTROPHOTOGRAPHIC PRINTING

ABSTRACT

The charge-to-mass ratio, q/m, of a two-component developer is the important factor in an electrophotographic system, since the toner charge controls the developed tone mass and the print quality. This article investigates the charging properties of differently shaped toners (spherical and irregular), and carrier particles that differ in their composition and surface oxide layer thickness by adjusting the applied current. The parameters for toner charging involving the mixing force, the toner concentration, the shape of the toner, the carrier type, and the current of the carrier surface are studied. The print quality is evaluated by focusing on the solid density, 60 and 40% halftone densities, background density, and edge sharpness of the characters. An explanation of the force between the toner and carrier particles is proposed.     

Electrostatic Microencapsulation Technique for Producing Composite Particles

The electrostatic microencapsulation process and the various means of achieving such encapsulation for developing composite particles with two or more powders is briefly reviewed, with a particular focus on the dual-function sorbent/scintillation particles for use in radionuclide selective sensing. In preparing the composite particles, two different types of particles, an ion-exchange resin and scintillating microbeads, were used. The sorbent particles capture and preconcentrate the radionuclide of interest (e.g., 99 Tc) from solution. The scintillating microbeads are used to convert the energy of radioactive decay into that detectable light that can be deducted by a photomultiplier tube arrangement. To simulate the electrostatic microencapsulation of resin and scintillators, several surrogate materials such as acrylic powder (mean particle diameter, d 50 =23 µm), red toner (d 50 =16 µm), resin (d 50 =134 µm), and fluorescent latex spheres (d 50 =2 µm) were used. A microencapsulation tower was constructed to use corona guns operating at high voltages of opposite polarity to charge the "host" and "guest" particles. Experimental arrangements and test results are presented. The results show that if polymer particles are used and if one of the two powders is smaller than 10 µm in diameter, the electrostatic and van der Waals forces provide enough interparticle adhesion to bond the guest and host particles through plastic deformation. Interparticles adhesion between resin (d 50 =133 µm) and toner (d 50 =15 µm) showed that the composite particles were stable in water suspension. For larger particles, such as resin and scintillators, the use of a binding agent is necessary to form stable composite particles. electrostatic microencapsulation particle coating groundwater monitoring composite particles radionuclide detection     

Electrostatic Microencapsulation Technique for Producing Composite Particles

The electrostatic microencapsulation process and the various means of achieving such encapsulation for developing composite particles with two or more powders is briefly reviewed, with a particular focus on the dual-function sorbent/scintillation particles for use in radionuclide selective sensing. In preparing the composite particles, two different types of particles, an ion-exchange resin and scintillating microbeads, were used. The sorbent particles capture and preconcentrate the radionuclide of interest (e.g., 99 Tc) from solution. The scintillating microbeads are used to convert the energy of radioactive decay into that detectable light that can be deducted by a photomultiplier tube arrangement. To simulate the electrostatic microencapsulation of resin and scintillators, several surrogate materials such as acrylic powder (mean particle diameter, d 50 =23 µm), red toner (d 50 =16 µm), resin (d 50 =134 µm), and fluorescent latex spheres (d 50 =2 µm) were used. A microencapsulation tower was constructed to use corona guns operating at high voltages of opposite polarity to charge the "host" and "guest" particles. Experimental arrangements and test results are presented. The results show that if polymer particles are used and if one of the two powders is smaller than 10 µm in diameter, the electrostatic and van der Waals forces provide enough interparticle adhesion to bond the guest and host particles through plastic deformation. Interparticles adhesion between resin (d 50 =133 µm) and toner (d 50 =15 µm) showed that the composite particles were stable in water suspension. For larger particles, such as resin and scintillators, the use of a binding agent is necessary to form stable composite particles.

electrostatic microencapsulation particle coating groundwater monitoring composite particles radionuclide detection     

Conductive Toner Cloud Confinement Using the Cone Shape of a Dented Electrode

Control of toner movement is an important parameter in the development of digital printing. Conductive toner has possibilities for a new, simple printing mechanism. Conductive toner particles were sprayed onto the lower electrode. An electric field was applied between the two electrodes. The toner moved up and down between the two electrodes by electrostatic force. When the cone shape of the dented electrode replaced the lower plate, conductive toner particles were confined in the dented electrode. This research studied the toner confinement conditions required to form a toner cloud state using the cone-shaped dented electrode. It was found that the depth of the cone-shaped dented lower electrode, the resistivity of conductive toner, and applied voltage between the electrodes were the influencing factors that determined the optimum size of toner cloud confinement and the toner-jump current. The deeper cone-shaped dented electrode reduced the size of the toner cloud confinement and the toner-jump current. A high resistivity toner produced a larger size toner cloud and decreased the toner-jump current. When a greater amount of toner was placed in the electrode, a larger size toner cloud and greater toner-jump current were obtained. A higher applied voltage reduced the size of the toner cloud and increased the toner-jump current.     

Toner Cloud Generation and its Supply over the Width of a Printing Area

Toner cloud generation along with controlling its movement is one of the important parameters in the development of digital printing by the toner cloud beam technique. In the experimental set-up for toner cloud generation, the conductive toner particles were sprayed at the center of a wide chamber-shaped dented electrode as the lower electrode was placed parallel with the upper electrode, leaving a small gap between them using two insulating sheets. An electrical, field was applied between the two electrodes. The toner moved up and down between the two electrodes by electrostatic force, forming the toner cloud, which propagated to both ends of the dented electrode. This research studies the toner cloud generation conditions using the wide chamber-shaped dented electrode, the slope of the nesa glass, and the slope of the system as the influencing factors that governed toner cloud generation and its movement. An increase in the applied voltage led to a faster toner cloud speed. When a greater amount of toner was applied into the dented electrode, a faster toner cloud movement was obtained. On the other hand, the toner cloud speed decreased when increasing the depth of the dented electrode. An increase of the slope of nesa glass increased the toner cloud speed. However, the toner cloud speed was not significant to the system when the slope was between 0 and 5 degrees. It was also found that the width of toner cloud decreased when the applied voltage increased. Furthermore, the two overlapped cone-shaped dented electrodes could be used for generating the toner transport to the printing system. This research also explains the possible phenomena for toner cloud generation and performance.     

Toner Cloud Generation and its Supply over the Width of a Printing Area

Toner cloud generation along with controlling its movement is one of the important parameters in the development of digital printing by the toner cloud beam technique. In the experimental set-up for toner cloud generation, the conductive toner particles were sprayed at the center of a wide chamber-shaped dented electrode as the lower electrode was placed parallel with the upper electrode, leaving a small gap between them using two insulating sheets. An electrical, field was applied between the two electrodes. The toner moved up and down between the two electrodes by electrostatic force, forming the toner cloud, which propagated to both ends of the dented electrode. This research studies the toner cloud generation conditions using the wide chamber-shaped dented electrode, the slope of the nesa glass, and the slope of the system as the influencing factors that governed toner cloud generation and its movement. An increase in the applied voltage led to a faster toner cloud speed. When a greater amount of toner was applied into the dented electrode, a faster toner cloud movement was obtained. On the other hand, the toner cloud speed decreased when increasing the depth of the dented electrode. An increase of the slope of nesa glass increased the toner cloud speed. However, the toner cloud speed was not significant to the system when the slope was between 0 and 5 degrees. It was also found that the width of toner cloud decreased when the applied voltage increased. Furthermore, the two overlapped cone-shaped dented electrodes could be used for generating the toner transport to the printing system. This research also explains the possible phenomena for toner cloud generation and performance.     

Adhesive interaction of elastically deformable spherical particles

Two spherical particles that attract each other by van der Waals volume forces and can undergo deformation as a result of the attraction are considered. Small deformations of such particles can be described by the solution of the Hertz problem. The deformation of particles, in turn, alters the force of attraction between them. It has been established that the relationship between the adhesion and elasticity of the indicated particles is determined by the degree to which these particles deform and that the adhesion force acting between the particles depends on their elasticity, size, and the Hamaker constants.     

Ultrastrong adhesion of graphene membranes

As mechanical structures enter the nanoscale regime, the influence of van der Waals forces increases. Graphene is attractive for nanomechanical systems because its Young's modulus and strength are both intrinsically high, but the mechanical behaviour of graphene is also strongly influenced by the van der Waals force. For example, this force clamps graphene samples to substrates, and also holds together the individual graphene sheets in multilayer samples. Here we use a pressurized blister test to directly measure the adhesion energy of graphene sheets with a silicon oxide substrate. We find an adhesion energy of 0.45±0.02 J m(-2) for monolayer graphene and 0.31±0.03 J m(-2) for samples containing two to five graphene sheets. These values are larger than the adhesion energies measured in typical micromechanical structures and are comparable to solid-liquid adhesion energies. We attribute this to the extreme flexibility of graphene, which allows it to conform to the topography of even the smoothest substrates, thus making its interaction with the substrate more liquid-like than solid-like.     

Calculated binding of gold atoms to alkali halide substrates

The contributions to the atomic desorption energy and activation energy for surface diffusion from electrostatic polarization forces and van der Waals dispersion forces for the deposition of gold on alkali halide substrates have been calculated assuming hard-sphere repulsion between adatom and ion. The results for different substrates are compared with each other and with experimental values for gold on ultrahigh-vacuum-cleaved NaF, NaCl, KCl and KBr surfaces. The magnitude of the polarization term is nearly equal to that of the van der Waals term and can be important in determining the adsorption site and diffusion path. This appears to be the case for NaF but not for NaCl.     

Measuring van der Waals and electrostatic forces for an atomic force microscope probe contacting with metal surfaces

A contact force spectrometry technique was used to measure the van der Waals and electrostatic forces acting on platinum-coated silicon probes contacting with metal films on silicon substrates. It is shown that the results of such measurements can be used for determining the geometric characteristics of probes and the Hamaker constant of contacting materials. The experimental data well agree with the theoretical values.     

Resuspension of particles from surfaces: Technological,environmental and pharmaceutical aspects

Particles that were previously deposited on the surface of any substrate are resuspended to the surrounding environment due to complex effects. The effectiveness of resuspension depends on the geometry of deposits in the form of mono- or multilayer geometries, material properties of the particle and the substrate and the interaction of particles with external excitations. The particle leaves the substrate or its surrounding neighbors, if the external force exceeds the adhesive/cohesive force. Different types of adhesive forces, such as van der Waals interactions, capillary forces and electrical double layer forces, are considered. The adhesive effects are extended to the cases of deformable bodies with the formation of the surplus of the contact area between the particle and the substrate. Finally, the adhesion of particles to the rough surface of the substrate is considered. The next sections of this paper are devoted to the analysis of the particle detachment process due to its interaction with a flowing gas of different flow properties, including a pulsating jet flow and a developed turbulent flow. The mechanisms of the pull-off forces as well as sliding and rolling effects in the presence of asperities are also presented. Finally, the detachment of particles from the multilayer structures of deposited particles is analyzed. The paper is summarized focusing on the practical aspects of resuspension, including the techniques of cleaning of the wafer surface, environmental consequences of resuspension with health risk and the application of resuspension for the production of inhalable particles from drug powder structures.     

Numerical simulation of the head-on collision of two equal-sized drops with van der Waals forces

The head-on collision of two equal-sized drops in a hyperbolic flow is investigated numerically. An axisymmetric volume-of-fluid (VOF) method is used to simulate the motion of each drop toward a symmetry plane where it interacts and possibly coalesces with its mirror image. The volume-fraction boundary condition on the symmetry plane is manipulated to numerically control coalescence. Two new numerical methods have been developed to incorporate the van der Waals forces in the Navier–Stokes equations. One method employs a body force computed as the negative gradient of the van der Waals potential. The second method employs the van der Waals forces in terms of a disjoining pressure in the film depending on the film thickness. Results are compared to theory of thin-film rupture. Comparisons of the results obtained by the two methods at various values of the Hamaker constant show that the van der Waals forces calculated from the two methods have qualitatively similar effects on coalescence. A study of the influence of the van der Waals forces on the evolution and rupture of the film separating the drops reveals that the film thins faster under stronger van der Waals forces. Strong van der Waals forces lead to nose rupture, and small van der Waals forces lead to rim rupture. Increasing the Reynolds number causes a greater drop deformation and faster film drainage. Increasing the viscosity ratio slows film drainage, although the effect is small for small viscosity ratio.     

The role of van der Waals forces in adhesion of micromachined surfaces

Interfacial adhesion and friction are important factors in determining the performance and reliability of microelectromechanical systems. We demonstrate that the adhesion of micromachined surfaces is in a regime not considered by standard rough surface adhesion models. At small roughness values, our experiments and models show unambiguously that the adhesion is mainly due to van der Waals dispersion forces acting across extensive non-contacting areas and that it is related to 1/Dave2, where Dave is the average surface separation. These contributions must be considered because of the close proximity of the surfaces, which is a result of the planar deposition technology. At large roughness values, van der Waals forces at contacting asperities become the dominating contributor to the adhesion. In this regime our model calculations converge with standard models in which the real contact area determines the adhesion. We further suggest that topographic correlations between the upper and lower surfaces must be considered to understand adhesion completely.     

EFFECT OF CCA AND CHARGING BEHAVIOR ON PRINT QUALITY

Fourteen test toners and two types of toner of irregular shape and spherical shape were studied for charging behavior. There are three types of CCA of various concentrations. They were mixed by rotation roller, developing roller, and hand shaking. Charging properties of the toners were measured by E-SPART analyzer and blow off measurement unit. Evaluations of print quality in terms of solid density, background density and percentage of dot gain were carried out to obtain correlation with charging properties. The charge of the toners with CCA increased to an equilibrium state within a shorter time. The toners without CCA have the lowest density. The higher the CCA amount, the higher the print density, but the background density of the toners without CCA were higher than the toners with CCA In addition, the presence of CCA and silica affects the toner charge when the humidity is varied. This article describes the effects of CCA type/its concentration and charging behavior on the extent of q/m values which controls the print quality.     

Closed-form approximation and numerical validation of the influence of van der Waals force on electrostatic cantilevers at nano-scale separations

In this paper the two-point boundary value problem (BVP) of the cantilever deflection at nano-scale separations subjected to van der Waals and electrostatic forces is investigated using analytical and numerical methods to obtain the instability point of the beam. In the analytical treatment of the BVP, the nonlinear differential equation of the model is transformed into the integral form by using the Green's function of the cantilever beam. Then, closed-form solutions are obtained by assuming an appropriate shape function for the beam deflection to evaluate the integrals. In the numerical method, the BVP is solved with the MATLAB BVP solver, which implements a collocation method for obtaining the solution of the BVP. The large deformation theory is applied in numerical simulations to study the effect of the finite kinematics on the pull-in parameters of cantilevers. The centerline of the beam under the effect of electrostatic and van der Waals forces at small deflections and at the point of instability is obtained numerically. In computing the centerline of the beam, the axial displacement due to the transverse deformation of the beam is taken into account, using the inextensibility condition. The pull-in parameters of the beam are computed analytically and numerically under the effects of electrostatic and/or van der Waals forces. The detachment length and the minimum initial gap of freestanding cantilevers, which are the basic design parameters, are determined. The results of the analytical study are compared with the numerical solutions of the BVP. The proposed methods are validated by the results published in the literature.     

喷墨打印颜料型墨水制备过程中颜料的分散

本文就颜料型墨水中颜料的分散进行了初步研究,颜料在其制造过程中,最初形成粒度为5纳米～1微米的初级粒子,能轻易的分散到涂料中去。但初级粒子在加工过程中,会因种种原因相互黏结成聚集体（aggregates）,聚集体之间聚集体与初级粒子之间还可以通过边、角之间的黏结形成附聚物（agglomerate）。通常附聚物分子之间的吸引力要弱的多,黏结不那么牢固,比较容易分散;但聚集体由于分子吸引力大,黏结比较牢固,较难分散。颜料在涂料中的分散过程由三个阶段组成一润湿、机械力分散聚集粒子及抗絮凝的稳定作用。润湿和聚集主要通过设备来完成,是创造稳定处理的前提,但不足以得到稳定的分散体系,当剪切力消除时,又可以重新附聚或凝聚。因此必须加入分散剂以稳定分散的颜料粒子。 颜料粒子的稳定主要取决于颜料粒子的相互接近时三个主要的作用力：范德华力,静电力,空间位阻力。三种力的相互作用构成了颜料的分散理论。     

Si芯片表面纳米粒子的粘结力及其干法清除

系统地研究了纳米粒子在硅芯片表面的各种附着力,如范德瓦耳斯力、塑性形变吸附力、毛细现象凝聚力、静电力和重力附加力,以及高速流体对它的拖动力和提拉力,并简单计算了在各种情况下这些力的大小。介绍了干法清除纳米污染物的几种新方法,如超临界流体清除法、高速气凝胶清除法、激光清除法、气相化学清除法和光化学清除法。     

EFFECT OF CCA AND CHARGING BEHAVIOR ON PRINT QUALITY

ABSTRACT

Fourteen test toners and two types of toner of irregular shape and spherical shape were studied for charging behavior. There are three types of CCA of various concentrations. They were mixed by rotation roller, developing roller, and hand shaking. Charging properties of the toners were measured by E-SPART analyzer and blow off measurement unit. Evaluations of print quality in terms of solid density, background density and percentage of dot gain were carried out to obtain correlation with charging properties. The charge of the toners with CCA increased to an equilibrium state within a shorter time. The toners without CCA have the lowest density. The higher the CCA amount, the higher the print density, but the background density of the toners without CCA were higher than the toners with CCA In addition, the presence of CCA and silica affects the toner charge when the humidity is varied. This article describes the effects of CCA type/its concentration and charging behavior on the extent of q/m values which controls the print quality.     

Length-dependent extraction of single-walled carbon nanotubes

A two-phase liquid-liquid extraction process is presented which is capable of extracting water-soluble single-walled carbon nanotubes into an organic phase. The extraction utilizes electrostatic interactions between a common phase transfer agent and the sidewall functional groups on the nanotubes. Large length-dependent van der Waals forces for nanotubes allow the ability to control the length of nanotubes extracted into the organic phase as demonstrated by atomic force microscopy.     

微机电系统中的微观黏滑、黏附与控制

微观黏滑和黏附失效是微机电系统中的常见现象,该现象主要是由于受包括静电力、范德华力及毛细力等各种表面力所起的主导作用而产生的．采用黏着接触理论和运动分析方法,得到了微观摩擦试验中黏滑出现的无量纲黏滑数,表微观黏滑是接触表面特性、形貌参数、接触载荷及滑动速度等综合作用的结果,进而获得黏滑现象的各种临界参数,提出了黏滑行为控制的表面修饰与形貌设计依据;针对微构件的黏附失效,采用Laplace公式并结合微构件的变形分析,探究了毛细力作用下微构件的变形特征与失稳行为,发现其变形过程中存在着不稳定的临界点,对应黏附行为的发生,进而提出了微构件防黏附的结构设计．