An ε-type copper phthalocyanine (ε-CuPc) film was prepared by the aqueous coating method, and used it as the charge generation layer (CGL), double-layered photoconductors were fabricated. A polyvinylcarvazole film was employed as the charge transport layer (CTL). This novel coating method utilizes electrochemical deposition of pigments from an aqueous pigment dispersion on an aluminum substrate. Centrifugal particle analysis of the ε-CuPc dispersion indicated that number-averaged and weight-averaged diameter of the ε-CuPc particles are < 0.01 and 0.173 μm, respectively. The latter value was confirmed by the transmission electron microscopic measurement. Reflection spectra and X-ray diffraction patterns of the CuPc films revealed that crystal form was maintained throughout electrochemical deposition process. Scanning electron microscopic measurements of surface and cross section of the ε-CuPc film indicated that rod-like crystals of 0.5 - 1 μm in length grow parallel or randomly to the surface of the aluminum substrate. Electrophotographic measurements of the layered photoreceptor revealed that properties such as initial potential, dark decay rate, and sensitivity were affected by the amount of electricity passed during the deposition of the CGL, i.e., the thickness of the CGL (d). The sensitivity of the photoreceptor has a maximum value at d ≅ 1000 Å that is never observed in layered photorecethors of binder-dispersed type.

View full abstract

In the high speed electrophotographic prosseces, the performance of the discharge devices using AC corona is very important for separating sheet stably from photo-conductive drum. This paper deals with the effects of corotron shapes and the gap length of the wire and the plate supplied charge on the performance of the discharge devices with two wires. In the examination, when a center shield exists between two wires, and the gap length between wires and the plate is short, the negative charge value supplied to the plate is more than the positive one. On these results, the methods to stabilize the performance of the discharge devices were proposed.

View full abstract

The film properties and the xerographic characteristics of charge blocking layers, made from alcoxide and acetylacetonate compounds of Ti and Zr, for overcoated xerographic photoreceptors have been investigated. These films are simillar to TiO₂ and ZrO₂, but superior in uniformity, solvent resistance and adhesive property. The charge acceptance of As₂Se₃ and Se-SeTe photoreceptors with a protective overcoat layer of 1,1'-Dimethylferrocene doped in polyarylate, or SnO₂/Sb₂O₃ conductive powder dispersed in polyacrylurethane, reduces to 1/10 of the value without the overcoat. An insertion of 0.2 μm thick film of this blocking layer restores the charge acceptance. The optimum materials, i.e. the alcoxide or acetylacetonate compounds of Zr with an additive of 20 ? 30 % silane coupling agent, can remove image blurring even under high humidity conditions. It is also found through I-V measurements and mathematical modeling that the charge blocking layer should be partially conductive, and the electric field dependence of resistivity should be small. The overcoated photoreceptors with the charge blocking layer have been used in the commercial copy machines.

View full abstract

High speed and high quality is obtained by sublimation-type resistive sheet themal transfer method. In this method, two key elements are considered. One is the print head and the other is the resistive sheet. The print head was developed using the relation between the electrode tip area and the optical density, which are analyzed by numerical simulation. The resistive sheet is composed of three layers as resistive, conductive and ink layer. Four kinds of resistive sheet with various resistivity were prepared, and were tested the relations of optical density with the printing energy and width of applying pulse as well as the gradation of images for various printing speeds. The optical density 1.8 of the printed images can be accomplished with a printing speed of 1.2 millisecond per a line keeping an excellent gradation without losing the glossiness at high optical density.

View full abstract

We have implemented a full-color electrophotographic process based on intensity modulated laser scanning exposure. Although such a method can realize high resolution as well as continuous tone reproduction, it was supposed to have a difficulty in system stability.
By analyzing the potential distributions of latent images formed by intensity modulated laser scanning exposure, we derived a model for “effective developing potential”, a dominant factor of determining the mass of toner developed. By constructing a process stabilizing system which is based on effective developing potential and which operates to constantly realize a target tone reproduction curve, the above-mentioned apprehension has been overcome.

View full abstract

Effects of overcoating layer (OCL)consisting of urethane and silicone on image qualities for multiple-layerd positive charging organic photoconductor (OPC) was studied by surface resistance measurement and computer simulated time dependence of electrostatic image on OPC. Surface resistance of OCL depend strongly on the enviromental condition. Cycle down of surface resistance under high temperature/humidity cause degradation of image quality. Lowest surface resistance with enough image quality determined surface resistance measurement of OCL is in good agreement with that estimated computer simulated time dependence of electrostatic image on OPC. Surface resistive lowering of OPC is controlled by the resistive lowering of OCL which involves absorbtion of ions (Cl^-, SO₄^2-) from paper to the surface of colloidal silica.

View full abstract

Computer program for obtaining time dependent positions of toner particles for any DC and/or AC bias as well as photoreceptor surface potential has been worked out with the use of a subroutine program (Fig.9) for calculating time dependent field strength including the contribution of the charge of toner particles. Typical simulation results are shown in Fig.12 and Fig.13 - 14 showing good agreement with the experimental results. Parameters for the simulation and experiment are shown in the figures.

View full abstract

The reduction of bad influence of ozone on a photoconductor is requested on the corona charger, which bears on the element part of electrophotography. To reduce the bad influence, the ozone wind against a photoonductor must be reduced.
But it is difficult to reduced ozone without reducing the surface potential. Two technically points are needed. The first point is the reduction of the quantity of ozone generated on corona charger. The second point is the control of the direction of ozone wind generated on the charger Therefore, the analysis software to visualize the phenomenon and the design system have been developed by utilizing finite element method. By using above-mentioned analysis software and design system the reduction of the quantity of ozone and the bad influence of ozone wind against a photoconductor and the progress in the quality of image are acomplished without reducing the surface potential.

View full abstract

Three different calculation methods of heat of fusion of wax type ink are studied in the thermal diffusion simulation in thermal melt transfer printing. The first is a well known one by the Finite difference method. The second was originally developed by G. Comini et al where the enthalpy is used in the Finite element method (FEM) of thermal diffusion, and the third is reported here for the first time. In this new method, a fictitious flow is introduced in the matrix calculation of FEM in the process of heat absorption and liberation. As a result, Little difference is found in the results of the three different methods. The third method especially gives almost the same results as the second one, and in addition the computing time is much shorter. The calculation predicts almost consistent results with the exprimental relationship between power and pulse width in thermal transfer printing.

View full abstract