Electrophotographic Characteristics Research Articles

Hole-Transporting Silsesquioxanes

The fluorene diol (I) has been chemically incorporated into a sol-gel formulation that was coated to produce a thin overcoat on an organic photoreceptor and cured into a silsesquioxane matrix that efficiently transports holes. The residual potential of the photoreceptor decreased as the amount of hole transport material (I) incorporated into the silsesquioxane matrix was increased. The charge transport was independent of humidity. At 30 wt.% the residual potential is identical to that of a photoreceptor without an overcoat. This methodology produces an organic photoreceptor with a protective overcoat without compromising the electrophotographic characteristics.

Charge Generation in a Bisazo-Based Layered Photoreceptor

In the past papers, we had proposed a new model of the charge generation process in a single layer organic photoconductor, supposing indirect process of charge generation. In this study, we expanded this concept into more general dual layered system. Photoreceptors comprising a charge generation layer (CGL) of bisazo pigments dispersion into polyvinyl-butyral resin and a charge transport layer (CTL) of solid solution of donor molecule into polycarbonate resin were employed in the experiment. The change of electrophotographic characteristics by thickness of CGL in both conventional dual layer system and plus charging inversed dual layer system suggested the location of charge generation site at the interface of CGL and CTL and the energy diffusion from the bulk CGL. The estimated energy diffusion length was much longer than those ever reported as exiton diffusion. It was also found that whole discussion derived in the previous study upon single layer OPC was applicable to this dual layer system.

Physical Properties and Electrophotographic Characteristics of a Toner

Physical Properties and Electrophotographic Characteristics of a Toner

Properties of Photoreceptor Devices Consisting of Metal Free Phthalocyanine and Polymer

The dispersion effect in solution making a positively charged monolayer photoreceptor consisting of x-type metal-free phthalocyanine (x-H2Pc) and a binder resin is studied. The photoreceptor is characterized by a high photosensitivity due to a new specific interaction between x-H2Pc and the binder resin.1 It is suggested that the characteristics of the solution structure and the chemical actions significantly affect the behavior of x-H2Pc. To clarify more this behavior, the solution state is examined by viscometry, and the solid state is examined by X-ray diffraction, transmission and scanning electron microscope, and ion potential and xerographic measurements. From these results, it was found that the dispersion process of the x-H2Pc pigment, depending on the composition and the dispersion time of the solution, significantly influences the physical properties and the electrophotographic characteristics of the monolayer photoreceptor.

Mixed State of Color Toner Particles in Two-Component Developer via Shaker

We have analyzed tribo-charging characteristics on black toner particles in two-component developer. The electrophotographic characteristics on toner in the developer are affected by various factors such as material component, shape and methods of tribo-charging or measurement. It is, therefore, important to evaluate not only tribo-charging behavior but also the mixed state of toner particles and carrier beads in the two-component developer. For this purpose, yellow color toner particles instead of black toner are adopted in the developer for evaluation of tribo-charging characteristics. Tribo-charging on toner is performed by using the two types of shaker with different arm length, 130mm and 200mm, where the shaker with 130mm arm length is based on the recommended design by the ISJ. From the results of photographs on the outside appearance of mixed toner samples in a glass bottle, the completely mixed state for toner is obtained after 20min of mixing time at 150rpm with arm length of 130mm and also after 1 min of mixing time at 150rpm with arm length of 200mm. For the tribo-charging behavior, it is showed that the charge to mass ratio q/m is −12.5μC/g for 20min of shaking time at 150rpm with the 130rpm arm length shaker and −19.0μC/g for 1min at 150rpm with the 200mm. In the case of 120rpm with the 130mm, the q/m shows to be slightly charged values corresponding to the insufficiently mixed states.

Silsesquioxane Sol-Gel Materials as Overcoats for Organic Photoreceptors

Organic photoreceptors for use in electrophotographic processes may be overcoated to impart wear and scratch resistance, to protect the surface from corona generated chemicals, and to improve the efficiency of electrophotographic process steps, such as toner transfer and cleaning. In this article, we will discuss the use of silsesquioxanes prepared by the sol-gel process as photoreceptor overcoats. Included in our discussion will be the chemistry and procedures involved in overcoat fabrication, the methods used to determine the effects of the overcoat on the physical and electrophotographic characteristics of the photoreceptor, and the effects of the silsesquioxane chemical structure on these characteristics.

Syntheses, characteristics and electrophotographic properties of new dithiosquarylium dyes

A new class of dithiosquarylium dyes (DTSQ) has been synthesized by the reaction of squarylium dye (SQ) with Lawesson's reagent or P 4S 10. The λ max , of DTSQ dyes undergoes a bathochromic shift of about 25 nm compared with corresponding SQ dyes. The visible absorption spectra of DTSQ dyes are well accounted for by Pariser-Parr-Pople Molecular Orbital (PPP-MO) calculations. Electrophotographic characteristics of negatively charged dual layered photoreceptors with DTSQ for charge generation materials (CGM) and 1-phenyl-1,2,3,4-tetrahydroquinoline-6-carboxyaldehyde-1′,1′-diphenylhydrazone as a charge transport material (CTM) have been investigated. The photoreceptor that used DTSQs exhibited high photosensitivity at white light.

Electrophotographic and Hole Transport Properties of Polycarbonates Doped by Organic Photoconductors and Their Light- and Corona Discharge Stabilization

Electrophotographic and hole transport properties of organic photoconductor layers on the base of a phenyltolyl-(β-naphtylamine) (PTNA) doped polycarbonate (PC) and pure (binderless) PTNA were investigated. PTNA was doped into different PCs of types PC-A and PC-Z. Hole drift mobility measured by conventional time-of-flight techniques in the PTNA+PC films was lower than that in the binderless PTNA films. Electrophotographic properties of OPC drums on the base of the PTNA and DEH doped PC layers were studied. An influence of light-, corona- and light + corona intensities on the electrophotographic characteristics of the OPC drums with stabilized or non stabilized charge transporting and generating layers was investigated as well. A stabilization of the electrophotographic layer compounds by various additives such as an antioxidant, an ultraviolet absorber, and an agent for preventing light- and corona induced deterioration was performed.

Investigation of diamond-like carbon films for protection and stabilization of selenium-containing photoreceptors in electrophotography

The possibilities of diamond-like carbon film applications for protection and stabilization of selenium-containing photoreceptors in electrophotography have been studied experimentally. We have determined the optimal conditions for deposition of diamond-like a-C:H films as well as their thickness at which the electrophotographic characteristics and the printing quality are not deteriorated as compared with control samples of a-Se. The effect of amorphous phase stabilization in the selenium photoreceptors when depositing the a-C:H layer has been revealed. The service life of copying cylinders with a protective a-C:H coating increases by a factor of 2–3.

Electrophotographic properties and ultraviolet light fatigue of dual- layered photoreceptors incorporating phthalocyanine and hole transport polymers

Dual-layered photoreceptors incorporating τ-form metal-free phthalocyanine (τ-H2Pc) for charge generation material and poly(methylphenylsilylene)(PMPS) for charge transport material(CTM) have been studied concerning their electric properties especially in the electrophotographic characteristics. The photoreceptor using PMPS exhibited high sensitivity; however, the fatigue due to ultraviolet(UV) light was observed. We compared them with well-known poly(N-vinylcarbazole) for CTM based on surface potentials, sensitivities, hole carrier mobilities, and conductivities. As a result of Gel permeation chromatography, Fourier transform infrared and x-ray photoelectron spectroscopy spectra before and after UV light irradiation, the PMPS was cleaved into lower molecular weight products and polymerized, which included cross-linking.

Electrophotographic characteristics of layers of amorphous selenium on substrates with different thicknesses of oxide barrier film

Electrophotographic characteristics of layers of amorphous selenium on substrates with different thicknesses of oxide barrier film

Influence of Space Charges in Carrier Generation Layer on Electrophotographic Characteristics of Layered Photoreceptors (II)

Influence of Space Charges in Carrier Generation Layer on Electrophotographic Characteristics of Layered Photoreceptors (II)

Photoelectric properties of Michler's ketone—Effects of curing

Solution-sprayed layers of Michler's ketone were cured at different temperatures. Layers cured by heating to 180°C showed the best electrophotographic characteristics. From a study of the change in the conduction current due to corona charging and the rate of decay of different polarity of corona charge, it was concluded that Michler's ketone exhibits P-type conductivity. The effect of different rates of curing on the structure of layers is shown by means of SEM photography and microphotographs, and the electrical properties correlated with surface structure.

Electrophotographic properties of Michlers ketone-polymer double-layer systems

Solution-sprayed cured layers of Michlers ketone were overcoated with various polymers to enhance their charge acceptance. It is found that an overlayer of poly(vinyl butyral) gives the best electrophotographic characteristics, showing a maximum charge acceptance of 825 V and a contrast potential of 540 V.

Photochemical oxidation of brominated poly-N-epoxypropyl carbazole

The results of study of the electron structure and fluorescence of bromine-substituted poly-N-epoxypropyl carbazole are presented. It has been established that the bathochromic shift in the absorption and luminescence bands of the polymers is associated with change in the electron structure of the carbazole chromophore on introducing bromine atoms into it. The special aspects of the photo-oxidation of bromine-substituted polymers and the character of the influence of the products thereby formed and also of the electron-acceptor impurities on the properties of the materials have been studied. The nature of the fluorescence of the bromine-substituted, sensitized and photo-oxidized samples is discussed. The electrophotographic characteristics of bromine-containing poly-N-epoxypropyl carbazoles are presented.

Influence of Space Charges in Carrier Generation Layer on Electrophotographic Characteristics of Layered Photoreceptors

Influence of Space Charges in Carrier Generation Layer on Electrophotographic Characteristics of Layered Photoreceptors

Electrophotographic characteristics of CdS binder layers after heat and light treatment effects

The effect of heat and simultaneous heat-light treatment on aged in darkness CdS binder layers is investigated. The CdS powder is doped with copper and iron in various concentrations. The heat treatment in the temperature range from 80 to 150°C with or without illumination in the spectral interval from 500 nm to 750 nm is studied. The dependence of the contrast potential vs the exposure time as well as the residual potential after various sample treatments are given. It is suggested that the applied treatments on the aged in darkness samples may be associated with the reversible changes in shape and structure of the intercrystalline or interface barriers and with photochemical reactions in the bulk of the CdS particles.

Study of the optoelectronic properties of HgS:Cd(S,Se): Cu mixed system for electrophotographic applications

A study of the electrophotographic characteristics of red HgS:Cd(S,Se):Cu mixed system has been conducted. Polystyrene was used as the binder. The composition 95:05 (by weight) of HgS and Cd(S,Se):Cu shows optimum electrophotographic properties when used with 30% (by weight) polystyrene binder. It shows 71.9% fractional decay of surface potential under illuminations as calculated 10 s after the start of illumination, with an incident light intensity of 3.6 mW/cm 2. The spectral sensitivity peaks of the system lie at 600 nm, 534 nm and 484 nm. This mixed system has an obvious advantage over either single HgS or Cd (S,Se):Cu single layer, for conventional electrophotographic applications, such as xerography and electrofax.

Electrophotographic characteristics of copper-phthalocyanine (CuPh)-polyvinyl cinnamate (PVCn) binder layers

Electrophotography is the science of document copying by selective dissipation of charge of corona charged layers. The recent trend in this field is to develop binder-layer type xerographic plates [1, 2]. Copper-phthalocyanine (CuPh) is a well studied photosensitive material and some work on its electrophotographic use has been' done using silicone resin as a binder [3, 4]. In the present paper, electrophotographic characteristics of copper-phthalocyanine (CuPh) in polyvinyl cinnamate (PVCn) binder are described. PVCn is also a photosensitive polymer. CuPh and PVCn used in the present study were obtained from Fluk: A. Chemische Fabrik CH-9470 BUCTIS and Polysciences Inc (USA), respectively. The desired weight ratios of these materials were milled in a mechanical grinder using benzene as a thinner. The films were made by pouring this mixture on an aluminium substrate. The layers were dried in atmospheric benzene and later in an oven maintained at 60°C for 48 h to remove all traces of benzene. The films were positively charged by a d.c. corona unit for 15 sec and then the surface potential decay was measured in the dark as well as in the light. The various samples studied during the present investigation were 20 : 80, 30: 70, 40:60, 50:50 and 60:40 weight ratio of CuPh and PVCn. The film thickness was 100 pro. The light from a 60 W tungsten lamp of intensity 1200 lux was used for photodischarge studies. The room temperature (30 ° C) and relative humidity (55%) were maintained constant during the course of investigations. The grid voltage and charging time were optimized to 1.5 kV and 15 sec, respectively, which were maintained constant throughout the experiments. The corona voltage was 6 kV. The effect of charging time and grid potential on the initial surface potential of 50:50 CuPh: PVCn samples are shown in Figs. 1 and 2, respectively. It has been observed that initially the surface potential increases both with charging time and grid potential and finally attains a saturation value. These results are expected. The number of charge carriers becoming trapped during corona charging increases with charging time and grid potential and hence the surface potential increases with the increase in time and grid potential. But the detrapping and recombination of charge carriers takes place simultaneously along with trapping. When these two, i.e. trapping and detrapping and recombination become equal, further charging of the film stops and we observed a saturation effect [5, 6]. The difference in surface potential decay in the dark and the light determines the use of a material in electrophotography. A good electro

PbO/Cd(S, Se): Cu Mixed Photoconductor System for Electrophotography

A mixed system, consisting of Lead monoxide (PbO) and Cadmium Sulfo selenide Cd (S, Se): Cu in Acrylonitrile-Butadiene-Stytene (ABS) binder resin has been inevstigated with respect to electrophotographic characteristics. PbO and Cd (S, Se): Cu in 80: 20 composition (by weight), when dispersed in ABS binder, (30% by weight) give optimum values for various electrophotographic parameters. Charge acceptance, dark and photo induced decay, contrast potential and spectroresponse were the important electrophotographic properties, studied. The acceptance potential of the charged layer was 1092 volts. The fractional dark decay (observed 60 seconds after the charging) and fractional photo induced decay (observed 10 seconds after the start of illumination) were 35.5% and 79.4% respectively. The intensity of illumination was 4.5 mW/cm2. The absorption spectrum of the material spreads over a wide range covering UV as well as visible region.