Behavior of the electric double layer around each particle was evaluated by experimental studies. An electric field was applied to each test liquid by a parallel electrodes ; one side of one of the electrodes was covered with dielectric thin film. Surface potential of the dielectric thin film was measured after certain periods of application of driving voltage. A rapid raise of the electric potential, which was almost the same value as the applied voltage, was measured at the hydrocarbon liquid mixed with metal soap with fine particles. On the other hand, such a quick rise of the surface potential was not observed at any other liquid : a hydrocarbon liquid, a hydrocarbon liquid mixed with the fine particles, and a hydrocarbon liquid mixed with the metal soap. This result means that the electric charge of the particles are probably brought by the ions derived not from the water content in the liquid but form the metal soap. The experimental results also indicate that the electric double layer was destroyed, when the driving voltage applied, and counter ions in the outer layer migrated to the opposite direction that of the particles.

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The objective of this paper is to analyze the particle mixing behavior in a two-component electrophotographic system by using parallel Discrete Element Method. 326 thousands particles(carrier and toner particles, toner concentration : 1.0wt%)were calculated for 75 millions steps. The effects of the electrostatic force and adhesion force on the mixing behavior were discussed in this work. The toner particles were segregated near the outer wall, when the adhesion force was not considered in the calculation. On the other hand, the toner particles were located between the carrier particles when the toner particles had 15μC/g in charge and the adhesion force was considered between particles. The number of contacts between particles increased under the condition of considering the adhesion force, however, the number of “new” contacts between them decreased. Thus, the most of toner particles are stuck to the surface of carrier particles, and they are moving together. It seems that the toner charge would be saturated in this condition because of the reduction of new contact.

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The kinetic charging theories analyzing the charge to mass ratio of toner in the two-component developer were reexamined.
In the previous two theories,(1)the toner charge to mass ratio becomes zero in infinite mixing time and(2)the toner charge to mass ratio does not depend on the toner to carrier mixing ratio, the construction of the charging equation and the mathematical translation of the equation were complemented by this study.
As a result, the relationship between the charge to mass ratio and the mixing ratio of toner to carrier deduced by the kinetic charging theories were almost consistent with the surface state theory.
Finally, this study concluded that the three theories, the surface state theory, the improved electric field theory and the kinetic charging theory were consistent with each others.

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The software development of magnetic brush simulator in a two-component electrophotographic system have been tried in this work. Three-dimensional modeling of magnetic brush behavior was conducted by using Discrete Element Method. The graphical user interfaces(GUI)for pre/post processes were developed by using Microsoft Visual Basic. The data of magnetic field around development nip can be imported from the ones analyzed by J-MAG Studio. The parameters which the users can change in the simulator are the diameters of photoreceptor or development roll, their rotational speeds and the directions, the length of development gap, particle size distribution, the magnet configuration, the position of development nip against the magnetic field, frictional coefficient, Hamaker constant for calculating adhesion force, and so on. The brushes behavior is visualized by using Micro AVS, after the calculation is finished. The computing time is basically proportional to the number of particles, and about half a day is required when 15000 carrier particles are simulated. Therefore, this simulator will be very useful in the process design of two-component development system in the industry.

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Recent years, inkjet technologies are adapting to practical applications to the electronic device field and medical field as well as the print field. The drupa2008 was an exhibition to which all over the world had paid attention as “Inkjet drupa” to which a lot of digital printing press using an inkjet technology was exhibited.
The trend of the digital printing press was observed from the each company device vender's product development. And this is the review of the example of applying an inkjet technology in the digital printing press introducing the approach and products of “Dainippon Screen Mfg. Co., Ltd.”

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Recently, Multi Function Printer(MFP)utilizing an electrophotography method have been making progress in its advancement to the print field. This demonstrates that the performance of the electrophotography method has approached to the print level, even though it is originally suitable for Print on Demand(POD). In this context, SHARP also took the first step to gain access to the POD market by releasing MFP MX-M1100/M950/M860 to the market as a flagship model in 2007.
This MFP was developed with the aim of raising basic performance such as “Productivity”, “Stability”, “Reliability”, and “Durability” to a higher level, which is the most requested in the POD market. This report shows photoconductor that serves as the core of electrophotography with a focus on (1) “molecular design of hole transport material” which made full use of simulation to realize high response required for speed-up and (2) “Long life design” which provides abrasion resistance and scratch resistance to achieve 1000 K life. Moreover, I describe various process designs required for high image quality of 1200 dpi in high-speed process, and a variety of control technology to stabilize image quality.

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RICOH Pro C900 is the first digital full-color printer as new Brand from Ricoh as “RICOH Pro Series” for the production printing market to meet the necessity of Print-On-Demand.
Main features of this printer are
1) Prints at the speed of 90ppm(A4 LEF, 70-300gsm)on fastest speed of this class with both full color and monochrome printing.
2) Consistent high quality out-put (Real 1200dpi, Three to five times longer life of photoconductor with conventional one, Accurate paper skew adjustment and registration technologies)
3) Standard equipped Fiery controller with high versatility and high function
4) Outstanding down sized dimension and lightened weight (W×D×H : 1,250×1,100×1,440mm, Weight : 700kg)

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Lately the market demand for short run and variable printing is increasing. And the digital presses match such applications. Printing market buys the electro-photography based models mostly because the good balance of productivity, quality and running cost. Within these “toner” printers, HP Indigo is famous in high quality using the unique “liquid toner”. This article explains the general process of the “HP Electro Ink technology” and refers to the newest model 7000 about the reliable high speed imaging process.

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700 Digital Color Press, which uses newly-developed toner called EA-Eco toner, provides high productivity, 71PPM for full color(64-176g/m² A4LEF)simplex mode. Machine is mainly for Print On Demand market but its size is similar to multi-function machine for general office market. 700 Digital Color Press has several functions to improve media capability such as front-to-back registration adjustment, auto duplex for media from post card size to 330×488mm, paper feed capability up to 300g/m², curl adjustment for various types of media, and transfer level adjustment, which office color mult-function products do not have. This document describes positioning in market and specification of 700 Digital Color Press, characteristics of EA-Eco toner, and technology of media feed and registration.

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[in Japanese]

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