In recent years, various studies using visible light for information communication have been actively conducted. In addition, a new code called “color · code”, in which color information is added to a black-and-white two-dimensional code such as a QR code, has been developed and used. We have focused on this color · code and have been developing a simple multiplex visible light communication system by combining it with ordinary electronic terminals. In this research, in order to realize even larger capacity communication, we constructed a system that communicates by converting color · codes into moving images. We report the results of an investigation into the performance of these systems.

We examined the penetration of ink droplets onto fabric during inkjet dyeing process using a cylindrical array yarn model. Through 1-D numerical modeling and CFD (computational fluid dynamics) simulations, we assessed the wicking speeds in directions parallel (√D_‖) and perpendicular √D_⊥) to the yarn. The results showed that √D_⊥/√D_‖ ratio diminishes as the effective pore diameter ϕ decreases. This implies that when the yarn is more tightly twisted, wicking tends to occur primarily along its length. Additionally, using CFD simulations based on fabric structures obtained via X-ray CT (computed tomography) imaging, we observed trends aligning with the outcomes from the cylindrical array yarn model.

The simulation methods to calculate a series of toner image formation processes in the electrophotographic system have been developed. These methods consist of a coupled calculation method for particle motion and electromagnetic fields that can accurately consider the electric forces acting on the toner, in addition to a large-area toner melting deformation calculation method. In the coupled calculation of particle motion and electromagnetic fields, the motion of the toner is computed by considering not only the Coulomb force acting on the toner charge but also the gradient force acting on the toner electric polarization. Additionally, in the toner melting deformation calculation, the three-dimensional toner image melting deformation within a large area is computed, considering the viscoelastic properties of the toner, various design factors of the fixing process, and the shape of the paper surface profile. This paper elaborates on these calculation methods and presents analysis examples of applying these methods.

We developed a new prediction model which satisfy requirements of both calculation cost and accuracy. In two component development process, which is widely used for its suitability of high speed, high image quality, and colorization, huge number of carrier and toner particles that consist of developer are complexly moved while applied to several forces such as magnetic and electrostatic force. This leads to difficulty in high-precision and high-speed numerical simulation. We developed method to predict toner movements from carrier movements and toner properties by decomposing forces that is applied to toner based on intermediate characteristics between several development parameters and development characteristics. Important development characteristics such as developability, toner scattering, and bead-carry-out were simulated with high accuracy at low calculation cost.

Spark discharge is used effectively in charging process and transfer process of electrophotography. For example, photoreceptor surface is uniformly charged by spark discharge between the charging roller and the photoreceptor. If the spark discharge is not uniform, the image becomes non-uniform or pattern by creeping discharge appears in the image. Therefore, non-uniform discharge should be avoided in the electrophotography process. In this paper, general information about discharge is introduced first and then spark discharge is explained in detail. As for spark discharge, difference between uniform discharge and non-uniform discharge and the feature of non-uniform discharge is discussed.

It is required to develop efficient design methods that find virtually good configurations of the fixing unit from the upstream design. However, it is not easy to realize the design that satisfies product specifications due to many trade-offs between performances. When a fixing unit is designed virtually, detailed performance evaluations by numerical analyses are required because nonlinear phenomena occur in the fixing unit. To find optimal configurations, it is difficult to evaluate many configurations because it requires a huge amount of analysis time. This paper reports a design method of optimal fixing units by using surrogate models and multi-objective optimization.

The new simulation method to calculate the three-dimensional toner image structure after the fixing process has been developed. This method has made it possible to achieve what was previously impossible by decomposing the complex physical phenomena in fusing process into the several computational steps : toners stress, toners temperature, toners compression, and toners spread. Validation against actual samples demonstrated that the simulations accurately reproduce the extent of toner spread area on paper. Additionally, the study identifies that density unevenness, caused by variations in toner image area across different paper position, results from two primary shape factors : millimeter-scale paper waviness and micrometer-scale paper fine textures.

The evaporation rates of pico-liter droplets of water are measured with a visualization system to verify an estimation model and to investigate the effect of surrounding droplets. The visualization system consists of a piezo inkjet head with a linear actuator, camera, LED (light emitting diode) light, media, and thermo-hygrometer, and can measure the contact radius and the volume of a droplet. The evaporation rate can be estimated from the evolution of the droplet volume. The experimental results are compared with an existing evaluation model and simulation results. In the case of a single droplet evaporation, the effect of latent heat due to evaporation is discussed with the comparison among the experiment, estimation model and simulation. With the consideration of droplet cooling that is estimated from the simulation, estimated evaporation rate and evolution of droplet volume show good agreement with the experiment. Temperature cooling due to evaporation is an important factor for a droplet evaporation. In the case of multi-droplet evaporation, the effect of surrounding droplets is investigated with the consideration of droplet cooling due to evaporation. The results confirm when the distance between droplets becomes closer, the effect of surrounding droplets becomes greater.

This paper offers an overview of studies of RICOH Collaborative Research Program on Advanced Digital Printing Technology at Institute of Science Tokyo. The Program started in 2019 and we are engaged in studying inkjet technology. Inkjet printer generates images with many droplets ejected from nozzles. The process is very simple, but it is difficult to understand phenomena without theoretical consideration and simulation. We have been struggling with these phenomena (ejection, deposition, evaporation, and penetration), and have reported our studies at conferences and journals ; mainly of the Imaging Society of Japan. These researches : ejection of non-Newton fluid, droplet-coalescence, image formation, deposition on CFRP (carbon fiber reinforced plastics) film and nozzle evaporation, will be introduced in this paper.

In the ink containing a polymer, even if the static viscosity is the same, the higher the polymer concentration, the higher the required driving voltage and the longer the distance between the separated droplets. Though this seems to be the effect of the viscoelasticity, the mechanism is not understood. In this paper, the effect of viscoelasticity is analyzed by the ejection simulation using the Oldroyd-B model. As a result, it was found that the required driving voltage increases as the solute viscosity increases, and that the distance between separated droplets increases as the solute viscosity increases, and that the distance decreases after taking the maximum value, and that it becomes one drop when the solute viscosity increases to some extent. This is because the constriction between the back end of the ink column and the meniscus and between the front end of the ink column and the head drop become slow due to the increase in the elongational viscosity.

In this paper, we discuss what can be expected in the thermal design of the printing process based on model-based design. The thermal design of electronic devices using plant models based on thermal network analysis is not new. On the other hand, thinking freely about design elements and exploring adventurous product designs is necessary to meet the diversified consumer demands for manufacturing. Thermal network analysis hints at how thermal design should approach the heat transfer process, which is the core of the printing process. We will introduce examples of recent issues that have come to light in general thermal design and the analysis of heat transfer processes in printing processes, and we will consider the ideal framework for thermal design.

This study proposes a method to integrate a surrogate model using neural networks into 1D-CAE (1 dimensional computer aided engineering) to accelerate thermal calculations in the thermal printing process. Thermal printing, which uses heat from resistive heating elements to print, requires precise and efficient computational models. In this research, we constructed a computational model of the thermal printing process using Modelica, creating head and media as separate components. The media component incorporates an RNN (recurrent neural network) using GRU (gated recurrent unit) to predict the complex causal relationships of heat flow and print indicator from head temperature and media speed. The RNN was trained using training data generated from an FEM (finite element method) model, completing the 1D-CAE computational model. This approach significantly reduces computation time compared to traditional FEM, providing an effective tool for examining complex thermal history control in thermal printing processes.

We have acquired a color texture appearance technology that performs printing simulations for special color printing such as gold, silver, transparent colors, and fluorescent colors. However, the special color materials used in printing have diversified in recent years, and their optical properties have made it difficult to reproduce them using only color reproduction techniques based on traditional measurement methods. In this paper, we have developed a color gloss prediction model based on multi-angle spectral measurements, realizing color texture reproduction that changes depending on the viewing angle. We will report on the technical details and reproducibility.

Third-party consumables such as compatible cartridges and compatible toner are widely used worldwide due to their low price. Their market share is quite large in the printer field. The world's largest exhibition for compatible products and used equipment is held annually in Zhuhai, China. Last October (October 17-19, 2024), I visited the exhibition, REMAX WORLD EXPO 2024. Here is an overview of the little-known market for interchangeable products, with a focus on electrophotography-related products.