Hematite, the most stable and rust-free iron oxide, is widely used as a red inorganic pigment in our daily products because of its attractiveness as a color material. Although there is a desire to enhance the chroma value in the various fields where hematite is used, it is difficult to realize such a demand. To utilize hematite as a color material by controlling its color, it is necessary to understand crystallographic structure, electronic structure, controlling factors for chroma value, and photocatalytic activity in a comprehensive manner and synthesize novel hematite. In this review, we summarize the information necessary to understand the color of hematite for developing a novel hematite-based red pigment.

Zinc oxide was added to phosphoric acid and shaken in a hot water bath to react the surface to phosphate, resulting in the preparation of novel white pigment with suppressed photocatalytic activity. The temperature of the hot water bath and the pH of phosphoric acid were examined as conditions for this treatment, and the preparation using condensed phosphates was also studied. The chemical composition, particle condition, and photocatalytic activity of the resulting powder samples were evaluated.

Development of novel inorganic pigments possessing high durability and vividness, which are composed of non-toxic elements, has been highly required. To obtain brilliant colors with only harmless elements, it is essential to control the crystal structure of pigments, especially the local structure around the color source atoms. In this account article, we introduce our recent research on environmentally friendly inorganic blue pigments developed by controlling the local structure in Cu containing solids.

Microplastic(MP) beads are widely used as texturing agents in sunscreens and makeup cosmetics. However, in recent years, ocean pollution due to environmental outflow of microplastics waste has been attracting worldwide attention, and alternative materials to MP beads are being sought. Therefore, we have focused on silica as an environmentally friendly material and synthesized spherical silica with excellent texture to solve this global problem. We have succeeded in developing surface-treated spherical silica that has the same “softness” as MP beads by applying composite multilayer treatment to silica particles with excellent texture.

Wide-gamut printed images are desired to support vibrant displays such as quantum dot (QD) and organic light emitting diode (OLED). Developing new dyes that satisfy the characteristics of the dye sublimation transfer printer is difficult and has not changed for several decades. We here report about the development of the new solvent dyes that is high chroma and high light stability for the wide color gamut dye sublimation thermal transfer printers. In other words, we designed and synthesized azamethine magenta dye (AZD-70), azomethine cyan dye (CAZ-19), and azo yellow dye (PAY-161) as main MCY color materials. By applying the newly developed dyes to the sublimation transfer ink ribbon, a color gamut volume equivalent to that of an IJ printer could be expressed. In print tests, we observed an improvement in the general chroma of true images of morpho butterfly, lemon, and strawberry and a remarkable improvement in the black density of a true image of a betta. Each dye gave a negative Ames test result. Besides, we can utilize these development dyes for toner design, and for the supercritical carbon dioxide dyeing of polypropylene fibers.