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Dive into the research topics where Hiroshi Kumai is active.

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Featured researches published by Hiroshi Kumai.


Liquid Crystal Displays and Applications | 1990

Phase diagram and phase separation in LC/prepolymer mixture

Yoshinori Hirai; Satoshi Niiyama; Hiroshi Kumai; Tomoki Gunjima

A new method to obtain liquid crystal and polymer composite(LCPC) material is reported. This material is a new electro-optic material which can control scattering and transparent states in an electric field. e obtained this material by the photo-polymerization-induced phase separation from liquid crystal and prepolymer mixture where both monomer and oligonier are used as prepolymer. We have found new type of phase diagram in this mixture which has a nematicisotropic line in addition to binodal and spinodal lines. Electro-optic properties of this material are strongly affected by the point on the phase diagram at which the polymerization-induced phase separation starts. This method enables us to control these properties such as voltage-transmittance characteristics. Typical devices using these materials are also shown. They have high contrast ratio and high transmittance in ON state and are suitable for display devices. Drive voltage can be reduced by optimizing this material and the device with high contrast ratio about 200:1 in low drive voltage below 6Vrms was obtained.


Proceedings of SPIE | 1998

Three-dimensional morphology of LCPC using confocal fluorescence microscopy

Shinya Tahara; Satoshi Niiyama; Hiroshi Kumai; Tsuneo Wakabayashi

We have developed a new method for characterizing morphology of LCPC based on confocal fluorescence microscopy. Not only two-dimensional but also three-dimensional morphology of LCPC can be observed nondestructively by this method. The morphology of LCPC was consisted of liquid crystal and polymer phases, both of which are three-dimensionally continuous. Quantitative analysis of morphology was also made to clarify the relation between morphology and electro-optical characteristics. The local size of structure was obtained quantitatively from the perimeter of liquid crystal and polymer. It was found that the change in the value matched well with the change in morphology and it was related with the electro-optical characteristics.


Liquid Crystal Materials, Devices, and Applications IV | 1996

Morphology and ordering control in LCPC

Hiroshi Kumai; Satoshi Niiyama; Yoshiharu Ooi; Shinya Tahara; Yoshinori Hirai; Tsuneo Wakabashi; Tomoki Gunjima

A phase separation under an applied electric field (PSUF treatment) in LCPC relaxes the energetic stress for dynamic operation of its device. Both higher dynamic response time and less hysteresis in dark gray scales which are significant issues in LCPC are achieved, since its treatment can control the interface between liquid crystal and matrix polymer without the damage to scattering in off state and contrast ratio. It is based on the morphological characteristic which is caused by the first step: a segregation of liquid crystal and ordering process of the liquid crystal under an applied field, and the second step: polymer/pre-polymer precipitation to maintain the early ordering of segregated liquid crystal. The essential structure of LCPC caused by the characteristic phase separation process, is characterized with confocal fluorescence microcopy, which also supports its process mechanism.


The Journal of The Institute of Image Information and Television Engineers | 1999

Display-Special Contribution from IDW '98. Reflective-type polymer dispersed LC-mode Projection Display.

Yoshiharu Ooi; Minoru Sekine; Masaya Kunigita; Satoshi Niiyama; Kunio Masumo; Shinya Tahara; Naoki Kato; Hiroshi Kumai

A new compact projection display has been developed using light valves based on a 2-inch diagonal low-temperature poly-Si TFT reflective XGA array and polymer dispersed LC-mode, 120-W ultrahigh-pressure short-arc lamp (UHP lamp), and simple optical components. Luminous flux of 1400 ANSI-lm, contrast ratio of 85, and the illuminance homogeneity of 90% were achieved. Simulation by basic optical theory in concentrators and experiments with a simplified reflective-type polymer dispersed LC-mode light valve indicates that the performance could be improved in future up to a luminous flux of 1600 ANSI-lm with contrast ratio of more than 150.


Archive | 1987

Liquid crystal optical device and process for its production and method for its operation

Tomoki Gunjima; Hiroshi Kumai; Shoichi Tsuchiya; Kaoriko Masuda


Archive | 1988

Liquid crystal optical device using U.V.-cured polymer dispersions and process for its production

Tomoki Gunjima; Hiroshi Kumai; Minoru Akatsuka; Shoichi Tsuchiya


Archive | 1992

Liquid crystal optical element with liquid crystal in polymer matrix with particular modulus of elasticity

Yoshinori Hirai; Satoshi Niiyama; Hiroshi Kumai; Tomoki Gunjima


Archive | 2012

Optical filter, solid-state imaging element, imaging device lens and imaging device

Makoto Hasegawa; Satoshi Kashiwabara; Hiroshi Shimoda; Kenta Sekikawa; Takashi Shibuya; Mitsuo Osawa; Katsushi Kamijyo; Hiroyuki Arishima; Hiroshi Kumai


Archive | 1988

Liquid crystal optical device and process for its production

Tomoki Gunjima; Hiroshi Kumai; Minoru Akatsuka; Shoichi Tsuchiya


Archive | 2006

Polymerizable liquid crystal compound, liquid crystal composition, optically anisotropic material, and optical element

Yuriko Asahi Glass Koriyama Electr.Mat. Kaida; Hiromichi Nagayama; Hiroshi Kumai

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