Ricoh Company, Ltd.

Ikuko Yamada

Akio Kojima

Kiyofumi Nagai

Masayuki Koyano

Masayuki Shoshi

Masato Igarashi

Akiko Konishi

Takanori Tsuyuki

Megumi Kawahara

Hiroyuki Mochizuki

An aqueous ink composition contains a colorant and a humectant, and has a surface tension &ggr; of less than 50 mN/m when measured by a maximum bubble pressure method at 25&deg; C., with a bubble frequency &ngr; of the aqueous ink composition being set at less than 1 Hz, and a surface tension &ggr; of more than 40 mN/m when measured by the maximum bubble pressure method at 25&deg; C., with the bubble frequency &ngr; of the aqueous ink composition being set at more than 5 Hz. In addition, an ink-jet printing method for forming ink images on an image-receiving medium has the step of ejecting the above-mentioned aqueous ink composition in the form of droplets according to the recording signals at a recording frequency of 8 kHz or more.

Aqueous ink compositions and ink-jet printing method using the same

An aqueous ink composition contains a colorant and a humectant, and has a surface tension .gamma. of less than 50 mN/m when measured by a maximum bubble pressure method at 25.degree. C., with a bubble frequency .nu. of the aqueous ink composition being set at less than 1 Hz, and a surface tension .gamma. of more than 40 mN/m when measured by the maximum bubble pressure method at 25.degree. C., with the bubble frequency .nu. of the aqueous ink composition being set at more than 5 Hz. In addition, an ink-jet printing method for forming ink images on an image-receiving medium has the step of ejecting the above-mentioned aqueous ink composition in the form of droplets according to the recording signals at a recording frequency of 8 kHz or more.

Aqueous ink composition and ink-jet printing method using the same

Cycolpentadiene derivative compounds, and an electrophotographic photoconductor comprising one cyclopentadiene derivative compound are disclosed. The cyclopentadiene derivative compounds are novel and useful for use in a photoconductive layer, and readily soluble in a binder resin. The electrophotographic photoconductor can be prepared by using a simple, effective production method. The electrophotographic photoconductor comprising one cyclopentadiene derivative compound provides a good light sensitivity and high durability.

Cyclopentadiene derivative compounds and electrophotographic

Cyclopentadiene derivative compounds, and an electrophotographic photoconductor comprising one cyclopentadiene derivative compound are disclosed. The cyclopentadiene derivative compounds are useful for use in a photoconductive layer, and readily soluble in a binder resin. The electrophotographic photoconductor can be prepared by using a simple, effective production method. The electrophotographic photoconductor comprising one cyclopentadiene derivative compound provides a good light sensitivity and high durability.

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Kawasaki, Japan

Ikuko Yamada