Abstract: There has been provided by the present invention a process for producing a single crystal of potassium niobate which comprises disposing a positive electrode directly or via a semi-insulating substance layer on one c-plane of a single crystal of potassium niobate and also a negative electrode via a semi-insulating substance layer on the other c-plane of the single crystal of potassium niobate, said positive and negative electrodes being disposed in mutually facing relationship, and applying voltage between the positive and negative electrodes so as to pole (convert to the single-domain state) the single crystal of potassium niobate, and which enables to pole the entire region of the single crystal of potassium niobate without quality deterioration.

Abstract: A discharge recording material produced by successively forming a colored layer comprising mainly carbonblack and a binder, a deposited metal layer and optionally a protective layer on a support is provided. In particular, the discharge recording material wherein said carbonblack being carbonblack aggregates obtained by pretreating carbonblack particles with a plasticizer is provided.

Abstract: A discharge recording medium having a colored insulating layer, a metal-vaporized layer and, as required, a protection layer formed in that order on a support member, wherein the colored insulating layer contains a graphite powder having particles of a specifically determined average size in an amount according to a specifically determined ratio with respect to a bonding resin in the colored insulating layer.