Abstract: The present invention relates to a process for producing magnetic metal particles for magnetic recording, comprising: heat-treating goethite particles having an aluminum content of 4 to 50 atom % in terms of Al based on whole Fe to obtain hematite particles; and heat-reducing the hematite particles at a temperature of 200 to 600° C., the goethite particles being obtained by adding a peroxodisulfate to a reaction solution comprising: a ferrous salt aqueous solution and a mixed alkali aqueous solution comprising: an alkali hydrogen carbonate aqueous solution or alkali carbonate aqueous solution and an alkali hydroxide aqueous solution before initiation of an oxidation reaction of the reaction solution, and then conducting the oxidation reaction.

Abstract: The present invention relates to ferromagnetic metal particles having an average major axis diameter (L) of 10 to 100 nm which satisfy a relationship between the average major axis diameter (L) and a particle SFD represented by the following formula: Particle SFD?0.0001 L2?0.0217 L+1.75; a process for producing the ferromagnetic metal particles; and a magnetic recording medium using the ferromagnetic metal particles.

Abstract: The present invention relates to ferromagnetic metal particles having a bulk density (?a) of not more than 0.25 g/cm3, a process for producing the above ferromagnetic metal particles and a magnetic recording medium comprising a non-magnetic substrate; a non-magnetic undercoat layer formed on the non-magnetic substrate which comprises non-magnetic particles and a binder resin; and a magnetic recording layer formed on the non-magnetic undercoat layer which comprises magnetic particles and a binder resin, wherein the above ferromagnetic metal particles were used as the magnetic particles.

Abstract: The present invention relates to a process for producing magnetic metal particles for magnetic recording, comprising: heat-treating goethite particles having an aluminum content of 4 to 50 atom % in terms of Al based on whole Fe to obtain hematite particles; and heat-reducing the hematite particles at a temperature of 200 to 600° C., the goethite particles being obtained by adding a peroxodisulfate to a reaction solution comprising: a ferrous salt aqueous solution and a mixed alkali aqueous solution comprising: an alkali hydrogen carbonate aqueous solution or alkali carbonate aqueous solution and an alkali hydroxide aqueous solution before initiation of an oxidation reaction of the reaction solution, and then conducting the oxidation reaction.

Abstract: Composite particles having an average particle diameter of 0.001 to 10.0 ?m, comprise: white inorganic particles as core particles; a gluing agent coating layer formed on surface of the white inorganic particle; and an organic pigment coat formed onto said gluing agent coating layer in an amount of from 1 to 500 parts by weight based on 100 parts by weight of the white inorganic particles. The composite particles are substantially free from desorption of an organic pigment from the surface thereof and contain no harmful element.

Abstract: Non-magnetic composite particles composed of non-magnetic core particles having an average particle size of 0.01 to 0.3 &mgr;m, and inorganic fine particles having an average particle size of 0.001 to 0.07 &mgr;m. The fine particles are present in an amount of 0.1 to 20% by weight based on the weight of the non-magnetic particles are on the surface of each non-magnetic particle, and are fixed or anchored on the surface of each non-magnetic particle through a silicon compound The non-magnetic composite particles have a high polishing effect and a high dispersibility, and are useful as a non-magnetic undercoat layer for a magnetic recording medium.

Abstract: Composite particles capable of an excellent dispersibility and an excellent light resistance of the present invention have an average particle diameter of 0.001 to 12.0 &mgr;m, comprise: white inorganic particles as core particles; a gluing agent-coating layer formed on at least a parts of the surface of said white inorganic particle; and a black pigment coat composed of carbon black, aniline black or both carbon black and aniline black, formed onto at least a part of the gluing agent-coating layer in an amount of from 1 to 500 parts by weight based on 100 parts by weight of said white inorganic particles.

Abstract: A black composite iron oxide pigment of the present invention comprises composite iron oxide particles having an average particle size of 0.08 to 1.0 &mgr;m, comprising: as core particles iron oxide particles, a coating formed on surface of said iron oxide particle, comprising at least one organosilicon compound selected from the group consisting of: (1) organosilane compounds obtainable from alkoxysilane compounds, and (2) polysiloxanes or modified polysiloxanes, and an organic blue-based pigment coat formed on said coating comprising said organosilicon compound, in an amount of from 1 to 50 parts by weight based on 100 parts by weight of said iron oxide particles.

Abstract: Non-magnetic composite particles composed of non-magnetic core particles having an average particle size of 0.01 to 0.3 &mgr;m, and inorganic fine particles having an average particle size of 0.001 to 0.07 &mgr;m. The fine particles are present in an amount of 0.1 to 20% by weight based on the weight of the non-magnetic particles are on the surface of each non-magnetic particle, and are fixed or anchored on the surface of each non-magnetic particle through a silicon compound The non-magnetic composite particles have a high polishing effect and a high dispersibility, and are useful as a non-magnetic undercoat layer for a magnetic recording medium.

Abstract: Organic and inorganic composite pigments having an average particle diameter of 0.01 to 10.0 &mgr;m composed of a white inorganic particle, an organosilane compound obtained from alkoxysilanes, or polysiloxanes coating on the white inorganic particle, and an organic pigment coat formed on said coating. An ultraviolet light-absorbing agent is present in any portion from the surface of the white inorganic particle to surface of the organic pigment coat. These composite pigments have reduced amounts of organic pigments desorbed from their surface and exhibit excellent light resistance due to their ultraviolet absorbing property.

Abstract: Magnetic composite particles of the present invention comprise:

Abstract: Composite particles capable of an excellent dispersibility and an excellent light resistance of the present invention have an average particle diameter of 0.001 to 12.

Abstract: Organic and inorganic composite pigments have an average particle diameter of 0.01 to 10.

Abstract: A plastic film which has a low hiding power and an improved heat resistance, and which exhibits an excellent color, is free from discoloration upon molding and shows a more excellent combustion efficiency upon incineration, and which comprises:

Abstract: Non-magnetic composite particles composed of non-magnetic core particles having an average particle size of 0.01 to 0.3 &mgr;m, and inorganic fine particles having an average particle size of 0.001 to 0.07 &mgr;m. The fine particles are present in an amount of 0.1 to 20% by weight based on the weight of the non-magnetic particles are on the surface of each non-magnetic particle, and are fixed or anchored on the surface of each non-magnetic particle through a silicon compound.The non-magnetic composite particles have a high polishing effect and a high dispersibility, and are useful as a non-magnetic undercoat layer for a magnetic recording medium.

Abstract: A black composite iron oxide pigment of the present invention comprises composite iron oxide particles having an average particle size of 0.08 to 1.

Abstract: Iron oxide hydroxide composite particles having an average particle diameter of 0.005 to 1.0 &mgr;m, comprises: iron oxide hydroxide particles as core particles, a coating formed on surface of said iron oxide hydroxide particles, comprising at least one organosilicon compound selected from the group consisting of: (1) organosilane compounds obtainable from alkoxysilane compounds, and (2) polysiloxanes or modified polysiloxanes, and an organic pigment coat formed on said coating layer comprising said organosilicon compound, in an amount of from 1 to 30 parts by weight based on 100 parts by weight of said iron oxide hydroxide particles. The iron oxide hydroxide composite particles of the present invention contain no harmful elements and exhibit not only excellent chemical resistances such as acid resistance and alkali resistance, but also excellent heat resistance.

Abstract: Composite particles having an average particle diameter of 0.001 to 10.

Abstract: Iron oxide hydroxide composite particles having an average particle diameter of 0.005 to 1.

Abstract: A fine red iron oxide pigment of the present invention comprises hematite particles and having a geometrical standard deviation of major axial diameter of not more than 1.5, a geometrical standard deviation of minor axial diameter of not more than 1.3 and an average major axial diameter of 0.005 to 0.1 &mgr;m. Such fine red iron oxide pigment is uniform in both major axial diameter and minor axial diameter thereof and exhibits an excellent transparency.