A process is provided for the preparation of magnetic particles to which a wide variety of molecules may be coupled. The magnetic particles can be dispersed in aqueous media without rapid settling and conveniently reclaimed from media with a magnetic field. Preferred particles do not become magnetic after application of a magnetic field and can be redispersed and reused. The magnetic particles are useful in biological systems involving separations.

Magnetic particles for use in separations

An optical information disk with an excellent mechanical precision is provided. Also provided is a multi-layer optical disk having a plurality of data layers wherein every data layer exhibits sufficient properties in reading. In addition, such multi-layer optical disk is provided at a low cost. The optical information comprises a disk-shaped substrate or a pair of disk-shaped substrates, and at least one annular data layer for storing at least recorded information and at least one annular resin layer disposed on said disk-shaped substrate or between said pair of disk-shaped substrates. In this medium, at least one of the substrate(s) has a configuration such that its surface facing toward the data layer is convex, and at least one of said resin layer(s) is formed such that it is thicker near its outer periphery compared to the region near its inner periphery.

Optical information medium

The invention relates to an isokinetic gantry arrangement for the isocentric guidance of a particle beam ( 12 ), that can be rotated about a horizontal longitudinal axis ( 16 ) and has a beam optical system, symbolized by magnets ( 36, 38, 40 ), that deflects the particle beam ( 12 ) axially infected by a particle beam accelerator, radially and vertically relative to the horizontal longitudinal axis ( 16 ), with a largely rotationally-symmetrical primary structure ( 18 ) and a secondary structure ( 30 ) that holds the magnets ( 36, 38, 40 ) and is supported by the primary structure ( 18 ), with the secondary structure ( 30 ) having a rigidity that is designed so that the vertical displacements of the magnets ( 36, 38, 40 ) due to their weight are essentially of equal magnitude (isokinetic) in all the angle of rotation positions of the gantry arrangement ( 10 ), and a method for its design.

Isokinetic gantry arrangement for the isocentric guidance of a particle beam and a method for constructing same

An organic solvent-based piezo ink is disclosed having (a) pigment particles; (b) binder; (c) plasticizer; (d) organic solvent; (e) a fluorochemical surfactant; and (f) an antifoaming agent comprising silica and silicone oil. Optionally light and heat stabilizers are also included. Method of making and using this ink are also disclosed.

Piezo inkjet inks and methods for making and using same

Encapsulated particles, such as magnetic particles, colored pigments, or carbon black, with high chemical affinity for ink vehicles. The encapsulated particles are suitable for printing inks, as well as for magnetic recording systems, such as audio and video tapes and magnetic storage disks. The encapsulated particles comprise particles having a coating on their surface formed from an ionomer or an oil, such as soya oil, or a mixture of ionomers and oil, and optionally a thixotropic agent, and/or a binder resin. The method for making such encapsulated particles avoids the use of volatile organic solvents and provides printing inks and coating compositions which also avoid the use of volatile organic solvents. Inks may be readily formulated, without the need for any complicated and expensive flushing process, by simply dispersing the encapsulated coloured pigment or carbon black in the desired vehicle.

Encapsulated magnetic particles pigments and carbon black, compositions and methods related thereto

Described are tape-type magnetic recording media (I) including a non-magnetic substrate (III), at least one film applied to the substrate and, in at least one of these films, an inorganic acicular pigment (II) suitable for use as a supporting pigment, the ratio of the mean length to the mean diameter of the pigment (II) being at least 3 and the mean modulus of elasticity of the films being not less than 15 GPa in the longitudinal direction of the tape-type recording medium (I).

Magnetic recording media

A magnetic recording medium comprising a nonmagnetic substrate and at least one magnetic layer applied thereon and containing an acicular chromium dioxide uniformly distributed in a polymeric binder and additives and having a coercive force of at least 60 kA/m, a mean particle length of the chromium dioxide of less than 300 nm, whose factor HD according to the formula ##EQU1## where KT is the coercive force of the magnetic layer in [kA/m], measured in an external field of 380 kA/m, L is the mean particle length and ΔL is the range of the particle size distribution, determined from the numerical distribution of the particle length, both measured in [nm], is greater than 1.85, and a process for the preparation of this chromium dioxide.

Process for preparing modified chromium dioxide

Finely divided, needle-like magnetic CrO2 modified with Fe, Te and/or Sb has a coercive field strength of at least 40 kA/m, a saturation magnetisation of at least 85 nTm /g, and a specific surface area (SSA) of a least 25 m /g. A temp. dependent drop of remanent magnetisation of around 50% is achieved only above 95 deg C. Prodn. of the CrO2 is also claimed.

Finely divided needle-like magnetic chromium di:oxide

A finely divided acicular CrO2 modified with iron, tellurium and/or antimony and having a high coercive force possesses improved heat stability of the residual induction and a relatively narrow distribution of the particle size and of the coercive force. This CrO2 pigment is obtained by a method in which the iron compound used for the modification is iron oxalate, which is employed in an amount of 1-10% by weight, based on the theoretical CrO2 yield.

Rudi Lehnert

Papers

Magnetic recording media

Process for preparing modified chromium dioxide

Finely divided needle-like magnetic chromium di:oxide

Finely divided acicular magnetic modified chromium dioxide