International Business Machines Corporation

Gerhard Trippel

Werner Steiner

Arwed Brunsch

Wolf-Dieter Ruh

Gerhard E Schmid

Johann Greschner

Olaf Wolter

Holger Hinkel

Upali Bandara

Wolf D Ruh

Jochen Schneider

Grooved substrates and multilayer structures, especially suitable for optical disks, are taught. The major process steps include spin coating of a supporting plate with dissolved material forming a soft layer thereon, stamping grooves into the soft layer to form a structured soft layer showing the negative image of the stamp and hardening the structured soft layer by thermal treatment. The dissolved material contains polymeric organometal compounds comprising polymer siloxane and/or polymer silicates. In one embodiment the structured soft layer is a dielectric layer containing various combinations of the oxides SiO.sub.2, La.sub.2 O.sub.3, PbO and TiO.sub.2. The multilayer structure completed by a magneto-optic layer, a reflector layer and a passivation layer.

Manufacturing process for grooved substrates and multilayer structure

An optical storage disk consists of a glass substrate (1) into which guide tracks (3) for servo-controlling the focussed light beams are directly stamped by a hot stamp process. After stamping, the glass substrate is thermally quenched in the stamping device to increase its breaking resistance through thermal curing. In order to achieve uniform guide tracks over the entire surface of an optical storage disk, flexible stamp stencils (35) in a flexible holder (34) are used whose curvature can be changed by applying hydro-static pressure. Suitable stamp stencils consist of monocristalline silicon disks with surface hardening, or of metal disks, structured in photolithographic processes. The stamp lands are made with bevelled edges to facilitate the separating of stamp and glass substrate after cooling.

System for stamping an optical storage disk

Method of manufacturing an optical Storage disk

A method and apparatus is provided for characterizing magnetic coating compositions that contain magnetic particles dispersed in a solvent resin matrix. The coating composition, as it passes through a tube, is subjected to an alternating magnetic field and perpendicular thereto a constant magnetic field of appropriate field strength and duration. Via a measuring coil surrounding the tube the induced signal in the composition is monitored and the degree of dispersion, is measured by measuring the magnetic susceptibility of the coating material. By applying a constant magnetic field the degree of dispersion cna be changed at least for a certain time. The method and apparatus of the present invention can be incorporated into a coating apparatus to monitor and improve the magnetic characteristics of the coating material being applied to a substrate.

Method and apparatus for characterizing magnetic coating compositions as

The magnetic disk contains on a disk substrate a magnetic layer comprising a binder, magnetic particles and abrasion-resistant particles, the abrasion-resistant particles being enveloped with a layer intensifying the bond between binder and abrasion-resistant particles. The enveloping layer either has a large specific surface and consists e.g. of SiO.sub.2 /Al.sub.2 O.sub.3 produced by processing the particles with an alkali metal silicate solution and an aluminum sulphate solution, or it is chemically bonded to the binder by enveloping the particles with poly(tetrafluroethylene) and coupling the latter, via an amino bridge to the binder, e.g. an epoxide resin.

Magnetic disk and method of making same

For characterizing coating compositions with magnetic particles the coating composition is subjected to an alternating magnetic field of variable frequency. The field induced by the coating composition after energization is recorded, and thus the susceptibility of the coating composition is measured. Depending on the variable frequency, conclusions can be made regarding the degree of dispersion, particle density, and viscosity of the coating composition. The variable frequency is between 1 and 100 cps, and the field intensity of the energizing field should be lower than 10 Oerstedt. The coating composition is fluid or stagnant in a pipe *1, 11 which is surrounded by field coil and measuring coil.

Method of determining dispersion, particle density or viscosity of

A test sample (7) of the same material, or with the same structure as the workpiece (5) exposed to subtractive processing is simultaneously exposed to such processing and consists of a wedge (10) with the angle .alpha. covered by two covering plates (11) which are complementary to its two surfaces (14). By measuring the distance x.sub.1 between the thus formed gaps (15), and by comparing it with the original distance x.sub.O, thickness z of the respectively removed layer can be determined from the equation ##EQU1##

Method of measuring the thickness of the removed layer in subtractive

For a metallic thin film magnetic disk, a chromium undercoat and a magnetic layer, in particular of an FeCoCr alloy, are obliquely sputtered by means of a sputtering system onto a substrate at an angle of incidence of about 60.degree.. The operating pressure of the argon gas atmosphere is between 5 and 15 .mu.bar and the thickness (t.sub.Cr) of the undercoat, which also influences the coercive field strength, is between about 50 and 180 nm. By means of a sector shutter of suitable shape, the thickness distribution between the inner diameter ID and the outer diameter OD of the storage area of the magnetic disk can be influenced in the desired manner.

Method of producing a metallic thin film magnetic disk

Multi-layer magnetic thin film disks comprising a synthetic resin layer on an aluminum-containing substrate and an overlying metallic magnetic layer, are liable to have pin holes in the synthetic resin layer caused by galvanic corrosion of the aluminum in the substrate. The pin holes are passivated by aluminum oxide produced therein by anodically oxidizing the aluminum of the substrate in an electrolytic bath, the electric voltage of which is well below the normal passivation voltage for aluminum.

Process for fabricating a multi-layer magnetic thin film disk

Direct method for measuring the magnetostriction constant .lambda..sub.s of soft magnetic and isotropic magnetic materials. A thin film sample is cantilevered and clamped at one edge. Under the influence of a magnetic AC field and the magnetostriction effect of the sample material, the free end of the cantilevered sample is deflected and oscillates with twice the frequency of the AC field. The resonance amplitude a.sub.res is measured by using a laser beam impinging upon the oscillating sample and measuring the reflected beam amplitude by means of a position-sensitive photodiode. The AC output signal of the photodiode is proportional to the sample amplitude. The magnetostriction constant .lambda..sub.s is directly proportional to the resonance amplitude a.sub.res multiplied by a constant factor which depends on known geometry and properties of the sample material.

Apparatus for measuring magnetostriction constant

A record carrier for a magnetic thin film metal layer includes a substrate coated with a pigmented epoxy resin as a synthetic substance layer. The pigment includes approximately 20% titanium dioxide and approximately 2% aluminum oxide. A thin getter metal layer is deposited over the synthetic substance layer for absorbing the outgasing from the synthetic substance layer. A relatively thicker metal layer such as chromium is then deposited over the getter layer for enhancing the magnetic properties of the subsequently deposited magnetic layer.

Magnetic record carrier

Several tapered viaducts or through-holes of uniform size are simultaneously fabricated by etching in a dielectric plate or substrate. The viaducts, which are designed in particular for nozzles for ink jet printers, have identical orifice widths, irrespective of differences in the thickness of the substrate or dielectric plate or different etch rates in the various areas of the dielectric plate. The holes are first chemically pre-etched until the first hole is about to penetrate through the plate and subsequently sputter etching is applied until all holes have penetrated through the plate, whereby the dielectric plate provides the necessary sputter etch capacity on which a negative bias occurs.

Method of simultaneously etching multiple tapered viaducts in

This method of forming viaducts or 'through-holes' in semiconductor material for transistor and integrated circuit fabrication and especially for ink jet printing systems forms viaducts of uniform diameter without critical registration of masks. A seed layer of Cr-Au is sputtered onto a silicon-dioxide substrate. The viaducts or holes to be made are imaged by a photoresist process with a 5 .mu. thick photoresist on this seed layer. A 4 .mu. thick gold layer is now applied on the seed layer by a plating process. After the dissolution of the photoresist this layer contains the hole pattern with the holes having the required diameter. In order to make a through-hole, the substrate has to be etched. For that purpose, the bare substrate surface is covered with photoresist and exposed from the back through gold holes, and subsequently developed. Problems owing to light diffraction at the edges of the gold with respect to the great distance of the gold mask - photoresist layer are not anticipated here because of the large holes and the high tolerances in this process step. Prior to etching the substrate, the gold layer with the hole pattern is covered by photoresist so that the substrate etching can take place from one side only. Now the substrate is etched until all of the gold holes are free. In that process, the extent of the substrate sub-etching is of small importance as the viaduct or hole diameter is defined by the gold mask. The photoresist is removed and the exposed substrate surfaces are protected against chemical reactions with the ink by a vapor-deposition of a protective layer.

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Sindelfingen, Germany

Gerhard Trippel