The outstanding feature of materials research in the eighties has been the convergence of basic research and practical application, leading to ever shorter cycles of innovation. This is especially true of materials which form the basis of key technologies. The mass storage units of the next generations of computers will be based on optical processes having a storage density which exceeds that of all hitherto known storage techniques that are practicable from the technical standpoint. In view of the fact that since 1982 read-only memories in the form of compact discs (CD-ROM) have become very successful in the field of audio electronics, research and development are now concentrated on materials for write-once (WORM) and erasable (EDRAW) storage systems. Suitable materials for optical data storage are substances in which data markings can be recorded and deleted respectively using semiconductor lasers. Materials development is centered on the synthesis of infrared-absorbing dyes for WORM memories and the production of rare earth/transition metal alloys for magneto-optical data recording. An introduction to CD-ROM technology will be followed by an overview of the state of development of the most important storage materials which are currently available commercially, and then the properties of these materials will be discussed with reference to selected examples.

Materials for Optical Data Storage

Die Materialforschung der achtziger Jahre ist durch das Zusammenwachsen von Grundlagenforschung und Anwendung zu immer kurzeren Innovationscyclen charakterisiert. In besonderem Mase gilt dies fur Materialien, die Basis von Schlusseltechnologien sind. Die Massenspeicher kunftiger Computergenerationen werden auf optischen Verfahren beruhen, durch die eine hohere Speicherdichte als mit den bislang bekannten und technisch praktikablen Speichertechniken zuganglich wird. Nach dem grosen Erfolg der reinen Lesespeicher (CD-ROM) in Form der Compact Disc seit 1982 im Bereich der Audioelektronik konzentrieren sich Forschung und Entwicklung derzeit auf Materialien fur einmal beschreibbare (WORM) und fur loschbare Speichersystem (EDRAW). Fur die optische Datenspeicherung geeignete Materialien sind Substanzen, in denen sich mit Halbleiter-Lasern Datenmarkierungen schreiben und loschen lassen. Schwerpunkte der Materialentwicklung sind die Synthese von im Infrarotbereich absorbierenden Farbstoffen fur WORM-Speicher und die Herstellung von Seltenerdelement-Ubergangsmetall-Legierungen fur die reversible magnetooptische Datenaufzeichung. Nach einer Einfuhrung in die CD-ROM-Technik werden ein Uberblick uber den Entwicklungsstand der wichtigsten zur Zeit kommerziell verfugbaren Speichermaterialien gegeben und an ausgesuchten Beispielen ihre Eigenschaften diskutiert.

Materialien für die optische Datenspeicherung

A method for forming a stamper used in the manufacture of CDs, DVDs, and other types of optical disks comprises forming a substrate by rolling. A layer of material is deposited (e.g. by plating) onto the substrate. Thereafter, a resist layer is formed on the layer of material and patterned. Because the substrate is formed by rolling, it is relatively inexpensive to form the substrate to a desired thickness. Because the layer of material is formed by deposition (e.g. plating), it is relatively inexpensive to ensure that the layer has a very smooth surface (i.e. without necessitating a great deal of polishing).

Method and apparatus for making a stamper for patterning CDs and DVDs

A storage device and method use a head that is fabricated using photolithography, and the head is purposely powered up during a material removal process, such as lapping, so that the head's expansion (that would be formed on being powered up during normal usage in a drive) is planarized. On being cooled to room temperature, the head has a concave shape in a pole tip region, the concavity indicative of a volume occupied by material that formed the head expansion, and that has been removed by planarization. Thereafter, the head is powered up in a storage device and method, so that the head has a surface other than flat but within a predetermined range, and the head supplies a signal through the surface to a recording medium.

Storage device and method of using a head that has a concave surface when powered down

A head is fabricated using photolithography, and the head is purposely powered up during a material removal process, such as lapping, so that the head's expansion (that would be formed on being powered up during normal usage in a drive) is planarized. Specifically, the head is energized in a manner identical (or similar) to energization of circuitry in the head during normal operation in a drive, even though fabrication of the head has not yet been completed. When energized, a shape that the head would have during normal operation is replicated (or approximated). Therefore, the head's shape includes a expansion of the pole tip region, although the head is only partially fabricated. Thereafter, a portion of the head in the expansion is partially or completely removed, by lapping while energized. The depth of material removal from the head is monitored e.g. by a controller sensitive to a change in electrical characteristic of a device (such as a resistor) that is normally fabricated during photolithography of the head.

Lapping a head while powered up to eliminate expansion of the head due to heating

A magnetic recording and reproducing device is disclosed in which one magnetic head or a plurality of magnetic heads are so disposed upon a rotary drum as to extend beyond the outer peripheral surface thereof with the slit gap or gaps in parallel with the axis of rotation of the rotary drum. Recesses are formed on both sides of the magnetic head in the outer peripheral surface of the rotary drum, and the point of the maximum thickness of the magnetic head which is generally similar in cross sectional configuration to an airfoil is located ahead of the midpoint or center of the magnetic head but behind the leading edge thereof. Both side edges of the magnetic head are rounded between the trailing edge and a point very close to the slit gap thereof.

Rotating air bearing head with shaped control slots

A substrate with a negative type photoresist applied rotates and is continuously subjected to surface exposure, heating, and developing/etching/removing the resist each in a dry process. As a result, signal projections are formed onto the surface, which is machined to a stamper size.

Optical disk stamper mastering method and apparatus

To establish the high density disc system, the most important point is how discs areproduced stably on high rate of yield. From the point of this view we developed a new lasercutting machine of master disc and a novel duplicator of replica disc. This cutting machinewhich is compactly designed has a improved optical system which are stabel against tempera-ture fluctuation and other environmental disturbance. And we can produce high quality discsat high rate of index time by our disc duplicator using liquid photo -polymer resin which iscured by ultra- violet ray.IntroductionIn several high density recorded disc system, the biggest technical problem which willdetermine whether the system is good or not is to fabricate discs in stable and high yieldrate and at low cost, that is how to produce soft -hard.Disc fablication has two major processes. One is mastering process which consist of re-cording of the glass master and production of the metal mold from the glass master. The another is replication process which produce discs from the mold which should be handed tofinal users.The main problem of the former process is how to record the recording medium. There aresome methods for that, for example mechnical recording method in which recording medium (forexample copper plate) is recorded by use of the stylus which is vibrated by the piezo-electric device, and electron beam method in which electron beam is exposed to the record-ing medium. And each has its own characteristic. For optical disc, optical cutting systemis generally used in which modulated laser beam is exposed to the recording medium.As for the replication process, there have been three methods. The first one is compre-ssion method which follow the conventional audio record manufucturing process. The secondone is injection method which was introduced as something like a new technique. The thirdone is injection -compression method which took the merits of the both methods aforementioned. -Presently the injection method using acrylic resin is generally used. But recently, 2Pmethod using the resin cured by ultra -violet light is being developed. And this methos isthought to be promising in future because of its simple equipment and extremely high fide-lity replication.In this paper, technical problem on optical disc fablication is reviwed, and the cuttingmachine in mastering process and the 2P duplicator in replication process which were deve-loped by us are introduced.Mastering processManufacturing process from glass master to metal mold (nickel stamper) is called master-ing process. Mastering process has several steps as shown in Fig. 1. First, glassmasterwhich is made of green glass is prepared and then polished to highly precise surface.

Developments In Fabrication Of Optical Disks

A method for manufacturing a direct stamper to be used for molding optical discs, includes forming a layer of a crosslinkable substance all over a surface of a base disc, subjecting the crosslinkable substance to a first crosslinking reaction, thereafter, forming a photoresist layer on the crosslinking substance, subsequently, subjecting the photoresist layer to exposure to a laser beam having been modulated by a signal to be recorded, and then to development, so that exposed portions of the photoresist are formed into bumps on the crosslinking substance, and thereafter, further subjecting the crosslinking substance and the photoresist bumps to a second crosslinking reaction.

Blank disc and direct stamper and its manufacturing method

PURPOSE: To remove foreign matter such as dust sticking to a disk without damaging signal unevenness by moving a shaving member, coming in contact with only the uppermost part of a signal track, in the radius direction on the recording disk prior to a reproducing stylus. CONSTITUTION: Shaving member 18 moving in the radius direction of disk 2 prior to reproducing stylus 5 comes in contact with only land parts of grooves 4 extending over signal concave grooves 4 forming the signal track on disk 2. While neither being fixed in grooves 4 nor damaging signal unevenness of grooves 4, member 18 removes foreign matter 22 such as dust sticking to disk 2 prior to stylus 5, preventing groove skipping due to the foreign matter. Additionally, the performance of shaving off foreign matter improves by giving front face 19 of member 19 relief face 20 and fixed rake angle α to the vertical axis of disk 2. COPYRIGHT: (C)1980,JPO&Japio

Kazuhiko Sano

Papers

Rotating air bearing head with shaped control slots

Optical disk stamper mastering method and apparatus

Developments In Fabrication Of Optical Disks

Blank disc and direct stamper and its manufacturing method

Signal reproducing device