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- Manufacturing Technology of Glass Substrates for Magnetic Disks
Research and Development
About
Nano-fabrication Field
Manufacturing Technology of Glass Substrates for Magnetic Disks
Konica Minolta has entered the business of glass substrates for magnetic disks from the 1990's basing on the development and manufacturing technology of glass lenses possessed by the company. At present, substrates of less than 2.5 inches are being manufactured by our Konica Minolta Glasstech Inc.
In order to manufacture this product, it is necessary to collect together a wide range of key technologies from development of glass composition to polishing, cleaning, and evaluation, etc.
The key technologies with good features possessed by our company are explained below.
1. Design of Glass Composition
The key factor in development is the hardness (relative strength) unlike in optical glass. Further, from the point of view of productivity and quality requirements, it is necessary to pursue mutually contradicting performance characteristics of low melting point, high transition temperature, low alkalinity, polishing characteristics, etc. By understanding in detail the effects of doping elements on various types of lattice structures, it is possible to carry out appropriate composition design in a short time. The glass compositions developed and put in the market by our company are the following.
| KONICA MINOLTA | Ordinary Glass | ||||
|---|---|---|---|---|---|
| MEL3 | EX5 | TUF | Raw plate (soda lime glass) |
||
| Features of Glass | High-toughness glass | Glass ceramics | High-hardness glass ceramics | Most common glass | |
| Density: d | g/cm3 | 2.46 | 2.60 | 2.82 | 2.51 |
| Young's modulus: E | GPa | 83 | 100 | 120 | 73 |
| Elastic modulus: E | GPa-cm3/g | 33.9 | 38.2 | 42.6 | 29.3 |
| Vickers hardness number: Hv | kg/mm2 | 580 | 790 | 850 | 540 |
2. Technology of Glass Melting and Molding
It is necessary to suppress the number of bubbles and foreign materials within the glass to a level of 1-2 digits lower than that of optical glass. In addition, due to the accumulation of technology and know-how regarding glass molding over many many years, we have realized reduced thickness of molded items and high flatness, and have achieved high productivity by reducing the load of finishing processes.
3. Technology of Machining Brittle Materials
Utilizing the technology of machining brittle materials accumulated in machining optical lenses or molds of ultra-hard or ceramics materials, we have completely eliminated machining by released abrasive particles in all the processes of rough machining and finishing machining. As a result, we have not only reduced the contamination to the product but also have realized great reductions in the quantity of waste materials at the same time.
4. Precision Cleaning Technology
The size of the magnetic film formed on the glass substrate is in the submicron range, and the level of surface defects required of the substrate is on the order of 0.1µm. By combining several types of cleaning methods, our company has not been able to remove effectively the adhering matter in the pre-processing steps, but have also established a process of suppressing fine defects during the cleaning process in a stable manner.
5. Evaluation Technology
The glass substrates of our company are installed in hard disk drives as magnetic media, and are being used as bookshelves by the end-user customers. It is not possible to cause trouble to the customers because of broken bookshelves. Exploiting the latest evaluation technology possessed by the Konica Minolta Group, we are carrying out thorough quality analysis from raw materials to finished products, and are providing the highest quality products to our customers.
