The areal density of magnetic recording media has increased by about 40% annually. For areal densities to continue to increase at this rate, a technical breakthrough is needed within the next one or two years. For example, SWR (shingled-write recording), energy assisted magnetic recording, patterned media and the like are promising candidates. Fuji Electric is evaluating these technologies. Fuji is also studying the substrate, a laminated ECC (exchange-coupled composite) media structure, the HDI (head-disk interface) and new highly anisotropic magnetic layer materials in order to realize higher densities.

In collaboration with Tohoku University, Fuji Electric has realized the first successful synthesis of a L11 type CoPt ordered alloy film having a high magnetic anisotropy constant Ku using sputter technique. The Ku value of this material reached a maximum value of 3.6×107 erg/ cm3. Moreover, this material is superior to other ordered alloys even if the order is low and the Ku value is high. Also, a ternary alloy formed by adding Ni to this material is capable of maintaining a crystalline structure and a high Ku value over a wide compositional range while controlling the saturation magnetization Ms. For example, with a ternary alloy having the same magnetic characteristics as a binary alloy of rare Pt at 75 at%, the amount of Pt can be decreased to 25 at%.

Energy assisted recording, is a next-generation high-density recording technology. This method enables writing even in the case of a low magnetic field by providing external energy to a recording layer, onto which the writing of signals has been difficult at room temperature. Fuji Electric is evaluating two methods of energy assisted recording; thermally assisted magnetic recording and microwave assisted magnetic recording. With thermally assisted magnetic recording using laser light as a heat source, an approximate 3 dB improvement in the SN ratio was confirmed and the inherent feasibility was verified. As material for this application, the coercive force temperature gradient of Co-based materials was improved to –85 Oe/K from the prior value of –15 Oe/K. With microwave assisted magnetic recording, the Pt in Co-Pt was replaced with another element, and a material having a low damping factor is being developed.

This paper describes three technologies for the recording layer, intermediate layer and soft magnetic underlayer, developed to increase the recording density of perpendicular magnetic recording media. The design and development of an optimal structure for a new multilayer magnetic recording layer constructed from four functionally-separated layers has enabled an increase in track density. A new material of an intermediate layer was developed. The magnetic grain sizes of the magnetic recording layer on the intermediate layer and the distribution of the grain sizes were reduced. The crystalline orientation was also improved. Materials having a high saturation magnetic flux density have been newly developed for the soft magnetic underlayer. The application of these materials has resulted in improved electromagnetic conversion characteristics.

To reduce the magnetic spacing and improve media characteristics, (1) a thinner carbon protective film and thinner lubricant layer, and (2) a lower magnetic head flying height are necessary. However, reducing the thickness of the protective film and the lubricant layer causes a significant deterioration in such reliability-related characteristics as corrosion resistance and durability. Thus, Fuji Electric controls the film properties of the protective layer so as to improve the corrosion resistance and sliding durability simultaneously with a reduction in the thickness. By controlling the molecular weight and composition of the PFPE (perfluoropolyether) used in the lubricant layer, and developing additives and post-processing technology, a thinner film with higher reliability can be realized. Additionally, while developing technology for evaluating the flying characteristics of the HDI (Head Disk Interface), Fuji Electric has been reducing the magnetic spacing.

Hard disk drives have come to have large capacities as a result of the synergy between the evolution of recording and playback components, as represented by the magnetic head and magnetic recording media, and the advances in signal processing technology, tracking technology and other drive-related technologies. With perpendicular magnetic recording media, Read/Write characteristics, including those of the low-frequency region, are critically important. Also, the realization of tracking precision of up to approximately 1.3 nm paves the way for higher density recording. Additionally, disturbances in the recording magnetization in the vicinity of the side shield of the side shield head were visualized and evaluated to optimize the configuration of the media layer and to mitigate the disturbances.

By 2011, the recording capacity of commercially available magnetic recording media in a single 3.5” disk format is forecast to reach 1 TB. The formation of an ultra-smooth surface and the reduction of 100 nm-class small defects are technical challenges that must be overcome in order to realize higher recording densities. For this purpose, Fuji Electric is improving its aluminum substrate manufacturing processes, which include a ground substrate production process, a plating process, a polishing process, a washing process and the like. The small defects typically occurring during these processes include foreign particles, scratches, pits and so on. By analyzing defects one-by-one, classifying them and then determining their cause, the individual processes can be improved and quality enhanced to establish a substrate manufacturing process suitable for next-generation media.

From the perspectives of energy and the environment, energy savings is also needed in the field of electrophotography. The market for electrophotography-based printers and copiers is forecast to grow at an annual rate of approximately 8%. Accordingly, that same growth rate is also forecast for photoconductors, which are key electrophotographic devices. Fuji Electric is consolidating its OPC production facilities in Shenzhen, China in order to meet worldwide demand. Also, newly adding positive electrification multi layer-type photoconductors for greater energy savings, Fuji Electric offers five lines of photoconductor products, i.e., negative electrification type photoconductors for printers, analog copiers and digital copiers, and monolayer type and multi layer-layer type positive electrification photoconductors for printers, and delivers products that are well suited for energy savings and that are friendly to the global environment.

Fuji Electric is developing organic photoconductors (OPCs) in response to requests for image forming functions with higher sensitivity and higher stability, and to reduce the environmental impact of electophotographic machines. Fuji Electric is developing functional materials, polymer materials and additives applying proprietary computer-aided molecular designs and chemical synthesis technology. In order to support the miniaturization of equipment, promote resource conservation and recycling and achieve higher durability, Fuji is also developing new OPC underlayer resin materials, charge generating materials, and additives for the charge transport layer, and has accomplished to improve OPC environmental stability, enhance sensitivity, conserve energy, and improve printing durability. Additionally, Fuji Electric has established a system that complies with material safety standards and environmental regulations.

Fuji Electric provides a product line of negatively charged organic photoconductors in three varieties, low sensitivity, medium sensitivity and high sensitivity, for compatibility with various amounts of exposure light. Also, in response to a diversifying range of applications and the desire for more advanced functionality and higher quality, Fuji Electric uses proprietary evaluation technology, analysis technology and material design techniques to realize higher responsiveness, higher resolution, higher durability and higher reliability. For positively charged organic photoconductors, which are environmentally friendly and provide high resolution, in addition to monolayer type that provides low-speed to high-speed and high printing durability, a multilayer type that provides high sensitivity and high-speed response has been fully commercialized for the first time in the world.

Fuji Electric provides type 10A (low sensitivity), type 10B (medium sensitivity) and type 10C (high sensitivity) OPCs for digital copiers. The OPCs are sensitive in the 600 to 800 nm wavelength range of laser and LED light used as the light source for copiers. The Charging characteristics of the OPCs have been improved in accordance with the shortening of the first copy time of the copiers. Computer-aided molecular design has been utilized to develop a binder for a highly durable charge transport layer and prevent the charging characteristics from deteriorating. As a result, printing durability has been improved by at least a factor of 2, contributing to a reduction in the running costs of the copier.

It is important that printing be made possible at high resolution to make electrophotographic machines faster, color image compatible, and expand the printing field,. Fuji Electric has developed a MASPP (Micro Area Surface Potential Probe) and an EFM (Electrostatic Force Microscope) to understand the mechanism of electrical latent image formation more clearly. The photoconductor surface charge is changed by the irradiation of laser light. MASPP detects the change of the charge as a current induced by it In the case of a high mobility photoconductor, the latent image potential was shown to be spread-out spatially to a greater extent than the potential distribution that corresponds to the exposure. In the case of a low mobility photoconductor, the distribution of surface potential was found to be more precise and similar to the surface potential distribution that closely corresponds to the exposure.