Metal Particle Tape for the Future

Transcription

1 Metal Particle Tape for the Future Presentation by Dr. Hans-Bertram Wiegemann EMTEC Magnetics GmbH Application Flexible media s role in the hierarchy of data storage has been changed, archive and back-up are now the primary functions. Retention period of archived media is expected to be > 10 years. Archived media must withstand exposure to fluctuations in temperature and humidity as well as risks of contamination during the course of its life including transportation, use and storage. Dr. Wiegemann - 1 -

2 Requirements High capacity, fast data transfer and low error rate. Thinner and more rigid base films (4-6 um) for increased total length of tape. Extremely thin coating ( um) for high density saturation recording. Pre-written servo tracks for high density recording. State-of-the-art manufacturing process for low raw error rate. Archivibility Automated handling of media (cartridge- or cassette-design). High performance, durability and stablility in pigments and coatings. Dr. Wiegemann Pigment Stability Improvements in stability over the last 15 years: 0 % Change in Signal Co-Fe2O3 MP`00 MP`95 MP`90 MP` Years Stored at Room Temperature Dr. Wiegemann - 3 -

3 Pigment Stability Small and very uniform particles through improved processes and surface layer passivation: Dr. Wiegemann Conventional Binder Systems Conventional binder systems use a dispersing polymeric binder customized to work with small particles and the surface chemistry of new iron metal particles. To obtain pigment holding capability, toughness, strenght and coatability a crosslinking process of the small molecules into a matrix have to be used. To improve temperature stability a chlorine containing hard resin is added. Dr. Wiegemann - 5 -

4 Conventional Binder Design Random Distribution of Functional Groups in a PVC Chain Vinyl Chloride Hydroxy Group for Crosslinking Chloride Scavenger Adsorbing Group Dr. Wiegemann Conventional Binders - Problems Potential of accelerated head corrosion due to chlorine resins. Non-controlable shrinkage introduces stress in the coating. Polymeric matrix pulls away from the particle surface resulting in a loss of cohesive integrity, i.e. debris will be generated. Dr. Wiegemann - 7 -

5 Development Concept Invent a glassy polymeric dispersing binder for the iron metal pigment which does not contain chlorine. The binder system must be stable over a broad temperature range to allow for extremes of storage and operation - 10 C to over 50 C. Dr. Wiegemann Methodology Extensive use of small scale milling iterations to optimize the mechanical behavior of free films of the experimental resins, with and without metal particles and other necessary constituents. Advanced analytical techniques such as dynamic mechanical analysis (DMA) were used to examine: a) The adsorption and cohesive interaction as a function of pigment loading, milling history, solvents and additives. b) The actual softening points (Tg) of the binders once adsorbed on the metal pigment. c) The effects of metal particles on the binder tensile strength (tensile modulus). Dr. Wiegemann - 9 -

6 Observations The onset of polymer film softening for unfilled film was found at about 17 C, while the film filled with pigments (42% by volume, 78% by weight) showed the onset shifted to 75 C. The tensile strenght went up substantially (factor 2-3). 3.5 Tensile Storage Modulus, E' (GPa) Temperature, deg C Unfilled Binder film 78% MP filled binder film Dr. Wiegemann New Binder The new binder achived all the desired objectives: A novel polyester-polyurethane binder in which the wetting groups are contained in the hard phase Soft Segment Hard Segment Soft Segment Spacer (IBM/EMTEC-patents applied for) Adsorbing Group Dr. Wiegemann

7 Design Verification The design has been verified and improved by: Evaluating coating samples using a more sensitive dynamic mechanical thermal analysis (DMTA). Studying the influence of oriented particles and of the compression of the coating due to calendering. Dr. Wiegemann Design Verification 20 Magcoat Modulus,E' GPa Tg= 38 oc Tg =52oC Temperature, deg. C EMTEC New Formulation Std Formulation Dr. Wiegemann

8 Conclusion With greater than 50 C Tg, the coating will remain stable under the severe operational specifications for any tape drive. The overall stablility of the coating is improved over conventional binder systems throughout the entire range of shipping, storage and use environments specified by drive manufacturers. Analysis of tapes aged for extreme periods at high temperatures and and humidities even indicate an improvement in mechnical strenght which does not happen with conventional formulations. Dr. Wiegemann Conclusion Use tests (short and long lenth durability tests, inhibitor tape test and end of life test) confirm that the new formulation is significantly better than the existing formulations. Dr. Wiegemann