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According to some estimates, 95% of information today is stored on paper, 3% on microfiche, and only 2% on magnetic/optical and semiconductor storage devices. Semiconductor storage is almost exclusively used for dy- namic random access memory (D-RAM) in computers, and constitutes a very small fraction of the total storage capacity. Magnetic storage devices include hard disk, flexible disk, and tape drives. Estimates for worldwide storage is 12,000 petabytes (12 million terabytes). It is estimated that mag- netic tapes store about 95% of the information, and the balance is stored equally by magnetic hard disk and optical disk drives (250 petabytes each). 14 For comparisons, the human brain has 10 neurons and holds approxi- mately 200 megabytes of information. For a world population of 6 billion people, the total human memory is therefore 1200 petabytes, which is about 10% of the electronically recorded information. Magnetic and optical storage industry for consumer and data recording applications is at present an industry grossing more than $80 billion per year. It is expected to grow at cumulative rate of about 10% per year.
Revenue is as follows: for magnetic disks and drives, about $35 billion; for flexible disks and drives, about $4 billion ($1.5b/$2.5b); for data tape and tape drives, about $8 billion ($2b/$6b); for consumer video- and audiotape and tape drives, about $25 billion ($8b/$17b); for CD/DVD read-only disk and disk drives, about $7 billion ($lb/$6b); and for other optical products, less than a $1 billion.
Contents
1. Introduction.- 1.1. Physics of Magnetic Recording.- 1.1.1. Basic Principle.- 1.1.1.1. Magnetism.- 1.1.1.2. Electromagnetic Induction.- 1.1.1.3. Magnetic Recording.- 1.1.2. Vertical Recording.- 1.1.3. Signal-Processing Methods.- 1.1.4. Design Considerations.- 1.1.4.1. Recording Density.- 1.1.4.2. Reproduced Signal Amplitude.- 1.1.4.3. Signal-to-Noise Ratio.- 1.2. Magnetic Storage Systems.- 1.2.1. History of Magnetic Recording.- 1.2.1.1. Storage Hierarchy.- 1.2.2. Examples of Modern Storage Systems Using Flexible Media.- 1.2.2.1. Tape Drives.- 1.2.2.2. Flexible-Disk Drives.- 1.2.3. Head Materials.- 1.2.3.1. Permalloys.- 1.2.3.2. Mu-Metal and Hy-Mu 800B.- 1.2.3.3. Sendust Alloys.- 1.2.3.4. Alfenol Alloys.- 1.2.3.5. Amorphous Magnetic Alloys.- 1.2.3.6. Ferrites.- 1.2.3.7. Some Examples of Head Constructions.- 1.2.4. Flexible Media Materials.- 1.2.4.1. Base Film.- 1.2.4.2. Magnetic Medium.- 1.2.4.3. Particulate Magnetic Coatings.- 1.2.4.4. Magnetic Thin Films.- 1.2.5. Functional Requirements.- 1.3. Manufacturing Processes of Flexible Magnetic Media.- 1.3.1. Particulate Media.- 1.3.1.1. Tapes.- 1.3.1.2. Flexible Disks.- 1.3.2. Thin-Film Media.- 1.3.2.1. Metal-Evaporated Media.- 1.3.2.2. Sputtered Media.- 1.3.2.3. Electro/Electroless Plated Media.- References.- 2. Physical and Chemical Properties of PET Substrate and Coated Magnetic Media.- 2.1. Manufacturing Process of PET Films.- 2.2. Structure of PET Films.- 2.2.1. One-Way Stretching.- 2.2.2. Two-Way Stretching.- 2.2.3. Heat Setting (or Crystallization).- 2.2.4. Post-Stretching.- 2.2.5. Strain Relaxation (or Annealing).- 2.2.6. Commercial Biaxially-Oriented PET (Mylar A).- 2.2.7. Summary.- 2.3. Physical and Chemical Properties.- 2.3.1. Density.- 2.3.2. Refractive Index, Birefringence, and Infrared Dichroism.- 2.3.3. In-Plane Mechanical Properties.- 2.3.3.1. Effect of Temperature and Strain Rate.- 2.3.3.2. Effect of Annealing.- 2.3.3.3. Effect of Solvents.- 2.3.4. Elastic Modulus in the Thickness Direction.- 2.3.5. Radial Elastic Modulus of the Wound Reels.- 2.3.5.1. Effect of Winding Parameters and Magnetic Coating.- 2.3.5.2. Effect of Storage.- 2.3.5.3. Radial Relaxation Modulus.- 2.3.6. Thermal Expansion Properties.- 2.3.6.1. Heating Rate Effects.- 2.3.6.2. Effect of Annealing.- 2.3.6.3. Mechanisms of Thermal Expansion.- 2.3.7. Hygroscopic Expansion Properties.- 2.3.7.1. Effect of Annealing.- 2.3.8. Long-Term Dimensional Stability (Shrinkage).- 2.3.8.1. Effect of Annealing.- 2.3.9. Hydrolytic Stability.- 2.3.10. Summary.- 2.4. Outlook for Improved PET Substrates.- 2.4.1. Mechanical Properties.- 2.4.2. Coefficient of Thermal Expansion.- 2.4.2.1. Isotropic Polymer Films.- 2.4.2.2. Oriented PET Films.- 2.4.2.3. Laminates.- 2.4.2.4. Incorporation of Fibers and Filaments.- 2.4.3. Coefficient of Hygroscopic Expansion.- 2.4.4. Long-Term Dimensional Stability (Shrinkage).- 2.4.5. Summary.- References.- 3. Viscoelastic Properties of PET Substrate and Coated Magnetic Media.- 3.1. Introduction to Viscoelasticity.- 3.1.1. Elasticity.- 3.1.1.1. Generalized Hooke's Law.- 3.1.1.2. Material Constants for Orthotropic Material.- 3.1.1.3. Material Constants for Isotropic Material.- 3.1.2. Viscous Liquids.- 3.1.3. Viscoelasticity.- 3.1.3.1. Constitutive Equation.- 3.1.3.2. Description of Time-Dependent Deformation Experiments.- 3.1.3.3. Mechanical Model Analogies of Linear Viscoelastic Behavior.- 3.1.3.4. Time (or Frequency) and Temperature Effects.- 3.2. Dynamic Modulus Data.- 3.2.1. Measurement Techniques.- 3.2.1.1. DMTA.- 3.2.1.2. DMA.- 3.2.2. Experimental Results.- 3.3. Tensile Relaxation and Creep Data.- 3.3.1. Descriptions of Creep and Relaxation Test Apparatuses.- 3.3.1.1. Creep.- 3.3.1.2. Relaxation.- 3.3.2. Constitutive Relations for Analysis of Isothermal Experimental Data.- 3.3.3. Experimental Results.- 3.3.3.1. Linearity of PET Material Response.- 3.3.3.2. Effect of PET Film Thickness.- 3.3.3.3. Effects of Temperature and Humidity in PET Films.- 3.3.3.4. Thermoviscoelastic Behavior of PET Films.- 3.3.3.5. Viscoelastic Behavior of Coated Tapes and Magnetic Coatings.- 3.3.3.6. Effects of Thermal Treatment of PET Films.- 3.4. Compressive Creep Data.- 3.4.1. Description of Creep Test Apparatus.- 3.4.2. Experimental Results.- 3.4.2.1. PET Films and Cast Films of Magnetic Coatings.- 3.4.2.2. Calendered Versus Uncalendered Magnetic Coatings.- 3.4.2.3. Recovery Experiments.- 3.4.2.4. Summary.- References.- Appendix 3.A Analysis of Flexural and Tensile Stress Relaxation of a Multilayered Tape.- 3.A.1. Flexural Relaxation at Constant Curvature.- 3.A.2. Tensile Relaxation at Constant Elongation.- Appendix 3.B Analysis of Thermal Curling of a Multilayered Magnetic Tape in the Elastic Regime.- 4. Physical Properties of Advanced Ultra-Thin Polymeric Substrates and Coated Magnetic Media.- 4.1. Standard and Advanced Substrates.- 4.2. Tensile Properties.- 4.3. Viscoelastic (Nonpermanent Deformation) Properties.- 4.3.1. Time-Dependent Creep Behavior.- 4.3.1.1. Description of Creep Test Apparatus and Experimental Procedure.- 4.3.1.2. Data Reduction Method.- 4.3.1.3. Experimental Results.- 4.3.2. Frequency-Dependent Dynamic Mechanical Behavior.- 4.4. Shrinkage, Thermal Expansion, and Hygroscopic Expansion (Permanent Deformation).- 4.4.1. Shrinkage.- 4.4.2. Thermal and Hygroscopic Expansion.- 4.5. Comparison of Deformation Characteristics of Various Substrates.- 4.6. Tribological Properties.- 4.6.1. Surface Roughness.- 4.6.2. Friction.- 4.6.3. Summary.- 4.7. Mechanical Design Considerations.- 4.7.1. Tape-to-Head Conformity and Dynamic Tape-Head Interactions.- 4.7.2. Transverse Curvature Due to Anisotropy.- 4.7.3. Critical Tension for Tape Flyability.- 4.7.4. Summary.- References.- 5. Stress Analysis of Flexible Media.- 5.1. Wound Magnetic Tape Reels.- 5.1.1. Initial Stress Field.- 5.1.1.1. Analytical Techniques.- 5.1.1.2. Measurement of Radial Stresses in a Wound Tape Reel.- 5.1.1.3. Role of Reel Geometry and Winding Parameters.- 5.1.1.4. Environmental Stresses.- 5.1.1.5. Summary.- 5.1.2. Stress Relaxation.- 5.1.2.1. Constitutive Relationships.- 5.1.2.2. Relaxation Matrix from Experimental Measurements.- 5.1.2.3. Axisymmetric Finite-Element Model.- 5.1.2.4. Numerical Results.- 5.1.2.5 Summary.- 5.2. Flexible Disks.- 5.2.1. Elasticity Solution.- 5.2.1.1. Orthotropic Solid Disk.- 5.2.1.2. Annular Disk: Fixed Inner Boundary.- 5.2.1.3. Approximate Scheme for Annular Disk: a/b Coating-Thickness Variations.- 6.3.1.2. Entrapped Air Pockets, Tension Ridges, and Scratches.- 6.3.2. How Does an Uneven Tape Stack Affect Data Reliability?.- 6.3.3. Summary.- 6.4. Mechanical Print-Through.- 6.5. Staggered Wraps.- 6.5.1. Sources of Tape Stagger.- 6.5.2. Effect of Winding Parameters and Storage Conditions.- 6.5.2.1. Analysis of Elastic Droop of a Staggered Wrap.- 6.5.2.2. Experimental Study.- 6.5.3. How Does Staggered Tape Cause Errors?.- 6.5.4. Methods of Preventing Tape Stagger.- 6.5.5. Summary.- 6.6. Design of Tape Reels.- 6.6.1. Hub.- 6.6.2. Flanges.- 6.6.3. Reel Materials.- References.- Appendix 6.A. Tension-to-Flatten Analysis for a Tape Reel with a Circumferential Bump.- 6.A.1. Tape Substrate.- 6.A.2. Composite Tape.- Appendix 6.B. Tension-Gradient Measurement Technique.- Appendix 6.C. Instantaneous Failure Rate Model to Assess Failures Due to Viscoelastic Deformation-Related Defects.- 6.C.1. Effect of "Burn-In".- 7. Long-Term Reliability of Flexible Disks.- 7.1. Analysis of Disk Deformation.- 7.1.1. Thermal Expansion.- 7.1.2. Hygroscopic Expansion.- 7.1.3. Shrinkage.- 7.1.4. Centrifugal Stresses and Displacements.- 7.1.5. Summary.- 7.2. Measurements of Disk Deformation.- 7.2.1. Description of Disk Deformation Measurement Apparatuses.- 7.2.1.1. Stroboscopic-Disk Deformation Measurement Apparatus.- 7.2.1.2. Scanning-Laser-Disk Deformation Measurement Apparatus.- 7.2.2. Experimental Results.- 7.2.2.1. Thermal and Hygroscopic Deformations.- 7.2.2.2. Shrinkage.- 7.2.2.3. Creep.- 7.2.2.4. Summary.- References.- Appendix A. Requirements and Supporting Test Methods for Magnetic Tapes and Tape Reels.- Appendix B. Analysis of Life Data.- Author Index.
