Polyurethane Binder Molecular Weight for Magnetic Recording Media
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Solution Overview
Problem
Conventional magnetic recording media face challenges in achieving high recording density due to insufficient dispersibility of ultrafine ferromagnetic powders, leading to inadequate electromagnetic conversion characteristics, coating strength, and transport durability.
Innovation Solution
A magnetic recording medium utilizing a polyurethane resin with a weight-average molecular weight of 200,000 to 400,000, which enhances the dispersibility of ferromagnetic powders and provides improved coating strength and durability, combined with a non-magnetic layer for enhanced electromagnetic conversion characteristics and storage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binders are used to disperse ferromagnetic powder, then the magnetic recording medium can be manufactured, but the dispersibility of ultrafine ferromagnetic powder is insufficient leading to inadequate electromagnetic conversion characteristics
Solution Approach 1:
The patent changes the molecular weight parameter of the polyurethane binder from conventional values to specifically 200,000-400,000, which fundamentally alters the binder's ability to disperse ultrafine ferromagnetic powder particles. This parameter change enables adequate dispersibility and electromagnetic conversion characteristics that were unachievable with conventional binders
Solution Approach 2:
The patent creates a composite system combining polyurethane resin with specific molecular weight characteristics and hydrophilic polar groups with ultrafine ferromagnetic powder particles. This composite approach enhances the interaction between binder and magnetic particles, improving both dispersibility and electromagnetic conversion characteristics
2Reliability
If conventional binders are used, then the magnetic layer can be formed, but sufficient coating strength and repetitive transport durability cannot be obtained
Solution Approach 1:
The patent modifies the molecular weight parameter of the polyurethane binder to 200,000-400,000, which fundamentally changes the mechanical properties of the magnetic layer. This parameter adjustment simultaneously improves both coating strength and transport durability, resolving the contradiction between these two requirements
3Reliability
If ferromagnetic powder is made finer to achieve higher recording density, then electromagnetic conversion characteristics can be improved, but dispersibility becomes more difficult to achieve
Solution Approach 1:
The patent addresses the dispersibility challenge of ultrafine ferromagnetic powder by changing the binder's molecular weight to 200,000-400,000. This parameter change provides sufficient binding strength and dispersibility control, enabling the use of finer magnetic particles for higher recording density without compromising manufacturing feasibility
Solution Approach 2:
The polyurethane binder with specific molecular weight acts as an intermediary between ultrafine ferromagnetic powder particles and the magnetic layer structure. This intermediary role enables adequate dispersibility and maintains manufacturing control while allowing finer particles to achieve the required electromagnetic conversion characteristics
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves excellent electromagnetic conversion characteristics, storage stability, and transport durability by effectively dispersing ultrafine ferromagnetic powders with a higher molecular weight polyurethane resin, while maintaining a high packing ratio and reducing low molecular weight component deposition.
Implementation Method 1
there has therefore been proposed a dispersion technique for carrying out planarization by introducing a hydrophilic polar group such as —SO3M (M denotes hydrogen, an alkali metal, or an ammonium salt) into a binder and making a binder chain adsorb on the magnetic substance
Data Source
AI summary
A magnetic recording medium is provided that comprises a non-magnetic support and at least one magnetic layer above the support, the magnetic layer comprising a ferromagnetic powder dispersed in a binder, and the binder comprising a polyurethane resin having a weight-average molecular weight of 200,000 to 400,000. There is also provided a magnetic recording medium that comprises a non-magnetic support, a non-magnetic layer above the support, the non-magnetic layer comprising a non-magnetic powder dispersed in a binder, and at least one magnetic layer above the non-magnetic layer, the magnetic layer comprising a ferromagnetic powder dispersed in a binder and the binder of the magnetic layer and/or the non-magnetic layer comprising a polyurethane resin having a weight-average molecular weight of 200,000 to 400,000.