Biaxially Oriented Polyester Film Surface Control
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Solution Overview
Problem
High-density magnetic recording media require extremely smooth surfaces, but achieving this surface smoothness leads to difficulties in air expulsion during film manufacturing, resulting in wrinkles and reduced productivity, and existing methods are insufficient in controlling protrusion heights and frequencies on rough surfaces, causing signal failures.
Innovation Solution
A biaxially oriented polyester film with specific protrusion height and frequency control, measured by a contactless surface shape device, and a 0.4% area bearing curve height within 65-90 nm range, ensuring excellent winding properties and electromagnetic conversion, with ethylene terephthalate or ethylene-2,6-naphthalenedicarboxylate as the main repeating unit and inert particles for improved surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the surface of the base film is highly smoothened to achieve high density recording, then the surface roughness is reduced, but air expulsion between layers becomes difficult leading to wrinkles and reduced productivity
Solution Approach 1:
The invention applies local quality by creating a double-layer structure where one surface has a rough texture (for air expulsion) and the other surface is smooth (for magnetic layer formation). This allows different regions of the film to have different surface properties optimized for their specific functions.
Solution Approach 2:
The base film is segmented into two distinct layers with different surface characteristics. The first layer provides a rough surface for air expulsion during manufacturing, while the second layer provides a smooth surface for high-density magnetic recording, thus resolving the contradiction between productivity and manufacturing precision.
2Productivity
If a rough surface is formed on one surface of the base film to improve air expulsion, then winding property is improved, but protrusions on the rough surface are transferred to the magnetic layer surface causing signal failures
Solution Approach 1:
The invention applies local quality by creating a double-layer structure where one surface has a rough texture (for air expulsion) and the other surface is smooth (for magnetic layer formation). This allows different regions of the film to have different surface properties optimized for their specific functions.
Solution Approach 2:
The base film is segmented into two distinct layers with different surface characteristics. The first layer provides a rough surface for air expulsion, while the second layer provides a smooth surface for high-density magnetic recording, thus resolving the contradiction between productivity and manufacturing precision.
3Manufacturing precision
If existing methods control void density in polyester films, then some surface uniformity is achieved, but protrusion height and frequency cannot be highly controlled for ultra high density recording
Solution Approach 1:
The invention changes the control parameters from general void density to specific protrusion height distribution and bearing curve characteristics. By controlling the 0.4% area bearing curve to be 65 nm or more and less than 90 nm, and controlling the frequency distribution of protrusions at specific height levels, the invention achieves the required surface precision for ultra high density recording.
Solution Approach 2:
The invention replaces conventional mechanical surface measurement and control methods with contactless surface shape measurement technology. This allows for non-contact, high-precision measurement of protrusion heights and frequency distributions, enabling better control of surface characteristics without mechanical interference.
Data Source
AI summary
A biaxially oriented polyester film, which exhibits an excellent winding property in a manufacturing process, and realizes an excellent electromagnetic conversion property and less failure of signals of a magnetic recording tape to be produced thereof, is provided. This biaxially oriented polyester film satisfies the formula y≤−24.9X+3.8, where the protrusion height X is 0.075 μm, 0.100 μm, and 0.125 μm, and y denotes a base-10 logarithm value of the number of protrusions having protrusion heights of X or more in a visual field of a region of 282 μm×211 μm, and a protrusion height that corresponds to a 0.4% area of a bearing curve based on protrusion height distribution is 65-90 nm.