Optical Recording Medium Cover Layer Segmentation
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Solution Overview
Problem
Optical information recording media using blue violet laser beams with high numerical aperture are sensitive to the thickness of the transparent cover layer, leading to lens collisions and defects such as scratches and dust, which can cause unevenness in the cover layer and degrade recording and reproducing characteristics, and the use of ultraviolet cure type resins can result in warpage due to curing and shrinkage.
Innovation Solution
A method of manufacturing an optical information recording medium with a transparent cover layer composed of a first and second transparent layer, where the first layer is formed with a specific thickness distribution using radiation cure type resins and the second layer is harder and formed to ensure uniformity, preventing lens collisions and warpage, and a warpage control layer can be added to further stabilize the medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a transparent substrate with thickness slightly less than 0.1 mm is bonded with adhesive to form the transparent cover layer, then the cover layer can be easily formed, but the substrate requires extremely uniform thickness which makes it expensive
Solution Approach 1:
The transparent cover layer is divided into two separate layers: a first transparent layer (0.05-0.08 mm thick) bonded to the signal substrate, and a second transparent layer (0.02-0.05 mm thick) bonded to the first layer. This segmentation allows each layer to be manufactured with relaxed thickness uniformity requirements while achieving a total thickness suitable for blue violet laser optical recording.
Solution Approach 2:
The patent uses composite material structure by combining two different transparent substrates with different thicknesses. The first substrate provides the base layer bonded to the signal substrate, while the second substrate provides the outer protective layer, together forming a composite cover layer with optimized total thickness for optical performance.
2Stability of the object's composition
If the transparent cover layer is made thinner to increase tolerance of tilt, then the tolerance of tilt is improved, but the surface can be damaged by lens collision
Solution Approach 1:
The patent creates a composite transparent cover layer structure where the first transparent layer (thinner, 0.05-0.08 mm) provides tilt tolerance while the second transparent layer (0.02-0.05 mm) provides additional protective function. The combination maintains overall structural integrity and resistance to lens collision while preserving tilt tolerance.
3Strength
If a protective layer is formed on the transparent cover layer to prevent damage, then the resistance to lens collision is improved, but the unevenness in thickness of the transparent cover layer increases
Solution Approach 1:
The protective function is segmented into a separate second transparent layer that is specifically designed and bonded onto the first transparent layer. This allows the first layer to maintain thickness uniformity for optical performance while the second layer provides the protective function against lens collision.
4Ease of manufacture
If ultraviolet cure type resin is used for the transparent resin layer, then the manufacturing process is simplified, but warpage occurs due to curing and shrinkage
Solution Approach 1:
The patent applies a warpage control layer to the signal substrate before bonding the first transparent layer. This preliminary countermeasure compensates for the warpage that will occur during ultraviolet curing of the transparent layers, preventing the final product from having excessive warpage while maintaining the simplified ultraviolet curing process.
5Quantity of substance
If blue violet laser beam with high numerical aperture is used for higher density recording, then the recording density is improved, but the laser beam becomes very sensitive to thickness of transparent cover layer
Solution Approach 1:
The transparent cover layer is segmented into two layers with specific thickness ranges (first layer: 0.05-0.08 mm, second layer: 0.02-0.05 mm). This segmentation provides flexibility in achieving the optimal total thickness (0.07-0.13 mm) required for blue violet laser recording while allowing each individual layer to be manufactured with standard precision tolerances.
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 method ensures a uniform and robust transparent cover layer that prevents lens collisions and maintains recording and reproducing quality, while the warpage control layer reduces optical information recording medium warpage to less than 0.35 degrees, ensuring good recording and reproducing characteristics even without warpage control in the recording/reproducing apparatus.
Implementation Method 1
the first transparent layer is formed by using a radiation cure type first resin
Data Source
AI summary
A method of manufacturing an optical information recording medium to/from which signals can optically be recorded and reproduced. The recording medium includes a signal substrate (100), a signal recording layer (110), and a transparent cover layer (125) having a first transparent layer (115) and a second transparent layer (120), which is harder than the first transparent layer (115). Signals can be recorded and reproduced to and from the recording medium by a light transmitted to the signal recording layer through the transparent cover layer (125). The first transparent layer is formed so as to have a first predetermined distribution of thickness. The second transparent layer is formed so as to have a second predetermined distribution of thickness to make the total thickness of the transparent cover layer (125) uniform. The first transparent layer (115) may be made of a plurality of thin laminated transparent layers.