Optical Disc Light Transmission Layer Warp and Creep Control
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Solution Overview
Problem
High-density optical discs face issues with warping due to asymmetric thickness and creep caused by static loads, which affect their planarity and recording/reproduction capabilities, especially in extreme usage environments.
Innovation Solution
A laminar structure optical recording medium with a light transmission layer composed of a liquid active energy line cure reactive bridge resin, having an elasticity modulus range of 1*10^7 to 5*10^8 Pa at 25°C and 4*10^8 to 5*10^9 Pa at -20°C, and a glass transition point temperature from -20°C to 0°C, combined with a bifunctional or multifunctional monomer component, to balance warp prevention and creep resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the elasticity modulus of the light transmission layer is decreased to prevent disc warp, then warp resistance is improved, but creep resistance deteriorates when static load is continuously applied
Solution Approach 1:
The patent applies parameter changes by precisely controlling the elasticity modulus within a specific range (1×10^7 to 5×10^8 Pa at 25°C) and the glass transition point temperature within a specific range (-20°C to 0°C). This optimized parameter range allows the light transmission layer to simultaneously achieve sufficient flexibility for warp prevention and adequate stiffness for creep resistance under static loads, resolving the technical contradiction between these two opposing requirements.
Solution Approach 2:
The patent uses composite materials by formulating the light transmission layer with a specific composition including a reactive bridge resin (30-70 wt%), a monomer (10-60 wt%), and a photopolymerization initiator (0.1-10 wt%). This composite resin system combines the advantages of different components to achieve the target elasticity modulus and glass transition point, enabling simultaneous warp prevention and creep resistance that cannot be achieved with single materials.
2Productivity
If the light transmission layer is formed only on a single side to achieve high density recording, then recording capacity is improved, but structural symmetry deteriorates causing increased warp
Solution Approach 1:
The patent applies local quality by concentrating the light transmission layer on the information readout face side where it is most needed for optical access and protection of the recording layer. The asymmetric placement is compensated by optimizing the material properties (elasticity modulus and glass transition point) of the light transmission layer to provide sufficient mechanical stability despite the asymmetric structure, enabling high-density recording while maintaining warp resistance.
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 effectively prevents warp and maintains planarity under static loads, ensuring durability and reliable recording/reproduction performance even in extreme environments, while maintaining the necessary mechanical characteristics within specified standards.
Implementation Method 1
a photopolymerization initiator component; As physical properties after cure reaction, an elasticity modulus at 25 deg C is in a range from 1×10^7 to 5×10^8 Pa both inclusive
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3(a)~3(b)
AI summary
Both decreasing disc warp and decreasing creep in a light transmission layer are realized. In the light transmission layer, the elasticity modulus at 25 deg C is in the range from 1*107 Pa to 5*108 Pa, the elasticity modulus at -20 deg C is in the range from 4*108 Pa to 5*109 Pa, and the glass transition point temperature is from -20 deg C to 0 deg C both inclusive. The Martens hardness of the light transmission layer is 10 N/mm2 or less. The indentation creep of the light transmission layer is 2% or less. The return value of the indentation depth of the light transmission layer is in the range from 0.2 to 2.0 microns.