Laminated Optical Film Surface Roughness Control
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Solution Overview
Problem
Existing reflective polarizers used in image display devices, such as those described in JP2011-053705A, JP2015-028656A, and JP6277088B, result in decreased image sharpness when partially reflecting external light to generate virtual and real images.
Innovation Solution
A laminated optical film comprising a reflective circular polarizer, a retardation layer that converts circularly polarized light into linearly polarized light, and a linear polarizer, with the reflective circular polarizer having a surface roughness of 100 nm or less on the side opposite to the linear polarizer, enhancing image sharpness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing reflective polarizers are used to partially reflect external light and light from an image display device to generate virtual and real images, then the light reflection function is achieved, but the image sharpness is decreased
Solution Approach 1:
The patent applies parameter changes by precisely controlling the surface roughness parameter of the reflective circular polarizer to be 100 nm or less. This parameter control resolves the contradiction by maintaining optical precision for sharp images while being achievable through standard manufacturing processes like spin coating and UV curing with controlled drying conditions
Solution Approach 2:
The patent uses composite materials by combining the reflective circular polarizer with specific retardation layers (including quarter-wave and half-wave retardation layers) and linear polarizers. This composite structure resolves the contradiction by distributing functional requirements across multiple layers, allowing each layer to be optimized for its specific function while maintaining overall image sharpness
2Adaptability or versatility
If the reflective circular polarizer is stretched or molded into curved shapes to fit display devices, then the adaptability to different display forms is improved, but the surface roughness increases and polarization efficiency decreases
Solution Approach 1:
The patent applies preliminary action by pre-treating the reflective circular polarizer with surface smoothing processes and optimizing the substrate properties before stretching or molding. This ensures that even when the polarizer is deformed to fit curved displays, the surface roughness remains at 100 nm or less, maintaining polarization efficiency
Solution Approach 2:
The patent uses flexible thin film structures for the reflective circular polarizer and supporting substrates that can be stretched and molded into curved shapes without permanently degrading optical properties. The thin film nature allows elastic deformation while maintaining surface smoothness and optical function
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 laminated optical film achieves high image sharpness in image display devices by maintaining low surface roughness and polarization efficiency, even when stretched or molded into curved shapes, thereby improving the clarity of virtual and real images generated.
Implementation Method 1
The reflective polarizer is a polarizer having a function of reflecting one polarized light in incidence rays and transmitting the other polarized light
Implementation Method 2
a retardation layer that converts circularly polarized light into linearly polarized light
Implementation Method 3
a film having a layer obtained by immobilizing a cholesteric liquid crystalline phase
Data Source
AI summary
An object of the present invention is to provide a laminated optical film including a reflective circular polarizer with high image sharpness of a reflected image, and an image display device formed of the laminated optical film. The object is achieved by providing the laminated optical film including at least a reflective circular polarizer, a retardation layer that converts circularly polarized light into linearly polarized light, and a linear polarizer in this order, in which a surface of the reflective circular polarizer on a side opposite to the linear polarizer has a surface roughness Ra of 100 nm or less.