Polarizing Sheet Retardation Balance for Bending Precision
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Solution Overview
Problem
Polarizing sheets formed from stretched polyamide resin films experience uneven deformation when bent with a heated mold due to temperature differences, leading to difficulties in achieving precise curved shapes without whitening.
Innovation Solution
A polarizing sheet with a laminate structure of a polyamide resin film (1) and a polarizing film, where the polyamide resin film (1) has a retardation value of 10 to 3000 nm, and the difference in retardation values between the two films is set to at least 10 nm, allowing for precise bending without whitening by compensating for thermal expansion and shrinkage differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stretched polyamide resin film is used in the polarizing sheet, then the polarizing lens can prevent whitening and maintain chemical resistance, but the film shrinks and deforms unevenly when heated due to temperature differences, causing difficulties in achieving precise bending
Solution Approach 1:
The invention divides the polyamide resin film into multiple layers with different retardation values. Specifically, it uses a laminate structure where at least one polyamide resin film has a retardation value of 10 to 3000 nm, and another has a different retardation value, creating segmented optical properties that compensate for thermal deformation differences during heating and bending processes
Solution Approach 2:
The invention changes the optical parameter (retardation value) of the polyamide resin films to control their thermal deformation characteristics. By selecting films with specific retardation values (10-3000 nm) and combining them in a laminate, the invention optimizes the balance between whitening prevention and bending precision without changing the fundamental material properties
2Ease of manufacture
If the polyamide resin film is exposed to higher temperature during bending, then the film softens and deforms easily, but this causes uneven deformation compared to cooler areas, resulting in imprecise curved shapes
Solution Approach 1:
The invention applies local quality by using polyamide resin films with different retardation values in different positions within the laminate. The film with retardation value of 10 to 3000 nm is positioned to compensate for the specific deformation characteristics of the film exposed to higher temperature during bending, creating localized optical compensation that maintains overall shape precision
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 enables the production of polarizing lenses with curved shapes of high precision and without whitening, maintaining chemical resistance and light weight, making them suitable for applications like sunglasses and goggles.
Implementation Method 1
setting a retardation value of a polyamide resin film on the side that is directly in contact with the mold (i.e. the side that is exposed to a higher temperature) to be at least 10 nm greater than a retardation value of the polyamide resin film on the opposite side can eliminate a difference in an amount of deformation caused by a difference in the heat exposure temperatures of the polyamide resin films (1) and (2) (that is, an amount of deformation due to a difference between thermal expansion and thermal shrinkage)
Data Source
AI summary
Provided is a polarizing sheet that can precisely impart a desired curved shape without causing whitening when bending is carried out. A polarizing sheet of an embodiment of the present invention having a structure in which a polyamide resin film (1), a polarizing film, and a polyamide resin film (2) are laminated in this order, wherein a retardation value of the polyamide resin film (1) is from 10 to 3000 nm, and the retardation value of the polyamide resin film (1) and a retardation value of the polyamide resin film (2) satisfy Formula (r):[Retardation Value of Polyamide Resin Film (1)]−[Retardation Value of Polyamide Resin Film (2)]≥10 nm (r).