Optical Laminate for Foldable Display Color Reproducibility
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Display devices, especially those with polyimide films, suffer from color reproducibility issues and blackout when viewed through polarization sunglasses, particularly when viewed obliquely, due to the negative C-plate property of polyimide films and the retardation effects of optical films.
Innovation Solution
An optical laminate comprising two films: a film A with a positive A-plate property and a film C with a negative C-plate property, where the film A has a higher refractive index in the plane and the film C has a higher refractive index in the thickness direction, designed to minimize retardation differences and maintain color accuracy regardless of viewing angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyimide film with negative C-plate property is used to provide folding durability, then folding resistance is improved, but color reproducibility deteriorates when viewed through polarization sunglasses
Solution Approach 1:
The optical laminate is divided into multiple functional films: a polyimide film (C) for folding durability and a compensation film (A) for optical compensation. This segmentation allows each film to specialize in one function while working together to solve the overall problem of color reproducibility with polarization sunglasses.
Solution Approach 2:
The patent uses a composite structure of two different polymer films with distinct optical properties. The polyimide film provides mechanical durability while the compensation film provides optical compensation, creating a composite material system that achieves both folding resistance and color accuracy.
2Illumination intensity
If optical films with retardation are disposed in the display device, then brightness and color gamut are improved, but color unevenness occurs when viewed through polarization sunglasses
Solution Approach 1:
The patent carefully controls the retardation parameters of the compensation film to fall within specific ranges (Ra(0) of 1000-5000 nm, Rth of 50-500 nm). By optimizing these parameters, the film compensates for the retardation effects of other display components, preventing color unevenness while maintaining brightness.
3Device complexity
If a single polyimide film is used as the optical film, then device complexity is reduced, but color reproducibility deteriorates in oblique viewing directions
Solution Approach 1:
Instead of using a single complex polyimide film, the patent segments the optical function into two simpler films: a polyimide film for durability and a compensation film for optical performance. This segmentation maintains simplicity while improving color reproducibility in oblique viewing directions.
4Illumination intensity
If the retardation value is increased to solve blackout, then visibility through polarization sunglasses is improved, but color accuracy deteriorates
Solution Approach 1:
The patent optimizes the retardation parameters of the compensation film to achieve a balance: Ra(0) of 1000-5000 nm and Rth of 50-500 nm. These parameter ranges are carefully selected to provide sufficient compensation to prevent blackout while maintaining color accuracy through polarization sunglasses.
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 optical laminate ensures good color reproducibility and prevents blackout when viewed through polarization sunglasses, even at oblique angles, making it suitable for foldable display devices.
Implementation Method 1
a film A satisfying the following condition (1) and a film C satisfying the following condition (2)... nx denotes a refractive index in a direction of a slow axis along which refractive index is highest in the plane of the film, ny denotes a refractive index in a direction of a fast axis orthogonal to the slow axis in the plane of the film, and nz denotes a refractive index in a thickness direction of the film
Data Source
AI summary
The present invention provides: an optical laminate comprising at least two films, the optical laminate comprising at least a film A satisfying a given condition (1) and a film C satisfying a given condition (2), wherein a retardation value Re(0) observed in a direction of an axis perpendicular to a plane of the optical laminate is 4,000 to 30,000 nm, and a retardation value Re(40) observed in a direction of an axis tilted from the axis perpendicular to the plane of the optical laminate toward a slow axis by 40 degrees in a plane lying perpendicular to the plane of the optical laminate and extending along the slow axis is 4,000 to 25,000 nm, the slow axis being an axis along which refractive index is highest in a plane of the film A; and a display device comprising the optical laminate.