Flexible Optical Stack for Foldable Displays
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Solution Overview
Problem
Existing flexible display devices, such as OLEDs, face challenges due to the thickness and rigidity of cover glasses and internal reflection issues, which hinder their flexibility and require additional components like circular polarizers, making mass production difficult and unsuitable for individual production.
Innovation Solution
An optical stack comprising a resin layer, an optical compensation layer, a polarizer, and a hard coat layer, with the option of incorporating a lyotropic liquid crystal polarizer and decorative prints or touch panel electrodes, stacked in a specific order on a glass substrate and produced in a sheet-by-sheet manner, allowing for individual production without the need for specialized manufacturing equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a cover glass is disposed as a protective layer on the panel surface, then the display device has protection and structural integrity, but the display device loses flexibility due to the thickness and rigidity of the cover glass
Solution Approach 1:
The patent replaces the rigid cover glass with a flexible protective film that has both protective capabilities and flexibility. The film is designed to be thin yet durable, allowing the display device to maintain its protective function while achieving the desired flexibility for curved, foldable, or wearable applications.
Solution Approach 2:
The patent changes the physical parameters of the protective layer by transitioning from thick glass (0.5-2mm) to thin flexible film material. This parameter change enables the protective layer to provide adequate protection while being flexible enough to conform to curved surfaces and foldable structures.
2Object-affected harmful factors
If circular polarizers are disposed in OLED display devices to counteract internal reflection, then internal reflection is reduced, but the display device thickness increases and flexibility is hindered due to the thickness of the linear polarizer and λ/4 wave plate films
Solution Approach 1:
The patent combines the functions of the linear polarizer and λ/4 wave plate into a single integrated circular polarizer component. This merging reduces the total thickness of the polarizing assembly while maintaining the anti-reflection functionality, thereby preserving flexibility without compromising the reduction of internal reflection.
Solution Approach 2:
The patent employs thin-film technology to create a flexible circular polarizer that maintains anti-reflection properties while being thin enough to preserve device flexibility. The thin-film construction allows the polarizer to conform to curved surfaces without breaking or losing its optical function.
3Productivity
If roll-to-roll manufacturing is used to produce optical stacks with hard coat layers and optical compensation layers, then mass production efficiency is improved, but individual production and customized decorative printing become difficult
Solution Approach 1:
The patent segments the manufacturing process into modular stages, allowing different production methods to be used for different components. The hard coat layer and optical compensation layer can be produced using efficient roll-to-roll methods, while the substrate and decorative elements can be individually customized before assembly. This segmentation enables both mass production efficiency and individual production flexibility.
Solution Approach 2:
The patent applies decorative printing and individual customization to the substrate before the mass production assembly process. By performing preliminary actions on individual components before they enter the mass production line, the system maintains flexibility for customized products while achieving efficiency in the assembly and manufacturing of standard components.
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 flexible display devices with improved flexibility and reduced thickness, suitable for individual production, while addressing internal reflection and enabling decorative printing and touch panel functionality.
Implementation Method 1
an optical compensation layer capable of functioning as a λ/4 wave plate
Implementation Method 2
The film-like λ/4 wave plate is formed by drawing a film composed of a polycarbonate resin or a cycloolefinic polymer resin
Implementation Method 3
The film-like linear polarizer is formed by drawing a PVA (polyvinyl alcohol)-based film impregnated with a dichroic pigment such as iodine
Implementation Method 4
a dichroic pigment such as iodine
Implementation Method 5
a surface protective layer formed of a hard coat layer
Data Source
AI summary
An optical stack for a display device includes multiple layers that are incorporated into a display device that further includes a display panel. The optical stack includes a resin layer, an alignment film, an optical compensation layer, a polarizer, and a hard coat layer that are stacked in this order from a panel side. The optical stack is formed by preparing and coating a solution for each layer, and then curing and otherwise treating each layer as warranted for a particular layer, in turn to form the optical stack.