Foldable Display Protecting Windows with Inclined Side Surfaces
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Solution Overview
Problem
Foldable display devices experience total reflection of light at the boundary surface between the protecting window and the flexible material, leading to a phenomenon where the image appears cut off due to the difference in refractive indexes, causing visibility issues.
Innovation Solution
Inclining the side surfaces of the protecting windows with respect to the upper or lower surfaces, increasing the interval between them, and using a flexible material layer with a lower refractive index, such as silicon resin, to reduce total reflection and maintain image continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard protecting window material is used, then protection strength is improved, but total reflection at the boundary surface increases causing image cut-off
Solution Approach 1:
The protecting window has different refractive index regions: the main body uses hard material (glass) for protection, while the side surfaces are coated with a layer having a refractive index intermediate between glass and flexible material. This local differentiation allows the bulk to provide strength while the interface regions minimize total reflection.
Solution Approach 2:
A refractive index matching layer is introduced as an intermediary between the hard protecting window and the flexible material. This intermediate layer has a refractive index that gradually transitions from the hard material to the flexible material, acting as a mediator that reduces the abrupt refractive index difference and prevents total reflection.
2Adaptability or versatility
If the protecting window and flexible material have different refractive indexes, then material properties are optimized, but light transmission is reduced due to total reflection
Solution Approach 1:
The protecting window structure uses different materials with different refractive indexes for different regions: the main body uses hard glass for protection while the side surfaces use a refractive index matching layer. This allows each region to have optimized properties for its specific function while maintaining overall light transmission.
Solution Approach 2:
The protecting window is constructed as a composite structure combining hard glass material with a refractive index matching layer. This composite design allows the system to simultaneously achieve the protective function of hard glass and the light transmission function of the matching layer, resolving the contradiction between material optimization and light transmission.
3Ease of manufacture
If the side surfaces are perpendicular to the upper surface, then manufacturing is simplified, but total reflection occurs at the boundary
Solution Approach 1:
The protecting window has different geometric characteristics in different regions: the upper surface maintains a simple perpendicular geometry for ease of manufacture, while the side surfaces are inclined at a specific angle to reduce total reflection. This local differentiation allows each region to be optimized for its specific requirement.
Solution Approach 2:
The side surfaces of the protecting window are designed with an inclined angle rather than being perpendicular, creating a curved or angled interface that reduces total reflection. This geometric modification at the boundary regions allows light to pass through more effectively while maintaining manufacturing feasibility.
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 inclined surfaces decrease the likelihood of total reflection, ensuring that light from the display devices passes through and reaches the observer, preventing the perception of a cut-off screen, thereby enhancing the display's visibility and image integrity.
Implementation Method 1
total reflection of light directed to the flexible material from the protecting window may occur at a boundary surface between the protecting window and the flexible material due to a difference between refractive indexes
Implementation Method 2
difference between refractive indexes of the protecting window and the flexible material
Data Source
AI summary
A foldable display device includes a first display panel which displays a portion of an image; a second display panel which displays a second portion different from the first portion of the image; a first protecting window on the first display panel; a second protecting window on the second display panel; and a flexible material layer between the first and second protecting windows. Side surfaces of the first and second protecting windows which contact the flexible material layer, respectively, are inclined with respect to a surface of each of the first and second protecting windows.