Thermoformed OLED Stack With Buffer Layer for Curved Display Forming
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Solution Overview
Problem
The challenge of embedding OLED displays in thermoformed devices is exacerbated by high temperatures and mechanical strain, leading to visual defects and potential damage during the thermoforming process, particularly in mono-foil approaches.
Innovation Solution
Incorporating a thermomechanical buffer layer between the front substrate and OLED display, made of a thermoplastic material with lower stiffness than the substrate, to absorb mechanical and thermal stresses during thermoforming, allowing the OLED to maintain functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If heat is applied to the stack during thermoforming to make the front substrate pliable, then the substrate becomes deformable, but the OLED display is exposed to thermal stress that can damage it
Solution Approach 1:
A buffer layer is introduced as an intermediary component between the front substrate and the OLED display. This buffer layer absorbs thermal stress and mechanical strain during thermoforming, protecting the OLED from direct exposure to high temperatures and deformation forces while allowing the front substrate to be adequately heated and shaped.
Solution Approach 2:
The buffer layer is positioned in advance between the substrate and OLED to provide protective cushioning before the thermoforming process begins. This pre-positioned protective layer prevents direct transmission of thermal and mechanical stresses to the OLED during the high-temperature deformation process.
2Ease of manufacture
If the front substrate is heated to high temperature for thermoforming, then the material becomes pliable for shaping, but mechanical strain transfers directly to the OLED causing damage
Solution Approach 1:
The buffer layer serves as a mechanical intermediary that decouples the front substrate from the OLED during thermoforming. It allows the substrate to undergo significant deformation and strain while the buffer layer absorbs these mechanical stresses, preventing direct force transmission to the fragile OLED structure.
Solution Approach 2:
The buffer layer is selected with specific material properties including lower stiffness compared to the front substrate, and a glass transition temperature below the substrate's processing temperature. These parameter changes enable the buffer layer to remain more compliant during heating, absorbing mechanical strain while protecting the OLED.
3Device complexity
If a mono-foil approach is used for in-mold electronics, then device complexity is reduced, but visual defects occur due to local deformations from components
Solution Approach 1:
The buffer layer is selectively positioned in the region where the OLED display is located, providing localized protection against deformation-induced visual defects. This targeted approach maintains the simplicity of the overall mono-foil structure while addressing specific quality issues in the display region through local material property optimization.
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 buffer layer effectively reduces mechanical and thermal stress on the OLED, preventing damage and visual defects, enabling the successful integration of OLED displays in curved devices without compromising functionality.
Implementation Method 1
the lower stiffness of the buffer layer which may allow it to deform more than the front substrate and thus lower mechanical stresses to the OLED
Implementation Method 2
During or before thermoforming, heat is applied to the stack for causing a temperature of the front substrate and buffer layer to increase to a processing temperature
Implementation Method 3
the thermoplastic material forming the buffer layer has a lower stiffness than that of the front substrate at the respective processing temperature. For example, the processing temperature at which the buffer layer undergoes phase transition can be lower than the processing temperature of the front substrate
Implementation Method 4
This can be at least partially explained by the additional heat capacity of the buffer layer. As will be appreciated, heat capacity of a material undergoing phase transition can be relatively high, when the heat is utilized in changing the state of the material rather than raising its temperature
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 3A~3B
AI summary
A curved human interface device is manufactured by thermoforming a stack. The stack comprises a front substrate formed of a transparent, first thermoplastic material; an OLED display configured to display an image through the front substrate; and a thermomechanical buffer layer formed of a transparent, second thermoplastic material arranged between the front substrate and the OLED display. Heat is applied to the stack for causing a temperature of the front substrate and buffer layer to increase to a respective processing temperature at which the first and second thermoplastic materials become pliable. The stack is thermoformed while the thermoplastic materials are pliable to form the curved human interface device. The second thermoplastic material has a lower stiffness at the respective processing temperature than the first thermoplastic material.