Silicone Optical Bonding for Display Lamination
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Solution Overview
Problem
Acrylate adhesives used in optical bonding for displays face issues such as yellowing at the edges of visible areas and air bubble problems, particularly in large size displays and automotive touch screens, where they fail to meet reliability and processing requirements, and UV-stabilized plastics prevent full curing of acrylate optical clear resins.
Innovation Solution
A lamination method using a liquid silicone optical bonding agent activated by UV irradiation in the 200 nm to 500 nm wavelength range, applied to a first substrate before the second substrate is applied, ensuring the agent remains in a liquid or semi-liquid state until lamination, with a one-component silicone material that includes polysiloxane, polyhydrosiloxane, and a photoactive platinum catalyst, allowing for stable bonding without full curing before assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If acrylate OCR is used for optical bonding, then bonding strength is achieved, but yellowing occurs at the edges of visible areas
Solution Approach 1:
The patent changes the chemical composition parameters of the optical bonding agent from acrylate-based to silicone-based materials with specific molecular structures (polysiloxane, polyhydrosiloxane). This fundamental material parameter change eliminates the yellowing issue while maintaining bonding strength, as silicone materials do not exhibit the same photodegradation characteristics as acrylates.
Solution Approach 2:
The patent employs composite silicone materials comprising multiple components (polysiloxane, polyhydrosiloxane, and photoactive catalyst) to achieve both optical clarity and bonding performance. This composite approach allows optimization of both strength and color stability properties that single-component materials cannot provide.
2Strength
If acrylate OCA is used for optical bonding, then bonding is achieved, but air bubbles are difficult to remove during processing
Solution Approach 1:
The patent changes the rheological parameters of the bonding agent by using silicone materials with adjustable viscosity and cure characteristics. The silicone-based optical bonding agent has different flow and curing properties compared to acrylate OCA, allowing for easier bubble removal during the lamination process while maintaining strong bonding.
3Reliability
If UV-stabilized plastic cover lenses are used in automotive displays, then UV protection is achieved, but acrylate OCR cannot be fully cured
Solution Approach 1:
The patent changes the photochemical parameters of the bonding agent by selecting silicone-based materials with different UV absorption and reactivity characteristics compared to acrylates. The silicone material's curing mechanism is not blocked by UV-stabilized plastics, allowing complete curing to occur even when UV protection layers are present, thus resolving the curing inhibition issue.
4Stability of the object's composition
If longer UV irradiation duration is used to ensure full curing, then curing completeness improves, but gel time is exceeded causing processing delays
Solution Approach 1:
The patent changes the photochemical reactivity parameters of the bonding agent by incorporating photoactive catalysts and adjusting the molecular structure of the silicone components. This enables the material to achieve complete curing with shorter UV irradiation exposure, reducing processing time while ensuring full curing completeness.
Solution Approach 2:
The patent employs a two-stage curing approach with periodic action: initial UV irradiation to achieve rapid setting and bonding, followed by extended UV or thermal curing to complete the reaction. This periodic curing strategy ensures complete curing while minimizing the time the material remains in a processable state.
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 method provides a stable and transparent bond with high adhesion strength and UV-Visible light transparency, overcoming the limitations of acrylate adhesives, including yellowing and air bubble issues, and meeting the requirements of large and automotive displays with improved reliability and durability.
Implementation Method 1
activating the liquid silicone optical bonding agent in step (a) by irradiation in a wavelength range of 200 nm to 500 nm
Data Source
AI summary
Substrates suitable for optoelectronic display devices are prepared by:(a) applying a liquid silicone optical bonding agent to a first substrate,(b) activating the liquid silicone optical bonding agent applied in step (a) by irradiation with light in a wavelength range of 200 nm to 500 nm, wherein the duration of the irradiation is less than the gel time of the liquid silicone optical bonding agent, and(c) applying a second substrate to the activated liquid silicone optical bonding agent before the liquid silicone optical bonding agent is gelled.