Adhesive Composition for HMD Optical Elements
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Solution Overview
Problem
Existing adhesive compositions for optical elements in head-mounted displays (HMDs) fail to maintain a constant cell gap and exhibit poor transparency and adhesiveness, especially under varying temperature and pressure conditions, which affects the performance and reliability of HMDs in augmented and mixed reality applications.
Innovation Solution
A novel adhesive composition comprising urethane (meth)acrylate with specific viscosity and thickener ratios, along with a spacer, to ensure transparency, adhesiveness, and maintainability of a constant cell gap, while allowing for uniform pattern printing and application processability, is developed. This composition includes urethane (meth)acrylate with 2 or more radical-curable functional groups, aliphatic polyol units, and fumed silica as a thickener, along with a spacer to maintain the desired gap between optical films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional adhesive compositions are used to laminate optical films, then the adhesive composition can be applied, but it fails to maintain a constant cell gap and exhibits poor transparency and adhesiveness
Solution Approach 1:
The patent applies parameter changes by carefully controlling the viscosity of the adhesive composition within a specific range (20,000-500,000 cP) and adjusting the molecular weight of polyol (5,000-50,000) and isocyanate compound (500-5,000) to achieve optimal gap maintaining ability and cell gap consistency in HMD optical elements
Solution Approach 2:
The patent uses composite materials by formulating an adhesive composition containing multiple components including polyol, isocyanate compound, and photoinitiator in specific ratios, creating a multi-component system that achieves both transparency and reliable gap maintenance between optical films
2Strength
If the adhesive composition has high viscosity, then adhesive force is improved, but application processability and pattern printability deteriorate
Solution Approach 1:
The patent resolves this contradiction by optimizing the viscosity parameter to a specific range (20,000-500,000 cP) and controlling the molecular weights of components, allowing the adhesive to have sufficient adhesive force while remaining printable and applicable in thin patterns with good flow characteristics
3Manufacturing precision
If the adhesive composition is printed into a thin pattern, then application precision is improved, but the width of the pattern may not be maintained under subsequent pressure
Solution Approach 1:
The patent maintains pattern width under pressure by optimizing the viscosity and molecular weight parameters of the adhesive components, creating a composition that is printable in thin patterns and simultaneously resistant to compression, maintaining its dimensional stability during assembly
Solution Approach 2:
The multi-component composite adhesive formulation provides both the printability for thin patterns and the mechanical stability to maintain pattern width under subsequent assembly pressures
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 adhesive composition achieves excellent transparency, adhesiveness, and gap maintenance, enabling the formation of reliable optical elements for HMDs with improved printability and application processability, ensuring consistent performance across varying conditions.
Implementation Method 1
The urethane (meth)acrylate may have at least two radical-curable functional groups. As the radical-curable functional group, for example, a (meth)acryloyl group is applied.
Implementation Method 2
The adhesive composition of the present application can suitably satisfy the above-mentioned required physical properties, thereby being usefully used for constituting an optical element for HMDs
Data Source
AI summary
The present disclosure provides an adhesive composition including an aliphatic urethane (meth)acrylate, a thickener and a spacer. The adhesive composition has printability that printing can be effectively performed into a pattern with a thin width or the like, and is capable of forming an adhesive having excellent physical properties such as transparency, a gap maintaining ability capable of maintaining a constant cell gap between films and adhesive force. The adhesive composition is useful for constituting an optical element for HMDs.