Light Guide Prism Bonding with Hydrophilic-Hydrophobic Surface Patterns
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Solution Overview
Problem
The challenge in manufacturing light guide devices for virtual image display apparatus, such as head-mounted displays, lies in ensuring proper adhesive filling on free-form surfaces, which is crucial for maintaining optical accuracy and preventing distortions, especially when bonding block-shaped members with inclined reflective surfaces.
Innovation Solution
A method involving a light guide prism with a mirror layer and an opposing prism, where the bonding surfaces are free-form and have specific inclination angles, allowing for controlled adhesive flow and precise alignment to ensure accurate bonding and optical functionality, resembling the shape of glasses for an excellent appearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive is applied to free-form bonding surfaces to bond the light guide prism and opposing prism, then the bonding strength is improved, but it becomes difficult to control the adhesive flow direction and achieve proper filling state
Solution Approach 1:
The patent applies different surface properties to different regions of the bonding interface. Specifically, the light guide prism has a hydrophilic region and a hydrophobic region on its bonding surface, creating localized adhesive flow control. The hydrophilic region attracts and guides adhesive flow along the desired path, while the hydrophobic region repels adhesive to prevent unwanted spreading. This local differentiation of surface properties enables precise control of adhesive filling on complex free-form surfaces without compromising bonding strength.
Solution Approach 2:
The patent prepares the bonding surfaces in advance by forming specific patterns of hydrophilic and hydrophobic regions before adhesive application. This preliminary surface treatment creates a predetermined flow path for the adhesive, ensuring that when adhesive is applied, it automatically flows in the correct direction and fills the bonding interface properly. This pre-prepared surface structure eliminates the need for complex real-time control during the bonding process.
2Adaptability or versatility
If block-shaped members with inclined reflective surfaces are bonded to achieve see-through function, then the optical functionality is improved, but distortion may be generated on the reflection surface
Solution Approach 1:
The patent creates distinct functional zones on the bonding surfaces, including hydrophilic regions for adhesive guidance and hydrophobic regions for adhesive repulsion. This local differentiation ensures that adhesive is precisely positioned and flows only where intended, preventing adhesive contamination of the reflective surfaces. By controlling adhesive placement at the local level, the optical quality of the reflective surfaces is maintained while achieving the see-through function.
Solution Approach 2:
The patent introduces surface energy differentiation (hydrophilic and hydrophobic regions) as an intermediary mechanism to control adhesive behavior. This intermediary surface property acts as a mediator between the adhesive and the bonding surfaces, guiding adhesive flow without requiring direct mechanical intervention. The hydrophilic-hydrophobic pattern serves as an intermediary field that automatically directs adhesive to the correct locations and prevents it from reaching sensitive reflective areas, thereby preventing distortion.
3Shape
If free-form surfaces are used for bonding to achieve glasses-like appearance, then the aesthetic form is improved, but the bonding workability deteriorates
Solution Approach 1:
The patent maintains the overall free-form shape for aesthetic purposes while introducing localized hydrophilic and hydrophobic regions on the bonding surfaces. These local surface property variations do not alter the external appearance but provide internal guidance for adhesive flow. The free-form geometry is preserved for glasses-like appearance, while the local surface energy differentiation enables manageable bonding workability by controlling adhesive behavior on the complex surface.
Solution Approach 2:
The patent pre-treats the free-form bonding surfaces by creating patterns of hydrophilic and hydrophobic regions before the bonding operation. This preliminary surface preparation converts the complex free-form geometry into a manageable bonding interface by establishing predetermined adhesive flow paths. The free-form shape is maintained for aesthetics, while the pre-established surface energy patterns enable reliable adhesive filling and positioning, improving bonding workability without compromising appearance.
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
This method enhances manufacturing workability, maintains high optical accuracy, and ensures an excellent appearance by allowing for precise control of adhesive flow and alignment, even on free-form surfaces, thereby improving the bonding process and reducing distortions.
Implementation Method 1
a light guide prism that includes a mirror layer which performs reflection of image light propagated inward on a first bonding surface
Data Source
AI summary
During the manufacturing of the light guide device (20), the first and second bonding ribs (R1,R2) are used such that the light guide prism (10) and the opposing prism (50) are connected with each other from a specific offset direction. In this case, a difference between sizes of clearances between the first bonding surface (AS) and the second bonding surface (BS) caused by a difference in inclination angles of the offset direction with respect to the first bonding surface is used such that a flow direction of the adhesive is controlled and filling is performed in a desire state, and thus high accuracy of the joint formed by the adhesive is maintained.