Optical Adhesive Layer Stray Light Reduction in Display Devices
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Solution Overview
Problem
Existing display devices with front light modules suffer from poor optical performance and limited full-angle visibility due to stray light generation when the light enters the touch panel, leading to reduced contrast and touch sensing experience, especially in reflective and transflective displays.
Innovation Solution
A display device configuration featuring a front light module with a light guide plate and an optical adhesive layer, where the optical adhesive layer is directly adhered between the touch panel and the light guide plate, with specific surface regions and protrusions to minimize light reflection and stray light generation, enhancing optical efficiency and contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an air layer is arranged between the front light module and the touch panel to expand the effective optical angle, then the light emission range is expanded and full-angle visibility is improved, but stray light is generated when light enters the touch panel, reducing optical performance and contrast
Solution Approach 1:
The patent removes the air layer from the structure and replaces it with an optical adhesive layer that has refractive index matching properties. This extraction of the harmful air layer eliminates the interface that causes stray light reflection, while the optical adhesive layer maintains the necessary optical coupling function.
Solution Approach 2:
The optical adhesive layer serves as an intermediary between the light guide plate and touch panel. With refractive index matching properties, it acts as an optical bridge that transmits light efficiently without creating the harmful reflection interfaces that would occur with air gaps, thus eliminating stray light while maintaining optical coupling.
2Object-generated harmful factors
If the surface of the optical adhesive layer is in direct contact with the light guide plate, then stray light is reduced and optical performance is improved, but the adhesive bonding strength may be insufficient
Solution Approach 1:
The patent applies different surface treatments to different regions of the optical adhesive layer. The first surface has a roughened texture to increase mechanical interlocking and bonding strength with the light guide plate, while the second surface remains smooth for optimal optical coupling with the touch panel. This local differentiation resolves the contradiction between bonding strength and optical performance.
Solution Approach 2:
The patent introduces a curved or roughened surface structure on the first surface of the optical adhesive layer. This curvature increase provides mechanical interlocking features that enhance bonding strength while the overall surface geometry maintains optical coupling efficiency by preventing air gap formation.
3Shape
If microstructures are disposed on the light guide plate surface facing the display to achieve Lambertian intensity distribution, then full-angle visibility is improved, but the light emission angle is limited and full-angle visibility remains poor for reflective displays
Solution Approach 1:
The patent changes the optical parameters of the system by introducing the optical adhesive layer with specific refractive index matching properties. This parameter change enables the light guide plate microstructures to achieve more effective light scattering and emission, improving full-angle visibility for reflective displays by optimizing the optical coupling conditions.
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 configuration effectively reduces stray light and improves optical performance and contrast, providing better full-angle visibility and touch sensing experience by preventing light reflection at the touch panel interface.
Implementation Method 1
a refractive index of the optical adhesive layer is less than a refractive index of the LGP
Implementation Method 2
The light emitted by the light source may travel in the LGP in a total internal reflection manner
Data Source
AI summary
A display device includes a touch panel, an optical adhesive layer, and a front light module that includes a light source and a light guide plate (LGP) including multiple microstructures recessed into the LGP from a first surface of the LGP to form voids. The optical adhesive layer is adhered between the touch panel and a first surface of the LGP. A surface of the optical adhesive layer facing the LGP is in contact with the first surface of the LGP in multiple first regions, and a surface of the optical adhesive layer facing the LGP and the plurality of microstructures being overlapped in multiple second regions. A maximum vertical distance between each void and the first surface is a first depth. A vertical distance between the first regions and the second regions is 0 to 0.7 times the first depth.