Touch Electrodes on Black Matrix Side Surfaces for Light Extraction
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Solution Overview
Problem
Electroluminescent display devices suffer from low light extraction efficiency due to light being trapped inside the device, leading to reduced luminous efficiency and visibility issues caused by light absorption and reflection.
Innovation Solution
A display device design featuring a substrate with sub-pixels, an encapsulation unit, a black matrix with open areas corresponding to sub-pixel emission areas, and touch electrodes on the black matrix's surface to enhance light extraction and minimize external light reflection, while also enabling touch functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If light emitting layer emits light in all directions, then light output is maximized, but light is trapped inside the device and extraction efficiency decreases
Solution Approach 1:
The patent introduces a micro-lens array structure that redirects light from the light emitting layer. The micro-lenses refract light that would otherwise travel at oblique angles and trap it within the device, redirecting it toward the viewing direction. This dimensional redirection of light paths resolves the contradiction between maximizing light output and improving extraction efficiency.
Solution Approach 2:
The patent introduces an intermediary optical element (micro-lens array or reflective layer) between the light emitting layer and the external environment. This intermediary structure modifies the light propagation paths, enabling light that would be trapped to escape efficiently, thus resolving the energy loss issue while maintaining high light output.
2Measurement precision
If black matrix is used to block light between sub-pixels, then color purity is improved, but light from light emitting layer is absorbed and luminous efficiency decreases
Solution Approach 1:
The patent applies a reflective layer to the back surface of the black matrix structure. Light that would be absorbed by the black matrix is instead reflected back toward the light emitting layer and redirected by the micro-lens array toward the viewing direction. This converts the harmful light absorption into a beneficial light redirection mechanism, maintaining color purity while improving luminous efficiency.
Solution Approach 2:
The patent creates different optical properties in different regions: the black matrix maintains its light-blocking function in the horizontal direction to ensure color purity, while the reflective layer on its back surface provides light redirection in the vertical direction to improve luminous efficiency. This local differentiation of optical properties resolves the contradiction.
3Ease of operation
If conventional touch electrodes are placed on top of color filters, then touch function is achieved, but light extraction efficiency and luminance viewing angle are reduced
Solution Approach 1:
The patent relocates touch electrodes from the conventional top surface position to the side surface of the pixel structure. This dimensional relocation allows light emitted from the light emitting layer to pass through the color filter and exit without being blocked or reflected by the touch electrode, thereby maintaining wide viewing angles and high luminance while still providing touch functionality.
Solution Approach 2:
The patent uses the side surface of the pixel structure as an alternative location for the touch electrode, effectively creating a copy of the touch sensing function in a different spatial location. This side-surface touch electrode configuration does not interfere with the optical path, resolving the contradiction between touch functionality and optical performance.
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
Improves luminous efficiency and visibility by reducing light absorption and reflection, and allows for touch functionality by strategically placing touch electrodes on the black matrix and using color filters for antireflection.
Implementation Method 1
a micro-lens disposed in each of the plurality of unit areas of the substrate; and a reflective layer disposed on a lower surface of the black matrix, wherein the micro-lens redirects light incident on the micro-lens
Implementation Method 2
a reflective layer disposed on a lower surface of the black matrix
Implementation Method 3
a color filter disposed on the light emitting layer and having a transmission main wavelength range corresponding to an emission main wavelength range of the light emitting layer
Data Source
AI summary
A display device according includes a substrate divided into a plurality of unit areas; a plurality of sub-pixels disposed in each of the plurality of unit areas of the substrate; an encapsulation unit disposed on the plurality of sub-pixels; a black matrix disposed on the encapsulation unit and having an open area corresponding to an emission area of each of the plurality of sub-pixels; and at least one touch electrode disposed on an upper surface and a side surface of the black matrix, thereby performing a touch function and improving light extraction efficiency.