Light Blocking Layer Openings for OLED Heat and Light Management
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Solution Overview
Problem
In organic light emitting displays, visibility failures and reduced contrast ratios occur due to light reflection and scattering from metal lines of thin film transistors, and existing light blocking layers absorb heat, causing defects and melting issues during processing.
Innovation Solution
A bottom emission-type organic light emitting display with a light blocking layer having openings over the semiconductor layer of thin film transistors, formed using chromium oxide, chromium nitride, or chromium layers, which prevents light leakage and reduces heat absorption, allowing for uniform crystallization of amorphous silicon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light blocking layer including metal having low reflectivity is formed to prevent light reflection and scattering, then visibility and contrast ratio are improved, but the light blocking layer absorbs heat easily causing defects and melting in subsequent processes
Solution Approach 1:
The light blocking layer is segmented by forming openings in specific regions (such as over the semiconductor layer) to divide the continuous metal layer into separate sections. This segmentation reduces the total heat absorption area while maintaining light blocking functionality in non-opening regions, thereby resolving the contradiction between visibility improvement and heat absorption reduction.
Solution Approach 2:
The light blocking layer is applied selectively in specific regions rather than uniformly across the entire substrate. By forming the layer only where light blocking is needed (e.g., in non-display regions or specific transistor areas) and leaving openings in other regions, the solution achieves local optimization of both light blocking performance and heat management.
2Reliability
If a continuous light blocking layer is formed to prevent light leakage, then light blocking performance is improved, but heat absorption increases causing substrate defects
Solution Approach 1:
The continuous light blocking layer is divided into separate segments by forming openings in strategic locations. This segmentation maintains light blocking effectiveness in the metal regions while creating heat dissipation pathways through the openings, thereby reducing heat-induced defects without compromising light blocking reliability.
Solution Approach 2:
Specific portions of the light blocking layer are extracted or removed to form openings. This extraction eliminates the harmful heat absorption function in those specific regions while preserving the light blocking function in the remaining metal regions, thus resolving the contradiction between light blocking performance and heat-induced defects.
3Ease of operation
If metal lines of thin film transistor are used to control the light emitting layer, then device functionality is achieved, but light reflection and scattering cause visibility failure
Solution Approach 1:
A light blocking layer is introduced as an intermediary element between the metal lines and the light emitting layer. This intermediary layer blocks light from reflecting off the metal lines while allowing the metal lines to continue controlling the light emitting layer electrically, thus resolving the contradiction between device functionality and visibility.
Solution Approach 2:
The light blocking layer is applied selectively in regions where light reflection from metal lines causes visibility problems (such as in the display region or near the light emitting layer), while leaving other regions open to maintain device functionality. This local application optimizes both visibility and operational 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
The solution effectively reduces visibility failures and substrate defects by preventing light leakage and heat absorption, enabling defect-free polycrystalline silicon formation and improving the operational stability of the display.
Implementation Method 1
the light may be reflected or scattered due to metal lines of the thin film transistor so that visibility failure may occur
Implementation Method 2
the light blocking layer including the metal having a low reflectivity prevents light from being reflected or scattered
Implementation Method 3
the light blocking layer easily absorbs heat due to the metal, so that the light blocking layer may cause defects because of heat in the subsequent processes
Implementation Method 4
the light blocking layer easily absorbs heat due to the metal
Implementation Method 5
The organic light emitting display includes a light blocking layer having an opening formed at a predetermined region of the light blocking layer
Implementation Method 6
The semiconductor layer includes a polycrystalline silicon layer
Data Source
AI summary
Disclosed is an organic light emitting display. In the organic light emitting display, a substrate is divided into a display region, in which an image is displayed, and a non-display region surrounding the display region. The organic light emitting display includes a plurality of pixels provided on the display region. At least one thin film transistor is formed on the non-display region. The display region includes a first electrode connected to the thin film transistor, an organic light emitting layer formed on the first electrode, and a second electrode formed on the organic light emitting layer to apply voltage to the organic light emitting layer with the first electrode. A light blocking layer having an opening formed below the semiconductor layer is formed on the non-display region.