UV Reflecting Layer for Flexible Display Laser Processing
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Solution Overview
Problem
Flexible display substrates are prone to damage during laser lift-off and laser annealing processes, leading to performance issues such as threshold voltage drift and carbonization of the flexible material layer.
Innovation Solution
A flexible display substrate with an ultraviolet reflecting layer made of alternately stacked transparent material layers, such as silicon nitride and silicon dioxide, is introduced between the flexible base and the display structure, which reflects ultraviolet light back and prevents it from irradiating onto the display structure during laser lift-off and annealing, while allowing visible light to pass through.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ultraviolet laser is used for laser lift-off to separate the flexible material layer from the glass base, then the flexible display substrate can be formed, but the display structure may be damaged due to laser irradiation
Solution Approach 1:
A protective layer is introduced as an intermediary between the flexible material layer and the display structure. This protective layer absorbs or reflects the ultraviolet laser energy during lift-off, preventing direct irradiation of the display structure while still allowing the flexible material layer to be separated from the glass base.
Solution Approach 2:
The protective layer is formed in advance before the display structure is created. This preliminary protective structure is already in place during the lift-off process, proactively preventing laser damage to the display structure before any irradiation can occur.
2Reliability
If ultraviolet laser is used for laser annealing to transform amorphous silicon into polycrystalline silicon, then the thin film transistor performance is improved, but the flexible material layer may be carbonized or separated from adjacent layers
Solution Approach 1:
The protective layer serves as a mediator during laser annealing, positioned between the laser source and the flexible material layer. It controls the transmission of laser energy, allowing sufficient energy to reach the amorphous silicon for crystallization while limiting the energy that would otherwise cause carbonization or delamination of the flexible material layer.
Solution Approach 2:
The protective layer modifies the laser energy parameters reaching the flexible material layer by adjusting transmission intensity and spectral distribution. This parameter control enables the annealing process to proceed effectively without exceeding the thermal tolerance of the flexible material layer.
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 solution effectively prevents damage to the display structure during laser processing, maintaining performance and enabling precise alignment without interfering with visual light transmission, thus enhancing the manufacturing process of flexible display substrates.
Implementation Method 1
an ultraviolet reflecting layer disposed on the flexible base and capable of reflecting ultraviolet light and transmitting visible light
Implementation Method 2
capable of reflecting ultraviolet light and transmitting visible light
Data Source
AI summary
The present invention provides a flexible display substrate, comprising a flexible base; an ultraviolet reflecting layer disposed on the flexible base and capable of reflecting ultraviolet light and transmitting visible light, comprising a stacked structure consisting of alternate first transparent material layers and second transparent material layers, wherein the numbers of the two kinds of transparent material layers are equal, and are at least two respectively, and the two kinds of transparent material layers also satisfy: 4nd=λ, wherein d is the thickness of any one of the transparent material layers, n is a refractive index of the transparent material layer and λ is the wavelength of ultraviolet light; and a display structure disposed above the ultraviolet reflecting layer. The present invention is applicable to flexible display substrates, particularly flexible array substrates comprising low-temperature polycrystalline silicon thin film transistors.