Thin Film Encapsulation Thermal Expansion Mismatch
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Solution Overview
Problem
The existing display screens face issues with the poor stability of atomic layer deposition films due to excessive thermal expansion coefficient differences, leading to peeling and disintegration phenomena, which compromises the reliability and yield of the encapsulation.
Innovation Solution
A thin film encapsulation structure is introduced, featuring a first encapsulation film with a thermal expansion coefficient between the film layer on the display unit and the atomic layer deposition film, improving interfacial properties and stability by using a silicon nitride or silicon oxynitride film with specific thickness and stress ranges, and optionally including additional inorganic and organic layers for enhanced protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If atomic layer deposition film is directly deposited on the display unit, then the encapsulation structure can be simplified, but the film stability deteriorates due to excessive thermal expansion coefficient differences causing peeling and disintegration
Solution Approach 1:
The patent introduces a buffer film as an intermediary layer between the display unit and the atomic layer deposition film. This buffer film has a thermal expansion coefficient that is intermediate between those of the display unit and the ALD film, serving as a thermal expansion coefficient transition layer that reduces the abrupt difference and prevents peeling and disintegration of the encapsulation structure
Solution Approach 2:
The patent changes the thermal expansion coefficient parameter by introducing a buffer film with specific thermal expansion properties. The buffer film's thermal expansion coefficient is designed to be between that of the display unit and the ALD film, creating a gradual transition that resolves the thermal expansion mismatch problem
2Reliability
If buffer film with intermediate thermal expansion coefficient is introduced, then film stability is improved, but device complexity increases
Solution Approach 1:
The encapsulation structure is segmented into multiple functional layers: the display unit, the buffer film with intermediate thermal expansion coefficient, and the atomic layer deposition film. This segmentation allows each layer to perform its specific function - the buffer film handles thermal expansion mismatch while the ALD film provides encapsulation, resolving the contradiction between stability and complexity
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 configuration significantly enhances the stability and reliability of the atomic layer deposition film, preventing peeling and disintegration, and improves the overall encapsulation yield by more than 20%, while effectively blocking moisture and oxygen penetration.
Implementation Method 1
a thermal expansion coefficient of the first encapsulation film is between a thermal expansion coefficient of a film layer immediately adjacent to the first encapsulation film on the display unit and a thermal expansion coefficient of the first atomic layer deposition film
Implementation Method 2
the atomic layer deposition (ALD) technology is considered to be a promising encapsulation technology due to its excellent three-dimensional shape retention self-limiting growth mode
Data Source
AI summary
The present application relates to a display screen and a display device. The display screen includes: a substrate; a display device disposed on the substrate, the display device including several film layers; and a thin film encapsulation structure disposed on a side of the display device away from the substrate, the thin film encapsulation structure including a first encapsulation film disposed on the display device, and a first atomic layer deposition film disposed on the first encapsulation film; wherein a thermal expansion coefficient of the first encapsulation film is between a thermal expansion coefficient of the film layer immediately adjacent to the first encapsulation film on the display unit and a thermal expansion coefficient of the first atomic layer deposition film.