Flat Panel Display Substrate Bending Compensation
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Solution Overview
Problem
Flat panel display devices using the active matrix method face issues with bending and reduced reliability due to differences in thermal expansion coefficients between substrates during the sealing process, leading to yield deterioration and increased manufacturing costs.
Innovation Solution
The use of insulating films with specific thermal expansion coefficients on the substrates to compensate for the thermal expansion differences between the non-alkali glass first substrate and soda lime or borosilicate glass second substrate, employing ultraviolet curing sealants and heat treatment to seal the light emitting unit, thereby preventing bending and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-alkali glass is used as the first substrate to protect thin film transistors from alkali ion diffusion, then transistor reliability is improved, but manufacturing cost increases
Solution Approach 1:
The substrate system is segmented into two distinct substrates with different material properties: the first substrate uses non-alkali glass for transistor protection, while the second substrate uses soda lime glass for cost-effective sealing, with each substrate optimized for its specific function
Solution Approach 2:
Different regions of the device structure are assigned different material qualities: the first substrate region requires non-alkali glass for electrical stability, while the second substrate region can use soda lime glass for sealing, allowing cost optimization without compromising transistor performance
2Ease of manufacture
If soda lime glass is used as the second substrate to reduce manufacturing cost, then manufacturing cost decreases, but substrate bending occurs due to thermal expansion differences
Solution Approach 1:
The thermal expansion parameters of the substrate system are balanced by selecting specific glass compositions for each substrate, ensuring that the first and second substrates have compatible thermal expansion coefficients to prevent bending during heat treatment
Solution Approach 2:
The substrate system uses a composite structure of two different glass materials (non-alkali glass and soda lime glass) with carefully selected thermal properties, creating a balanced assembly that resists thermal deformation while maintaining cost effectiveness
3Reliability
If heat treatment is applied to cure the ultraviolet curing sealant, then sealing reliability is improved, but substrate bending is caused by thermal expansion differences
Solution Approach 1:
The thermal expansion parameters of the substrate assembly are optimized by selecting glass materials with matched coefficients, allowing the system to withstand heat treatment temperatures without excessive thermal stress or bending
Solution Approach 2:
The substrate material selection is designed in advance to compensate for thermal expansion differences, creating a pre-balanced system that resists bending during the heat treatment process
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 implementation of insulating films with controlled thermal expansion coefficients effectively mitigates substrate bending, improves yield, and enhances the reliability of flat panel display devices by maintaining structural integrity during heat treatment processes.
Implementation Method 1
In order to cure the sealant, the sealant is subject to irradiation of ultraviolet rays
Implementation Method 2
is heat-treated for about one hour at a temperature of about 230° C.
Implementation Method 3
The heat treatment causes a thermal expansion of the sealed first substrate and second substrate. Because the first substrate and the second substrate are of materials different from each other, there is a drawback in that the sealed first substrate and second substrate are bent in one direction
Data Source
AI summary
Provided is a flat panel display device and a method for fabricating the same. The flat panel display device comprises a first substrate, a light emitting unit, a second substrate, and insulating films. The light emitting unit comprises thin film transistors positioned on the first substrate, a first electrode electrically connecting with the thin film transistors, a second electrode facing the first electrode, and an emission layer or a liquid crystal layer interposed between the first and second electrodes. The second substrate is sealed with the first substrate by an ultraviolet curing sealant, and has a greater thermal expansion coefficient than the first substrate. The insulating films are positioned on one or more surfaces of the first and/or second substrates.