Micro-LED Display Black Matrix Formation via Transfer Printing
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Solution Overview
Problem
The existing methods for manufacturing micro-LED display modules face challenges in forming a black matrix layer, leading to reduced contrast ratio and light emitting efficiency due to alignment tolerances and the risk of the black matrix covering the light-emitting surface of micro-LEDs.
Innovation Solution
A method involving the formation of a black matrix layer on a display module by attaching a black matrix formation layer to a film, transferring it onto the micro-LEDs and the adhesive layer, and removing the excess using a tape with a weaker adhesive force, ensuring the layer remains between the LEDs without covering them, thus enhancing the black color expressiveness and contrast ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a black matrix layer is formed through printing or exposure/development, then the black matrix can be formed in non-emitting areas, but alignment tolerances cause BM opening areas that reduce contrast ratio and expressiveness
Solution Approach 1:
The patent applies preliminary action by pre-forming the black matrix layer on the substrate before transferring the micro-LEDs. This ensures that the black matrix is already in position before the LEDs are placed, eliminating alignment issues during the LED transfer process. The black matrix opening areas are pre-defined, and the LEDs are subsequently transferred to align with these openings, ensuring precise positioning without requiring high alignment precision during the critical LED placement step.
2Ease of manufacture
If printing or exposure/development is used to form the black matrix, then the black matrix can be formed, but BM opening areas expose substrate parts that reduce contrast ratio
Solution Approach 1:
The patent applies the taking out principle by completely removing the black matrix material from the LED emission areas to create clean, precise openings. The black matrix layer is formed across the entire substrate and then selectively removed only in the regions where LEDs will be placed and where light should pass through. This extraction approach ensures that no residual black matrix material remains in the emission areas, maximizing the contrast ratio by preventing any light absorption or reflection from the substrate in the non-emitting areas.
3Ease of manufacture
If the black matrix is formed with alignment tolerances, then the formation process is simpler, but the black matrix may cover micro-LED light emitting surfaces reducing light emitting efficiency
Solution Approach 1:
The patent applies preliminary action by pre-forming the black matrix layer with precise opening areas before transferring the micro-LEDs. The openings are pre-defined with exact dimensions and positions, and the LEDs are subsequently transferred to align with these pre-formed openings. This approach eliminates the risk of the black matrix covering the LED emission surfaces, as the openings are already in place to receive the LEDs. The process maintains simplicity while ensuring high light emitting efficiency by preventing any black matrix material from covering the active emission areas.
4Illumination intensity
If the black matrix layer is formed to maximize coverage, then the black color expressiveness is improved, but alignment tolerances create BM opening areas that reduce coverage
Solution Approach 1:
The patent applies segmentation by dividing the black matrix layer into distinct regions: covered regions over the substrate for maximum black color expressiveness, and precise opening areas where LEDs will be placed. The black matrix is segmented to cover all non-emitting areas completely, maximizing the black color expressiveness and contrast ratio. The openings are precisely defined and segmented from the covered regions, ensuring that the black matrix provides maximum coverage wherever needed while maintaining clean, precise openings for LED placement.
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 approach simplifies the manufacturing process, minimizes the formation of BM opening areas, maximizes the black matrix coverage, and improves the contrast ratio and light emitting efficiency by preventing the black matrix from covering the micro-LEDs.
Implementation Method 1
The attaching includes attaching an anisotropic conductive film onto a portion of the adhesive layer, formed between the plurality of micro-LEDs, and onto the plurality of micro-LEDs
Implementation Method 2
the attaching further includes: melting bumps, the bumps applied on an electrode of each of the plurality of micro-LEDs or on the plurality of electrode pads, and electronically connecting each of the plurality of micro-LEDs to the plurality of electrode pads through the bumps
Data Source
Figure 1~2A
Figure 2B~3A
Figure 3B~4A
AI summary
A method of manufacturing a display module includes forming a driving circuit layer on a substrate, the driving circuit layer including a plurality of driving circuits and a plurality of electrode pads electronically connected with the plurality of driving circuits; forming an adhesive layer on the driving circuit layer; transferring each of a plurality of light emitting diodes (LEDs) onto a respective area of the adhesive layer corresponding to a respective one of the plurality of electrode pads; and forming a black matrix layer on the adhesive layer, between the plurality of LEDs.