Display Device Spacer Height Segmentation for Mask Contact
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Solution Overview
Problem
The existing manufacturing processes for OLED and QLED display devices face challenges in performing precise automated optical inspection (AOI) due to the contact between evaporation masks and spacers, leading to false defect detection and potential yield reduction from foreign substance transfer.
Innovation Solution
A display device design featuring a substrate with a thin-film transistor layer, subpixels, and spacers arranged in a specific pattern where first spacers with identical heights are placed at a constant pitch, and n-1 second spacers with smaller heights are interposed, allowing the evaporation mask to contact only the first spacers, thereby preventing foreign substance transfer and enabling precise AOI without yield reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If spacers are used to maintain distance between substrate and evaporation mask, then manufacturing precision is improved, but reliability deteriorates due to contact between evaporation mask and spacers causing breakage and foreign substance generation
Solution Approach 1:
The patent divides the spacer structure into two distinct types: first spacers with greater height positioned in the frame region, and second spacers with smaller height positioned in the display region. This segmentation allows the evaporation mask to contact only the taller first spacers during manufacturing, preventing contact with and damage to the shorter second spacers that support the light-emitting elements, thereby resolving the contradiction between maintaining precise distance control and preventing spacer breakage that reduces yield.
Solution Approach 2:
The patent applies local quality by assigning different heights to spacers based on their functional location. First spacers in the frame region have greater height to serve as primary contact points for the evaporation mask, while second spacers in the display region have smaller height to avoid contact. This localized differentiation enables the system to achieve both precise distance maintenance and protection against contact-induced damage in critical areas.
2Manufacturing precision
If first photo-spacers are made relatively high to maintain distance in display region, then manufacturing precision is improved, but measurement precision deteriorates due to false defect detection by automated optical inspection
Solution Approach 1:
The patent segments the spacer arrangement into frame region spacers and display region spacers with different heights. By placing taller first spacers only in the frame region and shorter second spacers in the display region, the system enables automated optical inspection to correctly identify the absence of tall spacers in the display region as normal rather than defective, eliminating false defect detection while maintaining precise distance control through the shorter second spacers.
Solution Approach 2:
The first spacers in the frame region act as intermediaries that absorb the evaporation mask contact, serving as sacrificial elements that protect the second spacers in the display region. This intermediary arrangement allows the display region spacers to maintain their smaller, inspection-friendly height while still achieving the required distance maintenance function through the protective first spacers.
Data Source
AI summary
A display device includes the following: a plurality of first spacers provided at a first pitch that is constant, in a given direction in the display region except where light-emitting elements are provided, the plurality of first spacers having heights that are identical; and n−1 second spacers provided between two of the plurality of first spacers adjacent to each other in the given direction, except where the light-emitting elements are provided, the n−1 second spacers having heights that are smaller than the heights of the plurality of first spacers, where n is a natural number equal to or greater than two. The pitch in the given direction of all spacers including the plurality of first spacers and the n−1 second spacers is a second pitch that is constant, and that is the first pitch divided into n equal parts.