OLED Pixel Isolation Layout for Uniform EL Layer Patterning
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Solution Overview
Problem
The manufacturing of high-resolution display apparatuses with organic EL devices faces challenges in achieving uniform thickness of island-shaped light-emitting layers due to low dimensional accuracy of metal masks and high manufacturing costs associated with photolithography methods.
Innovation Solution
A method involving the formation of pixel electrodes, insulating layers, and counter electrodes using metal masks, followed by processing with resist masks to achieve uniform thickness and reduce the need for multiple photolithography steps, thereby lowering costs and improving dimensional accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a vacuum evaporation method using a metal mask is used to form island-shaped light-emitting layers, then the manufacturing process is simplified, but the thickness of the light-emitting layer becomes non-uniform due to mask blurring and deformation
Solution Approach 1:
The patent applies preliminary action by forming a planarization layer before depositing the light-emitting layer. This planarization layer compensates for surface irregularities and mask blurring in advance, ensuring uniform thickness of the light-emitting layer even when using a metal mask for vapor deposition. The planarization layer is formed to cover the pixel electrodes and provide a flat surface for subsequent layer deposition.
2Manufacturing precision
If a photolithography method is used to process light-emitting layers into island shape, then thickness uniformity is maintained, but manufacturing cost increases due to multiple photomasks
Solution Approach 1:
The patent merges the functions of multiple photomasks into a single metal mask structure. Instead of using separate photomasks for each color layer (red, green, blue), the invention uses one metal mask with multiple openings that defines all light-emitting layer patterns simultaneously. This is achieved by forming a planarization layer that enables single-step patterning, combining what would otherwise require three separate photolithography processes into one operation, thereby reducing photomask costs while maintaining thickness uniformity.
3Ease of manufacture
If metal masks are used for film deposition to form island-shaped layers, then the process is simpler, but dimensional accuracy decreases due to heat deformation and mask blurring
Solution Approach 1:
The patent introduces a planarization layer as an intermediary between the pixel electrodes and the light-emitting layer. This intermediary layer serves multiple functions: it compensates for mask blurring by providing a flat deposition surface, maintains dimensional accuracy by preventing heat-induced deformation from affecting the light-emitting layer, and enables the use of simpler metal masks without sacrificing precision. The planarization layer acts as a buffer that isolates the light-emitting layer from the dimensional inaccuracies of the metal mask.
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 method enables the production of high-resolution, high-definition display apparatuses with uniform light-emitting layers, reducing manufacturing costs and enhancing reliability while maintaining high precision.
Implementation Method 1
an island-shaped light-emitting layer can be formed by a vacuum evaporation method using a metal mask (also referred to as a shadow mask)
Implementation Method 2
exposing part of the insulating layer by removing at least part of a region overlapping the insulating layer of at least one of the first layer, the second layer, the first counter electrode, and the second counter electrode using the resist mask
Data Source
AI summary
A high-resolution, high-definition, or large display apparatus is provided. A metal mask is placed over an EL layer and film deposition is performed with the metal mask, whereby an island-shaped counter electrode is formed. Then, the EL layer is processed using the counter electrode as a hard mask. Alternatively, after an EL layer and a counter electrode are formed over an entire surface, processing using a metal mask is performed. An insulating layer that electrically insulates adjacent pixel electrodes from each other is positioned between adjacent light-emitting devices. A resist mask is formed over the insulating layer. A plurality of EL layers and a plurality of counter electrodes overlapping each other over the insulating layer are partly removed using the resist mask, whereby part of the insulating layer is exposed. Thus, the adjacent light-emitting devices are electrically insulated from each other over the insulating layer.