Pixel Separation Layer Colorant for Organic EL Displays
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Solution Overview
Problem
Organic EL displays face challenges in achieving high light emission luminance and reliability due to the partial blocking of light by polarizing films and the adverse effects of colorants in photosensitive compositions, which also lead to increased voltage driving and reduced pattern processability.
Innovation Solution
The display device incorporates a pixel separation layer with a colorant (D-DL) that has an optical density of 0.5 to 3.0 in the visible light wavelength range, and satisfies specific ion detection intensity ratios measured by time-of-flight secondary ion mass spectrometry. This configuration enhances light blocking efficiency and surface modification, allowing for low voltage driving and high reliability of light emitting elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a polarizing film is disposed on the light extraction side to block external light, then external light reflection is suppressed, but light emission luminance from the light emitting element decreases
Solution Approach 1:
The patent extracts the light-blocking function from a separate polarizing film and integrates it into the pixel separation layer by incorporating colorants directly into the photosensitive composition. This eliminates the need for a dedicated polarizing film that would block light emission, while achieving the same external light reflection suppression through the colorant-containing pixel separation layer.
Solution Approach 2:
The patent merges multiple functions into the pixel separation layer: it simultaneously provides pixel definition, external light blocking, and maintains light emission transparency. By combining the light-blocking function with the pixel separation function in a single layer, the design avoids the trade-off between external light reflection suppression and light emission luminance.
2Object-affected harmful factors
If a colorant is included in the photosensitive composition to suppress external light reflection, then external light blocking efficiency is enhanced, but ultraviolet light is blocked during light exposure causing deteriorated pattern processability and development residues
Solution Approach 1:
The patent applies local quality by using a specific type of colorant (non-ultraviolet absorbing colorant) that selectively blocks visible light for external light reflection suppression while allowing ultraviolet light to pass through for photolithography processing. This localized property selection resolves the conflict between external light blocking and pattern processability.
Solution Approach 2:
The patent changes the optical absorption parameters of the colorant to specifically target visible light wavelengths while maintaining transparency in the ultraviolet range. This parameter modification enables the colorant to block external visible light reflection without interfering with ultraviolet-based photolithography and development processes.
3Object-affected harmful factors
If a colorant is included in the photosensitive composition to suppress external light reflection, then external light blocking is improved, but development residues occur leading to higher voltage driving and reduced reliability of light emitting elements
Solution Approach 1:
The patent changes the chemical and optical parameters of the colorant to ensure it is non-ultraviolet absorbing and has high development solubility. These parameter changes prevent development residues from forming, thereby maintaining low operating voltage and ensuring the reliability of the light emitting elements while still achieving external light reflection suppression.
Solution Approach 2:
The patent uses a colorant that is fully soluble in the developer solution, allowing complete removal during the development process. This ensures no permanent residues remain that could cause reliability issues, effectively making the colorant a temporary component that serves its light-blocking function during manufacturing but is then completely removed.
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 proposed solution achieves excellent light emission characteristics that enable low voltage driving and ensures high reliability of the light emitting elements, thereby realizing a desired current density in organic EL displays.
Implementation Method 1
the pixel separation layer contains a colorant (D-DL) and has an optical density of 0.5 to 3.0 in the visible light wavelength range
Implementation Method 2
a photosensitive composition including an alkali soluble resin (A), a photosensitizer (C), and a colorant (D)
Data Source
AI summary
The main object of the present invention is to provide an organic EL display that has excellent light emission characteristics to enable low voltage driving and has light emitting elements with high reliability, thereby serving to realize a desired current density. Provided is a display device including a substrate, a first electrode, a second electrode, a pixel separation layer, and an organic layer containing a light emitting layer, wherein the pixel separation layer contains a colorant (D-DL), has an optical density of 0.5 to 3.0 in the visible light wavelength range per μm of the thickness of the pixel separation layer, and has a plurality of pixel parts in a plan view. The detection intensity of the sulfur ion (S−), the detection intensity of the chlorine ion (Cl−), the detection intensity of the bromine ion (Br−), and the sum of the detection intensity of the chlorine ion (Cl−) and the detection intensity of the bromine ion (Br−), all measured by time-of-flight secondary ion mass spectrometry at a position 3 nm deep in each pixel part from the surface of the first electrode, the surface being in contact with the organic layer containing a light emitting layer, satisfy relationships represented by specific general formulas.