Top-Emission EL Display Color Selection Reflection Layer
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Solution Overview
Problem
High-definition or downsized electroluminescence (EL) display devices face challenges in achieving sufficient brightness and preventing color mixture due to the design of existing bottom and top emission type color-filter EL display devices, where the aperture ratio of pixels is low and light emission from the white organic EL layer can enter adjacent pixels, causing color contamination.
Innovation Solution
The proposed EL display device incorporates a color selection reflection layer with a dichroic mirror layer, a light absorbing layer, and a partial reflection film, along with pixel separation films and upper color filters, to enhance light extraction and prevent color mixture, while maintaining high brightness and contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a bottom emission type structure is used, then the device structure is simple, but the aperture ratio of pixels is reduced and sufficient brightness cannot be obtained
Solution Approach 1:
The patent inverts the light extraction direction from bottom emission to top emission. The EL layer is positioned above the TFT circuit layer, and light is extracted through the top surface through color filters and reflection layers, allowing circuit elements to be below the light path and enabling higher aperture ratios while maintaining structural simplicity
Solution Approach 2:
The patent introduces a vertical layering arrangement where the TFT circuit layer is positioned at the bottom, followed by the EL layer, color filters, and reflection layers above. This three-dimensional arrangement separates the circuit elements from the light extraction path, allowing both high aperture ratio and simple structure to coexist
2Illumination intensity
If a top emission type structure is used, then the aperture ratio can be increased, but light emission enters adjacent pixels causing color mixture
Solution Approach 1:
The patent divides the light management function into separate components: color filters that selectively transmit specific wavelengths and reflection layers that reflect light back through the color filters. This segmentation ensures that light from one pixel cannot enter adjacent pixels, preventing color mixture while maintaining high aperture ratios
Solution Approach 2:
The patent introduces reflection layers as intermediary elements between the EL layer and the external environment. These reflection layers bounce light back through the color filters, ensuring that only the intended pixel's light reaches the viewer and preventing cross-contamination between adjacent pixels
3Manufacturing precision
If pixels are made fine for high-definition display, then the resolution is improved, but the aperture ratio decreases and brightness is reduced
Solution Approach 1:
By inverting to top emission and positioning color filters above the EL layer, the patent enables more efficient light extraction from the front surface. This allows finer pixels to maintain adequate brightness because the light path is optimized and does not require passing through multiple layers from the back surface
4Length of moving object
If color filters are made thinner to reduce pixel size, then the pixel dimension is reduced, but light emission propagates through spaces and enters adjacent pixels
Solution Approach 1:
The patent introduces reflection layers as intermediary elements between adjacent pixel regions. These reflection layers are positioned to reflect light back through the color filters, creating a barrier that prevents light from one pixel from entering adjacent pixels, even when color filters are thin
Solution Approach 2:
The patent segments the light management function between color filters and reflection layers. The color filters provide wavelength selectivity while the reflection layers provide spatial confinement, allowing thin color filters to be used without causing color mixture between adjacent pixels
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 solution effectively increases the brightness and contrast of the EL display device, improves color purity, and reduces the risk of color mixture, even in fine-pixel designs, by optimizing light reflection and transmission through the use of a dichroic mirror layer and partial reflection film, and simplifies the manufacturing process by allowing for thinner color filters.
Implementation Method 1
a color selection reflection layer with a dichroic mirror layer
Implementation Method 2
the EL display device extracts light emission produced in the white organic EL layer from the insulating substrate side
Implementation Method 3
light emission produced in the white organic EL layer
Data Source
AI summary
There is provided an EL display device of a color filter system which obtains sufficient brightness and contrast while making it difficult to generate a color mixture even if pixels become fine. An EL display device 100 according to the present invention includes a first substrate 1, a circuit layer 2 formed on the first substrate 1, a color selection reflection layer 11 formed in an upper layer of the circuit layer 2, lower electrodes 5 formed in an upper layer of the color selection reflection layer 11, a white light emission EL layer 7 formed in an upper layer of the lower electrodes 5, an upper electrode 8 formed in an upper layer of the EL layer 7, and a sealing layer 9 formed in an upper layer of the upper electrode 8.