Optical Device Using Circular Polarization Separation for OLED Efficiency
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Solution Overview
Problem
Conventional organic electroluminescence (OLED) display devices suffer from low light use efficiency due to the absorption of light by antireflection films, which also fail to effectively prevent external light reflection, especially in bright environments.
Innovation Solution
An optical device comprising an organic electroluminescent substrate with a metallic reflecting portion, a circularly polarized light-separating layer with a liquid crystal alignment pattern, a patterned retardation layer, and a polarizer, which separates light into circularly polarized components and converts them into linearly polarized light, improving light utilization efficiency while preventing external light reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an antireflection film consisting of a polarizer and a λ/4 plate is provided on the organic EL display device, then external light reflection is prevented and contrast is improved, but light emitted from the organic EL element is absorbed and light use efficiency deteriorates
Solution Approach 1:
The invention divides the antireflection function into separate wavelength-specific components. A first antireflection film with first refractive index targets a first wavelength range, while a second antireflection film with second refractive index targets a second wavelength range. This segmentation allows each film to optimize for its specific wavelength without compromising overall light efficiency, resolving the contradiction between reflection prevention and light use efficiency.
Solution Approach 2:
The invention applies different refractive indices to different wavelength ranges rather than using a uniform antireflection coating. The first antireflection film has a first refractive index optimized for a first wavelength range, while the second antireflection film has a second refractive index optimized for a second wavelength range. This local optimization ensures high light use efficiency across the entire spectrum while maintaining effective reflection prevention.
2Object-affected harmful factors
If a conventional antireflection film is used, then external light reflection is reduced, but the device cannot fully demonstrate the performance of the organic EL element due to low light use efficiency
Solution Approach 1:
The broadband antireflection effect is achieved by segmenting the spectrum into multiple wavelength ranges, each handled by a dedicated antireflection film with optimized refractive index. This prevents the need to compromise between different wavelength requirements, maximizing overall light use efficiency while maintaining low surface reflectance across the entire visible spectrum.
Solution Approach 2:
The invention uses a composite structure with multiple antireflection films having different refractive indices. The first antireflection film with first refractive index and the second antireflection film with second refractive index work together as a composite system to achieve broadband antireflection performance, allowing the device to fully demonstrate organic EL element performance across all visible wavelengths.
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 enhances light use efficiency and maintains high contrast by effectively separating and directing light emitted from the OLED substrate, reducing external light reflection and improving the overall performance of OLED display devices.
Implementation Method 1
a circularly polarized light-separating layer that is formed of a composition including a liquid crystal compound, has a liquid crystal alignment pattern in which a direction of an optical axis derived from the liquid crystal compound changes while continuously rotating in at least one direction in a plane, and separates light emitted from the light emitting portions of the organic electroluminescent substrate into right-handed circularly polarized light and left-handed circularly polarized light
Implementation Method 2
a patterned retardation layer that converts the circularly polarized light separated by the circularly polarized light-separating layer into linearly polarized light, has constant in-plane retardation, and includes a plurality of regions among which a direction of a slow axis varies in the same plane
Implementation Method 3
an organic electroluminescent substrate having light emitting portions by organic electroluminescence and a non-light emitting portion which has a metallic reflecting portion
Data Source
AI summary
An object of the present invention is to provide an optical device that can accomplish both the effect of preventing external light reflection and the improvement of utilization efficiency of light emitted from an organic electroluminescent element. The object is achieved by an optical device having an organic electroluminescent substrate, a circularly polarized light-separating layer that has a liquid crystal alignment pattern, in which the direction of an optical axis derived from a liquid crystal compound changes while continuously rotating in one direction in a plane, and separates light into right-handed circularly polarized light and left-handed circularly polarized light, a patterned retardation layer that converts circularly polarized light into linearly polarized light and has a plurality of regions among which the direction of a slow axis varies in the same plane, and a polarizer.