Optical Element Mold Structure for Low-Directionality Diffraction
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Solution Overview
Problem
Optical elements produced using existing molds exhibit high directionality of diffracted light, leading to color shifting and anisotropic optical effects, making it difficult to achieve uniform light emission in light-emitting devices like organic EL devices.
Innovation Solution
A mold with a recessing and protruding layer having a random arrangement of conical protrusions, formed using a base material like stainless steel and materials such as Ti, Cr, and W, which allows for adjustable pitch and reduced directionality of diffracted light through precise control of modal pitch and height, and randomization of area and crystal orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a grating structure with fine recesses and protrusions is used in the mold, then light extraction efficiency is improved, but directionality of diffracted light increases causing color shifting and anisotropic optical effects
Solution Approach 1:
The patent applies asymmetry by randomizing the arrangement of recesses and protrusions in the grating structure. Instead of a regular periodic pattern, the positions are randomly distributed while maintaining controlled pitch and density. This randomization eliminates the directional preference inherent in periodic gratings, thereby reducing color shifting and anisotropic effects while preserving light extraction enhancement.
Solution Approach 2:
The patent implements local quality by allowing different regions of the grating structure to have varying local characteristics such as different pitch values, depths, and densities of recesses and protrusions. This local variation ensures that no single directional pattern dominates, thereby reducing overall directionality of diffracted light while maintaining effective light extraction across different areas of the optical element.
2Ease of operation
If the pitch of recesses and protrusions is reduced to decrease directionality, then color shifting is reduced, but it becomes difficult to achieve targeted optical functions
Solution Approach 1:
The patent employs parameter changes by independently controlling multiple parameters of the grating structure including pitch, depth, density, and size of recesses and protrusions. By adjusting these parameters within optimized ranges, the patent achieves both reduced directionality (through appropriate pitch and randomization) and targeted optical functions (through depth and density control), thereby resolving the contradiction between uniformity and adaptability.
3Ease of operation
If a random arrangement of recesses and protrusions is used, then directionality of diffracted light is reduced, but the pitch cannot be adjusted to achieve targeted optical functions
Solution Approach 1:
The patent combines randomization with local quality control by allowing the pitch to vary within a controlled range across different regions rather than being completely uniform or completely random. This approach maintains the benefits of randomization for reducing directionality while ensuring that pitch values remain within optimized ranges to achieve targeted optical functions, thereby resolving the contradiction between directionality reduction and pitch control.
Data Source
Figure 1~2
Figure 3
Figure 4~5B
AI summary
A mold for manufacturing an optical element is provided with a base material, and a recessing and protruding layer formed on a surface of the base material. The recessing and protruding structure of the recessing and protruding layer having a plurality of areas continuously arranged in a positional relationship in which the central point of seven adjacent protrusions is an intersection point of diagonal lines of six vertices of a regular hexagon, and the areas, shapes, and crystal orientations of the plurality of areas are random.