Photo-Aligned Optical Element Adhesion Gradient
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Solution Overview
Problem
Conventional optical elements with liquid crystal layers face issues of poor adhesion between the alignment film and the refractive index anisotropic layer, leading to peeling and alignment failures, especially in high temperature and humidity environments, and existing solutions either increase manufacturing costs or deteriorate optical characteristics.
Innovation Solution
An optical element comprising a transparent base material, an alignment property providing layer, and a refractive index anisotropic layer with a curing degree gradient, where the alignment film is formed using a photo-alignment method and the refractive index anisotropic layer is formed by curing a liquid crystalline composition with a polymerizable liquid crystal material, ensuring excellent adhesion and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional alignment film is used without rubbing treatment, then the alignment limiting force can be generated by photo-alignment method, but the adhesion between the alignment film and the refractive index anisotropic layer is poor
Solution Approach 1:
The patent changes the chemical composition parameters of the alignment film by incorporating a silane coupling agent and specific polymer materials (polyvinyl alcohol, gelatin, or polyimide) with controlled molecular weights. This chemical parameter modification enables both photo-alignment functionality and enhanced adhesion to the liquid crystal layer without requiring rubbing treatment.
Solution Approach 2:
The alignment film is constructed as a composite material system combining multiple components: polymer base material (polyvinyl alcohol, gelatin, or polyimide), silane coupling agent, and photo-alignment functional groups. This composite structure provides simultaneous adhesion enhancement and alignment limiting force generation.
2Reliability
If the adhesion between layers is improved by chemical modification, then the peeling problem is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent merges multiple functions into the alignment film layer: adhesion promotion, photo-alignment capability, and alignment limiting force generation are all integrated into a single layer through chemical modification, eliminating the need for separate adhesion promotion layers or additional processing steps.
Solution Approach 2:
The alignment film composition self-provides adhesion enhancement through the silane coupling agent and polymer material selection, without requiring external adhesion promotion treatments or additional manufacturing steps. The photo-alignment process itself serves dual purposes of creating alignment limiting force and verifying layer adhesion.
3Reliability
If rubbing treatment is applied to the alignment film, then the alignment limiting force is enhanced, but static electricity and dusts are generated on the surface
Solution Approach 1:
The patent replaces the mechanical rubbing treatment with a photo-alignment chemical process. Instead of mechanically rubbing the alignment film to generate alignment limiting force, ultraviolet light irradiation induces photochemical reactions that create the same alignment effect without mechanical contact, thereby eliminating static electricity and dust generation.
Solution Approach 2:
The patent extracts the alignment limiting force generation function from the mechanical rubbing process and relocates it to the photo-alignment chemical process. The harmful byproducts of mechanical rubbing (static electricity and dusts) are completely eliminated by using a chemical alternative.
4Adaptability or versatility
If the optical element is used in high temperature and high humidity environment, then the durability is tested, but mesh like wrinkles are generated in the refractive index anisotropic layer
Solution Approach 1:
The patent applies beforehand cushioning by incorporating silane coupling agents and specific polymer materials in the alignment film before the liquid crystal layer is formed. This pre-prepared adhesion enhancement structure prevents wrinkle formation when the optical element is later exposed to high temperature and humidity environments, cushioning against environmental stress before it can cause damage.
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 provides enhanced adhesion and durability, preventing peeling and alignment failures, even in challenging environments, while maintaining optical characteristics and preventing blocking issues during rolling.
Implementation Method 1
the alignment limiting force (anisotropy) is generated on the surface of the alignment film by irradiating light having an optional polarization state (polarized light). Such photo-alignment method includes: the 'photo anisotropic type' of reversibly changing the alignment state by changing only the molecule shape; and the 'photo reaction type' of changing the molecules themselves.
Implementation Method 2
a refractive index anisotropic layer comprising a liquid crystal layer formed by curing a liquid crystalline composition including a polymerizable liquid crystal material
Implementation Method 3
the alignment film provided in between the supporting member and the refractive index anisotropic layer has the alignment limiting force of limiting the alignment direction of the liquid crystal molecules in the refractive index anisotropic layer
Data Source
AI summary
The present invention provides an optical element capable of improving the adhesion between the alignment property providing layer, for providing the alignment property to the refractive index anisotropic layer, and the refractive index anisotropic layer, as well as improving durability of each layer.