Curable Composition Bilayer Structure for Low Reflectivity
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Solution Overview
Problem
The existing light-shielding films for solid-state imaging devices suffer from high reflectivity issues due to uneven distribution of fluorine-containing polymers, leading to poor developability and reflectivity, especially when using photosensitive resin compositions like those described in JP2009-244729A.
Innovation Solution
A curable composition comprising a fluorine-containing polymer with specific repeating units, a polymerizable compound, and a coloring agent, which forms a bilayer structure with a high-refractive-index layer and a low-refractive-index layer, enhancing developability and low reflectivity through interference cancellation and improved developer penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a fluorine-containing polymer is used in the photosensitive resin composition to achieve low reflectivity, then the low-refractive-index layer is formed on the upper layer, but the developer is repelled during alkali development resulting in poor developability
Solution Approach 1:
The patent applies local quality by creating distinct regions within the coating film with different properties: the lower layer near the substrate has high black pigment concentration for light shielding, while the upper layer has fluorine-containing polymer for low reflectivity. The key innovation is introducing a specific repeating unit (Formula A) with hydrophilic groups in the fluorine-containing polymer to create a localized hydrophilic region at the film surface that attracts developers, resolving the contradiction between low reflectivity and developability.
Solution Approach 2:
The patent uses composite materials by combining the fluorine-containing polymer with specific repeating units (Formula A and Formula B) and black pigments in a photosensitive resin composition. The composite structure creates a coating film with both low-refractive-index layer (fluorine-containing polymer) and high-refractive-index layer (black pigment), achieving interference cancellation for low reflectivity while the hydrophilic repeating units improve developer penetration.
2Volume of moving object
If the solid-state imaging device is made smaller and thinner, then the device size is reduced, but the light-shielding film requires even lower reflectivity to maintain performance
Solution Approach 1:
The patent utilizes optical phase interference by creating a bilayer structure with different refractive indices. The low-refractive-index layer (fluorine-containing polymer) and high-refractive-index layer (black pigment) create optical path differences that result in destructive interference for reflected light, achieving low reflectivity without increasing device thickness.
Solution Approach 2:
The patent employs composite materials with different refractive indices (fluorine-containing polymer and black pigment) to create an interference cancellation effect. This composite structure achieves superior light shielding performance in a thin film configuration, enabling smaller and thinner devices while maintaining low reflectivity requirements.
3Productivity
If a spin coating method is used to form the light-shielding film, then productivity is improved, but the fluorine-containing polymer is unevenly distributed resulting in poor developability
Solution Approach 1:
The patent applies parameter changes by modifying the chemical structure of the fluorine-containing polymer through the introduction of repeating unit (Formula A) with hydrophilic groups. This parameter change in the polymer structure alters its interaction with developers, ensuring proper wetting and penetration during spin coating and subsequent development processes, thus maintaining both high productivity and good developability.
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 curable composition achieves excellent developability and low reflectivity, improving the performance of light-shielding films and solid-state imaging elements by optimizing the layer structure and chemical resistance.
Implementation Method 1
enhancing developability and low reflectivity through interference cancellation
Implementation Method 2
A curable composition comprising a fluorine-containing polymer with specific repeating units, a polymerizable compound, and a coloring agent
Data Source
AI summary
An object of the present invention is to provide a curable composition satisfying both of excellent low reflectivity and excellent developability, a method for producing a cured film, an infrared color filter provided with a light-shielding film, and a solid-state imaging device.The curable composition of the present invention includes a fluorine-containing polymer including a repeating unit represented by Formula (A) and a repeating unit represented by Formula (B), a polymerizable compound, and a coloring agent.In Formula (A), R1 represents a hydrogen atom or an alkyl group, and L1 represents a divalent chained linking group having 3 or more carbon atoms in total, which may include an ester bond.In Formula (B), R2 represents a hydrogen atom or an alkyl group, L2 represents a single bond or a divalent linking group, and Rf represents a monovalent organic group including an fluorine atom.