High-Refractive-Index Composite Adhesive Film for Foldable Displays
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Solution Overview
Problem
Existing adhesive films used in optical display devices face challenges with high refractive index mismatch, leading to screen quality issues, increased thickness, and reduced peel strength, while also requiring additional processing steps, which complicates economic feasibility and foldability, especially in foldable displays.
Innovation Solution
An adhesive film composed of a hydroxyl group-containing (meth)acrylic copolymer and inorganic particles with a refractive index of 1.5 or more, combined with a specific peel strength and modulus ratio, to achieve high refractive index, high peel strength, thin thickness, and low haze, ensuring good optical characteristics and foldability across temperature ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the index of refraction of the acrylic adhesive film is increased to relieve the difference in index of refraction between the touchscreen panel and adhesive film, then screen quality is improved, but peel strength deteriorates and optical characteristics including haze worsen
Solution Approach 1:
The patent uses a composite adhesive film comprising a polyacrylonitrile-based polymer matrix combined with specific inorganic particles (silica, titania, or zirconia) having refractive indices of 1.5 or more. This composite structure allows the film to achieve a balanced refractive index (1.45-1.65) that relieves the index mismatch between touchscreen panel and adhesive film, while the polyacrylonitrile-based polymer matrix maintains adequate peel strength and controls haze, resolving the contradiction between optical performance and mechanical strength.
2Illumination intensity
If a separate adhesive film including a high refractivity layer or an optical film is added between the touchscreen panel and acrylic adhesive film to relieve the difference in index of refraction, then screen quality is improved, but thickness increases and processability deteriorates
Solution Approach 1:
The patent merges the functions of the adhesive film and the high refractivity layer into a single integrated adhesive film. By incorporating inorganic particles with refractive indices of 1.5 or more directly into the adhesive film composition, the film simultaneously provides adhesion and high refractive index properties, eliminating the need for separate adhesive films and optical films, thus reducing thickness and process complexity while maintaining screen quality.
3Adaptability or versatility
If the thickness of the adhesive film is reduced to improve foldability in foldable displays, then foldability is improved, but peel strength and optical characteristics may deteriorate
Solution Approach 1:
The patent optimizes the composition parameters of the adhesive film by using a polyacrylonitrile-based polymer with specific molecular weight and combining it with inorganic particles having controlled size (0.1-10 μm) and concentration (1-50 wt%). This parameter optimization enables the film to achieve adequate peel strength and optical characteristics even at reduced thickness (5-20 μm), thereby improving foldability for flexible displays while maintaining necessary mechanical and optical performance.
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 adhesive film maintains high refractive index and peel strength, provides excellent foldability at both low and high temperatures, and reduces thickness, thereby improving screen quality and processability in optical display devices.
Implementation Method 1
There is a great difference in index of refraction between the touchscreen panel and the acrylic adhesive film. Such a difference in index of refraction can affect screen quality.
Implementation Method 2
The optical elements may be stacked one above another via an acrylic adhesive film.
Data Source
AI summary
Provided are an adhesive film, an optical member comprising same, and an optical display device comprising same, the adhesive film being formed of a composition comprising a hydroxyl group-containing (meth)acrylic copolymer and particles having a refractive index of about 1.5 or greater, wherein the adhesive film has a refractive index of about 1.5 or greater, and the adhesive film satisfies expression 1 and expression 2.