Multilayer Polyester Film Coating for Light Diffusion
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Solution Overview
Problem
Conventional laminated polyester films used in light diffusion sheets for liquid crystal displays suffer from uneven interference due to light reflection and poor adhesion to light diffusion or anti-sticking layers, leading to visibility issues and potential health concerns, with existing solutions either being unstable, costly, or failing to provide adequate adhesion.
Innovation Solution
A laminated polyester film with coating layers comprising condensed polycyclic aromatic compounds and urethane or acrylic resins, along with an ultraviolet absorber, is used to achieve a high refractive index and improved adhesion, while maintaining transparency and preventing uneven interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional polyester film is used as a base film for light diffusion sheets, then the film provides good transparency and mechanical properties, but uneven interference (interference fringes) occurs due to light reflection
Solution Approach 1:
An intermediate coating layer is introduced between the polyester base film and the light diffusion layer or anti-sticking layer. This coating layer acts as an optical intermediary with a refractive index (1.50-1.70) that bridges the mismatch between the polyester film (n≈1.57) and the adjacent layers, thereby suppressing uneven interference caused by light reflection at interfaces.
Solution Approach 2:
The refractive index of the coating layer is specifically controlled within the range of 1.50-1.70, and the layer thickness is optimized to 1-20 μm. By adjusting these optical parameters, the coating layer effectively reduces light reflection and eliminates interference fringes while maintaining overall film transparency.
2Strength
If an easy-bonding coating layer is provided between the polyester film and the light diffusion layer or anti-sticking layer, then adhesion is enhanced, but the coating layer may cause uneven interference due to improper refractive index matching
Solution Approach 1:
The coating layer is designed with specific refractive index (1.50-1.70) and thickness (1-20 μm) parameters that simultaneously satisfy both adhesion requirements and optical compatibility. This parameter optimization ensures that the coating layer provides strong bonding without causing uneven interference.
Solution Approach 2:
The coating layer is formulated as a composite material containing polyester resin (5-50 parts by weight) combined with other resins or additives that adjust the refractive index to the optimal range. This composite composition enables the layer to function both as an adhesive promoter and an optical intermediary.
3Object-affected harmful factors
If a coating layer with high refractive index is used to suppress uneven interference, then visibility is improved, but adhesion to the light diffusion layer or anti-sticking layer may be insufficient
Solution Approach 1:
The coating layer uses a composite formulation where polyester resin (providing good adhesion) is combined with other resins or additives (adjusting refractive index to 1.50-1.70). This composite approach enables simultaneous achievement of strong adhesion and optimal optical properties.
Solution Approach 2:
The refractive index is precisely controlled within the range of 1.50-1.70, which is high enough to suppress uneven interference but not so high as to compromise adhesion. This optimized parameter range balances optical performance with bonding strength.
4Object-affected harmful factors
If metal chelate compounds are used to enhance refractive index of the coating layer, then uneven interference is suppressed, but the coating solution becomes unstable and adhesion property deteriorates
Solution Approach 1:
The invention replaces unstable metal chelate compounds with a more stable coating system based on polyester resin combined with other resins or additives. This alternative formulation achieves the same optical effect (refractive index 1.50-1.70) without the stability and adhesion problems associated with metal chelates.
5Object-affected harmful factors
If conventional coating materials are used to improve refractive index, then uneven interference is reduced, but the coating layer shows significant coloration when re-melted for reuse
Solution Approach 1:
The coating layer uses polyester resin with controlled composition and structure that maintains optical stability during re-melting processes. The specific resin formulation prevents coloration while maintaining the refractive index within the optimal range of 1.50-1.70, enabling multiple reuses without degradation.
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 effectively suppresses uneven interference and enhances adhesion properties, ensuring better visibility and reusability of the light diffusion sheets, while also providing protection against ultraviolet degradation.
Implementation Method 1
an ultraviolet absorber, is used to achieve a high refractive index and improved adhesion, while maintaining transparency and preventing uneven interference
Implementation Method 2
coating layers respectively formed on both surfaces of the polyester film, wherein the content of the condensed polycyclic aromatic moieties in the condensed polycyclic aromatic compound in the coating layer is in the range of 5 to 80 % by weight, and the content of the condensed polycyclic aromatic moieties in the coating layer is in the range of 1 to 70 % by weight
Data Source
AI summary
The present invention provides a laminated polyester film which is capable of reducing occurrence of uneven interference owing to reflection of light and exhibiting good adhesion to a functional layer such as a light diffusion layer and an anti-sticking layer and which can be suitably used, for example, in a backlight unit for liquid crystal displays, etc. The laminated polyester film of the present invention comprises a polyester film and coating layers respectively formed on both surfaces of the polyester film, said coating layers each comprising a condensed polycyclic aromatic compound, and a urethane resin or an acrylic resin.