Backlight Module Optical Film Microstructures for Light Collection
Solution Overview
Problem
Backlight modules with two brightness enhancement films struggle to balance light collecting efficiency and concealing ability, leading to poor assembly yield rates due to the low haze of reverse prism sheets and difficulty in detecting defects during quality control.
Innovation Solution
A backlight module design featuring a light guide plate, a light source, an optical film with microstructures at a 90-degree angle to the light incident surface, and two prism sheets positioned away from the optical film, which increases light emission at the normal viewing angle and enhances concealing ability by reducing internal reflections and defects detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reverse prism sheet is used to replace two laminated brightness enhancement films to increase light collecting efficiency, then the total amount of light emitted at the normal viewing angle increases and the thickness of the backlight module is reduced, but the concealing ability deteriorates because small defects and tiny objects are easily detected during optical inspection
Solution Approach 1:
The invention divides the optical film system into multiple independent layers: a light guide plate, a first prism sheet, a second prism sheet, and an optical film with microstructures. Each layer performs a specific function - the prism sheets redirect light at large angles to specific viewing angles, while the optical film with vertically extending microstructures further concentrates light at the normal viewing angle. This segmentation allows each component to be optimized independently, resolving the contradiction between light collecting efficiency and defect concealment.
Solution Approach 2:
The invention applies different optical properties to different regions and layers of the system. The prism sheets have specific refractive indices and prism angles optimized for light redirection, while the optical film has microstructures with specific geometries optimized for light concentration. This local optimization of optical properties allows the system to achieve high light collecting efficiency in the normal viewing angle direction while maintaining adequate defect concealment through the combined effect of multiple layers.
2Illumination intensity
If two brightness enhancement films are laminated to redirect light beams to improve overall intensity at the normal viewing angle, then the light intensity increases, but the device complexity and thickness increase
Solution Approach 1:
The invention merges the functions of multiple optical films into a unified multi-layer system where the first prism sheet, second prism sheet, and optical film with microstructures work together. The prism sheets handle light redirection from large angles, while the optical film with vertically extending microstructures handles light concentration at the normal viewing angle. This merging of functions into a coordinated multi-layer system achieves the desired light intensity improvement while managing complexity through functional integration.
Solution Approach 2:
The invention introduces vertically extending microstructures into the optical film, adding a vertical dimension to the optical control mechanism. These microstructures extend in the vertical direction perpendicular to the light propagation direction, creating a three-dimensional optical control system. This dimensional addition allows for more effective light concentration at the normal viewing angle without requiring excessive stacking of two-dimensional prism sheets.
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 design improves light collecting efficiency and assembly yield rates by increasing the total light emitted at the normal viewing angle while providing better concealment of defects, thus enhancing the overall performance of the backlight module.
Implementation Method 1
The optical film is overlapped with the light emitting surface of the light guide plate and has a plurality of optical microstructures facing the light emitting surface. An angle between the extending direction of the optical microstructures and the light incident surface is 90 degrees or between 75 degrees and 90 degrees.
Implementation Method 2
The first prism sheet and the second prism sheet are overlapped with the optical film and are positioned on a side of the optical film being far away from the light guide plate. An extending direction of a plurality of prism structures of the first prism sheet is not parallel to an extending direction of a plurality of prism structures of the second prism sheet.
Implementation Method 3
In the light-collecting backlight module, the light beams of the total internal reflection inside the light collecting reverse prism sheet are less, the reverse prism sheet has a low haze and cannot be used with a diffusion sheet.
Data Source
AI summary
A backlight module including a light guide plate, a light source, an optical film, a first prism sheet and a second prism sheet is provided. The light guide plate has a light incident surface and a light emitting surface connected to each other. The light source is disposed on a side of the light incident surface. The optical film is overlapped with the light emitting surface and has a plurality of optical microstructures facing the light emitting surface. An angle between the extending direction of the optical microstructures and the light incident surface is 90 degrees or between 45 degrees and 90 degrees. The first prism sheet and the second prism sheet are overlapped with the optical film and are positioned on a side of the optical film being far away from the light guide plate. A display apparatus adopting the backlight module is also provided.