Backlight Module Optical Film Defect Concealment
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Solution Overview
Problem
Backlight modules with high light collecting efficiency struggle to conceal small defects, leading to decreased assembly yield rates due to low haze in reverse prism sheets and difficulty in integrating diffusion sheets.
Innovation Solution
A backlight module design featuring a light guide plate, optical film with microstructures, and two prism sheets positioned away from the optical film, along with a diffusion sheet between the light guide plate and optical film, to enhance light collection efficiency and conceal small defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
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 normal viewing angle is increased and overall thickness is reduced, but the concealing ability to prevent small defects is poor resulting in decreased assembly yield rate
Solution Approach 1:
The patent combines a diffusion sheet with low haze (5-20%) and a prism sheet in a integrated optical film structure. The diffusion sheet layer provides defect concealment by scattering light to mask small defects and dust, while the prism sheet layer maintains light collecting efficiency by redirecting light at specific angles. This merged structure resolves the contradiction by providing both high light collecting efficiency and good concealing ability simultaneously.
2Length of stationary object
If the number of stacked optical film layers is decreased to reduce overall thickness, then the backlight module becomes more compact, but the concealing ability to prevent small defects is reduced making defects easier to detect
Solution Approach 1:
The patent applies local quality by using a diffusion sheet with specifically controlled low haze (5-20%) at the appropriate position in the optical film stack. This localized diffusion property provides defect concealment exactly where needed (in the backlight module structure) without significantly increasing overall thickness. The selective application of diffusion at this specific haze level resolves the contradiction between thinness and defect concealment.
3Reliability
If a diffusion sheet is added to improve concealing ability, then small defects are better concealed, but the overall thickness of the backlight module increases
Solution Approach 1:
The patent resolves this contradiction by precisely controlling the haze parameter of the diffusion sheet to be in the range of 5-20%. This parameter optimization ensures that the diffusion sheet provides sufficient defect concealment ability while maintaining a thin profile that does not significantly increase the overall backlight module thickness. The specific haze range is the key parameter change that balances concealment and thickness.
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 increases the total light emitted at normal viewing angles, improves concealing ability, and enhances assembly yield rates by optimizing the placement of prism sheets and the inclusion of a diffusion sheet.
Implementation Method 1
redirect the light beam emitted from the light guide plate at large angle to a specific viewing angle range
Implementation Method 2
a diffusion sheet is disposed between the light guide plate and the optical film
Data Source
AI summary
A backlight module including a light guide plate, a light source, an optical film, a diffusion sheet, 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. The diffusion sheet is disposed between the light guide plate and the optical film. 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.