Microreplicated Optical Films for Backlight Brightness Uniformity
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Solution Overview
Problem
Existing backlights for displays suffer from non-uniform brightness distribution, leading to visible luminance mura, which is undesirable in display performance.
Innovation Solution
The use of optical films with structured surfaces featuring through-holes or recesses, arranged in rows and columns, to improve brightness uniformity by controlling the ratio of opening areas and orientations relative to light sources, enhancing luminance and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional backlights use discrete light sources arranged in rows and columns, then the backlight structure is simple and easy to manufacture, but the brightness distribution is non-uniform causing visible luminance mura
Solution Approach 1:
The optical film incorporates an array of through-holes with specific aspect ratios (H/A2 ≥ 0.13) that allow light to pass through while controlling the distribution pattern. The porous structure with defined opening areas A1 and A2 at different surfaces creates selective light transmission paths that uniformize brightness without requiring complex additional components
Solution Approach 2:
The invention changes the geometric parameters of the optical film, specifically the aspect ratio of through-holes (H/A2 ≥ 0.13) and the relative opening areas (A1/A2), to optimize light distribution. By adjusting these parameters, the system achieves improved brightness uniformity while maintaining a relatively simple film-based structure rather than complex optical assemblies
2Illumination intensity
If optical films with through-holes are added to improve brightness uniformity, then luminance mura is reduced, but the overall device complexity increases
Solution Approach 1:
The optical film performs multiple functions simultaneously: it diffuses light to improve uniformity, controls the aspect ratio of through-holes to manage light distribution patterns, and maintains a thin-profile structure that doesn't significantly increase overall device thickness. This multi-functionality in a single component avoids the need for multiple separate optical elements
Solution Approach 2:
The optical film introduces local structural variations through the array of through-holes with specific geometric properties (aspect ratio H/A2 ≥ 0.13, opening areas A1 and A2) that create localized light modification zones. These local structural qualities collectively achieve global brightness uniformity improvement without requiring the entire device to be complex
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 optical films achieve an improvement in brightness uniformity by at least 2.8% over traditional backlights, with enhanced luminance and reduced luminance mura, thereby improving display quality.
Implementation Method 1
an optical film including a plurality of through-holes arranged in rows and columns of the through-holes and extending between first and second major surfaces of the optical film. Each through-hole has a first opening with a first open area, A1, at the first major surface, and a second opening with a second open area, A2, at the second major surface.
Data Source
AI summary
A backlight to a display includes an array of discrete light sources and a plurality of optical films disposed between the display and the light sources. Each film includes a regular array of intersecting ridges defining a plurality of through-holes. Each of the through-holes extends between first and second open ends of the through-hole. A cross-section of the optical film in a plane parallel to a thickness direction of the film includes two adjacent ridges in the array of ridges and a through-hole therebetween. The film has a maximum thickness hmax and the through-hole includes a side wall with a substantially vertical portion connected to the first open end of the through-hole and a substantially horizontal portion extending from the substantially vertical portion and connected to the second open end. The substantially horizontal portion has a minimum thickness hmin at a location between the two adjacent ridges, hmax/hmin≥2.