Backlight Module Prism Sheet Angles for Brightness and Viewing Angle
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Solution Overview
Problem
Conventional backlight modules with optical brightness enhancement films and reflectors suffer from insufficient directivity of emitted light, leading to suboptimal light emission brightness near the normal viewing angle.
Innovation Solution
A backlight module design featuring a light guide plate, optical film with specific microstructures, and a prism sheet, where the angles between the microstructures and prism structures are distinct, enhancing light collection and viewing angle range by optimizing the light path and scattering within the module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a stacked structure of prism sheet and two diffusers is used to guide light beams, then light-emitting intensity near the normal viewing angle is increased, but directivity of the emitted light becomes insufficient
Solution Approach 1:
The patent changes the geometric parameters of the optical structures by using prism structures with different inclination angles (first inclination angle for light guide plate interface, second inclination angle for display panel interface). This parameter variation enables the system to simultaneously achieve high light-emitting intensity and adequate directivity by optimizing the light path through angular differentiation.
Solution Approach 2:
The patent applies asymmetry by designing the prism structures with non-uniform inclination angles on different surfaces. The first inclination angle at the light guide plate interface differs from the second inclination angle at the display panel interface, creating an asymmetric optical path that improves both brightness and light directionality simultaneously.
2Illumination intensity
If diffusers scatter light from specific angles to increase normal direction emission, then light emission in normal direction is improved, but light collection properties in different directions become insufficient
Solution Approach 1:
The patent applies local quality by assigning different functional characteristics to different regions of the optical system. The prism structures have different inclination angles tailored to specific interfaces: the first inclination angle optimizes light collection from the light guide plate, while the second inclination angle optimizes light emission toward the display panel. This localized optimization enables the system to achieve both strong normal-direction emission and balanced light collection from multiple directions.
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 significantly increases light collection in the direction perpendicular to the light incident surface and expands the viewing angle range, achieving higher brightness and compliance with TCO 08 standards.
Implementation Method 1
The plurality of optical microstructures are disposed on the second surface of the first substrate, and each has a fifth surface away from the light incident surface. A first angle is present between the fifth surface and the second surface.
Implementation Method 2
The plurality of prism structures are disposed on the fourth surface of the second substrate, and each has a sixth surface away from the light incident surface. A second angle is present between the sixth surface and the fourth surface, and the second angle is different from the first angle.
Data Source
AI summary
A backlight module includes a light guide plate, a light source, an optical film, and a prism sheet. The optical film includes a first substrate having opposite first and second surfaces and multiple optical microstructures disposed on the second surface and each having a first light receiving surface away from a light incident surface. The prism sheet is located on a side of the second surface of the first substrate. The prism sheet includes a second substrate having opposite third and fourth surfaces and multiple prism structures disposed on the fourth surface and each having a second light receiving surface away from the light incident surface. A first angle between the first light receiving surface and the second surface is different from a second angle between the second light receiving surface and the fourth surface. A display apparatus includes the backlight module and a display panel.