Light Guide Plate Directivity Conversion Pattern for Side Leakage
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Solution Overview
Problem
In surface light source devices, light leakage occurs from the side surfaces and optical patterns due to the inclined surfaces in the light introduction parts, leading to reduced light use efficiency and luminance evenness.
Innovation Solution
A surface light source device with a light guide plate featuring a directivity conversion pattern between the light introduction part and the effective lighting region, which converts the light's directivity direction to reduce leakage by inclining pattern elements and forming them in a way that the light is guided closer to the vertical direction, preventing lateral spreading and leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an inclined surface is provided in the light introduction part to enable the light source to be lower than the end surface thickness, then the light use efficiency is improved, but light is reflected and spread horizontally causing light leakage from side surfaces and degradation of luminance evenness
Solution Approach 1:
The light introduction part is divided into two functional zones: an inclined surface region for light capture and a flat surface region for light direction control. This segmentation allows the inclined surface to efficiently capture light from the LED while the subsequent flat region prevents horizontal spreading and side surface leakage, resolving the contradiction between light use efficiency and light leakage prevention.
Solution Approach 2:
Different surface characteristics are applied to different regions of the light introduction part. The inclined surface region has a specific angle optimized for light capture, while the flat surface region provides a different local quality for controlling light propagation direction. This local differentiation enables simultaneous achievement of high light use efficiency and prevention of side surface leakage.
2Length of stationary object
If the thickness of the light guide plate is reduced to achieve low profile, then the device thickness is reduced, but the light source height becomes larger than the end surface thickness causing light to project above and partially leak
Solution Approach 1:
The solution transitions from a uniform thickness light guide plate to a light introduction part with variable thickness in the vertical dimension. By creating a thickness gradient (inclined surface) in the vertical dimension, the light source can be positioned lower while maintaining sufficient end surface thickness to contain the light, thus achieving low profile without light leakage.
3Productivity
If an inclined surface is provided to improve light introduction efficiency, then light use efficiency improves, but the angle formed by light and optical axis increases causing lateral spreading and leakage
Solution Approach 1:
The light introduction part is segmented into an inclined surface region that increases light introduction efficiency and a flat surface region that controls light propagation angle. This segmentation allows the light to be efficiently captured at an angle while subsequently being redirected to propagate at a smaller angle relative to the optical axis, preventing lateral spreading.
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 directivity conversion pattern enhances light use efficiency by at least 2% and prevents luminance degradation by ensuring light is directed vertically, reducing leakage from the side surfaces and optical patterns.
Implementation Method 1
the light guide plate body includes a directivity conversion pattern in a region located between the light introduction part and an effective lighting region of the light guide plate body... the directivity conversion pattern converting a directivity direction of the light passing from the light introduction part to the effective lighting region
Implementation Method 2
the light traveling in a direction oblique to an optical axis of the light source 12 in the light introduction part 15 is reflected by the inclined surface 17 and spread in a horizontal direction
Data Source
AI summary
In a surface light source device, a light guide plate includes a light introduction part that traps the light emitted from a point light source and incident from a light incident surface, and a light guide plate body. The light introduction part includes an inclined surface inclined from a surface in a portion having a thickness larger than that of the light guide plate body toward an end of the surface of the light guide plate body. The light guide plate body includes a directivity conversion pattern located between an effective lighting region of the light guide plate body and the light introduction part. The directivity conversion pattern converts a directivity direction of the light from the light introduction part to the effective lighting region such that an angle formed by the directivity direction and a direction perpendicular to the light incident surface decreases when viewed from above.