Light Guide Plate Wedge Design for LCD Illumination

Solution Overview

Problem

The challenge is to create a sidelight-type spread illumination apparatus with a thin light exit portion for liquid crystal display devices without degrading luminance and luminance distribution, as increasing the inclination angle of the light entrance wedge portion leads to light leakage and reduced luminance.

Innovation Solution

The apparatus features a light guide plate with a light entrance wedge portion having a continuous curved inclined surface, comprising first, second, and third inclined surface portions, where the average inclination angle of the second portion is greater than the first and third portions, effectively reducing light leakage by shaping the surface according to the risk distribution along the wedge portion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If the inclination angle of the light entrance wedge portion is increased to achieve a thinner light exit portion, then the thickness of the light exit portion is reduced, but light leakage increases and luminance distribution deteriorates

Engineering Contradiction:

Improvethickness of light exit portionVSAvoidlight leakage

Core Design Contradiction:

Length of moving objectVSObject-generated harmful factors

Solution Approach 1:

The inclined surface is divided into three distinct portions (first, second, and third) with different inclination angles. The first portion has a smaller inclination angle to reduce light leakage near the light entrance, the second portion has a larger inclination angle to achieve thinning at the light exit, and the third portion has a smaller inclination angle to control light leakage near the light exit. This segmentation allows each region to be optimized independently for its specific function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the inclined surface are assigned different inclination angles according to their specific requirements. Regions closer to the light entrance and light exit have smaller inclination angles to minimize light leakage, while the central region has a larger inclination angle to achieve the desired thinning effect. This local differentiation of geometric properties optimizes overall performance.

Inventive Principle:

Principle #3Local quality

2Length of moving object

If the inclination angle of the light entrance wedge portion is increased to achieve a thinner light exit portion, then the thickness of the light exit portion is reduced, but luminance distribution uniformity deteriorates

Engineering Contradiction:

Improvethickness of light exit portionVSAvoidluminance distribution uniformity

Core Design Contradiction:

Length of moving objectVSStability of the object's composition

Solution Approach 1:

The inclined surface is divided into three distinct portions (first, second, and third) with different inclination angles. The first portion has a smaller inclination angle to reduce light leakage near the light entrance, the second portion has a larger inclination angle to achieve thinning at the light exit, and the third portion has a smaller inclination angle to control light leakage near the light exit. This segmentation allows each region to be optimized independently for its specific function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the inclined surface are assigned different inclination angles according to their specific requirements. Regions closer to the light entrance and light exit have smaller inclination angles to minimize light leakage, while the central region has a larger inclination angle to achieve the desired thinning effect. This local differentiation of geometric properties optimizes overall performance.

Inventive Principle:

Principle #3Local quality

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

This configuration reduces light leakage by 25% and improves luminance by 4.5%, maintaining uniform luminance distribution and allowing for a thinner light exit portion without compromising illumination quality.

Implementation Method 1

a light guide plate having a light entrance surface on which the light source is disposed, and a light exit surface through which light incident from the light entrance surface is emitted

Methodology Applied

Scientific EffectLight guidance: Waveguide (optics)

Implementation Method 2

the light guide plate includes a light entrance wedge portion which has an inclined surface and of which thickness is thinner from the light entrance surface side toward the light exit surface side

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 3

the inclined surface includes, from the light entrance surface side, a first inclined surface portion, a second inclined surface portion, and a third inclined surface portion

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS9151885B2Spread illumination apparatus

Publication Date: 2015.10.06 MINEBEAMITSUMI INC

AI summary

A spread illumination apparatus includes: a light source; and a light guide plate having a light entrance surface on which the light source is disposed, and a light exit surface through which light introduced from the light entrance surface is emitted, wherein the light guide plate includes a light entrance wedge portion which has an inclined surface and of which thickness is thinner from the light entrance surface side toward the light exit surface side, the inclined surface includes a first, a second, and a third inclined surface portions, and an average inclination angle of the second inclined surface portion at an arbitrary cross section perpendicular to the light entrance surface and the light exit surface along the light entrance surface in a longitudinal direction is configured to be larger than average inclination angles of the first inclined surface portion and the third inclined surface portion.