Planar Illumination Frame with Inclined Absorbing Joint

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Solution Overview

Problem

Planar illumination devices using white plastic frames suffer from light leakage, which can interfere with sensors in modern cellular phones equipped with camera functions, due to the low reflectivity and high transmittance of white plastic materials.

Innovation Solution

A planar illumination device design featuring a frame with a reflecting part made of white plastic and an absorbing part made of black plastic, where the joint interface between the two is inclined vertically to the emitting surface, reducing light leakage by increasing the joint area and ensuring proper molding processes to minimize optical characteristic degradation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a white plastic frame is used to provide high reflectivity, then illumination efficiency is improved, but light leakage occurs at the outer circumference of the frame

Engineering Contradiction:

Improveillumination efficiencyVSAvoidlight leakage

Core Design Contradiction:

Illumination intensityVSObject-generated harmful factors

Solution Approach 1:

The frame is segmented into two distinct functional parts: a white reflecting part for high reflectivity and an black absorbing part for light absorption. This segmentation allows each part to perform its specific function optimally without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the frame are assigned different optical properties: the inner region (reflecting part) has high reflectivity to maximize illumination efficiency, while the outer region (absorbing part) has high light absorption to prevent light leakage. This local differentiation resolves the contradiction between illumination efficiency and light leakage prevention.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If the joint interface between reflecting part and absorbing part is vertical to the emitting surface, then manufacturing is simplified, but light leakage occurs through the joint interface

Engineering Contradiction:

Improvemolding simplicityVSAvoidlight leakage through joint interface

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The joint interface is designed with an inclined angle rather than being vertical, creating a sloped surface that prevents light from directly passing through the joint. This angular configuration blocks the light path while maintaining structural integrity.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The joint interface, which could be a source of light leakage, is converted into a light-blocking feature by inclining it. The inclination angle transforms the potential weakness into a strength by using geometry to block light paths that would otherwise penetrate through the joint.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Object-generated harmful factors

If the frame thickness is increased to suppress light leakage, then light leakage is reduced, but device thickness increases

Engineering Contradiction:

Improvelight leakage suppressionVSAvoidframe thickness

Core Design Contradiction:

Object-generated harmful factorsVSLength of stationary object

Solution Approach 1:

The absorbing part is strategically positioned at the outer circumferential surface where light leakage occurs, concentrating the light-blocking function at the critical location rather than uniformly increasing the entire frame thickness. This localized approach suppresses light leakage while maintaining overall frame thinness.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The frame uses a composite structure combining white reflecting material and black light-absorbing material in specific configurations. This composite design achieves superior light control performance without requiring increased thickness, as the functional properties arise from material composition and structure rather than sheer volume.

Inventive Principle:

Principle #40Composite materials

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 solution effectively suppresses light leakage while maintaining the optical and structural integrity of the device, ensuring that the illumination device provides a preferable optical characteristic without compromising luminance or increasing the frame's thickness.

Implementation Method 1

a reflecting part configured to reflect the light

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

an absorbing part, formed integral with at least a part of an outer circumferential surface of the reflecting part, configured to absorb the light

Methodology Applied

Scientific EffectAbsorption: Absorption (EM radiation)

Data Source

PatentUS8992064B2Planar illumination device and method of producing same

Publication Date: 2015.03.31 MINEBEAMITSUMI INC

AI summary

A planar illumination device includes a light source unit, including a substantially planar emitting surface, configured to emit light to illuminate a substantially planar object, and a frame, formed in a frame shape enclosing the light source unit, disposed on an outer circumferential side of the light source unit, configured to hold the light source unit. The frame includes a reflecting part configured to reflect the light, and an absorbing part, formed integral with at least a part of an outer circumferential surface of the reflecting part, configured to absorb the light. The reflecting part and the absorbing part include joint interface therebetween that is inclined to a direction vertical to the emitting surface.