Backlight Unit With Nano Crystal Conversion Layer

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Solution Overview

Problem

Conventional backlight units for LCD devices face challenges in achieving uniform brightness and color purity, particularly as screen size increases, with cold cathode fluorescent lamps (CCFLs) being inefficient and three-color LEDs being costly, while white LEDs compromise on color reproducibility.

Innovation Solution

A backlight unit utilizing a light emitting diode (LED) light source with a separate light conversion layer made of semiconductor nano crystals, which converts the LED's emitted light into white light, improving color purity and reproducibility, and includes a diffusion panel and light guide panel for uniformity and energy transfer control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If three color LEDs are used as light source, then color purity is improved, but manufacturing cost increases

Engineering Contradiction:

Improvecolor purityVSAvoidmanufacturing cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The invention separates the light conversion function from the LED light source by using a distinct light conversion layer containing semiconductor nanocrystals. This segmentation allows the use of cost-effective single-color LEDs while achieving high color purity through the specialized light conversion layer, thus resolving the contradiction between color purity and manufacturing cost.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention employs composite materials by combining LED light source with a light conversion layer containing semiconductor nanocrystals suspended in a matrix material. This composite structure enables the system to achieve the color purity of multi-color LEDs while using simpler, more cost-effective single-color LED components.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If light conversion layer is placed close to LED light source, then energy transfer efficiency is improved, but heat degradation occurs

Engineering Contradiction:

Improveenergy transfer efficiencyVSAvoidheat degradation

Core Design Contradiction:

Use of energy by moving objectVSTemperature

Solution Approach 1:

The invention introduces an intermediary substance (matrix material or encapsulant) between the LED light source and the semiconductor nanocrystals in the light conversion layer. This intermediary acts as a thermal buffer that allows efficient energy transfer while protecting the nanocrystals from direct heat exposure, thus resolving the contradiction between energy transfer efficiency and heat degradation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention applies local quality by creating a spatial gradient in the light conversion layer where nanocrystals are distributed within a matrix material. This distribution pattern optimizes the local interaction between light and nanocrystals while the matrix material provides localized thermal management, allowing efficient energy conversion without uniform heat exposure throughout the layer.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If white LED is used as light source, then manufacturing cost is reduced, but color reproducibility deteriorates

Engineering Contradiction:

Improvemanufacturing costVSAvoidcolor reproducibility

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The invention substitutes the conventional approach of using multi-color LEDs or complex phosphor mixes with a systematic approach using single-color LEDs combined with a engineered light conversion layer. This replacement strategy achieves superior color reproducibility through controlled nanocrystal conversion while maintaining the manufacturing simplicity and cost-effectiveness of single-color LED technology.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enhances color reproducibility and purity, maintains cost competitiveness, and prevents energy transfer degradation between layers, ensuring improved image quality and manufacturing simplicity.

Implementation Method 1

The light conversion layer includes a semiconductor nano crystal, and the light conversion layer converts light emitted from the light emitting diode light source to white light

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Implementation Method 2

A diffusion panel is provided between the light conversion layer and the liquid crystal panel or, alternatively, between the LED light source and the light conversion layer

Methodology Applied

Scientific EffectLight diffusion: Scattering

Data Source

PatentUS8436964B2Backlight unit and liquid crystal display device having the same

Publication Date: 2013.05.07 SAMSUNG ELECTRONICS CO LTD

AI summary

A backlight unit for a liquid crystal display (“LCD”) device includes a light emitting diode (“LED”) light source and a light conversion layer disposed separate from and above from the LED light source. The light conversion layer includes a semiconductor nano crystal, converts light emitted from the LED light source to white light and provides the white light to a liquid crystal panel of the LCD.