Hetero-conic Lens Backlight Unit for Brightness and Viewing Angle

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Solution Overview

Problem

Existing backlight units for liquid crystal displays face challenges in simultaneously improving brightness and viewing angle characteristics, as methods like using prism sheets or semispherical micro-lens array sheets either enhance brightness at the expense of viewing angle or fail to adequately improve both metrics.

Innovation Solution

A backlight unit incorporating a condensing film with two-dimensionally arranged hetero-conic lenses, formed by combining first and second conic lenses expressed by specific formulas, which are designed to optimize light distribution and reduce light recycling, thereby enhancing both brightness and viewing angle.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If prism sheets or lenticular sheets are used to improve brightness, then brightness characteristics are improved, but viewing angle characteristics deteriorate

Engineering Contradiction:

ImprovebrightnessVSAvoidviewing angle

Core Design Contradiction:

Illumination intensityVSAdaptability or versatility

Solution Approach 1:

The condensing film is divided into multiple regions with different lens types: a first region with first conic lenses having a first refractive index, and a second region with second conic lenses having a second refractive index different from the first. This segmentation allows different parts of the film to perform different optical functions, simultaneously improving brightness and viewing angle characteristics.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the condensing film are assigned different local optical properties through using conic lenses with different refractive indices. The first conic lenses in the first region provide one set of optical characteristics while the second conic lenses in the second region provide different characteristics, enabling optimized performance across different viewing zones.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If a stack of two or three semispherical micro-lens array sheets is used to prevent deterioration in viewing angle characteristics, then viewing angle characteristics are maintained, but brightness characteristics cannot be improved to satisfactory levels

Engineering Contradiction:

Improveviewing angleVSAvoidbrightness

Core Design Contradiction:

Adaptability or versatilityVSIllumination intensity

Solution Approach 1:

The invention changes the key parameter of refractive index by using conic lenses with different refractive indices in different regions. This parameter change enables the condensing film to achieve both wide viewing angles and high brightness, overcoming the limitations of uniform semispherical micro-lens arrays.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The condensing film uses a composite structure combining different types of conic lenses with different refractive indices within the same film. This composite approach allows the film to exhibit multiple optical characteristics simultaneously, achieving both improved brightness and maintained viewing angle characteristics.

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 proposed solution significantly improves both brightness and viewing angle characteristics of the backlight unit, providing better light distribution and reducing light recycling, leading to enhanced image quality in liquid crystal displays.

Implementation Method 1

hetero-conic lenses are two-dimensionally arranged on a surface of each of the condensing films, and each of the hetero-conic lenses is formed by combining a first conic lens and a second conic lens

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS8870399B2Backlight unit comprising condensing film having hetero-conic lenses

Publication Date: 2014.10.28 LG CHEM LTD

AI summary

Provided is a backlight unit. The backlight unit includes a light source, an optical member configured to uniformly distribute light emitted from the light source, and at least two condensing films configured to condense light from the optical member. Hetero-conic lenses are two-dimensionally arranged on a surface of each of the condensing films, and each of the hetero-conic lenses is formed by combining a first conic lens expressed by Formula (1) below and a second conic lens expressed by Formula (2) below:y=H1-x2/r11+1-(1+k1)⁢(1/r1)2⁢x2⁢⁢(0≤y≤y0)Formula⁢⁢(1)y=H2-x2/r21+1-(1+k2)⁢(1/r2)2⁢x2+y0⁢⁢(y0≤y≤H2).Formula⁢⁢(2)