Optical Laminate Gradient Dot Adhesion Brightness Uniformity

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Solution Overview

Problem

Conventional optical laminates used in light guide plates and peripheral optical members suffer from insufficient strength and brightness unevenness, particularly when laminated using a low-refractive index layer or air portions.

Innovation Solution

An optical laminate is designed with a light guide plate, an adhesion layer formed in a dot pattern with a gradient density along the light-guiding direction, and low-refractive index reinforcing portions at both ends of the plate, comprising a substrate with a low-refractive index layer and pressure-sensitive adhesive layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a low-refractive index layer or air portion is used for lamination, then light utilization efficiency is improved, but the strength of the laminate is insufficient

Engineering Contradiction:

Improvelight utilization efficiencyVSAvoidstrength of laminate

Core Design Contradiction:

Loss of energyVSStrength

Solution Approach 1:

The adhesion layer is formed with a dot pattern where the density of dots varies by position. Specifically, the dot density increases from the light-entering side toward the light-extraction side of the light guide plate, creating local variations in adhesive coverage that optimize both optical performance and mechanical strength at different locations.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention uses a composite structure combining a low-refractive index material (for optical efficiency) with a dot-pattern adhesion layer (for mechanical strength). This composite approach allows the low-refractive index layer to provide light extraction enhancement while the strategically placed adhesive dots provide the necessary bonding strength between the light guide plate and peripheral optical members.

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If a dot pattern adhesion layer is used, then brightness unevenness is reduced, but laminate strength may be compromised

Engineering Contradiction:

Improvebrightness uniformityVSAvoidlaminate strength

Core Design Contradiction:

Illumination intensityVSStrength

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the parameter of adhesive dot density as a function of position along the light guide plate. By increasing the dot density from the light-entering side to the light-extraction side, the laminate strength is enhanced at critical locations while maintaining the benefits of the dot pattern for reducing brightness unevenness.

Inventive Principle:

Principle #35Parameter changes

3Strength

If reinforcing portions are added to the light guide plate, then laminate strength is improved, but display area may be reduced

Engineering Contradiction:

Improvelaminate strengthVSAvoiddisplay area

Core Design Contradiction:

StrengthVSArea of stationary object

Solution Approach 1:

The reinforcing portions are strategically positioned at specific locations on the light guide plate (at the light-entering side and/or light-extraction side) rather than covering the entire surface. This localized reinforcement approach provides the necessary structural strength while minimizing the impact on the overall display area.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention applies reinforcement only where it is most needed - at the ends of the light guide plate where bonding to peripheral optical members occurs - rather than uniformly across the entire plate. This partial reinforcement approach achieves sufficient laminate strength without excessively reducing the display area.

Inventive Principle:

Principle #16Partial or excessive action

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 enhances the strength and uniformity of brightness in the optical laminate, minimizing brightness unevenness while maintaining high light transmittance and reducing the impact on display area.

Implementation Method 1

a light guide plate; an adhesion layer; and an optical member laminated on the light guide plate via the adhesion layer

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

the low-refractive index layer or the air portion is utilized, and hence light utilization efficiency is improved

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentEP3893047B1Optical laminate

Publication Date: 2023.08.30 NITTO DENKO CORP

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Figure 3

AI summary

There is provided an optical laminate, which has high brightness, is suppressed in brightness unevenness, and is excellent in strength as an integrated product. An optical laminate according to an embodiment of the present invention comprises: a light guide plate; an adhesion layer; and an optical member laminated on the light guide plate via the adhesion layer. The adhesion layer is formed in a dot pattern in plan view, and a density of the dots has such a gradient as to increase from a light-entering side of the light guide plate along a light-guiding direction thereof. In the optical laminate, low-refractive index reinforcing portions are arranged in both end portions of the light guide plate along the light-guiding direction.