Resin Light Guide Plate with Planarizing Films for High Contrast

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Solution Overview

Problem

Light guide plates using resin substrates suffer from low contrast and resolution, with the cause of this issue unknown until now, and existing solutions fail to provide high contrast and resolution at a low cost.

Innovation Solution

An optical device with a light guide plate featuring a substrate made from a resin material, such as cycloolefin polymer, coated with planarizing films containing organic materials on both surfaces to enhance surface smoothness and adhesion, allowing for high contrast and resolution equivalent to glass substrates, while maintaining a lightweight and cost-effective design.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If a resin substrate is used for the light guide plate, then the weight of the optical device is reduced, but the contrast and resolution deteriorate

Engineering Contradiction:
Improveweight of optical deviceVSAvoidcontrast and resolution
Core Design Contradiction:
Weight of moving objectVSMeasurement precision

Solution Approach 1:

The patent applies composite materials by combining a resin substrate with planarizing films having different refractive indices. The light guide plate consists of a resin substrate (first refractive index) with a first planarizing film (second refractive index) on the light incident surface and a second planarizing film (third refractive index) on the light emission surface. This multi-layer composite structure improves contrast and resolution while maintaining the weight advantage of resin substrates.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent changes optical parameters by carefully selecting materials with specific refractive indices. The first planarizing film has a refractive index lower than the resin substrate, while the second planarizing film has a refractive index higher than the resin substrate. This parameter optimization controls light reflection and transmission to achieve high contrast and resolution equivalent to glass substrates.

Inventive Principle:
Principle #35Parameter changes

2Ease of manufacture

If a resin substrate is used for the light guide plate, then manufacturing cost is reduced, but the contrast and resolution deteriorate

Engineering Contradiction:
Improvemanufacturing costVSAvoidcontrast and resolution
Core Design Contradiction:
Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent uses composite materials comprising a resin substrate with specially designed planarizing films. The first planarizing film with lower refractive index and the second planarizing film with higher refractive index create optimal light control. This composite structure achieves glass-substrate-level contrast and resolution while maintaining the cost-effectiveness and ease of manufacture of resin substrates.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent optimizes manufacturing by selecting planarizing film materials based on their refractive index parameters. The first planarizing film uses material with refractive index lower than the resin substrate, and the second planarizing film uses material with refractive index higher than the resin substrate. This parameter-based material selection achieves high optical performance through cost-effective resin materials rather than expensive glass.

Inventive Principle:
Principle #35Parameter changes

3Device complexity

If the surface of the resin substrate is left untreated, then the manufacturing process is simplified, but the surface is easily scratched and adhesion deteriorates

Engineering Contradiction:
Improvemanufacturing process complexityVSAvoidsurface durability and adhesion
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The patent applies preliminary action by forming planarizing films on the resin substrate surfaces before final assembly. The first planarizing film is formed on the light incident surface and the second planarizing film is formed on the light emission surface. These films are applied in advance to protect the resin substrate surface from scratching and to provide adequate adhesion for subsequent hologram optical element attachment, while maintaining a relatively simple manufacturing process.

Inventive Principle:
Principle #10Preliminary action

4Measurement precision

If planarizing films with appropriate refractive indices are added to the resin substrate, then contrast and resolution are improved, but the device complexity increases

Engineering Contradiction:
Improvecontrast and resolutionVSAvoidstructure complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent uses composite materials to improve contrast and resolution while minimizing structure complexity. The light guide plate consists of a resin substrate with a first planarizing film (lower refractive index) on the incident surface and a second planarizing film (higher refractive index) on the emission surface. This three-layer composite structure achieves glass-substrate-level optical performance through straightforward material layering rather than complex structural designs.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent achieves high contrast and resolution through parameter optimization rather than structural complexity. The first planarizing film uses material with refractive index lower than the resin substrate, and the second planarizing film uses material with refractive index higher than the resin substrate. This refractive index parameter arrangement optimizes light control at each interface, achieving superior optical performance with a simple three-layer structure.

Inventive Principle:
Principle #35Parameter changes

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 optical device achieves high contrast and resolution comparable to glass substrate-based light guide plates, improving surface flatness and adhesion, thus enhancing the optical performance and reducing manufacturing costs.

Implementation Method 1

light incident from an image forming device is propagated by total reflection inside and then emitted toward an observer

Methodology Applied
Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentEP3572863B1Optical device and display device
Publication Date: 2024.10.09 SONY GROUP CORP
  • EP3572863B1 patent drawingFigure 1
  • EP3572863B1 patent drawingFigure 2
  • EP3572863B1 patent drawingFigure 3

AI summary

An optical device includes: a light guide plate 120; a first deflection means 130 arranged on at least one of a first surface or a second surface of the light guide plate 120, the first deflection means 130 deflecting light incident on the light guide plate 120 to cause the light incident on the light guide plate 120 to be totally reflected inside the light guide plate 120; and a second deflection mean 140 arranged on at least one of the first surface or the second surface of the light guide plate 120, the second deflection means 140 deflecting the light propagated inside the light guide plate 120 by total reflection to cause the light propagated inside the light guide plate 120 by total reflection to be emitted from the light guide plate 120, in which the light guide plate 120 includes: a substrate 500 including a first surface and a second surface facing the first surface; a first planarizing film 511 formed on the first surface of the substrate 500, the first planarizing film 511 containing an organic material; and a second planarizing film 512 formed on the second surface of the substrate 500, the second planarizing film 512 containing an organic material. The substrate 500 can contain a resin material.