Polyimide Retardation Layers for Thin Display Devices

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Solution Overview

Problem

Liquid crystal display devices using polyimide substrates face challenges in reducing thickness while maintaining optical compensation, as polyimide-induced birefringence leads to viewing angle dependence and tonality changes, requiring additional retardation plates that increase thickness.

Innovation Solution

Incorporating perpendicularly-oriented liquid crystal retardation layers directly on polyimide substrates, eliminating the need for external retardation plates and adhesive layers, thereby reducing the overall thickness of the display device while compensating for optical anisotropy caused by polyimide birefringence.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a retardation plate is added to compensate for polyimide-induced birefringence, then viewing angle dependence is reduced, but the display device thickness increases

Engineering Contradiction:

Improveviewing angle dependenceVSAvoiddisplay device thickness

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent combines the base material and retardation plate into a single integrated structure where the polyimide base material itself provides the necessary retardation function. This eliminates the need for a separate retardation plate while maintaining optical compensation, thereby reducing overall device thickness while preserving viewing angle characteristics.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The polyimide base material serves dual functions: as the structural substrate and as the retardation layer. By designing the polyimide with specific optical anisotropy properties, it simultaneously provides mechanical support and optical compensation, eliminating the need for additional dedicated retardation components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If multiple layers including retardation plates are used for optical compensation, then display quality is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvedisplay qualityVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the base material layer and retardation layer into a single polyimide layer, reducing the number of manufacturing steps. Instead of separately producing and assembling multiple layers, the integrated structure is formed in one process, simplifying production while maintaining the necessary optical compensation functionality.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The polyimide base material performs multiple functions including substrate support, insulation, and optical compensation. This multi-functionality reduces the total number of components and assembly steps required, thereby simplifying the manufacturing process while ensuring display quality.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If external retardation plates are used, then optical anisotropy compensation is achieved, but mechanical strength and flexibility are compromised

Engineering Contradiction:

Improveoptical anisotropy compensationVSAvoidmechanical strength and flexibility

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

By integrating the retardation function into the base material itself, the patent eliminates the need for additional external plates that would add rigidity and reduce flexibility. The single integrated polyimide layer maintains the inherent mechanical properties of the base material while providing the necessary optical compensation.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The polyimide base material serves as both the structural foundation and the optical compensation element. This eliminates the need for additional external components that would compromise mechanical strength and flexibility, as the same material provides both structural and optical functions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 approach allows for a thinner display device with improved optical compensation, reducing mechanical strength and flexibility concerns, and simplifying the manufacturing process by integrating retardation layers directly on the substrates, thus achieving a balance between thickness reduction and display quality.

Implementation Method 1

polyimide-induced birefringence leads to viewing angle dependence and tonality changes

Methodology Applied

Scientific EffectBirefringence: Birefringence

Implementation Method 2

the first retardation layer includes a perpendicularly-oriented liquid crystal layer

Methodology Applied

Scientific EffectLiquid crystal optical anisotropy: Liquid Crystals

Data Source

PatentUS9921429B2Display device

Publication Date: 2018.03.20 MAGNOLIA WHITE CORP

AI summary

There is provided a display device including a first base material, a second base material, an optical layer placed between the first base material and the second base material, and a first retardation layer placed in contact with the first base material, wherein the first base material and the second base material are formed from a polyimide, and the first retardation layer and the second retardation layer are liquid crystal layers which are vertically aligned. Providing the first and second retardation layers in contact with the first and second base materials make it possible to achieve a reduction in the thickness of the display device.