LCD Alignment Film and Step Geometry for Contrast Control

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Solution Overview

Problem

Existing liquid crystal display devices face challenges in maintaining a high contrast ratio due to deviations in the alignment direction of liquid crystal molecules caused by step portions on the substrate, leading to light leakage and reduced display quality, particularly in high-definition displays for head-mounted devices.

Innovation Solution

The liquid crystal display device incorporates a first substrate with specific geometric configurations, including gate and source lines, nonlinear elements, electrodes, and alignment films, where the angle and taper of step portions are optimized to minimize deviations in liquid crystal molecule alignment, using a parameter P defined by Equation (1) to maintain alignment direction integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If step portions are introduced on the substrate to enable nonlinear element connections, then device functionality is improved, but liquid crystal molecule alignment deviation increases causing contrast ratio decrease

Engineering Contradiction:

Improvedevice functionalityVSAvoidliquid crystal molecule alignment

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent applies local quality by introducing step portions only at specific locations where nonlinear element connections are required, rather than uniformly across the entire substrate. The step portions are strategically positioned to enable electrical connections while minimizing their impact on liquid crystal molecule alignment in the display area. This localized approach allows the substrate to have different structural characteristics in different regions: step portions for electrical connectivity and smooth surfaces for optimal liquid crystal alignment.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If step portions are made larger to ensure adequate spacing, then ease of manufacture is improved, but alignment direction deviation increases leading to light leakage

Engineering Contradiction:

Improvespacing adequacyVSAvoidlight leakage

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent resolves the contradiction by transitioning from a two-dimensional planar structure to a three-dimensional structure with step portions. The step portions extend in the thickness direction (third direction) to provide adequate spacing between conductive patterns while maintaining a compact footprint in the planar view. This vertical dimension allows sufficient spacing for electrical isolation and manufacturing ease without increasing the lateral dimensions that would cause alignment deviation and light leakage.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Manufacturing precision

If the substrate surface is made flat to improve liquid crystal alignment, then manufacturing precision is improved, but ease of manufacture of multi-layer structures is reduced

Engineering Contradiction:

Improveliquid crystal alignmentVSAvoidmulti-layer structure fabrication

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent applies segmentation by dividing the substrate structure into multiple layers with distinct functions. The first substrate includes step portions for electrical connections, while the second substrate provides a flat surface for liquid crystal alignment. This segmentation allows each layer to be optimized independently: the first substrate handles electrical connectivity with its step portions, and the second substrate ensures optimal liquid crystal alignment with its flat surface, thereby resolving the contradiction between alignment precision and manufacturing ease.

Inventive Principle:

Principle #1Segmentation

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 effectively reduces or prevents a decrease in contrast ratio by stabilizing liquid crystal molecule alignment, thereby enhancing display quality and reducing light leakage, even in high-definition applications.

Implementation Method 1

a contact angle θa of the first alignment film with respect to pure water

Methodology Applied

Scientific EffectSurface interaction/Contact angle: Surface Tension

Implementation Method 2

the liquid crystal molecules have a positive anisotropy of dielectric constant

Methodology Applied

Scientific EffectDielectric anisotropy: Dielectric Permittivity

Data Source

PatentUS20260072313A1Liquid crystal display device

Publication Date: 2026.03.12 SHARP DISPLAY TECHNOLOGY CORP

AI summary

Provided is a liquid crystal display device that includes, in order: a first substrate including gate lines extending in a first direction, source lines extending in a second direction; a first alignment film; and a liquid crystal layer containing liquid crystal molecules. The second electrode has an elongated opening. The first substrate includes a step portion extending in a third direction. An angle α formed in a plan view between the third direction and an alignment direction of liquid crystal molecules located near the first alignment film and within a central portion of the opening with no voltage applied, is between 0° and 90°, exclusive. A parameter P is 0.77 or less, as calculated using the angle α, a taper angle β of the step portion, and a contact angle θa of the first alignment film with respect to pure water, from the following Equation (1):P=(θa/90⁢° )×{1+2⁢ sin⁢ (α)×cos⁢ (α)}×sin⁢ (β)(1)