Oxide TFT UV Absorbing Layer for LCD Photo Alignment

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Solution Overview

Problem

Liquid crystal display panels using oxide thin film transistors (TFTs) face issues with threshold voltage shift and time-dependent degradation due to ultraviolet light exposure during photo alignment, affecting the operation of peripheral circuits and image display quality.

Innovation Solution

Incorporating an ultraviolet absorbing layer, such as an alignment film, to cover the oxide thin film transistor in the liquid crystal display panel, which absorbs ultraviolet light and prevents it from affecting the TFTs, ensuring stable operation and high definition display.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If photo alignment treatment is applied to the liquid crystal display panel, then alignment control function is provided and light leakage is suppressed, but ultraviolet light causes defects in the oxide TFT semiconductor layer resulting in threshold voltage shift and time-dependent degradation

Engineering Contradiction:

Improvealignment control functionVSAvoidultraviolet light damage to oxide TFT

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A protective film is introduced as an intermediary layer between the ultraviolet light source and the oxide TFT. This protective film selectively transmits the wavelengths needed for photo alignment while blocking harmful ultraviolet wavelengths, thereby mediating the interaction between light and the semiconductor layer to prevent damage while maintaining alignment functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention utilizes the wavelength-selective properties of the protective film to convert the harmful effect of ultraviolet light into a beneficial process. By allowing specific wavelengths to pass through for photo alignment while blocking others, the system transforms what would be damaging radiation into a controlled alignment tool, protecting the oxide TFT from degradation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Productivity

If oxide TFT is used in peripheral circuits, then high mobility and performance are achieved, but threshold voltage shift and time-dependent degradation cause problems in normal circuit operation

Engineering Contradiction:

ImproveTFT mobility and performanceVSAvoidcircuit operation stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The protective film is applied in advance to prevent ultraviolet light from reaching the oxide TFT during photo alignment treatment. This preliminary protective action blocks the harmful wavelengths before they can cause defects in the semiconductor layer, thereby preventing threshold voltage shift and ensuring stable circuit operation while maintaining the high performance benefits of oxide TFT.

Inventive Principle:

Principle #9Preliminary anti-action

3Ease of manufacture

If ultraviolet light is irradiated onto the IGZO layer for photo alignment, then alignment treatment is completed, but defect levels are formed in the semiconductor layer accelerating time-dependent degradation

Engineering Contradiction:

Improvephoto alignment processVSAvoidTFT characteristic stability over time

Core Design Contradiction:

Ease of manufactureVSDuration of action of stationary object

Solution Approach 1:

The protective film serves as a wavelength-selective intermediary that enables the photo alignment process to proceed effectively while simultaneously protecting the IGZO layer from harmful ultraviolet wavelengths. This allows the alignment treatment to be completed successfully without forming defect levels that would accelerate time-dependent degradation.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution maintains good operation of peripheral circuits and achieves high definition liquid crystal display panels with excellent contrast, comparable to amorphous silicon TFTs in terms of process and cost, while preventing ultraviolet-induced degradation.

Implementation Method 1

an ultraviolet absorbing layer for absorbing the ultraviolet light is provided so as to cover the oxide thin film transistor

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Data Source

PatentUS9709853B2Liquid crystal display panel

Publication Date: 2017.07.18 MAGNOLIA WHITE CORP

AI summary

To maintain good operation of a peripheral circuit using an oxide thin film transistor in a liquid crystal display panel to which photo alignment is applied, the liquid crystal display panel includes: a transparent substrate provided with an oxide thin film transistor in the periphery of a pixel portion in which pixel electrodes are arranged, to control the pixel electrodes; and an alignment film to align liquid crystal provided in the pixel portion. The alignment film is subjected to photo alignment treatment by ultraviolet irradiation. Further, an ultraviolet absorbing layer is provided so as to cover the oxide thin film transistor. For example, an alignment film is used for the ultraviolet absorbing layer to absorb the ultraviolet light for the photo aliment treatment of the alignment film, in the peripheral circuit portion for controlling the pixel electrodes, thereby preventing the threshold voltage of the oxide thin film transistor from shifting.