Transflective Display Layout for TFT Light Blocking and Off Stability

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Solution Overview

Problem

Transflective display devices experience display defects such as hazy unevenness due to light from the backlight unit diffusively reflecting onto the TFT channel portion, causing shifts in gate threshold voltage and inadequate off characteristics, especially at low frequencies.

Innovation Solution

A transflective display device design with a light blocking layer positioned between the switching element and reflective layer, where the reflective layer has an uneven shape on the back face side, and a circular polarization plate is used to block light from reaching the TFT, combined with interlayer insulating films and specific materials for the oxide semiconductor layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a reflective layer with an uneven shape (MRS) is provided on the back face side to enable transflective display, then display versatility is improved, but light from the backlight unit is diffusively reflected onto the TFT channel portion causing gate threshold voltage shift and off characteristic deterioration

Engineering Contradiction:

Improvetransflective display capabilityVSAvoidTFT off characteristics

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The first substrate is divided into a display region and a non-display region, with the TFTs located in the non-display region. The light blocking layer is selectively formed only in the non-display region, segmenting the light blocking function from the display area while maintaining TFT protection from diffusive reflection.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A light blocking layer is introduced as an intermediary element between the backlight unit and the TFT channel portion. This layer blocks the diffusively reflected light from reaching the TFTs, preventing gate threshold voltage shift while allowing the reflective layer with MRS to maintain its transflective display function.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If the gate size is increased to prevent light from hitting the semiconductor layer, then light blocking is improved, but device complexity and area increase

Engineering Contradiction:

Improvelight blocking to TFTVSAvoidgate size configuration

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The light blocking function is extracted from the gate structure itself and implemented as a separate light blocking layer in the non-display region. This allows the gate to maintain its original size and function while the dedicated light blocking layer handles the light shielding requirement.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If a light blocking layer is formed on the back face side to block light, then TFT off characteristics are improved, but manufacturing precision requirements increase

Engineering Contradiction:

ImproveTFT off characteristicsVSAvoidlight blocking layer positioning

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The light blocking layer is formed selectively only in the non-display region where TFTs are located, rather than covering the entire back face. This localized approach reduces the complexity of alignment and positioning while effectively blocking light from reaching the TFT channel portion.

Inventive Principle:

Principle #3Local quality

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 design ensures favorable off characteristics and excellent display quality with low power consumption by effectively blocking light from the backlight unit and ambient light, preventing display defects like hazy unevenness.

Implementation Method 1

a light blocking layer configured to block light incident on the semiconductor element is formed on an element substrate side of the semiconductor element

Methodology Applied

Scientific EffectLight blocking: Absorption (EM radiation)

Implementation Method 2

the reflective layer 140 has an uneven shape such as the MRS on the back face side, the light from the backlight unit is diffusively reflected due to the uneven shape

Methodology Applied

Scientific EffectDiffuse reflection: Reflection

Implementation Method 3

a circular polarization plate is used to block light from reaching the TFT

Methodology Applied

Scientific EffectPolarization: Polarisation

Data Source

PatentUS20250377567A1Display device

Publication Date: 2025.12.11 SHARP DISPLAY TECHNOLOGY CORP

AI summary

A display device comprises a light source, a first substrate including a switching element including an oxide semiconductor layer, a display layer, and a second substrate, in this order from a back face side to an observation face side; and a plurality of pixels arranged in a matrix in a display region, wherein the first substrate includes a light blocking layer and a reflective layer on the observation face side relative to the switching element, the light blocking layer is positioned between the switching element and the reflective layer, at least a surface of the reflective layer on the back face side has an uneven shape, and each of the plurality of pixels includes a reflective region and a transmissive region, the reflective region is configured to reflect light at the reflective layer and to perform display, and the transmissive region is configured to transmit light and to perform display.