Trans-Reflective IPS LCD Single Cell Gap Design
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Solution Overview
Problem
Trans-reflective type ECB-LCD devices face challenges with dual cell gap structures causing low productivity and narrow viewing angles due to stepped portions and vertical electric fields, which hinder their application in portable devices and indoor use.
Innovation Solution
A trans-reflective type In-Plane Switching (IPS) LCD device with a single cell gap structure, featuring alignment layers that align LC molecules in the transmission region and twist them in the reflection region to achieve a horizontal electric field, minimizing disclination at the interface between transmission and reflection regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a dual cell gap structure is used in trans-reflective type ECB-LCD devices, then the optical characteristics in transmission and reflection regions can be compensated, but the productivity decreases due to stepped portions and complex manufacturing
Solution Approach 1:
The patent merges the transmission region and reflection region into a single cell gap structure, eliminating the need for dual cell gap configurations. This is achieved by forming a first pixel electrode and second pixel electrode on the same substrate plane, with the second pixel electrode having a stepped portion only in the thickness direction to maintain electrical connection while keeping the LC layer thickness uniform. This resolves the contradiction by combining previously separate structures into one integrated design.
Solution Approach 2:
The patent introduces a dimensional change by creating a stepped portion in the second pixel electrode only in the thickness direction (vertical dimension), while maintaining the same cell gap in the horizontal plane. This allows the electrode to extend into the reflection region without creating stepped portions that would affect LC layer uniformity, thereby maintaining manufacturing simplicity while achieving optical compensation.
2Manufacturing precision
If a dual cell gap structure with stepped portions is used, then optical characteristics can be adjusted, but the viewing angle becomes narrow due to vertical electric field configuration
Solution Approach 1:
The patent replaces the vertical electric field mechanism (mechanical field orientation) with a horizontal electric field mechanism generated by the in-plane switching configuration. The first and second pixel electrodes are positioned to generate electric fields parallel to the substrate plane, causing LC molecules to rotate horizontally rather than vertically. This substitution fundamentally changes the field orientation from vertical to horizontal, enabling wide viewing angles while maintaining optical control.
Solution Approach 2:
The patent changes the fundamental parameter of electric field orientation from vertical to horizontal by reconfiguring the pixel electrode arrangement. The first pixel electrode and second pixel electrode are positioned such that their interaction generates horizontal electric fields, transforming the LC molecule orientation from vertical to horizontal. This parameter change directly addresses the viewing angle limitation while preserving optical characteristic control through the aligned configuration.
3Manufacturing precision
If alignment layers are configured for both transmission and reflection regions, then LC molecule alignment can be optimized, but disclination occurs at the interface between regions
Solution Approach 1:
The patent applies different alignment configurations to different regions: the first alignment layer in the transmission region is configured for horizontal alignment, while the second alignment layer in the reflection region is configured for vertical alignment. This local differentiation optimizes LC molecule alignment for each region's specific optical requirements while the gradual transition through the stepped portion minimizes interface disclination.
Solution Approach 2:
The stepped portion of the second pixel electrode serves as an intermediary structure that mediates between the horizontal alignment requirement of the transmission region and the vertical alignment requirement of the reflection region. This intermediate structure allows for a gradual transition of LC molecule orientation, reducing the abrupt discontinuity that would cause disclination at the interface.
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 enables a wide viewing angle and minimizes disclination, enhancing the display quality and portability of the LCD device by maintaining a single cell gap across both regions, thus improving productivity and screen quality.
Implementation Method 1
an LC layer formed between the first substrate and the second substrate
Implementation Method 2
a first alignment layer formed on the first substrate; a second alignment layer formed in the transmission region on the second substrate facing the first substrate; a third alignment layer formed in the reflection region on the second substrate facing the first substrate
Implementation Method 3
a lower polarizer formed below the first substrate; an upper polarizer formed above the second substrate, and having a transmission axis perpendicular to a transmission axis of the lower polarizer
Implementation Method 4
a reflection layer formed in the reflection region on the first substrate, and reflecting light incident from outside
Data Source
AI summary
A trans-reflective type In-Plane Switching (IPS)-LCD device capable of implementing a single gap and a wide viewing angle, and minimizing an occurrence area of disclination at an interface between a transmission region and a reflection region, and a method for designing the same. First and second alignment layers have characteristics to allow LC in a transmission region can be aligned in the same direction as a transmission axis of a lower polarizer. A third alignment layer is aligned so that the LC in the reflection region can be twisted from a lower side to an upper side with a predetermined twisted angle (θ). Here, the twisted angle (θ) of the LC in the reflection region, and an angle (α) between an alignment direction of an uppermost LC in the reflection region and the transmission axis of the upper polarizer are set so that optical reflectivity in the reflection region is ‘0’ when the LC is not driven.