Liquid Crystal Mirror Voltage Sweep for Uniform Display Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The use of a vertical alignment (VA)-type liquid crystal layer in a mirror and image switching apparatus results in display unevenness due to fluctuations in pretilt angles of liquid crystal molecules and backflow phenomena during voltage transitions, leading to nonuniform transparent states.
Innovation Solution
A control circuit sweeps the drive voltage between transparent electrodes of a vertical alignment-type liquid crystal layer from an initial voltage to a saturated voltage over a predetermined time, ensuring uniform alignment of liquid crystal molecules by controlling the sweeping time and initial voltage to prevent backflow and display nonuniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vertical alignment-type liquid crystal layer is used in the liquid crystal mirror unit, then the mirror state can be achieved with liquid crystal molecules perpendicular to the substrate, but display unevenness occurs due to pretilt angle fluctuations and backflow phenomena during voltage transitions
Solution Approach 1:
The patent applies preliminary action by introducing a gradient voltage that increases gradually from 0V to the target voltage over a predetermined period before the actual switching occurs. This preliminary voltage application aligns the liquid crystal molecules in a controlled manner, preventing backflow phenomena and ensuring uniform display state transitions without the display unevenness that would otherwise occur with abrupt voltage changes
2Speed
If the drive voltage is rapidly changed to switch between mirror and image displaying states, then the switching speed is improved, but backflow phenomena cause nonuniform transparent states
Solution Approach 1:
The patent implements periodic action through a multi-stage voltage control method where the drive voltage is applied in a structured sequence: first a gradient voltage over a predetermined period, then a hold period, and finally the main switching voltage. This periodic, staged approach maintains uniform transparent states while achieving fast overall switching by optimizing each phase of the voltage transition
3Ease of manufacture
If pretilt angles of liquid crystal molecules fluctuate due to rubbing process unevenness, then the liquid crystal layer can be manufactured, but display unevenness occurs in the mirror state
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the drive voltage characteristics based on the liquid crystal layer's response. By monitoring and adapting the voltage parameters (gradient slope, hold duration, amplitude) during operation, the system compensates for manufacturing variations in pretilt angles, ensuring uniform display performance despite variations in the rubbing process
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 achieves uniform display states by aligning liquid crystal molecules in the same direction, eliminating display nonuniformity and ensuring consistent transitions between mirror and image displaying states.
Implementation Method 1
an absorption-type polarizing plate 24 provided on the side of the transparent electrode 22 having a horizontal transmission axis TX1 for transmitting first linearly polarized light and absorbing second linearly polarized light intersecting the first linearly polarized light
Implementation Method 2
a reflection-type polarizing plate 25 provided on the side of the transparent electrode 23 having a vertical transmission axis TX2 for transmitting the second linearly polarized light and reflecting the first linearly polarized light
Implementation Method 3
a twisted nematic (TN)-type liquid crystal layer 21... when the drive voltage VD between the transparent electrodes is in an OFF state (for example, VD=0V), since the polarization axis of the TN-type liquid crystal layer 21 is changed
Implementation Method 4
the first linearly polarized light of external light EL passes through the absorption-type polarizing plate 24 and the liquid crystal layer 21, and then, is reflected by the reflection-type polarizing plate 25
Data Source
AI summary
In apparatus capable of switching a mirror state and an image displaying state, a liquid crystal mirror unit 2′ is provided ahead of an image displaying unit 1. The liquid crystal mirror unit 2′ has as a vertical alignment-type liquid crystal layer 21′, first and transparent electrodes 22, 23 sandwiching the vertical alignment-type liquid crystal layer 21′, an absorption-type polarizing plate 24 having a first transmitting axis TX1 for transmitting first linearly polarized light and absorbing second linearly polarized light intersecting the first linearly polarized light, and a reflection-type polarizing plate 25 having a second transmitting axis TX2 for transmitting the second linearly polarized light and reflecting the first linearly polarized light. A control circuit 3 sweeps a drive voltage VD between the first and second transparent electrodes of the liquid crystal mirror unit 2′ for a predetermined sweeping time TS to increase the drive voltage from an OFF state of the vertical alignment-type liquid crystal layer 21′ via an initial voltage VS to a predetermined voltage Vmax causing an ON state of the vertical alignment-type liquid crystal layer 21′.