See-through LCD with Crossed Polarizers for Contrast
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Solution Overview
Problem
Liquid crystal display devices used for see-through displays face challenges in achieving sufficient contrast ratio and proper image display due to the limitations of PDLC or PNLC panels, which struggle with black displaying and efficient light utilization, especially when another display panel is placed behind them.
Innovation Solution
A liquid crystal display device comprising two panels, where the first panel is capable of a transparent displaying state, allowing light from the second panel to be transmitted, with specific polarizer configurations and alignment films to ensure proper image display through the first panel, including twisted nematic-type liquid crystal layers and polarizers in crossed Nicols or parallel configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If PDLC or PNLC panels are used for see-through display, then polarizing plates are unnecessary and light utilization efficiency is improved, but black displaying capability is lost and contrast ratio is insufficient
Solution Approach 1:
The patent combines a see-through panel with a rear panel into an integrated display system. The see-through panel uses PDLC or PNLC material without polarizing plates for high light efficiency, while the rear panel provides additional display content. This merging allows the system to achieve both high light utilization and sufficient contrast by layering multiple display functions.
Solution Approach 2:
The see-through panel serves multiple functions: it acts as both a display medium for front-side content and a transmission medium for rear panel content. By making the see-through panel capable of both displaying images and transmitting light from the rear panel, the system achieves multi-functionality that resolves the contradiction between light efficiency and contrast capability.
2Adaptability or versatility
If another display panel is placed on the rear face side of the see-through panel, then display content is enhanced, but image display quality deteriorates in some cases
Solution Approach 1:
The see-through panel acts as an intermediary between the rear panel and the viewer. By carefully controlling the optical properties and positioning of the see-through panel, it mediates the interaction between rear panel light and front display content, preventing image quality deterioration while enabling enhanced display capability.
Solution Approach 2:
The display system is segmented into distinct functional layers: the rear panel for background content, the see-through panel for foreground content and light transmission control, and the front display elements. This segmentation allows each layer to be optimized independently, maintaining image quality while enhancing overall display versatility.
3Loss of information
If color filters and polarizing plates are provided in liquid crystal display device, then color displaying is achieved, but light absorption increases and efficiency of light utilization decreases
Solution Approach 1:
The patent extracts and removes the polarizing plates from the PDLC or PNLC panel structure. By taking out the polarizing plates which cause significant light absorption, the system achieves high light utilization efficiency while maintaining color displaying capability through the field sequential method and rear panel integration.
Solution Approach 2:
The system uses field sequential driving with periodic switching between red, green, and blue color fields. This periodic action enables color displaying without requiring color filters for each pixel, thereby reducing light absorption and improving overall light utilization efficiency while maintaining full color capability.
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 enables proper display of images from a rear panel through the first panel, improving contrast ratio and light utilization, allowing for high-quality see-through displays with enhanced viewing angle characteristics.
Implementation Method 1
a liquid crystal layer (30) which is capable of modulating a direction of polarization of light passing through the liquid crystal layer (30)
Implementation Method 2
a pair of polarizing plates (15, 25) which are capable of controlling transmittance of light passing through the liquid crystal layer (30)
Implementation Method 3
first and second electrodes (11, 21) which are capable of generating an electric field across the liquid crystal layer (30)
Data Source
AI summary
A liquid crystal display device (100) includes a first liquid crystal display panel (1) configured to be capable of taking a transparent displaying state and a second liquid crystal display panel (2), such that the first liquid crystal display panel allows at least a portion of light going out of the second liquid crystal display panel to be transmitted in the transparent displaying state. The first liquid crystal display panel includes a first liquid crystal layer (1L) interposed between a pair of substrates, and first and second polarizers (1F, 1B) between which the first liquid crystal layer is interposed; the second liquid crystal display panel includes a second liquid crystal layer (2L) interposed between a pair of substrates, and a third polarizer (2F) placed on a side of the second liquid crystal layer that is closer to the first liquid crystal display panel; the second polarizer (1B) of the first liquid crystal display panel is on a side closer to the second liquid crystal display panel; and a transmission axis of the second polarizer (1B) and a transmission axis of the third polarizer (2F) are not orthogonal.