Transparent LCD with Light Guide Plate and A-Film
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Solution Overview
Problem
Conventional liquid crystal display devices cannot be used as transparent displays due to their inability to emit light spontaneously, requiring a non-transparent backlight and polarizing plates, which limits their application in achieving high yield, large-sized, high reliability, wide viewing angle, high luminance, and high contrast ratio.
Innovation Solution
A transparent liquid crystal display device is designed with a liquid crystal panel, a light source, first and second polarizing plates, a light guide plate, and compensation films to change the polarized state of light, enhancing the viewing angle characteristic by controlling light transmission and phase difference values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polarizing plates are provided at both front and rear surfaces of the liquid crystal panel to control light transmission, then the liquid crystal display can control image display, but the device becomes non-transparent when liquid crystals are not driven
Solution Approach 1:
The patent removes the rear polarizing plate from the conventional liquid crystal display structure. By extracting this component, the display becomes transparent when not displaying images while maintaining the ability to control light transmission when images are displayed, thus resolving the contradiction between image control reliability and transparency ease of manufacture
Solution Approach 2:
The patent inverts the conventional approach by using a light guide plate that can both guide backlight and transmit natural light. Instead of using two polarizing plates to control transparency, the system uses the light guide plate's dual functionality to achieve transparency when not displaying and image control when displaying, applying the inversion principle to the light control mechanism
2Illumination intensity
If a non-transparent backlight unit is provided at the rear surface to emit light for image display, then the liquid crystal display can achieve high luminance and contrast ratio, but the display cannot be transparent
Solution Approach 1:
The patent applies the multi-functionality principle by designing the light guide plate to perform both backlight guidance and natural light transmission functions. This single component replaces the conventional non-transparent backlight unit, enabling the display to achieve high luminance when displaying images while maintaining transparency when not displaying, thus resolving the contradiction between illumination intensity and transparency
Solution Approach 2:
The light guide plate acts as an intermediary component that mediates between the backlight source and the liquid crystal panel. It guides the backlight to achieve high luminance and contrast ratio while simultaneously allowing natural light to pass through, enabling transparency. This intermediary structure resolves the contradiction by providing a middle ground that satisfies both requirements
3Reliability
If conventional liquid crystal display structure is used with polarizing plates at both surfaces, then light transmission can be controlled for image display, but the viewing angle characteristic is limited
Solution Approach 1:
The patent extracts the rear polarizing plate from the conventional structure, which not only enables transparency but also improves viewing angle characteristics. By removing this component that limited light transmission control, the display achieves both adequate light control for images and enhanced adaptability for wide viewing angles
Solution Approach 2:
The patent changes the optical parameters of the system by using the light guide plate with specific refractive index properties and phase difference films. These parameter changes enable the display to maintain good light transmission control while achieving wide viewing angles, as the modified optical path allows light to pass through more effectively from different angles
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 allows for a transparent liquid crystal display device that enables objects behind the display to be seen while maintaining image quality, reducing light leakage and enhancing contrast ratio, particularly at diagonal viewing angles.
Implementation Method 1
a light guide plate disposed at a lower portion of the liquid crystal panel to reflect totally the light polarized in an axis-direction by the first polarizing plate to a lateral surface of the light guide plate to supply the light to the liquid crystal panel
Implementation Method 2
a first positive A-film disposed at a lower portion of the liquid crystal panel to change the polarized state of the light supplying to the liquid crystal panel through the light guide plate, the horizontal direction phase difference value (Re) of the first positive A-film being approximately 100-150 nm
Data Source
AI summary
Disclosed is a transparent liquid crystal display device provided with a compensation film of a liquid crystal panel to change the polarizing state of light in an image mode thereby enhancing a viewing angle characteristic, and the transparent liquid crystal display device may include a liquid crystal panel; a light source disposed at one side of a lower portion of the liquid crystal panel to emit light; a first polarizing plate for polarizing the light emitted from the light source; a light guide plate disposed at a lower portion of the liquid crystal panel to totally reflect the light polarized to an axis by the first polarizing plate to a lateral surface thereof and supply to the liquid crystal panel, and transmit natural light entered from a lower direction therethrough; a second polarizing plate disposed at an upper portion of the liquid crystal panel to control the amount of polarized light transmitting the liquid crystal panel; and a first positive A-film disposed at a lower portion of the liquid crystal panel to change the polarized state of the light outputted from the light guide plate and supplied to the liquid crystal panel, wherein the horizontal direction phase difference value (Re) is 120 nm.