Reflective Polarizing Plate for Thinned LCD with High Contrast
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Solution Overview
Problem
Existing liquid crystal display devices face challenges in thinning while maintaining high front contrast and avoiding coloration issues, particularly when replacing polarizing plates with reflective polarizing plates in the backlight unit.
Innovation Solution
Integrally laminating a reflective polarizing plate with a high degree of polarization (≥99.90% at 550 nm) with the liquid crystal cell, using a stretched film of polyethylene naphthalate or polyethylene terephthalate, and combining it with a polyvinyl alcohol-based film for the visible side polarizing plate to achieve thinning and improved contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a reflective polarizing plate is used as the backlight side polarizing plate, then the liquid crystal display device can be thinned, but the front contrast deteriorates and coloration occurs in black displays
Solution Approach 1:
The patent applies parameter changes by specifying that the reflective polarizing plate must have a degree of polarization P550 nm ≥ 99.90%, and by controlling the wavelength dependency of polarization through specific material selection (polyethylene naphthalate or polyethylene terephthalate stretched films). This ensures high front contrast while maintaining thinness.
Solution Approach 2:
The patent uses composite materials by combining the reflective polarizing plate (made from stretched polyethylene naphthalate or polyethylene terephthalate films) with a polyvinyl alcohol-based film for the visible side polarizing plate. This composite structure achieves both thinness and high front contrast without coloration.
2Length of stationary object
If a reflective polarizing plate is used as the backlight side polarizing plate, then the liquid crystal display device can be thinned, but coloration occurs in black displays
Solution Approach 1:
The patent controls the wavelength dependency of polarization by selecting specific materials (polyethylene naphthalate or polyethylene terephthalate) and controlling the stretching ratios, ensuring that the degree of polarization remains high across different wavelengths. This prevents coloration in black displays while maintaining device thinness.
3Ease of manufacture
If a reflective polarizing plate with insufficient degree of polarization is used, then manufacturing is easier, but the front contrast and degree of polarization deteriorate
Solution Approach 1:
The patent specifies precise parameter ranges: degree of polarization P550 nm ≥ 99.90%, stretching ratios in specific ranges, and temperature ranges for heating treatments. These controlled parameters ensure high manufacturing precision while maintaining ease of manufacture through standardized processes.
4Manufacturing precision
If the stretching ratio is increased to improve degree of polarization, then the degree of polarization improves, but photoelastic unevenness increases
Solution Approach 1:
The patent optimizes the stretching ratio to specific ranges (width direction: 2.0-4.0 times, longitudinal direction: 1.0-3.0 times) and controls the heating temperature ranges to achieve the desired degree of polarization while minimizing photoelastic unevenness. This balanced parameter control resolves the contradiction between polarization quality and optical uniformity.
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 enables the thinning of liquid crystal display devices while maintaining high front contrast and preventing coloration in black displays, reducing photoelastic unevenness and improving the degree of polarization across various wavelengths.
Implementation Method 1
a reflective polarizing plate which transmits only light vibrating in a specific polarization direction among light rays incident thereon while vibrating in all directions, and reflects light vibrating in the other polarization direction
Implementation Method 2
a stretched film of polyethylene naphthalate or polyethylene terephthalate
Data Source
AI summary
An aspect of the present invention relates to a liquid crystal panel including a visible side polarizing plate, a liquid crystal cell, and a backlight side polarizing plate, in which the backlight side polarizing plate is a reflective polarizing plate of which a degree of polarization P550 nm with respect to light at a wavelength of 550 nm is greater than or equal to 99.90%, and the reflective polarizing plate and the liquid crystal cell are integrally laminated, a liquid crystal display device, and a reflective polarizing plate and a manufacturing method thereof.