Liquid Crystal Display Polarizing Plate Light Leakage Control
Solution Overview
Problem
Liquid crystal display devices suffer from low contrast ratios due to light leakage in oblique directions caused by poor viewing angle characteristics of polarizing plates and prism sheets, leading to side lobes that increase luminance in specific directions, which deteriorates the contrast ratio in the front direction.
Innovation Solution
A liquid crystal display device configuration that includes a first polarizer, a liquid crystal panel, a second polarizer, a retarder, and a third polarizer with specific transmission axes and thickness retardation values, along with a prism sheet having uneven portions, to control light distribution and polarization, thereby reducing light leakage and improving contrast ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a prism sheet is used to increase backlight luminance, then the luminance in specific directions is increased, but side lobes are generated that cause light leakage in oblique directions and deteriorate contrast ratio
Solution Approach 1:
The invention utilizes the side lobe phenomenon of the prism sheet, which normally causes light leakage, and converts it into a beneficial effect by strategically positioning polarizing plates to block the leaked light. The polarizing plates are arranged with specific transmission axis orientations to intercept light from oblique directions, transforming the harmful side lobe effect into an opportunity to enhance contrast ratio through selective light blocking.
Solution Approach 2:
The invention introduces polarizing plates as intermediary elements between the backlight and the liquid crystal panel. These polarizing plates serve as mediators that selectively transmit or block light based on their polarization characteristics, thereby controlling the light distribution and preventing light leakage from reaching the display area while maintaining the luminance-enhancing function of the prism sheet.
2Ease of operation
If polarizing plates with viewing angle dependence are used, then polarization control is achieved, but light leakage occurs in oblique directions that reduces contrast ratio
Solution Approach 1:
The invention applies different polarization control characteristics to different regions by using multiple polarizing plates with different transmission axis orientations. Each polarizing plate is positioned and oriented to specifically address light leakage from particular oblique directions, creating localized polarization control that collectively prevents light leakage across the entire viewing angle range while maintaining effective polarization control.
3Adaptability or versatility
If multiple optical elements are stacked to control viewing angle characteristics, then viewing angle control is improved, but device complexity increases
Solution Approach 1:
The invention makes the polarizing plates serve multiple functions: they simultaneously control the polarization state of light for the liquid crystal panel operation and block light from oblique directions to prevent light leakage. This multi-functionality reduces the need for separate optical elements dedicated solely to viewing angle control, thereby managing device complexity while achieving improved viewing angle characteristics.
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 proposed configuration effectively restricts light leakage from oblique directions, enhancing the contrast ratio in the front direction by aligning the polarizing louver's dimming azimuth with the prism sheets' luminance increase azimuths, resulting in improved display quality.
Implementation Method 1
a first polarizer including a first transmission axis; a liquid crystal panel; a second polarizer including a second transmission axis
Implementation Method 2
a birefringent layer having a biaxial order parameter NZ satisfying 10≤NZ or NZ≤−9, the birefringent layer having an absolute value of thickness retardation |Rth| satisfying |Rth|≥200 nm
Implementation Method 3
a prism sheet used for increasing the luminance of a backlight (BL) also has poor viewing angle characteristics
Implementation Method 4
a third polarizing plate 113 that is a reflective polarizing plate
Data Source
AI summary
Provided is a liquid crystal display device and a polarizing plate capable of improving the contrast ratio in the front direction. The polarizing plate includes a pair of polarizers including a first polarizer and a second polarizer whose transmission axes are parallel to each other; a retarder between the paired polarizers; and a diffusion layer in at least one of a region between the paired polarizers or a region on a side without the retarder of the first polarizer.