Oblique Vapor Deposition Phase Difference Plate for Liquid Crystal Contrast
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Solution Overview
Problem
Existing phase difference plates used in liquid crystal display devices suffer from reduced contrast due to light scattering caused by the relaxation of columnar structures in oblique vapor deposition films, leading to a deterioration in the quality of the phase difference plate and decreased contrast ratios.
Innovation Solution
A phase difference plate with an oblique film having a columnar structure inclined with respect to the substrate's normal line, exhibiting refractivity anisotropy, where the principal refractive indices satisfy specific conditions, and the phase difference ratio Re(+30) to Re(-30) is between 1.1 and 4.0, suppressing haze to 0.1% or less, and using materials like silicon, niobium, or tantalum oxide to enhance optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an oblique vapor deposition film is used as a phase difference plate, then the phase difference compensation function is provided, but light scattering occurs due to relaxation of the columnar structure, causing cloudiness and deterioration of phase difference plate quality
Solution Approach 1:
The patent uses a composite structure consisting of an oblique vapor deposition film with a columnar structure and a front vapor deposition film with a planar or fine granular structure. This composite configuration allows the oblique film to provide phase difference compensation while the front film suppresses light scattering and prevents cloudiness, thereby resolving the contradiction between maintaining optical function and preventing harmful light scattering.
Solution Approach 2:
The patent applies different structural characteristics to different regions/layers of the phase difference plate. The oblique vapor deposition film has a columnar structure optimized for phase difference compensation, while the front vapor deposition film has a planar or fine granular structure optimized for suppressing light scattering. This local differentiation of structural quality allows each layer to perform its specific function without compromising the other.
2Stability of the object's composition
If the columnar structure in the oblique vapor deposition film relaxes, then the film structure becomes less stable, but light scattering increases and the film becomes cloudy, deteriorating phase difference plate quality
Solution Approach 1:
The front vapor deposition film acts as an intermediary layer between the oblique vapor deposition film and the incident light. This intermediate film suppresses light scattering before the light enters the oblique film, preventing the harmful effects of light scattering even when the columnar structure relaxes. The intermediary film thus protects the overall system from the weaknesses of the oblique film's columnar structure.
3Illumination intensity
If a phase difference compensation plate is used to improve black display contrast, then some light transmission through the analyzer is reduced, but the liquid crystal layer's refractivity anisotropy causes phase difference that allows light transmission, decreasing contrast
Solution Approach 1:
The composite structure of the oblique vapor deposition film and front vapor deposition film creates optimized optical properties. The oblique film provides the necessary phase difference compensation to counteract the liquid crystal layer's refractivity anisotropy, while the front film's light scattering suppression ensures that the compensation works effectively, thereby improving black display contrast and maintaining compensation reliability.
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 effectively improves contrast and reduces black display unevenness by minimizing light scattering, achieving a high contrast ratio and maintaining the quality of the phase difference plate, even when applied to liquid crystal display elements.
Implementation Method 1
the liquid crystal layer has refractivity anisotropy (also called birefringence) which causes a difference in refractive index between polarized light with different polarization axes
Implementation Method 2
the phase difference compensation plate reduces the amount of light transmitted through the analyzer by generating a phase difference which cancels the phase difference caused by the liquid crystal layer
Implementation Method 3
due to relaxation of a columnar structure formed by a forest of a plurality of columnar structure bodies, light scattering occurs in the oblique vapor deposition film
Data Source
AI summary
Provided is a phase difference plate including a substrate and a phase difference film which is an oblique film, in which, in a case where three principal refractive indices in a biaxial refractive index ellipsoid exhibiting the refractivity anisotropy are defined as nx, ny, and nz, Conditional Expression (1) is satisfied, and in a case where an incidence angle in a direction inclined to the X-axis side with respect to the normal line is regarded as positive, a phase difference ratio Re(30) ratio, which is a ratio of Re(+30) of a phase difference of the incidence light with an incidence angle of +30° to Re(−30) of a phase difference of the incidence light with an incidence angle of −30°, satisfies Conditional Expression (2).ny>nx>nz (1)Re(30) ratio=Re(30)/Re(−30)=1.1 to 4.0 (2)