Birefringent Layer Hardness for LCD Spacer Subsidence
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Solution Overview
Problem
In liquid crystal display devices, the thickness of the driving liquid crystal layer can vary unexpectedly due to external forces, leading to fluctuations in light retardation and image quality, particularly when softer spacer layers are used, as they tend to subside under external acting forces, and existing measurement methods like Vickers hardness and pencil hardness do not accurately reflect the conditions of cylindrical spacers commonly used in these devices.
Innovation Solution
An optical element with a birefringent layer formed by aligning and polymerizing liquid crystal molecules on a substrate, where the birefringent layer has an indentation depth of 6% or less relative to its thickness, measured using a cylindrical indenter, and is heated between 150°C to 260°C to enhance hardness and stability, reducing the likelihood of spacer subsidence and maintaining consistent layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a soft layer structure is formed on the substrate surface and spacers are dispersively arranged, then the device can be manufactured with standard processes, but the spacers readily subside under external acting forces causing the driving liquid crystal layer thickness to vary
Solution Approach 1:
The patent changes the physical parameter of the layer structure by forming a birefringent layer with specific optical properties (retardation value) and controlled hardness. This layer is created by polymerizing liquid crystal molecules in a specific alignment state, transforming the substrate surface properties to provide both manufacturability and thickness stability.
Solution Approach 2:
The patent creates a composite structure by polymerizing liquid crystal molecules within a resin matrix to form a birefringent layer. This composite material combines the optical properties of liquid crystals with the structural stability of polymerized resin, providing both functionality and mechanical support for spacer stability.
2Ease of manufacture
If Vickers hardness or pencil hardness measurement methods are used for the birefringent layer, then standard hardness testing can be performed, but these methods do not accurately reflect the actual conditions of cylindrical spacers used in liquid crystal display devices
Solution Approach 1:
The patent replaces conventional hardness measurement methods (Vickers, pencil hardness) with an indentation depth measurement method using a cylindrical indenter. This substitution creates a measurement system that better reflects the actual mechanical conditions experienced by cylindrical spacers in the display device, providing more accurate predictions of spacer stability.
3Reliability
If the birefringent layer is heated to enhance hardness, then the layer stability improves, but the heating process requires additional manufacturing steps and energy consumption
Solution Approach 1:
The patent utilizes phase transition during polymerization and subsequent heating to transform the birefringent layer from a soft, unstable state to a hard, stable state. The heating process completes the polymerization reaction and sets the molecular structure, permanently enhancing the layer's mechanical properties and spacer-supporting 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
The optical element effectively reduces the risk of spacer subsidence and maintains consistent driving liquid crystal layer thickness, improving image quality and stability in liquid crystal display devices by providing a birefringent layer with enhanced hardness and thermal resistance, suitable for use in IPS mode and reducing the need for adhesives, which can cause light scattering.
Implementation Method 1
liquid crystal molecules contained in the coating film are polymerized to make the coating film a birefringent layer
Implementation Method 2
the polymerizable liquid crystal molecules contained in the coating film are polymerized to make the coating film a birefringent layer as an optical functional layer having an optical compensation function that causes birefringence of light
Data Source
AI summary
The present invention intends to provide an optical element that can be incorporated in a liquid crystal display device, is provided with a birefringent layer obtained by aligning and polymerizing polymerizable liquid crystal molecules, and, while sufficiently reflecting an actual condition of a liquid crystal display device, can reduce fear that a thickness of a driving liquid crystal layer unexpectedly varies. An optical element includes a light-transmitting base material and a birefringent layer comprising of aligned and polymerized liquid crystal molecules and having a value of indentation depth of 6% or less relative to a thickness of the birefringent layer, wherein said value is measured under conditions where a cylindrical indenter having a diameter of 30 (μm) is applied at a load of 10 mN/sec up to the maximum load of 400 mN.