Cholesteric Liquid Crystal Optical Member for Handwriting Input

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Solution Overview

Problem

Existing optical pen systems for digitizing handwritten information face challenges in achieving high visible light transmittance and low haze, which are essential for integrating with displays without compromising optical performance.

Innovation Solution

A novel optical member is developed, comprising a reflection layer made by fixing a cholesteric liquid-crystalline phase, which selectively reflects circularly-polarized light and has a high specular reflectance in the infrared region while maintaining high visible light transmittance and low haze, integrated with an information presentation layer for efficient handwriting input.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a conventional reflection layer is used to achieve high infrared reflectance, then the infrared reflection performance is improved, but the visible light transmittance decreases and haze increases

Engineering Contradiction:

Improveinfrared reflection performanceVSAvoidvisible light transmittance

Core Design Contradiction:

Use of energy by moving objectVSIllumination intensity

Solution Approach 1:

The reflection layer is segmented into multiple functional sub-layers: a first cholesteric liquid crystal layer for infrared reflection, a second cholesteric liquid crystal layer for circularly polarized light reflection, and a third cholesteric liquid crystal layer for additional infrared reflection. Each layer has specific helical pitch and refractive index characteristics that work together to achieve high infrared reflectance while maintaining visible light transmittance and low haze.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The reflection layer uses a composite structure combining multiple cholesteric liquid crystal materials with different optical properties. The first layer uses a material with a first refractive index and first helical pitch for infrared reflection, the second layer uses a material with a second refractive index and second helical pitch for circularly polarized light reflection, and the third layer uses a material with a third refractive index and third helical pitch for additional infrared reflection. This composite approach enables simultaneous optimization of infrared reflection and visible light transmittance.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If a conventional reflection layer is used to achieve high infrared reflectance, then the infrared reflection performance is improved, but the haze increases

Engineering Contradiction:

Improveinfrared reflection performanceVSAvoidhaze

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention optimizes specific parameters of the cholesteric liquid crystal layers: the half-value width of the selective reflection band is controlled within 50-500 nm, the visible light transmittance is maintained at 50% or more, and the haze is reduced to 2% or less. These parameter optimizations enable high infrared reflectance while minimizing haze.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If a cholesteric liquid-crystalline phase layer is used for selective reflection, then the circularly-polarized light reflection is improved, but the visible light transmittance and haze control become challenging

Engineering Contradiction:

Improvecircularly-polarized light reflectionVSAvoidvisible light transmittance

Core Design Contradiction:

Use of energy by moving objectVSIllumination intensity

Solution Approach 1:

The second cholesteric liquid crystal layer acts as an intermediary between the first and third layers. It selectively reflects circularly polarized light while allowing other wavelengths to pass through, effectively mediating the optical interaction between the infrared-reflecting first layer and the third layer. This intermediary layer enables the system to achieve high circularly-polarized light reflection while maintaining visible light transmittance.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 member provides a high visible light transmittance and low haze, enabling its use as a handwriting input sheet that can be stuck to or integrated with displays, enhancing the optical performance and usability of optical pen systems.

Implementation Method 1

the circularly-polarized light reflection layer consisting of a layer obtained by fixing a cholesteric liquid-crystalline phase

Methodology Applied

Scientific EffectCholesteric liquid crystal selective reflection: Cholesteric Liquid Crystal

Implementation Method 2

the reflection layer including one or more circularly-polarized light reflection layers selected from the group consisting of a right circularly-polarized light reflection layer that selectively reflects right circularly-polarized light and a left circularly-polarized light reflection layer that selectively reflects left circularly-polarized light

Methodology Applied

Scientific EffectCircularly-polarized light reflection: Reflection

Implementation Method 3

the information presentation layer having a pattern of a material that absorbs or reflects light of the reflection wavelength

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentUS9910197B2Optical member and display including the optical member

Publication Date: 2018.03.06 FUJIFILM CORP

AI summary

The present invention provides an optical member including a reflection layer and an information presentation layer, the reflection layer comprising one or more circularly-polarized light reflection layers selected from the group consisting of a right circularly-polarized light reflection layer and a left circularly-polarized light reflection layer, the circularly-polarized light reflection layer consisting of a layer obtained by fixing a cholesteric liquid-crystalline phase, the reflection layer having a reflection wavelength at which a specular reflectance for non-polarized light is more than 20% in a wavelength region in which the circularly-polarized light reflection layer exhibits selective reflection, a diffuse reflectance for non-polarized light at the reflection wavelength less than 50%, the reflection wavelength being in an infrared wavelength region, and the information presentation layer having a pattern of a material that absorbs or reflects light of the reflection wavelength. The optical member can be used as a handwriting input sheet, which can be used by being stuck to the surface of a display.