Asad Khan

Stacked Color Liquid Crystal Display Device

Application

#6377321 Apr 23, 2002

Filed

Jun 10, 1999

Inventor

Asad A. Khan (Kent, OH) · Xiao-Yang Huang (Stow, OH) · Haiji Yuan (Cupertino, CA) · Minhua Lu (Mohegan Lake, NY) · Ellison C. Urban (Alexandria, VA)

Appl. No.

09/329587

Assignee

Kent Displays, Inc. (Kent, OH)

International Classification

G02F 1137

U.S. Classification

349 35, 349 74, 349 80, 349176

Abstract

A liquid crystal display device includes cell wall structure and a chiral nematic liquid crystal material. The cell wall structure and the liquid crystal cooperate to form focal conic and twisted planar textures that are stable in the absence of a field. A device applies an electric field to the liquid crystal for transforming at least a portion of the material to at least one of the focal conic and twisted planar textures. The liquid crystal material has a pitch length effective to reflect radiation having a wavelength in both the visible and the infrared ranges of the electromagnetic spectrum at intensity that is sufficient for viewing by an observer. One liquid crystal material may be disposed in a single region or two or more liquid crystal materials may be used, each in separate regions even without the infrared reflecting layer. One aspect of the invention is directed to a photolithography method for patterning a substrate of the display. The display may also have multicolor capabilities by including separate layers of at least two or three liquid crystal materials that reflect visible light.

Claim

What is claimed is: 1. A reflective full color liquid crystal display device comprising: first chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a first color, second chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a second color, and third chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a third color, the liquid crystal of said first material, said second material and said third material having positive dielectric anisotropy; planar substrates that form therebetween a first region in which said first material is disposed, a second region in which said second material is disposed and a third region in which said third material is disposed, wherein said first region, said second region and said third region are stacked relative to each other and each of said first material, said second material and said third material extends continuously from near one of said substrates to near an adjacent one of said substrates; wherein said substrates cooperate with said first material, said second material and said third material to form in said first region, said second region and said third region, scattering focal conic and reflecting planar textures that are stable in the absence of a field; wherein incident light travels in a direction sequentially through said first region, said second region and said third region, said first region being closest to a viewer, comprising a light absorbing back layer disposed downstream of said third region relative to said direction of incident light; wherein the incident light is reflected by the planar textures of said first region, said second region and said third region such that reflected light leaving the display exhibits a color that is an additive mixing of combinations of said colors which are reflected from said planar textures, and said incident light passing through said first region, said second region and said third region is absorbed by said light absorbing back layer; and addressing means for applying an electric field for transforming at least a portion of the liquid crystal of at least one of said first material, said second material and said third material, to at least one of the focal conic and planar textures, wherein a proportion of at least one of said first material, said second material and said third material exhibits a planar texture in the absence of a field and a proportion of the at least one of said first material, said second material and said third material exhibits a focal conic texture in the absence of a field, wherein said addressing means provides an electric field pulse of sufficient amplitude and duration to change the proportions of the at least one of said first material, said second material and said third material in said planar and focal conic textures, whereby the intensity of light reflected may be selectively adjusted. 2. The display device of claim 1 comprising a layer of visible colored material disposed downstream of at least one of said first region, said second region and said third region relative to said direction of incident light. 3. The display device of claim 1 wherein said light absorbing back layer is a black layer disposed downstream of said third region relative to said direction of incident light. 4.

Chiral Additives For Cholesteric Displays

Application

#6830789 Dec 14, 2004

Filed

Sep 24, 2001

Inventor

Joseph W. Doane (Kent, OH) · Asad A. Khan (Kent, OH) · Alexander J. Seed (Stow, OH)

Appl. No.

09/937210

Assignee

Kent Displays, Inc. (Kent, OH) · Kent State University (Kent, OH)

International Classification

C09K 1952

U.S. Classification

428 13, 25229901, 428 11, 549430, 549453

Abstract

A unique class of chiral additive materials is disclosed for use in cholesteric displays that possess a helical twist power substantially independent of temperature. The additives have a solubility and a helical twist power large enough to be used as a single chiral component with little dilution of the physical properties of the nematic liquid crystal host mixture. The chiral additives may be used in combination with non-chiral additives to provide a helical twisting power substantially independent of temperature suitable for cholesteric displays.

Claim

What is claimed is: 1. An optically active compound of the formula: where the R2 and R3 groups are a lower alkyl group or an aryl or biaryl unit while the R1 groups independently each are a hydroxyl, alkoxyl, aryloxy, or arylalkoxy group, the R groups each represent a group as follows: A1—[—Z—]q—A2— where A1 is an aromatic group, an acyclic aliphatic group, or an alicyclic group, and A1 can be a substituted or unsubstituted, Z is a group selected from —O—, —OCO—, or —S—, and the coefficient q is 0 or 1 or Z is (CH2)nO where the coefficient n is 0 to 5 and the coefficient q is 1, and A2 is a bivalent radical of a naphthalene group, and the cyclic structure of A2, or A1 if it is cyclic, can be heterocyclic. 2. The optically active compound of claim 1, where each R substituent is independently selected as: where R4 represents a group as follows: Y—[—X—]n—[—Z—]q— where n is an integer value of ≧0, X is —CH═CH—CH2—, or (CH2)m— where m is an integer value of ≧1, Y is a radical of an aromatic hydrocarbon, an acyclic aliphatic hydrocarbon, or an alicyclic hydrocarbon, and Y can be substituted or unsubstituted. 3. The optically active compound of claim 2, where R4 is an aryloxy radical, an arylalkoxy radical, an arylalkyleneoxy, or an arylalkenyleneoxy radical. 4.

Single Substrate Liquid Crystal Display

Application

#7170481 Jan 30, 2007

Filed

Jan 28, 2005

Inventor

Joseph W. Doane (Kent, OH) · Asad A. Khan (Kent, OH) · Irina Shiyanovskaya (Stow, OH) · Tod Schneider (Kent, OH) · Oleg Pishnyak (Kent, OH) · Seth E. Green (Kent, OH) · Forrest N. Nicholson (Kent, OH)

Appl. No.

11/046487

Assignee

Kent Displays Incorporated (Kent, OH)

International Classification

G09G 3/36

U.S. Classification

345 87, 345 31

Abstract

The present invention relates to a display film that may be transferred by lamination or otherwise onto a substrate. The display film is formed of a stack of layers that can include different types, arrangements, and functionality within the stack depending upon factors including the characteristics of the substrate (e. g. , upper or lower, transparent or opaque, substrates) and addressing of the display (e. g. , active or passive matrix, electrical or optical addressing). The layers of the stacked display film include one or more electrode layers and one or more liquid crystal layers and, in addition, may include various combinations of an adhesive layer, preparation layer, casting layer, light absorbing layer, insulation layers, and protective layers. The liquid crystal layer can include cholesteric or other liquid crystal material. The liquid crystal layer can be a dispersion of liquid crystal in a polymer matrix formed by a variety of techniques.

Drapable Liquid Crystal Transfer Display Films

Application

#7796103 Sep 14, 2010

Filed

Jan 28, 2005

Inventor

J. William Doane (Kent, OH) · Asad A. Khan (Kent, OH) · Irina Shiyanovskaya (Stow, OH) · Albert Green (Springfield, VA)

Appl. No.

10/587591

Assignee

Kent Displays Incorporated (Kent, OH)

International Classification

G09G 3/36

U.S. Classification

345 87, 345 31

Abstract

The present invention relates to a display film that may be transferred by lamination or otherwise onto a substrate. The display film is formed of a stack of layers that can include different types, arrangements, and functionality within the stack depending upon factors including the characteristics of the substrate (e. g. , upper or lower, transparent or opaque, substrates) and addressing of the display (e. g. , active or passive matrix, electrical or optical addressing). The layers of the stacked display film include one or more electrode layers and one or more liquid crystal layers and, in addition, may include various combinations of an adhesive layer, preparation layer, casting layer, light absorbing layer, insulation layers, and protective layers. The liquid crystal layer can include cholesteric or other liquid crystal material. The liquid crystal layer can be a dispersion of liquid crystal in a polymer matrix formed by a variety of techniques.

Low Viscosity Liquid Crystal Material

Application

#6172720 Jan 9, 2001

Filed

May 23, 1997

Inventor

Asad Aziz Khan (Kent, OH) · Stanley Joseph Laskos (Diamond, OH) · Michael E. Stefanov (Stow, OH)

Appl. No.

8/862561

Assignee

Kent Displays Incorporated (Kent, OH)

International Classification

G02F 1133, G02F 1137, C09K 1954, C09K 1930

U.S. Classification

349 35

Abstract

A liquid crystal material for a display device includes a first chiral nematic liquid crystal component and a second component that exhibits no liquid crystalline phase at any temperature. The second component is present in an amount effective to reduce the bulk viscosity of the liquid crystal material by at least about 26% at room temperature or is present in an amount of at least about 5% by weight based upon the total weight of the liquid crystal material. The liquid crystal material may have a positive dielectric anisotropy. The second component may have a molecular weight not exceeding 205 grams/mole. Embodiments relate to a display device comprising the present material. Another aspect includes a method of increasing the switching speed in a display that employs the present material.

Electronic Display With Semitransparent Back Layer

Application

#2016009 Mar 31, 2016

Filed

Apr 3, 2015

Inventor

Matthew Schlemmer (Kent, OH) · Erica Montbach (Kent, OH) · Asad Khan (Kent, OH)

Appl. No.

14/678482

Assignee

Matthew Schlemmer (Kent, OH) · Erica Montbach (Kent, OH) · Asad Khan (Kent, OH)

International Classification

G02F 1/1333, G02F 1/1335, G02F 1/137

Abstract

An electronic display includes electrically conductive layers. An active layer is disposed between adjacent electrically conductive layers. The active layer includes cholesteric liquid crystal material. At least one transparent front substrate is disposed adjacent one of the electrically conductive layers near a front of the display. A semitransparent back layer absorbs light that passes through the active layer, reflects grey light or light of a color and is light transmitting. Electronic circuitry applies a voltage to the conductive layers that enables at least one of erasing or writing of the active layer.