WO2014210165A2

WO2014210165A2 - Polymer-dispersed blue-phase liquid crystal films

Info

Publication number: WO2014210165A2
Application number: PCT/US2014/044112
Authority: WO
Inventors: Liang-Chy Chien; Jeoung-Yeon Hwang; Emine KEMIKLIOGLU
Original assignee: Kent State University
Priority date: 2013-06-25
Filing date: 2014-06-25
Publication date: 2014-12-31
Also published as: WO2014210165A3

Abstract

A polymer-dispersed blue-phase (PDBP) liquid crystal film is formed from a polymer-based latex and blue-phase liquid crystals that are combined using an emulsification process or a polymerization-induced phase separation process. The resultant PDBP liquid crystal film includes droplets formed by the polymer-based latex that encapsulate the blue-phase liquid crystals therein, so as to allow the blue-phase liquid crystals to have a blue phase at room temperature. As such, the PDBP liquid crystal film is conducive for use in manufacturing processes, such as LCD (liquid crystal display) manufacturing processes, while providing desirable optical features, such as field-induced birefringence at low switching voltages.

Description

POLYMER-DISPERSED BLUE-PHASE LIQUID CRYSTAL FILMS

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 61/839,047 filed June 25, 2013, the content of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to liquid crystal materials. In particular, the present invention relates to blue-phase liquid crystal dispersions that are encapsulated in polymer droplets. More particularly, the present invention relates to polymer-dispersed blue-phase (PDBP) liquid crystal films, in which the polymer encapsulated blue-phase liquid crystal droplets have a blue phase at room temperature.

BACKGROUND OF THE INVENTION

Blue-phase liquid crystals (BPLC) are locally-isotropic fluids in which the liquid crystal molecules organize themselves into complex three-dimensional (3D) structures that are characterized by crystallographic space group symmetry, whereby the blue-phase liquid crystals form double-twisted cylinders that are separated by defect lines. Specifically, as temperature increases, blue-phase liquid crystals enter one of these blue-phase (BP) network states, which are identified as: BP I, II and III. The blue-phase liquid crystals in the BP I and BP II network states, as shown in Figs. 1A and IB respectively, form soft, frequently coagulating platelet-domains, which are micrometer to sub-millimeter in size. Blue-phase liquid crystals in the BP I network state have a Bravis lattice that is body-centered, while the liquid crystals in the BP II network state have a Bravis lattice that is a simple cubic. However, blue-phase liquid crystals in the BP III network state have a cloudy and amorphous appearance, which is referred to as "blue fog", whereby light is selectively reflected, with light-scattering vectors forming a reciprocal Bravis lattice of a cubic periodic system.

As such, blue-phase liquid crystal (BPLC) materials have the potential to serve as a next-generation liquid crystal display (LCD) material due to their desirable operating features, which include field-induced birefringence, fast response or switching time between light- scattering and light-transmitting states, which may be in the the sub-millisecond range, and that is at least one order of magnitude faster than that attained by current nematic liquid crystal (NLC) type displays. Blue-phase liquid crystals are also desirable materials for LCD displays, as blue-phase liquid-crystal based devices and materials do not require a surface-alignment layer, which is normally required in standard LCD displays. As a result, the fabrication process of blue-phase liquid-crystal based LCDs and other devices is greatly simplified, and as a result, time and manufacturing costs are reduced.

Polymer-dispersed liquid crystals (PDLCs) are a class of optical materials that can be prepared by polymerization or through solvent evaporation- induced phase separation. PDLCs typically include micron-sized liquid crystal droplets that are encapsulated in matrices of optically transparent polymers. Specifically, the liquid crystal molecules nucleate and form droplets with a disparity in size and shape that depends on the particular attributes of the phase- separation process used, such as the rate of polymer gelation, for example. Thus, at zero- applied voltage, the indices of refraction between the polymer and the liquid crystal molecules are mismatched, causing the phase-separated PDLC film to normally appear milky and scatter incident ambient light. As a result, PDLC-based films can be switched from a light-scattering state to a light-transparent state or vice versa in response to an applied voltage. Compared to conventional nematic liquid crystal (NLC) type displays and devices, PDLC devices have many advantages, including high light transmittance and the lack for the need of polarizers and alignment films. Consequently, PDLC devices have been used in broad applications, ranging from switchable light modulators and smart windows to information displays, switchable lenses and holographically-formed optical elements and devices, for example.

Thus, it would be desirable to incorporate blue-phase liquid crystals (BPLC) into a polymer-dispersed liquid crystal (PDLC) material to form a polymer-dispersed blue-phase (PDBP) liquid crystal material, such as a film, which incorporates the benefits of typical PDLC materials (high light transmittance, lack of need of polarizers and alignment films) with that of blue-phase (BP) liquid crystals (field-induced birefringence, fast-response/switching time between light-scattering and light-transmitting states at low voltage levels). However, manufacturing such PDBP materials is made difficult in part due to the inability of the blue- phase liquid crystals to achieve their blue phase at room temperature.

Therefore, there is a need for a polymer-dispersed blue-phase (PDBP) liquid crystal material, such as a film that achieves its blue phase at room temperature to facilitate its fabrication and its use in various devices, such as optical retardation films, switchable light shutters, LCD display devices, and the like. Furthermore, there is a need for a polymer- dispersed blue-phase (PDBP) liquid crystal material, such as a film that is compatible for use in an electro -optical cell, such as an IPS (in-plane switching) cell, that utilizes flexible or drapeable substrates that may be mechanically flexed, bent, or deformed. Moreover, there is a need for a polymer-dispersed blue-phase (PDBP) liquid crystal material, such as a film, that has high light transmittance, lacks the need for use of polarizers and alignment films, allows field- induced birefringence, and provides fast-response/switching times between light-scattering and light-transmitting states. In addition, there is a need for a polymer-dispersed blue-phase (PDBP) liquid crystal material, such as a film, that is compatible for use with a continuous fabrication processes used to manufacture optical devices, such as LCD displays.

SUMMARY OF THE INVENTION

In light of the foregoing, it is a first aspect of the present invention to provide an electro-optical cell, and electro-optical cell comprising a first at least partially -transparent substrate; a second at least partially-transparent substrate; a light-control layer disposed between and first and second at least partially-transparent substrates, and light-control layer comprising a mixture of a polymer-based latex and a plurality of blue-phase liquid crystals to form an emulsion thereof, such that and polymer-based latex forms a plurality of droplets, such that at least one of and plurality of droplets encapsulate one or more of and plurality of blue- phase liquid crystals; and a first and a second at least partially-transparent electrode disposed on and first at least partially-transparent substrate, and electrodes spaced from each other and positioned adjacent to and light-control layer, wherein when a first voltage is applied across and electrodes, and light control is placed in a light-scattering state, and when a second voltage is applied across and electrodes, and light-control layer is placed in an at least partially light- transparent state.

It is a further aspect of the present invention to provide a method of forming an electro- optical cell comprising preparing a mixture of a plurality of blue-phase liquid crystals and a polymer-based latex; shaking and mixture; stirring and mixture in an ultrasonic bath at room temperature to form an emulsion, whereby and polymer-based latex forms a plurality of droplets, such that at least one and plurality of droplets encapsulates one or more of and plurality of blue phase crystals therein; and disposing and emulsion between a pair of spaced at least partially-transparent substrates to form a light-control layer, such that at least one of and substrates includes a pair of spaced at least partially-transparent electrodes thereon adjacent to and light-control layer.

It is yet another aspect of the present invention to provide a method of forming an electro-optical cell comprising preparing a mixture of a photopolymerizable monomer, a photoinitiator, and a plurality of blue-phase liquid crystals; stirring and mixture; disposing and stirred mixture between a pair of spaced at least partially-transparent substrates to form a light- control layer, such that at least one of and substrates includes a pair of spaced at least partially- transparent electrodes thereon adjacent to and light-control layer; and exposing and mixture to UV (ultraviolet) light, whereby and photopolymerizable monomer forms a plurality of droplets, such that at least one of and plurality of droplets encapsulates one or more of and plurality of blue phase crystals therein.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings wherein:

Fig. 1 A is a schematic view of blue-phase liquid crystals in blue-phase network state I;

Fig. IB is a schematic view of blue-phase liquid crystals in blue-phase network state II;

Fig. 2 is an exploded schematic view of an electro-optical cell that includes polymer- dispersed blue-phase (PDBP) liquid crystal material in accordance with the concepts of the present invention;

Fig. 2A is a cross-sectional schematic view of the electro-optical cell of Fig. 2 in accordance with the concepts of the present invention;

Fig. 3 A is a photomicrograph of the PDBP liquid crystal material, referred to herein as PDBP1, having a concentration of about 33% latex in accordance with the concepts of the present invention;

Fig. 3B is a photomicrograph of the PDBP liquid crystal material, referred to herein as PDBP2, having a concentration of about 68% latex in accordance with the concepts of the present invention; Fig. 4 is a graph showing the size of polymer encapsulated droplets of blue-phase liquid crystals of the PDBP liquid crystal material as temperature changes in accordance with the concepts of the present invention;

Fig. 5 is a graph showing light reflectance as wavelength changes for various temperatures of the PDBP liquid crystal material in accordance with the concepts of the present invention;

Fig. 6 is a graph showing the reflected wavelength versus applied voltage of the PDBP liquid crystal material in the electro-optical cell with top-down electrodes having a cell gap of about a 22μπι in accordance with the concepts of the present invention;

Fig. 7 is a graph showing the normalized light transmittance versus applied voltage of the PDBPl liquid crystal film with a concentration of about 33% latex in an in-plane-switching (IPS) cell with inter-digitated electrodes on one substrate and no electrodes on the other substrate, and having an about a 15μηι cell gap in accordance with the concepts of the present invention;

Fig. 8 is a graph showing the normalized light transmittance versus applied voltage of the PDBP2 liquid crystal film with a concentration of about 68% latex (PDBP2) in an IPS cell with about a 22 μιη cell gap in accordance with the concepts of the present invention;

Fig. 9 is a graph showing the response time of the PDBP2 liquid crystal film with a concentration of about 68% latex in accordance with the concepts of the present invention;

Fig. 10 is a top view SEM (scanning-electron microscope) image of the polymer- dispersed blue-phase (PDBP) liquid crystals in accordance with the concepts of the present invention;

Fig. 10A is a cross-sectional view of the SEM image of the polymer-dispersed blue- phase (PDBP) liquid crystals of Fig. 10 in accordance with the concepts of the present invention;

Fig. 11 is a graph showing the normalized light transmittance versus applied voltage of the PDBP liquid crystal film formed using a polymerization-induced phase separation (PIPS) process in accordance with the concepts of the present invention;

Fig. 11 A is a schematic view of the electro-optical cell in accordance with the present invention in a light scattering state in accordance with the concepts of the present invention; Fig. 11 B is a schematic view of the electro-optical cell in accordance with the present invention in a partially light-transmitting state in accordance with the concepts of the present invention;

Fig. 11 C is a schematic view of the electro-optical cell in accordance with the present invention in a fully light-transmitting state in accordance with the concepts of the present invention; and

Fig. 12 is a graph showing the response time of the PDBP liquid crystal film formed using the polymerization-induced phase separation (PIPS) process in accordance with the concepts of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A polymer-dispersed blue-phase (PDBP) liquid crystal material or film 10, hereinafter referred to as "PDBP material", which is disposed in an electro-optical cell 12 is shown in Figs. 2 and 2A of the drawings. In particular, the PDBP material 10 forms a film in the electro- optical cell 12 that includes a plurality of polymer encapsulated droplets that contain blue- phase liquid crystals, which will be discussed in detail below. It should also be appreciated that while the following discussion relates to the electro-optical cell 12, a plurality of cells 12 can be organized and coupled together using known techniques to form electro-optical devices of any desired dimension and shape. It should also be appreciated that while the PDBP material 10 may comprise a thin film, the PDBP material 10 may be configured to take on any suitable dimension, including any desired thickness dimension.

Specifically, the PDBP material 10 is formed by an emulsification process, whereby an optically-transparent polymer-based latex 14, such as the polyurethane-based latex NEOREZ 967 or PVA (polyvinyl alcohol), is combined with water and blue-phase liquid crystals (BPLC) 16. However, it should be appreciated that other techniques for preparing the PDBP material 10 may be used.

In one aspect, the blue-phase liquid crystals 16 utilized by the present invention may be formed from a mixture of nematic liquid crystals and chiral dopants. That is, the blue-phase liquid crystals 16 may comprise a cyanobiphenyl -based nematic eutectic mixture with positive dielectric anisotropy and a chiral dopant with a moderate helical twisting power. For example, the blue-phase liquid crystals 16 may be formed as a mixture by weight ratio of about 62% nematic liquid crystal material and about 38% chiral dopant, such as R811 sold by Merck. However, it should be appreciated that other formulations to produce the blue-phase liquid crystals 16 may be used.

Furthermore, the PDBP material 10 formed by the emulsification process contemplated by the present invention may comprise, by weight ratio, about 33% latex 14 and about 67% blue-phase liquid crystals 16. In another aspect, the preferable composition of the emulsified PDBP material 10 comprises a polymer latex concentration from about 15% to 90%, and more preferably, from about 20% to 70%, while the preferable concentration of blue-phase liquid crystals 16 is from about 85% to 10%, and more preferably, from about 80% to 30%.

Furthermore, the PDBP material 10 prepared via the emulsification process may use a polymer-based latex, such as polyvinyl alcohol (PVA) for example, as previously discussed. Thus, in one aspect, the PDBP material 10 may include about 20% PVA, about 3% surfactant, and about 77% blue-phase liquid crystals.

The emulsification process utilized by the present invention to prepare the PDBP material 10 is carried out initially by mixing the polymer-based latex 14, water, and blue-phase liquid crystals 16 in a vortex shaker for approximately three minutes. The emulsification process is then completed by stirring this mixture in an ultrasonic bath at room temperature for approximately two hours. The resulting emulsion forms the PDBP material 10, as shown in Figs. 2 and 2A, whereby the blue-phase liquid crystals 16 are encapsulated in droplets 20 that are suspended in the polymer-based latex material 14. In other words, the emulsification process creates droplets 20 that are suspended in the polymer-based latex material 14, whereby the polymer-based latex material 14 forms a shell or outer surface 22 of the droplets 20 that contains the blue-phase liquid crystals 16.

Continuing, the PDBP material 10 is disposed in a gap 24, shown in Fig. 2 A, formed by the electro-optical cell 12, by filling or other suitable process, whereby the gap 24 is defined as a void disposed between spaced-apart first and second substrates 30,40. That is, the PDBP material 10 forms a film, which serves as a light-control layer 42 that is disposed between the first and the second substrates 30 and 40 of the electro-optical cell 12. It should be appreciated that the first and second substrates 30,40 may be at least partially light transparent. However, in other aspects, one of the substrates 30,40 may be opaque, while the other substrate is at least partially light transparent. In one aspect, the substrate 30 may include electrodes 50 and 52 disposed thereon that are adjacent to the light-control layer 42, while the other substrate 40 does not include any electrodes 50 and 52 disposed thereon. In another aspect, the electrodes 50 and 52 may be interdigitated and/or arranged in a top-down pattern, and may be at least partially light transparent. In another aspect, the electrodes 50,52 may be formed of indium- tin-oxide (ITO), however any suitable material may be used. It should also be appreciated that the substrates 30,40 and/or electrodes 50,52 may be configured to be flexible, bendable, conformable, drapeable, or rigid. In one aspect, the electro-optical cell 12 may comprise an in- plane switching (IPS) optical cell for example. It should also be appreciated that the electrodes 50,52 may have an approximate ΙΟμηι electrode line width, and an approximate ΙΟμπι space between adjacent lines forming the electrodes 50 and 52. However, it should be appreciated that any other suitable dimension may be used with regard to electrode 50,52 line width, and electrode line spacing. Moreover, the electro-optical cell 12 is configured so that the gap 24 may be approximately 22μιη, which may be established by ball spacers, or other suitable component, although the gap 24 may take on any other suitable dimension. Thus, applying a suitable voltage across the electrodes 50,52 allows the PDBP material 12 of the light-control layer 42 to be switched into either of an opaque state ( . e. light-scattering) or a light-transparent state, as well as progressive states therebetween.

To evaluate the influence of the blue-phase liquid crystal droplets 20 on the electro- optical properties of the electro-optical cell 12, the polymer morphology of the PDBP material or film 10 was determined using a scanning electron microscope (SEM) after removal of the blue-phase liquid crystal molecules with organic solvent. Specifically, the electro-optical cell 12 was opened carefully, and the PDBP film 10 was deposited on a thin layer of gold under vacuum to enhance the contrast and resolution of the image generated by the microscope.

The texture of the PDBP film 10 was evaluated using a polarizing optical microscope and a computer-controlled hot stage. Figs. 3 A and 3B show images of two PDBP films 10 each having different concentrations of polymer latex, which are respectively designated herein as "PDBP1" and "PDBP2". Specifically the PDBP1 material 10 shown in Fig. 3 A, was prepared with a mixture of blue-phase liquid crystals 16 and 33% NEOREZ polymer latex 14, while the PDBP2 material, shown in Fig. 3B, was prepared with a mixture of blue-phase liquid crystals 16 and 68% NEOREZ polymer latex 14. As such, the PDBP1 material 10 and the PDBP2 material 10 had an average droplet 20 size of around 16μηι and 55μηι, respectively. The texture of the dispersed BPLC droplets 20 viewed between a pair of polarizers crossed at 90 degrees showed uniform texture and reflected bluish-green color of the BP I network state at room temperature. The photomicrograph images of Figs. 3A-B also show droplets 20 formed in clusters resulting from the coalescence of small interconnected droplets or partially merged droplets with the boundary lines that are clearly exhibited across the surface of the droplets for the PDBPl material 10.

Fig. 4 shows the size of the droplets 20 of the PDBP1 material 10 plotted as a function of temperature. Furthermore, the average size of the droplets 20 was analyzed based on the enlarged photomicrograph images of Fig. 3 A with an error bar of approximately +/-3μιη. Clusters of smaller droplets 20 were found to merge and form bigger droplets via thermal treatment, such as from the slow cooling transition from an isotropic temperature to room temperature. The reflection spectra of the droplets 20 was measured with an OCEAN OPTICS spectrometer at various temperatures, such that a plot of the reflectance versus Bragg reflection wavelength at various temperatures for the PDBP1 material 10 is shown in Fig. 5. As a result, a blue shift in reflected wavelength is observed as temperature increases.

The electrostriction effect (i.e. field-induced color change) of the electro-optical cell 12 using the PDBP1 material 10 was also evaluated, whereby Fig. 6 shows the plot of reflection wavelength versus the increase in the applied voltage for the polymer-dispersed blue-phase (PDBP) material 10 formed of NEOREZ latex 14 and blue-phase liquid crystals 16 in the electro-optical cell 12 with a top-down electrode 50,52 configuration and an approximate 22μιη cell gap 24 at room temperature. As such, a hysteresis was exhibited in the recovery of the color-reflected state, while the field-induced color change showed a blue shift of up to about 25 nm as the voltage applied to the cell 12 was increased from about 0V to 50V; while a red shift in reflected wavelength was observed for voltages above about 60V. Furthermore, as the applied voltage was decreased, the wavelength shift was found to be negligible.

The optical Kerr effect of the PDBP1 film or material 10 in the IPS electro-optical cell 12 with a cell gap 24 of approximately 15μηι was also evaluated. In particular, Fig. 7 shows a plot of normalized light transmittance versus applied voltage of the PDBP1 film 10. Specifically, the electro-optical cell 12 was tested with a blue laser (lambda=488nm), whereby the electro-optical cell 12 was switched from a dark or light-scattering state to a light- transmitting state, whereby the threshold voltage was found to be about 14.6V and the turn on voltage to be about 3 IV, as shown in Fig. 7.

Fig. 8 shows a plot of normalized light transmittance versus applied voltage of the PDBP2 material or film 10, whereby the IPS electro-optical cell 12 has a cell gap 24 of about 15μιη and its electrodes 50,52 aligned at approximately 45 degrees between a pair of polarizers crossed at 90 degrees. The threshold voltage was measured as to be about 9.66V and the turn- on voltage measured to be about 44.8V for the PDBP2 material 10. In addition, the response time of the PDBP2 material 10 was determined by switching the electro-optical cell 12 between the corresponding voltages of 10% light transmittance (Vio) and 90% light transmittance (V90), as shown in Fig. 9. Specifically, Fig. 9 shows that the response time of the PDBP2 material 10 at about 27°C achieved a rise time of approximately 144μ8 (x_rise, switched between V₁₀ and V90), and a fall time of about 1 14 8, (z_jau , switched between V₉₀ and V₁₀).

Continuing, Fig. 10 shows a scanning electron microscope (SEM) image of the PDBP1 material 10 in the electro-optical cell 12. The thickness of the film 10 was about 22μιη. The droplets 20 disposed on the substrate 30 with patterned electrodes 50,52 viewed at the normal angle exhibited two discrete size groups; one group of droplets 20 has an average size of about 10±3μηι, and the other group of droplets 20 had a size of about 50±5μηι, as shown in Fig. 10. The cross-sectional SEM image of the PDBP1 film, shown in Fig. 10A, shows that small droplets 20 are pinned to the substrate 30,40 surface, whereas droplets 20 with size comparable to or larger than the thickness of the film 10 are deformed in the direction parallel to the plane of the film 10. Since NEOREZ is a polyurethane-based latex 14, the strong dipole interactions between the polymer wall and the blue-phase liquid crystal stabilize the droplets 20 against deformation in the case of the electrostriction effect.

In another aspect, the PDBP film or material 10 of the present invention may be prepared by utilizing a polymerization-induced phase separation (PIPS) process. As such, the PDBP film 10 comprises a mixture of optically-transparent photopolymerizable monomer (PN393 sold by Merck), which is mixed with a blue-phase liquid crystals [about 62% nematic eutectic mixture (selected from E31 , BL006, MLC 6080, or ZLE 4792 sold by Merck) and about 38% chiral dopant (R-811 sold by Merck)], and a small amount of photoinitiator (Ciba Additive IRGACURE 651). Preferably, the PDBP material 10 formed using the PIPS process includes polymer latex content from about 15% to 90%, while the blue-phase liquid crystal content is in the range of about 85% to 10%. More preferably, the polymer content is in the range of about 20% to 80%, and the blue-phase liquid crystal content is from about 80%) to 20%. Thus, a representative mixture for use in the PIPS process may comprise about 34% of a pre-polymer mixture (i.e. photopolymerizable monomer) and about 66% blue-phase liquid crystals. In one aspect, the pre-polymer mixture may include approximately 25% hydroxyl butyl acrylate (HBA sold by Aldrich Chemical) and about 75% photopolymerizable monomer PN393 (sold by Merck).

To carry out the PIPS process, the photopolymerizable monomer/pre-polymer mixture, blue-phase liquid crystals, and photoinitiator were stirred for about two minutes using a vortex mixer. Next, the resultant polymerizable PDBP mixture 10 was disposed in the gap 24 of the electro-optical cell 12. Next, the polymerizable PDBP mixture 10 was exposed to UV (ultraviolet) light (365nm, 0.6mW/cm ) for about 30 minutes to polymerize the mixture to form the droplets 20 of PDBP material 10 that includes polymer 14 encapsulated blue-phase liquid crystals 16. The texture of the PDBP material 10 prepared by the polymerization-induced phase separation process created droplets 20 with uniform texture and reflected bluish-green color of the BP I network state at room temperature.

Fig. 11 shows a plot of normalized light transmittance versus applied voltage of the PDBP material or film 10 prepared by the PIPS process in the IPS cell 12 with about a ΙΟμηι cell gap 24. As such, the PDBP material or film 10 was evaluated with a blue laser (lambda=488nm), such that the PDBP material 10 was switched from a light-scattering state, which blocks or occludes the laser light from passing through the film 10, as shown in Fig. 11 A, to a light-transmitting state, as shown in Figs. 1 1B-C, which together show an increasingly larger amount of the laser light being permitted to pass through the film 10. It should be appreciated that the threshold voltage of the cell 12 is about 30.80V and the turn on voltage is about 127.0V.

Fig. 12 shows a plot of response time of the sample, whereby the response time was determined by switching between corresponding voltages V₁₀ and V of the PDBP film formed using the PIPS process at about 23°C. As such, the measured response times of the PDBP material 10 was about 903 for the rise time and about 709μ8 for the fall time.

Therefore, one advantage of the present invention is that a polymer-dispersed blue- phase (PDBP) liquid crystal film exhibits both electro-optical Kerr and electrostriction effects. Another advantage of the present invention is that a PDBP liquid crystal film or material has a blue phase at room temperature. Yet another advantage of the present invention is that a PDBP liquid crystal film or material has reflected color that exhibits minimum changes in response to applying an electric field. Still another advantage of the present invention is that a PDBP liquid crystal film or material may be utilized in a wide range of electro-optical and photonic devices, including LCDs, due to its desirable operating characteristics of field induced birefringence, fast response/switching time between light-scattering and light-transmitting states at low or reduced switching voltages. Yet another advantage of the present invention is that a PDBP liquid crystal film or material may be laminated between rigid, bendable, flexible, or drapeable substrates. Another advantage of the present invention is that a PDBP liquid crystal film or material may be created using an emulsification process or a polymerization-induced phase separation (PIPS) process.

Thus, it can be seen that the objects of the invention have been satisfied by the structure and its method for use presented above. While in accordance with the Patent Statutes, only the best mode and preferred embodiment has been presented and described in detail, it is to be understood that the invention is not limited thereto or thereby. Accordingly, for an appreciation of the true scope and breadth of the invention, reference should be made to the following claims.

Claims

CLAIMS What is claimed is:

1. An electro-optical cell, said electro-optical cell comprising:

a first at least partially-transparent substrate;

a second at least partially-transparent substrate;

a light-control layer disposed between said first and second at least partially-transparent substrates, said light-control layer comprising a mixture of a polymer-based latex and a plurality of blue-phase liquid crystals to form an emulsion thereof, such that said polymer- based latex forms a plurality of droplets, such that at least one of said plurality of droplets encapsulate one or more of said plurality of blue-phase liquid crystals; and

a first and a second at least partially-transparent electrode disposed on said first at least partially-transparent substrate, said electrodes spaced from each other and positioned adjacent to said light-control layer;

wherein when a first voltage is applied across said electrodes, said light control is placed in a light-scattering state, and when a second voltage is applied across said electrodes, said light-control layer is placed in an at least partially light-transparent state.

2. The electro-optical cell of claim 1, wherein said first and said second at least one partially- transparent substrates and said first and second at least partially-transparent electrodes are flexible.

3. The electro-optical cell of claim 1 , wherein said first and said second at least one partially- transparent substrates are rigid.

4. The electro-optical cell of claim 1, wherein said first and second electrodes are formed of indium-tin-oxide (ITO).

5. The electro-optical cell of claim 1, wherein said first and second electrodes are

interdigitated.

6. The electro-optical cell of claim 1 , wherein said light-control layer is about 22 urn in thickness.

7. The electro-optical cell of claim 1, wherein said polymer-based latex comprises

polyurethane-based latex NEOREZ 967.

8. The electro-optical cell of claim 7, wherein said polyurethane-based latex NEOREZ 967 comprises about 33% and said blue-phase liquid crystals comprise about 67%.

9. The electro-optical cell of claim 1 , wherein said polymer-based latex comprises polyvinyl alcohol (PVA).

10. The electro-optical cell of claim 1, wherein said blue-phase liquid crystal material comprises a mixture of a nematic liquid crystals and a chiral dopant.

1 1. A method of forming an electro-optical cell comprising:

preparing a mixture of a plurality of blue-phase liquid crystals and a polymer-based latex; shaking said mixture;

stirring said mixture in an ultrasonic bath at room temperature to form an emulsion, whereby said polymer-based latex forms a plurality of droplets, such that at least one said plurality of droplets encapsulates one or more of said plurality of blue phase crystals therein; and

disposing said emulsion between a pair of spaced at least partially-transparent substrates to form a light-control layer, such that at least one of said substrates includes a pair of spaced at least partially-transparent electrodes thereon adjacent to said light-control layer.

12. The method of claim 1 1, wherein said shaking step is performed for about 3 minutes.

13. The method of claim 12, wherein said stirring step is performed for about 2 hours.

14. The method of claim 11, wherein said polymer-based latex comprises polyurethane-based latex NEOREZ 967.

15. The method of claim 14, wherein said mixture comprises about 33% of said polyurethane- based latex NEOREZ 967 and about 67% of said blue-phase liquid crystals.

16. The method of claim 11, wherein said polymer-based latex comprises polyvinyl alcohol (PVA).

17. A method of forming an electro-optical cell comprising:

preparing a mixture of a photopolymerizable monomer, a photoinitiator, and a plurality of blue-phase liquid crystals;

stirring said mixture;

disposing said stirred mixture between a pair of spaced at least partially-transparent substrates to form a light-control layer, such that at least one of said substrates includes a pair of spaced at least partially-transparent electrodes thereon adjacent to said light-control layer; and

exposing said mixture to UV (ultraviolet) light, whereby said photopolymerizable monomer forms a plurality of droplets, such that at least one of said plurality of droplets encapsulates one or more of said plurality of blue phase crystals therein.

18. The method of claim 17, wherein said stirring step is performed for about 2 minutes.

19. The method of claim 18, wherein said exposing step is performed for about 30 minutes.

20. The method of claim 17, wherein said mixture comprises about 34% of said

photopolymerizable monomer and about 66% of said blue-phase liquid crystals.