This disclosure relates generally to optical components including thermotropic liquid crystals, alignment of the thermotropic liquid crystals on a surface of a substrate, and more particularly, to an alignment layer that includes a molecular crystalline material formed from a lyotropic liquid crystal material.
Thermotropic liquid crystals are widely used as a part of optical components, for example, in liquid crystal display (LCD) technology. They find their use as electro-optically active materials, as well as liquid crystal-based optical compensation plates in a variety of applications, such as cell phones, computers, large flat panel TVs, etc. There is a constant market demand for competitive improvement of display performance—either dynamic characteristics like switching times, or viewing angles and contrast ratios. Beyond that, liquid crystal devices are also used for non-display applications, such as sensors, light amplitude and phase modulation devices, infrared modulation devices, smart architectural windows, and so forth. These non-display applications are mostly in emerging markets and also require better performance, especially faster optical response.
Regardless of the specific applications of liquid crystal devices, manufacturers are concerned about production costs. The production cost of liquid crystal devices is governed by manufacturing processes and materials used at each process step. In particular, LCDs have a high manufacturing cost relative to sale price. If the liquid crystal device performs well in a certain application, the pressure for cost reduction of the liquid crystal device is relatively low; however, if the performance in a specific application is limited, the pressure for cost reduction becomes high.
Among the variety of functionalities, optical response time is important in liquid crystal devices. Therefore, if significant improvement in optical response time can be achieved with no change or even decrease in manufacturing costs, then the liquid crystal device can be adopted in the marketplace.
A similar statement is valid with respect to the angular dependence of contrast ratios of LCDs. If the compensation set within the LCD panel can be realized more cost efficiently then the liquid crystal device becomes more competitive.
For example, cell phone screens, especially smartphone screens, require very bright screen luminance, high contrast, but low power consumption. When cell phones are used in bright ambient light environments, such as on a sunny day outdoors, screen images are difficult to read due to the bright ambient light. Smartphone screen luminance is usually set brighter than that of computer screen luminance. Furthermore, due to significant developments in data transmission over ultra-high frequency (UHF) bands, cell phones need to have a data processing capability almost equivalent to that of laptop computers. The cell phone screens are also expected to have full motion video image capability with bright screen luminance.
In order to have an optical response fast enough for full motion video of satisfactory image quality, several types of liquid crystal drive modes have been developed and are used for the aforementioned applications. The liquid crystal drive modes can support full motion video images either on large size screen TVs or on small size, but high-resolution smartphone screens. However, due to the demand for extremely high resolution for the smartphone screen and given that thin film transistor (TFT) size remains nearly the same, the aperture ratios in smartphone screens are significantly compromised. Table 1 compares typical aperture ratio of display screens for 55-inch full HD (1920×1080 pixels) and 5-inch full HD (1920×1080 pixels) formats.
Table 1 shows that a smartphone screen has a significantly lower aperture ratio in spite of a need for low battery consumption. In a rough comparison, if the aperture ratio of a smartphone screen is a little less than half of that of a large TV screen, with a requirement for 4 times greater screen luminance, the smartphone screen would consume over 8 times greater power per unit area than a TV screen. This order-of-magnitude greater power requirement on unit area basis, compared to large TVs, places stringent demands on battery-driven equipment. Moreover, the aperture ratio comparison in Table 1 is based only on physical dimension factors. Current major LCD technologies use both in large TVs and smartphones also limit light transmission due to their complicated sub-pixel structures. Actual aperture ratios in the most advanced LCD drive modes are roughly 70% in a 55-inch diagonal screen and 30% in a 5-inch diagonal screen. The primary factor contributing to this significant reduction of aperture ratio for a smaller sized screen is the smaller pixel size, regardless of the LCD panel design. In addition to the smaller pixel size, the liquid crystal drive mode is a secondary factor in reducing the aperture ratio. The LCD industry needs to adopt liquid crystal driving modes with fast enough optical response time to enable satisfactory full motion video image quality, even if that entails sacrificing aperture ratio which results in significant reduction of light efficiency and concurrent reduction of power efficiency.
The flat panel display industry has been choosing lower light efficiency LCD drive modes which sacrifice power efficiency in order to achieve sufficiently fast optical response that enables sufficiently crisp full motion image quality. Under these conditions demand for higher contrast ratios becomes even more significant.
The need for fast response also relates to phase modulation devices. Unlike optical amplitude modulation devices like LCD devices, phase modulation devices have some complicated liquid crystal electrode structures. Regardless of the electrode structures, sufficiently fast phase modulation performance creates more opportunities for liquid crystal based phase modulation devices.
The current major LCDs such as Twisted Nematic (TN) LCDs, In-Plane Switching (IPS) LCDs, and Fringe Field Switching (FFS) LCDs, require a mechanical rubbing process for liquid crystal molecular alignment. Unlike most other LCD manufacturing processes, the mechanical rubbing process is a physical contacting and rubbing process that creates both electrostatic charges and tiny dust. Electrostatic charges are one of the major factors responsible for damage to thin film transistors (TFTs). Tiny dust causes uneven panel gaps in liquid crystal panels. Moreover, for both IPS LCDs and FFS LCDs, flexoelectric effects are the factors contributing to deterioration of display image quality. The current commercially available rubbing cloth has a single pile diameter much larger than the size of a liquid crystal molecule. Therefore the mechanical rubbing affects the top surface of the liquid crystal alignment layer on a length scale much larger than the size of a liquid crystal molecule. Since flexoelectric driving torque is linear to the applied electric field, unlike dielectric driving torque, flexoelectric driving torque is more sensitive than dielectric driving torque. Therefore, for both IPS LCDs and FFS LCDs, a much finer size liquid crystal molecular anchoring effect is required to suppress flexoelectric driving torque.
Current liquid crystal devices consist of stacks of different types of dielectric layers, such as liquid crystal molecular alignment layers, liquid crystal layers, passivation layers, and so forth. The externally applied electric field is divided among these dielectric layers depending on their dielectric properties; and the effective voltage over the liquid crystal layer is a fraction of the externally applied voltage. Therefore, adjusting the permittivities of some of the dielectric layers is one of the ways to improve the optical response time of liquid crystal devices. Current commercially available liquid crystal molecular alignment layer materials are polyimide, polyamide, polyimide-amide, polyvinyl alcohol and so forth. Permittivities of such materials are no more than 4, and permittivities of most of liquid crystal materials are over 10. This difference in permittivities reduces the effective electric field strength over the liquid crystal layer, resulting in a slower rise time. In order to achieve faster rise times, it would be desirable to increase the permittivities of liquid crystal alignment layer materials to be closer to the permittivities of liquid crystal materials.
The need for wide viewing angles and high contrast ratios on the panel level has also been a reason to sacrifice power efficiency. Thanks to significant improvements in the so-called optical compensation methods, in which an optical compensation film is placed outside the liquid crystal panels, wide viewing angles are now available with “external” optical compensation means outside of liquid crystal panels.
Current LCDs incorporate various types of birefringent films in order to compensate for the natural birefringence of the liquid crystal layer in the LC cell. These films possess birefringent properties complementary to the birefringent properties of the LC layer.
Conventional uniaxial or biaxial compensation films are usually prepared through uniaxial or biaxial stretching of polymer films. However the stretching puts limitations on the waveplate types that can be realized. At the same time the most natural way to compensate for the birefringence of the liquid crystal is to use other liquid crystal molecules and polymers.
Coatable compensation layers are deposited from liquid crystal materials in such a way the after solidifying the resultant molecular alignment realizes the required type of birefringence. Molecular arrangement in the thermotropic liquid crystals depends on the boundary conditions—the properties of the surfaces it is in contact with and their parameters like surface energy and surface morphology. Manipulating with the parameters one can realize conventional waveplates or more complex compensation properties.
There are products on the market utilizing this approach. For example the Fuji Wide View Angle film (negatively birefringent films with a tilted optical axis) comprises thermotropic liquid crystal layer and its production includes steps such as deposition of an alignment layer and mechanical rubbing in order to attain a specific molecular arrangement of the thermotropic liquid crystal ensuring the required functionality.
Thus, it would be desirable to provide the alignment layer capable of orienting the thermotropic liquid crystal on molecular scale. It would enable liquid crystal devices to have faster electro-optical response, higher contrast ratios, lower threshold voltages, and improved display quality, as well as liquid crystal device manufacturing methods free of mechanical rubbing.
Provided are liquid crystal optical components and methods for forming the same. The liquid crystal optical component comprises a substrate and an alignment layer deposited over the substrate. The alignment layer includes a molecular crystalline material formed from a lyotropic liquid crystal material. The liquid crystal optical component includes a thermotropic liquid crystal layer deposited over the alignment layer.
The present disclosure describes a ‘molecular crystalline alignment layer’. This molecular crystalline layer can be characterized as comprising a long-range uniaxially aligned, self-repeating structure, wherein the size of the repeating unit is comparable to the size of the thermotropic liquid crystal molecules.
According to one aspect of the present disclosure, provided is a liquid crystal article. The liquid crystal article comprises a first substrate and second substrate and an alignment layer on the first substrate. The alignment layer is formed of a molecular crystalline material comprising lyotropic liquid crystal materials. The liquid crystal article can include a thermotropic liquid crystal layer disposed between the first substrate and second substrate. The thermotropic liquid crystal layer comprises material selected from but not limited to nematic and smectic thermotropic liquid crystal materials.
According to another aspect of the present disclosure, a liquid crystal article is provided. The liquid crystal article comprises a substrate and an alignment layer deposited on the substrate. The alignment layer comprises a molecular crystalline material that is formed from a lyotropic liquid crystal material. The liquid crystal article optionally includes a primer layer that provides adhesion between the alignment layer and the substrate. The liquid crystal article further comprises a thermotropic liquid crystal layer deposited over the alignment layer.
According to yet another aspect of the present disclosure, a liquid crystal article comprises a substrate and an alignment layer deposited over the substrate. The alignment layer comprises a molecular crystalline material that is formed from a lyotropic liquid crystal material, wherein the molecular crystalline material is arranged on the surface of the substrate to form isolated discrete structures. These isolated discrete structures are collectively referred to as the alignment layer. The liquid crystal article further comprises a thermotropic liquid crystal layer deposited over the alignment layer.
According to one more aspect of the present disclosure, a method for forming a liquid crystal article is described. According to the method, a substrate is provided and an alignment layer is deposited over the substrate. The alignment layer is formed by shear coating lyotropic liquid crystal material onto the substrate. After deposition of the alignment layer, a thermotropic liquid crystal layer can be deposited over the alignment layer and the alignment layer is capable of aligning the thermotropic liquid crystal layer.
These and various other features and advantages will be apparent from a reading of the following detailed description.
Embodiments are illustrated by way of example, and not by limitation in the figures of the accompanying drawings, in which like references indicate similar elements and in which:
In the following description, reference is made to the accompanying figures that form a part hereof, and in which are shown by way of illustration several specific embodiments. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense.
All scientific and technical terms used herein have meanings commonly used in the art unless otherwise specified. The definitions provided herein are to facilitate understanding of certain terms used frequently herein and are not meant to limit the scope of the present disclosure.
Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein.
The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range.
As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” encompass embodiments having plural referents, unless the content clearly dictates otherwise.
As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
As used herein, “have”, “having”, “include”, “including”, “comprise”, “comprising” or the like are used in their open ended sense, and generally mean “including, but not limited to”. It will be understood that “consisting essentially of”, “consisting of”, and the like are subsumed in “comprising,” and the like.
The term “molecular crystalline” refer to a layer comprising a long-range uniaxially aligned, self-repeating structure, wherein the size of the repeating unit is comparable with the size of the liquid crystal molecules.
The term “shear coating” includes coating a material with shear force applied to the coating material, such as, printing, blade coating, microgravure, slit-die coating, slot-die coating, curtain coating, and the like, for example. The term “printing” includes ink jet printing, flexoprinting, screen printing, and the like.
The present disclosure relates to a molecular crystalline alignment layer deposited from a material in which molecules are capable of self-assembling into regular aggregates, the aggregates being aligned substantially in the same direction upon deposition and being comparable in size to thermotropic liquid crystal molecules found in the liquid crystal layer of the liquid crystal panel. Such material possessing translational symmetry in one or more directions is additionally called crystalline material. Periodic molecular arrangement creates directional electron surface density patterns on the molecular scale, which guides the anchoring of thermotropic liquid crystal molecules. In such a way the periodic structure of the alignment layer leads to thermotropic liquid crystal alignment, eliminating the necessity for mechanical rubbing step or an optical exposure step. In many embodiments the alignment layer is formed of lyotropic liquid crystal material. While the present disclosure is not so limited, an appreciation of various aspects of the disclosure will be gained through a discussion of the examples provided below.
The present disclosure gives both theoretical and experimental considerations to the problem. The theoretical portion consists of analysis of the voltage distribution in a liquid crystal device, which helps to specify requirements for an alignment layer. The experimental portion focuses on various aspects of practical implementation of the theory.
Cross-sectional structure a typical liquid crystal device is given in
In Equations 1 and 2, CTOTAL, CAL, and CLC represent total capacitance of the dielectric layer stack in the panel 100, capacitance of each of the alignment layers 130, and capacitance of the liquid crystal layer 140, respectively. V, VAL, and VLC represent total applied voltage to the panel 100 externally, applied voltage on the alignment layer 130 only, and applied voltage on the liquid crystal layer 140 only, respectively. QLC and QAL represent stored charge at the liquid crystal layer 140 and the alignment layer 130, respectively.
where τON and τOFF are the electro-optical response time for electric field application and electric field removal, respectively, γ1 is the rotational viscosity of the liquid crystal material, ∈0 is the dielectric constant of vacuum, Δ∈ is the anisotropy of the dielectric constant of liquid crystal material, E is the electric field strength in the liquid crystal layer, EC is the threshold electric field strength of the liquid crystal material, d is the liquid crystal layer thickness, and K is the elastic modulus of liquid crystal layer.
Equation 3 represents rise time or “on time,” and Equation 4 represents fall time or “off time.” Equation 3 shows that the rise time is strongly dependent on applied electric field strength, and Equation 4 shows that fall time is strongly dependent on both the liquid crystal layer thickness and the elastic modulus of the liquid crystal material. Although not explicitly mentioned in Equations 3 and 4, a liquid crystal panel that contains a stack of different dielectric materials, such as a liquid crystal layer, passivation layers, and alignment layers, requires consideration of a dynamic effective electric field strength. Due to a time delay between application of an external electric field and development of an actual electric field at each dielectric layer of the stack, the electro-optic response of the liquid crystal layer is governed by a dynamic effective electric field strength that sometimes is crucial in determining the actual response time.
Since the liquid crystal materials used in the most liquid crystal devices have relatively large permittivities in the range of 10-50, the alignment layer is expected to have its permittivity at least on the same level in order to reduce the voltage loss and reduce the threshold voltage of the liquid crystal device. Lower threshold voltage opens a way to lower power consumption.
Thermotropic liquid crystals used as an active layer in LCDs need certain boundary conditions to achieve uniform alignment, in other words the alignment of thermotropic liquid crystal molecules is not a self-sustaining effect. Conventionally, liquid crystal molecular alignment on certain surfaces has been primarily interpreted in terms of steric interactions between the topmost anchoring surface and the liquid crystal molecules. The specific boundary conditions are conventionally realized by rubbing of the alignment layer.
Characteristic length scale of surface modification by the mechanical rubbing is defined by the pile diameter of the rubbing cloth, which is about 20 μm. However, the correlation distance of thermotropic (i.e., nematic or smectic) liquid crystal molecular phases is several tens of liquid crystal molecules, which add up to about 100 nm. Therefore, in order to have uniform bulk liquid crystal molecular alignment in a liquid crystal panel for high electro-optical performance, it is desirable to realize surface anchoring with increments of 100 nm or less, as described in detail below.
In one embodiment, in order to implement periodic modulation of the alignment layer surface properties, thereby enabling favorable conditions for alignment of the thermotropic liquid crystal molecules, it is suggested to use an organic molecular crystalline alignment layer. This molecular crystalline alignment layer is seen to have a uniaxially aligned self-repeating structure, in which the size of the repeating unit is comparable in size to the thermotropic liquid crystal molecules. Since under these conditions most of the molecules of the thermotropic liquid crystal molecules at the interface with the alignment layer would be under the action of an aligning force, the electro-optic response can be effectively improved even in extremely fine pitch liquid crystal displays with IPS and FFS in accordance with the present disclosure. Such a molecular crystalline alignment layer then does not require any mechanical rubbing.
In another embodiment, the molecular crystalline layer as described above is obtained with the use of materials demonstrating a liquid crystalline phase, preferably lyotropic liquid crystalline phase, under certain conditions. Some types of liquid crystal molecules, such as discotic liquid crystal molecules, and rod-shaped liquid crystal molecules tend to form self-repeating structures, and usually possessing extended electron conjugation system show large permittivity.
A liquid crystalline material is called lyotropic′ if phases having long-ranged orientational order are induced by the addition of a solvent, such as water. Historically this term is used to refer to materials composed of amphiphilic molecules. Such molecules include a hydrophilic moiety (which may be ionic or non-ionic) attached to a hydrophobic moiety (polyaromatic structures or saturated/unsaturated hydrocarbon chains).
Amphiphilic molecules form aggregates through a self-assembly process that is driven by the hydrophilic-hydrophobic interactions when they are mixed with a solvent. The aggregates formed by amphiphilic molecules in water are characterized by structures in which the hydrophilic part shields its hydrophobic counterpart from contact with water. For most lyotropic systems aggregation occurs only when the concentration of the amphiphile exceeds a critical concentration (known variously as the ‘critical micelle concentration’ (CMC) or the ‘critical aggregation concentration (CAC)’).
At the process step of alignment layer formation, the lyotropic liquid crystal material contains a solvent such as water. After the appropriate alignment layer structure is formed, the layer should be converted to solid state by drying.
Materials that Form Lyotropic Liquid Crystals
The materials that form lyotropic liquid crystals can be made from various base materials having suitable optical and other properties, such as thermal stability, light transmittance, and the like. Of particular interest are lyotropic liquid crystal materials are water-soluble and exhibit a liquid crystal phase in water. These lyotropic liquid crystals can be deposited, or coated (preferably shear coated) onto a substrate via an aqueous solution. Once coated, the aligned lyotropic liquid crystals can be stabilized or made less water-soluble by cross-linking or by ion exchange, generally termed “passivation.”
The molecular alignment layer can be formed of one or more of the following structures or polymers:
Structure I is: 4,4′-(5,5-dioxidodibenzo[b,d]thiene-3,7-diyl)dibenzenesulfonic acid, and is described in US 2010/0215954, incorporated by reference herein.
Structure II is: cis-naphthoylenebis(sulfo-benzimidazole), and is described in US 2009/0268136, incorporated by reference herein.
Structure III is: 2(3)-sulfo-6,7-dihydrobenzimidazo[1,2-c]quinazoline-6-one-9(10)-carboxylic acid, and is described in US 2010/0039705, incorporated by reference herein.
Structure IV is: acenaphtho[1,2-b]benzo[9]quinoxaline disulfonic acid, and is described in U.S. Pat. No. 8,512,824, incorporated by reference herein.
Structure V represents a polymer where A is selected from SO3H or COOH and n is an integer from 5 to 10,000, preferably 20 to 50. Structure V where A=SO3H is referred to as poly(sulfo-p-xylene) and is described in US 2012/0113380, incorporated by reference herein.
Structure VI represents a polymer where A is selected from SO3H or COOH and n is an integer from 5 to 10,000, preferably 50 to 3000. Structure VI where A=SO3H is referred to as poly(2,2′-disulfo-4,4′-benzidine terephthalamide) and is described in U.S. Pat. No. 8,512,824, incorporated by reference herein.
These structures or polymers can be a salt of an alkali metal, ammonium, quaternary ammonium, alkali earth metal, Al3+, La3+, Fe3+, Cr3+, Mn2+, Cu2+, Zn2+, Pb2+, Sr2+ or Sn2+. These structures or polymers can be in the form of their free acid.
In yet another embodiment, the liquid crystal surface pre-tilt angle is controlled by adjusting the molecular packing density of the alignment crystalline material layer. The surface packing density up to 100 nm length scale is mainly controlled by the thickness of the alignment layer. In general, a thinner molecular crystalline material layer has a greater packing density of molecular crystalline layer. To provide sufficient surface coverage on surface topography of TFT arrays and color filter arrays, the thickness of the alignment layer is configured to be at least 30 nm.
The concept of surface liquid crystal molecular alignment is a function of surface energy comparison between the surface and liquid crystal molecules. Thermotropic nematic liquid crystal molecules are anchored on the surface of the alignment layer. Most of the thermotropic nematic liquid crystal materials have surface energies in the range of 26-30 dyn/cm. When surface energy of the alignment layer is smaller than that of liquid crystal molecules (less than 25 dyn/cm), the liquid crystal molecules are anchored homeotropically. When surface energy of the alignment layer is larger than that of liquid crystal molecules (more than 35 dyn/cm), the liquid crystal molecules are anchored as planar.
A practical way to control over the liquid crystal anchoring is to have surface modification of the top surface of the alignment layer.
The alignment layer 320 is formed from a lyotropic liquid crystal material. The lyotropic liquid crystal material is in a nematic liquid crystal phase at temperatures of 20° C. to 25° C. The liquid crystal device 300 further comprises a liquid crystal layer 330 deposited over the alignment layer 320. The liquid crystal layer 330 is preferably a thermotropic liquid crystal layer.
The liquid crystal device 350 comprises a substrate 360. An alignment layer 370 is deposited over the substrate 360. The alignment layer 370 includes molecular crystalline material formed from a lyotropic liquid crystal material. A top surface of the alignment layer 370 is modified with a surface modification agent or surfactant 380 (such as stearic acid and/or similar type of silane coupling agents) to make the top surface hydrophobic and decrease surface energy of the top surface of the alignment layer 370, resulting in a surface energy that is lower than a surface energy of the thermotropic liquid crystal material and inducing homeotropic alignment of the thermotropic liquid crystal molecules. The liquid crystal device 350 further comprises a liquid crystal layer 390 deposited over the surface modification agent or surfactant 380.
A modification of the liquid crystal device 400 is shown on
In general there are two physical mechanisms of liquid crystal alignment in the presence of the alignment layer. The first one, short range, is steric interaction amongst nematic liquid crystal molecules. A characteristic length scale of such interaction is several hundred nanometers. The second one, to be long-range in conventional technology, is the interaction of the liquid crystal molecules with the alignment layer. A characteristic length scale of this aligning interaction is defined by the period of modulation of the alignment layer surface conditions. In case of mechanical rubbing it is about 100 micrometers and there is a gap between the short-range and long-range ordering. Photo-alignment, which uses UV light exposure, can modulate surface conditions of the alignment layer on 200-300 nm scale.
In case of the alignment layer described in the present disclosure this characteristic length scale is reduced down to nm scale and the gap is eliminated. This comparison between currently used mechanically rubbed alignment layers and alignment layers described in the present disclosure is illustrated in
When pixel sizes are greater than 100 μm, the liquid crystal molecular alignment direction in each pixel will be sufficiently uniaxial in the conventional alignment technology. On the other hand, when the pixel size is reduced to ˜70 μm or smaller, variation in surface alignment direction in each pixel becomes more important. Each pixel has a slightly different direction of molecular alignment, resulting in lower contrast ratios and slower optical response times due to different alignment directions in the neighboring pixels. When an external electric field is applied to the liquid crystal panel, there is some conflict among liquid crystal molecules in their movement directions at the boundaries between adjacent pixels due to the slightly different molecular alignment directions.
On the other hand, the intrinsic ordering of the anchoring layer 650 shown in
Isolated structures in
Coating liquid comprising 12% solution of the compounds presented by Structures I and II taken in 80:20 ratio was coated on the prepared substrates using the Mayer Rods. Two pairs of electrode substrates were coated using MR#2.0 and MR#2.5, respectively. The coated substrates were dried with compressed nitrogen until the anisotropic film was formed on the substrate. Thickness of the coatings was measured by a profilometer Dektak 3ST and found to be 0.20 and 0.30 μm, respectively.
Then spacer particles were applied using spin coating method with 0.05 wt % concentration of the particles dispersed in isopropyl alcohol (IPA). Spin coating condition was set as 15 seconds at 200 rpm, then 35 seconds at 1,200 rpm, under dry nitrogen atmosphere. Substrates with deposited spacers were dried at 85° C., for 10 minutes on a hot plate. Then the substrates with the same coating thicknesses were laminated using photo-curable glue seal (Norland 65:Norland) with an angle of 87 degrees 1220 between the first (or top) substrate and the second (or bottom) substrate as shown in
Using the above prepared twisted nematic panel, the electro-optical response times and threshold voltage were measured.
Electrodes were prepared as described in the Example 2. Polyimide material SE-3510S (Nissan Chemical) of 1.5 wt % solids content was used. The polyimide precursor solution was formed as a 600 Å thickness layer by spin coating at 300 rpm, 15 seconds, followed by 2,500 rpm, 50 seconds. After spin coating, the substrates were dried on a hot plate set to 80° C. for 5 minutes. Then, the substrates were placed to a clean oven at 250° C. for 1 hour for curing. After that the surface of the cured polyimide was rubbed using a custom made rubbing machine under the following conditions: 2″ diameter rubbing cylinder, contact length 0.3 mm, three passes at 500 rpm and 5 mm/s stage speed. After the rubbing, a pair of substrates was laminated at 87 degrees in accordance with
Electrodes were prepared in accordance with the procedure described in the Example 2.
Coating liquid comprising 12% solution of the compounds presented by Structures I and II taken in 80:20 ratio was deposited on the prepared substrates with the use of the flexoprinting machine (Nihon Denshi Seiki Co., Ltd.). The printing pressure was varied for different pairs of electrodes from 0.02 to 0.15 mm gap between Anilox roll and the glass substrate. The printed material was further dried with compressed air until the anisotropic coating was formed on the substrate. For all cases the thickness of the coating was less than 0.08 μm based on multiple reflection observation.
A TN cell was assembled as explained in the Example 2 and filled with the nematic liquid crystal mixture (MDA-12-1518 Merck) at its isotropic temperature of 105° C. by capillary effect.
Experimental dependence of the liquid crystal pre-tilt angle is presented in
Samples having alignment layers printed with the pressures of 0.02-0.08 mm demonstrated planar liquid crystal alignment. As assembled they demonstrated the bright state with no voltage applied, and the black state with over-threshold voltage (over 4 V). Electro-optical response times and threshold voltage are in correspondence with the data presented in the Example 2.
Samples having alignment layers printed with the pressures of 0.10-0.15 mm demonstrated mostly homeotropic alignment with dark state in crossed polarizers. No switching was observed with and without voltage applied.
A 7% solution of a polymer according to the Structure VI (n=200) with A=SO3H was printed on the In2O3 transparent electrode patterned glass substrates prepared in accordance with the procedure described in the Example 4. Printing pressure set to 0.09 and 0.12 mm gap between Anilox roll and the glass substrate.
Cell assembling and filling was performed as described in the Example 4.
Electro-optical response data measured as explained in the Example 2 is presented in
Substrates were prepared as explained in the Example 2.
Coating liquid comprising 9% solution of the compounds presented by Structures I and II taken in 80:20 ratio was coated with a custom doctor blade (10 cm wide) on the prepared In2O3 transparent electrode patterned glass. Coated substrates were dried on the hot plate preheated to 80° C. for 10 minutes.
A pair of above layered substrates was laminated using 2.2 μm diameter size of silicon dioxide particles as spacers. The spacers were applied as described in Example 2. The cell lamination was performed in parallel configuration in the way described in Example 2.
The laminated panel was filled with chiral smectic C phase mixture (Merck ZLI-4851-100) using capillary effect at 120° C. Using multiple reflection method the panel gap was measured to be 3.1 μm.
As disclosed in US 2004/0196428, a unique chiral smectic C phase liquid crystal molecular alignment known as polarization shielded smectic (PSS)-LCD had been confirmed using a rubbed polyimide film on a glass substrate as the alignment layer. Unlike the usual chiral smectic C phase liquid crystal molecular alignment, in a PSS-LCD panel, the initial liquid crystal molecular alignment position does not show any tilt angle from the set azimuthal anchoring direction as shown in
Thus, various liquid crystal devices and methods for forming liquid crystal devices have been disclosed. Although the foregoing concepts have been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. It should be noted that there are many alternative ways of implementing the processes, systems, and apparatuses disclosed herein. Accordingly, the present embodiments are to be considered as illustrative and not restrictive.
Thus, embodiments of LIQUID CRYSTAL ARTICLE AND FABRICATION THEREOF are disclosed.
All references and publications cited herein are expressly incorporated herein by reference in their entirety into this disclosure, except to the extent they may directly contradict this disclosure. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof. The disclosed embodiments are presented for purposes of illustration and not limitation.
This application claims the benefit of U.S. Provisional Application Ser. No. 61/982,902, filed Apr. 23, 2014, and U.S. Provisional Application Ser. No. 62/008,855, filed Jun. 6, 2014, and U.S. Provisional Application Ser. No. 62/018,141, filed Jun. 27, 2014, which are incorporated herein by reference in their entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/IB2015/001101 | 4/23/2015 | WO | 00 |
Number | Date | Country | |
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61982902 | Apr 2014 | US | |
62008855 | Jun 2014 | US | |
62018141 | Jun 2014 | US |