Description:TECHNICAL FIELD
[0001] The present disclosure relates to the field of fabrication of electro-optical display devices. In particular, the present disclosure provides a method for nanoparticle film deposition that facilitates spontaneous vertical alignment of liquid crystals resulting in faster, cost-efficient and scalable fabrication method for liquid crystal display devices.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present disclosure. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed disclosure, or that any publication specifically or implicitly referenced is prior art.
[0003] Practical applications involving normally dark mode liquid crystal displays prefer vertically aligned liquid crystals because of high contrast, large viewing angles and fast response time. Existing methods for preparing vertical alignment include multi-domain, patterned, photo-alignment, polymer stabilized and self-alignment techniques. The fabrication steps involve oblique evaporation, photo-alignment, stacked Langmuir–Blodgett films and ion beam alignment methods. Different interactions like van der Waals interactions, dipolar interactions, steric interactions, hydrogen and chemical bonding, and surface topography are responsible for achieving surface alignment of liquid crystals.
[0004] One of the conventional molecular alignment techniques is the in-contact, method which requires the substrates to be coated with polyimide materials and further require mechanical surface treatment on the orientation layer. However, this method has certain drawbacks, like high temperature baking process, electrostatic discharge and impurity generation. Another preferred molecular alignment technique is the non-contact method which overcomes said drawbacks.
[0005] In another aspect, liquid crystal display panels were traditionally fabricated by employing different types of electrode structures or patterned electrodes for prefixing the pre-tilt angle of liquid crystals. Subsequently, multi-domain fabrication technique was introduced which required protrusion formation at the interface of liquid crystals and orientation-layer. Later, photo alignment and polymer stabilized approaches exhibited higher transmittance and faster response. Especially, polymer stabilized vertical alignment method has been found to offer reduced fabrication costs, but suffers from disadvantages like high processing time, low yield and high infrastructural cost.
[0006] Deposition of multi-layered nanoparticles facilitating in vertical alignment of liquid crystals is a recent development in the field. However, achieving vertical alignment on inorganic oxide layers is very difficult and the deposition rates on inorganic films are low. Therefore, there is need in the art to devise a technique that can bypass time-consuming pre-processing steps like mechanical rubbing, high temperature baking, formation of protrusions in multi-domain vertical alignment, polymer mixing and ultra violet curing. The proposed method does not require complex substrate treatments or additional alignment layers during fabrication. In addition to stability, higher transmittance and better contrast, the proposed approach presents a time saving, cost effective, easy to implement and scalable approach for fabrication of vertically aligned liquid crystal displays.

OBJECTS OF THE PRESENT DISCLOSURE
[0007] Some of the objects of the present disclosure, which at least one embodiment herein satisfies are as listed herein below.
[0008] It is an object of the present disclosure to provide a method for preparing vertically aligned liquid crystals by deposition of one or more nanoparticle layers on Indium Tin Oxide (ITO) coated glass substrate.
[0009] It is an object of the present disclosure to provide a nanoparticle deposition method for preparing vertically aligned liquid crystals that includes a step of preparing a solution of nanoparticles dispersed homogenously in a solvent.
[0010] It is an object of the present disclosure to provide a nanoparticle deposition method for preparing vertically aligned liquid crystals that includes a step of filling in a cell having a predetermined geometry and dimensions with the homogenous solution.
[0011] It is an object of the present disclosure to provide a nanoparticle deposition method for preparing vertically aligned liquid crystals that facilitates spacing between a pair of parallel ITO coated glass substrates of the cell to range between 3.5µm and 10µm.
[0012] It is an object of the present disclosure to provide a nanoparticle deposition method for preparing vertically aligned liquid crystals that includes a step of heating the homogenous solution for a predetermined duration and at a predetermined temperature.
[0013] It is an object of the present disclosure to provide a nanoparticle deposition method for preparing vertically aligned liquid crystals that includes a step of completely evaporating at an optimized rate, the solvent of the homogenous solution.
[0014] It is an object of the present disclosure to provide a nanoparticle deposition method for preparing vertically aligned liquid crystals that enables spatial self-assembling of the nanoparticles upon evaporation of the solvent.
[0015] It is an object of the present disclosure to provide a nanoparticle deposition method for preparing vertically aligned liquid crystals that includes a step of filling in the unoccupied regions of the cell with liquid crystal material.
[0016] It is an object of the present disclosure to provide a nanoparticle deposition method for preparing vertically aligned liquid crystals that facilitates spontaneous vertical alignment of the liquid crystals due to physical interaction between the liquid crystal material and the one or more layers of deposited nanoparticles.
[0017] It is an object of the present disclosure to provide a nanoparticle deposition method for preparing vertically aligned liquid crystals that discards requirement of complex surface treatment and pre-structuring of ITO coated substrates.
[0018] It is an object of the present disclosure to provide a nanoparticle deposition method for preparing vertically aligned liquid crystals that discards requirement of additional alignment layers for vertical alignment of liquid crystals.
[0019] It is an object of the present disclosure to provide a nanoparticle deposition method for preparing vertically aligned liquid crystals that discards requirement of additional alignment layers for vertical alignment of liquid crystals.
[0020] It is an object of the present disclosure to provide a nanoparticle deposition method for preparing vertically aligned liquid crystals that facilitates time saving, cost effective, easy to implement and scalable approach for fabrication of liquid crystal displays.
[0021] It is an object of the present disclosure to provide a nanoparticle deposition method for preparing vertically aligned liquid crystals that imparts stability, higher transmittance and better contrast to the fabricated liquid crystal display in comparison to already available liquid crystal display devices.

SUMMARY
[0022] The present disclosure relates to the field of fabrication of electro-optical display devices. In particular, the present disclosure provides a method for nanoparticle film deposition that facilitates spontaneous vertical alignment of liquid crystals resulting in faster, cost-efficient and scalable fabrication method for liquid crystal display devices.
[0023] An aspect of the present disclosure pertains to a method that may be used for preparing vertically aligned liquid crystals by deposition of one or more layers of nanoparticle material on Indium Tin Oxide (ITO) coated glass substrate.
[0024] In an aspect, the method may include a step of preparing a homogenous solution of nanoparticles dispersed in a solvent medium, the solvent being any or a combination of ethanol and deionized water.
[0025] In an aspect, the method may include a step of filling in a confined volume of a cell with the homogenous solution, the cell having a predetermined geometry and dimensions.
[0026] In an aspect, the confines of the cell may be limited by a first and a second glass substrate and a first and a second spacer.
[0027] In an aspect, the first and the second glass substrate may be parallel to each other and coated by Indium Tin Oxide (ITO), the ITO coated glass substrate requiring no complex surface treatment.
[0028] In an aspect, the first and the second spacers may be parallel to each other and perpendicular to the first and the second glass substrate.
[0029] In an aspect, the proposed method may facilitate spacing between the first and the second ITO coated glass substrates of the cell to range between 3.5µm and 10µm.
[0030] In an aspect, the method may include a step of heating the homogenous solution in the cell for a predetermined duration and at a predetermined temperature.
[0031] In an aspect, the method may include a step of completely evaporating the solvent of the homogenous solution in the cell, the rate of evaporation being predetermined by optimization.
[0032] In an aspect, upon evaporation of the solvent, the method may enable spatial self-assembling of the nanoparticles into one or more layers on the first and the second ITO coated glass substrates.
[0033] In an aspect, the method may include a step of filling in the remaining unoccupied regions of the cell with liquid crystal material.
[0034] In an aspect, the method may facilitate spontaneous vertical alignment of the liquid crystals, the alignment being a result of physical interaction between the liquid crystal material and the one or more layers of deposited nanoparticles.
[0035] In an aspect, the proposed method may discard requirement of complex surface treatment and pre-structuring of the first and the second ITO coated glass substrates.
[0036] In an aspect, the method may discard requirement of additional alignment layers during fabrication for vertical alignment of liquid crystals.
[0037] In an aspect, the method may impart stability, higher transmittance and better contrast to the fabricated liquid crystal display in comparison to already available liquid crystal display devices.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0038] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0039] The diagrams described herein are for illustration only, which thus are not limitations of the present disclosure, and wherein:
[0040] FIG. 1 illustrates exemplary method (100) of nanoparticle film deposition facilitating vertical alignment of liquid crystals, in accordance with an embodiment of the present disclosure.
[0041] FIG. 2 illustrates exemplary flow diagram (200) of the method illustrating the steps involved with preparation and deposition of the nanoparticle film facilitating vertical alignment of liquid crystals, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION
[0042] In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without some of these specific details.
[0043] If the specification states a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.
[0044] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0045] The present disclosure relates to the field of fabrication of electro-optical display devices. In particular, the present disclosure provides a method for nanoparticle film deposition that facilitates spontaneous vertical alignment of liquid crystals resulting in faster, cost-efficient and scalable fabrication method for liquid crystal display devices.
[0046] FIG. 1 illustrates exemplary method (100) of nanoparticle film deposition facilitating vertical alignment of liquid crystals, in accordance with an embodiment of the present disclosure.
[0047] In an embodiment, the method includes a step (102) of preparing a homogenous solution of nanoparticles dispersed in a solvent medium, the solvent being any or a combination of ethanol and deionized water. The nanoparticles may be of multiple sizes, depending on the composition of the nanoparticle material.
[0048] In an embodiment, the method (100) may include a step (104) of filling in a confined volume of a cell with the homogenous solution, the cell having a predetermined geometry and dimensions. In an embodiment, the confines of the cell may be limited by a first and a second glass substrate and a first and a second spacer. The first and the second glass substrate may be parallel to each other and may be coated with Indium Tin Oxide (ITO). The ITO coated glass substrate may not require further surface treatment procedures like rubbing, high temperature baking operations, formation of protrusions, polymer mixing and ultra violet curing.
[0049] In an embodiment, the first and the second spacers may be parallel to each other and perpendicular to the first and the second ITO coated glass substrates.
[0050] In an embodiment, the proposed method may facilitate spacing between the first and the second ITO coated glass substrates of the cell to range between 3.5µm and 10µm. The mentioned values of the spacing may be exclusive of a predetermined percentage of error.
[0051] In an embodiment, the method (100) may include a step (106) of heating the homogenous solution of nanoparticles dispersed in the solvent inside the cell. The heating process may be continued for a predetermined duration and at a temperature selected from a predetermined range of temperature.
[0052] In an embodiment, the method (100) may include a step (108) of completely evaporating the solvent of the homogenous solution in the cell. The rate of evaporation may be predetermined by optimization. In an embodiment, a controlled rate of evaporation of the solvent may induce spatial self-assembling of the multiple-sized nanoparticles within the confines of the cell. Depending on the selected rate of evaporation, the step (108) may result in deposition of one or more layers of nanoparticles on the first and the second ITO coated glass substrates of the cell.
[0053] In an embodiment, the method (100) may include a step (110) of filling in the remaining unoccupied regions of the cell with liquid crystal material of nematic phase. In an embodiment, the dielectric medium of the liquid crystals may be either positively or negatively anisotropic in nature.
[0054] In an embodiment, the method (100) may facilitate spontaneous vertical alignment of the liquid crystals upon physical interaction between the liquid crystal material and the one or more layers of deposited nanoparticles. In an embodiment, the deposited one or more layers of nanoparticles may provide a rough surface to the liquid crystal material. The molecules of the liquid crystal may tend to occupy the grooves of the rough surface created on substrate by the one or more layers of deposited nanoparticles. This may enable the molecules of the nanoparticles to generate a homeotropic anchoring force towards neighboring liquid crystal molecules. As a result, the liquid crystal molecules may be spontaneously oriented perpendicular to the first and the second glass substrates. Liquid crystal molecules in the vicinity of already aligned liquid crystal molecules may be further induced to align vertically.
[0055] In an embodiment, the proposed method (100) may not require additional alignment layers during fabrication for vertical alignment of liquid crystals. Bypassing additional alignment layers may further eliminate possibilities of generating toxic by-products that may be formed during polyimide processing.
[0056] FIG. 2 illustrates exemplary flow diagram (200) of the method illustrating the steps involved with preparation and deposition of the nanoparticle film facilitating vertical alignment of liquid crystals, in accordance with an embodiment of the present invention.
[0057] In an illustrative embodiment, the proposed method may include steps of dispersing nanoparticle molecules homogenously in a solvent, followed by filling in a cell defined by a pair of parallel ITO coated glass substrates and a pair of parallel spacers, perpendicular to the glass substrates with the homogenous solution. The next step may include heating of the homogenous solution in the cell at a predetermined temperature until the solvent is completely evaporated. Rate of evaporation may be optimized prior to the fabrication process. Depending on the rate of evaporation the nanoparticles may spatially self-assemble in one or more layers on the ITO coated glass substrates.
[0058] In an embodiment, the following step may include filing in the remaining unoccupied region of the cell with nematic liquid crystal material. In an embodiment, the deposited one or more layers of multiple-sized nanoparticles may create a rough surface on the substrates. Physical interaction of the liquid crystals with the rough surface may induce spontaneous vertical alignment of the liquid crystals.
[0059] While embodiments of the present invention have been illustrated and described in the accompanying drawings, the embodiments are offered only in as much detail as to clearly communicate the disclosure and are not intended to limit the numerous equivalents, changes, variations, substitutions and modifications falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0060] The terms, descriptions and figures used herein are set forth by way of illustration only. Many variations are possible within the spirit and scope of the subject matter, which is intended to be defined by the following claims and their equivalents in which all terms are meant in their broadest reasonable sense unless otherwise indicated.
[0061] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE INVENTION
[0062] The present disclosure provides for a method for preparing vertically aligned liquid crystals by deposition of one or more nanoparticle layers on Indium Tin Oxide (ITO) coated glass substrate.
[0063] The present disclosure provides for a nanoparticle deposition method for preparing vertically aligned liquid crystals that includes a step of preparing a solution of nanoparticles dispersed homogenously in a solvent.
[0064] The present disclosure provides for a nanoparticle deposition method for preparing vertically aligned liquid crystals that includes a step of filling in a cell having a predetermined geometry and dimensions with the homogenous solution.
[0065] The present disclosure provides for a nanoparticle deposition method for preparing vertically aligned liquid crystals that facilitates spacing between a pair of parallel ITO coated glass substrates of the cell to range between 3.5µm and 10µm.
[0066] The present disclosure provides for a nanoparticle deposition method for preparing vertically aligned liquid crystals that includes a step of heating the homogenous solution for a predetermined duration and at a predetermined temperature.
[0067] The present disclosure provides for a nanoparticle deposition method for preparing vertically aligned liquid crystals that includes a step of completely evaporating at an optimized rate, the solvent of the homogenous solution.
[0068] The present disclosure provides for a nanoparticle deposition method for preparing vertically aligned liquid crystals that enables spatial self-assembling of the nanoparticles upon evaporation of the solvent.
[0069] The present disclosure provides for a nanoparticle deposition method for preparing vertically aligned liquid crystals that includes a step of filling in the unoccupied regions of the cell with liquid crystal material.
[0070] The present disclosure provides for a nanoparticle deposition method for preparing vertically aligned liquid crystals that facilitates spontaneous vertical alignment of the liquid crystals due to physical interaction between the liquid crystal material and the one or more layers of deposited nanoparticles.
[0071] The present disclosure provides for a nanoparticle deposition method for preparing vertically aligned liquid crystals that discards requirement of complex surface treatment and pre-structuring of ITO coated substrates.
[0072] The present disclosure provides for a nanoparticle deposition method for preparing vertically aligned liquid crystals that discards requirement of additional alignment layers for vertical alignment of liquid crystals.
[0073] The present disclosure provides for a nanoparticle deposition method for preparing vertically aligned liquid crystals that facilitates time saving, cost effective, easy to implement and scalable approach for fabrication of liquid crystal displays.
[0074] The present disclosure provides for a nanoparticle deposition method for preparing vertically aligned liquid crystals that imparts stability, higher transmittance and better contrast to the fabricated liquid crystal display in comparison to already available liquid crystal display devices.

We Claims:

1. A method (100) for nanoparticle film deposition facilitating vertical alignment of liquid crystals, the method comprising steps of:
preparing (102), homogenous solution of multiple-sized nanoparticles in solvent medium, wherein the multiple-sized nanoparticles are uniformly dispersed among the molecules of the solvent and wherein the nanoparticles and the solvent are of predetermined composition;
filling (104), in a confined volume of a cell with the homogenous solution, wherein the confined volume has a predetermined geometry and dimensions, wherein the confines of the cell are limited by a first glass substrate and a second glass substrate and a first spacer and a second spacer; wherein the first and the second glass substrates are parallel to each other and are coated with a film of predetermined composition and wherein the first and the second spacers are parallel to each other and perpendicular to the first and the second glass substrates;
heating (106), the homogenous solution confined within the cell at a temperature selected from a predetermined range of temperatures, wherein the duration of heating is also predetermined;
evaporating (108), the solvent of the homogenous solution completely, wherein the rate of evaporation is predetermined by optimization;
filling (110), in the unoccupied regions of the confined volume of the cell with liquid crystal material, wherein the liquid crystals are in nematic phase.
2. The method as claimed in claim 1, wherein the solvent includes any or a combination of ethanol and deionized water.
3. The method as claimed in claim1, wherein the glass substrates are coated with one or more layers of Indium Tin oxide (ITO), wherein the ITO coated substrates do not require any surface treatment and pre-structuring steps pertaining to fabrication of a liquid crystal display device.
4. The method as claimed in claim1, wherein the spacing between the ITO coated substrates ranges from 3.5µm to 10µm, the values of spacing being exclusive of a predetermined percentage of error.
5. The method as claimed in claim1, wherein controlled rate of evaporation of the solvent induces spatial self-assembling of the multiple-sized nanoparticles within the confines of the cell.
6. The method as claimed in claim5, wherein, the self-assembly facilitates deposition of one or more layers of the multiple-sized nanoparticles on the ITO coated substrates, wherein the deposited layers of nanoparticles provide a rough surface to the liquid crystal material.
7. The method as claimed in claim5, wherein, physical interaction between the liquid crystal material and the one or more layers of deposited nanoparticles facilitates spontaneous orientation of the liquid crystals into vertical alignment.
8. The method as claimed in claim5, wherein, the dielectric medium of the liquid crystals are either positively or negatively anisotropic in nature.