JP2003508820A - Fabrication of aligned liquid crystal cells / films by simultaneous alignment and phase separation - Google Patents

Abstract

(57) Abstract: A method for simultaneously producing a microstructure having a phase-separated organic film and a liquid crystal having a desired alignment is disclosed. The method includes preparing a mixture of a liquid crystal material, a prepolymer, and a polarization sensitive material. The method is arranged on a substrate and a combination of ultraviolet or visible light or heat treatment simultaneously induces phase separation such that a layer or microstructure of a properly aligned liquid crystal material adjacent to the substrate is used. .

Description

Detailed Description of the Invention

[0001] Technical Field The present invention belongs to the technical of the optical modulator are made of a composite organic materials using self-aligned layer. In particular, the present invention involves in-situ photoalignment using polarized ultraviolet (UV) exposure and the process of one or more steps to align an aligned liquid crystal film adjacent to a polymer layer with or without pretilt. The two processes of the phase separation composite organic membrane used (PSCOF) and the anisotropic phase separation used are combined. In particular, this method allows the alignment of aligned liquid crystal cells without the requirement for two prefabricated alignment layers on each substrate.

[0002] PSCOF method has recently been invented in order to adjust the adjacent parallel layers of polymer and liquid crystal, it was used in Kent State University. This method is disclosed in US Pat. No. 5,949,508, which is incorporated herein by reference. This PSC
OF methods include processes similar to those used in the manufacture of polymer dispersed liquid crystal films.
The polymer and the liquid crystal are mixed in a predetermined ratio and placed between or on one substrate with a well-defined thickness. When the beam of ultraviolet light is incident from one side, the phase separation process is started. The rate of polymerization (and phase separation) is faster near the UV radiation source due to the higher intensity. When the phase separation starts, the organic or liquid crystal material is driven out of the polymerized part and starts to move away from the UV radiation source. As a result, a uniform film of polymer is obtained on one side of the cell and a substantially uniform layer of liquid crystal is formed on the opposite side of the cell away from the UV light source. Separation of the liquid crystal from the polymer can be facilitated by a pre-positioned alignment layer that the liquid crystal material is to wet on the substrate away from the UV source. As such, an aligned liquid crystal film may be formed.

Alignment layers are typically made of long chain polymeric materials that are subsequently subjected to treatments such as mechanical rubbing or UV exposure to alter surface properties. There are several commonly accepted techniques for forming alignment layers on the substrates of liquid crystal devices. Commonly used methods are rubbing or photoalignment of organic / polymer films and evaporation of inorganic materials. Although each method can align the liquid crystal material, each method has unique drawbacks.

The most commercially used method of forming alignment layers is the rubbing method. In this method, for example, polyamic acid is spin-coated or otherwise deposited on a substrate. Polyamic acid undergoes two heat treatments, a soft bake and a hard bake, to form a polyimide (PI) film. After a suitable cooling period, the PI membrane is rubbed with a velvet-like cloth in a uniform, single direction. When the liquid crystal later contacts the rubbed surface, the liquid crystal aligns along the rubbing direction. Unfortunately, this method produces mechanical damage and electrostatic charge, both of which adversely affect liquid crystal displays, especially those using thin film transistors. The rubbing method uses cloth and P that may contaminate the liquid crystal material.
Dust from I is also generated.

Another method of forming the alignment layer involves forming a PI film on the substrate as described above. The linearly polarized UV light is projected onto this surface to produce the desired molecular alignment. The ultraviolet radiation anisotropically photodissociates the photoelectric bond of PI including the photosensitive bond of imide. This selectively reduces the polarizability of the PI molecule, altering its surface properties and morphology. Unfortunately, this method results in an alignment layer with weak anchoring of the liquid crystal and unfavorable thermal and chemical stability.
Moreover, this method requires expensive multi-step processing. Yet another drawback of this method is that it provides only limited charge retention and relatively low thermal stability when compared to rubbing techniques.

Similar methods of adjusting the alignment layer by using photopolymers are also known. For example, poly (vinyl) 4-methoxy-cinnamate (PVMC
Photosensitive polymers such as films, poly (vinyl) cinnamate (PVC) films and polysiloxane cinnamate films can be used to align liquid crystal materials. When exposed to linearly polarized ultraviolet light (LPUV), these materials initiate a photoreaction after evaporation of the solvent. This method results in cross-linking and the resulting orientation of uniaxial side chains in the direction determined by the direction of linearly polarized light. However, this method does not chemically fix the molecular orientation, and the alignment is
It is lost during exposure because it usually produces unpolarized UV light. Furthermore, the chemical constituents of the material disappear over time. Therefore, the alignment layer thus produced does not provide a certain stable orientation of the liquid crystal material.

Yet another method of forming an alignment layer on a substrate is vapor deposition of an inorganic material on the surface of the substrate at various angles of incidence. This forms an alignment layer that physically aligns the alignment vector of the liquid crystal. The inorganic materials used include silicon oxide and magnesium oxide. This attachment method has proven to be cumbersome and difficult to use in the manufacturing process.

Another method of forming the alignment layer developed by Kent State University is the in situ UV exposure method. This method is described in US Pat.
No. 936,691 and incorporated herein by reference. The in-situ method is similar to the conventional method of exposing a PI film to polarized UV light. However, the in situ method exposes a polyimide film (PI) to ultraviolet radiation, but the film is soft baked and hard baked. The resulting alignment layer has higher anchoring energy and is more thermally stable than conventional UV exposure techniques. For example, a cell conditioned by the conventional method is
Whereas the cells prepared by the in situ method show no signs of degradation at 300 ° C. for 12 hours, whereas alignment is lost when kept at 0 ° C.
The in-situ method of forming the alignment layer avoids many of the drawbacks of other methods known in the art, but requires fewer steps and simpler processing steps.

Although the in situ method has been shown to be effective, the alignment film still requires that it be properly placed and processed. Moreover, in the case of the full alignment method described above, this alignment can be damaged if no care is taken when transferring substrates between manufacturing equipment. It is also theorized that currently known alignment layers only directly affect the liquid crystal material adjacent to it.

In light of the foregoing, the present technique requires light modulation techniques that include phase-separated composite organic films, and fabrication methods such as films that are homogeneously aligned in composition, and thus the preparation of distinct and well-defined alignment layers. And it is clear that no treatment is required.

[0011] In light of the disclosure above of the invention, a first aspect of the present invention is to provide a method of manufacturing an optical modulation apparatus and such apparatus comprises a phase separated composite organic film or microstructure , Where the device uniformly aligns the liquid crystal material without the requirement for two separate alignment layers.

Another aspect of the present invention is to provide a self-aligned phase-separated composite organic film prepared by using a one-step or multi-step method of simultaneous phase separation and photoalignment.

Yet another aspect of the present invention is to provide an anisotropic film or microstructure made by the method of simultaneous photoalignment and photopolymerization.

Yet another aspect of the present invention is to provide an anisotropic film or microstructure by a method of solvent induced phase separation or an anisotropic film made by a method of simultaneous photoalignment and solvent induced phase separation. Where the liquid crystal alignment is
Obtained at all internal polymer interfaces (walls) of the microstructure.

Another aspect of the invention is to provide a film or microstructure made by the method of simultaneous photoalignment and thermally induced polymerization.

Yet another aspect of the invention is to provide an anisotropic film or microstructure comprising two or more layers prepared using multiple steps, wherein a liquid crystal is provided. The material layers are separately aligned on each surface of the membrane and may have different orientations.

According to another aspect of the present invention, a step of spin-coating a polyimide capable of photo-crosslinking onto a substrate, a step of spin-coating a reactive liquid crystal monomer onto the polyimide, and using polarized light, simultaneously cross-linking a polyamic acid. And optically aligning the reactive monomer and polymerizing the reactive monomer. UV light is polyimide /
A suitable morphology is created at the liquid crystal interface, which in turn aligns the liquid crystal material.

Further, according to another aspect of the present invention, a step of spin-coating a liquid crystal polymer (LCP) on a substrate, a step of spin-coating a reactive monomer on the LCP, applying polarized light, and at the same time, applying light to the LCP. Aligning, photo-aligning the reactive monomers, and polymerizing, to obtain an anisotropic film.

Yet another aspect of the present invention is an anisotropic film including a step of adjusting a mixture of liquid crystal, a polymer and a solvent, and a step of applying polarized light and at the same time photo-aligning and phase-separating a liquid crystal material. It is obtained by the method of manufacturing.

Yet another aspect of the present invention is to prepare a mixture of liquid crystal material and a thermopolymerizable monomer, place the mixture on a substrate, subject the mixture to a heat treatment to polymerize the monomer, The method of manufacturing an anisotropic film, the method comprising receiving polarized light and optically aligning a liquid crystal material.

Another aspect of the invention is obtained by a method of manufacturing an anisotropic film and / or microstructure composed of two or more layers or microstructures, the method comprising two or more layers. Of the above method in sequence to prepare multiple layers of alignment material, where the liquid crystals are individually aligned individually at each interface / surface.

The foregoing and other objects of the present invention will become apparent as the detailed description proceeds, wherein a mixture of liquid crystals, prepolymers and polarization sensitive materials is prepared, the mixture is placed on a substrate, and a light source is provided. Phase separation of the co-mixture and alignment of the phase separated liquid crystals to form a layer of homogeneously aligned liquid crystal material on the substrate adjacent to the layer of polymer and polarization sensitive material. And a method of simultaneously producing a phase separation inducing film having alignment, which includes inducing.

Another aspect of the present invention provides a substrate, a first mixture comprising at least a first polarization sensitive chemical and a prepolymer, and at least a second polarization sensitive chemical. A second mixture including a prepolymer is provided, liquid crystals are mixed into the first or second mixture, the first mixture is disposed on a substrate, and the second mixture is mixed with the first mixture.
A mixture of at least visible light, ultraviolet light, heat-induced, chemically-induced, and solvent-induced first treatment of the mixture, and at least visible light, ultraviolet light, Obtained by a method of manufacturing a liquid crystal device having alignment properties, comprising initiating treatment of a second mixture from the group consisting of thermal induction, chemical induction, and solvent induction, and the treatment provides alignment alignment to liquid crystals. give.

Yet another object of the invention is obtained by a cell having alignment properties comprising at least one substrate and a mixture arranged on the substrate, the mixture comprising at least a liquid crystal material and a prepolymer material. , A polarization sensitive material, and the use of co-polymerization and polarization results in phase separation and photoalignment of the mixture, thus forming a polymer microstructure that imparts alignment properties to the liquid crystal material.

These and other objects of the present invention, as well as its advantages over the existing prior art as will become apparent from the following description, are accomplished by the improvements described and claimed below.

For a full understanding of the objects, techniques and structures of the present invention, reference should be made to the following detailed description and accompanying drawings.

Referring to the best mode now to Figure 1 for carrying out the invention, it is understood that the precursor of the light modulation device made in accordance with the present invention is generally designated by numeral 10. As will be apparent, the light modulation cell precursor 10
May be provided but does not include a separate well-defined alignment layer. The light modulator of the present invention may be manufactured by a method that does not require a separate spin coating step to deposit the alignment layer precursor material on the substrate. This method does not require soft and / or hard baking of the alignment layer. Furthermore, this method does not require rubbing or otherwise physically contacting the alignment layer to impart properties that later affect the liquid crystal material.

The light modulator precursor shown in FIG. 1 comprises a pair of opposing optically transparent substrates 12, which may be glass, plastic or other materials generally known to those skilled in the art. Advantageously, the device does not have to withstand the temperatures at which the prior art alignment layers need to be imidized. As will be apparent, temperature sensitive materials not heretofore suitable as substrates can be used in the present invention. In other words, flexible substrate materials such as plastic or polymer sheets may now be used for liquid crystal devices that do not have to withstand the high temperatures normally used in hard bake and soft bake alignment layer forming processes. .

A polariser 14 may be disposed on the outer surface of each substrate 12 for the purpose of modifying the optical properties of the transmitted light to provide a cell for operating in transmissive mode. The electrodes 18 may be provided on the inner surface of each of the substrates 12. In the preferred embodiment, each electrode 18 is an indium-tin oxide film material. Alternatively, a mirror or light diffuser may be added to the outside of the substrate facing the light source to provide a device that operates in reflective mode.

The power supply 20 is attached to the electrode 18 through the switch 22. This switch can be used to connect the power supply, short the two electrodes, disconnect the electrodes, and store charge on the electrodes. The application of electric or electromagnetic fields or other external forces results in optical switching of liquid crystals or organic materials placed between the substrates. Switch 22
The operations of may be driven by an electronic drive, as appropriate. The use of electronic driver circuitry allows addressing specific areas of the matrix cell device which in turn enable the formation of high contrast between areas. As shown in FIG. 1, the cell gap thickness between the electrodes is defined by dimension 26.

A composite organic material 28 comprising at least the following components, an organic or liquid crystal material, a prepolymer and an aligning agent such as a low temperature curable polyimide is deposited between the substrates 12. To obtain this material 28, the liquid crystal material is combined with the prepolymer and polyimide in solution and filled between the substrates 12 by capillary action. Of course, other known filling methods may be used. The edge of the substrate 12 is sealed using known methods. Alternatively, material 28 may be spin coated on a single substrate.

Referring now to FIG. 2, it can be seen that the light modulator cell manufactured by the one-step simultaneous phase separation and alignment method according to the present invention is generally designated by the numeral 30.

Usually, the “one-step method” is a method in which a layer of a material containing at least an organic or liquid crystal material, a prepolymer, a polarization-sensitive aligning agent such as a chromophore is deposited on a substrate, for example by spin coating. Where the coated substrate is visible light radiation,
Alternatively, it is subjected to a treatment selected from polarized ultraviolet radiation and some type of phase separation. The one-step method is thus characterized in that all components are subjected to the same treatment at the same time so as to uniformly align the phase separated liquid crystal material components.

A light source 32, such as ultraviolet light or visible light, is disposed adjacent and under the linear polarizer 36. When energized, a linearly polarized light beam 38 is passed through the substrate 12,
It produces a ray 34 that impinges on a linear polarizer 36 that is directed into the cell gap 26.
Light, or some other treatment shown, predominantly induces polymerization of the prepolymer mixed with the aligning agent. As the polymerization proceeds, phase separation occurs between the liquid crystal material and the polymer / alignment. This is known as polymerization-induced phase separation. In particular, the light transmissive solid polymer layer 40 is formed on the electrode 18 of the substrate 12 adjacent the light source 32. The liquid crystal film layer 42 is formed on the opposite substrate 12 adjacent to the other electrode 18.
At the same time as the phase separation, the linearly polarized light beam 38 breaks the photopolymerizable bond of the prepolymer / polyimide layer, causing the polymer segment to move along the direction perpendicular to the direction of polarization of the linearly polarized light beam. Align. Further, depending on the chemistry of the material, the light beam 38 may direct the polymer segments parallel or perpendicular to the substrate, or may crosslink the polymer material in a particular direction parallel to the substrate. This facilitates alignment of the liquid crystal film 42 at the interface 44 between the polymer layer 40 and the liquid crystal layer 42. At the interface 44, the liquid crystal appears to affect the aligned anchoring state of the alignment during phase separation. It is also believed that a minimal amount of polyimide material adheres to the opposing substrate and resembles the alignment orientation at interface 44. If desired, a separate and unique alignment layer may be provided on the substrate for interface 44.

As can be seen in FIG. 2, the thickness of the polymer layer is defined by the dimension 52 and the thickness of the liquid crystal is indicated by the dimension 54. The physical parameters of the liquid crystal film, such as the liquid crystal film thickness, alignment state and liquid crystal material, can be selected for the desired purpose by adjusting the composition and using an appropriately sized space. Homogeneously aligned cells using nematic liquid crystals were formed by the method of the present invention. Further, it has been found that the ferroelectric and antiferroelectric materials having such a structure have gray scale and smooth bistability. These cells have a very low threshold voltage, scatter almost no light (no haze at all), and are mechanically and electrically robust. Some liquid crystal materials exhibit the modified electro-optical (EO) behavior of phase separated composite organic films. Optically controllable birefringent devices can also be formed using this method. This method allows the production of uniform, very thin liquid crystal films. Several uniform films with thicknesses comparable to the wavelength of red light were prepared with the method of the invention.

It will be appreciated by those skilled in the art that, in the practice of the present invention, phase separation can be accomplished by thermal induction techniques, chemical induction techniques, or solvent induction techniques. Any of these techniques can be used with irradiation to perform simultaneous phase separation and photoalignment. Without wishing to be bound by theory, it is believed that the polarized light rays are important in aligning the liquid crystal material in a uniform manner at interfaces 44 and 46.

Suitable prepolymers for the practice of the present invention are photopolymerizable monomers that are sensitive to the direction of polarization of ultraviolet light, so that exposure to ultraviolet light simultaneously and directionally polymerizes the monomers. Align the polymer macroscopically. Prepolymers that are not normally sensitive to the polarization of UV light may be useful when modified, for example by the addition of chromophore components. Thus, suitable prepolymers include, but are not limited to, NOA-65 (commercially available from Norland Products, Inc.), vinyl ethers, acrylates, epoxies, diacetylenes, vinyls and the like. In the case of a chromophore, materials such as azobenzene, stilbenzene, cinnamate, chalcone, coumarin, dimaleimidimide and the like can be used. Useful polyimides are homopolyimides or copolyimides having side chains with low light absorption, SE-1180,610 (commercially available from Nissan Chemical Industries) and a functional group having a chromophore incorporated therein. Including.

The liquid crystal material can be selected depending on the desired type of light modulator. Suitable liquid crystal materials include, but are not limited to, nematic liquid crystal materials, ferroelectrics, antiferroelectrics, cholesteric liquid crystal materials and related liquid crystal materials.

As indicated above, the method of the present invention can be used to tailor a parallel film of polymer and aligned liquid crystals either inside the cell or on the substrate. Referring now to FIG. 3, it can be seen that the apparatus used to carry out either the one-step or multi-step method of the present invention is generally designated by the numeral 60. If heat-induced polymerization is used, the device is enclosed within heat source 62. Heat from the light source 32 may also be used if appropriate.

In one embodiment of the one-step method as defined above, a mixture of reactive liquid crystal monomer, photomonomer and cold cure polyimide is formulated to prepare an anisotropic film. The reactive liquid crystal monomer can be selected from nematic diacrylate monomers having acrylate polymerizable groups and chiral diacrylate dopants. A photomonomer such as NOA-65 and a low temperature cure polyimide such as SE-1180 are mixed with a reactive liquid crystal monomer to form a photosensitive material. This mixture is spin coated onto the substrate. As shown in FIG. 2, the ultraviolet light source 3
2 emits a ray 34 that passes through a linear polarizer 36. The linearly polarized light ray 38 passes through the substrate 12 and the electrode 18 and illuminates the coating mixture. At the interface 44, simultaneous polarized UV light induced phase separation and reactive liquid crystal monomer are obtained. The one-step method of the present invention results in liquid crystal alignment at interface 46 without a separate alignment layer, thereby eliminating the requirement for additional spin coating and rubbing steps.

Similarly, the reactive liquid crystal monomer can be selected from nematic diepoxy monomers having epoxy polymerizable groups and chiral diepoxy dopants. The photomonomer, photoinitiator, and cold cure polyimide are mixed with the reactive epoxy-based monomer. This mixture is spin-coated on a substrate and irradiated as described above. Illumination of polarized UV light causes simultaneous phase separation and photoalignment.

It is believed that the one-step method described above is most effective and efficient in forming a uniformly aligned liquid crystal device without a separate well-defined alignment layer. Other methods described above, such as methods utilizing light radiation, heat and / or solvent evaporation, may be implemented based on the above teachings to achieve approximately the same results.

In another example of the one-step method, photocrosslinking containing functional side groups such as cinnamate or coumarin is prepared and spin-coated on a substrate. Liquid crystal diacrylate, divinyl ether, diepoxy, liquid crystal diacetylene, or 2
The other monomers having the above functional groups and the reactive liquid crystal monomer of the photoinitiator are then spin-coated on top of the polyimide film. Subsequent polarized UV irradiation results in simultaneous photoalignment and photopolymerization. Spin-coating the reactive liquid crystal monomer onto the polyimide before the polyimide is cured may make this surface slightly non-uniform, but does not interfere with the alignment of the liquid crystal material.

In instances where multiple alignments of liquid crystals are required, multiple steps may be used. The "multi-step method" is where the substrate is coated and treated in the one-step method to produce an alignment layer and / or a layer / microstructure of liquid crystal material, after which the other layers are treated as previously described layers. Spin coated onto and further processed by one or more of the foregoing processes such as visible or UV radiation, heat treatment and combined radiation, or solvent evaporation and combined radiation. The multi-step method comprises a series of at least two material placement steps, in which at least one type of material is used during each step. More specifically, by utilizing the multi-step method of the present invention, uniquely aligned layers or microstructures of different liquid crystal material interfaces can be obtained. Further, as is apparent in FIG. 4, a mask 70 with appropriate apertures is placed between the polarizer and the substrate, repositioned, aligned, and electrically controllable microstructures 72 in various steps. Help the formation of.

An example of a shape that can typically be obtained using the multi-step method of the present invention is shown in FIG. It will be appreciated that the electrode layer 18 may be disposed adjacent to the substrate 12 with the various layers of alignment-inducing polymer having a liquid crystal material disposed thereon as described in the one-step method.

It may be a polyimide-doped polymer layer or may form a substrate or an equivalent film. It is desirable to provide different liquid crystal orientation vector alignments at the interfaces of liquid crystal materials adjacent to different material layers or microstructures. A method of process may be used. Alternatively, the multi-step method involves an anisotropic film in which the material forming the alignment layer is first deposited on the substrate, and other materials including liquid crystal material, prepolymer and aligning agent are deposited thereon. It may be used to form. This material is
It is then phase separated and photoaligned to form an anisotropic film. At a minimum, the end result of the multi-step method is to provide at least an alignment interface layer 63 adjacent the substrate 12 and a liquid crystal layer 66 adjacent the interface layer 63. Further, a second alignment interface layer 68 adjacent to the liquid crystal layer 66 may also be formed. The multi-step method allows the second alignment interface layer to provide the liquid crystal layer 66 with an orientation different from that of the first alignment interface layer 63. It is believed that the multi-step method will be very useful in constructing twisted nematic devices, ultra-twisted nematic devices, optically or electrically controllable birefringent devices or any device that requires a change in orientation of liquid crystal materials. . The materials making up layers 63, 66 and 68 may be arranged and formed depending on the desired end result. It will also be appreciated that a multi-step method may be used to form anisotropic films that cannot otherwise be formed. This method is also advantageous in that the film can be formed twice without spin coating material. Typically, the precursor device utilizes different polarized UV light wavelengths, different polarized visible light wavelengths, polarized UV and visible light, simultaneous visible light emission and heat, simultaneous ultraviolet light emission and solvent evaporation, And subjecting it to a treatment selected from the group consisting of utilizing ultraviolet light radiation. Various examples of multi-step methods and resulting devices are discussed next.

In one example of a multi-step method, an azobenzene liquid crystal polymer (LCP) is spin coated on a substrate. Liquid crystal diacrylate, divinyl ether, diepoxy,
Reactive monomers such as liquid crystal diacetylene or other monomers having two or more functional groups and a suitable photoinitiator are coated on top of the azobenzene LCP film. Subsequent use of polarized UV radiation results in simultaneous photoalignment and photopolymerization and formation of layers 63 and 66. The second spin coating may make the surface of the first film slightly non-uniform, but does not pose a problem for alignment.

In another example of a multi-step method, a photomonomer such as NOA65 and a chromophore material, including a chromophore material, is mixed and coated onto a substrate. The coated substrate is irradiated with linearly polarized UV light, causing periodic undulations of the polymer surface,
Form the layer 63. The reactive liquid crystal monomer is spin coated onto the polymer surface,
Polymerized by irradiation with ultraviolet light. The result is an anisotropic film.

In another example of a multi-step method, a first mixture comprising vinyl ether, a photoinitiator, and a polyimide having a chromophore component is spin coated onto the substrate, eg, less than about 320 nanometers. It is illuminated by linearly polarized UV light of small or equal wavelength. A second mixture including an acrylate, a photoinitiator, and a chromophore-bearing polyimide is spin-coated on the first layer, for example, linearly polarized light having a wavelength greater than or equal to about 350 nanometers. It is irradiated with the emitted ultraviolet light. It will be appreciated that the desired liquid crystal material may be incorporated into the first or second mixture. Moreover, the orientation of the linear polarizer 36 is optionally changed after the first exposure of the first material to obtain the desired second orientation. Further, the wavelength of light selected will depend on the chromophore / photoalignment material selected. Depending on which mixture contains the liquid crystal material, the light source 3
The position of 2 may be adjusted accordingly. The result is a multilayer anisotropic film,
Here, each layer is individually and uniquely oriented, which is useful for display devices that require optical compensation and different substrate surface orientation changes. It will be appreciated by those skilled in the art that the mixture can be used and processed in the reverse order. In other words, this layer may be used continuously and exposed to the application of UV light. Alternatively, one layer is arranged,
It may be exposed to UV light and then the second layer may be disposed and exposed to UV light.

Similarly, by selecting the appropriate combination of components, the multi-step method of the present invention can be utilized to manufacture a coated substrate, wherein one layer comprises vinyl ether, photoinitiator, and The second layer includes a polyimide having a chromophore and is treated with UV radiation as described above, and the second layer includes a polyimide having an acrylate and a chromophore and is treated with visible radiation. A sufficient amount of at least about 1% maleinimide is included in the mixture to polymerize and align the material such that the material is sensitive to visible light. As a result, the mixture is exposed to visible light having a wavelength of, for example, greater than or equal to 410 nanometers. As aforementioned,
The liquid crystal material may be in either the first or second mixture. of course,
The polarization direction may be changed to change the orientation of the liquid crystal material as needed.
Such a multi-step method has uses for the production of retardation films as well as other electro-optical components.

In another embodiment of the multi-step method of the present invention, a first layer comprising an epoxy monomer and a curing agent is coated on a substrate and heat treated to induce polymerization. A UV curable monomer, a photoinitiator, and a polyimide for photoalignment are coated on the first layer and irradiated with linearly polarized UV radiation. The layers may be used in reverse order if desired. In this case, the polyimide with the chromophore is included in the thermoforming layer. As shown above,
The liquid crystal material may be included in the mixture in either the first or second layers. Such devices provide different liquid crystal alignments for optical delay, optical compensation and adjustable delay.

In yet another embodiment, a first layer comprising a reactive liquid crystal monomer, a photoinitiator and a polyimide is coated on a substrate and linearly polarized as taught above. Is irradiated with visible radiation. A second layer containing an epoxy resin and a curing agent is added over the first layer and heated to cause solvent-induced phase separation of the second layer as taught above. The addition of this layer may also be reversed if desired.

Similarly, thermally induced layer separation can be utilized in the multi-step method of the present invention. In the layer containing PMMA and the reactive liquid crystal monomer, the ultraviolet or visible light irradiation layer can be attached before or after the treatment. When UV light is used, prepolymers such as PMMA or polyimide are used with reactive monomers, UV photoinitiators and liquid crystal materials. If visible light is used, the UV photoinitiator is replaced with a visible light photoinitiator.

Those skilled in the art will appreciate that the advantages of the present invention are numerous. First of all, the light modulator of the present invention is an optically and electrically controllable device. The disclosed method of manufacturing an aligned liquid crystal device without an alignment layer formed separately in a single UV exposure process is simpler, more cost effective, and any liquid crystal that currently uses an alignment layer. The device also replaces known methods for manufacturing. Removal of the rubbing procedure results in less damage to the device and improves manufacturing yield. The high temperature baking process used in the prior art allows the use of plastic substrates.

The method of the present invention is very versatile, a little named nematic material,
It may be used with ferroelectrics, antiferroelectrics, cholesteric liquid crystal materials. The method of the present invention can be used to produce multilayer anisotropic films, where each layer has a unique and unique orientation. By adjusting the incident angle of irradiation, a molecular pretilt can be obtained in the liquid crystal layer. Patterned microstructures that utilize masks during the application of ultraviolet or visible light can be switched optically, electrically, or can be used to fabricate active devices or anything that is sensitive to mechanical stimuli. Further, the method taught by this disclosure is applicable to any liquid crystal that requires alignment.

Therefore, it can be seen that the objects of the present invention are met by this structure and its method for use as set out above. While according to the patent statute, only the best mode and preferred embodiments have been shown and described in detail, it should be understood that the invention is not limited thereto or by this. Reference should therefore be made to the claims set forth above in order to understand the actual scope and breadth of the present invention.

[Brief description of drawings]

FIG. 1 is an enlarged partial cross-sectional schematic view of a precursor of a light modulation device according to the present invention before polymerization and alignment.

FIG. 2 is an enlarged partial cross-sectional schematic view of a light modulation device after simultaneous one-step alignment and polymerization according to the present invention.

FIG. 3 is an enlarged partial cross-sectional schematic view of an apparatus after performing a multi-step method according to the present invention.

FIG. 4 is an enlarged partial cross-sectional schematic view of a microstructure device after performing a multi-step method according to the present invention.

[Procedure for Amendment] Submission for translation of Article 34 Amendment of Patent Cooperation Treaty

[Submission date] October 26, 2001 (2001.10.26)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Contents of correction]

Production of aligned liquid crystal cells / membranes by simultaneous alignment and phase separation

[Claims]

Detailed Description of the Invention

[0001] Technical Field The present invention belongs to the technical of the optical modulator are made of a composite organic materials using self-aligned layer. In particular, the present invention involves in-situ photoalignment using polarized ultraviolet (UV) exposure and the process of one or more steps to align an aligned liquid crystal film adjacent to a polymer layer with or without pretilt. The two processes of the phase separation composite organic membrane used (PSCOF) and the anisotropic phase separation used are combined. In particular, this method allows the alignment of aligned liquid crystal cells without the requirement for two prefabricated alignment layers on each substrate.

[0002] PSCOF method has recently been invented in order to adjust the adjacent parallel layers of polymer and liquid crystal, it was used in Kent State University. This method is disclosed in US Pat. No. 5,949,508, which is incorporated herein by reference. This PSC
OF methods include processes similar to those used in the manufacture of polymer dispersed liquid crystal films.
The polymer and the liquid crystal are mixed in a predetermined ratio and placed between or on one substrate with a well-defined thickness. When the beam of ultraviolet light is incident from one side, the phase separation process is started. The rate of polymerization (and phase separation) is faster near the UV radiation source due to the higher intensity. When the phase separation starts, the organic or liquid crystal material is driven out of the polymerized part and starts to move away from the UV radiation source. As a result, a uniform film of polymer is obtained on one side of the cell and a substantially uniform layer of liquid crystal is formed on the opposite side of the cell away from the UV light source. Separation of the liquid crystal from the polymer can be facilitated by a pre-positioned alignment layer that the liquid crystal material is to wet on the substrate away from the UV source. As such, an aligned liquid crystal film may be formed.

Alignment layers are typically made of long chain polymeric materials that are subsequently subjected to treatments such as mechanical rubbing or UV exposure to alter surface properties. There are several commonly accepted techniques for forming alignment layers on the substrates of liquid crystal devices. Commonly used methods are rubbing or photoalignment of organic / polymer films and evaporation of inorganic materials. Although each method can align the liquid crystal material, each method has unique drawbacks.

The most commercially used method of forming alignment layers is the rubbing method. In this method, for example, polyamic acid is spin-coated or otherwise deposited on a substrate. Polyamic acid undergoes two heat treatments, a soft bake and a hard bake, to form a polyimide (PI) film. After a suitable cooling period, the PI membrane is rubbed with a velvet-like cloth in a uniform, single direction. When the liquid crystal later contacts the rubbed surface, the liquid crystal aligns along the rubbing direction. Unfortunately, this method produces mechanical damage and electrostatic charge, both of which adversely affect liquid crystal displays, especially those using thin film transistors. The rubbing method uses cloth and P that may contaminate the liquid crystal material.
Dust from I is also generated.

Another method of forming the alignment layer involves forming a PI film on the substrate as described above. The linearly polarized UV light is projected onto this surface to produce the desired molecular alignment. The ultraviolet radiation anisotropically photodissociates the photoelectric bond of PI including the photosensitive bond of imide. This selectively reduces the polarizability of the PI molecule, altering its surface properties and morphology. Unfortunately, this method results in an alignment layer with weak anchoring of the liquid crystal and unfavorable thermal and chemical stability.
Moreover, this method requires expensive multi-step processing. Yet another drawback of this method is that it provides only limited charge retention and relatively low thermal stability when compared to rubbing techniques.

Similar methods of adjusting the alignment layer by using photopolymers are also known. For example, poly (vinyl) 4-methoxy-cinnamate (PVMC
Photosensitive polymers such as films, poly (vinyl) cinnamate (PVC) films and polysiloxane cinnamate films can be used to align liquid crystal materials. When exposed to linearly polarized ultraviolet light (LPUV), these materials initiate a photoreaction after evaporation of the solvent. This method results in cross-linking and the resulting orientation of uniaxial side chains in the direction determined by the direction of linearly polarized light. However, this method does not chemically fix the molecular orientation, and the alignment is
It is lost during exposure because it usually produces unpolarized UV light. Furthermore, the chemical constituents of the material disappear over time. Therefore, the alignment layer thus produced does not provide a certain stable orientation of the liquid crystal material.

Yet another method of forming an alignment layer on a substrate is vapor deposition of an inorganic material on the surface of the substrate at various angles of incidence. This forms an alignment layer that physically aligns the alignment vector of the liquid crystal. The inorganic materials used include silicon oxide and magnesium oxide. This attachment method has proven to be cumbersome and difficult to use in the manufacturing process.

Another method of forming the alignment layer developed by Kent State University is the in situ UV exposure method. This method is described in US Pat.
No. 936,691 and incorporated herein by reference. The in-situ method is similar to the conventional method of exposing a PI film to polarized UV light. However, the in situ method exposes a polyimide film (PI) to ultraviolet radiation, but the film is soft baked and hard baked. The resulting alignment layer has higher anchoring energy and is more thermally stable than conventional UV exposure techniques. For example, a cell conditioned by the conventional method is
Whereas the cells prepared by the in situ method show no signs of degradation at 300 ° C. for 12 hours, whereas alignment is lost when kept at 0 ° C.
The in-situ method of forming the alignment layer avoids many of the drawbacks of other methods known in the art, but requires fewer steps and simpler processing steps.

Although the in situ method has been shown to be effective, the alignment film still requires that it be properly placed and processed. Moreover, in the case of the full alignment method described above, this alignment can be damaged if no care is taken when transferring substrates between manufacturing equipment. It is also theorized that currently known alignment layers only directly affect the liquid crystal material adjacent to it.

Polymer-dispersed liquid crystal (PDLC) devices may be manufactured by applying laser interference light to a polymerizable composition that includes a polymerizable compound having a photodimerizable structure and a low molecular weight liquid crystal. No. 6,083,575.
Laser interference light causes polymer phase separation. Polarized light is then applied to align the small molecule liquid crystals. As shown in this patent, a polymer-dispersed liquid crystal is a display device in which a liquid crystal is dispersed in a polymer gap having a three-dimensional structure. However, while US Pat. No. 6,083,575 teaches the use of photosensitive polymers, the teachings of this patent are limited to polymer dispersed liquid crystal cells. However, various limitations are inherent in PDLC cells, as compared to cells using, for example, phase-separated composite organic membranes. PDLC cells have higher voltage requirements, slower switching speeds and very low multiplexing. Phase-separated composite organic films also enable the formation and use of more defined geometries, especially for bulk type liquid crystal displays. No teaching or suggestion is made regarding the structure of liquid crystal elements of any type other than polymer dispersed liquid crystals, such as phase-separated composition organic films such as in this application or the use of photosensitive polymers to form alignment films.

In light of the foregoing, the present technology requires light modulation techniques that include phase-separated composite organic films, and fabrication methods such as films that are homogeneously aligned in composition, and thus the preparation of distinct and well-defined alignment layers. And it is clear that no treatment is required.

[0012] In light of the disclosure above of the invention, a first aspect of the present invention is to provide a method of manufacturing an optical modulation apparatus and such apparatus comprises a phase separated composite organic film or microstructure , Where the device uniformly aligns the liquid crystal material without the requirement for two separate alignment layers.

Another aspect of the present invention is to provide a self-aligned phase-separated composite organic film made by using a one-step or multi-step method of simultaneous phase separation and photoalignment.

Yet another aspect of the present invention is to provide an anisotropic film or microstructure made by the method of simultaneous photoalignment and photopolymerization.

Yet another aspect of the present invention is to provide an anisotropic film or a microstructure by a method of simultaneous photoalignment and solvent induced phase separation or a method of solvent induced phase separation. Where the liquid crystal alignment is
Obtained at all internal polymer interfaces (walls) of the microstructure.

Another aspect of the invention is to provide a film or microstructure made by the method of simultaneous photoalignment and thermally induced polymerization.

Yet another aspect of the present invention is to provide an anisotropic film or microstructure comprising two or more layers prepared using multiple steps, wherein a liquid crystal The material layers are separately aligned on each surface of the membrane and may have different orientations.

According to another aspect of the present invention, a step of spin-coating a polyimide capable of photocrosslinking onto a substrate, a step of spin-coating a reactive liquid crystal monomer onto the polyimide, and using polarized light, simultaneously crosslinking-linking a polyamic acid. And optically aligning the reactive monomer and polymerizing the reactive monomer. UV light is polyimide /
A suitable morphology is created at the liquid crystal interface, which in turn aligns the liquid crystal material.

Further, according to another aspect of the present invention, a step of spin-coating a liquid crystal polymer (LCP) on a substrate, a step of spin-coating a reactive monomer on the LCP, applying polarized light, and at the same time exposing the LCP to light. Aligning, photo-aligning the reactive monomers, and polymerizing, to obtain an anisotropic film.

Yet another aspect of the present invention is an anisotropic film including the steps of preparing a mixture of liquid crystal, polymer and solvent, and applying polarized light, and at the same time photoaligning the liquid crystal material and phase separation. It is obtained by the method of manufacturing.

Yet another aspect of the present invention is to prepare a mixture of liquid crystal material and a thermopolymerizable monomer, place the mixture on a substrate, subject the mixture to heat treatment to polymerize the monomer, The method of manufacturing an anisotropic film, the method comprising receiving polarized light and optically aligning a liquid crystal material.

Another aspect of the present invention is obtained by a method of producing an anisotropic film and / or microstructure composed of two or more layers or microstructures, which method comprises two or more layers. Of the above method in sequence to prepare multiple layers of alignment material, where the liquid crystals are individually aligned individually at each interface / surface.

The foregoing and other objects of the invention will become apparent as the detailed description proceeds, and a mixture of liquid crystals, prepolymers and polarization sensitive materials is prepared, the mixture is placed on a substrate, and a light source is provided. Phase separation of the co-mixture and alignment of the phase separated liquid crystals to form a layer of homogeneously aligned liquid crystal material on the substrate adjacent to the layer of polymer and polarization sensitive material. And a method of simultaneously producing a phase separation inducing film having alignment, which includes inducing.

Another aspect of the invention provides a substrate, a first mixture comprising at least a first polarization sensitive chemical and a prepolymer, and at least a second polarization sensitive chemical. A second mixture including a prepolymer is provided, liquid crystals are mixed into the first or second mixture, the first mixture is disposed on a substrate, and the second mixture is mixed with the first mixture.
A mixture of at least visible light, ultraviolet light, heat-induced, chemically-induced, and solvent-induced first treatment of the mixture, and at least visible light, ultraviolet light, Obtained by a method of manufacturing a liquid crystal device having alignment properties, comprising initiating treatment of a second mixture from the group consisting of thermal induction, chemical induction, and solvent induction, and the treatment provides alignment alignment to liquid crystals. give.

Yet another object of the present invention is obtained by a cell having alignment properties comprising at least one substrate and a mixture arranged on the substrate, the mixture comprising at least a liquid crystal material and a prepolymer material. , A polarization sensitive material, and the use of co-polymerization and polarization results in phase separation and photoalignment of the mixture, thus forming a polymer microstructure that imparts alignment properties to the liquid crystal material.

These and other objects of the present invention, as well as its advantages over the existing prior art as will become apparent from the following description, are accomplished by the improvements described and claimed below.

For a full understanding of the objects, techniques and structures of the present invention, reference should be made to the following detailed description and accompanying drawings.

Referring to the best mode now to Figure 1 for carrying out the invention, it is understood that the precursor of the light modulation device made in accordance with the present invention is generally designated by numeral 10. As will be apparent, the light modulation cell precursor 10
May be provided but does not include a separate well-defined alignment layer. The light modulator of the present invention may be manufactured by a method that does not require a separate spin coating step to deposit the alignment layer precursor material on the substrate. This method does not require soft and / or hard baking of the alignment layer. Furthermore, this method does not require rubbing or otherwise physically contacting the alignment layer to impart properties that later affect the liquid crystal material.

The light modulator precursor shown in FIG. 1 comprises a pair of opposing optically transparent substrates 12, which may be glass, plastic or other materials generally known to those skilled in the art. Advantageously, the device does not have to withstand the temperatures at which the prior art alignment layers need to be imidized. As will be apparent, temperature sensitive materials not heretofore suitable as substrates can be used in the present invention. In other words, flexible substrate materials such as plastic or polymer sheets may now be used for liquid crystal devices that do not have to withstand the high temperatures normally used in hard bake and soft bake alignment layer forming processes. .

A polariser 14 may be disposed on the outer surface of each substrate 12 for the purpose of modifying the optical properties of the transmitted light to provide a cell for operating in transmissive mode. The electrodes 18 may be provided on the inner surface of each of the substrates 12. In the preferred embodiment, each electrode 18 is an indium-tin oxide film material. Alternatively, a mirror or light diffuser may be added to the outside of the substrate facing the light source to provide a device that operates in reflective mode.

The power supply 20 is attached to the electrode 18 through the switch 22. This switch can be used to connect the power supply, short the two electrodes, disconnect the electrodes, and store charge on the electrodes. The application of electric or electromagnetic fields or other external forces results in optical switching of liquid crystals or organic materials placed between the substrates. Switch 22
The operations of may be driven by an electronic drive, as appropriate. The use of electronic driver circuitry allows addressing specific areas of the matrix cell device which in turn enable the formation of high contrast between areas. As shown in FIG. 1, the cell gap thickness between the electrodes is defined by dimension 26.

A composite organic material 28 comprising at least the following components, an organic or liquid crystal material, a prepolymer and an aligning agent such as a low temperature curable polyimide is deposited between the substrates 12. To obtain this material 28, the liquid crystal material is combined with the prepolymer and polyimide in solution and filled between the substrates 12 by capillary action. Of course, other known filling methods may be used. The edge of the substrate 12 is sealed using known methods. Alternatively, material 28 may be spin coated on a single substrate.

Referring now to FIG. 2, it can be seen that the light modulator cell produced by the one-step simultaneous phase separation and alignment method according to the present invention is generally designated by the numeral 30.

Usually, the “one-step method” is a method in which a layer of a material containing at least an organic or liquid crystal material, a prepolymer, a polarization-sensitive aligning agent such as a chromophore is deposited on a substrate, for example by spin coating. Where the coated substrate is visible light radiation,
Alternatively, it is subjected to a treatment selected from polarized ultraviolet radiation and some type of phase separation. The one-step method is thus characterized in that all components are subjected to the same treatment at the same time so as to uniformly align the phase separated liquid crystal material components.

A light source 32, such as ultraviolet light or visible light, is disposed below and in proximity to the linear polarizer 36. When energized, a linearly polarized light beam 38 is passed through the substrate 12,
It produces a ray 34 that impinges on a linear polarizer 36 that is directed into the cell gap 26.
Light, or some other treatment shown, predominantly induces polymerization of the prepolymer mixed with the aligning agent. As the polymerization proceeds, phase separation occurs between the liquid crystal material and the polymer / alignment. This is known as polymerization-induced phase separation. In particular, the light transmissive solid polymer layer 40 is formed on the electrode 18 of the substrate 12 adjacent the light source 32. The liquid crystal film layer 42 is formed on the opposite substrate 12 adjacent to the other electrode 18.
At the same time as the phase separation, the linearly polarized light beam 38 breaks the photopolymerizable bond of the prepolymer / polyimide layer, causing the polymer segment to move along the direction perpendicular to the direction of polarization of the linearly polarized light beam. Align. Further, depending on the chemistry of the material, the light beam 38 may direct the polymer segments parallel or perpendicular to the substrate or may crosslink the polymer material in a particular direction parallel to the substrate. This facilitates alignment of the liquid crystal film 42 at the interface 44 between the polymer layer 40 and the liquid crystal layer 42. At the interface 44, the liquid crystal appears to affect the aligned anchoring state of the alignment during phase separation. It is also believed that a minimal amount of polyimide material adheres to the opposing substrate and resembles the alignment orientation at interface 44. If desired, a separate and unique alignment layer may be provided on the substrate for interface 44.

As can be seen in FIG. 2, the thickness of the polymer layer is defined by the dimension 52 and the thickness of the liquid crystal is indicated by the dimension 54. The physical parameters of the liquid crystal film, such as the liquid crystal film thickness, alignment state and liquid crystal material, can be selected for the desired purpose by adjusting the composition and using an appropriately sized space. Homogeneously aligned cells using nematic liquid crystals were formed by the method of the present invention. Further, it has been found that the ferroelectric and antiferroelectric materials having such a structure have gray scale and smooth bistability. These cells have a very low threshold voltage, scatter almost no light (no haze at all), and are mechanically and electrically robust. Some liquid crystal materials exhibit the modified electro-optical (EO) behavior of phase separated composite organic films. Optically controllable birefringent devices can also be formed using this method. This method allows the production of uniform, very thin liquid crystal films. Several uniform films with thicknesses comparable to the wavelength of red light were prepared with the method of the invention.

It will be appreciated by those skilled in the art that, in the practice of the present invention, phase separation can be accomplished by thermal induction techniques, chemical induction techniques, or solvent induction techniques. Any of these techniques can be used with irradiation to perform simultaneous phase separation and photoalignment. Without wishing to be bound by theory, it is believed that the polarized light rays are important in aligning the liquid crystal material in a uniform manner at interfaces 44 and 46.

Suitable prepolymers for the practice of the present invention are photopolymerizable monomers that are sensitive to the direction of polarization of ultraviolet light, so that exposure to ultraviolet light simultaneously and directionally polymerizes the monomers. Align the polymer macroscopically. Prepolymers that are not normally sensitive to the polarization of UV light may be useful when modified, for example by the addition of chromophore components. Thus, suitable prepolymers include, but are not limited to, NOA-65 (commercially available from Norland Products, Inc.), vinyl ethers, acrylates, epoxies, diacetylenes, vinyls and the like. In the case of a chromophore, materials such as azobenzene, stilbenzene, cinnamate, chalcone, coumarin, dimaleimidimide and the like can be used. Useful polyimides are homopolyimides or copolyimides having side chains with low light absorption, SE-1180,610 (commercially available from Nissan Chemical Industries) and a functional group having a chromophore incorporated therein. Including.

The liquid crystal material can be selected depending on the desired type of light modulator. Suitable liquid crystal materials include, but are not limited to, nematic liquid crystal materials, ferroelectrics, antiferroelectrics, cholesteric liquid crystal materials and related liquid crystal materials.

As indicated above, by using the method of the present invention, a parallel film of polymer and aligned liquid crystals can be prepared either inside the cell or on the substrate. Referring now to FIG. 3, it can be seen that the apparatus used to carry out either the one-step or multi-step method of the present invention is generally designated by the numeral 60. If heat-induced polymerization is used, the device is enclosed within heat source 62. Heat from the light source 32 may also be used if appropriate.

In one embodiment of the one-step method as defined above, a mixture of reactive liquid crystal monomer, photomonomer and low temperature cure polyimide is formulated to prepare an anisotropic film. The reactive liquid crystal monomer can be selected from nematic diacrylate monomers having acrylate polymerizable groups and chiral diacrylate dopants. A photomonomer such as NOA-65 and a low temperature cure polyimide such as SE-1180 are mixed with a reactive liquid crystal monomer to form a photosensitive material. This mixture is spin coated onto the substrate. As shown in FIG. 2, the ultraviolet light source 3
2 emits a ray 34 that passes through a linear polarizer 36. The linearly polarized light ray 38 passes through the substrate 12 and the electrode 18 and illuminates the coating mixture. At the interface 44, simultaneous polarized UV light induced phase separation and reactive liquid crystal monomer are obtained. The one-step method of the present invention results in liquid crystal alignment at interface 46 without a separate alignment layer, thereby eliminating the requirement for additional spin coating and rubbing steps.

Similarly, the reactive liquid crystal monomer can be selected from nematic diepoxy monomers having epoxy polymerizable groups and chiral diepoxy dopants. The photomonomer, photoinitiator, and cold cure polyimide are mixed with the reactive epoxy-based monomer. This mixture is spin-coated on a substrate and irradiated as described above. Illumination of polarized UV light causes simultaneous phase separation and photoalignment.

It is believed that the one-step method described above is most effective and efficient in forming a homogeneously aligned liquid crystal device without a separate well-defined alignment layer. Other methods described above, such as methods utilizing light radiation, heat and / or solvent evaporation, may be implemented based on the above teachings to achieve approximately the same results.

In another example of a one-step method, photocrosslinks containing functional side groups such as cinnamate or coumarin are prepared and spin-coated on a substrate. Liquid crystal diacrylate, divinyl ether, diepoxy, liquid crystal diacetylene, or 2
The other monomers having the above functional groups and the reactive liquid crystal monomer of the photoinitiator are then spin-coated on top of the polyimide film. Subsequent polarized UV irradiation results in simultaneous photoalignment and photopolymerization. Spin-coating the reactive liquid crystal monomer onto the polyimide before the polyimide is cured may make this surface slightly non-uniform, but does not interfere with the alignment of the liquid crystal material.

In instances where multiple alignments of liquid crystals are required, multiple steps may be used. The "multi-step method" is where the substrate is coated and treated in the one-step method to produce an alignment layer and / or a layer / microstructure of liquid crystal material, after which the other layers are treated as previously described layers. Spin coated onto and further processed by one or more of the foregoing processes such as visible or UV radiation, heat treatment and combined radiation, or solvent evaporation and combined radiation. The multi-step method comprises a series of at least two material placement steps, in which at least one type of material is used during each step. More specifically, by utilizing the multi-step method of the present invention, uniquely aligned layers or microstructures of different liquid crystal material interfaces can be obtained. Further, as is apparent in FIG. 4, a mask 70 with appropriate apertures is placed between the polarizer and the substrate, repositioned, aligned, and electrically controllable microstructures 72 in various steps. Help the formation of.

An example of a shape that can typically be obtained using the multi-step method of the present invention is shown in FIG. It will be appreciated that the electrode layer 18 may be disposed adjacent to the substrate 12 with the various layers of alignment-inducing polymer having a liquid crystal material disposed thereon as described in the one-step method.

It may be a polyimide-doped polymer layer or may form a substrate or an equivalent film. It is desirable to provide different liquid crystal orientation vector alignments at the interface of liquid crystal materials adjacent to different material layers or microstructures. A method of process may be used. Alternatively, the multi-step method involves an anisotropic film in which the material forming the alignment layer is first deposited on the substrate, and other materials including liquid crystal material, prepolymer and aligning agent are deposited thereon. It may be used to form. This material is
It is then phase separated and photoaligned to form an anisotropic film. At a minimum, the end result of the multi-step method is to provide at least an alignment interface layer 63 adjacent the substrate 12 and a liquid crystal layer 66 adjacent the interface layer 63. Further, a second alignment interface layer 68 adjacent to the liquid crystal layer 66 may also be formed. The multi-step method enables the second alignment interface layer to provide the liquid crystal layer 66 with an orientation that is different from the orientation of the first alignment interface layer 63. It is believed that the multi-step method will be very useful in constructing twisted nematic devices, ultra-twisted nematic devices, optically or electrically controllable birefringent devices or any device that requires a change in orientation of liquid crystal materials. . The materials making up layers 63, 66 and 68 may be arranged and formed depending on the desired end result. It will also be appreciated that a multi-step method may be used to form anisotropic films that cannot otherwise be formed. This method is also advantageous in that the film can be formed twice without spin coating material. Usually, the precursor device utilizes different polarized UV light wavelengths, different polarized visible light wavelengths, polarized UV and visible light, simultaneous visible light emission and heat, simultaneous UV light emission and solvent evaporation, And subjecting it to a treatment selected from the group consisting of utilizing ultraviolet light radiation. Various examples of multi-step methods and resulting devices are discussed next.

In one example of a multi-step method, azobenzene liquid crystal polymer (LCP) is spin coated onto a substrate. Liquid crystal diacrylate, divinyl ether, diepoxy,
Reactive monomers such as liquid crystal diacetylene or other monomers having two or more functional groups and a suitable photoinitiator are coated on top of the azobenzene LCP film. Subsequent use of polarized UV radiation results in simultaneous photoalignment and photopolymerization and formation of layers 63 and 66. The second spin coating may make the surface of the first film slightly non-uniform, but does not pose a problem for alignment.

In another example of a multi-step method, photomonomers such as NOA65 and chromophore material, such as NOA65, are mixed and coated onto a substrate. The coated substrate is irradiated with linearly polarized UV light, causing periodic undulations of the polymer surface,
Form the layer 63. The reactive liquid crystal monomer is spin coated onto the polymer surface,
Polymerized by irradiation with ultraviolet light. The result is an anisotropic film.

In another example of a multi-step method, a first mixture comprising vinyl ether, a photoinitiator, and a polyimide having a chromophore component is spin coated onto the substrate, eg, less than about 320 nanometers. It is illuminated by linearly polarized UV light of small or equal wavelength. A second mixture including an acrylate, a photoinitiator, and a chromophore-bearing polyimide is spin-coated on the first layer, for example, linearly polarized light having a wavelength greater than or equal to about 350 nanometers. It is irradiated with the emitted ultraviolet light. It will be appreciated that the desired liquid crystal material may be incorporated into the first or second mixture. Moreover, the orientation of the linear polarizer 36 is optionally changed after the first exposure of the first material to obtain the desired second orientation. Further, the wavelength of light selected will depend on the chromophore / photoalignment material selected. Depending on which mixture contains the liquid crystal material, the light source 3
The position of 2 may be adjusted accordingly. The result is a multilayer anisotropic film,
Here, each layer is individually and uniquely oriented, which is useful for display devices that require optical compensation and different substrate surface orientation changes. It will be appreciated by those skilled in the art that the mixture can be used and processed in the reverse order. In other words, this layer may be used continuously and exposed to the application of UV light. Alternatively, one layer is arranged,
It may be exposed to UV light and then the second layer may be disposed and exposed to UV light.

Similarly, by selecting the appropriate combination of components, the multi-step method of the present invention can be utilized to make a coated substrate, wherein one layer comprises vinyl ether, photoinitiator, and The second layer includes a polyimide having a chromophore and is treated with UV radiation as described above, and the second layer includes a polyimide having an acrylate and a chromophore and is treated with visible radiation. A sufficient amount of at least about 1% maleinimide is included in the mixture to polymerize and align the material so that it is sensitive to visible light. As a result, the mixture is exposed to visible light having a wavelength of, for example, greater than or equal to 410 nanometers. As aforementioned,
The liquid crystal material may be in either the first or second mixture. of course,
The polarization direction may be changed to change the orientation of the liquid crystal material as needed.
Such a multi-step method has uses for the production of retardation films as well as other electro-optical components.

In another embodiment of the multi-step method of the present invention, a first layer comprising an epoxy monomer and a curing agent is coated on a substrate and heat treated to induce polymerization. A UV curable monomer, a photoinitiator, and a polyimide for photoalignment are coated on the first layer and irradiated with linearly polarized UV radiation. The layers may be used in reverse order if desired. In this case, the polyimide with the chromophore is included in the thermoforming layer. As shown above,
The liquid crystal material may be included in the mixture in either the first or second layers. Such devices provide different liquid crystal alignments for optical delay, optical compensation and adjustable delay.

In yet another embodiment, a first layer comprising a reactive liquid crystal monomer, a photoinitiator and a polyimide is coated on a substrate and linearly polarized as taught above. Is irradiated with visible radiation. A second layer containing an epoxy resin and a curing agent is added over the first layer and heated to cause solvent-induced phase separation of the second layer as taught above. The addition of this layer may also be reversed if desired.

Similarly, thermally induced layer separation can be utilized in the multi-step method of the present invention. In the layer containing PMMA and the reactive liquid crystal monomer, the ultraviolet or visible light irradiation layer can be attached before or after the treatment. When UV light is used, prepolymers such as PMMA or polyimide are used with reactive monomers, UV photoinitiators and liquid crystal materials. If visible light is used, the UV photoinitiator is replaced with a visible light photoinitiator.

Those skilled in the art will appreciate that the advantages of the present invention are numerous. First of all, the light modulator of the present invention is an optically and electrically controllable device. The disclosed method of manufacturing an aligned liquid crystal device without an alignment layer formed separately in a single UV exposure process is simpler, more cost effective, and any liquid crystal that currently uses an alignment layer. The device also replaces known methods for manufacturing. Removal of the rubbing procedure results in less damage to the device and improves manufacturing yield. The high temperature baking process used in the prior art allows the use of plastic substrates.

The method of the present invention is very versatile, a little named nematic material,
It may be used with ferroelectrics, antiferroelectrics, cholesteric liquid crystal materials. The method of the present invention can be used to produce multilayer anisotropic films, where each layer has a unique and unique orientation. By adjusting the incident angle of irradiation, a molecular pretilt can be obtained in the liquid crystal layer. Patterned microstructures that utilize masks during the application of ultraviolet or visible light can be switched optically, electrically, or can be used to fabricate active devices or anything that is sensitive to mechanical stimuli. Further, the method taught by this disclosure is applicable to any liquid crystal that requires alignment.

Therefore, it can be seen that the objects of the invention are met by this structure and its method for use as set out above. While according to the patent statute, only the best mode and preferred embodiments have been shown and described in detail, it should be understood that the invention is not limited thereto or by this. Reference should therefore be made to the claims set forth above in order to understand the actual scope and breadth of the present invention.

[Brief description of drawings]

FIG. 1 is an enlarged partial cross-sectional schematic view of a precursor of a light modulation device according to the present invention before polymerization and alignment.

FIG. 2 is an enlarged partial cross-sectional schematic view of a light modulation device after simultaneous one-step alignment and polymerization according to the present invention.

FIG. 3 is an enlarged partial cross-sectional schematic view of an apparatus after performing a multi-step method according to the present invention.

FIG. 4 is an enlarged partial cross-sectional schematic view of a microstructure device after performing a multi-step method according to the present invention.

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE), OA (BF, BJ , CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, K E, LS, MW, MZ, SD, SL, SZ, TZ, UG , ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, C N, CR, CU, CZ, DE, DK, DM, EE, ES , FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, KE, KG, KP, K R, KZ, LC, LK, LR, LS, LT, LU, LV , MA, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, S I, SK, SL, TJ, TM, TR, TT, TZ, UA , UG, US, UZ, VN, YU, ZA, ZW (72) Inventor Kim Jae Hoon             Republic of Korea Kyungui 449-840 Yong             Gin-City Sangyun-Listenwo             Apartment 103-702 F-term (reference) 2H049 BA02 BA06 BA42 BB42 BC01                       BC02 BC05 BC22                 2H089 HA04 JA04 KA08 NA22 QA12                 2H090 HB08Y HC05 LA09 LA16                       MA00 MA10 MB01 MB12

Claims (29)

[Claims] 1. Preparing a mixture of a liquid crystal, a prepolymer and a polarization sensitive material, disposing the mixture on a substrate, applying a polarization from a light source, and a layer of the polymer and the polarization sensitive material. Aligning the phase-separated organic film, comprising inducing simultaneous phase separation of the mixture and alignment of the phase-separated liquid crystals to form a layer of homogeneously aligned liquid crystal material adjacent to the substrate on the substrate. Method of manufacturing at the same time. 2. The method of claim 1, further comprising disposing a second substrate over the layer. 3. The method of claim 1, wherein the applying step mixes at least a major portion of the polarization sensitive material with the prepolymer, the polarization sensitive material imparting alignment properties to the liquid crystal material. Method. 4. The method of claim 1, further comprising inserting a polarizer between the light source and the substrate to provide a desired alignment alignment to the liquid crystal material. 5. The method of claim 4, further comprising positioning an ultraviolet light source near the substrate opposite the side having the placement mixture. 6. The method of claim 4, further comprising positioning a visible light source near the substrate opposite the side having the placement mixture. 7.   Preparing an initial mixture of an initial prepolymer and a material sensitive to initial polarization,   Coating the initial mixture on the substrate prior to the placing step, The method of claim 1, further comprising: 8. The method of claim 7, wherein the initial polarization sensitive material is sensitive to a different wavelength of light than the polarization sensitive material. 9. The method of claim 8, further comprising adding an initial polarization to the initial mixture to provide it with an alignment orientation prior to the placing step. 10. The method of claim 8 further comprising adding initial polarization to the initial mixture to provide it with an alignment orientation after the placing step. 11. The method of claim 10, further comprising positioning a mask and a polarizer between the light source and the substrate prior to the applying step to form a layer of the liquid crystal having a microstructure. Method. 12. The method of claim 11, further comprising positioning another mask between the light source and the substrate after the initial adding step. 13. The method of claim 7, wherein the initial polarization sensitive material and the polarizing material are activated with either ultraviolet light or visible light. 14. The method of claim 1, further comprising preparing the mixture having at least a heat-activated prepolymer, thermally activating the mixture to induce phase separation and impart alignment alignment to the liquid crystal. the method of. 15.   15. The method of claim 14, wherein the polarized light is either visible light or ultraviolet light. 16. The method further comprising: conditioning the mixture having an epoxy and a resin, enabling phase separation of the mixture and inducing phase separation of the mixture to impart alignment alignment to the liquid crystal. The method described in 1. 17.   17. The method of claim 16, wherein the polarized light is either visible light or ultraviolet light. 18. The method of claim 1, further comprising positioning a mask and a polarizer between the light source and the substrate prior to the applying step to form a layer of the liquid crystal having a microstructure. Method. 19. Providing a substrate, providing a first mixture comprising at least a first polarization sensitive chemical and a prepolymer, comprising at least a second polarization sensitive chemical and a prepolymer Providing a second mixture, mixing liquid crystals in the first or second mixture, disposing the first mixture on the substrate, adding the second mixture to the first mixture Initiating treatment of said first mixture from the group consisting of at least visible light polarization, ultraviolet light polarization, heat induction, chemical induction and solvent induction, at least visible light polarization, ultraviolet light polarization, Initiating the treatment of the second mixture from the group consisting of thermal induction, chemical induction and solvent induction, the treatment imparting an alignment alignment to the liquid crystal. Method of manufacturing a liquid crystal device having a cement properties. 20. One of the initiating steps comprises simultaneously using one of the polarization treatments and one of the derivation treatments to phase separate the liquid crystal from the prepolymer. The method according to claim 19. 21. The method of claim 19, further comprising securing a second substrate to the first substrate with the first and second mixture therebetween. 22.   The polarization process is   Positioning a light source near the substrate,   Positioning a polarizer between the substrate and the light source, 20. The method of claim 19, comprising: 23. The method further comprising repositioning the polarizer after the first starting step, wherein the polarization sensitive chemistry imparts a different alignment alignment to its respective interface with the liquid crystal. Item 19. The method according to Item 19. 24. The method of claim 17, wherein said inducing treatment phase separates said prepolymer and said polarization sensitive chemicals from said liquid crystal. 25. A cell having alignment properties, comprising at least one substrate and a mixture disposed on said substrate, said mixture being at least a liquid crystal material, a prepolymer material and a polarization sensitive material. Co-polymerization and application of polarized light causes phase separation and photo-alignment of the mixture to form a polymer microstructure that imparts alignment properties to the liquid crystal material. 26. Further comprising a second mixture disposed on said substrate prior to said first mixture, said second mixture comprising at least a second polarization sensitive material, wherein 26. The cell of claim 25, wherein applying causes photoalignment of the second mixture that imparts alignment properties to the liquid crystal material. 27. Separate discrete interfaces between the liquid crystal material and the polymer microstructure and the polarization sensitive material, and between the liquid crystal material and the second polarization sensitive material. 27. The cell of claim 26 formed. 28. The cell of claim 27, wherein the interface aligns the liquid crystal materials of different orientations. 29. The cell of claim 28, wherein the liquid crystal material is formed into a microstructure.