EP1221066A2 - Fabrication d'une cellule et d'un film a cristaux liquides alignes par alignement simultane et separation de phase - Google Patents

Fabrication d'une cellule et d'un film a cristaux liquides alignes par alignement simultane et separation de phase

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Publication number
EP1221066A2
EP1221066A2 EP00959728A EP00959728A EP1221066A2 EP 1221066 A2 EP1221066 A2 EP 1221066A2 EP 00959728 A EP00959728 A EP 00959728A EP 00959728 A EP00959728 A EP 00959728A EP 1221066 A2 EP1221066 A2 EP 1221066A2
Authority
EP
European Patent Office
Prior art keywords
liquid crystal
mixture
polarization
substrate
alignment
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00959728A
Other languages
German (de)
English (en)
Inventor
Satyendra Kumar
Liang-Chy Chien
Jae-Hoon Kim
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kent State University
Original Assignee
Kent State University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kent State University filed Critical Kent State University
Publication of EP1221066A2 publication Critical patent/EP1221066A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1334—Constructional arrangements; Manufacturing methods based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1337—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
    • G02F1/13378—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers by treatment of the surface, e.g. embossing, rubbing or light irradiation
    • G02F1/133788—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers by treatment of the surface, e.g. embossing, rubbing or light irradiation by light irradiation, e.g. linearly polarised light photo-polymerisation

Definitions

  • the present invention resides in the art of light modulating devices made with composite organic materials utilizing self-aligned layers. Specifically, the invention combines two processes, in-situ photoalignment using polarized ultraviolet (UV) light exposure and anisotropic phase separation using phase-separated composite organic film (PSCOF) technology using a one- or multi-step process to prepare aligned liquid crystal films adjacent a polymer layer with or without pre-tilt. In particular, this method permits preparation of aligned liquid crystal cells, without the need for two pre- fabricated alignment layers, one on each substrate.
  • UV polarized ultraviolet
  • PSCOF phase-separated composite organic film
  • the PSCOF method was recently invented and used at Kent State University to prepare adjacent parallel layers of polymer and liquid crystal. This method is disclosed in U.S. Patent No. 5,949,508, and is incorporated herein by reference.
  • the PSCOF method involves a process similar to that used in the fabrication of polymer dispersed liquid crystal films.
  • the polymer and liquid crystals are mixed in a predetermined proportion and placed between two substrates with well defined thickness or over one substrate.
  • the phase separation process is initiated.
  • the rate of polymerization (and phase separation) is faster near the source of UV radiation due to higher intensity.
  • the organic or liquid crystal material is expelled from the polymerizing portion and begins to migrate away from the source of UV radiation.
  • 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.
  • the separation of liquid crystal from polymer can be aided by a pre-disposed alignment layer which the liquid crystal material likes to wet, on the substrate away from the UV source. As such, an aligned liquid crystal film may be formed.
  • the alignment layer is typically made up of a long chain polymeric material which is traditionally later subjected to processes such as mechanical rubbing or ultraviolet exposure to alter the surface properties.
  • the most commercially used method of forming an alignment layer is the rubbing technique. In this method, for example, a polyamic acid is spin-coated or otherwise deposited on a substrate.
  • the polyamic acid is subjected to two heat treatments, soft-bake and hard-bake, to form a polyimide (PI) film.
  • PI polyimide
  • the PI film is rubbed by a cloth, such as velvet, in a uniform singular direction.
  • a cloth such as velvet
  • the liquid crystal aligns along the rubbing direction.
  • This method can cause mechanical damage and generate electrostatic charges, both of which adversely affect liquid crystal displays, especially those that employ thin-film transistors.
  • the rubbing method also generates dust from the cloth and PI, which may contaminate the liquid crystal material.
  • Another method of forming an alignment layer involves forming a PI film on a substrate, as described above.
  • a linearly polarized ultraviolet light is projected onto the surface of the PI film to produce the desired molecular alignment.
  • the UV radiation anisotropically photodissociates photosensitive bonds in the PI, including those in the imide ring. This selectively reduces the polarizability of PI molecules and changes the surface properties and morphology.
  • this method results in alignment layers with weak anchoring of liquid crystals and poor thermal and chemical stability.
  • this method requires costly multi-step processing.
  • Yet another drawback of this method is that it only provides a limited charge holding ratio and less thermal stability when compared to the rubbing technique.
  • a similar method of preparing an alignment layer by using photo-sensitive polymers is also known.
  • photo-sensitive polymers such as poly(vinyl)4- methoxycinnamate (PVMC); poly(vinyl)cinnamate (PVC); and polysiloxanecinnamate films may be used to align liquid crystal material.
  • PVMC poly(vinyl)4- methoxycinnamate
  • PVC poly(vinyl)cinnamate
  • polysiloxanecinnamate films may be used to align liquid crystal material.
  • PVMC poly(vinyl)4- methoxycinnamate
  • PVC poly(vinyl)cinnamate
  • polysiloxanecinnamate films may be used to align liquid crystal material.
  • an alignment layer does not provide a fixed, stable orientation of liquid crystal material.
  • Yet another method for forming an alignment layer on a substrate is deposition by evaporation of inorganic materials onto the surface of the substrate at various incidence angles. This forms an alignment layer which physically orients the director of the liquid crystal.
  • Inorganic materials which have been used include silicon oxides and magnesium oxides. This deposition method has proven to be cumbersome and difficult to use in a manufacturing process.
  • Another process for forming alignment layers developed by Kent State University, is the in-situ UV exposure method. This method is disclosed in U.S. Patent No. 5,936,691 , and is incorporated herein by reference.
  • the in-situ method is similar to the conventional process of exposing PI film to polarized UV light.
  • the in-situ method exposes the polyimide film (PI) to UV radiation while the film is being soft- and hard-baked.
  • the resulting alignment layers have higher anchoring energies and are thermally more stable compared to the conventional UV exposure technique. For example, cells prepared with the conventional method lose alignment when maintained at 100 °C for 12 hours, while cells prepared by the in-situ method, show no sign of deterioration at 300 °C for 12 hours.
  • the in-situ method of forming an alignment layer avoids many of the drawbacks of other methods known in the art, while requiring fewer and simpler processing steps.
  • the in-situ method has been shown to be effective, it still requires that the alignment film must still be properly disposed and processed. Moreover, for all the alignment methods discussed above, the alignment layer may be damaged if care is not taken in transferring the substrate between the manufacturing stations. It is also theorized that currently known alignment layers only directly affect the liquid crystal material adjacent thereto.
  • a light modulating device comprising a phase separated composite organic film, and a method for manufacturing such a film, that is homogeneously aligned during formation, thus obviating the need for the preparation and processing of a separate and distinct alignment layer.
  • DISCLOSURE OF INVENTION it is a first aspect of the present invention to provide a light modulating device comprising a phase separated composite organic film or micro-structures and a method for manufacturing such a device, wherein the device homogeneously aligns the liquid crystal material without the need 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- or multi-step method of simultaneous phase separation and photoalignment.
  • a further aspect of the present invention is to provide a film or micro-stmctures made by a process of simultaneous photoalignment and thermally-induced polymerization.
  • Yet a further aspect of the present invention is to provide an anisotropic film or micro- stmctures comprising two or more layers, prepared by using a multi-step method wherein the liquid crystal material layer is aligned separately at each surface of the film and may have a different orientation.
  • a method for fabricating an anisotropic film including the steps of spin-coating a photo-crosslinkable polyimide onto a substrate, spin-coating a reactive liquid crystalline monomer onto the polyimide, and applying polarized light to simultaneously crosslink the polyamic acid and photoalign and polymerize the reactive monomer.
  • the UV light causes a proper morphology at the polyimide/liquid crystal interface which, in turn, orients the liquid crystal material.
  • a method for fabricating an anisotropic film including the steps of spin-coating a liquid crystal polymer (LCP) onto a substrate, spin-coating a reactive monomer onto the LCP, and applying polarized light to simultaneously photoalign the LCP and photoalign and polymerize the reactive monomer.
  • LCP liquid crystal polymer
  • a method for fabricating an anisotropic film including the steps of preparing a mixture of a liquid crystal material, a polymer, and a solvent, disposing the mixture onto a substrate, evaporating the solvent, and applying polarized light to simultaneously photoalign and phase separate the liquid crystal material.
  • Still further aspects of the invention are achieved by a method for fabricating an anisotropic film, including the steps of preparing a mixture of a liquid crystal material and a thermally polymerizable monomer, disposing the mixture onto a substrate, and subjecting it to a thermal treatment to polymerize the monomer, and polarized light to photoalign the liquid crystal material.
  • Additional aspects of the invention are achieved by a method for fabricating an anisotropic film and/or microstructures comprising of two or more layers or microstructures, the method including the steps of sequentially performing two or more of the above methods, thereby preparing multiple layers of aligned material, wherein liquid crystal is individually and uniquely aligned at each interface/surface.
  • a method for fabricating simultaneously a phase separated organic film with alignment including preparing a mixture of liquid crystal, prepolymer and a polarization-sensitive material, disposing the mixture on a substrate, and applying a polarized light from a light source and inducing simultaneous phase separation of the mixture and alignment of the phase separated liquid crystal so as to form a layer of homogeneously aligned liquid crystal material adjacent a layer of polymer and the polarization-sensitive material on the substrate.
  • a method for fabricating a liquid crystal device with alignment properties including providing a substrate, providing a first mixture comprising at least a first polarization-sensitive agent, and a prepolymer, providing a second mixture comprising at least a second polarization-sensitive agent and a prepolymer, mixing into either the first or second mixture a liquid crystal, disposing the first mixture on to the substrate, disposing the second mixture over the first mixture, initiating a process to the first mixture from the group consisting of at least visible light polarization, ultraviolet light polarization, thermal induction, chemical induction, and solvent induction, initiating a process to the second mixture from the group consisting of at least visible light polarization, ultraviolet light polarization, thermal induction, chemical induction, and solvent induction, and the processes imparting orientational alignments to the liquid crystal.
  • Still another object of the present invention is attained by a cell having alignment properties, including at least one substrate and a mixture disposed on the substrate, the mixture comprising at least a liquid crystal material, a prepolymer material and a polarization-sensitive material, wherein simultaneous polymerization and application of polarized light causes phase separation and photo-alignment of the mixture, thus forming a microstructure of polymer that imparts alignment properties to the liquid crystal material.
  • FIG. 1 is an enlarged, partial cross-sectional, schematic view of a precursor to the light modulating device according to the present invention, prior to polymerization and alignment;
  • FIG. 2 is an enlarged, partial cross-sectional, schematic view of a light modulating device, after simultaneous one-step alignment and polymerization according to the present invention
  • FIG. 3 is an enlarged, partial cross-sectional, schematic view of a device after implementation of the multi-step method according to the present invention.
  • FIG. 4 is an enlarged, partial cross-sectional, schematic view of a microstructure device after implementation of the multi-step method according to the present invention.
  • the light modulating cell precursor 10 does not include ⁇ although one may be provided ⁇ a separate, distinct alignment layer.
  • the light modulating device of the present invention may be manufactured by a method which does not require a separate spin- coating step to deposit alignment layer precursor material onto the substrate. The method also does not require soft baking and/or hard baking the alignment layer. Further, the method does not require rubbing or otherwise physically contacting the alignment layer to impart properties that will later affect the liquid crystal material.
  • the light modulating device precursor shown in FIG. 1 , includes a pair of opposed, optically clear substrates 12 which may be glass, plastic or other material commonly known in the art.
  • the device does not need to withstand the temperatures necessary to imidize the alignment layers of the prior art.
  • temperature-sensitive materials heretofore not suitable as substrates can be utilized in the present invention.
  • flexible substrate materials such as plastic or polymer sheets may now be used for liquid crystal devices which do not need to withstand the high temperatures normally used in the hard-bake and soft-bake alignment layer formation processes.
  • a polarizer 14 may be disposed on the outer surface of each substrate 12 for the purpose of modifying the optical characteristics of transmitted light to provide a cell for operation in the transmissive mode.
  • An electrode 18 may be provided on the inside surfaces of each of the substrates 12. In the preferred embodiment, each electrode 18 is an indium- tin oxide material. Alternatively, to provide a device for operation in the reflective mode, a mirror or a light diffuser may be added to the outside of a substrate opposite to the light source.
  • a power source 20 is attached to the electrodes 18 through a switch 22. The switch
  • a cell gap thickness between the electrodes is defined by a 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 captured between the substrates 12.
  • the liquid crystal material is combined in a solution with the prepolymer and the polyimide, and filled between the substrates 12 by capillary action.
  • other known methods of filling may be employed.
  • the edges of the substrates 12 are sealed, utilizing known methods.
  • the material 28 may be spin-coated on a single substrate. Referring now to FIG. 2, it can be seen that a light modulating cell, fabricated by a one-step simultaneous phase separation and alignment method according to the present invention, is designated generally by the numeral 30.
  • the "one-step method” is a method in which a layer of material ⁇ which includes at least the organic or liquid crystal material, a prepolymer, and a polarization- sensitive aligning agent such as a chromophore — is disposed onto a substrate by, for example, spin-coating, wherein the coated substrate is exposed to a treatment selected from the group consisting of polarized visible light radiation, or polarized UV light radiation, and some type of phase separation.
  • the one-step method is thus characterized in that all components are subjected to the same treatment simultaneously to homogeneously align the phase separated liquid crystal material component.
  • a light source 32 such as an ultraviolet or visible light, is proximally positioned below a linear polarizer 36. When energized, the light source 32 generates rays 34 which impinge upon the linear polarizer 36 which directs linearly polarized rays 38 through the substrate 12 and into the cell gap 26.
  • the light or some other process to be described, induces polymerization of the prepolymer material which was primarily mixed with the aligning agent. As polymerization proceeds, phase separation between the liquid crystal material and the polymer/aligning agent occurs. This is known as polymerization induced phase separation.
  • a light transmissive solidified polymer layer 40 is formed on the electrode 18 of the substrate 12 adjacent the light source 32.
  • a liquid crystal film layer 42 is formed on the opposed substrate 12, adjacent to the other electrode 18. Simultaneous with the phase separation, the linearly polarized rays 38 break photosensitive bonds in the prepolymer/polyimide layer and align polymer segments along a direction perpendicular to the direction of the polarization of the linearly polarized rays. Additionally, depending on the chemical nature of the materials, the rays 38 may orient the polymer segments parallel or pe ⁇ endicular to the substrate or cross-link the polymer material in a specific direction parallel to the substrate. This facilitates alignment of the liquid crystal film layer 42 at an interface 44 between the polymer layer 40 and the liquid crystal layer 42. At the interface 44, the liquid crystal appears to imprint compatible anchoring conditions of alignment during the phase separation. It is also believed that a minimal amount of polyimide material may adhere to the opposed substrate and mimic the alignment orientation at the interface 44. If desired, a separate and distinct alignment layer may be provided on the substrate opposite the interface 44.
  • the thickness of the polymer layer is defined by a dimension 52
  • the thickness of the liquid crystal layer is shown by a dimension 54.
  • the physical parameters of the liquid crystal film such as its thickness, alignment conditions, and the liquid crystal material can be selected for desired objectives by adjusting composition and by the use of appropriately sized spaces to fix the cell gap. Homogeneously aligned cells using nematic liquid crystals have been prepared with the method of the present invention. Additionally, ferroelectric and antiferroelectric liquid crystal in such structures are found to have grey scale and even bistability. These cells possess much lower threshold voltages, scatter almost no light (no haziness), and are mechanically and electrically rugged. Some liquid crystal materials exhibit modified electro-optic (EO) behavior in phase separated composite organic films.
  • EO electro-optic
  • Optically controllable birefringent devices can also be formed using this method.
  • This method permits fabrication of uniform, very thin liquid crystal films. Several uniform films with thickness comparable to the wavelength of red light have been prepared with the method of the present invention.
  • phase separation can be achieved by utilizing thermal, chemical, or solvent induction techniques. Any of these techniques can be employed in conjunction with irradiation to achieve simultaneous phase separation and photoalignment. While not wanting to be bound by theory, it is believed that the polarized rays are critical in aligning the liquid crystal material in a uniform manner at the interfaces 44 and 46.
  • Suitable prepolymers for the practice of the present invention are photopolymerizable monomers which are sensitive to the direction of polarization of the UV light so that exposure to UV light simultaneously and directionally polymerizes the monomer and macroscopically aligns the polymer.
  • Prepolymers which are not normally sensitive to the polarization of UV light can be useful if modified by the addition of, for example, a chromophore component.
  • suitable prepolymers include, but are not limited to, NOA- 65 (available from Norland Products, Inc.), vinyl ether, acrylates, epoxies, diacetylanes, vinyls, and the like.
  • chromophores materials such as azobenzene, stilbenzene, cinnamate, chalcone, coumarin, dimaleimide, and the like can be used.
  • Useful polyimides are homo- or co-polyimides with side chains that have low light absorption, and include SE- 1180, 610 (available from Nissan Chemical Ind.), and functional groups with chromophores inco ⁇ orated therein.
  • the liquid crystal material can be selected dependent upon the type of light modulating device desired. Suitable liquid crystal materials include, but are not limited to, nematic, ferroelectric, antiferroelectric, cholesteric and related liquid crystal materials. As stated above, by using the method of the present invention it is possible to prepare parallel films of polymer and aligned liquid crystal either inside a cell or on a substrate. Referring now to FIG. 3, it can be seen that a device used to implement either the one-step or multi-step method of the present invention is designated generally by the numeral 60. The device may be enclosed within a heat source 62 when thermally induced polymerization is employed. If appropriate, heat from the light source 32 may also be used.
  • a mixture of a reactive liquid crystal monomer, a photomonomer and a low-temperature-cure polyimide is formulated for preparing anisotropic films.
  • the reactive liquid crystal monomer can be selected from nematic diacrylate monomers and a chiral diacrylate dopant having the acrylate polymerizable group.
  • a photomonomer such as NOA-65, and a low temperature curing polyimide such as SE- 1180 is mixed with a reactive liquid crystal monomer to form a photosensitive material. This mixture is spin-coated onto the substrate.
  • a UV light source 32 emits rays 34 which pass through a linear polarizer 36.
  • the linearly polarized rays 38 pass through the substrate 12 and electrode 18, and irradiate the coating mixture. Simultaneous polarized UV light induced phase separation and alignment of reactive liquid crystal monomers at the interface 44 is achieved.
  • the one-step method of the present invention produces alignment of the liquid crystal without a separate alignment layer at the interface 46, and thereby eliminates the need for additional spin-coating and rubbing steps.
  • the reactive liquid crystal monomer can be selected from nematic diepoxy monomers and a chiral diepoxy dopant having the epoxy polymerizable group.
  • a photomonomer, a photoinitiator, and a low-temperature-cure polyimide is mixed with the reactive epoxy-based monomer. This mixture is spin-coated onto a substrate and irradiated as described above. Polarized UV light irradiation results in simultaneous phase separation and photoalignment.
  • the one-step methods discussed above are believed to be the most effective and efficient for forming a homogeneously aligned liquid crystal device without a separate and distinct alignment layer.
  • the other methods mentioned above such as those that utilize light radiation, heat and/or solvent evaporation, may be implemented based on the above teachings to achieve substantially the same result.
  • a photo-crosslinkable polyimide comprising functional side groups such as cinnamate or coumarin is prepared and spin- coated onto a substrate.
  • a reactive liquid crystal monomer such as liquid crystal diacrylates, divinyl ether, di-epoxied, liquid crystal diacetylene, or other monomers with a functionality of 2 or greater and aphotoinitiator is 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 layer before the polyimide has been cured may make the surface slightly non-uniform, but will not interfere with alignment of the liquid crystal material.
  • multi-step method refers to a method in which a substrate is coated and treated as in the one-step method to produce an alignment layer and/or a layer/microstructure of liquid crystal material, and then further layers are spin-coated onto the previously applied layers and further treated by one or more of the treatments described above, such as visible or UV radiation, radiation in combination with heat treatment, or radiation in combination with solvent evaporation.
  • the multi-step method comprises a sequence of at least two material disposing steps, wherein during each step at least one type of material is applied. More specifically, by utilizing the multi-step method of the present invention, different layers or microstructures of uniquely aligned liquid crystal material interfaces can be obtained.
  • masks 70 with appropriate openings may be positioned between the polarizer and the substrate and re-positioned at various stages to assist in the formation of aligned and electrically controllable microstructures 72.
  • FIG. 3 an example of a configuration which could be achieved by using the multi- step method of the present invention is shown in FIG. 3. It can be seen that an electrode layer 18 may be disposed adjacent to a substrate 12, and various layers of alignment inducing polymer with liquid crystal material, as described in the one-step method, are disposed thereupon.
  • the multi-step method may be employed where it is desired to provide different liquid crystal director orientations at the interface of the liquid crystal material which is adjacent to layers or microstructures of dissimilar material which may be a polyimide-doped polymer layer or form, a substrate, or an equivalent film.
  • the multi-step method may be employed to form anisotropic films in which a material that will form the alignment layer is first disposed on the substrate and wherein another material which includes liquid crystal material, prepolymer and an aligning agent is disposed thereon. The materials are then phase-separated and photo-aligned to form an anisotropic film.
  • the end result of the multi-step method provides at least an alignment interface layer 63 adjacent to the substrate 12 and a liquid crystal layer 66 adjacent to the interface layer 63. Additionally, a second alignment interface layer 68 adjacent the liquid crystal layer 66 may also be formed.
  • the multi-step method allows for the second alignment interface layer to impart a different orientation to the liquid crystal layer 66 than the orientation of the first alignment interface layer 63. It is envisioned that the multi-step method would be extremely useful in the construction of twisted nematic devices, super twisted nematic devices, optically or electrically controllable birefringent devices or any device that requires orientational changes to the liquid crystal material.
  • the materials that make up the layers 63, 66, and 68 may be disposed and formed in various combinations, depending upon the end result desired. It will also be appreciated that the multi-step method may be employed to form anisotropic films that, otherwise, could not be formed. This method is also advantageous in that films can be formed without spin-coating materials twice.
  • the precursor device is exposed to a treatment selected from a group consisting of applications of different polarized UV light wavelengths, applications of different polarized visible light wavelengths, applications of polarized UV and polarized visible light, simultaneous visible light radiation and heat, simultaneous UV light radiation and solvent evaporation, and UV light radiation.
  • a treatment selected from a group consisting of applications of different polarized UV light wavelengths, applications of different polarized visible light wavelengths, applications of polarized UV and polarized visible light, simultaneous visible light radiation and heat, simultaneous UV light radiation and solvent evaporation, and UV light radiation.
  • an azobenzene liquid crystal polymer (LCP) is spin-coated onto a substrate.
  • a reactive monomer such as liquid crystal diacrylates, divinyl ether, di-epoxied, liquid crystal diacetylene, or other monomers with a functionality of 2 or greater and a suitable photo-initiator, is coated on top of the azobenezene LCP film.
  • polarized UV irradiation 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 will not cause problems with alignment.
  • a photomonomer such as NOA65 and polyimide that contains chromophore material are mixed and coated onto the substrate.
  • the coated substrate is irradiated with linearly polarized UV light, resulting in periodic undulation of the polymer surface to form the layer 63.
  • a reactive liquid crystal monomer is spin-coated onto the polymer surface and polymerized by irradiation with UV light. The result is an anisotropic film.
  • a first mixture comprising a vinyl ether, a photo-initiator, and polyimides with chromophore components are spin-coated onto a substrate and irradiated by linearly polarized UV light having a wavelength, for example, of less than or equal to about 320 nanometers.
  • a second mixture comprising acrylates, a photo-initiator, and polyimides with chromophores is spin-coated onto the first layer and irradiated by linearly polarized UV light having a wavelength, for example, of greater than or equal to about 350 nanometers. It will be appreciated that the desired liquid crystal material may be inco ⁇ orated into the first or the second mixture.
  • the orientation of the linear polarizer 36 is changed as needed after the first exposure of the first material so as to obtain the desired second orientation.
  • the wavelengths of light selected are dependent upon the chromophore/photoaligning materials selected.
  • the position of the light source 32 may be adjusted accordingly.
  • the result is a multi-layered anisotropic film, wherein each layer is individually and uniquely oriented that is useful for optical compensation and display devices which require change in orientation at different substrate surfaces. It will be appreciated by those of skill in the art that the mixtures can be applied and treated in the reverse order. In other words, the layers may be applied consecutively and exposed to the application of UV light.
  • one layer may be disposed, exposed to UV light, and then the second layer disposed and the exposed to UV light.
  • the multi-step method of the present invention can be utilized to fabricate coated substrates wherein one layer comprises a vinyl ether, a photo-initiator, and a polyimide with chromophores and is treated with UV radiation as discussed above, and a second layer comprises an acrylate and a polyimide with a chromophore and is treated with visible radiation.
  • a sufficient amount of at least about 1% maleimide is included in the mixture.
  • the mixture is exposed to visible light that has a wavelength, for example, greater than or equal to 410 nanometers.
  • the liquid crystal material may be in either the first or second mixture.
  • the polarization direction may be changed to vary the orientation of the liquid crystal material as needed.
  • Such a multi-step method has use for the fabrication of retardation films, as well as other electro-optical components.
  • a first layer comprising epoxy monomers and curing agents are coated onto a substrate and heat treated to induce polymerization.
  • a second layer comprising UV curable monomers, a photo- initiator, and polyimides for photoalignment are coated onto the first layer and irradiated with linearly polarized UV radiation.
  • the layers may be applied in reverse order if desired. If this is the case, the polyimides with chromophore will be included in the thermally formed layer.
  • the liquid crystal material may be included in either mixture of the first or second layers. Such devices provide different liquid crystal orientations for optical retardation, optical compensation and adjustable retardation.
  • a first layer comprising reactive liquid crystal monomers, a photoinitiator, and polyimides are coated onto the substrate and irradiated with linearly polarized visible radiation as taught above.
  • a second layer comprising epoxy resin and curing agents is applied onto the first layer and heated to cause solvent-induced phase separation of the second layer as taught above. The application of the layers may also be reversed if desired.
  • thermally-induced phase separation can be utilized in the multi-step method of the present invention.
  • a layer comprising PMMA, and reactive liquid crystal monomers can be deposited either before or after a UV- or visible-irradiated layer is processed. If UV light is employed, a pre-polymer such as PMMA or polyimides are used along with reactive monomers, UV photoinitiator, and the liquid crystal material. If visible light is used, the UV photoinitiator is replaced with a visible light photoinitiator.
  • the light modulating device of the present invention is useful in optically and electrically controllable devices.
  • the disclosed method for fabricating an aligned liquid crystal device without a separately formed alignment layer, in a single UV exposure step is simpler and more cost effective, and can replace known methods for fabricating any liquid crystal device which currently employs an alignment layer. Elimination of the rubbing procedure results in less damage to the device and improves manufacturing yields. Elimination of the high temperature baking steps used in the prior art allows the use of plastic substrates.
  • the method of the present invention is very versatile, and may be employed with nematic, ferroelectric, anti-ferroelectric, and cholesteric liquid crystal materials to name a few.
  • the methods of the present invention can be utilized to fabricate multi-layer anisotropic films wherein each layer has an individual and unique orientation. By adjusting the incident angle of irradiation, it is possible to obtain molecular pre-tilt in the liquid crystal layers. Patterned microstructures utilizing masks during application of the ultraviolet or visible can be used to manufacture active devices or anything that can be switched, optically, electrically, or that is sensitive to a mechanical stimulus.
  • the methods taught by this disclosure are applicable to any liquid crystal device that requires alignment.

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mathematical Physics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
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Abstract

L'invention concerne un procédé permettant de fabriquer simultanément un film organique à phases séparées et des microstructures à cristaux liquides disposés selon un alignement souhaité. Ce procédé consiste à préparer un mélange de matière à cristaux liquides, d'un prépolymère et d'une matière sensible à la polarisation. Ce mélange est disposé sur un substrat et on applique une combinaison d'UV ou de lumière visible ou un traitement thermique tout en induisant une séparation de phase afin de former une couche ou une microstructure de matière à cristaux liquides alignée de manière appropriée à proximité du substrat.
EP00959728A 1999-09-03 2000-09-01 Fabrication d'une cellule et d'un film a cristaux liquides alignes par alignement simultane et separation de phase Withdrawn EP1221066A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US15243099P 1999-09-03 1999-09-03
US152430P 1999-09-03
PCT/US2000/024025 WO2001018594A2 (fr) 1999-09-03 2000-09-01 Fabrication d'une cellule et d'un film a cristaux liquides alignes par alignement simultane et separation de phase

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EP1221066A2 true EP1221066A2 (fr) 2002-07-10

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EP (1) EP1221066A2 (fr)
JP (1) JP2003508820A (fr)
CN (1) CN1399729A (fr)
AU (1) AU7099800A (fr)
WO (1) WO2001018594A2 (fr)

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CA2330894A1 (fr) * 2001-01-12 2002-07-12 Universite De Sherbrooke Cristaux liquides ferroelectriques a base de monomeres de diacrylate azobenzeniques stabilises en reseau et alignes optiquement
PT102559A (pt) * 2001-01-26 2002-07-31 Liquid Crystal Technologies Te Processo para preparacao de camadas de alinhamento com propriedades de ancoragem predeterminadas para dispositivo de cristais liquidos
US7355668B2 (en) 2002-05-22 2008-04-08 Kent State University Polymer enhanced liquid crystal devices built with rigid or flexible substrates
KR101060829B1 (ko) 2003-08-08 2011-08-30 코닌클리즈케 필립스 일렉트로닉스 엔.브이. 액정 분자를 정렬하기 위해 반응성 메소젠을 갖는 정렬층
JP4341904B2 (ja) * 2003-09-12 2009-10-14 日東電工株式会社 異方性フィルムの製造方法
JP2005091480A (ja) * 2003-09-12 2005-04-07 Nitto Denko Corp 異方性フィルムの製造方法
CN100351677C (zh) * 2004-01-08 2007-11-28 电子科技大学 含纳米聚合物网络的液晶显示器
KR20050094011A (ko) * 2004-03-17 2005-09-26 비오이 하이디스 테크놀로지 주식회사 고분자 네크워크 액정 배열 방법
JP5181138B2 (ja) * 2006-11-02 2013-04-10 友達光電股▲ふん▼有限公司 液晶パネル製造装置及び液晶パネルの製造方法
JP5951936B2 (ja) * 2010-07-21 2016-07-13 Jsr株式会社 液晶表示素子の製造方法
CN103293585B (zh) * 2013-05-30 2015-11-25 京东方科技集团股份有限公司 相位差板、显示装置和相位差板制作方法
CN105182614B (zh) * 2014-06-03 2018-07-27 群创光电股份有限公司 显示面板及显示装置
CN105182615B (zh) * 2014-06-04 2018-08-03 群创光电股份有限公司 显示面板
US9921442B2 (en) * 2016-01-14 2018-03-20 Omnivision Technologies, Inc. Method for forming an alignment layer of a liquid crystal display device and display device manufactured thereby
RU2683873C1 (ru) * 2017-09-29 2019-04-02 Государственное образовательное учреждение высшего образования Московской области Московский государственный областной университет (МГОУ) Способ формирования поляризационно-чувствительного материала, поляризационно-чувствительный материал, полученный указанным способом, и поляризационно-оптические элементы и устройства, включающие указанный поляризационно-чувствительный материал
CN115220267B (zh) * 2022-08-01 2023-07-25 南京大学 一种液晶注液多孔光滑表面构建方法及其微流控应用

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CN1399729A (zh) 2003-02-26
AU7099800A (en) 2001-04-10
WO2001018594A2 (fr) 2001-03-15
WO2001018594A3 (fr) 2002-05-02
JP2003508820A (ja) 2003-03-04

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