CN113791508A - Silicon-based liquid crystal device based on photo-alignment technology and preparation method thereof - Google Patents
Silicon-based liquid crystal device based on photo-alignment technology and preparation method thereof Download PDFInfo
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- CN113791508A CN113791508A CN202111061914.5A CN202111061914A CN113791508A CN 113791508 A CN113791508 A CN 113791508A CN 202111061914 A CN202111061914 A CN 202111061914A CN 113791508 A CN113791508 A CN 113791508A
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- 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
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- 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
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/133553—Reflecting elements
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Abstract
The invention discloses a silicon-based liquid crystal device based on a photo-alignment technology and a preparation method thereof, wherein the silicon-based liquid crystal device comprises a PCB (printed Circuit Board) substrate, a silicon substrate arranged on the PCB substrate, and an ITO (indium tin oxide) glass substrate arranged opposite to the silicon substrate, wherein a liquid crystal layer is also arranged between the silicon substrate and the ITO glass substrate; a first alignment layer is arranged on one side, close to the liquid crystal layer, of the silicon substrate, a second alignment layer is arranged on one side, close to the liquid crystal layer, of the ITO glass substrate, and the first alignment layer and the second alignment layer are used for controlling horizontal arrangement of liquid crystal molecules of the liquid crystal layer; pixel electrodes which can be independently addressed are further arranged on the silicon substrate, and rotation of liquid crystal molecules in the liquid crystal layer at the corresponding pixel position in the vertical direction is controlled. The invention controls the horizontal azimuth angle of the liquid crystal molecules through the light-operated orientation layer, and simultaneously combines the micro-pixel structure in the silicon substrate to further regulate and control the inclination angle of the liquid crystal molecules, has the characteristics of miniaturization, easy integration and lightness and has great application potential in the fields of display, optical communication and the like.
Description
Technical Field
The invention relates to the technical field of liquid crystal orientation control, in particular to a silicon-based liquid crystal device based on a photo-orientation technology and a preparation method thereof.
Background
LCoS (Liquid Crystal on Silicon) is a matrix Liquid Crystal display device based on a reflective mode and having a very small size, and since Liquid Crystal on Silicon can modulate the wavelength and phase of a light beam in space, it has been widely used in display fields such as high definition projectors, augmented reality, and virtual reality. Meanwhile, in the field of optical communications, liquid crystal on silicon devices are also used for wavelength selective switches, optical modulation and demodulation apparatuses, and the like.
Liquid crystal molecules in a traditional silicon-based liquid crystal device are oriented by rubbing materials such as polyimide and the like, and the liquid crystal device has the advantages of simplicity, convenience, good stability and the like, but a large amount of dust and static electricity can be generated in the rubbing process to pollute the liquid crystal device. Meanwhile, the rubbing alignment method can only realize the fixed azimuth alignment of the liquid crystal molecules and cannot realize the multi-domain alignment of the liquid crystal molecules in the micro-area.
Accordingly, the prior art is yet to be improved and developed.
Disclosure of Invention
In view of the defects of the prior art, the invention provides a silicon-based liquid crystal device based on a photo-alignment technology and a preparation method thereof, aiming at solving the problems that in the prior art, liquid crystal molecules in the silicon-based liquid crystal device are aligned by rubbing through materials such as polyimide, and the rubbing alignment method can only realize the fixed azimuth alignment of the liquid crystal molecules and cannot realize the multi-domain alignment of the liquid crystal molecules in a micro-area.
The technical scheme of the invention is as follows:
a first embodiment of the present invention provides a liquid crystal on silicon device based on photoalignment technology, including: the liquid crystal display panel comprises a PCB substrate, a silicon substrate arranged on the PCB substrate, and an ITO glass substrate arranged opposite to the silicon substrate, wherein a liquid crystal layer is also arranged between the silicon substrate and the ITO glass substrate;
a first alignment layer is arranged on one side, close to the liquid crystal layer, of the silicon substrate and is a light control alignment layer;
one side of the ITO glass substrate close to the liquid crystal layer is provided with a second orientation layer,
the first alignment layer and the second alignment layer are used for controlling the horizontal arrangement of liquid crystal molecules of the liquid crystal layer;
and pixel electrodes which can be independently addressed are arranged on the silicon substrate and are used for controlling the rotation of liquid crystal molecules at the corresponding pixel positions in the liquid crystal layer in the vertical direction.
Optionally, the pixel electrode is a reflective electrode formed by a CMOS circuit corresponding to each pixel, and an electric field is formed between the reflective electrode and the ITO glass substrate to control rotation of liquid crystal molecules in the liquid crystal layer at a position corresponding to a pixel in a vertical direction.
Optionally, a spacer is further disposed between the silicon substrate and the ITO glass substrate to support the silicon substrate and the ITO glass substrate to form a filling space of the liquid crystal layer, and to control a thickness of the liquid crystal layer.
Optionally, the second alignment layer is a photoalignment layer or a rubbing alignment layer, and the alignment direction of the second alignment layer is horizontal or vertical.
Optionally, the second alignment layer is a photoalignment layer, and is aligned in the same manner as the photoalignment layer disposed on the silicon substrate, liquid crystal molecules in the liquid crystal layer are controlled to be horizontally arranged from the silicon substrate to the ITO glass substrate, and a horizontal azimuth angle of the liquid crystal molecules in the liquid crystal layer is controlled by the ITO glass substrate and the photoalignment layer disposed on the silicon substrate.
Optionally, the second alignment layer is a photoalignment layer, is aligned in the same manner as the photoalignment layer disposed on the silicon substrate, and is uniformly arranged in a single direction; the photoalignment layer of the silicon substrate and the photoalignment layer of the ITO glass substrate control liquid crystal molecules in the liquid crystal layer to be in gradual change twisted arrangement from the silicon substrate to the ITO glass substrate.
Optionally, the second alignment layer is a vertical alignment layer, liquid crystal molecules in the liquid crystal layer are controlled by the vertical alignment layer, and the director of the liquid crystal molecules is distributed in an alignment mode in the direction vertical to the ITO glass substrate; the inclination angles of liquid crystal molecules in the liquid crystal layer are controlled to be in mixed gradual change arrangement from the horizontal direction of the silicon substrate to the vertical direction of the ITO glass substrate by the light-operated orientation layer of the silicon substrate and the vertical orientation layer of the ITO glass substrate, and the horizontal azimuth angle distribution pattern is controlled by the light-operated orientation layer on the silicon substrate.
Optionally, the photoalignment layer is a dye molecule, and the material of the dye molecule is at least one of a photocrosslinking material, a photodegradation material, a photocis-trans isomerism material or a photomolecular rotation material;
the horizontal director of the dye molecule is irradiated and oriented by ultraviolet polarized light and is arranged along the direction vertical to the polarization direction to form a specific control pattern; the control pattern controls the horizontal azimuth angle of the adjacent liquid crystal molecules to form a specific arrangement pattern.
Optionally, a strip-shaped conductive layer is further disposed on the PCB substrate, and the strip-shaped conductive layer is electrically connected to the signal connection points of the ITO glass substrate and the silicon substrate, respectively.
Another embodiment of the present invention provides a method for manufacturing a liquid crystal on silicon device based on photoalignment technology, which is used for manufacturing any one of the above liquid crystal on silicon devices, and includes:
coating an orientation material on one side of the silicon substrate facing the ITO glass substrate to generate a first orientation layer; the first orientation layer is a light control orientation layer;
coating an orientation material on one side, facing the silicon substrate, of the ITO glass substrate to generate a second orientation film, wherein the second orientation layer is one of a photo-control orientation layer, a friction orientation layer or a vertical orientation layer;
carrying out multi-step overlapping exposure on the first orientation layer and the second orientation layer, and selecting a corresponding exposure pattern and a corresponding irradiation light polarization direction according to an exposure sequence by adopting a maskless dynamic projection exposure system to carry out exposure in sequence;
arranging spacing particles on the silicon substrate and encapsulating the spacing particles with the ITO glass substrate, wherein the first orientation layer and the second orientation layer are arranged oppositely;
a liquid crystal layer is poured between the silicon substrate and the ITO glass substrate, liquid crystal molecules in the liquid crystal layer controlled by the silicon substrate photo-alignment film and the ITO glass substrate are close to each other and are arranged in parallel, in a gradient way or in a mixed gradient way from the silicon substrate to the ITO glass substrate;
and pasting the silicon substrate to the PCB substrate, connecting the silicon substrate and the corresponding electrode of the PCB substrate by using a welding gold wire, and electrically connecting the ITO glass substrate and the PCB substrate by using a conductive layer.
Has the advantages that: based on the substrate design scheme, the embodiment of the invention can flexibly control the horizontal azimuth angle of liquid crystal molecules by controlling the polarization direction of the irradiated polarized light, thereby realizing the modulation of the geometric phase of the liquid crystal device. Meanwhile, the liquid crystal molecule inclination angle is further regulated and controlled by combining the micro pixel structure controlled by the independently addressable semiconductor electrode in the silicon substrate, the dynamic response photonic device is realized, and the photonic device has the characteristics of miniaturization, easy integration and lightness and thinness, and has great application potential in the fields of display, optical communication and the like.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a schematic diagram of a preferred embodiment of a liquid crystal on silicon device based on photoalignment technology;
FIG. 2 is a schematic diagram of a cross-sectional structure of a liquid crystal cell of an embodiment of a liquid crystal on silicon device based on photoalignment technology according to the present invention;
FIG. 3 is a flow chart of a preferred embodiment of a method for fabricating a liquid crystal on silicon device based on photoalignment technology according to the present invention;
fig. 4a is a diagram of arrangement of liquid crystal molecules between a patterned photoalignment silicon substrate and a patterned photoalignment glass substrate according to an embodiment of the present invention;
fig. 4b is a diagram of the arrangement of liquid crystal molecules between a patterned photoalignment silicon substrate and a single-direction oriented glass substrate according to an embodiment of the present invention;
fig. 4c is a liquid crystal molecule arrangement diagram between a patterned photoalignment silicon substrate and a vertically aligned glass substrate according to a specific application embodiment of a silicon-based liquid crystal device based on photoalignment technology.
Detailed Description
In order to make the objects, technical solutions and effects of the present invention clearer and clearer, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Embodiments of the present invention will be described below with reference to the accompanying drawings.
An embodiment of the present invention provides a liquid crystal on silicon device based on photoalignment technology, as shown in fig. 1, including a PCB substrate 13 and a silicon substrate 16 disposed on the PCB substrate 13. A liquid crystal layer 14 and an ITO (Indium Tin Oxide) transparent conductive glass substrate 11 are disposed on the silicon substrate 16, a projection of the ITO glass substrate 11 on the PCB substrate 13 includes a central area covering the silicon substrate 16 and a peripheral area surrounding the central area, and a strip-shaped conductive layer 12 is formed in the peripheral area and electrically connected to signal connection points of the ITO glass substrate 11 and the PCB substrate 13, respectively.
In specific implementation, the photo-alignment technology of liquid crystals refers to that the polymer film can cause phenomena such as photo-isomerism, photo-crosslinking, photo-degradation and the like under the irradiation of polarized ultraviolet light, and surface anisotropy is generated, so that liquid crystal molecules are aligned on the film. The non-contact alignment method can accurately control the horizontal azimuth angle of liquid crystal molecules in a micro-area, and can realize liquid crystal photonic devices such as Q wave plates, beam splitters, lenses, vortex glass slides and the like. The material of the liquid crystal layer includes at least one of nematic liquid crystal, dual-frequency liquid crystal, or ferroelectric liquid crystal.
Therefore, there is a need in the art to provide a liquid crystal on silicon device that can realize voltage modulation at the pixel level with a small size while precisely controlling the horizontal azimuth angle of liquid crystal molecules in a micro-area.
Optionally, the conductive layer 12 is made of conductive silver paste, and the conductive silver paste may be formed in a multi-point manner or in a layer formed by the entire conductive silver paste. The colloid material has certain adhesiveness, and compared with other conductive materials, the colloid material has better adhesiveness with elements electrically connected with the colloid material, and has better adhesiveness among the elements, and conductive silver colloid, especially nano silver colloid is used as a material with better conductivity, can form a required position in a dripping mode and is fixed through solidification, is commonly used for conductive connection of optical devices, and can also be selected from nano conductive materials such as nano conductive gold colloid, nano conductive copper colloid, nano conductive tin colloid and the like. In addition, zero ohm resistance can be preset on the conducting layer of the PCB substrate 13 to increase the height of the conducting layer 12, conductive silver paste is dripped on the zero ohm resistance or around the zero ohm resistance, and the ITO glass substrate 11 and the PCB substrate 13 are electrically connected by using the conductive silver paste and the zero ohm resistance as the conducting layer 12. The zero ohm resistance is used for only raising the electrodes, and is designed and provided by manufacturers of the silicon-based liquid crystal back plate, so that the zero ohm resistance can be used without adding. The conductive silver adhesive is also a recommended conductive material in a device preparation process provided by manufacturers, and can also be made of conductive silver paint and other conductive materials.
Fig. 2 is a schematic cross-sectional structure diagram of a liquid crystal cell in a liquid crystal on silicon optical device according to an embodiment of the present invention, as shown in fig. 2, the liquid crystal on silicon optical device includes: the liquid crystal display panel comprises an ITO glass substrate 11 and a silicon substrate 16 which are oppositely arranged, and a liquid crystal layer 14 positioned between the ITO glass substrate 11 and the silicon substrate 16; wherein, a spacing particle 15 is arranged between the ITO glass substrate 11 and the silicon substrate 16 to support the liquid crystal layer 14; and frame sealing glue is arranged between the silicon substrate 16 and the ITO glass substrate 11 and surrounds the periphery of the liquid crystal layer 14, so that the silicon-based liquid crystal device forms a sealed structure.
Here, it should be noted that one sides of the ITO glass substrate 11 and the silicon substrate 16, which are close to the liquid crystal layer 14, are respectively provided with a light control alignment film 110 and a light control alignment film 160, and the light control alignment film 110 and the light control alignment film 160 are arranged in a patterned manner in a director direction and are arranged oppositely; the ITO glass substrate 11 and the silicon substrate 16 are used to control the liquid crystal molecules in the liquid crystal layer 14 to be arranged in parallel from the ITO glass substrate 11 to the silicon substrate 16, that is, the horizontal azimuth angles of the liquid crystal molecules in the vertical direction are the same. In this embodiment, the photo- alignment films 110 and 160 disposed on the ITO glass substrate 11 and the silicon substrate 16 are aligned by the ultraviolet polarized light irradiation using the horizontal director of the azo dye SD1, and are aligned perpendicular to the polarization direction to form a specific control pattern. Due to the anisotropy of the surfaces of the dye molecules, anchoring energy of a horizontal direction is formed and applied to adjacent liquid crystal molecules, and the control pattern controls the horizontal direction angle of the adjacent liquid crystal molecules to form a specific arrangement pattern. The specific arrangement is controlled by the polarization direction of the linearly polarized ultraviolet light.
If the dye molecular director is in periodic gradient distribution around the central singular point, the dye molecular director surrounds the singular point in a polar coordinate system with the central singular point as an original point, the director angle and/or the Q value of the control graph on a polar axis change according to a preset rule, and the control graph controls the liquid crystal molecular director to be in periodic gradient distribution around the central singular point, so that the liquid crystal Q wave plate can be prepared, wherein the periodicity of the liquid crystal molecular director change is 2| Q |. The Q value refers to the topological charge in the Q wave plate prepared by linear polarization ultraviolet irradiation, and is one of the characteristics of the Q wave plate device.
Here, it is necessary to supplement that, as shown in fig. 1, the silicon substrate 16 is disposed on the PCB substrate 13, and a module connection is realized between the silicon substrate 16 and the PCB substrate. The silicon substrate 16 corresponds to a working area in a liquid crystal on silicon device, and a reflective electrode formed by a Complementary Metal Oxide Semiconductor (CMOS) circuit corresponding to each pixel is formed on the silicon substrate 16, and is used for forming an electric field with the ITO glass substrate 11 to control the rotation of liquid crystal molecules at a corresponding pixel position in the liquid crystal layer 14 in the vertical direction.
The liquid crystal molecules have anisotropic electrical characteristics, that is, the tilt angle of the liquid crystal molecules can be controlled by controlling the square wave amplitude applied in the electrodes at the two ends of the liquid crystal molecules through the control circuit, so that the effective refractive index in the pixel is controlled, and the phase of the reflected light is finally modulated. Each pixel of the silicon substrate 16 can be driven by active addressing, and the position of the corresponding pixel can be controlled by changing the voltage valueThe tilt angle of the liquid crystal molecules in the vertical direction, at which the polarization direction of the incident light forms an angle theta with the optical axis of the liquid crystal molecules, the effective birefringence n of the pixel positioneff(θ) is:
wherein n in formula 1eAnd noThe extraordinary and ordinary refractive indices of the liquid crystal molecules in said liquid crystal layer 14, respectively. Therefore, for the incident polarized light, the propagation phase retardation Γ after passing through the liquid crystal layer 14 is:
wherein λ is the wavelength of incident light in vacuum; d is the thickness of the liquid crystal layer 14.
In addition, in addition to the above-mentioned control of the tilt angle of the director of the liquid crystal molecules by applying a voltage to introduce different effective refractive indexes of the liquid crystal, the present invention utilizes the photoalignment film 110 and the photoalignment film 160 to control the horizontal azimuth angle of the liquid crystal molecules in the liquid crystal layer 14, so that the effective refractive indexes of the liquid crystal molecules aligned at different azimuth angles are different from each other for the same linear polarization. Note: the azimuth angle at this time, i.e. the above-mentioned included angle theta, and the corresponding effective birefringence index deltaneffComprises the following steps:
the optical path difference that the incident polarized light passes through is:
therefore, by controlling the alignment direction of the liquid crystal molecular directors in the liquid crystal layer 14, phase modulation of incident light can be realized, and vector beams of other arbitrary modes can be obtained.
In addition, it should be noted that the distance between the ITO glass substrate 11 and the silicon substrate 16, i.e. the thickness d of the liquid crystal layer 14, can be changed by changing the size of the spacer 15, so as to change the phase difference between the extraordinary and ordinary rays of the linearly polarized incident light in the liquid crystal on silicon device, thereby realizing the propagation phase retardation Γ of the linearly polarized incident light between the extraordinary and ordinary rays in the liquid crystal on silicon device. Wherein the spacer particles are usually silicon dioxide.
An embodiment of the present invention provides a method for manufacturing a liquid crystal on silicon device based on photoalignment technology, and please refer to fig. 3, where fig. 3 is a flowchart of a preferred embodiment of a method for manufacturing a liquid crystal on silicon device based on photoalignment technology according to the present invention. As shown in fig. 3, it includes the steps of:
step S100, coating an orientation material on one side of the silicon substrate facing the ITO glass substrate to generate a first orientation layer; the first orientation layer is a light control orientation layer;
step S200, coating an orientation material on one side, facing the silicon substrate, of the ITO glass substrate to generate a second orientation film, wherein the second orientation layer is one of a photo-control orientation layer, a friction orientation layer or a vertical orientation layer;
step S300, carrying out multi-step overlapping exposure on the first orientation layer and the second orientation layer, and selecting a corresponding exposure pattern and a corresponding irradiation light polarization direction according to an exposure sequence by adopting a maskless dynamic projection exposure system to sequentially carry out exposure;
step S400, arranging spacing particles on the silicon substrate and packaging the spacing particles with the ITO glass substrate, wherein the first orientation layer and one side of the second orientation layer are arranged oppositely;
step S500, a liquid crystal layer is poured between the silicon substrate and the ITO glass substrate, liquid crystal molecules in the liquid crystal layer controlled by the silicon substrate photo-alignment film and the ITO glass substrate are close to each other and are arranged in parallel, gradually changed or mixed gradually changed from the silicon substrate to the ITO glass substrate;
step S600, adhering the silicon substrate to a PCB substrate, connecting the silicon substrate and a corresponding electrode of the PCB substrate by using a welding gold wire, and electrically connecting the ITO glass substrate and the PCB substrate by using a conducting layer.
In specific implementation, a liquid crystal photoalignment material solution is prepared; coating a liquid crystal photoalignment material solution on the substrate; drying the substrate coated with the liquid crystal photoalignment material solution;
further, in the liquid crystal photoalignment material solution of the above step, the photoalignment material is a material capable of photoalignment, and comprises a cis-trans isomerization material, a photodegradation material, a photocrosslinking material, and a photo-induced molecular rotoazo dye, preferably a photo-induced molecular rotoazo dye SD 1; the organic solvent is N-methyl-2-pyrrolidone (NMP), Dimethylformamide (DMF) or various mixed solvents. The photoalignment material accounts for 0.1-5%, preferably 0.5-2% of the total weight of the solution.
Further, the substrate is the silicon substrate 16 or the ITO glass substrate 11. The coating mode is preferably spin coating, and the spin coating parameters are preferably as follows: the spin coating is carried out at a low speed for 5 seconds at a rotation speed of 800 rpm and at a high speed for 30 seconds at a rotation speed of 3000 rpm. In the step c, the substrate coated with the photoalignment material is dried at a temperature of about 80 ℃ to 110 ℃ for about 5 to 10 minutes to form a photoalignment film, and optionally, the thickness of the photoalignment film may be 10nm to 50 nm.
Further, the photoalignment film on the substrate is irradiated with polarized ultraviolet or blue light. Preferably 405nm polarized. Under polarized ultraviolet light irradiation, these azo dye molecules will rotate spatially to align themselves perpendicular to the polarization direction of the incident light. Optionally, the photoalignment film is processed, and a molecular director in the photoalignment film can be set by controlling a polarization direction of the illumination light, and specifically, a director angle distribution of 0 ° to 180 ° can be formed by multiple overlapping exposures. Accordingly, the photoalignment film is subjected to multiple exposures to form a predetermined molecular director direction distribution pattern.
Optionally, the photoalignment film is exposed in a manner that: interferometric methods, laser direct writing methods, dynamic maskless exposure methods based on DMD (Digital Micromirror Device) or SLM (spatial light modulator). The interference method is to record a hologram formed by the interference of a target beam and a plane reference beam on the photoalignment film. The laser direct writing method is characterized in that an emergent light beam of a laser is reduced to a small size range through a miniature objective lens, then a light control orientation film is scanned and exposed point by point, and a polarizing film is synchronously rotated to perform point-to-point accurate orientation control. The SLM-based dynamic maskless exposure method is characterized in that a beam of uniformly collimated polarized ultraviolet light is reflected to an SLM chip, the SLM chip is used as a dynamic polarization modulation device, different graphs are input through a computer control end to control the phase delay of each pixel, and the reflected ultraviolet light carries a pixel-level polarization distribution pattern and is recorded on the light-operated orientation film. The dynamic maskless exposure method based on the DMD is characterized in that a DMD chip replaces an SLM chip, and a corresponding exposure pattern and a corresponding irradiation light polarization direction are selected according to an exposure sequence and are sequentially recorded on the photoalignment film.
Here, it should be noted that the photoalignment molecular director is perpendicular to the polarization direction of the illumination light, and the director of the liquid crystal molecules in the neighboring liquid crystal layer is the same as the director of the photoalignment molecular director, so that the director distribution of the liquid crystal molecules in the liquid crystal layer can be controlled by changing the polarization direction distribution of the illumination light.
Here, it should be noted that the spacer particles may be uniformly disposed on the silicon substrate by spraying to control the spacing between the silicon substrate and the ITO glass substrate, i.e., the thickness of the liquid crystal layer. Wherein the thickness of the liquid crystal layer can be controlled by varying the spacer particles of different diameters. And manufacturing frame glue on the silicon substrate, and aligning the silicon substrate and the ITO glass to press the silicon substrate and the ITO glass into a box. The frame glue is ultraviolet glue, thermosetting glue or AB glue, preferably ultraviolet glue, and can be rapidly cured by ultraviolet irradiation.
Optionally, the spacer particles may be uniformly mixed with the sealant, and the thickness of the liquid crystal layer is controlled by the spacer particles. And using a dispenser to perform dispensing and sealing on the silicon substrate, framing the area where the liquid crystal layer is positioned, and reserving an opening for filling liquid crystal.
Here, it should be noted that after the liquid crystal is filled, the sealant is used for sealing.
In addition, it is necessary to supplement that the photoalignment films on the silicon substrate and the ITO glass substrate provide horizontal azimuthal anchoring energy to the liquid crystal molecules in the liquid crystal molecule layer, and the neighboring liquid crystal molecules are all arranged in parallel. Since the photoalignment films each have a patterned distribution, the neighboring liquid crystal molecule directors are arranged along the photoalignment film director distribution in the same direction, as shown in fig. 4a, wherein the liquid crystal molecules are arranged in parallel from the silicon substrate to the ITO glass substrate in the vertical direction, but the directors are arranged along the photoalignment layer director pattern in the horizontal direction. Specifically, the alignment film on the glass substrate is a photoalignment film, and the alignment mode and the horizontal azimuthal angle distribution of the photoalignment film are the same as those of one side of the silicon substrate. The control pattern controls the horizontal azimuth angle of the adjacent liquid crystal molecules to form a specific arrangement pattern. Furthermore, the liquid crystal molecules are arranged between the silicon substrate and the glass substrate in a horizontal direction, and the arrangement pattern is the same as the control pattern of the photoalignment layer.
Optionally, through the oriented polarized ultraviolet exposure of the photoalignment film 120 on the ITO glass substrate, the director of the photoalignment film is uniformly distributed in a single direction, that is, the director of the liquid crystal molecules in the neighboring liquid crystal layer is distributed along a single direction, as shown in fig. 4 b. The silicon substrate light control orientation film and the ITO glass substrate light control orientation film control liquid crystal molecules in the liquid crystal layer to be in gradual change and twisted arrangement from the silicon substrate to the ITO glass substrate.
In addition, the realization of the uniform distribution of the neighboring liquid crystal molecules in a single direction on the ITO glass substrate is not limited to the use of a photoalignment material, and a horizontal rubbing alignment agent may be used. The preparation process comprises the following steps: spin-coating a friction orientation agent on one side of the ITO glass substrate conductive film, curing at high temperature, and performing friction orientation under a friction machine. In specific implementation, the liquid crystal molecules are arranged between the silicon substrate and the glass substrate in a horizontal direction, but because the director arrangement patterns of the silicon substrate and the glass substrate are different, the horizontal azimuth angles of the adjacent liquid crystal molecules are arranged along with the direction pattern of the orientation layer, so that the liquid crystal molecules are arranged in a horizontal twisted type, and the twist angle range is between 0 degree and 90 degrees.
Optionally, a vertical alignment film 130 is disposed on the ITO glass substrate, and the preparation process includes: and spin-coating a vertical orientation agent on one side of the ITO glass substrate conductive film, and curing at high temperature. At this time, the liquid crystal molecules in the liquid crystal layer are controlled by the vertical alignment film adjacent to the liquid crystal layer, and the director of the liquid crystal molecules is aligned and distributed in the direction vertical to the ITO glass substrate, as shown in FIG. 4 c. The inclination angles of liquid crystal molecules in the liquid crystal layer are controlled by the silicon substrate light-operated orientation film and the ITO glass substrate vertical orientation film to be in mixed gradient arrangement from the horizontal direction of the silicon substrate to the vertical direction of the ITO glass substrate, and the horizontal azimuth angle distribution pattern is controlled by the light-operated orientation film on the silicon substrate. In specific implementation, the alignment film on the glass substrate is a vertical alignment film made of a light control alignment material or polyimide and the like, the director direction of the vertical alignment film is perpendicular to the glass substrate, and the director direction of the liquid crystal molecules is also perpendicular to the glass substrate. Further, the liquid crystal molecules are in hybrid alignment (hybrid alignment) between the silicon substrate and the glass substrate, that is, the liquid crystal molecules adjacent to the silicon substrate are horizontally aligned, the pretilt angle is 0 °, and the horizontal azimuth angle distribution is controlled by polarization exposure. Meanwhile, liquid crystal molecules adjacent to the glass substrate are vertically aligned, the pretilt angle is 90 degrees, and the director of the liquid crystal molecules is vertical to the direction of the glass substrate. The pretilt angles of the liquid crystal molecules in the two substrates are gradually changed.
The PCB substrate row seat 17 is connected with an external driver, and a control signal is input to control the pixel voltage, so that the inclination angle of liquid crystal molecules in the liquid crystal layer is controlled, and the phase modulation function of the liquid crystal on silicon device is finally realized.
All percentages listed in the above examples, to any particular number, are exemplary in nature and may be adjusted within reasonable limits depending on the application. All listed bake temperatures, times, irradiation wavelengths and doses are exemplary properties.
It should be noted that, a certain order does not necessarily exist between the above steps, and those skilled in the art can understand, according to the description of the embodiments of the present invention, that in different embodiments, the above steps may have different execution orders, that is, may be executed in parallel, may also be executed interchangeably, and the like.
Conditional language such as "can," "might," or "may" is generally intended to convey that a particular embodiment can include (yet other embodiments do not include) particular features, elements, and/or operations, among others, unless specifically stated otherwise or otherwise understood within the context as used. Thus, such conditional language is also generally intended to imply that features, elements, and/or operations are in any way required for one or more embodiments or that one or more embodiments must include logic for deciding, with or without input or prompting, whether such features, elements, and/or operations are included or are to be performed in any particular embodiment.
What has been described herein in the specification and drawings includes examples of an optimization method and apparatus capable of providing cue flows. It will, of course, not be possible to describe every conceivable combination of components and/or methodologies for purposes of describing the various features of the disclosure, but it can be appreciated that many further combinations and permutations of the disclosed features are possible. It is therefore evident that various modifications can be made to the disclosure without departing from the scope or spirit thereof. In addition, or in the alternative, other embodiments of the disclosure may be apparent from consideration of the specification and drawings and from practice of the disclosure as presented herein. It is intended that the examples set forth in this specification and the drawings be considered in all respects as illustrative and not restrictive. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Claims (10)
1. A silicon-based liquid crystal device based on a photo-alignment technology is characterized by comprising a PCB substrate, a silicon substrate arranged on the PCB substrate, and an ITO glass substrate arranged opposite to the silicon substrate, wherein a liquid crystal layer is also arranged between the silicon substrate and the ITO glass substrate;
a first alignment layer is arranged on one side, close to the liquid crystal layer, of the silicon substrate and is a light control alignment layer;
one side of the ITO glass substrate close to the liquid crystal layer is provided with a second orientation layer,
the first alignment layer and the second alignment layer are used for controlling the horizontal arrangement of liquid crystal molecules of the liquid crystal layer;
and pixel electrodes which can be independently addressed are arranged on the silicon substrate and are used for controlling the rotation of liquid crystal molecules at the corresponding pixel positions in the liquid crystal layer in the vertical direction.
2. The LCOS device according to claim 1, wherein the pixel electrode is a reflective electrode formed by CMOS circuit corresponding to each pixel, and an electric field is formed between the reflective electrode and the ITO glass substrate to control the rotation of liquid crystal molecules in the liquid crystal layer at the corresponding pixel position in the vertical direction.
3. The LCOS device according to claim 1, wherein spacers are further disposed between the silicon substrate and the ITO glass substrate to support the silicon substrate and the ITO glass substrate to form a filling space of the liquid crystal layer and to control a thickness of the liquid crystal layer.
4. The LCOS device of claim 1, wherein the second alignment layer is a photo-alignment layer or a rubbing alignment layer, and the alignment direction of the second alignment layer is a horizontal alignment or a vertical alignment.
5. The LCOS device according to claim 4, wherein the second alignment layer is a photo-alignment layer and is aligned in the same manner as the photo-alignment layer disposed on the Si substrate, the liquid crystal molecules in the liquid crystal layer are controlled to be horizontally adjacent to the Si substrate and the ITO glass substrate, and the horizontal azimuth angle of the liquid crystal molecules in the liquid crystal layer is controlled by the ITO glass substrate and the photo-alignment layer disposed on the Si substrate.
6. The LCOS device of claim 4, wherein the second alignment layer is a photoalignment layer, aligned in the same manner as the photoalignment layer disposed on the Si substrate, and uniformly aligned in a single direction; the photoalignment layer of the silicon substrate and the photoalignment layer of the ITO glass substrate control liquid crystal molecules in the liquid crystal layer to be in gradual change twisted arrangement from the silicon substrate to the ITO glass substrate.
7. The LCOS device according to claim 4, wherein said second alignment layer is a vertical alignment layer, liquid crystal molecules in said liquid crystal layer are controlled by the adjacent vertical alignment layer, and the director of said liquid crystal layer is aligned and distributed perpendicular to the direction of said ITO glass substrate; the inclination angles of liquid crystal molecules in the liquid crystal layer are controlled to be in mixed gradual change arrangement from the horizontal direction of the silicon substrate to the vertical direction of the ITO glass substrate by the light-operated orientation layer of the silicon substrate and the vertical orientation layer of the ITO glass substrate, and the horizontal azimuth angle distribution pattern is controlled by the light-operated orientation layer on the silicon substrate.
8. A liquid crystal on silicon device according to any of claims 1 to 7, wherein the photoalignment layer is dye molecules, the material of the dye molecules being at least one of a photocrosslinkable material, a photodegradable material, a photocis-trans isomeric material or a photomolecularly rotating material;
the horizontal director of the dye molecule is irradiated and oriented by ultraviolet polarized light and is arranged along the direction vertical to the polarization direction to form a specific control pattern; the control pattern controls the horizontal azimuth angle of the adjacent liquid crystal molecules to form a specific arrangement pattern.
9. The LCOS device according to claim 1, wherein a bar-shaped conductive layer is further disposed on said PCB substrate, said bar-shaped conductive layer being electrically connected to signal connection points of said ITO glass substrate and said silicon substrate, respectively.
10. A method for preparing a liquid crystal on silicon device based on photoalignment technology, which is used for preparing the liquid crystal on silicon device as claimed in any one of claims 1 to 9, and comprises the following steps:
coating an orientation material on one side of the silicon substrate facing the ITO glass substrate to generate a first orientation layer; the first orientation layer is a light control orientation layer;
coating an orientation material on one side, facing the silicon substrate, of the ITO glass substrate to generate a second orientation film, wherein the second orientation layer is one of a photo-control orientation layer, a friction orientation layer or a vertical orientation layer;
carrying out multi-step overlapping exposure on the first orientation layer and the second orientation layer, and selecting a corresponding exposure pattern and a corresponding irradiation light polarization direction according to an exposure sequence by adopting a maskless dynamic projection exposure system to carry out exposure in sequence;
arranging spacing particles on the silicon substrate and encapsulating the spacing particles with the ITO glass substrate, wherein the first orientation layer and the second orientation layer are arranged oppositely;
a liquid crystal layer is poured between the silicon substrate and the ITO glass substrate, liquid crystal molecules in the liquid crystal layer controlled by the silicon substrate photo-alignment film and the ITO glass substrate are close to each other and are arranged in parallel, in a gradient way or in a mixed gradient way from the silicon substrate to the ITO glass substrate;
and pasting the silicon substrate to the PCB substrate, connecting the silicon substrate and the corresponding electrode of the PCB substrate by using a welding gold wire, and electrically connecting the ITO glass substrate and the PCB substrate by using a conductive layer.
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