Micro display screen light field control structure and preparation method thereof

Abstract

The invention provides a micro display screen light field control structure and a preparation method thereof, and relates to the technical field of micro display. Comprising a substrate, a silicon-based OLED device, a thin film packaging layer and a liquid crystal control layer, wherein a pixel definition layer with a specific inverted trapezoidal structure is arranged on the substrate; the silicon-based OLED device is evaporated on the substrate; the thin film packaging layer covers the silicon-based OLED device and forms a water vapor isolation layer; the cover plate glass is carved into a strip-shaped conductive thin film and distributed with a strip-shaped cathode of the silicon-based OLED device in a crossed mode, the driving circuit is used for controlling the deflection state of liquid crystal molecules, and the silicon-based OLED device comprises a chiral OLED device film layer structure and is used for emitting circularly polarized light. According to the invention, the light field distribution can be stably regulated and controlled, the high-quality naked-eye 3D display effect is realized, and the stable operation of the silicon-based OLED device is effectively ensured.

Description

Technical Field

[0001] This invention relates to the field of microdisplay technology, specifically to a microdisplay light field control structure and its fabrication method. Background Technology

[0002] In the current field of microdisplay and 3D display technology, the demand for high-quality 3D display technology is growing rapidly with the rapid expansion of the augmented reality (AR) and virtual reality (VR) markets. It is projected that by 2036, annual shipments of AR headsets will exceed 35 million units, and VR devices will exceed 27 million units, demonstrating enormous market potential. However, existing AR / VR devices still face many challenges in 3D display technology, especially in achieving high-quality naked-eye 3D display effects, which has become a key factor restricting further market expansion.

[0003] Problems in the existing technology include:

[0004] 1. Currently, the 3D experience provided by a large number of AR / VR devices is still limited to the level of "2D giant screen" projection effect. Conventional 2D content cannot provide stereoscopic depth, which restricts the further development of the AR / VR application market.

[0005] 2. If a beam splitting (polarization / spectral beam splitting) technology is used, a large optical combiner needs to be placed outside the display, greatly increasing the size and weight of the optical engine, which does not meet the lightweight requirements of AR / VR devices. At the same time, the traditional method of placing lenses above pixels is difficult to use due to the extremely small pixel size of silicon-based OLEDs (OLEDoS), making it difficult to directly fabricate high-precision, switchable optical structures on them using traditional microfabrication methods.

[0006] 3. OLED materials are extremely sensitive to water and oxygen, requiring rigorous encapsulation. Traditional glass or thin-film encapsulation covers are rigid, making it impossible to fabricate complex electro-hydraulic liquid crystal structures inside, thus limiting the realization of 3D display functions.

[0007] To address these issues, existing technologies have proposed several solutions, such as using external optical combiners or complex optical lens arrays to achieve 3D displays. However, these solutions either increase the size and weight of the device or are difficult to apply on a large scale due to manufacturing precision and cost issues. Especially for high pixel density display technologies like silicon-based OLEDs, existing solutions cannot simultaneously meet the requirements of both high-quality 3D display and lightweight equipment. Summary of the Invention

[0008] To address the above problems, this invention provides a micro-display light field control structure and its fabrication method.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a micro-display light field control structure and its preparation method, comprising a substrate having a pixel definition layer with a specific inverted trapezoidal structure disposed thereon, a silicon-based OLED device deposited on the substrate, a thin film encapsulation layer covering the silicon-based OLED device and forming a moisture barrier layer, a liquid crystal control layer located above the thin film encapsulation layer and having liquid crystal material filled in the slots above the pixels, a cover glass having a strip-shaped conductive film disposed thereon and arranged in a cross shape with the strip-shaped cathode of the silicon-based OLED device, and a driving circuit for controlling the deflection state of liquid crystal molecules, wherein the silicon-based OLED device includes a chiral OLED device film layer structure for emitting circularly polarized light.

[0010] Preferably, the chiral OLED device uses enantiomers of chiral multi-resonance thermally activated delayed phosphor materials such as (R / S)-BN-FLCz and (R / S)-BN-FLTPA in the film structure to ensure that the OLED device emits circularly polarized light.

[0011] Preferably, the inverted trapezoidal structure of the pixel definition layer is formed by grayscale exposure or multiple patterning techniques, and is used to define the separation shape of the subsequent cathode.

[0012] Preferably, the liquid crystal material in the liquid crystal control layer is a nematic liquid crystal with a high birefringence Δn, which is used to achieve precise control of the light phase.

[0013] Preferably, the transparent conductive film on the cover glass is an ITO film, which is etched into strips by photolithography and wet / dry etching processes.

[0014] Preferably, the driving circuit applies voltage to specific strip-shaped ITO electrodes and strip-shaped cathodes in a precise pulse sweep pattern to achieve pixel-level phase modulation.

[0015] Preferably, it further includes a primary encapsulation layer disposed between the strip cathode and the thin film encapsulation layer to protect the strip cathode from moisture erosion.

[0016] Preferably, the liquid crystal control layer further includes bottom and top alignment layers for defining the initial twist state of the liquid crystal molecules. The alignment layer material is polyimide (PI) and has undergone photoalignment treatment.

[0017] A method for fabricating a micro-display light field control structure includes the following steps:

[0018] Step 1: Form a pixel definition layer with an inverted trapezoidal structure on the substrate;

[0019] Step 2: Evaporate the chiral OLED device film structure and fabricate a strip cathode;

[0020] Step 3: Deposit a thin film encapsulation layer;

[0021] Step 4: Construct the bottom liquid crystal contact layer and cavity on the thin-film encapsulation layer;

[0022] Step 5: Fabricate the top cover unit, including depositing strip-shaped ITO thin films;

[0023] Step Six: Precisely align the top cover plate with the silicon-based OLED substrate and fill it with liquid crystal;

[0024] Step 7: Bind the driver chip and verify the 2D / 3D display switching.

[0025] Preferably, in step six, after the top cover plate and the silicon-based OLED substrate are precisely aligned, a pre-pressurization process is first performed to initially bond the top cover plate and the silicon-based OLED substrate. Then, liquid crystal is filled in a vacuum environment. After filling, a second pressurization process is performed to reduce air bubbles generated during the liquid crystal filling process and improve the uniformity of the liquid crystal layer.

[0026] The beneficial effects of this invention are:

[0027] 1. The structural design of this invention is realized within the scope of traditional process technology, and is highly compatible with the high-density pixel technology of silicon-based OLEDs, without significantly increasing the size of the equipment or the difficulty of the process.

[0028] 2. By utilizing patterned electrodes aligned with pixels, independent phase modulation at the level of individual pixels or pixel groups can be achieved, thereby enabling extremely high-precision light field control and providing the possibility for high-quality naked-eye 3D displays.

[0029] 3. Liquid crystal materials are inexpensive, and China has mature manufacturing processes and a large number of suppliers, which helps reduce production costs and alleviate the development pressure on newly established enterprises.

[0030] 4. Compared with existing 3D display solutions, the structure of this invention does not require bulky optical components, which significantly reduces the size and weight of the device and better meets the lightweight requirements of AR / VR devices. Attached Figure Description

[0031] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0032] Figure 1 This is a schematic diagram of the strip-shaped ITO cover plate structure of the present invention.

[0033] Figure 2 This is a schematic diagram of the cross-shaped liquid crystal control structure of the present invention.

[0034] Figure 3 This is a schematic diagram illustrating the integrated device structure and working principle of the present invention. Detailed Implementation

[0035] To make the technical means, creative features, achieved objectives, and effects of this invention readily understandable, the invention is further described below with reference to specific embodiments and accompanying drawings. However, the following embodiments are merely preferred embodiments of this invention and not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments described herein without creative effort are all within the protection scope of this invention.

[0036] In the field of micro-display technology, traditional 3D display solutions rely on external optical combiners (such as polarized glasses or lens arrays), resulting in bulky devices that are difficult to integrate into lightweight applications (such as AR / VR glasses). Furthermore, the luminous efficiency and color purity of conventional OLED devices are limited by material properties, and the liquid crystal layer filling process easily introduces air bubbles, affecting display uniformity. To address these issues, this embodiment proposes an integrated micro-display light field control structure. By optimizing the pixel definition layer geometry, introducing chiral OLED devices, and employing a vacuum-pressurized liquid crystal filling process, high-resolution naked-eye 3D display and long-term device stability are achieved.

[0037] Example 1: Reference Figures 1-3 The micro-display light field control structure shown includes a substrate on which a pixel definition layer with a specific inverted trapezoidal structure is disposed, a silicon-based OLED device deposited on the substrate, a thin film encapsulation layer covering the silicon-based OLED device and forming a moisture barrier layer, a liquid crystal control layer located above the thin film encapsulation layer and having liquid crystal material filled in the slots above the pixels, a cover glass having a strip-shaped conductive film disposed thereon and arranged in a cross shape with the strip-shaped cathode of the silicon-based OLED device, and a driving circuit for controlling the deflection state of liquid crystal molecules. The silicon-based OLED device includes a chiral OLED device film layer structure for emitting circularly polarized light.

[0038] In this embodiment, during the operation of the micro-display light field control structure, the chiral OLED device film structure in the silicon-based OLED device first emits circularly polarized light. This light passes through the pixel definition layer with a specific inverted trapezoidal structure, ensuring precise light emission. Subsequently, the light enters the liquid crystal control layer located above the thin film encapsulation layer, where the liquid crystal material fills the slots above the pixels. The driving circuit applies a specific voltage to the conductive thin film etched into strips on the cover glass (intersecting with the strip cathodes of the silicon-based OLED device) and the strip cathodes, according to display requirements, thereby controlling the deflection state of the liquid crystal molecules. The deflection of the liquid crystal molecules changes the phase of the light, thus achieving precise control of the light field. By integrating the silicon-based OLED device and the liquid crystal control layer, combined with a specific driving circuit design, dynamic and precise control of the light field is achieved. Its core function is to produce high-quality naked-eye 3D display effects without the need for external optical combiners or complex lens arrays, significantly reducing the size and weight of the device while maintaining high pixel density and excellent display performance. Furthermore, this structure also has good moisture barrier capabilities, ensuring the long-term stable operation of the silicon-based OLED device.

[0039] The key materials and process details in this embodiment mainly include the following five parts:

[0040] 1. Chiral OLED Device Film Structure: Enantiomers of chiral multi-resonance thermally activated delayed phosphor materials such as (R / S)-BN-FLCz and (R / S)-BN-FLTPA are used to ensure that the OLED device emits circularly polarized light. These chiral multi-resonance thermally activated delayed phosphor materials are formed into films via vacuum evaporation at a rate of 0.1–0.5 Å / s, with film thickness controlled within the range of 50–100 nm. Experiments show that this material achieves a fluorescence quantum yield (PLQY) >95% and a narrow full width at half maximum (FWHM) of 24–27 nm under electroluminescence, ensuring high color purity of circularly polarized light (CIEy ≥ 0.72). Furthermore, the helical carbon chiral centers in the material are locked in configuration through sp³ hybridization, effectively suppressing racemization during the evaporation process and ensuring that the absolute value of gEL (electroluminescence asymmetry factor) remains stable above 1 × 10⁻³ throughout the device lifetime.

[0041] 2. Pixel Definition Layer: The inverted trapezoidal structure is formed through grayscale exposure or multiple patterning techniques to define the separation shape of the subsequent cathode. When using grayscale exposure, a positive photoresist (such as the AZ1500 series) is selected, and the sidewall slope is continuously varied by designing the grayscale mask. The exposure dose gradient is set to 50-300 mJ / cm², and the sidewall angle after development is controlled within the range of 60°-80°, with a bottom linewidth error ≤0.5μm. This structure can reduce stress concentration during cathode evaporation, increasing the coverage of the strip cathode to over 98%, while reducing optical coupling loss and improving the external quantum efficiency (EQE) by 15%-20%.

[0042] 3. Liquid Crystal Control Layer: The liquid crystal material is a nematic liquid crystal with a high birefringence Δn, used to achieve precise control of the light phase. The nematic liquid crystal uses Merck's MLC-6608 series material, with a birefringence Δn = 0.22 (589nm wavelength) and a clearing point temperature >100℃, meeting the requirements for wide-temperature operation. The bottom / top alignment layer uses polyimide (PI) material (such as Nissan Chemical SE-1211), and the pretilt angle of the liquid crystal molecules (2°-5°) is defined by rubbing alignment or photoalignment processes. During photoalignment treatment, linearly polarized ultraviolet light (λ = 254 nm, nitrile = 100 mJ / cm²) is used to irradiate the PI layer, achieving orientation control without mechanical damage and improving the response speed by 10%-15%.

[0043] 4. Cover glass: The transparent conductive film is an ITO film, which is etched into strips by photolithography and wet / dry etching processes.

[0044] 5. Primary Encapsulation Layer: Located between the strip cathode and the thin-film encapsulation layer, this layer protects the strip cathode from moisture erosion. The primary encapsulation layer is made of an inorganic-organic composite material (such as an Al2O3 / epoxy resin laminate) and formed through atomic layer deposition (ALD) and spin coating processes. The ALD-deposited Al2O3 layer has a thickness of 50-100 nm and a water vapor transmission rate (WVTR) ≤1×10⁻ 6 g / m²·day; the epoxy resin layer thickness is 2-5 μm, and the curing temperature is ≤120℃ to avoid damage to OLED devices from high temperatures. This composite structure can simultaneously block moisture and oxygen, extending device life to >5000 hours (under 60℃ / 90%RH conditions).

[0045] The liquid crystal control layer also includes bottom and top alignment layers to define the initial twist state of the liquid crystal molecules. The alignment layer material is polyimide (PI) and has undergone photo-alignment treatment.

[0046] A method for fabricating a micro-display light field control structure includes the following six steps:

[0047] Step 1: Fabrication of silicon-based OLEDs with strip-shaped cathodes

[0048] On a silicon wafer where the CMOS driver circuitry has been integrated, planarization is performed. In the pixel definition layer (PDL) process, a PDL with a specific inverted trapezoidal structure is formed through grayscale exposure or multiple patterning techniques. This structure will determine the separation shape of the subsequent cathode.

[0049] The anode and organic functional layers (hole injection / transport layer, light-emitting layer, electron transport layer, etc.) are deposited and patterned sequentially. A key step is to use chiral doped materials in the electron injection layer or cathode to ensure that the emitted light from the OLED is fixed circularly polarized light (such as left-handed circularly polarized light), which is the optical basis for working in conjunction with the subsequent liquid crystal layer.

[0050] Step 2: Forming the strip cathode and primary encapsulation

[0051] Metal cathodes are deposited using a lift-off process employing a shadow mask (FMM) or an inverted trapezoidal structure of a photomask (PDL), naturally separating them into parallel strip electrodes by the PDL. Subsequently, a first inorganic thin-film encapsulation layer is deposited to cover and protect these strip cathodes, forming a moisture barrier.

[0052] Step 3: Construct the bottom liquid crystal contact layer and cavity

[0053] On the thin-film encapsulation layer, a strip-shaped ITO film is deposited as a common electrode for driving the liquid crystal. A polyimide (PI) liquid is coated and photo-aligned to form an alignment layer with a uniform, defined orientation. This orientation is typically designed to form a specific angle (e.g., 90 degrees or 45 degrees) with the strip-shaped ITO orientation on the subsequent cover plate to define the initial twist state of the liquid crystal.

[0054] Using photolithography and etching processes, a portion of the PI layer and encapsulation layer are patterned above the pixel array area to form a series of "grooves" or "microcavities" aligned with the pixels, used to accommodate liquid crystal. The sidewalls of the grooves are composed of the remaining PDL and encapsulation layer.

[0055] Step 4: Fabrication of the top cover plate unit: An ITO thin film is deposited on a transparent glass or high-transmittance cover plate. The ITO is etched into parallel strip electrodes perpendicular to the substrate's strip cathode orientation using photolithography and wet / dry etching. These electrodes serve as independent addressing electrodes for liquid crystal driving. PI is also coated onto this strip ITO and photo-aligned, with the alignment direction matching the bottom alignment layer. A frame sealant is applied around the cover plate, and one or more liquid crystal injection ports are pre-drilled.

[0056] Step 5: Precision Cell Alignment and Liquid Crystal Filling: The top cover plate and the silicon-based OLED substrate are placed in a high-precision bonding device and aligned under a microscope to ensure that the strip-shaped ITO on the cover plate and the strip-shaped cathode on the substrate form a precise cross-shaped grid, with each intersection corresponding to an OLED light-emitting pixel. A pre-pressurization process is first performed to initially bond the top cover plate and the silicon-based OLED substrate. Then, under vacuum conditions, nematic liquid crystal material (typically with a high birefringence Δn) is vacuum-filled from the injection port into the cavity between the two substrates, filling the "grooves" above all pixels. After filling, a second pressurization process is performed to reduce air bubbles generated during liquid crystal filling and improve the uniformity of the liquid crystal layer. The injection port is sealed using ultraviolet light or thermal curing to complete the encapsulation of the liquid crystal cell.

[0057] Step Six: Verify Driver Chip Binding and 2D / 3D Display Switching

[0058] By binding the driver chip, the driver circuit applies voltage to specific strip-shaped ITO electrodes and strip-shaped cathodes in a precise pulse sweep mode according to time sequence, thereby achieving pixel-level phase modulation.

[0059] 2D display mode verification: Drive all OLED pixels to light up and display 2D images. At the same time, apply the same voltage (i.e., zero voltage difference) to all top strip ITO electrodes as to the bottom common electrode. The liquid crystal layer is in its initial alignment state and does not produce additional phase modulation to the light passing through it. The system works as a standard OLED display.

[0060] 3D Display Mode Driver: Input is a calculated 3D image / light field signal. The OLED backplane controls the brightness (amplitude) of each pixel. The liquid crystal driving circuit, based on a pre-calculated phase distribution map, applies voltage sequentially to specific strip-shaped ITO electrodes (X-direction) and a strip-shaped cathode (Y-direction) using a precise pulse sweep. Through cross-addressing, the deflection state of liquid crystal molecules at each cross-point (i.e., above each pixel) is independently controlled. The deflection of the liquid crystal molecules alters their birefringence properties, thereby applying a controllable phase delay to the circularly polarized light passing through that pixel, modulating its wavefront phase. Ultimately, the light emitted from the device carries both amplitude information from the OLED and pixel-level phase information from the liquid crystal layer. These modulated light waves propagate and interfere in space, reconstructing a depth-sensory stereoscopic image at a preset viewpoint, achieving high-resolution, dynamically switchable 3D display.

[0061] The overall detailed process of the micro-display light field control structure and its fabrication method proposed in this invention is as follows:

[0062] The final device structure from top to bottom is as follows: top glass cover plate → strip ITO electrode → top alignment layer → liquid crystal layer → bottom alignment layer → ITO common electrode → thin film encapsulation layer → strip cathode → chiral OLED light-emitting layer → anode → CMOS silicon-based backplane. The circularly polarized light emitted by each OLED pixel (driven by the CMOS circuitry below) passes upwards through the liquid crystal layer. The liquid crystal layer is located at the crossroads defined by the strip cathode (X direction) and the strip ITO (Y direction), forming independent liquid crystal phase modulation units.

[0063] This embodiment achieves dynamic and precise control of the light field by integrating an inverted trapezoidal pixel definition layer, a chiral OLED device, and a liquid crystal control layer. The inverted trapezoidal structure optimizes cathode coverage and luminous efficiency, while the chiral OLED device directly emits circularly polarized light. Combined with the phase modulation function of the liquid crystal layer, high-quality naked-eye 3D display effects can be generated without external optical combiners, while significantly reducing the size and weight of the device. The thin-film encapsulation layer and vacuum pressurization process ensure the reliability of the device and the uniformity of the liquid crystal layer, and the bonding of the driver chip enables flexible switching of display modes. This technical solution meets the core requirements of the micro-display field (such as AR / VR glasses) for high pixel density, lightweight, and low power consumption, and has significant economic and social benefits, providing strong technical support for the development of micro-display technology.

[0064] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A micro-display light field control structure, comprising a substrate having a pixel definition layer with a specific inverted trapezoidal structure disposed thereon, a silicon-based OLED device deposited on the substrate, a thin film encapsulation layer covering the silicon-based OLED device and forming a moisture barrier layer, a liquid crystal control layer located above the thin film encapsulation layer and having liquid crystal material filled in the slots above the pixels, a cover glass having a strip-shaped conductive film disposed thereon and arranged in a cross shape with the strip-shaped cathode of the silicon-based OLED device, and a driving circuit for controlling the deflection state of liquid crystal molecules, wherein the silicon-based OLED device includes a chiral OLED device film layer structure for emitting circularly polarized light.

2. The micro-display screen light field control structure according to claim 1, characterized in that: Chiral OLED devices use enantiomers of chiral multi-resonance thermally activated delayed phosphor materials such as (R / S)-BN-FLCz and (R / S)-BN-FLTPA in their film structure to ensure that the OLED devices emit circularly polarized light.

3. The micro-display screen light field control structure according to claim 1, characterized in that: The inverted trapezoidal structure of the pixel definition layer is formed through grayscale exposure or multiple patterning techniques and is used to define the separation shape of the subsequent cathode.

4. The micro-display screen light field control structure according to claim 1, characterized in that: The liquid crystal material in the liquid crystal control layer is a nematic liquid crystal with a high birefringence Δn, which is used to achieve precise control of the light phase.

5. The micro-display screen light field control structure according to claim 1, characterized in that: The transparent conductive film on the cover glass is an ITO film, which is etched into strips using photolithography and wet / dry etching processes.

6. The micro-display screen light field control structure according to claim 1, characterized in that: The driving circuit applies voltage to specific strip-shaped ITO electrodes and strip-shaped cathodes in a precise pulse sweep pattern to achieve pixel-level phase modulation.

7. The micro-display screen light field control structure according to claim 1, characterized in that: It also includes a primary encapsulation layer disposed between the strip cathode and the thin film encapsulation layer to protect the strip cathode from moisture erosion.

8. The micro-display screen light field control structure according to claim 1, characterized in that: The liquid crystal control layer also includes bottom and top alignment layers to define the initial twist state of the liquid crystal molecules. The alignment layer material is polyimide (PI) and has undergone photo-alignment treatment.

9. A method for fabricating a micro-display light field control structure, applied to the micro-display light field control structure of claim 1, characterized in that, Includes the following steps: Step 1: Form a pixel definition layer with an inverted trapezoidal structure on the substrate; Step 2: Evaporate the chiral OLED device film structure and fabricate a strip cathode; Step 3: Deposit a thin film encapsulation layer; Step 4: Construct the bottom liquid crystal contact layer and cavity on the thin-film encapsulation layer; Step 5: Fabricate the top cover unit, including depositing strip-shaped ITO thin films; Step Six: Precisely align the top cover plate with the silicon-based OLED substrate and fill it with liquid crystal; Step 7: Bind the driver chip and verify the 2D / 3D display switching.

10. The method for fabricating the micro-display screen light field control structure according to claim 9, characterized in that: In step six, after the top cover plate and the silicon-based OLED substrate are precisely aligned, a pre-pressurization process is first performed to initially bond the top cover plate and the silicon-based OLED substrate. Then, liquid crystal is filled in a vacuum environment. After filling, a second pressurization process is performed to reduce air bubbles generated during the liquid crystal filling process and improve the uniformity of the liquid crystal layer.

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