MIM structure optical filter and preparation method thereof

Abstract

An MIM structure optical filter is characterized in that a bottom Ag layer, a ZrO2 thin film and a top Ag layer are sequentially attached to the surface of a substrate, the ZrO2 thin film is prepared from ZrO2 photosensitive ink through an optical patterning method, and the ZrO2 photosensitive ink is a ZrO2 nanoparticle N, N-dimethylformamide solution added with 1-diazo-2-naphthol-4-sulfonic acid; the invention relates to a preparation method of an MIM structure optical filter, which comprises the following steps: sequentially evaporating Ag on a substrate, forming a patterned ZrO2 film by using an optical patterning method, evaporating Ag again, repeatedly coating the ZrO2 film before evaporating Ag again, and forming a multispectral optical filter array through an optical patterning process. The optical filter of the MIM structure has the advantages of being high in discrimination rate, easy in wavelength tuning, simple in process, low in cost, high in stability, wide in spectrum application range and the like. The preparation method of the optical filter of the MIM structure can be well applied to production and application of MIM structure monochromatic optical filters and MIM structure multispectral optical filter arrays.

Description

Technical Field

[0001] The invention belongs to the field of multi-spectral technology, and particularly relates to a MIM structure filter and a preparation method thereof. Background Art

[0002] Multispectral imaging can simultaneously obtain the multi-band spectral information and spatial information of the target, greatly improving the information dimension of target detection. With the development of image technology and display technology, multispectral filter arrays have gradually been widely used in image sensing, color display, spectral instruments, fiber optic communications, medical treatment, environmental monitoring and other fields. At present, spectral filters are mainly divided into absorption filters, interference filters and micro-nano structure filters.

[0003] The absorption filter has a large spectral bandwidth and low spectral resolution, which limits the acquisition of spectral detail information. Traditional preparation methods mainly include dyeing, pigment dispersion, electrodeposition, inkjet, etc. Among them, the dyeing method and pigment dispersion method are mature, but the process is complex and the cost is high; the electrodeposition method is low-cost, but the color layer can only be arranged in strips, with low flexibility; the inkjet method has a simplified process and high pigment utilization rate, but because the inks of different colors are flowing before solidification, it is easy to be stained and mixed between different colors and between color layers; the traditional inks used in the above processes are also easily affected by external environmental factors such as humidity, temperature and ultraviolet radiation, and there are problems such as fading and discoloration. The harmful substances contained in the ink are very harmful to operators and the environment.

[0004] Compared with traditional inks, the use of micro-nano structures to achieve color effects has the advantages of low pollution, bright colors and not easy to fade, including structural colors based on grating guided mode resonance, plasmon resonance, dielectric Mie resonance and other effects. However, there are still some problems: 1D / 2D grating units have inherent polarization sensitivity, low transmission efficiency, poor wavelength selectivity, etc. The material selection of the filtering structure is also very demanding, and the preparation process often involves complex geometric patterns. Its realization requires complex and expensive etching processes, which are not suitable for large-area and mass production.

[0005] FP thin film filters modulate the amplitude or phase of light propagating through them through a multi-layer thin film structure, so that the intensity of light within a certain wavelength range is redistributed or its polarization state is changed. This type of color filter has a small spectral bandwidth, high transmittance, tunable wavelength, stable properties, not easy to fade, bright colors, and environmentally friendly materials. Two structures are commonly used: (1) metal-dielectric-metal (MIM) layer structure, (2) 1D photonic crystal structure of dielectric stack. The preparation process of the MIM structure filter is simpler, requiring only a low-cost and highly scalable coating process, which is suitable for large-scale production. However, the preparation of spectral array filters involves complex and numerous photolithography and etching process steps.

[0006] In 2015, Zhongyang Li et al. studied ultra-thin metal film filters based on symmetrical MIM FP structures, achieving a high transmittance filtering effect with a transmittance of more than 60% in the entire visible light range. Its high transmission efficiency and the ability to achieve a wide range of colors through a flat smooth surface have great application prospects in camera-integrated filtering and display devices; however, this scheme mainly uses electron beam evaporation technology to deposit metal and dielectric films on the substrate, which can only realize the preparation of large-area monochrome filters. This scheme also demonstrates the preparation of multiple color filters on the same wafer, using a focused ion beam (FIB) etching process. Although its processing steps are simple, it has disadvantages such as redeposition, slow processing speed, and inability to process in batches.

[0007] In 2019, Calum Williams and others demonstrated a manufacturing process that combines grayscale lithography technology with MIM FP cavities. The cavity is directly prepared using cured photoresist, and the cavity thickness is controlled by the exposure dose. Wafer-level customized multi-spectral filter array manufacturing can be achieved in a single lithography step, maintaining high transmittance and narrow linewidth in the visible light to near-infrared range. This manufacturing process reduces the manufacturing complexity and cost of array filters, and provides an attractive alternative to traditional spectral filter array manufacturing; however, the photoresist used in this process is a resin material, which has good light transmittance in the visible light range, but poor light transmittance in the ultraviolet and infrared ranges, which limits the spectral range of the filter; at the same time, the resin material in the photoresist has poor stability under the influence of high temperature, strong light, ultraviolet light, etc., and the optical properties of the filter spectral channel such as wavelength and transmittance are prone to change. The above shortcomings of the resin material limit the actual application and application scenarios of this type of filter.

[0008] The invention with patent publication number "CN 102854749 A" ​​and name "Photosensitive resin composition for color filter and color filter using the same" discloses a method for preparing an array color filter using a photosensitive resin composition. By using a photosensitive resin composition with excellent heat resistance and chemical resistance, a color filter is prepared on a TFT array substrate, achieving a high aperture ratio and high contrast. However, since the composition is a resin material, it still has the above-mentioned disadvantages of limited spectral range and poor stability under high temperature, strong light, ultraviolet light, etc. Summary of the invention

[0009] In view of the deficiencies in the above-mentioned prior art, the purpose of the present invention is to propose a MIM structure filter and a preparation method thereof, wherein a ZrO2 thin film is prepared by a liquid phase coating process as a spacing medium layer to construct a MIM interference filter structure, and the wavelength of the filter channel is controlled by controlling the coating thickness of the ZrO2 thin film, and the integration of a multi-spectral filter channel array on a single filter is realized by utilizing direct optical patterning technology; this method has the advantages of high spectral resolution, easy wavelength tuning, and simple process, and can be combined with a digital mask lithography system to flexibly design the filter pattern, and is compatible with various substrates including flexible materials.

[0010] To achieve the above purpose, the technical solution adopted by the present invention is:

[0011] A MIM structure filter comprises a substrate, wherein a bottom Ag layer, a ZrO2 film, and a top Ag layer are sequentially attached to the surface of the substrate, wherein the ZrO2 film is prepared by an optical patterning method using ZrO2 photosensitive ink, and the ZrO2 photosensitive ink is an N,N-dimethylformamide (DMF) solution of ZrO2 nanoparticles (ZrO2 NPs) added with a photosensitizing additive 1-diazo-2-naphthol-4-sulfonic acid.

[0012] Furthermore, the concentration of ZrO2 nanoparticles (ZrO2 NPs) in the N,N-dimethylformamide (DMF) solution of the ZrO2 nanoparticles (ZrO2 NPs) is 30-120 mg / mL, and the content of the photosensitive additive 1-diazo-2-naphthol-4-sulfonic acid (DNS) in the ZrO2 photosensitive ink is 15-30 wt%.

[0013] Furthermore, the number of layers of the ZrO2 film is any number from one to four, the thickness of each ZrO2 film layer is 20-150nm, and the thickness of the bottom Ag layer and the top Ag layer are both 20-40nm.

[0014] Furthermore, the substrate is a glass substrate, an organic polymer substrate or a flexible glass substrate.

[0015] Furthermore, when the number of layers of the ZrO2 film is one, the ZrO2 film is an array-patterned ZrO2 film with a single thickness; when the number of layers of the ZrO2 film is any number from two to four, the ZrO2 film is an array-patterned ZrO2 film with different thicknesses in different regions.

[0016] A method for preparing a MIM structure filter comprises the following steps:

[0017] S1: Adding a photosensitive additive 1-diazo-2-naphthol-4-sulfonic acid (DNS) to a N,N-dimethylformamide (DMF) solution in which ZrO2 nanoparticles (ZrO2 NPs) are dispersed to form a ZrO2 photosensitive ink;

[0018] S2: using physical vapor deposition method to evaporate metal Ag on the substrate to form the bottom Ag layer of the MIM structure;

[0019] S3: coating the ZrO2 photosensitive ink in step S1 on the bottom Ag layer in step S2 by spin coating to form a ZrO2 thin film;

[0020] S4: performing partial ultraviolet exposure on the ZrO2 film in step S3 to form an exposed ZrO2 film;

[0021] S5: using N,N-dimethylformamide (DMF) solvent to develop the exposed ZrO2 film in step S4 to form an array patterned ZrO2 film;

[0022] S6: drying the array patterned ZrO2 thin film in step S5 to form a dried array patterned ZrO2 thin film;

[0023] S7: A metal Ag layer is deposited on the surface of the array patterned ZrO2 thin film after drying in step S6 by physical vapor deposition to form a top Ag layer of the MIM structure, and finally a MIM structure filter is formed.

[0024] Furthermore, step S3 describes the use of a spin coating process to coat the ZrO2 photosensitive ink on the bottom Ag layer. The specific process is: fix the substrate containing the bottom Ag layer on a coater, drop 25-50 μL of ZrO2 photosensitive ink with a concentration of 30-120 mg / mL on the bottom Ag layer, set the coater parameters to a low speed of 1700 rpm for 6 seconds and then a high speed of 2500 rpm for 40 seconds, turn on the coater, and the ZrO2 photosensitive ink is spin-coated on the substrate to form a ZrO2 film.

[0025] Furthermore, the local exposure in step S4 uses a designed mask pattern, and the mask pattern is preferably an array distribution pattern. The exposure wavelength in the local exposure is 405nm and the exposure dose is 30-40mJ / cm 2 .

[0026] Furthermore, the drying temperature of the drying process in step S6 is 60-120° C. and the drying time is 10-120 seconds.

[0027] Furthermore, in a method for preparing a MIM structure filter, step S7 comprises the following steps:

[0028] S7.1: Spin coating the ZrO2 photosensitive ink described in step S1 on the surface of the array patterned ZrO2 film and the surface of the bottom Ag layer where it is located after drying in step S6 to form an nth (n=2, 3, 4)th layer of ZrO2 film, wherein the concentration of the ZrO2 nanoparticles (ZrO2 NPs) described in step S1 is 30-55 mg / mL, the content of 1-diazo-2-naphthol-4-sulfonic acid (DNS) in the ZrO2 photosensitive ink described in step S1 is 15-30wt%, the thickness of the bottom Ag layer is 20-40nm, and the thickness of the nth (n=2, 3, 4)th layer of ZrO2 film is 20-50nm;

[0029] S7.2: In step S7.1, the surface of the nth (n=2, 3, 4)th ZrO2 film is locally exposed to ultraviolet light to form the nth (n=2, 3, 4)th exposed ZrO2 film. The local exposure uses a designed mask pattern, and the mask pattern is preferably an array distribution pattern. The exposure wavelength in the local exposure is 405nm and the exposure dose is 30-40mJ / cm 2 ;

[0030] S7.3: Using N,N-dimethylformamide (DMF) solvent, the nth (n=2, 3, 4) layer of the exposed ZrO2 film in step S7.2 is developed to form an nth (n=2, 3, 4) layer of array patterned ZrO2 film;

[0031] S7.4: drying the nth (n=2, 3, 4) layer of array patterned ZrO2 thin film described in step S7.3 to form the nth (n=2, 3, 4) layer of array patterned ZrO2 thin film after drying, wherein the drying temperature of the drying treatment is 60-120°C and the drying time is 10-120s;

[0032] S7.5: repeating steps S7.1 to S7.4, replacing the dried array patterned ZrO2 film in step S7.1 with the nth (n=2, 3, 4) layer of dried array patterned ZrO2 film in step S7.4, until the Nth (N=3, 4) layer of dried array patterned ZrO2 film is formed;

[0033] S7.6: After drying the nth (n=2, 3, 4) layer described in step S7.4 or the Nth (N=3, 4) layer described in step S7.5, the surface of the array patterned ZrO2 film is subjected to physical vapor deposition to form a top Ag layer of the MIM structure, wherein the thickness of the top Ag layer is 20-40 nm, thereby finally forming a MIM structure multi-spectral filter array.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The present invention uses inorganic nano ZrO2 material to prepare MIM structure filter, which solves the problems of fading, discoloration, poor stability and high harmfulness of raw materials of traditional absorption filters.

[0036] 2. The present invention prepares the MIM structure multi-spectral filter, which only requires the use of simple and low-cost physical vapor deposition, spin coating and direct optical lithography processes, which solves the problem of complex and expensive preparation processes for micro-nano structure and FP thin film array filters.

[0037] 3. The MIM structured monochrome filter or MIM structured multi-spectral filter array prepared by the present invention has the advantages of high spectral resolution (half-maximum width is 21 to 27 nm), easy wavelength tuning (the transmission peak wavelength can be tuned by simply controlling the thickness of the ZrO2 film, i.e., the thickness of the intermediate dielectric layer), simple process, and wide spectral application range. In addition, the liquid phase spin coating process used is compatible with various substrates including flexible materials such as organic polymers.

[0038] In summary, the MIM structure filter in the present invention has the advantages of high resolution, easy wavelength tuning, simple process, low cost, high stability, and wide spectral application range. The preparation method of the MIM structure monochrome filter and the MIM structure multi-spectral filter can be well used in the production and application of MIM structure monochrome filters and MIM structure multi-spectral filters. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the ZrO2 thin film patterning process using direct optical patterning technology.

[0040] Figure 2 This is the mechanism of direct photocuring of ZrO2 photosensitive ink modified with 1-diazo-2-naphthol-4-sulfonic acid (DNS) under light irradiation.

[0041] Figure 3 Schematic diagram of the multi-spectral filter array structure.

[0042] Figures 4a to 4c Schematic diagram of three digital masks used for photolithography in Example 1.

[0043] Figure 5 Microscopic images of ZrO2 films of different thicknesses of the multi-spectral filter array in Example 1.

[0044] Figure 6a This is a micrograph of individual channels of the multi-spectral filter array in Example 1 under a transmission microscope.

[0045] Figure 6b This is a micrograph of individual channels of the multi-spectral filter array in Example 2 under a transmission microscope.

[0046] Figure 6c This is a micrograph of individual channels of the multi-spectral filter array in Example 3 under a transmission microscope.

[0047] Figure 7 The transmittance measurement results of the filters with different ZrO2 film thicknesses in Example 1, Example 2, and Example 3 are shown. DETAILED DESCRIPTION

[0048] The present invention proposes a MIM structure filter and a method for preparing the MIM structure filter, wherein a ZrO2 thin film is prepared by a liquid phase coating process as a spacer medium layer to construct a MIM interference filter structure, the wavelength of the filter channel is regulated by controlling the coating thickness of the ZrO2 thin film, and a multi-spectral filter channel array is integrated on a single filter by using direct optical patterning technology; Figures 1 to 7 The present invention is described in further detail.

[0049] A MIM structure filter comprises a substrate, wherein a bottom Ag layer, a ZrO2 film, and a top Ag layer are sequentially attached to the surface of the substrate, wherein the ZrO2 film is prepared by an optical patterning method using ZrO2 photosensitive ink, and the ZrO2 photosensitive ink is an N,N-dimethylformamide solution of ZrO2 nanoparticles (ZrO2 NPs) added with a photosensitive additive 1-diazo-2-naphthol-4-sulfonic acid.

[0050] The number of layers of the ZrO2 film is any number from one to four, and the thickness of each layer of the ZrO2 film is the same or different; when the number of layers of the ZrO2 film is one, the thickness of the ZrO2 film is 20-150nm, and the ZrO2 film is an array patterned ZrO2 film with a single thickness. At this time, the MIM structure filter is a MIM structure monochrome filter; when the number of layers of the ZrO2 film is two to four, the thickness of each layer of the ZrO2 film is 20-50nm, and the preparation process of the ZrO2 films of different layers is: first, the film is prepared by spin coating using a spin coating process, and then the pattern of each layer of the film is defined by a patterning process, and the spin coating and patterning processes are repeated multiple times to form an array patterned ZrO2 film with different thicknesses in different areas. At this time, the MIM structure filter is a MIM structure multi-spectral filter, i.e., a color filter.

[0051] Each layer of ZrO2 film can be directly attached to the surface of the bottom Ag layer, or attached to the surface of the previous ZrO2 film. The distribution position of each layer of ZrO2 film can be the same or different on the projection surface of the substrate. Each layer of ZrO2 film with different thickness is distributed in an array pattern, and a regular array color pattern will appear after being irradiated with visible light.

[0052] The substrate may be a glass substrate, or may be replaced by a flexible material substrate. The flexible material substrate may be a variety of flexible materials such as an organic polymer substrate and a flexible glass substrate.

[0053] Figure 1 This is a flow chart of ZrO2 film patterning in the present invention. The present invention proposes integrating ZrO2 films with the same or different thicknesses on the surface of the underlying Ag layer through a direct optical patterning method, thereby realizing the preparation of a MIM structure multi-spectral filter array.

[0054] A method for preparing a MIM structure filter, specifically comprising the following steps:

[0055] S1: Adding a photosensitive additive 1-diazo-2-naphthol-4-sulfonic acid (DNS) to a N,N-dimethylformamide (DMF) solution in which ZrO2 nanoparticles (ZrO2 NPs) are dispersed to form a ZrO2 photosensitive ink;

[0056] We selected 1-diazo-2-naphthol-4-sulfonic acid (DNS) as the photosensitizer for functionalized ZrO2 nanoparticles (ZrO2 NPs). In order to prepare ZrO2 photosensitive ink, both 1-diazo-2-naphthol-4-sulfonic acid (DNS) compound and ZrO2 nanoparticles (ZrO2NPs) must be highly soluble in a suitable solvent. N,N-dimethylformamide (DMF) was selected as the solvent because it can dissolve both 1-diazo-2-naphthol-4-sulfonic acid (DNS) and electrostatically charged ZrO2 nanoparticles (ZrO2NPs).

[0057] The present invention utilizes the mechanism that ZrO2 photosensitive ink modified with 1-diazo-2-naphthol-4-sulfonic acid (DNS) can be directly photocured by light exposure; Figure 2 As shown, 1-diazo-2-naphthol-4-sulfonic acid (DNS) molecules interact with charged ZrO2 nanoparticles (ZrO2NPs) and condense around them. Before light irradiation, 1-diazo-2-naphthol-4-sulfonic acid (DNS) molecules act as spacers to effectively prevent the irreversible aggregation of ZrO2 nanoparticles (ZrO2NPs) due to van der Waals forces. After light irradiation, 1-diazo-2-naphthol-4-sulfonic acid (DNS) decomposes into 3-sulfo-3H-indene-1-carboxylic acid (SICA). The presence of two potential binding sites (sulfonic acid group and carboxyl group) in SICA makes it more strongly bound to the surface of ZrO2 nanoparticles (ZrO2NPs), consolidating the ZrO2 nanoparticles (ZrO2NPs) and making them no longer soluble in N,N-dimethylformamide (DMF) solvent.

[0058] The preparation process of ZrO2 photosensitive ink is as follows:

[0059] ① Add 15-20 mL of acetone to 2 mL of ZrO2 nanoparticles (ZrO2 NPs) (150-200 mg / mL) aqueous sol to precipitate ZrO2 nanoparticles (ZrO2 NPs), and centrifuge the suspension at 6000 rpm for 10 min and filter to form ZrO2 nanoparticles (ZrO2 NPs) after the first filtration;

[0060] ② Re-dispersing the ZrO2 nanoparticles (ZrO2 NPs) after the first filtration in 3 mL of N, N-dimethylformamide (DMF) solvent and standing for 4-10 hours to form a stable and transparent N, N-dimethylformamide (DMF) dispersion in which ZrO2 nanoparticles (ZrO2 NPs) are dispersed;

[0061] ③ Add 4 mL of toluene to the N,N-dimethylformamide (DMF) dispersion in which ZrO2 nanoparticles (ZrO2 NPs) are dispersed to precipitate ZrO2 NPs, and then centrifuge at 7000 rpm for 10 min to form ZrO2 nanoparticles (ZrO2 NPs) after the second filtration; wash the ZrO2 nanoparticles (ZrO2 NPs) after the second filtration with 4 mL of n-hexane to remove residual toluene, and then centrifuge at 3500 rpm for 10 min to form ZrO2 nanoparticles (ZrO2 NPs) after the third filtration;

[0062] ④ Re-dissolving the ZrO2 nanoparticles (ZrO2 NPs) after the third filtration in a N,N-dimethylformamide (DMF) dispersion at a desired concentration by vortexing, stirring, and ultrasound to form a more stable ZrO2 nanoparticles (ZrO2 NPs) N,N-dimethylformamide (DMF) dispersion. The concentration of the ZrO2 nanoparticles (ZrO2 NPs) DMF dispersion used in the present invention is 30-120 mg / mL;

[0063] ⑤ Mix the photosensitive compound 1-diazo-2-naphthol-4-sulfonic acid (DNS) with the ZrO2 nanoparticle (ZrO2 NPs) N,N-dimethylformamide (DMF) dispersion to form a ZrO2 photosensitive ink, wherein the content of 1-diazo-2-naphthol-4-sulfonic acid (DNS) in the mixed ZrO2 photosensitive ink is between 15-30wt%, and the ZrO2 photosensitive ink is allowed to stand for 8-24 hours to obtain a ZrO2 photosensitive ink with good stability.

[0064] S2: Using physical vapor deposition method to evaporate metal Ag on the substrate to form the bottom Ag layer of the MIM structure. The specific method is as follows:

[0065] In actual operation, the substrate is first ultrasonically cleaned in acetone for 10 minutes, and then ultrasonically cleaned in isopropyl alcohol (IPA) for 10 minutes to obtain a clean substrate. Using a Tycono vacuum evaporator, the nickel wire and Ag particles to be evaporated are placed in the vacuum chamber in advance, and then the cleaned substrate is placed, the vacuum chamber is closed, and the vacuum evaporator is turned on. After the molecular pump of the vacuum evaporator stops, the voltage of the channel where the nickel wire is placed is adjusted to 30V, and a 3-5nm nickel layer is first evaporated on the substrate at a speed of 0.05 angstroms / second as an adhesion layer, and then the channel is changed to the channel where the Ag particles are placed, and the voltage of the channel where the Ag particles are placed is adjusted to 90V, and a 20-40nm Ag layer is continued to be evaporated on the surface of the nickel layer at a speed of 0.05 angstroms / second, and the vacuum evaporator is turned off; the substrate can use a glass substrate or a flexible material substrate, and the flexible material substrate is an organic polymer substrate, a flexible glass substrate, etc.

[0066] S3: coating the ZrO2 photosensitive ink in step S1 on the bottom Ag layer in step S2 by spin coating to form a uniform and smooth ZrO2 film with a thickness of 20-150 nm;

[0067] The spin coating process is as follows: fix the substrate containing the bottom Ag layer on a spin coater, drop 25-50 μL of ZrO2 photosensitive ink with a concentration of 30-120 mg / mL on the bottom Ag layer, set the spin coater parameters to a low speed of 1700 rpm for 6 s and a high speed of 2500 rpm for 40 s, turn on the spin coater, and the ZrO2 photosensitive ink is spin-coated on the substrate to form a ZrO2 film.

[0068] S4: Design the required mask pattern, and use the DMD digital mask lithography system to partially expose the ZrO2 film in step S3 to ultraviolet light to form an exposed ZrO2 film. The exposure wavelength is 405nm, the exposure time is 10-20s, and the exposure dose is 30-40mJ / cm 2 ; The surface bonding between ZrO2 nanoparticles (ZrO2 NPs) in the exposed area is stronger, and the solubility in N,N-dimethylformamide (DMF) solvent is reduced;

[0069] S5: using N,N-dimethylformamide (DMF) solvent to develop the exposed ZrO2 film in step S4 to form an array patterned ZrO2 film corresponding to the mask pattern in step S4; specifically, immersing the exposed ZrO2 film in N,N-dimethylformamide (DMF) solvent developer for 1-3 minutes, rinsing with IPA, and drying with a nitrogen gun, the unexposed part is washed away by the developer, and the exposed pattern is left on the substrate after development, thereby realizing the transfer of the pattern from the mask pattern to the ZrO2 film, and obtaining a patterned ZrO2 film;

[0070] S6: drying the array patterned ZrO2 film in step S5 to form a dried array patterned ZrO2 film, the drying temperature is 60-120° C., and the drying time is 10-120 seconds;

[0071] S7: After the drying in step S6, metal Ag is evaporated on the surface of the array patterned ZrO2 film by physical vapor deposition to form a top Ag layer of MIM structure, wherein the thickness of the top Ag layer is 20-40 nm, thereby forming a MIM structure monochrome filter.

[0072] Furthermore, in a method for preparing a MIM structure filter, step S7 comprises the following steps:

[0073] S7.1: Spin coating the ZrO2 photosensitive ink of step S1 on the surface of the array patterned ZrO2 film and the surface of the bottom Ag layer after drying in step S6 to form an nth (n=2, 3, 4)th layer of ZrO2 film, wherein the concentration of ZrO2 NPs in step S1 is 30-55 mg / mL, the content of 1-diazo-2-naphthol-4-sulfonic acid (DNS) in the ZrO2 photosensitive ink of step S1 is 15-30 wt %, the thickness of the bottom Ag layer is 20-40 nm, and the thickness of the nth (n=2, 3, 4)th layer of ZrO2 film is 20-50 nm;

[0074] S7.2: In step S7.1, the surface of the nth (n=2, 3, 4)th ZrO2 film is locally exposed to ultraviolet light to form the nth (n=2, 3, 4)th exposed ZrO2 film. The local exposure uses a designed mask pattern, and the mask pattern is preferably an array distribution pattern. The exposure wavelength in the local exposure is 405nm and the exposure dose is 30-40mJ / cm 2 ;

[0075] S7.3: Using N,N-dimethylformamide (DMF) solvent, the nth (n=2, 3, 4) layer of the exposed ZrO2 film in step S7.2 is developed to form an nth (n=2, 3, 4) layer of array patterned ZrO2 film;

[0076] S7.4: drying the nth (n=2, 3, 4) layer of array patterned ZrO2 thin film described in step S7.3 to form the nth (n=2, 3, 4) layer of array patterned ZrO2 thin film after drying, wherein the drying temperature of the drying treatment is 60-120° C. and the drying time is 10-120 s;

[0077] S7.5: Repeat steps S7.1 to S7.4, wherein the dried array patterned ZrO2 film described in step S6 in step S7.1 is replaced by the nth (n=2, 3, 4) layer of dried array patterned ZrO2 film described in step S7.4, until the Nth (N=3, 4) layer of dried array patterned ZrO2 film is finally formed; each time steps S7.1 to S7.4 are repeated, one more layer of dried array patterned ZrO2 film is finally formed.

[0078] S7.6: After drying the nth (n=2, 3, 4) layer described in step S7.4 or the Nth (N=3, 4) layer described in step S7.5, metal Ag is evaporated by physical vapor deposition to form a top Ag layer of the MIM structure. The thickness of the top Ag layer is 20-40nm, forming a MIM structure multi-spectral filter array.

[0079] In the present invention, the different thicknesses of the spin-coated ZrO2 photosensitive ink determine the different thicknesses of each layer of the array patterned ZrO2 film after drying, and also determine the different interference light wave bands, and affect the visual color of each layer of the array patterned ZrO2 film after drying in the filter; at the same time, the exposure position of each layer of the ZrO2 film is different, which determines that each layer of the array patterned ZrO2 film formed after drying is distributed in a target array. In the present invention, array patterned ZrO2 films of different thicknesses can overlap on the previous layer of array patterned ZrO2 film, or can be located separately on the surface of the bottom Ag layer, and the overlapping part will also affect the visual color of the ZrO2 film in the filter.

[0080] Furthermore, the drying temperature of the drying process in step S6 or the drying process in step S7.4 is 60-120° C. and the drying time is 10-120 seconds.

[0081] The schematic diagram of the prepared multi-spectral filter array structure is shown in Figure 3 shown.

[0082] The following is a first embodiment of a method for preparing a multi-spectral filter array:

[0083] ① Digital mask production; such as Figures 4a to 4c As shown, we made three digital masks (digital mask 1, digital mask 2, digital mask 3) for photolithography;

[0084] ② Substrate pretreatment: The quartz glass substrate is first ultrasonically cleaned in acetone, then ultrasonically cleaned in isopropanol, and finally treated with an ozone treatment machine before use;

[0085] ③ Evaporation of the bottom Ag layer: Place the quartz glass substrate into a vacuum evaporator to evaporate a 30nm thick Ag layer;

[0086] ④ Spin-coat the ZrO2 photosensitive ink on the bottom Ag layer to obtain a uniform ZrO2 film; specifically, place the substrate containing the bottom Ag layer on a coating machine, use a pipette to take 30 μL of ZrO2 photosensitive ink with a ZrO2 NPs concentration of 55 mg / mL and drop it on the substrate, spin-coat at a low speed of 1700 rpm for 6 seconds and then at a high speed of 2500 rpm for 40 seconds to obtain a uniform first layer of ZrO2 film with a thickness of 50 nm;

[0087] ⑤ Use DMD digital mask lithography machine to perform the first layer of digital mask 1 on ZrO2 film, the exposure wavelength is 405nm, the exposure dose is 40mJ / cm 2 , obtaining an exposed ZrO2 film, immersing the exposed ZrO2 film in N,N-dimethylformamide (DMF) solvent for 2 min for development, washing with IPA, and drying with a nitrogen gun to obtain a patterned ZrO2 film array, and drying the film on a heating table at 100°C for 60 s;

[0088] ⑥ Repeat steps ④⑤, spin-coat the ZrO2 photosensitive ink on the surface of the ZrO2 film array patterned in the previous step, wherein 30 μL of ZrO2 photosensitive ink with a ZrO2 NPs concentration of 30 mg / mL is used, and digital mask 2 is used to continue overlaying to obtain a 30 nm dielectric layer, i.e., the second ZrO2 film;

[0089] ⑦ Repeat steps ④⑤, spin-coat the surface of the second ZrO2 film array patterned in the previous step with ZrO2 photosensitive ink, where 30 μL of ZrO2 photosensitive ink with a ZrO2 NPs concentration of 55 mg / mL is used, and digital mask 3 is used to continue overlaying to obtain a 50 nm dielectric layer, i.e., the third ZrO2 film;

[0090] In Example 1, by repeatedly exposing digital mask 1, digital mask 2, and digital mask 3, array patterned ZrO2 films of different thicknesses are overlapped on the previous array patterned ZrO2 film to prepare three ZrO2 films with different total thicknesses (i.e., a first ZrO2 film of 50 nm, a first and second ZrO2 film of 80 nm, and a first, second, and third ZrO2 film of 130 nm). The micrograph of the ZrO2 film array is shown in FIG. Figure 5 As shown;

[0091] ⑧ Evaporation of the top Ag layer; continuing to evaporate a 30nm thick top Ag layer on three ZrO2 film (dielectric layer) arrays with different total thicknesses; thus, the preparation of the first embodiment of the multi-spectral filter array filter with 64 channels (16 pixels, 4 channels per pixel) (each channel corresponds to the spectral transmittance of a specific band, and the ZrO2 film thickness is different, and the transmitted spectral band is different) is completed.

[0092] In order to demonstrate the wavelength adjustment capability of our prepared filter, we also prepared filter arrays with different ZrO2 film thicknesses, namely, Example 2 and Example 3, in which Figure 6a This is a micrograph of a ZrO2 thin film array with three thicknesses of 50nm, 80nm, and 130nm in Example 1. Figure 6a The lower left corner, upper left corner, lower right corner, and upper right corner represent ZrO2 films with thickness of 50nm, 80nm, and 130nm, respectively; Figure 6b This is a micrograph of the ZrO2 thin film array with three thicknesses of 50nm, 90nm and 160nm in Example 2. Figure 6b The lower left corner, upper left corner, lower right corner, and upper right corner represent ZrO2 films with thickness of 50nm, 90nm, and 160nm, respectively; Figure 6c This is a micrograph of the ZrO2 thin film array with three thicknesses of 35nm, 70nm, and 115nm in Example 3. Figure 6c The lower left corner, upper left corner, lower right corner, and upper right corner represent ZrO2 films with thicknesses of 35nm, 70nm, and 115nm, respectively.

[0093] like Figure 7 The results are shown in Figure 1 for the transmittance measurement of filters with different ZrO2 film thicknesses in Example 1, Example 2, and Example 3. In summary, it can be seen that the transmittance of the filter we prepared can reach up to 39%, the half-height width of the measured resonance is 21-27nm, the color is bright, the color pollution between filters is light, and the band can cover the entire visible light band.

Claims

1. A MIM structure filter, comprising a substrate, characterized in that: The substrate surface is sequentially attached with a bottom Ag layer, a ZrO2 film, and a top Ag layer. The ZrO2 film is prepared by an optical patterning method using ZrO2 photosensitive ink. The ZrO2 photosensitive ink is an N,N-dimethylformamide (DMF) solution of ZrO2 nanoparticles (ZrO2 NPs) added with a photosensitive additive 1-diazo-2-naphthol-4-sulfonic acid.

2. The MIM structure filter according to claim 1, characterized in that: The concentration of ZrO2 nanoparticles (ZrO2 NPs) in the ZrO2 nanoparticle (ZrO2 NPs) N,N-dimethylformamide (DMF) solution is 30-120 mg / mL, and the content of the photosensitive additive 1-diazo-2-naphthol-4-sulfonic acid (DNS) in the ZrO2 photosensitive ink is 15-30 wt%.

3. The MIM structure filter according to claim 1, characterized in that: The number of layers of the ZrO2 film is any number from one to four, the thickness of each ZrO2 film layer is 20-150nm, and the thickness of the bottom Ag layer and the top Ag layer are both 20-40nm.

4. The MIM structure filter according to claim 1, characterized in that: The substrate is a glass substrate, an organic polymer substrate or a flexible glass substrate.

5. The MIM structure filter according to claim 3, characterized in that: When the number of layers of the ZrO2 film is one, the ZrO2 film is an array-patterned ZrO2 film with a single thickness; when the number of layers of the ZrO2 film is any number from two to four, the ZrO2 film is an array-patterned ZrO2 film with different thicknesses in different regions.

6. A method for preparing a MIM structure filter according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: Adding a photosensitive additive 1-diazo-2-naphthol-4-sulfonic acid (DNS) to a N,N-dimethylformamide (DMF) solution in which ZrO2 nanoparticles (ZrO2 NPs) are dispersed to form a ZrO2 photosensitive ink; S2: using physical vapor deposition method to evaporate metal Ag on the substrate to form the bottom Ag layer of the MIM structure; S3: coating the ZrO2 photosensitive ink in step S1 on the bottom Ag layer in step S2 by spin coating to form a ZrO2 thin film; S4: locally exposing the ZrO2 film in step S3 to ultraviolet light to form an exposed ZrO2 film; S5: using N,N-dimethylformamide (DMF) solvent to develop the exposed ZrO2 film in step S4 to form an array patterned ZrO2 film; S6: drying the array patterned ZrO2 thin film in step S5 to form a dried array patterned ZrO2 thin film; S7: A metal Ag layer is deposited on the surface of the array patterned ZrO2 thin film after drying in step S6 by physical vapor deposition to form a top Ag layer of the MIM structure, and finally a MIM structure monochrome filter is formed.

7. The method for preparing the MIM structure filter according to claim 6, characterized in that: Step S3 describes the use of a spin coating process to coat the ZrO2 photosensitive ink on the bottom Ag layer. The specific process is: fix the substrate containing the bottom Ag layer on a coating machine, drop 25-50 μL of ZrO2 photosensitive ink with a concentration of 30-120 mg / mL on the bottom Ag layer, set the coating machine parameters to a low speed of 1700 rpm for 6 seconds and then a high speed of 2500 rpm for 40 seconds, turn on the coating machine, and the ZrO2 photosensitive ink is spin-coated on the substrate to form a ZrO2 film.

8. The method for preparing the MIM structure filter according to claim 6, characterized in that: The local exposure in step S4 uses a designed mask pattern, and the mask pattern is preferably an array distribution pattern. The exposure wavelength in the local exposure is 405nm and the exposure dose is 30-40mJ / cm 2 .

9. The method for preparing the MIM structure filter according to claim 6, characterized in that: The drying temperature of the drying process in step S6 is 60-120° C. and the drying time is 10-120 seconds.

10. The method for preparing the MIM structure filter according to claim 6, characterized in that: The step S7 comprises the following steps: S7.1: Spin coating the ZrO2 photosensitive ink described in step S1 on the surface of the array patterned ZrO2 film and the surface of the bottom Ag layer where it is located after drying in step S6 to form an nth (n=2, 3, 4)th layer of ZrO2 film, wherein the concentration of the ZrO2 nanoparticles (ZrO2 NPs) described in step S1 is 30-55 mg / mL, the content of 1-diazo-2-naphthol-4-sulfonic acid (DNS) in the ZrO2 photosensitive ink described in step S1 is 15-30wt%, the thickness of the bottom Ag layer is 20-40nm, and the thickness of the nth (n=2, 3, 4)th layer of ZrO2 film is 20-50nm; S7.2: In step S7.1, the surface of the nth (n=2, 3, 4)th ZrO2 film is locally exposed to ultraviolet light to form the nth (n=2, 3, 4)th exposed ZrO2 film. The local exposure uses a designed mask pattern, and the mask pattern is preferably an array distribution pattern. The exposure wavelength in the local exposure is 405nm and the exposure dose is 30-40mJ / cm 2 ; S7.3: Using N,N-dimethylformamide (DMF) solvent, the nth (n=2, 3, 4)th layer of the exposed ZrO2 film in step S7.2 is developed to form an nth (n=2, 3, 4)th layer of array patterned ZrO2 film; S7.4: drying the nth (n=2, 3, 4) layer of array patterned ZrO2 thin film described in step S7.3 to form the nth (n=2, 3, 4) layer of array patterned ZrO2 thin film after drying, wherein the drying temperature of the drying treatment is 60-120°C and the drying time is 10-120s; S7.5: repeating steps S7.1 to S7.4, replacing the dried array patterned ZrO2 film in step S7.1 with the nth (n=2, 3, 4) layer of dried array patterned ZrO2 film in step S7.4, until the Nth (N=3, 4) layer of dried array patterned ZrO2 film is formed; S7.6: After drying the nth (n=2, 3, 4) layer described in step S7.4 or the Nth (N=3, 4) layer described in step S7.5, the surface of the array patterned ZrO2 film is subjected to physical vapor deposition to form a top Ag layer of the MIM structure, wherein the thickness of the top Ag layer is 20-40 nm, thereby finally forming a MIM structure multi-spectral filter array.

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