A method for manufacturing a continuously variable optical filter using inkjet printing.

Abstract

The present invention relates to a method for manufacturing a continuously variable optical filter by inkjet printing, an optical component that can be obtained by such method, and the use of such optical component.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a continuous variable optical filter by inkjet printing, including a step of preparing a substrate, and a step of applying and solidifying a first dielectric layer with variable thickness and at least a second dielectric layer. Further, the present invention relates to an optical component manufactured by the above method, and the use of the above optical component in a sensor or in a thin film coating as a color filter, a dielectric filter / mirror.

Background Art

[0002] Optical filters are essential components in almost all optical systems and optoelectronic systems such as cameras, lasers, spectroscopy systems, and photometry. In optical devices that require wavelength selectivity, optical filters are usually used. In order to make the system compact in terms of size and function, continuous variable optical filters are used.

[0003] [[ID=1S]] Existing optical filters are manufactured, for example, by electron beam evaporation (EBE), ion beam sputtering (IBS), or atomic layer deposition (ALD). In the above methods, high vacuum and masking techniques in the deposition environment are required to continuously change the thickness of the deposited layer. As a result, the process becomes costly and complex. Further, the deposition of two or more different materials in an accurately controlled mixing ratio is technically complex and involves high costs in the above methods. That is, the typical price range of a single continuous variable filter starts from several hundred euros.

[0004] Furthermore, in order to control the spectral response in high-quality optical filters, it is usually necessary to control the layer thickness with an accuracy of less than 10 nm. When manufacturing an optical filter, it is impossible to control the layer thickness to achieve a continuous change in one or several dimensions with such accuracy by frequently used solution processing methods such as spin coating, blade coating, and screen printing.

[0005] In recent years, inkjet printing has been applied to form optical structures on substrates. However, known methods involve applying a printing ink containing a dielectric component to obtain a layer of a certain thickness. See, for example, Patent Document 1, Non-Patent Document 1, and Non-Patent Document 2. Unless the variable layer thickness is controlled in at least one lateral dimension, the applications will be limited or the optical properties will be inferior.

[0006] Other disadvantages of the above method include the fact that the use of masks limits the method to specific sizes, positions, thicknesses, and shapes; masking incurs additional costs; lamination of different materials is very difficult or time-consuming; and the method requires long process times to produce, for example, larger optical filters. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2011 / 003987 [Non-patent literature]

[0008] [Non-Patent Document 1] AV Yakovlev et al. Sci. Rep. 2016, 6, 37090 [Non-Patent Document 2] Q. Jin et al. Adv. Mater. Technol. 2022, 7, 2101026 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] Therefore, as described above, known methods for manufacturing optical filters have several disadvantages. Thus, in view of the prior art, the fundamental object of the present invention is to provide a method for manufacturing a continuously variable optical filter by inkjet printing, which is low-cost and readily available, and enables the manufacture of continuously variable optical filters that have excellent spectral response when used in optical systems. Furthermore, an object of the present invention is to provide optical components manufactured by the above method and the use of optical components. [Means for solving the problem]

[0010] Solutions to the above technical problems are provided by embodiments characterized in the claims.

[0011] Therefore, in a first embodiment, the present invention relates to a method for manufacturing a continuously variable optical filter, a) The process of preparing the substrate, b) A step of applying a first layer of a first liquid material onto the surface of a substrate by inkjet printing, wherein the first layer has a uniform or continuously variable thickness in at least one transverse dimension. c) A step of solidifying the first layer of the first liquid material to obtain the first dielectric layer, d) A step of applying a second layer of a second liquid material onto a first dielectric layer by inkjet printing, wherein the second layer has a uniform or continuously variable thickness in at least one transverse dimension. e) A step of solidifying the second layer of the second liquid material to obtain a second dielectric layer, The first liquid material and the second liquid material each contain at least one dielectric component. The present invention relates to a method wherein at least one of the first layer and the second layer has a continuously variable thickness in at least one transverse dimension.

[0012] The inventors conducted extensive research to provide a solution to the above problems and found that the manufacture of continuously variable optical filters can be successfully achieved by using inkjet printing in several processes. As a result, continuously variable optical filters exhibiting excellent spectral response due to the high-precision adjustment of layer thickness can be manufactured at low cost and under normal ambient conditions.

[0013] Generally, the method for manufacturing a continuously variable optical filter involves at least five steps: a) The process of preparing the substrate, b) A step of applying a first layer of a first liquid material onto the surface of a substrate by inkjet printing, wherein the first layer has a uniform or continuously variable thickness in at least one transverse dimension. c) A step of solidifying the first layer of the first liquid material to obtain the first dielectric layer, d) A step of applying a second layer of a second liquid material onto a first dielectric layer by inkjet printing, wherein the second layer has a uniform or continuously variable thickness in at least one transverse dimension. e) A step of solidifying the second layer of the second liquid material to obtain a second dielectric layer, A method comprising, wherein at least one of the first layer and the second layer has a continuously variable thickness in at least one transverse dimension.

[0014] The method described herein enables the fabrication of optical filters by direct layer deposition using inkjet printing under ambient conditions. High vacuum chambers and expensive masks are not required for the process. Material mixing in the printing ink is easily achieved at low cost.

[0015] The steps in the method for manufacturing a continuously variable optical filter are described in detail below. An exemplary inkjet printing process for manufacturing a continuously variable optical filter is shown in Figure 1. However, it should be noted that some features of the exemplary process are relevant to the specific embodiments discussed below. As can be seen from the figure, Figure 1 defines the coordinate system to be followed in the following application. In this context, the terms “z-direction” and “thickness direction” are used interchangeably.

[0016] In this specification, the term “continuously variable optical filter” is not particularly limited to optical filters in which the optical properties change continuously along one or more dimensions of the filter.

[0017] In step (a) of the method defined above, a substrate is prepared. The substrate may be, for example, a flexible foil, a rigid plate, or the top surface of a device, such as the top surface of a photodiode, CMOS / CCD sensor, or solar cell array. That is, the substrate may contain or consist solely of various materials such as glass, polymer, or metal. Furthermore, the substrate may be pre-treated to ensure sufficient adhesion of the layer to be printed thereon or to obtain suitable flow properties for at least one liquid material to be applied. For example, the surface of the substrate may be cleaned, etched, hydrophobized, or hydrophilized. The surface of the substrate may be treated and / or coated with a selected chemical, such as silane or hexamethyldisilazane. Treatment of the substrate surface may also be applied by plasma, flame, or thermal annealing.

[0018] In step (b) of the method defined above, a first layer of the first liquid material is applied to the surface of a substrate, wherein the first layer has a uniform or continuously variable thickness in at least one transverse dimension. That is, the thickness of the first layer may be uniform, continuously variable in a single transverse dimension, or continuously variable in two or more transverse dimensions, for example along the x and radial directions, or along several dimensions, for example along both the x and y directions.

[0019] In this context, the term "liquid material" relates to any material that is fluid at the temperature of inkjet printing and at room temperature (25 °C). By using such liquid materials, excellent handling and storage properties of the materials are obtained, and an effective printing process by inkjet printing becomes possible. The viscosity of such materials can be adjusted as necessary, for example, by using suitable solvents, dispersants and / or matrix materials as described below.

[0020] The term "surface of the substrate" is not particularly limited and includes the entire surface of the substrate, one or more surfaces of the substrate (i.e., for example, the main surface or side surface of a plate), or even only a part of one surface. For this reason, the expression "surface of the substrate" is not limited to complete coverage of the substrate.

[0021] In inkjet printing, the liquid material is printed by ejecting small droplets from the print head of an inkjet printer. The droplets are ejected from the print head through nozzles. In the example shown in FIG. 1, the print head has several nozzles. Usually, a print head developed for conventional inkjet printing may be used, or it may be adapted to the printing of the layer of the liquid material described herein. By continuously depositing droplets on the surface of the substrate operated by digital control of the printer, a continuous layer of liquid is generated on the surface. Generally, by manufacturing an optical filter by inkjet printing, the above manufacturing process is easily available and cost-effective while maintaining the high accuracy and reliability required to provide optical components.

[0022] [[ID=A]]

[0023] ​In step (c) of the method defined above, a first layer of the first liquid material is solidified to obtain a first dielectric layer. The first layer is solidified before any further liquid material is applied, thus preventing mixing of the liquid materials.

[0024] After the first layer of the first liquid material has solidified, at least a second layer of the second liquid material is applied, wherein the second layer has a uniform or continuously variable thickness in at least one transverse dimension (see step (d) of the method as defined above). As described above, the second layer may have a continuously variable thickness in two or more transverse dimensions, and these transverse dimensions may be the same as or different from the transverse dimensions of the first layer.

[0025] Generally, at least one of the first and second layers has a continuously variable thickness in at least one transverse dimension in order to achieve the effects of the present invention as described herein.

[0026] In step (e) of the method defined above, the second liquid material is solidified to obtain at least a second dielectric layer.

[0027] According to a first aspect of the present invention, the first liquid material and the second liquid material each independently contain at least one dielectric component. The dielectric component is necessary to achieve interaction between the resulting optical filter and the light incident on the filter, and this interaction is necessary for the optical filter to perform its function. Examples of dielectric components include inorganic substances such as acrylic polymers, vinyl polymers, or oxides. Considering solubility and / or dispersibility, dielectric components include poly(methyl methacrylate) (PMMA), polystyrene (PS), poly(vinyl alcohol) (PVA), liquid crystals, inorganic particles such as silica (SiO2), zinc dioxide (ZnO2), titanium dioxide (TiO2), alumina (Al2O3), zirconia (ZrO2), vanadium oxide (VO2O2), etc. x), tungsten(VI) oxide (WO3), magnesium oxide (MgO), cerium dioxide (CeO2), silicon monoxide (SiO), titanium dioxide (Ti3O5), titanium(III) oxide (Ti2O3), hafnium oxide (HfO2), yttrium(III) oxide (Y2O3), calcium fluoride (CaF2), barium fluoride (BaF2), magnesium fluoride (MgF2), cerium(III) fluoride (CeF3), silicon (Si), germanium (Ge), tellurium (Te) Preferably, the material is selected from the group consisting of particles of zinc selenide (ZnSe), zinc sulfide (ZnS), lead sulfide (PbS), lead selenide (PbSe), cadmium selenide (CdSe), cadmium sulfide (CdS), cadmium telluride (CdTe), lead telluride (PbTe), indium arsenide (InAs), indium phosphide (InP), silicon nitride (Si3N4), aluminum nitride (AlN), cryolite, lanthanides or rare earth oxides and fluorides, and combinations thereof.

[0028] The liquid material preferably contains a dielectric component in an amount of less than 50%, more preferably less than 20%, or even less than 10%, and at least 0.01%, preferably at least 0.1%. In this context, all percentages given are volume percent. For example, the dielectric component may be present in the range of 1% to 5% or 2% to 4%. The liquid preferably contains only a small amount of light-absorbing component, or no such component at all. For example, the light-absorbing component may preferably constitute less than 10%, more preferably less than 5%, less than 2%, or less than 1% of the liquid material. In other words, the liquid material preferably is optically transparent with a transparency of more than 90%, more than 95%, more than 98%, or more than 99%.

[0029] According to a particular embodiment, the above method is characterized in that the first liquid material and the second liquid material further comprise a solvent and / or a fluid matrix material. In this context, exemplary solvents include 1,3-dimethoxybenzene, cyclopentanone, cyclohexanone, isopropanol, cyclohexane, o-xylene, hexylbenzene, triethylene glycol monomethyl ether, 2-propoxyethanol, chlorobenzene, dichlorobenzene, ethyl acetate, dimethyl sulfoxide, toluene, water, N-methyl-2-pyrrolidone, butanone, ethylene glycol, propylene glycol methyl ether, dimethylacetamide, or combinations thereof. The solvent is preferably 1,3-dimethoxybenzene.

[0030] To ensure fluidity in inkjet printing inks, additional components may be required depending on the type of dielectric component contained in the liquid material. For example, additional wetting agents, such as glycerol, 1,3-propanediol, 1,2-propanediol, diethylene glycol, propylene glycol, or triethylene glycol, may be added to the ink. Furthermore, additional surfactants, such as the Triton X series, BYK-346, or BYK-333, may be added to the ink. In this context, it is preferable that the dielectric component contained in the first liquid material is soluble or dispersible in the solvent contained in the first liquid material, but insoluble in the solvent contained in the second liquid material. By applying such composition and dissolution behavior, it is ensured that the dielectric component of the already solidified underlying dielectric layer does not dissolve when each subsequent liquid material is applied. This allows for the achievement of clear and sharp interfaces between dielectric layers, thereby enhancing the sharpness of the changes in optical properties between layers.

[0031] Further specific embodiments relate to the method defined above, wherein the first and second liquid materials include dielectric components having different refractive indices and / or different concentrations. By using dielectric components having different refractive indices and / or different concentrations, the optical properties of the dielectric layers are tuned so that the optical processes occurring at the interlayer interfaces can be specifically controlled. Thus, the spectral response of the fabricated optical component is influenced by the type of dielectric components and the arrangement of the dielectric layers.

[0032] Therefore, in one embodiment, the dielectric components of the first liquid material and the second liquid material (and / or third liquid material) are different from each other. Alternatively, the dielectric components may be the same, but printed to achieve different porosity in the film and provide a refractive index contrast. For example, the dielectric components in various liquid materials can be selected such that the refractive index of the first dielectric component differs from that of the second component by at least 0.1, preferably at least 0.4, or at least 1.0. Having such different refractive indices in the dielectric layer allows the optical properties of the optical filter to be adjusted, for example, to obtain high light reflectance or high light transmittance for light irradiated at a specific wavelength.

[0033] In another embodiment, the dielectric component in the liquid material is the same substance but with different concentrations. In yet another embodiment, the dielectric component may be the same substance but with the same concentration, thereby allowing for greater thickness of a particular material through repeated deposition and solidification. In such a case, a shape of an optical filter with a large variation in thickness in the thickness direction can be achieved, which would not be possible by providing thinner dielectric layers.

[0034] According to a particular embodiment, in addition to steps (d) and (e), the method defined above may include corresponding additional steps (f) and (g), where a third layer of the third liquid material is inkjet printed onto the second dielectric layer (step (f)). A solidification step (g) is then performed following any step (f) above to obtain the third dielectric layer. Similar to the first and second layers, any third type of layer may have a uniform or continuously variable thickness in at least one lateral dimension and a continuously variable thickness in two or more lateral dimensions. Providing a third dielectric layer makes it possible to improve the fine-tuning of the optical properties of the manufactured optical component, which leads to a superior spectral response in the optical system.

[0035] As described above and below, the properties of the first liquid material and the second liquid material, as well as the first layer / dielectric layer and the second layer / dielectric layer, also apply to the respective third liquid material / layer / dielectric layer. That is, the third liquid material contains at least one dielectric component as described above.

[0036] A particular embodiment relates to the method defined above, wherein the continuously variable thickness of a first and / or second layer is controlled by one or more of the following: changing the distance between droplets applied during inkjet printing (process 1), changing the volume of droplets applied during inkjet printing (process 2), and changing the number of droplets applied to the same location during inkjet printing (process 3). Each of the above processes enables precise and reliable control of the thickness of the printed layer, resulting in excellent and consistent optical properties of the optical component manufactured by the described method. The above processes are described in more detail below.

[0037] Process 1: Dot-per-inch method Process 1 defines a method for controlling the thickness of the deposited layer in a continuously variable optical filter by printing at different dots per inch (dpi) per unit area. That is, dots per inch defines the number of ink droplets applied to a given area. The above process is schematically shown in Figure 2. After printing on the substrate, the ink droplets fuse to form a thin film. As the printing dpi increases, the thickness of the solid thin film increases. Δd is the thickness increment, obtained from Δb, which is the dpi increment. By printing at different dpi in the lateral direction, the thickness of the deposited layer in a continuously variable optical filter can be controlled. The resolution of the thickness control is on the nanometer scale, and Δd is in the sub-nanometer to micrometer range.

[0038] Process 2: Halftone Method Process 2 defines a method for controlling the thickness of the deposited layer in a continuously variable optical filter by printing with different halftone patterns. The above process is schematically shown in Figure 3a. Halftone is a copying technique that reconstructs a continuous grayscale image by dots, as shown in (1) of Figure 3b. (2) and (3) of Figure 3b are typical examples of halftone patterns, where the dots are usually of different sizes. The shape of the dots can be circular, triangular, square, star-shaped, or random. Figure 3a shows the halftone method in an inkjet printing process. By printing dots of different sizes on the surface of the substrate, the thickness of the thin film is controlled with a resolution of Δd.

[0039] Process 3: Grayscale Method Process 3 defines a method for controlling the thickness of the deposited layer in a continuously variable optical filter by printing with different grayscale (GS) values. This process is shown in Figure 4. In printing, GS defines the number of droplets printed at the same location on the substrate. GS can be a value x out of another value n. In this context, x represents the current setting of GS, and n represents the total number of possible levels. For example, GS can be 64 out of 255, i.e., the current GS is 64, and the total available GS value is 255. In inkjet printing, typically, considering the final thin film formation quality, the maximum number of droplets that can be printed at the same location is 256. For example, printing with GS 55 results in a thinner film than, for example, printing with GS 195. Variations in GS lead to changes in thickness, and the resolution is defined by Δd.

[0040] Furthermore, it has been found that precisely controlling the volume of a single droplet is difficult. Therefore, to improve controllability, two or more droplets can be deposited in the same location according to the described GS method. This allows for a statistical effect on droplet volume, potentially resulting in a printed liquid layer with a more uniform thickness.

[0041] To control the thickness of the deposited thin film, the dot-per-inch method, the grayscale method, and the halftone method can be applied individually or in combination. By using a combination of the above processes, even greater control can be achieved over the optical properties of the resulting optical component.

[0042] A particular embodiment of the present invention relates to the method described above, wherein the thickness of each of the first dielectric layer, the second dielectric layer, and an optional third dielectric layer is independently preferably less than 10 μm, less than 1 μm, less than 500 nm, less than 200 nm, and even less than 100 nm. The above thicknesses affect the reflection and refraction of incident light in the optical application of the resulting optical component. For this reason, the above range of thicknesses is very suitable for use in combination with light of various wavelengths that occur in various optical applications, particularly in combination with visible light, UV light, or infrared light.

[0043] The thickness accuracy of each layer of inkjet printing is preferably less than 20 nm, more preferably less than 10 nm, less than 5 nm, and even more preferably less than 1 nm. In this context, thickness accuracy is defined as the variation in thickness within a region having the same predetermined thickness. Thickness accuracy is a direct result of optimizing the ink formulation and printing parameters, such as the accuracy of droplet volume or the accuracy of the position where droplets are deposited. Ensuring the above thickness accuracy improves the applicability of optical components in advanced optical devices for consistent optical properties and performance.

[0044] Furthermore, it is preferable to adjust the thickness without using masking, which is generally required in conventional methods. Moreover, it is preferable to carry out the above method under ambient conditions, i.e., without applying reduced pressure or even a vacuum. Both of the above advantages make the method of the present invention readily available and cost-effective.

[0045] Further specific embodiments relate to the method defined above, wherein steps (b) to (e) are repeated at least once to obtain a stack of alternating dielectric layers. That is, the steps can be repeated, for example, once, twice, five times, ten times, or even more than 100 times. Repeating the steps multiple times generates a stack of dielectric layers, each having a continuously variable thickness. This stack includes an alternating layer arrangement of dielectric layers containing dielectric components of a first liquid material, a second liquid material, and optionally a third liquid material. By repeating steps (b) to (e) to stack the above layers, for example, the suitability of the manufactured optical component for a particular optical device can be improved.

[0046] Furthermore, in further embodiments, optional steps (f) and (g) relating to the deposition of the third layer can also be repeated as needed. However, according to the present invention, the application and solidification steps of the corresponding individual layers, (b) and (c), (d) and (e), and optionally (f) and (g), can each be repeated independently of each other.

[0047] Examples of such stacks include configurations such as (S / A / B / A / B...), (S / A / B / C / A / B / C...), (S / A / B / A / B / C / A / B / A / B / C...), (S / A / A / B / B / A / A / B / B...), (S / A / B / C / C / A / B / C / C...), (S / A / B / B / A / B / B...), etc., where S represents the substrate, A represents the first layer, B represents the second layer, and C represents an arbitrary third layer. The total number of layers is not particularly limited and can be adjusted according to the desired application. In this context, the exemplary stacks described above refer to materials A, B, and C, and the thickness of each layer can be adjusted independently of the other layers; that is, different layers of A may have different thicknesses, and the same applies to B and C.

[0048] In another specific embodiment, the method of the present invention may include the step (h) of providing a protective layer on the upper surface of a continuously variable optical filter. The protective layer is not particularly limited, as long as it provides protection and is sufficiently transparent to the incident light used in the intended application. For this reason, the protective layer can be scratch-resistant and resistant to ambient conditions such as moisture and high-intensity light irradiation.

[0049] Furthermore, certain embodiments relate to the above method of linearly, curvilinearly, or randomly changing the cross-sectional shape of an optical filter in the thickness direction, and / or linearly, curvilinearly, or randomly changing the cross-sectional shape of either the first layer, the second layer, or the third layer in the thickness direction. That is, the cross-sectional shape of an optical filter refers to the profile of the filter in the thickness direction. An exemplary shape of an optical filter is shown in Figure 5. The change in layer thickness in the lateral direction can be any shape, such as linear, exponential, or random. Combinations of the above shapes can be used in different application scenarios. Furthermore, different shapes can be combined laterally, i.e., patches of different shapes can be placed next to each other, or they can also be combined in the thickness direction, i.e., layers with different thickness changes can be stacked. In this context, by adjusting the cross-sectional shape of the optical filter in the thickness direction, it is possible to adapt the filter to various different applications in optical devices.

[0050] In a preferred embodiment of the method described above, the thickness of the optical filter and / or any of the first and second layers (and optionally a third layer) increases continuously in at least one transverse dimension, the transverse dimension being the same for each layer. Such a configuration can result in a wedge-shaped optical filter, as illustrated in Figure 1. The variable optical filter can be used, for example, in spectrometers and sensors, including use in microscopes, including spectrum-based imaging, multispectral and hyperspectral applications, and fluorescence-based applications. In other words, the variable optical filter is advantageous for these applications by achieving a more compact system instead of combining several different optical filters.

[0051] In another specific embodiment according to the first aspect of the present invention, the method is as described above, and the solidification steps (c) and (e) (and optional solidification step (g)) independently include one or more of drying, curing, heating, irradiation, or a combination thereof. By using such techniques, the liquid materials constituting each layer are effectively dried and substantially all volatile components are evaporated. These means can be carried out under reduced pressure as needed. Alternatively or additionally, any polymer or polymer precursor contained in the liquid material can be solidified using visible or UV light, thereby crosslinking and curing the polymer / precursor. The solidification method is not limited to the above method and may further include, for example, annealing or sintering of solid particles. Therefore, the type of solidification process is selected according to the dielectric components in each liquid material and optionally the combination of solvent / fluid matrix material. In other words, for example, if the dielectric component is a polymerizable monomer, solidification can be carried out by irradiating to cause crosslinking; if the dielectric component is inorganic particles dispersed in a solvent, solidification can be carried out by drying and / or heating to evaporate the solvent; or even if the dielectric component is inorganic particles dispersed in a polymerizable fluid matrix material, the matrix can be solidified by irradiating to cause crosslinking of the matrix.

[0052] In this context, the term “irradiate” refers to irradiation with light, including, for example, visible light (i.e., having wavelengths of 400 nm to 800 nm), ultraviolet light (i.e., having wavelengths of 150 nm to 400 nm), infrared light (i.e., having wavelengths of 800 nm to 3000 nm), or other wavelengths suitable for causing solidification of at least a portion of the liquid material. Furthermore, the term “heat” means exposing the liquid material to an elevated temperature, for example, at least 40°C, at least 100°C, or at least 200°C. Other techniques, including the application of plasma, vacuum, ultrasound, and / or embossing, can be used for surface solidification.

[0053] A second aspect of the present invention relates to an optical component manufactured by the method defined above.

[0054] Such optical components may include, for example, bandpass filters, dichroic filters, longpass filters, shortpass filters, notch filters, response-flattening filters, attenuation filters, beam splitters, polarizers, anti-reflective coatings, or waveplates. The optical components further include a substrate coated with an anti-reflective coating.

[0055] By using the methods defined above for manufacturing optical components, excellent spectral response of the optical components when used in optical systems can be ensured.

[0056] A third aspect of the present invention relates to the use of the above-mentioned optical components as color filters, dielectric filters / mirrors, or sensors, or in thin-film coatings. [Brief explanation of the drawing]

[0057] [Figure 1] This is a schematic diagram of an exemplary inkjet printing process for manufacturing a continuously variable optical filter. Multiple layers 3 and 4 are alternately stacked on a substrate 1. The layers are formed by ejecting droplets 2 from a print head 5 through a nozzle 6. [Figure 2] This figure shows a common process (dot-per-inch method) for controlling the thickness of the deposited layer by varying the distance between droplets applied during inkjet printing. [Figure 3a] This figure shows a common process (halftone method) that involves changing the volume of droplets applied during inkjet printing to control the thickness of the deposited layer. [Figure 3b] This figure shows an example of a halftone pattern. [Figure 4] This figure shows a common process (grayscale method) for controlling the thickness of the deposited layer by varying the number of droplets applied to the same location during inkjet printing. [Figure 5]This figure shows an exemplary profile of a printed, continuously variable optical filter in the z-direction.

[0058] Specifically, optical components can be used, for example, as color filters for camera chips, as dielectric filters / mirrors for various optical systems, especially for devices requiring large-area optical properties, in integrated spectrometers for optical sensing, in solar cell modules with aesthetic appearances, such as logos, and for light management films for displays. Typically, such optical components are used in industries related to optical systems, optoelectronics, sensors, photovoltaics, or thin-film coatings.

Claims

1. A method for manufacturing a continuously variable optical filter, a) The process of preparing the substrate, b) A step of applying a first layer of a first liquid material onto the surface of the substrate by inkjet printing, wherein the first layer has a uniform or continuously variable thickness in at least one transverse dimension. c) A step of solidifying the first layer of the first liquid material to obtain a first dielectric layer, d) A step of applying a second layer of a second liquid material onto the first dielectric layer by inkjet printing, wherein the second layer has a uniform or continuously variable thickness in at least one transverse dimension. e) A step of solidifying the second layer of the second liquid material to obtain a second dielectric layer, The first liquid material and the second liquid material each contain at least one dielectric component, A method wherein at least one of the first layer and the second layer has a continuously variable thickness in at least one transverse dimension.

2. The method according to claim 1, wherein the continuously variable thickness of the first layer and / or the second layer is adjusted by one or more of the following: changing the distance between droplets applied during inkjet printing, changing the volume of droplets applied during inkjet printing, and / or changing the number of droplets applied to the same position during inkjet printing.

3. The method according to claim 1 or 2, wherein steps b) to e) are repeated at least once to obtain a stack of alternating dielectric layers.

4. The method according to any one of claims 1 to 3, wherein the cross-sectional shape of the optical filter in the thickness direction is changed linearly, curved, or randomly, and / or the cross-sectional shape of either the first layer or the second layer in the thickness direction is changed linearly, curved, or randomly.

5. The method according to any one of claims 1 to 4, wherein the thickness of the optical filter and / or either the first layer or the second layer increases continuously in at least one transverse dimension.

6. The method according to any one of claims 1 to 5, wherein the first liquid material and the second liquid material further comprise a solvent and / or a fluid matrix material.

7. The method according to any one of claims 1 to 6, wherein the first liquid material and the second liquid material include dielectric components having different refractive indices and / or dielectric components having different concentrations.

8. The method according to any one of claims 1 to 7, wherein the solidification steps c) and e) independently include drying, curing, heating, irradiating, or a combination thereof of the first layer and the second layer.

9. An optical component manufactured by the method described in any one of claims 1 to 8.

10. Use of the optical component according to claim 9 as a color filter, dielectric filter, or mirror, or in a sensor or thin film coating.

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