Continuous photolithographic fabrication process for producing seamless microstructures used in electro-optic displays and light modulating films

Abstract

The invention provides a roll-to-roll method for manufacturing a seamless microstructure, which comprises the following steps of: (a) continuously forming a laminated structure, the laminated structure comprises a photomask film laminated on a base material, a photosensitive material layer is arranged between the base material and the photomask film, and the photomask film comprises patterns of a light-transmitting area and a light-shielding area; (b) irradiating the photomask film of the laminated structure formed in the step (a) to enable light to penetrate through a light-transmitting area of the photomask film so as to cure the photosensitive material part exposed by the light-transmitting area, and meanwhile, keeping the rest part of the photosensitive material covered by a shading area uncured; (c) stripping the photomask film from the selectively cured photosensitive material in the step (b); and (d) removing the uncured portion of the photosensitive material to form a microstructure layer on the substrate from the cured portion of the photosensitive material.

Description

(19) State Intellectual Property Office (12) Invention Patent Application (10) Application Publication Number (43) Application Publication Date (21) Application Number 202480062105.1 (22) Application Date 2024.10.16 (30) Priority Data 63 / 547747 2023.11.08 US (85) PCT International Application Entering National Phase Date 2026.03.26 (86) PCT International Application Application Data PCT / US2024 / 051557 2024.10.16 (87) PCT International Application Publication Data WO2025 / 101330 EN 2025.05.15 (71) Applicant: Einker Inc. Address: Massachusetts, USA (72) Inventors: Xia Yu, B. Dunn, S.J. Telfair, Kang Yiming, H.E.A. Huytma (74) Patent Agency: Beijing Panhua Weiye Intellectual Property Agency Co., Ltd. 11280 Patent Attorneys: Guo Guangxun, Zhao Yan (51) Int.Cl. G03F 7 / 00 (2006.01) G03F 7 / 20 (2006.01) (54) Invention Title: Continuous Photolithography Manufacturing Method for Seamless Microstructures Used in the Production of Electro-Optical Displays and Optical Modulation Films (57) Abstract: This invention provides a roll-to-roll method for manufacturing seamless microstructures, comprising the following steps: (a) continuously forming a stacked structure, the stacked structure comprising a photomask film superimposed on a substrate, a photosensitive material layer between the substrate and the photomask film, the photomask film comprising a pattern of light-transmitting regions and light-shielding regions; (b) Irradiate the photomask film of the stacked structure formed in step (a) so that light passes through the light-transmitting area of ​​the photomask film to cure the photosensitive material portion exposed by the light-transmitting area, while keeping the remaining portion of the photosensitive material covered by the light-shielding area uncured; (c) Peel the photomask film from the photosensitive material selectively cured in step (b); and (d) Remove the uncured portion of the photosensitive material to form a microstructure layer on the substrate from the cured portion of the photosensitive material.Claims 2 pages, Description 8 pages, Drawings 8 pages, CN 121909423 A 2026.04.21 CN 1 21 90 94 23 A 1. A roll-to-roll seamless microstructure manufacturing method, comprising the following steps: (a) continuously forming a stacked structure, the stacked structure comprising a photomask film superimposed on a substrate, a photosensitive material layer between the photomask film and the substrate, the photomask film comprising a pattern of light-transmitting regions and light-shielding regions; (b) irradiating the photomask film of the stacked structure formed in step (a) with light from a light source, such that a portion of the photosensitive material covered by the light-transmitting regions is exposed to light, while the remaining portion of the photosensitive material covered by the light-shielding regions is not exposed to light; (c) peeling the photomask film from the photosensitive material selectively irradiated in step (b); and (d) selectively removing the light-exposed portions or the light-unexposed portions of the photosensitive material to form a microstructure layer on the substrate. 2. The method of claim 1, wherein step (d) comprises selectively removing the light-exposed portion of the photosensitive material to form a microstructure layer on the substrate. 3. The method of claim 1, wherein step (d) comprises selectively removing the unexposed portion of the photosensitive material to form a microstructure layer on the substrate. 4. The method of claim 1, wherein in step (b), the light-exposed portion of the photosensitive material is photocured, while the remaining portion of the photosensitive material remains uncured; and wherein in step (d), the uncured portion of the photosensitive material is removed to form a microstructure layer on the substrate by the cured portion of the photosensitive material. 5. The method of claim 1, wherein the light comprises ultraviolet light. 6. The method of claim 1 or 5, wherein the photosensitive material comprises a negative ultraviolet photosensitive material. 7. The method of claim 1, 5, or 6, wherein the microstructure comprises a cross-linked ultraviolet-cured structure. 8. The method of any preceding claim, wherein step (a) comprises forward conveying a photomask, a substrate, and a photosensitive material layer between a pair of rollers to form the stacked structure. 9. The method according to any of the preceding claims, further comprising reusing the photomask film stripped in step (c) during subsequent microstructure fabrication. 10. The method according to any of the preceding claims, wherein steps (a) and (b) are performed in a multi-coating head production line. 11. The method according to any of the preceding claims, wherein step (b) is performed during the transfer of the stacked structure. 12. The method according to any of the preceding claims, wherein the photosensitive material layer is coated on the substrate prior to step (a). 13. The method according to any of the preceding claims, wherein the photosensitive material layer is coated on the substrate prior to step (a) using a bar coating, roller coating, doctor blade coating, or slot die coating process.14. The method of any preceding claim, wherein the substrates stacked in step (a) comprise a pre-existing set of microstructures formed thereon. 15. The method of claim 14, wherein the pre-existing set of microstructures is formed by a prior imprinting process performed on the substrate. 16. The method of claim 14, wherein the pre-existing set of microstructures is formed by a prior microstructure fabrication process for the substrate, including steps (a), (b), (c), and (d). 17. The method of any preceding claim, further comprising drawing the photomask film and the substrate from the roll material prior to step (a). 18. The method of claim 17, wherein the width of each roll material is greater than 1 meter. Claims 1 / 2 Page 2 CN 121909423 A 19. The method of any preceding claim, wherein the microstructure comprises the following features: an X / Y dimensional resolution of 20 micrometers to 2000 micrometers, and a Z dimensional resolution of 1 micrometer to 500 micrometers. 20. The method of any preceding claim, wherein the width of the substrate having the microstructure layer formed thereon is greater than 1 meter. 21. The method of any preceding claim, wherein the length of the substrate having the microstructure layer formed thereon is greater than 1 meter. 22. The method of any preceding claim, wherein the speed of the microstructure manufacturing process is greater than 3 meters per minute. 23. The method of any preceding claim, wherein step (d) includes introducing the photosensitive material and the substrate into a solvent bath to dissolve a portion of the photosensitive material to be removed. 24. The method of any preceding claim, wherein the microstructure manufacturing method produces a seamless roll of substrate having the microstructure layer thereon. 25. The method of any preceding claim, wherein the photomask film comprises a photomask pattern printed on a release liner. 26. The method of claim 25, wherein the photomask pattern faces and is adjacent to the photosensitive material. 27. The method of claim 25, wherein the release liner faces and is adjacent to the photosensitive material. 28. The method of any preceding claim, wherein the microstructure layer on the substrate is used to construct an electrophoresis apparatus. 29. The method according to any one of the preceding claims, wherein the photomask film includes grayscale features to change the intensity of light incident on the photosensitive material, thereby changing the height of the microstructure. 30. A microstructure layer on a substrate manufactured by the method of any one of the preceding claims.Claims 2 / 2 Page 3 CN 121909423 A Continuous photolithography manufacturing method for producing seamless microstructures used in electro-optic displays and light modulation films

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 547,747, filed November 8, 2023, entitled “Continuous photolithography manufacturing method for producing seamless microstructures used in electro-optic displays and light modulation films,” the entire contents of which are hereby incorporated by reference.

[0003] Background

[0004] This application generally relates to electrophoretic displays and other electro-optic displays and light modulation films, and more particularly to a continuous photolithography manufacturing method for producing seamless microstructures used in such displays and films.

[0005] Electrophoretic light modulation films modulate the amount of light or other electromagnetic radiation passing through an electrophoretic medium. In some cases, light will pass through the film completely (i.e., from top to bottom). In other cases, light can pass through the electrophoretic medium, be reflected / scattered at the surface, and then return through the medium a second time (i.e., from the top surface to the bottom surface and back to the top). In other cases, light will be absorbed by pigment particles present on the viewing surface. In still other cases, the selective absorption of light by the pigment particles will produce the rendered image, such as text or a picture. Such films can be incorporated into displays, signs, variable light transmission windows, mirrors, monitors, and similar devices. Typically, the film has an "on" state and an "off" state. In the "on" state, one or more groups of pigment particles are isolated to the sides or within holes, allowing most of the incident light to pass through the medium; in the "off" state, one or more groups of pigment particles are distributed throughout the medium to absorb some or all of the incident light.

[0006] For example, U.S. Patent No. 10,067,398 discloses an electrophoretic optical attenuator comprising a unit including a first substrate, a second substrate spaced apart from the first substrate, a layer disposed between the substrates and containing electrophoretic ink, and a monolayer of tightly packed microstructure protrusions protruding into the electrophoretic ink and arranged adjacent to the surface of the second substrate. The protrusions have surfaces defining a plurality of recesses between adjacent protrusions. The electrophoretic dielectric layer (ink layer) contains at least one type of charged particles that move between a first extreme optical state and a second extreme optical state in response to an electric field applied to the unit. In the first extreme optical state, the particles diffuse maximally within the unit, thereby being located in the optical path through the unit and thus strongly attenuating light transmitted from one substrate to the opposite substrate; in the second extreme optical state, the particles are maximally concentrated within the recesses, thereby allowing light to be transmitted. The total area corresponding to the particles concentrated within the recesses occupies a portion of the total surface area.

[0007] Such devices rely at least in part on the shape of their non-planar polymer structure to aggregate absorbing charged particles (e.g., black particles) in an electrophoretic ink in a transparent optical state, thereby forming (or exposing) light holes (i.e., transmission regions) and photoresist (i.e., strong absorption regions). This application also relates to more conventional electrophoretic displays, such as those described in U.S. Patents Nos. 9,921,451 and 9,812,073, which modulate the light reflected on the observation surface by the presence of charged pigment particles.

[0008] Prior art solutions having polymer structures in a fluid layer or gel layer include U.S. Patent No. 8,508,695 of Vlyte Innovations Ltd., which discloses dispersing fluid droplets (1 to 5 micrometers in diameter) in a continuous polymer matrix, which is in situ solidified onto two substrates to accommodate liquid crystal. Furthermore, U.S. Patent No. 10,809,590 of E Ink Corporation discloses microencapsulating and deforming fluid droplets to form a monolayer tightly packed polymer shell in a polymer matrix on a substrate, followed by applying an adhesive layer to bond the encapsulation layer to the substrate. Additionally, European Patent Application Publication EP1264210 of E Ink California discloses imprinting micro-unit structures (including multiple cavities or cups) on a substrate, filling these cups with a fluid having polymerizable components, and polymerizing the components to form a sealing layer on the fluid / cup surface, followed by applying an adhesive layer to bond to a second substrate. Furthermore, EP2976676 of Vlyte Innovations Ltd. discloses forming a wall structure on a substrate, coating the top of the walls with an adhesive, filling the cavities defined by the walls with fluid, and polymerizing the adhesive to bond the top of the walls to the opposing substrate. EP3281055 describes a flexible device comprising solid polymer microstructures embedded in its visible region, the microstructures being situated on two substrates. The microstructures connect (i.e., fix) the substrates of the device to each other by interlocking them in a direction perpendicular to the substrates. The interlocked microstructures incorporate wall structures that divide the fluid layer of the device into discrete monolayer volumes contained within respective cavities. This provides the device with high structural strength. In the described method, matching microstructures (i.e., male and female components) are formed on each substrate, then precisely aligned and joined together by press fitting, while simultaneously sealing the fluid layer within the cavities.

[0009] Particle-based electrophoretic displays, in which multiple charged particles move through a suspended fluid under the influence of an electric field, have been the subject of extensive research and development for many years.Compared to liquid crystal displays, such displays can have good brightness and contrast, wide viewing angles, state bistableness, and low power consumption. The terms “bistable” and “bistable” as used herein in their conventional sense in the art refer to a display comprising display elements having at least one first and second display states with different optical properties, wherein after any given element is driven by an addressing pulse of finite duration to present its first or second display state, the state persists for at least several times, for example, at least four times, the shortest duration of the addressing pulse required to change the state of the display element after the addressing pulse terminates. U.S. Patent No. 7,170,670 shows that some particle-based electrophoretic displays capable of displaying grayscale are stable not only in their extreme black and white states but also in their intermediate grayscale states, as are some other types of electro-optical displays. This type of display is aptly called “multistable” rather than bistable, but for convenience, the term “bistable” may be used herein to encompass both bistable and multistable displays.

[0010] As mentioned above, the electrophoretic medium requires the presence of a suspending fluid. In most existing electrophoretic media, the suspension fluid is a liquid, but gaseous suspension fluids can also be used to produce electrophoretic media; see, for example, Kitamura, T., et al., “Electrical toner movement for electronic paper-like display” IDW Japan, 2001, Paper HCS1-1, and Yamaguchi, Y., et al., “Toner display using insulative particles charged triboelectrically”, IDW Japan, 2001, Paper AMD4-4. See also European patent applications 1,429,178; 1,462,847; and 1,482,354; and international applications WO2004 / 090626; WO2004 / 079442; WO2004 / 077140; WO2004 / 059379; WO2004 / 055586; WO2004 / 008239; WO2004 / 006006; WO2004 / 001498; WO03 / 091799; and WO03 / 088495. When such gas-based electrophoretic media are used in an orientation that allows particle sedimentation, for example, when the media is placed in an indicator in a vertical plane, the media appears to face the same type of problems due to particle sedimentation as those of liquid-based electrophoretic media.In fact, particle sedimentation appears to be more severe in gas-based electrophoretic media than in liquid-based electrophoretic media because gaseous suspensions have lower viscosity than liquid suspensions, causing electrophoretic particles to settle more quickly.

[0011] Numerous patents and applications assigned to or belonging to MIT, E Ink, E Ink California, LLC, and related companies describe various techniques for encapsulated and micro-unit electrophoretic media, as well as other electro-optic media. Encapsulated electrophoretic media comprise a large number of vesicles, each vesicle containing an inner phase and a vesicle wall, the inner phase containing electrophoretically movable particles in a fluid medium, the vesicle wall surrounding the inner phase. Typically, the vesicles themselves are held within a polymer binder to form a coherent layer located between two electrodes. In micro-unit electrophoretic displays, charged particles and fluid are not encapsulated within microcapsules but are held within multiple cavities formed in a carrier medium, typically a polymer film.The technologies described in these patents and applications include:

[0012] (a) electrophoretic particles, fluids, and fluid additives; see, for example, U.S. Patent Nos. 7,002,728 and 7,679,814, page 2 / 8, CN 121909423 A;

[0013] (b) capsules, adhesives, and encapsulation methods; see, for example, U.S. Patent Nos. 6,922,276 and 7,411,719;

[0014] (c) microcell structures, wall materials, and methods of forming microcells; see, for example, U.S. Patent Nos. 7,072,095 and 9,279,906;

[0015] (d) methods for filling and sealing microcells; see, for example, U.S. Patent Nos. 7,144,942 and 7,715,088;

[0016] (e) Films and subassemblies containing electro-optic materials; see, for example, U.S. Patent Nos. 6,982,178 and 7,839,564;

[0017] (f) Backsheets, adhesive layers, and other auxiliary layers, and methods of use in displays; see, for example, U.S. Patent Nos. 7,116,318 and 7,535,624;

[0018] (g) Color formation and color adjustment; see, for example, U.S. Patent Nos. 7,075,502 and 7,839,564;

[0019] (h) Methods for driving displays; see, for example, U.S. Patent Nos. 7,012,600 and 7,453,445;

[0020] (i) Applications of displays; see, for example, U.S. Patent Nos. 7,312,784 and 8,009,348; and

[0021] (j) Non-electrophoretic displays, as described in U.S. Patent No. 6,241,921 and U.S. Patent Application Publication No. 2015 / 0277160; and applications of encapsulation and microcell technologies beyond displays; see, for example, U.S. Patent Application Publications Nos. 2015 / 0005720 and 2016 / 0012710.

[0022] Many of the foregoing patents and applications recognize that in encapsulated electrophoretic media, the walls surrounding discrete microcapsules can be replaced by a continuous phase, thereby forming a so-called polymer dispersion electrophoretic display, wherein the electrophoretic medium comprises a plurality of discrete electrophoretic fluid droplets and a continuous phase of polymer material, wherein the discrete electrophoretic fluid droplets in such a polymer dispersion electrophoretic display can be regarded as capsules or microcapsules, although there is no discrete capsule membrane associated with each individual droplet, see, for example, the aforementioned U.S. Patent Application Publication No. 2002 / 0131147. Therefore, for the purposes of this application, such polymer dispersion electrophoretic media are considered a subtype of encapsulated electrophoretic media.

[0023] Electrophoretic media are typically opaque (because, for example, in many electrophoretic media, the particles essentially block the transmission of visible light through the display) and operate in either a light absorption mode or a light reflection mode.However, electrophoresis apparatuses can also be configured to operate in a so-called "shutter mode," in which one display state is substantially opaque and the other is substantially translucent. See, for example, the aforementioned U.S. Patents 6,130,774, 6,172,798, and U.S. Patents 5,872,552, 6,144,361, 6,271,823, 6,225,971, and 6,184,856. Dielectrophoretic displays, similar to electrophoretic displays but dependent on changes in electric field strength, can also operate in a similar mode; see U.S. Patent 4,418,346. Other types of electro-optic displays can also be equipped with the ability to operate in a shutter mode. In particular, when such a "shutter mode" electrophoresis apparatus is constructed on a transparent substrate, the transmission of light through the apparatus can be modulated.

[0024] Encapsulated or micro-cell electrophoretic displays generally do not suffer from the agglomeration and sedimentation failure modes of conventional electrophoretic devices and offer other advantages, such as the ability to print or coat the display on a variety of flexible and rigid substrates (the term "printing" is intended to include all forms of printing and coating, including but not limited to: pre-quantity coating, such as patch die coating, slot or extrusion coating, ramp or step coating, curtain coating; roll coating, such as doctor blade roll coating, forward and reverse roll coating; gravure coating; dip coating; spray coating; meniscus coating; spin coating; brush coating; air knife coating; screen printing; electrostatic printing; thermal transfer printing; inkjet printing; electrophoretic deposition; and other similar techniques). Therefore, the resulting display can be flexible. Furthermore, because the display medium can be printed (using various methods), the display itself can be manufactured at low cost.

[0025] A potentially important market for electrophoretic media is windows with adjustable light transmittance. As building energy efficiency specifications become increasingly important (page 3 / 8, CN 121909423 A), electrophoretic media can be used as coatings on windows to electronically control the proportion of incident radiation transmitted through the window by altering the optical state of the electrophoretic media. Effective implementation of such "tunable transmittance ("VT")" technology in buildings promises to: (1) reduce undesirable heating effects during hot weather, thereby reducing the amount of energy required for cooling, the size of air conditioning equipment, and peak power demand; (2) increase the utilization of natural daylight, thereby reducing the energy used for lighting and peak power demand; and (3) enhance occupant comfort by improving both thermal and visual comfort. In automobiles or other vehicles, where the ratio of glass surface area to enclosed volume is much greater than in typical buildings, even greater benefits are expected.Specifically, the effective implementation of VT technology in automobiles not only provides the aforementioned benefits, but also achieves: (1) improved driving safety, (2) reduced glare, (3) enhanced rearview mirror performance (by using an electro-optic coating on the mirror surface), and (4) improved ability to use head-up displays. Other potential applications of VT technology include privacy glass and glare protection for electronic devices.

[0026] Many switchable electrophoretic light modulators and displays require coverage of large areas. For example, light modulators can be used for office building windows with an area of ​​several meters by several meters, or electrophoretic displays can be wide signs with a diagonal length of more than 1 meter. One factor limiting the manufacture of such large modulators and displays is the difficulty in fabricating large-area seamless patterns in the polymer structures used in the devices.

[0027] Polymer structures containing high-resolution three-dimensional microstructures can be manufactured by photolithography using photomasks or by imprinting processes using negative structure pads. Photolithography has high resolution, but is typically a slow sheet-to-sheet process. Roll-to-roll embossing is advantageous for continuous high-throughput production, but the roll width is limited by the size of the gaskets, and seamless patterns are difficult to create due to the connection area where the gaskets are mounted on the rollers. Photolithography using cylindrical masks also struggles to achieve seamless patterns. Currently, there is a need for a process to create seamless patterns of microstructures on rolls wider than 1 meter, preferably with a processing speed greater than 10 feet per minute. There is also a need for a process to create polymer structures with multi-layered microstructures that may contain different materials.

[0028] Overview

[0029] A roll-to-roll method for manufacturing seamless microstructures is provided, comprising the steps of: (a) continuously forming a stacked structure including a photomask film superimposed on a substrate, a photosensitive material layer between the substrate and the photomask film, the photomask film including a pattern of light-transmitting regions and light-shielding regions; (b) irradiating the photomask film of the stacked structure formed in step (a) such that light passes through the light-transmitting regions of the photomask film to cure portions of the photosensitive material exposed by the light-transmitting regions, while leaving the remaining portions of the photosensitive material covered by the light-shielding regions uncured; (c) peeling the photomask film from the photosensitive material selectively cured in step (b); and (d) removing the uncured portions of the photosensitive material to form a microstructure layer on the substrate by the cured portions of the photosensitive material.

[0030] According to one or more embodiments, step (a) of the method comprises: forward conveying the photomask film, the substrate and the photosensitive material layer between a pair of clamping rollers to form the stacked structure.

[0031] According to one or more embodiments, the light includes ultraviolet (UV) light.

[0032] According to one or more embodiments, the photosensitive material comprises a negative ultraviolet photosensitive material.

[0033] According to one or more embodiments, the microstructure comprises a cross-linked, ultraviolet-cured structure.

[0034] According to one or more embodiments, the method further includes: reusing the photomask film stripped in step (c) of the method during subsequent microstructure manufacturing processes.

[0035] According to one or more embodiments, steps (a) and (b) of the method are performed in a multi-coating head production line.

[0036] According to one or more embodiments, step (b) of the method is performed during the transfer of the stacked structure.

[0037] According to one or more embodiments, the photosensitive material layer is coated on a substrate prior to step (a), preferably using a bar coating, roller coating, doctor blade coating, or slot die coating process.

[0038] According to one or more embodiments, the substrate of the stack in step (a) includes a pre-existing microstructure group formed thereon.

[0039] According to one or more embodiments, the pre-existing microstructure group is formed by an imprinting process previously performed on the substrate.

[0040] According to one or more embodiments, the pre-existing microstructure group is formed by a prior microstructure manufacturing process for the substrate, including steps (a), (b), (c), and (d).

[0041] According to one or more embodiments, the method further includes drawing the photomask film and the substrate from their respective rolls prior to step (a).

[0042] According to one or more embodiments, each roll has a width greater than one meter.

[0043] According to one or more embodiments, the microstructure comprises an X / Y dimensional resolution of 200 to 2000 micrometers and a Z dimensional resolution of 1 to 500 micrometers.

[0044] According to one or more embodiments, the substrate having the microstructure layer formed thereon has a width greater than one meter.

[0045] According to one or more embodiments, the substrate having the microstructure layer formed thereon has a length greater than 1 meter.

[0046] According to one or more embodiments, the speed of the microstructure manufacturing process is greater than 3 meters per minute.

[0047] According to one or more embodiments, step (d) of the method includes: introducing a photosensitive material and a substrate into a solvent bath to dissolve an uncured portion of the photosensitive material, thereby forming a microstructure layer on the substrate.

[0048] According to one or more embodiments, the microstructure manufacturing method produces a seamless roll of material having a microstructure layer thereon.

[0049] According to one or more embodiments, the photomask film includes a photomask pattern printed on a release liner.

[0050] According to one or more embodiments, the photomask pattern faces and is adjacent to the photosensitive material.

[0051] According to one or more embodiments, the release liner faces and is adjacent to the photosensitive material.

[0052] According to one or more embodiments, the microstructure layer on the substrate is used to construct an electrophoresis apparatus.

[0053] According to one or more embodiments, the photomask film includes grayscale features to change the intensity of light incident on the photosensitive material, thereby changing the height of the microstructure.

[0054] These and other aspects of the invention will become apparent from the following description.

[0055] Brief Description of the Drawings

[0056] Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which:

[0057] Figures 1A-1D are simplified cross-sectional views illustrating an exemplary continuous lithography fabrication process for fabricating microstructures for electrophoresis apparatuses and other electro-optic devices according to one or more embodiments.

[0058] Figure 2 is a simplified cross-sectional view illustrating an exemplary continuous lithography fabrication process according to one or more embodiments, wherein the photomask film is flipped.

[0059] Figure 3 is a simplified cross-sectional view illustrating an exemplary continuous lithography fabrication process for fabricating multiple microstructure layers on a substrate according to one or more embodiments.

[0060] FIG4 is a simplified cross-sectional view illustrating an exemplary continuous photolithography manufacturing process for fabricating microstructures on a substrate having photomask elements, according to one or more embodiments.

[0061] FIG5 is a simplified cross-sectional view illustrating an exemplary continuous photolithography manufacturing process for fabricating microstructures on a substrate using two layers of photomask films, according to one or more embodiments.

[0062] FIG6 is a plan view of an exemplary thin-film photomask with an emulsion lithography pattern, according to one or more embodiments.

[0063] FIG7 shows a diagram of the measured morphology of a microstructure formed according to one or more embodiments.

[0064] FIG8 shows a diagram of the measured morphology of another set of microstructures formed according to one or more embodiments.

[0065] Similar or identical reference numerals are used to indicate common or similar elements.

[0066] The drawings depict one or more embodiments consistent with the inventive concept by way of example only and not by way of limitation.

[0067] Detailed Description

[0068] The various embodiments disclosed herein relate to a continuous photolithography fabrication process for manufacturing microstructures used in large-area electrophoretic displays and light modulation films. In one or more embodiments, a continuous photolithography process using a thin-film photomask, which may have the same length as the substrate on which the microstructure is formed. This process enables seamless roll-to-roll photolithographic patterning of microstructures on rolls with a width greater than 1 meter and preferably a process speed greater than 10 feet per minute, such as micro-unit walls and non-planar polymer structures used in electrophoresis apparatuses. Furthermore, the process enables improved control over microstructure thickness and allows for the patterning of multiple layers of potentially different materials to form more complex microstructures.For example, the process can fabricate transparent cones and porous microstructures covered with black walls for transmittance control of light-modulated films.

[0069] Figures 1A-1D are simplified cross-sectional views illustrating an exemplary continuous photolithography fabrication process for manufacturing microstructures used in an electrophoresis apparatus according to one or more embodiments. The process utilizes a thin-film photomask 100 shown in Figure 1A, which includes a printed light-shielding layer 105 on a release liner 104, which may be, for example, a plastic substrate. The light-shielding layer 105 can be formed by applying printed black ink or a reflective material to the release liner 104 to define a pattern of light-shielding regions 106 and light-transmitting regions 108. Various printing processes can be used to apply printed black ink or reflective material to the release liner 104, including but not limited to screen printing, offset printing, flexographic printing, inkjet printing, aerosol jet printing, and gravure printing. Some known printing methods include continuous roll-to-roll printing of seamless high-resolution photomasks (see, for example, U.S. Patent No. 10,479,905).

[0070] As shown in FIG1B, a stacked structure 110 is continuously formed, which includes a thin-film photomask 100, a photosensitive material 102, and a substrate 101. When the material shown is fed between a pair of clamping rollers 112, the photosensitive material 102 is nip-coated between the thin-film photomask 100 and the substrate 101.

[0071] The photosensitive material 102 can be a positive or negative photoresist, including various photosensitive polymers such as polyimide, acrylic resin, or epoxy resin. For example, the photosensitive material 102 can be a diazonaphthoquinone (DNQ)-phenolic resin, which is a common type of positive photoresist. The photosensitive material 102 may also contain dual-curing, thiol-ene, and other crosslinking chemical compositions commonly used as negative photoresists. In one or more preferred embodiments, the photosensitive material 102 comprises a negative ultraviolet (UV) photosensitive material.

[0072] The substrate 101 may comprise a variety of materials depending on its intended use in the electrophoresis apparatus. For example, the substrate may comprise an indium tin oxide (ITO) coated polyethylene terephthalate (PET) film to form a micro-unit cavity layer in the electrophoretic display apparatus; or, the substrate may comprise a polymer film to form a non-planar polymer structure that aggregates absorbing charged particles in a light attenuator. In other examples, the substrate comprises a flexible material, such as a transparent plastic or glass, which may be coated with a conductive layer (e.g., ITO). Suitable plastics include, for example, polycarbonate (PC), blends of polycarbonate and copolymers, polyethersulfone (PES), cellulose triacetate (TAC), polyamide, p-nitrophenyl butyrate (PNB), polyether ether ketone (PEEK), polyethylene naphthalate (PEN), polyetherimide (PEI), polyarylate (PAR), or other similar plastics known in the art.Flexible glass may include materials such as Corning® Willow® Glass. Specification 6 / 8 pages 9 CN 121909423 A

[0073] Next, as shown in FIG1C, the stacked structure 110 is irradiated by a light source 114 (e.g., an ultraviolet light source) as it travels. If the photosensitive material 102 is a negative photosensitive material, the light from the light source 114 passes through the light-transmitting area 108 of the photomask film 100 to cure the portion of the photosensitive material 102 exposed by the light-transmitting area 108, while leaving the remaining portion of the photosensitive material 102 covered by the light-shielding area 106 uncured.

[0074] The photomask film 100 is then peeled off from the selectively cured photosensitive material 102. This step can be performed continuously using a peeling roller.

[0075] Then, as shown in FIG1D, the uncured portion of the photosensitive material 102 is removed, leaving an ultraviolet-crosslinked microstructure 103 with the desired pattern on the substrate 101. The developing step can be performed, for example, by immersing the photosensitive material 102 in a solvent bath that dissolves the uncured portion of the photosensitive material 102. This step can be performed continuously during material travel.

[0076] If the photosensitive material 102 is a positive photosensitive material, the light from the light source 114 makes the exposed portion of the photosensitive material 102 more soluble in the solvent, allowing the exposed portion to be removed, thereby forming the microstructure 103 from the remaining unexposed portion of the photosensitive material.

[0077] This produces a seamless roll of microstructure 103 (e.g., a UV-crosslinked microstructure) as shown in FIG. 1D.

[0078] The thin-film photomask 100 can generally be made to any desired length. For example, the thin-film photomask 100 can have the same length as the substrate 101 on which the microstructure 103 is formed. Furthermore, the microstructure 103 can be formed on a roll with a width greater than 1 meter. Therefore, patterns of large-area seamless microstructures 103 can be produced for large-area electrophoretic light modulators and displays.

[0079] In one or more embodiments, the process is a roll-to-roll process with a processing speed greater than 10 feet per minute.

[0080] In one or more embodiments, the substrate 101 and release liner 104 are surface-energy modified to reduce residues when the photomask 100 is removed and to provide a robust microstructure 103 with good adhesion to the substrate 101.

[0081] In one or more embodiments, the thin-film photomask 100 can be reused multiple times in additional microstructure fabrication processes.

[0082] In one or more embodiments, the fabrication steps of the thin-film photomask and microstructure photolithography can be performed sequentially in a single multi-coating head production line.

[0083] In one or more alternative embodiments, the stacked structure 110 is formed by applying a photosensitive material 102 onto the substrate 101 and then laminating the photomask film 100 onto the photosensitive material 102.The photosensitive material 102 can be applied to the substrate 101 using rod coating, roller coating, blade coating, slot die coating, and various other coating methods to achieve a wider range of thickness control.

[0084] In one or more alternative embodiments, as shown in FIG2, the photosensitive material 102, the substrate 101, and the photomask 100 form a stacked structure 110', wherein the photomask 100 is flipped, i.e., the light-shielding layer 105 of the photomask 100 faces and contacts the photosensitive material 102. Using such a stacked structure 110' can reduce light scattering and enable the formation of higher resolution microstructures 103, such as microstructures with feature sizes less than 20 micrometers.

[0085] The continuous photolithography microstructure manufacturing process can be applied to fabricate multiple microstructure layers of the same or different materials. As shown in Figure 3, a substrate 101 with a set of microstructures 120 already thereon can be used to form a stacked structure 110 with a photosensitive material 102 and a photomask film 100. Then, a set of different microstructures 103 can be patterned on the substrate 101 using the photolithography process discussed above. In this way, multiple sets of microstructures 103, 120 containing the same or different materials can be formed on the substrate 101.

[0086] The initial microstructures 120 on the substrate 101 can be manufactured using the same continuous photolithography process discussed above, or other processes can be used, including, for example, manufacturing by pad imprinting. Microstructures 103 and 120 can perform the same or different functions in the device in which they are combined. Specification 7 / 8 pages 10 CN 121909423 A

[0087] In one or more embodiments, the thin-film photomask 100 may include grayscale features to change the exposure intensity level of the ultraviolet light source 114, thereby creating a highly variable and controllable three-dimensional microstructure 103.

[0088] In one or more further alternative embodiments, a stacked structure 110''' is formed, wherein a thin-film photomask 124 constitutes a bottom substrate located below the photosensitive material 102, as shown in FIG4. The thin-film photomask 124 is intended to be part of the final structure, rather than a sacrificial layer. A printed light-shielding layer 105' of the thin-film photomask 124 is disposed on the substrate 101. The release liner 104 is removed before the photosensitive material 102 is developed to form the microstructure 103. The printed light-shielding layer 105' is transparent to visible light for use, but blocks the transmission of g-lines (436 nm) and h-lines (405 nm) used for light patterning. As part of the final structure, the light-shielding layer 105' also has the additional benefit of blocking certain types of harmful light during use.

[0089] In one or more further embodiments, as shown in FIG5, a stacked structure 110'''' is formed, which includes a first thin-film photomask 100, a second thin-film photomask 124, and a photosensitive material 102 located between the two.The second thin-film photomask 124 includes a printed light-shielding layer 105' with grayscale features, similar to the printed light-shielding layer 105' in FIG. 4. The first thin-film photomask 100 includes light-shielding features, similar to the printed light-shielding layer 105 in FIG. 2. Photomasks 100 and 124 form patterns of microstructures 103' and 103. Either photomask 100 or 124 may be retained as part of the final structure, while the other photomask is removed after the photopatterning step. Example

[0090] The pattern of the microstructure is formed using the following process. A small drop of blue UV resin called 127-24PB from Creative Materials is cast onto an ITO-coated PET sheet. A 5 cm × 5 cm photomask 130 with an emulsion photolithography pattern as shown in FIG. 6 is manually superimposed on top of the resin on the PET-ITO sheet.

[0091] Then, the laminated structure was cured for 30 seconds using a DECO Delolux 03S curing lamp, thereby patterning the UV polymer into micro-unit walls using photomask 130. Subsequently, photomask 130 was peeled off, and the uncured resin, cured resin, and PET-ITO sheet were immersed in isopropanol (IPA) for 1 minute, then the uncured resin was wiped off with a cloth. Figure 7 shows the measured morphology of the microstructured wall formed using this process.

[0092] The above process was then repeated, but using a PET-ITO sheet already having microstructures, similar to the process described in Figure 3. Figure 8 shows the measured morphology of the microstructured wall formed using this process.

[0093] It will be apparent to those skilled in the art that various changes and modifications can be made to the specific embodiments of the invention described above without departing from the scope of the invention. Therefore, all the above descriptions should be understood as illustrative rather than restrictive. Instruction manual, page 8 / 8, 11 CN 121909423 A, Figure 1A, Figure 1B, Figure 1C, Figure 1D; Instruction manual, Figure 1 / 8, page 12 CN 121909423 A, Figure 2; Instruction manual, Figure 2 / 8, page 13 CN 121909423 A, Figure 3; Instruction manual, Figure 3 / 8, page 14 CN 121909423 A, Figure 4; Instruction manual, Figure 4 / 8, page 15 CN 121909423 A, Figure 5; Instruction manual, Figure 5 / 8, page 16 CN 121909423 A, Figure 6; Instruction manual, Figure 6 / 8, page 17 CN 121909423 A, Figure 7; Instruction manual, Figure 7 / 8, page 18 CN 121909423 A, Figure 8; Instruction manual, Figure 8 / 8, page 19 CN 121909423 A.

Claims

1. A method for manufacturing roll-to-roll seamless microstructures, comprising the following steps: (a) A continuously formed stacked structure, the stacked structure including a photomask film superimposed on a substrate, a photosensitive material layer between the photomask film and the substrate, the photomask film including a pattern of light-transmitting areas and light-blocking areas; (b) Irradiate the photomask film of the stacked structure formed in step (a) with light from the light source so that the portion of the photosensitive material covered by the light-transmitting area is exposed to light, while the remaining portion of the photosensitive material covered by the light-shielding area is not exposed to light; (c) Peel the photomask film from the photosensitive material selectively irradiated in step (b); as well as (d) Selectively remove the light-exposed portion of the photosensitive material or the light-unexposed portion of the photosensitive material to form a microstructure layer on the substrate.

2. The method of claim 1, wherein step (d) comprises selectively removing the light-exposed portion of the photosensitive material to form a microstructure layer on the substrate.

3. The method of claim 1, wherein step (d) comprises selectively removing the unexposed portions of the photosensitive material to form a microstructure layer on the substrate.

4. The method of claim 1, wherein in step (b), the light-exposed portion of the photosensitive material is photocured, while the remaining portion of the photosensitive material remains uncured; and wherein in step (d), the uncured portion of the photosensitive material is removed to form a microstructure layer on the substrate by the cured portion of the photosensitive material.

5. The method of claim 1, wherein the light comprises ultraviolet light.

6. The method according to claim 1 or 5, wherein the photosensitive material comprises a negative ultraviolet photosensitive material.

7. The method according to claim 1, 5 or 6, wherein the microstructure comprises a cross-linked UV-curable structure.

8. The method according to any of the preceding claims, wherein step (a) comprises forward conveying a photomask film, a substrate and a photosensitive material layer between a pair of rollers to form the stacked structure.

9. The method according to any of the preceding claims further comprises reusing the photomask stripped in step (c) during subsequent microstructure fabrication processes.

10. The method according to any one of the preceding claims, wherein steps (a) and (b) are carried out in a multi-coating head production line.

11. The method according to any of the preceding claims, wherein step (b) is performed during the transfer of the stacked structure.

12. The method according to any one of the preceding claims, wherein the photosensitive material layer is coated on the substrate prior to step (a).

13. The method according to any of the preceding claims, wherein the photosensitive material layer is applied to the substrate using a bar coating, roller coating, doctor blade coating or slot die coating process prior to step (a).

14. The method according to any of the preceding claims, wherein the substrate of the stack in step (a) includes a pre-existing set of microstructures formed thereon.

15. The method of claim 14, wherein the pre-existing microstructure group is formed by a prior imprinting process performed on a substrate.

16. The method of claim 14, wherein the pre-existing microstructure group is formed by a prior microstructure fabrication process for the substrate, including steps (a), (b), (c), and (d).

17. The method according to any of the preceding claims, further comprising drawing the photomask film and the substrate from the roll material prior to step (a).

18. The method of claim 17, wherein the width of each roll is greater than 1 meter.

19. The method according to any one of the preceding claims, wherein the microstructure comprises the following features: The X / Y dimension resolution ranges from 20 micrometers to 2000 micrometers, and the Z dimension resolution ranges from 1 micrometer to 500 micrometers.

20. The method according to any of the preceding claims, wherein the width of the substrate having the microstructure layer formed thereon is greater than 1 meter.

21. The method according to any of the preceding claims, wherein the length of the substrate having the microstructure layer formed thereon is greater than 1 meter.

22. The method according to any one of the preceding claims, wherein the speed of the microstructure manufacturing process is greater than 3 meters per minute.

23. The method according to any of the preceding claims, wherein step (d) comprises introducing the photosensitive material and the substrate into a solvent bath to dissolve a portion of the photosensitive material to be removed.

24. The method according to any one of the preceding claims, wherein the microstructure manufacturing method produces a seamless roll of substrate having a microstructure layer thereon.

25. The method according to any of the preceding claims, wherein the photomask film comprises a photomask pattern printed on a release liner.

26. The method of claim 25, wherein the photomask pattern faces and is adjacent to the photosensitive material.

27. The method of claim 25, wherein the release liner faces the photosensitive material and is adjacent to the photosensitive material.

28. The method according to any one of the preceding claims, wherein the microstructure layer on the substrate is used to construct an electrophoresis apparatus.

29. The method according to any one of the preceding claims, wherein the photomask film includes grayscale features to change the intensity of light incident on the photosensitive material, thereby changing the height of the microstructure.

30. A microstructure layer on a substrate, formed by the method of any one of the preceding claims.

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