Optical device with magnetic flakes and structured substrate

Abstract

An optical device is disclosed that includes a structured substrate, a reflective layer on the structured substrate, and a coating having magnetic flakes on the reflective layer. Methods of making and using the optical device are also disclosed.

Description

[0001] This application is a divisional application of the invention patent application with international application number PCT / US2020 / 029814, international application date of April 24, 2020, entry into the Chinese national phase date of October 25, 2021, national application number 202080031300.X, and invention title "Optical Device with Magnetic Sheet and Structured Substrate". Technical Field

[0002] This disclosure generally relates to optical devices, which include: a structured substrate, a reflective layer on the structured substrate, and a coating having magnetic flakes on the reflective layer. Methods for manufacturing and using the optical devices are disclosed herein. Background Technology

[0003] Optical devices exhibiting a view-dependent visual appearance are used as effective copy-proof devices on bank notes and secure documents. Optical variable inks are commonly used, comprising thin-film optical interference structures with a layered structure of reflective, dielectric, and absorbing layers. However, the thin-film optical interference structure is applied as an opaque coating on top of the substrate. In this way, and using this opaque coating, it is impossible to hide and reveal the image on the substrate at certain viewing angles. Only color variations are observed.

[0004] Magnetic sheets have been used to create a "Venetian blind effect" by aligning the sheets, thus creating a hidden and revealed effect. The venetian blind layer of the magnetic sheet absorbs a large amount of light at a transparent angle. Additionally, only light with precise right angles can pass through the venetian blind layer, thus contributing to the underlying image and color. However, this reduces the brightness and chromaticity of the image.

[0005] The goal is to brighten the image, for example, by increasing its contrast compared to the underlying image. Attached Figure Description

[0006] Features of this disclosure are illustrated by way of example rather than limitation in the following figures, wherein like reference numerals denote like elements, wherein:

[0007] Figure 1 This is a cross-sectional view of an optical device according to one aspect of the present invention;

[0008] Figure 2 This is a cross-sectional view of an optical device according to another aspect of the present invention;

[0009] Figure 3 This is a cross-sectional view of an optical device according to one aspect of the present invention; and

[0010] Figure 4 This is a cross-sectional view of an optical device according to another aspect of the present invention. Summary of the Invention

[0011] In one aspect, an optical device is disclosed, comprising: a structured substrate, a reflective layer on the structured substrate, and a coating having a magnetic sheet on the reflective layer or on the other side of the structured substrate.

[0012] On the other hand, a method for manufacturing an optical device is disclosed, the method comprising: forming an image on a structured substrate; applying a reflective layer on the structured substrate such that the reflective layer simulates the morphology of the structured substrate; and applying a coating having magnetic flakes.

[0013] On the other hand, a method for using an optical device is disclosed, the method comprising: forming an optical device including a structured substrate, a reflective layer on the structured substrate, and a coating having magnetic flakes on the reflective layer; and tilting the optical device to visualize an image formed on the structured substrate as a top layer.

[0014] On the other hand, a method for using an optical device is disclosed, the method comprising: forming an optical device including a structured substrate, a reflective layer on the structured substrate, and a coating having a magnetic sheet on an unstructured side of the substrate; and tilting the optical device to visualize an image formed on the structured substrate as a top layer.

[0015] Additional features and advantages of the various embodiments will be set forth in part in the description which follows, and will be apparent in part from the description, or may be learned by practice of the various embodiments. The objects and other advantages of the various embodiments will be realized and obtained by means of the elements and combinations particularly pointed out in the description herein. Detailed Implementation

[0016] For purposes of simplicity and illustration, this disclosure is described primarily by way of examples. Numerous specific details are set forth in the following description to provide a thorough understanding of this disclosure. However, it will be apparent that this disclosure may be practiced without being limited to these specific details. In other instances, some methods and structures have not been described in detail to avoid unnecessarily obscuring this disclosure.

[0017] Additionally, the elements depicted in the accompanying drawings may include additional components, and some of those components may be removed and / or modified without departing from the scope of this disclosure. Furthermore, the elements depicted in the drawings may not be drawn to scale, and therefore the elements may have different dimensions and / or configurations than those shown in the drawings.

[0018] It should be understood that the foregoing general description and the following detailed description are merely exemplary and illustrative, and are intended to provide an explanation of various embodiments of this teaching. In its broad and varied embodiments, what is disclosed herein are optical devices and methods of manufacturing and using optical devices.

[0019] This invention relates to optical device 10, such as Figure 1 As shown, the optical device 10 includes a structured substrate 12, a reflective layer 14, and a coating 16 with magnetic flakes. The coating 16 with magnetic flakes 20 can create angle-dependent transparency variations.

[0020] The structured substrate 12 may include surfaces arranged to form an image, such as multiple surfaces. The structured substrate 12 may include horizontal surfaces (i.e., unstructured planes) and structured surfaces (e.g., surfaces angled relative to the horizontal surfaces). For example, as... Figure 1 As shown, the horizontal surface 11 is illustrated at the left and right ends and the bottom edge, and the structured surface 13 is illustrated at the center. It should be noted that the structured surface 13 may be present at the top edge of the structured substrate. Figure 1 and Figure 2 ) or bottom edge ( Figure 3 and Figure 4 The structured substrate 12 may include surfaces forming images defined by region shapes and configurations. The images may reside on one or more surfaces of the substrate 12. The images may include, but are not limited to, text, symbols, numbers, patterns, and shapes.

[0021] Any substrate 12 typically used for manufacturing optical devices 10 can be used as a structured substrate 12. Suitable substrate materials include, but are not limited to, paper, cardboard, textiles, glass, polymers, plastics, or combinations thereof. The substrate 12 can be a transparent material. For example, the substrate 12 can be an imprinted UV-curable material, coated on polyethylene terephthalate, or applied to paper on the non-observation side. In one aspect, the structured substrate 12 can be a transparent material, wherein an image can be formed on or directly in the substrate surface to create the structured substrate 12.

[0022] In one aspect, the substrate 12 can be a structured material, i.e., provided with multiple surfaces forming an image and a background. In one aspect, the image can be formed by imprinting or by an array of micromirrors having coplanar surfaces. In another aspect, the image can be formed by a grating, such as a blazed grating or a variation thereof. For example, the image can be formed by a grating at a first angle, and the background can be formed by a grating at a second angle, offset from the first angle, such as at 90°. The blazed grating comprises multiple grating lines with triangular sawtooth cross-sections, thereby forming a stepped structure. The steps can be tilted relative to the surface of the substrate 12 at a so-called blazed angle. The blazed angle can be optimized to maximize the efficiency of the incident light angle and take into account the intended use of the optics 10. The multiple surfaces of the structured substrate 12 formed by the blazed grating can reflect light at a surface angle of 45°. For example, if the surface angle is 30°, the reflected light angle will be 75°. In one aspect, the multiple surfaces of the structured substrate 12 forming the image can be reflective at the transparency angle of the coating 16 of the magnetic sheet 20. In this way, the brightness of the image can be enhanced. Additionally, the image reflects much less at other angles, making it easier to achieve angle-dependent vanishing (i.e., hiding) effects. Some areas of the substrate 12 may be unstructured, such as horizontal planes, and the image formed by the structured surface may depend on the different reflection angles of the structured surface and / or the absence of structure in some areas.

[0023] The reflective layer 14 can be applied to the structured substrate 12. The reflective layer 14 can be applied in any manner, as long as it mimics the topography of the structured substrate 12, such as the shape and / or angles of each surface and / or multiple surfaces. Specifically, the reflective layer 14 can be a metallized surface on the structured substrate 12. The reflective layer 14 can be microstructured or can include the same grating as the structured substrate 12.

[0024] The reflective layer 14 may comprise a metal, a non-metal, or a metal alloy. In one example, the material of the reflective layer 14 may comprise any material having reflective properties within a desired spectral range. For example, any material with a reflectivity ranging from 5% to 100% within the desired spectral range. An example of a reflective material may be aluminum, which has good reflective properties, is inexpensive, and is easily formed or deposited as a thin layer. Non-limiting examples of reflective opaque materials for the reflective layer 14 include aluminum, copper, silver, gold, platinum, palladium, nickel, cobalt, niobium, chromium, tin, iron, and combinations or alloys of these or other metals may be used as the reflective layer 14. In one aspect, the material of the reflective layer 14 may be a white or light-colored metal. In other examples, the reflective layer 14 may include, but is not limited to, transition metals and lanthanides and combinations thereof; and metal carbides, metal oxides, metal nitrides, metal sulfides, combinations thereof, or mixtures of metals with one or more of these materials. In one aspect, the reflective layer 14 may comprise a transparent or translucent material selected from glass, silica, titanium dioxide, alumina, natural mica, synthetic mica, and bismuth oxychloride. On the other hand, the reflective layer 14 may include a quasi-metallic material selected from silicon, germanium and molybdenum.

[0025] The thickness of the reflective layer 14 can range from about 10 nm to about 3 micrometers, for example from about 30 nm to about 1 micrometer, and as a further example from about 40 nm to about 200 nm.

[0026] The coating 16 of the magnetic sheet 20 can be applied to the reflective layer 14. In one aspect, the coating 16 of the magnetic sheet 20 can be an outer layer of the optical device 10. The coating 16 can include a curable adhesive 18. Non-limiting examples of the curable adhesive 18 include vinyl resins, acrylic resins, urethane-alkyd resins, mixtures thereof, and mixtures with other polymers. The adhesive 18 can generally be transparent, such as clear and / or colorless, but can be colored, and the magnetic sheet 20 can be reflective.

[0027] In one example, the coating 16, including the magnetic sheet 20, can be applied to the reflective layer 14 and / or the structured substrate 12 in any manner, including but not limited to liquid coating processes. The coating 16 can be applied at a thickness that allows the magnetic sheet 20 to be oriented in all directions.

[0028] Many configurations of coating 16 are possible. In one configuration, the magnetic flakes 20 can be uniformly distributed throughout coating 16. In another configuration, the magnetic flakes 20 can have a higher concentration in some areas of coating 16 than in other areas. And in yet another configuration, some portions of the volume of coating 16 can be substantially free of magnetic flakes 20.

[0029] The magnetic sheet 20 can be of any size or shape and can comprise a material that can be magnetized in a magnetic field. When a magnetic field is applied, the magnetic sheet 20 can be oriented in a predetermined direction. Once the orientation of the magnetic sheet 20 is achieved, the coating 16 having the magnetic sheet 20 can be cured.

[0030] Magnetic flakes 20 are typically small, thin flakes that are flat or fairly flat. A typical size for magnetic flakes 20 can be approximately twenty micrometers wide and approximately one micrometer thick; however, these dimensions are merely exemplary and not limiting. Larger or smaller flakes can be used, as well as flakes with different aspect ratios. Optically Variable Pigment (“OVMP”) TM Pigment flakes comprise optical interference structures made of thin film layers, such as Fabry-Perot structures. OVMPs change color with viewing angle. Different optical interference designs can produce different hues and color propagation. Thin film layers of magnetic materials (such as nickel or ferrochrome layers about 25 nm to about 250 nm thick) can provide suitable magnetic structures for orienting or aligning the pigment flakes within coating 16. Other magnetic materials can be used, and suitable materials may or may not form permanent magnets, but it is generally desirable to avoid permanent magnetization of the flakes before application to prevent clumping. Some magnetic flakes 20 can be simply made of magnetic materials, such as nickel flakes, which can be used for reflective, non-color-changing effects.

[0031] The coating 16, including the magnetic sheet 20, can be applied to the reflective layer 14 and / or the structured substrate 12 using a deposition technique, such that the coating 16 is external to the reflective layer 14 and / or the structured substrate 12. The coating 16 of the magnetic sheet 20 can be applied to any layer of the optics 10 to completely cover a layer or a portion thereof. For example, the coating 16 of the magnetic sheet 20 can cover a portion of the reflective layer 14. A magnetic field can be applied to the magnetic sheet 20 to orient or align one or more sheets, while the adhesive 18 in the coating 16 remains fluid. The adhesive 18 can then be dried, cured, or configured to hold the alignment of the magnetic sheet 20 in place.

[0032] The magnetic sheets 20 can be arranged to achieve a Venetian blind effect. Specifically, the magnetic sheets 20 can be aligned such that, along a specific viewing direction, they make the reflective layer 14 and / or the structured substrate 12 visible, making the image present on or within the structured substrate 12 clear to the observer, while simultaneously obstructing visibility along another viewing direction. The alignment of the magnetic sheets 20 can be at similar angles across the entire coating 16, or the alignment of the magnetic sheets 20 can be at different angles within a portion of the coating 16, causing the Venetian blind effect to occur at different viewing angles or orientations.

[0033] At certain alignment angles, the magnetic sheet 20 can create a foil-like appearance by reflecting most of the incoming light, making the underlying image invisible. At other alignment angles, most of the incoming light passes between the aligned sheets and reaches the structured substrate 12 that reflects the light, and the underlying image is discernible.

[0034] In one aspect, the optical device 10 may further include at least one layer, such as a substrate 26, an adhesive 24, a multilayer coating 22, or a combination thereof. Depending on the desired visual effect, light source, viewing angle, etc., the at least one layer may be located at various locations throughout the optical device 10. In another aspect, the multilayer coating 22 may include a multilayer optical interference coating. In yet another aspect, the multilayer coating 22 may include a color-changing coating.

[0035] Figure 2 The illustration shows a cross-sectional view of an optical device 10 including a base 26, the base 26 having an adhesive 24 applied to its surface. Non-limiting examples of the base 26 include documents, bank notes, paper, cardboard, any material that can support the optics, or any material that can include security features. The adhesive 24 can be any colored or transparent material that can secure or bond the base 26 to other layers in the optical device 10. For example, a structured substrate 12 can be bonded to the base 26 via the adhesive 24.

[0036] like Figure 2 As shown, the optical device 10 may further include a multilayer coating 22. The multilayer coating 22 can be located anywhere within the optical device 10, such as between the reflective layer 14 and the coating 16 of the magnetic sheet 20. The multilayer coating 22 may be opaque or may provide transmission at one or more wavelengths. In the multilayer coating 22, each layer may be the same or different, for example, in terms of the material present in each of the multiple layers or the color visible by each layer. For example, the multilayer coating 22 may include a reflective layer, a dielectric layer, and an absorbing layer. The multilayer coating 22 may be opaque and may be located on a structured substrate and / or adjacent to the reflective layer 14. The multilayer coating 22 may be an optical interference coating.

[0037] Figure 3 The illustration shows a cross-section of an optical device 10 according to another aspect. The optical device 10 may include a base 26 having an adhesive 24 for attaching a multilayer coating 22 to the base 26. The multilayer coating 22 may be metallic, opaque, or capable of providing transmission at one or more wavelengths. The multilayer coating 22 may be located between the adhesive 24 and the reflective layer 14. A structured substrate 12 may be located between the reflective layer 14 and a coating 16 having a magnetic sheet 20.

[0038] Figure 4The illustration shows a cross-section of an optical device 10 according to another aspect. The optical device 10 may include a base 26, an adhesive 24, a reflective layer 14, a structured substrate 12, a multilayer coating 22, and a coating 16 of a magnetic sheet 20. The structured substrate 12 may be transparent, colorless, or may be colored. The multilayer coating 22 may be a transparent color-shifting dichroic multilayer coating. For example, the multilayer coating 22 may be a stack of alternating layers of high-refractive-index and low-refractive-index materials. As another example, the multilayer coating 22 may include a transparent colored resin.

[0039] A method of manufacturing an optical device 10 may include: forming an image on a structured substrate 12; applying a reflective layer 14 on the structured substrate such that the reflective layer 14 mimics the morphology of the structured substrate 12; and applying a coating 16 including a magnetic sheet 20. The method may include applying a multilayer coating 22 between the reflective layer 14 and the coating 16 of the magnetic sheet 20. The method may further include: providing a substrate 26 and applying an adhesive 24 to the substrate. The method may also include: adhering the structured substrate 12 to the substrate 26 via the adhesive 24. The method may further include: applying a multilayer coating 22 (such as an optical interference colorant) to the reflective layer 14 such that the multilayer coating 22 mimics the morphology of the reflective layer 14. In one aspect, the multilayer coating (such as an optical interference colorant) may include a color-shifting colorant.

[0040] Methods for manufacturing optical devices may include: providing a substrate 26; applying an adhesive 24 to the substrate; bonding a multilayer coating 22 to the adhesive 24; applying a reflective layer 14 to the multilayer coating 22; applying a structured substrate 12 to the multilayer coating 22; and applying a coating 16 having a magnetic sheet 20 to the structured substrate 12. The reflective layer 14 and / or the multilayer coating 22 may mimic the morphology of the structured substrate 12.

[0041] Methods for manufacturing optical devices may include: providing a substrate 26; applying an adhesive 24 to the substrate; applying a reflective layer 14 to the adhesive 24; applying a structured substrate 12 to the reflective layer 14; applying a multilayer coating 22 to the structured substrate 12; and applying a coating 16 having a magnetic sheet 20 to the multilayer coating 22. The reflective layer 14 and / or the adhesive 24 may mimic the morphology of the structured substrate 12.

[0042] Methods of using optical device 10 may include: forming optical device 10, which includes a structured substrate 12, a reflective layer 14 on the structured substrate 12, and a coating 16 having magnetic flakes 20 on the reflective layer 14; and tilting optical device 10 such that an image formed on the structured substrate 12 is visualized as a top layer. The coating 16 having magnetic flakes 20 may be an outer layer of optical device 10. The coating 16 having magnetic flakes 20 may exhibit a Venetian blind effect. In one aspect, the image may be visualized between the magnetic flakes 20 exhibiting the Venetian blind effect. In another aspect, the image may not be visualized between the magnetic flakes 20 exhibiting the Venetian blind effect. As an additional option, the area of ​​the reflective layer 14 covered by the coating 16 may be patterned so that not all areas of the reflective layer 14 are covered.

[0043] Methods of using the optical device 10 may include: forming the optical device 10, the optical device 10 including a structured substrate 12, a reflective layer 14 on the structured substrate 12, and a coating 16 having magnetic flakes 20 on the unstructured side of the structured substrate 12; and tilting the optical device 10 such that an image formed on the structured substrate 12 is visualized as a top layer. The coating 16 having magnetic flakes 20 may exhibit a Venetian blind effect. In one aspect, the image may be visualized between the magnetic flakes 20 exhibiting the Venetian blind effect. In another aspect, the image may not be visualized between the magnetic flakes 20 exhibiting the Venetian blind effect. As an additional option, the area of ​​the reflective layer 14 covered by the coating 16 may be patterned so that not all areas of the reflective layer 14 are covered.

[0044] Based on the foregoing description, those skilled in the art will understand that this teaching can be implemented in various forms. Therefore, although these teachings have been described in conjunction with specific embodiments and examples, the true scope of this teaching should not be so limited. Various changes and modifications can be made without departing from the scope of the teachings herein.

[0045] This disclosure should be interpreted broadly. This disclosure aims to disclose equivalents, apparatuses, systems, and methods for implementing the devices, activities, and mechanical actions disclosed herein. For each disclosed device, article, method, apparatus, mechanical element, or mechanism, this disclosure also aims to cover and teach equivalents, apparatuses, systems, and methods within its disclosure for practicing the many aspects, mechanisms, and devices disclosed herein. Additionally, this disclosure relates to coatings and many aspects, features, and elements thereof. Such devices can be dynamic in their use and operation, and this disclosure aims to cover equivalents, apparatuses, systems, and methods for using devices and / or manufacturing optical devices, and many aspects consistent with the operation and function disclosed herein. The claims of this application are also interpreted broadly. The description of the invention herein in its many embodiments is merely exemplary in nature, and therefore, variations without departing from the spirit of the invention are intended to fall within the scope of the invention. Such variations should not be considered as departing from the spirit and scope of the invention.

Claims

1. An optical device, comprising: A structured substrate includes a plurality of angled surfaces arranged to form an image on the structured substrate, wherein the plurality of angled surfaces are angled such that they reflect light at a predetermined reflection angle. A reflective layer on the structured substrate; and A coating with magnetic flakes on the reflective layer, The magnetic flakes in the coating are aligned in a specific direction along the predetermined reflection angle of the structured substrate to provide a transparent angle for viewing the image on the structured substrate.

2. The optical device of claim 1, wherein the plurality of angled surfaces comprise a micromirror array having coplanar surfaces.

3. The optical device of claim 1, wherein the plurality of angled surfaces comprise a grating for forming the image.

4. The optical device of claim 1, wherein the plurality of angled surfaces further form a background, wherein the image is formed by a grating at a first angle, and the background is formed by a grating at a second angle deviating from the first angle.

5. The optical device of claim 1, wherein the plurality of angled surfaces are angled to provide reflectivity at the transparency angle, such that the image can be viewed through the coating having a magnetic sheet.

6. The optical device of claim 1, wherein the reflective layer simulates the morphology of the structured substrate.

7. The optical device of claim 1 further includes a base fixed to the other side of the structured substrate by an adhesive.

8. The optical device of claim 1 further comprises a multilayer coating between the structured substrate and the coating having magnetic flakes.

9. The optical device according to claim 8, wherein the multilayer coating is a transparent color-shifting multilayer dichroic coating or a coating comprising a transparent colored resin.

10. The optical device of claim 3, wherein the grating is a blazed grating.

11. The optical device of claim 1, wherein the magnetic sheet aligned to provide the transparency angle is arranged to achieve a venetian blind effect.

12. The optical device of claim 1, wherein the reflective layer is a metallized surface on the structured substrate.

13. The optical device of claim 1 further comprises a multilayer coating between the coating of the reflective layer and the coating of the magnetic sheet, said multilayer coating being an optical interference coating.

14. The optical device of claim 1 further comprises a multilayer coating between the reflective layer and the adhesive.

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