Multi-layered magnetic pigments and foils

Multi-layered magnetic pigments and foils

<p>The present invention relates to pigments and foils. More particularly, the present invention relates to multilayered pigment flakes and foils having magnetic layers, and to pigment compositions comprising multilayered pigment flakes having magnetic layers.</p>

<p>Various pigments, colorants, and foils have been developed for a wide variety of applications. For example, magnetic pigments have been developed for use in applications such as decorative cookware, patterned surfacing, and security devices. Likewise, color shifting pigments are used in cosmetics, inks, coatings, jewelry, ornaments, ceramics, automotive paints, anti-counterfeiting hot stamps, and counterfeiting used in security documents and currency. It has been developed for use in applications such as anti-inflammatory inks.</p><p>Color-changing pigments, pigments, and foils exhibit a property of changing color as the angle of incident light changes, or as the angle at which an observer sees it changes. The color change properties of these pigments and foils can be achieved through the proper design of optical thin films, or the orientation of chemical molecules used to form the flakes or foils coating structures. can be controlled. A desired effect can be obtained by changing parameters such as the thickness of the layers forming the flakes and foils and the refractive index of each layer. The change in the perceived color caused by the change in the angle of the line of sight or the angle of the incident light is a result of a combination of the selective absorption effect of the material constituting the layer and the interference effect depending on the wavelength. The interference effect arises from the superposition of light waves that have undergone multiple reflections, causing the perceived color at different angles to change. The location and intensity of the reflection maxima is due to changes in interference effects resulting from differences in the lengths of the paths of light in the various layers of material that are selectively enhanced at specific wavelengths as the viewing angle changes. change</p><p>Various methods have been used to obtain such a color change effect. For example, small flakes having a multilayer structure, typically composed of several layers of thin film, are dispersed in a medium such as paint or ink and then applied to the surface of an object. Such flakes may optionally be coated with a protective coating to achieve the desired color and optical effect. Another method is to wrap a small metal or silicate substrate in several layers and then disperse the wrapped substrate in a medium such as paint or ink. In addition, foils made up of several layers of thin films attached to a substrate have been manufactured.</p><p>One way to fabricate a multilayer thin film structure is to form it on a flexible textile material to which a release layer is attached. By methods well known in the art for thin film coatings, such as PVD, sputtering, etc., the various layers are deposited onto the textile material. The multilayer thin film structure is then separated from the textile material in the form of thin film color shifting flakes, which can be used in the form of inks or paints with various pigment vehicles and It can be added to the same polymer medium. In addition to the color change flakes, additives may be added to these inks or paints to achieve the desired color change effect.</p><p>Color changing pigments or foils are formed from multilayer thin film structures comprising the same base layer. These include an absorber layer, a dielectric layer, and optionally a reflector layer, the order of which may be varied. Such a coating may be formed to have a symmetrical multilayer thin film structure, including, for example, an absorption layer/dielectric layer/reflective layer/dielectric layer/absorption layer; absorbent layer/dielectric layer/absorbent layer; etc.</p><p>The coating may also include an absorbing layer/dielectric layer/reflective layer; It may be formed to have an asymmetric multilayer thin film structure, such as, for example.</p><p>For example, U.S. Pat. No. 5,135,812 (Phillips et al.), incorporated herein by reference, discloses color-changing thin-film flakes having several different layer configurations, such as stacks of transparent dielectric layers and translucent metal layers. is starting U.S. Patent No. 5,278,590 (Phillips et al.), incorporated herein by reference, includes a first partially transmitting absorber layer and a second partially transmitting absorber layer having the same material and thickness as each other, and a first A symmetrical three-layer optical interference coating comprising a dielectric spacer layer positioned between a partially transmissive absorbing layer and a second partially transmissive absorbing layer is disclosed.</p><p>Color changing platelets used in paints are disclosed in US Pat. No. 5,571,624 (Phillips et al.), which is incorporated herein by reference. The platelet is formed from a symmetrical multilayer thin film structure in which a first semi-opaque layer, such as chromium, is formed over a substrate and a first dielectric layer is formed over the first semi-opaque layer. has been An opaque reflecting metal layer, such as aluminum, is formed over the first dielectric layer, with a second dielectric layer formed thereon having the same material and thickness as the first dielectric layer. A second semi-opaque layer having the same material and thickness as the first semi-opaque layer is formed over the second dielectric layer.</p><p>With respect to magnetic pigments, U.S. Patent No. 4,838,648 (Phillips et al.) (hereinafter referred to as "Phillips '648") discloses a thin film magnetic color changing structure, wherein the magnetic material is used as a reflective layer or an absorbing layer. can One magnetic material disclosed is a cobalt-nickel alloy. "Phillips '648" discloses flakes and foils having the following structure:</p><p>dyed superstrate/absorbent layer/dielectric layer/magnetic layer/substrate; dyed superstrate/absorbent layer/dielectric layer/magnetic layer/dielectric layer/absorbent layer/dyed superstrate; and adhesive layer/magnetic layer/dielectric layer/absorbing layer/releasable hardcoat/substrate.</p><p>Patterned surfaces have been provided by exposing magnetic flakes to magnetic forces to cause physical perturbation of the pigment structure. For example, US Pat. No. 6,103,361 (Batzar et al.) (hereinafter referred to as "Batzar") uses pigments made of magnetizable materials to decorate cookware. In particular, "Batzar" aims to control the orientation of stainless steel flakes in a fluoropolymer release coating to form a pattern, wherein at least some of the flakes are longer than the coating thickness. The patterned substrate applies a magnetic force through the edge of a magnetizable die located underneath the coated base to perturb the orientation of the flakes in the coating, thereby resulting in an image forming effect. or by inducing pattern formation. However, "Batzar" did not discuss the use of an optical thin film stack or platelet comprising a magnetic layer. In addition, although the stainless steel flakes used in "Batzar" are suitable for decoration of cookware, their reflective effect is poor.</p><p>U.S. Patent No. 2,570,856 to Pratt et al. (hereinafter referred to as "Pratt") discloses metallic flake pigments based on ferromagnetic metal platelets. However, like "Batzar", "Pratt" uses a poorly reflective metal and does not disclose the use of thin film optical stacks.</p><p>U.S. Patent Nos. 5,364,689 and 5,630,877 (Kashiwagi et al.) (hereinafter collectively referred to as the "Kashiwagi Patent"), which are incorporated herein by reference, form magnetically formed and drawn patterns. A method and apparatus are disclosed. The "Kashiwagi patent" discloses the use of a magnetic paint layer comprising non-spherical magnetic particles in a paint medium. A magnetic field having lines of magnetic force formed in the shape of a desired pattern is applied to the paint layer. The final pattern is formed by various magnetic particle orientations in the hardened paint.</p><p>An attempt to incorporate a magnetic layer into a multilayer flake is disclosed in European Patent Publication No. EP 686,675 B1 (Schmid et al.) (hereinafter referred to as "Schmid"), which includes a magnetic layer between a dielectric layer and a central aluminum layer. Laminar color shifting structures are described comprising:</p><p>oxide layer/absorption layer/dielectric layer/magnetic layer/Al layer/magnetic layer/dielectric layer/absorption layer/oxide layer.</p><p>That is, "Schmid" uses a piece of aluminum plate, and the plate piece is coated with a magnetic material. However, since aluminum is the second brightest metal (after silver) and any magnetic material is less reflective than that, the magnetic material covering the aluminum layer degrades the reflective properties of the pigment. Also, the "Schmid" issue starts with a piece of aluminum sheet produced from a ballmilling process, which limits the smoothness of the layer that can be obtained in this way.</p><p>European Patent Publication EP 710,508 A1 (Richter et al.) (hereinafter referred to as "Richter") discloses a method for providing a three-dimensional effect by drawing with magnetic tips. The "Richter" issue describes the three-dimensional effect achieved by aligning magnetically active pigments in a spatially varying magnetic field. "Richter" refers to barium ferrite, strontium ferrite, samarium/cobalt, Al/Co/Ni alloy, and manufactured by sintering and rapid quenching. Use standard pigments that do not consist of optical thin film stacks, such as metal oxides. Rather, the particles are of a hard magnetic type. "Richter" uses electromagnetic pole pices on top of the coating or on both sides of the coating. However, the "Richter" arc uses a moving system and requires "drawing" of the image. Such drawing is time consuming and not suitable for mass production processes.</p><p>U.S. Patent No. 3,791,864 (Steingroever) (hereafter referred to as "Steingroever") discloses, by orienting magnetic particles in a magnetic pattern generated in an underlying primary coat that has been pre-patterned by a magnetic field. A method for patterning magnetic particles is disclosed. Base coating is MO x 6Fe<sb>2</sb>O<sb>3</sb> It contains magnetic particles in the form of, in the above formula, M may be one or more elements selected from Ba, Sr, Co and Pb. After coating a continuous sheet of liquid coating of primer, it is allowed to harden, and then the area of the primer is magnetized with a magnetic field. Next, a pigment vehicle in which magnetic particles are suspended is applied. The magnetic particles suspended therein are finally oriented by the magnetic force generated in the magnetic pattern of the primer to form the final pattern. However, the "Steingroever" issue has the problem that a diffuse magnetic image is generated in the base coating, which in turn forms a diffuse image in the top coating. This reduction in resolution occurs because the resolution that a strong magnetic field can produce is limited. This limitation appears because strong lines of magnetic force surround the desired magnetic image and thus affect untargeted magnetic particles of the underlying coating, eventually blurring the image.</p>

<solutionproblem><p>Accordingly, there is a need for improved multilayer pigment flakes and foils with magnetic properties that can overcome or avoid the problems and limitations described above. </p></solutionproblem><meansproblemsolution><p>In one embodiment of the present invention, a pigment flake and foil having magnetic properties are provided. The pigment flakes may have a coating structure stacked symmetrically on both sides of a magnetic core layer, and may have an asymmetric coating structure in which all layers are located on one side of the magnetic layer, or It may be formed with one or more coatings wrapped around the core. The coating structure of the flakes and foils includes at least one magnetic layer and optionally one or more of a reflective layer, a dielectric layer, and an absorbing layer. In a color change embodiment of the present invention, the coating structure comprises a dielectric layer overlying the magnetic layer and the reflective layer, and an absorbing layer overlying the dielectric layer. A color change embodiment of the present invention provides a magnetic layer between two reflective layers or surrounded by a reflective layer, a magnetic layer between two dielectric layers or surrounded by a dielectric layer, a dielectric layer between two magnetic layers or surrounded by a magnetic layer, and It does not include a magnetic layer surrounded by a colorant layer. </p><p>The color change embodiment of the present invention exhibits discontinuous color change such that a first color is obtained at a first angle of the incident light or line of sight and a second color that is different from the first color is obtained at a second angle of the incident light or line of sight. The pigment flakes can be dispersed in a liquid medium, such as a paint or ink, to form a colorant composition that can be applied to an object or paper. The foils may be laminated on various objects and may be formed on a carrier substrate.</p><p>These and other features of the present invention will become more apparent from the following detailed description and claims, or may be learned in detail through the examples of the present invention set forth below. </p><p>In order to explain the advantages and features of the present invention mentioned above and the manner in which other advantages and features of the present invention are obtained, a more specific description of the present invention, briefly set forth above, is provided with reference to the specific embodiments shown in the accompanying drawings. , will be expressed It is to be understood that these drawings depict only typical embodiments of the present invention and are therefore not to be regarded as limiting the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be described and explained more specifically and in detail through the accompanying drawings.</p></meansproblemsolution><effectiveness><p>Some embodiments of the pigment flakes and foils of the present invention exhibit discontinuous color changes resulting in distinct colors at different angles of incident light or line of sight. The pigment flakes of the present invention can be dispersed in a liquid medium such as a paint or ink, thereby forming a colorant composition that can be applied to an object or paper. The foil of the present invention may be laminated to various objects or formed on a carrier substrate.</p></effectiveness>

<p>The present invention relates to multilayer pigment flakes and multilayer pigment foils having magnetic layers, and a pigment composition comprising said magnetic flakes. The flakes and foils can be used to form security features that are not visually perceptible to a security device and also to form a three-dimensional image, or to add decorative features to an article. The non-visual security feature is provided by burying a magnetic layer between the foil or other layers within the foil, leaving only the overlying layer exposed.</p><p>The three-dimensional effect can be provided by exposing the flakes or foils to external magnetic forces and thus orienting some pigments in a plane perpendicular to the surface of the coating. Non-oriented pigments lie along their planar surface parallel to the surface of the coating. The three-dimensional effect is due to the alignment of the particles, such that the aspect ratio is oriented according to the magnetic field, ie the longest part of the pigment is aligned along the magnetic field lines. In such a case, the surface of the pigment deviates from the observer's line of sight, the degree of which depends on the magnitude of the magnetic force. In the case of marginal or maximum orientation, the coating appears black. As it moves away from black, it gradually changes towards the color of the flat surface of the pigment. That is, color shifting, non-color shifting, such as blue or silver such as aluminum, for example, occurs. The result is a colored, three-dimensional effect, similar to the holographic effect, which appears to move with changing viewing angles. The method for forming a three-dimensional image using the magnetic pigment disclosed in the present invention includes an attorney docket No. of 13676.167 and "Methods for manufacturing an article having an imaged coating using a magnetic pigment (Methods)" For Producing Imaged Coated Articles By Using Magnetic Pigments), the disclosure of which is incorporated herein by reference.</p><p>Unlike many conventional magnetic flakes, the flakes disclosed herein do not consist solely of magnetizable materials, but include both magnetizable and non-magnetizable materials. For example, the present invention encompasses pigment flakes in which a magnetic layer is embedded within one or more reflective layers. In another embodiment, the pigment flakes comprise a magnetic core surrounded by a dielectric layer. In another embodiment, the pigment flakes comprise a dielectric core surrounded by a magnetic layer.</p><p>In the case of a magnetic layer embedded in or between overlying reflective layers, the present invention provides a significant improvement over the prior art by achieving substantially higher chroma and brightness. By locating the hazy magnetic material in the reflective layer, the present invention achieves two objectives. First, the reflectivity of the reflective layer is maintained, and second, the observer cannot distinguish a color change pigment without an inner core of magnetic material from those pigments having a core of magnetic material. For example, two coated articles viewed side-by-side will appear identical to the viewer, even if one has a magnetic material in the coating and the other does not. However, magnetic color-changing pigments provide concealed security features along with a color-changing effect. Thus, when applied to a magnetic detection system, the magnetic concealed signature written in the pigment can be read, for example by means of a Faraday rotator detector. </p><p>In various embodiments of the present invention, the pigment flakes and foils exhibit significant changes in chroma and hue with changes in the angle of the incident light or the viewing angle of the observer. Such an optical effect, known as goniochromaticity or "color shift", causes the perceived color to change with illumination or viewing angle. Accordingly, such pigment flakes and foils exhibit a first color at a first angle of incident light or line of sight and a second color that is different from the first color at a second angle of incident light or line of sight. Pigment flakes, such as paints or inks, can be dispersed in a liquid medium to form various color-changing colorant compositions, which can be applied to objects or paper. The foil may be laminated to various objects, or it may be formed on a carrier substrate.</p><p>In general, the color change pigment flakes may have a coating structure stacked symmetrically on both sides of a magnetic core layer, and may have an asymmetric coating structure in which most of the layers are located on one side of the magnetic layer. , or may be formed in a form having one or more encapsulating coatings surrounding the magnetic core layer. The foil and foil coating structures generally include a magnetic core, which includes a magnetic layer and other optional layers, i.e., a dielectric layer overlying the magnetic core, and an absorbing layer overlying the dielectric layer.</p><p>The color-changing flakes and foils of the present invention may be formed using conventional thin film forming techniques well known in the art of forming thin film coating structures. Non-limiting examples of such thin film formation techniques include physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma enhanced (PE) variants thereof (eg, PECVD, downstream PECVD), sputtering, electrolysis deposition, and other similar deposition methods capable of forming discrete, uniform thin film layers.</p><p>The color change pigment flakes of the present invention may be formed by various manufacturing methods. For example, pigment flakes are formed by sequentially depositing various layers on a web material by a conventional deposition technique to form a thin film structure, then crushing the thin film structure, and using a solvent such as , removed from the web to form a plurality of thin film flakes, and may be formed by a web coating process.</p><p>In another manufacturing method, one or more thin layers comprising at least a magnetic layer are deposited over a web to form a film, which is then crushed and removed from the web to form a plurality of pigment preflakes. If desired, these preflakes can be further crushed by grinding. At this time, the preflakes are coated with the remaining layers or layers in a subsequent encapsulation process to form a plurality of pigment flakes. A similar process is disclosed in more detail in US Patent Application Serial No. 09/512,116, filed on February 24, 2000, the contents of which are incorporated herein by reference.</p><p>In another manufacturing method, magnetic particles are coated in a sequential encapsulation process to form a plurality of pigment flakes. Where an encapsulating process is used to form the outer layers of flakes, each encapsulating layer will be a continuous layer of one material and of substantially equal thickness across the flake structure. will keep In some embodiments of the present invention, the encapsulation layer may be a colored dielectric material layer or an organic layer to which a pigment is added.</p><p>In the following with reference to the drawings, the same structural components are denoted by the same numbers, and the accompanying drawings show only the structures necessary for understanding the present invention. 1 shows a reflective magnetic flake (RMF) 20 according to one embodiment of the present invention. The RMF 20 is of a three-layer design with a schematically symmetric thin film structure, with a magnetic layer 22 at its center, and at least located on one or both major surfaces of the central magnetic layer. It has one reflective layer. Thus, the RMF 20 includes a magnetic layer interposed between the reflective layer 24 and the opposite reflective layer 26 . By interposing a magnetic layer between high-reflectance reflective layers, such as aluminum, the optical properties of the reflective layer are not deteriorated, and the reflective performance of the flakes is kept high. The RMF 20 can be used as a pigment flake, or it can be used as a core section to which an additional layer is applied, such as in color change pigments. In the case of color change pigments, maintaining a highly reflective layer is very important for maintaining high luminance and saturation. Each of these layers in the coating structure RMF 20 is discussed in more detail below.</p><p>The magnetic layer 22 may be formed from any magnetic material such as nickel, cobalt, iron, gadolinium, terbium, dysprosium, erbium, and alloys or oxides thereof. For example, a cobalt-nickel alloy may be used, and in this case, the weight percent of cobalt and nickel may be about 80 and about 20, respectively. These weight percentages for each of these metals in the cobalt-nickel alloy can vary by about ±10 weight percent, with still desirable results obtained. Thus, cobalt may be present in the alloy in an amount from about 70 to about 90 weight percent, and nickel may be present in the alloy in an amount from about 10 to about 30 weight percent. Other examples of alloys include Fe/Si, Fe/Ni, Fe/Co, Fe/Ni/Mo, and combinations thereof. SmCo<sb>5</sb>, NdCo<sb>5</sb>, Sm<sb>2</sb>Co<sb>17</sb>, Nd<sb>2</sb>Fe<sb>14</sb>B, Sr<sb>6</sb>Fe<sb>2</sb>O<sb>3</sb>, TbFe<sb>2</sb>, Al-Ni-Co, and combinations thereof can also be used, as well as Fe<sb>3</sb>O<sb>4</sb>, NiFe<sb>2</sb>O<sb>4</sb>, MnFe<sb>2</sb>O<sb>4</sb>, CoFe<sb>2</sb>O<sb>4</sb>Spinel ferrites of the same kind, or garnets of the same kind as YIG or GdIG, and combinations thereof may also be used. The magnetic material may be selected with reference to magnetic properties as well as reflection or absorption properties. When used to function as a reflector, the magnetic material is deposited to a thickness that renders it substantially opaque. When used as an absorber, the magnetic material is deposited to a thickness such that it is not substantially opaque. Typical thicknesses of magnetic materials when used as absorbers are from about 2 nm to about 20 nm.</p><p>Although this wide range of magnetic materials can be used, soft magnets are more preferred in some embodiments of the present invention. As used herein, the term "soft magnets" refers to any material that exhibits ferromagnetic properties, but whose remanence becomes substantially zero after exposure to a magnetic force. means the material of Soft magnetic materials show a fast response to an applied magnetic field, but have a magnetic signature that is very low (coercive fields (Hc) = 0.05 ~ 300 Oe(Oersteds)) or zero, or a magnetic field. After this is removed, it maintains a very low magnetic field line. Likewise, as used herein, the term "hard magnets" (also called permanent magnets) refers to any material that exhibits ferromagnetic properties and retains its residual magnetism long after exposure to magnetic forces. . A ferromagnetic material refers to a material exhibiting magnetic hysteresis properties as well as having a permeability substantially greater than 1.</p><p>The magnetic material used to form the flakes and magnetic layers of the foils of the present invention preferably has a coercive force of less than about 2000 Oe, more preferably less than about 300 Oe. Coercive force refers to the ability of a material to be demagnetized by an external magnetic field. The higher the value of the coercive force, the higher the magnetic field required to demagnetize the material after the magnetic field is removed. The magnetic layer used in some embodiments of the present invention is preferably a soft magnetic material (a material that is easily demagnetized), as opposed to a hard magnetic material having a higher coercive force (a material that is difficult to demagnetize). The coercive force of the foils, pigments or colorants of the magnetic color change design according to the present invention preferably ranges from about 50 Oe to about 300 Oe. This coercive force is lower than that of standard recording materials. Thus, a preferred embodiment of the present invention using a soft magnetic material for magnetic color shifting pigments and magnetic non color shifting pigments is a significant improvement over the prior art. If a soft magnetic material is used for the pigment flakes, the flakes can be more easily dispersed without clumping.</p><p>The magnetic layer 22 may be formed to have a suitable physical thickness in the range of about 200 Å to about 10,000 Å, preferably in the range of about 500 Å to about 1,500 Å. However, as will be appreciated by those skilled in the art upon consideration of the disclosure herein, the optimum magnetic layer thickness will vary depending upon the specific magnetic material used and the intended purpose of use. For example, based on the optical requirements for the absorbing and reflective layers, the magnetic absorbing layer will be thinner than the magnetic reflective layer, but the covert magnetic layer will have a thickness based solely on its magnetic properties.</p><p>The reflective layer 24 and the reflective layer 26 may be made of various reflective materials. In the present invention, the preferred material is one or more metals, one or more metal alloys, or a combination thereof because these materials have high reflectivity and are easy to use. However, non-metallic reflective materials may also be used. Non-limiting examples of suitable metallic materials for use in the reflective layer include aluminum, silver, copper, gold, platinum, tin, titanium, palladium, nickel, cobalt, rhodium, niobium, chromium, and combinations or alloys thereof. These can be selected based on the desired f. Reflective layer 24 and reflective layer 26 may be formed to have an appropriate physical thickness in the range of about 400 Angstroms to about 2,000 Angstroms, preferably in the range of about 500 Angstroms to about 1,000 Angstroms.</p><p>In another embodiment, two opposing dielectric layers may optionally be added, overlying the reflective layer 24 and the reflective layer 26 . These two opposing dielectric layers increase the durability, rigidity, and corrosion resistance of the RMF 20 . Alternatively, an encapsulating dielectric layer may be formed to substantially surround the reflective layer 24 , the reflective layer 26 , and the magnetic layer 22 . The dielectric layer may optionally be transparent, or may optionally be absorbent to contribute to the color effect of the pigment flakes. Examples of suitable dielectric materials used for the dielectric layer are described below.</p><p>2 shows a magnetic color changing pigment flake 40 based on RMF according to an embodiment of the present invention. Flakes 40 are generally symmetrical multilayer thin film structures with layers positioned on either side of RMF 42 . Thus, the first dielectric layer 44 and the second dielectric layer 46 are disposed on both sides of the RMF 42, respectively, and the first and second absorber layers 48 and 50 are respectively the dielectric layer 44 and the dielectric layer ( 46) is placed above. The RMF is as previously discussed with respect to FIG. 1 , and the dielectric and absorbing layers are described in more detail below.</p><p>Dielectric layer 44 and dielectric layer 46 act as spacers within the thin film stack structure of flakes 40 . These layers are formed to have an optical thickness effective to impart an interference color and desired color change properties. This dielectric layer may optionally be transparent, or may optionally be absorbent so as to contribute to the coloring effect of the pigment. Optical thickness, a well-known optical parameter, is defined as the product of η and d, ie ηd , where η is the refractive index of the layer and d is the physical thickness of the layer. Typically, the optical thickness of a layer is expressed in terms of quater wave optical thickness (QWOT), where QWOT is equal to 4 ηd/λ, where λ is the wavelength at which the QWOT condition occurs. The optical thickness of the dielectric layer may range from about 2 QWOT at a design wavelength of about 400 nm to about 9 QWOT at a design wavelength of about 700 nm, more preferably at 400-700 nm, depending on the desired color change effect. It can have a range of 2 to 6 QWOT. The dielectric layer typically has a physical thickness of from about 100 nm to about 800 nm, depending on the desired color properties.</p><p>Suitable materials for use in dielectric layer 44 and dielectric layer 46 include those having a "high" index of refraction, defined herein as greater than about 1.65, as well as a "low" index of refraction, defined herein as less than or equal to about 1.65. Included are those with Each of the dielectric layers may be formed of a single material, or may have various combinations and arrangements of materials. For example, the dielectric layer may be formed only of a low refractive index material, may be formed only of a high refractive index material, may be formed of a mixture or multilayer sublayer of two or more low refractive index materials, or may be formed of two or more high refractive index materials. It may be formed as a mixture or multilayer sublayer, or as a mixture or multilayer sublayer of a low refractive index material and a high refractive index material. Further, the dielectric layer may be formed, in part or in whole, in a high/low dielectric optical stack, as discussed in more detail below. Where the dielectric layer is formed in part into a dielectric optical stack, the remainder of the dielectric layer may be formed from a single material or from a combination and arrangement of various materials as described above. </p><p>Examples of suitable high refractive index materials for use in dielectric layers include zinc sulfide (ZnS), zinc oxide (ZnS), zirconium oxide (ZrO).<sb>2</sb>), titanium dioxide (TiO<sb>2</sb>), diamond-like carbon, indium oxide (In<sb>2</sb>O<sb>3</sb>), indium-tin-oxide (ITO), tantalum pentoxide (Ta<sb>2</sb>O<sb>5</sb>), cerium oxide (CeO<sb>2</sb>), yttrium oxide (Y<sb>2</sb>O<sb>3</sb>), europium oxide (Eu<sb>2</sb>O<sb>3</sb>), (II) diiron(III) oxide (Fe<sb>3</sb>O<sb>4</sb>) and ferric oxide (Fe<sb>2</sb>O<sb>3</sb>) such as iron oxides, hafnium nitride (HfN), hafnium carbide (HfC), hafnium oxide (HfO)<sb>2</sb>), lanthanum oxide (La<sb>2</sb>O<sb>3</sb>), magnesium oxide (MgO), neodymium oxide (Nd)<sb>2</sb>O<sb>3</sb>), praseodymium oxide (Pr<sb>6</sb>O<sb>11</sb>), samarium oxide (Sm<sb>2</sb>O<sb>3</sb>), antimony trioxide (Sb<sb>2</sb>O<sb>3</sb>), silicon monoxide (SiO), selenium trioxide (Se<sb>2</sb>O<sb>3</sb>), tin oxide (SnO<sb>2</sb>), tungsten trioxide (WO<sb>3</sb>), combinations thereof, and the like. </p><p>An example of a suitable low refractive index material for use in the dielectric layer is silicon dioxide (SiO2).<sb>2</sb>), aluminum oxide (Al<sb>2</sb>O<sb>3</sb>), magnesium fluoride (MgF<sb>2</sb>), aluminum fluoride (AlF<sb>3</sb>), cerium fluoride (CeF<sb>3</sb>), lanthanum fluoride (LaF<sb>3</sb>), sodium aluminum fluoride (e.g., Na<sb>3</sb>AlF<sb>6</sb> or Na<sb>5</sb>Al<sb>3</sb>F<sb>14</sb>), neodymium fluoride (NdF<sb>3</sb>), samarium fluoride (SmF<sb>3</sb>), barium fluoride (BaF<sb>2</sb>), calcium fluoride (CaF<sb>2</sb>), metal fluorides such as lithium fluoride (LiF), combinations thereof, any other low refractive index material having an index of refraction of about 1.65 or less, and the like. For example, organic monomers and polymers may be used as the low refractive index material, such as dienes such as acrylates (eg, methacrylates), perfluoroalkenes, or the like. alkenes, polytetrafluoroethylene (Teflon), fluorinated ethylene propylene (FEP), combinations thereof, and the like.</p><p>It should be noted that, depending on the specific method used to form the dielectric material as a coating layer, sometimes some of the dielectric materials listed above are typically in non-stoichiometric form, and that The point is that the name of a compound is an approximate stoichiometric notation. For example, silicon monoxide and silicon dioxide have nominal silicon:oxygen ratios of 1:1 and 1:2, respectively, but the actual silicon:oxygen ratio of a particular dielectric coating layer varies somewhat from these nominal values. Such non-stoichiometric dielectric materials are also within the scope of the present invention.</p><p>As previously mentioned, the dielectric layer may be formed into a high/low dielectric optical stack, which has alternating layers of low-index (L) and high-index (H) materials (i.e., the stack). In this case, layers made of a low-refractive-index material and layers made of a high-refractive-index material are alternately stacked). When the dielectric layers are formed in a high/low dielectric stack, the color change with angle depends on the composite refractive index of the layers in the stack. Examples of stack structures suitable for dielectric layers include LH, HL, LHL, HLH, HLHL, LHLH, (LHL)<sp>n</sp> or (HLH)<sp>n </sp>(At this time, there are those expressed by the general formula of n = 1 to 100), various repetitions and combinations thereof, and the like. In such a stack, for example, LH denotes discontinuous layers of low and high refractive index material. In another embodiment, the high/low dielectric stack may be formed to have a gradient index of refraction. For example, the refractive index of the layers constituting the stack increases from low to high, decreases from high to low, [low to high to low]<sp>n </sp>(n=1~100), [High~Low~High]<sp>n </sp>(n=1-100), or repeats and combinations thereof, can form gradients. Such a refractive index gradient may be formed by a gradual change in refractive index of adjacent layers, such as a low refractive index to a high refractive index or a high refractive index to a low refractive index. The refractive index gradient of the layers is formed by changing the gases during deposition, or by co-depositioning two materials (eg, L and H) in different ratios. can be For the pigments of the present invention, various high/low optical stacks can be used to enhance color change performance, provide antireflective properties to the dielectric layer, and change the color space possible.</p><p>Each of the dielectric layers may be made of the same material, may be made of different materials, and may have the same or different optical or physical layer thicknesses. If the dielectric layers are made of different materials or have different thicknesses, the flakes will exhibit a different color on each of their two sides, and when such flakes are mixed in a pigment or paint mixture, a new color that is a combination of the two colors is produced. will appear The resulting color will be based on the additive color theory of the two colors coming from both sides of the flake. If multiple flakes are used, the resulting color will be the sum of the two colors resulting from the random distribution of flakes with different sides facing the viewer.</p><p>Absorbent layer 48 and absorber layer 50 of flake 40 may be made of any absorptive material having desired absorption properties, including materials that absorb uniformly or non-uniformly in the visible region of the electromagnetic spectrum. Included. Thus, a selectively absorbent material or a non-selectively absorbent material may be used, depending on the desired color properties. For example, the absorbent layer may be formed of a non-selectively absorptive metallic material deposited to a thickness that renders the absorbent layer at least partially absorptive or semi-opaque. Non-limiting examples of suitable absorbent materials include metal absorbers such as chromium, aluminum, nickel, silver, copper, palladium, platinum, titanium, vanadium, cobalt, iron, tin, tungsten, molybdenum, rhodium, and niobium, as well as these metals. of oxides, sulfides, carbides, and the like. Other suitable absorbent materials include, but are not limited to, carbon, graphite, silicon, germanium, cermet, ferric oxide or other metal oxides, metals mixed in a dielectric matrix, other materials capable of acting as a uniform or selective absorber for the visible spectrum; etc. Various combinations, mixtures, composites, or alloys of the above absorbent materials may be used to form the absorbent layer of flake 40 .</p><p>Examples of suitable alloys of the absorbent material include Inconel (Ni-Cr-Fe), stainless steel, Hastalloys (eg, Ni-Mo-Fe; Ni-Mo-Fe-Cr; Ni-Si). -Cu), titanium mixed with carbon (Ti/C), titanium mixed with tungsten (Ti/W), titanium mixed with niobium (Ti/Nb), and titanium mixed with silicon (Ti/Si) titanium-based alloys, combinations thereof, and the like. As mentioned previously, the absorbent layer may also be made of an absorptive metal oxide, a metal sulfide, a metal carbide, or a combination thereof. For example, a preferred absorbent sulfide material is silver sulfide. Other examples of suitable compounds for use in the absorber layer include titanium nitride (TiN), titanium oxynitride (TiN).<sb>x</sb>O<sb>y</sb>), titanium carbide (TiC), titanium nitride carbide (TiN)<sb>x</sb>C<sb>z</sb>), titanium oxynitride carbide (TiN)<sb>x</sb>O<sb>y</sb>C<sb>z</sb>), titanium silicide (TiSi<sb>2</sb>), titanium boride (TiB<sb>2</sb>), such as titanium-based compounds, combinations thereof, and the like. TiN<sb>x</sb>O<sb>y </sb>with TiN<sb>x</sb>O<sb>y</sb>C<sb>z </sb>In the case of , preferably, x = 0 to 1, y = 0 to 1, z = 0 to 1, and TiN<sb>x</sb>O<sb>y </sb>In x+y= 1, TiN<sb>x</sb>O<sb>y</sb>C<sb>z </sb>where x+y+z = 1. TiN<sb>x</sb>C<sb>z</sb>In the case of , preferably x = 0 to 1, z = 0 to 1, and x+z = 1. Alternatively, the absorption layer may be made of a titanium-based alloy disposed in a Ti matrix, or may be made of Ti disposed in a titanium-based alloy matrix.</p><p>As will be appreciated by those skilled in the art, the absorber layer may also be formed of a magnetic material such as a cobalt-nickel alloy. This simplifies the manufacture of the magnetic color changing device or structure by reducing the number of materials required.</p><p>The absorber layer may be formed to have a physical thickness ranging from about 30 Å to about 500 Å, preferably from about 50 Å to about 150 Å, depending on the optical constants of the absorbing layer material and the desired maximum change. Each of the absorption layers may be made of the same material or different materials, and may have the same or different physical layer thicknesses.</p><p>In another embodiment of the flake 40, an asymmetric color change flake is provided comprising a thin film stack structure having the same layers disposed on one side of the RMF 42 shown in FIG. Accordingly, the asymmetric color change flake includes an RMF 42 , a dielectric layer 44 overlying the RMF 42 , and an absorbing layer 48 overlying the dielectric layer 44 . Each of these layers may be made of a material as previously described for the corresponding layers of flake 40 and may have such a thickness. In addition, the asymmetric color change flakes can be formed by a web coating process as described above, in which several layers are sequentially deposited on a web material to form a thin film structure, and then the thin film structure is crushed. and removed from the web to form a plurality of flakes.</p><p>In another embodiment of the present invention, the flakes 40 may be formed without an absorbent layer. In this embodiment, opposing dielectric layers 44 and 46 are formed from a high/low (H/L) dielectric optical stack as previously described. Thus, the dielectric layer 44 and the dielectric layer 46 can be arranged such that the flake 40 has a coating structure as follows: (HL)<sp>n</sp>/RMF/(LH)<sp>n</sp>, (LH)<sp>n</sp>/RMF/(HL)<sp>n</sp>, (LHL)<sp>n</sp>/RMF/(LHL)<sp>n</sp>, (HLH)<sp>n</sp>/RMF/(HLH)<sp>n</sp>, or other similar configuration, where n is 1-100 and the L and H layers are 1 QW (quarterwave) at the design wavelength.</p><p>3 shows a reflective magnetic flake or particle ("RMP") 60 according to another embodiment of the present invention. The RMP 60 is of a two-layer design with a reflective layer 62 that substantially surrounds a central magnetic layer 64 to form a capsule. By inserting the magnetic layer in the reflective layer, the optical properties of the reflective layer are not deteriorated, and the reflective layer maintains high reflective performance. The RMP 60 can be used as a pigment particle, or it can be used as a core to which additional layers are applied. The magnetic layer and the reflective layer may be made of materials such as those discussed with respect to RMF 20 .</p><p>In another embodiment of the present invention, a dielectric layer may optionally be added overlying the reflective layer 62 , thereby increasing the durability, stiffness, and corrosion resistance of the RMP 60 . The dielectric layer may optionally be clear and transparent, or may optionally be absorbent in order to contribute to the color effect of the pigment flakes.</p><p>4 shows another coating structure (indicated by phantom lines) for magnetic color changing pigment flakes 80 in the form of capsules based on RMF or RMP, according to another embodiment of the present invention. show Flake 80 has a magnetic core section 82 of RMF or RMP, which may be coated by a dielectric layer 84 in the form of an encapsulation, thus dielectric layer 84 . to substantially surround the magnetic core portion 82 . Absorbent layer 86, overcoating dielectric layer 84, provides an outer encapsulation of flake 80. In FIG. 4 , a hemispherical dotted line positioned on one side of the flake 80 indicates that the dielectric layer 84 and the absorbing layer 86 may be formed as a continuous layer around the magnetic core portion 82 .</p><p>Alternatively, the magnetic core portion 82 and the dielectric layer may take the form of a thin core flake stack, in which case opposing dielectric layers 84a and 84b are preformed over the top and bottom surfaces, but the magnetic core Absorbing layer 86 surrounds the thin film stack without being formed over at least one surface of portion 82 (RMF). The encapsulation process may also be used to form additionally disposed layers over the lamella 80 , such as a capping layer (not shown). Pigment flakes 80 exhibit a discontinuous color change such that the pigment flakes have a first color at a first angle of incident light or line of sight and a second color that is different from the first color at a second angle of incident light or line of sight.</p><p>In another embodiment, the lamella 80 may be formed without an absorbent layer. In this embodiment, dielectric layer 84 is formed of a continuous high/low (H/L) dielectric optical coating, similar to the dielectric optical stack previously described. Thus, the dielectric layer 84 may have a coating structure as follows: (HL)<sp>n</sp>, (LH)<sp>n</sp>, (LHL)<sp>n</sp>, (HLH)<sp>n</sp>, or other similar configuration, where n = 1-100 and the L and H layers are 1 QW at the design wavelength. </p><p>5 shows another coating structure for a color change pigment flake 100 according to the present invention. Flake 100 includes a magnetic core portion 82 and a single dielectric layer 84, the single dielectric layer 84 extending over the top and bottom surfaces of the magnetic core portion 82 such that the dielectric layer coated preflakes ( 86) is formed. The core part 82 may be an RMF, an RMP, or a magnetic layer. The dielectric layer coated preflake 86 has two sides 88 , 90 . The side surface 90 is homogeneous and formed only of the dielectric material of the dielectric layer 84, and the side surface 88 has a distinct surface area 88a, each of a dielectric material, a magnetic core portion, and a dielectric material, respectively. , a surface area 88b and a surface area 88c. The dielectric layer coated preflakes 86 may be further coated with an absorbent layer 92, on all sides. The absorbing layer 92 is in contact with the dielectric layer 84 and the magnetic core portion 82 on the side surface 88 .</p><p>The structure of the pigment flakes 100 typically results from a preflake coating process similar to that disclosed in previously described US Patent Application Serial No. 09/512,116. The preflakes may be flakes coated with a dielectric layer, wherein the dielectric coating completely encapsulates the RMF or RMP (see FIG. 4 ). Alternatively, the magnetic layer is completely encapsulated (see FIG. 10). The preflakes are broken into sized preflakes using any conventional grinding process, such as grinding. Some of the sized preflakes have a dielectric coating on the sides of the preflakes, as shown for the flake 40 embodiment of FIG. 2 where RMF 42 is coated with top and bottom dielectric layers 44, 46. It has top and bottom dielectric layers without them. Another portion of the sized preflakes will have a single dielectric layer extending over the top and bottom surfaces of the magnetic core flakes, as shown for the dielectric layer coated preflakes 86 in FIG. One side of the magnetic core flake will be exposed. Due to the grinding process, substantially all, at least a portion of the sides of the sized preflakes are exposed. The sized preflakes are then coated with an absorbent layer on all sides, as shown in the flakes in FIGS. 4 and 5 .</p><p>6 shows a composite magnetic flake ("CMF") 120 comprising a central dielectric support layer 122 having a first magnetic layer 124 and a second magnetic layer 126 on their opposite major surfaces. ) is shown. By interposing a dielectric layer between the magnetic layers, the CMF 120 is highly stabilized and strengthened, resulting in an increased modulus of stiffness. An additional dielectric layer (not shown) may optionally be added to overly the magnetic layer 124 and the magnetic layer 126 . This additional dielectric layer increases the durability, stiffness, and corrosion resistance of the CMF 120 . The CMF 120 may be used as a pigment flake itself, or as a magnetic core portion on which additional layers are added. Magnetic layer 124 and magnetic layer 126 may be formed of any of the magnetic materials described above.</p><p>The dielectric material used for the support layer 122 is preferably an inorganic material. The reason is that dielectric inorganic materials have been found to have excellent properties related to brittleness and stiffness. Various dielectric materials that can be used include metal fluorides, metal oxides, metal sulfides, metal nitrides, metal carbides, combinations thereof, and the like. The dielectric material may be in a crystalline, amorphous, or semicrystalline state. These materials are readily available and can be easily applied by physical or chemical vapor deposition methods. Examples of suitable dielectric materials include magnesium fluoride, silicon monoxide, silicon dioxide, aluminum oxide, titanium dioxide, tungsten oxide, aluminum nitride, boron nitride, boron carbide, tungsten carbide, titanium carbide, titanium nitride, silicon nitride, zinc sulfide, glass flakes. , diamond-like carbon, combinations thereof, and the like. Alternatively, the support layer 122 may be formed of a natural slab mineral (eg, mica, peroskovite, talc, etc.), or glass, alumina, silicon dioxide, carbon, mica. High aspect ratios, such as synthetic platelet materials formed from micaeous iron oxide, coated mica, boron nitride, boron carbide, graphite, bismuth oxychloride, various combinations thereof, etc. It may consist of a preformed dielectric or ceramic preflake material having an aspect ratio. </p><p>In another embodiment, instead of the dielectric support layer 122, various semiconductor materials and various conductive materials having sufficient tensile to compressive strength ratios may serve as the support layer. Examples of such materials include silicon, metal silicides, semiconductor compounds formed from Group III, IV, or V elements, metals having a body-centered cubic crystal structure, cermet compositions or compounds, semiconducting glasses, various combinations thereof, etc. There is this. However, as will be appreciated from the disclosure herein, any support material that provides the functions described herein and is capable of acting as a rigid layer of glass-like quality may be accepted as a substitute for these materials.</p><p>The thickness of the support layer 122 may range from about 10 nm to about 1,000 nm, preferably from about 50 nm to about 200 nm, but is not necessarily limited to this range. </p><p>7 illustrates a composite magnetic particle ("CMP") 140 according to another embodiment of the present invention. CMP 140 is of a two-layer design with a magnetic layer 142 that substantially surrounds a central support layer 144, such as a dielectric layer, to form an encapsulation. By inserting the support layer within the magnetic layer, the CMP 140 is very stable and rigid. The support layer increases the stiffness and durability of the pigment flakes. The magnetic layer 142 may be formed of any of the magnetic materials described above. The support layer 144 may be formed from the same material as previously described for the support layer 122 of the CMF 120 . The CMP 140 may be used as the pigment particle itself, or may be used as a magnetic core portion on which additional layers are added. For example, an external dielectric layer may be added overlying the magnetic layer 142 to form a capsule. This outer dielectric layer increases the durability, stiffness, and corrosion resistance of the CMP 140 . </p><p>8 shows the coating structure for the color change pigment flakes 160 in the form of a capsule. Flake 160 has a thin core layer 162 , which may be formed of a dielectric or other material as previously disclosed for support layer 122 . The core layer 162 may be overcoated on all sides with a magnetic layer 164 , which may be formed of the same material previously disclosed for the magnetic layer 22 of the RMF 20 . Optionally, a reflective layer 168 may be added over the magnetic layer 164 . Suitable materials for use in the reflective layer 168 include materials that have been described for the reflective layer 24 of the RMF 20, and the like. The reflective layer effectively provides the reflective function of the lamella 160 and blocks the magnetic layer 164 from being optically visible. Core layer 162 and magnetic layer 164 may be provided as CMP 166 overcoated with another layer. Alternatively, the CMP 166 may be replaced by a CMF as shown in FIG. 6 . A dielectric layer 170 forming a capsule substantially surrounds the reflective layer 168 and the magnetic layer 164 . An absorbent layer 172 overlies the dielectric layer 170 and provides an outer encapsulation of the flake 160 .</p><p>A variety of coating processes can be used to form the dielectric and absorbent layers by encapsulation. For example, preferred methods suitable for forming the dielectric layer include vacuum vapor deposition, sol-gel hydrolysis, CVD in a fluidized bed (CVD), downstream plasma to a particle-filled vibrating tray. (downstream plasma onto vibrating trays filled with particles), electrochemical deposition, and the like. Suitable SiO<sb>2</sb> A sol-gel process is disclosed in US Pat. No. 5,858,078 (Andes et al.), the disclosure of which is incorporated herein by reference. Other examples of suitable sol-gel coating methods useful in the present invention are described in U.S. Patent Nos. 4,756,771 (Brodalla); "Probes and properties of aluminosilicate glass prepared by the sol-gel method (Zink et al., Optical Probes and Properties of Aluminosilicate Glasses Prepared by Sol-Gel Method, Polym. Mater. Sci. Eng., 61, pp.204-208 (1989))"; "Emission and laser action of coumarin dyes doped on silicate and aluminosilicate glass prepared by sol-gel method (McKiernan et al., Luminescence and Laser) Action of Coumarin Dyes Doped in Silicate and Aluminosilicate Glasses Prepared by the Sol-Gel Technique, J. Inorg. Organomet. Polym., 1(1), pp. 87-103 (1991)), etc. The disclosure is incorporated herein by reference. </p><p>Preferred methods suitable for forming the absorber layer include vacuum vapor deposition, and sputtering onto a mechanically vibrating bed of particles, which are published on Sept. 3, 1999, "Improved It is disclosed in U.S. Patent Application Serial No. 09/389,962, entitled "Methods and Apparatus for Producing Enhanced Interference Pigments," the entire disclosure of which is incorporated herein by reference. . Alternatively, the absorbent coating may be formed by decomposition via pyrolysis of metal-organo compounds, or by an associated CVD process that may be performed in a fluidized bed, such as Methods are disclosed in US Pat. Nos. 5,364,467 and 5,763,086 (Schmid et al.), the disclosures of which are incorporated herein by reference. If no additional grinding is performed, the result of these methods will be a core flake encapsulated in a dielectric and absorbent material. Various combinations of the coating methods described above can be used in the manufacture of pigment flakes with multiple encapsulation coatings.</p><p>In one method of forming an absorbent coating, flakes or other coated preflakes in powder form can be placed on a square vibrating conveyor in a vacuum coating chamber, as disclosed in previously discussed US Patent Application Serial No. 09/389,962. have. The vibratory conveyor coating apparatus includes conveyor trays configured in an overlapping inclined arrangement to cause the powdery flakes to move along a circulating path within the vacuum chamber. As the flakes cycle along this path, the flakes are effectively mixed by constant agitation, resulting in a uniform exposure to the vaporized absorbent coating material. Efficient mixing also occurs at the end of each conveyor tray as the flakes cascade from one tray to the next. As the flakes move repeatedly in the presence of a source of coating material, an absorbent material may be sequentially coated over the flakes. </p><p>When using a vibrating conveyor tray to coat an absorbent material, flakes in powder form are randomly tumbling in the presence of a source of coating material such as sputter targets, resulting in "metal welding". It is important not to become "or stuck. Such metal welding or sticking can occur between two planar surfaces of an active metal when the active metal is deposited under vacuum. For example, aluminum has a very high tendency to stick to one another, whereas chromium does not. A suitable absorbent material may be applied as a single material or as a combined material, or may be applied as an outer capping layer over other underlying absorbent materials.</p><p>9 shows a dielectric coated magnetic flake ("DMF") 180 according to another embodiment of the present invention. The DMF 180 is of a three-layer design with an overall symmetrical thin film structure, and has a central magnetic layer and at least one dielectric layer overlying either or both of the major opposing surfaces of the central magnetic layer. Thus, as shown, the DMF 180 includes a magnetic layer 182 interposed between a dielectric layer 184 and an opposing dielectric layer 186 . By interposing a magnetic layer between the dielectric layers, the DMF has increased stiffness and durability.</p><p>10 illustrates a dielectric coated magnetic particle ("DMP") 200 according to another embodiment of the present invention. The DMP 200 is of a two-layer design with a dielectric layer 202 that substantially surrounds a central magnetic layer 204 to form an encapsulation.</p><p>Each of the layers within the coating structures DMF 180 and DMP 200 may be formed of the same material and thickness as the corresponding layers as described in the previous embodiment. For example, the dielectric layers of DMF 180 and DMP 200 may be formed from a range of materials and thicknesses as previously disclosed for dielectric layer 44 of flake 40, DMF 180 and DMP 200. ) may be formed of the same material and in the same thickness range as previously disclosed for the magnetic layer 22 of the flake 20 . The DMF 180 and the DMP 200 may be used as pigment flakes or particles, respectively, and may be used as a magnetic core part on which additional layers are added.</p><p>11 shows a color change pigment flake 220 that does not use a reflective layer (which is highly reflective, ie made of optical metal), in another embodiment of the present invention. The flake 220 has a three-layer design having an overall symmetric multi-layer thin film structure positioned on both sides of the magnetic core portion 222 , and in this case, the magnetic core portion may be DMF or DMP. Thus, the first absorption layer 224a and the second absorption layer 224b are formed on the opposite major surfaces of the magnetic core portion 222 . These layers of flake 220 may be formed by a web coating and flake removal process as previously described.</p><p>FIG. 11 also shows another coating structure (indicated by phantom lines) for the color change flake 220, wherein the absorbent layer is coated around the magnetic core portion 222 by an encapsulation process. Thus, the absorbent layer 224a and the absorbent layer 224b are formed as part of a continuous coating layer 224 that substantially surrounds the flake structure therein.</p><p>Thus, the pigment flakes 220 may be implemented as multilayer thin film stack flakes or multilayer thin film encapsulated particles. Suitable materials and thicknesses for the absorber, dielectric, and magnetic layers of flake 220 are as previously disclosed.</p><p>Some of the flakes of the present invention have the layers lying on parallel planes such that the flakes have first and second parallel planar outer surfaces and also have edge thicknesses perpendicular to the first and second parallel planar outer surfaces. can be characterized as a multilayer thin film interference structure. Such flakes are prepared to have an aspect ratio of at least about 2:1, preferably 5-15:1, and a narrow particle size distribution. The aspect ratio of the lamella is determined by taking the ratio of the longest planar dimension to the edge thickness dimension of the first and second outer surfaces of the lamella.</p><p>In the present invention, one of the preferred methods for producing a plurality of pigment flakes each having a multilayer thin film coating structure of flakes 40 as shown in FIG. 2 is a conventional web coating technique used to produce optical thin films. based on Although lamella 40 is described below, other lamella structures disclosed herein may also be fabricated in a manner similar to that described below. According to this, a first absorbent layer is deposited over a web of a flexible material such as polyethylene terephthalate (PET), which web may optionally have a release layer thereon. The absorption layer may be formed by a conventional deposition method such as PVD, CVD, PECVD, sputtering, or the like. The aforementioned deposition method makes it possible to form a discontinuous and uniform absorption layer with a desired thickness.</p><p>A first dielectric layer is then deposited to the desired optical thickness over the absorber layer by conventional deposition methods. Deposition of the dielectric layer can be accomplished by vapor deposition methods (e.g., PVD, CVD, PECVD), in which the dielectric layer cracks when stress is applied as the dielectric material transitions from the gaseous state to the solid state. do.</p><p>Then, a magnetic core is deposited. If there is a reflective layer, then a first reflective layer is deposited over the first dielectric layer, by PVD, CVD, or PECVD, resembling the properties of the underlying broken dielectric layer. A magnetic layer is then added by e-beam evaporation, sputtering, electrodeposition, or CVD, and then a second reflective layer is deposited.</p><p>A second dielectric layer is then deposited over the second reflective layer, preferably having the same optical thickness as the first dielectric layer. Finally, a second absorber layer is deposited over the second dielectric layer, preferably having the same physical thickness as the first absorber layer.</p><p>The flexible web is then removed by dissolution with some liquid or by a delamination layer, all of which are well known to those skilled in the art. As a result, a plurality of flakes are crushed along the cracks of the layers during web removal from the multilayer membrane. This method of making pigment flakes is similar to that disclosed in detail in US Pat. No. 5,135,812 (Phillips et al.), the disclosure of which is incorporated herein by reference. The pigment flakes may be further milled, if desired, by, for example, grinding the flakes to a desired size using an air grind, such that each of the pigment flakes is from about 2 μm to about 2 μm. It will have dimensions on any surface in the range of 200 μm.</p><p>An annealing process may be used to impart additional durability to the color-changing flakes, wherein at a temperature ranging from about 200 to about 300 °C, preferably from about 250 to about 275 °C, from about 10 minutes to about 24 hours , preferably for a time ranging from about 15 minutes to about 60 minutes, the flakes are heat treated. </p><p>Other pigment flake structures, methods of their formation, and additional features compatible with them are described in "Phillips '648", U.S. Patent No. 4,705,356 (Berning et al.), and U.S. Patent No. 6,157,489 (Bradley et al. ), US Patent Application Serial Nos. 09/685,468 (Phillips et al.), 09/715,937 (Coombs et al.), 09/715,934 (Mayer et al.), 09/389,962 (Phillips et al.) .), 09/539,695 (Phillips et al.) et al., the disclosures of which are incorporated herein by reference. As will be appreciated by those skilled in the art from the present disclosure, the magnetic layers discussed above may be combined with the coating structures disclosed in the preceding patents and patent applications, for example, the reflective layer with the RMF or RMP disclosed herein. Substitution may additionally yield useful coating structures.</p><p>12 shows a pigment flake 240 formed in accordance with another embodiment of the present invention. As shown, the flakes 240 are of a multilayer design with a generally symmetrical thin film structure disposed on opposite sides of a magnetic layer, such as a reflective magnetic core 242 , which core is disclosed herein or is It may be any non-color shifting magnetic pigment flakes or particles with reflective properties known in the art. For example, the reflective magnetic core 242 may be a single reflective magnetic layer, such as a monolithic layer of Ni or other magnetic reflective metal, or a multi-layered magnetic structure such as Al/Fe/Al. A first colored layer such as the selective absorption layer 244a and a second colored layer such as the selective absorption layer 244b are formed on the two opposed major surfaces of the reflective magnetic core 242 . This colored layer of flake 240 may be formed by a web coating and flake removal process as previously described. </p><p>12 further shows another coating structure (indicated by phantom lines) for flake 240, wherein a colored layer, such as selective absorbing layer 244, is encapsulated around reflective magnetic core 242 through an encapsulation process. is coated on Accordingly, the selective absorbent layer 244a and the selective absorbent layer 244b are formed as part of a continuous coating layer 244 that substantially surrounds the flake structure therein. A suitable encapsulation method for forming flakes 240 is disclosed in U.S. Patent Application Serial No. 09/626,041, filed July 27, 2000, the disclosure of which is incorporated herein by reference.</p><p>Thus, the pigment flakes 240 may be implemented as multilayer thin film stack flakes or multilayer thin film encapsulated particles. Suitable materials and thicknesses used for the reflective magnetic core of flake 240 are as previously disclosed as long as the reflective and magnetic particles are maintained.</p><p>The colored layer of flake 240 may be formed of a variety of different absorptive and/or reflective materials in one or more layers. Preferably, the colored layer, such as the selective absorption layer, is formed to have a thickness of from about 0.05 μm to about 5 μm, more preferably from about 1 μm to about 2 μm, wherein an organic dye is used to form the selective absorption layer. Where applicable, conventional coating processes applied to dye materials may be used. Preferably, the colored layer is formed to have a thickness of about 0.05 μm to about 0.10 μm, and in this case, a metallic coloring material or other inorganic coloring agent is used.</p><p>Examples of suitable organic dyes that may be used to form the selective absorption layer of flake 240 include copper phthalocyanine, perylene-based dyes, anthraquinone-based dyes, and the like; aluminum red (RLW), aluminum copper, aluminum bordeaux (RL), aluminum fire-red (ML), aluminum red (GLW), aluminum violet (aluminum) azo dyes and azo metal dyes such as violet) (CLW), and the like; combinations or mixtures thereof, and the like. Such dyes can be applied by evaporation as well as conventional coating techniques.</p><p>The colored layer of flakes 240 may also be formed from a variety of conventional organic or inorganic pigments, applied alone or dispersed in a pigment vehicle. Such pigments are disclosed in "NPIRI Raw Materials Data Handbook, Vol. 4, Pigments (1983)", the disclosure of which is incorporated herein by reference.</p><p>In another embodiment, the selective absorbent layer of flake 240 comprises a sol-gel matrix carrying a colored pigment or dye. For example, the selective absorbent layer can be formed of aluminum oxide or silicon dioxide applied by a sol-gel process, with which organic dyes can be absorbed into the pores of the sol-gel coating or bonded to the surface of the coating. . Suitable organic dyes used in the sol-gel coating method include those available under the trade names "Aluminiumrot GLW (aluminium red GLW)" and "Aluminiumviolett CLW (aluminium violet CLW)" from Sandoz Company. Aluminum Red GLW is an azo metal complex containing copper, and Aluminum Violet CLW is a purely organic azo dye. Examples of sol-gel coating techniques useful in the present invention are disclosed in US Pat. Nos. 4,756,771 (Brodalla, 1988); "Probes and Properties of Aluminosilicate Glasses Prepared by Sol-Gel Method (Zink et al., Optical Probes and Properties of Aluminosilicate Glasses Prepared by Sol-Gel Method, Polym. Mater. Sci. Eng., 61, pp. 204-208 (1989))"; "McKiernan et al., Luminescence and Laser Action of Coumarin Dyes Doped in Silicate and Aluminosilicate Glasses Prepared by the Sol-Gel Technique, J. Inorg. Organomet. Polym., 1(1), pp. 87-103 (1991))"; the disclosures of these documents are incorporated herein by reference.</p><p>In another embodiment, the colored layer of the flakes 240 may be formed of an inorganic colorant. Suitable inorganic colorants include selective absorbers such as titanium nitride, chromium nitride, chromium oxide, iron oxide, cobalt doped alumina, and the like, as well as colored metals such as copper, brass, titanium, and the like.</p><p>It should be understood that various combinations of the aforementioned dyes, pigments, and colorants may be used to achieve the desired color properties for flake 240 . The organic dyes, pigments, and colorants discussed herein can be used in the present invention to obtain brightly colored pigments with magnetic properties.</p><p>Various modifications and combinations of the embodiments discussed above are also contemplated within the scope of the present invention. For example, additional dielectric layers, absorbing layers, and/or other optical coatings may be formed around each of the flake or particle embodiments described above, or over the composite reflective film prior to flake formation, to further obtain desired optical properties. can Such additional coatings may provide additional color effects to the pigments. For example, a colored dielectric coating applied to a color changing flake can act as a color filter on the flake, thus providing a subtractive color effect that changes the color produced by the flake. can do.</p><p>The pigment flakes of the present invention may be dispersed in a pigment medium, thereby forming a colorant composition that can be applied to various types of articles or papers. The pigment flakes added to the medium generate a desired optical response through the incident light beam on the surface of the solidified medium. Preferably, the pigment medium contains a resin or resin mixture which can be dried or cured by thermal methods such as thermal crosslinking, thermal curing, or thermal solvent evaporation, or by photochemical crosslinking. Useful pigment media include alkyd resins, polyester resins, acrylic resins, polyurethane resins, vinyl resins, epoxy resins, styrene resins. various polymer compositions or organic binders, such as (styrenes), and the like. Suitable examples of such resins include ink and paint formulations based on melamine, acrylates such as methyl methacrylate, ABS resins, alkyd resins, various mixtures thereof, and the like. The flakes combined with the pigment medium form a colorant composition that can be used directly as a paint, ink, or moldable plastic material. The colorant composition may be used as an additive to conventional paints, inks, or plastic materials.</p><p>In addition, the pigment medium preferably contains a solvent for the resin. As the solvent, in general, an organic solvent or water can be used. Volatile solvents may also be used in the medium. In the case of a volatile solvent, it is preferable to use a solvent having dilution as well as volatility, such as a thinner. In particular, faster drying of the pigment medium can be achieved by increasing the amount of a solvent having a low boiling point composition, such as methylethylketone (MEK).</p><p>In addition, the flakes can be optionally mixed with various additives such as conventional pigment flakes, particles, or dyes having different colors, chroma, and brightness to obtain the desired color properties. For example, the flakes can be mixed with other conventional pigments, either in an interfering form or in a non-interfering form, so that they can exhibit a range of different colors. This premix composition may be dispersed in a polymeric medium such as paint, ink, plastic or other polymeric pigment vehicle and used in a conventional manner.</p><p>As an example of a suitable additive that may be combined with the flakes of the present invention, MgF<sb>2</sb>/Al/MgF<sb>2</sb> slabs, or SiO<sb>2</sb>/Al/SiO<sb>2</sb> There is a colorless, high-saturation or high-reflectance plate engraving that exhibits a unique color effect, such as plate engraving. Other suitable additives that can be mixed with magnetic color change flakes include multilayer color change flakes, aluminum flakes, graphite flakes, glass flakes, iron oxide, boron nitride, mica flakes, interferometric TiO<sb>2</sb><sb></sb>lamellar pigments such as interference pigments based on coated mica flakes, multi-coated lamellar silicate-based materials, metal-dielectric or all-dielectric interference pigments, and the like; Aluminum powder, carbon black, ultramarine blue, cobalt pigment, organic pigment or dye, rutile or spinel-based inorganic pigment, naturally occurring pigment, titanium dioxide, talc, non-lamellar pigments such as inorganic pigments such as china clay and the like; various mixtures thereof, and the like. For example, pigments such as aluminum powder or carbon black may be added to adjust brightness and other color properties.</p><p>The magnetic color changing flakes of the present invention are particularly suitable for use in applications where colorants with high saturation and durability are desirable. By using the magnetic color-changing flakes in the colorant composition, paints or inks having high chroma and durability can be produced, and in this case, various color effects can be perceived by the human eye. The color change flake of the present invention has a wide range of color change characteristics including a large change in saturation (degree of color purity) and a large change in hue (relative color) according to a change in viewing angle. Thus, an article colored with a paint containing the color-changing flakes of the present invention will change color with a change in the viewing angle or angle of the article with respect to the viewing angle.</p><p>The pigment flakes of the present invention can be applied to paints and inks that can be applied to a variety of articles or papers, such as automobiles, currency, security documents, home appliances, buildings, floor coverings, textiles, sporting goods, electrical packaging/housing, product packaging, and the like. , can be used easily and economically. Color changing flakes can also be used to form colored plastic materials, coating compositions, extrudates, electrostatic coatings, glass, and ceramic materials.</p><p>In general, the foils of the present invention have an asymmetric thin film coating structure, which may correspond to the layer structure disposed on one side of the RMF as shown in the embodiments described above with respect to the thin film stack flakes. The foil may be laminated to various articles and may be formed on a carrier substrate. The foils of the present invention may also be used in a hot stamping configuration, in which a thin film stack of foils is removed from the release layer of the substrate and adhered onto the mating surface by the use of a thermally active adhesive. The adhesive may be coated on the surface of the foil opposite to the substrate, or applied in the form of a UV-activated adhesive to the surface to which the foil is to be adhered.</p><p>13 shows the coating structure of a color change foil 300 formed over a substrate 302, which may be any suitable material, such as a flexible PET web, a carrier substrate, or other plastic material. A suitable thickness for the substrate 302 is, for example, about 2 to 7 mils. The foil 300 includes a magnetic layer 304 positioned over the substrate 302 , a reflective layer 306 positioned over the magnetic layer 304 , a dielectric layer 308 positioned over the reflective layer 306 , and a dielectric layer 308 positioned over the dielectric layer 308 . and an absorption layer 310 . The magnetic layer, the reflective layer, the dielectric layer, and the absorbing layer may be of the same thickness and of the material as previously described with respect to the corresponding layers of flakes 20 and 40 .</p><p>The foil 300 may be formed by a web coating process, wherein the various layers described above are sequentially deposited on the web by a conventional deposition technique to form a thin film structure. Foil 300 may be formed over the detachment layer of the web, such that the foil can be subsequently removed and adhered to the surface of the article. The foil 300 may be formed on a carrier substrate, in this case, the carrier substrate may be a web without a release layer.</p><p>14 depicts one embodiment of a foil 320 disposed over a web 322 optionally having a desorption layer 324, wherein a magnetic layer 326, a reflective layer 328, and a dielectric layer 330 over the desorption layer. , and an absorption layer 332 are deposited. The foil 320 may be used while being attached to the web 322 as a carrier, in which case there is no need to use a detachment layer. Alternatively, the foil 320 may be laminated to a transparent substrate (not shown) via an optional adhesive layer 334 such as a transparent adhesive or UV curable adhesive, in which case a release layer is used. The adhesive layer 334 is attached to the absorbent layer 332 .</p><p>FIG. 15 shows another embodiment, wherein a foil 340 having a thin layer, such as foil 320 , is disposed over a web 322 having an optional desorption layer 324 . Foil 340 is formed such that an absorbent layer 332 is deposited over web 322 . The foil 340 may be used by being attached to the web 322 used as a carrier, wherein the web is preferably transparent, and the detachment layer is not used. The foil 340 may also be attached to a substrate, such as a counter surface 342, via an adhesive layer 334, such as a hot stampable adhesive, a pressure sensitive adhesive, a permanent adhesive, or the like. In this case, a desorption layer is used. The adhesive layer 334 may be attached to the magnetic layer 326 and/or the mating surface 342 .</p><p>When applied to a hot stamp, the optical stack of foil is disposed such that the optically outer surface is adjacent to the release layer. Thus, for example, when the foil 340 of FIG. 15 is detached from the web 322 , the absorption layer 332 is optically visible to the outside. In one preferred embodiment, the release layer 324 is a transparent hardcoat that stays over the absorbent layer 332 , protecting the underlying layers after transfer from the web 322 .</p><p>Further details regarding the manufacture and use of optical stacks as hot stamping foils are disclosed in US Pat. Nos. 5,648,165, 5,002,312, 4,930,866, 4,838,648, 4,779,898 and 4,705,300. and the disclosures thereof are incorporated herein by reference.</p><p>16 shows another embodiment of the present invention in the form of an optical article 400 having a paired optical structure. Optical article 400 includes a substrate 402 having an upper surface 404 and a lower surface 406 . Substrate 402 may be flexible or rigid, may be made of any suitable material, such as paper, plastic, cardboard, metal, etc., and may be opaque or transparent. A non-overlapping pair of first and second coated structures 408 and 410 are disposed over upper surface 404 and overlying non-overlapping first and second non-overlapping regions of surface 404 . Thus, the first coating structure 408 and the second coating structure 410, although adjacent to each other, do not overlap on the surface 404 and are physically separated from each other. For example, in one embodiment, the first coating structure 408 may be in the form of a rectangle or square, and a rectangle or square forming a border or frame surrounding the first coating structure 408 . is disposed in a recess 412 formed by the second coating structure 410 which may be in the form of Thus, when the optical article 400 is viewed from above, the coating structure 408 and the coating structure 410 can be seen at the same time.</p><p>The first coating structure 408 has a first pigment 414 formed of magnetic pigment flakes or particles, such as color-changing magnetic flakes, configured in the manner described above to provide a magnetic signature. The magnetic properties of the pigment 414 are provided by one or more magnetic flakes or optically invisible magnetic layers within the particles. The second coating structure 410 has a second pigment 416 made of non-magnetic pigment flakes or particles, such as color change non-magnetic flakes. Alternatively, the second coating structure 410 may be formed to contain a magnetic pigment, and the first coating structure 408 may be formed to contain a non-magnetic pigment. Pigments 414, 416 are dispersed in solidified liquid pigment vehicles 418, 420 of the conventional kind, such that pigments 414, 416 exhibit desired optical properties. For example, the liquid vehicle may be a conventional ink vehicle or a conventional paint vehicle of a suitable kind.</p><p>In another embodiment, the optical article 400 may be modified by using a suitable magnetic foil structure, such as the color change magnetic foil disclosed above, instead of the coated structure 408 , and instead of the coated structure 410 , a conventional color change. By using a non-magnetic foil structure such as foil, it can be formed. Thus, the magnetic properties of the magnetic foil structure are provided by the optically non-observable magnetic layer. A non-overlapping pair of first and second foil structures, one magnetic and one non-magnetic, are disposed over the upper surface 404 of the substrate 402 , such that the non-overlapping first surface 404 overlies the first and second foil structures. and over the second region.</p><p>Another optical article having a paired optically variable structure, which can be modified to include a magnetic layer in one of the paired structures as disclosed herein, is disclosed in US Pat. No. 5,766,738 to Phillips et al. , the disclosure of which is incorporated herein by reference. </p><p>17 shows another embodiment of the present invention in the form of an optical article 450 having an overlapping pair of optical structures. The optics 450 includes a substrate 452 having an upper surface area 454 . Substrate 452 may be formed of a material such as that described for substrate 402 shown in FIG. 16 . The magnetic pigment coating structure 456 overlies the upper surface region 454 of the substrate 452 . The magnetic pigment coating structure 456 includes a plurality of multilayer magnetic pigments 458 as described above, which are dispersed in a solidified pigment vehicle. The magnetic properties of the pigment coating structure 456 are provided by an optically invisible magnetic layer within each multilayer magnetic pigment 458 . The non-magnetic pigment coating structure 460 overlies at least a portion of the magnetic pigment coating structure 456 . The non-magnetic pigment coating structure 460 includes a plurality of non-magnetic pigments 462 dispersed in a solidified pigment vehicle. </p><p>In another embodiment of the optics 450 , a non-magnetic pigment coating structure may be used in place of the magnetic pigment coating structure 456 overlying the upper surface region 454 of the substrate 452 . A magnetic pigment coating structure may be used in place of the non-magnetic pigment coating structure 460 .</p><p>In another embodiment, the optics 450 may be formed by using a suitable magnetic foil structure, such as the color changing magnetic foil disclosed above, instead of the coating structure 456 . At this time, a non-magnetic foil structure such as a conventional color change foil may be used instead of the coating structure 460 . Alternatively, a non-magnetic foil structure may be used in place of the coating structure 456 , and a magnetic foil structure may be used in place of the coating structure 460 .</p><p>The individual pigment coatings or foil structures in the optics 400 or 450 may be selected to provide the same coloring or the same color changing effect to the optics 400 and 450, or , may be selected to provide different coloring or other color changing effects. Of course, as one of ordinary skill in the art will appreciate, various combinations of optical features may be used, wherein various security features can be incorporated into optics 400 and 450 by selecting an appropriate coating or foil having the desired optical properties. ) can be added to</p><p>Although the optical article 400 and the pigment coating or foil structure used in the optical article 450 may have substantially the same color or color effect, eg, the same color change effect, only one A pigmented coating or foil structure retains a concealed magnetic signature. Therefore, even if the magnetic features of the pigment coating or foil structure cannot be detected with the naked eye, using a magnetic detection system such as a Faraday rotation detector, the concealed magnetic signature of the pigment or foil and any information magnetically recorded therein can be used. can be detected.</p><p>From the foregoing, it can be seen that thin film structures having both magnetic and optionally color change properties have been provided, and they have a wide variety of applications, and are particularly desirable for areas requiring additional security.</p><p>For example, a structure or device formed from the pigments of the present invention may be disposed in a bar code pattern, where it forms a color-changing barcode device that may appear on a label or on the surface of the article itself. something to do. Such barcodes will function as color changing barcodes that can be read by optical and magnetic readers. Such a barcode color changing device will provide three security features: the barcode itself, the color changing characteristic, and the magnetic characteristic. In addition, information may be encoded in the magnetic layer of the pigment of the present invention. For example, the magnetic layer may record information typical of a credit card held on a magnetic strip. In addition, the pigment of the present invention can be used to input a number at the bottom of a check, in which case the information held by the check can be read magnetically like a modern check, and in addition to this, an optically variable feature is additionally added. is provided</p><p>The following examples are illustrative of the present invention and do not limit the scope of the present invention. </p><p>&lt;Example 1&gt;</p><p>1000 A three-layer structure magnetic coating sample consisting of Å of aluminum, 1000 Å of iron, and 1000 Å of aluminum (Al/Fe/Al) was prepared. This coating sample was prepared in a roll coater using a 2 mil polyester web coated with an organic release layer (dissolvable in acetone). After the three-layer coating was peeled from the web to form pigment flake particles, the particles were placed in isopropyl alcohol and ultrasonically stirred for 5 minutes (using a "Branson sonic welder") to control the particle size and then filter the particles. . Particle size was measured using a "Horiba LA-300" particle sizer (a device based on laser scattering). As a result of the measurement, the average particle size was 44 μm (standard deviation 22 μm) in the plane dimension, forming a Gaussian distribution. After determining the particle size, the pigment flakes were filtered and dried.</p><p>A mixture of magnetic pigment and binder (Du Pont auto refinish paint vehicle) with a dry weight ratio of magnetic pigment to binder of 1:4 was drawn down onto a thin cardboard sheet ("Leneta card"). drawn down). The term "draw-down" refers to a sample of paint or ink spread over paper for color evaluation. Typically, draw-down is done by "drawing down" a small amount of paint or ink with the edge of a putty knife or spatula to obtain a thin film of the paint or ink. is formed Alternatively, the draw-down may be formed using a Mayer rod that is pulled across a Leneta card through a small amount of paint. While the draw-down was performed, a conventional sheet magnet was placed under the card and the magnet was left in place until the paint vehicle was dried. Under the action of the magnetic field on this pigment sample, light and dark areas formed parallel to the pigment. As a result of measurement using an ultra small area viewer (USAV, 2.3 mm) in a spectrophotometer (SF-600 DataColor spectrophotometer), the reflective luminance Y of the bright aluminum area of the pigment sample was 53%. , on the other hand, the reflectance of the dark region was 43%. However, it was difficult to fit the aperture within the dark line and the light line, suggesting that the difference in brightness may actually be larger than the above measurement results.</p><p>&lt;Example 2&gt;</p><p>0.5 g of the magnetic pigment sample of Example 1 (Al/Fe/Al) was mixed with 3.575 g of a standard Intaglio ink vehicle (which is a high-viscosity ink vehicle) and 0.175 g of an ink dryer, and a magnetic ink sample was prepared. This ink sample was drawn-down on paper with a flat trowel. A magnetic strip cut out in the form of the letters "FLEX" was placed under the paper during the drawing-down phase. The pattern of magnetic lines in the dried magnetic ink was easily seen as black and white (silver) bands with the words "FLEX" clearly visible. An optical image of the ink sample with the letters "FLEX" was observable at a normal angle of incidence and at a viewing angle of about 45 degrees.</p><p>&lt;Example 3&gt;</p><p>After preparing a magnetic ink sample in the same manner as in Example 2 using an Intaglio ink vehicle, it was coated on a paper having a sheet magnet disposed thereunder. The magnet was in a state in which the letter "F" was cut out. With a magnetic pigment (Al/Fe/Al) oriented along the lines of magnetic force, a cut-out "F" shape rose onto the paper, which was apparently bright silver. "F" protruded about 6 μm from the surrounding area. This was caused by the paper being pushed slightly into the "F" recess of the magnet by the force of the trowel drawing-down the high viscosity Intaglio ink. After slowing the paper, the "F" area remained bright due to the Al/Fe/Al flakes oriented parallel to the surface of the paper, but its height was higher than the surrounding coating.</p><p>&lt;Example 4&gt;</p><p>Using an exacto knife, the letter "F" was cut out of a flexible sheet-like magnet. A draw-down card was placed on top of a sheet-like magnet and in contact with the magnet. The magnetic color change pigment according to the present invention was mixed with an acrylic resin vehicle and applied to the card using a #22 wire metering rod. The draw-down thus obtained had striped superimposed black lines mimicking the field pattern outside the "F" of the sheet-like magnet under the card. The entire surface of the draw-down card exhibited a color change effect. When the pattern of "F" was observed, "F" only had a color change effect, but the background had both a color change effect and an overlapping black line.</p><p>Another draw-down was formed using a letter piece "F" cut out from a sheet-like magnet, a magnetic pigment and a vehicle as previously described in this example. The draw-down thus obtained had a striped overlapping black line that mimics the field pattern in a cut-out "F" magnet piece. The entire surface of the draw-down exhibited a color change effect. When the pattern of "F" was observed, "F" had both a color change effect and an overlapping black line, but the background had only a color change effect.</p><p>Thus, in both cases, the entire surface of the draw-down card exhibited a color change effect, but the region directly above the magnet additionally had an overlapping striped black line due to the magnetic field pattern.</p><p>The present invention may be implemented in other specific forms without departing from its technical spirit and essential characteristics. The embodiments described above are to be regarded in all respects as illustrative and not restrictive. Therefore, the scope of the present invention is defined by the following claims rather than the foregoing detailed description. All changes occurring within the meaning and scope equivalent to the claims are also within the scope of the present invention.</p>