Magnetic writing screen capable of realizing multicolor writing

Abstract

The invention belongs to the technical field of magnetic writing tools, and discloses a magnetic writing screen capable of realizing multicolor writing, which comprises a support plate and a writing screen main body arranged on the support plate, and the writing screen main body comprises a transparent substrate layer, a display layer and a protective layer; the display layer is formed by coating and curing an adhesive containing microcapsules, each microcapsule contains a capsule wall, a suspension and at least two different colors of nano magnetic particles, the writing screen body is further provided with a reversible color-changing material, and when the reversible color-changing material is subjected to the action of a non-magnetic field external stimulus, the reversible color-changing material can change color of the non-magnetic field external stimulus. An initial transparent state can be reversibly changed into a colored state; according to the invention, the reversible color-changing material is innovatively introduced into the writing screen main body, so that a user can use a magnetic pen to write in a basic color, and can activate the color-changing material by virtue of different non-magnetic field external stimulation sources to generate a second color or even a plurality of colors, thereby enriching writing expression modes and improving the writing efficiency. And the requirements of diversified scenes such as teaching, conferences and creativity are met.

Description

Technical Field

[0001] This invention relates to the field of magnetic writing instruments, and in particular to a magnetic writing screen capable of multi-color writing. Background Technology

[0002] Magnetic writing screens, as an environmentally friendly and reusable writing tool, have been widely used in teaching, office, and home settings. Their basic principle is to use a magnetic field to control the movement of magnetic particles within microcapsules to achieve display and erasure. A typical magnetic writing screen includes a support plate and a writing screen body mounted on it. This body usually consists of a transparent substrate layer, a display layer, and a protective layer. The display layer is formed by coating and curing an adhesive containing microcapsules. The microcapsules are filled with a suspension and two different colors (such as black and white) of nano-magnetic particles. When writing with a magnetic pen, the vertical magnetic field generated by the pen tip attracts particles of one color to the top of the microcapsules, thus displaying that color and forming the writing. When erasing with a magnetic eraser, the dispersing magnetic field generated by the eraser causes the particles to redisperse evenly, and the writing disappears.

[0003] However, existing magnetic writing screens have a significant limitation: they typically only display a single color. Although the microcapsules contain particles of two colors, only one particle responds to the magnetic field and displays color during a single writing operation. In practice, when it's necessary to distinguish key content, make annotations, or design multi-color instructional materials, this monochrome display cannot meet the user's needs, limiting its application scenarios and market appeal.

[0004] Therefore, there is an urgent need in this field for a magnetic writing screen solution that enables multi-color writing, has a simple structure, and does not affect the original writing and erasing functions. Summary of the Invention

[0005] The main objective of this invention is to provide a magnetic writing screen that enables multi-color writing, thereby solving the problem that some magnetic writing screens can only display a single color.

[0006] To achieve the above-mentioned objectives, the first aspect of the present invention proposes a magnetic writing screen capable of multi-color writing, comprising a transparent substrate layer, a display layer, and a protective layer;

[0007] The display layer is formed by coating and curing an adhesive containing microcapsules. Each microcapsule contains a capsule wall, a suspension, and at least two different colored magnetic nanoparticles: a first magnetic particle and a second magnetic particle.

[0008] The writing screen body is also provided with a reversible color-changing material. When subjected to an external stimulus source other than a magnetic field, the reversible color-changing material can reversibly change from an initial transparent state to a colored state. After the stimulus source is removed, it remains in the colored state for a period of time and then returns to the initial transparent state, so as to distinguish it from the color displayed by the nano-magnetic particles.

[0009] Furthermore, the reversible color-changing material is an ultraviolet-sensitive color-changing material, and the non-magnetic external stimulus source is ultraviolet light; the ultraviolet-sensitive color-changing material is disposed in the writing screen body in one or more of the following ways:

[0010] a) The surface of the nano-magnetic particles encapsulated within the microcapsules;

[0011] b) Added to the suspension within the microcapsules;

[0012] c) Mix with the adhesive that forms the display layer;

[0013] d) The display layer is mixed with the microcapsules containing nano-magnetic particles in the form of independent microcapsules containing ultraviolet photochromic materials.

[0014] Furthermore, the ultraviolet photochromic material is sensitive to ultraviolet light with wavelengths from 365nm to 395nm and changes color accordingly.

[0015] Furthermore, the reversible color-changing material is a pressure-sensitive color-changing material, and the non-magnetic external stimulus source is the mechanical pressure applied during writing; the pressure-sensitive color-changing material is disposed in the writing screen body in one or more of the following ways:

[0016] a) Mixed with the adhesive forming the display layer;

[0017] b) Coated between the transparent substrate layer and the display layer.

[0018] Furthermore, the pressure-sensitive color-changing material is effective under pressures greater than or equal to 5 N / mm². 2 The color change is triggered at certain times.

[0019] Furthermore, the reversible color-changing material is a temperature-controlled color-changing material, and the non-magnetic external stimulus source is heat provided by the writing instrument; the temperature-controlled color-changing material is disposed in the writing screen body in one or more of the following ways:

[0020] a) Mixed with the adhesive forming the display layer;

[0021] b) Coated between the transparent substrate layer and the display layer.

[0022] Furthermore, the color-changing trigger temperature of the temperature-controlled color-changing material is 40°C to 80°C.

[0023] Furthermore, the reversible color-changing material is coated on the transparent substrate layer to form an independent color-changing layer, and the display layer is coated on the color-changing layer.

[0024] Furthermore, the reversible color-changing material retains its colored state for 1 to 10 minutes after the stimulus is removed.

[0025] A second aspect of the present invention provides a writing board, comprising a support plate and a magnetic writing screen capable of multi-color writing as described in any one of claims 1 to 9.

[0026] Beneficial effects:

[0027] This invention relates to a magnetic writing screen capable of multi-color writing. By innovatively introducing reversible color-changing materials into the main body of the writing screen, it successfully breaks through the technical barrier of traditional magnetic writing screens that can only display a single color. Users can write in basic colors (such as black and white) using a magnetic pen, and can also activate the color-changing materials with different non-magnetic external stimuli to produce a second or even multiple colors (such as blue, red, and green). This allows for the highlighting of key information and color differentiation, greatly enriching the writing expression methods and meeting the needs of diverse scenarios such as teaching, meetings, and creative activities. Furthermore, this application proposes various integration methods for reversible color-changing materials (such as coating magnetic particles, adding to suspensions, mixing with adhesives, forming independent microcapsules or independent color-changing layers, etc.). This diverse design gives manufacturers great flexibility, allowing them to choose the most suitable implementation scheme based on cost, performance requirements, and process complexity, which is conducive to rapid product development and commercialization.

[0028] This invention relates to a magnetic writing screen capable of multi-color writing. The activation of the color-changing material relies on non-magnetic stimuli (light, force, heat), while the basic display depends on a magnetic field. These two mechanisms are physically independent, allowing multi-color writing functionality to coexist perfectly with traditional magnetic writing / erasing functions without mutual interference. Using a UV pen for color marking will not interfere with existing magnetic handwriting, and using a magnetic eraser will not affect colored handwriting that has not yet faded.

[0029] The magnetic writing screen of this invention enables multi-color writing. Using a selected reversible color-changing material, it retains its colored state for 1 to 10 minutes after the stimulus is removed, then automatically returns to transparency. This feature ensures that the colored handwriting has a sufficiently long visibility time for the user to read, while also achieving "automatic erasure," eliminating the need for a dedicated physical erasure device for colored content. This simplifies the product structure, reduces costs, and maintains the core advantages of magnetic writing screens: instant writing and display, convenience, and environmental friendliness.

[0030] Most embodiments of the present invention (such as mixing the color-changing material into an adhesive or suspension) can be improved based on existing magnetic writing screen manufacturing processes and equipment without requiring significant changes to the production line. Even the scheme with an independent color-changing layer is a mature coating and lamination process, easy to scale up production, and has high industrialization potential. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of a magnetic writing screen capable of multi-color writing according to an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of the structure of a reversible color-changing material in a magnetic writing screen capable of multi-color writing according to an embodiment of the present invention, when the material is an ultraviolet photosensitive color-changing material located inside a microcapsule.

[0033] Figure 3 These are schematic diagrams of two other structures of a magnetic writing screen capable of multi-color writing according to an embodiment of the present invention, where the reversible color-changing material is an ultraviolet photosensitive color-changing material.

[0034] Figure 4 This is a schematic diagram of two structures of a magnetic writing screen capable of multi-color writing according to an embodiment of the present invention, where the reversible color-changing material is a pressure-sensitive color-changing material.

[0035] Figure 5 This is a schematic diagram of two structures of a magnetic writing screen capable of multi-color writing according to an embodiment of the present invention, where the reversible color-changing material is a temperature-controlled color-changing material.

[0036] in:

[0037] 1-Transparent substrate layer; 21-Microcapsule; 211-Capsule wall; 212-Suspension; 213-First magnetic particle; 214-Second magnetic particle; 22-Adhesive; 23-Reversible color-changing material; 3-Protective layer; 4-Support plate.

[0038] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0039] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0040] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0041] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0043] Example 1

[0044] Reference Figures 1-3 An embodiment of the present invention provides a magnetic writing screen that enables multi-color writing, including a support plate 4 and a writing screen body disposed thereon, the writing screen body including a transparent substrate layer 1, a display layer and a protective layer 3;

[0045] The display layer is formed by coating and curing an adhesive 22 containing microcapsules 21. The microcapsules 21 contain a capsule wall 211, a suspension 212, and at least two different colored first magnetic particles 213 and second magnetic particles 214. The writing screen body is also provided with a reversible color-changing material 23. When the reversible color-changing material 23 is subjected to a non-magnetic external stimulus, it can reversibly change from an initial transparent state to a colored state. After the stimulus is removed, it remains in the colored state for a period of time and then returns to the initial transparent state, so as to achieve the distinction from the color displayed by the nano-magnetic particles.

[0046] The reversible color-changing material 23 is an ultraviolet-sensitive color-changing material, and the non-magnetic external stimulus source is ultraviolet light; the ultraviolet-sensitive color-changing material is disposed in the writing screen body in one or more of the following ways:

[0047] a) The surface of the nano-magnetic particles encapsulated within the microcapsule 21;

[0048] b) Added to the suspension 212 within the microcapsule 21;

[0049] c) Mix with the adhesive 22 that forms the display layer;

[0050] d) Mixed in the display layer in the form of independent microcapsules 21 containing ultraviolet photochromic materials, together with the microcapsules 21 containing nanomagnetic particles.

[0051] The ultraviolet photochromic material is sensitive to ultraviolet light with a wavelength of 365nm to 395nm and retains its colored state for 1 to 10 minutes after the ultraviolet light is turned off.

[0052] The reversible color-changing material 23 retains its colored state for 1 to 10 minutes after the stimuli are removed.

[0053] This embodiment describes a magnetic writing screen that uses ultraviolet-sensitive color-changing materials to enable multi-color writing.

[0054] like Figure 1 As shown, the magnetic writing screen includes a support plate 4 and a writing screen body 2 tightly attached thereto by pressure-sensitive adhesive. The support plate 4 can be made of rigid materials such as steel plates, aluminum plates, or hard plastic plates, or flexible materials such as rubber plates or soft plastic plates, and its thickness is usually between 1-10 mm, preferably 3 mm. The writing screen body 2 has a multi-layer composite structure, which includes, from front to back, a transparent substrate layer 1, a display layer, and a protective layer 3.

[0055] The transparent substrate layer 1 is made of a polymer film material with excellent transparency and high surface smoothness, preferably a polyethylene terephthalate film with a thickness of 0.1-0.5 mm, but polycarbonate film, polypropylene film, or cyclic olefin copolymer film can also be used. This substrate layer not only provides structural support but also ensures good optical transmission performance.

[0056] The display layer is the core layer for realizing the display function, and it is prepared through the following process: First, microcapsules 21 containing two different colored magnetic particles 213 and 214 are prepared. Specifically, microcapsules 21 are prepared using a gelatin-gum arabic composite wall material via a multiphase emulsion method, with the average particle size of the capsules controlled at 30-100 μm, preferably 50 μm. Each microcapsule 21 contains a silicone oil suspension 212, as well as white magnetite magnetic particles and black chromium dioxide magnetic particles. The particle size of both types of particles is 100-500 nm, and their density matches that of the suspension 212. The mass ratio of white particles to black particles is 1:1 to 3:1, preferably 2:1.

[0057] The key to this embodiment lies in the introduction of a UV-sensitive photochromic material, which is sensitive to ultraviolet light with wavelengths from 365 nm to 395 nm. Spiropyran compounds are selected as the UV-sensitive photochromic material. When not exposed to UV light, it is colorless and transparent. Upon exposure to UV light, its molecular structure undergoes a ring-opening reaction, turning it blue. Other colors can also be obtained through molecular structure modification. After the UV light is turned off, the material retains its colored state for 1-10 minutes, then gradually returns to a colorless and transparent state.

[0058] The ultraviolet-sensitive color-changing material is incorporated into the writing screen body through one or more of the following five methods:

[0059] Method 1: The ultraviolet-sensitive photochromic material is coated onto the surface of the nano-magnetic particles inside the microcapsule 21 to form a core-shell structure. The specific process is as follows: First, the nano-magnetic particles are dispersed in ethanol, then 5%-15% of the ultraviolet-sensitive photochromic material is added, the mixture is stirred and the solvent is evaporated to ensure that the photochromic material is uniformly coated on the particle surface, and then the microcapsules 21 are encapsulated.

[0060] Method 2: The UV-sensitive color-changing material is directly added to the suspension 212 inside the microcapsule 21, with the addition amount being 0.5%-2% of the mass of the suspension 212. First, the color-changing material is dissolved in a small amount of organic solvent, and then the silicone oil suspension 212 is added. The mixture is then dispersed by ultrasound to achieve uniform mixing.

[0061] Method 3: Mix the UV photochromic material with the adhesive 22 that forms the display layer. Use polyurethane adhesive 22 or epoxy resin adhesive 22, and add 1%-5% of the UV photochromic material powder (by weight of adhesive 22) to it, and disperse it evenly by high-speed stirring (1000-2000 rpm).

[0062] Method 4: The ultraviolet-sensitive color-changing material is incorporated into the display layer as an independent microcapsule 21 containing ultraviolet-sensitive color-changing material, mixed with microcapsules 21 containing nano-magnetic particles. First, ultraviolet-sensitive color-changing microcapsules 21 with urea-formaldehyde resin as the wall material are prepared, with an average particle size of 20-50 μm. Then, they are mixed with magnetic microcapsules 21 at a mass ratio of 1:4 to 1:1, and then mixed with adhesive 22 and coated.

[0063] Method 5: Apply UV-sensitive photochromic material between the transparent substrate layer 1 and the display layer to form an independent photochromic layer. First, mix the photochromic material with acrylic resin at a ratio of 1:10, and adjust the coating with ethyl acetate to a solid content of 20%. Apply the coating to the transparent substrate layer 1 using a microgravure coating method to form a 3-10 μm thick coating. After drying, apply the display layer.

[0064] The preparation process of the display layer is as follows: Microcapsules 21 containing UV-sensitive color-changing material are mixed with polyurethane adhesive 22 at a mass ratio of 1:1. An appropriate amount of solvent is added to adjust the viscosity to 1000-3000 cps. Butanone (MEK) can be used as the solvent. The mixture is then applied to the transparent substrate layer 1 via slit coating, resulting in a wet film thickness of 100-300 μm. The film is dried at 60-80℃ for 5-10 minutes, followed by UV curing (energy 500-1000 mJ / cm²). 2 This forms the final display layer.

[0065] Protective layer 3 is attached to the back of the display layer. It is made of black polyethylene terephthalate film with a thickness of 0.05-0.2mm and is bonded to the display layer with acrylic pressure-sensitive adhesive. It not only provides protection but also enhances the display contrast.

[0066] In use, users can write normally with a traditional magnetic pen. The magnetic pen tip generates a vertical magnetic field, causing magnetic particles of one color (such as white) inside the microcapsule 21 to float to the top of the capsule, displaying the corresponding color. When highlighting is needed, a writing pen with a built-in ultraviolet LED (emitting a wavelength of 385nm) is used to illuminate the writing area. The ultraviolet photosensitive material turns blue and remains so for about 5 minutes, then gradually returns to transparency, thus achieving multi-color differentiation. When erasing, a magnetic eraser generates a horizontal magnetic field, causing the particles to redisperse.

[0067] This embodiment integrates ultraviolet photosensitive color-changing materials into the writing screen through various methods, providing flexibility in process selection; ultraviolet-triggered color change and magnetic field-triggered color change are independent of each other and do not interfere with each other; the color-changing material retains its color for a period of time after the ultraviolet light is turned off, providing a good user experience; it realizes a true multi-color display function and expands the application range of magnetic writing screens.

[0068] Example 2

[0069] Reference Figure 1 , Figure 4 An embodiment of the present invention provides a magnetic writing screen that enables multi-color writing, including a support plate 4 and a writing screen body disposed thereon, the writing screen body including a transparent substrate layer 1, a display layer and a protective layer 3;

[0070] The display layer is formed by coating and curing an adhesive 22 containing microcapsules 21. The microcapsules 21 contain a capsule wall 211, a suspension 212, and two different colored first magnetic particles 213 and second magnetic particles 214. The writing screen body is also provided with a reversible color-changing material 23. When the reversible color-changing material 23 is subjected to a non-magnetic external stimulus, it can reversibly change from an initial transparent state to a colored state. After the stimulus is removed, it remains in the colored state for a period of time and then returns to the initial transparent state, so as to achieve the distinction from the color displayed by the nano magnetic particles.

[0071] The reversible color-changing material 23 is a pressure-sensitive color-changing material, and the non-magnetic external stimulus source is the mechanical pressure applied during writing; the pressure-sensitive color-changing material is disposed in the writing screen body in one or more of the following ways:

[0072] a) Mixed with the adhesive 22 that forms the display layer;

[0073] b) Coated between the transparent substrate layer 1 and the display layer.

[0074] The pressure-sensitive color-changing material is sensitive to pressure greater than or equal to 5 N / mm². 2 The color change is triggered at certain times.

[0075] The reversible color-changing material 23 retains its colored state for 1 to 10 minutes after the stimuli are removed.

[0076] This embodiment describes a magnetic writing screen that uses a pressure-sensitive color-changing material to enable multi-color writing.

[0077] The basic structure of this embodiment is the same as that of Embodiment 1, including a support plate 4 and a writing screen body 2. The body consists of a transparent substrate layer 1, a display layer, and a protective layer 3. The difference is that a pressure-sensitive color-changing material is used instead of an ultraviolet-sensitive color-changing material.

[0078] The pressure-sensitive color-changing material is a crystal violet lactone system microencapsulated 21 times. Its core components include crystal violet lactone (color-developing agent), bisphenol A (color-developing agent), and decadecyl alcohol (solvent). The material is colorless and transparent when not under pressure. When subjected to a pressure of ≥5 N / mm², the microcapsules 21 rupture, and the color-developing agent reacts with the color-developing agent to produce a red color. Other colors can also be obtained through formulation adjustments. After the pressure is removed, the material retains its colored state for 1-10 minutes, subsequently gradually returning to a colorless and transparent state due to the isolating effect of the solvent.

[0079] The pressure-sensitive color-changing material is incorporated into the writing screen body in the following three ways:

[0080] Method 1: Mix the pressure-sensitive color-changing material with the adhesive 22 that forms the display layer. Use polyurethane adhesive 22 and add 5%-15% by weight of pressure-sensitive color-changing microcapsules 21 (average particle size 10-30μm) to it. Disperse evenly by stirring at low speed (300-500rpm) to avoid capsule rupture.

[0081] Method 2: Apply pressure-sensitive color-changing material between the transparent substrate layer 1 and the display layer to form an independent color-changing layer. First, mix pressure-sensitive color-changing microcapsules 21 with water-based polyurethane emulsion at a ratio of 1:5, and form a 5-15μm thick coating on the transparent substrate layer 1 by wire rod coating. Dry at 50℃ for 3 minutes to form the color-changing layer.

[0082] Method 3: Add pressure-sensitive color-changing material to the transparent substrate layer 1. Add 2%-8% of pressure-sensitive color-changing microcapsules 21 to polyethylene terephthalate granules, granulate by twin-screw extrusion, and then extrude to form a substrate film, so that the color-changing material is uniformly dispersed throughout the substrate.

[0083] The preparation process of the display layer is similar to that in Example 1: microcapsules 21 containing black and white magnetic particles (average particle size 50 μm) are mixed with polyurethane adhesive 22 at a mass ratio of 1:1, solvent is added to adjust the viscosity, and the mixture is coated onto the substrate or color-changing layer by a doctor blade coating method. The wet film thickness is 150-250 μm, and the film is dried at 70°C for 8 minutes to form the display layer.

[0084] The protective layer 3 is made of black polyethylene terephthalate film, which is bonded to the display layer by a rubber-type pressure-sensitive adhesive.

[0085] When in use, the display shows a basic black and white color when the user writes with a magnetic pen; when highlighting, a hard-tipped pen (such as a ballpoint pen tip or ceramic pen tip) is used, and the applied pressure causes the pressure-sensitive color-changing material to show color, such as red. After the pressure is removed, the color gradually fades after about 3 minutes. The two display mechanisms are completely independent and do not affect each other.

[0086] In summary, the pressure-triggered color-changing method requires no dedicated energy source and is easy to use; it also features a pressure threshold design (≥5N / mm). 2 It avoids accidental triggering caused by daily touch; the color-changing response is rapid and the color display is obvious; it is perfectly integrated with the magnetic display system to achieve true multi-color display function.

[0087] Example 3

[0088] Reference Figure 1 , Figure 5 An embodiment of the present invention provides a magnetic writing screen that enables multi-color writing, including a support plate 4 and a writing screen body disposed thereon, the writing screen body including a transparent substrate layer 1, a display layer and a protective layer 3;

[0089] The display layer is formed by coating and curing an adhesive 22 containing microcapsules 21. The microcapsules 21 contain a capsule wall 211, a suspension 212, and two different colored first magnetic particles 213 and second magnetic particles 214. The writing screen body is also provided with a reversible color-changing material 23. When the reversible color-changing material 23 is subjected to a non-magnetic external stimulus, it can reversibly change from an initial transparent state to a colored state. After the stimulus is removed, it remains in the colored state for a period of time and then returns to the initial transparent state, so as to achieve the distinction from the color displayed by the nano magnetic particles.

[0090] The reversible color-changing material 23 is a temperature-controlled color-changing material, and the non-magnetic external stimulus source is the heat provided by the writing instrument; the temperature-controlled color-changing material is disposed in the writing screen body in one or more of the following ways:

[0091] a) Mixed with the adhesive 22 that forms the display layer;

[0092] b) Coated between the transparent substrate layer 1 and the display layer.

[0093] The color-changing trigger temperature of the temperature-controlled color-changing material is 40°C to 80°C.

[0094] The reversible color-changing material 23 retains its colored state for 1 to 10 minutes after the stimuli are removed.

[0095] This embodiment describes a magnetic writing screen that uses a temperature-controlled color-changing material to enable multi-color writing.

[0096] The basic structure of this embodiment is the same as that of Embodiment 1, including a support plate 4 and a writing screen body 2. The body consists of a transparent substrate layer 1, a display layer, and a protective layer 3. The difference is that a temperature-controlled color-changing material is used instead of an ultraviolet-sensitive color-changing material.

[0097] The temperature-controlled color-changing material is a thermochromic liquid crystal material or a molecular recombination-type thermochromic material, with a color-changing temperature range of 40℃-80℃, preferably 50℃-60℃. Taking a liquid crystal material as an example, a chiral nematic liquid crystal mixture is selected. The pitch of the mixture changes with temperature, causing a change in the wavelength of selectively reflected light, thus displaying different colors, such as colorless at low temperatures and green at high temperatures. After the temperature is removed, the material can maintain its colored state for 1-10 minutes, and then gradually returns to a colorless and transparent state.

[0098] The temperature-controlled color-changing material is incorporated into the writing screen body in the following three ways:

[0099] Method 1: Mix the temperature-controlled color-changing material with the adhesive 22 that forms the display layer. Select an epoxy resin adhesive 22 with good temperature resistance, and add 3%-10% of the mass of the temperature-controlled color-changing microcapsules 21 (average particle size 5-20μm) to it, and disperse it evenly by low-speed stirring.

[0100] Method 2: Apply a temperature-controlled color-changing material between the transparent substrate layer 1 and the display layer to form an independent color-changing layer. First, mix the temperature-controlled color-changing microcapsules 21 with silicone resin at a ratio of 1:4, and form an 8-12μm thick patterned coating on the transparent substrate layer 1 by screen printing. Then, cure at 80℃ for 10 minutes to form the color-changing layer.

[0101] Method 3: Add a thermochromic material to the surface of the transparent substrate layer 1. A 0.5-2 μm thick thermochromic vanadium oxide film is formed on the surface of the polyethylene terephthalate substrate by vapor deposition. This film undergoes a phase transition at a specific temperature, thereby changing its optical properties.

[0102] The preparation process of the display layer is similar to that in Example 1: microcapsules 21 containing black and white magnetic particles are mixed with epoxy resin adhesive 22 at a mass ratio of 1.5:1, solvent is added to adjust the viscosity, and the mixture is applied to the substrate or color-changing layer by spin coating. The wet film thickness is 100-200 μm, and the mixture is cured at 80°C for 15 minutes to form the display layer.

[0103] The protective layer 3 is made of black polyimide film, which has good temperature resistance, and is bonded to the display layer by silicone pressure-sensitive adhesive.

[0104] When in use, the magnetic pen displays a basic black and white color. For highlighting, a heated pen (with an adjustable tip temperature of 40-80℃) is used. The temperature triggers a thermochromic material to display a color (e.g., green). The color fades gradually after approximately 2 minutes once the heating is removed. Different colors can be displayed by controlling the heating temperature, such as light green at 40℃, dark green at 60℃, and blue at 80℃.

[0105] In summary, the temperature-controlled color-changing system offers sensitive response and vibrant colors; multi-level color changes can be achieved through temperature control, further enriching the color representation; it works in conjunction with magnetic display systems without interference; and it is particularly suitable for teaching, demonstration, and other scenarios requiring multi-color annotation.

[0106] Example 4

[0107] Reference Figures 1-5 An embodiment of the present invention provides a magnetic writing screen that enables multi-color writing, including a support plate 4 and a writing screen body disposed thereon, the writing screen body including a transparent substrate layer 1, a display layer and a protective layer 3;

[0108] The display layer is formed by coating and curing an adhesive 22 containing microcapsules 21. The microcapsules 21 contain a capsule wall 211, a suspension 212, and two different colored first magnetic particles 213 and second magnetic particles 214. The writing screen body is also provided with a reversible color-changing material 23. When the reversible color-changing material 23 is subjected to a non-magnetic external stimulus, it can reversibly change from an initial transparent state to a colored state. After the stimulus is removed, it remains in the colored state for a period of time and then returns to the initial transparent state, so as to achieve the distinction from the color displayed by the nano magnetic particles.

[0109] The reversible color-changing material 23 is coated on the transparent substrate layer 1 to form an independent color-changing layer, and the display layer is coated on the color-changing layer.

[0110] The reversible color-changing material 23 retains its colored state for 1 to 10 minutes after the stimuli are removed.

[0111] This embodiment describes a magnetic writing screen with an independent color-changing layer structure that enables multi-color writing.

[0112] like Figure 2 As shown, the magnetic writing screen in this embodiment features a significant structural improvement: an independent color-changing layer 24 is added between the transparent substrate layer 1 and the display layer, forming a four-layer composite structure. This design completely isolates the color-changing function from the magnetic display function, avoiding interference between materials and improving system reliability and lifespan.

[0113] The independent color-changing layer 24 can be selected from ultraviolet-sensitive, pressure-sensitive, or temperature-controlled color-changing materials as needed. The following explanation uses ultraviolet-sensitive color-changing materials as an example:

[0114] First, prepare the UV-sensitive color-changing coating: Mix spiropyran-based UV-sensitive color-changing material (sensitive to 365nm) with transparent acrylic resin in a 1:8 ratio, add an appropriate amount of light stabilizer (such as benzotriazole UV absorber) and leveling agent, and adjust the viscosity to 200-400cps with propylene glycol methyl ether acetate.

[0115] The above coating was applied to a transparent polyethylene terephthalate substrate (0.25 mm thick) using a precision micro-gravure coating method, with a wet film thickness of 15 μm. After drying at 65°C for 5 minutes, a color-changing layer was formed, with a dry film thickness of approximately 5 μm.

[0116] Then, a display layer is coated on the color-changing layer: microcapsules 21 containing black and white magnetic particles (average particle size 50 μm) are mixed with polyurethane adhesive 22 at a mass ratio of 1:1 and coated by slit coating. The wet film thickness is 200 μm, and the film is dried at 70°C for 10 minutes to form the display layer.

[0117] Finally, protective layer 3 is applied: a black polyethylene terephthalate film (0.1 mm thick) is used and bonded to the display layer with acrylic pressure-sensitive adhesive.

[0118] The advantages of this embodiment are: the color-changing layer is separated from the display layer, avoiding adverse reactions between materials; the performance parameters of each layer can be optimized independently; the production process is easier to control; the product quality is more stable; and the service life is longer.

[0119] When in use, users can write with both a magnetic pen and a UV pen, producing a basic black and white color and a UV-changing color (such as blue) respectively. The two display mechanisms are physically separate but visually integrated, providing a good multi-color display effect.

[0120] In summary, the layered structure design ensures that the two display mechanisms do not interfere with each other, improving system reliability; it allows for independent optimization of material formulations and process parameters for each layer to achieve optimal performance; it improves product consistency and stability; it extends service life; and it reduces manufacturing process difficulty.

[0121] Example 5

[0122] Reference Figures 1-5 This embodiment provides a complete multi-color writing board, including the magnetic writing screen described in any of the above embodiments and a matching multi-functional writing tool.

[0123] The writing board includes: a frame structure, a support plate 4, and a writing screen body 2. The frame is preferably made of aluminum alloy profile; the support plate 4 is a 3mm thick steel plate, which provides support and also serves as a magnetic conductive medium for the magnetic eraser; the writing screen body adopts the structure of Embodiment 4, and has an independent color-changing layer and a display layer.

[0124] The accompanying writing tools include:

[0125] Magnetic writing pen: The pen tip has a built-in neodymium iron boron permanent magnet with a surface magnetic field strength of 0.2-0.5T, which can produce basic black and white writing;

[0126] UV writing pen: The pen tip has a built-in 365nm UV LED with a power of 0.5-1W, which can trigger the color-changing layer to turn blue;

[0127] Pressure-sensitive writing pen: The tip is made of sapphire crystal and changes color upon mechanical pressure. (Option: Select the pressure-sensitive color-changing version.)

[0128] Thermo-controlled writing pen: The pen tip is a heatable metal tip with an adjustable temperature range of 40-80℃, which can trigger temperature-controlled color change;

[0129] Magnetic erasure: Built-in multi-pole magnetic ring, which erases magnetic writing through a horizontal magnetic field;

[0130] Overall eraser: Built-in ultraviolet light source and heating device, which can erase color-changing displays at the same time.

[0131] When in use, teachers can write the main teaching content (black) on the whiteboard with a magnetic pen, highlight key points (blue) with a UV pen, and add notes (green) with a thermal pen, creating a multi-color teaching record. After class, the overall eraser can completely clear all displayed content in seconds.

[0132] In summary, the following materials can be used for the capsule wall 211: gelatin-gum arabic, urea-formaldehyde resin, melamine-formaldehyde resin, polyurethane, polyurea, etc.

[0133] Optional materials for suspension 212 include: white oil, paraffin oil, silicone oil, fatty acid esters, etc.

[0134] The optional materials for nanomagnetic particles A213 and B214 are: iron(II,III) oxide or neodymium iron boron.

[0135] Optional materials for transparent substrate layer 1: polyethylene terephthalate, polycarbonate, cyclic olefin copolymers / cyclic olefin polymers, etc.;

[0136] Adhesive 22 Optional materials: water-based polyurethane dispersion, acrylic resin, epoxy resin, silicone resin, UV-curable resin.

[0137] Optional materials for protective layer 3: PET film, or possibly PET / ink / adhesive / release paper.

[0138] This application provides a complete multi-color writing solution to meet the needs of various scenarios such as modern teaching and meetings; multiple writing tools can be used together to fully leverage the advantages of multi-color display; erasing is convenient and thorough, and the system can be reused thousands of times; the system is stable, reliable, and has a long service life.

[0139] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A magnetic writing screen capable of multi-color writing, characterized in that, comprising a transparent substrate layer, a display layer and a protective layer; the display layer is formed by coating and curing of an adhesive containing microcapsules, the microcapsules containing within a capsule wall, a suspension and at least two different colors of nano magnetic particles: a first magnetic particle and a second magnetic particle, the writing screen body is further provided with a reversible color-changing material, which can reversibly change from an initial transparent state to a colored state when subjected to a non-magnetic external stimulus source, and remain in the colored state for a period of time after the stimulus source is removed and then return to the initial transparent state, so as to realize differentiation from the display color of the nano magnetic particles.

2. The multi-color writable magnetic writing screen of claim 1, wherein, The reversible color-changing material is an ultraviolet light-sensitive color-changing material, and the non-magnetic external stimulus source is ultraviolet light; the ultraviolet light-sensitive color-changing material is arranged in the writing screen body by one or more of the following ways: a) coated on the surface of the nano magnetic particles within the microcapsules; b) added to the suspension within the microcapsules; c) mixed with the adhesive forming the display layer; d) in the form of independent microcapsules containing ultraviolet light-sensitive color-changing material, mixed with the microcapsules containing nano magnetic particles in the display layer.

3. The multi-color writable magnetic writing screen of claim 2, wherein, The ultraviolet light-sensitive color-changing material is sensitive to ultraviolet light with a wavelength of 365nm to 395nm.

4. The multi-color writable magnetic writing screen of claim 1, wherein, The reversible color-changing material is a pressure-sensitive color-changing material, and the non-magnetic external stimulus source is mechanical pressure applied by writing; the pressure-sensitive color-changing material is arranged in the writing screen body by one or more of the following ways: a) mixed with the adhesive forming the display layer; b) coated between the transparent substrate layer and the display layer.

5. The multi-color writable magnetic writing screen of claim 4, wherein, The pressure sensitive color changing material triggers a color change when the pressure is greater than or equal to 5 N / mm 2 .

6. The multi-color writable magnetic writing screen of claim 1, wherein, The reversible color-changing material is a temperature-controlled color-changing material, and the non-magnetic external stimulus source is heat provided by a heat source writing tool; the temperature-controlled color-changing material is arranged in the writing screen body by one or more of the following ways: a) mixed with the adhesive forming the display layer; b) coated between the transparent substrate layer and the display layer.

7. The multi-color writable magnetic writing screen of claim 6, wherein, The temperature-controlled color-changing material has a color-changing trigger temperature of 40℃ to 80℃.

8. The multi-color writable magnetic writing screen of claim 1, wherein, The reversible color-changing material is coated on the transparent substrate layer to form an independent color-changing layer, and the display layer is coated on the color-changing layer.

9. The multi-color writable magnetic writing screen of any one of claims 2-9, wherein, The reversible color-changing material remains in the colored state for 1 minute to 10 minutes after the stimulus source is removed.

10. A writing board, characterized by: A magnetic writing screen capable of multi-color writing comprising a support plate and a magnetic writing screen as claimed in any one of claims 1 to 9.

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