A heat-assisted magnetic recording-erasing photonic crystal film, its preparation method and application

Abstract

This invention belongs to the field of photonic crystal display technology and discloses a heat-assisted magnetic recording-erasing photonic crystal film. It consists of a flexible polymer matrix and a magnetic phase-change photonic crystal embedded therein. The magnetic phase-change photonic crystal comprises superparamagnetic nanoparticles and a magneto-solid-color phase-change material, wherein the magneto-solid-color phase-change material is a sorbitan fatty acid ester-based phase-change material or a polyoxyethylene ether-based phase-change material. In the crystal film of this invention, the flexible polymer matrix plays a role in flexible self-support and protection, and restricts the flow of the magnetic phase-change photonic crystal. Combined with the magnetic phase-change photonic crystal, the resulting photonic crystal film is endowed with magnetic writing-stable display-erasing functions under heat-assisted conditions, possessing advantages such as repeated writing and low-energy color display. This provides a new approach for the fabrication of low-energy, reusable display devices. Furthermore, the fabrication method involved is relatively simple, easy to operate, and suitable for widespread application.

Description

Technical Field

[0001] This invention belongs to the field of photonic crystal display technology, specifically relating to a heat-assisted magnetic recording-erasing photonic crystal film, its preparation method, and its application. Background Technology

[0002] Magnetoresponsive photonic crystal liquids (MCCs) are considered by researchers to be a next-generation smart display material due to their advantages such as efficient and reversible structural color assembly, wide tunable structural color range, and simple structural color adjustment methods. However, their high flowability makes their application in some fields extremely inconvenient. Composite processing of MCCs with polymer matrices into films retains the inherent magnetic responsiveness of MCCs while providing them with ease of use, showing broad application prospects in fields such as photonic paper, photonic skin, anti-counterfeiting, camouflage materials, and outdoor displays.

[0003] While magnetoresistive photonic crystal films developed to date can rapidly perform magnetic writing and erasing, they typically require a continuous magnetic field to maintain the display state of the written color pattern, leading to drawbacks such as increased complexity and energy consumption in display devices. Therefore, developing a magnetically writeable and erasable display that can achieve stable display of the written pattern using only ambient temperature without the need for a continuous magnetic field is an important energy-saving display method. Summary of the Invention

[0004] One of the objectives of this invention is to provide a heat-assisted magnetic recording-erasing photonic crystal film, which, compared to traditional magnetically responsive photonic crystal films, enables energy-saving and stable display of information written under conditions without an external magnetic field.

[0005] The second objective of this invention is to provide a method for preparing a heat-assisted magnetic recording-erasing photonic crystal film, which involves a simple preparation process, good controllability, and environmental friendliness.

[0006] The third objective of this invention is to provide an application of a heat-assisted magnetic recording-erasing photonic crystal film, offering a new approach for the fabrication of low-energy-consumption, reusable display devices (optical devices).

[0007] One of the solutions adopted to achieve the objective of this invention is:

[0008] A heat-assisted magnetic recording-erasing photonic crystal film is composed of a flexible polymer matrix and a magnetic phase change photonic crystal embedded therein; the magnetic phase change photonic crystal comprises superparamagnetic nanoparticles and a magneto-solid color phase change material, wherein the magneto-solid color phase change material is a dehydrated sorbitan fatty acid ester phase change material and / or a polyoxyethylene ether phase change material.

[0009] Preferably, the flexible polymer matrix may be selected from one or more of polydimethylsiloxane, polyurethane acrylate, flexible epoxy resin, etc.

[0010] Furthermore, the flexible polymer matrix includes a precursor liquid (prepolymer liquid) and a curing agent for the flexible polymer matrix; after introducing the corresponding curing agent into the precursor liquid, the corresponding flexible polymer matrix is ​​obtained by curing.

[0011] Preferably, the superparamagnetic nanoparticles may be PVP-coated magnetic nanoparticles, etc.

[0012] Preferably, the particle size of the superparamagnetic nanoparticles is 100~200 nm.

[0013] Furthermore, the superparamagnetic nanoparticles exhibit monodispersity.

[0014] Furthermore, the magnetic nanoparticles may be selected from one or more of Fe3O4, CoFe2O4, NiFe2O4, etc.

[0015] Furthermore, the sorbitan fatty acid ester phase change material may be selected from one or more of the following: sorbitan monolaurate (Span20), sorbitan monopalmitate (Span40), sorbitan monostearate (Span60), and sorbitan oleate (Span80); the polyoxyethylene ether phase change material may be selected from one or more of the following: stearyl alcohol polyoxyethylene ether (AEO-3), fatty alcohol polyoxyethylene ether (AEO-7 or AEO-9, etc.).

[0016] Preferably, the magnetic phase change photonic crystal is embedded in a flexible polymer matrix in the form of microspheres, with the microsphere size being less than 20 μm.

[0017] Preferably, the phase transition temperature of the magnetic phase transition photonic crystal is 40~55℃.

[0018] Preferably, the mass ratio of the superparamagnetic nanoparticles to the magneto-solid phase change material is 1:3.5~100.

[0019] Preferably, the mass ratio of the magnetic phase change photonic crystal to the flexible polymer matrix is ​​1:1 to 50.

[0020] The solution adopted to achieve the second objective of this invention is:

[0021] A method for preparing a heat-assisted magnetic recording-erasing photonic crystal film includes the following steps:

[0022] 1) The magnetic solid phase change material and magnetic nanoparticles are ultrasonically dispersed under heating conditions to form a uniform dispersion.

[0023] Emulsification was performed by adding a precursor solution of a flexible polymer matrix to the obtained dispersion;

[0024] 2) After cooling the obtained emulsion to room temperature, add the curing agent of the flexible polymer matrix, mix evenly, and obtain a prepolymer liquid for later use;

[0025] 3) After the obtained prepolymer liquid is poured, it is cured and demolded to obtain the heat-assisted magnetic recording-erasing photonic crystal film.

[0026] In the above scheme, the concentration of magnetic nanoparticles in the dispersion is 10~300mg / mL.

[0027] In the above scheme, the temperature used for ultrasonic dispersion is 40~60 ℃.

[0028] Preferably, in step 1), the volume ratio of the precursor liquid to the dispersion liquid of the flexible polymer matrix is ​​1~50:1.

[0029] Preferably, the emulsification step employs ultrasonic and heat preservation conditions, with ultrasonic time of 1-3 hours, heat preservation temperature of 40-60°C, and time of 1-2 hours.

[0030] Preferably, the size of the emulsion droplets in the resulting emulsion is 10~20 μm.

[0031] Preferably, the curing agent of the flexible polymer matrix is ​​one or more of polymethylhydrosiloxane, azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, and diisopropyl peroxide dicarbonate; its amount accounts for 1 / 100 to 1 / 10 of the mass of the precursor liquid (prepolymer liquid) of the flexible polymer matrix.

[0032] Preferably, the curing time is 8~12 min.

[0033] Furthermore, the curing temperature is above 70 ℃.

[0034] Preferably, the curing temperature is 70~100℃.

[0035] The solution adopted to achieve the third objective of this invention is:

[0036] One application of the aforementioned heat-assisted magnetic recording-erasing photonic crystal film is to use it in the fabrication of devices such as photonic paper, photonic skin, camouflage materials, and outdoor displays. The specific recording and erasing steps include the following:

[0037] 1) Apply a magnetic field of 50~1000 Gs to a photonic crystal film (photonic crystal paper, the same below) at room temperature, write on the photonic crystal paper with a heated pen, and remove the magnetic field to complete the recording (writing) of the photonic crystal color pattern.

[0038] 2) Place the above photonic crystal paper in an environment without an external magnetic field and heat it to above 60°C to erase the color pattern of the photonic crystal.

[0039] In the above scheme, the temperature transmitted by the heating pen is above 80°C.

[0040] Furthermore, under conditions of no magnetic field and a temperature below 35 °C, the recorded photonic crystal color pattern (the information recorded in the above writing step) can be maintained for more than 3 months.

[0041] The principle of this invention is as follows:

[0042] Magnetoresistent photonic crystals are typically composed of magnetic nanoparticles and their dispersion medium. Traditional magnetoresistent photonic crystals require a continuous magnetic field to maintain the stable display of the written color pattern. When the magnetic field is removed, the recorded color pattern disappears, resulting in drawbacks such as increased complexity and energy consumption in the display device.

[0043] This invention is the first to propose the introduction of a magnetic solid-state color phase change material as a dispersion medium, which is then composited with monodisperse superparamagnetic nanoparticles and embedded in a flexible polymer matrix. When the phase change material is in a liquid state, it can serve as a dispersion medium for the magnetic nanoparticles. Under the induction of an external magnetic field, the magnetic nanoparticles assemble into an ordered structure, thereby generating structural color and realizing the writing of colored patterns. Under thermally assisted conditions, after the magnetic solid-state color phase change material used in this invention is cured, its rigid matrix can fix the ordered arrangement of nanoparticles, allowing the pattern to be maintained for a long time without the need for an additional magnetic field.

[0044] In addition, the resulting crystal film has good mechanical flexibility and practicality; it can also achieve repeatable magnetic writing and erasing of color patterns through phase change cycling, providing a new solution for the fabrication of low-energy, reusable display devices.

[0045] Compared with the prior art, the beneficial effects of the present invention include:

[0046] (1) The heat-assisted magnetic recording-erasing photonic crystal film of the present invention is composed of a flexible polymer matrix and a magnetic phase change photonic crystal embedded therein; the flexible polymer matrix plays the role of flexible self-support and protection, and restricts the flow of the magnetic phase change photonic crystal. At the same time, the magnetic phase change photonic crystal gives the photonic crystal film magnetic writing-stable display-erasing function under heat-assisted conditions. Compared with traditional magnetic responsive photonic crystal materials, it can realize the recording and stable display of color patterns without the need for continuous magnetic field application, and has the advantages of repeated writing and low-energy color display.

[0047] (2) The size of the magnetic phase transition photonic crystals in the heat-assisted magnetic recording-erasing photonic crystal film display unit of the present invention is 10~20 μm, which can give the photonic crystal film a uniform and continuous color display effect.

[0048] (3) The present invention adopts a simple one-pot preparation process, and there is no introduction or loss of excess materials in the preparation process. Attached Figure Description

[0049] Figure 1 The images show the morphology of the magnetic phase transition photonic crystal in the molten state (a) and the solidified state (b) without the application of a magnetic field in Example 1.

[0050] Figure 2 The image shows the reflection spectrum of the magnetic phase transition photonic crystal in the molten state of Example 1 in the range of 80~700 Gs magnetic field strength and the corresponding digital photographs of the change from red to blue (see illustration).

[0051] Figure 3 Microscopic images of the heat-assisted magnetic recording-erasing photonic crystal film prepared in Example 1 under different magnetic field intensities.

[0052] Figure 4 The curve showing the change in reflection wavelength of the heat-assisted magnetic recording-erasing photonic crystal film prepared in Example 1 under an alternating magnetic field.

[0053] Figure 5 The image shows the morphology of the heat-assisted magnetic recording-erasing photonic crystal film prepared in Example 1 after recording the green structural color, in its curled state.

[0054] Figure 6 The diagram shows the thermally assisted magnetic recording and thermal erasure process of the thermally assisted magnetic recording-erasing photonic crystal paper prepared in Example 1, which achieves a "WUT" pattern under thermal assistance.

[0055] Figure 7 Microscopic image (a) of the heat-assisted magnetic recording-erasing photonic crystal film prepared in Example 2, and the reflection spectrum (b) of the film under its response state when a magnetic field strength in the range of 80 to 700 Gs is applied.

[0056] Figure 8 Microscopic image (a) of the heat-assisted magnetic recording-erasing photonic crystal film prepared in Example 3, and its reflection spectrum (b) when a magnetic field strength in the range of 80~700 Gs is applied in its response state.

[0057] Figure 9 Microscopic image (a) of the heat-assisted magnetic recording-erasing photonic crystal film prepared in Example 4, and the reflection spectrum (b) corresponding to the magnetic field strength in the range of 80~700 Gs when applied in its response state.

[0058] Figure 10Microscopic image (a) of the heat-assisted magnetic recording-erasing photonic crystal film prepared in Example 5, and its reflection spectrum (b) when a magnetic field strength in the range of 80~700 Gs is applied in its response state.

[0059] Figure 11 Microscopic image (a) of the heat-assisted magnetic recording-erasing photonic crystal film prepared in Example 6, and the reflection spectrum (b) of the film under its response state when a magnetic field strength in the range of 80 to 700 Gs is applied.

[0060] Figure 12 Microscopic image (a) of the heat-assisted magnetic recording-erasing photonic crystal film prepared in Example 7, and its reflection spectrum (b) when a magnetic field strength in the range of 80 to 700 Gs is applied in its response state.

[0061] Figure 13 The images show the reflection spectrum (a) of the photonic crystal film prepared for Comparative Example 1 at 60 °C when a magnetic field strength in the range of 80 to 700 Gs is applied, the image (b) of the film when a magnetic field of 700 Gs is applied, and the image (c) of the film obtained by cooling it to room temperature under the induction of a magnetic field of 700 Gs.

[0062] Figure 14 The surface morphology and reflection spectrum of the photonic crystal film prepared for Comparative Example 2 are shown when magnetic fields of 0 Gs, 100 Gs, and 700 Gs are applied sequentially at 60 °C.

[0063] Figure 15 The image shows the morphology of the photonic crystal film prepared in Comparative Example 3. Detailed Implementation

[0064] To better understand the present invention, the following embodiments are further illustrations of the present invention, but the content of the present invention is not limited to the following embodiments.

[0065] In the following examples, the monodisperse superparamagnetic nanoparticles used were Fe3O4@PVP colloidal nanoparticle clusters, and the specific preparation method was based on the reference "Steric-repulsion-based magnetically responsive photoniccrystals. W. Luo, H. Ma, F. Mou, M. Zhu, J. Yan and J. Guan. Advanced Materials (Deerfield Beach, Fla.) 2013 Vol. 26 Issue 7 Pages 1058-1064".

[0066] In the following embodiments, the flexible polymer matrix adopts a polydimethylsiloxane raw material system or a polyurethane acrylate raw material system; wherein the polydimethylsiloxane raw material system includes Dow Corning 184 main agent (precursor liquid) and curing aid (curing agent), and the curing aid accounts for 1 / 10 of the mass of Dow Corning 184 main agent; the polyurethane acrylate raw material system includes polyurethane acrylate (liquid) and azobisisobutyronitrile curing agent (curing agent), and azobisisobutyronitrile accounts for 1 / 100 of the mass of polyurethane acrylate.

[0067] Example 1

[0068] A heat-assisted magnetic recording-erasing photonic crystal film, the preparation method of which includes the following steps:

[0069] 1) Emulsion preparation: Fe3O4@PVP colloidal nanoparticle clusters with an average particle size of 145 nm were ultrasonicated with Span 40 at 60℃ for 2 h to obtain a magnetic phase transition photonic crystal liquid with a concentration of 150 mg / mL. The morphologies of the magnetic phase transition photonic crystal liquid in the liquid and solid states are as follows: Figure 1 a in Figure 1 As shown in b (its magnetic response reflection spectrum is shown in...), Figure 2 );

[0070] The obtained magnetic phase transition photonic crystal liquid was mixed with polydimethylsiloxane precursor (Dow Corning 184 main agent, the same below) at a volume ratio of 1:2 and ultrasonicated at 60 °C for 1 h to obtain a homogeneous emulsion.

[0071] 2) Preparation of prepolymer: After cooling the obtained emulsion to room temperature, add polymethylhydrosiloxane curing agent (Dow Corning 184 curing aid, accounting for 1 / 10 of the main agent mass; the same below), stir evenly to obtain brown prepolymer, and cast the prepolymer onto a smooth and flat substrate.

[0072] 3) Thin film forming: The cast substrate is placed in a 70 ℃ oven for heat curing for 10 min. After removal, it is peeled off to obtain a brownish film, which is the heat-assisted magnetic recording-erasing photonic crystal film.

[0073] The magnetic phase-change photonic crystal microspheres embedded in the photonic crystal film obtained in this embodiment have an average size of 10 μm, and their color response under different magnetic fields is as follows: Figure 3 As shown.

[0074] The variation curve of the reflection wavelength of the photonic crystal film obtained in this embodiment under an alternating magnetic field is shown in the figure. Figure 4 During 100 thermal cycles, the magnetic response performance of the photonic crystal film under heating and its color retention at room temperature remained essentially unchanged, demonstrating excellent cycling stability.

[0075] The obtained photonic crystal film was kept under a magnetic field of 200 Gs. The film was heated to 60 °C, then cooled to room temperature and the magnetic field was removed, resulting in a film with a fixed green structural color (e.g., ...). Figure 5 ).

[0076] The product obtained in this embodiment is applied to the recording and erasing of color patterns. The specific steps are as follows: A magnetic field of 200 Gs is applied to the photonic crystal film at room temperature. Using a soldering pen heated to 100°C, "W", "U", and "T" are written sequentially on the photonic crystal paper. The magnetic field is then removed, completing the recording of the WUT photonic crystal color pattern. The recorded pattern can be maintained for more than 3 months under conditions of no magnetic field and below 35°C. The photonic crystal paper is then placed in an environment without an external magnetic field and heated to 60°C to erase the photonic crystal color pattern. Figure 6 As shown.

[0077] Example 2

[0078] A heat-assisted magnetic recording-erasing photonic crystal film, the preparation method of which includes the following steps:

[0079] 1) Emulsion preparation: Span 40 and Span 80 were mixed at a mass ratio of 7:3 and then sonicated with Fe3O4@PVP colloidal nanoparticle clusters with an average particle size of 145 nm at 40 °C for 2 h to obtain a magnetic phase transition photonic crystal liquid with a concentration of 10 mg / ml.

[0080] The obtained photonic crystal liquid was mixed with polydimethylsiloxane precursor liquid at a volume ratio of 1:50 and ultrasonicated at 40 °C for 1 h to obtain a homogeneous emulsion.

[0081] 2) Preparation of prepolymer: After cooling the emulsion to room temperature, add polymethylhydrosiloxane curing agent and stir evenly to obtain brown prepolymer. Cast the prepolymer onto a smooth and flat substrate.

[0082] 3) Thin film forming: The cast substrate is placed in a 70 ℃ oven for heat curing for 10 min. After removal, it is peeled off to obtain a brown film, which is the heat-assisted magnetically recordable-erasable photonic crystal film.

[0083] In this embodiment, the average size of the phase transition microspheres in the photonic crystal film is 5 μm. Figure 7 In the case of 'a', the reflectance spectrum of its magnetic response is as follows: Figure 7 As shown in b in the figure.

[0084] Example 3

[0085] A heat-assisted magnetic recording-erasing photonic crystal film, the preparation method of which includes the following steps:

[0086] 1) Emulsion preparation: Span 40 and Span 80 were mixed at a mass ratio of 7:3 and then ultrasonicated with Fe3O4@PVP colloidal nanoparticle clusters with an average particle size of 100 nm at 40 °C for 2 h to obtain a magnetic phase transition photonic crystal liquid with a concentration of 10 mg / ml.

[0087] The obtained photonic crystal liquid was mixed with polydimethylsiloxane precursor liquid at a volume ratio of 1:2 and ultrasonicated at 40 °C for 1 h to obtain a homogeneous emulsion.

[0088] 2) Preparation of prepolymer: After cooling the obtained emulsion to room temperature, add polymethylhydrosiloxane curing agent and stir evenly to obtain brown prepolymer. Cast the prepolymer onto a smooth and flat substrate.

[0089] 3) Thin film forming: The cast substrate is placed in a 70 ℃ oven for heat curing for 10 min. After removal, it is peeled off to obtain a brown film, which is the heat-assisted magnetically recordable-erasable photonic crystal film.

[0090] The average size of the phase transition microspheres in the photonic crystal film obtained in this embodiment is 12 μm. Figure 8 In the case of 'a', the reflectance spectrum of its magnetic response is as follows: Figure 8 As shown in b in the figure.

[0091] Example 4

[0092] A heat-assisted magnetic recording-erasing photonic crystal film, the preparation method of which includes the following steps:

[0093] 1) Emulsion preparation: Fe3O4@PVP colloidal nanoparticles with an average particle size of 170 nm were ultrasonicated with Span 40 at 60 °C for 2 h to obtain a magnetic phase transition photonic crystal liquid with a concentration of 150 mg / mL.

[0094] The obtained photonic crystal liquid was mixed with polyurethane acrylate precursor liquid (molecular weight ~2500g / mol) at a volume ratio of 1:2 and ultrasonicated at 60 °C for 1 h to obtain a homogeneous emulsion.

[0095] 2) Preparation of prepolymer: After cooling the emulsion to room temperature, add azobisisobutyronitrile curing agent (accounting for 1 / 100 of the mass of polyurethane acrylate), stir until uniform, and obtain a brown prepolymer. Cast the prepolymer onto a smooth and flat substrate.

[0096] 3) Thin film forming: The cast substrate is placed in a 70 ℃ oven for heat curing for 10 min. After removal, it is peeled off to obtain a brown film, which is the heat-assisted magnetically recordable-erasable photonic crystal film.

[0097] In this embodiment, the average size of the phase transition microspheres in the photonic crystal film is 8 μm. Figure 9 In the case of 'a', its responsiveness is as follows: Figure 9 As shown in b in the figure.

[0098] Example 5

[0099] A heat-assisted magnetic recording-erasing photonic crystal film, the preparation method of which includes the following steps:

[0100] 1) Emulsion preparation: Fe3O4@PVP colloidal nanoparticles with an average particle size of 145 nm were ultrasonicated with polyoxyethylene (40) nonylphenyl ether at 60 °C for 2 h to obtain a magnetic phase transition photonic crystal liquid with a concentration of 150 mg / mL.

[0101] The obtained photonic crystal liquid was mixed with polydimethylsiloxane prepolymer at a volume ratio of 1:2 and ultrasonicated at 60 °C for 1 h to obtain a homogeneous emulsion.

[0102] 2) Preparation of prepolymer: After cooling the emulsion to room temperature, add polymethylhydrosiloxane curing agent and stir until uniform to obtain brown prepolymer; cast the prepolymer onto a smooth and flat substrate;

[0103] 3) Thin film forming: The cast substrate is placed in a 70 ℃ oven for heat curing for 10 min. After removal, it is peeled off to obtain a brown film, which is the heat-assisted magnetically recordable-erasable photonic crystal film.

[0104] In this embodiment, the average size of the phase transition microspheres in the photonic crystal film is 8 μm. Figure 10 In the case of 'a', its responsiveness is as follows: Figure 10 As shown in b in the figure.

[0105] Example 6

[0106] A heat-assisted magnetic recording-erasing photonic crystal film, the preparation method of which includes the following steps:

[0107] 1) Emulsion preparation: Fe3O4@PVP colloidal nanoparticles with an average particle size of 145 nm were ultrasonicated with polyoxyethylene (40) nonylphenyl ether at 60 °C for 2 h to obtain a magnetic phase transition photonic crystal liquid with a concentration of 150 mg / mL.

[0108] The obtained photonic crystal liquid was mixed with polyurethane acrylate (same as in Example 4) at a volume ratio of 1:2 and sonicated at 60 °C for 1 h to obtain a uniform emulsion.

[0109] 2) Preparation of prepolymer: After cooling the emulsion to room temperature, add azobisisobutyronitrile curing agent (same as in Example 4), stir until uniform, and obtain a brown prepolymer; cast the prepolymer onto a smooth and flat substrate;

[0110] 3) Thin film forming: The cast substrate is placed in a 70 ℃ oven for heat curing for 10 min. After removal, it is peeled off to obtain a brown film, which is the heat-assisted magnetically recordable-erasable photonic crystal film.

[0111] In this embodiment, the average size of the phase transition microspheres in the photonic crystal film is 8 μm. Figure 11 In the case of 'a', its responsiveness is as follows: Figure 11 As shown in b in the figure.

[0112] Example 7

[0113] A heat-assisted magnetic recording-erasing photonic crystal film, the preparation method of which includes the following steps:

[0114] 1) Emulsion preparation: Superparamagnetic nanocrystal cluster core-shell particles with an average particle size of 200 nm were ultrasonicated with Span 40 at 60 °C for 2 h to obtain a magnetic phase transition photonic crystal liquid with a concentration of 300 mg / ml.

[0115] The obtained photonic crystal liquid was mixed with polydimethylsiloxane prepolymer at a volume ratio of 1:2 and ultrasonicated at 60 °C for 1 h to obtain a homogeneous emulsion.

[0116] (2) Preparation of prepolymer: After cooling the emulsion to room temperature, add polymethylhydrosiloxane and stir until uniform to obtain a brown prepolymer; cast the prepolymer onto a smooth and flat substrate;

[0117] (3) Thin film forming: The casting substrate is placed in a 70 ℃ oven for 10 min for heat curing. After taking it out, it is peeled off to obtain a brown film, which is the heat-assisted magnetic recordable-erasable photonic crystal film.

[0118] In this embodiment, the average size of the phase transition microspheres in the photonic crystal film is 8 μm. Figure 12 In the case of 'a', its responsiveness is as follows: Figure 12 As shown in b in the figure.

[0119] Comparative Example 1

[0120] A photonic crystal film is prepared in a manner largely the same as in Example 1, except that Span 40 is replaced with polyethylene glycol 2000.

[0121] The obtained crystalline film was heated to 70℃ and subjected to different magnetic fields. The film underwent structural and color changes, and its response spectrum is as follows: Figure 13 a. The obtained crystal film was placed under a magnetic field of 700 Gs, and by heating the crystal film to 60 °C, a blue structural color film was formed, as shown in Figure 1. Figure 13 b; subsequently cooled to room temperature and the magnetic field removed, the blue structure of the crystal film disappeared, as shown in Figure 1. Figure 13 c in the text.

[0122] Comparative Example 2

[0123] A photonic crystal film is prepared in a manner largely the same as in Example 1, except that Span 40 is replaced with paraffin No. 58.

[0124] The obtained crystal film was heated to 60℃, and magnetic fields of 0 Gs, 100 Gs, and 700 Gs were applied sequentially. No color change was observed. The morphology and spectrum of the crystal film under the corresponding magnetic fields are shown in the figure. Figure 14 .

[0125] Comparative Example 3

[0126] A photonic crystal film is prepared using the same method as in Example 1, but in the preparation process, Span 40, Fe3O4@PVP colloidal nanoparticle clusters and polydimethylsiloxane precursor solution are directly mixed according to the specified ratio, ultrasonically mixed evenly (ultrasonicated at 60 °C for 3 h), cooled, and then polymethylhydrosiloxane curing agent is added to cure the film.

[0127] When the obtained crystal film was heated to 60°C and different magnetic fields were applied, the film did not show any color change. Figure 15 .

[0128] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A heat-assisted magnetic recording-erasing photonic crystal film, characterized by, It is composed of a flexible polymer matrix and a magnetic phase change photonic crystal embedded therein; the magnetic phase change photonic crystal comprises superparamagnetic nanoparticles and a magnetic color fixing phase change material, wherein the magnetic color fixing phase change material is a sorbitan fatty acid ester phase change material; The sorbitan fatty acid ester phase change material is one or more of sorbitan monostearate, sorbitan monopalmitate, sorbitan monolaurate, and sorbitan oleate.

2. The heat-assisted magnetic recording-erasing photonic crystal film according to claim 1, wherein The flexible polymer matrix is one or more of polydimethylsiloxane, polyurethane acrylate, and flexible epoxy resin.

3. The heat assisted magnetic recording-erasing photonic crystal film according to claim 1, wherein The superparamagnetic nanoparticles are PVP-coated magnetic nanoparticles.

4. The heat-assisted magnetic recording-erasing photonic crystal film according to claim 3, wherein The magnetic nanoparticles are one or more of Fe3O4, CoFe2O4, and NiFe2O4 nanoparticles.

5. The heat assisted magnetic recording-erasing photonic crystal film according to claim 1, wherein The magnetic phase change photonic crystal is embedded in the flexible polymer matrix in the form of microspheres, and the size of the microspheres is less than or equal to 20 μm.

6. The heat assisted magnetic recording-erasing photonic crystal film of claim 1, wherein, The phase transition temperature of the magnetic phase change photonic crystal is 40-55℃.

7. The heat assisted magnetic recording-erasing photonic crystal film of claim 1, wherein, The mass ratio of the superparamagnetic nanoparticles to the magnetic color fixing phase change material is 1:3.5-100, and the mass ratio of the magnetic phase change photonic crystal to the flexible polymer matrix is 1:1-50.

8. The method for preparing the heat-assisted magnetic recording-erasing photonic crystal film according to any one of claims 1 to 7, characterized in that, The method comprises the following steps: 1) ultrasonic dispersion of the magnetic color fixing phase change material and the magnetic nanoparticles under heating to obtain a uniform dispersion liquid; emulsification of the obtained dispersion liquid with a precursor solution of the flexible polymer matrix to obtain an emulsion; 2) cooling of the obtained emulsion to room temperature, addition of a curing agent of the flexible polymer matrix, and uniform mixing to obtain a prepolymer liquid; 3) pouring and curing of the obtained prepolymer liquid, demolding, and thus obtaining the heat-assisted magnetic recording-erasing photonic crystal film.

9. Use of a thermal-assisted magnetic recording-erasing photonic crystal film according to any one of claims 1 to 7, characterized in that, The specific recording and erasing steps include the following: 1) application of a magnetic field of 50-1000 Gs to the heat-assisted magnetic recording-erasing photonic crystal film at room temperature, writing on the photonic crystal film with a heating pen, and removal of the magnetic field, thus completing the recording of the photonic crystal color pattern; 2) placement of the photonic crystal film in an environment without an external magnetic field, heating to above 60℃, and thus achieving the erasing of the photonic crystal color pattern.

Images