Preparation method of temperature-sensitive phosphorescent ultra-thin flexible temperature measuring film

Abstract

The application discloses a preparation method of a temperature-sensitive phosphorescent ultrathin flexible temperature measuring film, and belongs to the technical field of phosphorescent temperature measurement. The film preparation method comprises the following steps: uniformly mixing a high-molecular polymer precursor solution and phosphorescent material according to a predetermined mass ratio, and obtaining a polymer precursor suspension containing the phosphorescent material after vacuum defoaming; coating the defoamed suspension on a substrate to form a liquid film based on set spin-coating parameters; performing heating and curing treatment on the liquid film based on a set stepwise heating program; and soaking the cured film in an ethanol aqueous solution to perform film removal, so as to obtain a flexible temperature measuring film product. Compared with the prior art, the thickness of the temperature measuring film prepared according to the method can reach 5 microns or below, non-contact and high spatial resolution surface temperature visual sensing can be realized, and the method is suitable for fields such as bionic electronic skin, wearable health monitoring and intelligent robot skin system.

Description

Technical Field

[0001] This invention relates to the field of phosphorescent thermometry, specifically to a method for preparing a thermosensitive phosphorescent ultrathin flexible thermometric film. Background Technology

[0002] Phosphorescent thermometry, with its ability to convert temperature information into optical signals, offers advantages such as non-contact operation, resistance to electromagnetic interference, and high spatial resolution, demonstrating great potential for temperature detection in fields such as flexible electronics and biomimetic robotics. To apply phosphorescent materials to flexible test surfaces, current techniques typically involve incorporating the phosphorescent material into flexible substrates such as polyimide, and then fabricating flexible thermometric films using methods such as casting or coating.

[0003] Phosphorescent thermometry uses light signals to detect temperature, offering advantages such as anti-interference and visualization. When combined with a flexible substrate, it can be used for temperature measurement on deformable surfaces. Patent CN119978878A discloses a method for preparing a phosphorescent thermometric coating. While this method can utilize phosphorescent materials to achieve temperature sensing, the entire process system is designed for rigid surfaces. The resulting coating is difficult to deform with a flexible substrate, making it unsuitable for direct application in various flexible temperature measurement scenarios.

[0004] Currently, some scholars in the industry have conducted special research on flexible phosphorescent thermometric films. Cai Tao et al. selected a film with the chemical formula 3.5MgO·0.5MgF2·GeO2:Mn 4+Using phosphorescent material (MFG) and polyimide prepared from 4,4-diaminodiphenyl ether and 4,4′-oxydiphthalic anhydride as a flexible matrix, a flexible phosphorescent thermometric film fabrication scheme was developed. However, the film thickness obtained by this scheme is approximately 45 μm, much larger than the particle size of the phosphorescent material itself. During the film formation stage, the phosphorescent particles are prone to sedimentation under gravity, which hinders the penetration of ultraviolet excitation light into the film and weakens the thermal conductivity between the surface of the object being measured and the phosphorescent particles, ultimately leading to a significant decrease in the film's temperature measurement response speed. Meanwhile, the heating and curing process used in this technology takes up to 5 hours, and the low fabrication efficiency makes it unsuitable for industrial-scale production. To overcome these technical problems, the industry generally believes that the film thickness needs to be controlled to within 5 μm, while optimizing the heat treatment process to shorten the process time. However, among the various publicly available technologies, mature processes that can simultaneously achieve micron-level ultrathin phosphorescent film formation and efficient heat treatment are still very limited. Patent CN118580452A describes a long-life room-temperature phosphorescent thin film and its ultra-low temperature visualization detection method. This film can be applied to temperature visualization detection scenarios, but its film formation method, which involves directly casting a polymer mixture solution onto a substrate, cannot precisely control the film thickness and is not suitable for the preparation of ultra-thin films. Patent CN111961461A describes a phosphorescent thin film preparation process using a coating method, resulting in a film thickness in the range of 0.2-0.8 mm, which falls into the thick film category and also fails to meet the preparation standard for ultra-thin flexible phosphorescent thermometric films of 5 μm and below.

[0005] Therefore, we propose a method for preparing a thermosensitive phosphorescent ultrathin flexible temperature-measuring film to alleviate or solve the above problems.

[0006] The information disclosed above in this background section is only for enhancing the understanding of the background section of this invention, and therefore may include prior art that is not known to those skilled in the art. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a method for preparing a thermosensitive phosphorescent ultrathin flexible temperature-measuring film, thereby solving the problems in the prior art where it is difficult to simultaneously achieve micron-level ultrathin film formation and efficient heat treatment, resulting in large film thickness, easy sedimentation of phosphorescent particles, and low preparation efficiency.

[0008] To achieve the above objectives, the present invention provides a method for preparing a thermosensitive phosphorescent ultrathin flexible temperature-measuring film, the method comprising the following steps:

[0009] S1: A polymer precursor solution with a solid content of 5-20% is mixed with phosphorescent material at a mass ratio of 1:(5-100), and a suspension is obtained after vacuum defoaming; wherein, the polymer precursor solid content in the polymer precursor solution is used as the basis for calculation.

[0010] S2: Spin-coat the suspension onto the substrate to obtain a liquid film. The spin-coating speed is 800-3000 rpm, the time is 25-50 s, and the acceleration is 800-2000 rpm / s.

[0011] S3: The liquid film is heated and solidified using a stepped heating method, and then cooled and demolded to obtain a flexible phosphorescent thermometric film;

[0012] The stepped heating method is as follows: in the 40-80℃ stage, the heating rate is 1.0-2.0℃ / min; in the 80-110℃ stage, the heating rate is 1.5-2.5℃ / min; in the 110-200℃ stage, the heating rate is 2.0-4.0℃ / min; in the 200-300℃ stage, the heating rate is 3.0-6.0℃ / min; and after heating to 300℃, the temperature is held for 20-45 minutes.

[0013] Compared with the prior art, the beneficial effects of the present invention are:

[0014] This invention employs a spin-coating process combined with stepped temperature curing to stably produce an ultrathin flexible temperature-sensing film with a thickness of approximately 4.4 μm. Compared to existing films of similar thickness in the tens of micrometers and millimeters, this method suppresses the gravitational settling and localized accumulation of phosphorescent particles during film formation, ensuring a uniform distribution of phosphorescent particles within the polymer matrix. On one hand, this uniform particle distribution ensures that ultraviolet excitation light can smoothly penetrate the film, fully exciting the internal phosphorescent material. On the other hand, the ultrathin structure further enhances the thermal conductivity between the measured surface and the phosphorescent particles, improving the film's temperature sensitivity and temperature response speed.

[0015] The stepped temperature curing process of this invention can smoothly remove solvent at low temperatures, avoiding problems such as bubbles, wrinkles, and cracks in the film, while alleviating thermal stress concentration at high temperatures, ensuring film structural stability and surface integrity. While ensuring film quality, this heat treatment process reduces curing time, improves overall preparation efficiency, and is suitable for industrial-scale production. The resulting temperature-sensitive phosphorescent film combines ultra-thinness, excellent flexibility, and reliable temperature measurement performance, which can well meet the temperature measurement needs of complex deformation scenarios such as bionic electronic skin, wearable health monitoring, and intelligent robot skin, thus promoting the industrial application of flexible phosphorescent temperature measurement technology.

[0016] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the invention will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0017] Figure 1 This is a flowchart of the preparation method of the thermosensitive phosphorescent ultrathin flexible temperature-measuring film of the present invention.

[0018] Figure 2 This is a physical image of the polyimide temperature-sensing film containing MFG prepared in Example 1 of the present invention.

[0019] Figure 3 This is a partial cross-sectional view of the MFG-containing polyimide thermometric film prepared in Example 1 of the present invention under an electron microscope. In the figure, 1: MFG; 2: polyimide.

[0020] Figure 4 This is a partial cross-sectional view of the region without MFG observed in the thin film under an electron microscope, as shown in Embodiment 1 of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be noted that the drawings are schematic and not illustrated to scale. For clarity and convenience, the relative sizes and proportions of the parts shown in the drawings have been exaggerated or reduced in size. Any size is only exemplary and not limiting.

[0022] Example 1

[0023] This embodiment provides a method for preparing a thermosensitive phosphorescent ultrathin flexible temperature-sensing film, the process flow of which is shown in the attached figure. Figure 1 As shown, the specific steps are as follows:

[0024] S1: Take 5 g of a 20% solid content polyamic acid (PAA) solution in dimethylacetamide (DMAC) (polymer precursor solution), and add 0.05 g of 3.5MgO·0.5MgF2·GeO2:Mn with an average particle size of 5 μm. 4+ (MFG) phosphorescent powder. The mass ratio of MFG to PAA was 1:20, based on the polymer precursor solids content in the polymer precursor solution. The mixture was stirred at 600 rpm for 20 minutes at room temperature using a magnetic stirrer until fully homogeneous. Then, it was placed in a vacuum oven and defoamed under -0.1 MPa for 30 minutes to obtain a polyimide precursor suspension containing MFG.

[0025] S2: A circular glass substrate with a thickness of 2 mm and a diameter of 60 mm (after being ultrasonically cleaned sequentially with ethanol and deionized water to ensure surface cleanliness) is placed on the suction cup of a spin coater and concentrically fixed. A certain amount of suspension, after vacuum defoaming, is transferred onto the glass substrate using a pipette. The spin coating speed is set to 1000 rpm, the spin coating time to 30 s, and the spin coating acceleration to 1000 rpm / s. The spin coater is then started to spin coat the substrate to obtain a liquid film.

[0026] S3: Place the glass substrate coated with liquid film on a hot table for stepped heating and curing. The specific heat treatment procedure is as follows: in the 40-80℃ stage, the heating rate is 1.5℃ / min; in the 80-110℃ stage, the heating rate is 2.0℃ / min; in the 110-200℃ stage, the heating rate is 3.0℃ / min; in the 200-300℃ stage, the heating rate is 4.0℃ / min; after heating to 300℃, hold at that temperature for 30 minutes.

[0027] S4: After heat treatment, the coated glass substrate is placed in an air stream to cool to room temperature for 30 minutes. After the film cools to room temperature, it is immersed in a 10% (v / v) ethanol aqueous solution for film removal for 80 hours. After removal, it is washed with deionized water and dried to obtain the finished polyimide flexible phosphorescent thermometric film containing MFG.

[0028] Appendix Figure 2 Here is a photograph of the MFG-containing polyimide film prepared in this embodiment, with accompanying image. Figure 3 and attached Figure 4 This is a cross-sectional view of the thin film prepared in this embodiment under an electron microscope. (Attached image) Figure 3 This is a partial cross-sectional view of the MFG-containing region observed in the thin film. The cross-section shows that the phosphorescent material and the polymer are tightly bonded, and the polymer has a good coating effect on the phosphorescent material. Furthermore, the phosphorescent material is uniformly distributed along the thickness direction of the film, indicating that the sedimentation of phosphorescent particles is significantly suppressed. (Attached) Figure 4 This is a partial cross-sectional view of the region without MFG observed in the thin film. The three arrows in the figure indicate the locations where the film thickness was measured, with corresponding thicknesses of 4.35 μm, 4.43 μm, and 4.46 μm, respectively. The average thickness is approximately 4.4 μm.

[0029] Example 2

[0030] The difference between this embodiment and Embodiment 1 is that the phosphorescent material selected in step S1 is Y3Al5O 12 :Dy 3+(YAG:Dy), with an average particle size of 2 μm, and the mixing mass ratio of YAG:Dy to polyimide precursor is 1:20. The remaining steps are the same as in Example 1, and finally a flexible polyimide phosphorescent thermometric film containing YAG:Dy is prepared.

[0031] In summary, this invention achieves micron-level ultrathin film formation by controlling the specific ratio of precursor solution solid content (5-20%) to phosphorescent material and combining it with specific spin-coating process parameters. Due to the extremely thin film thickness, the gravitational settling of phosphorescent particles is fundamentally suppressed. At the same time, the four-stage stepped temperature curing process facilitates the gradual release of solvent in the liquid film during the solvent removal stage at 40-80℃, reducing the risk of surface bubbles, wrinkles, and local cracking. The high-temperature stage suppresses thermal stress concentration. Thus, while ensuring the quality of micron-level ultrathin film formation, the curing cycle is significantly shortened to less than 2 hours, improving the preparation efficiency and the temperature response characteristics of the film.

[0032] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0033] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a thermosensitive phosphorescent ultrathin flexible temperature-measuring film, characterized in that, The preparation method includes the following steps: S1: A polymer precursor solution with a solid content of 5-20% is mixed with phosphorescent material at a mass ratio of 1:(5-100), and a suspension is obtained after vacuum defoaming; wherein, the polymer precursor solid content in the polymer precursor solution is used as the basis for calculation. S2: Spin-coat the suspension onto the substrate to obtain a liquid film. The spin-coating speed is 800-3000 rpm, the time is 25-50 s, and the acceleration is 800-2000 rpm / s. S3: The liquid film is heated and solidified using a stepped heating method, and then cooled and demolded to obtain a flexible phosphorescent thermometric film; The stepped heating method is as follows: in the 40-80℃ stage, the heating rate is 1.0-2.0℃ / min; in the 80-110℃ stage, the heating rate is 1.5-2.5℃ / min; in the 110-200℃ stage, the heating rate is 2.0-4.0℃ / min; in the 200-300℃ stage, the heating rate is 3.0-6.0℃ / min; and after heating to 300℃, the temperature is held for 20-45 minutes.

2. The preparation method according to claim 1, characterized in that, In step S1, the polymer precursor is a polyamic acid solution, and the phosphorescent material is selected from 3.5MgO·0.5MgF2·GeO2:Mn 4+ Y3Al5O 12 :Dy 3+ ,BaMgAl 10 O 17 Eu 2+ Or one of ZnO.

3. The preparation method according to claim 1, characterized in that, In step S1, the mixing method is magnetic stirring at a speed of 500-800 rpm for 20-30 min; the vacuum defoaming conditions are vacuum defoaming at -0.1 MPa for more than 30 min at room temperature.

4. The preparation method according to claim 1, characterized in that, In step S3, the cooling method is to place the film and the substrate in an air stream to cool to room temperature; the film removal method is to place the film and the substrate together in an ethanol aqueous solution with a volume concentration of 10-20% for 60-100 hours.

5. A flexible phosphorescent thermometric film prepared by the preparation method according to any one of claims 1-4, characterized in that, The film has a thickness of 1-5 μm, and the phosphorescent material is uniformly distributed in the thickness direction of the polymer matrix without sedimentation.

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