Color electrothermal film based on optical interference regulation and preparation method thereof

Abstract

The invention discloses a colored electrothermal film based on optical interference regulation and a preparation method thereof. The electrothermal film comprises an electrothermal unit and an optical interference regulation and control layer arranged on the outer surface of the electrothermal unit, and the optical interference regulation and control layer is a multi-layer film system formed by alternately stacking high and low refractive index material layers. Structural colors are generated through thin film interference, the colorful and lasting decoration effect is achieved, and the original light transmitting and heating performance is not affected. The preparation method adopts a vacuum coating process to deposit the optical interference regulation and control layer. Optionally, a gradient color effect can be realized by using a mask plate during deposition; or the innermost layer of the optical layer is designed as the seed crystal induction layer of the transparent conductive layer, so that the electric heating performance is improved. The problem that an existing electrothermal film is single in color is solved, and the electrothermal film is suitable for the fields of high-end consumer electronics, smart home and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of functional electrothermal film materials, in particular to a transparent electrothermal film with optical decoration effect and a preparation method thereof. BACKGROUND

[0002] The transparent electrothermal film is widely used in the fields of anti-fog, anti-frost and low-temperature heating of automobile glass, building storefront, household appliances, etc. due to its good light transmittance and electrothermal conversion performance. The mainstream transparent electrothermal film currently usually adopts a flexible material such as polyethylene terephthalate (PET) as a substrate, deposits a transparent conductive film (such as indium tin oxide ITO) as a heating layer on the surface of the substrate by a magnetron sputtering process, and sets electrodes at both ends of the heating layer.

[0003] However, the existing transparent electrothermal film product has a single function, and its appearance is usually colorless and transparent or light yellow of the material itself, with a single color and a monotonous appearance. This limits its application in some consumer electronics, smart home, high-end automobile interiors and other fields that focus on appearance aesthetics. For example, in occasions where the color of the product as a whole needs to be coordinated, the traditional transparent electrothermal film often looks out of place and cannot meet the growing market demand for personalization and high-endization. In order to solve the color problem, the industry has tried to paste a color film on the surface of the electrothermal film or perform surface spraying. However, pasting a color film will introduce a new adhesive layer and film layer, significantly reducing the overall light transmittance of the electrothermal film, affecting the field of view and use effect; and the surface spraying process not only destroys the smoothness of the surface of the electrothermal film, but also easily produces scratches, affecting the appearance, and the adhesion and durability of the coating layer are poor, and in the long-term electrothermal cycle and external environment, problems such as discoloration, cracking and even peeling are prone to occur.

[0004] Therefore, how to provide a new electrothermal film product that can not only maintain good light transmittance and heating function, but also present rich and durable color, has become a technical problem that needs to be solved in the field. SUMMARY

[0005] The present application aims to provide a color electrothermal film based on optical interference regulation and a preparation method thereof, and aims to solve the technical problems of single color, poor decoration and poor performance of traditional coloring methods of the transparent electrothermal film in the prior art.

[0006] To achieve the above-mentioned purpose, the present application provides a color electrothermal film based on optical interference regulation, comprising: an electrothermal unit, the electrothermal unit comprising a first substrate, a transparent conductive heating layer formed on one side of the first substrate, and an electrode disposed on the transparent conductive heating layer; an optical interference regulation layer, the optical interference regulation layer being disposed on the outer surface of the electrothermal film; wherein the optical interference regulation layer is a multilayer film structure formed by alternately stacking at least one high refractive index material layer and at least one low refractive index material layer.

[0007] It can be seen that the present application fundamentally solves the problem of single color of the existing electrothermal film by setting an optical interference control layer on the outer surface of the electrothermal film, and generating structural color by using the thin film interference principle of light. The color is determined by the physical structure of the thin film, rather than chemical pigments, so the color is pure and bright, and has excellent stability and durability, and will not fade over time or electrothermal cycle. At the same time, the optical interference control layer does not affect the original transparent conductive heating performance and light transmittance of the product, and successfully integrates excellent electrothermal function and advanced aesthetic decoration effect.

[0008] Optionally, the thickness of the optical interference control layer changes in a gradient along a certain direction of the first substrate, so that the electrothermal film presents a gradient color effect.

[0009] It can be seen that by setting an optical interference control layer with a gradient change in thickness on the outer surface of the electrothermal film, and using the high sensitivity of interference color to thickness, the color can be continuously and smoothly transitioned on the same piece of electrothermal film, forming a unique gradient color effect, greatly improving the appearance grade and design freedom of the product.

[0010] Optionally, the electrothermal unit further comprises a second substrate encapsulating the transparent conductive heating layer and the electrode; the optical interference control layer is arranged on the outer surface of the side of the first substrate away from the transparent conductive heating layer, or on the outer surface of the second substrate.

[0011] It can be seen that the specific setting position of the optical interference control layer is clear, which ensures that it is located at the outermost layer of the entire device, thereby most effectively playing its decoration function, and also protecting the internal electrothermal core unit, and the structure design is reasonable.

[0012] Optionally, the transparent conductive heating layer is an indium tin oxide layer; the high refractive index material layer of the innermost layer of the optical interference control layer serves as a seed induction layer of the indium tin oxide layer.

[0013] It can be seen that this integrated design is very ingenious, so that part of the optical interference control layer (the high refractive index material of the innermost layer) simultaneously serves the electrothermal unit, and by serving as an induction layer of ITO crystallization, the microstructure of ITO can be improved, the sheet resistance can be effectively reduced, and the electrothermal conversion efficiency can be improved. This realizes the synergistic gain of optical layer and electrical function, embodies the design idea of "1+1>2", and improves the comprehensive performance of the product without adding additional process steps.

[0014] Optionally, the high refractive index material layer serving as the seed induction layer of the indium tin oxide layer is a niobium pentoxide layer.

[0015] It can be seen that by specifically defining the material of the seed crystal induction layer as niobium pentoxide, a verified and significantly effective preferred technical solution is provided, which can not only be used as part of the optical interference layer, but also effectively improve the ITO crystalline quality and reduce the resistivity, and has excellent technical effects and implementability.

[0016] Optionally, the optical interference regulation layer further comprises a metal layer embedded between the high refractive index material layer and / or the low refractive index material layer.

[0017] It can be seen that by introducing a nanoscale ultrathin metal layer in the dielectric film system, the unique optical response (such as strong reflection) of the metal is utilized in combination with the thin film interference effect, so that the special decorative effect of gold, champagne gold and the like with high-grade metal texture can be achieved, further enriching the color selection of the product.

[0018] Optionally, the metal layer is a silver layer.

[0019] It can be seen that by specifically defining the metal layer as a silver layer, a preferred scheme for realizing a color with a metal texture (such as champagne gold) is provided, which utilizes the semi-transparent and high-reflection optical properties of the ultrathin silver layer in combination with the dielectric film interference, and has outstanding decorative effect and mature process.

[0020] Optionally, the high refractive index material layer is selected from one or more of titanium dioxide, niobium pentoxide, silicon nitride, and zirconium oxide; and the low refractive index material layer is selected from one or more of silicon dioxide, magnesium fluoride, and aluminum oxide.

[0021] It can be seen that by selecting these mature, stable and excellent optical performance dielectric materials, a film system with a specific reflection spectrum can be accurately designed and prepared, ensuring the controllability of the color and the reliability of the product.

[0022] The application also provides a preparation method of the color electric heating film, comprising: depositing a transparent conductive heating layer on one side surface of a first substrate; forming electrodes at both ends of the transparent conductive heating layer; and depositing an optical interference regulation layer on the outer surface of the electric heating film by a vacuum plating process, the optical interference regulation layer being formed by alternately stacking at least one high refractive index material layer and at least one low refractive index material layer.

[0023] Optionally, in the step of depositing the optical interference regulation layer, a mask plate is arranged between the first substrate and the sputtering target source, and the relative motion between the mask plate and the first substrate is controlled to make the thickness of the deposited film layer have a gradient distribution.

[0024] As can be seen, this method clarifies a precise and controllable process for achieving gradient color effects. By introducing a specially designed mask, thin films with linearly or non-linearly varying thicknesses can be stably prepared on large-area planar substrates, thereby precisely controlling the transition effect of gradient colors. This method employs mature vacuum deposition technology, has good compatibility with the preparation process of transparent conductive heating layers (such as ITO), and can be easily completed on the same equipment or continuous production line, facilitating large-scale, low-cost industrial production.

[0025] Optionally, before depositing the transparent conductive heating layer on the first substrate, a high refractive index material layer of the innermost layer of the optical interference control layer is first deposited as a seed induction layer for the transparent conductive heating layer.

[0026] As can be seen, this method embodies the design concept of functional integration. By cleverly arranging the deposition sequence, one step (depositing a high-refractive-index material layer) serves two purposes (optical interference and seed induction), simplifying the process and improving the performance of the final product.

[0027] Optionally, it further includes: bonding a second substrate with an encapsulating adhesive layer to a first substrate to encapsulate the transparent conductive heating layer and the electrode.

[0028] As can be seen, this step ensures the sealing and reliability of the core functional parts of the electrothermal film (conductive layer and electrodes), protecting them from external environmental corrosion and ensuring the long-term stable use of the product. Attached Figure Description

[0029] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with their description, serve to explain the principles of the invention.

[0030] Figure 1 This is a schematic diagram of the structure of the colored electrothermal film in one embodiment of the present invention; Figure 2 This is a schematic diagram of the mask coating principle used in preparing a gradient color electrothermal film in one embodiment of the present invention.

[0031] Explanation of reference numerals in the attached figures: 1. Second PET substrate layer; 2. Encapsulating adhesive layer; 3. Transparent conductive heating layer; 4. First PET substrate layer; 5. Optical interference control layer; 6. Silver paste electrode; 7. Substrate; 8. Mask. Detailed Implementation

[0032] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0033] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0034] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0035] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0036] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0037] This invention provides a colored electrothermal film that combines electrothermal functionality with advanced decorative features. The core concept lies in precisely depositing a nanoscale multilayer optical thin film composed of various dielectric materials onto the outer surface of a standard transparent electrothermal film structure using vacuum deposition technology. This multilayer optical thin film utilizes the interference effect of light to generate brilliant and durable structural colors, fundamentally solving the problem of limited color options in traditional electrothermal films, while avoiding the performance degradation and poor durability defects caused by traditional coloring processes.

[0038] Please see Figure 1 The diagram illustrates a cross-sectional structure of a transparent electrothermal film in one embodiment of the present invention. The colored electrothermal film may include, from top to bottom, an electrothermal unit and an optical interference control layer 5.

[0039] The electrothermal unit is the core component for electrothermal conversion, and its structure can be a typical transparent electrothermal film structure. Specifically, it can include a flexible first PET substrate layer 4 as a support. It should be understood that the first substrate and the second substrate (described later) are preferably made of polyethylene terephthalate (PET), but are not limited to this; other polymer film materials with good light transmittance and flexibility can also be used. On the upper surface of the first PET substrate layer 4, a transparent conductive heating layer 3 is deposited using a magnetron sputtering process. This layer is typically made of indium tin oxide (ITO), but can also be made of other transparent conductive materials such as AZO, FTO, etc. At both ends of the transparent conductive heating layer 3, silver paste electrodes 6 are printed using processes such as screen printing for external power supply. To protect the internal conductive and electrode structure, an encapsulating adhesive layer 2 is usually applied over it, and a second PET substrate layer 1 is then attached to form a complete, encapsulated electrothermal core.

[0040] The key to this invention lies in the optical interference control layer 5. This layer is disposed on the outer surface of the entire electrothermal film structure to ensure that its color effect can be directly observed. Figure 1 In the illustrated embodiment, the optical interference control layer 5 is disposed on the outer surface of the first PET substrate layer 4 (i.e., the side away from the transparent conductive heating layer 3). Of course, in other embodiments, it can also be disposed on the outer surface of the outermost second PET substrate layer 1.

[0041] The optical interference control layer 5 itself is a multilayer film structure, consisting of at least one layer of high-refractive-index material and at least one layer of low-refractive-index material stacked alternately. For example, its film structure can be a (HL)^mH structure or a (LH)^mL structure, where H represents the high-refractive-index material layer, L represents the low-refractive-index material layer, and m is the period number (m≥1). The high-refractive-index material can be selected from titanium dioxide (TiO2, refractive index n≈2.3-2.5), niobium pentoxide (Nb2O5, n≈2.2-2.3), silicon nitride (Si3N4, n≈2.0-2.1), zirconium oxide (ZrO2, n≈2.0-2.1), etc., while the low-refractive-index material can be selected from silicon dioxide (SiO2, n≈1.46), magnesium fluoride (MgF2, n≈1.38), aluminum oxide (Al2O3, n≈1.63), etc. When light shines on this multilayer film system, complex reflection and transmission occur at the interfaces between the layers. By precisely designing the selection of materials and their physical thickness for each layer, it is possible to control the constructive or destructive interference of light of different wavelengths. Ultimately, light of a specific wavelength is selectively amplified and reflected, allowing the human eye to perceive a specific color, known as structural color. Theoretically, any color within the visible light range can be achieved by adjusting the film system design.

[0042] Example 1: Blue electric heating film This embodiment aims to prepare an electrothermal film that exhibits a uniform blue color.

[0043] First, a clean first PET substrate is provided. On one side of the substrate, an ITO thin film of moderate thickness is deposited as a transparent conductive heating layer using a magnetron sputtering process, with a sheet resistance of approximately 80 Ω / □. Subsequently, silver paste electrodes are screen-printed at both ends of the ITO layer and then baked for curing.

[0044] Next, the first PET substrate with the ITO layer and electrodes is flipped over and placed into a roll-to-roll magnetron sputtering apparatus. An optical interference modulation layer is then deposited sequentially on its other outer surface. The film structure is designed as: PET|SiO2(L)|Nb2O5(H)|SiO2(L)|Air.

[0045] The specific process parameters are as follows: The first layer (low refractive index layer L): Using a silicon (Si) target as the source, a silicon dioxide (SiO2) thin film is deposited by reactive sputtering in a mixed atmosphere of argon and oxygen, with its physical thickness controlled to be approximately 54.8 nm.

[0046] The second layer (high refractive index layer H): using a niobium (Nb) target as the source, reactive sputtering is performed in a mixed atmosphere of argon and oxygen to deposit a niobium pentoxide (Nb2O5) thin film, with its physical thickness controlled to be approximately 48.9 nm.

[0047] The third layer (low refractive index layer L): a silicon target is used again for reactive sputtering to deposit a silicon dioxide (SiO2) film, with the physical thickness also controlled at about 54.8 nm.

[0048] After sputtering is completed, a second PET substrate pre-coated with hot melt adhesive is provided and aligned and bonded with a first PET substrate with a functional layer. The finished product is then obtained through hot pressing encapsulation.

[0049] The prepared electrothermal film exhibits a uniform and pure blue color under natural light. Tests show that its average light transmittance in the visible light region is greater than 75%, and its heating performance after being energized is consistent with that of ordinary transparent electrothermal film, achieving a combination of function and aesthetics.

[0050] Example 2: Red electric heating film This embodiment uses a simpler membrane structure to achieve the red effect.

[0051] The electrothermal unit was prepared in the same manner as in Example 1. The film structure of the optical interference control layer was designed as: PET|TiO2(H)|SiO2(L)|Air.

[0052] The specific process parameters are as follows: First layer (high refractive index layer H): Using a titanium (Ti) target as the source, reactive sputtering is performed to deposit a titanium dioxide (TiO2) thin film with a physical thickness controlled to 60 nm.

[0053] The second layer (low refractive index layer L): Using a silicon (Si) target as the source, reactive sputtering is performed to deposit a silicon dioxide (SiO2) thin film with a physical thickness controlled to 90 nm.

[0054] After optical layer deposition and encapsulation, the resulting electrothermal film exhibits a bright red color.

[0055] Example 3: Gold-colored electric heating film This embodiment achieves a metallic gold effect by introducing an ultrathin metal layer into the dielectric film system.

[0056] The electrothermal unit was prepared in the same manner as in Example 1. The film structure of the optical interference control layer was designed as follows: PET|TiO2(H)|Ag(Metal)|TiO2(H)|SiO2(L)|Air.

[0057] The specific process parameters are as follows: First layer (H): A 25 nm thick TiO2 layer is deposited, which also serves as a promoting layer for the subsequent growth of the silver (Ag) layer.

[0058] The second layer (Metal): Using a metallic silver (Ag) target as the source, an ultrathin silver layer with a physical thickness of 12 nm is sputtered in an inert argon atmosphere. This thickness needs to be strictly controlled to ensure its translucency and high reflectivity.

[0059] The third layer (H): A 40 nm thick TiO2 layer is deposited to protect the Ag layer and participate in the overall interference effect.

[0060] Fourth layer (L): 85nm thick SiO2 is deposited as the outermost anti-reflection layer.

[0061] The final electrothermal film exhibits a champagne gold color with a high-end metallic luster.

[0062] Example 4: Gradient Color Electrothermal Film This embodiment aims to prepare a gradient color electrothermal film with a continuous color transition from blue to purple.

[0063] A three-layer film structure similar to that in Example 1 is adopted: PET|SiO2|Nb2O5|SiO2|Air. The key lies in the process of depositing the optical interference modulation layer.

[0064] Please see Figure 2 In the step of depositing the optical layer, a controllable speed-translating mask 8 is installed between the substrate 7 (i.e., the first PET substrate) and the sputtering target (not shown). The mask can be designed as, for example, a metal plate with triangular or other non-uniform openings.

[0065] During the deposition of each layer (SiO2, Nb2O5, SiO2), the mask 8 is activated and swept across the surface of the substrate 7 at a uniform speed. Because the masking effect is spatially variable, the final film thickness deposited in different regions of the substrate 7 exhibits a continuous gradient distribution. For example, the thickness of the first SiO2 layer can smoothly transition from 50 nm to 70 nm, and the thickness of subsequent layers can also vary proportionally.

[0066] Because interference colors are extremely sensitive to film thickness, this gradient distribution of physical thickness ultimately translates into a continuous color gradient. The resulting electrothermal film product exhibits a deep blue color at one end, which then smoothly transitions to a purplish-red at the other end, creating a unique gradient color visual effect.

[0067] Example 5: An electrothermal film with integrated functional design This embodiment demonstrates a scheme for the integrated and collaborative design of the optical control layer and the transparent conductive heating layer.

[0068] First, a clean first PET substrate is provided. On one side of its surface, a 30 nm thick Nb2O5 layer is deposited by magnetron sputtering. This layer not only serves as part of the subsequent optical film system, but more importantly, it can act as an inducing layer or seed layer for ITO crystallization.

[0069] Subsequently, a 150 nm thick ITO layer was deposited directly on the Nb2O5 layer. Due to the presence of the Nb2O5 underlayer, the subsequently grown ITO exhibited superior crystal quality and lower defect density.

[0070] After forming electrodes at both ends of the ITO layer, the substrate is flipped over, and a 90nm thick SiO2 layer is deposited on the outer surface of the other side as an anti-reflection layer to improve the overall light transmittance.

[0071] Finally, encapsulation is performed. Testing showed that the electrothermal film fabricated using this integrated design exhibits approximately 15% lower sheet resistance in its ITO layer compared to an ITO layer of the same thickness grown directly on PET, resulting in superior electrothermal performance. Simultaneously, due to the anti-reflective effect of the outermost SiO2 layer, the overall visible light transmittance is increased by approximately 5%, and the film layer as a whole displays specific interference colors. This approach simplifies the film structure and achieves synergistic performance enhancement of both the optical and electrical functions.

[0072] In summary, this invention provides an innovative colored electrothermal film and its preparation method. By combining mature optical interference thin film technology with electrothermal film technology, it not only solves the fundamental problem of the monotonous appearance of traditional electrothermal films, but also achieves advanced decorative effects such as gradient colors and metallic colors, as well as synergistic performance improvements, through the introduction of mask technology and integrated functional design. The product of this invention possesses excellent electrothermal performance, high light transmittance, and rich, long-lasting colors, and its preparation method is compatible with existing processes, exhibiting extremely high industrial application value and market prospects.

[0073] While specific embodiments of the invention have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims

1. A color electrocaloric film based on optical interference regulation, characterized in that, The application relates to an electrothermal film, which comprises the following components: an electrothermal unit, which comprises a first substrate, a transparent conductive heating layer formed on one side of the first substrate, and electrodes arranged on the transparent conductive heating layer; an optical interference regulation layer arranged on the outer surface of the electrothermal film; wherein the optical interference regulation layer is a multilayer film structure formed by alternately stacking at least one high-refractive-index material layer and at least one low-refractive-index material layer.

2. The colored electrocaloric film of claim 1, wherein, The thickness of the optical interference regulation layer changes in a gradient along a certain direction of the first substrate, so that the electrothermal film presents a gradual color effect.

3. The colored electrocaloric film of claim 1, wherein, The electrothermal unit further comprises a second substrate for encapsulating the transparent conductive heating layer and the electrodes; the optical interference regulation layer is arranged on the outer surface of the side of the first substrate away from the transparent conductive heating layer, or is arranged on the outer surface of the second substrate.

4. The colored electrocaloric film of claim 1 or 2, wherein, The transparent conductive heating layer is an indium tin oxide layer; the innermost high-refractive-index material layer of the optical interference regulation layer serves as a seed induction layer of the indium tin oxide layer.

5. The colored electrocaloric film of claim 1 or 2, wherein, The optical interference regulation layer further comprises a metal layer embedded between the high-refractive-index material layer and / or the low-refractive-index material layer.

6. The colored electrocaloric film of claim 1 or 2, wherein, The high-refractive-index material layer is selected from one or more of titanium dioxide, niobium pentoxide, silicon nitride and zirconium oxide; and the low-refractive-index material layer is selected from one or more of silicon dioxide, magnesium fluoride and aluminum oxide.

7. A method of producing a colored electrocaloric film as claimed in any one of claims 1-6, characterized in that, The application further relates to a method for manufacturing the electrothermal film. The method comprises the following steps: depositing a transparent conductive heating layer on one side surface of a first substrate; forming electrodes on both ends of the transparent conductive heating layer; 8. The preparation method according to claim 7, characterized in that, depositing an optical interference regulation layer on the outer surface of the electrothermal film by a vacuum plating process, wherein the optical interference regulation layer is formed by alternately stacking at least one high-refractive-index material layer and at least one low-refractive-index material layer.

9. The preparation method according to claim 7, characterized in that, In the step of depositing the optical interference regulation layer, a mask plate is arranged between the first substrate and a sputtering target source, and the relative motion between the mask plate and the first substrate is controlled to make the thickness of the deposited film layer be in a gradient distribution.

10. The method of claim 7, wherein, Before depositing the transparent conductive heating layer on the first substrate, the innermost high-refractive-index material layer of the optical interference regulation layer is first deposited to serve as a seed induction layer of the transparent conductive heating layer. The application further relates to a method for manufacturing the electrothermal film. The method comprises the following steps: attaching a second substrate with an encapsulating adhesive layer to the first substrate to encapsulate the transparent conductive heating layer and the electrodes.

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