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

Abstract

The application discloses a color electrothermal film based on optical interference regulation and a preparation method thereof. The electrothermal film comprises an electrothermal unit and an optical interference regulation layer arranged on the outer surface of the electrothermal unit, and the optical interference regulation layer is a multilayer film system formed by alternately stacking high and low refractive index material layers. The application utilizes thin film interference to generate structural color, realizes a decorative effect with rich and lasting color, and does not affect the original light transmission and heating performance. The preparation method adopts a vacuum coating process to deposit the optical interference regulation layer. Optionally, a gradual color effect can be realized by using a mask plate during deposition; or the innermost layer of the optical layer is designed as a seed induction layer of a transparent conductive layer to improve the electrothermal performance. The application solves the problem of single color of the existing electrothermal film and is suitable for high-end consumer electronics, smart home and other fields.

Description

Technical Field

[0001] This invention relates to the field of functional electrothermal thin film materials, and in particular to a transparent electrothermal film with optical decorative effects and its preparation method. Background Technology

[0002] Transparent electrothermal films are widely used in automotive glass, building windows, and household appliances for anti-fogging, anti-frost, and low-temperature heating due to their excellent light transmittance and electrothermal conversion performance. Currently, mainstream transparent electrothermal films typically use flexible materials such as polyethylene terephthalate (PET) as the substrate, and deposit a transparent conductive film (such as indium tin oxide, ITO) on its surface as the heating layer through processes such as magnetron sputtering, with electrodes placed at both ends of the heating layer.

[0003] However, existing transparent electric heating film products have relatively limited functions, and their appearance is usually colorless and transparent or the material itself is pale yellow, resulting in a monotonous appearance. This limits their application in certain fields that emphasize aesthetics, such as consumer electronics, smart homes, and high-end automotive interiors. For example, in situations where the color needs to coordinate with the overall appearance of the product, traditional transparent electric heating films often appear out of place and cannot meet the growing market demands for personalization and high-end products. To solve the color problem, the industry has tried to attach colored films or perform surface spraying on the outer surface of the electric heating film. However, attaching colored films introduces new adhesive and film layers, significantly reducing the overall light transmittance of the electric heating film, affecting visibility and usability; while surface spraying not only damages the smoothness of the electric heating film surface, making it prone to scratches and affecting aesthetics, but also results in poor adhesion and durability of the coating, making it prone to fading, cracking, and even peeling under long-term electric heating cycles and external environments.

[0004] Therefore, how to provide a new type of electrothermal film that can maintain good light transmittance and heating function while presenting rich and lasting colors has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a colored electrothermal film based on optical interference control and its preparation method, aiming to solve the technical problems of the existing transparent electrothermal film having a single color, poor decorative properties, and poor performance of traditional coloring methods.

[0006] To achieve the above objectives, the present invention provides a color electrothermal film based on optical interference control, comprising: an electrothermal unit, the electrothermal unit including 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; and an optical interference control layer disposed on the outer surface of the electrothermal film; wherein the optical interference control layer is a multilayer film structure formed by alternating stacking of at least one high refractive index material layer and at least one low refractive index material layer.

[0007] As can be seen, this invention fundamentally solves the problem of monochromatic colors in existing electrothermal films by setting an optical interference control layer on the outer surface of the electrothermal film and generating structural colors using the principle of thin-film interference of light. This color is determined by the physical structure of the film, not by chemical pigments; therefore, the color is pure, vibrant, and possesses excellent stability and durability, and will not fade over time or during electrothermal cycles. Simultaneously, while endowing the product with rich colors, the optical interference control layer does not affect its original transparent, conductive, and heating performance or light transmittance, successfully integrating superior electrothermal functionality with advanced aesthetic decorative effects.

[0008] Optionally, the thickness of the optical interference control layer varies in a gradient along a certain direction of the first substrate to give the electrothermal film a gradient color effect.

[0009] It is evident that by setting an optical interference control layer with a gradient thickness on the outer surface of the electrothermal film, and utilizing the high sensitivity of interference colors to thickness, a continuous and smooth transition of colors can be achieved on the same electrothermal film, forming a unique gradient color effect, which greatly enhances the appearance and design freedom of the product.

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

[0011] It is evident that this structure clearly defines the specific location of the optical interference control layer, ensuring that it is located on the outermost layer of the entire device, thereby maximizing its decorative function while also protecting the internal electrothermal core unit. The structural design is reasonable.

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

[0013] As can be seen, this integrated design is extremely ingenious, allowing a portion of the optical interference control layer (the innermost high-refractive-index material) to simultaneously serve the electrothermal unit. By acting as an inducing layer for ITO crystallization, it improves the microstructure, effectively reduces the sheet resistance, and enhances the electrothermal conversion efficiency. This achieves synergistic gains between the optical layer and the electrical function, embodying the design philosophy of "1+1>2," and improving the overall performance of the product without adding extra processing 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 is evident that by specifically defining the seed-inducing layer material as niobium pentoxide, a proven and effective preferred technical solution is provided. It can not only serve as part of the optical interference layer, but also effectively improve the crystal quality of ITO and reduce resistivity, demonstrating excellent technical effectiveness and feasibility.

[0016] Optionally, the optical interference control layer may also include a metal layer embedded between a high refractive index material layer and / or a low refractive index material layer.

[0017] It is evident that by introducing an ultrathin nanoscale metal layer into a dielectric film system, and utilizing the unique optical response of metal (such as strong reflection) in combination with the thin film interference effect, special decorative effects with a high-end metallic texture, such as gold and champagne gold, can be achieved, further enriching the color choices of the products.

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

[0019] It is evident that by specifically defining the metal layer as a silver layer, a preferred solution is provided to achieve a metallic texture and color (such as champagne gold). This solution utilizes the semi-transparent and highly reflective optical properties of the ultrathin silver layer combined with dielectric film interference, resulting in outstanding decorative effects and a 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; the low refractive index material layer is selected from one or more of silicon dioxide, magnesium fluoride, and aluminum oxide.

[0021] It is evident that by selecting these mature, stable, and optically superior dielectric materials, film systems with specific reflection spectra can be precisely designed and fabricated, ensuring the controllability of color and the reliability of the product.

[0022] The present invention also provides a method for preparing a colored electrothermal 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 control layer on the outer surface of the electrothermal film by a vacuum deposition process, wherein the optical interference control layer is formed by alternating stacking of 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 control layer, a mask is set between the first substrate and the sputtering target, and the thickness of the deposited film is made to have a gradient distribution by controlling the relative movement of the mask and the first substrate.

[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 functions 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 colored electrothermal film based on optical interference modulation, characterized in that, include: An electrothermal unit, comprising a first substrate, a transparent conductive heating layer formed on one side of the first substrate, and electrodes disposed on the transparent conductive heating layer; An optical interference control layer is disposed on the outer surface of the electrothermal film; The optical interference control layer is a multilayer film structure formed by alternating stacking of at least one high-refractive-index material layer and at least one low-refractive-index material layer; The transparent conductive heating layer is an indium tin oxide layer; the innermost high refractive index material layer of the optical interference control layer serves as the seed induction layer of the indium tin oxide layer.

2. The colored electrothermal film according to claim 1, characterized in that, The thickness of the optical interference control layer varies in a gradient along a certain direction of the first substrate, so that the electrothermal film presents a gradient color effect.

3. The colored electrothermal film according to claim 1, characterized in that, The electrothermal unit further includes a second substrate that encapsulates the transparent conductive heating layer and the electrode; the optical interference control layer is disposed on the outer surface of the first substrate away from the transparent conductive heating layer, or on the outer surface of the second substrate.

4. The colored electrothermal film according to claim 1 or 2, characterized in that, The optical interference control layer also includes a metal layer embedded between the high refractive index material layer and / or the low refractive index material layer.

5. The colored electrothermal film according to claim 1 or 2, characterized in that, The high refractive index material layer is selected from one or more of titanium dioxide, niobium pentoxide, silicon nitride, and zirconium oxide; the low refractive index material layer is selected from one or more of silicon dioxide, magnesium fluoride, and aluminum oxide.

6. A method for preparing a colored electrothermal film as described in any one of claims 1-5, characterized in that, include: 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. A transparent conductive heating layer is deposited on one side surface of the first substrate; Electrodes are formed at both ends of the transparent conductive heating layer; An optical interference control layer is deposited on the outer surface of the electrothermal film using a vacuum deposition process. The optical interference control layer is formed by alternating stacking of at least one high-refractive-index material layer and at least one low-refractive-index material layer.

7. The preparation method according to claim 6, characterized in that, In the step of depositing the optical interference control layer, a mask is placed between the first substrate and the sputtering target, and the thickness of the deposited film is gradient-distributed by controlling the relative movement of the mask and the first substrate.

8. The preparation method according to claim 6, characterized in that, Also includes: A second substrate with an encapsulating adhesive layer is bonded to the first substrate to encapsulate the transparent conductive heating layer and the electrode.

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