A transparent conductive thin film and its preparation method

Abstract

This invention relates to the field of new materials technology, providing a transparent conductive film and its preparation method. The transparent conductive film includes, from bottom to top, a composite substrate layer, an optical matching layer, a transition layer, and a composite conductive layer. The composite substrate layer includes, from top to bottom, a first hardening layer, a substrate layer, and a second hardening layer. The composite conductive layer includes, from bottom to top, a first ITO conductive layer, a first carrier doping layer, a second ITO conductive layer, a second carrier doping layer, and a third ITO conductive layer. This structure results in a transparent conductive film with both high conductivity and high light transmittance.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, and in particular to a transparent conductive film and its preparation method. Background Technology

[0002] Flexible transparent conductive films have wide applications in many fields, such as touch screens, polymer liquid crystal dimming films, membrane switches, transparent heating, transparent electromagnetic shielding, and flexible thin-film solar cells.

[0003] With technological innovation, many fields require transparent conductive films with low resistivity. For example, flexible solar cells require transparent conductive films with low resistivity and transmittance greater than 80% to transport charge carriers. Flexible electrochromic technology requires transparent conductive films with high transmittance and low resistivity to be used in structural devices to transport conductive charges under low voltage conditions.

[0004] In existing technologies, transparent conductive films are typically prepared on flexible resin substrates using magnetron sputtering. However, due to the limited high-temperature resistance of the resin substrate, ITO films can only be prepared by magnetron sputtering at low temperatures. Furthermore, the conductivity of ITO films at low temperatures is affected by tin doping and oxygen vacancy concentration. Additionally, the flexible resin substrate has a high moisture content. During magnetron sputtering, electrons from the ionized process gas splash onto the substrate surface, causing a temperature rise. This releases moisture from the substrate surface and interior, affecting the crystallinity of the ITO film and resulting in poor crystallinity, low transmittance, and high resistivity. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a transparent conductive film and its preparation method. This invention improves transmittance by combining an optical matching layer with a flexible composite substrate layer, and avoids direct electron sputtering to the substrate surface. It also employs multiple ITO conductive layers and multiple carrier-doped layers to enhance the film's conductivity. This invention aims to solve the technical problems of low transmittance and high resistivity in the preparation of transparent conductive films on flexible resin substrates in existing technologies.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] A transparent conductive film includes a composite substrate layer, an optical matching layer, a transition layer, and a composite conductive layer arranged sequentially from bottom to top. The composite substrate layer includes a first hardening layer, a substrate layer, and a second hardening layer arranged sequentially from top to bottom. The composite conductive layer includes a first ITO conductive layer, a first carrier doping layer, a second ITO conductive layer, a second carrier doping layer, and a third ITO conductive layer arranged sequentially from bottom to top.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows: By setting the composite substrate layer and the first hardening layer and the second hardening layer on the surface of the substrate layer, surface scratches can be prevented during substrate winding, and electrons after ionization of process gas during magnetron sputtering can be prevented from directly splashing onto the substrate surface, causing local temperature rise and releasing water vapor from the substrate, thus preventing interference with the ITO deposition process. Simultaneously, it prevents the phenomenon that the resistivity is difficult to reduce due to the influence of water vapor on the ITO stoichiometry. By setting the optical matching layer, the refractive index of the film is improved in conjunction with the composite substrate layer, resulting in excellent transmittance of the finished film. By setting the transition layer, the bonding quality between the optical matching layer and the composite conductive layer is increased, improving the surface roughness of the substrate. By setting the composite conductive layer, the carrier mobility is effectively improved through the stacked ITO conductive layer and carrier doping layer. The layered structure effectively improves the crystallinity of the ITO film, optimizes lattice defects and stress within the film layer, thereby effectively improving the conductivity of the transparent conductive film.

[0009] Furthermore, the thickness of the first ITO conductive layer is greater than 30 nm, and the thickness ranges of the first carrier doped layer and the second carrier doped layer are both 0.5 nm to 2 nm.

[0010] Furthermore, the materials of the first carrier doped layer and the second carrier doped layer are tin or indium.

[0011] Furthermore, the thickness of the optical matching layer ranges from 30 nm to 100 nm, and the refractive index ranges from 1.6 to 1.7.

[0012] Furthermore, the transition layer is made of silicon oxide, and its thickness ranges from 5 nm to 20 nm.

[0013] Furthermore, the thickness of both the first hardened layer and the second hardened layer ranges from 0.5μm to 3μm.

[0014] Furthermore, the thickness of the substrate layer ranges from 25μm to 300μm.

[0015] A method for preparing a transparent conductive film, comprising the steps described above:

[0016] A substrate layer is provided, and a first hardening layer and a second hardening layer are respectively prepared on both sides of the substrate layer to form a composite substrate layer;

[0017] An optical matching layer is formed on the side of the first hardened layer that faces away from the substrate layer, and a transition layer is formed on the side of the optical matching layer that faces away from the first hardened layer.

[0018] A first ITO conductive layer, a first carrier doped layer, a second ITO conductive layer, a second carrier doped layer, and a third ITO conductive layer are sequentially sputtered onto the side of the transition layer facing away from the optical matching layer, so as to form a composite conductive layer on the side of the transition layer facing away from the optical matching layer.

[0019] Furthermore, the first ITO conductive layer, the first carrier doped layer, the second ITO conductive layer, the second carrier doped layer, and the third ITO conductive layer are all prepared by magnetron sputtering. The magnetic field strength on the surface of the magnetron sputtering cathode target is greater than 1000 Gauss, and the magnetron sputtering process gas is argon or krypton. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the transparent conductive film in Embodiment 1 of the present invention;

[0021] Figure 2 This is a flowchart of the transparent conductive film preparation method in Embodiment 2 of the present invention;

[0022] Explanation of key component symbols:

[0023] 100, Substrate layer; 110, First hardening layer; 120, Second hardening layer; 200, Optical matching layer; 300, Transition layer; 410, First ITO conductive layer; 411, First carrier doping layer; 420, Second ITO conductive layer; 421, Second carrier doping layer; 430, Third ITO conductive layer.

[0024] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0025] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0026] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0028] Please see Figure 1 The transparent conductive film in Embodiment 1 of the present invention includes a composite substrate layer, an optical matching layer 200, a transition layer 300, and a composite conductive layer arranged sequentially from bottom to top. The composite substrate layer includes a first hardening layer 110, a substrate layer 100, and a second hardening layer 120 arranged sequentially from top to bottom. The thickness of the substrate layer 100 ranges from 25 μm to 300 μm, and the thicknesses of the first hardening layer 110 and the second hardening layer 120 both range from 0.5 μm to 3 μm. The thickness of the optical matching layer 200 ranges from 30 nm to 100 nm, and the refractive index ranges from 1.6 to 1.7. The transition layer 300 is made of silicon oxide, and its thickness ranges from 5 nm to 20 nm. Preferably, the substrate layer 100 is made of resin, and in this embodiment, PET material is selected. The thickness of the substrate layer 100 is 100 μm. The thickness of the first hardening layer 110 and the second hardening layer 120 is 1 μm, and the surface roughness is less than 2 nm. The main components of the first hardening layer 110 and the second hardening layer 120 are polyacrylate and additives and auxiliaries. The thickness of the optical matching layer 200 is 50 nm, and the main component is polyacrylate with added zirconium oxide and titanium oxide particles to improve the refractive index and perform optical matching with the composite substrate layer. The transition layer 300 is made of silicon oxide, with a thickness of 15 nm and a refractive index range of 1.45~1.55. Understandably, the first hardening layer 110 and the second hardening layer 120 not only increase the surface strength of the substrate layer 100 and prevent scratches on the surface of the flexible substrate during the winding operation, but also prevent electrons from being directly sputtered onto the surface of the substrate layer 100 during subsequent processes, thus preventing the release of water vapor due to temperature rise. This effectively prevents the deposition of ITO from being affected during the subsequent deposition of the composite conductive layer and prevents the phenomenon that the resistivity is difficult to reduce due to the influence of water vapor on the stoichiometry of ITO. The optical matching layer 200 performs optical matching with the composite substrate layer, which is beneficial to improving the refractive index and giving the transparent conductive film good light transmission performance. The transition layer 300 increases the bonding force between the composite conductive layer and the optical matching layer 200, which is beneficial to improving the roughness.

[0029] The composite conductive layer includes, from bottom to top, a first ITO conductive layer 410, a first carrier doped layer 411, a second ITO conductive layer 420, a second carrier doped layer 421, and a third ITO conductive layer 430. The thickness of the first ITO conductive layer 410 is greater than 30 nm. The thickness of the first carrier doped layer 411 and the second carrier doped layer 421 are both in the range of 0.5 nm to 2 nm. The material of the first carrier doped layer 411 and the second carrier doped layer 421 is tin or indium. Preferably, the ITO conductive layer is prepared by magnetron sputtering, using a strong magnetic field of 1500 Gauss for sputtering. The thickness of the first ITO conductive layer 410, the second ITO conductive layer 420, and the third ITO conductive layer 430 is 70 nm, and the thickness of the first carrier doped layer 411 and the second carrier doped layer 421 is 1 nm. Indium is selected as the material. It can be understood that the conductivity of the film can be improved by the first carrier doped layer 411 and the second carrier doped layer 421. By preparing the composite conductive layer in layers, it is beneficial to optimize the lattice defects and stress inside the film. Under the condition of a high tin oxide doping ratio, the crystallization performance of the thin film is effectively improved, and the resistivity of the transparent conductive film is significantly reduced.

[0030] Please see Figure 2 Embodiment 2 of the present invention provides a method for preparing a transparent conductive film, which is used to prepare the transparent conductive film described in the above technical solution. The method for preparing the transparent conductive film includes the following steps:

[0031] Step S10: Provide a substrate layer, and prepare a first hardening layer and a second hardening layer on both sides of the substrate layer to form a composite substrate layer;

[0032] Preferably, in this embodiment, the substrate layer is made of PET with a thickness of 188 μm, the first hardening layer and the second hardening layer are both 1 μm thick, and are coated onto the substrate layer using a coating process. The refractive index of the first hardening layer and the second hardening layer is 1.52.

[0033] Step S20: An optical matching layer is prepared on the side of the first hardened layer facing away from the substrate layer, and a transition layer is prepared on the side of the optical matching layer facing away from the first hardened layer;

[0034] Preferably, in this embodiment, the optical matching layer is coated using a coating process, the optical matching layer has a thickness of 60 nm and a refractive index of 1.68, the transition layer is a silicon dioxide layer, and is prepared using a magnetron sputtering process with a sputtering power of 10 kW, a sputtering current of 20 A, and a sputtering voltage of 450 V. The transition layer has a thickness of 10 nm and a refractive index of 1.48.

[0035] Step S30: A first ITO conductive layer, a first carrier doped layer, a second ITO conductive layer, a second carrier doped layer, and a third ITO conductive layer are sequentially sputtered on the side of the transition layer facing away from the optical matching layer, so as to form a composite conductive layer on the side of the transition layer facing away from the optical matching layer.

[0036] Preferably, in this embodiment, the mass ratio of indium oxide to tin oxide in the first ITO conductive layer, the second ITO conductive layer, and the third ITO conductive layer is 90:10, the thickness of the first ITO conductive layer and the second ITO conductive layer is 70 nm, the thickness of the third ITO conductive layer is 60 nm, the thickness of the first carrier doped layer and the second carrier doped layer is 2 nm, and the material of all layers is indium.

[0037] The first ITO conductive layer, the first charge carrier doped layer, the second ITO conductive layer, the second charge carrier doped layer, and the third ITO conductive layer are all prepared by magnetron sputtering. The magnetic field strength on the surface of the magnetron sputtering cathode target is greater than 1000 Gauss, and the magnetron sputtering process gas is argon or krypton.

[0038] Preferably, in this embodiment, the cathode magnetic field strength is 1500 Gauss, and the magnetron sputtering process gas is argon.

[0039] Embodiment 3 of the present invention provides a method for preparing a transparent conductive film. The difference between the method for preparing a transparent conductive film in this embodiment and the method for preparing a transparent conductive film in Embodiment 2 is as follows:

[0040] The gas used in magnetron sputtering is krypton.

[0041] Comparative Example 1

[0042] A method for preparing a transparent conductive film, which differs from the method for preparing a transparent conductive film in Example 2, is as follows:

[0043] The cathode magnetic field strength is 1000 Gauss.

[0044] Comparative Example 2

[0045] A method for preparing a transparent conductive film, which differs from the method for preparing a transparent conductive film in Example 2, is as follows:

[0046] A first ITO conductive layer, a carrier-doped layer, and a second ITO conductive layer are sequentially sputtered onto the side of the transition layer facing away from the optical matching layer, forming a composite conductive layer on the side of the transition layer facing away from the optical matching layer. The thickness of the composite conductive layer is 200 nm, and the magnetron sputtering process gas is krypton. Understandably, the conductive layer comprises two ITO conductive layers and one carrier-doped layer.

[0047] Comparative Example 3

[0048] A method for preparing a transparent conductive film, which differs from the method for preparing a transparent conductive film in Example 2, is as follows:

[0049] A first ITO conductive layer, a second ITO conductive layer, and a third ITO conductive layer are sequentially sputtered onto the side of the transition layer facing away from the optical matching layer, forming a composite conductive layer on the side of the transition layer facing away from the optical matching layer. The thickness of the composite conductive layer is 200 nm, and the magnetron sputtering process gas is krypton. It can be understood that the conductive layer consists of three ITO conductive layers.

[0050] Comparative Example 4

[0051] A method for preparing a transparent conductive film, which differs from the method for preparing a transparent conductive film in Example 2, is as follows:

[0052] An ITO conductive layer with a thickness of 200 nm is sputtered on the side of the transition layer facing away from the optical matching layer, and the magnetron sputtering process gas is krypton.

[0053] Comparative Example 5

[0054] A method for preparing a transparent conductive film, which differs from the method for preparing a transparent conductive film in Example 2, is as follows:

[0055] An ITO conductive layer with a thickness of 200 nm is sputtered onto the side of the transition layer facing away from the optical matching layer.

[0056] Comparative Example 6

[0057] A method for preparing a transparent conductive film, which differs from the method for preparing a transparent conductive film in Example 2, is as follows:

[0058] An ITO conductive layer is sputtered on the side of the transition layer facing away from the optical matching layer. The thickness of the ITO conductive layer is 200 nm, and the cathode magnetic field strength is 1000 Gauss.

[0059] The transparent conductive films prepared in Examples 2 and 3 and Comparative Examples 1 to 6 were subjected to performance tests, including impedance testing, transmittance testing, and flexibility testing. Impedance testing was performed using a four-probe detector (Laterta-AXMCP-T370), transmittance testing was performed using a photometer (Agilent Cary300), and flexibility testing was performed using a bending machine (YUASA DLDMLH). The corresponding preparation parameters and test results are shown in the table below.

[0060]

[0061] It should be noted that, in order to ensure the reliability of the verification results, when the transparent conductive films of Examples 2 and 3 and Comparative Examples 1 to 6 of the present invention are prepared, all other processes and parameters should be kept consistent except for the parameters mentioned above.

[0062] As can be seen from the table above, the transparent conductive film preparation method provided in Embodiment 2 of the present invention has lower sheet resistance and lower resistivity compared with the double-layer ITO conductive layer combined with a single-layer carrier doped layer structure, the carrier-free doped layer structure and the traditional single-layer ITO conductive layer structure, while ensuring good light transmittance.

[0063] In the description of this specification, 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 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.

[0064] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A transparent conductive film, characterized by, The device comprises, from bottom to top, a composite substrate layer, an optical matching layer, a transition layer, and a composite conductive layer. The composite substrate layer includes, from top to bottom, a first hardening layer, a substrate layer, and a second hardening layer. The composite conductive layer includes, from bottom to top, a first ITO conductive layer, a first carrier doping layer, a second ITO conductive layer, a second carrier doping layer, and a third ITO conductive layer. The first ITO conductive layer has a thickness greater than 30 nm. The thicknesses of the first and second carrier doping layers are both 0.5 nm to 2 nm. The optical matching layer has a thickness range of 30 nm to 100 nm and a refractive index range of 1.6 to 1.

7. The transition layer is made of silicon oxide, with a thickness range of 5 nm to 20 nm and a refractive index range of 1.45 to 1.

55. The first and second carrier doping layers are made of tin or indium. The thicknesses of the first and second hardening layers are both 0.5 μm to 3 μm. The main components of the first and second hardening layers are polyacrylate and additives / auxiliaries.

2. The transparent conductive film according to claim 1, wherein The thickness of the substrate layer ranges from 25μm to 300μm.

3. A method for producing a transparent conductive film according to any one of claims 1 to 2, characterized by The method for preparing the transparent conductive thin film includes the following steps: A substrate layer is provided, and a first hardening layer and a second hardening layer are respectively prepared on both sides of the substrate layer to form a composite substrate layer; An optical matching layer is formed on the side of the first hardened layer that faces away from the substrate layer, and a transition layer is formed on the side of the optical matching layer that faces away from the first hardened layer. A first ITO conductive layer, a first carrier doped layer, a second ITO conductive layer, a second carrier doped layer, and a third ITO conductive layer are sequentially sputtered onto the side of the transition layer facing away from the optical matching layer, so as to form a composite conductive layer on the side of the transition layer facing away from the optical matching layer. The first ITO conductive layer, the first carrier doped layer, the second ITO conductive layer, the second carrier doped layer, and the third ITO conductive layer are all prepared by magnetron sputtering. The magnetic field strength on the surface of the magnetron sputtering cathode target is greater than 1000 Gauss, and the magnetron sputtering process gas is argon or krypton.

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