Transparent conductive film and preparation method thereof

Abstract

The invention relates to the technical field of new materials, and provides a transparent conductive film and a preparation method thereof.The transparent conductive film comprises a composite base material layer, an optical matching layer, a transition layer and a composite conductive layer which are sequentially arranged from bottom to top, and the composite base material layer comprises a first hardened layer, a base material layer and a second hardened layer which are sequentially arranged from top to bottom; the composite conducting layer comprises a first ITO conducting layer, a first carrier doping layer, a second ITO conducting layer, a second carrier doping layer and a third ITO conducting layer which are sequentially arranged from bottom to top. Through the above structure, the conductive performance and the light transmittance of the transparent conductive film are high.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and particularly to a transparent conductive film and a preparation method thereof. Background Art

[0002] Flexible transparent conductive films are widely used 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, low-resistivity transparent conductive films are required in many fields. For example, in flexible solar cells, low-resistivity transparent conductive films with a transmittance greater than 80% are needed to transport carriers. For example, in flexible electrochromic technology, high-transmittance and low-resistivity transparent conductive films are required in structural devices to transport conductive charges under low-voltage conditions.

[0004] In the prior art, transparent conductive films are usually prepared on flexible resin substrates by magnetron sputtering. Due to the limited high-temperature resistance of the resin substrate, the ITO film can only be prepared by magnetron sputtering in a low-temperature environment. However, the conductivity of the ITO film in a low-temperature environment is affected by tin doping and the concentration of oxygen vacancies, and the water content of the flexible resin substrate is relatively high. During the magnetron sputtering process, the process gas is ionized and electrons splash onto the substrate surface, causing temperature rise and the release of water vapor on the substrate surface and inside, which affects the crystallization performance of the ITO film, resulting in poor crystallization performance of the ITO film, low transmittance, and high resistivity of the prepared ITO film. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a transparent conductive film and a preparation method thereof. The present invention improves the transmittance by an optical matching layer combined with a flexible composite substrate layer and avoids electrons directly splashing onto the substrate surface, and uses multiple ITO conductive layers and multiple carrier doping layers to improve the conductivity of the film. The present invention aims to solve the technical problems of low transmittance and high resistivity of transparent conductive films prepared on flexible resin substrates in the prior art.

[0006] To achieve the above purpose, the present invention is realized by the following technical solutions: A transparent conductive film includes a composite substrate layer, an optical matching layer, a transition layer, and a composite conductive layer arranged in sequence from bottom to top. The composite substrate layer includes a first hardening layer, a substrate layer, and a second hardening layer arranged in sequence 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 in sequence from bottom to top.

[0007] Compared with the prior art, the beneficial effects of the present invention are as follows: By providing the composite substrate layer and disposing the first hardening layer and the second hardening layer on the surface of the substrate layer, it can not only prevent surface scratches during the substrate winding operation, but also prevent electrons from directly splashing onto the substrate surface after the process gas is ionized during the magnetron sputtering process, causing local temperature rise and releasing water vapor from the substrate, preventing it from affecting the ITO deposition process, and at the same time preventing the phenomenon that it is difficult to reduce the resistivity due to the influence of water vapor on the ITO stoichiometry; By providing the optical matching layer and combining with the composite substrate layer, the refractive index of the thin film is increased, making the finished thin film have excellent transmittance; By providing the transition layer, the bonding quality between the optical matching layer and the composite conductive layer is increased, and the surface roughness of the substrate is improved; By providing the composite conductive layer, through the stacked ITO conductive layer and carrier doping layer, the carrier mobility is effectively improved, and the layered structure effectively improves the crystallization performance of the ITO thin film, optimizing the lattice defects and stress inside the film layer, thereby effectively improving the conductive performance of the transparent conductive thin film.

[0008] Further, the thickness of the first ITO conductive layer is greater than 30 nm, and the thickness ranges of the first carrier doping layer and the second carrier doping layer are both 0.5 nm to 2 nm.

[0009] Furthermore, the materials of the first carrier doping layer and the second carrier doping layer are tin or indium.

[0010] Furthermore, the thickness range of the optical matching layer is 30 nm to 100 nm, and the refractive index range is 1.6 to 1.7.

[0011] Furthermore, the material of the transition layer is silicon oxide, and the thickness range of the transition layer is 5 nm to 20 nm.

[0012] Furthermore, the thickness ranges of the first hardening layer and the second hardening layer are both 0.5 μm to 3 μm.

[0013] Still further, the thickness range of the substrate layer is 25 μm to 300 μm.

[0014] A method for preparing a transparent conductive thin film, which is used to prepare the transparent conductive thin film as described in the above technical solution, and the method for preparing the transparent conductive thin film includes the following steps: Provide a substrate layer, and respectively prepare a first hardening layer and a second hardening layer on both sides of the substrate layer to form a composite substrate layer; Prepare an optical matching layer on the side of the first hardening layer facing away from the substrate layer, and prepare a transition layer on the side of the optical matching layer facing away from the first hardening layer; On the side of the transition layer facing away from the optical matching layer, 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 are sequentially sputtered, so as to form a composite conductive layer on the side of the transition layer facing away from the optical matching layer.

[0015] Further, the first ITO conductive layer, the first carrier doping layer, the second ITO conductive layer, the second carrier doping layer, and the third ITO conductive layer are all prepared by a magnetron sputtering process. The magnetic field intensity on the surface of the magnetron sputtering cathode target is greater than 1000 gauss, and the process gas for magnetron sputtering is argon or krypton. Description of the Drawings

[0016] Figure 1 It is a schematic structural diagram of the transparent conductive film in Embodiment 1 of the present invention; Figure 2 It is a flowchart of the preparation method of the transparent conductive film in Embodiment 2 of the present invention; Main Element Symbol Description: 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.

[0017] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. Specific Embodiments

[0018] For the convenience of understanding the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0019] It should be noted that when an element is referred to as being "fixed on" another element, it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the description of the present invention herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0021] Please refer to 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 sequentially arranged from bottom to top. The composite substrate layer includes a first hardening layer 110, a substrate layer 100, and a second hardening layer 120 sequentially arranged from top to bottom. The thickness range of the substrate layer 100 is 25 μm to 300 μm, and the thickness ranges of the first hardening layer 110 and the second hardening layer 120 are both 0.5 μm to 3 μm. The thickness range of the optical matching layer 200 is 30 nm to 100 nm, and the refractive index range is 1.6 to 1.7. The material of the transition layer 300 is silicon oxide, and the thickness range of the transition layer 300 is 5 nm to 20 nm. Preferably, the material of the substrate layer 100 is resin, and PET material is selected in this embodiment. The thickness of the substrate layer 100 is 100 μm, and the thicknesses of the first hardening layer 110 and the second hardening layer 120 are both 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 both polyacrylate and additives and auxiliaries. The thickness of the optical matching layer 200 is 50 nm, and the main component is polyacrylate added with zirconia and titania microparticles to increase 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 the refractive index range is 1.45 to 1.55. It can be understood that the first hardening layer 110 and the second hardening layer 120 can not only increase the surface strength of the substrate layer 100 and prevent the surface of the flexible substrate from being scratched during winding operations, but also prevent electrons from directly sputtering onto the surface of the substrate layer 100 during subsequent processes, resulting in the release of water vapor due to temperature rise, effectively preventing the deposition of ITO from being affected during the subsequent deposition of the composite conductive layer, and preventing the phenomenon that it is difficult to reduce the resistivity 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 increasing the refractive index and enabling the transparent conductive film to have good light transmittance. 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.

[0022] The composite conductive layer includes a first ITO conductive layer 410, a first carrier doping layer 411, a second ITO conductive layer 420, a second carrier doping layer 421, and a third ITO conductive layer 430, which are sequentially arranged from bottom to top. The thickness of the first ITO conductive layer 410 is greater than 30 nm. The thickness ranges of both the first carrier doping layer 411 and the second carrier doping layer 421 are 0.5 nm to 2 nm. The materials of the first carrier doping layer 411 and the second carrier doping layer 421 are tin or indium. Preferably, the ITO conductive layer is prepared by magnetron sputtering, and sputtering is carried out with a strong magnetic field of 1500 gauss. The thicknesses of the first ITO conductive layer 410, the second ITO conductive layer 420, and the third ITO conductive layer 430 are all 70 nm. The thicknesses of both the first carrier doping layer 411 and the second carrier doping layer 421 are 1 nm, and the material is selected as indium. Understandably, the electrical conductivity of the film layer can be improved through the first carrier doping layer 411 and the second carrier doping layer 421. By preparing the composite conductive layer in layers, it is beneficial to optimize the lattice defects and stress inside the film layer, effectively improve the crystallization performance of the thin film in the case of a relatively high doping ratio of tin oxide, and greatly reduce the resistivity of the transparent conductive thin film.

[0023] Please refer to Figure 2 , Embodiment 2 of the present invention provides a method for preparing a transparent conductive thin film for preparing the transparent conductive thin film described in the above technical solution. The method for preparing the transparent conductive thin film includes the following steps: Step S10: Provide a substrate layer, and prepare a first hardening layer and a second hardening layer on both sides of the substrate layer respectively to form a composite substrate layer; Preferably, in this embodiment, the material of the substrate layer is selected as PET, with a thickness of 188 μm. The thicknesses of both the first hardening layer and the second hardening layer are 1 μm, and they are coated on the substrate layer by a coating process. The refractive indices of both the first hardening layer and the second hardening layer are 1.52.

[0024] Step S20: Prepare an optical matching layer on the side of the first hardening layer facing away from the substrate layer, and prepare a transition layer on the side of the optical matching layer facing away from the first hardening layer; Preferably, in this embodiment, the optical matching layer is coated by a coating process. The thickness of the optical matching layer is 60 nm, and the refractive index is 1.68. The transition layer is a silicon dioxide layer, which is prepared by magnetron sputtering. The sputtering power is 10 kw, the sputtering current is 20 A, and the sputtering voltage is 450 V. The thickness of the transition layer is 10 nm, and the refractive index is 1.48.

[0025] Step S30: Sputter 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 in sequence 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.

[0026] 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 thicknesses of the first ITO conductive layer and the second ITO conductive layer are both 70 nm, the thickness of the third ITO conductive layer is 60 nm, and the thicknesses of the first carrier doping layer and the second carrier doping layer are both 2 nm, and the materials are both indium.

[0027] The first ITO conductive layer, the first carrier doping layer, the second ITO conductive layer, the second carrier doping layer, and the third ITO conductive layer are all prepared by a magnetron sputtering process. The magnetic field strength on the surface of the magnetron sputtering cathode target is greater than 1000 gauss, and the process gas for magnetron sputtering is argon or krypton.

[0028] Preferably, in this embodiment, the cathode magnetic field strength is 1500 gauss, and the process gas for magnetron sputtering is argon.

[0029] 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: The process gas for magnetron sputtering is krypton.

[0030] Comparative Example 1 A method for preparing a transparent conductive film, the difference between which and the method for preparing a transparent conductive film in Embodiment 2 is as follows: The cathode magnetic field strength is 1000 gauss.

[0031] Comparative Example 2 A method for preparing a transparent conductive film, the difference between which and the method for preparing a transparent conductive film in Embodiment 2 is as follows: Sputter a first ITO conductive layer, a carrier doping layer, and a second ITO conductive layer in sequence 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. The thickness of the composite conductive layer is 200 nm, and the process gas for magnetron sputtering is krypton. It can be understood that the conductive layer structure includes two ITO conductive layers and one carrier doping layer.

[0032] Comparative Example 3 A method for preparing a transparent conductive film, which is different from the method for preparing the transparent conductive film in Example 2 in that: A first ITO conductive layer, a second ITO conductive 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. The thickness of the composite conductive layer is 200 nm, and the process gas for magnetron sputtering is krypton gas. It can be understood that the conductive layer structure includes three ITO conductive layers.

[0033] Comparative Example 4 A method for preparing a transparent conductive film, which is different from the method for preparing the transparent conductive film in Example 2 in that: 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 process gas for magnetron sputtering is krypton gas.

[0034] Comparative Example 5 A method for preparing a transparent conductive film, which is different from the method for preparing the transparent conductive film in Example 2 in that: 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.

[0035] Comparative Example 6 A method for preparing a transparent conductive film, which is different from the method for preparing the transparent conductive film in Example 2 in that: 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.

[0036] Performance tests were carried out on the transparent conductive films prepared in the above-mentioned Example 2, 3 and Comparative Examples 1-6, specifically including impedance test, transmittance test and flexibility test. The impedance test was carried out using a four-probe detector, and the specific model was Laterta-AXMCP-T370. The transmittance test was carried out using a photometer, and the specific instrument model was Agilent Cary300. The flexibility test was carried out using a bending machine, and the specific model was YUASA DLDMLH. The corresponding preparation parameters and test results are shown in the following table:

[0037] It should be noted that in order to ensure the reliability of the verification results, when the above-mentioned Example 2, 3 and Comparative Examples 1-6 of the present invention are prepared into transparent conductive films, except for the above-mentioned different parameters, other processes and parameters should be kept consistent.

[0038] As can be seen from the above table, the method for preparing a transparent conductive film 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 doping layer structure, the structure without a carrier doping layer, and the traditional single-layer ITO conductive layer structure, while ensuring good light transmittance.

[0039] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0040] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A transparent conductive film, characterized in that: It includes a composite substrate layer, an optical matching layer, a transition layer and a composite conductive layer arranged in sequence from bottom to top, the composite substrate layer includes a first hardened layer, a substrate layer and a second hardened layer arranged in sequence from top to bottom, and the composite conductive layer includes 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 arranged in sequence from bottom to top.

2. The transparent conductive film according to claim 1, characterized in that: The thickness of the first ITO conductive layer is greater than 30 nm, and the thickness of the first carrier doping layer and the second carrier doping layer are both in the range of 0.5 nm to 2 nm.

3. The transparent conductive film according to claim 1, characterized in that: The first carrier doping layer and the second carrier doping layer are made of tin or indium.

4. The transparent conductive film according to claim 1, characterized in that: The optical matching layer has a thickness ranging from 30 nm to 100 nm and a refractive index ranging from 1.6 to 1.

7.

5. The transparent conductive film according to claim 1, characterized in that: The material of the transition layer is silicon oxide, and the thickness of the transition layer ranges from 5nm to 20nm.

6. The transparent conductive film according to claim 1, characterized in that: The thickness of the first hardened layer and the second hardened layer are both in the range of 0.5 μm to 3 μm.

7. The transparent conductive film according to claim 1, characterized in that: The thickness of the substrate layer ranges from 25 μm to 300 μm.

8. A method for preparing a transparent conductive film, for preparing the transparent conductive film according to any one of claims 1 to 7, characterized in that: The method for preparing the transparent conductive film comprises the following steps: Providing a substrate layer, and preparing a first hardening layer and a second hardening layer on both sides of the substrate layer to form a composite substrate layer; An optical matching layer is formed on a side of the first hardened layer facing away from the substrate layer, and a transition layer is formed on a side of the optical matching layer facing 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 on a side of the transition layer facing away from the optical matching layer to form a composite conductive layer on a side of the transition layer facing away from the optical matching layer.

9. The method for preparing a transparent conductive film according to claim 8, characterized in that: 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 a magnetron sputtering process, 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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