Anti-reflection conductive composite film material with low optical loss

Abstract

The invention belongs to the technical field of photoelectric films, provides an anti-reflection conductive composite film material with low optical loss, and aims to solve the problems that conductivity and optical transmittance of a transparent conductive material are difficult to consider at the same time and optical loss in a metal-based structure is remarkable in the prior art. An optimized medium / metal / medium three-layer film structure is constructed, the medium layers with specific refractive indexes and thicknesses are introduced to the two sides of the metal layer, the multi-beam interference effect and the dielectric constant matching principle are utilized, the absorption and reflection loss of the metal layer in the visible light wave band is effectively restrained, and meanwhile the high conductivity characteristic of the metal layer is reserved; through fine design of the refractive index, the extinction coefficient and the thickness of a dielectric layer material, regulation and control of light field distribution are realized, so that the electric field intensity is minimized in a metal layer area, and the metal absorption loss is remarkably reduced; according to the structure, the surface resistance is kept to be lower than that of a traditional TCO material, and meanwhile the visible light wave band transmissivity is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic thin film technology, specifically providing an anti-reflective conductive composite film material with low optical loss, high transmittance and high conductivity for visible light in the wavelength range of 0.4~0.7 μm. Background Technology

[0002] With the continuous advancement of optoelectronic displays, smart windows, photovoltaic devices, and high-end optical systems, the demand for materials that combine high conductivity and high optical transmittance is becoming increasingly urgent. In fields such as touchscreens, transparent electrodes, electromagnetically shielded windows, and wearable electronic devices, these devices not only require transparent conductive materials to possess excellent conductivity to ensure signal transmission and electromagnetic compatibility, but also require them to maintain the highest possible transmittance in the visible light band to ensure imaging quality, display effects, or viewing field. How to simultaneously achieve low optical loss and high conductivity in a single material system has become a long-standing core technical challenge in the field of optoelectronic functional materials.

[0003] Among numerous transparent conductive materials, transparent conductive oxides (TCOs), such as indium tin oxide (ITO) and aluminum-doped zinc oxide (AZO), are widely used due to their excellent light transmittance and conductivity. However, with the increasing integration of devices and the increasing complexity of application scenarios, the conductivity of traditional TCO materials is no longer sufficient to meet the requirements of high frequency, high current density, or high shielding effectiveness. The inherent constraint between carrier concentration and mobility leads to an irreconcilable contradiction between optical transmittance and electrical conductivity. When conductivity is improved by increasing carrier concentration, free carrier absorption is significantly enhanced, especially in the near-infrared band, resulting in a sharp increase in optical loss. Conversely, if higher light transmittance is pursued, the conductivity often fails to meet the requirements of practical applications.

[0004] On the other hand, metal-based transparent conductive film structures, such as metal / dielectric / metal multilayer films, have attracted widespread attention in recent years because they can achieve conductivity far exceeding TCO under extremely thin metal layer conditions, while simultaneously achieving high visible light transmittance through anti-reflection design of the dielectric layer. However, these structures still face many challenges in practical applications. First, the refractive index and interface matching problem between the metal layer and the dielectric layer can easily introduce additional reflection loss, limiting further improvement in overall light transmittance. Second, the metal layer is prone to aggregation or oxidation in high-temperature or humid environments, leading to a decrease in structural stability. More importantly, existing metal-based multilayer film structures often lack systematic analysis and control of optical loss sources during the design process, making it difficult to achieve synergistic optimization of low absorption and low reflection over a wide wavelength range.

[0005] Although existing research has attempted to improve the overall performance of metal-based transparent conductive films by adjusting the thickness of the metal layer and optimizing the materials and thickness combinations of the dielectric layer, the existing technology system can usually only achieve a compromise in local performance and it is difficult to control the optical loss at an ideal level while maintaining a low surface resistivity. The fundamental reason is that the metal layer itself has a high extinction coefficient, and its intrinsic absorption and interface reflection together constitute a significant source of optical loss. If the selection and thickness design of the dielectric layer do not fully consider the optical field coupling effect with the metal layer, it often cannot effectively suppress the loss, and may even introduce new absorption peaks or reflection bands due to interference effects.

[0006] Therefore, how to achieve deep decoupling of conductivity and optical properties in metal-based multilayer film structures, while maintaining the high conductivity of the metal layer and improving the transmittance in the visible light band to a level close to that of TCO materials through reasonable film system design, while effectively suppressing interface reflection and metal absorption, has become a key scientific problem in the design of transparent conductive film materials. Summary of the Invention

[0007] Addressing the technical bottlenecks of existing transparent conductive materials where it is difficult to balance conductivity and optical transmittance, and the significant optical loss in metal-based structures, this invention aims to provide an anti-reflective conductive composite film material with low optical loss. By constructing an optimized dielectric / metal / dielectric three-layer film structure, dielectric layers with specific refractive indices and thicknesses are introduced on both sides of the metal layer. Utilizing the multi-beam interference effect and dielectric constant matching principle, absorption and reflection losses of the metal layer in the visible light band are effectively suppressed, while retaining the high conductivity of the metal layer. Through precise design of the refractive index, extinction coefficient, and thickness of the dielectric layer material, the light field distribution is controlled, minimizing the electric field intensity in the metal layer region, thereby significantly reducing metal absorption losses. This structure achieves a significant improvement in visible light transmittance while maintaining a lower sheet resistivity than traditional TCO materials, providing a technical solution for high-performance transparent conductive film materials that combines low optical loss and excellent conductivity.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] An anti-reflective conductive composite film material with low optical loss is characterized in that the composite film material comprises: a transparent substrate and a composite film layer disposed on the transparent substrate, wherein the composite film layer is composed of a bottom dielectric layer, a metal conductive layer and a top dielectric layer stacked sequentially; the metal conductive layer is a metal Ag thin film with a thickness of 8~12nm; the bottom dielectric layer and the top dielectric layer are both transparent dielectric thin films, specifically indium tin oxide (ITO) with a thickness of 25~35nm.

[0010] Furthermore, the thickness of the metal conductive layer is 10 nm.

[0011] Furthermore, the thickness of both the bottom dielectric layer and the top dielectric layer is 30 nm.

[0012] Furthermore, the transparent substrate can be made of glass, polyethylene terephthalate (PET), or polyimide (PI) to meet the substrate material requirements of different application scenarios.

[0013] Furthermore, the composite film material has an average transmittance of greater than 85% in the visible light band (400~700 nm), a sheet resistivity of less than 10 Ω / sq, and an average absorptivity of less than 5% in the visible light band.

[0014] Furthermore, the optical loss control mechanism of the composite film material is as follows: by matching the refractive index and thickness of the bottom dielectric layer and the top dielectric layer, the incident light generates an interference effect in the composite film structure, and the minimum electric field intensity is controlled to the location of the metal conductive layer, thereby significantly reducing the intrinsic absorption and free carrier absorption of the incident light by the metal layer, and minimizing the optical loss.

[0015] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0016] This invention provides an anti-reflective conductive composite film material with low optical loss, which can simultaneously achieve high transmittance in the visible light band, low optical absorption loss, and excellent conductivity in the same structure. Through an optimized dielectric / metal / dielectric three-layer film structure design, this composite film material combines the anti-reflection effect of the dielectric layer with the high conductivity of the metal layer, innovatively solving the contradiction between conductivity and light transmittance in transparent conductive materials, thereby meeting the requirements of high-end displays, touch screens, electromagnetic shielding windows, and photodetectors for comprehensive material performance.

[0017] More specifically, the composite film material in this invention is based on a three-layer film structure with specific refractive index matching and optical field modulation functions. Its film structure is: transparent substrate / bottom dielectric layer / metal conductive layer / top dielectric layer. The bottom and top dielectric layers are transparent dielectric thin film materials with appropriate refractive indices and low absorption coefficients, used to achieve optical impedance matching with air and the substrate, and to modulate the optical field distribution through interference effects. The metal conductive layer is a metal Ag thin film material with high conductivity and low resistivity, undertaking the main conductive function. The high transmittance of this composite film material in the visible light band is achieved through the multi-beam interference effect between the dielectric and metal layers, which enhances the coherence of transmitted light and cancels out the coherence of reflected light. The low optical loss characteristic of this composite film material is achieved by optimizing the refractive index and thickness of the dielectric layer, placing the metal layer at a node position in the electric field intensity distribution, thereby significantly reducing the absorption of free carriers and interband absorption of the metal. The high conductivity of this composite film material is achieved by selecting a high-conductivity metal material and controlling its thickness above the continuous film formation threshold.

[0018] In summary, this invention proposes a composite film material with a dielectric / metal / dielectric three-layer structure, which can largely improve the contradiction between conductivity and light transmittance in traditional transparent conductive films. While ensuring sufficiently low sheet resistance, it can greatly improve the transmittance in the visible light band and reduce optical absorption loss. At the same time, this structure has the advantages of simple preparation process, strong material system versatility, and high performance stability. It is particularly suitable for high-end optoelectronic applications with stringent requirements for transparent conductivity and can provide solutions to various engineering application problems. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the anti-reflective conductive composite film material with low optical loss in an embodiment of the present invention.

[0020] Figure 2 This is an optical test image of an anti-reflective conductive composite film material with low optical loss, as described in an embodiment of the present invention.

[0021] Figure 3 This is an electromagnetic shielding test diagram of an anti-reflective conductive composite film material with low optical loss, as shown in an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0023] This embodiment provides an anti-reflective conductive composite film material with low optical loss, such as... Figure 1As shown, the composite membrane material has a membrane structure of transparent substrate / bottom dielectric layer / metal conductive layer / top dielectric layer; wherein, the transparent substrate is Corning glass with a refractive index of about 1.52; the bottom dielectric layer is indium tin oxide (ITO) thin film with a thickness of 30 nm; the metal conductive layer is silver (Ag) thin film with a thickness of 10 nm; and the top dielectric layer is indium tin oxide (ITO) thin film with a thickness of 30 nm.

[0024] The composite membrane material can be prepared by the following steps:

[0025] Step 1. A bottom ITO layer, an Ag layer, and a top ITO layer are sequentially deposited on a clean Corning glass substrate (10×10×0.7 mm) using magnetron sputtering technology; the vacuum level before deposition reaches 5×10⁻⁶ mm. -5 Pa, the working gas is argon, the sputtering pressure is 0.3 Pa; the ITO layer is sputtered by radio frequency with a sputtering power of 100 W and a deposition temperature of room temperature; the Ag layer is sputtered by DC with a sputtering power of 50 W and a deposition temperature of room temperature;

[0026] Step 2. Anneal the composite membrane material obtained in Step 1 at a temperature of 200°C for 1 hour, and then allow it to cool naturally to obtain the composite membrane material.

[0027] The photoelectric properties of the composite film material prepared by the above steps were tested, such as... Figure 2 The image shown is an optical test diagram, as follows: Figure 3 The figure shows the electromagnetic shielding test results. As can be seen from the figure, the composite film material prepared in this embodiment has a transmittance of 91.9% at 550nm in the visible light band, a sheet resistivity of 6.8 Ω / sq, and an overall electromagnetic shielding effectiveness of 30dB+ in the GHz band. These results indicate that the composite film material provided by this invention achieves synergistic optimization of low optical loss and high conductivity, meeting the requirements of high-end transparent conductive applications for comprehensive material performance.

[0028] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A low-optical-loss anti-reflective conductive composite film material, characterized in that, The composite film material includes: a transparent substrate and a composite film layer disposed on the transparent substrate. The composite film layer is composed of a bottom dielectric layer, a metal conductive layer and a top dielectric layer stacked sequentially. The metal conductive layer is a metal Ag thin film with a thickness of 8~12nm. The bottom dielectric layer and the top dielectric layer are both transparent dielectric thin films, specifically indium tin oxide (ITO) with a thickness of 25~35nm.

2. The anti-reflective conductive composite film material with low optical loss according to claim 1, characterized in that, The thickness of the metal conductive layer is 10 nm.

3. The anti-reflective conductive composite film material with low optical loss according to claim 1, characterized in that, The thickness of both the bottom dielectric layer and the top dielectric layer is 30 nm.

4. The anti-reflective conductive composite film material with low optical loss according to claim 1, characterized in that, The transparent substrate is made of glass, polyethylene terephthalate (PET), or polyimide (PI).

5. The anti-reflective conductive composite film material with low optical loss according to claim 1, characterized in that, The composite film material has an average transmittance of more than 85% in the visible light band (400~700 nm), a sheet resistivity of less than 10 Ω / sq, and an average absorptivity of less than 5% in the visible light band.

6. The anti-reflective conductive composite film material with low optical loss according to claim 1, characterized in that, The optical loss control mechanism of the composite film material is as follows: by matching the refractive index and thickness of the bottom dielectric layer and the top dielectric layer, the incident light generates an interference effect in the composite film structure, and the minimum electric field intensity is controlled to the location of the metal conductive layer, thereby significantly reducing the intrinsic absorption and free carrier absorption of the incident light by the metal layer, and minimizing the optical loss.

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