A low-resistance flexible screen with improved bending resistance and a manufacturing method thereof

Abstract

The present invention relates to a low-resistance flexible screen with improved bending resistance and a method for manufacturing the same. The low-resistance flexible screen includes a base film and a functional circuit disposed on the base film. The base film is a polyimide film having a thickness of no more than 50 μm. The functional circuit includes a low-resistance circuit and multiple transparent electrodes. The main body of the low-resistance circuit is an electroplated copper layer having a thickness of no less than 5 μm. The transparent electrodes are formed by patterning a transparent conductive film. The external connection ends of each transparent electrode cover the end of the corresponding low-resistance circuit and form the junction between the transparent conductive film and the low-resistance circuit. The low-resistance flexible screen also includes an anti-bending layer, which is a transparent coating having an elastic modulus less than that of the electroplated copper layer. The anti-bending layer covers at least each junction. The present invention can effectively prevent the stress generated by the bending deformation from being excessively concentrated at the junction between the transparent conductive film and the low-resistance circuit when the low-resistance flexible screen is bent and deformed, thereby making the transparent conductive film at the junction less likely to break, thereby improving the bending resistance of the screen.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible screens, and in particular to a low-resistance flexible screen with improved bending resistance and a method for manufacturing the same. Background Art

[0002] A low-resistance flexible screen is a flexible screen with a low-resistance circuit. Its specific applications include as a current-driven display screen (such as an OLED display screen, a Microled display screen, etc.), or as the vibrating part of an ultrasonic screen that can emit ultrasonic waves.

[0003] like Figure 5 、 Figure 6 As shown, existing low-resistance flexible screens generally include a base film and a functional circuit disposed on the base film. The base film is typically a polyimide film with a thickness of no more than 50 μm, which is very thin and flexible. The functional circuit generally includes a low-resistance circuit and a transparent electrode. The low-resistance circuit is primarily composed of an electroplated copper layer with a thickness of no less than 5 μm, and the thickness of the electroplated copper layer can reach 5 μm or more. The transparent electrode is formed by patterning a relatively brittle transparent conductive film (such as an ITO film). Because the hardness of electroplated copper is generally higher than that of the flexible film, the flexibility of the low-resistance circuit on the flexible screen differs from that of other locations (the low-resistance circuit is significantly less flexible than other locations on the flexible screen). When the flexible screen bends, the stress generated by the bending deformation is easily concentrated at the junction between the transparent conductive film and the low-resistance circuit (i.e., the connection between the transparent conductive film and the copper circuit), making the transparent conductive film at this junction very susceptible to fracture (especially at the inner angle α at the edge of the low-resistance circuit, which is extremely prone to fracture), ultimately causing device failure. This results in poor bending resistance of such low-resistance flexible films. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a low-resistance flexible screen with improved bending resistance and a method for manufacturing the same. This low-resistance flexible screen can effectively prevent excessive concentration of stress generated by bending deformation at the junction between the transparent conductive film and the low-resistance circuit, thereby making the transparent conductive film at the junction less likely to break, thereby improving the bending resistance. The technical solution adopted is as follows:

[0005] A low-resistance flexible screen with improved bending resistance comprises a base film and a functional circuit arranged on the base film; the base film is a polyimide film with a thickness of not more than 50 μm; the functional circuit comprises a low-resistance circuit and a plurality of transparent electrodes, the main body of the low-resistance circuit is an electroplated copper layer with a thickness of not less than 5 μm, the transparent electrode is formed by patterning a transparent conductive film, the external connection end of each transparent electrode covers the end of the corresponding low-resistance circuit and constitutes the junction between the transparent conductive film and the low-resistance circuit; it is characterized in that: the low-resistance flexible screen also includes an anti-bending layer, the anti-bending layer is a transparent coating with an elastic modulus smaller than that of the electroplated copper layer, and the anti-bending layer at least covers each of the junctions.

[0006] In the structure of this low-resistance flexible screen, the anti-bending layer covers the junction of the transparent conductive film and the low-resistance circuit (that is, the connection between the transparent conductive film and the copper circuit). The anti-bending layer is a transparent coating and its elastic modulus is smaller than that of the electroplated copper layer. On the one hand, since the anti-bending layer is a transparent coating, the transparency of the low-resistance flexible screen is guaranteed; on the other hand, since the elastic modulus of the anti-bending layer is smaller than that of the electroplated copper layer, when the flexible screen is bent and deformed, the stress generated by the bending deformation can be effectively moved to the anti-bending layer, thereby reducing the bending stress at the junction of the transparent conductive film and the low-resistance circuit. Therefore, the anti-bending layer can effectively avoid the concentration of bending deformation at the junction, thereby making the transparent conductive film at the junction less likely to break, thereby making the low-resistance flexible screen have better bending resistance.

[0007] As a preferred embodiment of the present invention, the base film is a colorless polyimide film (CPI), which can ensure that the low-resistance flexible screen has good transparency.

[0008] As a preferred embodiment of the present invention, the transparent conductive film is an indium tin oxide film (ITO film). The thickness of the transparent conductive film is generally 10 to 100 nm.

[0009] As a preferred solution of the present invention, part of the transparent conductive film is stacked on the low-resistance circuit and electrically connected thereto.

[0010] As a preferred embodiment of the present invention, the anti-bending layer is a photosensitive resin coating. Using a photosensitive resin coating as the anti-bending layer facilitates forming a uniform and dense coating with good tensile strength consistency across the entire layer. Furthermore, the photosensitive resin coating is easily patterned, enabling the formation of a covering pattern specifically targeted at the junction between the transparent conductive film and the low-resistance circuit.

[0011] As a further preferred embodiment of the present invention, the thickness of the anti-bending layer is 0.8 to 2 times that of the low-resistance circuit.

[0012] As a further preferred embodiment of the present invention, the anti-bending layer is thicker than the low-resistance circuit and extends above the low-resistance circuit. Extending the anti-bending layer above the low-resistance circuit further effectively prevents stress generated by bending deformation from concentrating at the junction between the transparent conductive film and the low-resistance circuit.

[0013] As a preferred embodiment of the present invention, the anti-bending layer has a protrusion at the joint, so that the protrusion can specifically improve the anti-bending property of the joint and reduce the influence of the film layer on other positions.

[0014] As a preferred embodiment of the present invention, the low-resistance circuit includes a seed copper layer and an electroplated copper layer. The seed copper layer is disposed on the surface of the base film, and the electroplated copper layer is disposed on the surface of the seed copper layer. The seed copper layer is generally less than 1 μm thick, and the electroplated copper layer is generally greater than 5 μm thick.

[0015] As a further preferred embodiment of the present invention, the low-resistance circuit further includes an immersion gold layer, which is disposed on the surface of the electroplated copper layer. The immersion gold layer is disposed on the surface of the electroplated copper layer as a metal protective layer to reduce surface oxidation of the electroplated copper layer during the process and ensure the bonding strength of the transparent conductive film thereon. The immersion gold layer is generally composed of metals such as nickel and gold.

[0016] As a preferred embodiment of the present invention, the low-resistance flexible screen further comprises a transition metal layer. The transition metal layer covers the ends of the low-resistance circuit at the junction and is patterned to form transition connecting portions extending toward the transparent electrode. The external ends of the transparent electrode cover the corresponding transition connecting portions. By providing a transition metal layer on the low-resistance circuit and extending it inward to form a step, the inner corners of the low-resistance circuit edges can be filled, preventing the inner corners from being too sharp, thereby preventing the thin transparent conductive film from breaking at the inner corners of the low-resistance circuit edges. In combination with the anti-bending layer, the bending resistance of the low-resistance flexible screen is further improved.

[0017] As a further preferred embodiment of the present invention, the thickness of the transition metal layer is 5 to 10 times that of the transparent conductive film.

[0018] As a further preferred embodiment of the present invention, the transition metal layer is a molybdenum alloy layer, so that the transition metal layer and the oxide transparent conductive material have good film bonding strength.

[0019] As a further preferred embodiment of the present invention, the transition metal layer is a molybdenum-niobium alloy layer.

[0020] The present invention also provides a method for manufacturing the low-resistance flexible screen, comprising the following steps:

[0021] (1) Coating a layer of base film precursor on the glass motherboard and curing it to form a base film attached to the glass motherboard;

[0022] (2) Setting a low-resistance circuit on the surface of the base film;

[0023] (3) A layer of oxide transparent conductive film is provided on the surface of the base film and the low-resistance circuit, and patterned to form a transparent electrode;

[0024] It is characterized by: also including

[0025] (4) coating a transparent photosensitive resin on the low-resistance circuit and the transparent electrode, and forming a bending-resistant layer covering at least the joint through curing, exposure, and development;

[0026] (5) All material layers attached to the glass motherboard are peeled off from the glass motherboard to obtain the low-resistance flexible screen.

[0027] As a preferred embodiment of the present invention, the precursor of the base film is a polyamic acid solution.

[0028] As a preferred embodiment of the present invention, the operation process of step (2) is as follows: (2-1) forming a seed copper layer on the base film by magnetron sputtering; (2-2) electroplating the seed copper layer to form an electroplated copper layer by electroplating; (2-3) etching the seed copper layer and the electroplated copper layer into a low-resistance circuit pattern by photolithography. The thickness of the seed copper layer is generally less than 1 μm; the thickness of the electroplated copper layer is generally greater than 5 μm.

[0029] As a further preferred embodiment of the present invention, after step (2-3), (2-4) an immersion gold layer is formed on the surface of the electroplated copper layer using an immersion gold method. The immersion gold layer is composed of nickel and gold. By providing the immersion gold layer on the surface of the electroplated copper layer as a metal protective layer, surface oxidation of the electroplated copper layer during the process is reduced, thereby ensuring the bonding strength of the transparent conductive film thereon.

[0030] As a further preferred embodiment of the present invention, after step (2-4), (2-5) a transition metal layer is first formed on the surface of the low-resistance circuit by magnetron sputtering, and then the transition metal layer is patterned into a metal circuit pattern extension by photolithography. The transition metal layer may be a molybdenum-niobium alloy layer having a thickness 5 to 10 times that of the transparent conductive film.

[0031] As a preferred embodiment of the present invention, in step (3), the oxide transparent conductive film is first deposited on the surface of the base film and the low-resistance circuit by magnetron sputtering, and then the oxide transparent conductive film is patterned by photolithography to form the transparent electrode.

[0032] As a preferred embodiment of the present invention, the transparent photosensitive resin used in step (4) contains more than 20% of a diluent; and the anti-bending layer formed after step (4) has a protrusion at the junction. After the transparent photosensitive resin is coated on the low-resistance circuit and the transparent electrode, it accumulates more at the junction due to the topography of the edge of the low-resistance circuit and its own surface tension. After curing, exposure, and development, a thicker film layer is formed at the junction, i.e., the protrusion is formed.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] The present invention covers the junction of the transparent conductive film and the low-resistance circuit with an anti-bending layer. The anti-bending layer is a transparent coating and its elastic modulus is smaller than that of the electroplated copper layer. On the one hand, it can ensure the transparency of the low-resistance flexible screen; on the other hand, when the flexible screen is bent and deformed, the stress generated by the bending deformation can be effectively moved to the anti-bending layer, thereby reducing the bending stress at the junction of the transparent conductive film and the low-resistance circuit. Therefore, the anti-bending layer can effectively avoid the concentration of bending deformation at the junction, thereby making the transparent conductive film at the junction less likely to break, thereby making the low-resistance flexible screen have better bending resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of a low-resistance flexible screen according to a preferred embodiment of the present invention.

[0036] Figure 2 yes Figure 1 Schematic diagram of a partial cross-section of the low-resistance flexible screen shown.

[0037] Figure 3 It is a partial cross-sectional schematic diagram of the low-resistance flexible screen of Example 2 of the preferred embodiment of the present invention.

[0038] Figure 4 It is a partial cross-sectional schematic diagram of the low-resistance flexible screen of Example 3 of the preferred embodiment of the present invention.

[0039] Figure 5 It is a structural diagram of the existing low-resistance flexible screen design.

[0040] Figure 6 yes Figure 5 Schematic diagram of a partial cross-section of the low-resistance flexible screen shown. DETAILED DESCRIPTION

[0041] Example 1

[0042] like Figure 1 、 Figure 2 As shown, this low-resistance flexible screen with improved bending resistance includes a base film 1 and a functional circuit 2 arranged on the base film 1; the base film 1 adopts a polyimide film with a thickness of not more than 50μm; the functional circuit 2 includes a low-resistance circuit 21 and a plurality of transparent electrodes 22, the main body of the low-resistance circuit 21 is an electroplated copper layer with a thickness of not less than 5μm, and the transparent electrode 22 is formed by patterning a transparent conductive film 20, and the external connection end of each transparent electrode 22 covers the end of the corresponding low-resistance circuit 21 and constitutes a junction 23 between the transparent conductive film 20 and the low-resistance circuit 21; the low-resistance flexible screen also includes an anti-bending layer 3, which is a transparent coating with an elastic modulus smaller than that of the electroplated copper layer, and the anti-bending layer 3 at least covers each junction 23.

[0043] In this embodiment, the base film 1 is made of a colorless polyimide film (CPI), which can ensure that the low-resistance flexible screen has good transparency.

[0044] In this embodiment, the transparent conductive film 20 is an indium tin oxide film (ITO film) with a thickness of 10-100 nm. Part of the transparent conductive film 20 is stacked on the low-resistance circuit 21 and electrically connected thereto.

[0045] In this embodiment, the anti-bending layer 3 is a photosensitive resin coating. Using a photosensitive resin coating as the anti-bending layer 3 facilitates forming a uniform and dense coating with good tensile strength consistency across the entire layer. Furthermore, the photosensitive resin coating is easily patterned, enabling formation of a pattern specifically covering the junction 23 between the transparent conductive film 20 and the low-resistance circuit 21.

[0046] In this embodiment, the anti-bending layer 3 is thicker than the low-resistance circuit 21 and extends above the low-resistance circuit 21. By extending the anti-bending layer 3 above the low-resistance circuit 21, the stress generated by bending deformation is further effectively prevented from concentrating at the junction 23 between the transparent conductive film 20 and the low-resistance circuit 21.

[0047] In this embodiment, the low-resistance circuit 21 includes a seed copper layer 211, an electroplated copper layer 212, and an immersion gold layer 213. The seed copper layer 211 is arranged on the surface of the base film 1, and the thickness of the seed copper layer 211 is less than 1 μm; the electroplated copper layer 212 is arranged on the surface of the seed copper layer 211, and the thickness of the electroplated copper layer 212 is greater than 5 μm; the immersion gold layer 213 is arranged on the surface of the electroplated copper layer 212. The immersion gold layer 213 is composed of metals such as nickel and gold. By arranging the immersion gold layer 213 on the surface of the electroplated copper layer 212 as a protective layer, the surface oxidation of the electroplated copper layer 212 during the process is reduced, thereby ensuring the bonding force of the transparent conductive film 20 thereon.

[0048] This embodiment also provides a method for manufacturing the low-resistance flexible screen, comprising the following steps:

[0049] (1) coating a layer of polyamic acid solution on a glass motherboard and curing the solution to form a base film 1 attached to the glass motherboard;

[0050] (2) providing a low-resistance circuit 21 on the surface of the base film 1;

[0051] (3) first depositing an oxide transparent conductive film 20 on the surface of the base film 1 and the low-resistance circuit 21 by magnetron sputtering, and then patterning the oxide transparent conductive film 20 by photolithography to form a transparent electrode 22;

[0052] (4) A transparent photosensitive resin is coated on the low-resistance circuit 21 and the transparent electrode 22, and a bending-resistant layer 3 is formed by curing, exposing, and developing the resin so as to cover at least the joint 23;

[0053] (5) All material layers attached to the glass motherboard are peeled off from the glass motherboard to obtain the low-resistance flexible screen.

[0054] In this embodiment, the operation process of step (2) is as follows: (2-1) forming a seed copper layer 211 on the base film 1 by a magnetron sputtering method; (2-2) electroplating the seed copper layer 211 to form an electroplated copper layer 212 by an electroplating method; (2-3) etching the seed copper layer 211 and the electroplated copper layer 212 into a low-resistance circuit 21 pattern by a photolithography method; (2-4) forming a metal protective layer on the surface of the electroplated copper layer 212 by an immersion gold method;

[0055] In this embodiment, the operation process of step (2) is as follows: (2-1) a seed copper layer 211 is formed on the base film 1 by a magnetron sputtering method; (2-2) an electroplating method is used to form an electroplated copper layer 212 on the seed copper layer 211; (2-3) a photolithography method is used to etch the seed copper layer 211 and the electroplated copper layer 212 into a low-resistance circuit 21 pattern; (2-4) an immersion gold method is used to form an immersion gold layer 213 on the surface of the electroplated copper layer 212.

[0056] Example 2

[0057] refer to Figure 3 While all other aspects are identical to those of Example 1, the difference is that the low-resistance flexible screen further includes a transition metal layer 4. The transition metal layer 4 covers the end of the low-resistance circuit 21 at the joint 23 and is patterned to form a transition connection portion 41 extending toward the transparent electrode 22. The external end of the transparent electrode 22 covers the corresponding transition connection portion 41. By providing the transition metal layer 4 on the low-resistance circuit 21 and extending it inward to form a step, the inner corner of the edge of the low-resistance circuit 21 can be filled, preventing the inner corner from being too sharp, thereby preventing the transparent conductive film 20, which is too thin, from breaking at the inner corner of the edge of the low-resistance circuit 21. In combination with the anti-bending layer 3, the bending resistance of the low-resistance flexible screen is further improved.

[0058] In this embodiment, the transition metal layer 4 is a molybdenum-niobium alloy layer, and the thickness of the transition metal layer 4 is 5 to 10 times that of the transparent conductive film 20. In this way, the transition metal layer 4 and the oxide transparent conductive material can have good film bonding strength.

[0059] In the manufacturing method of the low-resistance flexible screen provided in this embodiment, the operation process of step (2) is as follows: (2-1) a seed copper layer 211 is formed on the base film 1 by a magnetron sputtering method; (2-2) an electroplating method is used to form an electroplated copper layer 212 on the seed copper layer 211; (2-3) the seed copper layer 211 and the electroplated copper layer 212 are etched into a low-resistance circuit 21 pattern by a photolithography method; (2-4) a metal protective layer is formed on the surface of the electroplated copper layer 212 by an immersion gold method; (2-5) a transition metal layer 4 is first formed on the surface of the low-resistance circuit 21 by a magnetron sputtering method, and then the transition metal layer 4 is patterned into a metal circuit pattern extension by a photolithography method.

[0060] Example 2

[0061] refer to Figure 4 , while all other parts are the same as those of the second embodiment, the difference is that in this embodiment, the anti-bending layer 3 has a protrusion 31 at the joint 23. Thus, the protrusion 31 can specifically improve the anti-bending property of the joint 23 and reduce the influence of the film layer on other positions.

[0062] In the method for manufacturing a low-resistance flexible screen provided in this embodiment, the transparent photosensitive resin used in step (4) contains more than 20% of a diluent; the anti-bending layer 3 formed after step (4) has a protrusion 31 at the joint 23. After the transparent photosensitive resin is coated on the low-resistance circuit 21 and the transparent electrode 22, it accumulates more at the joint 23 due to the topography of the edge of the low-resistance circuit 21 and its own surface tension. After curing, exposure, and development, a thicker film layer is formed at the joint 23, that is, the protrusion 31 is formed.

[0063] In addition, it should be noted that the names of the various parts of the specific embodiments described in this specification may be different. Any equivalent or simple changes made based on the structure, features, and principles described in the patent concept of the present invention are included in the scope of protection of the patent of this invention. Those skilled in the art of the technical field to which the present invention relates may make various modifications, supplements, or replace the specific embodiments described in the description with similar methods. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they shall fall within the scope of protection of the present invention.

Claims

1. A low-resistance flexible screen with improved bending resistance, comprising a base film and a functional circuit disposed on the base film; the base film is a polyimide film having a thickness of no greater than 50 μm; the functional circuit comprises a low-resistance circuit and a plurality of transparent electrodes, the low-resistance circuit comprising a main body of an electroplated copper layer having a thickness of no less than 5 μm, and the transparent electrodes being formed by patterning a transparent conductive film, with the external connection end of each transparent electrode covering the end of the corresponding low-resistance circuit and forming the junction between the transparent conductive film and the low-resistance circuit; characterized in that: The low-resistance flexible screen also includes an anti-bending layer, which is a photosensitive resin coating with an elastic modulus smaller than that of the electroplated copper layer. The thickness of the anti-bending layer is 0.8 to 2 times that of the low-resistance circuit. The anti-bending layer at least covers each of the joints, and the anti-bending layer has a protrusion at the joint.

2. The low-resistance flexible screen with improved bending resistance according to claim 1, characterized in that: The base film is a colorless polyimide film; the transparent conductive film is an indium tin oxide film, and a portion of the transparent conductive film is stacked on the low-resistance circuit and electrically connected thereto.

3. The low-resistance flexible screen with improved bending resistance according to claim 1, characterized in that: The anti-bending layer is thicker than the low-resistance circuit, and the anti-bending layer extends onto the low-resistance circuit.

4. A low-resistance flexible screen with improved bending resistance according to any one of claims 1 to 3, characterized in that: The low-resistance circuit includes a seed copper layer, an electroplated copper layer and an immersion gold layer. The seed copper layer is arranged on the surface of the base film, the electroplated copper layer is arranged on the surface of the seed copper layer, and the immersion gold layer is arranged on the surface of the electroplated copper layer.

5. A low-resistance flexible screen with improved bending resistance according to any one of claims 1 to 3, characterized in that: The low-resistance flexible screen also includes a transition metal layer, which covers the end of the low-resistance circuit at the joint and forms a transition connection portion extending toward the transparent electrode through patterning, and the external end of the transparent electrode covers the corresponding transition connection portion; the transition metal layer is a molybdenum alloy layer, and the thickness of the transition metal layer is 5 to 10 times that of the transparent conductive film.

6. A method for manufacturing a low-resistance flexible screen with improved bending resistance, comprising the following steps: (1) coating a layer of base film precursor on a glass motherboard and curing the layer to form a polyimide film with a thickness of no more than 50 μm attached to the glass motherboard as a base film; (2) a low-resistance circuit is provided on the surface of the base film, wherein the main body of the low-resistance circuit is an electroplated copper layer having a thickness of not less than 5 μm; (3) A layer of oxide transparent conductive film is provided on the surface of the base film and the low-resistance circuit, and patterned to form a transparent electrode; Its characteristics are: Also includes (4) A transparent photosensitive resin containing more than 20% of a diluent is coated on the low-resistance circuit and the transparent electrode, and an anti-bending layer is formed by curing, exposing, and developing to cover at least the joint. The anti-bending layer is a photosensitive resin coating having an elastic modulus smaller than that of the electroplated copper layer. The thickness of the anti-bending layer is 0.8 to 2 times that of the low-resistance circuit, and the anti-bending layer has a protrusion at the joint. (5) All material layers attached to the glass motherboard are peeled off from the glass motherboard to obtain the low-resistance flexible screen.

7. The method for manufacturing a low-resistance flexible screen with improved bending resistance according to claim 6, characterized in that: The operation process of step (2) is as follows: (2-1) forming a seed copper layer on the base film by a magnetron sputtering method; (2-2) electroplating the seed copper layer to form an electroplated copper layer by an electroplating method; (2-3) etching the seed copper layer and the electroplated copper layer into a low-resistance circuit pattern by a photolithography method; (2-4) forming an immersion gold layer on the surface of the electroplated copper layer by an immersion gold method; (2-5) first forming a transition metal layer on the surface of the low-resistance circuit by a magnetron sputtering method, and then patterning the transition metal layer into a metal circuit pattern extension by a photolithography method.

8. The method for manufacturing a low-resistance flexible screen with improved bending resistance according to claim 7, characterized in that: In the step (3), the oxide transparent conductive film is first deposited on the surface of the base film and the low-resistance circuit by magnetron sputtering, and then the oxide transparent conductive film is patterned by photolithography to form the transparent electrode.

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