conductive film

Abstract

The present invention provides a conductive film 100 with low resistance and high reliability while suppressing the visibility of the fine metal wires 30. [Solution] The conductive film 100 comprises a base material 10 containing an insulating resin and a metal fine wire 30 provided on the base material 10. If the wire width of the metal fine wire 30 is w and the height of the metal fine wire 30 is h, then 1 μm ≤ w ≤ 5 μm, 0.82 μm ≤ h ≤ 5.6 μm, and 0.82 ≤ h / w ≤ 1.12.

Description

[Technical Field]

[0001] This invention relates to a conductive film. [Background technology]

[0002] In recent years, conductive films, which consist of fine metal wires embedded in a resin substrate, have been adopted for applications such as antennas, heaters, and shields that can be attached to glass.

[0003] As an example of a conductive film, Patent Document 1 discloses a conductive film comprising a base layer, an adhesive layer for a heat-generating conductor disposed on one side of the base layer, and a heat-generating conductor bonded to the base layer by the adhesive layer for the heat-generating conductor and formed having an opening.

[0004] Furthermore, as another example of a conductive film, Patent Document 2 discloses a conductive film in which a patterned conductive article comprises a substrate 210 having a single layer, and includes a fine pattern of conductive traces 220 at least partially embedded in the single layer. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2018-206643 [Patent Document 2] Special Publication No. 2022-531872 [Overview of the project] [Problems that the invention aims to solve]

[0006] In conventional conductive films disclosed in Patent Document 1 or Patent Document 2, the cross-sectional area of ​​the heat-generating conductor (fine pattern) is small, resulting in a high resistance value. When a high voltage is applied, the heat-generating conductor (fine pattern) may be damaged, potentially reducing the reliability of the conductive film.

[0007] Furthermore, increasing the line width of the heat-generating conductor (fine pattern) in order to lower its resistance risked that users of the conductive film would be able to see the heat-generating conductor (fine pattern) (so-called "line visibility").

[0008] This disclosure has been made in view of the foregoing, and its purpose is to provide a conductive film with low resistance and high reliability while suppressing the visibility of fine metal wires. [Means for solving the problem]

[0009] To solve the above problems, a conductive film according to one aspect of the present disclosure comprises a base material 10 containing an insulating resin and a metal fine wire 30 provided on the base material 10, wherein the wire width of the metal fine wire 30 is w and the height of the metal fine wire 30 is h, then 1 μm ≤ w ≤ 5 μm, 0.82 μm ≤ h ≤ 5.6 μm, and 0.82 ≤ h / w ≤ 1.12. [Effects of the Invention]

[0010] According to this disclosure, a conductive film 100 with low resistance and high reliability is provided while suppressing the visibility of the metal fine wires 30. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a plan view of a conductive film according to Embodiment 1. [Figure 2] Figure 2 is an enlarged view of region II in Figure 1. [Figure 3] Figure 3 is an enlarged view of region III in Figure 2. [Figure 4] Figure 4 is a cross-sectional view of the conductive film according to Embodiment 1 along line IV-IV in Figure 3. [Figure 5A] Figure 5A is a graph showing the relationship between aspect ratio and cross-sectional area for a metal thin wire according to Embodiment 1. [Figure 5B] Figure 5B is an enlarged view of Figure 5A with an aspect ratio of 0.7 to 1.3. [Figure 6A]FIG. 6A is a graph showing the relationship between the value obtained by dividing the square of the outer circumference by the cross-sectional area and the cross-sectional area of the metal fine wire according to Embodiment 1. [Figure 6B] FIG. 6B is an enlarged view of the value obtained by dividing the square of the outer circumference in FIG. 6A by the cross-sectional area = 16 to 16.5. [Figure 7] FIG. 7 is a view corresponding to FIG. 1 of the conductive film according to Embodiment 2. [Figure 8] FIG. 8 is a view corresponding to FIG. 4 of the conductive film according to Embodiment 3. [Figure 9] FIG. 9 is a view corresponding to FIG. 3 of the conductive film according to the modified example.

BEST MODE FOR CARRYING OUT THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The following description of the preferred embodiments is merely illustrative in nature and is not intended to limit the present invention, its applications, or its uses.

[0013] In the present disclosure, the terms "upper" and "lower" do not refer to the upward (vertically upward) and downward (vertically downward) directions in an absolute spatial recognition, but are used as terms defined by a relative positional relationship. Further, the terms "upper" and "lower" are applicable not only when two components are spaced apart from each other and there is another component between the two components, but also when two components are arranged in close contact with each other and the two components are in contact. Terms indicating directions such as "up", "down", "left", "right", "front", and "rear" are also used as terms indicating a relative positional relationship, not an absolute positional relationship, like "upper" and "lower".

[0014] (Overview) The conductive film 100 includes a base material 10 containing an insulating resin and a metal fine wire 30 provided on the base material 10. When the line width of the metal fine wire 30 is w and the height of the metal fine wire 30 is h, 1 μm ≤ w ≤ 5 μm, 0.82 μm ≤ h ≤ 5.6 μm, and 0.82 ≤ h / w ≤ 1.12.

[0015] According to the above configuration, it is possible to provide a conductive film with low resistance and high reliability while suppressing the visibility of the metal wires 30.

[0016] The following will describe the embodiments in detail, divided into Embodiment 1, Embodiment 2, and Embodiment 3.

[0017] (Embodiment 1) The conductive film 100a according to Embodiment 1 will be described below with reference to Figures 1 to 6B.

[0018] Figure 1 is a plan view of the conductive film according to Embodiment 1. Figure 2 is an enlarged view of region II in Figure 1. Figure 3 is an enlarged view of region III in Figure 2. Figure 4 is a cross-sectional view of the conductive film according to Embodiment 1 along line IV-IV in Figure 3. Figure 5A is a graph showing the relationship between aspect ratio and cross-sectional area for a metal wire according to Embodiment 1. Figure 5B is an enlarged view of Figure 5A for aspect ratios of 0.7 to 1.3. Figure 6A is a graph showing the relationship between the value obtained by dividing the square of the perimeter by the cross-sectional area and the cross-sectional area for a metal wire according to Embodiment 1. Figure 6B is an enlarged view of Figure 6A for values ​​obtained by dividing the square of the perimeter by the cross-sectional area of ​​16 to 16.5.

[0019] As shown in Figure 1, the conductive film 100a has a base material 10, a first busbar 20a, a second busbar 20b, and a plurality of fine metal wires 30.

[0020] (base material) The base material 10 has a first layer 11 and a second layer 12. The first layer 11 is in the form of a sheet. The second layer 12 is also in the form of a sheet. Furthermore, the second layer 12 is laminated onto the first layer 11.

[0021] The first layer 11 and the second layer 12 contain insulating resin. The inclusion of insulating resin in the first layer 11 and the second layer 12 ensures the insulating properties between the multiple metal wires 30 described later.

[0022] The base material 10 is roughly rectangular in plan view. However, the shape of the base material 10 in plan view may be circular, polygonal, or a combination of these.

[0023] The first layer 11 and the second layer 12 are flexible. The thickness of the substrate 10 is 3 μm to 200 μm.

[0024] The first layer 11 and the second layer 12 are light-transmitting. Preferably, the visible light transmittance of the first layer 11 and the second layer 12 is 80% or more. That is, the substrate 10 is light-transmitting. Also, the visible light transmittance of the substrate 10 is 80% or more.

[0025] Furthermore, when the transparent conductive film 100a is used in substrates or organic interposers where light transmission is not required, the first layer 11 or the second layer 12 does not need to be light-transmitting.

[0026] Examples of insulating resin materials included in the base material 10 include PET (polyethylene terephthalate), PC (polycarbonate), COP (cycloolefin polymer), and COC (cycloolefin copolymer).

[0027] A groove 13 is provided on the surface of the second layer 12. The groove 13 is approximately trapezoidal in shape. That is, the width of the opening of the groove 13 is greater than the width of the bottom of the groove 13. As will be described later, the groove 13 does not have to be strictly trapezoidal.

[0028] The base material 10 may consist only of the second layer 12. This makes it possible to make the conductive film 100a thinner.

[0029] (Bus bar) The first busbar 20a has a first external connection section 21a and a first power supply section 22a. A positive voltage is applied to the first external connection section 21a of the first busbar 20a by an external power supply. The first power supply section 22a is connected to the first external connection section 21a.

[0030] The second busbar 20b has a second external connection section 21b and a second power supply section 22b. A negative voltage is applied to the second external connection section 21b by an external power supply. The second power supply section 22b is connected to the second external connection section 21b.

[0031] The first busbar 20a and the second busbar 20b are separated in a plan view.

[0032] The multiple thin metal wires 30, described later, connect the first power supply section 22a of the first busbar 20a and the second power supply section 22b of the second busbar 20b. In other words, the first busbar 20a and the second busbar 20b are connected via the multiple thin metal wires 30. To put it another way, the multiple thin metal wires 30 electrically connect the first busbar 20a and the second busbar 20b.

[0033] When a positive voltage is applied to the first external connection part 21a and a negative voltage to the second external connection part 21b by external electrodes, current flows through the metal thin wire 30.

[0034] (protective film) As shown in Figure 4, the conductive film 100a further comprises a protective film 40. The protective film 40 is laminated on the surface of the substrate 10. The protective film 40 also covers the upper surface of the metal wire 30. The protective film 40 prevents the metal wire 30 from corroding due to substances present in the air or on objects in contact with the conductive film. Therefore, a decrease in the reliability of the conductive film 100a can be suppressed.

[0035] Furthermore, the conductive film 100a does not necessarily have a protective layer 40. This allows the conductive film 100a to be made thinner.

[0036] (Structure of a thin metal wire) As shown in Figure 2, the multiple metal wires 30 form a wiring pattern. Here, the wiring pattern simply refers to the shape drawn by the multiple metal wires 30. In other words, the wiring pattern does not need to be a continuous periodic shape. To put it another way, the wiring pattern can be a random shape.

[0037] The average pitch P of multiple thin metal wires 30 is between 4 and 1000 times the wire width w of the thin metal wires 30. If the pitch P of multiple thin metal wires 30 is narrow, there is a risk that the user may perceive adjacent thin metal wires 30 as a single thick wire. In this case, the user may perceive the sum of the wire width w of the two thin metal wires 30 and the pitch P as the actual wire width, potentially causing the wire to appear invisible.

[0038] On the other hand, if the pitch P of the multiple metal wires 30 is wide, each individual metal wire becomes easier to see.

[0039] By setting the average pitch P of the metal wire 30 to 4 times or more than 1000 times the wire width of the metal wire 30, the visibility of the metal wire 30 to the user can be suppressed.

[0040] Here, the average value of the pitch P of multiple metal wires 30 is the average value of the distance between adjacent metal wires 30. However, as shown in Figure 2, when multiple closed spaces (hereinafter referred to as unit cells) are formed by multiple metal wires 30, the pitch is defined as the distance between the centroids G of adjacent unit cells. Therefore, the average value of the pitch P of multiple metal wires 30 is the average value of the distance between the centroids G of adjacent unit cells.

[0041] For simplicity, in the following description, one of the multiple metal wires 30 will be referred to as metal wire 30 and described in more detail. That is, metal wire 30 is one of multiple metal wires 30.

[0042] As shown in Figure 3, the metal wire 30 is bordered in plan view by a first end line 30a and a second end line 30b. That is, the first end line 30a and the second end line 30b are lines that represent the side surface of the metal wire 30 in plan view. Also, the first end line 30a and the second end line 30b are opposite to each other. The first end line 30a and the second end line 30b are parallel to each other.

[0043] As shown in Figure 3, the center line 30c is the line located midway between the first end line 30a and the second end line 30b. More specifically, the center line 30c is the trajectory of point C when point A, located on the first end line 30a, and point B, located on the second end line 30b, are moved along the first end line 30a and point B, located along the second end line 30b.

[0044] As shown in Figure 4, the line IV-IV in Figure 3 is a straight line perpendicular to the center line 30c. Hereafter, the direction perpendicular to the center line 30c will be referred to as the width direction. In other words, Figure 4 is a cross-sectional view of the metal wire 30 cut in the width direction.

[0045] As shown in Figure 4, the metal wire 30 is provided on the surface of the base material 10. The metal wire 30 is located in the groove 13. Note that "located in the groove 13" means that at least a part of the metal wire 30 is located in the groove 13. In other words, the entire metal wire 30 is not required to be located in the groove 13. More specifically, the upper surface of the metal wire 30 may be located above the surface of the base material 10. Alternatively, the upper surface of the metal wire 30 may be located below the surface of the base material 10.

[0046] As shown in Figure 4, the metal wire 30 has a conductive layer 31 and an adhesion layer 32.

[0047] The conductive layer 31 mainly contains copper. Alternatively, the conductive layer 31 may also mainly contain gold, silver, titanium, aluminum, or nickel. Because the conductive layer 31 contains metals with high conductivity, when current flows through a thin metal wire, it primarily flows through the conductive layer 31.

[0048] The adhesion layer 32 ensures the adhesion of the conductive layer 31 to the groove 13. The adhesion layer 32 is a metal layer composed of a metal nitride or metal oxide containing at least one metal selected from the group consisting of Ti, Ni, Al, V, W, Ta, Si, Cr, Ag, Mo, Cu, and Zn. The adhesion layer 32 may be a single layer or a laminate of multiple layers with different compositions.

[0049] When the conductive film 100a is used for a long period of time or in a harsh environment, the conductive layer 31 may peel off from the groove 13 of the substrate 10, potentially creating a gap between the conductive layer 31 and the groove 13 of the substrate 10. In this case, the conductive layer 31 may corrode due to substances present in the air or on objects in contact with the conductive film, increasing the resistance of the metal wire 30 and potentially reducing the reliability of the conductive film 100a. The presence of the adhesion layer 32 helps to suppress this reduction in the reliability of the conductive film 100a.

[0050] Furthermore, the adhesion layer 32 uses a material with a lower visible light reflectivity than the conductive layer 31. This reduces the overall reflectivity of the metal wire 30. Therefore, the visibility of the metal wire 30 to the user can be suppressed.

[0051] The metal wire 30 is roughly trapezoidal in shape. More specifically, the width w1 of the metal wire 30 at the opening of the groove 13 is greater than the width w2 of the metal wire 30 at the bottom of the groove 13. That is, the width w1 of the metal wire 30 on the surface side of the base material 10 is greater than the width w2 of the metal wire 30 on the side opposite to the surface of the base material 10.

[0052] The conductive film 100a may be used in a folded state. When the conductive film 100a is folded, stress is generated in the metal wire 30. In particular, the generation of stress is significant when the conductive film 100a is folded so that the ends in the width direction are brought closer together. When stress is generated in the metal wire 30, there is a risk that the metal wire 30 will break. In addition, there is a risk that the metal wire 30 will peel off from the base material 10, reducing the reliability of the conductive film 100a.

[0053] By making the width w1 of the metal wire 30 on the surface side of the substrate 10 larger than the width w2 of the metal wire 30 on the side opposite to the surface of the substrate 10, the stress on the metal wire 30 can be reduced. More specifically, the stress applied to the metal wire 30 on the surface of the substrate 10 can be released to the side opposite to the surface of the substrate 10. As a result, damage to the metal wire 30 and delamination of the metal wire 30 from the substrate 10 can be suppressed, and the reliability of the conductive film 100 can be ensured.

[0054] The sheet resistance of the metal wire 30 is 10Ω / □ or less. More preferably, it is 1Ω / □ or less. Therefore, the possibility of excessive thermal damage to the metal wire 30 can be reduced.

[0055] Note that, as shown in Figure 4, the groove 13 does not have to be a strict trapezoid. As shown in Figure 4, the cross-section of the metal wire 30 is a trapezoid with rounded corners on the lower side of the paper. In such a case, as shown in Figure 4, we consider a hypothetical trapezoid formed when we draw the tangent line in the cross-sectional view of the side wall at the opening of the metal wire 30 and the tangent line in the cross-sectional view of the side wall at the bottom of the metal wire 30. The width w2 of the metal wire 30 at the bottom of the groove 13 is the width of the bottom of this hypothetical trapezoid.

[0056] The wire width w of the metal wire 30 is 1 μm or more. During the manufacturing process of the conductive film, there is a risk of defects occurring where the metal wire 30 becomes partially thinner due to manufacturing tolerances. If the wire width of the metal wire 30 is less than 1 μm, the impact of this manufacturing tolerance becomes greater. In other words, the wire width of the metal wire 30 becomes too thin, increasing the risk of wire breakage due to heat during current flow. Therefore, the reliability of the conductive film 100a decreases.

[0057] The wire width w of the metal wire is 5 μm or less. This suppresses the visibility of the metal wire 30 to the user.

[0058] Furthermore, a line width w of 3 μm or less is more preferable. When the conductive film 100a is used in applications where the user uses it close to their eyes, such as for anti-fogging of goggles or touch panels, if the line width w is greater than 3 μm, there is a risk that the user may see the metal wire 30. By setting the line width w of the metal wire to 3 μm or less, the visibility of the metal wire 30 can be suppressed even when used close to the user's eyes.

[0059] Here, as shown in Figure 4, the line width w of the metal wire 30 is the longest length of the metal wire 30 parallel to the width direction in a cross-sectional view when the metal wire 30 is cut in the width direction. The line width w of the metal wire 30 is the width w1 of the metal wire 30 at the opening of the groove 13.

[0060] The height h of the metal wire 30 is between 0.82 μm and 5.6 μm. The aspect ratio h / w is between 0.82 and 1.12. The aspect ratio is calculated by dividing the height h of the metal wire 30 by the line width w of the metal wire 30 (hereinafter simply referred to as the aspect ratio).

[0061] Here, as shown in Figure 4, the height h of the metal wire 30 is the longest length among the lengths parallel to the height direction perpendicular to the width direction of the metal wire 30 in a cross-sectional view when the metal wire 30 is cut in the width direction.

[0062] Generally, the resistance of a material is inversely proportional to its cross-sectional area. Therefore, as the cross-sectional area of ​​the metal wire 30 increases, its resistance decreases. Conversely, as the cross-sectional area of ​​the metal wire 30 decreases, its resistance increases.

[0063] If the wire width w of the metal wire 30 is reduced to suppress wire visibility, the cross-sectional area of ​​the metal wire 30 decreases, and the resistance of the metal wire 30 increases. A higher resistance of the metal wire 30 leads to a greater amount of heat being generated when a current is passed through it. If the amount of heat generated by the metal wire 30 becomes too great, excessive heat may be applied to the metal wire 30, potentially causing it to burn out.

[0064] By increasing the height h of the thin metal wire 30, the resistance of the thin metal wire can be reduced while suppressing wire visibility. Specifically, increasing the height h of the thin metal wire 30 increases the cross-sectional area of ​​the thin metal wire 30, which lowers the resistance of the thin metal wire 30.

[0065] On the other hand, if the height h of the metal wire 30 is made too high, manufacturing problems arise. Specifically, when forming grooves 13 in the base material 10, the shape of the grooves 13 is unstable. As a result, there is a mixture of areas with large and small cross-sectional areas in the metal wire 30. Consequently, areas where the current concentrates occur within the metal wire 30, leading to breakage due to thermal damage to the metal wire 30 and uneven heating of the base material as a whole.

[0066] Furthermore, if the height h of the metal wire 30 is made too high, the risk of corrosion of the metal wire 30 due to substances present in the space between the metal wire 30 and the base material 10 increases. Specifically, the contact area between the metal wire 30 and the base material 10 increases, which increases the likelihood of a space forming between the metal wire 30 and the base material 10.

[0067] In other words, in order to lower the resistance value of the metal wire 30, the height of the metal wire 30 needs to be reduced, and in order to ensure the reliability of the metal wire 30, the height of the metal wire 30 needs to be reduced.

[0068] The following describes the optimal value for the height h of the metal wire 30, using the aspect ratio of the metal wire 30. More specifically, it describes the relationship between the aspect ratio and the cross-sectional area S when the circumference L of the metal wire is kept constant.

[0069] Figure 5A is a graph showing the relationship between the aspect ratio and cross-sectional area of ​​a metal wire according to Embodiment 1. In the graph of Figure 5A, the circumference of the metal wire 30 is kept constant. In the graph of Figure 5A, the aspect ratio of the metal wire is used as the horizontal axis, and the values ​​of the cross-sectional area of ​​the metal wire 30 when the aspect ratio is changed are normalized by dividing each value by the maximum value, and these values ​​are used as the vertical axis.

[0070] In the graph in Figure 5A, Width w2 of the metal wire 30 on the surface opposite to the base material 10 of Width w1 of the metal wire 30 on the surface side of the base material 10 The value obtained by dividing by w2 / w1 Samples S1, S2, and S3 are shown with different values. Sample S1 is, w2 / w1 = 1. Sample S2 teeth, w2 / w1 = 0.9. Sample S3 teeth, w2 / w1 = 0.8.

[0071] Figure 5B is an enlarged view of Figure 5A, showing the aspect ratios from 0.7 to 1.3. As shown in Figure 5B, the maximum cross-sectional area is found in sample S1, where the cross-sectional area is maximized at an aspect ratio of 1. Similarly, in sample S2, the cross-sectional area is maximized at an aspect ratio of 0.95. Furthermore, in sample S3, the cross-sectional area is maximized at an aspect ratio of 0.91. In other words, the values ​​on the vertical axis in sample S1 of Figure 5B are obtained by dividing the cross-sectional area values ​​at each aspect ratio by the cross-sectional area value at an aspect ratio of 1. Similarly, the values ​​on the vertical axis in sample S2 of Figure 5B are obtained by dividing the cross-sectional area values ​​at each aspect ratio by the cross-sectional area value at an aspect ratio of 0.95. Similarly, the values ​​on the vertical axis in sample S3 of Figure 5B are obtained by dividing the cross-sectional area values ​​at each aspect ratio by the cross-sectional area value at an aspect ratio of 0.91.

[0072] As shown in Figure 5B, sample S1 achieves a cross-sectional area of ​​99% or more of its maximum value by setting its aspect ratio between 0.82 and 1. Similarly, samples S2 and S3 achieve a cross-sectional area of ​​99% or more of their maximum value by setting their aspect ratios between 0.82 and 1.

[0073] For sample S3, setting the aspect ratio between 1 and 1.12 results in a cross-sectional area value of 99% or more of the maximum value. Similarly, for samples S1 and S2, setting the aspect ratio between 1 and 1.12 results in a cross-sectional area value of 99% or more of the maximum value.

[0074] Based on the above, by setting the aspect ratio between 0.82 and 1.12, the cross-sectional area can be increased to 99% or more of the maximum value. Therefore, a low-resistance thin metal wire 30 can be realized.

[0075] Figures 5A and 5B show the calculation of the cross-sectional area of ​​the metal wire 30 when the aspect ratio is changed while keeping the perimeter constant. If the aspect ratio is between 0.82 and 1.12, the value of the cross-sectional area at a certain perimeter will be 99% or more of the maximum value of the cross-sectional area. Therefore, by setting the aspect ratio between 0.82 and 1.12, the cross-sectional area of ​​the metal wire 30 can be increased without increasing the perimeter of the metal wire 30. Thus, a metal wire 30 with low resistance and high reliability can be realized.

[0076] Furthermore, if the wire width w of the metal wire is between 1 μm and 3 μm, the height h of the metal wire is between 0.82 μm and 3.36 μm.

[0077] In a cross-sectional view of a metal wire 30 cut in the width direction, the cross-sectional area S is between 0.7 and 1 times the product of the wire width w and the height h. By increasing the cross-sectional area S, the resistance value of the metal wire 30 can be lowered. As mentioned above, the wire width w is the longest length parallel to the width direction of the metal wire 30, and the height h is the longest length parallel to the height direction perpendicular to the width direction of the metal wire 30. Therefore, the cross-sectional area S of the metal wire 30 cut in the width direction is less than or equal to the product of the wire width w and the height h.

[0078] In a cross-sectional view obtained by cutting the metal wire 30 in the width direction, the length L around the metal wire 30 is 3.5 times or more and 4.2 times or less the wire width w.

[0079] By making the circumference L of the thin metal wire 30 3.5 times or more than the wire width w, the cross-sectional area S can be increased.

[0080] Increasing the circumference L of the metal wire 30 increases the risk of corrosion of the metal wire 30 due to substances present in the space between the metal wire 30 and the base material 10. Specifically, the contact area between the metal wire 30 and the base material 10 increases, making it more likely that a space will form between the metal wire 30 and the base material 10. By keeping the circumference L of the metal wire 30 at 4.2 times or less the wire width w, the risk of corrosion of the metal wire 30 can be reduced and the reliability of the metal wire 30 can be ensured.

[0081] In other words, in order to lower the resistance of the metal wire 30, it is necessary to increase the cross-sectional area S of the metal wire, and in order to improve the reliability of the metal wire 30, it is necessary to decrease the circumference L of the metal wire 30.

[0082] Therefore, the value L obtained by dividing the square of the circumference L of the metal wire 30 by the cross-sectional area S of the metal wire 30 2 By reducing / S, the reliability of the metal wire 30 can be improved while reducing the resistance value of the metal wire 30.

[0083] Divide the square of the circumference L of the metal wire 30 by the cross-sectional area S of the metal wire 30. value (Hereinafter, L 2 The value (referred to as / S) is between 16 and 16.27. 2 The value of / S is smaller when the cross-sectional shape of the metal wire 30 is rectangular than when it is trapezoidal. Also, L 2 The value of / S is smaller when the cross-sectional shape of the metal wire 30 is square than when it is rectangular. From the above, L 2 The value of / S is at its minimum of 16 when the cross-sectional shape of the metal wire 30 is square. In other words, L 2 The minimum value of / S is 16.

[0084] Below, the L of the metal thin wire 30 2 The optimal value for / S will be described, taking into account its relationship with the cross-sectional area S.

[0085] Figure 6A is a graph showing the relationship between the value obtained by dividing the square of the circumference by the cross-sectional area and the cross-sectional area for a metal wire according to Embodiment 1. In the graph of Figure 6A, the L of the metal wire 302 With / S on the horizontal axis and L 2 For the cross-sectional area S of the metal fine wire 30 when / S is changed, the vertical axis is the normalized value obtained by dividing each value by the maximum value.

[0086] In the graph of FIG. 6A, Width w2 of the metal wire 30 on the surface opposite to the base material 10 by Width w1 of the metal wire 30 on the surface side of the base material 10 the value divided by w2 / w1 different samples S1, S2, and S3 of the value are described. Sample S1 has w2 / w1 = 1. Sample S2 has w2 / w1 = 0.9. Sample S3 has w2 / w1 = 0.8.

[0087] FIG. 6B is an enlarged view of the value obtained by dividing the square of the length around FIG. 6A by the cross-sectional area, which is 16 to 16.5. As shown in FIG. 6B, for sample S1, when the value of L 2 / S is 16 or more and 16.16 or less, the cross-sectional area is 99% or more. Also, for sample S2, when the value of L 2 / S is 16.02 or more and 16.19 or less, the cross-sectional area is 99% or more. Also, for sample S3, when the value of L 2 / S is 16.09 or more and 16.27 or less, the cross-sectional area is 99% or more.

[0088] From the above, by setting the value of L 2 / S to 16 or more and 16.27 or less, the cross-sectional area can be made 99% or more of the maximum value. Therefore, a low-resistance metal fine wire 30 can be realized.

[0089] As shown in FIG. 4, in a cross-sectional view of the metal fine wire 30 cut in the width direction, among the diagonals of the metal fine wire 30, the longest diagonal is defined as the first diagonal 33. The length D of the first diagonal is 1.2 times or more and 1.6 times or less the line width w.

[0090] When the user views the conductive film 100a from an inclined position with respect to the height direction, the substantial line width w r of the metal fine wire 30 becomes larger than the above-mentioned line width w. The substantial line width w rThe maximum value is the length D of the first diagonal 33.

[0091] By making the length D of the first diagonal less than or equal to 1.6 times the line width w, the length D of the first diagonal can be reduced. Therefore, the effective line width w of the metal thin wire 30 is r This makes it possible to reduce the size of the metal wire 30. Therefore, it becomes more difficult for the user of the conductive film 100a to see the metal wire 30.

[0092] As shown in Figure 4, the cross-section of the metal wire 30 is a trapezoidal shape with rounded corners at the bottom of the paper. In this case, as shown in Figure 4, we consider a hypothetical trapezoid formed when we draw tangents to the side wall at the opening of the metal wire 30 and to the bottom of the metal wire 30 in the cross-sectional view. The first diagonal line 33 is a part of the metal wire 30 that is part of the straight line connecting the vertices of this hypothetical trapezoid.

[0093] The angle θ between the first diagonal line 33 and the lower or upper surface of the metal wire 30 is between 30° and 60°. By making the angle θ between the lower or upper surface of the metal wire 30 and 60° or less, the effective wire width of the metal wire 30 can be reduced. Therefore, it becomes more difficult for the user of the conductive film 100a to see the metal wire 30. Also, by making the angle θ between the lower or upper surface of the metal wire 30 and 30° or more, the height of the metal wire can be increased. Therefore, as mentioned above, the resistance value of the conductive film 100a can be reduced. Furthermore, reliability can be ensured.

[0094] (Embodiment 2) The conductive film 100b according to Embodiment 2 will be described below with reference to Figure 7. Figure 7 is a diagram of the conductive film according to Embodiment 2, corresponding to Figure 1.

[0095] In addition, for Embodiment 2, which is described in detail below, components similar to those in Embodiment 1 are denoted by the same reference numerals and their descriptions are omitted.

[0096] Unlike Embodiment 1, Embodiment 3 does not include the first busbar 20a and the second busbar 20b. That is, no voltage is applied to the metal thin wire 30 according to Embodiment 3.

[0097] Generally, in electromagnetic shielding, the greater the height of the metal wire 30 that provides the shielding effect, the greater the degree of attenuation within the metal wire 30. In other words, the higher the shielding performance. Also, the lower the resistance value, the higher the shielding performance at low frequencies (below 5 GHz). By using conductive film 100b as an electromagnetic shield, it is possible to realize an electromagnetic shield that is transparent and has high electromagnetic shielding characteristics.

[0098] (Embodiment 3) The conductive film 100c according to Embodiment 3 will be described below with reference to Figure 8. Figure 8 is a diagram of the conductive film according to Embodiment 3, corresponding to Figure 4.

[0099] In addition, for Embodiment 3, which is described in detail below, components similar to those in Embodiment 1 are denoted by the same reference numerals and their descriptions are omitted.

[0100] In Embodiment 1, the metal wire 30 is located in the groove 12 of the base material 10, whereas in Embodiment 3, the metal wire 30 is located on the surface of the base material 10.

[0101] Furthermore, the upper and side surfaces of the metal wire 30 are in contact with the protective film 40. Unlike Embodiment 1, in Embodiment 3, the side surfaces of the metal wire 30 do not come into contact with the substrate 10. The contact between the protective film 40 and the side surfaces of the metal wire 30 prevents the metal wire 30 from being corroded by substances present in the air. Thus, the reliability of the conductive film 100c can be ensured.

[0102] Furthermore, the width w3 of the metal wire 30 on its lower surface is greater than the width w4 of the metal wire 30 on its upper surface. That is, the width w3 of the metal wire 30 on the surface side of the base material 10 is greater than the width w4 of the metal wire 30 on the side opposite to the surface of the base material 10. This configuration reduces stress on the metal wire 30. More specifically, the stress applied to the metal wire 30 on the surface of the base material 10 can be released to the side opposite to the surface of the base material 10. As a result, damage to the metal wire 30 and delamination of the metal wire 30 from the base material 10 can be suppressed, and the deterioration of the reliability of the conductive film 100c can be suppressed.

[0103] (Summary of the modified example) The conductive film 100d according to the modified example will be described below with reference to Figure 9. Figure 9 is a diagram of the conductive film according to the modified example that corresponds to Figure 3.

[0104] As shown in Figure 9, the first end line 30d and the second end line 30e of the modified metal wire 30 are not parallel. Even in this case, the center line 30f is the line located midway between the first end line 30d and the second end line 30e.

[0105] As described above, the width direction of the metal wire 30 is perpendicular to the center line 30f. Therefore, in this modified example, the line width w of the metal wire 30 varies. If the line width w, height h, or aspect ratio of the metal wire 30 varies, and even if only a part of the area satisfies the scope of the present invention, it is considered to be within the scope of the present invention.

[0106] (summary) The conductive film 100 comprises a base material 10 containing an insulating resin and a metal fine wire 30 provided on the base material 10. If the wire width of the metal fine wire 30 is w and the height of the metal fine wire 30 is h, then 1 μm ≤ w ≤ 5 μm, 0.82 μm ≤ h ≤ 5.6 μm, and 0.82 ≤ h / w ≤ 1.12.

[0107] According to the above configuration, it is possible to provide a conductive film with low resistance and high reliability while suppressing the visibility of the metal wires 30.

[0108] The conductive film 100 has a thickness of 1 μm ≤ w ≤ 3 μm and a thickness of 0.82 μm ≤ h ≤ 3.36 μm.

[0109] According to the above configuration, the visibility of the thin metal wire 30 can be suppressed.

[0110] In a cross-sectional view, the conductive film 100 satisfies the condition 0.7w × h ≤ S ≤ w × h, where S is the cross-sectional area of ​​the metal wire 30.

[0111] According to the above configuration, a conductive film 100 with low resistance and high reliability can be provided.

[0112] In a cross-sectional view, the conductive film 100 satisfies the condition 3.5w ≤ L ≤ 4.2w, where L is the length around the metal wire 30.

[0113] According to the above configuration, a conductive film 100 with low resistance and high reliability can be provided.

[0114] In a cross-sectional view, the conductive film 100 has a cross-sectional area of ​​the metal wire 30, where S is the cross-sectional area and L is the length around the metal wire 30, and L is the length around the metal wire 30. 2 / S ≤ 16.27.

[0115] According to the above configuration, it is possible to provide a conductive film 100 with low resistance and high reliability while suppressing the visibility of the metal wires 30.

[0116] In a cross-sectional view, the conductive film 100 satisfies the following condition: 1.2w ≤ D ≤ 1.6w, where D is the length of the longest first diagonal 33 among the diagonals of the metal thin wire 30.

[0117] According to the above configuration, the visibility of the thin metal wire 30 can be suppressed.

[0118] The conductive film 100 satisfies the angle 30° ≤ θ ≤ 60°, where θ is the angle between the first diagonal 33 and the lower or upper surface of the metal wire 30.

[0119] According to the above configuration, it is possible to provide a conductive film 100 with low resistance and high reliability while suppressing the visibility of the metal wires 30.

[0120] The conductive film 100 further comprises a plurality of fine metal wires 30 provided on the base material 10, where each fine metal wire 30 is one of the plurality of fine metal wires 30, and the average pitch of the plurality of fine metal wires 30 is between 4 and 1000 times the wire width w of the fine metal wire 30.

[0121] According to the above configuration, the visibility of the thin metal wire 30 can be suppressed.

[0122] The conductive film 100 has a sheet resistance of 10Ω / □ or less relative to the metal wire 30.

[0123] According to the above configuration, a highly reliable conductive film 100 can be provided.

[0124] The conductive film 100a has grooves 13 on the surface of the base material 10, and the metal fine wires 30 are located in the grooves 13.

[0125] In the conductive film 100a, the width of the metal wire 30 at the opening of the groove 13 is greater than the width of the metal wire 30 at the bottom of the groove 13.

[0126] According to the above configuration, a highly reliable conductive film 100a can be provided.

[0127] The conductive film 100b further comprises a protective film 40 laminated on the upper surface of the substrate 10, and the upper and side surfaces of the metal fine wire 30 are in contact with the protective film 40.

[0128] According to the above configuration, a highly reliable conductive film 100b can be provided.

[0129] The width of the conductive film 100b on the lower surface of the metal wire 30 is greater than the width of the metal wire 30 on the upper surface.

[0130] According to the above configuration, a highly reliable conductive film 100b can be provided.

[0131] In the conductive film 100, the wire width of the metal wire 30 is the longest length parallel to the width direction of the metal wire 30 when viewed in a cross-sectional view of the metal wire 30 cut in the width direction, and the height of the metal wire 30 is the longest length parallel to the height direction perpendicular to the width direction of the metal wire 30 when viewed in a cross-sectional view. [Explanation of Symbols]

[0132] 100a, 100b, 100c, 100d, 100e conductive film 10 Base material 11 First layer 12 Second layer 13 Groove 20a First bus bar 21a First external connection section 22a First power feed section 20b Second bus bar 21b Second external connection section 22b Second power feed section 30 Fine metal wire 30a, 30d first end line 30b, 30e second end line 30c, 30f center line 31 Conductive layer 32. Adhesion layer 33 First diagonal 40 Protective film

Claims

1. A substrate containing insulating resin, A thin metal wire provided on the substrate, Equipped with, The surface of the substrate is provided with grooves, The thin metal wire is located in the groove, In a cross-sectional view, the width of the thin metal wire at the opening of the groove is defined as w1. In the cross-sectional view, the width of the thin metal wire at the bottom of the groove is defined as w2. If the height of the aforementioned thin metal wire is h, 1 μm ≤ w1 ≤ 5 μm, 0.8 ≤ w² / w1 < 1, 0.82 μm ≤ h ≤ 5.6 μm, 0.82 ≤ h / w1 ≤ 1.12, The tangents of the side wall at the opening of the aforementioned thin metal wire are defined as the first tangent and the second tangent. If the tangent to the side wall at the bottom of the aforementioned thin metal wire is defined as the third tangent, The width w2 of the metal wire at the bottom of the groove is the width of the bottom of the imaginary rectangle formed by the surface of the metal wire and the first tangent, the second tangent, the third tangent, and the fourth tangent. The width w1 of the metal wire at the opening of the groove is greater than the width w2 of the metal wire at the bottom of the groove. Conductive film.

2. 1 μm ≤ w ≤ 3 μm, 0.82 μm ≤ h ≤ 3.36 μm. The conductive film according to claim 1.

3. In a cross-sectional view, if the cross-sectional area of ​​the metal wire is S, 0.7w × h ≤ S ≤ w × h, The conductive film according to claim 1.

4. In a cross-sectional view, if the length around the metal wire is L, 3.5w ≤ L ≤ 4.2w, The conductive film according to claim 1.

5. In a cross-sectional view, if the cross-sectional area of ​​the metal wire is S and the circumference of the metal wire is L, 16 ≤ L ２ / S ≤ 16.27, The conductive film according to claim 1.

6. In a cross-sectional view, if we denote the length of the longest first diagonal among the diagonals of the thin metal wire as D, 1.2w ≤ D ≤ 1.6w, The conductive film according to claim 1.

7. If we let θ be the angle between the first diagonal and the lower or upper surface of the thin metal wire, 30° ≤ θ ≤ 60°. The conductive film according to claim 6.

8. The substrate further comprises a plurality of the aforementioned thin metal wires, The aforementioned metal wire is one of a plurality of such metal wires, The average pitch of the multiple metal nanowires is between 4 and 1000 times the wire width w of the metal nanowires. The conductive film according to claim 1.

9. The sheet resistance of the aforementioned thin metal wire is 10Ω / □ or less. The conductive film according to claim 1.

10. The visible light transmittance of the substrate is 80% or more. The conductive film according to claim 1.

11. The side wall of the metal wire has a first corner located at the bottom of the base material, The point at which the first tangent line separates from the side wall of the groove is defined as the first point. If we define the point where the third tangent line separates from the side wall of the groove as the second point, The first corner is located between the imaginary line connecting the first point and the second point, and the first tangent line and the second tangent line. The conductive film according to claim 1.

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