Flexible circuit board

Abstract

To provide a flexible substrate that can reduce the risk of breakage of wiring.SOLUTION: A flexible substrate comprises: an insulating base material having a plurality of first band parts, a plurality of second band parts, and a plurality of island-like parts; a plurality of electrical elements overlapping the island-like parts; a plurality of scan lines each extending overlapping the first band parts; a plurality of signal lines each extending overlapping the second band parts; a first inorganic insulating film covering the scan lines; and a second inorganic insulating film covering the signal lines. The first inorganic insulating film is formed in a band shape overlapping the first band parts. The second inorganic insulating film is formed in a band shape overlapping the second band parts. The scan line has a first side edge and a second side edge extending in an extension direction of the scan line. The first inorganic insulating film covers the first side edge and the second side edge. The signal line has a third side edge and a fourth side edge extending in an extension direction of the signal line. The second inorganic insulating film covers the third side edge and the fourth side edge.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Embodiments of the present invention relate to flexible substrates.

Background Art

[0002] In recent years, the use of flexible substrates having flexibility and stretchability has been studied in various fields. For example, a usage form in which a flexible substrate in which electrical elements are arranged in a matrix is attached to a curved surface such as a housing of an electronic device or a human body can be considered. As the electrical elements, for example, various sensors such as touch sensors and temperature sensors and display elements can be applied.

[0003] In a flexible substrate, it is necessary to take measures so that the wiring is not damaged by stress due to bending or stretching. As such measures, for example, providing a honeycomb-shaped opening in a base material that supports the wiring or making the wiring into a meandering shape (meander shape) has been proposed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present embodiment is to provide a flexible substrate capable of reducing the risk of wiring breakage.

Means for Solving the Problems

[0006] According to this embodiment, an insulating substrate having a plurality of first strips extending in a first direction and aligned in a second direction intersecting the first direction, a plurality of second strips extending in the second direction and aligned in the first direction, and a plurality of island-shaped portions located at the intersection of the first strips and the second strips, a plurality of electrical elements overlapping the island-shaped portions, a plurality of scanning lines each extending overlapping the first strips, a plurality of signal lines each extending overlapping the second strips, and a first inorganic insulating film covering the scanning lines, and The scanner comprises a first inorganic insulating film covering a signal line, wherein the first inorganic insulating film is formed in a strip shape overlapping the first strip portion, the second inorganic insulating film is formed in a strip shape overlapping the second strip portion, the scan line has a first side edge and a second side edge extending in the direction of extension of the scan line, the first inorganic insulating film covers the first side edge and the second side edge, the signal line has a third side edge and a fourth side edge extending in the direction of extension of the signal line, and the second inorganic insulating film covers the third side edge and the fourth side edge. stomach , The first and second band portions are each formed in a wave-like shape and have a plurality of peaks. A flexible circuit board is provided. According to one aspect of this embodiment, the first inorganic insulating film has a first sidewall in contact with the first side edge and a second sidewall in contact with the second side edge, the scanning line is interposed between the first sidewall and the second sidewall, the first sidewall has a first thin film portion at its top in a plan view, and the second sidewall has a second thin film portion at its top in a plan view. In another aspect of this embodiment, the second inorganic insulating film has a third sidewall in contact with the third side edge and a fourth sidewall in contact with the fourth side edge, the signal line is interposed between the third sidewall and the fourth sidewall, the third sidewall has a third thin film portion at its top in a plan view, and the fourth sidewall has a fourth thin film portion at its top in a plan view. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic plan view of the flexible substrate according to this embodiment. [Figure 2] Figure 2 is a magnified plan view of a portion of the flexible substrate shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view of the flexible substrate along the line A and B shown in Figure 2. [Figure 4] Figure 4 is a cross-sectional view of the flexible substrate along the CD line shown in Figure 2. [Figure 5] Figure 5 is a cross-sectional view of a flexible substrate showing a comparative example of the configuration shown in Figure 3. [Figure 6] Figure 6 is a cross-sectional view of a flexible substrate showing a comparative example of the configuration shown in Figure 4. [Figure 7]Figure 7 is a graph showing the amount of distortion as a function of the scan line elongation rate for this embodiment and comparative example. [Figure 8] Figure 8 is a graph showing the amount of strain as a function of the signal line elongation rate for this embodiment and comparative example. [Figure 9] Figure 9 is a graph showing the stress as a function of the scan line elongation rate for this embodiment and comparative example. [Figure 10] Figure 10 is a plan view showing the scan lines and insulating film. [Figure 11] Figure 11 is a plan view showing the signal lines and insulating film. [Modes for carrying out the invention]

[0008] Hereinafter, this embodiment will be described with reference to the drawings. It should be noted that the disclosure is merely an example, and any modifications that a person skilled in the art could easily conceive while maintaining the spirit of the invention are naturally included within the scope of the present invention. Furthermore, the drawings may schematically represent the width, thickness, shape, etc., of each part compared to the actual embodiment in order to clarify the explanation; however, these are merely examples and do not limit the interpretation of the present invention. In addition, in this specification and in each drawing, components that perform the same or similar functions as those described above in previously shown drawings are denoted by the same reference numerals, and redundant detailed explanations may be omitted as appropriate.

[0009] Figure 1 is a schematic plan view of the flexible substrate 100 according to this embodiment. In the present embodiment, as shown in the drawing, the first direction D1, the second direction D2, and the third direction D3 are defined. The first direction D1 and the second direction D2 are parallel to the main surface of the flexible substrate 100 and intersect each other. The third direction D3 is perpendicular to the first direction D1 and the second direction D2 and corresponds to the thickness direction of the flexible substrate 100. In the present embodiment, the first direction D1 and the second direction D2 intersect perpendicularly, but they may intersect at an angle other than perpendicular. In this specification, the direction toward the tip of the arrow indicating the third direction D3 is referred to as "up", and the direction opposite to the tip of the arrow is referred to as "down". Also, it is assumed that there is an observation position for observing the flexible substrate 100 on the tip side of the arrow indicating the third direction D3, and viewing from this observation position toward the D1-D2 plane defined by the first direction D1 and the second direction D2 is referred to as a plan view.

[0010] As shown in FIG. 1, the flexible substrate 100 includes a plurality of scanning lines 1, a plurality of signal lines 2, a plurality of electrical elements 3, a resin layer 81, a scanning line driver DR1, and a signal line driver DR2. The plurality of scanning lines 1, the plurality of signal lines 2, the plurality of electrical elements 3, the scanning line driver DR1, and the signal line driver DR2 are provided on the resin layer 81.

[0011] The plurality of scanning lines 1 each extend in the first direction D1 and are arranged in the second direction D2. The plurality of scanning lines 1 are each connected to the scanning line driver DRl. The plurality of signal lines 2 each extend in the second direction D2 and are arranged in the first direction D1. The plurality of signal lines 2 are each connected to the signal line driver DR2. The plurality of electrical elements 3 are each located at the intersection of the scanning line 1 and the signal line 2 and are electrically connected to the scanning line 1 and the signal line 2.

[0012] A scanning signal is supplied to the electrical element 3 via the scanning line 1. For example, when the electrical element 3 is one that outputs a signal such as a sensor, an output signal from the electrical element 3 is supplied to the signal line 2. Note that the scanning line 1 and the signal line 2 are an example of the wiring provided in the flexible substrate 100. The flexible substrate 100 may include other types of wiring such as a power supply line for supplying power to the electrical element 3 in addition to the scanning line 1 and the signal line 2.

[0013] The scanning line driver DR1 functions as a source for supplying a scanning signal to each of the scanning lines 1. Further, the signal line driver DR2 functions as a source for supplying a driving signal to each of the signal lines 2, or as a signal processing unit that processes the output signals output to each of the signal lines 2.

[0014] FIG. 2 is an enlarged plan view of a part of the flexible substrate 100 shown in FIG. 1. As shown in FIG. 2, in addition to the above, the flexible substrate 100 includes an insulating base material 4 that supports the scanning lines 1 and the signal lines 2. The insulating base material 4 has stretchability and flexibility. The insulating base material 4 is formed using, for example, polyimide, but is not limited to this example.

[0015] The insulating base material 4 includes a plurality of island portions 40, and a plurality of first band portions 41 and a plurality of second band portions 42 formed integrally with the island portions 40. The insulating base material 4 is formed in a mesh shape. The plurality of island portions 40 are arranged in a matrix in the first direction D1 and the second direction D2 with a space therebetween. The island portions 40 are located at the intersections of the first band portions 41 and the second band portions 42. Each of the island portions 40 is formed in, for example, a rectangular shape in plan view. Note that the island portions 40 may be formed in other polygonal shapes, or may be formed in a circular shape or an elliptical shape. The electrical element 3 overlaps the island portions 40.

[0016] The first band portion 41 extends generally in the first direction D1 and is arranged in the second direction D2. The first band portion 41 connects the plurality of island portions 40 arranged in the first direction D1. The second band portion 42 extends generally in the second direction D2 and is arranged in the first direction D1. The second band portion 42 connects the plurality of island portions 40 arranged in the second direction D2. The first band portion 41 and the second band portion 42 are each formed in a wavy shape in plan view. In other words, the first band portion 41 and the second band portion 42 are formed in a meandering shape (a meander shape) in plan view. The first band portion 41 and the second band portion 42 each have a plurality of apexes 43 in plan view. The apex 43 corresponds to the peak or valley portion of the waveform.

[0017] Multiple scan lines 1 each extend overlapping with the first band 41. Multiple signal lines 2 each extend overlapping with the second band 42. In other words, both scan lines 1 and signal lines 2 are formed in a meandering shape.

[0018] Figure 3 is a cross-sectional view of the flexible substrate 100 along the line A and B shown in Figure 2. As shown in Figure 3, the flexible substrate 100 further comprises insulating films 51 to 55 and a resin layer 82.

[0019] The insulating substrate 4 is located on the resin layer 81. The insulating film 51 is located on the insulating substrate 4. The insulating film 52 is located on the insulating film 51. The insulating film 53 is located on the insulating film 52. The scan line 1 is located on the insulating film 53. The scan line 1 has a first side edge SE1 and a second side edge SE2. The insulating film (first inorganic insulating film) 54 is located on the insulating film 53 and covers the scan line 1. The insulating film 54 covers the first side edge SE1 and the second side edge SE2. The insulating film 54 has a first side wall WA1 in contact with the first side edge SE1 and a second side wall WA2 in contact with the second side edge SE2. Furthermore, the insulating film 54 has a first end 54A and a second end 54B, with the first side wall WA1 corresponding to the region between the first side edge SE1 and the first end 54A, and the second side wall WA2 corresponding to the region between the second side edge SE2 and the second end 54B. The insulating film 55 is located on top of the insulating film 54. The resin layer 82 covers the insulating substrate 4 and the insulating films 51 to 55.

[0020] The insulating films 51 to 55 are all inorganic insulating films formed from inorganic insulating materials such as silicon oxide (SiO), silicon nitride (SiN), and silicon oxynitride (SiON).

[0021] Figure 4 is a cross-sectional view of the flexible substrate 100 along the CD line shown in Figure 2. The signal line 2 is located on the insulating film 54. The signal line 2 has a third side edge SE3 and a fourth side edge SE4. The insulating film (second inorganic insulating film) 55 is located on the insulating film 54 and covers the signal line 2. The insulating film 55 covers the third side edge SE3 and the fourth side edge SE4. The insulating film 55 has a third side wall WA3 that is in contact with the third side edge SE3 and a fourth side wall WA4 that is in contact with the fourth side edge SE4. The insulating film 55 also has a third end 55A and a fourth end 55B, with the third side wall WA3 corresponding to the region between the third side edge SE3 and the third end 55A, and the fourth side wall WA4 corresponding to the region between the fourth side edge SE4 and the fourth end 55B. Furthermore, as shown in Figures 3 and 4, the scan line 1, insulating film 54, signal line 2, and insulating film 55 are stacked in this order.

[0022] Figure 5 is a cross-sectional view of a flexible substrate 100 showing a comparative example of the configuration shown in Figure 3. The configuration shown in Figure 5 differs from the configuration shown in Figure 3 in the configuration of scan line 1. In the comparative example shown in Figure 5, the first and second side edges SE1 and SE2 of scan line 1 are not covered by the insulating film 54. In the illustrated example, the first and second side edges SE1 and SE2 are in contact with the resin layer 82.

[0023] Figure 6 is a cross-sectional view of a flexible substrate 100 showing a comparative example of the configuration shown in Figure 4. The configuration shown in Figure 6 differs from the configuration shown in Figure 4 in the configuration of signal line 2. In the comparative example shown in Figure 6, the third and fourth side edges SE3 and SE4 of the signal line 2 are not covered by the insulating film 55. In the illustrated example, the third and fourth side edges SE3 and SE4 are in contact with the resin layer 82.

[0024] Figure 7 is a graph showing the amount of distortion as a function of the elongation rate of scan line 1 for this embodiment and comparative example. The horizontal axis represents the elongation rate of scan line 1, and the vertical axis represents the amount of distortion of scan line 1. Line L11 shows the amount of strain with respect to the elongation rate of scan line 1 when the first side edge SE1 and the second side edge SE2 of scan line 1 are covered with the insulating film 54, as shown in Figure 3. Line L12 shows the amount of strain with respect to the elongation rate of scan line 1 when the first side edge SE1 and the second side edge SE2 of scan line 1 are not covered with the insulating film 54, as shown in Figure 5. It can be seen that the amount of strain in line L11 is reduced compared to the amount of strain in line L12. In other words, when the flexible substrate 100 is stretched, the amount of strain on scan line 1 can be reduced in the configuration in which the first side edge SE1 and the second side edge SE2 of scan line 1 are covered with the insulating film 54 compared to the configuration in which they are not covered.

[0025] Figure 8 is a graph showing the amount of strain as a function of the elongation rate of signal line 2 for this embodiment and comparative example. The horizontal axis represents the elongation rate of signal line 2, and the vertical axis represents the amount of strain of signal line 2. Line L21 shows the amount of strain with respect to the elongation rate of signal line 2 when the third side edge SE3 and the fourth side edge SE4 of signal line 2 are covered with the insulating film 55, as shown in Figure 4. Line L22 shows the amount of strain with respect to the elongation rate of signal line 2 when the third side edge SE3 and the fourth side edge SE4 of signal line 2 are not covered with the insulating film 55, as shown in Figure 6. It can be seen that the amount of strain in line L21 is reduced compared to the amount of strain in line L22. In other words, when the flexible substrate 100 is stretched, the amount of strain on signal line 2 can be reduced in the configuration in which the third side edge SE3 and the fourth side edge SE4 of signal line 2 are covered with the insulating film 55 compared to the configuration in which they are not covered.

[0026] Figure 9 is a graph showing the stress as a function of the elongation rate of scan line 1 for this embodiment and comparative example. The horizontal axis represents the elongation rate of scan line 1, and the vertical axis represents the stress acting on scan line 1. Line L31 shows the stress on the elongation rate of scan line 1 when the first side edge SE1 and the second side edge SE2 of scan line 1 are covered with the insulating film 54, as shown in Figure 3. Line L32 shows the stress on the elongation rate of scan line 1 when the first side edge SE1 and the second side edge SE2 of scan line 1 are not covered with the insulating film 54, as shown in Figure 5. It can be seen that the stress on line L31 is reduced compared to the stress on line L32. In other words, when the flexible substrate 100 is stretched, the stress on scan line 1 can be reduced in the configuration where the first side edge SE1 and the second side edge SE2 of scan line 1 are covered with the insulating film 54 compared to the configuration where they are not covered. Although not shown in the diagram, the same results can be obtained for signal line 2.

[0027] In this embodiment, the first and second side edges SE1 and SE2 of the scan line 1 are covered with an insulating film 54. The third and fourth side edges SE3 and SE4 of the signal line 2 are covered with an insulating film 55. Therefore, when the flexible substrate 100 is stretched, the insulating film 54 functions as a stress-relieving layer for the scan line 1, reducing the amount of strain generated in the scan line 1. Similarly, when the flexible substrate 100 is stretched, the insulating film 55 functions as a stress-relieving layer for the signal line 2, reducing the amount of strain generated in the scan line 2. Consequently, the risk of wiring breakage can be reduced.

[0028] Figure 10 is a plan view showing scan line 1 and insulating film 54. The insulating film 54 is formed in a strip shape that overlaps with the first strip portion 41. As described above, the insulating film 54 has a first side wall WA1 that is in contact with the first side edge SE1 and a second side wall WA2 that is in contact with the second side edge SE2. The scan line 1 is interposed between the first side wall WA1 and the second side wall WA2.

[0029] The first sidewall WA1 has a first thin film portion TP1 at its apex 43 in a plan view. For example, the width of the first sidewall WA1 between two adjacent apex 43s is defined as width W1, and the width of the first thin film portion TP1 is defined as width W11. Width W11 is formed to be smaller than width W1. The second sidewall WA2 has a second thin film portion TP2 at its apex 43 in a plan view. For example, the width of the second sidewall WA2 between two adjacent apex 43s is defined as width W2, and the width of the second thin film portion TP2 is defined as width W12. Width W12 is formed to be smaller than width W2. Here, widths W1, W2, W11, and W12 correspond to widths in the direction intersecting the extending direction of the insulating film 54. Widths W11 and W12 are, for example, about 5 μm or less each.

[0030] The first side edge SE1 and the second side edge SE2 extend in the direction of the scanning line 1. The scanning line 1 has a first expanded portion EP1 in which the line width is increased between the first thin film portion TP1 and the second thin film portion TP2.

[0031] In the configurations shown in Figures 3 and 4, the inorganic film covering the side edges of the wiring reduces the amount of strain on the wiring. However, because the inorganic film is highly rigid, it is preferable for the first sidewall WA1 and the second sidewall WA2 to be thin. In other words, the smaller the width of the first sidewall WA1 and the second sidewall WA2, the greater the maximum amount of strain before the scan line 1 breaks. Here, the maximum amount of strain can be rephrased as the maximum amount of strain in the state where the wiring does not break.

[0032] According to the configuration shown in Figure 10, the first sidewall WA1 and the second sidewall WA2 are thinned at the top 43 where the amount of strain is maximum when the flexible substrate 100 is stretched. Therefore, the maximum amount of strain of the scan line 1 can be increased at the top 43.

[0033] Figure 11 is a plan view showing the signal line 2 and the insulating film 55. The insulating film 55 is formed in a strip shape that overlaps with the second strip portion 42. As described above, the insulating film 55 has a third side wall WA3 that is in contact with the third side edge SE3 and a fourth side wall WA4 that is in contact with the fourth side edge SE4. The signal line 2 is interposed between the third side wall WA3 and the fourth side wall WA4.

[0034] The third sidewall WA3 has a third thin film portion TP3 at its apex 43 in a plan view. For example, the width of the third sidewall WA3 between two adjacent apex portions 43 is defined as width W3, and the width of the third thin film portion TP3 is defined as width W13. Width W13 is formed to be smaller than width W3. The fourth sidewall WA4 has a fourth thin film portion TP4 at its apex 43 in a plan view. For example, the width of the fourth sidewall WA4 between two adjacent apex portions 43 is defined as width W4, and the width of the fourth thin film portion TP4 is defined as width W14. Width W14 is formed to be smaller than width W4. Here, widths W3, W4, W13, and W14 correspond to widths in the direction intersecting the extending direction of the insulating film 55. Widths W13 and W14 are, for example, approximately 5 μm or less each.

[0035] The third side edge SE3 and the fourth side edge SE4 extend in the direction of extension of the signal line 2. The signal line 2 has a second extended portion EP2 in which the line width is increased between the third thin film portion TP3 and the fourth thin film portion TP4. The same effects as those shown in Figure 10 can be obtained with the configuration shown in Figure 11.

[0036] As described above, according to this embodiment, a flexible substrate can be obtained that can reduce the risk of wiring breakage.

[0037] Although several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0038] 100... Flexible substrate, 40... Island-shaped section, 41... First strip section, 42... Second strip section, 43...Top, 1...Scanning line, 2...Signal line, 3...Electrical element, 4...Insulating substrate, 54, 55... insulating film, EP1... first extension, EP2... second extension, SE1...first side edge, SE2...second side edge, SE3...third side edge, SE4...fourth side edge, WA1...First side wall, WA2...Second side wall, WA3...Third side wall, WA4...Fourth side wall, TP1...first thin film part, TP2...second thin film part, TP3...third thin film part, TP4...fourth thin film part.

Claims

1. An insulating substrate having a plurality of first strips extending in a first direction and aligned in a second direction intersecting the first direction, a plurality of second strips extending in the second direction and aligned in the first direction, and a plurality of island-shaped portions located at the intersections of the first strips and the second strips, Multiple electrical elements overlapping the aforementioned island-shaped portion, Each of the following scan lines extends overlapping with the first band, Each of the signal lines extends overlapping with the second band, A first inorganic insulating film covering the scan line, The signal line is covered by a second inorganic insulating film, The first inorganic insulating film is formed in a strip shape that overlaps with the first strip portion, The second inorganic insulating film is formed in a strip shape that overlaps with the second strip portion, The scan line has a first side edge and a second side edge extending in the direction of the scan line's extension, The first inorganic insulating film covers the first and second side edges, The signal line has a third side edge and a fourth side edge extending in the direction of extension of the signal line, The second inorganic insulating film covers the third and fourth side edges, The first and second band portions are each formed in a wave-like shape and have a plurality of peaks, The first inorganic insulating film has a first side wall in contact with the first side edge and a second side wall in contact with the second side edge. The scan line is interposed between the first side wall and the second side wall, The first side wall, in plan view, has a first thin film portion at its top, The second sidewall is a flexible substrate having a second thin film portion at its top when viewed from above.

2. The flexible substrate according to claim 1, wherein the scanning line has a first expanded portion in which the line width is increased between the first thin film portion and the second thin film portion.

3. An insulating substrate having a plurality of first strips extending in a first direction and aligned in a second direction intersecting the first direction, a plurality of second strips extending in the second direction and aligned in the first direction, and a plurality of island-shaped portions located at the intersection of the first strips and the second strips, Multiple electrical elements overlapping the aforementioned island-shaped portion, Each of the following scan lines extends overlapping with the first band, Each of the following signal lines extends overlapping the second band section, A first inorganic insulating film covering the scan line, The signal line is covered by a second inorganic insulating film, The first inorganic insulating film is formed in a strip shape that overlaps with the first strip portion, The second inorganic insulating film is formed in a strip shape that overlaps with the second strip portion, The scan line has a first side edge and a second side edge extending in the direction of the scan line's extension, The first inorganic insulating film covers the first and second side edges, The signal line has a third side edge and a fourth side edge extending in the direction of extension of the signal line, The second inorganic insulating film covers the third and fourth side edges, The first and second band portions are each formed in a wave-like shape and have a plurality of peaks, The second inorganic insulating film has a third side wall in contact with the third side edge and a fourth side wall in contact with the fourth side edge. The signal line is interposed between the third side wall and the fourth side wall. The third side wall, in plan view, has a third thin film portion at its top, The fourth sidewall is a flexible substrate having a fourth thin film portion at its top when viewed from above.

4. The flexible substrate according to claim 3, wherein the signal line has a second expanded portion between the third thin film portion and the fourth thin film portion in which the line width is increased.

5. The flexible substrate according to claim 1 or 3, wherein the scanning line, the first inorganic insulating film, the signal line, and the second inorganic insulating film are stacked in this order.

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