JP2020088271A - Flexible substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible substrate capable of improving the elongation rate and suppressing the occurrence of cracks.
A flexible insulating base material having a first surface and a second surface opposite to the first surface, and a plurality of wirings provided on the second surface side of the insulating base material, A first low-rigidity layer having a first inner surface facing the first surface and a first outer surface opposite to the first inner surface, and a second inner surface facing the second surface with the wiring interposed therebetween. And a second low-rigidity layer having a second outer surface opposite to the second inner surface, a first high-rigidity layer in contact with the first outer surface and having an elastic modulus higher than that of the first low-rigidity layer, A second high-rigidity layer that is in contact with a second outer surface and has an elastic modulus higher than that of the second low-rigidity layer, wherein the elastic modulus of the first low-rigidity layer and the elastic modulus of the second low-rigidity layer are respectively A flexible substrate having a smaller elastic modulus than the insulating base material.
[Selection diagram]

Description

Embodiments of the present invention relate to a flexible substrate.

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

In the flexible board, it is necessary to take measures so that the wiring is not damaged by the stress due to bending or expansion and contraction. As such measures, for example, it has been proposed to provide a honeycomb-shaped opening in a base material that supports the wiring, or to form the wiring in a meandering shape.

JP-A-2015-198101 JP-A-2015-198102 JP, 2017-118109, A JP, 2017-113088, A

An object of the present embodiment is to provide a flexible substrate capable of improving the elongation rate and suppressing the occurrence of cracks.

According to this embodiment, a flexible insulating base material having a first surface and a second surface opposite to the first surface, and a plurality of flexible insulating base materials provided on the second surface side of the insulating base material. A first low-rigidity layer having wiring, a first inner surface facing the first surface, and a first outer surface opposite to the first inner surface, and facing the second surface via the wiring. A second low-rigidity layer having a second inner surface and a second outer surface opposite to the second inner surface, and a first high-rigidity layer in contact with the first outer surface and having an elastic modulus higher than that of the first low-rigidity layer. And a second high-rigidity layer that is in contact with the second outer surface and has a higher elastic modulus than the second low-rigidity layer, the elastic modulus of the first low-rigidity layer and the elastic modulus of the second low-rigidity layer. A flexible substrate having a modulus of elasticity smaller than that of the insulating substrate is provided.

According to this embodiment, a flexible insulating base material, a first organic insulating layer covering the insulating base material, a second organic insulating layer in contact with the first organic insulating layer, and the first organic insulating layer. And a plurality of wirings having a scanning line located between the second organic insulating layer and a signal line in contact with the second organic insulating layer. A first low-rigidity portion located in the same layer as the insulating base material and lower in rigidity than the insulating base material; a first low-rigidity portion located in the same layer as the first organic insulating layer and lower in rigidity than the first organic insulating layer; There is provided a flexible substrate including at least one of a low rigidity part 2 and a third low rigidity part located in the same layer as the second organic insulating layer and having a rigidity lower than that of the second organic insulating layer. .

FIG. 1 is a schematic plan view of a flexible substrate according to the first embodiment. FIG. 2 is a schematic plan view in which a part of the flexible substrate is enlarged. FIG. 3 is a schematic sectional view of a part of the flexible substrate indicated by F3A-F3B in FIG. FIG. 4 is a schematic cross-sectional view of a part of the flexible substrate indicated by F4A-F4B in FIG. FIG. 5 is a graph showing the characteristics of deformation when the flexible substrate is expanded. FIG. 6 is a schematic cross-sectional view of the flexible substrate according to the second embodiment. FIG. 7 is a plan view showing a portion of the flexible substrate where cracks are likely to occur. FIG. 8 is a plan view showing another shape of the insulating base material. FIG. 9 is a plan view showing a part of the insulating base material shown in FIG.

Hereinafter, the present embodiment will be described with reference to the drawings. It should be noted that the disclosure is merely an example, and a person having ordinary skill in the art can easily think of appropriate modifications while keeping the gist of the invention, and are naturally included in the scope of the invention. Further, in order to make the description clearer, the drawings may schematically show the width, thickness, shape, etc. of each part as compared with the actual mode, but this is merely an example, and It does not limit the interpretation. Further, in the present specification and the drawings, components having the same or similar functions as those described above with reference to the drawings already described are denoted by the same reference numerals, and redundant detailed description may be appropriately omitted. ..

[First Embodiment]
FIG. 1 is a schematic plan view of a flexible substrate 100 according to the first embodiment.
In the present embodiment, as illustrated, the first direction D1, the second direction D2, the third direction D3, the fourth direction D4, and the fifth direction D5 are defined. The first direction D1, the second direction D2, the third direction D3, and the fourth direction D4 are all parallel to the main surface of the flexible substrate 100 and intersect with each other. The fifth direction D5 is a direction perpendicular to the first direction D1, the second direction D2, the third direction D3, and the fourth direction D4, and corresponds to the thickness direction of the flexible substrate 100. The first direction D1 and the second direction D2 intersect perpendicularly in the present embodiment, but may intersect at an angle other than vertical. Further, the third direction D3 and the fourth direction D4 intersect perpendicularly in the present embodiment, but may intersect at an angle other than vertical.

The flexible substrate 100 includes a plurality of scanning lines 1, a plurality of signal lines 2, and a plurality of electric elements 3. The scanning line 1 and the signal line 2 are an example of wiring included in the flexible substrate 100. The scanning line 1 and the signal line 2 can be formed of, for example, a metal material or a transparent conductive material, and may have a single layer structure or a laminated structure. The flexible substrate 100 may include, in addition to the scanning line 1 and the signal line 2, another type of wiring such as a power supply line that supplies power to the electrical element 3.

The plurality of scanning lines 1 extend in the first direction D1 as a whole and are arranged in the second direction D2. The plurality of signal lines 2 extend in the second direction D2 as a whole and are arranged in the first direction D1. Specifically, the scanning line 1 has a wavy shape in which a straight line portion parallel to the first direction D1, a straight line portion parallel to the third direction D3, and a straight line portion parallel to the second direction D2 are sequentially repeated. There is. Similarly, the signal line 2 has a wavy shape in which a straight line portion parallel to the second direction D2, a straight line portion parallel to the fourth direction D4, and a straight line portion parallel to the first direction D1 are sequentially repeated.

A polygonal area A is formed by the two adjacent scanning lines 1 and the two adjacent signal lines 2. In the example of FIG. 1, the region A having the same shape is repeated in the first direction D1 and the second direction D2.

The electrical element 3 is electrically connected to the scanning line 1 and the signal line 2. In the illustrated example, the electrical element 3 is arranged in a portion where the scanning line 1 and the signal line 2 are parallel to the second direction D2. However, the arrangement position of the electrical element 3 is not limited to this example.

For example, the electric element 3 is a sensor, a semiconductor element, an actuator, or the like. For example, as the sensor, an optical sensor that receives visible light or near infrared light, a temperature sensor, a pressure sensor, a touch sensor, or the like can be applied. For example, a light emitting element, a light receiving element, a diode, a transistor, or the like can be used as the semiconductor element. When the electric element 3 is a light emitting element, a flexible display having flexibility and stretchability can be realized. As the light emitting element, for example, a light emitting diode having a size of about 100 μm such as a mini LED or a micro LED or an organic electroluminescence element can be applied. When the electric element 3 is an actuator, for example, a piezo element can be applied. Note that the electrical element 3 is not limited to the one illustrated here, and other elements having various functions can be applied. The electric element 3 may be a capacitor or a resistor.

The scanning line 1 supplies a scanning signal to the electric element 3. For example, when the electric element 3 is accompanied by a signal output like a sensor, the signal line 2 is supplied with the output signal from the electric element 3. In addition, for example, when the electric element 3 is a light emitting element or an actuator that operates in response to an input signal, a drive signal is supplied to the signal line 2. A controller including a scan signal supply source, a drive signal supply source, a processor that processes an output signal, or the like may be provided in the flexible substrate 100 or in a device connected to the flexible substrate 100.

FIG. 2 is a schematic plan view in which a part of the flexible substrate 100 is enlarged.
In the vicinity of the electric element 3, the scanning line 1 and the signal line 2 are shown in a state of being close to each other and extending in parallel, but actually, as will be described later with reference to FIG. 3, the scanning line 1 and the signal line 2 are shown. Are stacked in the thickness direction of the flexible substrate 100.

The flexible substrate 100 includes a flexible insulating base material 4 that supports the scanning lines 1 and the signal lines 2. The insulating base material 4 can be formed of, for example, polyimide, but is not limited to this example.

The insulating base material 4 includes a plurality of line portions 41, a plurality of line portions 42 (dummy line portions), and a plurality of island-shaped portions 43. The line portion 41 overlaps at least one of the scanning line 1 and the signal line 2. The line portion 42 does not overlap with the scanning line 1 or the signal line 2. The line portion 41 and the line portion 42 are both linear. The island portion 43 overlaps with the electrical element 3 and is connected to the line portion 41.

The line portion 41 and the line portion 42 form a polygonal first opening AP1 and a polygonal second opening AP2 different from the first opening AP1. In the example of FIG. 2, the first opening AP1 is a star-shaped octagon having eight corners C1 to C8. The second opening AP2 is a rectangle having four corners C7 to C10. The corner portions C1 to C10 are portions in which two or more line portions 41 or line portions 41 and 42 are connected at different angles. The shapes of the first opening AP1 and the second opening AP2 are not limited to these examples, and various shapes can be adopted.

The line 41 between the corners C1 and C2 and the line 41 between the corners C7 and C10 overlap the scanning line 1 and are parallel to the first direction D1. The line portion 41 between the corner portions C5 and C6 and the line portion 41 between the corner portions C8 and C9 overlap the signal line 2 and are parallel to the first direction D1.

The line portion 41 between the corner portions C3 and C4 and the line portion 41 between the corner portions C9 and C10 overlap the scanning line 1 and the signal line 2 and are parallel to the second direction D2. Is. The line portion 42 between the corner portion C7 and the corner portion C8 does not overlap any of the scanning line 1 and the signal line 2 and is parallel to the second direction D2.

The line portion 41 between the corner portions C2 and C3 and the line portion 41 between the corner portions C6 and C7 overlap the scanning line 1 and are parallel to the third direction D3. The line portion 41 between the corner portions C1 and C8 and the line portion 41 between the corner portions C4 and C5 overlap the signal line 2 and are parallel to the fourth direction D4.

As described above, the first opening AP1 and the second opening AP2 are configured by the plurality of line portions 41 and 42 that extend in different directions of the four directions. The first opening AP1 and the second opening AP2 are included in one area A. The first opening AP1 and the second opening AP2 correspond to two areas obtained by dividing the area A by the line portion 42. From another point of view, the line portion 42 is arranged at the boundary between the first opening AP1 and the second opening AP2. By providing two or more line portions 42 in the area A, three or more openings may be formed in the area A.

The inner angle θ1 of the first opening AP1 at the corners C1, C3, C5, C7 is smaller than the inner angle θ2 of the first opening AP1 at the corners C2, C4, C6, C8 (θ1<θ2). In the example of FIG. 2, the interior angle θ1 is an acute angle (θ1<90°) and the interior angle θ2 is an angle exceeding 180° (θ2>180°).

The shape of the first opening AP1 is 4-fold symmetry, which is the same shape when rotated by 90°. Not limited to this example, the first aperture AP1 may have rotational symmetry of four times or more, such as five-fold symmetry and six-fold symmetry. Further, the first opening AP1 may have a symmetry of three times or less.

The island portion 43 is arranged near the center of the line portion 41 that overlaps the scanning line 1 and the signal line 2. The electrical element 3 is arranged above the island portion 43. The island-shaped portion 43 is larger than the electric element 3, and in FIG. 2, the island-shaped portion 43 protrudes from the edge of the electric element 3. For example, focusing on the line portion 41 between the corner portions C3 and C4, the length L1 from the upper end of the line portion 41 to the island-shaped portion 43 and the lower end of the line portion 41 to the island-shaped portion 43 The lengths L2 up to 43 are equal to each other. However, the length L1 and the length L2 may be different.

The scanning line 1 has a first portion 11 shown by a solid line and a second portion 12 shown by a broken line. The second portion 12 overlaps the electrical element 3. The first portion 11 and the second portion 12 are arranged in different layers, and are electrically connected to each other through the contact holes CH1 and CH2.

FIG. 3 is a schematic cross-sectional view of a part of the flexible substrate 100 indicated by F3A-F3B in FIG.
The flexible substrate 100 includes the first organic insulating layer 5, the second organic insulating layer 6, the coating layer 7, the first low-rigidity layer 81, the second low-rigidity layer 82, and the second low-rigidity layer 82 in addition to the above-described elements. The first high-rigidity layer 91 and the second high-rigidity layer 92 are further provided.

The insulating base material 4 has a first surface SF1 and a second surface SF2 opposite to the first surface SF1. The scanning line 1 and the signal line 2 are provided on the second surface SF2 side of the insulating base material 4. The first organic insulating layer 5 covers the second surface SF2 of the insulating base material 4. The scanning line 1 (first portion 11) is arranged on the first organic insulating layer 5. The second organic insulating layer 6 covers the scan line 1 and the first organic insulating layer 5. The signal line 2 is arranged on the second organic insulating layer 6. The coating layer 7 covers the signal line 2, the insulating base material 4, the first organic insulating layer 5, and the second organic insulating layer 6.

The first organic insulating layer 5 and the second organic insulating layer 6 may also be provided in regions (the first opening AP1 and the second opening AP2) without the insulating base material 4. However, from the viewpoint of flexibility and stretchability of the flexible substrate 100, the arrangement mode as shown in FIG. 3 is preferable.

The first low-rigidity layer 81 has a first inner surface IS1 facing the first surface SF1 and a first outer surface OS1 opposite to the first inner surface IS1. In the illustrated example, the first inner surface IS1 is in contact with the first surface SF1 and is in contact with the coating layer 7 in the region where the insulating base material 4 is not present. The second low-rigidity layer 82 has a second inner surface IS2 facing the second surface SF2 with the scanning line 1 and the signal line 2 interposed therebetween, and a second outer surface OS2 opposite to the second inner surface IS2. is doing. In the illustrated example, the second inner surface IS2 is in contact with the coating layer 7. The elastic modulus of the first low-rigidity layer 81 and the elastic modulus of the second low-rigidity layer 82 are smaller than the elastic modulus of the insulating base material 4, respectively. For example, the elastic modulus of the first low-rigidity layer 81 and the elastic modulus of the second low-rigidity layer 82 are each smaller than 1 MPa.

The first high-rigidity layer 91 is in contact with the first outer surface OS1. The first high-rigidity layer 91 has an elastic modulus higher than that of the first low-rigidity layer 81. The second high-rigidity layer 92 is in contact with the second outer surface OS2. The second high-rigidity layer 92 has an elastic modulus higher than that of the second low-rigidity layer 82. The elastic modulus of the first high-rigidity layer 91 and the elastic modulus of the second high-rigidity layer 92 are each several MPa. The first low-rigidity layer 81, the second low-rigidity layer 82, the first high-rigidity layer 91, and the second high-rigidity layer 92 have a plurality of line portions 41, 42, a first opening AP1, and a second opening AP2 in a plan view. It overlaps.

Both the first organic insulating layer 5 and the second organic insulating layer 6 are made of an organic material. The coating layer 7 is formed of parylene (polyparaxylylene), for example. The first low-rigidity layer 81, the second low-rigidity layer 82, the first high-rigidity layer 91, and the second high-rigidity layer 92 are formed by using a stretchable material, for example, acrylic-based, urethane-based, epoxy-based. Is formed by any of the organic insulating layers. The sum of the thicknesses of the first low-rigidity layer 81 and the first high-rigidity layer 91 is smaller than 150 μm. The sum of the thicknesses of the second low-rigidity layer 82 and the second high-rigidity layer 92 is smaller than 150 μm.

FIG. 4 is a schematic cross-sectional view of a part of the flexible substrate 100 indicated by F4A-F4B in FIG.
Below the electrical element 3, the island-shaped portion 43 of the insulating base material 4 is arranged. Thereby, the electric element 3 can be favorably supported. An inorganic insulating layer 9 (passivation layer) is formed between the electrical element 3 and the island portion 43. The inorganic insulating layer 9 has an island shape that overlaps with the electrical element 3 in a plan view. The first portion 11 of the scanning line 1 is arranged on the first organic insulating layer 5. The second portion 12 of the scan line 1 is arranged on the inorganic insulating layer 9 (that is, below the first organic insulating layer 5). The second portion 12 is electrically connected to the electric element 3. In the example of FIG. 4, the end of the second portion 12 is covered with the first organic insulating layer 5.

The above-mentioned contact holes CH1 and CH2 are provided in the first organic insulating layer 5 in a region overlapping the island-shaped portion 43 and the inorganic insulating layer 9 in a plan view. The first portion 11 of the scanning line 1 is electrically connected via connecting members CM1 and CM2 arranged in the contact holes CH1 and CH2, respectively. The connecting members CM1 and CM2 may be a part of the first portion 11 or may be provided separately from the first portion 11.

According to the present embodiment, the flexible substrate 100 has the first low-rigidity layer 81 that adheres to the insulating base material 4 and the second low-rigidity layer 82 that adheres to the coating layer 7. That is, the insulating base material 4, the scanning line 1, and the signal line 2 are sandwiched between the first low-rigidity layer 81 and the second low-rigidity layer 82. By reducing the rigidity of the stretchable resin that supports the flexible substrate 100, it is possible to improve the elongation of the flexible substrate 100 until the flexible substrate 100 expands and breaks. Therefore, the expansion rate of the flexible substrate 100 can be improved.

The flexible substrate 100 also includes a first high-rigidity layer 91 that contacts the first low-rigidity layer 81 and a second high-rigidity layer 92 that contacts the second low-rigidity layer 82. By reducing the rigidity of the stretchable resin that supports the flexible substrate 100, demerits such as easy tearing, insufficient supportability, and difficulty in handling may occur, but the outside of the first low-rigidity layer 81 and the second low-rigidity layer 82 may be removed. By supporting the first high-rigidity layer 91 and the second high-rigidity layer 92, these disadvantages can be eliminated. The first high-rigidity layer 91 and the second high-rigidity layer 92 overlap not only the line portion 41, the line portion 42, and the island-shaped portion 43 but also the first opening AP1 and the second opening AP2. By providing the first high-rigidity layer 91 and the second high-rigidity layer 92 as described above, the strength of the flexible substrate 100 is increased overall, and moisture intrusion from below can be prevented, so that reliability is also improved.

Further, according to the present embodiment, the insulating base material 4 has the first opening AP1 and the second opening AP2. In this way, by providing the first opening AP1 and the second opening AP2 having different shapes, it is possible to give the flexible substrate 100 elasticity and flexibility in various directions. Further, the line portion 41 and the line portion 42 forming the first opening AP1 and the second opening AP2 are linear shapes that are the basis of general array design. Therefore, the pitch of the scanning lines 1 and the signal lines 2 can be made narrower and the density of the electrical elements 3 can be made much easier than when a curved pattern such as a meander shape is used.

The line portion 42 does not overlap with either the scanning line 1 or the signal line 2. In this way, by providing the line portion 42 that does not support the wiring, it is possible to realize the preferable shapes of the first opening AP1 and the second opening AP2 regardless of the shapes of the scanning line 1 and the signal line 2.

The first opening AP1 and the second opening AP2 are included in a region A defined by two adjacent scanning lines 1 and two adjacent signal lines 2. Since the regions A are arranged in a matrix on the entire flexible substrate 100, the first openings AP1 and the second openings AP2 are also dispersed and arranged on the entire flexible substrate 100. As a result, it is possible to impart good stretchability and flexibility to the wide range of the flexible substrate 100.

Further, in the example shown in FIG. 2, the first opening AP1 has a four-fold symmetrical shape. Thereby, for example, the elasticity and the direction dependency of flexibility of the flexible substrate 100 can be reduced as compared with the case where the first opening AP1 has a two-fold symmetrical shape.

Further, in the example shown in FIG. 2, the first opening AP1 includes an interior angle θ2 of 180° or more. With such a shape including a large internal angle, the area of the first opening AP1 can be reduced as compared with the case where the first opening AP1 is formed only by the internal angle less than 180°. As a result, the scanning lines 1, the signal lines 2 and the electrical elements 3 can be formed with high density.

As shown in FIG. 4, an island-shaped inorganic insulating layer 9 is arranged between the electric element 3 and the insulating base material 4. Since the electrical element 3 and the second portion 12 of the scanning line 1 are protected by the inorganic insulating layer 9, the reliability of the flexible substrate 100 can be improved. On the other hand, the inorganic film is more likely to be cracked than the organic film. Therefore, when wiring is formed on the inorganic film, disconnection due to the crack may occur. However, in FIG. 4, the inorganic insulating layer 9 is not provided below the first portion 11 of the scanning line 1 or the signal line 2. Therefore, disconnection of the scanning line 1 and the signal line 2 is unlikely to occur. Further, if the inorganic insulating layer 9 is provided over the entire flexible substrate 100, the stretchability and flexibility of the flexible substrate 100 may be impaired. However, if the inorganic insulating layer 9 is formed in an island shape, Problem does not occur.

In addition, since the first portion 11 and the second portion 12 of the scanning line 1 arranged in different layers are connected by the contact holes CH1 and CH2, the degree of freedom of design in the vicinity of the electric element 3 is improved. .. Since these contact holes CH1 and CH2 are provided above the inorganic insulating layer 9, the reliability at the connection position of the first portion 11 and the second portion 12 is also increased.

As shown in FIG. 2, the electric element 3 is arranged in the line portion 41, and is located at a position apart from the connection point between the line portions 41. As a result, even when the flexible substrate 100 is expanded or contracted or bent, stress is unlikely to be transmitted to the vicinity of the electrical element 3. Therefore, the reliability of the electric element 3 is improved. As described above, if the lengths L1 and L2 from both ends of the line portion 41 to the island-shaped portion 43 are equal, the stress applied to the electrical element 3 can be reduced extremely well.
In addition to the above, various suitable effects can be obtained from this embodiment.

FIG. 5 is a graph showing the characteristic of deformation when the flexible substrate 100 is expanded.
The vertical axis of the graph indicates the tensile force F[N]. The horizontal axis of the graph indicates the extension width X [mm]. When the flexible substrate 100 is extended, it is deformed in the plane in the initial stage. Here, the in-plane deformation means deformation in a direction parallel to the D1-D2 plane defined by the first direction D1 and the second direction D2. The flexible substrate 100 switches from a certain extension or more to an out-of-plane deformation. Here, the out-of-plane deformation corresponds to the case of being deformed in the direction twisted with respect to the D1-D2 plane, that is, the fifth direction D5. In the embodiment described above, by sandwiching the insulating base material 4 by the first low-rigidity layer 81 and the second low-rigidity layer 82, it is possible to increase the extension width that can be deformed out of the plane with respect to the tensile force. Therefore, the expansion rate of the flexible substrate 100 can be increased.

The shape of the opening of the insulating base material 4 and the shape of the region formed by the scanning line 1 and the signal line 2 are not limited to those disclosed in the above embodiment. For example, the insulating base material 4 may not have the line portion 42 that does not overlap with the scanning line 1 or the signal line 2. Further, the insulating base material 4 may include a curved line portion in at least a part thereof in addition to the linear line portion. For example, the insulating base material 4 may have a corrugated shape as shown in FIG. 8 or may have various shapes such as a spiral shape.

[Second Embodiment]
FIG. 6 is a schematic sectional view of the flexible substrate 100 according to the second embodiment. 6 is different from the flexible substrate 100 shown in FIG. 4 in that it includes a first low-rigidity portion 71, a second low-rigidity portion 72, and a third low-rigidity portion 73. The scanning line 1 is located between the first organic insulating layer 5 and the second organic insulating layer 6, and the signal line 2 is in contact with the second organic insulating layer 6.

The first low-rigidity portion 71 is located in the same layer as the insulating base material 4 at a position overlapping the scanning line 1. The first low-rigidity portion 71 has a lower rigidity than the insulating base material 4. The second low-rigidity portion 72 is located in the same layer as the first organic insulating layer 5 at a position overlapping the scanning line 1. The second low-rigidity portion 72 has a lower rigidity than the first organic insulating layer 5. The third low-rigidity portion 73 is located in the same layer as the second organic insulating layer 6 at a position overlapping the scanning line 1. The third low-rigidity portion 73 has a lower rigidity than the second organic insulating layer 6.

The first low-rigidity portion 71, the second low-rigidity portion 72, and the third low-rigidity portion 73 include, for example, polyimide, and overlap in the fifth direction D5. The respective elastic moduli of the first low-rigidity portion 71, the second low-rigidity portion 72, and the third low-rigidity portion 73 are approximately 1 MPa.

For example, it is assumed that the region A is a place where cracks are likely to occur. In the illustrated example, the flexible substrate 100 has the first low-rigidity portion 71, the second low-rigidity portion 72, and the third low-rigidity portion 73 in the region A. Therefore, in the region A, as in the first embodiment, it is possible to increase the extension width that can be deformed out of the plane. Therefore, the elongation up to cracking can be improved. Therefore, the generation of cracks can be suppressed.

The flexible substrate 100 may have at least one of the first low-rigidity portion 71, the second low-rigidity portion 72, and the third low-rigidity portion 73. Any of the layers may be a low-rigidity layer at a position overlapping with a crack occurrence point. Further, by forming the low-rigidity portion not only in the scanning line 1 but also in the position overlapping the signal line 2, disconnection of the signal line 2 can be suppressed. Even if the low-rigidity portion is located away from the wiring that is desired to prevent disconnection, the effect can be obtained.

FIG. 7 is a plan view showing a portion of the flexible substrate 100 where cracks are likely to occur.
The part surrounded by a circle in the figure corresponds to a region A where cracks are likely to occur. The region A is located, for example, in the center of the line portion 41 extending in the first direction D1, the center of the line portion 41 extending in the second direction D2, and the center of the line portion 42 extending in the second direction D2. ing. Further, the region A is located near the corners C2, C3, C6, and C7 of the line portion 42 extending in the third direction D3, and the corner portion of the line portion 42 extending in the fourth direction D4. It is located near C1, C8, C4 and C5. In these areas A, the flexible substrate 100 has the same layer structure as the area A shown in FIG.

FIG. 8 is a plan view showing another shape of the insulating base material 4.
The insulating base material 4 includes a plurality of first portions PT1 extending in the first direction D1 and arranged side by side in the second direction D2 and a plurality of first portions PT1 extending in the second direction D2 and arranged side by side in the first direction D1. And a second portion PT2. The first portion PT1 and the second portion PT2 are each wave-shaped. Further, the insulating base material 4 has an intersection portion IT between the first portion PT1 and the second portion PT2. The scanning line 1 is located on the first portion PT1, extends in the first direction D1, and is arranged in the second direction D2. The signal line 2 is located on the second portion PT2, extends in the second direction D2, and is arranged in the first direction D1. The electrical element 3 is located on the intersection IT. The pattern of the insulating base material 4 shown in FIG. 8 may be applied to the first embodiment.

FIG. 9 is a plan view showing a part of the insulating base material 4 shown in FIG.
The part surrounded by a circle in the figure corresponds to a region A where cracks are likely to occur. Region A is located near the peak P of the waveform. Further, the region A is located between the tops P at a position where the bending is maximized when the flexible substrate 100 extends. In these areas A, the flexible substrate 100 has a low rigidity portion as in the area A shown in FIG. Even with such a pattern of the insulating base material 4, the same effect as that of the pattern shown in FIG. 7 can be obtained.

As described above, according to the present embodiment, it is possible to obtain a flexible substrate that can improve the elongation rate and can suppress the occurrence of cracks.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and the gist of the invention, and are also included in the invention described in the claims and an equivalent range thereof.

100... Flexible substrate, 4... Insulating base material, SF1... First surface, SF2... Second surface,
1... Scan line, 2... Signal line, 81... First low-rigidity layer, 82... Second low-rigidity layer,
91... 1st high rigidity layer, 92... 2nd high rigidity layer, IS1... 1st inner surface, IS2... 2nd inner surface,
OS1... First outer surface, OS2... Second outer surface, 7... Coating layer,
AP1... First opening, AP2... Second opening, 41, 42... Line portion,
PT1... First part, PT2... Second part, 5... First organic insulating layer, 6... Second organic insulating layer,
71... 1st low rigidity part, 72... 2nd low rigidity part, 73... 3rd low rigidity part.

Claims (10)

A flexible insulating substrate having a first surface and a second surface opposite to the first surface;
A plurality of wirings provided on the second surface side of the insulating base material;
A first low-rigidity layer having a first inner surface facing the first surface and a first outer surface opposite to the first inner surface;
A second low-rigidity layer having a second inner surface facing the second surface with the wiring interposed therebetween, and a second outer surface opposite to the second inner surface;
A first high-rigidity layer in contact with the first outer surface and having an elastic modulus higher than that of the first low-rigidity layer;
A second high-rigidity layer that is in contact with the second outer surface and has an elastic modulus higher than that of the second low-rigidity layer;
A flexible substrate in which the elastic modulus of the first low-rigidity layer and the elastic modulus of the second low-rigidity layer are smaller than the elastic modulus of the insulating base material, respectively. Each of the first low-rigidity layer, the second low-rigidity layer, the first high-rigidity layer, and the second high-rigidity layer is formed of an acrylic-based, urethane-based, or epoxy-based organic insulating layer. The flexible substrate according to claim 1. The flexible substrate according to claim 1 or 2, wherein the first inner surface of the first low-rigidity layer contacts the first surface of the insulating base material. Further, a coating layer covering the insulating base material and the wiring is provided,
The flexible substrate according to claim 1, wherein the second inner surface of the second low-rigidity layer contacts the coating layer. The flexible substrate according to any one of claims 1 to 4, wherein the elastic modulus of the first low-rigidity layer and the elastic modulus of the second low-rigidity layer are each smaller than 1 MPa. The insulating base includes a first opening, a second opening having a shape different from that of the first opening, and a line portion between the first opening and the second opening,
The flexible substrate according to claim 1, wherein the line portion does not overlap with the plurality of wirings in a plan view. The insulating base material extends in the first direction and extends in the second direction, and a plurality of corrugated first portions that are arranged side by side in the second direction intersecting the first direction. The flexible substrate according to claim 1, further comprising a plurality of corrugated second portions arranged side by side. A flexible insulating substrate,
A first organic insulating layer covering the insulating base material;
A second organic insulating layer in contact with the first organic insulating layer,
A flexible substrate comprising: a plurality of wirings having a scanning line located between the first organic insulating layer and the second organic insulating layer; and a signal line in contact with the second organic insulating layer,
A first low-rigidity portion located in the same layer as the insulating base material and having a lower rigidity than the insulating base material at a position overlapping the wiring, and the first organic insulating layer located in the same layer as the first organic insulating layer. At least one of a second low-rigidity portion having a lower rigidity and a third low-rigidity portion located in the same layer as the second organic insulating layer and having a lower rigidity than the second organic insulating layer, Flexible board. The flexible substrate according to claim 8, wherein the elastic modulus of the first low-rigidity portion, the elastic modulus of the second low-rigidity portion, and the elastic modulus of the third low-rigidity portion are each about 1 MPa. The flexible substrate according to claim 8 or 9, wherein the first low-rigidity portion, the second low-rigidity portion, and the third low-rigidity portion each include polyimide.

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