JP2020197747A - Flexible substrate - Google Patents

Abstract

To provide a flexible display device in which, when the display device is bent, disconnection of a wire in a bent region is suppressed.SOLUTION: In one embodiment, a display device includes a flexible substrate, a first insulating film disposed on the flexible substrate, a switching element disposed on the first insulating film, a signal wire electrically connected to the switching element, a first organic film disposed on the signal wire, a connection wire disposed on the first organic film, a second organic film disposed on the connection wire, and a pad electrode disposed on the second organic film. The connection wire is held between the first organic film and the second organic film, and is in contact with the first organic film and the second organic film.SELECTED DRAWING: Figure 1

Description

Embodiments of the present invention relate to flexible substrates.

Plane display devices such as liquid crystal panels and organic electroluminescence (EL) panels are used in various fields. In recent years, a flexible display device that can be bent has been developed by using a flexible substrate made of a flexible material as a substrate of the display device.

The display device generally includes a display area for displaying an image and a frame area located around the display area and connected to a drive circuit or an external circuit.

From the viewpoint of performance, design, and the like, such a display device is strongly required to narrow the frame area (narrowing the frame) so that the ratio of the display area becomes larger. As a means for narrowing the frame of the flexible display device, the frame area of the flexible display device is bent, the frame area outside the bent area is arranged on the back surface side of the flexible display device, and the area of the display area is practically expanded. It is done.

JP-A-2015-148728 Japanese Patent No. 5720222

However, in the conventional flexible display device described above, an inorganic insulating film is arranged on the entire surface of the flexible substrate in order to prevent the intrusion of moisture. Inorganic insulating films generally have higher resistance to bending stresses than flexible substrates. Therefore, when the inorganic insulating film is arranged in the bending region of the flexible display device, bending stress is applied to the inorganic insulating film at the time of bending, and cracks may occur in the inorganic insulating film. As a result, the wiring arranged on the inorganic insulating film may be broken due to the occurrence of cracks in the inorganic insulating film.

According to the present embodiment, the insulating substrate, the first insulating film arranged on the insulating substrate, the switching element arranged on the first insulating film, and the switching element are electrically connected to each other. The signal wiring, the first organic film arranged on the signal wiring, the connection wiring electrically connected to the signal wiring, the second organic film arranged on the connection wiring, and the connection wiring. It comprises a pad electrode electrically connected to and has a frame region surrounding a region in which the switching elements are arranged in a matrix, and the frame region is adjacent to a region in which the switching elements are arranged in a matrix. The first insulating film has a first region, a second region adjacent to the first region, and a third region adjacent to the second region, and the first insulating film is the first region and the third region. The first organic film is in contact with the insulating substrate in the second region, and the connection wiring and the second organic film are formed in the first region, the second region, and the third region. Provided in the region, the connecting wiring is located between the first organic film and the second organic film, is in contact with the first organic film and the second organic film, and the connecting wiring is the first organic film. The insulating substrate is connected to the signal wiring in the region and connected to the pad electrode in the third region, and at least a part of the third region is a region in which the switching elements are arranged in a matrix. A flexible substrate that is bent in the second region so as to be located below is provided.

The schematic plan view of the display device which concerns on one Embodiment of this invention. FIG. 2 is a schematic cross-sectional view taken along the line II-II of FIG. 1 according to the first embodiment of the present invention. FIG. 3 is a schematic cross-sectional view taken along the line III-III of FIG. 1 according to the first embodiment of the present invention. The enlarged plan view of the terminal area of the display device which concerns on one Embodiment of this invention. A schematic side view (A) showing a state before bending of the display device according to an embodiment of the present invention, and a schematic side view (B) showing a folded state of the display device. FIG. 2 is a schematic cross-sectional view taken along the line II-II of FIG. 1 according to the second embodiment of the present invention. FIG. 3 is a schematic cross-sectional view taken along the line III-III of FIG. 1 according to the second embodiment of the present invention.

Hereinafter, some embodiments will be described with reference to the drawings. The same or similar configurations shall be designated by the same reference numerals throughout the embodiments, and duplicate description will be omitted. In addition, each figure is a schematic view for promoting understanding of the embodiment, and its shape, dimensions, ratio, etc. may differ from the actual one, but it is merely an example and does not limit the interpretation of the present invention. ..

In the following embodiments, the case of an organic EL (electroluminescence) display device will be described as an example of the display device, but the present invention can be applied to other display devices, for example, a liquid crystal display device. Further, in the following embodiment, the case where the top emission type organic EL display device is used will be described, but it can also be applied to the bottom emission type organic EL display device.

(First Embodiment)
The display device DSP-1 according to the first embodiment will be described in detail with reference to FIGS. 1 to 5. FIG. 1 is a schematic plan view of a display device according to an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view taken along line II-II of FIG. 1 according to the first embodiment of the present invention, and FIG. , A schematic cross-sectional view taken along line III-III of FIG. 1 according to the first embodiment of the present invention, FIG. 4 is an enlarged plan view of a terminal region of the display device according to the first embodiment of the present invention, FIG. A) is a schematic side view showing a state before bending of the display device according to one embodiment of the present invention, and FIG. 5 (B) is a schematic side view showing a folded state of the display device according to one embodiment of the present invention. Is.

In the present embodiment, the direction parallel to the short side of the display device DSP-1 is the first direction X, the direction parallel to the long side of the display device DSP-1 is the second direction Y, and the first direction X and the first direction X. The direction perpendicular to the two directions Y is the third direction Z. Although the first direction X and the second direction Y are orthogonal to each other, they may intersect at an angle other than 90 °.

Further, in the present embodiment, the positive direction of the third direction Z is defined as up or up, and the negative direction of the third direction Z is defined as down or down. Further, in the case of "the second member above the first member" and "the second member below the first member", the second member may be in contact with the first member or may be separated from the first member. It may be located. In the latter case, a third member may be interposed between the first member and the second member. On the other hand, in the case of "the second member above the first member" and "the second member below the first member", the second member is in contact with the first member.

Further, in the present embodiment, viewing the flexible substrate SUB from the positive direction of the third direction Z is defined as a plan view.

As shown in FIG. 1, the display device DSP-1 includes an image display area DA arranged on the flexible substrate SUB and a frame-shaped non-display area FA surrounding the image display area DA. The non-display area FA has a terminal area TA located adjacent to, for example, the right side of the image display area DA. The terminal area TA includes a contact area CA adjacent to the image display area DA, a bending area BA adjacent to the contact area CA, and a pad area PA adjacent to the bending area BA. In the present embodiment, the contact region CA corresponds to the first region, the bending region BA corresponds to the second region, and the pad region PA corresponds to the third region.

The image display area DA is, for example, rectangular, and is composed of a plurality of pixels PX arranged in a matrix of m × n (where m and n are positive integers). The display device DSP-1 has a plurality of signal wirings (not shown) in the image display area DA. These signal wirings include a plurality of scanning lines, a plurality of power supply lines arranged in parallel with these scanning lines, and a plurality of data signal lines arranged orthogonal to the scanning lines (none of which are shown). It is composed of.

The display device DSP-1 includes a flexible substrate SUB as shown in FIGS. 2 and 3. The flexible substrate SUB is an insulating and bendable substrate, and is formed of, for example, a flexible material containing polyimide (PI) or the like as a main component. The flexible substrate SUB has a thickness of, for example, 5 to 30 μm. As the material of the flexible substrate SUB, in addition to polyimide, a material having high heat resistance such as polyamideimide and polyaramid is used. That is, the flexible substrate SUB is exposed to a high temperature process in the film formation of the first insulating film 11, the second insulating film 12, the third insulating film 13, and the like, the formation of the switching element SW, and the like. Therefore, the flexible substrate SUB has high heat resistance. The flexible substrate SUB of the display device DSP-1 of the first embodiment does not necessarily have to have transparency, and the flexible substrate SUB may be colored. The flexible substrate SUB can be formed by applying a material such as polyimide on a temporary substrate such as a glass substrate. The temporary substrate used in the step of forming the flexible substrate SUB is peeled off from the flexible substrate SUB after mounting the drive circuit and the external circuit on the display device DSP-1.

The first insulating film 11 is arranged on the flexible substrate SUB. The first insulating film 11 prevents ionic impurities, water, and the like from entering the switchon element described later from the flexible substrate SUB. Such a first insulating film 11 is formed of an inorganic material such as silicon nitride (SiN), silicon oxide film (SiO), or silicon oxynitride (SiON), and is composed of a single layer or a laminate. There is.

In the image display area DA, the plurality of switching elements SW1, SW2, and SW3 are provided on the first insulating film 11. Each of these switching elements SW1, SW2, and SW3 corresponds to one pixel PX. For example, the switching element SW1 corresponds to a red pixel, the switching element SW2 corresponds to a green pixel, and the switching element SW1 corresponds to a blue pixel. These switching elements SW1, SW2, and SW3 are, for example, thin film transistors (TFTs) each including a semiconductor layer SC. Since the switching elements SW1, SW2, and SW3 all have the same structure, the structure thereof will be specifically described here by focusing on the switching element SW1.

The switching element SW1 is configured as a top gate type, but may be a bottom gate type. The switching element SW1 includes, for example, a semiconductor layer SC made of amorphous silicon. The semiconductor layer SC includes a channel region, a source region, and a drain region. The semiconductor layer SC is covered with the second insulating film 12. The second insulating film 12 is also arranged on the first insulating film 11. The second insulating film 12 is made of an inorganic material such as ethyl orthotetrasilicate (TEOS).

The gate electrode WG of the switching element SW1 is arranged on the second insulating film 12 and is located directly above the channel region of the semiconductor layer SC. The gate electrode WG is covered with a third insulating film 13. The third insulating film 13 is also arranged on the second insulating film 12. The third insulating film 13 is made of an inorganic material such as ethyl orthotetrasilicate (TEOS). The source electrode WS and drain electrode WD of the switching element SW1 are located on the third insulating film 13 and are connected to the source region and drain region of the semiconductor layer SC via a contact hole formed in the third insulating film 13. ing.

The signal line SGL is located on the third insulating film 13 and is electrically connected to the switching element SW1. The signal line SGL extends to the contact area CA adjacent to the image display area DA. The signal line SGL is formed of, for example, MoW or the like.

The source electrode WS, the drain electrode WD, and the signal wiring SGL are covered with the first organic film 14. The first organic film 14 is also arranged on the third insulating film 13. The first organic film 14 is formed of an organic material having a high cushioning property, for example, a hard resin coat (HRC) or the like. The reflective layer 15 is arranged on the first organic film 14. The reflective layer 15 is made of, for example, aluminum or silver.

The first electrode PE is arranged on the reflective layer 15 and is electrically connected to the drain electrodes WD of each of the switching elements SW1, SW2, and SW3 via a contact hole formed in the first organic film 14. The first electrode PE is formed of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO).

The ribs 16 are arranged, for example, in a grid pattern or a stripe pattern in order to electrically insulate the first electrode PEs on the first organic film 14 in which the image display region DA is located.

As shown in FIG. 2, the first connection wiring LL1 is located on the first organic film 14 in the terminal region TA, and the third insulating film 13 passes through the first contact hole CH1 formed in the first organic film 14. It is electrically connected to the signal wiring SGL above. The first connection wiring LL1 is formed of, for example, MoW / Al or the like.

As shown in FIG. 3, the second connection wiring LL2 is located on the first organic film 14 in the terminal region TA, and the third insulating film 13 passes through the second contact hole CH2 formed in the first organic film 14. It is electrically connected to the other signal wiring SGL above. The second connection wiring LL2 is formed of, for example, MoW / Al or the like.

The first and second connection wirings LL1 and LL2 are covered with a second organic film 17. The second organic film 17 is also arranged on the first organic film 14. The second organic film 17 is formed of an organic material having a high cushioning property, for example, a hard resin coat (HRC), a photosensitive transparent acrylic resin, a photosensitive transparent polyimide, or the like. The second organic film 17 is made of the same material as the rib 16 and can be formed by the same process as the rib 16.

The first pad electrode PD1 is arranged on the second organic film 17 of the pad region PA as shown in FIGS. 2 and 4, and is first connected via the third contact hole CH3 formed in the second organic film 17. It is electrically connected to the wiring LL1.

The second pad electrode PD2 is arranged on the second organic film 17 of the pad region PA as shown in FIGS. 3 and 4, and is second-connected via the fourth contact hole CH4 formed in the second organic film 17. It is electrically connected to the wiring LL2.

The first and second pad electrodes PD1 and PD2 are electrically connected to a drive circuit and an external circuit (not shown), and can take in a power supply voltage and various signals from the drive circuit and the external circuit.

A plurality of the first and second contact holes CH1 and CH2 are alternately arranged in the first direction X as shown in FIG. That is, the first and second contact holes CH1 and CH2 are arranged in a staggered pattern in a plan view. As shown in FIG. 4, the third and fourth contact holes CH3 and CH4 are alternately arranged in a plurality of arrangements in the first direction X, that is, arranged in a staggered manner in a plan view. When the first and second contact holes CH1, CH2 or the third and fourth contact holes CH3 and CH4 are linearly arranged, the first and second contact holes CH1, CH2 or the third and fourth contact holes CH3 , There is a limit to increasing the arrangement density of the connection wiring and the pad electrode depending on the area area allocated to CH4 and the like. However, by arranging the first and second contact holes CH1, CH2, and / or the third and fourth contact holes in a staggered manner, the first contact hole CH1 and the second contact hole CH2 become the third contact again. Since the hole CH3 and the fourth contact hole CH4 are arranged so as to be offset from each other in the first direction X, the first and second connection wirings LL1, LL2, the first to fourth contact holes CH1, CH2, CH3, CH4, and the like. The pad electrode PD can be arranged at a higher density.

As shown in FIG. 5A, in the display device DSP-1 described above, in the terminal area TA, the contact area CA, the bending area BA, and the pad area PA are adjacent to each other in the second direction Y in the state before bending. Have been placed. In the folded state as shown in FIG. 5B, the bent region BA is bent so that the pad region PA is located below the image display region DA of the flexible substrate SUB.

The display device DSP-1 according to the first embodiment employs an active matrix type display device, and although not shown in the figure, an organic light emitting layer, a second electrode, and the like are placed on the first electrode PE. A sealing layer, an opposing substrate, etc. are arranged.

According to such a first embodiment, in the terminal area TA as shown in FIG. 5B, the bent area BA is set so that the pad area PA is located below the image display area DA of the flexible substrate SUB. By bending, the width of the terminal region TA can be narrowed, and the area of the image display region DA can be practically widened.

Further, when the bending region BA is bent from the state shown in FIG. 5A to the state shown in FIG. 5B, bending stress is applied to the first to third insulating films 11 to 13 located in the bending region BA. May be added and cracks may occur. Therefore, cracks may propagate to the first and second connection wirings LL1 and LL2 located on the first to third insulating films 11 to 13 located in the bent region BA.

However, in the display device DSP-1 according to the first embodiment, the first and second connection wirings LL1 and LL2 do not come into direct contact with the first to third insulating films 11 to 13 and are on the first organic film 14. It is provided in. Further, the first and second connection wirings LL1 and LL2 are covered with the second organic film 17. That is, the first and second connection wirings LL1 and LL2 are sandwiched between the first organic film 14 and the second organic film 17. As a result, even if cracks occur in the first to third insulating films 11 to 13 located in the bent region BA of the display device DSP-1, the generation of cracks can be absorbed by the first organic film 14. Further, since the first and second connection wirings LL1 and LL2 are sandwiched between the first and second organic films 14 and 17, the propagation of cracks can be suppressed. Therefore, disconnection of the first and second connection wirings LL1 and LL2 can be suppressed, and a highly reliable display device DSP-1 can be obtained.

(Second Embodiment)
The display device DSP-2 according to the second embodiment will be described in detail with reference to FIGS. 6 and 7. FIG. 6 is a schematic cross-sectional view taken along line II-II of FIG. 1 according to the second embodiment, and FIG. 7 is a schematic cross-sectional view taken along line III-III of FIG. 1 according to the second embodiment. The cross-sectional structure is different from that of FIGS. 2 and 3 of the first embodiment. The same members as those in FIGS. 1 to 5 described in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

In the display device DSP-2 according to the second embodiment, in the terminal region TA, the first insulating film 11, the second insulating film 12, and the third insulating film 13 are arranged in the contact region CA and the pad region PA, and the bending region BA. Is not placed in. That is, the first to third insulating films 11 to 13 do not exist on the flexible substrate SUB located in the bending region BA.

The signal line SGL is located on the third insulating layer 13 and is electrically connected to the switching element SW1. The signal line SGL extends to the contact area CA adjacent to the image display area DA. The signal line SGL is formed of, for example, MoW or the like. The source electrode WS, the drain electrode WD, and the signal wiring SGL are covered with the first organic film 21. The first organic film 21 is also arranged on the third insulating film 13. Further, it is also arranged on the flexible substrate SUB. The first organic film 21 is formed of an organic material having a high cushioning property, for example, a hard resin coat (HRC) or the like.

As shown in FIG. 6, the first connection wiring LL1 is arranged on the first organic film 21 in the terminal region TA, and the third insulating film 13 is provided through the first contact hole CH1 formed in the first organic film 21. It is electrically connected to the signal wiring SGL above. As shown in FIG. 7, the second connection wiring LL2 is arranged on the first organic film 21 in the terminal region TA, and the third insulating film 13 is provided through the second contact hole CH2 formed in the first organic film 21. It is electrically connected to the other signal wiring SGL above.

The first and second connection wirings LL1 and LL2 are covered with a second organic film 17. The second organic film 17 is also arranged on the first organic film 21. The second organic film 17 is formed of an organic material having a high cushioning property, for example, a hard resin coat (HRC), a photosensitive transparent acrylic resin, a photosensitive transparent polyimide, or the like.

In such a display device DSP-2, in the same state as in FIG. 5A described above, in the state before bending, the contact area CA, the bending area BA, and the pad area PA are adjacent to the second direction Y in the terminal area TA. It is arranged. In the display device DSP-2 according to the second embodiment, the bent region BA is bent so that the pad region PA is located below the image display region DA of the flexible substrate SUB, as in FIG. 5B described above. Has been done.

According to such a second embodiment, as shown in FIG. 5 (B), in the terminal region TA, the bent region BA is located below the image display region DA of the flexible substrate SUB. By bending the above, the width of the terminal region TA can be narrowed, and the area of the image display region DA can be practically widened.

Further, according to the second embodiment, as shown in FIGS. 6 and 7, the first to third insulating films 11 to 13 do not exist in the bent region BA. That is, according to the second embodiment, the first organic film 21, the first and second connection wirings LL1, LL2, and the second organic film 17 are arranged in the bent region BA. As a result, even if bending stress is applied to the bending region BA, the first to third insulating films 11 to 13 in which cracks are likely to occur do not exist as in the first embodiment described above, so that the first and second insulating films 11 to 13 do not exist. It is possible to suppress disconnection of the connection wirings LL1 and LL2. Further, since the first and second connection wirings LL1 and LL2 are sandwiched between the first and second organic films 21 and 17, it is possible to further suppress the disconnection of the first and second connection wirings LL1 and LL2. it can. Therefore, a highly reliable display device DSP-2 can be obtained.

Although some embodiments 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 embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.
The inventions described in the original claims of the original application are added below.
[1] Flexible substrate and
The first insulating film arranged on the flexible substrate and
The switching element arranged on the first insulating film and
The signal wiring electrically connected to the switching element and
The first organic film arranged on the signal wiring and
With the connection wiring arranged on the first organic film,
The second organic film arranged on the connection wiring and
It has a pad electrode arranged on the second organic film and has.
A display device in which the connection wiring is sandwiched between the first organic film and the second organic film and is in contact with the first organic film and the second organic film.
[2] The display device according to [1], wherein the connection wiring is not in contact with the first insulating film.
[3] The display device according to [1] or [2], wherein the signal wiring and the connection wiring are electrically connected via a first contact hole formed in the first organic film.
[4] The display device according to [1] or [2], wherein the connection wiring and the pad electrode are electrically connected via a second contact hole formed in the second organic film.
[5] The display device according to [3] or [4], wherein a plurality of the first contact hole and at least one of the second contact holes are arranged in a staggered pattern in a plan view.
[6] The flexible substrate is further added.
It has an image display area having a plurality of pixels and a non-display area surrounding the image display area.
The non-display region includes a first region in which the first contact hole is formed, a second region in which the connection wiring is arranged adjacent to the first region, and a pad electrode adjacent to the second region. The display device according to any one of [1] to [5], which has an arranged third region.
[7] The display device according to [6], wherein the flexible substrate is bent in the second region so that at least a part of the third region is located below the image display region.
[8] The display device according to [6] or [7], wherein the first insulating film is not arranged in the second region.
[9] The display device according to any one of [1] to [8], wherein the flexible substrate is made of polyimide.

DSP-1, DSP-2 ... Display device SUB ... Flexible substrate DA ... Image display area FA ... Frame area TA ... Terminal area CA ... Contact area (1st area) PA ... Pad area (3rd area) BA ... Bending area (Bending area) 2nd region) LL1 ... 1st connection wiring LL2 ... 2nd connection wiring PD ... Pad electrodes SW1, SW2, SW3 ... Switching element 11 ... 1st insulating film 12 ... 2nd insulating film 13 ... 3rd insulating film 14, 21 ... 1st organic film 15 ... Reflective layer 16 ... Ribs 17 ... 2nd organic film

Claims (8)

Insulating board and
The first insulating film arranged on the insulating substrate and
The switching element arranged on the first insulating film and
The signal wiring electrically connected to the switching element and
The first organic film arranged on the signal wiring and
The connection wiring that electrically connects to the signal wiring,
The second organic film arranged on the connection wiring and
A pad electrode that electrically connects to the connection wiring is provided.
The switching element has a frame region surrounding a region arranged in a matrix, and has a frame region.
The frame region includes a first region adjacent to a region in which the switching element is arranged in a matrix, a second region adjacent to the first region, and a third region adjacent to the second region. And
The first insulating film is provided in the first region and the third region.
The first organic film is in contact with the insulating substrate in the second region.
The connection wiring and the second organic film are provided in the first region, the second region, and the third region.
The connection wiring is located between the first organic film and the second organic film, and is in contact with the first organic film and the second organic film.
The connection wiring is connected to the signal wiring in the first region and is connected to the pad electrode in the third region.
The insulating substrate is a flexible substrate in which at least a part of the third region is bent in the second region so that the switching elements are located below the region in which the switching elements are arranged in a matrix. The flexible substrate according to claim 1, wherein the connection wiring is not in contact with the first insulating film. The first organic film has a first contact hole in the first region.
The flexible substrate according to claim 1 or 2, wherein the signal wiring and the connection wiring are connected via the first contact hole. The second organic film has a second contact hole in the third region.
The flexible substrate according to any one of claims 1 to 3, wherein the connection wiring and the pad electrode are connected via the second contact hole. The flexible substrate according to claim 3 or 4, wherein the second organic film covers the first contact hole in the first region. The flexible substrate according to any one of claims 1 to 4, wherein the first insulating film is not provided in the second region. The first organic film has a first thickness in the first region and the third region, and a second thickness in the second region.
The flexible substrate according to any one of claims 1 to 6, wherein the second thickness is larger than the first thickness. The signal wiring is located in a region where the switching elements are arranged in a matrix, and is provided between the first insulating film and the first organic film, according to any one of claims 1 to 7. The flexible substrate described in.

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