CN113471223B - Display substrate and display device - Google Patents

Abstract

The present application provides a display substrate and a display device, the display substrate comprising: a first flexible substrate; a plurality of second flexible substrates spaced apart and arranged above the first flexible substrate; wherein each of the second flexible substrates comprises an island region and a pad region arranged around the island region, the thickness of at least a portion of the second flexible substrate in the pad region gradually decreases in a direction away from the island region; a display structure at least partially located above the island region; a pad at least partially located above the pad region; a connection line located above the first flexible substrate and arranged between two adjacent second flexible substrates. The thickness of the substrate is thick at the location of the island region (display structure), thin at the location of the connection line (bridge region), and the thickness of at least a portion of the second flexible substrate in the pad region gradually decreases in a direction away from the island region, so that the elastic modulus from the location of the island region to the location of the connection line (bridge region) smoothly transitions, thereby avoiding damage to the connection line.

Description

Display substrate and display device

Technical Field

The present application relates to the field of display technology, and in particular to a display substrate and a display device.

Background technique

Organic Light-Emitting Diode (OLED) display is a display and lighting technology developed in recent years. It has the advantages of high response, high contrast, and flexibility, and is considered to have broad application prospects. In terms of flexible display, the deformable and bendable characteristics of OLED display devices further reflect the advantages of OLED display itself.

As one of the important development directions of flexible display products, stretchable display devices have received more and more attention. In particular, a stretchable display device that is manufactured to be able to stretch/contract in a specific direction and become various shapes by forming display units, wires, etc. on a flexible substrate made of flexible materials such as plastic has attracted much attention as the next generation of display devices. At present, in stretchable display substrates, the problem of wiring breakage caused by tensile stress is relatively serious, which can easily lead to failure of the display substrate.

Summary of the invention

In view of the above problems, the present application provides a display substrate and a display device, which solve the technical problem in the prior art that the wiring of a stretchable display substrate is damaged, resulting in failure of the display substrate.

In a first aspect, the present application provides a display substrate, comprising:

a first flexible substrate;

A plurality of second flexible substrates spaced apart above the first flexible substrate; wherein each of the second flexible substrates comprises an island region and a pad region disposed around the island region, and a thickness of at least a portion of the second flexible substrate located in the pad region gradually decreases in a direction away from the island region;

a display structure at least partially located above the island;

a pad at least partially located above the pad region;

A connecting line located above the first flexible substrate and arranged between two adjacent second flexible substrates; wherein the connecting line is electrically connected to the pads on the two adjacent second flexible substrates to achieve electrical connection of the display structures on the two adjacent second flexible substrates.

In some embodiments, in the above display substrate, an orthographic projection of the display structure on the first flexible substrate partially overlaps with an orthographic projection of the pad on the first flexible substrate.

In some embodiments, the display substrate further comprises:

A first buffer layer is disposed between the first flexible substrate and the second flexible substrate.

In some embodiments, in the above display substrate, the first buffer layer extends below the connecting line.

In some embodiments, the display substrate further comprises:

a second buffer layer located between the display structure and the second flexible substrate;

The second buffer layer extends to below the pad, and the thickness of at least a portion of the second buffer layer below the pad gradually decreases in a direction away from the display structure.

In some embodiments, in the above-mentioned display substrate, the display structure includes a driving structure layer located above the second flexible substrate, and a light emitting structure layer disposed above the driving structure layer;

The driving structure layer includes an active layer, a gate insulating layer, a gate layer, an interlayer insulating layer and a source-drain metal layer which are sequentially stacked on the second flexible substrate.

In some embodiments, in the above display substrate, the material of the pad is the same as the material of the gate layer or the source and drain metal layer.

In some embodiments, in the above display substrate, the gate insulating layer and/or the interlayer insulating layer extends above the pad area;

Wherein, the thickness of at least a portion of the gate insulation layer and/or the interlayer insulation layer located above the pad region gradually decreases in a direction away from the island region.

In some embodiments, the display substrate further comprises:

a flexible backing film disposed below the first flexible substrate;

Wherein, the elastic modulus of the flexible back film is smaller than the elastic modulus of the first flexible substrate and the second flexible substrate.

In a second aspect, the present application provides a display device, comprising a display substrate as described in any one of the first aspects.

By adopting the above technical solution, at least the following technical effects can be achieved:

The present application provides a display substrate and a display device, the display substrate comprising: a first flexible substrate; a plurality of second flexible substrates arranged at intervals above the first flexible substrate; wherein each of the second flexible substrates comprises an island region and a pad region arranged around the island region, and the thickness of at least part of the second flexible substrate in the pad region gradually decreases in a direction away from the island region; a display structure at least partially located above the island region; a pad at least partially located above the pad region; and a connection line located above the first flexible substrate and arranged between two adjacent second flexible substrates. The thickness of the flexible substrate is thick at the location of the island region (display structure), and thin at the location of the connection line (bridge region), and the thickness of at least part of the second flexible substrate in the pad region gradually decreases in a direction away from the island region, so that the elastic modulus from the location of the island region to the location of the connection line (bridge region) is smoothly transitioned, avoiding stress concentration caused by the display substrate when stretched, causing damage to the connection line (routing), greatly improving the stretching ability of the display substrate, and improving the product yield and reliability of the stretchable display substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present application but do not constitute a limitation to the present application. In the accompanying drawings:

FIG1 is a schematic front plan view of a display substrate shown in an exemplary embodiment of the present application;

Fig. 2 is a schematic diagram of the cross-sectional structure along the tangent line A-A' of Fig. 1;

FIG3 is a schematic cross-sectional structure diagram of another display substrate according to an exemplary embodiment of the present application;

FIG4 is a schematic cross-sectional structure diagram of another display substrate according to an exemplary embodiment of the present application;

FIG5 is a schematic cross-sectional structure diagram of another display substrate according to an exemplary embodiment of the present application;

FIG6 is a schematic cross-sectional structure diagram of another display substrate according to an exemplary embodiment of the present application;

FIG7 is a schematic cross-sectional structure diagram of another display substrate according to an exemplary embodiment of the present application;

FIG8 is a schematic flow chart of a method for preparing a display substrate according to an exemplary embodiment of the present application;

9 is a schematic cross-sectional view of a first intermediate structure formed in relevant steps of a method for preparing a display substrate according to an exemplary embodiment of the present application;

10 is a schematic cross-sectional view of a second intermediate structure formed in relevant steps of a method for preparing a display substrate according to an exemplary embodiment of the present application;

11 is a schematic cross-sectional view of a third intermediate structure formed in relevant steps of a method for preparing a display substrate according to an exemplary embodiment of the present application;

The accompanying drawings are marked as follows:

11-first flexible substrate; 12-first buffer layer; 13-second flexible substrate; 131-island area; 132-pad area; 14-second buffer layer; 15-display structure; 1501-active layer; 1502-gate insulating layer; 1503-gate layer; 1504-gate wiring; 1505-interlayer insulating layer; 1506-source and drain metal layer; 1507-organic flat layer; 1508-anode layer; 1509-pixel definition layer; 1510-light-emitting layer; 1511-cathode layer; 1512-encapsulation layer; 16-pad; 17-connecting line; 18-flexible back film; 19-glass substrate.

In the drawings, the same reference numerals are used for the same components, and the drawings are not drawn to scale.

Detailed ways

The following will describe the implementation methods of the present application in detail in conjunction with the accompanying drawings and embodiments, so that the implementation process of how the present application applies technical means to solve technical problems and achieve corresponding technical effects can be fully understood and implemented accordingly. The embodiments of the present application and the various features in the embodiments can be combined with each other without conflict, and the technical solutions formed are within the scope of protection of the present application. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. The same reference numerals throughout represent the same elements.

It should be understood that although the terms "first", "second", "third", etc. can be used to describe various elements, components, regions, layers and/or parts, these elements, components, regions, layers and/or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer or part discussed below can be represented as a second element, component, region, layer or part.

It will be appreciated that spatially relative terms, such as "above", "above", "below", "under", etc., may be used herein for convenience of description to describe the relationship of one element or feature to other elements or features shown in the figures. It will be appreciated that the spatially relative terms are intended to encompass different orientations of the device in use and operation in addition to the orientation shown in the figures. For example, if the device in the figures is turned over, then elements or features described as "below other elements" would be oriented "above" the other elements or features. Thus, the exemplary terms "below" and "under" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatial descriptors used herein interpreted accordingly.

The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present application. When used herein, the singular forms "one", "an" and "said/the" are also intended to include plural forms, unless the context clearly indicates another way. It should also be understood that the terms "consisting of" and/or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and/or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and/or groups. When used herein, the term "and/or" includes any and all combinations of the relevant listed items.

Embodiments of the present application are described herein with reference to cross-sectional views that are schematic diagrams of ideal embodiments (and intermediate structures) of the present application. Thus, variations from the shapes shown due to, for example, manufacturing techniques and/or tolerances can be expected. Therefore, embodiments of the present application should not be limited to the specific shapes of the regions shown herein, but include deviations in shapes due to, for example, manufacturing.

In order to thoroughly understand the present application, detailed structures and steps will be presented in the following description to illustrate the technical solution proposed by the present application. The preferred embodiments of the present application are described in detail below, but in addition to these detailed descriptions, the present application may also have other implementation methods.

In the stretchable display substrate, in order to ensure that the island area is not damaged during the process and at the same time ensure that it can be stretched or bent, a flexible substrate with a small elastic modulus (small hardness) can be used. However, due to the presence of driving components and light-emitting devices (OLED, micro LED, etc.), the film structure of the island area is complex, and its hardness is much greater than that of the bridge area (the connecting line area between adjacent island areas). This structure will cause obvious changes in the soft and hard interface from the island area to the bridge area, resulting in a sudden change in the elastic modulus. When the display substrate is stretched and deformed, it will still cause damage to the wiring, resulting in failure of the display substrate.

The embodiment of the present application provides a display substrate, which is a stretchable display substrate. Referring to FIG. 1 and FIG. 2 , the display substrate includes a first flexible substrate 11 , a second flexible substrate 13 , a display structure 15 , a pad 16 and a connection line 17 .

A plurality of second flexible substrates 13 are spaced apart above the first flexible substrate 11; wherein each second flexible substrate 13 includes an island area 131 and a pad area 132 arranged around the island area 131, and the thickness of at least a portion of the second flexible substrate 13 in the pad area 132 gradually decreases in a direction away from the island area 131.

The display structure 15 is at least partially located above the island area 131 .

The pad 16 is at least partially located above the pad region 132 .

The connection line 17 is located above the first flexible substrate 11 and disposed between two adjacent second flexible substrates 13 , wherein the connection line 17 is electrically connected to the pads 16 on the two adjacent second flexible substrates 13 to achieve electrical connection of the display structures 15 on the two adjacent second flexible substrates 13 .

In some embodiments, the thickness of the entire second flexible substrate 13 in the pad region 132 gradually decreases in a direction away from the island region 131 (the second flexible substrate 13 gradually decreases from a maximum thickness to 0).

In some embodiments, the thickness of at least a portion of the second flexible substrate 13 in the pad area 132 gradually decreases from the maximum thickness value to 0 in the direction away from the island area 131. That is, at the pad area 132, the total thickness of the flexible substrate of the display substrate gradually transitions from the total thickness of the first flexible substrate 11 and the second flexible substrate 13 to the thickness of the first flexible substrate 11 (i.e., transitions from the thickness of two layers of substrates to the thickness of one layer of substrate).

The total thickness of the flexible substrate at the island area 131 is the total thickness of the first flexible substrate 11 and the second flexible substrate 13, the total thickness of the flexible substrate in the bridge area (the area where the connecting line 17 is located) is the thickness of the first flexible substrate 11, and the gradual transition of the total thickness of the flexible substrate at the pad area 132 reduces the ratio of the substrate thickness change to the width of the wiring (connecting line 17) (depth-to-width ratio), which can achieve the purpose of fine wiring patterning process and reduce the process difficulty.

In some embodiments, the first flexible substrate 11 has a thickness of 3-20 μm.

In some embodiments, the second flexible substrate 13 has a thickness of 3-20 μm.

The first flexible substrate 11 and the second flexible substrate 13 are the basis for the display substrate to be stretchable.

In some embodiments, the material of the first flexible substrate 11 and the second flexible substrate 13 may be the same.

In some embodiments, the materials of the first flexible substrate 11 and the second flexible substrate 13 may both include polyimide (PI).

As shown in FIG. 3 , in some embodiments, the display substrate further includes: a first buffer layer 12 disposed between the first flexible substrate 11 and the second flexible substrate 13 .

Furthermore, as shown in FIG4 , the first buffer layer 12 may also extend below the connection line 17 . That is, the film structure at the location of the connection line 17 (bridge area) is a combination of the first flexible substrate 11 , the first buffer layer 12 and the connection line 17 .

The first buffer layer 12 may also function as an electrostatic blocking layer, an impurity ion blocking layer, and a heat insulating layer.

In some embodiments, the material of the first buffer layer 12 includes SiNx and/or SiOx.

As shown in FIG. 5 , in some embodiments, the display substrate further includes: a second buffer layer 14 located between the display structure 15 and the second flexible substrate 13 .

Furthermore, the second buffer layer 14 extends to below the pad 16 , and the thickness of at least a portion of the second buffer layer 14 below the pad 16 gradually decreases in a direction away from the display structure 15 .

That is to say, at the pad area 132 , not only the thickness of the second flexible substrate 13 gradually decreases, but also the thickness of inorganic layers such as the second buffer layer 14 can gradually decrease, so as to further achieve the transition of the elastic modulus on the substrate and further reduce the stress concentration during the stretching process.

In some embodiments, the material of the second buffer layer 14 includes SiNx and/or SiOx.

The second buffer layer 14 may also function as an electrostatic blocking layer, an impurity ion blocking layer, and a heat insulating layer.

In some embodiments, the orthographic projection of the display structure 15 on the first flexible substrate 11 partially overlaps with the orthographic projection of the pad 16 on the first flexible substrate 11 .

In other words, the pad 16 is not completely covered by the display structure 15. The pad 16 is a connection point structure protruding from the display structure 15. The connecting line 17 can directly contact the pad 16 without punching. In addition, the second flexible substrate 13 with a gradient thickness underneath can further improve the risk of stress concentration damage during stretching due to the difference in soft and hard interfaces (sudden change in elastic modulus).

In some embodiments, the display structure 15 includes a driving structure layer (not marked in the figure) located above the second flexible substrate 13, and a light-emitting structure layer (not marked in the figure) arranged above the driving structure layer; wherein the driving structure layer includes an active layer 1501, a gate insulating layer 1502, a gate layer 1503, an interlayer insulating layer 1505 and a source-drain metal layer 1506 stacked in sequence above the second flexible substrate 13.

In some embodiments, the active layer 1501 may be a semiconductor layer such as low-temperature polysilicon, single crystal silicon, or indium gallium zinc oxide, and the active layer 1501 is disposed above the second flexible substrate 13 .

In some embodiments, the gate insulating layer 1502 may be a SiOx layer, and the gate insulating layer 1502 is located above the active layer 1501 and covers the active layer 1501 .

In some embodiments, the gate layer 1503 is located above the gate insulating layer 1502 and at a position corresponding to the active layer 1501 (a position corresponding to the thin film transistor).

In some embodiments, the interlayer insulating layer 1505 is located above the gate layer 1503 , and the material thereof may include SiOx and/or SiNx.

The source-drain metal layer 1506 contacts the active layer 1501 through a contact hole penetrating the interlayer insulating layer 1505 and the gate insulating layer 1502. The source-drain metal layer 1506 is used to lead out the source and drain of the thin film transistor.

The active layer 1501, the gate insulating layer 1502, the gate layer 1503 and the source and drain metal layer 1506 constitute a thin film transistor.

In some embodiments, the gate insulation layer 1502 and/or the interlayer insulation layer 1505 extend above the pad area 132; wherein the thickness of at least a portion of the gate insulation layer 1502 and/or the interlayer insulation layer 1505 located above the pad area 132 gradually decreases in a direction away from the island area 131.

However, it should be noted that the inorganic layer (gate insulation layer 1502 and/or interlayer insulation layer 1505) extending above the pad area 132 does not completely cover the pad 16 to form a connection point structure of the protruding display structure 15, so that the connecting line 17 can directly contact the pad 16 without punching. In addition, the second flexible substrate 13 with a gradient thickness underneath can further improve the risk of stress concentration damage during stretching due to the difference in soft and hard interfaces (sudden change in elastic modulus).

In some embodiments, the driving structure layer further includes a capacitor unit (not shown in the figure), a gate wiring 1504 and a source-drain wiring (not shown in the figure).

In some embodiments, an organic planarization layer 1507 is further disposed between the light emitting structure layer and the driving structure layer to planarize the light emitting structure layer and reduce display defects.

In some embodiments, the light emitting structure layer includes a pixel definition layer 1509, and an anode layer 1508, a light emitting layer 1510, and a cathode layer 1511 which are stacked in sequence.

The pixel definition layer 1509 is used to form a pixel opening, and the pixel opening exposes the anode layer 1508 .

The anode layer 1508 contacts the source and drain metal layer 1506 of the driving structure layer through the anode contact hole penetrating the organic planar layer 1507 to achieve electrical connection.

The light-emitting layer 1510 may be an organic light-emitting layer 1510 , including an electron injection layer, an electron transport layer, an organic light-emitting material layer, a hole injection layer and a hole transport layer.

In some embodiments, the display structure 15 further includes an encapsulation layer 1512, which covers the light emitting structure layer to prevent external water vapor, oxygen, etc. from entering the light emitting structure layer to cause poor display. The encapsulation layer 1512 can be an inorganic material containing silicon (SiOx, SiNx or SiON) and/or an organic material.

In some embodiments, the encapsulation layer 1512 includes a first inorganic film layer, an organic film layer on the first inorganic film layer, and a second inorganic film layer on the organic film layer. The organic film layer is formed by inkjet printing and has good fluidity.

In some embodiments, the material of the pad 16 is the same as that of the gate layer 1503 or the source-drain metal layer 1506 in the display structure 15 .

The material of the pad 16 can be determined according to the electrode to be led out. For example, when the pad 16 leads out the gate of the thin film transistor (i.e., the pad 16 is electrically connected to the gate wiring), the material of the pad 16 can be the same as the material of the gate layer 1503. As shown in Figures 2 to 5; when the pad 16 leads out the source and drain of the thin film transistor (i.e., the pad 16 is electrically connected to the source and drain wiring), the material of the pad 16 can be the same as the material of the source and drain metal layer 1506, as shown in Figure 6.

When the material of the pad 16 is the same as that of the source and drain metal layer 1506, the pad 16 extends above the interlayer insulating layer 1505 of the display structure 15, and at this time, the etching of each film layer at the pad area 132 and the film layer at the connecting line 17 (bridge area) can be carried out synchronously with the etching of the contact holes corresponding to the source and drain metal layer 1506 of the display structure 15, and the bending area of the display substrate (the area bent after FPC binding) can also be etched at the same time.

In some embodiments, the material of the connection line 17 may be the same as that of the source-drain metal layer 1506 .

In some embodiments, the material of the connection line 17 can be other metal materials.

In some embodiments, the positive projection of the connecting line 17 on the first flexible substrate 11 is curved or even wavy, so that when the above-mentioned display substrate is stretched, the connecting line 17 has a certain stress buffer and stronger stretching performance, further improving the stretching ability of the display substrate.

As shown in FIG. 7 , in some embodiments, the display substrate further includes a flexible back film 18 located below the first flexible substrate 11 ; wherein the elastic modulus of the flexible back film 18 is smaller than the elastic modulus of the first flexible substrate 11 and the second flexible substrate 13 .

That is to say, the flexibility of the flexible back film 18 is better than that of the first flexible substrate 11 and the second flexible substrate 13, which can further improve the stretchability of the above-mentioned display substrate.

Furthermore, the material of the flexible back film 18 may be polydimethylsiloxane (PDMS) having a smaller elastic modulus (lower hardness) than polyimide (PI).

In the above-mentioned display substrate, the substrate thickness is thick at the island area 131 (display structure 15) and thin at the connecting line 17 (bridge area), and the thickness of at least part of the second flexible substrate 13 in the pad area 132 gradually decreases in the direction away from the island area 131, so that the elastic modulus from the island area 131 to the connecting line 17 (bridge area) transitions smoothly, avoiding stress concentration caused by stretching of the display substrate and causing damage to the connecting line 17 (routing), greatly improving the stretching ability of the display substrate, and improving the product yield and reliability of the stretchable display substrate.

The present application also provides a method for preparing a display substrate, wherein the "patterning" mentioned below includes processes such as coating photoresist, mask exposure, development, etching and stripping photoresist, etc. "Deposition" can be selected from any one or more of sputtering, evaporation and chemical vapor deposition, and etching can be selected from any one or more of dry etching and wet etching.

Referring to FIG. 8 , a method for preparing a display substrate provided in an embodiment of the present application includes the following steps:

Step S110: providing a glass substrate 19 .

Step S120 : forming a first flexible substrate 11 on the glass substrate 19 .

The first flexible substrate 11 is formed on the glass substrate 19 by coating. The material of the first flexible substrate 11 may include polyimide (PI).

Since the material of the first flexible substrate 11 is a flexible material, it is easy to cause curling during the process, so the flexible substrate 111 needs to be coated on the glass substrate 19 to facilitate the subsequent process.

In some embodiments, after step S120 , the method further includes: forming a first buffer layer 12 on the first flexible substrate 11 .

The first buffer layer 12 may also function as an electrostatic blocking layer, an impurity ion blocking layer, and a heat insulating layer.

In some embodiments, the material of the first buffer layer 12 includes SiNx and/or SiOx.

Step S130: forming a plurality of second flexible substrates 13 spaced apart from each other on the first flexible substrate 11; wherein each second flexible substrate 13 comprises an island area 131 and a pad area 132 arranged around the island area 131, and the thickness of at least a portion of the second flexible substrate 13 in the pad area 132 gradually decreases in a direction away from the island area 131.

In some embodiments, the thickness of the entire second flexible substrate 13 in the pad area 132 gradually decreases in a direction away from the island area 131 (the maximum thickness of the second flexible substrate 13 gradually decreases to 0).

In some embodiments, the thickness of at least a portion of the second flexible substrate 13 in the pad area 132 gradually decreases from the maximum thickness value to 0 in the direction away from the island area 131. That is, at the pad area 132, the total thickness of the flexible substrate of the display substrate gradually transitions from the total thickness of the first flexible substrate 11 and the second flexible substrate 13 to the thickness of the first flexible substrate 11 (i.e., transitions from the thickness of two layers of substrates to the thickness of one layer of substrate).

The total thickness of the flexible substrate at the island area 131 is the total thickness of the first flexible substrate 11 and the second flexible substrate 13, the total thickness of the flexible substrate in the bridge area (the area where the connecting line 17 is located) is the thickness of the first flexible substrate 11, and the gradual transition of the total thickness of the flexible substrate at the pad area 132 reduces the ratio of the substrate thickness change to the width of the wiring (connecting line 17) (depth-to-width ratio), which can achieve the purpose of fine wiring patterning process and reduce the process difficulty.

In some embodiments, the first flexible substrate 11 has a thickness of 3-20 μm.

In some embodiments, the second flexible substrate 13 has a thickness of 3-20 μm.

The first flexible substrate 11 and the second flexible substrate 13 are the basis for the display substrate to be stretchable.

In some embodiments, the material of the first flexible substrate 11 and the second flexible substrate 13 may be the same.

In some embodiments, the materials of the first flexible substrate 11 and the second flexible substrate 13 may both include polyimide (PI).

The thickness difference of the second flexible substrate 13 in the pad area 132 may be formed by etching or other processes. Before etching the second flexible substrate 13 , a second buffer layer 14 may be formed on the second flexible substrate 13 , as shown in FIG. 9 .

In some embodiments, the material of the second buffer layer 14 includes SiNx and/or SiOx.

The second buffer layer 14 may also function as an electrostatic blocking layer, an impurity ion blocking layer, and a heat insulating layer.

During the etching process of the second flexible substrate 13 , the second buffer layer 14 can be etched simultaneously.

After etching, the second buffer layer 14 may extend to below the pad 16 , and the thickness of at least a portion of the second buffer layer 14 below the pad 16 gradually decreases in a direction away from the display structure 15 .

That is to say, at the pad area 132 , not only the thickness of the second flexible substrate 13 gradually decreases, but also the thickness of inorganic layers such as the second buffer layer 14 can gradually decrease, so as to further achieve the transition of the elastic modulus on the substrate and further reduce the stress concentration during the stretching process.

In some embodiments, during the etching process of the second flexible substrate 13 , the first buffer layer 12 between two adjacent second flexible substrates 13 may be etched, or the first buffer layer 12 may not be etched.

Step S140: forming a display structure 15 at least partially located above the island area 131, forming a pad 16 at least partially located above the pad area 132, and forming a connecting line 17 above the first flexible substrate 11 and between two adjacent second flexible substrates 13; wherein the connecting line 17 is electrically connected to the pad 16 on the two adjacent second flexible substrates 13, so as to realize the electrical connection of the display structure 15 on the two adjacent second flexible substrates 13.

In some embodiments, the pads 16 and the connection lines 17 may be formed simultaneously during the formation of the display structure 15 , as shown in FIGS. 10 and 11 .

In some embodiments, the orthographic projection of the display structure 15 on the first flexible substrate 11 partially overlaps with the orthographic projection of the pad 16 on the first flexible substrate 11 .

In other words, the pad 16 is not completely covered by the display structure 15. The pad 16 is a connection point structure protruding from the display structure 15. The connecting line 17 can directly contact the pad 16 without punching. In addition, the second flexible substrate 13 with a gradient thickness underneath can further improve the risk of stress concentration damage during stretching due to the difference in soft and hard interfaces (sudden change in elastic modulus).

In some embodiments, forming the display structure 15 above the island area 131 includes the following steps: forming a driving structure layer above the second flexible substrate 13 , and forming a light emitting structure layer above the driving structure layer.

The step of forming a driving structure layer on the second flexible substrate 13 includes the following steps:

(a) forming an active layer 1501 on the second flexible substrate 13 (including deposition and patterning);

(b) forming a gate insulating layer 1502 on the active layer 1501;

(c) forming a gate layer 1503 on the gate insulating layer 1502 (including deposition and patterning);

(d) forming (depositing) an interlayer insulating layer 1505 on the gate layer 1503;

(e) forming a contact hole penetrating the interlayer insulating layer 1505 and the gate insulating layer 1502 (patterning process);

(f) Forming a source-drain metal layer 1506 filling the contact holes (including deposition and patterning).

The active layer 1501, the gate insulating layer 1502, the gate layer 1503 and the source and drain metal layer 1506 constitute a thin film transistor.

In some embodiments, the gate insulation layer 1502 and/or the interlayer insulation layer 1505 extend above the pad area 132; wherein the thickness of at least a portion of the gate insulation layer 1502 and/or the interlayer insulation layer 1505 located above the pad area 132 gradually decreases in a direction away from the island area 131.

However, it should be noted that the inorganic layer (gate insulation layer 1502 and/or interlayer insulation layer 1505) extending above the pad area 132 does not completely cover the pad 16 to form a connection point structure of the protruding display structure 15, so that the connecting line 17 can directly contact the pad 16 without punching. In addition, the second flexible substrate 13 with a gradient thickness underneath can further improve the risk of stress concentration damage during stretching due to the difference in soft and hard interfaces (sudden change in elastic modulus).

In some embodiments, the driving structure layer further includes a capacitor unit (not shown in the figure), a gate wiring 1504 and a source-drain wiring (not shown in the figure).

In some embodiments, while forming the source-drain electrode contact holes, the etching of the second flexible substrate 13 , the first buffer layer 12 , and the second buffer layer 14 in step S130 can be completed simultaneously.

Furthermore, while forming the source-drain electrode contact holes, the bending area of the display substrate (the area bent after the FPC is bound) can also be etched simultaneously.

In some embodiments, the material of the pad 16 is the same as that of the gate layer 1503 or the source-drain metal layer 1506 in the display structure 15. That is, the pad 16 can be formed during the formation of the gate layer 1503 or the source-drain metal layer 1506.

The choice of material for pad 16 can be determined based on the electrode to be led out. For example, when pad 16 leads out the gate of a thin film transistor (i.e., pad 16 is electrically connected to the gate wiring), the material of pad 16 can be the same as the material of gate layer 1503; when pad 16 leads out the source and drain of a thin film transistor (i.e., pad 16 is electrically connected to the source and drain wiring), the material of pad 16 can be the same as the material of source and drain metal layer 1506.

When the material of the pad 16 is the same as that of the source and drain metal layer 1506, the pad 16 extends above the interlayer insulating layer 1505 of the display structure 15, and at this time, the etching of each film layer at the pad area 132 and the film layer at the connecting line 17 (bridge area) can be carried out synchronously with the etching of the contact holes corresponding to the source and drain metal layer 1506 of the display structure 15, and the bending area of the display substrate (the area bent after FPC binding) can also be etched at the same time.

In some embodiments, the material of the connection line 17 may be the same as that of the source-drain metal layer 1506. That is, the connection line 17 may be formed during the formation of the source-drain metal layer 1506.

In some embodiments, the material of the connection line 17 can be other metal materials.

In some embodiments, the positive projection of the connecting line 17 on the first flexible substrate 11 is curved or even wavy, so that when the above-mentioned display substrate is stretched, the connecting line 17 has a certain stress buffer and stronger stretching performance, further improving the stretching ability of the display substrate.

Forming a light emitting structure layer above the driving structure layer includes the following steps:

(a) forming (depositing) an organic planarization layer 1507 on the driving structure layer;

(b) forming an anode contact hole penetrating the organic planar layer 1507 (patterning);

(c) forming an anode layer 1508 filling the anode contact hole (including deposition and patterning);

(d) forming a pixel definition layer 1509 around the anode layer 1508 including deposition and patterning);

(e) forming (depositing) a light emitting layer 1510 on the anode layer 1508;

(f) A cathode layer 1511 is formed (deposited) over the light emitting layer 1510 .

After the light emitting structure layer is formed on the driving structure layer, the method further includes: forming an encapsulation layer 1512 on the light emitting structure layer.

The encapsulation layer 1512 covers the light emitting structure layer to prevent external water vapor, oxygen, etc. from entering the light emitting structure layer to cause poor display. The first encapsulation layer 151214 can be an inorganic material containing silicon (SiOx, SiNx or SiON) and/or an organic material.

In some embodiments, the first encapsulation layer 1512 includes a first inorganic film layer, an organic film layer on the first inorganic film layer, and a second inorganic film layer on the organic film layer. The organic film layer is formed by inkjet printing and has good fluidity.

Step S150: removing the glass substrate 19.

Since the glass substrate 19 is rigid and plays a supporting role during the preparation process, after the above process is completed, the glass substrate 19 needs to be removed so as not to affect the tensile properties of the display substrate.

In some embodiments, after step S150, the following steps are further included:

Step S160 : forming a flexible back film 18 under the first flexible substrate 11 ; wherein the elastic modulus of the flexible back film 18 is smaller than the elastic modulus of the first flexible substrate 11 and the second flexible substrate 13 .

That is to say, the flexibility of the flexible back film 18 is better than that of the first flexible substrate 11 and the second flexible substrate 13, which can further improve the stretchability of the above-mentioned display substrate.

Furthermore, the material of the flexible back film 18 may be polydimethylsiloxane (PDMS) having an elastic modulus smaller than that of polyimide (PI).

In the above-mentioned method for preparing the display substrate, the thickness of the substrate is thick at the position of the island area 131 (display structure 15), and the thickness of the substrate is thin at the position of the connecting line 17 (bridge area), and the thickness of at least a portion of the second flexible substrate 13 in the pad area 132 gradually decreases in the direction away from the island area 131, so that the elastic modulus from the position of the island area 131 to the position of the connecting line 17 (bridge area) transitions smoothly, avoiding stress concentration caused by stretching of the display substrate and causing damage to the connecting line 17 (routing), greatly improving the stretching ability of the display substrate, and improving the product yield and reliability of the stretchable display substrate.

An embodiment of the present application further provides a display device, which includes the display substrate described in any of the above embodiments or a display substrate prepared by the preparation method described in any of the above embodiments.

In some embodiments, the display device is a display panel, and the display panel includes the above-mentioned display substrate and a glass cover.

In some embodiments, the display device may include a display panel and a housing, wherein the display panel is connected to the housing, for example, the display panel is embedded in the housing. The display device may be, for example, a mobile phone, a tablet computer, a television, a laptop computer, a digital photo frame, a navigator, or any other device having a display function.

The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application. Although the implementation methods disclosed in the present application are as above, the content is only an implementation method adopted to facilitate the understanding of the present application and is not intended to limit the present application. Any technician in the technical field to which the present application belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present application, but the protection scope of the present application shall still be subject to the scope defined by the attached claims.

Claims (9)

1. A display substrate, comprising: a first flexible substrate; A plurality of second flexible substrates spaced apart above the first flexible substrate; wherein each of the second flexible substrates comprises an island region and a pad region disposed around the island region, and a thickness of at least a portion of the second flexible substrate located in the pad region gradually decreases in a direction away from the island region; a display structure at least partially located above the island; a pad at least partially located above the pad area, the orthographic projection of the display structure on the first flexible substrate partially overlapping the orthographic projection of the pad on the first flexible substrate; A connecting line located above the first flexible substrate and arranged between two adjacent second flexible substrates; wherein the connecting line is electrically connected to the pads on the two adjacent second flexible substrates to achieve electrical connection of the display structures on the two adjacent second flexible substrates. 2. The display substrate according to claim 1, further comprising: A first buffer layer is disposed between the first flexible substrate and the second flexible substrate. 3 . The display substrate according to claim 2 , wherein the first buffer layer extends below the connecting line. 4. The display substrate according to claim 1, further comprising: a second buffer layer located between the display structure and the second flexible substrate; The second buffer layer extends to below the pad, and the thickness of at least a portion of the second buffer layer below the pad gradually decreases in a direction away from the display structure. 5. The display substrate according to claim 1, wherein the display structure comprises a driving structure layer located above the second flexible substrate, and a light emitting structure layer disposed above the driving structure layer; The driving structure layer includes an active layer, a gate insulating layer, a gate layer, an interlayer insulating layer and a source-drain metal layer which are sequentially stacked on the second flexible substrate. 6 . The display substrate according to claim 5 , wherein a material of the pad is the same as a material of the gate layer or the source and drain metal layer. 7. The display substrate according to claim 5, characterized in that the gate insulating layer and/or the interlayer insulating layer extends above the pad area; Wherein, the thickness of at least a portion of the gate insulation layer and/or the interlayer insulation layer located above the pad region gradually decreases in a direction away from the island region. 8. The display substrate according to claim 1, further comprising: a flexible backing film disposed below the first flexible substrate; Wherein, the elastic modulus of the flexible back film is smaller than the elastic modulus of the first flexible substrate and the second flexible substrate. 9. A display device, comprising the display substrate according to any one of claims 1 to 8.