Stacking structure and touch sensor using same

A stacking structure includes a substrate, a silver nanowire layer provided on a top of the substrate, and a metal layer provided on a top of the silver nanowire layer. The silver nanowire layer includes a plurality of silver nanowires and an indium tin oxide (ITO) covered on the plurality of silver nanowires. The silver nanowire layer has an overall thickness that is 2.35 to 24 times as thick as a thickness of the ITO. A touch sensor including the above described stacking structure is also disclosed.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure relates to a stacking structure and more particularly to a stacking structure including a silver nanowire layer. The present disclosure also relates to a touch sensor and more particularly to a touch sensor that includes the above-mentioned stacking structure.

2. Description of the Related Art

A stacking structure including silver nanowires and metal layers can be applied to the manufacturing of a touch sensor. Conventionally, surfaces of the silver nanowires in the stacking structure are covered with a protective layer, which is formed of a nonconductive resin and mainly used to protect the silver nanowires from scratches and peeling and to enhance the adherence between the silver nanowires and a substrate of the stacking structure. Since this protective layer is to be permanently attached to the substrate and the surfaces of the silver nanowires, the protective layer must have some optical characteristics like high transparency, low haze, and low b*, so as to satisfy the optical properties required by the visible area of the touch sensor.

Further, since the protective layer is to be permanently attached to the surfaces of the silver nanowires, the thickness of the protective layer plays a critical factor in the efficiency of etching the silver nanowires during the etching process. Besides, the protective layer often requires an etchant with high etch selectivity due to the protective layer being formed of a resin. Further, the protective layer tends to result in high contact impedance and poor electrostatic discharge (ESD) prevention due to the protective layer being formed of a nonconductive resin.

BRIEF SUMMARY OF THE DISCLOSURE

An objective of the present disclosure is to provide an improved stacking structure and a touch sensor including the same, so as to overcome the problem in the conventional stacking structure in which the protective layer, formed of a nonconductive resin, tends to cause high contact impedance and low electrostatic discharge (ESD) prevention.

To achieve at least the above objective, the stacking structure according to the present disclosure includes:a substrate;a silver nanowire layer provided on a top of the substrate; anda metal layer provided on a top of the silver nanowire layer;wherein the silver nanowire layer includes:a plurality of silver nanowires; andan indium tin oxide (ITO) covered on the plurality of silver nanowires; andwherein the silver nanowire layer has an overall thickness that is 2.35-24 times as thick as a thickness of the ITO.

In the above stacking structure, the overall thickness of the silver nanowire layer can range from 40 to 120 nm.

In the above stacking structure, the thickness of the ITO included in the silver nanowire layer can range from 5 to 17 nm.

In the above stacking structure, the silver nanowire layer has a sheet resistance ranging from 5 to 100 ohms per square (ops).

The above stacking structure may further include:

a second silver nanowire layer provided on an underside of the substrate; and

a second metal layer provided on an underside of the second silver nanowire layer;

wherein the second silver nanowire layer includes:

a plurality of silver nanowires, and

an indium tin oxide (ITO) covered on the plurality of silver nanowires; and

wherein the second silver nanowire layer has an overall thickness that is 2.35-24 times as thick as a thickness of the ITO of the second silver nanowire layer.

To achieve at least the above objective, the touch sensor according to the present disclosure includes the above described stacking structure.

In the above touch sensor, the silver nanowire layer and the metal layer of the stacking structure can be patterned.

The above touch sensor may include two layers of the above described stacking structure, and all the silver nanowire layers and the metal layers of the stacking structures can be patterned.

In the above touch sensor, the silver nanowire layer, the second silver nanowire layer, the metal layer, and the second metal layer in the stacking structures all can be patterned.

The stacking structure and the touch sensor of the present disclosure show reduced contact impedance, good ESD prevention, and upgraded tolerance in the reliability analysis (RA) without adversely influencing the optical conditions thereof.

DETAILED DESCRIPTION OF THE DISCLOSURE

To facilitate understanding of the objects, characteristics, and effects of this present disclosure, embodiments together with the attached drawings for the detailed description of the present disclosure are provided. A person of ordinary skill in the art can understand the advantages and benefits of the present disclosure from the contents of the specification. It is noted the present disclosure can be implemented or applied in other embodiments, and many changes and modifications in the described embodiments can be carried out without departing from the spirit of the disclosure, and it is also understood that the preferred embodiments are only illustrative and not intended to limit the present disclosure in any way.

In the specification and the appended claims, the use of the singular form of a word indicated by “a” or “the” shall construed to include the plural unless the context indicates otherwise.

In the specification and the appended claims, the use of the term “or” includes the meaning of “and/or” unless the context indicates otherwise.

First Embodiment

FIG. 1is a schematic sectional view of a stacking structure10according to a first embodiment of the present disclosure. As shown, the stacking structure10in the first embodiment includes a substrate11, a silver nanowire layer12provided on a top of the substrate11, and a metal layer13provided on a top of the silver nanowire layer12. The silver nanowire layer12includes a plurality of silver nanowires and an indium tin oxide (ITO) covered on the plurality of silver nanowires.

In the stacking structure10according to the first embodiment, the silver nanowire layer12has an overall thickness that is 8 times as thick as a thickness of the ITO (e.g., 40 nm:5 nm). However, it is understood that the present disclosure is not limited thereto. In some embodiments, the silver nanowire layer12is 2.35 to 24 times as thick as the ITO. Herein, the phrase “overall thickness of the silver nanowire layer” means a total thickness of the silver nanowire layer12, including a thickness of the plurality of silver nanowires and the thickness of the ITO.

In the stacking structure10according to the first embodiment, the substrate11is made of a polyethylene terephthalate (PET). Other suitable materials for the substrate11include, but are not limited to, cyclic olefin copolymer (COP), Colorless Polyimide (CPI), and ultra thin glass (UTG).

In the stacking structure10according to the first embodiment, the overall thickness of the silver nanowire layer12is 40 nm. However, the present disclosure is not limited thereto, and in some embodiments the silver nanowire layer12has an overall thickness ranging from 40 to 120 nm.

In the stacking structure10according to the first embodiment, the silver nanowire layer12has a sheet resistance being controlled to be 50 ohms per square (ops). However, it is understood that the present disclosure is not particularly limited thereto, and in some embodiments the sheet resistance for the silver nanowire layer12ranges from 5 to 100 ops.

In the stacking structure10according to the first embodiment, the metal layer13is made of a copper material. However, the present disclosure is not limited thereto. Other suitable materials for forming the metal layer13include, but are not limited to, molybdenum and aluminum.

The stacking structure10of the first embodiment can be non-restrictively prepared according to the following steps:

(1) providing a substrate;

(2) coating the substrate with a plurality of silver nanowires;

(3) forming a silver nanowire layer by providing an ITO on the silver-nanowires-coated substrate by sputter deposition; and

(4) covering a metal layer on the silver nanowire layer.

Second Embodiment

FIG. 2is a schematic sectional view of a stacking structure20according to a second embodiment of the present disclosure. Like the stacking structure10in the first embodiment, the stacking structure20in the second embodiment also includes a substrate11, a silver nanowire layer12provided on a top of the substrate11, and a metal layer13provided on a top of the silver nanowire layer12. The silver nanowire layer12includes a plurality of silver nanowires and an indium tin oxide (ITO) covered on the plurality of silver nanowires.

Compared to the stacking structure10in the first embodiment, the stacking structure20according to the second embodiment further includes a second silver nanowire layer22provided on an underside of the substrate11and a second metal layer23provided on an underside of the second silver nanowire layer22. The second silver nanowire layer22includes a plurality of silver nanowires and an indium tin oxide (ITO) covered on the plurality of silver nanowires.

In the stacking structure20according to the second embodiment, since the ratio of an overall thickness of the second silver nanowire layer22to a thickness of the ITO, the overall thickness of the second silver nanowire layer22, and the material for forming the second metal layer23are the same as those for the silver nanowire layer12and the metal layer13in the first embodiment, they are not repeatedly described herein.

In the stacking structure20according to the second embodiment, the second silver nanowire layer22and the second metal layer23can be prepared in the same steps as described in the first embodiment.

Third Embodiment

FIG. 3is a pictorial flowchart showing the steps of preparing a touch sensor30according to a third embodiment of the present disclosure. As shown inFIG. 3, the touch sensor30in the third embodiment includes the stacking structure10described in the first embodiment, and the stacking structure10is patterned to meet different requirements of the touch sensor30.

As shown in the flowchart ofFIG. 3, the steps for preparing the touch sensor30include:

1. providing the stacking structure10described in the first embodiment;

2. applying a photoresist31on a top of the metal layer13and performing a photolithography process on the photoresist31; a pattern of the applied photoresist31defines an operating area32located at a central area of the stacking structure10and a trace area33located at outer sides of the stacking structure10;

3. etching the metal layer13;

4. removing the remaining photoresist31;

5. etching the silver nanowire layer12;

6. applying a second photoresist34on the top of the metal layer13;

7. performing the photolithography process again on the second photoresist34;

8. etching the metal layer13again; and

9. removing the remaining second photoresist34to complete a touch sensor30according to the third embodiment of the present disclosure.

Fourth Embodiment

FIG. 4is a pictorial flowchart showing the steps of preparing a touch sensor40according to a fourth embodiment of the present disclosure. As shown, the touch sensor40in the fourth embodiment of the present disclosure includes two layers of the stacking structure described in the first embodiment (i.e. a stacking structure10and another stacking structure10′), and the two stacking structures10,10′ are patterned to meet different requirements of the touch sensor40.

As shown in the flowchart ofFIG. 4, the steps for preparing the touch sensor40in the fourth embodiment include:

1-1 providing the stacking structure10described in the first embodiment;

1-2 applying a photoresist41on a top of the metal layer13of the stacking structure10and performing a photolithography process on the photoresist41; a pattern of the applied photoresist41defines an operating area42located at a central area of the stacking structure10and a trace area43located at outer sides of the stacking structure10;

1-3 etching the metal layer13;

1-4 removing the remaining photoresist41;

1-5 etching the silver nanowire layer12of the stacking structure10;

1-6 applying a second photoresist44on the top of the metal layer13;

1-7 performing the photolithography process again on the second photoresist44;

1-8 etching the metal layer13again;

1-9 removing the remaining second photoresist44to complete a driving electrode Txfor the touch sensor40according to the fourth embodiment of the present disclosure;

2-1 providing another stacking structure10′ described in the first embodiment;

2-2 applying a third photoresist45on a top of the metal layer13′ of the stacking structure10′ and performing a photolithography process on the third photoresist45; a pattern of the applied third photoresist45defines an operating area46located at a central area of the stacking structure10′ and a trace area47located at outer sides of the stacking structure10′;

2-3 etching the metal layer13′;

2-4 removing the remaining third photoresist45;

2-5 etching the silver nanowire layer12′ of the stacking structure10′;

2-6 applying a fourth photoresist48on the top of the metal layer13′;

2-7 performing the photolithography process again on the fourth photoresist48;

2-9 removing the remaining fourth photoresist48to complete a sensing electrode Rxfor the touch sensor40according to the fourth embodiment of the present disclosure; and

3-1 providing a first covering layer49and a second covering layer49′ on a top of the driving electrode Txformed in the step 1-9 and the sensing electrode Rxformed in the step 2-9, respectively; and superposing the driving electrode Txcovered with the first covering layer49on the sensing electrode Rxcovered with the second covering layer49′ to complete the touch sensor40of the fourth embodiment.

Fifth Embodiment

FIG. 5is a pictorial flowchart showing the steps of preparing a touch sensor50according to a fifth embodiment of the present disclosure. As shown inFIG. 5, the touch sensor50in the fifth embodiment includes the stacking structure20described in the second embodiment, and the stacking structure20is patterned to meet different requirements of the touch sensor50.

As shown in the flowchart ofFIG. 5, the steps for preparing the touch sensor50in the fifth embodiment include:

1. providing the stacking structure20described in the second embodiment;

2. applying a photoresist51on a top of the metal layer13of the stacking structure20and on an underside of the second metal layer23of the stacking structure20and performing a photolithography process on the upper and the lower photoresist51, wherein patterns of the applied photoresists51define an operating area52located at a central area of the stacking structure20and a trace area53located at outer sides of the stacking structure20;

3. etching the metal layer13and the second metal layer23;

4. removing the remaining photoresists51from both sides of the stacking structure20;

5. etching the silver nanowire layer12and the second silver nanowire layer22of the stacking structure20;

6. applying a second photoresist54on the top of the metal layer13and on the underside of the second metal layer23;

7. performing the photolithography process again on the upper and the lower second photoresist54;

8. etching the metal layer13and the second metal layer23again; and

9. removing the remaining second photoresists54to complete the touch sensor50according to the fifth embodiment of the present disclosure.

Comparative Example 1

To find out how the ITO included in the silver nanowire layer of the stacking structure of the present disclosure influences the ability of ESD prevention of the stacking structure, a stacking structure is prepared according to the first embodiment with the ITO in the silver nanowire layer being omitted and replaced by a conventional nonconductive acrylic resin material. The stacking structure so prepared is used as a comparative example 1.

Test Example 1

In test example 1, a stacking structure according to the first embodiment and a stacking structure according to the comparative example 1 are used to find out which one has better performance with respect to ESD prevention. Both stacking structures have their metal layer removed therefrom and are subjected to an electrostatic discharge stress produced by an ESD simulation device. In the case of a stacking structure with better anti-electrostatic ability, only relatively minor damage (or a relatively small change in the resistance value) will be caused by the ESD stress. On the other hand, in the case of a stacking structure with inferior anti-electrostatic ability, relatively serious damage will be caused by the ESD stress, resulting in an increased resistance value or even broken silver nanowires of the stacking structure.

Test results from the test example 1 are shown below in Table 1 (unit of measurement: ohm):

As can be seen from the test results in Table 1, the stacking structure according to the first embodiment apparently has a superior anti-ESD ability than that of the stacking structure according to the comparative example 1. This is because the stacking structure of the first embodiment uses the ITO in the silver nanowire layer instead of the conventional nonconductive resin.

Test Example 2

In test example 2, a stacking structure is prepared according to the first embodiment with the silver nanowire layer thereof being controlled to have an overall thickness of 40 nm and a sheet resistance of 50 ops, and the stacking structure so prepared is used in the test example 2. In the test example 2, sample stacking structures used are different from one another only in their ratios of the overall thickness of the silver nanowire layer to the thickness of the ITO.

As shown in Table 2, when the silver nanowire layers are the same in their overall thickness, the stacking structures having an ITO thickness larger than or equal to 5 nm can show good anti-ESD ability. The influence of the ITO thickness on the visibility of the stacking structures is further examined. It is found that the stacking structures can have good anti-ESD ability and good visibility at the same time when the ITO thickness ranges from 5 to 17 nm; and that the visibility of the stacking structures is reversely affected when the ITO thickness is larger than 17 nm.

On the whole, in the stacking structures according to the present disclosure, the overall thickness of the silver nanowire layer can range from 40 to 120 nm and the thickness of the ITO can range from 5 to 17 nm. Therefore, the ratio of the overall thickness of the silver nanowire layer of the stacking structure to the thickness of the ITO ranges from 40:17 to 120:5. In other words, the overall thickness of the silver nanowire layer can be 2.35 to 24 times as thick as the thickness of the ITO.

In conclusion, the stacking structure and the touch sensor including same according to the present disclosure provide at least the following advantageous technical effects:

1. In the stacking structure of the present disclosure, an ITO is used in the silver nanowire layer instead of the conventional nonconductive resin, enabling easy selectivity of etchant; that is, an etchant that etches the metal layer without damaging the silver nanowires and the ITO can be used in the process of etching the metal layer, and another etchant that etches the silver nanowires and the ITO without etching the metal layer can be used in the process of etching the silver nanowires and the ITO.

2. By combining a network scalability provided by the silver nanowires with a continuous conduction provided by the ITO, the stacking structure of the present disclosure shows reduced contact impedance, good ESD prevention, and upgraded tolerance in the reliability analysis without adversely affecting the optical conditions of the stacking structure.

3. In response to the ITO conductive thin film that is currently a market mainstream, the stacking structure of the present disclosure can quickly introduce the silver nanowire thin film technique into the existing ITO optical thin film manufacturing process without causing too many changes in the production line and manufacturing process, so as to combine the advantages of these two types of materials while give the stacking structure even better optical and conducting properties.

While the present disclosure has been described by means of specific embodiments, numerous modifications and variations can be made thereto by those skilled in the art without departing from the scope and spirit of the present disclosure set forth in the claims.