Electronic element

An electronic element includes a carbon nanotube film, at least one first electrode and at least one second electrode spaced from the at least one first electrode. The carbon nanotube film includes a number of carbon nanotube linear units spaced from each other, and a number of carbon nanotube groups. The carbon nanotube linear units extend along a first direction to form a number of first conductive paths. The carbon nanotube groups are combined with the carbon nanotube linear units by van der Waals force in a second direction intercrossed with the first direction, to form a number of second conductive paths. The carbon nanotube groups between adjacent carbon nanotube linear units are spaced from each other in the first direction. The at least one first and second electrodes are electrically connected with the carbon nanotube film through the first conductive paths or the second conductive paths.

RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. §119 from China Patent Application No. 201210122623.7, filed on Apr. 25, 2012 in the China Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to electronic elements, and particularly to an electronic element based on carbon nanotubes.

2. Discussion of Related Art

Electronic elements, especially thin film electronic elements, are important elements in various electronic devices, such as touch panels, liquid crystal display devices, or field emission display devices.

Conventional thin film electronic elements usually includes electrically conductive layers, which mainly consist of metal or metal oxide, such as silver (Ag), copper (Cu), gold (Au), indium-tin oxide (ITO), or zinc oxide (ZnO). The conductive layers are difficult to fold, and the mechanical and chemical properties are not ideal. As such, the life spans of the electronic elements are affected. The conventional conductive layers in the electronic elements are mainly formed by applying electrically conductive materials on a substrate using deposition methods, evaporation methods, or sputtering methods. These methods need a process of high-temperature annealing, which will damage the substrate on which the electronic element is formed. Thus, the life spans of the electronic elements are short.

What is needed, therefore, is to provide an electronic element with a long life span to overcome the above shortages.

DETAILED DESCRIPTION

Referring toFIG. 1andFIG. 2, one embodiment of an electronic element100includes a carbon nanotube film12, a first electrode14and a second electrode16spaced from the first electrode14. The first electrode14and the second electrode16are electrically connected with the carbon nanotube film12.

The carbon nanotube film12includes a number of carbon nanotube linear units122and a number of carbon nanotube groups124. The carbon nanotube linear units122are spaced from each other. The carbon nanotube groups124join with the carbon nanotube linear units122by van der Waals force. The carbon nanotube groups124located between adjacent carbon nanotube linear units122are separated from each other.

Each carbon nanotube linear unit122includes a number of first carbon nanotubes extending substantially along a first direction X. Adjacent first carbon nanotubes extending substantially along the first direction X are joined end to end by van der Waals attractive force. In one embodiment, an axis of each carbon nanotube linear unit122is substantially parallel to the axes of first carbon nanotubes in each carbon nanotube linear unit122. The carbon nanotube linear units122extend substantially along the first direction X, and are separated from each other in a second direction Y intercrossed with the first direction X.

An intersection shape of each carbon nanotube linear unit122can be a semi-circle, circle, ellipse, oblate spheriod, or other shapes. In one embodiment, the carbon nanotube linear units122are substantially parallel to each other. Distances between adjacent carbon nanotube linear units122are substantially equal. The carbon nanotube linear units122are substantially coplanar. An effective diameter of each carbon nanotube linear unit122is larger than or equal to 0.1 micrometers, and less than or equal to 100 micrometers. In one embodiment, the effective diameter of each carbon nanotube linear unit122is larger than or equal to 5 micrometers, and less than or equal to 50 micrometers. A distance between adjacent two carbon nanotube linear units122is not limited and can be selected as desired. In one embodiment, the distance between adjacent two carbon nanotube linear units122is greater than 0.1 millimeters. Diameters of the carbon nanotube linear units122can be selected as desired. In one embodiment, the diameters of the carbon nanotube linear units122are substantially equal.

The carbon nanotube groups124are separated from each other and combined with adjacent carbon nanotube linear units122by van der Waals force in the second direction Y, so that the carbon nanotube film12is a free-standing structure. “Free-standing structure” means that the carbon nanotube film does not have to be supported by a substrate and can sustain the weight of itself when it is hoisted by a portion thereof without tearing. The carbon nanotube groups124are alternated with the carbon nanotube linear units122on the second direction Y. In one embodiment, the carbon nanotube groups124arranged in the second direction Y are separated from each other by the carbon nanotube linear units122. The carbon nanotube groups124arranged in the second direction Y can connect with the carbon nanotube linear units122.

The carbon nanotube group124includes a number of second carbon nanotubes joined by van der Waals force. Axes of the second carbon nanotubes can be substantially parallel to the first direction X or the carbon nanotube linear units122. The axes of the second carbon nanotubes can also be intercrossed with the first direction X or the carbon nanotube linear units122such that the second carbon nanotubes in each carbon nanotube group124are intercrossed into a network structure.

The axes of second carbon nanotubes and the first direction X define first angles. Each first angle can be greater than or equal to 0 degrees, and less than or equal to 90 degrees. In one embodiment, the first angle is greater than or equal to 45 degrees, and less than or equal to 90 degrees. In another embodiment, the first angle is greater than or equal to 60 degrees, and less than or equal to 90 degrees.

In one embodiment, the carbon nanotube groups124can be interlacedly located in the second direction Y and disorderly arranged in the second direction Y. As such, the carbon nanotube groups124in the second direction Y form non-linear conductive paths. In one embodiment, the carbon nanotube groups124are arranged into a number of columns in the second direction Y, thus the carbon nanotube groups124form consecutive and linear conductive paths in the second direction. In one embodiment, the carbon nanotube groups124in the carbon nanotube film are arranged in an array. A length of each carbon nanotube group124in the second direction Y is substantially equal to the distance between adjacent carbon nanotube linear units122. The length of each carbon nanotube group124in the second direction Y is greater than 0.1 millimeters. The carbon nanotube groups124are also spaced from each other along the first direction X. Spaces between adjacent carbon nanotube groups124in the first direction X are greater than or equal to 1 millimeter.

Therefore, the carbon nanotube film includes a number of carbon nanotubes. The carbon nanotubes can be formed into carbon nanotube linear units122and carbon nanotube groups124. In one embodiment, the carbon nanotube film consists of the carbon nanotubes. The carbon nanotube film defines a number of apertures. Specifically, the apertures are mainly defined by the separate carbon nanotube linear units122and the spaced carbon nanotube groups124. The arrangement of the apertures is similar to the arrangement of the carbon nanotube groups124. In the carbon nanotube film, if the carbon nanotube linear units122and the carbon nanotube groups124are orderly arranged, the apertures are also orderly arranged. In one embodiment, the carbon nanotube linear units122and the carbon nanotube groups124are substantially arranged in an array, and the apertures are also arranged in an array.

A ratio between a sum area of the carbon nanotube linear units122and the carbon nanotube groups124and an area of the apertures is less than or equal to 1:19. In other words, in the carbon nanotube film12, a ratio of the area of the carbon nanotubes to the area of the apertures is less than or equal to 1:19. In one embodiment, in the carbon nanotube film12, the ratio of the sum area of the carbon nanotube linear units122and the carbon nanotube groups124to the area of the apertures is less than or equal to 1:49. Therefore, a transparence of the carbon nanotube film12is greater than or equal to 95%. In one embodiment, the transparence of the carbon nanotube film12is greater than or equal to 98%.

The carbon nanotube film12is an anisotropic conductive film. The carbon nanotube linear units122form first conductive paths along the first direction, as the carbon nanotube linear units122extend substantially along the first direction X. The carbon nanotube groups124combined with the carbon nanotube linear units on the second direction form second conductive paths along the second direction Y. The second conductive paths can be curved second conductive paths, as the carbon nanotube groups are interlacedly arranged. The second conductive paths can be linear second conductive paths, as the carbon nanotube groups are arranged as a number of columns and rows. Therefore, a resistance of the carbon nanotube film12in the first direction X is different from a resistance of the carbon nanotube film12in the second direction Y. The resistance of the carbon nanotube film12in the second direction Y is 10 times greater than the resistance of the carbon nanotube film12in the first direction X. In one embodiment, the resistance of the carbon nanotube film12in the second direction Y is 20 times greater than the resistance of the carbon nanotube film12in the first direction X. In one embodiment, the resistance of the carbon nanotube film12in the second direction Y is about 50 times greater than the resistance of the carbon nanotube film12in the first direction X. In the carbon nanotube film12, the carbon nanotube linear units122are joined by the carbon nanotube groups124in the second direction Y, which makes the carbon nanotube film12strong and stable, and not broken easily.

There can be a few carbon nanotubes surrounding the carbon nanotube linear units and the carbon nanotube groups in the carbon nanotube film. However, these few carbon nanotubes have a small and negligible effect on the carbon nanotube film properties.

The first electrode14and the second electrode16are located at two opposite ends of the carbon nanotube film12. The first electrode14and the second electrode16are electrically connected with at least one conductive path of the first conductive paths and the second conductive paths. In one embodiment, the first electrode14and the second electrode16are separately located along the second direction Y on the carbon nanotube film12, and electrically connected with the first conductive paths. In another embodiment, the first electrode14and the second electrode16are separately located along the first direction X on the carbon nanotube film12, and electrically connected with the second conductive paths.

The first electrode14and the second electrode16consist of electrically conductive materials. Materials of the first electrode14and the second electrode16can be metal materials, electrically conductive polymer materials or carbon nanotubes. The metal materials can be gold, silver, or copper. The electrically conductive polymer materials can be polyacetylene, polyparaphenylene, polyaniline, polypyrrole, or polythiophene. In one embodiment, both the first electrode14and the second electrode16consist of silver paste.

The electronic element10can further include a substrate18supporting the carbon nanotube film12. The substrate18can be a curved structure or a sheet-shaped structure. The substrate18can be transparent. In one embodiment, a transparence of the substrate18is greater than 75%. The substrate18can be made of a hard material or a flexible material. The material of the substrate18can be glass, quartz, diamond, or plastics. More specifically, the flexible material of the substrate18can be a polycarbonate (PC), polyethylene (PE), polypropylene (PP), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polyether sulfone (PES), polyimide (PI), polyvinyl chloride (PVC), benzocyclobutene (BCB), cellulose ester, polyester, acrylic resin or any combination thereof. The material of the substrate18is not limited to the above mentioned materials. In one embodiment, the substrate18is a PET film with relatively good transparency.

The electronic element10also can include an adhesive layer19located between the substrate18and the carbon nanotube film12, to fix the carbon nanotube film12on the substrate18. Part of the adhesive layer19is exposed from the carbon nanotube film12through the apertures. The adhesive layer19can be made from thermoplastic adhesive, thermoset resin, or UV adhesive. A thickness of the adhesive layer19can be from about 1 nanometer to about 500 micrometers. In one embodiment, the thickness of the adhesive layer19is from about 1 micrometer to about 2 micrometers. The adhesive layer19can be transparent, and the transparency is greater than or equal to 75%. In one embodiment, the adhesive layer19is the UV adhesive layer with the thickness of about 1.5 micrometers.

The carbon nanotubes in the carbon nanotube film12of the electronic element10are excellent in mechanical properties and chemical endurance. The carbon nanotube film12also has mechanical properties and chemical endurance. In addition, the carbon nanotube linear units122are fixed through the carbon nanotube groups124to form the carbon nanotube film12, which makes the carbon nanotube film12strong and stable, and not broken easily. Thus, a life span of the electronic element10using the carbon nanotube film12is improved. If the electronic element10is in use, a voltage is applied to the first electrode14and the second electrode16, the first conductive paths or the second conductive paths in the carbon nanotube film12will be led, which can detect or sense electrical signals. The carbon nanotube film12is a transparent film. If the substrate18and the adhesive layer19are transparent, the electronic element10is also transparent and can be used in various electronic devices. The carbon nanotube film12is also flexible. If the substrate18is transparent and flexible, such as PET and PC, the electronic element10is also flexible and transparent.

Referring toFIG. 5andFIG. 6, one embodiment of an electronic element20is provided. The electronic element20includes a carbon nanotube film22, a number of first electrodes14, and a number of second electrodes16. The first electrodes14are separately located at a first same side of the carbon nanotube film22. The second electrodes16are separately located at a second same side of the carbon nanotube film22. In the carbon nanotube film22, the second same side is opposite to the first same side. The first and second electrodes14,16are electrically connected with the carbon nanotube film22. The structure of the electronic element20is similar to the structure of the electronic element10, except that the structure of the carbon nanotube film22is different from the structure of the carbon nanotube film12, and the number of the first and second electrodes14,16.

The carbon nanotube film22includes the carbon nanotube linear units122and a number of second carbon nanotube groups224. Each carbon nanotube group224includes a number of second carbon nanotubes extending along a direction which defines a second angle with the first direction X. The second angle can be greater than or equal to 0 degrees, and less than or equal to 45 degrees. In one embodiment, the second angle is greater than or equal to 0 degrees, and less than or equal to 30 degrees. In another embodiment, the carbon nanotubes in each carbon nanotube group224are substantially parallel to the first direction X and axes of the carbon nanotube linear units122. As such, the carbon nanotubes of the carbon nanotube film22substantially extend along a same direction.

In addition, in the carbon nanotube film22, there can be a few carbon nanotubes surrounding the carbon nanotube linear units122and the carbon nanotube groups224due to inherent limitations of the method for making the carbon nanotube structure.

The first electrodes14are electrically connected with the second electrodes16through the first conductive paths or the second conductive paths. The first electrodes14and the second electrodes16are located on two opposite ends of the carbon nanotube film22. The numbers of the first electrodes14, the second electrodes16, the first conductive paths or the second conductive paths can be equal or unequal. In one embodiment, the first electrodes14, the first conductive paths and the second electrodes16correspond to each other in a one to one manner. The first electrodes14are separately arranged in the second direction Y, and the second electrodes16are separately arranged in the second direction Y. The first electrodes14and the second electrodes16are located at two opposite ends of the carbon nanotube film22along the first direction X. In another embodiment, the first electrodes14and the second electrodes16can also be electrically connected with the second conductive paths. In one embodiment, the electronic element10includes a number of first electrodes14and a single second electrode16. If the electronic element10includes a number of second electrodes, it can include a single first electrode14.

Other structural characteristics of the electronic element20are substantially the same as structural characteristics of the electronic element10.

When the electronic element20is in use, and a voltage is applied to all the first electrodes14and the second electrodes16, electrical signals will pass through all the first conductive paths or the second conductive paths in the carbon nanotube film22, therefore the first conductive paths or the second conductive paths are in work. The carbon nanotube film22is an isotropic and electrically conductive film, and can define continual conductive paths respectively in the first direction X and the second direction Y. When a voltage is applied to selected first electrodes14and selected second electrodes16corresponding to the selected first electrodes14, strong electrical signals will pass through the first or second conductive paths corresponding to the selected first electrodes14; electrical signals in the other first conductive paths or the other second conductive paths will be weak, even if no electrical signals pass through the other first or second conductive paths. Therefore, the electronic element20can select work regions, and can detect or sense the electrical signals in order, according to regions generated by the electrical signals.

Referring toFIG. 7, one embodiment of an electronic element30is provided. The electronic element30includes a carbon nanotube film12, a number of first electrodes14and a number of second electrodes16. The structure of the electronic element30is similar to that of the electronic element20, except that the electronic element30includes the carbon nanotube film12rather than the carbon nanotube film22, and the electronic element30further includes at least one third electrode35and at least one fourth electrode37electrically connected with the carbon nanotube film12. The at least one third electrode35is opposite to the at least one fourth electrode37. In the electronic element30, the first electrodes14, the at least one third electrode35, a number of second electrodes16, and the at least one fourth electrode37are located on four ends of the carbon nanotube film12in sequence. If the first electrodes14and the second electrodes16are in electrical contact with the first conductive paths, the at least one third electrode35and the at least one fourth electrode37will be electrically connected with the second conductive paths. In addition, if the first electrodes14and the second electrodes16are in electrical contact with the second conductive paths, the at least one third electrode35and the at least one fourth electrode37will be electrically connected with the first conductive paths.

In one embodiment, the electronic element30includes a number of first electrodes14, a number of second electrodes16, a number of third electrodes35, and a number of fourth electrodes37. The first electrodes14and the second electrodes16are respectively connected with the first conductive paths. The first electrodes14, the second electrodes16, and the first conductive paths correspond to each other in a one by one manner. The third electrodes35and the fourth electrodes37are insulated and separately located on the first direction X. The third electrodes35and the fourth electrodes37are electrically connected with the second conductive paths. The third electrodes35, the second electrodes37, and the second conductive paths correspond to each other in a one to one manner.

Other structural characteristics of the electronic element30are substantially the same as the structural characteristics of the electronic element20.

The work theory of the electronic element30is similar to the work theory of the electronic element20, except that the work regions of the electronic element30can be selected not only in the first direction X or the second direction Y, but also in both the first and second directions X, Y. The work theory of the electronic element30in the first direction or the second direction is the same as the work theory of the electronic element20.

The numbers of the first electrodes, the second electrodes, the third electrodes, and the fourth electrodes in the electronic elements provided by the present disclosure are not limited, as long as the carbon nanotube films are in use when voltages are applied to the electrodes. The carbon nanotube films can be the carbon nanotube film10or20.

It is to be understood that the above-described embodiment is intended to illustrate rather than limit the disclosure. Variations may be made to the embodiment without departing from the spirit of the disclosure as claimed. The above-described embodiments are intended to illustrate the scope of the disclosure and not restricted to the scope of the disclosure.

It is also to be understood that the above description and the claims drawn to a method may include some indication in reference to certain steps. However, the indication used is only to be viewed for identification purposes and not as a suggestion as to an order for the steps.