Touch panel and display device using the same

A touch panel includes a first electrode plate and a second electrode plate. The first electrode plate includes a first substrate, a first conductive layer disposed on a lower surface of the first substrate, and two first-electrodes disposed on opposite ends of the first conductive layer. The second electrode plate separates from the first electrode plate and includes a second substrate, a second conductive layer disposed on an upper surface of the second substrate, and two second-electrodes disposed on opposite ends of the second conductive layer. At least one of the first-electrodes and the second-electrodes includes a carbon nanotube layer. Further, the present invention also relates to a display device. The display device includes a displaying unit and a touch panel.

RELATED APPLICATIONS

BACKGROUND

1. Field of the Invention

The present invention relates to touch panels and display device using the same and, particularly, to a carbon nanotube based touch panel and a display device using the same.

2. Discussion of Related Art

Following the advancement in recent years of various electronic apparatuses, such as mobile phones, car navigation systems and the like, toward high performance and diversification, there has been continuous growth in the number of electronic apparatuses equipped with optically transparent touch panels in front of their respective display devices (e.g., liquid crystal panels). A user of any such electronic apparatus operates it by pressing a touch panel with a finger, a pen, stylus, or another like tool while visually observing the display device through the touch panel. A demand thus exists for such touch panels that are superior in visibility and reliable in operation.

At present, different types of touch panels, including a resistance-type, a capacitance-type, an infrared-type and a surface sound wave-type have been developed. Due to the high accuracy and a low-cost of the production thereof, the resistance-type touch panels have been widely used.

A conventional resistance-type touch panel includes an upper substrate, a lower substrate and a plurality of dot spacers. The upper substrate includes an optically transparent upper conductive layer formed on a lower surface thereof, and two upper electrodes connected to the optically transparent upper conductive layer at two edges along the X direction. The lower substrate includes an optically transparent lower conductive layer formed on an upper surface thereof, and two lower electrodes connected to the optically transparent upper conductive layer at two edges along the Y direction. The plurality of dot spacers is formed between the optically transparent upper conductive layer and the optically transparent lower conductive layer. The optically transparent upper conductive layer and the optically transparent lower conductive layer are formed of conductive indium tin oxide (ITO). The upper electrodes and the lower electrodes are formed of a silver paste layer.

In operation, an upper surface of the upper substrate is pressed with a finger, a pen or the like tool, and visual observation of a screen on the display device provided on a back side of the touch panel is allowed. This causes the upper substrate to be deformed, and the upper conductive layer thus comes in contact with the lower conductive layer at the position where pressing occurs. Voltages are applied successively from an electronic circuit to the optically transparent upper conductive layer and the optically transparent lower conductive layer. Thus, the deformed position can be detected by the electronic circuit.

However, the material of the electrodes such as metal has poor wearability/durability and low chemical endurance. Further, when the substrate is deformable and made of soft material, the electrodes formed on the substrate is easily to be destroyed and break off during operation. The above-mentioned problems of the metallic electrodes make for a touch panel with low sensitivity, accuracy and durability. Additionally, the cost for forming the metallic electrodes is relatively high.

What is needed, therefore, is to provide a durable touch panel and a display device using the same having high sensitivity, accuracy, and brightness.

SUMMARY OF THE INVENTION

In one embodiment, a touch panel includes a first electrode plate and a second electrode plate. The first electrode plate includes a first substrate, a first conductive layer disposed on a lower surface of the first substrate, and two first-electrodes disposed on opposite ends of the first conductive layer. The second electrode plate separates from the first electrode plate and includes a second substrate, a second conductive layer disposed on an upper surface of the second substrate, and two second-electrodes disposed on opposite ends of the second conductive layer. At least one of the first-electrodes and the second-electrodes includes a carbon nanotube layer.

Other advantages and novel features of the present touch panel and the display device using the same will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate at least one embodiment of the present touch panel, in at least one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference will now be made to the drawings to describe, in detail, embodiments of the present touch panel and the display device using the same.

Referring toFIG. 1andFIG. 2, a touch panel10includes a first electrode plate12, a second electrode plate14, and a plurality of dot spacers16disposed between the first electrode plate12and the second electrode plate14.

The first electrode plate12includes a first substrate120, a first conductive layer122, and two first-electrodes124. The first substrate120includes an upper surface and a lower surface, each of which is substantially flat. The two first-electrodes124and the first conductive layer122are located on the lower surface of the first substrate120. The two first-electrodes124are located separately on opposite ends of the first conductive layer122. A direction from one of the first-electrodes124across the first conductive layer122to the other first electrode124is defined as a first direction. The two first-electrodes124are electrically connected with the first conductive layer122.

The second electrode plate14includes a second substrate140, a second conductive layer142, and two second-electrodes144. The second substrate140includes an upper surface and a lower surface, each of which is substantially flat. The two second-electrodes144and the second conductive layer142are located on the upper surface of the second substrate140. The two second-electrodes144are located separately on opposite ends of the second conductive layer142. A direction from one of the second-electrodes144across the second conductive layer142to the other second-electrodes144is defined as a second direction. The two second-electrodes144are electrically connected with the second conductive layer142.

The first direction is perpendicular to the second direction (i.e., the two first-electrodes124are orthogonal to the two second-electrodes144). That is, the two first-electrodes144are aligned parallel to the second direction, and the two second-electrodes146aligned parallel to the first direction.

The first substrate120is a transparent and flexible film/plate. The second substrate140is a transparent plate. The first conductive layer122and the second conductive layer142are conductive indium tin oxide (ITO) layers, carbon nanotube layers, conductive polymer layers, or layers made of any other transparent conductive material. In the present embodiment, the first substrate120is a polyester film, the second substrate140is a glass board, and the first conductive layer122and the second conductive layer142are ITO layers.

In the present embodiment, the two first-electrodes124are disposed on opposite ends of the first conductive layer122along the first direction and electrically connected to the first conductive layer122. The two second-electrodes144are disposed on opposite ends of the second conductive layer142along the second direction and electrically connected to the second conductive layer142. It is to be understood that the first-electrodes124and the second-electrodes144can be respectively disposed either on the first conductive layer122and the second conductive layer142, or on the first substrate120and the second substrate140.

An insulative layer18is provided between the first and the second electrode plates12and14. The first electrode plate12is located on the insulative layer18. The first conductive layer122is opposite to, but is spaced from, the second conductive layer142. The dot spacers16are located on the second conductive layer142. A distance between the second electrode plate14and the first electrode plate12is in an approximate range from 2 to 20 microns. The insulative layer18and the dot spacers16are made of, for example, insulative resin or any other suitable insulative material. Insulation between the first electrode plate12and the second electrode plate14is provided by the insulative layer18and the dot spacers16. It is to be understood that the dot spacers16are optional, particularly when the touch panel10is relatively small. They serve as supports given the size of the span and the strength of the first electrode plate12.

In one suitable embodiment, a transparent protective film126can be further disposed on the upper surface of the first electrode plate12. The transparent protective film126can, rather appropriately, be a slick film and receive a surface hardening treatment to protect the first electrode plate12from being scratched when in use. The transparent protective film126can, suitably, be adhered to the upper surface of the first electrode plate12or combined with the first electrode plate12by hot-pressing method. The transparent protective film126can, beneficially, be a plastic film or a resin film. The material of the resin film can, opportunely, be selected from a group consisting of benzocyclobutenes (BCB), polyester, acrylic resin, polyethylene terephthalate (PET), and any combination thereof. In the present embodiment, the material of the transparent protective film126is PET.

At least one electrode of the two first-electrodes124and the two second-electrodes144can, beneficially, include a carbon nanotube layer. The carbon nanotube layer is formed by a plurality of carbon nanotubes, ordered or otherwise, and has a uniform thickness. Quite suitably, the carbon nanotube layer can further include a carbon nanotube film or a plurality of carbon nanotube films stacked on each other. Alignment of the carbon nanotube films is set as desired. The carbon nanotube film can be an ordered film or a disordered film. In the ordered film, the carbon nanotubes are primarily oriented along a same direction in each film. Different stratums/layers of films can have the nanotubes offset from the nanotubes in other films. In the disordered film, the carbon nanotubes are disordered or isotropic. The disordered carbon nanotubes entangle with each other. The isotropic carbon nanotubes are substantially parallel to a surface of the carbon nanotube film.

The width of the carbon nanotube film can be in the approximate range from 1 micron to 10 millimeters. The thickness of the carbon nanotube film can, advantageously, be in the approximate range from 0.5 nanometers to 100 microns. The carbon nanotubes in the carbon nanotube film include single wall carbon nanotubes, double wall carbon nanotubes, or multi wall carbon nanotubes. Diameters of the single wall carbon nanotubes, the double wall carbon nanotubes, and the multi wall carbon nanotubes can, respectively, be in the approximate range from 0.5 to 50 nanometers, 1 to 50 nanometers, and 1.5 to 50 nanometers.

In the present embodiment, the two first-electrodes122and the two second-electrodes144are both carbon nanotube layers. Each carbon nanotube layer includes a plurality of carbon nanotube films stacked on each other. The alignment directions of the carbon nanotube films are set as desired. Typically, the carbon nanotubes in each carbon nanotube film are aligned substantially parallel to a same direction (i.e., the carbon nanotube film is an ordered film). As shown inFIG. 3, the majority of carbon nanotubes are arraigned along a primary direction; however, the orientation of some of the nanotubes may vary. More specifically, each carbon nanotube film includes a plurality of successive and oriented carbon nanotubes joined end to end by van der Waals attractive force.

Referring toFIGS. 3 and 4, each carbon nanotube film comprises a plurality of successively oriented carbon nanotube segments143joined end-to-end by van der Waals attractive force therebetween. Each carbon nanotube segment143includes a plurality of carbon nanotubes145parallel to each other, and combined by van der Waals attractive force therebetween. The carbon nanotube segments143can vary in width, thickness, uniformity and shape. The carbon nanotubes145in the carbon nanotube film143are also oriented along a preferred orientation.

A method for fabricating an above-described carbon nanotube film includes the steps of: (a) providing an array of carbon nanotubes, specifically and quite suitably, providing a super-aligned array of carbon nanotubes; (b) pulling out a carbon nanotube film from the array of carbon nanotubes, by using a tool (e.g., adhesive tape, pliers, tweezers, or another tool allowing multiple carbon nanotubes to be gripped and pulled simultaneously).

In step (a), a given super-aligned array of carbon nanotubes can be formed by the substeps of: (a1) providing a substantially flat and smooth substrate; (a2) forming a catalyst layer on the substrate; (a3) annealing the substrate with the catalyst layer in air at a temperature in the approximate range from 700° C. to 900° C. for about 30 to 90 minutes; (a4) heating the substrate with the catalyst layer to a temperature in the approximate range from 500° C. to 740° C. in a furnace with a protective gas therein; and (a5) supplying a carbon source gas to the furnace for about 5 to 30 minutes and growing the super-aligned array of carbon nanotubes on the substrate.

In step (a1), the substrate can be a P-type silicon wafer, an N-type silicon wafer, or a silicon wafer with a film of silicon dioxide thereon. Preferably, a 4-inch P-type silicon wafer is used as the substrate.

In step (a2), the catalyst can be made of iron (Fe), cobalt (Co), nickel (Ni), or any alloy thereof.

In step (a4), the protective gas can be made up of at least one of nitrogen (N2), ammonia (NH3), and a noble gas. In step (a5), the carbon source gas can be a hydrocarbon gas, such as ethylene (C2H4), methane (CH4), acetylene (C2H2), ethane (C2H6), or any combination thereof.

The super-aligned array of carbon nanotubes can have a height of about 50 microns to 5 millimeters and include a plurality of carbon nanotubes parallel to each other and approximately perpendicular to the substrate. The carbon nanotubes in the carbon nanotube film include single wall carbon nanotubes, double wall carbon nanotubes, or multi wall carbon nanotubes. Diameters of the single wall carbon nanotubes, the double wall carbon nanotubes, and the multi wall carbon nanotubes can, respectively, be in the approximate range from 0.5 to 50 nanometers, 1 to 50 nanometers, and 1.5 to 50 nanometers.

The super-aligned array of carbon nanotubes formed under the above conditions is essentially free of impurities such as carbonaceous or residual catalyst particles. The carbon nanotubes in the super-aligned array are closely packed together by the van der Waals attractive force.

In step (b), the carbon nanotube film can be formed by the substeps of: (b1) selecting one or more carbon nanotube having a predetermined width from the super-aligned array of carbon nanotubes; and (b2) pulling the carbon nanotubes to form carbon nanotube segments at an even/uniform speed to achieve a uniform carbon nanotube film.

In step (b1), the carbon nanotube segments having a predetermined width can be selected by using an adhesive tape as the tool to contact the super-aligned array. Each carbon nanotube segment includes a plurality of carbon nanotubes parallel to each other. In step (b2), the pulling direction is substantially perpendicular to the growing direction of the super-aligned array of carbon nanotubes.

More specifically, during the pulling process, as the initial carbon nanotube segments are drawn out, other carbon nanotube segments are also drawn out end to end due to van der Waals attractive force between ends of adjacent segments. This process of drawing ensures a substantially continuous and uniform carbon nanotube film having a predetermined width can be formed. Referring toFIG. 3, the carbon nanotube film includes a plurality of carbon nanotubes joined ends to ends. The carbon nanotubes in the carbon nanotube film are all substantially parallel to the pulling/drawing direction of the carbon nanotube film, and the carbon nanotube film produced in such manner can be selectively formed to have a predetermined width. The carbon nanotube film formed by the pulling/drawing method has superior uniformity of thickness and conductivity over a typical disordered carbon nanotube film. Further, the pulling/drawing method is simple, fast, and suitable for industrial applications.

The width of the carbon nanotube film depends on a size of the carbon nanotube array. The length of the carbon nanotube film can be arbitrarily set, as desired. In one useful embodiment, when the substrate is a 4-inch type wafer as in the present embodiment, the width of the carbon nanotube film is in the approximate range from 0.01 centimeter to 10 centimeters, and the thickness of the carbon nanotube film is in the approximate range from 0.5 nanometers to 100 microns. The carbon nanotubes in the carbon nanotube film includes single wall carbon nanotubes, double wall carbon nanotubes, or multi wall carbon nanotubes. Diameters of the single wall carbon nanotubes, the double wall carbon nanotubes, and the multi wall carbon nanotubes can, respectively, be in the approximate range from 0.5 to 50 nanometers, 1 to 50 nanometers, and 1.5 to 50 nanometers.

It is noted that because the carbon nanotubes in the super-aligned array have a high purity and a high specific surface area, the carbon nanotube film is adherent in nature. As such, the carbon nanotube film can be directly adhered to a surface of the first substrate120or the second substrate140and electrically connect to the first conductive layer122and the second conductive layer142to form the two first-electrodes124and the two second-electrodes144. Quite usefully, the two first-electrodes124are respectively adhered on opposite ends of the first conductive layer122along the first direction and electrically connected to the first conductive layer122, and the two second-electrodes144are respectively adhered on opposite ends of the second conductive layer142along the second direction and electrically connected to the second conductive layer142. It is to be understood that the first-electrodes124and the second-electrodes144can be respectively adhered on the first conductive layer122and the second conductive layer142.

It is to be understood that, a plurality of carbon nanotube films can be adhered to a surface of the first substrate120and the second substrate140and can be stacked on each other to form the carbon nanotube layers. The number of the films and the angle between the aligned directions of two adjacent films can be set as desired. When the carbon nanotube films are adhered along a same direction, the carbon nanotubes in the whole carbon nanotube layer are arranged along the same direction. When the carbon nanotube films are adhered along different directions, an angle α between the alignment directions of the carbon nanotubes in each two adjacent carbon nanotube films is in the range 0<α≦90°. The angle α is the difference in the two pulling directions of the adjacent carbon nanotube films. The adjacent carbon nanotube films are combined by van de Waals attractive force to form a stable carbon nanotube layer.

An additional step of treating the carbon nanotube films in the touch panel10with an organic solvent can be further provided. Specifically, the carbon nanotube film can be treated by applying organic solvent to the carbon nanotube film to soak the entire surface of the carbon nanotube film. The organic solvent is volatilizable and can, suitably, be selected from the group consisting of ethanol, methanol, acetone, dichloroethane, chloroform, any appropriate mixture thereof. In the present embodiment, the organic solvent is ethanol. After being soaked by the organic solvent, microscopically, carbon nanotube strings will be formed by adjacent carbon nanotubes in the carbon nanotube film, that are able to do so, bundling together, due to the surface tension of the organic solvent. In one aspect, part of the carbon nanotubes in the untreated carbon nanotube film that are not adhered on the substrate will come into contact with the substrate120,140after the organic solvent treatment due to the surface tension of the organic solvent. Then the contacting area of the carbon nanotube film with the substrate will increase, and thus, the carbon nanotube film can firmly adhere to the surface of the substrate120,140. In another aspect, due to the decrease of the specific surface area via bundling, the mechanical strength and toughness of the carbon nanotube film are increased and the coefficient of friction of the carbon nanotube films is reduced. Macroscopically, the film will be an approximately uniform carbon nanotube film.

It is to be understood that, a plurality of carbon nanotube films can, advantageously, be adhered to the first substrate120and/or the second substrate140and stacked on each other to form the carbon nanotube layer. The number of the films and the angle between the aligned directions of two adjacent films can be set as desired. The adjacent carbon nanotube films are combined by van de Waals attractive force to form a stable carbon nanotube layer. In the present embodiment, a plurality of carbon nanotube films are adhered on the first substrate120along different directions and electrically connected to the first conductive layer122to form the two first-electrodes124, and adhered on the second substrate140along different directions and electrically connected to the second conductive layer142to form the two second-electrodes144.

At least one of the first conductive layer122and the second conductive layer142can include a carbon nanotube layer. The fabricating method of the first conductive layer122and the second conductive layer142is similar to the above-described fabricating method of the first-electrodes and the second-electrodes. The carbon nanotube layer can include one or a plurality of carbon nanotube films. It is to be understood that the size of the touch panel10is not confined by the size of the carbon nanotube films. When the size of the carbon nanotube films is smaller than the desired size of the touch panel10, a plurality of carbon nanotube films can be disposed side by side and cover the entire surface of the first substrate120and the second substrate140. Unlike the first-electrodes124and the second-electrodes144, the carbon nanotube films in the first conductive layer122are aligned along the first direction, and the carbon nanotube films in the second conductive layer142are aligned along the second direction.

The touch panel10can further include a shielding layer (not shown) disposed on the lower surface of the second substrate140. The material of the shielding layer can be conductive resin films, carbon nanotube films, or other flexible and conductive films. In the present embodiment, the shielding layer is a carbon nanotube film. The carbon nanotube film includes a plurality of carbon nanotubes, and the alignment of the carbon nanotubes therein can be set as desired. In the present embodiment, the carbon nanotubes in the carbon nanotube film of the shielding layer can be arranged along a same direction. The carbon nanotube film is connected to the ground and plays a role of shielding, and, thus, enables the touch panel10to operate without interference (e.g., electromagnetic interference).

Referring toFIG. 5, a display device100includes the touch panel10, a display element20, a first controller30, a central processing unit (CPU)40, and a second controller50. Quite suitably, the touch panel10is opposite and adjacent to the display element20and is connected to the first controller30by an external circuit. Quite usefully, the touch panel10can be spaced at a distance from the display element20or can be installed directly on the display element20. The first controller30, the CPU40, and the second controller50are electrically connected. The CPU40is connected to the second controller50to control the display element20.

When the touch panel10includes a shielding layer22, a passivation layer24can be disposed on a surface of the shielding layer22, facing away from the second substrate140. The material of the passivation layer24can be selected from a group consisting of benzocyclobutenes, polyesters, acrylic resins, polyethylene terephthalate, and any combination thereof. The passivation layer24can be spaced at a certain distance from the display element20or can be directly installed on the display element20. When the passivation layer24is spaced at a distance from the display element30, understandably, two or more spacers can be used. Thereby, a gap26is provided between the passivation layer24and the display element20. The passivation layer24protect the shielding layer22from chemical damage (e.g., humidity of the surrounding) or mechanical damage (e.g., scratching during fabrication of the touch panel).

In operation, a voltage of 5V is respectively applied to the two first-electrodes124of the first electrode plate12and the two second-electrodes144of the second electrode plate14. A user operates the display by pressing the first electrode plate12of the touch panel10with a finger, a pen60, or the like while visually observing the display element20through the touch panel. This pressing causes a deformation70of the first electrode plate12. The deformation70of the first electrode plate12causes a connection between the first conductive layer122and the second conduction layer142of the second electrode plate14. Changes in voltages in the first direction of the first conductive layer142and the second direction of the second conductive layer142can be detected by the first controller30. Then, the first controller30transforms the changes in voltages into coordinates of the pressing point and sends the coordinates thereof to the CPU40. The CPU40then sends out commands according to the coordinates of the pressing point and controls the display of the display element20.

The properties of the carbon nanotubes provide superior toughness, high mechanical strength, and uniform conductivity to the carbon nanotube film. Thus, the touch panel and the display device using the same adopting the carbon nanotube film are durable and highly conductive. Further, the pulling method for fabricating the carbon nanotube film is simple, and the adhesive carbon nanotube film can be disposed directly on the substrate. As such, the method for fabricating the carbon nanotube film is suitable for the mass production of touch panels and display devices using the same and reduces the cost thereof. Additionally, the carbon nanotube film has uniform conductivity and can significantly decrease a contact resistance between the electrodes and the conductive layers especially for the touch panel adopting the carbon nanotube layers as the conductive layers.