JP2013134208A - Pressure sensitive element containing carbon nanotube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure-sensitive element having a new structure using a thin film containing carbon nanotubes.SOLUTION: The pressure-sensitive element containing carbon nanotubes includes a thin film layer containing carbon nanotubes, and a first electrode and a second electrode formed in contact with the thin film layer. The thin film layer contains an electrically insulating substance.

Description

  The present invention relates to a pressure-sensitive element containing carbon nanotubes.

  The carbon nanotube has a structure in which a graphene sheet is rolled into a cylindrical shape, and generally has a straw-like or straw-like structure. Carbon nanotubes are single-walled carbon nanotubes (SWCNT; Single-Walled Carbon Nanotube) consisting of a single tube, double-walled carbon nanotubes (DWCNT; Double-Walled Carbon NanoTube) with a structure in which two tubes with different diameters are stacked, diameter Are classified into multi-walled carbon nanotubes (MWCNT; Multi-Walled Carbon Nanotubes) having a structure in which a large number of different tubes are laminated, and applied research utilizing the characteristics of each of the structures is being promoted.

  In order to form a thin film by dispersing many carbon nanotubes, a thin film can be easily formed by using a solution or dispersion of carbon nanotubes (see, for example, Non-Patent Documents 1 to 4).

  On the other hand, with the development of ubiquitous society, the development of information input / output means is remarkable. Information output means have been developed first, and flat panel displays (FPD) such as liquid crystal displays (LCD) have become mainstream of information display devices. As flat panel displays different from LCDs, self-luminous displays such as organic electroluminescent displays (OLEDs) and plasma displays (PDPs) have also been put into practical use, depending on features such as size, brightness (luminance), and resolution. It is used properly.

  In addition, development of a nonvolatile display device aiming at low power consumption has been promoted, and a part of the electronic paper has been commercialized. For the development of a cloud information society, which is a further developed society of the ubiquitous information society, development of interactive display devices including information input means in these information display devices is being actively conducted. In order to realize an interactive display device, a method generally used at present is a touch panel system that allows intuitive input of information from displayed information. At present, there are two main types of touch panels, a resistance type and a capacitance type. If the touch panel has a size of about 21 inches, the two types are almost adopted.

N. Saran et al., “Fabrication and Characterisation of Thin Films of Single-Walled Carbon Nanotubes Bundles on Flexible Plastic Substrates”, J. Am. Am. Chem. Soc. 126, 4462, 2004 Z. Wu et al., “Transparent, conductive carbon nanotubes,” SCIENCE, 305, 1273, 2004. M.M. Zhang et al., “Strong, transparent, multi-functional, carbon nanotube sheets”, SCIENCE, 309, 1215, 2005. Y. Zhou et al., “A method of printing carbon nanotube thin films”, Appl. Phys. Lett. 88, 123109, 2006

  These methods are easy to manufacture and the specifications are almost fixed, so the adoption rate is high. However, when the screen becomes large, problems such as an increase in resistance value and an increase in power consumption occur, and 20 inches. It is difficult to apply to a size exceeding. In order to solve this problem, the adoption of another method has been promoted. However, as one of the methods being studied as a solution method, an active matrix is being studied. In particular, in the case of a flexible display or the like, a method using an IR sensor cannot be applied, and development of an active matrix method that can easily detect a change in physical quantity of each pixel is expected.

  Of the current touch panel methods, the two main methods are the resistance type and the capacitance type. However, each method has its own characteristics, and each application product depends on its characteristics. It is the actual situation that is used properly.

  In the case of the resistance type, it can be used by using a tool such as a pen in addition to the hand, the finger, and the resistance type is used particularly for applications that require pen input. On the other hand, since a general resistance type touch panel cannot support a plurality of inputs (multi-touch), the use is limited to a single input.

  On the other hand, the capacitance type is compatible with multi-touch input, so it can be used for multiple inputs, and can be input with two fingers to widen or narrow the field of view. It is a method that can be input manually. On the other hand, since the capacitive touch panel cannot handle general pen input, it is not suitable for inputting a fine pattern. As described above, a touch panel that is currently in practical use requires a very complicated structure if it can handle two general input methods such as multi-touch and pen input.

  In addition, when an active matrix type input method is incorporated in a display device, the display pixels and the input pixels are either superimposed vertically or arranged horizontally (horizontally), but vertically When overlapping, the brightness as a display is impaired, and the problem that the whole thickness will become thick generate | occur | produces. When arranged side by side, the display pixel area becomes small, and this also causes problems such as a dark screen.

  An object of the present invention is to provide a pressure-sensitive element having a new structure using a thin film containing carbon nanotubes.

  The inventor of the present application thought that the amount of current can be changed by performing some operation on the carbon nanotube-containing layer, because the conductivity of the layer containing the carbon nanotube changes depending on the concentration of the carbon nanotube. . As a result of repeated studies, it was discovered that the amount of current can be changed by applying pressure to a layer containing carbon nanotubes, and a configuration that can be used as a pressure-sensitive element has been invented.

  According to a first aspect of the present invention, a thin film layer containing carbon nanotubes, and a first electrode and a second electrode formed in contact with the thin film layer, the thin film layer contains an electrically insulating material. A carbon nanotube-containing pressure sensitive element is provided.

  According to a second aspect of the present invention, a thin film layer containing carbon nanotubes, a first electrode and a second electrode formed in contact with the thin film layer, and between the first electrode and the second electrode A carbon nanotube-containing sensation comprising: a third electrode for controlling a current flowing through the electrode; and an insulating layer formed between the thin film layer and the third electrode, wherein the thin film layer contains an electrically insulating material. A pressure element is provided.

  According to a third aspect of the present invention, there is provided a pressure sensitive sensor sheet in which the carbon nanotube-containing pressure sensitive elements described above are arranged in a matrix.

  In a fourth aspect of the present invention, the method for manufacturing a carbon nanotube-containing pressure sensitive element according to the present invention is the above-described method for manufacturing a carbon nanotube pressure-sensitive element, the step of forming an insulating layer on a substrate And a step of forming a thin film layer containing carbon nanotubes on the insulating layer, and the step of forming the thin film layer includes applying or printing a dispersion of carbon nanotubes to form the thin film layer. It is characterized by.

  According to the present invention, it is possible to obtain a pressure-sensitive element that uses a thin film layer containing carbon nanotubes and can change a flowing current according to an input pressure.

  The reason why the layer containing carbon nanotubes has a pressure-sensitive effect is not fully understood, but the layer containing no carbon nanotubes does not have a pressure-sensitive effect. This is probably because the resistance value decreases due to an increase in the number of contacts between carbon nanotubes and a reduction in the distance between carbon nanotubes.

It is a schematic sectional drawing of the pressure sensitive element which concerns on the 1st Embodiment of this invention. It is a schematic sectional drawing of the pressure sensitive element which concerns on the 2nd Embodiment of this invention. It is a schematic sectional drawing of the pressure sensitive element which concerns on the 3rd Embodiment of this invention. It is a schematic sectional drawing of the pressure sensitive element which concerns on the 4th Embodiment of this invention. It is the schematic which shows the electric current change in the pressure sensitive element shown in the Example of this invention.

  In the first aspect, the first electrode and the second electrode are formed on an insulating layer, and the thin film layer is formed between the first electrode and the second electrode on the insulating layer. preferable.

  In a second aspect, it is preferable that the thin film layer is formed on the insulating layer, and the first electrode and the second electrode are formed on the thin film layer.

  In a second aspect, the first electrode is formed on the insulating layer, the thin film layer is formed on the insulating layer so as to cover the first electrode, and the second electrode is formed on the thin film. It is preferably formed on the layer.

  In the first or second aspect, it is preferable that the electrically insulating substance contained in the thin film layer is a natural rubber or a synthetic rubber material.

  In addition, it is also preferable that the electrical insulating substance contained in the thin film layer is a general polymer material, particularly an acrylic polymer material. As this acrylic polymer material, for example, polymethyl methacrylate can be used.

  Moreover, it is preferable that carbon nanotube content of a thin film layer is 95 weight% or more.

(Embodiment 1)
A pressure-sensitive element according to the first embodiment of the present invention will be described. FIG. 1 shows a schematic cross-sectional view of a pressure-sensitive element according to the first embodiment of the present invention. The pressure sensitive element 10 includes a substrate 11, a first electrode 15 and a second electrode 16 formed on the substrate 11, and a thin film layer formed between and in contact with the first electrode 15 and the second electrode 16. 14.

  The thin film layer 14 contains carbon nanotubes. Preferably, 95 mass% or more of the thin film layer 14 is a carbon nanotube. Single-walled carbon nanotubes (SWCNT) can be used as the carbon nanotubes. If the semiconductor characteristic is shown, a double-walled carbon nanotube (DWCNT), a multi-walled carbon nanotube (MWCNT), and carbon nanohorn can also be used as a carbon nanotube. Alternatively, it may be a mixture of a plurality of carbon nanotubes. When single-walled carbon nanotubes are used, the diameter is preferably 0.5 nm to 2.0 nm, and more preferably 0.7 nm to 1.2 nm. The length of the single-walled carbon nanotube is preferably 0.5 μm to 10 μm, and more preferably 0.7 μm to 2.0 μm.

  The thin film layer 14 further includes an electrically insulating material. This may be, for example, a natural rubber or a synthetic rubber material or a polymer substance. As the polymer substance, an acrylic polymer material, particularly polymethyl methacrylate can be preferably used.

  With such a configuration, it was found that the amount of current flowing between the first electrode 15 and the second electrode 16 increases when pressure is applied to the thin film layer 14.

(Embodiment 2)
A pressure-sensitive element and a method for manufacturing the same according to the second embodiment of the present invention will be described. FIG. 2 is a schematic cross-sectional view of a pressure-sensitive element according to the second embodiment of the present invention. The pressure-sensitive element shown in FIG. 2 has the same structure as that generally known as a field effect transistor.

  As shown in FIG. 2, the pressure sensitive element 20 includes a substrate 21, a third electrode 22 formed on the substrate 21, an insulating layer 23 formed to cover the third electrode 22, and an insulating layer 23. And the thin film layer 24 formed between the first electrode 25 and the second electrode 26.

  The first electrode 25 and the second electrode 26 function as a source electrode and a drain electrode. The third electrode 22 functions as a gate electrode. That is, the current flowing between the first electrode 25 and the second electrode 26 is controlled by applying a voltage to the third electrode 22.

  The thin film layer 24 contains carbon nanotubes. The properties of the carbon nanotube are the same as those described in the first embodiment. Moreover, the thin film layer 2 contains an electrically insulating substance. This electrically insulating material is the same as that described in the first embodiment.

  The method for producing the carbon nanotube is not particularly limited. As a method for producing carbon nanotubes, for example, a CVD method, a laser ablation method, or the like can be used.

  The insulating layer 23 can be used without particular limitation as long as it is a material having electrical insulation. For example, materials that can be used for the insulating layer 23 include inorganic oxide thin films such as silicon oxide, polymer materials such as polyimide and polymethyl methacrylate, but are not limited to the exemplified materials. A laminated structure or a mixture of three kinds or three kinds of materials may be used.

  The material that can be used as the substrate 21 is not particularly limited as long as it can support the pressure-sensitive element having this structure. For example, an inorganic material such as glass or silicon, or an organic material such as acrylic resin can be used. Materials can be used. If the field effect transistor can be supported by other methods, the substrate may not be used.

  The thin film layer 24 may be formed by either a wet process or a dry process as long as the thin film can be formed uniformly. When forming a uniform thin film of single-walled carbon nanotubes, it is preferable to use a wet process. When the thin film layer 24 is formed by a wet process, for example, the thin film layer 24 can be formed by preparing an ink containing carbon nanotubes and applying or printing the ink. The carbon nanotube content in the carbon nanotube ink is preferably 1% to 10% from the viewpoint of consistency.

  Materials that can be used for the first electrode 25, the second electrode 26, and the third electrode 22 include indium tin oxide alloy (ITO), tin oxide (NESA), gold, silver, platinum, copper, indium, aluminum, In addition to metallic conductors such as magnesium, magnesium-indium alloy, magnesium-aluminum alloy, aluminum-lithium alloy, aluminum-scandium-lithium alloy, magnesium-silver alloy, organic material-based conductors such as conductive polymers are exemplified. However, it is not limited to these.

  The 1st electrode 25, the 2nd electrode 26, and the 3rd electrode 22 can be produced by normal electrode formation processes, such as a vacuum evaporation method, a sputtering method, an etching method, and lift-off, for example. Moreover, when forming an electrode with organic materials, such as a conductive polymer, solution processes, such as a spin coat method and a dip method, can also be utilized, for example.

  The pressure-sensitive element 20 according to the second embodiment can be manufactured, for example, by the following process. First, the third electrode 22 is formed on the substrate 21. Next, a natural rubber, synthetic rubber material or other insulating polymer compound is dissolved in water or an organic solvent to prepare a solution, and the solution is applied or printed on the third electrode 22 to form a thin film of the insulating layer 23. Form. Next, the first electrode 25 and the second electrode 26 are formed on the insulating layer 23 at a predetermined interval. Next, a dispersion liquid in which carbon nanotubes are dispersed in water or an organic solvent is applied on the first electrode 25 and the second electrode 26 to form the thin film layer 24.

(Embodiment 3)
FIG. 3 is a schematic cross-sectional view of a pressure-sensitive element according to the third embodiment of the present invention. 3 is formed on the substrate 31, the third electrode 32 formed on the substrate 31, the insulating layer 33 formed on the third electrode 32, and the insulating layer 33. A thin film layer 34, and a first electrode 35 and a second electrode 36 formed on the thin film layer 34.

  The composition of the substrate 31, the first electrode 35, the second electrode 36, the third electrode 32, the insulating layer 33, and the thin film layer 34 in the third embodiment can be configured similarly to the second embodiment. Even with such a structure, the same effects as those of the first and second embodiments can be obtained.

(Embodiment 4)
FIG. 4 is a schematic cross-sectional view of a pressure-sensitive element according to the fourth embodiment of the present invention. 4 is formed on the substrate 41, the third electrode 42 formed on the substrate 41, the insulating layer 43 formed on the third electrode 42, and the insulating layer 43. A thin film layer 44 and a second electrode 46 formed on the thin film layer 44. The first electrode 45 is formed on the insulating layer 43 and inside the thin film layer 44.

  The composition of the substrate 41, the first electrode 45, the second electrode 46, the third electrode 42, the insulating layer 43, and the thin film layer 44 in the fourth embodiment can be configured in the same manner as in the second embodiment. Even with such a structure, the same effects as those of the first and second embodiments can be obtained.

(Embodiment 5)
The pressure-sensitive sensor sheet can be formed by arranging the pressure-sensitive elements shown in the above embodiment in a matrix. When the pressure-sensitive elements according to Embodiment 1 are arranged in a matrix, a passive matrix pressure-sensitive sheet is obtained. When the pressure-sensitive elements according to Embodiment 2 and below are arranged in a matrix, an active matrix pressure-sensitive sheet is obtained. Such a sheet can be used as a touch sensor, and in particular, an active matrix pressure-sensitive sheet has a simplified structure because the pressure-sensitive element of the present invention also serves as an active element, compared to a conventional active touch sensor. The size can be reduced.

  As described above, by using the pressure sensitive element according to the present invention as a part of the driving transistor of the display panel, an information input device (such as a touch panel) that maintains a good aperture ratio without impairing the size of the display pixel. Can be obtained. Furthermore, it is possible to provide an input device having a simple structure that can handle both multi-touch and pen input.

Example 1
(Production of pressure-sensitive element)
A carbon nanotube-containing pressure-sensitive element having a thin film layer formed of carbon nanotubes was produced. What is described here is a pressure-sensitive element (similar structure to a field effect transistor) according to the second embodiment shown in FIG. First, a third electrode (gate electrode) was formed on a polyimide substrate by depositing chromium with a thickness of 100 nm by a vacuum deposition method. Next, a film having a film thickness of 300 nm is formed on the third electrode by spin coating (2000 rpm, 60 seconds) using a solution obtained by dissolving 1.5 wt% of the polymer compound synthesized by the above method in chloroform, An insulating layer was formed. Next, a magnesium-silver alloy was formed in a stripe shape with a thickness of 100 nm on the insulating layer through a metal mask to form a first electrode and a second electrode (corresponding to a source electrode and a drain electrode). Next, carbon nanotubes (CNI, purified Grecard) were mixed in dichloroethane at 5 ppm, treated with an ultrasonic device for 1 hour, monodispersed, further treated with an ultracentrifuge for 20 minutes, and impurities such as metals Then, polymethyl methacrylate was mixed with 10 times the amount of carbon nanotubes to prepare a carbon nanotube ink. This carbon nanotube ink was formed on the insulating layer by spin coating (2000 rpm, 60 seconds) to produce a carbon nanotube-containing pressure sensitive element.

(Measurement of pressure response)
The pressure responsiveness of the produced carbon nanotube pressure sensitive element was measured. FIG. 5 shows a schematic diagram for explaining the pressure responsiveness. The pressure responsiveness applies a voltage of -20V to the gate electrode, sweeps the voltage from 0V to -5V (0.1V step) to the drain electrode, measures the electrical characteristics, and applies the pressure to the carbon nanotube thin film layer. Evaluation was made based on the value of the drain current when not applied and when applied.

  The current value obtained when no pressure was applied was increased by applying pressure, and the applied pressure could be detected.

(Example 2)
A pressure-sensitive element having the structure shown in Embodiment 3 was manufactured as follows. A third electrode (gate electrode) was formed on a polyimide substrate by depositing chromium with a thickness of 100 nm by vacuum deposition. Next, a film having a film thickness of 300 nm is formed on the third electrode by spin coating (2000 rpm, 60 seconds) using a solution obtained by dissolving 1.5 wt% of the polymer compound synthesized by the above method in chloroform, An insulating layer was formed. On the insulating layer, carbon nanotubes (CNI, purified Grecard) are mixed in 5 ppm in dichloroethane, treated for 1 hour with an ultrasonic device, monodispersed, and further treated for 20 minutes with an ultracentrifuge. After removing impurities such as carbon nanotubes, a carbon nanotube thin film was formed by spin coating (2000 rpm, 60 seconds) using carbon nanotube ink prepared by mixing polymethyl methacrylate with 10 times the amount of carbon nanotubes. . Next, a magnesium-silver alloy is formed in a stripe shape with a film thickness of 100 nm on the carbon nanotube thin film through a metal mask to form a first electrode and a second electrode (source electrode and drain electrode), A carbon nanotube thin film transistor was fabricated.

  Also in the pressure sensitive element thus manufactured, the same properties as those of the pressure sensitive element of Example 1 were obtained.

(Example 3)
A pressure-sensitive element having the structure shown in Embodiment 4 was manufactured as follows. A third electrode (gate electrode) was formed on a polyimide substrate by depositing chromium with a thickness of 100 nm by vacuum deposition. Next, a film having a film thickness of 300 nm is formed on the third electrode by spin coating (2000 rpm, 60 seconds) using a solution obtained by dissolving 1.5 wt% of the polymer compound synthesized by the above method in chloroform, An insulating layer was formed. On the insulating layer, a magnesium-silver alloy was formed in a stripe shape with a thickness of 100 nm through a metal mask to form a first electrode (source electrode). On the insulating layer including the first electrode, 5 ppm of carbon nanotube (CNI, purified Grecard) is mixed in dichloroethane, treated with an ultrasonic device for 1 hour, monodispersed, and further treated with an ultracentrifuge. After removing impurities such as metals, carbon nanotubes were further prepared by spin coating (2000 rpm, 60 seconds) using carbon nanotube ink prepared by mixing polymethyl methacrylate with 10 times the amount of carbon nanotubes. A thin film was formed. Next, a magnesium-silver alloy was formed into a stripe shape with a thickness of 100 nm on the carbon nanotube thin film through a metal mask to form a second electrode (drain electrode), thereby producing a carbon nanotube thin film transistor.

  Also in the pressure sensitive element thus manufactured, the same properties as those of the pressure sensitive element of Example 1 were obtained.

  The pressure-sensitive element and the manufacturing method thereof according to the present invention have been described based on the above-described embodiment. However, the present invention is not limited to the above-described embodiment, and the entire disclosure (including claims and drawings) of the present invention. Within the frame, the embodiments and examples can be changed and adjusted based on the basic technical concept. Further, various combinations or selections of various disclosed elements (including each element of each claim, each element of each embodiment, each element of each drawing, etc.) are possible within the scope of the claims of the present invention. It is. That is, the present invention of course includes various variations and modifications that could be made by those skilled in the art according to the entire disclosure including the claims and the technical idea.

DESCRIPTION OF SYMBOLS 10 Pressure sensitive element 11 Board | substrate 14 Thin film layer 15 1st electrode 16 2nd electrode 20, 30, 40 Pressure sensitive element 21, 31, 41 Substrate 22, 32, 42 3rd electrode 23, 33, 43 Insulating layers 24, 34, 44 Thin film layer 25, 35, 45 1st electrode 26, 36, 46 2nd electrode

Claims (10)

A thin film layer containing carbon nanotubes;
A first electrode and a second electrode formed in contact with the thin film layer;
A carbon nanotube-containing pressure-sensitive element, wherein the thin film layer contains an electrically insulating substance.   The first electrode and the second electrode are formed on an insulating layer, and the thin film layer is formed between the first electrode and the second electrode on the insulating layer. 2. A carbon nanotube-containing pressure-sensitive element according to 1. A thin film layer containing carbon nanotubes;
A first electrode and a second electrode formed in contact with the thin film layer;
A third electrode for controlling a current flowing between the first electrode and the second electrode;
An insulating layer formed between the thin film layer and the third electrode,
A carbon nanotube-containing pressure-sensitive element, wherein the thin film layer contains an electrically insulating substance.   4. The carbon nanotube-containing pressure sensing device according to claim 3, wherein the thin film layer is formed on the insulating layer, and the first electrode and the second electrode are formed on the thin film layer. 5. element.   The first electrode is formed on the insulating layer, the thin film layer is formed on the insulating layer so as to cover the first electrode, and the second electrode is formed on the thin film layer. The carbon nanotube-containing pressure-sensitive element according to claim 3, wherein   The carbon nanotube-containing pressure-sensitive element according to any one of claims 1 to 5, wherein the electrically insulating substance contained in the thin film layer is a natural rubber or a synthetic rubber material.   The carbon nanotube-containing pressure-sensitive element according to claim 1, wherein the electrically insulating substance contained in the thin film layer is an acrylic polymer material.   The carbon nanotube-containing pressure-sensitive element according to claim 7, wherein the acrylic polymer material is polymethyl methacrylate.   A pressure-sensitive sensor sheet in which the carbon nanotube-containing pressure-sensitive elements according to any one of claims 1 to 8 are arranged in a matrix. A method for producing a carbon nanotube-containing pressure-sensitive element according to any one of claims 1 to 9,
Forming an insulating layer on the substrate;
Forming a thin film layer containing carbon nanotubes on the insulating layer,
The method for producing a carbon nanotube-containing pressure-sensitive element is characterized in that the step of forming the thin film layer comprises applying or printing a dispersion of carbon nanotubes to form the thin film layer.

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