JPWO2009116502A1 - Membrane switch and manufacturing method thereof - Google Patents

Abstract

Provided are a membrane switch and a method for manufacturing the same that enable multi-point input without impairing cost advantages. A first flexible substrate (11) and a second flexible substrate (21) are provided, and a semiconducting carbon nanotube paste (13) is used instead of the carbon paste (23) as one contact material of the membrane switch. The other contact material is carbon paste (23). By using carbon nanotubes, functions equivalent to diodes are realized by printing.

Description

  The present invention relates to a membrane switch including a flexible substrate and a manufacturing method thereof.

  The membrane switch is formed by facing two flexible substrates on which contacts and wiring are printed and overlapping them with an insulating spacer interposed therebetween. The contacts printed on each flexible substrate face each other through a hole formed in the spacer. When a force is applied from the outside to dent the flexible substrate, the contacts come into contact and turn on. In general, a silver paste is used as a conductive paste for forming wirings by printing. However, since silver lacks stability, carbon paste is used as a protective / contact material for covering and protecting the silver and obtaining good switching characteristics. These are printed on the surface of the flexible substrate by screen printing or the like. A polyester film or a polycarbonate film is used as the flexible substrate. Membrane switches are suitable for mass production because they are made by printing, and more than 100 switches can be printed on one sheet at a time, so they are often used for computer keyboards.

  In the case of a keyboard, it is necessary to know the state of many switches. As a method therefor, there is a method called a switch matrix in which keys (switches) are divided into rows and columns and circuits are arranged in a grid pattern. In this method, a switch is provided at each intersection of a row and a column. When viewed from the computer, if the column is output and the row is input, the state of each switch can be known by changing the potential of each column in order and scanning the potential appearing at the port on the row side.

  However, in this method, if a plurality of keys are pressed at the same time, an unintended key signal is generated. This is called a “phantom key” phenomenon, and a signal flows between a row and a column of keys that are not pressed via a plurality of keys that are pressed. In order to avoid this, a diode for controlling the signal flow in one direction may be connected in series with each key. By this avoidance measure, signal wraparound can be prevented, and multipoint input can be performed in a switch having a matrix configuration.

As a technique relating to a membrane switch for forming a flexible substrate as described above by printing, inventions of a switch and a wireless keyboard in which the number of parts is deleted are disclosed (for example, Patent Documents 1 and 2). In addition, carbon nanotubes (CNT) having both elasticity and toughness are used as movable beams, and electrical repulsion between a floating gate electrode provided on the beam and a forward gate electrode provided on the electrode is used. A technique is also disclosed in which a deflected beam is brought into contact with an output electrode to form a switch (for example, Patent Document 3). Furthermore, a technique of using a conductive fiber such as carbon fiber as a brush to configure a switch or the like is also disclosed (for example, Patent Document 4).
Japanese Patent Laying-Open No. 2005-038809 JP 2007-241887 A JP 2006-318670 A Japanese Patent Publication No. 07-11702

  As a workaround for the above-mentioned problem, a diode that controls the signal flow in one direction was connected in series with each key. However, in a membrane switch that uses a diode, the switch mechanism is made by printing. It is difficult to connect a diode to each switch. That is, it is necessary to fix a large number of diode chips so as not to be peeled off from the flexible substrate, and to be electrically connected so as not to cause disconnection due to bending. The manufacturing cost for realizing it is enormous, and the cost advantage inherent to the membrane switch is impaired. The features such as thinness, light weight and flexibility are lost at the same time.

  Therefore, in the present invention, attention was focused on carbon nanotubes (CNT). The carbon nanotube (CNT) is a carbon atom arrangement structure similar to that of graphite having a tube shape with a nanoscale diameter. CNT, like graphite, has good electrical conduction characteristics and excellent chemical stability, but exhibits metallic or semiconducting electrical characteristics depending on its diameter and winding method. In recent years, it has become possible to extract only CNTs having semiconducting characteristics due to the progress of chemical methods. The semiconductor CNT obtained by this method can be used as a semiconductor paste that can be applied and printed.

  None of the above patent documents disclose a technique that can solve the above-described problem. The present invention has been made in order to solve the above-described problem. However, Patent Document 3 is different from the technique of the present invention described later in that the deflection of the CNT that is a beam is used. Further, Patent Document 4 is a technique that uses contact at the tip of a conductive fiber, and the diameter of the conductive fiber is thick, which is different from the technique of the present invention described later.

  The present invention has been made in view of such circumstances, a membrane switch that uses carbon nanotubes to realize functions equivalent to those of a diode by printing, and enables multipoint input without impairing cost advantage, and the same An object is to provide a manufacturing method.

  The membrane switch of the present invention comprises a first flexible substrate and a second flexible substrate, and the first flexible substrate is characterized in that carbon nanotubes are provided on the surface.

  The method for manufacturing a membrane switch of the present invention is a method for manufacturing a membrane switch including a first flexible substrate and a second flexible substrate, and includes a step of disposing carbon nanotubes on the surface of the first flexible substrate. It is characterized by.

  According to the present invention, it is possible to provide a membrane switch and a method of manufacturing the same that enable multipoint input by providing diode characteristics to the contacts while maintaining low cost by printing the membrane switch.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 shows an example of a cross-sectional structure of a membrane switch according to an embodiment of the present invention. As shown in FIG. 1, the membrane switch includes an insulating spacer 3, flexible substrates 11 and 21, wirings 12 and 22, semiconductor carbon nanotubes 13, and carbon 23. The membrane switch according to the embodiment of the present invention is configured such that the wiring 12 and the semiconductor carbon nanotube 13 provided on the flexible substrate 11 and the wiring 22 and the carbon 23 provided on the flexible substrate 21 are overlapped so as to face each other. Yes. The insulating spacer 3 is provided except for the portion where the semiconductor carbon nanotubes 13 and the carbon 23 are provided.

  The flexible substrates 11 and 21 are used, for example, by processing a material such as polyethylene terephthalate (PET), polyethylene naphthalate, polyphenylene sulfide, polyetherimide, polyimide or the like into a film. It is suitably selected according to the conditions. As a material for forming the wirings 12 and 22, a conductive paste such as a silver paste or a carbon paste is used, but a metal foil made of a metal such as copper, silver, or gold may be used. The semiconductor carbon nanotube 13 may be a commercially available semiconductor-separated carbon nanotube paste. Carbon 23 is carbon paste. The insulating spacer 3 may be the same material as the flexible substrate.

  The reason why the membrane switch is configured as shown in FIG. 1 is that it has been found that when a semiconductor carbon nanotube paste and a carbon paste are brought into contact with each other, diode characteristics are exhibited. That is, a function similar to connecting a diode in series with a switch can be realized by simply replacing one carbon paste with a semiconductor carbon nanotube. The diode is considered to operate as a metal / semiconductor junction diode. It is also possible to replace the carbon 23 shown in FIG. 1 with the semiconductor carbon nanotube 13 as the contact material, and it is not limited to replacing only one carbon paste with the semiconductor carbon nanotube.

(Embodiment 2)
FIG. 2 shows an example of a cross-sectional structure of the membrane switch according to the embodiment of the present invention. Basically, it is the same as in Embodiment 1 described above, but 13 ′ is an N-type carbon nanotube paste, and 23 ′ is a P-type carbon nanotube paste.

  The reason why the membrane switch is configured as shown in FIG. 2 is that it has been found that when an N-type semiconductor carbon nanotube paste and a P-type semiconductor carbon nanotube paste are brought into contact with each other, diode characteristics are exhibited. The diode characteristic is similar to that of a PN junction type diode.

  According to this embodiment, the functionality of the membrane paste can be enhanced by using a carbon nanotube paste as an alternative to the carbon paste constituting the membrane switch. That is, it is possible to provide a membrane switch and a membrane switch manufacturing method that enable multipoint input by providing diode characteristics to the contacts while maintaining low cost by printing the membrane switch.

  Although specifically described based on the preferred embodiments, the present invention is not limited to the above-described membrane switch and the manufacturing method thereof, and it goes without saying that various modifications can be made without departing from the scope of the invention. Yes.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2008-070417 for which it applied on March 18, 2008, and takes in those the indications of all here.

It is a schematic diagram which shows the example of the cross-section of the membrane switch which concerns on embodiment of this invention. It is a schematic diagram which shows the example of the cross-section of the membrane switch which concerns on embodiment of this invention.

Explanation of symbols

3 Insulating spacer 11 Flexible substrate 12 Wiring 13 Semiconductor carbon nanotube 13 'N-type semiconductor carbon nanotube 21 Flexible substrate 22 Wiring 23 Carbon 23' P-type semiconductor carbon nanotube

Claims (6)

  A membrane switch comprising: a first flexible substrate; and a second flexible substrate, wherein the first flexible substrate is provided with carbon nanotubes on a surface thereof.   The membrane switch according to claim 1, wherein carbon nanotubes are provided on a surface of the second flexible substrate.   The membrane switch according to claim 1 or 2, wherein the carbon nanotube is one of an N-type carbon nanotube and a P-type carbon nanotube.   A method for manufacturing a membrane switch comprising a first flexible substrate and a second flexible substrate, comprising a step of disposing carbon nanotubes on the surface of the first flexible substrate. .   5. The method of manufacturing a membrane switch according to claim 4, further comprising a step of disposing carbon nanotubes on the surface of the second flexible substrate.   6. The method of manufacturing a membrane switch according to claim 4, wherein the carbon nanotube is any one of an N-type carbon nanotube and a P-type carbon nanotube.

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