Patent Application
20080085648
Embodiments of the present invention will now be described by way of examples and with reference to the accompanying drawings, in which:
Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
Firstly, a first method of producing the electric conductive material of the present invention comprises the steps of: forming a knitted, woven or unwoven fabric composed of yarns, each of which is composed of organic fibers and spirally wound on a core member; removing the core members; and carbonizing the fabric, so that the flexible and elastic electric conductive material can be produced.
Namely, the yarns, each of which is composed of organic fibers, are spirally wound on core members respectively. In this state, the yarns are formed into the knitted, woven or unwoven fabric. This step can be performed by a conventional apparatus for forming a knitted, woven or unwoven fabric.
Next, the core members are removed from the fabric.
To remove the core members, the core members are made of water-soluble yarns. By soaking the fabric in a hot bath, the core members are dissolved and easily removed. By controlling conditions of dissolving the core members and drying the yarns, the spiral shape of the yarns can be maintained.
Next, the fabric, from which the core members have been removed, is carbonized, in a furnace, under a nonoxidative atmosphere until the fabric is carbonized. By this step, the fabric-shaped electric conductive material composed of carbon is completed. By carbonizing the fabric, the spiral shapes of the yarns can be fixed.
By suitably setting carbonizing conditions, e.g., temperature, time period, electric conductivity of the electric conductive material can be adjusted. Namely, in case of carbonizing at high temperature, the electric conductivity of the electric conductive material can be improved; in case of carbonizing at low temperature, the electric conductivity of the electric conductive material is lowered. Therefore, the carbonizing conditions may be properly set on the basis of use of the electric conductive material.
The organic yarns may be composed of natural fibers or synthetic fibers.
Silk yarns may be suitably used as the natural yarns. Namely, a highly flexible carbonized fabric can be produced by carbonizing the fabric composed of silk yarns. To maintain the spiral shapes of the yarns, spun silk yarns are suitable. Each of the spun silk yarn is formed by twisting short fibers. The spun silk yarns do not have large stiffness, so their spiral shapes can be properly maintained.
Further, cellulose fibers may be used as the natural fibers.
By the above described method, the fabric-shaped electric conductive material composed of the carbonized spiral yarns can be produced. The electric conductive material is a flexible and elastic. Further, the electric conductivity is less varied even if the material is extended and shrunk. The electric conductive material, which is produced from the knitted or woven fabric, can be elasticized in two axial directions thereof; the electric conductive material, which is produced from the unwoven fabric, can be elasticized in every direction.
Even if the electric conductive material is extended or shrunk, the spiral shapes are extended and compressed without changing the lengths of the yarns, so that the electric conductivity is less varied.
In case of using mere straight yarns instead of the spiral yarns, a woven fabric can be slightly extended and shrunk in oblique directions, but not extended and shrunk in the warp direction and the weft direction. An unwoven fabric can be slightly extended and shrunk in every direction. A knitted fabric has elasticity, but has anisotropy, so use of the electric conductive material must be limited.
In the electric conductive material of the present invention, the carbonized spiral yarns can be extended and shrunk. Therefore, the woven fabric composed of the carbonized spiral yarns can be extended and shrunk in the warp direction and the weft direction without mutual interruption.
Since the yarns can be extended and shrunk in the warp direction and the weft direction without mutual interruption, the electric conductive material can have a wide array of uses.
For example, the electric conductive material may be used as an electrode material of an electrostriction actuator composed of a high polymer sheet. In the electrostriction actuator, the electrodes are respectively attached to the both surfaces of the high polymer sheet, and the high polymer sheet is deformed by applying electric power to the electrodes. By employing the electrodes made of the electric conductive material of the present invention, the electrodes can be extended and shrunk in the two-axial directions, etc., so that the high polymer sheet can be freely deformed.
The electric conductive material may be used as electrodes of sensors, which will be attached to human bodies. The electrodes can deform and follow movement of the human body, so the sensors are not badly influenced.
Preferably, a diameter of each of the core members (core yarns) is 2-1000 times as thick as that of the yarn to be wound on the core member. By using large-diameter core member, a diameter of the spiral yarn (coiled yarn) is increased, so that flexibility is also improved. Further, the flexibility can be improved by using the thinner spiral yarns. By using the core members whose diameter is 2-1000 times as thick as that of the yarn to be wound, the flexibility of the electric conductive material can be adjusted on the basis of uses thereof.
Preferably, spiral-winding number of each of the spiral yarns, which is composed of the organic fibers, is 102-106 times per meter. The flexibility can be improved by increasing the spiral-winding number.
The spiral yarns, whose spiral shapes are fixed, have elasticity as well as coil springs. By changing the diameter of the yarns, the spiral-winding number thereof, the material thereof, etc., physical or mechanical characteristics of the electric conductive material can be controlled.
The electric conductivity of the electric conductive material can be controlled by changing the material of the yarns, the carbonizing conditions, density of the fabric (numbers of the warp yarns and the weft yarns per unit length), etc.
In the first method, the electrode material is produced by the steps of: forming the knitted, woven or unwoven fabric composed of the yarns, each of which is composed of organic fibers and spirally wound on the core member; removing the core members; and carbonizing the fabric. In a second method, the core members are dissolved and removed during the step of carbonizing the fabric.
Namely, the core members in the second method are composed of an organic material which can be gasified at the carbonizing temperature. For example, polyethylene yarns may be used as the organic material.
In the above described methods, the knitted, woven or unwoven fabric composed of the yarns, each of which is composed of organic fibers and spirally wound on the core member, is carbonized so as to produce the fabric-shaped electric conductive material. In another case, a wire-shaped electric conductive material can be produced by carbonizing the yarn, which is composed of organic fibers and spirally wound on the core member, until the yarn is carbonized. In this case, the core member may be removed during the carbonizing step. Namely, the core members may be composed of an organic material which can be gasified at the carbonizing temperature. For example, polyethylene yarns may be used as the organic material.
Preferably, in the above described embodiments, two yarns, which are S-twisted or Z-twisted yarns of Example 4 (described later), or three yarns, which constitute a braided thread of Example 3 (described later), are spirally wound on each of the core members. If the yarn to be wound has larger diameter than the core member, spiral-winding number of the yarn is limited to a small number. The spiral-winding number influences the flexibility and maximum extension rate of the coiled yarn. Preferably, a small-diameter yarn, which will be carbonized, is spirally wound on a large-diameter core member so as to produce a flexible electric conductive material. However, the electric conductivity of the small-diameter yarn is low. To solve this problem, a plurality of yarns may be wound, so that the electric conductive material having high flexibility and high electric conductivity can be produced.
In case that one yarn is wound on each of the core members, each of the yarns has low electric conductivity and low mechanical strength. However, in case that the yarns are formed into a fabric and the fabric is carbonized, the fabric can be practically used. Further, in case of carbonizing the single yarn so as to produce a wire-shaped electric conductive material, the large-diameter single yarn is suitable.
On the other hand, in case that four or more yarns are wound on a core member, elasticity must be lowered. And, the yarns entirely cover an outer circumferential face of the core member, so it is difficult to remove the core member. Further, in case that four or more yarns are wound on the core member, productivity of twisting the yarns must be lowered.
Core members were water-soluble vinylon yarns (600 denier); spun silk yarns (EC 140/two-folded yarns) were spirally wound on the core members; spiral-winding number of each of the spun silk yarns was 1500 times per meter; and the wounded spun silk yarns were used as warp yarns and weft yarns so as to form a flat woven fabric, in which density of the warp yarns was 37 pieces/inch and that of the weft yarns was 34 pieces/inch. A sample of the electric conductive material was produced by the steps of: soaking the fabric into a hot bath, whose temperature was 70° C., so as to remove the water-soluble vinylon yarns; drying the fabric; primarily carbonizing the dried fabric in a furnace, under a nonoxidative atmosphere, for six hours at 700° C.; cooling the fabric until reaching the room temperature; and secondarily carbonizing the fabric for three hours at 1400° C. so as to carbonize the fabric. With this method, the fabric-shaped sample, which was composed of carbonized spiral yarns and whose thickness was 0.35 mm, was produced.
Core members were water-soluble vinylon yarns (300 denier); spun silk yarns (EC 140/two-folded yarns) were spirally wound on the core members; spiral-winding number of each of the spun silk yarns was 1500 times per meter; and the wounded spun silk yarns were used as warp yarns and weft yarns so as to form a flat woven fabric, in which density of the warp yarns was 50 pieces/inch and that of the weft yarns was 47 pieces/inch. A sample of the electric conductive material was produced by the steps of: soaking the fabric into the hot bath, whose temperature was 70° C., so as to remove the water-soluble vinylon yarns; drying the fabric; primarily carbonizing the dried fabric in the furnace, under a nonoxidative atmosphere, for six hours at 700° C.; cooling the fabric until reaching the room temperature; and secondarily carbonizing the fabric for three hours at 1400° C. so as to carbonize the fabric. With this method, the fabric-shaped sample, which was composed of carbonized spiral yarns and whose thickness was 0.34 mm, was produced.
A sample of the electric conductive material was produced by the conventional production steps of: primarily carbonizing a plain-circular-knitted fabric (spun silk yarns MC210/two-folded yarns/32 gauge) in the furnace, under a nonoxidative atmosphere, for six hours at 700° C.; cooling the fabric until reaching the room temperature; and secondarily carbonizing the fabric for three hours at 1400° C. so as to carbonize the fabric. With this method, the fabric-shaped sample, which was composed of carbonized spiral yarns and whose thickness was 0.15 mm, was produced.
Another sample of the electric conductive material was produced by the conventional production steps of: primarily carbonizing a silk-fraise-knitted fabric (spun silk yarns MC210/two-folded yarns/22 gauge) in the furnace, under a nonoxidative atmosphere, for six hours at 700° C.; cooling the fabric until reaching the room temperature; and secondarily carbonizing the fabric for three hours at 1400° C. so as to carbonize the fabric. With this method, the fabric-shaped sample, which was composed of carbonized spiral yarns and whose thickness was 0.32 mm, was produced.
External forces and electrical resistance values with respect to extension strain of the above described samples were measured. Each of the samples was cut and formed into a strip-shaped sample, whose width was 10 mm. The strip-shaped samples were arranged at intervals of 10 mm and fixed by an upper metallic jig and a lower metallic jig. A digital force gauge, which was connected to the upper metallic jig by an insulation shaft, was vertically moved upward so as to measure external forces while the samples were extended. Further, the upper metallic jig and the lower metallic jig were connected to an electric power source so as to form a electrical circuit including the samples. Electrical resistance values were calculated, by Ohm's law, on the basis of input voltage and current measured while the samples were extended.
Note that, “extension strain” is defined by the following formula:
Extension strain=(a length of the extended sample−an initial length thereof)/(the initial length thereof)
The initial lengths of the samples were 10 mm.
The measurement results are shown in
In
According to
According to
According to
Note that, according to
When the samples of Comparative Examples, which were conventional fabrics, were extended in the vertical direction, they were shrunk in the horizontal direction. On the other hand, even if the samples of Examples were extended in the vertical direction, they were not shrunk in the horizontal direction. In the case of the samples of Examples in present invention, each of the spiral yarns could be solely extended and shrunk, so the extension and shrink in one direction was occurred without reference to those in the other direction. Therefore, the electric conductive materials of Examples 1 and 2 can be elasticized in two axial directions.
In the samples of Examples in present invention, the electrical resistance values were constant in spite of extending a distance between measuring terminals. Lengths of the samples were varied by the extension and the shrink, but the actual lengths of the yarns were not varied. Namely, lengths of electric paths were not varied.
A core member was a polyethylene yarn (400 denier); and three spun silk yarns (140/two-folded yarns) were spirally wound on the core member so as to form a braided thread. The thread was burned in the furnace, under a nonoxidative atmosphere, for six hours at 700° C.
A core member was a polyethylene yarn (400 denier); and one spun silk yarn (EC140/two-folded yarns) was spirally wound, on the core member, in a Z-twisting direction with spiral-winding number of 1500 times per meter; and another spun silk yarn (EC140/two-folded yarns) was spirally wound, on the silk yarn wound on the core member, in a S-twisting direction with spiral-winding number of 1500 times per meter.
A sample of the electric conductive material was produced by the steps of: primarily carbonizing the yarns in the furnace, under a nonoxidative atmosphere, for six hours at 700° C.; cooling the fabric until reaching the room temperature; and secondarily carbonizing the yarns for three hours at 1400° C. so as to carbonize the yarns. With this method, the wire-shaped sample, which was composed of carbonized fibers, was produced. The carbon fibers can be used as the wire-shaped electric conductive materials.
External forces and electrical resistance values with respect to extension strain of the above described samples (the carbonized spiral yarns) were measured. The samples were arranged at intervals of 10 mm and fixed by the upper metallic jig and the lower metallic jig. The digital force gauge, which was connected to the upper metallic jig by the insulation shaft, was vertically moved upward so as to measure external forces while the samples were extended. Further, the upper metallic jig and the lower metallic jig were connected to the electric power source so as to form a electrical circuit including the samples. Electrical resistance values were calculated, by Ohm's law, on the basis of input voltage and current measured while the samples were extended.
The measurement results are shown in
The invention may be embodied in other specific forms without departing from the spirit of essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-272463 | Oct 2006 | JP | national |
| 2007-231955 | Sep 2007 | JP | national |
