JPS5952487B2 - Anisotropically conductive elastomer sheet having conductivity only in the thickness direction and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an elastomer sheet that freely conducts electricity in its thickness direction but is an insulator in its planar direction, and a method for manufacturing the same.

Elastomer sheets with such functions can reliably and simultaneously connect multiple electrodes simply by sandwiching and crimping them.
It is known that it is useful as a type of connector material because it can be bonded independently. Examples of elastomer materials with such functions include those obtained by laminating and adhering a large number of insulating elastomer sheets and conductive elastomer sheets containing conductive fine particles alternately and slicing them at right angles to the laminated surfaces, and elastomer sheets. Among these, there are those in which a controlled amount of conductive fine particles is added so that contact between the particles occurs only when a compressive force is applied to the sheet. However, these methods have drawbacks such as limitations in the arrangement of electrodes and high dependence on compressive force. It can be said that the ideal form of an elastomer sheet having such a function is one in which an infinite number of conductive paths exist in the elastomer sheet in a direction perpendicular to the sheet surface, independently of each other. The inventors of the present invention have arrived at this invention as a result of pursuing an ideal form that has an elastic elastomer sheet. A fibrous substance having magnetic properties and ferromagnetism is added in an amount within the range shown by Y in the following formula, and the fibrous substance is oriented in the thickness direction of the elastomer sheet only in the thickness direction of the sheet. It relates to an anisotropically conductive elastomer sheet that is a conductor of electricity and insulating in other directions, where x is the thickness of the product sheet in millimeters and Y is the thickness of the sheet. It represents the number of fibers present in a square millimeter.

The elastomer sheet of the present invention is manufactured as follows.

In other words, a fibrous object having both conductivity and ferromagnetism and having a length substantially equivalent to the thickness of the sheet is dispersed in an elastomer stock solution and held in the form of a sheet, and a magnetic field is applied. The fibers are arranged in the thickness direction of the sheet, and the elastomer is cured while maintaining this arrangement. In the elastomer sheet obtained in this way, there are countless conductive fibers arranged and dispersed perpendicularly to the sheet surface, and each fiber has an electrical conductor that penetrates from the front surface to the back surface of the sheet. It forms a conduction path. Due to this unique configuration, this sheet conducts electricity freely in the thickness direction, but has an insulating property in the lateral direction that is substantially equivalent to that of the components used as the matrix. The most preferable material for the fiber used here is one in which the same material has both conductivity and ferromagnetism, such as iron, nickel, cobalt, or a magnetic alloy.

Alternatively, composite fibers containing the above-mentioned materials as one component may also be used. For example, glass fiber, carbon fiber,
There are synthetic fibers whose surfaces are coated with the above-mentioned magnetic metals, electrical properties, etc. In order to improve chemical stability, it is useful to plate the surface with gold or silver, or conversely to coat the copper fiber with a magnetic metal. It is also possible that the substance responsible for conductivity and the substance responsible for magnetism are completely different. An example of this type is a synthetic resin fiber containing fine ferrite powder plated with silver. There are no particular restrictions on the thickness of fibers, but when used as connectors,
It is sufficient that the elastomer sheet of the present invention has a thickness that allows it to be elastically deformed when compressed, and it also depends on the thickness of the sheet.Generally, if the sheet is thick, even thicker fibers can be used. As the fiber becomes thinner, it is desirable to use thinner fibers. As an example of the standard thickness, it is generally preferable to use a thickness of 5.0 μm or less, preferably 25 μm or less. Fiber length is an important factor in achieving stable conductivity, and in order for each fiber to be effective for conduction, it is necessary that the fiber has a length that is substantially equivalent to the thickness of the sheet. More specifically, the sheet thickness is 0.
It needs to be in the range of 9 times to 2.0 times.

It is preferably in the range of 1.0 to 1.5 times, particularly preferably in the range of 1.0 to 1.1 times, and is particularly preferably exactly equal to or slightly longer than the thickness of the sheet. If the length is shorter than 0.9 times, the efficiency as a conductive path will be significantly lowered and it will become meaningless.

Anything longer than 2.0 times can cause entanglement, so it is desirable to actively remove it.

Certain limitations also need to be placed on the amount of fiber added.

That is, when the amount of fibers added exceeds a certain limit, the fibers become significantly entangled due to collisions with each other when oriented by a magnetic field, and irregular conduction paths are created in the surface direction of the sheet, making it impossible to obtain a sheet useful as a connector. As a result of various studies on this point, the present inventors found that the sheet can be useful as a connector only when the amount of fiber added falls within the range shown by the following formula (1). However, x is the thickness of the abrasive sheet in millimeters and is 0.
．． It ranges from 1 to 2.0, where Y is the number of effective fibers present in 1 mm2 of the sheet.

For example, when calculating the upper limit of the amount of fiber added when creating a sheet with a thickness of 0.5 mm using fibers with a length of 0.5 mm and a thickness of 6 μ, it is found that the upper limit of the amount of fiber added is only 1
．． It becomes 13 volume percent, and it can be seen that this restriction is very severe. The requirements for the matrix components used are that the polymer, prepolymer, or monomer stage is sufficient to disperse the fibers at a temperature below one point per block of the magnetic material. Any material may be used as long as it has melt fluidity and forms an elastic polymer by polymerization or solidification.

Silicone rubbers, urethanes, and the like, which can be obtained as liquid monomers or prepolymers at room temperature and polymerize to form elastomers at low temperatures, are particularly suitable for operation.

By using an elastomer, it is possible to reliably connect multiple electrodes simply by sandwiching and crimping the elastomer.Even if the electrodes are uneven or have a small amount of dust attached, the elastomer prevents them from coming apart. This will greatly reduce the chance of connection failures. If the matrix is made of hard resin and the electrodes are uneven or have hard dust attached to them, they will not adhere tightly even when pressure is applied, resulting in poor connection. Example 1 Short fibers with an average length of 0.32 mm and a standard deviation of length of 0.02 mm obtained by cutting ferrite type stainless steel fibers with a diameter of 12 μm were added to a polyurethane rubber stock solution at 0.3 mm.
After adding 50% by volume, mixing and defoaming, the mixed liquid was placed between two 50 μm thick polyester films sandwiching a 0.32 mm thick aluminum spacer until the liquid layer had a thickness of 0.38 mm. The volume was determined and injected.

When the mold spacing is 1.0 mm, the strength of the magnetic field between the mold surfaces is 3.
000 Gauss, a flat mold that also serves as a magnetic pole is heated to 60°C, a film holding the above mixed liquid is inserted between the mold surfaces, and the 5 minutes necessary to orient the fibers in the thickness direction of the sheet elapse. Afterwards, the mold was gradually closed while the magnetic field was still applied. Two hours after insertion, the mold was opened and the urethane rubber sheet was taken out. The appearance of the sheet from the surface was substantially transparent, and almost no entanglement of fibers was observed. The electrical resistance of this sheet is 0.02Ω・in the thickness direction.
Cm, and 1010 Ω·Cm or more in the lateral direction. Example 2 Short fibers with an average length of 0.33 mm and a standard deviation of length of 0.02 mm obtained by cutting carbon fibers having a diameter of 6 μ and electroplated with nickel to a thickness of 0.2 μ were made into low-temperature curing silicone rubber. 0.25% by volume was added to the stock solution, mixed, and defoamed, and the mixed solution was placed between two 50μ thick polyester films sandwiching a 0.33mm thick aluminum spacer so that the liquid layer had a thickness of 0.25% by volume. The volume was determined to be 40 mm and was injected.

Thereafter, the same operations as in Example 1 were performed to obtain a silicone rubber sheet.

The appearance of the sheet from the surface was substantially transparent, and almost no entanglement of fibers was observed. The electrical resistance of this sheet was 0.3 Ω·Cm in the thickness direction and 10 10 Ω·Cm or more in the lateral direction. Example 3 Short fibers with an average length of 0.50 mm and a standard deviation of length of 0.02 mm obtained by cutting carbon fibers having a diameter of 6 μ and electroplated with nickel to a thickness of 0.2 μ were made into low-temperature curing silicone rubber. The stock solution contains (A) 0.8 volume percent and (B
) Added 2.0% by volume; mixed and defoamed to make two types of mixed liquids.

In each case, a volume of 1 volume was injected so that the liquid layer would have a thickness of 0.60 mm between two sheets of polyester having a thickness of 50 μm with an aluminum spacer having a thickness of 0.50 mm in between.

A film holding the above mixture was placed on a horizontal aluminum plate with a thickness of 1 mm, and a pair of magnetic poles with a magnetic field strength of 1500 Gauss at the center between the magnetic poles was sandwiched between the aluminum plates. The fibers were placed at a 45 degree angle and scanned repeatedly over the stock solution to promote fiber orientation.

Thereafter, two types of silicone rubber sheets were obtained using the film holding the stock solution in the same manner as in Example 1. Sheet A had a substantially transparent appearance from the surface, and almost no entanglement of fibers was observed.

The electrical resistance of this sheet was 0.1 Ω·Cm in the thickness direction and 10 10 Ω·Cm or more in the lateral direction. Sheet B had many clusters of entangled fibers and was opaque when viewed from the surface.

Claims (1)

[Claims] 1. A fibrous material having a length substantially equivalent to the thickness of the elastic elastomer sheet and having conductivity and ferromagnetism is added in an amount within the range shown by Y in the following formula. 1. An anisotropically conductive elastomer sheet which is an electrical conductor only in the thickness direction of the sheet and has insulation properties in other directions, the fibrous material being oriented in the thickness direction of the elastomer sheet. Y≦(200/X)0.1≦X≦2.0, where X is the thickness of the product sheet expressed in millimeters, and Y represents the number of fibers present in 1 square millimeter of the sheet. 2. A liquid polymer stock solution that can be cured to form an elastic elastomer has conductivity and ferromagnetism,
A fiber dispersion mixture obtained by adding and mixing a fibrous material having a length substantially equivalent to the thickness of the sheet within the range shown by Y in the following formula is held in a sheet form, and a magnetic field is applied. A method for producing an elastomer sheet that is an electrical conductor only in the thickness direction and insulating in other directions, which is characterized by curing a polymer stock solution as a matrix with fibers oriented in the thickness direction of the sheet. Y≦(200/X)0.1≦X≦2.0 where X is the thickness of the product sheet in millimeters, and Y is the number of fibers present in 1 square millimeter of the sheet.