JPS6028320B2 - Conductive pressure sensitive adhesive composition - Google Patents

Description

[Detailed description of the invention] The present invention relates to a pressure-sensitive adhesive composition having electrical conductivity.

In recent years, there has been a strong demand for conductive adhesives in various industrial fields including the electronic equipment field. For example, by bonding and fixing electrical parts using a conductive adhesive, it is possible to eliminate leakage current and use it as a grounding wire, and it is also necessary to remove static electricity from materials that may generate static electricity due to friction. In some cases, this can be accomplished by attaching a conductor, such as a metal sheet, to the material using a conductive adhesive and grounding it. Conventionally known conductive adhesives include
As shown in Japanese Patent No. 122-2, 45 to 95 parts by weight of silver powder, metal powder such as molybdenum powder, or carbon black is added to a reactive adhesive such as epoxy resin based on 10 parts by weight of the adhesive composition. There are some things that are made to exhibit military leadership by being mixed in with them.

As described above, when bonding adherends using a reactive adhesive, it is necessary to accurately mix the adhesive and curing agent, and
High temperature curing or long-term curing is necessary to ensure sufficient adhesive strength.

Further, temporary adhesion is not possible until the adhesion is completed, and a very special fastener is required for adhesion of parts with complex shapes. On the other hand, pressure-sensitive adhesives, which can be bonded with pressure similar to finger pressure, are widely used in conventional adhesive fixing because of their good workability.

Therefore, it can be fully expected that conductive pressure-sensitive adhesives can meet the demands of various industrial fields as they combine ease of bonding work and the functionality of conductivity.

However, when powder, etc. is mixed into pressure-sensitive adhesives, the adhesiveness decreases significantly, and when conductive powders, such as those used in the above adhesives, are added in an amount sufficient to show sufficient conductivity. Conductive pressure-sensitive adhesives or tapes have hitherto been technically difficult to produce because they have no tack.

A conductive adhesive tape is proposed in Japanese Patent Publication No. 47-517, which uses a metal foil as a base material on which a large number of conductive protrusions having substantially uniform height are formed on at least one surface. , an adhesive is applied to a height that does not exceed this protrusion, and current flows through this protrusion.

Therefore, according to this invention, the adhesive itself does not have military guiding properties, and there is a limitation that it is necessary to use a crab guiding base material, so it cannot be applied to adhesive fixing of two types of adherends. However, it has the disadvantage that it can only be used for special purposes. An object of the present invention is to provide a pressure-sensitive adhesive composition that has excellent tackiness and adhesive strength and exhibits good conductivity and properties.

As a result of extensive research, the present inventors have found that by mixing conductive fibers into pressure-sensitive adhesives, sufficient conductivity can be achieved with a smaller amount than in conventional systems with the addition of fine particles such as carbon black or metal powder. It was found that the tackiness of the product showed almost no decrease, and the product was released. However, even in this case, when it is made into a sheet, it is inevitable that there will be variations in the continuity of the conductive fibers when focusing on the fine area of the whole, and the uniformity of conductivity remains unsatisfactory. However, as a result of further intensive research by the present inventors, it was surprisingly found that by adding a surfactant to the mixture of the above-mentioned conductive fiber and pressure-sensitive adhesive, the conductive performance was greatly improved and the conductive performance was significantly improved. It was found that the uniformity was also good, and the present invention was completed. The gist of the present invention is to provide a conductive material comprising a pressure-sensitive adhesive, 1% to 3% by weight of conductive fibers having an average length of 2 to 5 ribs, and 0.2% to 5% by weight of a surfactant. pressure sensitive adhesive composition. The pressure-sensitive adhesive used as a base in the present invention may be a so-called rubber adhesive that is a combination of commonly used natural rubber or synthetic rubber with tackifiers, softeners, and other additives, or acrylic acid ester or methacrylic acid ester. So-called acrylic adhesives, which are copolymerized with polar monomers such as acrylic acid, methacrylic acid, acrylamide, etc. as main components, and vinyl monomers that can be copolymerized with other monomers, or silicone adhesives, whose main component is silicone rubber. can be used.

The conductive fibers used in the present invention include carbon fibers, metal fibers, metal plated fibers, etc., and the average length of the conductive fibers must be in the range of 2 to 5 proboscises. , a range of 3 ribs to 3 broadsides is more preferable.

If the average length of the conductive fibers is shorter than 2 skins, in order to obtain the necessary conductivity, it is necessary to add an amount exceeding the limit that impairs adhesion, and both conductivity and adhesion are unsatisfactory. It cannot be made into a composition that can be used. On the other hand, if fibers with an average length longer than 5 cm are used, the intertwining of the fibers will be more severe than necessary, so a pressure-sensitive adhesive layer such as an adhesive tape or sheet may be used. When producing a thin layer of about microns to several hundred microns, uniform or clear coating becomes difficult. The amount of conductive fibers to be added is preferably in the range of 1% to 3% by weight of the total solid composition.

In order to make the composition substantially conductive, 1% by weight of the total composition solid content is required, and the conductivity is increasing as the amount of conductive fibers added increases, but it is necessary to increase the solid content by 30% by weight. If an excess amount is added, the pressure-sensitive adhesive almost loses its tackiness, making it difficult to bond with finger pressure or the like, and hardly exhibiting its excellent functions as a pressure-sensitive adhesive. In the present invention, in order to further improve conductivity uniformity and conductive performance, a surfactant is added, and examples of the surfactant include the following anionic surfactants, nonionic surfactants, and cationic surfactants Both surfactants and amphoteric surfactants can be used effectively.

Examples of anionic surfactants include alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, higher alcohol sulfate ester salts such as sodium lauryl sulfate, sodium lauryl alcohol sulfate, and triethanolamine lauryl sulfate, alkyl phosphate salts, and polyesters. Examples include oxyethylene sulfate salts.

Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; sorbitan fatty acid esters such as sorbitan monolaurylate and sorbitan monostearate; Examples include polyoxyethylene acyl esters such as polyethylene glycol monolaurate and polyethylene glycol monostearate.

Examples of cationic surfactants include alkylamines such as laurylamine acetate and stearylamine acetate, lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, distearyldimethylammonium chloride, alkylbenzyldimethylammonium chloride, laurylpicolinium chloride, etc. quaternary ammonium salts, polyoxyethylene alkyl amines, and the like.

Examples of amphoteric surfactants include alkyl betaines such as lauryl betaine and stialyl betaine. It is also possible to use a mixture of two or more of the above surfactants.

The amount of surfactant added in the present invention is 0.00% of the total solid composition. % to 5% by weight are effective, preferably 0.5% to 5% by weight.
Milk weight % to 3 weight %.

If the amount of surfactant added is less than 0.2% by weight, it has no effect on conductive performance, while if it exceeds 5% by weight, the surfactant bleeds, which is undesirable as it lowers the pressure-sensitive adhesive and adhesive strength. A conductive pressure-sensitive adhesive composition can be obtained by uniformly mixing the pressure-sensitive adhesive, conductive fibers, and surfactant using a homomixer or the like.

Further, by forming this conductive pressure-sensitive adhesive composition on a Motomura sheet by the following method, a conductive pressure-sensitive adhesive tape or sheet can be produced.

That is, a predetermined amount of conductive fibers is added to a solvent solution of a pressure sensitive adhesive;
A surfactant is added and uniformly dispersed and mixed using a homomixer, main roll, ball mill, etc. to form a solution of the conductive pressure-sensitive adhesive composition, and then coated onto the base sheet using a roll coater or knife coater. It can be made into a conductive pressure-sensitive adhesive tape or sheet by drying the solvent under hot conditions.A conductive sheet such as aluminum foil can also be used as the base sheet, and conductive adhesive tape or sheet can be formed on both sides of the Motomura sheet. By applying the pressure-sensitive adhesive composition or transferring it from a release paper, a conductive double-sided tape for adhesive fixing can be obtained.

Since the low-conductivity pressure-sensitive adhesive composition of the present invention is configured as described above, the probability of continuity of the conductor is high due to the long conductive fibers, and the conductive fibers are bonded to the surfactant. It is uniformly dispersed, exhibits sufficient conductivity even with a small amount of addition, and hardly reduces the tackiness of pressure-sensitive adhesives, so it has excellent tack and adhesive strength and exhibits good conductivity. .

Furthermore, since the tortoise-guiding fiber is contained, the strength of the composition is also increased.

The present invention will be explained below with reference to Examples.

Example 1 An ethyl acetate solution of a copolymer consisting of 45% by weight of butyl acrylate, 5% by weight of 2-ethylhexyl acrylate, and 5% by weight of acrylic acid (solid content concentration 4% by weight) 100 pieces, average fiber length 6 Then, 2 parts of carbon fiber having an average diameter of 10.5 microns and 0.2 parts of a surfactant (lauryltrimethylammonium chloride) were added, and the mixture was mixed with a homomixer.

Next, the obtained mixed composition solution was uniformly applied onto silicone-treated release paper using a knife coater, and
The sheet was dried with 0 hot air for 5 minutes to obtain a sheet with a pressure-sensitive adhesive layer having a thickness of 70 microns.

This was transferred onto both sides of an aluminum foil having a thickness of 20 microns, and crosslinked by irradiation with an electron beam of milk Mrad to produce a double-sided pressure-sensitive adhesive sheet.

The conductivity, adhesion properties, and adhesive properties of the obtained conductive double-sided pressure-sensitive adhesive sheet were measured by the following method, and the volume resistivity was 2 × 10-20·c, indicating good conductivity.
Peeling force is 7509/15 ribs, holding force is over 200 knots,
With a tack of 10, both adhesive strength and adhesiveness were good.

The volume resistivity was evaluated by cutting out a test piece with an area of 100 mm from the sheet in 1 from any location in 5, and measuring the resistance between the electrodes of 1 crucian carp.

The peeling force was determined when a sample with a width of 15 legs was attached to a stainless steel plate, and then a 2K9 roll was pressed back and forth 5 times, and after leaving it for 1 powder, it was peeled off at a rate of 1800 at a speed of 3 skins per minute. The strength was measured.

To determine the holding power, the sample was attached to a stainless steel plate so that the adhesive surface had dimensions of 1 inch in width and 15 mm in length, and a 2K9 o-ru was passed back and forth once, and the sample was left for each line. After that, fix one end of the stainless steel plate and attach lk9 to the other end of the sample.
A weight was hung, and the time (minutes) it took for the weight to fall was measured.

Tuck is J. It was measured by the Dow method and expressed as the diameter of the largest steel ball that remained on the sample.

Examples 2, 3, 4 Conductive double-sided pressure-sensitive adhesive sheets were produced in the same manner as in Example 1, except that the amounts of conductive fibers and surfactant added in Example 1 were changed as shown in Table 1. Then, conductivity, adhesive properties, and adhesive properties were measured.

The results are shown in Table 1. Comparative Example 1 A conductive double-sided pressure-sensitive adhesive sheet was prepared using the same machine as in Example 1 except that the surfactant was removed, and the conductivity, adhesive properties, and adhesive properties were measured.

The results are shown in Table 1. Incidentally, there was a very large variation in conductivity (volume resistivity). Comparative Examples 2 and 3 Conductive double-sided pressure-sensitive adhesive sheets were prepared in the same manner as in Example 1, except that carbon black was added in the amount shown in Table 1 instead of the conductive fibers in Example 1, and conductive double-sided pressure-sensitive adhesive sheets were prepared. , adhesive physical properties, and adhesive physical properties were measured.

The results are shown in Table 1. Note that the sheet of Comparative Example 3 in which 30 tons of carbon black was added could not be pressure-bonded to a stainless steel plate with a roller. Table 1 Example 5 A length of 9 was added to an ethyl acetate solution (solid content concentration 4% by weight) of a copolymer consisting of 9% by weight of 2-ethylhexyl acrylate, 3% by weight of ethyl acrylate, and 7% by weight of acrylic acid. Rib, 2 glass fibers with an average diameter of 20 microns covered with aluminum on both sides, 0.
After mixing and dispersing with a ball mill, it was applied and dried on silicone-treated iso pattern paper, and the thickness of the pressure-sensitive attachment agent eyebrow was 9.
A sheet of 0 micron was obtained.

This was transferred onto both sides of an aluminum foil having a thickness of 20 microns, and then carefully irradiated with an AD electron beam to obtain a conductive double-sided pressure-sensitive adhesive sheet.

The physical properties of the obtained conductive double-sided pressure-sensitive adhesive sheet were measured in the same manner as in Example 1, and the volume resistivity was 5 x 10-2.
Shows good conductivity at 0.0% and peeling force is 690/15.
Fence, holding power is 200 powder or more, tack is 11 and adhesive strength,
Adhesion was also good.

Claims (1)

[Claims] 1. A pressure-sensitive adhesive, 1% to 30% by weight of conductive fibers with an average length of 2 mm to 50 mm, and 0.2% to 30% by weight of a surfactant.
5% by weight of an electrically conductive pressure-sensitive adhesive composition. 2. The conductive pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive is an acrylic adhesive. 3. The conductive pressure-sensitive adhesive composition according to claim 1 or 2, wherein the conductive fibers are carbon fibers. 4. The conductive pressure-sensitive adhesive composition according to claim 1 or 2, wherein the conductive fiber is a metal-plated fiber.