JP2001146578A - Electrically conductive silicone based pressure-sensitive adhesive composition and electrically conductive pressure-sensitive adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrically conductive silicone based pressure-sensitive adhesive composition having good adhesion to an electrically conductive silicone rubber and conductivity in the thickness direction, and an electrically conductive pressure-sensitive adhesive tape using the same. SOLUTION: The electrically conductive silicone based pressure-sensitive adhesive composition is obtained by dispersing electrically conductive particles having an apparent density of <=1.5 g/cm3 in a compounding amount of 30-80 PHR into a polyalkylsilicone based pressure-sensitive adhesive having a gel fraction of 10-40%. The electrically conductive pressure-sensitive adhesive tape uses the composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive pressure-sensitive adhesive composition and conductive pressure-sensitive adhesive tapes using the same, and more particularly, to good adhesion to conductive silicone rubber and thickness. The present invention relates to a silicone-based conductive pressure-sensitive adhesive excellent in direction conductivity, and a conductive pressure-sensitive adhesive tape obtained by applying the pressure-sensitive adhesive to at least one of metal foils.

[0002]

2. Description of the Related Art Silicone rubber is widely used for keys, switches, sealing materials and the like of portable electronic devices and the like.

[0003] Among them, there is a case of using silicone rubber having conductivity for measures against electromagnetic waves, and an adhesive tape for bonding the silicone rubber has good adhesiveness to the conductive silicone rubber and has conductivity in the thickness direction. It was necessary to have JP-A-49-107337, No. 2928944
In the gazette, there is a description of a conductive pressure-sensitive adhesive tape characterized by dispersing conductive particles in a silicone-based pressure-sensitive adhesive,
There is no description regarding the adhesiveness to the conductive silicone rubber. Further, from the results of the studies by the inventors, it was found that the pressure-sensitive adhesives described above did not provide good adhesion to the conductive silicone rubber.

Japanese Patent Application Laid-Open No. 5-320592 discloses a double-sided pressure-sensitive adhesive tape characterized in that at least one is a silicone-based pressure-sensitive adhesive layer, but does not suggest a conductive silicone pressure-sensitive adhesive.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a conductive silicone-based pressure-sensitive adhesive composition having good adhesion to a conductive silicone rubber and having conductivity in the thickness direction, and use of the same. To provide a conductive adhesive tape.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the use of a conductive silicone-based pressure-sensitive adhesive composition obtained by dispersing specific conductive particles in a specific silicone-based pressure-sensitive adhesive provides an object of the present invention. Came to a solution. That is, in the first configuration of the present invention, in a pressure-sensitive adhesive composition in which conductive particles are dispersed in a polyalkyl silicone pressure-sensitive adhesive, the gel fraction of the polyalkyl silicone pressure-sensitive adhesive is 10 to 40%, The conductive silicone pressure-sensitive adhesive composition, wherein the apparent density of the conductive particles is 1.5 g / cm ³ or less, and the amount of the conductive particles is 30 to 80 PHR (g per 100 g of resin solid content). Things.

Further, according to the constitution of the present invention, the above-mentioned polyalkyl silicone-based pressure-sensitive adhesive comprises a blend of an addition-curable pressure-sensitive adhesive and a condensation-reaction-curable pressure-sensitive adhesive, and the compounding ratio is 10:90 by weight. 50:50, which is a conductive silicone-based pressure-sensitive adhesive composition that is a polyalkyl silicone-based pressure-sensitive adhesive obtained by curing only an addition reaction-curable pressure-sensitive adhesive. Further, in the configuration of the present invention, the above-described conductive particles have an average particle diameter of 10 to 10.
It is a conductive silicone-based pressure-sensitive adhesive composition that is 50 μm electrolytic copper powder.

The second configuration of the present invention has a gel fraction of 10 to 10.
In a 40% polyalkylsilicone-based pressure-sensitive adhesive, conductive particles having an apparent density of 1.5 g / cm ³ or less
A conductive pressure-sensitive adhesive tape using a conductive silicone-based pressure-sensitive adhesive composition in which 0 to 80 PHR is blended, wherein an adhesive force to a conductive silicone rubber is 30 N / 25 mm or more at a peeling speed of 300 mm / min. The conductive pressure-sensitive adhesive tape has a resistance value in the vertical direction of 100 mΩ / 6.25 cm ² or less.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

As the silicone pressure-sensitive adhesive used in the present invention, a polyalkyl silicone pressure-sensitive adhesive is used. In particular, a silicone pressure-sensitive adhesive containing no phenyl group is preferable since it has good adhesion to conductive silicone rubber. The polyalkyl silicone-based pressure-sensitive adhesive includes an addition reaction-curable type and a condensation reaction-curable type, and a known silicone-based pressure-sensitive adhesive can be used. Examples of the addition-curable silicone adhesive include X-40-306 manufactured by Shin-Etsu Chemical Co., Ltd.
8, X-40-3104, X-40-3098 and BY-24-74 manufactured by Dow Corning Toray Silicone Co., Ltd.
0, SD4590, SD4592 and the like are known.

As a method of curing the addition reaction-curable pressure-sensitive adhesive, a method of curing a polyalkyl hydrogen siloxane composition with a platinum catalyst is generally used. A catalyst can be used.

The condensation-curing reaction-type pressure-sensitive adhesives include KR-101-10, KR-100, and KR-12 manufactured by Shin-Etsu Chemical Co., Ltd.
0 or SH428 manufactured by Dow Corning Toray Silicone Co., Ltd.
0, SH4282, BY24-717, Q2-7735
And the like, but are not limited thereto.

A peroxide such as benzoyl peroxide is generally used for curing the condensation-curable pressure-sensitive adhesive.

The conductive silicone pressure-sensitive adhesive composition used in the present invention is characterized in that the gel fraction after the curing reaction is 10 to 40%. When the gel fraction is less than 10%, the cohesive force of the pressure-sensitive adhesive is insufficient particularly at high temperature, and when the gel fraction exceeds 40%, sufficient adhesive force to silicone rubber and good conductivity are obtained. It is not preferable because it cannot be obtained.

As described above, in the conductive silicone pressure-sensitive adhesive composition of the present invention, an addition reaction-curable silicone pressure-sensitive adhesive and a condensation reaction-curable silicone pressure-sensitive adhesive are used alone or in combination. From the viewpoint of curability, it is preferable to use both of them.

Therefore, as the conductive silicone pressure-sensitive adhesive composition used in the present invention, two kinds of polyalkyl silicone-based pressure-sensitive adhesives of addition-curable type and condensation-curable type are used in a weight ratio of 10:90 to 50:50. It is characterized in that it is blended in a proportion and only the addition-curable component is crosslinked. By defining the addition-curable polyalkyl silicone pressure-sensitive adhesive component, the gel fraction can be easily controlled to 10 to 40%, and both a sufficient adhesive force to the conductive silicone rubber and good conductivity can be achieved. The quality during production becomes more stable. When the weight ratio of the addition reaction-curable type is less than 10, the cohesive strength becomes insufficient, and when it exceeds 50, it becomes difficult to control the gel fraction.

Regarding the crosslinking method, peroxides such as benzoyl peroxide, which are generally used for curing a condensation-curable pressure-sensitive adhesive, have safety during handling and have benzoic acid as a decomposition residue. It is preferable to cure only the addition-reaction-type pressure-sensitive adhesive, since it may remain in the agent and cause corrosion of the metal foil and the conductive particles.

The apparent density of the conductive particles used in the conductive silicone pressure-sensitive adhesive composition of the present invention is 1.5 g / cm ³ or less, preferably 1.1 g / cm ³ or less. 30 for adhesive resin
８０80 PHR.

The apparent density of the conductive particles is 1.5 g / cm.
If it exceeds ³ , when dispersed in an adhesive, the sedimentation speed of the conductive particles is high, so that it is difficult to obtain a uniform coating solution during production. In addition, since the conductive particles having a low apparent density are bulky, the conductive particles contact each other efficiently in the pressure-sensitive adhesive layer, so that both the adhesion to the conductive silicone rubber and the good conductivity can be achieved. .

The amount of the conductive particles to be added is 30 to 80 PHR, preferably 40 to 75 PHR, in consideration of the balance between the adhesive force and the conductivity.
PHR is desirable. If the added amount is less than 30 PHR, the conductivity is extremely reduced, and if it is more than 80 PHR, the adhesion to the conductive silicone rubber is undesirably reduced.

In order to provide both sufficient conductivity and sufficient adhesive strength, the conductive silicone pressure-sensitive adhesive composition of the present invention preferably has a coating thickness of 20 to 80 μm, more preferably 30 to 50 μm.

Examples of the conductive particles include metal powders such as gold, silver, copper, nickel, and aluminum; conductive resins such as carbon and graphite; and resin or solid glass beads or hollow glass beads, which have a metal coating on the surface. Known conductive particles, such as those, can be used. Among them, coniferous electrolytic copper powder, nickel powder prepared by a nickel carbonyl method, and the like can be preferably used.

When the conductive particles used in the conductive silicone pressure-sensitive adhesive composition of the present invention are electrolytic copper powder, the average particle size is 10%.
５０50 μm, preferably 15-45 μm. When the average particle size is less than 10 μm, the conductivity is extremely reduced. When the average particle size is more than 50 μm, good adhesiveness cannot be obtained, which is not preferable. In addition, in the case of these electrolytic copper powders, in order to improve the stability of conductivity over time, it is more preferable to use those having an organic titanate coupling agent on the surface depending on the use.

As the surface substrate of the conductive silicone pressure-sensitive adhesive tape of the present invention, gold, silver, copper, nickel, tin, iron,
Known metal foils such as aluminum and stainless steel can be used. In particular, when using copper foil, the electrodeposited copper foil is coated with an adhesive, and in the case of rolled copper foil, the roughened surface is applied to the adhesive-coated side to make contact with the conductive silicone adhesive. This is preferable because the area is improved.

[0025]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Example 1 25 parts by weight of an addition reaction-curable polyalkyl silicone adhesive (SD4570, manufactured by Dow Corning Toray Silicone Co., Ltd.) and a condensation-curable polyalkyl silicone adhesive (SH4280, Toray 75 parts by weight of Dow Corning Silicone Co., Ltd., 1.8 parts by weight of a crosslinking agent for addition reaction curing (BY24-741, Dow Corning Toray Silicone Co.), catalyst for addition reaction curing (SRX212, Dow Corning Toray Co., Ltd.) ) Was used as conductive particles, and the average particle size was 2
0 μm, electrolytic copper powder having an apparent density of 1.0 g / m ³ (F-1
15, Fukuda Metal Co., Ltd.) (20 parts by weight (50 PHR based on resin solid content)) to obtain an adhesive solution. This adhesive solution was dried using an applicator to a thickness of 35 μm after drying.
And dried at 120 ° C. for 3 minutes. After drying, it was passed through a roll heated to 80 ° C. on a rough surface of an electrolytic copper foil having a thickness of 35 μm to be laminated, thereby producing a conductive adhesive tape of the present invention.

Example 2 The conductive particles were prepared with an average particle size of 20.
28 μm (70 PHR based on resin solid content) of titanate-coupled electrolytic copper powder having a particle size of 1.0 μm / m ³ and an apparent density of 1.0 g / m ³ were mixed, and the substrate was subjected to one-side roughening treatment (roughened surface Is 35μ thick.
A conductive pressure-sensitive adhesive tape was prepared in the same manner as in Example 1, except that the rolled copper foil was m.

Example 3 40 parts by weight of an addition-curable polyalkyl silicone-based pressure-sensitive adhesive (SD4570)
Condensation reaction-curable polyalkyl silicone adhesive (S
H4280), 60 parts by weight of conductive particles, and 14 parts by weight of nickel powder (# 255, manufactured by INCO) having an average particle size of 2.6 μm and an apparent density of 0.6 g / m ³ (35 PHR based on resin solid content). A) Conductive pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the composition was blended.

Example 4 An addition reaction curing type polyalkyl silicone-based pressure-sensitive adhesive (SD4570) was used in an amount of 100 parts by weight, and an addition reaction curing catalyst (SRX212, manufactured by Dow Corning Toray Silicone Co., Ltd.) was used. Example 1
In the same manner as in the above, a conductive pressure-sensitive adhesive tape was obtained.

Comparative Example 1 70 parts by weight of an addition reaction-curable polyalkyl silicone-based pressure-sensitive adhesive (SD4570)
Condensation reaction-curable polyalkyl silicone adhesive (S
H4280) was changed to 30 parts by weight to obtain an adhesive solution in the same manner as in Example 1.

[Comparative Example 2] An average particle diameter of 10
changed to electrolytic copper powder with an apparent density of 1.7 g / m ^{3 in} μm,
A conductive pressure-sensitive adhesive tape was obtained in the same manner as in Example 1, except that the substrate was made into a rolled copper foil having a thickness of 35 μm obtained by performing a one-sided roughening treatment (laminating a pressure-sensitive adhesive on the roughened surface).

Comparative Example 3 Except that the conductive particles were changed to 8 parts by weight (20 PHR based on the resin solid content),
A conductive adhesive tape was obtained in the same manner as in Example 1.

Comparative Example 4 A conductive adhesive tape was obtained in the same manner as in Example 1 except that the amount of the conductive particles was changed to 40 parts by weight (100 PHR based on the solid content of the resin).

The evaluation method according to the present invention will be described below.

<Gel Fraction> A test piece of a conductive pressure-sensitive adhesive tape of 20 cm ² was immersed in 50 ml of toluene for 24 hours and calculated by the following formula. That is, the tape weight before immersion:
A, tape weight after immersion: A ', conductive substrate weight:
B and the weight of the conductive particles in the adhesive: C: gel fraction = (A′−BC) ÷ (ABC) × 100
(%).

<Adhesive force of conductive silicone rubber> 25 mm
A test piece having a width of 100 mm and a conductive silicone rubber sheet (Masasheet, manufactured by INOAC) was pasted back and forth on the test piece with a 2 kg rubber roller at 23 ° C.
After leaving for 1 hour in an environment of 65% RH, 180
The adhesive strength when peeled at a tensile speed of 300 mm / min in the ° direction was measured. This measuring method is defined as the adhesive force to the conductive silicone rubber.

<Holding force> Affixing area is 25 mm x 25 mm
The test piece was affixed to the stainless steel plate by reciprocating once over the test piece with a rubber roller weighing 2 kg at 23 ° C and 65 ° C.
After leaving for 1 hour in an environment of% RH, a load of 0.5 kg was applied in a shearing direction at 70 ° C., and the time required for falling was measured. The measurement was performed until 24 hours later, and when it did not drop, it was described as “24 or more”.

<Resistance value> A test piece having a width of 25 mm and a length of 80 mm was stuck on a copper plate such that a rubber roller having a weight of 2 kg was reciprocated once over the test piece so that the stuck area became 6.25 cm ^2. After leaving for 1 hour in an environment of 65% RH, the terminals were connected to the end of the test piece and the end of the copper foil under the same environment, and the resistance when a constant current of 10 μA was passed through a milliohm meter (manufactured by NF Corporation). The value was measured.

<Stability> A glass bottle having a capacity of 450 cm ³ was filled with about 400 cm ³ of the adhesive solution containing the conductive particles, and the degree of sedimentation of the conductive particles was visually evaluated. ：: No sedimentation after 60 minutes. Δ: Sedimentation confirmed after 60 minutes. ×: Sedimentation confirmed after 20 minutes.

[0040]

[Table 1]

The electrolytic copper powder (*) in Tables 1 and 2 indicates a titanate-treated electrolytic copper powder. The particle size is (μm), the apparent density is (g / cm ³ ), and the amount added is (PHR).

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

[Table 4]

[0045]

The conductive silicone-based pressure-sensitive adhesive composition and the conductive pressure-sensitive adhesive tape of the present invention have good adhesion to conductive silicone rubber and good conductivity in the thickness direction. It can be suitably used for bonding conductive silicone rubber keys, switches, sealing materials and the like used in electronic devices.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akihiro Kuwashita 34-2 Maison Shiibashi 34-2 Sasame Minamicho, Toda City, Saitama Prefecture 4J004 AA11 AA18 AA19 AB04 CA08 CC02 FA05 4J040 EK031 HA046 HA066 HA096 JA09 JB09 KA32 LA02 NA19 PA23 5E321 BB32 CC16 GG05

Claims (4)

[Claims] 1. A pressure-sensitive adhesive composition in which conductive particles are dispersed in a polyalkyl silicone pressure-sensitive adhesive, the gel fraction of the polyalkyl silicone pressure-sensitive adhesive is 10 to 40%, and the apparent density of the conductive particles is A conductive silicone-based pressure-sensitive adhesive composition, which has a content of 1.5 g / cm ³ or less and a conductive particle content of 30 to 80 PHR. 2. The polyalkyl silicone-based pressure-sensitive adhesive comprises a mixture of an addition-curable pressure-sensitive adhesive and a condensation-curable pressure-sensitive adhesive, and the compounding ratio is 10:90 to 5 by weight.
The conductive silicone-based pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive is a polyalkyl silicone-based pressure-sensitive adhesive obtained by curing only an addition reaction-curable pressure-sensitive adhesive. 3. The method according to claim 1, wherein the conductive particles have an average particle size of 10 to 10.
The conductive silicone-based pressure-sensitive adhesive composition according to claim 1, which is 50 μm of electrolytic copper powder. 4. The polyalkyl silicone-based pressure-sensitive adhesive having a gel fraction of 10 to 40% has an apparent density of 1.5 g /
A conductive pressure-sensitive adhesive tape using a conductive silicone-based pressure-sensitive adhesive composition containing 30 to 80 PHR of conductive particles having a particle size of not more than ³ cm ³ , wherein an adhesive force to a conductive silicone rubber has a peeling speed of 300 mm / min. 30N / 25 at
mm or more, and the resistance value in the thickness direction is 100 mΩ / 6.
A conductive pressure-sensitive adhesive tape having a size of 25 cm ² or less.