JPH11349910A - Electroconductive tacky agent and tacky agent article provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroconductive tacky agent not only capable of providing high visibility by itself and facilitating the visual examination of a material to be bonded, but also having excellent bond strength to the material to be bonded and removability and yet capable of sufficiently protecting the material to be bonded mechanically and electrically. SOLUTION: In this electroconductive tacky agent provided with electroconductive tacky microspheres having an ionic conductive substance bonded through a graft bond to the surface, the interior of the tacky microspheres is cross-linked and/or the microspheres are mutually cross-linked, the tacky microspheres have 0.01-1 μm particle diameter and the maximum electrostatic potential generated by the release of the electroconductive tacky agent is 50 V/25 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a conductive pressure-sensitive adhesive and a pressure-sensitive adhesive article provided with the same. The pressure-sensitive adhesive article of the present invention particularly relates to a conductive pressure-sensitive adhesive article such as an antistatic pressure-sensitive adhesive sheet that protects not only mechanically but also electrically the surface of a member.

[0002]

2. Description of the Related Art For the purpose of mechanically protecting the surface of a product, member or the like as an adherend (hereinafter referred to as "member"), the member is kept until immediately before its use, for example, with an adhesive sheet. It is often practiced to coat with an adhesive article. In particular, when the member is a polarizing plate or an electronic substrate, an antistatic treatment is applied to the adhesive sheet to prevent adhesion of dust and damage to an electronic circuit due to static electricity generated when the sheet is peeled off. I have. For example, JP-A-4-
Japanese Patent No. 292943 discloses a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive is laminated on an antistatic base material. Also, Japanese Patent Application Laid-Open
JP-A-253482 discloses an adhesive sheet using an adhesive containing an antistatic agent such as a surfactant. Alternatively, Japanese Patent No. 1844440 discloses a pressure-sensitive adhesive sheet using a pressure-sensitive adhesive containing a metal filler or carbon particles.
No. 5,378,405 and Japanese Patent Application Laid-Open No. 9-208910 each disclose an adhesive sheet using adhesive microspheres provided with an ion conductive substance on the surface. .

An adhesive sheet applied to a member such as a polarizing plate or an electronic substrate is not sufficient if it can provide mechanical and electrical protection as described above. Such an adhesive sheet usually needs to be removed from the member when the member is used. Therefore, the pressure-sensitive adhesive sheet needs to have a predetermined removability and facilitate the use of the member.

However, as described above, in the case of a pressure-sensitive adhesive sheet made of a conductive base material, the above-described requirements are satisfied if the pressure-sensitive adhesive in contact with a member as an adherend does not have an antistatic ability. Can not do. Further, in the case of a pressure-sensitive adhesive sheet using a pressure-sensitive adhesive containing an antistatic agent such as a surfactant, generally, the antistatic agent is concentrated on the surface of the pressure-sensitive adhesive after coating, and is significantly affected by humidity. Moisture reduces the cohesive force of the pressure-sensitive adhesive, when peeling the pressure-sensitive adhesive sheet,
A so-called glue residue may be generated on the surface of the member, and contaminate the surface of the member.

[0005] Further, the member itself must have a predetermined quality at the time of use, and therefore the quality of the member must be in a state where it can be constantly monitored. In other words, before the member is actually used,
It is necessary that the appearance of the member can be constantly inspected through the adhesive sheet. Therefore, it is necessary that the pressure-sensitive adhesive sheet itself be transparent and have no optical defects.

However, in the case of a pressure-sensitive adhesive sheet using a metal filler or a pressure-sensitive adhesive having carbon particles, the metal filler or carbon particles serve as a scatterer, and the transparency is remarkably reduced. Can not be inspected. On the other hand, the pressure-sensitive adhesive sheet using the above-mentioned pressure-sensitive adhesive microspheres becomes transparent when attached to a member, so that the appearance of the member can be substantially inspected via the pressure-sensitive adhesive sheet. However, if the surface of the pressure-sensitive adhesive sheet has a defect, the appearance inspection cannot be performed accurately. When the adhesive microspheres have a relatively large particle size of about 1 μm, the adhesive sheet itself is translucent due to the adhesive microspheres as a scatterer, and the translucent adhesive is used. This is because it is difficult to easily find defects on the surface of the sheet itself. Defects on the surface of the pressure-sensitive adhesive sheet are found only after the pressure-sensitive adhesive sheet is attached to the member.

In order to avoid the above-mentioned problems, it is conceivable to reduce the particle size of the adhesive microspheres. However, the pressure-sensitive adhesive sheet disclosed in JP-A-9-208910, which discloses the use of pressure-sensitive adhesive microspheres having a particle size of less than about 1 μm, has only an antistatic function against an electrostatic potential on the order of kV. . Such an antistatic function may sufficiently cause the adhesion of dust and the destruction of electronic circuits.

[0008]

SUMMARY OF THE INVENTION It is therefore an object of the present invention not only to provide high visibility by itself to facilitate visual inspection of an adherend, but also to achieve good adhesion and good adhesion to the adherend. An object of the present invention is to provide a conductive pressure-sensitive adhesive which has removability and can sufficiently protect an adherend mechanically and electrically, and a conductive pressure-sensitive adhesive article using the same.

[0009]

SUMMARY OF THE INVENTION The present invention provides, in one aspect, a conductive adhesive comprising conductive adhesive microspheres having an ion conductive substance bonded to the surface via a graft bond. Crosslinking is performed inside the adhesive microspheres and / or between the adhesive microspheres, the adhesive microspheres have a particle size of 0.01 to 1 μm, and are generated by peeling of the conductive adhesive. Maximum electrostatic potential is 50
V / 25 mm.

In another aspect, the present invention provides a conductive pressure-sensitive adhesive layer comprising the conductive pressure-sensitive adhesive of the present invention,
And a substrate supporting the conductive pressure-sensitive adhesive layer.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. FIG. 1 is a cross-sectional view showing a configuration of an antistatic pressure-sensitive adhesive sheet 10 which is one embodiment of the conductive pressure-sensitive adhesive article of the present invention. This antistatic pressure-sensitive adhesive sheet 10 is
0 and the conductive pressure-sensitive adhesive layer 30 formed on the base material 20
When applied to a member (not shown) as an adherend, the surface can be mechanically protected until the member is used.

The substrate 20 is usually made of a transparent resin material such as polyethylene, polypropylene, polyester or ethylene-vinyl acetate copolymer. Further, the base material 20 has flexibility, and when the antistatic pressure-sensitive adhesive sheet 10 is peeled from the member, the peeling can be easily performed. The conductive pressure-sensitive adhesive layer 30 is made of a conductive pressure-sensitive adhesive having adhesive microspheres (not shown). Adhesive microspheres basically have a particle size on the order of submicrons, that is, a particle size of about 0.01 to 1 μm, and have a high transmittance to visible light by suppressing scattering of visible light. I have. In this case, the antistatic adhesive sheet 10
Has high transparency by itself, so that even if the pressure-sensitive adhesive sheet 10 itself has a defect such as a scratch, it can be easily found before attaching to the member.

Further, the adhesive microspheres constituting the conductive adhesive of the present invention are, in detail, formed by bonding an ion conductive substance to the surface of a spherical adhesive. The spherical adhesive is basically 2-ethylhexyl carbitol acrylate, 2-ethylhexyl acrylate,
Isooctyl acrylate, dodecyl methacrylate,
It is made of a polymer or copolymer of a (meth) acrylic monomer such as butyl acrylate. The above monomers may be used alone or in combination of two or more.

Further, the conductive pressure-sensitive adhesive has a structure in which the pressure-sensitive adhesive is crosslinked inside and / or between the pressure-sensitive adhesive microspheres, and contributes to imparting excellent heat resistance. . Such a conductive adhesive having heat resistance can suitably protect members such as a polarizing plate and an electronic substrate which are exposed to a high temperature (about 100 ° C.) in an assembling process. Further, the conductive pressure-sensitive adhesive having a crosslinked structure can maintain the adhesive strength of the conductive pressure-sensitive adhesive at a desired value. In particular, when the spherical pressure-sensitive adhesive is made of a polymer or copolymer of 2-ethylhexyl carbitol acrylate, the adhesive strength is 1%.
It becomes 0 to 60 g / inch (about 4 to 24 g / cm), so that easy peeling of the antistatic pressure-sensitive adhesive sheet can be suitably realized when the member is used.

The ionic conductive substance is preferably made of nonylphenoxy polyethylene glycol acrylate containing ethylene oxide, and can form a complex with a cation to provide ionic conductivity to the conductive adhesive. Nonylphenoxy polyethylene glycol acrylate preferably contains an average of 8 to 100 ethylene oxide. Ethylene oxide is about 8 on average
If less than the number, the conductive pressure-sensitive adhesive does not have ionic conductivity, and conversely, if the average amount of ethylene oxide is more than about 100, the cohesive force of the conductive pressure-sensitive adhesive is reduced, which causes adhesive residue. It is. Further, the cation is preferably a lithium ion (Li ⁺ ), a potassium ion (K ⁺ ), or a sodium ion (Na ⁺ ) having a relatively small ionic radius. These cations have a high mobility, can quickly neutralize the charge, and can provide a low resistance to the antistatic pressure-sensitive adhesive sheet. In particular, in the present embodiment, not only the surface resistance is reduced to about 1 × 10 ¹¹ Ω / □, but also the electrostatic potential generated due to the peeling of the conductive adhesive is suppressed to a maximum of 50 V / 25 mm. Such a value can sufficiently prevent adhesion of dust and destruction of an electronic circuit.

The adhesive microspheres of the present embodiment are basically
It can be formed by aqueous emulsion polymerization using a water-soluble initiator such as ammonium persulfate. At this time, as a surfactant, a copolymerizable surfactant capable of copolymerizing with a (meth) acrylic monomer such as Aqualon HS-10 or Aqualon RN-20 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). Preferably, an agent is added to the reaction system. This is because the copolymerizable surfactant can not only suppress the concentration on the surface of the dried spherical pressure-sensitive adhesive, but also ensure the stability of the adhesive force and the moisture resistance.

Further, a crosslinking reaction may be used for forming the adhesive microspheres. In particular, when a monomer containing a keto group such as diacetone acrylamide is added during the above-mentioned emulsion polymerization, a crosslinking reaction may be carried out by adding adipic dihydrazide as a crosslinking agent to the reaction system.
At this time, the keto group of the monomer becomes a crosslinking point and reacts with the hydrazide group of adipic dihydrazide. The crosslinking reaction is performed in an aqueous solution, and water acts as an inhibitor of the crosslinking reaction. Therefore, the pot life of the emulsion can be extended.

[0018]

Next, the present invention will be described with reference to examples. In each example, the composition of each component used for preparing the adhesive microsphere emulsion and the antistatic adhesive and the measured adhesive properties are summarized in Table 1 below for reference. Please refer to them as well. In addition, "parts"
Means "parts by weight" unless otherwise specified. Example 1 Preparation of Adhesive Microspheres: First, Aqualon H was used as a copolymerizable surfactant in 100.0 parts of ion-exchanged water.
1.0 part of S-10, 3.0 parts of Aqualon RN-20
Part A, 1.0 part of sodium p-styrenesulfonate and 2.0 parts of diacetone acrylamide were respectively dissolved to prepare a solution A. Next, as a (meth) acrylate, 83.0 parts of 2-ethylhexyl carbitol acrylate, 8.0 parts of nonylphenoxy polyethylene glycol acrylate (including an average of 8 ethylene oxides), 2.0 parts of acrylic acid, and Solution B was prepared by mixing and dissolving 2.5 parts of stearyl acrylate.

Solution A and solution B prepared as described above
And a high-speed rotary stirrer (RO) manufactured by Tokushu Kika Co., Ltd.
Using BOMICS ^™ ), the mixture was stirred at 15,000 rpm for 15 minutes to perform emulsification and dispersion. Next, the obtained dispersion was charged into a reactor equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen gas inlet,
0.2 parts of ammonium persulfate as a polymerization initiator was charged, and a polymerization reaction was carried out at 65 ° C. for 5 hours under a nitrogen gas atmosphere to prepare an acrylic emulsion copolymer. Preparation of antistatic pressure-sensitive adhesive and antistatic pressure-sensitive adhesive sheet: 1 of acrylic emulsion copolymer prepared in the above steps
After neutralizing 00.0 parts with 5% lithium hydroxide aqueous solution,
1.5 parts of a 20% aqueous solution of lithium nitrate and 5.0 parts of 1
A 0% aqueous solution of adipic dihydrazide was added to prepare an emulsion containing a conductive adhesive.

Next, a 25 μm-thick polyethylene terephthalate substrate is coated with an emulsion containing the above-mentioned conductive adhesive using a knife coater.
After drying, an antistatic pressure-sensitive adhesive sheet provided with a conductive pressure-sensitive adhesive layer having a thickness of 25 μm was obtained. Example 2 An antistatic pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 above. However, in this example, as (meth) acrylate,
Instead of using 83.0 parts of 2-ethylhexyl carbitol acrylate and 2.0 parts of diacetone acrylamide, 62.5 parts of 2-ethylhexyl acrylate, 21.5 parts of n-butyl acrylate and 1 .
0 parts of 1,6-hexanediol diacrylate were used. As a crosslinking agent, instead of 5.0 parts of 10% adipic dihydrazide, 1.0 part of Denacol EX was used.
-421 was used. Example 3 An antistatic pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 above. However, in this example, as (meth) acrylate,
Instead of using 83.0 parts of 2-ethylhexyl carbitol acrylate and 2.0 parts of diacetone acrylamide, use 91.0 parts of n-butyl acrylate and 8.0 parts of nonylphenoxy polyethylene glycol. Instead of using acrylate (containing an average of 8 ethylene oxide), 2.0 parts of nonylphenoxy polyethylene glycol acrylate (containing an average of 16 ethylene oxide) was used. Further, instead of 5.0 parts of 10% adipic dihydrazide, 1.0 part of Denacol EX-421 was used as a crosslinking agent. Example 4 An antistatic pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 above. However, in this example, as (meth) acrylate,
Instead of using 83.0 parts of 2-ethylhexyl carbitol acrylate and 1.0 part of sodium p-styrenesulfonate, 82.3 parts of isooctyl acrylate and 0.7 part of 1,6-hexane Instead of using diol diacrylate and 8.0 parts of nonylphenoxy polyethylene glycol acrylate (containing an average of 8 ethylene oxides), 12.0 parts of the same nonylphenoxy containing an average of 8 ethylene oxides Polyethylene glycol acrylate was used.
Further, only 1.0 part of Aqualon HS-10 was used as a copolymerizable surfactant (Aqualon RN-2).
0 is omitted). Example 5 An antistatic pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 above. However, in this example, as (meth) acrylate,
Instead of using 83.0 parts of 2-ethylhexyl carbitol acrylate and 2.0 parts of diacetone acrylamide, 79.5 parts of 2-ethylhexyl carbitol acrylate and 5.0 parts of diacetone acrylamide; 0.5 part of 1,6-hexanediol diacrylate and 5.0 parts of 10
Instead of the% adipic dihydrazide, 13.0 parts of the same 10% adipic hydrazide were used. [Evaluation of properties of antistatic pressure-sensitive adhesive sheet] Examples 1 to 5
The antistatic pressure-sensitive adhesive sheet prepared in each of the above was used for the following items: (a) surface resistance value, (b) electrostatic potential generated by peeling from the adherend, (c) adhesive force before and after heating, and (d) heating The optical light transmittance before and after was evaluated. The adherend, Sumitomo Chemical Co., Ltd. of the polarizing plate (trade name: Sumikalan ^TM,
(Anti-glare type) was used. Surface resistance (Ω /
□) and electrostatic potential (V) were measured under the conditions of 25 ° C. and 50% RH according to the test method of EOS / ESD Association Standard S11.11. The measurement of the adhesive force (g / 25 mm)
The test was carried out by a 180 ° peel test, and the presence or absence of adhesive residue was also evaluated. The optical light transmittance (%) was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH-SENSO).
R). In each test, the condition of the heat treatment was 100 ° C. for 4 hours.

The results of the evaluation of each item are shown in Table 1 below.

[0022]

[Table 1]

According to the results shown in Table 1 above, the surface resistance of the antistatic pressure-sensitive adhesive sheet was 9.4 × 10 ⁹ at the maximum.
Ω / □, which is about the same as the conventional product, but the electrostatic potential is 5.0 to 16.0 V, which is about 1000
It can be seen that it has decreased to one-half. Such a low level of electrostatic potential indicates that the antistatic pressure-sensitive adhesive sheet of the present invention is much more effective than conventional products in order to suppress the adhesion of dust and the destruction of general electronic circuits. In addition, the adhesive force has a value that is easy to re-peel within a desired range before and after heating, and no adhesive residue is observed, which indicates that the adhesive sheet itself can be easily handled. Further, it was also found that the optical transmittance was 90% or more. Therefore, it was clarified that the antistatic pressure-sensitive adhesive sheet of the present invention not only can enhance the visibility of the antistatic pressure-sensitive adhesive sheet itself and members, but also has a sufficient antistatic function.

As described above, the conductive pressure-sensitive adhesive of the present invention and the pressure-sensitive adhesive article using the same have been described particularly with reference to an antistatic pressure-sensitive adhesive sheet. However, it is understood that the present invention is not limited to this. I want to. For example, those skilled in the art will easily recognize that the conductive pressure-sensitive adhesive of the present invention may be applied to a tape or the like, or may be applied to other pressure-sensitive adhesive products.

[0025]

As described above, according to the present invention, not only high visibility is provided by itself to facilitate visual inspection of the adherend, but also good adhesion to the adherend. The present invention can provide a conductive pressure-sensitive adhesive which has removability and can sufficiently protect an adherend mechanically and electrically, and a conductive pressure-sensitive adhesive article using the same.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of an antistatic pressure-sensitive adhesive sheet which is a preferred embodiment of a conductive pressure-sensitive adhesive article according to the present invention.

[Explanation of symbols]

 10 antistatic pressure-sensitive adhesive sheet 20 base material 30 conductive pressure-sensitive adhesive layer

Claims (2)

[Claims] 1. A conductive adhesive comprising conductive adhesive microspheres having an ion conductive substance bonded to a surface via a graft bond, wherein said adhesive microspheres have an interior and / or an adhesive microsphere. The adhesive microspheres have a particle diameter of 0.01 to 1 μm, and the maximum electrostatic potential generated by peeling of the conductive adhesive is 50 V / 25 mm. Conductive adhesive. 2. A conductive pressure-sensitive adhesive article, comprising: a conductive pressure-sensitive adhesive layer comprising the conductive pressure-sensitive adhesive according to claim 1; and a base material supporting the conductive pressure-sensitive adhesive layer.