JP2000328016A - Re-peelable adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a re-peelable adhesive tape which hinders the price rise of the adhesive and makes a complex process management unnecessary by laminating a specific acrylic adhesive on at least one side of a support and specifying the adhesiveness. SOLUTION: An acrylic polymer is obtained by copolymerizing a 4-12C alkyl (meth)acrylate monomer and 3-20 wt.% of a radical-polymerizable monomer having a carboxy group. An acrylic adhesive is obtained by crosslinking this acrylic polymer with a crosslinking agent having, in its molecule, a functional group which reacts with a carboxylic group to achieve a gel fraction of not less than 80 wt.%. By laminating this acrylic adhesive on at least one side of a support, a re-peelable adhesive tape having an adhesiveness by the 180 deg. peeling method specified by JIS-Z-02-37-8 of 300-700 g/25 mm at 40 deg.C and not less than 10 g/25 mm at 120 deg.C is obtained. This acrylic adhesive may contain 0.05-4 wt.% of a plasticizer and a benzotriazole metal corrosion inhibitor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for protecting a substrate resin and a circuit pattern in various manufacturing processes such as etching in the manufacture of a circuit board.
The present invention relates to a pressure-sensitive adhesive tape which is easily peeled off after the end of the process.

[0002]

2. Description of the Related Art Conventionally, in the production of circuit boards and the like, there have been various processing steps such as etching and pressing, and a removable tape for the purpose of protecting the surface of an adherend in those steps has been used. I have. For example, a circuit board is formed by laminating a resist agent on a metal foil carried on an adhesive tape, exposing it to a desired pattern and then performing etching to form a circuit, transferring the circuit onto a substrate, and removing the adhesive tape again. (For example, Japanese Patent Application Laid-Open No. 64-643)
No. 92). The pressure-sensitive adhesive tape used in this method is required to firmly support the metal foil in the etching step and to be capable of easily separating from the metal in the peeling step after the transfer. In other words, it is essential that the adhesive and the metal foil are firmly adhered to each other when the etching is performed, and no slippage or peeling occurs, and that the etching solution can be prevented from entering the interface between the adhesive and the metal foil. After the transfer to the substrate, the adhesive tape is no longer needed and is peeled off, but at this time, the transferred circuit must not be deformed or peeled off.

As an adhesive tape satisfying such requirements, for example, an adhesive tape using an adhesive which is cured by ultraviolet rays or the like is used. 3D cross-linking to reduce adhesive strength, or adhesive tape containing microencapsulated foaming agent in adhesive, heating before foaming step to foam and reduce adhesive area And a pressure-sensitive adhesive whose adhesive force changes at the melting point of the pressure-sensitive adhesive as disclosed in JP-A-9-217043. There have been proposed, for example, ones which are held with adhesive force and made easy to peel at a temperature lower than the melting point in the peeling step.

However, according to the method using these adhesive tapes, the price of the adhesive increases, and in addition, equipment costs increase due to the installation of an ultraviolet irradiation device and a high-temperature heating device, and complicated temperature control for each process is required. Inevitably, the price of the product rebounds.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and can suppress an increase in the price of an adhesive, without complicating the process management, and without increasing the circuit board. It is intended to provide a removable pressure-sensitive adhesive tape suitable for use in the production of, for example,.

[0006]

According to the present invention, a (meth) acrylic acid alkyl ester monomer having an alkyl group of 4 to 12 carbon atoms is used as a main monomer, and 3 to 3 of the total monomers are used. 2
An acrylic polymer obtained by copolymerizing 0% by weight of a carboxyl group-containing radical polymerizable monomer is crosslinked to a gel fraction of 80% by weight or more with a crosslinking agent having a functional group that reacts with a carboxyl group in the molecule. Acrylic pressure-sensitive adhesive layer is laminated on at least one surface of the support, and has an adhesive strength by a 180-degree peeling method defined in JIS Z 0237-8 of 300 to 700 g / 25 at 40 ° C.
mm, 10 g / 25 mm or more at 120 ° C.
It is completed. Hereinafter, the present invention will be specifically described.

The pressure-sensitive adhesive layer constituting the removable pressure-sensitive adhesive tape of the present invention comprises, as a main monomer, an alkyl (meth) acrylate monomer having an alkyl group of 4 to 12 carbon atoms, and a carboxyl group. The main component is an acrylic polymer obtained by copolymerizing a radical polymerizable monomer having Examples of the alkyl (meth) acrylate monomer having 4 to 12 carbon atoms in the alkyl group include n-butyl (meth) acrylate, isobutyl (meth) acrylate,
Examples include n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and isononyl (meth) acrylate.

Examples of the carboxyl group-containing monomer include monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid and itaconic acid; dicarboxylic acids such as fumaric acid and maleic acid; and monoesters thereof. Of these carboxyl group-containing monomers, acrylic acid and methacrylic acid are preferably used.

The carboxyl group-containing monomer is copolymerized in an amount of 3 to 20% by weight of the whole monomer. If the amount is less than 3% by weight, the adhesive force after crosslinking is insufficient, and peeling is likely to occur in the etching step and the pressing step. If the amount exceeds 20% by weight, the polarity of the pressure-sensitive adhesive becomes too large, and the peeling step tends to be difficult. Cannot be avoided, and none of them can achieve the object of the present invention.

In the acrylic polymer of the present invention, in addition to the above (meth) acrylic acid alkyl ester monomer and carboxyl group-containing monomer, a small amount of a single component of a modifying component for the purpose of adjusting the glass transition temperature, polarity, etc. The body may be copolymerized.
Examples of such a monomer include methyl (meth) acrylate, ethyl (meth) acrylate, acrylamide, vinyl acetate, styrene, acrylonitrile, and vinylpyrrolidone. These may be used alone or in an appropriate combination of two or more depending on the purpose, but are preferably kept within about 30% by weight of the whole monomer. Excessive copolymerization may affect the original adhesive performance of the acrylic polymer.

The copolymerization reaction for obtaining the acrylic polymer may be performed according to a conventionally known method, and is not particularly limited. However, since the obtained polymer needs to be cross-linked with a cross-linking agent, a cross-linkable monomer is used. It is preferable to avoid a polymerization method in which a monomer is copolymerized. Suitable polymerization methods include:
For example, radical polymerization, suspension polymerization, emulsion polymerization, bulk polymerization and the like by heat or radiation in an inert organic solvent can be mentioned.

Weight average molecular weight Mw of acrylic polymer
Is gel permeation chromatography (GPC)
200,000 to 3,000,000, more preferably about 300,000 to 1,500,000 in terms of polystyrene. M
If w is less than 200,000, the cohesive force of the pressure-sensitive adhesive tends to be insufficient even if crosslinked, and if it exceeds 3,000,000, coating suitability becomes poor, and a uniform pressure-sensitive adhesive layer may not be obtained. .

[0013] A crosslinking agent is blended with the acrylic polymer in order to perform crosslinking. As the crosslinking agent, a low-molecular compound having two or more functional groups that react with a carboxyl group in the molecule is used. Examples of this type of crosslinking agent include isocyanate group-containing compounds, epoxy group (or glycidyl group) -containing compounds, aziridinyl group-containing compounds, metal complexes, and melamine-based compounds.

The amount of the crosslinking agent is adjusted so that the gel fraction of the acrylic polymer after crosslinking is at least 80% by weight, preferably at least 90% by weight. However, depending on the type of the cross-linking agent, as a result of excessive self-reaction of the cross-linking agent, the resulting product may adversely affect the cross-linking system. If the gel fraction is less than 80% by weight, the formed circuit pattern tends to be easily displaced on the adhesive tape during pressing in the transfer step, so that accurate transfer may not be performed. In addition, adhesive residue of the pressure-sensitive adhesive is likely to be generated in a peeling step after the transfer.

[0015] The gel fraction in the present invention is defined as the dry weight of the insoluble matter, which is obtained by dissolving a sample in a large excess of tetrahydrofuran (THF) with shaking and filtering through a 200 mesh net, relative to the dry weight before dissolution. The ratio is expressed as a percentage.

The above-mentioned acrylic polymer and cross-linking agent are essential components of the pressure-sensitive adhesive used in the removable pressure-sensitive adhesive tape of the present invention. A small amount of optional components may be blended depending on the conditions.

For example, since the surface of a metal foil generally has fine irregularities, it is easy to entrap fine bubbles when laminating the metal foil with an adhesive tape. If the etching process is performed with air bubbles involved, the etching solution may enter, resulting in discoloration due to metal corrosion. In order to prevent such a phenomenon, it is important to improve the followability of the pressure-sensitive adhesive to the metal surface so that air bubbles are hardly involved, and it is effective to add a plasticizer in the pressure-sensitive adhesive composition. I found it.

The type of the plasticizer to be blended is not necessarily limited, and esters of aliphatic polycarboxylic acids,
Esters of aromatic polycarboxylic acids, low-molecular plasticizers such as phosphate esters and high-molecular plasticizers such as polyesters can be exemplified, but esters of aliphatic dibasic acids are particularly effective by various experiments, Among them, it has been found that adipic acid diester is most suitable. The compounding amount is preferably 0.05 to 4% by weight, and the molecular weight is desirably 300 or more. Excessive compounding reduces the cohesive force of the adhesive, which may cause adhesive residue in the peeling process. In addition, when the molecular weight is small, bleeding out to the interface between the adhesive and the metal is likely to occur. This will contaminate the metal surface after peeling.

It is more preferable to add a benzotriazole compound to the adhesive. A benzotriazole-based compound is known to have an action of preventing metal corrosion, and by blending it, it is possible to more effectively prevent discoloration due to metal corrosion caused by an etchant. The benzotriazole-based compound may be added in an effective amount of about 0.01 to 5% by weight.

The acrylic polymer optionally containing the above optional components is usually dissolved in an appropriate organic solvent and then a crosslinking agent is added thereto. The acrylic polymer is preferably added directly to the support within a so-called pot life time. And then dried or coated on a process paper that has been subjected to a release treatment and then dried and transferred onto a support to form an adhesive tape. There is no limitation on the coating means and the drying method, and known ones can be employed.

The thickness of the coated and dried pressure-sensitive adhesive layer is not particularly limited. However, if the pressure-sensitive adhesive layer is too thin, the pressure-sensitive adhesive strength may be insufficient or uniform coating may be hindered.
Conversely, if the thickness is too large, the adhesive strength may be too high, or the circuit pattern may shift on the tape.
It may be about μm.

As the support used for the removable adhesive tape of the present invention, a thermoplastic synthetic resin film having flexibility, low elongation and high breaking strength is preferably used. Resin films such as polyesters such as terephthalate, polybutylene terephthalate and polyethylene naphthalate, polyimides, polycarbonates, polysulfones, polyethersulfones, polypropylenes, polystyrenes, polyvinyl chlorides and the like, and these may be used in a single layer. It may be used in a laminate having more than two layers.

In addition, the support is required to have durability against an etching solution, heat resistance to a high temperature of about 150 ° C., and a small heat shrinkage rate so as not to affect the dimensional accuracy of the circuit. A resin film such as polyethylene naphthalate can be suitably used.

The thickness of the support is not particularly limited and may be appropriately designed, but is preferably 6 to 200 μm.
More preferably, it is selected in the range of 10 to 100 μm.
When the thickness is 6 μm or less, the support may be easily wrinkled and the accuracy of the circuit may be deteriorated. When the thickness is more than 200 μm, the handleability may be deteriorated depending on the balance with the elastic modulus,
It may be difficult to peel off the adhesive tape,
It is economically disadvantageous.

When a thermoplastic synthetic resin film is used as a support, the surface thereof is subjected to physical treatment such as sandblasting or flame treatment or chemical treatment such as corona treatment or plasma treatment in order to enhance the adhesion to the adhesive. Alternatively, it is preferable to perform a primer treatment or the like.

The back surface of the support, that is, the surface opposite to the surface on which the pressure-sensitive adhesive layer is laminated, which is in contact with the surface of the pressure-sensitive adhesive layer when wound into a roll, is provided with In order to reduce a peeling force (also referred to as a developing force), a release treatment is usually performed. Examples of the release treatment include, but are not limited to, application of a silicone-based release agent, a fluorine-based release agent, and a long-chain alkyl graft polymer-based release agent accompanied by a curing reaction, if necessary.

The thus-prepared removable pressure-sensitive adhesive tape of the present invention has an adhesive strength by a 180-degree peeling method specified in JIS Z 0237-8 of 30 ° C. at 40 ° C.
0-700g / 25mm, 10g / 25mm at 120 ° C
It is necessary to be above.

The patterning of the circuit by the etching method is usually performed at a temperature of about 40 ° C., but if the adhesive strength at 40 ° C. is less than 300 g / 25 mm, the metal foil is peeled off from the adhesive tape during the etching process. This is because there is fear. However, if the adhesive strength is excessively large, re-peeling may be difficult due to an increase in the adhesive strength after the transfer step. Therefore, the upper limit should be designed to be about 700 g / 25 mm.

Further, in the step of transferring the metal foil on which the circuit pattern is formed to the substrate, the metal foil is exposed to a high temperature of about 120 ° C.
If the thickness is less than / 25 mm, the formed circuit pattern is displaced on the adhesive tape during the transfer pressing, and as a result, there is a possibility that a problem that the pattern cannot be accurately transferred onto the insulating resin serving as the substrate may occur. Is more preferable.

[0030]

[Example 1]

(Preparation of acrylic polymer solution) In a separable flask equipped with a stirring blade, a condenser, and a nitrogen gas inlet tube,
100 parts by weight of n-butyl acrylate, acrylic acid 10
A monomer mixture consisting of parts by weight and 100 parts of ethyl acetate
After mixing the parts by weight, bubbling was performed with nitrogen gas under stirring to remove dissolved oxygen. Next, the nitrogen gas inlet tube was raised above the liquid surface, the temperature of the system was raised to 80 ° C. while controlling the flow rate of the nitrogen gas, and the polymerization reaction was started using azobisisobutyronitrile as a polymerization initiator. The temperature of the system was kept at 80 ° C. for 6 hours until the completion of the polymerization. The ethyl acetate solution of the acrylic polymer thus obtained was diluted with toluene while cooling to obtain a pressure-sensitive adhesive solution having a solid content concentration of 20% by weight. The Mw of the acrylic polymer determined by GPC analysis was about 400,000.

(Preparation of pressure-sensitive adhesive tape) An aromatic isocyanate-based crosslinking agent (trade name "Coronate L-45", manufactured by Nippon Polyurethane Co., Ltd.) was added to a solution of 9 parts by weight with respect to 100 parts by weight of the solid content of the obtained pressure-sensitive adhesive solution. 5 parts by weight
Apply on a polyester substrate to make μ
× 3 minutes drying to obtain an adhesive tape. This adhesive tape
After curing for one week in a 3 ° C., 65% RH atmosphere, it was subjected to a performance evaluation test.

Example 2 1 part by weight of an adipic acid diester-based plasticizer (trade name "RS-700"; molecular weight: 550, manufactured by Asahi Denka Co., Ltd.) was added to 100 parts by weight of the solid content of the adhesive solution. Except for this, an adhesive tape was obtained in the same manner as in Example 1.

Example 3 1 part by weight of an adipic acid diester plasticizer (trade name "RS-700", manufactured by Asahi Denka Co., Ltd .; molecular weight: 550) and 100 parts by weight of benzoic acid were added to 100 parts by weight of the solid content of the pressure-sensitive adhesive solution. An adhesive tape was obtained in the same manner as in Example 1 except that 3 parts by weight of a triazole-based metal corrosion inhibitor (trade name “TTR” manufactured by Shiraishi Calcium Co., Ltd.) was added.

Comparative Example 1 An adhesive tape was obtained in the same manner as in Example 1 except that the amount of the crosslinking agent was changed to 5 parts by weight.

Comparative Example 2 n-butyl acrylate 10
Polymerization was carried out in the same manner as in Example 1 using a monomer mixture consisting of 0 parts by weight and 1 part by weight of acrylic acid and 90 parts by weight of ethyl acetate to obtain an acrylic polymer having a Mw of 500,000, and 20% by weight of toluene. To prepare an adhesive solution.
A pressure-sensitive adhesive tape was obtained in the same manner as in Example 1, except that this pressure-sensitive adhesive solution was used and the amount of the crosslinking agent added was changed to 4 parts by weight.

The following performance evaluation tests were performed on the pressure-sensitive adhesive tapes produced in Examples 1 to 3 and Comparative Examples 1 and 2. Evaluation item (gel fraction) Sample adhesive on adhesive tape and weigh accurately (W1)
Then, the mixture was dissolved by shaking with a large excess of THF, and the dry weight of the undissolved material filtered off with a 200 mesh net was precisely weighed (W2).
did. The gel fraction is represented by (W2 / W1) × 100% by weight.

Evaluation Items (Adhesive Strength) An adhesive tape shredded to a width of 10 mm was laminated on a copper foil having a thickness of 12 μm, and a tensile tester in which a thermostat adjusted to a predetermined temperature (40 ° C. or 120 ° C.) was set. Use 18
The peeling strength at 0 degree was measured.

Evaluation items (etching suitability, transfer suitability,
Removability) After laminating the pressure-sensitive adhesive tape on a copper foil having a thickness of 12 μm,
Laminating a resist layer on the copper foil surface, then forming a circuit by exposure, development, and etching, when transferring the circuit to the substrate by pressing to produce a circuit board, the shift of the adhesive tape in the etching process, The presence or absence of peeling, the infiltration of the etchant, the presence of distortion in the circuit pattern transferred to the substrate, the removability of the adhesive tape (adhesive residue, deformation of the circuit pattern), and the presence of corrosion on the circuit surface were observed. .

Evaluation Items (Applicability for Pressing and Removability) Two substrates on which a circuit was formed were laminated, and an adhesive tape was laminated on the surface of the substrate where the circuit was exposed to protect it.
After press lamination at 50 ° C. and 50 kg / cm ² for 60 seconds, the presence or absence of floating and peeling of the adhesive tape and the removability of the adhesive tape were evaluated by the presence or absence of adhesive residue. Table 1 shows the evaluation results.

[0040]

[Table 1]

[0041]

According to the present invention, for example, a method for manufacturing a circuit board by transferring a metal foil typified by a copper foil on an adhesive tape and forming the circuit on a substrate, The process of circuit pattern formation, transfer, and peeling of the adhesive tape after transfer can be performed reliably without increasing the cost of the agent and without the need for complicated process control. It is possible to provide a removable adhesive tape that does not come.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shigeru Dangami 3535 Kurohama, Hasuda-shi, Saitama F-term (reference) 4J004 AA10 AA17 AB01 CA04 CA05 CA06 FA04 FA05 4J040 DF041 DF051 EB132 EC002 ED002 EF181 GA07 HB32 HB34 HC22 HC25 HD24 HD43 JA09 JB09 KA16 KA29 KA31 LA01 LA06 NA20

Claims (4)

[Claims] An acrylic acid ester of (meth) acrylic acid having 4 to 12 carbon atoms in an alkyl group as a main component monomer,
An acrylic polymer obtained by copolymerizing at least 3 to 20% by weight of a carboxyl group-containing radical polymerizable monomer of all monomers is crosslinked with a crosslinking agent having a functional group that reacts with a carboxyl group in the molecule. An acrylic pressure-sensitive adhesive layer crosslinked to a gel fraction of 80% by weight or more is laminated on at least one surface of the support, and its JIS Z 02
The adhesive strength by the 180-degree peeling method specified in 37-8 is 300 to 700 g / 25 mm at 40 ° C and 1 at 120 ° C.
Removable pressure-sensitive adhesive tape of 0 g / 25 mm or more. 2. The plasticizer contains 0.05 to 4% by weight of the pressure-sensitive adhesive.
The removable pressure-sensitive adhesive tape according to claim 1, which is contained. 3. The removable tape according to claim 2, wherein the plasticizer is adipic acid diester. 4. The pressure-sensitive adhesive tape according to claim 1, wherein the benzotriazole-based metal corrosion inhibitor is contained in an effective amount in the pressure-sensitive adhesive.