JP5001530B2 - Removable adhesive, removable adhesive sheet, and circuit board manufacturing method using the same - Google Patents

Description

  The present invention relates to a releasable pressure-sensitive adhesive useful in the production of circuit boards such as flexible printed boards, a releasable pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive, and a method for producing a circuit board using these. It is.

  A circuit board such as a flexible printed circuit (FPC) is used in various electronic devices. In particular, FPC has excellent features such as flexibility, flexibility, easy deformation, and the ability to be stored in a narrow space. Miniaturization of mobile phones, personal digital assistants, notebook computers, digital video cameras, etc. Widely used as circuit boards and the like for small electronic devices requiring high density.

  As a method for manufacturing such an FPC, for example, a laminated board (such as a copper clad laminated board (CCL)) in which a metal thin film is formed on one surface of a flexible insulating substrate is used as a starting material. There is a method of forming a wiring pattern by removing unnecessary portions of the metal thin film by performing a selective etching process (referred to as a subtractive process).

  However, since such a laminate is rich in flexibility and flexibility, the handling strength is not sufficient in the state as it is, and it is difficult to perform a selective etching process or the like. Therefore, a releasable pressure-sensitive adhesive sheet is attached to the surface of the laminated plate where the metal thin film is not formed, subjected to selective etching in a state in which handling strength is temporarily improved, and a wiring pattern is formed. Many methods for obtaining an FPC by peeling a releasable sheet from a plate are employed.

  The FPC manufactured in this way is often used as a circuit board in which a reinforcing sheet is bonded to the surface on which the wiring pattern is not formed. This reinforcing sheet (also referred to as a stiffener) can improve the strength of the substrate, prevent warping, or maintain the shape.

  Examples of the releasable pressure-sensitive adhesive sheet used in the above-described applications include, for example, at least three isocyanates that have already been disclosed by the present applicant and have a predetermined peeling force and the pressure-sensitive adhesive layer is made of a cyclic polymer of diisocyanate. Examples thereof include a pressure-sensitive adhesive sheet comprising a reaction product of a curing agent having a group and a pressure-sensitive adhesive polymer having an active hydrogen-containing group (for example, see Patent Document 1).

JP 2001-106998 A

  The pressure-sensitive adhesive sheet is excellent in re-peelability and can be easily peeled from the laminate, and therefore has a preferable feature that it is difficult to bend or wrinkle on a circuit board such as an FPC at the time of peeling. And widely used in the manufacture of circuit boards such as FPC. However, the above-described method for manufacturing a circuit board such as an FPC using an adhesive sheet has a problem that it is difficult to secure the adhesive strength between the circuit board and the reinforcing sheet when the reinforcing sheet is bonded to the obtained circuit board. It had been. If the adhesive strength between the circuit board and the reinforcing sheet is insufficient, the reinforcing sheet is likely to fall off, which causes a decrease in the strength of the board, occurrence of warpage, a decrease in shape stability, etc. It is not preferable in that it causes a decrease in sex.

  As described above, at present, a method for manufacturing a highly reliable circuit board that can secure sufficient adhesion strength between a circuit board such as an FPC and a reinforcing sheet has not yet been disclosed. The industry is eager to create such measures. The present invention has been made in order to solve such a problem of the prior art, and can ensure a sufficient adhesive strength between the FPC and the reinforcing sheet, and manufacture a highly reliable circuit board. The present invention provides a releasable pressure-sensitive adhesive, a releasable pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive, and a method for producing a circuit board using these.

  As a result of intensive studies to solve the above problems, the present inventors have found that the adhesive layer of the releasable adhesive sheet partially remains on the circuit board when the releasable adhesive sheet is peeled off from the circuit board. It was found that the adhesive strength between the sheet and the FPC was reduced. And it discovered that the said subject could be solved by using a material with high adhesiveness with a reinforcement sheet as an adhesive of a releasable adhesive sheet. That is, according to the present invention, the following removable pressure-sensitive adhesive, removable pressure-sensitive adhesive sheet, and a method for producing a circuit board using the same are provided.

[1] Copolymerization formed from a monomer component containing (a component) an acrylic acid alkyl ester or methacrylic acid alkyl ester and (b component) a monomer having a carboxyl group as a functional group, and having an acid value of 40 mgKOH / g or more Removable pressure-sensitive adhesive formed from a raw material composition containing a coalesced (hereinafter sometimes referred to as “acrylic resin”) and an epoxy-based crosslinking agent, and having an adhesive strength of 0.4 N / 25 mm or more according to the following adhesive strength test Agent.
Adhesive strength test:
(1) A pressure-sensitive adhesive layer in which a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive having a thickness of 7 μm is disposed on the surface of a PET film having a thickness of 50 μm is cut into a width of 25 mm and a length of 250 mm. A 25 μm thick adhesive sheet (trade name: Pyralax (registered trademark) LF-0100, manufactured by DuPont) and a 175 μm thick polyimide film are laminated to ^each other at 30 ° C. and 200 kg / cm ^2. A test piece is formed by pressure bonding by heating and pressurizing for minutes.
(2) After leaving the test piece for 20 minutes at a temperature of 23 ° C. and a humidity of 65% RH, from the test piece under the conditions of a temperature of 23 ° C., a humidity of 65% RH, a tensile speed of 300 mm / min, and a 180 ° direction. The adhesive strength when peeling the releasable pressure-sensitive adhesive sheet is measured.

[ 2 ] A re-peelable pressure-sensitive adhesive sheet comprising a film-like base material and an adhesive layer disposed on one surface of the base material, wherein the adhesive layer is the re-peeling according to [1 ] above. A releasable pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive.

[ 3 ] Patterning the conductor layer by processing a laminated board comprising an insulating substrate, a conductor layer disposed on the surface of the insulating substrate, and a releasable adhesive sheet disposed on the back surface of the insulating substrate. And a circuit board manufacturing method including a step of removing the releasable pressure-sensitive adhesive sheet from the laminate,
The manufacturing method of the circuit board whose said releasable adhesive sheet is the releasable adhesive sheet as described in said [ 2 ].

[ 4 ] After the step of peeling the releasable adhesive sheet from the laminate,
The method for producing a circuit board according to the above [ 3 ], further comprising a step of disposing a reinforcing sheet on the peeled surface.

  Since the releasable pressure-sensitive adhesive of the present invention has a bond strength of not less than a predetermined value, when it is used as a pressure-sensitive adhesive for a releasable pressure-sensitive adhesive sheet when manufacturing a circuit board such as an FPC, the pressure-sensitive adhesive sheet is peeled off. In this step, for example, in the step of attaching the reinforcing sheet, sufficient adhesion strength between the reinforcing sheet and the circuit board can be ensured, so that the dropping off of the reinforcing sheet is suppressed. That is, a reduction in the strength of the substrate, occurrence of warpage, a decrease in shape stability, and the like are suppressed, and a highly reliable circuit board can be manufactured.

  Hereinafter, although an embodiment of the present invention is described concretely, the present invention is not limited to the following form.

[1] Re-peelable pressure-sensitive adhesive The re-peelable pressure-sensitive adhesive of the present invention has an adhesive strength of 0 . 4N / 25mm or more.

Adhesive strength test:
(1) A pressure-sensitive adhesive layer in which a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive having a thickness of 7 μm is disposed on the surface of a PET film having a thickness of 50 μm is cut into a width of 25 mm and a length of 250 mm. A 25 μm thick adhesive sheet (trade name: Piralux (registered trademark) LF-0100, manufactured by DuPont Co., Ltd.) and a 175 μm thick polyimide film are laminated, and 30 ° C. under conditions of 180 ° C. and 200 kg / cm ^2. A test piece is formed by pressure bonding by heating and pressurizing for minutes.
(2) After leaving the test piece for 20 minutes at a temperature of 23 ° C. and a humidity of 65% RH, from the test piece under the conditions of a temperature of 23 ° C., a humidity of 65% RH, a tensile speed of 300 mm / min, and a 180 ° direction. The adhesive strength when peeling the releasable pressure-sensitive adhesive sheet is measured.

  Pillalux (registered trademark) LF-0100 is a butyl acrylate adhesive sheet mainly composed of butyl acrylate and butyl methacrylate, and is generally widely used for bonding reinforcing sheets in the production of circuit boards. . Accordingly, the adhesive strength between the adhesive sheet and the releasable pressure-sensitive adhesive is used as an index, and when the adhesive strength is set to the above value or more, the adhesive residue (that is, the releasable pressure-sensitive adhesive) is peeled off when the releasable pressure-sensitive adhesive sheet is peeled off. Even when the phenomenon in which the agent remains on the peeled surface of the adherend occurs, sufficient adhesive strength between the reinforcing sheet and the circuit board can be ensured.

  On the other hand, if this adhesive strength is too high, the removability of the laminate may be deteriorated. Accordingly, the adhesive strength is preferably 10 N / 25 mm or less, more preferably 5 N / 25 mm or less, and particularly preferably 3 N / 25 mm or less.

As the acrylic resin forming the removable pressure sensitive adhesive, by using a high acid value acrylic resin, it is possible to improve the adhesive strength between the adhesive sheet. Further, by combining the acid value of high acrylic resin and e epoxy based crosslinking agent, moderately crosslinked can be obtained an acrylic removable pressure sensitive adhesive, the preferred range of bonding strength between the adhesive sheet It can be strength. Hereinafter, the suitable component of the raw material composition which forms the removable adhesive of this invention is demonstrated.

Acrylic resin:
As described above, the raw material composition for forming the removable pressure sensitive adhesive is seen containing an acrylic resin, the A acrylic-based resins are, (a component) acrylic acid alkyl ester or methacrylic acid alkyl ester (hereinafter, acrylic acid and methacrylic acid and may be referred to inclusively "(meth) acrylic acid"), Ru copolymer der formed from a monomer component containing a monomer having a carboxyl group as the (b component) functional group.

  The component a is an acrylic monomer having a structure in which an alkyl group is ester-bonded to a carboxyl group of (meth) acrylic acid. The type of alkyl group to be ester-bonded is not particularly limited, but is an alkyl group having 3 to 8 carbon atoms, such as a 1-propyl group (n-propyl group), in that tackiness and removability can be imparted. ), 1-butyl group (n-butyl group), 1-pentyl group (n-pentyl group), 1-hexyl group (n-hexyl group), 1-heptyl group (n-heptyl group), 1-octyl group (N-octyl group), 6-methylheptyl group (iso-octyl group), 2-ethylhexyl group and the like are preferable.

  That is, as the (meth) acrylic acid alkyl ester, for example, 1-butyl (meth) acrylate (n-butyl), 1-hexyl (meth) acrylate (n-hexyl), 1-heptyl (meth) acrylate ( n-heptyl), 1-octyl (meth) acrylate (n-octyl), 6-methylheptyl (iso-octyl) (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like are preferable. It is particularly preferable to use 1-butyl acrylate because it is excellent in removability and improves the adhesive strength with the adhesive sheet.

  On the other hand, the component b is a monomer having a carboxyl group as a functional group. Examples of such monomers include carboxyl group-containing vinyl monomers, specifically (meth) acrylic acid, fumaric acid, crotonic acid, maleic acid, itaconic acid and the like. When a monomer having a carboxyl group is used, the acrylic resin to be formed is cross-linked by a cross-linking agent described later, and suitable tackiness, removability and adhesive strength with an adhesive sheet can be easily obtained. In addition, the use of a monomer having a carboxyl group is also preferable from the viewpoint of improving the adhesive strength with metals and various adherends.

The mixing ratio of the component b in the monomer component forming the acrylic resin, the proportion der the acid value of the obtained acrylic resin becomes 4 0 mgKOH / g or more is, is the ratio of the acid value is 60 mg KOH / g or more it is not particularly preferred. On the other hand, if the acid value is too high, Tg tends to be too high and sticking tends to be difficult. Therefore, the blending ratio of component b is preferably such that the acid value of the resulting acrylic resin is 250 mgKOH / g or less, and more preferably 160 mgKOH / g.

  In addition, the monomer component which forms acrylic resin may also contain other monomers (regardless of whether it is an acrylic monomer or a non-acrylic monomer). Although it does not specifically limit about the kind of other monomer, Styrene, vinyl acetate, or N-vinyl pyrrolidone etc. other than acrylic monomers, such as acrylonitrile and acrylamide, are mentioned.

  The blending ratio of component a, component b and other monomers in the monomer component forming the acrylic resin is 70 to 99% by mass for component a, 1 to 30% by mass for component b, etc. The monomer is preferably 0 to 10% by mass, the a component is 80 to 99% by mass, the b component is 1 to 20% by mass, and the other monomers are further preferably 0 to 7% by mass, Is preferably 90 to 99% by mass, the component b is 1 to 10% by mass, and other monomers are 0 to 5% by mass.

  The weight average molecular weight (Mw) of the acrylic resin is preferably 100,000 to 2,000,000, more preferably 200,000 to 1,500,000, and particularly preferably 300,000 to 1,000,000. If it is less than the above range, the acrylic resin can be easily transferred to the adherend, and if it exceeds the above range, the viscosity of the coating liquid increases, and the production efficiency, including the amount of the diluting solvent, from the cost and environmental viewpoints as well. It is not preferable. In addition, an acrylic resin may be used independently and may be used in combination of 2 or more type.

Cross-linking agent:
Material composition to form a removable pressure sensitive adhesive is including further a crosslinking agent. This crosslinking agent can react with the carboxyl group of the acrylic resin. Specifically, an epoxy-based crosslinking agent.

  The epoxy-based crosslinking agent is a crosslinking agent having an epoxy group, and a crosslinking agent having two or more epoxy groups in the molecule is preferable. Preferred epoxy-based crosslinking agents include, for example, ethylene glycol diglycidyl ether, tridiglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diglycidylamine, N, N, N ', N'-tetraglycidyl-m-xylenediamine, 1,3-bis (N, N'-diglycidylaminomethyl) cyclohexane and the like, and in particular, N, N, N', N'-tetraglycidyl- m-xylenediamine, 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane and the like can be suitably used.

  These cross-linking agents are preferable in that they can provide excellent removability and heat resistance. In addition, a crosslinking agent may be used independently and may be used in combination of 2 or more types of crosslinking agents.

  The blending amount of the crosslinking agent is preferably 0.3 to 20 parts by mass, more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the acrylic resin. When the blending amount of the crosslinking agent is less than 0.3 parts by mass, sufficient crosslinking may not be performed, and the adhesive residue generated on the adherend may be excessive, or the peelability may be impaired. When the compounding amount of the agent exceeds 20 parts by mass, the adhesive strength with the adherend in the vicinity of normal temperature may be reduced.

  The raw material composition preferably further contains an antioxidant. As antioxidants, for example, aromatic amine-based antioxidants, phenol-based antioxidants, or phosphite-based antioxidants are known. However, the re-peelability after high-temperature heating as in FPC production is known. In required applications, phenolic antioxidants are preferred in that they are excellent in removability after high-temperature heating and have little adhesive residue. The blending ratio of the antioxidant is preferably 0.01 to 1.0 part by mass and more preferably 0.05 to 0.5 part by mass with respect to 100 parts by mass of the acrylic resin. If the amount of the antioxidant is less than this range, the re-peelability after heating decreases (becomes difficult to peel off), which is not preferable. If the amount exceeds this range, the acid value antioxidant is deposited on the surface of the pressure-sensitive adhesive, and is deposited. Since it adheres to a body etc., it is not preferable. In addition, an antioxidant may be used independently and may be used in combination of 2 or more type.

  Various conventionally used additives such as surfactants, lubricants, stabilizers, viscosity modifiers, tackifier resins, colorants, or organic or inorganic fillers may be added to the raw material composition. it can.

  As tackifying resins, α-pinene-based, β-pinene-based, dipentene-based, terpene-phenol-based terpene-based resins, gum-based, wood-based, tall-based and other natural rosins, or hydrogenation and disproportionation thereof Rosin resins such as rosin derivatives treated by polymerization, maleation, esterification and the like. As the organic filler, acrylic or urethane spherical resin fine particles can be suitably used, and as the inorganic filler, silica, calcium carbonate, alumina or the like can be suitably used.

  The re-peelable pressure-sensitive adhesive can be obtained by heating and crosslinking the raw material composition as described above. For example, the releasable pressure-sensitive adhesive is obtained by dissolving or dispersing the raw material composition in a medium such as a solvent to obtain a raw material coating liquid, applying the raw material coating liquid to a substrate, heating and drying, and crosslinking. Can be obtained.

[2] Re-peelable pressure-sensitive adhesive sheet The re-peelable pressure-sensitive adhesive sheet of the present invention is obtained by disposing the above-described re-peelable pressure-sensitive adhesive on one surface of a film-like substrate and forming an adhesive layer.

  The material of the base material constituting the releasable pressure-sensitive adhesive sheet is not particularly limited, and may be appropriately selected according to the application field of the removable pressure-sensitive adhesive sheet. For example, synthetic resin such as polyethylene terephthalate, polyethylene naphthalate, polyethylene, polycarbonate, triacetyl cellulose, cellophane, polyimide, polyamide, polyphenylene sulfide, polyether imide, polyether sulfone, aromatic polyamide, or polysulfone, or glass, metal, Materials such as ceramics can be mentioned. The substrate may be transparent, or may be colored by blending various pigments and dyes with the material constituting the substrate, and the surface may be processed into a mat shape. Moreover, in order to improve adhesiveness with an adhesion layer, you may use what gave surface treatments, such as a discharge process, a roughening process, and a chemical treatment.

  When using the releasable pressure-sensitive adhesive sheet of the present invention in the field exposed to a temperature condition exceeding 140 ° C. for a long time, in order to avoid problems such as dimensional change and curling as much as possible, It is preferable to use a base material having a heat shrinkage of 0.5% or less, and it is more preferable to use a base material having a heat shrinkage of 0.2% or less. Here, the heat shrinkage rate referred to in the present invention refers to a value defined in JIS C 2318. Usually, it is preferable to select a substrate having a heat shrinkage of 0.2% or less from among a polyethylene terephthalate film and a polyethylene naphthalate film. The thickness of the substrate may be appropriately selected according to the application field of the releasable pressure-sensitive adhesive sheet, but is usually 12 to 250 μm, and preferably 25 to 125 μm from the viewpoint of followability to the adherend and transportability. .

  The re-peelable pressure-sensitive adhesive sheet is prepared by dissolving or dispersing the above-described raw material composition in a liquid medium such as a solvent to prepare a raw material coating liquid having a solid content concentration of about 20 to 80% by mass, and then using the base material or as desired. On the primer layer, it can manufacture by apply | coating by normal application means, for example, methods, such as a roll coater, and heat-drying and forming an adhesion layer. Examples of the solvent used in this case include aromatic hydrocarbon solvents such as toluene and xylene, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, and ester solvents such as ethyl acetate and cellosolve. Needless to say, when is water-soluble, an aqueous solvent can be used. The drying temperature is preferably a temperature at which the acrylic resin crosslinks, and is usually 60 to 150 ° C, preferably 80 to 140 ° C.

  The thickness of the adhesive layer is not particularly limited, but is preferably 1 to 30 μm, more preferably 3 to 20 μm, and particularly preferably 5 to 10 μm.

[3] Method for Manufacturing Circuit Board A circuit board can be suitably manufactured using the above-described releasable pressure-sensitive adhesive sheet. Specifically, a releasable pressure-sensitive adhesive sheet is affixed to the back surface of a laminate having a conductor layer disposed on the surface of an insulating substrate. The laminate with the adhesive sheet is processed to pattern the conductor layer. Patterning can be performed by selectively etching the conductor layer. Then, a circuit board (FPC etc.) can be obtained by peeling a releasable adhesive sheet from a laminated board. Furthermore, a circuit board with a reinforcing sheet can be manufactured by attaching a reinforcing sheet to the peeled surface.

  According to such a manufacturing method, it is possible to obtain good adhesive strength between the reinforcing sheet and the circuit board after the releasable pressure-sensitive adhesive sheet is peeled off and the reinforcing sheet is attached to the surface.

  The insulating substrate is not particularly limited as long as it has the above insulating properties, but it is excellent in flexibility and flexibility, and is made of a material having high heat resistance that can withstand high temperatures when mounted on an electronic device or the like. It is preferable to use a structured film or sheet. Especially, what was comprised from the film which consists of engineering plastics, such as a polyimide film excellent in heat resistance, an aramid film, and LCP, can be used suitably.

  The conductor layer is a part to be patterned, and is preferably made of a conductive metal that can be etched, such as copper.

  Taking the above points into consideration, a copper clad laminate in which a copper foil is formed on the surface of a film made of polyimide can be suitably used. This copper-clad laminate is a two-layer CCL formed by applying polyimide in a molten state on a copper foil and bonding the copper foil and polyimide film with an adhesive such as an epoxy adhesive. A so-called three-layer CCL may also be used.

  Patterning of the conductor layer can be performed by selectively etching a predetermined portion of the conductor layer and removing unnecessary portions of the conductor layer by using, for example, a subtractive method. The method of the selective etching treatment is not particularly limited. For example, after applying a resist (photosensitive resin) to the surface of the conductor layer, the pattern is subjected to exposure / development treatment, so that either an unexposed portion or an exposed portion is obtained. For example, a method may be used in which only the unnecessary portion of the conductor layer is exposed by removing the resist and the exposed portion is removed by etching.

  About another process, it can carry out according to a conventionally well-known method. For example, after applying a selective etching process, after attaching a thermosetting sheet made of a thermosetting resin (hereinafter sometimes referred to as “coverlay film”) so as to cover the formed wiring pattern The wiring protective layer may be formed by heating under a high temperature condition of 160 ° C. or higher and thermosetting the thermosetting sheet. After various treatments for the laminate are completed, the releasable adhesive sheet is peeled from the laminate to obtain a circuit board, and then a circuit board with a reinforcement sheet can be obtained by adhering the reinforcement sheet to the peeled surface. it can.

  The reinforcing sheet is a member which is also called a stiffener, and is installed for the purpose of improving the strength of the circuit board, preventing warpage, maintaining the shape, or the like. Usually, it is made of a material having heat resistance and high strength such as polyimide, aramid, polyester, and LCP. The shape and thickness are not particularly limited, and those having a shape and thickness suitable for the purpose of use can be used. The reinforcing sheet is generally bonded using an adhesive. The adhesive is appropriately selected in consideration of heat resistance, adhesiveness, and the like, but an epoxy adhesive or an acrylic adhesive is preferably used. Among these, an acrylic adhesive is preferable, and a butyl acrylate adhesive is particularly preferable. Specifically, it is preferable to use the Pillalux (registered trademark) series manufactured by DuPont.

  Hereinafter, although the releasable adhesive and releasable adhesive sheet of this invention are demonstrated concretely using an Example, the barrier film and laminated body of this invention are not limited by these Examples.

  In addition, about the releasable adhesive sheet of an Example and a comparative example, the initial stage adhesive force, the post-heating adhesive force, the adhesive strength with an adhesive sheet, and the adhesive strength between a laminated board and a reinforcement sheet were evaluated with the following method.

[Initial adhesive strength]
After the production, the releasable pressure-sensitive adhesive sheets of Examples and Comparative Examples that were not subjected to heat treatment or ultraviolet irradiation treatment were cut into a width of 25 mm and a length of 250 mm. A polyimide film (trade name: Kapton (registered trademark) 100H, manufactured by Toray DuPont Co., Ltd.) having a thickness of 25 μm is attached to the adhesive layer of the cut releasable adhesive sheet, and the mass is 2 kg at a speed of 300 mm / min. The rubber roller was reciprocated once to make a test piece. After leaving the test piece for 20 minutes, the peeling force when the polyimide film was peeled off from the test piece in the 180 ° direction at a tensile speed of 300 mm / min was measured with a tensile tester. did. These steps were all performed under conditions of a temperature of 23 ° C. and a humidity of 65% RH.

[Adhesive strength after heating]
A test piece was prepared in the same manner as the initial adhesive strength and left for 20 minutes. The test piece was heated at 180 ° C. for 2 hours, then cooled under conditions of a temperature of 23 ° C. and a humidity of 65% RH, and the peel strength was measured in the same manner as the initial adhesive strength. It was.

[Adhesive strength with adhesive sheet]
After the production, the releasable pressure-sensitive adhesive sheets of Examples and Comparative Examples that were not subjected to heat treatment or ultraviolet irradiation treatment were cut into a width of 25 mm and a length of 250 mm. The adhesive layer of the cut releasable pressure-sensitive adhesive sheet has a 25 μm-thick adhesive sheet (trade name: Pyralax (registered trademark) LF-0100, manufactured by DuPont Co., Ltd., mainly composed of butyl acrylate and butyl methacrylate. A butyl acrylate adhesive sheet formed from a monomer component) and a polyimide film having a thickness of 175 μm were laminated, and pressure-bonded by heating and pressing for 30 minutes at 180 ° C. and 200 kg / cm ² to obtain a test piece. After leaving this test piece for 20 minutes under conditions of a temperature of 23 ° C. and a humidity of 65% RH, removability from the test piece under the conditions of a temperature of 23 ° C., a humidity of 65% RH, a tensile speed of 300 mm / min, and a 180 ° direction. The peeling force at the time of peeling off the adhesive sheet was measured, and this peeling force was defined as the adhesive strength with the adhesive sheet.

[Adhesive strength between laminate and reinforcing sheet]
After the production, the releasable pressure-sensitive adhesive sheets of Examples and Comparative Examples that were not subjected to heat treatment or ultraviolet irradiation treatment were cut into a width of 25 mm and a length of 250 mm. A polyimide layer of a laminate of a polyimide layer having a thickness of 25 μm and a copper foil having a thickness of 12 μm (trade name: Espanex SC12-25-00AE, manufactured by Nippon Steel Chemical Co., Ltd., hereinafter referred to as “two-layer CCL”) was cut again. A peelable pressure-sensitive adhesive sheet was attached, hot-pressed for 30 minutes at 180 ° C. and 150 kg / cm ² , further heated at 160 ° C. for 30 minutes, and then cooled under conditions of a temperature of 23 ° C. and a humidity of 65% RH. The releasable pressure-sensitive adhesive sheet is peeled off from the two-layer CCL with the re-peelable pressure-sensitive adhesive sheet, and a 25 μm-thick adhesive sheet (trade name: Piralux (registered trademark) LF-0100, DuPont) Co., Ltd.) and a 175 μm thick reinforcing sheet (polyimide film) are sequentially laminated, hot pressed for 30 minutes at 180 ° C. and 150 kg / cm ² , and then cooled under conditions of a temperature of 23 ° C. and a humidity of 65% RH. And it cut | disconnected to the size of width 10mm and length 200mm, and it was set as the test piece. The peel strength when the two-layer CCL was peeled from the test piece in the 180 ° direction at a tensile speed of 50 mm / min was measured with a tensile tester under the conditions of a temperature of 23 ° C. and a humidity of 65% RH, The adhesive strength between the laminate and the reinforcing sheet was used.

  In the examples and comparative examples, the acrylic resin (component A) and the crosslinking agent (component B) shown below were used.

(A-1 component)
It is an acrylic resin having a weight average molecular weight of 390,000 and a glass transition temperature of −42 ° C. 2-ethylhexyl acrylate, vinyl acetate, 2-methacrylic acid 2-ester formed from monomer components of 63.7% by weight of 2-ethylhexyl acrylate, 35% by weight of vinyl acetate, and 1.3% by weight of 2-hydroxyethyl methacrylate It is a hydroxyethyl copolymer (hydroxyl value 5.6 mgKOH / g).

(A-2 component)
It is an acrylic resin having a weight average molecular weight of 550,000 and a glass transition temperature of −49 ° C. This is a butyl acrylate / acrylic acid copolymer (acid value 48.7 mgKOH / g) formed from a monomer component of 94.0% by mass of butyl acrylate and 6.0% by mass of acrylic acid.

(A-3 component)
It is an acrylic resin having a weight average molecular weight of 550,000 and a glass transition temperature of −49 ° C. This is a butyl acrylate / acrylic acid copolymer (acid value 62.2 mgKOH / g) formed from monomer components of butyl acrylate 92.0 mass% and acrylic acid 8.0 mass%.

(B-1 component)
It is an isocyanate-based crosslinking agent, and its constituent component is a trimer of hexamethylene diisocyanate (trade name: Takenate D-170N, manufactured by Mitsui Takeda Chemical Co., Ltd., NCO: 20.7%).

(B-2 component)
It is an epoxy-based crosslinking agent, and its constituent component is 1,3-bis (N, N′diglycidylaminomethyl) cyclohexane.

Example 1
A-2 component is used as an acrylic resin, and B-2 component is used as a crosslinking agent. With respect to 34 parts by mass of this A-2 component, 2.5 parts by mass of a crosslinking agent (product name: AO-330). , Manufactured by Asahi Denka Kogyo Co., Ltd.) 0.07 parts by mass, and 300 parts by mass of a mixed solvent obtained by mixing methyl ethyl ketone and toluene at a mass ratio of 1: 1 were added and stirred and mixed to prepare a raw material coating solution. .

  Next, this raw material coating solution was applied to the surface of a PET film having a thickness of 50 μm serving as a substrate with a baker type applicator so that the film thickness after drying was 7 μm, and this was applied at 80 ° C. for 1 minute. Further, an adhesive layer was formed by heating and drying at 130 ° C. for 3 minutes. A stretched polypropylene (OPP: Oriented Polypropylene, trade name: Alphan, Oji Paper Co., Ltd.) film with a thickness of 30 μm was stuck on the surface of this adhesive layer as a release liner, and cured at a temperature of 23 ° C. for 1 week. By doing so, a releasable pressure-sensitive adhesive sheet was obtained.

(Example 2)
30 parts by mass of A-3 component as an acrylic resin, 2.7 parts by mass of B-2 component as a crosslinking agent, 0.06 mass of phenolic antioxidant (trade name: AO-330, manufactured by Asahi Denka Kogyo Co., Ltd.) A releasable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the part was used.

(Comparative Example 1)
A releasable pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that 29 parts by mass of the A-1 component was used as the acrylic resin, 1.0 part by mass of the B-1 component was used as the crosslinking agent, and the antioxidant was not used. Obtained.

The removable adhesive sheet obtained in Examples and Comparative Examples are shown initial adhesion, post-heating adhesive strength, the adhesive strength of the adhesive sheet, the result of evaluating the adhesive strength between the laminate and the reinforcing sheet in Table 1. From the results of Table 1, removable adhesive sheets of Examples 1 and 2, since the post-heating adhesive strength is not increased much, were able to be easily peeled from the adherend. Furthermore, since the adhesive strength with the adhesive sheet is high, the peelable adhesive sheet is peeled from the adherend, and then the adhesive strength is high when the reinforcing sheet is attached to the peeled surface. It did not peel easily.

  The releasable pressure-sensitive adhesive and the releasable pressure-sensitive adhesive sheet of the present invention can be suitably used for the production of a circuit board such as a flexible printed board, and the produced circuit board is, for example, a mobile phone, a portable information terminal, a notebook It can be suitably used as a circuit board for small electronic devices such as personal computers and digital video cameras that require miniaturization and high density.

Claims (4)

(Component a) alkyl acrylate or alkyl methacrylate,
(Component b) formed from a monomer component containing a monomer having a carboxyl group as a functional group and formed from a raw material composition containing a copolymer having an acid value of 40 mgKOH / g or more and an epoxy-based crosslinking agent. A releasable pressure-sensitive adhesive having an adhesive strength of 0.4 N 2/25 mm or more according to a strength test.
Adhesive strength test:
(1) A pressure-sensitive adhesive layer in which a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive having a thickness of 7 μm is disposed on the surface of a PET film having a thickness of 50 μm is cut into a width of 25 mm and a length of 250 mm. A 25 μm thick adhesive sheet (trade name: Pyralax (registered trademark) LF-0100, manufactured by DuPont) and a 175 μm thick polyimide film are laminated to ^each other at 30 ° C. and 200 kg / cm ^2. A test piece is formed by pressure bonding by heating and pressurizing for minutes.
(2) After leaving the test piece for 20 minutes at a temperature of 23 ° C. and a humidity of 65% RH, from the test piece under the conditions of a temperature of 23 ° C., a humidity of 65% RH, a tensile speed of 300 mm / min, and a 180 ° direction. The adhesive strength when peeling the releasable pressure-sensitive adhesive sheet is measured. It is a releasable adhesive sheet provided with a film-form base material and the adhesion layer arrange | positioned on one surface of the said base material, Comprising: The said adhesion layer is from the releasable adhesive agent of Claim 1. A re-peelable pressure-sensitive adhesive sheet. A step of patterning the conductive layer by processing a laminated board comprising an insulating substrate, a conductive layer disposed on the surface of the insulating substrate, and a releasable adhesive sheet disposed on the back surface of the insulating substrate. ,as well as
The process of peeling a releasable adhesive sheet from the laminate
A circuit board manufacturing method comprising:
The manufacturing method of the circuit board whose said releasable adhesive sheet is the releasable adhesive sheet of Claim 2. After the step of peeling the releasable adhesive sheet from the laminate,
The method for manufacturing a circuit board according to claim 3, further comprising a step of disposing a reinforcing sheet on the peeled surface.