JP2020104518A - Mold release sheet for hot pressing and method for producing flexible printed wiring board using the same - Google Patents

Abstract

To provide a mold release sheet for hot pressing, which can be easily peeled off without leaving adhesive residue even after hot press processing is performed when a flexible printed wiring substrate having a two-layer CCL structure is produced.SOLUTION: A mold release sheet for hot pressing of the present invention is a mold release sheet for hot pressing having an adhesive layer on one of a surface of a base film, in which the adhesive layer has a glass transition temperature of 10°C to 45°C, and is formed of at least acrylic resin (A) and a cross-linking agent (B), and the acrylic resin (A) is a copolymer formed of at least ethyl methacrylate (A-1), a (meth)acrylate (A-2) having a functional group and having an alkyl group having 2 to 8 carbon atoms, and a monomer (A-3) having an ethylenic unsaturated double bond.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a release sheet for hot press that can be easily peeled off after being subjected to hot press processing during manufacturing of a flexible printed wiring board.

The flexible printed wiring board has a circuit pattern of a conductor made of a metal material such as copper foil (hereinafter, copper foil will be described as an example) on at least one surface of a synthetic resin film such as polyimide (hereinafter, polyimide film will be described as an example). Since it is formed by being formed and has flexibility, it is widely used in various electronic devices and optical devices.

Such a flexible printed wiring board, in the process of manufacturing an electronic device or an optical device, before mounting the electric/electronic components in order to suppress solvent contamination, contamination of foreign matter, generation of scratches, etc. on the wiring board, (1) A coverlay film is attached to the copper foil portion and hot pressed to cure the adhesive layer of the coverlay film to protect the circuit pattern.
Further, since the flexible printed wiring board is thin and soft, it is not possible to mount heavy parts as it is and cannot be inserted into the card edge connector for the printed circuit board. A reinforcing plate with a thermosetting adhesive is attached to the surface opposite to the surface having it, and the adhesive of the reinforcing plate is cured by hot pressing with a hot plate.

When hot pressing is performed using a hot plate as described above, heat is applied between (1) the hot plate and the coverlay film or (2) the hot plate and the surface having the circuit pattern of the flexible printed wiring board. By interposing a release sheet for presses, it is possible to prevent scratches on the surface of the flexible printed wiring board having the circuit pattern and foreign matter from being mixed by the hot plate, and absorb the irregularities of the circuit pattern and the reinforcing plate to provide the flexible printed wiring board. It is used to give uniform heating and pressure to.

However, such a release sheet for hot pressing does not sufficiently peel after hot pressing and leaves adhesive on the surface having the circuit pattern of the cover lay film or the flexible printed wiring board, or the heat release during hot pressing. The elution from the release sheet for press causes discoloration on the circuit surface formed of a conductor such as copper and the gold-plated surface by terminal plating, which causes a problem of deterioration in connection reliability.

As a solution to such a problem, a resin layer which is a reaction product of an acrylic resin and a cross-linking agent and has a glass transition temperature (Tg) of −50 to 20° C. is provided on at least one surface of a substrate film. A release sheet for heat press having the above has been proposed (Patent Document 1).

Japanese Patent No. 4890539 (claim 1)

By the way, the metal-clad laminate constituting the flexible printed wiring board is described below as a three-layer metal-clad laminate (hereinafter referred to as a three-layer copper-clad laminate as an example, referred to as a three-layer CCL. The CCL is a Copper Clad Laminate). Is abbreviated.) and a two-layer metal-clad laminate (hereinafter referred to as a two-layer CCL). Since the quality and characteristics are stable and the cost is low, the three-layer CCL has been the mainstream in the past. However, in recent years, these electronic devices and optical devices have been made lighter, smaller, thinner, and higher in density, and thinner flexible printed wiring boards have been required. Is increasing.

In the three-layer CCL, a polyimide film and a copper foil having a circuit pattern formed thereon are bonded together via an adhesive layer, so that the copper foil-free portion of the film is covered with the adhesive layer, When the conventional release sheet for hot press is peeled off after hot pressing, the pressure-sensitive adhesive layer of the release sheet for heat press is peeled off from this adhesive layer, so that it can be peeled off with a comparatively light force.

On the other hand, the two-layer CCL is a casting type in which a copper foil is coated with a polyimide varnish, a laminate type in which a polyimide film and a copper foil are bonded with a polyimide-based adhesive, or a metal is vapor-deposited or sputtered on the polyimide film and then copper-plated. There are three types of sputter type, but in all types, when the release sheet for hot press is peeled off after hot pressing, the adhesive layer of the release sheet for hot press is peeled off from the polyimide surface. Since the material is different from the adhesive layer of the three-layer CCL, the peeling force increases after hot press working, resulting in adhesive residue on the polyimide surface and deformation of the two-layer CCL. doing.

In order to avoid such adhesive residue, the present inventors reduced the thickness of the pressure-sensitive adhesive layer of the conventional release sheet for hot pressing, and after hot pressing, the adherend (two-layer CCL having a circuit pattern) Although it was possible to eliminate the adhesive residue, the adhesive layer could not follow the uneven portion of the metal material on the surface having the circuit pattern or the uneven portion to which the coverlay film was attached, so that the heat press At times, the metal material cannot be protected from the outgas generated from the synthetic resin film (polyimide film and/or coverlay film), which causes a problem that the metal material is discolored. In addition, the metal material mentioned here means a gold-plated portion applied to the copper foil portion on the surface having the circuit pattern and the contact surface of the edge connector terminal or the contact portion. When the metal material is discolored in this way, the connection reliability is reduced, which is not preferable.
Further, the metal material must not cause discoloration due to elution from the release sheet for hot pressing, for example, low molecular weight components contained in the adhesive layer during hot pressing.
Therefore, the present invention is capable of easily peeling a flexible printed wiring board having a two-layer CCL structure without leaving an adhesive residue on the flexible printed wiring board even after hot pressing, and at the time of hot pressing. Provided is a release sheet for a hot press in which the metal material of a flexible printed wiring board is not easily discolored by outgas generated from a synthetic resin film (polyimide film and/or coverlay film) or eluate from the release sheet for a hot press. The purpose is to

The release sheet for hot press of the present invention is a release sheet for hot press having an adhesive layer on one surface of a base film, wherein the adhesive layer has a glass transition temperature of 10°C to 45°C, and It is formed of at least (A) acrylic resin and (B) cross-linking agent, and the (A) acrylic resin has at least (A-1) ethyl methacrylate and (A-2) functional group and carbon. It is a copolymer of (meth)acrylate having an alkyl group of 2 to 8 and (A-3) a monomer having an ethylenically unsaturated double bond.

Further, preferably, the functional group of the component (A-2) is at least one selected from a hydroxyl group and an amino group.

Further, preferably, the component (A-2) is at least one selected from 2-hydroxyethyl methacrylate and 2-hydroxyethyl acrylate.

In the release sheet for hot pressing of the present invention, the monomer having an ethylenically unsaturated double bond of the component (A-3) is ethyl acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, methyl. It is characterized by being at least one or more selected from (meth)acrylate, acrylonitrile and vinyl acetate.

The release sheet for hot pressing of the present invention is characterized in that the crosslinking agent as the component (B) is an isocyanate crosslinking agent.

Further, it is preferable that the isocyanate cross-linking agent as the component (B) has three or more reactive functional groups.

Further, in the release sheet for hot press of the present invention, the acrylic resin (A) has a component (A-1) of 30% by mass or more and 65% by mass or less, and a component (A-2) of 0.1% by mass or more and 10% by mass. % Or less and the component (A-3) is 25% by mass or more and 65% by mass or less, which is a copolymer.

Further, the release sheet for hot pressing of the present invention is characterized in that the adhesive layer contains, as the component (C), a resin having a glass transition temperature of -70°C to -30°C.

Further, preferably, the component (C) is at least one selected from resins containing vinyl acetate and/or 2-ethylhexyl (meth)acrylate as a monomer, and urethane resins.

The release sheet for hot pressing of the present invention is characterized in that the content of the component (C) in the adhesive layer is 50% by mass or less based on the entire adhesive layer.

The release sheet for hot press of the present invention is characterized in that the adhesive layer has a thickness of 4 to 40 μm.

Further, the release sheet for hot press of the present invention is a release sheet for heat press having an adhesive layer on one surface of a base film, and has a circuit pattern of a flexible printed wiring board having a two-layer metal-clad laminate structure. The surface having the adhesive layer of the release sheet for hot pressing is adhered, and hot pressing is performed for 30 minutes under the conditions of a temperature of 180° C. and a pressure of 5 N/mm ² , and then conforms to JIS Z0237:2009. With the measurement method
(A) The peeling force with respect to a film made of a synthetic resin used for a flexible printed wiring board is 1.5 N/25 mm or less,
(B) The peeling force with respect to the metal material forming the circuit pattern used for the flexible printed wiring board is 1 N/25 mm or less,
(C) The color change degree according to the following color change degree test is in the range of 0 to 3.
Discoloration test:
(C-1) A lightness index and a chromatinex index by a L ^* a ^* b ^* color system of a surface of the two-layer metal-clad laminate having a metal material are measured,
(C-2) The surface of the two-layer metal-clad laminate having the metal material and the surface of the release sheet for heat press having the adhesive layer are attached to each other, and thermocompression bonding is performed under the conditions of 180° C. and 1 N/mm ² for 1 hour. did. After being left to cool, the release sheet for hot press was peeled off, and the lightness index and the chromatinex index by the L ^* a ^* b ^* color system of the surface of the two-layer metal-clad laminate having the metal material were measured,
(C-3) The degree of discoloration of the surface having the metal material before and after hot pressing is calculated based on the color difference according to the L ^* a ^* b ^* colorimetric system defined in JIS Z8730.

The method for manufacturing a flexible printed wiring board according to the present invention is a method for manufacturing a flexible printed wiring board having a two-layer metal-clad laminate structure, in which a circuit pattern of the flexible printed wiring board is obtained by hot pressing using a hot plate. In a sticking step of sticking a cover lay film on the surface having, the hot press release sheet, the adhesive layer of the hot press release sheet at least between the hot plate and the cover lay film is the cover lay. It is interposed so as to face the film.

The method for manufacturing a flexible printed wiring board according to the present invention is a method for manufacturing a flexible printed wiring board having a two-layer metal-clad laminate structure, in which a circuit pattern of the flexible printed wiring board is obtained by hot pressing using a hot plate. In a laminating step of laminating a thermosetting adhesive reinforcing plate on the side opposite to the surface having, in the release sheet for heat press, at least the surface having the hot plate and the circuit pattern of the flexible printed wiring board The adhesive layer of the release sheet for hot press is interposed therebetween so as to face the surface having the circuit pattern of the flexible printed wiring board.

The “glass transition temperature” in the present invention means a value (° C.) obtained by differential scanning calorimetry (DSC) of the adhesive layer peeled from the release sheet for hot press.

According to the release sheet for hot pressing of the present invention, when a flexible printed wiring board having a two-layer CCL structure is manufactured, the flexible printed wiring board is easily peeled off without leaving an adhesive residue even after hot pressing. In addition, outgas generated from the synthetic resin film (polyimide film and/or coverlay film) during hot pressing and elution from the release sheet for hot pressing prevent the metallic material of the flexible printed wiring board from discoloring.
Further, according to the method for manufacturing a flexible printed wiring board of the present invention, a synthetic resin film (polyimide film and/or cover) does not cause adhesive residue on the flexible printed wiring board even after being subjected to hot pressing, and at the time of hot pressing. It is possible to obtain a flexible printed wiring board in which the metal material of the flexible printed wiring board is less likely to discolor due to outgas generated from the ray film) or elution from the release sheet for hot pressing.

The release sheet for hot pressing of the present invention has an adhesive layer on one surface of the substrate film, wherein the adhesive layer comprises an acrylic resin obtained by copolymerizing a specific monomer and a specific crosslinking agent. It is formed. Hereinafter, an embodiment of the release sheet for hot press of the present invention will be described.

The substrate film used in the present invention is not particularly limited, but one having a melting point of 210° C. or higher is preferably used. Examples of such a film include polyethylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polycarbonate, triacetyl cellulose, polyimide, polyamide, polyether sulfone, aromatic polyamide, polysulfone, acrylic, polyvinyl chloride, It is a synthetic resin film such as a fluororesin. Among them, polyethylene terephthalate is preferable from the viewpoint of heat resistance, chemical resistance, and unevenness followability. The film may be transparent or may be colored by mixing various pigments and dyes into the material forming the film, or the surface thereof may be processed into a matte shape. Although the thickness of the film is not particularly limited, it is preferably 2 μm to 150 μm from the viewpoint of not impairing cushioning properties at the time of hot pressing, more preferably 5 μm to 100 μm from the viewpoint of handleability, and further preferably 10 μm to 75 μm. preferable.

Such a base film should contain known additives such as a heat resistance stabilizer, an oxidation resistance stabilizer, a weather resistance stabilizer, an ultraviolet absorber and an antistatic agent as long as the effects of the present invention are not impaired. You can Further, in order to improve the adhesion between the base film and the adhesive layer described below, the surface of the base film is subjected to plasma treatment, corona discharge treatment, flame treatment, ozone treatment, ultraviolet irradiation treatment, electron beam irradiation treatment, radiation irradiation. An easy adhesion treatment such as a treatment, an acid treatment, an alkali treatment, a chemical treatment, a sandblasting treatment, an embossing treatment, or an undercoating easy adhesion layer coating formation may be performed.

If necessary, the surface of the base film opposite to the surface provided with the adhesive layer may be subjected to surface treatment such as antistatic treatment, peeling treatment, concealing treatment and embossing treatment. In particular, a silicone-based, fluorine-based or alkyd-based release agent may be applied as the release treatment.

Next, the adhesive layer will be described. The lower limit of the glass transition temperature of the adhesive layer is 10° C. or higher, preferably 15° C. or higher, and the upper limit thereof is 45° C. or lower, preferably 30° C. or lower. If the glass transition temperature is lower than the lower limit, cohesive failure is likely to occur and adhesive residue tends to remain, and if the glass transition temperature is higher than the upper limit, adhesiveness to the substrate film tends to be low, and adhesive residue tends to occur.

The adhesive layer is formed of at least (A) acrylic resin and (B) crosslinking agent.

The (A) acrylic resin is at least (A-1) ethyl methacrylate, (A-2) a functional group-containing (meth)acrylate having a C2-8 alkyl group, and (A-3) ethylenic. It is a copolymer with a monomer having an unsaturated double bond, and is affixed to the surface having a circuit pattern of a flexible printed wiring board having a two-layer metal-clad laminate structure without reducing the thickness of the adhesive layer and heat-pressed. It is essential to use (A-1) ethyl methacrylate from the viewpoint that it can be peeled off without leaving an adhesive residue on the flexible printed wiring board even after the process. By using (A-1) ethyl methacrylate in this way, the adhesive layer can be peeled off without leaving an adhesive residue on the flexible printed wiring board without reducing the thickness of the adhesive layer, and the metal material of the surface having the circuit pattern can be peeled off. Since the pressure-sensitive adhesive layer can sufficiently follow the uneven portion and the uneven portion to which the coverlay film is attached, the synthetic resin film (polyimide film and/or coverlay film) of the flexible printed wiring board at the time of hot pressing. It is possible to prevent the metallic material from being discolored by the outgas emitted from (1). An example of the coverlay film is a polyimide film laminated with an epoxy resin.

Further, from the viewpoint of improving the cohesive force of the adhesive layer and preventing adhesive residue from being generated on the adherend, it has a functional group (A-2) and an alkyl group having 2 to 8 carbon atoms (meth). It is essential to use acrylate, and as the functional group, a hydroxyl group, a carboxyl group, an amino group, an acetoacetoxyethyl group, an epoxy group and the like can be mentioned, but from the viewpoint of not easily corroding a metal material, a hydroxyl group and an amino group are used. At least one selected from the above is preferable. Examples of the monomer of the component (A-2) having such a functional group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth) as a monomer having a hydroxyl group. Acrylate, diethylene glycol mono(meth)acrylate, N-methylol acrylamide, allyl alcohol, p-hydroxystyrene and the like, β-carboxyethyl (meth)acrylate as a monomer having a carboxyl group, (meth)acrylic acid, itaconic acid, crotonic acid, As amino group-containing monomers such as maleic acid and maleic anhydride, aminomethyl(meth)acrylate, methylaminomethyl(meth)acrylate, methylaminoethyl(meth)acrylate, methylaminopropyl(meth)acrylate, acrylamide, etc. Examples of the acetoxyethyl group-containing monomer include acetoacetoxyethyl (meth)acrylate, and examples of the epoxy group-containing monomer include glycidyl (meth)acrylate. Among them, a hydroxyl group-containing monomer such as 2-hydroxyethyl methacrylate and 2 By using at least one selected from hydroxyethyl acrylate, it is possible to further improve the cohesive force of the pressure-sensitive adhesive layer and further prevent adhesive residue from being generated on the adherend.

Next, as the monomer (A-3) having an ethylenically unsaturated double bond, the peeling force from the printed wiring board can be adjusted, and the glass transition temperature of the adhesive layer can be easily adjusted to an appropriate range. As such a monomer, as such a monomer, a (meth)acrylate having an alkyl group having 2 to 8 carbon atoms, for example, ethyl acrylate, methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth ) Acrylate, propyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, vinyl acetate, vinyl propionate, vinyl ether, styrene, (meth)acrylonitrile and the like, among which ethyl acrylate and butyl (meth) By using at least one or more selected from acrylate, acrylonitrile, methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate and vinyl acetate, it is easier to adjust the peeling force from the printed wiring board and the adhesive layer The glass transition temperature of can be easily adjusted to an appropriate range. If the peeling force becomes too heavy, the metal material will easily deform when the release sheet for hot pressing is peeled off after hot pressing, and adhesive residue will easily occur on the metal material forming the synthetic resin film or circuit pattern. Become.

The component (A-1), the component (A-2), and the component (A-3) constituting the acrylic resin (A) as described above have a glass transition temperature of 10 to 45° C. when formed into an adhesive layer. It must be compounded within the range, but the cohesive force of the adhesive layer is increased to prevent discoloration of the metal material and adhesive residue does not occur, and the flexible printed wiring board with a two-layer metal-clad laminate structure is used. From the viewpoint of adjusting the peeling force of (A-1), the lower limit is 30 mass% or more, further 35 mass% or more, the upper limit is 65 mass% or less, further 55 mass% or less, (A The component (-2) has a lower limit of 0.1% by mass or more, further 1% by mass or more, an upper limit of 10% by mass or less, and further 5% by mass or less, and the component (A-3) has a lower limit of 25%. It is preferably at least 35% by mass, more preferably at least 35% by mass, and the upper limit is preferably at most 65% by mass, more preferably at most 60% by mass.

Next, the cross-linking agent as the component (B) is used to cross-link by reacting with the functional group in the acrylic resin (A), and examples thereof include an isocyanate cross-linking agent, a metal chelate cross-linking agent, and an epoxy cross-linking agent. , Melamine-based crosslinking agents, urea-based crosslinking agents, and the like. Among them, isocyanate-based ones are resistant to corrosion to metal materials, adhesion to base film, adhesive residue prevention to flexible printed wiring board after hot pressing and easy adjustment of peeling force. A crosslinking agent is preferably used. Examples of the isocyanate cross-linking agent include tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, methyldiphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and lysine isocyanate. However, it is preferable that the compound has three or more functional groups. By using an isocyanate-based cross-linking agent having three or more functional groups, the adhesion to the base material film becomes better and the cross-link density becomes higher, so the eluate from the release sheet for hot-pressing during hot-pressing, For example, the discoloration of the metal material caused by the transfer of the low molecular weight component contained in the adhesive layer to the metal material can be further suppressed. Examples of such an isocyanate cross-linking agent include isophorone diisocyanate-based and hexamethylene diisocyanate-based.

Further, the adhesive layer may contain another resin as the component (C) in addition to the components (A) and (B) described above, and adjusts the peeling force from the printed wiring board and From the viewpoint that the glass transition temperature of the layer can be easily adjusted to an appropriate range, it is preferable to include a resin having a glass transition temperature of −70° C. to −30° C. Examples of the resin having a glass transition temperature of component (C) from −70° C. to −30° C. include resins containing vinyl acetate and/or 2-ethylhexyl (meth)acrylate as a monomer, and urethane resins. By using at least one selected from these, it is possible to more easily adjust the peeling force from the printed wiring board and easily adjust the glass transition temperature of the adhesive layer to an appropriate range.

The content of the component (C) when the component (C) is added to the pressure-sensitive adhesive layer is not particularly limited as long as the effect of the present invention is not impaired. From the viewpoint of not hindering and adjusting the peeling force from the printed wiring board, it is preferably 50% by mass or less, and more preferably 30% by mass or less based on the whole adhesive layer. When the component (C) is too much, the peeling force tends to increase with respect to the flexible printed wiring board having a two-layer metal-clad laminate structure. Therefore, when a thinner board is used, the board is hot-pressed. When the release sheet for hot press is subsequently peeled off, the substrate is likely to be deformed, so that the component (C) is preferably in such a range.

Further, in such an adhesive layer, a reaction accelerator, a surfactant, a pigment, a lubricant, a coloring agent, an antistatic agent, a flame retardant as long as the function as the release sheet for press of the present invention is not impaired. , Various additives such as an antibacterial agent, an antifungal agent, an ultraviolet absorber, a light stabilizer, an antioxidant, a leveling agent, a flow control agent and an antifoaming agent can be included.

Although the thickness of the adhesive layer varies depending on the depth and shape of the unevenness of the circuit pattern, it cannot be generally stated, but the lower limit is 4 μm or more, preferably 8 μm or more, and the upper limit is 40 μm or less, preferably 20 μm or less. When the thickness of the adhesive layer is 4 μm or more, it is easy to follow the irregularities of the circuit pattern of the flexible printed wiring board having a two-layer CCL structure, and it is possible to further suppress the generation of outgas, and thus it is easy to prevent discoloration of the metal material. When it is 40 μm or less, discoloration of the metal material caused by the transfer of the low molecular weight component contained in the adhesive layer to the metal material can be further suppressed, and the handleability and the productivity can be improved. You can

In the method for producing a release sheet for press of the present invention, the above-mentioned (A) acrylic resin, (B) crosslinking agent, (C) other resin and additives optionally used are dissolved in a diluting solvent as necessary. Alternatively, it is prepared by dispersing it to obtain a coating liquid, and applying the coating liquid to one surface of the above-mentioned substrate film by a conventionally known coating method such as a bar coating method, drying, and curing if necessary.

Further, the release sheet for hot press of the present invention is a release sheet for heat press having an adhesive layer on one surface of a base film, and has a circuit pattern of a flexible printed wiring board having a two-layer CCL structure. And the surface having the pressure-sensitive adhesive layer of the release sheet for hot pressing are bonded together, and hot pressing is performed for 30 minutes under the conditions of a temperature of 180° C. and a pressure of 5 N/mm ² , followed by measurement according to JIS Z0237:2009. (A) the peeling force with respect to the film made of synthetic resin used for the flexible printed wiring board is 1.5 N/25 mm or less, preferably 1 N/25 mm or less, and (b) the circuit pattern used for the flexible printed wiring board. The peeling force with respect to the metal material forming the is 1 N/25 mm or less, preferably 0.5 N/25 mm or less.

Further, the release sheet for hot press of the present invention has (c) the degree of discoloration in the discoloration test within a range of 0 to 3, and the discoloration test is (c-1) a surface having a two-layer CCL metal material. The lightness index and chromatinex index of the L ^* a ^* b ^* color system of (c-2) the two-layer CCL surface having the metal material and the surface of the release sheet for hot press having the adhesive layer The pieces are stuck together and thermocompression bonded for 1 hour under the conditions of 180° C. and 1 N/mm ² . After allowing to cool, the release sheet for hot press was peeled off, and the lightness index and chromatinex index by the L ^* a ^* b ^* color system of the surface of the two-layer CCL having the metal material were measured, (c-3). It is calculated based on the color difference according to the L ^* a ^* b ^* color system specified in JIS Z8730, and the degree of discoloration of the surface having the metal material before and after hot pressing is calculated.

By setting the above-mentioned (a) and (b) in such ranges, adhesive residue is further generated on the flexible printed wiring board even after hot pressing during manufacturing of the flexible printed wiring board having the two-layer CCL structure. Can be peeled off more easily. Further, by setting (c) in such a range, it is possible to further prevent discoloration of the metal material during hot pressing during manufacturing of the flexible printed wiring board having the two-layer CCL structure.

Next, a method for manufacturing the flexible printed wiring board of the present invention will be described. The method for producing a flexible printed wiring board of the present invention is a method for producing a flexible printed wiring board having a two-layer metal-clad laminate structure, in which a circuit pattern of the flexible printed wiring board is formed by hot pressing with a hot plate. In the sticking step of sticking the cover lay film on the surface having the release sheet for hot press of the present invention described above, the adhesive layer of the release sheet for hot press is at least between the hot plate and the cover lay film. It is interposed so as to face the cover lay film.

Another method of manufacturing the flexible printed wiring board according to the present invention is a method of manufacturing a flexible printed wiring board having a two-layer CCL structure, which comprises hot pressing using a hot plate. In the attaching step of attaching the thermosetting adhesive-reinforced plate to the side opposite to the side having the circuit pattern, the hot press release sheet of the present invention described above is at least the hot plate and the flexible printed wiring board. The adhesive layer of the release sheet for hot press is interposed between the surface having the circuit pattern and the surface having the circuit pattern of the flexible printed wiring board.

As described above, by producing a flexible printed wiring board having a two-layer CCL structure using the release sheet for hot pressing of the present invention, adhesive residue does not occur on the flexible printed wiring board even after hot pressing, Moreover, it is possible to obtain a flexible printed wiring board in which the metal material is not discolored due to outgas generated from the synthetic resin film during hot pressing and elution from the release sheet for hot pressing.

Hereinafter, the present invention will be described in more detail based on examples. In this example, “part” and “%” are based on mass unless otherwise specified.

[Examples and Comparative Examples]
1. (A) Synthesis of acrylic resin In a reaction vessel equipped with a stirrer, a condenser, a thermometer and a nitrogen introducing tube, ethyl acetate was used as a solvent, and the monomer components shown in Tables 1 and 2 and 0.15 parts of azobisisobutyronitrile were blended. Then, after stirring until uniform, bubbling was carried out at a flow rate of 100 ml/min for 60 minutes to degas the dissolved oxygen in the reaction system. Next, the temperature was raised to 80° C. over 1 hour, and after the temperature was raised, polymerization was carried out for 4 hours. Thereafter, the temperature was raised to 90° C. over 1 hour, the temperature was further maintained at 90° C. for 1 hour, and then cooled to room temperature. Next, toluene was added to adjust the solid content in the acrylic resin solution to 25%. When the weight average molecular weight (converted to polystyrene) of the polymerized acrylic resin was measured by GPC, it was in the range of 200,000 to 400,000.

In Tables 1 to 3, "Tg" is a glass transition temperature, "EMA" is ethyl methacrylate, "2-HEMA" is 2-hydroxyethyl methacrylate, "AA" is acrylic acid, and "HEA" is hydroxyethyl acrylate. "DMAEMA" is dimethylaminoethyl methacrylate, "EA" is ethyl acrylate, "AN" is acrylonitrile, "BMA" is butyl methacrylate, "MA" is methyl acrylate, "BA" is butyl acrylate, and "MMA" is methyl methacrylate. "Vinyl acetate" is vinyl acetate, "2-EHA" is 2-ethylhexyl acrylate, "HDI" is hexamethylene diisocyanate cross-linking agent (3 functional groups), "IPDI" is isophorone diisocyanate cross-linking agent (3 functional groups). ), "B*1" is a hexamethylene diisocyanate biuret type cross-linking agent (two functional groups), "B*2" is an epoxy-type cross-linking agent (Tetrad C: manufactured by Mitsubishi Gas Chemical Company), and "C*1" is Copolymer (glass transition temperature -42°C) obtained by copolymerizing 2-ethylhexyl acrylate, vinyl acetate monomer and hydroxyethyl methacrylate at 63.7:35:1.3, "C*2" is 2-ethylhexyl acrylate and A copolymer obtained by copolymerizing 2-hydroxyethyl methacrylate at 97:3 (glass transition temperature −65° C.), “C*3” is a urethane resin (US-902A: manufactured by Yatasha Yushi Kogyo Co., Ltd.) (glass transition temperature). (-58°C).

2. Preparation of Release Sheet for Hot Pressing Methyl isobutyl ketone was added to (A) acrylic resin having the composition shown in Tables 1 and 2, (B) cross-linking agent, and (C) other resin as needed, and the examples were mixed. And the coating liquid for the adhesive layer of the comparative example was produced. Next, on one surface of a polyethylene terephthalate film (Diafoil T-100: manufactured by Mitsubishi Plastics Co., Ltd.) having a thickness of 25 μm, Table 3 shows the thickness after drying the adhesive layer coating liquids of the above Examples and Comparative Examples. After being coated so as to have a value and dried at 180° C. for 1 minute, it was laminated on one side of a 30 μm thick silicone-free separator (stretched polypropylene, Alphan SSD-101: manufactured by Oji Ftex Co., Ltd.). After curing this film in an environment of 40° C. for 4 days, the silicone-free separator was peeled off and removed to prepare release sheets for hot press of Examples and Comparative Examples.

Next, regarding the release sheets for hot pressing of Examples and Comparative Examples, (1) the glass transition temperature of the adhesive layer, (2) the peeling force to the polyimide film after hot pressing, (3) the copper after hot pressing. Peeling force for foil, (4) Adhesive residue on polyimide film after peeling release sheet for heat press, (5) Deformation of two-layer CCL after peeling release sheet for heat press, (6) Copper foil due to low molecular weight component And (7) Discoloration of copper foil due to outgas were measured and evaluated by the following methods. The results are shown in Table 3.

(1) Measurement of glass transition temperature Only the pressure-sensitive adhesive layers of the release sheets for heat press of Examples and Comparative Examples were peeled off, and the temperature was raised using a differential scanning calorimeter (DSC3200S: manufactured by Bruker AXS). The measurement was performed at a speed of 10° C./min.

(2) Peeling force for polyimide film after hot press working The hot press release sheets of Examples and Comparative Examples were cut into a test piece by cutting into a width of 25 mm and a length of 250 mm, and this test piece was a two-layer CCL (ESPANEX). SC18-25-00CE: manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) is arranged so that the adhesive layer contacts the polyimide film with respect to the part (polyimide film, surface roughness Ra=0.28 μm) from which the copper foil part has been removed. Then, it was pressure-bonded by thermal lamination (80° C., 0.3 MPa, 1.5 m/min). This evaluation sample was hot-pressed under predetermined conditions (180° C., 30 minutes, 5 N/mm ² ) and then cooled under conditions of a temperature of 23° C. and a humidity of 65% RH, according to JIS Z0237:2009. The peeling force was measured by peeling the hot press release sheet from the polyimide film by the measuring method.

(3) Peeling force for copper foil after hot press working The hot press release sheets of Examples and Comparative Examples were cut into test pieces by the same size as in (2) above, and the test pieces were The copper foil surface of the two-layer CCL similar to 2) was subjected to thermal lamination and hot pressing under the same conditions as in (2) above, and then cooled under the same conditions as in (2) above, according to JIS Z0237:2009. The peeling force was measured by peeling the hot-press release sheet from the copper foil surface of the two-layer CCL by a measuring method according to.

(4) Adhesive residue on the polyimide film after peeling the release sheet for hot pressing Whether or not adhesive residue is generated on the polyimide film when measuring the peeling force on the polyimide film after the hot pressing in (2) above It was confirmed by magnifying 50 times with a scope (VHX-1000: manufactured by Keyence Corporation). In the evaluation, those in which adhesive residue was not confirmed by a microscope were evaluated as ◯, those which could not be visually confirmed but were slightly confirmed by a microscope were evaluated as Δ, and those in which adhesive residue was clearly visible were evaluated as ×.

(5) Deformation of the two-layer CCL after peeling the release sheet for hot-pressing When measuring the peeling force to the copper foil after the hot-pressing of (3) above, it is visually checked whether the two-layer CCL is deformed. Evaluated. In the evaluation, one in which the two-layer CCL was not deformed was evaluated as ◯, and one in which the two-layer CCL was deformed was evaluated as x.

(6) Discoloration of copper foil due to low molecular weight component Regarding the copper foil surface of the two-layer CCL similar to the above (2), the discoloration of the metal material caused by the transfer of the low molecular weight component contained in the adhesive layer to the metal material was evaluated. I went. For the evaluation, a spectrophotometer (CM-5: manufactured by Konica Minolta Sensing Co., Ltd.) was used to measure a lightness index and a chromatinex index based on the L ^* a ^* b ^* color system. Next, the release sheets for hot press of Examples and Comparative Examples were arranged so that the adhesive layer was in contact with the copper foil surface of the two-layer CCL, and heat-pressed for 1 hour under the conditions of 180° C. and 1 N/mm ² . After allowing to cool, the release sheet for hot press was peeled off, and the brightness index and the chromatinex index of the copper foil surface were measured. The degree of discoloration of the copper foil surface before and after hot pressing was calculated based on the formula difference according to the L ^* a ^* b ^* color system specified in JIS Z8730.
(7) Discoloration of copper foil due to outgas A coverlay film is attached to about 1/3 of the circuit part of the two-layer CCL similar to the above (2), but a coverlay film is attached to the remaining about 2/3. A sample in a non-existing state was prepared. At that time, the copper foil surface of the circuit portion to which the coverlay film was not attached had a width of 235 μm, a length of 1000 μm to 1300 μm, and was arranged at intervals of 250 μm. Then, the release sheets for hot press of Examples 4 to 6 and Comparative Examples 3 to 5 were placed thereon so that the pressure-sensitive adhesive layers of the release sheets for hot press were in contact with each other, and the same conditions as in (2) above were applied. It was heat laminated and crimped.
Next, hot pressing was performed under the same conditions as the above (2) to cool. After that, the release sheet for heat press was peeled off, and the discoloration of the boundary between the copper foil surface and the polyimide film surface of the circuit part on which the coverlay film was not attached was observed with a microscope (200 times magnification, VHX-1000: KEYENCE). (Manufactured by the company) was used for evaluation.
The evaluation is that when the length of the longer side of the copper foil surface is 100, the ratio of the length where discoloration occurs is 0% or more and less than 5% ◎, and 5% or more and less than 15% is ◯, 15 % And less than 30% were evaluated as Δ, and 30% or more were evaluated as x.

As shown in Table 3, in the release sheets for hot pressing of Examples, the glass transition temperature of the adhesive layer was from 10°C to 45°C, and (A-1) ethyl methacrylate and (A-2) functional groups were added. (A) Acrylic resin and (B) crosslinked, which is a copolymer of (meth)acrylate having an alkyl group having 2 to 8 carbon atoms and (A-3) a monomer having an ethylenically unsaturated double bond. The adhesive layer formed from the agent was provided on one surface of the substrate. As a result, none of the release sheets for hot pressing was deformed without causing adhesive residue on the flexible printed wiring board having the two-layer CCL structure after hot pressing. Furthermore, the discoloration of the metal material caused by the transfer of the low molecular weight component contained in the adhesive layer to the metal material and the discoloration of the metal material due to the outgas generated from the polyimide film and/or the coverlay film during the hot pressing are less likely to occur. It was Further, in the example, the peeling force for the polyimide film of the two-layer CCL was 1.5 N/25 mm or less, and the peeling force for the copper foil portion was 1 N/25 mm or less.

On the other hand, in the release sheet for hot press of Comparative Example 1, the adhesive layer used the (A) acrylic resin containing the components (A-1), (A-2) and (A-3), The transition temperature was 8° C., which was lower than the lower limit. As a result, the peeling force for the polyimide film of the two-layer CCL after hot pressing exceeds 1.5 N/25 mm, and the peeling force for the copper foil portion exceeds 1 N/25 mm. Although there was no adhesive residue on the polyimide film, the two-layer CCL was deformed.

Next, in the release sheet for hot pressing of Comparative Example 2, the adhesive layer contains the component (A-1) as the acrylic resin (A), but contains the components (A-2) and (A-3). The glass transition temperature was 55° C., which was higher than the upper limit. As a result, the adhesive layer caused interfacial damage to the polyimide film of the two-layer CCL and the copper foil portion after the hot pressing, and the whole surface was transferred. As a result, it becomes impossible to measure the peeling force of the two-layer CCL on the polyimide film and the peeling force of the copper foil portion after hot pressing, the discoloration of the copper foil due to the low molecular weight component of the adhesive layer, and the discoloration of the copper foil due to outgassing. It was also impossible to evaluate the deformation of the two-layer CCL.

In addition, comparing Comparative Examples 3 to 5 and Examples 4 to 6, Comparative Examples 3 to 5 are those in which the adhesive layer does not use ethyl methacrylate as the (A) acrylic resin, and the glass transition temperature is 7°C. It was lower than the lower limit and had different thicknesses. As a result, Examples 4 to 6 satisfied all the evaluation items, but Comparative Examples 3 to 5 did not satisfy all the items. Below, Comparative Examples 3 to 5 and Examples 4 to 6 will be specifically compared.

First, when Comparative Example 3 and Example 4 were compared, Comparative Example 3 had a thin adhesive layer having a thickness of 5 μm, but adhesive residue remained on the polyimide film of two-layer CCL after hot pressing. However, it was inferior to that of Example 4. In Comparative Example 3, the peeling force for the polyimide film of the two-layer CCL after hot pressing exceeds 1.5 N/25 mm, and the peeling force for the copper foil portion exceeds 1 N/25 mm, which is more than that of Example 4. It became inferior. Further, in Comparative Example 3, the two-layer CCL after peeling off the release sheet for hot press was deformed, which was inferior to that in Example 4. Further, Comparative Example 3 and Example 4 did not cause discoloration of the metal material caused by the transfer of the low molecular weight component contained in the adhesive layer to the metal material, but Comparative Example 3 did not generate the polyimide film at the time of hot pressing. And/or the outgas generated from the coverlay film causes discoloration of the metal material, which is inferior to that of Example 4.

Next, when comparing Comparative Example 4 and Example 6, the release sheet for hot press of Comparative Example 4 had a thickness of 10 μm, which was the same as that of Example 6. As a result, Comparative Example 4 was inferior to Example 6 in that adhesive residue was left on the polyimide film of the two-layer CCL after hot pressing. Further, in Comparative Example 4, the peeling force with respect to the polyimide film of the two-layer CCL after hot pressing exceeds 1.5 N/25 mm, and the peeling force with respect to the copper foil portion exceeds 1 N/25 mm. It was inferior to the comparison. Further, in Comparative Example 4, the two-layer CCL after peeling the release sheet for hot press was deformed, which was inferior to that of Example 6. Further, in Comparative Example 4, since the thickness of the adhesive layer was relatively thin, discoloration of the metal material caused by the transfer of the low molecular weight component contained in the adhesive layer to the metal material did not occur, but Comparative Example 4 The outgas generated from the polyimide film and/or the coverlay film during hot pressing caused discoloration of the metal material, which was inferior to that of Example 6.

Next, comparing Comparative Example 5 with Example 5, the release sheet for hot press of Comparative Example 5 had a thickness of 40 μm, which was the same as that of Example 5. As a result, the adhesive layer of the double-layered CCL polyimide film after hot pressing caused interface destruction and was transferred to the entire surface. As a result, deformation of the two-layer CCL after peeling the release sheet for hot pressing, discoloration of the metal material caused by transfer of low molecular weight components contained in the adhesive layer to the metal material, and polyimide film and/or coverlay film during hot pressing It was not possible to evaluate the discoloration of the metallic material caused by the outgas generated from.

Further, in the release sheet for hot press of Comparative Example 6, the adhesive layer used was the one containing the components (A-1), (A-2) and (A-3) as the acrylic resin (A). (B) Since no cross-linking agent was used, the adhesive layer causes interfacial damage to the two-layer CCL polyimide film and copper foil portion after hot press processing, which causes transfer to the entire surface. After the mold sheet was peeled off, the two-layer CCL could not be evaluated for deformation, and adhesive residue remained on the polyimide film and copper foil portion of the two-layer CCL after hot pressing. Further, the discoloration of the metal material caused by the transfer of the low molecular weight component contained in the adhesive layer to the metal material was impossible to measure because the adhesive layer was transferred.

Next, the release sheets for hot press of Examples will be compared.
First, comparing Example 1 and Examples 6 to 16, in the release sheets for hot press of Examples 6 to 16, the glass transition temperature of the adhesive layer is 15°C to 30°C, whereas in the examples, Since 1 has a relatively low glass transition temperature of 11° C., the release sheets for hot pressing of Examples 6 to 16 are more peelable than the peeling force for the polyimide film of the two-layer CCL after hot pressing as compared with Example 1. The peeling force for the copper foil portion was also excellent. However, the one of Example 1 was also sufficiently durable for practical use.

Next, when comparing Example 3 with Examples 6 to 16, the release sheet for hot press of Example 3 had a glass transition temperature of 41° C. higher in the adhesive layer, and therefore the heat of Examples 6 to 16 was improved. The press release sheet had better adhesiveness to the base film than Example 3, and was less likely to cause adhesive residue on the two-layer CCL polyimide film after hot press processing. However, the one of Example 3 was also sufficiently durable for practical use.

In addition, comparing Example 12 with Examples 6 to 11 and 14 to 16, the release sheets for hot press of Examples 6 to 11 and 14 to 16 have three or more (B) functional groups in the adhesive layer. Since the isocyanate-based crosslinking agent having the above is used, the crosslinking density is high and the adhesiveness is higher than that of the release sheet for hot press of Example 12 in which the isocyanate-based crosslinking agent having two (B) functional groups is used in the adhesive layer. The discoloration of the metal material caused by the transfer of the low molecular weight component contained in the layer to the metal material is less likely to occur. However, the material of Example 12 was also sufficiently practical.

In addition, comparing Example 13 with Examples 6 to 11 and 14 to 16, the release sheets for hot press of Examples 6 to 11 and 14 to 16 have a carboxyl group as the component (A-2) in the adhesive layer. Compared with the release sheet for hot press of Example 13 using acrylic acid having (B) and an epoxy-based cross-linking agent, corrosion of metal materials is less likely to occur, and thus discoloration of copper foil is less likely to occur. became. However, the material of Example 13 was also sufficiently durable for practical use.

Moreover, when comparing Example 15 with Examples 6 to 13, the release sheets for hot press of Examples 6 to 13 contain the component (C) in the adhesive layer at 15% by mass of the entire adhesive layer. Therefore, compared with the release sheet for hot pressing of Example 15 in which the content of the component (C) is 52% by mass of the entire adhesive layer, the polyimide film of the two-layer CCL after hot pressing is performed. The peeling force to the copper foil and the peeling force to the copper foil portion were also more excellent. However, the material of Example 15 was also sufficiently practical.

Further, when comparing Example 16 with Examples 6 to 13, the release sheets for hot press of Examples 6 to 13 are similar to the release sheet for hot press of Example 16 containing no component (C). In comparison, the peeling force to the polyimide film and the peeling force to the copper foil portion of the two-layer CCL after hot pressing were also more excellent. However, the material of Example 16 was also sufficiently practical.

Further, in the sticking step of sticking the cover lay film on the surface having the circuit pattern of the flexible printed wiring board having the two-layer metal-clad laminate structure by hot pressing using a hot plate, the release for hot pressing of Example 6 is performed. The sheet, with the pressure-sensitive adhesive layer of the release sheet for heat press interposed between the hot plate and the coverlay film so as to face the coverlay film, a flexible printed wiring board was manufactured, The metal material did not discolor due to outgas during hot pressing, and could be easily peeled off without leaving adhesive residue on the flexible printed wiring board after hot pressing.

The release sheet for hot pressing of the present invention is applied to a flexible printed wiring board having a two-layer metal-clad laminate structure having a circuit pattern on a synthetic resin film by hot pressing with a cover plate or a heat laying film. It is used for producing a laminate having a reinforcing plate with a curable adhesive attached, and is separated from the laminate after hot pressing ,
Having an adhesive layer on one surface of the base film,
The surface of the release sheet for hot press having the adhesive layer is laminated so as to face the surface of the flexible printed wiring board having the circuit pattern, and heat-pressed from the laminate obtained.
When releasing the release sheet for
(A) The peeling force 1 of the pressure-sensitive adhesive layer (for a synthetic resin film, measured according to JIS Z0237:2009, hot press condition: condition 1) is 1.5 N/25 mm or less,
(B) The peeling force 2 of the pressure-sensitive adhesive layer (for a metal material forming a circuit pattern, measured according to JIS Z0237:2009, hot press condition: condition 1) is 1 N/25 mm or less,
And
(C) a surface having a circuit pattern before and after hot ^{pressing, L * a * b * L} * a * b * tables providing the degree of discoloration (JIS Z8730 based on measurements of the lightness and chromaticness next-index by color system According to the calculation method based on the color difference due to the color system, the hot press condition: condition 2) is in the range of 0 to 3.
Condition 1: temperature 180° C., pressure 5 N/mm ² , 30 minutes
Condition 2: temperature 180° C., pressure 1 N/mm ² , 1 hour

The method for manufacturing a flexible printed wiring board of the present invention is a method for manufacturing a flexible printed wiring board having a two-layer metal-clad laminate structure, in which a circuit pattern of the flexible printed wiring board is obtained by hot pressing using a hot plate. In a sticking step of sticking a cover lay film on the surface having, the hot press release sheet, the adhesive layer of the hot press release sheet is at least between the hot plate and the cover lay film. The heat-releasing release sheet is separated from the cover lay film after being attached so as to face the film.

The method for manufacturing a flexible printed wiring board according to the present invention is a method for manufacturing a flexible printed wiring board having a two-layer metal-clad laminate structure, in which a circuit pattern of the flexible printed wiring board is obtained by hot pressing using a hot plate. In a laminating step of laminating a thermosetting adhesive reinforcing plate on the side opposite to the surface having, in the release sheet for heat press, at least the surface having the hot plate and the circuit pattern of the flexible printed wiring board The release sheet for heat press is interposed so as to face the surface having the circuit pattern of the flexible printed wiring board, and the release sheet for heat press is separated from the flexible printed wiring board after pasting. It is a thing.

Claims (14)

A release sheet for hot press having an adhesive layer on one surface of a substrate film, wherein the adhesive layer has a glass transition temperature of 10°C to 45°C, and at least (A) acrylic resin and (B) crosslink. The (A) acrylic resin has at least (A-1) ethyl methacrylate and (A-2) functional group and an alkyl group having 2 to 8 carbon atoms ( A release sheet for hot pressing, which is a copolymer of (meth)acrylate and (A-3) a monomer having an ethylenically unsaturated double bond. The release sheet for hot press according to claim 1, wherein the functional group of the component (A-2) is at least one selected from a hydroxyl group and an amino group. The release sheet for hot press according to claim 2, wherein the component (A-2) is at least one selected from 2-hydroxyethyl methacrylate and 2-hydroxyethyl acrylate. The monomer having an ethylenically unsaturated double bond as the component (A-3) is selected from ethyl acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, methyl (meth)acrylate, acrylonitrile and vinyl acetate. The release sheet for hot press according to claim 1, wherein the release sheet is at least one kind. The release sheet for hot press according to any one of claims 1 to 4, wherein the crosslinking agent as the component (B) is an isocyanate crosslinking agent. The release sheet for hot press according to claim 5, wherein the isocyanate-based crosslinking agent as the component (B) has three or more reactive functional groups. In the acrylic resin (A), the component (A-1) is 30% by mass or more and 65% by mass or less, the component (A-2) is 0.1% by mass or more and 10% by mass or less, and the component (A-3) is 25% by mass. The release sheet for hot press according to any one of claims 1 to 6, wherein the release sheet is a copolymer having a content of from 65% by mass to 65% by mass. The release sheet for hot press according to any one of claims 1 to 7, wherein the adhesive layer contains a resin having a glass transition temperature of -70°C to -30°C as the component (C). .. 9. The hot press according to claim 8, wherein the component (C) is at least one selected from a resin containing vinyl acetate and/or 2-ethylhexyl (meth)acrylate as a monomer, and a urethane resin. Release sheet for. The release sheet for hot pressing according to claim 8 or 9, wherein the content of the component (C) in the adhesive layer is 50% by mass or less of the adhesive layer. The release sheet for hot press according to claim 1, wherein the adhesive layer has a thickness of 4 to 40 μm. A release sheet for heat press having an adhesive layer on one surface of a base film, the side having a circuit pattern of a flexible printed wiring board having a two-layer metal-clad laminate structure, and the release sheet for heat press. The surface having the adhesive layer is attached, and hot pressing is performed at a temperature of 180° C. and a pressure of 5 N/mm ² for 30 minutes, and then a measurement method according to JIS Z0237:2009 is performed.
(A) The peeling force with respect to a film made of a synthetic resin used for a flexible printed wiring board is 1.5 N/25 mm or less,
(B) The peeling force with respect to the metal material forming the circuit pattern used for the flexible printed wiring board is 1 N/25 mm or less,
(C) A release sheet for hot press, which has a color change degree of 0 to 3 according to the following color change test.
Discoloration test:
(C-1) A lightness index and a chromatinex index by a L ^* a ^* b ^* color system of a surface of the two-layer metal-clad laminate having a metal material are measured,
(C-2) The surface of the two-layer metal-clad laminate having the metal material and the surface of the release sheet for heat press having the adhesive layer are attached to each other, and thermocompression bonding is performed under the conditions of 180° C. and 1 N/mm ² for 1 hour. To do. After being left to cool, the release sheet for hot press was peeled off, and the lightness index and the chromatinex index by the L ^* a ^* b ^* color system of the surface of the two-layer metal-clad laminate having the metal material were measured,
(C-3) The degree of discoloration of the surface having the metal material before and after hot pressing is calculated based on the color difference according to the L ^* a ^* b ^* colorimetric system defined in JIS Z8730. A method for manufacturing a flexible printed wiring board having a two-layer metal-clad laminated board structure, comprising: applying a coverlay film to a surface having a circuit pattern of the flexible printed wiring board by hot pressing with a hot plate. The release sheet for hot press according to any one of claims 1 to 12, wherein the adhesive layer of the release sheet for hot press faces the coverlay film at least between the hot plate and the coverlay film. A method for manufacturing a flexible printed wiring board which is interposed so as to intervene. A method for producing a flexible printed wiring board having a two-layer metal-clad laminate structure, comprising a thermosetting adhesive on the surface opposite to the surface having a circuit pattern of the flexible printed wiring board by hot pressing with a hot plate. In the attaching step of attaching the attached reinforcing plate, the release sheet for heat press according to any one of claims 1 to 12 is provided between at least the hot plate and a surface having a circuit pattern of the flexible printed wiring board. A method for manufacturing a flexible printed wiring board, wherein the adhesive layer of the release sheet for hot pressing is interposed so as to face the surface having the circuit pattern of the flexible printed wiring board.