JP2014098138A - Release film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a release film which is excellent in releasability, particularly releasability from an epoxy resin adhesive, has heat resistance, and does not require application of a silicone mold release agent or the like.SOLUTION: There are provided: the release film which contains polybutylene terephthalate (A) and is characterized in that the amount of oligomers contained in the release film is 2500 ppm or less; and a method of manufacturing a printed wiring board using the release film.

Description

  The present invention relates to a release film excellent in releasability suitable for use in pressure-forming a film or a sheet-like laminate using an adhesive, and more specifically, an electronic device and an electric device. The present invention relates to a release film that is excellent in releasability and is used when a coverlay is pressure-bonded with an adhesive to a flexible printed wiring board body on which an electric circuit used in the above is formed.

  In the production process of a printed wiring board, a flexible printed wiring board, a multilayer printed wiring board, etc., a release film is used when a copper-clad laminate or a copper foil is hot-pressed through a prepreg or a heat-resistant film. Further, in the manufacturing process of the flexible printed circuit board, when the cover lay film or the reinforcing plate is hot press bonded to the flexible printed circuit board body on which the electric circuit is formed by the thermosetting adhesive or the thermosetting adhesive sheet, the cover lay film is used. A release film is used to prevent the hot plate and the press hot plate from adhering to each other.

  As a release film used for such applications, a method using a crystalline polymethylpentene film (Patent Document 1: JP-A-2-175247), triacetate, fluororesin, polypropylene, polyethylene terephthalate, polybutylene terephthalate, etc. It has been proposed to use various films having heat resistance, such as a method of using a film (Patent Document 2: JP-A-7-15103), and depending on the temperature at the time of pressure molding with a copper-clad laminate, It is appropriately selected and used.

  And, since the release film needs to be removed easily after the copper-clad laminate and pressure molding, the mold release is excellent in releasability (low peel strength) in order to improve workability. The demand for film is increasing.

  On the other hand, in the configuration shown in FIG. 1, a printed wiring board 3 and a coverlay film (protective film) 2 having an epoxy resin having a window portion 4 as an adhesive are overlapped, and the release film 1 is sandwiched between the upper and lower sides. It has been found that when the release film 1 is peeled off from the coverlay film 2 after being heated and pressure-molded in step 1, the coverlay film 2 and the release film 1 may not be removed cleanly.

  Therefore, the present inventors investigated the cause, and as shown in FIG. 2, the reason why the cover lay film 2 and the release film 1 cannot be removed cleanly is the cover lay film at the time of heating and pressure forming. 2 and the release film 1 are in contact with the flow-out portion 5 of the epoxy resin adhesive that has flowed out of the end portion of the cover lay film 2 due to the softening and melting of the epoxy resin adhesive. As a result, it has been found that the flow-out part 5 of the epoxy resin adhesive and the release film 1 are bonded and cannot be removed cleanly.

  And when the release property of the flow-out part 5 of the epoxy resin adhesive and the release film 1 is insufficient, the epoxy resin adhesive is missing at the time of release and the coverlay film 2 and the printed wiring board 3 are removed. It has been found that if the adhesive strength of the cover layer 2 is impaired and the cover lay 2 is peeled off from the printed wiring board 3 or a fragment of the epoxy resin adhesive remains, it will lead to problems in the subsequent steps.

  In addition, as a method for improving the releasability, a method of applying a silicone-based release agent or the like to a release surface of a polyester film such as polyethylene terephthalate, polybutylene terephthalate, polyethylene isophthalate, or polyethylene naphthalate (Patent Document 3) : JP-A-2003-62939) and the like have been proposed.

Furthermore, in order to seal the oligomer precipitated on the film surface from the polymer by heat treatment or the like and to obtain a polyester film having excellent adhesion to the release layer, an amino group is formed on at least one surface of the polyester film. A method of applying a coating liquid containing a silane compound having an epoxy group and a silane compound having an epoxy group so that the amount of cyclic trimer deposited on the surface of the coating layer is 2.80 mg / m ² or less (Patent Document 4: Special In order to obtain a polyethylene terephthalate-based resin sheet and a molded product thereof that hardly cause casting roll stains during extrusion molding and / or mold stains during thermoforming and molded products thereof, the intrinsic viscosity is 0.60. 1.30 dl / g, containing germanium metal (hereinafter abbreviated as Ge), and oligomer (cyclic trimer) content A method of forming a polyethylene terephthalate-based resin sheet of 0.6% by weight or less (Patent Document 5: Japanese Patent Application Laid-Open No. 2001-294682), preventing process contamination during the production of a biaxially stretched polyester film and eliminating surface defects In order to increase productivity, polyester resin is supplied to the extruder, carbon dioxide is pressed into the extruder, the resin is molded into a sheet from the die, extruded, rapidly solidified on a cooling drum, and unstretched Various methods such as a method of obtaining a sheet and then biaxially stretching (Patent Document 6: Japanese Patent Laid-Open No. 10-138331) have been proposed. In each case, a polyethylene terephthalate film is described in the examples. There is only.

JP-A-2-175247 Japanese Patent Laid-Open No. 7-15103 JP 2003-62939 A JP 2002-105230 A JP 2001-294682 A JP 10-138331 A

  The present invention is to obtain a release film that is excellent in releasability, in particular, releasability with an epoxy resin adhesive, has heat resistance, and does not need to be coated with a silicone release agent. Objective.

  The present invention provides a release film comprising polybutylene terephthalate (A), wherein the amount of oligomer contained in the release film is 2500 ppm or less.

  Further, in the process of heating and pressurizing the protective film via the epoxy resin adhesive layer on the printed wiring board, the present invention includes heating and pressurizing the release film interposed between the protective film and the pressure plate. It is a method for manufacturing a printed wiring board including a step of performing thermal bonding and peeling the release film after heating and pressurization.

  A polyimide film is preferable as the protective film used in the present invention. A film made of a polyimide film and an epoxy resin adhesive is used as a coverlay on a printed wiring board. A window is punched in advance in the coverlay film, and only the punched portion is plated in the conductive wire portion of the printed wiring substrate in a subsequent plating step.

  The release film of the present invention has, for example, a low peel strength of 0.1 to 2.5 N / 15 mm with an epoxy adhesive, excellent release properties, heat resistance, and contamination resistance. It can be suitably used for the production of a printed wiring board, a flexible printed wiring board, a multilayer printed wiring board and the like in which a resin adhesive is used.

FIG. 1 is a schematic view showing a manufacturing process of a printed wiring board by overlapping a printed wiring board and a protective film. FIG. 2 is a schematic view after the structure shown in FIG. 1 is heated and pressurized.

<Polybutylene terephthalate (A)>
The polybutylene terephthalate (A) constituting the release film of the present invention is a polybutylene terephthalate having an oligomer amount of usually 2500 ppm or less, preferably 2000 ppm or less, more preferably 1500 ppm or less.

The lower limit of the amount of oligomer contained in polybutylene terephthalate is not particularly limited, but is usually 100 ppm.
The oligomer contained in the polybutylene terephthalate (A) according to the present invention is a cyclic dimer and a cyclic trimer composed of 1,4-butanediol and terephthalic acid generated during polymerization of polybutylene terephthalate.

The amount of the oligomer according to the present invention is an amount measured by high performance liquid chromatography (HPLC).
The polybutylene terephthalate (A) according to the present invention preferably has an intrinsic viscosity (IV) in the range of 1.0 to 1.3, more preferably 1.0 to 1.2.

  The intrinsic viscosity (IV) of the polybutylene terephthalate (A) according to the present invention is determined from the solution viscosity measured at 30 ° C. using a mixed solvent of phenol / tetrachloroethane (weight ratio 1/1).

  As the polybutylene terephthalate (A) according to the present invention, it is preferable to use a raw material that is solid-phase polymerized at a temperature of 200 ° C. or higher under reduced pressure or under an inert gas flow. It can be adjusted to an intrinsic viscosity that is easy to form a film by solid phase polymerization, and a decrease in the amount of terminal carboxylic acid groups and a decrease in oligomers can be expected.

  The polybutylene terephthalate (A) according to the present invention is referred to as so-called PBT composed of 1,4-butanediol and terephthalic acid as long as it has a polymer of 1,4-butanediol and terephthalic acid in the skeleton. The polybutylene terephthalate may be a block copolymer of polybutylene terephthalate and polyether, polyester, or polycaprolactam.

  Polybutylene terephthalate (A) according to the present invention is, for example, from Mitsubishi Engineering Plastics Co., Ltd. under the trade names NOVADURAN 5010CS (oligomer amount: 1300 ppm, IV: 1.1), NOVADURAN 5505S (oligomer amount: 2100 ppm, IV: 1. It is manufactured and sold as 2).

  The polybutylene terephthalate (A) according to the present invention has a melting point of 10 mg of a sample obtained by heating and melting at 300 ° C. for 5 minutes using a differential scanning calorimeter (DSC) and then rapidly cooling with liquid nitrogen. The peak temperature of the endothermic peak accompanying melting when the exothermic / endothermic curve was measured at a heating rate of 10 ° C./min was defined as the melting point (Tm) (° C.).

  The polybutylene terephthalate (A) according to the present invention can be blended with conventional additives and the like within a range not impairing the object of the present invention. Such additives are not particularly limited and include, for example, stabilizers such as antioxidants and heat stabilizers, lubricants, ultraviolet absorbers, catalyst deactivators, crystal nucleating agents, and the like. These additives can be added during or after the polymerization. Furthermore, in order to give the desired performance to the polybutylene terephthalate (A) according to the present invention, a flame retardant, a coloring agent such as a dye / pigment, an antistatic agent, a foaming agent, a plasticizer, and an impact resistance improving agent are blended. I can do it.

  Stabilizers include phenol compounds such as 2,6-di-t-butyl-4-octylphenol and pentaerythrityl-tetrakis [3- (3 ′, 5′-t-butyl-4′-hydroxyphenyl) propionate]. , Thioether compounds such as dilauryl-3,3′-thiodipropionate, pentaerythrityl-tetrakis (3-laurylthiodipropionate), triphenyl phosphite, tris (nonylphenyl) phosphite, tris (2,4 -Anti-oxidants such as phosphorus compounds such as -di-t-butylphenyl) phosphite and lubricants include paraffin wax, microcrystalline wax, polyethylene wax, long chain fatty acids represented by montanic acid and montanic acid ester, and esters thereof Etc.

  Examples of the crystal nucleating agent include aliphatic esters, aliphatic amides, fatty acid metal salts, etc., and aliphatic esters include fatty acid esters such as stearic acid monoglyceride and behenic acid monoglyceride, and hydroxy fatty acids such as 12-hydroxystearic acid triglyceride. Esters: aliphatic amides such as hydroxy fatty acid monoamides such as 12-hydroxystearic acid monoethanolamide, aliphatic bisamides such as ethylene bislauric acid amide, ethylene biscapric acid amide and ethylene biscaprylic acid amide, ethylene bis 12-hydroxy stearin Hydroxy fatty acid bisamides such as acid amide and hexamethylene bis 12-hydroxystearic acid amide; As fatty acid metal salts, hydroxy fats such as calcium 12-hydroxystearate Acid metal salts and the like. From the viewpoints of crystallization speed, heat resistance, temperature sensitivity, and transparency, 12-hydroxystearic acid triglyceride, behenic acid monoglyceride, ethylene bis 12-hydroxystearic acid amide, hexamethylene bis 12-hydroxystearic acid amide, 12 -Hydroxystearic acid monoethanolamide, ethylene biscaprylic acid amide, ethylene biscapric acid amide are preferred, 12-hydroxystearic acid triglyceride, ethylene bis 12-hydroxystearic acid amide, hexamethylene bis 12-hydroxystearic acid amide, 12-hydroxy More preferred is stearic acid monoethanolamide, 12-hydroxystearic acid triglyceride, ethylene bis 12-hydroxystearic acid amide, hexamethyle More preferably bis 12-hydroxystearic acid amide, ethylenebis 12-hydroxystearic acid amide, hexamethylene bis hydroxystearic acid amide are particularly preferred.

  Examples of the flame retardant include organic halogen compounds, antimony compounds, phosphorus compounds, other organic flame retardants, and inorganic flame retardants. Examples of the organic halogen compound include brominated polycarbonate, brominated epoxy resin, brominated phenoxy resin, brominated polyphenylene ether resin, brominated polystyrene resin, brominated bisphenol A, polypentabromobenzyl acrylate and the like. Examples of the antimony compound include antimony trioxide, antimony pentoxide, sodium antimonate, and the like. As a phosphorus compound, phosphate ester, polyphosphoric acid, ammonium polyphosphate, red phosphorus etc. are mentioned, for example. Examples of other organic flame retardants include nitrogen compounds such as melamine and cyanuric acid. Examples of other inorganic flame retardants include aluminum hydroxide, magnesium hydroxide, silicon compound, and boron compound.

  A reinforcing filler can be blended with the polybutylene terephthalate (A) according to the present invention as long as the object of the present invention is not impaired. The reinforcing filler is not particularly limited. For example, plate-like inorganic filler, ceramic beads, asbestos, wollastonite, talc, clay, mica, zeolite, kaolin, potassium titanate, barium sulfate, titanium oxide, silicon oxide , Aluminum oxide, magnesium hydroxide, glass fiber, carbon fiber, silica / alumina fiber, zirconia fiber, boron fiber, boron nitride fiber, silicon nitride potassium titanate fiber, metal fiber and other inorganic fibers, aromatic polyamide fiber, fluorine Examples thereof include organic fibers such as resin fibers. These reinforcing fillers can be used in combination of two or more. Among the above reinforcing fillers, inorganic fillers, particularly glass fibers, are preferably used.

  In order to improve the interfacial adhesion with the polybutylene terephthalate (A), the reinforcing filler is preferably used after being surface-treated with a sizing agent or a surface treatment agent. Examples of the sizing agent or surface treatment agent include functional compounds such as epoxy compounds, acrylic compounds, isocyanate compounds, silane compounds, and titanate compounds. The reinforcing filler can be surface-treated in advance with a sizing agent or a surface treating agent, or the surface of the reinforcing filler can be added by adding a sizing agent or a surface treating agent during the preparation of the polybutylene terephthalate (A) composition. It can also be processed. The addition amount of the reinforcing filler is usually 150 parts by mass or less, preferably 1 to 50 parts by mass with respect to 100 parts by mass of the polybutylene terephthalate (A).

  The polybutylene terephthalate (A) according to the present invention includes polyethylene, polypropylene, polymethylpentene, polystyrene, polyacrylonitrile, polymethacrylic acid ester, ABS resin, polycarbonate, polyamide, polyphenylene sulfide, polyethylene terephthalate, and liquid crystal as necessary. Thermosetting resins such as thermoplastic resins such as polyester, polyacetal, and polyphenylene oxide, phenol resins, melamine resins, silicone resins, and epoxy resins can be blended. These thermoplastic resins and thermosetting resins can be used in combination of two or more.

  In addition to the polybutylene terephthalate (A) according to the present invention, the nucleating agent (B) is preferably 3 parts by mass or less, more preferably 0.01 to 0.5, relative to 100 parts by mass of the polybutylene terephthalate (A). When a part by mass is contained, and more preferably by 0.05 to 0.3 parts by mass, a release film having more excellent peelability can be obtained.

As the nucleating agent (B) used by blending with the polybutylene terephthalate (A) according to the present invention, known organic crystal nucleating agents and inorganic crystal nucleating agents can be used.
Inorganic crystal nucleating agents include talc, kaolin, montmorillonite, synthetic mica, clay, zeolite, silica, graphite, carbon black, zinc oxide, magnesium oxide, titanium oxide, calcium sulfide, boron nitride, calcium carbonate, barium sulfate, oxidation Examples thereof include aluminum, neodymium oxide, dibasic aluminum phosphate, tricalcium phosphate, and metal salts of phenylphosphonate. These inorganic crystal nucleating agents may be modified with an organic substance in order to enhance the dispersibility in the composition.

  Organic crystal nucleating agents include phenylphosphonic acid (salts) or derivatives thereof, such as zinc phenylphosphonate, phenylphosphonic dichloride, dimethyl phenylphosphonate, melamine phosphate, bis (p-methylpentylidene) sorbitol, bis (p-Toluylidene) sorbitol and the like are preferable.

  Other organic crystal nucleating agents include sodium benzoate, potassium benzoate, lithium benzoate, calcium benzoate, magnesium benzoate, barium benzoate, lithium terephthalate, sodium terephthalate, potassium terephthalate, calcium oxalate, Sodium laurate, potassium laurate, sodium myristate, potassium myristate, calcium myristate, sodium octacosanoate, calcium octacosanoate, sodium stearate, potassium stearate, lithium stearate, calcium stearate, magnesium stearate, barium stearate , Sodium montanate, calcium montanate, sodium toluate, sodium salicylate, potassium salicylate, zinc salicylate, Organic carboxylic acid metal salts such as minium dibenzoate, potassium dibenzoate, lithium dibenzoate, sodium β-naphthalate, sodium cyclohexanecarboxylate, etc., organic sulfonates such as sodium p-toluenesulfonate, sodium sulfoisophthalate, stearic acid amide , Carboxylic acid amides such as ethylenebislauric acid amide, palmitic acid amide, hydroxystearic acid amide, erucic acid amide, trimesic acid tris (t-butylamide), sodium salt of ethylene-acrylic acid or methacrylic acid copolymer, styrene-maleic anhydride Sodium salt or potassium salt of polymer having carboxyl group such as sodium salt of acid copolymer (so-called ionomer), benzylidene sorbitol and its derivatives, nato Examples include phosphorus compound metal salts such as 2,2,2'-methylenebis (4,6-ditert-butylphenyl) phosphate, sodium 2,2-methylbis (4,6-di-t-butylphenyl), etc. Can do.

  Among these nucleating agents, bis (4-methylbenzylidene) sorbitol, sodium 2,2'-methylenebis (4,6-ditert-butylphenyl) phosphate, magnesium stearate, ethylene / bisstearic acid amide and the like are preferable.

<Release film>
The release film of the present invention is a release film containing the polybutylene terephthalate (A), and the amount of oligomers contained in the release film is 2500 ppm or less, preferably 2000 ppm or less, more preferably 1500 ppm or less. . Although the lower limit of the amount of oligomer contained in the release film is not particularly limited, it is usually 100 ppm.

The amount of the oligomer according to the present invention is the amount measured by high performance liquid chromatography (HPLC) as described above.
When the composition containing 0.01 parts by mass or more of the nucleating agent (B) is used as the release film of the present invention with respect to 100 parts by mass of the polybutylene terephthalate (A), The release film is more excellent in releasability from the epoxy resin adhesive layer.

The release film of the present invention may be laminated with other layers as long as it has a layer containing the polybutylene terephthalate (A).
The release film according to the present invention contains the polybutylene terephthalate (A). However, when the release film contains other thermoplastic resin and thermosetting resin, the polybutylene terephthalate ( The amount of A) is usually 50% by mass or more, preferably 80% by mass or more, and it is a release film made of polybutylene terephthalate (A) that does not contain other thermoplastic resins and thermosetting resins. Good.

  When a laminated film is used as the release film of the present invention, at least one side, that is, a layer made of polybutylene terephthalate (A) needs to be a release layer, that is, a bonding surface with an adhesive such as an epoxy resin adhesive. There is.

  When using the release film of this invention, the pressure of a heating press can be applied uniformly and it can be used by laminating | stacking with the other layer which can follow the unevenness | corrugation of a printed wiring. As such other layers excellent in cushioning properties, specifically, a film containing a resin that softens in the range of 50 ° C. to 150 ° C., preferably 70 ° C. to 120 ° C. is preferable, specifically low density polyethylene, Polyolefin resins such as polypropylene, ethylene methyl methacrylate copolymer, ethylene vinyl acetate copolymer, ethylene propylene copolymer, ethylene butene copolymer, propylene butene copolymer, or these may be used alone or in combination of two or more May be used in combination.

  The release film and cushion layer of the present invention can be multilayered by coextrusion. In that case, for example, using a three-layer T-die film molding machine comprising three extruders, the release layer comprising the polybutylene terephthalate (A) of the present invention is used as the outer layer, and the low density polyethylene layer is used as the inner layer. A two-layer three-layer film can be formed. In addition, in order to use an acid-modified polyethylene such as an ethylene methyl methacrylate copolymer instead of the low density polyethylene, or to increase the interlayer adhesion strength with the release layer, the ethylene methyl methacrylate copolymer and the polybutylene terephthalate are used. The composition (A) may be used for the inner layer. The composition in that case is preferably an ethylene methyl methacrylate copolymer as a main component and a matrix, ethylene methyl methacrylate copolymer is 50 to 95% by mass, polybutylene terephthalate (A) is 5 to 50% by mass, preferably The ethylene methyl methacrylate copolymer is preferably 60 to 85% by mass and the polybutylene terephthalate (A) is preferably 15 to 40% by mass. In order to further increase the interlayer adhesive strength, an adhesive layer may be provided between the release layer and the cushion layer.

  In the release film of the present invention, the peel strength between the epoxy resin adhesive layer and the release film by 180 degree peeling at a tensile speed of 300 mm / min is usually 2.5 N / 15 mm or less, preferably 0.1 to 0.1 mm. Since it exists in the range of 2.0N / 15mm, it is excellent in peelability with an epoxy resin adhesive layer.

<Method for producing release film>
The release film of the present invention can be produced by various known film forming methods. For example, when producing a monolayer film comprising the polybutylene terephthalate (A), it can be produced by a molding method such as T-die film molding or inflation film molding.

Moreover, when manufacturing a laminated | multilayer film as a release film of this invention, it can manufacture by coextrusion molding using a multilayer T-die or a multilayer cyclic | annular die.
Among these, the coextrusion method using a multilayer T-die is excellent in that the thickness of each layer can be made uniform and the width can be increased. Furthermore, after manufacturing a wide laminate, it is easy to slit to a width corresponding to a wide variety of FPC widths, which is preferable as a method for manufacturing a release film for FPC manufacturing.

The release film of the present invention is preferable since the release property is improved when the film obtained by the production method described above is further heat-treated.
As heating conditions, a heating temperature of 100 to 200 ° C is preferable in the air, and 150 to 190 ° C is more preferable. The heating time may be determined appropriately depending on the heating method.

  The method for heat-treating the release film of the present invention can be performed by various known methods, specifically, a roll-shaped release film obtained by molding with a T-die is passed through a heated hot air oven by roll-to-roll. Method, or a method of heating a release film by installing a heater such as an IR heater on a line passing through a roll-to-roll, or cutting a roll-shaped release film into a sheet and then heating in a hot air oven The method of processing, the method of making the roll-shaped release film shape | molded with the T-die contact the roll heated with the roll toe roll, etc. can be illustrated.

Although it does not specifically limit as a heat source which heats a release film, A far-infrared heater, a short wavelength infrared heater, a medium wavelength infrared heater, a carbon heater, etc. are preferable.
Among them, the method of bringing a roll-shaped release film formed with a T-die into contact with a roll heated with a roll-to-roll makes the heat transfer on the surface of the release film fast because the release film directly contacts the heated roll. Therefore, productivity is high because the heat treatment time can be made relatively short.

EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to a following example, unless the summary is exceeded. The resin composition used is as follows.
The polybutylene terephthalate used in Examples and Comparative Examples of the present invention is shown below.

(1) Polybutylene terephthalate (homopolymer)
(A-1) Tm = 224 ° C., IV = 1.1, [Mitsubishi Engineering Plastics Co., Ltd., trade name: Nova Duran 5010CS]
(D-1) Tm = 224 ° C., IV = 1.2, [Mitsubishi Engineering Plastics Co., Ltd., trade name: Nova Duran 5020]
(D-2) Tm = 224 ° C., IV = 1.2, [manufactured by Toray Industries, Inc., trade name: Toraycon 1400S]
(D-3) Tm = 224 ° C., IV = 1.0, [manufactured by Toray Industries, Inc., trade name: Toraycon 1200S]
(D-4) Tm = 224 ° C., IV = 0.8, [manufactured by Toray Industries, Inc., trade name: Toraycon 1100S]
(2) Copolymer of polybutylene terephthalate and polytetramethylene glycol (A-2) Tm = 222 ° C., IV = 1.2, [Mitsubishi Engineering Plastics Co., Ltd., trade name: NOVADURAN 5505S]

2. Crystal nucleating agent (B-1) Bis (4-methylbenzylidene) sorbitol, Tm = 260 ° C. (trade name: Gelol MD, manufactured by Shin Nippon Rika Co., Ltd.)
(B-2) Sodium 2,2′-methylenebis (4,6-ditert-butylphenyl) phosphate [trade name: ADK STAB NA-11, manufactured by Adeka Corporation]
(B-3) Magnesium stearate, Tm = 125 ° C., manufactured by Sakai Chemical Industry Co., Ltd.
(B-4) Ethylene bisstearic acid amide, Tm = 144 ° C. [trade name: Kao wax EB-P, manufactured by Kao Corporation]
The oligomer amount of the release film was measured by the following method.

<Standard solution preparation>
(1) 10 mg of each standard product was weighed into a 10 ml volumetric flask and dissolved in dimethylformamide (DMF).
(2) Dilute standard 1000 μg / ml DMF solution with DMF to prepare 0.2 and 20 μg / ml standard solutions.

<Sample measurement solution preparation>
(1) After weighing 0.2 g of sample, 5 ml of HFIP / chloroform = 1/1 (volume ratio) solution was added to dissolve the sample.
(2) After adding 20 ml of chloroform and diluting, it was added dropwise to 70 ml of acetonitrile, and precipitation treatment was performed upon dissolution.
(3) Filtration through filter paper, and the filtrate is evaporated to dryness by evaporation and nitrogen purge.
(4) After dissolving with DMF, constant volume to 5 ml.

<Device and measurement conditions>
Device: waters alliance2695 / 2487
Column: Develosil ODS-KH-3 (3μ 4.6 × 150mm) manufactured by Nomura Chemical Co., Ltd.
Mobile phase: 0.5% acetic acid aqueous solution / acetonitrile gradient Detection: UV = 254 nm
<Quantitative>
The amount of oligomer was determined by a calibration curve method using a peak area of 20 μg / ml of a bishydroxyethyl terephthalate (BHET) standard product solution.

[Examples 1-7 and Comparative Examples 1-6]
<Preparation method of crystal nucleating agent master batch>
After blending at a composition ratio of polybutylene terephthalate described above: 100 parts by mass and each crystal nucleating agent described above: 5 parts by mass, using a twin screw extruder (“TEX-30” manufactured by JSW), A crystal nucleating agent master batch having a concentration of 5% by mass of the crystal nucleating agent was prepared by melting and kneading at a cylinder temperature and pelletizing.

Next, after blending the polybutylene terephthalate and crystal nucleating agent master batch described above in the ratio shown in Table 1, in a T-die film molding machine of an extruder with a screw diameter of 40 mm, a resin temperature of 250 ° C., a chill roll temperature of 80 ° C., A single-layer film of 50 μm polybutylene terephthalate was obtained under conditions of an air chamber static pressure of 440 mmH ₂ O.

<Oven heat treatment method>
The above single-layer film was heat-treated at 180 ° C. for 5 minutes in an air atmosphere using a hot air circulation oven, and the film after natural cooling was used as a release film.
The release film was evaluated for release properties by the following method.
Table 1 shows the results.

(1) Evaluation of epoxy releasability Coverlay film (protective film) [trade name: Coverlay CISV1215 (manufactured by Nikkan Kogyo Co., Ltd., polyimide film thickness: 12 μm, epoxy resin adhesive layer thickness: 15 μm)] and release The mold films were overlaid with the same machine direction (MD). At that time, the release layer of the release film and the epoxy resin adhesive layer of the coverlay film were in contact with each other at the surface. Further, it was sandwiched between an aluminum plate and a SUS plate on the outside, and press molding was performed. The press was bonded at a pressure of 4 MPa at 180 ° C. for 30 minutes. After the press molding was completed, the press pressure was released, and after natural cooling, a laminate in which the coverlay film and the release film overlapped was obtained. This is cut into a width of 15 mm in the MD direction, and using a tensile tester (manufactured by Toyo Seiki Co., Ltd.), the peel strength between the epoxy resin adhesive layer of the coverlay film and the release film is peeled 180 degrees at a tensile speed of 300 mm / min. And the release strength with respect to the epoxy resin adhesive.

(2) Evaluation of wrinkle resistance A coverlay film 2 [manufactured by Nikkan Kogyo Co., Ltd., trade name: CISV1215] comprising the polyimide film 2-1 and the epoxy resin adhesive layer 2-2 shown in FIG. 1 was used. In the coverlay film 2, a portion corresponding to the terminal portion of the printed wiring board 3 is punched out as a window portion 4. The size of the window 4 is 4 mm × 20 mm, and is formed at a plurality of locations on one coverlay film 2. On the other hand, the printed wiring board 3 used a size of 240 mm × 300 mm in which a wiring pattern is formed of a 12 μm thick copper foil (not shown) on a 25 μm thick polyimide film. The printed wiring board 3 and the coverlay film 2 were positioned and overlapped, and the both sides were sandwiched between the release films 1 and set in a heating press. Heat pressing was performed under the conditions of a temperature of 180 ° C., a pressure of 4 MPa, and a pressing time of 120 seconds. In this process, the epoxy adhesive of the cover lay film flows out somewhat in the window part 4, and the flow-out part 5 of the epoxy resin adhesive is formed. Next, after a press plate (not shown) was opened and cooled, the release film 1 was released from the printed wiring board 3 to which the coverlay film 2 was adhered. At the time of mold release, if the mold release is heavy at the flow-out portion 5 of the epoxy resin adhesive, the printed wiring board 3 is broken and wrinkled. The case where wrinkles occurred even at one place was evaluated as x, and the case where wrinkles did not occur was determined as ◯.

  The release film of the present invention has a low peel strength of 0.1 to 2.5 N / 15 mm from the epoxy adhesive, has excellent release properties, and has heat resistance and stain resistance, so it is safe and easy. In the manufacturing process of a printed wiring board, flexible printed wiring board, or multilayer printed wiring board, when heat-pressing a copper-clad laminate or copper foil via a prepreg or a heat-resistant film, press heat It is suitably used to prevent adhesion between the board and the printed wiring board, flexible printed wiring board, or multilayer printed wiring board.

1: Release film 2: Coverlay film (protective film)
2-1: Polyimide film 2-2: Epoxy resin adhesive layer 3: Printed wiring board 4: Window portion 5: Flow-out portion of epoxy resin adhesive

Claims (5)

  A release film containing polybutylene terephthalate (A), wherein the amount of oligomers contained in the release film is 2500 ppm or less.   The release film according to claim 1, comprising 0.01 parts by mass or more of the nucleating agent (B) with respect to 100 parts by mass of the polybutylene terephthalate (A).   The release film according to claim 1 or 2, wherein the polybutylene terephthalate (A) has an intrinsic viscosity (IV) of 1.0 to 1.3.   The release film in which the film in any one of Claims 1-3 is heat-processed.   The release film according to any one of claims 1 to 4 is provided between the protective film and the pressure plate in the step of heating and pressing the protective film to the printed wiring board via an epoxy resin adhesive layer. A method for producing a printed wiring board, comprising the steps of heat-bonding by interposing and heat-bonding, and peeling the release film after heat-bonding.

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