JP2007196663A - Multilayer release film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer release film which is used in heat press cementing between an FPC (flexible printed circuit) and a overlay, excels in a mold-release characteristic and the followability for a shape, in which the oozing of an adhesive bond from the end of the overlay is inhibited and the contamination of an FPC product by the elution of a resin component composing the intermediate layer is made not to generate. <P>SOLUTION: The multilayer release film comprises a surface layer integrally laminating the both surfaces of an intermediate layer. The intermediate layer consists of a resin composition comprising: 50-100 wt.% of a polypropylene resin having 160°C or higher of a melting point and 240,000-650,000 of a weight average molecular weight, and in which the resin elution volume in each temperature range measured by a cross fractionation method has a predetermined proportion; and 0-50 wt.% of a vinyl aromatic-based elastomer. The surface layer consists of a polypropylene resin having 140°C or higher of a melting point and 240,000-650,000 of a weight average molecular weight. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multilayer release film that is used when a film or sheet-like laminate is hot-press bonded using an adhesive, and more specifically, a flexible printed board is hot-pressed with an adhesive-coated overlay. The present invention relates to a multilayer release film used for bonding.

  A flexible printed board (hereinafter referred to as FPC) is obtained by laminating and integrating a copper foil on one or both sides of a heat insulating film such as polyimide, and etching the copper foil to form an electric circuit. Then, for the purpose of insulation and heat insulation, a heat-resistant film with an adhesive called overlay is hot-press bonded on the electric circuit (copper foil) surface of the FPC, and the electric circuit surface is covered with the FPC (hereinafter, “ It is usually used as "FPC product").

  In such a hot press bonding step, a release film is interposed between the FPC or overlay and the press hot plate in order to prevent the FPC or overlay from being bonded to the press hot plate. As such a release film, it is necessary not only for releasability to FPC, overlay and press hot plate, but also to give the overlay bite to the recess of the electric circuit surface of FPC (conformability to shape). With excellent flexibility, releasability of FPC (FPC product) not covered by overlay for electrical connection with other parts to copper terminals, and prevention of adhesive seepage from the end face of overlay Has been demanded.

  For this reason, conventionally, many release films have been used in which two types of films are laminated and integrated into three layers so that the surface layer has releasability and the intermediate layer has heat fluidity. As such a release film, for example, in Patent Document 1, the intermediate layer is a copolymer resin of ethylene and methyl methacrylate, and the upper and lower layers sandwiching the intermediate layer are polypropylene or polymethylpentene. A release multilayer film for circuit laminating process is disclosed.

Japanese Patent No. 2659404

  However, the release multilayer film for the printed circuit laminating process is disclosed in the example of Patent Document 1, and is printed circuit laminating process when it is hot pressed at a pressure of 2.9 MPa and a temperature of 150 ° C. for 60 minutes. The copolymer resin of ethylene and methyl methacrylate elutes from the intermediate layer of the release multilayer film, and the press hot plate, overlay, copper terminals of FPC and FPC are affected by the copolymer resin of ethylene and methyl methacrylate and its decomposition products. There was a problem of being contaminated.

  Moreover, since the copolymer resin of ethylene and methyl methacrylate in the intermediate layer is eluted, the flexibility of the release multilayer film for the printed circuit laminating process is lost, and the conformability to the shape becomes insufficient. The FPC product has a problem that a gap is generated between the electric circuit surface and the overlay.

  The present invention has been made in view of the above-described problems, and the object of the present invention is excellent in releasability and conformability to the shape, and prevents the adhesive from seeping out from the end of the overlay. At the same time, it provides a multilayer release film that does not contaminate the hot plate, overlay, flexible printed circuit board and copper terminal of the flexible printed circuit board by elution of the resin component constituting the intermediate layer and its decomposition product. There is to do.

  The multilayer release film of the present invention is a multilayer release film in which surface layers are laminated and integrated on both surfaces of an intermediate layer, and the intermediate layer has a melting point of 160 ° C. or higher and a weight average molecular weight of 240,000 to 650. The resin elution amount measured by the cross fractionation method was 45 to 60% by weight of the total polypropylene resin at 0 ° C. or more and 10 ° C. or less, and 15% of the total polypropylene resin at 10 ° C. or more and 70 ° C. or less. Polypropylene resin 50 that is ˜22 wt%, greater than 70 ° C. and less than or equal to 95 ° C., and 3 to 20 wt% of the total polypropylene resin, and greater than 95 ° C. and less than or equal to 125 ° C. The surface layer has a melting point of 140 and a resin composition composed of ˜100% by weight and a vinyl aromatic elastomer of 0 to 50% by weight. And a weight average molecular weight above is characterized by comprising the polypropylene resin is 240,000～650,000.

  It does not specifically limit as a polypropylene resin used for the said intermediate | middle layer, For example, a homopolypropylene, a propylene-vinyl acetate copolymer, a propylene-alpha-olefin copolymer etc. are mentioned. Examples of the α-olefin include ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and the like.

  Also, if the melting point of the polypropylene resin used for the intermediate layer is low, the resin composition constituting the intermediate layer and the decomposition product thereof are eluted during the hot press bonding, and the press hot plate, overlay, FPC and FPC The copper terminal is contaminated, so the temperature is limited to 160 ° C. or higher, and preferably 160 to 250 ° C. The melting point of the polypropylene resin refers to the melting peak temperature of the DSC curve measured according to JIS K7121, and when there are a plurality of melting peak temperatures, the melting point is the peak temperature with the largest area of the melting curve. .

  And when the weight average molecular weight (Mw) of the polypropylene resin constituting the intermediate layer is low, the resin composition constituting the intermediate layer and its decomposition product are eluted during the hot press bonding, On the other hand, the copper terminal of the overlay, FPC and FPC is contaminated. On the other hand, if it is high, the film forming stability of the multilayer release film is lowered, so it is limited to 240,000 to 650,000, Is preferred. In addition, the measuring method of the weight average molecular weight of the polypropylene resin in this invention says the polystyrene conversion value measured by GPC (Gel Permeation Chromatography) method.

  When the resin elution amount at 0 ° C. or higher and 10 ° C. or lower measured by the cross fractionation method in the polypropylene resin constituting the intermediate layer of the multilayer release film of the present invention is small, the flexibility of the multilayer release film is insufficient. On the other hand, if the shape-following property becomes insufficient, the release property of the multilayer release film becomes insufficient if it is large.

  In addition, if the resin elution amount at 10 ° C. or more and 70 ° C. or less measured by the cross fractionation method in the polypropylene resin constituting the intermediate layer is small, the flexibility of the multilayer release film is insufficient, so On the other hand, if the amount is too large, the release property of the multilayer release film becomes insufficient, so the amount is limited to 15 to 22% by weight of the total polypropylene resin.

  And if the amount of resin elution at 70 ° C. and below 95 ° C. measured by the cross-fractionation method in the polypropylene resin constituting the intermediate layer is small, the flexibility of the multilayer release film is insufficient, and the anti-shape follow-up On the other hand, if the amount is too large, the strength of the multilayer release film is insufficient, so that it is limited to 3 to 20% by weight of the total polypropylene resin.

  Furthermore, if the amount of resin elution at 95 ° C. and below 125 ° C. measured by the cross fractionation method in the polypropylene resin constituting the intermediate layer is small, the strength of the multilayer release film becomes insufficient while it is large. Then, the flexibility of the multilayer release film is insufficient, and the conformability to the shape is insufficient, so that it is limited to 10 to 35% by weight of the total polypropylene resin.

  Here, in the present invention, the cross fractionation method is performed as follows. First, the polypropylene resin is dissolved in o-dichlorobenzene at a temperature at which the polypropylene resin is completely dissolved, and the solution in which the polypropylene resin is dissolved is cooled to 0 ° C. at a constant rate and prepared beforehand. A thin polymer layer is formed on the surface of the active carrier in the order of high crystallinity and high molecular weight. Next, the temperature is raised continuously or stepwise, the concentration of the components eluted in sequence is detected, and the composition distribution (crystallinity distribution) is measured. This is called temperature rising elution fractionation (TREF = Temperature Rising Elution Fraction).

  Along with this temperature rise elution fractionation, the weight average molecular weight and molecular weight distribution of the sequentially eluted components are measured by high-temperature GPC, and the resin elution amount in each temperature range is calculated based on this. In the present invention, for example, cross fractionation sold under the trade name “CFC-T150A type” by Mitsubishi Yuka Co., Ltd., which includes a temperature rise elution fractionation part and a high temperature GPC (SEC = Size Exclusion Chromatography) part as a system. A chromatographic apparatus can be used.

  Examples of commercially available polypropylene resins that satisfy the above conditions include “PER” from Tokuyama and “Cataloy” from Basel.

  Here, the polypropylene resin is produced, for example, by allowing a propylene monomer to flow in a pipe in the presence of a titanium catalyst and polymerizing in a short time. At this time, by changing the polymerization time, the block chain length of the polypropylene resin can be changed, and the resin elution amount in each temperature range can be adjusted.

  In addition, in order to obtain a polypropylene resin having a low elution temperature, that is, low crystallinity, when polymerizing propylene monomer in the presence of a catalyst, the addition of ethylene monomer or the like is increased to obtain a resin having lower crystallinity. Control may be performed as follows. In addition, by polymer blending the resin obtained by polymerization, the ratio of the resin elution amount in each temperature range and the weight average molecular weight can be appropriately adjusted to a necessary configuration.

  And if content of the polypropylene resin in the resin composition which comprises the intermediate | middle layer of the multilayer release film of this invention is small, since film forming stability will become inadequate, it is limited to 50 to 100 weight%. 70 to 100% by weight is preferable.

  The resin composition constituting the intermediate layer of the multilayer release film of the present invention may contain a vinyl aromatic elastomer for the purpose of improving the flexibility of the multilayer release film and enhancing the conformability to the shape. Good.

  The vinyl aromatic elastomer is a block copolymer or a random copolymer of a vinyl aromatic compound (a) and a conjugated diene (b). In the block copolymer of the vinyl aromatic elastomer, the vinyl aromatic compound (a) and the conjugated diene (b) are A- (BA) m or B- (ABA) n. (A is a block polymer of a vinyl aromatic compound, B is a block polymer of a conjugated diene, and m and n are natural numbers).

  The vinyl aromatic compound (a) is not particularly limited, and examples thereof include styrene, p-tert-butylstyrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylstyrene, and the like. Styrene is preferred.

  The conjugated diene (b) is not particularly limited. For example, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1, Examples include 3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, and 1,3-butadiene and isoprene are preferable.

  The vinyl aromatic elastomer was hydrogenated (hydrogenated) to improve heat resistance and weather resistance, and the double bond in the block polymer portion of the conjugated diene of the vinyl aromatic elastomer was saturated. It is preferable.

  In addition, if the content of the vinyl aromatic elastomer in the resin composition constituting the intermediate layer of the multilayer release film of the present invention is large, the film-forming stability of the multilayer release film is lowered. It is limited to% by weight, and preferably 0 to 30% by weight.

  The resin composition constituting the intermediate layer of the multilayer release film of the present invention includes resin components other than polypropylene resins and vinyl aromatic elastomers as long as the physical properties of the multilayer release film of the present invention are not impaired. Additives may be included.

  Surface layers are laminated and integrated on both surfaces of the intermediate layer of the multilayer release film of the present invention. Although it does not specifically limit as polypropylene-type resin which comprises this surface layer, For example, a homopolypropylene, a propylene-vinyl acetate copolymer, a propylene-alpha-olefin copolymer etc. are mentioned. In addition, although the polypropylene resin which comprises both surface layers may not be the same, it is preferable that it is the same. In addition, you may add an additive to a surface layer in the range which does not impair the physical property of the multilayer release film of this invention.

  Examples of the α-olefin constituting the propylene-α-olefin copolymer include ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and the like.

  If the melting point of the polypropylene resin constituting the surface layer is low, the polypropylene resin and its decomposition product will elute from the surface layer during hot press bonding, and press hot plate, overlay, FPC and FPC copper terminals Since it will contaminate, it is limited to 140 degreeC or more, 160 degreeC or more is preferable and 160-175 degreeC is more preferable. In addition, although the melting point of the polypropylene resin of both surface layers may not be the same, it is preferable that it is the same.

  Moreover, when the weight average molecular weight (Mw) of the polypropylene resin constituting the surface layer is low, the polypropylene resin and its decomposition product are eluted from the surface layer during the hot press bonding, and the hot plate, overlay, While it will contaminate the FPC and FPC copper terminals, if it is high, the film forming stability of the multilayer release film will decrease, so it is limited to 240,000 to 650,000, preferably 250,000 to 600,000. . The weight average molecular weights of the polypropylene resins of both surface layers may not be the same, but are preferably the same.

  If there is a resin elution amount at 0 ° C. or higher and 10 ° C. or lower as measured by the cross fractionation method in the polypropylene resin constituting the surface layer of the multilayer release film of the present invention, the release property of the multilayer release film is insufficient. Therefore, it is preferably 0% by weight of the total polypropylene resin.

  Moreover, if the amount of resin elution at 10 ° C. and below 70 ° C. measured by the cross fractionation method in the polypropylene resin constituting the surface layer is large, the release property of the multilayer release film becomes insufficient. Therefore, it is preferably 0 to 3% by weight of the total polypropylene resin.

  And if the amount of resin elution at 70 ° C. or more and 95 ° C. or less measured by the cross fractionation method in the polypropylene resin constituting the surface layer is small, the flexibility of the multilayer release film is insufficient, and the anti-shape following On the other hand, if the amount is too large, the release property of the multilayer release film may be insufficient. Therefore, the content is preferably 1 to 5% by weight of the total polypropylene resin.

  Furthermore, if the amount of resin elution at 95 ° C. and below 125 ° C. measured by the cross fractionation method in the polypropylene resin constituting the surface layer is small, the release property of the multilayer release film becomes insufficient. On the other hand, if it is large, the flexibility of the multilayer release film may be insufficient, and the conformal followability may be insufficient. Therefore, the content is preferably 92 to 99% by weight of the total polypropylene resin.

  In addition, the resin elution amount in each temperature range in the polypropylene resin of both surface layers is not necessarily the same, but is preferably the same.

  And in the surface layer, you may contain the vinyl aromatic elastomer mentioned above in order to improve the softness | flexibility of a multilayer release film and to improve anti-trackability. The vinyl aromatic elastomer is preferably contained in both surface layers, but may be contained only in one of the surface layers. Further, when vinyl aromatic elastomers are contained in both surface layers, the vinyl aromatic elastomers contained in both surface layers are not necessarily the same, but are preferably the same.

  Thus, when the above-mentioned polypropylene resin and vinyl aromatic elastomer are contained in the surface layer, when the content of the polypropylene resin in the surface layer is small, the film forming stability of the multilayer release film is improved. On the other hand, if it is low, the flexibility of the multilayer release film may be low, so 75 to 95% by weight is preferable. For the same reason, the content of the vinyl aromatic elastomer in the surface layer is preferably 5 to 25% by weight.

  The surface layer of the multilayer release film may contain a resin component other than the polypropylene resin and vinyl aromatic elastomer as long as the physical properties of the multilayer release film are not impaired.

  The thickness of the multilayer release film of the present invention is not particularly limited, but if it is thin, the strength of the multilayer release film may be insufficient. On the other hand, if it is thick, the thermal conductivity during hot press bonding may be insufficient. Since it exists, it is preferable that it is 50-300 micrometers.

  In addition, the thickness ratio (intermediate layer / surface layer) between the intermediate layer and the surface layer of the multilayer release film is not particularly limited, but if it is small, the flexibility of the multilayer release film is insufficient and the conformability to the shape is not good. On the other hand, if it is sufficient, the release property of the multilayer release film may be insufficient. In addition, although it is preferable that the thickness of both surface layers is the same, it does not necessarily need to be the same. Further, when the thicknesses of the two surface layers are different, it is preferable that the ratio of the thickness of each surface layer to the thickness of the intermediate layer is within the above range.

  The method for forming the multilayer release film of the present invention is not particularly limited, and examples thereof include a coextrusion laminating method, an extrusion laminating method, and a dry laminating method, and the coextrusion laminating method is preferable.

  Next, a method for producing an FPC product by hot-press bonding an FPC and an overlay using the multilayer release film of the present invention will be described. The method of using the multilayer release film of the present invention includes these methods. It is not limited.

  First, as a method of heat-press bonding an FPC having an electric circuit provided on one side of a heat insulating film and an overlay, for example, on the electric circuit surface of the FPC, the overlay is coated with the adhesive applied surface of the FPC. A laminated body that is laminated so as to face the substrate is prepared, and a multilayer release film is laminated on both sides of the laminated body to produce a laminated body for hot pressing.

  Subsequently, the laminate for hot pressing is supplied to a multi-stage press, and both sides of the laminate for hot pressing are 30 to 60 in the thickness direction of the laminate for hot pressing at a pressure of 2 to 6 MPa and a temperature of 150 to 180 ° C. Pressurize for a minute, then cool with pressure until 25-50 ° C. Thereafter, the laminate for hot press is taken out from the multistage press, and the multilayer release film is peeled off from the laminate for hot press to produce an FPC product.

  In addition, as a method of heat-pressing the overlay on both sides of the FPC in which the electric circuits are provided on both sides of the heat insulating film, for example, the overlay is placed on both sides of the FPC so that the adhesive coating surface faces the FPC. Then, a laminate is prepared by laminating, and a multilayer release film is laminated on both sides of the laminate to produce a laminate for hot pressing. And the method of manufacturing an FPC product is mentioned in the same way as the hot press adhesion process of FPC with which the electric circuit was provided in the one side mentioned above, and an overlay.

  The multilayer release film of the present invention is a multilayer release film in which surface layers are laminated and integrated on both surfaces of an intermediate layer, and the intermediate layer has a melting point of 160 ° C. or higher and a weight average molecular weight of 240,000 to 650. And the resin elution amount measured by the cross fractionation method is composed of a resin composition comprising 50 to 100% by weight of a polypropylene resin and 0 to 50% by weight of a vinyl aromatic elastomer in a predetermined ratio in each temperature range Since the surface layer is composed of a polypropylene resin having a melting point of 140 ° C. or higher and a weight average molecular weight of 240,000 to 650,000, it is excellent in releasability. According to the mold film, after the FPC and the overlay are hot-press bonded, the multilayer release film from the press hot plate, the FPC product and its copper terminal When removing, press release plate, FPC product and its copper terminal will not be peeled off while the multilayer release film is attached and will not contaminate them, so improve the production efficiency of FPC product Can do.

  In addition, since the multilayer release film has the above-described configuration, when the FPC and the overlay are subjected to hot press bonding, the resin composition constituting the intermediate layer or a decomposition product thereof is eluted, and the press hot plate , Overlay, FPC and FPC copper terminals are not contaminated.

  And since the said multilayer release film takes the structure as mentioned above, when heat-press-bonding FPC and an overlay, it expresses a moderate softness | flexibility, and the adhesive agent apply | coated to the overlay fuse | melts. It deforms before flowing and adheres along the shape of the copper terminal of the overlay, FPC and FPC, and does not allow the adhesive to ooze out. Therefore, according to the multilayer release film of the present invention, the adhesive applied to the overlay does not ooze out and contaminate the copper terminal of the FPC. You can get a product.

  In addition, as described above, the multilayer release film of the present invention exhibits an appropriate flexibility when the FPC and the overlay are heat-press bonded, and thus has excellent conformability. That is, according to the multilayer release film, the overlay can be firmly bitten into the concave portion of the electric circuit surface of the FPC, and an FPC product can be manufactured in which there is almost no gap between the opposing surfaces of the FPC and the overlay.

  Furthermore, since the multilayer release film has the above-described configuration, bubbles do not remain between the opposing surfaces of the FPC and the overlay. Therefore, in the FPC product manufactured by the multilayer release film of the present invention, the electric circuit is not oxidized over time by the air remaining in the FPC product, and the life of the electric circuit is not shortened. As a long-life FPC product, it is suitably used for an electric circuit board such as an electronic device.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples. In addition, the melting points, weight average molecular weights, and resin melting amounts in the respective temperature ranges measured by the cross fractionation method of the following polypropylene resins A to D are as shown in Table 1.

Example 1
A co-extrusion film forming apparatus is prepared in which three extruders are connected to one co-extrusion die via a connector, and polypropylene resin A (manufactured by Sun Allomer Co., Ltd.) is used as a resin component for the intermediate layer in one extruder. A resin composition comprising 90% by weight of a trade name “Cataloy Q200F”) and 10% by weight of a hydrogenated product of styrene-butadiene block copolymer (trade name “Tuftec” styrene content: 12% by weight, manufactured by Asahi Kasei Chemicals) Then, after supplying polypropylene resin B (trade name “E100GP” manufactured by Idemitsu Petrochemical Co., Ltd.) as a resin component for the surface layer to both of the remaining two extruders, By co-extrusion film formation, a multilayer release film having a surface layer laminated and integrated on both surfaces of the intermediate layer was obtained. In addition, the thickness of the intermediate | middle layer of this multilayer release film was 120 micrometers, and the thickness of both surface layers was 20 micrometers, respectively. The styrene-butadiene block copolymer is a block copolymer represented by the formula B- (ABA) n (A is a block polymer of styrene, and B is a block polymer of butadiene). is there.

(Example 2)
In the same manner as in Example 1 except that polypropylene resin C (trade name “E203” manufactured by Idemitsu Petrochemical Co., Ltd.) was used as the resin component for the surface layer, the thickness of the intermediate layer was 120 μm and the thickness of both surface layers. A multilayer release film having a thickness of 20 μm was obtained.

(Example 3)
As a resin component for the surface layer, polypropylene resin B (trade name “E100GP” manufactured by Idemitsu Petrochemical Co., Ltd.) 90% by weight and hydrogenated product of styrene-butadiene block copolymer (trade name “Tuftec” styrene manufactured by Asahi Kasei Chemicals Co., Ltd.) (Content: 12 wt%) Multilayer release with the same procedure as in Example 1 except that a resin composition consisting of 10 wt% was used, with an intermediate layer thickness of 120 μm and both surface layers of 20 μm thickness. A film was obtained.

(Comparative Example 1)
Polypropylene resin D (trade name “F724” manufactured by Idemitsu Petrochemical Co., Ltd.) is used as the resin component for the surface layer, and ethylene-methyl methacrylate copolymer (trade name “ACRIFTH WH102 manufactured by Sumitomo Chemical Co., Ltd.” is used as the resin component for the intermediate layer. ]) Was used in the same manner as in Example 1 to obtain a multilayer release film having an intermediate layer thickness of 60 μm and both surface layers of 50 μm thickness.

(Manufacturing of FPC products)
Next, FPC products were manufactured in the following manner using the multilayer release films obtained in the above-mentioned Examples and Comparative Examples.

  Prepared in advance as described above on both sides of the laminated body laminated so that the electric circuit surface of the FPC in which the electric circuit is provided on one side of the heat insulating film and the adhesive application surface of the overlay are opposed to each other. The obtained multilayer release film was laminated to produce a laminate for hot pressing.

  Subsequently, the laminate for hot press was supplied to a multistage press machine (trade name “compression molding machine NSF-37” manufactured by Shinto Metal Industry Co., Ltd.) provided with a pair of press hot plates, pressure 4.9 MPa, temperature At 160 ° C., both surfaces of the hot-press laminate were pressurized in the thickness direction of the hot-press laminate for 45 minutes, and then cooled while being pressurized to 50 ° C. And the laminated body for hot press after cooling was taken out from the multistage type press, and the multilayer release film was peeled from the laminated body for hot press, and FPC product was obtained.

  And the releasability when the multi-layer release film is peeled off from the press hot plate and the FPC product, the shape followability of the obtained FPC product, the presence or absence of air bubbles between the facing surfaces of the FPC and overlay of the FPC product The presence or absence of contamination of the copper terminal of the FPC product and the seepage of the adhesive from the end face of the FPC product were evaluated according to the following criteria, and the results are shown in Table 2. In Table 2, the hydrogenated product of the styrene-butadiene block copolymer was expressed as “SB”, and the ethylene-methyl methacrylate copolymer was expressed as “EMMA”.

(Releasability)
After completion of the hot press bonding step as described above, the release property when the multilayer release film was manually peeled from the FPC product and the press hot plate was evaluated based on the following criteria.
A: The multilayer release film could be peeled off very easily.
○: The multilayer release film could be easily peeled off.
Δ: It was somewhat difficult to peel off the multilayer release film.
X: It was difficult to peel off the multilayer release film.

(Compatibility with shape)
The opposing surfaces of the FPC and the overlay of the obtained FPC product were visually observed, and the conformability of the multilayer release film was evaluated based on the following criteria.
A: The overlay bite into the recesses of the FPC without gaps, and the number of FPC products having defects was less than 3% of the total.
○: The overlay bite into the recesses of the FPC without gaps, but there were 3 to 10% of the FPC products having defects.
X: The overlay did not sufficiently penetrate into the concave portion of the FPC, and a gap was generated.

(With or without air bubbles)
The space between the opposing surfaces of the FPC and the overlay of the obtained FPC product was visually observed, and the case where bubbles did not remain was evaluated as ◯, and the case where bubbles remained as x.

(FPC copper terminal contamination)
The copper terminal portion of the obtained FPC product was visually observed to determine the presence or absence of contamination.

(Adhesive penetration length)
The both ends of the overlay of the obtained FPC product were visually observed, the lengths of the adhesive leached from the both ends of the overlay of the FPC product were measured, and the total value of the lengths was taken as the evaluation value.

Claims (3)

A multilayer release film in which surface layers are laminated and integrated on both surfaces of an intermediate layer, and the intermediate layer has a melting point of 160 ° C. or higher, a weight average molecular weight of 240,000 to 650,000, and measured by a cross fractionation method. The resin elution amount is 45 to 60% by weight of the total polypropylene resin at 0 ° C. or higher and 10 ° C. or lower, and exceeds 10 to 10 ° C. and 15 to 22% by weight of the total polypropylene resin at 70 ° C. or lower and exceeds 70 ° C. In addition, 3 to 20% by weight of the total polypropylene resin at 95 ° C. or less, 50 to 100% by weight of the polypropylene resin that exceeds 95 ° C. and 10 to 35% by weight of the total polypropylene resin at 125 ° C. or less, and vinyl aromatic The surface layer has a melting point of 140 ° C. or higher and a weight average molecular weight. Multilayer release film, characterized by comprising the polypropylene resin is 40,000～650,000. The surface layer has a melting point of 160 ° C. or higher, a weight average molecular weight of 240,000 to 650,000, and a resin elution amount measured by a cross fractionation method of 0 ° C. or higher and 10 ° C. or lower and 0% by weight of all polypropylene resins. % Of the total polypropylene resin at 0 to 10 ° C. and 70 ° C. or less, 1 to 5% by weight of the total polypropylene resin at 70 ° C. and 95 ° C. or less, 95 ° C. to 125 ° C. or less 2. The multilayer release film according to claim 1, comprising a polypropylene resin that is 92 to 99% by weight of the total polypropylene resin. The surface layer has a melting point of 160 ° C. or higher, a weight average molecular weight of 240,000 to 650,000, and a resin elution amount measured by a cross fractionation method of 0 ° C. or higher and 10 ° C. or lower and 0% by weight of all polypropylene resins. % Of the total polypropylene resin at 0 to 10 ° C. and 70 ° C. or less, 1 to 5% by weight of the total polypropylene resin at 70 ° C. and 95 ° C. or less, 95 ° C. to 125 ° C. or less 2. The multilayer release film according to claim 1, comprising 75 to 95% by weight of polypropylene resin which is 92 to 99% by weight of the total polypropylene resin and 5 to 25% by weight of vinyl aromatic elastomer.