JP2008105319A - Multi-layer release film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-layer release film which has heat resistance to such an extent that the film does not generate creases by heat during thermal press molding, and can restrain the run-off of an adhesive during thermal press molding and the oozing of a cushioning layer from the edge face of the film while retaining releasability and follow-up properties to the surface of a substrate, and can suppress such a phenomenon that the cushioning layer oozing out of the film sticks to a press hotplate and is retained there, when the cushioning layer oozes out from the edge face of the film. <P>SOLUTION: The multi-layer release film has at least a release layer and the cushioning layer. The cushioning layer contains a polyolefin-based resin A with a melting point of 70 to 130°C measured by a differential scanning calorimeter and a polyolefin-based resin B with a melting point of 150 to 180°C measured by the differential scanning calorimeter. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a multilayer release film having heat resistance that does not cause wrinkles due to heat during hot press molding. Furthermore, while having releasability and followability to the substrate surface, it is possible to suppress the flow of the adhesive during hot press molding and the bleeding of the cushion layer at the film end surface. When the cushion layer oozes out, it relates to a multilayer release film in which the cushion layer oozed out from the film does not adhere and remain on the hot press plate.

In the manufacturing process of a printed 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. In order to prevent the hot plate and the press plate from adhering to each other, a release film is widely used.

Conventionally, as a release film, a fluorine-based film, a silicone-coated polyethylene terephthalate film, a polypropylene film, or the like as disclosed in Patent Document 1 or Patent Document 2 has been used.

However, although the fluorine-based film is excellent in heat resistance, releasability and non-contamination, it is expensive and has a problem that it is difficult to burn in waste incineration after use and generates toxic gas. there were.
In addition, the silicone-coated polyethylene terephthalate film may cause contamination of a printed wiring board, particularly a copper circuit, due to the migration of a low molecular weight substance contained in silicone, and may impair quality.
In addition, the polypropylene film has a problem that it has poor heat resistance and insufficient releasability.

In recent years, a multilayer release film composed of a release layer and a cushion layer as disclosed in Patent Document 3, for example, has been used for such a problem. Such a multilayer release film is said to have good heat resistance, release properties and followability.
In addition to heat resistance, releasability, and follow-up functions, it suppresses the flow of adhesive during hot press molding, and if the cushion layer oozes out from the film end face, the oozed cushion layer can be easily removed Release films that can be removed are also being used.

Furthermore, in recent years, with the miniaturization of electronic devices, flexible printed circuit boards and the like that have been made lighter and thinner have been demanded. Along with this, the coverlay used for flexible printed boards and the like has become the mainstream, and the press temperature has become higher.
In contrast to the current situation, when hot press molding is performed using the current (multilayer) release film, even a small wrinkle that has not been a problem in the past occurs in the (multilayer) release film. There has been a problem that wrinkles are transferred to the cover lay that has been made thin, and this makes the yield of the flexible printed circuit board worse.
Therefore, in addition to functions such as releasability and followability, there is currently a demand for heat resistance that does not cause any wrinkles due to heat during hot press molding.
JP-A-2-175247 Japanese Patent Laid-Open No. 5-283862 Japanese Patent Laid-Open No. 2003-246019

An object of this invention is to provide the multilayer release film which has the heat resistance which does not produce a wrinkle by the heat | fever at the time of hot press molding in view of the said present condition. Furthermore, while having releasability and followability to the substrate surface, it is possible to suppress the flow of the adhesive during hot press molding and the bleeding of the cushion layer at the film end surface. It is an object of the present invention to provide a multilayer release film in which when the cushion layer oozes out, the cushion layer oozing out from the film does not adhere to the press hot plate and remains.

The present invention is a multilayer release film having at least a release layer and a cushion layer, wherein the cushion layer has a melting point of 70 to 130 ° C. measured using a differential scanning calorimeter, and a differential resin. It is a multilayer release film containing polyolefin resin B having a melting point of 150 to 180 ° C. measured using a scanning calorimeter.
The present invention is described in detail below.

As a result of intensive studies, the present inventors have made use of a resin having a low melting point and a resin having a high melting point as a resin constituting the cushion layer in a multilayer release film having at least a release layer and a cushion layer. In addition to the effects required of conventional multilayer release films such as releasability and followability to the substrate surface, it is possible to obtain a multilayer release film having heat resistance that does not cause wrinkles due to heat during hot press molding The inventors have found that this is possible and have completed the present invention.

The multilayer release film of the present invention has at least a release layer and a cushion layer.
The cushion layer contains a polyolefin resin A having a melting point of 70 to 130 ° C. measured using a differential scanning calorimeter and a polyolefin resin B having a melting point of 150 to 180 ° C. measured using a differential scanning calorimeter. To do.
In the present invention, when the cushion layer contains the polyolefin resin A, the multilayer release film of the invention has followability to the substrate surface, and the cushion layer contains the polyolefin resin B. The multilayer release film of the present invention will not be wrinkled even by heat during hot press molding.

The minimum of melting | fusing point measured using the differential scanning calorimeter of the said polyolefin resin A is 70 degreeC, and an upper limit is 130 degreeC. If the temperature is lower than 70 ° C, the cushion layer oozes out from the film end face when the temperature of the storage place is high, and if it exceeds 130 ° C, the followability to the substrate surface is deteriorated, and also protected during hot press molding. The adhesive that bonds the circuit board to the coverlay easily flows out. A preferred lower limit is 80 ° C and a preferred upper limit is 120 ° C.
In addition, it does not specifically limit as said differential scanning calorimeter, For example, DSC 2920 (made by TA Instruments) etc. can be used.

The polyolefin resin A is not particularly limited, and examples thereof include a low density polyethylene resin, a linear low density polyethylene, a high density polyethylene, an ethylene copolymer, and a polypropylene resin. Among them, it is easy to obtain release film followability by melting at a certain low temperature, the adhesive that bonds the circuit board to be protected and the coverlay is difficult to flow out, and has high melt tension even at the time of melting. For this reason, a low-density polyethylene resin or an ethylene copolymer is preferably used for the reason that the cushion layer hardly oozes out.

Specific examples of commercially available low-density polyethylene resins include Novatec LD: LC720 (manufactured by Nippon Polyethylene, melting point 110 ° C.), Novatec LD: LF547 (manufactured by Nippon Polyethylene, melting point 114 ° C.), and the like. Is mentioned.
Examples of the ethylene copolymer include an ethylene-α-olefin copolymer, an ethylene-vinyl acetate copolymer, an ethylene-ethyl acrylate copolymer, and an ethylene methyl methacrylate copolymer. Examples of the α-olefin include propylene, 1-butene, 1-pentene and the like. These may be used independently and 2 or more types may be used together.
Moreover, as said polypropylene resin, a random type is especially preferable from a viewpoint of the followable | trackability requested | required of a cushion layer. Propylene-α-olefin copolymers and the like can also be used. As said alpha olefin, ethylene, 1-butene, 1-pentene etc. are mentioned, for example. These may be used independently and 2 or more types may be used together.

The minimum of melting | fusing point measured using the differential scanning calorimeter of the said polyolefin resin B is 150 degreeC, and an upper limit is 180 degreeC. If the temperature is less than 150 ° C, the heat resistance of the multilayer release film as a whole cannot be obtained sufficiently, wrinkles occur due to heat during hot press molding, and if it exceeds 180 ° C, the followability to the substrate surface becomes worse. Voids are likely to occur. In addition, the adhesive that bonds the circuit board to be protected and the coverlay easily flows out. A preferred upper limit is 170 ° C.

The polyolefin resin B is not particularly limited, and examples thereof include polypropylene. Specific examples of commercially available products include PF724S (manufactured by Sun Allomer, melting point 150 ° C.), PC412A (manufactured by Sun Allomer, melting point 158 ° C.), PC600S (manufactured by Sun Allomer, melting point 162 ° C.), PHA03A (Sun Allomer) Manufactured, melting point 164 ° C.) and the like.

Although it does not specifically limit as content of the said polyolefin-type resin A in the said cushion layer, A preferable minimum is 10 weight% and a preferable upper limit is 50 weight%. If it is less than 10% by weight, followability to the substrate surface may be deteriorated and voids may be generated. If it exceeds 50% by weight, the adhesive flows out during hot press molding or the cushion layer oozes out from the film end face. Sometimes. A more preferred lower limit is 20% by weight.

Although it does not specifically limit as content of the said polyolefin resin B in the said cushion layer, A preferable minimum is 10 weight% and a preferable upper limit is 50 weight%. If it is less than 10% by weight, the heat resistance of the multilayer release film as a whole cannot be obtained sufficiently, and wrinkles may occur due to heat during hot press molding. If it exceeds 50% by weight, The followability becomes poor and voids may occur. A more preferred lower limit is 20% by weight.

Moreover, it is preferable that the said cushion layer contains crystalline aromatic polyester resin whose melting | fusing point measured using the differential scanning calorimeter is 200 degreeC or more. Thereby, more heat resistance can be imparted to the multilayer release film of the present invention.
In addition, when the crystalline aromatic polyester resin is contained in the cushion layer, the content is 50% by weight or less so as not to lower the followability to the substrate surface of the obtained multilayer release film. It is preferable that

The crystalline aromatic polyester resin having a melting point of 200 ° C. or higher measured using the differential scanning calorimeter is not particularly limited. For example, polyethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polyethylene naphthalate, polybutylene. Naphthalate, butanediol terephthalate polytetramethylene glycol copolymer, and the like. These may be used independently and 2 or more types may be used together.
Among them, polybutylene terephthalate is preferably used because it is excellent in non-contamination and crystallinity. Examples of commercially available products include Novaduran 5010R5 (manufactured by Mitsubishi Engineering Plastics, melting point 224 ° C.) and the like. Is mentioned.

In the cushion layer, a preferable lower limit of the storage elastic modulus at 185 ° C., a strain amount of 100%, and 10 rad / s is 5.0 × 10 ³ Pa, and a preferable upper limit is 1.0 × 10 ⁵ Pa. If it is less than 5.0 × 10 ³ Pa, the cushion layer oozes out from the end face of the multilayer release film, and when the multilayer release film is peeled off from the press plate, it cannot aggregate with high strain caused by peeling. The cushion layer that breaks down and oozes out from the multilayer release film may adhere to the press hot plate and remain, and if it exceeds 1.0 × 10 ⁵ Pa, the formability of the cushion layer may deteriorate. A more preferable lower limit is 1.0 × 10 ⁴ Pa, and a more preferable upper limit is 8.0 × 10 ⁴ Pa.

Conventionally, in order to improve the followability to the substrate surface, the melt flow rate of the cushion layer has exceeded 0.3 g / 10 min. However, in the multilayer release film of the present invention, as described later. Combining a release layer with a thickness of 30 μm or less and a cushion layer allows the cushion layer to bleed out while maintaining sufficient followability even when the melt flow rate is 0.3 g / 10 min or less, which was impossible in the past. Can be suppressed.

Although it does not specifically limit as thickness of the said cushion layer, A preferable minimum is 30 micrometers and a preferable upper limit is 150 micrometers. When the thickness is less than 30 μm, the thickness is too thin, and when the resin constituting the cushion layer is softened during hot press molding, a portion where the cushion layer does not exist partially occurs, and the press pressure is uniformly applied to the flexible printed circuit board. May not be able to load. If it exceeds 150 μm, the stiffness of the multilayer release film becomes too strong and the flexibility is impaired, and the followability may be lowered. Furthermore, since it is thicker than necessary, the excess part may ooze out from the end face of the film, causing problems. A more preferable lower limit is 60 μm, and a more preferable upper limit is 100 μm.
The cushion layer may be used in combination with a commercially available release film.

In addition, the cushion layer is within a range that does not impair the effects of the present invention, and resins other than polyolefin resins such as polystyrene, polypropylene, polyvinyl chloride, polyamide, polycarbonate, polysulfone, and polyester, fibers, inorganic fillers, You may contain additives, such as a flame retardant, a ultraviolet absorber, an antistatic agent, an inorganic substance, and a higher fatty acid salt.

The fibers are not particularly limited, and examples thereof include glass fibers, carbon fibers, boron fibers, silicon carbide fibers, alumina fibers, amorphous fibers, inorganic fibers such as silicon / titanium / carbon fibers, and organic fibers such as aramid fibers. Can be mentioned.

The inorganic filler is not particularly limited, and examples thereof include calcium carbonate, titanium oxide, mica and talc.
The flame retardant is not particularly limited, and examples thereof include hexabromocyclododecane, tris- (2,3-dichloropropyl) phosphate, pentabromophenyl allyl ether, and the like.

The ultraviolet absorber is not particularly limited, and examples thereof include pt-butylphenyl salicylate, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2′-carboxybenzophenone, 2,4,5- And trihydroxybutyrophenone.
The antistatic agent is not particularly limited, and examples thereof include N, N-bis (hydroxyethyl) alkylamine, alkylallyl sulfonate, and alkyl sulfonate.

It does not specifically limit as said inorganic substance, For example, barium sulfate, an alumina, a silicon oxide etc. are mentioned.
The higher fatty acid salt is not particularly limited, and examples thereof include sodium stearate, barium stearate, and sodium palmitate.

In the present invention, the cushion layer having the above-described configuration allows the multilayer release film of the present invention to follow the substrate surface, has heat resistance that does not cause wrinkles due to heat during hot press molding, etc. Can be granted.

The multilayer release film of the present invention has a release layer.
The release layer is preferably made of a crystalline aromatic polyester resin having a melting point of 200 ° C. or higher measured using a differential scanning calorimeter.
Since the hot press molding process is usually performed at less than 200 ° C., if the melting point is less than 200 ° C., the release layer is melted and the heat resistance of the multilayer release film is lowered in the hot press molding process. There is. More preferably, it is 220 ° C. or higher. Moreover, although the preferable upper limit of melting | fusing point is not specifically limited, In the case of melt-molding, a more preferable upper limit is 400 degreeC from the reason of the cost of heating equipment.

By using such a resin having a high melting point for the release layer, the release layer has a release property without melting even in the hot press molding step, and the release layer is destroyed. Can be prevented.
In addition, it does not specifically limit as a crystalline aromatic polyester resin used for the said mold release layer, The thing similar to the crystalline aromatic polyester resin which can be used for the said cushion layer can be used.

The release layer may contain a stabilizer. The stabilizer is not particularly limited, and examples thereof include 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, 3,9-bis. {2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) -propionyloxy] -1,1-dimethylethyl} -2,4,8,10-tetraoxaspiro [5 5] hindered phenol antioxidants such as undecane; tris (2,4-di-t-butylphenyl) phosphite, trilauryl phosphite, 2-t-butyl-α- (3-t-butyl-4 -Hydroxyphenyl) -p-cumenylbis (p-nonylphenyl) phosphite, dimyristyl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, pentaerythryl Tetrakis (3-laurylthiopropionate), thermal stabilizers such as ditridecyl 3,3'-thiodipropionate and the like.

The release layer may contain a thermoplastic resin and a rubber component in order to modify its properties. The thermoplastic resin is not particularly limited, and examples thereof include polyolefin, modified polyolefin, polystyrene, polyvinyl chloride, polyamide, polycarbonate, polysulfone, and polyester.
The rubber component is not particularly limited. For example, natural rubber, styrene-butadiene copolymer, polybutadiene, polyisoprene, acrylonitrile-butadiene copolymer, ethylene-propylene copolymer (EPM, EPDM), polychloroprene, Examples include butyl rubber, acrylic rubber, silicon rubber, urethane rubber, olefin-based thermoplastic elastomer, styrene-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, ester-based thermoplastic elastomer, and amide-based thermoplastic elastomer.

The release layer may contain an inorganic compound having a large aspect ratio. By including an inorganic compound having a large aspect ratio, the resulting multilayer release film of the present invention has improved release properties at high temperatures, and additives and low molecular weight substances contained in the film bleed out to the film surface. That can be suppressed, and cleanliness during hot press molding is improved.
The inorganic compound having a large aspect ratio is not particularly limited, and examples thereof include layered silicates such as clay; layered double hydrates such as hydrotalcite.

Moreover, the said release layer may contain additives, such as a fiber, an inorganic filler, a flame retardant, an ultraviolet absorber, an antistatic agent, an inorganic substance, a higher fatty acid salt similarly to the said cushion layer.

Although it does not specifically limit as thickness of the said mold release layer, A preferable minimum is 5 micrometers and a preferable upper limit is 50 micrometers. If the thickness is less than 5 μm, the thickness is too thin and the strength of the release layer is impaired. Therefore, the release layer may be destroyed in the hot press molding step or the release step of the multilayer release film. If it exceeds, the stiffness of the multilayer release film becomes too strong and the flexibility is impaired, and the followability may be lowered.
Furthermore, in the present invention, by setting the thickness of the release layer to 30 μm or less, it is sufficient to combine the above-described cushion layer having a low melt flow rate of less than 0.3 g / 10 minutes and the release layer. It is possible to suppress the seepage of the cushion layer while maintaining the followability.

The surface of the release layer preferably has smoothness, but for the purpose of slipping necessary for handling, anti-blocking properties, and air release during hot press molding, at least one side has an appropriate embossed pattern and fine irregularities. May be provided.
The method of the treatment is not particularly limited, and examples thereof include a method of rubbing the surface of the release layer using a metal roll or the like having an embossed pattern, a cloth such as gauze, a brush, or the like.

The release layer may be subjected to heat treatment or friction treatment in order to improve heat resistance, dimensional stability, and release properties.
Although it does not specifically limit as the method of the said heat processing, For example, the method of passing between the rolls heated to the fixed process temperature, the heating with a heater, etc. are preferable.
The temperature of the heat treatment is not particularly limited as long as it is not lower than the glass transition temperature of the resin constituting the release layer and not higher than the melting point, but a preferable lower limit is 120 ° C. and a preferable upper limit is 200 ° C. When the temperature is lower than 120 ° C., the effect of improving the releasability by heat treatment may be hardly obtained. When the temperature exceeds 200 ° C., the release layer is likely to be deformed during the heat treatment and may not be manufactured. A more preferable lower limit is 170 ° C., and a more preferable upper limit is 190 ° C.

The friction treatment method is not particularly limited, and examples thereof include a method of rubbing the surface of the release layer using a cloth such as a metal roll or gauze, a brush, or the like.

Although it does not specifically limit as the whole thickness of the multilayer release film of this invention, A preferable minimum is 50 micrometers and a preferable upper limit is 200 micrometers. When it is less than 50 μm, the strength of the multilayer release film is insufficient, and when it exceeds 200 μm, flexibility is impaired and handling properties are deteriorated. In addition, the manufacturing cost increases.

The multilayer release film of the present invention preferably has a dimensional change rate of 1.5% or less when pressed at 170 ° C. with a load of 3 MPa for 60 minutes. If it exceeds 1.5%, the circuit pattern may be damaged during hot press molding. More preferably, it is 1.0% or less. Furthermore, it is preferable that the dimensional change rate in the width direction (hereinafter also referred to as TD) and the length direction (hereinafter also referred to as MD) of the film is in the same direction and in the same order. When the vertical and horizontal dimensional changes such that one (for example, MD) contracts and the other (for example, TD) expands are different, the circuit pattern may be damaged during hot press molding.

The method for producing the multilayer release film of the present invention is not particularly limited. For example, a water-cooled or air-cooled coextrusion inflation method, a method of forming a film by a coextrusion T-die method, and a film to be a release layer were produced. Thereafter, a method of laminating a cushion layer on this film by an extrusion laminating method, a method of dry lamination of a film to be a release layer and a film to be a cushion layer, a solvent casting method, a hot press molding method and the like can be mentioned. Especially, the method of forming into a film by the coextrusion T die method is suitable from the point which is excellent in the thickness control of each layer.

In the solvent casting method, for example, after the anchor layer is undercoated on the film to be the cushion layer, the resin composition dissolved in the solvent is applied on the anchor layer, and the coating film is uniformly heated and dried. A multilayer release film is produced by forming a release layer.
Moreover, in the said hot press molding, the film used as a mold release layer and the film used as a cushion layer are overlap | superposed and hot press molded, for example.

ADVANTAGE OF THE INVENTION According to this invention, the multilayer release film which has heat resistance which does not produce a wrinkle with the heat | fever at the time of hot press molding can be provided. Furthermore, while having releasability and followability to the substrate surface, it is possible to suppress the flow of the adhesive during hot press molding and the bleeding of the cushion layer at the film end surface. When the cushion layer oozes out, it is possible to provide a multilayer release film in which the cushion layer oozed from the film does not adhere to the press hot plate and remain.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(1) Resin material used for release layer Polybutylene terephthalate (manufactured by Mitsubishi Engineering Plastics, Novadejuran 5010R5) was used as the crystalline aromatic polyester resin for the release layer.

(2) Resin material used for cushion layer 1 For cushion layer 1, Novatec LD: LF547 (manufactured by Nippon Polyethylene Co., Ltd., melting point (DSC method) 114 ° C.) and PF724S (manufactured by Sun Allomer Co., melting point (DSC method)) 150 ° C.) at a weight ratio of 50:50 was used.
The DSC method in the melting point measurement means that DSC 2920 (manufactured by TA Instruments) was used as a differential scanning calorimeter. The same applies hereinafter.

(3) Resin material used for cushion layer 2 The cushion layer 2 includes Novatec LD: LF547 (polyolefin resin, manufactured by Nippon Polyethylene, melting point (DSC method) 114 ° C.) and PF724S (polyolefin resin, manufactured by Sun Allomer, Melting point (DSC method) 150 ° C.) and polybutylene terephthalate: Novaduran 5010R5 (Mitsubishi Engineering Plastics, melting point (DSC method) 224 ° C.) as crystalline aromatic polyester resin, respectively, 47.5: 47.5: 5 What was mixed by the weight ratio of 0.0 was used.

(4) Resin Material Used for Cushion Layer 3 For the cushion layer 3, Novatec LD: LC720 (manufactured by Nippon Polyethylene, melting point (DSC method) 110 ° C.) and Novatec HD: HF562 (manufactured by Nippon Polyethylene, melting point) are used as polyolefin resins. (DSC method) 132 ° C.) at a weight ratio of 50:50 was used.

(5) Resin material used for cushion layer 4 For the cushion layer 4, Novatec LD: LC720 (manufactured by Nippon Polyethylene Co., Ltd., melting point (DSC method) 110 ° C.) and PC630A (manufactured by Sun Allomer Co., Ltd., melting point (DSC method)) 142 ° C.) at a weight ratio of 50:50 was used.

(6) Resin material used for cushion layer 5 Cushion layer 5 includes Novatec LD: LC720 (polyolefin resin, manufactured by Nippon Polyethylene, melting point (DSC method) 110 ° C.) and UF840 (polyolefin resin, manufactured by Nippon Polyethylene). , Melting point (DSC method) 125 ° C.) and polybutylene terephthalate: Novaduran 5010R5 (manufactured by Mitsubishi Engineering Plastics, melting point (DSC method) 224 ° C.) as crystalline aromatic polyester resins, respectively, 47.5: 47.5: What was mixed by the weight ratio of 5.0 was used.

(Example 1)
(1) Production of multi-layer release film A resin material for a release layer and a resin material for a cushion layer 1 were prepared by using an extruder (GM Engineering Extruder GM30-28 (screw diameter 30 mm, L / D28). )) And melted, and co-extruded with a multilayer T die having a T die width of 400 mm to produce a multilayer release film. At that time, a two-layer release film was prepared so that the film thicknesses of the release layer and the cushion layer 1 were 20 μm and 80 μm, respectively, and cut into 200 mm × 200 mm.

(2) Production of flexible printed circuit board A laminate of copper-clad laminate cut to 150 mm x 150 mm, coverlay film cut to 150 mm x 150 mm, and multilayer release film obtained by cutting to 250 mm x 250 mm in this order As one set, 32 sets were placed on a hot press, subjected to hot press molding under conditions of a press temperature of 185 ° C., a press pressure of 35 kg / cm ² , and a press time of 30 minutes, then the press pressure was released, and a multilayer release film was formed. The flexible printed circuit board was obtained by peeling off.
The coverlay film was installed with the epoxy adhesive side on the copper clad laminate side, and the multilayer release film was installed with the release layer side on the coverlay film side.
As a copper-clad laminate, a 25 μm thick polyimide film (manufactured by DuPont, Kapton) is used as a base film, and after curing, an epoxy adhesive equivalent to 20 μm is applied to a copper foil having a thickness of 35 μm and a width of 50 μm. Used were bonded at intervals of 50 μm.
As the coverlay film, a film obtained by applying an epoxy adhesive having a flow start temperature of 80 ° C. to a thickness of 35 μm on a 25 μm-thick polyimide film (manufactured by DuPont, Kapton) was used.
Moreover, the hole for an adhesive flow-out was produced for the copper clad laminated board for evaluation.

(Example 2)
A multilayer release film was prepared by coextruding the resin material for the release layer and the resin material for the cushion layer 2 in the same manner as in Example 1.
A flexible printed circuit board was produced in the same manner as in Example 1 except that the obtained multilayer release film was used.

(Comparative Example 1)
A multilayer release film was prepared by co-extruding the resin material for the release layer and the resin material for the cushion layer 3 in the same manner as in Example 1.
A flexible printed circuit board was produced in the same manner as in Example 1 except that the obtained multilayer release film was used.

(Comparative Example 2)
A multilayer release film was produced by coextruding the resin material for the release layer and the resin material for the cushion layer 4 in the same manner as in Example 1.
A flexible printed circuit board was produced in the same manner as in Example 1 except that the obtained multilayer release film was used.

(Comparative Example 3)
A multilayer release film was prepared by coextruding the resin material for the release layer and the resin material for the cushion layer 5 in the same manner as in Example 1.
A flexible printed circuit board was produced in the same manner as in Example 1 except that the obtained multilayer release film was used.

<Evaluation>
The following evaluation was performed about the multilayer release film obtained in Examples 1-2 and Comparative Examples 1-3, and the flexible printed circuit board. The results are shown in Table 1.

(1) Wrinkle presence / absence CCL (Flexible board with copper foil, manufactured by Nikkan Kogyo Co., Ltd .: F-30VC1-25RC11 (H)) (20 cm × 20 cm, polyimide thickness 25 μm, copper foil 35 μm) Twenty parallel patterns of L / S 200 μm were formed at 30 mm. In addition, a 2 mm × 5 mm through hole was formed for evaluation of adhesive flow.
This CCL, coverlay (manufactured by Nikkan Kogyo Co., Ltd .: CISV-2535 (DF)) (20 cm × 20 cm, polyimide thickness 15 μm, epoxy resin adhesive layer 25 μm), and the obtained multilayer release film from the bottom in this order And placed between press dies preheated at 180 ° C. using a slide-type vacuum heater press (MKP-3000V-WH-ST, manufactured by Mikado Technos Co., Ltd.), and then the press was started (installation) To about 10 seconds from when the pressure was actually applied) to 50 kg / cm ² for 2 minutes.
Then, after taking out CCL, a coverlay, and a multilayer release film and peeling off a multilayer release film, the number of wrinkles transcribe | transferred on the coverlay surface was measured.

(2) Follow-up evaluation (presence / absence of voids)
Light was applied to the coverlay film surface of the obtained flexible printed circuit board, and the presence or absence of voids was confirmed visually (microscopic observation), and evaluated according to the following criteria.
○: No void was seen.
X: A void was observed.

(3) Adhesive flow-out amount The end portion of the adhesive flow-out hole of the obtained flexible printed circuit board was visually confirmed (microscopic observation) and evaluated according to the following criteria.
○: 100 μm or more Δ: 125 μm or more ×: 150 μm or more

(4) Exuding amount of film end face The length of resin exuding from the film end face during the production of the flexible printed circuit board was measured and evaluated according to the following criteria.
○: Less than 2 mm Δ: 2 mm or more and less than 5 mm x: 5 mm or more

ADVANTAGE OF THE INVENTION According to this invention, the multilayer release film which has heat resistance which does not produce a wrinkle with the heat | fever at the time of hot press molding can be provided. Furthermore, while having releasability and followability to the substrate surface, it is possible to suppress the flow of the adhesive during hot press molding and the bleeding of the cushion layer at the film end surface. When the cushion layer oozes out, it is possible to provide a multilayer release film in which the cushion layer oozed from the film does not adhere to the press hot plate and remain.

Claims (4)

A multilayer release film having at least a release layer and a cushion layer, wherein the cushion layer comprises a polyolefin resin A having a melting point of 70 to 130 ° C. measured using a differential scanning calorimeter, and a differential scanning calorimeter. A multilayer release film comprising a polyolefin resin B having a melting point of 150 to 180 ° C. measured using the same. 2. The multilayer separation according to claim 1, wherein at least one of the polyolefin resins A having a melting point of 70 to 130 ° C. measured using a differential scanning calorimeter is a low density polyethylene resin or an ethylene copolymer. Mold film. The multilayer release film according to claim 1 or 2, wherein at least one of the polyolefin resins B having a melting point of 150 to 180 ° C measured using a differential scanning calorimeter is polypropylene. Furthermore, a cushion layer contains crystalline aromatic polyester resin whose melting | fusing point measured using the differential scanning calorimeter is 200 degreeC or more, The multilayer release film of Claim 1, 2 or 3 characterized by the above-mentioned.