JP5180826B2 - Film and release film - Google Patents

Description

  The present invention provides a film excellent in heat resistance and releasability including a layer formed from a 4-methyl-1-pentene copolymer, and a film or sheet-like laminate by manufacturing by pressure molding. It is related with the release film used suitably. More specifically, when a coverlay, which is a protective layer, is bonded to a surface of a flexible printed circuit board (hereinafter also referred to as “FPC”) on which an electric circuit (copper foil) is formed by heating and pressing with an adhesive. It is related with the release film used suitably for.

When a laminate is produced by pressing a plurality of raw material films or sheets on a metal plate, etc., a release film is generally used to prevent adhesion between the metal plate and the obtained laminate. Used for. In addition, pressure molding is often accompanied by heating, and a release film is required to have high heat resistance and excellent release properties.

The release film is a release film for manufacturing a flexible printed circuit board (hereinafter also referred to as “FPC”), a release film for ACM materials used for aircraft parts, a release film for manufacturing a rigid printed circuit board, and a semiconductor encapsulation. It is used as a release film for materials, a release film for FRP molding, a release film for rubber sheet curing, a release film for special adhesive tape, and the like.

  In FPC, a substrate on which an electric circuit is formed and a cover lay are usually bonded with a thermosetting adhesive. In the case where an electrical circuit is formed only on one side of the substrate, the coverlay is provided only on one side of the substrate on which the electrical circuit is formed, and on both sides or multiple layers of the substrate. If it is, it is bonded to both sides of the substrate. And in the case of the adhesion | attachment, a board | substrate and the coverlay which apply | coated the thermosetting adhesive are normally pinched | interposed into a metal plate, and it heats and pressurizes. And in order to prevent adhesion | attachment with this coverlay and a metal plate, the release film for FPC manufacture is used between the metal plate and a coverlay.

  Conventionally, as release films for FPC production, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, fluoropolymer films such as polyvinyl fluoride, and polymethylpentene films have been used. ing.

  On the surface on which the electric circuit of the FPC is formed, the height of the printed part where the electric circuit is formed is different from that of the non-printed part where the electric circuit is not formed. Therefore, when covering with a film-like cover lay, there is a problem that a void is formed in the non-printed portion, and the electric circuit is oxidized by the residual air sealed in the void, and the life of the electric circuit is significantly reduced. .

  In the FPC, a terminal portion of an electric circuit is formed for electrical connection with other components, and the terminal portion is not covered with a coverlay but exposed. Then, the adhesive applied to the cover lay to cover other than the terminal part melts when bonded by heating and pressing, and often flows out to the terminal part of this electric circuit, and the adhesive coating layer is formed. There is a problem that it is formed and causes electrical connection failure. Also, since the conventional release film has a large coefficient of thermal expansion with respect to the substrate, cover lay and metal plate, when the cover lay is bonded by heating and pressing, the surface of the release film is wrinkled. Occur. Therefore, in the portion where the wrinkles are generated, there is a problem that a gap is generated between the electric circuit and the release film due to a follow-up failure of the release film. Further, since the wrinkles are transferred to the FPC, the FPC has a sufficiently satisfactory appearance. There is a problem that cannot be obtained.

Patent Documents 1 and 2 disclose release films aimed at solving the above problems. However, these release films have a satisfactory appearance because the effect of preventing wrinkles generated in the film is not always sufficient in the process of heating and pressurizing for bonding the coverlay to the electric circuit on the substrate surface. There is a problem that FPC cannot be obtained.
JP-A-2-175247 JP 2003-211602 A

The present invention is a film suitable for a release film, in particular, adhesion between a cover lay and a metal plate in a heating and pressing process for manufacturing an FPC, and prevents the adhesive from flowing out and adhering to other members. In addition, no gap is formed in the non-printed part, exposed parts such as the terminal part of the electric circuit are not contaminated by the melted out flow of the adhesive, and a film suitable for a release film that does not generate wrinkles is provided. It is to be.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention include a layer formed from a specific 4-methyl-1-pentene copolymer, and has a specific thickness structure and heat shrinkage rate. Has found that the above problems can be solved, and has completed the present invention.

That is, the present invention
[1] Structural units derived from 95.5% by mass to 99.5% by mass of 4-methyl-1-pentene and carbon other than 0.5% by mass to 4.5% by mass of 4-methyl-1-pentene It has at least one layer (A) formed from a 4-methyl-1-pentene copolymer having a structural unit derived from an olefin having 3 to 20 atoms, and the total thickness of the layer (A) is 40 μm to Provision of a film having a thickness of 90 μm and a thermal shrinkage ratio of the whole film of 1% to 5%.
[2] The provision of the film according to [1], which is a single-layer film of the layer (A).
[3] In addition to the layer (A), the layer further includes a layer (B) formed from a soft polyolefin having a Vicat softening temperature of 50 ° C. to 150 ° C. based on ASTM D1525, and at least one layer described above The provision of the film according to the above [1], wherein (A) is an outermost layer and is composed of multiple layers.
[4] It has a layer (B) formed from a soft polyolefin having a Vicat softening temperature of 50 ° C to 150 ° C based on ASTM D1525, and at least two layers (A), and the layer (A) The film according to [1], wherein the two layers are outermost layers on both sides of the film.
[5] The olefin having 3 to 20 carbon atoms other than 4-methyl-1-pentene is at least one selected from 1-octene, 1-decene, 1-tetradecene, and 1-octadecene. ] Provision of the film in any one of [3].
[6] In the above [3] or [4], the soft polyolefin is a polymer obtained by (co) polymerizing one or more olefins selected from ethylene, propylene, butene, pentene, hexene, and methylpentene. Provision of the described film.
[7] A soft polyolefin is a copolymer of ethylene and acrylic acid ester, a copolymer of ethylene and methacrylic acid ester, a copolymer of ethylene and acrylic acid, a copolymer of ethylene and methacrylic acid, and The provision of the film according to the above [3] or [4], which is a copolymer selected from those partially ionically crosslinked products.
[8] The film according to any one of [3] to [7], wherein the thickness of the entire layer (A) is 25% to 80% of the thickness of the entire film.
[9] The film according to any one of [2] to [8], wherein at least one of the film surfaces formed from the layer (A) is embossed.
[10] The film according to any one of [1] to [9] obtained by an extrusion molding method or a coextrusion molding method.
[11] To provide a release film obtained from the film according to any one of [1] to [10].

Since the film of the present invention comprising a layer formed from a specific 4-methyl-1-pentene copolymer and having a specific thickness configuration and heat shrinkage ratio is excellent in heat resistance and releasability, It can be suitably used as a release film. In particular, when used as a release film during the manufacture of FPC, when the substrate and the cover lay are bonded by heating and pressing, the adhesion between the metal plate and the cover lay, and the adhesive flows out to other members. In addition, no gap is formed in the non-printed portion during molding, and exposed portions such as the terminal portions of the electric circuit are not contaminated by the melted out flow of the adhesive.
Also, when the coverlay is bonded by heating and pressurization, the release film does not wrinkle, so there is no generation of voids due to poor tracking, and FPC with improved appearance defects due to wrinkle transfer is efficiently It can be molded and is extremely valuable industrially.

  Furthermore, the layer containing a specific soft polyolefin gives a good cushioning property for following the unevenness of the release film on the substrate surface on which the electric circuit is formed, and has little protrusion during heating and pressurization. It does not cause problems such as a decrease in product yield of FPC and a decrease in workability due to adhesion to a substrate surface on which a circuit is formed or a metal plate used for heating and pressing.

Sectional drawing of the film of this invention. Sectional drawing which shows an example of the state which shape | molds a flexible printed circuit board using the film of this invention. Sectional drawing which shows an example of the terminal exposure part of the flexible printed circuit board shape | molded using the film of this invention. The figure which shows an example of the manufacturing apparatus of the film of this invention.

[Explanation of symbols]
1 Layer formed from 4-methyl-1-pentene copolymer (A)
2 Layer formed from soft polyolefin (B)
3 Metal plate for heating and pressurization 4 Stainless steel plate 5 Release film (single layer)
6 Coverlay 7 Thermosetting adhesive 8 applied to coverlay Film of the present invention 9 Flexible printed circuit board 10 Copper foil of electric circuit 11 Electric circuit section 20 of flexible printed circuit board Extruder 21 Multi-manifold type three layers Co-extruded T-type die 22 Cooling roll 23 Heating roll 24 First embossing roll 25 Second embossing roll 26 First press roll 27 Second press roll

The film of the present invention has at least one layer (A) formed from a 4-methyl-1-pentene copolymer, the total thickness of the layer (A) is 40 μm to 90 μm, and the entire film It is a film having a heat shrinkage rate of 1% to 5%.

[4-Methyl-1-pentene copolymer]
The 4-methyl-1-pentene copolymer used in the present invention is a structural unit derived from 95.5% by mass to 99.5% by mass of 4-methyl-1-pentene and 0.5% by mass to It is a crystalline copolymer having a structural unit derived from an olefin having 3 to 20 carbon atoms other than 4.5% by mass of 4-methyl-1-pentene. Preferably, the structural unit derived from 4-methyl-1-pentene is 96 mass% to 99 mass%, and the structural unit derived from olefin having 3 to 20 carbon atoms other than 4-methyl-1-pentene is 1 mass% to 4 mass%. More preferably, the structural unit derived from 4-methyl-1-pentene is 97% by mass to 98% by mass, and the structural unit derived from olefin having 3 to 20 carbon atoms other than 4-methyl-1-pentene is 2% by mass to 3%. % By mass.

  When the film of the present invention is used as a release film for the production of FPC, if the structural unit derived from an olefin having 3 to 20 carbon atoms other than 4-methyl-1-pentene is not more than the above upper limit value, the release is performed. The film can be prevented from wrinkling, and if it is above the lower limit, the release film has good cushioning properties. Therefore, the release film follows the unevenness caused by the printed part and non-printed part of the electric circuit surface. Can be transformed.

  Examples of the olefin having 3 to 20 carbon atoms other than 4-methyl-1-pentene used in the present invention include propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-tetradecene, and 1- There may be mentioned at least one olefin selected from octadecene. Of these, 1-decene, 1-tetradecene and 1-octadecene are preferred because they have good copolymerizability with 4-methyl-1-pentene and provide good toughness.

  The 4-methyl-1-pentene copolymer used in the present invention has a melt flow rate based on ASTM D1238 (temperature 260 ° C., load 5.0 kg) of 0.5 g / 10 min to 200 g / 10 min, preferably Is 5 g / 10 min to 100 g / 10 min, more preferably 10 g / 10 min to 50 g / 10 min. If the melt flow rate is 200 g / 10 min or less, sufficient mechanical strength can be obtained. On the other hand, if the melt flow rate is 0.5 g / 10 min or more, good moldability can be obtained. To preferred.

  The melting point (Tm) measured by DSC of the 4-methyl-1-pentene copolymer used in the present invention is preferably in the range of 220 ° C to 240 ° C, and is in the range of 225 ° C to 240 ° C. Is more preferable. Further, the Vicat softening temperature obtained by measurement according to ASTM D1525 is preferably in the range of 160 ° C to 200 ° C, and more preferably in the range of 170 ° C to 200 ° C.

  The 4-methyl-1-pentene copolymer used in the present invention can be produced by a conventionally known method, and the polymerization catalyst and the polymerization method are not particularly limited.

  Examples of the catalyst include a Ziegler type catalyst (based on a combination of a supported or unsupported halogen-containing titanium compound and an aluminum compound), a Philips type catalyst (based on a supported chromium oxide), a Kaminsky type catalyst (supported or unsupported metallocene type). Compounds based on combinations of compounds and organoaluminum compounds, in particular alumoxanes).

  Examples of the polymerization method include a slurry polymerization method in the presence of the catalyst, a gas phase fluidized bed polymerization method, a solution polymerization method, or a high-pressure bulk polymerization method at a pressure of 20 MPa or more and a polymerization temperature of 100 ° C. or more.

  Specifically, as described in JP-A-59-206418, JP-A-61-113604, and JP-A-2003-105022, 4-methyl-1- The 4-methyl-1-pentene copolymer used in the present invention can be obtained by copolymerizing pentene and other olefins having 3 to 20 carbon atoms.

  The film of the present invention may be a single layer film of the above layer (A).

In addition to the layer (A), the film of the present invention further has a layer (B) formed from a soft polyolefin having a Vicat softening temperature of 50 ° C. to 150 ° C. based on ASTM D1525, and A multilayer film in which at least one layer (A) is the outermost layer may be used.
[Soft polyolefin]
The soft polyolefin imparts a softening property to the release film during heating and pressurization when the film of the present invention is used as a release film.

  Vicat softening temperature of soft polyolefin based on ASTM D1525 is 50 ° C to 150 ° C, preferably 60 ° C to 150 ° C, more preferably 70 ° C to 150 ° C, based on ASTM D1238 (load 5.0 kg, temperature 260 ° C) The melt flow rate is 0.5 g / 10 min to 200 g / 10 min, preferably 5 g / 10 min to 100 g / 10 min, and the melting point (Tm) measured by DSC is 80 ° C. to 240 ° C., preferably 100 ° C to 240 ° C.

  When using the multilayer film of this invention as a release film for FPC manufacture, the said soft polyolefin is used in order to provide what is called cushion property to a release film.

  Therefore, the flexible polyolefin improves the followability of the unevenness of the substrate surface on which the electric circuit is formed on the surface during FPC manufacture, and prevents the adhesive from flowing out from the end surface of the coverlay onto the electric circuit.

  Specific examples of the flexible polyolefin that satisfies the above conditions include a homopolymer or copolymer of one or more olefins selected from ethylene, propylene, butene, pentene, hexene, and methylpentene, and ethylene and an acrylate ester. Copolymer of ethylene and methacrylic acid ester, copolymer of ethylene and acrylic acid, copolymer of ethylene and methacrylic acid, and their partially ionic cross-linked products, a plurality of ethylene and acrylic Examples thereof include blends of acid or acrylate ester copolymers, and other examples include soft polyolefins disclosed in JP-A-2-175247. These may be used alone or in combination of two or more.

  Among these, for example, a propylene / butene-1 copolymer and an ethylene / ethyl acrylate copolymer can be particularly preferably used because they have appropriate flexibility and cushioning properties. These soft polyolefins can be used as a single layer, but can also be used as a multilayer of two or more layers.

These flexible polyolefins can be easily obtained from the market, and examples thereof include Mitsui Chemicals Co., Ltd., trade name: Tafmer XR, Mitsui DuPont Polychemical Co., Ltd., trade name: Evaflex, etc. .
[Film of the present invention]
The film of the present invention comprises a structural unit derived from 95.5% by mass to 99.5% by mass of 4-methyl-1-pentene and 0.5% by mass to 4.5% by mass of 4-methyl-1-pentene. And having at least one layer (A) formed from a 4-methyl-1-pentene copolymer having a structural unit derived from an olefin having 3 to 20 carbon atoms, and the total thickness of the layer (A) Is a film having a thermal shrinkage of 1% to 5%.

  The film of the present invention is characterized by having the layer (A). Therefore, the film of the present invention is a single-layer film composed only of the layer (A) or a multilayer film having at least one layer (A).

  When the multilayer film is used as a release film, the layer (A) is excellent in releasability, so that at least one layer (A) is preferably the outermost layer.

  If the layer (A) does not impair the object of the present invention, examples of the polymer other than 4-methyl-1-pentene copolymer include fluorine resins such as polytetrafluoroethylene, polyphenylene sulfide, and polyester. The layer (A) may contain 90% to 100% by mass of the 4-methyl-1-pentene copolymer, more preferably 95% to 100% by mass, and more preferably 100% by mass. % Is particularly preferable.

  When the multilayer film of the present invention is used as a release film for FPC production, particularly when there is a large undulation difference on the surface of the substrate having an electric circuit formed on the surface and a better cushioning property is required, a soft polyolefin is used. It is preferable that it is a multilayer film which has the layer (B) formed, and the said layer (B) may be a multilayer of two or more layers.

  The layer (B) is a polymer other than the soft polyolefin as long as the object of the present invention is not impaired, for example, polymethylpentene, polyethylene terephthalate (PET), polyester such as polybutylene terephthalate (PBT), Polyamide such as polyamide-6, polyamide-6,6, polyamide 11, polyamide 12 and the like may be included, but the layer (B) preferably contains 90% to 100% by mass of soft polyolefin, and 95% to 100% by mass. % Is more preferable, and 100% by mass is particularly preferable.

  The multilayer film of the present invention may have a layer (C) other than the layer (A) and the layer (B) as long as the object of the present invention is not impaired.

  The resin that can be used for the layer (C) is preferably a thermoplastic resin having high heat resistance. Examples thereof include polyolefins such as polypropylene, polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), and polyamides such as polyamide-6, polyamide-6,6, polyamide 11, and polyamide 12. These resins can be easily obtained from the market. For example, Prime Polymer Co., Ltd., Prime Polypro, manufactured by Mitsubishi Engineering Plastics Co., Ltd., trade name: Novapet, manufactured by Toray Industries, Inc., trade name: Amilan, and the like can be mentioned. These resins may be used alone or in combination of two or more.

  Specifically, as the multilayer film of the present invention, a laminate having a two-layer structure of layer (A) / layer (B) and layer (A) / layer (C), layer (A) / layer (B) / layer ( C), layer (A) / layer (C) / layer (A) and layer (A) / layer (B) / layer (A) three-layer structure.

  Since it eliminates the trouble of identifying the front and back when using as a release film, it has at least two layers (A), and the two layers (A) are the outermost layers on both sides of the film. It is preferable that the above layer (B) is included because good cushioning properties are obtained. In particular, a three-layer film of layer (A) / layer (B) / layer (A) is preferable.

  In the multilayer film of the present invention, the layer (A) acts as a release layer, and the layer (B) acts as a cushion layer. Moreover, since the layer (B) has an appropriate cushioning property, the cover lay is surely pushed into the non-printed part in the pressing process of FPC manufacturing, and there is no gap at all. FPC molding is achieved.

  In the film of the present invention, when the layer (A) is a single layer, the thickness of the layer (A) is preferably 40 μm to 90 μm, and more preferably 40 μm to 80 μm.

  Moreover, in the multilayer film of this invention, when the said layer (A) is two or more layers, it is preferable that the thickness of the said layer (A) whole is 40 micrometers-90 micrometers, and it is further more preferable that they are 40 micrometers-80 micrometers.

  When the layer (A) is the outermost layer on both sides, it is preferable that the thickness of these layers (A) is the same because the multilayer film does not warp, that is, does not bend in a bow.

  It is preferable for the thickness of the layer (A) to be not less than the above lower limit value because wrinkles can be prevented and the cushioning property can be maintained if it is not more than the above upper limit value.

  The layer (B) has a thickness of 30 to 100 μm, preferably 40 to 90 μm.

  Cushioning properties can be maintained when the thickness of the layer (B) is not less than the above lower limit value, and it is preferable that the thickness of the layer (B) is not more than the above upper limit value because the amount of protrusion of the layer (B) when heated and pressurized is reduced. preferable.

  In the multilayer film of the present invention, the ratio of the total thickness of the layer (A) to the total thickness of the film is 25% to 80%, preferably 30% to 60%, more preferably 30 to 50%. .

  In the case of a multilayer film including the layer (B), the generation of wrinkles can be prevented when the ratio of the total thickness of the layer (A) to the total film thickness is not less than the above lower limit, and not more than the upper limit. If there is, it is preferable because good cushioning properties can be obtained.

  The heat shrinkage ratio of the entire film of the present invention is 1% to 5%, preferably 1% to 3%, more preferably 1.5% to 2.5%. If the heat shrinkage rate is 1% or more, particularly when the film of the present invention is used as a release film for bonding a coverlay to an FPC, it is preferable that no wrinkles are generated on the film surface. Moreover, when the heat shrinkage rate is 5% or less, it is preferable that no gap occurs between the electric circuit surface and the release film when the coverlay is bonded.

  The thermal contraction rate in the film of the present invention is the ratio of the film contracted with respect to the length of the film before heating when the film of the present invention is heated and contracted. That is, the length L1 of the film measured at room temperature before heating and the length L2 corresponding to the L1 measured after 30 minutes after leaving at room temperature 170 ° C. for 30 minutes after cooling at room temperature. The value obtained by the following formula (1) is defined as the heat shrinkage rate.

Thermal contraction rate (%) = (L1−L2) / L1 × 100 (1)
(In the formula, L1: length of the film before heating; cm, L2: length of the portion corresponding to L1 after heating; cm)
The heat shrinkage rate of the film of the present invention is a value in the stretching direction of the film. That is, the length of the film when measuring the thermal shrinkage is the length in the direction parallel to the stretching direction of the film.

  For example, immediately after the film of the present invention is extrusion-molded or co-extrusion-molded, when it is continuously stretched using a stretching roll, it is the length in the MD direction, that is, the extrusion direction. The film of the present invention may be biaxially stretched, and the biaxial stretching may be sequential or simultaneous biaxial stretching. The thermal contraction rate in the case of biaxial stretching is a value in each stretching direction. The extrusion direction is a direction parallel to the die line generated on the film surface, and can be easily specified from the die line.

  In the film of the present invention, at least one of the film surfaces formed from the layer (A) is preferably embossed. The surface roughness Ry based on JIS B0601 of the film surface layer after the embossing treatment is 0.01 to 20 μm, preferably 0.1 to 10 μm, more preferably 0.1 to 5 μm, particularly preferably 0.1 μm to 2 μm. It is. When the surface roughness of the film surface layer is within the above range, good releasability can be obtained.

The film of the present invention preferably has an elastic modulus (E ′) at a temperature of 150 ° C. in the range of 1.5 × 10 ^{7 to} 8.5 × 10 ⁷ MPa. Here, the elastic modulus (E ′) at a temperature of 150 ° C. indicates a dynamic storage elastic modulus at a temperature of 150 ° C. in the stretching direction. Specifically, a sample having a length of 0.13 mm in the stretching direction and a thickness of 5 mm in the direction perpendicular to the stretching direction was cut out from the film of the present invention, and a dynamic storage modulus measuring device, for example, manufactured by TA (RSA-II). ) Is used to measure the elastic modulus (E ′) at a temperature of 150 ° C. by measuring at a temperature of −150 to 200 ° C., a rate of temperature increase: 3 ° C./min, a measurement mode; Can be sought.

When using the film of this invention as a release film for FPC manufacture, the temperature of the release film at the time of heating in order to adhere | attach a coverlay on FPC is close to 150 degreeC. Therefore, when the elastic modulus at a temperature of 150 ° C. is equal to or higher than the lower limit value, the release film can prevent wrinkles, and when the elastic modulus is equal to or lower than the upper limit value, the release film can obtain good cushioning properties. .
[Production Method of Film of the Present Invention]
The film of the present invention comprises a structural unit derived from 95.5% by mass to 99.5% by mass of 4-methyl-1-pentene and 0.5% by mass to 4.5% by mass of 4-methyl-1-pentene. And having at least one layer (A) formed from a 4-methyl-1-pentene copolymer having a structural unit derived from an olefin having 3 to 20 carbon atoms, and the total thickness of the layer (A) Is a film having a thermal shrinkage of 1% to 5%.

  The film of the present invention is formed by a known method such as laminating a single layer of each layer formed by extrusion molding using a T-die apparatus, co-extrusion molding, heating press or solvent casting, and then thermocompression bonding. Can be manufactured. In particular, the extrusion method or coextrusion method using a T-die device can control the thickness of each layer easily and uniformly by adjusting the distance between the die orifices of the die lip part, and widening the width. It is excellent in that it can be done. Furthermore, after manufacturing a wide film, it is easy to slit to a width that matches the width of a wide variety of FPCs. Therefore, an extrusion molding method using a T-die device or a coextrusion molding method is a mold release for FPC manufacturing. This is preferable as a film production method. Further, according to the coextrusion molding method, since the mixing in the molten state is often performed at the bonding interface between the resins, a laminated film having excellent adhesive strength can be obtained.

Specifically, when producing a single layer film consisting only of the layer (A), for example, using an extruder with a single layer T die, the temperature of the extruder and the T die is set to 260 to 330 ° C. Can be extruded.

Specifically, in the case of producing the three-layer film composed of layer (A) / layer (B) / layer (A), for example, using an extruder with two types of three-layer T-die, an extruder and a T-die Can be extruded at a temperature of 230 to 330 ° C.

  In addition, this multilayer film can be made into a multilayer film by integrating each layer with an adhesive, and an adhesive such as urethane, isocyanate, or epoxy is applied between each layer in a thin film, and if necessary, these layers are applied. It can be formed by pressure bonding.

  Alternatively, an adhesive resin such as maleic anhydride grafted polyethylene or maleic anhydride grafted polypropylene can be extruded and laminated simultaneously with each resin layer between the resin layers. Moreover, the method of hot-pressing or hot-rolling the preformed film or sheet in the order mentioned above is also employable.

  Moreover, when the film having a heat shrinkage rate of 1% to 5% according to the present invention is a single layer film, the film can be obtained by stretching the film after producing the single layer film of the layer (A). In addition, in the case of a multilayer film, it has a layer (B) formed from the soft polyolefin, and at least one of the layers (A) is an outermost layer, after manufacturing a multilayer film, It can be obtained by stretching a film composed of the multilayer.

  Moreover, as a stretching method, a conventionally known method can be appropriately employed, and stretching can be performed by a method such as a tenter method or a roll stretching method. For example, when a multilayer film composed of the layer (A) / layer (B) / layer (A) is stretched, the heating temperature at the time of stretching is set to 1% to 5% in the stretching direction. Is in the range of 50 ° C to 200 ° C, preferably 100 ° C to 150 ° C. Moreover, it is necessary to extend | stretch by a trace stretch ratio, and a stretch ratio is 1%-5% normally, Preferably it is 2%-4%. The stretching can be performed by uniaxial stretching or biaxial stretching, and the biaxial stretching may be performed sequentially or simultaneously.

  Specifically, the film of the present invention may be obtained by stretching a raw material film obtained by an extrusion molding method or a coextrusion molding method using a roll. When the raw material film obtained by the extrusion molding method or the coextrusion molding method is brought into contact with the surface of at least two or more independently rotating rolls having different peripheral speeds, the raw material film comes into contact first. The peripheral speed (m / min) of the roll with which the raw film comes into contact later is made faster than the peripheral speed (m / min) of the roll. That is, the film stretching method of the present invention is such that the peripheral speed of the roll is controlled so that the speed at which the raw material film passes through the roll surface that comes into contact later is faster than the speed at which the raw material film passes through the roll surface that comes in contact first. The film is stretched when the film passes between the two or more rolls.

  As the roll used for stretching, it is also possible to use a roll having a mirror surface or an embossing roll. In the case of an embossing roll, as the embossing depth, it is preferable to use a roll having an average roughness (Ra) of 1 μm to 200 μm, preferably 2 μm to 100 μm.

  Next, the case where the film which consists of the said layer (A) / layer (B) / layer (A) is manufactured is illustrated. In FIG. 4 showing an example of the film production apparatus of the present invention, the 4-methyl-1-pentene copolymer and the flexible polyolefin respectively melted by three extruders 20 are multi-manifold type three-layer coextrusion. It is extruded through a T-die 21 and once cooled to 50 ° C. to 150 ° C. by a cooling roll 22 to form a film. Next, the film is heated with a heating roll 23 having a temperature of 50 ° C. to 200 ° C., subsequently embossed with a first embossing roll 24 having a temperature of 50 ° C. to 200 ° C., and then with a second embossing roll 25, and the first embossing roll The peripheral speed of the second embossing roll is made faster than the peripheral speed of the second embossing roll, that is, the speed at which the film passes between the first pressing roll 26 and the first embossing roll 24 is increased. By increasing the speed of passing between the rolls 25, the film 8 of the present invention can be obtained by stretching the film between the first embossing roll and the second embossing roll.

  In order to obtain a film having a heat shrinkage rate of 1% to 5%, when the film is stretched, the peripheral speed of the roll that comes into contact with the film later is compared to the peripheral speed of the roll surface that comes into contact with the film first. Is preferably 1.01 to 1.05 times, more preferably 1.02 to 1.04 times. Moreover, the roll temperature in that case is 50 to 200 degreeC, Preferably it is the range of 100 to 150 degreeC. The peripheral speed of the roll surface that comes into contact with the film later, that is, the processing speed, is 5 m / min to 100 m / min, preferably 10 m / min to 70 m / min. Further, if the thermal shrinkage rate is within a range not less than 1%, an annealing treatment at a temperature lower than the melting point of the resin may be performed after the stretching treatment in order to prevent spontaneous shrinkage during storage of the release film.

  The film forming step and the film stretching step can be performed separately.

  When the film forming process and the stretching process are performed separately, the film may be stretched after being annealed at a temperature lower than the melting point of the resin in order to prevent spontaneous shrinkage of the film obtained by molding. good. As a matter of course, the film forming process and the stretching process can be performed continuously. Devices for carrying out such steps are generally commercially available.

[Release film]
The film of the present invention is excellent in heat resistance and releasability, and can be suitably used as a release film. Specifically, release films for FPC production, release films for ACM materials used for aircraft parts, release films for rigid printed circuit board production, release films for semiconductor sealing materials, release films for FRP molding, Examples include a release film for curing a rubber sheet and a release film for a special adhesive tape.

  Among these, the film of this invention can be used conveniently as a release film for FPC manufacture.

  In FPC manufacturing, there is a step of using a thermosetting adhesive to bond a substrate on which an electric circuit is formed and a coverlay layer by heating and pressing between metal plates. In this step, in order to avoid a situation where the coverlay layer and the metal plate are bonded when heated and pressed, the release film of the present invention is sandwiched between them.

  FIG. 1 is a cross-sectional view of the multilayer film of the present invention. Moreover, FIG. 2 is sectional drawing of the state at the time of the press at the time of shape | molding FPC using the release film of this invention. By using the release film of the present invention, the voids in the non-printed part are completely pressed and adhered by the coverlay and integrated. In FIG. 2, 8 is the film of the present invention, and 9 is the FPC.

  The release film of the present invention is deformed before the thermosetting adhesive applied by the coverlay at the time of press molding starts to flow by heating, and the cushioning property of the intermediate layer (B) and the outermost layer (A 3), the film 8 of the present invention, which is a release film, adheres closely to the end face of the cover lay 6 and the copper foil surface 10 of the electric circuit, as shown in FIG. The FPC can be molded in a state where the boundary between the exposed portion and the coverlay covering portion is clear without causing the agent to flow out.

  Furthermore, since the release film of the present invention is less likely to wrinkle in the release film during heating and pressure molding for bonding the coverlay, the release film is unevenly formed on the surface of the electric circuit at the wrinkled portion. There is no generation of voids due to poor tracking, and wrinkles are not transferred to the FPC, so that an FPC with an extremely good appearance can be obtained.

  Further, since there is little protrusion of the layer (B) at the time of heating and pressure forming for bonding the cover lay, the substrate surface on which the layer (B) forms an electric circuit, or a metal plate used for heating and pressure forming There are no problems such as a decrease in the product yield of the FPC and a decrease in workability due to adhering to the substrate.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.
[Measurement of resin]
(1) Measurement object Resin (4-methyl-1-pentene copolymer, soft polyolefin)
(2) Melt flow rate (MFR)
The MFR of the resin was measured at a load of 5.0 kg and a temperature of 260 ° C. according to ASTM D1238.

(3) Density The density of the resin was measured by a density gradient tube method according to ASTM D1505.

(4) Melting | fusing point Melting | fusing point of resin was measured with the DSC apparatus (made by Seiko Instruments).

  The DSC apparatus (manufactured by Seiko Instruments) was used, and the endothermic peak temperature based on melting when the temperature was raised at 10 ° C./min to 30 ° C. higher than the melting point of each resin in the air was defined as the melting point of the resin. Then, it hold | maintained at 30 degreeC temperature higher than melting | fusing point of each resin for 3 minutes, and then it cooled to room temperature at 10 degreeC / min.

(5) Vicat softening temperature The Vicat softening temperature of the resin was measured according to ASTM D1525 using a 1/6 inch thick plate of each resin obtained by injection molding.
[Film measurement]
(1) Heat Shrinkage For the production of the film, an extruder with a T die or a coextrusion machine was used. The set temperature of the extruder and the set temperature of the T die were 290 ° C. The width of the film obtained by extrusion molding is 600 mm. A film having a length of 30 cm in the extrusion direction (hereinafter referred to as the MD direction) and a length of 30 cm in the direction perpendicular to the MD direction (hereinafter referred to as the TD direction) was cut out from an arbitrary position of the film, and this was tested. It was. The length in the MD direction at room temperature of the test film before heating described below was defined as L1 (cm). The test film was heated in an air oven at a temperature of 170 ° C. for 30 minutes and then taken out and cooled at room temperature for 30 minutes. The length in the MD direction at room temperature of the test film after cooling was L2 (cm). The value obtained by the following formula (1) was defined as the heat shrinkage rate of the film.

Thermal contraction rate (%) = (L1−L2) / L1 × 100 (1)
(2) Appearance wrinkle For the production of the film, an extruder with a T die or a coextrusion machine was used. The set temperature of the extruder and the set temperature of the T die were 290 ° C. The width of the film obtained by extrusion molding is 600 mm. A total of 10 films having a length of 30 cm in the MD direction and a length of 21 cm in the TD direction were cut out every 5 m, and used as test films. This test film was set at a position 8 shown in FIG. 2 and subjected to heating and pressurizing steps. The process conditions were a temperature of 160 ° C., a pressure of 2 MPa, and a heating and pressing time of 30 minutes. An epoxy adhesive having a flow start temperature of 80 ° C. was applied to the coverlay with a thickness of 30 μm. A coverlay (thickness: 25 μm) made of a polyimide film was bonded to the electric circuit surface formed on the substrate. Thereafter, the test film was taken out, and the occurrence of wrinkles on the film was visually evaluated as follows.
When wrinkles are not confirmed on all 10 test films visually;
When wrinkles are visually confirmed on 1 to 4 of 10 test films;
When wrinkles are confirmed on 5 to 10 of 10 test films visually; ×
(3) Extrusion amount For production of the film, an extrusion molding machine with a T-die or a coextrusion molding machine was used. The set temperature of the extruder and the set temperature of the T die were 290 ° C. The width of the film obtained by extrusion molding is 600 mm. A total of four films having a length of 10 cm in the MD direction and a length of 10 cm in the TD direction were cut out from arbitrary positions of this film, and this was designated as test film [S1].

  Stainless steel plate (32 cm x 32 cm x thickness 5 mm) [A], 10 sheets of newspaper (30 cm x 30 cm) as cushioning material [B], aluminum plate (30 cm x 30 cm x thickness 0.1 mm) [C] did.

  As a specimen for measuring the amount of protrusion, the specimens stacked in the order of [A] / [B] / [C] / [S1] / [C] / [B] / [A] from the bottom were used. Here, the four test films [S1] stacked on [C] were arranged so as not to overlap each other.

Next, the specimen was heated and pressurized at a temperature of 180 ° C. and a pressure of 8 MPa for 10 minutes, then held at a pressure of 5 MPa, cooled to room temperature in 3 minutes, and four test films [S1] were taken out. The length of the layer (B) protruding from the end of the layer (A) of the four test films [S1] taken out was measured, and the maximum value was taken as the amount of protrusion.

(4) Surface roughness (Ry)
For the production of the film, an extruder with a T-die or a co-extrusion machine was used. The set temperature of the extruder and the set temperature of the T die were 290 ° C. The width of the film obtained by extrusion molding is 600 mm. From an arbitrary position of this film, a film having a length of 10 cm in the MD direction and a length of 10 cm in the TD direction was cut out and used as a test film. The surface roughness of the surface layer of the film was determined based on JIS B0601, with 5 cm as the reference length in any direction from the center of the test film.

(5) Elastic modulus (E ')
The elastic modulus (E ′) of the film was evaluated by measuring the dynamic storage elastic modulus at a temperature of 150 ° C. in the MD direction of the film.

  For the production of the film, an extruder with a T-die or a co-extrusion machine was used. The set temperature of the extruder and the set temperature of the T die were 290 ° C. The width of the film obtained by extrusion molding is 600 mm. From an arbitrary position of this film, a film having a length of 0.13 mm in the MD direction and a length of 5 mm in the TD direction was cut out and used as a test film. The dynamic storage elastic modulus at a temperature of 150 ° C. in the MD direction of the test film was measured by a dynamic storage elastic modulus measuring apparatus (TAA, RSA-II). The measurement conditions are a measurement temperature range; -150 ° C to 200 ° C, a rate of temperature increase: 3 ° C / minute, a measurement mode; a tension, a measurement frequency: 1 Hz. From the measurement results, the elastic modulus (E ′) of the film at a temperature of 150 ° C. was determined.

[Example 1]
For production of the film, a multi-manifold type three-layer coextrusion extruder with a T-die was used. (A1) 4-methyl-1-pentene copolymer (1-decene content; 2.4% by mass, MFR; 25 g / 10 minutes, melting point; 233 ° C.) in the first extruder and the third extruder Plasticization was performed at a temperature of 300 ° C. In addition, (B1) propylene / 1-butene copolymer (density: 0.89 g / cm ³ , MFR: 30 g / 10 min, melting point: 110 ° C., Vicat softening temperature: 78 ° C., containing 1-butene in the second extruder Amount; 20 mol%) was plasticized at a temperature of 300 ° C.

  The layer (A) / layer (B) / layer (A) was composited in a co-extruded T-type die with A1 as the layer (A) and B1 as the layer (B). Further, a multilayer film consisting of three layers was produced while taking this composite with a roll (20 m / min).

Next, the surface of the obtained multilayer film was embossed with two embossing rolls having an average roughness (Ra) of 25 μm. The roll temperature was 130 ° C. and the embossing speed was 20 m / min. The circumferential speed of the 2nd embossing roll which a multilayer film contacts later with respect to the circumferential speed of the 1st embossing roll which a multilayer film contacts previously was 1.03 times. By setting the ratio of both peripheral speeds to 1.03 times, with a configuration of A1 / B1 / A1 = 25/70/25 μm, the total thickness is 120 μm, and the elastic modulus (E ′) in the MD direction (stretching direction) is 5 × 10. A multilayer film with ⁷ MPa and a heat shrinkage of 2.1% was obtained.

  Next, the obtained multilayer film was set in the heating and pressurizing steps shown in FIG. 2, and the coverlay was adhered to the electric circuit surface formed on the substrate to prepare an FPC. The temperature was 160 ° C., the pressure was 2 MPa, and the heating and pressing time was 30 minutes. The cover lay is made of a polyimide film and has a thickness of 25 μm. In addition, an epoxy adhesive having a flow start temperature of 80 ° C. was applied to the coverlay with a thickness of 30 μm.

  In the prepared FPC, the coverlay and the substrate main body were completely adhered, and no remaining portion of air was observed.

  In addition, wrinkles were not generated in the multilayer film (three-layer film) used for adhesion of the coverlay by visual evaluation, and the appearance of the obtained flexible printed board was also good. The evaluation results are summarized in Table 1.

[Example 2]
Instead of B1, (B2) an ethylene / ethyl acrylate copolymer (MFR; 27 g / 10 min, melting point: 90 ° C., Vicat softening temperature; 70 ° C. and ethyl acrylate content; 15 mol%) was used. A multilayer film was produced in the same procedure as in Example 1 under the conditions shown in Table 1.

  Next, this multilayer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 1.

[Example 3]
(B3) propylene / 1-butene / 4-methyl-1-pentene copolymer (propylene content; 36 mol%, 1-butene content; 14 mol%, 4-methyl-1-pentene instead of B1) Content: 50 mol%, density 0.880 g / cm3, MFR: 27 g / 10 min, Vicat softening temperature: 80 ° C., 50% by mass, linear low density polyethylene (density; 0.92 g / cm3, MFR; Example 1 under the conditions shown in Table 1 except that a blend of 15 g / 10 min, Vicat softening temperature; 100 ° C. and 50% by mass ((MFR; 20 g / 10 min, Vicat softening temperature; 85 ° C.)) was used. A multilayer film was produced in the same procedure as described above.

  Next, this multilayer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 1.

[Example 4]
A multilayer film was produced in the same procedure as in Example 1 under the conditions shown in Table 1 except that the thickness of the layer (A) was changed to 20 μm by changing the extrusion amounts of the first extruder and the third extruder. .

  Next, this multilayer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 1.

[Example 5]
A multilayer film was produced in the same procedure as in Example 1 under the conditions shown in Table 1, except that the thickness of the layer (A) was changed to 35 μm by changing the extrusion amounts of the first extruder and the third extruder. .

  Next, this multilayer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 1.

[Example 6]
A single-layer film was produced in the same procedure as in Example 1 under the conditions shown in Table 1, except that the thickness of the layer (A) was 50 μm using only the first extruder.
Manufactured.

  Next, this single layer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 1.

[Example 7]
Instead of A1, (A2) 4-methyl-1-pentene copolymer (1-decene content; 1.0% by mass, MFR; 25 g / 10 min, melting point; 238 ° C.) was used. A multilayer film was produced in the same procedure as in Example 1 under the conditions shown in Table 1.

  Next, this multilayer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 1.

[Example 8]
Instead of A1, (A3) 4-methyl-1-pentene copolymer (1-decene content; 4.0% by mass, MFR; 27 g / 10 min, melting point; 229 ° C.) was used. A multilayer film was produced in the same procedure as in Example 1 under the conditions shown in Table 1.

  Next, this multilayer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 1.

[Example 9]
Instead of A1, (A4) A4: 4-methyl-1-pentene copolymer (1-tetradecene content; 2% by mass, MFR; 22 g / 10 min, melting point; 232 ° C.) was used. A multilayer film was produced in the same procedure as in Example 1 under the conditions shown in Table 1.

  Next, this multilayer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 1.

[Comparative Example 1]
A multilayer film was produced in the same procedure as in Example 1 under the conditions shown in Table 2, except that the thickness of the layer (A) was changed to 5 μm by changing the extrusion amounts of the first extruder and the third extruder. .

  Next, this multilayer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 2.

[Comparative Example 2]
A multilayer film was produced in the same procedure as in Example 1 under the conditions shown in Table 2 except that the thickness of the layer (A) was changed to 50 μm by changing the extrusion amounts of the first extruder and the third extruder. .

  Next, this multilayer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 2.

[Comparative Example 3]
Instead of A1, (A5) 4-methyl-1-pentene copolymer (1-decene content; 5.0% by mass, MFR; 24 g / 10 min, melting point; 226 ° C.) was used. A multilayer film was produced in the same procedure as in Example 1 under the conditions shown in Table 2.

  Next, this multilayer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 2.

[Comparative Example 4]
Instead of A1, (A5) 4-methyl-1-pentene copolymer (1-decene content; 5.0% by mass, MFR; 24 g / 10 minutes, melting point; 226 ° C.), and instead of B1 A multilayer film was produced in the same procedure as in Example 1 under the conditions shown in Table 2 except that B2 was used.

  Next, this multilayer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 2.

[Comparative Example 5]
Instead of A1, (A5) 4-methyl-1-pentene copolymer (1-decene content; 5.0% by mass, MFR; 24 g / 10 minutes, melting point; 226 ° C.), and instead of B1 A multilayer film was produced in the same procedure as in Example 1 under the conditions shown in Table 2 except that B3 was used.

  Next, this multilayer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 2.

[Comparative Example 6]
Instead of A1, (A6) 4-methyl-1-pentene copolymer (1-decene content; 0.2% by mass, MFR; 25 g / 10 min, melting point; 241 ° C.) was used. A multilayer film was produced in the same procedure as in Example 1 under the conditions shown in Table 2.

  Next, this multilayer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 2.

[Comparative Example 7]
Table 2 except that (A7) 4-methyl-1-pentene copolymer (1-decene content; 10% by mass, MFR; 22 g / 10 min, melting point; 221 ° C.) was used instead of A1. A multilayer film was produced by the same procedure as in Example 1 under the conditions shown in FIG.

  Next, this multilayer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 2.

[Comparative Example 8]
It shows in Table 2 except having used (A8) 4-methyl- 1-pentene type copolymer (ethylene content; 2 mass%, MFR; 26 g / 10min, melting | fusing point; 241 degreeC) instead of A1. A multilayer film was produced under the same conditions as in Example 1.

  Next, this multilayer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 2.

[Comparative Example 9]
An unstretched multilayer film was produced in the same manner as in Example 1 except that the peripheral speeds of the first embossing roll and the second embossing roll were the same.

  Next, the film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  As a result of visual evaluation, wrinkles were generated in the release film used for bonding the coverlay, and the wrinkles were transferred to the flexible print base, resulting in a flexible printed board having a problem in appearance. The evaluation results are shown in Table 2.

[Comparative Example 10]
A multilayer film was produced in the same manner as in Example 1 except that the second embossing roll peripheral speed was 1.15 times the peripheral speed of the first embossing roll and the film was stretched 15% in the MD direction.

  Next, this multilayer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The completed flexible printed circuit board had poor adhesion between the coverlay and the substrate body, and air-borne portions were generated. Moreover, the pattern resulting from the stretching unevenness was transferred to the flexible printed circuit board, and the appearance of the flexible printed circuit board was poor. The evaluation results are shown in Table 2.

[Comparative Example 11]
A single-layer film was produced in the same procedure as in Example 1 under the conditions shown in Table 2, except that the thickness of the layer (A) was 20 μm using only the first extruder.

  Next, this single layer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 2.

[Comparative Example 12]
A single layer film was produced in the same procedure as in Example 1 under the conditions shown in Table 2, except that the thickness of the layer (A) was 150 μm using only the first extruder.
Manufactured.

  Next, this single layer film was heated and pressed under the same conditions as in Example 1 to adhere the coverlay to the electric circuit surface formed on the substrate.

  The results evaluated in the same manner as in Example 1 are shown in Table 2.

  Since the film of the present invention comprising a layer formed from a specific 4-methyl-1-pentene copolymer and having a specific thickness configuration and heat shrinkage ratio is excellent in heat resistance and releasability, It can be suitably used as a release film. In particular, it can be used as a release film during the manufacture of FPC, preventing adhesion between the metal plate and the coverlay and preventing the adhesive from flowing out and adhering to other members, and non-printing during molding. No gap is formed in the portion, and exposed portions such as terminal portions of the electric circuit are not contaminated by the melted out flow of the adhesive.

  Since the release film does not wrinkle when the coverlay is bonded by heating and pressurization, the gap due to the follow-up failure of the release film to the unevenness of the substrate surface where the electric circuit is formed in the wrinkled part In addition, since an FPC having an improved appearance defect due to the transfer of wrinkles can be efficiently formed, it can be suitably used as a release film for FPC production.

  Furthermore, when a film having a layer containing a specific soft polyolefin is used as a release film during FPC production, the release film has good cushioning properties and can follow the unevenness of the FPC surface, There is little protrusion of the adhesive during heating and pressurization, which may cause problems such as a decrease in FPC product yield and workability due to adhesion of the adhesive to the metal plate used during heating and pressurization. Absent.

Claims (11)

Number of carbon atoms other than structural units derived from 95.5% to 99.5% by weight of 4-methyl-1-pentene and 0.5% to 4.5% by weight of 4-methyl-1-pentene It has at least one layer (A) formed from a 4-methyl-1-pentene copolymer having a structural unit derived from -20 olefins, and the total thickness of the layer (A) is 40 μm to 90 μm And the film whose heat shrinkage rate of the whole film is 1%-5%.   The film according to claim 1, which is a monolayer film of the layer (A). In addition to the layer (A), it further has a layer (B) formed from a soft polyolefin having a Vicat softening temperature of 50 ° C. to 150 ° C. based on ASTM D1525, and at least one layer (A) The film according to claim 1, wherein is an outermost layer. It has a layer (B) formed from a soft polyolefin having a Vicat softening temperature of 50 ° C. to 150 ° C. based on ASTM D1525, and at least two layers (A), and two layers of the layer (A) The film according to claim 1, wherein the film is a multi-layered film which is an outermost layer on both sides of the film.   The olefin having 3 to 20 carbon atoms other than 4-methyl-1-pentene is at least one selected from 1-octene, 1-decene, 1-tetradecene, and 1-octadecene. The film in any one.   The film according to claim 3 or 4, wherein the soft polyolefin is a polymer obtained by (co) polymerizing one or more olefins selected from ethylene, propylene, butene, pentene, hexene, and methylpentene.   Soft polyolefin is a copolymer of ethylene and acrylic acid ester, a copolymer of ethylene and methacrylic acid ester, a copolymer of ethylene and acrylic acid, a copolymer of ethylene and methacrylic acid, and parts thereof The film according to claim 3 or 4, which is a copolymer selected from ionic cross-linked products.   The film in any one of Claims 3-7 whose thickness of the said layer (A) whole is 25%-80% of the thickness of the whole film.   The film according to any one of claims 2 to 8, wherein at least one of the film surfaces formed from the layer (A) is embossed.   The film according to claim 1, which is obtained by an extrusion molding method or a coextrusion molding method.   A release film obtained from the film according to claim 1.

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