TW201922495A - Multilayer releasing film, method for producing multilayer releasing film, and method for producing flexible printed circuit - Google Patents

Abstract

The purpose of the present invention is to provide a multilayer releasing film which can be peeled after thermocompression bonding of a cover film and part of which can be recycled. Provided is a multilayer releasing film comprising a supporting layer, an intermediate layer, and a releasing layer, wherein: the supporting layer, the intermediate layer, and the releasing layer are stacked in this order; the supporting layer has a thickness of 75 [mu]m or more; and a measured value of adhesion between the supporting layer and the intermediate layer as obtained when the multilayer releasing film with a width of 50 mm is tested using a peeling strength tester under conditions of a peeling angle of 170 DEG and a peeling rate of 2.5 mm/sec is 5-25 g/50 mm.

Description

Multilayer release film, method for manufacturing multilayer release film, and method for manufacturing flexible printed circuit board

The present invention relates to a multilayer release film, a method for manufacturing a multilayer release film, and a method for manufacturing a flexible printed circuit board.

In order to protect the surface of the circuit pattern of the flexible printed circuit board, the circuit pattern is covered with a cover film by an adhesive. Generally, the cover film is covered, for example, by thermocompression bonding a composite film and a flexible printed circuit board. At this time, for example, in order to protect the cover film or remove air between the cover film adhesive and the substrate, a release film is used. As the release film, for example, TPX or PP film is used. In such a thermocompression bonding of a cover film, a multilayer release film having a buffer layer is required in order to absorb a step during thermocompression bonding. For example, Patent Documents 1 and 2 describe a release film having a multilayer structure formed by coextrusion.

"Existing Technology Literature"
Patent Document 1: Japanese Patent Gazette No. 5180826 Patent Document 2: Japanese Patent Gazette No. 5438367

After using such a release film, for example, deformation due to thermocompression bonding and step marks on the surface shape of the substrate, the used release film cannot be reused. Therefore, the used release film is usually discarded. However, there are problems in that the price of a release film becomes higher and higher due to the multilayered structure having a buffer layer and the high function for ensuring the mold release property. The object of the present invention is to solve such problems. That is, it is an object of the present invention to provide a multilayer release film which can be peeled off after thermocompression bonding of a cover film and a part of which can be reused, and a method for producing the multilayer release film. In addition, a method for manufacturing a flexible printed circuit board using such a multilayer release film, which has a high release property to the cover film and can suppress wrinkles and air from entering the cover film, is provided.

As a result of intensive studies, the present inventors have found that the above problems can be solved by the following contents. That is, the multilayer release film of this embodiment includes a support layer, an intermediate layer, and a release layer. The support layer, the intermediate layer, and the release layer are sequentially stacked, and the support layer has a thickness of 75 μm or more. The measured value of the adhesion between the support layer and the intermediate layer when the multilayer release film with a width of 50 mm was measured with a peel strength tester at a peel angle of 170 ° and a speed of 2.5 mm / sec was 5 to 25 g. / 50mm.

According to this embodiment, it is possible to provide a multilayer release film that can be peeled off after thermocompression bonding of a cover film and a part of which can be reused. In addition, it is possible to provide a method for manufacturing a flexible printed circuit board using such a multilayer release film, which has a high release property with respect to the cover film, and can suppress the occurrence of wrinkles and air from the cover film.

In the present invention, as long as there is no particular limitation, descriptions such as "more than X and less than Y" and "X to Y" that indicate a numerical range are ranges including the lower limit and the upper limit as the boundary points. In the multilayer film of the present invention, a support layer, an intermediate layer, and a release layer are sequentially laminated. In addition, the support layer has a thickness of 75 μm or more. In addition, the measured values of the adhesion between the support layer and the intermediate layer when the multilayer release film having a width of 50 mm was measured with a peel strength tester at a peel angle of 170 ° and a speed of 2.5 mm / sec were 5 to 5 25g / 50mm.

Using a peel strength tester, the measurement value of the adhesive force between the support layer and the intermediate layer when the multilayer release film of the present invention was measured at a peel angle of 170 ° and a speed of 2.5 mm / sec was 50 to 25 g / 50mm. The adhesion force is preferably 5 to 14 g / 50 mm. If the adhesive force is 25 g / 50 mm or less, the support layer and the intermediate layer are easily peeled off after the thermocompression bonding of the cover film. Therefore, it is advantageous for their reuse, especially for the reuse of the support layer. In addition, workability is not affected because peeling or the like during operation is less likely to occur. If the peeling force is less than 5 g / 50 mm, there is a problem that each layer is peeled off during the thermocompression bonding operation of the cover film.

In addition, the measured value of the adhesion between the release layer and the intermediate layer when the multilayer release film of the present invention at a width of 50 mm is measured using a peel strength tester under conditions of a peel angle of 170 ° and a speed of 2.5 mm / sec. It is 5 to 25 g / 50 mm, and more preferably 5 to 14 g / 50 mm. When the adhesive force is in the above range, the release layer and the intermediate layer are easily peeled after the thermocompression bonding of the cover film. Therefore, in addition to the reuse of the support layer, it is also beneficial to the reuse of the release layer and the intermediate layer. In addition, from the viewpoint of suppressing the occurrence of wrinkles in the cover film, it is preferable that the adhesion between the release layer and the intermediate layer is in the above range. The adhesive force can be obtained by, for example, the same method as described above.

Conventionally, considering the workability of a cover film at the time of thermocompression bonding, as a method for manufacturing a multilayer release film, forming by coextrusion or the like is usually performed so that each layer is not peeled during thermocompression bonding. In this case, each layer is thermally fusion-bonded and the adhesive force tends to be very high. Therefore, it is not easy to obtain the laminated body of the said adhesive force. As an example of the manufacturing method of the multilayer release film for obtaining the adhesive force of the said range, the thermal lamination method using a laminated support layer, an intermediate layer, and a release layer is mentioned. A preferred method for producing a multilayer release film will be described later. In addition, the adhesion force can be controlled by, for example, temperature and pressure during thermal lamination. A schematic diagram of a multilayer release film in which a support layer, an intermediate layer, and a release layer are laminated is shown in FIG. 1. In this embodiment, it is preferable that the support layer, the intermediate layer, and the release layer are not laminated with an adhesive. According to this structure, after thermocompression bonding of a cover film, each layer is easily peeled.

The adhesive force can be measured by the following method. Using a peel strength tester (PFT-50S, manufactured by PALMEC), a sample of a multilayer release film having a width of 50 mm and a length of 150 mm was cut at an angle of 170 ° and 2.5 mm / sec at room temperature (25 ° C). Peel off. Thereby, the adhesive force was measured. The sample was set so that it peeled from the 50 mm width side of the cut sample. In the measurement of the adhesion between the support layer and the intermediate layer, the intermediate layer side fixes and peels off the support layer. In the measurement of the adhesion between the release layer and the intermediate layer, the release layer was fixed and peeled off from the intermediate layer side. In Comparative Example 5 described later, it was peeled at a peel strength of 60 g / 50 mm. However, when a peeled sample was produced, the peeling at the interface could not be clearly and easily confirmed. Therefore, a peeling strength of 60 g / 50 mm or more is determined as a value that cannot be peeled.

In addition, in a lamination test in which a cover film was laminated on a substrate having a width of 250 mm, a length of 300 mm, and a step of 0.035 mm of a circuit pattern using a multilayer release film, the shape of the step derived from the substrate of the support layer was transferred. The depth of the unevenness is preferably less than 10% of the step of the substrate. On the other hand, the lower limit is not particularly limited. However, the depth of the unevenness is preferably 0% or more. In addition, the dimensional change rate in the width direction of the support layer before and after the lamination test is preferably less than 1%. On the other hand, the lower limit is not particularly limited. However, the depth of the unevenness is preferably 0% or more. From the viewpoint of the reuse of the support layer, it is preferable that the shape transfer ratio and the dimensional change rate are in the above-mentioned ranges. The shape transfer ratio and dimensional change rate can be controlled by the thickness of the support layer and the like.

The measurement methods of the shape transfer ratio and the dimensional change rate are as follows. On a substrate (made of polyimide) having a circuit pattern (copper foil) having a width of 250 mm, a length of 300 mm, and a step of 0.035 mm, a cover film (polyimide having a thickness of 12.5 μm coated with an epoxy-based adhesive material) membrane). Further, a multilayer release film of a measurement object was laminated thereon. By doing so, a laminate is obtained. The obtained laminated body was preheated by a laminating apparatus under a pressure of 10 MPa for 10 seconds. Next, the same device was used and the same pressure was applied at the temperature of the lower one of the melting point of the release layer and the melting point of the support layer to a temperature of -10 ° C. for 50 seconds to obtain a laminated body. In addition, the preheating temperature is the same as the temperature of heating and pressing. Subsequently, a laser microscope (LEXTOLS-4000, manufactured by Olympus Corporation) was used to measure the depth of the unevenness of the shape transfer from the stepped shape of the substrate of the support layer of the laminate. The ratio of the obtained measurement value to the step of the substrate is defined as the ratio (%) of the shape transfer. An average of the measurements at 10 points was used as the average. In addition, the length in the width direction of the support layer of the laminated body was measured with a ruler. In addition, the ratio of the amount of change in the length to the length in the width direction of the support layer before lamination (| length before lamination-length before lamination | / length before lamination x 100 (%)) is defined as the size Rate of change. An average of the measurements at 10 points was used as the average. In the examples described later, the ratio of shape transfer of less than 10% was determined to be ○｡, and the ratio of shape transfer of 10% or more was determined to be ×. In addition, a dimensional change rate of less than 1% was determined to be ○.

In a preferred embodiment, a plurality of layers (for example, 2 to 6 layers, preferably 2 to 4 layers) of an intermediate layer and a release layer are alternately laminated on the support layer. FIG. 2 is an example in which three layers of the intermediate layer 2 and the release layer 1 are alternately stacked on the support layer 3. In this way, after the thermocompression bonding of the cover film, the release layer and the intermediate layer on the surface are peeled off one by one, which can be reused. In this case, the materials of the plurality of release layers may be all the same or different from each other. The materials of the plurality of intermediate layers may all be the same or different from each other.

Next, each material will be described. First, the release layer will be described. In the multilayer release film, the release layer is in contact with the cover film. The release layer exhibits releasability from the cover film after thermocompression bonding of the cover film. The thickness of the release layer is preferably 25 to 50 μm, and more preferably 25 to 40 μm. When the thickness is 25 μm or more, it is possible to suppress the occurrence of wrinkles in the cover film during the thermocompression bonding of the cover film. The material of the release layer is not particularly limited. The following materials can be used.

Examples of the materials that can be used include polyethylene terephthalate, polybutylene terephthalate (PBT), polyethylene naphthalate, and polybutylene naphthalate. And other aromatic polyesters; polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymers, and fluorine resins such as polyfluoroethylene; polymethylpentene (TPX), polypropylene (PP) (including biaxial stretching Polypropylene (OPP), unstretched polypropylene (CPP)), and polyethylene (PE) (including high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE) ) And other olefin resins; polystyrene (PS); polyvinyl chloride (PVC). Among them, preferred are materials selected from polybutylene terephthalate (PBT), polymethylpentene (TPX), polypropylene (PP), and high-density polyethylene (HDPE). These materials can be used individually. Alternatively, a plurality of selected materials may be mixed and used.

The release layer is preferably a single layer. In addition, the release layer is preferably crystalline. Having crystallinity means that a clear melting point can be confirmed by differential scanning calorimetry. From the viewpoints of workability at the time of manufacturing the multilayer release film and appropriate release properties at the time of thermocompression bonding of the cover film, it is preferable that the melting point Tm1 of the release layer is sufficiently high so as not to melt during lamination. For example, the melting point Tm1 is equal to or higher than the temperature assumed as the temperature during lamination, and is preferably 130 ° C or higher, more preferably 150 ° C or higher, and even more preferably 180 ° C or higher. On the other hand, the upper limit is not particularly limited. For example, the melting point Tm1 is preferably 240 ° C or lower, more preferably 230 ° C or lower, and even more preferably 220 ° C or lower. In addition, the melting point Tm can be measured in accordance with JISK7121 using a differential scanning calorimetry (DSC) at a temperature rise rate of 10 ° C / min and a measurement temperature range of 25 to 250 ° C. The temperature at the top of the melting peak was defined as the melting point Tm.

The thickness of the intermediate layer is preferably 35 to 90 μm, and more preferably 40 to 80 μm. From the viewpoint of removing air between the substrate and the cover film, the thickness of the intermediate layer within the above range is preferred. The material of the intermediate layer is not particularly limited. For example, the following materials can be used. That is, for example, polypropylene (PP) (including biaxially oriented polypropylene (OPP), unstretched polypropylene (CPP)), polyethylene (PE) (including high-density polyethylene (HDPE), and low-density polypropylene Ethylene (LDPE), linear low density polyethylene (LLDPE)), polyvinyl chloride (PVC), or acrylic elastomer.

Among them, preferred are materials selected from polypropylene (PP), low density polyethylene (LDPE), and high density polyethylene (HDPE). These materials can be used alone. Alternatively, a plurality of selected materials may be mixed and used. The melting point Tm2 of the intermediate layer is, for example, a temperature that is assumed to be the temperature at the time of lamination, or lower, preferably 180 ° C or lower, more preferably 160 ° C or lower, and even more preferably 150 ° C or lower. The lower limit is not particularly limited. For example, the melting point Tm2 is preferably 100 ° C or higher, and more preferably 110 ° C or higher. In addition, from the viewpoint of exerting an appropriate adhesive force and good workability, the difference (Tm1-Tm2 (° C)) between the melting point Tm1 of the release layer and the melting point Tm2 of the intermediate layer is preferably 20 ° C or higher. The upper limit of the temperature difference is not particularly limited. However, it is preferable that the temperature difference is 120 ° C or lower.

The thickness of the support layer is 75 μm or more. As a result, it is possible to suppress a change in the shape of the support layer due to the thermocompression bonding of the cover film and the transfer of the unevenness from the step of the substrate. Therefore, it is advantageous for the reuse of the support layer. The thickness of the support layer is preferably 80 μm or more, and more preferably 90 μm or more. On the other hand, the upper limit is not particularly limited. For example, the thickness of the support layer is preferably 150 μm or less, and more preferably 125 μm or less. The material of the support layer is not particularly limited. For example, as the material of the support layer, the same material as the above-mentioned release layer can be used. In addition, for example, polyimide or glass cloth may be used. Polybutylene terephthalate (PBT) is a particularly preferred material. These materials can be used alone. Alternatively, a plurality of selected materials may be mixed and used. It is preferable that the melting point of the support layer is high enough to not melt during lamination. For example, the melting point of the support layer is equal to or higher than the temperature assumed as the temperature during lamination, preferably 130 ° C or higher, more preferably 150 ° C or higher, and even more preferably 180 ° C or higher. On the other hand, the upper limit is not particularly limited. However, the melting point of the support layer is preferably 300 ° C or lower, more preferably 270 ° C or lower, and even more preferably 250 ° C or lower.

Next, the manufacturing method of a multilayer release film is demonstrated. The manufacturing method of a multilayer release film is not specifically limited. For example, a known method can be used. From the viewpoint of achieving a specific adhesive force, a preferred manufacturing method is a thermal lamination method. A thermocompression bonded laminated structure was obtained by a thermal lamination method. That is, a preferred method for producing a multilayer release film includes a step of obtaining a laminate by sequentially laminating a support layer, an intermediate layer, and a release layer, and a step of thermally laminating the obtained laminate.

First, a support layer, an intermediate layer, and a release layer are laminated sequentially (preferably without passing through an adhesive) to form a laminate. It is preferable not to use an adhesive from the viewpoint of ease of peeling of each layer after the cover film is thermocompression bonded and easy reuse. At this time, as described above, a plurality of layers (for example, 2 to 6 layers, preferably 2 to 4 layers) of the intermediate layer and the release layer may be alternately laminated on the support layer.

Next, a multilayer release film can be obtained by thermally laminating the obtained laminate. For the thermal lamination, a known laminating apparatus can be used. The thermal lamination is preferably performed by a continuous conveyance operation called a so-called roll-to-roll method. The temperature at the time of thermal lamination can be appropriately set according to the material used. The temperature is not particularly limited. However, the temperature is preferably 100 to 180 ° C. The temperature at the time of thermal lamination is preferably a temperature that is equal to or higher than the melting point of the intermediate layer and the lower of the melting points of the release layer and the support layer. A more preferable temperature is a temperature of the intermediate layer + 10 ° C. or higher and the lower one of the melting points of the release layer and the support layer −10 ° C. or lower. If it is such a temperature, it can shape | mold so that not all layers may be melted and fusion-bonded, that is, only an intermediate layer may be melted. Therefore, it is easy to obtain a specific adhesive force. Therefore, in the selection of materials, among the melting points of the support layer, the intermediate layer, and the release layer, it is preferable that the intermediate layer has the lowest melting point. From the viewpoint of obtaining a suitable adhesive force, the pressure during thermal lamination is preferably 300 to 600 kPa. It is preferable that each layer is laminated with a roller thermal laminator having a conveyance speed of 0.5 m / min or more.

The multilayer release film obtained in this way can be suitably used for thermocompression bonding for lamination of printed wiring boards and the like. For example, it can be used as a release film when thermocompression bonding a flexible printed circuit board and a cover film. Can be used for various printed circuit boards such as single-sided flexible printed circuit boards or double-sided flexible printed circuit boards. The multilayer release film is preferably used in the following method for manufacturing a flexible printed circuit board.

The method for manufacturing a flexible printed circuit board of the present invention includes a step of sequentially laminating a substrate, a cover film, and a multilayer release film; and a step of thermocompression bonding the substrate and the cover film. The multilayer release film is a multilayer release film in which the support layer, the intermediate layer, and the release layer are sequentially laminated. In addition, the temperature of the thermocompression bonding is the melting point of the intermediate layer + 5 ° C or more and the melting point of the release layer-5 ° C or less.

If the temperature of the thermocompression bonding is the melting point of the intermediate layer + 5 ° C or more, the cushioning property of the intermediate layer works well. Therefore, it is possible to suppress air from entering between the substrate and the cover film. Therefore, good embedding can be performed. The temperature is preferably the melting point of the intermediate layer + 10 ° C or more. In addition, if the temperature of the thermocompression bonding is −5 ° C. or lower, the mold release property is good. The temperature is preferably -10 ° C or lower, which is the melting point of the release layer. The temperature of the thermocompression bonding is usually in the range of about 110 to 190 ° C. In the present embodiment, the temperature of the thermocompression and the temperature of the thermocompression bonding are set temperatures of the device to be used.

As the substrate, a substrate widely used can be used. For example, a substrate obtained by bonding a circuit pattern of a copper foil to a base film such as polyimide can be used. As the cover film, a generally widely used cover film can also be used. For example, polyimide or the like coated with an adhesive such as an epoxy-based adhesive can be used. For the thermocompression bonding of the cover film, a known device such as a laminating device can be used. When a laminating device is used, the pressure at the time of thermocompression bonding is preferably 8 to 12 MPa. In addition, it is preferable that after preheating at the same temperature as the lamination temperature for 5 to 30 seconds, pressurization is performed at the above-mentioned specific temperature for 40 to 180 seconds.

[Example]

Hereinafter, this embodiment will be specifically described with reference to examples. However, this embodiment is not limited to the following embodiments.

The devices and evaluation methods used in the examples are described below. The methods for evaluating the adhesion, shape transfer, and dimensional change rate are as described above. However, the lamination temperature at the time of shape transfer and dimensional change measurement in the examples is the lamination temperature described in Table 1.

<Laminating Device>

As the laminating apparatus, a flat-plate thermal laminating apparatus was used. With the laminating apparatus, the cover film and the substrate were laminated. The obtained laminate and multilayer release film are integrated by heating under pressure. The multilayer film and the laminate were laminated so that the release layer of the multilayer release film was in contact with the cover film including the laminate of the cover film and the substrate during pressure heating.

<Releasability>

On a substrate (polyimide product) having a circuit pattern (copper foil) having a width of 250 mm × a length of 300 mm and a step of 0.035 mm, a polyimide film having a thickness of 12.5 μm and containing an epoxy-based adhesive material was laminated. Cover film. In addition, a multilayer release film as a test object was laminated on the obtained laminate, and then laminated. The conditions of the laminating apparatus were: preheating at a pressure of 10 MPa for 10 seconds and heating and pressing for 50 seconds. Subsequently, it was judged whether the multilayer release film can be easily peeled from the cover film. A case where it could be easily peeled off was determined to be ○. On the other hand, a case where peeling was difficult was judged as ×. In each evaluation of the examples, the temperature of the heating and pressing during lamination of the cover film was set to the cover lamination temperature described in Table 1. The preheating temperature is set to the same temperature as the heating and pressing.

<Wrinkles of cover film>

On a substrate (polyimide product) having a circuit pattern (copper foil) having a width of 250 mm × a length of 300 mm and a step of 0.035 mm, a polyimide film having a thickness of 12.5 μm and containing an epoxy-based adhesive material was laminated. Cover film. In addition, a multilayer release film as a test object was laminated on the obtained laminate, and then laminated. The conditions of the laminating apparatus were: preheating at a pressure of 10 MPa for 10 seconds and heating and pressing for 50 seconds. Subsequently, the appearance was visually observed to determine the presence or absence of wrinkles in the cover film. It was judged as ○ when no wrinkles were found. When wrinkles were considered, it was judged as x. The temperature of heating and pressing during lamination was set to the lamination temperature described in Table 1. The preheating temperature is set to the same temperature as the heating and pressing.

<Buried (with or without air)>

On a substrate (polyimide product) having a circuit pattern (copper foil) having a width of 250 mm × a length of 300 mm and a step of 0.035 mm, a polyimide film having a thickness of 12.5 μm and containing an epoxy-based adhesive material was laminated. Cover film. In addition, a multilayer release film as a test object was laminated on the obtained laminate, and then laminated. The conditions of the laminating apparatus were: preheating at a pressure of 10 MPa for 10 seconds and heating and pressing for 50 seconds. Subsequently, the presence or absence of air ingress was determined by observing on the circuit pattern and between the circuit patterns with a microscope (8x magnification). The temperature of heating and pressing during lamination was set to the lamination temperature described in Table 1. The preheating temperature is set to the same temperature as the heating and pressing. If no air is considered to enter, it is judged as (circle). It is judged as Δ if it is considered that there is air in one place in the sheet. It is judged that X was obtained when two or more places of air entered the sheet.

(Example 1)

The following materials were used for each layer.
Support layer: Polybutylene terephthalate (PBT) with a thickness of 100 μm, solution mass flow rate (MFR) 4.3, melting point 220 ° C,
Interlayer: Low-density polyethylene (LDPE) with a thickness of 40 μm, MFR 1.0, melting point 110 ° C
Release layer: 25 μm thick polypropylene (PP), MFR 0.35, melting point 160 ° C

The support layer, the intermediate layer, and the release layer were laminated in this order and formed into a film using a roll heat laminator. Lamination was performed under conditions of a temperature of 170 ° C, a pressure of 500 kPa, and a conveyance speed of 1.0 m / min. Using the obtained multilayer release film, the aforementioned evaluation was performed. The results are shown in Table 1. No fusion bonding of the support layer was confirmed in Example 1. Therefore, the support layer can be peeled, and the dimensional change rate is sufficiently small. Therefore, the support layer can be reused. In addition, the solution mass flow rate (MFR) and melt volume flow rate (MVR) of plastics-thermoplastics were measured based on JISK7210: 1999 plastic-thermoplastic test methods. The unit of MFR is g / 10min.

(Examples 2 to 12, Comparative Examples 1 to 5, Reference Examples 1 to 4)

Except that the layers used and the film forming temperature during lamination were changed as shown in Table 1, Examples 2 to 12, Comparative Examples 1 to 5, and Reference Examples 1 to 12 were obtained by the same method and conditions as in Example 1. 4 multilayer release film. The evaluation results are shown in Table 1. In Examples 2 to 12, the support layer can be reused. In Comparative Example 1, the multilayer release film was peeled off during the laminating operation. Therefore, evaluation of the printed circuit board could not be performed. In Comparative Examples 2 and 3, since the dimensional change rate was large, the support layer could not be reused. In Comparative Examples 4 and 5, a commercially available release film described in Table 1 was used. These release films are films produced by extrusion molding. The release film has high adhesion. Therefore, each layer cannot be peeled.

Table 1

In the table, the numerical value described in the material column is the melting point Tm (° C).

In the table, the materials of each layer are as follows.

(Release layer)
Polybutylene terephthalate (PBT), MFR4.3, melting point 220 ° C
Polymethylpentene, Opulent X-88B manufactured by Mitsui Chemicals Toyo Cell Corporation
High density polyethylene (HDPE), MFR 0.35, melting point 130 ° C
Polypropylene (PP) with a thickness of 20 μm, polyolefin film made by Kitakoshi Kasei Co., Ltd. Polypropylene (PP) with a thickness of 40 μm, polyolefin film made by Kitakoshi Kasei Co., Ltd.

(middle layer)
Polypropylene (PP), a high-density polyethylene (HDPE) with a thickness of 40 μm, a polyolefin film manufactured by Kitakoshi Kasei Co., Ltd., MFR 0.35, melting point 130 ° C
High-density polyethylene (HDPE) with a thickness of 60 μm, MFR 0.35, melting point 130 ° C
Low-density polyethylene (LDPE) with a thickness of 80 μm, MFR 1.0, melting point 110 ° C

(Support layer)
40μm thickness PBT, MFR4.3, melting point 220 ℃
65μm thick PBT, MFR4.3, melting point 220 ℃
80μm thick PBT, MFR4.3, melting point 220 ℃
120μm thick PBT, MFR4.3, melting point 220 ℃

1‧‧‧ release layer

2‧‧‧ middle layer

3‧‧‧ support layer

FIG. 1 is a schematic diagram showing a layer structure of a multilayer release film.

FIG. 2 is a schematic diagram showing a layer structure of a multilayer release film.

Claims (12)

A multilayer release film includes a support layer, an intermediate layer, and a release layer. The multilayer release film is characterized in that the support layer, the intermediate layer, and the release layer are sequentially stacked, and the support layer Measurement of the adhesion between the support layer and the intermediate layer when the multilayer release film having a thickness of 75 μm or more was measured with a peel strength tester at a peel angle of 170 ° and a speed of 2.5 mm / sec at a thickness of 50 mm The value is 5 to 25g / 50mm. The multilayer release film according to claim 1, wherein the release layer and the release layer when the multilayer release film having a width of 50 mm is measured with a peel strength tester at a peel angle of 170 ° and a speed of 2.5 mm / sec are used. The measurement value of the adhesion of the intermediate layer is 5 to 25 g / 50 mm. The multilayer release film according to claim 1 or 2, further comprising a lamination test in which a cover film is laminated on a substrate having a width of 250 mm, a length of 300 mm, and a step of a circuit pattern of 0.035 mm using the multilayer release film. In the support layer, the depth of the unevenness of the shape transfer from the step of the substrate is less than 10% of the step of the substrate, and the depth of the support layer before and after the lamination test is The dimensional change rate in the width direction is less than 1%. The multilayer release film according to claim 1, wherein the release layer has a thickness of 25 to 50 μm. The multilayer release film according to claim 1, wherein the support layer, the intermediate layer, and the release layer are not laminated with an adhesive. The multilayer release film according to claim 1, wherein the release layer is a single layer, has a crystallinity, and has a melting point of 130 to 240 ° C. The multilayer release film according to claim 1, wherein the intermediate layer has a melting point of 100 to 180 ° C. The multilayer release film according to claim 1, wherein the intermediate layer has a thickness of 35 to 90 μm. The multilayer release film according to claim 1, wherein the multilayer release film is a multilayer release film for lamination of a printed circuit board. The multilayer release film according to claim 1, wherein a plurality of the intermediate layer and the release layer are alternately laminated on the support layer. A manufacturing method, characterized in that the manufacturing method is a method for manufacturing a multilayer release film according to any one of claims 1 to 10, and the manufacturing method includes: by supporting the support layer and the intermediate layer A step of sequentially stacking with the release layer to obtain a laminated body; and a step of thermally laminating the obtained laminated body. A method for manufacturing a flexible printed circuit board, characterized in that the method for manufacturing a flexible printed circuit board includes: a step of sequentially laminating a substrate, a cover film and a multilayer release film; and a step of thermocompression bonding the substrate and the cover film. The multilayer release film is the multilayer release film according to any one of claims 1 to 10, and the temperature of the thermocompression bonding is the melting point of the intermediate layer + 5 ° C or more and is the release layer. Melting point: -5 ° C or lower.