Release film

Abstract

The present invention provides a release film which, when the release film is peeled from a flexible printed circuit board, enables the release film to be peeled off quickly and excellently, and enables the molded article to be manufactured with excellent productivity. A release film according to the present invention has a release layer, said release film being characterized by containing a resin having a melting point of 180°C or higher, and, in the infrared absorption spectrum, when the absorbance at 2855 ± 7 cm-1 is defined as Xa, the absorbance at 2920 ± 7 cm-1 is defined as Xb, and the absorbance at 2960 ± 7 cm-1 is defined as Xc, satisfying the relationship Xc / Xb ≤ 1.6 and the relationship Xc / Xa ≤ 2.6.

Description

[Technical Field]

[0001] This invention relates to a release film. [Background technology]

[0002] For example, as shown in Patent Document 1, when forming a flexible printed circuit board, i.e., a laminate, by bonding a coverlay film to a flexible circuit board with exposed circuits via the adhesive layer provided by the coverlay film using a heat press, a release film is generally used.

[0003] After lamination of a coverlay film onto a flexible circuit board, it is required that the release film be easily peeled off the formed flexible printed circuit board with excellent release properties.

[0004] More specifically, when peeling the release film from a flexible printed circuit board, it is required that the release film exhibits excellent release properties from the flexible printed circuit board, thereby suppressing the occurrence of creases and breakage in the flexible printed circuit board.

[0005] However, conventional release films have not been adequately considered in terms of achieving excellent release properties, which can lead to transport problems such as creases and breakage of flexible printed circuit boards. Furthermore, the release properties between the adhesive layer of the coverlay film and the release film are not sufficiently guaranteed, resulting in defects where parts of the release film remain on the flexible circuit board. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2011-88351 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The object of the present invention is to provide a release film that can be quickly and efficiently peeled off a flexible printed circuit board, enabling the manufacture of molded products with excellent productivity. [Means for solving the problem]

[0008] The purpose of this is as follows: (1) This is achieved by the present invention as described above. (1) A release film comprising a first release layer, a cushion layer provided on one side of the first release layer, and a second release layer provided on the side of the cushion layer opposite to the first release layer, The first release layer is composed of a resin material consisting of polybutylene terephthalate and polybutylene terephthalate copolymer. The content of polybutylene terephthalate in the resin material is 0% by mass or more and 80% by mass or less. The content of the polybutylene terephthalate copolymer in the resin material is 20% by mass or more and 100% by mass or less. The average thickness T1 of the first release layer is 7 μm or more and 38 μm or less. The average thickness Tk of the cushion layer is 40 μm or more and 110 μm or less. The average thickness T2 of the second release layer is 7 μm or more and 38 μm or less. In the first release layer In the infrared absorption spectrum, 2855±7 cm⁻¹ -1 The absorbance at Xa is 2920±7cm². -1 Absorbance at Xb, 2960±7cm -1 When the absorbance at is Xc, The aforementioned Xa is 0.0548% or more and 0.20929% or less, the aforementioned Xb is 0.0623% or more and 0.184% or less, and the aforementioned Xc is 0.0705% or more and 0.0985% or less. A release film characterized by satisfying the relationship Xc / Xb ≤ 1.6 and Xc / Xa ≤ 2.6. [Effects of the Invention]

[0010] According to the present invention, the release layer contains a resin having a melting point of 180°C or higher, and has an infrared absorption spectrum of 2855±7cm². -1 The absorbance at Xa is 2920±7cm². -1 Absorbance at Xb, 2960±7cm -1 When the absorbance at point Xc is denoted as Xc, the relationship Xc / Xb ≤ 1.6 and Xc / Xa ≤ 2.6 are satisfied. Therefore, the release film can be peeled off quickly and efficiently, and molded products can be manufactured with excellent productivity. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a side view showing the main part of a roll-to-roll press machine used for manufacturing a flexible printed circuit board. [Figure 2] Figure 2 is a longitudinal sectional view showing each step in a method for manufacturing a flexible printed circuit board using the roll-to-roll press machine shown in Figure 1. [Figure 3] Figure 3 is a longitudinal sectional view showing a hot press step in a method for manufacturing a flexible printed circuit board using the roll-to-roll press machine shown in Figure 1. [Figure 4] Figure 4 is a longitudinal sectional view showing an embodiment of the release film of the present invention. [Figure 5] Figure 5 is a partially enlarged longitudinal sectional view of part A of the release film shown in Figure 4. [Figure 6] Figure 6 is a graph showing the infrared absorption spectrum of the first release layer (release layer) shown in Figure 4.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, the release film of the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

[0013] In the following, the case of manufacturing a flexible printed circuit board using the release film of the present invention by using a roll-to-roll press machine will be described as an example. Also, prior to describing the release film of the present invention, first, the roll-to-roll press machine used for manufacturing this flexible printed circuit board will be described.

[0014] <Roll-to-Roll Press Machine> Figure 1 is a side view showing the main part of a roll-to-roll press machine used in the manufacture of flexible printed circuit boards. Figure 2 is a longitudinal cross-sectional view showing each step in the manufacturing method of flexible printed circuit boards using the roll-to-roll press machine shown in Figure 1. Figure 3 is a longitudinal cross-sectional view showing the heating press step in the manufacturing method of flexible printed circuit boards using the roll-to-roll press machine shown in Figure 1. For the sake of explanation, in the following, the upper side in Figures 1 to 3 will be referred to as "up" or "upper," the lower side as "down" or "downward," the left side as "left," and the right side as "right."

[0015] As shown in Figures 1 to 3, the roll-to-roll press machine 100 (RtoR press machine) includes a transport means (not shown) for transporting release films 10 (10A, 10B), a flexible printed circuit board 200 (hereinafter sometimes referred to as "FPC"), and glass cloths 300A, 300B, a heating press means 50 for joining the flexible circuit board 210 and the coverlay film 220 (hereinafter sometimes referred to as "CL film") of the FPC 200 by heating and pressing the CL film 220 against the flexible circuit board 210 using the release film 10, and a release means 60 for releasing (peeling off) the release film 10 from the FPC 200 on which the CL film 220 has been joined to the flexible circuit board 210.

[0016] The conveying means conveys the FPC 200, release films 10A and 10B, and glass cloths 300A and 300B, each wound on different unwinding rollers, along their respective longitudinal directions by the rotation of tensioners (tension rollers), and after processing by the heating press means 50 and the release means 60, the winding rollers wind them.

[0017] Each roller is made of a metal material, such as stainless steel. Furthermore, the pivot axes (central axes) of these rollers are aligned in the same direction and are spaced apart from one another.

[0018] As shown in Figure 1, the heating press means 50 has a heating and pressing section 52. The heating and pressing section 52 has a pair of heating and pressing plates 521. The heating and pressing plates 521 are transported by a transport means and are positioned one above and one below the overlapping glass cloth 300A, release film 10A, FPC 200, release film 10B, and glass cloth 300B. As the overlapping glass cloth 300A, release film 10A, FPC 200, release film 10B, and glass cloth 300B pass between the heating and pressing plates 521, the heating and pressing plates 521 heat and pressurize the FPC 200 through the glass cloth 300A, 300B and the release film 10A, 10B. Therefore, as shown in Figure 2(a), the curing reaction of the adhesive layer 222 of the CL film 220 proceeds due to this heating, and in the FPC 200, the overlapping flexible circuit boards 210 and the CL film 220 are joined together via the adhesive layer 222.

[0019] In other words, the coverlay 221 and the flexible circuit board 210 are joined via the adhesive layer 222 (see Figure 2(a)). Furthermore, when the FPC 200 is heated and pressurized, that is, when the coverlay 221 and the flexible circuit board 210 are joined via the adhesive layer 222, the release film 10 is embedded in the recesses 223 formed in the coverlay 221. As a result, the leakage of adhesive originating from the adhesive layer 222 within the recesses 223 is suppressed (see Figure 2(b)).

[0020] Before being heat-pressed by the heat-pressure plate 521, the FPC 200 is in a laminated state with the flexible circuit board 210 and the CL film 220 stacked on top of each other, but the flexible circuit board 210 and the CL film 220 are not joined via the adhesive layer 222 of the CL film 220. Then, when pressed by the heat-pressure plate 521, the adhesive layer 222 of the CL film 220 adheres closely to the flexible circuit board 210, and in this state, the curing reaction of the adhesive layer 222 proceeds due to heating by the heat-pressure plate 521, so that the flexible circuit board 210 and the CL film 220 are joined via the adhesive layer 222.

[0021] As shown in Figure 1, the release mechanism 60 is positioned downstream of the heating press mechanism 50 in the transport direction. This release mechanism 60 is configured to separate the FPC 200 from the release films 10A and 10B. Here, in the heating and pressing section 52 of the heating press mechanism 50, as shown in Figure 2(b), the release film 10 is embedded in the recess 223 formed in the coverlay 221. As a result, the release film 10 is bonded to the CL film 220 (FPC 200), but the release mechanism 60 is configured to allow the release film 10 to be peeled (released) from the CL film 220 (FPC 200) (see Figure 2(c)). Therefore, based on the action of the release mechanism 60, the FPC 200, in which the flexible circuit board 210 and the CL film 220 are bonded via the adhesive layer 222, is obtained in a state where it is peeled from the release film 10.

[0022] The release means 60 may be configured to separate the release film 10 from the FPC 200 by sandwiching (inserting) a release member between the FPC 200 and the release film 10, or it may be configured to separate by installing a vacuum device on the outside and creating a vacuum, or it may be configured to separate by blowing air between the FPC 200 and the release film 10.

[0023] A flexible printed circuit board (FPC200) can be manufactured using the roll-to-roll press machine 100 described above. The manufacturing method for the FPC200 using this roll-to-roll press machine 100 will be described below.

[0024] In this embodiment, the manufacturing method of FPC200 includes, as shown in Figures 1 to 3, a first step of creating a laminate in which glass cloth 300A, release film 10A, FPC200, release film 10B, and glass cloth 300B, each in the form of a sheet, are stacked in this order; a second step of bonding the coverlay 221 (CL film 220) to the flexible circuit board 210 in the FPC200 via an adhesive layer 222 by heating and pressing the laminate; and a third step of releasing the release films 10 (10A, 10B) from the FPC200 to obtain an FPC200 in which the CL film 220 is bonded to the flexible circuit board 210.

[0025] The following explains each of these steps in order. (First step) First, the glass cloth 300A, release film 10A, FPC 200, release film 10B, and glass cloth 300B, each in sheet form and wound onto an unwinding roller, are stacked in this order during transport by the transport means to form a laminate (see release film placement process, Figures 1 and 2(a)).

[0026] The method of laminating each component (each layer) into the laminate is not particularly limited; for example, they may be laminated while being pressed with a roll, or while being pressed with a press. The order in which each component is laminated can also be arbitrary. For example, all components may be laminated simultaneously, or the coverlay film 220 and the flexible circuit board 210 may be laminated in advance, and then the other components may be laminated simultaneously.

[0027] Furthermore, the formation of the laminate in this first step constitutes a step of placing the release film 10 on the object (FPC200).

[0028] (Second step) Next, the laminate, in which the glass cloth 300A, release film 10A, FPC 200, release film 10B, and glass cloth 300B are stacked in this order, is heated and pressed (heated press) using the heating press means 50 (heated pressing unit 52). As the adhesive layer 222 adheres tightly to the flexible circuit board 210, the curing reaction of the adhesive layer 222 proceeds, and in the FPC 200, a bond is formed in which the coverlay 221 (CL film 220) is bonded to the flexible circuit board 210 via the adhesive layer 222 (heated press process, see Figures 1, 2(b), and 3).

[0029] Furthermore, as the release film 10A adheres closely to the coverlay 221 and is embedded in the recess 223 formed in the coverlay 221, the seepage of adhesive originating from the adhesive layer 222 within the recess 223 is suppressed.

[0030] In this second step (heating and pressing step), the temperature at which the FPC200 is heated is not particularly limited, but is preferably between 100°C and 250°C, and more preferably between 150°C and 200°C.

[0031] Furthermore, in the second step, when pressurizing the FPC200, the pressure set in the heating and crimping section 52 is not particularly limited, but is preferably set to 1 MPa or more and 14 MPa or less, and more preferably to 5 MPa or more and 14 MPa or less.

[0032] Furthermore, the transport speed for transporting the laminate is preferably set to 40 mm / sec or more and 400 mm / sec or less, and more preferably to 100 mm / sec or more and 350 mm / sec or less. In other words, in the second step (this step), the laminate is heated and pressed using the heating press means 50, and in the third step (next step), the adhesion time until the release film 10 is peeled off the bonded body is preferably set to 1.0 sec or more and 10.0 sec or less, and more preferably to 4.0 sec or more and 7.0 sec or less.

[0033] Furthermore, the second step involves applying a heat press to the object (FPC 200) on which the release film 10 is placed. In addition, if the coverlay 221 (molded product) is made of a material containing a semi-cured thermosetting resin, the coverlay 221 forms the surface of the object (FPC 200) on which the release film 10 is placed. The release film 10 is used on top of the surface of the coverlay 221 so that the surface on the side of the first release layer 1, which will be described later, is in contact with the surface of the coverlay 221. As a result, the release film 10 maintains the shape of the coverlay 221 with the recess 223 formed thereon, and the thermosetting resin can be cured, so that the coverlay 221 (molded product) can be molded on the flexible circuit board 210 with excellent precision. In addition, since the adhesion time is set within the range, the release film 10 maintains the shape of the coverlay 221 with the recess 223 formed thereon, and the curing reaction of the thermosetting resin constituting the coverlay 221 can proceed.

[0034] Furthermore, the method for manufacturing the molded product includes a first step of placing the release film 10 on the object (FPC 200) such that the first release layer 1 of the release film 10 faces the object (FPC 200), and a second step of performing a heat press on the object (FPC 200) on which the release film 10 is placed. In the step of placing the release film 10, the surface of the object (FPC 200) on which the release film 10 is placed is formed of a material containing a semi-cured thermosetting resin. As a result, the release film 10 maintains the shape of the coverlay 221 with the recesses 223 formed thereon, allowing the thermosetting resin to harden, and thus enabling the coverlay 221 (molded product) to be molded on the flexible circuit board 210 with excellent precision. In addition, since the adhesion time is set within the range, the release film 10 maintains the shape of the coverlay 221 with the recesses 223 formed thereon, allowing the curing reaction of the thermosetting resin constituting the coverlay 221 to proceed.

[0035] Furthermore, although this embodiment shows a means of heating by a heating press, it is not necessarily limited to this method, and heating may also be performed by infrared radiation or by a heating roll.

[0036] (Third step) Next, the release mechanism 60 releases the release films 10 (10A, 10B) from the FPC 200. That is, the release films 10A and 10B are peeled off from the bond between the coverlay film 220 and the flexible circuit board 210. This results in an FPC 200 with the CL film 220 bonded to the flexible circuit board 210 (peeling process, see Figures 1 and 2(c)).

[0037] Subsequently, the bonded assembly of the coverlay film 220 and the flexible circuit board 210, along with the glass cloth 300A, release film 10A, release film 10B, and glass cloth 300B, are wound up using their respective winding rollers.

[0038] This winding method allows the flexible circuit board 210 and the CL film 220 to be obtained continuously as the FPC 200, which is bonded via the adhesive layer 222 provided on the CL film 220, is wound onto the winding roller.

[0039] As described above, by applying the manufacturing method for flexible printed circuit boards 200 using a roll-to-roll press machine 100 with a release film 10, flexible printed circuit boards 200 can be manufactured continuously.

[0040] Furthermore, after the third step described above, the process may include a step in which the flexible printed circuit board 200, which is wound onto a winding roller, or the individual sheets obtained by cutting the wound flexible printed circuit board 200 into separate pieces, is heated in an oven or the like to further advance the curing reaction of the thermosetting resin constituting the coverlay 221, thereby curing the coverlay 221.

[0041] The release film of the present invention is applied to the release film 10 used in the manufacture of this flexible printed circuit board 200. The release film 10 to which the release film of the present invention is applied will be described below.

[0042] <Release film 10> Figure 4 is a longitudinal cross-sectional view showing an embodiment of the release film of the present invention, and Figure 5 is a partially enlarged longitudinal cross-sectional view showing a portion A of the release film shown in Figure 4.

[0043] As shown in Figure 4, in this embodiment, the release film 10 is composed of a laminate in which a first release layer 1 (release layer), a cushion layer 3, and a second release layer 2 are laminated in this order, and is used by overlapping it with the CL film 220 of the FPC 200 so that the surface on the side of the first release layer 1 is in contact with it.

[0044] The following describes each layer that makes up this release film 10. <Cushion layer 3> First, let's describe the cushion layer 3. As shown in Figures 4 and 5, this cushion layer 3 is positioned as an intermediate layer between the first release layer 1 and the second release layer 2.

[0045] This cushion layer 3 is made of a third thermoplastic resin composition, and this third thermoplastic resin composition preferably contains multiple types of thermoplastic resins in order to give the release film 10 conformability to the recesses 223.

[0046] Examples of combinations of multiple thermoplastic resins include combinations of polyester resins and polyolefin resins, combinations of polyolefin resins, and combinations of polyamide resins and polyolefin resins. Among these, selecting a combination of polyester resins and polyolefin resins allows for the above-mentioned effects to be achieved more reliably.

[0047] The polyester resin is not particularly limited, but examples include polyethylene terephthalate (PET), polycyclohexane terephthalate (PCT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polycyclohexanedimethylene terephthalate, and polypropylene terephthalate. One or more of these can be used in combination. When two or more of these are used in combination, the polyester resin may be a blend of these or a copolymer. Among these, polybutylene terephthalate is particularly preferred. This allows the cushion layer 3 to be given excellent conformability to the recesses 223. Furthermore, if the first release layer 1 contains polybutylene terephthalate, the cushion layer 3 can exhibit excellent adhesion to the first release layer 1.

[0048] Furthermore, the polyolefin resin is not particularly limited, and examples include polyethylene such as low-density polyethylene and high-density polyethylene, α-olefin polymers such as polypropylene, and α-olefin copolymers having ethylene, propylene, butene, pentene, hexene, octene, etc. as polymer components, such as copolymers of ethylene and hexene, copolymers of ethylene and octene, copolymers of α-olefin and (meth)acrylic acid ester, copolymers of ethylene and vinyl acetate, and copolymers of ethylene and (meth)acrylic acid. One or more of these can be used in combination. Among these, it is preferable that at least one of copolymers of ethylene and vinyl acetate (ethylene vinyl acetate copolymer) and copolymers of ethylene and (meth)acrylic acid (ethylene (meth)acrylic acid copolymer) be used. This makes it possible to impart excellent conformability to the recesses 223 to the cushion layer 3.

[0049] When a combination of polyester resin and polyolefin resin is used, the polyester resin content in this third thermoplastic resin composition is preferably 5% by weight or more, and more preferably 8% by weight or more and 40% by weight or less. This makes it possible to provide the release film 10 with excellent conformability to recesses 223.

[0050] Furthermore, the third thermoplastic resin composition constituting the cushion layer 3 may contain additives such as nucleating agents, antioxidants, slip agents, antiblocking agents, antistatic agents, colorants, and stabilizers, in addition to the resin material (thermoplastic resin) described above.

[0051] Furthermore, the storage modulus E' of the cushion layer 3 at 150°C is preferably 0.1 MPa or more, more preferably 0.5 MPa to 150 MPa, and even more preferably 1 MPa to 100 MPa. By setting the storage modulus E' of the cushion layer 3 at 150°C as described above, it is possible to effectively suppress or prevent a portion of the cushion layer 3 from protruding from the edge of the release film 10 and adhering to the FPC 200 when the release film 10 is embedded in the recess 223 in the second step. Therefore, contamination of the FPC 200 can be effectively suppressed or prevented. In addition, it becomes possible to easily peel off (remove) the release film 10 in the third step.

[0052] The storage modulus E' of the cushion layer 3 at 150°C can be obtained, for example, by preparing a cushion layer 3 with a width of 4 mm and a length of 20 mm in accordance with JIS K7244-4, and measuring it using a dynamic viscoelasticity measuring device (Hitachi High-Tech Science Corporation, "DMA7100") in tensile mode, with a frequency of 1 Hz and a heating rate of 5°C / min.

[0053] Furthermore, the average thickness Tk of this cushion layer 3 is preferably set to 40 μm or more and 110 μm or less, and more preferably to 50 μm or more and 90 μm or less. This provides the release film 10 with excellent cushioning properties.

[0054] <First release layer 1 (mold release layer)> Next, the first release layer 1 will be described. As shown in Figures 4 and 5, this first release layer 1 is laminated on one side of the cushion layer 3.

[0055] The first release layer 1 is flexible, and in the manufacturing method of the flexible printed circuit board 200 using the release film 10 described above, the release film 10 is superimposed on the CL film 220 of the FPC 200 so that the first release layer 1 is in contact with it. Then, in the second step of this manufacturing method, when the superimposed flexible circuit board 210 and CL film 220 are joined via the adhesive layer 222, the first release layer 1 is pressed in to conform to the shape of the recess 223 formed by the flexible circuit board 210 and CL film 220, and functions as a protective (cushioning) material that prevents the release film 10 from tearing. Furthermore, in the third step, the first release layer 1 functions as a contact layer to enable the release film 10 to exhibit excellent release properties from the CL film 220 (FPC 200).

[0056] Therefore, in the second step, the release film 10 can effectively suppress or prevent the adhesive derived from the adhesive layer 222 from seeping into the recesses 223 formed in the FPC 200. Furthermore, in the third step, after the formation of the FPC 200 in which the flexible circuit board 210 and the CL film 220 are joined via the adhesive layer 222 of the CL film 220, the release film 10 can be peeled off the FPC 200, thereby effectively suppressing or preventing stretching and breakage of the FPC 200. In addition, if the third thermoplastic resin composition constituting the cushion layer 3 contains a polyester resin, the first release layer 1 can exhibit excellent adhesion to the cushion layer 3.

[0057] Furthermore, the first release layer 1 is used in the manufacturing method of the flexible printed circuit board 200 to come into contact with the CL film 220 provided on the FPC 200. Therefore, in the second step of this manufacturing method, when the FPC 200 is heated and pressed, the first release layer 1 also has the function of transferring heat from the heating and pressing plate 521 to the CL film 220.

[0058] Here, in the conventional release film, there has been insufficient consideration regarding the exhibition of excellent releasability, and there was a possibility of conveyance failures such as the occurrence of folding wrinkles and breakage in the flexible printed circuit board. Also, the releasability between the adhesive layer provided in the coverlay film and the release film was not sufficiently ensured, and there was also a problem that a part of the release film remained on the flexible circuit board. Regarding such problems, as a result of intensive studies by the present inventor, it has been found that by adopting a configuration in which the first release layer 1 has the following characteristics, excellent releasability can be exhibited, and the present invention has been completed. This will be described below.

[0059] Characteristic: The first release layer 1 contains a resin having a melting point of 180°C or higher, and in the infrared absorption spectrum, the absorbance at 2855 ± 7 cm -1 is Xa, the absorbance at 2920 ± 7 cm -1 is Xb, and the absorbance at 2960 ± 7 cm -1 is Xc, when the relationship Xc / Xb ≤ 1.6 and the relationship Xc / Xa ≤ 2.6 are satisfied.

[0060] Thereby, the first release layer 1 can exhibit excellent releasability and can quickly and favorably peel off the release film. Therefore, molded products can be manufactured with excellent productivity.

[0061] The graph shown in FIG. 6 is a graph showing the infrared absorption spectrum of the first release layer 1 shown in FIG. 4, and more specifically, it is a graph showing a Fourier transform infrared (FTIR) spectrum. The graph shown in FIG. 6 has the vertical axis representing infrared reflectance (%R) and the horizontal axis representing the wave number. The FTIR spectrum has a peak Pa at 2855 ± 7 cm -1 and a peak Pb at 2920 ± 7 cm -1 and a peak at 2960 ± 7 cm -1It has a peak Pc. Absorbance X is calculated by X = log(I0 / I) (where %R = I / I0 × 100), where the maximum infrared absorptivity at peak Pc is absorbance Xc, the maximum infrared absorptivity at peak Pb is absorbance Xb, and the maximum infrared absorptivity at peak Pa is absorbance Xa.

[0062] Peak Pa is a peak originating from CH2 (CH2 symmetric stretching) among the materials constituting the first release layer 1, which will be described later. Peak Pb is a peak originating from CH3 (CH3 antisymmetric stretching) among the materials constituting the first release layer 1. Peak Pc is a peak originating from CH2 (CH2 antisymmetric stretching) among the materials constituting the first release layer 1.

[0063] The first release layer 1 contains a resin with a melting point of 180°C or higher, and its infrared absorption spectrum is 2855±7cm². -1 The absorbance at Xa is 2920±7cm². -1 Absorbance at Xb, 2960±7cm -1 When the absorbance at Xc is denoted as Xc, the relationship Xc / Xb ≤ 1.6 and Xc / Xa ≤ 2.6 are satisfied, allowing for excellent release properties and enabling the release film 10 to be peeled off quickly and efficiently. Therefore, molded products can be manufactured with excellent productivity.

[0064] If Xc / Xb > 1.6, sufficient release properties from the adhesive cannot be guaranteed, resulting in a decrease in yield, and thus the effects of the present invention cannot be fully realized.

[0065] Furthermore, if Xc / Xa > 2.6, sufficient release properties from the adhesive cannot be guaranteed, resulting in a decrease in yield, and thus the effects of the present invention cannot be fully realized.

[0066] Furthermore, if the melting point of the resin constituting the first release layer 1 is less than 180°C, the standard heating and pressing temperature (approximately 160°C to 180°C) is such that the first release layer 1 cannot be properly released, which is a disadvantage and prevents the full effect of the present invention from being realized.

[0067] The first release layer 1 only needs to satisfy Xc / Xb ≤ 1.6, but it is preferable that it satisfies 0 ≤ Xc / Xb ≤ 1.5, and more preferably that it satisfies 0 ≤ Xc / Xb ≤ 1.4. This allows the above effects to be exhibited more significantly.

[0068] Furthermore, the first release layer 1 only needs to satisfy Xc / Xa ≤ 2.6, but it is preferable that it satisfies 0 ≤ Xc / Xa ≤ 2.6, and more preferably that it satisfies 0 ≤ Xc / Xa ≤ 2.3. As a result, the first release layer 1 can exhibit better release properties.

[0069] Furthermore, it is preferable that the first release layer 1 contains a polyester resin. This makes it possible to more reliably satisfy the relationships Xc / Xb ≤ 1.6 and Xc / Xa ≤ 2.6.

[0070] In the present invention, the constituent material of the first release layer 1 is not limited to polyester resin, as long as it can satisfy the above-mentioned relationships Xc / Xb≦1.6 and Xc / Xa≦2.6, but it is preferable that it contains polybutylene terephthalate (first resin component) and a substituted product (second resin component) in which a portion of at least one of terephthalic acid and 1,4-butanediol constituting the polybutylene terephthalate is substituted with another monomer component. This makes the effects of the present invention more pronounced.

[0071] The following explanation will primarily focus on the case where the first release layer 1 is composed of a material containing polybutylene terephthalate (first resin component) and a substituted material (second resin component). The first and second resin components are not limited to those listed below.

[0072] <First resin component> The first release layer 1 contains polybutylene terephthalate (PBT) as the first resin component.

[0073] Polybutylene terephthalate is a polymer compound formed by the polymerization of terephthalic acid as a dicarboxylic acid and 1,4-butanediol as a diol component, with the introduction of an ester structure.

[0074] The first resin component is not limited to the above, and may include other polyester resins such as polyethylene terephthalate.

[0075] <Second resin component> The second resin component is a substituted product (polymer) in which at least one of terephthalic acid and 1,4-butanediol, which constitute polybutylene terephthalate, is substituted with another monomer component. In other words, the second resin component contains terephthalic acid as a dicarboxylic acid component and 1,4-butanediol as a diol component, as well as at least one of a dicarboxylic acid component other than terephthalic acid and a diol component other than 1,4-butanediol.

[0076] Examples of dicarboxylic acid components other than terephthalic acid include isophthalic acid and naphthalenedicarboxylic acid, and one or more of these can be selected and used in combination.

[0077] Examples of diol components other than 1,4-butanediol include 1,2-butanediol and 1,6-hexanediol, and one or more selected from these can be used in combination. This allows for a more pronounced effect of the present invention.

[0078] When the first release layer 1 contains a compound in which a portion of the terephthalic acid constituting polybutylene terephthalate is replaced with another dicarboxylic acid component as the second resin component (substituted product), it is preferable that the proportion of the other dicarboxylic acid component in the total dicarboxylic acid component constituting the substituted product is 2 mol% or more and 50 mol% or less. This makes the effects of the present invention more pronounced.

[0079] When the first release layer 1 contains a compound in which a portion of the 1,4-butanediol constituting polybutylene terephthalate is substituted with another diol component as the second resin component (substituted product), it is preferable that the proportion of the other diol component in the total diol components constituting the substituted product is 1 mol% or more and 20 mol% or less. This allows the effects of the present invention to be obtained more significantly.

[0080] The first release layer 1 may contain multiple types of resin components as the second resin component (substitute).

[0081] If the first release layer 1 is made of a material containing polybutylene terephthalate (first resin component) and a substitution agent (second resin component), the content of the substitution agent (second resin component) in the first release layer 1 is 20% of the resin composition constituting the first release layer 1. mass% The above 100 mass% Preferably, it is 25 mass% The above 100 mass% It is more preferable that the following 30 mass% The above 100 mass% The following is even more preferable. This allows the effects of the present invention to be obtained more significantly.

[0082] The first release layer 1 may contain other components in addition to the polybutylene terephthalate (first resin component) and the substituted material (second resin component) mentioned above. Examples of other components include resin materials other than the first and second resin components, as well as fillers such as inorganic particles and organic particles.

[0083] Inorganic particles are not particularly limited, but examples include aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, alumina, aluminum nitride, aluminum borate whiskers, boron nitride, crystalline silica, amorphous silica, antimony oxide, E glass, D glass, S glass, etc., and one or more of these can be used in combination.

[0084] Furthermore, while the organic particles are not particularly limited, examples include polystyrene particles, acrylic particles, polyimide particles, polyester particles, silicone particles, polypropylene particles, polyethylene particles, fluororesin particles, and core-shell particles, and one or more of these can be used in combination.

[0085] Furthermore, the inorganic and organic particles preferably have an average particle diameter of 3 μm or more and 20 μm or less, and more preferably 5 μm or more and 20 μm or less.

[0086] Furthermore, the first release layer 1 having such a configuration preferably has a storage modulus E' of 50 MPa or more at 150°C, more preferably 50 MPa to 1000 MPa, and even more preferably 50 MPa to 300 MPa. This ensures that the first release layer 1 is reliably given the functions of the first release layer 1 as described above.

[0087] The storage modulus E' of the first release layer 1 at 150°C can be obtained in accordance with JIS K7244-4 by preparing a first release layer 1 with a width of 4 mm and a length of 20 mm, and measuring it using a dynamic viscoelasticity measuring device (Hitachi High-Tech Science Corporation, "DMA7100") in tensile mode, with a frequency of 1 Hz and a heating rate of 5°C / min.

[0088] Furthermore, the average thickness T1 of the first release layer 1 is preferably set to 7 μm or more and 38 μm or less, and more preferably to 10 μm or more and 30 μm or less. As a result, the average thickness T1 of the first release layer 1 is set within an appropriate range, so that the first release layer 1 can be more reliably given the function of the first release layer 1 as described above.

[0089] Furthermore, the average thickness T1 of the first release layer 1 is the average of the measured values ​​obtained when the surface of the first release layer 1 opposite the cushion layer 3 has an uneven shape, specifically when the thickness is measured at the position including the convex portion and at the position including the concave portion.

[0090] <Second release layer 2> Next, we will explain the second release layer 2.

[0091] As shown in Figures 4 and 5, the release film 10 is laminated on the other side of the cushion layer 3, that is, on the side of the cushion layer 3 opposite to the first release layer 1, and has a second release layer 2 made of a second thermoplastic resin composition.

[0092] The second release layer 2 is flexible and, in the second step of the manufacturing method for the flexible printed circuit board 200, has the function of transferring force from the heating and pressing plate 521 to the cushion layer 3 when the stacked flexible circuit boards 210 and CL film 220 are joined via the adhesive layer 222. Furthermore, in the third step, the second release layer 2 has the function of providing excellent release properties between the glass cloths 300A and 300B and the release film 10. In addition, in the second step of this manufacturing method, the second release layer 2 also has the function of transferring heat from the heating and pressing plate 521 to the cushion layer 3 when the FPC 200 is heated and pressed.

[0093] The second release layer 2 is made of a second thermoplastic resin composition. Preferably, this second thermoplastic resin composition mainly contains a polyester resin. This ensures that the aforementioned functions are reliably imparted to the second release layer 2.

[0094] Furthermore, while the polyester resin is not particularly limited, for example, the same resins as those mentioned in the third thermoplastic resin composition described above can be used, and among them, polybutylene terephthalate (PBT) is particularly preferred. This makes the effects obtained by using the polyester resin more pronounced.

[0095] Furthermore, if the second thermoplastic resin composition is mainly composed of a polyester resin, it may also contain thermoplastic resins other than polyester resins. Examples of such thermoplastic resins include polyethylene, polypropylene, poly-methyl-pentene (a type of polyolefin resin), and syndiotactic polystyrene (a type of polystyrene resin). One or more of these can be used in combination.

[0096] Furthermore, the second thermoplastic resin composition may also contain at least one of inorganic particles and organic particles in addition to the thermoplastic resin described above.

[0097] The inorganic and organic particles are not particularly limited, but those similar to those described above can be used.

[0098] The second release layer 2 having such a configuration preferably has a storage modulus E' of 50 MPa or more at 150°C, and more preferably between 50 MPa and 1000 MPa. This ensures that the second release layer 2 is reliably given the functions described above.

[0099] Furthermore, the average thickness T2 of the second release layer 2 is preferably set to 7 μm or more and 38 μm or less, and more preferably to 10 μm or more and 30 μm or less. This makes it possible to more reliably impart the aforementioned functions to the second release layer 2.

[0100] Furthermore, the second thermoplastic resin composition constituting the second release layer 2 may contain additives similar to those listed for the third thermoplastic resin composition, in addition to the resin material, inorganic particles, and organic particles mentioned above.

[0101] Furthermore, the constituent materials of the first release layer 1 and the second release layer 2 may be the same or different, but from the viewpoint of substitutability, it is preferable that they be the same or of the same quality. In addition, the average thicknesses T1 and T2 of the first release layer 1 and the second release layer 2 may be the same or different.

[0102] In the release film 10 having the above-described structure in which the first release layer 1, cushion layer 3, and second release layer 2 are laminated, the average thickness Tt is preferably 50 μm or more and 180 μm or less, and more preferably 80 μm or more and 150 μm or less. By keeping it within this range, the cushioning properties of the release film 10 can be ensured.

[0103] In this embodiment, the release film 10 is composed of a laminate in which a first release layer 1, a cushion layer 3, and a second release layer 2 are stacked in this order. However, the present invention is not limited to this configuration, and may be composed of a laminate that includes, for example, an intermediate layer such as an adhesive layer, placed between the first release layer 1 and the cushion layer 3, and between the second release layer 2 and the cushion layer 3.

[0104] Furthermore, if the release film 10 can maintain excellent release properties between the glass cloths 300A and 300B and the release film 10 in the third step, the second release layer 2 that comes into contact with the glass cloths 300A and 300B may be omitted.

[0105] The release film of the present invention has been described above, but the present invention is not limited to these descriptions.

[0106] For example, in the above embodiment, the case in which the release film of the present invention is applied to a press molding method in which flexible printed circuit boards are stacked in one layer between heat-pressure plates was described. However, the number of stacked flexible printed circuit boards is not limited to one layer, but may be two or more layers.

[0107] Furthermore, although the release film of the present invention is intended to be applied when pressurizing a flexible printed circuit board placed between heat-sealing plates using a roll-to-roll press, it is not limited to this, and pressurizing the flexible printed circuit board can also be carried out, for example, by press molding, or even by vacuum pressure forming.

[0108] Furthermore, the first release layer 1 contains a resin with a melting point of 180°C or higher, and its infrared absorption spectrum is 2855±7cm². -1 The absorbance at Xa is 2920±7cm². -1 Absorbance at Xb, 2960±7cm -1 When the absorbance at Xc is denoted as Xc, a configuration satisfying the relationship Xc / Xb ≤ 1.6 and Xc / Xa ≤ 2.6 has been described. However, the present invention is not limited to this, and a configuration in which only the second release layer 2 satisfies the above conditions is also possible, or a configuration in which both the first release layer 1 and the second release layer 2 satisfy the above conditions is also possible. [Examples]

[0109] The present invention will be described in detail below based on examples, but the present invention is not limited thereto.

[0110] 1. Preparation of raw materials The following materials were prepared as raw materials for manufacturing the release film.

[0111] Low-density polyethylene (LDPE, manufactured by Ube Maruzen Polyethylene Co., Ltd., "R300") Ethylene vinyl acetate copolymer (EVA, manufactured by Mitsui Dow Polychemicals, "P1403") Polybutylene terephthalate (PBT, manufactured by Changchun Petrochemical Co., Ltd., "1100-630S", melting point: 224℃) Polybutylene terephthalate copolymer (manufactured by Mitsubishi Chemical Corporation, "5505S", melting point: 223℃) Polybutylene terephthalate copolymer (manufactured by Bell Polyester Products, "P02220", melting point: 207°C) Polybutylene terephthalate copolymer (manufactured by Mitsubishi Chemical Corporation, "GK320", melting point: 183℃) Polybutylene terephthalate copolymer (manufactured by Mitsubishi Chemical Corporation, "B1932N", melting point: 216℃) Polybutylene terephthalate copolymer (manufactured by Mitsubishi Chemical Corporation, "B1902N", melting point: 166℃)

[0112] 2. Manufacturing of release film <Example 1> First, a resin composition for the first release layer was prepared, consisting of 80 parts by weight of polybutylene terephthalate (PBT, 1100-630S), 10 parts by weight of polybutylene terephthalate copolymer (5505S), and 10 parts by weight of polybutylene terephthalate copolymer (P02220). A second thermoplastic resin composition was also prepared, consisting of 100 parts by weight of polybutylene terephthalate (PBT, 1100-630S). Furthermore, a third thermoplastic resin composition was prepared, consisting of 40 parts by weight of low-density polyethylene (LDPE, R300), 40 parts by weight of ethylene vinyl acetate copolymer (EVA, P1403), and 20 parts by weight of polybutylene terephthalate (PBT, 1100-630S).

[0113] Next, the first release layer 1 was obtained by forming the resin composition for the first release layer into a film using an extrusion T-die method.

[0114] Next, the first release layer 1 was sequentially subjected to an extrusion T-die method using the aforementioned second thermoplastic resin composition and third thermoplastic resin composition to form films, thereby forming a laminate in which the cushion layer 3 and the second release layer 2 were laminated in that order on the first release layer 1. Subsequently, this laminate was annealed at 80°C for 5 minutes to obtain the release film 10 of Example 1. The constituent materials and physical properties of the first release layer 1 are shown in Table 1.

[0115] In the obtained release film 10, the average thickness T1 of the first release layer 1 was 20 μm, the average thickness Tk of the cushion layer 3 was 80 μm, and the average thickness T2 of the second release layer 2 was 20 μm.

[0116] Furthermore, the infrared reflectance (%R) of the first release layer 1 was measured using a JASCO "FT / IR-4100" with a diamond prism, ATR method, 20 cumulative measurements, and a range of 4000-400 cm. -1 The measurements were taken using the following method. The absorbances Xc, Xb, and Xa were calculated using the formula for infrared reflectance %R = I / I0 × 100. The absorbances and wavenumbers of each peak are shown in Table 1.

[0117] Specifically, 2854.3cm -1 The absorbance Xa at 2925.48 cm² is 0.0596%. -1 The absorbance Xb at 2960.2 cm⁻¹ is 0.0841. -1 The absorbance Xc was 0.092. Furthermore, Xc / Xb was 1.09 and Xc / Xa was 1.54. Thus, the first release layer 1 according to Example 1 satisfies both relationships: Xc / Xb ≤ 1.6 and Xc / Xa ≤ 2.6.

[0118] <Examples 2-9, Comparative Example 1> Release films 10 for Examples 2-9 and Comparative Example 1 were obtained in the same manner as in Example 1, except that the blending ratios of polybutylene terephthalate (PBT, 1100-630S), polybutylene terephthalate copolymer (5505S), and polybutylene terephthalate copolymer (P02220) were changed as shown in Table 1.

[0119] The absorbances Xc, Xb, Xa, and the wavenumbers of each peak are shown in Table 1. Examples 2-9 satisfy the relationships Xc / Xa ≤ 2.6 and Xc / Xb ≤ 1.6, while Comparative Example 1 does not satisfy either relationship. Furthermore, the melting point of the first release layer 1 was 180°C or higher in all examples 2-9 and Comparative Example 1.

[0120] <Examples 10, 11> Release films 10 for Examples 10 and 11 were obtained in the same manner as in Example 1, except that polybutylene terephthalate (GK320) and polybutylene terephthalate copolymer (B1932N) were used as the resin composition for the first release layer, in the proportions shown in Table 1. The absorbances Xc, Xb, Xa and the wavenumbers of each peak are as shown in Table 1, and in Examples 10 and 11, the relationships Xc / Xa ≤ 2.6 and Xc / Xb ≤ 1.6 were satisfied. In addition, the melting point of the first release layer 1 was 180°C or higher in both Examples 10 and 11.

[0121] 3. Evaluation The release film 10 of each example and comparative example was evaluated as follows.

[0122] 3-1. Release properties of release film 1 For each example and comparative example, the release film 10 was set to have a width of 270 mm. A coverlay film 220 (manufactured by Arisawa Seisakusho Co., Ltd., "CMA0525KA") was attached to a flexible circuit board 210 with the adhesive layer 222 of the coverlay film 220 facing the flexible circuit board 210, forming an FPC 200 (laminated structure) with a pitch of 50 μm, a width of 50 μm, and a height of 18 μm. Then, as shown in Figure 3, the release film 10 was applied to the laminated FPC 200 using an RtoR press (manufactured by TRM, "RR Q-CURE 100TON CONTINUOUS LAMINATOR") at 180°C and 110 kg / cm². 2The FPC 200 was pressed down under the set conditions of 150 seconds. Subsequently, a configuration was applied in which a rod was inserted between the FPC 200 and the release film 10 as the release means 60 to separate them. The transport speed was set to 200 mm / sec, the feed amount to 500 mm, and the distance from the heated pressure plate 521 to the release means 60 was set to 50 mm, and the release film 10 was peeled off. The ease of peeling off the release film 10 (release properties) at that time was evaluated according to the following criteria.

[0123] [Evaluation Criteria] ○: It can be peeled off when removing the release film. ×: When peeling off the release film, it is difficult to remove due to fusion of the cushion layer or stretching or tearing of the release film.

[0124] 3-2. Release properties of release film 2 For each example and comparative example, the release film 10 was placed so that the first release layer 1 was in contact with the adhesive layer 222 of the coverlay film 220 (manufactured by Nikkan Industries, "CISV2535"), and pressed using a quick press machine (manufactured by TRM, "HH46 LAMINATOR") under vacuum conditions at 185°C and 20 kg / cm². 2 The material was pressed under the following conditions: vacuum evacuation time of 10 seconds and molding time of 900 seconds. The material was cut to a width of 25 mm, and a peel test was performed by pulling the coverlay film 220 at a test speed of 300 mm / min and a peel angle of 90°.

[0125] [Evaluation Criteria] A: 1.0N / less than 25mm B:1.0N / 25mm or more

[0126] 3-3. Summary Table 1 shows the evaluation results obtained for the release properties 1 and 2 of the aforementioned release film.

[0127] [Table 1]

[0128] As shown in Table 1, in each embodiment, the first release layer 1 was set to satisfy all the following relationships: melting point of 180°C or higher, Xc / Xb ≤ 1.6, and Xc / Xa ≤ 2.6. As a result, excellent release properties were observed.

[0129] In contrast, in Comparative Example 1, the first release layer was not set to satisfy all the relationships of a melting point of 180°C or higher, Xc / Xb ≤ 1.6, and Xc / Xa ≤ 2.6. As a result, it did not show excellent release properties.

[0130] Furthermore, the second release layer 2 may or may not be set to satisfy all of the following conditions: melting point of 180°C or higher, Xc / Xb ≤ 1.6, and Xc / Xa ≤ 2.6. In either case, if only one of the first release layer 1 or the second release layer 2 satisfies the above conditions, the results showed excellent release properties. [Industrial applicability]

[0131] According to the present invention, when peeling the release film from a flexible printed circuit board, it is possible to provide a release film that can be peeled off quickly and efficiently, and that enables the manufacture of molded products with excellent productivity. Therefore, the present invention has industrial applicability. [Explanation of Symbols]

[0132] 1 First release layer 2 Second release layer 3. Cushioning layer 10 Release film 10A Release film 10B Release film 50 Heating press means 52 Heat-sealed section 60 Release means 100 Roll-to-Roll Press Machine 200 Flexible Printed Circuit Boards (FPCs) 210 Flexible Circuit Boards 220 Coverlay Film (CL Film) 221 Coverlay 222 Adhesive layer 223 Recess 300A glass cloth 300B Glass Cloth 521 Heat-sealed crimping plate T1 Average thickness of the first release layer T2 Average thickness of the second release layer Tk average thickness of cushion layer Tt Average thickness of release film

Claims

[Claim 1] A release film comprising a first release layer, a cushion layer provided on one side of the first release layer, and a second release layer provided on the side of the cushion layer opposite to the first release layer, The first release layer is composed of a resin material consisting of polybutylene terephthalate and polybutylene terephthalate copolymer. The content of polybutylene terephthalate in the resin material is 0% by mass or more and 80% by mass or less. The content of the polybutylene terephthalate copolymer in the resin material is 20% by mass or more and 100% by mass or less. The average thickness T1 of the first release layer is 7 μm or more and 38 μm or less. The average thickness Tk of the cushion layer is 40 μm or more and 110 μm or less. The average thickness T2 of the second release layer is 7 μm or more and 38 μm or less. In the infrared absorption spectrum of the first release layer, 2855 ± 7 cm⁻¹ －１ The absorbance at Xa is 2920 ± 7 cm. －１ The absorbance at Xb, 2960 ± 7 cm² －１ A release film characterized in that, when the absorbance at Xc is denoted as Xc, Xa is 0.0548% or more and 0.20929% or less, Xb is 0.0623% or more and 0.184% or less, Xc is 0.0705% or more and 0.0985% or less, satisfying the relationship Xc / Xb ≤ 1.6 and Xc / Xa ≤ 2.6.

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