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

Release film

[0001] The present invention relates to a release film.

[0002] For example, as shown in Patent Document 1, a release film is generally used when a coverlay film is bonded to a flexible circuit board having an exposed circuit by hot pressing via an adhesive layer provided on the coverlay film to form a flexible printed circuit board, i.e., a laminate.

[0003] After laminating the coverlay film onto the flexible circuit board, the release film is required to be peeled off from the formed flexible printed circuit board with excellent releasability.

[0004] More specifically, when the release film is peeled off from the flexible printed circuit board, it is required that the release film exhibits excellent releasability with respect to the flexible printed circuit board, thereby suppressing the occurrence of creases and breaks in the flexible printed circuit board.

[0005] However, with conventional release films, sufficient consideration has not been given to exhibiting excellent releasability, which can lead to transport defects such as creases and breakage of the flexible printed circuit board.In addition, the releasability between the adhesive layer of the coverlay film and the release film is not sufficiently ensured, which can result in problems such as part of the release film remaining on the flexible circuit board.

[0006] JP 2011-88351 A

[0007] An object of the present invention is to provide a release film that can be quickly and satisfactorily peeled from a flexible printed circuit board, and that can be used to produce molded products with excellent productivity.

[0008] The above object can be achieved by the present invention as described in the following (1) and (2). (1) A release film having a release layer, wherein the release layer contains a resin having a melting point of 180° C. or higher and has a wavelength of 2855±7 cm in an infrared absorption spectrum.－１ The absorbance at Xa is 2920 ± 7 cm －１ The absorbance at Xb is 2960 ± 7 cm －１ wherein Xc is the absorbance at 1000 nm, the relationship of Xc / Xb≦1.6 is satisfied and the relationship of Xc / Xa≦2.6 is satisfied.

[0009] (2) The release film according to (1) above, wherein the release layer contains a polyester resin.

[0010] According to the present invention, the release layer contains a resin having a melting point of 180° C. or higher, and has a wavelength of 2855±7 cm in an infrared absorption spectrum. －１ The absorbance at Xa is 2920 ± 7 cm －１ The absorbance at Xb is 2960 ± 7 cm －１ When the absorbance at 1000 nm is Xc, the relationship of Xc / Xb≦1.6 and the relationship of Xc / Xa≦2.6 are satisfied. Therefore, the release film can be peeled off quickly and satisfactorily, and molded articles can be produced with excellent productivity.

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

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

[0013] In the following, a case where a flexible printed circuit board using the release film of the present invention is produced using a roll-to-roll press will be described as an example. Prior to describing the release film of the present invention, the roll-to-roll press used in the production of this flexible printed circuit board will be described.

[0014] <Roll-to-roll press machine> Fig. 1 is a side view showing the main parts of a roll-to-roll press machine used in manufacturing a flexible printed circuit board, Fig. 2 is a vertical cross-sectional view showing each step in a method for manufacturing a flexible printed circuit board using the roll-to-roll press machine shown in Fig. 1, and Fig. 3 is a vertical cross-sectional view showing a heat pressing step in the method for manufacturing a flexible printed circuit board using the roll-to-roll press machine shown in Fig. 1. Note that, for convenience of explanation, the upper side in Figs. 1 to 3 will be referred to as "top" or "upper", the lower side will be referred to as "bottom" or "lower", the left side will be referred to as "left", and the right side will be referred to as "right".

[0015] As shown in Figures 1 to 3, the roll-to-roll press machine 100 (RtoR press machine) is equipped with a conveying means (not shown) that conveys the release film 10 (10A, 10B), the flexible printed circuit board 200 (hereinafter also referred to as "FPC"), and the glass cloths 300A, 300B, a heat pressing means 50 that uses the release film 10 to heat-press and bond the CL film 220 to the flexible circuit board 210 and the cover lay film 220 (hereinafter also referred to as "CL film") that the FPC 200 is equipped with, and a releasing means 60 that releases (peels off) the release film 10 from the FPC 200 in which the CL film 220 is bonded to the flexible circuit board 210.

[0016] The conveying means conveys the FPC 200, the release films 10A and 10B, and the glass cloths 300A and 300B, each wound around a different unwinding roller, along their longitudinal directions by the rotation of a tensioner (tension roller), and after processing by the heat pressing means 50 and the releasing means 60, the take-up roller winds them up.

[0017] Each roller is made of a metal material such as stainless steel, etc. The rotation axes (central axes) of these rollers are oriented in the same direction, and they are arranged at a distance from each other.

[0018] 1, the heat pressing means 50 has a heat pressing unit 52. The heat pressing unit 52 has a pair of heat pressing plates 521. The heat pressing plates 521 are transported by a transport means and are disposed above and below the overlapping glass cloth 300A, the release film 10A, the FPC 200, the release film 10B, and the glass cloth 300B. When the overlapping glass cloth 300A, the release film 10A, the FPC 200, the release film 10B, and the glass cloth 300B pass between the heat pressing plates 521, the heat pressing plates 521 heat and press the FPC 200 via the glass cloths 300A, 300B and the release films 10A, 10B. Therefore, as shown in FIG. 2( a), the curing reaction of the adhesive layer 222 provided on the CL film 220 progresses due to this heating, and in the FPC 200, the overlapping flexible circuit board 210 and the CL film 220 are bonded via the adhesive layer 222.

[0019] In other words, the coverlay 221 and the flexible circuit board 210 are bonded together via the adhesive layer 222 (see FIG. 2A). When the FPC 200 is heated and pressurized, that is, when the coverlay 221 and the flexible circuit board 210 are bonded together via the adhesive layer 222, the release film 10 is embedded in a recess 223 formed in the coverlay 221. This prevents the adhesive from seeping out of the recess 223 due to the adhesive layer 222 (see FIG. 2B).

[0020] Before being heated and compressed by the heating and compression plate 521, the FPC 200 is in a laminated state by overlapping the flexible circuit board 210 and the CL film 220, but the flexible circuit board 210 and the CL film 220 are not bonded via the adhesive layer 222 provided on the CL film 220. Then, by compression bonding using the heating and compression plate 521, the adhesive layer 222 provided on the CL film 220 is brought into close contact with the flexible circuit board 210, and further, in this state, heating by the heating and compression plate 521 causes a curing reaction of the adhesive layer 222 to proceed, thereby bonding the flexible circuit board 210 and the CL film 220 via the adhesive layer 222.

[0021] As shown in FIG. 1 , the release means 60 is disposed downstream of the heat press means 50 in the conveying direction. This release means 60 is configured to separate the FPC 200 from the release films 10A and 10B. Here, in the heat pressing unit 52 provided in the heat press means 50, the release film 10 is embedded in a recess 223 formed in the coverlay 221, as shown in FIG. 2( b). As a result, the release film 10 is bonded to the CL film 220 (FPC 200). The release means 60 is configured to peel (release) the release film 10 from the CL film 220 (FPC 200) (see FIG. 2( c)). Therefore, based on the action of the release means 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 has been peeled from the release film 10.

[0022] The release means 60 may be configured to peel the release film 10 from the FPC 200 by sandwiching (inserting) a peeling member between the FPC 200 and the release film 10, or may be configured to peel the FPC 200 by vacuuming using a vacuum device installed on the outside, or may be configured to peel the FPC 200 and the release film 10 by blowing air between them.

[0023] A flexible printed circuit board 200 (FPC 200) can be manufactured using the above-described roll-to-roll press machine 100. A method for manufacturing the FPC 200 using this roll-to-roll press machine 100 will now be described.

[0024] In this embodiment, as shown in Figures 1 to 3, the manufacturing method of the FPC 200 includes a first step of forming a laminate in which glass cloth 300A, release film 10A, FPC 200, release film 10B, and glass cloth 300B, each of which has a sheet-like shape, are stacked in this order; a second step of hot-pressing this laminate to bond a coverlay 221 (CL film 220) to the flexible circuit board 210 in the FPC 200 via an adhesive layer 222; and a third step of releasing the release film 10 (10A, 10B) from the FPC 200 to obtain the FPC 200 in which the CL film 220 is bonded to the flexible circuit board 210.

[0025] Each of these steps will be described below in order. (First Step) First, the glass cloth 300A, the release film 10A, the FPC 200, the release film 10B, and the glass cloth 300B, each of which is in a sheet form and wound around a winding roller, are laminated in this order during transport by a transport means (release film arrangement step, see FIGS. 1 and 2(a)).

[0026] The method for laminating each component (each layer) to the laminate is not particularly limited, and for example, the components may be laminated while being pressed by a roll or a press. The components may also be laminated in any order. For example, all components may be laminated at the same time, or the coverlay film 220 and the flexible circuit board 210 may be laminated in advance, and then the other components may be laminated at the same time.

[0027] Furthermore, the formation of the laminate in this first step constitutes a step of placing the release film 10 on the object (FPC 200).

[0028] (Second step) Next, the laminate in which the glass cloth 300A, the release film 10A, the FPC 200, the release film 10B, and the glass cloth 300B are stacked in this order is heated and pressurized (heat-pressed) using the heat press means 50 (heat-compression bonding unit 52). As a result, the curing reaction of the adhesive layer 222 progresses while the adhesive layer 222 is in close contact with the flexible circuit board 210, and a bonded body is formed in the FPC 200 in which the coverlay 221 (CL film 220) is bonded to the flexible circuit board 210 via the adhesive layer 222 (heat press step; see FIGS. 1, 2(b), and 3).

[0029] At this time, the release film 10A adheres closely to the coverlay 221, and the release film 10A is embedded in the recess 223 formed in the coverlay 221, thereby suppressing the seepage of adhesive originating from the adhesive layer 222 into the recess 223.

[0030] In this second step (heat pressing step), the temperature to which the FPC 200 is heated is not particularly limited, but is preferably 100°C or higher and 250°C or lower, and more preferably 150°C or higher and 200°C or lower.

[0031] In addition, in the second step, when applying pressure to the FPC 200, the pressure set in the thermocompression bonding unit 52 is not particularly limited, but is preferably set to 1 MPa or more and 14 MPa or less, and more preferably 5 MPa or more and 14 MPa or less.

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

[0033] The second step constitutes a step of performing a heat press on the object (FPC 200) on which the release film 10 is disposed. Furthermore, when the coverlay 221 (molded product) is made of a material containing a semi-cured thermosetting resin, the coverlay 221 constitutes the surface of the object (FPC 200) on which the release film 10 is disposed. The release film 10 is superimposed on the surface of the coverlay 221 so that the surface on the side of the first release layer 1 (described later) contacts the surface of the coverlay 221. Therefore, the release film 10 can maintain the shape of the coverlay 221 with the recesses 223 formed therein while curing the thermosetting resin, thereby enabling the coverlay 221 (molded product) to be molded with excellent precision on the flexible circuit board 210. Furthermore, because the adhesion time is set within the above range, the release film 10 can promote the curing reaction of the thermosetting resin constituting the coverlay 221 while maintaining the shape of the coverlay 221 with the recesses 223 formed therein.

[0034] The method for manufacturing a molded product includes a first step of placing a release film 10 on an object (FPC 200) so 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. This allows the release film 10 to maintain the shape of the coverlay 221 with the recesses 223 formed therein while curing the thermosetting resin, thereby enabling the coverlay 221 (molded product) to be molded with excellent precision on the flexible circuit board 210. Furthermore, because the adhesion time is set within the above range, the release film 10 allows the curing reaction of the thermosetting resin constituting the coverlay 221 to proceed while maintaining the shape of the coverlay 221 with the recesses 223 formed therein.

[0035] Furthermore, although the heating means is a hot press in this embodiment, the present invention is not limited to this method, and heating may be performed by infrared rays or by a heating roll, for example.

[0036] (Third Step) Next, in a releasing means 60, the release films 10 (10A, 10B) are released from the FPC 200. That is, the release films 10A and 10B are peeled from the bonded body of the coverlay film 220 and the flexible circuit board 210. This results in an FPC 200 in which the CL film 220 is bonded to the flexible circuit board 210 (peeling step, see FIGS. 1 and 2(c)).

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

[0038] By winding in this manner, the FPC 200 bonded via the adhesive layer 222 provided on the CL film 220 is wound around the winding roller, and the flexible circuit board 210 and the CL film 220 are continuously obtained.

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

[0040] After the third step, the process may include a step of heating the flexible printed circuit board 200 wound around a winding roller, or the wound flexible printed circuit board 200 cut into individual sheets, in an oven or the like, to further promote the curing reaction of the thermosetting resin that constitutes the coverlay 221 and harden the coverlay 221.

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

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

[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 surface on the first release layer 1 side in contact with the CL film 220 provided on the FPC 200.

[0044] Below, we will explain each layer that makes up this release film 10. <Cushion layer 3> First, we will explain the cushion layer 3. This cushion layer 3 is disposed as an intermediate layer between the first release layer 1 and the second release layer 2, as shown in Figures 4 and 5 .

[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 the ability to conform to the recesses 223.

[0046] Examples of combinations of multiple types of thermoplastic resins include a combination of a polyester-based resin and a polyolefin-based resin, a combination of two polyolefin-based resins, and a combination of a polyamide-based resin and a polyolefin-based resin. Of these, the above-mentioned effects can be more reliably achieved by selecting a combination of a polyester-based resin and a polyolefin-based resin.

[0047] The polyester-based resin is not particularly limited, but examples thereof 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-based resin may be a blend or copolymer of these. Among these, polybutylene terephthalate is particularly preferred. This allows the cushion layer 3 to have excellent conformability to the recesses 223. Furthermore, when the first release layer 1 contains polybutylene terephthalate, the cushion layer 3 can exhibit excellent adhesion to the first release layer 1.

[0048] The polyolefin resin is not particularly limited, and examples thereof include α-olefin polymers such as polyethylene (e.g., low-density polyethylene, high-density polyethylene), polypropylene, and α-olefin copolymers having ethylene, propylene, butene, pentene, hexene, octene, or the like as polymer components, such as ethylene-hexene copolymers, ethylene-octene copolymers, α-olefin-(meth)acrylic acid ester copolymers, ethylene-vinyl acetate copolymers, and ethylene-(meth)acrylic acid copolymers. One or more of these may be used in combination. Among these, at least one of ethylene-vinyl acetate copolymers and ethylene-(meth)acrylic acid copolymers is preferred. This allows the cushion layer 3 to have excellent conformability to the recesses 223.

[0049] When a polyester resin and a polyolefin resin are combined, the content of the polyester resin in the 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, which allows the release film 10 to have excellent conformability to the recesses 223.

[0050] Furthermore, the third thermoplastic resin composition constituting the cushion layer 3 may contain, in addition to the resin material (thermoplastic resin) described above, additives such as a nucleating agent, an antioxidant, a slip agent, an antiblocking agent, an antistatic agent, a colorant, and a stabilizer.

[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 or more and 150 MPa or less, and even more preferably 1 MPa or more and 100 MPa or less. By setting the storage modulus E' of the cushion layer 3 at 150°C as described above, it is possible to appropriately 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 appropriately suppressed or prevented. Furthermore, it is possible to easily peel off 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, in accordance with JIS K7244-4 by preparing a cushion layer 3 having a width of 4 mm and a length of 20 mm, and measuring the storage modulus E' at 150°C using a dynamic viscoelasticity measuring device (Hitachi High-Tech Science Corporation, "DMA7100") in a tensile mode at a frequency of 1 Hz and a heating rate of 5°C / min.

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

[0054] <First Release Layer 1 (Release Layer)> Next, a description will be given of the first release layer 1. This first release layer 1 is laminated on one surface of the cushion layer 3, as shown in Figs.

[0055] The first release layer 1 is flexible, and in the above-described method for manufacturing a flexible printed circuit board 200 using the release film 10, the release film 10 is superimposed on the CL film 220 of the FPC 200 so that the first release layer 1 comes into contact with the CL film 220. In the second step of this manufacturing method, when the superimposed flexible circuit board 210 and the CL film 220 are bonded via the adhesive layer 222, the first release layer 1 is pressed into the flexible circuit board 210 and the CL film 220, conforming to the shape of the recess 223 formed by the flexible circuit board 210 and the CL film 220, and functions as a protective (buffer) material that prevents the release film 10 from breaking. Furthermore, in the third step, the first release layer 1 functions as a contact layer for exhibiting excellent releasability of the release film 10 from the CL film 220 (FPC 200).

[0056] Therefore, in the second step, the release film 10 can reliably suppress or prevent the adhesive from seeping out of the adhesive layer 222 into the recesses 223 formed in the FPC 200. Furthermore, after the formation of the FPC 200 in the second step in which the flexible circuit board 210 and the CL film 220 are bonded together via the adhesive layer 222 provided on the CL film 220, when the release film 10 is peeled off from the FPC 200 in the third step, the release film 10 can reliably suppress or prevent the FPC 200 from elongating and breaking. Furthermore, when the third thermoplastic resin composition constituting the cushion layer 3 contains a polyester-based resin, the first release layer 1 can exhibit excellent adhesion to the cushion layer 3.

[0057] Furthermore, in the manufacturing method of the flexible printed circuit board 200, the first release layer 1 is used so as 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 hot-pressed, the first release layer 1 also has the function of transferring heat from the heat-bonding plate 521 to the CL film 220.

[0058] Here, with conventional release films, sufficient consideration has not been given to exhibiting excellent releasability, which can lead to transport problems such as creases and breakage in the flexible printed circuit board. Furthermore, the releasability between the adhesive layer of the coverlay film and the release film is not sufficiently ensured, resulting in problems such as part of the release film remaining on the flexible circuit board. As a result of extensive research into these problems, the present inventors have found that excellent releasability can be exhibited by configuring the first release layer 1 to have the following characteristics, thereby completing the present invention. This is explained below.

[0059] Characteristics: The first release layer 1 contains a resin having a melting point of 180° C. or higher, and has a peak intensity of 2855±7 cm in an infrared absorption spectrum. －１ The absorbance at Xa is 2920 ± 7 cm －１ The absorbance at Xb is 2960 ± 7 cm －１ When the absorbance at is Xc, the relationship of Xc / Xb≦1.6 is satisfied, and the relationship of Xc / Xa≦2.6 is also satisfied.

[0060] This allows the first release layer 1 to exhibit excellent releasability, allowing the release film to be peeled off quickly and smoothly, thereby enabling molded products to be produced with excellent productivity.

[0061] The graph shown in Figure 6 is a graph showing the infrared absorption spectrum of the first release layer 1 shown in Figure 4, more specifically, a graph showing the Fourier transform infrared (FTIR) spectrum. In the graph shown in Figure 6, the vertical axis represents infrared reflectance (% R) and the horizontal axis represents wave numbers. The FTIR spectrum has a wavelength of 2855±7 cm －１ It has a peak Pa at 2920±7 cm －１It has a peak Pb at 2960±7 cm －１ The absorbance X is expressed as X = log(I ０ / I) (where %R = I / I ０ × 100), the maximum value of infrared absorptivity at peak Pc is absorbance Xc, the maximum value of infrared absorptivity at peak Pb is absorbance Xb, and the maximum value of infrared absorptivity at peak Pa is absorbance Xa.

[0062] The peak Pa is determined by the CH ２ (CH ２ The peak Pb is a peak derived from the CH ３ (CH ３ Peak Pc is a peak derived from the antisymmetric stretching of the CH ２ (CH ２ This peak is due to antisymmetric stretching.

[0063] The first release layer 1 contains a resin having a melting point of 180° C. or higher, and has an infrared absorption spectrum of 2855±7 cm －１ The absorbance at Xa is 2920 ± 7 cm －１ The absorbance at Xb is 2960 ± 7 cm －１ When the absorbance at 1000 nm is Xc, the relationship of Xc / Xb≦1.6 and the relationship of Xc / Xa≦2.6 are satisfied, and thereby excellent releasability can be exhibited, and the release film 10 can be rapidly and satisfactorily peeled off. Therefore, molded products can be produced with excellent productivity.

[0064] If Xc / Xb>1.6, the releasability from the adhesive cannot be sufficiently ensured, which is demeritous in that the yield decreases, and the effect of the present invention cannot be fully exhibited.

[0065] Furthermore, if Xc / Xa>2.6, the releasability from the adhesive cannot be sufficiently ensured, which is disadvantageous in that the yield decreases, and the effect of the present invention cannot be fully exhibited.

[0066] Furthermore, if the melting point of the resin constituting the first release layer 1 is less than 180°C, the standard heat pressing temperature (approximately 160°C to approximately 180°C) will result in the disadvantage that the first release layer 1 cannot be released properly, and the effects of the present invention cannot be fully achieved.

[0067] The first release layer 1 only needs to satisfy Xc / Xb≦1.6, but preferably satisfies 0≦Xc / Xb≦1.5, and more preferably 0≦Xc / Xb≦1.4, which allows the above-mentioned effects to be exhibited more significantly.

[0068] Furthermore, the first release layer 1 only needs to satisfy Xc / Xa≦2.6, but preferably satisfies 0≦Xc / Xa≦2.6, and more preferably 0≦Xc / Xa≦2.3, which allows the first release layer 1 to exhibit even better release properties.

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

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

[0071] The following description will focus on the case where the first release layer 1 is made of a material containing polybutylene terephthalate (first resin component) and a substitute (second resin component). Note that the first resin component and the second resin component are not limited to the following.

[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 obtained by polymerizing terephthalic acid as a dicarboxylic acid and 1,4-butanediol as a diol component, and introducing an ester structure.

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

[0075] <Second Resin Component> The second resin component is a substitution product (copolymer) in which at least one of terephthalic acid and 1,4-butanediol constituting polybutylene terephthalate is partially 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 selected from these may be 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 the effects of the present invention to be more pronounced.

[0078] When the first release layer 1 contains, as the second resin component (substitution product), a compound in which a part of the terephthalic acid constituting polybutylene terephthalate is substituted with another dicarboxylic acid component, the proportion of the other dicarboxylic acid component in the total dicarboxylic acid components constituting the substitution product is preferably 2 mol % or more and 50 mol % or less, thereby achieving the effects of the present invention more significantly.

[0079] When the first release layer 1 contains, as the second resin component (substitution product), a compound in which part of the 1,4-butanediol constituting polybutylene terephthalate is substituted with another diol component, the proportion of the other diol component in the total diol components constituting the substitution product is preferably 1 mol % or more and 20 mol % or less, thereby achieving the effects of the present invention more significantly.

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

[0081] When the first release layer 1 is composed of a material containing polybutylene terephthalate (first resin component) and a substituent (second resin component), the content of the substituent (second resin component) in the first release layer 1 is preferably 20 parts by mass or more and 100 parts by mass or less, more preferably 25 parts by mass or more and 100 parts by mass or less, and even more preferably 30 parts by mass or more and 100 parts by mass or less, in the resin composition constituting the first release layer 1. This makes it possible to obtain the effects of the present invention more significantly.

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

[0083] The inorganic particles are not particularly limited, but examples thereof 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, and the like, and these can be used alone or in combination of two or more.

[0084] The organic particles are not particularly limited, but examples thereof 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 may be used in combination.

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

[0086] The first release layer 1 having such a configuration preferably has a storage modulus E' at 150°C of 50 MPa or more, more preferably 50 MPa or more and 1000 MPa or less, and even more preferably 50 MPa or more and 300 MPa or less, thereby ensuring that the first release layer 1 has the above-described function as the first release layer 1.

[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 having 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, at a frequency of 1 Hz, and at a temperature rise rate of 5°C / min.

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

[0089] As described above, when the surface of the first release layer 1 opposite the cushion layer 3 has an uneven shape, the average thickness T1 of the first release layer 1 is the average value of the measured values ​​obtained by measuring the thickness at positions including the convex portions in the case of convex portions, and at positions including the concave portions in the case of concave portions.

[0090] <Second Release Layer 2> Next, the second release layer 2 will be described.

[0091] As shown in Figures 4 and 5, the release film 10 is laminated to the other side of the cushion layer 3, i.e., the side of the cushion layer 3 opposite 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 has the function of transmitting the force from the thermocompression plate 521 to the cushion layer 3 when the overlapping flexible circuit board 210 and the CL film 220 are bonded via the adhesive layer 222 in the second step of the manufacturing method for the flexible printed circuit board 200. Furthermore, the second release layer 2 has the function of providing excellent releasability between the glass cloths 300A, 300B and the release film 10 in the third step. The second release layer 2 also has the function of transmitting heat from the thermocompression plate 521 to the cushion layer 3 when the FPC 200 is hot-pressed in the second step of this manufacturing method.

[0093] The second release layer 2 is made of a second thermoplastic resin composition. Preferably, the second thermoplastic resin composition contains a polyester resin as a main component. This ensures that the second release layer 2 has the aforementioned functions.

[0094] The polyester resin is not particularly limited, but may be, for example, the same as those listed for the third thermoplastic resin composition described above, and among them, polybutylene terephthalate (PBT) is particularly preferred, which allows the effects obtained by using the polyester resin to be more significantly exhibited.

[0095] In addition, when the second thermoplastic resin composition is mainly composed of a polyester-based resin, it may contain a thermoplastic resin other than a polyester-based resin. Examples of such a thermoplastic resin include polyolefin-based resins such as polyethylene, polypropylene, and poly-4-methyl-1-pentene, and polystyrene-based resins such as syndiotactic polystyrene. One or a combination of two or more of these may be used.

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

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

[0098] The second release layer 2 having such a configuration preferably has a storage modulus E' at 150°C of 50 MPa or more, more preferably 50 MPa or more and 1000 MPa or less, thereby ensuring that the second release layer 2 has the above-mentioned functions.

[0099] The average thickness T2 of the second release layer 2 is preferably set to be 7 μm or more and 38 μm or less, and more preferably 10 μm or more and 30 μm or less, so that the second release layer 2 can be provided with the above-mentioned functions more reliably.

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

[0101] 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 are the same or of the same quality. Furthermore, 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 laminated structure of the first release layer 1, the cushion layer 3, and the second release layer 2, 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 setting the thickness 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 laminated in this order, but the present invention is not limited to this configuration, and may be composed of a laminate having, for example, an intermediate layer such as an adhesive layer arranged at least either between the first release layer 1 and the cushion layer 3 or between the second release layer 2 and the cushion layer 3.

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

[0105] Although the release film of the present invention has been described above, the present invention is not limited thereto.

[0106] For example, in the above embodiment, the case where the release film of the present invention is applied to a press molding method in which flexible printed circuit boards arranged between thermocompression plates are laminated in one layer to produce the film has been described. However, the number of laminated flexible printed circuit boards is not limited to one layer, and may be two or more layers.

[0107] Furthermore, although the release film of the present invention is applied to a case where it is pressed against a flexible printed circuit board arranged between thermocompression plates using a roll-to-roll press, the application is not limited thereto, and the pressurization of the flexible printed circuit board can be carried out, for example, by a press molding method, or further by a vacuum pressure molding method.

[0108] The first release layer 1 contains a resin having a melting point of 180° C. or higher, and has a peak intensity of 2855±7 cm in an infrared absorption spectrum. －１ The absorbance at Xa is 2920 ± 7 cm －１ The absorbance at Xb is 2960 ± 7 cm －１We have described a configuration in which, when the absorbance at Xc is Xc, the relationship Xc / Xb≦1.6 and the relationship Xc / Xa≦2.6 are satisfied, but the present invention is not limited to this, and it is also possible for only the second release layer 2 to be configured to satisfy the above conditions, or for both the first release layer 1 and the second release layer 2 to be configured to satisfy the above conditions.

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

[0110] 1. Preparation of Raw Materials The following raw materials were prepared for producing a 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 Chang Chun Petrochemical Co., Ltd., "1100-630S", melting point: 224°C) Polybutylene terephthalate copolymer (manufactured by Mitsubishi Chemical Corporation, "5505S", melting point: 223°C) Polybutylene terephthalate copolymer (manufactured by Bell Polyester Products Co., Ltd., "P02220", melting point: 207°C) Polybutylene terephthalate copolymer (manufactured by Mitsubishi Chemical Corporation, "GK320", melting point: 183°C) Polybutylene terephthalate copolymer (manufactured by Mitsubishi Chemical Corporation, "B1932N", melting point: 216°C) Polybutylene terephthalate copolymer (manufactured by Mitsubishi Chemical Corporation, "B1902N", melting point: 166°C)

[0112] 2. Production of Release Film Example 1 First, a first release layer resin composition was prepared for forming a first release layer, which consisted 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 prepared, which consisted of 100 parts by weight of polybutylene terephthalate (PBT, 1100-630S). A third thermoplastic resin composition was prepared, which consisted 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 resin composition for the first release layer was formed into a film by an extrusion T-die method, thereby obtaining a first release layer 1 .

[0114] Next, the first release layer 1 was subjected to the extrusion T-die method using the second thermoplastic resin composition and the third thermoplastic resin composition described above, successively forming each into a film, thereby forming a laminate in which the cushion layer 3 and the second release layer 2 were laminated in this order on the first release layer 1, and then this laminate was annealed under conditions of 80°C and 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] The infrared reflectance (%R) of the first release layer 1 was measured using JASCO's "FT / IR-4100" with a diamond prism, ATR method, 20 integration times, and a range of 4000 to 400 cm －１ The absorbances Xc, Xb, and Xa were calculated by the infrared reflectance %R = I / I ０ The absorbance and wavenumber of each peak are shown in Table 1.

[0117] Specifically, 2854.3 cm －１ The absorbance Xa at －１ The absorbance Xb at －１ The absorbance Xc at 1.05 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 the relationships Xc / Xb≦1.6 and Xc / Xa≦2.6.

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

[0119] The absorbances Xc, Xb, and Xa and the wave numbers of each peak are as shown in Table 1. In Examples 2 to 9, the relationships Xc / Xa≦2.6 and Xc / Xb≦1.6 were satisfied, while in Comparative Example 1, the relationships Xc / Xa≦2.6 and Xc / Xb≦1.6 were not satisfied. In addition, the melting point of the first release layer 1 was 180° C. or higher in all of Examples 2 to 9 and Comparative Example 1.

[0120] Examples 10 and 11 The release films 10 of 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 blending ratios shown in Table 1. The absorbances Xc, Xb, and 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. Furthermore, 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 films 10 of the examples and comparative examples were each evaluated as follows.

[0122] 3-1. Releasability of Release Film 1 The release film 10 of each example and comparative example was set to a width of 270 mm, and a cover lay film 220 (manufactured by Arisawa Manufacturing Co., Ltd., "CMA0525KA") was attached to a flexible circuit board 210 with the adhesive layer 222 of the cover lay film 220 facing the flexible circuit board 210 to form an FPC 200 (laminate) having irregularities with a pitch of 50 μm, a width of 50 μm, and a height of 18 μm. The release film 10 was then applied to the laminated FPC 200 as shown in FIG. 3 using a R-to-R press (manufactured by TRM, "RR Q-CURE 100TON CONTINUOUS LAMINATOR") at 180° C. and 110 kg / cm. ２ , and pressed in under set conditions of 150 seconds. Thereafter, a configuration in which a rod is sandwiched between the FPC 200 and the release film 10 to separate them was applied as the releasing means 60, and the release film 10 was peeled off at a conveying speed of 200 mm / sec, a feed amount of 500 mm, and a distance from the heating and pressing plate 521 to the releasing means 60 of 50 mm. The ease of peeling (releasability) of the release film 10 at this time was evaluated according to the following criteria.

[0123] [Evaluation Criteria] ◯: The release film was releasable when peeled off. ×: When peeling off the release film, peeling was difficult due to fusion of the cushion layer or stretching or breaking of the release film.

[0124] 3-2. Release Properties of Release Film 2 For the release films 10 of each of the Examples and Comparative Examples, the first release layer 1 was placed on the coverlay film 220 (manufactured by Nikkan Industries Co., Ltd., "CISV2535") so that it was in contact with the adhesive layer 222 provided on the coverlay film 220, and the first release layer 1 was pressed against the adhesive layer 222 using a quick press machine (manufactured by TRM Co., Ltd., "HH46 LAMINATOR") under vacuum conditions of 185°C and 20 kg / cm. ２ The pressing was performed under the set conditions of a vacuuming time of 10 seconds and a molding time of 900 seconds. The film 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: Less than 1.0 N / 25 mm B: 1.0 N / 25 mm or more

[0126] 3-3. Summary The evaluation results obtained for the release properties 1 and 2 of the release films are shown in Table 1.

[0127]

[0128] As shown in Table 1, in each example, the first release layer 1 was set to have a melting point of 180°C or higher, and to satisfy the relationships Xc / Xb≦1.6 and Xc / Xa≦2.6, and 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 of the following relationships: a melting point of 180°C or higher, Xc / Xb≦1.6, and Xc / Xa≦2.6. As a result, the results showed that the release properties were not excellent.

[0130] The second release layer 2 may or may not satisfy all of the following relationships: melting point of 180° C. or higher, Xc / Xb≦1.6, and Xc / Xa≦2.6. In either case, excellent release properties were obtained as long as only one of the first release layer 1 and the second release layer 2 satisfied the above conditions.

[0131] According to the present invention, it is possible to provide a release film that can be quickly and satisfactorily peeled from a flexible printed circuit board, and that can be used to produce molded products with excellent productivity. Therefore, the present invention has industrial applicability.

[0132] 1 First release layer 2 Second release layer 3 Cushion layer 10 Release film 10A Release film 10B Release film 50 Heat press means 52 Heat compression bonding unit 60 Release means 100 Roll-to-roll press machine 200 Flexible printed circuit board (FPC) 210 Flexible circuit board 220 Coverlay film (CL film) 221 Coverlay 222 Adhesive layer 223 Recess 300A Glass cloth 300B Glass cloth 521 Heat compression bonding plate T1 Average thickness of first release layer T2 Average thickness of second release layer Tk Average thickness of cushion layer Tt Average thickness of release film

Claims

1. A release film having a release layer, wherein the release layer contains a resin having a melting point of 180°C or higher and has an infrared absorption spectrum of 2855±7cm －１ The absorbance at Xa is 2920 ± 7 cm －１ The absorbance at Xb is 2960 ± 7 cm －１ wherein Xc is the absorbance at 1000 nm, the relationship of Xc / Xb≦1.6 is satisfied and the relationship of Xc / Xa≦2.6 is satisfied.

2. The release film according to claim 1, wherein the release layer contains a polyester resin.

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