JP2020131461A - Release film - Google Patents

Abstract

To provide a release film which can suppress occurrence of wrinkles while maintaining releasability, suppresses sticking to a hot press plate, and is suitable for manufacture of a flexible circuit board.SOLUTION: A release film includes an intermediate layer, a first release layer laminated on one surface of the intermediate layer and a second release layer laminated on the other surface of the intermediate layer, in which the first release layer contains a first thermoplastic resin and first inorganic particles, an unevenness average interval Sm of the outer surface of the first release layer is 100 μm or more and 350 μm or less, the second release layer contains a second thermoplastic resin and second inorganic particles, and a ten-point average height roughness Rz of the outer surface of the second release layer is 6.5 μm or more and 15 μm or less.SELECTED DRAWING: None

Description

The present invention relates to a release film. More specifically, the present invention relates to a release film used in the manufacture of flexible printed wiring boards.

In the process of manufacturing a flexible circuit board, a coverlay film is hot-press-bonded to a flexible circuit board body on which a copper circuit is formed by a thermosetting adhesive or a thermosetting adhesive sheet. At this time, a release film is widely used to prevent the coverlay film and the hot press plate from adhering to each other.

So far, release films made of various resins such as polymethylpentene resin have been proposed (Patent Document 1). For example, Patent Document 1 describes a release film containing a surface coating, an adhesive layer and a cushion layer, and the surface layer contains a poly4-methyl-1-methylpentene resin.

In recent years, with the spread of smartphones, tablet PCs, etc., flexible circuit boards have become more sophisticated and thinner. In addition, automation of manufacturing methods such as the roll-to-roll (RtoR) method is also progressing, and with the automation of such manufacturing methods, wrinkles generated on the release film in the manufacturing process of the flexible circuit board are transferred to the flexible circuit board. It was sometimes transferred. Further, after the heat press bonding, the release film may stick to the heat press plate, which may reduce workability or break the flexible circuit board.

International Publication No. 06/120983

The present invention has been made in view of the above problems, and is suitable for the production of a flexible circuit board, which can suppress the generation of wrinkles and suppress the sticking to a hot press plate while maintaining the releasability. Providing a film.

According to the present invention
With the mesosphere
The first release layer laminated on one surface of the intermediate layer and
Includes a second release layer laminated on the other surface of the mesosphere.
The first release layer contains a first thermoplastic resin and a first inorganic particle.
The average unevenness interval Sm on the outer surface of the first release layer is 100 μm or more and 350 μm or less.
The second release layer contains a second thermoplastic resin and a second inorganic particle.
A release film having a ten-point average height roughness Rz of the outer surface of the second release layer of 6.5 μm or more and 15 μm or less is provided.

Further, according to the present invention.
A step of arranging the release film on the object so that the first release layer is on the object side.
Provided is a method for producing a molded product, which comprises a step of heat-pressing the object on which the release film is arranged using a heat-pressed plate.

According to the present invention, there is provided a release film suitable for manufacturing a flexible circuit board, which can suppress the occurrence of wrinkles while maintaining the releasability and suppress the sticking to a hot press plate.

It is a schematic diagram which shows the mode of the heat press process used for evaluating the sticking of a release film to a heat press plate, and the air residue.

Hereinafter, embodiments of the present invention will be described.

The release film of the present embodiment includes an intermediate layer, a first release layer laminated on one surface of the intermediate layer, and a second release layer laminated on the other surface of the intermediate layer. .. In other words, the first release layer, the intermediate layer, and the second release layer have a structure in which they are laminated in this order. In the release film of the present embodiment, the first release layer contains the first thermoplastic resin and the first inorganic particles, and the unevenness average spacing Sm of the outer surface of the first release layer is 100 μm or more. It is 350 μm or less. Further, the second release layer contains the second thermoplastic resin and the second inorganic particles, and the ten-point average height roughness Rz of the outer surface of the second release layer is 6.5 μm or more. It is 15 μm or less.

The release film of the present embodiment is arranged so that the first release layer is on the flexible circuit board side and the second release layer is on the hot press plate side in the production of a molded product such as a flexible printed circuit board. Will be used. According to the present inventor, both the average unevenness interval Sm of the outer surface of the first release layer and the ten-point average height roughness Rz of the outer surface of the second release layer are within a predetermined range. We have found that the mold film can suppress the generation of wrinkles due to the residual air and the sticking to the hot press plate while maintaining the releasability, and have completed the present invention.

In the release film of the present embodiment, the unevenness average interval Sm of the outer surface of the first release layer is 100 μm or more and 350 μm or less. In one embodiment, the average unevenness spacing Sm on the outer surface of the first release layer is preferably 150 μm or more and 310 μm or less, and more preferably 180 μm or more and 300 μm or less. When the average interval Sm of the unevenness on the outer surface of the first release layer is within the above range, air bleeding is good, so that the generation of voids and wrinkles due to the remaining air is suppressed. The unevenness average interval Sm can be measured according to JIS-B0601-1994. The smaller the value of Sm, the better the air bleeding of the release film, but in order to achieve such a small Sm, it is necessary to increase the blending amount of the inorganic particles. However, the larger the amount of the inorganic particles, the lower the strength of the release film tends to be. By setting the Sm value in the above range, the release film of the present embodiment can improve the strength of the release film and the air bleeding property in a good balance.

In the release film of the present embodiment, the ten-point average height roughness Rz of the outer surface of the second release layer is 6.5 μm or more and 15 μm or less. In one embodiment, the ten-point average height roughness Rz is preferably 7 μm or more and 14 μm or less, and more preferably 8 μm or more and 13 μm or less. When the ten-point average height roughness Rz of the outer surface of the second release layer is within the above range, there is little or no sticking to the heat press plate. Therefore, workability in manufacturing the flexible printed circuit board is improved, and damage to the flexible printed circuit board is prevented. The larger the value of Rz, the more difficult it is to stick to the hot press plate. In order to increase the value of Rz, it is necessary to increase the amount of the inorganic particles blended. However, the larger the amount of the inorganic particles, the lower the strength of the release film tends to be. By setting the Rz value in the above range, the release film of the present embodiment can improve the strength of the release film and the stickiness to the heat press plate in a well-balanced manner.

Here, the "ten-point average height roughness Rz" means that the elevations of the highest peaks to the fifth highest peaks in the reference length L are Yp1, Yp2, Yp3, Yp4 and Yp5, respectively, and the deepest valley bottom. When the elevations of the valley bottoms from to the fifth depth are Yv1, Yv2, Yv3, Yv4 and Yv5, respectively, it means the value obtained by the following equation (1). "Ten-point average height roughness Rz" is a method based on JIS B0601: 1994 using a stylus type surface roughness measuring machine (for example, surf test SJ-210 manufactured by Mitutoyo), and has a tip radius of 2 μm. , Using a stylus with a conical taper angle of 60 °, measuring force 0.75 mN, cutoff value λs = 2.5 μm (Note that if the surface roughness of the object to be measured is less than the cutoff value, cutoff The value may be adjusted), and the measurement can be performed under the condition of λc = 0.8 mm.
Rz = (| Yp1 + Yp2 + Yp3 + Yp4 + Yp5 | + | Yv1 + Yv2 + Yv3 + Yv4 + Yv5 |) / 5 ... Equation (1)

The uneven average spacing Sm of the outer surface of the first release layer and the ten-point average height roughness Rz of the outer surface of the second release layer are the types of thermoplastic resins used for each release layer and inorganic. It can be controlled within a desired range by adjusting the type of particles, the particle size and particle size distribution of the inorganic particles, the blending amount thereof, and the like.

In the release film of the present embodiment, the first release layer contains a first thermoplastic resin and a first inorganic particle. Examples of the first thermoplastic resin include, but are not limited to, polymethylpentene resin, polyester resin, polystyrene resin, polypropylene resin, polyethylene resin and the like. These may be used alone or in combination of two or more. Above all, it is preferable to use a polymethylpentene resin as the first thermoplastic resin because a release layer having good releasability and followability can be obtained.

Examples of the polymethylpentene resin include a poly4-methyl-1-pentene resin or a copolymer of 4-methyl-1-pentene and an olefin having 2 to 20 carbon atoms other than 4-methyl-1-pentene. ..

As the polyester resin, a polyalkylene terephthalate resin such as polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), polytrimethylene terephthalate resin (PTT), polyhexamethylene terephthalate resin (PHT), and other components are used together. Examples thereof include a polymerized polyester-based copolymer resin. These may be used alone or in combination of two or more. Above all, it is preferable to use polybutylene terephthalate resin from the viewpoint of improving the balance between releasability and followability. The polyester resin may be a crystalline polyester resin or an amorphous polyester resin.

Examples of the first inorganic particles include, but are not limited to, calcium carbonate, zinc oxide, alumina, silica, zeolite and the like. These may be used alone or in combination of two or more.

In the release film of the present embodiment, the second release layer contains a second thermoplastic resin and a second inorganic particle. As the second thermoplastic resin and the second inorganic particles, the same or different ones as those of the first thermoplastic resin and the first inorganic particles can be used.

The first and second release layers further contain additives such as antioxidants, crystal nuclei, fibers, flame retardants, ultraviolet absorbers, and antistatic agents, as long as the effects of the present invention are not impaired. You may.

In one embodiment, the first release layer, the average particle diameter D ₅₀ includes the following first inorganic particles 40μm or 10 [mu] m, the first inorganic particles, for the entire first release layer, The amount is preferably 10% by mass or more and 30% by mass or less. With the above configuration, the average unevenness interval Sm on the outer surface of the first release layer can be adjusted to a desired value, and thus a release film with improved air bleeding property can be obtained.

In one embodiment, the maximum height roughness Rz of the outer surface of the first release layer can be 5 μm or more and 15 μm or less, and more preferably 7 μm or more and 10 μm or less. By setting the above range, a release film having further improved air release property can be obtained.

The thickness of the first release layer is preferably 20 μm or more and 40 μm or less. When the thickness of the second release layer is within the above range, it is possible to suppress the occurrence of wrinkles while maintaining the release property.

In one embodiment, the second release layer, the average particle diameter D ₅₀ includes the following second inorganic particles 40μm or 10 [mu] m, the second inorganic particles, for the entire second release layer, The amount is preferably 10% by mass or more and 30% by mass or less. With the above configuration, the ten-point average roughness Rz of the outer surface of the second release layer can be adjusted to a desired value, so that the release film with no or reduced sticking to the heat press plate can be obtained. can get.

In one embodiment, the average unevenness spacing Sm on the outer surface of the second release layer can be 50 μm or more and 400 μm or less, and more preferably 100 μm or more and 350 μm or less. By setting the above range, a release film with reduced sticking to the heat press plate can be obtained.

The thickness of the second release layer is preferably 20 μm or more and 40 μm or less. When the thickness of the second release layer is within the above range, it is possible to suppress the occurrence of wrinkles while maintaining the release property.

As the resin constituting the intermediate layer included in the release film of the present embodiment, α-olefin-based polymers such as polyethylene and polypropylene, ethylene, propylene, butene, penten, hexene, methylpentene and the like are contained as polymer components. Examples thereof include engineering plastics-based resins such as α-olefin copolymers, polyether sulfones, and polypropylene sulfides. These may be used alone or in combination of two or more. Of these, α-olefin copolymers are preferable because they have a good cushioning function. Examples of the α-olefin copolymer include a copolymer of α-olefin such as ethylene and (meth) acrylic acid ester, a copolymer of ethylene and vinyl acetate, and a copolymer of ethylene and (meth) acrylic acid. Examples thereof include polymers and partially ionic crosslinked products thereof. Further, from the viewpoint of obtaining a good cushioning function, an α-olefin- (meth) acrylic acid ester copolymer such as ethylene is used alone, or a polybutylene terephthalate and a 1,4 cyclohexanedimethanol copolymerized polyethylene terephthalate. , And a mixture of an α-olefin polymer and an α-olefin- (meth) acrylic acid ester copolymer such as ethylene are preferable. For example, a mixture of ethylene and ethylene-methylmethacrylate copolymer (EMMA), a mixture of polypropylene (PP) and ethylene-methylmethacrylate copolymer (EMMA), polybutylene terephthalate (PBT), polypropylene (PP) and ethylene. -A mixture with methyl methacrylate copolymer (EMMA), etc. is more preferable.

In one embodiment, the intermediate layer may further contain a rubber component. Examples of the rubber component include styrene-based thermoplastic elastomers such as styrene-butadiene copolymers and styrene-isoprene copolymers, olefin-based thermoplastic elastomers, amide-based elastomers, and thermoplastic elastomer materials such as polyester-based elastomers, and natural rubber. , Isoprene rubber, chloroprene rubber, rubber materials such as silicon rubber and the like.

The intermediate layer may further contain additives such as antioxidants, crystal nuclei, fibers, flame retardants, ultraviolet absorbers, and antistatic agents as long as the effects of the present invention are not impaired.

The thickness of the intermediate layer can be 30 μm or more and 70 μm or less. If the thickness of the intermediate layer is less than 30 μm, the cushioning property of the release film provided with the release film may be lowered in the hot press bonding using the release film, and the coverlay adhesive may flow out. If the thickness of the intermediate layer exceeds 70 μm, wrinkles may occur on the release film.

In one embodiment, the thickness of the release film is not particularly limited, but is preferably 70 μm or more and 150 μm or less, and more preferably 90 μm or more and 130 μm or less. Further, the total thickness of the first release layer and the second release layer preferably occupies more than half of the thickness of the release film. In such a release film, the generation of wrinkles is effectively suppressed, and the sticking to the hot press plate is suppressed.

The method for producing the release film of the present embodiment is not particularly limited, and for example, a water-cooled or air-cooled coextrusion inflation method, a coextrusion T-die method, or a film serving as one of the release layers is produced. After that, an intermediate layer is laminated on this film by an extrusion laminating method, and then the other release layer is dry-laminated, one release layer film, an intermediate layer film, and the other release layer. Examples thereof include a dry lamination method, a solvent casting method, and a hot press molding method.

The release film of this embodiment is used for manufacturing a molded product such as a flexible circuit board.
The method for producing a molded product of the present embodiment includes the following steps.
(Step 1) A step of arranging the release film of the present embodiment on an object so that the first release layer is on the object side.
(Step 2) A step of performing a heat press on an object on which a release film is placed using a heat press plate.
In step 1, the first release layer of the release film is arranged so as to be on the object side. In step 2, the object is heat-pressed with a heat-pressed plate via a release film. Further, the plate material may be arranged on the second release layer of the release film before the heat press is performed. As a result, even when the surface of the object is uneven, the adhesion between the release film and the object can be improved, and the object can be evenly pressurized.
As the plate material, a material having a cushioning property is preferable, and examples thereof include paper, rubber, a fluororesin sheet, and glass paper.

In one embodiment, the surface on which the release film of the object is placed may include a layer containing a thermosetting resin. The release film of the present embodiment does not cause wrinkles even when it is placed on the thermosetting resin layer of such an object, and the obtained molded product has a good appearance.

Examples of the molded product include a flexible circuit board. When the molded product is a flexible circuit board, the release film of this embodiment is used in the coverlay press laminating step.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than the above can be adopted.

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

(Examples 1 to 5, Comparative Examples 1 to 3)
(Preparation of resin composition)
The thermoplastic resin composition for forming the first release layer was prepared by mixing the thermoplastic resin and the inorganic filler in the blending amounts shown in Table 1.
The thermoplastic resin composition for forming the second release layer was prepared by mixing the thermoplastic resin and the inorganic filler in the blending amounts shown in Table 1.
The resin composition for forming the intermediate layer (cushion layer) is 40 parts by weight of a modified polyethylene resin (ethylene-methylmethacrylate copolymer (EMMA) resin) (Sumitomo Chemical Co., Ltd., WD106), polypropylene resin (Prime Polymer Co., Ltd.). , E-105GM) and 40 parts by weight of polymethylpentene resin (TPX®) (Mitsui Chemicals, Inc., RT18) were mixed and prepared.

The materials used in the examples and comparative examples are as follows.
(Thermoplastic resin)
-Thermoplastic resin 1: Polymethylpentene resin (TPX (registered trademark)) (manufactured by Mitsui Chemicals, trade name "RT18")
(Inorganic filler)
-Inorganic filler 1: Fused silica (manufactured by Denka, trade name "FB-105FD", average particle size (D ₅₀ ) 11.1 μm, spherical)
-Inorganic filler 2: fused silica (manufactured by Denka, trade name "FB-907FD", average particle size (D ₅₀ ) 16.7 μm, spherical)
-Inorganic filler 3: fused silica (manufactured by Denka, trade name "FB-875FD", average particle size (D ₅₀ ) 23.0 μm, spherical)
-Inorganic filler 4: Fused silica (manufactured by Nippon Steel Chemical & Materials Co., Ltd., trade name "SC-30F", average particle size (D ₅₀ ) 35.6 μm, spherical)

(Making a release film)
The obtained resin composition for the first release layer, the resin composition for the intermediate layer, and the resin composition for the second release layer are co-extruded by separate extruders, and the first A three-layer laminated film having a structure of a release layer / an intermediate layer / a second release layer and having a thickness of 110 μm was produced. The thickness of each layer is shown in Table 1.
(Measurement of surface roughness)
The surface roughness and characteristics (Rz and Sm) of the outer surface of the first release layer and the outer surface of the second release layer of the obtained laminated sheet were measured by a stylus type surface roughness measuring machine (manufactured by Mitutoyo). It was measured using the surf test SJ-210). The results are shown in Table 1.

(Performance evaluation of release film)
The obtained release film was evaluated for the following items. The evaluation results are shown in Table 1.
<Attachment to heat press plate>
The electromagnetic wave shield film is applied so that the surface of the flexible circuit board on which the circuit is formed and the coverlay is attached is in contact with the surface of the electromagnetic wave shield film (SF-PC5000 manufactured by Tatsuta Electric Wire Co., Ltd.) coated with the adhesive. A temporarily fixed test piece was prepared.
Next, the release film and the test piece were superposed so that the release surface of the first release layer of the release film was opposed to the surface of the test piece on the side having the electromagnetic wave shield film. After that, in the press configuration of FIG. 1, a hot press treatment was performed under vacuum conditions at 180 ° C., 2 MPa, vacuuming for 20 seconds, and 3 minutes. The upper heat press plate immediately after pressing was observed, and the presence or absence of sticking of the release film and FPC was confirmed.
◯: Immediately after pressing, the release film and FPC are not attached to the upper heat press plate.
X: Immediately after pressing, the release film and FPC are attached to the upper heat press plate.

<Air remaining>
The electromagnetic wave shield film is applied so that the surface of the flexible circuit board on which the circuit is formed and the coverlay is attached is in contact with the surface of the electromagnetic wave shield film (SF-PC5000 manufactured by Tatsuta Electric Wire Co., Ltd.) coated with the adhesive. A temporarily fixed test piece was prepared.
Next, the release film and the test piece were superposed so that the release surface of the first release layer of the release film was opposed to the surface of the test piece on the side having the electromagnetic wave shield film. After that, in the press configuration of FIG. 1, a hot press treatment was performed under vacuum conditions at 180 ° C., 2 MPa, vacuuming for 20 seconds, and 3 minutes to obtain a molded product. The appearance of the molded product and the release film thus obtained was observed, and the air residue was evaluated based on the following criteria.
◯: There is no air residue on the release film and FPC, and there are no voids or wrinkles on the appearance.
X: There is air residue on the release film and FPC, and voids and wrinkles occur.

<Embedability (adhesive outflow)>
First, a 1 mm square opening was made in a coverlay (CM type) manufactured by Arisawa Mfg. Co., Ltd. Next, a test piece was prepared in which a coverlay having the above-mentioned opening was temporarily fixed so that the surface on the side coated with the adhesive was in contact with the surface of the copper-clad plate for the flexible wiring board. Next, the release film and the test piece are overlapped so that the first release surface of the first release layer in the release film faces the surface of the test piece on the side having the coverlay. After the combination, heat pressing was performed under vacuum conditions at 180 ° C., 2 MPa, vacuuming for 20 seconds, and 3 minutes to obtain a molded product. With respect to the molded product thus obtained, the adhesive coated on the surface of the cover tape exudes from the outer edge of the opening in the opening formed in the cover lay (adhesive exudation). The shape) was observed, and the followability was evaluated based on the following criteria.
◯: The difference in unevenness of the exuded shape of the adhesive was less than 100 μm.
X: The difference in unevenness of the exuded shape of the adhesive was 100 μm or more.

<Slit property>
The release film was slit using a rotating leather blade at a winding tension of 200 N and a line speed of 50 m / min, and a film having a length of 500 M was wound. The cross section of the slit was observed with a microscope, the presence or absence of fluff was observed, and the slit property was evaluated based on the following criteria.
◯: Observe the slit cross section and there is no fluffing.
X: Observe the slit cross section and there is no fluffing.

The release film of the example had good releasability, did not generate wrinkles and did not stick to the heat press plate, and could be suitably used for manufacturing a flexible circuit board.

Claims (15)

With the mesosphere
The first release layer laminated on one surface of the intermediate layer and
Includes a second release layer laminated on the other surface of the mesosphere.
The first release layer contains a first thermoplastic resin and a first inorganic particle.
The average unevenness interval Sm on the outer surface of the first release layer is 100 μm or more and 350 μm or less.
The second release layer contains a second thermoplastic resin and a second inorganic particle.
The ten-point average height roughness Rz of the outer surface of the second release layer is 6.5 μm or more and 15 μm or less.
Release film. The average particle size D ₅₀ of the first inorganic particles is 10 μm or more and 40 μm or less.
The release film according to claim 1, wherein the amount of the first inorganic particles is 10% by mass or more and 30% by mass or less with respect to the entire release layer. The average particle size D ₅₀ of the second inorganic particles is 10 μm or more and 40 μm or less.
The release film according to claim 1, wherein the amount of the second inorganic particles is 10% by mass or more and 30% by mass or less with respect to the entire release layer. The release film according to claim 1, wherein the first inorganic particle is at least one selected from the group consisting of calcium carbonate, zinc oxide, alumina, silica and zeolite. The release film according to claim 1, wherein the second inorganic particle is at least one selected from the group consisting of calcium carbonate, zinc oxide, alumina, silica and zeolite. The release film according to claim 1, wherein the first thermoplastic resin contains a poly4-methyl1-pentene resin. The release film according to claim 1, wherein the second thermoplastic resin contains a poly4-methyl1-pentene resin. The release film according to claim 1, wherein the maximum height roughness Rz of the outer surface of the first release layer is 5 μm or more and 15 μm or less. The release film according to claim 1, wherein the uneven average spacing Sm on the outer surface of the second release layer is 50 μm or more and 400 μm or less. The release film according to claim 1, wherein the first release layer has a thickness of 20 μm or more and 40 μm or less. The release film according to claim 1, wherein the second release layer has a thickness of 20 μm or more and 40 μm or less. The release film according to claim 1, wherein the intermediate layer has a thickness of 30 μm or more and 70 μm or less. A step of arranging the release film according to any one of claims 1 to 12 on an object so that the first release layer is on the object side.
A method for producing a molded product, which comprises a step of heat-pressing the object on which the release film is arranged using a heat-pressed plate. The method for producing a molded product according to claim 13, further comprising a step of arranging a plate material on the second release layer after the step of arranging a release film on an object. The manufacturing method according to claim 13 or 14, wherein the molded product is a flexible circuit board.

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