JP2003053896A - Release film - Google Patents

Abstract

(57) [Problem] To release a mold in each process such as cutting, stacking, and opening pin holes of a release film without reducing the wettability of the surface of a prepreg or a copper foil after hot pressing. Provided is an inexpensive release film that is less likely to be displaced, has excellent workability, and is inexpensive. A release film used in a prepreg press step in the production of a conductor foil laminate, wherein at least one release agent is a mixture of a silicone release agent and a cellulose derivative, and is biaxially stretched. Laminated with polyethylene terephthalate film, 180 ℃, 30at
After a 20 minute press treatment under the condition of m, the film was peeled off, and the wettability of the portion of the film in contact with the release agent coated surface was measured by the method specified in JIS K6768. It has a physical property satisfying the condition of 32 mN / m or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a release film used in a prepreg pressing process for producing a conductor foil laminate, and more specifically, it is suitable for producing a laminated wiring board widely used in electronic devices and the like. The present invention relates to a release film used in.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing a laminated wiring board having a multilayer conductor circuit, a prepreg is laminated on an inner layer material having a conductor circuit on one side or both sides, a conductor foil is arranged on the outermost layer thereof, and heat pressing A common method is to integrate them. In such a method, powdered substances and other foreign substances generated from the prepreg easily enter the conductor foil, which causes local pressure on the conductor foil and may cause dents on the surface of the conductor foil. There is. In order to prevent this problem, a method has been proposed in which a release film made of resin or the like is placed between the conductor foil and the mirror surface plate to relieve the local pressure caused by the foreign matter. The release film is cut into a predetermined size in advance, and the release film is supplied to the laminated wiring board manufacturing process in a stacked state. In the manufacturing process of a laminated wiring board, a conductor foil or prepreg and a release film are laminated and heated and pressed. However, during this lamination, alignment of the conductor foil, prepreg and release film is required. Therefore, the release film supplied to the manufacturing process of the laminated wiring board is generally provided with pin holes at several positions for alignment. The pin holes are not perforated on the release films one by one, but usually, a method of perforating them in a state of being cut and stacked is adopted.

In the manufacturing process of a laminated wiring board, a release film, a prepreg cut into a predetermined size, a copper foil, etc. are laminated and a laminated wiring board is prepared by hot pressing. As such a release film, a film obtained by applying a release agent such as silicone to one or both sides of a polyester film typified by a polyethylene terephthalate film, a fluorine-based film, a polyolefin-based film, or the like has been used. However, in a film in which a release agent such as silicone is applied to one side or both sides of a polyethylene terephthalate film, the component of the release agent at the time of hot pressing at the time of manufacturing the laminated wiring board has a prepreg or a prepreg which is in contact with the release film at the time of hot pressing. Transfer to the surface of copper foil,
There is a problem that the surface wettability of prepreg, copper foil, etc. is deteriorated. When the surface wettability of prepreg or copper foil decreases, when further prepreg or copper foil is laminated to the laminate obtained in that state, the adhesion of the surface to which the release agent has migrated Since there is a concern that it will deteriorate, it requires a step to remove the transferred release agent by polishing the surface of the prepreg or copper foil that was in contact with the release film during hot pressing, and the workability is poor was there.

A conventional polyethylene terephthalate film coated with a release agent such as silicone on one or both sides has good heat resistance and releasability in the hot pressing process during the production of laminated wiring boards and is easy to use. However, when the release film is cut into a predetermined size and stacked in the step before being supplied to the laminating step, the release agent surface is slippery, so the release film slips when stacked, There was also the problem of difficulty. Further, even in the step of forming a pin hole in the release film cutting stack, if the release film is slippery, the position may be displaced during the opening. on the other hand,
There is also a method in which the release film is supplied to the hot pressing step in a roll state without cutting and continuously hot pressed with a roll-to-roll method, but even in this case, the release surface is slippery, so it is wound into a roll shape. There is a problem that the release film is likely to cause winding deviation, and care must be taken in handling the roll, and once the winding deviation occurs, it cannot be applied to the pressing machine in the hot pressing step.

When a fluorine-based film or a polyolefin-based film is used, such a release agent does not cause problems such as poor workability during stacking and misalignment during punching, but the fluorine-based film Since the film itself is expensive, there is a problem that the manufacturing cost becomes high. Further, when the polyolefin film is used, the heat resistance of the polyolefin film itself is poor, and therefore, the film cannot be used at the time of pressing.
There is a problem that it cannot be used in applications where the temperature is 0 ° C or higher.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and does not reduce the wettability of the surface of a prepreg or copper foil after hot pressing, Provided is an inexpensive release film which is less likely to be displaced in the release film in each step such as cutting, stacking, opening of pin holes, and transportation of the release film, has excellent workability. Another object of the present invention is to provide a release film in which winding misalignment is less likely to occur even when handled in a roll state and static electricity is less likely to occur during feeding.

[0007]

[Means for Solving the Problems] The present inventors have investigated the release agent having good surface wettability such as prepreg and copper foil after hot-pressing. When laminating the prepreg, copper foil, and the like, it was examined how much the release agent migrates to reduce the adhesiveness of the prepreg resin. As a result, they have found certain physical properties and additives for realizing them, and have completed the present invention.

That is, the release film of the present invention is used in a prepreg pressing step in the production of a conductor foil laminate, and has a release agent containing a silicone-based release agent applied to at least one surface of a synthetic resin film. A film,
It is characterized in that the release agent on at least one surface is a mixture of a silicone release agent and a cellulose derivative and has physical properties that satisfy the following condition (1). (1) The release agent-coated surface is superposed on the biaxially stretched polyethylene terephthalate film, press-treated for 20 minutes at 180 ° C. and 30 atm, and then the biaxially stretched polyethylene terephthalate film is peeled off. The wettability of the part that was in contact with JIS K67
The wettability of the surface is 32 mN / m or more when measured by the method specified in 68. That is, the inventor of the present invention, if the wettability of the polyethylene terephthalate film surface is 32 mN / m or more after the release agent-coated surface and the biaxially stretched polyethylene terephthalate film are superposed and heated and pressed under predetermined conditions. It was found that other prepregs, copper foils, and the like can be laminated without polishing the laminated plate formed by the heat press treatment, and the invention of the release film using the release agent having such physical properties was made.

In a preferred aspect of the present invention, the release agent on at least one surface has physical properties such that the coefficient of static friction between the treated surfaces of the release agent is in the range of 0.10 to 0.50. However, by satisfying this condition, it is possible to realize a further improvement in that the release films are easy to stack at the time of stacking after cutting the release films, and the release films are less likely to shift when the pin holes are opened. . That is, unless the static friction resistance of the release agent coating surface is increased to a certain extent, when the release films are cut, the release films are likely to be misaligned when they are stacked, and when they are stacked, they collapse.
Even when the pin holes are opened, or when the roll is fed to the hot press process in the roll state, winding misalignment is likely to occur, but if the static friction coefficient is too high, the release films may be separated from the stacked release films. It becomes difficult to take when taking one,
Workability in the hot pressing process during manufacturing of the laminated wiring board becomes poor. Therefore, the optimum range of the coefficient of static friction between the surfaces coated with the release agent has been found. Further, within the range of this friction coefficient, when used in a roll state, it is possible to suppress the generation of static electricity due to friction during roll feeding,
It is possible to prevent the dust in the work environment from being attracted by static electricity and the entry of foreign matter into the laminated wiring board. Therefore, the workability in the cutting process and the hot pressing process is remarkably improved by using the one having the static friction resistance of the release agent coating surface of 0.10 or more and 0.50 or less.

The release film according to claim 3 of the present invention is
A feature that a silicone-based release agent is applied to one surface of a synthetic resin film, and a release agent that is a mixture of a silicone-based release agent and ethyl cellulose and that satisfies the physical properties of (1) above is applied to the other surface. And As the synthetic resin film, a polyester film is preferable from the viewpoint of cost and heat resistance of the product, and a film obtained by coating a release agent such as silicone on one side or both sides of the film is preferable, but the release film on both sides is preferable. When applying the agent, the release agent having improved surface wettability, which is the effect of the present invention, may be applied on one surface, and the surface not requiring improvement of wettability has releasability,
A conventional silicone-based release agent having excellent heat resistance may be used.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below. The release film of the present invention is one in which a release agent is applied to at least one surface of a synthetic resin film as a base material to provide a release agent layer. As the film used as the base material in the release film of the present invention, among synthetic resin films, a film having appropriate elasticity at the time of hot pressing and capable of withstanding heating is used. The synthetic resin film as the base material is not particularly limited as long as it satisfies the above points, and specifically, a polyolefin film, a polyester film, a polyamide film, a polyimide film, a polyphenylene film. Sulfide film, polyetheretherketone film,
Examples thereof include vinyl chloride film, vinylidene chloride film, polyvinyl alcohol film, and fluorine film. A polyester film or a polyamide film is preferable from the viewpoint of heat resistance and cost, and a polyester resin film is more preferable from the viewpoint of dimensional stability when absorbing moisture. From the viewpoint of heat resistance, aromatic polyester is preferable as the polyester resin film. Specific examples of those preferably used in the present invention include polyethylene terephthalate film, polybutylene terephthalate film, polyethylene isophthalate film, polyethylene naphthalate film, polyethylene adipate film, polyethylene liquid crystal polymer film, polyester thermosetting resin. Examples thereof include resins and mixed resin films of the above resins. Among them, polyethylene terephthalate film and polyethylene naphthalate film are particularly preferable from the viewpoint of heat resistance and cost.

As the synthetic resin film, a film formed by depositing the synthetic resin by a known method may be used. Also,
It may be unstretched, uniaxially stretched or biaxially stretched, but a biaxially stretched film is preferable from the viewpoint of heat resistance. The thickness of the film is not particularly limited, but is preferably about 25 to 125 μm from the viewpoint of heat resistance, mechanical strength, cost and the like. The film may be transparent, semi-transparent, or colored, and may be coated with an antistatic agent if necessary. Further, those whose surface has been subjected to corona treatment, coating with an easily adhesive agent, or matting treatment may be used.

The release film of the present invention is obtained by applying a release agent to one or both sides of the synthetic resin film. If the release film is applied to one side, the release agent is applied to both sides. The release agent on at least one surface is a release agent composed of a mixture of a silicone-based release agent and a cellulose derivative (hereinafter, appropriately referred to as a specific silicone-based release agent). By mixing a cellulose derivative with the silicone-based release agent, it is possible to suppress the migration of silicone and the slipperiness of the release agent-coated surface, which are problems in the silicone-based release agent.

First, preferable physical properties of the specific silicone type release agent will be described. A specific guide for the degree of release agent transfer is to wet the surface of the polyethylene terephthalate film after the release agent application surface and the biaxially stretched polyethylene terephthalate film are superposed and pressed for 20 minutes at 180 ° C. and 30 atm. It can be preferably used when the property is 32 mN / cm or more. If the wettability of the polyethylene terephthalate film surface is 32 mN / m or more,
Without polishing the laminated plate made by hot pressing,
Other prepregs, copper foil, etc. can be laminated. When the wettability of the polyethylene terephthalate film surface after the press treatment under the above conditions is less than 32 mN / m, the surface wettability of the laminated plate obtained by the heat press treatment deteriorates, and other prepregs, copper foils, etc. When these are laminated, the adhesion may be reduced. Here, the upper limit of the surface wettability is not particularly limited, but in this test method, the upper limit is the surface wettability of the polyethylene terephthalate film before the press treatment.

Further, as a concrete measure of the slipperiness, it is desirable that the coefficient of static friction between the surfaces coated with the release agent is in the range of 0.10 to 0.50. If the coefficient of static friction is less than 0.10, the release films are likely to collapse when they are stacked after cutting the release films, and the release films are likely to shift even when a pin hole is opened, resulting in the problem that the holes shift. Occur. Further, when the roll film is supplied to the hot pressing step, there is a problem that the release film is likely to be misaligned. On the other hand, when the coefficient of static friction exceeds 0.50, it becomes difficult to remove one release film from the stacked release films, and the workability in the hot pressing step during the production of the laminated wiring board deteriorates. Further, in the case of being supplied to the hot pressing step in a roll state, there is a problem that static electricity is easily generated when the release film is fed out, and dust or dirt in the work environment is easily absorbed.

Next, the composition of the specific silicone type release agent will be described. This specific silicone type release agent is characterized by being a mixture of a general silicone type release agent and a cellulose derivative. Silicone release agents
It is used because of its excellent heat resistance and releasability, and any known silicone-based releasing agent can be used in the present invention. As the silicone type release agent, any of solventless type, emulsion type and solvent type silicone release agents may be used depending on the product form. Further, in terms of the reaction mode, any of a heat reaction type (heat addition reaction type, heat condensation reaction type), an ultraviolet ray reaction type, an electron beam reaction type, and a heat and ultraviolet ray combined reaction type silicone release agent can be used. . However, when the polyester film has release agent layers on both sides, a blocking phenomenon occurs when a heat condensation reaction type is used, and therefore other silicone release agents are preferable. From the viewpoint of easy mixing with the cellulose derivative, the solvent type and the solventless type are preferable in that order, and the emulsion type is not so suitable.

Specific examples of commercially available silicone release agents applicable to the present invention include those manufactured by Shin-Etsu Chemical Co., Ltd.
Product name) KS-770, KS-776A, KS-83
8, KS-856, KS-770L, KS-776L,
KS-847, KS-705F, KS-709, KS-
779H, KS-837, KS-778, KS-84
3, KS-835, KS-775, KS-830, KS
-830E, KS-839, KS-774, KS-84
1, KS-719, KS-723A / B, KS-88
3, KS-718, KS-708A, KNS-303,
KNS-305, KNS-320, KNS-319, K
NS-316, KNS-310, KNS-5003A /
B, KNS-5100, KNS-5300, KM-76
6, KM-768, KM-764, KM-765 and the like. Toray Dow Corning Silicone release agents include SRX211, SD7220, SRX34.
5, SRX357, SD7227, SRX370, SD
7223, SD7226, SD7229, SYL-OF
F23, SRX244, SRX290, SYL-OFF
22, SM7270, SM7273, BY24-40
3, BY24-405, BY24-407, SP724
8, BY24-413, SP-7259, BY24-4
11, SP7268, BY24-420, BY24-4
12, BY24-416, LTC series and the like.

GE Toshiba Silicone release agents include
TPR6500, TPR6501, UV9300, UV
9315, UV9425, XS56-A2775, XS
56-A2982, UV9430, TPR6600, X
S56-B1794, SL6100, TPR6604,
SM3000, SM3200, SM3030, TPR6
705, TPR6722, TPR6721, TPR67
02, TPR6700, XS56-A8012, TPR
6701, TPR6707, TPR6708, TPR6
710, TPR6712, XS56-A3969, X5
6-A5730, XSR7029, XS56-A3-7
5, YSR3022 and the like. As a mold release agent made by Dow Corning Asia, DK Q3-202, 20
3, 210, 240, 3050 and the like.

The present invention is characterized in that the release agent on at least one side of the polyester film is a release agent composed of a mixture of the above silicone release agent and a cellulose derivative. The type of cellulose derivative is not particularly limited, and the type and degree of polymerization may be arbitrarily selected. Specific examples include carboxymethylcellulose, methylcellulose, ethylcellulose, ethylhydroxycellulose, aminoethylcellulose and the like. Ethyl cellulose is more preferable because it is soluble in an organic solvent. The mixing ratio of the silicone-based release agent and the cellulose derivative is 180 ° C., 3 ° C. when the release agent-coated surface and the biaxially stretched polyethylene terephthalate film are superposed.
The wettability of the polyethylene terephthalate film surface is 32 m after pressing for 20 minutes under the condition of 0 atm.
If it is N / m or more, it is not particularly limited,
Usually, the mixing ratio of silicone type release agent / cellulose derivative is about 1/100 to 100/1 in terms of solid content.
This mixing ratio is appropriately selected according to the characteristics of the silicone-based release agent and the cellulose derivative used in combination, while taking the above physical properties into consideration. Specifically, as the mixing ratio of the cellulose derivative is improved, the transfer suppressing effect of the release agent is improved, but if it is too large, the releasability tends to decrease. For example, in the case of a mixture of general-purpose solvent-type addition reaction type silicone and ethyl cellulose as a silicone-based release agent, the mixing ratio of the two is 1 in terms of solid content.
The range of 00/30 to 100/200 is preferable.

The cellulose derivative is usually in the form of a solid powder, but when it is used in the present invention, it is used by dissolving it in an organic solvent such as toluene when preparing the mixture, or It is generally used by dissolving it in a solvent type silicone release agent. If the cellulose derivative is used in the form of a solid powder, uniform mixing becomes difficult, and it becomes difficult to suppress migration and slipperiness of the silicone release agent, which is a problem in the silicone release agent.

The release film may be a polyester film having a release treatment on only one side or a release treatment on both sides.
In the case of a release film which is sandwiched between the multilayer plates when hot-pressed by a single pressing process, a release treatment is required on both sides, so in this case a double-sided release film is preferable. In the case of a conventional double-sided release film, it may be a problem that it is difficult to distinguish between the front and back when cutting, but one side of the polyester film is coated with a silicone-based release agent, and the other side is coated with a silicone-based and ethyl cellulose film. By using the release film coated with the specific silicone-based release agent of the present invention composed of a mixture, there is also an advantage that the front and back can be easily distinguished from each other due to the difference in slipperiness and wettability of the surface. In particular, if it is used in a usage method in which the migration of a silicone-based release agent does not cause a problem, for example, a method in which a surface polishing step is performed after manufacturing a laminated wiring board, a general silicone-based release agent is applied on one side. However, a release film having the opposite surface coated with a release agent composed of a mixture of the silicone release agent of the present invention and a cellulose derivative is desirable. Here, as a general silicone-based release agent, the same as those described as the release agent for adjusting the specific silicone-based release agent can be used.

Further, when the polyester film has release agent layers on both sides, if the release agent comprising a mixture of the silicone type release agent and the cellulose derivative according to the present invention is used on at least one side, the opposite side is used. Not only the silicone-based release agent, but also other known release agents (other than silicone-based) can be used. As the release agent other than the silicone-based release agent that can be used here, specifically, a fluorine-based release agent, a long-chain alkyl group-containing release agent, an alkyd resin-based release agent, an aminoalkyd resin-based release agent, organic Examples of the release agent include a copolymer or a mixture of a polymer and silicone, a shellac resin, and a polyolefin-based release agent.
From the viewpoint of heat resistance, a general silicone release agent is often used.

The release agent is applied by a known method such as gravure coating, Meyer bar coating, air knife coating, etc., and then a known release coating method such as heat treatment, ultraviolet ray irradiation, electron beam irradiation or the like. A method of drying and curing by a method to form a release agent layer can be applied. In order to improve the adhesion between the base material and the release agent when applying the release agent, the wettability of the base material surface can be improved by applying corona discharge treatment to the base material surface or applying an easy-adhesion coating agent to the surface. May be improved, or an adhesion improver such as a silane coupling agent may be internally added to the release agent. The thickness of the release agent layer is not particularly limited as long as the required release effect is obtained, but it is preferably about 0.02 to 1.0 μm from the viewpoint of obtaining an appropriate release property.

The release film of the present invention thus obtained has less migration of the release agent, and the release film is cut,
Easy to stack when stacked, and the release film does not easily slip when pin holes are opened. Also, it is very easy to take the release films one by one from the release film stack, and an inexpensive release film is obtained, and winding misalignment is less likely to occur even when handled in a roll state. In addition, the release film has less static electricity generated when it is fed out. further,
When the polyester film is used as a substrate, a release film having good heat resistance can be obtained in addition to the advantages described above.

[0025]

EXAMPLES The present invention will be further described below with reference to examples. [Example 1] Silicone-based release agent Toray Dow Corning Silicone addition reaction type release agent S having a solid content of 30%
RX-211 (catalyst SRX-212 to SRX-211
Addition of 1 part to 100 parts by weight) and 10% of ethyl cellulose (Etocel STD-100 manufactured by Dow Chemical)
1/2 weight ratio of toluene solution (solid content ratio: 100/6
7) are mixed and diluted with a toluene solvent to prepare a release agent solution. Biaxially stretched polyethylene terephthalate film with a thickness of 25 μm (Toyobo Ester E50
00) on one side with 0.2 parts solids of this release agent solution.
After coating so as to be g / m ² , it was dried and cured by heat treatment for 30 seconds in a hot air circulation type oven at 140 ° C. to form a specific silicone type release agent layer on one surface. Thereafter, the back surface of the polyethylene terephthalate film of this one-sided specific silicone-based release agent-treated product was also treated with the specific silicone-based release agent in the same manner as above to obtain a release film A subjected to double-sided release treatment. .

[Example 2] The mixing ratio of the silicone type release agent used in Example 1 and the 10% ethylcellulose toluene solution was 1/4 by weight (solid content ratio: 100/13).
A release film B subjected to release treatment on both sides was obtained in the same manner as in Example 1 except that the mixture was mixed so as to be 3). Example 3 Used in Example 1 on the back surface of the polyethylene terephthalate film of the one-sided specific silicone-based release agent-treated product coated with the release agent composed of the mixture of the silicone-based release agent and ethyl cellulose used in Example 1 above. A release film C subjected to double-sided release treatment was obtained in the same manner as in Example 1 except that only the silicone-based release agent was applied so that the solid content was 0.2 g / m ² . [Example 4] A release agent was applied to the back surface of a polyethylene terephthalate film of a single-sided specific silicone release agent-treated product coated with the release agent composed of a mixture of the silicone release agent and ethyl cellulose used in Example 1 above. A release film D subjected to a single-sided release treatment was obtained in the same manner as in Example 1 except that it was not used.

[Comparative Example 1] [Comparative Example 1] Except that only the silicone-based release agent used in Example 1 was applied so as to have a solid content of 0.2 g / m ² and treated with the silicone-based release agent. In the same manner as in Example 1, a release film E subjected to release treatment on both sides was obtained. [Comparative Example 2] A release film F subjected to release treatment on both sides in the same manner as in Example 1 except that only the ethyl cellulose used in Example 1 was applied so as to have a solid content of 0.2 g / m ^2. Got

[Evaluation Method of Release Film] The transferability of the release agent of the obtained sample, the coefficient of static friction of the surface coated with the release agent, the release property, the stackability of cut products, and the workability in the hot press process are as follows. Evaluation was performed by the method described in. The results are shown in Table 1 below. (1. Release agent migration property) A release agent-coated surface and a 25 μm-thick biaxially stretched polyethylene terephthalate film are superposed and pressed for 20 minutes at 180 ° C. and 30 atm, and then a biaxially stretched polyethylene terephthalate film. Is peeled off, and the wettability of the portion of the film that is in contact with the release agent coating surface is measured by the method specified in JIS K6768. The higher the surface wettability of the biaxially stretched polyethylene terephthalate film, the better the wettability.

(2. Static friction coefficient of release agent coated surface) JI
The coefficient of static friction between the release agent-coated surfaces (same release surfaces) is measured by the method specified in SK-7125. (For Example 3, the surface of the release agent coated with a mixture of silicone release agent and ethyl cellulose was measured.) (3.2 Preparation of Layer Board (Evaluation of Releasability)) Copper foil / prepreg / copper foil was laminated. The product is sandwiched between two release films obtained in Examples and Comparative Examples, and this laminated product is further sandwiched between two stainless plates. With a press machine at 180 ° C,
A pressing process is performed for 30 minutes at a pressing pressure of 50 kg / cm ² to cure the prepreg resin to form a two-layer board. After cooling, it is observed whether the release film can be easily peeled from the stainless plate and the two-layer plate.

(4. Stackability of cut products) The obtained sample is cut into a size of 30 cm square. Then, after stacking 100 sheets of the cut product, it is visually observed whether the stack product is misaligned when the stacked product is held in a hand and installed in a puncher. (5. Workability in hot press process)
Cut to a size of 0 cm square. Then, cut the product 10
After stacking 0 sheets, hold the stacked product in a hand and set it in a hole puncher, and make a hole having a diameter of 2 mm at each corner of the sample. Then, the ease of taking the release films one by one from the stacked product by hand is measured.

[0031]

[Table 1]

From the results shown in Table 1, the release films of Examples 1 to 4 of the present invention have good release agent transferability, releasability, stackability of cut products, and workability in the hot pressing process. On the other hand, the release film of Comparative Example 1 had good release properties, but there was migration of the release agent, which greatly reduced the surface wettability of the polyester film fitted to the release surface. It was Moreover, a deviation occurred when stacking the cut products. For this reason, great effort was required to align the positions in the drilling process.
Further, the release film of Comparative Example 2 had a good stacking property of the cut product, but the release property was poor, and the resin of the prepreg protruding during pressing did not peel off. Further, when the release films were taken one by one from the stacked product, the release films hardly slipped, so that they could not be easily removed. As a result, workability in the hot pressing process is deteriorated.

[0033]

EFFECTS OF THE INVENTION The release film of the present invention is used in various steps such as cutting, stacking, opening pin holes, etc. of the release film without lowering the wettability of the surface of the prepreg or copper foil after hot pressing. In, the release film is difficult to shift,
The workability is excellent, the cost is low, the winding deviation is unlikely to occur even when handled in a roll state, and the static electricity at the time of feeding is small.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Motoki Kiritani             1-4-16 Nibashi Bakurocho, Chuo-ku, Tokyo Wisteria             Mori Kogyo Co., Ltd. F-term (reference) 4F100 AJ04B AJ04C AK01A AK42A                       AK52B AK52C AL05B AL05C                       BA02 BA03 BA06 BA10B                       BA10C BA15 EH46 EH46B                       EH46C EJ38A EJ42 GB43                       JK16B JK16C JL02 JL05                       JL14B JL14C YY00B YY00C                 5E346 AA06 AA12 AA15 AA22 AA32                       AA51 CC02 CC08 CC31 DD02                       DD12 EE09 EE13 EE18 GG28                       HH31

Claims (3)

[Claims] 1. A release film which is used in a prepreg pressing step at the time of manufacturing a conductor foil laminate, in which a release agent containing a silicone release agent is applied to at least one side of a synthetic resin film, A release film, wherein the release agent is a mixture of a silicone-based release agent and a cellulose derivative, and has physical properties that satisfy the following condition (1). (1) The release agent-coated surface is superposed on the biaxially stretched polyethylene terephthalate film, press-treated for 20 minutes at 180 ° C. and 30 atm, and then the biaxially stretched polyethylene terephthalate film is peeled off. The wettability of the part that was in contact with JIS K67
The wettability of the surface is 32 mN / m or more when measured by the method specified in 68. 2. The release agent according to claim 1, wherein the release agent on at least one surface has physical properties such that the coefficient of static friction between the treated surfaces of the release agent is in the range of 0.10 to 0.50. Mold film. 3. A release agent which is a mixture of a silicone release agent and ethyl cellulose and which has one surface of a synthetic resin film coated with a silicone release agent and which has the physical properties of the above (1). The release film according to claim 1 or 2, which is applied.