JP2006321113A - Multi-layer release film - Google Patents

Abstract

PROBLEM TO BE SOLVED: There is no delamination at the time of mold release, and it is excellent in heat resistance, mold release property, followability to substrate surface, generation of voids in hot press molding, flow of adhesive and at the film end face Provided is a multilayer release film capable of suppressing the seepage of the cushion layer resin.
A release film comprising at least a release layer made of a thermoplastic saturated polyester resin having a melting point of 200 ° C. or higher measured using a differential scanning calorimeter, and a cushion layer, wherein the cushion layer comprises: The melting point measured using a differential scanning calorimeter is 70 to 130 ° C., and contains as a main component linear low density polyethylene obtained by copolymerizing ethylene and an α-olefin having 6 or more carbon atoms. Multi-layer release film.
[Selection figure] None

Description

The present invention does not cause delamination at the time of mold release, and is excellent in heat resistance, mold release property, followability to the substrate surface, generation of voids during hot press molding, flow of adhesive, and film end face. The present invention relates to a multilayer release film capable of suppressing the seepage of the cushion layer resin.

Conventionally, a release film has been used when a copper-clad laminate or a copper foil is hot-pressed through a prepreg or a heat-resistant film in a manufacturing process of a printed wiring board, a flexible printed wiring board, a multilayer printed wiring board, or the like. ing. In addition, in the manufacturing process of the flexible printed circuit board, the cover lay film and the hot press plate are also bonded to the flexible printed circuit board body on which the electric circuit is formed by hot press bonding the cover lay film with a thermosetting adhesive. In order to prevent this, release films are widely used.

In recent years, for release films, in addition to functions such as heat resistance that can withstand hot press molding and releasability for printed wiring boards and hot press plates, environmental issues and increased social demands for safety have led to disposal. The ease of processing has been demanded. In addition, non-contamination for copper circuits has become important in order to improve product yield during hot press molding.

Conventionally, as a release film, a fluorine-based film, a silicone-coated polyethylene terephthalate film, a polymethylpentene film, a polypropylene film and the like as disclosed in Patent Document 1 and Patent Document 2 have been used.

However, the fluorine-based film is excellent in heat resistance, releasability, and non-contamination, but is expensive and has a problem that it is difficult to burn when incinerated in the disposal process and generates toxic gas. . On the other hand, the silicone-coated polyethylene terephthalate film and the polymethylpentene film have a problem that the silicone or the low molecular weight component in the constituent component may be transferred to cause contamination of the printed wiring board, particularly the copper circuit, thereby impairing the quality. . In addition, the polypropylene film has a problem that it has poor heat resistance and insufficient releasability.

Also, in the hot press molding process, it is necessary for the release film to follow the unevenness of the substrate surface, but since conventional release films are inferior in conformity to shape, they are flexible during hot press molding. There have been problems such as voids occurring in the printed circuit board, and the adhesive of the coverlay film oozes out from the electrode part, which impedes the plating process of the electrode part.

Moreover, in the conventional multilayer release film, low density polyethylene (LDPE), polypropylene, etc. were mainly used as resin used for an intermediate | middle layer. However, the release multilayer film using low-density polyethylene or polypropylene as the resin for the intermediate layer has poor adhesiveness between the release layer and the intermediate layer, and the release layer and the intermediate layer are separated when released from the flexible printed circuit board. Peeled off, and the productivity of the flexible printed circuit board was greatly reduced.
Therefore, there is no delamination when releasing from a flexible printed circuit board, etc., and it has excellent heat resistance, release properties, and followability to the substrate surface, as well as void generation and adhesive flow-out during hot press molding. In addition, there has been a demand for a release film capable of suppressing the seepage of the resin at the film end face.
JP-A-2-175247 Japanese Patent Laid-Open No. 5-283862

The present invention does not cause delamination at the time of mold release, and is excellent in heat resistance, mold release property, followability to the substrate surface, generation of voids during hot press molding, flow of adhesive, and film end face. An object of the present invention is to provide a multilayer release film capable of suppressing the seepage of the cushion layer resin.

The present invention is a release film having at least a release layer composed of a thermoplastic saturated polyester resin having a melting point of 200 ° C. or higher measured using a differential scanning calorimeter, and the cushion layer, The melting point measured using a differential scanning calorimeter is 70 to 130 ° C., and contains as a main component linear low density polyethylene obtained by copolymerizing ethylene and an α-olefin having 6 or more carbon atoms. It is a multilayer release film.
The present invention is described in detail below.

As a result of intensive studies, the present inventors have used a thermoplastic saturated polyester resin having a predetermined melting point for the release layer of the multilayer release film, and has a predetermined melting point for the cushion layer, and ethylene and 6 or more carbon atoms. Multi-layer release with excellent heat resistance, releasability, and non-contamination by using linear low-density polyethylene copolymerized with α-olefin of the above, without causing delamination during release The present invention was completed by finding that it can be used as a film, and that it is possible to solve the problems of void generation, adhesive flow-out and cushion layer resin seepage at the film end face during hot press molding. I came to let you.

The multilayer release film of this invention has a release layer which consists of a thermoplastic saturated polyester resin whose melting | fusing point measured using the differential scanning calorimeter is 200 degreeC or more.
By using such a resin for the release layer, the thermoplastic saturated polyester resin interacts with a linear low-density polyethylene (hereinafter also simply referred to as LLDPE) of the cushion layer described later, thereby releasing the release layer. And the cushion layer can be firmly bonded. Further, by using a resin having a high melting point for the mold release layer, the mold release layer does not melt even in the hot press molding process and has mold release properties, and the mold release layer is destroyed. Can be prevented.
As the differential scanning calorimeter, for example, DSC 2920 (manufactured by TA Instruments) or the like can be used.

The lower limit of the melting point of the thermoplastic saturated polyester resin measured using a differential scanning calorimeter is 200 ° C. Since the hot press molding step is usually performed at less than 200 ° C., if the melting point is less than 200 ° C., the release layer melts in the hot press molding step, and the heat resistance of the multilayer release film is lowered. A preferred lower limit is 220 ° C.

As the thermoplastic saturated polyester resin having a melting point of 200 ° C. or higher measured using the differential scanning calorimeter, aromatic dicarboxylic acid and non-aromatic are used because of strong interaction with LLDPE constituting the cushion layer. A polyester resin obtained by reacting with alkylene glycol is preferred.
Examples of the aromatic dicarboxylic acid include terephthalic acid, and examples of the non-aromatic alkylene glycol include ethylene glycol and butylene glycol.

Examples of the polyester resin obtained by reacting the aromatic dicarboxylic acid with a non-aromatic alkylene glycol include polyethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate. These may be used alone or in combination of two or more. Of these, polybutylene terephthalate is preferred.
Moreover, it is preferable that the said release layer contains the polyester-polyether copolymer which has a polyether component in addition to the said thermoplastic saturated polyester resin. By containing the said polyester-polyether copolymer, interaction with LLDPE which comprises a cushion layer becomes still stronger, and the adhesiveness of a mold release layer and a cushion layer can be improved.
Examples of such a polyester-polyether copolymer include butanediol terephthalate polytetramethylene glycol copolymer.

The release layer may contain a stabilizer. Examples of the stabilizer include 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, 3,9-bis {2- [ 3- (3-t-butyl-4-hydroxy-5-methylphenyl) -propionyloxy] -1,1-dimethylethyl} -2,4,8,10-tetraoxaspiro [5,5] undecane, etc. Hindered phenolic antioxidants; tris (2,4-di-t-butylphenyl) phosphite, trilauryl phosphite, 2-t-butyl-α- (3-t-butyl-4-hydroxyphenyl) -P-cumenylbis (p-nonylphenyl) phosphite, dimyristyl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, pentaerystyryltetrakis ( - laurylthiopropionate), thermal stabilizers such as ditridecyl 3,3'-thiodipropionate and the like.

The said release layer may contain additives, such as a fiber, an inorganic filler, a flame retardant, an ultraviolet absorber, an antistatic agent, an inorganic substance, a higher fatty acid salt, in the range which does not impair the effect of this invention. Examples of the fibers include glass fibers, carbon fibers, boron fibers, silicon carbide fibers, alumina fibers, amorphous fibers, inorganic fibers such as silicon / titanium / carbon fibers, and organic fibers such as aramid fibers.

Examples of the inorganic filler include calcium carbonate, titanium oxide, mica, talc, and the like.
Examples of the flame retardant include hexabromocyclododecane, tris- (2,3-dichloropropyl) phosphate, pentabromophenyl allyl ether, and the like.

Examples of the ultraviolet absorber include pt-butylphenyl salicylate, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone, 2,4,5-trihydroxybutyrophenone, and the like. Is mentioned. Examples of the antistatic agent include N, N-bis (hydroxyethyl) alkylamine, alkylallyl sulfonate, and alkyl sulfonate.

Examples of the inorganic material include barium sulfate, alumina, and silicon oxide.
Examples of the higher fatty acid salt include sodium stearate, barium stearate, sodium palmitate and the like.

The release layer may contain a thermoplastic resin and a rubber component in order to modify its properties. Examples of the thermoplastic resin include polyolefin, modified polyolefin, polystyrene, polyvinyl chloride, polyamide, polycarbonate, polysulfone, polyester, and the like. Examples of the rubber component include natural rubber, styrene-butadiene copolymer, polybutadiene, polyisoprene, acrylonitrile-butadiene copolymer, ethylene-propylene copolymer (EPM, EPDM), polychloroprene, butyl rubber, and acrylic rubber. And silicon rubber, urethane rubber, olefin thermoplastic elastomer, styrene thermoplastic elastomer, vinyl chloride thermoplastic elastomer, ester thermoplastic elastomer, amide thermoplastic elastomer, and the like.

The release layer may contain an inorganic compound having a large aspect ratio. By including an inorganic compound having a large aspect ratio, the resulting multilayer release film of the present invention has improved release properties at high temperatures, and additives and low molecular weight substances contained in the film bleed out to the film surface. It can be suppressed, and the cleanliness at the time of hot press molding is improved.
Examples of the inorganic compound having a large aspect ratio include layered silicates such as clay; layered double hydrates such as hydrotalcite.

A preferable lower limit of the thickness of the release layer is 5 μm, and a preferable upper limit is 30 μm. If the thickness is less than 5 μm, the thickness is too thin and the strength of the release layer is impaired, so that the release layer may be destroyed in the hot press molding process or the multilayer release film peeling process. If it exceeds 30 μm, the stiffness of the multilayer release film becomes too strong and the flexibility is impaired, so that the shape followability may be lowered. A more preferable lower limit is 10 μm, and a more preferable upper limit is 20 μm.

The surface of the release layer preferably has smoothness, but may have been provided with slip properties, anti-blocking properties, etc. necessary for handling, and at least for the purpose of air escape during hot press molding. An appropriate embossed pattern may be provided on one side.

The release layer may be subjected to heat treatment or friction treatment in order to improve heat resistance, dimensional stability, and release properties.
Although it does not specifically limit as the method of the said heat processing, For example, the method of passing between the rolls heated to the fixed process temperature, the heating with a heater, etc. are preferable.
The temperature of the heat treatment is not particularly limited as long as it is not lower than the glass transition temperature and not higher than the melting point of the resin constituting the release layer, but a preferable lower limit is 120 ° C. and a preferable upper limit is 200 ° C. When the temperature is lower than 120 ° C., the effect of improving the releasability by heat treatment may be hardly obtained. When the temperature exceeds 200 ° C., the release layer is likely to be deformed during the heat treatment and may not be manufactured. A more preferred lower limit is 170 ° C., and a more preferred upper limit is 190 ° C.

The friction treatment method is not particularly limited, and examples thereof include a method of rubbing the surface of the release layer using a cloth such as a metal roll or gauze, a brush, or the like.

The multilayer laminated film of the present invention has a melting point of 70 to 130 ° C. measured using a differential scanning calorimeter, and is a linear low density obtained by copolymerizing ethylene and an α-olefin having 6 or more carbon atoms. It has a cushion layer containing polyethylene as a main component.

The LLDPE has a lower limit of melting point of 70 ° C. and an upper limit of 130 ° C. measured using a differential scanning calorimeter. By using LLDPE having a melting point within the above range for the cushion layer, the cushion layer starts to soften near the temperature at which the adhesive starts to melt, and improves the followability to the irregularities on the surface of the flexible printed circuit board, It is possible to prevent the adhesive from flowing out. If it is less than 70 ° C., the function of the cushion layer for uniformly applying the pressing pressure to the flexible printed circuit board in the hot press molding process cannot be performed sufficiently, and the ambient temperature during storage of the film is 50 depending on the situation. Although it may be ˜60 ° C., in that case, the cushion layer resin may melt and ooze out depending on the ambient temperature and cause blocking. When the temperature exceeds 130 ° C., the cushion layer is not sufficiently softened in a temperature range where the adhesive melts, and a problem of the adhesive flowing out occurs. A preferred lower limit is 80 ° C and a preferred upper limit is 100 ° C.

The LLDPE is obtained by copolymerizing ethylene and an α-olefin having 6 or more carbon atoms. Since the LLDPE obtained by copolymerizing ethylene and an α-olefin having 6 or more carbon atoms has an alkylene group in the side chain, the above-mentioned alkylene group and the thermoplastic saturated polyester constituting the release layer. When the alkylene glycol part, which is an amorphous part of the resin, is entangled in a molten state and interacts, it is possible to exhibit excellent interlayer adhesion. When the number of carbon atoms of the α-olefin is less than 6, the side chain alkylene group becomes short, and the interaction with the thermoplastic saturated polyester resin constituting the release layer becomes insufficient. Adhesiveness with the cushion layer decreases. Preferably, it has 8 or more carbon atoms.

The α-olefin is not particularly limited, and for example, a compound represented by the following formula (1) can be used. Specifically, for example, 1-hexene, 1-octene, 1-decene, 1-dodecene 1-tetradecene, 1-hexadecene, 1-octadecene and the like.

なお、ｎは３以上の整数を表す。

Note that n represents an integer of 3 or more.

The cushion layer preferably further contains less than 25% by weight of a thermoplastic saturated polyester resin having a melting point of 200 ° C. or higher measured using a differential scanning calorimeter.
By containing such a resin, the affinity between the release layer and the cushion layer is further improved and the interlayer adhesion is enhanced, so that delamination can be more reliably prevented. In particular, it is more preferable to contain the same resin as that used in the release layer from the viewpoint of improving affinity.
If it is 25% by weight or more, the melting point of the cushion layer rises, and the cushion layer is not sufficiently softened in the temperature range where the adhesive melts, which may cause a problem of the adhesive flowing out.

Further, the cushion layer may contain additives such as fibers, inorganic fillers, flame retardants, ultraviolet absorbers, antistatic agents, inorganic substances, higher fatty acid salts, etc., as in the case of the release layer. .

The preferable lower limit of the thickness of the cushion layer is 30 μm, and the preferable upper limit is 150 μm. When the thickness is less than 30 μm, the thickness is too thin, and when the resin constituting the cushion layer is softened during hot press molding, a portion where the cushion layer does not exist partially occurs, and the press pressure is uniformly applied to the flexible printed circuit board. May not be able to load. If it exceeds 150 μm, the stiffness of the multilayer release film becomes too strong and the flexibility is impaired, so that the shape followability may be lowered. Furthermore, since it is thicker than necessary, the excess part may ooze out from the end face of the film, resulting in a problem. A more preferable lower limit is 60 μm, and a more preferable upper limit is 100 μm.

In the multilayer release film of the present invention, a preferred layer thickness ratio between the release layer and the cushion layer is in the range of 1: 2 to 1:10. When the cushion layer is thinner than 1: 2, the press stress transmission force of the cushion layer becomes smaller than the stiffness of the release layer, and the shape followability of the multilayer release film may be impaired. When the cushion layer is thicker than 1:10, the excess strength oozes out from the end surface of the film because the thickness of the release layer is thicker than the thickness required for the press stress transmission force of the cushion layer. It can be a problem. Moreover, flexibility may be impaired, and handling properties may be reduced. Further, the manufacturing cost increases. A more preferable range is 1: 3 to 1: 8.

The preferable lower limit of the total thickness of the multilayer release film of the present invention is 50 μm, and the upper limit is 200 μm. When it is less than 50 μm, the strength of the multilayer release film is insufficient, and when it exceeds 200 μm, flexibility is impaired and handling properties are deteriorated. In addition, the manufacturing cost increases.

The multilayer release film of the present invention preferably has a dimensional change rate of 1.5% or less when pressed at 170 ° C. with a load of 3 MPa for 60 minutes. If it exceeds 1.5%, the circuit pattern may be damaged during hot press molding. More preferably, it is 1.0% or less. Furthermore, it is preferable that the dimensional change rate in the width direction (hereinafter referred to as TD) and the length direction (hereinafter referred to as MD) of the film is in the same direction and approximately the same. When the vertical and horizontal dimensional changes such that one (for example, MD) contracts and the other (for example, TD) expands, the circuit pattern may be damaged during hot press molding.

The method for producing the multilayer release film of the present invention is not particularly limited. For example, a water-cooled or air-cooled coextrusion inflation method, a method of forming a film by a coextrusion T-die method, and a film to be a release layer were produced. Thereafter, a method of laminating a cushion layer on this film by an extrusion lamination method, a method of dry lamination of a film to be a release layer and a film to be a cushion layer, a solvent casting method, a hot press molding method and the like can be mentioned. Especially, the method of forming into a film by the coextrusion T die method is suitable from the point which is excellent in the thickness control of each layer.

In the solvent casting method, for example, after the anchor layer is undercoated on the film to be the cushion layer, the resin composition dissolved in the solvent is applied on the anchor layer, and the coating film is uniformly heated and dried. A multilayer release film is produced by forming a release layer.
Moreover, in the said hot press molding, the film used as a mold release layer and the film used as a cushion layer are overlap | superposed and hot press molded, for example.

According to the present invention, delamination does not occur at the time of mold release, and the heat resistance, mold release property, and followability to the substrate surface are excellent, and void generation, adhesive flow-out, and film during hot press molding are achieved. It is possible to provide a multilayer release film capable of suppressing the seepage of the cushion layer resin on the end surface.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
(1) Production of multilayer release film Polybutylene terephthalate (Novaduran 5010R5, manufactured by Mitsubishi Engineering Plastics, melting point 224 ° C) as a thermoplastic saturated polyester resin for a release layer, and LLDPE (PF1140G as a resin for a cushion layer) , Manufactured by Dow Co., Ltd., having 8 carbon atoms and a melting point of 94 ° C.), co-extruded from a T-die, and a multilayer release film having a release layer thickness of 20 μm and a cushion layer thickness of 80 μm Got.
The melting point was measured using a differential scanning calorimeter (DSC 2920, manufactured by TA Instruments). Moreover, the carbon number of LLDPE means the carbon number of the alpha olefin used for superposition | polymerization.

(2) Fabrication of flexible printed circuit board One set of the laminates of the copper-clad laminate, the coverlay film, and the obtained multilayer release film in this order was placed in a hot press, and 32 sets were placed on a hot press. After hot press molding under the conditions of a press pressure of 300 N / cm ² and a press time of 60 minutes, the press pressure was released, and the multilayer release film was peeled off to obtain a flexible printed board.
As a copper-clad laminate, a polyimide film (made by DuPont: Kapton) with a thickness of 25 μm is used as a base film, and a copper foil with a thickness of 35 μm and a width of 50 μm is an epoxy adhesive layer with a thickness of 20 μm. As the cover lay film, an adhesive having a flow starting temperature of 80 ° C. applied at a thickness of 20 μm on a 25 μm-thick polyimide film (manufactured by DuPont: Kapton) was used as the coverlay film. .

(Example 2, Comparative Examples 1-3)
A multilayer release film and a flexible printed circuit board were produced in the same manner as in Example 1 except that those shown in Table 1 were used as the release layer resin and the cushion layer resin. In Table 1, the resin used as the main component was used as the base resin, and the other resin was used as the other resin. Moreover, in Table 1, the carbon number of the alpha olefin used for LLDPE was described only as the carbon number.

(Evaluation)
The following evaluation was performed about the multilayer release film and flexible printed circuit board obtained in Examples 1 and 2 and Comparative Examples 1 to 3. The results are shown in Table 1.

(1) Delamination The presence or absence of delamination between the release layer and the cushion layer at the time of peeling the multilayer release film in the flexible printed circuit board production process was visually confirmed and evaluated according to the following criteria.
○: The release layer and the cushion layer were peeled together and nothing was left on the flexible printed circuit board.
(Triangle | delta): Although the interlayer of a mold release layer and a cushion layer peeled partially, a mold release layer did not remain on a flexible printed circuit board.
X: The release layer and the cushion layer were peeled off, and the release layer remained on the flexible printed board.

According to the present invention, delamination does not occur at the time of mold release, and the heat resistance, mold release property, and followability to the substrate surface are excellent, and void generation, adhesive flow-out, and film during hot press molding are achieved. It is possible to provide a multilayer release film capable of suppressing the seepage of the cushion layer resin on the end surface.

Claims (2)

At least a release film comprising a release layer made of a thermoplastic saturated polyester resin having a melting point of 200 ° C. or higher measured using a differential scanning calorimeter, and a cushion layer,
The cushion layer is mainly composed of linear low-density polyethylene having a melting point of 70 to 130 ° C. measured using a differential scanning calorimeter and copolymerizing ethylene and an α-olefin having 6 or more carbon atoms. A multilayer release film comprising as a component. The multilayer release film according to claim 1, wherein the cushion layer contains less than 25% by weight of a thermoplastic saturated polyester resin having a melting point of 200 ° C or higher measured using a differential scanning calorimeter.