JP2011252094A - Release film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a release film excellent in a mold releasability, and excellent in non-staining properties to a copper circuit.SOLUTION: In the release film having a surface that contains an engineering plastic, the engineering plastic has a storage modulus of 100-2,000 MPa which is measured by the dynamic viscoelastic measurement device at a hot pressing molding temperature.

Description

The present invention relates to a release film having excellent releasability and excellent non-contamination for copper circuits.

In the manufacturing process of a printed wiring board, a flexible printed board, a multilayer printed wiring board, etc., a release film is used when a copper-clad laminate or a copper foil is hot-pressed through a prepreg or a heat-resistant film. In the manufacturing process of the flexible printed circuit board, when the cover lay film is hot-press bonded to the flexible printed circuit board body on which the copper circuit is formed with a thermosetting adhesive or a thermosetting adhesive sheet, Release films are widely used to prevent the hot press plate from adhering.

For the release film, for example, heat resistance that can withstand hot press molding, release properties for printed wiring boards and hot press plates, ease of disposal, and the like are required. In addition, non-contamination to the copper circuit is also important for improving the 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 have been used (for example, Patent Document 1).
However, the fluorine-based film is excellent in heat resistance, releasability, and non-contamination, but is expensive and hardly burns when incinerated in the disposal process, and generates toxic gas. In addition, the silicone-coated polyethylene terephthalate film and the polymethylpentene film may cause contamination of a printed wiring board, particularly a copper circuit, due to migration of a low molecular weight substance in silicone or a constituent component, and may impair quality. Moreover, a polypropylene film is inferior in heat resistance, and its mold release property is also insufficient.

In addition, release films made of polyester resins such as polybutylene terephthalate have been studied. Such release films are excellent in heat resistance, ease of disposal, and non-contamination, but release. There is room for improvement in terms of sex.
In order to improve releasability, it has been studied to subject the release film to heat treatment or friction treatment. However, the heat treatment is performed at a high temperature and requires a long time, so that the manufacturing process becomes complicated. In addition, since the friction treatment is performed at a high pressure while rotating the friction treatment roll at a high speed, it causes damage such as wrinkles and scratches on the surface of the release film. Inconveniences such as a decrease in followability of the film occur. Therefore, there is a need for a release film that is excellent in releasability even without such treatment, and that is excellent in other properties such as non-contamination for copper circuits.

Japanese Patent Laid-Open No. 5-283862

An object of this invention is to provide the release film excellent in the mold release property and excellent in the non-contamination property with respect to a copper circuit.

The present invention is a release film having a surface layer containing an engineering plastic, wherein the engineering plastic has a storage elastic modulus of 100 to 2000 MPa measured at a hot press molding temperature with a dynamic viscoelasticity measuring device. It is. The present invention is described in detail below.

The inventors of the present invention provide a release film having a surface layer containing an engineering plastic, wherein the release film satisfying a predetermined range of storage elastic modulus measured under a predetermined condition of the engineering plastic is a printed wiring board, a hot press plate It has been found that the release film is excellent in releasability with respect to, and the like, and is excellent in non-contamination on the copper circuit, and has completed the present invention.

The release film of the present invention has a surface layer containing an engineering plastic. In the present specification, the engineering plastic means a synthetic resin whose functions according to a predetermined purpose such as heat resistance are reinforced, among synthetic resins such as plastic materials and thermoplastic resins.
The engineering plastic has a lower limit of storage elastic modulus of 100 MPa and an upper limit of 2000 MPa measured at a hot press molding temperature with a dynamic viscoelasticity measuring apparatus.
By using an engineering plastic satisfying the storage elastic modulus in the above range, the release film of the present invention is excellent in releasability from a printed wiring board, a hot press plate, and the like. Further, by using an engineering plastic that satisfies the storage elastic modulus in the above range, the component of the release film is mitigated to migrate to and adhere to the copper circuit, and the release film of the present invention is non-polluting to the copper circuit. Excellent in properties.

When the storage elastic modulus is less than 100 MPa, the obtained release film has too high followability to surface irregularities of a printed wiring board or the like, and the release property is lowered. When the storage elastic modulus exceeds 2000 MPa, the obtained release film is too hard to function as a release film. The preferable lower limit of the storage elastic modulus is 120 MPa, and the preferable upper limit is 1300 MPa.

In the present specification, the hot press molding temperature is a temperature usually used when a printed wiring board or the like is hot press molded using a release film, and specifically, in the range of 130 to 200 ° C. It means temperature. The storage elastic modulus can be obtained, for example, by measuring using a dynamic viscoelasticity measuring device such as Model DVA-225 manufactured by IT Measurement Control Co., Ltd.

The engineering plastic is not particularly limited as long as the storage elastic modulus in the above range is satisfied. Specifically, for example, polyphenylene ether, liquid crystal polymer, polybutylene terephthalate, and the like are preferable. Of these, polyphenylene ether or liquid crystal polymer is more preferable.
In the present specification, the liquid crystal polymer means a synthetic resin belonging to a thermoplastic resin that exhibits liquid crystal-like properties in which a linear chain of molecules is regularly arranged in a molten state, and specifically, for example, Econol (Sumitomo Chemical Co., Ltd.). Manufactured) and the like.

The surface layer containing the engineering plastic may contain a stabilizer. The said stabilizer is not specifically limited, For example, a hindered phenolic antioxidant, a heat stabilizer, etc. are mentioned.
The hindered phenol antioxidant is not particularly limited. For example, 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-tetraoxa Examples include spiro [5,5] undecane.
The heat stabilizer is not particularly limited, and examples thereof include 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, pentaerythryltetrakis (3-laurylthiopropio) Nate), ditridecyl 3,3′-thiodipropionate and the like.

The surface layer containing the engineering plastic also contains additives such as fibers, inorganic fillers, flame retardants, ultraviolet absorbers, antistatic agents, inorganic substances, higher fatty acid salts, and the like within a range not impairing the effects of the present invention. Also good.

The fiber may be an inorganic fiber or an organic fiber. The inorganic fiber is not particularly limited, and examples thereof include glass fiber, carbon fiber, boron fiber, silicon carbide fiber, alumina fiber, amorphous fiber, and silicon-titanium-carbon fiber. The said organic fiber is not specifically limited, For example, an aramid fiber etc. are mentioned.

The inorganic filler is not particularly limited, and examples thereof include calcium carbonate, titanium oxide, mica and talc.
The flame retardant is not particularly limited, and examples thereof include hexabromocyclododecane, tris- (2,3-dichloropropyl) phosphate, pentabromophenyl allyl ether, and the like.

The ultraviolet absorber is not particularly limited. For example, pt-butylphenyl salicylate, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2′-carboxybenzophenone, 2,4,5-tri And hydroxybutyrophenone.
The antistatic agent is not particularly limited, and examples thereof include N, N-bis (hydroxyethyl) alkylamine, alkylallyl sulfonate, and alkyl sulfonate.

The inorganic material is not particularly limited, and examples thereof include barium sulfate, alumina, and silicon oxide.
The higher fatty acid salt is not particularly limited, and examples thereof include sodium stearate, barium stearate, and sodium palmitate.

The surface layer containing the engineering plastic may contain a thermoplastic resin and a rubber component in order to modify the properties of the surface layer.
The thermoplastic resin is not particularly limited, and examples thereof include polyolefin, modified polyolefin, polystyrene, polyvinyl chloride, polyamide, polycarbonate, polysulfone, and polyester.
The rubber component is not particularly limited. For example, natural rubber, styrene-butadiene copolymer, polybutadiene, polyisoprene, acrylonitrile-butadiene copolymer, ethylene-propylene copolymer (EPM, EPDM), polychloroprene, butyl rubber. Acrylic rubber, silicone rubber, urethane rubber, olefin thermoplastic elastomer, styrene thermoplastic elastomer, vinyl chloride thermoplastic elastomer, ester thermoplastic elastomer, amide thermoplastic elastomer, and the like.

The surface layer containing the engineering plastic may contain an inorganic compound having a large aspect ratio.
By including an inorganic compound having a large aspect ratio, the release film obtained has improved release properties at high temperatures, and further, additives, low molecular weight substances, etc. contained in the release film are brought to the release film surface. Bleed-out can be suppressed, and cleanliness during hot press molding is improved.
The inorganic compound having a large aspect ratio is not particularly limited, and examples thereof include layered silicates such as clay and layered double hydrates such as hydrotalcite.

The surface of the surface layer containing the engineering plastic preferably has smoothness, but may be provided with slip properties, anti-blocking properties and the like necessary for handling. Moreover, the surface of the surface layer containing the engineering plastic may be provided with an appropriate embossed pattern or fine irregularities for the purpose of air removal during hot press molding. The method of such treatment is not particularly limited, and examples thereof include a method of rubbing the surface of the surface layer containing the engineering plastic using a metal roll provided with an embossed pattern, a cloth such as gauze, a brush or the like.

The surface layer containing the engineering plastic may be subjected to heat treatment or friction treatment in order to further improve the heat resistance, dimensional stability and releasability of the obtained release film. Further, heat treatment and friction treatment may be performed.
Although the method of the said heat processing is not specifically limited, For example, the method of passing a film between the rolls heated to fixed temperature, the method of heating a film with a heater, etc. are preferable.
Moreover, the temperature of the said heat processing will not be specifically limited if it is more than the glass transition temperature and below melting | fusing point of the said engineering plastic, However, a preferable minimum is 120 degreeC and a preferable upper limit is 200 degreeC. If the temperature of the heat treatment is less than 120 ° C., the effect of improving the releasability by the heat treatment may be hardly obtained. When the temperature of the heat treatment exceeds 200 ° C., the surface layer containing the engineering plastic is easily deformed during the heat treatment, and a release film may not be produced. The more preferable lower limit of the heat treatment temperature is 170 ° C., and the more preferable upper limit is 190 ° C.

The method of the said friction process is not specifically limited, For example, the method etc. which rub the surface of the surface layer containing the said engineering plastic using cloth, brushes, etc., such as a metal roll and gauze, etc. are mentioned.

The thickness of the surface layer containing the engineering plastic is not particularly limited, but a preferable lower limit is 5 μm and a preferable upper limit is 20 μm. When the thickness of the surface layer is less than 5 μm, the surface layer containing the engineering plastic is impaired in strength and may be destroyed at the time of hot press molding or peeling of the release film. When the thickness of the surface layer exceeds 20 μm, the resulting release film may have a poor followability to surface irregularities such as a printed wiring board. The more preferable lower limit of the thickness of the surface layer is 10 μm, and the more preferable upper limit is 15 μm.

The release film of the present invention may be a single layer film or a multi-layer film of two or more layers as long as it has a surface layer containing the engineering plastic.
When the release film of the present invention is a multilayer film, it may have an intermediate layer. The intermediate layer preferably contains a polyolefin resin having a melting point of 60 ° C. or higher and lower than 130 ° C. measured using a differential scanning calorimeter.

The release film is also required to follow the unevenness of the surface of a printed wiring board or the like. If a release film with low conformability is used, voids may occur during hot press molding, or the adhesive of the coverlay film will flow out to the electrode part of the flexible printed circuit board, which may hinder the plating process of the electrode part. . On the other hand, since the intermediate layer obtained by using the polyolefin-based resin starts to soften near the temperature at which the adhesive starts to melt, the release film having such an intermediate layer is, for example, 100 μm or less. Even a flexible printed circuit board having a fine copper circuit pitch such as a sufficient followability.

When the melting point of the polyolefin resin measured using a differential scanning calorimeter is less than 60 ° C., the interlayer resin melts and stains when the ambient temperature is 50 to 60 ° C. during storage of the release film. May cause blocking. When the melting point of the polyolefin resin measured using a differential scanning calorimeter is 130 ° C. or higher, the obtained release film may have a low followability to surface irregularities such as a printed wiring board. The melting point of the polyolefin-based resin measured using a differential scanning calorimeter is preferably 80 ° C. or higher and 100 ° C. or lower.

Specific examples of the polyolefin resin include polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, ethylene-methyl methacrylate copolymer, ethylene-vinyl acetate copolymer, and ethylene-ethyl acrylate copolymer. Examples thereof include ethylene and acrylic acid copolymer. These may be used alone or in combination of two or more. Among these, low density polyethylene, linear low density polyethylene, ethylene-methyl methacrylate copolymer, and ethylene-vinyl acetate copolymer are preferable.

The intermediate layer preferably further contains a resin having a melting point of 130 ° C. or higher measured using a differential scanning calorimeter.
When a resin having a low softening temperature such as a polyolefin resin having a melting point of 60 ° C. or higher and lower than 130 ° C. measured using the above differential scanning calorimeter is used for the intermediate layer, the release temperature depends on the pressure during hot press molding. The resin may ooze out from the intermediate layer at the end of the mold film and may contaminate the printed wiring board, the hot press plate, and the like. On the other hand, by using a resin having a melting point of 130 ° C. or higher measured using the differential scanning calorimeter, the resin oozes out from the intermediate layer generated at the end of the release film during hot press molding. Can be suppressed.
The resin having a melting point of 130 ° C. or higher measured using the differential scanning calorimeter is not particularly limited, and examples thereof include polypropylene and crystalline aromatic polyester resin.

When the intermediate layer contains a resin having a melting point of 130 ° C. or higher measured using the differential scanning calorimeter, the amount of such a resin is not particularly limited, but a preferred lower limit in the intermediate layer is 5% by weight. The preferred upper limit is 50% by weight. When the blending amount of the resin having a melting point of 130 ° C. or higher measured using the differential scanning calorimeter is less than 5% by weight, the resin stain from the intermediate layer generated at the end of the release film during hot press molding The effect of suppressing the ejection may not be sufficiently obtained. When the blending amount of the resin having a melting point measured using the differential scanning calorimeter of 130 ° C. or higher exceeds 50% by weight, the obtained release film has a poor followability to surface irregularities of a printed wiring board or the like. Sometimes.

The said intermediate | middle layer may contain additives, such as a fiber, an inorganic filler, a flame retardant, a ultraviolet absorber, an antistatic agent, an inorganic substance, and a higher fatty acid salt similarly to the release film of this invention.

Although the thickness of the said intermediate | middle layer is not specifically limited, A preferable minimum is 10 micrometers and a preferable upper limit is 200 micrometers. When the thickness of the intermediate layer is less than 10 μm, the intermediate layer is too thin, and when the intermediate layer is softened during hot press molding, a portion where the intermediate layer does not exist partially occurs, and the press pressure is uniformly applied to the substrate. May not be able to load. If the thickness of the intermediate layer exceeds 200 μm, the intermediate layer is unnecessarily thick, so that the resin exudation from the intermediate layer that occurs at the end of the film during hot press molding may not be suppressed. A more preferable lower limit of the thickness of the intermediate layer is 20 μm, and a more preferable upper limit is 100 μm.

The method for producing the 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 surface layer containing the engineering plastic resin were prepared. Thereafter, a method of laminating an intermediate layer on this surface layer by an extrusion lamination method, a method of dry laminating a film to be a surface layer containing the engineering plastic resin and a film to be an intermediate layer, a solvent casting method, a hot press molding method Etc. In particular, when the release film of the present invention is a film having a plurality of layers, a method of forming a film by a coextrusion T-die method is preferable because of excellent thickness control of each layer.

In the solvent casting method, for example, after an undercoat treatment of an anchor layer on a film to be an intermediate layer, a resin composition to be a surface layer in which the engineering plastic resin or the like is dissolved in a solvent is applied on the anchor layer, The coating film is uniformly heated and dried to form a surface layer.
In the hot press molding method, for example, a film serving as a surface layer containing the engineering plastic resin and a film serving as an intermediate layer are superposed and hot press molded.

In the release film of the present invention, after the printed wiring board or the like is hot press molded using the release film and the release film is peeled off, the upper limit of the water contact angle of the copper circuit is preferably 80 °. If the water contact angle of the copper circuit is more than 80 °, plating failure of the electrode portion may occur when forming an electrode on a printed wiring board or the like, leading to a decrease in product yield. A more preferable upper limit of the water contact angle of the copper circuit is 70 °.

The 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 the dimensional change rate exceeds 1.5%, the circuit pattern of the flexible printed circuit board may be damaged during hot press molding. The dimensional change rate is more preferably 1.0% or less.
Moreover, it is preferable that the dimensional change rate of the width direction (henceforth TD) and length direction (henceforth MD) of the release film of this invention is the same direction and is equivalent grade. When the vertical and horizontal dimensional changes are different such that one (for example, MD) contracts and the other (for example, TD) expands, the release film damages the circuit pattern of the flexible printed circuit board during hot press molding. Sometimes.

ADVANTAGE OF THE INVENTION According to this invention, the mold release film excellent in the mold release property and excellent in the non-contamination property with respect to a copper circuit can be provided.

Examples of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1
Polyphenylene ether (trade name AH40, manufactured by Mitsubishi Engineering Plastics) as an engineering plastic, and linear low density polyethylene (Excellen FX (CX5501), manufactured by Sumitomo Chemical Co., Ltd., melting point 66 ° C.) as a polyolefin resin for an intermediate layer An ethylene-methyl methacrylate copolymer (Aklift (WH401), manufactured by Sumitomo Chemical Co., Ltd., melting point 86 ° C.) and polypropylene (PS207A, manufactured by Sun Allomer Co., Ltd., melting point 160 ° C.) were put into a co-extrusion molding machine, Extrusion molding was performed to obtain a release film having a surface layer thickness of 10 μm and an intermediate layer thickness of 80 μm. The melting point was measured using a differential scanning calorimeter (DSC 2920, manufactured by TA Instruments).

In addition, about the used engineering plastic, the storage elastic modulus measured in the hot press molding temperature with the dynamic viscoelasticity measuring apparatus (model DVA-225, the IT measurement control company make) was 240 Mpa.

(Example 2)
Liquid crystalline polymer (trade name A950, manufactured by Polyplastics Co., Ltd.) as engineering plastic, and linear low density polyethylene (Excellen FX (CX5501), manufactured by Sumitomo Chemical Co., Ltd., melting point 66 ° C.) and ethylene as polyolefin resin for intermediate layer -Methyl methacrylate copolymer (Aklift (WH401), manufactured by Sumitomo Chemical Co., Ltd., melting point 86 ° C) and polypropylene (PS207A, manufactured by Sun Allomer Co., Ltd., melting point 160 ° C) are put into a coextrusion molding machine and coextruded from a T die. Molding was performed to obtain a release film having a surface layer thickness of 10 μm and an intermediate layer thickness of 80 μm. The melting point was measured using a differential scanning calorimeter (DSC 2920, manufactured by TA Instruments).

In addition, about the used engineering plastic, the storage elastic modulus measured in the hot press molding temperature with the dynamic viscoelasticity measuring apparatus (model DVA-225, the IT measurement control company make) was 1210 MPa.

(Comparative Example 1)
Polyphenylene sulfide (trade name HF2000, manufactured by Polyplastics Co., Ltd.) as an engineering plastic, and linear low density polyethylene (Excellen FX (CX5501), manufactured by Sumitomo Chemical Co., Ltd., melting point 66 ° C.) and ethylene as a polyolefin resin for an intermediate layer -Methyl methacrylate copolymer (Aklift (WH401), manufactured by Sumitomo Chemical Co., Ltd., melting point 86 ° C) and polypropylene (PS207A, manufactured by Sun Allomer Co., Ltd., melting point 160 ° C) are put into a coextrusion molding machine and coextruded from a T die. Molding was performed to obtain a release film having a surface layer thickness of 10 μm and an intermediate layer thickness of 80 μm. The melting point was measured using a differential scanning calorimeter (DSC 2920, manufactured by TA Instruments).

In addition, about the used engineering plastic, the storage elastic modulus measured in the hot press molding temperature with the dynamic viscoelasticity measuring apparatus (model DVA-225, the IT measurement control company make) was 73 Mpa.

(Comparative Example 2)
Liquid crystal polymer (trade name A330S, manufactured by Polyplastics Co., Ltd.) as engineering plastic, and linear low density polyethylene (Excellen FX (CX5501), manufactured by Sumitomo Chemical Co., Ltd., melting point 66 ° C.) and ethylene as polyolefin resin for intermediate layer -Methyl methacrylate copolymer (Aklift (WH401), manufactured by Sumitomo Chemical Co., Ltd., melting point 86 ° C) and polypropylene (PS207A, manufactured by Sun Allomer Co., Ltd., melting point 160 ° C) are put into a coextrusion molding machine and coextruded from a T die. Molding was performed to obtain a release film having a surface layer thickness of 10 μm and an intermediate layer thickness of 80 μm. The melting point was measured using a differential scanning calorimeter (DSC 2920, manufactured by TA Instruments).

In addition, about the used engineering plastic, the storage elastic modulus measured in the hot press molding temperature with the dynamic viscoelasticity measuring apparatus (model DVA-225, the IT measurement control company make) was 2020 Mpa.

<Evaluation>
The following evaluation was performed about the release film obtained by the Example and the comparative example. The results are shown in Table 1.

(1) Releasability (peeling force)
The obtained release film and the epoxy adhesive surface of a cover lay film (CISV-2535, manufactured by Nikkan Kogyo Co., Ltd.) cut out to 200 mm square were stacked, and a slide type vacuum heater press (MKP-3000v-MH-ST, Mikado). After pressing at 180 ° C. for 6 minutes at a pressure of 30 kgf, the material was cured for 1 day under the conditions of 23 ° C. and 50% RH. Thereafter, the obtained film was cut into a width of 30 mm and a length of 150 mm, and using Tensilon (STA-1150, manufactured by A & D), a release rate of 500 mm / min and a release angle of 180 ° (release force) ( N / 30 mm).
In addition, since the mold release film obtained by the comparative example 2 produced the film destruction at the time of a press, it was not able to evaluate mold release property (peeling force) (N / 30mm).

(2) Non-contaminating property against copper circuit The obtained release film and the copper foil surface of a copper-clad laminate (L6504-C1, manufactured by Nikkan Kogyo Co., Ltd.) cut into a 200 mm square are stacked, and a slide type vacuum heater press ( MKP-3000v-MH-ST (manufactured by Mikado Technos) was pressed at 180 ° C. for 6 minutes at a pressure of 30 kgf, and then cured for one day under the conditions of 23 ° C. and 50% RH. Then, after peeling off the release film from the copper-clad laminate, the water contact angle (°) of the copper foil surface was measured using a contact angle measuring device (M1040S-IGM, manufactured by Shiro Sangyo Co., Ltd.), thereby producing a copper circuit. The non-contaminating property against was evaluated.
In addition, since the release film obtained in Comparative Example 2 caused film breakage at the time of pressing, it was not possible to evaluate the non-contamination property with respect to the copper circuit.

ADVANTAGE OF THE INVENTION According to this invention, the mold release film excellent in the mold release property and excellent in the non-contamination property with respect to a copper circuit can be provided.

Claims (2)

A release film having a surface layer containing engineering plastic,
The engineering plastic has a storage elastic modulus of 100 to 2000 MPa measured at a hot press molding temperature with a dynamic viscoelasticity measuring device. 2. The release film according to claim 1, wherein the engineering plastic is polyphenylene ether or liquid crystal polymer.