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US-12617128-B2 - Release film and method for manufacturing release film

US12617128B2US 12617128 B2US12617128 B2US 12617128B2US-12617128-B2

Abstract

To provide a release film having an electrostatic dissipative property. The present invention provides a release film comprising a base layer formed of a polyester resin and a surface layer formed of a tetrafluoroethylene resin that comprises an electrically conductive filler, and the release film has a surface resistivity Rs of 1×10 11 Ω or less. Preferably, the electrically conductive filler comprises carbon black, and the tetrafluoroethylene resin further comprises particles having an average particle size of 1 μm to 15 μm determined by laser diffraction particle size analysis.

Inventors

  • Keisuke Sakai
  • Nanae TANAKA

Assignees

  • KOBAYASHI & CO., LTD.

Dates

Publication Date
20260505
Application Date
20200306
Priority Date
20191016

Claims (16)

  1. 1 . A release film, comprising: a base layer comprised of a polyester resin; and a surface layer comprised of a tetrafluoroethylene resin comprising an electrically conductive filler, wherein: the release film has a surface resistivity (Rs) of 1×10 11 Ω or less, the electrically conductive filler comprises carbon black, the tetrafluoroethylene resin is a cured product which comprises a reactive functional group-containing tetrafluoroethylene polymer and a curing agent, the reactive functional group-containing tetrafluoroethylene polymer comprises a polymer unit based on a hydroxy group-containing monomer and a polymer unit based on perfluoroolefin comprising tetrafluoroethylene and one or more of hexafluoropropylene and perfluoro (alkyl vinyl ethers), the tetrafluoroethylene resin comprises silicon dioxide particles each having an average particle size of 1 μm to 15 μm, as determined by laser diffraction particle size analysis, and an amount of the silicon dioxide particles relative to 100 parts by mass of the tetrafluoroethylene resin is 5.15 parts by mass to 15.79 parts by mass.
  2. 2 . The release film according to claim 1 , wherein the carbon black comprises ketjen black.
  3. 3 . The release film according to claim 2 , wherein the ketjen black has a dibutyl phthalate (DBP) oil absorption amount of 250 ml/100 g or more.
  4. 4 . The release film according to claim 1 , wherein the carbon black further comprises furnace black, and wherein a DBP oil absorption amount of the furnace black is 200 ml/100 g or less.
  5. 5 . The release film according to claim 1 , wherein the carbon black further comprises a ketjen black, and wherein the ketjen black has an average particle size of 1 μm to 20 μm, as determined by laser diffraction particle size analysis.
  6. 6 . The release film according to claim 1 , wherein the carbon black further comprises a furnace black, and wherein the furnace black has an average particle size of 30 nm to 150 nm, as determined by electron microscopy particle size analysis.
  7. 7 . The release film according to claim 1 , wherein the curing agent is an isocyanate curing agent.
  8. 8 . The release film according to claim 7 , wherein the isocyanate curing agent is: (i) a single polyisocyanate, or (ii) hexamethylene diisocyanate (HDI) polyisocyanate and one or more polyisocyanates selected from isocyanurate-containing polyisocyanates, adduct-containing polyisocyanates, and biuret-containing polyisocyanates.
  9. 9 . The release film according to claim 1 , wherein an amount of the electrically conductive filler contained in the tetrafluoroethylene resin composition is 1 part by mass to 25 parts by mass relative to 100 parts by mass of the reactive functional group-containing tetrafluoroethylene polymer.
  10. 10 . The release film according to claim 1 , wherein the polyester resin is a polyethylene terephthalate resin.
  11. 11 . The release film according to claim 1 , wherein the polyester resin has a glass transition temperature of 60° C. to 95° C.
  12. 12 . The release film according to claim 1 , wherein the surface layer is laminated on one face of two faces of the base layer.
  13. 13 . The release film according to claim 12 , wherein on another face of the two faces of the base layer, a surface layer comprised of a fluororesin is laminated.
  14. 14 . The release film according to claim 1 , wherein, when sealing a semiconductor with the release film, the release film is placed so that the surface layer that is comprised of the tetrafluoroethylene resin comprising the electrically conductive filler comes into contact with a sealing resin.
  15. 15 . A method for manufacturing a release film, the method comprising: a surface layer forming step of forming, on one face of two faces of a base layer that is comprised of a polyester resin, a surface layer comprised of a tetrafluoroethylene resin comprising an electrically conductive filler, wherein: the electrically conductive filler comprises carbon black, the tetrafluoroethylene resin is a cured product of a tetrafluoroethylene resin composition containing a reactive functional group-containing tetrafluoroethylene polymer and a curing agent, the reactive functional group-containing tetrafluoroethylene polymer contains a polymer unit based on a hydroxy group-containing monomer and a polymer unit based on perfluoroolefin comprising at least tetrafluoroethylene and one or more of hexafluoropropylene and perfluoro (alkyl vinyl ethers), the tetrafluoroethylene resin comprises silicon dioxide particles, an average particle size of the silicon dioxide particles is 1 μm to 15 μm, as determined by laser diffraction particle size analysis, an amount of the silicon dioxide particles relative to 100 parts by mass of the tetrafluoroethylene resin is 5.15 parts by mass to 15.79 parts by mass, and the manufactured release film has a surface resistivity Rs of 1×10 11 Ω or less.
  16. 16 . The method according to claim 15 , wherein in the surface layer forming step, the tetrafluoroethylene resin composition applied to the surface of the base layer is cured to form the cured product.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a national stage of International Application No. PCT/JP2020/009726, filed Mar. 6, 2020, which claims the benefit of Japanese Application No. 2019-189755, filed Oct. 16, 2019, in the Japanese Patent Office, the disclosures of which are incorporated herein by reference. TECHNICAL FIELD The present invention relates to a release film and a method for manufacturing the film, more specifically relates to a release film used to seal a semiconductor device and a method for manufacturing the film, and further specifically relates to a release film used for transfer molding or compression molding and a method for manufacturing the film. BACKGROUND ART In order to seal a semiconductor device with a resin, a molding technique such as transfer molding and compression molding is used. In the molding technique, a release film is often used to facilitate the release of a molded article from a mold after a resin is cured in the mold, and various release films have been developed. For example, Patent Document 1 discloses a release film that comprises a coated film formed of a composition containing a fluorine resin (A) having a functional group X and a release component (B) and comprises a layer formed of a non-fluorinated polymer. Patent Document 2 discloses a gas-barrier release film for semiconductor resin molding. The release film at least comprises a release layer (I) having excellent mold release properties and a plastic support layer (II) supporting the release layer. The plastic support layer (II) has a strength of 1 MPa to 50 MPa at 200% elongation at 170° C., and the release film has a xylene gas permeability of 5×10−15 (kmol·m/(s·m2·kPa)) at 170° C. CITATION LIST Patent Documents Patent Document 1: JP-A No. 2015-74201Patent Document 2: WO20081020543 SUMMARY OF THE INVENTION Technical Problem A release film is used to facilitate the release of a molded article from a mold, as described above. It is desirable that the release film be easily released from a molded article after resin curing. In manufacturing semiconductor devices, it is necessary to prevent electrostatic destruction of semiconductor devices. The electrostatic destruction is caused by electrostatic discharge (ESD). The destruction of a semiconductor device by ESD may be caused by instantaneous discharge of a charged conductor (or a semiconductor device). ESD causes discharge current to flow in a semiconductor device, and the resulting local heat generation and/or electric field concentration may destruct the semiconductor device. In recent years, rapid progress of miniaturization of semiconductor devices has rendered the semiconductor devices more vulnerable to ESD. In order to prevent ESD, the manufacturing line of semiconductor devices is provided with an electrostatic destruction preventing means such as an antistatic device. However, to provide the manufacturing line of semiconductor devices with the electrostatic destruction preventing means may increase manufacturing costs. If an electrostatic dissipative property can be imparted to a release film used, for example, in a sealing step of a semiconductor device of the manufacturing steps of the semiconductor device, ESD in the sealing step can be prevented at lower costs. In view of the above circumstances, the present invention is mainly intended to provide a release film having an electrostatic dissipative property. Solution to Problem The inventors of the present invention have found that a release film having a specific configuration has excellent mold release properties and is suitable for an electrostatic dissipative property. The present invention provides a release film comprising a base layer formed of a polyester resin and a surface layer formed of a tetrafluoroethylene resin comprising an electrically conductive filler, and the release film has a surface resistivity Rs of 1×1011Ω or less. According to an aspect of the present invention, the electrically conductive filler may comprise carbon black, and the tetrafluoroethylene resin may further comprise particles having an average particle size of 1 μm to 15 μm as determined by laser diffraction particle size analysis. In the aspect, the carbon black may comprise ketjen black. The ketjen black may have a DBP oil absorption amount of 250 ml/100 g or more. The carbon black may further comprise furnace black. In the aspect, the carbon black may comprise furnace black. The particles may be inorganic particles. The inorganic particles may be silicon dioxide particles. According to another aspect of the present invention, the electrically conductive filler may comprise carbon black, and the carbon black may comprise ketjen black and furnace black. The polyester resin may be a polyethylene terephthalate resin. The polyester resin may have a glass transition temperature of 60° C. to 95° C. The surface layer may be laminated on one face of two faces of the base layer. On the other face