JP2008231411A - Resin composition for releasing sheet, releasing sheet, and method for producing flexible print circuit substrate or prepreg using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a releasing sheet which can furnish a coverlay film or a prepreg with so suitable a property when the coverlay film is pressed to pile up by the load of a heating plate on a flexible print circuit substrate or when the prepreg is molded by the load of a heating plate, that the coverlay film or the prepreg may be easily released from the heating plate and treated or molded in the succeeding process to be free from being fragilely broken. <P>SOLUTION: The resin composition for the releasing sheet comprises a resin mixture comprising a cyclic olefin resin and an ethylene-α-olefin copolymer, wherein the cyclic olefin resin has a glass transition point of 100-250°C; and the resin mixture has a temperature of 140-200°C at the maximum peak of the secondary differential curve for a temperature-strain curve within a range of 0-12% of strain in the temperature-strain curve obtained by thermal mechanical analysis. The releasing sheet comprises the resin composition for the releasing sheet. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a resin composition for a release sheet, and more particularly to a release sheet used in the production of various composite materials such as a flexible printed circuit board (hereinafter also referred to as FPC) and a prepreg.

  Since printed circuit boards for electronic circuits use metals such as copper and silver for their wiring, fine wiring may corrode metal. For this reason, the coverlay film is heated and pressure-bonded or a resin-dried coating film of the resin solution is used to prevent intrusion of water vapor and trace acid substances in the air.

  The cover lay film is suitably used for a flexible printed circuit board. In addition to the above-described necessity, the cover lay film is effective as a protective film that can withstand wiring work with solder that melts at about 280 ° C., and is also effective in avoiding dust. A general coverlay film has a configuration in which an epoxy resin adhesive layer is disposed on one side of a heat-resistant film such as a polyimide film.

  When the cover lay film is heat-bonded to the flexible printed circuit board, the epoxy resin may ooze out from the end of the cover lay film or a via hole and adhere to the heating plate, making it difficult to peel off. Then, the method of preventing adhesion | attachment of a cover-lay film and a heating plate by pinching and heating a release sheet between a heating plate and a cover-lay film is known. Alternatively, a release sheet may be disposed on the flexible printed circuit board contact side as a laminated structure of the coverlay film. In addition, when a prepreg made of epoxy resin is subjected to hot press molding, a release sheet is used in order to prevent adhesion between the mold and the prepreg (for example, see Patent Document 1).

  In addition, when a composite material such as a prepreg is used for an exterior material such as a bumper or furniture for a passenger car, the surface is given for the purpose of giving fine irregularities (hereinafter also referred to as “shibo”) for decoration to the surface. A rough release sheet may be used.

  As a release sheet used for these applications, conventional fluorine-based films are excellent in heat resistance, releasability, and non-contamination, but they are expensive and in waste incineration after use. There is a problem that it is difficult to burn and generates toxic gas.

On the other hand, it is known that cyclic olefin-based resins exhibit excellent release properties. For example, use for a surface protective film that easily peels after use (for example, see Patent Document 2) has been disclosed, and use for a release sheet has also been proposed (for example, see Patent Document 1). . In addition, proposals for improving the heat resistance and impact resistance of films and containers by using a mixed resin composition of a cyclic olefin resin and an ethylene / α-olefin copolymer are also disclosed (for example, Patent Documents). 3).
JP 2006-257399 A Japanese Patent No. 3596901 JP 2005-525952 A

  Since the surface of the flexible printed circuit board has irregularities due to the wiring of the circuit, irregularities are generated on the surface of the heat-pressed coverlay film. Therefore, the heated release sheet is softened and deformed so as to bite into the irregularities of the coverlay film.

  As a result, in the post-manufacturing process of the flexible printed circuit board, when the release sheet is peeled off from the cover lay film, the release sheet is caught on the unevenness, thereby causing local elongation and shredding to make the release sheet uniform. It may not be possible to remove it. Similarly, when the surface of the prepreg has irregularities in the process of thermoforming the prepreg, when the release sheet used for thermoforming is peeled off, the release sheet is caught by the irregularities, resulting in local elongation and tearing. Thus, the release sheet may not be peeled off uniformly.

  Therefore, the present invention provides a cover plate film or prepreg that is heated when a cover lay film is stacked on the flexible printed circuit board by applying a load by a heating plate, or when a prepreg is formed by applying a load by a heating plate. Resin composition for use in a release sheet for making it easy to peel off and having a characteristic of being brittle and not cracked during handling or molding in the subsequent subsequent processes, and a release sheet comprising the resin composition The purpose is to provide.

  Furthermore, in the process of heat-pressing the coverlay film to the flexible printed circuit board or thermoforming the prepreg, a method for producing a flexible printed circuit board or prepreg using a release sheet that is easily peeled off in the subsequent process is provided. Objective.

  The resin composition for a release sheet according to the present invention is a resin mixture composed of a cyclic olefin resin and an ethylene / α-olefin copolymer, and the glass transition point (Tg) of the cyclic olefin resin is 100 to 250 ° C. Yes, the temperature at the maximum peak position of the second derivative curve of the temperature-strain curve in the range of 0-12% of the strain amount in the temperature-strain curve obtained by thermomechanical analysis (TMA) of the resin mixture is 140. It is -200 degreeC.

  The release sheet which concerns on this invention consists of the resin composition for release sheets which concerns on this invention as a resin component, It is characterized by the above-mentioned. The release sheet according to the present invention comprises only the resin composition for a release sheet according to the present invention as a resin component, and additives such as inorganic powder, antioxidants, stabilizers and pigments are blended as other blending components. Includes cases. Hereinafter, the release sheet made of the resin composition for a release sheet includes a case where a component that is not a resin component is blended.

  The release sheet according to the present invention includes a case in which at least one surface layer has a layer made of the resin composition for a release sheet as a resin component.

  In the release sheet according to the present invention, the case where at least one of the layers excluding the surface layer made of the resin composition for release sheet as a resin component is an ethylene / α-olefin copolymer layer is included.

  In the release sheet according to the present invention, the maximum shrinkage at the crystal melting temperature of the ethylene / α-olefin copolymer of the release sheet resin composition is substantially less than 20%. Preferably there is. If the shrinkage is small, unnecessary stress is not applied to an object such as a coverlay film or a prepreg during heating.

  In the release sheet according to the present invention, is the ethylene / α-olefin copolymer of the resin composition for a release sheet, any one type of copolymer having 6 to 12 carbon atoms of the α-olefin? Or a combination of the copolymers. Mechanical strength and heat resistance required for the release sheet can be obtained.

  In the release sheet according to the present invention, the ethylene / α-olefin copolymer of the resin composition for a release sheet is preferably a copolymer of hexene or octene as the α-olefin. When ethylene-α-olefin copolymer comonomer α-olefin is 1-hexene or 1-octene, it is excellent in melt dispersibility in cyclic olefin resin, so it has excellent processability to sheet or film, and its machine The mechanical strength is also increased. Further, since the cyclic olefin-based resin is difficult to precipitate from the resin composition of the release sheet, it does not cause contamination. Furthermore, these ethylene / α-olefin copolymers can maintain releasability because of their low surface energy.

  In the release sheet according to the present invention, the cyclic olefin resin of the release sheet resin composition is preferably an ethylene-norbornene copolymer. The ethylene-norbornene copolymer can easily obtain a high Tg by increasing the molar fraction of norbornene.

  In the release sheet according to the present invention, the sheet surface made of the resin composition for release sheet as a resin component is superimposed on the surface of the cover lay film or prepreg, and is applied for 30 minutes at a pressure of 10 MPa with a heating plate at 200 ° C. After the pressing, when the atmosphere is returned to 23 ° C., it is preferable that the sheet surface has a releasability that is not adhered to the surface of the coverlay film or the prepreg. As a result, the release sheet can be peeled off uniformly without being stretched or broken in the subsequent process of heating and pressing.

  In the release sheet according to the present invention, it is preferable that the sheet surface has the release property when the surface of the coverlay film or the prepreg has irregularities. Even in the case where the release sheet is caught by the unevenness, the release sheet can be peeled off uniformly without being stretched or broken in the subsequent process of heating and pressing.

  In the release sheet according to the present invention, it is preferable that the sheet surface has the release property when the cover lay film or the prepreg is made of an epoxy resin. The release sheet can be peeled off uniformly without causing local elongation or tearing in the subsequent process of heating and pressurizing the epoxy resin surface.

  In the release sheet according to the present invention, it is preferable that at least one surface has irregularities. When the surface of the sheet is uneven, when a composite material such as a prepreg is used as the exterior material, the “shrinkage” can be imparted to the exterior material by the release sheet. Further, when the release sheet is put on the cover lay film or the prepreg, it becomes difficult to adhere to the object, and the workability is improved because the position to be put can be easily finely adjusted by shifting the release sheet. Furthermore, since the contact area between the release sheet and the object is reduced due to the unevenness of the surface, the peelability after heating and pressing is improved.

  In the release sheet according to the present invention, the arithmetic mean roughness (Ra) of at least one surface is preferably 0.5 μm or more and 2.0 μm or less. This is a range of irregularities suitable for imparting “wrinkles” to the object, and the workability of the release sheet is also improved.

  In the release sheet according to the present invention, a resin composition comprising 3 parts by mass or more and 20 parts by mass or less of an inorganic powder having an average particle diameter of 1 μm or more and less than 10 μm with respect to 100 parts by mass of the resin composition for the release sheet. It is preferable to consist of a thing. Sufficient irregularities can be imparted to the sheet surface without impairing the strength and flexibility of the release sheet.

  In the release sheet according to the present invention, the inorganic powder is preferably calcium carbonate. By using inexpensive calcium carbonate, a release sheet can be provided at low cost, and there is no generation of gas that may contaminate the object during heating.

  The method for producing a flexible printed circuit board or prepreg according to the present invention is characterized in that the release sheet according to the present invention is used in the step of thermoforming the flexible printed circuit board or prepreg.

  A release sheet made of the resin composition for a release sheet according to the present invention, and further a multilayer release sheet in which a layer made of the resin composition is arranged on the surface layer is applied to a flexible printed circuit board by applying a load by a heating plate. When the cover lay film is stacked on the surface, or when a prepreg is formed by applying a load from the heating plate, the cover lay film or the prepreg is easily peeled off from the heating plate. It is brittle and sometimes has an effect of being easily peeled off without cracking. Furthermore, the manufacturing method of the flexible printed circuit board or prepreg according to the present invention can obtain the above-described effects by using the release sheet according to the present invention.

  Hereinafter, the present invention will be described in detail with reference to embodiments. The embodiment described below is an example of the configuration of the present invention, and the present invention is not limited to the following embodiment.

  The resin composition for a release sheet according to this embodiment is a resin mixture comprising a cyclic olefin resin (hereinafter also referred to as COC) and an ethylene / α-olefin copolymer (hereinafter also referred to as EO). The glass transition point (Tg) of the cyclic olefin-based resin is 100 to 250 ° C., and the strain amount in the temperature-strain curve obtained by thermomechanical analysis (TMA) of the resin mixture is in the range of 0 to 12%. The temperature of the maximum peak position of the second derivative curve of the temperature-strain curve is 140-200 ° C.

  Cyclic olefin resin is a copolymer formed by addition polymerization of an α-olefin and a cyclic olefin, a polymer formed by ring-opening polymerization of a cyclic olefin, a ring-opened copolymer thereof, As well as these hydrogenated products.

Cyclic olefins are cyclic olefins or cyclic dienes. Specific examples of the cyclic olefin include one-ring cyclic olefin such as cyclopentene, cyclohexene, and cyclooctene;
Bicyclo [2.2.1] hept-2-ene (common name: norbornene), 5-methyl-bicyclo [2.2.1] hept-2-ene, 5,5-dimethyl-bicyclo [2.2. 1] Hept-2-ene, 5-ethyl-bicyclo [2.2.1] hept-2-ene, 5-butyl-bicyclo [2.2.1] hept-2-ene, 5-ethylidene-bicyclo [ 2.2.1] hept-2-ene, 5-hexyl-bicyclo [2.2.1] hept-2-ene, 5-octyl-bicyclo [2.2.1] hept-2-ene, 5- Octadecyl-bicyclo [2.2.1] hept-2-ene, 5-methylidene-bicyclo [2.2.1] hept-2-ene, 5-vinyl-bicyclo [2.2.1] hept-2- Ene, 5-propenyl-bicyclo [2.2.1] hept-2-ene, etc. Cyclic olefin ring;
Tricyclo [4.3.0.1 ^2,5 ] deca-3,7-diene (common name: dicyclopentadiene), tricyclo [4.3.0.1 ^2,5 ] dec-3-ene; tricyclo [ 4.4.0.1 ^2,5 ] undeca-3,7-diene or tricyclo [4.4.0.1 ^2,5 ] undeca-3,8-diene or a partially hydrogenated product thereof (or cyclopentadiene) Tricyclo [4.4.0.1 ^2,5 ] undec-3-ene, 5-cyclopentyl-bicyclo [2.2.1] hept-2-ene, 5-cyclohexyl-bicyclo) [2.2.1] hept-2-ene, 5-cyclohexenylbicyclo [2.2.1] hept-2-ene, 5-phenyl-bicyclo [2.2.1] hept-2-ene A cyclic olefin of the ring;
Tetracyclo [4.4.0.1 ^2,5.17,10 ] ^dodec -3-ene (also simply referred to as tetracyclododecene), 8-methyltetracyclo [4.4.0.1 ^{2,5.17 , 10} ] ^dodec -3-ene, 8- ^{ethyltetracyclo} [4.4.0.1 ^2,5.17,10 ] ^dodec -3-ene, 8-methylidenetetracyclo [4.4.0.1. ^2,5 . 1 ^7,10] dodeca-3-ene, 8-ethylidene tetracyclo [4.4.0.1 ^2,5.17,10] dodeca-3-ene, 8-vinyl-tetracyclo [4,4.0. 1 ^2,5 . Tetracyclic olefins such as 1 ^7,10 ] dodec-3-ene, 8-propenyl-tetracyclo [4.4.0.1 ^2,5.17,10 ] ^dodec -3-ene;
8-cyclopentyl-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-cyclohexyl-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-cyclohexenyl-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-phenyl-cyclopentyl-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene; tetracyclo [7.4.1 ^3,6 . 0 ^1,9 . 0 ^2,7 ] tetradeca-4,9,11,13-tetraene (also referred to as 1,4-methano-1,4,4a, 9a-tetrahydrofluorene), tetracyclo [8.4.1 ^4,7 . 0 ^1,10 . 0 ^3,8 ] pentadeca-5,10,12,14-tetraene (also referred to as 1,4-methano-1,4,4a, 5,10,10a-hexahydroanthracene), pentacyclo [6.6.1 ^.1,3,6 . 0 ^2,7 . 0 ^9,14 ] -4-hexadecene, pentacyclo [6.5.1.1 ^3,6 . 0 ^2,7 . 0 ^9,13] -4-pentadecene, pentacyclo [7.4.0.0 ^2,7. 1 ^3,6 . 1 ^10,13] -4-pentadecene; heptacyclo [8.7.0.1 ^2,9. 14, ⁷ . 1 ^{11, 17} . 0 ^3,8 . 0 ^12,16 ] -5-eicosene, heptacyclo [8.7.0.1 ^2,9 . 0 ^3,8 . 14, ⁷ . 0 ^12,17 . 1 ^{13, l6} ] ^-14-eicosene , cyclopentadiene tetramer, and other polycyclic cyclic olefins.

  These cyclic olefins can be used alone or in combination of two or more.

  Specific examples of the cyclic dienes include 1,3-cyclobutadiene, 1,3-cyclopentadiene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, 1,3-cycloheptadiene, 1,4-cyclohepta. Examples include diene, 1,3-cyclooctadiene, 1,3,5-cyclooctatriene, 1,4-cyclooctadiene, dicyclopentadiene, and the like.

  In addition, the cyclic diene should just have at least 2 double bond, for example, cyclic triene etc. are also included.

  Specific examples of α-olefin for copolymerization with cyclic olefins include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1 2 to 20 carbon atoms such as -hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene, etc., preferably Is an ethylene or α-olefin having 2 to 8 carbon atoms, particularly preferably ethylene.

  In the case of producing a cyclic diene / α-olefin copolymer as the cyclic olefin-based resin, it is heat resistant that the proportion of α-olefin units in the copolymer is 0.1 to 80 mol%. Is preferable.

  These α-olefins can be used alone or in combination of two or more.

  There are no particular restrictions on the method of ring-opening polymerization of a cyclic olefin or the addition polymerization of a cyclic olefin and an α-olefin, and the method of hydrogenating the obtained polymer, and can be carried out according to known methods.

  The cyclic olefin-based resin used for the release sheet of the present embodiment is preferably an addition copolymer of ethylene and norbornene. This ethylene-norbornene copolymer can obtain a high Tg by increasing the molar fraction of norbornene.

  The structure of such a cyclic olefin-based resin is not particularly limited, and may be a chain, branched, or crosslinked, but is preferably a straight chain. Moreover, as a molecular weight of such cyclic olefin resin, the number average molecular weight by gel permeation chromatography (GPC) analysis is 50,000 to 300,000, preferably 10,000 to 150,000, and more preferably 15,000 to 100,000. If the number average molecular weight is too low, the mechanical strength is lowered, and if it is too high, the moldability tends to deteriorate.

  The Tg of the cyclic olefin resin used in the present embodiment is 100 ° C to 250 ° C, more preferably 130 ° C to 250 ° C, and particularly preferably 170 ° C to 240 ° C. The higher the Tg, the higher the retention of the film shape at a high temperature and the better the release from the metal surface, but the better the releasability. It is not preferable because the product value is lost. On the other hand, when the Tg is less than 100 ° C., the film is deformed at the time of heating and pressing, and is easily peeled off from the coverlay film, prepreg, FPC, mold, etc., and is not suitable for practical use as a release sheet. Also, two or more kinds of cyclic olefin resins having different Tg can be used in combination.

  In order to obtain the release sheet resin composition according to the present embodiment, as a specific example of α-olefin to be used for copolymerization of ethylene / α-olefin copolymer mixed with the cyclic olefin resin, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 4-methyl-1-pentene, cyclopentene, cyclopentadiene, butadiene, 1,5-hexadiene, 1,4-hexadiene 1,4-pentadiene and the like. Also, these two or more α-olefins can be mixed and used for copolymerization with ethylene.

  In the release sheet according to the present embodiment, the ethylene / α-olefin copolymer of the resin composition for release sheet is any one of 6 to 12 carbon atoms of the α-olefin. Or a combination of these copolymers, and more preferably, the α-olefin is a copolymer of hexene or octene. The mechanical strength and heat resistance required for the release sheet can be further improved.

  Further, the molar fraction of the monomer in the ethylene / α-olefin copolymer used in the present embodiment is not particularly limited, but preferably ethylene monomer / α-olefin monomer = 10000 to 0. .5, more preferably 1000-10.

The lower limit of the density range of the ethylene · alpha-olefin copolymer can achieve is possible to 800 kg / ^{m 3,} preferably is used in the range of 890~940kg / ^{m 3.} In the polymerization of an ethylene / α-olefin copolymer, it is known to use a Kaminsky catalyst (metallocene / methylaluminoxane) as a homogeneous catalyst for olefin polymerization. It is also known that an ethylene / α-olefin copolymer can be efficiently polymerized by using a metallocene catalyst. The metallocene catalyst is, for example, the following (Chemical Formula 1)

（（化１）中、Ｍは、Ｔｉ、Ｚｒ、Ｈｆのいずれかの遷移金属を意味する。Ｘ¹及びＸ² は、互いに同じでも異なってもよく、水素原子、炭素原子数１から１０の炭化水素基、又は、アルキルシリル基、ハロゲン原子を意味する。Ｒ¹、Ｒ²、Ｒ³、Ｒ⁶、Ｒ⁷は、水素原子、炭素原子数１から１０の炭化水素基、アルキルシリル基を意味し、Ｒ¹、Ｒ²のうちどちらか一方は水素原子でない。また、Ｒ⁴、Ｒ⁵は、炭素数１から１０の炭化水素基又は、アルキルシリル基、を意味し、互いに結合して環を形成してもよい。Ｙは、炭素原子又は、ケイ素原子又は、ゲルマニウム原子を意味する。式中ｎは、１から３の整数を示す。）で表わすことが出来る。このうち、（化１）のＹが炭素原子であるメタロセン化合物であることが好ましい。また、（化１）のＲ⁴、Ｒ⁵が互いに結合して環を形成するインデニル環であることが好ましい。

(In (Chemical Formula 1), M means a transition metal of Ti, Zr, or Hf. X ¹ and X ² may be the same or different from each other, and may be a hydrogen atom or a carbon atom having 1 to 10 carbon atoms. A hydrocarbon group, an alkylsilyl group, or a halogen atom means R ¹ , R ² , R ³ , R ⁶ , or R ⁷ is a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms, or an alkylsilyl group. Which means that one of R ¹ and R ² is not a hydrogen atom, and R ⁴ and R ⁵ represent a hydrocarbon group having 1 to 10 carbon atoms or an alkylsilyl group, which are bonded to each other. A ring may be formed, and Y represents a carbon atom, a silicon atom, or a germanium atom, where n represents an integer of 1 to 3. Of these, a metallocene compound in which Y in (Chemical Formula 1) is a carbon atom is preferable. In addition, R ⁴ and R ⁵ in (Chemical Formula 1) are preferably an indenyl ring which is bonded to each other to form a ring.

  The resin composition for a release sheet according to the present embodiment is composed of a cyclic olefin resin and an ethylene / α-olefin copolymer. The blending ratio of each resin is not particularly limited, but the blending ratio of the ethylene / α-olefin copolymer is preferably 1 to 100 parts by weight, more preferably 3 to 50 parts by weight with respect to 100 parts by weight of the cyclic olefin resin. Parts, particularly preferably 5 to 25 parts by weight. When the blending ratio of the ethylene / α-olefin copolymer exceeds 100 parts by mass, the release property and heat resistance of the release sheet tend to deteriorate. On the other hand, when the blending ratio of the α-olefin copolymer is less than 1 part by mass, elongation and tearing tend to occur when the release sheet is peeled off. Furthermore, when the ethylene / α-olefin copolymer is less than 1 part by mass, the cyclic olefin-based resin is easily gelled, and the surface smoothness of the extruded film is impaired. Moreover, powders, such as a calcium carbonate, a talc, a kaolin, a mica, and a metal oxide, can be suitably mixed with the resin composition for release sheets which concerns on this embodiment. Furthermore, the release sheet resin composition according to the present embodiment includes an antioxidant, a stabilizer, a lubricant, a plasticizer, an organic pigment, an inorganic pigment, a surfactant, a coupling agent, or a fatty acid such as calcium stearate. Additives such as metal salts can be appropriately blended within a range that does not impair the problems of the present invention.

  The resin composition for a release sheet according to the present embodiment has two temperature-strain curves in the range of 0 to 12% in the temperature-strain curve obtained by thermomechanical analysis (TMA) of the resin mixture. The temperature of the maximum peak position of the second derivative curve is 140 to 200 ° C, preferably 160 to 180 ° C. Here, thermal mechanical analysis (TMA) will be described. Thermomechanical analysis (TMA) is a thermomechanical analyzer (trade name Thermal Mechanical, manufactured by Seiko Instruments Inc.) equipped with a jig for tensile testing according to JIS: K7115 (Plastic-Test method for creep characteristics-Part 1: Tensile creep). Analyzer TMA-SS6100 type) was used.

  A resin composition to be subjected to thermomechanical analysis (TMA) is cut out into a strip shape from a sheet molded into a sheet having a predetermined thickness to obtain a specimen for tensile test. At this time, the sample piece is cut out so that a tensile load is applied in the transverse direction (TD) of the sheet. If the sheet forming direction (MD) is the direction of the tensile test, the thermomechanical analysis (TMA) measurement results are not stable. This is because non-uniform stretching occurs in the forming direction of the sheet along with winding during forming. In general, when a mixture of synthetic resins is formed into an extruded film, it is flow-oriented with respect to the sheet forming direction (MD) to form a continuous phase. Therefore, in the thermomechanical analysis (TMA) of the sheet forming direction (MD). The temperature of the maximum peak position of the second derivative curve of the temperature-strain curve may be 0-20 ° C. higher than the temperature of the maximum peak position in the transverse direction (TD) of the sheet. Therefore, the temperature at the maximum peak position of the second derivative curve of the temperature-strain curve in the transverse direction (TD) of the sheet is used.

  This tensile test specimen was attached to a tensile test jig of the thermomechanical analyzer, and the temperature dependence of strain at a constant load was measured as a temperature-strain curve, and its second derivative curve was obtained. The maximum peak of the second derivative curve is a peak generated by softening before the sample piece melts down (the sample piece becomes hot and melts without retaining the original shape), There is a peak that occurs when it melts down and breaks. In order to prevent damage to the thermomechanical analyzer due to meltdown, a mechanism that stops measurement when the strain amount reaches a predetermined amount is generally used. Therefore, in order to obtain a strength characteristic at the time of softening of the sample piece by excluding a peak caused by meltdown, the temperature in the range of 0 to 12% of the strain amount in the temperature-strain curve obtained by thermomechanical analysis (TMA). -The temperature indicated by the maximum peak of the second derivative curve of the strain curve was determined.

In the temperature-strain curve in thermomechanical analysis (TMA), the vertical axis represents the strain of the sample piece and is expressed in TMA (%). The horizontal axis is temperature (° C.). In the temperature-strain curve obtained by thermomechanical analysis (TMA), the rate of change of strain with respect to temperature is expressed by (Equation 1) as a first derivative curve, where T is the temperature.
(Expression 1) Strain change rate = (d (TMA) / dT)
What differentiated (Equation 1) further by temperature is a second derivative curve of a temperature-strain curve in thermomechanical analysis (TMA) called DTMA (Derivative TMA), and is represented by (Equation 2).
(Equation 2) DTMA = d ² (TMA) / dT ²
The purpose of DTMA is to accurately capture the inflection point generated in the temperature-strain curve as a peak.

  The temperature at the maximum peak position of the second derivative curve of the temperature-strain curve in the range of 0-12% in the temperature-strain curve obtained by thermomechanical analysis (TMA) is difficult to extend even when softened. A mold having a release sheet made of the resin composition or a surface layer made of the resin composition, the temperature of the maximum peak position being in the range of 140 to 200 ° C. The sheet is easy to peel off from the heating plate, and when the release sheet is peeled off from the flexible printed circuit board or prepreg in a subsequent process, the release sheet is not sufficiently stretched or broken up by being caught in the unevenness. Since it has excellent creep resistance, it can be peeled off uniformly.

  When the temperature at the maximum peak position is less than 140 ° C., the peelability from the heating plate is deteriorated, and when it exceeds 200 ° C., the film becomes brittle and tends to be broken when peeled off.

  The release sheet which concerns on this embodiment consists of the said resin composition for release sheets, The arithmetic mean thickness becomes like this. Preferably it is 20-150 micrometers, More preferably, it is 30-80 micrometers. If it is too thin, the strength of the release sheet is insufficient and tends to be easily broken. On the other hand, if it is too thick, the flexibility of the release sheet is impaired, and the adhesion to an object such as a coverlay film or a prepreg tends to deteriorate.

  Moreover, although it may be a multilayer release sheet having a layer made of the resin composition for release sheet in at least one surface layer, in this case, the arithmetic average thickness of the surface layer is 3 to 150 μm. Preferably, it is 10-50 micrometers. In addition, 20-500 micrometers is preferable and, as for the total thickness of such a multilayer release sheet, 30-200 micrometers is more preferable.

  If the thickness of the resin composition for the release sheet as the surface layer is too thin, the surface layer is easily broken, resulting in inconvenience that the resin of the intermediate layer adheres to an object such as a coverlay film or a prepreg. On the other hand, if it is too thick, the flexibility of the film is impaired, and the adhesiveness to objects such as a coverlay film and a prepreg tends to deteriorate.

  When unevenness is imparted to the surface of the release sheet according to this embodiment, the average arithmetic roughness (Ra) is preferably 0.5 μm or more and 2.0 μm or less, more preferably 0.7 μm or more and 1.5 μm or less. is there. When the average arithmetic roughness (Ra) of the sheet surface is less than 0.5 μm, the unevenness is insufficient and sufficient “wrinkle” cannot be given to the object. In addition, since there is little reduction in the contact area with the object due to the unevenness, it is difficult to shift and adjust the position of the release sheet placed on the object, and the workability improvement effect may not be sufficiently obtained. . On the other hand, if it is larger than 2.0 μm, it may be easy to come off when the edge of the sheet is mechanically chucked and moved in the process of using the sheet.

  As a method for imparting unevenness to the surface of the release sheet according to the present embodiment, there is a roller process in which the release sheet is heated and pressurized by a roller with unevenness as a regular method. It is also possible to add unevenness to the sheet surface. When the inorganic powder is blended, the blending ratio is preferably 3 parts by weight or more and 20 parts by weight or less, more preferably 5 parts by weight or more and 20 parts by weight or less, particularly preferably 100 parts by weight of the resin composition for the release sheet. Is 5 parts by mass or more and less than 10 parts by mass. The unevenness on the surface of the sheet can be controlled by the mixing ratio of the inorganic powder, but when the mixing ratio exceeds 20 parts by mass, it is easy to come off when the edge of the sheet is mechanically chucked and moved in the process of using the sheet. There is. If the blending ratio is further increased, the flexibility of the sheet is impaired and the sheet may not be formed. On the other hand, if the blending ratio is less than 3 parts by mass, the unevenness of the sheet surface is insufficient.

  In addition, when the blending ratio of the inorganic powder is 20 parts by mass or less, there is almost no influence on the temperature showing the maximum peak of the second derivative curve of the temperature-strain curve in the thermomechanical analysis (TMA) of the resin composition for the release sheet. I can't.

  When inorganic powder is blended in the resin composition for a release sheet according to the present embodiment to provide unevenness on the sheet surface, the average particle size of the inorganic powder is preferably 1 μm or more and less than 10 μm, more preferably 3 μm or more and 8 μm. Is particularly preferably 4 μm or more and less than 7 μm. When the average particle size is 10 μm or more, the sheet is easily torn, and handling properties are impaired. When the average particle size is less than 1 μm, the unevenness of the sheet surface is insufficient. The average particle diameter is a median diameter which is a cumulative 50% point of the particle size distribution obtained by a laser diffraction particle size distribution measuring apparatus.

  When inorganic powder is mix | blended with the resin composition for mold release sheets which concerns on this embodiment, and an unevenness | corrugation is provided to the sheet | seat surface, it is preferable that inorganic powder is a calcium carbonate. There is no possibility of generating gas that may contaminate an object such as a flexible circuit board during heating, and a release sheet can be provided at low cost by using inexpensive calcium carbonate. The calcium carbonate powder can be used regardless of heavy calcium carbonate or light calcium carbonate as long as the particle size is in a preferred range.

  In the multilayer release sheet according to this embodiment, at least one layer excluding the surface layer made of the release sheet resin composition may be an ethylene / α-olefin copolymer layer. The layer of ethylene / α-olefin copolymer has the effect of imparting more flexibility and cushioning to the release sheet at the operating temperature of the release sheet, and it can be applied to objects such as coverlay film or prepreg during heating and pressurization. Unnecessary stress is not applied.

  In the release sheet according to the present embodiment, the maximum shrinkage at the crystal melting temperature of the ethylene / α-olefin copolymer of the release sheet resin composition is substantially less than 20%. More preferably, it is less than 10%, and particularly preferably less than 5%. The term “substantially unstretched” means that the sheet is not actively stretched during the extrusion of the sheet. In general, in the extrusion of the sheet, even if no stretching operation is actively applied, the sheet is molded as it is molded. It produces a flow orientation of up to 20% in the direction. In the release sheet according to this embodiment, the shrinkage is maximized at the crystal melting temperature of the ethylene / α-olefin copolymer of the resin composition. The maximum shrinkage is preferably as small as possible, but generally less than 20%, the stress applied to an object such as a coverlay film or prepreg during heating and pressurization is small, and it is suitable as a release sheet.

  By using the release sheet according to the present embodiment, the release sheet is easily peeled after heating and pressurizing the cover lay film or prepreg, and particularly when the surface of the cover lay film or prepreg has irregularities. Even when the release sheet is caught on the unevenness, the release sheet can be uniformly peeled without causing elongation or tearing. In addition, as a condition of heating and pressing, the sheet surface is overlapped on the surface of the cover lay film or the prepreg, pressurized with a heating plate at 200 ° C. for 30 minutes at a pressure of 10 MPa, and then returned to the atmosphere at 23 ° C. It can have releasability to such an extent that it does not adhere to the surface of the coverlay film or the prepreg.

  The release sheet according to the present embodiment can have release properties similar to those described above when the coverlay film or prepreg is made of an epoxy resin. The cover lay film made of epoxy resin has a laminated structure in which the contact side with the heating plate is made of polyimide. In this case, too, terminal holes corresponding to the terminals of the flexible printed circuit board are provided in the cover lay film. Therefore, the epoxy resin melted at the time of heating and pressing exudes from the terminal hole and directly contacts the release sheet. At this time, the release sheet according to the present embodiment has an advantage that it can be easily peeled off without being bonded and without causing local elongation or tearing.

  The release sheet according to the present embodiment is used for heat-pressure bonding of a coverlay film to a flexible printed circuit board or thermoforming of a prepreg, so that the release sheet on the process is caused by non-uniform peeling of the release sheet in a subsequent process. Obstacles such as adhesion of dust due to the release film on the flexible printed circuit board or prepreg can be eliminated, which can contribute to higher quality improvement.

  Next, the present invention will be described in more detail with reference to examples.

(Example 1)
<Manufacture of resin composition for release sheet>
97% by mass of cyclic olefin resin (Polyplastics, Tg 180 ° C), ethylene / α-olefin copolymer, ethylene / 1-octene copolymer (Dow Chemical Co., product name Engage, crystal melting temperature) 55 ° C.) at a ratio of 3% by mass to a twin screw extruder and mixed, and then pelletized by a pelletizer to obtain a resin composition for a release sheet.

<Manufacture of release sheet>
The pellet of the resin composition for the release sheet is supplied to a single screw extruder, the molten resin is extruded from a T-type die having a lip clearance of 0.9 mm, cooled by a cooling roll, and separated by an arithmetic average thickness of 60 μm. A mold sheet was obtained.

<Measurement of maximum temperature indicated by second derivative peak of temperature-strain curve in thermomechanical analysis (TMA)>
Thermomechanical analysis (TMA) is a thermomechanical analyzer (trade name Thermal Mechanical manufactured by Seiko Instruments Inc.) equipped with a jig for tensile testing according to JIS: K7115 (Plastics-Test method for creep characteristics-Part 1: Tensile creep). Analyzer TMA-SS6100 type) was used. The test piece (20 mm in length and 3 mm in width) subjected to the tensile test was cut out with the transverse direction (TD) of the release sheet as the length direction of the test piece, and a tensile load (per 1 μm thickness of the test piece) in the length direction. A load was set at a ratio of 1 mN.) Was added, and the temperature was increased at a rate of 10 ° C./min, and a temperature-strain curve was obtained until the specimen softened and the strain amount reached 12%. It was 174 degreeC as a result of calculating | requiring the temperature which the maximum peak position of the secondary differential curve of this temperature-strain curve shows.

(Example 2)
A release sheet of Example 2 was obtained in the same manner as in Example 1 except that the ratio of the cyclic olefin resin was changed to 95% by mass and the ratio of the ethylene / 1-octene copolymer was changed to 5% by mass. The arithmetic average thickness of the release sheet was 50 μm. The measured value of the temperature indicated by the maximum peak of the second derivative curve of the temperature-strain curve in thermomechanical analysis (TMA) was 175 ° C.

(Example 3)
A release sheet of Example 3 was obtained in the same manner as in Example 1 except that the ratio of the cyclic olefin-based resin was changed to 70% by mass and the ratio of the ethylene / 1-octene copolymer was changed to 30% by mass. The arithmetic average thickness of the release sheet was 55 μm. The measured value of the temperature indicated by the maximum peak of the second derivative curve of the temperature-strain curve in thermomechanical analysis (TMA) was 173 ° C.

(Comparative Example 1)
A release sheet of Comparative Example 1 was obtained in the same manner as in Example 1 except that the ratio of the cyclic olefin-based resin was changed to 50% by mass and the ratio of the ethylene / 1-octene copolymer was changed to 50% by mass. The arithmetic average thickness of the actual release sheet was 55 μm. The measured value of the temperature indicated by the maximum peak of the second derivative curve of the temperature-strain curve in thermomechanical analysis (TMA) was 75 ° C.

Example 4
The ethylene / α-olefin copolymer to be mixed is changed to an ethylene / 1-butene-1-hexene copolymer (manufactured by Dow Chemical Co., Ltd., trade name: flexomer, crystal melting temperature: 122 ° C.). Ratio of cyclic olefin resin The release sheet of Example 4 was obtained in the same manner as in Example 1 except that 95% by mass and 5% by mass of the ethylene / 1-hexene copolymer were used. The arithmetic average thickness of the release sheet was 60 μm. Moreover, the measured value of the temperature indicated by the maximum peak of the second derivative curve of the temperature-strain curve in thermomechanical analysis (TMA) was 174 ° C.

(Example 5)
Release sheet of Example 5 in the same manner as in Example 4 except that the ratio of the cyclic olefin-based resin was changed to 80% by mass and the ratio of the ethylene / 1-butene-1-hexene copolymer was changed to 20% by mass. Got. The arithmetic average thickness of the release sheet was 60 μm. The measured value of the temperature indicated by the maximum peak of the second derivative curve of the temperature-strain curve in thermomechanical analysis (TMA) was 173 ° C.

(Comparative Example 2)
The release sheet of Comparative Example 2 was prepared in the same manner as in Example 4 except that the ratio of the cyclic olefin resin was changed to 50% by mass and the ratio of the ethylene / 1-butene-1-hexene copolymer was changed to 50% by mass. Obtained. The arithmetic average thickness of the release sheet was 60 μm. The measured value of the temperature indicated by the maximum peak of the second derivative curve of the temperature-strain curve in thermomechanical analysis (TMA) was 130 ° C.

(Example 6)
The ethylene / α-olefin copolymer to be mixed is changed to an ethylene / 1-octene copolymer (manufactured by Dow Chemical Co., Ltd., product name Engage, crystal melting temperature 59 ° C.), and the ratio of the cyclic olefin resin is 80% by mass. A release sheet of Example 6 was obtained in the same manner as in Example 1 except that the ratio of the ethylene / 1-octene copolymer was 20% by mass. The arithmetic average thickness of the release sheet was 65 μm. The measured value of the temperature indicated by the maximum peak of the second derivative curve of the temperature-strain curve in thermomechanical analysis (TMA) was 148 ° C.

(Example 7)
The ethylene / α-olefin to be mixed is changed to an ethylene / 1-octene copolymer (manufactured by Dow Chemical Co., Ltd., trade name Engage, crystal melting temperature 60 ° C.), the ratio of cyclic olefin resin is 80% by mass, A release sheet of Example 7 was obtained in the same manner as in Example 1 except that the ratio of the 1-octene copolymer was 20% by mass. The arithmetic average thickness of the release sheet was 60 μm. The measured value of the temperature indicated by the maximum peak of the second derivative curve of the temperature-strain curve in thermomechanical analysis (TMA) was 173 ° C.

(Comparative Example 3)
The ethylene / α-olefin copolymer to be mixed is changed to an ethylene / 1-butene copolymer (Mitsui Chemicals Co., Ltd., trade name: buron, crystal melting temperature: 80 ° C.), and the ratio of the cyclic olefin resin is 80% by mass. The release sheet of Comparative Example 3 was formed in the same manner as in Example 1 except that the ratio of ethylene / 1-butene copolymer was 20% by mass. Therefore, a sheet that can be evaluated for releasability and thermomechanical analysis (TMA) was not obtained.

(Comparative Example 4)
Cyclic olefin resin (Polyplastics, Tg 180 ° C) 80% by mass, high density polyethylene (Nippon Polyethylene, product name Novatec HY530, crystal melting temperature 135 ° C) at a ratio of 20% by mass, twin screw A release sheet of Comparative Example 4 was obtained in the same manner as in Example 1 except that it was supplied to an extruder, mixed, and then pelletized by a pelletizer to obtain a resin composition for a release sheet. The arithmetic average thickness of the release sheet was 50 μm. The measured value of the temperature indicated by the maximum peak of the second derivative curve of the temperature-strain curve in thermomechanical analysis (TMA) was 173 ° C.

(Example 8)
A release sheet of Example 8 was obtained in the same manner as in Example 1 except that the ratio of the cyclic olefin-based resin was changed to 80% by mass and the ratio of the ethylene / 1-octene copolymer was changed to 20% by mass. The arithmetic average thickness of the release sheet was 50 μm. The temperature showing the maximum peak of the second derivative curve of the temperature-strain curve in thermomechanical analysis (TMA) was 175 ° C.

Example 9
<Manufacture of resin composition for release sheet>
80% by mass of cyclic olefin-based resin (manufactured by Polyplastics Co., Ltd., Tg 180 ° C.), 20% by mass of ethylene / 1-octene copolymer (manufactured by Dow Chemical Co., Ltd., trade name engagement, crystal melting temperature 55 ° C.) 5 parts by mass of heavy calcium carbonate powder (product name SL-100, product name SL-100, average particle size 6) with respect to a total of 100 parts by mass of the cyclic olefin resin and ethylene / 1-octene copolymer 0.0μm), supplied to a twin screw extruder, mixed, and then pelletized by a pelletizer to obtain a resin composition for a release sheet.

<Manufacture of release sheet>
A release sheet of Example 9 was obtained in the same manner as in Example 1. The arithmetic average thickness of the release sheet was 50 μm. The temperature showing the maximum peak of the second derivative curve of the temperature-strain curve in thermomechanical analysis (TMA) was 175 ° C.

(Example 10)
A release sheet of Example 10 was obtained in the same manner as in Example 9 except that the amount of heavy calcium carbonate powder was changed to 10 parts by mass. The arithmetic average thickness of the release sheet was 50 μm. Moreover, the measured value of the temperature indicated by the peak of the second derivative curve of the temperature-strain curve in thermomechanical analysis (TMA) was 175 ° C.

(Example 11)
A release sheet of Example 11 was obtained in the same manner as Example 9 except that the amount of heavy calcium carbonate powder was changed to 20 parts by mass. The arithmetic average thickness of the release sheet was 50 μm. Moreover, the measured value of the temperature indicated by the peak of the second derivative curve of the temperature-strain curve in thermomechanical analysis (TMA) was 175 ° C.

(Example 12)
Heavy calcium carbonate powder with a small particle diameter (manufactured by Takehara Chemical Industry Co., Ltd., trade name SL-700,
A release sheet of Example 12 was obtained in the same manner as in Example 10 except that the average particle diameter was changed to 4.5 μm. The arithmetic average thickness of the release sheet was 50 μm. Moreover, the measured value of the temperature indicated by the peak of the second derivative curve of the temperature-strain curve in thermomechanical analysis (TMA) was 175 ° C.

(Comparative Example 5)
A resin composition for a release sheet was obtained in the same manner as in Example 9 except that the amount of heavy calcium carbonate powder was changed to 40 parts by mass. An attempt was made to form a release sheet of Comparative Example 5 in the same manner as in Example 1. However, since the resin composition was too brittle and ruptured, a sheet that can be evaluated for releasability and thermomechanical analysis (TMA) It was not obtained.

The temperature-strain curve and its second derivative curve obtained by the thermomechanical analysis (TMA) of Examples 1 to 7 and Comparative Examples 1 to 2 are shown in FIGS. 1 to 3, the horizontal axis represents temperature, and the left vertical axis represents TMA (%) which is strain. The vertical axis on the right side shows DTMA (% · ° C. ⁻² ), which is the second derivative value of the strain in the temperature-strain curve, and overlaps with the temperature-strain curve so that the maximum peak position is clear. Avoid the positive direction.

  The release sheets obtained in the above Examples 1 to 12, Comparative Example 1, Comparative Example 2 and Comparative Example 4 were applied to various flexible printed circuit boards having irregularities due to the circuit with coverlay films (polyimide resin and epoxy). The resin adhesive layer laminated film) was used in the step of thermocompression bonding. In this post-process, it was observed whether the release sheet could be peeled uniformly from the coverlay film without causing elongation or tearing.

  As a result, all of the release sheets of Examples 1 to 12 could be peeled off uniformly without causing elongation or tearing. On the other hand, Comparative Example 1, Comparative Example 2 and Comparative Example 4 were caught by the unevenness on the surface of the cover lay film when peeled off from the cover lay film, resulting in elongation and tearing.

  Next, for Examples 1 to 12, Comparative Example 1, Comparative Example 2, and Comparative Example 4, the epoxy resin that is the adhesive layer of the coverlay film is heated and pressurized from the terminal opening of the coverlay film. The release properties (relative to epoxy) of the release sheet when exuded were compared by the following evaluation methods.

<Evaluation method of epoxy releasability>
Two types of cover lay films (manufactured by Nikkan Kogyo Co., Ltd. and Shin-Etsu Chemical Co., Ltd.) laminated with a thermosetting epoxy resin and a polyimide resin were used as the releasability evaluation objects. The release sheets of Examples and Comparative Examples were cut into dimensions of 30 mm in width and 100 mm in length, and superimposed on the coverlay film having dimensions of 20 mm in width and 80 mm in length, and heated and pressed at 200 ° C., 10 MPa for 30 minutes. Went. In addition, in order to evaluate the influence on the mold release property of the epoxy resin exuded at the time of heating and pressing, the surface of the epoxy resin adhesive layer of the cover lay film was brought into contact with the release sheet. After heating and pressing, the release sheet was peeled off from the coverlay film by hand, and the release property was determined according to the following criteria.

<Method of judging releasability>
A: Almost no adhesion.
○: It peels easily.
Δ: Peel off when force is applied. (Lower level where there is no practical problem)
X: Not peeled off (because it is strongly bonded, there is a problem in practical use).

  Similarly to the above, for Examples 1 to 12, Comparative Example 1, Comparative Example 2 and Comparative Example 4, when the copper terminal of the flexible printed circuit board is in direct contact with the release sheet through the terminal hole of the coverlay film The effect of the release sheet on the release property of the release sheet was compared by a model test as the release property to copper by the following evaluation method.

<Copper releasability evaluation method>
Copper foil (made by Fukuda Metal Foil Powder Industry Co., Ltd., trade name CF-T9FZ-SV, standard thickness 18 μm) was used as the releasability evaluation object. The release sheets of Examples and Comparative Examples were cut into dimensions of 30 mm in width and 100 mm in length, superimposed on the copper foil having dimensions of 20 mm in width and 80 mm in length, and subjected to heating and pressing at 200 ° C., 10 MPa for 30 minutes. went. In addition, the copper foil used two types, a smooth surface and a rough surface (brown surface treatment surface). After the heat and pressure, the release sheet was peeled off from the copper foil by hand, and the release property was determined according to the same criteria as the release property determination method in the evaluation for release property against epoxy.

  Further, in the same manner as described above, the releasability with respect to the epoxy resin prepreg was compared by the following evaluation method for Examples 1 to 12, Comparative Example 1, Comparative Example 2, and Comparative Example 4.

<Method for evaluating prepreg releasability>
A prepreg (epoxy resin prepreg made of glass fiber, Matsushita Electric Works, standard thickness 100 μm) was used as a releasability evaluation object. The release sheets of the examples and comparative examples were cut into dimensions of 30 mm in width and 100 mm in length, and superimposed on the prepreg having dimensions of 20 mm in width and 80 mm in length, and the heating and pressing conditions at 200 ° C. and 10 MPa for 30 minutes were performed. Set and went. After heat-pressing, the release sheet was peeled off from the prepreg by hand, and the release property was determined according to the same criteria as the release property determination method in the evaluation for release property against epoxy.

  About Example 8-Example 12, the arithmetic mean roughness (Ra) of the release sheet surface was measured by the following method.

<Measurement method of arithmetic mean roughness (Ra) of release sheet surface>
About Examples 8-12, arithmetic mean roughness prescribed | regulated to JIS: B0601 (surface roughness-definition and display) of a release sheet surface using a surface roughness measuring device (product name Surfcom made by Tokyo Seimitsu Co., Ltd.) (Ra) was measured. The measurement conditions are a cut-off value of 0.25 mm, an evaluation length of 1.25 mm, and a scanning speed of 0.03 mm / min.

  As described above, the evaluation results of the releasability against epoxy, the releasability against copper, and the releasability against prepreg are summarized in Tables 1 and 2. Table 3 shows the measurement results of the arithmetic average roughness (Ra) of the release sheet surface.

footnote:
(1) Peak temperature: temperature indicated by the maximum peak of the second derivative curve of the temperature-strain curve in thermomechanical analysis (TMA) (2) COC: cyclic olefin resin, manufactured by Polyplastics, Tg 180 ° C
(3) Octene copolymer A: ethylene / 1-octene copolymer, trade name Engage, manufactured by Dow Chemical Co., Tm = 55 ° C.
(4) Octene copolymer B: ethylene / 1-octene copolymer, trade name Engage, manufactured by Dow Chemical Co., Tm = 59 ° C.
(5) Octene copolymer C: ethylene / 1-octene copolymer, trade name Engage, manufactured by Dow Chemical Co., Tm = 60 ° C.
(6) Hexene copolymer: ethylene / 1-butene / 1-hexene copolymer, trade name flexomer, manufactured by Dow Chemical Co., Tm = 122 ° C.
(7) Butene copolymer: ethylene / 1-butene copolymer, trade name Bureon, manufactured by Mitsui Chemicals, Tm = 80 ° C.
(8) HDPE: high density polyethylene, product name Novapack HY530, manufactured by Nippon Polyethylene Co., Ltd., Tm = 135 ° C.
(9) Calcium carbonate A: Heavy calcium carbonate powder, trade name SL-100, manufactured by Takehara Chemical Industry Co., Ltd., average particle size = 6.0 μm
(10) Calcium carbonate B: Heavy calcium carbonate powder, product name SL-700, manufactured by Takehara Chemical Industry Co., Ltd., average particle size = 4.5 μm

  From the evaluation results shown in Tables 1 and 2, all of the release sheets of the examples subjected to the epoxy release property and copper release resistance evaluation test were obtained from the epoxy resin that exudes from the opening of the cover lay film. The releasability was good, and it was hardly adhered or peeled easily. Further, the release property to copper was at a level that could be peeled off without any problem in practical use, although the browned surface-treated rough surface was somewhat adhered. On the other hand, in the comparative example, with respect to the epoxy releasability, the adhesiveness to the epoxy resin is low as in the examples, and there is a practical problem in terms of releasability for a flat coverlay film having no unevenness on the surface. However, in the evaluation of the releasability to copper, there was a problem in practical use because it adhered strongly to the rough copper foil.

  Furthermore, as shown in Table 1 and Table 2, the release sheet of the Example used for the prepreg releasability evaluation test had a releasability that could be peeled off without any practical problem. On the other hand, the comparative example has a problem in practical use because it adheres strongly to the prepreg and cannot be peeled off.

  Results of comparison of change in arithmetic mean roughness (Ra) of release sheet surface due to blending of calcium carbonate powder for Examples 8 to 12 having the same composition of cyclic olefin resin and ethylene / α-olefin copolymer Is shown in Table 3. In Examples 9 to 12, irregularities are imparted to the surface of the release sheet by blending calcium carbonate powder, and the arithmetic average roughness (Ra) of the surface of the release sheet is used to impart a “texture” to the object. It was suitable. Moreover, as shown in Table 2, Examples 9 to 9 in which the arithmetic average roughness (Ra) of the release sheet surface was increased by blending the inorganic powder as compared with the release sheet of Example 8 not blended with the inorganic powder. In Example 12, the releasability was improved with respect to rough surface copper and prepreg, and it could be peeled off more easily.

  As can be seen from the above results, each example does not cause elongation or tearing due to catching on the unevenness of the coverlay film surface after heating and pressurization of the coverlay film to the flexible printed circuit board, as compared with the comparative example, In addition, it has excellent releasability in contact with the epoxy resin adhesive layer assumed in the heating and pressurizing process and in contact with copper terminals, and has excellent releasability after heat molding to epoxy prepreg. Was confirmed.

It is the temperature-strain curve obtained by the thermomechanical analysis (TMA) which concerns on Examples 1-3 and Comparative Example 1, and its secondary differential curve, (a) is Example 1, (b) is Example 2, (C) is Example 3 and (d) is Comparative Example 1. The solid line shows the temperature-strain curve, and the dotted line shows the temperature of the second derivative curve of the temperature-strain curve and its maximum peak position (excluding the meltdown peak). It is the temperature-strain curve obtained by the thermomechanical analysis (TMA) which concerns on Example 4, 5 and the comparative example 2, and its secondary differential curve, (a) is Example 4, (b) is Example 5, (C) is Comparative Example 2. The solid line shows the temperature-strain curve, and the dotted line shows the temperature of the second derivative curve of the temperature-strain curve and its maximum peak position (excluding the meltdown peak). It is the temperature-strain curve obtained by the thermomechanical analysis (TMA) which concerns on Example 6 and 7, and its secondary differential curve, (a) is Example 6, (b) is Example 7. FIG. The solid line shows the temperature-strain curve, and the dotted line shows the temperature of the second derivative curve of the temperature-strain curve and its maximum peak position (excluding the meltdown peak).

Claims (16)

  In a resin mixture composed of a cyclic olefin resin and an ethylene / α-olefin copolymer, the glass transition point (Tg) of the cyclic olefin resin is 100 to 250 ° C., and by thermomechanical analysis (TMA) of the resin mixture. Release sheet characterized in that the temperature at the maximum peak position of the second derivative curve of the temperature-strain curve in the range of the strain amount in the range of 0-12% in the obtained temperature-strain curve is 140-200 ° C Resin composition.   A release sheet comprising the resin composition for a release sheet according to claim 1 as a resin component.   The release sheet according to claim 2, wherein the release sheet has a layer made of the resin composition for a release sheet as a resin component in at least one surface layer.   The release sheet according to claim 3, wherein at least one of the layers excluding the surface layer made of the resin composition for release sheet as a resin component is an ethylene / α-olefin copolymer layer.   The maximum shrinkage ratio at the crystal melting temperature of the ethylene / α-olefin copolymer of the release sheet resin composition is substantially unstretched, and is less than 20%. 3. A release sheet according to 3 or 4.   The ethylene / α-olefin copolymer of the resin composition for release sheet is a copolymer of any one of 6 to 12 carbon atoms of the α-olefin, or a combination of the copolymers. The release sheet according to claim 2, wherein the release sheet is provided.   The ethylene / α-olefin copolymer of the resin composition for a release sheet is a copolymer of hexene or octene as an α-olefin. Release sheet.   The release sheet according to claim 2, 3, 4, 5, 6 or 7, wherein the cyclic olefin-based resin of the resin composition for a release sheet is an ethylene-norbornene copolymer.   The sheet surface comprising the resin composition for the release sheet as a resin component is superimposed on the surface of the cover lay film or prepreg, pressed with a heating plate at 200 ° C. for 30 minutes at a pressure of 10 MPa, and then placed in an atmosphere at 23 ° C. 9. The sheet according to claim 2, 3, 4, 5, 6, 7 or 8, wherein when the sheet is returned, the sheet surface does not adhere to the surface of the coverlay film or the prepreg. Release sheet.   The release sheet according to claim 9, wherein the sheet surface has the release property when the surface of the coverlay film or the prepreg has irregularities.   The release sheet according to claim 9 or 10, wherein the sheet surface has the release property when the coverlay film or the prepreg is made of an epoxy resin.   The release sheet according to claim 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11, wherein at least one surface has irregularities.   The release sheet according to claim 12, wherein the arithmetic average roughness (Ra) of at least one surface is 0.5 µm or more and 2.0 µm or less.   The resin composition comprising 3 parts by mass or more and 20 parts by mass or less of an inorganic powder having an average particle diameter of 1 μm or more and less than 10 μm with respect to 100 parts by mass of the resin composition for a release sheet. Item 14. A release sheet according to Item 12 or 13.   The release sheet according to claim 14, wherein the inorganic powder is calcium carbonate.   The release sheet according to claim 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 is used in the step of thermoforming the flexible printed circuit board or prepreg. A method for producing a flexible printed circuit board or prepreg.

Images