Release film

Abstract

The purpose of the present invention is to provide a mold release film having more excellent embeddability than conventional mold release films. The present invention relates to a multilayer release film having a surface layer, the surface layer containing at least one type of resin having a weight average molecular weight of 5000 or more and having a polyether skeleton in the main chain, and the ether ratio (ER) of the surface layer determined according to formula (1) being 0.005-1. Er = [sigma] Y / [sigma] Z (1) (In formula (1), Y represents the number of repeating units of a polyether moiety in each resin having a weight-average molecular weight of 5000 or more and having a polyether skeleton in the main chain contained in the surface layer. And Z represents the number of repeating units of structural units in each resin having a weight-average molecular weight of 5000 or more contained in the surface layer. Sigma is the sum of the number of repeating units for each resin.

Description

Technical Field

[0001] The invention relates to a release film. Background Art

[0002] In the hot press process of producing flexible printed circuit boards (FPCs), a release film is used to prevent the cover film from adhering to the hot press plate to protect the FPC. The release film is arranged between the cover film and the hot press plate, and follows the unevenness of the substrate surface during hot press molding to suppress the adhesive layer of the cover film from flowing out (for example, see Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2004-2593 Summary of the invention

[0006] Problems to be solved by the invention

[0007] In recent years, the use of FPC has expanded. As the amount of current applied to FPC increases, the thickness of copper wiring installed in FPC increases, or the copper wiring is finer. Accordingly, the embedding property (followability to unevenness) required of the release film becomes higher. The previous release film cannot meet the embedding property requirements, and sometimes gaps are generated in the FPC during hot press molding, or the adhesive of the cover film flows out to the electrode part and becomes an obstacle to the plating process of the electrode part.

[0008] An object of the present invention is to provide a release film having better embedding properties than conventional ones.

[0009] Means for solving problems

[0010] The present disclosure 1 relates to a release film, which is a multilayer release film having a surface layer, wherein the surface layer contains at least one resin having a weight average molecular weight of 5000 or more and having a polyether skeleton in the main chain,

[0011] The ether ratio ER of the surface layer determined by the following formula (1) is 0.005 or more and 1 or less.

[0012] ER=ΣY / ΣZ (1)

[0013] In the present disclosure 1, in formula (1), Y represents the number of repeating units of the polyether part in each resin having a weight average molecular weight of 5000 or more and having a polyether skeleton in the main chain contained in the above-mentioned surface layer. Z represents the number of repeating units of the structural unit in each resin having a weight average molecular weight of 5000 or more contained in the above-mentioned surface layer. Σ means the sum of the number of repeating units of each resin.

[0014] Present Disclosure 2 relates to the release film of Present Disclosure 1, wherein the ether ratio ER is less than 0.5.

[0015] The third disclosure relates to the release film of the first or second disclosure, wherein the surface layer further comprises at least one selected from a polyester resin and a poly-4-methyl-1-pentene resin.

[0016] Present Disclosure 4 relates to the release film of Present Disclosure 1, 2 or 3, wherein the thickness thereof is 90 μm or more.

[0017] Present disclosure 5 relates to the mold release film of present disclosure 1, 2, 3 or 4, further comprising a layer containing a polyolefin resin.

[0018] Present Disclosure 6 relates to the release film of Present Disclosure 1, 2, 3, 4 or 5, which is used in a heat press process in the production of a printed circuit board.

[0019] The present disclosure 7 relates to a release film, which is a multilayer release film having a surface layer, wherein the surface layer comprises a copolymer of polybutylene terephthalate and polytetramethylene glycol,

[0020] The ether ratio ER of the surface layer determined by the following formula (1) is 0.005 or more and 1 or less.

[0021] ER=ΣY / ΣZ (1)

[0022] In the present disclosure 7, in formula (1), Y represents the number of repeating units of the tetramethylene glycol-derived portion in each resin having a weight average molecular weight of 5,000 or more contained in the surface layer. Z represents the sum of the number of repeating units of the structural unit derived from butylene terephthalate and the structural unit derived from tetramethylene glycol in each resin having a weight average molecular weight of 5,000 or more contained in the surface layer. Σ means the sum of the number of repeating units of each resin.

[0023] The present disclosure 8 relates to a release film, which is a multilayer release film having a surface layer, wherein the surface layer comprises: polybutylene terephthalate; and a copolymer of polybutylene terephthalate and polytetramethylene glycol,

[0024] The ether ratio ER of the surface layer determined by the following formula (1) is 0.005 or more and 1 or less.

[0025] ER=ΣY / ΣZ (1)

[0026] In the present disclosure 8, in formula (1), Y represents the number of repeating units of the tetramethylene glycol-derived portion in each resin having a weight average molecular weight of 5000 or more contained in the surface layer. Z represents the sum of the number of repeating units of the structural unit derived from butylene terephthalate and the structural unit derived from tetramethylene glycol in each resin having a weight average molecular weight of 5000 or more contained in the surface layer. Σ means the sum of the number of repeating units of each resin.

[0027] The present disclosure 9 relates to a release film, which is a multilayer release film having a surface layer, wherein the surface layer comprises: polybutylene terephthalate; poly(4-methyl-1-pentene); and a copolymer of polybutylene terephthalate and polytetramethylene glycol,

[0028] The ether ratio ER of the surface layer determined by the following formula (1) is 0.005 or more and 1 or less.

[0029] ER=ΣY / ΣZ (1)

[0030] In the present disclosure 9, in formula (1), Y represents the number of repeating units of the tetramethylene glycol-derived portion in each resin having a weight average molecular weight of 5000 or more contained in the surface layer. Z represents the sum of the number of repeating units of the structural unit derived from butylene terephthalate, the structural unit derived from tetramethylene glycol, and the structural unit derived from 4-methyl-1-pentene in each resin having a weight average molecular weight of 5000 or more contained in the surface layer. Σ means the sum of the number of repeating units of each resin.

[0031] The present disclosure 10 relates to a mold release film, which is a multilayer mold release film having a surface layer, wherein the surface layer comprises poly(4-methyl-1-pentene); polyphenylene ether; and polystyrene,

[0032] The ether ratio ER of the surface layer determined by the following formula (1) is 0.005 or more and 1 or less.

[0033] ER=ΣY / ΣZ (1)

[0034] In the present disclosure 10, in formula (1), Y represents the number of repeating units of the phenylene ether-derived portion in each resin having a weight average molecular weight of 5,000 or more contained in the surface layer. Z represents the sum of the number of repeating units of the structural unit derived from 4-methyl-1-pentene, the structural unit derived from phenylene ether, and the structural unit derived from styrene in each resin having a weight average molecular weight of 5,000 or more contained in the surface layer. Σ means the sum of the number of repeating units of each resin.

[0035] Hereinafter, the present invention will be described in detail.

[0036] The present inventors studied a method of improving the embedding property of a release film by multi-layering a release film to provide a surface layer (release layer) and a layer different from the surface layer, and using a soft raw material for the layer different from the surface layer (e.g., a buffer layer). However, in order to obtain a release film with better embedding property, a method of improving the softness of the surface layer was studied in depth. As a result, it was found that by introducing a polyether into the resin constituting the surface layer of the release film, the other characteristics required for the surface layer, such as release property and heat resistance, can be made above a certain level, and the softness can be improved. Furthermore, as a result of further in-depth research, it was found that by setting the introduction amount of a polyether having a weight average molecular weight of 5,000 or more in the resin contained in the surface layer to a certain range, a release film having better embedding property than before can be obtained, and the present invention was completed.

[0037] The release film of the present invention is a multilayer release film having a surface layer (release layer). The surface layer is preferably a layer disposed on the outermost surface of the release film of the present invention. The release film of the present invention may be Figure 1 A two-layer laminate having a surface layer 11 on one side of another layer 12 (surface layer 11 / other layer 12) as shown in FIG. Figure 2 As shown, the laminate is a three-layer structure (surface layer 11 / other layer 12 / surface layer 11) having the surface layer 11 on both sides of the other layer 12. The other layer 12 is preferably a buffer layer.

[0038] In addition, the release film of the present invention may have layers other than the above-mentioned surface layer and the above-mentioned buffer layer, for example, it may be in a form in which other layers such as an adhesive layer are interposed between the above-mentioned surface layer and the above-mentioned buffer layer; or it may have the above-mentioned surface layer on one side of the above-mentioned buffer layer and have other surface layers in which the amount of polyether introduced is not within a certain range on the other side of the above-mentioned buffer layer.

[0039] The release film of the present invention preferably has the outermost surface layer in direct contact with the buffer layer. When the surface layer and the buffer layer do not have a clear boundary when observing the cross section of the release film of the present invention, the two can be distinguished by the difference in composition.

[0040] The surface layer contains at least one resin having a weight average molecular weight of 5000 or more and having a polyether skeleton in the main chain. The resin having a weight average molecular weight of 5000 or more and having a polyether skeleton in the main chain may be a homopolymer (polyether resin) or a copolymer. The homopolymer and the copolymer may also be used in combination. By making the resin constituting the surface layer contain at least one of the homopolymer and the copolymer, the softness of the release film can be improved. As the resin having a polyether skeleton in the main chain for improving the softness of the release film, a polymer having a weight average molecular weight of 5000 or more is selected from the viewpoint of not reducing the heat resistance of the release film, but a resin having a weight average molecular weight of less than 5000 and having a polyether skeleton in the main chain may also be included in the resin constituting the surface layer. In the surface layer, the content of the resin having a polyether skeleton in the main chain having a weight average molecular weight of less than 5000 is, for example, less than 5% by weight. The weight average molecular weight of the resin having a polyether skeleton in the main chain is preferably more than 10,000, and from the viewpoint of formability, it is preferably less than 500,000.

[0041] The homopolymer (polyether resin) is not particularly limited as long as the weight average molecular weight is 5000 or more, and examples thereof include polyether glycol, polyphenylene ether, polyacetal, polyether ether ketone, polyether ketone, polyether sulfone, polyether imide, and the like. As the polyether glycol, for example, polytetramethylene glycol (PTMG) can be mentioned. The polyphenylene ether can be used as a modified body, and for example, a material obtained by blending polyphenylene ether and polystyrene at a weight ratio of 1:1 and alloying can be mentioned. The homopolymer can be used alone or in combination of two or more.

[0042] The copolymer is not particularly limited as long as the weight average molecular weight is 5000 or more, and examples thereof include copolymers of aromatic polyesters and aliphatic polyethers, copolymers of polyurethanes and aliphatic polyethers, copolymers of polyamides and aliphatic polyethers, etc. The aromatic polyester is not particularly limited, and examples thereof include polybutylene terephthalate, polyethylene terephthalate, etc. The aliphatic polyether is not particularly limited, and examples thereof include polytetramethylene glycol (PTMG), polyethylene glycol, polyethylene glycol, polypropylene glycol, etc. As the copolymer of aromatic polyesters and aliphatic polyethers, preferably a copolymer of polybutylene terephthalate and aliphatic polyethers. The copolymers may be used alone or in combination of two or more.

[0043] The surface layer has an ether ratio (ER) calculated from the following formula (1) of 0.005 or more and 1 or less. When the ether ratio ER is 0.005 or more and 1 or less, excellent embeddability is obtained.

[0044] ER=ΣY / ΣZ (1)

[0045] In formula (1), Y represents the number of repeating units of the polyether part in each resin with a weight average molecular weight of 5000 or more and having a polyether skeleton in the main chain contained in the above-mentioned surface layer. Z represents the number of repeating units of the structural unit in each resin with a weight average molecular weight of 5000 or more contained in the above-mentioned surface layer. Σ refers to the sum of the number of repeating units of each resin. It should be noted that in this specification, the resin mainly refers to a polymer compound, and the repeating unit in each resin refers to the repeating unit of the chemical structure in the polymer compound (in other words, the structural unit derived from the monomer). In addition, the number of repeating units refers to the amount of repetition, not the number of types of structural units, but the number of times the same structural unit is repeated.

[0046] The number of repeating units of the polyether moiety in each resin and the number of repeating units of the structural unit in each resin can also be calculated based on the average degree of polymerization of each resin, the mixing ratio in the surface layer, and the abundance ratio of each structural unit.

[0047] The polyether moiety in each resin having a weight average molecular weight of 5,000 or more contained in the surface layer may be used alone or in combination of two or more. The type of the polyether moiety is not distinguished in the calculation of the ether ratio ER.

[0048] The ether ratio ER theoretically takes a value of 0 to 1. That is, when all the resins with a weight average molecular weight of 5,000 or more contained in the surface layer do not contain a polyether moiety as a repeating unit (monomer unit), it is "0", and when all the repeating units in all the resins with a weight average molecular weight of 5,000 or more contained in the surface layer are polyether moieties, it is "1". The ether ratio ER indicates the existence ratio of the polyether moieties in all the resins with a weight average molecular weight of 5,000 or more contained in the surface layer.

[0049] The larger the ether ratio ER, the higher the ratio of the polyether part in the resin, and the easier it is to ensure the softness of the release film, so it is advantageous in terms of improving embedding. The smaller the ether ratio ER, the more advantageous it is in terms of ensuring the release property of the release film, or reducing thermal shrinkage and improving the dimensional stability before and after the hot pressing process, but if it is less than 0.005, the embedding of the release film cannot be fully improved. From the viewpoint of improving the embedding of the release film and making other properties such as the release property and heat resistance required for the surface layer excellent, the ether ratio ER is preferably 0.01 or more, preferably less than 0.5, more preferably less than 0.25, and further preferably less than 0.14.

[0050] As can be understood from the above formula (1), the above ether ratio ER can be adjusted by changing the average degree of polymerization of each resin having a weight average molecular weight of 5000 or more contained in the above surface layer, the molar ratio of each resin having a weight average molecular weight of 5000 or more contained in the above surface layer, and the average number of repeating units of the polyether part in each resin having a weight average molecular weight of 5000 or more contained in the surface layer. The above ether ratio ER can be calculated based on information related to the raw materials of the above surface layer, or it can be calculated by analyzing the materials constituting the above surface layer. As an analysis method, for example, there can be cited: a method using a nuclear magnetic resonance (NMR) method and using information such as peak position and area in the obtained spectrum. It should be noted that when calculating the above ether ratio ER, components with a weight average molecular weight of less than 5000 are not considered. When the above ether ratio ER is calculated by analyzing the materials constituting the above surface layer, the analysis is performed after removing components with a weight average molecular weight of less than 5000 by methods such as gel permeation chromatography (GPC).

[0051] The surface layer may contain other resins besides the resin having a weight average molecular weight of 5,000 or more and having a polyether skeleton in the main chain, and preferably contains a resin having a higher hardness than the resin constituting a layer different from the surface layer (such as the buffer layer). Thus, mold release properties can be easily ensured.

[0052] The surface layer preferably further comprises at least one selected from polyester resin, poly-4-methyl-1-pentene resin, polyamide resin and polypropylene resin, and more preferably comprises at least one selected from polyester resin and poly-4-methyl-1-pentene resin.

[0053] The polyester resin preferably contains an aromatic polyester resin. By containing the aromatic polyester resin, embedding properties and anti-bleeding properties of the adhesive formed in the cover film can be improved.

[0054] The aromatic polyester resin is not particularly limited, but is preferably a crystalline aromatic polyester resin. Specifically, for example, polyethylene terephthalate resin, polybutylene terephthalate resin, polyhexamethylene terephthalate resin, polyethylene naphthalate resin, polybutylene naphthalate resin, butylene terephthalate-polytetramethylene glycol copolymer, etc. These aromatic polyester resins can be used alone or in combination of two or more. Among them, polybutylene terephthalate resin is preferred from the viewpoint of balance of heat resistance, demoulding property, embedding property, etc.

[0055] Also preferred are polybutylene terephthalate resins and mixed resins of copolymers of polybutylene terephthalate and aliphatic polyethers. The aliphatic polyethers are not particularly limited, and examples thereof include polyethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

[0056] Among the aromatic polyester resins, commercially available products include, for example, “PELPRENE (registered trademark)” (manufactured by Toyobo Co., Ltd.), “HYTREL (registered trademark)” (manufactured by Toray DuPont Co., Ltd.), “DURANEX (registered trademark)” (manufactured by Polyplastics Co., Ltd.), and “NOVADURAN (registered trademark)” (manufactured by Mitsubishi Engineering Plastics Co., Ltd.).

[0057] Since the surface layer contains poly-4-methyl-1-pentene resin, the release film of the present invention has excellent releasability from a stainless steel hot platen, a cover film composed of a polyimide film, and the like, and also has good heat resistance in a hot pressing process at around 170°C.

[0058] As the poly 4-methyl-1-pentene resin, in addition to a homopolymer of 4-methyl-1-pentene, a copolymer of 4-methyl-1-pentene and a monomer other than 4-methyl-1-pentene can be used.

[0059] The monomers other than the above-mentioned 4-methyl-1-pentene are not particularly limited, and examples thereof include α-olefins having 20 or less carbon atoms, such as ethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene.

[0060] When the poly 4-methyl-1-pentene resin is a copolymer, the content of the structural unit derived from 4-methyl-1-pentene is preferably 80% by weight or more, more preferably 90% by weight or more, from the viewpoint of exhibiting higher releasability and heat resistance.

[0061] As the poly-4-methyl-1-pentene resin, for example, a commercially available product such as TPX (registered trademark) manufactured by Mitsui Chemicals, Inc. can be used.

[0062] The surface layer may contain a rubber component. When the surface layer contains a rubber component, embedding properties of the release film are improved.

[0063] The rubber component is not particularly limited, and examples thereof include natural rubber, styrene-butadiene copolymer, polybutadiene, polyisoprene, acrylonitrile-butadiene copolymer, ethylene-propylene copolymer (EPM, EPDM), polychloroprene, butyl rubber, acrylic rubber, silicone rubber, urethane rubber, etc. In addition, examples of the rubber component include olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, ester-based thermoplastic elastomers, and amide-based thermoplastic elastomers.

[0064] The surface layer may contain a stabilizer.

[0065] The stabilizer is not particularly limited, and examples thereof include hindered phenol-based antioxidants and heat stabilizers.

[0066] The hindered phenol antioxidant is not particularly limited, and examples thereof include 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)-propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane, and the like. The heat stabilizer is not particularly limited, and examples thereof include tris(2,4-di-tert-butylphenyl) phosphite, trilauryl phosphite, 2-tert-butyl-α-(3-tert-butyl-4-hydroxyphenyl)-p-isopropylphenylbis(p-nonylphenyl) phosphite, dimyristyl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, pentaerythritol tetra(3-laurylthiopropionate), and di(tridecyl)-3,3'-thiodipropionate.

[0067] The surface layer may further contain conventionally known additives such as fibers, inorganic fillers, flame retardants, ultraviolet absorbers, antistatic agents, inorganic substances, and higher fatty acid salts.

[0068] Preferred forms of the surface layer include: (A) a form comprising a copolymer of polybutylene terephthalate and polytetramethylene glycol; (B) a form comprising polybutylene terephthalate and a copolymer of polybutylene terephthalate and polytetramethylene glycol; (C) a form comprising polybutylene terephthalate, poly(4-methyl-1-pentene), and a copolymer of polybutylene terephthalate and polytetramethylene glycol; (D) a form comprising poly(4-methyl-1-pentene), polyphenylene ether, and polystyrene. The polyphenylene ether and polystyrene in the form (D) may be a product obtained by blending and alloying polyphenylene ether and polystyrene at a weight ratio of 1:1.

[0069] In the case of the above-mentioned forms (A) and (B), Y in the above-mentioned formula (1) represents the number of repeating units of the tetramethylene glycol-derived portion in each resin having a weight average molecular weight of 5,000 or more contained in the above-mentioned surface layer, and Z represents the sum of the number of repeating units of the structural unit derived from butylene terephthalate and the structural unit derived from tetramethylene glycol in each resin having a weight average molecular weight of 5,000 or more contained in the above-mentioned surface layer.

[0070] In the case of the above-mentioned form (C), Y in the above-mentioned formula (1) represents the number of repeating units of the tetramethylene glycol-derived portion in each resin having a weight average molecular weight of 5,000 or more contained in the above-mentioned surface layer, and Z represents the sum of the number of repeating units of the structural unit derived from butylene terephthalate, the structural unit derived from tetramethylene glycol, and the structural unit derived from 4-methyl-1-pentene in each resin having a weight average molecular weight of 5,000 or more contained in the above-mentioned surface layer.

[0071] In the case of the above-mentioned form (D), Y in the above-mentioned formula (1) represents the number of repeating units of the tetramethylene glycol-derived portion in each resin having a weight average molecular weight of 5,000 or more contained in the above-mentioned surface layer, and Z represents the sum of the number of repeating units of the structural unit derived from 4-methyl-1-pentene, the structural unit derived from phenylene ether, and the structural unit derived from styrene in each resin having a weight average molecular weight of 5,000 or more contained in the above-mentioned surface layer.

[0072] The thickness of the surface layer is not particularly limited. The thinner the surface layer is, the easier it is to ensure the softness of the release film through a layer different from the surface layer (preferably the buffer layer), so even if the ether ratio ER of the surface layer is reduced, it is easy to ensure the embedding property of the release film, which is advantageous in this respect. The thicker the surface layer is, the more advantageous it is in ensuring the demolding property of the release film or reducing thermal shrinkage to improve the dimensional stability before and after the hot pressing process. The thickness of the surface layer is preferably 5 μm or more, more preferably 7 μm or more. In addition, the thickness of the surface layer is preferably less than 100 μm, more preferably less than 50 μm.

[0073] The release film of the present invention obtains excellent embedding property by increasing the ether ratio ER of the surface layer (release layer), but the embedding property of the release film can also be controlled by the thickness of the surface layer. Therefore, when the thickness of the surface layer is small, the ether ratio ER of the surface layer can be adjusted to be small, and other properties such as the release property and heat resistance required by the surface layer can be improved. In addition, when the thickness of the surface layer is large, it is preferred to adjust the ether ratio ER of the surface layer to be large so as to fully obtain the effect of improving embedding property. For example, when the thickness of the surface layer is less than 50 μm, the ether ratio ER of the surface layer is preferably 0.02 or more, when the thickness of the surface layer is 50 μm or more and less than 100 μm, the ether ratio ER of the surface layer is preferably 0.04 or more, and when the thickness of the surface layer is 100 μm or more, the ether ratio ER of the surface layer is preferably 0.1 or more.

[0074] From the viewpoint of improving the embedding property of the release film, the buffer layer is preferably softer than the surface layer. In the manufacturing process of a flexible printed substrate, when hot pressing is performed with a release film disposed between the cover film and the hot press plate, the surface layer in direct contact with the cover film and the hot press plate is required to have excellent demolding properties, so there is a certain limit to the improvement of embedding properties. By providing a soft layer as the buffer layer, the embedding property of the release film can be improved, and a release film having both excellent demolding properties and embedding properties can be easily produced.

[0075] The material constituting the buffer layer is not particularly limited, but preferably contains at least one resin.

[0076] Examples of the resin constituting the cushion layer include polyolefins, polystyrenes, polyvinyl chlorides, polyamides, polycarbonates, polysulfones, and polyesters, and polyolefins are preferably used. That is, the release film of the present invention preferably further comprises a layer containing a polyolefin resin as a layer different from the surface layer.

[0077] The above-mentioned polyolefin resin is not particularly limited, and for example, polyethylene resin (for example, high-density polyethylene, low-density polyethylene, linear low-density polyethylene), polypropylene resin, ethylene-vinyl acetate copolymer, etc. can be mentioned. In addition, ethylene-acrylic acid monomer copolymers such as ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-acrylic acid copolymer can also be mentioned. These polyolefin resins can be used alone or in combination of two or more. Among them, polypropylene resin is preferred from the aspect of easy embedding property and heat resistance.

[0078] The content of the polyolefin resin in the buffer layer is not particularly limited, but the preferred lower limit is 50% by weight, and the preferred upper limit is 90% by weight. If the content of the polyolefin resin is 50% by weight or more, the softness of the buffer layer becomes sufficient, and the embedding property of the release film is improved. If the content of the polyolefin resin is 90% by weight or less, the adhesion between the release layer and the buffer layer is improved. The more preferred lower limit of the content of the polyolefin resin is 60% by weight, and the further preferred lower limit is 65% by weight. The more preferred upper limit of the content of the polyolefin resin is 80% by weight, and the further preferred upper limit is 75% by weight.

[0079] The cushion layer preferably contains the resin constituting the surface layer.

[0080] By making the buffer layer contain the resin constituting the surface layer, the adhesion between the surface layer and the buffer layer is improved. The buffer layer more preferably contains the main component resin of the surface layer, and further preferably contains the main component resin of the surface layer and a polyolefin resin. Here, the main component resin of the surface layer refers to the resin with the highest content among the resins contained in the surface layer. It should be noted that the buffer layer may contain a resin with a weight average molecular weight of more than 5000 having a polyether skeleton in the main chain, or may not contain a resin with a weight average molecular weight of more than 5000 having a polyether skeleton in the main chain.

[0081] The content of the resin constituting the surface layer in the buffer layer is not particularly limited, but the preferred lower limit is 10% by weight, and the preferred upper limit is 50% by weight. If the content of the resin constituting the surface layer is 10% by weight or more, the adhesion between the surface layer and the buffer layer is improved. If the content of the resin constituting the surface layer is 50% by weight or less, the softness of the buffer layer becomes sufficient, and the followability of the release film to the concave and convex is improved. The more preferred lower limit of the content of the resin constituting the surface layer is 15% by weight, and the further preferred lower limit is 20% by weight. The more preferred upper limit of the content of the resin constituting the surface layer is 40% by weight, and the further preferred upper limit is 35% by weight.

[0082] The buffer layer may further contain additives such as fibers, inorganic fillers, flame retardants, ultraviolet absorbers, antistatic agents, inorganic substances, and higher fatty acid salts.

[0083] The buffer layer may have a single-layer structure consisting of a single layer or a multi-layer structure consisting of a laminate of multiple layers. When the buffer layer has a multi-layer structure, the multiple layers may be laminated and integrated via an adhesive layer.

[0084] The thickness of the buffer layer is not particularly limited, but the preferred lower limit is 15 μm, and the preferred upper limit is 200 μm. If the thickness of the buffer layer is 15 μm or more, the embedding property of the release film is further improved. If the thickness of the buffer layer is 200 μm or less, the resin exudation from the buffer layer generated at the film end during the hot pressing process can be suppressed. The more preferred lower limit of the thickness of the buffer layer is 30 μm, and the more preferred upper limit is 170 μm.

[0085] The thickness of the release film of the present invention is not particularly limited. The thinner the overall thickness of the release film, the more advantageous it is for suppressing the resin seepage from a layer different from the surface layer (such as the above-mentioned buffer layer). The thicker the overall thickness of the release film, the more advantageous it is for following the large height difference of the substrate surface during hot press forming. The thickness of the release film of the present invention is preferably 70 μm or more, more preferably 90 μm or more. In addition, the thickness of the release film of the present invention is preferably less than 250 μm, more preferably less than 210 μm.

[0086] The method for producing the release film of the present invention is not particularly limited. For example, there may be mentioned: a method of producing a film by water-cooled or air-cooled coextrusion blow molding, a coextrusion T-die method; a method of producing a film by solvent casting, a hot press molding method, etc.

[0087] In the case of a structure having the surface layer on both sides of the buffer layer, the following method can be cited: after preparing a film to be the surface layer on one side, laminating the buffer layer on the film by extrusion lamination, and then dry laminating the surface layer on the other side. In addition, a method can be cited: dry laminating a film to be the surface layer on one side, a film to be the buffer layer, and a film to be the surface layer on the other side.

[0088] Among them, a method of forming a film by a co-extrusion T-die method is suitable from the viewpoint of excellent control of the thickness of each layer.

[0089] The release film of the present invention can exhibit better embedding properties (conformability to uneven surfaces) than before during hot pressing, and is therefore preferably used in a hot pressing process, and is particularly preferably used in a hot pressing process in the manufacture of a printed circuit board. Conditions for the hot pressing process using the release film of the present invention include, for example, a temperature of 100 to 220° C. and a pressure of 0.5 to 100 MPa.

[0090] The use of the release film of the present invention is not particularly limited, and the release film can be suitably used in the production process of a flexible printed circuit board (FPC), a printed wiring board, a multilayer printed wiring board, and the like.

[0091] Specifically, for example, in the process of manufacturing FPC, the release film of the present invention can be used when thermocompression bonding a cover film to a flexible circuit board body having a copper circuit formed thereon via a thermosetting adhesive or a thermosetting adhesive sheet.

[0092] The mold release film of the present invention has extremely excellent mold releasability and can therefore be suitably used in the production of FPC by the RtoR method which requires high mold releasability.

[0093] Effects of the Invention

[0094] According to the present invention, a release film having better embedding properties than conventional ones can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0095] Figure 1 This is a cross-sectional view schematically showing a release film composed of two layers: a surface layer (release layer) and other layers.

[0096] Figure 2 This is a cross-sectional view schematically showing a release film composed of three layers: surface layer (release layer) / other layer / surface layer (release layer). DETAILED DESCRIPTION

[0097] Hereinafter, the embodiments of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[0098] (Example 1)

[0099] As the resin composition for the surface layer (mold release layer), a copolymer of polybutylene terephthalate (PBT) and polytetramethylene glycol (PTMG) (PBT / PTMG copolymer, manufactured by Hetron Elastomer Co., Ltd., model number: H72DMG) was used.

[0100] As the resin composition for the cushion layer, a mixture of 75 parts by weight of polypropylene (PP) and 25 parts by weight of polybutylene terephthalate (PBT) was used.

[0101] Using an extruder (GM ENGINEERING, GM30-28 (screw diameter 30 mm, L / D 28)), the resin composition for the surface layer and the resin composition for the buffer layer were co-extruded in three layers under the conditions of a molding temperature of 250°C and a T-die width of 400 mm, and the extruded molten resin was cooled by a cooling roller (temperature 90°C, arithmetic mean roughness of the surface Ra 0.1 μm). Thus, a film having a three-layer structure with a surface layer on both sides of the buffer layer was obtained. The thickness of the surface layer was set to 20 μm, the thickness of the buffer layer was set to 80 μm, and the thickness of the entire film was set to 120 μm. It should be noted that during cooling, the contact time between the molten resin and the cooling roller was set to 1.0 second, and the elongation stress when the molten resin was cooled by the cooling roller was set to 450 kPa.

[0102] (Example 2)

[0103] A multilayer release film having a three-layer structure was obtained in the same manner as in Example 1 except that the thickness of the surface layer was 105 μm, the thickness of the buffer layer was 20 μm, and the thickness of the entire film was 230 μm.

[0104] (Example 3)

[0105] A multilayer release film with a three-layer structure was obtained in the same manner as in Example 1 except that a mixture of 50 parts by weight of polybutylene terephthalate having a weight average molecular weight of 5,000 or more and 50 parts by weight of a PBT / PTMG copolymer (manufactured by Hetron Elastomer, model: H72DMG) was used as the resin composition for the surface layer, and the thickness of the surface layer was set to 15 μm, the thickness of the buffer layer was set to 90 μm, and the thickness of the entire film was set to 120 μm.

[0106] (Example 4)

[0107] A multilayer release film having a three-layer structure was obtained in the same manner as in Example 3 except that the thickness of the surface layer was 70 μm, the thickness of the buffer layer was 55 μm, and the thickness of the entire film was 195 μm.

[0108] (Example 5)

[0109] A multilayer release film with a three-layer structure was obtained in the same manner as in Example 1 except that a mixture of 75 parts by weight of polybutylene terephthalate having a weight average molecular weight of 5,000 or more and 25 parts by weight of a PBT / PTMG copolymer (manufactured by Hetron Elastomer, model: H72DMG) was used as the resin composition for the surface layer, and the thickness of the surface layer was set to 10 μm, the thickness of the buffer layer was set to 100 μm, and the thickness of the entire film was set to 120 μm.

[0110] (Example 6)

[0111] A multilayer release film with a three-layer structure was obtained in the same manner as in Example 1 except that a mixture of 80 parts by weight of polybutylene terephthalate having a weight average molecular weight of 5,000 or more and 20 parts by weight of a PBT / PTMG copolymer (manufactured by Hetron Elastomer, model: H72DMG) was used as the resin composition for the surface layer, and the thickness of the surface layer was set to 15 μm, the thickness of the buffer layer was set to 160 μm, and the thickness of the entire film was set to 190 μm.

[0112] (Example 7)

[0113] A multilayer release film having a three-layer structure was obtained in the same manner as in Example 6 except that the thickness of the surface layer was 55 μm, the thickness of the buffer layer was 80 μm, and the thickness of the entire film was 190 μm.

[0114] (Example 8)

[0115] A multilayer release film with a three-layer structure was obtained in the same manner as in Example 1 except that a mixture of 40 parts by weight of polybutylene terephthalate having a weight average molecular weight of 5,000 or more, 40 parts by weight of poly(4-methyl-1-pentene) resin (manufactured by Mitsui Chemicals, Inc., TPX (registered trademark)) and 20 parts by weight of a PBT / PTMG copolymer was used as the resin composition for the surface layer, the molding temperature was set to 280° C., the thickness of the surface layer was set to 20 μm, the thickness of the buffer layer was set to 150 μm, and the thickness of the entire film was set to 190 μm.

[0116] (Example 9)

[0117] As the resin composition for the surface layer, a mixture of 91.5 parts by weight of a poly(4-methyl-1-pentene) resin having a weight average molecular weight of 5000 or more (manufactured by Mitsui Chemicals, Inc., TPX (registered trademark)) and 8.5 parts by weight of a modified polyphenylene ether obtained by blending and alloying polyphenylene ether and polystyrene at a weight ratio of 1:1 (manufactured by Asahi Kasei Corporation, XYRON (registered trademark) 600H) was used. The molding temperature was set to 280° C., the thickness of the surface layer was set to 30 μm, the thickness of the buffer layer was set to 50 μm, and the thickness of the entire film was set to 110 μm. A multilayer release film with a three-layer structure was obtained in the same manner as in Example 1, except that the molding temperature was set to 280° C., the thickness of the surface layer was set to 30 μm, the thickness of the buffer layer was set to 50 μm, and the thickness of the entire film was set to 110 μm.

[0118] (Example 10)

[0119] A multilayer release film having a three-layer structure was obtained in the same manner as in Example 9 except that the thickness of the surface layer was 105 μm, the thickness of the buffer layer was 20 μm, and the thickness of the entire film was 230 μm.

[0120] (Example 11)

[0121] As the resin composition for the surface layer, a mixture of 97 parts by weight of polybutylene terephthalate having a weight average molecular weight of more than 5000 and 3 parts by weight of modified polyphenylene ether obtained by blending and alloying polyphenylene ether and polystyrene in a weight ratio of 1:1 was used, the molding temperature was set to 270°C, the thickness of the surface layer was set to 25 μm, the thickness of the buffer layer was set to 70 μm, and the thickness of the entire film was set to 120 μm. Except for this, a multilayer release film with a 3-layer structure was obtained in the same manner as in Example 1.

[0122] (Example 12)

[0123] A multilayer release film with a three-layer structure was obtained in the same manner as in Example 1 except that a mixture of 92.2 parts by weight of polybutylene terephthalate having a weight average molecular weight of 5,000 or more and 7.8 parts by weight of a PBT / PTMG copolymer (manufactured by Hetron Elastomer, model: H72DMG) was used as the resin composition for the surface layer, and the thickness of the surface layer was set to 15 μm, the thickness of the buffer layer was set to 70 μm, and the thickness of the entire film was set to 100 μm.

[0124] (Example 13)

[0125] A multilayer release film having a three-layer structure was obtained in the same manner as in Example 1 except that a mixture of 95 parts by weight of polybutylene terephthalate having a weight average molecular weight of 5,000 or more and 5 parts by weight of a PBT / PTMG copolymer (manufactured by Hetron Elastomer, model: H72DMG) was used as the resin composition for the surface layer, and the thickness of the surface layer was set to 60 μm, the thickness of the buffer layer was set to 75 μm, and the thickness of the entire film was set to 195 μm.

[0126] (Example 14)

[0127] A multilayer release film having a three-layer structure was obtained in the same manner as in Example 13 except that the thickness of the surface layer was 20 μm, the thickness of the buffer layer was 80 μm, and the thickness of the entire film was 120 μm.

[0128] (Example 15)

[0129] A multilayer release film having a three-layer structure was obtained in the same manner as in Example 1 except that a mixture of 97.5 parts by weight of polybutylene terephthalate having a weight average molecular weight of 5,000 or more and 2.5 parts by weight of a PBT / PTMG copolymer (manufactured by Hetron Elastomer, model: H72DMG) was used as the resin composition for the surface layer, and the thickness of the surface layer was set to 25 μm, the thickness of the buffer layer was set to 70 μm, and the thickness of the entire film was set to 120 μm.

[0130] (Example 16)

[0131] A multilayer release film having a three-layer structure was obtained in the same manner as in Example 1 except that a mixture of 99 parts by weight of polybutylene terephthalate having a weight average molecular weight of 5,000 or more and 1 part by weight of a PBT / PTMG copolymer (manufactured by Hetron Elastomer, model: H72DMG) was used as the resin composition for the surface layer, and the thickness of the surface layer was set to 15 μm, the thickness of the buffer layer was set to 90 μm, and the thickness of the entire film was set to 120 μm.

[0132] (Comparative Example 1)

[0133] As the resin composition for the surface layer, polybutylene terephthalate having a weight average molecular weight of more than 5000 was used, the molding temperature was set to 250°C, the thickness of the surface layer was set to 20 μm, the thickness of the buffer layer was set to 80 μm, and the thickness of the entire film was set to 120 μm. Except for this, a multilayer release film with a three-layer structure was obtained in the same manner as in Example 1.

[0134] (Comparative Example 2)

[0135] A multilayer release film having a three-layer structure was obtained in the same manner as in Comparative Example 1 except that the thickness of the surface layer was 30 μm, the thickness of the buffer layer was 130 μm, and the thickness of the entire film was 190 μm.

[0136] (Comparative Example 3)

[0137] A multilayer release film with a three-layer structure was obtained in the same manner as in Comparative Example 2 except that a poly(4-methyl-1-pentene) resin (manufactured by Mitsui Chemicals, Inc., TPX (registered trademark)) having a weight average molecular weight of 5000 or more was used as the resin composition for the surface layer, the molding temperature was set to 280° C., the thickness of the buffer layer was set to 70 μm, and the thickness of the entire film was set to 130 μm.

[0138] (Comparative Example 4)

[0139] A three-layer multilayer release film was obtained in the same manner as in Example 1 except that a mixture of 99.5 parts by weight of polybutylene terephthalate having a weight average molecular weight of 5,000 or more and 0.5 parts by weight of a PBT / PTMG copolymer (manufactured by Hetron Elastomer, model: H72DMG) was used as the surface layer resin composition.

[0140] (Comparative Example 5)

[0141] A three-layer multilayer release film was obtained in the same manner as in Example 1 except that a mixture of 99.9 parts by weight of polybutylene terephthalate having a weight average molecular weight of 5,000 or more and 0.1 parts by weight of a PBT / PTMG copolymer (manufactured by Hetron Elastomer, model: H72DMG) was used as the surface layer resin composition.

[0142] <Evaluation>

[0143] The release films obtained in Examples and Comparative Examples were evaluated by the following methods.

[0144] Table 1 shows the results.

[0145] (1) Calculation of the surface ether ratio (ER)

[0146] The surface layer of the obtained release film was taken out as a measurement sample and was subjected to the following conditions. 1 H NMR (nuclear magnetic resonance) determination.

[0147] <Measurement conditions>

[0148] Equipment: Bruker Corporation, Bruker AVANCE 400

[0149] Solvent: HFIP-d7 / CDCl3=3 / 7

[0150] Sample concentration: about 1wt / vol%

[0151] Temperature: 25℃

[0152] Based on the spectrum of the NMR spectrum obtained by the above measurement, it is estimated that the molecular weight of the PBT / PTMG copolymer (manufactured by Hetron Elastomer, model: H72DMG) is 5000 or more, the molar ratio of the PBT unit is 57%, and the molar ratio of PTMG (polyether part) is 43%. The molecular weight of the modified polyphenylene ether (manufactured by Asahi Kasei Corporation, XYRON (registered trademark) 600H) obtained by blending and alloying polyphenylene ether and polystyrene at a weight ratio of 1:1 is estimated to be 5000 or more, and the molar ratio of the polyphenylene ether (polyether part) in the blend is 46%.

[0153] Based on the above measurement results, the ether ratio ER defined by the following formula (1) was calculated.

[0154] ER=ΣY / ΣZ (1)

[0155] In formula (1), Y represents the number of repeating units of the polyether part in each resin having a weight average molecular weight of 5000 or more and having a polyether skeleton in the main chain contained in the above-mentioned surface layer. Z represents the number of repeating units of the structural unit in each resin having a weight average molecular weight of 5000 or more contained in the above-mentioned surface layer. Σ refers to the sum of the number of repeating units of each resin.

[0156] (2) Evaluation of embeddability

[0157] A cover film (15 cm × 15 cm, polyimide thickness 25 μm, epoxy adhesive layer thickness 35 μm) with a hole of φ = 0.5 mm was laminated on the copper foil surface of a copper clad laminate (CCL) (15 cm × 15 cm, polyimide thickness 25 μm, copper foil thickness 35 μm) so that the epoxy adhesive layer was in contact with it. A release film was further laminated so that the surface layer was in contact with the cover film. The laminate was heated at 180°C and 30 kgf / cm 2 The mold release film was then peeled off and the epoxy adhesive that had flowed out onto the copper clad laminate (CCL) was observed using an optical microscope. The epoxy adhesive oozing width was measured at 12 locations and the average value was calculated.

[0158] Based on the measurement results, the embedding property of the release film was evaluated as follows.

[0159] ◎: Less than 45μm

[0160] ○: 45 μm or more and less than 55 μm

[0161] △: 55 μm or more and less than 65 μm

[0162] ×: 65μm or more

[0163] [Table 1]

[0164]

[0165] Industrial Applicability

[0166] According to the present invention, a release film having better embedding properties than conventional ones can be provided.

[0167] Description of Reference Numerals

[0168] 11: Surface

[0169] 12: Other layers

Claims

1. A release film, which is a multilayer release film having a surface layer, The surface layer comprises at least one resin having a polyether skeleton in the main chain and a weight average molecular weight of 5000 or more, The ether ratio ER of the surface layer calculated according to the following formula (1) is 0.005 or more and 1 or less, ER=ΣY / ΣZ (1) In formula (1), Y represents the number of repeating units of the polyether part in each resin having a weight average molecular weight of 5000 or more and having a polyether skeleton in the main chain contained in the surface layer; Z represents the number of repeating units of the structural unit in each resin having a weight average molecular weight of 5000 or more contained in the surface layer; Σ refers to the sum of the number of repeating units of each resin.

2. The release film according to claim 1, wherein The ether ratio ER of the surface layer is less than 0.

5.

3. The release film according to claim 1 or 2, wherein The surface layer further includes at least one selected from a polyester resin and a poly-4-methyl-1-pentene resin. The release film according to claim 1 or 2, which has a thickness of 90 μm or more. The release film according to claim 1 or 2, further comprising a layer containing a polyolefin resin. The release film according to claim 1 or 2, which is used in a heat pressing step in the production of a printed circuit board.

7. A release film, which is a multilayer release film having a surface layer, wherein the surface layer comprises a copolymer of polybutylene terephthalate and polytetramethylene glycol, The ether ratio ER of the surface layer calculated by the following formula (1) is 0.005 or more and 1 or less, ER=ΣY / ΣZ (1) In formula (1), Y represents the number of repeating units of the tetramethylene glycol portion in each resin having a weight average molecular weight of 5000 or more contained in the surface layer; Z represents the sum of the number of repeating units of the structural unit derived from butylene terephthalate and the structural unit derived from tetramethylene glycol in each resin having a weight average molecular weight of 5000 or more contained in the surface layer; Σ refers to the sum of the number of repeating units of each resin.

8. A release film, which is a multilayer release film having a surface layer, wherein the surface layer comprises: polybutylene terephthalate; and a copolymer of polybutylene terephthalate and polytetramethylene glycol, The ether ratio ER of the surface layer calculated by the following formula (1) is 0.005 or more and 1 or less, ER=ΣY / ΣZ (1) In formula (1), Y represents the number of repeating units of the tetramethylene glycol portion in each resin having a weight average molecular weight of 5000 or more contained in the surface layer; Z represents the sum of the number of repeating units of the structural unit derived from butylene terephthalate and the structural unit derived from tetramethylene glycol in each resin having a weight average molecular weight of 5000 or more contained in the surface layer; Σ refers to the sum of the number of repeating units of each resin.

9. A release film, which is a multilayer release film having a surface layer, wherein the surface layer comprises: polybutylene terephthalate; poly(4-methyl-1-pentene); and a copolymer of polybutylene terephthalate and polytetramethylene glycol, The ether ratio ER of the surface layer calculated according to the following formula (1) is 0.005 or more and 1 or less, ER=ΣY / ΣZ (1) In formula (1), Y represents the number of repeating units of the tetramethylene glycol portion in each resin having a weight average molecular weight of 5000 or more contained in the surface layer; Z represents the sum of the number of repeating units of the structural unit derived from butylene terephthalate, the structural unit derived from tetramethylene glycol, and the structural unit derived from 4-methyl-1-pentene in each resin having a weight average molecular weight of 5000 or more contained in the surface layer; Σ refers to the sum of the number of repeating units of each resin.

10. A release film, which is a multilayer release film having a surface layer, the surface layer comprising poly(4-methyl-1-pentene); polyphenylene ether; and polystyrene, The ether ratio ER of the surface layer calculated according to the following formula (1) is 0.005 or more and 1 or less, ER=ΣY / ΣZ (1) In formula (1), Y represents the number of repeating units of the phenylene ether-derived portion in each resin having a weight average molecular weight of 5000 or more contained in the surface layer; Z represents the sum of the number of repeating units of the structural unit derived from 4-methyl-1-pentene, the structural unit derived from phenylene ether and the structural unit derived from styrene in each resin having a weight average molecular weight of 5000 or more contained in the surface layer; and Σ refers to the sum of the number of repeating units of each resin.

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