release film

Abstract

The present invention provides a release film which is excellent in both release property and following property to unevenness and in which resin bleeding is less likely to occur. The present invention is a release film in which the relaxation time (T2) of a soft component at 180°C measured by CPMG method using pulse NMR is 220 msec or more and 330 msec or less, and in which the ratio of a soft component at 30°C measured by Solid Echo method using pulse NMR after exposure to the following temperature condition is 0.1% or more and 15% or less. Temperature condition: temperature is raised from 30°C to 180°C at a rate of 10°C / min, and then, temperature is lowered from 180°C to 30°C at a rate of 10°C / min.

Description

Technical Field

[0001] This invention relates to release films. Background Technology

[0002] Release films are used in the manufacturing processes of printed wiring boards, flexible circuit boards, multilayer printed wiring boards, etc.

[0003] In the manufacturing process of flexible circuit boards, a cover film is thermopressed onto the flexible circuit board body on which copper circuits are formed using a thermosetting adhesive or a thermosetting adhesive sheet. At this time, by placing a release film between the cover film and the hot press plate, it is possible to prevent the cover film from sticking to the hot press plate, and also to prevent adhesive leakage from becoming an obstacle to the plating process of the electrode parts.

[0004] Release films are required to have good release properties, allowing for easy peeling after hot pressing. To improve release properties, for example, the crystallinity of the release film is adjusted. Patent Document 1 describes a release film having a release layer comprising polyester resin on at least one side, the crystallinity of which is 10% or more and 50% or less.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2016-2730 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] In recent years, with the thinning of flexible circuit boards, the requirements for release films have become increasingly stringent in terms of release performance. In addition, in order to ensure release performance and conformability to unevenness (embedding) while also addressing the thinning of the line / span (L / S) of flexible circuit boards, multi-layered release films containing release layers and buffer layers have been used.

[0010] From the perspective of improving conformability to uneven surfaces, it is advisable to further soften the release film (especially the buffer layer). However, if the release film (especially the buffer layer) is softened, the elastic modulus decreases and the release performance deteriorates, making it difficult to improve both release performance and conformability to uneven surfaces. In addition, if the buffer layer is over-softened, there is a problem of resin seepage during hot-press bonding.

[0011] The purpose of this invention is to provide a release film with excellent release properties and conformability to uneven surfaces, and which is less prone to resin leakage.

[0012] Methods for solving problems

[0013] The present invention relates to a release film in which the relaxation time (T2) of the soft component at 180°C, as measured by pulsed NMR (pulsed nuclear magnetic resonance) and CPMG, is 220 ms or more and 330 ms or less. Furthermore, after exposure to the following temperature conditions, the soft component ratio at 30°C, as measured by pulsed NMR and Solid Echo, is 0.1% or more and 15% or less.

[0014] [Temperature conditions]

[0015] The temperature is increased from 30°C to 180°C at a rate of 10°C / minute, and then decreased from 180°C to 30°C at a rate of 10°C / minute.

[0016] The present invention will now be described in detail.

[0017] Hot pressing is typically performed at a high temperature of around 160–180°C, followed by peeling off the release film after returning to room temperature. To improve both release properties and conformability to uneven surfaces, a release film needs to be manufactured that softens at the high temperature of hot pressing but hardens upon peeling at room temperature, possessing a suitable modulus of elasticity. To obtain a release film exhibiting such behavior, the inventors used… 1 The pulsed NMR spectroscopy data obtained from H-core measurements was analyzed using a demolded film. For pulsed NMR, the data was segmented into multiple components, such as a highly crystalline hard component and a less crystalline soft component. The relaxation time of each component was measured, thereby evaluating molecular mobility. Specifically, by obtaining... 1 The free-induction decay curve waveform of spin-spin relaxation in the H nucleus can be separated into multiple components, thus obtaining the relaxation time of each component. It should be noted that the spin-spin relaxation time is also called the transverse relaxation time, usually denoted as T2. On the other hand, the spin-lattice relaxation time is also called the longitudinal relaxation time, usually denoted as T1.

[0018] The inventors focused on the soft component with low crystallinity in release films and investigated the following scheme: The relaxation time (T2) of the soft component at 180°C, measured by pulsed NMR and CPMG, and the ratio of the soft component at 30°C, measured by pulsed NMR and Solid Echo after exposure to specific temperature conditions, were adjusted to a specific range. The inventors found that such a release film softens at the high temperature during hot-pressing and hardens upon peeling at room temperature, exhibiting a suitable elastic modulus. Therefore, it demonstrates excellent release properties and conformability to uneven surfaces, and is less prone to resin exudation, thus completing the present invention.

[0019] The relaxation time (T2) of the soft component at 180°C, measured by pulsed NMR and CPMG of the release film of the present invention, has a lower limit of 220 ms and an upper limit of 330 ms.

[0020] Here, "soft component" refers to the low-crystallinity component when data obtained by pulsed NMR is segmented into highly crystalline components, low-crystallinity components, and components with intermediate properties. It should be noted that highly crystalline components are designated as "hard components," and components with intermediate properties are designated as "intermediate components."

[0021] "Hard components" are equivalent to the parts containing intramolecular or intermolecular bonds (such as crystal structures, cross-linked structures, etc.), "soft components" are equivalent to amorphous parts, and "intermediate components" are equivalent to the parts that can carry out molecular motion (such as folded parts of crystals, etc.).

[0022] It should be noted that the segmentation of each component is carried out as follows: the data (free induction decay curve) obtained by pulse NMR is analyzed by the least squares method and segmented into three parts: "hard component" with low molecular mobility where the magnetization decays immediately, "soft component" with high molecular mobility where the magnetization decays over time, and "intermediate component" with intermediate properties.

[0023] The relaxation time is the time it takes for the electron spin to return from the excited state to the ground state after a magnetic field is applied. The longer the relaxation time, the higher the molecular mobility.

[0024] If the relaxation time (T2) of the soft component at 180°C is 220 milliseconds or more, the molecular mobility of the soft component at high temperatures during hot pressing increases, thus the release film softens sufficiently and exhibits excellent conformability to uneven surfaces. If the relaxation time (T2) of the soft component at 180°C is 330 milliseconds or less, it is possible to prevent excessive molecular mobility of the soft component from causing resin exudation. The preferred lower limit of the relaxation time (T2) of the soft component at 180°C is 250 milliseconds, the preferred upper limit is 310 milliseconds, the more preferred lower limit is 270 milliseconds, and the more preferred upper limit is 290 milliseconds.

[0025] The relaxation time (T2) of the soft component at 180°C can be determined, for example, as follows: using a pulsed NMR such as the minispecmq20 (manufactured by BRUKER) and analytical software (e.g., TD-NMRA, manufactured by BRUKER, etc.), the demolded film is used as the test sample, and the temperature is increased from 30°C to 180°C at a heating rate of 10°C / min. After maintaining at 180°C for 10 minutes, the temperature is measured using the CPMG method.

[0026] The release film of the present invention, after being exposed to the following temperature conditions, has a soft component ratio at 30°C that is determined by pulsed NMR and by Solid Echo method, with a lower limit of 0.1% and an upper limit of 15%.

[0027] [Temperature conditions]

[0028] The temperature is increased from 30°C to 180°C at a rate of 10°C / minute, and then decreased from 180°C to 30°C at a rate of 10°C / minute.

[0029] The above temperature conditions are set assuming that hot-press bonding is typically performed at a high temperature of 160-180°C, followed by a return to room temperature before peeling off the release film. If the soft component ratio at the above 30°C is within the above range, the crystallinity of the release film after being temporarily heated to the high temperature of hot-press bonding and then returned to room temperature is sufficiently high. Therefore, the release film has a suitable elastic modulus and can exhibit excellent release properties. The preferred lower limit of the soft component ratio at the above 30°C is 1%, the preferred upper limit is 10%, the more preferred lower limit is 3%, and the more preferred upper limit is 5%.

[0030] The soft component ratio at 30°C can be determined using pulsed NMR and analytical software (e.g., TD-NMR, BRUKER) such as the Minispec MQ20 ​​(manufactured by BRUKER). More specifically, the release film can be used as the sample, heated from 30°C to 180°C at a rate of 10°C / min, held at 180°C for 10 minutes, then cooled from 180°C to 30°C at a rate of 10°C / min, held at 30°C for 10 minutes, and then measured using the Solid Echo method. It should be noted that the determination of the soft component ratio at 30°C can be performed after the determination of the relaxation time (T2) of the soft component at 180°C.

[0031] It should be noted that both the CPMG and Solid Echo methods mentioned above are types of electromagnetic pulse irradiation conditions in pulsed NMR. The determination method is usually selected based on the relaxation time; the Solid Echo method is used when the goal is to determine components with short relaxation times, while the CPMG method is used when the goal is to include components with long relaxation times.

[0032] The method for adjusting the relaxation time (T2) of the soft component at 180°C to the aforementioned range is not particularly limited, but it is preferable to use a resin with weaker intermolecular interactions and higher molecular mobility at 180°C as the resin constituting the release film. More specifically, an example is using a polyolefin resin with a linear structure as the resin constituting the buffer layer, as described later. Furthermore, as the resin constituting the buffer layer, examples include using resins with low molecular weights, non-polar polymers, and resins without unsaturated bonds.

[0033] The method for adjusting the soft component ratio at 30°C to the aforementioned range is not particularly limited, but preferably involves promoting crystallization upon recovery to room temperature after temporary heating to the high temperature required for hot pressing. More specifically, examples include adding a nucleating agent to the buffer layer as described later. Furthermore, examples include adjusting cooling conditions, controlling the stereoregularity of the resin constituting the buffer layer, and combining highly crystalline and low-crystalline resins in the buffer layer.

[0034] The structure of the release film of the present invention is not particularly limited; it can be a single-layer structure or a multi-layer structure, and preferably has a release layer and a buffer layer. Furthermore, it is more preferable to have release layers on both sides of the buffer layer.

[0035] The aforementioned release layer serves to enable the release film to exhibit excellent release properties. Furthermore, by including the aforementioned buffer layer, the release film's ability to follow uneven surfaces is improved. By manufacturing a release film having the aforementioned release layer and buffer layer, with the release layer on both sides of the buffer layer, it is easy to adjust the relaxation time (T2) of the soft component at 180°C and the soft component ratio at 30°C to the aforementioned range, allowing the release film to exhibit even better release properties and uneven surface following.

[0036] It should be noted that the release layers on both sides can be made of the same resin or different resins. Additionally, the release layers on both sides can be of the same thickness or different thicknesses. Furthermore, the release layer and the cushioning layer can be in direct contact and integrated, or they can be integrated through an adhesive layer.

[0037] The resin constituting the above-mentioned release layer is not particularly limited, but from the viewpoint of improving the release properties of the release film, it is preferred to select at least one resin selected from polyester, polyolefin and polystyrene.

[0038] The aforementioned polyester preferably contains an aromatic polyester resin. The aforementioned polyolefin preferably contains a poly(4-methyl-1-pentene) or alicyclic olefin resin. The aforementioned polystyrene preferably contains a polystyrene resin having a syndiotactic structure. From the perspective of excellent conformability to uneven surfaces and excellent prevention of exudation of the adhesive formed on the cover film, the aforementioned release layer more preferably contains an aromatic polyester resin.

[0039] It should be noted that when using the resin exemplified here, the release layer becomes relatively hard, therefore it is assumed that the release layer monomer (single layer) contains almost no soft components at 30°C.

[0040] The aforementioned aromatic polyester resins are not particularly limited, but crystalline aromatic polyester resins are preferred. Specifically, examples include polyethylene terephthalate resin, polybutylene terephthalate resin, polyhexamethylene terephthalate resin, polyethylene naphthalate resin, polybutylene naphthalate resin, and butylene terephthalate-polytetramethylene glycol copolymer. These aromatic polyester resins can be used alone or in combination of two or more. From the viewpoint of balancing heat resistance, mold release properties, and conformability to uneven surfaces, polybutylene terephthalate resin is preferred.

[0041] Alternatively, a mixed resin in which a block copolymer of polybutylene terephthalate and an aliphatic polyether is incorporated into a polybutylene terephthalate resin is preferred. The aliphatic polyether is not particularly limited, and examples include polyethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

[0042] From the viewpoint of membrane-forming properties, the melt volume flow rate of the above-mentioned aromatic polyester resin is preferably 30 cm⁻¹. 3 / 10min or less, preferably 20cm 3 / less than 10 min. It should be noted that the melt volumetric flow rate can be measured according to ISO 1133 at a test temperature of 250°C and a load of 2.16 kg.

[0043] Commercially available examples of the aforementioned aromatic polyester resins include "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.).

[0044] Among the above-mentioned polyolefins containing poly(4-methyl-1-pentene), it is preferable to contain more than 90% by weight of poly(4-methyl-1-pentene) resin.

[0045] The aforementioned poly(4-methyl-1-pentene) resin can be, for example, a commercially available product such as TPX (registered trademark) manufactured by Mitsui Chemicals Co., Ltd.

[0046] The aforementioned alicyclic olefin resins refer to olefin resins with cyclic aliphatic hydrocarbons in the main chain or side chain. From the perspectives of heat resistance and strength, thermoplastic saturated norbornene resins are preferred.

[0047] Examples of the aforementioned thermoplastic saturated norbornene resins include, for instance, resins obtained by hydrogenating ring-opening polymers or copolymers of norbornene monomers (after modification such as maleic acid addition or cyclopentadiene addition as needed). Other examples include resins obtained by addition polymerization of norbornene monomers, resins obtained by addition polymerization of norbornene monomers with olefin monomers such as ethylene or α-olefins, and resins obtained by addition polymerization of norbornene monomers with cyclic olefin monomers such as cyclopentene, cyclooctene, and 5,6-dihydrodicyclopentadiene. Furthermore, modified versions of these resins can also be cited.

[0048] In polystyrene containing the above-mentioned polystyrene resin with a syndiotactic structure, it is preferable to contain 70% to 90% by weight of the polystyrene resin with a syndiotactic structure.

[0049] It should be noted that polystyrene resins with a syndiotactic structure refer to resins with a syndiotactic structure, that is, a stereoregular structure in which phenyl and substituted phenyl groups, which are side chains relative to the main chain formed by carbon-carbon sigma bonds, are alternately located in opposite directions.

[0050] The aforementioned polystyrene resins with a syndiotactic structure are not particularly limited. Examples include polystyrene, poly(alkylstyrene), poly(arylstyrene), poly(halostyrene), poly(haloalkylstyrene), poly(alkoxystyrene), and poly(vinylbenzoate), which have a syndiotactic regularity of 75% or more of racemic binomial units or 30% or more of racemic pentamiral units. Additionally, examples include their hydrogenated polymers, mixtures thereof, and copolymers with them as the main components. For instance, commercially available products manufactured by Idemitsu Kosan Co., Ltd., under the trade name XAREC (registered trademark) can be used.

[0051] The aforementioned release layer may contain a rubber component. By including a rubber component in the release layer, the release film's ability to follow uneven surfaces is improved.

[0052] The aforementioned rubber components are not particularly limited, and examples include natural rubber, styrene-butadiene copolymer, polybutadiene, polyisoprene, acrylonitrile-butadiene copolymer, ethylene-propylene copolymer (EPM, EPDM), polychloroprene, butyl rubber, acrylic rubber, silicone rubber, and urethane rubber. Additionally, examples of the aforementioned rubber components include olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, ester-based thermoplastic elastomers, and amide-based thermoplastic elastomers.

[0053] The aforementioned release layer may contain stabilizers.

[0054] The stabilizers mentioned above are not particularly limited; examples include hindered phenolic antioxidants and heat stabilizers.

[0055] The aforementioned hindered phenolic antioxidants are not particularly limited, and examples 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, etc. The heat stabilizers mentioned above are not particularly limited, but examples include: tris(2,4-di-tert-butylphenyl) phosphite, trilauryl phosphite, 2-tert-butyl-α-(3-tert-butyl-4-hydroxyphenyl)-p-cumenyl bis(p-nonylphenyl) phosphite, dimyristyl 3,3'-thiodipropionate, distearate 3,3'-thiodipropionate, pentaerythritol tetrakis(3-lauryl thiopropionate), and di(tetrazyl) 3,3'-thiodipropionate, etc.

[0056] The aforementioned release layer may also contain previously known additives such as fibers, inorganic fillers, flame retardants, ultraviolet absorbers, antistatic agents, inorganic substances, and higher fatty acid salts.

[0057] The thickness of the release layer is not particularly limited. By relatively thinning the release layer and increasing the thickness of the buffer layer, the contribution of the buffer layer to the overall release film can be increased, thereby increasing the soft component ratio. This allows the release film to exhibit superior conformability to unevenness. The preferred lower limit for the thickness of the release layer is 10 μm, and the preferred upper limit is 40 μm. If the thickness of the release layer is 10 μm or more, the heat resistance of the release film is improved. If the thickness of the release layer is 40 μm or less, the conformability of the release film to unevenness is improved. A more preferred lower limit for the thickness of the release layer is 15 μm, and a more preferred upper limit is 30 μm.

[0058] The resin constituting the above-mentioned buffer layer is not particularly limited, but polyolefin resin is preferred.

[0059] The aforementioned polyolefin resins are not particularly limited, and examples include polyethylene resins (such as high-density polyethylene, low-density polyethylene, and linear low-density polyethylene), polypropylene resins, and ethylene-vinyl acetate copolymers. Additionally, examples include ethylene-acrylic acid monomer copolymers such as ethylene-methyl methacrylate copolymers, ethylene-ethyl acrylate copolymers, and ethylene-acrylic acid copolymers. These polyolefin resins can be used alone or in combination of two or more. Among these, polyethylene resins are preferred from the perspective of obtaining a release film that exhibits superior mold release properties and conformability to uneven surfaces.

[0060] The aforementioned polyolefin resin preferably contains a polyolefin resin having a linear structure.

[0061] Specifically, for example, when the aforementioned polyolefin resin contains the aforementioned polyethylene resin, in addition to the branched low-density polyethylene (LDPE) commonly used in buffer layers, it is preferable to use linear high-density polyethylene (HDPE) in an appropriate amount. This makes it easier to adjust the relaxation time (T2) of the soft component at 180°C to the aforementioned range, allowing the release film to exhibit superior conformability to uneven surfaces. This is because, compared to branched low-density polyethylene (LDPE), linear high-density polyethylene (HDPE) exhibits less intermolecular interaction and higher molecular mobility at temperatures above its melting point.

[0062] Furthermore, high-density polyethylene (HDPE) with a linear structure readily forms a crystalline structure when cooled to temperatures below its melting point and then returned to room temperature, thus increasing its crystallinity. Therefore, by using HDPE, it is also easy to adjust the soft component ratio at 30°C to the aforementioned range, and the release film can also exhibit superior release properties.

[0063] The content of the linear-chain polyolefin resin in the aforementioned buffer layer is not particularly limited. From the viewpoint of adjusting the relaxation time (T2) of the soft component at 180°C and the ratio of the soft component at 30°C to the aforementioned range, a preferred lower limit is 5% by weight, and a preferred upper limit is 25% by weight. If the content of the linear-chain polyolefin resin is 5% by weight or more, the release film can easily exhibit better release properties and conformability to uneven surfaces. If the content of the linear-chain polyolefin resin is 25% by weight or less, it is possible to further suppress the situation where the molecular mobility of the soft component becomes too high and resin exudation occurs. A more preferred lower limit for the content of the linear-chain polyolefin resin is 10% by weight, a more preferred upper limit is 20% by weight, and a more preferred lower limit is 15% by weight.

[0064] The content of the polyolefin resin in the aforementioned buffer layer is not particularly limited, but a preferred lower limit is 50% by weight, and a preferred upper limit is 90% by weight. If the content of the polyolefin resin is 50% by weight or more, the buffer layer becomes sufficiently flexible, and the mold release film's conformability to unevenness is improved. If the content of the polyolefin resin is 90% by weight or less, the adhesion between the mold release layer and the buffer layer is improved. A more preferred lower limit for the content of the polyolefin resin is 60% by weight, and a further preferred lower limit is 65% by weight. A more preferred upper limit for the content of the polyolefin resin is 80% by weight, and a further preferred upper limit is 75% by weight.

[0065] The aforementioned buffer layer may contain the resin constituting the aforementioned release layer. By including the resin constituting the aforementioned release layer in the buffer layer, the adhesion between the aforementioned release layer and the aforementioned buffer layer is improved. More preferably, the aforementioned buffer layer contains the main component resin of the aforementioned release layer. Here, the main component resin of the aforementioned release layer refers to the resin with the highest content among the resins contained in the aforementioned release layer.

[0066] The content of the resin constituting the release layer in the aforementioned buffer layer is not particularly limited, but a preferred lower limit is 10% by weight, and a preferred upper limit is 50% by weight. If the content of the resin constituting the release layer is 10% by weight or more, the adhesion between the release layer and the buffer layer is improved. If the content of the resin constituting the release layer is 50% by weight or less, the softness of the buffer layer becomes sufficient, and the conformability of the release film to unevenness is improved. A more preferred lower limit of the content of the resin constituting the release layer is 20% by weight, and a more preferred lower limit is 25% by weight. A more preferred upper limit of the content of the resin constituting the release layer is 40% by weight, and a more preferred upper limit is 35% by weight.

[0067] The aforementioned buffer layer may also contain resins such as polystyrene, polyvinyl chloride, polyamide, polycarbonate, polysulfone, and polyester.

[0068] The aforementioned buffer layer preferably also contains a nucleating agent.

[0069] By including the nucleating agent in the buffer layer, crystallization of the resin constituting the buffer layer is promoted after temporary heating to the high temperature during hot pressing and subsequent return to room temperature. This makes it easier to adjust the soft component ratio at 30°C to the aforementioned range, resulting in a release film with superior release properties.

[0070] The nucleating agents mentioned above are not particularly limited to compounds that promote the crystallization of polymers. For example, nucleating agents for the polypropylene resin mentioned above include: phosphate ester metal salts, carboxylic acid metal salts, pimelic acid metal salts, rosin metal salts, sorbitol-based nucleating agents, quinacridone, phthalocyanine blue, talc, etc.

[0071] Examples of carboxylic acid metal salt nucleating agents include sodium benzoate, aluminum dibenzoate, and potassium benzoate. Examples of sorbitol-based nucleating agents include dibenzylsorbitol and dialkylbenzylsorbitol.

[0072] In addition, nucleating agents for the aforementioned polyethylene resins include: cyclohexane-1,2-dicarboxylate, anthracene, potassium hydrogen phthalate, benzoic acid compounds, ultra-high molecular weight polyethylene, phosphate metal salts, talc, calcium carbonate, titanium dioxide, silicon dioxide, barium sulfate, vermiculite, carbon nanotubes, etc.

[0073] The content of the nucleating agent in the aforementioned buffer layer is not particularly limited, but the preferred lower limit is 0.5% by weight, the preferred upper limit is 5% by weight, the more preferred lower limit is 1% by weight, and the more preferred upper limit is 3% by weight. If the content of the nucleating agent is 1% by weight or more, the release film can exhibit better release properties. If the content of the nucleating agent is 3% by weight or less, resin exudation can be suppressed while maintaining the softness of the aforementioned buffer layer. A further preferred lower limit for the content of the nucleating agent is 1.5% by weight, and a further preferred upper limit is 2% by weight.

[0074] The aforementioned buffer layer may also contain additives such as fibers, inorganic fillers, flame retardants, ultraviolet absorbers, antistatic agents, inorganic substances, and higher fatty acid salts. By including the aforementioned inorganic fillers in the buffer layer, the relaxation time (T2) of the soft component at 180°C and the soft component ratio at 30°C are not adversely affected, thus further suppressing resin exudation.

[0075] The aforementioned buffer layer can be a single-layer structure composed of individual layers, or a multi-layer structure composed of multiple layers stacked together. In the case of a multi-layer buffer layer, the multiple layers can be stacked together as a single unit using adhesive layers.

[0076] The thickness of the aforementioned buffer layer is not particularly limited. By making the thickness of the release layer relatively thinner and the thickness of the buffer layer relatively thicker, the contribution of the buffer layer to the overall release film can be increased, and the soft component ratio can be increased. As a result, the release film can exhibit better conformability to uneven surfaces.

[0077] The preferred lower limit for the thickness of the aforementioned buffer layer is 15 μm, and the preferred upper limit is 200 μm. If the thickness of the buffer layer is 15 μm or more, the conformability of the release film to uneven surfaces is improved. If the thickness of the buffer layer is 200 μm or less, resin seepage from the buffer layer at the film ends during hot-press bonding can be suppressed. A more preferred lower limit for the thickness of the buffer layer is 30 μm, and a more preferred upper limit is 150 μm.

[0078] The method for manufacturing the release film of the present invention is not particularly limited. Examples include: water-cooled or air-cooled co-extrusion blow molding, film making using co-extrusion T-die method, solvent casting method, hot pressing method, etc.

[0079] In the case of a structure having the aforementioned release layers on both sides of the aforementioned buffer layer, an example is a method of: after fabricating a film as a release layer, laminating a buffer layer onto the film using an extrusion lamination method, and then dry laminating another release layer. Alternatively, an example is a method of dry laminating a film that serves as a release layer, a film that serves as a buffer layer, and a film that serves as another release layer.

[0080] Among them, considering the excellent control of the thickness of each layer, the method of film formation using co-extrusion T-die method is preferred.

[0081] The application of the release film of the present invention is not particularly limited, and it can be used in the manufacturing process of printed wiring substrates, flexible circuit boards, multilayer printed wiring boards, etc. Specifically, for example, in the manufacturing process of flexible circuit boards, when a cover film is thermo-pressed onto the flexible circuit board body on which copper circuits are formed using a thermosetting adhesive or a thermosetting adhesive sheet, the release film of the present invention can be used.

[0082] Invention Effects

[0083] According to the present invention, a release film with excellent release properties and conformability to uneven surfaces can be provided, and resin exudation is not easily caused. Detailed Implementation

[0084] The present invention will be described in more detail below with reference to specific embodiments, but the present invention is not limited to these embodiments.

[0085] (Example 1)

[0086] (1) Manufacturing of release film

[0087] A resin composition for a release layer is obtained by mixing 60 parts by weight of polybutylene terephthalate resin (PBT) and 40 parts by weight of a copolymer of polybutylene terephthalate and polytetramethylene glycol (PBT / PTMG copolymer).

[0088] A resin composition for a buffer layer was obtained by mixing 39 parts by weight of low-density polyethylene (LDPE) (SUNTEC-LD(M2102), manufactured by Asahi Kasei Corporation), 59.5 parts by weight of ethylene-methyl methacrylate copolymer (EMMA1) (ACRYFT WH401, manufactured by Sumitomo Chemical Co., Ltd.), and 1.5 parts by weight of PE nucleating agent (Rikemaster CN, manufactured by Riken VITAMIN Co., Ltd.).

[0089] The obtained release layer resin composition and buffer layer resin composition were co-extruded using an extruder with a T-die width of 400 mm to produce a release film with release layers (15 μm thick on one side) on both sides of the buffer layer (90 μm thick). The extruder used was a GM30-28 manufactured by GM Engineering, with a screw diameter of 30 mm and an L / D ratio of 28.

[0090] (2) Pulse NMR measurement

[0091] Roll approximately 10g of the release film, which will be used as the test sample, into a cylindrical shape and insert it into a glass sample tube (manufactured by BRUKER, product number 1824511, length 180mm, flat bottom) with a height of 20mm.

[0092] Using pulsed NMR "the minispec mq20" (manufactured by BRUKER), the release film in the above sample tube was heated from 30°C to 180°C at a heating rate of 10°C / min. After maintaining at 180°C for 10 minutes, the relaxation time (T2) of the soft component at 180°C was determined by CPMG.

[0093] [CPMG determination conditions]

[0094] Scans: 128

[0095] Recycle Deray: 2 seconds

[0096] 90-180 plus searation: 0.05

[0097] Total number of acquired echoes:3000

[0098] In addition, the soft component ratio at 30°C was determined using pulsed NMR "the minispec mq20" (manufactured by BRUKER). More specifically, the release film in the sample tube was heated from 30°C to 180°C at a heating rate of 10°C / min, maintained at 180°C for 10 minutes, and then cooled from 180°C to 30°C at a cooling rate of 10°C / min, maintained at 30°C for 10 minutes, and the soft component ratio at 30°C was determined using the Solid Echo method.

[0099] [Solid Echo Method Determination Conditions]

[0100] Scans: 64

[0101] Recycle Deray: 2 seconds

[0102] Acquisition scale: 1 ms

[0103] The relaxation time (T2) of the soft component at 180 °C based on the CPMG method and the soft component ratio at 30 °C based on the Solid Echo method are calculated by the following method.

[0104] The 1 free induction decay curve (vertical axis: magnetization intensity, horizontal axis: time) of the spin-spin relaxation of the H nucleus, which is obtained as the measurement result of pulsed NMR, is separated into three curves from three components, namely the soft component, the intermediate component, and the hard component, and the component ratios and relaxation times of the soft component, the intermediate component, and the hard component are obtained. The waveform separation is performed by using both a Gaussian type and an exponential type and fitting them. Specifically, using the analysis software "TD-NMRA (Version 4.3 Rev 0.8)" manufactured by BRUKER Corporation, according to the product manual, in the Solid Echo method at 30 °C, the hard component is fitted with a Gaussian type, and the intermediate component and the soft component are fitted with an exponential type. In the CPMG method at 180 °C, all of the hard component, the intermediate component, and the soft component are fitted with an exponential type. In addition, in the Solid Echo method, the points up to 0.5 milliseconds of the obtained free induction decay curve (relaxation curve) are used for fitting, and in the CPMG method, all the points are used for fitting. The fitting is performed by the least squares method using the following formula.

[0105] [Equation 1]

[0106]

[0107] Here, Y is the free induction decay curve, and w1, w2, and w3 are Weibull coefficients. For the Solid Echo method, w1 takes a value of 2, and w2 and w3 take values of 1. For the CPMG method, w1 to w3 take values of 1. A1 is the component ratio of the hard component (unit: %), B1 is the component ratio of the intermediate component (unit: %), C1 is the component ratio of the soft component (unit: %), and A1 + B1 + C1 = 100 is satisfied. T2A is the relaxation time of the hard component (unit: ms), T2B is the relaxation time of the intermediate component (unit: ms), T2C is the relaxation time of the soft component (unit: ms), and T2A < T2B < T2C is satisfied. T is the time (unit: ms).

[0108] Note that, in the embodiments of the present invention, the value of Recycle Deray is set to 2 sec. However, in the case where appropriate measurement results (relaxation curves) cannot be obtained, it is set to a value 5 times that of T1 (spin-lattice relaxation time; longitudinal relaxation time). In T1 measurement, the saturation recovery method (Japanese: 飽和回復法) and the inversion recovery method (Japanese: 反転回復法) are usually applied.

[0109] (Examples 2 to 5, Comparative Examples 1 to 6)

[0110] Except for changing the composition of the buffer layer as shown in Table 1, a release film was obtained in the same manner as in Example 1. Note that the respective materials shown in Table 1 are as follows.

[0111] High-density polyethylene (HDPE) (SUNTEC-HD (F371), manufactured by Asahi Kasei Corporation)

[0112] EMMA2 (ACRYFT WD106, manufactured by Sumitomo Chemical Co., Ltd.)

[0113] <Evaluation>

[0114] For the release films obtained in the examples and comparative examples, the following evaluations were performed. The results are shown in Table 1.

[0115] (1) Evaluation of releasability

[0116] The release film was overlapped on an epoxy adhesive sheet (manufactured by NIKKAN INDUSTRIES Co., Ltd., CISV2535) and hot-pressed at 180 °C and 30 kgf / cm 2 for 5 minutes. Then, it was cut into a width of 25 mm, and a peel test was performed at a test speed of 500 mm / minute and a peel angle of 180°. When the peel strength was 20 gf / cm 2 or less, it was set as ○, when it exceeded 20 gf / cm 2 and was 30 gf / cm 2 or less, it was set as ×, and when it exceeded 30 gf / cm 2 , it was set as ××.

[0117] (2) Evaluation of followability to unevenness

[0118] On the copper foil surface of a copper-clad laminate (CCL) (12.5 cm × 12.5 cm, polyimide thickness 25 μm, copper foil thickness 35 μm), a cover film (12.5 cm × 12.5 cm, polyimide thickness 25 μm, epoxy adhesive layer thickness 35 μm) having holes with φ = 1 mm was laminated in contact with the epoxy adhesive layer. Further, the release film was laminated on the cover film. The laminate was heated at 180 °C and 30 kgf / cm 2Under the specified conditions, the epoxy adhesive was hot-pressed for 2 minutes. Then, the release film was peeled off, and the epoxy adhesive flowing onto the copper clad laminate (CCL) was observed using an optical microscope. The penetrating width of the epoxy adhesive at 12 points was measured, and its average value was calculated to evaluate the follow-through of the release film to uneven surfaces. Cases with an average epoxy adhesive penetrating width less than 55 μm were designated as ○, those between 55 μm and 65 μm as △, and those exceeding 65 μm as ×.

[0119] (3) Evaluation of resin exudation

[0120] Cut the release film into 10cm squares. Layer a 25cm square SUS board, cushioning paper, SiPET sheet, release film, SiPET sheet, cushioning paper, and another 25cm square SUS board in sequence, and perform hot pressing using a sliding vacuum heater press (MKP-3000v-MH-ST, MIKADO TECHNOS). Measure the distance between the end of the resin that oozes from the release film, forming the cushioning layer, and the end of the release layer of the release film; this distance is recorded as the oozing distance. A oozing distance of less than 1mm is marked as 0, a distance greater than 1mm but less than 2mm is marked as △, and a distance greater than 2mm is marked as ×.

[0121]

[0122] Industrial availability

[0123] According to the present invention, a release film with excellent release properties and conformability to uneven surfaces can be provided, and resin exudation is not easily caused.

Claims

1. A release film, characterized in that, The relaxation time T2 of the soft component at 180 °C, determined by pulsed nuclear magnetic resonance and CPMG, is greater than 220 ms and less than 330 ms. After being exposed to the following temperature conditions, the soft component ratio of the release film at 30°C, as determined by pulsed nuclear magnetic resonance and solid-state echo method, is ≥0.1% and ≤15%. Temperature conditions The temperature is increased from 30°C to 180°C at a rate of 10°C / minute, and then decreased from 180°C to 30°C at a rate of 10°C / minute. The release film has a release layer and a buffer layer, with the release layer located on both sides of the buffer layer. The buffer layer contains polyolefin resin.

2. The release film according to claim 1, characterized in that, Polyolefin resins contain polyethylene resin.

3. The release film according to claim 1 or 2, characterized in that, Polyolefin resins contain polyolefin resins with a linear chain structure.

4. The release film according to claim 1 or 2, characterized in that, The buffer layer contains a nucleating agent.

5. The release film according to claim 1 or 2, characterized in that, The release layer contains at least one resin selected from polyester, polyolefin and polystyrene.

Images