Release film

Abstract

To provide a release film which is excellent in releasability and followability to unevenness and can be suitably used for production of a flexible circuit board by R to R method.SOLUTION: A release film has at least one release layer containing an aromatic polyester resin, and when an area derived from (010) is represented by X and an area derived from (100) is represented by Y among profiles obtained by an oblique incident wide angle X-ray diffraction method with an incident angle of 0.06°, the release film satisfies X / Y>0.7.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a release film.

Background Art

[0002] Release films are used in the manufacturing processes of printed wiring boards, flexible circuit boards, multilayer printed wiring boards, and the like. In the manufacturing process of a flexible circuit board, a coverlay film is thermally press-bonded to a flexible circuit board body on which a copper circuit is formed via a thermosetting adhesive or a thermosetting adhesive sheet. At this time, by disposing a release film between the coverlay film and the hot press plate, it is possible to prevent the coverlay film and the hot press plate from adhering to each other, and it is also possible to prevent problems such as the adhesive oozing out and hindering the plating process of the electrode portion. In recent years, in order to ensure performance such as releasability and followability (embeddability) to unevenness even in response to the miniaturization of L / S (line / space) of flexible circuit boards, a multilayer release film including a release layer and a cushion layer is also used.

[0003] The release film is required to have a releasability that allows for easy peeling after thermocompression bonding. In order to improve the releasability, for example, the polarity of the surface of the release film is adjusted. In addition, the crystallinity of the release film is also adjusted. Patent Document 1 describes a release film having a surface layer containing a polyester resin, and in a region from the surface of the surface layer to a thickness of 1 μm, the ratio of carbonyl groups oriented parallel to the surface among the carbonyl groups contained in the polyester resin is 45% or more. Patent Document 2 describes a release film having a release layer containing a polyester resin on at least one surface, and the crystallinity of the release layer is 10% or more and 50% or less.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] In recent years, with the thinning of flexible circuit boards, further improvement in releasability has been demanded for release films. Also, in recent years, the production of flexible circuit boards has been progressing in automation by methods such as the roll-to-roll (RtoR) method. In the RtoR method, a flexible circuit board body, a release film, etc. fed out from a roll are each conveyed between heat press plates, heat press bonded, and then wound back onto the roll again. In such an RtoR method, when peeling the release film from the flexible circuit board after heat press bonding, the peeling angle tends to be a low angle. Therefore, when using a conventional release film, a larger force may have to be applied during peeling, which may lead to the occurrence of defects. Accordingly, further improvement in releasability is demanded for release films. In order to improve releasability, it is conceivable to adjust the molecular orientation in the crystalline phase on the surface of the release film. However, as described in Patent Document 1, simply adjusting the orientation of carbonyl groups in the region from the surface of the surface layer to a thickness of 1 μm has been difficult to obtain the high releasability required in recent years.

[0006] An object of the present invention is to provide a release film that is excellent in both releasability and followability to unevenness and can be suitably used in the production of flexible circuit boards by the RtoR method. [Means for Solving the Problems]

[0007] The present invention relates to a release film having at least one release layer containing an aromatic polyester resin, wherein the release layer satisfies X / Y > 0.7, where X is the area derived from (010) and Y is the area derived from (100) in the profile obtained by the grazing incidence wide-angle X-ray diffraction method with an incident angle of 0.06°. Hereinafter, the present invention will be described in detail.

[0008] The inventors of the present invention have found that in a release film having at least one release layer containing an aromatic polyester resin, in order to improve the releasability, the orientation of carbonyl groups in an extremely thin region (the outermost surface) among the surface regions of the release layer is particularly important. The inventors have found that by adjusting the orientation of carbonyl groups in an extremely thin thickness region (the outermost surface) of the surface of the release layer, the releasability can be dramatically improved without impairing the followability to unevenness, and thus the present invention has been completed.

[0009] The release film of the present invention has at least one release layer containing an aromatic polyester resin. The above release layer satisfies X / Y > 0.7, where X is the area derived from (010) and Y is the area derived from (100) in the profile obtained by the grazing incidence wide-angle X-ray diffraction method (In-Plane method) with an incident angle of 0.06°. By setting the incident angle to 0.06° in the grazing incidence wide-angle X-ray diffraction method, it is possible to obtain a profile of only the outermost surface of the release layer, rather than a profile of the entire release layer or a relatively thick surface region of the release layer. The outermost surface refers to an extremely thin region on the surface, and more specifically, a region from the surface to a thickness of about 4 nm.

[0010] The area X derived from the above (010) indicates the amount of carbonyl groups oriented so as to penetrate into the plane of the release layer (parallel to the plane), and the area Y derived from the above (100) indicates the amount of carbonyl groups oriented so as to face the surface of the release layer (perpendicular to the plane). Therefore, the value of X / Y indicates the relative ratio of the amount of carbonyl groups oriented so as to penetrate into the plane of the release layer (parallel to the plane) to the amount of carbonyl groups oriented so as to face the surface of the release layer (perpendicular to the plane). The carbonyl groups mainly originate from the aromatic polyester resin contained in the release layer. When the value of X / Y at the extreme surface of the release layer is greater than 0.7, the proportion of carbonyl groups oriented so as to penetrate into the plane of the release layer (parallel to the plane) increases, and the polarity of the extreme surface of the release layer decreases. For this reason, it is possible to sufficiently suppress the penetration of the adhesive (epoxy adhesive) formed on the coverlay film into the release layer during thermal press bonding, and it is possible to suppress the electrostatic interaction between the adhesive (epoxy adhesive) and the release film, so the releasability of the release film is greatly improved. It should be noted that at least one surface of the release layer may have the value of X / Y at such an extreme surface. On the other hand, even if the release layer has the value of X / Y at such an extreme surface, the flexibility of the entire release film is maintained, and the followability to unevenness does not decrease. The value of X / Y at the extreme surface of the release layer is preferably greater than 1.0, and more preferably greater than 2.0.

[0011] The upper limit of the value of X / Y at the extreme surface of the release layer is not particularly limited, but the preferred upper limit is 10.0. If the value of X / Y at the extreme surface of the release layer is 10.0 or less, it is possible to prevent contamination of the flexible circuit board caused by the release layer components. The more preferred upper limit of the value of X / Y at the extreme surface of the release layer is 8.0.

[0012] The X / Y value on the extreme surface of the release layer can be obtained as follows. That is, a baseline is drawn on the diffraction measurement plot obtained by analyzing the surface of the release layer by the grazing incidence wide-angle X-ray diffraction method with the incident angle of X-rays being 0.06°, and fitting is performed for the crystalline phase and the amorphous phase respectively. Further, by performing fitting, the area X derived from (010) and the area Y derived from (100) in the crystalline phase are obtained respectively, and the X / Y value can be obtained from the obtained X and Y.

[0013] As an X-ray diffractometer for obtaining the X / Y value on the extreme surface of the release layer, for example, a multifunctional X-ray diffractometer for surface structure evaluation (ATX-G type) manufactured by Rigaku Corporation set under the following conditions can be used. X-ray source CuKα ray Tube voltage - tube current 50 kV - 300 mA Incident optical system Concentration method Incident angle (ω) 0.06° Measurement range 5 - 70° Measurement interval 0.02° Scanning speed 1.0° / min Scanning method In-Plane method

[0014] The method for adjusting the X / Y value on the extreme surface of the release layer to the above range is not particularly limited, but it is preferable to perform surface treatment on the surface of the release layer after reducing the arithmetic mean roughness Ra before the surface treatment of the release layer and / or increasing the glossiness before the surface treatment of the release layer. By reducing the arithmetic mean roughness Ra before the surface treatment of the release layer and / or increasing the glossiness before the surface treatment of the release layer, when surface treatment is performed on the surface of the release layer, the effect of the carbonyl group penetrating into the plane is greatly improved, and the X / Y value on the extreme surface of the release layer can be adjusted to the above range.

[0015] The method for reducing the arithmetic mean roughness Ra before the surface treatment of the release layer and / or increasing the glossiness before the surface treatment of the release layer is not particularly limited. However, when the resin constituting the release layer is melt-extruded and the molten resin is cooled, it is preferable to adopt the following methods, for example. That is, a method of using a cooling roll having a smoother surface and transferring the roll surface shape to the film, or a method of adjusting so that the elongation stress applied to the molten resin becomes large during cooling is preferable.

[0016] Note that although the reason for the improvement in the effect of the carbonyl group penetrating into the plane by the surface treatment by adjusting the arithmetic mean roughness Ra and glossiness before the surface treatment is not clear, it can be estimated as follows. When the arithmetic mean roughness Ra is relatively large, the influence on the outermost surface by the surface treatment may vary. However, when the arithmetic mean roughness Ra is relatively small, the influence on the outermost surface by the surface treatment becomes uniform, and it is considered that the probability and amount of the carbonyl group on the outermost surface penetrating into the plane are improved. In addition, since the glossiness is affected by the surface roughness of the object and the size of the internal crystal grains, a large glossiness means that the surface roughness is small and the crystal grains are small (below a certain size). When the crystal grains before the surface treatment are relatively large, the plurality of crystal grains become three-dimensional obstacles to each other, and the orientation of the outermost surface by the surface treatment is hindered. On the other hand, when the crystal grains before the surface treatment are relatively small, the orientation of the outermost surface by the surface treatment is promoted without receiving the above-described three-dimensional obstacles, and as a result, it is considered that the effect of the carbonyl group on the outermost surface penetrating into the plane is improved. In addition, it can be considered that the size of the crystal grains is affected by the cooling and elongation stress during melt extrusion. The crystal grain size of the outermost surface can be calculated using the Scherrer equation from the measurement results of grazing incidence wide-angle X-ray diffraction.

[0017] The arithmetic mean roughness Ra of the surface of the release layer is not particularly limited, but the preferable lower limit is 0.01 μm, the preferable upper limit is 0.50 μm, the more preferable lower limit is 0.02 μm, and the more preferable upper limit is 0.40 μm. When the arithmetic mean roughness Ra of the surface of the release layer is within the above range, the releasability of the release film is likely to be improved. The arithmetic mean roughness Ra of the surface of the release layer is the arithmetic mean roughness Ra conforming to JIS B 0601:2013, and can be measured, for example, using a Surf Test SJ-301 manufactured by Mitutoyo Corporation. Note that the arithmetic mean roughness Ra of the surface of the release layer is usually less affected by the change due to the surface treatment after film formation even when the surface treatment is performed after film formation in the manufacturing process of the release film, and the value does not change significantly before and after the surface treatment. The arithmetic mean roughness Ra of the surface of the release layer is mainly affected by the conditions during film formation. However, when a treatment such as heat pressing (press annealing) is applied, the unevenness on the surface is flattened, so generally the value of the arithmetic mean roughness Ra becomes smaller.

[0018] The glossiness of the surface of the release layer is not particularly limited, but the preferable lower limit is 100%, the preferable upper limit is 200%, the more preferable lower limit is 120%, and the more preferable upper limit is 180%. When the glossiness of the surface of the release layer is within the above range, it becomes easier to adjust the X / Y value on the outermost surface of the release layer to the above range, and the releasability of the release film is likely to be improved. The glossiness of the surface of the release layer is the glossiness measured in accordance with JIS Z8741 with an incident angle of 60°, and can be measured, for example, using a gloss meter VG-1D manufactured by Nippon Denshoku Industries Co., Ltd. Note that the glossiness of the surface of the release layer is usually less affected by the change due to the surface treatment after film formation even when the surface treatment is performed after film formation in the manufacturing process of the release film, and the value does not change significantly before and after the surface treatment. The glossiness of the surface of the release layer is mainly affected by the conditions during film formation.

[0019] The above surface treatment is not particularly limited, and examples include friction treatment, heat treatment, uniaxial stretching or biaxial stretching treatment, etc. These surface treatments may be used alone or in combination of two or more. The method of the above-mentioned friction treatment is not particularly limited, but it is preferable to use a friction treatment apparatus (for example, a polishing treatment apparatus manufactured by Yamagata Machinery Co., Ltd., model YCM-150M) and perform the friction treatment using a fabric as the material on the surface of the friction treatment material. The method of the above-mentioned heat treatment is not particularly limited, but methods such as passing the film between rolls heated to a certain temperature and heating the film with a heater are preferable. The method of the above-mentioned uniaxial or biaxial stretching treatment is not particularly limited, but a method of stretching the film after film formation at a certain temperature is preferable.

[0020] The crystallinity of the entire release layer is not particularly limited, but the preferable lower limit is 25% and the preferable upper limit is 50%. While the release layer has the X / Y value on the outermost surface as described above, by having an appropriate crystallinity within the above range as the entire release layer, the release film becomes even more excellent in both releasability and followability to unevenness. If the crystallinity of the entire release layer is 25% or more, the heat resistance of the release film is improved. If the crystallinity of the entire release layer is 50% or less, the followability of the release film to unevenness is improved. The more preferable lower limit of the crystallinity of the entire release layer is 30%, and the further preferable lower limit is 35%. The more preferable upper limit of the crystallinity of the entire release layer is 45%, the further preferable upper limit is 40%, and the particularly preferable upper limit is 35%.

[0021] The crystallinity of the entire release layer can be obtained by drawing a baseline on the diffraction measurement plot obtained by analyzing the entire release layer by wide-angle X-ray diffraction method, performing fitting for the crystalline phase and the amorphous phase respectively, and calculating according to the following formula (1) from the total peak area of the crystalline phase and the total peak area of the amorphous phase obtained. When the release film is composed of multiple layers, by peeling each layer of the release film and analyzing the sample composed of only the above-mentioned release layer, the crystallinity of the entire release layer can be evaluated. Crystallinity (%) = Total peak area of crystalline phase / (Total peak area of crystalline phase + Total peak area of amorphous phase) × 100 (1)

[0022] As an X-ray diffractometer for determining the crystallinity of the entire release layer, for example, a horizontal thin-film evaluation sample X-ray diffractometer (Smart Lab) manufactured by Rigaku Corporation set under the following conditions can be used. X-ray source CuKα ray Tube voltage - tube current 45 kV - 200 mA Incident optical system Concentration method Measurement range 5 - 80° Measurement interval 0.02° Scanning speed 5.0° / min Scanning method Out-of-Plane method

[0023] The method for adjusting the crystallinity of the entire release layer to the above range is not particularly limited, but when the resin constituting the release layer is melt-extruded and the molten resin is cooled, for example, the following method is preferably adopted. That is, a method of adjusting the contact time between the molten resin and the cooling roll, a method of adjusting the cooling roll temperature, etc. are preferable.

[0024] The release layer contains an aromatic polyester resin. Since the release layer contains the aromatic polyester resin, the release film of the present invention is excellent in both release properties and followability to unevenness, and is also excellent in preventing bleeding of the adhesive formed on the coverlay film.

[0025] The aromatic polyester resin is not particularly limited, but a crystalline aromatic polyester resin is preferable. Specifically, for example, polyethylene terephthalate resin, polybutylene terephthalate resin, polyhexamethylene terephthalate resin, polyethylene naphthalate resin, polybutylene naphthalate resin, butanediol terephthalic acid polytetramethylene glycol copolymer, etc. can be mentioned. These aromatic polyester resins may be used alone or in combination of two or more. Among them, from the viewpoint of balance such as heat resistance, release properties, and followability to unevenness, polybutylene terephthalate resin is preferable. In addition, a mixed resin obtained by mixing a block copolymer of polybutylene terephthalate and an aliphatic polyether with polybutylene terephthalate resin is also preferable. The aliphatic polyether is not particularly limited, and examples thereof include polyethylene glycol, polydiethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like.

[0026] From the viewpoint of film-forming properties of the aromatic polyester resin, the melt volume flow rate is preferably 30 cm 3 / 10 min or less, and more preferably 20 cm 3 / 10 min or less. The melt volume flow rate can be measured in accordance with ISO 1133 at a measurement temperature of 250 °C and a load of 2.16 kg.

[0027] Among the above aromatic polyester resins, commercially available products include, for example, "Perplen (registered trademark)" (manufactured by Toyobo Co., Ltd.), "Hytrel (registered trademark)" (manufactured by Toray DuPont Co., Ltd.), "Juranex (registered trademark)" (manufactured by Polyplastics Co., Ltd.), "Novaduran (registered trademark)" (manufactured by Mitsubishi Engineering Plastics Corporation), and the like.

[0028] The release layer may further contain other resins. The other resins are not particularly limited, and examples thereof include polyolefins and polystyrene. The polyolefin preferably contains poly(4-methyl-1-pentene) or an alicyclic olefin resin. The polystyrene preferably contains a polystyrene resin having a syndiotactic structure.

[0029] The polyolefin containing poly(4-methyl-1-pentene) preferably contains 90% by weight or more of poly(4-methyl-1-pentene) resin. As the poly(4-methyl-1-pentene) resin, commercially available products such as the product name TPX (registered trademark) manufactured by Mitsui Chemicals, Inc. can be used.

[0030] The above alicyclic olefin resin is an olefin resin having an alicyclic hydrocarbon in the main chain or side chain, and from the viewpoints of heat resistance, strength, etc., a thermoplastic saturated norbornene resin is preferred. Examples of the above thermoplastic saturated norbornene resin include resins obtained by hydrogenating a ring-opening polymer or ring-opening copolymer of a norbornene monomer (after performing modifications such as maleic acid addition or cyclopentadiene addition if necessary). Further, resins obtained by addition-polymerizing a norbornene monomer, resins obtained by addition-polymerizing a norbornene monomer and an olefin monomer such as ethylene or α-olefin, and resins obtained by addition-polymerizing a norbornene monomer and a cyclic olefin monomer such as cyclopentene, cyclooctene, 5,6-dihydrodicyclopentadiene, etc. can be mentioned. Furthermore, modified products of these resins, etc. can also be mentioned.

[0031] In the polystyrene containing the polystyrene resin having the above syndiotactic structure, it is preferable that the polystyrene resin having the syndiotactic structure is contained in an amount of 70% by weight or more and 90% by weight or less. The polystyrene resin having the above syndiotactic structure is a resin having a syndiotactic structure, that is, a stereoregular structure in which phenyl groups or substituted phenyl groups, which are side chains with respect to the main chain formed by carbon-carbon sigma bonds, are alternately located in opposite directions.

[0032] The polystyrene resin having the above syndiotactic structure is not particularly limited. For example, polystyrene having a syndiotacticity of 75% or more with a racemic diad or 30% or more with a racemic pentad, poly(alkylstyrene), poly(arylstyrene), poly(halogenated styrene), poly(halogenated alkylstyrene), poly(alkoxystyrene), poly(vinyl benzoate), etc. can be mentioned. Further, hydrogenated polymers of these, mixtures thereof, copolymers having these as main components, etc. can be mentioned. The polystyrene resin having the above syndiotactic structure can be commercially available, for example, under the trade name Zarec (registered trademark) (XAREC (registered trademark)) manufactured by Idemitsu Kosan Co., Ltd.

[0033] The release layer may contain a rubber component. By containing a rubber component in the release layer, the followability of the release film to unevenness is improved. 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, and the like. Further, examples of the rubber component include olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, ester-based thermoplastic elastomers, amide-based thermoplastic elastomers, and the like.

[0034] The release layer may contain a stabilizer. The stabilizer is not particularly limited, and examples thereof include hindered phenol-based antioxidants, heat stabilizers, and the like. The hindered phenol-based antioxidant is not particularly limited, and examples thereof include 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 3,9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)-propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane, and the like. The heat stabilizer is not particularly limited, and examples thereof include tris(2,4-di-t-butylphenyl)phosphite, trilauryl phosphite, 2-t-butyl-α-(3-t-butyl-4-hydroxyphenyl)-p-cumenyl bis(p-nonylphenyl)phosphite, dimyristyl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, pentaerythrityl tetrakis(3-laurylthiopropionate), ditridecyl 3,3'-thiodipropionate, and the like.

[0035] The release 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.

[0036] The thickness of the release layer is not particularly limited, but the preferable lower limit is 10 μm and the preferable 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 followability of the release film to unevenness is improved. The more preferable lower limit of the thickness of the release layer is 15 μm, and the more preferable upper limit is 30 μm.

[0037] The release film of the present invention preferably further has a cushion layer. By having the cushion layer, the followability of the release film to unevenness is improved. When having the cushion layer, the release film of the present invention only needs to have at least one release layer and a cushion layer, and may have a two-layer structure or a structure of three or more layers. Among them, it is preferable to have a structure having release layers on both sides of the cushion layer. In this case, the release layers on both sides may have the X / Y value on the extreme surface as described above, or only one of the release layers on one side may have the X / Y value on the extreme surface as described above. Also, the release layers on both sides may have the same resin composition or different resin compositions. Further, the release layers on both sides may have the same thickness or different thicknesses. Also, the release film of the present invention may have a structure in which the release layer and the cushion layer are directly in contact and laminated integrally, or may have a structure in which the release layer and the cushion layer are laminated integrally via an adhesive layer.

[0038] The resin constituting the cushion layer is not particularly limited, but a polyolefin resin is preferable. The above polyolefin resin is not particularly limited, and examples thereof include polyethylene resins (e.g., high-density polyethylene, low-density polyethylene, linear low-density polyethylene), polypropylene resins, ethylene-vinyl acetate copolymers, and the like. Further, ethylene-acrylic monomer copolymers such as ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-acrylic acid copolymer are also included. These polyolefin resins may be used alone or in combination of two or more. Among them, polypropylene resin and polyethylene resin are preferable, and it is more preferable to use polypropylene resin and polyethylene resin in combination because it is easy to achieve both followability to unevenness and heat resistance.

[0039] Further, it is preferable that the cushion layer contains the resin constituting the release layer. When the cushion layer contains the resin constituting the release layer, the adhesion between the release layer and the cushion layer is improved. It is more preferable that the cushion layer contains the main component resin of the release layer, and it is still more preferable that the cushion layer contains the main component resin of the release layer and a polyolefin resin. Here, the main component resin of the release layer means the resin having the highest content among the resins contained in the release layer.

[0040] The content of the resin constituting the release layer in the cushion layer is not particularly limited, but the preferable lower limit is 10% by weight, and the preferable upper limit is 50% by weight. When the content of the resin constituting the release layer is 10% by weight or more, the adhesion between the release layer and the cushion layer is improved. When the content of the resin constituting the release layer is 50% by weight or less, the flexibility of the cushion layer becomes sufficient, and the followability of the release film to unevenness is improved. The more preferable lower limit of the content of the resin constituting the release layer is 20% by weight, and the still more preferable lower limit is 25% by weight. The more preferable upper limit of the content of the resin constituting the release layer is 40% by weight, and the still more preferable upper limit is 35% by weight.

[0041] The content of the polyolefin resin in the cushion layer is not particularly limited, but the preferable lower limit is 50% by weight and the preferable upper limit is 90% by weight. If the content of the polyolefin resin is 50% by weight or more, the flexibility of the cushion layer becomes sufficient and the followability to the unevenness 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 cushion layer is improved. The more preferable lower limit of the content of the polyolefin resin is 60% by weight, and the further preferable lower limit is 65% by weight. The more preferable upper limit of the content of the polyolefin resin is 80% by weight, and the further preferable upper limit is 75% by weight.

[0042] The cushion layer may further contain resins such as polystyrene, polyvinyl chloride, polyamide, polycarbonate, polysulfone, and polyester. The cushion layer may further contain additives such as fibers, inorganic fillers, flame retardants, ultraviolet absorbers, antistatic agents, inorganic substances, and higher fatty acid salts.

[0043] The cushion layer may have a single-layer structure composed of a single layer or a multilayer structure composed of a laminate of a plurality of layers. When the cushion layer has a multilayer structure, the plurality of layers may be laminated and integrated via an adhesive layer.

[0044] The thickness of the cushion layer is not particularly limited, but the preferable lower limit is 15 μm and the preferable upper limit is 200 μm. If the thickness of the cushion layer is 15 μm or more, the followability to the unevenness of the release film is improved. If the thickness of the cushion layer is 200 μm or less, bleeding of the resin from the cushion layer occurring at the film end during hot press adhesion can be suppressed. The more preferable lower limit of the thickness of the cushion layer is 30 μm, and the more preferable upper limit is 150 μm.

[0045] The method for manufacturing the release film of the present invention is not particularly limited, and examples thereof include a water-cooled or air-cooled coextrusion inflation method, a method of forming a film by a coextrusion T-die method, a solvent casting method, and a hot press molding method. When having a structure with the release layers on both sides of the cushion layer, after producing a film to be one of the release layers, a cushion layer is laminated on this film by the extrusion lamination method, and then the other release layer is dry laminated. Also, a method of dry laminating a film to be one of the release layers, a film to be the cushion layer, and a film to be the other release layer is available. Among these, from the viewpoint of excellent thickness control of each layer, a method of forming a film by the co-extrusion T-die method is suitable.

[0046] The use of the release film of the present invention is not particularly limited, but it can be suitably used in the manufacturing processes of printed wiring boards, flexible circuit boards, multilayer printed wiring boards, etc. Specifically, for example, in the manufacturing process of a flexible circuit board, when thermally press-bonding a coverlay film to a flexible circuit board body on which a copper circuit is formed via a thermosetting adhesive or a thermosetting adhesive sheet, the release film of the present invention can be used. The release film of the present invention is excellent in both releasability and followability to unevenness, and particularly excellent in releasability. Therefore, it can also be suitably used in the manufacture of flexible circuit boards by the RtoR method that requires high releasability.

Effects of the Invention

[0047] According to the present invention, it is possible to provide a release film that is excellent in both releasability and followability to unevenness and can also be suitably used in the manufacture of flexible circuit boards by the RtoR method.

Modes for Carrying Out the Invention

[0048] Examples are given below to explain the aspects of the present invention in more detail, but the present invention is not limited only to these examples.

[0049] (Example 1) (1) Manufacture of Release Film As the resin constituting the release layer, polybutylene terephthalate resin (PBT) was used. As the resin constituting the cushion layer, 60 parts by weight of polypropylene resin (PP) and 40 parts by weight of high-density polyethylene (HDPE) were used. The resin constituting the release layer and the resin constituting the cushion layer were co-extruded in three layers at a T-die width of 400 mm using an extruder (manufactured by GM Engineering Co., Ltd., GM30-28 (screw diameter 30 mm, L / D 28)), and the extruded molten resin was cooled by a cooling roll (temperature 70 °C). As a result, a three-layer structure film having release layers (thickness 20 μm) on both sides of a cushion layer (thickness 60 μm) was obtained. In addition, during cooling, the contact time between the molten resin and the cooling roll was set to 1.0 second, and the elongation stress when cooling the molten resin by the cooling roll was set to 450 kPa.

[0050] In addition, the elongation stress is represented by the following formula (2). Elongation stress (Pa) = Strain rate (1 / s) × Extensional viscosity of molten resin (Pa·s) (2) In addition, the strain rate and the extensional viscosity of the molten resin are represented by the following formulas (3) and (4), respectively. Strain rate (1 / s) = 9 × V × {(V / V0)^(1 / 9) - 1} / L (3) Extensional viscosity of molten resin (Pa·s) = Zero-shear viscosity (Pa·s) × Strain rate (1 / s)^(-0.1) (4) In formula (3), V is the roll speed (m / s), V0 is the flow rate of the molten resin at the die outlet (m / s), and L is the distance (m) from the die outlet to the roll contact point of the molten resin.

[0051] The surface of one of the release layers of the obtained film was subjected to friction treatment using a friction treatment device (a polishing treatment device manufactured by Yamagata Machinery Co., Ltd., model YCM-150M), and a fabric was used as the material of the surface of the friction treatment material to obtain a release film. In addition, the amount of work energy applied during the friction treatment was 350 kJ. Also, the crystal grain size of (010) on the extreme surface before the friction treatment was 60 Å, the arithmetic mean roughness Ra was 0.05 μm, and the glossiness was 188%.

[0052] (2) Measurement of arithmetic mean roughness Ra Based on JIS B 0601:2013, the arithmetic mean roughness Ra of the surface of the release layer after friction treatment was measured using a Surftest SJ-301 manufactured by Mitutoyo. The results are shown in Table 1.

[0053] (3) Measurement of glossiness Based on JIS Z8741, with an incident angle of 60°, the glossiness of the surface of the release layer after friction treatment was measured using a gloss meter VG-1D manufactured by Nippon Denshoku Industries Co., Ltd. The results are shown in Table 1.

[0054] (4) Calculation of the X / Y value on the extreme surface The surface of the release layer after friction treatment was analyzed by the grazing incidence wide angle X-ray diffraction method with an X-ray incident angle of 0.06°. The incident direction of the X-ray was measured in accordance with the film flow (MD: Machine Direction) direction. A linear baseline was drawn on the obtained diffraction measurement plot in the range of 2θ = 9.5 to 35°. Gaussian function fitting was performed for the crystalline phase and the amorphous phase respectively, the area X derived from (010) and the area Y derived from (100) in the crystalline phase were obtained respectively, and the X / Y value was obtained from the obtained X and Y. The results are shown in Table 1.

[0055] As the grazing incidence wide angle X-ray diffractometer, a multifunctional X-ray diffractometer for surface structure evaluation (ATX-G type) manufactured by Rigaku Corporation set under the following conditions was used. X-ray source CuKα ray Tube voltage - tube current 50 kV - 300 mA Incident optical system Concentration method Incident angle (ω) 0.06° Measurement range 5 - 70° Measurement interval 0.02° Scanning speed 1.0° / min Scanning method In-Plane method

[0056] (5) Analysis of the orientation of carbonyl groups in the region from the surface to a thickness of 1 μm The surface of the release layer was analyzed by the grazing incidence X-ray diffraction method with an X-ray incident angle of 0.19°. The X-ray incident direction was measured in accordance with the film flow (MD: Machine Direction) direction. A linear baseline was drawn on the obtained diffraction measurement plot in the range of 2θ = 9.5 to 35°, and fitting was performed using a Gaussian function for the crystalline phase and the amorphous phase, respectively. Furthermore, by performing the fitting, the relative ratio of the amount of carbonyl groups oriented parallel to the surface to the total amount of carbonyl groups oriented parallel to the surface and carbonyl groups oriented perpendicular to the surface was determined. The results are shown in Table 1.

[0057] As the grazing incidence wide-angle X-ray diffractometer, a multifunctional X-ray diffractometer for surface structure evaluation (ATX-G type) manufactured by Rigaku Corporation, set under the following conditions, was used. X-ray source CuKα ray Tube voltage - tube current 50 kV - 300 mA Incident optical system Concentration method Incident angle (ω) 0.19° Measurement range 5 - 70° Measurement interval 0.02° Scanning speed 1.0° / min Scanning method In-Plane method

[0058] (6) Measurement of the crystallinity of the entire release layer Each layer of the release film was peeled off to obtain a sample consisting only of the release layer after the friction treatment. The release layer after the friction treatment was analyzed by the wide-angle X-ray diffraction method. A baseline was drawn on the obtained diffraction measurement plot. Fitting was performed using a Gaussian function for the crystalline phase and the amorphous phase, respectively, and the crystallinity of the entire release layer was determined from the total peak area of the crystalline phase and the total peak area of the amorphous phase obtained by the following formula (1). The results are shown in Table 1. Crystallinity (%) = Total peak area of crystalline phase / (Total peak area of crystalline phase + Total peak area of amorphous phase) × 100 (1)

[0059] As the wide-angle X-ray diffractometer, a sample horizontal type X-ray diffractometer for thin film evaluation (Smart Lab) manufactured by Rigaku Corporation, set under the following conditions, was used. X-ray source CuKα ray Tube voltage - tube current 45 kV - 200 mA Incident optical system Concentration method Measurement range 5 - 80° Measurement interval 0.02° Scanning speed 5.0° / min Scanning method Out-of-Plane method

[0060] (Example 2) As the resin constituting the release layer, polybutylene terephthalate resin (PBT) and PBT-polytetramethylene glycol copolymer were used at a weight ratio of 85:15. A release film was obtained in the same manner as in Example 1 except that the contact time between the molten resin and the cooling roll, the cooling roll temperature, the elongation stress, and the amount of work energy during the friction treatment were changed as shown in Table 1. For the obtained release film, each physical property was determined in the same manner as in Example 1.

[0061] (Examples 3 - 4, Comparative Examples 1, 3 - 4) A release film was obtained in the same manner as in Example 1 except that the contact time between the molten resin and the cooling roll, the cooling roll temperature, the elongation stress, and the amount of work energy during the friction treatment were changed as shown in Table 1. For the obtained release film, each physical property was determined in the same manner as in Example 1.

[0062] (Comparative Example 2) A release film was obtained in the same manner as in Example 2 except that the cooling roll temperature, the elongation stress, and the amount of work energy during the friction treatment were changed as shown in Table 1. For the obtained release film, each physical property was determined in the same manner as in Example 1.

[0063] <Evaluation> For the release films obtained in the examples and comparative examples, the following evaluations were performed. The results are shown in Table 1.

[0064] (1) Evaluation of release property Place the release film on the epoxy adhesive sheet such that the release layer after the friction treatment contacts the epoxy adhesive sheet (manufactured by Nikkan Kogyo Co., Ltd., CISV2535), and stack them. Then, perform hot pressing at 180 °C and 30 kgf / cm 2 for 5 minutes under these conditions. After that, the release film peeled off naturally in some samples. For the samples where the release film did not peel off naturally even 10 minutes after the hot pressing, cut them into pieces with a width of 30 mm, and perform a peel test at a test speed of 500 mm / min and a peel angle of 30° to obtain the 30° peel strength (30° peel value). When the release film peeled off naturally, it was marked as ○, and when it did not peel off naturally, it was marked as ×.

[0065] (2) Evaluation of Followability Stack a coverlay film (12.5 cm × 12.5 cm, polyimide thickness 25 μm, epoxy adhesive layer thickness 35 μm) with a hole of φ = 1 mm 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) such that the epoxy adhesive layer contacts. Further stack the release film such that the release layer after the friction treatment contacts the coverlay film. Heat press this laminate at 180 °C and 30 kgf / cm 2 for 2 minutes under these conditions. After that, peel off the release film and observe the epoxy adhesive that flowed out on the copper-clad laminate (CCL) with an optical microscope. Measure the bleeding width of the epoxy adhesive at 12 points and calculate the average value to evaluate the followability of the release film. When the average value of the bleeding width of the epoxy adhesive was less than 55 μm, it was marked as ○, and when it was 55 μm or more, it was marked as ×.

[0066]

Table 1

Industrial Applicability

[0067] According to the present invention, it is possible to provide a release film that is excellent in both releasability and followability to unevenness, and can be suitably used for manufacturing a flexible printed circuit board by the RtoR method.

Claims

1. A release film having at least one release layer containing an aromatic polyester resin, wherein, in the profile obtained by the grazing incidence wide-angle X-ray diffraction method with an incident angle of 0.06°, when the area derived from (010) is X and the area derived from (100) is Y, X / Y > 0.7 is satisfied. A release film characterized by the above.

2. The release film according to Claim 1, characterized in that the crystallinity of the entire release layer is 25 to 50%.

3. The release film according to Claim 1 or 2, characterized in that the arithmetic mean roughness Ra of the surface of the release layer is 0.50 μm or less.

4. The release film according to Claim 1, 2 or 3, characterized in that the glossiness of the surface of the release layer is 100% or more.

5. The release film according to Claim 1, 2, 3 or 4, further having a cushion layer and having release layers on both sides of the cushion layer.

6. The release film according to Claim 1, 2, 3, 4 or 5, characterized in that the aromatic polyester resin contains a polybutylene terephthalate resin.

7. The release film according to Claim 1, 2, 3, 4, 5 or 6, characterized in that it is used in the production of a flexible printed circuit board by the RtoR method.

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