JP2012015441A - Film for reinforcing flexible printed circuit board, flexible printed circuit reinforcing plate composed of the same, and flexible printed circuit board laminate composed of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film for reinforcing a flexible printed circuit board, as a film for reinforcing an FPC board, which suppresses occurrence of curling in a solder reflow process, and to provide a flexible printed circuit reinforcing plate composed of the film for reinforcing the flexible printed circuit board, and a flexible printed circuit board laminate composed of them.SOLUTION: In a film for reinforcing a flexible printed circuit board having a biaxially oriented polyester film substrate layer, heat shrinkage percentage of the reinforcing film when heat treated at 230°C for 10 min. is -1% or more to less than 4% in both longitudinal and width directions, and storage elastic modulus (E') at a frequency of 1 Hz is 350-2000 MPa at 200°C in the longitudinal and width directions.

Description

  The present invention relates to a flexible printed circuit board reinforcing film in which curling is suppressed. Moreover, it is related with the flexible printed circuit board which consists of this flexible printed circuit board reinforcement film, and the flexible printed circuit board laminated body which consists of them.

  In recent years, with the technical progress of electronic devices such as mobile phones, the demand for flexible printed circuit (hereinafter sometimes abbreviated as FPC) substrates has increased rapidly. As such an FPC board, the thickness of the substrate film has been reduced along with the weight reduction and miniaturization of electronic devices, but the rigidity of the substrate film itself has been lowered accordingly, and the processing when manufacturing the FPC becomes more difficult. It has become to. As a method for improving such workability degradation, an FPC reinforcing film is used as a reinforcing plate in addition to the substrate film, and the reinforcing plate is bonded to a portion of the FPC substrate where workability is required via an adhesive sheet. Is used, and a method of giving rigidity as a whole is used.

  Conventionally, a laminated film in which two or more polyimide films are bonded together has been used for the FPC reinforcing film. However, due to the nature of the material, polyimide is difficult to form into a film or to produce a film having a film thickness of 75 μm or more, and is very expensive. In addition, polyimide has a characteristic that it is relatively easy to absorb water and is difficult to handle as an electronic material such as FPC. Furthermore, although it is excellent in heat resistance, it cannot be denied that it is excessive quality in this application.

  On the other hand, materials other than polyimide have been studied as FPC substrate films. For example, Patent Document 1 proposes an FPC substrate film using a polyethylene naphthalate film, which is used as a reinforcing film during processing. It is disclosed that However, when the solder reflow process is performed using the polyethylene naphthalate film disclosed in Patent Document 1, there is a problem that curling occurs.

JP 2005-129699 A

  An object of the present invention is to provide a flexible printed circuit board reinforcing film in which curling is suppressed in a solder reflow process as a reinforcing film for an FPC board. Moreover, it is providing the flexible printed circuit reinforcement board which consists of this film for flexible printed circuit board reinforcement, and the flexible printed circuit board laminated body which consists of them.

The inventors adopt the following configuration in order to solve the above-described problems.
1. A flexible printed circuit board reinforcing film having a biaxially oriented polyester film substrate layer, wherein the heat shrinkage rate of the reinforcing film when heat-treated at 230 ° C. for 10 minutes is in both the film longitudinal direction and the width direction − A flexible printed circuit board reinforcing film having a storage elastic modulus (E ′) of 1 to 4% at a frequency of 1 Hz in a longitudinal direction and a width direction of 350 to 2000 MPa at 200 ° C.

Moreover, this invention includes the following.
2. 2. The flexible printed circuit board reinforcing film as described in 1 above, wherein the biaxially oriented polyester film base layer contains an inorganic filler having an aspect ratio of 10 or more of 2 wt% or more and 50 wt% or less based on the weight of the layer.
3. 3. The flexible printed circuit board reinforcing film as described in 2 above, wherein the inorganic filler is at least one selected from the group consisting of carbon nanotubes, carbon nanofibers, carbon fibers, artificial graphite, and boron nitride.
4). 4. The flexible printed circuit board reinforcing film according to any one of 1 to 3 above, wherein a coating layer containing a polymer binder containing an acrylic resin having an oxazoline group is provided on at least one surface of the biaxially oriented polyester film base layer.
5. 5. The flexible printed circuit board reinforcing film as described in 4 above, wherein the content of the polymer binder in the coating layer is 10% by weight or more and 80% by weight or less based on the weight of the coating layer.
6). 6. The flexible printed circuit board reinforcing film as described in 4 or 5 above, wherein the content of the acrylic resin having an oxazoline group is 3% by weight or more and 90% by weight or less based on the weight of the polymer binder.
7). 7. The flexible printed circuit board reinforcing film according to any one of 1 to 6, wherein the polyester constituting the biaxially oriented polyester film base layer is polyethylene naphthalene dicarboxylate.
8). The flexible printed circuit reinforcement board using the film for flexible printed circuit board reinforcement in any one of said 1-7.
9. The flexible printed circuit board laminated body by which the flexible printed circuit reinforcement board of said 8 was bonded together via the adhesive sheet to the flexible printed circuit board.
10. 10. The flexible printed circuit board laminate according to 9 above, wherein the adhesive sheet is an epoxy adhesive sheet or an acrylic adhesive sheet.
11. 11. The flexible printed circuit board laminate according to 9 or 10 above, wherein the base film of the flexible printed circuit board is polyimide or polyester.

  ADVANTAGE OF THE INVENTION According to this invention, the flexible printed circuit board reinforcement film by which generation | occurrence | production of the curl was suppressed in the solder reflow process can be provided as a reinforcement film of an FPC board. Moreover, the flexible printed circuit reinforcement board which consists of this flexible printed circuit board reinforcement film, and the flexible printed circuit board laminated body which consists of them can be provided.

  In the present invention, the continuous film forming direction may be referred to as a vertical direction, a longitudinal direction, or MD. In addition, a direction perpendicular to the continuous film forming direction may be referred to as a lateral direction, a width direction, or TD.

<Biaxially oriented polyester film substrate layer>
The flexible printed circuit board reinforcing film of the present invention has a biaxially oriented polyester film base layer. The polyester constituting the base material layer is not particularly limited, but a polyester composed of a dicarboxylic acid component and a diol component is preferable. Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, and the like. Examples of the diol component include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, and the like.

  As the polyester, polyethylene terephthalate and polyethylene naphthalene dicarboxylate are preferable, and polyethylene naphthalene dicarboxylate is particularly preferable. The polyester may be a homopolymer, or may be a copolymer or a blend thereof as long as the object of the present invention is not impaired.

(Polyethylene naphthalene dicarboxylate)
As the polyester constituting the biaxially oriented polyester film substrate layer of the present invention, polyethylene naphthalene dicarboxylate obtained by polycondensation of naphthalene dicarboxylic acid or a derivative thereof and ethylene glycol is preferable, and polyethylene-2,6-naphthalene is particularly preferable. Dicarboxylate is preferred. By using polyethylene naphthalene dicarboxylate as the polyester, the effect of improving the heat-resistant dimensional stability of the film can be enhanced.

  The polyester of the present invention may be a homopolymer, or may be a copolymer or a mixture of two or more kinds of polyesters. The other components in the copolymer or mixture are preferably 10 mol% or less, more preferably 5 mol% or less, based on the total acid components. Examples of the copolymer component include diol components such as diethylene glycol, neopentyl glycol, and polyalkylene glycol, and dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, and 5-sodium sulfoisophthalic acid.

  Polyester can be produced by applying a known method. For example, it can be produced by a method in which a diol, a dicarboxylic acid and, if necessary, a copolymerization component are esterified, and then a reaction product obtained is polycondensed to form a polyester. Alternatively, these raw material monomer derivatives may be transesterified, and then the resulting reaction product may be subjected to a polycondensation reaction to obtain a polyester.

  The intrinsic viscosity of the polyester is preferably 0.40 dl / g or more, more preferably 0.40 dl / g or more and 0.80 dl / g or less at 35 ° C. in o-chlorophenol. When the intrinsic viscosity is less than 0.40 dl / g, cutting may occur frequently during film formation, or the strength of the product after forming may be insufficient. On the other hand, when the intrinsic viscosity exceeds 0.80 dl / g, productivity during polymerization may be lowered.

  In the base material layer, the polyethylene naphthalene dicarboxylate is preferably 50% by weight or more and 98% by weight or less, more preferably 70% by weight or more and 98% by weight or less, and particularly preferably 80% by weight based on the weight of the layer. % To 98% by weight. When the content of polyethylene naphthalene dicarboxylate is less than the lower limit, the reinforcing plate becomes brittle and the reinforcing effect may not be sufficient. On the other hand, when the content of polyethylene naphthalene dicarboxylate exceeds the upper limit, it tends to be difficult to set the storage elastic modulus (E ′) at 200 ° C. within the numerical range defined by the present invention, and the curl suppression is improved. The effect tends to be low. In addition, the heat dissipation effect may not be sufficiently exhibited.

(Inorganic filler)
The biaxially oriented polyester base layer in the present invention preferably contains an inorganic filler having an aspect ratio of 10 or more, preferably 20 or more, more preferably 100 or more. By containing the inorganic filler having such a specific aspect ratio, it becomes easy to set the storage elastic modulus (E ′) at 200 ° C. within the numerical range defined by the present invention, and the effect of improving curling suppression is increased. be able to. The upper limit of the aspect ratio is not particularly limited, but is substantially 1500 or less, preferably 1000 or less.

  The content of the inorganic filler is preferably 2% by weight or more and 50% by weight or less based on the weight of the biaxially oriented polyester base material layer, and the present invention defines the storage elastic modulus (E ′) at 200 ° C. It becomes easier to set the numerical value range, and the effect of improving curling suppression can be further enhanced. When the content of the inorganic filler is less than the lower limit value, the storage elastic modulus (E ′) at 200 ° C. tends to be low, and the effect of suppressing curling that occurs in the solder reflow process tends to be low. On the other hand, when the content of the inorganic filler exceeds the upper limit value, the reinforcing plate becomes brittle, and the reinforcing effect may not be sufficient when bent, and cutting is likely to occur during film formation. From such a viewpoint, the content of the inorganic filler is more preferably 2% by weight to 30% by weight, and particularly preferably 2% by weight to 20% by weight. Note that, within the above numerical range, the storage elastic modulus (E ′) at 200 ° C. tends to increase as the content of the inorganic filler increases, and the curling suppression improving effect tends to increase.

  The inorganic filler includes a group consisting of carbon nanotubes, carbon nanofibers, carbon fibers, artificial graphite, and boron nitride from the viewpoint of increasing the storage elastic modulus (E ′) at 200 ° C. and improving the curling suppression effect. It is preferably at least one inorganic filler selected from the above. Among these inorganic fillers, carbon nanotubes and carbon nanofibers are preferable because they can increase the storage elastic modulus (E ′) at 200 ° C. even when added in a small amount and easily exhibit the curl suppressing effect.

  The average particle diameter or average fiber length of the inorganic filler is preferably 0.5 to 300 μm, more preferably 0.5 to 200 μm, and particularly preferably 0.5 to 50 μm. When the average particle diameter or the average fiber length is in the above numerical range, it becomes easy to set the storage elastic modulus (E ′) at 200 ° C. to the numerical range specified by the present invention, and the effect of improving curling suppression can be increased. it can. When the average particle diameter is less than the lower limit, dispersibility tends to deteriorate and the inorganic filler tends to aggregate, so that coarse protrusions are formed on the film, which may cause trouble in the production process. Further, the aggregation tends to lower the effect of improving the storage elastic modulus (E ′) at 200 ° C., and the effect of improving curling suppression tends to be reduced. On the other hand, when the average particle diameter or the average fiber length exceeds the upper limit value, the surface of the film tends to become rough and the inorganic filler tends to fall off easily.

  The average thickness or average fiber diameter of the inorganic filler is preferably 0.001 to 15 μm, more preferably 0.01 to 15 μm, and particularly preferably 0.1 to 1 μm. When the average thickness or the average fiber diameter is in the above numerical range, it becomes easy to set the storage elastic modulus (E ′) at 200 ° C. within the numerical range defined by the present invention, and the effect of improving curling suppression can be enhanced. . When the average particle diameter is less than the lower limit, dispersibility tends to deteriorate and the inorganic filler tends to aggregate, so that coarse protrusions are formed on the film, which may cause trouble in the production process. Further, the aggregation tends to lower the effect of improving the storage elastic modulus (E ′) at 200 ° C., and the effect of improving curling suppression tends to be reduced. On the other hand, when the average thickness or the average fiber diameter exceeds the upper limit value, the surface of the film tends to become rough, and the inorganic filler tends to fall off easily.

  The inorganic filler in the present invention may be subjected to a surface treatment in order to enhance the adhesion with the polyester. Such surface treatment is not particularly limited, and examples thereof include a method of attaching a functional group to the surface by epoxy silane, vinyl silane treatment, strong acid treatment, or the like.

Various methods can be used as a method of incorporating the inorganic filler into the polyester constituting the base material layer, and typical methods include the following methods.
(A) A method of adding before transesterification or esterification reaction at the time of polyester synthesis or adding before the start of polycondensation reaction.
(A) A method of introducing into a extruder together with a polyester chip and melt-kneading at the time of film formation.
(C) A method in which, in the methods (a) and (b), master pellets to which a large amount of inorganic filler is added are produced, and these and a polyester not containing an additive are kneaded to contain a predetermined amount of additive.
(D) A method of using the master pellet of (c) as it is.

In addition, when using the method added at the time of the polyester synthesis | combination of (a), it is preferable to add to a reaction system as a slurry which disperse | distributed the filler to glycol.
In general, these inorganic fillers often agglomerate into coarse aggregate fillers. In order to reduce the number of coarse aggregate fillers, an average opening 10 made of stainless steel fine wires having a wire diameter of 15 μm or less is used as a filter during film formation. It is preferable to filter the molten polymer using a non-woven fabric filter having a mean opening of 100 to 100 μm, preferably 20 to 50 μm.

(Other additives)
The polyester constituting the base material layer is mixed with other additives such as an antioxidant, an ultraviolet absorber, and a fluorescent brightening agent as long as they do not deviate from the purpose of the present invention. Also good. When these additives are included, the content thereof is preferably 5% by weight or less, more preferably 3% by weight or less, and particularly preferably 1% by weight or less, based on the weight of the base material layer.

<Coating layer>
The flexible printed circuit board reinforcing film of the present invention preferably has a coating layer containing a polymer binder containing an acrylic resin having an oxazoline group on at least one surface of the above-described biaxially oriented polyester film base material layer. . Thereby, it is excellent in adhesiveness with a commercially available adhesive sheet, and even in the case where the FPC board and the reinforcing plate are bonded together using a commercially available adhesive sheet in the solder reflow process, The occurrence of swelling can be further suppressed.

(Polymer binder)
The polymer binder constituting the coating layer contains an acrylic resin having an oxazoline group. By using such a polymer binder, the adhesiveness between the flexible printed circuit board and the flexible printed circuit board reinforcing film can be further enhanced through a commercially available adhesive sheet.

Examples of the acrylic resin having an oxazoline group include acrylic resins composed of the following monomers having an oxazoline group.
Examples of the monomer having an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2 -Isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline can be mentioned, and one or a mixture of two or more thereof can be used. Among these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially.

  By using an acrylic resin having an oxazoline group, the cohesive force of the coating layer can be improved and the occurrence of cohesive failure in the coating layer can be prevented. Therefore, by adhering to the coating layer surface when adhering to the adhesive sheet, the adhesiveness with the adhesive sheet becomes strong, and at the same time, the thermal shrinkage rate of the reinforcing film is in a certain range, so that the solder reflow process is performed. Even if it passes, the adhesion interface with an adhesive sheet cannot peel easily, generation | occurrence | production of a swelling can be suppressed, and a circuit board can fully be reinforced as a flexible printed circuit board reinforcement board.

  The monomer component having an oxazoline group is preferably 5 mol% or more and 80 mol% or less, more preferably 10 mol% or more and 50 mol% or less, based on the repeating unit of the acrylic resin.

  The acrylic resin may further contain a monomer having a polyalkylene oxide chain as a copolymerization component. Examples of the monomer having a polyalkylene oxide chain include those obtained by adding polyalkylene oxide to an ester part of acrylic acid or methacrylic acid. Examples of the polyalkylene oxide chain include polyethylene oxide, polypropylene oxide, and polybutylene oxide. The repeating unit of the polyalkylene oxide chain is preferably 3 to 100.

  When a polyester resin is further included in the coating layer, the use of an acrylic resin having a polyalkylene oxide chain improves the compatibility between the polyester resin and the acrylic resin compared to an acrylic resin not containing a polyalkylene oxide chain.

  When the acrylic resin contains a monomer having a polyalkylene oxide chain, if the number of repeating units of the polyalkylene oxide chain is less than 3, the compatibility between the polyester resin and the acrylic resin may not be sufficiently improved. On the other hand, if the repeating unit of the polyalkylene oxide chain is larger than 100, the wet heat resistance of the coating layer is lowered, and the adhesion to the adhesive sheet may be lowered at high humidity and high temperature.

  Furthermore, as other copolymerization components constituting the acrylic resin, alkyl acrylate, alkyl methacrylate (alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group) Group, 2-ethylhexyl group, cyclohexyl group, etc.); hydroxyl group-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate; glycidyl acrylate, glycidyl methacrylate, allyl glycidyl Epoxy group-containing monomers such as ether; acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid and salts thereof (sodium salt, potassium salt, Monomers having a carboxyl group such as ammonium salt, tertiary amine salt, etc. or salts thereof; acrylamide, methacrylamide, N-alkyl acrylamide, N-alkyl methacrylamide, N, N-dialkyl acrylamide, N, N-dialkyl methacryl Amides (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, cyclohexyl, etc.), N-alkoxyacrylamide, N -Alkoxymethacrylamide, N, N-dialkoxyacrylamide, N, N-dialkoxymethacrylamide (alkoxy groups include methoxy group, ethoxy group, butoxy group, isobutoxy group, etc.), acryloylmorpholine, N-methylolacrylamido Monomers having an amide group such as N-methylol methacrylamide, N-phenyl acrylamide, N-phenyl methacrylamide; monomers of acid anhydrides such as maleic anhydride and itaconic anhydride; vinyl isocyanate, allyl isocyanate, styrene, α- Methyl styrene, vinyl methyl ether, vinyl ethyl ether, vinyl trialkoxysilane, alkyl maleic acid monoester, alkyl fumaric acid mono ester, alkyl itaconic acid mono ester, acrylonitrile, methacrylonitrile, vinylidene chloride, ethylene, propylene, vinyl chloride, Examples include vinyl acetate and butadiene.

  In addition to the acrylic resin, other components can be used in combination as the polymer binder. For example, it is preferable to use a polyester resin. By using a polyester resin in combination, the adhesion between the polyester base layer and the coating layer can be enhanced.

  As the polyester resin, a polyester obtained from a polybasic acid component and a diol component is preferably used. As polyvalent base components, terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, pyromellitic acid, dimer Examples of the acid include 5-sodium sulfoisophthalic acid. As the polyester resin constituting the polymer binder, it is preferable to use a copolymerized polyester using two or more kinds of dicarboxylic acid components. The polyester resin may contain an unsaturated polybasic acid component such as maleic acid or itaconic acid, or a hydroxycarboxylic acid component such as p-hydroxybenzoic acid, if it is in a slight amount.

  Examples of the diol component of the polyester resin include ethylene glycol, trimethylene glycol, 1,4-butanediol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, xylene glycol, dimethylolpropane, and the like. And poly (ethylene oxide) glycol and poly (tetramethylene oxide) glycol.

  The glass transition point of the polyester resin of the polymer binder is preferably 40 to 100 ° C, more preferably 60 to 80 ° C. If it is this range, in addition to the outstanding adhesiveness with a polyester base material layer, the further outstanding scratch resistance can be obtained. On the other hand, when the glass transition temperature is less than 40 ° C., blocking tends to occur between the films, and when it exceeds 100 ° C., the coating film may be hard and brittle.

  The content of the polymer binder is preferably 10% by weight or more and 80% by weight or less based on the weight of the coating layer. Further, the lower limit of the content of the polymer binder is more preferably 20% by weight, and the upper limit of the content of the polymer binder is more preferably 50% by weight. When the content of the polymer binder is in such a range, the adhesiveness with the adhesive sheet can be strengthened, and when the thermal shrinkage rate of the reinforcing film is in a certain range, after solder reflow Generation of peeling and swelling of the interface can be suppressed.

  The content of the acrylic resin having an oxazoline group is preferably 3% by weight or more and 90% by weight or less based on the weight of the polymer binder. Further, the lower limit of the content of the acrylic resin is more preferably 15% by weight, and further preferably 25% by weight. Moreover, the preferable upper limit of content of this acrylic resin is 80 weight%.

  When the ratio of the acrylic resin having an oxazoline group in the polymer binder is within such a range, the cohesive force of the coating layer is improved and the cohesive failure is less likely to occur, and the peeling and swelling at the adhesive interface after solder reflow are suppressed. The effect becomes higher as the preferable range is reached. On the other hand, when the acrylic resin is less than the lower limit, the cohesive force of the coating layer is lowered, and the adhesion with the adhesive sheet may be insufficient. Moreover, when this acrylic resin exceeds an upper limit, the adhesiveness of a polyester film and an application layer may fall.

  When the polymer binder further contains a polyester resin, the content of the polyester resin is preferably 5% by weight or more and 95% by weight or less based on the weight of the polymer binder. Further, the lower limit of the content of the polyester resin is more preferably 10% by weight, and further preferably 20% by weight. Further, the upper limit of the content of the polyester resin is more preferably 90% by weight, further 85% by weight, and particularly preferably 75% by weight.

(Fine particles)
The coating layer of the present invention can contain fine particles for the purpose of enhancing the slipperiness of the film. The type of fine particles is not particularly limited, but calcium carbonate, magnesium carbonate, calcium oxide, zinc oxide, magnesium oxide, silicon oxide, sodium silicate, aluminum hydroxide, iron oxide, zirconium oxide, barium sulfate, titanium oxide, tin oxide, Inorganic fine particles such as antimony trioxide, carbon black, and molybdenum disulfide, and organic fine particles such as acrylic cross-linked polymers, styrenic cross-linked polymers, silicone resins, fluororesins, benzoguanamine resins, phenol resins, and nylon resins. . Among these, for the water-insoluble solid substance, it is preferable to select fine particles whose specific gravity does not exceed 3 in order to avoid sedimentation in the aqueous dispersion.

The average particle diameter of the fine particles is preferably in the range of 40 to 120 nm. If the average particle size is larger than 120 nm, the particles are likely to fall off, and if it is smaller than 40 nm, sufficient lubricity and scratch resistance may not be obtained.
The content of the fine particles is preferably in the range of less than 10% by weight based on the weight of the coating layer. If it exceeds 10% by weight, the cohesive force of the coating film becomes low and the adhesiveness may deteriorate. Moreover, it is preferable that the minimum of content of microparticles | fine-particles is 0.1 weight% on the basis of the weight of a coating layer.

(Aliphatic wax)
An aliphatic wax may be added to the coating layer for the purpose of preventing blocking. When the aliphatic wax is added for this purpose, the content is preferably 0.5 to 30% by weight, more preferably 1% to 10% by weight, based on the weight of the coating layer. When content is less than a minimum, the lubricity of a film surface is not acquired and films may block. On the other hand, when content exceeds an upper limit, the adhesiveness with respect to a polyester film base material layer and an adhesive sheet may be insufficient.

  Specific examples of the aliphatic wax include plant-based waxes such as carnauba wax, candelilla wax, rice wax, wood wax, jojoba oil, palm wax, rosin modified wax, cucumber wax, sugar cane wax, esparto wax, and bark wax. Animal waxes such as beeswax, lanolin, whale wax, ibota wax, shellac wax, mineral waxes such as montan wax, ozokerite, ceresin wax, petroleum waxes such as paraffin wax, microcrystalline wax, petrolactam, and fishertro push wax And synthetic hydrocarbon waxes such as polyethylene wax, oxidized polyethylene wax, polypropylene wax, and oxidized polypropylene wax. Among these, carnauba wax, paraffin wax, and polyethylene wax are particularly preferable because they have good adhesion to the adhesive sheet and good sliding properties. These are preferably used as water dispersions because they can reduce the environmental burden and are easy to handle.

(Other ingredients)
In the present invention, as a component for forming the coating layer, in addition to the above components, a wetting agent such as a surfactant may be used in order to improve wettability when coating. Moreover, other components can be mix | blended as desired. Other compounding agents include other resins such as melamine resin, antistatic agents, colorants, soft polymers, fillers, heat stabilizers, weathering stabilizers, anti-aging agents, leveling agents, slip agents, antiblocking agents, Antifogging agents, natural oils, synthetic oils, emulsions, fillers, curing agents, flame retardants and the like can be mentioned, and the blending ratio thereof is selected as long as the object of the present invention is not impaired.

(Formation method of coating layer)
Regarding the formation of the coating layer, for example, after applying an aqueous solution containing a component for forming a coating film on at least one surface of a stretchable polyester film, the polyester film can be laminated by drying, stretching, and heat treatment as necessary. More specifically, with respect to the formation time of the coating layer, more specifically, an unstretched film, a uniaxially oriented film oriented in either the longitudinal direction or the transverse direction, or a low-magnification oriented orientation in two directions, the longitudinal direction and the transverse direction. It is preferable to apply the coating solution at any time of the film (biaxially stretched film before finally re-stretching in the machine direction or the transverse direction to complete the orientation crystallization), and then further longitudinally stretching and / or Or the method of carrying out lateral stretching is mentioned.

The solid content concentration of the coating solution is preferably 1 to 20% by weight based on the weight of the coating solution. When it exists in this range, it is easy to suppress the occurrence of coating spots.
As a coating method, any known coating method can be applied. For example, a roll coating method, a gravure coating method, a roll brush method, a spray coating method, an air knife coating method, an impregnation method, and a curtain coating method can be used alone or in combination.

<Film characteristics>
(Storage elastic modulus (E '))
The flexible printed circuit board reinforcing film of the present invention has a storage elastic modulus (E ′) at a frequency of 1 Hz of 350 to 2000 MPa at 200 ° C. in the longitudinal direction and the width direction. When the storage elastic modulus (E ′) at 200 ° C. is in the above numerical range, curling in the solder reflow process can be suppressed. When the storage elastic modulus (E ′) at 200 ° C. is too low, curling cannot be suppressed. The higher the storage elastic modulus (E ′) at 200 ° C., the higher the curl-inhibiting effect tends to be. On the other hand, film formation with a storage elastic modulus (E ′) at 200 ° C. exceeding 2000 MPa is realistic. Difficult. From such a viewpoint, the storage elastic modulus (E ′) at 200 ° C. is preferably 400 to 1500 MPa, and more preferably 500 to 1100 MPa.

  In order to set the storage elastic modulus (E ′) within the above numerical range, the intrinsic viscosity, melting point, stretching conditions, heat setting conditions, and the like of the polyester may be appropriately adjusted. For example, the storage elastic modulus (E ′) tends to increase by increasing the orientation crystallization by increasing the intrinsic viscosity or melting point of the polyester, increasing the draw ratio, or increasing the heat setting temperature. It is in. It is also effective to use polyethylene naphthalene dicarboxylate as the polyester. Furthermore, the storage elastic modulus (E ′) can also be achieved by adding an inorganic filler having an aspect ratio of 10 or more to the film in the above-described manner, and can be mentioned as a preferable achievement method in the present invention.

(Heat shrinkage)
The film for reinforcing a flexible printed circuit board of the present invention has a heat shrinkage rate of not less than −1% and less than 4% in both the film longitudinal direction and the width direction when heat-treated at 230 ° C. for 10 minutes. The lower limit of the heat shrinkage rate is preferably −0.5%, more preferably 0%. Further, the upper limit of the heat shrinkage rate is preferably 0.5% or less, and more preferably 0%.

  When the thermal shrinkage rate of the reinforcing film is less than the lower limit value or exceeds the upper limit value, even if it has the above-mentioned coating layer, it is in close contact with a commercially available adhesive sheet used for bonding to the FPC board And the adhesion cannot be maintained after solder reflow, and peeling or swelling occurs at the adhesive interface between the adhesive sheet and the reinforcing plate. Further, in the solder reflow process, curling occurs as the FPC laminate. Even within the above numerical range, as the thermal shrinkage rate of the reinforcing film becomes a preferable range, the strain with the FPC substrate is further reduced, and the peeling area of the interface portion with the adhesive sheet is reduced, and as the FPC laminate, There is a tendency that curling of the sheet is further reduced.

  The flexible printed circuit board reinforcing film of the present invention is required to have such heat shrinkage characteristics in both the film longitudinal direction and the width direction. On the other hand, if the thermal shrinkage is deviated, the curl suppressing effect is insufficient. Moreover, the adhesiveness cannot be maintained after solder reflow, causing peeling or swelling at the adhesive interface between the adhesive sheet and the reinforcing plate, and a decrease in peel strength.

  Such heat shrinkage can be achieved by appropriately adjusting the type of polyester, stretching conditions, heat setting temperature, heat relaxation treatment conditions, annealing treatment conditions, and the like. For example, polyester having a high glass transition point Tg or melting point Tm is selected, the draw ratio is lowered, the heat setting temperature is increased, the relaxation rate in the thermal relaxation treatment is increased, the temperature is increased, annealing is performed. The heat shrinkage rate tends to be lowered by increasing the temperature in the treatment or increasing the time.

  As a preferable method for achieving such heat shrinkage rate, polyethylene naphthanedicarboxylate is selected as the type of polyester, and after performing biaxial stretching under the stretching conditions described later, the heat setting treatment temperature is ( Tm-100 ° C) or higher, preferably 220 ° C to 250 ° C, followed by 1 to 3% thermal relaxation treatment at 150 ° C to 250 ° C. A method of performing heat treatment (annealing) at ˜250 ° C. for 5 minutes or more and removing the temperature at 50˜80 ° C. In addition, by increasing the temperature within the range of the heat treatment conditions or increasing the treatment time, the heat shrinkage rate can be brought into a preferable range.

  In the present invention, the storage elastic modulus (E ′) at 200 ° C. and the heat shrinkage rate when heat-treated at 230 ° C. for 10 minutes are in the above numerical range at the same time, which is very excellent in curling suppression.

(curl)
In this invention, the curl calculated | required by the below-mentioned method is less than 20 mm. Preferably it is 10 mm or less, More preferably, it is 5 mm or less, More preferably, it is 4 mm or less, Most preferably, it is 3 mm or less. When the curl is in the above numerical range, it means that the warp when the FPC board is formed is small, and an FPC board having excellent quality can be obtained.

<Film thickness>
The film thickness of the flexible printed circuit board reinforcing film of the present invention is preferably 50 μm or more and 250 μm or less, and an appropriate handling property can be obtained in such applications.

<Film formation>
The method for obtaining the film of the present invention is specifically described below, but is not particularly limited to the following examples.
The polyester is dried, if desired, and then supplied to an extruder to be formed into a sheet from a T-die.

  The sheet-like molded product extruded from the T-die is cooled and solidified with a cooling drum having a surface temperature of 10 to 60 ° C., and this unstretched film is heated by, for example, roll heating or infrared heating, and then in the longitudinal direction (continuous film forming direction). Stretch to obtain a longitudinally stretched film. Such longitudinal stretching is preferably performed by utilizing the difference in peripheral speed between two or more rolls. The longitudinal stretching temperature is preferably higher than the glass transition point (Tg) of the polyester, more preferably 20 to 40 ° C. higher than Tg. The longitudinal stretching ratio is preferably 1.5 to 3.5 times, more preferably 1.5 to 3.0 times, particularly preferably 2.0 to 3.0 times. The range is as follows. By setting the longitudinal draw ratio to the above numerical range, it becomes easy to achieve the storage elastic modulus (E ′). When the longitudinal draw ratio is less than the lower limit, the strength as a reinforcing plate may not be sufficient, and the thickness unevenness of the film may deteriorate and a good film may not be obtained. On the other hand, when the longitudinal draw ratio exceeds the upper limit, the heat shrinkage characteristics of the present invention cannot be obtained, and problems such as breakage of the film occur.

  The obtained longitudinally stretched film is subsequently subjected to transverse stretching (stretching in a direction perpendicular to the continuous film-forming direction), and then subjected to heat fixation and thermal relaxation treatment in order to obtain a biaxially oriented film. Is done while running the film.

The transverse stretching process starts at a temperature 20 ° C. higher than the glass transition point (Tg) of the polyester. And it heats up to (120-30) degree C temperature lower than melting | fusing point (Tm) of polyester. The transverse stretching start temperature is preferably (Tg + 40) ° C. or lower. The maximum transverse stretching temperature is preferably (100 to 40) ° C. lower than Tm.
Although the temperature increase in the transverse stretching process may be continuous or stepwise (sequential), the temperature is usually increased stepwise. For example, the transverse stretch zone of the stenter is divided into a plurality along the film running direction, and the temperature is raised by flowing a heating medium having a predetermined temperature for each zone.

  The transverse draw ratio is preferably in the range of 2.85 times to 4.0 times, more preferably in the range of 3.00 times to 3.5 times, particularly preferably in the range of 3.00 times to 3.30 times. The range is as follows. By setting the transverse draw ratio to the above numerical range, the storage elastic modulus (E ′) can be easily achieved. When the transverse draw ratio is less than the lower limit value, the strength as a reinforcing plate may not be sufficient, and the thickness unevenness of the film may deteriorate and a good film may not be obtained. On the other hand, when the transverse draw ratio exceeds the upper limit, the heat shrinkage characteristics of the present invention cannot be obtained, and problems such as film breakage occur.

  The biaxially stretched film is then heat set. The heat setting treatment temperature can be (Tm-100 ° C) or higher, more preferably (Tm-70) ° C to (Tm-40) ° C, particularly preferably 220 ° C to 250 ° C. . After heat setting treatment, heat relaxation treatment of 1% to 3% is performed under a temperature condition of 150 ° C. to 250 ° C., and further heat treatment (annealing treatment) is performed at 150 to 250 ° C. for 30 seconds or more in an offline process, and 50 ° C. to 80 ° C. Remove the cooling. By passing through these steps, the film having the heat shrinkage characteristics of the present invention can be obtained. In the annealing process performed in the off-line process, the heat shrinkage rate can be set within a preferable range by increasing the temperature within the range of the heat treatment conditions or increasing the treatment time. The upper limit of the annealing treatment time is not particularly limited, but if it is too long, the film physical properties may be lowered, and therefore it is preferably at most 1 hour.

<Adhesive sheet>
When the flexible printed circuit board reinforcing film of the present invention and the flexible printed circuit board are bonded together, it is preferable to bond them together via an adhesive sheet. A commercially available adhesive sheet can be used as such an adhesive sheet, for example, an epoxy adhesive sheet or an acrylic adhesive sheet can be used. Specific examples of these commercially available adhesive sheets include TFA-880CC35 (manufactured by Kyocera Chemical Co., Ltd.), SAFV (manufactured by Nikkan Kogyo Co., Ltd.), and D3410 (manufactured by Sony Chemical & Information Device Co., Ltd.).

<Flexible printed circuit board laminate>
The flexible printed circuit board reinforcing film of the present invention is used to process into a flexible printed circuit board reinforcing plate, and the obtained reinforcing plate can be attached to a portion where the flexible printed circuit board needs to be reinforced.

  Examples of the base film of the flexible printed circuit board used by being bonded to the flexible printed circuit board reinforcing film of the present invention include polyimide and polyester. Examples of the polyester include polyethylene terephthalate and polyethylene naphthalate. The thickness of the flexible printed circuit board is usually about 7.5 to 250 μm.

  Moreover, the flexible printed circuit board laminated body of this invention has the structure which bonded the flexible printed circuit board reinforcement board of this invention to the flexible printed circuit board through the adhesive sheet. The flexible printed circuit board laminate has no peeling, swelling or warping at the bonding interface via the adhesive sheet after the solder reflow process, and has high peel strength and high reinforcing effect. It can be suitably used for a part that requires more reinforcing properties, such as a part that is likely to be bent or a part that is easily bent when attached to a connector, such as a connector connection part.

  In addition, there is no restriction | limiting in particular about the circuit pattern formed in the base film or board | substrate of the flexible printed circuit of this invention, The general thing used conventionally is used. Since the flexible printed circuit board laminate of the present invention is excellent in the adhesiveness of the reinforcing plate and the heat resistance of the bonded portion, and also excellent in the heat dissipation of the heat generated in the flexible printed circuit board, It is useful for electric circuits of electronic equipment used in high temperature environments.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited thereto.

1. Heat shrinkage rate Marks are applied to film samples at intervals of 10 cm, heat treatment is performed in an oven at 230 ° C. for 10 minutes without applying a load, and the distance between the marks after heat treatment is measured to determine the film continuous film forming direction (MD). In the direction perpendicular to the film forming direction (TD), the thermal shrinkage rate was calculated by the following formula.
Thermal shrinkage (%)
= {(Distance between the pre-heat treatment gauge points -Distance between the heat treatment gauge points) / Distance between the pre-heat treatment gauge points} × 100

2. Dynamic Viscoelasticity Using a dynamic viscoelasticity measuring apparatus (R HEOVIBRON model DDV-01FP manufactured by Orientec Co., Ltd.), the sample was set in the longitudinal direction or the width direction, and the measurement was performed under the following condition settings in each direction.
Measurement mode: Temperature characteristics Tensile Sample dimensions: Between chucks = 30 mm, width = 3 mm
Static load: 10g
Measurement temperature: room temperature to 230 ° C
Temperature rising rate: 2 ° C / min Interval: 2 ° C
Excitation mode: Single waveform Constant displacement amplitude: 25 μm
Minimum load amplitude: 0g
Measurement frequency: 1Hz

3. Solder reflow test The solder reflow was subjected to a reflow treatment for 15 seconds at a peak temperature of 260 ° C. using a solder reflow furnace (TNX25-537EM) manufactured by Tamura Corporation, and the appearance was evaluated after the treatment. In the evaluation, a flexible printed circuit board laminate composed of a single-sided copper-clad laminate based on a biaxially oriented polyester film / commercially available adhesive film for reinforcing film adhesive / polyimide film prepared by the following method was used. .

3-1. Method for producing flexible printed circuit board laminate On the prepared biaxially oriented polyester film, a commercially available adhesive sheet for reinforcing film adhesion (SAFV (trade name): manufactured by Nikkan Kogyo Co., Ltd.) and further polyimide on the adhesive sheet A single-sided copper-clad laminate (F-30VC1 (trade name) manufactured by Nikkan Kogyo Co., Ltd.) with a film as a base material was placed with the polyimide film side facing the adhesive sheet. The laminated body was pressed at a temperature of 100 ° C. and a pressure of 3 MPa for 5 minutes, then further raised in temperature, pressed at 160 ° C. and a pressure of 3 MPa for 5 minutes, and directly subjected to a heat treatment for 60 minutes. Thereafter, it was cooled to room temperature and taken out.

3-2. Appearance evaluation (bubbles, swelling)
For the flexible printed circuit board laminate after reflow treatment, observe the bubble or bulge at the interface between the adhesive sheet and the reinforcing plate from the reinforcing plate side. Obtained and evaluated according to the following criteria.
A: The area where bubbles and blisters are generated is less than 10%. B: The area where bubbles and blisters are generated is 10% or more and less than 15%. C: The area where bubbles and blisters are generated is 15% or more. )
The sample dimensions were set to 15 cm × 15 cm, and the flexible printed circuit board laminate sample after the reflow treatment was allowed to stand for 24 hours in an atmosphere at a relative humidity of 55% and 23 ° C., and then leveled so that the curl of the film was convex downward While placed on the board, the curl heights (mm) at the four corners from the board were measured, and the largest value was taken as the warp (curl) of the substrate.

4). Inorganic filler The size of the inorganic filler was determined by the following measuring method.

4-1. When the inorganic filler is spherical (average particle size)
The average particle size was measured using a LA-750 particle size analyzer (Particle Size Analyzer) manufactured by HORIBA. The particle size corresponding to 50 mass percent was read and this value was taken as the average particle size.

4-2. When the inorganic filler is flat (average thickness)
First, about 10 wt% of an inorganic filler was dispersed in an epoxy resin and cured to prepare an embedded sample in which the inorganic filler was embedded. At this time, the directions of the flat inorganic fillers are substantially aligned so that the flat plate faces upward (or downward). Next, from this embedded sample, a slice sample is cut out in a direction as perpendicular as possible to the plane of the flat plate-like inorganic filler, and the cross section is observed using a scanning electron microscope (SEM) to obtain 50 inorganic samples. A cross section of the filler (cross section cut in a direction substantially perpendicular to the plane of the flat plate) was observed, the thickness was measured, and the average value thereof was determined as the average thickness.
(Average particle size)
The average particle size was measured using a LA-750 particle size analyzer (Particle Size Analyzer) manufactured by HORIBA. The particle size corresponding to 50 mass percent was read and this value was taken as the average particle size.
(aspect ratio)
The aspect ratio was calculated by the following formula using the average particle diameter and the average thickness.
Aspect ratio = average particle size / average thickness

4-3. When the inorganic filler is fibrous (average fiber diameter)
The average fiber diameter is in accordance with JIS R7607, graphitized carbon short fibers are measured with an optical microscope, vapor-grown carbon fibers and thermally conductive fillers are measured with a scanning electron microscope (SEM), and the average fiber diameter is obtained from the average value. It was.
(Average fiber length)
The average fiber length is the number average fiber length, the graphitized carbon short fibers are measured with an optical microscope, the vapor grown carbon fibers and the thermally conductive filler are measured with 2000 scanning electron microscopes (SEM) (10 fields, 200 fields). Measured one by one) and obtained from the average value. The magnification was appropriately adjusted according to the yarn length.
(aspect ratio)
The aspect ratio was calculated by the following formula using the average fiber diameter and average fiber length.
Aspect ratio = average fiber length / average fiber diameter

[Resin composition in coating layer and blending ratio of each component]
Table 1 shows the composition and composition of the coating layers used in Examples and Comparative Examples.

Here, the following components were used for each component constituting the coating layer.
Acrylic resin (Tg = 50 ° C.) composed of 30% by mole of methyl methacrylate / 2% by mole of 2-isopropenyl-2-oxazoline / 10% by mole of polyethylene oxide (n = 10) methacrylate / 30% by mole of acrylamide Using. The acrylic resin was produced by the following method, and conformed to the method described in Production Examples 1 to 3 of JP-A No. 63-37167. That is, 302 parts of ion-exchanged water was charged into a four-necked flask and heated to 60 ° C. in a nitrogen stream, and then 0.5 parts of ammonium persulfate and 0.2 part of sodium hydrogen nitrite were added as a polymerization initiator. Furthermore, a mixture of monomers, 23.3 parts of methyl methacrylate, 22.6 parts of 2-isopropenyl-2-oxazoline, 40.7 parts of polyethylene oxide (n = 10) methacrylic acid, and 13.3 parts of acrylamide. The solution was added dropwise over 3 hours while adjusting the liquid temperature to 60 to 70 ° C. After completion of dropping, the reaction was continued with stirring while maintaining the same temperature range for 2 hours, and then cooled to obtain an acrylic aqueous dispersion having a solid content of 25%.
Polyester: The acid component is composed of 63 mol% of 2,6-naphthalenedicarboxylic acid / 32 mol% of isophthalic acid / 5 mol% of 5-sodium sulfoisophthalic acid, and the glycol component is composed of 90 mol% of ethylene glycol / 10 mol% of diethylene glycol. Polyester (Tg = 76 ° C., average molecular weight 12000) was used. Polyester was produced by the following method, and conformed to the method described in Example 1 of JP-A-06-116487. That is, 42 parts of dimethyl 2,6-naphthalenedicarboxylate, 17 parts of dimethyl isophthalate, 4 parts of dimethyl 5-sodium sulfoisophthalate, 33 parts of ethylene glycol and 2 parts of diethylene glycol were charged into a reactor. 05 parts were added and heated under a nitrogen atmosphere while controlling the temperature at 230 ° C., and the produced methanol was distilled off to conduct a transesterification reaction. Subsequently, the temperature of the reaction system was gradually raised to 255 ° C., and the pressure inside the system was reduced to 1 mmHg to carry out a polycondensation reaction to obtain a polyester.
Fine particles: inorganic silica particles (average particle size: 100 nm) were used.
Wetting agent: Polyoxyethylene (n = 7) lauryl ether (manufactured by Sanyo Chemical Co., Ltd., trade name “Naroacty N-70”) was used.
Additive: Carnauba wax (manufactured by Chukyo Yushi Co., Ltd., trade name “Cerosol 524”) was used.

[Example 1]
Polyethylene naphthalene dicarboxylate resin containing 2 wt% of carbon nanofibers (VGCF-S, manufactured by Showa Denko KK) having an average fiber diameter of 80 nm and an average fiber length of 10 μm and an aspect ratio of 125 (based on the weight of the base material layer) An intrinsic viscosity of 0.60 dl / g (in o-chlorophenol, 35 ° C.) was supplied to an extruder heated to 290 ° C., and formed into a sheet form from a 290 ° C. die. Further, the unstretched film obtained by cooling and solidifying this sheet with a cooling drum having a surface temperature of 60 ° C. is led to a roll group heated to 140 ° C., and stretched 3.0 times in the longitudinal direction (longitudinal direction). After cooling, the coating agent 1 (aqueous coating solution having a solid content concentration of 3%) composed of the composition for coating layer shown in Table 1 was uniformly applied on one side with a roll coater. Subsequently, both ends of the longitudinally stretched film were guided to a tenter while being held with clips, and stretched 3.0 times in a direction perpendicular to the longitudinal direction (lateral direction) in an atmosphere heated to 150 ° C. Thereafter, heat setting was performed at 250 ° C. in a tenter, and after 2% relaxation at 240 ° C., the film was uniformly removed and cooled to room temperature to obtain a biaxially stretched film having a thickness of 175 μm. Further, the obtained film was subjected to a thermal annealing treatment at 230 ° C. for 1 minute using an IR heater and then cooled in a temperature atmosphere of 50 ° C. The properties of the obtained film are shown in Table 2.

  Using the obtained film, a flexible printed circuit board laminate was prepared according to the evaluation method, and a solder reflow test was performed. The area of bubbles or blisters generated at the interface between the reinforcing plate and the adhesive sheet was less than 10%. The adhesion was good. Also, the curl was small.

[Examples 2 to 12, Comparative Example 1]
A film was obtained in the same manner as in Example 1 except that the coating agent type, inorganic filler type and addition amount, and annealing treatment temperature were as shown in Table 2. The properties of the obtained film are shown in Table 2.

[Comparative Example 2]
The carbon nanofiber content is 5% by weight based on the weight of the base material layer, and the draw ratio is 3.1 times in the longitudinal direction (longitudinal direction) and 3.2 in the direction perpendicular to the longitudinal direction (lateral direction). The film was obtained in the same manner as in Example 1 except that the heat setting temperature was 230 ° C., and the annealing process using an IR heater was not performed. The properties of the obtained film are shown in Table 2.

[Comparative Examples 3 and 4]
A film was obtained in the same manner as in Comparative Example 2 except that the coating agent type, inorganic filler type and addition amount, and annealing treatment temperature were as shown in Table 2. The properties of the obtained film are shown in Table 2.

In addition, the inorganic filler in Table 2 is as follows.
VGCF: Carbon nanofiber having an average fiber diameter of 80 nm, an average fiber length of 10 μm, and an aspect ratio of 125 (VGCF-S, manufactured by Showa Denko KK)
CF: carbon fiber having an average fiber diameter of 8 μm, an average fiber length of 200 μm, and an aspect ratio of 25 (Teijin Limited, Lahima R-301)
BN: Boron nitride having an average thickness of 0.1 μm, an average particle size of 8.9 μm, and an aspect ratio of 89 (manufactured by Showa Denko KK, UHP-1)
Artificial graphite: artificial graphite having an average thickness of 0.1 μm, an average particle diameter of 10 μm, and an aspect ratio of 100 (manufactured by Showa Denko KK, UFG-30)
TiO ₂ : Titanium oxide having an average particle size of 1.5 μm

  The flexible printed circuit board reinforcing film of the present invention is curled in the solder reflow process and has an extremely high industrial value.

Claims (11)

  A flexible printed circuit board reinforcing film having a biaxially oriented polyester film substrate layer, wherein the heat shrinkage rate of the reinforcing film when heat-treated at 230 ° C. for 10 minutes is in both the film longitudinal direction and the width direction − A flexible printed circuit board reinforcing film having a storage elastic modulus (E ′) of 1 to 4% at a frequency of 1 Hz in a longitudinal direction and a width direction of 350 to 2000 MPa at 200 ° C.   2. The flexible printed circuit board reinforcing film according to claim 1, wherein the biaxially oriented polyester film base material layer contains an inorganic filler having an aspect ratio of 10 or more of 2 wt% or more and 50 wt% or less based on the weight of the layer.   The flexible printed circuit board reinforcing film according to claim 2, wherein the inorganic filler is at least one selected from the group consisting of carbon nanotubes, carbon nanofibers, carbon fibers, artificial graphite, and boron nitride.   The film for reinforcing a flexible printed circuit board according to any one of claims 1 to 3, further comprising a coating layer containing a polymer binder containing an acrylic resin having an oxazoline group on at least one surface of the biaxially oriented polyester film base material layer. .   The flexible printed circuit board reinforcing film according to claim 4, wherein the content of the polymer binder in the coating layer is 10% by weight or more and 80% by weight or less based on the weight of the coating layer.   The flexible printed circuit board reinforcing film according to claim 4 or 5, wherein the content of the acrylic resin having an oxazoline group is 3% by weight or more and 90% by weight or less based on the weight of the polymer binder.   The flexible printed circuit board reinforcing film according to any one of claims 1 to 6, wherein the polyester constituting the biaxially oriented polyester film substrate layer is polyethylene naphthalene dicarboxylate.   The flexible printed circuit reinforcement board using the film for flexible printed circuit board reinforcement in any one of Claims 1-7.   The flexible printed circuit board laminated body by which the flexible printed circuit reinforcement board of Claim 8 was bonded together via the adhesive sheet to the flexible printed circuit board.   The flexible printed circuit board laminate according to claim 9, wherein the adhesive sheet is an epoxy adhesive sheet or an acrylic adhesive sheet.   The flexible printed circuit board laminate according to claim 9 or 10, wherein the base film of the flexible printed circuit board is polyimide or polyester.