JP2006120432A - Flat cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply an inexpensive flat cable with excellent fire retardant property and heat resistance by an inexpensive thermoplastic resin film instead of an expensive heat-resistant film. <P>SOLUTION: Of the flat cable made by aligning in parallel, pinching and heat-sealing a plurality of conductors between two sheets of insulation base materials each composed of a thermoplastic resin film and an adhesive layer with each adhesive layer laid inside, a resin coated layer mainly composed of polyimide is made laminated on an outside surface of the outermost thermoplastic resin film. Further, the flat cable has the adhesive layer provided at each face of the plurality of conductors, with the thermoplastic film fitted outside each adhesive layer, and has the resin coated layer with polyimide as a main component laminated on the outside face of the outermost thermoplastic resin film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a flat cable used for wiring of an electronic device or the like. In particular, it relates to a flat cable excellent in heat resistance and flame retardancy.

  In recent years, the wiring of various devices has become complicated due to the development of the semiconductor industry. In order to save wiring work and prevent incorrect wiring, video devices, audio devices, OA devices, computer devices, automobiles, robots, etc. A multi-core flat cable is used as the wiring.

  In general, a flat cable is manufactured by sandwiching a plurality of conductors in parallel between two insulating base materials and fusing the insulating base materials together by heat fusion. In general, as the insulating base material, a biaxially stretched polyester film having excellent mechanical and electrical properties and a two-layer structure of an adhesive layer for heat-sealing it have been widely used. As the adhesive layer, polyvinyl chloride, polyethylene, thermoplastic saturated copolymer polyester, thermosetting polyester, and the like have been used.

  These flat cables also have applications that require a high degree of flame retardancy, and as a technology to improve the flame retardancy of polyester films, brominated, phosphorous, and inorganic flame retardants are tempered into polyester films. A method of copolymerizing a soldering method, a halogen-containing component, and a phosphorus-containing component has been proposed (see, for example, Patent Documents 1 to 3).

  Moreover, as a technique for improving the flame retardancy of a polyester film, a method in which two films are bonded together with an adhesive containing a flame retardant has been proposed (see, for example, Patent Documents 4 and 5).

Furthermore, flame retardants containing halogens such as bromine and chlorine, such as decabromodiphenyl ether and hexabromodiphenyl ether, have been added to the adhesive layer of flat cables.
JP-A-5-279494 (page 1-2) JP-A-9-272734 (page 1-2) JP-A-10-278206 (page 1-2) Japanese Patent Laid-Open No. 2-8278 (first page) Japanese Patent Laid-Open No. 2-7315 (first page)

  However, the inventions described in Patent Documents 1 to 3 have problems such as expansion of combustion when repeatedly exposed to a flame, and flame extinguishing performance is insufficient. In addition, these technologies add a flame retardant to the polyester film or copolymerize a halogen-containing component or a phosphorus-containing component on the polyester film, so that the original mechanical properties of the polyester are deteriorated. There was also.

  On the other hand, in the inventions described in Patent Documents 4 and 5, in order to obtain sufficient flame retardancy, it is necessary to add a large amount of flame retardant in the adhesive layer for laminating two films. The flame retardant oozes out and contaminates the process, or the heat treatment decomposes the flame retardant and discolors the processed product. The same problem occurs when a large amount of a flame retardant containing halogen is added to the adhesive layer of the flat cable.

  In addition, when a flat cable using a flame retardant containing halogen is burned due to a fire, there is a concern that toxic gas containing halogen may be generated or that toxic substances such as dioxin may be generated depending on the combustion conditions, etc. There was a problem of adversely affecting the environment.

  Therefore, in order to obtain high flame retardancy without containing halogen, it is conceivable to use a film with high flame retardancy, such as a polyimide film, as an insulating base material. Since it is relatively expensive, there is a problem that the cost becomes high, and it is not practical.

  In view of the background of such conventional technology, the present invention uses an inexpensive thermoplastic resin film without using an expensive heat-resistant film, and provides an inexpensive flat cable with excellent flame resistance and heat resistance. To do.

The present invention employs the following means in order to solve the problems of the prior art. That is, the flat cable according to the present invention has an adhesive layer provided on both surfaces of a plurality of conductors, and a flat cable in which a thermoplastic resin film is provided outside the adhesive layer. A resin coating layer mainly composed of polyimide is laminated on the outer surface of the thermoplastic resin film. As a preferable aspect of such a flat cable,
(1) The resin layer contains a flame retardant composed of phosphorus and / or metal hydroxide,
(2) The adhesive layer contains a flame retardant composed of phosphorus and / or metal hydroxide,
It is.

  According to this invention, since the resin coating layer which has a polyimide as a main component is laminated | stacked on both surfaces of the thermoplastic resin film, the flat cable excellent in the flame retardance and heat resistance can be produced at low cost.

  The present invention has been intensively studied on the above-mentioned problem, that is, a flat cable that is excellent in flame retardancy, heat resistance and is inexpensive by using an inexpensive thermoplastic resin film without using an expensive heat-resistant film. After coating the outer surface of the outermost thermoplastic resin film of the flat cable with a conductor sandwiched between the adhesive layers between them, a polyimide-forming resin coating layer made of polyamic acid is coated and then heat-treated to form the polyamic acid of the coating layer As a result of forming a resin coating layer containing polyimide as a main component, it was found that this problem can be solved all at once.

  The thermoplastic resin film in the flat cable of the present invention is not particularly limited as long as it is a film manufactured from a thermoplastic resin that can be melt extruded. Examples of the thermoplastic resin that can be used include polyester, polyolefin, polyamide, polyphenylene sulfide, and polycarbonate. Polyester, polyolefin, polyamide, and polyphenylene sulfide are preferable, and a polyester film is particularly preferable in terms of transparency, dimensional stability, mechanical properties, and the like. Here, although it does not specifically limit as preferable polyester, For example, a polyethylene terephthalate, a polyethylene naphthalate, a polypropylene terephthalate, a polybutylene terephthalate, a polypropylene naphthalate etc. are mentioned, You may mix and use these 2 or more types. These may be copolymerized with other dicarboxylic acid components or diol components. Moreover, the composite film which consists of two or more layers of an inner layer and a surface layer may be sufficient. The thickness of the thermoplastic resin film is preferably about 10 to 50 μm.

  When the above-mentioned polyester is used as the thermoplastic resin constituting the thermoplastic resin film of the present invention, its intrinsic viscosity (measured in o-chlorophenol at 25 ° C.) is 0.4 to 1.2 dl / g. Is preferable, and it is more preferable that it is 0.5-0.8 dl / g.

  Further, the thermoplastic resin film of the present invention may contain various additives, resin compositions, cross-linking agents and the like as long as the effects of the present invention are not inhibited. For example, acrylic resin, polyester resin, urethane resin, polyolefin resin, polycarbonate resin, alkyd resin, epoxy resin, urea resin, phenol resin, silicone resin, rubber resin, wax composition, melamine compound, oxazoline crosslinking agent, methylolation , Alkylolized urea crosslinking agent, acrylamide, polyamide, epoxy resin, isocyanate compound, aziridine compound, various silane coupling agents, various titanate coupling agents, antioxidants, heat stabilizers, UV absorbers, organic , Inorganic particles, pigments, dyes, antistatic agents, nucleating agents, and the like can be used.

  Among these, when inorganic particles such as silica, colloidal silica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate, barium sulfate, carbon black, zeolite, titanium oxide, metal fine powder, etc. are added, it is easy to slip. This is preferable because the property and scratch resistance are improved. The average particle diameter of the inorganic particles is preferably 0.005 to 5 μm, more preferably 0.05 to 1 μm. Moreover, the addition amount is preferably 0.05 to 20% by weight, more preferably 0.1 to 10% by weight.

  Moreover, in order to express the effect of this invention more effectively, various flame retardants may be added, or a copolymer with a phosphorus compound may be used. Although it does not specifically limit as a flame retardant to add, If the example is given, phosphorus flame retardants, such as halogen flame retardants, such as a fluorine, a bromine, and chlorine, phenylsulfonic acid, t-butylsulfonic acid, phenylsulfinic acid, and ammonium polyphosphate Flame retardant, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, barium hydroxide, tin oxide hydrate, basic magnesium carbonate, antimony trioxide, zinc borate, zinc stannate, zirconium flame retardant, molybdenum flame retardant And inorganic flame retardants. Of these, non-halogen compounds that are friendly to the environment and do not generate toxic gases during a fire are more preferable, and the use of halogen-based flame retardants is preferably as small as possible. In particular, metal hydroxides such as aluminum hydroxide and magnesium hydroxide are more preferable. Also, it is not preferable to add more than necessary for the copolymerization with a phosphorus compound which causes a decrease in heat resistance.

  The thermoplastic resin film in the present invention is preferably biaxially oriented in terms of mechanical strength, dimensional stability, and the like. Biaxially oriented means that the pattern of biaxial orientation is shown by wide-angle X-ray diffraction, for example, unstretched, that is, the thermoplastic resin film before crystal orientation is completed in the longitudinal direction and the width direction, respectively. The film is stretched about 2.5 to 5.0 times, and then crystal orientation is completed by heat treatment. When the thermoplastic resin film is not biaxially oriented, the dimensional stability of the flat cable, particularly the dimensional stability and mechanical strength under high temperature and high humidity, is insufficient, or the flatness deteriorates. Sometimes.

  Moreover, as this thermoplastic resin film, the composite film which consists of two or more layers of an inner layer and a surface layer may be sufficient. The film thickness of such a thermoplastic resin film is preferably about 10 to 50 μm, and is appropriately selected and used. For example, as a preferred embodiment of such a composite film, the inner layer substantially does not contain particles, and a composite film in which a layer containing particles is provided on the surface layer, the inner layer contains coarse particles, and the surface layer contains fine particles. And a composite film in which the inner layer is a layer containing fine bubbles and the surface layer is a layer containing substantially no bubbles. Further, the composite film may be a polymer of the same type or of a different type in the inner layer and the surface layer.

  In order to improve the adhesive strength between the thermoplastic resin film and the resin coating layer mainly composed of polyimide, the thermoplastic resin film is preliminarily subjected to primer treatment, corona treatment, plasma treatment, sand blast treatment, etc., to enhance the adhesive strength. Is preferred. Preferred examples of the primer that is highly effective in improving the adhesive force include polyurethane resins, methoxylated nylon resins, polyester resins, acrylic resins, and epoxy resins. These primers may be formed by applying, drying and curing on a thermoplastic resin film, but may also be formed by a so-called in-line coating method.

  Moreover, what added inorganic particle | grains in the primer layer has a further more preferable slipperiness and blocking resistance, and is more preferable. In this case, silica, colloidal silica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate, or the like can be used as the inorganic particles to be added. The inorganic particles used preferably have an average particle size of 0.005 to 5 μm, more preferably 0.01 to 3 μm, and particularly preferably 0.05 to 2 μm, although the mixing ratio to the resin in the primer layer is not particularly limited. The solid content is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight.

  Next, the resin coating layer will be described. The present invention relates to a flat cable formed by sandwiching a plurality of conductors in parallel between two insulating base members each composed of a thermoplastic resin film and an adhesive layer, with each adhesive layer inside, and heat-sealing. The flat cable is characterized in that a resin coating layer mainly composed of polyimide is laminated on the surface opposite to the adhesive layer of the thermoplastic resin film.

  In the present invention, the method of laminating the resin coating layer on the thermoplastic resin film includes applying a solution containing a polyamic acid that is soluble in an organic solvent as a main component, drying, and then heat-treating the amide group and carboxyl. A means for dehydrating and ring-closing the group and imidizing it is preferably employed.

The polyimide used for the resin coating layer of the present invention preferably has an imidization ratio of polyamic acid of 50% or more. When the imidation ratio is less than 50%, the heat resistance and flame retardancy functions cannot be sufficiently exhibited, which is not preferable. The imidation ratio is more preferably 75% or more, and further preferably 90% or more. The imidation rate referred to here is the ratio of dehydration ring closure reaction between the amide group and the carboxyl group in the polyamic acid to form an imide group. The method for measuring the imidization ratio is not particularly limited, but in the present invention, the infrared absorption spectrum of the resin coating layer is measured by an ATR method using an infrared spectrophotometer, and at that time, from 1400 cm ⁻¹ to 1300 cm ^−. Calculation was performed using a method obtained from the characteristic absorption intensity of the imide group appearing in ¹ .

  As the polyamic acid used in the resin coating layer of the present invention, the structural unit represented by the following formulas (I) and / or (II) is 70% of all structural units from the viewpoints of heat resistance and flame retardancy. What is more than mol% is preferable, More preferably, it is more than 90 mol%.

R in the formulas (I) and (II) is at least one group selected from the following formula (III), where X and Y in the formula (III) are O, CH ₂ , CO , SO ₂ , S, C (CH ₃ ) ₂ .

  When the portion exceeding 30 mol% of the structural unit of the polyamic acid is not the structural unit represented by the above formula (I) and / or (II), there is no effect of heat resistance and flame retardancy, If it is not thickened, the effects of heat resistance and flame retardancy may not be obtained, and there may be no advantage in productivity and cost.

  Moreover, since the polyamic acid which has more than 30 mol% of structural units other than the structural unit represented by the said formula (I) and / or (II) becomes high in raw material cost when synthesize | combining this, flat cable Problems such as high costs may arise.

  The polyamic acid in the present invention is more preferably a polyamic acid having 70 mol% or more of a structural unit represented by the following formula (IV), particularly preferably a structural unit unit structure represented by the following formula (IV) of 90 It is a polyamic acid having a mol% or more.

  Solvents for these polyamic acid resins are not particularly limited, but N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, N, N, N ′, N′-tetramethylurea Amide solvents such as N, N-dimethylimidazolidinone and hexamethylphosformamide, and lactam solvents such as γ-butyrolactam are used.

  When the resin coating layer of the present invention is formed by applying the polyamic acid solution, the solution contains a hydroxypyridine compound represented by the following formula (V), an imidazole compound represented by the following formula (VI), It is preferable that at least one compound selected from m-hydroxybenzoic acid, p-hydroxyphenylacetic acid, and p-phenolsulfonic acid is contained in an amount of 1 mol% or more based on the repeating unit of the polyamic acid.

  In the formula, at least one of R 1, R 2, R 3, R 4 and R 5 represents a hydroxyl group, and the others represent any of hydrogen atom, aliphatic group, aromatic group, cycloalkyl group, aralkyl group and formyl group, respectively. Show.

  In the formula, each of R1, R2, R3 and R4 represents a hydrogen atom, an aliphatic group, an aromatic group, a cycloalkyl group, an aralkyl group or a formyl group. As R1, R2, R3 and R4, for example, an aliphatic group is preferably an alkyl group having 1 to 17 carbon atoms, a vinyl group, a hydroxyalkyl group or a cyanoalkyl group, and in the case of an aromatic group, a phenyl group is preferred. In the case of an aralkyl group, a benzyl group is preferred.

  The hydroxypyridine compound represented by the above formula (V), the imidazole compound represented by the formula (VI), m-hydroxybenzoic acid, p-hydroxyphenylacetic acid, and p-phenolsulfonic acid include an amide acid component. Since at least one compound selected from these compounds is added due to the effect of promoting dehydration and cyclization, the imidization rate can be increased by a heat treatment at a lower temperature and in a shorter time than when not added. It is preferable because efficiency is improved.

  Specific examples of the hydroxypyridine compound of the formula (V) include 2-hydroxypyridine, 3-hydroxypyridine, 4-hydroxypyridine, 2,6-dihydroxypyridine, 3-hydroxy-6-methylpyridine, 3-hydroxy- Examples include 2-methylpyridine.

  Specific examples of the imidazole compound of the formula (VI) include 1-methylimidazole, 1-ethylimidazole, 1-propylimidazole, 1-phenylimidazole, 1-benzylimidazole, 1-vinylimidazole, 1-hydroxyethylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-propylimidazole, 2-isopropylimidazole, 2-butylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 2-benzylimidazole, 4-methyl Imidazole, 4-phenylimidazole, 4-benzylimidazole, 1,2-dimethylimidazole, 1,4-dimethylimidazole, 1,5-dimethylimidazole, 1-ethyl-2-methylimidazo 1-vinyl-2-methylimidazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 2-butyl-4-hydroxymethylimidazole, 2-butyl- 4-formylimidazole, 2,4-diphenylimidazole, 4,5-dimethylimidazole, 4,5-diphenylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1,2,5- Trimethylimidazole, 1,4,5-trimethylimidazole, 1-methyl-4,5-diphenylimidazole, 2-methyl-4,5-diphenylimidazole, 2,4,5-trimethylimidazole, 2,4,5-tri Phenylimidazole, 1-cyanoethyl-2-methylimi Examples include dazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, and the like.

  The amount of these compounds added is more preferably 10 mol% or more, and still more preferably 50 mol% or more, based on the repeating unit of the polyamic acid. When the addition amount is less than 1 mol% with respect to the repeating unit of the polyamic acid, it is difficult to obtain the effect of increasing the imidization rate at a low temperature in a short time. The upper limit of the amount added is not particularly limited, but is preferably 300 mol% or less with respect to the repeating unit of the polyamic acid. Even if it exceeds 300 mol%, the effect is not remarkably improved, and conversely, the use amount increases, which may be disadvantageous in terms of cost.

  In the resin coating layer of the present invention, a resin or an organic compound other than the polyimide resin component may be contained by copolymerization or mixing. Examples of resins and organic compounds other than polyimide resin components include organic particles, pigments, dyes, acrylic resins, polyester resins, urethane resins, polyolefin resins, polycarbonate resins, alkyd resins, epoxy resins, urea resins, phenol resins, and silicone resins. , Rubber resin, wax composition, melamine compound, oxazoline crosslinking agent, methylolated, alkylolized urea crosslinking agent, acrylamide resin, polyamide resin, isocyanate compound, aziridine compound, various silane coupling agents, various titanates Coupling agents, antioxidants, heat stabilizers, ultraviolet absorbers and the like can be used. In particular, an insulating material is preferable. However, if the resin or organic compound other than the polyimide resin component is excessively contained, the heat resistance and flame retardancy may be lowered. The layer means that the content of the polyamic acid resin having an imidization ratio of 50% or more in the resin coating layer is 70% by weight or more. More preferably, it is 80 weight% or more, More preferably, it is 90 weight% or more.

  Various inorganic additives and flame retardants may be added to the resin coating layer of the present invention as long as the effects of the present invention are not inhibited. As the inorganic additive, an insulating material is preferable, and examples thereof include silica, colloidal silica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate, barium sulfate, zeolite, and titanium oxide. When these are added, since slipperiness, scratch resistance, heat resistance, flame retardance, etc. improve, it is preferable. The average particle diameter of the inorganic particles is preferably 0.005 to 5 μm, and more preferably 0.05 to 1 μm from the viewpoint of the above effect.

  In addition, as flame retardants, halogen flame retardants such as fluorine, bromine and chlorine; phosphorus flame retardants such as phenyl sulfonic acid, t-butyl sulfonic acid, phenyl sulfinic acid and ammonium polyphosphate; magnesium hydroxide, aluminum hydroxide, There are inorganic flame retardants such as calcium hydroxide, barium hydroxide, tin oxide hydrate, basic magnesium carbonate, antimony oxide, zinc borate, zinc stannate, zirconium flame retardant and molybdenum flame retardant. In particular, as a flame retardant, a non-halogen compound is more preferable as an environmentally friendly material that does not generate toxic gases in the event of a fire. Metal hydroxides such as aluminum hydroxide and magnesium hydroxide, phosphorus-based compounds are more preferable. Flame retardants are particularly preferred. The addition amount of these inorganic additives and flame retardants is preferably 0.05 to 60% by weight, more preferably 0.1 to 40% by weight, and still more preferably 0.5 to 20% by weight. If it is less than this, there is no effect, and if it is added more than this, the stretchability of the resin coating layer is reduced, so that cracking tends to occur when the flat cable is bent.

  In the flat cable of the present invention, the thickness of the resin coating layer is preferably 0.5 μm or more and 30 μm or less, more preferably 1 μm or more and 20 μm or less, and further preferably 1.5 μm or more and 10 μm or less. The ratio of the thickness of the resin coating layer to the entire flat cable is preferably 1% to 30%, more preferably 2% to 15%, and still more preferably 3% to 10%.

  Here, the thickness of the resin coating layer is the total thickness of the resin coating layers of both insulating base materials. When the ratio of the thickness of the resin coating layer to the entire flat cable is less than 1%, or the thickness of the resin coating layer is less than 0.5 μm, problems such as insufficient heat resistance and flame retardancy occur. It is not preferable. Further, if the ratio of the thickness of the resin coating layer to the entire flat cable exceeds 30% or the thickness of the resin coating layer exceeds 30 μm, the productivity tends to decrease and the raw material price tends to increase. Absent.

  In the present invention, the polyamic acid solution is applied by various known coating methods such as reverse coating, gravure coating, rod coating, bar coating, Mayer bar coating, die coating, and spray coating. be able to.

  Thereafter, the amide group and carboxyl group in the polyamic acid are dehydrated and closed by heat treatment to imidize. As the heat treatment method, a method in which dehydration and cyclization is preferably performed with hot air or far infrared rays of 150 ° C. or higher, more preferably 180 ° C. or higher, and further preferably 200 ° C. or higher is used. The heat treatment time is preferably 1 second to 120 seconds, more preferably 5 seconds to 60 seconds, and further preferably 10 seconds to 30 seconds. If the temperature is lower than this, or if the heat treatment time is short, the imidization rate is low. On the other hand, if the heat treatment time is longer than this, there is a problem that productivity is deteriorated, which is not preferable.

  Next, the adhesive layer will be described. As the adhesive layer used in the present invention, known adhesives can be used. For example, polyethylene resin, polypropylene resin, ionomer resin, ethylene-vinyl acetate copolymer, ethylene-acrylic acid or methacrylic acid copolymer. Polymer, ethylene-acrylic ester or methacrylic ester copolymer, ethylene-propylene copolymer, polyvinyl acetate resin, acrylic or methacrylic resin, polystyrene resin, polyvinyl chloride resin, polyacrylonitrile Resin, polybutene resin, polypentene resin, saturated polyester resin, polyamide resin, polyvinyl acetal resin, thermoplastic polyurethane resin, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, polycarbonate -Bonate Resin, thermoplastic polyester resin, fluorine resin, polyvinyl alcohol resin, thermoplastic polyimide resin, and other thermoplastic resins, or, for example, phenol resin, epoxy resin, silicon resin At least one of thermosetting resins such as urea resins, melamine resins, unsaturated polyester resins, diallyl phthalate resins, xylene resins, and the like, or prepolymers thereof can be used.

  In the adhesive layer of the present invention, various inorganic additives and flame retardants may be added in the same manner as in the resin coating layer. As the inorganic additive, an insulating material is preferable, and examples thereof include silica, colloidal silica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate, barium sulfate, zeolite, and titanium oxide. When these are added, since slipperiness, scratch resistance, heat resistance, flame retardance, etc. improve, it is preferable. The average particle diameter of the inorganic particles is preferably 0.005 to 5 μm, more preferably 0.05 to 1 μm.

  Examples of the flame retardant include halogen flame retardants such as fluorine, bromine and chlorine, phosphorus flame retardants such as phenyl sulfonic acid, t-butyl sulfonic acid, phenyl sulfinic acid and ammonium polyphosphate, magnesium hydroxide, aluminum hydroxide, and hydroxide. There are inorganic flame retardants such as calcium, barium hydroxide, tin oxide hydrate, basic magnesium carbonate, antimony oxide, zinc borate, zinc stannate, zirconium flame retardant and molybdenum flame retardant. In particular, as a flame retardant, a non-halogen compound is more preferable as an environmentally friendly material that does not generate toxic gases in the event of a fire. Metal hydroxides such as aluminum hydroxide and magnesium hydroxide, phosphorus-based compounds are more preferable. Flame retardants are particularly preferred.

  The addition amount of these inorganic additives and flame retardants is preferably 0.05 to 60% by weight, more preferably 0.1 to 40% by weight, and still more preferably 0.5 to 20% by weight. Since the adhesive layer is thicker than the resin coating layer, it is preferable to increase the amount of the flame retardant added compared to the inorganic additive. If it is less than this, there will be no effect, and if it is added more than this, the stretchability of the adhesive layer will decrease, so if the flat cable is bent, cracks will easily occur or the adhesiveness will be poor.

  The adhesive layer can be formed by various conventionally known methods such as a reverse coating method, a gravure coating method, a rod coating method, a bar coating method, a Mayer bar coating method, a die coating method, and a spray coating method. A coating method can be used. Moreover, when manufacturing a thermoplastic resin film by melt-extrusion, it is also possible to laminate by coextrusion. The thickness of the adhesive layer is usually about 20 to 150 μm, preferably about 30 to 100 μm, and more preferably about 40 to 80 μm. In the adhesive layer, an antioxidant, a filler, a colorant, a crosslinking agent, a crosslinking aid and the like can be appropriately added as necessary.

  After arranging a plurality of tin-plated soft conductors, etc. on the adhesive layer of the insulating base material obtained in this way, and then arranging another insulating base material so that the adhesive layers are aligned with each other This is thermocompression bonded to produce a flat cable.

  The flat cable of the present invention can have high flame retardancy even if it does not contain a halogen-based flame retardant in any of the thermoplastic resin film, the resin coating layer, and the adhesive layer, and therefore burns due to a fire or the like. In addition, there is no fear of generation of toxic hydrogen halide or the like, which is very useful.

  The flat cable of this invention is demonstrated using drawing. First, FIG. 1 shows an example of a method for producing a flat cable of the present invention. A resin coating layer containing polyimide as a main component is laminated on the thermoplastic resin film 1. Next, an adhesive layer is laminated on the surface opposite to the resin coating layer of the thermoplastic resin film. In this way, two insulating base materials 4 each having a resin coating layer and an adhesive layer provided on both surfaces of the thermoplastic resin film are prepared, and the conductors 5 are sandwiched and heated together so that the adhesive layers face each other. A flat cable can be produced by fusing.

  In addition to this, two sheets of a thermoplastic resin film laminated with an adhesive layer are prepared, and after being heat-sealed by heating and bonding so that the adhesive layer faces each other with the conductor in between, the thermoplastic resin film A method of manufacturing a flat cable by laminating a resin coating layer containing polyimide as a main component on the outer surface of the resin, heat-sealing with heat bonding so that the adhesive layer faces each other with the conductor in between, and then thermoplastic Various production methods are possible, such as preparing two sheets of a resin film on which a resin coating layer containing polyimide as a main component is laminated, and bonding the surface of the thermoplastic resin film opposite to the resin coating layer and the adhesive layer.

  FIG. 2 is a schematic cross-sectional view showing the configuration of the flat cable of the present invention, in which an adhesive layer 3 is provided on both sides of a plurality of conductors 5 and a thermoplastic resin film 1 is provided on both sides thereof. It has been. A resin coating layer mainly composed of polyimide is laminated on the outer surface of each thermoplastic resin film.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited only to these Examples.
[Characteristic measurement method and effect evaluation method]
The characteristic measurement method and effect evaluation method in the present invention are as follows.

(1) Thickness of resin coating layer, adhesive layer, and flat cable Using a transmission electron microscope HU-12 manufactured by Hitachi, Ltd., from the photograph of the cross section of the flat cable, The thickness, the thickness of the adhesive layer, the thickness of the resin coating layer on the other surface, and the thickness of the entire flat cable were determined.

(2) Ratio of the thickness of the resin coating layer to the entire flat cable: R
The ratio R of the thickness of the resin coating layer to the entire flat cable was determined from the following formula from the sum (TB) of the thicknesses of the resin coating layers on both sides determined in (1) above and the thickness (T) of the entire flat cable. %) = 100 × TB / T.

(3) Imidization rate: Im
The infrared absorption spectrum of the resin coating layer of the flat cable was measured using an ATR method using a Fourier transform infrared absorption spectrophotometer FT / IR-5000 manufactured by JASCO Corporation and a 45 ° crystal of Ge as a prism. measured by, determined absorbance of characteristic absorption of the benzene ring which appears from 1550 cm ^-1 to 1450 cm ^-1 (a1) and the absorbance of characteristic absorption of an imide group appearing from 1400 cm ^-1 to 1300 cm ^-1 to (a2). At this time, a relative value of a2 with respect to a1 is obtained from the following equation, and is defined as r. R = a2 / a1
Subsequently, this flat cable was heat-treated at 250 ° C. for 120 minutes, and the infrared absorption spectrum of the resin coating layer in this film was similarly measured by the ATR method. Based on the absorbance (a1 ′) of the characteristic absorption of the benzene ring. The relative value of the absorbance (a2 ′) of the characteristic absorption of the imide group obtained is determined, and this is defined as r ′. Here, the imidation ratio of the polyamic acid after the heat treatment is 100%. R ′ = a2 ′ / a1 ′
In the present invention, from the following formula, the relative value of r based on r ′ is obtained and set as the imidation ratio Im: Im (%) = 100 × (r / r ′).

(4) Flammability test UL510 VW-1 flammability test was performed to evaluate flame retardancy. The combustion time after 15 seconds of indirect flame was measured, and this was repeated 5 times. Each combustion time was determined to be acceptable if it was 60 seconds or less and exceeded 60 seconds. Moreover, the case where the damage by burning or carbonization of an indicator flag was 255 or less was made into the pass, and when there was more damage, it was made into the failure. Also, if there were combustion products or falling objects that would ignite absorbent cotton, they were rejected.

<Thermoplastic resin film>
Polyethylene terephthalate resin pellets containing 0.015% by weight of colloidal silica having an average particle size of 0.4 μm and 0.005% by weight of colloidal silica having an average particle size of 1.4 μm (hereinafter sometimes referred to as PET pellets) ( After being sufficiently dried in a vacuum at an intrinsic viscosity of 0.63 dl / g), it is supplied to an extruder, melted at 285 ° C., extruded into a sheet form from a T-shaped die, and a surface temperature of 25 ° C. using an electrostatic application casting method. The film was wound around a mirror casting drum and cooled and solidified to obtain an unstretched film. This unstretched film was heated to 90 ° C. and stretched 3.3 times in the longitudinal direction to obtain a uniaxially stretched film (substrate PET film). Both surfaces of this base PET film were subjected to corona discharge treatment in the air, the wet tension of the uniaxially stretched base PET film was 55 mN / m, and a primer coating liquid having the following composition was applied to the treated surface. Next, the uniaxially stretched film coated with the primer coating liquid is guided to a preheating zone while being gripped with a clip, dried at 90 ° C., and continuously stretched 3.5 times in the width direction in a heating zone at 105 ° C., Heat treatment was performed in a heating zone at 230 ° C. to obtain a laminated PET film in which crystal orientation was completed. The PET film thickness was 25 μm, and the primer layer thickness was 0.1 μm per side.

<Composition of primer coating solution>
An aqueous solution of a resin in which the following polyester resin 1 and polyester resin 2 were mixed so as to have a solid content weight ratio of 70/30 was used as a primer coating solution.
(1) Polyester resin 1 (Tg 82 ° C.)
Acid component 90 mol% terephthalic acid
5-sodium sulfoiphthalic acid 10 mol%
・ Diol component Ethylene glycol 98 mol%
Diethylene glycol 2 mol%
(2) Polyester resin 2
・ Acid component Isophthalic acid 95mol%
5-sodium sulfoiphthalic acid 5 mol%
・ Diol component Ethylene glycol 8mol%
92% by mole of diethylene glycol.

<Polyamic acid solution 1 for resin coating layer formation>
A weighed 4,4′-diaminodiphenyl ether was added together with N-methyl-2-pyrrolidone to a stainless steel polymerization kettle and dissolved by stirring. Next, pyromellitic dianhydride was added to this solution so that 100 mol and reaction temperature might be 60 degrees C or less with respect to 100 mol of 4,4'- diaminodiphenyl ether. Thereafter, when the viscosity became constant, the polymerization was terminated to obtain a polyamic acid polymerization solution. To this, aluminum hydroxide (manufactured by Showa Denko Co., Ltd., “Hajilite” (R) H-42M) was added and dispersed so that the solid weight ratio was polyamic acid / aluminum hydroxide = 70/30. It was. This solution is appropriately diluted with N-methyl-2-pyrrolidone so as to obtain a desired concentration according to the thickness of the resin coating layer, and 4-hydroxypyridine is added in an amount of 100 mol with respect to the repeating unit of polyamic acid before coating. % Was added to obtain a polyamic acid solution. This polyamic acid was a mixture of both two structural units in the following formula (7).

<Polyamic acid solution 2 for forming resin coating layer>
Phosphorus flame retardant (manufactured by Sanko Co., Ltd., HCA-HQ, phosphorus content 9.5 wt%) was further added to the same polyamic acid and aluminum hydroxide as the polyamic acid solution 1 for resin coating layer formation. These components were added and dispersed so that the weight ratio of solid components was polyamic acid / aluminum hydroxide / phosphorous flame retardant = 70/15/15. Thereafter, this solution is appropriately diluted with N-methyl-2-pyrrolidone so as to have a desired concentration according to the thickness of the resin coating layer, and 4-hydroxypyridine is further added to the polyamic acid repeating unit before coating. 100 mol% was added to obtain a polyamic acid solution.

<Adhesive 1>
To 100 parts by weight of a polyester resin obtained by reacting the following acid component and diol component, 5 parts by weight of xamethylene diisocyanate was added and diluted with toluene. Furthermore, 40 parts by weight of phenylphosphonic acid was added as a flame retardant.
・ Acid component terephthalic acid 50mol%
Isophthalic acid 50 mol%
・ Diol component Ethylene glycol 44 mol%
Neopentyl glycol 44 mol%
1,4-cyclohexanedimethanol 9 mol%.

<Adhesive 2>
To 100 parts by weight of a polyester resin having the same composition as that of the adhesive 1, 5 parts by weight of xamethylene diisocyanate was added and diluted with toluene. Further, 30 parts by weight of phenylphosphonic acid and 30 parts by weight of aluminum hydroxide were added as flame retardants.

Example 1
The polyamic acid solution 1 was applied on the entire surface of a 25 μm thick polyester film with a gravure coater and dried at 150 ° C. for 20 seconds to form a resin coating layer. Then, it was cured at 200 ° C. for 20 seconds. The film thickness of the resin coating layer was 2.3 μm, and the imidization ratio Im was 95%. Adhesive 1 was applied to the opposite surface of the polyester film and dried at 150 ° C. for 20 seconds to form an adhesive layer. The film thickness of the adhesive layer was 40 μm. As shown in FIG. 1, the two adhesive layers of the adhesive base material are opposed to each other, and a conductor in which six copper foils having a thickness of 35 μm and a width of 3 mm are arranged at intervals of 1 mm is sandwiched between the two adhesive layers. Then, lamination was performed by heat sealing with a laminator under conditions of 170 ° C. and 6 kg / cm to produce a flat cable as shown in FIG. The ratio R of the thickness of the resin coating layer to the entire flat cable was 2.9%. In the flame retardant test, all were self-extinguished within 60 seconds, and the indicator flag and absorbent cotton were not burned and passed.

(Example 2)
A flat cable was produced in the same manner as in Example 1. However, the adhesive layer was prepared by applying the adhesive 2. The ratio R of the thickness of the resin coating layer to the entire flat cable was 2.9%. In the flame retardant test, all were self-extinguished within 60 seconds, and the indicator flag and absorbent cotton were not burned and passed.

(Example 3)
A flat cable was produced in the same manner as in Example 1. However, the resin coating layer was prepared by applying the polyamic acid solution 2. The ratio R of the thickness of the resin coating layer to the entire flat cable was 2.9%. In the flame retardant test, all were self-extinguished within 60 seconds, and the indicator flag and absorbent cotton were not burned and passed.

(Comparative Example 1)
Adhesive 1 was applied to one side of a 25 μm thick polyester film and dried at 150 ° C. for 20 seconds to form an adhesive layer. The film thickness of the adhesive layer was 40 μm. A resin coating layer was not provided. Adhesive layers of the two insulating bases are opposed to each other, and a conductor in which six copper foils having a thickness of 35 μm and a width of 3 mm are arranged at intervals of 1 mm is sandwiched between both adhesive layers, and a laminator is used at 170 ° C. The flat cable was produced by laminating by heat sealing under the condition of 6 kg / cm. In the flame retardant test, it burned violently at the time of flame contact, the indicator flag burned, and the absorbent cotton burned, which was unacceptable.

It is a cross-sectional schematic diagram explaining an example of the production method of the flat cable of this invention. It is a cross-sectional schematic diagram which shows the structure of the flat cable of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermoplastic resin film 2 Resin coating layer 3 Adhesive layer 4 Insulation base material 5 Conductor

Claims (3)

  In a flat cable in which an adhesive layer is provided on both surfaces of a plurality of conductors and a thermoplastic resin film is provided on the outer side of the adhesive layer, polyimide is formed on the outer surface of the outermost thermoplastic resin film of the flat cable. A flat cable characterized in that a resin coating layer containing as a main component is laminated.   The flat cable according to claim 1, wherein the resin layer includes a flame retardant composed of phosphorus and / or metal hydroxide.   The flat cable according to claim 1, wherein the adhesive layer contains a flame retardant composed of phosphorus and / or metal hydroxide.

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