JP2007311133A - Insulating film and flexible flat cable equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible flat cable excellent in flame resistance and adhesive strength between a conductor and an adhesive layer, and capable of preventing exfoliation of an insulating film from the conductor during a plating process. <P>SOLUTION: The flexible flat cable 1 consisting of a plurality of conductors 2, an adhesive layer 4, and a resin film 5, is also provided with an insulating film 3 coating both sides of the conductors 2. The adhesive layer 4 does not contain halogen elements and has as a principal component copolymerized polyester introducing phosphorus atoms in a molecule. Further, as the copolymerized polyester, either a non-crystalline one, or one with a volume of fusion heat derived from a crystalline component measured by a differential thermal analysis method based on JIS k7122 of 15J/g or less at a temperature-raising condition of 10°C/min. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an insulating film that covers both surfaces of a conductor, in particular, an insulating film that does not contain a halogen element, and a flexible flat cable including the same.

  Conventionally, for example, as an internal wiring material of an electronic device such as an in-vehicle car navigation system or an audio device, both surfaces of a plurality of flat conductors are made of a resin film such as polyethylene terephthalate and a flame-retardant material formed on the resin film. A flexible flat cable having a structure covered with an insulating film composed of a polyester-based adhesive layer is used.

  Here, it is necessary to pass the UL (Underwriters Laboratories inc.) Standard vertical combustion test (VW-1 test) from the viewpoint of safety of the internal wiring material of the electronic device in which the flexible flat cable is used. . Therefore, in the conventional flexible flat cable using a flammable resin film such as polyethylene terephthalate, it is designed to pass the above-mentioned VW-1 test by making the polyester-based adhesive layer flame-retardant. ing.

  In order to make the polyester adhesive layer flame-retardant, brominated flame retardants such as bis (polybrominated phenyl) ethane and ethylenebistetrabromophthalimide, chlorinated paraffins such as chlorinated paraffin and perchloropentacyclodecane A method of blending antimony trioxide or the like as a flame retardant aid together with a halogen flame retardant such as a flame retardant has been employed.

  However, a flexible flat cable containing such a halogen-based flame retardant generates harmful gases such as hydrogen halide when an electronic device using the flexible flat cable is incinerated. Depending on the case, harmful substances such as dioxin derivatives may be generated, which is not preferable.

  Therefore, in order to avoid these disadvantages, a flexible flat cable using a non-halogen flame retardant adhesive layer in which a polyester adhesive layer is made flame retardant with a non-halogen flame retardant has been proposed. More specifically, for example, a flat cable using a flame retardant adhesive mixture in which magnesium hydroxide and aluminum hydroxide are blended in a polyester resin is used as an adhesive layer (for example, see Patent Document 1).

  In addition, the conductor at the end of the flexible flat cable is connected to a connection terminal provided on a printed circuit board or an electric / electronic component. In order to improve the connection reliability between the conductor and the connection terminal, A plating layer formed of solder was provided on the surface of the conductor at the end.

  However, due to the restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment (RoHS), the use of heavy metals such as lead, mercury, cadmium and hexavalent chromium has been restricted. In place of the formed plating layer, a plating layer containing no lead has been required.

  As a flexible flat cable having a plating layer not containing lead, for example, a flexible flat cable provided with a tin plating layer that is inexpensive and excellent in electrical characteristics is disclosed (for example, see Patent Document 2). .

However, when using a tin plating layer, depending on the material of the connection terminal connected to the conductor, acicular tin whisker grows from the tin plating layer over a long period of use, and between the conductor and the connection terminal. There was a problem that the connection reliability of the system deteriorated. Therefore, in order to prevent a decrease in connection reliability between the conductor and the connection terminal, a flexible flat cable provided with a gold plating layer instead of a tin plating layer has been proposed. The plating process on the conductor surface is generally performed by an electroless plating method or an electrolytic plating method. When a gold plating layer is provided, first, nickel plating as a diffusion preventing layer is applied to the exposed conductor surface. After forming the layer, a method of forming a gold plating layer on the surface of the nickel plating layer is employed (see, for example, Patent Document 3).
JP 2004-189771 A JP-A-8-264030 JP-A-8-293214

  However, the conventional non-halogen flame retardant adhesive layer has a problem that flame retardancy and adhesive strength with a conductor are lowered as compared with a flame retardant adhesive layer using a halogen flame retardant. It was.

  In general, when manufacturing a flexible flat cable, after forming a plating layer on the entire surface of the conductor, a method of providing an insulating film on both sides of the conductor is known, but a metal material used for forming the plating layer From the viewpoint that it is less advantageous and is advantageous in terms of cost, first, after providing an insulating film on both sides of the conductor, a method of continuously forming a plating layer only on the exposed conductor surface is widely adopted. Yes.

  However, when a plating layer (for example, a gold plating layer) is continuously formed only on the exposed conductor surface, the entire flexible flat cable is strongly acidic or strongly alkaline at 30 ° C to 90 ° C. It is necessary to pass through a washing bath, a catalyst bath, a plating bath, and the like. Therefore, when a polyester-based adhesive layer is used for the insulating film, the conductor adhesive strength of the insulating film is reduced during the plating process, and the conductor is peeled off from the insulating film. . In particular, when the conventional non-halogen flame retardant polyester adhesive is used, there has been a problem that the peeling of the insulating film and the conductor becomes remarkable during the plating process.

  Therefore, the present invention has been made in view of the above problems, and is excellent in flame retardancy and adhesive strength between the conductor and the adhesive layer, and prevents peeling of the insulating film and the conductor during the plating process. It aims at providing the flexible flat cable which can do.

  In order to achieve the above object, the invention according to claim 1 is directed to an adhesive layer mainly composed of a copolyester having a phosphorus atom introduced into the molecule, and an insulating film comprising a resin film. The heat of fusion derived from the crystal component measured by the differential thermal analysis method based on JIS K7122 of the copolyester is non-crystalline or the copolyester is not amorphous, and the temperature rise condition is 10 ° C./min. It is characterized by being 15 J / g or less.

  According to the same configuration, for example, in a flexible flat cable in which both sides of a conductor are covered with an insulating film, the adhesive strength between the conductor and the adhesive layer is improved. Even when a flame-retardant polyester adhesive layer is used, it is possible to prevent a decrease in the conductor adhesive force of the insulating film when performing the plating treatment. Therefore, it is possible to avoid the inconvenience that the conductor is peeled off from the insulating film. In addition, since phosphorus atoms are introduced into the copolyester molecule, it must pass the UL vertical combustion test (VW-1 test) even when a non-halogen polyester adhesive layer is used. Therefore, it is possible to provide a halogen-free flexible flat cable that is excellent in flame retardancy.

  Invention of Claim 2 is an insulating film of Claim 1, Comprising: While an adhesive bond layer has as a main component the copolymerization polyester which introduce | transduced the carbon-carbon unsaturated bond in the molecule | numerator, it is copolymerization The polyester is crosslinked by irradiation with ionizing radiation. According to this configuration, in a flexible flat cable including an insulating film, a flexible flat cable excellent in heat aging resistance with a temperature rating of 105 ° C. or higher that satisfies the UL standard can be obtained.

  Invention of Claim 3 is the insulating film of Claim 1 or Claim 2, Comprising: The density | concentration of the phosphorus atom with respect to the whole copolyester is 0.2-2.7 weight%. Features. According to this configuration, it is possible to further improve the flame retardancy of a flexible flat cable including an insulating film and to improve mechanical strength.

  In addition, it is preferable that resin which comprises the resin film of this invention is at least 1 or more types chosen from the group which consists of a polyester resin, a polyphenylene sulfide resin, and a polyimide resin like the invention of Claim 4. In particular, a resin film made of a polyester resin is preferably used from the viewpoints of electrical characteristics, mechanical characteristics, low cost, and the like. In addition, by using a resin film made of a polyimide resin, a flexible flat cable having an insulating film has a heat aging resistance of 105 ° C. or higher that meets the UL standard, and mounting of electronic components using lead-free solder It is possible to provide a flexible flat cable that can handle work.

  A fifth aspect of the present invention is a flexible flat comprising the insulating film according to any one of the first to fourth aspects and a conductor, wherein both sides of the conductor are covered with the insulating film. It is a cable. According to this configuration, since the insulating film according to any one of claims 1 to 4 is provided, the same effect as the invention according to any one of claims 1 to 4 can be obtained.

  The invention according to claim 6 is the flexible flat cable according to claim 5, wherein the surface of the conductor at the end of the cable is covered with a gold plating layer. According to this configuration, when the conductor is connected to a connection terminal provided on a printed circuit board or an electric / electronic component, it is possible to effectively prevent a decrease in connection reliability between the conductor and the connection terminal.

  According to the present invention, for example, in a flexible flat cable in which both surfaces of a conductor are covered with an insulating film, it is possible to avoid the inconvenience that the conductor is peeled off from the insulating film when plating is performed. In addition, it is possible to provide a non-halogen flexible flat cable excellent in flame retardancy.

  Hereinafter, a preferred embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing a configuration of a flexiflat cable according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line AA of FIG. 3 is a cross-sectional view taken along the line BB in FIG.

  As shown in FIGS. 1 and 2, the flexible flat cable 1 in the present embodiment covers both surfaces of a plurality of flat conductors 2 having a predetermined width and thickness with an insulating film 3 that does not contain a halogen element. Has the structure. The insulating film 3 includes a resin film 5 and an adhesive layer 4 laminated on the resin film 5, and the flexible flat cable 1 includes a plurality of conductors between the two insulating films 3. In a state where 2 is sandwiched, the two insulating films 3 are bonded together.

  Further, as shown in FIG. 3, at the end 1a of the flexible flat cable 1 (hereinafter referred to as "cable end 1a"), the conductor 2 is connected to a printed circuit board, an electrical / electronic component or the like (not shown). In other words, the conductor 2 is exposed to the outside without forming the insulating film 3. Further, the surface of the conductor 2 at the cable end 1 a is covered with the plating layer 6 in order to improve the connection reliability between the conductor 2 and the connection terminal.

  As a method of manufacturing the flexible flat cable 1, first, the conductor 2 is bonded to the adhesive layer 4 by sandwiching both surfaces of the conductor 2 with the insulating film 3 and performing a heat and pressure treatment using a known thermal laminator or a hot press device. Thus, a long product in which both surfaces of the conductor 2 are covered with the insulating film 3 is manufactured by laminating and bonding continuously. At this time, in order to provide an exposed portion of the conductor 2 on which the plating layer 6 is formed at the cable end portion 1a, the insulating film 3 is made into a conductor while forming a hole in one insulating film 3 by punching. Then, the long product is cut into a certain length. Subsequently, the flexible flat cable 1 is manufactured by forming the plating layer 6 continuously only on the exposed surface of the conductor 2.

  The resin film 5 is made of a resin material that is excellent in flexibility and does not contain a halogen-based substance. For example, the resin film 5 is made of a polyester resin, a polyphenylene sulfide resin, a polyimide resin, or the like, and is versatile for a flexible flat cable. Any resin film can be used. Polyester resins include polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene terephthalate resin, polybutylene naphthalate resin, polytrimethylene terephthalate resin, polytrimethylene naphthalate resin, polycyclohexane dimethyl terephthalate resin, polycyclohexane dimethyl naphthalate poly Examples include arylate resin. Of these resin films, a resin film 5 made of polyethylene terephthalate resin is preferably used from the viewpoint of electrical characteristics, mechanical characteristics, cost, and the like. In addition, by using the resin film 5 made of polyimide resin, the flexible flat cable has heat aging resistance with a temperature rating of 105 ° C. or higher that meets the UL standard, and can also be used for mounting electronic components using lead-free solder. It becomes possible to provide. If necessary, the surface of the resin film 5 may be subjected to corona treatment, plasma treatment, or primer treatment.

  Moreover, in this embodiment, it is set as the structure which uses the plating layer 6 which does not contain lead from consideration to an environment, and lead from the viewpoint of preventing the connection reliability fall between the conductor 2 and a connection terminal. A gold plating layer is used as the plating layer 6 containing no. The plating process on the surface of the conductor 2 is performed by an electroless plating method or an electrolytic plating method. When a gold plating layer is provided, first, nickel plating as a diffusion preventing layer is applied to the exposed conductor surface. After forming the layer, a method of forming a gold plating layer on the surface of the nickel plating layer is employed.

  The adhesive layer 4 is made of a resin material that does not contain a halogen-based substance. In the present invention, the adhesive layer 4 is mainly composed of a copolyester having a phosphorus atom introduced into the molecule. The configuration is as follows. Examples of the copolyester having a phosphorus atom introduced into the molecule include aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid and lower alkyl esters thereof, lower alkyl esters of aliphatic dicarboxylic acids such as adipic acid and sebacic acid, Known acid components such as aliphatic oxycarboxylic acids such as ε-caprolactone, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, cyclohexanedimethanol, polytetramethylene glycol It can be obtained by copolymerizing a known diol such as phosphonate type polyol, phosphonate type polyol, phosphinate type polyol, vinyl phosphonate, allyl phosphonate and other monomer components containing phosphorus atoms. That.

  Further, the above copolyester having a phosphorus atom introduced can be synthesized by a known polymerization method. More specifically, for example, a lower alkyl ester such as a methyl ester of an aromatic or aliphatic dicarboxylic acid and a diol component are transesterified at a temperature of about 250 ° C. in the presence of a catalyst such as tetraalkoxytitanium to form an oligomer. After the synthesis, if necessary, a catalyst can be further added, the degree of vacuum is increased, and polycondensation is allowed to proceed under conditions where methanol can be easily distilled off, so that the polymer can be synthesized.

  The adhesive layer 4 is formed by dissolving a copolymerized polyester introduced with phosphorus atoms in a solvent, coating the resin film 5 on the resin film 5 and drying it, or by a melt molding method such as T-die or inflation. Can be formed. Further, from the viewpoint of improving the processability of these coatings, the number average molecular weight of the copolymerized polyester into which phosphorus atoms are introduced is preferably in the range of 3000 to 40000, and the wettability with the resin film 5 is improved. From the viewpoint of improvement, the resin film 5 can be subjected to corona treatment, and can be applied after applying a known anchor coating agent.

  In the present embodiment, the copolymer polyester having a phosphorus atom introduced into the molecule is non-crystalline, or the heat of fusion derived from the crystal component of the copolymer polyester measured by differential thermal analysis based on JIS K7122. However, it is set as the structure which is 15 J / g or less in the temperature rising conditions of 10 degree-C / min. This is because the durability of the insulating film 3 with respect to nickel plating or gold plating is related to the crystalline state of the copolymerized polyester introduced with the phosphorus atoms, and as the heat of fusion increases. This is because the conductor adhesive force of the insulating film 3 due to the plating treatment is lowered and the peeling becomes easier. In this embodiment, since the adhesive strength between the conductor 2 and the adhesive layer 4 is improved by using the insulating film 3 including the adhesive layer 4 mainly composed of such a copolyester, the insulating film 3 Even when a polyester-based adhesive layer, particularly a non-halogen flame-retardant polyester adhesive layer, is used, when performing the plating process, it is continuously only on the exposed conductor 2 surface. When forming the plating layer 6 (that is, the gold plating layer), it is possible to prevent the conductor adhesive force of the insulating film 3 from being lowered. As a result, it is possible to avoid the disadvantage that the conductor 2 is peeled off from the insulating film 3 during the plating process. In addition, as described above, since phosphorus atoms are introduced into the copolyester molecule, even when a non-halogen polyester adhesive layer is used, a UL vertical combustion test (VW-1 test). It is possible to provide a non-halogen flexible flat cable excellent in flame retardancy that can pass the above. The term “non-crystalline” as used herein refers to a copolymer polyester having a phosphorus atom introduced into the molecule when a differential thermal analysis method based on JIS K 7122 is performed at a temperature rising condition of 10 ° C./min. An endothermic or melting peak is not observed between the glass transition temperature and the decomposition temperature.

  Moreover, the higher one of the density | concentration of the phosphorus atom with respect to the whole copolyester is preferable from a viewpoint of improving a flame retardance. More specifically, although it is difficult to determine unconditionally depending on the type and thickness of the polymer film to be used, from the viewpoint of passing the flexible flat cable 1 to the above-described VW-1 test, the concentration of phosphorus atoms is determined. What is necessary is just to set to 0.2 weight% or more. However, if the phosphorus concentration is too high, it is difficult to increase the degree of polymerization and the mechanical strength of the flexible flat cable 1 may be lowered, so 0.2 to 2.7% by weight is a preferable range.

  The glass transition temperature of the copolyester introduced with a phosphorus atom can be appropriately designed by selecting the type and composition ratio of the monomer, and the conductor adhesive strength before forming the gold plating layer (hereinafter referred to as “initial stage”). -20 to 60 [deg.] C. is preferable from the viewpoint of improving the "conductor adhesive strength". From the viewpoint of heat resistance, it is preferable to design at room temperature (25 [deg.] C.) to 80 [deg.] C. In addition, it is good also as a structure which blends and uses the copolyester which introduce | transduced two or more types of phosphorus atoms from which glass transition temperature differs.

  Moreover, as copolymer polyester which introduce | transduced the phosphorus atom, what copolymerized the monomer which has a carbon-carbon unsaturated bond in molecules, such as fumaric acid and itaconic acid, can be used. And in this case, the adhesive resin composition which has as a main component the copolyester which introduce | transduced the phosphorus atom and the carbon-carbon unsaturated bond is applied on the resin film 5, and the adhesive bond layer 4 is applied on the resin film 5. After forming and bonding to the conductor 2 by performing heat and pressure treatment using a known thermal laminator or hot press apparatus, it is irradiated with ionizing radiation such as an accelerated electron beam or gamma ray to form phosphorus atoms and carbon. -It is possible to crosslink a copolyester introduced with a carbon unsaturated bond. With such a configuration, it is possible to obtain the flexible flat cable 1 excellent in heat aging resistance with a temperature rating of 105 ° C. or higher that satisfies the UL standard.

  In addition, the concentration of the carbon-carbon double bond with respect to the entire copolymerized polyester is preferably 0.5 to 10 mol%. This is because if the amount is less than 0.5 mol%, the crosslink density is lowered, and even if it is introduced in excess of 10 mol%, the crosslink density is saturated, which is disadvantageous in terms of cost.

  Further, the acceleration voltage of the accelerating electron beam can be appropriately set according to the thickness of the insulating film 3. For example, when the thickness of the insulating film 3 is 200 μm or less, an electron beam with an acceleration voltage of 150 to 300 kV may be irradiated from both sides of the flexible flat cable 1. The irradiation amount depends on the concentration of the carbon-carbon double bond introduced into the copolyester, but if the concentration is in the range of 0.5 to 10 mol%, the absorption is 50 to 500 kGy. The dose is appropriate.

  Further, the copolyester can be cross-linked by blending a polyfunctional isocyanate compound and heat-treating after lamination with the conductor 2, but there are problems such as storage stability. It can be said that crosslinking by irradiation is a simple method.

  In addition to the above phosphorus copolymerized polyester, the adhesive layer 4 may contain phosphorus-based materials such as triphenyl phosphite, ammonium polyphosphate, red phosphorus, condensed phosphate ester, and phosphaphenanthrene-based flame retardant as necessary. Flame retardants such as flame retardants and nitrogen-based flame retardants such as melamine cyanurate, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, and metal carbonates such as calcium carbonate and magnesium carbonate can also be added.

  It is also possible to add known compounding agents such as antioxidants, colorants (for example, titanium oxide), masking agents, hydrolysis inhibitors, lubricants, processing stabilizers, plasticizers, foaming agents and the like. In addition, in the case of solution mixing, a ball mill, a sand mill, a three-roll, an impeller mill, etc. may be used for mixing these compounding agents. When a film is formed by a melt molding method, a single-screw mixer, biaxial mixing is used. It can be performed by a melt mixing method using a machine.

  Below, this invention is demonstrated based on an Example and a comparative example. In addition, this invention is not limited to these Examples, These Examples can be changed and changed based on the meaning of this invention, and they are excluded from the scope of the present invention. is not.

(Production of copolymer polyester)
First, tetrabutyl titanate was added as a catalyst to the types of monomers shown in Table 1 so that the concentration would be 300 ppm, and the esterification was carried out at 230 ° C. for 2 hours. Thereafter, the same amount of catalyst was added, the pressure was reduced to 2 hPa, and the polycondensation reaction was carried out for 2 hours. The saturated phosphorus copolymer polyesters (1) to (5), unsaturated phosphorus copolymer polyesters shown in Table 1, and saturated Copolyesters (1) to (2) were prepared.

(Measurement of melting point, glass transition temperature, heat of fusion)
Next, for each of the produced saturated phosphorus copolymer polyester (1) to (5), unsaturated phosphorus copolymer polyester, and saturated copolymer polyester (1) to (2), the melting point, glass transition temperature, and JIS K7122 The amount of heat of fusion derived from the crystalline components measured by differential thermal analysis based on it was measured. The results are shown in Table 1. In addition, the measurement of melting | fusing point and glass transition temperature was performed at the temperature increase rate of 10 degree-C / min using the thermal analyzer (The Shimadzu Corporation make, brand name DSC-50) based on JISK7122. Further, the heat of fusion was also measured at a heating rate of 10 ° C./min using a thermal analyzer (manufactured by Shimadzu Corporation, trade name DSC-50) based on JIS K7122. As shown in Table 1, since the saturated phosphorus copolymerized polyester (1) and the saturated copolymerized polyester (1) were amorphous, the melting point could not be measured.

(Creation of adhesive resin composition)
Next, the types and amounts (unit: mol%) of the copolyester shown in Table 2 were added to the amount (unit: mol%) of melamine cyanurate, titanium oxide, antioxidant (Ciba Specialty) shown in Table 2. Chemicals, trade name Irganox 1010), magnesium hydroxide, and phosphorus-based flame retardant (Clariant, trade name EXOLIT AP462) were added and mixed uniformly using a twin-screw mixer. Examples 1-4 The adhesive resin compositions shown in Comparative Examples 1 to 5 were prepared.

(Preparation of insulation film)
Next, the produced adhesive resin composition of Example 1 was extruded into a film shape with a T-die, laminated on a resin film (thickness 0.012 mm) made of polyethylene terephthalate, and the resultant was carried out on the resin film. A film-like insulating film having an overall thickness of 0.047 mm on which an adhesive layer made of the adhesive resin composition of Example 1 was formed was produced. Similarly, an insulating film having an overall thickness of 0.047 mm in which an adhesive layer made of each of the adhesive resin compositions of Examples 2 to 4 and Comparative Examples 1 to 5 was formed. did.

(Production of flexible flat cable)
Next, the adhesive which consists of the adhesive resin composition of Example 1 which produced the said copper wire in the state which arranged in parallel the copper wire (thickness 0.035mm, width 0.8mm) which is a conductor. The both sides of the copper wire were coat | covered with the insulating film by inserting | pinching between the two insulating films in which the layer was formed, and performing a heat press process using a thermal laminator. In addition, in order to provide an exposed portion of the copper wire on which the plating layer is formed, one of the above-described two insulating films, using one in which a hole portion is previously formed by punching, The above-described heat and pressure treatment was performed. Similarly, both surfaces of the copper wire were covered with two insulating films on which adhesive layers made of the adhesive resin compositions of Examples 2 to 4 and Comparative Examples 1 to 5 were formed. . After the above coating, the adhesive layer made of the adhesive resin composition of Example 4 was irradiated with an acceleration electron beam having an acceleration voltage of 200 kV from both sides of the insulating film so as to be 50 kGy, respectively. The agent layer was crosslinked.

Subsequently, a flexible flat cable (hereinafter referred to as “flexible of Example 1”) is formed by continuously forming a gold plating layer only on the exposed surface of the conductor and having an adhesive layer made of the adhesive resin composition of Example 1. "Flat cable"). More specifically, first, an electric field degreasing solution (made by Okuno Pharmaceutical Co., Ltd., trade name Top Cleaner Sun 20) is used to remove oils and dirt on the conductor surface, the temperature is 40 ° C., the cathode Electrolysis was performed for 1 minute under the condition where the current density was 7.5 A / dm ² , and cathode electrolytic degreasing was performed. Thereafter, washing with water was performed, and acid treatment was performed at room temperature for 10 seconds using a 5% hydrochloric acid solution in order to remove the oxide film and the like on the conductor surface. Thereafter, washing with water was performed, and then a nickel bath plating step was performed for 2 minutes under the conditions of a temperature of 45 ° C. and a current density of 2 A / dm ² . Thereafter, washing with water is performed, and a strike gold plating process is performed for 10 seconds under the conditions of a temperature of 32 ° C. and a voltage of 6 V using a gold strike solution (Nippon Electroplating Engineers Co., Ltd., trade name Aurobond). Carried out. Thereafter, washing with water is performed, and an electrolytic gold-cobalt alloy plating solution (Nippon Electroplating Engineers Co., Ltd., trade name Autoronex CI) is used to perform the gold-cobalt alloy plating step at a temperature of 32 ° C. and a current density. Was carried out for 1 minute under the condition of 1 A / dm ² , and then washed with water to prepare a flexible flat cable in which a gold plating layer was formed on the surface of the exposed conductor. Similarly, an adhesive made of the adhesive resin compositions of Examples 2 to 4 and Comparative Examples 1 to 5 is formed by continuously forming a gold plating layer only on the exposed conductor surface. A flexible flat cable having a layer (hereinafter referred to as “flexible flat cables of Examples 2 to 4 and Comparative Examples 1 to 5”) was produced.

(Flame retardance evaluation)
Subsequently, the vertical combustion test prescribed | regulated to VW-1 of UL specification 1581 was done with respect to each produced flexible flat cable of Examples 1-4 and Comparative Examples 1-5. More specifically, 10 flexible flat cables of Examples 1 to 4 and Comparative Examples 1 to 5 were prepared, and after ignition, one or more of the 10 were burned, and the sample was a burning fallen object. The case where the absorbent cotton placed under the flexible flat cable burned or the case where the kraft paper attached to the upper part of the flexible flat cable as a sample burned was rejected, and the others were accepted. The results are shown in Table 2.

(Evaluation of conductor adhesion)
Moreover, conductor adhesive force evaluation was performed with respect to each produced flexible flat cable of Examples 1-4 and Comparative Examples 1-5. More specifically, the exposed conductors at the ends of the flexible flat cables of Examples 1 to 4 and Comparative Examples 1 to 5 are in the longitudinal direction of the flexible flat cable (the direction of the arrow X shown in FIG. 1). Peeling was performed at a speed of 100 mm / min, and the conductor adhesive force was measured. In addition, initial conductor adhesive strength (that is, conductor adhesive strength before forming a gold plating layer), conductor adhesive strength after aging at 113 ° C. for 7 days (in Example 4, after further aging at 136 ° C. for 7 days), And it measured about the conductor adhesive force after forming a gold plating layer. Moreover, the measurement of the conductor adhesive force was performed using the tensile testing machine (The product made from INSTRON, brand name INSTRON MODEL4301). The results are shown in Table 2.

  As shown in Table 2, the flexible flat cables of Examples 1 to 4 and Comparative Examples 1 to 5 must pass the vertical combustion test defined in VW-1 of UL standard 1581 in any case. I understand. On the other hand, in any case, the flexible flat cables of Examples 1 to 4 have a conductor adhesive strength after aging at 113 ° C. for 7 days (or after aging at 136 ° C. for 7 days) as compared to the initial conductor adhesive strength. In addition, the flexible flat cable of Comparative Examples 1 to 5 has a gold plated layer compared to the initial conductor adhesive force in any case, although the conductor adhesive strength after forming the gold plated layer is hardly reduced. It can be seen that the conductor adhesive strength after the formation is remarkably reduced (reduced to 0.5 N / mm or less). In particular, it can be seen that the flexible flat cables of Comparative Examples 3 to 5 have a low initial conductor adhesive force in any case.

  In Examples 1 to 3, as the adhesive resin composition constituting the adhesive layer, the heat of fusion derived from the crystal component measured by the differential thermal analysis method based on JIS K7122 is 15 J / g or less. This is considered to be because saturated phosphorus copolymerized polyester is used. Moreover, in Example 4, as the adhesive resin composition constituting the adhesive layer, unsaturated phosphorus having a heat of fusion of 15 J / g or less derived from a crystal component measured by a differential thermal analysis method based on JIS K7122 This is presumably because the copolymerized polyester is used, and the copolymerized polyester introduced with phosphorus atoms and carbon-carbon unsaturated bonds is cross-linked by irradiation with an accelerated electron beam. On the other hand, in Comparative Examples 1 and 2, as in Examples 1 to 3, a saturated phosphorus copolymerized polyester is used as the adhesive resin composition constituting the adhesive layer, but differential thermal analysis based on JISK7122 Since the heat of fusion derived from the crystal component measured by the method is 15 J / g or more, it is considered that the conductor adhesive strength after forming the gold plating layer was significantly reduced. In Comparative Examples 3 to 5, as the adhesive resin composition constituting the adhesive layer, the amount of heat of fusion derived from crystal components measured by differential thermal analysis based on JIS K7122 is 15 J / g or less. Although copolyester is used, because the polyester does not contain phosphorus that functions as a flame retardant, the initial conductor adhesion is reduced and the conductor adhesion after the gold plating layer is formed is significantly reduced. it is conceivable that.

  As an application example of the present invention, there is a flexible flat cable in which insulating films are provided on both surfaces of a plurality of conductors, and in particular, a flexible flat cable that does not contain a halogen element in the insulating film.

It is the schematic which shows the structure of the flexible flat cable which concerns on embodiment of this invention. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Flexible flat cable, 1a ... Cable edge part, 2 ... Conductor, 3 ... Insulating film, 4 ... Adhesive layer, 5 ... Resin film, 6 ... Plating layer

Claims (6)

In an insulating film comprising an adhesive layer mainly composed of a copolyester having a phosphorus atom introduced into the molecule and a resin film,
The adhesive layer does not contain a halogen element, and the copolyester is non-crystalline, or the heat of fusion derived from the crystalline component of the copolyester measured by differential thermal analysis based on JIS K7122 is 10 ° C. An insulating film, wherein the temperature is 15 J / g or less under the temperature rising condition per minute.   The adhesive layer is mainly composed of a copolyester having a carbon-carbon unsaturated bond introduced in the molecule, and the copolyester is cross-linked by irradiation with ionizing radiation. Item 10. The insulating film according to Item 1.   The insulating film according to claim 1 or 2, wherein a concentration of the phosphorus atom with respect to the whole of the copolymerized polyester is 0.2 to 2.7% by weight.   4. The insulation according to claim 1, wherein the resin constituting the resin film is at least one selected from the group consisting of a polyester resin, a polyphenylene sulfide resin, and a polyimide resin. the film.   A flexible flat cable comprising the insulating film according to any one of claims 1 to 4 and a conductor, wherein both surfaces of the conductor are covered with the insulating film.   The flexible flat cable according to claim 5, wherein a surface of the conductor at a cable end is covered with a gold plating layer.

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