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(11) | EP 0 772 206 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Flat cable and fabrication thereof |
| (57) A flat cable comprising a conductor, an insulating layer (a) formed via an adhesive
layer on one longitudinal plane of the conductor, and a different insulating layer
(b) formed on the opposite plane thereof via a 0.01-3 µm thick primer layer, said
conductor being sandwiched between the insulating layers (a) and (b). The flat cable
of the present invention can be made thin to improve bending property and to reduce
necessary space for wiring and the like. In addition, such flat cable can be provided
economically. The flat cable can be used in high temperature, high humidity environments
where it could not be heretofore applied, since the insulating property can be maintained
for a long time. |
FIELD OF THE INVENTION
[0001] The present invention relates to a flat cable comprising a conductor coated with an electrically insulating synthetic resin, and a method for fabrication thereof.
BACKGROUND OF THE INVENTION
[0002] Flat cables having a flat section which are prepared by sandwiching plural conductors (e.g., copper conductor) between electrically insulating synthetic resin films have been widely used for mounting wires, since they enable efficient wiring. They are used for, for example, under-carpet wiring for placing wires under carpet to conceal the wiring connecting each electric equipment in a building, wiring of equipments which is used as an internal wiring of electronic and electric equipments such as office automation equipments, and wiring to electrically connect operation elements before the driver's seat and various electric equipments of an automobile.
[0003] Inasmuch as flat cables are light and easy to install, application of flat cables has been particularly contemplated for efficient wiring and production of light weight automobile bodies in the automobile industry. When a flat cable is used in a door portion of an automobile, for example, a circuit pattern thereof should include curves and bends according to the application site to facilitate wiring of the cable in a narrow space. When the number of the circuit pattern should be increased to cope with increasing numbers of electric equipments, plural flat cables are laminated. In addition, in rain or during car washing, water intrudes into the door from the gap in the neighborhood of a window, thereby producing a high humidity atmosphere inside the door, which, being heated by the direct rays of the sun, becomes a high temperature and high humidity atmosphere. Therefore, the wires to be mounted inside the door which have curves or bends, as well as branches, will be exposed to the above-mentioned harsh conditions for a long time. The wires are required to be free of degradation of electrically insulating property even when exposed to such environment for a long time.
[0004] In view of such requirement, conventional flat cables have been fabricated by sandwiching a conductor between laminate tapes comprising an adhesive layer laminated on an insulating film. For an electrically insulating property to be fully exhibited even in the above-mentioned harsh conditions of high temperature and high humidity atmosphere, it is needed to insulate each circuit by completely enclosing the conductor by sandwiching the conductor between insulating films each having an adhesive layer, and tightly bonding said adhesive layers. However, this method is disadvantageous in that bonding of electrically insulating films laminated with an adhesive at both sides of the conductor makes the flat cable obtained this way thick to affect bending property. Moreover, the adhesive to be used for this end, particularly hot-melt adhesive, is expensive and the final product flat cable fabricated using said adhesive also becomes expensive.
[0005] Japanese Patent Examined Publication No. 120492/1995 discloses and proposes a flat cable wherein a flat conductor is sandwiched between an insulating film composed of insulating layer (substrate)/thermosetting adhesive layer/thermoplastic adhesive layer, and an insulating film composed of insulating layer (substrate)/thermosetting adhesive layer. This flat cable has thick adhesive layers, since thermosetting and thermoplastic adhesives are bonded to each other. The obtained flat cable also becomes thick in proportion to the thickness of each adhesive layer. This is disadvantageous in that it degrades bending property, and the final product becomes expensive, since thermosetting adhesive and thermoplastic adhesive are both expensive.
[0006] It is therefore an object of the present invention to provide an economical, thin flat cable capable of retaining insulating property for a long time even when used in an environment involving high temperature and high humidity, or when used in a bent state.
SUMMARY OF THE INVENTION
[0007] It has now been found that the thickness of the final product flat cable can be reduced without degrading adhesion property of insulating films by forming, instead of an adhesive layer, a primer layer for an improved adhesion on one insulating film of the two insulating films.
[0008] According to the present invention, there are provided the following.
(1) A flat cable comprising a conductor, an insulating layer (a) formed via an adhesive layer on one longitudinal plane of the conductor, and a different insulating layer (b) formed on the opposite plane thereof via a 0.01-3 µm thick primer layer, said conductor being sandwiched between the insulating layers (a) and (b).
(2) The flat cable of above (1), wherein the adhesive layer is a layer of a hot-melt adhesive.
(3) The flat cable of above (2), wherein the hot-melt adhesive is a polyolefin adhesive or a polyester adhesive.
(4) The flat cable of above (1), wherein the primer layer is a urethane primer layer or an organic titanium primer layer.
(5) The flat cable of above (1), wherein the adhesive layer is a polyolefin adhesive layer, and the primer layer is a urethane primer or an organic titanium primer layer.
(6) The flat cable of above (5), wherein the adhesive layer is a polyolefin adhesive layer, and the primer layer is a urethane primer layer.
(7) The flat cable of above (1), wherein the adhesive layer is a polyester adhesive layer, and the primer layer is a urethane primer layer.
(8) The flat cable of above (1), further comprising an intermediate layer between the insulating layer (a) and the adhesive layer.
(9) A method for fabrication of a flat cable, comprising sandwiching a conductor between a film comprising an adhesive layer on one side of an insulating layer, and a film comprising a primer layer on one side of an insulating layer, in such a manner that the above-mentioned adhesive layer and said primer layer are brought in contact.
(10) The method of above (9), wherein the adhesive layer is a layer of a hot-melt adhesive.
(11) The method of above (10), wherein the hot-melt adhesive is a polyolefin adhesive or a polyester adhesive.
(12) The method of above (9), wherein the primer layer is a urethane primer layer or an organic titanium primer layer.
(13) The method of above (9), wherein the adhesive layer is a polyolefin adhesive layer, and the primer layer is a urethane primer or an organic titanium primer layer.
(14) The method of above (13), wherein the adhesive layer is a polyolefin adhesive layer, and the primer layer is a urethane primer layer.
(15) The method of above (9), wherein the adhesive layer is a polyester adhesive layer, and the primer layer is a urethane primer layer.
BRIEF DESCRIPTION OF THE DRAWING
[0009] Fig. 1 is a cross section showing one embodiment of the flat cable of the present invention, wherein 1 is a conductor, 2 is an adhesive layer, 3 is an insulating layer (a), 4 is a primer layer and 5 is an insulating layer (b).
DETAILED DESCRIPTION OF THE INVENTION
[0010] The present invention is described in detail by referring to illustrative Fig. 1 which is a cross section showing one embodiment of the flat cable of the present invention. In this Figure, shown is a flat cable comprising a conductor 1 sandwiched between insulating layers 3 and 5, wherein one insulating layer 3 is formed via an adhesive layer 2 on one longitudinal plane of the conductor 1, and the other insulating layer 5 is formed via a primer layer 4 on the opposite plane.
[0011] The conductor 1 may be made of naked copper, tin-plated copper, silver and the like, which may be a foil or rectangular in shape.
[0012] While the thickness of the conductor is not particularly limited, it is generally 0.065-0.2 mm, preferably 0.08-0.15 mm, to secure rigidity, current capacity and a surface area for achieving heat release from a wired pattern.
[0013] The synthetic resin to be used as insulating layers 3 and 5 is not particularly limited. Those having heat resistance, tensile strength and water resistance that a flat cable is required to have are preferably used.
[0014] Examples of such synthetic resin include polyesters (e.g., polyethylene terephthalate and polybutylene terephthalate), polyamides (e.g., nylon and aramide), polyolefins (e.g., polyethylene and polypropylene), polyvinyl chloride, polyimide, polyarylate, polyphenyl sulfide, polyether sulfone, poly(ether ether ketone), polyether imide and the like, with particular preference given to polyethylene terephthalate in view of heat reistance and bendability.
[0015] The insulating layers 3 and 5 may be made from the same kind or different kinds of insulating synthetic resin.
[0016] The thickness of said insulating layer is not particularly limited, and is appropriately determined according to the thickness of a conductor, desired voltage resistance, bendability, durability and the like. It is generally 10-300 µm, preferably 25-200 µm.
[0017] Said insulating layer may contain known additives such as inorganic fillers, antioxidants, copper inhibitors, ultraviolet absorbents, flame retardants, flame retarders, and the like.
[0018] The adhesive to be used in the present invention may be known, and is not particularly limited as long as it can adhere to the primer layer. For example, the adhesive may be an electrically insulating resin which has a lower melting point and/or a lower softening point than does the resin to be used for the insulating layer, and which is capable of inhibiting contact of the conductor with other adjacent conductors by enclosing the conductor in said adhesive layer or by filling the periphery of the conductor and fixing the conductor during configuration. Specifically, polyolefin adhesive and/or polyester adhesive, particularly hot-melt adhesive, is preferable.
[0019] Examples of the above-mentioned polyolefin adhesive include high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (L-LDPE), ultralow density polyethylene, polypropylene (PP) and their copolymers, graftcopolymers thereof with unsaturated carboxylic acids (e.g., acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid and citraconic acid) or acid anhydrides (e.g., maleic anhydride, itaconic anhydride and citraconic anhydride), and the like. In addition, ethylene-vinyl acetate (EVA) copolymer, ethylene-ethyl acrylate (EEA) copolymer, ethylene-methacrylic acid (EMAA) copolymer, ethylene-vinyl acetate-glycidyl methacrylate (E-VA-GMA) copolymer, these resins grafted with alkoxysilane, ionomers (e.g., ethylene-acrylic acid metal ion copolymer and ethylene-methacrylic acid metal ion copolymer), and the like may be used. Preferred are graftcopolymers with acid anhydrides (e.g., maleic anhydride, itaconic anhydride and citraconic anhydride).
[0020] Saturated polyester copolymer hot-melt adhesive is obtained by condensation polymerization of one or more acid components, e.g., aromatic dicarboxylic acid such as terephthalic acid and isophthalic acid and aliphatic carboxylic acid such as adipic acid and sebacic acid with one or more diol components, e.g., ethylene glycol, 1,4-butanediol, diethylene glycol and neopentyl glycol. Where necessary, antioxidants and copper inhibitors may be added.
[0021] The saturated polyester copolymer hot-melt adhesive to be used in the present invention preferably has a glass transition temperature (Tg) of about 40-70°C and a softening point of about 130-160°C.
[0022] The antioxidant to be added to the adhesive may be, for example, phenolic antioxidants such as 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 4,4'-thiobis-(6-tert-butyl-3-methylphenol), 4,4'-thiobis-(6-tert-butyl-o-cresol) and tetrakis[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenylpropionate)]methane, and copper inhibitors may be, for example, benzotriazole copper inhibitors such as 1,2,3-benzotriazol and 3-(N-salicyloyl)amino-1,2,4-triazole. The adhesive may contain flame retardants such as antimony oxide, decabromodiphenyl ether, red phosphorus, aluminum hydroxide and magnesium hydroxide, coloring agents and the like as appropriate.
[0023] Said adhesive may contain known additives such as tackifiers and stabilizers where necessary.
[0024] The thickness of the adhesive layer is appropriately determined according to the thickness of the conductor 1, and is generally 1-300 µm, preferably 30-200 µm.
[0025] The primer layer 4 to be formed on one side of the insulating layer 5 is preferably one that exhibits superior adhesion to the insulating layer 5 and adhesive layer 2, as well as water resistance, heat resistance and voltage resistance.
[0026] Examples of said primer include polyurethane primers, organic titanium primers, silane-modified polyolefin primers and the like.
[0027] The polyurethane primer is exemplified by polyurethane (isocyanate) primers having active isocyanate (NCO), such as those comprising, as main components, polyesterpolyol comprising copolymers of dibasic acid component, e.g., phthalic acid, terephthalic acid and adipic acid, and glycols, e.g., ethylene glycol, triethylene glycol, neopentyl glycol and 1,4-butanediol, or polycaprolactone; and multifunctional isocyanate (e.g., 2,4-trilenediisocyanate, 2,6-trilenediisocyanate, diphenylmethane-4,4'-diisocyanate, polymethylene polyphenyl diisocyanate, hexamethylene diisocyanate, hexahydromethaxylylene diisocyanate and triphenylmethane-p,p',p''-triisocyanate), mixture thereof or modified polymer thereof. The polyurethane primer may be of a single fluid or double fluid curing type.
[0028] The organic titanium primer may be, for example, an organic titanium primer having alkoxyl, such as alkyl titanate of the formula: Ti(OR1)(OR2)(OR3)(OR4) wherein R1-R4 may be the same or different and each is alkyl having 1 to 27, preferably 3-19, carbon atoms or allyl. Specifically, tetra-i-propyltitanate (TPT), tetra-n-butyltitanate (TBT), tetra(2-ethylhexyl)titanate (TOT), tetrastearyltitanate (TST), di-i-propoxy · bis(acetylacetonato)titanium (TAA) and the like may be used with or without combination. The organic titanium primer forms, due to the dissociation by hydrolysis at -OR group in the molecule of the above-mentioned alkyl titanate, a colorless, transparent, very thin titanium oxide polymer membrane having a structure similar to the structure of titanium oxide.
[0029] The silane modified polyolefin primer is exemplified by copolymers obtained by graftcopolymerization of ethylene-ethylacrylate (EEA), ethylene-vinyl acrylate (EVA) and the like with alkoxysilane such as methoxysilane and butoxysilane.
[0030] The thickness of the primer layer is 0.01-3 µm, preferably 0.1-1 µm. When the thickness of the primer layer is less then 0.01 µm, partial absence of primer and non-uniform coating occur due to poor wettability of the primer solution to the coated surface, insufficient amount of primer, convex and concave on the coated surface, staining of the coated surface and the like, which in turn results in insufficient initial adhesion and marked decrease in adhesion after use under the aforementioned harsh conditions to produce unfavorable insulating property of the flat cable. When it is thicker than 3 µm, however, adhesion drastically falls as a result of cohesive failure of said primer layer itself due to insufficient drying of the primer layer and insufficient cohesion of the primer, which in turn degrades bending property, thus causing problems in terms of insulating property of the flat cable.
[0031] The combination of the above-said adhesive layer 2 and primer layer 4 is preferably such as polyolefin adhesive and urethane primer or organic titanium primer, or polyester adhesive and urethane primer, in consideration of the adhesion of the both layers, as well as voltage resistance, heat resistance and water resistance.
[0033] In the present invention, an intermediate layer may be formed between insulating layer 3 and adhesive layer 2 for an increased adhesion of said layers. The material of the intermediate layer may be those exemplified above with regard to the primer, and the intermediate layer may be about 0.5-30 µm thick.
[0034] The fabrication of the flat cable of the present invention characteristically comprises sandwiching a conductor between a film comprising an adhesive layer on one side of an insulating layer and a film comprising a primer layer on one side of an insulating layer, in such a manner that the above adhesive layer and the above primer layer are brought into contact.
[0035] The film having an adhesive layer on one side of an insulating layer can be prepared by a method known per se, such as gravure rolling, direct rolling, dip rolling, extrusion and the like. Where necessary, a prime layer may be formed between layers.
[0036] The film having a primer layer on one side of an insulating layer can be prepared by, for example, applying a primer diluted with a solvent onto an insulating layer and drying same by a known method.
[0037] The film is generally dried at 30-150°C, preferably 80-120°C, generally for 30 seconds to 10 minutes, preferably 2-5 minutes.
[0038] The film is preferably cured at 20-50°C, preferably 30-40°C for 1-168 hours, preferably 2-48 hours.
[0039] A conductor is interposed between the film having an adhesive layer on one side of an insulating layer and the film having a primer layer on one side of an insulating layer obtained above and bonded to give a flat cable.
[0040] The conductor and the films are bonded by a conventional method such as thermocompression and lamination press.
[0041] The bonding conditions in the case of thermocompression are: bonding temperature generally 100-250°C, preferably 150-200°C, bonding time generally 15 seconds-5 minutes, preferably 1-2 minutes, and bonding pressure generally 0.5-20 kg/cm, preferably 2-10 kg/cm.
[0042] In the case of lamination press, bonding temperature is generally 100-250°C, preferably 150-200°C, bonding pressure is generally 4-13 kg/cm, preferably 6-10 kg/cm, and bonding rate is generally 0.5-5 m/min, preferably 0.5-4 m/min.
[0043] When prepared under the above-mentioned bonding conditions, the flat cable is free of bonding failure between the primer layer and the adhesive layer, insulation failure caused by less amount of the adhesive to fill the space between conductors, and problems of extrusion of adhesive and poor appearance after forming.
[0044] The present invention is explained in more detail by way of illustrative Examples to which the present invention is not limited.
Example 1
[0045] Five 3.0 mm wide copper conductors were placed, at 1 mm conductor intervals, on an adhesive layer of 80 µm thick polyolefin hot-melt adhesive (linear low density polyethylene modified with maleic acid) on one side of a 50 µm thick polyethylene terephthalate (PET) film, and temporarily bonded to give a linear bond film having 4 mm wide selvage on each side. A double liquid curing type polyurethane primer (polyester polyol modified with MDI) was applied to an electric use PET film (50 µm) with a direct roll coater, dried at 100°C for 2 minutes to give a PET film having a primer layer (thickness; 0.02 µm). The primer layer surface of said PET film was superimposed on the adhesive layer side of the above-mentioned bond film, and laminated at 180°C × 0.5 m/min × 9 kg/cm to give a flat cable.
Example 2
[0046] In the same manner as in Example 1 except that the thickness of the primer layer was 0.1 µm, a flat cable was obtained.
Example 3
[0047] In the same manner as in Example 1 except that the thickness of the primer layer was 1.0 µm, a flat cable was obtained.
Example 4
[0048] In the same manner as in Example 1 except that the thickness of the primer layer was 2.0 µm, a flat cable was obtained.
Example 5
[0049] In the same manner as in Example 1 except that the thickness of the primer layer was 2.5 µm, a flat cable was obtained.
Comparative Example 1
[0050] In the same manner as in Example 1 except that the primer layer was not used, a flat cable was obtained.
Comparative Example 2
[0051] In the same manner as in Example 1 except that the thickness of the primer layer was 0.005 µm, a flat cable was obtained.
Comparative Example 3
[0052] In the same manner as in Example 1 except that the thickness of the primer layer was 4.0 µm, a flat cable was obtained.
Comparative Example 4
[0053] In the same manner as in Example 1 except that the thickness of the primer layer was 10.0 µm, a flat cable was obtained.
Example 6
[0054] In the same manner as in Example 1 except that an organic titanium primer (a mixture of TTP, TOT and TST) was used as the primer and the thickness of the primer layer was 0.015 µm, a flat cable was obtained.
Example 7
[0055] In the same manner as in Example 2 except that the same organic titanium primer as used in Example 6 was used as the primer, a flat cable was obtained.
Example 8
[0056] In the same manner as in Example 3 except that the same organic titanium primer as used in Example 6 was used as the primer, a flat cable was obtained.
Example 9
[0057] In the same manner as in Example 4 except that the same organic titanium primer as used in Example 6 was used as the primer, a flat cable was obtained.
Example 10
[0058] In the same manner as in Example 1 except that the same organic titanium primer as used in Example 6 was used as the primer, and the thickness of the primer layer was 2.8 µm, a flat cable was obtained.
Comparative Example 5
[0059] In the same manner as in Comparative Example 2 except that the same organic titanium primer as used in Example 6 was used as the primer, a flat cable was obtained.
Comparative Example 6
[0060] In the same manner as in Example 1 except that the same organic titanium primer as used in Example 6 was used as the primer, and the thickness of the primer layer was 5 µm, a flat cable was obtained.
Comparative Example 7
[0061] In the same manner as in Comparative Example 4 except that the same organic titanium primer as used in Example 6 was used as the primer, a flat cable was obtained.
Example 11
[0062] In the same manner as in Example 6 except that a polyester adhesive (saturated polyester copolymer hot-melt adhesive comprising, as an acid component, terephthalic acid and isophthalic acid, and ethylene glycol and 4-butanediol as diol components) was used as the adhesive, a flat cable was obtained.
Example 12
[0063] In the same manner as in Example 2 except that the same polyester adhesive as used in Example 11 was used as the adhesive, a flat cable was obtained.
Example 13
[0064] In the same manner as in Example 3 except that the same polyester adhesive as used in Example 11 was used as the adhesive, a flat cable was obtained.
Example 14
[0065] In the same manner as in Example 4 except that the same polyester adhesive as used in Example 11 was used as the adhesive, a flat cable was obtained.
Example 15
[0066] In the same manner as in Example 5 except that the same polyester adhesive as used in Example 11 was used as the adhesive, a flat cable was obtained.
Comparative Example 8
[0067] In the same manner as in Example 11 except that the primer layer was not used, a flat cable was obtained.
Comparative Example 9
[0068] In the same manner as in Comparative Example 2 except that the same polyester adhesive as used in Example 11 was used as the adhesive, a flat cable was obtained.
Comparative Example 10
[0069] In the same manner as in Comparative Example 6 except that the same polyester adhesive as used in Example 11 was used as the adhesive, a flat cable was obtained.
Comparative Example 11
[0070] In the same manner as in Comparative Example 4 except that the same polyester adhesive as used in Example 11 was used as the adhesive, a flat cable was obtained.
Comparative Example 12
[0071] Saturated polyester resin (100 parts by weight, trademark UE-3221, manufactured by UNITIKA Ltd.) was dissolved in methyl ethyl ketone (35 parts by weight), and curing agent tolylene diisocyanate (TDI, 1 part by weight, trademark CORONATE, manufactured by NIPPON POLYURETHANE INDUSTRY CO., LTD.) was dissolved in toluene (15 parts by weight). The mixtures were respectively diluted and mixed to give a primer solution. Using this primer solution, a flat cable was prepared (thickness of primer layer; 5 µm) in the same manner as in Example 1.
Comparative Example 13
[0072] In the same manner as in Comparative Example 12 except that the same polyester adhesive as used in Example 11 was used as the adhesive, a flat cable was obtained.
[0073] The flat cables obtained above were used as test samples to be subjected to the following water resistance test, heat resistance test and folding-heating test, and appearance, peeling and voltage resistance of each sample were examined.
[Water resistance test]
[0074] The above test samples were immersed in hot water at 80°C and taken out 168 hours later. The appearance was observed and the samples were subjected to the following peeling test and voltage resistance test. The samples without abnormality were rated ○.
① Voltage resistance test
[0075] The center portion (30 cm) of the test samples was immersed in 5 wt% aqueous solution of sodium chloride for one hour, and a voltage of 1 kV×1 min was applied in the aqueous solution of sodium chloride from a direct current power source. The samples suffered from electric breakdown were rated X (rejection) and those free of electric breakdown were rated ○ (acceptance).
② Peeling test
[0076] Peeling strength was determined by a Tensilon tester (UCT-500, manufactured by Orientech) with regard to 180° peeling (tension at electrically insulating resin layer having the primer) at peeling rate 50 mm/min.
[Heat resistance test]
[0077] After standing the test samples in a gear oven at 135°C for 168 hours, the appearance was examined. In the same manner as in the above-mentioned water resistance test, voltage resistance and peeling test were performed.
[Folding-heating test]
[0078] The test samples were folded at the middle part (complete folding at 180°) and left standing in this state in a gear oven at 90°C for 120 hours. The samples were taken out, restored at room temperature and subjected to appearance observation. Then, the samples were subjected to voltage resistance testing as above.
[0079] The results are shown in Tables 1 - 4. The flat cables of Examples showed superior results in initial values, heat resistance test, water resistance test and folding-heating test. In contrast, the flat cables of Comparative Examples 1, 2, 5, 8 and 9 showed, in water resistance test and folding-heating test, peeling of insulation layer (PET) which was assumed to be caused by partial absence of primer and non-uniform coating of primer, as well as lower adhesion and poor voltage resistance. In Comparative Examples 3, 4, 6, 7, 10 and 11, the insulating film peeled mainly at both selvages at the folded portion of test samples subjected to folding-heating test. In Comparative Examples 12 and 13, peeling of insulating layer and remarkable loss of adhesion in water resistance test and peeling of selvages at the folded portion of test samples and poor voltage resistance in folding-heating test were observed, which are considered to be attributable to the poor compatibility between thermosetting adhesive used as a primer and polyolefin adhesive or polyester adhesive, as well as hydrolysis of primer layer.
Table 4
| Com.Ex. 12 | Com.Ex. 13 | ||
| Insulation layer (thickness: µm) | PET (50) | ||
| Adhesive layer (thickness: µm) | Polyolefin (80) | Polyester (80) | |
| Primer (thickness: µm) | thermosetting adhesive (saturated polyester + TDI) (5) | ||
| Initial value | Appearance | ○ | ○ |
| Adhesion (N/10mm) | 7.0 | 14.5 | |
| Voltage resistance | ○ | ○ | |
| Water resistance Test | Appearance | peeling of insulation layer | partial peeling of insulation layer |
| Adhesion (N/10mm) | - | 3.7 | |
| Voltage resistance | X | ○ | |
| Heat resistance Test | Appearance | ○ | ○ |
| Adhesion (N/10mm) | 9.4 | 18.1 | |
| Voltage resistance | ○ | ○ | |
| Folding-heating Test | Appearance | peeling at bent selvage | partial peeling at bent selvage |
| Voltage resistance | X | X | |
[0080] According to the present invention, the adhesive layer of the flat cable can be made thin to improve bending property and to reduce necessary space for wiring and the like. In addition, such flat cable can be provided economically. Having superior water resistance and heat resistance, the flat cable can be used in high temperature, high humidity environments where it could not be heretofore applied. A light weight flat cable is advantageous in that it can be used for a wide range of uses.
1. A flat cable comprising a conductor, an insulating layer (a) formed via an adhesive
layer on one longitudinal plane of the conductor, and an insulating layer (b) formed
on the opposite plane thereof via a 0.01-3 µm thick primer layer, said conductor being
sandwiched between the insulating layers (a) and (b).
2. The flat cable of claim 1, wherein the adhesive layer is a layer of a hot-melt adhesive.
3. The flat cable of claim 2, wherein the hot-melt adhesive is a polyolefin adhesive
or a polyester adhesive.
4. The flat cable of claim 1, wherein the primer layer is a urethane primer layer or
an organic titanium primer layer.
5. The flat cable of claim 1, wherein the adhesive layer is a polyolefin adhesive layer,
and the primer layer is a urethane primer or an organic titanium primer layer.
6. The flat cable of claim 5, wherein the adhesive layer is a polyolefin adhesive layer,
and the primer layer is a urethane primer layer.
7. The flat cable of claim 1, wherein the adhesive layer is a polyester adhesive layer,
and the primer layer is a urethane primer layer.
8. The flat cable of above (1), further comprising an intermediate layer between the
insulating layer (a) and the adhesive layer.
9. A method for fabrication of a flat cable, comprising sandwiching a conductor between
a film comprising an adhesive layer on one side of an insulating layer, and a film
comprising a primer layer on one side of an insulating layer, in such a manner that
the above-mentioned adhesive layer and said primer layer are brought in contact.
10. The method of claim 9, wherein the adhesive layer is a layer of a hot-melt adhesive.
11. The method of claim 10, wherein the hot-melt adhesive is a polyolefin adhesive or
a polyester adhesive.
12. The method of claim 9, wherein the primer layer is a urethane primer layer or an organic
titanium primer layer.
13. The method of claim 9, wherein the adhesive layer is a polyolefin adhesive layer,
and the primer layer is a urethane primer or an organic titanium primer layer.
14. The method of claim 13, wherein the adhesive layer is a polyolefin adhesive layer,
and the primer layer is a urethane primer layer.
15. The method of claim 9, wherein the adhesive layer is a polyester adhesive layer, and
the primer layer is a urethane primer layer.