JP2012119177A - Insulating film and flat cable using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulating film capable of reducing a dielectric constant and excellent in flame resistance, and a flat cable using the insulating film.SOLUTION: An insulating film comprises a resin film on which a flame retardant resin layer is laminated. The flame retardant resin layer comprises a resin composition containing, relative to 100 pts. mass of a copolymer polyester resin: 5 pts. mass or more and 40 pts. mass or less of a hollow particle having an average particle size of 0.1 μm or more and 20 μm or less; and 10 pts. mass or more and 100 pts. mass or less of at least one flame retardant selected from the group consisting of a phosphorous flame retardant, a nitrogen flame retardant, a metal hydroxide, a halogen flame retardant and an antimony flame retardant.

Description

  The present invention relates to an insulating film that can be suitably used as a covering material for a flat cable, particularly as a covering material for a flat cable for high-speed transmission, and a flexible flat cable using the insulating film.

  A multi-core flat flexible flat cable is used as an electric wire for internal wiring of electronic equipment. A flat cable is manufactured by sandwiching a plurality of conductors in parallel between two insulating films and fusing the insulating films together to integrate them. This insulating film generally has an adhesive layer in contact with a conductor and a resin film on the outside thereof. As the resin film, a biaxially stretched polyethylene terephthalate (PET) film having excellent mechanical properties and electrical properties is widely used. For the base polymer of the adhesive layer, polyvinyl chloride (PVC), saturated copolyester or the like is used.

  Flat cables are also used as wiring cables for high-speed transmission of electronic devices such as liquid crystal displays and plasma displays. In this case, a shield layer (metal layer) is provided on the outside of the insulating layer for noise suppression. In the LVDS standard, in order to obtain high-speed transmission characteristics, it is necessary to set the characteristic impedance to 100Ω, which is the same as the impedance of the high-speed digital signal transmission / reception IC. In order to control the capacitance, which is a factor of characteristic impedance, it is necessary to lower the dielectric constant of the insulating layer (adhesive layer, resin film).

  In order to reduce the dielectric constant of the insulating layer, Patent Document 1 discloses a flat cable in which an adhesive layer portion is foamed. Prepare an insulating tape with a resin film and an adhesive layer laminated, sandwich a plurality of conductors between two insulating tapes, and laminate with a heating roll to make the adhesive layer part foam and flat cable Is manufacturing. By foaming the adhesive layer, the dielectric constant is lowered to 1.5 to 2.1 (paragraphs 0012 and 0013).

  Patent Document 2 discloses an insulating tape for a flexible flat cable that includes an adhesive layer and an insulating layer, and the insulating layer is made of a foam of a polyolefin resin or a polyester resin. Similar to Patent Document 1, the dielectric constant is lowered by using an insulating layer as a foam.

  On the other hand, Patent Document 3 includes a conductor, an insulating layer covering both sides of the conductor, a low dielectric layer provided outside the insulating layer, and a shield layer provided outside the low dielectric layer, A flat cable whose main component is a resin composition in which the low dielectric layer is made of a polyolefin resin is disclosed. The characteristic impedance of the flexible flat cable can be adjusted by providing a low dielectric layer.

Japanese Patent No. 3006409 JP 2008-251261 A JP 2008-47505 A

  Flat cables are required to have flexibility and bendability. Since the foam insulator used in Patent Document 1 and Patent Document 2 has low strength, when the flat cable is bent, the bubbles collapse and the portion buckles, and the capacitance changes, resulting in deterioration of electrical characteristics. There is a case. Further, when a low dielectric layer is provided as in Patent Document 3, the electrical characteristics are excellent, but the flexibility of the flat cable is reduced, and it becomes difficult to bend it well.

  In addition, flat cables have applications that require high flame retardancy, and flame retardance such as the vertical flame test (VW-1 test) of the US UL standard is specified. In order to satisfy the flame retardant standard, it is necessary to contain a flame retardant in the low dielectric layer, as a flame retardant, a brominated flame retardant, a halogen flame retardant such as a chlorine flame retardant, or a phosphorus flame retardant, Use non-halogen flame retardants such as nitrogen flame retardants. The polyolefin resin used in the adhesive layer of Patent Document 2 has low flame retardancy, and a large amount of flame retardant needs to be added to satisfy the flammability standards. In particular, when a non-halogen flame retardant is used, it is necessary to add a larger amount of flame retardant than when a halogen flame retardant is used, and as a result, the flexibility of the insulating layer is lowered.

  Then, this invention makes it a subject to provide the insulating film which can make a dielectric constant low, and is excellent in a softness | flexibility and a flame retardance, and a flat cable using the same. This flat cable can be suitably used as a flat cable for high-speed transmission.

  The present invention is an insulating film in which a flame retardant resin layer is laminated on a resin film, and the flame retardant resin layer includes hollow particles having an average particle size of 0.1 μm or more and 20 μm or less with respect to 100 parts by mass of a copolyester resin. 10 parts by mass of one or more flame retardants selected from the group consisting of 5 parts by mass to 40 parts by mass, a phosphorus flame retardant, a nitrogen flame retardant, a metal hydroxide, a halogen flame retardant, and an antimony flame retardant It is an insulating film which consists of a resin composition containing 100 parts by mass or more.

  Since the copolyester resin is more excellent in flame retardancy than the polyolefin resin, the intended flame retardancy can be obtained even if the content of the flame retardant is relatively small. However, since the copolyester resin has a high dielectric constant, the flame retardant resin layer has a higher dielectric constant than when a polyolefin resin is used. Thus, it has been found that it is possible to achieve both flame retardancy and low dielectric constant by incorporating hollow particles in an amount of 5 to 40 parts by mass with respect to 100 parts by mass of the copolyester resin. is there.

  By containing the hollow particles, void portions are generated in the flame-retardant resin layer. Since this void portion is a closed cell and has higher strength than a void portion (bubble) formed by foaming, stable electric characteristics can be obtained without being crushed even when the flat cable is bent.

  As the flame retardant, at least one selected from the group consisting of a phosphorus flame retardant, a nitrogen flame retardant, a metal hydroxide, a halogen flame retardant, and an antimony flame retardant is used, and the copolymer polyester resin 100 mass 10 parts by mass or more and 100 parts by mass or less with respect to the part. If the amount of the flame retardant is less than 10 parts by mass, flame retardancy that passes the VW-1 vertical flame retardant test cannot be obtained. Moreover, a dielectric constant will become high when content of a flame retardant becomes more than 100 mass parts. Among the flame retardants, it is preferable to use a phosphorus flame retardant because the dielectric constant can be kept low. When using a phosphorus flame retardant, the amount of the particularly preferred flame retardant is 40% by mass or more and 100% by mass or less with respect to 100 parts by mass of the copolyester resin.

  The hollow ratio of the hollow particles is preferably 25% by volume or more (Claim 3). The larger the hollow ratio, the lower the dielectric constant. FIG. 3 (1) is a schematic view showing hollow particles, and FIG. 3 (2) is a cross-sectional view taken along the line A-A 'of FIG. 3 (1). The hollow ratio is the volume of the void portion 12 with respect to the entire volume of the hollow particles 11, and can be obtained by measuring and calculating the outer diameter a and the inner diameter b from a cross-sectional photograph of the hollow particles. Since the thickness t of the shell 13 hardly changes even if the particle size of the hollow particles changes, generally the hollow ratio increases as the particle size of the hollow particles increases. The average particle diameter of the hollow particles is 0.1 μm or more and 20 μm or less. When the average particle diameter of the hollow particles is smaller than 0.1 μm, the hollow ratio is lowered and the dielectric constant reducing effect is reduced. On the other hand, if the average particle size exceeds 20 μm, the smoothness of the surface of the flame-retardant resin layer is deteriorated, and the adhesion to the conductor is also lowered. The average particle size of the hollow particles is more preferably 1 μm or more and 10 μm or less. In addition, let an average particle diameter be a particle diameter (D50) from which a cumulative value becomes 50% in a laser type particle size distribution measurement.

  It is preferable to have an anchor coat layer between the resin film and the flame retardant resin layer. By having the anchor coat layer, the adhesive force between the resin film and the flame retardant resin layer is improved.

  Moreover, this invention provides the flat cable which used said flame-retardant resin sheet as a coating | covering material (Claim 5). This flat cable has excellent impedance characteristics, flexibility and flame retardancy.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to make a dielectric constant low, the flat cable which used the insulating film excellent in a softness | flexibility and a flame retardance, and this insulating film as a coating | covering material can be obtained.

It is a figure which shows the flat cable of this invention. It is a figure which shows the flat cable of this invention, and is A-A 'sectional drawing of FIG. It is a schematic diagram which shows the hollow particle used for this invention.

  First, various materials constituting the insulating film of the present invention will be described. Hollow particles are substantially spherical fine particles having voids inside. As a constituent material of the hollow particles, inorganic materials such as silica, glass, calcium carbonate and the like mainly composed of silicon oxide, and organic materials such as a crosslinked styrene-acrylic copolymer resin can be used. Hollow silica containing silica as a constituent material is preferable in terms of availability and cost.

  The void ratio of the hollow particles is preferably 25% or more. However, if the porosity is too high, the strength of the hollow particles becomes weak, and the particles may be destroyed when mixed with other materials such as a copolyester resin. The porosity and the particle size are correlated to some extent, and the particle size increases as the porosity increases. Therefore, the upper limit of the porosity is preferably about 70%.

  As the copolyester resin, a saturated copolyester resin such as polyethylene terephthalate / sebacate, polybutylene terephthalate / sebacate, polybutylene terephthalate / adipate, polyethylene terephthalate / isophthalate can be used. These resins are obtained by polymerizing alcohol components such as ethylene glycol, 1,4-butanediol and 1,6-hexanediol and acid components such as terephthalic acid, naphthalenecarboxylic acid, adipic acid, sebacic acid and isophthalic acid. Obtainable. Moreover, you may use the unsaturated polyester which copolymerized the monomer which has a carbon-carbon unsaturated bond in molecules, such as fumaric acid and itaconic acid.

  As the flame retardant used in the present invention, a phosphorus flame retardant, a nitrogen flame retardant, a halogen flame retardant, and an antimony flame retardant can be used. One flame retardant may be used, or a plurality of flame retardants may be used in combination. Phosphorus flame retardants include cyclic organic phosphorus compounds such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phosphoric acids such as triphenyl phosphate and bisphenol A bis (diphenyl) phosphate Examples thereof include esters, ammonium polyphosphate, aluminum polyphosphate, and aluminum hypophosphite. Examples of the nitrogen-based flame retardant include melamine resin and melamine cyanurate. Phosphorus flame retardants and nitrogen flame retardants are preferable because they do not contain a halogen element and do not generate toxic gases such as hydrogen halides even if incinerated after use. It is preferable to use a combination of a phosphorus-based flame retardant and a nitrogen-based flame retardant because flame retardancy is improved. However, if the content of the nitrogen-based flame retardant in the flame retardant resin layer is excessively increased, the dielectric constant of the flame retardant resin layer may be increased. Moreover, the adhesive force with a conductor also falls. Therefore, the amount of the nitrogen-based flame retardant is preferably 30 parts by mass or less with respect to 100 parts by mass of the copolyester resin. From the viewpoint of lowering the dielectric constant, it is preferable to use only a phosphorus-based flame retardant.

  Halogen flame retardant Flame retardants include chlorine flame retardants such as chlorinated paraffin, chlorinated polyethylene, chlorinated polyphenyl, perchlorpentacyclodecane, ethylene bispentabromodiphenyl, tetrabromoethane, tetrabromobisphenol A, Examples of the brominated flame retardant include hexabromobenzene, decabromobiphenyl ether, tetrabromophthalic anhydride, polydibromophenylene oxide, hexabromocyclodecane, and ammonium bromide. Examples of the antimony flame retardant include antimony trioxide, antimony trichloride, antimony borate, and antimony molybdate. Examples of the metal hydroxide include magnesium hydroxide, aluminum hydroxide, and zirconium hydroxide.

  The above materials are mixed to obtain a resin composition. Furthermore, you may mix antioxidant, an antioxidant, a lubricant, a processing stabilizer, etc. with a resin composition as needed. After these materials are mixed using a known melt mixer such as a short-shaft extrusion mixer, a pressure kneader, or a Banbury mixer, a flame-retardant resin layer is produced by a method such as extrusion molding. Alternatively, a liquid obtained by dissolving the above resin composition in a solvent may be applied on a resin film and then dried to form a flame retardant resin layer.

  As the resin film, a resin material having excellent flexibility is used, and examples thereof include polyester resin, polyphenylene sulfide resin, and polyimide resin. Polyester resins include polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, polybutylene naphthalate resin, polytrimethylene terephthalate resin, polytrimethylene naphthalate resin, polycyclohexanedimethyl terephthalate resin, polycyclohexanedimethyl naphthalate polyarylate Examples thereof include resins. Among these resins, polyethylene terephthalate resin is preferably used as the resin film from the viewpoint of electrical characteristics, mechanical characteristics, cost, and the like. Moreover, it is preferable that the thickness of a resin film shall be 12-50 micrometers.

  It is preferable to have an anchor coat layer between the resin film and the flame retardant resin layer because the adhesive force between the resin film and the flame retardant resin layer is improved. Any material can be used for the anchor coat layer. For example, a urethane-based anchor coat material in which an isocyanate-based curing agent is mixed with a polyurethane resin as a main component can be preferably used. The thickness of the anchor coat layer is preferably 0.5 to 5 μm. An insulating film can be obtained by laminating the above materials.

  Next, the flat cable of the present invention will be described. FIG. 1 is a view showing an example of a flat cable using the insulating film of the present invention, and FIG. 2 is a cross-sectional view taken along the line A-A 'of FIG. Both sides of the flat rectangular conductor 1 are covered with an insulating film 5 composed of a flame retardant resin layer 2, a resin film 3 and an anchor coat layer 4. When manufacturing a flat cable, two insulating films 5 are placed on the outside of a plurality of conductors 1 so that the resin film 3 faces outside, and heated and pressurized using a known thermal laminator or a hot press device. The conductor 1 is bonded to the insulating film 5 and the insulating film 5 by processing. At this time, in the portion to be the end portion of the flat cable, the conductor 1 at the end portion can be exposed by making a hole in a part of the insulating film 5. A long flat cable can be obtained by continuously performing thermal lamination or hot pressing. Thereafter, it can be cut to a certain length to obtain a flat cable having an arbitrary length. Further, a shield layer may be provided outside the flat cable.

  As the conductor, a conductive metal such as copper, tin-plated annealed copper, or nickel-plated annealed copper can be used. The conductor preferably has a rectangular shape, and its thickness corresponds to the amount of current used, but is preferably 15 μm to 100 μm in consideration of the flexibility of the flat cable.

  Next, the present invention will be described based on examples and comparative examples. In addition, an Example does not limit the scope of the present invention.

(Examples 1 to 3, Comparative Example 1)
(Preparation of insulation film)
Urethane adhesive (trade name Takelac A-610, manufactured by Mitsui Chemicals Polyurethanes Co., Ltd.) and isocyanate curing agent (trade name Takenate A-50, manufactured by Mitsui Chemicals Polyurethanes Co., Ltd.) 10: 2 in terms of solid content. An anchor coating agent mixed at a ratio of 5% was prepared and applied to the surface of a biaxially stretched polyester film (Diafoil (registered trademark), thickness: 12 μm, manufactured by Mitsubishi Plastics, Inc.) subjected to corona treatment on the surface, and then dried. By removing the solvent, an anchor coat layer having a thickness of 3 μm was formed on the surface of the resin film.

  A material composition shown in Table 1 was added to a 33% toluene / methyl ethyl ketone solution of a polyester resin (Toyobo Co., Ltd., Byron (registered trademark) GK780), and mixed with a paint shaker to prepare a resin composition solution. In addition, the numerical value of the polyester resin in a table | surface is a solid content conversion amount. A resin composition solution was applied to the resin film having the anchor coat layer formed thereon so that the thickness after drying was 30 μm, and then dried to obtain an insulating film.

(Measurement of dielectric constant)
About the obtained insulating film, the dielectric constant at 1 kHz was measured by the method prescribed | regulated by ASTM standard D150-98 using the dielectric constant measuring device (Nippon Hewlett-Packard Co., Ltd. make, brand name 4276A LCZ meter).

(Flat cable production)
A tin-plated annealed copper foil (thickness 35 μm, width 0.3 mm), which is a conductor, is sandwiched between two insulating films in a state where 10 wires are arranged in parallel at a pitch of 0.5 mm. After covering both surfaces with an insulating film, the flat cable was produced by cutting into an arbitrary length.

(Measurement of characteristic impedance)
In order to evaluate the high-speed transmission characteristics of the produced flat cable, the characteristic impedance was measured with a network analyzer E8362B (frequency 1 GHz) manufactured by Agilent Technologies. The higher the characteristic impedance, the better the high-speed transmission characteristics.

(Flame retardance evaluation)
About the produced flat cable, the vertical combustion test prescribed | regulated to VW-1 of UL standard 1581 was done. More specifically, 10 flat cables are prepared, and after ignition, one or more of the 10 burned, the absorbent cotton placed under the flat cable burned by burning fallen objects, or the upper part of the flat cable The fired attached kraft paper was rejected, and the others were accepted.

(Adhesive strength evaluation)
The conductor adhesive force was measured using the produced flat cable. Specifically, the conductor (thickness 35 μm, width 0.3 mm) exposed at the end of the flat cable was pulled in the 180 ° direction, and the peel strength was measured. A peel strength of 20 g or more is regarded as an acceptable level. The results are shown in Table 1.

(footnote)
(1) ExolitOP935, manufactured by Clariant Japan
(2) Irganox 1010, manufactured by Ciba Specialty Chemicals Co., Ltd.
(3) Cross-linked styrene-acrylic copolymer resin SX866 (A) manufactured by JSR Corporation
(Average particle size 0.3 μm, hollow rate 30% by volume)
(4) Hollow silica BS-0340, manufactured by Denki Kagaku Kogyo Co., Ltd.
(Average particle size 3μm, hollow rate 40% by volume)
(5) Denki Kagaku Kogyo Co., Ltd., hollow silica BS-0660
(Average particle size 6μm, hollow rate 60% by volume)

  The dielectric constant of Comparative Example 1 to which hollow particles are not added is 3.80, whereas Examples 1 to 3 to which hollow particles are added have a low dielectric constant. It can also be seen that the higher the hollowness of the hollow particles, the lower the dielectric constant. Also, the value of the characteristic impedance increases as the hollow ratio increases. There is no difference in flame retardancy and adhesive strength between Examples and Comparative Examples, and it can be seen that the properties are not deteriorated even when hollow particles are added.

1 conductor 2 flame-retardant resin layer 3 resin film 4 anchor coat layer 5 insulating film 11 hollow particle 12 void portion of hollow particle 13 shell of hollow particle

Claims (5)

An insulating film in which a flame retardant resin layer is laminated on a resin film,
The flame retardant resin layer comprises 5 to 40 parts by mass of a hollow particle having an average particle size of 0.1 to 20 μm, phosphorous flame retardant, nitrogen flame retardant, metal, and 100 parts by mass of the copolyester resin. An insulating film comprising a resin composition containing 10 parts by mass or more and 100 parts by mass or less of one or more flame retardants selected from the group consisting of hydroxides, halogen flame retardants, and antimony flame retardants.   The insulating film according to claim 1, wherein the flame retardant is a phosphorus-based flame retardant.   The insulating film according to claim 1 or 2, wherein a hollow ratio of the hollow particles is 25% by volume or more.   The insulating film according to any one of claims 1 to 3, further comprising an anchor coat layer between the resin film and the flame-retardant resin layer.   The flat cable which used the insulating film of any one of Claims 1-4 as a coating | covering material.

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