JPH04271603A - Spiral coil - Google Patents

Abstract

PURPOSE:To realize the spiral coil with small size whose operation is stable and which is inexpensively mass-produced as the antenna coil used for a contactless individual object recognition card. CONSTITUTION:A pillar 4 obtained by winding a metallic foil layer 2 and an adhesive insulation layer 3 alternately in spiral onto a circumferential face of an insulating round or square pillar core member 1 and adhering and integrating them is sliced almost at a right angle to the axial direction of the said core member 1.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is directed to radio frequency (RF)
Individual recognition using electromagnetic waves in the band
It is used as a high-performance and inexpensive antenna coil built into an individual recognition card (hereinafter referred to as RF-ID card) for a non-contact type automatic identification system (hereinafter referred to as RF-ID system) using technology. Regarding spiral coils.

0002

[Prior Art] Automatic recognition technologies used in entry/exit control systems, automatic ticket gate systems, automatic logistics recognition systems, etc. include OCR (optical character reading) methods that identify patterns of characters and symbols, and patterns from television cameras. There are two methods that directly recognize the object, such as a machine vision method that processes image data that cannot be converted into a digital image using software, and a method that recognizes the object by reading signs attached to the object such as barcode methods and magnetic stripe card methods. There are methods for determining objects, and the latter is often used from the viewpoint of automatic recognition, but the above-mentioned RF-ID system has recently been developed and its use has begun.

[0003] This RF-ID system is divided into an RF-ID card that carries data and a device that reads and writes data.The RF-ID card is composed of an antenna coil, a modulation/demodulation circuit, a memory IC, and a control circuit. The read/write device has a head that integrates an antenna and a modulation/demodulation circuit,
It consists of a controller that exchanges data with a host computer system through a communication circuit.

The above-mentioned RF-ID card is a plastic package containing the above-mentioned antenna coil, memory IC, etc., and is capable of data communication using an electromagnetic induction method using weak electromagnetic waves. That is, R.F.
- When an ID card is brought close to a dedicated automatic recognition device (hereinafter referred to as a reader), it is sensitive to electromagnetic waves of 100 to 400 kHz in the RF band generated by the device, and an electromotive force is induced in the antenna coil and the memory is activated. Drive the IC. Conversely, when a data signal current previously written in the memory IC flows through the antenna coil, magnetic flux is generated by electromagnetic induction and is sent to a reading device and recognized.

[0005] However, in addition to the feature of non-contact data recognition, the RF-ID system has the feature that both the RF-ID card and the reader can be made into a sealed system. , unaffected by the environment such as dust. (b) Data can be written on site. In addition, compared to magnetic stripe card systems, (c) the processing speed of inserting and removing cards into and out of devices does not become a bottleneck. (d) Data is not erased due to the influence of magnetism. Because of these features, reading devices can be linked with gates, automatic doors, electronic locks, etc. to control entry and exit of factories, offices, condominiums, hotels, amusement parks, ski resort lift gates, parking lots, etc., and use employee ID cards. , application to identification cards such as membership cards and student ID cards is being considered, and is beginning to be used in some cases.

[0006] This RF-ID card has external dimensions of JI
Credit card with magnetic stripe (hereinafter referred to as JIS card) standard of S
68~0.80mm, long side 85.47~85.72m
The above-mentioned antenna coil, memory IC, etc. are packaged in plastic so as to satisfy the requirements of 53.92 to 54.03 mm on the short side. A wire coil made by winding several hundred turns of electric wire (hereinafter collectively referred to as enamelled wire), which has a thermosetting resin or thermoplastic resin baked onto it, and is called a formal wire, polyurethane wire, polyester wire, etc. depending on the type of baked resin. Also used are printed coils in which a coil pattern is formed on a thin printed circuit board by a printing etching method, a photo etching method, or the like.

[0007]

Therefore, the characteristics required for the above antenna coil are that it should fit within the above card dimensions, have an inductance L of 1 to 3 mH or more, and a coil resistance of 200 to 300 Ω or less. The inductance L determines the operating distance, that is, the sensitivity, when the RF-ID card is brought close to the reader, and according to experiments, it is approximately 200 mm at 50 mH, and 5 m
It was about 100 mm at H, and about 50 mm at 1.5 mH. If the coil resistance is large, Q (a value representing the sharpness of resonance of the vibration system) becomes small, so it is preferable to set the upper limit to about 1 kΩ.

When this antenna coil is manufactured using the wire-wound coil method described above, since the inductance L is proportional to the outer diameter of the wire-wound coil, it is necessary to use an air-core coil with an outer diameter as large as possible. Processing irregularly shaped wire windings requires special technology, so the number of contract manufacturers is limited. ■To obtain an inductance L of 1 to 3 mH or more, approximately 2
00 turns or more is required, but since several layers overlap in the winding process, due to card thickness constraints, the diameter of 5 turns is required.
It is necessary to use a thin enameled wire of 0 to 60 μm,
Product efficiency decreases due to wire breakage during work. ■It is very difficult to solder the terminals of the thin enameled wire of the winding coil. ■This coil has drawbacks such as a high defective rate due to winding irregularities during transportation.

[0009] In addition, when creating an antenna coil by the above printed coil method, the pattern pitch is 0.2 m.
Since the limit is 100 turns for a single-sided board due to card size constraints, it is necessary to fabricate a double-sided through-hole board. Obtaining such a fine pattern requires many processes such as photomask production → photoresist coating → exposure → development → etching → resist peeling. Moreover, since the above processes are performed on both sides of the substrate, it is necessary to It has the disadvantage that it is very expensive compared to other methods, and when forming a fine rectangular spiral pattern, there is also the disadvantage that the corner portions of the pattern are easily broken during etching. The present invention
In addition to the above-mentioned problems, the present invention provides an antenna coil that can solve problems such as mass productivity and manufacturing cost that could not be solved by conventional manufacturing methods.

0010

[Means for Solving the Problems] As shown in FIGS. 1(a), (b), and 2, the spiral coil of the present invention includes a metal foil layer on the circumferential surface of an insulating cylindrical or prismatic core 1. 2 and an adhesive insulating layer 3 are alternately wound spirally in multiple layers and bonded together, and a columnar body 4 is sliced perpendicular to the axial direction of the core material 1.

Materials for the metal foil of the present invention include copper, zinc, tin, solder, titanium, beryllium copper, stainless steel, brass, bronze, phosphor bronze, nickel silver, aluminum, nickel,
iron, gold, silver, platinum, palladium, tantalum, nichrome,
Examples include niobium, which has low electrical resistance and is inexpensive.
In consideration of mechanical strength, availability, etc., it is most preferable to use copper.

[0012] The thickness of the foil should be 10 to 100 μm because if it is too thin, the mechanical strength will be low and handling workability will be poor, and if it is too thick, the spiral pitch will become large and the outer circumference after 200 turns will not fit within the card dimensions. It is best to use a thickness in the range of 18 to 35 μm, which is commonly used for electrical applications.

[0013] The adhesive insulating layer is formed by forming a thermoplastic or thermosetting adhesive into a film, or by coating a non-adhesive film base material such as a polyester film with a thermoplastic or thermosetting adhesive. However, if the film base material is coated with an adhesive, it will be thicker and the spiral pitch will become larger as mentioned in the case of metal foil, so it is more preferable to use an adhesive alone.

[0014] Examples of the thermoplastic adhesive include copolyester adhesives, polyamide adhesives, polyvinyl acetate adhesives, polyvinyl alcohol adhesives, polyvinyl chloride adhesives, and vinyl chloride-vinyl acetate copolymer adhesives. Examples include adhesives based on ethylene-vinyl acetate copolymers, adhesives based on styrene-isoprene-styrene copolymers, adhesives based on styrene-butadiene-styrene copolymers, and the like.

Thermosetting adhesives include epoxy resin adhesives, phenolic resin adhesives, resorcinol resin adhesives, urea resin adhesives, melamine resin adhesives, polyurethane adhesives, and natural rubber adhesives. Examples include recycled rubber adhesives, nitrile rubber adhesives, chloroprene rubber adhesives, styrene-butadiene rubber adhesives, butyl rubber adhesives, silicone rubber adhesives, and the like. Among the above, silicone rubber adhesives have excellent heat resistance and electrical properties, as well as rubber elasticity, so silicone rubber adhesives have a columnar body that is integrated with metal foil alternately wound in multiple spirals around the circumferential surface of a columnar core material. It is most preferable to use a silicone rubber adhesive because it can be easily sliced thinly with a rotating blade perpendicular to the axial direction of the core material.

[0016] This adhesive layer is preferably topping or coating a metal foil, and after volatilizing a solvent-containing agent as necessary, it is preferably wound spirally around a core material and integrated. The thickness of this adhesive layer is in the range of 10 to 100 μm, preferably 20 to 100 μm, because if it is too thin, pinholes will easily occur and poor insulation will occur between the metal foils, and if it is too thick, the spiral pitch will become too large as described above. The range is preferably 50 μm.

[0017] The core material of the present invention may be any material as long as it can be easily cut with a rotary blade, but in addition to prismatic or cylindrical pillars made by cutting lumber, prismatic or cylindrical pillars molded from a rubber material such as silicone rubber, etc. Examples include the use of paper tubes, PVC pipes, polyethylene pipes, etc. Examples of the slicing method of the present invention include the use of an internal slicing machine using a diamond blade or an external slicing machine using a cemented carbide blade. In the present invention, the slice thickness may satisfy the JIS card thickness considering the thickness of the plastic package, but if it is too thin, the coil resistance will increase and the Q will decrease. It is preferable to set it as a range. The process of taking out terminals from the inside and outside of the spiral coil of the present invention can be easily carried out by soldering thin enameled wires.

[0018]

[Example] Electrolytic copper foil with a thickness of 18 μm and a width of 100 mm,
Solvent-free addition type vulcanized self-adhesive silicone RTV
Rubber, KE1800 (A, B, C) RTV (manufactured by Shin-Etsu Chemical Co., Ltd., trade name) was coated using a comma roll coater so that the thickness after vulcanization and curing was 15 μm, and this was Inch paper tube (inner diameter 25.4 mm, outer diameter 3
5 mm) and heat-treated at 150° C. for 1 hour to vulcanize the silicone rubber layer and bond and integrate the copper foil layer and silicone rubber layer to form a columnar body.

The above spiral roll columnar body was sliced using an internal slicing machine, model ASM-10C (manufactured by Okamoto Machine Tools Co., Ltd., trade name), into a round shape with a thickness of 0.2 mm. I got a spiral coil. The terminals of this spiral coil were processed by soldering enamelled wires with a diameter of 60 μm.

[0020] This round spiral coil has an inner diameter D2
=35mm, spiral pitch P=0.0033cm,
Number of turns N200, outer diameter D1 = 48.2mm,
Since the volume resistivity ρ of copper is 1.724×10-6 Ω・cm, the total resistance R=ρ×π×N×[D
2 + (N+1)×P]/(0.0018×0.02)
= 125Ω, but when checked with a commercially available tester, almost identical values were obtained. Also, the inductance L of the round spiral coil is a = (D1 + D2)/4 [
mm], c=(D1 - D2)/2 [mm], L=32×10-6×a2×N2/(6×a+
10×c) [mH] and is calculated to be 2.9 mH, but it is actually about 3 mH when measured using a commercially available 4274A multi-frequency LCR meter (manufactured by Yokogawa Hewlett-Packard Co., Ltd., trade name). was gotten. Since the spiral coil has a thickness of 0.2 mm and a diameter of 48.2 mm, it can be fully accommodated within the JIS card standard.

[0021]

[Effects of the Invention] The spiral coil of the present invention is easy to process, does not require any special technology, has good mass productivity, good yield, and low manufacturing cost, has high mechanical strength, and can be transported not only during use. It is extremely useful industrially as it does not produce any defective products.

[Brief explanation of the drawing]

FIG. 1(a) is a perspective view of a columnar body before slicing to obtain a round spiral coil of the present invention, and FIG. 1(b) is a perspective view of the round spiral coil after slicing.

FIG. 2 is a perspective view of a rectangular spiral coil of the present invention.

[Explanation of symbols]

1 Heartwood, 2 Metal foil layer, 3 Adhesive insulating layer, 4 Column.

Claims (1)

[Claims] Claim 1: A columnar body obtained by alternately winding metal foil layers and adhesive insulating layers multiple times in a spiral shape and bonding them together on the circumferential surface of an insulating columnar core material, at approximately right angles to the axial direction of the core material. A spiral coil that is characterized by being sliced into .