JP2020113848A - Laminated antenna and manufacturing method thereof - Google Patents

Abstract

To provide a thin laminated antenna indicating high inductance, which is made of an inexpensive material, and a manufacturing method thereof.SOLUTION: A laminated antenna 1 is configured by laminating wiring patterns 13-1, 13-2, 13-3, 13-4, and 13-5 formed by a conductive paste, and insulating coating layers 14-1, 14-2, 14-1, 14-3, and 14-4 having through holes 15-1, 15-2, and 15-13 on one side of an insulating substrate 11. The insulating coat layers 14-1, 14-2, 14-1, 14-3, and 14-4 are formed of a polyester resin, a plate-like inorganic filler, fumed silica, rubber phase, and an epoxy resin.SELECTED DRAWING: Figure 1

Description

The present invention relates to a laminated antenna obtained by laminating a wiring pattern formed of a plurality of conductive pastes on one surface of an insulating substrate with an insulating coat interposed therebetween.

2. Description of the Related Art In recent years, the demand for thin antenna parts has increased due to the development of wireless communication technology, and the use of a small antenna device in a communication terminal device used in NFC (Near Field Communication), a small radio, or the like. Is proposed.

Generally, these antennas are manufactured by a subtractive method in which a copper foil laminated on an insulating substrate is patterned using a photoresist and an etchant, but the process is long and complicated, and a large amount of waste is generated.

Also, in the electromagnetic induction type and electromagnetic transfer type antennas, multiple antenna patterns are arranged orthogonally to perform position detection, so multiple antennas are low cost, simple, short, and with less waste. A manufacturable antenna is desired.

Also, as an antenna for wireless communication such as RFID, an antenna pattern is often formed on a PET film or the like, and since these cannot be used in a metal environment, it is a patent as an IC card that can be used in a metal environment. What is laminated with a magnetic material as in Reference 1 is used. This is for the purpose of suppressing the influence of metal by the magnetic substance and improving the coupling coefficient with the antenna of the reader/writer.

The communication characteristic of a magnetic antenna having a magnetic body and a conductor is represented by a quality factor (hereinafter also referred to as Q) as an index. Here, Q is represented by Q=2π×f×L/R (f: communication frequency L: inductance R: resistance). Since the electromagnetic induction effect is used, the inductance (L) is large and the resistance (R) is It is required to be small.

In a magnetic material antenna, when a current is applied to the antenna pattern, the current concentrates on the surface of the pattern conductor, so it is desirable that the magnetic material and the pattern line are close to each other. Therefore, in order to bring the patterned conductor and the magnetic material as close to each other as possible, it is desirable to make the base material, which is a carrier on which the conductor is provided, as thin as possible. Further, it is important to reduce the resistance of the conductor in order to increase Q.

The communication characteristics of the magnetic antenna are η=k×Q1×Q2, (k: coupling coefficient of transmitting/receiving antenna, Q1: Q of transmitting antenna, Q2: receiving antenna) with communication sensitivity η as another index. It is represented by Q).

However, the conventional manufacturing method for obtaining such a magnetic antenna has a drawback that it requires a long process. Then, in order to bring the surface of the antenna pattern conductor and the magnetic material as close to each other as possible, it is required to make the carrier base material thin as described above, but the thin carrier base material has a drawback that the process passability is deteriorated.

Patent Document 2 discloses a printed circuit board in which a conductor material is pattern-printed on a substrate, an insulating material is pattern-printed thereon, and this step is repeated if necessary. However, in order to form an insulating layer having a sufficient insulating property by pattern printing, there are problems such as thickening the layer and using an expensive resin.

For example, Patent Document 3 discloses a thermosetting resin composition of a polyurethane resin having a carboxylic acid group in a side chain and an epoxy resin as an insulating material. Patent Document 4 discloses a shock-resistant insulating composition in which rubber fine particles or an epoxy resin in which rubber fine particles are dispersed is dispersed in an epoxy curing system. Patent Document 5 discloses application of an acid-modified polyester resin and an epoxy resin to an adhesive for circuit boards.

However, further improvement in the mechanical properties of the insulating layers between layers, which is required when forming a multilayer laminated structure, is desired, and is still insufficient.

JP, 2005-117174, A JP, 10-112586, A JP, 2006-274258, A Japanese Unexamined Patent Publication No. 9-40751 JP, 2006-137793, A

The present invention provides a laminated antenna in which a wiring pattern is provided on one surface of an insulating substrate, which has a high inductance by using an inexpensive material and which is miniaturized and has high performance by laminating a plurality of wiring patterns. The purpose is to provide.

Another object of the present invention is to provide a method for manufacturing the laminated antenna at a low cost with a smaller number of steps than the conventional manufacturing method.

The present inventor has completed the present invention as a result of intensive studies to solve the above problems. That is, the present invention is as follows.

According to the present invention, a laminated antenna in which a plurality of wiring patterns formed of a conductive paste are laminated on one surface of an insulating substrate with an insulating coat layer having a through hole interposed therebetween, and the wiring patterns are connected through the through hole. The insulating coating layer is a cured product of a resin containing the following (A) to (E).
(A) Polyester resin (B) Plate-shaped inorganic filler (C) Fumed silica (D) Rubber phase (E) Epoxy resin

Moreover, in the laminated antenna of the present invention, the acid value of the polyester resin used is preferably 800 to 2500 equivalents per ton of resin.

Further, in the laminated antenna of the present invention, the conductive paste used preferably contains conductive particles, a binder resin and a solvent, and the conductive particles contain copper or copper as a main component.

Further, in the laminated antenna of the present invention, the wiring pattern is preferably a plane spiral coil pattern, and the coil patterns are connected through a through hole to form an antenna coil.

Further, in the laminated antenna of the present invention, the insulating base is preferably a magnetic body.

Further, in the laminated antenna of the present invention, the insulating substrate is preferably a resin film.

Further, in the laminated antenna of the present invention, the wiring pattern is preferably formed on the insulating substrate with the adhesive layer interposed therebetween.

Further, in the laminated antenna of the present invention, the heat loss after curing the adhesive layer is preferably 25% by weight or less in 10 minutes at 300° C. under superheated steam atmosphere.

According to the present invention, a wiring pattern is formed on one surface of an insulating substrate by printing a conductive paste, and an insulating coating agent containing the following (A) to (E) is printed to form an opening to be a through hole on the wiring pattern. A method of manufacturing a laminated antenna, comprising forming a pattern of an insulating coat layer which is provided, and forming a wiring pattern including filling of through holes by printing a conductive paste on the insulating coat layer.
(A) polyester resin,
(B) plate-like inorganic filler,
(C) fumed silica,
(D) Rubber phase (E) Epoxy resin

Further, the present invention is preferably a method for manufacturing a laminated antenna in which a conductive paste is heat-treated at 130° C. or higher to form a wiring pattern.

Further, the present invention is preferably a method for producing a laminated antenna in which an insulating coating agent is cured by heat treatment at 120° C. or higher to form an insulating coating layer.

The laminated antenna of the present invention is thin, compact, and capable of high performance because the wiring pattern and the insulating coating layer having a predetermined composition having a through hole are formed and laminated by printing.

Further, when a laminated antenna is formed on one surface of an insulating base made of a magnetic material, the magnetic material can suppress the influence of metal to improve the coupling coefficient with the antenna of the reader/writer, and to obtain an antenna that can be used even in a metal environment. Is possible.

Further, according to the method for manufacturing a laminated antenna of the present invention, it is possible to manufacture the laminated antenna with a smaller number of steps and at a lower cost than the conventional method.

It is a schematic cross section of the laminated antenna of one embodiment of the present invention. It is a schematic cross section of the laminated antenna of one embodiment of the present invention. It is a schematic cross section of the laminated antenna of one embodiment of the present invention. It is a SEM photograph of the cross section of the laminated antenna of this invention. It is a SEM photograph of the section of the insulation coat layer of the lamination antenna of the present invention.

Hereinafter, the present invention will be described with reference to the drawings. In the drawing, illustrations of external connection terminals, communication processing circuits, and the like are omitted. The present invention is not limited to the embodiments below.

FIG. 1 is a partial sectional view of a laminated antenna according to an embodiment of the present invention. According to the present invention, a plurality of wiring patterns 13 made of a conductive paste are laminated on one surface of the insulating substrate 11 if necessary with an adhesive layer 12 sandwiching an insulating coat layer 14 having a through hole 15, and the wiring pattern 13 is formed through. It is a laminated antenna connected through a hole 15. In order to manufacture the laminated antenna 1 of this embodiment, after the adhesive layer 12 is formed on one surface of the insulating substrate 11, the wiring pattern 13-1 is formed by printing a conductive paste, and the through hole 15-1 is removed. An insulating coating layer 14-1 is formed by printing an insulating coating agent so as to cover the wiring pattern 13-1, and a wiring pattern 13-2 is formed on the insulating coating layer 14-1 by printing a conductive paste. The through hole 15-1 can be filled with a conductive paste together with the formation of the wiring pattern 13-2, and the wiring patterns 13-1 and 13-2 are electrically connected. An insulating coat layer and a wiring pattern are further laminated on the wiring pattern 13-2 by the same method to form a laminated antenna having a predetermined structure having antenna coils 16A and 16B. In the present embodiment, a laminated antenna in which two or more independent antennas that are magnetically coupled are laminated, and if the insulating substrate is a magnetic body, the antenna can be used even in a metal environment.

FIG. 2 is a partial cross-sectional view of the laminated antenna according to the embodiment of the present invention. In order to manufacture the laminated antenna 2 of the present embodiment, the wiring pattern 23-1 is formed on the insulating substrate 21 provided with the adhesive layer 22 if necessary, and the insulating coat layer and the wiring pattern are further laminated by the same method. A laminated antenna having a predetermined structure having an antenna coil 26 is used. In the present embodiment, it is possible to provide a multilayer wiring by printing on one surface of the substrate, and since a base material such as a film is not required between the wirings to be laminated, it is possible to reduce the size and performance of the antenna. Since the step of providing a through hole in the base material is also unnecessary, the number of steps can be reduced.

FIG. 3 is a partial cross-sectional view of a laminated antenna according to an embodiment of the present invention, which has a structure in which a magnetic material 37 is attached to an insulating substrate 31 made of a resin film of the laminated antenna 2 shown in FIG. Is a laminated antenna 3 having. According to this embodiment, the laminated antenna of the present invention can be used even in a metal environment.

FIG. 4 is a SEM photograph of a cross section of the laminated antenna of the present invention. From the bottom, a magnetic body (ferrite sintered body), an adhesive layer, a wiring pattern in which conductive particles are sintered, an insulating coat layer, and a wiring pattern are laminated again in this order.

FIG. 5 is a SEM photograph of a cross section of the insulating coating layer of the laminated antenna of the present invention. In the photography of this photograph, in order to observe the distribution of the rubber phase having no contrast with the resin, the surface is etched with toluene to elute the rubber phase. It can be confirmed that the plate-like inorganic filler (kaolin), fumed silica, and particulate rubber phase are dispersed and present in the insulating coat layer.

Hereinafter, each component will be described in detail.

In the laminated antenna according to the present invention, the wiring pattern and the insulating coat layer are laminated on the insulating substrate.

First, the insulating substrate will be described.

The insulating substrate is preferably sheet-shaped from the viewpoint of thinning the antenna component, and a magnetic material, a resin film, or the like can be used depending on the desired function.

The magnetic material used in the present invention is preferably a soft magnetic material having a large magnetic permeability real part (μ′) and a small magnetic permeability imaginary part (μ″) at a frequency used. A sheet is prepared by mixing a metal soft magnetic powder with a resin. It is preferable to use a sheet-shaped product, a sintered sheet of spinel magnetic ferrite or the like, or a composite magnetic sheet in which a resin film is attached to the sintered sheet to give flexibility. When used, Ni-Zn ferrite or the like is preferable.

In the present invention, the Ni-Zn ferrite-based sintered ferrite sheet obtained by the green sheet method is preferable because the wiring pattern is heat-treated to make it conductive. Although not limited, the sheet thickness is preferably 50 to 300 μm.

The resin film used in the present invention must be resistant to heat treatment. Examples thereof include a polyimide resin sheet or film, an aromatic polyamide resin sheet or film, or a glass epoxy laminated plate, and among them, a polyimide resin sheet or film is preferable.

Examples of the polyimide-based resin include a polyimide precursor resin, a solvent-soluble polyimide resin, and a polyamideimide resin. The polyimide resin can be polymerized by a usual method. For example, in a solution of a tetracarboxylic dianhydride and a diamine, a method of obtaining a polyimide precursor solution by reacting at a low temperature, a method of reacting a tetracarboxylic dianhydride and a diamine in a solution to obtain a solvent-soluble polyimide solution, a raw material There is a method using an isocyanate as the above, a method using an acid chloride as a raw material, and the like.

Next, the wiring pattern will be described.

In the present invention, the wiring pattern is formed by the conductive paste on the insulating substrate or the insulating coat layer. The wiring pattern may be a wiring forming an antenna, may be filled in a through hole, may form a terminal, or may be formed in a pattern or on an arbitrary place.

The wiring forming the antenna is a wiring formed on one plane where all or a part of the antenna coil is formed, and is preferably a plane spiral coil pattern. The coil pattern on each plane may be an antenna coil that is electrically independent of the coils on other planes, and the coils formed on a plurality of planes are connected through through holes provided in the insulating coat layer. Although it may be an antenna coil, it is preferable that a plurality of planar spiral coil patterns are connected to each other through a through hole provided in the insulating coat layer to form the antenna coil. In addition, a plurality of coils may be provided on one plane and each may form another antenna coil.

The thickness of the wiring pattern is determined mainly by the required conductivity, but is preferably 0.05 to 100 μm. If the thickness of the wiring pattern is less than 0.05 μm, sufficient conductivity may not be obtained, and if it exceeds 100 μm, the pattern is defective due to bumping of the solvent remaining in the pattern during heat treatment. This is not preferable from the viewpoint of thinning the antenna. The thickness of the wiring pattern is more preferably 0.2 to 50 μm. The thickness of the wiring pattern is more preferably 5 to 50 μm in order to obtain a sufficiently small coil resistance.

The conductive paste used in the present invention is one in which a conductive alloy powder and a binder resin are dispersed as main components in a solvent, and after printing a wiring pattern, high conductivity is exhibited by sintering by heat treatment. However, it is not particularly limited as long as it exhibits a sufficiently low resistance.

Examples of the conductive particles used in the conductive paste include metals such as gold, silver, copper, nickel and aluminum. Among them, the conductive particles forming the conductive paste used in the present invention are preferably copper or metal particles containing copper as a main component, and the proportion of copper may be a copper alloy having a weight ratio of 80% by weight or more. The surface may be coated with silver. The silver coating on the copper powder may be complete or may be a coating in which a part of copper is exposed. Further, the copper powder may have an oxide film on the surface of its particles to the extent that conductivity is not impaired. The shape of the copper powder may be substantially spherical, dendritic, flake-shaped or the like. As the copper powder or the copper alloy powder, wet copper powder, electrolytic copper powder, atomized copper powder, vapor-phase reduced copper powder and the like can be used.

The conductive paste used in the present invention preferably contains copper powder of 1 μm or less in order to improve conductivity by heat treatment. The copper powder used in the embodiment of the present invention has an average particle size of 0.01 to 20 μm. When the average particle size of the copper powder is larger than 20 μm, it becomes difficult to form a fine wiring pattern on the insulating substrate. If the average particle size is smaller than 0.01 μm, distortion due to fusion between the fine particles during heat treatment will increase, and the adhesion to the substrate will decrease. The average particle size of the copper powder is more preferably in the range of 0.02 μm to 15 μm, still more preferably 0.04 to 4 μm, and even more preferably 0.1 to 2 μm. The copper powder used in the present invention may be a mixture of two or more kinds of copper powders having different particle diameters as long as the average particle diameter is 0.01 to 20 μm. Particularly, in the case of a copper paste for screen printing, it is preferable to use a powder of 0.05 to 0.5 μm and a powder of 1 to 10 μm in a mixture for the purpose of imparting fluidity characteristics, and non-spherical particles of 1 to 10 μm size. Is more preferable, and the compounding ratio of the non-spherical particles of micron size is more preferably 10 to 60% by weight of the total copper powder.

The optimum range of heat treatment conditions for the conductive paste varies depending on the conductivity target, metal powder characteristics, and binder resin. The temperature of the heat treatment is 130° C. or higher, preferably 250° C. or higher, more preferably 300° C. or higher. The upper limit temperature of the heat treatment varies depending on the material used, but is preferably 400° C. or lower due to deterioration of the binder resin and the like. The heat treatment time is 10 seconds to 10 minutes, more preferably 20 seconds to 5 minutes. As a heat treatment method, superheated steam treatment is preferable because it has high heating efficiency and can suppress deterioration of adhesion due to treatment at high temperature. Further, the superheated steam treatment is preferable in order to shorten the treatment time required for reducing the oxide on the surface of the copper powder and to obtain sufficiently high conductivity. The superheated steam treatment is steam which has a larger heat capacity, a larger heat capacity and a higher specific heat than air, and further heats saturated steam to raise its temperature.

The conductive paste used in the present invention uses a polymer compound as a binder resin. A conductive paste containing a polymer compound as a binder resin is known as a polymer type conductive paste. The polymer-type conductive paste can secure the fixing of the conductive particles and the adhesiveness to the base material by the binder resin, but the binder resin hinders the contact between the conductive particles and deteriorates the conductivity. However, when the ratio of the conductive particles is increased and the binder resin ratio is decreased, not only the adhesiveness with the substrate is deteriorated but also the wiring pattern becomes brittle, the flex resistance is deteriorated, and the durability is deteriorated. Therefore, in the present invention, the ratio of the conductive particles in the conductive paste is preferably 90% by weight to 98% by weight.

The solvent used for the conductive paste used in the present invention may be an organic compound or water as long as it dissolves the binder resin. The solvent has the role of adjusting the viscosity of the dispersion in addition to the role of dispersing the copper powder in the conductive paste. Examples of organic solvents include alcohols, ethers, ketones, esters, aromatic hydrocarbons, amides and the like.

Examples of the binder resin used in the conductive paste used in the present invention include resins such as polyester, polyurethane, polycarbonate, polyether, polyamide, polyamideimide, polyimide and acrylic. It is preferable that the resin has an ester bond, a urethane bond, an amide bond, an ether bond, an imide bond or the like in its main chain from the viewpoint of the stability of the copper powder.

The ratio of each component of the conductive paste used in the present invention is preferably in the range of 5 to 400 parts by weight of solvent and 0.5 to 20 parts by weight of binder resin to 100 parts by weight of conductive particles. When the amount of the binder resin in the conductive paste is less than 0.5 parts by weight with respect to 100 parts by weight of copper powder, the adhesiveness to the substrate is significantly deteriorated, which is not preferable. On the other hand, if the amount of the binder resin exceeds 20 parts by weight, it is not possible to secure conductivity because the chance of contact between the conductive particles is reduced. The binder resin is more preferably 1 to 6 parts by weight, further preferably 2 to 5 parts by weight.

In the conductive paste used in the present invention, the ratio of conductive particles in the total nonvolatile content (conductive particle content ratio) is preferably 94% by weight or more, and more preferably 96% by weight or more. Here, the non-volatile component is a component of the conductive paste other than the volatile solvent, and is a conductive particle, a binder resin, a filler, a curing agent, a dispersant, or the like. The conductivity can be increased by increasing the ratio of the conductive particles in the total nonvolatile content. If the proportion of conductive particles in the total nonvolatile content is less than 94% by weight, the effect of improving conductivity is poor. The upper limit of the proportion of conductive particles in the total nonvolatile content varies depending on the binder resin used, but is preferably 99% by weight, more preferably 98% by weight.

When the proportion of the conductive particles in the total nonvolatile content is increased, a small amount of the binder resin allows the binder resin to have a required function. Therefore, the binder resin having a higher molecular weight is preferable. Although the desirable molecular weight varies depending on the type of binder resin, the number average molecular weight of polyester, polyurethane or polycarbonate is 10,000 or more, preferably 20,000 or more. The upper limit of the molecular weight of the binder resin is about 500,000 due to the viscosity of the dispersion and the like.

It is necessary for the conductive particles to maintain a good dispersed state in the conductive paste in order to exhibit good conductivity. In order to provide the binder resin with a necessary function with a small amount of the binder resin, the binder resin may contain a polymer having a functional group capable of adsorbing to a metal such as a sulfonate group or a carboxylate group. desirable.

The inclusion of a sulfonate group is represented by the sulfur content in the binder resin, and the sulfur content in the binder resin is preferably 0.05 to 3% by weight, more preferably 0.1 to 1% by weight. is there. The carboxylic acid group is contained as the original carboxylic acid group in an amount of preferably 30 to 500 mol, and more preferably 50 to 200 mol, per ton of the binder resin.

A curing agent may be added to the conductive paste used in the present invention, if necessary. Examples of the curing agent that can be used in the present invention include phenol resins, amino resins, isocyanate compounds, epoxy resins, oxetane compounds, and maleimide compounds. The amount of the curing agent used is preferably in the range of 1 to 50% by weight of the binder resin, more preferably 1 to 20% by weight.

The conductive paste used in the present invention may contain a dispersant. Examples of the dispersant include higher fatty acids such as stearic acid, oleic acid and myristic acid, fatty acid amides, fatty acid metal salts, phosphoric acid esters and sulfonic acid esters. The amount of the dispersant used is preferably in the range of 0.1 to 10% by weight of the binder resin.

As a method of obtaining the conductive paste, a general method of dispersing powder in a liquid can be used. For example, a mixture of conductive particles, a binder resin solution and, if necessary, an additional solvent may be mixed and then dispersed by an ultrasonic method, a mixer method, a three-roll method, a ball mill method or the like. It is also possible to perform a dispersion by combining a plurality of these dispersion means. These dispersion treatments may be performed at room temperature, or may be performed by heating in order to reduce the viscosity of the dispersion.

Next, the insulating coat layer will be described.

In the present invention, the insulating coating layer is a layer formed by an insulating coating agent between a plurality of wiring patterns, and includes a polyester resin (A), a plate-like inorganic filler (B), fumed silica (C), a rubber phase (D). ) And a cured product of a resin containing an epoxy resin (E). Through holes are provided in the insulating coat layer, and the wiring patterns are connected through the through holes.

The thickness of the insulation coating layer provided in the present invention is determined by the specifications of the product incorporating the multilayer circuit board, but the thickness after drying after evaporation of the solvent is preferably 25 μm or less in view of insulation properties and durability. it can. If the thickness of the insulating coat layer exceeds 25 μm, the step difference with the non-coated portion becomes large, and cracks may occur at the step portion in the wiring pattern formed on the insulating coat layer. The thickness of the insulating coat layer is preferably 5 to 23 μm, more preferably 8 to 20 μm, and further preferably 10 to 18 μm. If the thickness of the insulating coat layer is less than 5 μm, the insulating property may be unstable, and the durability under high temperature and high humidity may be poor. The thickness of the insulating coat layer is measured at the flat portion without the wiring pattern. The insulating coating layer on the wiring pattern may become thinner than the flat portion due to the sagging of the coating agent. However, if the insulating coating layer is formed with the above-mentioned thickness, the upper and lower wiring patterns are sufficiently insulated.

The insulating coat layer in the present invention is provided with through holes by pattern printing when connecting the wiring patterns which are stacked one above the other with the insulating coat layer interposed therebetween. It is preferable to reduce the volume of the through hole portion so that the copper paste can be filled in the through hole portion at the same time when the wiring pattern is printed. When the diameter of the through hole is in the range of 100 to 1000 μm, the copper paste can be filled in the through hole at the same time as printing when the thickness of the insulating coat layer is 25 μm or less. If the diameter and thickness of the through hole portion are within the above ranges, it is not always necessary to newly provide a step of filling the through hole portion with the copper paste.

Since the insulating coat layer provided in the present invention has excellent adhesiveness to the conductive layer and heat resistance, it is effective in preventing dielectric breakdown due to sintering of the wiring pattern provided on the insulating coat layer.

The insulating coating agent used in the present invention contains a polyester resin (A), a plate-like inorganic filler (B), fumed silica (C), a rubber phase (D) and an epoxy resin (E).

The polyester resin (A) is preferably a highly oxidized polyester having an acid value of 800 to 2500 equivalents per ton of resin, more preferably 1000 to 2300 equivalents, and further preferably 1100 to 2100 equivalents.

Further, the number average molecular weight of the polyester resin (A) is preferably 5,000 to 30,000.

The polyester resin (A) is preferably a reaction product of polyester diol and/or polycarbonate diol and tetracarboxylic dianhydride. The reaction product of polyester diol and/or polycarbonate diol and tetracarboxylic dianhydride is preferably a polyester diol and/or polycarbonate diol having a number average molecular weight of 500 to 5000, more preferably 700 to 2000, and a tetracarboxylic acid. It is the product of a chain extension reaction involving the formation of an ester bond and a carboxylic acid group by reaction with an acid dianhydride group. The molecular weight and acid value are determined by the molecular weight of the polyester diol and/or polycarbonate diol, the ratio of the hydroxyl group of the diol compound and the acid anhydride group of the tetracarboxylic dianhydride, and the like. Glycols such as ethylene glycol and neopentyl glycol may be used as a part of the diol compound to increase the acid value. The acid anhydride group may be reacted with the hydroxyl group of the diol compound under a condition of a slight excess, and the terminal acid anhydride group may be terminated with a primary amino compound after the molecular weight reaches a predetermined molecular weight.

The insulating coating agent used in the present invention forms a crosslinked structure by the reaction of a carboxylic acid group and an epoxy group. Carboxylic acid groups are present in the polyester, but when the molecular weight of the ester diol and/or polycarbonate diol used as a raw material is 500 or more, the concentration of cross-linking points can be prevented, the strain of the cross-linked product can be reduced, and the insulating coating layer Contributes to the improvement of heat resistance and physical properties.

The polyester used for the insulating coating agent in the present invention has a glass transition temperature of preferably 40° C. or lower, and more preferably 30° C. or lower in order to reduce curling due to crosslinking and maintain adhesiveness. The lower limit of the glass transition temperature is preferably −30° C., more preferably −20° C., from the physical properties of the cured product.

The reaction between the polyester diol and/or polycarbonate diol and the tetracarboxylic dianhydride may be carried out in a molten state, but it is preferably carried out in an organic solvent in the presence of a tertiary amino compound.

Examples of the tetracarboxylic dianhydride used in the reaction between the polyester diol and/or polycarbonate diol and the tetracarboxylic dianhydride include pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, and biphenyltetracarboxylic dianhydride. Compounds, diphenyl sulfone tetracarboxylic dianhydride, diphenyl ether tetracarboxylic dianhydride, naphthalene tetracarboxylic dianhydride, pyromellitic dianhydride, hydrogenated biphenyl tetracarboxylic dianhydride and the like, benzophenone- 3,3',4,4'-tetracarboxylic dianhydride, biphenyl-3,3',4,4'-tetracarboxylic dianhydride, diphenylsulfone-3,3',4,4'-tetra Carboxylic dianhydride and diphenyl ether-3,3',4,4'-tetracarboxylic dianhydride are preferable. The tetracarboxylic dianhydride may be used alone or in combination.

The insulating coating agent used in the present invention further contains a plate-like inorganic filler (B), fumed silica (C), a rubber phase (D) and an epoxy resin (E).

The plate-like inorganic filler (B) can provide mechanical reinforcement effect and heat resistance improvement of the insulating coat layer. By using the plate-like inorganic filler (B) and the fumed silica (C) in combination, the elastic modulus, tensile strength, toughness, and heat resistance are improved by the interaction between the silanol groups on the surface of the fumed silica and the plate-like inorganic filler. Further improve.

The particle size of the plate-like inorganic filler (B) is preferably in the range of 10 to 0.1 μm, and the aspect ratio is 5.0 or more, preferably 10.0 or more. Examples of the plate-like inorganic filler include talc, mica, kaolin, montmorillonite, synthetic mica and plate-like alumina, and talc, mica and kaolin are preferable. The addition amount of the plate-like inorganic filler is in the range of 10 to 100 parts by weight, preferably 30 to 80 parts by weight, when the polyester is 100 parts by weight.

Further, the fumed silica (C) contributes not only to improving the physical properties of the insulating coat layer but also to improving the fluidity of the insulating coat and imparting a sagging prevention function. The particle size of fumed silica (C) is preferably 50 nm or less, and more preferably 30 nm or less. The amount of fumed silica added is in the range of 0.5 to 8 parts by weight, preferably 2 to 5 parts by weight, based on 100 parts by weight of polyester.

If the addition amount of the plate-like inorganic filler (B) or fumed silica (C) is less than the above range, the mechanical reinforcing effect is poor, and if it is more than the above range, the interlayer adhesion of the insulating coat layer deteriorates. There is. If the amount of fumed silica (C) added exceeds the above range, the fluidity may deteriorate and the surface roughness after coating may be severe even if the leveling agent for the insulating coat is optimized.

The rubber phase (D) is added to the insulating coating agent used in the present invention. The rubber phase has a function of relieving internal stress generated during curing of the insulating coat layer or sintering of the wiring pattern formed on the insulating coat layer. In addition, the rubber phase is a thermo-mechanical property of the insulation coating layer and the existing wiring pattern generated during the sintering of the wiring pattern, particularly when the wiring pattern is further formed on the wiring pattern. It has the function of relieving the strain caused by the difference and preventing the upper wiring pattern from breaking. In addition, the rubber phase has a function of relieving the strain generated at the interface between the insulating coat and the wiring pattern due to the volume contraction of the wiring pattern formed on the insulating coat layer during the heat treatment, and preventing the peeling of the wiring pattern. These functions are more remarkable in the third layer and the layer further above the second layer of the wiring pattern, and the presence of the rubber phase does not cause disconnection or short circuit even if the wiring pattern is repeatedly sintered by heat treatment. Stacked antennas can be manufactured.

Further, the insulating coating layer of the present invention has a high crosslink density of the resin composed of polyester and epoxy in order to improve heat resistance and insulating properties, and has a high elastic modulus due to the addition of the plate-like filler and fumed silica, and becomes brittle. Although tending, the rubber phase can be dispersed in the insulating coat to improve the toughness and prevent, for example, breakage or cracking of the base material. Therefore, the rubber phase is also effective for improving the toughness and heat resistance of the insulating coat layer.

Examples of the constitution of the rubber phase include polybutadiene, polystyrene butadiene, polyacrylonitrile butadiene, polyacrylic acid ester and silicone rubber. The rubber phase is selected from those which do not dissolve in the solvent of the coating agent or other components or in which the rubber phase undergoes phase separation after drying or curing. Examples of the form of such a rubber phase include a form of a liquid rubber in a coating agent before coating, which forms a rubber phase by phase separation at the time of curing. For example, a carboxyl group-terminated butadiene nitrile rubber ( Examples thereof include CTBN), polybutadiene, and a block polymer composed of a silicone rubber block and a block polymer of a parent epoxy at both ends thereof. As another form, in order to prevent blocking, the fine particles have a core-shell structure, the core is a cross-linked rubber, the shell is a core-shell fine particles such as acrylic having a high glass transition temperature cured with a polyfunctional acrylic, or the like, or Those composed of a rubber component that has been subjected to antiblocking treatment such as crosslinking are preferable, and it is more preferable to mix rubber particles monodispersed in advance with an epoxy resin with a polyester resin.

The rubber phase (D) used in the insulating coating agent in the present invention preferably has an average particle size of 0.05 to 5 μm. The content of the rubber phase is 5 to 50 parts by weight, preferably 15 to 30 parts by weight, when 100 parts by weight of polyester is used. When the amount is less than 5 parts by weight, the heat resistance and the physical properties are insufficiently improved, and when the amount is more than 50 parts by weight, the physical properties may be deteriorated and the interlayer adhesiveness may be deteriorated.

The epoxy resin (E) used for the insulating coating agent in the present invention is a resin having two or more epoxy groups in one molecule, and examples thereof include glycidyl ether type, glycidyl ester type, glycidyl amine type and olefin oxidation type epoxy resins. To be The amount of the epoxy resin added is preferably in the range of from the equivalent of the acid value of the polyester used in the present invention to twice the equivalent, and when the amount of epoxy is less than or equal to the acid value of the polyester, unreacted carboxylic acid is used. Due to hydrolysis, the long-term durability of the insulating coat layer may be inferior, and if it exceeds twice the acid value of the polyester, the crosslink density may be reduced and the heat resistance may be inferior. Further, a catalyst that promotes the reaction between the epoxy resin and the carboxyl group may be added. Examples of the catalyst include tertiary amine compounds, imidazole compounds and phosphine compounds.

Next, a method for manufacturing the laminated antenna according to the present invention will be described.

In the laminated antenna according to the present invention, a wiring pattern is formed on an insulating substrate by printing a conductive paste, and an insulating coating layer pattern is formed on the wiring pattern by printing an insulating coating agent. It can be manufactured by printing a conductive paste on the insulating coating layer to form a wiring pattern including filling of through holes.

Since the conductive paste used in the present invention has high conductivity, it is preferable to reduce the ratio of the binder component in the paste. Therefore, if the conductive paste is directly printed on the insulating substrate, the adhesiveness may be insufficient. Therefore, in order to impart adhesiveness to the insulating substrate, it is preferable to provide an adhesive layer on the insulating substrate and form the wiring pattern via the adhesive layer. Further, the adhesive layer used in the present invention is characterized by maintaining sufficient adhesive strength by heat treatment.

The resin used for the adhesive layer is selected from those having excellent adhesiveness to the insulating substrate, and examples thereof include polyester, polyurethane, polycarbonate, aromatic polyether, polyamide, polyamideimide, and polyimide. A resin having an ester bond, an imide bond, an amide bond, or the like is preferable in terms of heat resistance of the adhesive layer and adhesiveness to the substrate. It is also desirable that the adhesive layer contains a curing agent in view of the heat resistance of the adhesive layer and the adhesiveness with the insulating substrate. Examples of the curing agent include phenol resin, amino resin, isocyanate compound, epoxy resin, oxetane compound, and maleimide compound. The amount of the curing agent used is preferably in the range of 1 to 50% by weight based on the weight of the resin in the adhesive layer.

The adhesive layer may contain a heterocyclic compound containing nitrogen in the heterocycle and/or a hydrazide compound. Heterocyclic compounds and hydrazide compounds containing nitrogen in the heterocycle may be used as a rust preventive agent for copper foil or copper powder, but in the present invention, these compounds are heat treated to form a copper powder-containing coating film. Exhibits strong adhesion. Heterocyclic compounds containing nitrogen and hydrazide compounds have high affinity for copper and strongly adsorb on the copper surface. It is necessary to apply energy to adsorb nitrogen-containing heterocyclic compounds and hydrazide compounds, which are present in the adhesive layer with excellent adhesion to the insulating substrate, onto the copper powder surface, and heat treatment is effective, and superheated steam is used. The process has the highest thermal efficiency.

As the heterocyclic compound containing nitrogen in the heterocycle, for example, pyridine, oxazole, isoquinoline, indole, thiazole, imidazole, benzimidazole, bipyridyl, pyrazole, benzothiazole, pyrimidine, purine, triazole, benzotriazole, benzoguanamine, or the like, or These structural isomers are also included. These may have a substituent such as an alkyl group, a phenyl group, a phenol group, a carboxyl group, an amino group, a hydroxyl group, a thiol group and an aromatic ring. Further, these may be condensed with an aromatic ring or a heterocycle. Of these, imidazole compounds and benzotriazole compounds are desirable.

The hydrazide compound is a compound having a structure in which hydrazine or a derivative thereof and a carboxylic acid are condensed, and examples thereof include salicylic acid hydrazide, isophthalic acid dihydrazide, and a condensate of salicylic acid hydrazide and dodecanedicarboxylic acid.

The adhesive layer of the present invention preferably contains the heterocyclic compound containing nitrogen in the heterocycle and/or the hydrazide compound in an amount of 1 to 30 parts by weight with respect to 100 parts by weight of the adhesive layer resin. When the amount of the heterocyclic compound containing nitrogen in the heterocycle and/or the hydrazide compound is less than 1 part by weight with respect to 100 parts by weight of the adhesive layer resin, the adhesion to the copper powder-containing layer may be insufficient, If it exceeds 30 parts by weight, the physical properties of the adhesive layer may deteriorate.

In order to form the adhesive layer on the insulating substrate, a general method used when coating or printing the resin forming the adhesive layer on a film or sheet can be used. For example, a screen printing method, a dip coating method, a spray coating method, a spin coating method, a roll coating method, a die coating method, a paste jet method, a relief printing method, an intaglio printing method and the like can be mentioned. The adhesive layer can be formed by evaporating the solvent from the coating film formed by printing or coating by heating or reducing the pressure. The adhesive layer may be provided entirely or partially on the insulating substrate, and is preferably provided at least in the portion where the wiring pattern is formed.

The adhesive layer formed on the insulating substrate in the present invention preferably has a thickness of 25 μm or less, particularly 20 μm or less. In particular, when the insulating substrate is a magnetic body, it is desirable that the magnetic body be close to the coil line from the viewpoint of antenna performance. Therefore, the adhesive layer preferably has a thickness of 25 μm or less. Further, from the viewpoint of adhesiveness, when the thickness of the adhesive layer exceeds 25 μm, the adhesiveness may be deteriorated due to the sintering strain of the copper powder caused by the heat treatment. If the thickness is less than 0.01 μm, the adhesiveness may be significantly reduced due to decomposition of the binder resin due to heat treatment.

Further, the heat loss after curing of the adhesive layer is preferably 25% by weight or less. However, the heating loss after curing is the heating loss after curing under the condition of 300° C. superheated steam atmosphere for 10 minutes. If the heating loss is more than 25% by weight, the adhesiveness cannot be maintained due to decomposition or carbonization of the adhesive layer in the step of heat-treating the conductive paste. The lower limit of the weight loss due to heating is about 0.01% by weight.

In order to form a wiring pattern on an insulating substrate using a liquid conductive paste and optionally an adhesive layer, a general method used when applying or printing the conductive paste on a film or sheet is used. be able to. For example, a screen printing method, a dip coating method, a spray coating method, a spin coating method, a roll coating method, a die coating method, an inkjet method, a letterpress printing method, an intaglio printing method, a dispenser and the like can be mentioned. Above all, in order to obtain a sufficiently small coil resistance in the present invention, a screen printing method, a dispenser method or the like is preferable as a method for forming the wiring pattern of the laminated antenna.

The wiring pattern can be formed by evaporating the solvent from the pattern formed by printing or coating by heating or reducing the pressure. Generally, in the case of a conductive paste, the wiring pattern at this stage has a specific resistance of 1 Ω·cm or more, and the conductivity required for a conductive circuit has not been obtained.

The thickness of the wiring pattern before the heat treatment is mainly determined by the required conductivity, but the thickness after drying by evaporating the solvent contained in the conductive paste is preferably 0.05 to 100 μm. If the thickness of the wiring pattern before heat treatment is less than 0.05 μm, sufficient conductivity may not be obtained even if heat treatment is applied, and if it exceeds 100 μm, the solvent may remain in the pattern. The remaining solvent may bump during the heat treatment, in which case the pattern may have defects. The thickness of the wiring pattern before heat treatment is more preferably 0.2 to 50 μm. In order to obtain a sufficiently small coil resistance, the thickness of the wiring pattern before the heat treatment is more preferably 5 to 50 μm.

In the present invention, the wiring pattern is preferably made conductive by heat treatment at 130° C. or higher, and more preferably at 250° C. or higher. As a heat treatment method, superheated steam treatment is preferable from the viewpoint of heating efficiency, safety, economical efficiency, and obtained conductivity. The superheated steam treatment uses superheated steam having a heat capacity and a specific heat larger than that of air as a heat source for heat treatment, and the superheated steam is steam that further heats saturated steam to raise its temperature. The superheated steam treatment condition varies depending on many factors, but generally, the temperature of the superheated steam treatment is 300° C. or higher, preferably 320° C. or higher. The superheated steam treatment time is 10 seconds to 10 minutes, preferably 20 seconds to 5 minutes. The superheated steam treatment as a heating method is particularly preferable because the heating efficiency is good and the treatment time can be shortened, so that the deterioration of the adhesiveness due to the treatment at high temperature can be suppressed.

In order to form an insulation coating layer on the wiring pattern with an insulation coating agent, a general method used when coating or printing a resin on a film or sheet can be used. For example, a screen printing method, a dip coating method, a spray coating method, a spin coating method, a roll coating method, a die coating method, an inkjet method, a letterpress printing method, an intaglio printing method and the like can be mentioned. The insulating coat layer can be formed by evaporating the solvent from the coating film formed by printing or coating by heating or reducing the pressure.

To provide a through hole in the insulating coat layer, for example, when the insulating coat layer is provided by screen printing, printing may be performed using a plate having a mask in the through hole portion. When a through hole is provided in the insulating coating layer by screen printing, the above-mentioned fumed silica acts as an anti-sagging agent, but if necessary, other rheology control agents such as higher fatty acid amide may be added.

Further, a leveling agent such as an acrylic polymer or a vinyl ether polymer may be added to smooth the printed surface of the insulating coat layer.

It is desirable that the insulating coating layer provided in the present invention is cured after the insulating coating agent is applied and dried. The curing treatment can be performed by a heat treatment at 120° C. or higher, and the superheated steam treatment is preferable because the heat treatment efficiency and the oxidation of the existing wiring pattern can be prevented. The superheated steam treatment condition varies depending on many factors, but generally, the temperature of the superheated steam treatment is 150° C. or higher, preferably 200° C. or higher. The superheated steam treatment time is 10 seconds to 10 minutes, preferably 20 seconds to 5 minutes. The superheated steam treatment as a heating method is particularly preferable because the heating efficiency is good and the treatment time can be shortened, so that the deterioration of the adhesiveness due to the treatment at high temperature can be suppressed.

In the present invention, the formation of the wiring pattern and the formation of the insulating coat layer are repeated on the insulating substrate so that the layers are sufficiently insulated and the wiring pattern is laminated. The outermost layer may be a wiring pattern for IC mounting or other purposes, or may be an insulating coat layer. By connecting the wiring patterns with through holes, an antenna coil and wiring having a desired design can be obtained, and the laminated antenna is manufactured.

The laminated antenna manufactured by the above method functions as an antenna as it is, regardless of the type of the insulating substrate. However, when used in a metal environment, it is necessary to laminate it with a magnetic material. When used, the laminated antenna can be attached to a magnetic material. When the laminated antenna is attached to a magnetic material, as the form of the adhesive for a film, an adhesive layer may be directly formed on the surface of the film and/or the magnetic material by a known method, or an adhesive layer may be formed on both surfaces of the base material. You may adhere|attach via what is called the double-sided adhesive film which formed. The adhesive layer for a film may be, for example, acrylonitrile butadiene rubber/phenol resin, acrylonitrile butadiene rubber/epoxy resin/phenol resin, acrylonitrile butadiene rubber/epoxy resin, epoxy resin/polyester resin, epoxy resin/acrylic resin, acrylic resin, silicone resin, or the like. Used.

The following examples are provided to describe the present invention in more detail, but the present invention is not limited to the examples. The measurements and materials used in the examples were measured or manufactured by the following methods.

The conductive paste was 1.14 parts of a solution of copolyester (RV290 manufactured by Toyobo Co., Ltd., a 35 wt% solution of ethyl carbitol), 9.6 parts of copper powder (average particle size 0.15 μm), and ethyl carbitol acetate 0. 0.25 parts dispersed by three rolls were used.

As the insulating coating agent, the resins shown in Table 1 were used, and the compositions shown in Tables 2 and 3 were blended.

The polyester resins 1 to 5 are, as shown in Table 1, an isophorone solution of a polyester resin having a number average molecular weight of 2000 (“RV-220” manufactured by Toyobo Co., Ltd.) and a polyester polyol “P-1010” manufactured by Kuraray Co., Ltd., manufactured by Asahi Kasei Corporation. Polycarbonate diol “Duranol T-5651”, a solution containing triethylamine as a reaction catalyst, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), pyromellitic dianhydride as a tetracarboxylic dianhydride. Anhydrous (PMDA) was added and reacted at 80° C. for 6 hours to obtain polyester resins shown in Table 1.

Comparative resin 1 is, as shown in Table 1, an isophorone solution of a polyester resin having a number average molecular weight of 2000 (“RV-220” manufactured by Toyobo Co., Ltd.) and a polycarbonate diol “Duranol T-5651” manufactured by Asahi Kasei Co., 4, 4′. -Diphenylmethane diisocyanate (MDI) and 2,2-bis(hydroxymethyl)butyric acid (DMBA) were charged and reacted at 80°C for 6 hours to obtain a polyurethane resin.

As plate-shaped inorganic filler, "Mica A-11" manufactured by Yamaguchi Mica Co., Ltd. (average particle size 3 µm), Kaolin "Ecarite ED" manufactured by Imerys Co., Ltd. (average particle size 0.32 µm), and fumed silica manufactured by Tokuyama Corporation "Reolosil PM-" 20" (average particle diameter 12 µm), "Reolosil MT-10" (average particle diameter 15 µm), and Aica Kogyo Co., Ltd. core-shell type acrylic rubber particles "Zefiac F351" (average particle diameter 0.3 µm) as rubber components, It was dispersed in a polyester resin with three rolls. To the obtained dispersion, an epoxy resin (EXA-835LV: bisphenol F type epoxy manufactured by DIC), (828: bisphenol A type epoxy manufactured by Mitsubishi Chemical Co.), and a curing accelerator (BDMA::benzyldimethylamine) as needed. Compounded. Alternatively, as plate-like inorganic filler, "Mica A-11" manufactured by Yamaguchi Mica Co., Ltd. (average particle size 3 µm), Kaolin "Ecarite ED" manufactured by Imerys Co., Ltd. (average particle size 0.32 µm), and "Leoroseal" manufactured by Tokuyama Corporation as fumed silica “PM-20” (average particle size 12 μm) and “Reorosil MT-10” (average particle size 15 μm) were selected and dispersed in a polyester resin or polyurethane resin with a three-roll mill. To the obtained dispersion, "Kane Ace MX-154" manufactured by Kaneka Co., Ltd. in which butadiene rubber-based core-shell type rubber particles were dispersed in a bisphenol A type epoxy resin was added, if necessary, a curing accelerator (BDMA: benzyldimethylamine).

As a composition for the adhesive layer, 15 parts of a phenol novolac type epoxy resin (jER (registered trademark) 152 manufactured by Mitsubishi Chemical Corporation) as a curing agent in 100 parts of a polyamide-imide solution (HR-11NN manufactured by Toyobo Co., Ltd.), and triphenyl as a curing catalyst. 3 parts of phosphine (TPP), 10 parts of 2-phenylimidazole as an additive, and 200 parts of tetrahydrofuran as a diluting solvent were mixed.

(Measurement of heating loss)
The adhesive layer composition was molded into a film having a thickness of 10 μm, and a test piece cut into a width of 10 mm and a length of 10 mm was heated in a superheated steam atmosphere at 300° C. for 10 minutes, and the heating loss after heating was measured. Then, (weight before heating−weight after heating)/weight before heating×100. The weight loss upon heating was 1.8% by weight.

(Example 1)
Using the coating agent 1 shown in Table 2 as the insulating coating agent, four layers of a 4-turn flat coil were laminated on one surface of the insulating substrate in the following procedure, and two antennas connected in series were laminated in two layers. A laminated antenna having a different structure was manufactured.

The composition for the adhesive layer is applied to one side of a Kaneka polyimide film “Kapton EN thickness 5 μm” so that the thickness after drying becomes 0.5 μm, and dried and heat-treated at 200° C. for 5 minutes to form the adhesive layer. An insulating substrate was obtained. Next, a spiral wiring pattern is printed on the adhesive layer by screen printing with a conductive paste, temporarily dried at 100° C. for 10 minutes, and then heat-treated under superheated steam at 350° C. for 2 minutes to form a wiring pattern having a thickness of 25 μm. Got The insulation coating layer pattern is printed on the wiring pattern after the heat treatment with an insulation coating agent by screen printing in which the through holes are masked, temporarily dried at 100° C. for 10 minutes, and then heat treated under superheated steam at 350° C. for 2 minutes. An insulating coat layer having a thickness of 15 μm was obtained. A spiral wiring pattern is printed on the obtained insulating coat layer with a conductive paste while simultaneously filling through holes, temporarily dried at 100° C. for 10 minutes, and then heat-treated at 350° C. for 2 minutes under superheated steam treatment. A wiring pattern having a thickness of 25 μm was obtained. On the heat-treated wiring pattern, an insulating coat layer and a wiring pattern were sequentially printed, dried, and heat-treated in the same manner as described above to repeatedly form. Finally, a wiring pattern is printed on the insulating coating layer with a conductive paste while simultaneously filling the through holes, temporarily dried at 100° C. for 10 minutes, and then heat-treated under superheated steam at 350° C. for 2 minutes to mount an IC with a thickness of 25 μm. As a wiring pattern for, a laminated antenna was obtained.

(Example 2)
As the insulating coating agent, various coating agents shown in Table 2 were used. On the insulating substrate provided with the adhesive layer obtained in the same manner as in Example 1, four layers of 4-turn plane coils were laminated by the same means as in Example 1, and all four layers were connected in series. Got an antenna.

(Example 3)
Ni-Zn-Cu ferrite powder (FRX-950 manufactured by Toda Kogyo Co., Ltd.) was previously sintered for 2 hours at 920° C. for 2 hours by a green sheet method to obtain a sintered ferrite sheet having slits with a thickness of 150 μm. .. Using Coating Agent 1 shown in Table 2 as an insulating coating agent, an antenna wiring pattern was laminated in the same manner as in Example 2 and attached to the sintered ferrite sheet with a double-sided tape having a thickness of 10 μm to obtain a laminated antenna.

(Comparative Example 1)
Using an FCCL in which a copper foil having a thickness of 35 μm is laminated on a PET having a thickness of 25 μm via an adhesive layer having a thickness of 20 μm, an antenna having an area four times as large as that of the wiring patterns laminated in Examples 1 and 2 is used as a normal photoresist. Was formed by an etching process using.

(Comparative Examples 2-9)
It carried out like Example 2 using the insulating coating agent of various compositions shown in Table 3.

(Measurement of communication characteristics)
An IC chip (IC chip I CODE SLI manufactured by NXP) is mounted on one surface of the laminated antenna, a capacitor for resonance frequency adjustment is connected in parallel, and the resonance frequency is adjusted to 13.56 MHz. (Takaya TR3-C201) was used to compare and evaluate the communication distance. The results are shown in Tables 4 to 6.

In Example 1, two magnetically coupled antennas that were not electrically connected were stacked, one antenna was mounted with an IC chip, and the other antenna was only frequency-adjusted by a capacitor. The antenna whose resonance frequency is adjusted without mounting the IC chip functions as a booster antenna, improves the directivity of the antenna mounting the IC chip, and can extend the communication distance compared to the case without the booster antenna. It was

Since the antennas of Examples 2 and 3 have a structure in which the antenna wiring patterns are laminated in four layers, the communication distance equivalent to that of Comparative Example 1 was obtained with the area of 1/4 of the antenna of Comparative Example 1. Further, when the antenna was installed on the metal, reading was not possible in Example 2 because there was no magnetic substance, but in Example 3 in which magnetic substances were laminated, an equivalent communication distance was obtained. In the antennas of Comparative Examples 2 to 9, when printed and laminated, the wiring pattern has cracks, bleeding, or the like, which causes the antenna circuit to be in a short circuit or open state, and the resonance frequency of the laminated antenna from the design value of 13.56 MHz. It was out of alignment and could not be read.

(Temperature cycle test)
A temperature cycle test was carried out on 100 laminated antennas that were able to communicate based on the JIS standard (JIS C 60068-2-14).

The temperature cycle test was carried out at 125° C. for 30 minutes, at −40° C. for 30 minutes, and at each holding temperature for 5 minutes, and the communication characteristics after 100 cycles were evaluated. Table 5 shows the number of laminated antennas that became unable to communicate after 100 cycles.

(Example 4)
Regarding the laminated antenna of Example 1, it was confirmed that when a total of two IC chips were mounted on each independent antenna, two ICs were read simultaneously.

The laminated antenna obtained by the present invention can be miniaturized, improved in performance, and reduced in cost by laminating the wiring pattern formed of the conductive paste with the insulating coat layer interposed therebetween. These laminated antennas can be used as an RFID communication antenna, an electromagnetic transfer type antenna, and the like.

1, 2, 3 laminated antennas 11, 21 insulating base 31 insulating base (resin film)
12, 22, 32 Adhesive layers 13, 23, 33 Wiring patterns 14, 24, 34 Insulation coat layers 15, 25, 35 Through holes 16, 17, 26, 36 Antenna coil 38 Magnetic material 39 Double-sided tape

Claims (11)

A laminated antenna in which a plurality of wiring patterns formed of a conductive paste are laminated on one surface of an insulating substrate with an insulating coat layer having a through hole interposed therebetween, and the wiring patterns are connected through the through hole, The insulating coating layer is a cured product of a resin containing the following (A) to (E).
(A) Polyester resin (B) Plate-shaped inorganic filler (C) Fumed silica (D) Rubber phase (E) Epoxy resin The multilayer antenna according to claim 1, wherein the acid value of the polyester resin is 800 to 2500 equivalents per ton of resin. The laminated antenna according to claim 1, wherein the conductive paste contains conductive particles, a binder resin, and a solvent, and the conductive particles contain copper or copper as a main component. The laminated antenna according to any one of claims 1 to 3, wherein the wiring pattern is a planar spiral coil pattern, and the coil patterns are connected through a through hole to form an antenna coil. The laminated antenna according to claim 1, wherein the insulating substrate is a magnetic body. The laminated antenna according to claim 1, wherein the insulating substrate is a resin film. The laminated antenna according to any one of claims 1 to 6, wherein a wiring pattern is formed on the insulating substrate via an adhesive layer. The laminated antenna according to any one of claims 1 to 7, wherein the weight loss after curing of the adhesive layer is 25% by weight or less in 10 minutes at 300°C superheated steam atmosphere. A wiring pattern is formed on one surface of an insulating substrate by printing a conductive paste, and an insulating coating layer is formed on the wiring pattern by printing an insulating coating agent containing the following (A) to (E). And forming a wiring pattern including filling of through holes by printing a conductive paste on the insulating coat layer.
(A) Polyester resin (B) Plate-shaped inorganic filler (C) Fumed silica (D) Rubber phase (E) Epoxy resin The method for manufacturing a laminated antenna according to claim 9, wherein the conductive paste is heat-treated at 130° C. or higher to form a wiring pattern. The method for manufacturing a laminated antenna according to claim 9, wherein the insulating coating agent is cured by heat treatment at 120° C. or more to form an insulating coating layer.