JP2006155224A - Polyester film for rfid tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film suitable for an RFID tag, which does not cause disadvantages, such as communication interference, even IC chip deterioration or destruction due to static electricity generated when being processed, attached to goods or boxes, or being read. <P>SOLUTION: The polyester film for RFID tags includes an antistatic layer having surface electrical resistance of 1×10<SP>13</SP>Ω/square or less on at least one side of the film, wherein the antistatic layer is provided in a film manufacturing process. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an RFID tag film, and more particularly to an antistatic polyester film suitable for an RFID tag.

  Recently, RFID tags have attracted attention as terminals in the ubiquitous information era, as transport labels in the global era, and as traceable labels. An RFID tag is a tag that can communicate information in a non-contact manner using radio waves as a medium of an RFID (Radio Frequency Identification) system. The “RFID tag” is expressed by various names such as “IC tag”, “electronic tag”, “wireless IC tag”, “non-contact IC”, “non-contact IC label”, “transponder”, and the like. In some cases. In addition, a card that has a chip shape with enhanced chip security is a “contactless card”. In the present invention, the term “RFID tag” is representatively used.

  An RFID tag is usually composed of a tag body called an inlet made of an antenna circuit provided on a polyester film and an RFID chip connected to the circuit, and, if necessary, the surface is made of another base material such as paper or film. A tag or label is formed by bonding to the front cover, or a card. In some cases, it may be bonded to a substrate with an adhesive layer for application to a product or box to form an adhesive label. To improve design, it was printed on a polyester film or printed on a surface cover. Sometimes paper or film is used.

  The antenna circuit of the RFID tag serves to receive electric power and signals by radio waves transmitted from an antenna of a device that reads and writes information of the RFID tag called a reader / writer. The signal is processed by a calculation unit in the RFID chip and stored in a memory unit in the RFID chip. In the case of reading, the information in the memory unit is processed by the electric power from the radio wave received from the reader / writer and sent back from the antenna circuit to the reader / writer. As such communication methods, two methods of an electromagnetic induction method and a radio wave communication method are known according to the wavelength of the radio wave to be used. As an antenna circuit attached to the RFID tag, a loop antenna circuit is required in the electromagnetic induction method, and an antenna circuit having a structure that resonates with a transmitted radio wave is required in the radio wave communication method.

An RFID tag is processed as described above, or attached to a product or a box, or read from it. In each process, static electricity may be generated, which hinders communication. There is a concern that the RFID chip may deteriorate. As a method for preventing this, a method of blending an antistatic agent and a method of coating and drying an antistatic agent on a film base have been proposed, but the former method has an adverse effect due to bleeding out of the antistatic agent. In the latter method, it is necessary to consider the operating cost of the coat and the drying apparatus and the working environment, and there is a problem that the cost is high (Patent Document 1).
JP 2003-288560 A

  This invention is made | formed in view of the said situation, Comprising: The solution subject is preventing generation | occurrence | production of static electricity and providing a suitable film for RDID tags.

  As a result of intensive studies to solve the above problems, the present inventor has found that a film having a specific configuration is suitable as an RFID tag, and has completed the present invention.

That is, the gist of the present invention is that at least one surface of the film has an antistatic layer having a surface resistance of 1 × 10 ¹³ Ω / □ or less, and the antistatic layer is provided in the film production process. It exists in the polyester film for RFID tags characterized.

Hereinafter, the present invention will be described in detail.
The polyester in the present invention is a dicarboxylic acid such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid, 1,4-cyclohexyldicarboxylic acid or the like It is a polyester produced by melt polycondensation of an ester and glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanedimethanol. Polyesters comprising these acid components and glycol components can be produced by arbitrarily using a commonly used method. For example, a transesterification reaction between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol, or a direct esterification of an aromatic dicarboxylic acid and a glycol, to form a substantially bisglycol of an aromatic dicarboxylic acid A method is employed in which an ester or a low polymer thereof is formed and then polycondensed by heating under reduced pressure. Depending on the purpose, an aliphatic dicarboxylic acid may be copolymerized.

  Typical examples of the polyester used in the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, and the like. It may be a copolymerized polyester and may contain other components and additives as necessary. These polyesters include inorganic particles such as calcium carbonate, kaolin, silica, aluminum oxide, titanium oxide, alumina, and barium sulfate, organic particles such as acrylic resin and guanamine resin, and catalysts for the purpose of improving film runnability. Precipitated particles in which the residual is made into particles can be contained. The particle size and amount of these particles can be appropriately determined according to the purpose. In addition, various stabilizers, lubricants, antistatic agents, and the like can be added as appropriate.

  The polyester film of the present invention is preferably a biaxially stretched polyester film. The film forming method for obtaining the biaxially stretched polyester film may be a generally known film forming method, and is not particularly limited. For example, an unstretched film obtained by melt extrusion from an extruder is first stretched 2 to 6 times at 60 to 120 ° C. by a roll stretching method to obtain a uniaxially stretched polyester film, and then the previous stretching in a tenter. It may be a sequential biaxial stretching film forming method in which the film is stretched 2 to 6 times at 80 to 130 ° C. in a direction perpendicular to the direction, and further subjected to heat treatment at 150 to 250 ° C. for 1 to 600 seconds. Moreover, the simultaneous biaxial stretching film-forming method of extending | stretching an unstretched film to the length and width simultaneously, and heat-processing with a tenter after that may be sufficient. The film forming method of the present invention may be a multilayer film using a plurality of extruders.

  In the RFID tag manufacturing process, heat is applied to the polyester film, so that the heat shrinkage rate after treating the polyester film of the present invention at 150 ° C. for 30 minutes is 2.0% or less in both the vertical and horizontal heat shrinkage rates. It is preferable that it is 1.2% or less. In order to reduce curling and warping of the RFID tag, it is preferable to use a polyester film having a heat shrinkage rate of 0.6% or less after treatment at 150 ° C. for 30 minutes.

The thickness of the polyester film of the present invention is preferably a biaxially stretched film having a thickness of 12 to 125 μm.
In the present invention, it is essential to provide an antistatic layer at the time of forming a polyester film, and the surface resistance of the antistatic layer needs to be 1 × 10 ¹³ Ω / □ or less, preferably 1 × 10 ¹² Ω. / □ or less.

  As a method of providing an antistatic layer on a film during film formation, for example, in a sequential biaxial stretching method, a method of stretching a film laterally after applying a coating solution containing an antistatic agent to a film after longitudinal uniaxial stretching, Or there exists the method of apply | coating and drying after a biaxially stretched film. Although there is no restriction on the method, the method of applying to a uniaxially stretched film, then laterally stretching, and heat-treating is preferable because there is a feature that the coating layer can be uniformly thinned. Further, in the simultaneous biaxial stretching method, a method of applying to an amorphous film before stretching, simultaneous biaxial stretching, and then heat treatment is preferable.

  Examples of the antistatic agent used in the present invention include sulfonates, alkyl sulfate esters, and cationic compounds.

  Examples of the sulfonic acid metal salt include an alkyl sulfonic acid metal salt, an alkyl benzene sulfonate, an alkyl sulfoisophthalate, and an alkyl naphthalene sulfonate. As the metal of the metal salt, lithium, potassium, and sodium are preferable. Here, as an alkyl group, a C8-C30 thing is good. When the number of carbon atoms is small, the compatibility with the resin constituting the coating agent is poor, and when the number of carbon atoms is large, the effect of the antistatic ability may be deteriorated. In actual use, a mixture of compounds having different carbon numbers is often used.

  Examples of the cationic antistatic agent used in the present invention include compounds having a quaternary ammonium base. This refers to a compound having a component containing a quaternary ammonium base in the main chain or side chain in the molecule. Examples of such constituents include, for example, a pyrrolidinium ring, an alkylamine quaternized product, a copolymer of these with acrylic acid or methacrylic acid, an N-alkylaminoacrylamide quaternized product, a vinylbenzyltrimethylammonium salt, 2-hydroxy 3-methacryloxypropyltrimethylammonium salt etc. can be mentioned. Further, these may be combined or copolymerized with other resins. In addition, examples of anions that serve as counter ions for these quaternary ammonium salts include ions such as halogen, alkyl sulfate, alkyl sulfonate, and nitric acid.

  In the present invention, the compound having a quaternary ammonium base is preferably a polymer compound. The number average molecular weight is usually 1000 or more, further 2000 or more, particularly 5000 or more and 500000 or less. When the molecular weight is too low, the antistatic agent bleeds out, causing a trouble of transferring to the contacting surface. When the molecular weight is too high, the viscosity of the coating solution becomes too high, and a trouble that the coating property deteriorates may occur.

  In addition to the antistatic agent, a polyolefin-based resin and / or a fluorine-based resin may be blended as the antistatic layer of the present invention. Further, in the antistatic layer, water-soluble or water other than the above may be added as necessary. One or two or more dispersible binder resins may be used in combination to improve coatability. Examples of the binder resin include polyester, polyurethane, acrylic resin, vinyl resin, epoxy resin, amide resin, and polyvinyl alcohol. In these, each skeleton structure may have a composite structure substantially by copolymerization or the like. Examples of the binder resin having a composite structure include acrylic resin graft polyester, acrylic resin graft polyurethane, vinyl resin graft polyester, and vinyl resin graft polyurethane.

  Further, in the present invention, the antistatic layer may contain a crosslinking reactive compound. The cross-linking reactive compound crosslinks with the functional group of the component compound constituting the antistatic layer to prevent the transfer property of the antistatic agent, and the antistatic layer fixing property (blocking property), water resistance, Solvent resistance and mechanical strength are improved. Examples of the crosslinking agent used in the present invention include a melamine crosslinking agent and an epoxy crosslinking agent. Examples of the melamine-based crosslinking agent include methoxymethylated melamine and butoxymethylated melamine which are alkylol or alkoxyalkylolated melamine compounds, and those obtained by co-condensing urea or the like with a part of melamine can also be used. The epoxy-based crosslinking agent may be a compound having an epoxy group that is water-soluble or has a water-solubilization rate of 50% or more.

  The antistatic layer of the present invention may contain at least one additive such as an antifoaming agent, a coating property improver, a thickener, an organic lubricant, organic particles, and inorganic particles, if necessary. Good.

  The thickness of the antistatic layer is a dry thickness, and is usually 0.003 to 1.5 μm, preferably 0.005 to 0.5 μm. When the thickness of the antistatic layer is less than 0.003 μm, sufficient performance may not be obtained, and when it exceeds 1.5 μm, blocking between the films tends to occur.

  The antistatic layer is preferably provided on both sides of the film, but even if it is a single side, it may be a film coated on one side as long as the effect is not impaired.

  As a method of applying to a polyester film, for example, a coating technique as shown in “Coating system” published by Yuji Harasaki, Tsuji Shoten, published in 1979 can be used. Specifically, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, impregnation coater, reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, cast coater, spray coater, curtain coater, calendar coater And techniques such as an extrusion coater and a bar coater.

  As a typical method for creating an antenna circuit, a method of laminating a metal foil and a method of printing a conductive ink are known. The method of laminating a metal foil is a method of forming a loop-shaped antenna circuit or a resonance type antenna circuit by etching a metal foil laminated on a polyester film as a base material via an adhesive. The method of printing the conductive ink is to print the conductive ink in which a powder of carbon, graphite, silver, aluminum, or a mixture thereof is dispersed in a vehicle by screen printing or ink jet printing, and is cured by electron beam or ultraviolet light. A method of curing by heating. As the vehicle, it is preferable to use a resin curable with an electron beam or ultraviolet light, or a resin curable with heat. Typical examples include acrylate compounds, methacrylate compounds, propenyl compounds, allyl compounds, vinyl compounds, and acetylenes. Compounds, unsaturated polyesters, epoxy poly (meth) acrylates, poly (meth) acrylate polyurethanes, polyester polyols poly (meth) acrylates, polyether polyols poly (meth) acrylates, phenoxyethyl (meth) acrylate, tetrahydro Examples thereof include thermosetting or radiation curable curable resins such as furfuryl (meth) acrylate, styrene, α-alkylstyrene, and other epoxy compounds. You may use these in mixture of 2 or more types.

  The antistatic layer of the present invention preferably has good adhesion to the above-described conductive ink for antenna circuit printing. Also. In the case where design printing or the like is performed on the surface opposite to the antenna circuit of the present invention, it is preferable that the ink adhesion is good. Moreover, it is preferable that the adhesiveness with the adhesion layer or adhesive layer used when processing into a tag or an adhesive label is excellent. As the surface cover and the base material, a polyester film may be used, and examples thereof include a transparent film, a white film having high concealment, and a black film. These films are preferably antistatic.

  As a method for connecting the RFID chip and the antenna circuit, a known method using wire bonding, anisotropic conductive film, conductive paste, or cream solder ball may be used, and a method of piercing the RFID chip bump into the circuit through an insulating resin Etc.

  According to the present invention, a polyester film suitable for an RFID tag that can prevent inconveniences such as communication being hindered by static electricity generated during handling or in a manufacturing process, or in some cases deterioration or destruction of an IC chip can be obtained. It can be offered at a low price.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In addition, the evaluation method and the processing method of a sample in an Example and a comparative example are as follows. In the examples and comparative examples, “parts” represents “parts by weight”.

(1) Method for Measuring Intrinsic Viscosity [η] (dl / g) of Polymer 1 g of polymer is dissolved in 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio), and 30 ° C. using an Ubbelohde viscometer. Measured in

(2) Measuring method of surface specific resistance value Using a high resistance measuring instrument (HP4339B) and measuring electrode (HP16008B) manufactured by Hewlett-Packard Japan, after sufficient conditioning of the sample in a measurement atmosphere of 23 ° C. and 50% RH, The surface specific resistance value of the coating layer after 1 minute at an applied voltage of 100 V was measured.

(3) Measurement method of heat shrinkage rate A film was cut into a strip of 35 mm width × 1000 mm length in the length direction and width direction, and an oven set at 150 ° C. in a tension-free state (manufactured by Tabay Espec Corp .: In the hot air circulating furnace), heat treatment was performed for 30 minutes, the length before and after the heat treatment was measured with a straight scale, and the thermal shrinkage rate was obtained by the following formula.
Thermal contraction rate (%) = [(ab) / a] × 100
(In the above formula, a represents the length (mm) of the sample before heat treatment, and b represents the length (mm) of the sample after heat treatment)

A chip of polyethylene terephthalate having an intrinsic viscosity of 0.66 containing 0.18 part of amorphous silica having an average particle size of 2.5 μm was obtained by an ordinary melt polymerization method. This chip is dried, the water content is reduced to 50 ppm or less, melted at 295 ° C., melt-extruded on a cooled drum to obtain an amorphous sheet, and then lengthened 3.5 times vertically at 85 ° C. to 100 ° C. Stretched to obtain a longitudinally uniaxially stretched film. The film was coated with 5 μm of the following antistatic agent solution with a gravure coater, stretched 4.0 times horizontally in an atmosphere of 90 ° C. to 120 ° C., and then heat treated at 235 ° C. The stretched polyester film was wound up into a roll. The heat shrinkage ratio of this film at 150 ° C. for 30 minutes was 1.0% in the vertical direction and 0.5% in the horizontal direction. The surface resistance of the antistatic layer was 3 × 10 ⁹ Ω / □.
Antistatic agent composition:
65 parts of polydiallyldimethylammonium chloride (average molecular weight: about 30000), 5 parts of partially saponified polyvinyl alcohol (degree of saponification: about 88 mol%), methoxymethylol melamine (Dainippon Ink, Becamine J101) An aqueous solution having a concentration of 2.0% was prepared so as to be 30 parts.

In Example 1, except that the heat treatment temperature was changed to 242 ° C., the heat shrinkage rate at 150 ° C. for 30 minutes was 0.5% in the vertical direction and 0.3% in the horizontal direction. A film having a surface resistance of 3 × 10 ⁹ Ω / □ was obtained.

  On the antistatic layer of the film of Example 1 and Example 2, “Electrodag PF-046” manufactured by Atchison Co., a conductive ink containing silver powder, was screen-printed, and the heat-dried conductive layer was peeled off with a cellophane tape. Even if it did so, it showed favorable adhesiveness without peeling.

(Comparative Example 1)
In Example 1, the antistatic layer was not provided, and a 38 μm biaxially stretched polyester film was obtained. The surface resistance of this polyester film is 1 × 10 ¹⁵ Ω / □, and since it is a film that is easily charged, it was unsuitable as an RFID tag.

  The film of the present invention can be suitably used for RFID tags.

Claims (1)

A polyester film for an RFID tag, comprising an antistatic layer having a surface resistance of 1 × 10 ¹³ Ω / □ or less on at least one surface of the film, and the antistatic layer is provided in a film manufacturing process. .