CN105260765B

CN105260765B - Silk screen printing-based RFID tag of water-washing label UHF frequency band

Info

Publication number: CN105260765B
Application number: CN201510717776.XA
Authority: CN
Inventors: 胡吉永; 李国豪; 洪虹; 江红艳; 杨旭东; 晏雄; 丁辛; 杨杰
Original assignee: Donghua University
Current assignee: Donghua University
Priority date: 2015-10-29
Filing date: 2015-10-29
Publication date: 2020-08-11
Anticipated expiration: 2035-10-29
Also published as: CN105260765A

Abstract

The invention relates to a silk-screen printing-based RFID label of a water-washed label UHF frequency band, which is characterized in that the manufacturing method comprises the following steps: selecting label washing cloth as a substrate for printing the antenna, then printing conductive ink on the substrate by adopting a screen printing method to form the antenna, bonding a connecting band of the RFID label chip of the UHF frequency band on the antenna by using a conductive adhesive after drying, and finally performing coating protection on the chip, wherein the coating material adopts flexible resin. Compared with the prior art, the invention has the beneficial effects that: the label keeps the flexibility of the water-washed label; the label is perfectly combined with the garment; endowing the UHF RFID antenna with certain flexibility and bearing certain bending or deformation; the label has simple structure and is convenient to manufacture; the label is printed by a screen printer, mass production can be realized, and the label is suitable for popularization.

Description

Silk screen printing-based RFID tag of water-washing label UHF frequency band

Technical Field

The invention relates to a technology for printing a wearable and water-fast UHF frequency band RFID tag by using a screen printing method and taking a flexible wash label textile material as a substrate, belongs to the technical field of combination of radio frequency identification and textile clothing, and is mainly used for logistics, management and anti-counterfeiting of the textile clothing.

Background

RFID (radio frequency identification) is taken as a 21 st century high-intelligence advanced Internet of things technology, and has penetrated into the daily life of human beings and gradually developed. A complete, properly functioning RFID system includes at least two parts: electronic tags and reading devices. The electronic tag is an ultrathin integrated circuit tag consisting of a coupling element and a chip, and the core components of the electronic tag are the chip and an antenna responsible for receiving and sending signals. Compared with the traditional information tag, such as a bar code and a two-dimensional code, the RFID tag has many advantages, and particularly, the RFID tag (hereinafter referred to as UHF RFID tag) which reads a UHF (ultra high frequency) frequency band with a long distance mainly has five advantages of strong adaptability to reading environment, simultaneous reading, large storage capacity, good safety and reading and writing. In view of these benefits, UHF RFID tags are widely used in logistics, libraries, merchandise, toll booths, military, and other applications. Certainly, in the textile and clothing industry, information identification, inventory management, clothing anti-counterfeiting and the like of textile and clothing products have great requirements on UHF RFID tags, but currently, commercially applied UHF RFID tags are not water-fast, or have poor flexibility and the like, the service performance or functionality of clothing is affected by different degrees after application, and the defects hinder the popularization and application of the UHF RFID tag technology in the textile and clothing industry.

In the field of combination of textile clothing and RFID, the UHF RFID tag is expected to be perfectly combined with the clothing to form a part of the clothing, and the appearance of the clothing and the comfort of the clothing are not influenced. There are many non-adhesive paper stitched UHF RFID tags on the market today and are used to some extent, but their production costs are relatively high in relation to the profit margin of the textile garment industry and their mechanical and physical properties differ greatly in relation to the marked textile garment products. Chinese patent (patent publication No. CN203311453U) A UHF-band RFID tag for clothing products, which is mainly characterized in that the front and back sides of the UHF-band RFID tag for clothing products are stuck by adhesive sticker and then sewn into the clothing products to complete the identification and tracking of clothing. The UHF RFID tag has great limitation on the use of clothes, such as thin shirts, underwear and other close-fitting clothes, even if the problem caused by the sewing process of the tag is not considered, the self-adhesive sticker is harder relative to textile fabrics and the body surface of a human body, is difficult to become a part of the clothes naturally and does not cause potential damage to the skin of a wearer. For thin clothing materials, the adhesive RFID label is sewn outside to influence the appearance of the clothing, the adhesive RFID label is sewn inside to influence the wearing comfort, and when the adhesive is deformed, the inner label is difficult to restore to the original shape, so that the reading effect of the label is influenced to a certain extent. In the Chinese patent (patent publication No. CN202563538U) of the internally-adhered anti-uncovering RFID adhesive label, the label structure is sequentially provided with a first non-dry adhesive layer, a front printing layer, an electronic chip layer, a back printing layer, a second non-dry adhesive layer and a PET layer from inside to outside. Such garment in-line labels also suffer from the problems of the labels described in the aforementioned patents, which affect the comfort of wear. In addition, the reading performance of the label is influenced by the difference of the dielectric properties of the marked clothing materials, the label stated in the patent does not provide a specific solution, and the label can still better keep the original reading effect after the clothing is protected by mechanical acting forces such as washing and the like, and the label also has a certain defect, so that the label is required to be reasonably designed.

Printing a UHF RFID tag antenna by a screen printing method is the first choice for printing antennas at home and abroad at present, and the principle of the printing is mainly to print by using the basic principle that the meshes of image-text parts (RFID antenna patterns) of a screen printing plate are ink-permeable and the meshes of non-image-text parts are ink-impermeable. When printing, ink is poured into one end of the screen printing plate, a scraping scraper plate is used for applying a certain pressure on the ink part on the screen printing plate, and meanwhile, the ink moves towards the other end of the screen printing plate. The ink is pressed by the scraper blade from the mesh of the image-text part to the printing material during the movement. In addition, there are other printing alternatives, such as letterpress, gravure, ink jet, etc., as well as conventional textile processing methods to produce a pattern for the tag antenna. Compared with the prior art, the production technology of the screen printing tag antenna is mature, the stability is good, the precision is high, the good performance of the RFID tag antenna is guaranteed, the power loss can be reduced to a certain extent, a tag with the best effect is obtained, and the requirement of rapid mass production can be met.

Disclosure of Invention

The invention aims to provide a flexible UHF RFID tag which takes a water-washed label as a substrate and is perfectly combined with textile and clothes.

In order to achieve the aim, the technical scheme of the invention provides a water-washed label UHF frequency band RFID label based on silk-screen printing, which is characterized in that the flexibility of the water-washed label is not reduced when the function of the UHF RFID label is added on the water-washed label, and the manufacturing method comprises the following steps: selecting label washing cloth as a substrate for printing the antenna, then printing conductive ink on the substrate by adopting a screen printing method to form the antenna, bonding a connecting band of the RFID label chip of the UHF frequency band on the antenna by using a conductive adhesive after drying, and finally performing coating protection on the chip, wherein the coating material adopts flexible resin.

Preferably, the conductive ink is conductive silver ink.

Preferably, the antenna adopts a dipole antenna, and the loads at two ends of the dipole antenna are hollow circular rings.

Preferably, after the antenna printed on the substrate is dried, the connection tape with the chip is adhered to the antenna by a conductive adhesive, and the label chip is protected from damage.

Preferably, the processing is: a flexible coating is covered at the label chip.

At present, in the product development design of the screen printing process by adopting conductive ink, certain rigid base materials such as coated paper, metal plates, plastic plates and the like are mainly printed. The conductive ink is printed on the label of the fabric, the conductive ink is a multiphase mixed suspension system consisting of conductive phase powder particles, binder resin, solvent and related auxiliaries, the conductive ink has good wettability and cohesiveness, and the label-washing fabric is also of a porous structure. In the silk-screen printing process, a certain pressure is applied to the scraper to extrude the printing ink onto the label washing cloth, so that the printing ink is tightly combined with the label washing cloth and simultaneously enters pores of the label washing cloth, the distance between the conductive printing ink and the label washing cloth is greatly reduced, when the distance is a certain value, the attractive force strength between the conductive printing ink and the label washing cloth is enhanced, the solvent is volatilized after solidification, the distance between molecules is reduced again, and the conductive printing ink can be firmly combined with the label washing cloth. However, fabric voids tend to cause the thickness of the printed ink layer to be non-uniform throughout, ultimately affecting the antenna impedance and the tag reading performance. Of course, we can treat the surface of the label washing cloth before printing. For example, the flexible coating is covered on the surface of the label washing cloth, so that the printing quality is improved, and the thickness of the printed antenna is more uniform; the conductive ink binder is water-resistant and solvent-resistant resin, so that the water washing resistance of the label is improved.

The label washing cloth as a part of the clothes is widely used and accepted by consumers, and is skillfully combined with the RFID as a substrate, so that compared with an RFID label sewn by using the adhesive sticker, the problem of discomfort caused by the contact of the adhesive sticker and the skin or poor appearance of the clothes in the existing scheme is perfectly solved; the antenna is printed by adopting a screen printing method, so that the precision of the RFID label is improved, and the good reading effect of the label is ensured; the washing label cloth is soft in texture, and the conductive ink containing flexible curing resin is adopted, so that the bending resistance of the UHF RFID label is ensured; the impedance matching is adjusted by controlling the thickness of the printed antenna, which is mainly determined by the screen printing process parameters and the conductive ink parameters. The screen printing process parameters mainly include the screen mesh number, the scraper pressure, the scraper speed and other factors influencing the thickness of the printed antenna; the change in antenna thickness in conductive ink parameters is primarily due to ink viscosity.

For the selection of the tag antenna, a design scheme of a relatively mature dipole antenna of the existing UHF RFID tag is taken as a primary selection; then, on the basis, correction is carried out according to a conductive silver ink formula and a printing process, loads at two ends of the conductive silver ink are changed into a hollowed circular ring shape, the hollowed circular ring saves the use of conductive ink on one hand, and on the other hand, the bandwidth of the antenna is expanded, so that a broadband UHF RFID tag antenna which needs to be obtained is obtained, the embarrassment that the tag is narrow in reading bandwidth under different dielectric environments is further met, the design can effectively expand the bandwidth of the antenna, and even around materials with large dielectric constants, the fact that the reading bandwidth completely covers UHF standard bandwidth such as 902MHz-928MHz can be guaranteed. The UHF RFID label can adapt to clothes of various fabrics by the setting, and the applicability range is expanded.

The water-washed label provides great feasibility for the label in the invention, and in terms of materials, the water-washed label is not only a part of clothes, but also serves as a substrate for printing a UHF RFID label; in terms of printing feasibility, the traditional label washing content is generally printed by adopting screen printing, so that the label washing material is suitable for screen printing, meanwhile, the screen printing has a plurality of advantages in the direction of printing a radio frequency circuit, and the feasibility of printing the conductive ink on the label washing by using a screen printing machine is also described. The antenna with uniform and precise thickness is obtained by controlling parameters such as the speed of a scraper, the pressure of the scraper, the mesh number of a screen printing plate and the like in the screen printing process, wherein the precision mainly means that once the thickness is determined, the impedance of the antenna is perfectly matched with the chip, so that the power reflection coefficient is reduced.

The characterization indexes of the UHF RFID are mainly two: minimum power and read distance. The minimum power activates the power of the chip to transmit the signal to the reader-writer; the reading distance is the maximum distance from the tag to the antenna of the reader-writer (without environmental interference and external influence). The minimum power is generally characterized by its power reflection coefficient, and in order to achieve maximum power transfer, it is necessary to match the antenna impedance to the chip impedance well, so the invention must have a power reflection coefficient small enough to also minimize the power that activates the chip.

In the formula (1), f is frequency, (f) is power reflection coefficient, Z_C(f) Representing the impedance of the chip, Z_aThe impedance of the antenna is shown, as to the maximum distance the test reader can read the tag in terms of read distance.

After the printed antenna is protected by the chip coating, the printed antenna can be used in clothes. Of course, the label must have the properties of the garment, such as some bending, stability under the mechanical forces of washing. The antenna through screen printing is through the adhesion effect of drying back on washing mark firm, the label substrate texture is soft, can not have great influence to the performance of label under general big deformation, and antenna and chip mainly lie in wash mark inboard (outside printing washing characters pattern content), this fine prevention UHF RFID label suffer wearing and tearing, in the aspect of the washing because the back printing ink of drying is firm with washing mark adhesion, the focus is resin coating protection chip region in addition, consequently, can satisfy the washing or the washing standard commonly used of certain degree.

Compared with the prior art, the invention has the beneficial effects that: (I) the label keeps the softness of the water-washed label, is perfectly combined with the clothes, and does not influence the appearance and the comfort of the clothes; (II) the tag antenna is a broadband antenna, so that the influence of objects and materials close to the tag is greatly reduced; (III) the antenna substrate is made of a water-washed label raw material, so that the UHF RFID antenna has certain flexibility and can bear certain bending or deformation; (IV) the label has simple structure and is convenient to manufacture; and (V) the label is printed by a screen printer, so that mass production can be realized, and the method is suitable for popularization.

Drawings

FIG. 1 is a schematic plan view of a conventional UHF RFID tag;

FIG. 2 is a schematic plan view of a modified UHF RFID tag;

FIG. 3 is a graph of frequency versus input reflection coefficient;

FIG. 4 is a graph of frequency versus input impedance;

FIG. 5 is a graph of simulation results of electric field strength around a conventional UHF RFID tag;

FIG. 6 is a graph of simulation results of electric field strength around the modified UHF RFID tag.

Detailed Description

The invention is described in further detail below with reference to the figures and the examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. After reading the teaching of the present invention, the skilled in the art can make various changes or modifications to the invention, and these equivalents also fall within the scope of the claims appended to the present application.

As shown in figures 1 and 2, the planar structures of two UHF RFID tag antennas are shown, the first is a common UHF RFID antenna, the second is a little improved on the basis of the first antenna, and the two antennas have the same length and width of 100 × 20mm²The small size of the antenna is more practical due to the consideration of silk screening on the wash marksAnd (4) sex. The distance D of the port is 2mm, the loads at two ends of the improved antenna are of a hollow circular ring structure, the outer circle radius R1 is 10mm, and the small circle radius R2 is 9 mm. Since the current is mainly distributed at the edge of the antenna for the load at both ends of the antenna, the design has the effect of saving conductive ink. It can also be seen that there is a connecting strip at the antenna port to which the IC chip is attached, thus forming a complete RFID tag. One specific embodiment of the present invention is: the antenna pattern mentioned above is drawn on the screen of the screen printer, and the principle is mainly that the basic principle that the meshes of the image-text part of the screen plate are ink-permeable and the meshes of the non-image-text part are ink-impermeable is utilized for printing; the antenna impedance characteristic is controlled by the conductive ink with a certain proportion. Spreading prepared water-washed label raw materials on a printing platform below a screen printing plate, pouring a certain amount of conductive ink on the screen printing plate, applying a certain pressure on a scraper to scrape the ink from left to right, and printing the ink on the screen printing plate on the water-washed label materials on the printing platform to finish the printing of the antenna; then, placing the printed antenna into a drying box, and curing the conductive printing ink on the water-washed label; and finally, adhering and fixing the RFID chip at the connecting band by adopting conductive epoxy resin to finish the manufacture of the label.

Theoretically, the performance of the labels of the examples of the present invention is shown in fig. 3-6. As can be seen from the figure, the impedance of the modified UHFRFID tag is reduced, and the impedance change of the modified antenna tag in the UHF (902MHz-928MHz) frequency band is smaller than that of the previous tag, which means that the impedance bandwidth of the modified tag is obviously increased when the impedance change range is the same; at the same time we can find that there is little change in the strength of the electric field around the tag and before and after improvement in the input reflection coefficient. Certainly, for the conductive silver paste material adopted in the experiment, copper paste, aluminum paste and the like can also be adopted, and the influence on the final experiment effect is not great.

Claims

1. The utility model provides a wash RFID label of mark UHF frequency channel based on screen printing, a serial communication port, it has the washing mark compliance to remain when realizing UHF RFID label function, the dipole antenna design scheme with current UHF RFID label is the primary election, then, revise according to electrically conductive silver ink formula and printing technology on this basis, change the load at its both ends into the fretwork ring form, the use of electrically conductive printing ink has been practiced thrift to the fretwork ring on the one hand, on the other hand has enlarged the frequency width of antenna, manufacturing method includes: selecting label washing cloth as a substrate for printing the antenna, then printing conductive ink on the substrate by adopting a screen printing method to form the antenna, bonding a connecting band of an RFID label chip in a UHF frequency band on the antenna by using a conductive adhesive after drying, and finally coating and protecting the chip, wherein the coating material adopts flexible resin, the antenna adopts a dipole antenna, and the two ends of the dipole antenna are loaded in a hollow circular ring shape.

2. The RFID tag of UHF band of water-washable mark based on silk-screen printing of claim 1, wherein the conductive ink is conductive silver ink.