KR20070006415A - A conductive-reinforced security thread and a security paper using the same - Google Patents

Abstract

A conductivity-reinforced hidden line and a security paper using the same are provided to improve electrical property of the hidden line by coating a transparent plastic film with a conductive polymer. The conductivity-reinforced hidden line is composed of at least one transparent plastic film; at least one conductive polymer layer applied on the film layer; at least a first conductive paint print layer formed by applying the conductive paints on the upper surface of the conductive polymer layer; and at least a second conductive paint print layer formed by applying the fibrous conductive paints on the upper surface of the conductive polymer layer or the first conductive paint print layer. The thickness of the transparent plastic film is 16~25 micrometers.

Description

Conductive-reinforced Security Thread and a Security Paper Using the Same}

1 is a clear text type hidden line and a cross-sectional view thereof according to the prior art,

2 is a cross-sectional view of the silver wire manufactured according to an embodiment of the present invention,

3 is a cross-sectional view of a silver wire manufactured according to an embodiment of the present invention.

The present invention relates to a silver wire having enhanced conductivity and a security paper using the same, and more particularly, to a silver wire including a conductive polymer layer formed by coating a conductive polymer on a transparent plastic film and a security paper including the same.

In general, a silver line cut to a predetermined size is inserted in the paper to be used as a paper of various securities in a banknote to prevent forgery.

Common anti-counterfeiting silver wire sheets are disclosed in US Pat. Nos. 4,813,989 and 5,419,424, and the like. These silver wire sheets are manufactured by printing a printed layer of black or colored letters or patterns on a transparent film. In addition to the fluorescence treatment on the upper surface of the layer, or by applying a variety of factors such as conductive, magnetic, holographic properties, color conversion to a transparent or metal film, these silver wire sheets are cut to a width of about 0.5-5 mm When the paper is manufactured, it is inserted into the paper.

On the other hand, as the method of imparting conductivity to the silver wire in the above processing method, a method of sputtering a metal into a thin film or a thin film, a method of coating a conductive pigment such as a metal pigment through printing, or printing a conductive polymer on a film Methods and the like are known. As a method of depositing the metal, US Pat. No. 4,652,015, etc., deposits a metal material such as aluminum on a film to manufacture a silver wire sheet, and then inserts a silver wire cut into a predetermined size to produce a silver wire when manufacturing paper. An example of manufacturing the present invention is disclosed, and the most commonly used method is a method known in US Patent No. 4,652,015 and Korean Patent Registration No. 10-0155252 to deposit a metal coating layer so that letters or patterns appear transparently on a transparent film. And a form of clear text (see FIG. 1) formed by a metal removal method. Such a shape may have a letter confirmation effect by a clear text form as well as conductivity, and may also provide an optical effect such that the metal layer is invisible or appears in transmitted light when light is reflected. In addition, Korean Patent Registration No. 146,374 proposes to complement the electrical characteristics by a sputtering method using indium-tin oxide in a clear text type. However, indium-tin oxide is a very expensive material and is not suitable for use as a silver wire and is incompatible. Furthermore, if the sputtering method is applied, the manufacturing speed of the paper is remarkably low, resulting in a remarkable increase in manufacturing cost. On the other hand, French Patent No. 2,717,421, European Patent No. 1,359,792, US Patent No. 454,624 and the like produce a dispersion or ink containing graphite, silver or metal pigments as a conductive material and then apply the film to a film by applying a conductive silver wire to the film. An example of manufacturing is also disclosed. However, in general, conductive pigments for imparting conductivity may be used by mixing pastes of an alloy of silver and palladium, metals such as nickel, titanium, aluminum, and carbon, alone or in a mixed form with a suitable ink material. Most of these are known to be suitable only for products that are high in viscosity and therefore require large amounts of coating. Therefore, it is difficult to obtain sufficient conductivity in a gravure printing method in which the ink is low viscosity and the ink amount applied to a film which is a printing medium or the like is small. Furthermore, the metal powder or the metal paste itself containing these powders have problems such as lack of miscibility with gravure ink, rapid rise in viscosity, and a dry condition of 30 minutes at 130 ° C. It is not easy to apply to manufacturing a hidden wire sheet.

In order to solve this problem, Korean Patent Application No. 2003-93767 uses two kinds of conductive pigments having the shape of fibers, so that even if a small amount is applied, the connection between the pigment particles is easy and the conductivity is easily expressed. Although the manufacturing method of is disclosed, since the pigment having excellent conductivity among the two conductive pigments has a black color in itself, it is observed with the naked eye when it is put into the paper after the production of the silver wire. Had.

Meanwhile, European Patent No. 1,357,226 discloses a method of manufacturing a conductive film or substrate by applying a transparent conductive polymer such as polyethyenedioxythiophen (PEDT) and Polyethylendioxythiophen-Toluolsulfonat (PEDT / TS, P-DOT). There is no application example.

An object of the present invention is to solve the above problems, to provide a silver wire significantly improved conductivity by introducing a conductive polymer layer and two or more conductive pigment printing layer in a more efficient and simple process in the silver line.

Another object of the present invention to provide a security paper including the hidden line.

Hereinafter, with reference to the accompanying drawings will be described in more detail with respect to the present invention.

To achieve the object of the present invention, the enhanced conductive silver wire includes at least one transparent plastic film layer; At least one conductive polymer layer formed by coating on the film layer; And at least two conductive pigment printing layers formed of conductive pigments in the form of fibers.

That is, referring to Figure 2 or Figure 3 showing an embodiment of the present invention, the silver line according to the present invention is one or more conductive polymer layer coated on both sides of the transparent plastic film layer, and two or more formed using different pigments A conductive pigment printing layer is essentially included.

First, examples of the material used to form the transparent plastic film layer include polyamide resin, polyester resin, polyacrylic resin, polyvinylacetate resin, polyethylene resin, and polyvinyl resin. It is preferable that the thickness of the said transparent plastic film layer is 16-25 micrometers. When inserting the manufactured silver wire into the security paper, since the paper of the portion where the hidden line is inserted becomes thin, when the thickness of the transparent film exceeds the range, a hole may be formed in the security paper of the portion where the hidden line is inserted, If the thickness is thinner than the above range because the strength of the transparent film may be weakened.

The conductive polymer layer is formed by coating and drying the transparent plastic film layer, the coating method is not particularly limited. For simpler processes, a roll coating method may also be used.

As the conductive polymer material used to form the conductive polymer layer, a conventional one may be used. More preferably, 3,4-ethylenedioxythiophene (EDOT), polyaniline, polyti Polythiophene and the like can be used. As the binder, polymer binders such as polyurethane-based, silicone-based, polyimide-based, phenol-based, polyester-based and the like including epoxy resins can be used, and the amount thereof is more preferably 5 to 7%.

For the purpose of improving conductivity, the amount of the conductive polymer material used may be controlled by conventional methods, and the film may be corona-sided to increase the coating amount.

On the other hand, it is preferable that the transparency of the transparent plastic film layer coated with the conductive polymer is 89% or more. This is because most of the conductive polymers have a color, and when the excess is processed, the conductivity may be improved, but the color of the film itself is blue and green. This is because a phenomenon in which the color shines out when the paper is added to the paper and appears dark when the paper is dark may occur. In addition, as described above, the conductive polymer layer may be treated two or three times or more on both sides of the film as necessary, but for controlling the transparency and the final thickness of the silver wire, preferably, the thickness after drying of the conductive polymer layer is at most 3 μm. It is effective to make it more preferably 2-3 micrometers so that it may not exceed.

In the silver wire according to the present invention, the conductive pigment printing layer may include two or more, and they are formed on the upper surface of the conductive film for the clear text effect (hereinafter referred to as 'first conductive pigment printing layer'). ) Or a pure conductive layer (hereinafter referred to as a 'second conductive pigment printing layer'). Such a conductive pigment printing layer can be formed by printing a composition in which a conductive pigment and an ink suitable for a printing method are mixed through a printing method that is not particularly limited.

The first conductive pigment printing layer is for imparting a clear text effect to the already formed conductive polymer layer, and may be formed by simply gravure printing a conductive pigment composition in which a conductive pigment is added to a general ink or metal ink. This is because when the clear text portion of a general silver line deposits a metal layer on a transparent plastic film, the metal and other metal compounds are heated and evaporated under high temperature and vacuum conditions, and the evaporated metal is condensed on the surface of the object to form a metal layer, and then a letter or a pattern It offers the advantage of being formed in a much simpler process compared to the manufacture of parts by demetallization in various ways.

The second conductive pigment printing layer is to enhance the conductivity of the silver wire according to the present invention and to prevent the color of the first conductive pigment from being exposed to the outside of the silver wire, and is on the first conductive pigment printing layer or the conductive polymer layer. It may be formed on, and like the first conductive pigment printing layer, it may be formed by a conventional printing method including gravure printing. However, the second conductive pigment printing layer may be formed of a composition different from the composition of the composition for forming the first conductive pigment printing layer, it is preferable to include a pigment of a color lighter than the color of the first conductive pigment. .

On the other hand, as the conductive pigment that can be used for forming the first and second conductive pigment printing layers, it is more preferable to use a product in which silver or titanium is coated on the ceramic fiber by a vapor deposition method. This is to solve the problem that the metal powder used in the general conductive pigment or the metal paste to which these are added have low compatibility with the gravure ink and the viscosity increases rapidly. In addition, since the conventional conductive pigments have a drying temperature of 150 ° C. or more and a drying time of 30 minutes or more at the time of drying, they are not suitable for the printing conditions of the gravure method according to the present invention. Furthermore, in consideration of workability, aluminum particles used in the general conductive pigments or silver fine particles of 5 μm or less, which are known to have the highest conductivity, are maximally added to an ink varnish or a metal ink to prepare an ink, and After producing the silver wire sheet by printing in a gravure method, and looking at the result of measuring the electrical properties, the electrical properties of a sufficient degree required as a hidden line does not appear. This is because, due to the printing characteristics of the gravure method, common conductive pigments remain after gravure printing and drying, because they are not interconnected to connect the electrical flow due to the characteristics of the pigment form in the printing layer. Therefore, in forming the conductive pigment printing layer in the manufacturing process of the silver wire according to the present invention, by using the fiber type as described above as the conductive pigment to facilitate the interconnection than the conventional metal particles, as a result It is possible to achieve a smooth electrical flow.

On the other hand, the pigment particles are more effective in the form of fibers in the range of 10-20 μm, and more preferably prepared by adding silver or titanium to ceramic fibers. If necessary, two or more pigment particles may be mixed and used.

Specific examples of the conductive pigments in the form of fibers having the above-mentioned characteristics include Otsuka Chemical's Dental WK-500 or SD-100. Since the SD-100 itself has a dark color, it can be used to form a printing layer (negative character) for clear text effect, that is, the first conductive pigment printing layer, and is made of white ink WK-500. By forming the second conductive pigment printing layer in the form of full-printing thereon, the conductivity of the SD-100 may be further suppressed while the dark color of the SD-100 is added to the paper after the final silver line is produced.

In preparing the printing liquid for forming the conductive pigment printing layer in the production of the silver wire of the present invention, the amount of the conductive pigment in the form of the fiber is preferably 10 to 40% by weight, more preferably 15 to 20% by weight. . If it is less than this range, an electroconductive effect may be inadequate, and when it exceeds this range, a viscosity may rise and printing troubles, such as a scratch at the time of printing, may arise.

On the other hand, the silver wire of the present invention can further improve the effect of anti-counterfeiting by adding various additional functions by additionally including a fluorescent printing layer such as ultraviolet ray or upconversion fluorescence in addition to the conductive pigment printing layer.

The security paper according to the present invention includes the hidden line described above.

The hidden line may be inserted into the security paper in a form that is completely concealed or partially exposed.

More specifically, the silver wire may be used as a silver wire that is cut when the security paper is cut to a width of 1 to 5 mm, and the silver wire manufactured as described above may be used in paper or paper in the process of manufacturing the security paper. It is put in the process of production is made of security paper, or after the paper is produced is put between the paper in the process of laminating the two papers are made of security paper. The hidden line may be completely inserted or partially exposed to the inside of the paper during the manufacturing process of the security paper.

Hereinafter, the present invention will be described in more detail with reference to the following examples and comparative examples, which are merely illustrative and are not intended to limit the scope of the present invention.

Preparation of Conductive Film

Preparation Example 1

A conductive film was prepared by coating 3,4-ethylenedioxythiophene (3,4-Ethylenedioxythiophene), a conductive polymer, using a roll coater on a transparent (plastic) film having a thickness of 25 μm. The conductive polymer was coated once on one side and twice on the opposite side to prepare a conductive film, and the thickness thereof was measured to be about 1 μm on the basis of drying. In addition, in order to increase the coating amount of the conductive polymer on the transparent film, the corona discharge treatment on the transparent film in advance.

Preparation Example 2

A conductive film was prepared in the same manner as in Preparation Example 1, except that 3,4-ethylenedioxythiophene, which is a conductive polymer, was coated on both sides of the transparent plastic film once.

Manufacture of hidden line and security paper

Example 1

A first conductive pigment printing layer was formed using the conductive pigment composition A using a gravure printing machine to form a character pattern for a clear text effect on the conductive film prepared in Preparation Example 1, and the conductive pigment composition thereon. B was printed on the entire surface twice to form a second conductive pigment print layer. The conductive pigment composition B was printed once on the opposite side to form a second conductive pigment printed layer, and an infrared fluorescent printed layer was formed thereon, thereby producing a counterfeit-proof silver wire having a cross section shown in FIG. 2.

At this time, the conductive pigment composition A for forming the first conductive pigment printing layer is 5% by weight of silver powder and 15% by weight of Dental SD-100 in a varnish for PET, slowly stirred to be sufficiently mixed, and then contrasted. 2.5% by weight of methyl ethyl ketone and 2.5% by weight of toluene were added again and prepared by stirring. On the other hand, the conductive pigment composition B for forming the second conductive pigment printing layer 15% by weight of Dental WK-500 in a 80% by weight PET varnish, stirred and mixed well, and then methyl ethyl ketone and toluene like composition A Was added to the mixture was prepared by stirring.

As described above, the silver wire was cut to a width of 1.5 mm, and when the security paper was manufactured, a hidden type security paper was prepared by inputting a conventional silver wire input method in a paper machine.

Example 2

The conductive pigment composition A was printed by an ink gravure method so that a character pattern was formed on the conductive film prepared in Preparation Example 2 as a printing layer (first conductive pigment printing layer) for a clear text effect, and a B type conductive pigment thereon. The entire surface of the composition was printed to form a second conductive pigment printing layer, and on the opposite side, a fluorescent printing layer was formed to prepare an anti-counterfeiting silver wire as shown in FIG. 3. The conductive pigment compositions A and B used to form the conductive layer were the same as those used in Example 1, respectively.

The silver wire manufactured as described above was cut to a width of 1.5 mm, and a concealed type security paper was prepared by adding a conventional silver wire input method in a ring paper machine when manufacturing a security paper.

Comparative Example 1

After depositing a metal coating layer on a transparent plastic film having a thickness of 25 μm in a general manner, metal was selectively removed to form letters and patterns, thereby manufacturing a clear text-type silver wire sheet as shown in FIG. 1. The anti-counterfeiting silver wire sheet prepared as described above was cut to a width of 1.5 mm to prepare a silver wire.

When the silver wire thus prepared was manufactured in a security paper, a concealed security paper was prepared by adding a conventional silver wire input method in a paper machine.

Comparative Example 2

A conductive ink according to the present invention was printed on a transparent plastic film having a thickness of 25 μm, and a Nega type letter pattern printing layer was printed by a gravure method to produce a letter text effect on the clear text portion.

At this time, the ink composition for forming the conductive layer is 20% by weight of 20% by weight Dental SD-100 and 5% by weight of Dental WK-500 in a varnish for PET and slowly stirred to be sufficiently mixed and 2.5% by weight of methyl ethyl Ketone and 2.5% by weight of toluene were added again and prepared by stirring.

The anti-counterfeiting silver wire sheet manufactured as described above was cut to a width of 1.5 mm to manufacture a silver wire, and when the security paper was manufactured, it was put in a conventional silver wire input method in a papermaking machine to manufacture a concealed security paper.

Electrical properties

Electrical properties of the silver wires prepared by the examples and the comparative examples were measured. The silver wire manufactured in the preparation example was capable of direct contact, and the surface resistance thereof was measured. When inserted into the paper as in the example or the comparative example, the capacitance was measured to confirm the maintenance of electrical characteristics. The state after paper input of the hidden wire which concerns on this invention, and the hidden wire by the existing method was visually examined. The results are shown in Table 1 below.

In Table 1, there is no absolute value of the capacitance value for the electrical properties, and relative comparison between the measurements was performed because it may vary by country or by type.

Applying a conductive pigment to a conductive film obtained by coating a conductive polymer by a conventional printing method In Examples 1 and 2, a conductive pigment layer is formed on a general transparent film (Comparative Example 2) or conductive silver wire Compared to the case of the clear text-type hidden line (Comparative Example 1), which is representative of, it can be seen that the capacitance is larger.

As a result of visually examining the state after the prepared silver wire was put into the paper, in the case of Comparative Example 2, there was a dark appearance due to the presence of the SD-100 pigment. In Example 2, the conductive pigment composition composed of black SD-100 was printed first, and the conductive pigment composition composed of white WK-500 was printed thereon, so that the darkness of the color was much reduced. Was not visually confirmed.

As described above, the silver wire according to the present invention has excellent electrical properties compared to the case of printing only conventional conductive ink or silver wire in the form of clear text by coating a conductive polymer on a transparent plastic film. It can act as an excellent device-sensing factor in line with society's machine automation

While specific embodiments of the present invention have been described above, the present invention is not limited to the above-described specific embodiments, and the technical field to which the present invention pertains without departing from the gist of the present invention as claimed in the claims. Anyone of ordinary skill in the art that various modifications can be made, as well as such modifications are within the scope of the claims.

Claims (10)

At least one transparent plastic film layer; At least one conductive polymer layer formed by coating on the film layer; At least one first conductive pigment printing layer formed by coating with a conductive pigment in the form of fiber on the conductive polymer layer; And The silver wire comprising at least one second conductive pigment printing layer formed by coating with a conductive pigment in the form of fiber on the conductive polymer layer or the first conductive pigment printing layer. The hidden line according to claim 1, wherein the transparent plastic film layer has a thickness of 16 µm to 25 µm. The hidden line according to claim 1, further comprising an ultraviolet fluorescent printing layer or an upconversion fluorescent printing layer on the conductive polymer layer or the conductive pigment printing layer. The method of claim 1, wherein the conductive polymer layer is formed of 3,4-ethylenedioxythiophene (EDOT), polyaniline (Polyaniline), or polythiophene (Polythiophene), the thickness is 2-3㎛, the transparent The transparency of the conductive film containing a plastic film layer and a conductive polymer layer is 89 to 100%, The silver wire characterized by the above-mentioned. The silver wire of claim 1, wherein the conductive polymer layer is formed by roll coating a conductive polymer. The method of claim 1, wherein the conductive pigment in the form of fibers used to form the first or second conductive pigment printing layer has a particle size of 10 ~ 20㎛, characterized in that formed by depositing silver or titanium on the ceramic fiber Hidden line. The silver wire of claim 6, wherein the fibrous conductive pigment is prepared by adding 10 to 40 wt% of a printing liquid for forming the first or second conductive pigment printing layer. The silver line according to claim 6, wherein the color of the conductive pigment forming the second conductive pigment printing layer is brighter than the color of the conductive pigment forming the first conductive pigment printing layer. Security paper comprising a hidden line according to any one of claims 1 to 8. The security paper according to claim 9, wherein the hidden wire is cut into a width of 0.5 to 5 mm and inserted into the security paper.

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