WO2013146937A1 - Watermarked printing medium for forgery prevention - Google Patents

Description

Anti-counterfeit printing medium with watermark

The present invention relates to a watermarked anti-counterfeit print medium.

In order to suppress or prevent forgery of printed matter, a watermarked print medium may be used. For the formation of the watermark, a dandy roll or press roll is used in the paper making process, and a technology for engraving characters and patterns, or a transparent or translucent thin paper is bonded to the printing surface of a plastic sheet having characters and patterns printed thereon, A technique (Patent Document 1) is known in which opaque paper is pasted on the back surface to make a watermark.
In addition, as a paper having a watermark, a laminated paper in which a synthetic resin film and paper are bonded together and a code for authenticity determination is printed with a printing ink containing carbon as an infrared absorbing pigment on the bonding surface is known ( Patent Document 2).

Patent Document 1: Japanese Utility Model Publication No. 49-14965 Patent Document 2: Japanese Patent Laid-Open No. 2-167771

When forming a watermark using dandy roll, it is necessary to create a watermark type in advance and attach it to the dandy roll, so it is difficult to handle a wide variety of watermark patterns, characters, or figures. It is difficult to determine the authenticity only by examining the state of the watermark.
The laminate of Patent Document 1 is obtained by stacking thin paper on a plastic sheet so that characters or patterns printed on the plastic sheet can be seen through. Although it is easy to deal with a wide variety of watermark patterns, characters or figures, since the thin paper is transparent or translucent, the printed characters and patterns can be seen without being transparent to light. For this reason, the laminated body of patent document 1 was not able to be used for the use aiming at forgery prevention.
The laminated paper of Patent Document 2 has a problem that since the carbon has a dark color, the code can be easily seen through the paper, and the watermark can be easily visually confirmed, so that it is easily forged. Therefore, in order to prevent counterfeiting, it is necessary to print a dummy pattern with a dye-type black ink having different infrared absorption characteristics around the code, which increases the labor and cost of manufacturing.

In view of these problems, an object of the present invention is to provide a print medium having a watermark that can be visually confirmed when watermarked with natural light and can be effectively confirmed by means other than visual observation.
As a result of diligent research on a print medium provided with a watermark, the present inventors have a printing layer of an ink containing an antimony-doped tin oxide pigment on a core sheet, and both surfaces of the core sheet are bonded with a cover sheet. In print media, the watermark (print layer) cannot be confirmed under natural light (visible light) reflection conditions, but it can be confirmed through natural light, and it can be confirmed under infrared irradiation other than visible light. The invention has been completed.

The present invention is a laminate having a core sheet, a cover sheet provided on both surfaces of the core sheet, and a printed layer containing an antimony-doped tin oxide pigment on at least one surface of the core sheet. Provided is a watermarked anti-counterfeit print medium in which the relationship between the opacity x (%) and the solid content weight ratio y (wt%) of the antimony-doped tin oxide pigment satisfies the approximate expressions 1 and 2.

In the above laminate, the opacity x of the cover sheet is preferably 62.7% or more and less than 100%.
The solid content weight ratio y of the antimony-doped tin oxide pigment contained in the printed layer is preferably 2.2% by weight or more and 28.3% by weight or less.

The present invention is also a laminate comprising a core sheet, cover sheets provided on both surfaces of the core sheet, and a printed layer containing an antimony-doped tin oxide pigment on at least one surface of the core sheet, and visible Provided is a watermarked anti-counterfeit print medium that cannot be confirmed under light (natural light) reflection conditions, but can be confirmed with either reflected light or transmitted light under conditions of transmission of visible light and irradiation of infrared light.

The watermarked anti-counterfeit print medium of the present invention is a laminate having a print layer in which a character or pattern is printed on a core sheet as a watermark, and thus can be applied to various character or pattern watermarks. In addition, the watermark of the present invention cannot be confirmed at first glance under visible light, but can be confirmed by seeing through visible light, so that it has an anti-counterfeit effect.
Further, since the watermark pattern or character is printed using infrared absorbing ink, the authenticity can be determined by measuring the infrared absorptivity of the watermark pattern or character.

The relationship between the solid content weight ratio y (wt%) of the antimony-doped tin oxide pigment and the opacity x (%) of the cover sheet with respect to the watermark under visible light, and the straight line of the approximate expression obtained from these relation data It is a graph to show. The relationship between the solid content weight ratio y (wt%) of the antimony-doped tin oxide pigment and the opacity x (%) of the cover sheet with respect to the watermark under infrared irradiation, and the straight line of the approximate expression obtained from these relation data It is a graph to show. It is a figure which shows the straight line of FIG. 1 and the straight line of FIG. 2 together. Graph showing relational data of solid weight ratio y (wt%) of carbon black and opacity x (%) of cover sheet regarding watermark under visible light, and a straight line representing an approximate expression obtained from these relational data It is. Graph showing relationship data between opacity x (%) of cover sheet and watermark weight ratio y (wt%) of carbon black regarding watermark under infrared irradiation, and a straight line representing an approximate expression obtained from these relationship data It is. It is a figure which shows the straight line of FIG. 4 and the straight line of FIG.

Hereinafter, the present invention will be described in detail based on embodiments.
The watermarked anti-counterfeit printing medium according to the present embodiment includes a core sheet, a cover sheet provided on both sides of the core sheet, and a printed layer containing an antimony-doped tin oxide pigment on at least one side of the core sheet. Is the body. This printed layer cannot be confirmed under the condition of reflecting visible light, but can be confirmed under the condition of transmitting visible light and under irradiation of infrared light. In addition, the core sheet and the cover sheet are fixed via an adhesive.

The core sheet is not particularly limited, and a synthetic resin film can be used. The synthetic resin film is transparent or colored transparent made of polyester resin such as polyethylene terephthalate and polybutylene terephthalate, polyolefin resin such as polyethylene and polypropylene, acrylic resin, polystyrene resin, polyvinyl chloride resin, polyvinylidene chloride resin, etc. These films may be used, and may be a single-layer film or a multi-layer film made of different or similar resins. The thickness of the core sheet is not particularly limited, but is usually in the range of 10 to 200 μm.

As described below, the opacity of the core sheet is more preferably less than or equal to the opacity of the cover sheet. As will be described later, if the opacity of the cover sheet is 62.7% or more and less than 100% and the opacity of the core sheet is less than or equal to the opacity of the cover sheet, a printed layer is formed only on one side of the core sheet. Even if it is, it can confirm similarly from both surfaces of a laminated body. Conversely, when the opacity of the core sheet is higher than the opacity of the cover sheet, when the printed layer is formed only on one side of the core sheet, the laminate is formed with the side on which the printed layer is formed facing the eye. When watermarked with visible light, the printed layer can be confirmed without problems, but when watermarked from the opposite side, the printed layer cannot be confirmed or the image of what can be confirmed is blurred, and the watermark is the same from both sides of the laminate. Become invisible.
Therefore, it is desirable to select the opacity of the core sheet lower than that of the cover sheet. However, when the printing layer is formed on both surfaces of the core sheet, such a problem does not occur, and therefore, the opacity of the core sheet does not need to be lower than the opacity of the cover sheet.

The cover sheet is preferably paper with an opacity of 62.7% or more and less than 100%. If the opacity is less than 62.7%, it is not preferable because the printed layer containing the antimony-doped tin oxide pigment in the lower layer can be seen easily even under visible light reflection conditions. Moreover, in order to transmit visible light, it is necessary to be less than 100%. It is desirable that the opacity of the cover sheets disposed on both sides of the core sheet is the same. If different opacity levels are used, the printed pattern will look different, which is not preferable.

The opacity is a value defined in JIS 8149 (ISO 2469), which is a numerical value obtained by quantifying the state in which the printed pattern on the underlay cannot be seen through a single blank sheet. The higher the value, the less visible it is. Represents. Generally, it is measured with a Hunter white meter.

The printing layer formed with the ink containing an antimony dope tin oxide pigment is provided in the one or both surfaces of the core sheet. The print layer is a pattern and / or characters printed on the core sheet. And both surfaces of the core sheet which has a printing layer are bonded together with the cover sheet, and a printing layer will be covered with a cover sheet.

The antimony-doped tin oxide pigment is obtained by mixing an antimony oxide powder and a tin oxide powder with water, drying, and further pulverizing the powder obtained by adjusting the average particle diameter. Antimony-doped tin oxide pigments may be used. Examples thereof include TDL (manufactured by JEMCO), T1 (manufactured by Mitsubishi Materials Corporation), and the like.

In addition to antimony-doped tin oxide pigments, the printed layer contains resins and additives (such as antifoaming agents, dispersants, fillers, slip agents, anti-settling agents) that adjust the concentration of antimony-doped tin oxide pigments. It is. Examples of the resin include vinyl resin, acrylic resin, polyester resin, polyamide resin, amino resin, epoxy resin, urethane resin, alkyd resin, and cyclohexanone resin.

In the watermarked anti-counterfeit printing medium of this embodiment, the solid content weight ratio y (wt%) of the antimony-doped tin oxide pigment in the printing layer (weight of antimony-doped tin oxide pigment / weight of antimony-doped tin oxide pigment + resin weight) Hereinafter referred to as solid content weight ratio y) satisfies the following approximate expression 1 in relation to the opacity x (%) of the cover sheet.

This condition is a range where the print layer can be watermarked, although the print layer cannot be confirmed under the reflection condition of visible light, but can be confirmed in a state of being watermarked in visible light (under transmitted light). Under the condition of Y> 0.6992x-41.6043, the printed layer can be seen without seeing through visible light. Under the condition of Y <0.3320x-18.5943, the printed layer cannot be confirmed even when watermarked with visible light.

Since the intersection of the left side and the right side of the approximate expression 1 is in the vicinity of x = 62.6634 and y = 2.2099, the opacity of the cover sheet is 62.6634% or more, and the solid content of the antimony-doped tin oxide pigment It can be understood that the weight ratio is 2.2099% by weight or more. The upper limit of the opacity x is 100%, but the paper has less than 100%. If the opacity x of the cover sheet is 100%, the upper limit of the solid content weight ratio y of the antimony-doped tin oxide pigment is 28.3157% by weight from the left side of the approximate expression 1. The approximate expression 1 is obtained by applying the least square method based on experimental data.

Therefore, the range of the opacity x of the cover sheet is 62.7% or more and less than 100%. Further, the range of the solid content weight ratio of the antimony-doped tin oxide pigment may be not less than 2.2 wt% and not more than 28.3 wt%.
That is, in a laminate having a core sheet, cover sheets provided on both surfaces of the core sheet, and a printed layer containing an antimony-doped tin oxide pigment in at least one of the core sheets, the opacity x of the cover sheet is 62.7% or more and less than 100%; if the solid content weight ratio of the antimony-doped tin oxide pigment is in the range of 2.2% by weight or more and 28.3% by weight or less, the printed layer is under the reflection condition of visible light Although it cannot be confirmed, it can be set as a watermarked anti-counterfeit print medium that can be confirmed in the state of being watermarked in light (under transmitted light).
In addition, it cannot be confirmed under the reflection condition of visible light is a result based on the observation under the reflection condition of visible light by ten observers, and this is the case when one person could not see the printed layer. Say. Further, “can be confirmed in the state of being watermarked in the light” is a result based on observation by 10 persons under visible light transmission light, and means that everyone can see the printed layer. The method described later (Example 1) is applied to each observation method under the condition of reflecting visible light and under transmitted light. From the observation results of applying this method, it was concluded that the printed layer cannot be confirmed under visible light reflection conditions.

The antimony-doped tin oxide pigment is a pigment having an infrared absorption effect. However, when the opacity of the cover sheet is increased or the solid content weight ratio y of the antimony-doped tin oxide pigment is decreased, the infrared absorption effect may be lost. is there.

However, in addition to the approximate expression 1, when the relationship between the solid content weight ratio y of the antimony-doped tin oxide pigment and the opacity x of the cover sheet satisfies the following approximate expression 2, the infrared absorption effect may not be lost. found. In other words, the printed layer cannot be confirmed under visible light reflection conditions, but can be confirmed in a state of being watermarked in light (under transmitted light) and can be confirmed under infrared irradiation.

In addition to the approximate expression 1, the print layer of the print medium satisfying the approximate expression 2 cannot be confirmed under the reflection condition of visible light, but can be confirmed in a state of being watermarked with light (under transmitted light) and under infrared irradiation. When this printing medium is irradiated with infrared rays and the transmitted light or reflected light is observed with an apparatus capable of visualizing infrared rays such as an infrared camera, the printed layer looks black and clear, and the portion where the printed layer does not exist looks white. This is because the antimony-doped tin oxide pigment contained in the printing layer absorbs infrared rays, and the portion where no printing layer exists does not absorb infrared rays. That is, the authenticity of the print medium can be determined by irradiating infrared rays and inspecting the pattern and / or characters of the print layer. In addition, if it is an apparatus which can measure the intensity | strength of infrared rays etc., such as measuring the change of the infrared rays permeate | transmitted or reflected with the photodiode etc., a printed layer can be confirmed under infrared irradiation. This makes it possible to determine the authenticity of the print medium.
Note that “can be confirmed under infrared irradiation” means a result based on the observation of 10 persons, and all of them can confirm the shape of the pattern of the printed layer in black under infrared irradiation. As an observation method under infrared irradiation, a method described later (Example 2) is applied.

The printing medium satisfying the approximate expression 1 and the approximate expression 2 has a higher anti-counterfeit effect because it is difficult to identify that the print layer absorbs infrared rays in a state where visible light is watermarked (under transmitted light).

Similar to the approximate expression 1, the approximate expression 2 is obtained by applying the least square method based on the experimental data.
The intersection of the left side of approximate expression 1 (0.6992x−41.6043 ≧ y) and approximate expression 2 is near x = 61.99631, y = 1.7203, the right side of approximate expression 1 (y ≧ 0.3320x−18) .5943) and the approximate expression 2 are near x = 63.3240 and y = 2.4293.

The watermarked anti-counterfeit printing medium of this embodiment uses an ink composition containing an antimony-doped tin oxide pigment, forms a printing layer on one or both sides of the core sheet, and then bonds the core sheet and the cover sheet with an adhesive. Can be manufactured together. The printing layer can be formed on the core sheet by using a conventionally known printing method such as gravure printing, silk screen printing, flexographic printing, offset printing, and ink jet printing.

The ink composition comprises an antimony-doped tin oxide pigment, medium and a solvent. The medium contains the above-mentioned resin, and the solvent is for adjusting the viscosity of the ink composition, and uses an organic solvent according to the characteristics of the core sheet or cover sheet to be printed and the printing method. can do.

In the ink composition, the solid content weight ratio y of the antimony-doped tin oxide pigment may be adjusted so as to satisfy the conditions of the approximate expression 1 and the approximate expression 2 at 2.2 wt% or more and 28.3 wt% or less. . The opacity x of the cover sheet is 62.7% or more and less than 100%.

The adhesive is not particularly limited, but preferably does not contain a colorant, and may be any adhesive that can bond the core sheet and the cover sheet.

Hereinafter, the present invention will be further described with reference to examples.

The conditions under which the watermark of the printing medium was established were examined by changing the solid content weight ratio of the antimony-doped tin oxide pigment and the opacity of the cover sheet.

The ink composition consists of antimony-doped tin oxide pigment (T1, manufactured by Mitsubishi Materials Corporation), medium (vinyl ink H-type halftone, manufactured by Jujo Chemical Co., Ltd.), and solvent (vinyl standard solvent, Jujo Chemical Co., Ltd.). )) (0.2 parts by weight relative to 1 part by weight of the medium)) and a solid content weight ratio of antimony-doped tin oxide in the print layer of the print medium is 9.1 to 28.6. %.

As the cover sheet, OK quality paper and OK Prince quality paper (both manufactured by Oji Paper Co., Ltd.) shown in Table 1 were used. The opacity of the cover sheet was measured according to JIS8149.

Silk screen printing (10 μm film thickness after drying) using an ink composition on one side of a polyester film (NF-PET50, manufactured by Lintec Corporation, thickness 50 μm, opacity less than 30%) Cover sheets were bonded to both surfaces using a spray paste 55 manufactured by Sumitomo 3M Co. to obtain a laminate. For each cover sheet, samples of various laminates were prepared by changing the solid content weight ratio of antimony-doped tin oxide within a range of 9.1 to 28.6%.

With respect to the obtained laminate, the conditions under which the watermark was established were examined by the following methods (1) and (2).
(1) Determination of conditions under which the printed layer under the cover sheet cannot be confirmed under visible light reflection conditions:
The laminate was placed on a standard type color stand (part number: 123060, manufactured by Ayase Digital Create), and it was judged from both sides whether the printed layer could be seen through the cover sheet with the fluorescent lamp lit. Judgment is performed by 10 observers, and when all 10 persons can see the printed layer from at least one side of the front and back, it is judged as “can be confirmed”, and in other cases, “cannot be confirmed”. It was judged.
Table 2 shows the maximum value of the solid content weight ratio of the antimony-doped tin oxide pigment determined that the printed layer cannot be confirmed for each opacity of the cover sheet as “upper limit value”. When the solid content weight ratio of the antimony-doped tin oxide pigment is less than or equal to this upper limit, the printed layer cannot be confirmed under visible light reflection conditions, but the solid content weight ratio of the antimony-doped tin oxide pigment is higher than this upper limit. In this case, it is determined that the print layer can be confirmed. When the opacity of the cover sheet was 82.6% to 99.9%, the upper limit value of the solid content weight ratio of the antimony-doped tin oxide pigment was distributed in the range of 16.7 to 28.6% by weight.

(2) Determination of conditions under which the printed layer under the cover sheet can be confirmed in a visible light transmission state:
Using a fluorescent lamp having a color temperature of 5000K (Panasonic FHF32EX-NH, manufactured by Panasonic Corporation), the observer's naked eye, the laminate, and the fluorescent lamp were arranged in a straight line, and the both sides of the laminate were judged. At this time, the distance between the eye and the laminate was 50 cm, and the interval between the laminate and the fluorescent lamp was 150 cm. Judgment is performed by 10 observers, and when all 10 persons can see the printed layer from at least one side of the front and back, it is judged as “can be confirmed”, and in other cases, “cannot be confirmed”. It was judged.
Table 3 shows the minimum value of the solid content weight ratio of the antimony-doped tin oxide pigment determined to be able to confirm the printed layer by transmitting the laminate with visible light for each opacity of the cover sheet. When the solid content weight ratio of the antimony-doped tin oxide pigment is not less than this lower limit value, the printed layer can be confirmed in a visible light transmission state, but when the solid content weight ratio of the antimony-doped tin oxide pigment is lower than this lower limit value. It is determined that the print layer cannot be confirmed. When the opacity of the cover sheet was 81.9% to 99.9%, the lower limit of the solid content weight ratio of the antimony-doped tin oxide pigment was distributed in the range of 9.1 to 14.3% by weight.

FIG. 1 shows a straight line representing an approximate expression obtained using the least square method from the results of the opacity of the cover sheet and the solid content weight ratio of the antimony-doped tin oxide pigment shown in Tables 2 and 3.
Reference numeral 1 is a straight line representing an approximate expression obtained from the opacity of the cover sheet in Table 2 and the upper limit value of the solid content weight ratio of the antimony-doped tin oxide pigment, and y = 0.6992x-41.6043 (described above) This is a straight line represented by the left side of the approximate expression 1. The region above the straight line of reference numeral 1 is a range in which the printed layer can be easily confirmed under the visible light reflection condition.

Reference numeral 2 is a straight line representing an approximate expression obtained from the opacity of the cover sheet in Table 3 and the lower limit value of the solid content weight ratio of the antimony-doped tin oxide pigment, and y = 0.3320x-18.5943 (described above) This is a straight line represented by the right side of the approximate expression 1. The region below the straight line of reference numeral 2 is a range that cannot be confirmed even when the print layer transmits visible light. The intersection coordinates of the straight line with the reference numeral 1 and the straight line with the reference numeral 2 are (x = 62.6634, y = 2.2099).

That is, the layered body in the region between the straight line 1 and the straight line 2, that is, in the range of 0.6992x−41.6043 ≧ y ≧ 0.3320x−18.55943 (which is approximate expression 1) is The printed layer cannot be confirmed under visible light reflection conditions, but the printed layer can be confirmed when transmitted through visible light.

As described above, the straight line 1 and the straight line 2 are straight lines representing approximate expressions obtained by the least square method using the lower limit value or the upper limit value obtained in this example. The lower limit value or the upper limit value shown in Table 3 is not necessarily distributed on each straight line, but is distributed with a certain width.

For the laminate obtained in Example 1, the conditions under which the printed layer covered with the cover sheet could be confirmed under infrared irradiation were examined.

Place the layered product on the stand of the standard type color viewing table (product number: 123060, manufactured by Ayase Digital Create), irradiate the layered product with infrared light in the wavelength range of 800 to 1000 nm without turning on the fluorescent lamp, and infrared camera (YASHICA Observation was performed in the infrared night mode of EZ Digital F537IR, manufactured by EXE MODE Co., Ltd., and it was determined whether the print layer could be confirmed. The infrared light source was installed in the infrared camera, and the distance between the sample and the infrared camera was 5 cm. The determination is performed by 10 observers, and infrared rays are absorbed by the print layer, and the image of the print layer is black, and the portion where the print layer is not formed is imaged white, so that all 10 people are printed layers. When it was possible to see the shape of the print layer, it was judged as “can be confirmed”, and when even one person could not see the shape of the printed layer, it was judged as “cannot be confirmed”.

Table 4 shows the minimum solid content weight ratio (lower limit value) of the antimony-doped tin oxide pigment that can confirm the printed layer by irradiating the laminate with infrared rays for each opacity of the cover sheet. When the opacity of the cover sheet was 76.8% to 96.8%, the lower limit of the solid content weight ratio of the antimony-doped tin oxide pigment was in the range of 9.1 to 21.1% by weight.

FIG. 2 shows a straight line representing an approximate expression obtained from the results of Table 4. Reference numeral 3 in the figure represents a straight line y = 0.5210x−30.597 (described above) representing an approximate expression obtained from the relationship data between the solid content weight ratio y of the antimony-doped tin oxide pigment and the opacity x of the cover sheet. It is expressed by approximate expression 2.). A region above the reference numeral 3 is a range in which infrared absorption can be determined.
As described in FIG. 1, the straight line 3 represents an approximate expression obtained by the least square method using the lower limit value obtained in this embodiment, and the lower limit value is always on each straight line. It is not distributed but distributed with a certain distance.

FIG. 3 also shows the straight lines of approximate expression 1 and approximate expression 2. The area below the straight line of reference numeral 1 and the area above each of the straight lines of reference numerals 2 and 3 (the hatched area in FIG. 3) indicates that “the printed layer cannot be confirmed under visible light reflection conditions, but visible light It is the range that can be confirmed under the condition of passing through and under infrared irradiation. The intersection coordinates of the straight line 1 and the straight line 2 are (x = 62.6634, y = 2.2099), and the intersection coordinates of the straight line 1 and the straight line 3 are x = 61.9963, y = 1.7203 (indicated by perpendicular lines to the X-axis and Y-axis in the figure), and the intersection coordinates of the straight line 2 and the straight line 3 are (x = 63.3240, y = 2.4293). . From this result, it is understood that the conditions of the approximate expression 1 and the approximate expression 2 satisfy x = 62.6634% or more and y = 2.2099% by weight or more. On the other hand, the opacity x of the cover sheet needs to be less than 100% in order to transmit visible light. The upper limit value of the solid content weight ratio y of the antimony-doped tin oxide pigment is 28.3157% by weight from the left side of the approximate expression 1 when the opacity x of the cover sheet is 100% (see FIG. Corresponds to a solid content ratio value of 1 corresponding to 100% transparency). Therefore, in the present invention, “the range in which the printed layer cannot be confirmed under visible light reflection conditions but can be confirmed under visible light transmission conditions and under infrared irradiation” has an opacity x of the cover sheet of 62. 7% or more and less than 100%, and the solid content weight ratio y of the antimony-doped tin oxide pigment is 2.2% by weight or more and 28.3% by weight or less.

[Comparative example]
Instead of antimony-doped tin oxide pigment, a typical carbon black is used as an infrared absorbing material, and a laminate is produced under the conditions shown below. The print layer can be confirmed under conditions allowing watermark judgment and under infrared irradiation. The conditions were examined.

Carbon black (Mitsubishi Carbon Black, general-purpose color (RCF) # 44, manufactured by Mitsubishi Chemical Corporation), medium (vinyl ink H-type halftone, manufactured by Jujo Chemical Co., Ltd.), and solvent (vinyl standard solvent, Jujo Chemical ( Co., Ltd.) (0.2% by weight with respect to the medium)) was mixed with a jet mill to prepare an ink composition.

The ink composition was prepared so that the weight ratio of carbon black contained in the printed layer of the laminate was 0.15 to 3.0%.
Moreover, the same OK fine paper and OK Prince fine paper as Example 1 were used for the cover sheet.

The same conditions as in Example 1 were used, and it was determined whether the print layer could be confirmed by changing the solid weight ratio of carbon black when using a cover sheet of each opacity. When the opacity of the cover sheet was 91% or less, the hue of carbon black was so dark that even if the density was reduced, the printed layer could be seen and did not form a watermark. Table 5 shows the upper and lower limits of the solid content weight ratio of carbon black in a laminate using a cover sheet having an opacity of 91% or more. Moreover, the straight line showing the approximate expression calculated | required from the result of Table 5 in FIG. 4 is shown.

4 is a straight line representing an approximate expression obtained from the result of the upper limit of the opacity of the cover sheet and the solid content weight ratio of carbon black in Table 5. In the region above the straight line 11, the solid content weight ratio of carbon black is too large, so that the printed layer becomes dark, and the printed layer can be confirmed under reflective conditions, even under visible light transmission conditions. . Reference numeral 12 is a straight line representing an approximate expression obtained from the lower limit of the opacity of the cover sheet and the solid weight ratio of carbon black in Table 5. In the region below the straight line of reference numeral 12, the solid weight ratio of the carbon black is too small, so that the color of the print layer becomes light and the print layer cannot be confirmed even under visible light transmission conditions.

The range in which the printed layer can be confirmed under infrared irradiation was examined under the same conditions as in Example 2. The results are shown in Table 6. Moreover, the straight line showing the approximate expression calculated | required from the opacity of the cover sheet | seat calculated | required from the result of Table 6, and the solid content weight ratio of carbon black is shown in FIG.

Reference numeral 13 in FIG. 5 is a straight line representing an approximate expression obtained from the lower limit of the solid content weight ratio of the carbon black and the opacity with which the printed layer can be confirmed under infrared irradiation in Table 6. The area above the reference numeral 13 is a range in which the printed layer can be confirmed under infrared irradiation. In the region below the straight line 13, since the amount of carbon black (solid content weight ratio) is too small, the color of the print layer is light and the print layer cannot be confirmed under infrared irradiation.

6 shows the straight line in FIG. 4 and the straight line in FIG. 5 together. Unlike FIG. 3, in FIG. 6, there is no coexistence of a region where the range where the watermark is formed and the range where the print layer can be confirmed under infrared irradiation. In other words, when carbon black is used as an infrared absorbing material, the printed layer cannot be confirmed under visible light reflection conditions, but the printed layer can be confirmed under visible light transmission conditions and under infrared irradiation. It can be seen that a print medium for use cannot be obtained.

The effect of the difference in the transparency of the core sheet on the watermark and infrared absorption judgment of the laminate was investigated in relation to the opacity of the cover sheet.
Using the ink composition shown in Table 7, silk screen printing (film thickness 10 μm) was performed on one side of each core sheet shown in Table 8, and then the cover sheet (35 Inde W, manufactured by Nippon Paper Papillia Co., Ltd.) was used on the core sheet. , Opacity 80%) was laminated to produce three types of samples. The solid content weight ratio of the antimony-doped tin oxide pigment was 14.3%.

That is, the characteristics of the three types of samples are as follows.
Sample No. 1: The opacity of the core sheet is lower than the opacity of the cover sheet (80%) and the lower limit (about 62%) at which the watermark under visible light and the printed layer under infrared irradiation can be confirmed.
Sample number 2: The opacity of the core sheet is higher than the opacity of the cover sheet (80%) and the lower limit (about 62%) at which the watermark under visible light and the printed layer under infrared irradiation can be confirmed.
Sample number 3: The opacity of the core sheet is lower than the opacity of the cover sheet (80%) and higher than the lower limit (about 62%) at which the watermark can be confirmed under visible light and the printed layer under infrared irradiation. .

The determination of the watermark under the same conditions as the “determination of conditions under which the printed layer under the cover sheet can be confirmed in a visible light transmission state” in Example 1 and the same conditions as the “confirmation of the printed layer under infrared irradiation” in Example 2 Table 9 shows the results of the infrared absorption determination performed at. In the table, ◯ indicates that “the watermark was confirmed from both sides in the visible light transmission state” or “the infrared absorbing layer was confirmed from both sides under infrared irradiation”, and the △ indicates “from one side The watermark has been confirmed. "

For sample number 3 only, in the visible light transmission state, the printed layer formed on the surface closer to the eyes of the core sheet was confirmed, but the printed layer formed on the surface farther from the eyes was confirmed. could not. This is presumably because the light transmission was blocked by the core sheet and the shadow was blurred.
That is, in a laminate in which the printed layer is formed only on one side of the core sheet, when the opacity of the core sheet is higher than the opacity of the cover sheet, the watermark does not look the same when viewed from both sides. I understand.

1: A straight line representing the left side of the approximate expression 1: 2: A straight line representing the right side of the approximate expression 1: 3: A straight line representing the approximate expression 2: 11: From the result of the upper limit of the opacity of the cover sheet regarding the watermark and the solid content weight ratio of the carbon black A straight line representing the obtained approximate expression 12: A straight line representing an approximate expression obtained from the result of the lower limit of the weight ratio of the solid content of the carbon black and the cover sheet relating to the watermark 13: The opacity of the cover sheet relating to infrared absorption and the carbon black A straight line representing the approximate expression obtained from the lower limit of the solid content weight ratio

Claims (8)

A core sheet, cover sheets provided on both surfaces of the core sheet, and a printed layer containing an antimony-doped tin oxide pigment on at least one surface of the core sheet,
A watermarked anti-counterfeit printing medium in which the relationship between the opacity x of the cover sheet and the solid content weight ratio y of the antimony-doped tin oxide pigment contained in the printing layer satisfies the following approximate expression 1 and the following approximate expression 2.

A core sheet, a cover sheet provided on both surfaces of the core sheet, and a printed layer containing an antimony-doped tin oxide pigment on at least one surface of the core sheet. A watermarked anti-counterfeit printing medium that cannot be confirmed under reflection conditions but can be confirmed under conditions of transmission of visible light and irradiation of infrared rays. The watermarked anti-counterfeit printing medium according to claim 1, wherein the opacity of the cover sheet is 62.7% or more and less than 100%. The watermarked anti-counterfeit printing medium according to claim 2, wherein the opacity of the cover sheet is 62.7% or more and less than 100%. The watermarked anti-counterfeit printing medium according to claim 1, wherein the solid content weight ratio of the antimony-doped tin oxide pigment contained in the printing layer is 2.2 wt% or more and 28.3 wt% or less. The watermarked anti-counterfeit printing medium according to claim 2, wherein a solid content weight ratio of the antimony-doped tin oxide pigment contained in the printing layer is 2.2 wt% or more and 28.3 wt% or less. The watermarked anti-counterfeit printing medium according to claim 1, wherein the opacity of the core sheet is equal to or less than the opacity of the cover sheet. The watermarked anti-counterfeit printing medium according to claim 2, wherein the opacity of the core sheet is equal to or less than the opacity of the cover sheet.

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