Method for producing security ink

Abstract

To provide a method for producing a security ink, by which the security ink having stable quality can be obtained even when the ink is prepared at a printing site.SOLUTION: The method for producing the security ink includes a step A of preparing a concentrated ink by mixing a medium with a functional pigment, and a step B of preparing a security ink having a functional pigment content lower than that of the concentrated ink by adding the medium to the concentrated ink and mixing them.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing security ink, and more particularly to a method for producing security ink used for anti-counterfeit printed matters such as security labels, booklets, and security prints. [Background technology]

[0002] 2. Description of the Related Art Various anti-counterfeiting technologies are applied to securities such as stock certificates, bonds, checks, gift certificates, lottery tickets, and commuter passes, as well as to anti-counterfeiting labels, in order to prevent counterfeiting, alteration, and tampering. For example, there are anti-counterfeiting technologies that use plate-making technology, such as micro-text, latent images, and color printing; intaglio printing that uses printing technology; watermarks that use paper manufacturing technology; and security inks that incorporate anti-counterfeiting technology into the ink itself.

[0003] Security ink is an ink that has been given a special effect by mixing a pigment containing anti-counterfeiting technology (hereinafter referred to as "functional pigment") into a medium (see, for example, Patent Document 1). Examples of effects that can be given include ultraviolet fluorescence, ultraviolet absorption, infrared light absorption, infrared light transmission, infrared fluorescence, and optical effects (pearl pigments, glass beads, polarized light). These inks are applied using a variety of printing methods, but offset printing is often used in combination with platemaking techniques, which has the advantage of lowering ink costs compared to intaglio printing.

[0004] To prevent counterfeiters from realizing that security inks have been added with anti-counterfeiting technology, the ink itself is made transparent or the same color as other printed parts. In either case, the functional pigment must be contained in a specified amount or more in the medium, and it is important to control that amount. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2023-506825 Summary of the Invention [Problem to be solved by the invention]

[0006] If such security inks were to be distributed in large quantities and used for general purposes, they would become easily available to counterfeiters, and their effectiveness would be significantly reduced.For this reason, security inks are now often prepared by mixing functional pigments and mediums at the printing site. However, when a large amount of pigment is mixed into the medium, even if the amount of pigment meets the requirements, the pigment may not be uniformly dispersed in the finished ink. When printing is performed using such an ink, printing defects such as unevenness and clumps may occur, and the effects of the functional pigment may not be fully realized.

[0007] In view of the above circumstances, an object of the present invention is to provide a method for producing security ink that can provide security ink of stable quality even when prepared on-site. [Means for solving the problem]

[0008] The present invention provides a method for producing security ink, comprising step A of mixing a medium and a functional pigment to prepare a concise ink, and step B of adding a medium to the concise ink and mixing them to prepare a security ink having a lower content of functional pigment than the concise ink. [Effects of the Invention]

[0009] According to the present invention, a method for producing security ink can be provided that can produce security ink of stable quality even when prepared on-site. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing an anti-counterfeit printed matter produced using a security ink according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention will be described with reference to FIG. The inventors have investigated the mixing and preparation of security inks by varying the ratio of medium to functional pigment, and have concluded that there is a limit to how much uniformity can be improved in the functional pigment in security inks prepared by mixing and adjusting the medium and functional pigment at the printing site using a spatula or the like.

[0012] Therefore, we prepared a concentrated ink by uniformly mixing the medium and functional pigment in advance, and then diluted it at the printing site, thereby achieving a security ink at the printing site that contains a certain amount or more of functional pigment and in which the functional pigment is uniformly dispersed within the medium.

[0013] The concentrated ink according to this embodiment contains a medium and a functional pigment. Since the concentrated ink is not intended to be used for printing as is, it contains a higher content of the functional pigment than the security ink used for printing. For example, when the concentrated ink is used as an ink for offset printing, the amount of functional pigment in the concentrated ink is 25% by mass or more.

[0014] Although there is no upper limit to the amount of functional pigment in a conc ink, as the amount of functional pigment increases, the viscosity of the conc ink also increases, making it difficult to dilute with a spatula at the printing site. From the perspective of smooth dilution with a spatula, it is preferable that the viscosity of the conc ink be 150 Pa·s or less. The viscosity of the thick ink can be measured using a cone-plate viscometer. The measurement conditions are, for example, a cone diameter of 20 mm, 0.5°C, and a shear rate of 117 sec. -1 , can be set to 25℃.

[0015] The medium used for the concentrated ink varies depending on the properties of the security ink after preparation. If the security ink after preparation is to be UV-curable, examples of the medium include acrylic monomers. If the security ink after preparation is to be UV-curable, examples of the medium include linseed oil and soybean oil.

[0016] The functional pigment used in the conc ink can be appropriately selected depending on the security effect to be achieved, and is not particularly limited. Examples include fluorescent pigments that emit visible light when excited by ultraviolet light, fluorescent pigments that emit visible or infrared light when excited by infrared light, ultraviolet absorbing pigments, infrared transmitting pigments, infrared absorbing pigments, and pearl pigments that emit a luster when tilted.

[0017] Concrete ink can be prepared by mixing a medium and a functional pigment to a certain degree of uniformity. Concrete ink can be prepared using a known three-roll mill, such as that described in JP 2006-247482 A. A typical three-roll mill has three rolls that rotate at low, medium, and high speeds, respectively, and crushes, kneads, disperses, and degasses the mixed material by compressing it between the rolls and by shearing it due to the difference in roll speeds. The three rolls may be made of metal, preferably with a hard chrome surface. The diameter of the three rolls may be 50 mm or more and 200 mm or less. The rotation ratio of each roll may be, for example, 1:2 to 3:7 to 9.

[0018] In addition to the medium and functional pigment, the concentrated ink may contain a color-forming pigment to impart a desired color. By using a color-forming pigment, the security ink can be printed in the same color as the base, making it less noticeable on printed materials under normal conditions. Therefore, the appearance of the concentrated ink according to this embodiment is diverse, ranging from transparent inks, including colorless transparent inks, to inks with various colors.

[0019] When producing security ink using the above-mentioned concentrated ink, the concentrated ink is scooped up with a spatula and spread on a stage, and then medium is added to the ink and diluted while mixing with the spatula. The medium used for dilution is preferably the same as the medium of the concentrated ink, but may be a different type. Furthermore, the medium to be diluted may be a color ink containing a color pigment. In this case, the concentrated ink may not contain a color pigment, or the color pigment of the concentrated ink may have a different color from the color pigment of the color ink. For example, if the conk ink does not contain a color-forming pigment, a wide variety of colored security inks can be produced from a single conk ink by using a desired colored ink as the desired medium. As another example, if the security ink is to be printed in two places on a yellow and green background in the target printed matter, a security ink that can be used for both printings can be produced by adding a yellow color-forming pigment to the conk ink and diluting it with a blue ink.

[0020] The security ink of this embodiment, which is produced by adding a medium to a concentrated ink, contains a functional pigment at a lower content than the concentrated ink. The specific functional pigment content, tack, flow, and other parameters of the security ink can be adjusted appropriately depending on the printing conditions, and this adjustment can be easily achieved by changing the amount of medium added. To give an example of tack and flow, the tack is approximately 7 to 12 when measured with an incometer at 400 rpm, 30°C, and 1 minute, and the flow is approximately 14 to 20 mm radius when measured with a spreadmeter at 25°C and 1 minute. These parameters are suitable for printing colored patterns and microtext, and can achieve high print quality.

[0021] The process of diluting the concentrated ink according to this embodiment is significantly more difficult to achieve uniform mixing of the components than when diluting a general ink with high fluidity using a solvent such as thinner, because both the concentrated ink and the medium are in a highly viscous paste form. However, this embodiment uses concentrated ink in which the functional pigment is uniformly dispersed in advance, so security ink with a highly uniform distribution of the functional pigment can be produced even when mixing is performed using a spatula, scraper, or the like. Furthermore, if the viscosity of the concentrated ink is 150 Pascal seconds or less, there is an advantage that dilution work using a spatula becomes easier.

[0022] The dispersion of functional pigments in concentrated inks can be measured and controlled using a grindmeter. JIS K5600-2-5 Dispersity can be used as a measurement method. Results of grindmeter measurements in the range of 5 μm to 15 μm are considered acceptable, and anything else is considered unacceptable. The temperature of the measurement chamber can be room temperature. The surface temperature of the grindmeter is preferably room temperature, between 15°C and 25°C, but room temperature between 5°C and 35°C is also acceptable. The groove depth of the grindmeter can be 50 μm or 25 μm. For periodic control, a grindmeter with a 50 μm groove is particularly suitable. This reduces variations due to the operator and is suitable for pass / fail control. It is particularly recommended to use a grindmeter with two grooves, and a value of 5 μm to 15 μm for both grooves is considered acceptable. If there is a difference of 5 μm or more between the two grooves, a remeasurement is required. In other words, it is preferable that the difference between the two grooves is less than 5 μm, and that each groove is within the range of 5 μm to 15 μm. Alternatively, measurements can be taken with a 25 μm groove, which has poor measurement reproducibility but allows for higher accuracy, and can be used for statistical quality control such as variations between production days (due to the relationship with the materials used, manufacturing variations, etc.). When using a grindmeter with a 25 μm groove for pass / fail judgment, measurements can be taken three to five times and the average value can be used. In this case, too, the product is considered pass if the difference between the two grooves is less than 5 μm and is in the range of 5 μm to 15 μm, respectively. If there is a difference of 5 μm or more between the two grooves, re-measurement can be performed.

[0023] 1 is a diagram showing an anti-counterfeit printed matter 1 according to this embodiment. The anti-counterfeit printed matter 1 has a configuration in which a printed portion 20 is formed on a substrate 10. The printed portion 20 of this embodiment has a picture display portion 21 and a character display portion 22 formed with normal ink, and an identification portion 23 formed with the security ink according to this embodiment.

[0024] Various types of paper, such as art paper, fine paper, coated paper, and synthetic paper, as well as synthetic resin sheets, can be used as the substrate 10. When a paper substrate is used, other security features may be added, such as watermarking, incorporating fibers, or transferring a hologram. The identification section 23 according to this embodiment is formed on the substrate 10 by offset printing using the security ink prepared by the procedure described above. In the example shown in FIG. 1 , the identification section 23 is formed in region R1, which is free of either the picture display section 21 or the text display section 22. However, the location where the identification section 23 is provided is not limited to this, and the identification section 23 can also be formed, as in region R2, overlapping all or part of the picture display section 21 and the text display section 22. If the security ink is transparent or the same color as the overlaid picture display section 21 and text display section 22, it becomes difficult to distinguish between areas where the identification section 23 is provided and areas where it is not provided, making it difficult to recognize that the printed matter has been subjected to anti-counterfeiting treatment. The method for forming the picture display portion 21 and the character display portion 22 is not limited to offset printing, but may be other printing methods such as intaglio printing or screen printing.

[0025] When the identification section 23 of the anti-counterfeit printed matter 1 undergoes a process corresponding to the security ink used, it exhibits a predetermined visual effect, such as a change in appearance. This allows for reliable authentication and contributes to the prevention and suppression of counterfeiting. Furthermore, since the functional pigment is uniformly dispersed in the security ink, it can produce a good visual effect even when prepared at the printing site.

[0026] The concentrated ink according to this embodiment is diluted before use, and therefore has a small volume before dilution. Because functional pigments are generally expensive, even when used in anti-counterfeit printed matter 1, the identification section 23 is often formed in a very small area, and the amount used is often significantly less than the ink used to form the picture display section 21 and the character display section 22. Because the concentrated ink has a small volume before dilution, it can be stored for long periods without occupying a large space, and its quality is less likely to deteriorate than diluted ink. By using security ink that uses concentrated ink, even when anti-counterfeiting printed materials are produced at multiple locations, the quality of the security ink prepared at each printing site can be stabilized, and as a result, the quality of the anti-counterfeiting printed materials produced at each location can also be stabilized.

[0027] To summarize the above, the method for producing security ink according to this embodiment comprises the following two steps. Step A: Mix the medium and functional pigment to make a concentrated ink. Step B: Add medium to the concentrated ink and mix to produce a security ink that has a lower functional pigment content than the concentrated ink.

[0028] The method for producing the security ink according to the present invention will be further explained using examples and comparative examples. The present invention is not limited solely to the specific content of each example.

[0029] Example 1 A UV-curable offset medium (FD Karton X Medium M manufactured by Toyo Ink Co., Ltd.) and a functional pigment with infrared fluorescence that is colorless and transparent under visible light (IR-S manufactured by Nemoto Specialty Chemical Co., Ltd.) were used. These materials were mixed using a three-roll mill to prepare the colorless and transparent concentrated ink of Example 1 containing 35% by mass of the functional pigment. When this concentrated ink was measured under the above conditions using a cone-plate viscometer, the viscosity was found to be 150 Pa s or less. The concentrated ink of Example 1 was scooped up with a spatula and spread on a stage, and the offset medium (FD Carton X Medium M) was added and mixed with a spatula to dilute, producing the colorless and transparent security ink of Example 1 containing 20% ​​by mass of functional pigment. The concentrated ink had little dripping and could be spread appropriately, allowing for smooth dilution. When the infrared fluorescence function was confirmed using anti-counterfeit printed material with an identification section formed by offset printing using this security ink, uniform fluorescence was observed in the identification section, confirming that the functional pigment was uniformly dispersed. The physical properties of the security ink prepared were measured, and the tack was 10 when measured at 400 rpm, 30°C, and 1 minute, and the flow was 15 mm radius when measured at 25°C and 1 minute using a spread meter. When the security ink was spread using a 0.1 cc full-surface roll using an RI tester, there were no lumps in the ink transfer, and no fading of the spread ink, so there were no problems. This confirmed that the security ink prepared using the concentrated ink of Example 1 had no problems with dispersibility.

[0030] Example 2 The concentrated ink of Example 1 was scooped up with a spatula and spread onto a stage, and the offset medium and a pigment-containing offset color ink (FD Carton X Crimson, manufactured by Toyo Ink Co., Ltd.) were added, mixed with a spatula, and diluted to produce the crimson security ink of Example 2, containing 20% ​​by mass of functional pigment. When the infrared fluorescence function was confirmed using an anti-counterfeit printed matter on which an identification section was formed by offset printing using this security ink, uniform fluorescence was observed in the identification section, confirming that the functional pigment was uniformly dispersed.

[0031] (Comparative Example 1) Without using concentrated ink, the same offset medium and functional pigment as in Example 1 were mixed on a stage using a spatula to produce a colorless and transparent security ink containing 20% ​​by mass of functional pigment according to Comparative Example 1. When the infrared fluorescence function was checked using an anti-counterfeit printed matter on which an identification section was formed by offset printing using this security ink, unevenness was observed in the fluorescence of the identification section, confirming that the functional pigment was not uniformly dispersed.

[0032] (Comparative Example 2) An attempt was made to produce a crimson security ink according to Comparative Example 2 containing 20% ​​by mass of functional pigment by mixing the same offset color ink (FD Carton X Crimson) as in Example 2 on a stage without using concentrated ink. However, the functional pigment formed clumps and was not sufficiently dispersed, making it impossible to produce the security ink itself.

[0033] As described above, in the method for manufacturing security ink according to this embodiment, it has been shown that both colorless and colored security inks can be suitably manufactured through preparation using a spatula or the like at the printing site. In the above examples and comparative examples, 5 kg of security ink can be produced from 1 kg of functional pigment, and while a normal production run would require 5 kg of storage space, in the form of concentrated ink this amounts to 2.85 kg, roughly halving the storage space required. Furthermore, because only the required amount of concentrated ink can be extracted to produce security ink and the remainder can be continued to be stored as concentrated ink, it is less susceptible to deterioration than when stored in the form of security ink.

[0034] Although one embodiment of the present invention has been described above, the specific configuration is not limited to this embodiment, and modifications and combinations of the configuration within the scope that does not depart from the gist of the present invention are also included. [Explanation of symbols]

[0035] 1 Anti-counterfeiting printed matter 10 Base material 20 Printing Department 23 Identification unit

Claims

1. Step A: mixing a medium and a functional pigment to prepare a concentrated ink; Step B: adding a medium to the concentrated ink and mixing them to prepare a security ink having a lower content of the functional pigment than the concentrated ink; Equipped with Method for manufacturing security ink.

2. The content of the functional pigment in the concentrated ink is 25 mass percent or more. A method for producing the security ink according to claim 1.

3. The viscosity of the thick ink is 150 Pascal seconds or less. A method for producing the security ink according to claim 1.

4. In step B, a color ink containing a medium and a color-forming pigment is mixed. A method for producing the security ink according to claim 1.

5. The same medium is used for step A and step B. A method for producing the security ink according to claim 1.

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