JP2021187006A - Liquid discharge device and printed matter - Google Patents

Abstract

To provide a liquid discharge device and a printed matter which can improve security property related to a concealment image.SOLUTION: A liquid discharge device includes: a liquid discharge head capable of discharging a liquid which is substantially invisible under visible light irradiation and has ultraviolet excitation type fluorescent emission characteristics; and a control part which controls the liquid discharge head, and forms a concealment image where a main pattern whose luminous color is a first color and a sub-pattern including a thin line whose luminous color is a second color are alternately arranged on a recording medium according to information of an image.SELECTED DRAWING: Figure 5

Description

The present invention relates to a liquid ejection device and printed matter.

In the liquid discharge device, in order to prevent falsification and forgery, a hidden image that is difficult to confirm its existence under visible light irradiation may be formed on a recording medium such as a passport, a vehicle verification, a cash card, or a banknote.

In Patent Document 1, a first ink that has the same color under visible light irradiation and emits light under ultraviolet irradiation and a second ink that does not emit light are prepared, and a camouflage element group is provided on a base material with the first ink. It is described that printing is performed and the latent image element group is printed with a second ink. As a result, according to Patent Document 1, the latent image element group is hidden by the camouflage element group having the same color under visible light irradiation and is invisible, and the latent image element group has a contrast with the camouflage element group under ultraviolet irradiation. It is said that it becomes visible and the effect of changing the image by irradiation with ultraviolet rays can be obtained.

In the technique described in Patent Document 1, the emission color (color when irradiated with ultraviolet rays) of a concealed image by a liquid which is substantially invisible under visible light irradiation and has ultraviolet excitation type fluorescence emission characteristics is a single color. Therefore, once the emission wavelength of the liquid is known, it is not so difficult to forge a similar concealed image with a dye having the same fluorescence wavelength, and the security may not be high.

The present invention has been made in view of the above, and an object of the present invention is to provide a liquid ejection device and a printed matter which can improve the security of a hidden image.

In order to solve the above-mentioned problems and achieve the object, the liquid ejection device according to one aspect of the present invention ejects a liquid which is substantially invisible under visible light irradiation and has ultraviolet excitation type fluorescence emission characteristics. A possible liquid discharge head and a sub that controls the liquid discharge head and includes a main pattern having a first color of emission and a thin line having a second color of emission on a recording medium according to image information. It is characterized by having a control unit for forming a hidden image in which patterns are alternately arranged.

According to the present invention, there is an effect that the security property of the hidden image can be improved.

FIG. 1 is a diagram showing an external configuration of a liquid discharge device according to an embodiment. FIG. 2 is a diagram showing a schematic configuration of a liquid discharge device according to an embodiment. FIG. 3 is a diagram showing a configuration of a liquid discharge head according to an embodiment. FIG. 4 is a diagram showing colors of printed matter in the embodiment. FIG. 5 is a diagram showing the configuration and characteristics of the printed matter in the embodiment. FIG. 6 is a diagram showing the configuration and characteristics of the printed matter in the embodiment. FIG. 7 is a diagram showing the configuration and characteristics of the printed matter in the embodiment. FIG. 8 is a diagram showing a state of light emission of a hidden image in the embodiment. FIG. 9 is a diagram showing an emission spectrum of a concealed image in the embodiment. FIG. 10 is a diagram showing the characteristics of the hidden image in the embodiment.

(Embodiment)
The liquid ejection device according to the embodiment forms a concealed image on a recording medium such as a passport, a vehicle verification, a cash card, or a banknote, which is difficult to confirm its existence under visible light irradiation, in order to prevent falsification or forgery. The recording medium on which the concealed image is formed is also called a luminescent printed matter, and the image that can be visually recognized under visible light irradiation in the printed image changes to a different image that has no correlation when irradiated with ultraviolet rays, so-called image change. Has an effect. Therefore, the visible image is not reflected in the luminescent image that appears when irradiated with ultraviolet rays, and both the visible image and the luminescent image have high visibility, so that the authenticity discrimination is excellent.

For example, there is a technique for printing a concealed image on a seemingly blank sheet by using a substantially colorless and transparent ultraviolet-excited fluorescent light-emitting liquid under visible light irradiation. In this technique, the emission color of the concealed image is a single color, and once the emission wavelength of the emission liquid (emission ink) is known, it is not so much to forge a similar concealed image with a dye having the same fluorescence wavelength. It's not difficult and may not be very secure.

Therefore, in the present embodiment, in the liquid ejection device, light is emitted according to the information of the image in which the original image is negatively inverted by the liquid which is substantially invisible under visible light irradiation and has ultraviolet excitation type fluorescence emission characteristics. By forming a concealed image on the recording medium in which the main pattern whose color is the first color and the sub-pattern containing the fine lines whose emission color is the second color are alternately arranged, the security of the concealed image is improved. Try.

Specifically, as a liquid (ink) having ultraviolet-excited fluorescence emission characteristics, a liquid whose emission color is the three primary colors of light (Red, Green, Blue) is used. The liquid ejection device ejects these three types of liquids (inks) from the liquid ejection head onto the recording medium, and the main pattern having the first color (for example, Red) and the second emission color on the recording medium. Sub-patterns containing thin lines of color (eg, Green and / or Blue) are arranged alternately at equal pitches without mixing. As a result, the color of the main pattern that emits light appears to be discolored by irradiating the recording medium with ultraviolet rays. Not only does this discoloration appear to the naked eye, but it is also discolored and recorded using an image recording device such as a digital camera. Due to this phenomenon, it is possible to make it difficult to accurately record the color of the hidden image existing on the recording medium for authenticity determination and to reproduce the color, and it is possible to improve the security of the hidden image.

More specifically, the liquid discharge device 3 may be configured as shown in FIGS. 1 and 2. 1A and 1B are views showing the appearance configuration of the liquid discharge device 3, FIG. 1A shows the overall appearance configuration of the liquid discharge device 3, and FIG. 1B shows the vicinity of a window in the liquid discharge device 3. Shows the state during the imprinting of. FIG. 2 is a diagram showing a schematic configuration of the liquid discharge device 3.

The liquid ejection device 3 has three types of liquids (three types of ink) corresponding to the three primary colors (Cyan, Magenta, Yellow) and three types of emission colors corresponding to the three primary colors of light (Red, Green, Blue). It can be replaced with liquid. That is, the liquid ejection device 3 ejects a liquid such as CMY three-color ink, which is the three primary colors of color, or RGB three-color ink whose emission color is the three primary colors of light, and ejects the liquid to the surface of printing paper or the like. An ink printer or the like that forms an image. Of these, the RGB color ink whose emission color is the three primary colors of light may be, for example, a liquid having ultraviolet excitation type fluorescence emission and whose emission color under ultraviolet irradiation is the three primary colors of light.

As shown in FIG. 2, the liquid discharge device 3 includes a CPU (Central Processing Unit) 301, a ROM (Read Only Memory) 302, a RAM (Random Access Memory) 303, and an NVRAM (Non-Volatile Random Access Memory) external device 304. It includes a connection I / F (Inter Face) 308, a network I / F 309, and a bus line 310. Further, the liquid ejection device 3 includes a paper transport unit 311, a sub-scanning driver 312, a main scanning driver 313, a carriage 320, an ultraviolet irradiation light source 330, a window 340, and an operation panel 350.

The CPU (control unit) 301 controls the operation of the entire liquid discharge device 3. The ROM 302 stores a program or the like used to drive the CPU 301 such as an IPL (Initial Program Loader). The RAM 303 is used as a work area of the CPU 301. The NVRAM 304 stores various data such as a program, and holds various data even while the power of the liquid discharge device 3 is cut off.

The external device connection I / F 308 is connected to a PC (Personal Computer) by a USB (Universal Bus) cable or the like, and communicates control signals and printed data with the PC. The network I / F 309 is an interface for performing data communication using a communication network such as the Internet. The bus line 310 is an address bus, a data bus, or the like for electrically connecting each component such as the CPU 301.

The transport unit 311 is, for example, a roller and a motor for driving the roller, and transports a recording medium (for example, printing paper) in a sub-scanning direction along a transport path in the liquid discharge device 3. The sub-scan driver 312 controls the movement of the transport unit 311 in the sub-scan direction. The main scanning driver 311 controls the movement of the carriage 320 in the main scanning direction.

The carriage 320 includes a liquid discharge head 321 and a liquid discharge head driver 322. The liquid ejection head 321 has a plurality of nozzles for ejecting a liquid such as ink, and is mounted on the carriage 320 so that the ejection surface (nozzle surface) faces the recording medium side. The liquid discharge head 321 discharges the liquid to a recording medium intermittently conveyed in the sub-scanning direction while moving in the main scanning direction, thereby discharging the liquid to a predetermined position on the recording medium to form an image. The liquid discharge head driver 322 is a driver for controlling the drive of the liquid discharge head 321.

The ultraviolet irradiation light source 330 is arranged near the upper side of the carriage 320, for example, and irradiates the surface of the recording medium on which the image is formed with ultraviolet rays. The UV-excited fluorescent light-emitting liquid described above is substantially colorless and transparent under visible light irradiation. When the image on the recording medium is formed by using the ultraviolet-excited fluorescent-emitting liquid, the ultraviolet-irradiated light source 330 excites the ultraviolet-excited fluorescent-emitting liquid by ultraviolet irradiation. Visualize the image of the liquid.

The window 340 is arranged in the vicinity of the ultraviolet irradiation light source 330, and is configured so that the image formed on the recording medium can be visually recognized from outside the liquid ejection device 3. When the image on the recording medium is formed by using an ultraviolet-excited fluorescent light-emitting liquid, the image visualized by the ultraviolet rays emitted by the ultraviolet irradiation light source 330 is visually recognized.

The operation panel 350 is composed of a touch panel, an alarm lamp, or the like that displays current setting values, selection screens, and the like and accepts input from an operator.

The liquid discharge head driver 322 may not be mounted on the carriage 320 and may be configured to be connected to the bus line 310 outside the carriage 320. Further, the main scanning driver 313, the sub-scanning driver 312, and the liquid discharge head driver 322 may each have a function realized by a command of the CPU 301 according to the program.

Next, the detailed configuration around the carriage 320 of the liquid discharge device 3 will be described with reference to FIG. FIG. 3 is a schematic view showing an example of a detailed configuration around the carriage 320 of the liquid discharge device 3.

As described above, the carriage 320 includes a liquid discharge head 321. In the liquid ejection device 3, for example, the carriage 320 reciprocates left and right to print an image on a recording medium (printing paper) 10.

Here, it is assumed that the liquid ejection device 3 ejects an ultraviolet-excited fluorescent-emitting liquid whose emission color is the three primary colors (RGB) of light to form an image. In this case, the carriage 320 has a liquid discharge head 321R, 321G, 321B that discharges an ultraviolet-excited fluorescent light-emitting liquid having three colors of emission RGB, and a liquid discharge head that discharges a black liquid for visible information. It is equipped with 321K (Key Plate).

When an image of a liquid that is substantially invisible under visible light irradiation and has ultraviolet-excited fluorescence emission is output by inkjet printing using a liquid ejection head 321, at least the emission color is light in order to obtain a full-color image. A combination of three colors of RGB, which are the three primary colors of, is required. This is based on the principle that a cathode ray tube, a liquid crystal display, an organic EL (Electro-Luminesis) display, a light emitting diode (LED: Light Emitting Diode) display, etc. emit three colors of RGB cells to display a full-color image. Is the same.

In full-color printing using ordinary liquid (ink), the information of RGB, which is the three primary colors of light, is complicatedly numerically converted inside the device, and then an image is formed with the liquid (ink) of CMY, which is the three primary colors of color. ing. Therefore, in order to apply an RGB liquid (ink) based on the three primary colors of light emitted by irradiating ultraviolet excitation light, Cyan's liquid utilizes the fact that CMY and RGB have a complementary color relationship. Replace (ink) and Red liquid (ink), Magenta liquid (ink) and Green liquid (ink), Yellow liquid (ink) and Blue liquid (ink), and use image editing software to replace the positive original image. Inverts the hue and light and shade by converting to a negative image. When the negative image converted in this way is inkjet-printed, an output image close to the positive original image can be obtained. Furthermore, with the addition of RIP (Raster Image Processor) software and development technology for a printer driver for RGB ink output, images with good color reproducibility can be obtained.

However, in image formation by inkjet printing such as the liquid ejection device 3, the liquid ejection head 321 causes the droplets to fly and land the droplets of different colors on a recording medium such as printing paper so as to overlap each other. To form an image. Therefore, unlike the above-mentioned display in which independent cells are made to emit light, the image formation is premised on the mixing of liquids (inks) of different colors. In image formation using an ultraviolet-excited fluorescent light-emitting liquid, in inkjet printing, which originally performs image formation on the premise of color mixing of the three primary colors, image formation on the premise of color mixing by the emission colors of the three primary colors of light is performed. It is possible.

These liquid discharge heads 321R, 321G, 321B, and 321K are arranged in parallel with each other in a direction orthogonal to the stretching direction of, for example, the liquid discharge heads 321R, 321G, 321B, and 321K, that is, in the direction in which the printing paper 10 is discharged. , The image is printed on the printing paper 10 by scanning on the printing paper 10 in a direction orthogonal to the paper ejection direction of the printing paper 10.

An ultraviolet irradiation light source 330 is arranged in the upper vicinity of the liquid discharge heads 321K, 321R, 321G, and 321B. The ultraviolet irradiation light source 330 is configured in a ribbon shape, for example, in which a plurality of LEDs that irradiate ultraviolet rays are arranged on a support. More specifically, the ultraviolet irradiation light source 330 is above the area where the liquid ejection heads 321K, 321R, 321G, and 321B are scanned on the printing paper 10, and the image 10im is ultraviolet rays on the printing paper 10 being printed. Is arranged at a position where the liquid discharge heads 321K, 321R, 321G, and 321B can be irradiated in a direction orthogonal to the stretching direction.

Generally, in the carriage 320, the liquid ejection heads 321K, 321R, 321G, 321B, the ink tank, and the cartridge need only be contained within a predetermined height, and there is almost no extra space around the carriage 320. For example, the distance between the carriage 320 and the top plate (not shown) above the carriage 320 is about several mm to a dozen mm. By configuring the ultraviolet irradiation light source 330 in a ribbon shape, the ultraviolet irradiation light source 330 can be arranged in the vicinity above the carriage 320 having such a narrow gap.

As a result, the ultraviolet irradiation light source 330 irradiates the printing paper 10 during image formation and before being discharged to the outside of the liquid ejection device 3 with ultraviolet rays, and records using an ultraviolet-excited fluorescent light-emitting liquid. The image 10im printed on the medium (printing paper) 10 can be made to emit light and visualized.

The ultraviolet light emitted by the ultraviolet irradiation light source 330 preferably has a wavelength of 315 nm or more and 400 nm or less, more preferably 350 nm or more and 380 nm or less, and has a peak wavelength of, for example, 365 nm. Thereby, the excitation energy suitable for fluorescence emission can be given to a general fluorescent dye of an ultraviolet-excited fluorescent emission type liquid.

The illuminance on the recording medium (printing paper) 10 of the ultraviolet rays emitted by the ultraviolet irradiation light source 330 is an observation value by an ultraviolet illuminometer having a measurement wavelength peak of 360 nm, and is 0.1 mW / cm ² or more and 2.0 mW / cm ² or less. , more preferably 0.5 mW / cm ² or more 2.0 mW / cm ² or less. When the illuminance is ^{less than 0.1 mW / cm 2} , the fluorescence emission intensity of a general fluorescent dye of an ultraviolet-excited fluorescent emission liquid is weak, and as described later, when the operator confirms the image 10im. , It is difficult to perceive the difference in output color and color loss due to nozzle clogging. Further, when the illuminance is ^{higher than 2.0 mW / cm 2} , the fluorescence emission intensity by the fluorescent dye may be too strong and the color may look different.

A window 340 is arranged in the vicinity of the ultraviolet irradiation light source 330. More specifically, the window 340 is between the ultraviolet irradiation light source 330 and the scanning area of the liquid ejection heads 321K, 321R, 321G, 321B, and the image 10im being printed on the printing paper 10 is irradiated with ultraviolet rays. It is arranged in a position where it can be visually recognized in a state visualized by irradiation of ultraviolet rays from the light source 330.

The window 340 is made of, for example, a transparent resin that transmits visible light and shields ultraviolet rays. More specifically, the window 340 is composed of, for example, polycarbonate or polymethylmethacrylate. Polycarbonate and polymethylmethacrylate have a shielding effect of 95% or more against ultraviolet rays having a wavelength of 350 nm or more and 380 nm or less. As for polycarbonate and polymethylmethacrylate, it is more preferable to use polymethylmethacrylate, which has higher transparency.

As a result, the operator can confirm the image 10im on the recording medium (printing paper) 10 before the recording medium (printing paper) 10 is discharged to the outside of the liquid ejection device 3. At this time, the operator visually confirms whether the imprinted image has a desired color and whether color omission due to nozzle clogging has occurred. If there is a problem with the imprinting, the worker may immediately take measures such as stopping the imprinting.

It is also possible to cause the liquid ejection device 3 to eject liquids (inks) of three colors of CMY, which are the three primary colors of the colors, to form an image. In this case, three liquid discharge heads 321 for discharging CMY three colors of visible liquid (visible ink) and a liquid discharge head 321K for discharging black liquid (ink) may be set. At this time, as the CMY liquid discharge head 321, the above-mentioned liquid discharge heads 321R, 321G, and 321B can be washed and used.

Next, the colors formed on the printed matter will be described with reference to FIG. 4A and 4B are diagrams showing colors of printed matter, FIG. 4A shows colors created on a computer screen, and FIG. 4B is printed on a recording medium and irradiated with ultraviolet rays. Indicates the color of the ink observed in the state. In the following, except for FIG. 9, the description will be given using a drawing in which each color is grayscale-converted. FIGS. 4 (a) and 4 (b) can be referred to as a reference between the shade of gray and the color of the color shown on the drawing. That is, as for the color of the color before grayscale conversion on the drawing of FIG. 4A, the color indicated by "R" is cyan, the color indicated by "G" is magenta, and " The color indicated by "B" is yellow. As for the color of the color before grayscale conversion on the drawing of FIG. 4 (b), the color indicated by "R" is red (Red), the color indicated by "G" is green (Green), and "B". The color indicated by is blue.

In the liquid ejection device 3 of the present embodiment, the liquid (ink) of the three primary colors CMY is composed of a liquid that is substantially colorless and transparent under visible light irradiation and has ultraviolet excitation type fluorescence emission, and the emission color is light. Replace with the liquid of the three primary colors RGB. As a result, the original image is negatively inverted as shown in FIG. 4A on the computer connected to the liquid ejection device 3 without changing the image processing mechanism of the liquid ejection device 3, and then the printing process is performed. As shown in FIG. 4B, a hidden image having basically the same emission color as the original image can be reproduced on the recording medium under ultraviolet irradiation.

For example, in an inkjet printing system capable of normal full-color printing, the information of the three primary colors RGB of light as displayed on the monitor of a personal computer is complicatedly numerically converted internally, and then the image is output with the three primary colors CMY ink. It is made. In order to apply an ink whose emission color emitted by irradiating ultraviolet excitation light is the three primary colors (RGB) of light, Cyan's liquid (ink) utilizes the fact that CMY and RGB have a complementary color relationship. And Red liquid (ink), Magenta liquid (ink) and Green liquid (ink), Yellow liquid (ink) and Blue liquid (ink) are replaced, and the positive original image displayed on the monitor is image editing software. The hue and lightness and darkness are reversed by converting to a negative image by means of the like.

The following can be considered as the merits of using the negative image. That is, if the light emitting Red ink is replaced with the color Cyan ink and the image is negatively inverted with the software on the PC screen, when the Cyan is drawn on the screen, the output becomes the light emitting Red. This means that, as shown in FIG. 4C, the opposite color of the color wheel is set in the printer. Similar to the above example, the color Magenta ink and the luminescent Green ink can be replaced, and the colored Yellow ink and the luminescent Blue ink can be replaced.

When the negative image converted in this way is inkjet-printed on a recording medium and irradiated with ultraviolet rays, a light emission output image close to the positive original image displayed on the monitor is basically obtained. However, the color reproducibility is not perfect, and an emission output image having the same color as the monitor display color cannot be obtained without making some fine adjustments to the hue.

Of course, the development of RIP (Raster Image Processor) software and printer drivers for RGB ink output is also an effective means, but it requires a lot of infrastructure to be commercialized.

When forming an image on a recording medium, when outputting a Red image, create an image pattern of Cyan (R: 0, G: 255, B255), and when imprinting on the recording medium, Red liquid (ink). Is discharged, and a Red color emission pattern is obtained by irradiation with ultraviolet rays. Similarly, use Magenta (R: 255, G: 0, B: 255) for the output of the Green image, and prepare an image pattern of Yellow (R: 255, G: 255, B: 0) for the output of the Blue image. It is only necessary to easily obtain an output image of three colors.

When using an invisible UV-excited fluorescent luminescent liquid for anti-counterfeiting purposes, the simpler output color imprint as described above, without the need for complex, multicolored images such as photographs. It was examined whether an image pattern that is difficult to forge and easy to determine the authenticity can be obtained by the method. In the examination of the color pattern (color pattern / fine pattern) used for banknotes and gold bills, in the light emission output image under ultraviolet irradiation that combines the monochromatic light emission logo mark and the single color light emission color pattern, FIG. 5 (a). As shown in, it was discovered that the emission color of the logo mark appeared to be discolored. FIG. 5 is a diagram showing the structure and characteristics of the printed matter. In FIG. 5A, a main pattern that emits light in a single color and a sub-pattern that includes fine lines of different emission colors without being mixed with the main pattern are alternately arranged under ultraviolet irradiation. This shows an example in which the main pattern is perceived as a different emission color from the original emission color.

A printed matter having a main pattern of monochromatic light emission and a sub-pattern of light emission color different from the main pattern of monochromatic light emission is formed by a liquid having a plurality of colors of emission color having ultraviolet excitation type fluorescence emission that is substantially invisible under visible light irradiation. In the sub-pattern, thin lines are arranged alternately with the main pattern without mixing with the main pattern. As a result, not only is the color perceived by the naked eye as a color different from the original emission color of the main pattern, but also the color is discolored and recorded even when an image recording device such as a digital camera is used (see the figure below in FIG. 5A). ) Was confirmed.

The principle of color change and perception as described above is also called "color assimilation phenomenon", which is a phenomenon in which the attributes of adjacent colors are perceived as being close to each other, and is usually the three primary colors (CMY). As explained in the printed matter printed by the printer and the display image displayed by the emission of RGB cells, the discovery of this case is made by irradiating a substantially invisible ultraviolet-excited fluorescent-emitting liquid with ultraviolet rays to fluoresce. The fact that it is a printed matter that emits light is unprecedented. Double security that it is colorless and transparent (see Fig. 5 (b)) without UV irradiation and cannot be visually confirmed, and that even if it can be visualized by UV irradiation, the true emission color cannot be recognized accurately and it is difficult to forge. It also has an effect. A hidden image having this double security effect has been realized by arranging patterns of at least two colors. FIG. 5B is an image of the output image of FIG. 5A, which is substantially invisible under visible light irradiation and is output as a liquid having ultraviolet excitation type fluorescence emission. Therefore, FIG. 5B is ultraviolet irradiation. It is colorless and transparent without the above, indicating that it has a concealing property that cannot be visually confirmed.

Since the ultraviolet-excited liquid having fluorescence emission has three colors of emission, Red, Green, and Blue, the remaining two colors are used for the thin line sub-pattern as opposed to the main pattern printed in a single emission color. be able to. When the main pattern was a single color Red and the sub pattern was applied as a two-color gradation of Green and Blue, the Red main pattern combining the sub patterns on the Green side was orange under ultraviolet irradiation, as shown in FIG. The Red main pattern, which is perceived as a closer color and the sub-patterns on the Blue side are combined, is perceived as a color closer to the rose, and although the emission color of the main pattern is a single emission color, it becomes a gradation as a whole. It is perceived as being. The principle of color change and perception is the same as the "color assimilation phenomenon", and as an application of the phenomenon in which the attributes of adjacent colors are perceived as approaching, the emission color of the adjacent sub-pattern gradually becomes hue. This is a phenomenon due to the gradation that changes the color, and is the result of combining all the emission colors of Red, Green, and Blue, which are the three primary colors of light.

Although FIG. 6 illustrates a configuration in which the emission color Red is used as the main pattern, the combination of the main and sub-patterns of the ultraviolet-excited fluorescent emission-type liquid having a total of three colors is not limited to this. It can be selected in any way according to preference and situation, and further, the emission color may be freely adjusted by intentional mixing without using each of the three colors as a single color.

This embodiment modifies or forges hidden images, codes, etc. that cannot be confirmed under visible light irradiation and cannot be read by a scanner, which are used for passports, vehicle verifications, cash cards, banknotes, etc. The purpose is to easily produce special printing to prevent. Therefore, the size of the recording medium is about A4 size at most, and the concealed image does not need to be a particularly large size, and the authenticity can be basically visually judged by setting the distance suitable for visual confirmation of the image to about 30 cm. Just do it. As a result, the size may be about several centimeters both vertically and horizontally, and various examinations of the line-to-line pitch of the thin line sub-patterns lined up at substantially equal intervals with respect to the main pattern of the concealed image of that degree are various as shown in FIG. As a result of the test, it was found that the thickness should be 0.5 mm or more and 3.0 mm or less.

FIG. 7 shows an output emission image as a result of various studies for optimizing the line-to-line pitch of thin line sub-patterns arranged at substantially equal intervals. FIG. 7 (a) shows an output emission image when the line pitch of thin lines is 1 pt (≈0.35 mm), and FIG. 7 (b) shows an output emission image when the line pitch of thin lines is 5 pt (≈1.76 mm). 7 (c) shows an output emission image when the line-to-line pitch of the thin line is 10 pt (≈3.70 mm).

In the case of a high-density array with a sub-pattern line pitch of less than 0.5 mm, especially when the sub-pattern fine lines are thick, the sub-pattern emits too much light under ultraviolet irradiation, making it difficult to recognize the shape of the main pattern. Not only that, when bleeding is likely to occur in the combination of the ink and the recording medium, the main pattern and the sub pattern are mixed. As a result, it becomes extremely difficult to cut out only the main pattern into strips when confirming the fluorescence emission wavelength with a spectrofluorescence meter in a detailed authenticity determination.

On the other hand, when the line-to-line pitch exceeds 3.0 mm, especially when the thin line sub-pattern is thin, the "color assimilation phenomenon" becomes diluted and the emission color of the main pattern does not appear to be discolored. Therefore, it is considered that the line pitch of the more effective sub-pattern is 1.0 mm or more and 2.0 mm or less.

For the above-mentioned detailed authenticity determination, for example, when the fluorescence emission of the main pattern has a characteristic wavelength peak distribution, identification and appraisal analysis of the emission wavelength distribution is performed while irradiating ultraviolet rays using a spectrofluorescence meter or the like. Will be done.

In the present embodiment, only the main pattern that emits light in the Red color is cut out with a width of about 0.9 mm from the concealed image in which the emission sub-patterns having a pitch of 1.0 mm are arranged, and is the main pattern as shown in FIG. 8 (a). The distribution of the fluorescence emission wavelength peak can be confirmed by inserting only the ink image portion of the emission color Red into the sample holder of the spectrofluorescence meter and irradiating with ultraviolet rays having an excitation wavelength of 365 nm as shown in FIG. 8 (b). can. In FIG. 8, only the main pattern that emits light in Red color is cut out in a thin strip shape having a width of about 0.9 mm from the concealed image in which the emission sub-pattern is arranged, inserted into the sample holder of the spectrofluorescence meter, and has an excitation wavelength of 365 nm. This is an example of fluorescent light emission by irradiating with ultraviolet rays.

The ink of the emission color Red verified in the present embodiment has, for example, a fluorescence emission spectrum having small peaks of 592 nm and 580 nm in addition to the main peak having a wavelength of 613 nm as shown in FIG. Therefore, if the coincidence of the spectra can be confirmed, it can be judged to be genuine. If the spectra do not match, it is determined to be a counterfeit product. Needless to say, the combination of the main and sub-patterns of the ultraviolet-excited fluorescent ink having a total of three colors is not limited to those whose main pattern is the emission color Red, and is not shown, but depends on the fluorescence spectra of the Green ink and Blue ink. Identification and appraisal are also possible. FIG. 9 shows a fluorescence emission spectrum when the ink of the emission color Red having the ultraviolet excitation type fluorescence emission property verified in the present embodiment is irradiated with an excitation wavelength of 365 nm with a spectrofluorometer.

The reason why the main pattern is used for the true / false determination analysis is that since the sub pattern is a thin line, it is easier to secure the spectral intensity by cutting the main pattern as a sample. Further, in the spectrofluorometer, light emitted from a light source containing each wavelength component (usually a xenon lamp) is decomposed into each wavelength component by an excitation wavelength spectroscope, and then a specific wavelength light (here, an ultraviolet ray of 365 nm) is thinned. Since the sample is irradiated through the slit, the excitation light emitted to the sample has a thin linear shape with a width of about 1 mm, and a strip-shaped sample with the main pattern cut out is suitable in terms of size, making detailed authenticity judgment analysis easy. Therefore, it is convenient that the fine line pitch of the sub-pattern is in the above range. As the measuring instrument, for example, a spectroscopic fluorometer "FP-6500" manufactured by JASCO Corporation can be used.

The thin line sub-pattern is not only horizontal straight lines arranged alternately as shown in FIGS. 5 (a) and 6 but also vertical, diagonal, intersecting, and curved lines as long as they emit light in a hue different from that of the main pattern. May be good. As an example, FIG. 10 shows a printing unit in which a net-shaped Green emission sub-pattern in which diagonal straight lines are crossed is combined with a Red emission main pattern. Also in FIG. 10, the “color assimilation phenomenon” can be perceived as a color different from the emission color originally possessed by the main pattern.

In the present embodiment, the emission color Red is used as the main pattern, but the combination of the main and sub-patterns of the liquid having the fluorescence emission of the ultraviolet excitation type having a total of three colors is not limited to this, and it depends on the preference and the situation. You can choose any way you like. Further, the emission color may be freely adjusted by intentional mixing without using each of the three colors as a single color.

As described above, in the present embodiment, in the liquid ejection device 3, a plurality of emission colors (for example, the three primary colors of light RGB) that are substantially invisible under visible light irradiation and have ultraviolet excitation type fluorescence emission characteristics are used. A sub-pattern in which thin lines of the second color are alternately arranged so that the emission color does not mix with the main pattern of the first color according to the information of the image in which the original image is negatively inverted by the liquid. A concealed image with is formed on the recording medium. As a result, it is perceived as a color different from the emission color (first color) originally possessed by the main pattern, which makes it difficult to accurately record the color of the hidden image and reproduce the color, improving security. can. That is, the security of the hidden image formed on the recording medium can be improved.

Further, in the present embodiment, the fine lines of the sub-pattern may be a gradation of at least two or more second colors. By making the fine lines of the sub-pattern a gradation with at least two or more second colors, the emission color (first color) of the main pattern is also perceived as a gradation, and accurate color recording of the hidden image and color can be performed. Reproduction can be made more difficult and security can be improved.

Further, in the present embodiment, the pitch between the fine lines of the sub-pattern in which the fine lines are alternately arranged is 0.5 mm or more and 3.0 mm or less. By setting the line-to-line pitch of the sub-patterns in which thin lines are alternately arranged to be 0.5 mm or more and 3.0 mm or less, it is possible to perceive as a color different from the emission color (first color) originally possessed by the main pattern. Further, since only the image portion, which is the main pattern, can be cut out in the shape of an elongated strip, it is convenient when the fluorescence spectrum is analyzed in detail with a spectrofluorometer.

Further, in the present embodiment, the sub-pattern of the thin line does not necessarily have to be a straight line, and may be vertical, horizontal, diagonal, intersecting, or curved. The sub-pattern of thin lines can be perceived as a color different from the original emission color (first color) of the main pattern, not only in straight lines arranged alternately, but also in vertical, horizontal, diagonal, intersection, and curved lines. , It can be designed relatively freely according to taste, situation, and security application.

Further, in the present embodiment, as a liquid having ultraviolet excitation type fluorescence emission, at least a plurality of colors having the three primary colors of Red, Green, and Blue as emission colors can be used, and printing can be performed by the liquid ejection device 3. be. As a result, it is possible to easily create an image simply by drawing with an emission color having a complementary color relationship with the image to be printed, without requiring a complicated color conversion process.

The "liquid discharge head" may be a head other than the recording head for the inkjet recording device as long as it is a functional component that discharges and ejects liquid from the nozzle. The liquid to be discharged may have a viscosity and surface tension that can be discharged from the head, and is not particularly limited, but has a viscosity of 30 mPa · s or less at room temperature, under normal pressure, or by heating or cooling. Is preferable. More specifically, solvents such as water and organic solvents, colorants such as dyes and pigments, functionalizable materials such as polymerizable compounds, resins and surfactants, biocompatible materials such as DNA, amino acids and proteins, and calcium. , Solvents, suspensions, emulsions, etc. containing edible materials such as natural dyes, etc., for example, inks for inkjets, surface treatment liquids, components of electronic elements and light emitting elements, and formation of electronic circuit resist patterns. It can be used in applications such as liquids and material liquids for three-dimensional modeling. Piezoelectric actuators (laminated piezoelectric elements and thin-film piezoelectric elements), thermal actuators that use electric heat conversion elements such as heat-generating resistors, and electrostatic actuators that consist of a vibrating plate and counter electrodes are used as energy sources for discharging liquid. Includes what to do.

Further, in the present specification, image formation, recording, printing, stamping, printing, modeling, etc. are all synonymous.

Further, the "liquid discharge unit" is a liquid discharge head integrated with other functional parts and mechanisms, and is a collection of parts related to the function of discharging liquid. For example, the "liquid discharge unit" includes a head tank, a carriage, a supply mechanism, a maintenance / recovery mechanism, a main scanning movement mechanism in which at least one of the configurations is combined with a liquid discharge head, and the like.

Here, the term "integration" means, for example, a liquid discharge head and a functional component, a mechanism in which the mechanism is fixed to each other by fastening, bonding, engagement, etc., or one in which one is movably held with respect to the other. include. Further, the liquid discharge head, the functional component, and the mechanism may be configured to be detachable from each other.

For example, as a liquid discharge unit, there is a unit in which a liquid discharge head and a head tank are integrated. In some cases, the liquid discharge head and the head tank are integrated by being connected to each other by a tube or the like. Here, a unit including a filter can be added between the head tank of these liquid discharge units and the liquid discharge head.

Further, as a liquid discharge unit, there is a unit in which a liquid discharge head and a carriage are integrated.

Further, there is a liquid discharge unit in which the liquid discharge head and the scanning movement mechanism are integrated by holding the liquid discharge head movably by a guide member constituting a part of the scanning movement mechanism. In some cases, the liquid discharge head, the carriage, and the main scanning movement mechanism are integrated.

Further, as a liquid discharge unit, there is a carriage to which a liquid discharge head is attached, in which a cap member which is a part of the maintenance / recovery mechanism is fixed, and the liquid discharge head, the carriage, and the maintenance / recovery mechanism are integrated. ..

Further, as a liquid discharge unit, there is a liquid discharge unit in which a tube is connected to a head tank or a liquid discharge head to which a flow path component is attached, and the liquid discharge head and a supply mechanism are integrated. The liquid of the liquid storage source is supplied to the liquid discharge head through this tube.

The main scanning movement mechanism shall include a single guide member. Further, the supply mechanism includes a single tube and a single loading unit.

The "liquid discharge device" is a device provided with a liquid discharge head or a liquid discharge unit, and drives the liquid discharge head to discharge liquid. The device for discharging a liquid includes not only a device capable of discharging a liquid to a device to which the liquid can adhere, but also a device for discharging the liquid into the air or into the liquid.

This "liquid discharge device" can also include means related to feeding, transporting, and discharging paper to which a liquid can adhere, as well as a pretreatment device, a posttreatment device, and the like.

For example, as a "liquid ejection device", an image forming apparatus that ejects ink to form an image on paper, and a powder in which powder is formed in layers in order to form a three-dimensional model (three-dimensional model). There is a three-dimensional modeling device (three-dimensional modeling device) that discharges the modeling liquid to the body layer.

Further, the "liquid discharge device" is not limited to a device in which a significant image such as characters and figures is visualized by the discharged liquid. For example, those that form patterns that have no meaning in themselves and those that form a three-dimensional image are also included.

The above-mentioned "thing to which a liquid can adhere" means a material to which a liquid can adhere at least temporarily, such as a material to which the liquid adheres and adheres, and a material to which the liquid adheres and permeates. Specific examples include paper, recording paper, recording paper, film, recorded media such as cloth, electronic substrates, electronic components such as piezoelectric elements, powder layers (powder layers), organ models, and media such as inspection cells. Yes, and includes everything to which the liquid adheres, unless otherwise specified.

The material of the above-mentioned "material to which a liquid can adhere" may be paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics or the like as long as the liquid can adhere even temporarily.

The "liquid" may have a viscosity and surface tension that can be discharged from the head, and is not particularly limited, but has a viscosity of 30 mPa · s or less at room temperature, under normal pressure, or by heating or cooling. It is preferable to have. More specifically, solvents such as water and organic solvents, colorants such as dyes and pigments, functionalizable materials such as polymerizable compounds, resins and surfactants, biocompatible materials such as DNA, amino acids and proteins, and calcium. , Solvents, suspensions, emulsions, etc. containing edible materials such as natural dyes, etc., for example, inks for inkjets, surface treatment liquids, components of electronic elements and light emitting elements, and formation of electronic circuit resist patterns. It can be used in applications such as liquids and material liquids for three-dimensional modeling.

Further, the "liquid discharge device" includes, but is not limited to, a device in which the liquid discharge head and the device to which the liquid can adhere move relatively. Specific examples include a serial type device that moves the liquid discharge head, a line type device that does not move the liquid discharge head, and the like.

In addition, as a "liquid ejection device", a processing liquid application device that ejects a treatment liquid onto a paper in order to apply the treatment liquid to the surface of the paper for the purpose of modifying the surface of the paper, and a solution of raw materials. There is an injection granulation device that granulates fine particles of raw materials by injecting a composition liquid dispersed therein through a nozzle.

3 Liquid discharge device 10 Recording medium 301 CPU
321 Liquid discharge head

Japanese Patent No. 6028346

Claims (12)

A liquid ejection head that is substantially invisible under visible light irradiation and is capable of ejecting a liquid having ultraviolet-excited fluorescence emission characteristics.
By controlling the liquid ejection head, a main pattern having a first color of emission and a sub-pattern containing fine lines having a second emission color are alternately arranged on a recording medium according to the information of an image. The control unit that forms the hidden image and
Liquid discharge device equipped with. The liquid discharge device according to claim 1, wherein the image is an image in which the current image of the image is negatively inverted. The liquid ejection device according to claim 1 or 2, wherein the emission color is an emission color under ultraviolet irradiation. The liquid discharge device according to claim 1, wherein the control unit controls the liquid discharge head so that the fine lines of the sub-pattern have a gradation of at least two or more second colors. The liquid discharge device according to claim 1, wherein the control unit controls the liquid discharge head so that the pitch between the fine lines in the sub pattern is 0.5 mm or more and 3.0 mm or less. The control unit controls the liquid discharge head so that the thin line in the sub-pattern includes at least one of a vertical line, a horizontal line, an oblique line, an intersection line, and a curved line in addition to a straight line. The liquid discharge device described. Due to the liquid that is substantially invisible under visible light irradiation and has ultraviolet-excited fluorescence emission characteristics, the main pattern whose emission color is the first color and the thin line whose emission color is the second color, depending on the information in the image. A printed matter in which a hidden image is formed in which sub-patterns including are alternately arranged. The printed matter according to claim 7, wherein the image is an image in which the current image of the image is negatively inverted. The printed matter according to claim 7 or 8, wherein the emission color is an emission color under ultraviolet irradiation. The printed matter according to claim 7, wherein the fine lines of the sub-pattern are gradations of at least two or more second colors. The printed matter according to claim 7, wherein the pitch between the fine lines in the sub-pattern is 0.5 mm or more and 3.0 mm or less. The printed matter according to claim 7, wherein the thin line in the sub-pattern includes at least one of a vertical line, a horizontal line, an oblique line, an intersecting line, and a curved line in addition to a straight line.

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