JP7167254B2 - Particulates, Readers, and Printers - Google Patents

Description

TECHNICAL FIELD The present invention relates to an edible granular material, a reading device for reading information contained in an image printed on the surface of the edible granular material, and a printing apparatus for printing an image on the surface of the edible granular material by an inkjet method. .

A character string such as a drug name is recorded on the surface of a tablet, which is a drug. Such a character string may be recorded by engraving, but engraving has a problem of low visibility. In particular, in recent years, the types of tablets have diversified due to the spread of generic drugs. Therefore, it is required to clearly record a character string on the surface of the tablet so that the tablet can be identified with certainty. Moreover, since tablets are vulnerable to pressure, it is preferable to reduce the pressure applied to the tablets during printing. Under these circumstances, in recent years, attention has been paid to a technique for printing an image on the surface of a tablet by an inkjet method.

A conventional printing apparatus that prints an image on the surface of a tablet by an inkjet method is described in Patent Document 1, for example.

JP 2015-3883 A

This type of printing device is required to print a large amount of information in an extremely narrow space on the surface of the tablet. For example, the print image is required to include not only information such as drug names that should be displayed to the consumer, but also management information that should be confirmed only by the manufacturer of the tablet or the pharmacist. However, simply printing more information on the surface of the tablet results in a smaller display of each piece of information. Also, if the amount of information that the consumer sees is too large, the consumer may be confused.

Patent Document 1 describes an example of printing a two-dimensional barcode on the surface of a tablet. In this example, the two-dimensional barcode can contain a lot of information. However, printing two-dimensional barcodes requires a certain amount of space. For this reason, it may be difficult in terms of space to print the names of medicines and the like to be displayed to consumers in a large size and print the two-dimensional bar code in the remaining space. In addition, depending on the type of tablet, it may be difficult to print a two-dimensional barcode precisely due to ink permeation or bleeding.

The present invention has been made in view of such circumstances, and includes edible granules on which a lot of information is printed in a manner that is less likely to cause confusion for consumers, a device for reading information from the granules, and a printing apparatus for printing on the surface of the granular material.

A first invention of the present application is an edible granular material having an image printed on its surface by an inkjet method, wherein the image comprises a main image visible under normal ambient light and the main image visible under normal ambient light. and a sub-image that is less visible than the main image, wherein the sub-image is printed on the same surface as the main image, and the absorbance of the sub-image to light of a specific wavelength is the absorbance of the surface to the light. and the absorbance of the main image to the light , the main image and the sub-image are printed with colored ink, and the hue and brightness of the sub-image are higher than the hue and brightness of the main image. close to the hue and lightness of

A second invention of the present application is the granular material according to the first invention , wherein the sub-image includes a code image symbolized for each character.

A third invention of the present application is the granular material according to the second invention, wherein the code image is Braille.

A fourth invention of the present application is the granules according to any one of the first to third inventions, wherein the sub-image is printed with an ink containing zinc oxide or titanium oxide.

A fifth invention of the present application is a reading device for reading information contained in an image printed on the surface of edible granular material by an inkjet method, wherein the main image printed with colored ink on the surface of the granular material and the A sub-image printed with colored ink on the same surface, which is less visible than the main image visible under normal ambient light, and whose absorbance for light of a specific wavelength is greater than that of the surface. A sub-image having an absorbance to light and different from the absorbance to light of the main image, wherein the sub-image has a hue and lightness closer to the hue and lightness of the surface than the hue and lightness of the main image can be photographed. An imaging unit and an information acquisition unit that acquires information from an imaging result of the imaging unit, and the imaging unit has a light irradiation unit that irradiates the light.

A sixth invention of the present application is the reading device according to the fifth invention, wherein the sub-image is printed with ink containing zinc oxide or titanium oxide.

A seventh invention of the present application is a printing apparatus for printing an image on the surface of an edible granular material by an inkjet method, comprising: a conveying mechanism for conveying the granular material; and a surface of the granular material conveyed by the conveying mechanism. a first printing unit that prints a main image visible under normal ambient light with colored ink ; A sub-image having low visibility and having a different absorbance to light of a specific wavelength from the absorbance to the light of the surface and the absorbance to the light of the main image, wherein the hue and lightness are the hue and lightness of the main image a second printing unit that prints a sub-image closer to the hue and brightness of the surface than the main image on the same surface as the main image with colored ink .

An eighth invention of the present application is the printing apparatus according to the seventh invention , wherein the second printing unit is arranged downstream of the first printing unit in the conveying direction of the granular material.

A ninth invention of the present application is the printing apparatus according to the seventh invention or the eighth invention, wherein the second printing unit prints the sub-image with ink containing zinc oxide or titanium oxide.

According to the first to fourth inventions of the present application, information to be displayed to consumers can be included in the main image, and information to be confirmed only by specific parties can be included in the sub-image. Since the information contained in the sub-image is difficult for the consumer to notice, it is possible to prevent the consumer from being confused by too much information.

In particular, according to the first to fourth inventions of the present application, the main image and the sub-image can be printed using only colored inks.

Further, according to the first to fourth inventions of the present application, information contained in the sub-image can be read using the difference in absorbance.

In particular, according to the second invention of the present application, it is possible to make it more difficult for persons other than specific related persons to recognize the information contained in the sub-image.

In particular, according to the third invention of the present application, a braille code image can be printed with fine detail by the inkjet method.

Further, according to the fifth and sixth inventions of the present application, information to be displayed to consumers is included in the main image, and information to be confirmed only by specific parties is included in the sub-image, and the latter information is included in the sub-image. can be read by a reader. Since the information contained in the sub-image is difficult for the consumer to notice, it is possible to prevent the consumer from being confused by too much information.

Further, according to the fifth and sixth inventions of the present application, sub-images with low visibility can be clearly photographed using the difference in absorbance. Therefore, information can be easily obtained from the photographed result.

Further, according to the seventh to ninth inventions of the present application, information to be displayed to consumers can be included in the main image, and information to be confirmed only by specific parties can be included in the sub-image. Since the information contained in the sub-image is difficult for the consumer to notice, it is possible to prevent the consumer from being confused by too much information.

In particular, according to the eighth invention of the present application, after the main image is printed, the sub-image can be superimposed and printed on the main image. As a result, the sub-image can be printed over a wide range without being restricted by the print range of the main image.

1 is a diagram showing the configuration of a printing device; FIG. 4 is a partial perspective view of the transport mechanism; FIG. It is a bottom view of a head. 3 is a block diagram showing connections between a control unit and each unit in the printing apparatus; FIG. FIG. 4 is a diagram showing an example of a tablet printed with a main image and a sub-image; FIG. 4 is a diagram showing an example of a tablet printed with a main image and a sub-image; It is the figure which showed the structure of the reading device. FIG. 4 is a diagram showing an example of a tablet irradiated with imaging light;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the direction in which a plurality of tablets are conveyed is called "conveying direction", and the direction perpendicular and horizontal to the conveying direction is called "width direction".

<1. About the printer>
FIG. 1 is a diagram showing the configuration of a printing apparatus 1 according to one embodiment of the invention. This printing apparatus 1 is an apparatus for printing an image on the surface of each tablet 9 by an inkjet method while conveying a plurality of tablets 9 which are edible granular materials. As shown in FIG. 1 , the printing apparatus 1 of this embodiment includes a transport mechanism 10 , a first printing section 20 , a second printing section 30 , a drying mechanism 40 and a control section 50 .

The conveying mechanism 10 is a mechanism that holds and conveys a plurality of tablets 9 . The transport mechanism 10 has a pair of pulleys 11 and an annular transport belt 12 stretched between the pair of pulleys 11 . A plurality of tablets 9 loaded into the printing apparatus 1 are aligned at equal intervals and supplied to the outer peripheral surface of the transport belt 12 by a loading mechanism 101 composed of a vibrating feeder, a transport drum, and the like. One of the pair of pulleys 11 is rotated by power obtained from the transport motor 13 . As a result, the conveyor belt 12 rotates in the direction of the arrow in FIG. At this time, the other of the pair of pulleys 11 is driven to rotate as the conveyor belt 12 rotates.

FIG. 2 is a partial perspective view of the transport mechanism 10. FIG. As shown in FIG. 2, the conveyor belt 12 is provided with a plurality of suction holes 14 . The plurality of suction holes 14 are arranged at regular intervals in the transport direction and the width direction. Further, as shown in FIG. 1 , the transport mechanism 10 has a suction mechanism 15 that sucks gas from the space inside the transport belt 12 . When the suction mechanism 15 is operated, the space inside the conveying belt 12 becomes a negative pressure lower than the atmospheric pressure. The plurality of tablets 9 are adsorbed and held in the adsorption holes 14 by the negative pressure.

In this manner, the conveying mechanism 10 conveys the plurality of tablets 9 by rotating the conveying belt 12 while holding the plurality of tablets 9 in the plurality of suction holes 14 at regular intervals. Below the first printing unit 20 and the second printing unit 30, the plurality of tablets 9 are conveyed horizontally.

Further, as shown in FIG. 1 , the transport mechanism 10 has a blow mechanism 16 inside the transport belt 12 . When the blow mechanism 16 is operated, only the suction holes 14 facing the carry-out mechanism 102 among the plurality of suction holes 14 of the conveying belt 12 have a positive pressure higher than the atmospheric pressure. As a result, the adsorption of the tablets 9 in the adsorption holes 14 is released, and the tablets 9 are transferred from the conveying belt 12 to the carry-out mechanism 102 . The carry-out mechanism 102 carries out the tablets 9 delivered from the transport belt 12 to the outside of the printing apparatus 1, for example, by another transport belt.

The first printing section 20 is a section that records a main image on the surface of the tablet 9 conveyed by the conveying belt 12 . The main image includes information to be displayed to the consumer, such as the product name, company name, logo mark, and weight of the tablet 9, for example. As shown in FIG. 1 , the first printing section 20 of this embodiment has four heads 21 . The four heads 21 are positioned above the transport belt 12 and arranged in a row along the transport direction of the tablets 9 . Each head 21 ejects colored ink that is visible under normal ambient light toward the surface of the tablet 9 . For example, the four heads 21 each eject cyan, magenta, yellow, and black ink droplets. As a result, the main image, which is a multicolor image, is printed on the surface of the tablet 9 .

The ink ejected from each head 21 is edible ink manufactured from raw materials approved by the Food Sanitation Law.

FIG. 3 is a bottom view of one head 21. FIG. In FIG. 3, the conveyor belt 12 and the plurality of tablets 9 held by the conveyor belt 12 are indicated by two-dot chain lines. As shown enlarged in FIG. 3, a plurality of nozzles 211 capable of ejecting ink droplets are provided on an ejection surface 210 that is the lower surface of the head 21 . In this embodiment, a plurality of nozzles 211 are two-dimensionally arranged in the transport direction and width direction on the lower surface of the head 21 . The nozzles 211 are arranged with their positions shifted in the width direction. By arranging the plurality of nozzles 211 two-dimensionally in this manner, the positions of the nozzles 211 in the width direction can be brought closer to each other. However, the plurality of nozzles 211 may be arranged in a row along the width direction.

As a method for ejecting ink droplets from the nozzles 211, for example, a so-called piezo method is used, in which ink in the nozzles 211 is pressurized and ejected by applying a voltage to a piezo element, which is a piezoelectric element, to deform the element. However, the method of ejecting ink droplets may be a so-called thermal method in which the heater is energized to heat and expand the ink in the nozzles 211 to eject the ink droplets.

The second printing section 30 is a section that records a sub-image on the surface of the tablet 9 conveyed by the conveying belt 12 . The sub-image contains management information that should be confirmed only by a specific person concerned such as the manufacturer of the tablet 9 or a pharmacist. For example, the date of manufacture, expiry date, factory of manufacture, ingredients contained, etc. of the tablet 9 can be included in the sub-image. The second printing unit 30 of this embodiment has one head 31 . The head 31 is arranged above the transport belt 12 and downstream of the four heads 21 of the first printing unit 20 in the transport direction. In this embodiment, the head 31 of the second printing unit 30 ejects colorless and transparent ink toward the surface of the tablet 9 . As a result, a sub-image that is less visible than the main image under normal ambient light is printed on the surface of the tablet 9 .

Edible ink manufactured from raw materials approved by the Food Sanitation Act is used as the ink ejected from the head 31 . Also, the structure of the head 31 is the same as the structure of the head 21 shown in FIG. That is, the head 31 ejects ink droplets from a plurality of nozzles 211 provided on the bottom surface.

The drying mechanism 40 is a mechanism for drying ink adhering to the surface of the tablet 9 . The drying mechanism 40 is provided around the conveying belt 12 at a position downstream of the second printing unit 30 in the conveying direction. For the drying mechanism 40, for example, a hot air supply mechanism that blows heated gas (hot air) toward the tablets 9 conveyed by the conveying belt 12 is used. The ink ejected from the first printing unit 20 and the second printing unit 30 is dried by hot air and fixed on the surface of the tablet 9 .

In addition to the drying mechanism 40 , a drying mechanism (intermediate drying mechanism) may be provided between the first printing unit 20 and the second printing unit 30 . Then, only the colored inks forming the main image may be dried in the intermediate drying mechanism before the sub-image is printed.

The control unit 50 is means for controlling the operation of each unit in the printing apparatus 1 . FIG. 4 is a block diagram showing connections between the control unit 50 and each unit in the printer 1. As shown in FIG. As conceptually shown in FIG. 4, the control unit 50 is configured by a computer having a processor 51 such as a CPU, a memory 52 such as a RAM, and a storage unit 53 such as a hard disk drive. A computer program P for executing print processing is installed in the storage unit 53 .

Further, as shown in FIG. 4, the control unit 50 controls the above-described transport motor 13, the suction mechanism 15, the blow mechanism 16, the four heads 21 of the first printing unit 20, the head 31 of the second printing unit 30, the drying It is communicably connected to the mechanism 40, the loading mechanism 101, and the unloading mechanism 102, respectively. The control unit 50 temporarily reads the computer program P and data stored in the storage unit 53 to the memory 52, and the processor 51 performs arithmetic processing based on the computer program P, thereby controlling the operation of each unit. do. As a result, the printing process for the plurality of tablets 9 proceeds.

<2. About main image and sub image>
Next, the main image 91 and sub-image 92 printed on the surface of the tablet 9 will be described in more detail. FIG. 5 is a diagram showing an example of tablet 9 on which main image 91 and sub-image 92 are printed.

In the example of FIG. 5, a character string of "TABLET A", which is the product name, and a character string of "200 mg", which indicates the weight, are printed as the main image 91 on the surface of the tablet 9. FIG. These main images 91 are clearly printed with colored ink. Therefore, the consumer of the tablet 9 can easily view the main image 91 under normal ambient light.

Pigment-based or dye-based ink can be used for the colored ink that forms the main image 91 . Pigment-based inks include, for example, carbon black and iron oxide (yellow iron oxide, yellow iron sesquioxide, iron sesquioxide, red iron oxide, black iron oxide, etc.). Further, the dye-based ink can be appropriately selected from, for example, synthetic edible coloring matter, natural coloring matter derivatives, natural synthetic coloring matter, natural edible coloring matter, and the like. Examples of synthetic food coloring include Food Red No. 2, Food Red No. 3, Food Red No. 40, Food Red No. 102, Food Red No. 104, Food Red No. 105, Food Red No. 106, Food Yellow No. 4 and Food Yellow. No. 5, Food Blue No. 1, Food Blue No. 2, and Food Green No. 3. Natural pigment derivatives include, for example, sodium copper chlorophyllin. Examples of natural synthetic pigments include β-carotene. Examples of natural edible pigments include anthocyanin pigments, carotenoid pigments, quinone pigments, and flavonoid pigments. These may be used individually by 1 type, and may be used in mixture of 2 or more types. In addition, the ink forming the main image 91 is not limited to these examples.

Further, in the example of FIG. 5, braille is printed on the surface of the tablet 9 as the sub-image 92 . The Braille characters in FIG. 5 represent the character string "20170404", which is the expiry date of the tablet 9, in Braille. Since the printing method of this printing apparatus 1 is an inkjet method, fine Braille characters can be printed by ink droplets ejected from the head 31 .

In this embodiment, the sub-image 92 is printed with colorless and transparent ink. For colorless and transparent ink, for example, zinc oxide or titanium oxide can be used. The sub-image 92 is less visible than the main image 91 under normal ambient light. Therefore, consumers of tablet 9 have difficulty in recognizing sub-image 92 under normal ambient light. However, a specific person concerned such as the manufacturer of the tablet 9 or a pharmacist can confirm the information contained in the sub-image 92 using the reading device 2 described later.

In this way, if the main image 91 and the sub-image 92 with lower visibility than the main image 91 are printed on the surface of the tablet 9, the information to be displayed to the consumer of the tablet 9 and the specific relationship It is possible to distinguish between information that should only be confirmed by a third party. In addition, since the sub-image 92 is difficult for the consumer to visually recognize, what the consumer is aware of is only the information contained in the main image 91 . This reduces the amount of information visible to the consumer to prevent consumer confusion, and allows more information to be shown to specific parties.

In particular, in the example of FIG. 5, a portion of the sub-image 92 is printed over the main image 91 . Since the sub-image 92 is colorless and transparent, even if it is printed over the main image 91, the visibility of the main image 91 is hardly affected. Further, by printing the sub-image 92 over the main image 91, the sub-image 92 can be printed over a wide range without being restricted by the print range of the main image 91. FIG. Therefore, the sub-image 92 can contain more information.

In this embodiment, colorless and transparent ink is used for the sub-image 92 , but colored ink may be used for the sub-image 92 . In that case, it is preferable to use ink of a color close to the color of the surface of the tablet 9 . For example, the hue of the sub-image 92 should be closer to the hue of the surface of the tablet 9 than the hue of the main image 91 . Preferably, the hue of the sub-image 92 should be substantially the same as the hue of the surface of the tablet 9 . Also, the brightness of the sub-image 92 should be closer to the brightness of the surface of the tablet 9 than the brightness of the main image 91 . Preferably, the brightness of the sub-image 92 is made substantially the same as the brightness of the surface of the tablet 9 . This makes it possible to reduce the visibility of the sub-image 92 under normal ambient light.

Moreover, when printing the sub-image 92 with colored ink, there is no need to provide the head 31 in addition to the four heads 21 of the first printing unit 20 . Therefore, the head 31 may be omitted and the four heads 21 may serve as both the first printing section 20 that prints the main image 91 and the second printing section 30 that prints the sub-image 92 .

Also, in the example of FIG. 5, braille is printed as the sub-image 92 . In this way, the use of Braille can make it more difficult for people other than the specific concerned parties to recognize the information contained in the sub-image 92 . However, the sub-image 92 may include other code images that are symbolized for each character instead of Braille or together with Braille. Also, as shown in FIG. 6, the sub-image 92 may be a normal character string such as numbers. Also, the sub-image 92 does not have to overlap the main image 91 .

<3. About reading device>
Next, the reading device 2 for reading information included in the image printed on the tablet 9 will be described. FIG. 7 is a diagram showing the configuration of the reading device 2. As shown in FIG. A specific party, such as the manufacturer of the tablet 9 or a pharmacist, can use the reader 2 to confirm the information contained in the sub-image 92 . As shown in FIG. 7 , the reading device 2 has an imaging section 60 , an information acquisition section 70 and a display section 80 .

The photographing unit 60 is a device capable of photographing at least the sub-image 92 . The imaging unit 60 has a light irradiation unit 61 and a camera 62 . When the photographing unit 60 is operated, the camera 62 photographs the surface of the tablet 9 while irradiating the tablet 9 with light from the light irradiation unit 61 . Here, it is difficult to clearly capture the sub-image 92 under normal ambient light. However, if the absorbance of the sub-image 92 for the light of the specific wavelength is different from the absorbance of the surface of the tablet 9 to the light of the specific wavelength and the absorbance of the main image 91 to the light of the specific wavelength, the difference in absorbance can be used to capture the sub-image 92 . In this case, the light irradiation section 61 emits the photographing light L of the specific wavelength. When the photographing light L is received, the sub-image 92 is clarified due to the difference in absorbance, as shown in FIG. 8, for example. In this state, the imaging unit 60 performs imaging with the camera 62 . As a result, it is possible to obtain an imaging result in which the sub-image 92 clearly appears.

If the reflectance of the sub-image 92 differs from the reflectance of the surface of the tablet 9 and the reflectance of the main image 91, the sub-image 92 may be captured using the difference in reflectance. . For example, the reflected light may be photographed while irradiating the photographing light L obliquely from the light irradiation unit 61 toward the sub-image 92 .

Also, the sub-image 92 may be printed with ink containing a fluorescent material that emits light with a specific wavelength of light (for example, black light with a shorter wavelength than normal ambient light). In that case, the light irradiation unit 61 emits the photographing light L of the specific wavelength. Upon receiving the photographing light L, the fluorescent material forming the sub-image 92 emits light. Thereby, the sub-image 92 is clarified. In this state, the imaging unit 60 performs imaging with the camera 62 . As a result, it is possible to obtain an imaging result in which the sub-image 92 clearly appears.

The information acquisition unit 70 is a processing unit that acquires information from the photographed result of the camera 62 . A computer having a processor and a memory is used for the information acquisition unit 70, for example. The information acquisition unit 70 extracts braille by image processing from the photographed result of the camera 62 . Then, the extracted braille is converted into a character string and displayed on the display unit 80 . For example, a liquid crystal display is used for the display unit 80 .

By using such a reading device 2, the sub-image 92 with low visibility under normal ambient light can be clearly photographed. Therefore, the information contained in the sub-image 92 can be easily read by a specific party such as the manufacturer of the tablet 9 or a pharmacist.

<4. Variation>
Although the main embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.

In the above embodiment, the image is printed only on one of the front and back surfaces of the tablet 9 . However, images may be printed on both the front and back surfaces of tablet 9 . For example, the main image 91 may be printed on one side of the tablet 9 and the sub-image 92 may be printed on the other side of the tablet 9 . Also, the main image and the sub-image may be printed on both the front and back surfaces of the tablet 9 .

Further, in the above embodiment, the four heads 21 are provided in the first printing unit 20 . However, the number of heads 21 included in the first printing unit 20 may be 1 to 3, or may be 5 or more. Further, in the above embodiment, the second printing unit 30 is provided with one head 31 . However, the number of heads 31 included in the second printing unit 30 may be two or more.

In addition, the "edible granules" in the present invention may be scored tablets as shown in Figs. Tablets (FC tablets), sugar-coated tablets, capsule tablets and the like may also be used. In addition, the "edible granules" in the present invention are not limited to tablets as pharmaceuticals, but may be tablets as health foods, tablet confectionery such as soda pop.

Also, the elements appearing in the above embodiments and modifications may be appropriately combined as long as there is no contradiction.

1 printing device 2 reading device 9 tablet 10 transporting mechanism 11 pulley 12 transporting belt 13 transporting motor 14 suction hole 15 suction mechanism 16 blowing mechanism 20 first printing unit 21 head 30 second printing unit 31 head 40 drying mechanism 50 control unit 60 Photographing unit 61 Light irradiation unit 62 Camera 70 Information acquisition unit 80 Display unit 91 Main image 92 Sub-image 101 Carry-in mechanism 102 Carry-out mechanism 210 Ejection surface 211 Nozzle L Photographing light

Claims (9)

An edible granular material having an image printed on its surface by an inkjet method,
The image is
a main image visible under normal ambient light;
a secondary image that is less visible than the primary image under normal ambient light;
including
wherein the secondary image is printed on the same side as the primary image;
the absorbance of the sub-image to light of a particular wavelength is different from the absorbance of the surface to the light and the absorbance of the main image to the light;
the main image and the sub-image are printed with colored ink;
The hue and lightness of the sub-image are closer to the hue and lightness of the surface than the hue and lightness of the main image . The granules according to claim 1 ,
The sub-image is a granular material including a code image encoded for each character. The granules according to claim 2 ,
The granules, wherein the code image is Braille. The granules according to any one of claims 1 to 3 ,
A particulate article in which said sub-image is printed with an ink comprising zinc oxide or titanium oxide. A reading device for reading information contained in an image printed on the surface of an edible granular material by an inkjet method,
A sub-image printed with colored ink on the same surface as the main image printed with colored ink on the surface of the granule, and is more visible than the main image visible under normal ambient light. a sub-image having a low absorbance to light of a specific wavelength and different from the absorbance of said surface to said light and the absorbance of said main image to said light, wherein the hue and lightness are the hue and lightness of said main image; a photographing unit capable of photographing a sub-image closer to the hue and brightness of the surface than
an information acquisition unit that acquires information from the imaging result of the imaging unit;
with
The reading device, wherein the photographing unit includes a light irradiation unit that irradiates the light. A reader according to claim 5 , wherein
A reading device, wherein said sub-image is printed with an ink containing zinc oxide or titanium oxide. A printing device for printing an image on the surface of edible granules by an inkjet method,
a conveying mechanism for conveying the granular material;
a first printing unit that prints, with colored ink , a main image visible under normal ambient light on the surface of the granular material transported by the transport mechanism;
On the surface of the granular material transported by the transport mechanism, visibility is lower than that of the main image under normal ambient light, and the absorbance for light of a specific wavelength is determined by the absorbance of the surface and the absorbance of the main image. A sub-image having a different absorbance to light and having a hue and brightness closer to the hue and brightness of the surface than the hue and brightness of the main image is formed on the same surface as the main image with colored ink . a second printing unit that prints by
A printing device with The printing device according to claim 7 , wherein
The second printing unit is a printing device arranged downstream of the first printing unit in the conveying direction of the granular material. The printing device according to claim 7 or 8 ,
The second printing unit is a printing device that prints the sub-image with ink containing zinc oxide or titanium oxide.

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