Tablet printing apparatus and tablet printing method

Abstract

To provide a technology improving productivity of a tablet printing device by an ink jet method by reducing the frequency with which nozzle cleaning is performed.SOLUTION: A control part of a tablet printing device performing printing on a surface of the tablet 9 includes: a data holding part holding input data showing an image of a character string to be printed; a printing data determination part which determines printing data for performing printing on the surface of the tablet 9 on the basis of the input data; and a discharge control part controlling discharge of ink in a nozzle 420 on the basis of printing data determined by the printing data determination part. A direction heading from one end to the other of a line segment of each character included in printing data is not parallel to a transportation direction in which the tablet 9 is transported. Thus, when nozzle missing occurs, lowering of visibility of printed characters can be suppressed. Therefore, it is possible to lower the frequency with which nozzle cleaning is performed so as to prevent the nozzle missing.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a tablet printing apparatus and a tablet printing method for printing on the surface of a tablet.

Background Art

[0002] Characters and codes for identifying a product are printed on the surface of a tablet, which is a pharmaceutical product. Such characters and codes may be printed 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, in order to reliably identify tablets, it is required to perform clear printing on the surface of the tablets.

[0003] In addition, in recent years, orally disintegrating tablets that can be taken without using water have been gradually spreading. Since orally disintegrating tablets are weak against pressure, it is preferable to perform printing without applying pressure when printing on orally disintegrating tablets. For this reason, a technique for printing an image on the surface of a tablet by an inkjet method has attracted attention. In an inkjet tablet printing apparatus, an image can be printed more clearly on the surface of a tablet than by engraving. In addition, an image can be printed non-contact without applying pressure to the surface of the tablet.

[0004] Printing on the surface of a tablet generally has a lower printing rate than printing on other substrates such as paper. Therefore, when printing on the surface of a tablet by an inkjet method, there are many nozzles that are not used for a long time. Therefore, ink may dry inside the nozzles that are not used for a long time, resulting in so-called nozzle chipping where ink is not ejected normally from the nozzles. Depending on the location where nozzle chipping occurs, the image printed on the tablet is greatly missing, and the visibility of the printed information is greatly reduced. Therefore, it is necessary to perform regular cleaning to prevent nozzle chipping, which has led to a decrease in productivity.

[0005] Therefore, in the solid dosage form printing method of Patent Document 1, printing is performed on a rotation-free solid dosage form based on reference printing data D3 and based on printing data D3 obtained by rotating the reference printing data D3 to an arbitrary rotation angle. This makes it possible to improve the discharge rate of each nozzle without moving the printing device and to prevent nozzle clogging without reducing the operating rate. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2017-221244 [Overview of the project] [Problems that the invention aims to solve]

[0007] The solid dosage form printing method described in Patent Document 1 can prevent nozzle clogging of each nozzle only when the position of the tablet is kept constant. However, if the position of the tablet supplied to the tablet printing device shifts, a nozzle that has not been used for a long time will suddenly be used. In this case, because the nozzle is dry, ink may not be ejected immediately, which can cause nozzle chipping. Therefore, considering the possibility of the tablet being printed shifting, it was still necessary to perform periodic nozzle cleaning. This led to a decrease in the productivity of the tablet printing device.

[0008] This invention has been made in view of these circumstances, and aims to provide a technology that improves the productivity of an inkjet-type tablet printing apparatus by reducing the frequency of nozzle cleaning. [Means for solving the problem]

[0009] To solve the above problems, the first invention of the present application is a tablet printing apparatus for printing on the surface of a tablet, comprising: an inkjet type head having a plurality of nozzles for ejecting ink droplets, which ejects the ink droplets toward the surface of the tablet and performs printing; and a control unit for controlling the ejection of the ink droplets from the head, wherein the control unit comprises: a data holding unit for holding input data representing an image of a string of characters to be printed; a print data determination unit for determining print data for printing on the surface of the tablet based on the input data; and an ejection control unit for controlling the ejection of ink from the nozzles based on the print data determined by the print data determination unit, wherein the print data determination unit determines the angle information of the line segments of each character included in the input data The direction from one end to the other of the line segment of each character included in the print data is not parallel to the direction in which the tablets are transported. The aforementioned print data is determined. The second invention of the present application is a tablet printing apparatus for printing on the surface of a tablet, comprising: an inkjet type head having a plurality of nozzles for ejecting ink droplets, which ejects the ink droplets toward the surface of the tablet and performs printing; and a control unit for controlling the ejection of the ink droplets from the head, wherein the control unit comprises: a data holding unit for holding input data representing an image of a string of characters to be printed; a print data determination unit for determining print data for printing on the surface of the tablet based on the input data; and a ejection control unit for controlling the ejection of ink from the nozzles based on the print data determined by the print data determination unit, wherein the input data is a plurality of rotation data obtained by rotating the image of the string of characters to be printed at a plurality of rotation angles, the rotation data is raster data divided into regions arranged in a grid, and the print data determination unit determines the distribution of ink ejection regions in the raster data based The direction from one end to the other of the line segment of each character included in the print data is not parallel to the direction in which the tablets are transported. The ejection control unit selects the print data from a plurality of rotation data, and controls the ejection of ink from the nozzle based on the print data selected by the print data determination unit.

[0010] This application 3The invention is a tablet printing apparatus according to the first invention, wherein the input data is a plurality of rotation data obtained by rotating an image of a string to be printed at a plurality of rotation angles, the print data determination unit selects the print data from the plurality of rotation data, and the ejection control unit controls the ejection of ink from the nozzle based on the print data selected by the print data determination unit.

[0011] This application 4 The invention is the first invention. or the second invention The tablet printing apparatus comprises a reference data representing an image of a string of characters to be printed in an unrotated state, a print data determination unit generating the print data by rotating the reference data, and an ejection control unit controlling the ejection of ink from the nozzle based on the print data generated by the print data determination unit.

[0012] This application 5 The invention is the first invention. or the second invention A tablet printing apparatus, wherein the characters included in the printing data Tablets The inclination relative to the transport direction is neither 0°, 45°, 90°, 135°, nor 180°.

[0013] This application 6 The invention is, 5 The tablet printing apparatus of the invention, wherein the inclination of the characters included in the printing data with respect to the transport direction is one of the angles within the ranges of 20° to 25°, 65° to 70°, 110° to 115°, and 155° to 160°.

[0016] This application 7 The invention is a tablet printing method for printing on the surface of a tablet using an inkjet head, comprising: a) a step of determining print data for printing on the surface of the tablet based on input data representing an image of a string of characters to be printed; and b) a step of printing an image on the surface of the tablet based on the print data, wherein in step a), based on the angle information of the line segments of each character included in the input data The direction from one end to the other of the line segment of each character included in the print data is not parallel to the direction in which the tablets are transported. The aforementioned print data is determined. The eighth invention of the present application is a tablet printing method for performing printing processing on the surface of a tablet by an inkjet head, comprising: a) determining print data for printing on the surface of the tablet based on input data representing an image of a character string to be printed; and b) printing an image on the surface of the tablet based on the print data, wherein the input data is a plurality of rotation data obtained by rotating an image of the character string to be printed at a plurality of rotation angles, the rotation data is raster data segmented for each region arranged in a grid pattern, and in step a), based on the distribution of ink ejection regions in the raster data The direction from one end to the other of the line segment of each character included in the print data is not parallel to the direction in which the tablets are transported. selecting the print data from the plurality of rotation data, and in step b), controlling the ejection of ink from the nozzles of the head based on the print data selected in step a).

Advantages of the Invention

[0017] According to the first to eighth inventions of the present application, when nozzle dropout occurs, it is possible to suppress a decrease in the visibility of printed characters. Thereby, the frequency of performing nozzle cleaning to prevent nozzle dropout can be reduced. Therefore, the productivity of an inkjet type tablet printing apparatus can be improved.

[0018] In particular, according to Inventions 2 and 8 of the present application, the usage frequency of each nozzle becomes uniform. Therefore, the occurrence of nozzle dropout itself can be suppressed.

Brief Description of the Drawings

[0019] [Figure 1] It is a diagram showing the configuration of a tablet printing apparatus. [Figure 2] It is a perspective view near a conveying drum. [Figure 3] It is a bottom view of a head. [Figure 4] It is a block diagram showing the connection between a control unit and the inside of a tablet printing apparatus. [Figure 5]It is a block diagram conceptually showing the configuration related to the printing process of a tablet printing device. [Figure 6] It is a diagram showing the influence of nozzle chipping on the printing on the tablet surface. [Figure 7] It is a diagram showing the influence of nozzle chipping on the printing on the tablet surface. [Figure 8] It is a diagram showing the raster data of the image to be printed. [Figure 9] It is a diagram showing the raster data of the image to be printed. [Figure 10] It is a flowchart showing the flow of the printing process in a tablet printing device.

Embodiments for Carrying Out the Invention

[0020] 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 referred to as the "conveying direction", and the direction perpendicular and horizontal to the conveying direction is referred to as the "width direction".

[0021] <1. Regarding the Configuration of the Tablet Printing Device> FIG. 1 is a diagram showing the configuration of a tablet printing device 1 according to an embodiment of the present invention. This tablet printing device 1 is a device that prints images such as product names, product codes, company names, etc. on the surfaces of a plurality of tablets 9 that are pharmaceuticals while conveying them. As shown in FIG. 1, the tablet printing device 1 of this embodiment includes a hopper 10, a feeder unit 20, a conveying drum 30, a first printing unit 40, a second printing unit 50, an unloading conveyor 60, and a control unit 70.

[0022] The hopper 10 is an input unit for collectively receiving a large number of tablets 9 into the device. The hopper 10 is disposed at the uppermost part of the housing 100 of the tablet printing device 1. The hopper 10 has an opening 11 located on the upper surface of the housing 100 and a funnel-shaped inclined surface 12 that gradually converges downward. The plurality of tablets 9 introduced into the opening 11 flow into the straight feeder 21 along the inclined surface 12.

[0023] The feeder unit 20 is a mechanism that transports multiple tablets 9, which have been fed into the hopper 10, to the transport drum 30. The feeder unit 20 in this embodiment has a linear feeder 21, a rotary feeder 22, and an inclined feeder 23. The linear feeder 21 has a flat vibrating trough 211. Multiple tablets 9 supplied from the hopper 10 to the vibrating trough 211 are transported to the rotary feeder 22 by the vibration of the vibrating trough 211. The rotary feeder 22 has a disc-shaped turntable 221. Multiple tablets 9 that have fallen from the vibrating trough 211 to the upper surface of the turntable 221 are gathered near the outer circumference of the turntable 221 by the centrifugal force caused by the rotation of the turntable 221.

[0024] The inclined feeder 23 has a plate-shaped slope 231 that extends diagonally downward from the outer circumference of the turntable 221 to the conveying drum 30. Figure 2 is a perspective view of the area near the conveying drum 30. As shown in Figure 2, multiple (eight in the example in Figure 2) conveying grooves 232 are provided on the upper surface of the slope 231. Multiple tablets 9 that have been conveyed to the outer circumference of the turntable 221 are each supplied to one of the multiple conveying grooves 232 and flow diagonally downward along the conveying groove 232. In this way, multiple tablets 9 are supplied to multiple conveying grooves 232 and arranged into multiple conveying rows. Then, multiple tablets 9 in each conveying row are supplied to the conveying drum 30 in order from the front.

[0025] The conveying drum 30 is a mechanism that transfers multiple tablets 9 from the inclined feeder 23 to the first conveying conveyor 41. The conveying drum 30 has a substantially cylindrical outer surface. The conveying drum 30 rotates in the direction of the arrows in Figures 1 and 2, about a rotation axis that extends in the width direction, by power obtained from a motor (not shown). As shown in Figure 2, multiple suction holes 31 are provided on the outer surface of the conveying drum 30. The multiple suction holes 31 are arranged along the circumferential direction on the outer surface of the conveying drum 30 at width direction positions corresponding to each of the multiple conveying rows described above.

[0026] The transport drum 30 is equipped with a suction mechanism (not shown) inside. When the suction mechanism is activated, a negative pressure lower than atmospheric pressure is generated in each of the multiple suction holes 31. The suction holes 31 use this negative pressure to adsorb and hold the tablets 9 supplied from the inclined feeder 23 one by one. The transport drum 30 is also equipped with a blow mechanism (not shown) inside. The blow mechanism blows locally pressurized gas from the inside of the transport drum 30 toward the first transport conveyor 41, which will be described later. As a result, the suction state of the tablets 9 is maintained in the suction holes 31 that do not face the first transport conveyor 41, while the suction of the tablets 9 is released only in the suction holes 31 that face the first transport conveyor 41. In this way, the transport drum 30 can rotate while adsorbing and holding multiple tablets 9 supplied from the inclined feeder 23, and transfer those tablets 9 to the first transport conveyor 41.

[0027] The first printing unit 40 is a processing unit for printing an image on one side of the tablet 9. As shown in Figure 1, the first printing unit 40 includes a first transport conveyor 41, a first head unit 42, a first inspection camera 43, and a first fixing unit 44.

[0028] The first conveyor 41 is a conveying mechanism having a pair of pulleys 411 and an annular conveyor belt 412 stretched between the pair of pulleys 411. A portion of the conveyor belt 412 is positioned to face and be close to the outer surface of the conveyor drum 30. One of the pair of pulleys 411 is rotated by power obtained from a motor (not shown). This causes the conveyor belt 412 to rotate in the direction of the arrows in Figures 1 and 2. At this time, the other pulley 411 rotates in association with the rotation of the conveyor belt 412.

[0029] As shown in Figure 2, the conveyor belt 412 is provided with a plurality of suction holes 413. The plurality of suction holes 413 are arranged in the conveying direction at widthwise positions corresponding to each of the plurality of conveying rows. That is, the plurality of suction holes 413 are arranged with spacing in both the widthwise and conveying directions. The widthwise spacing of the plurality of suction holes 413 on the conveyor belt 412 is equal to the widthwise spacing of the plurality of suction holes 31 on the conveyor drum 30.

[0030] A suction mechanism (not shown) is provided inside the conveyor belt 412. When the suction mechanism is activated, a negative pressure lower than atmospheric pressure is generated in each of the multiple suction holes 413. The suction holes 413 then adsorb and hold the tablets 9 passed from the conveyor drum 30 one by one due to this negative pressure. As a result, the first conveyor belt 41 conveys the tablets 9 while holding them in an aligned state in multiple conveyor rows spaced apart in the width direction. In addition, a blow mechanism (not shown) is provided inside the conveyor belt 412. When the blow mechanism is activated, the pressure in the suction holes 413 facing the second conveyor belt 51 (described later) becomes a positive pressure higher than atmospheric pressure. As a result, the suction of the tablets 9 in the suction holes 413 is released, and the tablets 9 are transferred from the first conveyor belt 41 to the second conveyor belt 51.

[0031] The first head unit 42 is an inkjet type head unit that ejects ink droplets toward the surface of tablets 9 being transported by the first transport conveyor 41. The first head unit 42 has four heads 421 arranged along the transport direction. The four heads 421 eject ink droplets of different colors (for example, cyan, magenta, yellow, and black) toward the surface of the tablet 9. A multicolor image is recorded on the surface of the tablet 9 by superimposing the monochrome images formed by each of these colors. The ink ejected from each head 421 is edible ink manufactured from raw materials approved under the Japanese Pharmacopoeia, the Food Sanitation Law, etc.

[0032] Figure 3 is a bottom view of one head 421. In Figure 3, a conveyor belt 412 and a plurality of tablets 9 held on the conveyor belt 412 are shown by dashed lines. As shown in the enlarged view in Figure 3, a plurality of nozzles 420 capable of ejecting ink droplets are provided on the bottom surface of the head 421. In this embodiment, the plurality of nozzles 420 are arranged two-dimensionally on the bottom surface of the head 421 in the conveying direction and the width direction. Each nozzle 420 is arranged with a staggered position in the width direction. By arranging the plurality of nozzles 420 two-dimensionally in this way, the positions of each nozzle 420 in the width direction can be brought closer to each other. However, the plurality of nozzles 420 may also be arranged in a single line along the width direction.

[0033] The method for ejecting ink droplets from the nozzle 420 is, for example, a so-called piezoelectric method, in which a voltage is applied to a piezoelectric element, which deforms, thereby pressurizing and ejecting the ink inside the nozzle 420. The head 421 of this embodiment can switch the size of the ink droplets ejected from the nozzle 420 by changing the magnitude of the voltage applied to the piezoelectric element. Specifically, it can eject any ink droplet from three types of ink droplets: "small size" which is the finest ink droplet, "large size" which is the largest ink droplet, and "medium size" which is an intermediate size. However, the number of sizes of ink droplets that can be ejected may be one or two, or four or more. In addition, the method for ejecting ink droplets may be a so-called thermal method, in which the ink inside the nozzle 420 is heated and expanded by energizing a heater.

[0034] Returning to Figure 1, the first inspection camera 43 is an imaging unit for checking the printing results from the first head unit 42. The first inspection camera 43 is located downstream of the first head unit 42 in the transport direction and photographs the surface of multiple tablets 9 being transported by the first transport conveyor 41, and transmits the obtained image data to the control unit 70. Based on the received image data, the control unit 70 determines whether there are any printing defects such as misalignment or missing dots in the image printed on the surface of each tablet 9.

[0035] The first fixing unit 44 is a mechanism that fixes the ink ejected from the first head unit 42 onto the tablet 9. In this embodiment, the first fixing unit 44 is located downstream of the first inspection camera 43 in the transport direction. However, the first fixing unit 44 may be located between the first head unit 42 and the first inspection camera 43. The first fixing unit 44 uses, for example, a hot air drying heater that blows hot air towards the tablet 9 being transported by the first transport conveyor 41. The ink adhering to the surface of the tablet 9 is dried by the hot air and fixed to the surface of the tablet 9.

[0036] The second printing unit 50 is a processing unit for printing an image on the other side of the tablet 9 after printing by the first printing unit 40. As shown in Figure 1, the second printing unit 50 includes a second transport conveyor 51, a second head unit 52, a second inspection camera 53, and a second fixing unit 54. The second transport conveyor 51 transports multiple tablets 9 while holding them received from the first transport conveyor 41. The second head unit 52 ejects ink toward the surface of the tablets 9 being transported by the second transport conveyor 51. The second inspection camera 53 photographs the surface of the multiple tablets 9 being transported by the second transport conveyor 51 downstream of the second head unit 52 in the transport direction. The second fixing unit 54 fixes the ink ejected from each head 521 of the second head unit 52 onto the tablets 9.

[0037] Details of the second conveyor belt 51, the second head unit 52, the second inspection camera 53, and the second fixing unit 54 are the same as those of the first conveyor belt 41, the first head unit 42, the first inspection camera 43, and the first fixing unit 44 described above, so redundant explanations will be omitted.

[0038] The discharge conveyor 60 is a mechanism for discharging multiple printed tablets 9 to the outside of the housing 100 of the tablet printing device 1. The upstream end of the discharge conveyor 60 is located below the second transport conveyor 51. The downstream end of the discharge conveyor 60 is located outside the housing 100. For example, a belt transport mechanism is used for the discharge conveyor 60. After the printing process in the second printing section 50, the multiple tablets 9 fall from the second transport conveyor 51 to the upper surface of the discharge conveyor 60 as the suction of the suction holes is released. The multiple tablets 9 are then discharged to the outside of the housing 100 by the discharge conveyor 60.

[0039] <2. Regarding the configuration of the control unit> The control unit 70 is a means for controlling the operation of each part within the tablet printing device 1. Figure 4 is a block diagram showing the connections between the control unit 70 and each part within the tablet printing device 1. As conceptually shown in Figure 1, the control unit 70 is composed of a computer having an arithmetic processing unit 701 such as a CPU, memory 702 such as RAM, and a storage unit 703 such as a hard disk drive. A computer program P for executing the printing process is installed in the storage unit 703.

[0040] Furthermore, as shown in Figure 4, the control unit 70 is communicated with the linear feeder 21, rotary feeder 22, transport drum 30 (including motor, suction mechanism, and blow mechanism), first transport conveyor 41 (including motor, suction mechanism, and blow mechanism), first head unit 42 (including multiple nozzles 420 for each head 421), first inspection camera 43, first fixing unit 44, second transport conveyor 51 (including motor, suction mechanism, and blow mechanism), second head unit 52 (including multiple nozzles for each head 521), second inspection camera 53, second fixing unit 54, and discharge conveyor 60, respectively.

[0041] The control unit 70 temporarily reads the computer program P and data D stored in the storage unit 703 into the memory 702, and the arithmetic processing unit 701 performs arithmetic processing based on the computer program P, thereby controlling the operation of each of the above-mentioned parts. As a result, the printing process for the multiple tablets 9 proceeds.

[0042] Figure 5 is a block diagram conceptually showing the configuration related to the printing process of the tablet printing apparatus 1. As shown in Figure 5, the control unit 70 has a data holding unit 71, a print data determination unit 72, and a dispensing control unit 73. The function of the data holding unit 71 is realized by the storage unit 703 described above. The functions of the print data determination unit 72 and the dispensing control unit 73 are realized by the operation of the computer as the control unit 70 according to the computer program P described above.

[0043] External input data is received by the data holding unit 71. The input data received by the data holding unit 71 consists of multiple rotation data D2 obtained by rotating an image of a string to be printed by 0° (no rotation), 1°, 2°, 3°, ..., 359°. The rotation data D2 is raster data in which the image to be printed is divided into grid-like regions. The data holding unit 71 holds (stores) the multiple rotation data D2 received from the external as input data. In this embodiment, the rows of the raster data are parallel to the width direction, and the columns of the raster data are parallel to the transport direction. Each region constituting the rotation data D2 consists of a region where ink should be ejected (ink ejection region) and a region where ink should not be ejected (non-ink ejection region). Note that the rotation angle of the rotation data D2 is not limited to 1° increments. The rotation angle of the rotation data D2 may be 2° increments, 1.5° increments, 3° increments, or other angles.

[0044] Furthermore, the data holding unit 71 may receive a single input data from an external source. The data holding unit 71 may then generate multiple rotation data D2 by rotating the single input data to multiple rotation angles. In this case as well, the data holding unit 71 will hold the multiple rotation data D2 as input data.

[0045] When inputting a single data from an external source to the data holding unit 71, the input data may be raster data, but it is preferable that it be vector data. When rotating raster data to obtain rotation data D2, each pixel that made up the raster data is tilted in the vertical and horizontal directions, so it needs to be rasterized again. The data that has been rasterized again will have more jaggedness compared to the unrotated raster data, which may reduce print quality. On the other hand, if rotation data D2 obtained by rotating vector data is rasterized, there will be no reduction in print quality compared to the unrotated raster data.

[0046] Furthermore, the angle at which the data holding unit 71 rotates the input data is not limited to 1° increments. The rotation angle when the data holding unit 71 rotates the input data may be 2° increments, 1.5° increments, 3° increments, or any other angle.

[0047] If rotation degrades print quality, it becomes impossible to use strict thresholds when inspecting the print results with inspection cameras 43 and 53. However, if the degradation of print quality due to rotation is suppressed, inspection cameras 43 and 53 can use strict thresholds to inspect the print results. Therefore, the degradation of print quality can be further suppressed.

[0048] <3. Regarding the determination of print data in the print data determination unit> Figures 6 and 7 illustrate the effect of nozzle failure on printing on the surface of tablet 9. Each character in the input data representing the image to be printed consists of line segments connecting points and curves connecting points. When the orientation of the image in the input data is parallel to the transport direction (rotation angle is 0° or 180°), the input data often includes characters where the direction from one end of the line segment to the other is parallel to the transport direction. In this case, as shown in Figure 6, if nozzle failure occurs in the nozzle 420 corresponding to the line segment, the printing of that line segment will be significantly impaired, greatly reducing the visibility of the image printed on tablet 9. Furthermore, if adjacent nozzles 420 fail, the line segment may not be printed at all. This is also true when the orientation and width direction of the image in the input data are parallel (rotation angle is 90° or 270°).

[0049] Therefore, in this embodiment, the printing process on the tablet 9 is performed using an image that has been rotated so that the direction from one end to the other of the line segments of each character included in the image to be printed is not parallel to the transport direction. As a result, as shown in Figure 7, it is possible to suppress the decrease in the visibility of the image printed on the tablet 9 when nozzle chipping occurs. In the following description, "the line segments of each character" may be simply referred to as "line segments".

[0050] Furthermore, the tablet 9 in this embodiment has a circular shape when viewed from above, and does not have a score line on its surface. This allows printing to be performed on the tablet 9 in the same way regardless of the angle at which the image is rotated.

[0051] The print data determination unit 72 selects print data D3 from a plurality of rotation data D2 held by the data holding unit 71. Specifically, the print data determination unit 72 selects as print data D3 the rotation data D2 such that the direction from one end of the line segment to the other end is not parallel to the transport direction. The print data determination unit 72 selects print data D3 from a plurality of rotation data D2 using one of the following methods 1 to 3. The method by which the print data determination unit 72 selects print data D3 will be described below.

[0052] <3-1. 1st method> As shown in Figure 6, numbers and katakana characters are commonly used for printing on tablets. The shapes of numbers contain many horizontal and vertical line segments. Katakana characters are represented by line segments with inclinations of 0°, 45°, 90°, and 135° relative to the character, as well as curves close to these line segments.

[0053] Therefore, in the first method, the print data determination unit 72 selects one rotation data D2 as print data D3 from among rotation data D2 having angles other than 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°. In particular, it is preferable for the print data determination unit 72 to select one rotation data D2 from among a plurality of rotation data D2 having angles of 20° to 25°, 65° to 70°, 110° to 115°, 155° to 160°, 200° to 205°, 245° to 250°, 290° to 295°, and 335° to 340°. This allows printing to be performed in a state where the direction from one end of the line segment to the other end is not parallel to the transport direction. Therefore, even if nozzle chipping occurs, a decrease in the visibility of the characters printed on the tablet 9 can be suppressed.

[0054] <3-2.Second method> In the second method, the print data determination unit 72 selects print data D3 based on the distribution of ink ejection areas in the rotation data D2. Figure 8 shows the raster data in rotation data D2 when the image to be printed is not rotated (0°). As shown in Figure 8, when rotation data D2 contains line segments parallel to the transport direction, the ink ejection areas of those line segments exist in the same column in the raster data of rotation data D2. That is, when the number of occurrences of ink ejection areas in the raster data is aggregated for each column, the distribution of occurrences is biased towards certain columns.

[0055] Figure 9 shows the raster data in rotation data D2 when the image to be printed is rotated by a predetermined angle. As shown in Figure 9, rotation data D2 with a predetermined rotation angle results in a less biased distribution when the ink ejection area is aggregated for each column of raster data. By selecting such rotation data D2 as print data D3, it is possible to avoid the direction from one end of a line segment to the other being parallel to the transport direction.

[0056] In the second method, the print data determination unit 72 refers to a plurality of rotation data D2 held by the data holding unit 71 and aggregates the number of occurrences of the ink ejection area for each column of raster data of each rotation data D2. Next, the print data determination unit 72 calculates the variance for the number of occurrences of the ink ejection area for each column. This makes it possible to quantify the bias of the ink ejection area for each column for each rotation data D2. After that, the print data determination unit 72 selects the rotation data D2 that has the largest variance as the print data D3. This makes it possible to print so that the direction from one end of a line segment to the other is not parallel to the transport direction. Therefore, even if nozzle chipping occurs, it is possible to suppress a decrease in the visibility of the characters printed on the tablet 9.

[0057] Furthermore, in the second method, the rotation data D2, which has the largest variance in the number of occurrences of the ink ejection area across columns, is selected as the print data D3, resulting in uniform usage frequency for each nozzle 420. Therefore, it is possible to suppress the occurrence of nozzle chipping itself.

[0058] <3-3. Third method> In the third method, the print data determination unit 72 selects print data D3 from multiple rotation data D2 by measuring the inclination angle of each line segment for each of the multiple rotation data D2. First, the print data determination unit 72 refers to each rotation data D2 held by the data holding unit 71 and measures the inclination angle of each line segment included in each rotation data D2. Next, the print data determination unit 72 selects as print data D3 the rotation data D2 in which none of the inclination angles of each line segment match the angle of the transport direction. This makes it possible to print so that the direction from one end of the line segment to the other is not parallel to the transport direction. Therefore, even if nozzle chipping occurs, a decrease in the visibility of the characters printed on the tablet 9 can be suppressed.

[0059] The inclination angle information for each line segment of each rotation data D2 may be pre-input into the data holding unit 71 from an external source. In this case, the print data determination unit 72 refers to the inclination angle information held in the data holding unit 71 and selects a predetermined rotation data D2 as the print data D3.

[0060] In addition, in the first to third methods, the print data determination unit 72 may select two or more rotation data D2s. In this case, in the second method, the print data determination unit 72 may select the rotation data D2 with the maximum variance and the rotation data D2 with the second largest variance.

[0061] The print data determination unit 72 transfers the print data D3 selected using one of the first to third methods described above to the ejection control unit 73.

[0062] The ejection control unit 73 controls the ejection of ink from each nozzle of the first head unit 42 and the second head unit 52 based on the print data D3 received from the print data determination unit 72, and ejects ink onto the surface of each tablet 9.

[0063] <4. Flow of the printing process in a tablet printing machine> The following describes the printing process in the tablet printing device 1, with reference to Figure 10. Figure 10 is a flowchart showing the printing process in the tablet printing device 1.

[0064] As shown in Figure 10, in the printing process of the tablet printing apparatus 1, first, multiple rotation data D2 are input to the control unit 70 from an external source. As a result, the data holding unit 71 holds the multiple rotation data D2 (step S101). The rotation data D2 stored in the data holding unit 71 may be stored as table data that associates rotation angle information with the rotation data D2.

[0065] Next, the print data determination unit 72 uses one of the first to third methods to select the rotation data D2 as the print data D3, which has a rotation angle such that the direction from one end to the other of the line segment of the rotation data D2 is not parallel to the transport direction (step S102). The print data determination unit 72 then passes the print data D3 to the ejection control unit 73.

[0066] Next, the ejection control unit 73 causes the first head unit 42 and the second head unit 52 to perform printing based on the print data D3 received from the print data determination unit 72 (step S103). As a result, an image corresponding to the print data D3 selected by the print data determination unit 72 is recorded on each of the multiple tablets 9 being transported.

[0067] As described above, this tablet printing device 1 prints in such a way that the direction from one end to the other of the line segments of each character included in the print data D3 is not parallel to the transport direction. Therefore, even if nozzle chipping occurs, a decrease in the visibility of the printed characters can be suppressed. This reduces the frequency of nozzle cleaning required to prevent nozzle chipping. Consequently, the productivity of the tablet printing device 1 can be improved.

[0068] <5. Variation> Although the main embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above.

[0069] In the above embodiment, the input data was an image representing a string of characters using katakana and numbers. However, the input data may also be an image representing a string of characters using kanji or the alphabet.

[0070] Furthermore, in the above embodiment, the tablet printing apparatus 1 was a device that printed on both sides of the tablet 9 using the first printing unit 40 and the second printing unit 50. However, the tablet printing apparatus 1 may print on only one side of the tablet 9.

[0071] Furthermore, in the above embodiment, the print data determination unit 72 selected print data D3 from a plurality of rotation data D2 using one of the first to third methods. However, the print data determination unit 72 may also select print data D3 by combining multiple methods from the first to third methods.

[0072] Furthermore, in the above embodiment, the data holding unit 71 held multiple rotation data D2 obtained by rotating the image to be printed at 0° (no rotation), 1°, 2°, 3°, ..., 359°. The print data determination unit 72 selected the print data D3 to be printed on each tablet 9 from the data holding unit 71 and passed it to the dispensing control unit 73. However, the data holding unit 71 may hold only one reference data D1 representing the image of the string to be printed in an unrotated state. The print data determination unit 72 may then generate the print data D3 to be printed on each tablet 9 by rotating the reference data D1 to a predetermined angle.

[0073] The following describes the printing process flow related to this modified example. First, one reference data D1 is input to the control unit 70 from an external source. As a result, the data holding unit 71 stores the one reference data D1.

[0074] Next, the print data determination unit 72 determines the print data D3. In this modified example, the method by which the print data determination unit 72 determines the print data D3 differs from that of the above embodiment. In the above embodiment, the print data D3 was selected from a plurality of rotation data D2 held by the data holding unit 71. In contrast, in this modified example, first, the data holding unit 71 hands over the reference data D1 to the print data determination unit 72. The print data determination unit 72 generates the print data D3 by rotating the reference data D1 by a predetermined angle. In this modified example, the print data D3 is generated using the same rules as the first or third method of the above embodiment. Therefore, redundant explanations will be omitted, and the differences will be explained.

[0075] Regarding the first method, in the above embodiment, the print data determination unit 72 determined the print data D3 by selecting one rotation data D2 having a predetermined angle from a plurality of rotation data D2. In contrast, in this modified example, the print data determination unit 72 generates the print data D3 by rotating the reference data D1 by a predetermined angle.

[0076] Regarding the third method, in the above embodiment, the print data determination unit 72 selected the rotation data D2 in which none of the inclination angles of each line segment matched the angle of the transport direction as the print data D3. In contrast, in this modified example, the print data determination unit 72 generates the print data D3 by rotating the reference data D1 such that none of the inclination angles of each line segment included in the print data D3 match the angle of the transport direction.

[0077] Next, the ejection control unit 73 causes the first head unit 42 and the second head unit 52 to perform printing based on the print data D3 received from the print data determination unit 72. As a result, an image corresponding to the print data D3 generated by the print data determination unit 72 is recorded on each of the multiple tablets 9 being transported.

[0078] Furthermore, the "tablets" to be processed in this invention include, for example, uncoated tablets, orally disintegrating tablets (OD tablets), film-coated tablets (FC tablets), and sugar-coated tablets, but are not necessarily limited to tablets used as pharmaceuticals. The tablet printing apparatus of this invention may also be used to print on tablets used as health foods or on candies such as ramune.

[0079] Furthermore, the detailed configuration of the tablet printing device 1 may differ from that shown in the figures of this application. In addition, the elements that appear in the above embodiments and modifications may be combined as appropriate, to the extent that no inconsistencies arise. [Explanation of Symbols]

[0080] 1: Tablet printing machine 9: Tablets 10: Hopper 11: Opening 12: Inclined surface 20: Feeder section 21: Straight feeder 22: Rotary feeder 23: Inclined feeder 30: Conveyor Drum 31: Adsorption hole 40: 1st printing department 41: First conveyor 42: First head unit 43: First inspection camera 44: First Fixing Section 50: 2nd printing department 51: Second conveyor 52: Second head unit 53: Second inspection camera 54: Second Fixing Section 60: Discharge conveyor 70: Control Unit 71: Data storage unit 72: Print Data Determination Unit 73: Discharge control unit 100: Cabinet 211: Vibration trough 221: Rotating stand 231: Slope 232: Conveyor groove 411: Pulley 412: Conveyor belt 413: Adsorption hole 420: Nozzle 421: Head 521: Head 701: Arithmetic Processing Unit 702: Memory 703: Storage section D1: Reference data D2: Rotation data D3: Print data P: Computer program

Claims

1. A tablet printing apparatus that prints on the surface of a tablet, An inkjet head having multiple nozzles for ejecting ink droplets, which ejects the ink droplets toward the surface of the tablet to perform printing, A control unit that controls the ejection of ink droplets from the head, Equipped with, The control unit, A data storage unit that holds input data representing an image of the string of characters to be printed, A print data determination unit that determines print data for printing on the surface of the tablet based on the input data, Based on the print data determined by the print data determination unit, the ejection control unit controls the ejection of ink from the nozzle, Equipped with, A tablet printing apparatus in which the print data determination unit determines the print data based on the angle information of the line segments of each character included in the input data, such that the direction from one end to the other of the line segments of each character included in the print data is not parallel to the transport direction in which the tablets are transported.

2. A tablet printing apparatus that prints on the surface of a tablet, An inkjet head having multiple nozzles for ejecting ink droplets, which ejects the ink droplets toward the surface of the tablet to perform printing, A control unit that controls the ejection of ink droplets from the head, Equipped with, The control unit, A data storage unit that holds input data representing an image of the string of characters to be printed, A print data determination unit that determines print data for printing on the surface of the tablet based on the input data, Based on the print data determined by the print data determination unit, the ejection control unit controls the ejection of ink from the nozzle, Equipped with, The aforementioned input data consists of multiple rotation data obtained by rotating an image of the text to be printed at multiple rotation angles. The rotation data is raster data divided into regions arranged in a grid, The print data determination unit selects the print data from a plurality of rotation data, based on the distribution of ink ejection areas in the raster data, such that the direction from one end to the other of the line segments of each character included in the print data is not parallel to the transport direction in which the tablets are transported. The ejection control unit controls the ejection of ink from the nozzle based on the print data selected by the print data determination unit, in a tablet printing apparatus.

3. A tablet printing apparatus according to claim 1, The aforementioned input data consists of multiple rotation data obtained by rotating an image of the text to be printed at multiple rotation angles. The print data determination unit selects the print data from the plurality of rotation data, The ejection control unit controls the ejection of ink from the nozzle based on the print data selected by the print data determination unit, in a tablet printing apparatus.

4. A tablet printing apparatus according to claim 1 or claim 2, The aforementioned input data is reference data representing the image of the string to be printed in an unrotated state. The print data determination unit generates the print data by rotating the reference data, The ejection control unit controls the ejection of ink from the nozzle based on the print data generated by the print data determination unit, in a tablet printing apparatus.

5. A tablet printing apparatus according to either claim 1 or claim 2, A tablet printing apparatus in which the inclination of the characters included in the print data with respect to the tablet transport direction is not 0°, 45°, 90°, 135°, or 180°.

6. A tablet printing apparatus according to claim 5, A tablet printing apparatus in which the inclination of the characters included in the print data with respect to the transport direction is one of the angles within the ranges of 20° to 25°, 65° to 70°, 110° to 115°, and 155° to 160°.

7. A tablet printing method in which printing is performed on the surface of a tablet using an inkjet head, a) A step of determining print data for printing on the surface of the tablet based on input data representing an image of the string of characters to be printed, b) A step of printing an image on the surface of the tablet based on the print data, It has, A tablet printing method, wherein in step a), the print data is determined based on the angle information of the line segments of each character included in the input data, such that the direction from one end to the other of the line segments of each character included in the print data is not parallel to the transport direction in which the tablets are transported.

8. A tablet printing method in which printing is performed on the surface of a tablet using an inkjet head, a) A step of determining print data for printing on the surface of the tablet based on input data representing an image of the string of characters to be printed, b) A step of printing an image on the surface of the tablet based on the print data, It has, The aforementioned input data consists of multiple rotation data obtained by rotating an image of the text to be printed at multiple rotation angles. The rotation data is raster data divided into regions arranged in a grid, In step a), based on the distribution of ink ejection areas in the raster data, the print data is selected from a plurality of rotation data such that the direction from one end to the other of the line segments of each character included in the print data is not parallel to the transport direction in which the tablets are transported. A tablet printing method comprising, in step b), controlling the ejection of ink from the nozzles of the print head based on the print data selected in step a).

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