Inkjet printer and printing method

Abstract

To provide an inkjet printer capable of achieving both reduced graininess of printed images and reduced ink mist. [Solution] The inkjet printer according to the present invention has registered therein a plurality of dot tables, each defining a correspondence between ink values ​​and the composition ratio of each ink droplet. The plurality of dot tables differ from one another in the composition ratio of the smallest first ink droplet for at least some ink values. The inkjet printer associates one of the plurality of dot tables with a print image or each object within the print image (S11, S12A, S12B). When forming the print image or each object, the inkjet printer ejects a plurality of ink droplets based on the composition ratio of each ink droplet defined by the dot table corresponding to the print image or each object (S16).

Description

[Technical Field]

[0001] The present invention relates to an inkjet printer and a printing method. [Background technology]

[0002] Inkjet printers that form images by ejecting ink onto a recording medium have been known for some time. A typical inkjet printer is configured to be able to eject multiple types of ink droplets with different sizes. For example, Patent Document 1 discloses an inkjet printer that can form three or more ink droplets with different sizes.

[0003] Furthermore, as disclosed in Patent Document 2, for example, a conversion table that defines the relationship between the ink value of print image data and the composition ratio of multiple types of ink droplets with different sizes has been known. Using such a conversion table, the composition ratio of ink droplets corresponding to the ink value of the print image data is calculated. According to such a conversion table, when the ink value of the print image data is small, the ratio of ink droplets with small dots is high. Furthermore, when the ink value of the print image data is large, the ratio of ink droplets with small dots is low and the ratio of ink droplets with large dots is high. Inkjet printers are configured to eject multiple types of ink droplets with different sizes according to the composition ratio calculated using the conversion table. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-159463 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-201666 Summary of the Invention [Problem to be solved by the invention]

[0005] The conversion table (hereinafter referred to as "dot table") described above is adjusted in various ways by inkjet printer designers, etc. For example, the dot table can be created so that small ink droplets are used preferentially up to a region where the ink value is relatively large. In that case, the ink value at which large ink droplets begin to be ejected becomes relatively large. Alternatively, the dot table can be created so that large ink droplets begin to be ejected in a region where the ink value is relatively small.

[0006] When forming an image, if the composition ratio of ink droplets that are small dots is high, the texture of the image becomes finer, and so-called graininess is improved. However, if the composition ratio of ink droplets that are small dots is high, there is a tendency for the amount of ink mist that disperses as the ink droplets fly to increase. If this ink mist adheres to the nozzles of the recording head and hardens, there is a risk that the ink will no longer be ejected from the nozzles or that the direction of flight of the ink will be deflected. From the perspective of graininess of the printed image, a high composition ratio of ink droplets that are small dots is desirable, while from the perspective of reducing ink mist, a low composition ratio of ink droplets that are small dots is desirable. However, achieving a balance between these two is not necessarily easy.

[0007] The present invention has been made in consideration of the above points, and its object is to provide an inkjet printer that can achieve both reduced graininess in printed images and reduced ink mist, and also to provide a printing method that can achieve both reduced graininess in printed images and reduced ink mist. [Means for solving the problem]

[0008] The inkjet printer disclosed herein includes an ink head that ejects multiple ink droplets and a control device that controls the ink head. The control device includes a discharge control unit, a dot table registration unit, a data storage unit, and a dot table selection unit. The discharge control unit causes the ink head to eject multiple ink droplets, including a first ink droplet (the smallest) and one or more other ink droplets larger than the first ink droplet. The dot table registration unit registers multiple dot tables, each defining a correspondence between an ink value and a composition ratio of each ink droplet. The multiple dot tables have different composition ratios of the first ink droplet for at least some ink values. The data storage unit stores print image data. The dot table selection unit associates one of the multiple dot tables with the print image or each object within the print image. When forming the print image or each object, the discharge control unit causes the ink head to eject multiple ink droplets based on the composition ratio of each ink droplet defined by the dot table corresponding to the print image or each object.

[0009] The printing method disclosed herein is a method for printing an image using an inkjet printer capable of ejecting a plurality of ink droplets, including a first ink droplet that is the smallest, and one or more other ink droplets that are larger than the first ink droplet, and includes the steps of: associating, with the print image or each object in the print image, one of a plurality of dot tables prepared in advance, each of which defines a correspondence between ink values ​​and a composition ratio of each ink droplet; and forming the print image or each object based on the composition ratio of each ink droplet defined by the dot table corresponding to the print image or each object. The plurality of dot tables have different composition ratios of the first ink droplets for at least some ink values.

[0010] According to the inventor's knowledge, the degree to which poor graininess affects the appearance varies depending on the image. For example, according to the inventor's knowledge, poor graininess is often not very noticeable in dark solid images, while poor graininess is often relatively noticeable in bright images.

[0011] Therefore, the inkjet printer is configured to associate one of a plurality of dot tables, each having a different composition ratio of the smallest first ink droplets, with the printed image or each object within the printed image. The printing method also includes a step of associating one of a plurality of dot tables, each having a different composition ratio of the smallest first ink droplets, with the printed image or each object within the printed image. The inkjet printer and printing method make it possible to associate a suitable dot table depending on the image, such as associating a dot table with a relatively small composition ratio of the first ink droplets with a dark solid image, and a dot table with a relatively large composition ratio of the first ink droplets with a bright image. Therefore, the inkjet printer and printing method can achieve both reduced graininess in the printed image and reduced ink mist. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view of an inkjet printer according to an embodiment. [Figure 2] FIG. 2 is a front view showing the main part of the printer. [Figure 3] FIG. 2 is a partial cross-sectional view of the vicinity of a nozzle of an ink head. [Figure 4] 10 is a waveform diagram showing an example of a drive signal for ejecting S droplets, M droplets, and L droplets. FIG. [Figure 5] 1 is a block diagram of a printer according to a first embodiment. [Figure 6] 10 is a chart showing a first dot table registered in a dot table registration unit. [Figure 7] 10 is a chart showing a second dot table registered in a dot table registration unit. [Figure 8] FIG. 1 is a schematic diagram illustrating an example of a print image including a plurality of objects. [Figure 9] 1 is a flowchart illustrating an example process for forming a print image that includes multiple objects. [Figure 10] FIG. 10 is a block diagram of a printer according to a second embodiment. [Figure 11] 10 is a flowchart showing an example of a process for forming one object in a print image in the second embodiment. [Figure 12] FIG. 10 is a block diagram of a printer according to a third embodiment. [Figure 13] 10 is a graph showing a conversion table between a first dot table and a second dot table. [Figure 14] 11 is a flowchart showing an example of a process for forming one object in a print image in a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of an inkjet printer according to the present invention will be described with reference to the drawings. The embodiments described here are, of course, not intended to limit the present invention in any particular way. Although several embodiments will be described below, components and parts that perform the same function will be given the same reference numerals, and redundant descriptions will be omitted or simplified.

[0014] (First embodiment) FIG. 1 is a perspective view of an inkjet printer (hereinafter, printer) 10 according to one embodiment. FIG. 2 is a front view showing the main components of the printer 10. In FIGS. 1 and 2, the letters L and R indicate left and right, respectively. The letters F and Rr indicate front and rear, respectively. However, these directions are merely provided for the convenience of explanation and do not limit the installation mode of the printer 10 in any way.

[0015] The printer 10 is used to print on a recording medium 5. The recording medium 5 is an object onto which ink is ejected. Recording media include not only plain paper and other types of paper, but also recording media made from various materials such as resin materials such as polyvinyl chloride (PVC) and polyester, aluminum, iron, and wood.

[0016] The printer 10 includes a casing 2 and a guide rail 3 disposed within the casing 2. The guide rail 3 extends in the left-right direction. A carriage 1, which is equipped with an ink head 15 that ejects ink, engages with the guide rail 3. The carriage 1 reciprocates left and right along the guide rail 3 (scanning direction) by a carriage movement mechanism 8. The carriage movement mechanism 8 has pulleys 19b and 19a disposed on the left and right ends of the guide rail 3. A carriage motor 8a is connected to the pulley 19a. The carriage motor 8a may also be connected to the pulley 19b. The pulley 19a is driven by the carriage motor 8a. An endless belt 6 is wound around each of the pulleys 19a and 19b. The carriage 1 is fixed to the belt 6. When the pulleys 19a and 19b rotate and the belt 6 moves, the carriage 1 moves left and right.

[0017] The recording medium 5 is transported in a paper feed direction by a paper feed mechanism (not shown). Here, the paper feed direction refers to the front-to-rear direction. A platen 4 that supports the recording medium 5 is provided inside the casing 2. A grit roller (not shown) is provided on the platen 4. A pinch roller (not shown) is provided above the grit roller. The grit roller is connected to a feed motor 7 (see Figure 5). The grit roller is driven and rotated by the feed motor 7. When the grit roller rotates with the recording medium 5 sandwiched between the grit roller and the pinch roller, the recording medium 5 is transported in the front-to-rear direction.

[0018] The printer 10 is equipped with a plurality of ink cartridges 11. Inks of different colors are stored in the plurality of ink cartridges 11. For example, the printer 10 is equipped with five ink cartridges 11, each storing cyan ink, magenta ink, yellow ink, black ink, and white ink.

[0019] An ink head 15 is provided for each color of ink. The ink head 15 of each color and the ink cartridge 11 are connected by an ink supply path 12. The ink supply path 12 is an ink flow path that supplies ink from the ink cartridge 11 to the ink head 15. The ink supply path 12 is formed, for example, from a flexible tube. The ink supply path 12 is provided with a liquid feed pump 13. However, the liquid feed pump 13 is not necessarily required and can be omitted. A portion of the ink supply path 12 is covered by a cable protection and guide device.

[0020] The ink head 15 ejects ink toward the recording medium 5, forming ink dots on the recording medium 5. A large number of these dots are arranged in an array to form an image or the like on the recording medium 5. The ink head 15 has a plurality of nozzles 25 (see FIG. 3) for ejecting ink on the surface facing the recording medium 5 (the lower surface of the ink head 15 in this embodiment).

[0021] FIG. 3 is a partial cross-sectional view of the ink head 15 near one nozzle 25. The ink head 15 includes a hollow case 21 having an opening 21a, and a diaphragm 22 attached to the case 21 so as to close the opening 21a. The diaphragm 22, together with the case 21, defines a pressure chamber 23 in which ink is stored. The diaphragm 22 partitions a portion of the pressure chamber 23. The diaphragm 22 is elastically deformable inward and outward of the pressure chamber 23. The diaphragm 22 is configured to be deformable so as to increase and decrease the volume of the pressure chamber 23. The diaphragm 22 is typically a resin film or metal foil.

[0022] An ink inlet 24 through which ink flows in is formed in the case 21. The position of the ink inlet 24 is not limited as long as it is connected to the pressure chamber 23. Ink is supplied to the pressure chamber 23 from the ink cartridge 11 through the ink inlet 24, and the ink is stored therein. Nozzles 25 are formed in the bottom surface 21b of the case 21.

[0023] An actuator 26 abuts against the surface of the vibration plate 22 opposite the pressure chamber 23 side. In this embodiment, the actuator 26 is a piezoelectric element. A portion of the actuator 26 is fixed to a fixing member 29. The actuator 26 is connected to the control device 100 via a flexible cable 27. A signal is supplied to the actuator 26 via the flexible cable 27. In this embodiment, the actuator 26 is a laminate in which piezoelectric materials and conductive layers are alternately stacked. The actuator 26 expands or contracts when it receives a signal from the control device 100, thereby elastically deforming the vibration plate 22 toward the outside or inside of the pressure chamber 23. In this embodiment, a piezoelectric element (PZT) of a longitudinal vibration mode is used. The longitudinal vibration mode PZT is expandable in the lamination direction, contracting when discharged and expanding when charged, for example. However, the type of the actuator 26 is not particularly limited.

[0024] In the ink head 15 configured as described above, for example, by decreasing the potential of the actuator 26 from the reference potential, the actuator 26 contracts. Following this, the diaphragm 22 elastically deforms from its initial position toward the outside of the pressure chamber 23, causing the pressure chamber 23 to expand. The expansion of the pressure chamber 23 refers to the volume of the pressure chamber 23 increasing due to the deformation of the diaphragm 22. Next, by increasing the potential of the actuator 26, the actuator 26 extends in the stacking direction. This causes the diaphragm 22 to elastically deform toward the inside of the pressure chamber 23, causing the pressure chamber 23 to contract. The contraction of the pressure chamber 23 refers to the volume of the pressure chamber 23 decreasing due to the deformation of the diaphragm 22. The pressure inside the pressure chamber 23 fluctuates due to this expansion and contraction of the pressure chamber 23. This pressure fluctuation inside the pressure chamber 23 pressurizes the ink inside the pressure chamber 23, causing it to be ejected from the nozzle 25. Thereafter, by returning the potential of the actuator 26 to the reference potential, the diaphragm 22 returns to its initial position, and the pressure chamber 23 expands. At this time, ink flows into the pressure chamber 23 from the ink inlet 24.

[0025] The ink head 15 is configured to be able to simultaneously form a plurality of ink droplets of different sizes. In this example, the ink head 15 ejects S, M, and L droplets of different sizes. The ink head 15 ejects ink droplets while changing the composition ratio of S, M, and L droplets depending on the total ink volume of the S, M, and L droplets (hereinafter referred to as the ink value). The composition ratio of S, M, and L droplets is commanded by the control device 100.

[0026] FIG. 4 is a waveform diagram showing an example of a drive signal for ejecting S droplets, M droplets, and L droplets. As shown in FIG. 4, the printer 10 generates a drive signal including five drive pulses P1 to P5 for each drive cycle. When forming an L droplet, the control device 100 supplies all of the drive pulses P1 to P5 to the actuator 26. When forming an M droplet, the control device 100 supplies the third drive pulse P3 and the fifth drive pulse P5 to the actuator 26. When forming an S droplet, the control device 100 supplies only the fifth drive pulse P5 to the actuator 26. However, the drive signal shown in FIG. 4 is merely an example, and the form of the drive signal is not limited.

[0027] FIG. 5 is a block diagram of printer 10. As shown in FIG. 5, control device 100 is electrically connected to feed motor 7 of the paper feed mechanism, carriage motor 8a of carriage movement mechanism 8, liquid supply pump 13, and ink head 15. Control device 100 controls the operations of these components. Control device 100 is typically a computer. Control device 100 includes, for example, an interface (I / F) that receives print data and the like from an external device such as a host computer, a central processing unit (CPU) that executes instructions of a control program, a ROM that stores the program executed by the CPU, RAM used as a working area for expanding the program, and a storage device such as a memory that stores the program and various data.

[0028] 5, the control device 100 includes a dot table registration unit 110, a data storage unit 120, a dot table selection unit 130, an input unit 140, a color conversion unit 150, a halftone processing unit 160, and a discharge control unit 170. The control device 100 may include other processing units, but illustration and description thereof will be omitted here.

[0029] A plurality of dot tables are registered in the dot table registration unit 110. Each of the plurality of dot tables defines a correspondence relationship between the ink value and the composition ratio of each ink droplet (here, S droplets, M droplets, and L droplets). The composition ratio of S droplets differs among the plurality of dot tables for at least some ink values. The number of dot tables registered in the dot table registration unit 110 is not limited, but here it is two.

[0030] FIG. 6 is a chart showing the first dot table T1 registered in the dot table registration unit 110. FIG. 7 is a chart showing the second dot table T2 registered in the dot table registration unit 110. The horizontal axes in FIGS. 6 and 7 represent ink values ​​where the ink value when all dots are L droplets is 100%. The vertical axes in FIGS. 6 and 7 represent the respective composition ratios of S droplets, M droplets, and L droplets when the maximum number of dots that can be ejected per area is 100%. However, the first dot table T1 and the second dot table T2 are merely examples, and other embodiments are possible.

[0031] Rs1 in FIG. 6 represents the composition ratio of S droplets in the first dot table T1. As shown in FIG. 6, the first dot table T1 is configured to eject only S droplets up to the ink value I1. In the first dot table T1, the S droplets increase linearly until the ink value reaches I1. The composition ratio of S droplets when the ink value is I1 is Vs1. After that, the S droplets decrease linearly to reach a composition ratio of 0% at the ink value I2.

[0032] Rm1 in FIG. 6 represents the composition ratio of M droplets in the first dot table T1. As shown in FIG. 6, the first dot table T1 starts ejecting M droplets at an ink value of I1. In the first dot table T1, the M droplets increase linearly until the ink value reaches I2. When the ink value is I2, only M droplets are ejected. After that, the M droplets decrease linearly until the composition ratio reaches 0% at an ink value of 100%.

[0033] In FIG. 6, Rl1 represents the composition ratio of L droplets in the first dot table T1. As shown in FIG. 6, the first dot table T1 starts ejecting L droplets at an ink value of I2. In the first dot table T1, L droplets increase linearly until the ink value reaches 100%. When the ink value is 100%, only L droplets are ejected.

[0034] Rs2 in FIG. 7 represents the composition ratio of S droplets in the second dot table T2. As shown in FIG. 7, the second dot table T2 is configured to eject only S droplets up to an ink value I3 that is smaller than the ink value I1. In the second dot table T2, the S droplets increase linearly until the ink value reaches I3. The composition ratio of S droplets at the ink value I3 is Vs2. After that, the S droplets decrease linearly to reach a composition ratio of 0% at the ink value I2.

[0035] Rm2 in FIG. 7 represents the composition ratio of M droplets in the second dot table T2. As shown in FIG. 7, the second dot table T2 starts ejecting M droplets at an ink value of I3. In the second dot table T2, the M droplets increase linearly until the ink value reaches I2. When the ink value is I2, only M droplets are ejected. After that, the M droplets decrease linearly until the composition ratio reaches 0% at an ink value of 100%.

[0036] In FIG. 7, Rl2 represents the composition ratio of L droplets in the second dot table T2. As shown in FIG. 7, the second dot table T2 starts ejecting L droplets at an ink value of I2. In the second dot table T2, L droplets increase linearly until the ink value reaches 100%. When the ink value is 100%, only L droplets are ejected.

[0037] In this way, for ink values ​​from 0% to I3, only S droplets are ejected, and the composition ratio of S droplets is the same for both the first dot table T1 and the second dot table T2. For ink values ​​from I3 to I2, the composition ratio of S droplets and M droplets differs between the first dot table T1 and the second dot table T2. In this case, the composition ratio of L droplets is 0%. For ink values ​​from I2 to 100%, both the first dot table T1 and the second dot table T2 eject M droplets and L droplets, and the composition ratio of M droplets and L droplets is the same between the first dot table T1 and the second dot table T2.

[0038] The relationship between the first dot table T1 and the second dot table T2 is not limited to the above, but the second dot table T2 is configured so that the composition ratio of S droplets is equal to or less than that of the first dot table T1 for all ink values, and is smaller than that of the first dot table T1 for at least some ink values. Hereinafter, "the composition ratio of S droplets is the same or small for all ink values, and is small for at least some ink values" will also be referred to simply as "a low occurrence rate of S droplets." The opposite will also be referred to as "a high occurrence rate of S droplets."

[0039] The data storage unit 120 stores print image data. Here, the data storage unit 120 temporarily stores image data transmitted from an external computer or the like.

[0040] The dot table selection unit 130 is configured to associate either the first dot table T1 or the second dot table T2 with each object in the print image. The printer 10 can have several variations depending on the method by which the dot table selection unit 130 associates a dot table with each object in the print image. In this embodiment, the dot table selection unit 130 includes a first selection unit 131 that associates the first dot table T1 or the second dot table T2 with each object in the print image based on a user specification. The control device 100 also includes an input unit 140 that is configured to be able to specify the association of a dot table with each object in the print image.

[0041] The input unit 140 displays an operation screen on, for example, a display device of an external computer connected to the printer 10. Here, the user operates the operation screen to associate the first dot table T1 or the second dot table T2 with each object in the print image. The first selection unit 131 associates the dot table specified in the input unit 140 with each object in the print image.

[0042] The color conversion unit 150 performs color conversion on each object in the print image using an ICC profile to obtain the ink values ​​of each object, here CMYK ink values. In this embodiment, the color conversion unit 150 selects an ICC profile corresponding to the dot table (here, the first dot table T1 or the second dot table T2) associated with each object. Each object is converted to CMYK ink values ​​using the selected ICC profile. The color conversion process is performed for each object.

[0043] The halftone processor 160 performs halftone processing on each color-converted object, thereby converting the CMYK ink values ​​of each object into ink dot data.

[0044] The ejection control unit 170 causes the ink head 15 to eject a plurality of ink droplets, including the smallest S droplets and one or more other ink droplets larger than the S droplets. As described above, in this embodiment, the ejection control unit 170 causes the ink head 15 to eject the smallest S droplets, M droplets larger than the S droplets, and L droplets even larger than the M droplets. However, the number of types of ink droplets ejected from the ink head 15 may be two, four, or more. When forming each object, the ejection control unit 170 causes the ink head 15 to eject the S droplets, M droplets, and L droplets based on the composition ratio of each ink droplet determined by the dot table corresponding to each object (here, the first dot table T1 or the second dot table T2). The ejection control unit 170 causes the ink head 15 to eject the S droplets, M droplets, and L droplets by selectively supplying some or all of the drive signals.

[0045] An example of a process for forming a print image including multiple objects will be described below. FIG. 8 is a schematic diagram illustrating an example of a print image including multiple objects. FIG. 9 is a flowchart illustrating an example of a process for forming a print image including multiple objects. In the example shown in FIG. 8, the print image includes a first object O1 and a second object O2. In the example described here, the first object O1 is an image with a light hue overall. The second object O2 is a solid image with a dark hue. A solid image is an image that is uniformly filled with one color (which may be a single ink color or a mixture of multiple ink colors). The second object O2 may be a high-density image with a high dot density overall. However, the types of objects the first object O1 and the second object O2 are not limited, and it is up to the user to decide whether to associate the first object O1 and the second object O2 with the first dot table T1 or the second dot table T2, respectively.

[0046] As mentioned above, when forming an image, if the composition ratio of small-sized S droplets is high, the texture of the image becomes finer, improving what is known as graininess. However, if the composition ratio of S droplets among ink droplets is high, there is a tendency for the amount of ink mist that disperses during flight of the ink droplets to increase. If this ink mist adheres to the nozzles 25 of the ink head 15 and hardens, there is a risk that the ink will no longer be ejected from the nozzles 25 or that the flight direction of the ink will be deflected. From the perspective of graininess of the printed image, a high composition ratio of S droplets is desirable, but from the perspective of reducing ink mist, a low composition ratio of S droplets is desirable. Achieving a balance between these two has not always been easy in the past.

[0047] In response to the above problem, the present inventors have discovered that the degree to which poor graininess affects the appearance varies depending on the image. According to the inventors' findings, for example, poor graininess is often not very noticeable in a dark, solid image. In contrast, for example, poor graininess is often relatively noticeable in a bright image. Therefore, in the case of an image such as that shown in FIG. 8, it is preferable to associate the first dot table T1, which has a high rate of S droplet generation, with the first object O1. It is also preferable to associate the second dot table T2, which has a low rate of S droplet generation, with the second object O2.

[0048] 9 shows a print image formation process in which a first dot table T1 is associated with a first object O1 and a second dot table T2 is associated with a second object O2. As shown in FIG. 9, in processing the first object O1, in step S01A, the composition ratio of each ink droplet of the first object O1 is determined based on the first dot table T1. In step S02A, the first object O1 is color-converted using a first ICC profile corresponding to the first dot table T1. In processing the second object O2, in step S01B, the composition ratio of each ink droplet of the second object O2 is determined based on the second dot table T2. In step S02B, the second object O2 is color-converted using a second ICC profile corresponding to the second dot table T2.

[0049] The color-converted data of the first object O1 and the color-converted data of the second object O2 are subjected to halftone processing in step S03. In step S04, an image is formed based on the dot data of the print image obtained by the halftone processing.

[0050] As described above, the printer 10 according to this embodiment is configured to associate either the first dot table T1 or the second dot table T2 with each object in a printed image. Therefore, with this printer 10, for example, a dot table with a relatively small S-droplet composition ratio (here, the second dot table T2) can be associated with a dark solid image, and a dot table with a relatively large S-droplet composition ratio (here, the first dot table T1) can be associated with a bright image. By selecting an appropriate dot table according to the image in this way, it is possible to improve the graininess of an image where graininess is desired, and to reduce ink mist when forming an image where graininess is not a priority. Therefore, it is possible to achieve both graininess in a printed image and reduced ink mist.

[0051] The printer 10 according to this embodiment is configured to allow the user to specify the correspondence between the dot table and each object in the printed image. How to evaluate the risk of image graininess and ink mist is up to the user. Therefore, the printer 10 according to this embodiment allows the user to balance the reduction of image graininess and ink mist according to the user's circumstances, preferences, etc.

[0052] (Second embodiment) In the second embodiment, a dot table is automatically associated with each object in a print image. FIG. 10 is a block diagram of a printer 10 according to this embodiment. As shown in FIG. 10, a dot table selection unit 130 according to this embodiment includes a second selection unit 132 that associates a first dot table T1 or a second dot table T2 with each object in a print image. The second selection unit 132 is configured to associate the first dot table T1 with objects whose brightness is equal to or greater than a predetermined first brightness, and to associate the second dot table T2 with objects whose brightness is less than the first brightness. The brightness of each object is calculated based on the print image data stored in the data storage unit 120. The brightness here refers to, for example, the average, median, maximum, or minimum brightness value of each part of each object.

[0053] The printer 10 may be configured to allow the user to select between a mode in which the dot table is associated with each object in the print image automatically and a mode in which the user does so. In this case, the control device 100 may further include a first selection unit 131 and an input unit 140, as shown in FIG.

[0054] FIG. 11 is a flowchart showing an example of a process for forming one object in a print image. As shown in FIG. 11, in the process for forming one object in a print image, in step S11, it is determined whether the brightness of the object is equal to or greater than a predetermined first brightness. If the brightness of the object is equal to or greater than the predetermined first brightness (the result of step S11 is YES), in step S12A, a first dot table T1 is associated with the object. As a result, the composition ratio of each ink droplet in the object is determined based on the first dot table T1. Then, in step S13A, a first ICC profile corresponding to the first dot table T1 is selected. In step S14A, the object is color converted using the first ICC profile. As a result, the ink values ​​of the object are determined. The color-converted image data is halftoned in step S15. In the halftoning process of step S15, dot data for each ink (CMYK and W in this case) is created according to the ink values ​​obtained by color conversion and the composition ratio of each ink droplet based on the first dot table T1. In step S16, printing is performed based on the dot data obtained by the halftone process.

[0055] If the brightness of the object is less than the predetermined first brightness (if the result of step S11 is NO), a second dot table T2 is associated with the object in step S12B. As a result, the composition ratio of each ink droplet in the object is determined based on the second dot table T2. Then, in step S13B, a second ICC profile corresponding to the second dot table T2 is selected. In step S14B, the object is color converted using the second ICC profile. Steps S15 and S16 are the same as for an object whose brightness is equal to or greater than the first brightness.

[0056] As described above, in this embodiment, the first dot table T1 is associated with objects whose brightness is equal to or greater than a predetermined first brightness, and the second dot table T2 is associated with objects whose brightness is less than the first brightness. Since images with high brightness are images in which poor graininess is relatively noticeable, the first dot table T1, which has a high rate of S droplet generation, is associated with images with a brightness of equal to or greater than the first brightness. Since images with low brightness are images in which poor graininess is relatively inconspicuous, the second dot table T2, which has a low rate of S droplet generation, is associated with images with a brightness less than the first brightness. This reduces ink mist.

[0057] Note that three or more dot tables may be registered. For example, if a first dot table T1, a second dot table T2, and a third dot table with a lower S droplet generation rate than the second dot table T2 are registered, the second dot table T2 may be associated with objects whose brightness is less than the first brightness but equal to or greater than the second brightness (the second brightness is lower than the first brightness), and the third dot table may be associated with objects whose brightness is less than the second brightness. The same applies when four or more dot tables are registered.

[0058] (Modification 1 of the second embodiment) In one variation of the second embodiment, as shown in FIG. 10 , the dot table selector 130 may include a third selector 133 that associates a first dot table T1 with an object whose print density is less than a predetermined first density. In this case, the third selector 133 may be configured to associate a second dot table T2 with an object whose print density is equal to or greater than the first density. The print density here refers to, for example, the average, median, maximum, or minimum print density of each part of each object. According to the inventor's findings, an image with low print density is an image in which poor graininess is relatively noticeable, while an image with high print density is an image in which poor graininess is relatively inconspicuous. Therefore, the print density can also be used to classify the degree of impact of graininess on the appearance of an image into multiple categories.

[0059] (Modification 2 of the second embodiment) In another variation of the second embodiment, as shown in FIG. 10, the dot table selector 130 may include a fourth selector 134 that associates a first dot table T1 with an object made up of line art. Line art is equivalent to an image that is sensitive to graininess, since it is preferable for the contours to be shown sharply. Since it is well known that line art can be distinguished from other objects, a description of how to distinguish line art will be omitted. For objects other than line art, a corresponding dot table may be selected based on, for example, lightness or print density.

[0060] (Modification 3 of the second embodiment) In yet another modification of the second embodiment, as shown in FIG. 10, the dot table selection unit 130 may include a fifth selection unit 135 that associates a first dot table T1 with an object whose area ratio belonging to a predetermined color gamut is equal to or greater than a first threshold. In one preferred example, the predetermined color gamut is a skin color gamut. According to the knowledge of the inventors of the present application, the skin color gamut is a color gamut in which poor graininess is relatively noticeable, and in areas where skin color occupies more than a certain percentage, poor graininess is relatively easy to notice. For objects other than those mentioned above, a corresponding dot table may be selected based on, for example, lightness or print density. Note that the "skin color" referred to here refers to L * L in the range of 0 to 100 on the axis * The value is set and a * Axis is in the range of -128 to 127 * The value is set and b * b in the range of -128 to 127 on the axis * Value set L * a * b * In color space, L * The value is between 60 and 90, and a * The value is between 0 and 20, and b * This refers to a color gamut with a value between 0 and 30. However, the fifth selection unit 135 may set a threshold value as described above for the color gamut of colors other than skin tones, and associate the first dot table T1 with objects whose proportion of the area belonging to that color gamut is equal to or greater than the threshold value.

[0061] Although FIG. 10 illustrates all of the first through fifth selection units 131 through 135 and the input unit 140, the dot table selection unit 130 may include all or only some of the first through fifth selection units 131 through 135 and the input unit 140. For example, the printer 10 may be configured to allow the user to select whether to select a dot table based on lightness, print density, line art, or color gamut. Alternatively, the printer 10 may be configured to select an object to which the first dot table T1 or the second dot table T2 is to be associated based on one of lightness, print density, line art, and color gamut, and then additionally select an object to which the first dot table T1 or the second dot table T2 is to be associated based on another of the lightness, print density, line art, and color gamut. The same applies to selecting additional objects. However, these methods are merely preferred examples. There is no limitation on which of the first through fifth selection units 131 through 135 the printer 10 includes, nor is there any limitation on the priority order in which the functions of the included units are to be performed.

[0062] (Third embodiment) A printer 10 according to the third embodiment is configured so that, when different dot tables are associated with multiple objects in a print image, the ink values ​​of objects associated with one dot table are adjusted to match those of other dot tables. Figure 12 is a block diagram of a printer 10 according to the third embodiment. As shown in Figure 12, the printer 10 according to this embodiment includes a conversion table registration unit 180, an ink value correction unit 190, and a color conversion unit 150A that has functions different from those of the first and second embodiments.

[0063] The color conversion unit 150A according to this embodiment is set to color convert the data of all objects in the print image using an ICC profile corresponding to one predetermined dot table among multiple dot tables. In this embodiment, it is also assumed that a first dot table T1 and a second dot table T2 are registered in the printer 10. Here, the color conversion unit 150A color converts the data of all objects in the print image using the ICC profile corresponding to the first dot table T1.

[0064] A conversion table Te (see FIG. 13) that converts ink values ​​between multiple dot tables is registered in the conversion table registration unit 180. The ink value correction unit 190 determines the composition ratio of each ink droplet based on a dot table (here, second dot table T2) that is different from one predetermined dot table (here, first dot table T1), and converts the ink values ​​of an object that has been color-converted using an ICC profile that corresponds to the one predetermined dot table (here, first dot table T1) based on the conversion table Te. The conversion table Te and the ink value conversion process will be described below.

[0065] 13 is a graph showing the conversion table Te between the first dot table T1 and the second dot table T2. The horizontal axis of the conversion table Te represents the ink values ​​of the first dot table T1. The vertical axis of the conversion table Te represents the ink values ​​of the second dot table T2. On the graph G1 of the conversion table Te, the print density of a single ink color is equal between the first dot table T1 and the second dot table T2.

[0066] As shown in FIGS. 6 and 7, for ink values ​​0% to I3, the composition ratio of each ink droplet is the same between the first dot table T1 and the second dot table T2. Therefore, in this section, the slope of graph G1 in FIG. 13 is "1" (the dotted line L1 represents a line with a slope of "1"). In this section, graph G1 and line L1 match. For ink values ​​I3 to I2, the composition ratio of each ink droplet is different between the first dot table T1 and the second dot table T2. Therefore, in this section, graph G1 does not match line L1. In the section where graph G1 and line L1 do not match, a slight difference in print density occurs between when the first dot table T1 is used and when the second dot table T2 is used. This difference in print density is due to the difference in how the ink dots spread after landing. In this example, in the section of ink values ​​I3 to I2, the print density is higher when the first dot table T1 is used than when the second dot table T2 is used. In other words, the ink value required to achieve the same print density is smaller when using the first dot table T1 than when using the second dot table T2. For ink values ​​I2 to 100%, the composition ratio of each ink droplet is the same between the first dot table T1 and the second dot table T2. Therefore, in the above section, the graph G1 and line L1 coincide.

[0067] The conversion table Te is a conversion table for correcting the ink values ​​of each object after color conversion to match the print density between an object using the first dot table T1 and an object using the second dot table T2. The conversion table Te is created based on the results of measuring the color of a test patch image printed using the first dot table T1 and a test patch image printed using the second dot table T2. Here, the conversion table Te is a conversion table for determining the composition ratio of each ink droplet based on the second dot table T2 and for correcting the ink values ​​of an object color-converted using the ICC profile corresponding to the first dot table T1. When the ink values ​​of the first dot table T1 are input into the conversion table Te, the ink values ​​of the second dot table T2 on the graph G1 corresponding to the ink values ​​of the first dot table T1 are obtained.

[0068] FIG. 14 is a flowchart showing an example of a process for forming one object in a print image. As shown in FIG. 14, in the process for forming one object in a print image, in step S21, it is determined whether the brightness of the object is equal to or greater than a predetermined first brightness. If the brightness of the object is equal to or greater than the predetermined first brightness (if the result of step S21 is YES), in step S22A, a first dot table T1 is associated with the object. As a result, the composition ratio of each ink droplet in the object is determined based on the first dot table T1. In step S23A, the object is color-converted using a first ICC profile associated with the first dot table T1. No ICC profile is selected in step S23A. The ICC profile used in step S23A is predetermined and is the first ICC profile.

[0069] If the brightness of the object is less than the predetermined first brightness (if the result of step S21 is NO), a second dot table T2 is associated with the object in step S22B. As a result, the composition ratio of each ink droplet in the object is determined based on the second dot table T2. In step S23B, the object is color converted using the first ICC profile corresponding to the first dot table T1. No ICC profile is selected in step S23A. Even if the second dot table T2 is selected in step S22B, the ICC profile used in step S23B is the first ICC profile. The ICC profile used in step S23B is predetermined.

[0070] As a result of step S23B, a slight difference in print density occurs between the object using the first dot table T1 and the object using the second dot table T2. Therefore, in step S24B following step S23B, the ink values ​​of the object are corrected using conversion table Te. This makes it possible to match the print density between the object using the first dot table T1 and the object using the second dot table T2.

[0071] The color-converted image data is halftoned in step S25, and printing is performed in step S26 based on the halftoned print image data.

[0072] The method according to the third embodiment can reduce both the graininess of the printed image and the ink mist, while also reducing the labor required to create the ICC profile and the memory capacity of the printer 10. This method eliminates the need to create multiple ICC profiles corresponding to multiple dot tables. This reduces the labor required to create the ICC profile. Furthermore, because the number of ICC profiles stored can be reduced, the memory capacity required to store the ICC profiles can be reduced.

[0073] The dot table that serves as the reference for print density may be the second dot table T2. When there are three or more registered dot tables, the dot table that serves as the reference for print density is not limited. In addition, in the above description of the third embodiment, the dot table was selected based on the brightness of the object, but the dot table may also be selected based on other criteria (for example, print density, line drawing, color gamut). Alternatively, the dot table may be selected by the user.

[0074] Although some preferred embodiments have been described above, the inkjet printer of the present invention is not limited to the above-described embodiments.

[0075] For example, in the above embodiment, the dot table to be used is selected for each object in the print image, but the dot table to be used may also be selected for each print image.

[0076] In the above-described embodiment, the dot table to be used is selected automatically by the printer 10 or by the user using the printer 10's operation screen. However, a similar printing method can be used with other printers. The printing method of the present invention is not limited to a method using a specific printer, as long as it includes the steps of associating one of a plurality of pre-prepared dot tables with a print image or each object in the print image, and forming the print image or each object based on the composition ratio of each ink droplet determined by the dot table corresponding to the print image or each object. Note that the composition ratio of the first ink droplets differs from each other for at least some ink values ​​in the above-described plurality of dot tables.

[0077] In the above-described embodiment, the criteria for selecting the dot table to be used are exemplified by the brightness of the image, print density, etc. However, the criteria for selecting the dot table to be used need only be criteria that enable evaluation of the effect that the composition ratio of small dot ink droplets has on the graininess of the image, and are not limited beyond that.

[0078] The configuration of the printer 10 according to the embodiment described above is an example and does not limit the configuration of the printer.

[0079] Unless otherwise specified, the above-described embodiments do not limit the present invention. [Explanation of symbols]

[0080] 5. Recording media 10 Printers 15 Ink head 100 control device 110 Dot table registration section 120 Data storage unit 130 Dot table selection section 131 1st Selection Department 132 2nd Selection Department 133 Third Selection Department 134 4th Selection Department 135 5th Selection Department 140 Input section 150 Color conversion unit 150A Color conversion unit (third embodiment) 160 Halftone Processing Unit 170 Discharge control section 180 Conversion table registration section 190 Ink value correction unit O1 First Object O2 Second Object T1 First dot table T2 Second dot table Te Conversion Table

Claims

1. an ink head that ejects a plurality of ink droplets; a control device for controlling the ink head; Equipped with The control device an ejection control unit that causes the ink head to eject a plurality of ink droplets, including a first ink droplet that is the smallest, and one or more other ink droplets that are larger than the first ink droplet; a dot table registration unit in which a plurality of dot tables are registered, each defining a correspondence relationship between an ink value and a composition ratio of each ink droplet; a data storage unit that stores print image data; a dot table selection unit that associates one of the plurality of dot tables with a print image or each object in the print image; Equipped with the ejection control unit, when forming a print image or each object, causes the ink head to eject a plurality of ink droplets based on a composition ratio of each ink droplet determined by a dot table corresponding to the print image or each object; the plurality of dot tables have different composition ratios of the first ink droplets for at least some ink values; Inkjet printer.

2. the control device includes an input unit configured to be able to specify a correspondence between a dot table and a print image or each object in the print image; the dot table selection unit includes a first selection unit that associates a dot table designated in the input unit from among the plurality of dot tables with the print image or each object in the print image, 2. The inkjet printer according to claim 1.

3. The plurality of dot tables include: a first dot table; a second dot table in which the composition ratio of the first ink droplets is equal to or less than the first dot table for all ink values, and the composition ratio of the first ink droplets is smaller than the first dot table for at least some ink values; Including, the dot table selection unit includes a second selection unit that associates the first dot table with a print image or object having a brightness equal to or greater than a predetermined first brightness; 3. The inkjet printer according to claim 1 or 2.

4. the second selection unit is configured to associate the second dot table with a print image or object whose brightness is less than the first brightness; 4. The inkjet printer according to claim 3.

5. The plurality of dot tables include: a first dot table; a second dot table in which the composition ratio of the first ink droplets is equal to or less than the first dot table for all ink values, and the composition ratio of the first ink droplets is smaller than the first dot table for at least some ink values; Including, the dot table selection unit includes a third selection unit that associates the first dot table with a print image or object having a print density less than a predetermined first density; 5. The inkjet printer according to claim 1.

6. the third selection unit is configured to associate the second dot table with a print image or object having a print density equal to or higher than the first density; 6. The inkjet printer according to claim 5.

7. The plurality of dot tables include: a first dot table; a second dot table in which the composition ratio of the first ink droplets is equal to or less than the first dot table for all ink values, and the composition ratio of the first ink droplets is smaller than the first dot table for at least some ink values; Including, the dot table selection unit includes a fourth selection unit that associates the first dot table with a print image or object that is configured as a line drawing; 7. The inkjet printer according to claim 1.

8. The plurality of dot tables include: a first dot table; a second dot table in which the composition ratio of the first ink droplets is equal to or less than the first dot table for all ink values, and the composition ratio of the first ink droplets is smaller than the first dot table for at least some ink values; Including, the dot table selection unit includes a fifth selection unit that associates the first dot table with a print image or object having a ratio of an area belonging to a predetermined color gamut equal to or greater than a first threshold value; The inkjet printer according to any one of claims 1 to 7.

9. The predetermined color gamut is L ＊ The axis has a range of L between 0 and 100. ＊ The value is set, and a ＊ Axis is in the range of -128 to 127 ＊ The value is set, and b ＊ The axis is in the range of -128 to 127. ＊ The value is set to L ＊ a ＊ b ＊ In color space, L ＊ The value is 60 or more and 90 or less, a ＊ The value is between 0 and 20, b ＊ A color gamut with a value between 0 and 30, 9. The inkjet printer according to claim 8.

10. The control device a conversion table registration unit in which a conversion table for converting ink values ​​between the plurality of dot tables is registered; a color conversion unit that converts the color of data of all objects in a print image using an ICC profile that corresponds to one predetermined dot table among the plurality of dot tables; an ink value correction unit that determines the composition ratio of each ink droplet based on a dot table different from the one predetermined dot table, and converts the ink values ​​of an object that has been color converted by an ICC profile corresponding to the one predetermined dot table based on the conversion table; Equipped with 10. The inkjet printer according to claim 1.

11. 1. A method for printing an image using an inkjet printer capable of ejecting a plurality of ink droplets, including a first ink droplet that is smallest, and one or more other ink droplets that are larger than the first ink droplet, comprising: A step of associating one of a plurality of dot tables prepared in advance, each of which defines a correspondence relationship between ink values ​​and composition ratios of each ink droplet, with the print image or each object in the print image; forming a print image or each object based on the composition ratio of each ink droplet defined by a dot table corresponding to the print image or each object; Including, A printing method, wherein the plurality of dot tables have mutually different composition ratios of the first ink droplets for at least some ink values.

Images