JP5849469B2 - Printing apparatus and printing method - Google Patents

Description

  The present invention relates to a printing apparatus, and more particularly, to a printing apparatus using a photocurable ink and a printing method.

  2. Description of the Related Art Conventionally, printing apparatuses that perform printing using photocurable ink that is cured by irradiation with light such as ultraviolet rays are known. For example, a printing apparatus ejects photocurable ink onto a sheet or the like, and then irradiates the sheet with ultraviolet rays to cure the photocurable ink to form a printed matter (see, for example, Patent Document 1). .

  Since the above-described photocurable ink is limited in the amount of ink that can be ejected in one pass, the reproducible reproduction color gamut is also limited. For this reason, in order to obtain a reproduction color gamut desired by a user for a printed matter, there are cases where printing is performed with layers overlapping.

JP 2000-158793 A

  When printing is performed by layering on a printing apparatus using photocurable ink, the user determines whether the reproduction color gamut of the printed material has the color gamut intended by the user. There was no choice but to confirm by visual inspection. That is, when the layers are printed in layers, there is no standard for determining the color gamut that can be reproduced in each layer, so that the determination can be made only by visual confirmation. As a result, it has been difficult to form a uniform printed matter in a printing apparatus using photocurable ink.

  The present invention has been made in view of the above problems, and provides a user with an indication of a reproduction color gamut for each layer even when printing is performed with layers overlapping in a printing apparatus using photocurable ink. An object of the present invention is to provide a printing apparatus and a printing method capable of printing.

  In order to solve the above-described problems, in the present invention, a printing apparatus that forms a printed matter composed of a plurality of print layers by ejecting a photocurable ink onto a medium, the component values of input color data and the print layers. Ink that generates ink amount data in which the amount of ink for printing each print layer is set from the input color data, using a profile that defines a correspondence relationship with the ink amount of the photocurable ink used in An amount data generation unit, and a print execution unit that performs printing by overlaying each print layer using ink amount data corresponding to each of the generated print layers, and the profile overlaps each print layer. The amount of ink is defined so that the reproduction color gamut is enlarged each time printing is performed.

  In the invention configured as described above, the ink amount data generation unit uses the profile that defines the correspondence between each component value of the input color data and the ink amount of the photocurable ink used for each print layer. Then, ink amount data in which the ink amount for printing each printing layer is set is generated from the input color data. Further, the print execution unit performs printing by superimposing the print layers using the ink amount data corresponding to the generated print layers. Here, in the profile used by the ink amount data generation unit, the component value of the input color data and the ink amount are defined so that the reproduction color gamut is expanded each time the print layers are overlaid and printed.

FIG. 1 is a block configuration diagram for explaining the configuration of the printing apparatus 100. FIG. 2 is a block configuration diagram for explaining the configuration of the printing apparatus 100. It is a figure explaining creation of a layered LUT. It is a flowchart which shows creation of a stratified LUT. It is a flowchart which shows the process of step S1 in detail. It is a figure explaining the process which produces a color correction LUT from LUT without color correction. 3 is a flowchart illustrating a printing method in the printing apparatus 100. It is a flowchart which shows in detail the process of step S1 of FIG. 4 which concerns on 2nd Embodiment. It is a figure which shows the printed matter printed with the printing apparatus 100 which concerns on 2nd Embodiment.

Hereinafter, embodiments of the present invention will be described in the following order.
1. First embodiment:
1.1. Configuration of printing device:
1.2. Creation of stratified LULT:
1.3. Printing method:
1.4. Variation:
2. Second embodiment:

1. First embodiment:
1.1. Configuration of printing device:
Hereinafter, a first embodiment of a printing apparatus according to the present invention will be described with reference to the drawings. 1 and 2 are block configuration diagrams for explaining the configuration of the printing apparatus 100. In the present embodiment, the printing apparatus 100 is configured by connecting a personal computer (hereinafter also referred to as a PC) 10 and a printer 20 to a cable 50.

  The PC 10 includes a recording unit 11, a CPU (Central Processing Unit) 12, a RAM (Random Access Memory) 13, a USB I / F (Universal Serial Bus Interface) 14, a video I / F 15, an input I / F 16, and the like. Each unit is connected through a bus and receives integrated control by the CPU 12. The recording unit 11 is realized by, for example, a hard disk drive (HDD), and records programs and data for causing the CPU 12 to realize various functions. In this embodiment, the recording unit 11 includes a driver program 11a for printing, a layered LUT (Look Up Table) 11b, and a profile creation program 11c for creating a color correction LUT. Is recorded. In this embodiment, the layered LUT 11b functions as a color profile.

  The PC 10 is connected to the display 30 via the video I / F 15 and is connected to the operation unit 40 such as a keyboard and a mouse via the input I / F 16. Further, the PC 10 executes an operation according to the driver program 11a, and controls the printer 20 via the USB I / F 14 or the like, thereby outputting an ink amount data generation unit 12a that outputs ink amount data to the printer 20, and It functions effectively as a print execution unit 12b that causes the printer 20 to execute printing using the ink amount data. Further, the CPU 12 effectively functions as a profile creation unit 12c that executes the profile creation program 11c and creates the layered LUT 11b.

  The printer 20 ejects an ultraviolet curable ink (photo curable ink, hereinafter also referred to as UV ink, also simply referred to as ink) that is cured by irradiation with ultraviolet rays (hereinafter also referred to as UV) to thereby form an image on the medium. Form. The UV ink is prepared by adding auxiliary agents such as a polymerization inhibitor and a surfactant to a mixture of oligomers and monomers having photopolymerization curability, a photopolymerization initiator, and a pigment. Therefore, when UV ink is irradiated with UV, a photopolymerization reaction occurs and the ink is cured.

  The printer 20 includes a transport unit 21, a head unit 22, an irradiation unit 23, a detector group 24, and a controller 25. The head unit 22 is detachably connected to C (cyan), M (magenta), Y (yellow), and K (black) toners, and ejects ink supplied from the toners to form a printed matter. To do. This toner is filled with the above-described UV ink. Further, the transport unit 21, the head unit 22, the irradiation unit 23, and the detector group 24 are each connected to the controller 25 and are subjected to integrated control by the controller 25. Further, the controller 25 can be connected to the USB I / F 14 of the PC 10 through the cable 50 and receives print data from the PC 10.

  Further, the irradiation unit 23 irradiates the medium on which the UV ink is ejected with ultraviolet rays in order to cure the UV ink ejected from the head unit 22. For this reason, the UV ink starts to be cured by being irradiated with ultraviolet rays from the irradiation unit 23. In addition, since the printer 20 uses UV ink, the amount of ink ejected in one pass is limited. Here, one pass refers to a period during which UV ink is ejected while the paper is being transported by the transport unit 21 from the front end to the rear end in the transport direction. In the present embodiment, ink that is ejected in a single pass in consideration of the stability until the UV ink is cured, the ejection capability of the print head, the recording characteristics of the paper used, and the resolution of the formed image. There is a limit to the amount. For this reason, it is necessary to overlap the ink layer a plurality of times in order to perform desired color reproduction. Hereinafter, a layer formed of UV ink printed by one pass in this way is also referred to as a printed layer or simply a layer.

1.2. Creating a stratified LUT:
FIG. 3 is a diagram illustrating creation of a stratified LUT. FIG. 4 is a flowchart showing creation of a stratified LUT. The layered LUT is a table used when the PC 10 creates ink amount data corresponding to each layer, and component values (sRGB values) of image data (input color data) and ink amounts are recorded in association with each other. Has been. For example, when printing a printed material consisting of three layers, the PC 10 converts the component values of the image data into ink amounts using the LUTs for each of the first to third layers, and causes the printer 20 to execute printing. By this process, the profile creation process according to the present invention is realized.

  In the present embodiment, when creating the layered LUT, as shown in FIG. 4, the reproduction color gamut of each layer is set in step S1. The reproduction color gamut of each layer means the maximum color gamut that can be reproduced by overlapping each layer. Next, in step S2, an LUT without color correction is created so as to satisfy the set reproduction color gamut. The color correction LUT is a table in which component values in the device-independent space (RGB color system) are associated with the ink amount of UV ink. Next, in step S3, a color correction LUT is created from the LUT without color correction. The color correction LUT is a table in which component values in the device-dependent space (sRGB color system) are associated with the ink amount of UV ink. In step S4, a layered LUT is created from the color correction LUT. Hereinafter, each step will be described in detail.

<< Step S1 >>
FIG. 5 is a flowchart showing in detail the process of step S1.
In step S11, the PC 10 acquires the reproduction color gamut range of the first layer based on the amount of ink that can be ejected in one pass (FIG. 3A). For example, the PC 10 considers the stability until the first UV ink is cured, the print head ejection capability, the recording characteristics of the paper used, and the amount of ink that can be ejected in one pass in consideration of the resolution. To get. Then, the PC 10 acquires a reproduction color gamut range based on the acquired ink amount. As an example of a method for obtaining a reproduction color gamut, a first layer is formed with an amount of ink that can be ejected in one pass while taking the above-described conditions into consideration, and the first layer is measured by a colorimeter (not shown). Obtained at.

  In step S12, the PC 10 acquires the maximum color gamut. The maximum color gamut indicates the maximum reproduction color gamut that can be reproduced by overlapping a plurality of layers to form a printed material. In this embodiment, the color gamut reproduced when three layers are stacked is set as the maximum color gamut. Therefore, the PC 10 acquires a reproduction color gamut based on the amount of ink that can be ejected in three passes (FIG. 3B).

  In step S13, the PC 10 determines the number N of layers for reproducing the maximum color gamut. The number of layers is a value for setting how many layers the maximum color gamut is reproduced. In the present embodiment, the following description will be made assuming that the number of layers N = 3.

  In step S <b> 14, the PC 10 sets an increase amount of the color gamut that is increased by printing with overlapping layers. The increase amount indicates the proportion of the reproduction color gamut that increases when the printer 20 prints each layer on top of each other. In the present embodiment, the saturation increase amount ΔC * is set so that the increase in the reproduction color gamut of each layer is uniform in the saturation direction.

  In step S15, the PC 10 determines the reproduction color gamut of the first layer. That is, the reproduction color gamut of the first layer is set in a range not exceeding the actual reproduction color gamut of the first layer acquired in step S11. Since the reproduction color gamut expands evenly as each layer increases, the reproduction color gamut of the first layer may not be the same as the actual reproduction color gamut set in step S11. In the present embodiment, the reproduction color gamut of the first layer set in this step is ΔC ** (3- (3) from each point constituting the outer periphery of the maximum color gamut in the L * a * b * space. 1) Acquired as an area surrounded by the outer periphery advanced in the low saturation direction.

  In step S <b> 16, the PC 10 reproduces when each layer is printed based on the values determined in the above steps (maximum color gamut, number of layers N, increase amount ΔC *, reproduction color gamut of the first layer). Set the color gamut. That is, the outer periphery of the reproduction color gamut in which the first layer and the second layer are superimposed (hereinafter also referred to as the reproduction color gamut having two layers) is the maximum color gamut (the reproduction color gamut in which the first to third layers are superimposed). ) Is a circumference constituted by points that have advanced in the low saturation direction by an increase amount ΔC * from each point constituting the circumference. Note that the outer circumference of the reproduction color gamut of the first layer is the value set in step S15.

<< Step S2 >>
The PC 10 creates an LUT without color correction corresponding to each layer based on the reproduction color gamut for each number of layers set in step S1. The LUT without color correction is represented as a spatial address defined by address points (also referred to as grids) having the color components of the RGB color system, which are device-independent colors, as axes, and the values of the color components as positions on the axes. be able to. In the present embodiment, in accordance with the input range of the display 30, the input value ranges are 0 ≦ R ≦ 255, 0 ≦ G ≦ 255, 0 ≦ B ≦ 255, and 16 pieces arranged at equal intervals on the axis. A predetermined ink amount is set for the address point. When an ink amount for input color data that is not set in the LUT without color correction is selected, a predetermined ink amount is calculated by performing an interpolation calculation between these grids.

  Further, the amount of ink set for each grid increases or decreases according to the number of layers. For example, in an LUT without color correction of 3 layers, the maximum ink amount set for each grid is set by the sum of the ink amounts that can be ejected in three passes. For example, when the ink gradation value in one pass (the ink amount is defined by a value from 0 to 255) is 255, the color (C, C, A maximum of 765 (255 × 3) ink gradation values are set for each of M, Y, and K) (FIG. 3C). In the present embodiment, the PC 10 creates a layer number 3 color correction-free LUT, a layer number 2 color correction-less LUT, and a layer number 1 color-correction LUT. In each LUT without color correction, an ink amount is set in accordance with the reproduction color gamut for each number of layers set in step S1.

<< Step S3 >>
FIG. 6 is a diagram for explaining a process of creating a color correction LUT from an LUT without color correction. The PC 10 creates a color correction LUT based on the LUT without color correction created in step S2. By creating the color correction LUT, the correspondence between the value of the device-independent color space and the ink amount (LUT without color correction) is the correspondence between the value of the device-dependent color space (sRGB color space) and the ink amount (color correction). LUT).

  First, RGB values are converted into ink amounts by an LUT without color correction. The converted ink amount is converted into an L * a * b * value by an FM (Forward Model) converter that defines the relationship between the RGB value and the ink amount. On the other hand, the sRGB values associated with the color correction LUT are converted into L * a * b * values according to a known conversion formula. The converted L * a * b * values are gamut-mapped so that the color gamut matches the color gamut of the L * a * b * values converted by the FM converter.

  On the other hand, a reverse conversion LUT is created using the L * a * b * values converted from the RGB values through the LUT without color correction and the FM converter as a reverse lookup table. That is, the inverse transformation LUT is an LUT that associates L * a * b * values with RGB values. Further, the gamut-mapped L * a * b * values are converted into RGB values by the inverse transformation LUT. This RGB value is converted again into the ink amount Ij by the LUT without color correction. Then, the color correction LUT is created by registering the correspondence between the last ink amount Ij and the first sRGB value in the lookup table.

<< Step S4 >>
By this step, the layer-specific LUT used when printing each layer from the color correction LUT is created. Since the color gamut that expands as the number of layers increases is proportional to the amount of ink that increases as the number of passes increases, in this embodiment, a layered LUT is created by associating the increasing layer with the increase in ink amount. . That is, the PC 10 subtracts the ink amount set in the same grid of the color correction LUT with the number of layers N-1 from the ink amount set in each grid of the color correction LUT with the number of layers N to increase the color gamut. The corresponding ink amount is calculated. Then, by setting this ink amount for each grid of the layered LUT, an N layered layered LUT is created. For example, as shown in FIG. 3C, the ink calculated by subtracting the ink amount set in the same grid of the layer 2 color correction LUT from the ink amount set in each grid of the layer 3 color correction LUT. A third layered LUT is created by setting the amount for the same grid.
Since the color correction LUT with one layer is created based on the reproduction color gamut in the first layer, it is applied as it is as a layered LUT in the first layer.

  As described above, a layered LUT corresponding to each layer is created and recorded in the recording unit 11. Thereafter, the PC 10 selects the ink amount corresponding to the input color data using the layered LUT and outputs it to the printer 20.

1.3. Printing method:
FIG. 7 is a flowchart for explaining a printing method in the printing apparatus 100.
In step S50, the PC 10 acquires image data that is a source for forming a printed material. For example, it is assumed that image data indicating a predetermined image is formed by an application program recorded in the PC 10 and a print command for executing printing of the image data is input to the PC 10.

  In step S <b> 51, the PC 10 displays a color gamut that can be reproduced according to the number of layers on the display 30. The PC 10 displays a color gamut that can be reproduced according to the number of layers by using the corresponding color correction LUT. For example, at lightness L * = 50, as the number of layers increases from 1 to 3, the reproduction color gamut reproduced by the layered LUT increases at a rate of ΔC * in the saturation direction. Therefore, the user can determine the number of layers to be printed by visually checking the reproduction color gamut on the display.

  When the user determines the reproduction color gamut on the display and selects the number of layers to be printed, the PC 10 (ink amount data generation unit 12a) receives this operation input (step S52: YES), and step S53. Then, ink amount data corresponding to the selected number of layers is generated. For example, when the number of layers selected in step S53 is 3, the PC 10 uses the third layer LUT, the second layer LUT, and the first layer LUT to determine the color of the image data. The ink amount corresponding to the component value is converted into ink amount data (ink amount) corresponding to each layer. By the processing in step S53, the ink amount data generation step according to the present invention is realized.

  In step S <b> 54, the PC 10 (print execution unit 12 b) converts the ink amount data of each layer into raster data and outputs it to the printer 20. Here, the raster data is obtained by replacing the ink amount data with binary values that can be reproduced by the printer 20.

  In step S55, upon receiving the raster data of each layer, the printer 20 performs printing according to the designated number of layers on the paper. When the designated number of layers is N = 3, a predetermined image is formed by forming a printing layer on the sheet in the first layer, the second layer, and the third layer. Therefore, the printing execution process according to the present invention is realized by the processes of steps S54 and S55. The printing method has been described above.

1.4. Variation:
In the above-described embodiment, the profile is configured such that the reproduction color gamut increases in the saturation direction as the number of layers increases. However, the characteristics of the profile are not limited to this. For example, the profile (layered LUT) may be created so that the reproduction color gamut increases in the dark portion (for example, L * = 50 or less) in the lightness direction (L * direction in the Lab color space) as the number of layers increases. Good.

  As described above, in this embodiment, since the reproduction color gamut is uniformly expanded according to the number of layers of the printed material, the user of the printing apparatus 100 may form the printed material with how many layers when performing printing. Such a determination can be made easier than before.

2. Second embodiment:
The second embodiment differs from the first embodiment in a configuration in which the amount of increase in the reproduction color gamut of each layer is not evenly formed. That is, the reproduction color gamut of the first layer is defined based on the maximum amount of ink that can be ejected in one pass. In addition, the color gamut reproduced by overlapping each layer is not uniform between hues. Also in the second embodiment, the layered LUT is created based on the color correction LUT, and therefore the description will be made with reference to the flowchart of FIG.

<< Step S1 >>
FIG. 8 is a flowchart showing in detail the process of step S1 of FIG. 4 according to the second embodiment. In step S111, the PC 10 acquires a color gamut range that can be reproduced in one pass. PC10 is a color that can be reproduced in a single pass, taking into account the stability until the first photo-curing ink is cured, the print head ejection capability, the recording characteristics of the paper used, and the resolution. Get the range of the area.

  In step S112, the PC 10 acquires the maximum color gamut. The maximum color gamut indicates the maximum reproduction color gamut that can be reproduced by overlapping a plurality of layers to form a printed material. In step S113, the PC 10 determines the number N of layers for reproducing the maximum color gamut.

  In step S114, a reproduction color gamut that can be reproduced in each layer set in step S113 is acquired. In the second embodiment, the reproduction color gamut of each layer is set with the amount of ink that can be printed in one pass. For example, when the reproduction color gamut of the second layer is acquired, the reproduction color gamut is acquired using the amount of ink that can be ejected in two passes.

  In step S115, the PC 10 adjusts the color gamut so that the shape of the reproduction color gamut is similar for each number of layers. In the second embodiment, the reproduction color gamut for each number of layers is defined according to the amount of ink that can be ejected by each layer. For example, the reproduction color gamut for one layer and the reproduction color gamut for three layers are It is also assumed that the shape of the reproduction color gamut differs greatly between the two. For this reason, the PC 10 is an ink in which the hue (Hue) of each vertex and the lightness characteristic (L * value) are set to a grit so as to resemble the shape of the reproduction color gamut with three layers for the reproduction color gamut with one layer. Adjust the amount. Of course, the adjustment of the ink amount is performed within a range not exceeding the ink amount that can be ejected in each layer (number of layers). By setting it as the said structure, it can prevent that the color gamut reproduced by each layer number differs greatly.

<< Step S2 >>
The PC 10 creates an LUT without color correction for each number of layers based on the reproduction color gamut corresponding to the number of layers. As in the first embodiment, the ink amount corresponding to the reproduction color gamut is set for each grid of the space address.

<< Step S3 >>
The PC 10 creates a color correction LUT from each color-corrected LUT. Similar to the first embodiment, the color correction LUT is created from the LUT without color correction by the method shown in FIG.

<< Step S4 >>
The PC 10 creates a layered LUT from the color correction LUT. Also in the second embodiment, as in the first embodiment, the ink amount set to the same grit of the color correction LUT of the number N of layers from the ink amount set to the predetermined grit of the color correction LUT of the number N of layers. By subtracting, a layered LUT of the Nth layer is created. The creation of the layered LUT in the second embodiment has been described above.

  FIG. 9 is a diagram illustrating a printed matter printed by the printing apparatus 100 according to the second embodiment. Hereinafter, FIG. 9A is a printed matter printed with one layer. FIG. 9B shows a printed matter printed with two layers. FIG. 9C shows a printed matter printed with three layers.

  As shown in FIGS. 9A to 9C, also in this embodiment, the reproduction color gamut of the printed material increases as the number of layers is increased. However, in the second embodiment, even if the number of layers is increased, the reproduction color gamut is not uniformly expanded in the saturation direction. For example, as shown in FIG. 9A, when the reproduction color gamut of the first layer is close to the maximum color gamut other than the hue R direction on the a * b * plane with the lightness L * = 50 (that is, hues C, M, (When values close to the maximum color gamut are taken in the Y, G, and B directions), even if the second layer is superimposed on the first layer to form an image, the saturation other than the hue R is not greatly expanded (see FIG. 9B). This is because the ink amount of the layered LUT is set according to the color gamut that can be reproduced in each layer. Therefore, thereafter, each time the layers are stacked, only the saturation in the hue R direction greatly increases (FIG. 9C).

  As described above, in the second embodiment, a printed matter printed with a predetermined number of layers has a color gamut that can be reproduced in that layer, and therefore it is possible to suppress image quality failure of the printed matter. In addition, since it is easy to check the printed matter for each number of layers, it is possible to select the number of layers according to the color development.

  Needless to say, the present invention is not limited to the above embodiments. That is, the mutually replaceable members and configurations disclosed in the above embodiments are applied by changing their combinations as appropriate. The members and configurations disclosed in the examples can be replaced with the members and configurations interchangeable with each other as appropriate, and the combination thereof is changed and applied. It is one of the present invention that a person skilled in the art can appropriately substitute the members and configurations that can be assumed as substitutes for the members and configurations disclosed in the above-described embodiments based on the above, and change the combination to apply. It is disclosed as an example.

DESCRIPTION OF SYMBOLS 10 ... PC, 11 ... Recording part, 12 ... CPU, 13 ... RAM, 14 ... USB I / F, 15 ... Video I / F, 16 ... Input I / F, 20 ... Printer, 21 ... Conveyance unit, 22 ... Head unit , 23 ... Irradiation unit, 24 ... Detector group, 25 ... Controller, 30 ... Display, 40 ... Operation unit, 50 ... Cable, 100 ... Printing device

Claims (4)

A printing apparatus that forms a printed matter composed of a plurality of printing layers by jetting photocurable ink onto a medium,
Ink for printing each print layer from the input color data using a profile that defines the correspondence between each component value of the input color data and the ink amount of the photocurable ink used for each print layer An ink amount data generating unit for generating ink amount data in which the amount is set;
A print execution unit that performs printing by overlapping each print layer using ink amount data corresponding to each of the generated print layers;
The profile defines the ink amount so that the reproduction color gamut is expanded each time the print layers are overlaid, and when the print layers are overlaid, the reproduction color gamut is in the saturation direction, etc. The printing apparatus, wherein the correspondence relationship is set so as to expand to an interval . The printing apparatus according to claim 1 , wherein the profile defines a correspondence relationship between a component value of input color data and an ink amount for each printing layer. The ink amount of the Nth layer defined by the profile is set based on a value obtained by subtracting the ink amount used for the printed matter with the number of layers N-1 from the ink amount used for the printed matter with the number of layers N. The printing apparatus according to claim 2 . A printing method in which a photocurable ink is jetted onto a medium to form a printed matter comprising a plurality of printing layers,
Ink for printing each print layer from the input color data using a profile that defines the correspondence between each component value of the input color data and the ink amount of the photocurable ink used for each print layer An ink amount data generating step for generating ink amount data in which the amount is set;
A print execution step of performing printing by overlapping each print layer using ink amount data corresponding to each of the generated print layers,
The profile defines the ink amount so that the reproduction color gamut is expanded each time the print layers are overlaid, and when the print layers are overlaid, the reproduction color gamut is in the saturation direction, etc. The printing method, wherein the correspondence relationship is set so as to expand to an interval .

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