JP2015063141A - Printing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To match colors of an image when seen through a transparent medium and when seen without the transparent medium.SOLUTION: The printing device comprises: (A) a metallic ink nozzle that ejects metallic ink to form an image using the metallic ink; (B) a color ink nozzle that ejects color ink to form an image using the color ink; and (C) a control portion that converts data on an input image to data on an output image and ejects ink from the color nozzle and the metallic ink nozzle according to the data on the output image, which has a first mode for forming, on a medium having a front face and a rear face, a color metallic image that appears color metallic when viewed from the front face using the metallic ink and the color ink and a second mode for forming the color metallic image that appears color metallic when viewed from the rear face using the metallic ink and the color ink, and changes conversion tables used for the conversion between the first mode and the second mode.

Description

  The present invention relates to a printing apparatus and a printing method.

  By forming a color ink image on a metallic ink image, it is possible to form an image with high glossiness with a changed color tone (color metallic printing). For example, an image close to gold can be formed by overlaying metallic ink and yellow ink.

  When an image is formed using metallic ink and color ink, a transparent film-like medium may be used. At this time, when a metallic ink image is formed on the medium and a color ink image is formed on the medium for printing that can be viewed from the color image side (front printing mode), a color image is formed on the medium. In some cases, an image of a metallic ink is formed thereon and printing that can be viewed from the medium side (back printing mode) is performed.

JP 2010-52248 A JP 2010-52225 A

  In performing the above-described front printing mode and back printing mode, if the order of forming the metallic ink image and the color ink image is simply changed, there is a large difference between the front printing mode image and the back printing mode image. Color differences may occur. In particular, in the case of metallic ink, for example, there is a tendency to darken, and when viewed from the back side, the color may be greatly different from the front surface. Therefore, it is desirable to match the image colors when viewed through a transparent medium (front printing mode) and when viewed through a transparent medium (back printing mode).

  The present invention has been made in view of such circumstances, and it is an object of the present invention to align the colors of an image when viewed through a transparent medium and when viewed through a transparent medium.

The main invention for achieving the above object is:
(A) a metallic ink nozzle that ejects metallic ink to form an image of the metallic ink;
(B) a color ink nozzle that ejects color ink to form an image of the color ink;
(C) a control unit that converts input image data into output image data, and ejects ink from the color nozzle and the metallic ink nozzle according to the output image data,
A first mode for forming a color metallic image that looks like a color metallic from the front surface using the metallic ink and the color ink on a medium having a front surface and a back surface; and the back surface using the metallic ink and the color ink. A second mode for forming a color metallic image that appears to be a color metallic, and a control unit that varies the conversion table used for the conversion between the first mode and the second mode;
Is a printing apparatus.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

1 is an overall configuration block diagram of a printer 1. FIG. 1 is a perspective view of a printer 1. FIG. FIG. 3 is a diagram illustrating an arrangement of nozzles provided on the lower surface of a head 41. FIG. 4A is a diagram illustrating the front printing mode, and FIG. 4B is a diagram illustrating the back printing mode. It is a figure explaining double-sided mode. It is a table | surface which shows the colorimetry result when using several lookup table. It is explanatory drawing of the double-sided mode in another aspect. It is a table | surface of the result of 1st test printing. It is a table | surface of the result of a 2nd test printing. It is a table | surface of the result of 3rd test printing. 5 is a flowchart of a printing method in the present embodiment. It is explanatory drawing of a dot incidence rate table.

  At least the following matters will become clear from the description of the present specification and the accompanying drawings.

(A) a metallic ink nozzle that ejects metallic ink to form an image of the metallic ink;
(B) a color ink nozzle that ejects color ink to form an image of the color ink;
(C) a control unit that converts input image data into output image data, and ejects ink from the color nozzle and the metallic ink nozzle according to the output image data,
A first mode for forming a color metallic image that looks like a color metallic from the front surface using the metallic ink and the color ink on a medium having a front surface and a back surface; and the back surface using the metallic ink and the color ink. A second mode for forming a color metallic image that appears to be a color metallic, and a control unit that varies the conversion table used for the conversion between the first mode and the second mode;
A printing apparatus comprising:
By doing in this way, the color of the image when it sees through a transparent medium and when it sees without passing through a transparent medium can be arrange | equalized.

In this printing apparatus, it is preferable that the conversion table that is different between the first mode and the second mode is a conversion table that converts input image data of the color ink image.
In this way, an appropriate output image can be obtained simply by converting the input image data of the color ink image.

The conversion table used in the second mode is preferably a conversion table that makes the ink ejection amount in the output image of the color ink different from the conversion table used in the first mode. .
By doing so, it is possible to make the colors of the images uniform when viewed from the front surface without passing through the transparent medium and when viewed from the back surface through the transparent medium.

Further, the conversion table used in the second mode is a conversion table that uses the color ink of a different color in the output image of the color ink image with respect to the conversion table used in the first mode. It is desirable.
This also makes it possible to align the colors of the image when viewed from the front surface without passing through the transparent medium and when viewed from the back surface through the transparent medium.

Further, the conversion table used in the second mode is a conversion table that converts the color ink image so as to have a higher brightness in the output image than the conversion table used in the first mode. desirable.
This also makes it possible to properly align the color viewed from the front surface of the medium and the color viewed from the back surface.

Moreover, it is preferable that the control unit varies the conversion table used in the second mode according to an index value given priority by the user.
By doing so, it is possible to approximate the user-preferred characteristics between the first mode and the second mode, and more preferable printing is possible.

Further, it is preferable that the conversion table used in the first mode and the conversion table used in the second mode are different according to the transparency of the medium.
By doing so, it is possible to appropriately align the colors of the images when viewed from the front surface and the back surface according to the transparency of the medium.

The first mode is a mode in which a metallic ink image is formed on the medium and a color ink image is formed on the metallic ink image. The second mode is in the medium. In this mode, the color ink image is formed and the metallic ink image is formed on the color ink image.
By doing in this way, a color metallic image can be printed appropriately.

A first mode for forming a color metallic image that looks like a color metallic from the front surface using the metallic ink and the color ink on a medium having a front surface and a back surface; and the back surface using the metallic ink and the color ink. Determining whether to perform printing in a second mode of forming a color metallic image that appears to be color metallic from
When printing in the first mode, converting input image data to output image data using the first conversion table for the first mode, and printing in the first mode;
When printing in the second mode, input image data is converted to output image data using a second conversion table for the second mode different from the first conversion table, and printing in the second mode is performed. To do and
Including printing method.
By doing in this way, the color of the image when it sees through a transparent medium and when it sees without passing through a transparent medium can be arrange | equalized.

=== Embodiment ===
Hereinafter, an embodiment will be described with an example of a printing system in which a printer is an inkjet printer (hereinafter referred to as a printer) and the printer and the computer are connected. In this embodiment, the control unit of a printer driver of a computer, which will be described later, may be referred to as a printing apparatus.

  FIG. 1 is a block diagram of the overall configuration of the printer 1. FIG. 2 is a perspective view of the printer 1. The computer 60 is communicably connected to the printer 1 and outputs print data for causing the printer 1 to print an image to the printer 1. The computer 60 is installed with a program (printer driver) for converting image data output from the application program into print data. The printer driver is recorded on a recording medium (computer-readable recording medium) such as a CD-ROM or can be downloaded to a computer via the Internet.

  The controller 10 is a control unit for controlling the printer 1. The interface unit 11 is for transmitting and receiving data between the computer 60 and the printer 1. The CPU 12 is an arithmetic processing unit for controlling the entire printer 1. The memory 13 is for securing an area for storing a program of the CPU 12, a work area, and the like. The CPU 12 controls each unit by the unit control circuit 14. The detector group 50 monitors the situation in the printer 1, and the controller 10 controls each unit based on the detection result.

The transport unit 20 feeds the medium S to a printable position, and transports the medium S by a predetermined transport amount in the transport direction during printing.
The carriage unit 30 is for moving the head 41 in a movement direction that intersects the conveyance direction, and includes a carriage 31.

  The head unit 40 is for ejecting ink onto the medium S and has a head 41. The head 41 is moved in the moving direction by the carriage 31 of the carriage unit 30. A plurality of nozzles, which are ink ejecting portions, are provided on the lower surface of the head 41, and each nozzle is provided with an ink chamber (not shown) containing ink.

  FIG. 3 is a diagram illustrating an arrangement of nozzles provided on the lower surface of the head 41. In addition, the figure is the figure which looked at the nozzle virtually from the upper surface of the head 41. FIG. On the lower surface of the head 41, five nozzle rows in which 180 nozzles are arranged at a predetermined interval (nozzle pitch D) in the transport direction are formed. As illustrated, a metallic nozzle row Me for ejecting metallic ink, a black nozzle row Bk for ejecting black ink, a cyan nozzle row Cy for ejecting cyan ink, a magenta nozzle row Ma for ejecting magenta ink, and a yellow ink are ejected. The yellow nozzle row Ye is lined up in the movement direction. Note that the 180 nozzles in each nozzle row are numbered sequentially from the nozzles on the downstream side in the transport direction (# 1 to # 180).

  In such a printer 1, dot formation processing in which ink droplets are intermittently ejected from the head 41 moving along the moving direction to form dots on the medium, and the medium is conveyed with respect to the head 41 in the conveying direction. The conveyance process is repeated. By doing so, dots can be formed by subsequent dot formation processing at a position on the medium that is different from the position of the dots formed by the previous dot formation processing, and a two-dimensional image is printed on the medium can do.

  Next, the composition of the metallic ink used in this embodiment will be described. The metallic ink used here contains silver particles. The content of silver particles in the ink composition is preferably 0.5% by mass or more and 30% by mass or less. Thereby, the discharge stability by the inkjet system of the ink composition and the storage stability of the ink composition can be made particularly excellent. Also, to achieve good image quality and abrasion resistance in a wide density range from low to high density of silver particles (content per unit area) on the recording medium when printed. Can do. For this reason, for example, even if the printed material to be manufactured has a region where the density of silver particles is different, the image quality of the printed material can be made excellent.

  The silver particles may be prepared by any method. For example, the silver particles can be suitably formed by preparing a solution containing silver ions and reducing the silver ions. Further, the volume-based average particle diameter of the silver particles is not particularly limited, but is preferably 3 nm or more and 100 nm or less.

  The pigments used in the metallic ink are not limited to the above silver particles, but metals such as aluminum, gold, platinum, nickel, chromium, tin, zinc, indium, titanium, copper, and palladium, and these An alloy of

The ink composition may contain water. Specifically, a water-based ink having a water content of 50% by mass or more and a non-aqueous ink having a water content of less than 50% by mass may be used.
In the ink composition, water mainly functions as a dispersion medium for dispersing silver particles. When the ink composition contains water, the dispersion stability of the silver particles can be improved, and the ink composition is unintentionally dried in the vicinity of the nozzle of the droplet discharge device as described above. Since drying on the recording medium to which the ink composition is applied can be performed quickly while preventing (evaporation of the dispersion medium), high-speed printing of a desired image can be suitably performed over a long period of time. .
In the case of containing water, the content of water in the ink composition is not particularly limited, but is preferably 20% by mass or more and 80% by mass or less, and more preferably 50% by mass or more and 80% by mass or less. preferable.

The ink composition may contain components other than those described above (other components).
Examples of such components include penetrants such as alkanediols and glycol ethers, humectants such as alkanetriols and saccharides, nonionic, anionic and cationic surfactants, pH adjusters such as alkanolamines, resins and the like. Examples thereof include waxes such as organic binders, aliphatic hydrocarbon waxes, fatty acid ester waxes, and fatty acid amide waxes.

  The viscosity of the ink composition is not particularly limited, but is preferably 2.0 mPa · s or more and 12.0 mPa · s or less. As a result, the discharge stability of the droplets can be made excellent, and the unintentional wetting and spreading of the ink composition that has landed on the recording medium can be more reliably prevented, resulting in a fine image. Can also be suitably formed.

The adjustment method is as follows.
Polyvinyl pyrrolidone (weight average molecular weight 10,000) was heated at 70 ° C. for 15 hours and then cooled at room temperature. The polyvinyl pyrrolidone (PVP) 1000g was added to the ethylene glycol solution 500ml, and the PVP solution was adjusted. In another container, 500 ml of ethylene glycol was added, 128 g of silver nitrate was added, and the mixture was sufficiently stirred with a magnetic stirrer to prepare a silver nitrate solution. While stirring the PVP solution using an overhead mixer at 120 ° C., the silver nitrate solution was added and the reaction was allowed to proceed by heating for about 80 minutes. And it was made to cool at room temperature after that. The obtained solution was centrifuged for 10 minutes with a centrifuge at 2200 rpm. Thereafter, the separated silver particles were taken out and added to 500 ml of an ethanol solution in order to remove excess PVP. Then, further centrifugation was performed to take out silver particles. Furthermore, the taken-out silver particle was dried on 35 degreeC and 1.3 Pa conditions with the vacuum dryer.

  10% by mass of the silver particles obtained as described above, 3% by mass of 1,2-hexanediol, 10% by mass of trimethylolpropane, and Olfine E1010 (manufactured by Nisshin Chemical Co., Ltd.) as a surfactant. ) 1% by mass, triethanolamine 1% by mass, and ion-exchanged water as a residue to obtain an ink composition.

Next, print modes that can be realized in the present embodiment will be described.
FIG. 4A is a diagram illustrating the front printing mode. In the figure, a sheet S as a medium, a metallic layer formed of metallic ink, and a color layer formed of color ink are shown. The sheet S here is a transparent film sheet.

  The front printing mode is a printing mode for performing printing for viewing an image from the ink side landed on the medium. In this front printing mode, an image with metallic ink is first formed on the medium, and an image with color ink is formed thereon. As shown in the figure, a metallic image (color metallic printing) in which the color tone is adjusted by landing a small amount of color ink on a dense metallic layer can be visually recognized. For example, a gold image can be formed by landing a small amount of yellow ink on a metallic layer made of silver ink.

  In order to realize the front printing mode, for example, the nozzles of the head are used as follows. In the front printing mode, the metallic ink is ejected first, and then the color ink is ejected thereon. Therefore, metallic ink is ejected from the nozzles # 91 to # 180 upstream of the metallic nozzle Me to form a metallic layer first. Then, color ink is ejected from the nozzles # 1 to # 90 downstream of the color nozzles (Bk, Cy, Ma, Ye) to form a color layer on the metallic layer.

  FIG. 4B is a diagram illustrating the reverse printing mode. Also here, a color layer formed of a color ink on a transparent film sheet S as a medium and a metallic layer formed of a metallic ink thereon are shown.

  The reverse printing mode is a printing mode in which printing for viewing an image from the side opposite to the side on which ink has landed in the sheet S is performed. In the reverse printing mode, an image is first formed with color ink on the medium, and an image with metallic ink is formed thereon. As shown in the figure, a metallic image in which the color tone is adjusted by landing a metallic ink with a high density on a color layer with a low density becomes visible from the medium side.

  In order to realize the back printing mode, for example, the nozzles of the head are used as follows. In the reverse printing mode, the color ink is ejected first, and then the metallic ink is ejected thereon. Therefore, color ink is ejected from the nozzles # 91 to # 180 upstream of the color nozzles (Bk, Cy, Ma, Ye) to form a color layer first. Then, metallic ink is ejected from the nozzles # 1 to # 90 on the downstream side of the metallic nozzle Me to form a metallic layer on the color layer.

  FIG. 5 is a diagram for explaining the duplex mode. Here, a color layer formed with color ink, a metallic layer formed with metallic ink on the transparent film sheet S as a medium, and a color layer formed thereon are shown. Yes.

  The double-sided mode is a printing mode in which two images, that is, an image viewed from the side on which ink has landed on the sheet S and an image viewed from the side opposite to the side on which ink has landed are printed. In this duplex mode, an image is first formed with color ink on the medium, an image with metallic ink is formed thereon, and an image with color ink is further formed thereon. As shown in the figure, by forming a low-density color ink layer on both sides of a high-density metallic ink layer, it becomes possible to visually recognize a metallic image (color metallic printing) in which the color tone is adjusted on each surface. .

  In order to realize the duplex mode, for example, the nozzles of the head are used as follows. In the duplex mode, the color ink is ejected first, then the metallic ink is ejected thereon, and further the color ink is ejected thereon. Therefore, color ink is ejected from the nozzles # 121 to # 180 upstream of the color nozzles (Bk, Cy, Ma, Ye) to form a color layer first. Then, metallic ink is ejected from # 61 to # 120 nozzles of the metallic nozzle Me to form a metallic layer on the color layer. Further, color ink is ejected from the nozzles # 1 to # 60 downstream of the color nozzles (Bk, Cy, Ma, Ye) to form a color layer.

  FIG. 6 is a table showing the color measurement results when a plurality of lookup tables are used. The table shows the color measurement results when several look-up tables (LUT) are used.

  The lookup table LUT used here is a color conversion table from the RGB color space to the CMYK color space. However, a plurality of LUTs are used here. The LUT 1 is a look-up table for the front printing mode in the present embodiment, and is a look-up table for performing color metallic printing. The LUT 2 is a look-up table for the back printing mode in the present embodiment, and is a look-up table for performing color metallic printing. The LUT 3 is a look-up table dedicated to color printing.

  The recording medium used here is a PET sheet with an ink receiving layer. Specifically, a clear proof film WXCPF17R manufactured by Seiko Epson is used after sheet cutting.

  In performing color measurement, the color ink is an RGB image in which all pixels have the same color, print data is created by each LUT, and a test pattern of 3 × 3 cm is formed on the film sheet S. The recording resolution here is 720 × 720 dpi. Further, the metallic ink overlapping the color image is printed with a duty of 100% (dots are formed on all pixels of 720 × 720 dpi).

The colorimetry and the glossiness were measured using a MULTIGROSS 268 manufactured by Konica Minolta Co., Ltd. according to JIS Z 8741 for the above test pattern. Further, based on JIS Z 8729, the value of L ^* a ^* b ^* was measured using 938 Spectrodensitometer (manufactured by X-rite) under the conditions of an observation light source D50 and an observation viewing angle of 2 °.

  Of course, when printing in front printing mode, measurement is performed from the ink landing side (from the front), and during printing in back printing mode, measurement is performed from the opposite side (from the back) of ink landing. ing.

A specific example for explaining the contents of the present embodiment will be given. FIG. 6 is an example for explanation, and is not an embodiment based on actual colorimetric data. Example 1 and Example 2 are color measurement results when printing in the front printing mode and printing in the back printing mode are performed using the lookup tables LUT1 and LUT2 in the present embodiment. In this case, since printing is performed according to the characteristics of the front printing and the back printing, the values of L ^* a ^* b ^* are in good agreement with each other when the evaluation results of both are referred to. Further, since glossiness is also evaluated through media, perfect matching is difficult, but it can be approximated.

On the other hand, reference is made to Comparative Example 1. This is because the second embodiment performs printing in the reverse printing mode using the lookup table LUT2, whereas the comparative example 1 performs printing in the reverse printing mode using the same lookup table LUT1 as in the first embodiment. Is going. When each value of L ^* a ^* b ^* is compared between Comparative Example 1 and Example 1, a large shift occurs in the evaluation result. Further, when the gloss level is compared between the comparative example 1 and the example 1, a large shift occurs in the evaluation result.

On the other hand, the comparative example 2 and the comparative example 3 will be compared. In both the comparative example 2 and the comparative example 3, the lookup table LUT3 is used. In Comparative Example 2, printing is performed in the front printing mode using the lookup table LUT3, and in Comparative Example 3, printing is performed in the reverse printing mode using the lookup table LUT3. In both cases, metallic ink is not used. When each value of L ^* a ^* b ^* is compared between Comparative Example 2 and Comparative Example 3, it can be seen that almost the same value is obtained for both L ^* a ^* b ^* and glossiness.

  When color metallic printing is performed using metallic ink, if the same look-up table is used in both the front printing mode and the back printing mode, printing that expresses the same color may not be possible. If color metallic printing of the same color is to be performed in the front printing mode and the back printing mode, it is necessary to use the look-up table LUT1 for front printing and the look-up table LUT2 for back printing separately as in this embodiment. Will occur.

  FIG. 7 is an explanatory diagram of the duplex mode in another aspect. In FIG. 5 described above, the metallic layer is used as a common layer and the front and back color metallics are printed. However, the present invention is not particularly limited to this, and as shown in FIG. Layers arranged in parallel may be formed, then a white layer may be formed, and finally a layer in which color ink and metallic ink are arranged in parallel may be formed again. Moreover, you may perform the color metallic printing of the front surface and a back surface using another printing method. The embodiment based on FIG. 5 described above is preferable to the embodiment described in FIG. 7 in that it is not necessary to use white ink.

  The table for converting the input image data into the output image data is made different between the front printing mode and the back printing mode. “Different” means color printing prepared separately when different color printing tables are used. Including a case where only one of the tables for metallic printing is made different, and a case where printing is performed using at least one different table.

In the specific example described above, the LUT1 and the LUT2 are created so that the glossiness and each value of L ^* a ^* b ^* are close to each other, but the invention is not particularly limited to this. For example, depending on the media characteristics and ink characteristics, it may be difficult to make both values precisely close. In this case, the LUT may be created so that one of the values of glossiness or L ^* a ^* b ^* is preferentially approached. In the case of colored metallic (color metallic), there is anisotropy that appears to differ greatly in color (color) depending on the viewing angle, compared to a layer with general ink. Is precisely required.

Further, for example, the LUT used for the back surface may be changed according to the glossy priority mode or each value priority mode of L ^* a ^* b ^* by the user priority setting from the host device or the like. This makes it possible to approximate the user's priority characteristics in the front printing mode and the back printing mode, and more preferable printing is possible. The color sensation may be not only the value of L ^* a ^* b ^* but also a thing expressed by another color system. In addition, index values relating to color metallic such as “glossiness”, “color feeling”, “metallic feeling”, and the like are set as priorities.

  As described above, in the present embodiment, the look-up look-up table LUT1 and the look-up look-up look-up table LUT2 are properly used, but these look-up tables are obtained experimentally. Hereinafter, an example of how to obtain the lookup table will be described.

FIG. 8 is a table showing the results of the first test printing.
The recording medium used in the test printing also uses a clear proof film WXCPF17R manufactured by Seiko Epson with a sheet cut. In addition, a 3 × 3 cm test pattern was formed on the film sheet S in the same manner as described above, and this was measured. As an example of the color ink, magenta ink (ICM33: manufactured by Seiko Epson Corporation) is used.

  Here, printing is performed in the duplex mode. In the figure, the first layer is a color layer formed on the film sheet S. The second layer is a metallic layer formed on the first layer (color layer). The third layer is a color layer formed on the second layer (metallic layer). The reason why printing is performed in the duplex mode is that printing in the front printing mode and printing in the back printing mode can be performed substantially simultaneously.

  In the test printing, after the first layer was printed, it was dried at room temperature for 1 hour, and then the second layer was printed with metallic ink. Further, it was then dried for 1 hour, and the third layer was printed with color ink.

  In the table, what is shown from the first layer to the third layer is the duty value when printing with the ink of each layer. For example, in the first layer described as the reference, color ink (magenta ink here) is printed with a duty of 30%. The 30% duty is a duty capable of filling 30% of pixels with ink.

  In order to obtain the lookup table, first, a reference duty value is determined and test printing is performed. Here, the color ink of the first layer is printed with a duty of 30%. The second layer of metallic ink is printed with a duty of 40%. The third layer of color ink is printed with a duty.

The colorimetric values from the surface when such printing is performed are the L ^* value, the a ^* value, and the b ^* value indicated by “from the table (third layer side)”. On the other hand, the colorimetric values from the back side are the L ^* value, a ^* value, and b ^* value indicated by “from the back side (media side)”. In the test printing here, the same look-up table for printing the front surface and the look-up table for printing the back surface are used (both use the look-up table LUT1). In addition, when performing each test printing, the printer driver performs conversion from the RGB color space to the CMYK color space as described later, but the RGB value pair used when the test printing is performed at each duty value. It is assumed that CMYK values are also recorded.

Then, a Euclidean distance in the surface of the L ^* a ^* b ^* color difference of the back surface of the L ^* a ^* b ^* values for the value (L ^* a ^* b ^* color space at the time when printing is performed in reference duty value Delta] E (L ^* a ^* b ^* ) = [((ΔL ^* ) ^ 2+ (Δa ^* ) ^ 2+ (Δb ^* ) ^ 2) ^ (1/2)]). Then, the determination is made according to the following criteria according to the color difference. When the value is less than 3.2, “A” is set. When the value is 3.2 or more and less than 4.0, “B” is set. When the value is 4.0 or more and less than 6.5, “C” is set. When the value is 6.5 or more, “D” is set.

  Referring to FIG. 8, the color measurement result of the front surface and the back surface when printing is performed with a reference duty value indicates 3.76 as a color difference. In this case, the determination is B determination. FIG. 7 shows colorimetric values, color differences, and determinations when the duty values in the third layer are made different in this way.

  The most appropriate duty value in the third layer can be obtained based on the evaluation and the color difference obtained in this way. The RGB value versus the CMYK value at the most appropriate duty value is adopted as one of the comparison tables included in the back-up lookup table LUT2. For example, the RGB value versus the CMYK value used when the duty value of the third layer is 50% (color difference 3.36) is adopted as one of the values of the lookup table LUT2.

  FIG. 9 is a table showing the results of the second test printing. Here, the reference duty value is 80% for the first layer, 40% for the second layer, and 80% for the third layer. FIG. 9 shows the colorimetric values of the back surface obtained by changing the duty value of the third layer at this time.

  In FIG. 9, a plurality of determinations of “A” are listed. As described above, it is most preferable that the look-up table LUT2 for the reverse printing mode is created by recording the RGB value versus the CMYK value at the time of the determination of “A”. In FIG. 9, there are five “A” determinations. In such a case, the one with the smallest color difference is used. That is, the RGB value versus the CMYK value used when the duty value of the third layer is 50% (color difference 1.99) is adopted as one of the values of the lookup table LUT2.

  FIG. 10 is a table showing the results of the third test printing. Here, the reference duty value is 80% for the first layer, 40% for the second layer, and 60% for the third layer. FIG. 10 shows the colorimetric values of the back surface obtained by varying the duty value of the third layer at this time.

  Here too, a plurality of “A” determinations are listed. At this time, the smallest color difference is the one when the duty value is 60% (color difference 2.57). Therefore, the RGB vs. CMYK value when the duty value of the third layer is 80% is adopted as one of the values of the lookup table LUT2.

  Here, three tables are shown as examples of the experiment, but by performing many experiments as shown in FIGS. 8 to 10 above, a table of RGB values versus CMYK values of the look-up table LUT2 for back printing. Will be made. Further, although magenta ink has been described here as an example, it goes without saying that the same experiment is performed for other ink colors and the lookup table LUT2 is created. In addition, since the color difference can be reduced by using only one magenta ink, the color difference can be further reduced between the front printing mode and the back printing mode by using other color inks in combination.

When the table of RGB values versus CMYK values thus obtained (lookup table LUT2) is compared with the lookup table LUT1 for the front printing mode, the LUT2 used in the reverse printing mode is used in the front printing mode. It has been found that there is a feature that is a look-up table in which the brightness of a color image output image (CMYK image) becomes higher than that of LUT1. In other words, the LUT 2 used in the reverse printing mode has a higher L ^* value when converted to the L ^* a ^* b ^* color space of the output image (CMYK image) of the color image than the LUT 1 used in the front printing mode. Thus, a table for performing conversion may be used.

  Here, an example in which the look-up table is made different between the front printing mode and the back printing mode has been described, but the dot generation rate described later may be made different. That is, by reducing the dot generation rate in the reverse printing mode to that in the front printing mode, the brightness of the image printed in the reverse printing mode is higher than that printed in the front printing mode. It is good to do. That is, the color ink ejection amount in the reverse printing mode may be made different (reduced or increased) from the color ink ejection amount in the front printing mode. Furthermore, the means for bringing the color difference closer is not limited to the above-described mode, and the color ink used in the front printing mode and the back printing mode may be different. The lightness is one of the three attributes of color, hue, saturation, and lightness.

  FIG. 11 is a flowchart of the printing method in the present embodiment. Hereinafter, the printing method in the present embodiment will be described according to the flowchart.

  First, when a printing command is issued from the application side, RGB data of an image to be printed is input to the printer driver. Also, information on whether the image is surface printing, back printing, or duplex printing is also input to the printer driver (S102).

  Next, the input RGB data is converted into CMYK data (S104). At this time, when an image is printed in the surface printing mode, the surface printing lookup table LUT1 is referred to and data conversion is performed. Further, when an image is printed in the reverse printing mode, the reverse printing lookup table LUT2 is referred to and data conversion is performed. In the case of duplex printing, an image to be printed is converted by a look-up table LUT1 for front printing, and an image to be printed is converted by a look-up table LUT2 for back printing.

  Next, the converted CMYK data is converted into dot occurrence rate data (S106). The printer 1 according to the present embodiment can form three sizes of dots, small dots, medium dots, and large dots. Therefore, conversion is performed to dot generation rate data indicating which size dot is formed in each pixel according to YMCK data (tone value for each ink color). Conversion of the dot occurrence rate data is performed by referring to the dot occurrence rate table.

  FIG. 12 is an explanatory diagram of a dot occurrence rate table. The horizontal axis indicates the input value (that is, the gradation value) of CMYK data, and the corresponding dot occurrence rate is assigned to the vertical axis. Thereby, the gradation value for each ink color of each pixel is converted into the dot occurrence rate.

  The dot occurrence rate data of each pixel obtained in this way is assigned to which pixel corresponds to which nozzle, and is converted to print data (S108). When the printer forms only one type of dot size, binarization is performed by a known binarization unit.

  The print data converted in this way is sent from the printer driver to the printer 1 for printing (S110).

  In this way, even when metallic ink is used, the colors of the front and back images can be appropriately aligned.

  Note that although the conversion processing from step S102 to step S106 is performed by the printer driver here, it may be performed by the printer 1. In the present embodiment, the processing unit that performs these conversions and the ejection unit that ejects ink based on the print data obtained by these conversion processes are collectively referred to as a printing apparatus.

=== Other Embodiments ===
In the above-described embodiment, the transparent medium is described. However, a slightly colored medium (for example, a cloudy medium) may be used. When a colored medium is used, the look-up table LUT2 may be obtained in consideration of the coloring degree (transparency) of the medium.

  In the above-described embodiment, the printer 1 has been described as a printing apparatus. However, the printer 1 is not limited to this, and other fluids (liquids and liquids in which particles of functional materials are dispersed, gels, and the like) are not limited thereto. It is also possible to embody the present invention in a liquid ejecting apparatus that ejects or ejects a fluid. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, gas vaporizer, organic EL manufacturing apparatus (especially polymer EL manufacturing apparatus), display manufacturing apparatus, film formation You may apply the technique similar to the above-mentioned embodiment to the various apparatuses which applied inkjet technology, such as an apparatus and a DNA chip manufacturing apparatus. These methods and manufacturing methods are also within the scope of application.

  The above-described embodiments are for facilitating the understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof.

<About the head>
In the above-described embodiment, ink is ejected using a piezoelectric element. However, the method for discharging the liquid is not limited to this. For example, other methods such as a method of generating bubbles in the nozzle by heat may be used.

1 printer, 10 controller, 11 interface,
12 CPU, 13 memory, 14 unit control circuit,
20 transport unit, 30 carriage unit,
40 head units, 41 heads,
50 detector groups, 60 computers

The main invention for achieving the above object is:
(A) a metallic ink nozzle that ejects metallic ink to form an image of the metallic ink;
(B) a color ink nozzle that ejects color ink to form an image of the color ink;
(C) a control unit that converts input image data into output image data, and ejects ink from the color nozzle and the metallic ink nozzle according to the output image data,
A first mode for forming a color metallic image that looks like a color metallic from the front surface using the metallic ink and the color ink on a medium having a front surface and a back surface; and the back surface using the metallic ink and the color ink. A second mode for forming a color metallic image that appears to be a color metallic, and a control unit that varies the conversion table used for the conversion between the first mode and the second mode;
Equipped with a,
The first mode and the second mode are printing apparatuses in which one or more color inks to be used are the same ink .

Referring to FIG. 8, the color measurement result of the front surface and the back surface when printing is performed with a reference duty value indicates 3.76 as a color difference. In this case, the determination is B determination. FIG. 8 shows colorimetric values, color differences, and determinations when the duty values in the first layer are made different in this way.

The most appropriate duty value in the first layer can be obtained based on the evaluation and the color difference obtained in this way. The RGB value versus the CMYK value at the most appropriate duty value is adopted as one of the comparison tables included in the back-up lookup table LUT2. Eg, RGB values versus CMYK values used when the% duty value of the first layer 50 (color difference 3.75) is employed as one of the values of the look-up table LUT 2.

FIG. 9 is a table showing the results of the second test printing. Here, the reference duty value is 80% for the first layer, 40% for the second layer, and 80% for the third layer. FIG. 9 shows the colorimetric values of the back surface obtained by changing the duty value of the first layer at this time.

In FIG. 9, a plurality of determinations of “A” are listed. As described above, it is most desirable to create the look-up table LUT2 for the reverse printing mode by recording the RGB value versus the CMYK value at the time of the determination of “A”. In FIG. 9, there are five “A” determinations. In such a case, the one with the smallest color difference is used. That is, the RGB value versus the CMYK value used when the duty value of the first layer is 50% (color difference 1.99) is adopted as one value of the lookup table LUT2.

FIG. 10 is a table showing the results of the third test printing. Here, the reference duty value is 80% for the third layer, 40% for the second layer, and 60% for the first layer. FIG. 10 shows the colorimetric values of the back surface obtained by changing the duty value of the first layer at this time.

Here too, a plurality of “A” determinations are listed. At this time, the smallest color difference is the one when the duty value is 80 % (color difference 2.81 ). Therefore, the RGB vs. CMYK value when the duty value of the first layer is 80% is adopted as one of the values of the lookup table LUT2.

Claims (9)

(A) a metallic ink nozzle that ejects metallic ink to form an image of the metallic ink;
(B) a color ink nozzle that ejects color ink to form an image of the color ink;
(C) a control unit that converts input image data into output image data, and ejects ink from the color nozzle and the metallic ink nozzle according to the output image data,
A first mode for forming a color metallic image that looks like a color metallic from the front surface using the metallic ink and the color ink on a medium having a front surface and a back surface; and the back surface using the metallic ink and the color ink. A second mode for forming a color metallic image that appears to be a color metallic, and a control unit that varies the conversion table used for the conversion between the first mode and the second mode;
A printing apparatus comprising:   The printing apparatus according to claim 1, wherein the conversion table different between the first mode and the second mode is a conversion table for converting input image data of the color ink image.   The conversion table used in the second mode is a conversion table that varies an ink ejection amount in an output image of the color ink image with respect to the conversion table used in the first mode. The printing apparatus according to 2.   The conversion table used in the second mode is a conversion table that uses the color ink of a different color in an output image of the color ink image with respect to the conversion table used in the first mode. Item 3. The printing apparatus according to Item 1 or 2.   The conversion table used in the second mode is a conversion table that converts the color ink image so as to have higher brightness in the output image than the conversion table used in the first mode. The printing apparatus in any one of -4.   The printing apparatus according to claim 1, wherein the control unit varies the conversion table used in the second mode according to an index value given priority by a user.   The printing apparatus according to claim 1, wherein the conversion table used in the first mode and the conversion table used in the second mode are different according to the transparency of the medium. The first mode is a mode in which a metallic ink image is formed on a medium and a color ink image is formed on the metallic ink image.
The second mode is a mode in which an image of the color ink is formed on a medium and an image of the metallic ink is formed on the image of the color ink. Printing device. A first mode for forming a color metallic image that looks like a color metallic from the front surface using the metallic ink and the color ink on a medium having a front surface and a back surface; and the back surface using the metallic ink and the color ink. Determining whether to perform printing in a second mode of forming a color metallic image that appears to be color metallic from
When printing in the first mode, converting input image data to output image data using the first conversion table for the first mode, and printing in the first mode;
When printing in the second mode, input image data is converted to output image data using a second conversion table for the second mode different from the first conversion table, and printing in the second mode is performed. To do and
Including printing method.

Images