JP7243189B2 - THERMAL TRANSFER PRINTER, INK RIBBON, CONTROLLER AND DATA PROCESSING METHOD - Google Patents

Description

The present invention relates to a thermal transfer printer, an ink ribbon, a controller, and a data processing method.

As image pickup devices are increasingly digitalized, there is a demand to replace silver salt printing with printing by a thermal transfer printer. A thermal transfer printer presses an ink ribbon coated with ink containing a heat-transferable dye (coloring material) against a print medium, and the heat generated by the thermal head transfers the dye in the ink of the ink ribbon to the print medium. At this time, the dye diffuses between the ink ribbon and the print medium, penetrates the receiving layer of the print medium, and migrates. Thermal transfer printers can continuously control the color density on the print medium by controlling the temperature of the thermal head, and it is relatively easy to obtain a texture similar to that of silver halide photography, such as color gradation due to the diffusion of dyes.

The ink ribbon used in thermal transfer printers is a transfer layer in which basic color ink layers (Y (yellow) layer, M (magenta) layer, and C (cyan) layer) are periodically arranged in a plane-sequential manner along the longitudinal direction. have A conventional thermal transfer printer reproduces a desired color by mixing three colors of Y (yellow), M (magenta), and C (cyan) on a printing medium. Recently, a method of providing a gold or silver ink layer on an ink ribbon (see Patent Document 1) and a method of providing a black or white ink layer on an ink ribbon (see Patent Document 2) have been proposed.

Japanese Patent Application Laid-Open No. 2017-007298 Japanese Patent Application Laid-Open No. 2017-019232

Since conventional thermal transfer printers reproduce chromatic colors by mixing basic colors, color representation tends to be inferior to that of silver halide prints in part of the color gamut. For example, silver halide prints are characterized by high contrast in shadow areas and bright and clear color representation, while conventional thermal transfer printers have been unable to improve the color representation characteristic of silver halide prints. There is room.

Therefore, according to one aspect of the present invention, it is an object of the present invention to provide a thermal transfer printer, an ink ribbon, a control device, and a data processing method capable of improving color expression power in thermal transfer printing. .

According to a first aspect of the present disclosure, a storage capable of storing an ink ribbon having an ink layer of a basic color group including yellow, magenta, and cyan and an ink layer of one or more chromatic colors different from the basic color group a thermal head for heating the ink ribbon accommodated in the accommodation unit; and a first apparatus for reproducing a specified color by mixing a color included in the basic color group with one or more chromatic colors. A thermal transfer printer is provided that includes a storage unit that stores profile information, and a control unit that controls the temperature of a thermal head based on designated color information and first profile information.

Also according to a second aspect of the present disclosure, an ink ribbon is provided for use in thermal transfer printing. This ink ribbon has an ink layer of a basic color group including yellow, magenta, and cyan, and an ink layer of one or more chromatic colors different from the basic color group.

Further, according to the third aspect of the present disclosure, a specified color is reproduced by mixing a basic color group including yellow, magenta, and cyan and one or more chromatic colors different from the basic color group. a storage unit for storing profile information; for each color of the basic color group and each of the one or more chromatic colors, information on the amount of dye used to reproduce a designated color is generated based on the profile information; A controller for providing dye amount information to a thermal transfer printer that prints with an ink ribbon having an ink layer and one or more chromatic ink layers is provided.

Further, according to the fourth aspect of the present disclosure, a specified color is reproduced by mixing a basic color group including yellow, magenta, and cyan with one or more chromatic colors different from the basic color group. Acquiring profile information, for each color of the basic color group and each of one or more chromatic colors, generating information on the amount of dye used to reproduce the designated color based on the profile information, A data processing method is provided for causing a computer to execute processing for providing dye amount information to a thermal transfer printer that prints using an ink ribbon having the above chromatic ink layers.

According to the present invention, the color expression power in thermal transfer printing is improved.

1 is a schematic diagram schematically showing one configuration example of a thermal transfer printer; FIG. FIG. 2 is a diagram schematically showing a configuration example of image receiving paper; FIG. 1 is a diagram schematically showing one configuration example of an ink ribbon according to an embodiment; It is a schematic diagram for demonstrating the principle of thermal transfer printing. 4 is a chart showing a comparison result between a color gamut reproduced by a multicolor printing method and a color gamut reproduced by a conventional printing method by the thermal transfer printer according to the present embodiment; 2 is a block diagram for explaining functions of the thermal transfer printer according to the embodiment; FIG. 3 is a block diagram showing a configuration example of hardware capable of realizing the functions of the control device according to the embodiment; FIG. 4 is a flow chart for explaining the operation of the thermal transfer printer according to this embodiment; FIG. 4 is a chart for explaining gradation characteristics and color reduction characteristics of a thermal transfer printer; FIG. 4 is a first flow chart for explaining a spot color selection method according to the embodiment; FIG. 9 is a second flowchart for explaining the spot color selection method according to the embodiment; 5 is a diagram schematically showing a modified example of the ink ribbon according to the present embodiment; FIG.

One embodiment of the present invention (hereinafter referred to as the present embodiment) will be described below with reference to the accompanying drawings. Elements having substantially the same functions in the present specification and drawings may be denoted by the same reference numerals, thereby omitting redundant description.

[1. Structure of thermal transfer printer]
The configuration of the thermal transfer printer will be described with reference to FIG. FIG. 1 is a schematic diagram schematically showing one configuration example of a thermal transfer printer. The thermal transfer printer 10 shown in FIG. 1 is an example of a thermal transfer printer, and the application range of the technology according to this embodiment is not limited to this.

As shown in FIG. 1, the thermal transfer printer 10 includes a roll-shaped ink ribbon 11, transport shafts 11a and 11b, a roll-type image receiving paper 12, paper feed rollers 13a and 13b, a feed roller 14, a motor 15, a platen roller 16, It has a thermal head 17 and a paper cutter 18 .

Although not shown, the ink ribbon cartridge containing the ink ribbon 11 is loaded at a predetermined location of the thermal transfer printer 10, or the ink ribbon cartridge is a roll-shaped ink ribbon that is replaceable. With the ink ribbon 11 stored in the set, the ink ribbon cassette is loaded at a predetermined location of the thermal transfer printer 10 . These ink ribbon cartridges and ink ribbon cassettes have conveying shafts 11a and 11b around which the stored ink ribbon 11 is wound, and the ink ribbon 11 is taken up by the rotation of the conveying shafts 11a and 11b. The ink ribbon 11 can be transported, for example, in at least one of the direction in which it is taken up by the transport shaft 11a (hereinafter referred to as the forward direction) and the direction in which it is taken up by the transport shaft 11b (hereinafter referred to as the reverse direction).

The ink ribbon 11 has a plurality of ink layers corresponding to a plurality of colors, as will be described later. An ink layer corresponding to the color to be transferred is conveyed between the platen roller 16 and the thermal head 17 by the rotation of the conveying shafts 11a and 11b. The dye in the ink layer positioned between the platen roller 16 and the thermal head 17 is transferred to the image receiving paper 12 by the heat of the thermal head 17 .

The image receiving paper 12 has, for example, a configuration as shown in FIG. FIG. 2 is a diagram schematically showing one configuration example of the image receiving paper. Types of the image receiving paper 12 include, for example, a roll type and a sheet type (see the front view of FIG. 2). However, in this paper, for convenience of explanation, the roll-type receiving paper 12 will be taken as an example.

The image-receiving paper 12 has, for example, a laminated structure composed of, in order from the printing surface, an image-receiving layer, a base layer, a foamed PP (polypropylene) film, PE (polyethylene), paper, PE, and a back layer (schematic in FIG. 2). (see diagram). The dye transferred from the ink ribbon 11 by the heat of the thermal head 17 permeates the image receiving layer of the image receiving paper 12 and migrates.

The roll-type image receiving paper 12 is loaded into the thermal transfer printer 10 while being wound around a roll, as in the configuration example shown in FIG. Further, the image receiving paper 12 is guided to the feed roller 14 by the paper feed roller 13a, and conveyed between the platen roller 16 and the thermal head 17 by the rotation of the feed roller 14. FIG. The feed roller 14 is electrically connected to a motor 15 and controlled to rotate by the motor 15 . The image receiving paper 12 passes between the platen roller 16 and the thermal head 17 and is guided to the paper cutter 18 via the paper feed roller 13b.

In the area sandwiched between the platen roller 16 and the thermal head 17, the ink ribbon 11 is arranged on the thermal head 17 side, and the ink layer surface (dye-coated surface) of the ink ribbon 11 and the image receiving layer of the image receiving paper 12 are formed. The image receiving paper 12 is arranged on the side of the platen roller 16 so that the . During printing, the ink ribbon 11 is sandwiched between the platen roller 16 and the thermal head 17 and pressed against the image receiving paper 12 .

A paper cutter 18 cuts the printed area of the image receiving paper 12 . If the image receiving paper 12 is of the sheet-fed type, the paper cutter 18 can be omitted. The number of various rollers, the shape of the thermal head 17, the arrangement of the image receiving paper 12, and the like are not limited to the example shown in FIG.

Here, the configuration of the ink ribbon 11 according to this embodiment will be further described with reference to FIG. FIG. 3 is a diagram schematically showing one configuration example of the ink ribbon according to the present embodiment. FIG. 3 schematically shows a front view and a sectional view of the ink ribbon 11. As shown in FIG.

The ink ribbon 11, as shown in FIG. 3 (cross-sectional view), has a film substrate, a transfer layer, and an overcoat layer (hereinafter referred to as an OC layer).

The transfer layer is an ink layer containing a dye coated on a film substrate such as PE. The OC layer is a protective film for protecting the printed surface. For example, it is a clear layer made of a hot-melt resin material. becomes the surface layer. The clear layer is preferably composed of two layers, a release layer having excellent plasticizer resistance and an adhesive layer for adhering to the image receiving paper during thermal transfer and protecting the printing surface, or is separated from the film substrate. It can be composed of three layers including a release layer that improves the releasability from the layers. A barrier layer (anchor layer) may be provided between the ink layer and the film substrate to prevent the dye from diffusing toward the film substrate. A coat layer (back layer) may be provided.

As shown in FIG. 3 (front view), the ink ribbon 11 according to the present embodiment includes ink layers of Y (yellow), M (magenta), and C (cyan) (Y layer, M layer, C layer), and , Y, M, and C (hereinafter referred to as special colors).

In the example of FIG. 3, ink layers of special colors S1 and S2 (S1 layer and S2 layer) are provided on the ink ribbon 11 as the special color ink layers. Also, along the longitudinal direction of the ink ribbon 11, the ink layers are repeatedly arranged in the order of Y layer, M layer, C layer, S1 layer, S2 layer, and OC layer. In this paper, Y, M, and C are sometimes referred to as basic colors. Also, the Y layer, the M layer, and the C layer may be referred to as basic color ink layers, and the S1 layer and S2 layer may be referred to as special color ink layers.

When the ink ribbon 11 of FIG. 3 is loaded into the thermal transfer printer 10, the ink ribbon 11 is taken up by the rotation of the transport shaft 11a during printing, and the Y layer, M layer, and C layer are formed between the platen roller 16 and the thermal head 17. layer, S1 layer, S2 layer, and OC layer are conveyed in order. Then, by the heat of the thermal head 17, the color materials of the Y layer, M layer, C layer, S1 layer, and S2 layer are sequentially transferred onto the image receiving paper 12, and finally the image receiving paper 12 is coated with the resin material of the OC layer. .

Note that the arrangement of each ink layer shown in FIG. 3 is an example, and the number of special color ink layers and the arrangement order of the ink layers can be variously modified according to the embodiment. Also, a modification is possible in which ink layers corresponding to achromatic colors such as K (black) and W (white) are further added. These modifications also naturally belong to the technical scope of the present embodiment.

Next, the principle of thermal transfer printing by the thermal transfer printer 10 will be described with reference to FIG. FIG. 4 is a schematic diagram for explaining the principle of thermal transfer printing. Here, the case where the dye of the Y layer is transferred to the image receiving paper 12 will be described as an example, but the principle of thermal transfer printing is the same even when the dye of another ink layer is transferred to the image receiving paper 12 .

When the color material of the Y layer is transferred to the image receiving paper 12, the Y layer of the ink ribbon 11 is conveyed between the platen roller 16 and the thermal head 17 by the rotation of the conveying shaft 11a. When the Y layer is arranged between the platen roller 16 and the thermal head 17 , the ink ribbon 11 is pressed against the image receiving paper 12 while being sandwiched between the platen roller 16 and the thermal head 17 .

The heat of the thermal head 17 is transferred to the transfer layer (ink layer) via the film base material and the barrier layer of the ink ribbon 11 . Due to this heat, the coloring material applied to the ink layer diffuses between the transfer layer and the image receiving layer of the image receiving paper 12 , and the diffused coloring material permeates the image receiving layer of the image receiving paper 12 . The amount of dye that permeates the image receiving layer of the image receiving paper 12 (hereinafter referred to as dye transfer amount) depends on the thermal energy transferred from the thermal head 17 to the ink ribbon 11 . That is, the dye transfer amount changes according to the temperature of the thermal head 17 .

The temperature of the thermal head 17 can be controlled continuously. Therefore, in principle, the dye transfer amount can be controlled continuously. Therefore, thermal transfer printing can realize continuous gradation expression. Further, various colors can be reproduced on the image receiving paper 12 by overlapping and transferring a plurality of color materials while adjusting the dye transfer amount of each color. Further, in thermal transfer printing, the dye diffuses and then permeates and migrates into the image receiving layer of the image receiving paper 12, so that high-quality printing results with less graininess can be obtained.

As already described, the ink ribbon 11 according to the present embodiment is provided with a special color ink layer. The color reproduction range (color gamut) can be expanded by adding the special color ink layer. For example, when considering the color gamut in the L ^* a ^* b ^* color space, when special color ink layers of green (G) and blue (B) are provided on the ink ribbon 11, the color gamut is projected onto the a ^* -b ^* plane. The color gamut can be expanded in the second and fourth quadrants of the a ^* -b ^* plane when referring to the projection view. This is advantageous in enhancing the contrast in shadow areas and expressing bright and clear colors.

As an example, FIG. 5 shows the result of comparison between the color gamut (example) for the ink ribbon 11 to which the special color ink layer is added and the color gamut for the comparative example. FIG. 5 is a chart showing the comparison result between the color gamut reproduced by the multicolor printing method and the color gamut reproduced by the conventional printing method by the thermal transfer printer according to the present embodiment.

In the comparison results of FIG. 5, as a comparative example, the color gamut of thermal transfer printing (hereinafter referred to as 3C printing) using a general ink ribbon having basic color ink layers of Y, M, and C, and yellow, magenta, cyan, and green , orange, gray, black, light cyan, light magenta, and light gray. Here, as an example, the color gamut of thermal transfer printing (hereinafter referred to as 5C printing) with an ink ribbon 11 employing G layers and B layers as special color ink layers is shown.

Gamut comparison A in FIG. 5 shows the result of comparing the 3C printing color gamut and the 5C printing color gamut by projecting them onto the a ^* -b ^* plane. Gamut comparison A shows that the addition of the G and B layers expands the color gamut in the second quadrant (upper left region) and fourth quadrant (lower right region) of the a ^* -b ^* plane. ing.

Gamut comparison B in FIG. 5 shows the result of comparing the IJP printing color gamut and the 5C printing color gamut by projecting them onto the a ^* -b ^* plane. Gamut comparison B shows that the addition of the G and B layers can extend the color gamut of 5C printing to a color gamut that approximates the color gamut of IJP printing.

Thus, by applying the ink ribbon 11 according to the present embodiment, it is possible to obtain higher color reproducibility than 3C printing (color reproducibility approaching that of IJP printing that employs 10 color inks) due to the addition of the special color ink layer. . In addition to smooth gradation expression based on the principle of thermal transfer printing, the addition of a special color ink layer improves color reproducibility. be possible.

[2. Functions of Thermal Transfer Printer]
Next, the functions of the thermal transfer printer 10 will be further described with reference to FIG. FIG. 6 is a block diagram for explaining the functions of the thermal transfer printer according to this embodiment. Note that the functions of the thermal transfer printer 10 shown in FIG. 6 are an example of functions possessed by the thermal transfer printer according to the present embodiment, and can be appropriately modified according to the mode of implementation.

(function block)
As shown in FIG. 6, the thermal transfer printer 10 has a thermal head 101, a paper feed mechanism 102, a ribbon transport mechanism 103, a control device 104, and a storage device 105.

Although the control device 104 and the storage device 105 are included in the thermal transfer printer 10 in the example of FIG. In addition, although the control device 104 and the storage device 105 are described as separate units in the example of FIG.

In the example of FIG. 6, for convenience of explanation, the image data is input from the computer 20 connected to the thermal transfer printer 10. , semiconductor memory, etc.), or the image data may be input to the thermal transfer printer 10 via wired or wireless communication. The computer 20 is a smart phone, a tablet terminal, a digital camera, a mobile phone, a PC (Personal Computer), or the like.

A thermal head 101 corresponds to the thermal head 17 in FIG. The paper feed mechanism 102 corresponds to the paper feed rollers 13a and 13b, the feed roller 14, the motor 15, the platen roller 16, and the paper cutter 18 in FIG. The ribbon conveying mechanism 103 corresponds to a rotating mechanism (not shown) that rotates the conveying shafts 11a and 11b in FIG.

A control device 104 is a computer for controlling the operation of the thermal transfer printer 10 . The control device 104 also has a paper feed control section 141 , a transport axis control section 142 , a head control section 143 and a data processing section 144 .

The paper feed control unit 141 controls the operation of the paper feed mechanism 102 to transport the image receiving paper 12 so that the print area of the image receiving paper 12 comes to a predetermined position where the thermal head 17 is located. The transport shaft controller 142 controls the rotation of the transport shafts 11 a and 11 b to wind the ink ribbon 11 and align the ink layer to be transferred with the printing area of the image receiving paper 12 .

The head control unit 143 controls the temperature of the thermal head 17 based on control parameters (hereinafter referred to as device setting values) output from the data processing unit 144 according to image data input to the thermal transfer printer 10 . The device setting value corresponds to, for example, the density gradation (0 to 255) of each color represented by 256 gradations. Further, the device setting value corresponds to the temperature of the thermal head 17 corresponding to the density gradation, and corresponds to the dye transfer amount of the dye transferred to the printing area of the image receiving paper 12 at that temperature.

The data processing unit 144 converts the color data (hereinafter referred to as input color data) of the input system (computer 20 in the example of FIG. 6) into the color data (hereinafter referred to as output color data) of the printing system (thermal transfer printer 10) using the color conversion profile. color data). An ICC (International Color Consortium) profile is an example of a color conversion profile. The color conversion profile is created, for example, by actually using the ink ribbon 11 to print patches and based on the colorimetric results of the printed patches.

If the input color data is expressed in a colorimetric value other than the standard color space (for example, XYZ color space, L ^* a ^* b ^* color space, sRGB color space, etc.), the data processing unit 144 converts the input color data into After converting to the colorimetric values of the standard color space, output color data is generated using a color conversion profile for obtaining output color data. On the other hand, if the input color data is represented by the colorimetric values of the standard color space, the data processing unit 144 uses the color conversion profile for obtaining the output color data to directly obtain the output color data from the input color data. Generate.

The above color conversion profile consists of three components (hereinafter referred to as input values) representing the color values of the standard color space, and H (H is an integer of 3 or more) color components (hereinafter referred to as output values) in the printing system. Defines the correspondence between One output value corresponds to the density tone of the corresponding color component. In thermal transfer printing, the temperature of the thermal head 17 determines the density gradation, so one output value corresponds to the device set value of the thermal head 17 .

In the following description, it is assumed that the output values in the color conversion profile are the device setting values of the thermal head 17 . In this case, the color conversion profile provides conversion information for converting a color represented by a set of three input values into H sets of device setting values (H is an integer equal to or less than the number of ink layers). . This color conversion profile is stored in advance in the storage device 105 in the form of, for example, an LUT (Look-Up Table).

N is the number of ink layers that the ink ribbon 11 has. In the case of the ink ribbon 11 shown in FIG. 3, N=5 because there are ink layers corresponding to the five colors Y, M, C, S1, and S2. When using three colors of Y, M, and C, H is 3. When using Y, M, C, and S1 (or S2), H is 4. Y, M, C, S1, and S2 are all used. If used, H is 5.

Below, the color conversion profile used when N is 3 (when only basic colors are used) is the "basic color profile" (basic color profile 152), and when N is 3 or 4 (when special colors are used). ) may be referred to as a “multicolor profile” (multicolor profile 151). The multicolor profile 151 and basic color profile 152 are stored in advance in the storage device 105 .

The data processing unit 144 inputs output color data (N device setting values) generated based on the color conversion profile to the head control unit 143 . The head control section 143 controls the temperature of the thermal head 17 based on the output color data input from the data processing section 144 .

(controller hardware)
Here, the hardware of the control device 104 will be described with reference to FIG. FIG. 7 is a block diagram showing a configuration example of hardware capable of realizing the functions of the control device according to this embodiment.

The functions of the control device 104 can be implemented using, for example, the hardware resources shown in FIG. That is, the functions of the control device 104 are realized by controlling the hardware shown in FIG. 7 using a computer program.

As shown in FIG. 7, this hardware mainly has a processor 104a, a memory 104b, a display I/F (Interface) 104c, a communication I/F 104d, and a connection I/F 104e.

The processor 104a is, for example, a CPU (Central Processing Unit), DSP (Digital Signal Processor), ASIC (Application Specific Integrated Circuit), FPGA (Field Programmable Gate Array), or the like.

The memory 104b is, for example, a storage device such as ROM (Read Only Memory), RAM (Random Access Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), and flash memory.

The display I/F 104c is an interface for connecting display devices such as LCD (Liquid Crystal Display) and ELD (Electro-Luminescence Display). For example, the display I/F 104c controls display via a GPU (Graphic Processing Unit) mounted on the processor 104a or the display I/F 104c.

The communication I/F 104d is an interface for connecting to a wired and/or wireless network. The communication I/F 104d is connected to, for example, a wired LAN (Local Area Network), a wireless LAN, an optical communication network, a mobile phone network, and the like.

The connection I/F 104e is an interface for connecting external devices. The connection I/F 104e is, for example, a USB (Universal Serial Bus) port, an IEEE1394 port, or the like. The connection I/F 104e can be connected to, for example, an input interface such as a touch panel or a touch pad, or a portable non-temporary recording medium 104f.

The recording medium 104f includes, for example, optical discs such as CDs (Compact Discs), DVDs (Digital Versatile Discs), BDs (Blu-ray Discs; registered trademark), magneto-optical discs, and nonvolatile memories such as USB memories and flash memories. and so on. Various data such as image data and programs can be stored in the recording medium 104f.

The processor 104a described above can read the program stored in the recording medium 104f, store it in the memory 104b, and control the operation of the control device 104 according to the program read out from the memory 104b. In addition, the program which controls operation|movement of the control apparatus 104 may be previously stored in the memory 104b, and may be downloaded from a network via communication I/F104d.

The functions of the paper feed control unit 141, the transport axis control unit 142, the head control unit 143, and the data processing unit 144 described above can be realized using the processor 104a described above. Also, in the case where the control device 104 includes the storage device 105, the function of the storage device 105 can be realized using the memory 104b described above. Also, the functions of the computer 20 shown in FIG. 6 can be implemented by the hardware shown in FIG.

[3. Operation of thermal transfer printer]
The operation of the thermal transfer printer 10 will now be further described with reference to FIG. FIG. 8 is a flowchart for explaining the operation of the thermal transfer printer according to this embodiment.

For convenience of description, the following description is based on the premise that the thermal transfer printer 10 has a basic color print mode and a multicolor print mode. The basic color print mode is an operation mode in which only Y, M, and C of the ink ribbon 11 are used for printing. The multicolor print mode is an operation mode in which Y, M, C, S1, and S2 of the ink ribbon 11 are used for printing. However, the thermal transfer printer 10 may be equipped with only the multicolor printing mode. In this case, the processing related to the basic color print mode among the processing shown in FIG. 8 is omitted.

( S<b>101 ) The data processing unit 144 reads image data and stores it in the storage device 105 . The image data is obtained from the computer 20 connected to the thermal transfer printer 10 by wire or wirelessly, or from the recording medium 104f connected to the connection I/F 104e of the control device 104, for example.

The input color data representing each pixel value of the image data is represented by colorimetric values in the color space of the input system. When the color space of the input system is a color space (eg, RGB color space) other than the standard color space (eg, XYZ color space, L ^* a ^* b ^* color space, sRGB color space, etc.), the data processing unit 144 inputs Converts color data to standard color space colorimetric values.

(S102) The data processing unit 144 determines whether the operation mode of the thermal transfer printer 10 is the multicolor printing mode.

The operating mode of thermal transfer printer 10 may be user selectable at the time of printing. For example, the data processing unit 144 displays an operation mode selection screen on the display connected to the display I/F 104c, and also displays a message prompting the user to select an operation mode. Then, the data processing unit 144 determines the operation mode of the thermal transfer printer 10 according to the user's selection operation.

If the user selects the basic color print mode, the process proceeds to S105. On the other hand, if the user selects the multicolor print mode, the process proceeds to S103.

As a modification, the data processing unit 144 may automatically select the basic color print mode when the ink ribbon loaded in the thermal transfer printer 10 is a general ink ribbon that does not have a special color ink layer. As a method for discriminating the type of ink ribbon, for example, an ink ribbon cartridge is provided with a discriminating structure (e.g., unevenness, claws, etc.) or a discriminating code (e.g., bar code, QR code (registered trademark), etc.). , there is a method to discriminate based on these structures and codes.

(S103) Using the multicolor profile 151, the data processing unit 144 converts the input color data (colorimetric values of the standard color space) corresponding to each pixel value of the image data into the output color data (Y, M, C, S1). , S2) to generate print data composed of output color data for each pixel. Print data is input from the data processing unit 144 to the head control unit 143 .

(S104) The thermal transfer printer 10 uses the Y layer, M layer, C layer, S1 layer, and S2 layer of the ink ribbon 11 to print the image data. That is, in the multicolor print mode, the special color ink layer of the ink ribbon 11 is used for printing.

When the ink ribbon 11 illustrated in FIG. 3 is applied, the transport axis controller 142 transports the Y layer, M layer, C layer, S1 layer, and S2 layer in order to the printing area under the thermal head 101 . The head control unit 143 controls the temperature of the thermal head 101 for each of the Y layer, M layer, C layer, S1 layer, and S2 layer based on the print data generated by the data processing unit 144 .

After the dye of each ink layer is transferred, the transport axis controller 142 transports the OC layer to the printing area. The head controller 143 controls the thermal head 101 to a predetermined temperature to transfer the resin material of the OC layer to the image receiving paper 12 . The predetermined temperature is a temperature suitable for peeling the resin material of the OC layer from the film substrate and transferring it to the image receiving paper 12 .

When the transfer process for each ink layer and OC layer is completed, the paper feed control unit 141 controls the paper feed mechanism 102 to transport the image receiving paper 12 to a predetermined position. If the image receiving paper 12 is of roll type, the image receiving paper 12 is cut by a paper cutter 18 . When the process of S104 is completed, the process proceeds to S107.

(S105) Using the basic color profile 152, the data processing unit 144 converts the input color data (colorimetric values in the standard color space) corresponding to each pixel value of the image data into the output color data (Y, M, C). (three device setting values corresponding to ) to generate print data composed of output color data for each pixel. Print data is input from the data processing unit 144 to the head control unit 143 .

(S106) The thermal transfer printer 10 prints image data using the Y layer, the M layer, and the C layer. That is, in the basic color print mode, the special color ink layer of the ink ribbon 11 is not used for printing. Therefore, the transport axis controller 142 controls the operation of the ribbon transport mechanism 103 so as to skip the special color ink layer.

When using the ink ribbon 11 illustrated in FIG. 3 , the transport axis controller 142 transports the Y layer, M layer, and C layer in order to the printing area under the thermal head 101 . The head control unit 143 controls the temperature of the thermal head 101 for each of the Y layer, M layer, and C layer based on the print data generated by the data processing unit 144 .

After completing the transfer process for the basic color ink layer, the transport axis controller 142 transports the OC layer to the printing area. Although the S1 and S2 layers pass through the printing area under the thermal head 17 while the OC layer is being conveyed, the S1 and S2 layers are not conveyed in line with the printing area (skip operation of the special color ink layer). Then, the head control unit 143 controls the thermal head 101 to a predetermined temperature to transfer the resin material of the OC layer to the image receiving paper 12 .

Note that when a general ink ribbon that does not include a special color ink layer is loaded in the thermal transfer printer 10, the data processing unit 144 controls the transport axis control unit 142 so as to avoid the above-described skip operation of the special color ink layer. do. This is to avoid transporting an ink layer different from the target ink layer to the printing area due to the above skipping operation.

When the transfer of the basic color ink layers and the OC layer is completed, the paper feed control unit 141 drives the paper feed mechanism 102 to transport the image receiving paper 12 to a predetermined position. If the image receiving paper 12 is of roll type, the image receiving paper 12 is cut by a paper cutter 18 . When the process of S106 is completed, the process proceeds to S107.

(S107) The data processing unit 144 determines whether or not to end printing. For example, if there is image data for an image to be printed next, or if multiple copies of the same image are to be printed, the data processing unit 144 determines not to end printing, and advances the process to S101. On the other hand, if there is no print job in the buffer, the data processing unit 144 determines to end printing, and ends the series of processes shown in FIG.

As described above, by using the ink ribbon 11 including the special color ink layer, it is possible to realize thermal transfer printing with high color reproducibility. Further, by providing a mechanism for selecting the basic color print mode and the multicolor print mode, it becomes possible to switch between use and non-use of the special color ink layer without exchanging the ink ribbon cartridge. Further, by using the above-described color conversion profiles (multicolor profile 151 and basic color profile 152), more faithful color reproduction can be realized.

[4. How to select a spot color]
As described above, in this embodiment, by providing the ink ribbon 11 with the special color ink layer, the color gamut can be widened, and color expression approaching that of silver salt printing can be realized. However, as the number of special color ink layers increases, the printing time increases, and the number of sheets that can be printed with one roll of the ink ribbon 11 decreases. Therefore, if a wider color gamut can be realized with as few special color ink layers as possible, it contributes to the improvement of convenience and the reduction of printing costs. However, repeating trial and error to select the optimum spot color from among a myriad of dyes is a heavy workload and entails a huge cost.

As a method of selecting a spot color, set a large number of candidate colors for the spot color (hereafter, candidate colors), manufacture an ink ribbon with an ink layer of each candidate color, print patches, and measure the printing result. There is a way to select the preferred candidate color from the values. However, in this method, the production of ink ribbons and the measurement work must be repeated for a huge number of candidate colors, resulting in enormous cost burden and work burden as described above. Therefore, the present embodiment proposes a method of narrowing down candidate colors and selecting spot colors by computer simulation.

In order to faithfully reproduce the printing characteristics of the thermal transfer printer 10, the computer simulation proposed in this embodiment considers the gradation characteristics and the color reduction characteristics, which will be described later.

(Gradation characteristics)
As already explained with reference to FIG. 4, in thermal transfer printing, the heat of the thermal head 17 is transferred from the film substrate side of the ink ribbon 11 to the transfer layer, and the dye eluted by the heat is transferred to the ink ribbon 11 and the image receiving paper. 12 and permeates the image receiving layer of the image receiving paper 12 . Since the dye is transferred to the image-receiving layer of the image-receiving paper 12 through such a process, the relationship between the dye transfer amount and the temperature of the thermal head 17 is normally non-linear.

Considering the device setting value (100% signal value) at temperature T100 corresponding to single-color solid printing (e.g., equivalent to 100% of the tone value range of 0% to 100%), for example, Even if the thermal head 17 is controlled with a device setting value (20% signal value) corresponding to 20% (temperature T20), the above non-linear characteristic causes the dye transfer amount to be slightly less than 20% during solid printing. Become. On the other hand, when the thermal head 17 is controlled with the device set value (80% signal value) corresponding to 80% of the temperature T100 (temperature T80), the dye transfer amount is slightly larger than 80% during solid printing.

In the following description, the non-linear relationship between the device setting value and the dye transfer amount in monochromatic printing as described above may be referred to as "gradation characteristics". The gradation characteristics of thermal transfer printing are, for example, as shown in the upper graph of FIG. In this graph, the amount of dye transfer on the vertical axis is a relative value with the amount of dye transfer during solid printing as a reference being 1.0. The device setting value on the horizontal axis is a relative value (%) based on the device setting value (100% signal value) corresponding to the temperature T100 during solid printing.

The above gradation characteristics are obtained by printing monochromatic patches on the receiving paper 12 with the thermal transfer printer 10 while changing the device setting values, and measuring the spectral reflectance of the actually printed patches for each device setting value. . The dye transfer amount is proportional (proportional within an allowable error range) to the spectral density calculated based on the spectral reflectance. Therefore, the above gradation characteristics can be obtained by obtaining the relationship between the device setting value and the spectral density from the measured spectral reflectance.

For example, if the device setting value is t (relative value with 100% signal value as 100), the wavelength of the light source is λ, the color of the colorant is q, and the spectral reflectance is R _q (t, λ), the spectral density is D _q (t, λ) is given by the following equation (1).

D _p (λ) included in the following formula (1) is the spectral density of the image receiving paper 12 given by the following formula (2). The spectral reflectance R _q (t, λ) of an actually printed patch includes a reflection component due to the color of the coloring material permeated into the image receiving paper 12 and a reflection component due to the color of the image receiving paper 12 (background color). be Therefore, in order to evaluate the dye transfer amount alone, it is necessary to subtract the spectral density D _p (λ) of the receiving paper 12 on which no dye has been transferred from the spectral density D _q (t, λ). Therefore, the spectral density D _p (λ) is subtracted in the following equation (1).

_Dq ( _t ,λ)=- _log10Rq (t,λ) _-Dp (λ)
…(1)
D _p (λ)=−log ₁₀ R _p (λ)
…(2)

Here, spectral density D _q (100, λ) of color q observed during solid printing and spectral density D _q (t, λ). As noted above, the spectral density D _q (t,λ) is proportional to the dye transfer amount of color q. Therefore, the above gradation characteristics can be obtained by obtaining the gradation coefficient V _q (t) representing the relationship between the spectral densities D _q (100, λ) and D _q (t, λ).

The gradation coefficient V _q (t) can be calculated, for example, based on the following formula (3). In equation (3) below, Av _λ represents the function for calculating the average value for λ. For example, _when spectral reflectance D _q (t, λ _l ) is measured for wavelengths _{λ 1} , . D _q (t, λ)} is given by the following equation (4).

V _q (t)=Av _λ {D _q (t, λ)}/Av _λ {D _q (100, λ)}
…(3)
Av _λ {D _q (t, λ)}=Σ _{l=1,..., L} {D _q (t, λ _l )}/L
…(4)

Although the average value is calculated using the function Av _λ in the above equation (3), the gradation coefficient V _p (t) is a coefficient that does not depend on the wavelength λ. Therefore, the gradation coefficient V _q (t) can be obtained based on the spectral reflectances D _q (t, λ) and D _q (100, λ) obtained at a certain wavelength λ. However, by calculating the gradation coefficient V _q (t) using the average value as shown in the above equation (3), it is possible to suppress the influence of errors that may occur randomly during measurement.

Considering that the gradation coefficient V _q (t) does not depend on the wavelength λ of the light source, the spectral density D _q (t, λ) is given by Equation (5) below. The actually measured spectral density F _q (t, λ) of the color (spectral density including the influence of the background color) is given by the following equation (6). Once the dyes of the ink ribbon 11 and the type of the receiving paper 12 are determined, the gradation coefficient V _q (t) can be obtained in advance. Then, using the gradation coefficient V _q (t) obtained in advance, the spectral density F _q (t, λ) can be calculated from the following equations (5) and (6).

D _q (t, λ) = V _q (t) x D _q (100, λ)
…(5)
F _q (t, λ) = D _q (t, λ) + D _p (λ)
… (6)

Note that the gradation coefficient V _q (t) corresponds to an index value representing the density gradation based on the dye transfer amount during solid printing. The relationship between the thermal energy applied from the thermal head 17 and the dye transfer amount does not depend on the color q within an allowable error range. Therefore, if the above gradation coefficient V _q (t) is obtained for one color q (for example, Y), it is possible to evaluate the spectral density for each color (for example, M, C, S1, S2) of the ink ribbon 11. , and its tone coefficient V _q (t) can be used.

However, when the types of dyes are different (such as when an ink layer of dye ink and an ink layer of pigment ink are mixed on the ink ribbon 11), the above gradation coefficient V _q (t) is obtained for each type of dye. may In the following description, it is assumed that the dyes of each color are of the same type, and the index q of the gradation coefficient V _q (t) is omitted and expressed as V(t). Information about the gradation coefficient V(t) can be stored in advance in the storage device 105 as information indicating gradation characteristics.

When the information on the gradation coefficient V(t) is obtained, the data processing unit 144 calculates the spectral density D _q (100, λ) during solid printing and the received image based on the above equations (5) and (6). From the spectral density D _p (λ) of the paper 12, the halftone spectral density F _q (t,λ) can be calculated.

The above spectral density F _q (t, λ) is converted from the definition of spectral density (see formula (1) above) to spectral reflectance R _q (t, λ) based on formula (7) below. can do. Further, by using known light source spectral distributions and color matching functions, each component of the colorimetric value corresponding to the spectral reflectance R _q (t, λ) (for example, X, Y, Z in the XYZ color system, It is possible to calculate the color values of the standard color space such as L ^* , a ^* , b ^* of the L ^* a ^* b ^* color system. That is, a correspondence relationship between the device set value t and the colorimetric values of the standard color space is obtained.

_Rq (t,λ)=10 ^-Fq(t,λ)
… (7)

The correspondence relationship between the device set value t and the colorimetric values of the standard color space may be stored in the storage device 105 in advance. In the above description, the intermediate gradation spectral density F _q (t, λ) is obtained by calculation, but the intermediate gradation spectral density F _q (t, λ) may be obtained by actual measurement.

(color reduction characteristic)
Up to this point, we have discussed the non-linear characteristics (gradation characteristics) that appear in single-color printing. Since a phenomenon (hereinafter referred to as "kickback") occurs in which the light is pulled out of the image receiving paper 12, it is necessary to consider the nonlinear characteristics associated with this phenomenon. In the following description, the property that the preprinted dye is reduced by kickback may be referred to as "color reduction property".

The above subtractive color characteristics are obtained by preparing two different color materials q ₁ and q ₂ and actually printing patches while changing the device set values t ₁ and t ₂ used when transferring the color materials q ₁ and q ₂ . , obtained by measuring the spectral reflectance R _q1,q2 (t ₁ ,t ₂ ,λ) of each patch. In the following description, the dye _q1 that is transferred first may be referred to as the preprinted dye, and the dye _q2 that is transferred over the preprinted dye _q1 may be referred to as the postprinted dye.

The mixed color spectral densities D _q1,q2 (t ₁ ,t ₂ ,λ) are defined by the following equation (8). Also, the spectral densities D _{q1, q2} (t _{1 ,} t ₂ , λ) are the dye transfer amounts D _q1 (t ₁ , _λ ) and D _q2 (t ₂ , λ), it is given by the following equation (9).

W(t ₁ , t ₂ ) included in the following formula (9) is an index (hereinafter referred to as a color reduction coefficient) indicating the amount of decrease in the preprinted dye q ₁ due to kickback. The color reduction coefficient W(t ₁ , t ₂ ) is expressed as a function using the device setting value t ₁ used when transferring the pre-printing dye q ₁ and the device setting value t ₂ used when transferring the post-printing dye q ₂ as parameters. be done. This is because the magnitude of kickback depends on the amount of preprinted dye _q1 that has already permeated the image receiving paper 12 and the amount of heat applied when the postprinted dye _q2 is transferred.

As described above, the spectral densities D _q1 (t ₁ , λ) and D _q2 (t ₂ , λ) during monochromatic transfer are obtained by calculation or actual measurement. Therefore, from the measured values of the spectral reflectance R _q1,q2 (t ₁ ,t ₂ ,λ), the color reduction coefficient W(t ₁ ,t ₂ ) is calculated based on the following equations (8) and (9). be able to.

D _q1,q2 (t ₁ ,t ₂ ,λ)=−log ₁₀ R _q1,q2 (t ₁ ,t ₂ ,λ)−D _p (λ)
... (8)
Dq1 _,q2 ( _t1 , _t2 ,λ)=W( _t1 , _t2 )× _Dq1 ( _t1 ,λ)+ _Dq2 ( _t2 ,λ)
... (9)

As an example, the calculation result of the color reduction coefficient W(t ₁ , t ₂ ) is shown in the lower part of FIG. The vertical axis of the graph shown in the lower part of FIG. 9 indicates the value of (W(t ₁ , t ₂ )−1)×V(t1), and the horizontal axis indicates the device set value t ₂ . From this graph, it can be seen that the device set value t ₁ is large (the amount of the pre-printed dye q ₁ penetrating the image receiving paper 12 is large) and the device set value t ₂ is large (the amount of heat applied when the post-printed dye q ₂ is transferred ), the decrease in the preprinting dye _q1 increases.

Note that the spectral reflectance R _{q1, q2} (t ₁ , t ₂ , λ) depends on the reflection component due to the color mixture of the pre-printed dye q ₁ and the post-printed dye q ₂ and the color of the image receiving paper 12 (color of the base color). and a reflective component. Therefore, the actually measured spectral density F _q1,q2 (t ₁ ,t ₂ ,λ) of the mixed color (color including the background color) is given by the following equation (10).

Fq1 _,q2 ( _t1 , _t2 ,λ)= _Dq1,q2 ( _t1 , _t2 ,λ)+ _Dp (λ)
... (10)

Data of the color reduction coefficient W(t ₁ , t ₂ ) is stored in the storage device 105 as information indicating color reduction characteristics. Once the information indicating the subtractive color characteristics is obtained, the spectral densities D _q1 (t ₁ , λ) of the pre-printed dye q ₁ and the spectral densities of the post-printed dye q ₂ are calculated based on the above equations (9) and (10). From D _q2 (t ₂ , λ), the mixed color spectral density F _q1,q2 (t ₁ ,t ₂ ,λ) can be calculated in consideration of the kickback effect.

Here, a case where dyes of three or more colors are superimposed and transferred will be described. In the following description, the dye to be transferred to the n- _{th (} n= ₁ , . First, the case where N is 3 will be specifically described.

By referring to the information on the subtractive color characteristics described above, the spectral density (D _q1 (t _1R , λ)=W(t ₁ , t ₂ )×D _q1 (t ₁ , λ)) is obtained. where t _1R is the device setting corresponding to the spectral density of the first residual dye. The device set value t _1R can be identified by searching for a gradation coefficient V(t _1R ) that satisfies Equation (11) below.

V( _t1R )=Av _[lambda] {W( _t1 , _t2 )* _Dq1 ( _t1 ,[lambda])/ _Dq1 (100,[lambda])}
…(11)

Once the above device set value t _1R is obtained, the color reduction coefficient W(t _1R , t ₃ ) for the amount by which the first dye is reduced by the third dye transfer can be obtained from the color reduction characteristic information. Similarly for the second dye, a color reduction coefficient W(t ₂ , t ₃ ) for the amount of dye that is reduced by the third dye transfer is obtained. The spectral densities D _{q1 , q2, q3} (t ₁ , t ₂ , t ₃ , λ) for the mixed colors of three colors are given by the following equation (12). The actually measured spectral densities F _{q1 , q2, q3} (t ₁ , t ₂ , t ₃ , λ) of mixed colors (colors including the base color) are given by the following equation (13).

_Dq1,q2,q3 ( _t1 , _t2 , _t3 ,λ)=W( _t1R , _t3 )× _Dq1 ( _t1R ,λ)+W( _t2 , _t3 )× _Dq2 ( _t2 , λ)+D _q3 (t ₃ , λ)
…(12)
_Fq1,q2,q3 ( _t1 , _t2 , _t3 ,λ)= _Dq1,q2,q3 ( _t1 , _t2 , _t3 ,λ)+ _Dp (λ)
…(13)

By repeating the _same procedure as above, spectral densities F _{q1 , . . . , qN} (t ₁ , . Once the spectral densities F _{q1,..., qN} (t ₁ ,..., t _N , λ) are obtained, the spectral reflectances R _{q1,..., qN} (t ₁ ,..., t _N , λ) can be calculated. When the spectral reflectance is obtained, colorimetric values (for example, X, Y, and Z in the XYZ color system, L ^* in the L ^* a ^* b ^* color system, a ^* , b ^* , etc.) can be calculated.

_Rq1,...,qN ( _t1 ,..., _tN ,λ) = 10 ^{-Fq1,...,qN(t1,...,tN,λ)}
…(14)

By applying the above method, the correspondence relationship between the device setting values t ₁ , . . . , t _N and the colorimetric values of the standard color space is obtained. From this correspondence relationship, for any combination _of colors set on the ink ribbon 11, while changing the device set values t ₁ , . can be calculated. In other words, computer simulation makes it possible to calculate the color gamut for any combination of colors.

Since the above computer simulation takes into account the color reduction characteristics, a color gamut corresponding to the print result of the thermal transfer printer 10 can be obtained more faithfully.

For example, a computer simulation that considers the color reduction characteristic is called simulation A, and a computer simulation that does not consider the color reduction characteristic is called simulation B. In this case, for an ink ribbon having a certain color combination (hereinafter referred to as a ribbon sample), the color gamut A calculated by the simulation A and the color gamut R reproduced by actually printing patches with the thermal transfer printer 10 The difference is smaller than the difference between color gamut B and color gamut R calculated in simulation B. In other words, the simulation A is closer to the actual print result.

Simulation B corresponds to the case where the color reduction coefficient W is set to a fixed value of one. Using computer simulations with more faithful color reproduction allows for better spot color selection.

The spot color selection method according to the present embodiment will be further described below with reference to FIGS. 10 and 11. FIG. FIG. 10 is a first flowchart for explaining the spot color selection method according to this embodiment. FIG. 11 is a second flowchart for explaining the spot color selection method according to this embodiment.

Among the steps shown in FIGS. 10 and 11, the arithmetic processing is executed by a computer (hereinafter referred to as simulation device 30) having the same configuration (eg, processor and memory) as the hardware illustrated in FIG. sell. The simulation device 30 is, for example, a computer such as a PC, workstation, or server device.

(S201) The simulation device 30 sets the number M of spot colors and the sample colors _q1 and _q2 . For example, the simulation device 30 sets the number M of spot colors and the sample colors q ₁ and q ₂ according to the input of the user executing the computer simulation. M is an integer of 1 or more. The sample colors q ₁ and q ₂ are colors used when calculating the tone coefficient V and color reduction coefficient W described above, and are selected from basic colors and candidate colors. However, q ₁ and q ₂ are different colors.

(S202-S205) Steps S202-S205 include work processes performed by the user using the thermal transfer printer . The simulation device 30 executes the process of calculating the spectral density from the spectral reflectance based on the above equation (1).

S202 is a work step for preparing candidate color dyes that are candidates for spot colors. The number Q of candidate color dyes is M or more. For convenience of explanation, it is assumed that S1, . . . , SQ are prepared as candidate colors. In S203, the spectral reflectance is measured using the patch printed on the image receiving paper 12 by the thermal transfer printer 10, and the spectral density D _p (λ) of the background color (see the above equation (2)), the basic color and This is a work process for acquiring spectral densities D _q (100, λ) (q=Y, M, C, S1, . . . , SQ) during solid printing for each of the candidate colors.

S204 is a work step of printing patches of a single color (sample color q ₁ ) using the thermal transfer printer 10 while changing the device set value t. For example, patches corresponding to each device setting value t are printed while changing between 10% and 90% in increments of 10%. S205 is a work step of measuring the spectral reflectance of each patch printed in S204 and obtaining the spectral density D _q (t, λ) (q=q ₁ ) corresponding to each device setting value t.

Through the work processes of S202 to S205, the spectral density D _p (λ) of the background color, the spectral density D _q (100, λ) (q=Y, M, C, S1, . . . , SQ) during solid printing, and the spectral density D _q (t, λ) (q=q ₁ ) corresponding to the device setting t. Note that the spectral density D _q (t, λ) may be expressed as a continuous function by interpolation processing (such as spline interpolation) by the simulation device 30 .

(S206) The simulation device 30 calculates the gradation coefficient V(t) based on the above equations (3) and (4).

(S207, S208) S207 uses the thermal transfer printer 10 to print mixed color (q ₁ +q ₂ ) patches while changing the device set values t ₁ and t ₂ corresponding to the sample colors q ₁ and q ₂ , respectively. It is a work process to do. For example, patches corresponding to each pair of device setting values t ₁ and t ₂ are printed while changing between 10% and 100% in increments of 10%.

In S208, the spectral reflectance of the patch printed in S207 is measured, and spectral densities D _q1,q2 ( _t1 , _t2 , λ) corresponding to each set of device setting values _t1 , _t2 are acquired. It is a process. Note that the spectral densities D _{q1 , q2} (t ₁ , t ₂ , λ) may be expressed as continuous functions by interpolation processing (such as spline interpolation) by the simulation device 30 . Hereinafter, for convenience of explanation, the printing of the sample color _q1 will be referred to as the pre-printing, and the printing of the sample color _q2 will be referred to as the post-printing.

(S209) The simulation device 30 uses the spectral density D _q (t, λ) for monochrome printing acquired in S205 to calculate the color reduction coefficient W(t ₁ , t ₂ ) based on the above equation (9). do.

(S210) The simulation device 30 selects a candidate color set (c ₁ , . . . , c _M ) including M candidate colors from the prepared Q candidate colors. It should be noted that since the processes after S210 are repeatedly executed, an unselected candidate color set is selected in S210.

(S211) The simulation device 30 uses the gradation coefficient V(t) and the spectral density D _q (100, λ) during solid printing to calculate the colors Y, M, C, Compute the monochromatic spectral densities D _q (t _q , λ) (q=Y, M, C, c ₁ , _. . . , c _M ) for each of c ₁ , . _Further , _the simulation _device 30 calculates the spectral reflectance _R Compute _q (t _q , λ).

Further, _the simulation device 30 calculates from _{ Y, M, C, c ₁ , _. . . , c _M } _to Compute the spectral densities of a mixture of two or more selected colors. For example, the spectral densities D _c1,c2 (t _c1 ,t _c2 ,λ) of the mixture of candidate colors c ₁ and c ₂ are calculated based on the above equation (9). The spectral density of any two-color mixture is similarly calculated based on equation (9) above.

The spectral densities D _{c1,c2,c3 (} t _c1 ,t _c2 ,t _c3 ,λ) of the mixture of the candidate colors c ₁ ,c 2 ,c ₃ are obtained by calculating the device settings corresponding to the residual dye (the above equation ( 11)) is then calculated based on equation (12) above. The spectral densities of any three color mixtures are similarly calculated based on equations (11) and (12) above. The spectral densities of mixed colors of four or more colors are also calculated in a similar manner. Then, the simulation device 30 calculates the spectral reflectance from the spectral density of the mixed color.

(S212) The simulation device 30 converts each spectral reflectance calculated in S211 into a colorimetric value of the standard color space using the known light source spectral distribution and color matching function. Note that a known method can be applied as a method of obtaining a colorimetric value from the spectral reflectance.

(S213) The simulation device 30 identifies the shape and size of the color gamut from the distribution of colorimetric values in the standard color space.

For example, the simulation device 30 uses a mesh-like region obtained by connecting adjacent color values with straight lines or smooth curves among the color values discretely plotted in the standard color space as the shape of the color gamut. Identify. The simulation device 30 also calculates the volume of the color gamut whose shape is specified, and specifies the calculated volume as the size of the color gamut. As a modification, instead of the volume of the color gamut, the area of the cross section obtained by cutting the color gamut along a predetermined plane may be used.

(S214) The simulation device 30 determines whether the color gamut shape satisfies a predetermined condition. Predetermined conditions include, for example, no deep unevenness on the surface of the color gamut, expansion of the color gamut in a specific area of the standard color space, target color gamut (for example, 10-color IJP color gamut and silver halide print). color gamut) is equal to or less than a threshold in all areas. If the gamut shape satisfies the predetermined condition, the process proceeds to S215. On the other hand, if the color gamut shape does not satisfy the predetermined condition, the process proceeds to S216.

(S215) If the color gamut size specified this time in S213 is larger than the color gamut size (already held color gamut size) specified in S213 in the past, the simulation device 30 changes the color gamut size to the already held color gamut size. Instead, the color gamut size specified this time is held. If the already held color gamut size is larger than the currently specified color gamut size, the simulation device 30 continues to hold the already held color gamut size.

(S216) The simulation device 30 determines whether or not there is an unselected candidate color set. If there is an unselected candidate color set, the process proceeds to S210. On the other hand, if there is no unselected candidate color set, the process proceeds to S217.

(S217) The simulation device 30 stores information indicating a candidate color set (candidate color set for the maximum color gamut) corresponding to the retained color gamut size. That is, a combination of candidate colors that can effectively expand the color gamut using a limited number N of spot colors is selected. When the process of S217 is completed, the series of processes shown in FIGS. 10 and 11 ends.

[5. Modification]
Here, a modified example of the ink ribbon according to this embodiment will be described with reference to FIG. 12 . FIG. 12 is a diagram schematically showing a modification of the ink ribbon according to this embodiment.

As already described, the configuration of the ink ribbon to which the technology of this embodiment can be applied is not limited to the example shown in FIG. be. Although five modifications (modifications #1 to #5) are shown in FIG. 12, modifications other than these naturally belong to the technical scope of the present embodiment.

Modification #1 is an example in which the special color ink layer S2 is omitted and a K (black) layer, which is an achromatic ink layer, is added. Modification #2 is an example in which the special color ink layers S1 and S2 are arranged in front of the basic color ink layers Y, M, and C (in front along the winding direction of the ink ribbon).

Modification #3 is an example in which the basic color ink layers Y, M, and C are arranged so as to be sandwiched between the special color ink layers S1 and S2. Modification #4 is an example in which a chromatic ink layer (basic color ink layer and special color ink layer) is arranged before the K layer. Modification #5 is an example in which the basic color ink layers and the special color ink layers are alternately arranged.

Dividing the area into the front and back by the special color ink layer group and the basic color ink layer group as in Modifications #1 to #3 facilitates control when applying the basic color print mode. For example, in the case of modification #2, if the ink ribbon is sent to the top of the Y layer after printing for one sheet is completed, the Y layer, M layer, C layer, and OC layer are arranged continuously. Printing with only the basic colors can be executed simply by carrying out the same transport control as with a normal ink ribbon.

Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to the configuration examples disclosed herein. It is obvious that a person skilled in the art can conceive of various modifications or modifications within the scope of the claims, which naturally belong to the technical scope of the present technology.

REFERENCE SIGNS LIST 10 thermal transfer printer 30 simulation device 101 thermal head 102 paper feed mechanism 103 ribbon transport mechanism 104 controller 105 storage device 141 paper feed controller 142 transport axis controller 143 head controller 144 data processor 151 multicolor profile 152 basic color profile

Claims (10)

A thermal transfer printer using an ink ribbon having an ink layer of a basic color group including yellow, magenta, and cyan and an ink layer of a chromatic color different from the basic color group, wherein the combination of chromatic colors in the ink ribbon is a chromatic color combination that achieves the largest gamut size in said thermal transfer printer , selected from among chromatic color combinations composed of up to a preset number N of available chromatic colors; N is an integer of 2 or more, and the thermal transfer printer is
a thermal head for heating the ink ribbon;
a storage unit storing first profile information for reproducing a designated color by mixing colors included in the basic color group and the chromatic colors;
A thermal transfer printer, comprising: a controller that controls the thermal head based on the first profile information so that the specified color is expressed on a print medium. The combination of chromatic colors in the ink ribbon is L ^* a ^* b ^* a in color space ^* -b ^* A combination of chromatic colors whose color gamut is extended in the second and fourth quadrants of the plane,
A thermal transfer printer according to claim 1. The combination of chromatic colors in the ink ribbon includes green and blue.
A thermal transfer printer according to claim 2. The combination of chromatic colors in the ink ribbon is determined by a computer simulation that takes into account the color reduction characteristic in which the amount of the first dye decreases when the second dye is transferred over the first dye that has already been transferred to the printing medium. 2. The thermal transfer printer according to claim 1, wherein the first profile information selected using and created based on the selection result is stored in the storage unit. the storage unit stores second profile information for reproducing the specified color by mixing colors included in the basic color group;
The controller controls the thermal head using the first profile information when the operation mode of the thermal transfer printer is set to the first operation mode, and the operation mode of the thermal transfer printer is set to the second operation mode. 5. The thermal transfer printer according to any one of claims 1 to 4, wherein the thermal head is controlled using the second profile information when the operation mode is set. When the operation mode of the thermal transfer printer is set to the second operation mode, the control unit uses only the ink layer of the basic color group of the ink ribbon to print the specified color on the print medium. 6. The thermal transfer printer according to claim 5 , wherein said thermal head is controlled based on said second profile information as expressed by: a storage unit storing profile information for reproducing a specified color by mixing a basic color group including yellow, magenta, and cyan with a chromatic color different from the basic color group;
a control unit for generating , based on the profile information, information on the amount of dye used to reproduce the designated color for each color of the basic color group and each of the chromatic colors;
wherein the control unit provides information on the amount of the dye to a thermal transfer printer that prints using an ink ribbon having the ink layer of the basic color group and the ink layer of the chromatic color, The chromatic color combination is a chromatic color combination that achieves the largest color gamut size in said thermal transfer printer, selected from chromatic color combinations consisting of up to a preset number N of available chromatic colors. and N is an integer greater than or equal to 2 Controller. Obtaining profile information for reproducing a specified color by mixing a basic color group including yellow, magenta, and cyan with a chromatic color different from the basic color group, and used in a thermal transfer printer. The combination of chromatic colors in the printed ink ribbon is selected from a set of chromatic color combinations consisting of no more than a preset number N of available chromatic colors to achieve the maximum color gamut size in said thermal transfer printer. is a combination of chromatic colors, and N is an integer of 2 or more ;
For each color of the basic color group and each chromatic color in the ink ribbon , information on the amount of dye used to reproduce the designated color is generated based on the profile information, and the ink layer of the basic color group and the providing the dye amount information to the thermal transfer printer that prints using the ink ribbon having a chromatic ink layer;
A data processing method for causing a computer to execute a process including In order to improve the color reproducibility of thermal transfer printing using an ink ribbon having an ink layer of a basic color group including yellow, magenta, and cyan, and an ink layer of a chromatic color different from the basic color group , A method of selecting a coloring , said method comprising:
Chromatic colors in the ink ribbon using a computer simulation that takes into account a color reduction characteristic in which the amount of the first dye is reduced when the second dye is transferred over the first dye that has already been transferred to the printing medium. wherein the combination of chromatic colors in the ink ribbon is selected from a set of chromatic colors consisting of no more than a preset number N of available chromatic colors, the thermal transfer A combination of chromatic colors that achieves the maximum color gamut size in printing, and N is an integer of 2 or more ;
A method, including In order to improve the color reproducibility of thermal transfer printing using an ink ribbon having an ink layer of a basic color group including yellow, magenta, and cyan, and an ink layer of a chromatic color different from the basic color group , A device for selecting a coloration , said device comprising:
Chromatic colors in the ink ribbon using a computer simulation that takes into account a color reduction characteristic in which the amount of the first dye is reduced when the second dye is transferred over the first dye that has already been transferred to the printing medium. wherein the chromatic color combinations in the ink ribbon are selected from chromatic color combinations composed of no more than a preset number N of available chromatic colors. is a combination of chromatic colors that achieves the largest gamut size in , where N is an integer of 2 or greater .

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