JP2007313815A - Thermal transfer recording apparatus, image forming method, and printed matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal recording apparatus and the like, which reduce unevenness in printing, caused by step heights of halftone dots of CMYK, reduce material costs and a printing time, and bring about the proper reproducibility of a color tone. <P>SOLUTION: A control portion 9 of a thermal printer 1 performs CMYK-CMY conversion processing for deleting a K (black) component of input CMYK image data 3, and subsequently, performs resolution conversion and gradation conversion. Furthermore, the control portion 9 applies shift processing, halftone dot processing, reverse shift processing and thermal storage correction processing, and prints acquired image data. The CMYK-CMY conversion processing is performed by a method for adding the K component to CMY depending on the magnitude of the component value of the CMY, or a method in which the K component is deleted by color matching brought about by the profile conversion of CMYK-Lab and Lab-CMYK. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thermal recording apparatus or the like that reduces printing unevenness and has good color tone reproducibility.

  A thermal printer is a device that heats the back of an ink ribbon superimposed on a recording sheet with a thermal head and thermally transfers the ink on the ink ribbon onto the recording sheet for printing. The ink ribbon is a thermal transfer sheet having a heat-meltable colored ink layer, and the recording sheet is an image receiving sheet such as an intermediate transfer material (polycarbonate film), paper, or a plastic sheet.

  The thermal head is composed of a plurality of heating resistors formed in a line on the substrate. The thermal printer includes a plurality of ink ribbons, and color printing can be performed by transferring the inks of a plurality of color ink ribbons on the same position of the recording sheet. For example, a plurality of ink ribbons are installed in a rotating manner, and the ink ribbon for performing thermal transfer is moved to the position of the thermal head. Further, the recording paper transport device transports the recording paper to the position of the thermal head that is the printing position, and a predetermined printing range of the recording paper is printed. When image data is input to the thermal head, energy corresponding to the image data is applied to the thermal head, and an image is output to the recording sheet.

  Conventionally, in order to obtain smooth gradation images that are free from color shifts, blurring, and the effects of heat accumulated in the thermal head, thermal recording devices that perform overprinting in search of optimum printing energy, and various colors A thermal recording apparatus that performs a shift process on the image data and performs a double-tone printing, and a method for correcting the thermal storage of the thermal head by estimating from the image data have been proposed (see Patent Document 1, Patent Document 2, and Patent Document 3). ).

JP 2006-62084 A Japanese Patent Application No. 2005-319583 JP 05-169709 A

  However, these methods use cyan (C), magenta (M), yellow (Y), and black (K) inks to obtain a full-color print image. Further, in the method of Patent Document 2, in order to perform double-tone printing, the above-described inks of the respective colors are printed twice. Therefore, as shown in FIG. 15, even if an attempt is made to print a uniform CMYK gray image (left figure), printing unevenness occurs as shown in the right figure due to the influence of the steps of the CMYK halftone image. There is. In addition, in the case of double-tone printing, since four color inks are used twice each, there is a problem that the ink material increases and the printing time also takes longer.

  Further, when CMYK-RGB conversion for printing a CMY image from which black (K) has been deleted is used to reduce the influence of the steps in the halftone image, the color tone of the print image is yellowish, and the CMYK-reverse UCR conversion is used. There is a problem that a CMY image becomes reddish.

  The present invention has been made in view of such problems. The object of the present invention is to reduce unevenness in printing due to steps in CMYK halftone dots, reduce material costs and printing time, and reproducibility of color tone. It is to provide a heat sensitive recording apparatus and the like.

  According to a first aspect of the present invention, the black (K) component is removed from the first image data, the second image data is generated, and the resolution of the second image data is increased. Shift processing is performed on the third image data obtained by the conversion, gradation conversion, and color separation to generate fourth image data and fifth image data, and the fourth and fifth image data are generated. 8th image data and 9th image data are generated by performing reverse shift processing on the 6th image data and 7th image data that have been subjected to halftone dot conversion processing on the 8th image data, and the 8th image data And heat storage correction processing is performed on the ninth image data, tenth image data and eleventh image data are generated, and the tenth image data and the eleventh image data are heat-sensitive by a thermal head. By recording device Superimposed on the photographic material is a photographic material which is characterized in that it is obtained by printing.

  According to a second aspect of the present invention, there is provided a thermal recording apparatus having a thermal head, wherein the second image data is generated by removing black (K) components from the first image data and generating second image data. Generating a third image by performing resolution conversion, gradation conversion, and color separation on the image, and shifting the third image data to generate fourth image data and fifth image data Means for performing halftone dot conversion processing on the fourth image data and the fifth image data, and generating sixth image data and seventh image data, and the sixth image data and the seventh image data. Means for reversely shifting the image data to generate the eighth image data and the ninth image data, and performing a heat storage correction process on the eighth image data and the ninth image data to obtain the tenth image Raw data and eleventh image data Means for a thermal recording apparatus characterized by comprising, means for printing superimposed image data of the image data and the 11 of the margin 10 as printed matter.

Here, the means for removing the black (K) is to change the component values of black (K) to cyan (C) for cyan (C), magenta (M), and yellow (Y) as other colors. , Magenta (M) and yellow (Y) are added according to the component values, and the black (K) component values are deleted.
Less when the component values of cyan (C), magenta (M), and yellow (Y) are large, and black (K) when the component values of cyan (C), magenta (M), and yellow (Y) are small. It is preferable to add a large number of component values.

That is, black (K) is expressed by adding the component value of black (K) to cyan (C), magenta (M), and yellow (Y), which are other colors. At this time, for example, when the component value of cyan (C) is large, the component value of black (K) added to cyan (C) is decreased.
In this way, the CMY image data from which the black (K) component has been deleted is subjected to resolution conversion, gradation conversion, shift processing for double tone, halftone processing, reverse shift processing, and heat storage correction processing, thereby printing. A CMY image with good color tone reproducibility can be obtained. Also, since black (K) is not printed, the ink material and the printing time can be reduced.

  Further, as means for removing the black (K), a profile table for printing and a profile table of the thermal recording apparatus are used, and the first image data is converted into cyan by the profile conversion of the first image data. (C), magenta (M), and yellow (Y) values may be converted.

In the printing profile table, the dot area ratios of cyan (C), magenta (M), yellow (Y), and black (K) are 0%, 20%, 40%, 60%, and 80%, respectively. , A CMYK-Lab conversion table generated by measuring a color chart by 1296 printings in the case of 100% in the Lab color space.
In the profile table of the thermal recording apparatus, the dot area ratios of cyan (C), magenta (M), and yellow (Y) are 0%, 20%, 40%, 60%, 80%, and 100, respectively. %, The black (K) halftone dot area ratio is 0%, 216 color charts by thermal transfer printing are measured in Lab space, and the obtained 216 Lab space measurement values are obtained as black (K) It is a Lab-CMYK conversion table generated by embedding the point area ratios in 20%, 40%, 60%, 80%, and 100%.

That is, the image data of the original image (offset printing) is converted into image data in the Lab color space using the CMYK-Lab conversion table, and the image data in the Lab color space is converted into CMY image data using the Lab-CMYK conversion table. Thus, the black (K) component is deleted.
In this way, the CMY image data from which the black (K) component has been deleted is subjected to resolution conversion, gradation conversion, shift processing for double tone, halftone processing, reverse shift processing, and heat storage correction processing, thereby printing. In addition, a color-matched print image is formed on the offset print image, and printing with CMY reduces the effect of steps in the halftone dot image. Furthermore, since black (K) is not printed, the ink material and print time are also reduced. I can plan.

  According to the present invention, it is possible to provide a thermal recording apparatus and the like that can reduce printing unevenness due to the steps of CMYK halftone dots, reduce material costs and printing time, and have good color tone reproducibility.

  Hereinafter, a first preferred embodiment of a thermal recording apparatus and the like according to the present invention will be described in detail with reference to the accompanying drawings.

(1. System configuration)
First, the configuration of a thermal recording apparatus (thermal printer 1) according to an embodiment of the present invention will be described with reference to FIG.
FIG. 1 is a diagram illustrating a configuration of the thermal printer 1.

  As shown in FIG. 1, the thermal printer 1 heats the back of an ink ribbon (not shown) superimposed on a recording paper (not shown) with a thermal head (not shown) so that the ink on the ink ribbon is recorded on the recording paper. This is a device that prints by thermal transfer to the printer. The thermal printer 1 includes an image input unit 5, a storage unit 7, a control unit 9, a printing unit 11, and the like, which are connected by a bus 13.

  The image input unit 5 receives image data 3 to be printed. The storage unit 7 stores input image data 3, temporarily stored data being calculated, processed image data, parameters for image processing, and the like. The control unit 9 includes a CPU (central processing unit) that executes a program and a memory such as a ROM (read only memory) and a RAM (random access memory) for storing program instructions or data. The unit 5 is instructed to capture the image data 3, the image data 3 is subjected to image processing, the processed image data is sent to the printing unit 11, and a printing instruction is performed.

Although not shown, the printing unit 11 includes a thermal head composed of a plurality of heating resistors formed in a row on a substrate, a thermal head driving unit, and the like. When the image data to be printed is sent by the instruction of the control unit 9, the printing unit 11 applies energy according to the pixel value to the thermal head, whereby the applied portion of ink melts and adheres to the recording paper, and the output image 15 is output. If the pixel value is large, the print recording density is high. Conversely, if the pixel value is small, the print recording density is low.
There are four types of ink ribbons, cyan C, magenta M, yellow Y, and black K, and color printing is performed by transferring these inks in a superimposed manner.

  FIG. 2 is a diagram showing the relationship between the configuration of the thermal printer 1 in FIG. 1 and the processing content. The image input unit 5 performs image reading 21 of the image data 3, records the read image in the image memory 27 of the storage unit 7, and sends it to the control unit 9 at the same time. The control unit 9 performs image processing 23 on the image data 3.

  The image processing 23 is processing steps such as processing for deleting black (K) (CMYK-CMY conversion), resolution conversion processing, gradation conversion processing, image shift processing, halftone processing, image reverse shift processing, and heat storage correction processing. Yes, the image data in the image memory 27 of the storage unit 7 is subjected to image processing using each processing parameter 29 to obtain final image data. The image data being processed is stored in the image memory 27 of the storage unit 7. The control unit 9 sends the finally obtained image data to the printing unit 11, and the printing unit 11 performs the image printing 25.

(2. Flow of image processing)
Next, the flow of the image processing 23 according to the present embodiment will be described with reference to FIGS. FIG. 3 is a flowchart showing the flow of the image processing 23, and FIG. 4 is a diagram showing details of the storage unit 7.
The image processing 23 is a program composed of various processes to be described later, and is stored as an image processing program 31 in the storage unit 7 as shown in FIG. In addition to the image processing program 31, the storage unit 7 includes an image memory 27 and processing parameters 29. Although not shown, the storage unit 7 also stores other control programs, control parameters of the printing unit 11 such as a thermal head, and the like.

Image data 3 read by the image input unit 5 of the thermal printer 1 is stored in the image memory 27 of the storage section 7 as the image D _1, the image processing 35 is executed to the image data D ₁ to the original. The image data _{D 1} is C (cyan), magenta (M), yellow (Y), the image data of each color black (B).
First, a process (CMYK-CMY conversion) for deleting black (K) in the CMYK image data D ₁ is performed to generate image data D ₂ and save it in the image memory 27 of the storage unit 7 (step 101). . Image data _{D 2} is, cyan (C), magenta (M), which is three colors of data comprising a yellow (Y).
Details of the CMYK-CMY conversion process will be described later. The parameters used for the CMYK-CMY conversion process are stored in advance as the CMYK-CMY conversion parameter 41 in the processing parameter 29 area of the storage unit 7.

Next, the control unit 9 performs resolution conversion processing and gradation conversion of the image data D ₁ in accordance with the resolution of the printing unit 11 for the image data D ₂ to generate image data D ₃ , and a storage unit 7 in the image memory 27 (step 102).

Here, the resolution of the printing unit 11 is, for example, 600 dpi (dots per inch), and is stored in the processing parameter 29 of the storage unit 7 as the resolution conversion parameter 43 in advance.
In the gradation conversion process, in the case of a double tone in which the same color is separated into two, shifted, and overprinted, ideally, it is only necessary to perform gradation conversion of 50%. Since a gap is formed when overprinting is performed, gradation conversion of 60 to 65% is performed. The optimum gradation conversion varies depending on the resolution of the printing unit 11, the number of lines of the print image, and the like. Therefore, the gradation conversion parameter 45 may be stored in advance in the processing parameter 29 of the storage unit 7.
For example, 60% is determined for a resolution of 600 dpi and the number of lines is 60 lpi (lines per inch) and 75 lpi, and 65% is determined for 100 lpi and 120 lpi, and is stored in the processing parameter 29 of the storage unit 7. Search for and use tone conversion parameters that are suitable at times.

The control section 9 of the thermal printer 1 performs image shift processing for the image data _{D 3} of the respective colors after gradation conversion (CMY) (step 103), generates a _{D 4} and the image data _{D 5,} the storage unit 7 Stored in the image memory 27.

As the image shift process (step 103), for example, a shift process for shifting with a double tone is applied.
In shift processing for shifting the double tone shifts the pixels of the image data D ₃ to the right by L1 pixels a predetermined respectively, further shifted by L2 pixels determined in advance in a downward direction, and generates the image data D ₅ . In order to double tone, it generates the image data D ₄ is not performed shift processing. Image data D ₄ is the same data as the image data D _3. The generated image data D ₄ and image data D ₅ are stored in the image memory 27 of the storage unit 7.

Here, L1 and L2, which are the number of pixels shifted to the right and down, differ depending on the resolution and the number of lines of the thermal head 23. The predetermined shift pixel numbers L1 and L2 are stored in the processing parameter 29 of the storage unit 7 as the shift processing parameter 47.
For example, when the resolution of the thermal head is 600 dpi, L1 = 5 (5 pixels to the right) if the number of lines is 60 lpi, L2 = 5 (5 pixels to the bottom), and L1 = 4 (4 pixels to the right) if 75 lpi. , L2 = 4 (4 pixels down), L1 = 3 (3 pixels down to the right) if 100 lpi, L2 = 3 (3 pixels down), L1 = 2 (2 pixels to the right) if 120 lpi, L2 = 2 (2 pixels downward) is determined in advance and stored in the processing parameter 29 as the shift processing parameter 47.

Further, as the image shift process (step 103), a shift process for each color and a shift process for shifting with a double tone may be combined.
In this case, the image data D _3, performs first shift processing of each color, the image data D _4.
The shift processing for each color, the color (C, M, Y) predetermined number of pixels for each _{(L C, L M, L} Y) are those performing the shifting amount, cyan image data _{D 5} (C the image data L _C pixels), the image data of magenta (M) is L _M pixels, the image data of yellow (Y) shifted to the respective right by L _Y pixels, and generates image data D _4.

Further, the shift processing for double-tone above performed on the image data D _4, and generates the image data D _5.
That is, by shifting the pixels of the image data D ₄ to the right by L1 pixels a predetermined respectively, further shifted by L2 pixels determined in advance in a downward direction, the image data D _5. The generated image data D ₄ and image data D ₅ are stored in the image memory 27 of the storage unit 7.

Here, the shift pixel numbers L _C , L _M , and L _{Y for each} color differ depending on the resolution and the number of lines of the thermal head 23. The predetermined shift pixel numbers L _C , L _M , and L _Y are stored in the processing parameter 29 of the storage unit 7 as the shift processing parameter 47.
For example, when the resolution of the thermal head is 600 dpi, if the number of lines is 60 lpi or 75 lpi, L _C = 2, L _M = 0, L _Y = 1, and 100 lpi, L _C = 1, L _M = 0, L _Y = The shift processing parameter 47 is determined in advance as 1.

After the image shift processing, the control unit 9 performs halftone dot processing on the image data D ₄ and D ₅ to generate image data D ₆ and image data D ₇ respectively (step 104), and stores them in the image memory 27 of the storage unit 7. Store.
The halftone dot matrix size varies depending on the resolution of the thermal head and the number of lines of the image. For example, when the resolution is 600 dpi, the line number is 60 lpi, 10 × 10 pixels, 75 lpi is 8 × 8 pixels, 100 lpi is 6 × 6 pixels, and 120 lpi. And 5 × 5 pixels in advance, and stored as the halftone processing parameter 48 in the processing parameter 29 of the storage unit 7.
The image data is based on the premise that CMY is expressed with the same angle, and is assumed to be, for example, 90 ° of the line type.

Next, the control unit 9 performs an image reverse shift process on the image data that has been subjected to the image shift process (step 105). That is, when only the shift processing for shifting with the double tone is performed, the image reverse shift processing is performed on the image data D ₇ after the halftone processing, and the image data D ₉ is stored in the image memory 27 of the storage unit 7. . In this case, the image data D ₆ that has not been subjected to the shift processing is directly used as image data D ₈ and stored in the image memory 27 of the storage unit 7.
Further, if the shift processing for shift processing and duotone for each color is performed in conjunction performs image reverse shift processing for the image data D ₆ and the image data D ₇ after halftone processing The image data D ₈ and the image data D ₉ are respectively stored in the image memory 27 of the storage unit 7.

  In the image reverse shift process, the same number of pixels are shifted in the opposite direction to the image shift process in step 103. For the number of pixels to be reversely shifted, the shift processing parameter 47 of the processing parameter 29 of the storage unit 7 may be used. As a result, the pixel position of the halftone dot conversion processing data moves to the correct position.

Next, the control unit 9 executes the accumulated-heat correction process on the image data _{D 8} and the image data _{D 9} (step 106), generates image data _{D 10, D 11} after the correction, the image storage unit 7 Store in the memory 27.
The heat storage correction process is a process for correcting the influence of heat stored in the thermal head of the thermal printer 1 by continuous printing. There are various methods of heat storage correction processing, for example, a method of performing pixel correction calculation in consideration of heat storage history of a plurality of peripheral pixels for one pixel (Japanese Patent Laid-Open No. Hei 5-169709), A pixel heat storage correction process (Japanese Patent Application No. 2004-102164) that takes into account the difference between the contour portion of the image data and the area other than the contour is used.

Finish the image processing 23 by the above, the control unit 9 sends the image data _{D 10} and _{D 11} obtained as a result to the printing unit 11.
Printing unit 11, printing of double tone is executed by the image printing image data D ₁₀ and D ₁₁ received.

(3. CMYK-CMY conversion process)
Next, the CMYK-CMY conversion process (step 101) according to the first embodiment of the present invention will be described in detail with reference to FIG.
First, the control unit 9 reads the original CMYK image data _{D 1} from the image memory 27 (step 200). Here, the image data _{D 1} C (cyan), M (magenta), Y (yellow), the image data _D 1C K _(black), D _1M, D _1Y, and _{D 1K.} The image data D _1C , D _1M , D _1Y , and D _1K are, for example, halftone dot area ratios and take values from 0 to 100.

Next, CMYK-CMY conversion processing is performed. First, subjected to CMYK-CMY conversion processing on the image data _{D 1C} of cyan (C), to obtain the image data _{D 2C,} stored in the image memory 27 (step 201). Here, the CMYK-CMY conversion process is performed by the equation (1) in FIG.
That is, as shown in equation (1), but adds the components of the image data _{D 1K} of black image data _{D 1C} for cyan (C) (K), then the image data _{D 1C} for cyan (C) Depending on the value, the value of {(100−D _1C ) / 100} in the second term on the right side takes a value between 0 and ₁ , and if the image data D _1C is large, the black (K) component is added, If the image data D _1C is small, a large amount of black (K) component is added.

Next, the magenta (M) image data D _1M is also subjected to CMYK-CMY conversion processing in the same manner as in the case of cyan (C) according to the equation (2) to obtain image data D _2M and stored in the image memory 27. (Step 202). Further, the CMYK-CMY conversion process is similarly performed on the yellow (Y) image data _D1Y according to the equation (3) to obtain the image data _D2Y, which is stored in the image memory 27 (step 203).

As described above, by using expressions (1) to (3), the components of the image data _{D 1K} for black (K) is, cyan (C), magenta (M), yellow three colors (Y), The image data is added according to each color component.
Finally, image data _D2K from which the components of the black (K) image are deleted is generated (step 204), and the CMYK-CMY conversion process is terminated.

FIG. 6 shows an example of printing when the above-described CMYK-CMY conversion process is performed.
The left figure shows a uniform CMYK gray image of the original image, and the right figure shows a CMY gray image when the CMYK-CMY conversion process of the present embodiment is performed.
Compared with the conventional method of FIG. 13, a high-quality gray image with no printing unevenness is obtained, and it is shown that the influence of the step difference of the halftone image is improved.
Also, although an example of printing is not shown, when a color image is printed by the CMYK-CMY conversion process of the present embodiment, the color tone when using the above-described CMYK-RGB conversion or CMYK-reverse UCR conversion is used. The difference was reduced and the color tone very close to the current image was obtained.

Next, a second embodiment of the present invention will be described.
In the second embodiment, the configuration of the thermal printer 1, the flow of the image processing 23, and the configuration of the storage unit 7 are the same, as shown in FIGS. The method of CMYK-CMY conversion processing (step 101) in the flow of the image processing 23 of FIG. 3 is different from that of the first embodiment.

FIG. 7 is a conceptual diagram of CMYK-CMY conversion processing according to the second embodiment.
In this CMYK-CMY conversion process, a source profile table 51 that converts CMYK image data into Lab color space data and a destination profile table 53 that converts Lab color space data into target CMYK data are used.
First, original image data D ₁ 61 composed of CMYK image data is converted into Lab color space data by the source profile table 51, and the Lab color space data is converted using the destination profile table 53. converted into CMY data _{D 2,} and executes the processing of steps 102 to 106 of the image processing 23 to the data _{D 2,} to obtain a CMY conversion image 63, performs the printing process.
That is, the original image data D ₁ 61 is converted into CMY data D ₂ by profile conversion.

  The source profile table 51 and the destination profile table 53 are created in advance and stored as the CMYK-CMY conversion parameter 41 in the processing parameter 29 of the storage unit 7.

Next, a method for creating the source profile table 51 and the destination profile table 53 will be described. Both the source profile table 51 and the destination profile table 53 use the ICC (International Color Consortium) format.
FIG. 8 is a flowchart showing the flow of profile table creation, FIG. 9 is an explanatory diagram of a color chart used for profile table creation, FIG. 10 is an explanatory diagram of the source profile table 51, and FIG. FIG. 12 is a diagram for explaining a method for creating the destination profile table 53. FIG.

The source profile table 51 is a table for converting CMYK data of the original image 61 into data in the Lab color space, and is created using a color chart for offset printing.
Each gradation of CMYK is usually 256 gradations, and when combining the gradations of each color, there are about 4.3 billion colors, but since there are too many colors, each dot area ratio of CMYK is 0, 20 , 40, 60, 80, and 100 (%) are used in all 1296 colors (FIG. 9).

First, the above-mentioned 1296 color patch / color chart is offset printed, all 1296 patches are measured with a color measuring device, Lab color space data for each patch is measured, and CMYK data and Lab data correspondence table. A source profile table 51 is created (step 300).
FIG. 10 is an example of the created source profile table 51.
The left side is the value of CMYK data, and the right side is the value of Lab data. For example, the CMYK values and Labs for all 1296 patches such as L = 92, a = 7.1, and b = 2.1 are Lab values obtained by color measurement of patches with C = M = Y = K = 0 (%). A value correspondence table is created.

  Since this source profile table 51 is a table for a color chart of 1296 patches, interpolation processing is performed when CMYK data is actually converted into Lab data using this source profile table 51. .

On the other hand, the destination profile table 53 is a table showing the relationship between CMYK data and Lab data for the thermal printer 1. Therefore, the color chart obtained by thermal transfer printing by the thermal printer 1 is used.
FIG. 11 shows the destination profile table 53 (Lab-CMYK conversion table). In the destination profile table 53 of the present invention, a table is created in which all black (K) values are zero.
Next, a method for creating the destination profile table 53 will be described.

First, as the color chart, there are six CMY halftone dot area ratios of 0, 20, 40, 60, 80, 100 (%), and all 216 colors with K = 0 (%). That is, the leftmost color chart of 216 colors in FIG. 9 is used for creating the destination profile table.
The color chart of 216 colors is subjected to thermal transfer printing by the thermal printer 1, all 216 patches are measured by a color measuring device, and Lab color space data for each patch is measured (step 301).

As a result, Lab data for 216 colors of CMY = 0, 20, 40, 60, 80, 100 (%) and K = 0 (%) is obtained, and a correspondence table is created as shown in the upper left of FIG. .
That is, the Lab measurement value when C = M = Y = K = 0 (%) is Lab (1), the Lab measurement value when C = 20 (%) and M = Y = K = 0 (%) is Lab (2),... A correspondence table is created as Lab measurement value Lab (216) when C = M = Y = 100 (%) and K = 0 (%). However, Lab (n) consists of L value, a value, and b value, respectively.

Next, Lab measurement values (Lab (1) to Lab (216)) for 216 colors of CMY = 0, 20, 40, 60, 80, 100 (%) and K = 0 (%) obtained above. For K = 20, 40, 60, 80, 100 (%).
That is, as shown in FIG. 12, the value of Lab (1) is C = M = Y = 0 (%) and K = 20, 40, 60, 80, 100 (%), Lab (2 ) Are copied at K = 20, 40, 60, 80, 100 (%) where C = 20% and M = Y = 0 (%).

  As described above, a correspondence table of CMYK-Lab for thermal transfer printing as shown in FIG. 12 is created, this is inversely transformed, and interpolation processing is performed, whereby the destination profile table 53 (Lab--) shown in FIG. A CMYK conversion table is created (step 302).

Next, the flow of CMYK-CMY conversion processing by profile conversion using the source profile table 51 and the destination profile table 53 will be described.
FIG. 13 is a flowchart showing the flow of CMYK-CMY conversion processing by profile conversion.

First, CMYK image data D ₁ (D _1C , D _1M , D _1Y , D _1K ) of the original image is read from the image memory 27 (step 400).
Based on the image data D ₁ (D _1C , D _1M , D _1Y , D _1K ), the source profile data 51 is referred to, interpolation processing is performed, and the image data D ₁ (D _1C , D _1M , D _1Y , The optimal Lab value corresponding to D _1K ) is obtained and set as Lab ₁ (step 401).

Next, the destination profile table 53 is referred to based on the Lab1 value, interpolation processing is performed, and image data D ₂ (D _2C , D _2M , D _2Y , which is optimum CMYK data corresponding to the Lab1 value) D _2K ) is obtained (step 402).
At this time, by referring to the destination profile table 53 in the portion where K = 0 (%), CMY data from which black (K) where K = 0 (%) is deleted can be obtained.

The processing of step 401 and step 402 can also be executed by a program such as Adobe ACE or Microsoft ICM. In this case, the above-described source profile table 53 is designated as the source color space, and the above-described destination profile table 53 is designated as the profile color space after conversion.
It is desirable to select absolute color gamut maintenance as a matching method.

If the above-described existing program is used, the black (K) value D _2K may remain to some _extent due to matching processing, interpolation processing, etc., so the black (K) component is deleted as D _2K ← 0, and the image data D ₂ (D _2C , D _2M , D _2Y , D _2K ) is stored in the image memory 27 (step 403), and the process ends.

FIG. 14 is a diagram schematically illustrating the processing result of the second CMYK-CMY conversion.
The original image (CMYK image) before profile conversion has C, M, Y, and K image components (before profile conversion). When the CMYK image data is profile-converted by the CMYK-CMY conversion process of FIG. Part) are represented as C, M, and Y components, and the K component is reduced (ideally, it is desirable that the K component is deleted). By deleting the remaining K component (a part of the pentagonal outer frame), it is possible to print only CMY without the K (black) component.

  By performing the CMYK-CMY conversion using the profile conversion described above, it is possible to form a print image color-matched to the CMYK offset print image with the CMY print image. In addition, by printing in CMY, it is also possible to reduce the influence of the step difference in the halftone image. Furthermore, since printing can be performed without using black (K) ink, material cost and printing time can be reduced.

  The preferred embodiment of the thermal recording apparatus according to the present invention has been described with reference to the accompanying drawings, but is not limited to the above-described embodiment. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the technical idea described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs.

The figure which shows the structure of the thermal printer 1 The figure which shows the relationship between the structure of the thermal printer 1, and the processing content The flowchart which shows the flow of a process of the image process 23 of this Embodiment. The figure which shows the detail of the memory | storage part 7 of the thermal printer 1 Flow chart showing the flow of the first CMYK-CMY conversion process Example of printing when the first CMYK-CMY conversion process is used The figure explaining the concept of the 2nd CMYK-CMY conversion process Flow chart showing the flow of profile table creation processing Diagram explaining color chart The figure which shows the example of the source profile table 51 The figure which shows the example of the destination profile table 53 The figure explaining the creation method of the destination profile table 53 Flowchart showing the flow of second CMYK-CMY conversion processing Explanatory drawing of a print when the second CMYK-CMY conversion process is used Gray image printing example by conventional method

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ......... Thermal printer 3 ......... Image data 5 ......... Image input part 7 ......... Storage part 9 ......... Control part 11 ......... Print part 13 ......... Bus 15 ......... Output image 21 ... ...... Image reading 23 ...... Image processing 25 ...... Image printing 27 ...... Image memory 29 ...... Processing parameter 31 ...... Image processing program 41 ............ CMYK-CMY conversion parameter 51 ...... Source Profile table 53 ... Destination profile table

Claims (8)

Removing the black (K) component from the first image data to generate second image data;
A shift process is performed on the third image data obtained by resolution conversion, gradation conversion, and color separation for the second image data, and the fourth image data and the fifth image data are converted. Generate
The sixth image data and the seventh image data obtained by performing the halftone dot conversion process on the fourth and fifth image data are subjected to the reverse shift process, and the eighth image data and the ninth image data are generated. ,
A heat storage correction process is performed on the eighth image data and the ninth image data, and tenth image data and eleventh image data are generated,
A printed matter obtained by printing the tenth image data and the eleventh image data by superimposing the tenth image data and the eleventh image data on an object to be printed by a thermal recording apparatus having a thermal head. A thermal recording apparatus having a thermal head,
Means for removing the black (K) component from the first image data and generating second image data;
Means for performing resolution conversion, gradation conversion, and color separation on the second image data to generate a third image;
Means for shifting the third image data to generate fourth image data and fifth image data;
Means for performing halftone dot conversion processing on the fourth image data and the fifth image data, and generating sixth image data and seventh image data;
Means for reversely shifting the sixth image data and the seventh image data to generate eighth image data and ninth image data;
Means for performing a heat storage correction process on the eighth image data and the ninth image data, and generating tenth image data and eleventh image data;
Means for superimposing the tenth image data and the eleventh image data as prints;
A thermal recording apparatus comprising:   The means for removing the black (K) is to change the component values of black (K) to cyan (C), magenta (other than cyan (C), magenta (M), and yellow (Y) as other colors. 3. The thermal recording apparatus according to claim 2, wherein addition is performed according to the component values of M) and yellow (Y), and the component value of black (K) is deleted.   The means for deleting the black (K) is such that the component value of black (K) is small when the component values of cyan (C), magenta (M), and yellow (Y) are large, and cyan (C), magenta. 4. The thermal recording apparatus according to claim 3, wherein when the component values of (M) and yellow (Y) are small, a large amount is added.   The means for removing the black (K) uses a profile table for printing and a profile table of the thermal recording apparatus, and converts the first image data into cyan (C) of the thermal recording apparatus by profile conversion. ), Magenta (M), and yellow (Y) values.   In the printing profile table, the dot area ratios of cyan (C), magenta (M), yellow (Y), and black (K) are 0%, 20%, 40%, 60%, and 80%, respectively. The thermal recording apparatus according to claim 4, wherein the thermal recording apparatus is a CMYK-Lab conversion table generated by measuring in a Lab color space a color chart obtained by printing 1296 patterns at 100%.   In the profile table of the thermal recording apparatus, the dot area ratios of cyan (C), magenta (M), and yellow (Y) are 0%, 20%, 40%, 60%, 80%, 100%, 216 color charts by thermal transfer printing when the dot area ratio of black (K) is 0% are measured in Lab space, and the obtained 216 Lab space measurement values are used as the dot area of black (K). 5. The thermal recording apparatus according to claim 4, wherein the rate is a Lab-CMYK conversion table generated by embedding 20%, 40%, 60%, 80%, and 100%. Removing the black (K) component from the first image data to generate second image data;
Performing resolution conversion, gradation conversion, and color separation on the second image data to generate a third image;
Shifting the third image data to generate fourth image data and fifth image data;
Performing a halftone dot conversion process on the fourth image data and the fifth image data to generate sixth image data and seventh image data;
Reversely shifting the sixth image data and the seventh image data to generate eighth image data and ninth image data;
Performing a heat storage correction process on the eighth image data and the ninth image data to generate tenth image data and eleventh image data;
A step of superimposing the image data of the cost 10 and the eleventh image data as a printed material,
An image forming method comprising:

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