JP3412251B2 - Color inkjet recording method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording method for a color ink jet printer.

[0002]

2. Description of the Related Art Generally, a color printer prints by superimposing each color of yellow, magenta, and cyan.
In the case of ink jet recording, there is a big problem that liquid inks mix with each other or flow out.

Therefore, in order to solve the above problems, the surface tension of the recording liquid of each color forming a color image is 2 as disclosed in JP-A-60-197778.
It is in the range of 30 to 60 mN / m at 0 ° C., and by using a recording liquid of each color having a uniform surface tension, the time required for fixing the recording liquid of each color to the recording material and the degree of bleeding are equalized. A method for suppressing image deterioration has been proposed. However, in the method of using the recording ink, although it is possible to prevent the inks from being mixed with each other, the degree of bleeding of the outline of the ink is not reduced, and it cannot be a means for improving all the image deterioration. In the case of recording ink, when an image output recorded with only black ink is compared with an output image output by a monochrome printer, there is a problem in that the print quality is inferior in terms of ink contour bleeding.

Then, as described in JP-A-3-41171, after printing a color aqueous ink having a surface tension in the range of 30 to 40 mN / m on a recording material, the surface tension is 45 to 73 mN / m. By printing with a color water-based ink within the range, it prevents the paper feed roller from becoming dirty due to the inflow of ink between adjacent colors and insufficient drying, and high resolution suitable for documents. There has been proposed a color ink jet printing method capable of obtaining various characters. However, when inks having different surface tensions are used as in the above method, it is necessary to make a sufficient printing time difference between the inks having different surface tensions in order to prevent color mixture between them. If priority is given, there is a conflicting problem that the printing speed cannot be increased.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to obtain a sharp and clear color image in which monochrome printing has high printing quality corresponding to plain paper, has little bleeding when mixed with other color inks. And to realize a color inkjet printer capable of high-speed printing.

[0006]

According to the color ink jet recording method of the present invention, the surface tension at 20 ° C. is 40 mN.
In a color ink jet recording method using a color ink of less than 1 m / m and a black ink having a surface tension of 40 mN / m or more, when the black area and the color area of the image are close to each other, substantially the entire black area of the image is It is characterized in that it is composed of the black ink and the color ink. Further, the color inks are yellow ink, magenta ink, and cyan ink. Further, the weight ratio of the black ink forming the black area of the image to the total ink forming the black area of the previous image is 0.55 or more and 0.75 or less. Further, the weight ratio of the black ink forming the black area of the image to the total ink forming the black area of the previous image is 0.63 or more and 0.72 or less. Further, the color ink forming the black area of the image is magenta ink,
It is characterized in that it is cyan ink. Further, when the interval between the black area and the color area of the image is within 2 dots, the black area of the image is constituted by both the black ink and the color ink.

[0007]

EXAMPLES The color ink jet recording method of the present invention will be specifically described with reference to FIGS.

FIGS. 1 to 3 are views for explaining a color ink jet recording method according to an embodiment of the present invention. FIG. 1 is an image pattern used for evaluation of the color ink jet recording method of the present invention. It has an image pattern in which the letter A of the alphabet is recorded in black. FIG. 2 is an enlarged view of a portion (a portion corresponding to a portion indicated by a circle 4) of a recording dot (FIG. 1) when the image pattern of FIG. 1 is recorded on a recording paper by the color inkjet recording method of the embodiment of the present invention. It has been shown. Further, FIG. 3 is a diagram showing a state of recording dots when the image pattern of FIG. 1 is recorded on a recording paper by the conventional color ink jet recording method, similarly to FIG.

In FIG. 2, 21 is a yellow ink dot recorded with a yellow ink, 31 is a black ink dot recorded with a black ink, 41 is a magenta + cyan ink dot recorded with a magenta ink and a cyan ink. In FIG. 3, 22 indicates a yellow ink dot recorded with a yellow ink, and 32 indicates a black ink dot recorded with a black ink.

As is clear from comparison between FIG. 2 and FIG. 3, the black area 3 recorded with only the black ink dots 32 in the conventional color ink jet recording method, the black ink dot in the color ink jet recording method of the embodiment of the present invention. 31 and magenta + cyan ink dots 41 are recorded, and black ink dots in the black area of the conventional color ink jet recording method are converted into magenta + cyan ink dots at a ratio of 1 dot to 3 dots and recorded. It has become.

By recording with such a recording dot structure, the black ink dots 31 having a surface tension of 40 mN / m or more are recorded with the magenta ink and the cyan ink having the surface tension of less than 40 mN / m, and the magenta + cyan ink dots 41 are recorded. Mixed on the recording paper to reduce the surface tension,
Since the difference in surface tension between the yellow ink dots 21 which is a low surface tension color ink outside the black region is small, bleeding due to color mixing can be prevented. Further, since such an effect can be obtained regardless of the printing order of the black ink and the color ink or the time difference of printing, the printing quality can be improved without lowering the printing speed. In the case of the conventional color ink jet recording method, the black ink dot 32 having a high surface tension has a low permeability to the recording paper, and the difference in the surface tension with the surrounding yellow ink is large, so that it is easy to mix colors, and the black having a high surface tension is used. The ink dots 32 are pulled by the yellow ink 22 having low surface tension and high permeability to the recording paper, and bleeding easily occurs due to color mixing.

We are In order to evaluate the print quality recorded by the color inkjet recording method of the embodiment of the present invention, black, yellow, magenta, and cyan were recorded at a recording density of 360 DPI (DPI indicates the number of recording dots that can be recorded per 25.4 mm). We made a prototype of a color inkjet printer equipped with an inkjet head that can control and discharge each ink. Table 1 shows the ink composition used to evaluate the print quality of the samples recorded by the color inkjet recording methods of the examples of the present invention and the comparative example. It was done with a set of inks. Also, the dot weight of each ink is the commercially available PPC paper (Fuji Xerox Co .; X
EROX-P) is set so that the recording dots have a diameter of about 100 μm when recorded by the above-mentioned inkjet printer.

[0013]

[Table 1]

FIG. 4 is a diagram for explaining the construction of the image data converting means of the embodiment of the color ink jet recording method of the present invention.

The image data 201 is color data having information of 8 colors per pixel that can be expressed by the printer of the prototype of this embodiment, and the print data conversion unit 210 can directly control yellow and magenta by the color ink jet printer. The print data is converted into print data composed of four types of data, cyan, black, and stored in the temporary storage unit 202. In the recorded data, the contour dot of the black data is discriminated by the contour discriminator 203, and the information is 2
No. 04 temporary storage means. The color mixture area determination unit 205 records the color ink on the data at the position of 8 dots around the contour dot of the black data, using the contour data of the black data stored in 204 and the print data recorded in 202. If there is a dot for recording color ink in the surrounding 8 dots, it is determined that the inside of the contour including the contour dot is a color mixture area, and the contour dot is also present inside the contour. The black data to be converted will be converted by a predetermined method described below. Areas that have not been determined to be color mixing areas by the color mixing area determination unit 205 are stored in the temporary storage unit 207 as they are.

FIG. 5 shows the contents of the table stored in the storage means 206. In the present embodiment, 1 or 0 is stored as 3 × 3 matrix data as shown in FIG. Also, the temporary storage means of 208 has a capacity of at least four colors constituted by a 3 × 3 matrix. 205
The black data and the color data including the area determined to be the color mixture area in step are sequentially stored in the temporary storage unit 208.
Then, the data conversion unit 209 converts the data corresponding to the address stored as 1 in the table stored in the storage unit 208 so that the magenta ink and the cyan ink are ejected instead of the black ink. 207
It is recorded in the temporary storage means of. By repeating this series of operations in all the areas determined to be the color mixture area, the data conversion of the entire color mixture area is performed, and magenta + instead of the black ink dot at a ratio of 1 dot to 3 dots as shown in FIG. It is possible to realize a configuration of recording dots that prints cyan ink dots. In addition, in the case where there are no color dots in the periphery, the black area remains as a black area without data conversion.Therefore, when printing a sentence or the like composed of only a black image, only black ink with high surface tension is recorded. , A sharp outline can be printed, and a high-quality output image equivalent to the output of a normal monochrome printer can be obtained. The converted print data stored in 207 is sent to the printer by a predetermined means, and an output image is obtained.

In the above description, the data conversion is performed when the black area and the color area are adjacent to each other on the data, but since the recording dots on the output image recorded by the ink jet printer are circular, normal pixels are The recording dots having a larger area than that of the recording dots are formed. Also,
The size of the dots recorded varies depending on the type of recording paper,
In some recording papers, the recording dots tend to spread due to ink bleeding. Therefore, even if the data is one dot apart, the recording dots may be adjacent to each other on the recording paper, causing bleeding due to color mixing. In such a case, for example, 20
By determining the data outside the dot determined as the contour of the black data by the contour discrimination unit 3 of the above, even when the interval between the black region and the color region is close by 1 dot or more in the data, the above Data conversion can be performed, and even in such a case, bleeding due to color mixture can be prevented. In order to prevent bleeding due to color mixture on so-called plain paper such as commercially available PPC paper, in our evaluation using the above prototype inkjet printer, the above data conversion is performed when the color area and the black area are within 2 dots. It was necessary to set to.

In the evaluation of the color ink jet recording method of the embodiment of the present invention, the ink having the ink composition shown in Table 1 was used, but inks having other compositions as shown below can also be used.

For example, as a colorant for the ink, a water-soluble dye used in conventional inks for ink jet recording can be used. I. Direct Red 2, 4, 9, 23, 26, 31, 39, 6
2, 63, 72, 75, 76, 79, 80, 81, 8
3, 84, 89, 92, 95, 111, 173, 18
4, 207, 211, 212, 214, 218, 22
1, 223, 224, 225, 226, 227, 23
2, 233, 240, 241, 242, 243, 24
7, C.I. I. Direct Violet 7, 9, 47, 4
8, 51, 66, 90, 93, 94, 95, 98, 10
0, 101, C.I. I. Direct Yellow 8, 9, 1
1, 12, 27, 28, 29, 33, 35, 39, 4
1, 44, 50, 53, 58, 59, 68, 86, 8
7, 93, 95, 96, 98, 100, 106, 10
8, 109, 110, 130, 132, 142, 14
4, 161, 163, C.I. I. Direct Blue 1, 1
0, 15, 22, 25, 55, 67, 68, 71, 7
6, 77, 78, 80, 84, 86, 87, 90, 9
8, 106, 108, 109, 151, 156, 15
8, 159, 160, 168, 189, 192, 19
3, 194, 199, 200, 201, 202, 20
3, 207, 211, 213, 214, 218, 22
5,229,236,237,244,248,24
9, 251, 252, 264, 270, 280, 28
8, 289, 291, C.I. I. Direct black 9,
17, 19, 22, 32, 51, 56, 62, 69, 7
7, 80, 91, 94, 97, 108, 112, 11
3, 114, 117, 118, 121, 122, 12
5, 132, 146, 154, 166, 168, 17
3, 199, C.I. I. Acid Red 35, 42, 5
2, 57, 62, 80, 82, 111, 114, 11
8, 119, 127, 128, 131, 143, 15
1, 154, 158, 249, 254, 257, 26
1, 263, 266, 289, 299, 301, 30
5, 336, 337, 361, 396, 397, C.I.
I. Acid Violet 5, 34, 43, 47, 4
8, 90, 103, 126, C.I. I. Acid Yellow 17, 19, 23, 25, 39, 40, 42, 44, 4
9, 50, 61, 64, 76, 79, 110, 127,
135, 143, 151, 159, 169, 174, 1
90, 195, 196, 197, 199, 218, 21
9, 222, 227, C.I. I. Acid Blue 9,2
5, 40, 41, 62, 72, 76, 78, 80, 8
2, 92, 106, 112, 113, 120, 127:
1, 129, 138, 143, 175, 181, 20
5, 207, 220, 221, 230, 232, 24
7, 258, 260, 264, 271, 277, 27
8, 279, 280, 288, 290, 326, C.I.
I. Acid Black 7, 24, 29, 48, 52:
1, 172, C.I. I. Reactive Red 3, 13, 1
7, 19, 21, 22, 23, 24, 29, 35, 3
7, 40, 41, 43, 45, 49, 55, C.I. I. Reactive Violet 1, 3, 4, 5, 6, 7, 8,
9, 16, 17, 22, 23, 24, 26, 27, 3
3, 34, C.I. I. Reactive Yellow 2, 3, 1
3, 14, 15, 17, 18, 23, 24, 25, 2
6, 27, 29, 35, 37, 41, 42, C.I. I. Reactive Blue 2, 3, 5, 8, 10, 13, 14,
15, 17, 18, 19, 21, 25, 26, 27, 2
8, 29, 38, C.I. I. Reactive Black 4,
5, 8, 14, 21, 23, 26, 31, 32, 34,
C. I. Basic Red 12, 13, 14, 15, 1
8, 22, 23, 24, 25, 27, 29, 35, 3
6, 38, 39, 45, 46, C.I. I. Basic Violet 1, 2, 3, 7, 10, 15, 16, 20, 2
1, 25, 27, 28, 35, 37, 39, 40, 4
8, C.I. I. Basic Yellow 1, 2, 4, 11, 1
3, 14, 15, 19, 21, 23, 24, 25, 2
8, 29, 32, 36, 39, 40, C.I. I. Basic Blue 1, 3, 5, 7, 9, 22, 26, 41, 4
5, 46, 47, 54, 57, 60, 62, 65, 6
6, 69, 71, C.I. I. Basic Black 8, as the pigment, an inorganic pigment (carbon black), an organic pigment (insoluble azo pigment, soluble azo pigment, phthalocyanine pigment, isoindolinone pigment, quinacridone pigment,
Perinone / perylene pigments) can be used. In addition, processed pigments (grafted carbon etc.) in which the pigment surface is treated with a resin or the like can also be used.

The content of these colorants in the ink composition is preferably in the range of 1 to 10 wt% in terms of solid content in consideration of the print density, clogging and ejection characteristics of the recorded matter.

The solvent used in the ink jet recording ink of the present invention is a water-soluble organic solvent other than ion-exchanged water, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol and n-butyl alcohol. , Sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, and other alkyl alcohol ethers having 1 to 4 carbon atoms;
Amides such as dimethylformamide and dimethylacetamide; ketones or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol, propylene glycol, 1 , 2, 6-
Alkylene glycols such as hexanetriol, thiodiglycol, hexyleneglycol containing 2 to 6 carbon atoms; glycerin; ethylene glycol methyl ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ) Lower alkyl ethers of polyhydric alcohols such as ethers and the like can be mentioned.

Among the above water-soluble organic solvents, polyhydric alcohols are used as anti-drying agents for preventing ejection failure due to nozzle clogging caused by evaporation of water in the ink jet recording ink and deposition of the recording agent. Is preferable because it has a large effect.

Further, as the water-soluble organic solvent used in the black ink used in the color ink jet recording method of the present invention, in addition to the water-soluble organic solvent serving as the wetting agent, for example, monohydric alcohol such as ethyl alcohol or n-propyl alcohol. Alcohol is preferable, and these prevent the recording ink from penetrating and diffusing more than necessary on the recording paper, so that bleeding is suppressed and it is effective in realizing high print quality compatible with plain paper.

These water-soluble organic solvents may be used alone, or two or more kinds of solvents may be mixed and used.

Further, in order to obtain a surface tension of less than 40 mN / m, a surfactant such as acetylene glycol is added to the three color inks of yellow, magenta and cyan used in the color ink jet recording method of the present invention.
These surfactants used as the surface tension adjusting agent are preferably added in the range of 0.1 to 2 wt% in order to prevent adverse effects such as generation of satellites and foaming during ejection.

In addition to the above, the recording ink used in the color ink jet recording method of the present invention includes a conventionally known dispersant, a surfactant, a viscosity adjusting agent, a surface tension adjusting agent, a specific resistance adjusting agent, a pH adjusting agent, and an oxidizing agent. Inhibitors, fungicides, chelating agents and the like can be added as necessary.

The content of these various additives in the ink composition varies depending on the purpose, but since an excessive amount causes bubbling, precipitation, deterioration of storability, etc., 0.001 to 5
It is desirable to use in the range of wt%.

We show below the results of evaluation of various examples in addition to the color ink jet recording method of converting black data into blue data at a ratio of 1 dot to 3 dots.

The following two tests were conducted to evaluate the print quality.

Test 1: Blurring by color mixture in the image pattern shown in the figure (black characters on the yellow background) By the color ink jet recording method of the present invention, the pattern shown in the FIG. 1 pattern on a commercially available PPC paper (Fuji Xerox Co .; XEROX-P). Black character is printed on the yellow background,
Bleeding due to color mixture in the black region and the yellow region was visually observed and evaluated as follows. X: Bleeding is remarkable and the image is deteriorated. Δ: Bleeding is noticeable. ◯: Some bleeding is seen, but there is no effect on the entire image. ◎: Bleeding is not noticeable.

Test 2: Deviation of hue in black area of color image Commercially available PPC paper (manufactured by Fuji Xerox Co .; X
EROX-P) and the sample obtained by the evaluation method of Test 1 are the same as black on plain (on recording paper) A only
The hues of the black areas of both of the samples on which the characters are printed were visually observed and evaluated as follows. (When a black character is printed on a solid color, only the black ink is used for recording in both the color inkjet recording method of the example of the present invention and the color inkjet recording method of the comparative example.) X: Difference in hue between both samples Is clear. Δ: There is a difference in hue between both samples, but it can be said that both are black. ◯: The hue difference can be found only after comparing both samples. ⊚: The difference in hue is not recognized even when both samples are arranged and compared.

6, 7, 8, 9, 10, 11, 12,
13 shows various embodiments of the color ink jet recording method of the present invention. What kind of recording dot configuration is used for each black area determined to be a mixed color area according to each embodiment of the color ink jet recording method of the present invention. It shows whether or not it is recorded on recording paper. FIG. 12 similarly shows the case of the first embodiment described so far for the sake of clarity. Each embodiment can be implemented by appropriately changing the table configuration of the storage unit 206 and the configuration of the temporary storage unit 208 of FIG.

FIG. 14 shows a comparative example 2 of the present invention in which the black areas are so-called yellow, magenta, and cyan.
1 illustrates an example of a general color inkjet recording method for printing and recording color inks, and Comparative Example 1 shows an example of a conventional color inkjet recording method in which a black area is always composed of only black ink. ing.

Table 2 summarizes the results of the above-described two types of tests performed on the color ink jet recording methods of the examples and comparative examples described above using the ink jet printer described above and the inks of Table 1.

[0035]

[Table 2]

In Table 2, the Bk weight ratio is the ratio of the weight of the black ink to the total ink weight of the black area determined to be the color mixture area, and is calculated from the dot weight in the table and the configuration of the recording dots according to the reference diagram. It is a value. Further, the ink weight ratio represents the ratio of the total ink weight when the mixed color area is printed with the recording dot configuration of the embodiment to the total ink weight when the mixed color area is printed only with black ink. It is a value calculated from the dot weight in the table and the configuration of the recording dots according to the reference diagram. The Bk weight ratio and the ink weight ratio of the actually recorded sample may be slightly larger or smaller than this value depending on the shape of the black region, but it is considered to be roughly close to this value.

In order to prevent the bleeding due to the color mixture of the color area and the black area by using the color ink and the black ink having different surface tensions, the print quality evaluation results of Examples 1, 2, 3, 4 and Comparative Example 1 were used. As is apparent, by forming the black region with the black ink, the magenta ink, and the cyan ink, the further the Bk weight ratio is reduced, the more the bleeding prevention effect is enhanced. However, the smaller the Bk weight ratio, the more the hue of black shifts. Therefore, when the color inkjet recording method of the present invention is practiced as a printer, it is necessary to determine the Bk weight ratio while considering the balance between the two. . In the evaluation this time, when the ink of ink composition 1 is used, the color inkjet recording method that can balance the two is shown in FIG.
The color ink jet recording method of Example 1 has a recording dot configuration shown in 2 and a Bk weight ratio of about 0.68. Further, when the ink of the ink composition 2 was used, the recording dot configuration shown in FIG. 12 or 8 and the Bk weight ratio of 0.68 to 0.76 were obtained from the evaluation results of Examples 5, 6, 7, and 8. In the region where the Bk weight ratio is slightly higher than that in the case of Ink Composition 1, there was a region where both were balanced. Example 1 in which ink composition 1 was used for both the bleeding hue at this time
A sample with high print quality was obtained compared to This is because the ink composition 2 has a smaller surface tension difference between the color ink and the black ink than the ink composition 1, and therefore bleeding can be prevented even if the Bk weight ratio is high. Also, Bk
Since the weight ratio is high, the hue difference is small, and the print quality is higher than that of the case where the ink composition 1 is used for both bleeding and hue. However, there is also a drawback that when the black character samples are compared with each other in plain color, the outline of the character is slightly blurred as compared with the sample of the first embodiment. This is because the black ink of the ink composition 1 has a higher surface tension than the black ink of the ink composition 2, and therefore the outline of the recording dot is less likely to bleed.

As described above, in the color ink jet recording method of the present invention, the optimum recording dot configuration changes depending on the ink composition, particularly the difference in the double-sided tension between the black ink and the color ink, and qualitatively, when the difference in surface tension is small. Is Bk
When the weight ratio is large, and when the weight ratio is large, the Bk weight ratio is reduced, so that a color image output with bleeding and a balanced hue can be obtained.

Example 9 is a color ink jet recording method having the same ink composition and Bk weight ratio as in Example 4,
The color inkjet recording method is different from that of Example 4 in the configuration of the recording dots, but the evaluation results of the output samples are almost the same. However, for example, when a 1-dot line descending to the right by 45 degrees is drawn on a color background, in the color inkjet recording method of the fourth embodiment, the black line is recorded only with black ink dots or only with magenta + cyan ink dots. There may be a problem in hue and hue. On the other hand, in Example 8, such a situation is less likely to occur, and at least the black ink dots can be prevented from being formed. However, in the color ink jet recording method in which the constitution pattern of the recording dots is constant as described above, there is a possibility that a certain pattern may cause a problem to a greater or lesser extent, so it is necessary to select a recording dot configuration that causes the problem as little as possible. is there. In order to solve such a problem from the ground up, the recording dot structure after conversion is changed at random so that the Bk weight ratio is as described above in an area of a certain size or more where it can be determined that the print quality is not affected. It is easily conceivable to use a conversion method that gives a value that balances bleeding and hue. However, this method can avoid the problem with a specific pattern as compared with the method of the embodiment of the present invention having a constant conversion pattern, but on the other hand, since the processing becomes complicated, a high-speed data conversion processing means is required, It is rather unsuitable for inexpensive printers, and is a method suitable for high-quality, high-priced printers.

Example 10 is the same as Example 1 except that the ink composition is Bk.
The color inkjet recording method has the same weight ratio, but the configuration of the recording dots is different from that of the fourth embodiment, and the same processing is performed in units of 4 dots (2 × 2 dots). Then, the evaluation results of the output samples are almost the same. The method of the ninth embodiment in which the same processing is performed in units of several dots is not suitable for an image that requires high resolution such as a small character or a line with a width of several dots. Since the conversion can be collectively processed in units of several dots, there is an advantage that the processing method can be simplified.

The eleventh embodiment is a color ink jet recording method in which the data conversion of one dot into three dots is performed similarly to the first embodiment, but the recording dot configuration after conversion is similar to that of the first embodiment except that yellow ink is further added. This is a color inkjet recording method. The sample obtained in Example 10 is not significantly different from the sample in Example 1 in terms of print quality, and it is possible to prevent bleeding due to color mixing even with a dot configuration in which yellow ink is added as a color ink. In addition to this, ink dots of cyan only, yellow only, magenta only, cyan + yellow, and magenta + yellow are also possible, and if bleeding is the same as the above Bk weight ratio, roughly the same result is obtained, but regarding hue Due to the characteristics of the color inks of yellow, magenta, and cyan inks used in general color inkjet printers, a recording dot configuration that uses only yellow ink with high brightness has a blue color that is represented by cyan + magenta ink dots with low brightness. It can be said that the difference in hue is more conspicuous than that of the recording dot configuration including dots. However, since the hue shift direction differs depending on the configuration of each recording dot, it cannot be generally said that the configuration of any recording dot is the best. For example, when using an ink in which the hue of black ink is inclined to blue, it is possible to obtain an output closer to black by using a dot configuration including yellow ink.

Example 12 is a color ink jet recording method in which the Bk weight ratio is the same as that in Example 1, but the ink weight ratio is smaller than that in Example 1. The ink weight ratio is smaller than that in Example 1. Although the density in the black region is somewhat low, even if the Bk weight ratio is the same as that in Example 1, the absolute amount of black ink is smaller than that in Example 1, so that bleeding due to color mixing is improved. This is a color inkjet recording method that can be applied when it is desired to improve bleeding even if the density is slightly lowered.

From all the results of Examples 1 to 12 above, there is no problem in the results of Test 1 and Test 2 (both evaluations are good).
The Bk weight ratio range of (above) is 0.55 or more and 0.75 or less, and a more favorable range (combination of evaluation results ○ and ◎).
Was found to be 0.63 or more and 0.72 or less.

Comparative Example 1 is a conventional color ink jet recording method for recording both colored and plain characters with black ink. Since plain characters can be recorded with black ink having a high surface tension, high sharpness of the contour is obtained. Although it is possible to output characters of print quality, since the outline of yellow characters is blurred due to color mixing, the bleeding evaluation result of Test 1 is naturally poor, but the hue of Test 2 is also affected by color mixing in the character outline. Also, since there is a partial shift, there is no hue difference at a place sufficiently away from the contour, but a comprehensive evaluation result resulted in x due to the shift in the hue of the contour portion.

Comparative Example 2 is a method of forming black characters on a color background with yellow + magenta + cyan ink dots, and is used when a black area is represented by a color printer having no black ink head.
In the case of such a color inkjet recording method, since the black area of the color background is recorded only with the color ink having a low surface tension, there is no bleeding due to color mixture and the result of Test 1 is good, but it is clear that the hue is black. Unfortunately, the result of Test 2 was x. Of course 3
It is possible to obtain an output closer to black by adjusting the hue, lightness, and saturation of each color ink so that black can be expressed with each color ink. The hue of the image changes, and it is difficult to improve both color output and black output. However, in the color ink jet recording method of the embodiment of the present invention, the color output can obtain a good expression color by adjusting the characteristics of each ink, and the black output can be the optimum output by appropriately changing the Bk weight ratio. The color is obtained. Therefore, it is possible to adjust color output and black output separately,
The finally output image can be better in both color expression and black expression by the color inkjet recording method of the present invention.

[0046]

According to the color ink jet recording method of the present invention, a color ink jet recording method using a color ink having a surface tension of less than 40 mN / m at 20 ° C. and a black ink having a surface tension of 40 mN / m or more, When the black area and the color area of the image are close to each other, the black area and the color ink of the image are used to configure the black area and the color ink so that the monochrome printing has a high print quality corresponding to plain paper. There is little bleeding when mixed with other color inks, and it is possible to realize a color inkjet printer capable of high-speed printing capable of obtaining a sharp and clear color image.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an example of an image pattern output by a color inkjet recording method of the present invention.

FIG. 2 is a diagram illustrating a configuration of recording dots of an output image obtained by recording the image pattern of FIG. 1 by the color inkjet recording method according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration of recording dots of an output image obtained by recording the image pattern of FIG. 1 by a conventional color inkjet recording method.

FIG. 4 is a diagram illustrating a configuration of image data conversion means in an embodiment of a color inkjet recording method according to the present invention.

FIG. 5 is a diagram showing contents of a table stored in a storage unit of the color inkjet recording method according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration of recording dots of an output image obtained by printing a black area of a color mixture area by the color inkjet recording methods according to the second and sixth embodiments of the present invention.

FIG. 7 is a diagram illustrating a configuration of recording dots of an output image obtained by printing a black area of a color mixture area by the color inkjet recording methods of the third and seventh embodiments of the present invention.

FIG. 8 is a diagram illustrating a configuration of recording dots of an output image obtained by printing a black area of a color mixture area by the color inkjet recording methods according to the fourth and eighth embodiments of the present invention.

FIG. 9 is a diagram illustrating a configuration of recording dots of an output image obtained by printing a black area of a color mixture area by a color inkjet recording method according to a ninth embodiment of the present invention.

FIG. 10 is a diagram illustrating a configuration of recording dots of an output image obtained by printing a black area of a color mixture area by a color inkjet recording method according to a tenth embodiment of the present invention.

FIG. 11 is a diagram illustrating a configuration of recording dots of an output image obtained by printing a black area of a color mixture area by a color inkjet recording method according to an eleventh embodiment of the present invention.

FIG. 12 is a diagram illustrating a configuration of recording dots of an output image obtained by printing a black area of a color mixture area by the color inkjet recording methods according to the first and fifth embodiments of the present invention.

FIG. 13 is a diagram illustrating a configuration of recording dots of an output image obtained by printing a black area of a color mixture area by a color inkjet recording method according to a twelfth embodiment of the present invention.

FIG. 14 is a diagram illustrating a configuration of recording dots of an output image obtained by printing a black area of a mixed color area by a color inkjet recording method of a comparative example of the present invention.

[Explanation of symbols]

1 ... Image pattern 2 ... Yellow area 3 ... Black area 21: Yellow ink dot 22 ... Yellow ink dot 31 ... Black ink dot dot 32: Black ink dot dot 41 ... Magenta + cyan ink dot 51: Black + magenta + cyan ink dot 61 ... Yellow + magenta + cyan ink dot 71 ... Cyan ink dot 81 ... Magenta ink dot 201 ... Image data 202 ... Temporary storage means 203 ... Outline discriminating unit 204 ... Temporary storage means 205 ... Mixed color area determination unit 206 ... Storage means 207 ... Temporary storage means 208 ... Temporary storage means 209 ... Data conversion unit 210 ... Print data conversion unit

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41M 5/00 B41J 2/01-2/215

Claims (6)

(57) [Claims] 1. The surface tension at 20 ° C. is 40 mN / m.
In the color inkjet recording method using a color ink of less than 1 and a black ink having a surface tension of 40 mN / m or more, when the black area and the color area of the image are close to each other,
A color ink jet recording method, wherein substantially the entire black area of the image is composed of the black ink and the color ink. 2. The color ink jet recording method according to claim 1, wherein the color ink is a yellow ink, a magenta ink, or a cyan ink. 3. The weight ratio of the black ink forming the black area of the image to the total ink forming the black area of the previous image is 0.55 or more and 0.75 or less. 2. The color inkjet recording method described in 2. 4. The weight ratio of the black ink forming the black area of the image to the total ink forming the black area of the previous image is 0.63 or more and 0.72 or less. 2. The color inkjet recording method described in 2. 5. The color ink jet recording method according to claim 1, wherein the color ink forming the black area of the image is magenta ink or cyan ink. 6. The black area of the image is composed of both the black ink and the color ink when the distance between the black area of the image and the color area is within 2 dots. Or the color inkjet recording method described in 2.