JPS60174651A - Color picture forming apparatus - Google Patents

Abstract

PURPOSE:To supress the generation of pseudo contours and the rough feeling in the color picture forming apparatus of 4 colors containing black, by a method wherein the ink dot of black is so arranged as to be double recorded after the ink dots of other colors. CONSTITUTION:By considering that the ink dotted in the first place becomes dominant in the case of color mixture, the ink dot of high lightness is formed in the first place and the effect of black ink dot is made to be avoided. The heads are arranged on a carriage 11 in the order of magenta 12M, black 12BK, cyanogen 12C, and yellow 12Y from left. Therefore, ink dots are formed in the order of Y C BK M for the forward motion of carriage 11 and in the order of M BK C Y for the backward motion of carriage 11. Thus, the area of black ink dot is controlled and rough feeling due to dense black can be supressed. Therefore, even when the black ink dot and the ink dot of magenta, cyanogen, etc. are formed at the same point to represent black near magenta, or black near cyanogen, etc., the extent of black ink dot is restricted and the same effect can be obtained.

Description

Detailed Description of the Invention (Technical Field) The present invention uses at least four colors including black (Background of the Invention) In conventional color printers, cyan, magenta,
If the six primary colors of yellow are used, black can be expressed by subtractive color mixture, but high-density black cannot be expressed due to bleeding of ink, toner, etc., or misalignment of coloring positions. Therefore, black coloring material is used to express black in the above 3Jl: Song of Colors, but the highest optical density expressed by black coloring material (
The contrast of the entire image is determined by the OD) value. Furthermore, when trying to express low pD values using black coloring material, it became difficult to express high OD values, and the contrast of the image could not be obtained.

Therefore, the applicant filed Japanese Patent Application No. 58-57699 (Showa 58
By setting the highest OD value expressed by the black colorant higher than the highest OD value expressed by other colorants, a deeper black can be expressed, and We proposed that low OD values be expressed by a mixture of cyan, magenta, and yellow to obtain a high-contrast image.

However, when ink is used as a coloring material and an I\II image is formed with ink dots, the hue expressed changes depending on the order in which the ink dots are stacked.

For example, as shown in FIG. 1, heads are mounted on carriage 1 with black 2BK, cyan 2C1, magenta 2M, and yellow a-
A case will be described in which the printers are arranged in the order of 2Y and the carriage 1 is moved in both directions of arrows a and b to perform reciprocating printing. At this time,
By combining the black expressed by cyan C1 magenta M1 yellow Y and the black expressed by black BK,
Expressing intermediate density, in printing in the forward direction (arrow IL), black BK dots are always formed later as shown in FIG. 2, so the area occupied by black BK is small. Here, the reason why the M and C dots are shifted from the Y dots is that the ink printed later does not adhere to the same spot, but there is a phenomenon in which the ink flows and swims. and the posterior path (arrow b
In printing in the ) direction, black BK dots are printed first, so the black BK occupies a large area as shown in FIG.

As mentioned earlier, the maximum OD value for black is set to be drier than other inks, so in the case shown in Figure 6, black dots stand out and give the viewer a rough feeling, and black ink dots This may cause false contours.

(Object of the Invention) In view of the above-mentioned problems, the present invention provides roughness by limiting the area occupied by black ink dots.

(Description of Embodiment) In this embodiment, the above-mentioned phenomenon of ink flowing and swimming is taken into consideration. This phenomenon occurs because when ink dots are concentrated at one point, the ink absorption capacity of the recording paper exceeds its limit. In other words, if you concentrate the ink dots on one point on the recording paper and strike them over and over again, the color of the first ink dot will be reproduced well, but the ink that was struck later will swim on the surface of the first ink dot and spread to other places. absorbed into
The color is not fully expressed.

When mixing colors, ink dots with high brightness are formed first to avoid the appearance of black ink dots, taking into account that the first ink applied becomes dominant.

FIG. 4 shows one embodiment.

In FIG. 4, the heads are arranged on the carriage 11 in this order from the left: magenta 12M1 black 128K, cyan 12C1 yellow 12Y. Therefore, when the carriage 11 moves forward, ink dots are formed in the order of numbers Y-+C-+BK-+M, and black ink dots are formed as shown in FIG.

Note that the spacing between the ink heads is set to an integral multiple of the spacing d between the formed pixels.

Also, when the carriage 11 moves backward, M-+B K-)
Ink dots are formed in the order of C→Y, and black ink dots are formed as shown in FIG.

In this way, the area of the black ink dots is controlled,
It is possible to suppress the roughness caused by dark black.

Therefore, even when forming black ink dots and magenta, cyan, etc. ink dots at the same point to express a black close to magenta or a black close to cyan, the spread of the black ink dots is limited and the same effect can be obtained. be able to.

FIG. 7 shows the optical density value (maximum OD value) for white light obtained when each ink dot is uniformly formed with a maximum dot diameter of one dot per pixel. As shown in FIG. 7, the highest OD value is in the first ratio of Y<M<C<BK. Therefore, in addition to the example shown in Figure 4, the arrangement is Y-C-BK-M, Y-M.
-BK-C, C-BK-MY, etc. can also be implemented.

Next, a case will be described in which two types of ink having different densities are used for each color ink in order to further improve gradation.

The head is placed on the carriage 11 as shown in FIG. The subscript n indicates dark ink, and t indicates light ink. FIG. 9 shows the maximum OD value of each ink. The heads may be arranged as shown in FIG. 10 in addition to the method shown in FIG. 8, so that the maximum OD value becomes higher toward the center.

Figure 11 shows dark, medium, and light 3 colors for cyan and magenta, respectively.
Equipped with 6 heads that discharge liquid, black and yellow
- indicates a head arrangement when one head is provided to eject ink of a certain density. The subscript f indicates the intermediate density. Figure 12 shows the maximum O of each ink for white light.
It shows the D value. In this way, by using three-density ink for cyan and magenta and one-density ink for black and yellow, the low-density region can be expressed by overlapping Y, M, and C, and the high-density This is because the area can be expressed with black ink dots, so gradation can be ensured. In addition, the human eye is less sensitive to Yep-ink than magenta and cyan, so it does not affect image quality much, but cyan and magenta are highly sensitive, and pale cyan and magenta are especially necessary for expressing human skin. That's why.

In this way, it is possible to obtain sufficiently high Va tonality and image quality with a small number of heads. Regarding the head arrangement, see 1. As in the second embodiment, various arrangement directions are possible.

As described above, in this embodiment, the recording means for each color are arranged so that black ink dots are superimposed and recorded after at least one other color ink dot at the same printing position.

In all of the above embodiments, the ink heads are arranged in consideration of reciprocal printing, but in the case of unidirectional printing, the black ink head may be arranged as far back as possible with respect to the recording paper.

Furthermore, although inkjet recording has been described as an example, the present invention is also applicable to a type of printer that records using ink dots, such as a conventional pen recorder.

(Explanation of effects) As described above, according to the present invention, the size of high-density black ink dots is controlled, it is possible to suppress the occurrence of false contours and roughness, and it is possible to achieve high quality and high resolution. It is possible to obtain a color image with different colors.

[Brief explanation of drawings]

Figure 1 is a diagram showing the arrangement of conventional inkjet heads.
2 and 6 are diagrams showing the printing pattern according to the arrangement of FIG. 1, FIG. 4 is a diagram showing the arrangement of inkjet heads according to the first embodiment of the present invention, and FIGS. FIG. 4 is a diagram showing the printing pattern according to the arrangement; FIG. 7 is a diagram showing the maximum OD value that can be expressed by each ink used in the first embodiment;
FIG. 8 is a diagram showing the arrangement of inkjet heads in the second embodiment, FIG. 9 is a diagram showing the maximum OD value that can be expressed by each ink used in the second embodiment, and FIG. FIG. 11 is a diagram showing the arrangement of the inkjet head of the third embodiment; FIG. 12 is a diagram showing the maximum OD value that can be expressed by each ink used in the sixth embodiment. . In the figure, 11 is a carriage, 12C, 12M, 12Y
, -12BKLt respectively cyan, magenta, yellow,
O showing an inkjet head that ejects black ink Applicant Canon Co., Ltd. - 1NN5 'N5 Seven Sleeps (卦誂

Claims (1)

[Claims] At least pu? The black ink dots are set higher than the ink dots of other colors, including black ink dots, and the black ink dots are superimposed after at least one other color ink dot at the same printing position.