JPH0347756A - Ink jet printer - Google Patents

Abstract

PURPOSE:To control a lightness and to improve the colour expression of a whole recording by a method wherein a lower density ink is used as black ink in comparison with the other colour inks in a printer using inks of four colours. CONSTITUTION:A low-density ink having a density ratio of approximately 1/2 is used for black. In this manner, the highest density of black is lower than that of any other three colours, but the number of gradation steps in the expression of a density range is increased in inverse proportion to a density ratio of a shade. For example, in the expression wherein a density range from the minimum to the maximum is divided into 6 steps, 6 gradation steps are available for black for expressing a density ranging from zero to (a), but only 3 steps are available for the other three colours. As a result, it may be said that a density difference between unit gradation steps is small with respect to black in comparison with the other colours. A density ratio may be determined to have an optimum value by taking characteristics of ink, paper, and the like into consideration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet printer, and particularly to an inkjet printer that performs color recording using multicolor ink.

[Conventional technology]

In recent years, with the spread of computer graphics technology,
Advanced image processing has become possible on color displays, and there is an increasing demand for hard copies of these images. As a printer that satisfies these demands, full-color inkjet printers having a gradation expression function are being put into practical use.

FIG. 3 is a density characteristic diagram showing an example of gradation expression in such a conventional printer.

As shown in Figure 3, the density of each of the yellow, magenta, cyan, and black inks is the same, and the expression at each gradation step is the unit change in gradation expressed by changing the diameter, etc. The concentrations are also set to be equal.

[Problem to be solved by the invention]

In the conventional inkjet printer described above, in its method of expressing gradations, the same gradation step, including black, produces the same density, resulting in an unnatural density of a color that stands out in human visual characteristics, that is, black. The disadvantage is that the increase is noticeable.

Furthermore, since black uses the high density area less frequently in recording, the number of commonly used steps in the gradation steps divided from the highest density to the lowest density is reduced. Therefore, there is a drawback that recording is inevitable with poor gradation effects.

An object of the present invention is to provide an inkjet that can eliminate unnatural changes in brightness by reducing density changes for each unit gradation, and that can also improve brightness control and color expressivity of the entire recording.・Providing printers.

[Means to solve the problem]

The inkjet printer of the present invention is an inkjet printer that performs color recording using inks of four colors: yellow, magenta, cyan, and black, and is characterized in that only the black ink is a low-density ink compared to other inks. There is.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of the main parts of an inkjet printer showing one embodiment of the present invention.

As shown in FIG. 1, this embodiment shows the main parts of an apparatus for color recording, and connects ink tanks of each color provided at arbitrary positions in the apparatus (not shown) to connectors 5 and 5. Ink is supplied to the head 1 via the supply tube 4. This head 1 is fixed on a carrier 2 that can slide on a guide shaft 3 that is arranged parallel to the axial direction of a drum 7 with a recording paper 8 wound thereon at a constant interval. Furthermore, this head 1 is fixed in a direction with its leading end facing the recording paper 8.

In the recording operation, the drum 7 around which the recording paper 8 is wound is rotated, and the carrier 2 is moved until all the heads 1 scan the surface of the recording paper 8. During this time, an output signal having both timing and gradation steps is sent from a control section (not shown) to each head via a signal line (also not shown).
Color recording is performed over the entire area of the recording paper 8 by applying 0 or more operations to eject the ink droplets 6.

FIG. 2 is a density characteristic diagram showing an example of gradation expression in the printer of the present invention.

As shown in FIG. 2, a low density ink is used for black, and here is an example where the density ratio is approximately 1/2. As a result, the maximum density of black is not as high as that of the other three colors, but the number of gradation steps when expressing a certain density range increases in inverse proportion to the density ratio of shading.

For example, in the model shown in the figure, which divides and expresses the lowest to highest concentration into six steps, the concentration is 0.
In order to express ~a, black must be 6 gradation steps.
Steps can be used, while the other three colors can only use 3 steps. As a result, it can be said that the density difference in a unit gradation step is smaller for black. In the example used this time, an ink with a density ratio of 1/2 is used for explanation, but in actual application, the optimum value should be determined by taking into account the characteristics of the ink, the characteristics of the paper, etc. Just do it.

〔Effect of the invention〕

As explained above, the inkjet printer of the present invention uses a low-density black ink to reduce density changes for each unit gradation step, thereby reducing unnatural brightness on recording. It becomes possible to eliminate the change, and this also has the effect that the brightness can be controlled more delicately at the same time. In turn, this has the effect of improving the color expressivity of the record as a whole.

[Brief explanation of drawings]

Fig. 1 is a plan view of the main parts of an inkjet printer showing an embodiment of the present invention, Fig. 2 is a density characteristic diagram showing an example of gradation expression in the printer of the invention, and Fig. 3 is an example of conventional gradation expression. FIG. DESCRIPTION OF SYMBOLS 1... Head, 2... Carrier, 3... Guide shaft, 4... Supply tube, 5... Connector, 6
... Ink droplets, 7... Drum, 8... Recording paper.

Claims (1)

[Claims] An inkjet printer that performs color recording using inks of four colors: yellow, magenta, cyan, and black, characterized in that only the black ink is used as an ink with a lower density than the other inks.