JPH01297259A - Ink jet printer - Google Patents

Abstract

PURPOSE:To represent gradation of fine texture, by a method wherein a plurality of nozzles about a same color are established, are united into one bundle or one piece at their top parts, and ink of different density is supplied to each ink nozzle to be jetted simultaneously. CONSTITUTION:Ink which has respectively a same color and only different density is put in ink tanks 1a and 1b. Supply of ink of each density to ink nozzles 3a, 3b is performed by an ordinary method. By simultaneously sending ink in nozzle 3a, 3b directions by taking piezoelectric elements 2a', 2b' built-in head parts 2a, 2b as driving sources, ink is jetted from an opening part 6 of a united nozzle. Voltage is applied to those piezoelectric elements 2a', 2b' according to an image signal, and each ink is jetted toward recording paper from a nozzle top. By, for instance, uniting the ink nozzle 3a and the ink nozzle 3b capable of representation of four steps of gradation at their tops and by applying voltage to the piezoelectric element according to each gradation number p2, 8 steps of gradation can be represented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to an inkjet printer, and more particularly, to gradation control of an inkjet printer, and is a method for controlling the simultaneous ejection of two or more types of ink of the same color with different densities. The present invention relates to an inkjet printer that improves gradation reproducibility by doing so.

[Conventional technology] In conventional inkjet printers, gradation expression is
A method of changing the number of dots placed in a single area (matrix) (hereinafter referred to as dot density control method), or a method of changing the area of dots by controlling the amount of ink ejection (ink droplet diameter) (hereinafter referred to as dot area control method) It was carried out by law).

[Problem to be solved by the invention] However, in the dot density control method, as the number of expression gradations increases, the number of dots per pixel also increases, so it is necessary to reduce the diameter of the ink nozzle, but it is necessary to reduce the diameter of the ink nozzle. There is a limit to the nozzle diameter due to the occurrence of such problems, and it has been difficult to express multiple gradations without reducing pixel density.

Further, the dot area control method has a problem in that it is difficult to control the diameter of ejected ink droplets, so it is not possible to increase the number of gradations.

That is, in general, the gradation expression of conventional inkjet printers has not been fully satisfactory in terms of gradation reproducibility.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inkjet printer that solves the above-mentioned problems of conventional inkjet printers and improves gradation reproducibility, which is extremely important for printer performance.

[Means to solve the problem]

The present invention provides an inkjet printer that performs printing by ejecting ink from an ink nozzle toward recording paper.
It has a plurality of nozzles of two or more for the same color, the ink nozzles are combined into one bundle or one at the tip, and ink of different density is supplied to each ink nozzle, and these inks are printed on recording paper. This is an inkjet printer characterized by ejecting ink toward both directions at the same time.

[Effect]

Ink nozzles used for the same color according to the present invention,
In other words, it consists of two or more ink nozzles, which are combined into one bundle or one ink nozzle at the tip (hereinafter referred to as
The combined nozzle mixes the inks with different densities sent out from each ink nozzle before and after the ejection port (including on the recording paper), and directs the ink with the intermediate density of the supplied inks toward the recording paper. gush. As a result, 1
Compared to the case where a single ink nozzle is used for each color, it is possible to express finer gradations at intermediate densities.

〔Example〕

FIG. 1 is a diagram showing an embodiment of an ink jet printer of the present invention, and in particular is a schematic diagram of a mechanism for supplying ink to an ink nozzle.

In this figure, both la and lb are ink tanks, and the ink tanks la and lb each contain ink of the same color but different density. For example, if the ink concentration in the ink tank 1a is 1, then the ink tank 1b contains ink with an ink concentration of 2 (twice the concentration of the former). 2a and 2b are head portions of each ink supply mechanism, and these have built-in piezoelectric elements 2a' and 2b' which are driving sources for ejecting ink. 3
Both a and 3b indicate ink nozzles for each ink. Further, 5 is a combined nozzle according to the invention, and 6 is an opening of the combined nozzle 5.

As illustrated in FIG. 1, the combined nozzle 5 according to the present invention collects the tips of conventional single ink nozzles 3a and 3b into a bundle, and combines the respective openings into one opening. The structure has a structure in which a portion 6 is formed, or a structure in which they are assembled into one bundle and their openings are joined to each other. However, it is not limited to this as long as it has the effect described above. The area of the opening 6 (30 to 60 μm in diameter) is preferably approximately the same as the area of the opening of a single conventional ink nozzle. Further, the number of ink nozzles per color is usually preferably about 2 to 3 in consideration of the dot area.

Next, the operation of the ink supply mechanism will be explained.

In the ink supply mechanism according to the present invention, ink of each concentration is supplied to the ink nozzles 3a, 3b according to a conventional method. That is, piezoelectric elements 2a' built into the head parts 2a and 2b.

The ink is ejected from the opening 6 of the combined nozzle by simultaneously sending ink toward the nozzles 3a and 3b using the drive source 2b'. A predetermined voltage is applied to the piezoelectric elements 2a' and 2b' according to the image signal to be printed, and each ink is ejected from the nozzle tip toward the recording paper by deformation of the piezoelectric element at this time.

Next, gradation expression in the inkjet printer of the present invention will be explained with reference to FIG. 2 and the above-mentioned FIG. 1.

Now, the voltage applied to the piezoelectric elements 2a', 2b' is controlled in four stages, and the amount of ink ejected from the tips of the ink nozzles 3a, 3b of each density is controlled in four stages accordingly. This will be explained using an example.

FIG. 2 is a schematic explanatory diagram of the gradation control method according to the present invention in this case, and FIG. It is something. Actually, the print dot diameter changes depending on the number of gradations p+, but for the sake of simplicity, a schematic diagram in which one circle is divided into four is used. FIG. 2B is a diagram showing the voltage applied to the piezoelectric element corresponding to each gray scale number p1. Also, the same figure (
C) shows the number of gradations p2 and the corresponding ink amount (in the figure) in the combined nozzle 5 according to the present invention, in which the ink nozzle 3a and the ink nozzle 3b, which are capable of expressing four levels of gradation, are combined at their tips. Figure (d) shows the head portion 3a corresponding to each gradation number p2.

The voltage applied to each piezoelectric element in 3b, and the dot area corresponding to each gradation number p2 in the same figure (e) are calculated using the single nozzle as the gradation number p1=
The case where 4 is printed is expressed as 1. In the case of the present invention, a combined nozzle 5 is used, which is a combination of two ink nozzles 3a and 3b, and ink of different density is introduced to each nozzle. ) is applied to the piezoelectric element, it is possible to express 8 levels of gradation.

As an example, let us consider the case where dots are printed at the number of gradations p2=5. 1/4 dot of ink with a density of 1 is sent from the head section 2a, and a dot of ink with a density of 2 is sent out from the head section 2b. In the combined nozzle 5 according to the present invention, these inks have one tip (
Alternatively, since the ink is sent out from each of the head sections 2a and 2b, the ink jets out and mixes as it flies toward a recording paper (not shown) to form one dot. The dot area at this time is 3/4. Other gradations can be expressed in the same way, making it possible to express fine-grained gradations.

〔Effect of the invention〕

As explained in detail above, according to the present invention, a plurality of inks of the same color with different densities are used and are ejected and printed as one dot. It is possible to express far more tones than can be expressed by area control, and it is possible to express fine-grained tones that are faithful to the original image.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the ink supply mechanism of the inkjet printer of the present invention, and FIG. 2 is a schematic explanatory diagram of the gradation control method of the present invention. The amount of ink, the figure (b) shows the applied voltage corresponding to the number of gradations p, the figure (C) shows the number of gradations p2 and the ink amount of the combined nozzle according to the present invention, and the figure (d) shows the number of gradations. The applied voltage corresponding to p2 and (8) in the same figure show the dot area. la, 1b・”ink tank, 2a′, 2b′ −・
・Piezoelectric element, 3a, 3b... Ink nozzle, 5...
Combined nozzle, 6... opening. Patent applicant Kunio Kakiki, representative of Victor Japan Co., Ltd. Figure 1

Claims (1)

[Claims] An inkjet printer that performs printing by ejecting ink from ink nozzles toward recording paper, which has two or more nozzles for the same color, and the ink nozzles are combined into one bundle or one ink nozzle at their tips. An inkjet printer characterized in that inks of different densities are supplied to each ink nozzle, and these inks are ejected simultaneously toward recording paper.