JPH064337B2 - Inkjet recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field In the present invention, ink is ejected in the form of droplets, and the ink is landed on a recording material such as recording paper to print characters,
The present invention relates to a recording apparatus according to a so-called jet recording method for recording an image or the like, and particularly to a recording apparatus suitable for recording a halftone.

(2) Prior Art Inkjet recording is a method in which droplets of a recording liquid (hereinafter referred to as ink) are ejected according to various operating principles, and the droplets are deposited on a recording material to perform recording. Hereinafter, this kind of technique will be described by taking as an example a so-called ink-on-demand system in which ink droplets are ejected toward a recording material and ejected to perform recording only when necessary for recording.

FIG. 2 is a diagram for explaining a schematic configuration of a cylindrical piezo type ink jet nozzle used for one type of ink jet called an ink on demand system and a droplet forming principle thereof.

As shown in FIG. 2, generally, a cylindrical piezo type ink jet nozzle has a cylindrical shape around a hard glass capillary tube 2 having an inner diameter of several hundred μm and having an opening (orifice) 1 whose tip is narrowed down to a size of several tens of μm. Piezo element 3 (for example, PZ
(Made by T, etc.). The other end of the glass thin tube 2 is connected to an ink supply source (not shown) so that ink can be supplied to the nozzle. A uniform metal electrode (not shown) is provided on the surface and the inner surface of the cylindrical piezo element 3, and when a pulse voltage of several tens of V and about 10 μs is applied between the electrodes, the piezo element 3 will be shown in FIG. As shown in 2), it deforms into a state that it is grasped by the hand. Due to the displacement applied to the ink in the hard glass thin tube 2 due to this deformation,
From the orifice 1, the ink becomes droplets having a diameter of several tens of μm and flies forward. Piezo element 3 when the pulse voltage is cut off
Returns to its original shape as shown in FIG. 2 (3), and then the ink in the orifice returns due to the surface tension of the ink as shown in FIG. 2 (4), completing one ejection operation.

In such an ink jet nozzle, when the voltage applied to the piezo element 3 is changed, the amount of ink ejected,
That is, the diameter also changes. Therefore, by controlling the applied voltage and pulse width applied to the piezo element 3, it is possible to change the ink droplet diameter and control the recording density.

FIG. 3 is a diagram showing the relationship between the pulse voltage value applied to such a piezo element and the recording density.

As shown in FIG. 3, as the pulse voltage is increased, the ejected ink droplet diameter is increased, and the size of the ink dot on the recording paper is increased as shown in the figure. Here, if the same ink is used and the dot density per unit area is made constant, the ink density is constant regardless of the size of the recorded dot diameter, and the dot density per unit area is also Since it is constant, the density when viewed as a whole in a certain area on the recording paper can be changed as the visual density by changing the area of each dot.

By changing the pulse voltage value applied to the piezo element in this way and changing the recording area of the ink dots,
It is possible to change the recording density.

Conventionally, as a method of expressing a halftone by such an ink jet method, since the ink jet method ejects ink in the form of droplets, a method of controlling the area of recording dots as shown in FIG. However, this has a problem that when the voltage is changed, the ejection speed is also changed, and the accuracy of landing of the ink droplets on the recording paper is lowered. Also, there is a limit in the half-tone range, especially in the low density region. It was difficult to express. In order to improve this, a method of changing the number of dots per unit area is also adopted. However, since this method takes a matrix configuration of mxn, the larger the number of halftones, the larger one pixel unit becomes. For example, high resolution is required. However, it is a problematic method because of its low resolution despite its high cost.

In order to solve these problems, a method of using two or more kinds of inks having different densities and controlling the applied voltage to obtain a wider range of density change (JP-A-53-102034), or an ink erasing liquid A method has been proposed in which a white paint is ejected and the concealment ratio of dots is changed by a kind of masking to realize a halftone in a wide area (JP-A-56-150557).

In the former case, for example, in the case of color recording, it is necessary to use two or more kinds of dark and light inks for each color of Y (yellow), M (magenta), C (cyan), and Bk (black). The number of ink tanks, ink supply system, drivers, etc. are required at least twice, resulting in a complicated and expensive impractical recording device. On the other hand, in the latter case, a material such as white paint is hard to obtain with a dye and becomes a pigment, which easily solidifies, which makes environmental conditions and the burden on the device very large and difficult to realize. Further, regarding the ejection of the ink erasing liquid, there is an unknown number of studies of incorporating the liquid in the ink jet, and there are problems such as dot bleeding and sharpness on the recording paper, which is not always a good method.

(3) Disclosure of the Invention The present invention has been made in view of the above points, and an object of the present invention is to provide a novel inkjet that solves the problems of the above-mentioned conventional examples with regard to the expression of a halftone in an inkjet recording method. To provide a recording device.

That is, according to the present invention, in an ink jet recording apparatus that ejects ink in the form of droplets and lands them on a recording material to perform recording, in addition to a nozzle that ejects a colored ink for recording, a coloring component is provided. A nozzle for ejecting the removed colorless transparent ink is further provided, the ejection timing of the colorless transparent ink and the ejection timing of the colored ink are controlled, and the landing position of the colorless transparent ink and the colored ink on the recording material. The present invention provides an ink jet recording apparatus characterized in that multi-tone expression is performed by changing the amount of deviation of the color transparent ink and changing the amount of overlap of the colorless transparent ink and the colored ink.

(4) Embodiments of the Invention Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 4 is a sectional view of the recording dots for explaining the state of the recording dots as described above on the recording paper.

The colored ink droplets ejected from the nozzles for ejecting the colored ink land on the recording material such as the recording paper 5 to form the recording dots 6. Because the dots are the discharge pressure, they are shown in FIG.
As in (1), the recording paper has a hemispherical shape that penetrates in the thickness direction. When the colorless and transparent ink is landed on the recording dots 6, the recording dots 6 are pushed into the recording paper 5 by the landing pressure of the colorless and transparent ink, and are spread slightly in the lateral direction as shown in FIG. 4 (2). Becomes At this time, the coloring component in the recording dots is mixed with the colorless transparent ink and sinks inside the recording paper, so that the apparent reflection intensity is lowered and an effect similar to that obtained by recording with the light color ink is obtained. In the figure, the colored ink portion is indicated by diagonal lines, and the colorless and transparent ink portion is indicated by dotted lines. Further, 7 and 8 are dot diameters when the colored ink and the colorless transparent ink are landed, respectively.

Of course, contrary to the case shown in FIG. 4, when the colorless transparent ink is ejected first and the colored ink is superposed on this,
It goes without saying that the same effects as above can be obtained. However, when a highly volatile ink is used, a part of the colorless and transparent ink volatilizes before landing of the colored ink, resulting in insufficient mixing of the colored ink and the colorless and transparent ink, resulting in a lightening effect. In some cases, it is preferable to overlay the colorless transparent ink on the colored ink as in the former case.

An example of an ink jet recording apparatus for implementing such a light color expression is shown in FIG. 1 (1). It should be noted that in FIG. 1 (1), only the nozzle head portion is shown for simplification of description, and for comparison, an example of a conventional nozzle head is shown in FIG. 1 (2).
Shown in.

As shown in FIG. 1 (1), the ink jet recording apparatus of this example uses Y (yellow), M (magenta), C (cyan), and Bk (black) inks for performing color recording as described above. In addition to the conventional nozzle head having four nozzles for ejecting (see FIG. 1 (2)), a nozzle head 4 in which one nozzle T for ejecting colorless transparent ink according to the present invention is added is provided. There is. These nozzles have the same structure as the conventional nozzle shown in FIG. The nozzle head 4 is mounted on a carriage (not shown), and the recording surface of the recording paper 5 is operated in the left-right direction in the drawing. The nozzles for ejecting the Y, M, C, and Bk colored inks and the nozzles T for ejecting the colorless transparent ink have their ejection positions controlled by a control mechanism (not shown) similar to the conventional one. When the ink reaches the discharge position on the recording paper, a desired ink droplet is discharged. The colorless transparent ink is ejected only on the portion of the recording dot that needs to be expressed in a light color, and the recording dot is lightened by the principle shown in FIG.

That is, the present invention provides an ink jet recording apparatus capable of expressing a light color with a simple configuration such as the addition of one nozzle T for ejecting colorless transparent ink to the conventional nozzle head as in the present example. it can. of course,
A plurality of nozzles for ejecting the colorless transparent ink may be provided as desired.

By the way, in FIG. 4, only the principle of light color expression in the present invention has been described. However, in the ink jet recording apparatus of the present invention as described above, for example, the following multi-tone expression is also possible.

FIG. 5 is a diagram showing a relationship between ink droplets and ejection positions, which is shown for explaining such multi-tone expression.

The carriage equipped with the nozzle head as in the above example is scanned at a scanning speed Vn = 0.8 m / s, and the ink droplet ejection speed is Vd.
= 8 m / s and the distance L between the nozzle and the recording paper is L = 1 mm, the deviation distance l between the ink droplet ejection point a and the ink droplet landing point b on the recording paper is l = (L / Vd) × Vn = (1 × 800) /8000=0.1 mm and l = 100 μm.

Here, if the dot size on the recording paper is 300 μm,
By delaying the ink droplet ejection time by 187.5 μs,
187.5 μs × 0.8 m / s = 150 μm on the recording paper, that is, it can be landed with a half dot offset.

Therefore, if the colorless and transparent ink is ejected at a position where the colored ink is ejected with a delay of 187.5 μs from the time when the colored ink is ejected, the colorless and transparent ink is applied on the recording dots of the colored ink while being shifted by half a dot. be able to.

By changing the ejection timings of the colorless transparent ink and the colored ink in this way, it is possible to change the amount of deviation between the landing positions of the two on the recording material, and as shown in FIG. Colored ink and colorless transparent ink on the recording material are not only overlapped with the colored ink as it is, but also the colored ink and the colorless transparent ink are overlapped by shifting the colored ink and the colorless transparent ink as shown in FIGS. 6 (1) and (2). It is possible to arbitrarily control the degree of overlap of the two by controlling the discharge timings of both. The difference in the overlapping degree between the colored ink and the colorless and transparent ink appears as a change in the apparent density of the recording dots, so that the same multi-tone expression as when using several kinds of light color inks can be achieved.

(5) Effects of the Invention As described above, in addition to the nozzle for ejecting the colored ink, the apparatus of the present invention provided with a nozzle for ejecting the colorless transparent ink, the colored ink and the colorless transparent ink It became possible to express halftones with the simple method of overlapping on the recording material. In addition, by controlling the overlapping of the colored ink and the colorless transparent ink, it is possible to express in multiple gradations, and the expressible density range can be expanded.

[Brief description of drawings]

FIGS. 1 (1) and 1 (2) are views for explaining an example of an inkjet recording apparatus of the present invention and an example of a conventional inkjet recording apparatus shown for comparison, and FIG. 2 is a cylindrical piezo type. FIG. 3 is a diagram illustrating a schematic configuration of an inkjet nozzle and a droplet formation principle thereof, FIG. 3 is a diagram showing a relationship between a pulse voltage value applied to a piezo element and a recording density, and FIGS. 4 and 6 are recording dots. FIG. 5 is a cross-sectional view of recording dots for explaining the state on the recording paper, and FIG. 5 is a diagram showing the relationship between ink droplets and their ejection positions. 1 --- Aperture 2--Hard glass thin tube 3--Piezo element 4--Nozzle head 5--Recording paper Y, M, C, Bk, T --- Nozzle

Claims (4)

[Claims] 1. An ink jet recording apparatus for ejecting ink in the form of liquid droplets and landing the ink on a recording material to perform recording, in addition to a nozzle for ejecting a colored ink for recording, a coloring component is provided. A nozzle for ejecting the removed colorless transparent ink is further provided, the ejection timing of the colorless transparent ink and the ejection timing of the colored ink are controlled, and the landing position of the colorless transparent ink and the colored ink on the recording material. An ink jet recording apparatus, wherein multi-gradation expression is performed by changing the amount of deviation of the color transparent ink and changing the amount of overlap of the colorless transparent ink and the colored ink. 2. The ink jet recording apparatus according to claim 1, wherein the colorless transparent ink and the colored ink are selectively ejected and mixed on a recording material. 3. The ink jet recording apparatus according to claim 1 or 2, wherein the colorless transparent ink is superposed and mixed on the colored ink on the recording material. 4. The ink jet recording apparatus according to claim 1, further comprising a plurality of nozzles for ejecting the colorless transparent ink.