JPH0454587B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dot recording method for achieving improved image quality.

In conventional multi-nozzle color inkjet recording, one of the causes of image quality deterioration is periodic missing prints on recording paper due to misalignment in the direction of ink droplet ejection between nozzles.

Color images including halftones have many solid areas, and when recording with a multi-nozzle ink jet head, the unevenness in the ejection direction between nozzles has a very large effect on the image quality. Since this occurs on the recording paper at the correct period, it is easily noticeable to the human eye and unnecessarily worsens the quality of the recorded image.

Such problems cannot be solved by screen angle processing conventionally performed in the printing field. This is because a large number of nozzles cannot be individually controlled.

The present invention has been made in view of the above points, and is intended to solve the problem of periodic image blanking during recording, which occurs when the recording method, especially the ejection direction of ink droplets ejected from each nozzle of a multi-nozzle ink jet head, becomes uneven. The purpose is to suggest ways to prevent this.

That is, the present invention solves a problem peculiar to an on-demand type inkjet recording head equipped with a large number of ejection ports. This is to improve striped image unevenness that occurs when a predetermined image cannot be formed due to changes in the ink ejection state.

The present invention provides the steps of: relatively moving a multi-ink jet recording head having a plurality of ejection ports and a recording material in a direction crossing the arrangement direction of the plurality of ejection ports;
During the relative movement, ink is ejected as droplets from the ejection opening of the inkjet recording head based on the recording signal, and dots are recorded on the recording material. While the recording head is being moved, ink is ejected from the ejection ports based on a recording signal while randomly vibrating the recording head in a direction crossing the relative movement direction, so that ink droplets are randomly covered. To provide a dot type recording method characterized by improving image quality unevenness by landing on a recording material.

The present invention uses random vibrations of the recording head to eliminate periodic image omissions of recording dots that occur due to variations in the ejection ports of an on-demand recording head or changes in the ink ejection state of the recording head. It is possible to visually eliminate periodic image omissions from the final image, and visually eliminate periodic disturbances in the overall image due to periodic vibrations.

In particular, in the case of recording heads that use thermal energy to eject ink from the ejection ports, the head itself has excellent ink ejection characteristics, so slight disturbances in the ink ejection characteristics or slight manufacturing errors can cause overall problems. The effects of the present invention are particularly excellent because even slight disturbances in image quality become more noticeable.

The present invention will be specifically described below with reference to the drawings.

FIG. 1 shows an example of a conventional multi-nozzle ink jet head. 101 is a substrate having a heating element for ejecting liquid ink and forming flying droplets, and a lead wire section for applying an electric signal to the heating element; 102 is a liquid ink inlet made of glass; Board cut into a semicircular shape for the purpose, 103
indicates one of the multi-nozzles. 104 is a power supply cable to the head, and 105 is an ink supply cable.

In such a multi-nozzle ink jet head, when the heating element is energized, the ink is heated, bubbles are generated, and the ink is ejected. During this ink ejection, the angle of the ejection direction is not necessarily constant for each nozzle. Conventionally, the recording position can be controlled by controlling the ink droplet ejection timing in the head scanning direction or recording paper scanning direction, but it is not possible to control the recording position in the direction perpendicular to the scanning direction. Nakatsuta.

FIG. 2 shows an example of solid black recording using a head of the same type as the multi-nozzle inkjet head shown in FIG. 1, and shows an image sample when the head is moved in the direction of the arrow. The numbers 1, 2, 3, etc. indicate the direction of change over time, and ABC... indicates the nozzle position.
In this figure, the ink droplets ejected from the nozzles A to D, F, and G are printed normally, and the ink droplet E is printed with a position shift of half a dot. As is clear from FIG. 2, there is a gap between the dot rows 206 and 207, which causes horizontal stripes in the image and makes it very difficult to see. This type of printing misalignment is
Even if the gap is about 10 μm, if it occurs uniformly over a long period, it will become very noticeable to the human eye.

The present invention enables the head to move in the same direction as the multi-nozzle arrangement direction, whereas the conventional head or printing paper was moved only in the direction perpendicular to the multi-nozzle arrangement direction. The feature is that the ink droplets can be moved arbitrarily in any direction.

FIG. 3 is an example of solid black recorded by the recording method of the present invention. Each time an example is recorded, the multi-nozzle head is moved in the same direction as the nozzle arrangement by an arbitrary distance and at fine intervals. The figure shows an example in which half of the print dot diameter is shifted for each line. As a result, the gap between the straight lines 206 and 207 in FIG. 2 is narrowed, and the portion that cannot be recorded is reduced compared to FIG.

However, even if the recording head is changed at regular intervals in this way, periodic oscillations will cause periodic disturbances in the overall image, resulting in visual disturbances.
Image unevenness occurs at regular intervals.

In order to solve this problem, the present invention visually improves the periodic image unevenness in the image shown in Figure 3 by applying random vibrations to a multi-inkjet recording head equipped with multiple ejection ports. However, as a result, it was possible to form a high-quality image that was not affected by the recording head. In the case of color images, in order to superimpose three or four colors, if you shift the moving distance in the nozzle arrangement direction for each color plate,
This gap can be made almost inconspicuous.

In FIG. 3, the numbers having the same last two digits as in FIG. 2 indicate the same items.

FIG. 4 shows one preferred embodiment of a recording head for implementing the recording method of the present invention.

The recording head shown in FIG. 4 has the same structural parts as the recording head shown in FIG. 1, including a glass member 401, a heating element 402, an orifice 403,
404 is a vibration means for vertically moving the entire head in the nozzle arrangement direction. 405 is a stand for fixing the head unit.

The vibrating means 404 can be constituted by a commonly used means such as a motor with a built-in cam mechanism, an electrostrictive element, or a pipelator using an electromagnetic element.

The present invention solves a problem peculiar to on-demand inkjet recording heads equipped with a large number of ejection ports due to random vibrations of the print head, namely, manufacturing variations in at least one of the many ejection ports.
Alternatively, it can improve the striped image unevenness that occurs when a predetermined image cannot be formed due to changes in the ink ejection state during recording, etc., and eliminate periodic image omissions of recorded dots from the final image, and eliminate periodic vibrations. It is also possible to visually eliminate periodic disturbances in the overall image due to

In particular, in the case of a recording head that uses thermal energy to eject ink from the ejection ports, the head itself has excellent ink ejection characteristics, so slight disturbances in the ink ejection characteristics or slight manufacturing errors may cause the entire head to eject ink. The effects of the present invention are particularly excellent because even slight disturbances in image quality become more noticeable.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of a conventional recording head.
FIG. 2 is an explanatory diagram for explaining the recording state according to the conventional method, FIG. 3 is an explanatory diagram for explaining the recording method of the present invention, and FIG. 4 is a suitable diagram of a recording head for embodying the present invention. FIG. 2 is a schematic perspective view for explaining an example. 101...Substrate part, 102...Glass plate, 10
3... Nozzle, 104... Energizing cable, 105
...Ink supply cable.

Claims (1)

[Scope of Claims] 1. A multi-ink jet recording head having a plurality of ejection ports and a recording material are relatively moved in a direction intersecting the arrangement direction of the plurality of ejection ports, and during the relative movement. In the dot type recording method, in which ink is ejected as droplets from the ejection opening of the inkjet recording head based on a recording signal to record dots on the recording material, the above-mentioned droplets are recorded while the recording head and the recording material are moving relative to each other. While the recording head is randomly vibrated in a direction crossing the relative movement direction, ink is ejected from the ejection ports based on the recording signal, and ink droplets randomly land on the recording material. A dot recording method that is characterized by improving uneven image quality. 2. A recording method for forming a color image using a plurality of recording heads each ejecting a plurality of different inks as the recording head, wherein the plurality of recording heads move distances deviated from each other in the arrangement direction. A dot-type recording method according to claim 1. 3. The dot type recording method according to claim 1 or 2, wherein the recording head discharges ink using heat generated by a heating element.