JP2001353857A - Ink jet head and ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet head suitable for reduction in size and for high speed highlight printing. SOLUTION: The ink jet head 4 of an ink jet printer 1 comprises first and second ink nozzle arrays 100, 200 and the interval e of these nozzle arrays is less than 1 mm. Ink nozzles of both arrays are staggered mutually at one half pitch P/2. Furthermore, the quantity of ink m (ng) being ejected for printing one dot on a recording sheet is set lower than P/2. Since overlap can be reduced between a dot of first color being ejected from the first ink nozzle and a dot of second color being ejected from the second ink nozzle, color mixing due to blur can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head and an ink jet printer having first and second ink nozzle arrays for discharging different color inks.
In particular, the present invention relates to an inkjet head and an inkjet printer which are suitable for miniaturization and suitable for high-speed printing of highlight printing or the like without causing ink bleeding.

[0002]

2. Description of the Related Art In general, an ink-jet printer reciprocates an ink-jet head mounted on a carriage in a printing direction (sub-scanning direction) orthogonal to a conveying direction (main scanning direction) of a recording medium as a recording medium. In synchronization with the above, ink droplets are ejected from a plurality of ink nozzles formed in the ink jet head to form a desired print image on recording paper. As an ink jet printer having this configuration, a printer equipped with a so-called two-color ink jet head in which two ink nozzle rows for discharging different color inks are formed on an ink jet head is known.

[0003] A two-color ink jet head discharges a first ink nozzle array in which first ink nozzles for discharging a first color ink, generally a black ink, are arranged at a fixed pitch, and a second color ink. And a second ink nozzle row in which the second ink nozzles are arranged at a constant pitch. Generally, the first and second ink nozzle rows are arranged in the main scanning direction, and the diameter of ink dots ejected from the ink nozzles and formed on a recording medium (landing dot diameter) is larger than the nozzle pitch. For this reason, the portion where the print dot diameter from the adjacent nozzle overlaps the ink amount is approximately twice that of the other nozzles, and it takes a long time to fix the recording paper.

In the printing operation, in order to avoid color mixture (bleeding) due to bleeding between the first and second color inks on the recording paper, the ink nozzles are included in the head nozzle row on the head side in the main scanning direction during scanning of the ink jet head. After a predetermined time has elapsed after driving the ink nozzles to be driven, the ink nozzles included in the subsequent ink nozzle row are driven. In particular, print characters in a certain color,
In the case of performing so-called highlight printing in which the background is printed in another color, it is necessary to minimize bleeding.

In general, in order to avoid bleeding, it is necessary to allow several milliseconds between ink discharges. Here, considering that the moving speed of the ink jet head is about 50 cm / s, it is necessary to provide a gap of several mm between the first and second ink nozzle rows.

[0006]

As described above, the conventional 2
In a color inkjet head, a predetermined amount of ink nozzle row distance is required to avoid bleeding,
It is difficult to reduce the distance between the ink nozzle rows due to downsizing of the inkjet head. If the scanning speed of the ink jet head is reduced, the distance between the ink nozzle rows can be reduced, but this is not practical because the printing speed is reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink jet head and an ink jet printer which are advantageous for miniaturization and which can perform highlight printing or the like at a high speed without causing ink bleeding.

[0008]

In order to solve the above-mentioned problems, the present invention has first and second ink nozzle rows arranged at regular intervals, and the first ink nozzle row is A plurality of first ink nozzles for discharging the first color ink are arranged at a constant pitch P (μm), and the second ink nozzle row is a plurality of first ink nozzles for discharging the second color ink. In the ink jet head in which two ink nozzles are arranged at the same pitch as the pitch, the first and second ink nozzle rows are relatively displaced in the ink nozzle arrangement direction by a half pitch. The diameter of an ink dot ejected from a nozzle and formed on a recording medium is smaller than P.

In the present invention, each of the ink nozzles forming the first ink nozzle row and each of the ink nozzles forming the second ink nozzle row are arranged in a staggered manner, which are shifted from each other by a half pitch. ing. Accordingly, ink dots formed by the ink nozzles of the second ink nozzle row are formed between the ink dots formed on the recording medium by the ink nozzles of the first ink nozzle row.

If the diameter of the ink dot formed on the recording medium (landing dot diameter) is set to a value smaller than P as in the present invention, the ink is ejected from the same row of ink nozzles and formed on the recording medium. Since the overlapped portions of the ink dots do not occur, the ink is fixed in a short time. For that reason,
Since the ink ejected from the ink nozzles of the other rows uniformly penetrates into the recording medium until the ink is superimposed, a decrease in print quality due to bleeding can be reduced to such an extent that no problem occurs.

Therefore, if the configuration of the present invention is adopted,
Since the interval between the first and second ink nozzle rows can be reduced to a value less than the production limit of 0.07 to less than 1 mm, the size of the ink jet head can be reduced. In addition, it is possible to perform highlight printing at high speed without causing ink bleeding.

Next, an ink jet printer according to the present invention is provided with the ink jet head having the above configuration. In the ink jet printer having this configuration, the size of the ink jet head can be reduced, so that the overall configuration can be reduced accordingly. In addition, highlight printing and the like can be performed at high speed without bleeding.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an ink jet printer having an ink jet head according to the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of the ink jet printer of this embodiment. The ink jet printer 1 is composed of a recording paper 2
A platen 3 for transporting the ink jet head in the main scanning direction Y, an ink jet head 4 having a nozzle surface facing the platen 3, and a carriage 5 for reciprocating the ink jet head 4 in the sub scanning direction X. And an ink tank 6 for supplying ink to each ink nozzle of the inkjet head 4. The ink tank 6 is the first
And an ink tank in which the second color ink is stored. Each ink nozzle of the eject head 4 is assigned with each color ink as described later.

A nozzle cap 7 is disposed at a position deviated from the platen 3 in the sub-scanning direction X. The nozzle cap 7 communicates with the discharged ink recovery unit 9 via an ink pump 8. By using the nozzle cap 7, drying of the ink nozzle, prevention of clogging, and the like, recovery operation thereof, and the like are performed.

FIG. 2A is an explanatory view showing the ink nozzle arrangement of the ink jet head 4 as viewed from the nozzle surface side. As shown in this drawing, the inkjet head 4 of the present example has a first ink nozzle 11 (1) to 11 (64) having a plurality of, for example, 64 first ink nozzles 11 (1) to 11 (64) arranged along the main scanning direction Y. Ink nozzle row 100
And a plurality of, for example, 64 second ink nozzles 12 (1) to 12 (12) also arranged along the main scanning direction Y.
(64).

The first ink nozzle row constituting the first ink nozzle row
Ink nozzles 11 (1) to 11 (64)
, For example, black ink is supplied, from which the first color ink is ejected. The second ink nozzles 12 (1) to 12 (64) constituting the second ink nozzle row have second color inks, for example, red, green,
Color inks such as yellow, orange, and purple are supplied, and the second color ink is ejected from these inks.

More specifically, the first ink nozzles 11 constituting the first ink nozzle row 100 will be described.
(1) to 11 (64) are constant pitches P, for example, 1
The second ink nozzles 12 (1) to 12 (64), which are arranged in a line at an interval equivalent to 80 dpi (141 μm) and constitute the second ink nozzle row 200,
They are arranged in a line at a constant pitch P. However, the second ink nozzles 12 (1) to 12 (64) constituting the second ink nozzle row 200 have a half pitch (P / 2) as a whole, for example, 360 dpi (70 μm).
It is arranged at a position shifted considerably in the ink nozzle row direction. Therefore, the first and second ink nozzles 11
(1) to 11 (64) and 12 (1) to 12
(64) are in a staggered arrangement at P / 2.

The first and second ink nozzle arrays 1
The interval (nozzle row interval) e between 00 and 200 is set to a value less than 1 mm. In the present embodiment, it is set to 0.5644 mm of 8/360 inches, but it can be reduced to the head manufacturing limit of 0.070.

FIG. 2B shows the first ink nozzle 11
The print dots (portions indicated by circles with diagonal lines) formed on the printing paper by (1) to 11 (64) and the print dots (portions formed by the second ink nozzles 12 (1) to 12 (64)) FIG. 4 is an explanatory diagram illustrating an overlapping state of ink dots with a portion indicated by a white circle).

The print dot diameter d varies depending on the discharge amount of ink or recording paper. In this embodiment, the print dot diameter d was confirmed to be d = 2 × m. Is set to P or less, the ejection ink amount m (ng) for one dot formed on the recording paper 3 is set as follows.

M <P / 2 The driving conditions of the ink jet head, particularly the driving voltage and the driving pulse waveform, are controlled so as to satisfy the above relational expression. The flow path dimensions of the head and the driving conditions, specifically, the nozzle diameter and the driving pulse may be set so as to correspond to the printing paper having a high market share.

When printing is performed under these conditions, even if print dots of different ink colors are adjacent at intervals of the pitch P, if the print dot diameter d is smaller than the nozzle pitch P, the oblique line printed and printed from the ink nozzle array 100 Since the overlapping portion of the print dots does not occur, there is no portion where the ink amount is extremely large, and the ink is easily fixed in a short time. After that, even if the print dots in the white portions ejected from the ink nozzle row 200 are printed, the ink in the hatched portions has already begun to penetrate into the recording paper, and bleeding hardly occurs.

Further, the vacant area between the print dots in the hatched portion is wide, and the ink nozzle array 20 is located in the widened vacant area.
Since the printing dots of the white portion ejected from 0 are printed, the color mixture becomes inconspicuous due to the sharpness of the second color printed in the empty area, and as a result, a good printing quality can be obtained.

FIG. 3 is a schematic block diagram showing an example of a control circuit of the ink jet printer 1. The control circuit 30 is constituted by a microcomputer, and various processes are realized by the operation of the central processing unit CPU which is the center of control. That is, various control programs are stored in a read-only memory ROM composed of a nonvolatile memory or the like.
Various control operations are realized by executing a part of the random access memory RAM as a work area. These components are connected to each other via an internal bus 31, and the calculation results and the like are output to a motor driver and other peripheral devices via an input / output port I / O. It is also connected to the host computer 32, from which print image data is supplied. The data is converted into serial data via the print image data developing unit 33,
It is supplied to a head unit 35 composed of a head driver 34 and the inkjet head 4.

In the ink jet head 4 of the ink jet printer 1 of this embodiment, the ink nozzle rows 100 and 200 are arranged as described above. As an example, when the ink nozzle pitch P is 141 μm, the ejection ink amount m for one dot is a half of the numerical value 70.5 (n
g) is set to less than As described above, in a general inkjet head, the print dot diameter d (landing dot diameter) formed on the recording surface is proportional to the ejection ink amount m. For example, when the ejection ink amount m is set to 50 ng so as to satisfy the above expression (m <P / 2), the print dot diameter d is about 100 μm by the proportional expression d = 2 × m.

In this case, as shown in FIG.
Print dots formed by the first ink nozzles 11 (1) to 11 (64) (portions indicated by hatched circles)
And the second ink nozzles 12 (1) to 12 (64)
Is small, and even if the printing interval is less than several milliseconds as in the prior art, a decrease in saturation due to bleeding or the like occurs. Nothing.

In the case where the discharge ink amount exceeds 70.5 (ng), which is the limit of the above equation (m <P / 2), the print dot diameter d becomes larger than the nozzle pitch of 141 μm. Ink nozzles 11 (1) to 11 (64)
(Dotted portion) and the second dot
Since the overlapping area with the printing dots (indicated by white circles) formed by the ink nozzles 12 (1) to 12 (64) of the first embodiment occupies a large area, the bleeding color mixture becomes remarkable, and the area other than the hatched area becomes The vacant portion is reduced, and the ratio of clear printing for printing in the vacant portion of the printing by the second ink nozzle row is reduced, and bleeding color mixture becomes conspicuous, and as a result, it is impossible to secure good print quality.

[0029]

As described above, in the ink jet head according to the present invention and the ink jet printer provided with the ink jet head, each ink nozzle constituting the first ink nozzle row and the second ink nozzle row Are arranged in a zigzag pattern with a half pitch offset from each other.

The diameter of the ink dot formed on the recording medium (landing dot diameter) is set to a value smaller than the ink nozzle pitch.

Therefore, according to the present invention, ink dots formed by the ink nozzles of the second ink nozzle row are formed between ink dots formed on the recording medium by the ink nozzles of the first ink nozzle row. . Further, the overlapping portion between the ink dots formed on the recording medium can be reduced to such an extent that the deterioration of the print quality due to the bleeding does not pose a problem.

Therefore, according to the present invention, even if the interval between the first and second ink nozzle arrays is reduced to a value less than the production limit of 0.07 to 1 mm without causing a reduction in printing speed, bleeding or the like can be prevented. Since no adverse effects occur, the size of the inkjet head can be reduced. In addition, it becomes possible to perform highlight printing or the like at high speed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an example of an inkjet printer to which the present invention has been applied.

2A is an explanatory diagram illustrating a state of two ink nozzle rows formed on a nozzle surface of the ink jet head of FIG. 1, and FIG. 2B is a diagram illustrating overlapping of ink dots formed on a recording sheet; It is explanatory drawing which shows a state.

FIG. 3 is a schematic block diagram illustrating an example of a control circuit of the ink jet printer of FIG.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 inkjet printer 2 recording paper 3 platen 4 inkjet head 5 carriage 6 ink tank 100 first ink nozzle row 200 second ink nozzle row 11 (1) to 11 (64), 12 (1) to 12
(64) Ink nozzle P Ink nozzle pitch e Distance between ink nozzle rows

Claims (3)

[Claims] A first and a second array arranged at regular intervals;
The first ink nozzle row has a plurality of first ink nozzles that eject a first color ink arranged at a constant pitch P (μm).
In an ink jet head in which a plurality of second ink nozzles for ejecting a second color ink are arranged at the same pitch as the pitch, the first and second ink nozzle rows are relatively An ink jet head, which is shifted by a half pitch in the ink nozzle arrangement direction, and wherein a diameter of an ink dot ejected from the ink nozzle and formed on a recording medium is smaller than P; 2. The ink jet printer according to claim 1, wherein an interval between the first and second ink nozzle rows is 0.07.
An ink jet head characterized in that it is set within a range of less than 1 mm. 3. An ink jet printer comprising the ink jet head according to claim 1.