JP3213107B2 - Inkjet printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer, and more particularly to an ink jet printer capable of performing multi-value recording by combining large and small ink droplets.

[0002]

2. Description of the Related Art FIGS. 8 (a), 8 (b) and 8 (c) are views showing the basic structure of an ink jet head of an ink jet printer as an example to which the present invention is applied. FIG. 8 (b) is a perspective view showing the back surface of the flow channel plate, and FIG. 8 (c) is a perspective view when the components are integrally joined. In FIG. 2 is a nozzle plate,
Reference numeral 3 denotes an orifice, 4 denotes a partition, 5 denotes a pressurizing chamber, 6 denotes an ink chamber, 7 denotes an ink supply port, 8 denotes a piezoelectric body, 9 denotes a partition slit, 10 denotes a distortion portion, 11 denotes a filler, and 12 denotes a substrate. .

In FIG. 8, an ink chamber 6 for receiving ink from an ink supply port 7 and containing ink is provided in the ink flow path plate 1 as a concave portion on the back surface as shown in FIG. Further, a plurality of pressurizing chambers 5 are provided in parallel with each other, which are communicated with the ink chamber 6 and are partitioned by the partition walls 4 to form ink flow paths, and generate pressure waves in the ink by pressurization. A piezoelectric body 8 and a substrate 12 are sequentially joined to the ink flow path plate 1, and the piezoelectric body 8 is provided with a strain portion 10 that presses the pressure corresponding to the pressurizing chamber 5. The distortion portion 10 is defined by a partition slit 9, and the partition slit 9 is filled with an elastic soft filler 11. Channel plate 1
The nozzle plate 2 having the orifice 3 corresponding to the pressure chamber 5 is joined to the nozzle plate side 5a of the pressure chamber 5 of FIG.
It is integrally configured as shown in FIG. When a signal based on image information is applied to the distortion unit 10, the pressure chamber 5 changes in volume to generate a pressure wave, and ejects ink droplets from the orifice 3 to record an image on a recording medium.

As described above, an ink jet printer is a printer that records an image while ejecting ink droplets. There are two methods for performing multi-value recording with such an ink jet printer. A plurality of ink liquids having different densities are prepared, and a plurality of ink jet heads are prepared to perform multi-value recording. The main scanning is performed twice on the same location on the recording medium (hereinafter, paper), and ternary recording is performed where two ink droplets of the same size overlap, where only one droplet is present, and where nothing is present. Do. The method requires a large number of heads, so that the size of the apparatus is increased and the cost is increased. Is, for example, 1
When the amount of the ink droplet is set such that the density of only the droplet becomes 1.0D, the amount becomes 1.3D when two droplets overlap.

[0005]

FIG. 9 is a diagram showing the relationship between the number of ink droplets and the density in the case of FIG.
The image density is 0.04D when there is no ink droplet (point A).
After that, 1.0 when one ink drop suddenly (point B)
D, and 1.3 for two ink drops (point C).
D, the gradation of the highlight portion (between A and B) cannot be expressed. In addition, in order to forcefully express the gradation of the highlight portion, the amount of ink droplets must be reduced or the ink density must be reduced. However, in this case, there is a disadvantage that the maximum density does not increase.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink jet printer capable of expressing gradation in a highlight portion with a single head and sufficiently reproducing a maximum density.

[0007]

According to the present invention, there is provided an ink jet head which discharges an ink liquid in an ink tank from an orifice as ink droplets, and scans the ink jet head in a main scanning direction. Let
An inkjet printer for performing recording by ejecting ink droplets in accordance with image data from the orifice, the upper image data to eject ink droplets larger the image data, and the lower image data to eject the small ink droplets, wherein and recording by the upper image data, in an ink jet printer which performs switching the recording by the lower image data for each main scan, the relative height relationship between the previous SL orifice and the liquid surface of the ink tank and the upper image data and the lower image variable and then and the upper image data according to the data
After recording, the recording paper is sub-scanned to the lower-order image data.
This is characterized in that the recording by

[0008]

The upper image data and the lower image data change the relative height relationship between the orifice and the liquid level in the ink tank, change the size of the ink droplet to be ejected, and change the sub-scanning method.
Multi-level recording is performed by shifting the direction and repeatedly hitting.

[0009]

FIG. 1 is a diagram showing an embodiment of the present invention.
In the figure, 100 is a printer, 101 is a paper cassette, 10
2 is paper, 103 is a paper feed roller, 104 is a substrate, 105
Are microcomputers, 106Y, 106M, 106
C and 106BK are heads for yellow (Y), magenta (M), cyan (C), and black (BK), respectively.
07 is an ink droplet, 108 is a carriage, 109 is a rail, 110 is a feed roller, 113Y, 113M, 113
C and 113BK are ink tanks, 114 is an ink tank position sensor, 115 is a stepping motor, 116 is a worm gear, 117 is a tip detection sensor, 120 is a head driver, 200 is a computer,
201 is a cable.

When a printing start signal is sent from the computer 200 through the cable 201, the printer 100 rotates the paper feed roller 103, feeds the paper 102 from the cassette 101, and detects the leading edge of the paper 102 as the leading edge detection sensor. 1
When the number reaches 17, the microcomputer 105 on the control board 104 notifies the computer 200 via the cable 201 that the preparation for image data reception is completed. Next, the computer 200 connects to the cable 201.
The transfer of the image data is started through the interface, and the image processing circuit of the substrate 104 performs image processing on the image data.

FIG. 2 is a block diagram of the image processing circuit. In FIG. 2, reference numeral 131 denotes a density conversion circuit, 132 denotes an under color removal and black signal generation circuit, and 133 denotes a binarization circuit. Image data consists of R (red), G (green), and B (blue).
This is the luminance signal for the color, and the image data R, G, B
Is divided into upper image data for discharging large ink droplets and lower image data for discharging small ink droplets for each of the luminance signals R, G, and B by the computer 200. Make a luminance signal. This multi-valued R, G, B luminance signal is converted into a density conversion circuit 13.
The signal is converted into density signals Y, M, and C at 1, and then the under color removal and black signal generation circuit 132 removes the common under color from this signal, and simultaneously generates a black signal (BK). Next, the binarization circuit 133 converts the multi-level signal into a binary signal,
A switching signal L for selecting only lower-order image data is set by the microcomputer 105, and only the lower-order image data is sent to the head driver 120. The head driver 120 performs power amplification, and the heads 106Y, 106M,
106C and 106BK to drive the computer 200
106Y, 106M, 1 according to the image signal from
The ink droplets 107 are ejected from 06C and 106BK.

Prior to the image output of the lower-order image data, the stepping motor 115 is rotated, and the worm gear 116 is used to drive the ink tanks 113Y, 113M, 113M.
C, 113BK lowered, the relative height relationship between the liquid level of the orifice of the nozzle plate and the ink tank (hereinafter referred to as the head difference)
When is increased, the negative head pressure in the head increases, and the amount of ejected ink droplets decreases. The smaller the amount of ink droplet, the smaller the dot diameter recorded on the paper,
Image density decreases.

FIG. 3 shows Xerox 4024 or Ricoh paper
FIG. 9 is a diagram showing the relationship between the water head difference and the image density when the 6200 is used.
mm to -10 mm, the concentration is 0.25D to 2.0D.
It shows that it changes.

Heads 106Y, 106M, 106C, 1
06BK is mounted on the carriage 108, discharges the above ink droplets, performs main scanning along the rail 109, performs recording using lower image data, and completes the main scanning using lower image data. The carriage 108 is returned to the initial position (main scanning start position) in preparation for the main scanning. During this returning operation, the home position sensor 1
14, the home position of the ink tank 113 is detected, and the height of the ink tank 113 is controlled based on this position. That is, during this returning operation period, the stepping motor 115 is rotated, and the worm gear 116 rotates the ink tanks 113Y, 113M, 113M.
C, 113BK is increased to reduce the negative head pressure in the head, and the ink droplet amount is increased so as to prepare for the next main scanning by the upper image data.

After the recording with the lower image data is completed, the switching signal of the microcomputer 105 is a signal H for selecting only the upper image data, and sends only the upper image data to the head driver 120. The head driver 120 performs power amplification, and the head 106
Y, 106M, 106C, and 106BK are driven, and the heads 106Y,
The ink droplets 107 are ejected from 106M, 106C, and 106BK.

That is, during the first (lower image data) and the second (upper image data) main scanning, the sub-scanning is not performed, and these two-bit image data are 11 (lower image data H, upper image data). At the point H), an image as shown in FIG. 4 is recorded by overlapping small dots and large dots. Where the 2-bit image data is 01 (lower image data L, upper image data H), an image as shown in FIG. 5 is recorded with one large dot. The 2-bit image data is 10 (lower image data H, upper image data L).
In the place, an image as shown in FIG. 6 is recorded with one small dot. Where the 2-bit image data is 00 (lower image data L, upper image data L), no image is recorded. When the first and second main scans are completed, the feed roller 110 is rotated by a sub-scanning motor (not shown) to convey the paper by a distance equal to the width of the head, and to prepare for the next main scan. The carriage 108 is returned to the initial position (main scanning start position), recording is performed in the same manner as the first time, and the main scanning and the sub-scanning are repeated in the same manner while changing the water head pressure in the same manner. Record color images of the number of sheets.

Here, when the above-described image is recorded, if the image density of the larger ink droplet is recorded as 1.2D and the image density of the smaller ink droplet is recorded as 0.34, FIG. As shown in FIG. 7, the image density was measured when there was no recording (A
Point) is 0.04D, for small dots (point D) is 0.34D,
A large dot (point B) is 1.2D, and a small dot and a large dot are overlapped (point C) is 1.3D. The highlight part (between A and B) is a small dot (point D). Can be reproduced, and
The maximum density (points B and C) can be sufficiently obtained.

In the above, multi-value recording has been described in which the amount of ink droplets is changed by changing the head difference by taking an ink jet printer using a piezoelectric element as an example.
The ink jet printer to which the present invention is applied is not limited to the ink jet printer using the piezoelectric element as described above, and it can be easily understood that the present invention can be used for all types of ink jet printers such as a bubble jet method and a charge control method. I can do it.

[0019] In the above description mentioned are, during the lower image data and upper image data has be recorded without sub-scan, in the present invention, slightly shifting the lower image data and upper image data, i.e. , Sub-scan and record the image
In this way, the maximum density can be further increased to make it reproducible.
You .

[0020] In the case of an ink jet printer using a piezoelectric element type, by changing the voltage applied to the piezoelectric element, it is possible to change the amount of ink droplets in the ink jet printer employing piezoelectric element, the aforementioned water head The amount of ink droplet may be changed in combination with the method of changing the difference.

[0021]

EFFECT ink droplets having different two quantities one image by recording the combination which is shifted in the sub-scanning direction, the highlight section can be expressed, and can be performed multi-value recording the maximum concentration can be sufficiently reproduced. By changing the water head difference, since the so varying the amount of ink droplets, Ru can change the amount of ink droplets with a simple structure.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention.

FIG. 2 is a diagram illustrating an image processing circuit.

FIG. 3 is a diagram showing a relationship between a head difference and a concentration.

FIG. 4 is a diagram of a dot according to an embodiment of the present invention.

FIG. 5 is a diagram of a dot according to an embodiment of the present invention.

FIG. 6 is a diagram of dots according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a density of ink droplets of different amounts according to an embodiment of the present invention.

FIG. 8 is a diagram illustrating a conventional example.

FIG. 9 is a diagram illustrating a relationship with the density when ink droplets of the same amount are superimposed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Flow path plate, 2 ... Nozzle plate, 3 ... Orifice, 4 ... Partition wall, 5 ... Pressurizing chamber, 6 ... Ink chamber, 7 ... Ink supply port, 8
... Piezoelectric body, 9 partition slit, 10 distortion part, 11 filler, 12 substrate, 100 printer, 101 paper cassette, 102 paper, 103 paper feed roller, 104 substrate, 105 microcomputer (Head driver), 106 head, 107 ink drop, 108 carriage, 109 rail, 110 feed roller, 11
3 ... ink tank, 114 ... position sensor, 11
5 stepper motor, 116 worm gear, 11
7: Tip detection sensor, 120: Head driver, 132
... under color removal and black signal generation circuit, 133 ... binarization circuit,
200: Computer, 201: Cable.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/205 B41J 2/175 B41J 2/01

Claims (1)

(57) [Claims] An ink jet head for ejecting an ink liquid in an ink tank from an orifice as ink droplets; causing the ink jet head to scan in a main scanning direction;
An inkjet printer for performing recording by ejecting ink droplets in accordance with image data from the orifice, the upper image data to eject ink droplets larger the image data, and the lower image data to eject the small ink droplets, wherein and recording by the upper image data, in an ink jet printer which performs switching the recording by the lower image data for each main scan, the relative height relationship between the previous SL orifice and the liquid surface of the ink tank and the upper image data and the lower image variable and then and the upper image data according to the data
After recording, the recording paper is sub-scanned to the lower-order image data.
An ink jet printer characterized in that the recording is performed by the following method.