JPH0872268A - Ink jet recorder - Google Patents

Abstract

PURPOSE: To gradation represent by nozzles of the minimum number and to output an image for severe consideration of high spatial frequency by aligning M pieces of nozzles on a scanning line of a main scanning direction in a gradation severe consideration mode and regulating to align one nozzle on the line in a spatial frequency severe consideration mode. CONSTITUTION: A gradation severe consideration mode corresponds to the state in which the recording heads of a spatial frequency severe consideration mode is rotated counterclockwise at an angle α, N pieces of nozzle rows in the spatial frequency severe consideration mode are disposed at an equal interval on a scanning line parallel with the main scanning direction. A nozzle row interval Phhmm of the frequency severe consideration mode is the interval of the scanning lines, and the nozzle row interval Phh of the frequency severe consideration mode is adjacent dot interval of a subscanning direction in the gradation severe consideration mode. Accordingly, the resolution Rfg in the gradation severe consideration mode is Phh=25.4/Rgv. A sheet is fed at each predetermined amount each time this recording head is scanned once to alter the relative positions between the head and a recording sheet, thereby recording without gap.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for obtaining an ink image on a recording medium capable of reproducing multiple gradations in minimum pixel units.

[0002]

2. Description of the Related Art Due to the widespread use of multimedia, there is an increasing demand for faithful output of images such as photographs displayed on a display by a printing device. Therefore, gradation printing can be performed in addition to printing only characters. Inkjet recording devices are attracting attention.

In order to carry out this faithful gradation recording, Japanese Patent Laid-Open No. 58-39468 and Japanese Patent Laid-Open No. 59-115853.
JP-A-59-190862, JP-A-62-62
It is preferable to perform gradation expression in the minimum pixel unit without providing the gradation pixel matrix as disclosed in JP-A-13357, JP-A-3-189166 and the like. For example, in JP-A-58-39468, two kinds of inks having different densities, dark and light, are used.
In Japanese Patent No. 5853, gradation is expressed by overlapping the white or transparent ink to change the density level of one dot.

Further, in Japanese Patent Laid-Open No. 59-190862, two or more types of nozzle holes having different sizes are provided, and in Japanese Patent Laid-Open No. 62-13357, flying is performed by changing the pulse width of the driving voltage. In JP-A-3-189166, by modulating the amount of ink droplets, a plurality of ink droplets are deposited at the same location to change the formation area of one dot for gradation expression.

On the other hand, as compared with the conventional character printing, printing closer to the printed characters is required.
It is also necessary to increase the recording density by changing the inclination of the nozzle arrangement of the recording head, which is seen in Japanese Patent Laid-Open No. 290263/1990 and Japanese Patent Laid-Open No. 6-218951.

[0006]

As described above, it is necessary to make both image recording and text recording compatible with one printer. However, image information generally has a low spatial frequency, and it is necessary to emphasize gradation rather than recording density. On the other hand, in text recording, recording density is important and gradation is not necessary. In other words, in the gradation technology of the above publication, the mechanism and structure specialized for gradation expression and the ink are, on the contrary, useless at the time of text recording and do not function at all.

The present invention is intended to solve such a problem and requires a minimum necessary number of nozzles without providing a special mechanism or structure specialized for improving gradation expression and further ink. An object of the present invention is to provide an inkjet recording apparatus that can output both an image such as a text image that emphasizes high spatial frequency and an image that emphasizes gradation expression such as a picture with good quality.

[0008]

In an ink jet recording apparatus of the present invention, a recording head on which a plurality of nozzles are formed is mounted on a carriage, and main scanning accompanying movement of the carriage in the column direction and the main scanning direction are performed. In an inkjet recording apparatus that repeatedly performs sub-scanning in which a recording sheet is conveyed in a perpendicular direction, an angle formed by a main scanning direction and a reference line of the recording head has two types of printing modes, a gradation-oriented mode and a spatial frequency-oriented mode. A print head tilt variable mechanism that adjusts the angle to a different angle is provided, and in the gradation-oriented mode, adjustment is performed so that M (where M is an integer of 2 or more) nozzles are arranged on the scanning line in the main scanning direction. In the spatial frequency emphasizing mode, only one nozzle is aligned on the scanning line.

[0009]

According to the above construction, by changing the mounting angle of the head, switching between high density text recording and gradation recording in which a plurality of ink droplets are deposited at the same position and the formation area of one dot can be adjusted. It can be done without waste.

[0010]

EXAMPLES The ink jet recording apparatus of the present invention will be described in detail below.

FIG. 1 is a perspective view showing an ink jet printer according to a first embodiment of the present invention. Reference numeral 2 denotes a carriage on which the recording head 3 is mounted, which is movably supported by the carriage guide shaft 1 and is driven by a carriage motor (not shown). In response to a print timing signal output in synchronization with the movement of the carriage 2 by a predetermined amount, ink droplets are ejected from the recording head 3 to record characters or images on the recording paper 10. Then, when recording of one line is completed, the recording paper transport mechanism 20 feeds a predetermined amount of paper.
By repeating the above operation, desired recording is performed on the recording paper 10.

The recording head 3 mounted on the carriage 2 has a link mechanism 6 and a plunger 5 as shown in FIG.
The head inclination changing mechanism 4 is rotatably supported by the angle changing amount α. The inclination angle of the recording head 3 is a recording mode (not shown) in which the plunger 5 is turned ON / OFF (spatial frequency-oriented mode or gradation-oriented mode).
Adjusted by the change signal, when the plunger 5 is in the ON state, the inclination angle of the gradation-oriented mode shown in FIG. 2A is displayed, and when the plunger 5 is in the OFF state, the spatial frequency is emphasized shown in FIG. 2B. Set to mode. The structure of the recording head tilt changing mechanism can be realized by, for example, connecting a step motor on the rotary shaft of the recording head and rotating the step motor by a predetermined step to adjust the tilt angle. It is not limited to the examples.

FIG. 3 is a diagram showing the state of the nozzle arrangement of the recording head 3 in the first embodiment of the present invention, with the horizontal scanning direction being the main scanning direction (scanning direction of the carriage).
The positional relationship of the nozzles when (a) is in the gradation importance mode,
FIG. 3B shows the positional relationship of the nozzles in the spatial frequency priority mode. In FIG. 3B, the recording head is illustrated as rotating about the point A for convenience, but the center of rotation is not particularly limited to the point A.

Here, the terms and characters used in the following description are defined. In the diagram showing the spatial frequency priority mode in FIG. 3B, the array of nozzles in the substantially main scanning direction (AD direction) is called a row, and the array in the substantially sub-scanning direction (AB direction) is called a column. Further, in order to distinguish between the spatial frequency-oriented mode and the gradation-oriented mode, subscripts of t and g (representative of spatial frequency-oriented: te
xt, a typical example that attaches importance to gradation: shows the initial letter of graphic).

In the spatial frequency-oriented mode of FIG. 3B,
In order to increase the resolution in the sub-scanning direction, the nozzles are arranged in a staggered pattern and in a staircase pattern, and scanning lines in the sub-scanning direction (@ t1, @ t2, ...
The nozzle rows of the recording heads 3 are supported at an angle of α with respect to the main scanning direction so as to be lined up one by one on @tMN). If the number of nozzle rows in this spatial frequency priority mode is N rows (8 rows in the figure), and the nozzle spacing of one nozzle row in the sub-scanning direction is Pv (mm), Pv / N is the scanning line (@ t1, @ t2, ..., @tMN) adjacent distance. This adjacent distance is set to the distance between adjacent dots in the sub-scanning direction in the spatial frequency priority mode. Therefore, the resolution Rtv in the Pv and spatial frequency priority mode is Pv
/N=25.4/Rtv. The resolution referred to here means the number of print dots per inch. In FIG. 3B, the outer contour of the nozzles is shown as a parallelogram, but if each nozzle exists on a different scanning line, each nozzle row may be arranged in zigzag. I do not care.

The gradation-oriented mode of FIG. 3A is as shown in FIG.
The recording head 3 in the spatial frequency priority mode of FIG.
When rotated in the counterclockwise direction, the N nozzle rows in the spatial frequency priority mode are evenly spaced on the scanning lines (@ g1, @ g2, ..., @gN) parallel to the main scanning direction. To position. Here, the nozzle row interval Phh (mm) in the spatial frequency emphasis mode is the scanning line (@ g1, @ g2, ...
, @@ gN), and the nozzle row interval Phh in the spatial frequency priority mode is the distance between adjacent dots in the sub-scanning direction in the gradation priority mode. Therefore, the resolution Rgv in the gradation-oriented mode is Phh = 25.4 / Rgv.

Each time the recording head 3 configured as described above is scanned once, a predetermined amount of paper is fed to change the relative position between the recording head 3 and the recording paper 10 to perform recording on the recording paper without any gap. The conveyance of the recording paper 10 is a combination of a feed for the minimum resolution determined by the resolution in the sub-scanning direction (fine feed) and a feed for the length in the sub-scanning direction that can be printed by one scan (constant pitch feed) For example, if there is a continuous print area in the sub-scanning direction, after scanning the recording head,
Constant paper feed Repeats the pitch feed operation, but if the non-printing area is continuous in the sub-scanning direction, the print head is not scanned to continuously scan the non-printing area distance in order to increase throughput. After the recording paper is conveyed, the printing operation starts. In this case, the distance of the non-printing area is arbitrary, and a fractional amount that cannot be fed at the constant paper feed pitch occurs, but this is processed by minute feed.

By the way, since the desired resolution is different between the spatial frequency-oriented mode and the gradation-oriented mode, the feed pitch required for each mode must be set differently. Therefore, in the case of this embodiment,
For the resolutions Rtv and Rgv in the sub-scanning direction in both modes, the minute feed pitches Ltmin and Lgmin are set to Ltmin = 25.
4 / Rtv = Pv / N and Lgmin = 25.4 / Rgv = Phh are set. That is, Ltmin and Lgmin are the adjacent scanning line distances in the main scanning direction in the respective modes described above.

Further, the printable range by one scan of the recording head 3 is different between the gradation emphasis mode and the spatial frequency emphasis mode as shown in FIGS. 4 (a) and 4 (b). It is necessary to set the constant paper feed pitch to different values depending on the mode. In the case of this embodiment, the constant paper feed pitch amount, Ltnom, and Lgnom are set to Ltnom = 25.4MN /
Rtv = MPv, Lgnom = 25.4N / Rgv = NPhh. Here, M indicates the number of nozzles that form one nozzle row in the spatial frequency emphasis mode, and is shown by M = 6 in the drawing, but it is easy to manufacture the head, cost, and per unit area of the recording paper. It is a value that should be comprehensively considered from the amount of ink that can be impregnated, and may be any value greater than 2.

As described above, the features of the present invention are that the inclination of the recording head 3 is changed according to the desired recording mode, high resolution is realized without modulating the dot diameter in the spatial frequency emphasis mode, and gradation is increased. In the sex-oriented mode, as shown in FIG.
The arrangement is such that a plurality of nozzles are arranged side by side on the scanning line in the main scanning direction so that the dot diameter can be modulated. As a result, a predetermined number of ink droplets can be deposited at the same position as shown in FIG. 5, so that the dot diameter can be modulated.

In this embodiment, the scanning speed of the carriage is
Since the distance between nozzles arranged in parallel in the main scanning direction (for example, the distance between nozzle # 1 and nozzle # 2) is set to several mm, the nozzles # 1, # 2, ...
By # 6, it becomes possible to deposit 6 ink droplets at the same location on the recording paper within a time difference of about several tens of msec. The time required for the evaporation component in one drop of ink to evaporate and the time for the permeation into the recording paper fiber depend on the ink component and the type of recording paper, but at room temperature it is several hundreds.
msec or more, which is the difference in the above-mentioned landing time (about several 10s).
The maximum number of ink droplets that have landed at the same location is 6 large, which can be formed on the recording paper and the number of droplets can be adjusted. Then, the dot diameter can be modulated as shown in FIG. In the present embodiment, the amount of ejected ink of one drop is 0.
It is optimized in the range of 01 to 0.15 μg. Further, FIG. 6B shows the recording dots in the spatial frequency-oriented mode.

As described above, according to the present embodiment, it is possible to use the minimum number of nozzles without providing a special mechanism or structure or ink specialized for improving gradation expression. It is possible to satisfactorily record both images such as a text image that emphasizes high spatial frequency and an image that emphasizes gradation expression such as a graphic image.

Next, a second embodiment will be described.

FIG. 7 shows the nozzle arrangement of the recording head according to the second embodiment of the present invention. The difference from the first embodiment is the nozzle arrangement in the gradation-oriented mode. The recording paper conveyance pitch. In order to facilitate comparison with the first embodiment, the resolution in the sub-scanning direction in each mode, the number of nozzles, and the number of gradation expressions per dot in the gradation priority mode are the same as those in the first embodiment. Same as the example. Therefore, the nozzle positional relationship and the recording paper conveyance in the spatial frequency emphasis mode are the same as those in the first embodiment, and the gradation property emphasis mode will be mainly described in detail in the following description.

As shown in FIG. 7A, in the gradation importance mode, the recording head is rotated counterclockwise by the angle α with respect to the spatial frequency importance mode. And the scanning lines (@ g1, @ g2, ...) in which the N nozzle rows each having an angle α are parallel to the main scanning direction.
・ 、 @ GN) will be lined up at even intervals. The interval between the N scanning lines parallel to the main scanning direction is the nozzle array interval Phh in the spatial frequency priority mode. Up to here the first
However, in the present embodiment, the recording density in the sub-scanning direction in the gradation importance mode is set to 1 / K times Phh (where K is an integer of 2 or more), and Phh = 2
It is 5.4K / Rgv. Therefore, the minute feed pitches Ltmin and Lgm in the spatial frequency-oriented mode and the gradation-oriented mode
In, Ltmin = 25.4 / Rtv = Pv / N, Lgmin = 2
5.4 / Rgv = Phh / K.

In the gradation-oriented mode, since the nozzle spacing of the recording head 3 in the sub-scanning direction is K times the recording density as described above, the recording head 3 is scanned K times and the unit area is not separated. The recording method in this case can be performed by interlace recording described in the specification of US Pat. No. 4,198,642, for example. In this case, N and K are made to be relatively prime integers, and the paper is fed at a constant pitch of LgminN each time the recording head 3 scans.

FIG. 8A shows the positional relationship of the print head 3 in the sub-scanning direction and the scan lines that can be printed when K = 3 and N = 8 when the gradation-oriented mode printing is performed by interlaced printing.
The case is shown as an example. Generally, in interlaced recording, the resolution R in the sub-scanning direction starts from the {(N-1) (K-1) +1} line, that is, the 15th line in this embodiment.
You can record without gaps with gv. Here, from the 1st to 14th lines, recording is not possible at the resolution Rgv, but a predetermined amount of NULL data is added to the beginning of the image data so that the output start position of the image data is from the 15th line. It may be added and recorded. FIG. 8B shows recording in the spatial frequency-oriented mode. In this case, Ltnom
= MPv = 25.4 MN / Rtv With constant paper feed pitch, recording is possible without gaps.

In this embodiment, in addition to the effect of the first embodiment, since the nozzle row interval Phh in the spatial frequency emphasis mode can be set large, the mounting density of ink ejection elements (not shown) in the print head can be increased. Even if the height is not increased, it is possible to form an image with a desired resolution, and the head design is relaxed. Further, in the gradation-oriented mode, the formation of the ink dot images adjacent to each other in the sub-scanning direction or the sub-scanning direction can always secure the above-mentioned difference of about 100 msec required for scanning the print head. For this reason, the ink deposited in the previous scan is in a state of considerably penetrating into the recording paper by the formation of the next adjacent dot, and does not affect the ink deposited in the next scan. Bleeding can be prevented.
Further, since the recording density in one scanning is sparser than that in the first embodiment, the increase in the vapor pressure of the ink on the recording paper surface becomes gentler than that in the first embodiment. Drying of the ink image is accelerated.

Although the outer contours of the nozzles are shown as parallelograms in FIG. 7B as well, if each nozzle exists on a different scanning line, each nozzle row is zigzag. It may be placed in.

Next, a third embodiment will be described with reference to FIG.

In the present embodiment and the first embodiment, the nozzle group which is aligned in parallel in the main scanning direction in the gradation priority mode is a nozzle row which is aligned in the sub-scanning direction in the spatial frequency priority mode in the first embodiment. In contrast to this, the present embodiment is different in that the nozzle rows are arranged substantially in the main scanning direction.

Also in this embodiment, the nozzles of the recording head 3 are arranged in a zigzag pattern as shown in FIG. 9B, and the number of nozzles is approximately M in the main scanning direction with an angle α with respect to the main scanning direction. Nozzle rows (eg # 1, # N + 1, ...
# (M-1) N + 1 rows) are formed. Further, the nozzle rows are arranged in N rows at equal intervals in the substantially sub-scanning direction, and the nozzle rows (for example, # 1, # 2,
... A column of #N. ) Are arranged at an angle β with the main scanning direction. As a result, in the spatial frequency-oriented mode shown in FIG. 9B, MN nozzles (# 1, # 2, ...
.., #MN) exist on the different virtual lines (@ t1, @ t2, ..., @tMN) of MN parallel to the main scanning direction.

If the distance in the sub-scanning direction between adjacent nozzles in the same nozzle row is Pv, then Pv / M is
It is the adjacent distance of the virtual line group consisting of MN. This adjacent distance is set to 25.4 / Rtv between adjacent dots in the sub-scanning direction in the spatial frequency priority mode. Therefore, the relationship between the Pv and the resolution Rtv in the spatial frequency priority mode is
Pv / M = 25.4 / Rtv.

In the gradation-oriented mode, the recording head is rotated by the angle α with respect to the spatial-frequency-oriented mode. Therefore, the N nozzle rows having the angle α with the main scanning direction in the spatial-frequency-oriented mode. (For example, # 1, # N + 1, ... # (M-1)
The line consisting of N + 1) is parallel to the main scanning direction. Therefore,
Each of the N nozzle lines (in the spatial frequency priority mode) has a virtual line (@ g1, @ g2, ...) Parallel to the main scanning direction.
・, @GN) are placed so that they are evenly spaced. Here, the adjacent distance Pvv between each nozzle row (in the spatial frequency emphasis mode) is the adjacent distance of the virtual line group consisting of the N lines, and the adjacent distance Pvv is between the adjacent dots in the sub-scanning direction in the gradation importance mode. The distance is set to 25.4 / Rgv.

In the present embodiment, as in the first embodiment, the conveyance amount of the recording paper is sequentially determined according to a desired image pattern by a combination of minute feeding and fixed paper feeding.
The minute feed pitches Ltmin and Lgmin in the spatial frequency-oriented mode and the gradation-oriented mode are adjacent distances of the virtual line groups in each mode, that is, Ltmin = 25.4 / Rtv = Pv / M, Lg.
It is set to min = 25.4 / Rgv = Pvv.

FIG. 10 is a diagram showing a print area to be printed in each scan when recording is continuously performed at a constant paper feed pitch in each of the image modes in which the gradation is emphasized and the spatial frequency is emphasized. In the spatial frequency emphasizing mode shown in (b), one scan of the recording head causes regions where the recording density becomes sparse with respect to the desired resolution in the upper and lower portions of the band-shaped printing region. However, the lower sparse print area printed by the previous scan is made up by overlapping the upper sparse print area of the next scan, and image formation at a desired print density (resolution) can be performed. According to this, it is possible to suppress the banding caused by the variation in the sheet conveyance amount as compared with the first embodiment. The constant paper feed pitches Ltnom and Lgnom in each mode are Ltnom = 25.4MN /
Rtv = NPv and Lgnom = 25.4N / Rgv = NPvv.

Next, a fourth embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 11, in the gradation-oriented mode, the recording head 3 is rotated by the angle α with respect to the spatial-frequency-oriented mode, so that the spatial frequency-oriented mode has an angle α with the main scanning direction. Each N nozzle rows (for example, #
Nozzle row consisting of 1, # N + 1, ..., # (M-1) N + 1)
Is parallel to the main scanning direction. Therefore, N nozzle rows (in the spatial frequency emphasis mode) are arranged so as to be present at equal intervals on a virtual line (@ g1, @ g2, ..., @gN) parallel to the main scanning direction. Here, the distance Pvv between each nozzle row in the spatial frequency emphasis mode is the adjacent distance of the virtual line group consisting of the N lines, and the adjacent distance is K which is the distance between adjacent dots in the sub-scanning direction in the gradation emphasis mode. It is set to double (K is an integer). The integer K and the number of nozzle rows N are set to be relatively prime. Therefore,
The relationship between the Pvv and the resolution Rgv in the gradation priority mode is P
vv = 25.4K / Rgv. As a result, in the gradation priority mode, the same interlaced recording as described in the second embodiment can be performed.

Next, a fifth embodiment will be described.

The present embodiment has a configuration in which the condition that MRgv / Rtv is an integer is added to the configurations of the first and third embodiments. According to this, in the spatial frequency priority mode The ratio of the fixed paper feed pitch Ltnom of No. to the fixed paper feed pitch Lgnom in the gradation-oriented mode is Lgnom / Ltnom = M
It is an integer in Rgv / Rtv.

Therefore, in the case of printing an image pattern shown in FIG. 12 in which the graphic image in which the gradation is emphasized and the text image in which the spatial frequency is emphasized are mixed,
A predetermined line of text is printed by one scan, and then the recording head is rotated counterclockwise by an angle α to shift to the gradation-oriented mode, and the main scan and fixed paper feed are repeated a predetermined number of times (Fig. 12). In this example, it is possible to print a graphic image three times in main scanning and two times in fixed paper feed, shift to the spatial frequency priority mode again, and print the next line of text. This prevents misalignment between the text and graphic image recording positions, and there is no need to reverse feed the recording paper back to the beginning of the recording paper to print the graphic image after printing the text for one page. The output becomes faster.

If the condition that MRgv / Rtv is an integer is also applied to the second or fourth embodiment and interlace recording is performed in the gradation-oriented mode, text and graphic images are mixed in the same recording procedure. Can be printed.

Next, a sixth embodiment will be described.

In this embodiment, Rtv / Rgv is set to an integer in addition to the configurations described in the first to fifth embodiments. As a result, the fine feed pitch in the gradation priority mode can be made an integral multiple of the fine feed pitch in the spatial frequency priority mode, and the fine paper feed pitch in both modes can be effectively set in the spatial frequency priority mode. Can be unified on the pitch. Therefore, it is possible to simplify the recording paper transport mechanism, specifically, the gear train configuration of the gears that transmit the power from the paper feed motor.

Next, a seventh embodiment will be described.

In this embodiment, in addition to the configurations described in the first to sixth embodiments, the nozzle rows in the spatial frequency priority mode are arranged in parallel with the sub-scanning direction. In an inkjet recording apparatus, dots, which are generally the minimum units of a recorded image, are arranged on orthogonal grid points consisting of the main scanning direction and the sub-scanning direction for image formation, so that each nozzle row is parallel to the sub-scanning direction. If they are arranged, ink can be ejected from the same nozzle row at the same timing, and thus the load of timing adjustment for each nozzle when driving the head can be reduced.

Next, an eighth embodiment will be described.

In the present embodiment, in addition to the configurations described in the first to seventh embodiments, a control means for varying the ink ejection amount in the spatial frequency emphasis mode and the gradation property emphasis mode is provided. is there.

In general, the optimum recording dot diameter is closely related to the recording density, and the optimum ink ejection amount in the gradation priority mode and the optimum ink ejection amount in the spatial frequency priority mode are not always the same. However, according to this embodiment, an optimum ink amount can be set for each mode. This ink ejection amount is a voltage value applied to the piezoelectric element in a recording head in which ink droplets are ejected by utilizing the strain force of the piezoelectric element,
This can be done by changing the voltage waveform and the application time width.

[0050]

As described above, according to the present invention,
The head mounting angle is controlled so that one nozzle is arranged on one main scanning line in the spatial frequency emphasizing mode, and a predetermined number of plural nozzles are arranged on one main scanning line in the gradation emphasizing mode. The text can be recorded with high density by using, and in a graphic that requires gradation expression, a predetermined number of ink droplets can be deposited at the same position to adjust the formation area of one dot.

[Brief description of drawings]

FIG. 1 is a perspective view of an inkjet recording apparatus of the present invention.

FIG. 2 is a plan view showing a carriage peripheral portion of the inkjet recording apparatus shown in FIG.

FIG. 3 is a diagram showing a state of a nozzle array according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a print area for each scan of the recording head in the first embodiment.

FIG. 5 is a conceptual diagram showing how ink droplets land in a gradation-oriented mode.

FIG. 6 is a conceptual diagram showing an output image result in a gradation-oriented mode and a spatial frequency-oriented mode.

FIG. 7 is a diagram showing a state of a nozzle array of a recording head according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a print area for each scan of the recording head according to the second embodiment.

FIG. 9 is a diagram showing a state of a nozzle array of a recording head according to a third embodiment of the present invention.

FIG. 10 is a diagram showing a print area for each scan of the recording head according to the third embodiment.

FIG. 11 is a diagram showing a state of a nozzle array of a recording head according to a fourth embodiment of the present invention.

FIG. 12 is a diagram for explaining the fifth embodiment of the present invention.

[Explanation of symbols]

 1: Carriage guide 2: Carriage 3: Recording head 4: Recording head tilt angle changing mechanism 10: Recording paper (recording medium) 20: Recording paper transport mechanism

Claims (11)

[Claims] 1. A recording head having a plurality of nozzles formed therein is mounted on a carriage, and main scanning is performed in accordance with movement of the carriage in the digit direction, and sub-scanning for conveying recording paper in a direction orthogonal to the main scanning direction. In an inkjet printing apparatus that is repeatedly used, the angle of the main scanning direction and the reference line of the printhead are adjusted to different angles for two types of print modes, a gradation-oriented mode and a spatial frequency-oriented mode, and a printhead tilt variable In the gradation priority mode, M nozzles (where M is an integer of 2 or more) are adjusted so as to be aligned on the scan line in the main scanning direction. In the spatial frequency priority mode, the nozzles are aligned on the scan line. An inkjet recording apparatus, wherein only one nozzle is adjusted so as to be aligned. 2. The inkjet recording apparatus according to claim 1, wherein the M nozzles are formed at equal intervals on a reference line of the recording head. 3. The ink jet recording apparatus according to claim 2, wherein the recording head has N rows of nozzle rows composed of the M nozzles at predetermined intervals in the sub-scanning direction (where N is the gradation row). Is an integer of 2 or more), the inkjet recording device is characterized in that the nozzles are formed so as to be arranged. 4. The inkjet recording apparatus according to claim 3, wherein N nozzles are formed on each of M lines parallel to a second reference line different from the reference line. apparatus. 5. The inkjet recording apparatus according to claim 4, wherein the second reference line is parallel to the sub-scanning direction. 6. The inkjet recording apparatus according to claim 3, wherein the predetermined interval is a printing pitch in the sub-scanning direction in the gradation-oriented mode. 7. The inkjet recording apparatus according to claim 3, wherein the predetermined interval is K times a printing pitch in the sub-scanning direction in the gradation-oriented mode (where K is an integer of 2 or more), and K An inkjet recording device, wherein N is relatively prime. 8. The inkjet recording apparatus according to claim 7, wherein the recording paper conveyance amount in the gradation importance mode is set to N times the printing pitch in the sub-scanning direction. 9. The inkjet recording apparatus according to claim 1, wherein the resolution Rgv in the gradation importance mode and the resolution Rtv in the spatial frequency importance mode are set such that M.Rgv / Rtv is an integer. An inkjet recording device characterized by the above. 10. The ink jet recording apparatus according to claim 1, wherein the resolution Rgv in the gradation emphasis mode and the resolution Rtv in the spatial frequency emphasis mode are set such that Rgv / Rtv is an integer. Inkjet recording device. 11. The ink jet recording apparatus according to claim 1, further comprising control means for varying an ink ejection amount in a spatial frequency emphasizing mode and a gradation characteristic emphasizing mode. apparatus.