JPH1148464A - Test printing method and ink jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate image irregularity and to develop a high gradation degree and reproducibility faithful to an original image in a test printing method and an ink jet recording apparatus. SOLUTION: This ink jet recording apparatus contains a recording head wherein a large number of nozzles ejecting ink to a recording sheet 501 are arranged so as to be shifted at a predetermined interval in the direction shown by an arrow X, a carriage 512 moving the recording head in the direction shown by an arrow Y at a predetermined speed, a feed motor 507 feeding the recording sheet 501 at a constant speed in the direction shown by the arrow X and a densitometer 526 provided on the downstream side on the recording head in the feed direction by the feed motor 507. A test pattern is recorded on the region corresponding to the densitometer 526 of the recording medium by the recording head and read by the densitometer 526 while the recording medium is fed at a constant speed by the feed motor 507 and the distribution of a density signal along the direction shown by the arrow X is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a test printing method for easily specifying a nozzle in which an ink ejection failure has occurred, and an ink jet recording apparatus capable of performing the method to obtain a high-quality image with less image unevenness. .

[0002]

2. Description of the Related Art In recent years, in the field of medicine and the like in which an affected part is visualized and diagnosis or treatment is performed, when an image of the affected part is printed, diagnosis or the like is performed based on the printed matter. There is a demand for the printing of few high-quality images.

Conventional printing methods include a method of recording on a silver halide film using a laser, and a method of transferring ink onto a sheet by applying heat by applying an ink ribbon coated with an ink layer to the sheet and applying heat thereto. A method of forming an image and the like are known.

However, all of these methods require expensive silver halide films, ink ribbons, special papers, and the like, so that a printing method that is inexpensive and can easily obtain high-quality images can be employed. It is being sought.

[0005] As a printing method that meets such demands, a printing method using an ink jet recording apparatus is advantageous. That is, the ink jet recording apparatus uses a recording head having a nozzle composed of an ink discharge port and an ink flow path communicating with the ink discharge port, ejects ink from the nozzle to fly ink droplets, and attaches the ink droplets to a recording sheet. This is done by recording. For this reason, any printing medium that can penetrate the attached ink can be used as a recording medium in this printing method, so that inexpensive plain paper can be used, and the running cost can be significantly reduced as compared with the conventional method. Is possible. Further, the printing method using the ink jet method is advantageous in that an image can be easily formed as compared with the conventional method.

[0006] In the ink ejection method in such an ink jet system, a heating element (for example, an electric heat energy conversion element) is provided in an ink flow path near an ejection port, and an electric signal is supplied to the heating element as necessary. By supplying the ink, the ink in the vicinity of the heating element is locally heated to generate bubbling, and the ink is ejected from an ejection port by a change in pressure accompanying this, or an electromechanical device such as a piezoelectric element is used instead of the heating element. There is known a method of ejecting ink by a volume change caused by using a converter.

In either case, a plurality of fine nozzles are arranged on the recording head, and the heating elements and the like in the plurality of nozzles are simultaneously activated within a short time when the recording head is relatively moved with respect to the recording paper. The recording speed is increased by driving.

However, in the above-described ink jet recording apparatus, if the recording pause time is long, the viscosity of the ink increases due to the evaporation of the solvent of the ink due to the evaporation of the solvent of the ink when the ink comes into contact with the outside air through the discharge port. Since the fluidity is extremely reduced, the discharge port may be clogged with the thickened material. This clogging causes the above-mentioned image unevenness.

When manufacturing a recording head having such fine nozzles, a defect may occur in some of the plurality of nozzles, and some nozzles may not be able to perform a predetermined ejection operation.

Further, during use of the recording head having no defect at the time of manufacturing as described above, a malfunction may occur in some of the nozzles for some reason, and a predetermined ejection cannot be performed.

Regarding the above-mentioned nozzle clogging, the ink is prevented from evaporating by capping covering the ejection port forming surface of the recording head when printing is stopped, and the nozzle is capped between the cap member performing the capping and the ejection port forming surface. Is performed under reduced pressure, and a recovery operation such as removing the clogging by sucking ink from the clogged nozzle toward the discharge port side is performed.

However, in order to perform such a recovery operation, a clogged nozzle must be specified from a plurality of nozzles, which is not easy.

As one of the specifying methods, Japanese Patent Publication No.
A test pattern printing method described in 78019 is known. In this method, a straight line obtained by sequentially selecting and driving only one nozzle from a plurality of nozzles and a straight line obtained by simultaneously driving a plurality of nozzles are alternately and sequentially printed. According to this method, the clogged nozzle can be easily specified, and the recovery operation can be performed only on the specified nozzle.

If clogging is still not resolved by such a recovery operation, the recording head must be replaced.

[0015] In addition, non-uniformity of an image also occurs due to causes other than the nozzle clogging described above. For example, ink landing position deviation caused by a subtle change in the angle at which droplets are ejected due to the state of the tip of the nozzle, and differences in the size of print dots when the amount of ink ejected differs by nozzle In this case, a portion having a high ink density and a portion having a low ink density also occur on the image, resulting in image unevenness.

Next, with reference to the drawings, a specific description will be given of a case where image unevenness occurs when printing is performed by the ink jet method.

FIG. 1A is a plan view showing an image by solid printing using a head having no defective nozzles.
FIG. 2B is a plan view showing the size and position of each dot constituting the image by enlarging the image shown in FIG. The recording head has a plurality of nozzles arranged along the arrow X direction in the figure. Referring to FIGS. 1A and 1B,
Each normal dot 1 formed by ink droplets ejected from each nozzle lands uniformly at a predetermined position with a predetermined size, and no image unevenness is observed.

On the other hand, FIG. 2A is a plan view showing an image formed by solid printing using a head having a defective ejection nozzle, and FIG. 2B is an enlarged plan view of FIG. FIG.
Referring to (a), white streaks 2 and black streaks 3 are formed and occur due to various causes. In FIG. 2B, reference numeral 4 denotes a position shift dot that is shifted in the direction of the arrow X and overlaps with the normal dot 1, 5 denotes a position shift dot that is shifted in the direction of the arrow Y (a direction orthogonal to the direction of the arrow X), 6 indicates a missing dot which is missing due to nozzle clogging or the like, 7 indicates a dot which has a larger area due to a larger ink ejection amount than the normal dot 1, and 8 indicates a dot which has a smaller ink ejection amount. This shows a dot having a reduced area. The above-mentioned white stripes 2 and black stripes 3 are formed by these various abnormal dots. The symbol L in FIGS. 1A and 2A indicates a width that can be printed by all the nozzles of one recording head.

As shown in FIGS. 2 (a) and 2 (b), the above-mentioned abnormal dots are arranged in the arrow Y direction to form white stripes and black stripes in the arrow Y direction in the arrow X direction. This is because an ink jet recording apparatus configured to perform recording while moving a recording head having a plurality of nozzles arranged in the arrow Y direction is taken as an example.

The above-described image unevenness may occur due to the positional relationship of a plurality of nozzles, in addition to the case of one abnormal nozzle among a plurality of nozzles. Even when the degree of abnormality of the nozzle is small, as in the case of the dot 4, white stripes or black stripes may occur depending on the combination of adjacent nozzles.

Further, in order to increase the number of gradations to be expressed, dots are sometimes overlapped by overprinting at the same position with different heads or different nozzles. May be streaks or black streaks.

[0022]

The elimination of such image unevenness is a very important issue in a field where high gradation and faithful reproducibility with respect to the original image are required, such as the above-mentioned medical image. is there.

However, according to the conventional method, it is possible to detect clogging of the nozzle, but it is not possible to detect a discharge failure such as a landing position deviation and a discharge amount failure.

In order to solve the above-mentioned image unevenness, the present invention specifies not only clogged nozzles but also defective discharge nozzles, and generates image unevenness caused by a combination of a plurality of adjacent nozzles and multiple overprinting. The present invention provides a test printing method capable of efficiently detecting image unevenness caused by the combination of the nozzles described above, and an ink jet recording apparatus capable of performing the method.

[0025]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a recording head in which a plurality of nozzles for ejecting ink on a recording medium are arranged at predetermined intervals in a first direction, and the recording head is arranged in the first direction. A recording head moving means for moving at a predetermined speed in a second direction orthogonal to the recording medium; a constant speed conveying means for conveying the recording medium at a constant speed in the first direction; A print density detecting means provided on the downstream side in the transport direction by means of the inkjet printing apparatus, wherein a test is performed by using the print head in an area of the recording medium corresponding to the print density detecting means. The test pattern is recorded, the test pattern is read by the print density detecting unit while the recording medium is conveyed at a constant speed by the constant speed conveying unit, and the test pattern is read along the first direction. Characterized in that to obtain a distribution of the concentration signal.

Here, the test pattern may be formed by solid printing in which ink is ejected from all nozzles of the recording head.

When the density signal exceeds a predetermined threshold value, it may be determined that the nozzle corresponding to the density signal has an ejection failure.

When the density signal exceeds a predetermined threshold value, it is possible to determine which nozzle among the plurality of nozzles of the recording head has a discharge failure based on the time from the rise of the density signal. Good.

When the integrated value of the density signal over a predetermined width exceeds a predetermined threshold value, it may be determined that the nozzle corresponding to the density signal has an ejection failure.

When the integrated value of the density signal having a predetermined width exceeds a predetermined threshold value, the number of nozzles among the plurality of nozzles of the recording head having a discharge failure is determined by the time from the rise of the density signal. May be determined. The determination result may be displayed, and the display may include printing on the recording medium.

[0031] A plurality of recording heads may be provided, and a test pattern by the plurality of recording heads may be recorded while shifting a predetermined interval in the first direction.

[0032] The predetermined interval may be such that the test patterns are separated from each other.

The present invention also relates to an ink jet recording apparatus, comprising: a recording head in which a plurality of nozzles for discharging ink on a recording medium are arranged at predetermined intervals in a first direction;
Recording head moving means for moving the recording head at a predetermined speed in a second direction orthogonal to the first direction; and moving the recording medium in the first direction when recording a test pattern on the recording medium. A transport unit that transports the recording medium intermittently in the first direction when transporting the recording medium at a constant speed and recording a normal image on the recording medium; and a transport direction downstream of the transport unit with respect to the recording head. And a print density detecting means provided in the recording medium.A test pattern is recorded on the recording medium in an area corresponding to the print density detecting means by the recording head, and the recording medium is conveyed at a constant speed by the conveying means. The test pattern is read by the print density detecting means to obtain a density signal distribution along the first direction. Note that the phrase “shifted by a predetermined distance in the first direction” means that the pitch in the first direction is a predetermined distance, and includes a case where the pitch is slightly shifted in the second direction.

In the present invention, not only clogged nozzles but also defective discharge nozzles are specified, and image unevenness caused by a combination of a plurality of adjacent nozzles and image unevenness caused by a combination of a plurality of overprinted nozzles are determined. It is possible to provide a test printing method capable of efficiently detecting the same and an ink jet recording apparatus capable of performing the method.

[0035]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a schematic perspective view showing an embodiment of the ink jet recording apparatus of the present invention, and FIG.
FIG. 5 is a plan view showing the arrangement of a plurality of recording heads arranged in the recording unit of the recording apparatus shown in FIGS. 3 and 4, and FIG. FIG. 6B is an enlarged plan view showing the ejection port formation surface of the recording head, which is shown in FIG.
4A is a plan view showing print dots formed by landing of ink droplets discharged by the recording head shown in FIG. 4A corresponding to discharge ports of the recording head.

In FIGS. 3 and 4, reference numeral 501 denotes a recording sheet for forming an image. A pair of transport rollers 50
2 and 503 are opposed via a recording sheet 501, and another pair of transport rollers 504 and 505 are also opposed via a recording sheet 501. These transport rollers are transport members that transport the recording sheet 501 in the direction of arrow X. In particular, the transport rollers 5 located on the downstream side in the transport direction
A bulge 506 is partially formed on the outer surface of the recording medium 05, and the bulge 506 comes into direct contact with the recording sheet 501. The bulging portion 506 is provided on the recording sheet 5.
01 to protect the image by reducing the contact area with the recording surface, and to suppress the floating of the recording sheet 501. A pulley 508 is attached to a motor shaft of the transport motor 507, and pulleys 509 and 510 are attached to one ends of transport rollers 502 and 504, which are driving rollers, of the transport rollers described above. Pulley 508 is pulley 509
And 510. Therefore, the transport motor 507
Is transmitted to the conveying rollers 502 and 504 via each pulley and belt. The transport rollers 503 and 505, which are driven rollers, are urged by a mechanism (not shown) in a direction pressed against the opposing rollers, so that the recording sheet 501 is held between the opposing rollers, and the rotation of each roller is performed. Thus, the sheet can be conveyed in the direction of the arrow X.

Reference numeral 512 denotes a plurality of recording heads 513A to 513A.
The carriage on which the 513L is mounted. The carriage 512 is slidably held by a pair of shafts 516 and 517 extending in the arrow Y direction. That is, the shaft 516 penetrates the hole 518 of the carriage 512, and the projection 519 of the carriage 512 projecting in the direction of the arrow X is placed on the shaft 517.

Each recording head mounted on such a carriage 512 has a plurality of ejection ports 514 arranged in the direction of arrow X as shown in FIG. The print dots 515 formed by discharging ink from such discharge ports 514 are formed along the arrangement direction of the discharge ports 514 as shown in FIG. 6B. The ejection ports 514 of these recording heads are arranged toward the recording sheet 501, and the distance d between the recording surface of the sheet 501 and the ejection port forming surface of the recording head is always kept constant as shown in FIG. I have.

In this embodiment, twelve recording heads are arranged. One of the reasons for mounting a large number of recording heads on the same carriage 512 is to perform recording with a plurality of recording heads at the same time. The second is to increase the recording speed, and the second is to form a color image or a density gradation image by using inks of different colors or inks of different densities.
Particularly, in the case of a medical image, a black-and-white high gradation image is preferably used, so that it is advantageous to form a density gradation image.

Reference numeral 520 denotes a belt partially fixed to the carriage 512, which connects a pulley 522 attached to the shaft of the carriage drive motor 521 and a pulley 524 rotatably attached to the fixed shaft 523. .
The rotation of the carriage drive motor 521 allows the carriage 512 to reciprocate in the arrow Y direction and the opposite direction. The moving area of the carriage 512 includes the entire area in the width direction (the arrow Y direction) of the recording sheet 501 and a home position 512a (shown by a two-dot chain line in FIG. 3) located outside the transport area of the recording sheet 501.

As described above, the carriage 512 moves over a relatively wide range. Even when the carriage 512 moves, the separation distance between the ejection port forming surface of the recording head mounted on the carriage 512 and the recording surface of the recording sheet 501 is increased as described above. If the recording head is not always kept at a constant level, the discharge port forming surface of the recording head may be soiled due to contact between the two, which may lead to a discharge failure. For this reason, in the present embodiment, as shown in FIG.
A sheet guide 525 is provided between the two pairs of transport rollers. This sheet guide 525 is a recording sheet 501.
A large number of small holes are provided on the surface in contact with the recording sheet 501, and the recording sheet 501 is sucked by the sheet guide 525 by means (not shown) to maintain the flatness of the recording surface of the recording sheet 501.

Reference numeral 526 denotes a densitometer for optically measuring the density of an image formed on the recording surface of the recording sheet 501. The densitometer 526 is disposed on the downstream side in the transport direction of the recording area of the recording sheet 501, and generally includes a light emitting unit and a light receiving unit disposed at a position facing the light emitting unit with the recording sheet 501 interposed therebetween. Either the light emitting unit or the light receiving unit may be the upper or lower part. According to the densitometer 526, the light emitted from the light emitting unit is blocked by the recording sheet 501, and the light transmitted through the recording sheet 501 is detected by the light receiving unit, so that the transmittance of the recording sheet 501, that is, the transmitted image of the sheet Can be detected. As another mode of the densitometer, a light emitting unit and a light receiving unit are provided adjacently on the upper side, which is the recording surface side of the recording sheet 501, and light emitted from the light emitting unit is reflected on the sheet and reflected by the light receiving unit. A configuration for detecting is also possible. According to this configuration, the density distribution of the reflection image on the sheet can be detected.

In this embodiment, one set of densitometers 526 is provided as shown in FIGS. 3 and 4. However, a plurality of sets of densitometers are provided so that the densities at a plurality of locations can be measured simultaneously. Is also good.

In the case of performing normal recording in the ink jet recording apparatus according to the present embodiment having the above-described configuration, first, the recording sheet 501 is fed between the conveying rollers 502 and 503, and the rotation of the conveying motor 507 is performed. Is intermittently sent in the direction of the arrow X by a predetermined distance. While the conveyance of the recording sheet 501 is stopped, the carriage 512 on which the recording head is mounted is moved at a constant speed in the arrow Y direction by the rotation of the carriage drive motor 521. At this time, a nozzle discharge command signal corresponding to the image signal is sent to a heating element or the like in each nozzle by a control unit (not shown), and ink droplets are selectively discharged from each nozzle in accordance with the signal. While the recording head is at the home position 512a, which is a position away from the recording sheet, the recording sheet is moved by a predetermined distance in the arrow X direction, and the carriage 512 on which the recording head is mounted is moved again by the rotation of the carriage drive motor 521 to the arrow Y. The ink droplets are selectively ejected while moving at a constant speed in the direction.
By repeating this series of recording operations, a desired image can be formed on the recording sheet. Then, the recording sheet on which the image formation has been completed is conveyed by conveying rollers 504 and 505.
Is discharged along the arrow X direction.

Next, a case where recording is performed in the test print mode in the present embodiment will be described.

The recording in the test print mode is the same as the normal recording mode described above in that the recording sheet is intermittently conveyed in the direction of arrow X and the carriage on which the recording head is mounted is moved in the direction of arrow Y to perform recording. Is the same as The feature of recording in this test print mode is that the densitometer 526
Is that solid printing is performed on a part of the recording sheet for each recording head within the range that can be read. FIG. 7A is a plan view showing an example of solid printing in the test print mode. FIG.
As shown in FIG. 5A, a plurality of recording heads 5 shown in FIG.
Solid printing areas 527A to 527L having a predetermined area are formed in a line in the arrow X direction by all the nozzles 13A to 513L.

After completing such a test print,
Immediately before the recording sheet 501 is separated from the conveyance rollers 504 and 505, the conveyance motor 507 is reversely rotated to return the recording sheet 501 until the solid printing area 527A comes to a position on the upstream side in the conveyance direction from the densitometer 526. Next, the transport motor 5
07 rotates forward at a constant speed, and the recording sheet 501
It is transported at a constant speed in the direction. At this time, the densitometer 526 operates, and density signals of various patterns as shown in FIG. 7B can be obtained. Here, when the density signal of the solid print area 527B shown in FIG. 7A is checked in FIG. 7B, a protrusion corresponding to the lower black stripe is seen, and the protrusion corresponding to the upper white stripe is observed. You can see the dent part.

In the present embodiment, by determining a predetermined threshold value for each of the above-described patterns, a position exceeding the threshold value is specified, and a nozzle such as a discharge failure is detected from a plurality of nozzles. Can be. FIG. 8 shows FIG.
5 is an enlarged graph showing a pattern of an image signal corresponding to a solid print area 527B shown in FIG. In FIG. 8, the vertical axis represents concentration, and the horizontal axis represents time. FIG. 7 (b)
In the graph, the vertical axis represents time, and the horizontal axis represents density. FIG.
, K and L are predetermined thresholds, and K and L
A dot is a normal dot if it is in the range between. However, by comparing the threshold values K and L with the test pattern reading values actually obtained by the densitometer 526, a portion where the read value is out of the range between the threshold values K and L can be identified as a discharge failure. . More specifically, a nozzle having an ejection failure can be identified by determining the number of nozzles that deviate from the threshold value based on the time from the rise of the density signal (reference A in FIG. 8). Further, the time from the rising signal C to the falling signal D may be equally divided by the number of nozzles, and a defective nozzle may be specified based on which part of the divided portion is outside the threshold value.

In the case where the rise or fall of the signal has a slope, the rise may be made at a point exceeding a predetermined threshold M, and the fall may be made at a point below the threshold.

Although the test printing method described above is within the threshold value, black streaks or white streaks may occur due to, for example, a change in the ejection direction due to an abnormal nozzle state. In this case, the following method is effective.
Referring to FIG. 9, the interval between the rising signal and the falling signal is equally divided by the number of nozzles, and the signal is integrated for one of the divided widths. If the integrated value is larger or smaller than a predetermined threshold value, it is determined as abnormal.
This focuses on the characteristic that the human eye perceives that the area of a certain density part is dark when the area is large and that it is light when the area is narrow (area gradation). By expressing the value, an abnormality can be detected.

Next, even if the state of one nozzle is not abnormal at all, a black streak and a white streak may appear depending on the positional relationship between a plurality of adjacent nozzles. In this case, in the above-described method, the integration width is set to a plurality of division widths, a threshold value for the integrated value is determined in advance, and an abnormality can be detected by comparing the threshold value with the integrated value.

Next, even if no image unevenness occurs when printing is performed by each head alone, image unevenness may occur when another head or the same head is overprinted while being shifted in the X direction. Also in this case, the above-described test pattern is printed in a predetermined over-strike state, and this can be dealt with by determining an abnormality by the above-described method.

Next, as shown in FIG. 10, when the printed dot and the peak of the signal detected by the densitometer correspond one to one, the highest point tp of the signal peak is set to the center of the dot. It is determined that the position of the center of each dot is deviated from a predetermined position separated by a predetermined distance from the center position of the first dot,
Alternatively, it is possible to detect the extent to which the distance between the centers of adjacent dots deviates from a predetermined position, and to specify a nozzle that has hit a dot whose amount deviates from a predetermined value. When it is difficult to specify the position of the highest point of the signal peak, the midpoint t12 between the positions t1 and t2 that intersect with the predetermined threshold value q may be determined as the dot center position.

Next, as shown in FIG. 11 corresponding to FIG. 7, printing is performed with every other nozzle among a plurality of nozzles to form a print area 527A '.
Printing is performed in the area adjacent to A 'using the remaining nozzles to form a print area 527A ". Two densitometers are provided to correspond to the two print areas, and these densitometers are used. The density of each print area is read, and an example of the obtained density signal is shown in Fig. 12. In the graph of Fig. 12, the density is plotted on the vertical axis and time is plotted on the horizontal axis. Then, every other dot is hit, so that the signal of each dot is clearly separated, which is convenient for determining the center position of each dot. Need not be arranged in the X direction and may be arranged in the Y direction, in which case there is no need to prepare a plurality of densitometers.
It is not always necessary to set every other, and every two or more intervals may be provided.

As described above, according to the present invention, the density distribution signal of the test pattern is obtained by the densitometer and the constant-speed sheet feeding, and the nozzle or the nozzle causing the image abnormality such as the white stripe or the black stripe is obtained from the signal. This specifies a combination of a plurality of nozzles. Based on such a result, a printing method described in, for example, JP-A-60-104338 can be applied to the present invention. That is, this printing method provides a spare nozzle corresponding to the main nozzle,
When a trouble occurs in the main nozzle, the corresponding spare nozzle ejects ink droplets in place of the main nozzle,
The drive timing is determined by adjusting only the scanning time corresponding to the distance from the main nozzle.

When the test printing method of the present invention is used to determine that the nozzle is defective, the result of the determination is displayed on a display screen of a CRT or printed on a recording sheet. To display.

[0058]

As described above, according to the present invention,
A test printing method that can identify not only clogged nozzles but also defective ejection nozzles and efficiently detect image unevenness caused by a combination of multiple adjacent nozzles and image unevenness caused by a combination of multiple overprinted nozzles And an ink jet recording apparatus capable of performing the method.

[Brief description of the drawings]

FIG. 1A is a plan view showing an image obtained by solid printing using a head having no ejection failure nozzle, and FIG. 1B is an enlarged image of FIG. It is a top view which shows a magnitude | size and a position.

FIG. 2A is a plan view showing an image formed by solid printing using a head having a discharge failure nozzle, and FIG. 2B is an enlarged plan view of FIG.

FIG. 3 is a schematic perspective view showing an embodiment of the ink jet recording apparatus of the present invention.

FIG. 4 is a view taken in the direction of arrow A in FIG. 3;

FIG. 5 is a plan view showing an arrangement configuration of a plurality of print heads arranged in a printing unit of the printing apparatus shown in FIGS. 3 and 4.

6A is a plan view showing, on an enlarged scale, an ejection port forming surface of the recording head shown in FIG. 5, and FIG. 6B is a plan view of ink droplets ejected by the recording head shown in FIG. FIG. 3 is a plan view showing print dots formed by landing corresponding to ejection openings of a recording head.

FIG. 7A is a plan view illustrating an example of solid printing in a test print mode, and FIG. 7B is a graph illustrating a distribution of density signals obtained by reading a test pattern.

FIG. 8 is a schematic plan view showing a part of FIG. 7B in an enlarged manner.

FIG. 9 is a graph showing a modified example of the test printing method of the present invention.

FIG. 10 is a graph showing another modified example of the test printing method of the present invention.

FIG. 11 is a plan view showing a modified example of the test pattern shown in FIG.

FIG. 12 is a graph showing a distribution of density signals of the test pattern shown in FIG.

[Explanation of symbols]

 1 Normal dot 2 White stripe 3 Black stripe 501 Recording sheet (recording medium) 502 Transport roller (constant speed transport unit) 503 Transport roller (constant speed transport unit) 504 Transport roller (constant speed transport unit) 505 Transport roller (constant speed transport) Means) 506 Swelling part (constant speed conveying means) 507 Conveying motor (constant speed conveying means) 508 Pulley 509 Pulley 510 Pulley 511 Belt 512 Carriage (Recording head moving means) 512a Home position 513A-513L Recording head 514 Discharge port 515 Printing Dot 516 Shaft 517 Shaft 518 Hole 519 Projection 520 Belt 521 Carriage drive motor (Recording head moving means) 522 Pulley 523 Fixed shaft 524 Pulley 525 Sheet guide 526 Densitometer (Print density detecting means)

Claims (11)

[Claims] 1. A print head in which a plurality of nozzles for ejecting ink on a print medium are arranged at predetermined intervals in a first direction, and the print head is moved in a predetermined direction in a second direction orthogonal to the first direction. A recording head moving means for moving the recording medium at a constant speed, a constant speed conveying means for conveying the recording medium at a constant speed in the first direction, and a recording head provided downstream of the recording head in the conveying direction of the constant speed conveying means. A test printing method performed by using an ink jet recording apparatus including a print density detection unit, wherein a test pattern is recorded in an area corresponding to the print density detection unit on the recording medium by the recording head, Reading the test pattern by the print density detecting means while conveying the recording medium at a constant speed to obtain a density signal distribution along the first direction. Test printing method to be. 2. The test printing method according to claim 1, wherein the test pattern is formed by solid printing in which ink is ejected from all nozzles of the recording head. 3. The test printing method according to claim 1, wherein when the density signal exceeds a predetermined threshold value, it is determined that a nozzle corresponding to the density signal has an ejection failure. 4. When the density signal exceeds a predetermined threshold value, it is determined which nozzle among the plurality of nozzles of the recording head has an ejection failure based on a time from a rise of the density signal. The test printing method according to claim 1, wherein: 5. The test according to claim 1, wherein when the integrated value of the density signal over a predetermined width exceeds a predetermined threshold value, it is determined that the nozzle corresponding to the density signal has a discharge failure. Printing method. 6. When the integrated value of a predetermined width of the density signal exceeds a predetermined threshold, the number of nozzles out of the plurality of nozzles of the recording head is determined to be defective due to the time from the rise of the density signal. The test printing method according to claim 1, wherein it is determined whether or not the test printing is performed. 7. The test printing method according to claim 3, wherein the determination result is displayed. 8. The test print method according to claim 7, wherein the display includes a print on the recording medium. 9. The test printing method according to claim 1, wherein there are a plurality of recording heads, and a test pattern by the plurality of recording heads is recorded while shifting a predetermined interval in the first direction. 10. The test printing method according to claim 9, wherein the test patterns are separated from each other at the predetermined interval. 11. A recording head in which a plurality of nozzles for ejecting ink on a recording medium are arranged at predetermined intervals in a first direction, and the recording head is disposed in a predetermined direction in a second direction orthogonal to the first direction. Recording head moving means for moving at a speed,
When recording a test pattern on the recording medium, the recording medium is transported at a constant speed in the first direction, and when recording a normal image on the recording medium, the recording medium is moved to the first direction.
And a print density detecting means provided intermittently in the direction of the print medium and a print density detecting means provided downstream of the recording head in the direction of conveyance by the transport means, wherein the print head detects the print density of the recording medium by the recording head. A test pattern is recorded in an area corresponding to, and the test pattern is read by the print density detection means while the recording medium is conveyed at a constant speed by the conveyance means.
An ink jet recording apparatus, wherein a density signal distribution is obtained along the first direction.