Abstract:
An image recording apparatus includes: a conveying section that accelerates a long-length recording medium to a predetermined speed, conveys the long-length recording medium, and decelerates the long-length recording medium to a stopped state; a recording section that records an image on the recording medium, and forms a first test pattern on the recording medium after the image is recorded at a time of deceleration of the recording medium; a reading section that reads the image that the recording section has recorded and the first test pattern that the recording section has formed; an image converting section that converts inputted image data into image data that the recording section outputs; a maintenance section that performs maintenance of the recording section; and a controller that decides, on the basis of first data obtained by reading the first test pattern, whether or not the maintenance is needed and the content thereof.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 USC 119 from Japanese Patent Application No. 2010-191274 filed on Aug. 27, 2010, the disclosure of which is incorporated by reference herein. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to an image recording apparatus. 
     2. Related Art 
     Conventionally, in image recording apparatus that record character information, images, and so forth on a recording medium by methods such as conveying a recording medium such as a web (continuous paper) in a conveyance direction and jetting ink droplets or the like from a head that opposes a recording surface or making impacts by the dot, acceleration and deceleration of the recording medium become necessary a lot. 
     During acceleration and deceleration of the recording medium, ordinarily recording of images is not performed, but the continuous paper is conveyed also during acceleration and deceleration, so if the number of times of acceleration and deceleration increases, portions where recording is not performed arise in the continuous paper and end up becoming waste paper. 
     In consideration of this point, an image recording apparatus that corrects with high precision image formation position deviations between different color bars and deviations between short-length modules configuring a single-color bar type inkjet recording head in acceleration, deceleration, and steady speed of continuous paper has been disclosed (e.g., see Japanese Patent Application Laid-Open (JP-A) No. 2008-000903). 
     However, in JP-A No. 2008-000903, the target to be corrected is mechanical position deviations between bars and between modules configuring a single-color bar, and ordinarily these do not fluctuate that much once the bars are disposed. 
     On the other hand, jetting disturbances (position deviation and misfiring) of nozzles change greatly due to deterioration of the head over time and environmental fluctuations. When image formation that ignores these is performed, image deterioration such as stripe unevenness ends up arising, and there is the fear that the quality level will drop. 
     However, when information collection needed for maintenance for correcting the jetting disturbances in image recording using continuous paper—that is, test printing for identifying misfiring nozzles and identifying the cause of jetting direction deviations—is performed separately from the current printing, there is the problem that the number of times of acceleration and deceleration increases as described above and waste paper ends up increasing in accompaniment therewith. 
     SUMMARY 
     In consideration of the above-described circumstances, the present invention provides an image recording apparatus that has excellent maintenance efficiency and in which waste paper is kept little. 
     An image recording apparatus of a first aspect of the invention includes: a conveying section that accelerates a long-length recording medium from a stopped state to a predetermined speed, that conveys the long-length recording medium, and that decelerates the long-length recording medium to the stopped state; a recording section that records an image on the recording medium, and that forms a first test pattern on the recording medium after the image is recorded at a time of deceleration of the recording medium; a reading section that reads the image that the recording section has recorded and the first test pattern that the recording section has formed; an image converting section that converts inputted image data into image data that the recording section outputs; a maintenance section that performs maintenance of the recording section; and a controller that decides, on the basis of first data obtained by reading the first test pattern, whether or not the maintenance is needed and the content thereof. 
     According to the image recording apparatus of the first aspect of the invention, there can be provided an image recording apparatus that has excellent maintenance efficiency and in which waste paper is kept little. 
     An image recording apparatus of a second aspect of the invention forms a second test pattern on the recording medium at the time of acceleration of the recording medium, and decides, on the basis of the first data and second data obtained by reading the second test pattern, whether or not the maintenance is needed and the content thereof. 
     According to the image recording apparatus of the second aspect of the invention, nozzles that are constantly jetting-defective and nozzles that have become defective in the current printing can be separated, and maintenance conditions whose precision is higher can be set. 
     An image recording apparatus of a third aspect of the invention forms the second test pattern with a plurality of colors, and an output color order of the second test pattern is in descending order of proportions of intermediate densities of the image data. 
     According to the image recording apparatus of the third aspect of the invention, the image recording apparatus measures at a stage where the conveyance speed is low in order beginning with the color in which the proportion of the intermediate density is large, so time for correcting the data of a color in which dot position deviation and dot diameter precision are easily noticeable can be ensured. 
     An image recording apparatus of a fourth aspect of the invention forms a second test pattern with a plurality of colors, and an output color order of the second test pattern is in ascending order of S/N values of the image data read in the reading section. 
     According to the image recording apparatus of the fourth aspect of the invention, the image recording apparatus measures at a stage where the conveyance speed is low in order beginning with the color whose read S/N value is low, so time can be applied for reading color data whose read S/N value is low, and reading precision can be improved. 
     In an image recording apparatus of a fifth aspect of the invention, the recording section is equipped with an inkjet recording head, and at least one of the first test pattern and the second test pattern is a pattern for detecting jetting defects per nozzle of the inkjet recording head. 
     According to the image recording apparatus of the fifth aspect of the invention, misfiring nozzles can be detected by a unit of the nozzle. 
     An image recording apparatus of a sixth aspect of the invention does not perform the maintenance in a case where a number of misfiring nozzles detected in the pattern for detecting jetting defects is equal to or less than a predetermined number. 
     According to the image recording apparatus of the sixth aspect of the invention, the image recording apparatus does not go ahead and perform the maintenance if there are few misfiring nozzles, so process time and costs can be reduced. 
     In an image recording apparatus of a seventh aspect of the invention, at least one of the first test pattern and the second test pattern is a pattern for detecting average density of a predetermined region. 
     According to the image recording apparatus of the seventh aspect of the invention, misfiring of plural nozzles can be made detectable. 
     An image recording apparatus of an eighth aspect of the invention forms a first test pattern with a plurality of colors, and an output color order of the first test pattern is in descending order of S/N values of the image data read in the reading section. 
     According to the image recording apparatus of the eighth aspect of the invention, the image recording apparatus measures at a stage where the conveyance speed is high in order beginning with the color whose read S/N value is high, so time can be applied for reading color data whose read S/N value is low, and reading precision can be improved. 
     An image recording apparatus of a ninth aspect of the invention further includes a distance controlling section that controls a distance between the recording section and the recording medium, wherein the image recording apparatus forms the first test pattern a plural number of times while changing the distance during one deceleration and decides, from a relationship between the distance and recording position deviation information extracted from plural sets of the first data read by the reading section, whether or not the maintenance is needed and the content thereof. 
     According to the image recording apparatus of the ninth aspect of the invention, position deviation causes can be separated into jetting direction deviations and nozzle position deviations from changes in landing position deviation amounts resulting from the distance (TD) between the recording section and the recording medium and can be handled individually. 
     In an image recording apparatus of a tenth aspect of the invention, the recording section is equipped with an inkjet recording head, and the content of the maintenance includes wiping a nozzle surface of the inkjet recording head and forced jetting. 
     According to the image recording apparatus of the tenth aspect of the invention, the image recording apparatus performs forced jetting (purging) of ink as needed in addition to maintenance resulting from common wiping of the nozzle surface, so maintenance that is even more effective can be performed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a conceptual diagram showing the main portions of an image recording apparatus pertaining to the exemplary embodiment of the present invention; 
         FIG. 2  is a diagram showing an example of a misfiring nozzle detection pattern of a recording head pertaining to the exemplary embodiment of the present invention; 
         FIG. 3  is a diagram showing an example of dot arrangement patterns by density pertaining to the exemplary embodiment of the present invention; 
         FIG. 4  is a perspective view showing a raising-and-lowering mechanism of the recording head pertaining to the exemplary embodiment of the present invention; and 
         FIG. 5  is a side view showing landing position deviations resulting from the position of the recording head pertaining to the exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     An exemplary embodiment pertaining to the present invention will be described below with reference to the drawings. 
     &lt;Overall Configuration&gt; 
     As shown in  FIG. 1 , in an image recording apparatus  100  pertaining to the present exemplary embodiment, a feed section  10  that feeds and conveys a web (continuous paper) P serving as a recording medium is disposed on an upstream side in a conveyance direction of the web P. On the conveyance direction downstream side of this feed section  10 , an infeed section  20 , a process liquid applying section  30 , a first drying section  40 , an image forming section  50 , a second drying section  60 , a fixing and reading section  70 , an outfeed section  80 , and a collecting section  90  are sequentially disposed along the conveyance direction of the web P. The infeed section  20  pulls out the web P from the feed section  10  and temporarily stores the web P. The process liquid applying section  30  applies a process liquid to a recording surface of the web P. The first drying section  40  dries the web P. The image forming section  50  forms an image on the recording surface of the web P. The second drying section  60  dries the image and fixes it to the web P. The fixing and reading section  70  fixes the image and reads it with a scanner or the like. The outfeed section  80  temporarily stores the web P. The collecting section  90  collects the web P to which the image has been fixed. An unillustrated controller that controls the actions of each section is also disposed, and the controller all-inclusively controls the actions of the entire apparatus. 
     Further, although there are no particular restrictions on the recording medium that is used as the web P, general printing paper whose main constituent is cellulose—such as so-called wood-free paper, coated paper, and art paper—and which is used in general offset printing and so forth can be used. As described later, the recording medium is not limited to roll paper and may also be sheets (cut paper). 
     With general printing paper whose main constituent is cellulose, in image recording resulting from general inkjet methods using water-based ink, ink absorption and drying are comparatively slow, color material migration easily occurs after ejection, and image quality easily drops, but according to the inkjet recording of the present invention, the recording of a high-quality image in which color material migration is suppressed and which has excellent color density and color hue is possible. Each of the processing sections will be described below. 
     &lt;Feed Section&gt; 
     As shown in  FIG. 1 , the feed section  10  is equipped with a reel stand  14  onto which a feed roll  12  (feed reel) is loaded. When a feed roll  11  in use in the middle of a printing operation is near its end, the feed section  10  prepares the new feed roll  12 , connects the roll paper on the old feed roll  11  and the roll paper on the new feed roll  12  to each other, and feeds the web P (band-like paper) continuously so that there is no break in the continuous process. 
     In  FIG. 1 , the feed roll  11  is a feed roll that is in use, the feed roll  12  is a feed roll that has been prepared to be used next, and a feed roll  13  is a feed roll that has been used up and whose web P has finished being consumed. As for the method of replacing the old feed roll with the new feed roll, an arm of the reel stand  14  is rotated clockwise in the drawing and brought closer to the traveling line of the web P. The circumferential speed of the feed roll  12  is synchronized with the traveling speed of the web P, an unillustrated paper splicing device is actuated to press a gluing part of the leading end of the feed roll  12  against the web P and splice the two together, and the feed roll  11  that is currently in use and the web P are cut apart by a cutter of the paper splicing device. Therefore, the feed roll  11  becomes the feed roll  13  that has been used up. 
     &lt;Infeed Section&gt; 
     As shown in  FIG. 1 , in the infeed section  20 , there is disposed an infeed roller pair  21  that pulls out the web P from the feed section  10 . The rotational speed of the infeed roller pair  21  can be freely set. A dancer roller  22  that is swung and held up and down in the drawing by an unillustrated actuator and performs adjustment of the tension in the web P is disposed in order to temporarily store an adjustment margin of the web P needed for time to splice the web P as described above and changing the conveyance speed of the web P. 
     That is, the infeed section  20  has a role as a paper accumulating section that temporarily stores the web P stretched across the infeed roller pair  21  and the dancer roller  22  when the infeed roller pair  21  and the dancer roller  22  are a maximum distance apart from each other. While the web P is temporarily not fed from the feed section  10 , such as during the time when the web P is being spliced, the infeed section  20  decreases the distance between the infeed roller pair  21  and the dancer roller  22  and conveys the web P to the process liquid applying section  30  on the conveyance direction downstream side. 
     &lt;Process Liquid Applying Section&gt; 
     As shown in  FIG. 1 , in the process liquid applying section  30 , there is placed an applying roller unit  31  that applies to the recording surface (the surface on which an image is recorded, the top side in the drawings) of the web P a process liquid that causes a flocculation reaction with the ink that is ejected in the later-described image forming section  50 . The process liquid that is applied here includes a flocculant that causes the components in the ink composition to aggregate. 
     By applying this process liquid, the ink and the process liquid cause a flocculation reaction at the recording surface of the web P after image recording, problems and image failure such as bleeding, landing interference (unity), and color mixing after ink landing do not occur, and the formation of a high-quality image becomes possible. 
     The flocculant that is used may be a compound that can change the pH of the ink composition, or may be a multivalent metal salt, or may be a polyallylamine. Preferred examples of compounds that can lower the pH include highly water-soluble acidic substances (phosphoric acid, oxalic acid, malonic acid, citric acid, or derivatives of these compounds, or salts of these compounds, etc.). One type of acidic substance may be used alone, or two or more types of acidic substances may be combined. This raises cohesion and immobilizes the whole ink. It is preferred that the pH (25° C.) of the ink composition be equal to or greater than 8.0 and that the pH (25° C.) of the process liquid be in the range of 0.5 to 4. This makes it possible to improve image density and resolution, and to speed up inkjet recording. 
     Further, other additives (publicly known additives such as an anti-drying agent (=a wetting agent), an anti-fading agent, an emulsion stabilizer, a permeation enhancer, a UV absorber, a preservative, an antifungal agent, a pH modifier, a surface tension modifier, a defoamer, a viscosity modifier, a dispersant, a dispersion stabilizer, a corrosion inhibitor, a chelating agent, etc.) can also be included in the process liquid. 
     &lt;First Drying Section&gt; 
     As shown in  FIG. 1 , in the first drying section  40 , dancer rollers  41  that are swung and held in the vertical direction in the drawing by an unillustrated actuator and perform adjustment of the tension in the web P are disposed in order to temporarily store the web P needed for time to splice the web P as described above and changing the conveyance speed of the web P. The ink drying section  40  is given a configuration where it blows a heated air flow onto the web P from an unillustrated fan heater to thereby heat and dry the web P that is stretched across these dancer rollers  41 . 
     At this time, the air volume and the air temperature of the heated air flow in the first drying section  40  may also be weakened (lowered) at the times of acceleration and deceleration as described later. This is to prevent overdrying because the amount of time required for the web P to pass through the first drying section  40  becomes longer at the times of acceleration and deceleration than at the time when the web P is conveyed at its ordinary speed (at the time of recording). 
     &lt;Image Forming Section&gt; 
     As shown in  FIG. 1 , in the image forming section  50 , one or plural recording heads  51  are disposed in positions opposing the recording surface of the web P. 
     In the example shown in  FIG. 1 , four recording heads  51  jet ink droplets of the colors of C, M, Y, and K onto the recording surface of the web P to form an image thereon. The conveyance path of the web P is given a convex shape in which the recording surface side bulges, and tension is applied to the web P, whereby flapping of the web P is suppressed and a clearance between each of the recording heads  51  and the recording surface is ensured. 
     The ink jetted from the recording heads  51  is a water-based ultraviolet-curable ink, for example, and includes a pigment, polymer particles, and a water-soluble polymerizable compound that is polymerized by an active energy ray. A water-based ultraviolet-curable ink is curable as a result of ultraviolet light being applied thereto and forms on the recording surface an image that has excellent ability to withstand scratches and whose film strength is high. 
     For the pigment, for example, a water-dispersible pigment in which at least part of the surface thereof is coated with a polymeric dispersant is used. It is preferred that the acid value of the polymeric dispersant be in the range of 25 to 100 KOH mg/g. Therefore, the stability of self-dispersion becomes good and cohesion when the process liquid makes contact becomes good. Further, for the polymer particles, self-dispersing polymer particles whose acid value is 20 to 50 KOH mg/g are preferably used. Therefore, the ink can be made into one in which the stability of self-dispersion is good and cohesion when the process liquid makes contact is good. 
     As the polymerizable compound, a nonionic or cationic polymerizable compound is preferred in terms of not impeding the reaction between the flocculant and the pigment and polymer particles, and a polymerizable compound whose solubility with respect to water is equal to or greater than 10% by mass (or equal to greater than 15% by mass) is preferred. 
     At least one of the ink composition and the process liquid may further include an initiator that initiates the polymerization of the polymerizable compound by the active energy ray. For the initiator, a compound that can initiate the polymerization reaction by the active energy ray can be appropriately selected and included; for example, an initiator (e.g., a photopolymerization initiator) that generates an active species (radical, acid, base, etc.) by radiation, light, or an electron beam can be used. 
     Further, the ink includes water at 50 to 70% by mass, and other water-soluble organic solvents and publicly known additives—such as an anti-drying agent (a wetting agent), an anti-fading agent, an emulsion stabilizer, a permeation enhancer, a UV absorber, a preservative, an antifungal agent, a pH modifier, a surface tension modifier, a defoamer, a viscosity modifier, a dispersant, a dispersion stabilizer, a corrosion inhibitor, a chelating agent, etc.—may also be added. 
     &lt;Second Drying Section&gt; 
     As shown in  FIG. 1 , the second drying section  60  basically has the same configuration as that of the first drying section  40 . In the second drying section  60 , dancer rollers  61  that are swung and held in the vertical direction in the drawing by an unillustrated actuator and perform adjustment of the tension in the web P are disposed in order to temporarily store the web P needed for time to splice the web P as described above and changing the conveyance speed of the web P. The ink drying section  60  is given a configuration where it blows a heated air flow onto the web P from an unillustrated fan heater to thereby heat and dry the web P that is stretched across these dancer rollers  61 . 
     At this time, like in the first drying section  40 , the air volume and the air temperature of the heated air flow in the second drying section  60  may also be weakened (lowered) at the times of acceleration and deceleration. This is to prevent overdrying because the amount of time required for the web P to pass through the second drying section  60  becomes longer at the times of acceleration and deceleration than at the time when the web P is conveyed at its ordinary speed (at the time of recording). 
     &lt;Fixing and Reading Section&gt; 
     As shown in  FIG. 1 , in the fixing and reading section  70 , there is disposed an ultraviolet emitting light source  71 . The ultraviolet emitting light source  71  applies ultraviolet light to the recording surface of the web P after image recording to thereby solidify the aggregate of the process liquid and the ink. After this, a cooling device  72  disposed on the conveyance direction downstream side cools the web P to an appropriate temperature and fixes the image to the web P. 
     The cooling device  72  is equipped with plural cooling rollers  73 . As the web P is conveyed between the plural cooling rollers  73 , the web P loses its conductive heat and is cooled because of contact with the cooling rollers  73 . 
     After the image on the recording surface has been fixed, a scanner  74  reads the image on the recording surface to detect jetting defects, landing position deviations, density deviations, and so forth resulting from problems in the recording heads  51  when the image was formed on the recording surface in the image forming section  50  and feeds back information to an unillustrated controller for correction and adjustment. 
     &lt;Outfeed Section&gt; 
     As shown in  FIG. 1 , in the outfeed section  80 , there is disposed an outfeed roller pair  81  that pulls out the web P from the fixing and reading section  70 . The rotational speed of the outfeed roller pair  81  can be freely set. A dancer roller  82  that is swung and held up and down in the drawing by an unillustrated actuator and performs adjustment of the tension in the web P is disposed in order to temporarily store an adjustment margin of the web P needed for time to splice the web P as described above and changing the conveyance speed of the web P. 
     That is, the outfeed section  80  has a role as a paper accumulating section that temporarily stores the web P stretched across the outfeed roller pair  81  and the dancer roller  82  when the outfeed roller pair  81  and the dancer roller  82  are a maximum distance apart from each other. While the web P is temporarily not fed from the upstream side, such as during the time when the web P is being spliced, the outfeed section  80  decreases the distance between the outfeed roller pair  81  and the dancer roller  82  and conveys the web P to the collecting section  90  on the conveyance direction downstream side. 
     &lt;Collecting Section&gt; 
     As shown in  FIG. 1 , in the collecting section  90 , there is disposed a reel stand  94  to which plural winding cores  91  are attached. At the time of collection of the web P, an arm of the reel stand  94  is rotated to bring a winding core  91  closer to the conveyance path of the web P, an unillustrated core joining device presses the web P against an adhering part of that winding core  91  to join the web P to that adhering part, and thereafter a cutter of the core joining device cuts apart a roll  92  and the web P. Therefore, the web P that has been conveyed thereto is sequentially taken up and collected on the winding core  91 . Alternatively, the collecting section  90  may also be given a configuration where a folder is disposed instead of the winding cores  91  so that the web P is folded and collected rather than being collected in a roll form. 
     &lt;Test Pattern Formation&gt; 
     A test pattern that is recorded at the time of deceleration of the web P in the image recording apparatus  100  pertaining to the present invention will be described below. 
     In the present invention, the image recording apparatus  100  prints a predetermined test pattern on the web P at the time of deceleration (and at the time of acceleration as needed) of the web P, uses the data of the test pattern at the time of deceleration to decide whether or not maintenance is needed and to select the content of maintenance, and uses the data of the test pattern at the time of acceleration to correct the data of the current printing. 
     Examples of types of test patterns used in the present invention include a test pattern  57 , which is a nozzle check pattern in which lines  54  like in  FIG. 2  (or dots  55  like in  FIG. 3 ) are drawn from nozzles  53  of each of the recording heads  51  to acquire data of jetting defects (misfiring, direction deviation) of the nozzles  53 . 
     For example, when the lines  54  have been test-outputted from the nozzles  53  onto the web P conveyed in the direction of arrow C like in  FIG. 2 , patterns such as lines  54 A is obtained from nozzles  53 A from which the ink is being jetted properly, but a pattern is not obtained from a nozzle  53 B in which there is a jetting defect, so this area becomes blank such as a line  54 B. 
     Moreover, as shown in  FIG. 3 , a test pattern  59 , which is a density check pattern in which patches are simultaneously outputted from the plural nozzles  53  to acquire density data of a predetermined region (e.g., 20 mm in a nozzle row direction), is conceivable. 
     Next, methods of deciding the printing order of the test pattern of the present invention include a method of dividing by density data of an input image at the time of the subsequent printing and a method of dividing by reading levels (S/N ratios at the time of reading) by color. 
     First, in relation to the method of dividing by the density data of an input image, usually in the case of inkjet printing, unevenness tends to be most easily noticeable in intermediate density portions. This is because, as shown in  FIG. 3 , in a low density region, the dots  55  do not overlap in the first place, and even if the landing positions (formation positions) of the dots  55  and the diameters of the dots  55  deviate somewhat from their normal positions and assumed sizes, the effect that error in positional precision and dot diameter has on visibility is small. 
     Further, similarly, as shown in  FIG. 3 , in a high density region, the dots  55  densely overlap, so in this case also, even if the landing positions of the dots  55  and the dot diameters deviate somewhat from their normal positions and assumed sizes, the effect that those have on visibility is small. 
     In contrast, in an intermediate density region, the difference between a given dot  55  that overlaps another dot  55  and a given dot  55  that does not overlap another dot  55  is smaller than in the low-density region and the high-density region, so if the landing positions of the dots  55  and the dot diameters deviate, the difference ends up becoming more easily noticeable compared to the dots  55  in the high density region and the low density region. Consequently, it is necessary to perform maintenance before printing in order to reduce as much as possible unevenness in the pattern of the intermediate density region. That is, at the time of deceleration, it is preferable to print a test pattern in a color order in which there is a little data of the intermediate density region of the input image of the subsequent printing, and conversely, at the time of acceleration, it is preferable to print a test pattern in a color order in which there is a lot of data of the intermediate density region of the input image of the subsequent printing (not an image to be printed after the acceleration but an image to be printed after the web P has decelerated after that and has then accelerated anew). 
     In relation to which density region is to taken as intermediate density, generally it is preferable to take it to be about 30 to 70% of the maximum density of each color, but it is not invariably necessary for it to be in this range and it may also be appropriately changed depending on the parameters of the recording heads  51 , such as the density of the ink to be used, the resolution (inter-nozzle distance) of the recording head, and dot diameter. 
     In the present invention, the image recording apparatus  100  is given a configuration where it reads the test pattern with a reading section (the scanner  74 ) as described above. At the time of this reading, it is preferable to apply an RGB filter to the incident light or the reflected light in order to improve the read S/N ratio per ink color, but depending on the spectral characteristics (spectral absorption characteristics) of the filter and the spectral absorption characteristics of the color material of each color, there are colors whose read S/N ratio is large (whose measurement error is small) and colors whose read S/N ratio is small (whose measurement error is large). As a way of determining the S/N ratios, for example, the S/N ratios can be expressed such that S=the output value after the reading of the ink jetting portion and N=the output value after the reading of the paper portion. 
     At this time, during acceleration of the web P, the scanner  74  reads in order beginning with the color whose read S/N ratio is small, and during deceleration of the web P, the scanner  74  reads in order beginning with the color whose S/N ratio is large, whereby passage time (=reading time) can be gained in colors whose read S/N ratios are small, and as a result measurement precision can be improved. 
     &lt;Effect: Deciding Whether or not Maintenance is Needed&gt; 
     First data obtained by outputting the test patterns  57  and  59  during deceleration of the web P and reading the test patterns  57  and  59  with the scanner  74  can be used to determine various conditions at the time of maintenance of the recording heads  51  thereafter. 
     Maintenance conditions may be decided from only the first data formed during deceleration of the web P, but more preferably an aspect of determining the difference between second data obtained as a result of being outputted during acceleration (before the current printing) of the web P and the first data obtained as a result of being outputted during deceleration (after the current printing), deciding on the basis of this difference whether or not maintenance is needed, and changing the maintenance level in a case where it has been decided that maintenance is needed is preferable. 
     Therefore, for example, even in a jetting-defective nozzle  53  in the same way, a nozzle  53  that is constantly jetting-defective and a nozzle  53  that has become jetting-defective during the current printing can be separated. That is, if the data during acceleration (before jetting) are normal and there is a jetting defect in the data during deceleration (after jetting), it can be decided that the jetting defect has occurred in the current printing. 
     The image recording apparatus  100  may also be configured such it does not perform maintenance when the difference between the second data obtained during acceleration and the first data obtained during deceleration is equal to or less than a first threshold value, and such that it performs ordinary maintenance when the difference exceeds the first threshold value and is equal to or less than a second threshold value, and such that it performs forced maintenance when the difference exceeds the second threshold value. 
     Divisions are conceivable by which the ordinary maintenance mentioned here entails only wiping the nozzle  53  surface and the forced maintenance entails purging (forced jetting) from the nozzles  53  that are misfiring and then wiping the nozzle  53  surface. Therefore, it becomes possible to cut back on unneeded maintenance, and the amount of ink that becomes wasted at the time of maintenance and the amount of maintenance time can be reduced. 
     &lt;Effect: Deciding Whether or Not Maintenance is Needed by Recording Head Position&gt; 
     Each of the recording heads  51  disposed in the image forming section  50  of the image recording apparatus  100  pertaining to the present invention may be equipped with a moving mechanism exemplified below, whereby the recording head  51  is supported so as to be movable in a direction toward and away from the conveyance surface of the web P. Therefore, the recording head  51  is given a configuration in which its throw distance (TD) can be changed. 
     For example, the recording head  51  may be raised and lowered (moved toward and away from the recording surface of the web P) by a raising-and-lowering mechanism  140  such as shown in  FIG. 4 . 
     As shown in  FIG. 4 , on both lengthwise direction ends of the recording head  51 , guide pins  170  that are disposed in the toward-and-away direction with respect to the web P penetrate the recording head  51 , and the recording head  51  is made movable in the toward-and-away (up-and-down) direction along the guide pins  170 . 
     Threaded holes  171  penetrate the recording head  51  in the toward-and-away direction, and shafts  172  that screw along the threaded holes  171  are disposed extending in the toward-and-away direction. The shafts  172  are driven to turn by an unillustrated stepping motor. Threads are cut into the outer peripheral surfaces of the shafts  172 , and when the shafts  172  turn in the direction of arrow R in  FIG. 4 , the shafts  172  screw along the threaded holes  171  and enable the recording head  51  to be moved (raised and lowered) in the direction of arrow H (toward-and-away direction). 
     Using the recording head  51  with this configuration, data pertaining to the determination of whether or not maintenance is needed can be acquired by moving the recording head  51  up and down (in directions toward and away from the web P) during deceleration of the web P and recording a test pattern. 
     By raising the recording head  51  (the nozzles  53 ) during deceleration of the web P, recording a test pattern a plural number of times, and determining differences between the plural test patterns, causes of jetting direction defects in the nozzles  53  can be separated. That is, it becomes possible to classify the causes into two types of causes: deviations in the jetting direction and deviations in the positions of the nozzles  53  themselves (where the liquid droplets are jetted perpendicularly with respect to the web P but the positions of the nozzles  53  are shifted). 
     As shown in  FIG. 5 , in a case where position deviation becomes large like from d 1  to d 2  when the TD is raised from h 1  to h 2 , the cause of the jetting direction defect in the nozzles  53  can be considered a “deviation in the jetting direction”. In this case, a case where the neighborhoods of the open portions of the nozzles  53  are soiled with residual ink or the like is conceivable, so the defect can be remedied by carefully performing maintenance thereafter with respect to the nozzles  53 . 
     On the other hand, in a case where the position deviation d 1  does not change (does not become larger) even when the TD is raised to h 2 , the positions of the nozzles  53  themselves shifting can be considered to be the cause of the jetting direction defect. Therefore, in this case the defect cannot be remedied even if maintenance is performed, so the image recording apparatus  100  determines to perform ordinary maintenance. 
     Therefore, jetting direction defects that can be remedied with maintenance can be remedied with forced maintenance including wiping the nozzle surface, for example, and with respect to jetting direction defects that cannot be remedied even if maintenance is performed, the wasting of ink and process time can be saved by performing only ordinary maintenance. 
     &lt;Other&gt; 
     An exemplary embodiment of the present invention has been described above, but the present invention is in no way limited to the above exemplary embodiment and, it goes without saying, can be implemented in various aspects in a scope not departing from the gist of the present invention. 
     For example, in the above exemplary embodiment, a configuration that conveys the web P that is long continuous paper was taken as an example, but the recording medium is not limited to this, and single sheets of a recording medium may also be used. That is, the image recording apparatus can be given a configuration where, when it conveys and records on single sheets of a recording medium one sheet at a time, it forms a test pattern at the time of deceleration of a test print and uses the test pattern to decide maintenance. 
     Moreover, the liquid that is jetted is not limited to ink for image recording, character printing, and so forth and may also be applied to substrate pattern formation at the time of etching, for example.