JP2012025139A - Measuring method of expansion and contraction amount of recording medium, image forming method, and image recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image recording method and image recording device which estimate a paper feeding property of an output image from a difference of cockle quantities of test images formed of white ground parts and solid parts.SOLUTION: The test image output on a recording medium for measuring a cockle quantity includes a plurality of measurement points arranged with predetermined intervals on an upstream side and a downstream side in a delivery direction. A distance between delivery directions between the measurement points is previously determined, and the measurement points are arranged so as to measure how much the recording medium expands or contracts after an image is formed. A correspondence table of an image and probability of paper floating jam is previously stored as a database, and it is used to estimate a jam rate of an image to be printed from the jam rate of an image similar to the image to be printed. When a jam rate of an image #14 printed at a certain density is 10%, a jam rate of an image #2 printed at the same density is estimated as 10*0/45=0%, and a jam rate of an image #13 is estimated as 10*5/45≒1%.

Description

  The present invention relates to a method for measuring the amount of expansion / contraction of a recording medium, an image forming method, and an image recording apparatus.

  2. Description of the Related Art Conventionally, in an image recording apparatus that records character information, an image, or the like on a recording medium by transporting a recording medium such as recording paper in the transport direction and ejecting ink droplets or the like from a head facing the recording surface, It is known that when a fixed time elapses after a droplet adheres to a recording paper, paper floating called cuckling or curling occurs.

  For example, when water-based ink is used in the ink jet recording method, the printing paper is deformed by breaking hydrogen bonds in cellulose and recombining hydrogen bonds by drying. In such a double-sided printing machine, when such a deformation occurs during front surface printing, an image recording apparatus is disclosed that functions to protect the IJ (inkjet) head during back surface printing and prevents interference between the paper and the IJ head (for example, Patent Document 1).

  Alternatively, an image recording apparatus that determines the distance of the recording head with respect to the platen in consideration of recording conditions related to occurrence of cuckling before recording is disclosed (for example, see Patent Document 2).

  In addition, based on either the paper information of the paper or the image information formed on the paper, the degree of the wave generated on the paper on which the droplet has landed is predicted, and the suction mechanism is set according to the degree of the wave. An image recording apparatus that controls suction force is disclosed (for example, see Patent Document 3).

JP 2010-76872 A JP 2009-119713 A JP 2009-83480 A

  In the example of Patent Document 1, when the paper floating sensor detects paper deformation, the paper passing is stopped to protect the IJ head, and the paper passing property at the time of back side printing is deteriorated. It can be predicted that whether the paper-passing state is good or bad is likely to correspond to the state of paper after surface printing (paper deformation state). However, there have been no large-sized IJ printers that are required to have higher printing accuracy until now. For example, there is no data associating the cockle state and the paper passing property during double-sided printing.

  In the example of Patent Document 2, the distance from the print head to the platen is determined in consideration of conditions relating to the occurrence of cuckling, and the amount of paper cuckling is measured or the appropriateness of the back side of the paper according to the image / paper is estimated. Not what you want.

  Alternatively, in Patent Document 3, it is necessary to suck the sheet so as to maintain a small sheet floating amount in order to ensure the sheet passing property. However, if the cockle state is large, the sheet is wrinkled at the time of sucking. There is a possibility that the paper passing property is deteriorated.

  Therefore, in the present invention, the correspondence between the amount of expansion and contraction of the image and the ease of passing through the back surface is clarified, and an image for measuring paper expansion and contraction, which is most suitable for confirming the sheet passing property, is defined and used. A method for measuring the amount of expansion and contraction is presented. By measuring the amount of cuckling in the expansion / contraction amount measurement image, the ease of passing the back side of the paper type and the jam (conveyance failure) rate data of the test image registered in advance are compared with the image data to be actually output. This makes it possible to estimate the jam rate of the image.

  In consideration of the above-described facts, the present invention provides a recording medium expansion / contraction amount measuring method, an image forming method, and an image recording apparatus for estimating the paper passing property of an output image from a difference in the amount of cuckling of a test image composed of a white background portion and a solid portion. The task is to do.

  The method for measuring the amount of expansion and contraction of a recording medium according to claim 1, wherein the recording medium is sucked and transported in the transport direction, droplets are ejected onto the recording medium, and a white background portion and a solid portion are formed on the recording medium over the length in the transport direction. A creepage distance measured along the surface of the recording medium, and a measurement distance between measurement points provided at a distance along the conveying direction in each of the white background portion and the solid portion. A difference in the amount of cockle in the transport direction between the white background portion and the solid portion of the test image is calculated from the difference between the distance between the points projected onto a plane extending along the transport direction.

  According to the above-described invention, the difference in the amount of cuckling between the solid portion with the largest amount of liquid ejected on the recording medium and the white background portion with the smallest amount is calculated, and the image of predicting the paper floating probability or paper passing performance from this value It can be a recording method.

  According to a second aspect of the present invention, the creepage distance is measured by a laser displacement meter, and the distance projected onto the plane is measured by an in-line sensor.

  According to the above invention, the measurement of the unevenness of the recording medium is measured with the laser displacement meter, and the distance projected onto the plane is measured with the in-line sensor that is normally used, so that accurate measurement of the amount of cockle can be performed at low cost. Can do.

  The method for measuring the amount of expansion / contraction of the recording medium according to claim 6 is characterized in that the test image is provided with a solid portion at both ends in the conveyance width direction and a white background portion sandwiched between the solid portions.

  According to the above invention, the difference in the amount of cuckling between the solid portion with the largest amount of liquid ejected in the transport direction on the recording medium and the small white background portion can be calculated. Gender prediction.

  The image forming method according to claim 4 is characterized in that, in double-sided printing, if the difference in the amount of cuckling exceeds a predetermined value, it is determined that the reverse side paper passing performance has deteriorated and a warning is given to the user.

  According to the above invention, it is possible to prevent a conveyance failure in advance by warning the user when the difference in the amount of cuckles between the white background portion and the solid portion exceeds a predetermined value.

  6. The image forming method according to claim 5, wherein in double-sided printing, when the gap between the measurement points is 469 mm, if the difference in the amount of cockle exceeds 300 μm, it is determined that the reverse side paper passing performance has deteriorated, and a warning is given to the user. It is characterized by doing.

  According to the above invention, it is possible to prevent a conveyance failure in advance by warning the user that the difference in the amount of cuckling between the white background portion and the solid portion exceeds a predetermined value in the chrysanthemum half-cut plate.

  The image forming method according to claim 6 is characterized in that, when it is determined that the reverse side paper passing performance is deteriorated, the drying temperature at the time of drying the recording medium after the image formation is lowered.

  According to the above-described invention, when the back surface paper passing property is deteriorated, the difference in the amount of cockle is reduced by lowering the drying temperature, and the paper passing property can be improved.

  The image forming method according to claim 7 is characterized in that when it is determined that the back side paper passing performance has deteriorated, the amount of liquid droplets to be discharged is reduced.

  According to the above-described invention, when the back surface paper passing performance is deteriorated, the amount of liquid droplets is reduced, thereby reducing the difference in the amount of cockle and improving the paper passing performance.

  The image forming method according to claim 8 is characterized in that, when it is determined that the reverse side paper passing performance is deteriorated, the user is warned that seasoning is necessary after printing.

  According to the above-described invention, when the reverse side paper passing property is deteriorated, the difference in the amount of cockle is reduced by urging the user to perform seasoning after printing, and the paper passing property at the time of reverse side printing can be improved.

  In the image forming method according to claim 9, when it is determined that the paper passing property of the back surface is deteriorated, if the average liquid amount of liquid droplets ejected from the solid portion is 4.3 pl or more, the image forming method after the image formation is completed. The drying temperature at the time of drying the recording medium is limited to a range of 60 ° C to 70 ° C.

  According to the above invention, when the back side paper-passability is deteriorated, if the average discharge liquid amount of the solid portion is 4.3 pl or more, the drying temperature at the time of drying the recording medium after image formation is 60 ° C. to 70 ° C. By limiting to the range, the difference in the amount of cockle can be reduced and the paper passing property can be improved.

  An image recording apparatus according to a tenth aspect records an image by the image forming method according to any one of the fourth to ninth aspects.

  According to the above-described invention, the difference in the amount of cuckling between the solid portion with the largest amount of liquid ejected on the recording medium and the white background portion with the smallest amount is calculated, and the image of predicting the paper floating probability or paper passing performance from this value It can be set as a recording device.

  Since the present invention has the above-described configuration, a recording medium expansion / contraction amount measuring method, an image recording method, and an image recording apparatus for estimating the paper passing property of an output image from a difference in the amount of cuckling of a test image composed of a white background portion and a solid portion. be able to.

It is a conceptual diagram which shows the test image for cockle amount measurement which concerns on embodiment of this invention. It is a figure which shows the test image for various cockle amount measurement which concerns on embodiment of this invention, and each sheet | seat floating probability. It is a side view showing a deformation of a recording medium on which a test image according to an embodiment of the present invention is printed and a method for calculating the amount of cockle. It is a graph which shows the relationship between the amount of cockles and paper passing property for every droplet discharge amount. It is a table | surface which shows the experimental condition at the time of measuring the relationship between the amount of cockle and the paper passing property. It is a table | surface which shows the relationship between the amount of cockles and paper passing property for every droplet discharge amount. It is a graph which shows the relationship between the drying cylinder temperature and paper passing property according to image. It is a graph which shows the relationship between drying cylinder temperature and the amount of residual water of a paper. It is a graph which shows the relationship between the drying cylinder temperature according to solid / white background, and the expansion-contraction amount of a paper. It is a graph which shows the relationship between the drying drum temperature and the amount of cockles according to solid / white background. It is a conceptual diagram which shows the example of the image recording device based on embodiment of this invention.

  Hereinafter, an exemplary embodiment according to the present invention will be described with reference to the drawings.

  In the image recording method according to the present embodiment, by measuring and comparing the amount of white background and solid cuckling in a test image (paper expansion / contraction amount measurement image), the ease of passing the back side of the paper type, and a typical registered in advance It is possible to estimate in advance the jam rate of the output image by comparing the jam rate data of the correct test image with the content of the image data to be output.

  That is, the present invention clarifies the correspondence relationship between the amount of expansion / contraction of the output image and the ease of backside paper feeding, which can be predicted from the jam rate data of the test image. In particular, a test image (paper expansion / contraction measurement image) that is optimal for confirming paper passing properties is defined, and an expansion / contraction amount measurement method using the test image is presented.

<Test image>

  For example, an image as shown in FIG. 1 is used as the test image 10 (= measurement image) output on the recording medium 122 to measure the amount of cockle.

  In the example of FIG. 1, approximately 1/3 each of both ends (both sides) in the transport width direction is a solid portion 12, and approximately 1/3 of the central portion sandwiched between the solid portions 12 is a white background portion 14.

  In the solid portion 12 and the white background portion 14, a plurality of (two or more) measurement points 20 (about φ0.5 mm) are provided at predetermined intervals on the upstream side and the downstream side in the transport direction. The distance d between the measurement points 20 in the transport direction is determined in advance, and is arranged so that it is possible to measure how much the recording medium 122 has expanded and contracted after image formation.

  In addition to the typical test image 10 shown in FIG. 1, various test images such as # 1 to # 14 shown in FIG. 2 may be used. As a result of examination based on the knowledge obtained by the inventors' experiment, it was found that the test image with the highest paper floating jam probability was # 14, that is, the test image 10 shown in FIG.

  In addition, as shown in FIG. 2, a correspondence table of image and paper floating jam probability is stored in advance as a database, and the jam rate of an image to be printed is estimated from the jam rate of an image similar to the image to be printed. It can also be used.

  For example, if the jam rate of image # 14 in FIG. 2 printed at a certain density is 10%, the jam rate of image # 2 in FIG. 2 printed at the same density is 10 × 0/45 = 0%, and image # The jam rate of 13 images can be estimated as 10 × 5 / 45≈1%. From the estimated jam rate, the user may be able to examine imposition (image layout) change and print density change as necessary.

  That is, when an output image having a layout close to # 14 is required, a high density portion such as the solid portion 12 is not separated and arranged at both ends in the transport width direction, but is arranged at one end like the image of # 10. By arranging them together, the expected jam rate can be greatly reduced.

  Alternatively, when it is difficult to change the imposition, measures may be taken to reduce the jam density by reducing the print density by suppressing the expansion and contraction of the recording medium 122 instead of changing the layout.

  Further, the correspondence table between the image and the paper floating jam probability is not limited to the image described as an example in FIG. 2, but may be added / updated as needed.

<Measurement of expansion / contraction amount (cuckle amount)>

  FIG. 3 is a cross-sectional view of the distance between the two measurement points 20 shown in FIG. 1 as viewed from the side (conveyance width direction).

  In FIG. 1, the distance of the measurement point 20 on the recording medium 122 in the transport direction, indicated by dW or dB, is represented by L3d as a creepage distance as it is along the surface of the recording medium 122. Further, a length obtained by projecting the distance of the measurement point 20 onto the conveyance surface of the recording medium 122 is represented by L2d.

  3 shows the surface shape of the recording medium 122 that is deformed (cuckled) after printing by the wavy line indicated by the alternate long and short dash line.

ΔL (3d−2d) = L3d−L2d

It is. At this time, if the recording medium 122 is uniformly deformed (cuckled) on the entire surface.

 Since L3d = L2d and ΔL (3d−2d) = 0, there is at least no catching in the transport direction.

  In addition, the sheet floating generation mode accompanying the adsorption of the recording medium 122 has many vertical lines in the white background portion at the rear end of the recording medium 122, and the image portion (for example, the solid portion 12 of the test image 10) and the white background portion (for example, The expansion / contraction amount difference with the white background portion 14) is considered to be the cause of the vertical fly.

  Therefore, when ΔL (3d−2d) of the image portion (solid portion 12) and the white background portion 14 is ΔL (solid) and ΔL (white background), ΔL = ΔL (solid) −ΔL (white background) It can be said that this is the amount of cockle that contributes to the occurrence of paper floating.

  Further, FIG. 4 shows the influence of the amount of cockle (the amount of expansion / contraction) on the back side paper passing.

  In FIG. 4, the vertical axis represents the average number of sheets passed (maximum 200), the horizontal axis represents ΔL (corresponding to the short side of the chrysanthemum half), and the results plotted for each average liquid volume (4.3 to 2.4 pL) of the droplets. If the amount of liquid is small, ΔL is small and the influence on the average number of sheets that can be passed is small. However, as the amount of liquid increases, ΔL increases and the average number of sheets that can be passed decreases.

  Regarding the method for measuring the amount of expansion and contraction as described above, for example, the position of the measurement dot (measurement point 20) is read by an inline sensor having a general configuration as disclosed in Japanese Patent Application Laid-Open No. 2010-76322, and in addition, in the vicinity of the inline sensor. A method is conceivable in which a laser displacement meter is provided and the surface irregularities of the recording medium 122 are measured with the laser displacement meter.

  When measuring the amount of expansion and contraction in an image forming apparatus that grips and conveys the recording medium 122 on the drum surface, the nip is fixed by the fixing drum 184 so that the recording medium 122 does not float off the drum surface. It is desirable to measure immediately after.

  Further, since ΔL is affected by the basis weight, surface finish, etc. of the recording medium 122 used, the recording medium 122 used for output of the test image 10 needs to have the basis weight, surface finish, etc. used for the actual JOB. There is.

  Alternatively, a change in ΔL (back side paper passing property) due to basis weight, surface finish, etc. of the recording medium 122 (paper) may be stored in a database in advance and extrapolated as a difference in the amount of cuckling of the recording medium 122 (paper) used for output. . You may make it use the influence which the change of the water absorption amount by the basic weight (thickness) and the change of the water absorption amount by the difference in surface finish gives to ΔL as a coefficient when calculating ΔL.

<Results of transport experiment>

  FIG. 6 shows the result of actual processing of 200 sheets / 1 job under the experimental conditions shown in FIG.

  In other words, an image having a resolution of 1200 dpi × 1200 dpi was recorded on 200 sheets of A2 coated paper having a basis weight of 104 g, and when a float of 0.7 mm or more occurred, a conveyance test was performed under the condition for determining paper lift. The following results were obtained.

  As shown in FIG. 6, it can be seen that ΔL (μm) and paper passing properties (paper passing properties: ◯ to ×) have a correlation. ΔL is a value obtained by converting the amount of expansion / contraction between the measurement points 20 (corresponding to the aforementioned ΔL (3d-2d)) into the amount of expansion / contraction in the length (469 mm) in the short side direction of the paper size chrysanthemum half (636 × 469 mm). It is described. For example, when the distance between the measurement points 20 is 300 mm and the expansion / contraction amount is 100 μm, this is converted to 469 mm and described as 469 × 100/300 = 156.3 μm.

  For example, in double-sided printing, when the distance between measurement points 20 is 469 mm, the average number of sheets that can be passed is about 100/200 when the expansion / contraction amount (ΔL (3d-2d)) exceeds 300 μm as shown in FIG. Accordingly, it may be configured that when the expansion / contraction amount is 300 μm or more, it is determined that the back side paper passing property is deteriorated, and the user is warned to take countermeasures.

  Further, as shown in FIG. 6, when the average liquid volume of the droplets used for image formation is 4.3 to 2.4 pL, the expansion and contraction ΔL of the recording medium 122 is small and the liquid volume is equal if the average liquid volume is small. If so, the lower the drying drum temperature (weaker drying), the smaller the expansion / contraction ΔL of the recording medium 122 is.

  The average droplet amount here is calculated as follows when, for example, large droplets: 9 pl, medium droplets: 6 pl, and small droplets: 2.4 pl. When all the solid portions are ejected as small droplets, it is calculated that the ejection is performed at 2.4 × 1 = 2.4 pl, and this corresponds to # 12 to 16 having the smallest average droplet amount in FIG.

  Next, when discharging at a ratio of 30% medium droplets and 70% small droplets: It is calculated that the droplets were discharged at an average droplet amount of 6 × 0.3 + 2.4 × 0.7 = 3.48 pl. This corresponds to # 7 to 12 in FIG.

  Furthermore, when discharging at a ratio of 30% large droplets and 65% small droplets: It is calculated that the droplets were discharged at an average droplet amount of 9 × 0.3 + 2.4 × 0.65 = 4.26 pl. This corresponds to # 13 to 18 in FIG.

  At this time, when an image having an average appropriate amount of 4.3 pl with the most severe conditions is processed, if the drying cylinder temperature can be maintained between 60-70 ° C., both the film quality and the paper passing property are practically problematic as shown in FIG. You can keep no level.

<Influence of drying drum temperature>

  FIG. 7 shows the relationship between the drying cylinder temperature for drying the front (front) surface during double-sided printing, the reverse side paper passing property, and fixing wrinkles.

  As shown in FIG. 7, the three-color side solid image (eg, image # 14 in FIG. 2) that originally has poor paper-passability has a large variation due to machine conditions. However, along with the normal image, the drying cylinder temperature during surface printing is 70 It can be seen that when the temperature exceeds ℃, the reverse side paper passing performance deteriorates.

  The reason for this is thought to be that when the drying cylinder temperature at the time of surface printing becomes high, the water content difference between the white background portion and the solid portion inside the recording medium 122 (paper) increases, and the amount of cockle increases. Yes.

  8, 9, and 10 show the relationship between the drying drum temperature and the amount of residual water in the paper, the drying drum temperature and the amount of paper expansion / contraction, and the drying drum temperature and the amount of cockle.

  As shown in FIG. 8, the moisture content of the solid portion is less affected by the drying temperature if it has been sufficiently dried over time (= after seasoning, indicated by ■), but the moisture content of the white background portion is less time consuming. Even after drying sufficiently (indicated by ◎), the water content does not return well. This is because the dry white background without droplets being discharged is further strongly dried by the drying drum 176, so that the cellulose structure inside the recording medium 122 (paper) changes and moisture remains after a sufficient time has passed. Since the amount cannot be fully returned and the deformed state of the sheet is kept, it is estimated that the cockle has deteriorated as a result.

  Further, FIG. 9 shows that when the drying temperature (drying drum temperature) in the drying drum 176 is high, the shrinkage amount of the white background portion is large, and the shrinkage of the solid portion is less dependent on the temperature change. It is considered that cockle is caused by the difference in the amount of expansion / contraction (shrinkage amount) between the solid portion and the white background portion, and as shown in FIG.

  In such a case, for example, if the average discharge liquid amount of the solid portion is 4.3 pl or more, the drying temperature at the time of drying the recording medium after image formation is limited to a range of 60 ° C. to 70 ° C. By suppressing the difference in the amount of expansion / contraction (contraction amount) in the white background portion and reducing the amount of cockle, it is possible to maintain the back side paper passing property.

<Image recording device>

  Below, with reference to FIG. 11, the example of a structure of the inkjet type image recording apparatus for enforcing the image recording method of this invention is shown and demonstrated.

  The inkjet recording apparatus 1 forms a desired color image by ejecting a plurality of colors of ink from inkjet heads 172M, 172K, 172C, and 172Y onto a recording medium 122 held on the impression cylinder (drawing drum 170) of the drawing unit 114. An impression cylinder direct drawing type ink jet recording apparatus, which applies a treatment liquid onto the recording medium 122 before ink ejection and causes the treatment liquid and ink to react to form an image on the recording medium 122 (aggregation). ) Method is an on-demand type image forming apparatus.

  The ink jet recording apparatus 1 mainly includes a paper feeding unit 110, a processing liquid application unit 112, a drawing unit 114, a drying unit 116, a fixing unit 118, and a paper discharge unit 120.

  The paper supply unit 110 is a mechanism that supplies the recording medium 122 to the treatment liquid application unit 112, and the recording medium 122 that is a sheet is stacked on the paper supply unit 110. The paper feeding unit 110 is provided with a paper feeding tray 150, and the recording medium 122 is fed from the paper feeding tray 150 to the processing liquid application unit 112 one by one. In the inkjet recording apparatus 1, a plurality of types of recording media 122 having different paper types and sizes (medium sizes) can be used as the recording medium 122. In the present embodiment, a case where a sheet (cut sheet) is used as the recording medium 122 will be described.

  The processing liquid application unit 112 is a mechanism that applies the processing liquid to the recording surface of the recording medium 122. The treatment liquid contains a color material aggregating agent that agglomerates the color material in the ink applied by the drawing unit 114. When the treatment liquid and the ink come into contact with each other, the ink is separated from the color material and the solvent. Promoted.

  As shown in FIG. 11, the treatment liquid application unit 112 includes a paper feed cylinder 152, a treatment liquid drum 154, and a treatment liquid application device 156. The treatment liquid drum 154 is a drum that holds the recording medium 122 and rotates and conveys it. The processing liquid drum 154 includes a claw-shaped holding means (gripper) on the outer peripheral surface thereof, and the recording medium 122 is sandwiched between the claw of the holding means and the peripheral surface of the processing liquid drum 154 so that the tip of the recording medium 122 is positioned. It can be held.

  The treatment liquid drum 154 may be provided with a suction hole on the outer peripheral surface thereof and connected to a suction unit that performs suction from the suction hole. As a result, the recording medium 122 can be held in close contact with the peripheral surface of the treatment liquid drum 154.

  A treatment liquid coating device 156 is provided outside the treatment liquid drum 154 so as to face the peripheral surface thereof. The processing liquid coating device 156 is in pressure contact with the processing liquid container in which the processing liquid is stored, the anilox roller partially immersed in the processing liquid in the processing liquid container, and the recording medium 122 on the anilox roller and the processing liquid drum 154. And a rubber roller that transfers the measured processing liquid to the recording medium 122. According to the processing liquid coating apparatus 156, the processing liquid can be applied to the recording medium 122 while being measured.

  The recording medium 122 to which the processing liquid is applied by the processing liquid applying unit 112 is transferred from the processing liquid drum 154 to the drawing drum 170 of the drawing unit 114 via the intermediate transport unit 124. The drawing unit 114 includes a drawing drum 170 and inkjet heads 172M, 172K, 172C, and 172Y. Similar to the treatment liquid drum 154, the drawing drum 170 includes a claw-shaped holding means (gripper) on its outer peripheral surface. The recording medium 122 fixed to the drawing drum 170 is conveyed with the recording surface facing outward, and ink is applied to the recording surface from the inkjet heads 172M, 172K, 172C, 172Y.

  The inkjet heads 172M, 172K, 172C, and 172Y are full-line inkjet recording heads (inkjet heads) each having a length corresponding to the maximum width of the image forming area on the recording medium 122. Is formed with a nozzle row in which a plurality of nozzles for ink ejection are arranged over the entire width of the image forming area. Each inkjet head 172M, 172K, 172C, 172Y is installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 122 (the rotation direction of the drawing drum 170).

  The droplets of the corresponding color ink are ejected from the respective ink jet heads 172M, 172K, 172C, 172Y toward the recording surface of the recording medium 122 held in close contact with the drawing drum 170, whereby the processing liquid application unit 112 The ink comes into contact with the treatment liquid previously applied to the recording surface, and the pigment and resin particles dispersed in the ink are aggregated to form aggregates. As a result, pigment flow or the like on the recording medium 122 is prevented, and an image is formed on the recording surface of the recording medium 122.

  The recording medium 122 on which an image is formed by the drawing unit 114 is transferred from the drawing drum 170 to the drying drum 176 of the drying unit 116 via the intermediate conveyance unit 126. The drying unit 116 is a mechanism for drying moisture contained in the solvent separated by the aggregating action, and as shown in FIG. 11, the drying drum 176, the IR heaters 178, 182 and the temperature arranged between the IR heaters. A wind ejection nozzle 180. Similar to the treatment liquid drum 154, the drying drum 176 includes a claw-shaped holding unit (gripper) on its outer peripheral surface, and the holding unit can hold the leading end of the recording medium 122. Various drying conditions are realized by appropriately adjusting the temperature and air volume of the hot air blown from the hot air jet nozzle 180 toward the recording medium 122 and the temperature of each IR heater.

  The surface temperature of the drying drum 176 is set to 50 ° C. or higher. Drying is accelerated by heating from the back surface of the recording medium 122, and image destruction during fixing can be prevented. The upper limit of the surface temperature of the drying drum 176 is not particularly limited, but from the viewpoint of safety of maintenance work such as cleaning ink adhering to the surface of the drying drum 176 (preventing burns due to high temperatures). It is preferably set to 75 ° C. or lower (more preferably 60 ° C. or lower).

  Further, as described above, it has been found that the lower the drying drum temperature (the surface temperature of the drying drum 176) (the lower the drying temperature), the less the expansion and contraction (ΔL) of the recording medium 122, so that the film quality strength is not impaired. In addition, the lower the surface temperature of the drying drum 176, the less the influence of cockle.

  The recording drum 122 is held on the outer peripheral surface of the drying drum 176 so that the recording surface of the recording medium 122 faces outward (that is, in a state where the recording surface of the recording medium 122 is convex), and is dried while being rotated and conveyed. By doing so, it is possible to prevent the recording medium 122 from being wrinkled or lifted, and to prevent drying unevenness caused by these.

  The recording medium 122 that has been dried by the drying unit 116 is transferred from the drying drum 176 to the fixing drum 184 of the fixing unit 118 via the intermediate conveyance unit 128. The fixing unit 118 includes a fixing drum 184, a first fixing roller 186, a second fixing roller 188, an in-line sensor 190, a laser displacement meter 191, and the like.

  Like the processing liquid drum 154, the fixing drum 184 includes a claw-shaped holding unit (gripper) on the outer peripheral surface thereof, and the holding unit can hold the leading end of the recording medium 122. By the rotation of the fixing drum 184, the recording medium 122 is conveyed so that the recording surface faces outward. The fixing process by the first fixing roller 186 and the second fixing roller 188 and the inline sensor 190 are performed on the recording surface. Inspection is performed.

  The first fixing roller 186 and the second fixing roller 188 are roller members for welding resin particles (particularly self-dispersing polymer particles) in the ink by heating and pressurizing the ink to form a film of the ink. The recording medium 122 is configured to be heated and pressurized. Specifically, the first fixing roller 186 and the second fixing roller 188 are arranged so as to be in pressure contact with the fixing drum 184 and constitute a nip roller with the fixing drum 184. Yes. As a result, the recording medium 122 is sandwiched between the first fixing roller 186 and the second fixing roller 188 and the fixing drum 184 and is nipped at a predetermined nip pressure (for example, 0.15 MPa) to perform the fixing process. It is.

  Further, the first fixing roller 186 and the second fixing roller 188 are configured by a heating roller in which a halogen lamp is incorporated in a metal pipe such as aluminum having good thermal conductivity, and have a predetermined temperature (for example, 60 to 80 ° C.). Controlled. By heating the recording medium 122 with these heating rollers, thermal energy equal to or higher than the Tg (glass transition temperature) of the resin particles contained in the ink is applied, and the resin particles are melted so that the unevenness of the recording medium 122 is formed. While pressing and fixing are performed, unevenness on the surface of the image is leveled and gloss is obtained.

  The in-line sensor 190 is a measuring unit for measuring a check pattern, a moisture content, a surface temperature, a glossiness, and the like for an image fixed on the recording medium 122, and a CCD line sensor or the like is applied.

  Here, the amount of cockle can be measured when the test image 10 is output. That is, as described above, the position of the measurement dot (measurement point 20) is read by the inline sensor 190, and in addition, a laser displacement meter 191 is provided near the inline sensor at a position facing the recording medium 122, and the recording medium is recorded by the laser displacement meter 191. A method for measuring the unevenness of the surface 122 is conceivable.

  When measuring the amount of expansion / contraction of the recording medium 122, it is desirable to measure immediately after nipping the fixing drum 184 so that the recording medium 122 does not float from the surface of the fixing drum 184. However, in the example shown in FIG. 11, since the recording medium 122 is held along the surface shape (cylindrical shape) of the fixing drum 184, the distance between the measurement points 20 measured by the in-line sensor 190 is not projected onto a plane. Alternatively, the correction may be made in consideration of the point on the cylindrical surface.

  Further, a temperature / humidity sensor (not shown) may be provided in the fixing unit 118 to measure the temperature / humidity inside the apparatus. The measured temperature and humidity may be added as a factor affecting the drying of the recording medium 112 to a parameter when calculating the difference in the amount of cockle. In other words, the effect of the temperature and humidity in the apparatus on ΔL may be tabulated in advance and used as a correction coefficient for ΔL.

  The measured amount of cockle is sent as data to a control unit (not shown) together with various parameters such as paper type, drying conditions, and type of test image 10. Further, when the amount of the cockle exceeds a predetermined value, it may be determined that the paper passing performance has deteriorated and a warning is given to the user. Alternatively, the ink jet heads 172M, 172K, 172C, 172Y may be used in the drawing unit 114. It may be configured to reduce the amount of ink ejected more and suppress the amount of cockle. Alternatively, the temperature of the first fixing roller 186 and the second fixing roller 188 may be lowered to lower the temperature, thereby reducing the amount of cockle.

  Alternatively, instead of measuring the amount of cockle in the inkjet recording apparatus 1, the discharged test image 10 may be measured and determined outside the apparatus (offline). In this case, it is desirable to consider the influence of temperature and humidity in the room where the apparatus is installed.

  In the fixing unit 118, the resin particles in the thin image layer formed by the drying unit 116 are heated and pressurized by the fixing roller 188 and melted, and can be fixed on the recording medium 122. Further, the surface temperature of the fixing drum 184 is set to 50 ° C. or higher, and the drying is promoted by heating the recording medium 122 held on the outer peripheral surface of the fixing drum 184 from the back surface, thereby preventing image destruction during fixing. The image intensity can be increased by the effect of increasing the image temperature.

  As shown in FIG. 11, a paper discharge unit 120 is provided downstream of the fixing unit 118 in the recording medium conveyance direction. The paper discharge unit 120 includes a discharge tray 192. Between the discharge tray 192 and the fixing drum 184 of the fixing unit 118, a transfer drum 194, a conveying belt 196, and a stretching roller 198 are in contact with each other. Is provided. The recording medium 122 is sent to the transport belt 196 by the transfer drum 194 and discharged to the discharge tray 192.

  Further, the discharge tray 192 is provided with a cold air ejection nozzle 199, and the recording medium 122 can be cooled by blowing cold air from the cold air ejection nozzle 199.

  Although not shown in FIG. 11, in addition to the above-described configuration, the inkjet recording apparatus 1 performs processing on the ink storage tank that supplies ink to the inkjet heads 172M, 172K, 172C, and 172Y, and the treatment liquid application unit 112. In addition to a means for supplying liquid, the head maintenance unit that cleans each ink jet head 172M, 172K, 172C, 172Y (wiping, purging, nozzle suction, etc. of the nozzle surface) and the position of the recording medium 122 on the medium transport path A position detection sensor for detecting, a temperature sensor for detecting the temperature of each part of the apparatus, and the like are provided.

  When forming images on both sides, in the inkjet recording apparatus 1 of FIG. 11, after forming an image on one side (front side) of the recording medium, seasoning is performed for a predetermined time by a seasoning device (not shown). Then, the seasoned recording medium bundle is returned to the paper feeding unit 110, and further image formation is performed on the back surface. Thereby, good double-sided printing can be realized in a short time.

  The ink jet recording apparatus 1 illustrated in FIG. 11 may include a plurality of seasoning devices used for the discharge tray 192 and each seasoning device may be moved between the paper discharge unit 120 and the paper supply unit 110.

  According to the experiments by the inventors, it is known that there is a clear difference in the amount of cuckling of the recording medium immediately after printing and after seasoning, and the knowledge that the amount of cuckling decreases after seasoning has been obtained. For this reason, it is possible to suppress the influence of cockling on the paper passing property by positively performing seasoning.

<Others>

  As mentioned above, although the Example of this invention was described, it cannot be overemphasized that this invention is not limited to said Example at all, and can implement in a various aspect in the range which does not deviate from the summary of this invention. In addition, the above-described plurality of embodiments can be implemented in combination as appropriate.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 10 Test image 12 Solid part 14 White background part 20 Measurement point 122 Recording medium

Claims (10)

Adsorb the recording medium and transport it in the transport direction.
A droplet is ejected onto the recording medium, a test image of a white background portion and a solid portion is formed on the recording medium over the length in the transport direction, and the distance between the white background portion and the solid portion along the transport direction From the difference between the creepage distance measured along the recording medium surface and the distance measured between the measurement points provided on the recording medium surface, and the distance projected onto the plane extending along the conveyance direction, the white background of the test image A method for measuring the amount of expansion / contraction of a recording medium, comprising calculating a difference in the amount of cockle in the transport direction between the recording section and the solid section. The method according to claim 1, wherein the creeping distance is measured with a laser displacement meter, and the distance projected onto the plane is measured with an in-line sensor. The method for measuring the amount of expansion / contraction of a recording medium according to claim 1, wherein the test image has a solid portion at both ends in the conveyance width direction and a white background portion sandwiched between the solid portions. Using the method for measuring the amount of expansion and contraction of a recording medium according to any one of claims 1 to 3, in double-sided printing, if the difference in the amount of cockle exceeds a predetermined value, it is determined that the reverse side paper passing performance has deteriorated. An image forming method characterized by warning a user. When the recording medium expansion / contraction amount measuring method according to any one of claims 1 to 3 is used and the distance between the measurement points is set to 469 mm in double-sided printing, the back surface is larger than 300 μm. An image forming method characterized in that it is determined that the paper passing property has deteriorated and a warning is given to a user. 6. The image forming method according to claim 4 or 5, wherein when it is determined that the reverse side paper passing property is lowered, the drying temperature at the time of drying the recording medium after image formation is lowered. The image forming method according to any one of claims 4 to 6, wherein when it is determined that the reverse side paper passing performance is deteriorated, the liquid amount of the liquid droplets to be discharged is reduced. The image formation according to any one of claims 4 to 7, wherein when it is determined that the reverse side paper passing performance is deteriorated, the user is warned that seasoning is necessary after printing. Method. When it is determined that the reverse side paper passing performance has been reduced, if the average liquid volume of the liquid droplets ejected from the solid portion is 4.3 pl or more, the drying temperature at the time of drying the recording medium after image formation is 60 ° C. to The image forming method according to any one of claims 4 to 8, wherein the image forming method is limited to a range of 70 ° C. An image recording apparatus for recording an image by the image forming method according to claim 4.

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