Method for detecting abnormalities in application state of applied liquid and liquid ejection apparatus

Abstract

To accurately detect abnormalities in the application state of an applied liquid.SOLUTION: A method for detecting abnormalities in an application state of UC liquid, executes: a first detection method of detecting, by an optical sensor 28, a sheet S to which the UC liquid has been applied, through ejection, upstream in a sheet conveying direction A from a position formed with an image on the sheet, and after the application of the UC liquid, irradiated with light by a black light 27, and of further detecting, on the basis of the detection result of the optical sensor 28, abnormalities in the application state of the UC liquid applied to the sheet S; a second detection method of detecting, by a density sensor 29, the sheet S to which the UC liquid has been applied and which has been ejected with the liquid to form an image across a width of the sheet S, and of further detecting, on the basis of the detection result of the density sensor 29, abnormalities in the application state of the UC liquid applied to the sheet S; and a third detection method of capturing, by a camera (30), an image of the sheet S to which the UC liquid has been applied and which has been ejected with liquid to form a line image E, and of further detecting, on the basis of the captured image, abnormalities in the application state of the UC liquid applied to the sheet.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for detecting an abnormality in the application state of a pre-application liquid and a liquid ejection device. [Background technology]

[0002] Among liquid ejection devices that eject liquid to form an image on the surface of a recording medium, there are those that apply a pre-application liquid to the recording medium before forming the image in order to suppress ink coalescence and improve image quality.

[0003] In such a liquid ejection device, if the pre-application liquid is not applied properly, it will have a negative effect on the quality of the image that is formed, so it is important to detect any abnormalities in the application state of the pre-application liquid.

[0004] As a method for detecting abnormalities in applied liquid, for example, Patent Document 1 (JP 2007-230109 A) describes applying ink to the surface of a drum-shaped blanket, then bringing the blanket into contact with a glass substrate to transfer the ink to the glass substrate. An image of the blanket surface before transfer is captured by a line camera, and the presence of abnormalities such as uneven application is visually detected. Summary of the Invention [Problem to be solved by the invention]

[0005] When the pre-coating liquid is transparent, it is difficult to check for coating unevenness by imaging as in Patent Document 1, and there is a problem in that erroneous detection occurs.

[0006] An object of the present invention is to accurately detect abnormalities in the application state of the pre-application liquid. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present invention provides a method for detecting abnormalities in the application state of a pre-application liquid, which comprises: a first detection method in which a pre-application liquid is applied to the recording medium upstream in the recording medium transport direction from a position where an image is formed on the recording medium by ejecting liquid, and the recording medium to which the pre-application liquid has been applied and which has been irradiated with light by an irradiation element is detected by an optical sensor, and an abnormality in the application state of the pre-application liquid applied to the recording medium is detected based on the detection result of the optical sensor; a second detection method in which the recording medium to which the pre-application liquid has been applied and which has been ejected with liquid to form an image across the width direction is detected by a density sensor, and an abnormality in the application state of the pre-application liquid applied to the recording medium is detected based on the detection result of the density sensor; and a third detection method in which the recording medium to which the pre-application liquid has been applied and which has been ejected with liquid to form a line image is imaged by an imaging element, and an abnormality in the application state of the pre-application liquid applied to the recording medium is detected based on the image imaged. [Effects of the Invention]

[0008] In the present invention, abnormalities in the application state of the pre-application liquid can be detected with high accuracy. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram illustrating the configuration of an image forming apparatus. [Figure 2] FIG. 2 is a functional block diagram of the image forming apparatus. [Figure 3] FIG. 2 is a schematic bottom view showing an image forming unit. [Figure 4] FIG. 2 is a schematic diagram showing the coating mechanism of the UC liquid coating unit. [Figure 5] FIG. 2 is a schematic diagram showing the configuration of an image forming apparatus used in a first detection method. [Figure 6] FIG. 10 is a schematic diagram showing the configuration of an image forming apparatus used in a second detection method. [Figure 7] FIG. 10 is a schematic diagram showing the configuration of an image forming apparatus used in a third detection method. [Figure 8] FIG. 2 is a schematic diagram showing a line image formed on a sheet. [Figure 9]FIG. 10 is a schematic diagram showing a modified example of the configuration of an image forming apparatus used in the first detection method. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be appropriately simplified or omitted.

[0011] FIG. 1 is a schematic diagram showing an image forming apparatus 100 according to an embodiment. FIG. 2 is a block diagram showing an image forming apparatus according to an embodiment. The image forming apparatus 100 shown in FIGS. 1 and 2 is an on-demand line-scan inkjet recording apparatus. The image forming apparatus 100 is an example of a liquid ejection apparatus. The image forming apparatus 100 includes a sheet supply unit 1, a first UC liquid application unit 20 and a second UC liquid application unit 50 as pre-application liquid application units, a first image forming unit 3 and a second image forming unit 4 as liquid ejection units, a front / back reversing unit 5, a first drying unit 6, a second drying unit 7, and a sheet recovery unit 2. The image forming apparatus 100 forms an image by ejecting ink onto a sheet S, which is a recording medium. The ink is an example of a liquid. As shown in FIG. 2, the image forming apparatus 100 includes a control unit 9.

[0012] The sheet supply unit 1 has a supply roller 11 around which a long sheet S is wound in a roll shape. The supply roller 11 is rotatable in the direction of the arrow shown in FIG. 1. The rotation of the supply roller 11 causes the sheet S to be fed out. The sheet S is an example of a recording medium. The direction in which the sheet S is fed out is referred to as the sheet transport direction (recording medium transport direction), and the upstream side and downstream side of the sheet transport direction are simply referred to as the upstream side and downstream side. The first UC liquid application unit 20 is provided upstream of the first image forming unit 3 that forms an image on the sheet S, and the second UC liquid application unit 50 is provided upstream of the second image forming unit 4 that forms an image on the sheet S.

[0013] The recording medium may be a paper medium or other medium. The recording medium may be a sheet material, and the sheet material may be cut sheet material. The sheet material may be a large sheet material, such as wallpaper.

[0014] The configuration of the first UC liquid applying unit 20 will be described later. The first UC liquid applying unit 20 applies a UC (Under Coat) liquid as a pre-applying liquid to the front surface of the sheet S.

[0015] A plurality of conveying rollers are provided from the upstream side to the downstream side in the conveying direction of the sheet S to bridge the sheet S and convey the sheet S. The sheet S is conveyed by the rotation of the plurality of conveying rollers. The conveying rollers include a pipe and a shaft with a circular cross section.

[0016] The first image forming unit 3 has multiple head units 12K, 12C, 12M, and 12Y that eject liquid ink onto the sheet S. Each head unit 12K, 12C, 12M, and 12Y ejects ink onto the front side of the sheet S based on image data generated by the control unit 9, the image data being formed on the front side of the sheet S, to form an image on the sheet S. Here, the ink may be a liquid containing a colorant, a solvent, and crystalline resin particles dispersed in the solvent. The crystalline resin is a resin that undergoes a phase change when heated above a predetermined melting point, melting from a crystalline state into a liquid. Note that when there is no need to distinguish between the head units 12K, 12C, 12M, and 12Y, they may be referred to as head unit 12.

[0017] The first drying unit 6 has a heating drum 13 that heats the sheet S. The heating drum 13 promotes drying of the ink on the sheet S. The heating drum 13 includes a cylindrical member that rotates with the sheet S wrapped around its outer circumferential surface. A halogen heater, for example, is disposed inside the cylindrical member as a heat source. The heat source is not limited to a halogen heater, and other heaters may be used.

[0018] The heating drum 13 is disposed below the conveying path along which the sheet S is conveyed (on the back side of the sheet S). Therefore, when the sheet S is conveyed from the first image forming unit 3, the lower surface (back surface) of the sheet S comes into contact with the outer peripheral surface of the heating drum 13. The heating drum 13 conveys the sheet S while heating it. In this way, the heating drum 13 promotes the drying of the ink on the sheet S.

[0019] The control unit 9 also controls the rotation speed of the heating drum 13. The control unit 9 controls the rotation speed of the heating drum 13 to be approximately the same as the conveying speed of the conveying rollers of the sheet supply unit 1, the sheet recovery unit 2, etc. This allows the sheet S to be conveyed without being shifted relative to the outer circumferential surface of the heating drum 13 in the sheet conveying direction.

[0020] The front-back reversing unit 5 is composed of a known device that reverses the positions of the front and back sides of the sheet S. The sheet S transported from the first drying unit 6 is reversed when passing through the front-back reversing unit 5. The reversed sheet S is transported to the second image forming unit 4. When the sheet S is transported with the front side facing up, the front-back reversing unit 5 reverses the sheet so that the front side faces down (the back side faces up) and transports it.

[0021] The second UC liquid application unit 50 has basically the same configuration as the first UC liquid application unit 20. The second UC liquid application unit 50 applies the UC liquid to the back surface (inverted surface) of the sheet S.

[0022] The second image forming unit 4 basically has the same configuration as the first image forming unit 3. The second image forming unit 4 has a plurality of head units 14K, 14C, 14M, and 14Y that eject liquid ink onto the sheet S. Each of the head units 14K, 14C, 14M, and 14Y ejects ink onto the rear surface of the sheet S based on image data to be formed on the rear surface of the sheet S, out of the image data generated by the control unit 9, to form an image on the sheet S.

[0023] Like the first drying unit 6, the second drying unit 7 has a heating drum 15 that heats the sheet S. The heating drum 15 is arranged below the transport path along which the sheet S is transported (on the front side of the sheet S). Therefore, when the sheet S is transported from the second image forming unit 4, the lower surface (front side) of the sheet S comes into contact with the outer circumferential surface of the heating drum 15. The heating drum 15 heats the sheet S while transporting it. In this way, the heating drum 15 promotes the drying of the ink on the sheet S. Even if an image has been formed on the front side of the sheet S, the drying of the ink has already been promoted by the first drying unit 6, so the image will not be distorted by the heating drum 15 coming into contact with the image on the front side.

[0024] The sheet collection unit 2 has a collection roller 16 that winds up and collects the sheet S. The collection roller 16 is rotatable in the direction of the arrow shown in FIG. 1. When the collection roller 16 rotates, the sheet S is wound up in a roll and collected. The sheet collection unit 2 may also include a post-processing unit that performs post-processing such as cutting the sheet S to a predetermined length and aligning the cut sheets S.

[0025] 2 may include an information processing device such as a PC (Personal Computer). The control unit 9 generates image data to be formed on the front and back surfaces of the sheet S. The control unit 9 controls various operations of the sheet supply unit 1, conveyance unit 8, first UC liquid application unit 20, second UC liquid application unit 50, first image forming unit 3, second image forming unit 4, front / back reversing unit 5, first drying unit 6, second drying unit 7, and sheet collection unit 2. For example, the control unit 9 controls the rotation speeds of the supply roller 11, collection roller 16, and each conveyance roller, as well as the temperatures of the heat sources that heat the heating drums 13 and 15.

[0026] Next, the image forming unit will be described with reference to Figure 3. Figure 3 is a schematic bottom view showing the image forming unit. In Figure 3, the sheet S is shown by an imaginary line. The image forming unit includes a first image forming unit 3 and a second image forming unit 4. The first image forming unit 3 and the second image forming unit 4 basically have the same configuration. Below, the first image forming unit 3 will be described, and a description of the second image forming unit 4 will be omitted.

[0027] In the first image forming unit 3, four head units 12K, 12C, 12M, and 12Y that eject black (K), cyan (C), magenta (M), and yellow (Y) inks are arranged in this order from the upstream side in the sheet conveying direction A in which the sheet S is conveyed. Note that the arrangement order of the head units 12K, 12C, 12M, and 12Y of each color is not limited to this and may be other orders. Furthermore, the ink colors used are not limited to yellow, magenta, cyan, and black and may include other colors. Furthermore, the number of head units is not limited to four.

[0028] Each of the head units 12K, 12C, 12M, and 12Y has a plurality of liquid ejection heads 18. Hereinafter, the liquid ejection heads will be abbreviated as "ejection heads." The ejection heads 18 are an example of a liquid ejection section. In each of the head units 12K, 12C, 12M, and 12Y, the number of ejection heads 18 may be, for example, four. The number of ejection heads 18 is not limited to four. Each of the head units 12K, 12C, 12M, and 12Y is a line head type head unit that is longer than the width of the sheet S.

[0029] The ejection head 18 has a plurality of nozzles 19. The plurality of nozzles 19 eject ink onto the sheet S. The plurality of ejection heads 18 are arranged alternately across the entire width direction B of the image forming area on the sheet S. When the sheet S is transported to a position facing each of the head units 12K, 12C, 12M, and 12Y, the ejection heads 18 eject ink. As a result, an image is formed on the sheet S.

[0030] The ejection head 18 includes an ink flow path through which ink flows, a drive element for ejecting the ink, a pressure chamber for applying pressure to the ink, and a nozzle plate in which nozzles for ejecting the ink are formed. The bottom surface of the nozzle plate includes a nozzle surface in which a plurality of nozzles 19 are formed. The drive element is, for example, a piezoelectric element. When the drive element is driven, the pressure of the ink in the pressure chamber increases, and the ink is ejected from the nozzle 19. The ink droplets ejected from the nozzle 19 land on the sheet S.

[0031] Note that the "width direction of the sheet S (width direction of the recording medium)" referred to here may be a direction parallel to the conveying surface along which the sheet S is conveyed and perpendicular to the sheet conveying direction A. The width direction of the sheet S is the direction indicated by arrow B in FIG. 3. The "conveying surface" is the surface through which the conveyed sheet passes, and is, for example, a virtual surface connecting the contact portions of multiple conveying rollers that convey the sheet. The "conveying surface" may also include the sheet placement surface of a conveying belt that places and conveys the sheet S. The width direction B of the sheet S may also be referred to as the "sheet width direction."

[0032] Next, the configuration of the first UC liquid applying unit 20 will be described in more detail with reference to FIG.

[0033] 4, the first UC liquid application unit 20 includes an application mechanism 21. The application mechanism 21 includes a contact roller 22, a roller holding member 23, a cam 24, an application roller 25 as an application member, and a supply roller 26. The first UC liquid application unit 20 includes the application mechanisms 21 at two different positions in the sheet conveyance direction, and the application roller 25 contacts the same surface of the sheet S onto which the liquid is ejected (see FIG. 1).

[0034] Roller holding member 23 holds contact roller 22 and is rotatable about fulcrum 23a. Roller holding member 23 abuts against cam 24 at end 23b opposite fulcrum 23a. Cam 24 rotates about fulcrum 24a. As cam 24 rotates and changes the contact position with roller holding member 23, end 23b of roller holding member 23 moves up and down, and roller holding member 23 rotates about fulcrum 23a. As a result, contact roller 22 moves in the up and down direction in FIG. 4, which is the direction in which contact roller 22 moves toward and away from application roller 25.

[0035] The contact roller 22 and the application roller 25 come into contact with each other to form a nip therebetween. When the sheet S passes through this nip, the UC liquid on the surface of the application roller 25 is applied to the surface of the sheet S.

[0036] The supply roller 26 rotates and slides against the application roller 25. The supply roller 26 scoops up the UC liquid stored in a tank or the like on the side opposite to the side that contacts the application roller 25. The supply roller 26 then slides against the application roller 25, thereby supplying the UC liquid on its surface to the application roller 25.

[0037] The contact roller 22, the application roller 25, and the supply roller 26 are provided to extend in the width direction of the sheet S, which is a direction perpendicular to the paper surface of Figure 4. In other words, the application roller 25 can apply the UC liquid to the sheet S across the width direction.

[0038] The application roller 25 and the supply roller 26 are provided so as to be movable in the vertical direction in FIG. 4, which is the direction in which they approach and separate from the contact roller 22. As this movement mechanism, any appropriate configuration can be adopted, such as providing a contact and separation mechanism using a cam similar to that of the contact roller 22. When the UC liquid is not to be applied to the sheet S, the contact roller 22 and the application roller 25 are retracted from the sheet S. In other words, the contact roller 22 is moved downward in FIG. 4, and the application roller 25 and the supply roller 26 are moved upward in FIG. 4.

[0039] By applying the UC liquid to the sheet S before applying the ink, it is possible to prevent ink droplets that land in adjacent positions from coalescing together, thereby improving the quality of the image formed on the sheet S.

[0040] However, if the UC liquid is not applied properly to the sheet S due to a malfunction of the application roller 25 or the like, the inks may coalesce, which may adversely affect the quality of the image formed on the sheet S.

[0041] 5 to 9, an abnormality detection method of this embodiment for detecting whether the UC liquid is properly applied to the sheet S, that is, whether there is an abnormality in the application state of the UC liquid, will be described. In the following description, a case will be described in which the UC liquid applied by the first UC liquid application unit 20 is detected upstream of the first image forming unit 3. However, a similar configuration may be provided downstream of the second UC liquid application unit 50, and the UC liquid applied by the second UC liquid application unit 50 may be detected.

[0042] In the liquid ejection device of this embodiment, three abnormality detection methods are combined to detect whether the UC liquid is being applied properly. The direction of arrow A shown in Figure 5 etc. is the conveyance direction of the sheet S in the first image forming unit 3.

[0043] First, the first detection method of this embodiment and the configuration within the image forming apparatus for performing the first detection method will be described with reference to FIG.

[0044] 5, the liquid ejection device of this embodiment has a black light 27 as an irradiation member and an optical sensor 28, located upstream of the first image forming unit 3 and downstream of the first UC liquid application unit 20. The optical sensor 28 is provided downstream of the black light 27.

[0045] After the first UC liquid applicator 20 applies the UC liquid to the sheet S, the black light 27 irradiates the surface of the sheet S with ultraviolet light. This causes the portion of the sheet S to which the UC liquid has been applied to emit light (change color). Specifically, the fluorescent brightening agent contained in the UC liquid emits light. The optical sensor 28 detects the light emitted from the surface of the sheet S and changes from a non-detection state to a detection state.

[0046] In the first detection method, it is possible to detect whether the UC liquid has been applied to the surface of the sheet S, that is, whether there is an abnormality in the state of application of the pre-applying liquid to the sheet S, depending on whether the optical sensor 28 is in a detection state. Note that, although the irradiation member irradiates ultraviolet light in the above example, the present invention is not limited to this. In other words, it is sufficient if the pre-applying liquid is applied and the presence or absence of the application can be detected by the light detection member. For example, the irradiation member may irradiate infrared light, and the light detection member may detect the UC liquid that has emitted light as a result.

[0047] Next, the second detection method of this embodiment and the configuration within the image forming apparatus for performing the second detection method will be described with reference to FIG.

[0048] As shown in FIG. 6, a density sensor 29 is provided downstream of the first image forming unit 3.

[0049] When the second detection method is carried out, the first UC liquid applying unit 20 applies the UC liquid to the surface of the sheet S, and then the first image forming unit 3 forms a black solid image on the surface of the sheet S.

[0050] When a solid black image is formed on the sheet S, the density of the black color differs between areas where the UC liquid is not applied and areas where it is applied. In other words, the density of the areas where the UC liquid is not applied is lower than that of the areas where the UC liquid is applied. Therefore, in the second detection method, the density sensor 29 detects the density of the solid black image printed on the surface of the sheet S and determines whether the UC liquid is applied to the sheet S with a sufficient density, i.e., whether there is an abnormality in the state of application of the UC liquid to the sheet S, based on whether the density meets a predetermined reference value. Multiple density sensors 29 are provided in the width direction of the sheet S, which is a direction perpendicular to FIG. 6. This allows the density to be detected at each position in the width direction, thereby enabling the determination of whether the UC liquid is applied sufficiently at each position in the width direction. Note that the solid black image need only be formed across the width of the sheet S; it does not necessarily have to be formed across the entire image formation area of ​​the sheet S. For example, the density sensor 29 may read a band-like image formed across a portion of the image formation area of ​​the sheet S in the conveyance direction, from one end of the width to the other. Furthermore, the color of the image to be formed may be any color as long as the density can be detected by the density sensor 29.

[0051] Next, the third detection method of this embodiment and the configuration within the image forming apparatus for performing the third detection method will be described with reference to FIGS.

[0052] As shown in FIG. 7, downstream of the first image forming unit 3, a camera 30 is provided as an imaging member.

[0053] In this embodiment, after the first UC liquid application unit 20 applies the UC liquid to the surface of the sheet S, the first image forming unit 3 forms a line image on the sheet S outside the image forming area. Specifically, as shown in FIG. 8 , a non-image forming area D is provided between the image forming area C1 and the image forming area C2 of the sheet S, which are continuous in the conveying direction. A line image E is formed in this non-image forming area D. The line image E is formed across the width direction, for example, from one end to the other end of the width direction of the image forming areas C1 and C2, as a line image parallel to the width direction. A plurality of line images E are formed continuously in the conveying direction. However, the shape of the line image E is not limited to this, and it is sufficient that the line image E is provided across the width direction.

[0054] The camera 30 captures an image of the line image E formed on the sheet S from above. An operator then visually checks the captured image to determine whether the line image E is printed with the intended thinness, for example, whether the line image E is bleeding. By capturing an image of the line image E formed on the sheet S and determining whether this is the case, it is possible to detect whether the UC liquid is properly applied to the sheet S, that is, whether there is an abnormality in the application state. By capturing an image of the line image E and determining whether this is the case, it is possible to visually check for abnormalities in the application state even for transparent UC liquid. However, a method in which the captured image is automatically diagnosed using image diagnostic software or the like may also be used.

[0055] In this embodiment, the first to third detection methods are used to detect whether or not there is an abnormality in the state of application of the UC liquid to the sheet S. For the first and second detection methods, the control unit 9 (see FIG. 2) in the image forming apparatus determines whether or not there is an abnormality. For the third detection method, the operator makes the determination. For example, if the operator determines that there is an abnormality using the third detection method, this may be input to the image forming apparatus, which may then issue an alert. Note that while FIGS. 5 to 7 only show the configuration used for each detection method, the image forming apparatus of this embodiment is provided with all of these configurations.

[0056] In this embodiment, three detection methods can be used to evaluate different items related to the application of the UC liquid. These evaluation items are shown in Table 1 below. For each detection method in Table 1, an item marked with "O" indicates the evaluation item for that detection method. The first detection method can detect whether the UC liquid is applied to the surface of the sheet S. The second detection method can detect whether the UC liquid is applied to the surface of the sheet S at an appropriate concentration. The third detection method can detect the quality of the image on the sheet S resulting from the application of the UC liquid, for example, whether an image is properly formed on the sheet S without ink coalescence. [Table 1]

[0057] If an abnormality is determined by the first or third detection method, the application roller 25 (see FIG. 4) is not properly applying the UC liquid to the sheet S. In this case, the image forming apparatus issues an alert to notify an operator or the like that the UC liquid is not being properly applied. The pressure applied to the sheet S by the application roller 25, that is, the pressure applied to the sheet S at the nip between the application roller 25 and the contact roller 22, is then reduced. This can be achieved by moving the application roller 25, the contact roller 22, or both, in a direction away from the sheet S. This increases the space between the application roller 25 and the sheet S, allowing more UC liquid to be applied to the sheet S. The above method allows for countermeasures to be taken without turning off the power to the image forming apparatus.

[0058] Furthermore, if the second detection method results in an unsatisfactory result, there may be a problem with the rollers, such as the contact roller 22 or application roller 25, due to scratches or a problem with their installation. In this case, a roller defect alert is issued. The image forming apparatus is then powered off and the rollers are inspected. Note that if the first or third detection method determines that there is an abnormality, and the first or third detection method still determines that there is an abnormality after adjusting the pressure on the sheet S, the application roller 25 or contact roller 22 can be inspected with the power turned off, as with the second detection method.

[0059] By performing both the first and second detection methods, it is possible to appropriately address abnormalities in the application of UC liquid. In other words, if the UC liquid is not properly applied to the sheet S and the application of UC liquid to the sheet S cannot be confirmed using the first detection method, there may be a problem with the contact state between the application roller 25 and the contact roller 22 and the sheet S, and the positions of both rollers relative to the sheet S can be adjusted. On the other hand, if no abnormality is found using the first detection method but an abnormality is found using the second detection method—that is, if it is confirmed that the UC liquid is applied to the sheet S but the application state is uneven—it is possible that the application roller 25 or the contact roller 22 is tilted or that there are scratches on the roller surface, causing the UC liquid to be improperly applied to only a portion of the sheet width direction. In this case, the image forming apparatus should be powered off as described above, and the status of the application roller 25 and the contact roller 22 should be checked.

[0060] Furthermore, by implementing both the second and third detection methods, abnormalities can be confirmed using different detection methods, thereby improving the accuracy of abnormality detection. In other words, even if the second detection method determines that the UC liquid is sufficiently applied in the sheet width direction, the third detection method forms a line image on the sheet S and actually checks that image to confirm whether there is a problem with the quality of the image on the sheet S, which is the final product. Furthermore, unlike the concentration sensor 29 used in the second detection method, the third detection method checks the quality visually or otherwise and detects abnormalities using a different method. These features improve the accuracy of abnormality detection.

[0061] Each of the above detection methods can be used to detect whether the UC liquid is applied to the sheet S, whether the concentration is appropriate, and whether the quality of the image to be formed is ensured. Therefore, by combining these detection methods, it is possible to comprehensively determine whether the UC liquid is appropriately applied to the sheet S, and measures can be taken that are suited to each detection method. The second UC liquid application unit 50 (see FIG. 1) also has a similar configuration and can perform the same detection method. However, it is also possible to use only one of them.

[0062] The above three abnormality detection methods may be implemented by the user or by a service technician. For example, these abnormality detection methods can be implemented when the user feels that the quality of the formed image is insufficient, or when a service technician replaces the contact roller 22 or the application roller 25.

[0063] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0064] 9, a temperature sensor 31 may be provided. The temperature sensor 31 is provided downstream of the first UC liquid application unit 20 and upstream of the first image forming unit 3, particularly upstream of the black light 27. The temperature sensor 31 detects the surface temperature of the sheet S after the UC liquid has been applied.

[0065] Applying the UC liquid reduces the temperature of the surface of the sheet S. Therefore, by detecting the temperature of the surface of the sheet S with the temperature sensor 31, it can be determined that the UC liquid has been properly applied to the surface of the sheet S if the detected temperature is equal to or lower than a predetermined value. In addition to the first detection method described above, determining whether the UC liquid has been applied based on the detection result of the temperature sensor 31 can detect with higher accuracy whether the UC liquid has been applied.

[0066] In the present application, the liquid to be ejected may have a viscosity and surface tension that allows it to be ejected from the head, and is not particularly limited, but preferably has a viscosity of 30 mPa·s or less at room temperature and normal pressure, or upon heating or cooling. More specifically, the liquid may be a solution, suspension, emulsion, or the like containing a solvent such as water or an organic solvent, a colorant such as a dye or pigment, a polymerizable compound, a resin, a surfactant, or the like, a biocompatible material such as DNA, amino acids, proteins, or calcium, or an edible material such as a natural colorant, and the like. These liquids can be used, for example, as inkjet inks, surface treatment liquids, liquids for forming components of electronic devices or light-emitting elements, or electronic circuit resist patterns, and material liquids for 3D modeling.

[0067] This "liquid ejection device" can also include means for feeding, transporting, and discharging items onto which liquid can be attached, as well as pre-processing devices and post-processing devices.

[0068] For example, examples of "liquid ejection devices" include image forming devices that eject ink to form an image on a recording medium, and three-dimensional modeling devices (three-dimensional modeling devices) that eject modeling liquid onto a powder layer formed by layering powder in order to form a three-dimensional object (a three-dimensional model).

[0069] Furthermore, the term "liquid ejection device" is not limited to devices that visualize meaningful images such as letters and figures using ejected liquid. For example, it also includes devices that form patterns that have no meaning in themselves, and devices that create three-dimensional images.

[0070] The recording medium "to which a liquid can adhere" means a medium to which a liquid can adhere at least temporarily, to which the liquid adheres and sticks, or to which the liquid adheres and penetrates, and is the recording medium in the above embodiment. Specific examples include media such as paper, recording paper, film, and cloth, electronic substrates, electronic components such as piezoelectric elements, powder layers, organ models, and test cells, and unless otherwise specified, includes all media to which a liquid can adhere.

[0071] The material of the "substance to which a liquid can adhere" may be any material to which a liquid can adhere, even temporarily, such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, or ceramics.

[0072] Other examples of "liquid ejection devices" include treatment liquid application devices that eject treatment liquid onto paper to apply the treatment liquid to the surface of the paper for purposes such as modifying the surface of the paper, and spray granulation devices that spray a composition liquid in which raw materials are dispersed through a nozzle to granulate fine particles of the raw materials.

[0073] In the present application, the terms image formation, recording, printing, copying, printing, modeling, etc. are all synonymous.

[0074] The aspects of the present invention are as follows, for example. <1> a pre-application liquid is applied to the recording medium upstream in a recording medium conveyance direction from a position where an image is formed on the recording medium by ejecting a liquid; a first detection method in which the recording medium, onto which the pre-coating liquid has been applied and which has been irradiated with light by an irradiation member, is detected by an optical sensor, and an abnormality in the coating state of the pre-coating liquid coated on the recording medium is detected based on the detection result of the optical sensor; a second detection method in which the recording medium onto which the pre-applying liquid has been applied and onto which an image has been formed across the width direction by ejecting the liquid is detected by a density sensor, and an abnormality in the application state of the pre-applying liquid applied to the recording medium is detected based on the detection result of the density sensor; a third detection method for detecting abnormalities in the application state of the pre-application liquid, which comprises: capturing an image of the recording medium onto which the pre-application liquid has been applied and the liquid has been ejected to form a line image using an imaging element; and detecting abnormalities in the application state of the pre-application liquid applied to the recording medium using the captured image. <2> an application member contacting the recording medium and applying the pre-application liquid; When an abnormality is determined by the first detection method or the third detection method, the pressure applied to the recording medium by the applying member is reduced. <1> This is a method for detecting abnormalities in the application state of the pre-application liquid described above. <3> The irradiation member irradiates ultraviolet light. <1> or <2> This is a method for detecting abnormalities in the application state of the pre-application liquid described above. <4> The irradiation member irradiates infrared light. <1> or <2> This is a method for detecting abnormalities in the application state of the pre-application liquid described above. <5> a temperature sensor is used to detect the temperature of the surface of the recording medium onto which the pre-coating liquid has been applied; The first detection method detects an abnormality based on the detection result of the temperature sensor in addition to the detection result of the optical sensor. <1> from <4> The method for detecting an abnormality in the application state of the pre-application liquid described above is also provided. <6> a pre-coating liquid application unit; a liquid ejection unit provided downstream of the pre-applying liquid application unit in a recording medium conveyance direction; an irradiation member that irradiates the recording medium with light downstream of the pre-applying liquid application unit in a recording medium conveyance direction; an optical sensor that detects the recording medium downstream of the irradiation member in the recording medium conveyance direction; a density sensor that detects the recording medium downstream of the liquid ejection unit in a recording medium conveyance direction; an imaging member that images a recording medium downstream of the liquid ejection unit in a recording medium conveyance direction, This liquid ejection device is characterized by detecting abnormalities in the state of the pre-application liquid applied to the recording medium based on the detection results of the optical sensor and the density sensor and the image captured by the imaging member. [Explanation of symbols]

[0075] 3 First image forming section (liquid ejection section) 4 Second image forming section (liquid ejection section) 20 First UC liquid application section (first coating liquid application section) 25 Application roller (application member) 27 Black light (infrared radiation component) 28 Optical Sensor 29 Concentration sensor 30 Camera (imaging component) 31 Temperature Sensor 50 Second UC liquid application section (first coating liquid application section) 100 Image forming device (liquid ejection device) A Sheet transport direction (recording medium transport direction) B Sheet width direction (recording medium width direction) E-ray image S sheet (recording medium) [Prior art documents] [Patent documents]

[0076] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-230109

Claims

1. a pre-application liquid is applied to the recording medium upstream in a recording medium conveyance direction from a position where an image is formed on the recording medium by ejecting a liquid; a first detection method in which the recording medium, onto which the pre-coating liquid has been applied and which has been irradiated with light by an irradiation member, is detected by an optical sensor, and an abnormality in the application state of the pre-coating liquid applied to the recording medium is detected based on the detection result of the optical sensor; a second detection method in which the recording medium onto which the pre-applying liquid has been applied and onto which an image has been formed across the width direction by ejecting the liquid is detected by a density sensor, and an abnormality in the application state of the pre-applying liquid applied to the recording medium is detected based on the detection result of the density sensor; A method for detecting abnormalities in the application state of a pre-application liquid, characterized by carrying out a third detection method in which the recording medium to which the pre-application liquid has been applied and the liquid has been ejected to form a line image is imaged using an imaging element, and abnormalities in the application state of the pre-application liquid applied to the recording medium are detected using the imaged image.

2. an application member contacting the recording medium and applying the pre-application liquid; 2. The method for detecting an abnormality in the application state of the pre-applying liquid according to claim 1, wherein when an abnormality is determined by the first detection method or the third detection method, the pressure applied to the recording medium by the application member is reduced.

3. 2. The method for detecting an abnormality in the application state of a pre-application liquid according to claim 1, wherein the irradiating member irradiates ultraviolet light.

4. 2. The method for detecting an abnormality in the application state of a pre-application liquid according to claim 1, wherein the irradiating member irradiates infrared light.

5. a temperature sensor is used to detect the temperature of the surface of the recording medium onto which the pre-coating liquid has been applied; 2. The method for detecting an abnormality in the application state of the pre-applying liquid according to claim 1, wherein the first detection method detects an abnormality based on the detection result of the temperature sensor in addition to the detection result of the optical sensor.

6. a pre-coating liquid application unit; a liquid ejection unit provided downstream of the pre-applying liquid application unit in a recording medium conveyance direction; an irradiation member that irradiates the recording medium with light downstream of the pre-applying liquid application unit in a recording medium conveyance direction; an optical sensor that detects the recording medium downstream of the irradiation member in the recording medium conveyance direction; a density sensor that detects the recording medium downstream of the liquid ejection unit in a recording medium conveyance direction; an imaging member that images a recording medium downstream of the liquid ejection unit in a recording medium conveyance direction, A liquid ejection device characterized in that an abnormality in the state of the pre-application liquid applied to the recording medium is detected based on the detection results of the optical sensor and the density sensor and the image captured by the imaging member.

Images