JP2014162081A - Overcoat agent detection device, method of detecting overcoat agent, and image formation device - Google Patents

Abstract

Provided are an overcoat agent detection device, an overcoat agent detection method, and an image forming apparatus capable of detecting that there is a portion where no overcoat agent is applied even when nozzle clogging occurs. .
An overcoat agent detection device 10-1 is an overcoat agent detection device that detects the presence or absence of application of an overcoat agent mixed with a substance having a characteristic of transmitting visible light and absorbing invisible light. The invisible light irradiation means 12A for irradiating the surface of the paper SH coated with the overcoat agent with invisible light, and the invisible light detection means 12B for detecting the light intensity of the invisible light reflected from the paper SH are detected. It is determined whether or not the light intensity is equal to or higher than a predetermined first threshold value, and there is a portion where the overcoat agent is not applied when the detected light intensity is equal to or higher than the predetermined first threshold value. And control means 17 for detecting.
[Selection] Figure 2

Description

  The present invention relates to, for example, an overcoat agent detection device, an overcoat agent detection method, and an image forming apparatus provided with the overcoat agent detection device.

  For example, in an image forming apparatus such as a copying machine or a printer, a so-called overcoat process of applying a transparent overcoat agent may be performed. In this overcoat process, a predetermined image is formed by ejecting ink of three primary colors (yellow, cyan, magenta) and black ink on plain paper, a recording medium or the like (hereinafter referred to as paper). This is done by spraying an overcoat agent. By forming such an overcoat agent, it becomes possible to improve the scratch resistance of the paper or to improve the image quality by controlling the gloss of the printing surface of the paper.

  However, in the above-described overcoat process, it is difficult to detect even a portion where the overcoat agent is not applied on the paper due to clogging of the nozzles of the print head that ejects the overcoat agent. There was a problem of being. This problem is due to the property that the overcoat agent is transparent to transmit most of visible light.

  Further, as described above, since it is difficult to detect a portion where the overcoat agent is not applied, there is a problem that clogging of the nozzles of the print head that ejects the overcoat agent cannot be detected. For this reason, the overcoat agent is discharged in a state where the overcoat agent is not applied to a part or the entire surface of the paper, and there is a risk that the number of defective products having a portion where the overcoat agent is not applied increases.

  Here, for example, in Patent Document 1, a pattern image for detecting clogging is formed, the image is irradiated with light, the reflected light is read by an optical sensor, and ink of the pattern image is not ejected. An ink jet type image forming apparatus for detecting a location is disclosed. According to such an image forming apparatus, it is possible to detect a portion where ink has not been ejected, and to prevent clogging by forcibly ejecting ink from a nozzle where ink has not been ejected. is there. As described above, in the case of colored ink, it is possible to easily detect that ink is not applied by irradiating light and reading the reflected light. Further, it is possible to easily detect the ink out of the nozzles that are not ejected by visually checking the remaining amount of ink in the ink tank.

  On the other hand, in the case of an overcoat agent, the overcoat agent itself has a characteristic that it is transparent to transmit most of visible light. Therefore, by simply irradiating visible light and reading the reflected light, It is not easy to optically detect the presence or absence of the coating agent. Furthermore, it is not easy to visually detect clogging of the nozzles of the print head that ejects the overcoat agent.

  An object of the present invention is to provide an overcoat agent detection device that solves the above-described problems and can detect a portion where an overcoat agent is not applied due to nozzle clogging or the like.

  An overcoat agent detection device according to one embodiment of the present invention is an overcoat agent detection device that detects the presence or absence of application of an overcoat agent mixed with a substance having a property of transmitting visible light and absorbing invisible light. Invisible light irradiation means for irradiating the surface of the paper to which the overcoat agent is applied, invisible light detection means for detecting the light intensity of the invisible light reflected from the paper, and the detected light intensity Control for determining whether or not a predetermined first threshold value is exceeded and detecting that there is a portion where the overcoat agent is not applied when the detected light intensity is equal to or higher than the predetermined first threshold value Means.

  According to the said structure, even if it is a case where clogging of a nozzle generate | occur | produces, it can detect that there exists a part to which the overcoat agent is not apply | coated.

1 is a schematic diagram illustrating an image forming apparatus 100-1 according to a first embodiment of the present invention. It is a block diagram which shows the whole structure of the overcoat agent detection apparatus 10-1 of FIG. The detailed configuration of the invisible light source 12A and the invisible light detection unit 12B included in the detection unit 12 of FIG. 2 and the relationship between the overcoat agent 201 applied to the paper SH and the portion 202 where the overcoat agent 201 is not applied will be described. It is an enlarged view for doing. It is a graph which shows the relationship between the wavelength of the incident light 206I of the invisible light source 12A of FIG. 3, and relative luminous intensity. It is a graph which shows each spectral transmittance 201A-201D of each ultrafine particle oxide which permeate | transmits the visible light mixed in the overcoat agent 201 of FIG. 3, and absorbs ultraviolet light. It is a flowchart which shows the presence-and-absence detection process of the application of the overcoat agent performed by the overcoat agent detection apparatus 10-1 of FIG. It is a schematic diagram showing an image forming apparatus 100-2 according to the second embodiment. It is a block diagram which shows the whole structure of the precoat agent detection apparatus 10-2 of FIG. It is a flowchart which shows the presence or absence detection process of the application | coating of the precoat agent performed by the precoat agent detection apparatus 10-2 of FIG. It is a flowchart which shows the presence or absence detection process of application | coating of the overcoat agent performed by the overcoat agent detection apparatus which concerns on other embodiment. It is a flowchart which shows the presence or absence detection process of the application | coating of the precoat agent performed by the precoat agent detection apparatus which concerns on other embodiment.

(First embodiment)
FIG. 1 is a schematic diagram showing an image forming apparatus 100-1 according to the first embodiment of the present invention. As shown in FIG. 1, an image forming apparatus 100-1 according to the first embodiment includes an image forming unit 101, an unwinding roller 107, a winding roller 108, guide rollers 111 and 112, and an overcoat agent. The detection apparatus 10-1 and the overall control unit 117 are provided. Here, the image forming apparatus 100-1 shown in FIG. 1 forms an image by an inkjet method on a continuous form sheet SH wound in a roll shape.

  An image forming unit (an example of an image forming unit) 101 includes ink ejecting units 101K to 101Y that eject inks of four colors. Each ink is ejected onto a sheet SH to form characters, patterns, and the like. A predetermined image is formed on the SH. The ink ejecting unit 101K includes a printer head (not shown) and an ink cartridge including black (K) ink, and ejects black ink in the ink cartridge as droplets from the print head onto the paper SH, thereby displaying a predetermined image. Form. The ink ejecting units 101C, 101M, and 101Y have the same configuration as the ink ejecting unit 101K described above, and each of the three primary colors of cyan (C), yellow (Y), and magenta (M) is similarly applied. The liquid droplets are ejected onto the paper SH to form a predetermined image.

  The unwinding roller 107 is a roller for unloading the roll-shaped paper SH in the paper discharge direction 109. As the roller 107 rotates, the paper SH is carried out in the paper discharge direction 109. The take-up roller 108 is a roller that takes up the paper SH discharged from the paper discharge direction 109 in a roll shape. As the roller 108 rotates, the paper SH discharged from the paper discharge direction 109 is again wound into a roll.

  The guide roller 111 guides the paper SH carried out from the unwinding roller 107 to the image forming unit 101 as the roller 111 rotates. The guide roller 112 guides the paper SH discharged from the paper discharge direction 109 to the take-up roller 108 as the roller 112 rotates.

  Here, the overcoat agent detection device 10-1 is configured to include an overcoat agent application unit 11 and a detection unit 12, and detects whether or not the overcoat agent is applied to the paper SH as will be described later. The overcoat agent application unit 11 applies an overcoat agent mixed with a substance having a characteristic of transmitting visible light and absorbing invisible light onto the paper SH on which a predetermined image is formed by the image forming unit 101. Configured. The detection unit 12 detects the light intensity of the invisible light reflected from the paper SH and the invisible light source 12A that irradiates invisible light onto the surface of the paper SH on which an overcoat agent (not shown in FIG. 1) is applied. And a detector 12B. Details of these will be described later. The overall control unit 117 controls the overall operation of the image forming apparatus 100-1. For example, the overall control unit 117 selectively ejects ink of each color from each print head of the ink ejecting units 101K to 101Y according to the conveyance speed of the paper SH, and forms an image on the paper SH. The forming unit 101 is controlled.

Here, there are the following four main purposes for applying the overcoat agent on the paper SH.
(1) To control the gloss of the printing surface. The type of overcoat agent is selected according to the purpose of use of the printed matter, and the printing surface is controlled to have a glossy state or a matte state with reduced reflection.
(2) To improve the scratch resistance of the printing surface. By applying an overcoat agent to the printing surface, when the printing surface is rubbed with something, it is protected from scratches.
(3) Prevent blocking. When the printed sheets SH are stacked, the blocking phenomenon in which the ink on the printing surface adheres to the back surface of another sheet SH is prevented by applying an overcoat agent.
(4) To improve water resistance and weather resistance. By applying an overcoat agent on the paper SH, water penetration into the paper SH is prevented, and deterioration of the paper due to ultraviolet rays or the like is prevented, thereby improving the water resistance and weather resistance of the paper.

  Various methods such as spraying the overcoat agent or using a squeegee are conceivable as a method for applying the overcoat agent to the paper SH. The overcoat agent application unit 11 shown in FIG. The ink ejecting units 101K to 101Y include a print head similar to the print head. When the print head is used for jetting the overcoat agent, the application amount of the overcoat agent can be easily controlled, and the overcoat agent can be selectively applied.

  FIG. 2 is a block diagram showing the overall configuration of the overcoat agent detection device 10-1 of FIG. As shown in FIG. 2, the overcoat agent detection device 10-1 includes an overcoat agent application unit 11, a detection unit 12, and a control unit 17 that are electrically connected to each other through a control line 19. The

  The overcoat agent application unit (an example of an overcoat agent application unit) 11 is made of a substance having a characteristic of transmitting visible light and absorbing invisible light on the paper SH on which a predetermined image is formed by the image forming unit 101. Apply the mixed overcoat agent. The overcoat agent application unit 11 includes a print head, an ink tank, and the like similar to the print heads included in the ink ejecting units 101K to 101Y. The detection unit 12 includes an invisible light source 12A and an invisible light detection unit 12B. The invisible light source (an example of the invisible light irradiation unit) 12A irradiates the surface of the paper SH coated with the overcoat agent with invisible light. The invisible light irradiated by the invisible light source 12A is ultraviolet light as will be described later. The invisible light detection unit (an example of the invisible light detection unit) 12B detects the light intensity of the invisible light reflected from the paper SH.

  The control unit (an example of a control unit) 17 controls the overall operation of the overcoat agent detection device 10-1, and detects whether or not the overcoat agent is applied, as will be described later. The control unit 17 is controlled by the overall control unit 117 of the image forming apparatus 100-1 shown in FIG.

  3 shows a detailed configuration of the invisible light source 12A and the invisible light detection unit 12B included in the detection unit 12 of FIG. 2, an overcoat agent 201 applied to the paper SH, and a portion 202 where the overcoat agent 201 is not applied. It is an enlarged view for demonstrating the relationship. As shown in FIG. 3, the invisible light source 12 </ b> A includes an ultraviolet light source 203. The ultraviolet light source 203 is disposed at a predetermined angle with respect to the paper SH, and irradiates the surface of the paper SH with incident light 206I in the ultraviolet region. Here, as described later with reference to FIG. 4, for example, an ultraviolet light emitting diode that outputs ultraviolet light having a wavelength of about 355 nm can be applied to the ultraviolet light source 203.

  FIG. 4 is a graph showing the relationship between the wavelength of the incident light 206I of the invisible light source 12A of FIG. 3 and the relative luminous intensity. As the invisible light source 12A shown in FIG. 4, for example, an ultraviolet light-emitting diode having a model number of NS355C-2SAA manufactured by Nitride Semiconductor Co., Ltd. can be used. Here, the incident light 206I of the invisible light source 12A shown in FIG. 4 is 1.0 (arbitrary unit) under the condition that the ambient temperature Ta is about 25 ° C. and the forward current IF of the light emitting diode is about 20 mA. The relative light intensity has a peak at a wavelength near 355 nm.

  Returning to FIG. 3, the invisible light detection unit 12 </ b> B includes an ultraviolet light detection element 204. The ultraviolet light detection element 204 is disposed at a predetermined angle with respect to the paper SH, receives the ultraviolet light 206RC, 206RS reflected from the paper SH, and detects the light intensity of the received ultraviolet light 206RC, 206RS. As the ultraviolet light detection element 204, for example, an ultraviolet light detection sensor using gallium nitride (GaN) and aluminum gallium nitride (ALGaN), a general phototransistor, other photodiodes, and the like can be applied. However, the ultraviolet light detection element 204 needs to be sensitive to the wavelength (near 355 nm) of the incident light 206I irradiated from the ultraviolet light source 203. Further, even if the ultraviolet light detection element 204 is sensitive to wavelengths other than the incident light 206I, the ultraviolet light source 203 can selectively output only the specific wavelength (near 355 nm) shown in FIG. It is not necessary to filter other than the specific wavelength using a filter or the like.

  The overcoat agent 201 applied to the paper SH shown in FIG. 3 is mixed with a substance having a characteristic of transmitting visible light and absorbing ultraviolet light, such as each ultrafine metal oxide of FIG. It has the property of transmitting visible light and absorbing ultraviolet light. Therefore, in the case of the reflected light 206RC of the portion to which the overcoat agent 201 shown in FIG. 3 is applied, the light intensity of the ultraviolet light near 355 nm detected by the ultraviolet light detection element 204 is compared with the light intensity of the reflected light 206RS. Thus, it is detected as very small, for example, about 0. On the other hand, in the case of the reflected light 206RS of the portion 202 where the overcoat agent 201 is not applied, the light intensity of the ultraviolet light in the vicinity of 355 nm of the detected reflected light 206RS is substantially the reflection characteristic of the paper SH. Corresponding to Therefore, the light intensity of the sheet SH is detected by the ultraviolet light detection element 204 as a large light intensity compared to the light intensity of the reflected light 206RC of the portion where the overcoat agent 201 is applied.

  FIG. 5 is a graph showing the spectral transmittances 201A to 201D of the ultrafine particle oxides that transmit visible light and absorb ultraviolet light mixed in the overcoat agent 201 of FIG. Here, each of the spectral transmittances 201A to 201D in FIG. 5 is obtained by using, as disclosed in Non-Patent Document 1, for example, a metal oxide of ultrafine particles having a filler ratio of 60% and a dried film thickness of 4 μm. (Polyethylene terephthalate) formed on a film and measured. Here, each metal oxide shown in FIG. 5 needs to be ultrafine particles having a particle size of 0.1 μm or less. In general, visible light refers to electromagnetic waves having a wavelength of about 400 nm to about 800 nm. Electromagnetic waves of other wavelengths are called invisible light because they cannot be detected with the naked eye. Here, the range from about 400 nm to about 280 nm is referred to as ultraviolet light, and the range from about 800 nm to about 3000 nm is referred to as infrared light.

  For example, the spectral transmittance 201A of zinc oxide (ZnO) in FIG. 5 exceeds 80% in the visible light region having a wavelength of about 400 nm to about 800 nm, and is substantially transparent to visible light. I can say that. On the other hand, in the ultraviolet light region of about 400 nm or less, the spectral transmittance 201A rapidly decreases, and is less than 10% at about 380 nm or less. This is because zinc oxide (ZnO) absorbs ultraviolet electromagnetic waves and converts them into heat. For example, in the ultraviolet light near 355 nm irradiated by the invisible light source 12A, as shown by A in FIG. 5, the spectral transmittance 201A of zinc oxide is about 5%.

Similarly, it can be said that the spectral transmittance 201B of titanium oxide (TiO ₂ (rutile)) in FIG. 5 is transparent because it exceeds 80% in the visible light range of about 400 nm to about 800 nm. On the other hand, in the ultraviolet light region of about 400 nm or less, the spectral transmittance 201B rapidly decreases, and is less than 10% at about 380 nm or less. For example, in the ultraviolet light near 355 nm irradiated by the invisible light source 12A, as shown by B in FIG. 5, the spectral transmittance 201B of titanium oxide is about 4%. Here, there are anatase type (tetragonal), rutile type (tetragonal), and brookite type (orthorhombic) in the crystal structure of titanium oxide, but the titanium oxide in FIG. 5 is a rutile type. Further, when anatase type titanium oxide is heated to 900 ° C. or higher, it changes to a rutile type, and even if brookite type titanium oxide is heated to 650 ° C. or higher, it also changes to a rutile type. Since the rutile type has the most stable structure, once the transition to the rutile type, the titanium oxide maintains the rutile type even when the temperature is lowered.

Similarly, the spectral transmittance 201C of cesium oxide (CeO ₂ ) in FIG. 5 exceeds 80% in the range of visible light from about 400 nm to about 800 nm, and can be said to be transparent because it substantially transmits visible light. However, in the ultraviolet light near 355 nm irradiated by the invisible light source 12A, the spectral transmittance 201C is about 30%, which is higher than the spectral transmittances 201A and 201B of zinc oxide and titanium oxide. Further, the spectral transmittance 201D of iron oxide (Fe ₂ O ₃ ) in FIG. 5 rapidly decreases in the ultraviolet light region of less than about 400 nm. However, in the visible light range of about 400 nm to about 600 nm, the spectral transmittance 201D does not exceed 80%, and it can be said that the transparency is low. Therefore, as a substance that transmits visible light and absorbs ultraviolet light mixed in the overcoat agent 201 in FIG. 3, each particle having the spectral transmittances 201A and 201B in FIG. Fine particles such as zinc oxide (ZnO) and titanium oxide (TiO ₂ ) are preferred.

  Next, with reference to FIG. 6, the overcoat agent application presence / absence detection process executed by the overcoat agent detection apparatus 10-1 in the above configuration will be described. FIG. 6 is a flowchart showing an overcoat agent application presence / absence detection process executed by the overcoat agent detection apparatus 10-1 in FIG. As shown in FIG. 6, in step S <b> 11, the control unit 17 causes the overcoat agent application unit 11 to transmit visible light and absorb invisible light on the surface of the paper SH on which an image is formed. Apply the agent. For example, by mixing zinc oxide or titanium oxide showing the spectral transmission characteristics 201A and 201B in FIG. 5, the applied overcoat agent 201 transmits visible light and absorbs ultraviolet light in the vicinity of 355 nm as invisible light. With characteristics.

  Next, in step S12, the control unit 17 irradiates invisible light onto the surface of the paper SH on which the overcoat agent is applied by the invisible light source 12A. In step S13, the control unit 17 detects the light intensity of the invisible light reflected from the paper SH by the invisible light detection unit 12B.

  Next, in step S14, the control unit 17 determines whether or not the light intensity of the invisible light detected by the invisible light detection unit 12B is equal to or higher than a predetermined threshold value. For example, as shown in FIG. 3, when detecting the reflected light 206RC of the portion where the overcoat agent 201 is applied, the light intensity of the ultraviolet light of the reflected light 206RC is compared with the reflected light 206RS from the paper SH. Very small. Therefore, the predetermined threshold value is set between the light intensity of the reflected light 206RC from the overcoat agent and the light intensity of the reflected light 206RS from the paper SH. Therefore, when the reflected light 206RC from the overcoat agent is detected, the detected light intensity is less than the predetermined threshold value, and this determination is not satisfied (NO). When the determination in step S14 is not satisfied (NO), it is determined that the overcoat agent is applied on the sheet SH, and therefore the control unit 17 returns to step S12 and performs the same control.

  On the other hand, for example, when detecting the reflected light 206RS from the sheet SH of the portion 202 where the overcoat agent is not applied in FIG. 3, the detected light intensity is the reflected light 206RC from the overcoat agent. It is detected as a larger light intensity than the light intensity. Therefore, the detected light intensity is equal to or higher than the predetermined threshold value and satisfies this determination (YES). As a result, in step S15, the control unit 17 detects that there is a portion 202 to which the overcoat agent is not applied, and outputs a detection signal. Further, the display unit (not shown in FIG. 2) that has received the detection signal displays that the nozzle of the overcoat agent application unit 11 is clogged. It may be displayed that there is a portion where the overcoat agent is not applied. Further, the overall control unit 117 of the image forming apparatus 100-1 of FIG. 1 that has received the detection signal may stop the rotation of the unwinding roller 107 and the winding roller 108. In the above detection processing, the detection unit 12 performs scanning in the width direction SHW of the paper SH that intersects the paper discharge direction 109 to detect clogging of all the nozzles of the print head.

  As described above, the overcoat agent detection device 10-1 according to the first embodiment determines whether or not the detected light intensity is equal to or greater than a predetermined threshold value (S14), and determines the predetermined threshold value. At this time, the control unit 17 is provided for detecting that there is a portion 202 on which the overcoat agent is not applied on the paper SH. As described above, in the first embodiment, for example, a substance showing the spectral transmittances 201A to 201D in FIG. 5 is mixed into the overcoat agent 201 at a predetermined ratio. Then, by utilizing the difference in light intensity between the reflected light 206RC and 206RS of the ultraviolet light, the overcoat agent 201 on the paper SH is applied even when the nozzle of the overcoat application unit 11 is clogged. It can be detected that there is an unfinished portion 202.

  Furthermore, the transparent overcoat agent has a property of absorbing invisible light such as ultraviolet rays, and the overcoat agent absorbs ultraviolet light, so that the ink constituting the predetermined image formed under the overcoat agent can be obtained. The amount of light that the ultraviolet light reaches the pigment (dye or pigment) can be reduced. Therefore, the effect of reducing the deterioration over time such as fading or discoloration of ink due to ultraviolet light can be expected.

(Second Embodiment)
FIG. 7 is a schematic diagram illustrating an image forming apparatus 100-2 according to the second embodiment. In the following description, descriptions of portions substantially overlapping with the first embodiment are omitted. As illustrated in FIG. 7, the image forming apparatus 100-2 according to the second embodiment has the following (1) and (2) as compared with the image forming apparatus 100-1 according to the first embodiment. It is different in point.

(1) The precoat agent detection device 10-2 is provided. Here, the precoat agent detection device 10-2 includes a precoat agent application unit 21, a drying unit 22, and a detection unit 23.

(2) The guide rollers 111A to 111C are provided instead of the guide roller 111. Here, the two guide rollers 111 </ b> A and 111 </ b> B are arranged so as to face each other with the print head of the precoat agent application unit 21. With this arrangement, the paper SH carried out from the unwinding roller 107 is guided directly below the precoat agent application unit 21. The guide roller 111C guides the sheet SH on which the precoat agent has been applied to the drying guide roller 22B of the precoat agent detection device 10-2.

Further, in the precoat agent detection apparatus 10-2, the precoat agent application unit 21 uses the paper SH on which the precoat agent mixed with a substance having a property of transmitting visible light and absorbing invisible light is conveyed from the unwinding roller 107. Apply to. In addition, as a substance having a characteristic of transmitting visible light and absorbing invisible light mixed in the precoat agent, each particle having spectral transmittances 201A and 201B in FIG. Some zinc oxide (ZnO), titanium oxide (TiO ₂ ), etc. can be used similarly. Here, in order for the image forming apparatus 10-2 to form an image by, for example, an ink jet method, a pre-processing called a pre-coating process may be required depending on the paper SH. Generally, the amount of ink droplets ejected from the nozzles of the print head of the image forming unit 101 is about 1 picoliter, and the diameter of the droplets is said to be 100 μm or less. However, when a droplet is ejected onto the paper SH, the diameter of the ink droplet expands more than twice. This is because the ink is absorbed and permeated into the fiber voids of the paper SH, and bleeding occurs in the paper SH in the process. For example, when the image forming unit 101 includes a plurality of ink ejecting units 101K to 101Y, inks of different colors may be mixed together and image quality may be deteriorated. Therefore, a pre-coating step is performed to form a polymer compound film or an inorganic fine particle film on the surface of the inkjet dedicated paper SH to prevent ink droplets from spreading and spreading, or different inks from being mixed together. . As described above, in the second embodiment, when the paper SH not subjected to the surface treatment as described above is used, a precoat agent for forming a polymer compound film or an inorganic fine particle film is applied so as not to deteriorate the image quality. .

  The drying unit 22 includes a drying fan 22A and a plurality of drying guide rollers 22B, and dries the paper SH on which the precoat agent has been applied. The drying fan 22A blows air heated by a heater (not shown) as warm air on the paper SH conveyed by the drying guide roller 22B, and dries moisture and solvent in the precoat agent applied to the paper SH. The plurality of drying guide rollers 22 </ b> B are arranged in a zigzag shape under the warm air blown from the drying fan 22 </ b> A, and convey the paper SH coated with the precoat agent along this arrangement. In this way, by transporting the paper SH along the arrangement of the guide roller 22B for drying, the hot air from the warm air fan 22A is efficiently blown, and the precoat agent is dried at high speed.

  Like the detection unit 12 according to the first embodiment, the detection unit 23 includes an invisible light source 23A and an invisible light detection unit 23B (not shown in FIG. 7). The invisible light source 23A irradiates the surface of the paper SH on which the precoat agent is applied with invisible light. The invisible light detection unit 23B detects the light intensity of the invisible light reflected from the paper SH. In the above configuration, the detection unit 23 is for detecting whether or not the precoat agent is applied. This is because the pre-coating agent is basically transparent like the coating agent, and even if there is coating unevenness, it is difficult to detect it visually. In addition, the ink tank filled with the precoat agent in the precoat agent application unit 21 is empty, and it is difficult for the nozzles of the print head to detect clogging.

  FIG. 8 is a block diagram showing the overall configuration of the precoat agent detection device 10-2 of FIG. As shown in FIG. 7, the precoat agent detection device 10-2 includes a precoat agent application unit 21, a drying unit 22, and a detection unit 23. The precoat agent application unit 21 and the drying unit 22 are as described in FIG.

  The detection unit 23 includes an invisible light source 23A and an invisible light detection unit 23B. The invisible light source 23A irradiates the surface of the paper SH on which the precoat agent is applied with invisible light. The invisible light emitted from the invisible light source 23A is, for example, ultraviolet light near 355 nm shown in FIG. The invisible light detection unit 23B detects the light intensity of the invisible light reflected from the paper SH. Similarly to the invisible light detection unit 12B, the invisible light detection unit 23B can employ, for example, an ultraviolet detection sensor sensitive to ultraviolet light in the vicinity of 355 nm, a general phototransistor, and other photodiodes.

  Next, the pre-coating agent application presence / absence detection process executed by the pre-coating agent detection apparatus 10-2 in the above configuration will be described with reference to FIG. FIG. 9 is a flowchart showing the pre-coating agent application presence / absence detection process executed by the pre-coating agent detection apparatus 10-2 of FIG. As shown in FIG. 9, in step S <b> 21, the control unit 27 uses the precoat agent application unit 21 to apply a precoat agent having characteristics of transmitting visible light and absorbing invisible light onto the surface of the paper SH. In step S <b> 22, the control unit 27 causes the drying unit 22 to dry the paper SH coated with the precoat agent.

  Next, in step S23, the control unit 27 irradiates the surface of the paper SH coated with the precoat agent with the invisible light source 23A. In step S24, the control unit 27 detects the light intensity of the invisible light reflected from the paper SH by the invisible light detection unit 23B. In step S25, it is determined whether or not the light intensity detected by the invisible light detection unit 23B is equal to or greater than a predetermined threshold value as described above. If the determination in step S25 is not satisfied (NO), since it is determined that the precoat agent is applied, the control unit 17 returns to step S23 and performs the same control. On the other hand, when the determination in step S25 is satisfied (YES), the control unit 27 detects that there is a portion where the precoat agent is not applied in the subsequent step S26 and outputs a detection signal. Further, the display unit (not shown in FIG. 8) that has received the detection signal displays that the nozzle of the precoat agent application unit 21 is clogged.

  As described above, the precoat agent detection device 10-2 according to the second embodiment determines whether or not the detected light intensity is equal to or greater than a predetermined threshold value, and the detected light intensity is not predetermined. When it is equal to or higher than the threshold value, a control unit 27 is provided for detecting that there is a portion where the precoat agent is not applied. Therefore, even when the nozzle of the precoat application unit 21 is clogged, it can be detected that there is a portion where the precoat agent is not applied. In addition, since the image forming apparatus 10-2 according to the second embodiment includes the coating agent detection device 10-1, it is possible to detect the presence / absence of application of the coating agent as a whole as in the first embodiment. .

(Other embodiments)
In the above-described first and second embodiments, the image forming apparatuses 100-1 and 100-2 are exemplified by the inkjet type, but are not limited thereto. For example, the present invention can be similarly applied to an image forming apparatus using an electrophotographic method or an image forming apparatus that forms an image on a cut sheet as the sheet SH. In addition, the present invention is similarly applied to other image forming apparatuses such as a copying machine, a printer, a facsimile, and a multi-function machine that are integrally provided with the overcoat agent detection device 10-1 or the precoat agent detection device 10-2. It is possible.

  Further, the invisible light detection units 12B and 23B are not limited to the configuration shown in FIG. 3, and a line sensor such as a CCD or CMOS sensor having sensitivity to invisible light such as ultraviolet light may be used as the light detection element. In that case, there is no need to scan in the width direction SHW of the paper SH that intersects the paper discharge direction 109, which is advantageous in that it can be detected at high speed.

  The invisible light emitted by the invisible light sources 12A and 23A is not limited to ultraviolet light having a peak in the vicinity of 355 nm as shown in FIG. 4, and may be infrared light having a wavelength of 800 nm or more, for example. However, since infrared light has a long wavelength, the resolution of the invisible light detectors 12B and 23B that optically detect the presence / absence of application of the overcoat agent and the precoat agent is larger than that of ultraviolet light. Therefore, in order to detect clogging of a more precise nozzle, for example, clogging as fine as 1 dot, it is better to irradiate ultraviolet light with a smaller resolution and detect it by the invisible light detection units 12B and 23B. It is valid.

  Further, even when an overcoat agent and a precoat agent mixed with a substance having a characteristic of transmitting visible light and reflecting invisible light to some extent are used, as shown in FIGS. This can be implemented in the same manner as in the second embodiment, and the same effects can be obtained. FIG. 10 is a flowchart showing an overcoat agent application presence / absence detection process executed by an overcoat agent detection apparatus according to another embodiment. Here, the overcoat application presence / absence detection process according to another embodiment shown in FIG. 10 is compared with the overcoat application presence / absence detection process according to the first embodiment shown in FIG. (1), (2) is different.

(1) Step S11A is provided instead of step S11. Here, in step S <b> 11 </ b> A of FIG. 10, a substance having a characteristic of transmitting visible light and reflecting invisible light with a predetermined reflectance onto the surface of the paper SH on which an image is formed by the overcoat agent application unit 11. Apply the mixed overcoat agent. Here, as the substance having the property of transmitting visible light and reflecting invisible light to some extent, for example, titanium oxide or zinc oxide having a particle diameter of more than 0.1 μm can be used, and more preferably. For example, titanium oxide or zinc oxide having a particle size of 0.2 μm or more and 0.4 μm or less can be used.

(2) Step S14A is provided instead of Step S14. Here, in step S14A of FIG. 10, the control unit 17 determines whether or not the light intensity of the invisible light detected by the invisible light detection unit 12B is equal to or less than a predetermined threshold value. Here, the overcoat agent mixed with the substance having the characteristic of reflecting invisible light as described above substantially totally reflects the invisible light, but the paper SH reflects the invisible light to some extent according to the reflection characteristics. reflect. For this reason, the light intensity of the reflected light from the paper SH is smaller than the light intensity of the reflected light of the overcoat agent. Therefore, the predetermined threshold value is set between the light intensity of the reflected light from the overcoat agent and the light intensity of the reflected light from the paper SH. As a result, when the detected light intensity is equal to or lower than a predetermined threshold value (YES), it is similarly detected in step S15 that there is a portion where the overcoat agent is not applied, and a detection signal is output.

  FIG. 11 is a flowchart showing pre-coating agent application presence / absence detection processing executed by a pre-coating agent detection apparatus according to another embodiment. Here, the precoat application presence / absence detection processing according to another embodiment shown in FIG. 11 is compared with the following (1) in comparison with the precoat application presence / absence detection processing according to the first embodiment shown in FIG. ) And (2).

(1) Step S21A is provided instead of step S21. Here, in step S21A of FIG. 11, a precoat agent in which a substance having a characteristic of transmitting visible light and reflecting invisible light with a predetermined reflectance is mixed on the surface of the paper SH by the precoat agent application unit 21. Apply. In addition, as a substance having the characteristic of transmitting visible light and reflecting invisible light to some extent, similarly, for example, titanium oxide or zinc oxide having a particle diameter of more than 0.1 μm can be used. Preferably, for example, titanium oxide or zinc oxide having a particle size of 0.2 μm or more and 0.4 μm or less can be used.

(2) Step S25A is provided instead of Step S25. Here, in step S25A of FIG. 11, the control unit 27 determines whether or not the light intensity of the invisible light detected by the invisible light detection unit 23B is equal to or less than a predetermined threshold value. Here, the predetermined threshold is as described above. As a result of the determination, when the detected light intensity is equal to or lower than a predetermined threshold (YES), the control unit 27 detects that there is a portion where the precoat agent is not applied in step S26 and outputs a detection signal. Output.

  As described above with reference to FIGS. 10 and 11, the difference between the light intensity of the reflected light from the overcoat agent and the precoat agent and the light intensity of the reflected light from the paper SH is detected by the invisible light detection units 12B and 23B. By optically detecting, it is possible to similarly detect that there is a portion where the overcoat agent and the precoat agent are not applied.

  Furthermore, not only the overcoat agent and the precoat agent, but also a similar substance having a characteristic of absorbing light of a specific wavelength other than visible light is contained in the ink of the ink ejecting units 101K to 101Y included in the image forming unit 101. By mixing, the ink can have a characteristic of absorbing light of a specific wavelength other than visible light. According to the above configuration, it is possible to detect the presence / absence of application of ink on the paper SH, clogging of the nozzles of the print head provided in the ink ejecting units 101K to 101Y, and ink out of the ink tank. For example, when yellow ink is applied to white paper by the ink ejecting unit 101Y, the density difference due to the presence or absence of the yellow ink on the paper SH is small, and accurate detection may be difficult depending on the optical sensor. In such a case, the yellow ink has the above-mentioned property of absorbing invisible light, and the same processing as the above-described presence / absence detection processing of the overcoat agent is performed, and the difference in light intensity of invisible light is determined. By using this, even when the clogging of the print head of the ink ejecting portion 101Y that ejects the yellow ink occurs, it can be detected that there is a portion where the yellow ink is not applied.

10-1: Overcoat agent detection device,
11 ... overcoat agent application part,
12 ... detection part,
12A ... Invisible light source,
12B ... Invisible light detection unit,
17 ... control unit,
100-1, 100-2 ... image forming apparatus,
101. Image forming unit.

Japanese Patent Laid-Open No. 10-138513

Tanaka Sakurai, Kanehiro Saito, “Development of Function of Zinc Oxide as a UV Protection Agent”, FRAGRANCE JOURNAL May 1999, p. 79-83

Claims (5)

An overcoat agent detection device for detecting the presence or absence of application of an overcoat agent mixed with a substance having a characteristic of transmitting visible light and absorbing invisible light,
Invisible light irradiation means for irradiating invisible light onto the paper on which the overcoat agent is applied;
Invisible light detection means for detecting the light intensity of the invisible light reflected from the paper;
It is determined whether or not the detected light intensity is equal to or higher than a predetermined first threshold value, and no overcoat agent is applied when the detected light intensity is equal to or higher than the predetermined first threshold value. An overcoat agent detection device comprising: control means for detecting the presence of a portion. An overcoat agent detection device for detecting the presence or absence of application of an overcoat agent mixed with a substance having a characteristic of transmitting visible light and reflecting invisible light with a predetermined reflectance,
Invisible light irradiation means for irradiating invisible light onto the paper on which the overcoat agent is applied;
Invisible light detection means for detecting the light intensity of the invisible light reflected from the paper;
It is determined whether or not the detected light intensity is equal to or less than a predetermined second threshold value, and no overcoat agent is applied when the detected light intensity is equal to or less than the predetermined second threshold value An overcoat agent detection device comprising: control means for detecting the presence of a portion. An image forming apparatus comprising image forming means for forming a predetermined image on the paper,
An image forming apparatus comprising the overcoat agent detection device according to claim 1. An overcoat agent detection method for detecting the presence or absence of application of an overcoat agent mixed with a substance having a property of transmitting visible light and absorbing invisible light,
Irradiating the sheet on which the overcoat agent is applied with invisible light;
Detecting the light intensity of invisible light reflected from the paper;
Determining whether the detected light intensity is greater than or equal to a predetermined first threshold;
And a step of detecting that there is a portion where no overcoat agent is applied when the detected light intensity is equal to or greater than the first threshold value. An overcoat agent detection method for detecting the presence or absence of application of an overcoat agent mixed with a substance having a characteristic of transmitting visible light and reflecting invisible light at a predetermined reflectance,
Irradiating the sheet on which the overcoat agent is applied with invisible light;
Detecting the light intensity of invisible light reflected from the paper;
Determining whether the detected light intensity is less than or equal to a predetermined second threshold;
An overcoating agent detection method comprising: detecting that there is a portion where no overcoating agent is applied when the detected light intensity is equal to or less than the predetermined second threshold value. .

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