JP2006110895A - Image recorder and its driving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that an image recorder using conventional photo-curing inks is kept turn on a light even during the standby (non-recording operation) of a lamp indicating the irradiation of active light (ultraviolet rays) making inks cured and, even at the time of the lamp putting the lights out, the recording head is irradiated with a natural light and then nozzles are clogged. <P>SOLUTION: The recorder performs the operation of delivering to a recording medium conveyed with the droplets of the photo-curing inks cured with the irradiation of the active light from a plurality of nozzles. When the active light is irradiated near the opening of nozzles at not delivering, the environment near the nozzle openings of the recording head is established with the oxygen concentration not making the light-curing inks cured by feeding an oxygen gas. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that records an image by ejecting photocurable ink onto a recording medium, and a driving method thereof.

  2. Description of the Related Art In recent years, many image recording apparatuses, so-called inkjet printers, that record an image by ejecting ink onto a recording medium have been used as an apparatus that can form an image easily and inexpensively. This image recording apparatus includes a recording head in which a large number of nozzles are arranged in the width direction of the recording medium. When the recording medium is conveyed in front of the nozzle row and passes, ink droplets are ejected from the head to the recording medium by a piezo element or a heater, and an image is recorded on the recording medium. Examples of the recording medium include recording paper that absorbs ink and a film made of a resin that does not absorb ink.

  As an ink used for recording an image on this film, for example, there is a photocurable ink that is cured by irradiation with an active light such as an ultraviolet ray. This photo-curable ink, for example, generates a radical (active species) by irradiation of light energy (mainly ultraviolet energy) with a pigment, a monomer or oligomer that becomes a precursor of a polymer compound, and the monomer is generated by this radical. Or it is comprised as a mixture containing the photoinitiator etc. which advance the crosslinking reaction or polymerization reaction of an oligomer, and these harden | cure by the crosslinking reaction or polymerization reaction by irradiation of light.

  An image recording apparatus for recording with such a photocurable ink has a relatively low odor compared with an apparatus using solvent-based ink, and can record not only on recording paper but also on a recording medium having no ink absorbability. In recent years, it has been attracting attention in terms of what it can do.

  However, since such a photo-curable ink contains a curing agent in the ink, when it is irradiated with ultraviolet rays in the vicinity of the nozzle opening, it hardens so as to block the opening and clogging is impossible to recover. There is a problem that will occur.

  In order to deal with this nozzle clogging problem, for example, in Patent Document 1, the nozzle plate itself has a light shielding property, and an ink-repellent eutectoid plating layer is formed in the vicinity of the nozzle opening. With this configuration, in the non-ink droplet ejection state, the ink is retracted to the back of the pressure generation chamber due to the water repellency of the eutectoid plating layer, and ultraviolet rays are blocked by the nozzle plate. Thereby, hardening of the ink by the ultraviolet rays in the nozzle opening and the flow path forming substrate can be prevented. Patent Document 2 proposes a technique in which an aliphatic polyhydric alcohol such as glycerin is added to an ultraviolet curable ink so that it is difficult to cure in the vicinity of the nozzle opening.

Further, in Patent Document 3, after an ink droplet has landed by supplying an inert gas that is inert to the actinic curable ink to a portion where the ink droplet landed on the recording medium is irradiated by the irradiation unit. It has been proposed to suppress the spread of ink droplets and to form a high-definition image with an active photocurable ink.
Japanese Patent Laid-Open No. 11-10874 JP-A-8-48922 JP2003-285423

  When the above-mentioned photo-curable ink is irradiated with a certain amount or more of ultraviolet rays, the photoinitiator in the ink first absorbs the ultraviolet rays to generate radicals, causing a polymerization reaction of the reactive oligomer / monomer, There is a feature that forms a cured coating instantly.

  Further, the UV lamp that emits ultraviolet rays requires an elapsed time of about 10 minutes from the start of lighting in order to stably obtain the rated (100%) luminance. For this reason, normally, if the apparatus is activated, the lamp is turned on to maintain the lighting state even during non-recording.

  Further, as a recording medium for photo-curable ink, for example, a film having a glossy surface and high reflectivity may be used. At this time, the ultraviolet light irradiated from the ultraviolet lamp is reflected on the film surface and irradiated as reflected light on the nozzle and its vicinity, and the ink in the nozzle opening is cured, resulting in an unrecoverable clogging. There is a problem.

  Furthermore, even when the lamp is turned off, depending on the installation location of the image recording apparatus, minute ultraviolet rays contained in natural light may be reflected by the film and irradiated to the nozzles of the recording head. If left in the irradiated state for a long time, clogging may occur as well.

  With respect to such a problem, in Patent Document 1, as shown in FIG. 9A, the nozzle plate 41 has a light shielding property, and an ink water-repellent eutectoid plating layer 43 is provided in the vicinity of the nozzle opening 42. . According to such a configuration, as shown in FIG. 9B, the meniscus M of the ink 44 existing in the vicinity of the nozzle opening 42 after the completion of the image formation is formed on the eutectoid plating layer 43 formed in the nozzle opening 42. Due to the oil repellency, the ink retreats to the back side of the pressure generating chamber, and the ultraviolet light is blocked by the nozzle plate 41. Therefore, the amount of ultraviolet light received by the ink 44 near the nozzle opening 42 and the ink K in the pressure generating chamber is extremely small, and curing is performed. Is prevented over a long period of time, and clogging is prevented. However, this method complicates the manufacturing process of the recording head. Furthermore, since the retracted meniscus must be held at the position of the meniscus at the time of image formation, it must be held at a site with high oil repellency, and it can be expected that it is difficult to hold the meniscus stably.

  Patent Document 2 proposes to add an aliphatic polyhydric alcohol such as glycerin to the ultraviolet curable ink. According to this, the time until clogging can be extended, but basically it is cured by ultraviolet rays, so if ultraviolet rays are irradiated in the vicinity of the nozzle opening including natural light, clogging that cannot be recovered will be caused. There is a problem that arises.

  Furthermore, in Patent Document 3, irradiation light may be reflected by the recording medium during non-recording, and since the reflected light reaches the nozzle, curing of the ink in the nozzle and its vicinity cannot be prevented, and the nozzle is clogged. It cannot be prevented.

  Therefore, in the present invention, even when a one-position meniscus recording head is employed using a recording head having a simple configuration, the nozzle is not clogged at the time of non-recording including when the lamp power is turned off by the radical polymerization type ink. An object is to provide an image recording apparatus and a driving method thereof.

  In order to achieve the above-mentioned object, the present invention provides a recording head having a plurality of nozzles for ejecting ink droplets of a photocurable ink that is cured by irradiation with active light to a recording medium to be transported, and a transport downstream side of the recording head An oxygen gas is supplied to the light irradiating portion for irradiating the ink droplets landed on the recording medium with active light and curing the ink droplets, and to the vicinity of the nozzle opening when not ejected. And an oxygen gas supply unit that sets an atmosphere in the vicinity of the nozzle opening of the recording head to be higher than the oxygen concentration of air.

  Furthermore, there is provided a method for driving an image recording apparatus for recording an image by ejecting ink droplets of a photocurable ink that is cured by irradiation of actinic light from a plurality of nozzles onto a transported recording medium, wherein the nozzle opening during non-ejection Provided is a method for driving an image recording apparatus in which oxygen gas is supplied to the vicinity to set the atmosphere in the vicinity of the nozzle opening of the recording head to be higher than the oxygen concentration of air.

  According to the present invention, even when a one-position meniscus recording head is employed using a recording head having a simple configuration, the nozzle is clogged at the time of non-recording including when the lamp power is turned off by the photocurable ink. Image recording apparatus and a driving method thereof can be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a conceptual configuration example of an ink jet printer as an example of the image recording apparatus according to the first embodiment of the present invention. Note that the direction in which the recording medium is conveyed is defined as the sub-scanning direction or the X direction, and the direction orthogonal thereto is defined as the main scanning direction or the Y direction or the width direction of the recording medium. In the present embodiment, the photocurable ink used in the image recording apparatus is a radical polymerization type among ultraviolet curable inks, and is composed of a photopolymerization reactive resin, a photopolymerization initiator, a colorant, and an auxiliary agent. Yes. In addition, as the active light for curing the ink, ultraviolet light (or light in the ultraviolet region) is taken as an example. The recording medium is paper or film.

This image recording apparatus mainly includes a transport mechanism 1 that transports a recording medium and an image recording unit 2 that records an image.
The transport mechanism 1 is configured as a belt platen composed of an annular endless belt 4 rotatably spanned between two rollers 3a and 3b, and is rotated by a drive mechanism such as a motor (not shown) to transport a recording medium.

  The endless belt 4 is formed of a rubber material or the like and has a structure that allows air to pass therethrough, for example, a large number of holes are opened, and negative pressure means (not shown) provided below the endless belt 4 is provided. As a result, the recording medium is conveyed while being adsorbed to the endless belt 4 and passes in front of the nozzle outlet of the image recording unit 2.

  Further, the image recording unit 2 has a plurality of, for example, four recording heads 5 fixed, and ejects ink droplets of four different colors (for example, 5K: Black, 5C: Cyan, 5M: Magenta, 5Y: Yellow), respectively. A color image is formed by landing on the recording medium to be conveyed.

  In the image recording unit 2, four recording heads 5K, 5C, 5M, and 5Y are integrally arranged with a maintenance station 6 (6a, 6b, 6c, and 6d) sandwiched therebetween from the upstream side in the X direction. Composed. These maintenance stations 6 can be moved by a mechanism (not shown) as needed, just below the recording head 5, that is, so as to face the nozzle surface, to perform maintenance processing.

  On the downstream side of the image recording unit 2, an ultraviolet (UV) lamp unit (hereinafter referred to as a UV lamp) 7 serving as a light irradiation unit for curing the ink on the recording medium ejected by each recording head 5 is provided. ing. Among these, the recording head 5 is an inkjet head, and as a UV lamp, for example, a D bulb manufactured by Fusion UV Systems Japan may be used. FIG. 2 shows the characteristics of the D valve.

  Further, a head cover 8 is provided so as to cover the recording head 5 and the maintenance station 6. An oxygen gas supply port 9 is provided above the upstream side surface of the head cover 8, and is connected to an oxygen gas supply system 10 using an oxygen gas cylinder or an oxygen-enriched film by a tube or the like. An oxygen concentration meter 11 is attached to the recording head 5M which is substantially the center of the image recording unit. The head cover 8 creates an atmosphere of oxygen gas supplied from the oxygen gas supply system 10 and acts so as to obtain a desired oxygen concentration around the head.

  In general photopolymerization initiators for ultraviolet curable inks, radicals are generated in the initiation reaction. However, radicals are consumed when oxygen in the air reacts with the radicals, and the activity of the photocurable ink is influenced by oxygen. And the photocurable ink is not cured.

  The oxygen concentration of normal air is about 21%. If the oxygen concentration is about 15% or more, the activity of the photocurable ink starts to decrease. Note that the oxygen concentration in the air in the present plan indicates the oxygen concentration in the air outside the image recording apparatus, which is not affected by the oxygen gas supply unit or the nitrogen gas supply unit used in the present plan. Is about 21%. On the other hand, the curing by the polymerization reaction is influenced not only by the oxygen concentration but also by the illuminance of the UV lamp. This is affected by the degree of curing of the ink in the vicinity of the nozzle opening, depending on the positional relationship between the UV lamp and the recording head, and also the reflectance of the recording medium. That is, the polymerization reaction is accelerated and the curing may proceed by lowering the activity of the photocurable ink with oxygen and inhibiting the curing faster than when the illuminance of the UV lamp is high.

  That is, in order to reduce the activity of the radicalized photopolymerization initiator of the ink in the vicinity of the nozzle, it is always necessary to contact the photopolymerization initiator with oxygen quickly and efficiently. For this purpose, the oxygen concentration in the normal air alone is insufficient, and an oxygen concentration of about 21% or more in the air is required.

  On the other hand, if the oxygen concentration is too high, the ozone concentration generated by ultraviolet rays will increase. Furthermore, it is said that an excessively high concentration of oxygen affects the human body. Generally, if the concentration is about 35% or less, there is little influence on the human body.

  Therefore, the oxygen concentration of the supplied oxygen gas is 1.1 to 1.7 times that of normal air, and about 23 to 35%, which is 1.5 to 2.3 times the inhibition start concentration, may be safe. In this embodiment, it is 30%, but may be determined as appropriate depending on the activity of the photocurable ink to be used, the illuminance of the UV lamp 7, the performance of the oxygen gas supply system 10, and the like.

  The flow rate of the oxygen gas is appropriately determined so that the oxygen concentration around the nozzle becomes a desired concentration in a desired time based on the internal volume of the head cover 8 and the flow rate of the oxygen gas leaking from the gap between the recording head 5 and the head cover 8. Just do it. In this embodiment, the flow rate is about 2 L / min.

  Since the oxygen gas supplied to the head cover 8 is heavier than air, it diffuses and moves downward from the top of the recording head. These oxygen concentrations are managed by the oxygen concentration meter 11.

Next, image recording in the image recording apparatus will be described with reference to the flowchart shown in FIG.
First, the main power supply of the main body of the image recording apparatus is turned on and activated (step S1).

  Next, supply of oxygen gas to the vicinity of the recording head 5 is started by the oxygen gas supply system 10 (step S2). It waits until the measured value by the oxygen concentration meter 11 reaches 25% (step S3).

  After that, if the measured value reaches 25% (YES), the UV lamp 7 is turned on and lit to start light emission (step S4), and about 10 minutes are recorded until the lighting state is stabilized. The standby mode is set (step S5). During this standby time, the state in which oxygen gas is supplied is maintained, but the transport mechanism 2 is in a stopped state and the recording medium is not transported. Further, a shutter may be provided on the irradiation side of the UV lamp 7 so that unnecessary ultraviolet rays are not irradiated. However, in some cases, leaked ultraviolet light or natural light ultraviolet light is reflected on the film and reaches around the nozzles of the recording head. The ink near the meniscus, which is the interface between the air layer near the nozzle opening and the ink, initiates a reaction due to the reflected ultraviolet rays, and generates radicals. However, oxygen in the oxygen gas supplied in advance reacts with the radicals. It is consumed and the polymerization reaction does not proceed any further. Therefore, even when the reflected ultraviolet light is incident, the polymerization reaction is not promoted at the nozzle opening and its periphery, and the nozzle is not clogged.

  Thereafter, when the lighting state of the UV lamp 7 is stabilized in step S5 (YES), the supply of oxygen gas is stopped (step S6), and the process waits until the oxygen concentration is lowered to about 21% (step S7). ).

  Next, if the oxygen concentration is lowered to a predetermined value (YES), each maintenance station 6 is brought into contact with the nozzle surface of the recording head 5 to suck ink around the nozzles and perform a maintenance process (step S8). The nozzle periphery is the inside of the nozzle and the surface of the nozzle plate. That is, the ink contained in the nozzles of the recording head is discharged, and the surface of the nozzle plate is wiped and cleaned. The ink discharged at this time is in a state where it cannot be cured even when irradiated with ultraviolet rays because oxygen and the radicalized photopolymerization initiator react. The ink in this state is only the ink existing at the interface in contact with the air in the vicinity of the nozzle, but the ink in the nozzle affects the ink in the convection. Therefore, although it depends on the time of exposure to oxygen in the vicinity of the nozzle, it affects the maximum thickness of the general nozzle plate (about 75 μm in this embodiment). That is, at least ink existing within the thickness of the nozzle plate may be discharged.

  After the maintenance process of the recording head 5 is completed, image recording is started (step S9). That is, the recording medium is transported by the transport mechanism, and the recording head 5 ejects ink droplets to the recording medium according to the image signal to form an image, and then passes under the UV lamp 7 to cure the ink. . The image is fixed on the recording medium.

  Next, it is determined whether or not to continuously record images (step S10). If the image is recorded as it is, the process returns to step S9 to continue recording. However, if the recording work is not continued (NO), it is determined whether the recording work is completed (step S11). If the determination is not completed but temporarily interrupted (NO), the recording head 5 is set in the standby state, and the UV lamp is kept on to supply oxygen to the vicinity of the head as described above (step S12). Return to S5. On the other hand, when the image formation is completed (YES), the UV lamp 7 is turned off and turned off (step S13), the main power of the apparatus is turned off (step S14), and a series of image recording processing routines are performed. Exit. In the present embodiment, for example, a D bulb manufactured by Fusion UV Systems Japan Co., Ltd. is suitable as the UV lamp. However, basically, the emission wavelength is in the range of 200 nm to 500 nm, and the same effect can be obtained particularly with a lamp near 360 nm. In this embodiment, the oxygen supply concentration is about 30%. However, even if oxygen is supplied at a concentration of 100% using an oxygen cylinder, only the oxygen concentration leaking from the head cover becomes a problem. Yes, even if oxygen having a concentration of 100% is supplied by an oxygen cylinder instead of the oxygen-enriched film, the same effect can be obtained.

  As described above, according to the present embodiment, oxygen is supplied to the vicinity of the nozzle during non-recording to inhibit the ink polymerization reaction in the vicinity of the nozzle, thereby preventing nozzle clogging and dot (landing) in image recording. A suitable recording without missing ink droplets) can be achieved.

Next, an image recording apparatus according to a second embodiment of the present invention will be described. FIG. 4 is a perspective view showing a conceptual configuration example of an ink jet printer.
In the first embodiment described above, an example in which the maintenance station is sandwiched between the recording heads and the one UV lamp is disposed on the downstream side is an example. A maintenance station and a UV lamp are arranged for each head.

  In the constituent parts shown in FIG. 4, parts that are the same as the constituent parts of the first embodiment described above are given the same reference numerals, and descriptions thereof are omitted.

  In the image forming apparatus according to the present embodiment, the image recording unit 2 causes the above-described four recording heads 5 (5K, 5C, 5M, and 5Y) to eject ink droplets of different colors, respectively, onto a transported recording medium. A color image is formed by landing.

  The image recording unit 2 includes a maintenance station 6 (6a, 6b, 6c, 6d) and a UV lamp 7 (7a) between the four recording heads 5 (5K, 5C, 5M, 5Y) in the X direction from the upstream side. , 7b, 7c, 7d) are arranged integrally with each other. These are covered with a head cover 8. As described above, the oxygen supply port 9 for supplying oxygen is provided above the side surface of the head cover 8, and oxygen is supplied from the oxygen supply system 10 or the oxygen cylinder so as to obtain a desired oxygen concentration around the head. Supplied. Further, it is attached to the side surface of the UV lamp 7c above the maintenance station 6c located substantially at the center of the head cover 8 of the oximeter 11. Of course, the mounting position is not limited to this.

  These maintenance stations 6 can be moved by a mechanism (not shown) as necessary underneath each recording head 5, that is, so as to face the nozzle surface, and perform maintenance processing. As the UV lamp 7, the aforementioned D bulb may be used. The ink is a radical polymerization type among ultraviolet curable inks. This ink is composed of a photopolymerization reactive resin, a photopolymerization initiator, a colorant and an auxiliary agent. An example of the recording medium is a film that does not soak ink. In this example, the supplied oxygen concentration is about 30% and the flow rate is about 2 L / min. Since the supplied oxygen is heavier than air, it moves in the head cover 8 so as to diffuse downward from the top of the recording head.

  According to the image recording apparatus configured as described above, since the UV lamp is provided on the downstream side of each recording head, the next downstream ink is ejected after the upstream ink is cured. Therefore, mixing between inks is eliminated, color blur does not occur, and a clear image can be recorded. In addition, since the ink ejected by one recording head is cured, the curing effect can be sufficiently realized even if the amount of UV irradiation per UV lamp is small. Further, in the case of image recording by only the recording head 5K, curing can be performed only by driving the adjacent UV lamp 7a.

  When the distance between the recording head 5 and the UV lamp 7 is reduced, there is a concern about the polymerization reaction in the vicinity of the nozzle due to reflection on the surface of the recording medium or the conveyor belt. However, as in the present invention, oxygen is supplied during non-recording. By inhibiting the polymerization reaction of the ink in the vicinity of the nozzle, nozzle clogging can be prevented, and a comfortable image recording without missing dots in the recorded image can be realized.

  Next, an image recording apparatus according to a third embodiment of the present invention will be described. FIG. 5 is a perspective view showing a conceptual configuration example of an ink jet printer. In the constituent parts shown in FIG. 5, the same reference numerals are assigned to the same parts as those in the first embodiment described above, and the description thereof is omitted.

  In this embodiment, a nitrogen supply system 26 is further added to the configuration of the first embodiment described above. The head cover 8 is provided with a nitrogen supply port 25 in addition to the oxygen supply port 9 and is connected to the nitrogen supply system 26 by piping such as a tube (not shown).

  The nitrogen supply port 25 opens upward in the direction of gravity with respect to the oxygen supply port 9. This is because oxygen has a heavier specific gravity than nitrogen, so that the nitrogen supply port can be replaced with oxygen more quickly.

  In this embodiment, the nitrogen supply system includes a nitrogen cylinder and a valve, and the concentration of nitrogen supplied by the nitrogen cylinder is about 100% and the flow rate is 2 L / min or more. The oxygen concentration meter 11 for managing the oxygen concentration is attached to the side surface of the recording head 5M above the maintenance station 6b, as in the first embodiment.

Next, image recording by the image forming apparatus according to the third embodiment will be described with reference to a flowchart shown in FIG.
First, the main power source (not shown) of the image recording apparatus main body is turned on and activated to initialize (step S21). Next, the oxygen supply system 10 starts supplying oxygen to the vicinity of the recording head 5 (step S22). It waits until the measured value by the oxygen concentration meter 11 reaches 25% (step S23).

  After that, when the measured value reaches 25% (YES), the UV lamp 7 is turned on and turned on to start light emission (step S24). The recording head is turned on for about 10 minutes until the lighting state is stabilized. The start of driving is waited (step S25). Meanwhile, the film is stopped and the supply of oxygen continues. At this time, the UV light is reflected on the film or the conveyor belt, and the reflected light (including the ultraviolet rays 20) reaches around the nozzles of the recording head. At this time, the ink near the interface between the air layer and the ink near the nozzle opening undergoes a start reaction due to the reflected light and generates radicals, but the oxygen supplied in advance reacts with the radicals and is consumed, The polymerization reaction does not proceed any further. During this standby time, oxygen is supplied in the same manner as in the first embodiment described above, so even if the ultraviolet light from the reflected UV lamp reaches the periphery of the nozzle of the recording head, the supplied oxygen remains. The ink does not cure by reacting with the generated radicals, and clogging does not occur.

  If the UV lamp 7 is stably operated by waiting for about 10 minutes (YES), the supply of oxygen is stopped immediately before the start of the recording operation, and the supply of nitrogen is started at the same time (step S26). It is determined whether or not the oxygen concentration has become 21% or less by this nitrogen substitution (step S27). Next, the maintenance stations 6 are moved below the respective recording heads 5 to perform recording head maintenance processing in the same manner as in the first embodiment (step S28). At the end of the maintenance process, the supply of nitrogen is stopped (step S29).

  Next, while moving the recording medium, the recording head 5 is driven in accordance with the image signal to eject ink and form an image on the recording medium. Further, after the image is recorded, UV light passes through the UV lamp 7. To cure the ink and fix the image on the recording medium (step S30).

  Further, it is determined whether or not image recording is continuously performed on the next recording medium (step S31). When the next image is continuously recorded on the recording medium (YES), the process returns to step S30 and recording is performed. Continue processing. On the other hand, if the image recording is not continued (NO), it is determined whether the image recording operation is completed (step S32). If the image recording operation is not completed and is temporarily interrupted (NO), the recording head is stopped during that time, but the UV lamp is kept on and oxygen is supplied to the vicinity of the recording head (step S33). ), The process returns to step S25. On the other hand, when the image recording is not interrupted but completed (YES), the UV lamp is turned off (step S34), and the main power supply of the apparatus is turned off (step S35).

  As described above, in a state where the image recording is not performed and the apparatus is activated and the UV lamp is lit, the ink is cured in the vicinity of the nozzle by supplying oxygen to a predetermined concentration in the vicinity of the nozzle. Prevents nozzle clogging, and at the start of image recording, by supplying nitrogen around the nozzle and replacing it with oxygen, it can immediately shift to image recording operation, and there is no missing dot due to nozzle clogging, Comfortable image recording can be realized.

  In this embodiment, nitrogen is introduced as a means for lowering the oxygen concentration. However, the present invention is not limited to this, and the same effect can be obtained even with air. In this case, it is only necessary to provide a fan, which eliminates the need for a nitrogen gas generator or a cylinder and simplifies the apparatus.

Next, an image recording apparatus according to the fourth embodiment of the present invention will be described.
Image recording by the image forming apparatus according to the fourth embodiment will be described with reference to the flowchart shown in FIG. The image forming apparatus according to the fourth embodiment is different in image recording operation from the image recording apparatus according to the third embodiment described above, but the apparatus configuration is the same, and the same reference numerals are given to the components. The description of the configuration is omitted.
First, after the main power source of the image recording apparatus main body is turned on to start and initialize (step S41), the oxygen supply system 10 starts supplying oxygen to the vicinity of the recording head 5 (step S42). Further, it waits until the measured value by the oximeter 11 reaches 25% (step S43). If the measured value reaches 25% (YES), the UV lamp 7 is turned on and lit to emit light. It starts (step S44) and waits for about 10 minutes until the lighting state is stabilized (step S45). As described above, during this standby, the ultraviolet rays irradiated from the UV lamp 7 and reflected by the recording medium and the conveying belt reach the periphery of the nozzles of the recording head, but the ink is prevented from curing by oxygen, Noise clogging does not occur.

  Thereafter, if the lighting state of the UV lamp 7 is stabilized (YES), the supply of oxygen is stopped (step S46), and the image recording apparatus shifts to a standby state for image recording. Immediately before the start of recording, the supply of oxygen is stopped, and the process waits for the oxygen concentration to fall to a predetermined value, for example, about 21% (step S47).

  Next, if the oxygen concentration falls to a predetermined value (YES), each maintenance station 6 is moved and brought into contact with the nozzle surface of the recording head 5 to suck up ink around the nozzle, which is the same as in the first embodiment. Maintenance processing is performed (step S48). After completion of the maintenance process for the recording head 5, image recording is started (step S49). In the image recording, the recording medium is conveyed by a conveying mechanism, and the recording head 5 ejects ink droplets onto the recording medium in accordance with the image signal to form an image, and then passes under the UV lamp 7 to make the ink. Is cured. The image is fixed on the recording medium.

  Next, it is determined whether or not to continuously record images (step S50). When image recording is to be continued (YES), the process returns to step S49 and image recording is performed in the same manner. However, when the image recording is not continued (NO), the recording head 5 is once set in the standby state, and oxygen is supplied to the vicinity of the head as described above in order to continue the lighting state of the UV lamp 7 (step S1). S51).

  Thereafter, it is determined whether or not the image recording operation is completed (step S52). If the image recording operation is not completed (NO), the process returns to step S45 to enter a recording standby state. If the image recording operation is completed (YES), after maintaining a predetermined time in this state (the UV lamp 7 is lit and oxygen is supplied) (step S53), The UV lamp 7 is turned off to stop irradiation (step S54), the main power supply of the apparatus is turned off (step S55), and a series of image recording processing routines is completed.

  As described above, in step S53, the UV lamp 7 is turned on and oxygen is supplied to radicalize the photoinitiator, react the oxygen with oxygen, and the thickness of the nozzle plate around the nozzle. The polymerization power of the ink in minutes is lost. Thereby, after the main power supply of the image recording apparatus is turned off, it is possible to prevent ink from being cured in the vicinity of the nozzles due to incidence of ultraviolet rays in natural light. This process prevents clogging of the nozzles by inhibiting the polymerization reaction of the ink in the vicinity of the nozzles by ultraviolet rays such as natural light when the image recording apparatus is stopped. No optimal image can be recorded.

Next, an image recording apparatus according to a fifth embodiment of the present invention will be described.
Image recording by the image forming apparatus according to the fifth embodiment will be described with reference to the flowchart shown in FIG. The image forming apparatus in the fifth embodiment is different in image recording operation from the image recording apparatus in the third embodiment described above, but the apparatus configuration is the same, and the same reference numerals are given to the components. The description of the configuration is omitted.

  First, the main power source (not shown) of the image recording apparatus main body is turned on and activated to perform initialization (step S61). Next, supply of oxygen to the vicinity of the recording head 5 is started by the oxygen supply system 10 (step S62). At this time, it waits until the measured value by the oxygen concentration meter 11 reaches 25% (step S63).

  Thereafter, if the measured value of the oxygen concentration reaches 25% (YES), the UV lamp 7 is turned on and lit to start light emission (step S64), and about 10 minutes until the lighting state is stabilized. The recording head drive start is waited (step S65).

  If the UV lamp 7 is stably operated by waiting for about 10 minutes (YES), the supply of oxygen is stopped immediately before the start of the recording operation, and the supply of nitrogen is started at the same time (step S66). It is determined whether or not the oxygen concentration is 21% or less by this replacement (step S67). Next, when the oxygen concentration becomes 21% or less (YES), the maintenance stations 6 are moved under the respective recording heads 5 to perform maintenance processing of the recording heads 5 in the same manner as in the first embodiment (step). S68).

  Next, while moving the recording medium, the recording head 5 is driven according to the image signal to eject ink droplets to form an image on the recording medium (step S69). After the image recording, when the recording medium passes under the UV lamp 7, UV light is irradiated to cure the ink, and the image is fixed on the recording medium.

  Further, it is determined whether or not to continuously record an image on the next recording medium (step S70). When the next image is continuously recorded on the recording medium (YES), the process returns to step S69 to record. Continue processing. On the other hand, when the image recording operation is not continuously performed (NO), the driving of the recording head is stopped, the lighting state of the UV lamp is maintained, and the supply of nitrogen to the vicinity of the recording head is stopped (step S71). ). Thereafter, it is determined whether or not the image recording operation is completed (step S72). If the image recording operation is not completed (NO), the supply of oxygen to the vicinity of the nozzle is started assuming that the operation is temporarily stopped ( Step S73) and the standby state of Step S65 is entered. On the other hand, when the image recording is completed, the UV lamp is turned off to stop the irradiation (step S74), the main power supply of the apparatus is turned off (step S75), and the series of sequence processing ends.

As described above, in a state where the image recording is not performed and the apparatus is activated and the UV lamp is lit, the ink is cured in the vicinity of the nozzle by supplying oxygen to a predetermined concentration in the vicinity of the nozzle. Prevents nozzle clogging, and at the start of image recording, by supplying nitrogen around the nozzle and replacing it with oxygen, it can immediately shift to image recording operation, and there is no missing dot due to nozzle clogging, Optimal image recording can be realized.
In this embodiment, nitrogen is introduced as a means for lowering the oxygen concentration. However, the present invention is not limited to this, and the same effect can be obtained even with air. In this case, it is only necessary to provide a fan, which eliminates the need for a nitrogen gas generator or a cylinder and simplifies the apparatus.

1 is a perspective view illustrating a conceptual configuration example of an image recording apparatus according to a first embodiment of the present invention. It is a figure which shows the example of 1 characteristic of UV lamp applied to the image recording device of 1st Embodiment. 3 is a flowchart for explaining image recording by the image forming apparatus according to the first embodiment. It is a perspective view which shows the conceptual structural example of the image recording device by 2nd Embodiment. It is a perspective view which shows the conceptual structural example of the image recording device by 3rd Embodiment. 10 is a flowchart for explaining image recording by an image forming apparatus according to a third embodiment. 10 is a flowchart for explaining image recording by an image forming apparatus according to a fourth embodiment. 10 is a flowchart for explaining image recording by an image forming apparatus according to a fifth embodiment. It is a figure which shows the cross-sectional structure of the nozzle opening vicinity in the conventional nozzle plate.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Conveyance mechanism, 2 ... Image recording part, 3a, 3b ... Roller, 4 ... Endless belt, 5, 5K, 5C, 5M, 5Y ... Recording head, 6, 6a, 6b, 6c, 6d ... Maintenance station, 7 ... Ultraviolet lamp unit (UV lamp), 8 ... head cover, 9 ... oxygen supply port, 10 ... oxygen supply system, 11 ... oxygen concentration meter.

Claims (12)

A recording head having a plurality of nozzles for ejecting ink droplets of a photocurable ink that is cured by irradiation of active light to a recording medium to be conveyed;
A light irradiator disposed on the transport downstream side of the recording head and irradiating the ink droplets landed on the recording medium with active light to cure the ink droplets;
An oxygen gas supply unit that supplies oxygen gas to the vicinity of the nozzle opening at the time of non-ejection to set the atmosphere in the vicinity of the nozzle opening of the recording head higher than the oxygen concentration of air;
An image recording apparatus comprising: In the image recording apparatus,
Furthermore, a nitrogen supply part for supplying nitrogen is provided near the opening of the nozzle,
The image recording apparatus according to claim 1, wherein an oxygen concentration in the vicinity of the nozzle opening is lowered before starting image recording by ink ejection from the nozzle. In the image recording apparatus,
And a maintenance unit for performing a cleaning process for removing the ink at the nozzle openings in the recording head,
2. The image recording apparatus according to claim 1, wherein an oxygen concentration in the vicinity of the nozzle opening is lowered and a cleaning process for the nozzle opening is performed before the start of image recording by ink ejection from the nozzle. In the image recording apparatus,
And a maintenance unit for performing a cleaning process for removing the ink at the nozzle openings in the recording head,
The oxygen gas supply to the vicinity of the nozzle opening is stopped to reduce the oxygen concentration and the cleaning process for the nozzle opening is performed before starting image recording by ink ejection from the nozzle. The image recording apparatus described. In the image recording apparatus,
Further, the entire recording head is covered from above, an oxygen gas supply port by the oxygen gas supply unit is provided at a position higher than the position of the nozzle, and the diffusion of the supplied oxygen gas to the outside is suppressed, The image recording apparatus according to claim 2, further comprising: a head cover that allows the oxygen concentration in the vicinity of the nozzle opening to be set to a desired concentration. [ In the head cover of the image recording apparatus,
6. The image recording apparatus according to claim 5, wherein the supply port of the nitrogen supply unit is provided above the supply port of the oxygen gas supply unit in the direction of gravity. In the image recording apparatus,
2. The image recording apparatus according to claim 1, wherein a radical polymerization reaction type ink is used as the photocurable ink, and the active light is an ultraviolet ray. A plurality of recording heads for recording an image on a recording medium by discharging ink droplets of different colors of photocurable ink from the respective nozzles, and a cleaning process for removing the ink in the nozzle openings of the recording heads are performed. An image recording unit arranged alternately along the conveyance direction of the recording medium with the maintenance unit,
A transport unit that transports a recording medium so as to pass in front of the nozzle;
A light irradiating unit disposed downstream of the image recording unit in the transport direction and irradiating active light that cures the ink droplets landed on the recording medium;
An oxygen gas supply unit that supplies oxygen gas to the vicinity of the nozzle opening at the time of non-ejection to set the atmosphere in the vicinity of the nozzle opening of the recording head higher than the oxygen concentration of air;
The entire recording head is covered from above, and an oxygen gas supply port by the oxygen gas supply unit is provided at a position higher than the position of the nozzle to prevent diffusion of the supplied oxygen gas, and oxygen in the vicinity of the nozzle opening. A head cover that allows the density to be set to a desired density;
An image recording apparatus comprising: A plurality of recording heads for recording an image on a recording medium by discharging ink droplets of different colors of photocurable ink from the respective nozzles, and a cleaning process for removing the ink in the nozzle openings of the recording heads are performed. A maintenance unit and a light irradiation unit that is disposed downstream in the transport direction for each recording head and irradiates active light that cures ink droplets that have landed on the recording medium form a set for each ink color, An image recording unit arranged along the conveyance direction of the recording medium;
A transport unit that transports a recording medium so as to pass in front of the nozzle;
An oxygen gas supply unit that supplies oxygen gas to the vicinity of the nozzle opening at the time of non-ejection to set the atmosphere in the vicinity of the nozzle opening of the recording head higher than the oxygen concentration of air;
The entire recording head is covered from above, and an oxygen gas supply port by the oxygen gas supply unit is provided at a position higher than the position of the nozzle to suppress diffusion of the supplied oxygen gas to the outside, and the nozzle opening A head cover that allows the oxygen concentration in the vicinity to be set to a desired concentration; and
An image recording apparatus comprising: A method of driving an image recording apparatus that discharges ink droplets of a photocurable ink that is cured by irradiation of actinic light from a plurality of nozzles onto a transported recording medium, and records an image,
An image recording apparatus driving method, wherein oxygen gas is supplied to the vicinity of the nozzle opening during non-ejection to set the atmosphere in the vicinity of the nozzle opening of the recording head higher than the oxygen concentration of air. In the driving method of the image recording apparatus,
Before starting image recording by ink ejection from the nozzle, the supply of the oxygen gas is stopped, the oxygen concentration in the vicinity of the nozzle opening is reduced to the air concentration, and then image recording is started. The method for driving an image recording apparatus according to claim 10. In the driving method of the image recording apparatus,
Before starting image recording by ink ejection from the nozzle, the oxygen gas supply is switched to nitrogen gas supply to reduce the oxygen concentration in the vicinity of the nozzle opening, and then image recording is started. The method for driving an image recording apparatus according to claim 10.

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