JP5029052B2 - Droplet discharge device - Google Patents

Description

  The present invention relates to a droplet discharge device.

  In an ink jet printer as a droplet discharge device, a sheet P is pressed by a charging member such as a charging roll against a conveying member such as a conveying belt and charged, or an alternating electric field is formed on the conveying member. An electrostatic attracting force is generated between the conveying member and the sheet is attracted to the conveying member. In this state, the paper is conveyed in the ink ejection area of the recording head, and an image is recorded on the paper (see, for example, Patent Documents 1 and 2). This increases the uniformity of the distance between the paper and the nozzle surface of the recording head (hereinafter referred to as TD: Throw Distance), improves the accuracy of the ink droplet landing position on the paper, and improves the image quality.

  In recent years, the TD is narrowed to 1 to 2 mm for the purpose of improving the accuracy of the ink droplet landing position on the paper, that is, for further improving the image quality. On the other hand, in order to improve the uniformity of TD, it is required to increase the electrostatic adsorption force between the paper and the conveying member. Also, the uniformity of TD depends on the environmental change such as temperature and humidity and the difference in the type of paper. In order to prevent the decrease in the electrostatic force, it is required to further increase the electrostatic attraction between the paper and the conveying member.

  For this reason, the separation failure of the paper from the conveyance member occurs, or the electrostatic adsorption force between the recording head 32 and the conveyance belt 28 becomes excessive, so that the conveyance belt 28 floats and contacts the recording head 32. In some cases, troubles occur (see FIG. 13).

  When the conveyance belt 28 comes into contact with the recording head 32, the conveyance belt 28 is stained with ink, ink is transferred from one recording head 32 to another recording head 32 via the conveyance belt 28, color mixing occurs, or the conveyance belt 28. There arises a problem that foreign matter adhered to the recording head 32 is mixed into the recording head 32 from the nozzles. In particular, a system that uses a transparent ink (reaction liquid) that mixes with yellow (Y), magenta (M), cyan (C), and black (K) inks to cause an agglomeration reaction, mainly for the purpose of improving image quality. In a so-called two-liquid system or a system in which different color inks such as K and Y are mixed and reacted (a so-called inter-ink reaction system), ink aggregation or discoloration occurs in the recording head 32, and recovery is not possible. It becomes possible.

  Here, as shown in FIG. 14, in the normal state, the contact portion between the charging roll 36 and the conveyance belt 28 has a high resistance, so that the movement of electric charge between the charging roll 36 and the conveyance belt 28 is caused by the charging roll. This is due to the discharge in the region of the minute gap between the belt 36 and the conveyor belt 28. However, when water droplets, ink droplets, or the like adhere to the contact portion between the charging roll 36 and the conveyor belt 28, the resistance is low, and the charge is moved in this portion. For this reason, as shown in the graph of FIG. 15, the surface potential on the conveyor belt 28 in the abnormal state increases as compared with the normal state.

On the other hand, when the charging roll 36 slips with respect to the conveying belt 28 due to the entry of foreign matter between the charging roll 36 and the conveying belt 28, the sheet conveying force is insufficient. Since a conveyance failure of the sheet occurs between the charging roll 36 and the conveyance belt 28, some countermeasure is required.
JP-A-10-193585 JP 2003-103857 A

  The present invention has been made in consideration of the above-described facts, and suppresses excessive charging of the conveying belt by the charging roll, and also suppresses the occurrence of conveyance failure of the recording medium between the charging roll and the conveying belt. With the goal.

  The liquid droplet ejection apparatus according to claim 1, a liquid droplet ejection head that ejects liquid droplets, a conveyance belt that holds a recording medium and conveys the recording medium facing the liquid droplet ejection head, and a recording medium that includes the recording medium A charging roll that electrostatically attracts to the transport belt; a liquid supply means that supplies a high resistance liquid having a volume resistivity higher than the liquid discharged from the droplet discharge head onto the transport belt; and a shaft of the charging roll Arranged in contact with the conveying belt at both ends in the direction, making the charging roll non-contact with the conveying belt, making the gap between the charging roll and the conveying belt less than the thickness of the recording medium, and And a spacer member having a recess formed in a contact portion with the conveyance belt.

  In the liquid droplet ejection apparatus according to the first aspect, the recording medium is held on the conveyance belt and conveyed while facing the liquid droplet ejection head, and the liquid droplet ejection head ejects the liquid droplets. Thereby, an image or the like is recorded on the recording medium. At this time, since the recording medium is charged by the charging roll and electrostatically attracted to the conveyance belt, the uniformity of the distance between the droplet discharge head and the recording medium is increased, and the landing position of the droplet on the recording medium is increased. Increases accuracy.

  Here, a high resistance liquid having a volume resistivity higher than that of the liquid discharged from the droplet discharge head is supplied onto the transport belt by the liquid supply means. For this reason, when the liquid, water droplet, etc. which are discharged from a droplet discharge head intervene between a charging roll and a conveyance belt, the fall of the electrical resistance between a charging roll and a conveyance belt is suppressed.

  In addition, since the charging roll is not in contact with the conveying belt by the spacer members disposed in contact with the conveying belt at both ends in the axial direction of the charging roll, the charging roll is not in contact with the conveying belt. All the movement of charges is due to discharge.

  Therefore, excessive charging of the conveyance belt by the charging roll can be suppressed.

  Further, the gap between the charging roll and the conveyance belt is made smaller than the thickness of the recording medium by the spacer member. Thereby, since the recording medium is pressed against the conveyance belt by the charging roll, the electrostatic adsorption force between the conveyance belt and the recording medium can be efficiently increased, and the adsorption force between the conveyance belt and the recording medium can be secured. .

  Moreover, the recessed part is formed in the contact part with the conveyance belt of a spacer member. For this reason, in the contact part of a spacer member and a conveyance belt, the excess high resistance liquid is hold | maintained by a recessed part.

  Therefore, since the occurrence of slippage of the spacer member with respect to the conveyance belt can be suppressed, it is possible to suppress the follow-up failure of the charging roll with respect to the conveyance belt, thereby preventing the occurrence of a conveyance failure of the recording medium between the charging roll and the conveyance belt. Can be suppressed.

The droplet discharge device according to claim 2 is the droplet discharge device according to claim 1, wherein the recess formed in the contact portion of the spacer member with the transport belt is a groove that makes one round along the circumferential direction. The droplet discharge device according to claim 3 is the droplet discharge device according to claim 2, wherein the spacer member is provided with a plurality of the grooves, The droplet discharge device according to claim 4 is a groove that makes one round along a circumferential direction, and the droplet discharge device according to claim 3 is the droplet discharge device according to claim 2 The groove formed in the spacer member has a spiral shape that is inclined downward from the central portion in the axial direction of the charging roll and the spacer member from the upstream side to the downstream side in the rotation direction of the spacer member. The droplet discharge device according to claim 5, wherein 2. The droplet discharge device according to claim 1, wherein the recess formed in the contact portion of the spacer member with the transport belt is a plurality of dimple-like recesses formed along the circumferential direction and the width direction. Features.

In the droplet discharge device according to claim 2, when the amount of the high resistance liquid (silicone oil or the like) becomes excessive between the spacer member and the conveyor belt, the excessive high resistance liquid is temporarily inside the groove. Since the liquid droplets are held on the surface and then reattached to the transport belt, fluctuations in the contact state between the spacer member and the transport belt can be suppressed. Since it is temporarily held inside the two or more grooves and then reattached to the conveyor belt, the variation in the contact state between the spacer member and the conveyor belt is greater than in the case where the groove is one. It can be effectively suppressed. In the droplet discharge device according to the fourth aspect, since the groove moves from the axial outer end side to the center side, the high resistance liquid staying at the contact portion between the spacer member and the transport belt is transferred to the center of the transport belt. The liquid droplet ejection apparatus according to claim 5, wherein the high-resistance liquid staying at the contact portion between the spacer member and the transport belt is temporarily held by the dimple-shaped recess. Therefore, fluctuations in the contact state between the spacer member and the conveyor belt can be suppressed.

  Since the present invention has the above-described configuration, it is possible to suppress excessive charging of the conveyance belt by the charging roll and to suppress the occurrence of paper conveyance failure between the charging roll and the conveyance belt.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The rotation direction of the conveyor belt (hereinafter referred to as belt rotation direction) is indicated by an arrow X in the figure, and the width direction of the conveyor belt (hereinafter referred to as belt width direction) is indicated by an arrow Y in the figure.

  FIG. 1 shows an ink jet recording apparatus 12 of the present embodiment. A paper feed tray 16 is provided in the lower part of the casing 14 of the ink jet recording apparatus 12, and the sheets P stacked in the paper feed tray 16 can be taken out one by one by a pickup roll 18. The taken paper P is transported by a plurality of transport roller pairs 20 constituting a predetermined transport path 22.

  Above the paper feed tray 16, an endless transport belt 28 is stretched around a drive roll 24 and driven rolls 26 and 27. The driving roll 24 and the driven roll 26 are disposed substantially horizontally, and a driven roll 27 is disposed below the driving roll 24 and the driven roll 26.

  A recording head array 30 is disposed above the conveyor belt 28 and faces a flat portion 28 </ b> F of the conveyor belt 28 between the drive roll 24 and the driven roll 26. This opposed area is an ejection area SE where ink droplets are ejected from the recording head array 30. The paper P transported in the transport path 22 is held by the transport belt 28 and reaches the discharge area SE, and ink droplets corresponding to the image information are attached from the recording head array 30 while facing the recording head array 30. The

  In this embodiment, the recording head array 30 has a long shape in which the effective recording area is equal to or larger than the width of the paper P (the length in the direction orthogonal to the transport direction), and is yellow (Y) and magenta (M). , Cyan (C), and Black (K), four ink jet recording heads (hereinafter referred to as recording heads) 32 corresponding to the four colors are arranged along the transport direction, so that a full color image can be recorded. ing.

  Each recording head 32 is driven by a head drive circuit (not shown). The head drive circuit has a configuration in which, for example, the ejection timing of ink droplets and the ink ejection port (nozzle) to be used are determined according to image information and a drive signal is sent to the recording head 32.

  The recording head array 30 may be stationary in a direction orthogonal to the transport direction. However, if the recording head array 30 is configured to move as necessary, an image with higher resolution can be obtained by multi-pass image recording. Can be recorded, or the trouble of the recording head 32 can be prevented from being reflected in the recording result.

  Four maintenance units 34 corresponding to the respective recording heads 32 are arranged on both sides of the recording head array 30. As shown in FIG. 2, when performing maintenance on the recording head 32, the recording head array 30 is moved upward, and the maintenance unit 34 moves into the gap formed between the conveyance belt 28 and enters. . Then, a predetermined maintenance operation (suction, wiping, capping, etc.) is performed while facing the nozzle surface.

  Further, an ink tank 35 for storing ink of each color is disposed above the recording head array 30. Each recording head 32 is connected to each ink tank 35.

  As shown in FIG. 3, a charging roll 36 connected to a power source 38 is disposed on the upstream side in the transport direction of the recording head array 30. The charging roll 36 is driven while sandwiching the conveyance belt 28 and the paper P with the driven roll 26, and presses the paper P against the conveyance belt 28. At this time, since a predetermined potential difference is generated between the grounded follower roll 26, it is possible to charge the paper P and electrostatically attract the paper P to the transport belt 28.

  A peeling plate 40 is disposed on the downstream side of the recording head array 30 in the transport direction, and the paper P is peeled from the transport belt 28. As shown in FIG. 1, the peeled paper P is transported by a plurality of discharge roller pairs 42 constituting a discharge path 44 on the downstream side in the transport direction of the peeling plate 40, and is discharged on the top of the housing 14. It is discharged to the tray 46.

  Further, as shown in FIG. 3, a belt cleaning unit 48 is disposed below the peeling plate 40. The belt cleaning unit 48 is in contact with a portion of the transport belt 28 wound around the drive roll 24 and scrapes off the ink and the like adhering to the transport belt 28, and is scraped off from the transport belt 28 by the blade 49. And a collection box 51 for collecting ink and the like.

  An oil application unit 62 is disposed below the driven roll 26. The oil application unit 62 includes an oil application roll 64 as liquid supply means rotatably supported by a frame (not shown). The oil application roll 64 is in contact with a portion of the conveyor belt 28 that is wound around the driven roll 26 and rotates following the conveyor belt 28. The oil application roll 64 is a roll capable of absorbing a liquid formed of a porous material such as polyethylene or urethane, impregnated with silicone oil, and applies the silicone oil to the conveyor belt 28.

  The oil application roll 64 may be a drive roll. In this case, the oil application roll 64 can be prevented from slipping with respect to the transport belt 28. Further, as a means for applying a liquid having a high volume resistivity such as silicone oil (hereinafter referred to as a high resistance liquid) to the conveying belt 28, other means such as a web can be applied.

The conveyor belt 28 is formed of a resin such as PET, PI, PA, or PC, or a rubber material such as CR, NBR, HNBR, or urethane rubber, and has a surface resistance value of 10 ⁸ to 10 ¹³ Ω · cm, volume resistance. The one with a rate of 10 ⁹ to 10 ¹⁴ Ω · cm is used.

The charging roll 36 has an elastic layer in which a conductivity imparting material is dispersed on the outer peripheral surface of a rod-like or pipe-like shaft made of aluminum, stainless steel or the like, and has a volume resistivity of 10 ⁴ to 10 ^8. A roll having a diameter of 10 to 25 mm adjusted to about Ω · cm can be used.

  The material of the elastic layer may be a resin material such as urethane resin, thermoplastic elastomer, epichlorohydrin rubber, ethylene-propylene-diene copolymer rubber, acrylonitrile-butadiene copolymer rubber, polynorbornene rubber, or a single material. Usable as a mixture, urethane foam resin is desirable.

  In addition, the surface of the elastic layer may be covered with a water-repellent skin layer having a thickness of 5 to 100 μm. In that case, the property change (volume resistance) due to the interaction with the high resistance liquid, the adhesion of ink mist, etc. Rate change).

Further, as described above, silicone oil is used as the high resistance liquid, and water-based ink is used as the ink. Here, the high resistance liquid is preferably a liquid having a volume resistivity of 10 ¹² Ω · cm or more, more preferably a liquid having a volume resistivity of 10 ¹⁴ Ω · cm or more, but at least a liquid having a higher volume resistivity than ink. Furthermore, a liquid having a volume resistivity equal to or higher than that of the conveyor belt 28 is desirable.

  High-resistance liquids are suitable for repelling ink. For water-based inks, in addition to silicone oil, higher fatty acids such as oleic acid and linoleic acid, dibutyl phthalate, diisodecyl phthalate, and dibutyl maleate Water-repellent liquids such as water-insoluble alcohols such as n-decanol and dimethylbutanol, fluorine oil, mineral oil, and vegetable oil can be used. These may be used singly or a plurality of types may be mixed and used as long as they can be mixed uniformly.

In order to stabilize the application of the high resistance liquid to the transport belt 28, the kinematic viscosity of the high resistance liquid is desirably in the range of 10 to 10 ⁵ mm ² / s, and is preferably 50 to 10 ² mm ² / s. It is more desirable to be in the range.

  In addition, if the coating thickness of the high-resistance liquid is too thick, oil may permeate the paper P and the paper P will repel ink, causing image quality degradation when printing on the back side, etc. On the contrary, if the coating thickness of the high resistance liquid is too thin, the coating layer cannot be stably formed. Therefore, it is necessary to set the coating thickness of the high resistance liquid within an appropriate range. An appropriate range of the coating thickness of the high resistance liquid is 1 nm to 20 μm, but 10 nm or more is desirable for stably forming the coating layer, and the adhesion of the high resistance liquid to the paper P is reduced. For this purpose, 2 μm or less is desirable.

  Further, the color of the high resistance liquid is preferably colorless and transparent in order to reduce the influence on the image quality when adhering to the paper P.

  The high resistance liquid needs to be non-volatile at room temperature. Specifically, the vapor pressure is 13.33 Pa or less at 25 ° C. Further, the high resistance liquid needs to have a property that is not compatible with an aqueous liquid such as ink. Specifically, the solubility in an aqueous liquid such as ink is 0.1 wt% or less at normal temperature (25 ° C.).

Further, the surface tension of the high resistance liquid is preferably 30 mN / m or less, and more preferably 25 mN / m or less. However, since the high resistance liquid needs to spread on the conveyor belt 28, the relationship of the following formula (1) is satisfied. is necessary. However, the surface tension of the coating layer is γ ₀ , and the critical surface tension γ _b of the conveyor belt 28 is set. The critical surface tension is the relationship between the surface tension of various liquids and the contact angle θ of the solid surface, when cos θ is corrected to 1 (that is, when the contact angle of the liquid with respect to the solid surface becomes 0 °). Refers to the surface tension. In general, a solid surface wets well with a liquid having a surface tension smaller than the critical surface tension of the surface.

γ ₀ <γ _b (1)

Further, in order to give the high resistance liquid water repellency, the relationship of the following formula (2) is required. However, the surface tension of the ink I is γ _i .

γ ₀ <γ _i (2)

  Further, as shown in FIGS. 4 and 5, the charging roll 36 is supported by a support mechanism 52. The support mechanism 52 includes a frame 54, a pair of bearings 56, and a pair of compression coil springs (biasing members) 58.

  The frame 54 is supported by a frame (not shown) of the ink jet recording apparatus 12 on the upper side of the charging roll 36, extends in the longitudinal direction in the axial direction of the charging roll 36, and is bent at both ends in the longitudinal direction toward the conveying belt 28 at a substantially right angle. ing. The frame 54 has a U-shaped elongated hole 54A extending from both ends in the longitudinal direction toward the bent portion. Each bearing 56 is fitted in each elongated hole 54A so as to be slidable along the longitudinal direction of each elongated hole 54A, and can rotate one end or the other end in the axial direction of the rotating shaft 36A of the charging roll 36. I support it.

  Further, a boss 54B extending toward the opening is formed at the deepest portion of the long hole 54A, and a boss 56A facing the boss 54B is formed on the bearing 56, and both end portions of the compression coil spring 58 are The boss 54B and the boss 56A are fitted. For this reason, the charging roll 36 is urged toward the conveying belt 28 by the compression coil spring 58. Further, stoppers 59 are provided at both ends in the longitudinal direction of the frame 54 to block the opening of the long hole 54A and prevent the bearing 56 from coming out of the long hole 54A.

  Also, spacer members 60, which are annular members having a larger diameter than the roll portion 36B, are attached to both axial ends of the roll portion 36B of the charging roll 36. The spacer member 60 is a member having insulating properties and high rigidity that is not deformed by pressing, and is formed of a resin such as POM, PMMA, or PET, or an insulated metal or ceramic. For this reason, only the spacer member 60 is pressed against the conveying belt 28 by the urging force of the compression coil spring 58, and the roll portion 36B of the charging roll 36 and the conveying belt 28 are not in contact with each other. Further, current does not flow from the spacer member 60 to the transport belt 28.

  Here, the gap between the roll part 36 </ b> B and the conveying belt 28 is less than the thickness of the paper P (preferably the thickness of the paper P × 0.6 or less).

  In addition, a V-groove 61 as a recess is formed at the center in the width direction (axial direction of the spacer member 60) of the peripheral surface 60A of the spacer member 60. The V groove 61 makes one round along the circumferential direction of the spacer member 60.

  Next, the operation in this embodiment will be described.

  Silicone oil is applied to the transport belt 18 by the oil application roll 64 on the downstream side of the blade 49 in the belt rotation direction and on the downstream side of the charging roll 36 in the belt rotation direction.

Here, the silicone oil is insoluble in an aqueous liquid, has a surface tension of, for example, 20.8 [mN / m], a surface tension of the aqueous ink (for example, 30 [mN / m]), water It is lower than the surface tension (for example, 70 [mN / m]). Silicone oil is a liquid having a high resistance and a high insulating property such as a volume resistivity of 10 ¹⁴ Ω · cm or more.

  For this reason, as shown in FIGS. 6A and 6B, mist-like ink generated when the recording head 32 ejects ink droplets or water-based liquid W such as water due to condensation is formed on the conveying belt 28. In the case where it adheres, the silicone oil wets and spreads on the aqueous liquid W. That is, a silicone oil layer (hereinafter referred to as a coating layer) O covering the aqueous liquid W is formed on the transport belt 28. Since silicone oil has a high volume resistivity and a high insulating property, the coating layer O functions as an insulating layer.

  By the way, as shown in FIGS. 7A and 7B, when the paper P is interposed between the charging roll 36 and the transport belt 28, a minute gap region is formed between the charging roll 36 and the paper P. The electric charge is moved by the electric discharge in the paper, and the electric charge is moved between the paper P and the transport belt 28 at the contact portion between the paper P and the transport belt 28, but the contact portion between the paper P and the transport belt 28. There is a proportional relationship between the amount of charge movement in the sheet and the amount of charge discharged between the charging roll 36 and the paper P.

  For this reason, as shown in FIG. 7A, the lower the resistance of the contact portion between the paper P and the conveyor belt 28, the greater the amount of moving charge between the charging roll 36 and the paper P, causing abnormal charging. It becomes easy to do. However, as shown in FIG. 7B, in this embodiment, since the coating layer O having high resistance and high insulation is formed between the paper P and the transport belt 28, the charging roll 36 and the paper An increase in the amount of mobile charge with P can be suppressed, and abnormal charging can be prevented.

  Here, the volume resistivity of the high-resistance liquid is higher than that of the ink and is equal to or higher than that of the transport belt 28. By making the volume resistivity of the high resistance liquid higher than that of the ink, the contact between the paper P and the conveyance belt 28 when an aqueous liquid such as water or ink is interposed between the charging roll 36 and the conveyance belt 28. It is possible to suppress a decrease in electrical resistance at the portion. As a result, the movement of charges at the contact portion between the paper P and the conveying belt 28 can be suppressed, so that excessive charge movement from the charging roll 36 to the paper P can be suppressed, and an abnormal increase in the charging potential of the paper P can be suppressed. it can.

  In addition, by making the volume resistivity of the high resistance liquid equal to or greater than the volume resistivity of the transport belt 28, the electrical resistance at the contact portion between the paper P and the transport belt 28 is always reduced by water or liquid such as ink. Since it is equal to or greater than that when there is no interposition, the abnormal increase in the charging potential of the paper P can be further suppressed.

  Further, only the spacer members 60 provided at both ends in the axial direction of the charging roll 36 are brought into pressure contact with the conveying belt 28, and the roll portion 36B of the charging roll 36 and the conveying belt 28 are not in contact with each other and are conveyed from the spacer member 60. Since the current does not flow to the belt 28, as shown in FIG. 8, the movement of charges between the roll portion 36B and the transport belt 28 is all due to the discharge, and the surface potential of the transport belt 28 is reduced. Stabilize. That is, since the surface potential of the conveyance belt 28 can be prevented from rising abnormally, the electrostatic force between the conveyance belt 28 and the recording head 32 can be prevented from rising abnormally.

  From the above, it is possible to increase the charge amount of the conveyance belt 28 and narrow the TD while preventing contact between the conveyance belt 28 and the nozzle surface 32N of the recording head 32. The landing accuracy can be further improved, so that the image quality can be further improved.

  Further, since it is not necessary to increase the tension applied to the conveyance belt 28 in order to prevent the conveyance belt 28 from lifting, wrinkles generated in the conveyance belt 28 can be suppressed, and the conveyance performance of the paper P by the conveyance belt 28 can be improved. . Further, since the charging roll 36 is driven to rotate and the discharge location of the roll portion 36B is constantly moving, there is little discharge deterioration. Further, since the gap between the roll portion 36B and the conveyor belt 28 is made constant by the spacer member 60 regardless of the variation in the thickness of the conveyor belt 28, the surface potential of the conveyor belt 28 is stabilized.

  Further, the gap between the roll unit 36B and the conveyance belt 28 is less than the thickness of the paper P, and the paper P is pressed against the conveyance belt 28 by the roll unit 36B of the charging roll 36. The electrostatic adsorption force between the paper P and the conveyance belt 28 can be increased efficiently, and the adsorption force between the conveyance belt 28 and the paper P can be secured.

  Further, since the charging roll 36 is not in contact with the transport belt 28 and is in contact with only the paper P, the wear deterioration of the charging roll 36 can be reduced.

  By the way, the silicone oil on the transport belt 28 does not adhere to the charging roll 36 that is not in contact with the transport belt 28, and does not stay between the transport belt 28 and the charging roll 36. However, the silicone oil on the conveyor belt 28 adheres to the spacer member 60 that contacts the conveyor belt 28, and depending on conditions such as the contact force between the spacer member 60 and the conveyor belt 28, the spacer member 60 and the conveyor belt 28 Stay between.

  Here, a V-groove 61 that makes one turn along the circumferential direction of the spacer member 60 is formed in the center in the width direction of the circumferential surface 60 </ b> A of the spacer member 60. For this reason, when the silicone oil stays between the spacer member 60 and the conveyor belt 28 and the amount of silicone oil between the spacer member 60 and the conveyor belt 28 becomes excessive, the excess silicone is retained. The oil flows into the V groove 61 and is temporarily held by the V groove 61. Then, the silicone oil held in the V-groove 61 is reattached to the conveyor belt 28 and finally scraped off by the blade 49.

  Therefore, variation in the contact state between the spacer member 60 and the conveyance belt 28 can be suppressed, and the occurrence of slippage of the spacer member 60 with respect to the conveyance belt 28 can be suppressed. Accordingly, it is possible to suppress the charging roll 36 from causing a follow-up failure with respect to the conveyance belt 28, and thus it is possible to suppress the clogging of the paper P between the charging roll 36 and the conveyance belt 28, so-called occurrence of conveyance jam. .

  Next, a modified example of the spacer member 60 will be described.

  FIG. 9 shows a charging roll 36 that includes spacer members 70 according to a first modification of the spacer member 60 at both ends in the axial direction. As shown in this figure, two (a plurality of) V-grooves 61 are formed on the circumferential surface 70A of the spacer member 70 at predetermined intervals along the width direction.

  Next, the operation of this embodiment will be described.

  When silicone oil stays between the spacer member 70 and the conveyor belt 28 and the amount of silicone oil between the spacer member 70 and the conveyor belt 28 becomes excessive, excess silicone oil is It flows into the two V grooves 61 and is temporarily held by the two V grooves 61.

  As a result, the amount of silicone oil retained by the V-groove 61 is increased as compared with the case where the spacer member 60 is provided on the charging roll 36, so that the variation in the contact state between the spacer member 70 and the conveying belt 28 is further increased. It can suppress and it can suppress further that the spacer member 70 raise | generates a slip with respect to the conveyance belt 28. FIG. Therefore, it is possible to further suppress the charging roller 36 from causing a follow-up failure with respect to the conveyance belt 28, thereby further suppressing the occurrence of the conveyance jam of the paper P between the charging roll 36 and the conveyance belt 28. it can.

  Further, FIG. 10 shows a charging roll 36 provided with spacer members 80 according to a second modification of the spacer member 60 at both axial ends. As shown in this figure, a V-shaped groove 81 as a spiral concave portion continuous in the width direction of the spacer member 80 is formed on the peripheral surface 80A of the spacer member 80.

  The V-groove 81 is inclined from the center side in the axial direction of the charging roll 36 and the spacer member 80 to the end side from the upstream side to the downstream side in the rotation direction of the charging roll 36 and the spacer member 80 (in the direction of arrow A in the figure). ing.

  Next, the operation of this embodiment will be described.

  During rotation of the conveyance belt 28 and the charging roll 36, the V-groove 81 moves from the axial outer end side to the center side at the contact portion between the spacer member 80 and the conveyance belt 28. For this reason, the silicone oil staying at the contact portion between the spacer member 80 and the conveyor belt 28 is swept (moved) from the outer end side in the axial direction to the center side by the V-groove 81, and the spacer member 80 and the conveyor belt. It is discharged from the abutting portion with 28.

  Further, FIG. 11 shows a charging roll 36 provided with spacer members 90 according to a third modification of the spacer member 60 at both axial ends. As shown in this figure, a U-shaped groove 91 is formed on the peripheral surface 90 </ b> A of the spacer member 90 as a spiral concave portion continuous in the width direction of the spacer member 90.

  The U-groove 91 is the same as the above-described V-groove 81 in the axial direction center of the charging roll 36 and the spacer member 90 from the upstream side to the downstream side in the rotation direction of the charging roll 36 and the spacer member 90 (direction of arrow A in the figure). It is inclined from the side to the outer end side. Therefore, the same operation and effect as when the above-described spacer member 80 is provided on the charging roll 36 can be obtained.

  FIG. 12 shows a charging roll 36 provided with spacer members 100 according to a fourth modification of the spacer member 60 at both axial ends. As shown in this figure, a plurality of dimple-like recesses 101 are formed on the circumferential surface 100A of the spacer member 100 along the circumferential direction and the width direction.

  Next, the operation of this embodiment will be described.

  Silicone oil staying between the spacer member 100 and the conveyor belt 28 flows into the recess 101 and is temporarily held by the recess 101. As a result, fluctuations in the contact state between the spacer member 100 and the transport belt 28 can be suppressed, and slippage of the spacer member 100 with respect to the transport belt 28 can be suppressed.

  In the present embodiment, the present invention has been described by taking an ink jet recording apparatus as an example. However, the present invention is not limited to an ink jet recording apparatus, and the present invention is not limited to an ink jet recording apparatus. The present invention can be applied to a general liquid droplet ejection apparatus for various industrial uses, such as production of an EL display panel formed by discharging an organic EL solution onto a substrate.

  In addition, the “recording medium” that is a target of image recording in the droplet discharge device of the present invention includes a wide range of objects as long as the droplet discharge head discharges droplets. Accordingly, the recording medium includes recording paper, an OHP sheet, and the like, but also includes, for example, a polymer film.

  Furthermore, in the present embodiment, the present invention has been described by taking an inkjet recording head that is longer than the width of the paper P as an example. However, the present invention is not limited thereto, and for example, an inkjet recording head that is shorter than the width of the paper P is used. The present invention can also be applied to a configuration in which the sheet P is moved in the width direction.

1 is a side view illustrating an outline of an ink jet recording apparatus according to an embodiment of the present invention. 1 is a side view illustrating an outline of an ink jet recording apparatus according to an embodiment of the present invention. It is a side view showing the outline of the printing part of the ink jet recording device of one embodiment of the present invention. 1 is a perspective view illustrating a charging roll provided in an ink jet recording apparatus according to an embodiment of the present invention. 1 is a front view showing a charging roll provided in an ink jet recording apparatus according to an embodiment of the present invention. FIGS. 2A and 2B are enlarged side sectional views showing a conveyance belt provided in the ink jet recording apparatus according to the embodiment of the present invention. FIGS. (A) and (B) are side views schematically showing the state of electric charge between a charging roll and a conveyor belt provided in the ink jet recording apparatus of one embodiment of the present invention. FIG. 3 is a side view schematically illustrating a state of electric charge between a charging roll and a conveyance belt provided in the ink jet recording apparatus according to the embodiment of the present invention. It is a front view which shows the 1st modification of the charging roll with which the inkjet recording device of one Embodiment of this invention was equipped. It is a front view which shows the 2nd modification of the charging roll with which the inkjet recording device of one Embodiment of this invention was equipped. It is a front view which shows the 3rd modification of the charging roll with which the inkjet recording device of one Embodiment of this invention was equipped. It is a front view which shows the 4th modification of the charging roll with which the inkjet recording device of one Embodiment of this invention was equipped. It is a side view which shows typically the behavior of the conveyance belt in the conventional inkjet recording device. It is a side view which shows typically the mode of the discharge between the charging roll and conveyance belt in an inkjet recording device. It is a graph which shows the relationship between the applied voltage to the charging roll in an inkjet recording device, and the surface potential on a conveyance belt.

Explanation of symbols

12 Inkjet recording device (droplet ejection device)
28 Conveying belt 32 Inkjet recording head (droplet ejection head)
36 Charging roll 60 Spacer member 61 V groove (recess)
64 Oil application roll (liquid supply means)
66 Charging roll (charging means)
70 Spacer member 80 Spacer member 81 V groove (concave, spiral groove)
90 Spacer member 91 U groove (recess, spiral groove)
100 Spacer member 101 Concavity P Paper (recording medium)

Claims (5)

A droplet discharge head for discharging droplets;
A conveying belt that holds the recording medium and conveys the recording medium to face the droplet discharge head;
A charging roll for electrostatically attracting a recording medium to the transport belt;
Liquid supply means for supplying a high resistance liquid having a higher volume resistivity than the liquid discharged from the droplet discharge head onto the transport belt;
The charging roll is disposed at both axial ends of the charging roll so as to be in contact with the conveying belt, the charging roll is not in contact with the conveying belt, and the gap between the charging roll and the conveying belt is less than the thickness of the recording medium. And a spacer member having a recess formed in a contact portion with the conveyor belt;
A droplet discharge apparatus comprising: The droplet discharge device according to claim 1, wherein the concave portion formed in the contact portion of the spacer member with the transport belt is a groove that makes one round along the circumferential direction . The droplet discharge device according to claim 2, wherein a plurality of the grooves are provided in the spacer member. The groove formed in the spacer member is a spiral groove that is inclined downward from the axial center to the end of the charging roll and the spacer member from the upstream side to the downstream side in the rotation direction of the spacer member. The droplet discharge device according to claim 2. The droplet discharge device according to claim 1, wherein the recess formed in the contact portion of the spacer member with the transport belt is a plurality of dimple-shaped recesses formed along the circumferential direction and the width direction.

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