JP4678216B2 - Droplet discharge head and droplet discharge apparatus - Google Patents

Description

  The present invention relates to a droplet discharge head and a droplet discharge device.

  An ink jet recording apparatus is of a type in which ink is filled in a pressure chamber, the pressure chamber is expanded / contracted by applying a voltage according to image information to a piezoelectric element, and ink droplets are ejected from nozzles communicating with the pressure chamber. is there.

  In general, the characteristics of the piezoelectric element deteriorate depending on the environment. That is, in a high humidity environment, the characteristics of the piezoelectric element often deteriorate over time. This is considered to be because water vapor is electrolyzed at the electrode portion of the piezoelectric element, and hydrogen is generated to reduce the piezoelectric element.

On the other hand, Patent Document 1 describes an ink jet recording head in which an inert gas is sealed in a cap fixed to a flow path forming substrate. Patent Document 1 describes an oxidizing gas as an example of an inert gas. Gas is mentioned , and this oxidizing gas can prevent the piezoelectric element from being reduced.

However, in this configuration, since the concentration of the oxidizing gas in the case decreases with time, the reduction of the piezoelectric element over a long period cannot be prevented.
JP-A-10-305578

  In consideration of the above facts, an object of the present invention is to obtain a droplet discharge head capable of preventing the reduction of the piezoelectric element over a long period of time and a droplet discharge device including the droplet discharge head.

According to the first aspect of the present invention, there is provided a droplet discharge head that expands and contracts the pressure chamber by applying a voltage to the piezoelectric element and discharges the liquid in the pressure chamber as a droplet from the nozzle, and the piezoelectric element is disposed therein. A case that forms a predetermined space between the piezoelectric element and a portion of the case in a direction in which the anode is inside the case and the cathode is outside the case. And a solid electrolyte membrane capable of supplying a regulated gas having a low humidity and a high oxygen concentration into the case and capable of relieving a pressure difference between the inside and outside of the case by deformation .

Therefore, a gas with low humidity and high oxygen concentration is supplied from the solid electrolyte membrane into the case. Thereby, it can prevent that a piezoelectric element is reduce | restored over a long period of time.

  It should be noted that the “predetermined space” formed between the case and the piezoelectric element may be a space having a sufficient capacity that does not inhibit the vibration of the piezoelectric element.

In addition, since the adjustment gas is supplied using the solid electrolyte membrane, the adjustment gas can be generated efficiently with a small and simple configuration.

Furthermore, the solid electrolyte membrane, that make up a part of the case.

Thereby, the droplet discharge head can be further reduced in size. Specific placement of the solid electrolyte membrane, an anode of the prior SL solid electrolyte membrane inside of the case, are arranged such cathode is on the outside of the case.
In addition, the solid electrolyte membrane can relieve the pressure difference inside and outside the case by deformation. This eliminates the need to form an atmosphere communication hole in the case for communicating the inside with the atmosphere.

According to a second aspect of the present invention, in the first aspect of the invention, a humidity sensor is provided in the case, and the solid electrolyte membrane can be applied with a voltage based on the humidity measured by the humidity sensor. It is characterized by that.

Therefore, if the humidity in the case is measured by the humidity sensor and the voltage is applied to the solid electrolyte membrane when the humidity exceeds a certain value, the inside of the case can be efficiently and reliably maintained at a low humidity.

According to a third aspect of the present invention, the oxygen concentration sensor is provided in the case according to the first or second aspect of the invention, and the solid electrolyte membrane is based on the oxygen concentration measured by the oxygen concentration sensor. Before the voltage can be applied .

Therefore, if the oxygen concentration in the case is measured by the oxygen concentration sensor and the voltage is applied to the solid electrolyte membrane when the oxygen concentration is below a certain value, the case can be efficiently and reliably maintained at a high oxygen concentration.

According to a fourth aspect of the present invention, the liquid droplet ejection head according to any one of the first to third aspects is provided.

Since the droplet discharge head according to any one of claims 1 to 3 is provided, the piezoelectric element can be prevented from being reduced over a long period of time.

  Since the present invention is configured as described above, the piezoelectric element can be prevented from being reduced over a long period of time.

FIG. 1 shows an ink jet recording apparatus 112 according to a reference example of the present invention. A paper feed tray 116 is provided in the lower part of the casing 114 of the ink jet recording apparatus 112, and the sheets P stacked in the paper feed tray 116 can be taken out one by one by a pickup roll 118. The taken paper P is transported by a plurality of transport roller pairs 120 constituting a predetermined transport path 122. Hereinafter, the “conveying direction” simply refers to the conveying direction of the paper P that is a recording medium, and the “upstream” and “downstream” refer to upstream and downstream in the conveying direction, respectively.

  Above the paper feed tray 116, an endless transport belt 128 stretched between a drive roll 124 and a driven roll 126 is disposed. A recording head array 130 is disposed above the conveyor belt 128 and faces the flat portion 128F of the conveyor belt 128. This opposed area is an ejection area SE where ink droplets are ejected from the recording head array 130. The sheet P transported along the transport path 122 is held by the transport belt 128 and reaches the discharge area SE, and ink droplets corresponding to image information are attached from the recording head array 130 while facing the recording head array 130. The

  Then, by rotating the paper P while being held by the transport belt 128, it is possible to perform image recording by so-called multi-pass by allowing the paper P to pass through the ejection region SE a plurality of times. Of course, the sheet P may be passed through the ejection region SE only once, and image recording may be performed in a so-called one pass.

For example, the transport belt 128 is made of a semiconductive polyimide material (surface resistance value 10 ¹⁰ to 10 ¹³ Ω / □, volume resistance value 10 ⁹ to 10 ¹² Ω · cm), thickness 75 μm, width 380 mm, circumference What was shape | molded in length 1000mm can be used. Moreover, as the drive roll 124 and the driven roll 126, as an example, a φ50 mm SUS roll can be used.

  Instead of the conveyor belt 128, for example, a recording medium (paper P) may be sucked and held on the outer periphery of a conveyance roller formed in a cylindrical shape or a columnar shape and rotated. However, since the flat portion 128F is formed when the conveyor belt 128 is used as in the present embodiment, the recording head array 130 can be disposed corresponding to the flat portion 128F, which is preferable.

  In this embodiment, the recording head array 130 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 a so-called FWA (Full Width Array). Yes. In the recording head array 130, four inkjet recording heads 132 corresponding to four colors of yellow (Y), magenta (M), cyan (S), and black (K) are arranged along the transport direction. Therefore, a full color image can be recorded.

  Each inkjet recording head 132 is controlled by recording head control means (not shown). The recording head control means, for example, determines the ink droplet ejection timing and the ink ejection port (nozzle) to be used according to the image information, and sends a drive signal to the inkjet recording head 132.

  The recording head array 130 may be stationary in a direction orthogonal to the transport direction. However, if the recording head array 130 is configured to move as necessary, an image with higher resolution can be obtained by multipass image recording. Can be recorded, or troubles of the ink jet recording head 132 can be prevented from being reflected in the recording result.

  Four maintenance units 134 corresponding to the respective ink jet recording heads 132 are arranged in the vicinity of the recording head array 130 (in this embodiment, both sides in the transport direction). When performing maintenance on the inkjet recording head 132, the recording head array 130 moves upward as shown in FIG. 2, and the maintenance unit 134 moves to the gap formed between the conveyance belt 128 and the maintenance unit 134. Get in. Then, a predetermined maintenance operation (vacuum, dummy jet, wiping, capping, etc.) is performed while facing the nozzle surface (see FIG. 3).

  In the present embodiment, the four maintenance units 134 are divided into two sets of two, and are arranged on the recording head array 130 and on the upstream side and the downstream side of the recording head array 130 at the time of image recording, respectively. .

  On the upstream side of the recording head array 130, a charging roll 136 connected to a power source (not shown) is disposed. The charging roll 136 is driven between the driven roll 126 while sandwiching the conveyance belt 128 and the paper P, and moves between a pressing position for pressing the paper P against the conveyance belt 128 and a separation position separated from the conveyance belt 128. It is possible. At the pressing position, a predetermined potential difference is generated between the driven roll 126 and the ground, so that the sheet P can be charged and electrostatically attracted to the transport belt 128.

As the charging roll 136, for example, a roll having a diameter of 14 mm in which conductive carbon is coated on the surface of silicone rubber and the volume resistance value is adjusted to about 10 ⁶ to 10 ⁷ Ω · cm can be used.

  The power source may be a DC power source or an AC power source as long as the paper P can be charged to a predetermined potential.

  Note that a registration roll (not shown) is provided further upstream than the charging roll 136, and the paper P is aligned before reaching between the conveyance belt 128 and the charging roll 136.

  A peeling plate 140 is disposed on the downstream side of the recording head array 130, and the paper P can be peeled from the transport belt 128. As the peeling plate 140, for example, an aluminum plate having a thickness of 0.5 mm, a width of 313.0 mm, and a length of 100 mm can be used.

  The peeled paper P is conveyed by a plurality of discharge roller pairs 142 constituting a discharge path 144 on the downstream side of the peeling plate 140, and is discharged to a paper discharge tray 146 provided on the top of the housing 114.

  Below the peeling plate 140, a cleaning roll 148 capable of sandwiching the conveying belt 128 with the driving roll 124 is disposed, and the surface of the conveying belt 128 is cleaned.

  A reversing path 152 composed of a plurality of reversing roller pairs 150 is provided between the paper feed tray 116 and the conveying belt 128, and the sheet P on which an image is recorded on one side is reversed and held on the conveying belt 128. By doing so, it is possible to easily record images on both sides of the paper P.

Between the transport belt 128 and the paper discharge tray 146, an ink tank 154 is provided for storing each of the four color inks. The ink in the ink tank 154 is supplied to the recording head array 130 through an ink supply pipe (not shown). As the ink, various known inks such as water-based ink, oil-based ink, and solvent-based ink can be used.

  As shown in FIG. 2, the ink jet recording head 132 includes a flow path substrate 156 and a vibration plate 158. The flow path substrate 156 is formed with a pressure chamber 160 for storing ink and an ink supply path 162 for supplying ink from the ink tank (see FIG. 1) to the pressure chamber 160.

  Piezoelectric elements 164 corresponding to the respective pressure chambers 160 are disposed on the opposite side of the flow path substrate 156 across the vibration plate 158, and a flexible printed wiring board 168 is connected by solder balls 166. Electric power (drive signal) from a control device (not shown) is applied to the piezoelectric element 164 via the flexible printed wiring board 168 and the solder balls 166. The vibration generated by the piezoelectric element 164 is applied to the pressure chamber 160, and the ink in the pressure chamber 160 is ejected from the nozzle 170 as an ink droplet.

  The flexible printed wiring board 168 is made of polyimide in this embodiment and has moisture permeability. In addition, a predetermined gap D1 (for example, about 0.2 to 0.3 mm) is formed by the solder ball 166 between the flexible printed wiring board 168 and the upper surface of the piezoelectric element 164.

  A case 172 is disposed on the upper portion of the diaphragm 158. The case 172 is formed in a rectangular parallelepiped box shape, and the lower surface is opened. An air supply port 188 and an exhaust port 190 are formed on one side surface 174A (left side surface in FIG. 2), but the other three side surfaces 174B are sealed. The upper surface 176 is formed with an air communication port 172H for absorbing a pressure difference between the inside and outside of the case 172, but the case 172 as a whole is sealed. The space between the lower edge of the side surface 174A and the diaphragm 158 is sealed with a sealing material 180. Therefore, the piezoelectric element 164 is located in the space in the case 172. The space in the case 172 has a sufficient capacity that does not hinder the vibration of the piezoelectric element 164.

  An air conditioning box 182 is provided outside the case 172. The air conditioning box 182 is formed in a substantially box shape, and the inside is a drying chamber. The air conditioning box 182 also has an air supply port 184 and an exhaust port 186 that are connected to the air supply port 188 and the exhaust port 190 of the case 172 by an air supply tube 192 and an exhaust tube 194, respectively. Further, a pump 196 is disposed in the supply pipe 192, and the gas in the air conditioning box 182 can be sent into the case 172 by driving the pump 196. The pump 196 is controlled by the control device 202 described later.

  A part of at least one surface of the air conditioning box 182 is formed of a solid electrolyte membrane 198, and the anode 198 A is located inside the air conditioning box 182 and the cathode 198 C is located outside the air conditioning box 182.

Further, a DC power source 200 is provided outside the air conditioning box 182 so as to apply a DC voltage to the solid electrolyte membrane 198. By applying this voltage, on the anode 198A side of the solid electrolyte membrane 198,
H ₂ O → 2H ⁺ + (1/2) O ₂ + 2e ⁻ (1)
Reaction occurs. That is, water vapor is electrolyzed to produce oxygen.

On the other hand, on the cathode 198C side,
2H ⁺ + (1/2) O ₂ + 2e ⁻ → H ₂ O (2)
Reaction occurs. As a whole, moisture in the drying chamber (in the air-conditioning box 182) is released to the outside, and it is equivalent to that external oxygen is taken into the drying chamber. For this reason, the drying chamber is kept in a low humidity and high oxygen concentration state.

  A humidity sensor 204 and an oxygen concentration sensor 206 are attached in the case 172, and the control device 202 controls the DC power supply 200 based on humidity data and oxygen concentration data detected by these sensors. .

  In the ink jet recording apparatus 112 of this embodiment configured as described above, the paper P taken out from the paper feed tray 116 is transported and reaches the transport belt 128 as described above. Then, it is pressed against the conveyance belt 128 by the charging roll 136 and is held by adhering (adhering) to the conveyance belt 128 by the voltage applied from the charging roll 136. In this state, while the paper P passes through the ejection area SE by circulation of the transport belt, ink droplets are ejected from the recording head array 130 and an image is recorded on the paper P. When recording an image in only one pass, the paper P is peeled from the transport belt 128 by the peeling plate 140, transported by the discharge roller pair 142, and discharged to the paper discharge tray 146. On the other hand, when performing image recording by multi-pass, after the paper P is circulated and passed through the ejection region SE until the required number of times is reached, the paper P is peeled from the transport belt 128 by the peeling plate 140, The paper is conveyed by the discharge roller pair 142 and discharged to the paper discharge tray 146.

  Here, in the ink jet recording head 132 of this embodiment, the humidity or oxygen concentration in the case 172 is detected by the humidity sensor 204 or the oxygen concentration sensor 206, respectively, and the data is sent to the control device 202. For example, when the humidity exceeds a predetermined value set in advance, the control device 202 drives the DC power source 200 and applies a DC voltage to the solid electrolyte membrane 198. Further, also when the oxygen concentration becomes equal to or lower than a predetermined value set in advance, the control device 202 drives the DC power source 200 and applies a DC voltage to the solid electrolyte membrane 198.

  By the driving of the DC power source 200, the reactions (1) and (2) occur in the solid electrolyte membrane 198, and the gas in the air conditioning box 182 has a low humidity and a high oxygen concentration (adjusted gas according to the present invention). There will be many states.

  Further, the control device 202 drives the pump 196. As a result, gas is circulated in the air conditioning box 182 and the case 172, the adjustment gas in the air conditioning box 182 is supplied into the case 172, and the gas in the case 172 is discharged into the air conditioning box 182.

  In this way, the inside of the case 172 is always maintained in a low humidity and high oxygen concentration state, so that deterioration due to reduction of the piezoelectric element 164 is prevented. In addition, since the inside of the case 172 can always be kept in a low humidity and high oxygen concentration state, the deterioration of the piezoelectric element 164 can be prevented over a long period of time.

FIG. 3 shows an inkjet recording apparatus 212 according to the first embodiment of the present invention. In the first embodiment, the configuration of the ink jet recording head is the same as that of the reference example , but the configuration for maintaining the inside of the case 172 in a low humidity and high oxygen concentration state by adjusting air is different.

As can be seen from FIG. 3, in the ink jet recording apparatus 212 of the first embodiment , the air conditioning box 182, the air supply pipe 192, and the exhaust pipe 194 are not provided, and the solid electrolyte membrane 198 is part of the case 172 (see FIG. 3). In the example shown, a part of the upper surface 176 is configured. As in the reference example , a direct current voltage is applied to the solid electrolyte membrane 198 from the direct current power source 200.

Also in the first embodiment having the above basic configuration, the humidity or oxygen concentration in the case 172 is detected by the humidity sensor 204 or the oxygen concentration sensor 206, respectively, as in the reference example. When the value becomes equal to or higher than a predetermined value set in advance or when the oxygen concentration becomes equal to or lower than a predetermined value set in advance, the DC power source 200 is driven and a DC voltage is applied to the solid electrolyte membrane 198.

  In the solid electrolyte membrane 198, the above reactions (1) and (2) occur, and the case 172 is in a state where more gas with low humidity and high oxygen concentration (regulated gas according to the present invention) exists. In this way, the inside of the case 172 is always maintained in a low humidity and high oxygen concentration state, so that deterioration due to reduction of the piezoelectric element 164 is prevented. In addition, since the inside of the case 172 can always be kept in a low humidity and high oxygen concentration state, the deterioration of the piezoelectric element 164 can be prevented over a long period of time.

In general, the solid electrolyte membrane 198 can be configured to have flexibility by adjusting its thickness. In the first embodiment , the pressure difference between the inside and outside of the case 172 can be reduced by the deformation of the solid electrolyte membrane 198, so that the air communication port 172H of the reference example is not necessary.

In the above description, the solid electrolyte membrane 198 has been described as the adjustment gas supply means of the present invention . However, the adjustment gas supply means is not particularly limited as long as a gas having a low humidity and a high oxygen concentration can be obtained as needed. For example, the means for absorbing gaseous water vapor to reduce the humidity and the means for supplying oxygen to the gas to achieve a high oxygen concentration may be separate. Of course, it is preferable to use the solid electrolyte membrane 198 as in the above embodiment, since these can be performed simultaneously and large equipment is not required.

  In each of the above embodiments, the ink jet recording apparatus provided with the ink jet recording head for ejecting ink droplets of each color of black, yellow, magenta, and cyan is exemplified as the liquid droplet ejecting apparatus of the present invention. The head and the droplet discharge device are not limited to those that record images (including characters) on the recording paper P. That is, the recording medium is not limited to paper, and the liquid to be ejected is not limited to ink. For example, it is used for industrial purposes, such as creating color filters for displays by discharging ink onto polymer films or glass, or forming bumps for component mounting by discharging solder in a welded state onto a substrate. In general, the liquid droplet ejection apparatus is widely included.

  In these droplet discharge devices, the present invention may be applied not only to the FWA but also to a partial width array (PWA) having a main scanning mechanism and a sub-scanning mechanism. Furthermore, instead of the multipath type, a single path type may be used.

1 is a schematic diagram illustrating an overall configuration of an ink jet recording apparatus according to a reference example of the present invention. It is the schematic which shows partially the inkjet recording head of the inkjet recording device of the reference example of this invention. It is the schematic which shows partially the inkjet recording head of the inkjet recording device of 1st Embodiment of this invention.

Explanation of symbols

112 Inkjet recording device 114 Case 116 Paper feed tray 118 Pickup roll 120 Conveying roller pair 122 Conveying path 124 Drive roll 126 Driven roll 128 Conveying belt 128F Flat portion 130 Recording head array 132 Inkjet recording head 134 Maintenance unit 136 Charging roll 140 Release plate 142 discharge roller pair 144 discharge path 146 discharge tray 148 cleaning roll 150 reverse roller pair 152 reverse path 154 ink tank 156 flow path substrate 158 vibration plate 160 pressure chamber 162 ink supply path 164 piezoelectric element 166 solder ball 168 flexible printed wiring board 170 Nozzle 172 Case 172H Air communication port 174A Side surface 174B Side surface 176 Upper surface 180 Sealing material 182 Air conditioning box 184 Air inlet 186 outlet 188 the air supply port 190 outlet 192 feed pipe 194 exhaust pipe 196 pump 198 solid electrolyte membrane 198A anode 198C cathode 200 DC power supply 202 controller 204 and humidity sensor 206 an oxygen concentration sensor 212 ink-jet recording apparatus P sheet SE ejection region

Claims (4)

A droplet discharge head that expands and contracts a pressure chamber by applying a voltage to a piezoelectric element and discharges the liquid in the pressure chamber as a droplet from a nozzle,
A case in which the piezoelectric element is arranged inside, and a predetermined space is formed between the piezoelectric element;
A part of the case is configured such that the anode is inside the case and the cathode is outside the case. By applying a voltage, a regulated gas having a lower humidity than the outside air and a high oxygen concentration is supplied into the case. A solid electrolyte membrane that can relieve the pressure difference inside and outside the case,
A droplet discharge head characterized by comprising: A humidity sensor is provided in the case,
The droplet discharge head according to claim 1 , wherein the solid electrolyte membrane is capable of applying a voltage based on humidity measured by the humidity sensor. An oxygen concentration sensor is provided in the case,
3. The droplet discharge head according to claim 1, wherein the solid electrolyte membrane can be applied with a voltage based on an oxygen concentration measured by the oxygen concentration sensor. A droplet discharge apparatus comprising the droplet discharge head according to any one of claims 1 to 3 .

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