JP2007307865A - Inkjet recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable inkjet recording head which prevents the defective delivering phenomenon to the problem of non-delivering and delivering direction change because of evaporation from a delivering opening. <P>SOLUTION: The inkjet recording head has a plurality of pressure generating means, a plurality of ink flow paths, and a delivering opening plate in which a plurality of the delivering openings are formed. A jet opening 6 from which a humidified air is jetted is formed in the vicinity of one or a plurality of rows of delivering opening arrays 1 in which a plurality of the delivering openings are aligned. The inkjet recording head has a humidifying tube 8 with a humidifier 9 which humidifies the air. A first end of the humidifying tube is connected to the jet opening formed in a surface parallel to a delivering opening plate surface of the head. A second end of the humidifying tube is connected to an air introduction opening 7 formed in a surface nearly perpendicular to the delivering opening plate surface of the head. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording head used in an ink jet recording apparatus that performs recording by ejecting ink to form ink droplets.

  Ink-jet recording methods that are widely used today are a method that uses an electrothermal transducer (heater) and a piezoelectric element (piezo) as a pressure generating element used to eject ink droplets. In any case, ejection of ink droplets can be controlled by an electrical signal. For example, the principle of the ink droplet ejection method using an electrothermal conversion element is that an electric signal is given to the electrothermal conversion element to instantaneously boil ink near the electrothermal conversion element, and the phase change of the ink at that time Ink droplets are ejected at high speed by the rapid bubble growth that occurs. On the other hand, the principle of the ink droplet ejection method using a piezoelectric element is that an electric signal is given to the piezoelectric element, whereby the piezoelectric element is displaced and the ink droplet is ejected by the pressure at the time of the displacement. Here, the former method does not require a large space for the pressure generating element, and has an advantage that the structure of the ink jet recording head is simple and high integration is easy.

  In recent years, the demand for high-speed color images has been increasing due to the increase in processing speed of personal computers and the spread of the Internet, etc., and so-called very high-quality recorded materials with high definition or gradation can be quickly produced. There is an increasing demand for recording, and there is a demand for printers with high image quality and high speed. An ink jet recording apparatus records an image on a recording medium such as paper or an OHP film by ejecting minute ink droplets from a minute ejection port of a recording head. Therefore, when the non-recording operation state continues and the recording head does not eject ink, the ink in the ejection port evaporates and dries, and thickened and solidified ink is generated in the ejection port, resulting in a twist ( It has been found that a change in the ink ejection direction) and ejection failure occur. Hereinafter, this ejection failure phenomenon will be referred to as a firing phenomenon.

  The smaller the droplet size, the shorter the time until the occurrence of the phenomenon occurs. For example, in an ink jet recording head having an ejection volume of 2 pl to 4 pl, the occurrence of the occurrence phenomenon occurs in a few seconds, causing a twist or ejection failure. The occurrence of a phenomenon in a few seconds means that if a certain color of ink is not ejected for several seconds during printing, it will not be ejected normally when the ejection of this color is started.

In the case of occurrence of a discharge phenomenon, for example, as disclosed in Japanese Patent Laid-Open No. 6-40042, there is a method for performing a recovery operation such as discharging at a place other than the medium (paper) area to prevent the occurrence of discharge failure. Are known.
JP-A-6-40042

  The method according to Patent Document 1 has a problem that the frequency of the recovery operation increases as the firing characteristics become worse, and as a result, the printing speed decreases. Therefore, it is very important to make it difficult for the phenomenon to occur during printing.

  It is known that the occurrence phenomenon is caused by the evaporation and drying of the ink from the ejection ports that are not ejected, so that the humidity around the ejection ports greatly affects. According to the inventor's study, there was a large difference in the phenomenon between 25 ° C./10% and 25 ° C./45%, and non-ejection occurred in a shorter time when the humidity was 10%.

  Accordingly, the present invention pays attention to the conventional problems as described above, and provides a highly reliable ink jet recording head that is less likely to cause a discharge phenomenon due to evaporation from the discharge port. Objective.

  To achieve the above object, an ink jet recording head of the present invention comprises a plurality of pressure generating means, a plurality of pressure chambers provided with the pressure generating means, and a plurality of ink flow paths for guiding ink to the pressure chambers. And a discharge port plate formed with a plurality of discharge ports for discharging ink and communicating with each of the ink flow paths, wherein one or a plurality of discharge port arrays are arranged. In the ink jet recording head having the above, it is characterized in that a jet outlet through which humidified air is jetted is provided in the vicinity of the one or a plurality of discharge port rows.

  Since humidified air is ejected from the ejection port and the humidity near the ejection port is increased, the droplets are ejected normally even during ejection after a longer rest time.

  The ink jet recording head of the present invention has a humidifying tube having a humidifying device for humidifying air, and the first end of the humidifying tube is connected to the jet port formed on a surface parallel to the discharge port plate surface of the head. The second end of the humidifying tube is connected to an air inlet formed on a surface substantially perpendicular to the discharge port plate surface of the head.

  It is desirable that the dimension of the air inlet port in the direction perpendicular to the discharge port plate surface is larger than the distance between the head and the printing medium.

  The air inlet is located upstream in the main scanning direction of the head, and humidified air from the outlet is ejected by a pressure difference generated by the movement of the head accompanying printing. In this case, a pressurizing motor or the like for ejecting the humidified air is not necessary, and it is possible to realize the ejection of the humidified air while suppressing an increase in cost.

  Water supply to the humidifier is supplied from a water tank mounted on the head.

  The humidifier may have a heating means.

  As described above, according to the present invention, in an ink jet recording head having one or a plurality of discharge port rows in which a plurality of discharge ports are arranged, a jet port from which humidified air is jetted in the vicinity of the discharge port row. Since the humidified air is ejected from the ejection port and the humidity in the vicinity of the ejection port is increased, evaporation from the ejection port is suppressed and the occurrence of the occurrence phenomenon can be made difficult.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the dimensions, numerical values, etc. used are merely examples, and the present invention is not limited to these.

(First embodiment)
FIG. 1 is a schematic perspective view of the ink jet recording apparatus of the present invention.

  An ink jet recording apparatus 100 according to the present invention sends an electrical signal to an ink jet cartridge from a carriage 101 on which an ink jet head is mounted, a carriage drive motor 102 that scans and moves the carriage 101, and a control unit (not shown) of the ink jet recording apparatus 100. Flexible cable 103, recovery means 104 for performing recovery processing of the inkjet head, paper feed tray 105 for storing recording media such as paper in a stacked state, and optical position sensor 106 for optically reading the position of the carriage 101. And a paper discharge tray 107 that holds the recording medium that has been recorded and discharged.

  The inkjet recording apparatus 100 having such a configuration moves the carriage 101 in the main scanning direction orthogonal to the recording medium conveyance direction (sub-scanning direction), and performs recording with a width corresponding to the width of the ejection port array of the inkjet recording head. On the other hand, the recording medium is intermittently conveyed by a predetermined amount during non-recording.

  In FIG. 1, the exterior (cover) is not shown for easy understanding of the configuration of the inkjet recording apparatus 100. In an actual ink jet recording apparatus, a carriage, a drive motor, and the like are covered with an exterior.

  FIG. 2 shows a schematic diagram of the structure of a chip mounted with the ink jet recording head of the present invention and formed with a heater, a discharge port, and the like. FIG. 2 shows a case where an electrothermal conversion element (heater) is used as the pressure generating element.

  FIG. 2 is a plan view of the chip as viewed from the surface on which the heater is disposed. In FIG. 2, 201 is a chip made of a silicon substrate, 202 is a heater made of TaN, TaSiN, TaAl or the like, and 203 is a supply port for guiding ink from the ink tank (not shown) provided on the back surface of the chip to the chip surface. . FIG. 2 shows only the arrangement of the heater 202 and the supply port 203.

  FIG. 3 is a schematic diagram of a chip mounted on the ink jet recording head. 3 is a cross-sectional view taken along line A-A 'in FIG.

  In FIG. 3, 201 is a chip, 202 is a heater, 203 is a supply port, 204 is an insulating film, 205 is a protective film, 206 is a cavitation resistant film made of Ta or the like, 207 is a flow path, 208 is a pressure chamber, and 209 is discharge. An outlet, 210 is a discharge port plate, and 211 is an insulating film on the back surface of the substrate.

  As shown in FIG. 3, the discharge port 209 is disposed almost directly above the heater 202. As shown in FIG. 2, the heaters may be disposed at both ends of the supply port 203, or may be disposed only on one side of the supply port 203. The arrangement of adjacent heaters is generally 300 dpi to 1200 dpi. As shown in FIG. 2, the heater arrangement having a substantially double density can be realized at both ends of the supply port with an offset of a half of the interval between adjacent heaters.

  In FIG. 3, the number of heaters is 24 in order to clearly explain the structure of the chip, but in a general ink jet recording head, the number of ejection openings arranged in each row is 64 to 2048.

  The insulating films 204 and 211 may be any film such as a thermal oxide film formed by thermally oxidizing a silicon substrate, or an oxide film or a nitride film formed by CVD.

  The protective film 205 may be any film such as an oxide film or a nitride film formed by CVD.

  The discharge port plate 210 forming the discharge port 209 and the flow path 207 may be formed by attaching a discharge port plate having a discharge port and a flow path to a semiconductor substrate in advance or used in a semiconductor process. You may form on the chip | tip 201 using a photolithographic technique.

  A wiring (not shown) made of aluminum or the like is connected to both ends of the heater 202, and a desired voltage pulse is applied to both ends of the heater 202 through the wiring.

  As shown in FIG. 4, the ink is guided to the substrate surface through the supply port 203 from the back surface of the substrate, and is guided to the discharge port 209 through the flow path 207. When a desired voltage pulse is applied to both ends of the heater 202, the ink in the vicinity of the heater is heated rapidly and boils instantaneously, and the ink is ejected as shown in FIG.

  The supply port 203 is produced by anisotropic etching of silicon using, for example, a tetramethylammonium hydroxide (TMAH) solution. In this case, as shown in FIG. 3, the opening is inclined with respect to the substrate surface at an angle of about 54.7 °.

  A semiconductor element for driving the heater may be provided in the chip, or the semiconductor element may not be provided in the chip, and may be configured only by wiring and a heater for transmitting an electric signal input from the outside of the chip.

  Next, the structure of the head, which is a feature of the embodiment of the present invention, will be described with reference to the drawings.

  FIG. 5 is a schematic perspective view of the ink jet recording head of the present invention mounted on the ink jet recording apparatus shown in FIG.

  In FIG. 5, 1 is a discharge port array in which a plurality of discharge ports are arranged, 2 is a discharge port plate, 3 is flexible wiring, 4 is a contact portion, 5 is a tank holder, 6 is a jet port, and 7 is an air inlet port. is there.

  FIG. 5 shows a case where there are four rows of ejection port rows. Each row corresponds to an ejection port row that ejects yellow, magenta, cyan, and black ink, respectively.

  Ink is discharged by a pressure generating element (not shown) provided on a chip (not shown) bonded to the discharge port plate 2. As described above, heaters and piezo elements are known as pressure generating elements.

  Electric power is supplied to the chip through flexible wiring to drive the pressure generating element. Power is supplied to the head from the ink jet recording apparatus via a contact portion.

  Next, the humidifying device, which is a feature of the present invention, will be described in detail.

  FIG. 6 shows a schematic plan view of the inkjet head.

  FIG. 7 shows a schematic cross-sectional view of the inkjet head. FIG. 7 is a cross-sectional view taken along line B-B ′ shown in FIG. 6.

  6 and 7, 1 is a discharge port array, 2 is a discharge port plate, 5 is a tank holder, 6 is a spout, 7 is an air inlet, 8 is a humidification tube, 9 is a humidifier, 10 is an ink tank, 11 is a water tank, 12 is a discharge port.

  As described above, the discharge port array 1 includes a plurality of discharge ports 12 arranged at a desired interval.

  In the present embodiment, the humidifying device 9 is formed of a material that can hold moisture, such as polypropylene fiber, and water is supplied from the water tank 11 via a flow path (not shown). At least a part of the humidifier 9 is exposed on the inner surface of the humidifying tube 8. Therefore, in the vicinity of the humidifying device 9 in the humidifying tube 8, the water held in the humidifying device 9 evaporates and the humidity becomes high.

  Next, the present invention will be described in more detail with reference to FIG.

  In FIG. 8, 1 is a discharge port array, 2 is a discharge port plate, 6 is a spout, 7 is an air inlet, 8 is a humidification tube, 9 is a humidifier, and 13 is paper.

  When the head moves in the direction of the block arrow shown in black in FIG. 8 for printing, the pressure at the air inlet 7 becomes higher than the pressure at the jet outlet 6 due to the air flow accompanying the movement of the head. 8, an air flow as indicated by white block arrows is generated. At this time, air in a high humidity region flows from the jet port 6 to the vicinity of the discharge port, and printing is performed in a humidified state. Therefore, as compared with the conventional ink jet recording apparatus, an ink jet recording apparatus having excellent discharge characteristics that can be normally discharged even if the pause time is long can be realized.

  In order to generate air flow positively, it is necessary to make the dimension of the air introduction port 7 in the direction perpendicular to the paper surface larger than the interval between the discharge port plate and the paper.

  Further, in this configuration, air humidified only when printing is efficiently supplied to the vicinity of the discharge port that requires humidification, so that water necessary for humidification is not unnecessarily consumed.

  In addition, since the humidified air is ejected from the ejection port using the pressure difference generated by the movement of the head accompanying printing, the motor and the special control for driving the motor are not required, and the cost increase is suppressed. The launch characteristics can be improved.

  The ink jet recording head of the present embodiment and the conventional ink jet recording head without a humidifier were compared with each other in a 15 ° C./10% environment where the ink viscosity increased and ejection was difficult. The inkjet recording head used for the comparison was a thermal inkjet with a discharge volume of 4 pl using a heater as a pressure generating element.

  A comparison between the two shows that when the conventional head without a humidifier does not discharge for 4 seconds, some of the discharge ports fail to discharge, whereas the head of this embodiment does not discharge for 6 seconds. Non-ejection occurred. As described above, the ink jet recording head of the present embodiment in which the humidifying device is formed is about 1.5 times longer until the occurrence of the occurrence of the phenomenon, confirming that the occurrence of the occurrence of the phenomenon can be suppressed. .

  The position of the humidifying device 9 is not limited to the position shown in FIG. 7, and may be above and below the humidifying tube 8 as shown in FIG. 9, or in the entire inner surface of the humidifying tube 8. Also good.

  In addition, the humidifying device 9 is not limited to a substance that can hold moisture, such as polypropylene fiber, and may be one in which a plurality of thin tubes having openings are gathered in the humidifying tube as shown in FIG. FIG. 11 shows a configuration of the thin tube 14 arranged on the inner surface of the humidifying tube 8. The opening of the thin tube 14 is two-dimensionally arranged on the inner surface of the humidifying tube 8 as shown in FIG. Water is supplied into each narrow tube from a water tank. Water in the narrow tube is held by surface tension, and water evaporates from the opening. Therefore, the humidity is high in the vicinity of the narrow tube opening.

(Second Embodiment)
FIG. 12 is a schematic cross-sectional view of the ink jet recording head in the second embodiment of the present invention.

  In this embodiment, a heating device 15 is provided in the ink jet recording head. The ink jet recording head of this embodiment is the same as the ink jet recording head shown in the first embodiment except that the humidifying device 15 is provided. Therefore, the detailed description is omitted, and the reference numerals other than the heating mechanism 15 are described using the reference numerals used in the first embodiment.

  The heating device 15 is composed of a resistor (heater), and starts printing by supplying power to the resistor immediately before starting printing. In this case, printing is performed in a state where the humidifying device 8 is heated. At this time, more water evaporates, so that the humidity in the humidifying tube becomes higher and the humidity of the air ejected from the ejection port becomes higher. Therefore, the launch characteristics can be further improved.

  The heating temperature is 40 ° C to 100 ° C.

  The ink jet recording head of the present embodiment and the conventional ink jet recording head without a humidifier were compared with each other in a 15 ° C./10% environment where the ink viscosity increased and ejection was difficult. The inkjet recording head used for the comparison was a thermal inkjet with a discharge volume of 4 pl using a heater as a pressure generating element. The heating temperature of the heating device 15 was 60 ° C.

  Comparing the two results, when the conventional head without a humidifier does not discharge for 4 seconds, some of the discharge ports fail to discharge, whereas the head of this embodiment does not discharge for 10 seconds. Non-ejection occurred. In the ink jet recording head of this embodiment in which the humidifying device 9 and the heating device 15 are thus formed, the time until the occurrence of the occurrence of the phenomenon is about 2.5 times, and the occurrence of the occurrence can be suppressed. I was able to confirm.

(Third embodiment)
FIG. 13 is a schematic cross-sectional view of the ink jet recording head in the third embodiment of the present invention.

  In the second embodiment, the heating device 15 is used to heat the humidifying device 8 to increase the humidity in the vicinity of the humidifying device 8, but in the third embodiment, the ink jet recording head using the electrothermal conversion element is printed. The humidifier 8 is heated using the heat generated in the process to increase the humidity. In the present embodiment, as shown in FIG. 13, the low thermal resistance material 16 is disposed from the vicinity of the discharge port plate 2 of the ink jet recording head using the electrothermal conversion element to the vicinity of the humidifier 8. The ink jet recording head of this embodiment is the same as the ink jet recording head shown in the first embodiment, except that the low thermal resistance material 16 is provided. Therefore, the detailed description is omitted, and the reference numerals other than the low thermal resistance substance 16 will be described using the reference numerals used in the first embodiment. The low thermal resistance material 16 may be a metal such as copper, silver, or a heat pipe.

  As described above, in the ink droplet discharge method using the electrothermal conversion element, by supplying an electric signal to the electrothermal conversion element, the ink in the vicinity of the electrothermal conversion element is instantaneously boiled, and the phase change of the ink at that time Ink droplets are ejected at a high speed by the rapid bubble growth caused by the above. At this time, not all the heat energy is used for ejecting the ink droplets, and as a result, the temperature of the chip (not shown) on which the electrothermal conversion element is arranged rises. As described above, the chip is bonded to the discharge port plate 2.

  In the present embodiment, the heat of increasing the temperature of the chip is transferred to the humidifier 8 through the low thermal resistance material 16, and the humidifier 8 is heated to promote evaporation. In this case, the heating temperature is limited to the chip temperature or less, and the heating timing is not freely selected. However, there is no need to newly provide a heating resistor and a resistor driving device. Cost can be reduced.

1 is a schematic perspective view of an example of an ink jet recording apparatus on which an ink jet recording head of the present invention can be mounted. The schematic diagram (plan view) for demonstrating the structure of the chip | tip mounted in the inkjet recording head of this invention. The schematic diagram (sectional drawing) for demonstrating the structure of the chip | tip mounted in the inkjet recording head of this invention. FIG. 4 is a schematic diagram (cross-sectional view) for explaining an ink droplet ejection operation of the ink jet recording head of the present invention. 1 is a schematic perspective view of an ink jet recording head according to a first embodiment of the present invention. 1 is a schematic diagram (plan view) of an ink jet recording head according to a first embodiment of the present invention. FIG. 1 is a schematic diagram (cross-sectional view) of an ink jet recording head according to a first embodiment of the present invention. FIG. 3 is a schematic diagram (cross-sectional view) for explaining the operation of the ink jet recording head according to the first embodiment of the present invention. 1 is a schematic diagram (cross-sectional view) of an ink jet recording head according to a first embodiment of the present invention. 1 is a schematic diagram (cross-sectional view) of an ink jet recording head according to a first embodiment of the present invention. Schematic diagram (plan view) of an ink jet recording head in the first embodiment of the present invention Schematic diagram (cross-sectional view) of an ink jet recording head according to a second embodiment of the present invention. Schematic diagram (cross-sectional view) of an ink jet recording head according to a third embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Discharge port row | line | column 2 Discharge port plate 3 Flexible wiring 4 Contact part 5 Tank holder 6 Jet outlet 7 Air inlet 8 Humidification pipe | tube, 9 is 10, 11 is a water tank, 12 is a nozzle 9 Humidifier 10 Ink tank 11 Water Tank 12 Ejection port 13 Paper 14 Narrow tube 15 Heating device 16 Low thermal resistance material 100 Inkjet recording device 101 Carriage 102 Carriage drive motor 103 Flexible cable 104 Recovery means 105 Optical position sensor 106 Paper feed tray 107 Paper discharge tray 201 Chip 202 Heater 203 Supply port 204 Insulating film 205 Protective film 206 Anti-cavitation film 207 Flow path 208 Pressure chamber 209 Discharge port 210 Discharge port plate 211 Insulating film on the back surface of the substrate

Claims (7)

A plurality of pressure generating means; a plurality of pressure chambers provided with the pressure generating means; a plurality of ink flow paths for guiding ink to the pressure chambers; and communicating with the ink flow paths to eject ink. And a discharge port plate on which a plurality of discharge ports are formed,
In an inkjet recording head having one to a plurality of rows of ejection port arrays in which a plurality of the ejection ports are arranged,
An ink jet recording head, comprising: a jet outlet through which humidified air is jetted in the vicinity of the one or a plurality of discharge outlet rows.   A humidifying pipe having a humidifying device for humidifying air, wherein the first end of the humidifying pipe is connected to the jet port formed on a plane parallel to the discharge port plate surface of the head, 2. The ink jet recording head according to claim 1, wherein the two ends are connected to an air introduction port formed on a surface substantially perpendicular to the ejection port plate surface of the head.   2. The air introduction port is located upstream in a head main scanning direction, and humidified air is ejected from the ejection port due to a pressure difference generated by movement of the head accompanying printing. 3. The ink jet recording head according to 2.   4. The ink jet recording head according to claim 1, wherein the humidifier is composed of fibers and a plurality of thin tubes having a diameter of several μm to several mm.   4. The ink jet recording head according to claim 1, wherein the humidifying device has a heating means.   The ink jet recording head includes a low thermal resistance material, wherein one end of the low thermal resistance material is positioned in the vicinity of the humidifier and the other end is positioned in the vicinity of the discharge port plate. 3. The ink jet recording head according to 3.   4. The ink jet recording head according to claim 1, wherein the ink jet recording head includes a water tank, and water is supplied from the water tank to the humidifier.

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