JP2007245615A - Inkjet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet printer which is simple in structure, and unerringly and quickly discharges dust, bubbles or the like existing in an ink channel and a recording head without damaging the ink channel and the recording head and without causing ink leakage, and its ink supply method. <P>SOLUTION: The inkjet printer has ink tanks storing inks, pumps which exist between the ink tanks and the recording heads and transfer the inks, atmosphere communication/cutoff valve which is arranged in the ink channel between the pump and the recording head and communicates with or cuts off the atmosphere, a deaeration valve which is arranged in the ink channel and discharges air in the ink channel, and a control section which controls the atmosphere communication/cutoff valve so as to open and introduce air into the ink channel from the atmosphere by operating the pump. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus.

  In recent years, the inkjet recording method can easily and inexpensively create an image, and thus has been applied to various printing fields such as photographs, various printing, marking, and special printing such as a color filter.

  Ink jet printers have a serial printing method in which printing is performed while the recording head is reciprocated in the paper width direction and the paper is conveyed intermittently, and ejection heads are arranged throughout the paper width direction to fix the recording head. There is a line head system that performs printing. The recording head is supplied with ink directly from an ink tank or through an ink tube. The recording head has problems such as clogging of the recording head at the time of ink ejection and ejection failure due to increased viscosity of the ink.

  In view of this, a method has been proposed in which ink is pumped from the ink tank when the recording head is cleaned and recovered, and foreign matter such as dust and air bubbles in the recording head is ejected together with ink from the ejection port (see, for example, Patent Document 1). ).

In addition, a plurality of ink discharge channels are divided into a plurality of groups, and a plurality of manifolds for distributing the ink from the ink supply source to the ink discharge channels are provided for each group, and the group includes the channels in which the ink discharge failure occurs. Only the valve corresponding to is opened, and ink is pressurized and supplied by a pump. This forcibly discharges bubbles and thickened ink, reduces the amount of ink that is wasted for recovery operations, and reduces the chances that the ink discharge channels that were normally discharged are blocked by bubbles. Then, a method for efficiently performing the recovery operation in a short time has been proposed (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 3-184872 JP 2002-225302 A

  However, in the invention described in Patent Document 1, since the ink channel is made of a tank or tube made of a hard material, when the ink is pumped into the channel filled with ink, the inside of the ink channel and the recording head are rapidly changed. May cause ink leakage from the ink flow path joint or the like.

  Further, in the invention described in Patent Document 2, if the printer is not used for a long time, if pressure maintenance is performed by a pump when all the nozzles of the printer are clogged, a sudden pressure change occurs. Similar to the above, there is a problem of causing ink leakage from the joint portion of the ink flow path.

  Therefore, the present invention discharges dust, bubbles, etc. existing in the ink flow path and the recording head with a simple structure reliably and quickly without damaging the ink flow path and the recording head and without causing ink leakage. It is an object of the present invention to provide an ink jet recording apparatus and an ink supply method thereof.

The object of the present invention can be achieved by the following constitution.
(1)
A recording head having a plurality of ejection openings for ejecting ink and forming an image on a recording medium with the ejected ink;
An ink jet recording apparatus having an ink supply unit for supplying ink to the recording head;
An ink tank for storing ink;
A pump that pumps ink between the ink tank and the recording head;
An atmosphere communication shut-off valve that communicates with or shuts off the atmosphere disposed in the ink flow path between the pump and the recording head;
An air vent valve for discharging air from the ink flow path disposed in the ink flow path;
An ink jet recording apparatus comprising: a control unit that opens the atmosphere communication shut-off valve and controls the pump to operate to introduce air from the atmosphere into the ink flow path.
(2)
The controller is configured to close the air communication shut-off valve after air is introduced into the ink flow path and operate the pump to discharge ink from the ink tank from the ejection port of the recording head. The ink jet recording apparatus according to (1), wherein:
(3)
The controller, after discharging ink from the ink tank from the ejection port of the recording head, opens the air vent valve, operates the pump, and removes air introduced into the ink flow path from the air vent valve. The inkjet recording apparatus according to (2), wherein the inkjet recording apparatus is controlled so as to be discharged.
(4)
The ink contains at least water, a water-soluble organic solvent, and a pigment, and the water content is 10% by mass or more and less than 50% by mass of the total ink mass, and is contained most in the water-soluble organic solvent. The SP value of the water-soluble organic solvent is 16.5 or more and less than 24.6, and the content of the water-soluble organic solvent is 30% by mass or more of the total ink mass (1) to (3) The ink jet recording apparatus according to any one of the above.

  According to the present invention, after air is introduced into the ink flow path, the air introduced for pressurization functions as a buffer, so that the pressure in the ink flow path does not increase rapidly, and a joint or the like Therefore, the inside of the printer is not soiled because no ink leaks or breaks.

  In addition, by discharging air after pressurization and discharging ink whose degassing degree has decreased during pressurization, it is possible to emit with ink having a high degassing degree, and thus it is possible to print with good print quality. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 3 is an example of a cross-sectional view of the ink jet recording apparatus according to the present invention.

  A denotes the entire inkjet recording apparatus, and 3 denotes a paper discharge unit on which a recording medium (paper) P on which an image is recorded is discharged and stacked. The ink jet recording apparatus A includes a recording head 50, an ink tank 11, a liquid feed pump (pump) 22, an intermediate tank 31, a transport unit 2, and a recording medium P that constitute a liquid ejecting apparatus according to the invention. A paper section 1 is provided.

  The control unit 4 operates various means constituting the ink jet recording apparatus according to a program stored in the ROM, for example, reads image information of a document, or from an external information device via an interface (not shown). Printer function that executes a series of image information recording control that inputs image information etc., stores that information, and records and outputs it on a recording medium, and adjustment and maintenance of various means so that the printer function can be executed reliably Maintenance function to perform etc.

  For the recording head 50, for example, recording heads having a plurality of ejection openings are provided for four colors in order to eject each ink of cyan (C), magenta (M), yellow (Y), and black (BK). In addition, although not shown, for example, a drive circuit or the like for performing an ink discharge operation corresponding to each recording head is integrated.

  The maintenance stand 60 is provided with a cap that covers the vicinity of the discharge port so that dust or dust adheres to the discharge port of the recording head 50 or the ink does not dry and become clogged when the printing operation is interrupted for a while. Recover the clogged state by installing or cleaning the discharge port before starting the next print operation after suspending the print operation or at regular intervals. Thus, a normal ink ejection operation can be performed.

  For transporting the recording medium P, the recording medium P stored in the paper feeding unit 1 is taken out one by one by the feed roller R1. The pair of rollers R2 sends the taken recording medium P in the direction of the pair of rollers R3. The recording medium P sandwiched between the rollers R3 is further sent to the transport unit 2.

  The recording medium P conveyed via the conveying unit 2 faces the recording head 50 and records an image while being conveyed at a constant speed.

  Thereafter, a paper discharge conveyance operation is executed, and the recording medium P on which an image is recorded is sandwiched by a pair of rollers R8 and discharged to the paper discharge unit 3.

  FIG. 1 is an example of a schematic diagram showing the configuration of an ink supply and head recovery system in an ink jet recording apparatus according to the present invention.

  The back pressure required for the recording head 50 is set by the water head difference between the intermediate tank 31 made of a flexible bag and the discharge port of the recording head 50.

  At the time of printing, the ink is supplied from the intermediate tank 31 by the discharge of the individual head 51 through the supply valve 33, the common channel 34, the distributor 41, and the individual head supply channel 45. Supply to the intermediate tank 31 is pumped from the ink tank 11 through the supply passage 21 by the liquid feed pump 22 when the bulge detection sensor 32 determines that supply is required, and is supplied to the supply valve 23 and the intermediate tank 31 by a predetermined amount. The liquid is replenished. A distributor 41 provided in the middle of the common flow path 34 is provided to equalize the flow path resistance of the ink supplied to the individual heads 51 constituting the print head 50, and serves as a short-time supply source.

  When the recording head 50 recovers, the atmosphere communication shut-off valve 43 disposed above the distributor 41 is opened and the liquid feed pump 22 is reversed to slightly suck air into the distributor 41 which is a part of the ink flow path. Then, the air communication shut-off valve 43 is closed. Thereafter, the ink is fed by rotating the liquid feed pump 22 in the forward direction, and passes through the replenishing valve 25 and the pressurizing flow path 24 that bypass the intermediate tank 31, and the individual head 51 selected by the individual head valve 46. Extruded from the nozzle. After the ink dripping from the nozzles of the individual heads is accommodated, the nozzle surface is wiped by the wiper blade 61 disposed on the maintenance table 60.

  An air vent channel 71 having an air vent valve 44 is piped from the upper part of the distributor 41, and air is discharged from this channel at the time of initial ink introduction and when air enters the ink supply channel.

  FIG. 2 is an example of a flowchart of the recording head recovery operation according to the present invention.

  The operation will be described with reference to FIG.

  In step S1, the supply valve 33 and the supply valve 23 are closed. The intermediate tank 31 is removed by closing these valves.

  In step S2, the pressurizing valve 25 is opened. The pressurized flow path 24 is opened.

  In step S3, all the individual head valves 46 are closed.

  In step S4, the atmosphere communication cutoff valve 43 is opened. The ink flow path communicates with the atmosphere.

  In step S5, the liquid feed pump 22 is reversed. By reversing the ink, the ink is fed from the recording head 50 toward the ink tank 11 and air enters the ink flow path.

  In step S6, it is determined whether a predetermined amount of ink has been fed. If a predetermined amount has been delivered (step S6: YES), the process proceeds to step S7. If the predetermined amount is not reached (step S6: NO), the liquid feeding is continued. When the ink flow path is pressurized in step S9, the sucked air becomes a buffer to absorb overpressure. For this reason, the overpressure does not damage the ink flow path or the recording head. The predetermined amount is an ink amount equivalent to the sucked air, for example, 1 ml. In addition, the predetermined amount is measured by counting the number of rotations of the liquid feed pump and determining the count. For example, using a liquid feed pump that delivers 0.1 ml of ink when rotated once, when the predetermined amount is 1 ml, the predetermined amount is reached after 10 rotations. That is, it is determined whether the count number has reached 10.

  In step S7, the liquid feed pump 22 is stopped.

  In step S8, the atmosphere communication cutoff valve 43 is closed.

  In step S9, the liquid feed pump 22 is rotated forward. By normal rotation, the ink is fed from the ink tank 11 toward the recording head 50.

  In step S10, it is determined whether a predetermined amount of ink has been fed. If a predetermined amount has been delivered (step S10: YES), the process proceeds to step S11. If the predetermined amount is not reached (step S10: NO), the liquid feeding is continued.

  During this time, the sudden overpressure is absorbed by the air taken into the ink flow path in step S6 and does not damage the flow path. Here, the predetermined amount is an amount of ink necessary for feeding ink from the ink tank 11 and pressurizing the ink flow path to push it out from the ejection port of the recording head. Although it depends on the volume of the ink flow path including the recording head, the ink amount is set to an ink amount at which the pressure of the ink flow path is twice the normal pressure, that is, about 2 atmospheres. The predetermined amount may be measured by the same method as described in step 6.

  In step S11, the liquid feed pump is stopped. The ink flow path is in a pressurized state.

  In step S12, all the individual head valves 46 are opened. Here, the ink is discharged at once from the discharge port of the recording head. At that time, bubbles and dust in the nozzles of the recording head are discharged together with the ink.

  In step S13, the elapse of time t1 is awaited. During time t1, ink, bubbles and dust are discharged from the discharge port, the pressure of the ink flow path is lowered, and ink dripping is stopped from the discharge port of the print head. The time t1 is the time until the ink drip is settled.

  In step S14, the air vent valve 44 is opened.

  In step S15, the liquid feed pump is rotated forward. Ink is sent from the ink tank 11 to the air vent channel 71 via the air vent valve 44. At that time, the air that has entered in step S5 above the distributor 41 is discharged from the air vent channel 71 together with the ink. Further, the ink whose deaeration level is low when pressurized in step 9 is also discharged.

  In step S16, it is determined whether a predetermined amount of ink has been fed. If a predetermined amount has been delivered (step S16: YES), the process proceeds to step S17. If the predetermined amount is not reached (step S16: NO), the liquid feeding is continued. Here, the predetermined amount of ink means the amount of air that has entered + the amount of ink that has become less degassed, depending on the volume of the ink flow path including the recording head. Determined by experiment.

  In step S17, the liquid feed pump is stopped.

  In step S18, the air vent valve 44 is closed.

  In step S19, the supply valve 33 and the supply valve 23 are opened. That is, the intermediate tank 31 is connected to the ink flow path.

  In step S20, the pressurizing valve 25 is closed. That is, the pressure channel 24 is closed.

  In step S21, the same wiping difference is executed to wipe away ink droplets, dust, etc. adhering to and around the ejection opening of the recording head.

  Next, an example of ink used in the ink jet recording apparatus will be described.

  Ink for an ink jet recording apparatus (hereinafter also simply referred to as ink) contains at least water, a water-soluble organic solvent, and a pigment. Here, the water-soluble organic solvent is not particularly limited as long as it can be mixed with water. Two or more water-soluble organic solvents can be used in combination. However, in order to suppress the occurrence of cavitation when continuously emitting light, the SP value of the most water-soluble organic solvent among the water-soluble organic solvents is 16.5 or more and less than 24.6, It is preferable that the content of the water-soluble organic solvent having an SP value of 16.5 or more and less than 24.6 is 30% by mass or more of the total ink mass. Since this solvent composition contains a large amount of a water-soluble organic solvent having a higher hydrophobicity than water, the solubility of the entire ink is high, and as a result, cavitation is unlikely to occur during continuous emission.

  The solvent solubility parameter (SP value) is a value expressed by the square root of the molecular cohesive energy. F. Fedors, Polymer Engineering Science, 14, p147 (1974). The unit is (MPa) 1/2, and refers to the value at 25 ° C.

  Hereinafter, examples of water-soluble organic solvents having an SP value of 16.5 or more and less than 24.6 are shown together with the SP value. Needless to say, the present ink is not limited to this.

Ethylene glycol monomethyl ether (SP value: 24.5)
Ethylene glycol monoethyl ether (23.5)
Ethylene glycol monobutyl ether (22.1)
Ethylene glycol monoisopropyl ether (22.3)
Diethylene glycol monomethyl ether (23.0)
Diethylene glycol monoethyl ether (22.4)
Diethylene glycol monobutyl ether (21.5)
Diethylene glycol diethyl ether (16.8)
Triethylene glycol monomethyl ether (22.1)
Triethylene glycol monoethyl ether (21.7)
Triethylene glycol monobutyl ether (21.1)
Propylene glycol monomethyl ether (23.0)
Propylene glycol monophenyl ether (24.2)
Dipropylene glycol monomethyl ether (21.3)
Tripropylene glycol monomethyl ether (20.4)
1,3-dimethyl-2-imidazolidinone (21.8)
In this ink, in addition to the water-soluble organic solvent having an SP value of 16.5 or more and less than 24.6, conventionally known various water-soluble organic solvents can be used in combination.

  Examples of the water-soluble organic solvent preferably used as the solvent to be used in combination include alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexane). Hexanol, benzyl alcohol, etc.), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, Thiodiglycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanedio , 1,2-pentanediol, 1,2-hexanediol, 1,2,6-hexanetriol, etc.), amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine) , Morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocyclic rings (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone, etc.), sulfoxides For example, dimethyl sulfoxide, etc.), sulfones (e.g., sulfolane), urea, acetonitrile, and acetone.

  As the pigment that can be used in the present ink, conventionally known pigments can be used without particular limitation, and any of water-dispersible pigments, solvent-dispersible pigments, and the like can be used, for example, organic pigments such as insoluble pigments and lake pigments, An inorganic pigment such as carbon black can be preferably used. This pigment is present in a dispersed state in the ink, and the dispersion method may be any of self-dispersion, dispersion using a surfactant, polymer dispersion, and microcapsule dispersion. Dispersion is particularly preferred from the standpoint of fixability.

  The insoluble pigment is not particularly limited. Dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole and the like are preferable.

  Specific pigments that can be preferably used include the following pigments.

  Examples of the magenta or red pigment include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 202, C.I. I. Pigment red 222, C.I. I. Pigment violet 19 and the like.

  Examples of the pigment for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 15: 3, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 94, C.I. I. And CI Pigment Yellow 138.

  Examples of the pigment for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  Examples of black pigments include C.I. I. Pigment black 1, C.I. I. Pigment black 6, C.I. I. Pigment black 7 and the like.

  The average particle size of the dispersed state of the pigment contained in the ink is preferably 50 nm or more and less than 200 nm. When the average particle size of the pigment dispersion is less than 50 nm or 200 nm or more, the stability of the pigment dispersion tends to deteriorate, and the storage stability of the ink tends to deteriorate.

  The particle size of the pigment dispersion can be determined by a commercially available particle size measuring instrument using a dynamic light scattering method, an electrophoresis method, or the like. Accurate and often used.

  The pigment to be used is preferably used after being dispersed by a disperser together with a dispersant and other additives necessary for various desired purposes. As the disperser, a conventionally known ball mill, sand mill, line mill, high-pressure homogenizer, or the like can be used. In particular, the particle size distribution of the ink produced by dispersion with a sand mill is sharp and preferable. The material of the beads used for sand mill dispersion is preferably zirconia or zircon from the viewpoint of contamination of bead fragments and ionic components. Furthermore, the bead diameter is preferably 0.3 mm to 3 mm.

  In the present ink, it is preferable to use a polymer dispersant in the dispersion.

  The polymer dispersant has a polymer component having a molecular weight of 5000 or more and 200000 or less. The polymer dispersant is selected from styrene, styrene derivatives, vinyl naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid and fumaric acid derivatives. Examples thereof include a block copolymer comprising at least one kind of monomer, a random copolymer and salts thereof, polyoxyalkylene, and polyoxyalkylene alkyl ether.

  In the case of an acidic polymer dispersant, it is preferably added after neutralization with a neutralizing base. Here, the neutralizing base is not particularly limited, but is preferably an organic base such as ammonia, monoethanolamine, diethanolamine, triethanolamine, or morpholine.

  Moreover, it is preferable that it is 10-100 mass% with respect to a pigment as addition amount of a polymer dispersing agent.

  In this ink, in addition to the above description, if necessary, various known additions may be made depending on the purpose of improving the emission stability, compatibility with the print head and ink cartridge, storage stability, image storage stability, and other various performances. Agents, for example, polysaccharides, viscosity modifiers, specific resistance regulators, film forming agents, ultraviolet absorbers, antioxidants, anti-fading agents, antifungal agents, rust inhibitors, etc. can be appropriately selected and used, For example, oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, 57-74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091 and 3-13376, etc. Anti-fading agents, fluorescent whitening agents described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-228771, JP-A-4-219266, etc. be able to.

  The ink having the above-described structure preferably has an ink surface tension of 25 to 40 mN / m at 25 ° C., more preferably 25 to 35 mN / m, and still more preferably 30 to 35 mN / m. . The ink viscosity is preferably 1 to 40 mPa · s at 25 ° C., more preferably 5 to 40 mPa · s, and still more preferably 5 to 20 mPa · s.

  Of course, the ink jet recording apparatus is not limited to the ink described above.

  The detailed configuration and detailed operation of each component constituting the ink jet recording apparatus can be changed as appropriate without departing from the spirit of the present invention.

It is an example of the schematic diagram which shows the structure of the ink supply which concerns on this invention, and a head recovery system. 4 is an example of a flowchart of a recording head recovery operation according to the present invention. 1 is an example of a cross-sectional view of an ink jet recording apparatus using an ink supply unit according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Ink tank 21 Replenishment flow path 22 Liquid feed pump 31 Intermediate tank 41 Distributor 43 Atmospheric communication shut-off valve 44 Air vent valve 46 Individual head valve 50 Print head

Claims (4)

A recording head having a plurality of ejection openings for ejecting ink and forming an image on a recording medium with the ejected ink;
An ink jet recording apparatus having an ink supply unit for supplying ink to the recording head;
An ink tank for storing ink;
A pump that pumps ink between the ink tank and the recording head;
An atmosphere communication shut-off valve that communicates with or shuts off the atmosphere disposed in the ink flow path between the pump and the recording head;
An air vent valve for discharging air from the ink flow path disposed in the ink flow path;
An ink jet recording apparatus comprising: a control unit that opens the atmosphere communication shut-off valve and controls the pump to operate to introduce air from the atmosphere into the ink flow path. The controller is configured to close the air communication shut-off valve after air is introduced into the ink flow path and operate the pump to discharge ink from the ink tank from the ejection port of the recording head. The inkjet recording apparatus according to claim 1, wherein: The controller, after discharging ink from the ink tank from the ejection port of the recording head, opens the air vent valve, operates the pump, and removes air introduced into the ink flow path from the air vent valve. The inkjet recording apparatus according to claim 2, wherein the inkjet recording apparatus is controlled so as to be discharged from the printer. The ink contains at least water, a water-soluble organic solvent, and a pigment, and the water content is 10% by mass or more and less than 50% by mass of the total ink mass, and is contained most in the water-soluble organic solvent. The SP value of the water-soluble organic solvent is 16.5 or more and less than 24.6, and the content of the water-soluble organic solvent is 30% by mass or more of the total ink mass. The inkjet recording apparatus of any one.

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