JP2010167784A - Inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To re-disperse a pigment aggregate included in ink without causing defective discharging of the ink from nozzles and irregularities of the re-dispersion, and moreover without affecting a printing speed. <P>SOLUTION: This inkjet recording apparatus for carrying out printing by an inkjet head to a surface of a recording medium with the use of a liquid ink which has a pigment dispersed in a dispersion medium, is provided with a centrifugal separator 201 for centrifugally separating pigment aggregate dispersed in a liquid ink by centrifugal force and an ink storage part (damper tank) for storing the liquid after the pigment aggregate is separated in the centrifugal separation part 201, wherein the liquid ink stored in the ink storage part (damper tank ) is supplied to the inkjet head. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that performs printing with an ink jet head on a recording medium using a liquid ink in which a pigment is dispersed in a dispersion medium.

  In order to print a high-definition image with an inkjet recording apparatus, a technique using a liquid ink in which a pigment is dispersed in a dispersion medium has been conventionally known. In such a liquid ink, a dye or a pigment is used as a color material, and an aqueous system containing a highly volatile organic solvent or a low volatile oil or alcohol is used as a dispersion medium. As a recent trend, various inks in which a pigment excellent in fixing property, sharpness, color density, printing bleeding, water resistance, light resistance, etc. is dispersed in a dispersion medium as a coloring material have been reported and put into practical use. It is coming.

  In recent years, liquid ink having photosensitivity and an ink jet recording apparatus using the same have begun to attract attention. In this ink jet recording apparatus, photosensitive liquid ink discharged onto a printing surface is quickly photocured by irradiating active energy rays such as ultraviolet rays or electron beams. As the photosensitive ink to be used, a radical polymerizable ink containing a pigment, a polymerizable monomer and a polymerization initiator and a photocation curable ink are typical.

  According to the technique of photocuring photosensitive ink, the ink layer can be made non-fluidized by light irradiation, so that a printed matter having a relatively high quality can be obtained. However, in the above-mentioned radical polymerizable ink and photocation curable ink, the pigment dispersed in the dispersion medium aggregates to several μm over time to form huge particles, thereby forming a pigment aggregate. This pigment aggregate has an adverse effect in the vicinity of the nozzles of the inkjet head, and causes the problem that the ejection stability of the inkjet head becomes unstable.

  As a countermeasure against such a problem, an ink jet recording apparatus capable of prompting redispersion of the pigment aggregate has been proposed. For example, Patent Document 1 describes that the entire inkjet head is vibrated by an ultrasonic actuator installed on the wall of the head to redisperse the pigment aggregate in the ink supplied to the inside of the head.

  According to the technique described in Patent Document 1, there is a problem that it is easy to cause defective ejection of ink from the nozzles. Such ejection failure occurs when the meniscus formed at the gas-liquid interface near the nozzle is disturbed or bubbles are involved when the entire inkjet head is vibrated.

  The technique described in Patent Document 1 also has a problem that ultrasonic waves are not transmitted evenly to the ink in the ink jet head, thereby causing unevenness in re-dispersion of the pigment aggregates contained in the ink.

  In addition, since it takes time until the crushing effect by ultrasonic waves reaches the entire ink, it is not suitable for high-speed printing.

  An object of the present invention is to redisperse pigment aggregates contained in ink without causing defective ejection of ink from nozzles, without causing unevenness of redispersion, and without affecting printing speed. That is.

  This reference example is an ink jet recording apparatus that performs printing on a recording medium using an ink jet head using a liquid ink in which a pigment is dispersed in a dispersion medium, and the liquid ink is applied with ultrasonic vibrations. The pigment aggregate dispersed therein is redispersed, and the liquid ink after ultrasonic vibration is applied is stored in an ink storage unit, and the liquid ink stored in the ink storage unit is stored in the inkjet The head was supplied.

  The present invention relates to an ink jet recording apparatus that performs printing on a recording medium using an ink jet head using a liquid ink in which a pigment is dispersed in a dispersion medium, and a centrifugal force is applied to the liquid ink. The dispersed pigment aggregate is centrifuged, the liquid ink after the pigment aggregate is centrifuged is stored in an ink storage section, and the liquid ink stored in the ink storage section is stored in the inkjet The head was supplied.

  According to the present invention, the pigment aggregate contained in the liquid ink is regenerated without causing defective discharge of the liquid ink from the nozzle, without causing unevenness of redispersion, and without affecting the printing speed. Can be dispersed.

It is a front view which shows schematic structure of the inkjet recording device of this Embodiment. It is a longitudinal front view which shows the structure for re-dispersing the pigment aggregate contained in liquid ink. It is a vertical front view of an ultrasonic vibration provision part and a 1st temperature control part. It is a schematic diagram which illustrates the area of the part to which liquid ink is exposed to an ultrasonic wave in an intermediate pipe. It is a vertical front view of a centrifuge part and a 1st temperature control part. It is the graph which took the passage time of the liquid ink (temperature 24 ± 1 degreeC) which passes an ultrasonic vibration provision part on the horizontal axis, and took the discharge error rate on the vertical axis. It is the graph which took the passage time of the liquid ink (temperature 35 +/- 1 degreeC) which passes an ultrasonic vibration provision part on the horizontal axis, and took the discharge error rate on the vertical axis | shaft. It is the graph which took the passage time of the liquid ink (temperature 50 ± 1 degreeC) which passes an ultrasonic vibration provision part on the horizontal axis, and took the discharge error rate on the vertical axis. 6 is a graph showing the relationship between the range of ultrasonic vibration application energy that can minimize ejection errors and the temperature of liquid ink. 6 is a graph in which the horizontal axis represents the passage time of liquid ink (applied centrifugal force 7500G) passing through the centrifugal separator, and the vertical axis represents the discharge error rate. 6 is a graph in which the horizontal axis represents the passage time of liquid ink (applied centrifugal force 15000 G) passing through the centrifugal separation unit and the vertical axis represents the discharge error rate.

1. Reference Example A reference example of the present invention will be described with reference to FIGS.

[Basic configuration]
FIG. 1 is a front view showing a schematic structure of an ink jet recording apparatus 101 of this reference example.

  The ink jet recording apparatus 101 transports a recording medium 102 fed from an automatic paper feeding apparatus 103 that stacks and holds a plurality of recording media 102 by a transport apparatus 104 having a conveyor structure. 102 has a schematic structure of printing predetermined items. A UV irradiation light source 106 and a heating unit 107 are sequentially arranged on the downstream side in the transport direction of the recording medium 102 from the inkjet head 105. The UV irradiation light source 106 irradiates the liquid ink 108 (see FIG. 2) discharged from the inkjet head 105 onto the recording medium 102 with ultraviolet rays, and cures the liquid ink 108. The heating unit 107 heats the liquid ink 108 after UV curing. The heating of the liquid ink 108 by the heating unit 107 promotes the curing of the liquid ink 108. In this reference example, since the liquid ink 108 that is cured by ultraviolet irradiation is used as the ink, the UV irradiation light source 106 and the heating unit 107 are required. When a normal pigment-based liquid ink is used as the ink, the UV irradiation light source 106 and the heating unit 107 are unnecessary. Details of each part will be described below.

(1) Liquid ink 108
As an example of the liquid ink 108, a photocationically curable inkjet pigment ink is used. However, as long as it is a pigment-based ink for inkjet, it is not limited to the type of photocationic curable type, and pigment-based inks such as water-based aqueous pigment inks, solvent-based pigment inks, and low-volatile oil-based oily pigments. Ink and radical photopolymerization type pigment inks based on acrylic monomers can be used.

  The photo-cation curable ink-jet pigment ink is dissolved in at least one solvent that polymerizes in the presence of an acid, a photoacid generator that dissolves in the solvent and generates an acid upon irradiation with light, and the solvent. Or it is a composition containing the dispersed color component. Such a photocationic curable ink-jet pigment ink is cured by heating after exposure.

Such a composition of the liquid ink 108 usually contains a pigment in a cationically polymerizable monomer. The cationically polymerizable monomer may be a single monomer or a mixture thereof. For example, monomers having a vinyl bond capable of cationic polymerization are used. As such monomers, for example,
・ Compounds with a molecular weight of 1000 or less having cyclic ether groups such as epoxy groups, oxetane groups, oxolane groups, etc. ・ Acrylic or vinyl compounds having substituents in the side chain ・ Carbonate compounds ・ Low molecular weight melamine compounds ・ Vinyl ethers and vinyl Carbazoles, styrene derivatives, alpha-methylstyrene derivatives, vinyl alcohol and vinyl alcohol esters including ester compounds such as acrylic and methacrylic are used.

As the pigment component, any pigment can be used as long as it is a color material generally known as a pigment and basically dispersible. Among these, in particular, a cationic curable material uses an acid for its mechanism, and therefore, a pigment that is difficult to fade by an acid is desirable. Examples of usable pigments include light-absorbing pigments. For example,
・ Carbon pigments such as carbon black, carbon refined and carbon nanotubes ・ Metal oxide pigments such as iron black, cobalt blue, zinc oxide, titanium oxide, chromium oxide and iron oxide ・ Sulfide pigments such as zinc sulfide・ Phthalocyanine pigments ・ Pigments made of salts such as metal sulfates, carbonates, silicates, and phosphates, and pigments made of metal powders such as aluminum powder, bronze powder, and zinc powder be able to. Other organic pigments such as
・ Nitroso pigments such as dye chelates, nitro pigments, aniline black, and naphthol green B ・ Azo pigments such as Bordeaux 10B, Lake Red 4R, and Chromoval Red (azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, etc. Including)
・ Lake pigments such as peacock blue lake and rhodamine lake ・ Phthalocyanine pigments such as phthalocyanine blue ・ Polycyclic pigments (perylene pigment, perinone pigment, anthraquinone pigment, quinacridone pigment, dioxane pigment, thioindigo pigment, isoindolinone pigment, quinofuranone Pigment)
-Sulene pigments such as thioindigo red and indatron blue-quinacridone pigments-quinacridine pigments-isoindolinone pigments can also be used. Furthermore,
-White pigments such as natural clay, lead white, zinc oxide and metal carbonates such as magnesium carbonate, and metal oxides such as barium and titanium are also useful as color components. The liquid ink containing a white pigment can be used not only for white printing, but also for printing correction and overlay correction by overwriting.

  The pigment used in the liquid ink 108 may have magnetism in addition to color development and colorability. In order to give the pigment magnetism, for example, magnetic pigments such as iron, cobalt, nickel, alloys or oxides thereof may be contained in the pigment. Further, the pigment may be provided with conductivity. In order to give conductivity to the pigment, for example, silver, gold, copper, aluminum, carbon, nickel, iron, cobalt, lead, tin, antimony, alloy powders of any combination thereof, and a composite of these and organic matter Or the like may be contained in the pigment. The pigment may have a dielectric property. In order to make the pigments dielectric, the pigments can contain dielectric powders such as alloys such as barium lead, bismuth, iridium, ruthenium, tantalum, platinum, titanium, strontium, chromium, their oxides, and ceramic powder. It ’s fine. Further, the pigment may have electromagnetic wave heat generation properties. In order to make the pigment have an electromagnetic exothermic property, the pigment may contain an electromagnetic exothermic ceramic or a silicon resin. Furthermore, the pigment may exhibit other properties such as fluorescence.

(2) Recording medium 102
The type of the recording medium 102 is not particularly limited as long as it is a printable medium. As the recording medium 102, for example, paper, an OHP sheet, a resin film, a nonwoven fabric, a porous film, a plastic plate, a circuit board, a metal substrate, or the like can be used.

(3) Transport device 104
The conveyance device 104 conveys the recording medium 102 so that the recording medium 102 sequentially passes through the front surface of the inkjet head 105, the UV irradiation light source 106, and the heating unit 107. In FIG. 1, a transport device 104 transports the recording medium 102 from the right side to the left side. The conveying device 104 includes a belt winding mechanism 111 in which a belt 110 is wound around a pair of pulleys 109 and a drive unit (not shown) that rotationally drives one pulley 109. As another reference example, the belt winding mechanism 111 may be configured by a plurality of pairs of transport rollers that transport the recording medium 102.

(4) Inkjet head 105
The ink jet head 105 ejects liquid ink 108 to the recording medium 102 in response to the image signal, and forms an ink layer on the surface of the recording medium 102. As the inkjet head 105, for example, a serial scanning head mounted on a carriage or a line scanning head having a width equal to or larger than the width of the recording medium 102 can be used. From the viewpoint of high-speed printing, the line scanning head is usually more advantageous than the serial scanning head.

  Various methods can be used for discharging the liquid ink 108 in the inkjet head 105. For example, it is possible to use a piezo-type ink jet head that applies a voltage to the piezoelectric element and causes energy due to deformation of the piezoelectric element to act on the pressure chamber, thereby ejecting the liquid ink 108. Piezo-type ink jet heads perform effective ink ejection especially for low-volatility oil-based pigment inks, heat-sensitive monomer-based radical polymerization-type pigment inks, and photocationic-polymerization-type pigment-based inks. be able to.

(5) UV irradiation light source 106
The UV irradiation light source 106 irradiates light to the ink layer formed on the surface of the recording medium 102 to generate an acid in the ink layer. Examples of the UV irradiation light source 106 include mercury lamps such as low, medium, and high pressure mercury lamps, tungsten lamps, arc lamps, excimer lamps, excimer lasers, semiconductor lasers, YAG lasers, and lasers that combine non-linear optical crystals. A system, a high frequency induced ultraviolet ray generator, an electron beam irradiation device, an X-ray irradiation device, or the like can be used. In order to simplify the system, it is desirable to use a high frequency induced ultraviolet ray generator, a high / low pressure mercury lamp, a semiconductor laser, or the like.

(6) Heating unit 107
The heating unit 107 heats the ink layer on the surface of the recording medium 102 and promotes a crosslinking reaction using an acid as a catalyst. As the heating unit 107, for example, an infrared lamp, a ceramic heater, a roller (heat roller) with a built-in heating element, warm air or a blower that blows hot air can be used.

[Structure for redispersing the pigment aggregate contained in the liquid ink 108]
As described above, the photocation curable ink used in the embodiment of the present reference example forms a pigment aggregate by aggregating the pigment dispersed in the dispersion medium to several μm over time to form large particles. . This pigment aggregate has an adverse effect in the vicinity of the nozzles of the inkjet head 105 and makes the ejection stability of the inkjet head unstable. Therefore, in this reference example, a redispersion structure for redispersing the pigment aggregate is provided. Such a redispersion structure will be described next.

  FIG. 2 is a longitudinal front view showing a structure for redispersing the pigment aggregates contained in the liquid ink 108. As shown in FIGS. 1 and 2, the liquid ink 108 supplied to the inkjet head 105 is supplied from the ink container 151 to the inkjet head 105 via the ink processing unit 152.

  The ink container 151 is filled with liquid ink 108. The liquid ink 108 is sucked up by the operation of the first pump 153. As a structure for this purpose, a fluid suction port (not shown) of the first pump 153 is connected to the other end of an ink suction pipe 154 having one end disposed inside the ink container 151. The liquid ink 108 sucked up from the ink container 151 by the first pump 153 is supplied to the ink processing unit 152.

  The ink processing unit 152 includes an ultrasonic vibration applying unit 155, a first temperature adjusting unit 156, a damper tank 157 as an ink storage unit, a second pump 158 as an ink supply unit, and a pressure sensor 159. It is configured.

  The ultrasonic vibration applying unit 155 applies ultrasonic vibration to the liquid ink 108 sucked up from the ink container 151 in accordance with the operation of the first pump 153 and supplies the liquid ink 108 to the damper tank 157. The pigment aggregates contained in the liquid ink 108 are redispersed by application of ultrasonic vibration. At this time, the first temperature adjusting unit 156 adjusts the temperature of the liquid ink 108 to which ultrasonic vibration is applied, and assists in redispersion of the pigment aggregate. The damper tank 157 stores the liquid ink 108 to which the ultrasonic vibration is applied and the pigment aggregate is redispersed. The second pump 158 sucks up the processed liquid ink 108 stored in the damper tank 157 and supplies it to the inkjet head 105. At this time, the pressure sensor 159 detects and outputs the pressure of the liquid ink 108 supplied to the inkjet head 105. A control unit (not shown) monitors the output of the pressure sensor 159 and drives and controls the second pump 158 so that the output value becomes a predetermined value.

  FIG. 3 is a longitudinal front view of the ultrasonic vibration applying unit 155 and the first temperature adjusting unit 156. The ultrasonic vibration applying unit 155 includes an intermediate pipe 160 that guides the liquid ink 108 discharged from a discharge port (not shown) of the first pump 153 to the damper tank 157. The intermediate pipe 160 has a cup-shaped bent portion 161 at a part thereof. The bent portion 161 has a larger volume than the conduction space of the other liquid ink 108. An ultrasonic wave transmitting part 162 is arranged in the bent part 161 whose volume has increased. The ultrasonic transmitter 162 is connected to the ultrasonic generator 163 and is driven by the ultrasonic generator 163 to generate ultrasonic vibrations. In order to arrange such an ultrasonic transmission part 162 in the bent part 161, an insertion hole 164 is formed in the intermediate pipe 160 at the position of the bent part 161, and the ultrasonic transmission part 162 is intermediate in the part of the insertion hole 164. It is inserted into the pipe 160. A fitting portion between the insertion hole 164 and the ultrasonic wave transmitting portion 162 is sealed by a seal member 165, and leakage of the liquid ink 108 from the fitting portion is prevented.

  The ultrasonic vibration generated by the ultrasonic transmission unit 162 driven by the ultrasonic generation unit 163 acts on the liquid ink 108 that passes through the intermediate pipe 160. Thereby, the pigment aggregate aggregated and dispersed in the liquid ink 108 is crushed by ultrasonic vibration and redispersed. At this time, a temperature rise occurs in the liquid ink 108. Depending on the type of the liquid ink 108, when the temperature rises above a predetermined temperature, the components contained in the liquid ink 108 react with each other to cause a chemical change, which may cause alteration. For example, as the liquid ink 108, the photocationic curable inkjet pigment ink used in the present reference example is deteriorated due to a chemical change or the like when the temperature rises to about 50 ° C. or higher. For this reason, when continuous discharge is performed by the ink jet head 105, the crushing effect by ultrasonic vibration of the pigment aggregate is not stably performed. On the other hand, if the crushing vibration energy is applied too much, re-aggregation occurs. Therefore, the temperature rise of the liquid ink 108 narrows the effective range of the ultrasonic vibration energy generated by the ultrasonic wave transmitting unit 162. For this reason, a rise in the temperature of the liquid ink 108 causes problems such as an increase in ejection errors during continuous ejection. The first temperature adjustment unit 156 suppresses such a temperature increase of the liquid ink 108 and eliminates a problem caused by the temperature increase of the liquid ink 108.

  The first temperature adjustment unit 156 includes a cooling pipe 166 formed integrally with the intermediate pipe 160 of the ultrasonic vibration application unit 155. The cooling pipe 166 is formed by being partitioned from the intermediate pipe 160 by a partition wall 167 at the bent portion 161 of the intermediate pipe 160. The partition wall 167 is made of a material having a relatively good thermal conductivity and not corroded by the liquid ink 108, for example, a SUS material or copper. In the cooling pipe 166 thus formed, a refrigerant, for example, cooling water circulates inside. As a structure for this purpose, a circulation mechanism 168 for circulating the refrigerant inside the cooling pipe 166 is provided (see FIG. 2). The first temperature adjustment unit 156 adjusts the temperature of the liquid ink 108 by controlling the circulation of the refrigerant circulated inside the cooling pipe 166.

FIG. 4 is a schematic view illustrating the area of the portion of the intermediate pipe 160 where the liquid ink 108 is exposed to ultrasonic waves. The volume of the portion where the liquid ink 108 is exposed to ultrasonic waves, that is, the volume of the portion where the liquid ink 108 is circulated in the bent portion 161 of the intermediate pipe 160 is set to 30 ml as an example. As an example, the ultrasonic transmitter 162 has a diameter of 2.6 cm and a height of 5 cm. In this case, the contact area S of the portion where the ultrasonic wave transmitting portion 162 and the liquid ink 108 are in contact at the bent portion 161 of the intermediate pipe 160 is:
S = 2.6π × 5 + 1.32π = 46.15 cm ²
Can be expressed as Therefore, the ultrasonic vibration application energy (J / cm ² · ml) applied to the liquid ink 108 flowing through the bent portion 161 of the intermediate pipe 160 is a unit of the surface of the ultrasonic transmission unit 162 that is in contact with the liquid ink 108. It can be expressed by the following equation 1 per area.

[Action]
When printing using the inkjet recording apparatus 101, the recording medium 102 is conveyed by the conveying apparatus 104. The conveyance direction is a direction from right to left in FIG. At this time, the conveyance speed of the recording medium 102 is set within a range of 0.1 m / min to several hundreds m / min, for example.

  The inkjet head 105 is supplied with processed liquid ink 108 stored in a damper tank 157 sucked up by the second pump 158. Therefore, when the recording medium 102 is conveyed to the front surface of the ink jet head 105, the ink jet head 105 ejects the liquid ink 108 in accordance with the image signal. As a result, an ink layer is formed on the surface of the recording medium 102.

When the recording medium 102 is conveyed to the front of the UV irradiation light source 106, the UV irradiation light source 106 irradiates light toward the ink layer formed on the surface of the recording medium 102, and generates an acid in the ink layer. The irradiation light intensity at this time varies depending on the wavelength of the light source to be used, but is usually within a range of several mW / cm ² to 1 KW / cm ² . The exposure amount to the ink layer can be appropriately set according to the sensitivity of the liquid ink 108, the conveyance speed of the recording medium 102, and the like.

  Subsequently, when the recording medium 102 passes through the heating unit 107, the ink layer formed on the surface of the recording medium 102 is heated. Thereby, the crosslinking reaction in the ink layer is promoted. At this time, the heating time by the heating unit 107 is relatively short, about several seconds to several tens of seconds. Accordingly, in order to cause the ink layer to harden almost completely by heating the heating unit 107, the maximum temperature reached is, for example, about 200 ° C. or less, desirably 80 ° C. to 200 ° C. Heat to reach temperature.

  Thereafter, the recording medium 102 is conveyed to, for example, a stocker (not shown), and printing is completed.

  Here, in order to stably perform ink jet recording, it is necessary to stably discharge the liquid ink 108 from the ink jet head 105. The stability of the discharge state of the liquid ink 108 from the inkjet head 105 is greatly related to the state of pigment particles that are the color material components of the liquid ink 108 supplied to the inkjet head 105. That is, in order to stably discharge the liquid ink 108 from the inkjet head 105, it is important to make the pigment particles contained in the liquid ink 108 supplied to the inkjet head 105 finely and evenly. According to this reference example, the ultrasonic vibration applying unit 155 applies ultrasonic vibration to the liquid ink 108 sucked up from the ink container 151 by the first pump 153.

  That is, the liquid ink 108 passes through the intermediate pipe 160 in the ultrasonic vibration applying unit 155, and the ultrasonic vibration generated by the ultrasonic transmission unit 162 driven by the ultrasonic generation unit 163 acts on the liquid ink 108 when passing. To do. As for the ultrasonic vibration frequency at this time, the vicinity of 45 kHz is effective. Thereby, the pigment aggregate aggregated and dispersed in the liquid ink 108 is crushed by ultrasonic vibration and redispersed. The liquid ink 108 in which the pigment aggregate is redispersed is stored in the damper tank 157 and supplied to the inkjet head 105. Accordingly, the liquid ink 108 supplied to the inkjet head 105 is a liquid ink 108 in which pigment particles are finely and uniformly arranged after the pigment aggregate is redispersed. Therefore, according to the present reference example, the liquid ink 108 can be stably ejected from the ink jet head 105, and thus it is possible to stably perform ink jet recording.

  In the present reference example, storing the liquid ink 108 in the damper tank 157 has another technical significance in that the re-dispersion operation of the pigment aggregate is satisfactorily performed. That is, in order to impart ultrasonic vibration to the liquid ink 108 in the ultrasonic vibration applying unit 155 and thereby favorably redisperse the pigment gaze, the ultrasonic vibration applying energy applied to the liquid ink 108 by the ultrasonic transmitting unit 162. Must be set to the optimal value. At this time, the ultrasonic vibration application energy applied to the liquid ink 108 varies depending on the flow velocity of the liquid ink 108 that passes around the ultrasonic wave transmission unit 162 in the intermediate pipe 160. For this reason, in order to maintain the value of the ultrasonic vibration application energy applied to the liquid ink 108 by the ultrasonic transmission unit 162 at the optimum value, the flow velocity of the liquid ink 108 passing around the ultrasonic transmission unit 162 is maintained constant. Must.

  Based on such a premise, it is assumed that the liquid ink 108 to which ultrasonic vibration is applied by the ultrasonic vibration applying unit 155 is not stored temporarily in the damper tank 157 but is directly supplied to the inkjet head 105. In this case, when the liquid ink 108 is consumed in the inkjet head 105 along with the discharge operation of the liquid ink 108, the liquid ink 108 is supplied to the inkjet head 105 while applying ultrasonic vibration in the ultrasonic vibration applying unit 155. Become. However, the consumption amount of the liquid ink 108 in the ink jet head 105 greatly fluctuates every printing operation. This is because the consumption amount of the liquid ink 108 in the inkjet head 105 varies greatly depending on various factors such as the printing width, the printing speed, and the printing rate. As an example, it is assumed that printing is performed at a speed of 25 m / min by ejecting 42 pl per nozzle with an inkjet head 105 having 2 inches and 318 nozzles. In this case, solid printing (100% printing) consumes about 240 ml of liquid ink per hour and about 4 ml of liquid ink per minute. That is, the consumption amount of the liquid ink 108 in the inkjet head 105 varies at about 0 to 4 ml / min. Using such an ink jet head 105, for example, when printing is performed at a resolution of 300 dpi on an A4 recording medium 102, ink consumption is 0 to 192 ml / min when printing is performed at a resolution of 600 dpi. Table 1 illustrates the relationship among the printing rate, resolution, paper size, and ink consumption.

  For this reason, under the premise that the liquid ink 108 is directly supplied to the inkjet head 105 while applying ultrasonic vibration to the liquid ink 108 in the ultrasonic vibration applying unit 155, the periphery of the ultrasonic transmitting unit 162 is The flow rate of the liquid ink 108 that passes through this also fluctuates. Then, the value of the ultrasonic vibration application energy given to the liquid ink 108 by the ultrasonic transmission unit 162 also fluctuates, and as a result, the pigment staring body contained in the liquid ink 108 cannot be redispersed well.

  In contrast, in this reference example, the liquid ink 108 is temporarily stored in the damper tank 157, and when the liquid ink 108 is consumed in the inkjet head 105, the liquid ink 108 stored in the damper tank 157 is stored in the inkjet head 105. Supply. For this reason, it is possible to always keep the flow velocity of the liquid ink 108 passing through the periphery of the ultrasonic wave transmission part 162 constant only by controlling the driving of the first pump 153. As a result, the value of the ultrasonic vibration application energy applied to the liquid ink 108 by the ultrasonic transmission unit 162 can always be maintained at an optimal setting value, and the pigment staring body contained in the liquid ink 108 can be well redispersed. Can do.

2. Second Embodiment A second embodiment of the present invention will be described with reference to FIG. The ink jet recording apparatus 101 of the present embodiment is not different from the first embodiment in the basic structure. The difference from the first embodiment is a structure for redispersing the pigment aggregates included in the liquid ink 108 in the ink processing unit 152. In other words, in this first embodiment, ultrasonic vibrations are applied to the liquid ink 108 to redisperse the pigment aggregates contained in the liquid ink 108 as compared with this structure. In form, the pigment aggregates in the liquid ink 108 are centrifuged. That is, in this embodiment, the ultrasonic vibration applying unit 155 of the first embodiment is replaced with the centrifuge 201. Accordingly, the first temperature adjustment unit 156 provided integrally with the ultrasonic vibration applying unit 155 in the first embodiment is replaced with the second temperature adjustment unit 251 provided integrally with the centrifugal separation unit 201. Has been replaced.

  FIG. 5 is a longitudinal front view of the centrifugal separator 201 and the first temperature controller 156. A dome-shaped lower housing 202 and an upper housing 203 that constitute the centrifugal separation unit 201 are joined and fixed to form a centrifugal separation space CSS into which the liquid ink 108 is introduced. The lower housing 202 and the upper housing 203 are housed and held inside a temperature adjustment housing 252 that constitutes the second temperature adjustment unit 251.

  The temperature adjustment housing 252 may cause a refrigerant introduced from the refrigerant introduction port 253, for example, cooling water, to flow inside the temperature adjustment housing 252 and to the outer periphery of the lower housing 202 and the upper housing 203 and be discharged from the refrigerant discharge port 254. It has a structure. The refrigerant is introduced from the refrigerant introduction port 253, flows through the inside of the temperature control housing 252, is discharged from the refrigerant discharge port 254, and is introduced into the refrigerant introduction port 253 again. It is the circulation mechanism 168 that realizes such circulation of the refrigerant (see FIG. 2). Thus, by circulating the refrigerant, the temperature of the liquid ink 108 introduced into the lower housing 202 and the upper housing 203 constituting the centrifugal separator 201 is adjusted. Here, the first temperature adjusting unit 156 is configured.

  A partition wall between the centrifugal separator 201 and the second temperature controller 251 is made of a material having high thermal conductivity, such as copper, aluminum, stainless steel, or the like. The partition wall may corrode depending on the type of the liquid ink 108. In this case, the surface of the partition wall with which the liquid ink 108 contacts is coated with a corrosion resistant resin or the like. Thereby, the corrosion of the said part is prevented.

  Next, the centrifuge unit 201 will be described. A rotating body 204 is rotatably disposed in a centrifugal separation space CSS formed inside the lower housing 202 and the upper housing 203. The rotating body 204 has a cup shape along the lower housing 202, and has a vertical spindle 205 at a position serving as a rotation center. The vertical spindle 205 is inserted through an insertion hole 206 formed in the lower housing 202 and is rotatably held by a bearing 207 provided in the temperature adjustment housing 252. The bearing 207 also serves as a seal for preventing liquid leakage. Such a vertical spindle 205 rotates by being driven by a motor (not shown). The rotational force of the motor is transmitted to the vertical spindle 205 via, for example, a belt transmission mechanism. The principle of centrifugal separation of the liquid ink 108 by the centrifugal separator 201 is that the rotating body 204 is driven to rotate, thereby increasing the fluid component having a relatively low specific gravity, and the pigment aggregate group having a solid component having a relatively high specific gravity. In other words, it is driven to the joint portion between the lower housing 202 and the upper housing 203 which is the outermost peripheral portion. Therefore, the pigment aggregate group which is a solid content obtained by centrifuging from the fluid content of the liquid ink 108 is discharged to one place (the right side portion in FIG. 5) at the joint portion between the lower housing 202 and the upper housing 203. For this purpose, a pigment aggregate discharge port 208 is provided.

  As a structure for introducing the liquid ink 108 into the centrifugal separation unit 201 having such a structure, an ink introduction pipe 209 is inserted into the top of the upper housing 203 or the centrifugal separation space CSS. One end of the ink introduction pipe 209 is connected to a fluid discharge port (not shown) of the first pump (see FIG. 2) and receives supply of the liquid ink 108. The ink introduction pipe 209 is disposed coaxially with the vertical spindle 205 that forms the rotation center of the rotating body 204, and discharges the liquid ink 108 in the vicinity of the bottom surface of the rotating body 204.

  The uppermost position of the upper housing 203 in the centrifugal separation unit 201 serves as a reservoir 210 for the liquid ink 108 consisting only of the fluid after the pigment aggregate group has been centrifuged. In the reservoir 210, a pairing disk pump 211 is fixedly provided on the upper part of the ink introduction pipe 209, and an ink discharge port 212 is formed in the upper housing 203 so as to be positioned above the pairing disk pump 211. . The pairing disk pump 211 discharges the fluid component of the liquid ink 108 raised by the rotation of the rotating body 204 from the ink discharge port 212.

  In such a configuration, the liquid ink 108 sucked up from the ink container 151 by the first pump 153 is introduced into the centrifugal separation space CSS of the centrifugal separator 201 through the ink introduction pipe 209. In the centrifugal separation space CSS, the rotator 204 is driven to rotate, so that the liquid ink 108 is centrifuged, and the liquid ink 108 is centrifuged at the particle size. That is, the pigment aggregate group which is the solid content contained in the liquid ink 108 is centrifuged from the fluid content. The centrifugally separated pigment aggregate group is discharged from the pigment aggregate discharge port 208 to the outside. The fluid component of the liquid ink 108 remaining after the pigment aggregate group discharged outside in this way is centrifuged is raised by the rotation of the rotating body 204 and discharged from the ink discharge port 212 by the pairing disk pump 211. The discharged liquid ink 108 is supplied to the damper tank 157 and temporarily stored.

  Here, the centrifugal force generated by the pigment aggregate separation operation by the centrifugal separation unit 201 can be expressed by the following Expression 2.

  The centrifugal force represented by Equation 2 is also referred to as centrifugal acceleration, and represents the force acting on the distance from the center of the rotating object.

  Moreover, the sedimentation speed of the particles present in the liquid can be defined by the following Stokes equation (Equation 3).

  From the Stokes equation shown in Equation 3, it can be seen that the sedimentation speed of particles existing in the liquid increases in proportion to the acceleration of gravity and in proportion to the square of the radius of the particles. This causes large particles to settle quickly. Also, if the gravitational acceleration is increased by centrifugal force, larger particles can be settled and separated faster. That is, it can be said that the centrifugal separation unit 201 of the present embodiment is a method of removing the pigment aggregate by replacing the gravity acceleration of Stokes' formula with centrifugal acceleration = centrifugal force.

  Here, in order to stably perform ink jet recording, it is necessary to stably discharge the liquid ink 108 from the ink jet head 105. The stability of the discharge state of the liquid ink 108 from the inkjet head 105 is greatly related to the state of pigment particles that are the color material components of the liquid ink 108 supplied to the inkjet head 105. That is, in order to stably discharge the liquid ink 108 from the inkjet head 105, it is important to make the pigment particles contained in the liquid ink 108 supplied to the inkjet head 105 finely and evenly. According to the present embodiment, the centrifugal separation unit 201 centrifuges the pigment aggregate with respect to the liquid ink 108 sucked up from the ink container 151 by the first pump 153. Thereby, the pigment aggregates aggregated and dispersed in the liquid ink 108 are separated from the liquid component of the liquid ink 108 and removed. The liquid ink 108 from which the pigment aggregate has been removed is stored in the damper tank 157 and supplied to the inkjet head 105. Therefore, the liquid ink 108 supplied to the inkjet head 105 is a liquid ink 108 in which pigment particles are finely and uniformly arranged after the pigment aggregate is removed. Therefore, according to the present embodiment, it is possible to stably discharge the liquid ink 108 from the inkjet head 105, thereby enabling inkjet recording to be performed stably.

  In the present embodiment, storing the liquid ink 108 in the damper tank 157 has another technical significance in that the operation of removing the pigment aggregate is performed well. That is, in order to centrifuge the pigment aggregate from the liquid ink 108 in the centrifugal separator 201, the amount of the liquid ink 108 to be centrifuged in the centrifugal space CSS of the centrifugal separator 201 must be set to an optimum value. . For this purpose, the flow rate of the liquid ink 108 supplied to the centrifuge space CSS of the centrifuge 201 according to the operation of the first pump 153 needs to be within a certain range. This is because the separation rate of the pigment aggregate is limited to a certain range from the Stokes' formula described above. That is, in order to efficiently separate the pigment aggregate from the liquid ink 108, the centrifugal separation unit 201 having a fixed structure (centrifugal radius) is used, and the separation operation is stably performed at a fixed flow rate (liquid ink flow rate). It is necessary to do. In this case, when the flow rate is set to a certain range or more, there is a problem that the pigment aggregates to be originally removed cannot be separated. On the other hand, when the flow rate is set to a certain range or less, excessive pigment is added. This causes problems such as separation and removal of even pigment particles having a particle size that is essentially necessary. This is the reason why the flow rate of the liquid ink 108 supplied to the centrifuge space CSS of the centrifuge 201 must be within a certain range according to the operation of the first pump 153.

  Based on such a premise, it is assumed that the liquid ink 108 obtained by centrifuging the pigment aggregate by the centrifuge 201 is supplied directly to the inkjet head 105 without being temporarily stored in the damper tank 157. In this case, when the liquid ink 108 is consumed in the inkjet head 105 as the liquid ink 108 is ejected, the liquid ink 108 is supplied to the inkjet head 105 while centrifuging the liquid ink 108 in the centrifugal separation space CSS. . However, the consumption amount of the liquid ink 108 in the ink jet head 105 greatly fluctuates every printing operation. This is because the consumption amount of the liquid ink 108 in the inkjet head 105 varies greatly depending on various factors such as the printing width, the printing speed, and the printing rate. Therefore, under the premise that the liquid ink 108 is directly supplied to the inkjet head 105 while centrifuging the liquid ink 108 in the centrifugal separation space CSS, the centrifugal separation of the centrifugal separator 201 is performed according to the operation of the first pump 153. Assuming that the flow rate of the liquid ink 108 supplied to the space CSS is constant, the amount of the liquid ink 108 centrifuged in the centrifugal separation space CSS varies each time. As a result, the pigment stare contained in the liquid ink 108 cannot be removed satisfactorily.

  In contrast, in the present embodiment, when the liquid ink 108 is temporarily stored in the damper tank 157 and the liquid ink 108 is consumed in the inkjet head 105, the liquid ink 108 stored in the damper tank 157 is stored in the inkjet head 105. To supply. For this reason, the amount of the liquid ink 108 to be centrifuged in the centrifugal separation space CSS can always be kept constant only by driving and controlling the first pump 153. As a result, the pigment staring body contained in the liquid ink 108 can be satisfactorily removed.

  Further, by providing a defoaming or degassing means (not shown) positioned downstream of the centrifugal separation unit 201 in the flow path of the liquid ink 108, bubbles and the like that cannot be removed by the centrifugal separation unit 201 are more efficiently obtained. Can be removed. Thereby, it is possible to provide the ink jet recording apparatus 101 with more excellent discharge performance.

  It should be noted that the internal volume V (ml) of the centrifugal separation space CSS is practically in the range of 1000 <V <3000, and the centrifugal radius r (cm) is practically in the range of 5 <r <15.

3. Matters common to the first embodiment and the second embodiment Both the first embodiment and the second embodiment of the present invention described above perform monochromatic printing as the ink jet recording apparatus 101. An example of application to an inkjet printer is shown. On the other hand, in practice, the present invention may be applied to an inkjet printer that performs multicolor printing of two or more colors, for example, full color printing, or may be applied to an image forming apparatus other than a printer such as a copying machine. good.

  The first embodiment and the second embodiment are both application examples to the line-type ink jet recording apparatus 101. The line-type inkjet recording apparatus 101 performs printing while transporting and moving the recording medium 102 to the stationary inkjet head 105. On the other hand, the present invention may be applied to a serial type inkjet recording apparatus 101 that performs printing while moving the inkjet head 105 with respect to a stationary recording medium 102.

  Hereinafter, an actual example of the reference example and the second example will be described. An example of the reference example corresponds to the reference example. The second example corresponds to the second embodiment.

1. Example of reference example [Experimental conditions]
The inventor of this application performed continuous printing under the following conditions.

  A liquid ink 108 having an average pigment particle size of about 350 nm was prepared and filled in an ink container 151. The amount of liquid ink was 300 ml. As the liquid ink 108, an epoxy monomer-based dispersion medium in which a pigment is dispersed through a dispersant is used. Pigment Yellow 180 was used as the pigment. As the ultrasonic transmitter 162, an ultrasonic dispersion apparatus US-300T (output: 300w, frequency: 19.5 ± 1 kHz, φ26 mm chip (ultrasonic transmitter)) manufactured by Nippon Seiki Seisakusho Co., Ltd. was used.

  When re-dispersing the pigment aggregate contained in the liquid ink 108, the liquid ink 108 is sucked up by the first pump 153, passed through the ultrasonic vibration applying unit 155, applied with ultrasonic vibration, and stored in the damper tank 157. did. The flow rate (flow velocity) of the liquid ink 108 at this time was adjusted by the first pump 153. In the experiment, six types of liquid ink 108 were tested: 15 ml / min, 30 ml / min, 60 ml / min, 100 ml / min, 150 ml / min, and 300 ml / min. Such flow rate adjustment was performed by changing the passage time of 300 ml of liquid ink to 1 min, 2 min, 3 min, 5 min, 10 min, and 20 min.

  Then, the liquid ink 108 temporarily stored in the damper tank 157 was supplied to the inkjet head 105 by operating the second pump 158, and the ink ejection operation was executed. At this time, the temperature of the liquid ink 108 is adjusted by the first temperature adjusting unit 156, and the temperature conditions of the liquid ink 108 passing through the ultrasonic vibration applying unit 155 are set to 24 ± 1 ° C., 35 ± 1 ° C., 50 ± 1. Inkjet discharge printing was carried out under the respective conditions, changing from 0 ° C.

[Effect of temperature and flow rate of liquid ink 108 on ejection error]
As described above, in order to impart ultrasonic vibration to the liquid ink 108 in the ultrasonic vibration applying unit 155 and thereby favorably redisperse the pigment gaze, the ultrasonic wave applied to the liquid ink 108 by the ultrasonic transmission unit 162. The value of the vibration application energy needs to be set optimally. At this time, as described above, the ultrasonic vibration application energy applied to the liquid ink 108 varies depending on the flow velocity of the liquid ink 108 that passes around the ultrasonic wave transmission unit 162 in the intermediate pipe 160. Therefore, in the actual example of the reference example, in order to maintain the value of the ultrasonic vibration application energy applied to the liquid ink 108 by the ultrasonic transmission unit 162 at the optimum value, the liquid ink 108 that passes around the ultrasonic transmission unit 162 is used. The flow rate must be kept constant. In the example of the reference example, the technical significance of adjusting the temperature of the liquid ink 108 by the first temperature adjusting unit 156 was mentioned. The experimental results that serve as the basis for the matters mentioned in the examples of these reference examples will now be described.

  Tables 2 to 4 show ejection error rates obtained by experiments corresponding to the passage time and flow rate of the liquid ink 108. The ejection error was grasped as the dot missing frequency (%). The ejection performance is better when the dot missing frequency (%) is smaller. Table 2 shows the result when the temperature condition of the liquid ink 108 is set to 24 ± 1 ° C., Table 3 shows the result when the temperature condition of the liquid ink 108 is set to 35 ± 1 ° C., and Table 4 shows the result. The results when the temperature condition of the liquid ink 108 is set to 50 ± 1 ° C. are shown.

  The graph of FIG. 6 is a graph corresponding to Table 2 in which the horizontal axis represents the passage time of the liquid ink 108 passing through the ultrasonic vibration applying unit 155 and the vertical axis represents the ejection error rate. The graph of FIG. 7 is a graph corresponding to Table 3 in which the horizontal axis represents the passage time of the liquid ink 108 passing through the ultrasonic vibration applying unit 155 and the vertical axis represents the ejection error rate. The graph of FIG. 8 is a graph corresponding to Table 4 in which the horizontal axis represents the passage time of the liquid ink 108 passing through the ultrasonic vibration applying unit 155 and the vertical axis represents the ejection error rate.

  From the graphs in Tables 2 to 4 and FIGS. 6 to 8, it can be seen that the redispersion effect of the pigment aggregates when ultrasonic vibration energy is applied to the liquid ink 108 varies depending on the temperature of the liquid ink 108.

When the temperature of the liquid ink 108 is 24 ± 1 ° C., the discharge error is reduced when the flow rate is around 60 ml / min or less. At this time, the unit amount of the liquid ink 108 and the ultrasonic vibration applied energy per unit area of the surface of the ultrasonic wave transmitting portion 162 in contact with the liquid ink 108 are about 6.5 J / cm ² · ml or more.

When the temperature of the liquid ink 108 is 35 ± 1 ° C., the discharge error is reduced when the flow rate is about 30 ml / min or more and 100 ml / min or less. The unit amount of the liquid ink 108 and the ultrasonic vibration applied energy per unit area of the surface of the ultrasonic wave transmitting portion 162 that is in contact with the liquid ink 108 are about 3.9 to about 13 J / cm ² · ml. Become.

When the temperature of the liquid ink 108 is 50 ± 1 ° C., the discharge error is reduced when the flow rate is about 30 ml / min or more and 150 ml / min or less. At this time, the ultrasonic vibration application energy per unit area of the unit amount of the liquid ink 108 and the surface of the ultrasonic wave transmission unit 162 in contact with the liquid ink 108 is about 2.6 to about 13 J / cm ² · ml. Become.

  FIG. 9 is a graph showing the relationship between the range of ultrasonic vibration application energy that can minimize ejection errors and the temperature of the liquid ink 108. In the graph of FIG. 9, the ultrasonic vibration applied energy is on the vertical axis, and the temperature of the liquid ink 108 is on the horizontal axis. From the graph of FIG. 9, it can be seen that when the temperature of the liquid ink 108 increases, the re-dispersion effect of the pigment aggregate occurs even if the flow rate is high. However, when the temperature of the liquid ink 108 is high, the re-dispersion effect of the pigment aggregate tends to become unstable, and the material constituting the liquid ink 108 is likely to be adversely affected. From this, it is desirable that the ultrasonic vibration applying unit 155 performs the ultrasonic treatment slowly at a temperature as close to room temperature as possible.

  Note that the range in which the discharge error exemplified in FIG. 9 can be minimized is a result based on the condition setting in the actual example of this reference example, and is not universal.

2. Second Example [Experimental conditions]
The inventor of this application performed continuous printing under the following conditions.

  A liquid ink 108 having an average pigment particle size of about 141 nm was prepared and filled in an ink container 151. The amount of liquid ink was 3000 ml. As the centrifugal separator 201, for example, LAPX404 manufactured by Alfa Laval, JCF-Z manufactured by Beckman Coulter, or the like can be used. In the second embodiment, a centrifugal separator 201 having a centrifugal radius of 14.1 cm and a volume of 1000 ml was used. The liquid ink 108 prepared in the ink container 151 is sucked up by the first pump 153 and put into the centrifuge space CSS of the centrifuge 201. The ink flow rate at this time is controlled by the first pump 153.

In the experiment, the conditions of the flow rate (defined by the time that 1000 ml passes) and the centrifugal force (the number of rotations of the rotating body 204 in the centrifugal separation unit 201) are
Flow rate: 100ml / min
Centrifugal force: 15000G
As fixed. In the experiment, the temperature of the liquid ink 108 discharged through the pairing disk pump 211 was measured by a contact-type thermometer (not shown) attached in the flow path of the liquid ink 108. The measured temperature of the liquid ink 108 was controlled by the second temperature adjustment unit 251 so as to be a constant temperature. Here, the liquid ink temperature was set to 30 ± 2 ° C. (normal temperature).

[Confirmation of effect on discharge error]
Using the liquid ink 108 from which the pigment aggregate was centrifuged and removed under the above conditions, the inkjet head 105 was caused to eject ink, and the ejection error was measured. In comparison, it was confirmed that the liquid ink 108 subjected to the centrifugal separation treatment has fewer ejection errors. As a specific numerical value, when the initial liquid ink 108 not subjected to the centrifugal separation process was used, the ejection error was 12.2%, but when the liquid ink 108 subjected to the centrifugal separation process was used. The discharge error was improved to about 8.9%.

[Effect of flow rate of liquid ink 108 on ejection error]
Table 5 shows ejection error rates obtained in experiments corresponding to the passage time and flow rate of the liquid ink 108 in the centrifugal separator 201. The ejection error was grasped as the dot missing frequency (%). The ejection performance is better when the dot missing frequency (%) is smaller.

  The graphs of FIGS. 10 and 11 are graphs corresponding to Table 5 in which the horizontal axis represents the passage time of the liquid ink 108 that passes through the centrifugal separator 201 and the vertical axis represents the ejection error rate. FIG. 10 shows the results when the centrifugal force applied to the liquid ink 108 is 7500G, and FIG. 11 shows the results when the centrifugal force applied to the liquid ink 108 is 15000G.

  From the graphs of Table 5, FIG. 10, and FIG. 11, the optimum flow rate range of the liquid ink 108 can be seen.

  Table 6 is a graph showing the relationship between the centrifugal force applied to the liquid ink 108 and the passage time / flow rate of the liquid ink 108 in the centrifugal separator 201.

  When the centrifugal force is smaller than 2500 G, the effect of separating the pigment aggregates in the liquid ink by the centrifugal force is reduced. On the other hand, in the range where the centrifugal force exceeds 40000G, it is necessary to increase the accuracy of the centrifugal separator 201 or to rotate it at high speed. This increases the cost of the device and is not practical.

DESCRIPTION OF SYMBOLS 102 Recording medium, 105 Inkjet head, 106 Light irradiation part (UV irradiation light source), 108 Liquid ink, 155 Ultrasonic vibration provision part, 156 1st temperature control part, 157 Ink storage part (damper tank), 158 Ink supply part (Second pump), 201 centrifuge, 251 second temperature controller

JP-A-4-216940

Claims (5)

An inkjet recording apparatus that performs printing by an inkjet head on a recording medium using a liquid ink in which a pigment is dispersed in a dispersion medium,
A centrifuge that applies centrifugal force to the liquid ink to centrifuge the pigment aggregates dispersed in the liquid ink;
An ink reservoir for storing the liquid ink after the pigment aggregate has been centrifuged by the centrifuge; and
An ink supply unit that supplies the liquid ink stored in the ink storage unit to the inkjet head; and
An ink jet recording apparatus comprising:   The inkjet recording apparatus according to claim 1, further comprising a deaeration unit that deaerates the liquid ink before being stored in the ink storage unit.   The inkjet recording apparatus according to claim 1, further comprising a temperature adjusting unit that adjusts a temperature of the liquid ink that passes through the centrifugal separation unit.   The inkjet recording apparatus according to claim 1, further comprising a light irradiation unit configured to irradiate the liquid ink after being ejected from the inkjet head and attached to the recording medium. As the liquid ink,
At least one solvent that polymerizes in the presence of an acid;
A photoacid generator that dissolves in the solvent and generates an acid by light irradiation;
A color component dissolved or dispersed in the solvent;
The ink-jet recording apparatus according to claim 1, wherein the liquid ink containing a liquid crystal is used.

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