JP2014141053A - Ink filling method and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink filling method capable of achieving high ink discharging performance immediately after (e.g., within 3 hours from ink filling) an ink head is filled with ink.SOLUTION: An ink filling method includes the first filling step of heating filling start liquid containing an acetylene glycol surface active agent and water represented by a general formula (1) to 30°C or higher to 90°C or lower, and filling the ink jet head with the filling start liquid, and the second filling step of filling the ink jet head with ink containing a pigment and water after filling with the filling start liquid. [In the general formula (1), Rto R: hydrogen atoms, and linear, branch and annular alkyl groups of carbon numbers 1 to 8, Yto Y: alkylene group of carbon numbers 2 to 6, and x, y: average addition mol number (1≤x+y≤85)]. General formula (1).

Description

  The present invention relates to an ink filling method and an image forming method.

  Image forming methods based on the inkjet method are widely used because, for example, high-quality images can be recorded on a wide variety of recording media by ejecting ink droplets from a large number of nozzle holes provided in an inkjet head. Has been. In such an image forming method, an image is formed by ejecting ink onto a recording medium from an ink jet head filled with ink.

  Various techniques for removing bubbles mixed in the ink have been studied for the ink used in the image forming method by the inkjet method.

For example, a technique is known in which ink in an ink tank heated by a heating means (for example, a temperature higher than the ambient temperature by 5 ° C. or more) is supplied into an inkjet head through an ink supply tube (see, for example, Patent Document 1). ). Ink that injects ink at a temperature of about 30 to 60 ° C. when the ink is injected into the treatment chamber of the ink cartridge having a storage chamber in which the porous body is disposed to absorb the ink in the porous body. A method for injecting ink into a cartridge is known (for example, see Patent Document 2).
Furthermore, an ink jet recording apparatus including a deaeration device for removing bubbles in the ink is known (see, for example, Patent Document 3).

JP-A-1-297251 Japanese Patent Laid-Open No. 10-258517 JP 2010-83021 A

  However, in the image formation by the ink jet method using so-called water-based ink containing water and pigment, ink ejection failure (decrease in ejection performance) may occur even when the conventional technique is used. In some cases, white spots may occur in the formed image due to poor ink ejection. In order to improve such ink ejection failure, it is conceivable to reduce the surface tension of the ink by containing a surfactant in the ink. However, in the case of ink containing a surfactant, particularly immediately after the ink is filled in the ink jet head (for example, within 3 hours from the filling of the ink), compared with the case where the ink containing no surfactant is used. Dischargeability may be reduced.

  The present invention has been made in view of the above situation, and an ink filling method that realizes good ink discharge performance immediately after ink is filled into an ink jet head (for example, within 3 hours from ink filling), and ink in an ink jet head An object of the present invention is to provide an image forming method in which an image with excellent ink ejection properties and suppression of white spots is formed immediately after filling (for example, within 3 hours from ink filling). The task is to do.

The inventor of the present invention fills an inkjet head with a filling start liquid containing a specific surfactant heated to a specific temperature range before filling and discharging an aqueous ink containing a pigment into the inkjet head. The liquid wettability on the inner wall surface of the head is improved, and it is possible to suppress the bubble adhering to the wall surface, and the bubbles that affect the ink ejection (the bubbles adhering to the wall surface gradually separate and float in the ink) The present inventors have obtained the knowledge that the remaining of the bubbles is reduced and is effective in solving the above problems, and have completed the present invention based on such knowledge.
That is, the specific means for achieving the subject in the present invention is as follows.

  <1> A filling start liquid containing an acetylene glycol surfactant represented by the following general formula (I) and water is heated to 30 ° C. or higher and 90 ° C. or lower, and the heated filling start liquid is filled in the inkjet head. And a second filling step of filling the inkjet head with an ink containing a pigment and water after filling with a filling start liquid.

In the general formula (I), R ⁵² , R ⁵³ , R ⁵⁴ and R ⁵⁵ each independently represent a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 8 carbon atoms. Y ² and Y ³ each independently represents an alkylene group having 2 to 6 carbon atoms. x and y represent an average added mole number and satisfy 1 ≦ x + y ≦ 85.

<2> The ink filling method according to <1>, wherein the inkjet head before the first filling step is an unfilled inkjet head.
<3> The first filling step is the ink filling method according to <1> or <2>, wherein the filling start liquid is heated to 40 ° C. or higher and 70 ° C. or lower.
<4> The ink filling method according to any one of <1> to <3>, wherein the filling start liquid further contains a silicone-based antifoaming agent.
<5> The filling start liquid is an ink filling method according to any one of <1> to <4>, in which a surface tension is 40 mN / m or less.
<6> The ink filling method according to any one of <1> to <5>, wherein the ink further contains polymer particles.

<7> A circulation system including an inkjet head and a supply unit for switching and supplying the filling start liquid and the ink to the inkjet head, and a temperature adjusting means for adjusting the temperature of the filling start liquid and the ink circulating in the circulation system. And an ink filling step of filling the ink jet head with the ink by the ink filling method according to any one of <1> to <6>, and after the ink filling step The image forming method includes a temperature adjustment step of adjusting the temperature of the ink to 20 ° C. or more and 50 ° C. or less, and an ink discharge step of discharging the temperature-controlled ink from the inkjet head onto the recording medium.
<8> Further, in the ink filling step, after the first filling step in the ink filling method and before the second filling step, circulation in which a filling start liquid of 30 ° C. or more and 90 ° C. or less is circulated in the circulation system. It is an image forming method as described in <7> which has a process.
<9> An ink filling step of filling the ink jet head with ink by the ink filling method according to any one of <1> to <6> above, and discharging the filled ink from the ink jet head onto a recording medium. And an ink ejection step.
<10> The ink forming step is the image forming method according to <9>, wherein the temperature of the filled ink is adjusted to 20 ° C. or more and 50 ° C. or less and then discharged.
<11> The image forming method according to any one of <7> to <10>, further comprising a treatment liquid application step of applying a treatment liquid containing an aggregation component that aggregates the components in the ink onto the recording medium. It is.

According to the present invention, there is provided an ink filling method that realizes good ink discharge performance immediately after ink is filled in an ink jet head (for example, within 3 hours from ink filling).
In addition, according to the present invention, an image forming method for forming an image that is excellent in ink ejection and suppresses occurrence of white spots immediately after ink is filled in an ink jet head (for example, within 3 hours from ink filling). Is provided.

1 is a schematic view showing an example of an image forming apparatus suitable for an image forming method of the present invention. 1 is a schematic diagram showing an ink circulation system as an example of an image forming apparatus suitable for an image forming method of the present invention. FIG. 3 is a schematic diagram illustrating a head temperature adjusting unit as an example of an image forming apparatus suitable for the image forming method of the present invention.

Hereinafter, the ink filling method and the image forming method of the present invention will be described in detail.
<Ink filling method>
The ink filling method of the present invention is a method of filling an ink jet head that has not been filled with ink with a filling start liquid in advance and then filling the ink.
A filling start liquid containing an acetylene glycol surfactant represented by the general formula (I) and water shown below is heated to 30 ° C. or higher and 90 ° C. or lower, and the heated filling start liquid is filled into the inkjet head. The first filling step and the second filling step for filling the inkjet head with ink containing a pigment and water after filling with the filling start liquid are provided.
The ink filling method of the present invention may be configured by further providing other processes such as a degassing process for degassing ink as necessary.

In the image formation by the inkjet method using water-based ink containing water as a solvent, ink ejection failure (decrease in ejection performance) may occur. In the formed image due to ink ejection failure. White spots may occur on the screen.
In order to suppress ink ejection failure, it is conceivable to reduce the surface tension of the ink by containing a surfactant in the ink. However, in the case of the ink containing the surfactant, the ink jet head (hereinafter, also simply referred to as “head”) is filled with the ink (for example, within 3 hours from the filling of the ink. It has been found that may decrease. This is because air bubbles are likely to be generated in the ink immediately after the head is filled with ink, and the generated air bubbles are likely to remain in the ink, and further, the air bubbles adhere to the inner wall of the head or the ink supply path and are not easily detached. Conceivable.
In contrast, in the present invention, in addition to the ink, a filling start liquid (hereinafter also simply referred to as “starting liquid”) is prepared for performing the filling process on the head prior to the ink filling. The liquid is composed of an acetylene glycol surfactant having a predetermined structure, and the temperature of the starting liquid is adjusted to a range of 30 ° C. or higher and 90 ° C. or lower to fill the head. As a result, when ink is subsequently filled in the ink jet head, a decrease in ink discharge performance immediately after ink filling is suppressed.
The reason why such an effect is obtained is estimated as follows. That is,
Before the ink is filled into the head, the wettability of the ink with respect to the inner wall surface of the head is enhanced by pre-wetting the inner wall surface of the head with a liquid having a low surface tension, and bubbles do not easily adhere to the wall surface. Further, by increasing the temperature of the starter liquid itself to 30 ° C. or higher, the solubility of the gas in the starter liquid is lowered and the dissolved gas is reduced, so that the amount of gas that can be bubbles can be reduced. That is, the filling start liquid does not contain dispersed particles such as pigments and polymer particles, and has a low surface tension, so that the amount of gas can be controlled without worrying about dispersion instability and precipitation.
In this way, by adjusting the combination of the decrease in surface tension and the temperature rise of the liquid, wetting the inner wall surface of the head, preventing bubbles from adhering to the wall surface, the amount of bubbles adhering to the wall surface is significantly reduced. Therefore, it is considered that a decrease in dischargeability immediately after ink filling is suppressed.

Note that the above-described white spots in the image may occur in a streak shape, and in the present specification, this streaky white spot is sometimes referred to as a “white streak”.
White stripes are also referred to as nozzles that do not eject ink (hereinafter also referred to as “non-ejection nozzles”) to some of the plurality of nozzles of an inkjet head having a plurality of ejection holes (hereinafter also referred to as “nozzles”). ) Occurs. That is, when an image is formed by ejecting (applying) ink from a plurality of nozzles onto a recording medium, ink is not applied to the recording medium at a position corresponding to the non-ejection nozzle, resulting in streak-like white spots.

In the ink filling method of the present invention, when the temperature of the filling start liquid filled in the head prior to the ink is less than 30 ° C., when filling the head with ink after filling the filling start liquid, particularly immediately after the ink filling. Ink discharge performance is likely to be lowered (ink discharge failure is likely to occur). That is, since the effect of using the filling start liquid is reduced, it is considered that bubbles still remain in the ink. Therefore, if the temperature of the filling start liquid is less than 30 ° C., the remaining air bubbles deteriorate the ink discharge performance immediately after ink filling.
On the other hand, when the temperature of the filling start liquid exceeds 90 ° C., the evaporation of water in the filling start liquid becomes remarkable, the liquid composition cannot be maintained by the evaporation of water, and the effect of using the filling start liquid is reduced. . In some cases, precipitates are likely to be generated in the vicinity of the nozzles of the inkjet head. Furthermore, there is a risk of damage to members of the supply system including the ink jet head. For this reason, if the temperature of the filling start liquid exceeds 90 ° C. and becomes too high, the ink ejection performance is degraded.

  In the ink filling method of the present invention as described above, instead of the acetylene glycol surfactant represented by the general formula (I) contained in the filling start liquid, another surfactant (for example, the general formula (I When using acetylene glycol surfactants other than the acetylene glycol surfactants represented by), acetylene alcohol surfactants, polyoxyethylene nonylphenyl ether, sodium lauryl sulfate, etc.) Even if the temperature of the ink at that time is adjusted to 30 ° C. or more and 90 ° C. or less, immediately after the ink is filled in the head, the discharge property tends to be lowered. This is presumably because when other surfactants are used, bubbles tend to be generated and bubbles are likely to be generated in the ink, and bubbles are likely to remain in the ink.

Various studies have been made on the technology for improving the ink ejection property, and a technology for removing bubbles in the ink as described above is also known. However, it has been difficult to improve the ink discharge performance immediately after the ink is filled in the head (particularly, the unfilled head) only with the conventional technique. In the present invention, separately from the ink, a starting liquid for filling the head prior to the ink filling is prepared, and the type of surfactant constituting the starting liquid and the filling of the starting liquid into the head By selecting the temperature at which the ink is discharged, the ink discharge performance immediately after the ink is filled is improved.
Here, in order to improve the ink discharge performance, not only the discharge failure of the ink from the nozzle is reduced, but also the variation in the ink discharge amount from the nozzle is reduced (that is, the ink discharge stability is improved). Improvement).

  In addition, according to the present invention, the ink discharge performance is improved particularly immediately after ink filling, but is not limited to just after ink filling, and is excellent even after a certain amount of time has passed since ink filling. Ink discharge performance is maintained.

  The effects of the present invention described above are particularly prominent when ink is filled into an unfilled inkjet head (so-called initial filling).

In the present invention, an unfilled inkjet head refers to an inkjet head that is substantially not filled with ink. Specifically, the volume of ink that exists in the inkjet head is an ink that can be filled in the inkjet head. This refers to an inkjet head in a state of 10% by volume or less (preferably 5% by volume or less, more preferably 1% by volume or less, particularly preferably 0% by volume) with respect to the maximum value of the volume. A thing that is in contact and dry.
As an unfilled inkjet head, for example, an inkjet head after removing the filled ink in order to suspend use for maintenance reasons, or an inkjet that is filled with ink for testing at the time of shipment and then drained. Heads include inkjet heads that have never been filled with ink (ie, unused).

  Hereinafter, the first and second filling steps constituting the ink filling method of the present invention, and the filling start liquid and ink used in each step will be described in detail.

[First filling step]
In the first filling step of the present invention, the filling start liquid containing the acetylene glycol surfactant represented by the general formula (I) and water is heated to 30 ° C. or higher and 90 ° C. or lower, and the heated filling start liquid is obtained. Is filled into the inkjet head. In the present invention, this step is provided prior to ink filling, including a predetermined acetylene glycol surfactant, and adjusting the temperature of the filling start liquid to 30 ° C. or higher and 90 ° C. or lower, thereby specifically ink. The ink discharge performance immediately after the ink is supplied to the head is improved.
The ink jet head will be briefly described in the second filling step described later.

  In this step, before the head is filled with ink, a filling start liquid heated to a temperature of 30 ° C. or higher and 90 ° C. or lower is filled. The temperature here refers to the temperature at which the filling start liquid is filled in the head. The temperature of the filling start liquid filled in the head is preferably 40 ° C. or higher and 70 ° C. or lower, and more preferably 50 ° C. or higher and 70 ° C. or lower.

There is no restriction | limiting in particular about the heating method which heats a filling start liquid, The well-known method using heating means, such as a heater, is applicable. Moreover, there is no restriction | limiting in particular also in the filling method which fills an inkjet head with a filling start liquid.
As a specific form of the heating method and the filling method, an image provided with a circulation system that does not include an inkjet head and includes a supply unit for ink or the like (a supply unit for switching and supplying a filling start liquid and ink to the inkjet head). Using a forming apparatus (for example, image forming apparatus 10 described later), the filling start liquid is circulated through the circulation system, and the filling start liquid circulating through the circulation system is heated to 30 ° C. or more and 90 ° C. or less, and then 30 ° C. or more and 90 ° C. or less. A mode in which the heated filling start liquid is supplied to the inkjet head by supplying the heated filling start liquid to the inkjet head can be mentioned. In this case, after the filling of the filling start liquid into the head is completed, the filling start liquid in the circulation system is drained, the ink is circulated through the circulation system, and the ink circulating in the circulation system is kept at a predetermined temperature (preferably 20 ° C. or higher). After adjusting the temperature to 50 ° C. or lower), the temperature-adjusted ink is supplied to the inkjet head, so that the ink can be filled into the inkjet head so that bubbles that impair the ejection performance do not remain.

-Filling start liquid-
The filling start liquid in the present invention contains at least an acetylene glycol surfactant represented by the following general formula (I) and water. The filling initiating liquid of the present invention may be constituted by using other components such as a basic compound and an antifoaming agent as necessary. However, the filling start liquid in the present invention is not a liquid for forming an image, and preferably the content of a colorant such as a pigment is less than 0.1% by mass, and further no colorant is contained.

(Acetylene glycol surfactant)
The filling starter in the present invention contains at least one acetylene glycol surfactant represented by the general formula (I). By containing this acetylene glycol surfactant, the ink discharge performance immediately after the ink is supplied to the head is improved.

In the general formula (I), R ⁵² , R ⁵³ , R ⁵⁴ and R ⁵⁵ each independently represent a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 8 carbon atoms. Y ² and Y ³ each independently represents an alkylene group having 2 to 6 carbon atoms. x and y represent an average added mole number and satisfy 1 ≦ x + y ≦ 85.

Examples of the linear, branched, or cyclic alkyl group having 1 to 8 carbon atoms represented by R ⁵² and R ⁵⁴ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, and an isobutyl group. , 2-butyl group, t-butyl group, hexyl group, cyclohexyl group, octyl group and the like. If R ⁵² and R ⁵⁴ represents a cyclic alkyl group, the carbon number of the alkyl group is preferably in the range of 3-8.
R ⁵² and R ⁵⁴ are more preferably an alkyl group having 1 to 3 carbon atoms, and most preferably a methyl group.

Examples of the linear, branched, or cyclic alkyl group having 1 to 8 carbon atoms represented by R ⁵³ and R ⁵⁵ include, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, Examples include isobutyl group, 2-butyl group, t-butyl group, hexyl group, cyclohexyl group, octyl group and the like. When R ⁵³ and R ⁵⁵ represent a cyclic alkyl group, the alkyl group preferably has 3 to 8 carbon atoms.
R ⁵³ and R ⁵⁵ are preferably a linear, branched, or cyclic alkyl group having 3 to 8 carbon atoms, and particularly preferably an isobutyl group.

x and y represent the average number of moles added.
The sum of x and y is 1 to 85 (1 ≦ x + y ≦ 85), preferably 3 to 50, more preferably 3 to 30, and more preferably 5 to 30. .
When the sum of x and y is 3 or more, the solubility is further improved and the cloud point is further increased. Thereby, isolation | separation and precipitation at the time of heating the filling start liquid in this invention to 30 degreeC or more are suppressed more.
On the other hand, when the sum of x and y is 30 or less, the effect of reducing surface tension and improving wettability appears more effectively. Thereby, when discharging the filled ink after filling the filling start liquid, the discharge stability of the discharged ink is further improved.

Y ² and Y ³ each independently represent an alkylene group having 2 to 6 carbon atoms, more preferably an alkylene group having 2 to 4 carbon atoms, still more preferably an alkylene group having 2 or 3 carbon atoms, and 2 carbon atoms. An alkylene group (ethylene group) is particularly preferred.
That is, among the compounds represented by the general formula (I), an acetylene glycol surfactant represented by the following general formula (II) is more preferable.

In formula ^{(II), R 52, R} 53, R 54, R 55, x, and y, ^R 52 in the general formula ^{(I), R 53, R} 54, R 55, x, and y respectively synonymous The preferred range is also the same.

  Examples of the compound represented by the general formula (I) include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6- Alkylene oxide adducts (preferably ethylene oxide adducts) such as diol, 2,5,8,11-tetramethyl-6-dodecine-5,8-diol, 2,5-dimethyl-3-hexyne-2,5-diol ). In particular, an ethylene oxide adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (3 ≦ x + y ≦ 30, more preferably 5 ≦ x + y ≦ 30) is preferable.

The acetylene glycol surfactant represented by the general formula (I) can be used alone or in combination with various additives.
As the acetylene glycol surfactant represented by the general formula (I), a commercially available product may be used, and as a commercially available product, Surfynol manufactured by Air Products or Nissin Chemical Industry Co., Ltd. may be used. Series (for example, Surfinol 420, Surfinol 440, Surfinol 465, Surfinol 485, Orphine series (for example, Orphin E1010, Orphin E1020), Dinol series (for example, Dinol 604), etc., and Kawaken Fine Chemical Co., Ltd.) These are also available from Dow Chemical Company, General Aniline Company, etc.

The acetylene glycol surfactants represented by the general formula (I) may be used singly or in combination of two or more.
The content of the acetylene glycol surfactant in the filling start liquid is preferably 0.01 to 5% by weight, more preferably 0.1 to 2% by weight with respect to the total weight of the filling start liquid. is there. When the content of the acetylene glycol surfactant is within the above range, the ink discharge performance immediately after the ink is supplied to the head is improved, and the generation of bubbles in the ink is promoted. I don't give it.
In addition, when 2 or more types of acetylene glycol-type surfactant is included, it is preferable to satisfy | fill said range with a total amount.

  In the present invention, the surface tension of the filling start liquid can be lowered by including an acetylene glycol surfactant. The filling start liquid having a low surface tension enhances the wettability of the inner wall surface of the head or the like, thereby improving the ink discharge performance. An acetylene glycol surfactant having a higher cloud point is preferred from the viewpoint of further suppressing precipitation caused by heating the filling initiation liquid to 30 ° C to 90 ° C. From this viewpoint, an ethylene oxide adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (3 ≦ x + y ≦ 30, more preferably 5 ≦ x + y ≦ 30) is most preferable. In addition, as commercially available products of ethylene oxide adduct (3 ≦ x + y ≦ 30) of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, Surfynol 440, Surfynol manufactured by Air Products 465, Surfynol 485, Nissin Chemical Industry Co., Ltd. Olfine E1010, Olfine E1020.

(Defoamer)
The filling starter in the present invention preferably contains at least one antifoaming agent.
Examples of the antifoaming agent include silicone compounds (silicone defoaming agents) and pluronic compounds (pluronic defoaming agents). Among these, silicone antifoaming agents are preferable.
As the silicone-based antifoaming agent, a silicone-based antifoaming agent having a polysiloxane structure is preferable.

A commercial item can be used as an antifoamer. Commercially available products include BYK-012, 017, 021, 022, 024, 025, 038, 094 (above, manufactured by Big Chemie Japan Co., Ltd.), KS-537, 604, KM- 72F (manufactured by Shin-Etsu Chemical Co., Ltd.), TSA-739 (manufactured by Momentive Performance Materials Japan GK), Olfin AF104 (manufactured by Nissin Chemical Industry Co., Ltd.) and the like.
Of these, BYK-017, 021, 022, 024, 025, 094, KS-537, 604, KM-72F, and TSA-739, which are silicone antifoaming agents, are preferable. BYK-024 is most preferable in terms of ejection stability.

The antifoaming agent may be used alone or in combination of two or more.
The content of the antifoaming agent in the filling start liquid is preferably 0.0001 to 1.0% by weight, more preferably 0.001 to 0.1% by weight, based on the total weight of the filling start liquid. When the content of the antifoaming agent is within the above range, the ink ejection property immediately after the ink is supplied to the head can be further improved.

(water)
The filling start liquid in the present invention contains water. That is, the filling start liquid in the present invention is an aqueous liquid.

Although there is no restriction | limiting in particular in content of the water in the filling start liquid in this invention, 60 mass% or more is preferable with respect to the whole quantity of a filling start liquid, 70 mass% or more is further more preferable, and 80 mass% or more is especially preferable. preferable.
Although there is no restriction | limiting in particular about the upper limit of water content, Since it is related with surfactant content, it can be set to 99.8 mass%. The upper limit of the water content is preferably 99.5% by mass.

(Other ingredients)
In addition to the above, the filling start liquid of the present invention may contain other components such as a basic compound and an organic solvent.

The filling start liquid in the present invention may contain, for example, at least one basic compound. By containing the basic compound, it is possible to provide a buffering action for preventing the pH from being lowered due to decomposition of the contained components or the like when the filling start liquid has elapsed with storage or the like.
The basic compound is preferably a compound having a pKa value of 6.0 to 8.5 in that it exhibits pH buffering capacity in the pH range of the filling start solution. The basic compound may be either an inorganic compound or an organic compound, and a basic organic compound is preferable from the viewpoints of easily obtaining a desired pKa value and good solubility. The pKa value of the basic organic compound is the pKa value of the conjugate acid.
Examples of the basic compound include cacodylic acid (pKa: 6.2), 2,2-bis (hydroxymethyl) -2,2 ′, 2 ″ -nitrilotriethanol (pKa: 6.5), piperazine-N, N′-bis- (2-ethanesulfuric acid) (pKa: 6.8), phosphoric acid (pKa2: 6.86), imidazole (pKa: 7.0), N′-2-hydroxyethylpiperazine-N ′, 2-ethane sulfate (pKa: 7.6), N-methylmorpholine (pKa: 7.8), triethanolamine (pKa: 7.8), hydrazine (pKa: 8.11), trishydroxymethylaminomethane ( pKa: 8.3) and the like.
When the basic compound is contained, the content of the basic compound in the filling start liquid is preferably in the range of 0.0001 to 0.1% by mass with respect to the total mass of the filling start liquid, and is 0.001 to 0.00. A range of 01% by weight is particularly preferred.
The pH of the starting liquid is not particularly limited, but the pH at 25 ° C. is 6.5 from the viewpoint of preventing aggregation with the coloring material when mixed with ink and increasing the liquid contact resistance inside the head. The range of 10 to 10 is preferable, and the range of 7 to 9 is more preferable. The pH can be adjusted by adding an acid such as nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid or succinic acid after adding a basic compound. The acid used for the adjustment is most preferably nitric acid from the viewpoint of metal corrosion resistance.

~ Physical properties of filling start liquid ~
The surface tension of the filling start liquid is preferably 40 mN / m (= dyn / cm) or less, more preferably 15 mN / m or more and 35 mN / m or less, and 20 mN / m or more and 30 mN at the temperature of the filling start liquid of 25 ° C. / M or less is more preferable. The surface tension of the filling start liquid can be adjusted by, for example, the content of the acetylene glycol surfactant described above.
The surface tension of the filling start liquid is a value measured at 25 ° C. using a plate method.

[Second filling step]
In the second filling step in the present invention, following the filling of the filling start liquid in the first filling step, an ink containing a pigment and water is filled in the inkjet head.

There is no particular limitation on the filling method for filling the ink jet head with ink.
As a specific form of the ink filling method, an image forming apparatus (for example, an image forming apparatus 10 to be described later) provided with the circulation system as described above is used, and the filling start liquid is circulated in the circulation system in the first filling step. Then, after filling the heated filling start liquid into the inkjet head, the filling start liquid in the circulation system is drained, the ink is circulated through the circulation system, and the ink circulating through the circulation system is kept at a predetermined temperature (preferably 20 ° C. to 50 ° C. The temperature may be adjusted to the following), and then the temperature-adjusted ink may be supplied to the inkjet head to fill the inkjet head with the ink.

The inkjet head is not particularly limited, and may be an on-demand system or a continuous system.
In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, a thermal type) Specific examples include an ink jet type, a bubble jet (registered trademark) type, an electrostatic suction type (for example, an electric field control type, a slit jet type, etc.) and a discharge type (for example, a spark jet type). However, any discharge method may be used.
In addition, there is no restriction | limiting in particular about the discharge hole (nozzle) etc. which are provided in an inkjet head, According to the objective, it can select suitably.

As an inkjet head, a short head used in a shuttle system that performs recording while scanning the head in the width direction of the recording medium, a line in which nozzles are arranged corresponding to the entire area of one side of the recording medium used in a line system. A head or the like. In the line method, an image is recorded on the entire surface of the recording medium by scanning the recording medium in a direction perpendicular to the nozzle arrangement direction. In this line system, a transport system such as a carriage for scanning a short head is not necessary. Further, since complicated scanning control of the carriage movement and the recording medium is not required, and only the recording medium is moved, the recording speed can be increased as compared with the shuttle system.
The image forming method of the present invention can be applied to any of these, but in general, when applied to a line system in which no dummy jet is performed (that is, when the ink jet head is a line head), the effect of improving the ejection performance. In addition, the effect of suppressing white spots is great.
For details of the structure of the line head, for example, the structure described in paragraphs 0052 to 0063 (FIGS. 3 to 5) of JP2010-83021A, paragraphs 0111 to 0117 of JP2011-202117A, and the like. Reference can be made to the structure of the head provided with the silicon nozzle plate described in FIGS.

-Ink-
The ink in the present invention contains at least a pigment and water. The ink preferably further contains polymer particles, and may further contain other components such as an organic solvent, a surfactant, and an additive as necessary.

(Pigment)
The ink in the present invention contains at least one pigment.
There is no restriction | limiting in particular as a pigment, A conventionally well-known organic and inorganic pigment can be used. For example, polycyclic pigments such as azo lakes, azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, diketopyrrolopyrrole pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, basic Examples include dye lakes such as dye type lakes and acid dye type lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments, and inorganic pigments such as titanium oxide, iron oxide, and carbon black. It is done. Any pigment not described in the color index can be used as long as it can be dispersed in the aqueous phase. Further, it is of course possible to use a pigment obtained by surface-treating the above pigment with a surfactant, a polymer dispersing agent or the like, or graft carbon. Among the above pigments, it is particularly preferable to use an azo pigment, a phthalocyanine pigment, an anthraquinone pigment, a quinacridone pigment, or a carbon black pigment. Specific examples include pigments described in JP-A-2007-100071.

~ Dispersant ~
The ink in the present invention preferably has a form in which the pigment is dispersed by a dispersant.
Among these forms, a form in which the pigment is dispersed by the polymer dispersant, that is, a form in which at least a part of the pigment is coated with the polymer dispersant is particularly preferable. Hereinafter, the pigment at least partially coated with the polymer dispersant is also referred to as “polymer-coated pigment”.

The dispersant may be a polymer dispersant or a low molecular surfactant type dispersant. The polymer dispersant may be a water-soluble polymer dispersant or a water-insoluble polymer dispersant.
As the low molecular surfactant type dispersant, the surfactant type dispersant described in paragraphs 0016 to 0020 of JP 2010-188661 A can be used.

Among the polymer dispersants, hydrophilic polymer compounds can be used as the water-soluble polymer dispersant.
As the water-soluble polymer dispersant, for example, natural hydrophilic polymer compounds described in paragraphs 0021 to 0022 of JP 2010-188661 A can be used.

As the water-soluble polymer dispersant, a synthetic hydrophilic polymer compound may be used.
Synthetic hydrophilic polymer compounds include vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyvinyl methyl ether, polyacrylamide, polyacrylic acid or alkali metal salts thereof, acrylic resins such as water-soluble styrene acrylic resins, Water-soluble styrene maleic acid resin, water-soluble vinyl naphthalene acrylic resin, water-soluble vinyl naphthalene maleic resin, polyvinyl pyrrolidone, polyvinyl alcohol, alkali metal salts of β-naphthalene sulfonic acid formalin condensate, cations such as quaternary ammonium and amino group And a high molecular compound having a salt of a functional functional group in the side chain.

  Among these, from the viewpoint of pigment dispersion stability and aggregation, a polymer compound containing a carboxyl group is preferable. For example, an acrylic resin such as a water-soluble styrene acrylic resin, a water-soluble styrene maleic resin, and a water-soluble vinyl naphthalene. High molecular compounds containing a carboxyl group such as an acrylic resin and a water-soluble vinyl naphthalene maleic resin are particularly preferred.

As the water-insoluble dispersant among the polymer dispersants, a polymer having both a hydrophobic part and a hydrophilic part can be used. For example, styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, (meth) acrylic acid ester- (meth) acrylic acid copolymer, polyethylene glycol ( Examples thereof include a meth) acrylate- (meth) acrylic acid copolymer and a styrene-maleic acid copolymer.
Styrene- (meth) acrylic acid copolymer, (meth) acrylic acid ester- (meth) acrylic acid copolymer, polyethylene glycol (meth) acrylate- (meth) acrylic acid copolymer, styrene-maleic acid copolymer May be a binary copolymer or a ternary or higher copolymer.
Among these, (meth) acrylic acid ester- (meth) acrylic acid copolymer is preferable as the polymer dispersant, and benzyl (meth) acrylate- (meth) acrylic acid-methyl (meth) acrylate ternary copolymer is preferable. Is particularly preferred.
Here, (meth) acrylic acid refers to acrylic acid or methacrylic acid, and (meth) acrylate refers to acrylate or methacrylate.

  The weight average molecular weight of the polymer dispersant is preferably 3,000 to 200,000, more preferably 5,000 to 100,000, still more preferably 5,000 to 80,000, and particularly preferably 10,000 to 60. , 000.

  The acid value of the polymer dispersant is not particularly limited, but from the viewpoint of cohesiveness, the acid value of the polymer dispersant should be larger than the acid value of the polymer particles (preferably self-dispersing polymer particles) described later. Is preferred.

  In the ink of the present invention, the mass ratio of pigment to dispersant (pigment: dispersant) is preferably in the range of 1: 0.06 to 1: 3, and in the range of 1: 0.125 to 1: 2. Is more preferable, and more preferably 1: 0.125 to 1: 1.5.

The average particle size of the pigment (in the case of a polymer-coated pigment, the average particle size of the polymer-coated pigment; hereinafter the same) is preferably 10 to 200 nm, more preferably 10 to 150 nm, and even more preferably 10 to 100 nm. When the average particle size is 200 nm or less, the color reproducibility is good, the droplet ejection characteristics when droplets are ejected by the ink jet method are good, and when it is 10 nm or more, the light resistance is good. The particle size distribution of the pigment is not particularly limited, and may be either a wide particle size distribution or a monodisperse particle size distribution. Two or more color materials having a monodisperse particle size distribution may be mixed and used.
The average particle size and particle size distribution of the pigment are determined by measuring the volume average particle size by a dynamic light scattering method using a nanotrack particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.). Is.

In the present invention, the content of the pigment in the ink is preferably from 1 to 25 mass%, more preferably from 2 to 20 mass%, more preferably from 2 to 10 mass%, based on the total amount of the ink, from the viewpoint of image density. % Is particularly preferred.
You may use a pigment individually by 1 type or in combination of 2 or more types.

(water)
The ink in the present invention contains water. That is, the ink in the present invention is a water-based ink.
Although there is no restriction | limiting in particular in water content in the ink of this invention, 30 mass% or more is preferable with respect to the whole quantity of an ink, 50 mass% or more is further more preferable, and 60 mass% or more is especially preferable. Although there is no restriction | limiting in particular in the upper limit of water content, For example, this content can be 90 mass% or less, Preferably it is 80 mass% or less.

(Polymer particles)
The ink in the present invention preferably contains polymer particles. When the ink contains polymer particles in addition to the above-described polymer dispersant covering the pigment, the fixing property of the ink to the recording medium and the scratch resistance of the formed image are further improved.
On the other hand, when the polymer particles are contained in the ink, bubbles tend to be generated in the ink, compared to the case where the polymer particles are not contained, and the ink discharge property is reduced and white spots are likely to occur. Become. Therefore, in the ink containing polymer particles, the effect of improving the ink ejection property and the effect of suppressing white spots according to the present invention are more remarkably exhibited.

Polymers constituting the polymer particles include acrylic polymers, vinyl acetate polymers, styrene-butadiene polymers, vinyl chloride polymers, acrylic-styrene polymers, butadiene polymers, styrene polymers, crosslinked acrylic polymers, and crosslinked styrene polymers. A polymer, a benzoguanamine polymer, a phenol polymer, a silicone polymer, an epoxy polymer, a urethane polymer, a paraffin polymer, a fluorine polymer, or a latex thereof can be used. Preferred examples include acrylic polymers, acrylic-styrene polymers, styrene polymers, crosslinked acrylic polymers, and crosslinked styrene polymers.
The polymer particles can also be used in the form of latex.

The polymer constituting the polymer particles preferably has a weight average molecular weight of 10,000 or more and 200,000 or less, more preferably 20,000 or more and 200,000 or less.
The average particle size of the polymer particles is preferably in the range of 1 nm to 1 μm, more preferably in the range of 1 nm to 200 nm, still more preferably in the range of 1 nm to 100 nm, and particularly preferably in the range of 1 nm to 50 nm.
The glass transition temperature Tg of the polymer constituting the polymer particles is preferably 30 ° C. or higher, more preferably 40 ° C. or higher, and further preferably 50 ° C. or higher.

As the polymer particles, it is preferable to use self-dispersing polymer particles (self-dispersing polymer particles).
A self-dispersing polymer can be dispersed in an aqueous medium due to functional groups (particularly acidic groups or salts thereof) possessed by the polymer itself when it is dispersed by a phase inversion emulsification method in the absence of a surfactant. A water-insoluble polymer.
The dispersed state is both an emulsified state (emulsion) in which a water-insoluble polymer is dispersed in a liquid state in an aqueous medium and a dispersed state (suspension) in which a water-insoluble polymer is dispersed in a solid state in an aqueous medium. Is included.

As the self-dispersing polymer particles, the self-dispersing polymer particles described in paragraphs 0090 to 0121 of JP2010-64480A and paragraphs 0130 to 0167 of JP2011-066805A can be used.
In the present invention, two or more kinds of polymer particles having a monodispersed particle size distribution may be mixed and used.

The molecular weight of the water-insoluble polymer constituting the self-dispersing polymer particles is preferably 3000 to 200,000, more preferably 5000 to 150,000, and more preferably 10,000 to 100,000 in terms of weight average molecular weight. Further preferred. By setting the weight average molecular weight to 3000 or more, the amount of water-soluble components can be effectively suppressed. Moreover, self-dispersion stability can be improved by making a weight average molecular weight into 200,000 or less.
Further, the particle size distribution of the polymer particles is not particularly limited, and may be either a wide particle size distribution or a monodispersed particle size distribution.

  The weight average molecular weight is measured by gel permeation chromatography (GPC). For GPC, HLC-8220GPC (manufactured by Tosoh Corporation) is used, and as columns, TSKgeL SuperHZM-H, TSKgeL SuperHZ4000, TSKgeL SuperHZ2000 (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) are used as eluents. Use THF (tetrahydrofuran). The conditions are as follows: the sample concentration is 0.35 mass%, the flow rate is 0.35 ml / min, the sample injection amount is 10 μl, the measurement temperature is 40 ° C., and the RI detector is used. In addition, the calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, It is prepared from 8 samples of “A-2500”, “A-1000”, “n-propylbenzene”.

The water-insoluble polymer constituting the self-dispersing polymer particles is a structural unit derived from an aromatic group-containing (meth) acrylate monomer (preferably a structure derived from phenoxyethyl (meth) acrylate) from the viewpoint of controlling hydrophilicity / hydrophobicity of the polymer. It is preferable that 15-80 mass% of the total mass of a self-dispersing polymer particle is included as a copolymerization ratio for the unit and / or the structural unit derived from benzyl (meth) acrylate.
In addition, the water-insoluble polymer has a constitution derived from a carboxyl group-containing monomer having a copolymerization ratio of 15 to 80% by mass of a constitutional unit derived from an aromatic group-containing (meth) acrylate monomer from the viewpoint of controlling the hydrophilicity / hydrophobicity of the polymer. And a structural unit derived from an alkyl group-containing monomer (preferably a structural unit derived from an alkyl ester of (meth) acrylic acid), and a structural unit derived from phenoxyethyl (meth) acrylate and / or Alternatively, a structural unit derived from benzyl (meth) acrylate as a copolymerization ratio of 15 to 80% by mass, a structural unit derived from a carboxyl group-containing monomer, and a structural unit derived from an alkyl group-containing monomer (preferably (meth) A structural unit derived from an alkyl ester having 1 to 4 carbon atoms of acrylic acid) More preferably, the acid value is 25 to 100 and the weight average molecular weight is preferably 3000 to 200,000, the acid value is 25 to 95, and the weight average molecular weight is 5000 to 150,000. It is more preferable that

  The content of the polymer particles (for example, self-dispersing polymer particles) is preferably 0.1 to 20% by mass and more preferably 0.1 to 10% by mass with respect to the total mass of the ink.

(Defoamer)
The ink in the present invention preferably contains an antifoaming agent as well as an antifoaming agent in the above-described filling start liquid.
As the antifoaming agent, the same antifoaming agents that can be used for the above-mentioned filling start liquid can be used. Specifically, a preferable antifoaming agent includes a silicone-based antifoaming agent having a polysiloxane structure. Examples of commercially available antifoaming agents include BYK-012, 017, 021, 022, 024, 024, 025, 038, 094 (above, manufactured by Big Chemie Japan Co., Ltd.), KS-537, 604, KM-72F (above, manufactured by Shin-Etsu Chemical Co., Ltd.), TSA-739 (manufactured by Momentive Performance Materials Japan GK), Orphine AF104 (manufactured by Nissin Chemical Industry Co., Ltd.) and the like. . Among these, BYK-017, 021, 022, 024, 025, 094, KS-537, 604, KM-72F, and TSA-739, which are silicone antifoaming agents, are preferable.
When it contains an antifoamer, content of the antifoamer in a filling start liquid has the preferable range of 0.001 mass%-0.1 mass% with respect to the total mass of a filling start liquid.

(Organic solvent)
The ink in the present invention may further contain at least one organic solvent (preferably a water-soluble organic solvent) as necessary. By containing the water-soluble organic solvent, drying of the ink can be further suppressed and the ink can be further wetted.

Examples of water-soluble organic solvents include alkanediols (polyhydric alcohols) such as glycerin, ethylene glycol, and propylene glycol; sugar alcohols; alkyl alcohols having 1 to 4 carbon atoms such as ethanol, methanol, butanol, propanol, and isopropanol. Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, Diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n- Chill ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol monoethyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t- Butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol Mono-iso-propyl ether, tripropylene glycol monomethyl ether And the like of the glycol ethers. These can be used individually by 1 type or in combination of 2 or more types.
When the ink of the present invention contains an organic solvent, the content of the organic solvent with respect to the total amount of the ink is not particularly limited, but may be, for example, 1 to 30% by mass, preferably 5 to 25% by mass. -20 mass% is more preferable.

In the ink composition of the present invention, the solvent is at least one selected from a solvent A selected from compounds represented by the following structural formula (1) and a diol compound having 3 to 4 carbon atoms. It is more preferable to contain a certain solvent B. By setting it as such a composition, the image by which the roughness was suppressed can be formed and the curl of the recording medium after image formation and stacker blocking are suppressed.
In addition, when a fluorosurfactant is used in combination, it is further effective in suppressing stacker blocking.
Here, stacker blocking means that recording media on which images are formed are stacked, and the front surface (the surface on which the image is formed) of the recording media and the back surface of another recording medium (the image is formed). This refers to a phenomenon in which an image formed on a recording medium is destroyed by contact with a non-contact surface. The destruction of the image occurs, for example, when the image is transferred to the back surface of the recording medium or between the recording media.
Stacker blocking is described in, for example, Japanese Patent Application Laid-Open No. 2011-088323.
In the present invention, the content of the solvent A with respect to the total amount of the ink composition is 1.0% by mass to 5.0% by mass, and the content (mass basis) of the solvent B with respect to the total amount of the ink composition is the ink of the solvent A. The content (mass basis) is preferably 1.0 to 20.0 times the total amount of the composition.
In the present invention, the content (mass basis) of the solvent B with respect to the total amount of the ink composition is a times to b times (for example, 1.0 times to 20.0 times) the content (mass basis) of the solvent A with respect to the total amount of the ink composition. That the ratio [mass of solvent B / mass of solvent A] is a to b (for example, 1.0 to 20.0).

  In Structural Formula (1), l, m, and n each independently represent an integer of 0 or more and satisfy l + m + n = 0-15. In Structural Formula (1), AO represents an ethyleneoxy group or a propyleneoxy group. When l + m + n ≧ 2, two or more AOs may be the same or different.

  The above-described effect of suppressing the roughness of the image and the effect of suppressing the curling of the recording medium were formed by using the ink composition of the present invention together with a treatment liquid containing an aggregating component that aggregates the components in the ink composition. This is particularly noticeable in some cases. Details of the treatment liquid will be described later.

  The ratio [mass of solvent B / mass of solvent A] is preferably 2.4 to 20.0, and more preferably 3.2 to 16.0.

  In the present invention, the total content of the solvent A and the solvent B is preferably 6.0% by mass to 30.0% by mass with respect to the total amount of the ink composition, and 10.0% by mass to 25.%. It is more preferably 0% by mass, and particularly preferably 15.0% by mass to 20.0% by mass.

  In the present invention, the content of the solvent B is preferably 4.0% by mass to 20.0% by mass and more preferably 8.0% by mass to 20.0% by mass with respect to the total amount of the ink composition. It is more preferable and it is especially preferable that they are 12.0 mass%-20.0 mass%.

<Solvent A>
The solvent A in the present invention is at least one selected from compounds represented by the following structural formula (1). The solvent A may be a (single component) solvent selected from the compounds represented by the following structural formula (1), or may be selected from the compounds represented by the following structural formula (1). It may be a mixed solvent composed of two or more kinds.

In Structural Formula (1), l, m, and n each independently represent an integer of 0 or more and satisfy l + m + n = 0-15. In Structural Formula (1), AO represents an ethyleneoxy group or a propyleneoxy group. When l + m + n ≧ 2, two or more AOs may be the same or different.
As the compound represented by the structural formula (1), glycerin and Sanniks GP-250 (manufactured by Sanyo Chemical Industries, Ltd.) are preferable.

<Solvent B>
The solvent B in the present invention is at least one selected from diol compounds having 3 to 4 carbon atoms. The solvent B may be a (single component) solvent selected from diol compounds having 3 to 4 carbon atoms, or from two or more selected from diol compounds having 3 to 4 carbon atoms. It may be a mixed solvent.

  Examples of the diol compound having 3 to 4 carbon atoms include propylene glycol (also known as 1,2-propanediol), 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4 -Butanediol, 2,3-butanediol, and diethylene glycol are exemplified, and propylene glycol (also known as 1,2-propanediol), 1,3-propanediol, and 1,3-butanediol are preferable.

(Acetylene glycol surfactant)
The ink in the present invention preferably contains at least one acetylene glycol surfactant. In particular, the acetylene glycol surfactant preferably contains at least one acetylene glycol surfactant represented by the general formula (I) described above.
The content of the acetylene glycol surfactant in the ink is preferably 0.5% by mass to 2% by mass, more preferably 0.75% by mass to 1.5% by mass with respect to the total mass of the ink. .

(Additive)
The ink in the present invention may further contain other components such as additives in addition to the above components. Other additives include, for example, solid wetting agents (such as urea and its derivatives), antifading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, antifungal agents, pH adjusters, viscosity adjusters. , Known additives such as dispersion stabilizers, rust inhibitors, chelating agents and the like. Further, the ink of the present invention may contain a surfactant other than the acetylene glycol-based surfactant as long as the effects of the present invention are not impaired. These various additives may be added directly after the ink is prepared, or may be added when the ink is prepared.

As the surfactant other than the acetylene glycol surfactant, a fluorine surfactant is preferable. Examples of the fluorine-based surfactant include anionic surfactants, nonionic surfactants, and betaine surfactants. Among these, an anionic surfactant is more preferable.
Examples of the anionic surfactant include Capstone FS-63, Capstone FS-61 (manufactured by Dupont), Footent 100, Footent 110, and Footgent 150 (manufactured by Neos Co., Ltd.).
When the acetylene glycol surfactant and the fluorine surfactant are used in combination, the content of the fluorine surfactant in the ink is 0.001% by mass to 0.1% by mass with respect to the total mass of the ink. Preferably, it is 0.002 mass%-0.05 mass%.

Further, the ink in the present invention may be configured as an active energy ray (for example, ultraviolet ray) curable ink by containing at least one polymerizable compound. In this case, the ink preferably further contains a polymerization initiator.
Examples of the polymerizable compound include known water-soluble polymerizable compounds described in paragraphs 0128 to 0144 of JP2011-184628A and paragraphs 0019 to 0034 of JP2011-178896A. And known (meth) acrylamide compounds (preferably bifunctional or higher functional (meth) acrylamide compounds). Examples of the polymerization initiator include known polymerization initiators described in paragraphs 0186 to 0190 of JP2011-184628A and paragraphs 0126 to 0130 of JP2011-178896A.

~ Physical properties of ink ~
The surface tension of the ink is preferably 20 mN / m or more and 60 mN / m or less, more preferably 30 mN / m or more and 50 mN / m or less at an ink temperature of 25 ° C. The surface tension of the ink can be adjusted, for example, by changing the type and content of the surfactant.
The surface tension of the ink is a value measured at 25 ° C. using a plate method.

The pH of the ink is not particularly limited, but the pH at 25 ° C. is preferably in the range of pH 6.5 to 12, from the viewpoint of preventing aggregation of the coloring material contained in the ink and improving the cleaning property, and pH 7 to A range of 10 is more preferred.
In order to adjust the pH of the ink within the above range, a pH adjusting agent can be used as necessary. As the pH adjuster, a neutralizer (organic base, inorganic alkali) can be used.

The viscosity of the ink is preferably in the range of 1 to 30 mPa · s, more preferably in the range of 1 to 20 mPa · s, from the viewpoint of ejection stability when ejected by the inkjet method and the aggregation rate when using the treatment liquid described below. More preferably, the range of 2-15 mPa * s is further more preferable, and the range of 2-10 mPa * s is especially preferable.
The viscosity is measured using a VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD) under the condition of 25 ° C.

<Image forming method>
The image forming method of the present invention includes an ink filling step of filling an ink jet head with ink by the ink filling method of the present invention described above, and an ink discharging step of discharging the filled ink from the ink jet head onto a recording medium. It is provided and configured. The image forming method of the present invention may be configured by providing other steps as necessary.
The ink filling step is a step performed in accordance with the above-described ink filling method. The details of the ink filling method are as described above, and the preferred configuration is also the same.
Since the image forming method of the present invention is filled with ink by the ink filling method of the present invention described above, the ink discharge performance immediately after the ink is filled in the inkjet head is excellent, and white spots are suppressed. An image is formed.

[Ink ejection process]
In the ink ejection process according to the present invention, the ink filled in the inkjet head in the ink filling process can be ejected as it is.
In the case of using an image forming apparatus (for example, an image forming apparatus 10 to be described later) including a circulation system including an inkjet head and a supply unit for switching and supplying a filling start liquid and ink to the inkjet head. After the ink filling step, the ink may be ejected from the inkjet head after the ink is circulated in the circulation system (or while being circulated).

In the ink ejection process, there is no particular limitation on the method of ejecting ink from the inkjet head, and a known method, for example, a charge control method that ejects ink using electrostatic attraction, or the vibration pressure of a piezo element is utilized. The drop-on-demand method (pressure pulse method), the acoustic ink jet method that changes the electrical signal into an acoustic beam, irradiates the ink and ejects the ink using the radiation pressure, and heats the ink to form bubbles. Any of a thermal ink jet (bubble jet (registered trademark)) system using pressure may be used. As an ink jet method, in particular, the method described in Japanese Patent Application Laid-Open No. Sho 54-59936 causes an abrupt volume change of the ink subjected to the action of thermal energy, and the ink is ejected from the nozzle by the action force due to this state change. Ink jet method can be used effectively.
As a method of discharging from an inkjet head, a method of ejecting a large number of low-density inks called photo inks in a small volume, a method of improving image quality using a plurality of inks having substantially the same hue and different concentrations, A method using colorless and transparent ink is included.

In this step, there is no particular limitation on the temperature of the ink when ejected from the inkjet head. For example, the ink may be ejected at the temperature when the head is filled. Further, the ink may be ejected after being cooled to a temperature lower than the temperature when the head is filled.
In the present invention, from the viewpoint of further suppressing ink evaporation, the ink temperature when the ink is supplied to the head is adjusted to 20 ° C. or more and 50 ° C. or less. At this time, when the ink temperature when the ink is supplied to the head exceeds the range of 20 ° C. or more and 50 ° C. or less, it is preferable to discharge the ink after cooling to a temperature lower than the ink temperature.
The temperature of the ink when ejecting the ink is preferably 25 ° C. or higher and 45 ° C. or lower, and more preferably 25 ° C. or higher and 40 ° C. or lower.
When the temperature of the ink is 20 ° C. or higher, the viscosity of the ink at the time of ejection can be lowered, and more excellent ejection stability can be ensured. Further, when the temperature of the ink is 50 ° C. or less, ink evaporation on the nozzle surface of the head is further suppressed, and ejection failure can be further suppressed.

Furthermore, when the ink is filled in the ink jet head, the temperature of the ink may be adjusted to a relatively high temperature of 65 ° C. or more and 90 ° C. or less. Thereby, generation | occurrence | production of the bubble in an ink is suppressed more effectively. In such a case, the temperature of the ink during ink ejection is preferably 10 ° C. or more (more preferably 20 ° C. or more, particularly preferably 30 ° C. or more) lower than the temperature when the head is filled. Thereby, the evaporation of the ink ejected from the head is further suppressed, and the viscosity of the ink at the time of ejection can be further reduced.
When it is necessary to cool the ink, the cooling method is not particularly limited, and the ink may be cooled (cooled) without using the temperature adjusting means, or may be cooled using the temperature adjusting means.

  In the image forming method of the present invention, a particularly preferable embodiment when the temperature of the ink at the time of ejection is 20 ° C. or higher and 50 ° C. or lower (more preferably 25 ° C. or higher and 45 ° C. or lower, particularly preferably 25 ° C. or higher and 40 ° C. or lower). A circulation system including an inkjet head, and a supply unit for switching and supplying the filling start liquid and the ink to the inkjet head, and temperature adjusting means for adjusting the temperature of the filling start liquid or the ink circulating in the circulation system. An image forming apparatus (for example, an image forming apparatus 10 to be described later) provided is used, and an ink filling process for filling an ink jet head with ink by the ink filling method of the present invention described above, and ink filling in the ink filling process Later, the temperature of the ink circulating in the circulation system is 20 ° C. or higher and 50 ° C. or lower (more preferably 25 ° C. or higher and 45 ° C. or lower, particularly preferably A form having a temperature control step of adjusting the 25 ° C. or higher 40 ° C. or less), and the ink discharge step of discharging the temperature-controlled ink onto a recording medium from an inkjet head.

[Processing liquid application process]
The image forming method of the present invention preferably further includes a treatment liquid application step of applying a treatment liquid containing an aggregating component for aggregating the components in the ink to the recording medium.
Thereby, the ink and the aggregating component are mixed on the recording medium, and the aggregation of the pigment and the like stably dispersed in the ink is promoted. Details of the treatment liquid will be described later.

  The treatment liquid can be applied by applying a known method such as a coating method, an ink jet method, or an immersion method. As a coating method, a known coating method using a bar coater, an extrusion die coater, an air doctor coater, a blade coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, a bar coater or the like can be used. The details of the inkjet method are as described above.

  The treatment liquid application step may be provided before or after the ink discharge step, but an embodiment provided before the ink discharge step is preferable. In this embodiment, before the ink is applied (droplet ejection) on the recording medium, a treatment liquid for aggregating components (pigments, etc.) in the ink is applied in advance, and the processing applied on the recording medium is performed. An image is formed by ejecting ink so as to come into contact with the liquid. As a result, inkjet recording can be performed at higher speed, and an image with high density and resolution can be obtained even at high speed recording.

  Further, it is preferable to heat dry the treatment liquid on the recording medium after the treatment liquid is applied on the recording medium and before the ink is applied. As a result, ink coloring properties such as bleeding prevention are improved, and a visible image with good color density and hue can be recorded.

Heating and drying can be performed by known heating means such as a heater, air blowing means using air blowing such as a dryer, or a combination of these.
As the heating method, for example, a method of applying heat with a heater or the like from the side opposite to the treatment liquid application surface of the recording medium, a method of applying warm air or hot air to the treatment liquid application surface of the recording medium, or an infrared heater was used. The heating method etc. are mentioned, You may heat combining these two or more.

-Treatment liquid-
The treatment liquid in the present invention includes at least an aggregating component for aggregating the components in the ink described above, and if necessary, further comprises a water-soluble polymer compound, an organic solvent, other additives, and the like. Can do.

(Aggregating component)
The aggregation component is preferably at least one selected from a cationic polymer, an acidic compound, and a polyvalent metal salt from the viewpoint of image quality.
As for the polyvalent metal salt and the cationic polymer, for example, the polyvalent metal salt and the cationic polymer described in paragraphs 0155 to 0156 of JP2011-042150A can be used.

  Examples of the acidic compound include compounds that can change the pH of the ink. Examples of the acidic compound include a compound having a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group, or a carboxyl group or a salt thereof (for example, a polyvalent metal salt). Among these, from the viewpoint of the ink aggregation rate, a compound having a phosphate group or a carboxyl group is preferable, and a compound having a carboxyl group is more preferable. Compounds having a carboxyl group include polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, sulfonic acid, orthophosphoric acid , Pyrrolidone carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, derivatives of these compounds, or salts thereof (for example, polyvalent metal salts) Etc.

  When an acidic compound is used, the pH (25 ° C.) of the treatment liquid is preferably in the range of 0.5 to 3, more preferably in the range of 0.6 to 2, and more preferably in the range of 0.7 to 1, from the viewpoint of the ink aggregation rate. A range of .5 is more preferred. At this time, the pH (25 ° C.) of the ink is preferably 7.5 or more, and more preferably 8 or more. Among them, the case where the pH of the ink (25 ° C.) ≧ 7.5 and the pH of the treatment liquid (25 ° C.) = 0.7 to 1.5 is preferable in terms of image density, resolution, and high-speed recording. .

  The content of the acidic compound in the treatment liquid is preferably 5 to 95% by mass and more preferably 10 to 80% by mass with respect to the total amount of the treatment liquid in terms of the aggregation effect.

(Water-soluble polymer compound)
The treatment liquid preferably contains at least one water-soluble polymer compound.
The water-soluble polymer compound is not particularly limited, and known water-soluble polymer compounds such as polyvinyl alcohol, polyacrylamide, polyvinyl pyrrolidone, and polyethylene glycol can be used.
Further, as the water-soluble polymer compound, the specific polymer compound described later is also suitable.

  Although there is no limitation in particular in the weight average molecular weight of a water-soluble high molecular compound, For example, it can be set as 10000-100,000, Preferably it is 20000-80000, More preferably, it is 30000-80000.

The content of the water-soluble polymer compound in the treatment liquid is not particularly limited, but is preferably 0.1% by mass to 10% by mass, and 0.1% by mass to 4% by mass with respect to the total amount of the treatment liquid. % Is more preferable, 0.1% by mass to 2% by mass is further preferable, and 0.1% by mass to 1% by mass is particularly preferable.
When the content of the water-soluble polymer compound is 0.1% by mass or more, spreading of the ink droplets can be further promoted, and when the content of the water-soluble polymer compound is 10% by mass or less, the treatment is performed. The thickening of the liquid can be further suppressed. Moreover, if content of a water-soluble polymer compound is 10 mass% or less, the application | coating nonuniformity of the process liquid resulting from the bubble in a process liquid can be suppressed more.

As the water-soluble polymer compound, a polymer compound containing a hydrophilic structural unit having an ionic group (preferably an anionic group) (hereinafter also referred to as “specific polymer compound”) is preferable. Thereby, the spreading of the ink droplets applied to the recording medium can be further promoted, and the roughness of the image is further suppressed.
Examples of the ionic group in the specific polymer compound include a carboxyl group, a sulfonic acid group, a phosphoric acid group, a boronic acid group, an amino group, an ammonium group, and salts thereof. Among them, preferred is a carboxyl group, a sulfonic acid group, a phosphoric acid group, or a salt thereof, more preferred is a carboxyl group, a sulfonic acid group, or a salt thereof, and still more preferred is a sulfonic acid group or a salt thereof. Salt.
The hydrophilic structural unit having an ionic group (preferably an anionic group) is preferably a structural unit derived from a (meth) acrylamide compound having an ionic group (preferably an anionic group).
The content of the hydrophilic structural unit having an ionic group (preferably an anionic group) in the water-soluble polymer compound is, for example, 10 to 100% by mass in the total mass of the water-soluble polymer compound. It is preferably 10 to 90% by mass, more preferably 10 to 70% by mass, further preferably 10 to 50% by mass, and particularly preferably 20 to 40% by mass.

The specific polymer compound includes at least one hydrophobic structural unit in addition to at least one hydrophilic structural unit having the ionic group (preferably anionic group, particularly preferably sulfonic acid group). More preferably. By including the hydrophobic structural unit, the specific polymer compound is more likely to be present on the surface of the treatment liquid, so that the spread of the ink droplets applied to the recording medium is further promoted, and the roughness of the image is further suppressed.
As the hydrophobic structural unit, a structural unit derived from (meth) acrylic acid ester (preferably, alkyl ester having 1 to 4 carbon atoms of (meth) acrylic acid) is preferable.

  Content of the hydrophobic structural unit in a specific high molecular compound can be 10-90 mass% in the total mass of a specific high molecular compound, for example, it is preferable that it is 30-90 mass%, 50-90 It is more preferable that it is mass%, and it is especially preferable that it is 60-80 mass%.

(water)
The treatment liquid in the present invention can be constituted using water. Although there is no restriction | limiting in particular in content of water, The range of 10-99 mass% is preferable, More preferably, it is 50-90 mass%, More preferably, it is 60-80 mass%.

(Organic solvent)
The treatment liquid in the present invention preferably contains at least one organic solvent.
As the water-soluble organic solvent, the same water-soluble organic solvents as those contained in the ink can be used. Among these, from the viewpoint of curling suppression, polyalkylene glycol or a derivative thereof is preferable. Diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, dipropylene glycol, tripropylene glycol monoalkyl ether, polyoxypropylene glyceryl ether, polyoxypropylene More preferably, it is at least one selected from oxyethylene polyoxypropylene glycol.
The content of the organic solvent in the treatment liquid is not particularly limited, but from the viewpoint of curling suppression, it is preferably 1 to 30% by mass, and preferably 5 to 15% by mass with respect to the entire treatment liquid. More preferred.

(Other additives)
The treatment liquid may contain other additives in addition to the components described above. Other additives include, for example, antifading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, antiseptics, antifungal agents, pH adjusters, surfactants, antifoaming agents, viscosity modifiers, and dispersion stabilizers. Well-known additives, such as an agent, a rust preventive agent, and a chelating agent, are mentioned.

~ Physical properties of treatment liquid ~
The viscosity of the treatment liquid is preferably 1 to 30 mPa · s, more preferably 1 to 20 mPa · s, still more preferably 2 to 15 mPa · s, and particularly preferably 2 to 10 mPa · s from the viewpoint of the ink aggregation rate. The viscosity is a value measured at 20 ° C. using VISCOMETER TV-22 (manufactured by TOKI SANGYO CO.LTD). Further, the surface tension of the treatment liquid is preferably 20 to 60 mN / m, more preferably 20 to 45 mN / m, and still more preferably 25 to 40 mN / m from the viewpoint of the ink aggregation rate. The surface tension is a value measured at 25 ° C. using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

[Other processes]
The image forming method of the present invention may appropriately include other steps such as a drying step of drying the ink or treatment liquid applied on the recording medium.
Further, when the ink further contains a polymerizable compound, it may further include a curing step of irradiating the image formed by the ink application step with an active energy ray to cure the image. Thereby, the abrasion resistance of the formed image and the adhesion to the recording medium are further improved.

The active energy ray irradiated in the curing step is not particularly limited as long as the polymerizable compound can be polymerized. For example, ultraviolet rays, electron beams and the like can be mentioned. Among them, ultraviolet rays are preferable from the viewpoint of versatility. Examples of the source of active energy rays include an ultraviolet irradiation lamp (such as a halogen lamp and a high-pressure mercury lamp), a laser, an LED, and an electron beam irradiation device. The ultraviolet intensity is preferably 500 to 5000 mW / cm ² in a wavelength region effective for curing.
As the means for irradiating ultraviolet rays, a commonly used means may be used, and an ultraviolet irradiation lamp is particularly suitable. As the ultraviolet irradiation lamp, a so-called low-pressure mercury lamp, high-pressure mercury lamp, mercury lamp coated with a phosphor, UV-LED light source, or the like whose mercury vapor pressure is 1 to 10 Pa during lighting is suitable. The emission spectrum in the ultraviolet region of mercury lamps and UV-LEDs is 450 nm or less, particularly in the range of 184 nm to 450 nm, and is suitable for efficiently reacting a polymerizable compound in a black or colored ink composition. Yes. Further, it is suitable for mounting a power source in a printer in that a small power source can be used. As the mercury lamp, for example, a metal halide lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a xenon flash lamp, a deep UV lamp, a lamp that uses a microwave to excite a mercury lamp from the outside without using an electrode, a UV laser, and the like are in practical use. Since the above-mentioned range is included as the emission wavelength region, it is basically applicable if the power source size, input intensity, lamp shape, etc. are allowed. The light source is selected in accordance with the sensitivity of the polymerization initiator used.

<Image forming apparatus>
The image forming apparatus that can be used in the image forming method of the present invention is not particularly limited, and is publicly known as described in JP 2010-830221 A, JP 2009-234221 A, JP 10-175315 A, and the like. The image forming apparatus can be used.

Hereinafter, an example of an image forming apparatus that can be used in the image forming method of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram illustrating a configuration example of an image forming apparatus that forms an image by the image forming method of the present invention, and FIG. 2 is a schematic diagram illustrating an example of a circulation system of the image forming apparatus 10.
As shown in FIG. 2, the image forming apparatus 10 includes an inkjet head 78, a circulation system including a supply unit 14 for switching and supplying the filling start liquid and the ink to the inkjet head 78, and filling that circulates in the circulation system. Temperature adjusting means (buffer tank temperature adjusting unit 58 and head temperature adjusting unit 74) for adjusting the temperature of the starter liquid and ink. Details will be described later.
In the image forming apparatus 10, the configuration other than the deaeration device and the treatment liquid applying unit described later is the same as the configuration described in Japanese Patent Application Laid-Open No. 2009-234221, and the preferred form is also the same.

  As shown in FIG. 1, the image forming apparatus 10 includes a plurality of inkjet heads provided corresponding to each color ink of black (K), cyan (C), magenta (M), and yellow (Y). Each of the head portions 12K, 12C, 12M, and 12Y (hereinafter collectively referred to as the head portion 12), and each of the supply portions 14K, 14C, 14M, and 14Y (hereinafter collectively referred to as the supply portion 14) that supplies ink thereto. ), A paper feeding unit 18, a decurling unit 20, a belt conveyance unit 22, an image detection unit 24, a paper discharge unit 26, and the like.

The head unit 12 is arranged in the order of black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side along the feeding direction of the recording paper 16. However, the arrangement order of the head portions of the respective colors can be changed as appropriate.
The ink jet heads included in the head portions 12 of the respective colors are line heads, and are fixedly installed so that the longitudinal direction of the heads is substantially orthogonal to the conveyance direction of the recording paper 16.

  In this example, a configuration is shown in which an image is formed using KCMY standard colors (four colors). However, the present invention is not limited to this. Ink, special color ink, etc. may be added. For example, a head unit that discharges light ink such as light cyan and light magenta may be added. Further, the arrangement order of the head portions of the respective colors is not particularly limited.

  The supply unit 14 is a buffer tank (for example, the buffer tank 56 in FIG. 2) for supplying the color ink or filling start liquid corresponding to the head unit 12 of each color, and an ink tank (for example, the ink tank in FIG. 2) for storing ink. 82), and a tank (for example, tank 62 in FIG. 2) for storing the filling start liquid. Each tank communicates with the head unit 12 through a circulation system. Detailed configurations of the supply unit 14, the head unit 12, and the circulation system will be described later (FIG. 2).

  The paper supply unit 18 is for supplying recording paper 16 as a recording medium. In this embodiment, a magazine for rolled paper (continuous paper) is shown as an example. However, the present invention is not limited to this, and a plurality of magazines having different paper widths, paper quality, and the like may be provided. Further, instead of the roll paper magazine or in combination with this, the paper may be supplied by a cassette in which cut sheets are stacked and loaded.

The decurling unit 20 is for removing curl that has remained on the recording paper 16 delivered from the paper supply unit 18, and the recording paper 16 is heated by the heating drum 30 in the direction opposite to the curl direction of the magazine. Give heat to.
The cutting cutter 28 is for cutting the roll paper (recording paper 16) into a desired size. Note that when the cut paper is used, the cutting cutter 28 may not be provided. The cut recording paper 16 is sent to the belt conveyance unit 22.
The belt conveyance unit 22 is arranged to face the nozzle surface (ink ejection surface) of the head unit 12 and conveys the recording paper 16 while maintaining the flatness of the recording paper 16. It is comprised so that the structure in which the endless belt 33 was wound between may be included.

  The belt 33 is for transporting the held recording paper 16. The belt 33 has a width that is greater than the width of the recording paper 16, and a plurality of suction holes (not shown) are formed on the belt surface. As shown in FIG. 1, at the position facing the roll coater 15, the nozzle surface of the head unit 12, and the sensor surface of the image detection unit 24 on the inner side of the belt 33 spanned between the rollers 31 and 32. A chamber 34 is provided, and the recording paper 16 is sucked and held on the belt 33 by sucking the suction chamber 34 with a fan 35 to a negative pressure. In place of the suction adsorption method, an electrostatic adsorption method may be adopted.

  When the power of a motor (not shown) is transmitted to at least one of the rollers 31 and 32 around which the belt 33 is wound, the belt 33 is driven in the clockwise direction in FIG. The recording paper 16 is conveyed from left to right in FIG.

  The belt cleaning unit 36 is for cleaning ink adhering to the belt 33 when borderless printing or the like is performed, and is provided at a predetermined position outside the belt 33 (an appropriate position other than the print area). Yes.

In the image forming apparatus 10, a roll coater 15 is provided on the upstream side of the head unit 12 and a heating fan 40 described later as a processing liquid application unit for applying the above-described processing liquid to the recording medium.
As the treatment liquid applying means, instead of the roll coater 15, an ink jet head having the same configuration as the ink jet head of each color may be used, or other application means other than the roll coater may be used.
Examples of other application means include an air doctor coater, a blade coater, a lot coater, a knife coater, a squeeze coater, an impregnation coater, a gravure coater, a cast coater, a spray coater, a curtain coater, and an extrusion coater.

On the downstream side of the roll coater 15, a heating fan 40 is disposed as a processing liquid drying means. With this heating fan, the treatment liquid is dried by applying warm air to the treatment liquid application surface.
The treatment liquid drying means is not limited to the heating fan 40, and may be configured using a known heating means such as a heater. For example, a means for installing a heating element such as a heater on the side opposite to the image forming surface of the recording medium, a heating means using an infrared heater, a means combining these, or the like may be used.
In addition, since the surface temperature of the recording medium changes depending on the type (material, thickness, etc.) of the recording medium (recording paper 16), the environmental temperature, and the like, it is measured by the measuring unit that measures the surface temperature of the recording medium and the measuring unit. It is preferable to apply the treatment liquid while controlling the temperature by providing a control mechanism that feeds back the surface temperature value of the recording medium to the heating control unit. As a measurement part which measures the surface temperature of a recording medium, a contact or non-contact thermometer is preferable.
Further, the solvent may be removed using a solvent removal roller or the like. As another embodiment, a method of removing excess solvent from the recording medium with an air knife is also used.

  In each head unit 12, the processing liquid of the recording paper 16 is applied by ejecting ink of different colors based on the image data from each head unit 12 while conveying the recording paper 16 by the belt conveyance unit 22. A color image is formed on the surface.

  The image detection unit 24 is configured to include an image sensor (line sensor or area sensor, not shown) for capturing the droplet ejection result of the head unit 12, and reads the droplet ejection image captured by the image sensor and requires The image processing (the presence / absence of ejection, landing position error, dot shape, optical density, etc.) is detected by performing the above signal processing.

  The post-drying unit 42 is provided on the downstream side of the image detection unit 24 and is for drying the surface on which the image is formed. A specific example is a heating fan.

  The heating / pressurizing unit 44 is provided on the downstream side of the post-drying unit 42 and controls the glossiness of the image surface. While the image surface is heated, pressure is applied by a pressure rotor 45 having a predetermined surface uneven shape, and the uneven shape is transferred to the image surface.

  The paper discharge unit 26 is for discharging recording paper (printed material) on which an image is formed to the outside of the image forming apparatus 10. The paper discharge unit 26 includes paper discharge units 26A and 26B that discharge the printed material of the main image and the printed material of the test image. In this embodiment, sorting means (not shown) is provided for switching between a path for discharging paper to the paper discharge section 26A and a path for discharging paper to the paper discharge section 26B. Note that when the main image and the test print are simultaneously formed in parallel on a large sheet, the test print portion is separated by a cutter (second cutter) 48. The cutter 48 is provided immediately before the paper discharge unit 26, and cuts the main image and the test print unit when the test print is performed on the image margin.

Next, the circulation system of the image forming apparatus 10 will be described with reference to FIG.
As illustrated in FIG. 2, the image forming apparatus 10 includes a head unit 12 that is an example of an inkjet head, a supply unit 14 that supplies a filling start liquid or ink to the inkjet head, and a circulation path 50 that is an example of a circulation system. Etc. are provided.
Note that the image forming apparatus 10 has this configuration for the number of loaded inks (in this embodiment, four colors of KCMY), but FIG. 2 shows only the configuration for one ink color. Yes.

  The supply unit 14 includes a buffer tank 56, a buffer tank temperature adjustment unit 58 that adjusts the temperature of the buffer tank, a buffer tank temperature detection unit 60, a start liquid tank 62, an ink tank 82, and the like. The supply unit 14 is disposed at a position separated from the head unit 12. In the image forming apparatus 10 that performs image formation that consumes a large amount of ink, the buffer tank 56, the start liquid tank 62, and the ink tank 82 are large. Therefore, it is not preferable to dispose a large ink tank in the head unit 12. For this reason, they are arranged at spaced apart positions.

The start liquid tank 62 stores the filling start liquid and replenishes the buffer tank 56 with the filling start liquid. Since the temperature of the start liquid tank 62 is not adjusted, the temperature of the ink in the start liquid tank 62 is the same as the ambient temperature, for example, 20 ° C. to 40 ° C. The filling start liquid is transferred to the buffer tank 56 by the pump 64 through the filter 63.
In this embodiment, the start liquid tank for storing the filling start liquid is provided separately from the ink tank 82, but one tank is shared and the ink and the filling start liquid are alternately replaced in one tank. May be configured.

  The ink tank 82 stores ink and replenishes the buffer tank 56 with ink. Since the ink tank 82 does not adjust the temperature, the temperature of the ink in the ink tank 82 is the same as the ambient temperature, for example, 20 ° C. to 40 ° C. The ink is transferred to the buffer tank 56 by the pump 84 through the filter 83.

  The buffer tank 56 is for storing ink to be supplied to the head unit 12 and is provided with a liquid level sensor (not shown), so that the liquid level in the buffer tank 56 is constant. By switching the driving of the pumps 64 and 84, the filling start liquid from 62 or the ink from the ink tank 82 can be transferred as desired.

  The buffer tank temperature adjustment unit 58 is for heating the buffer tank 56 to a predetermined temperature (set temperature), whereby the ink in the buffer tank 56 is heated. Since the buffer tank temperature adjusting unit 58 may change the properties of the ink if the temperature of the portion that comes into contact with the ink is high, the buffer tank temperature adjusting unit 58 may have a heater embedded in the outer wall having a high thermal conductivity, such as metal. It is preferable that a sheet-like heater is attached to the outside.

  The buffer tank temperature detection unit 60 is for detecting the temperature of the ink flowing out from the buffer tank 56, and is provided near the ink outlet. An example is a temperature sensor using a thermistor. The buffer tank temperature detection unit 60 may directly detect the temperature of the ink, or may detect the temperature of a member having high thermal conductivity that forms the flow path.

  The image forming apparatus 10 includes one buffer tank 56, but includes two buffer tanks 56 (two stages) in order to provide a degassing unit for reducing bubbles in the ink. It is good.

  The circulation path 50 is for connecting the head unit 12 and the supply unit 14 to circulate ink, and the forward path 50A from the supply unit 14 to the head unit 12 and the supply unit from the head unit 12 14 is formed by a return path 50B to No.14. An example of the circulation path 50 is a tube or the like.

A deaeration device 51 is provided in the forward path 50A.
The deaeration device 51 is a means for mainly removing dissolved gas in the filling start liquid, and is provided with a hollow fiber bundle (not shown) made of a Teflon (registered trademark) tube or a silicon tube through which the filling start liquid passes, The gas dissolved in the filling start liquid can be separated and removed by vacuum degassing with a vacuum pump (not shown). In the deaeration device 51, when the ink flows through the circulation path 50, the dissolved gas in the ink can be removed. In addition, as the degassing method of the filling start liquid in the degassing device 51, a known technique such as the vacuum (depressurized degassing) method described above can be applied, and various methods such as an ultrasonic vibration method and a centrifugal separation method can be applied. Is applicable.
In the present invention, the combination of the type of surfactant in the filling start liquid and the temperature of the filling start liquid when filling the head is specified as described above, and the head is filled prior to ink filling. By filling the start liquid and starting filling the ink head after filling the fill start liquid, the generation of bubbles in the ink can be suppressed immediately after the ink is filled. Therefore, although this deaeration device 51 is not necessarily an essential configuration, a configuration provided with the deaeration device 51 is preferable in that it can further suppress the generation of bubbles.

  An ambient temperature detection unit 52 is provided around the forward path 50A, so that the temperature around the forward path 50A and the temperature inside the image forming apparatus 10 can be measured. An example of the ambient temperature detection unit 52 includes a temperature sensor using a thermistor.

  The ink or the starting liquid in the buffer tank 56 is sent to the supply tank 66 of the head unit 12 through the forward path 50A by the pump 54A. Ink that has not been used for image formation is fed from the recovery tank 68 to the buffer tank 56 through the return path 50B by the pump 54B.

  The head unit 12 includes a supply tank 66, a recovery tank 68, a valve unit 72, a head temperature adjustment unit 74, a head temperature detection unit 76, an inkjet head 78, and the like.

The filling start liquid or ink circulates in the forward path 50A. In the supply tank 66, the filling start liquid or ink sent from the buffer tank 56 through the forward path 50A is stored, and the stored filling start is stored. The liquid or ink is supplied to the plurality of inkjet heads 78 via the tube 70A, the valve unit 72 that controls ON / OFF of the flow path to the inkjet head 78, the flow path of the head temperature adjusting unit 74, and the tube 71A. . Normally, the filling start liquid is first supplied to the unfilled inkjet head 78, and after the filling start liquid is drained from the circulation path 50 and the buffer tank 56 to become empty, the ink is supplied from the ink tank 82 to the buffer tank 56. Then, the ink is supplied to the ink jet head 78 through the circulation path 50.
In the present embodiment, a plurality of inkjet heads 78 are provided. However, the present invention is not limited to this, and the number of inkjet heads 78 may be one. Note that in the case of performing image formation with high throughput, it is preferable to have a configuration including a plurality of inkjet heads 78.

  The head temperature adjustment unit 74 is for heating the ink fed from the supply tank 66 to the inkjet head 78.

FIG. 3 is a schematic diagram of an example of the head temperature adjustment unit 74.
As shown in FIG. 3, the head temperature adjustment unit 74 includes a flow path block 75 and a heater 77. The flow path block 75 is preferably formed of a material having good thermal conductivity such as aluminum or copper. A specific example of the heater 77 is a silicon rubber heater.
When a plurality of inkjet heads 78 are provided, the head temperature adjustment unit 74 is long. The head temperature adjusting unit 74 and the inkjet head 78 are coupled one-to-one with short tubes 71A and 71B.
The head temperature detection unit 76 is for detecting the temperature of the head temperature adjustment unit 74, and a specific example includes a temperature sensor using a thermistor.

  Returning to FIG. 2, the collection tank 68 is for storing the ink supplied to the inkjet head 78 and returned without being consumed by printing, and returns it to the buffer tank 56. At this time, the ink in the inkjet head 78 is sent to the recovery tank 68 through the tube 71B, the head temperature adjustment unit 74, the valve unit 72, and the tube 70B in this order.

  The supply tank 66 and the recovery tank 68 are controlled so that the ink pressure in the tank is detected by pressure sensors 67 and 69, respectively, and adjusted to a predetermined pressure, and the pressure between the supply tank 66 and the recovery tank 68 is controlled. Due to the difference, ink circulation of the inkjet head 78 is performed.

  The circulation amount of ink varies depending on the presence or absence of image formation, but the circulation flow path in the inkjet head 78 is designed so that predetermined circulation is performed even in the case of full ejection (solid image formation).

In this image forming apparatus 10, a first circulation system including an ink jet head 78 and a supply unit 14 (buffer tank 56 → deaeration device 51 → outward path 50 A → supply tank 66 → valve unit 72 → head temperature adjustment unit 74 → inkjet head 78 → head temperature adjusting unit 74 → valve unit 72 → recovery tank 68 → return path 50B → buffer tank 56 path circulation system), and the temperature of the filling start liquid circulating through the first circulation system is adjusted. There are provided temperature adjusting means (buffer tank temperature adjusting unit 58 and head temperature adjusting unit 74).
The operations of the circulation process, the cooling process, and the ink discharge process described above can be performed while circulating the filling start liquid through the first circulation system.
In the image forming apparatus 10, the second circulation system that does not include the inkjet head 78 and includes the supply unit 14 (buffer tank 56 → deaeration device 51 → outward path 50 </ b> A → supply tank 66 → recovery tank 68 → return path 50 </ b> B → buffer tank The circulation system of 56 paths is configured, and temperature adjusting means (buffer tank temperature adjusting unit 58) for adjusting the temperature of the filling start liquid circulating in the second circulation system is provided.
In the ink filling step described above, prior to the ink filling of the head, the filling start liquid is heated while circulating the filling start liquid in the second circulation system, and then the valve unit 72 is turned on (the valve is turned on). In the open state), the heated filling start liquid can be filled in the head.

The image forming apparatus 10 may be provided with other means other than those described above.
As other means, for example, active energy ray (for example, ultraviolet ray) irradiation means suitable for the case of using an ink containing a polymerizable compound can be mentioned.
For the configuration of other means including the active energy ray irradiation means, for example, known configurations described in JP 2011-184628 A, JP 2011-184628 A, and the like can be referred to as appropriate.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” is based on mass.

The weight average molecular weight was measured by gel permeation chromatography (GPC). GPC was isolated by removing the solvent from the obtained polymer, and the obtained solid content was diluted to 0.1% by mass with tetrahydrofuran, and HLC-8020 GPC (manufactured by Tosoh Corporation) was used. Measurement was performed using a column in which three TSKgel Super Multipore HZ-H (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) were connected in series. The conditions were as follows: the sample concentration was 0.35 mass%, the flow rate was 0.35 mL / min, the sample injection amount was 10 μL, the measurement temperature was 40 ° C., and the RI detector was used. The calibration curve is “Standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, “A -2500 "," A-1000 ", and" n-propylbenzene ".
The acid value of the polymer was determined by the method described in JIS standard (JIS K0070: 1992).

<Preparation of water-soluble polymer compound (water-soluble polymer)>
A water-soluble polymer compound (water-soluble polymer 1) having the following structure used for preparing the treatment liquid was prepared as follows. In the water-soluble polymer 1, the number on the lower right of each structural unit represents a mass ratio (mass%), and Mw represents a weight average molecular weight. The same applies to the structural formulas of the subsequent polymers.

The water-soluble polymer 1 was synthesized as follows.
In a 200 ml three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, 30.0 g of isopropyl alcohol was charged, and the temperature was raised to 65 ° C. in a nitrogen atmosphere.
Next, methyl methacrylate (hereinafter also referred to as “MMA”) (30.0 g), ethyl acrylate (hereinafter also referred to as “EA”) (6.5 g), acrylamido-2-methylpropanesulfonic acid (hereinafter referred to as “AMPS”). (Also referred to as “13.5 g”), isopropyl alcohol (30 g), water (15 g), and “V-601” (a polymerization initiator manufactured by Wako Pure Chemical Industries, Ltd.) (2.97 g (0.0129 mol)). ); 3 mol% with respect to the total number of moles of monomers (0.430 mol)) was dropped at a constant speed so that the dropping was completed in 2 hours. After completion of the dropwise addition, the mixture was stirred for 2 hours, then “V-601” (1.5 mol% (1.48 g) based on the total number of moles of monomers) and isopropyl alcohol (3.0 g) were added, and the mixture was stirred for 2 hours. I did it.
The obtained polymer solution was neutralized with an aqueous solution of acrylamide-2-methylpropanesulfonic acid and an equimolar number of sodium hydroxide, and isopropyl alcohol was distilled off by concentration under reduced pressure, so that the total amount of the polymer solution became 310 g. Water was added to obtain a polymer aqueous solution containing 16% by mass of water-soluble polymer 1.
The obtained water-soluble polymer 1 had a weight average molecular weight (Mw) of 45,000.

<Synthesis of Polymer Dispersant P-1>
A polymer dispersant P-1 used as a pigment dispersant used in preparing the ink was synthesized according to the following scheme.

Details of the scheme are as follows.
To a 1000 ml three-necked flask equipped with a stirrer and a condenser tube, 88 g of methyl ethyl ketone was added and heated to 72 ° C. in a nitrogen atmosphere. Here, 50 g of methyl ethyl ketone was mixed with 0.85 g of dimethyl 2,2′-azobisisobutyrate and 60 g of benzyl methacrylate. Then, a solution in which 10 g of methacrylic acid and 30 g of methyl methacrylate were dissolved was dropped over 3 hours. After completion of the dropwise addition, the reaction was further continued for 1 hour, and then a solution of 0.42 g of dimethyl 2,2′-azobisisobutyrate in 2 g of methyl ethyl ketone was added, heated to 78 ° C. and heated for 4 hours. The obtained reaction solution was reprecipitated twice in a large excess amount of hexane, and the precipitated polymer was dried to obtain 96 g of polymer dispersant P-1. In addition, the number of each structural unit of the polymer dispersant P-1 shown above represents a mass ratio.
The composition of the obtained polymer was confirmed by ¹ H-NMR, and the weight average molecular weight (Mw) determined by GPC was 44,600. Furthermore, when the acid value was calculated | required by the method as described in JIS specification (JISK0070: 1992), it was 65.2 mgKOH / g.

<Preparation of pigment dispersion>
(Preparation of cyan dispersion)
Pigment Blue 15: 3 (phthalocyanine blue A220, manufactured by Dainichi Seika Co., Ltd.) which is a cyan pigment, 5 parts of polymer dispersant P-1, 42 parts of methyl ethyl ketone, and 5.5 parts of 1N NaOH aqueous solution And 87.2 parts of ion-exchanged water were mixed and dispersed with a bead mill using 0.1 mmφ zirconia beads for 2 to 6 hours.
After removing methyl ethyl ketone at 55 ° C. under reduced pressure and further removing a part of the water under reduced pressure, using a high-speed centrifugal cooler 7550 (manufactured by Kubota Seisakusho), using a 50 mL centrifuge tube, Centrifugation was performed at 8000 rpm for 30 minutes, and the supernatant liquid other than the precipitate was collected. Thereafter, the pigment concentration was determined from the absorbance spectrum, and a dispersion (cyan dispersion C) of polymer-coated pigment particles (pigment coated with a polymer dispersant) having a pigment concentration of 10.2% by mass was obtained. The average particle size of the obtained Cyan Dispersion C was 105 nm.

(Preparation of magenta dispersion)
In the preparation of the cyan dispersion, the same procedure as in the preparation of the cyan dispersion was used, except that Pigment Red 122, which is a magenta pigment, was used instead of Pigment Blue 15: 3 (Phthalocyanine Blue A220, manufactured by Dainichi Seika Co., Ltd.). A dispersion (magenta dispersion M) of polymer-coated pigment particles (pigment coated with a polymer dispersant) was prepared. The average particle size of the obtained magenta dispersion M was 85 nm.

(Preparation of yellow dispersion)
A polymer-coated pigment was prepared in the same manner as in the preparation of the cyan dispersion, except that Pigment Yellow 74, which is a yellow pigment, was used instead of Pigment Blue 15: 3 (Phthalocyanine Blue A220, manufactured by Dainichi Seika Co., Ltd.). A dispersion (yellow dispersion Y) of particles (pigment coated with polymer dispersant) was prepared. The average particle size of the obtained yellow dispersion Y was 82 nm.

(Preparation of black dispersion)
In the preparation of the cyan dispersion liquid, except that carbon black (NIPEX 160-IQ manufactured by Degussa), which is a black pigment, was used instead of Pigment Blue 15: 3 (Phthalocyanine Blue A220, manufactured by Dainichi Seika Co., Ltd.) A dispersion (black dispersion K) of polymer-coated pigment particles (pigment coated with a polymer dispersant) was prepared by the method described above. The average particle size of the obtained black dispersion K was 130 nm.

<Preparation of self-dispersing polymer particles>
360.0 g of methyl ethyl ketone was charged into a 2-liter three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, and the temperature was raised to 75 ° C. While maintaining the temperature in the reaction vessel at 75 ° C., 180.0 g of phenoxyethyl acrylate, 162.0 g of methyl methacrylate, 18.0 g of acrylic acid, 72 g of methyl ethyl ketone, and “V-601” (manufactured by Wako Pure Chemical Industries, Ltd.) 1 .44 g of the mixed solution was added dropwise at a constant speed so that the addition was completed in 2 hours. After completion of the dropwise addition, a solution consisting of 0.72 g of “V-601” and 36.0 g of methyl ethyl ketone was added, stirred for 2 hours at 75 ° C., and then a solution consisting of 0.72 g of “V-601” and 36.0 g of isopropanol was added. After stirring at 75 ° C. for 2 hours, the temperature was raised to 85 ° C. and stirring was further continued for 2 hours. The weight average molecular weight (Mw) of the obtained copolymer was 64000 (calculated in terms of polystyrene by gel permeation chromatography (GPC), columns used were TSKgel SuperHZM-H, TSKgel SuperHZ4000, TSKgel SuperHZ200 (manufactured by Tosoh Corporation)), The acid value was 38.9 (mgKOH / g).
Next, 668.3 g of the polymerization solution was weighed, 388.3 g of isopropanol and 145.7 ml of 1 mol / L NaOH aqueous solution were added, and the temperature in the reaction vessel was raised to 80 ° C. Next, 720.1 g of distilled water was added dropwise at a rate of 20 ml / min to disperse in water. Thereafter, the temperature in the reaction vessel was maintained at 80 ° C. for 2 hours, 85 ° C. for 2 hours, and 90 ° C. for 2 hours under atmospheric pressure, and then the reaction vessel was evacuated to a total of 913. 7 g was distilled off to obtain an aqueous dispersion (emulsion) of self-dispersing polymer particles (B-01) having a solid content concentration of 28.0%.

<Preparation of ink>
Using the pigment dispersions (cyan dispersion C, magenta dispersion M, yellow dispersion Y, black dispersion K) and self-dispersing polymer particles (B-01) obtained above, the compositions shown in Table 1 below are used. Each component was mixed so that it might become (%: mass%). The obtained liquid mixture was filtered with a plastic disposable syringe using a PVDF 5 μm filter (Millex SV, Millipore, diameter 25 mm), and each ink (magenta ink M1, black ink K1, cyan ink C1, yellow ink). Y1) was obtained.
About each ink, pH (25 degreeC) was measured using pH meter WM-50EG (made by Toa DKK Co., Ltd.). Moreover, surface tension (25 degreeC) was measured in FASE Automatic Surface Tensionmeter CBVP-Z (made by Kyowa Interface Science Co., Ltd.). The measurement results are shown in Table 1 below.

Details of the components in Table 1 are as follows.
Sanix GP-250: Organic solvent manufactured by Sanyo Chemical Industries, Ltd. Orphine E1010: Acetylene glycol surfactant manufactured by Nissin Chemical Industry Co., Ltd. (in the general formula (I) described above, R ⁵² and R ⁵⁴ is a methyl group, R ⁵³ and R ⁵⁵ are isobutyl groups, Y ² and Y ³ are ethylene groups, and x + y is 10.
Olfin E1020: An acetylene glycol surfactant manufactured by Nissin Chemical Industry Co., Ltd. (in the general formula (I), R ⁵² and R ⁵⁴ are methyl groups, and R ⁵³ and R ⁵⁵ are isobutyl groups. Y ² and Y ³ are ethylene groups, and x + y is 20)
BYK-024: Silicone (polysiloxane) defoamer manufactured by Big Chemie Japan Co., Ltd.

<Preparation of treatment liquid>
The processing liquid was prepared by mixing components having the following composition.
<Composition of treatment liquid>
・ Diethylene glycol monoethyl ether 4.8% by mass
・ Tripropylene glycol monomethyl ether: 4.8% by mass
-Malonic acid: 8.0% by mass
・ Malic acid: 8.0% by mass
・ Phosphoric acid 85% ・ ・ ・ 5.0% by mass
・ The aforementioned water-soluble polymer 1... 0.5 mass%
・ Benzotriazole: 1.0% by mass
-Antifoaming agent: 100ppm as the amount of silicone oil
(Momentive Performance Materials Japan GTS TSA-739 (15%); emulsion type silicone antifoam)
・ Ion-exchanged water: Remaining amount of 100% by mass

<Preparation of filling start liquid>
Components of the following composition were mixed to prepare a filling start liquid 01. The surface tension of the filling start liquid 01 was 28.0 mN / m. The surface tension was measured by adjusting the temperature to 25 ° C. with FASE Automatic Surface Tensionmeter CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).
<Composition of filling start liquid 01>
・ Olfin E1010 ・ ・ ・ 1.0% by mass
[Acetylene glycol surfactant manufactured by Nissin Chemical Industry Co., Ltd. (in the general formula (I) described above, R ⁵² and R ⁵⁴ are methyl groups, R ⁵³ and R ⁵⁵ are isobutyl groups, Y ² and Y ³ are ethylene groups and x + y is 10)]
・ Proxel GXL (manufactured by AVECIA) ・ ・ ・ 0.05% by mass
・ Imidazole (basic compound): 0.1% by mass
・ BYK-024 (silicone-based antifoaming agent): 0.01% by mass
・ Ion-exchanged water: Remaining amount of 100% by mass
(Adjusted to pH 7.6 with 1N nitric acid)

Example 1
<1. Filling start liquid and ink>
An image forming apparatus 10 shown in FIGS. 1 and 2 was prepared.
At this stage, the ink jet head 78 in FIG. 2 is in an unfilled state, more specifically, no ink is present in the ink jet head (the ink volume present in the ink jet head can be filled in the ink jet head). And 0% by volume with respect to the maximum volume).
Further, the valve unit 72 is turned off (each valve is closed), and the buffer tank 56, the deaeration device 51, the supply tank 66, the recovery tank 68, and the buffer tank 56 are sequentially circulated (that is, the inkjet head 78 is turned off). A circulation system that does not pass through) is configured.

  The filling start liquid 01 produced as described above was accommodated in the start liquid tank 62, and then the filling start liquid 01 was sent from the start liquid tank 62 to the buffer tank 56. In addition to the starting liquid tank 62, an ink tank 82 for loading ink was prepared, and the magenta ink M1 was stored in the ink tank 82.

  Next, the filling start liquid 01 in the buffer tank 56 is heated by the buffer tank temperature control unit 58, and the heated filling start liquid 01 is converted into the buffer tank 56, the deaerator 51, the supply tank 66, the recovery tank 68, the buffer Circulation was performed in the order of the tank 56. This filling start liquid 01 was circulated for 5 minutes. At this time, heating of the filling start liquid 01 by the buffer tank temperature adjusting unit 58 was performed so that the temperature of the filling start liquid 01 measured by the buffer tank temperature detecting unit 60 became a temperature shown in Table 2.

Next, the valve between the supply tank 66 and the recovery tank 68 is closed, the valve unit 72 is turned on (each valve is opened), and the filling start liquid 01 is sent from the supply tank 66 to the ink jet head 78 to inject the ink jet head. The filling start liquid 01 was filled in 78, and the filling start liquid 01 was sent from the inkjet head 78 to the collection tank 68.
Thus, the filling start liquid 01 is supplied in the order of the circulation system of the buffer tank 56, the deaerator 51, the supply tank 66, the inkjet head 78, the recovery tank 68, and the buffer tank 56 (that is, the circulation system via the inkjet head 78). It was circulated. This circulation was carried out for 5 minutes.
At this time, the temperature of the filling start liquid 01 is finely adjusted by the head temperature adjustment unit 74, and the temperature of the filling start liquid 01 detected by the head temperature detection unit 76 is measured by the buffer tank temperature detection unit 60. The temperature was the same as that of 01 (the temperature shown in Table 2).

  Thereafter, the valve unit 72 is turned off, the valve between the supply tank 66 and the recovery tank 68 is opened, the heating of the buffer tank temperature adjusting unit 58 is turned off, the filling start liquid 01 is taken out from the buffer tank 56, and the buffer tank 56, deaerated The filling start liquid 01 in the circulation system (that is, the circulation system that does not pass through the inkjet head 78) in the order of the apparatus 51, the supply tank 66, the recovery tank 68, and the buffer tank 56 was all evacuated.

  Next, the magenta ink M1 was fed from the ink tank 82 to the buffer tank 56, and the magenta ink M1 was filled in exactly the same manner as when the filling start liquid was filled. However, at this time, the temperature of the magenta ink M1 was set to 30 ° C. by the buffer tank temperature adjusting unit 58. Then, the magenta ink M1 was circulated for 5 minutes in the order of the buffer tank 56, the deaeration device 51, the supply tank 66, the recovery tank 68, and the buffer tank 56.

  Next, the valve between the supply tank 66 and the recovery tank 68 is closed, the valve unit 72 is turned on (each valve is opened), and the magenta ink M1 is fed from the supply tank 66 to the ink jet head 78 to thereby eject the ink jet head. 78 was filled with magenta ink M1. At this time, the filling start liquid 01 remaining in the ink jet head 78 is mixed with the magenta ink M1, but the magenta ink M1 mixed from the nozzles of the ink jet head 78 is discharged by 5000 shots and discarded. The magenta ink M1 was circulated in the circulation system in the order of the gas device 51, the supply tank 66, the inkjet head 78, the recovery tank 68, and the buffer tank 56 (that is, the circulation system via the inkjet head 78). This circulation was carried out for 10 minutes.

<2. Image formation>
After the circulation for 10 minutes, the temperature of the magenta ink M1 measured by the buffer tank temperature detecting unit 60 and the head temperature detecting unit 76 is 30 ° C. by the buffer tank temperature adjusting unit 58 and the head temperature adjusting unit 74. Adjusted.
Next, a solid image of magenta was formed on the OK top coat + (manufactured by Oji Paper Co., Ltd.) as the recording paper 16 in FIG. Specifically, the recording paper 16 is conveyed, an anilox roller (line number: 100 to 300 / inch) is used as the roll coater 15, and the treatment liquid prepared above is applied at a rate of 1.5 g / m ^2. The recording liquid was applied to the entire surface of the recording paper 16, and the applied processing liquid was dried by the heating fan 40. Next, the magenta ink M1 was applied to the entire surface of the treatment liquid application surface from the inkjet head of the head unit 12M, and the applied magenta ink M1 was dried by the post-drying unit 42 to obtain a magenta solid image.
The above-described magenta solid image was continuously formed on 50 OK top coats +.

<3. Evaluation (white stripes)>
The ink ejection property was evaluated by confirming the number of white lines (striated white spot failure) generated in the image formed as described above. Here, white streaks are caused by the occurrence of non-ejection nozzles (that is, ejection failure nozzles) in the ink jet head, so that ink is not applied to the locations corresponding to the non-ejection nozzles, and the locations are white spots. It is caused by becoming.
The number of white stripes is shown as the number of solid images for 50 “OK topcoat +”. However, white streaks that occurred at locations common to a plurality of sheets were counted as one. The white stripes were evaluated immediately after ink filling and 24 hours after ink filling. The evaluation results are shown in Table 2 below.

The notation of Table 2 will be described below.
“The number of white stripes” indicates that the smaller the number, the higher the ink ejection performance.
“The temperature of the filling start liquid” indicates the temperature detected by the buffer tank temperature detection unit 60 of the filling start liquid used during ink filling.
“Immediately after ink filling” indicates that the formation of the first solid image was started within 3 hours after the magenta ink M1 was filled in the unfilled inkjet head 78 (the same applies hereinafter). .
“After 24 hours from ink filling” indicates a condition in which the formation of the first solid image is started about 24 hours after the magenta ink M1 is filled in the unfilled inkjet head 78 (hereinafter the same) Is).

As shown in Table 2, when the temperature of the filling start liquid was set to 30 ° C. or higher and 90 ° C. or lower (especially 40 ° C. or higher and 70 ° C. or lower), the number of white streaks immediately after ink filling and 24 hours after ink filling drastically decreased. If it exceeds 70 ° C., it is considered that the surfactant of the filling start liquid is separated and the effect becomes small.
Moreover, when the temperature of the filling start liquid was set to a range of less than 30 ° C. or more than 90 ° C. (Nos. 1 and 9), generation of white stripes was not suppressed. Further, when the temperature of the filling start liquid exceeded 90 ° C., composition change and precipitation due to water evaporation were likely to occur, and damage to the head became significant.

Next, the magenta ink M1 is changed to the black ink K1, the cyan ink C1, or the yellow ink Y1, and the head portions 12K, 12C, and 12Y corresponding to the inks of the respective colors are used. Images were formed and white streaks were evaluated.
As a result, even when the black ink K1, the cyan ink C1, or the yellow ink Y1 is used, the ink temperature at the time of filling is 30 ° C. or more and 90 ° C. or less (particularly 40 ° C.) as in the case of using the magenta ink M1. It was confirmed that the number of white streaks was drastically reduced immediately after ink filling and 24 hours after ink filling.

(Example 2)
In Example 1, No. 1 in Example 1 except that Olphine E1010, which is the surfactant used for the preparation of the filling start liquid 01, was replaced with an equal weight surfactant shown in Table 3. In the same manner as in No. 4 (temperature of filling start liquid = 50 ° C.), an image was formed and white streaks were evaluated. The evaluation results are shown in Table 3.

The details of the surfactant described in Table 3 are as follows.
Surfynol 104E: acetylene glycol surfactant manufactured by Air Products (2,4,7,9-tetramethyl-5-decyne-4,7-diol: in the general formula (I) described above, R ⁵² And R ⁵⁴ is a methyl group, R ⁵³ and R ⁵⁵ are isobutyl groups, Y ² and Y ³ are ethylene groups, and x + y is 0)
Surfynol 420: an acetylene glycol surfactant manufactured by Air Products (in the general formula (I) described above, R ⁵² and R ⁵⁴ are methyl groups, R ⁵³ and R ⁵⁵ are isobutyl groups, Y ² and Y ³ are ethylene groups, and x + y is 1)
Surfynol 440: Acetylene glycol surfactant manufactured by Air Products (in the general formula (I), R ⁵² and R ⁵⁴ are methyl groups, R ⁵³ and R ⁵⁵ are isobutyl groups, Y ² and Y ³ are ethylene groups, and x + y is 3)
Surfynol 465: an acetylene glycol surfactant manufactured by Air Products (in the general formula (I), R ⁵² and R ⁵⁴ are methyl groups, R ⁵³ and R ⁵⁵ are isobutyl groups, Y ² and Y ³ are ethylene groups, and x + y is 8)
Surfynol 485: an acetylene glycol surfactant manufactured by Air Products (in the general formula (I), R ⁵² and R ⁵⁴ are methyl groups, R ⁵³ and R ⁵⁵ are isobutyl groups, Y ² and Y ³ are ethylene groups and x + y is 24).

As shown in Table 3, when the filling start liquid containing the acetylene glycol surfactant represented by the general formula (I) was used (No. 15 to No. 19), immediately after ink filling and for 24 hours. Later, the number of white streaks was small and the dischargeability was excellent.
On the other hand, in the comparative example (No. 11) using the filling start liquid not containing the surfactant, the discharge stability was remarkably poor. In addition, when a surfactant other than the acetylene glycol surfactant represented by the general formula (I) is used (No. 12 to No. 14), it is difficult to obtain good discharge stability. .

Next, the magenta ink M1 is changed to the black ink K1, the cyan ink C1, or the yellow ink Y1, and an image is obtained in the same manner as above except that the head portions 12K, 12C, and 12Y corresponding to the inks of the respective colors are used. The white streaks were evaluated.
As a result, when the black ink K1, cyan ink C1, or yellow ink Y1 is used, if the ink temperature during filling is set to 30 ° C. or higher and 90 ° C. or lower (particularly 40 ° C. or higher and 70 ° C. or lower), When the ink containing the acetylene glycol surfactant represented by the formula (I) was used, the number of white streaks was small immediately after ink filling and 24 hours later, and the dischargeability was excellent.

(Example 3)
In Example 1, BYK-024 (antifoaming agent) used for the preparation of the filling start liquid 01 was replaced with BYK-012, 017, 021, 022, 025, 038, 094 (Big Chemie Japan ( KS-537, 604, 72F (manufactured by Shin-Etsu Chemical Co., Ltd.), TSA-739 (manufactured by Momentive Performance Materials Japan GK), or Olfin AF104 (Nisshin Chemical Industry ( An image was formed and white streaks were evaluated in the same manner as in Example 1 except that the same weight was used.

As a result, it was confirmed that by adding these antifoaming agents, white streaks are less likely to occur than in the case where no antifoaming agent is contained, and an image in which the occurrence of white streaks is suppressed can be obtained. In particular, when using BYK-017, 021, 022, 025, 094, KS-537, 604, 72F, and TSA-739, which are silicone antifoams, BYK-024 was used. The same excellent white stripe suppression effect as in the case was observed.
Further, from the viewpoint of ejection stability, BYK-024 was most preferable.

(Example 4)
In the filling start liquid 01 of Example 1, the water content was reduced by 10% by mass, and diethylene glycol, dipropylene glycol, and glycerin were added as humectants, respectively, except that 10% by mass corresponding to the reduced amount of water was added. The effect was confirmed in the same manner as in Example 1 by preparing the filling start solution in the same manner as in the filling start solution 01 of Example 1 and changing the temperature between 30 ° C. and 90 ° C.
As a result, it was confirmed that by adding the moisturizing agent, the wall surface in the head was more difficult to dry, and the effects of the present invention were more suitably expressed.

(Example 5)
An image was formed in the same manner as in Example 1 except that the ink composition of Example 1 was changed to the following ink composition (cyan ink C2, magenta ink M2, yellow ink Y2, black ink K2). The streak was evaluated.
As a result, even when the magenta ink M2, the black ink K2, the cyan ink C2, or the yellow ink Y2 is used, the ink temperature at the time of filling is 30 ° C. or higher and 90 ° C. or lower (as in the case of using the magenta ink M1). In particular, it was confirmed that the number of white lines immediately after ink filling and 24 hours after ink filling drastically decreases when the temperature is 40 ° C. or more and 70 ° C. or less.

(Composition of cyan ink C2)
・ Cyan pigment (Pigment Blue 15: 3) ・ ・ ・ 4% by mass
-Polymer dispersant (P-1) solution ... 2% by mass
・ Aqueous dispersion of self-dispersing polymer fine particles B-01 8 mass%
・ Propylene glycol: 16% by mass
(Wako Pure Chemical Industries, hydrophilic organic solvent)
・ Sanix GP250 ・ ・ ・ 3% by mass
(Sanyo Chemical Industries, hydrophilic organic solvent)
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant): 1% by mass
・ Ion exchange water: 66% by mass

(Composition of magenta ink M2)
・ Magenta pigment (Pigment Red 122) ・ ・ ・ 4% by mass
-Polymer dispersant (P-1) solution ... 2% by mass
・ Aqueous dispersion of self-dispersing polymer fine particles B-01 8 mass%
・ Propylene glycol: 16% by mass
(Wako Pure Chemical Industries, hydrophilic organic solvent)
・ Sanix GP250 ・ ・ ・ 3% by mass
(Sanyo Chemical Industries, hydrophilic organic solvent)
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant): 1% by mass
・ Ion exchange water: 66% by mass

(Composition of yellow ink Y2)
・ Yellow pigment (Pigmen Yellow 74) ・ ・ ・ 4% by mass
-Polymer dispersant (P-1) solution ... 1.6% by mass
・ Aqueous dispersion of self-dispersing polymer fine particles B-01 8 mass%
・ Propylene glycol: 16% by mass
(Wako Pure Chemical Industries, hydrophilic organic solvent)
・ Sanix GP250 ・ ・ ・ 3% by mass
(Sanyo Chemical Industries, hydrophilic organic solvent)
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant): 1% by mass
・ Ion-exchanged water: 66.4% by mass

(Composition of black ink K2)
・ Carbon black: 4% by mass
-Polymer dispersant (P-1) solution ... 1.2% by mass
・ Aqueous dispersion of self-dispersing polymer fine particles B-01 8 mass%
・ Propylene glycol: 16% by mass
(Wako Pure Chemical Industries, hydrophilic organic solvent)
・ Sanix GP250 ・ ・ ・ 3% by mass
(Sanyo Chemical Industries, hydrophilic organic solvent)
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant): 1% by mass
・ Ion-exchanged water: 66.8% by mass

(Example 6)
An image was formed in the same manner as in Example 1 except that the ink composition of Example 1 was changed to the following ink composition (cyan ink C3, magenta ink M3, yellow ink Y3, black ink K3). The streak was evaluated.
As a result, even when the magenta ink M3, the black ink K3, the cyan ink C3, or the yellow ink Y3 is used, the ink temperature at the time of filling is 30 ° C. or higher and 90 ° C. or lower (as in the case of using the magenta ink M1). In particular, it was confirmed that the number of white lines immediately after ink filling and 24 hours after ink filling drastically decreases when the temperature is 40 ° C. or more and 70 ° C. or less.

(Composition of cyan ink C3)
・ Cyan pigment (Pigment Blue 15: 3) ・ ・ ・ 4% by mass
-Polymer dispersant (P-1) solution ... 2% by mass
・ Aqueous dispersion of self-dispersing polymer fine particles B-01 8 mass%
・ Propylene glycol: 15% by mass
(Wako Pure Chemical Industries, hydrophilic organic solvent)
・ Glycerin: 2% by mass
(Daiichi Kogyo Seiyaku, hydrophilic organic solvent)
・ Tripropylene glycol monomethyl ether: 2% by mass
(Nippon Emulsifier, hydrophilic organic solvent)
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant): 0.5% by mass
・ Orphine E1020 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant): 1% by mass
・ Capstone FS-63 (manufactured by Dupont, surfactant): 0.01% by mass
・ Ion exchange water: 65.49% by mass

(Composition of magenta ink M3)
・ Magenta pigment (Pigment Red 122) ・ ・ ・ 4% by mass
-Polymer dispersant (P-1) solution ... 2% by mass
・ Aqueous dispersion of self-dispersing polymer fine particles B-01 8 mass%
・ Propylene glycol: 15% by mass
(Wako Pure Chemical Industries, hydrophilic organic solvent)
・ Glycerin: 2% by mass
(Daiichi Kogyo Seiyaku, hydrophilic organic solvent)
・ Tripropylene glycol monomethyl ether: 2% by mass
(Nippon Emulsifier, hydrophilic organic solvent)
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant): 0.5% by mass
・ Orphine E1020 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant): 1% by mass
・ Capstone FS-63 (manufactured by Dupont, surfactant): 0.01% by mass
・ Ion exchange water: 65.49% by mass

(Composition of yellow ink Y3)
・ Yellow pigment (Pigment Yellow 74) ・ ・ ・ 4% by mass
-Polymer dispersant (P-1) solution ... 2% by mass
・ Aqueous dispersion of self-dispersing polymer fine particles B-01 8 mass%
・ Propylene glycol: 15% by mass
(Wako Pure Chemical Industries, hydrophilic organic solvent)
・ Glycerin: 2% by mass
(Daiichi Kogyo Seiyaku, hydrophilic organic solvent)
・ Tripropylene glycol monomethyl ether: 2% by mass
(Nippon Emulsifier, hydrophilic organic solvent)
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant): 0.5% by mass
・ Orphine E1020 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant): 1% by mass
・ Capstone FS-63 (manufactured by Dupont, surfactant): 0.01% by mass
・ Ion exchange water: 65.49% by mass

(Composition of black ink K3)
・ Carbon black: 4% by mass
-Polymer dispersant (P-1) solution ... 2% by mass
・ Aqueous dispersion of self-dispersing polymer fine particles B-01 8 mass%
・ Propylene glycol: 15% by mass
(Wako Pure Chemical Industries, hydrophilic organic solvent)
・ Glycerin: 2% by mass
(Daiichi Kogyo Seiyaku, hydrophilic organic solvent)
・ Tripropylene glycol monomethyl ether: 2% by mass
(Nippon Emulsifier, hydrophilic organic solvent)
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant): 0.5% by mass
・ Orphine E1020 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant): 1% by mass
・ Capstone FS-63 (manufactured by Dupont, surfactant): 0.01% by mass
・ Ion exchange water: 65.49% by mass

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus 12, 12K, 12C, 12M, 12Y ... Head part 14, 14K, 14C, 14M, 14Y ... Ink supply part 16 ... Recording paper 50 ... Circulation path 51. .... Deaeration device 52 ... Ambient temperature detector 56 ... Buffer tank 58 ... Buffer tank temperature controller 60 ... Buffer tank temperature detector 62 ... Main tank 66 ... Supply tank 68 ... Recovery tank 72 ... Valve unit 74 ... Head temperature adjustment unit 76 ... Head temperature detection unit 78 ... Inkjet head

Claims (11)

A first filling liquid containing an acetylene glycol-based surfactant represented by the following general formula (I) and water is heated to 30 ° C. or higher and 90 ° C. or lower, and the heated filling initial liquid is filled in an inkjet head. Filling process,
A second filling step of filling the inkjet head with an ink containing a pigment and water after filling the filling start liquid;
An ink filling method comprising:

[In General Formula (I), R ⁵² , R ⁵³ , R ⁵⁴ and R ⁵⁵ each independently represents a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 8 carbon atoms. Y ² and Y ³ each independently represents an alkylene group having 2 to 6 carbon atoms. x and y represent an average added mole number and satisfy 1 ≦ x + y ≦ 85. ]   The ink filling method according to claim 1, wherein the ink jet head before the first filling step is an unfilled ink jet head.   3. The ink filling method according to claim 1, wherein in the first filling step, the filling start liquid is heated to 40 ° C. or more and 70 ° C. or less.   The ink filling method according to claim 1, wherein the filling start liquid further contains a silicone-based antifoaming agent.   The ink filling method according to claim 1, wherein the filling start liquid has a surface tension of 40 mN / m or less.   The ink filling method according to any one of claims 1 to 5, wherein the ink further contains polymer particles. A circulation system including an inkjet head and a supply unit for switching and supplying the filling start liquid and the ink to the inkjet head; and a temperature adjusting means for adjusting the temperature of the filling start liquid and the ink circulating in the circulation system. Provided with an image forming apparatus,
An ink filling step of filling the ink jet head with the ink by the ink filling method according to any one of claims 1 to 6,
A temperature adjustment step of adjusting the temperature of the ink to 20 ° C. or more and 50 ° C. or less after the ink filling step;
An ink discharge step of discharging the temperature-controlled ink from the inkjet head onto a recording medium;
An image forming method comprising:   Further, in the ink filling step, after the first filling step in the ink filling method and before the second filling step, the filling start liquid at 30 ° C. or more and 90 ° C. or less is supplied to the circulation system. The image forming method according to claim 7, further comprising a circulation step for circulation. An ink filling step of filling the ink jet head with the ink by the ink filling method according to any one of claims 1 to 6,
An ink discharge step of discharging the filled ink from the inkjet head onto a recording medium;
An image forming method comprising:   The image forming method according to claim 9, wherein, in the ink discharge step, the temperature of the filled ink is adjusted to 20 ° C. or more and 50 ° C. or less.   The image forming method according to claim 7, further comprising a treatment liquid application step of applying a treatment liquid containing an aggregation component that aggregates the components in the ink onto the recording medium.