JP6735065B2 - Ink jet recording apparatus and water-based ink composition - Google Patents

Description

The present invention relates to an inkjet recording device and an aqueous ink composition used therein.

An ink jet recording apparatus, which is an example of a liquid ejecting apparatus, includes an ejection head having nozzle holes for ejecting ink, a driving unit (for example, a piezoelectric vibrator or a heating element) for ejecting ink from the nozzle holes, and a data ejection unit according to data. And a control means for controlling the driving means. The ink is supplied to the nozzle holes by, for example, an ink cartridge, an ink supply chamber that receives ink from the ink cartridge, and an ink supply channel that extends from the ink supply chamber to the nozzle holes. The ink cartridge is usually replaceable.

As an example of the structure of the ejection head, a nozzle plate provided with a nozzle hole and a vibrating plate arranged in parallel with the nozzle plate and vibrated by a piezoelectric element are provided, and a space between the nozzle plate and the vibrating plate is provided. There is a type in which ink is ejected by changing the volume of the pressure chamber formed in the above by the vibration of the vibration plate (for example, refer to Patent Document 1).

However, in this type of ejection head, since the space volume upstream of the nozzle hole is small, if the time during which the ink droplet is not ejected from the nozzle hole becomes long, the ink in the vicinity of the nozzle hole thickens due to drying and, for example, the ejection of the ink droplet. There are problems that the direction is not stable and that ejection failure occurs such that ink droplets are not ejected.

In view of this, a new ejection head has been developed in which the space volume upstream of the nozzle hole is made larger than the conventional one while achieving downsizing and space saving (for example, refer to Patent Document 2). The ejection head has a liquid flow path extending in the planar direction having a vibrating plate and a plurality of vertical flow paths connected to the liquid flow path, thereby obtaining a spatial volume upstream of the nozzle hole. Since this ejection head has a larger space volume upstream of the nozzle than that of the conventional one, even if the ink near the nozzle hole is thickened by drying, it is easy to diffuse and the thickening of the ink can be alleviated.

Japanese Patent Laid-Open No. 08-020107 JP, 2014-184606, A

However, if the ink contains an oxidized self-dispersion pigment, the ink starts to freeze from the nozzle plate side when the inkjet recording apparatus including the new ejection head is placed in a low temperature environment. It has been clarified that there is a problem that the ink liquid flow path is gradually blocked from the nozzle plate side so that there is no escape route for the volume expansion force of the ink and the diaphragm and the piezoelectric element are damaged.

Therefore, some aspects according to the present invention solve at least a part of the above-mentioned problems, and thereby a liquid channel extending in a plane direction having a vibrating plate and a plurality of vertical liquids connected to the liquid channel. Disclosed is a water-based ink composition capable of forming an image in which a discharge head having a flow path can prevent failure of the discharge head during freezing, is excellent in storage stability, and is excellent in color development and abrasion resistance. To do.

Further, some aspects according to the present invention solve at least a part of the above-mentioned problems, thereby providing a high-density and small-sized ejection head, and even when placed in a low temperature environment, An inkjet recording device that is less likely to be damaged.

The present invention has been made to solve at least a part of the problems described above, and can be realized as the following aspects or application examples.

[Application example 1]
One aspect of the water-based ink composition according to the present invention is
A water-based ink composition for use in an inkjet recording apparatus including an ejection head having a liquid channel extending in a plane direction having a vibrating plate, and a plurality of vertical liquid channels connected to the liquid channel,
An oxidation-treated pigment and a self-emulsifying resin having an acid value of 10 to 90 mg/KOH are included,
The surface of the oxidation-treated pigment has a carboxyl group and a lactone group having a molar ratio of 0.8 to 1.1 times that of the carboxyl group and a molar number per pigment mass of 500 μmol/g or more. , Are included.

According to the water-based ink composition of Application Example 1, it is possible to prevent a failure such as a crack of the ejection head that occurs when the ink contains the oxidized self-dispersion pigment. That is, when the ink contains a self-emulsifying resin having an acid value of 10 to 90 mg/KOH, the freezing point of the ink does not change, but the properties of the solidified product can be changed. When freezing of the ink begins, the self-emulsifying resin enters between the crystal structures of the solidified product, thereby forming a softer solidified product. As a result, it is possible to prevent the above-mentioned cracks in the ejection head during freezing. Further, since the self-dispersion pigment that has been subjected to the oxidation treatment is contained, it is possible to form a recorded matter which is excellent in storage stability and color development. Further, since the self-emulsifying resin is contained, the abrasion resistance of the recorded matter can be improved.

[Application example 2]
In the water-based ink composition of Application Example 1,
The number of moles of lactone groups per mass of the pigment on the surface of the oxidation-treated pigment may be 700 μmol/g or more.

[Application example 3]
In the water-based ink composition of Application Example 1 or Application Example 2,
The content ratio of the oxidation-treated pigment and the self-emulsifying resin (oxidation-treated pigment/self-emulsifying resin) may be 0.5 or more and 6.0 or less.

[Application example 4]
In the water-based ink composition according to any one of Application Example 1 to Application Example 3,
The self-emulsifying resin may be a urethane resin.

[Application example 5]
In the water-based ink composition according to any one of Application Example 1 to Application Example 4,
The pigment may be carbon black.

[Application example 6]
One aspect of the inkjet recording apparatus according to the present invention is
An inkjet recording apparatus comprising: an aqueous ink composition; and an ejection head that ejects the aqueous ink composition,
The discharge head includes a flow path having a vibrating plate and extending in a plane direction, and a plurality of vertical flow paths connected to the flow path,
The water-based ink composition includes an oxidation-treated pigment and a self-emulsifying resin having an acid value of 10 to 90 mg/KOH,
The surface of the oxidation-treated pigment has a carboxyl group and a lactone group having a molar ratio of 0.8 to 1.1 times that of the carboxyl group and a molar number per pigment mass of 500 μmol/g or more. , Are included.

According to the inkjet recording apparatus of Application Example 6, it is possible to prevent a failure such as a crack in the ejection head that occurs when the ink used contains the oxidized self-dispersion pigment. That is, since the ink used contains the self-emulsifying resin having an acid value of 10 to 90 mg/KOH, the freezing point of the ink does not change, but the properties of the solidified product can be changed. When freezing of the ink begins, the self-emulsifying resin enters between the crystal structures of the solidified product, thereby forming a softer solidified product. As a result, it is possible to prevent the above-mentioned cracks in the ejection head during freezing.

[Application example 7]
In the inkjet recording apparatus of application example 6,
The number of moles of lactone groups per mass of the pigment on the surface of the oxidation-treated pigment may be 700 μmol/g or more.

[Application example 8]
In the inkjet recording apparatus of Application Example 6 or Application Example 7,
The content ratio of the oxidation-treated pigment and the self-emulsifying resin (oxidation-treated pigment/self-emulsifying resin) may be 0.5 or more and 6.0 or less.

[Application example 9]
In the inkjet recording apparatus according to any one of Application Examples 6 to 8,
The self-emulsifying resin may be a urethane resin.

[Application Example 10]
In the inkjet recording apparatus according to any one of Application Examples 6 to 9,
The pigment may be carbon black.

FIG. 3 is an exploded perspective view schematically showing the ejection head according to the embodiment. FIG. 3 is a plan view schematically showing the ejection head according to the embodiment. FIG. 3 is a cross-sectional view schematically showing the ejection head according to the embodiment. FIG. 3 is an enlarged cross-sectional view schematically showing a main part of the ejection head according to the embodiment. FIG. 1 is a schematic diagram schematically showing an inkjet recording device according to an embodiment. FIG. 6 is an enlarged cross-sectional view schematically showing a main part of an ejection head (head B) according to a comparative example.

Hereinafter, some embodiments of the present invention will be described. The embodiment described below describes an example of the present invention. The present invention is not limited to the following embodiments at all, and includes various modifications that are carried out within the scope without changing the gist of the present invention. Note that not all of the configurations described below are essential configurations of the present invention.

1. Inkjet recording apparatus 1.1. Device Configuration First, the device configuration of the inkjet recording apparatus according to the present embodiment will be described. FIG. 1 is an exploded perspective view of an ink jet recording head which is an example of an ejection head according to this embodiment. FIG. 2 is a plan view schematically showing the ink jet recording head according to this embodiment. 3 is a cross-sectional view taken along the line AA' in FIG. 2, and FIG. 4 is a cross-sectional view enlarging a main part of FIG.

As shown in the figure, the ink jet recording head II according to the present embodiment includes a head body 11, a case member 40 fixed to one side of the head body 11, and a cover head 130 fixed to the other side of the head body 11. And the like. In the present embodiment, the head body 11 includes a flow path forming substrate 10, which is a flow path member, a communication plate 15, and a spacer 25, a nozzle plate 20 attached to one surface side of the flow path member, a protective substrate 30, And a compliance substrate 45. The flow path member of the present embodiment includes the flow path forming substrate 10, the communication plate 15, and the spacer 25. In addition, the protective member of the present embodiment includes the compliance substrate 45 and the cover head 130 that is a protective plate.

The flow path forming substrate 10 constituting the head main body 11 is made of a metal such as stainless steel or Ni, a ceramic material typified by ZrO ₂ or Al ₂ O ₃ , a glass ceramic material, an oxide such as MgO or LaAlO ₃ , and the like. Can be used. In this embodiment, the flow path forming substrate 10 is made of a silicon single crystal substrate. By anisotropically etching the flow path forming substrate 10 from one surface side, a plurality of nozzle openings 21 through which the pressure generating chambers 12 partitioned by a plurality of partition walls eject ink are arranged in parallel. Are installed side by side. Hereinafter, this direction will be referred to as the direction in which the pressure generating chambers 12 are arranged in parallel, or the first direction X. Further, the flow path forming substrate 10 is provided with a plurality of rows in which the pressure generating chambers 12 are arranged in parallel in the first direction X, and in this embodiment, two rows are provided. The direction in which the pressure generating chambers 12 are formed along the first direction X and in which a plurality of rows of the pressure generating chambers 12 are arranged will be hereinafter referred to as a second direction Y.

In addition, in the flow path forming substrate 10, the flow path resistance of the ink flowing into the pressure generation chamber 12 has a smaller opening area than the pressure generation chamber 12 at one end side in the second direction Y of the pressure generation chamber 12. A supply path or the like may be provided.

Further, the communication plate 15, the spacer 25, and the nozzle plate 20 are sequentially stacked on the one surface side of the flow path forming substrate 10. That is, the communication plate 15 provided on one surface of the flow path forming substrate 10, the spacer 25 provided on the surface of the communication plate 15 opposite to the flow path forming substrate 10, and the communication plate 15 of the spacer 25 are opposite to each other. A nozzle plate 20 having a nozzle opening 21 provided on the surface side.

The communication plate 15 is provided with a first nozzle communication passage 16 that connects the pressure generating chamber 12 and the nozzle opening 21. The communication plate 15 has a larger area than the flow path forming substrate 10, and the nozzle plate 20 has a smaller area than the flow path forming substrate 10. By providing the communication plate 15 in this way, the nozzle opening 21 of the nozzle plate 20 and the pressure generating chamber 12 can be separated from each other, so that the ink in the pressure generating chamber 12 is the same as the ink generated in the ink near the nozzle opening 21. Less susceptible to thickening due to evaporation of water. Further, since the nozzle plate 20 only needs to cover the opening of the first nozzle communication passage 16 that connects the pressure generating chamber 12 and the nozzle opening 21, the area of the nozzle plate 20 can be made relatively small, and the cost can be reduced. Can be planned. In the present embodiment, the surface on which the nozzle openings 21 of the nozzle plate 20 are opened and ink droplets are ejected is referred to as a liquid ejection surface 20a.

Further, the communication plate 15 is provided with a first manifold portion 17 and a second manifold portion 18 which form a part of the manifold 100. The first manifold portion 17 is provided so as to penetrate the communication plate 15 in the thickness direction (the stacking direction of the communication plate 15 and the flow path forming substrate 10).

Further, the second manifold portion 18 is provided so as to open to the nozzle plate 20 side of the communication plate 15 without penetrating the communication plate 15 in the thickness direction. Further, the communication plate 15 is provided with a supply communication passage 19 that communicates with one end of the pressure generation chamber 12 in the second direction Y, independently for each pressure generation chamber 12. The supply communication passage 19 connects the second manifold portion 18 and the pressure generating chamber 12 with each other.

As the communication plate 15, a metal such as stainless steel or Ni, a ceramic such as zirconium, or the like can be used. The communication plate 15 is preferably made of a material having the same linear expansion coefficient as that of the flow path forming substrate 10. That is, when a material having a linear expansion coefficient that is greatly different from that of the flow path forming substrate 10 is used as the communication plate 15, the material is warped due to the difference in the linear expansion coefficient between the flow path forming substrate 10 and the communication plate 15 when heated or cooled. Will occur. In this embodiment, by using the same material as the flow path forming substrate 10 as the communication plate 15, that is, a silicon single crystal substrate, generation of warpage due to heat, cracks due to heat, peeling, and the like can be suppressed.

The spacer 25 has substantially the same area as the nozzle plate 20 (area in the first direction X and the second direction Y). Therefore, the spacer 25 is provided only at the position where the nozzle plate 20 is attached. That is, the spacer 25 is not provided at the position where the compliance substrate 45, which is a protection member for the communication plate 15, is attached. For this reason, as will be described later in detail, the position of the flow path member where the nozzle plate 20 is attached, that is, the position of the surface of the spacer 25 where the nozzle plate 20 is attached, and the flow path member protection member (compliance substrate 45) are attached. The position where the communicating plate 15 is directly attached to the communicating plate 15 is different from the ejecting direction of the ink droplets, that is, the third direction Z which is the stacking direction of the communicating plate 15 and the flow path forming substrate 10. There is.

The spacer 25 is provided with a second nozzle communication passage 26 that communicates with the first nozzle communication passage 16 and the nozzle opening 21. That is, the pressure generating chamber 12 communicates with the nozzle opening 21 via the first nozzle communication passage 16 of the communication plate 15 and the second nozzle communication passage 26 of the spacer 25.

As the spacer 25, for example, a metal such as stainless steel or Ni, or a ceramic such as zirconium or silicon can be used. In the present embodiment, by using the same silicon single crystal substrate as the communication plate 15 as the spacer 25, it is possible to suppress warpage due to heating and cooling, cracks due to heat, and peeling.

In addition, the spacer 25 is based on the laminated thickness (total thickness in the third direction Z) of the compliance substrate 45, which is a protective member, and the cover head 130, which is a protective plate, and the thickness of the nozzle plate 20. The step h between the liquid ejecting surface 20a and the surface of the cover head 130 (the surface on the liquid ejecting surface 20a side) may be selected to have a desired value.

The nozzle plate 20 is formed with a nozzle opening 21 that communicates with each pressure generating chamber 12 via the first nozzle communication passage 16 and the second nozzle communication passage 26. That is, the nozzle openings 21 that eject the same type of liquid (ink) are arranged in parallel in the first direction X, and the row of the nozzle openings 21 arranged in parallel in the first direction X is the second direction. Two rows are formed in Y.

As such a nozzle plate 20, for example, a metal such as stainless steel (SUS), an organic substance such as a polyimide resin, or a silicon single crystal substrate can be used. By using a silicon single crystal substrate as the nozzle plate 20, the nozzle plate 20 and the communicating plate 15 have the same linear expansion coefficient, and the occurrence of warpage due to heating and cooling, cracking due to heat, and peeling is suppressed. can do.

On the other hand, a vibration plate 50 is formed on the surface of the flow path forming substrate 10 opposite to the communication plate 15. In this embodiment, as the diaphragm 50, an elastic film 51 made of silicon oxide provided on the flow path forming substrate 10 side and an insulating film 52 made of zirconium oxide provided on the elastic film 51 are provided. I chose The liquid flow paths such as the pressure generating chambers 12 are formed by anisotropically etching the flow path forming substrate 10 from one surface side (the surface side where the nozzle plate 20 is joined). The other surface of the liquid flow path such as is defined by the elastic film 51.

Further, a protective substrate 30 having substantially the same size as the flow channel forming substrate 10 is bonded to the surface of the flow channel forming substrate 10 on the piezoelectric actuator 300 side. The protective substrate 30 has a holding portion 31 which is a space for protecting the piezoelectric actuator 300.

Further, a case member 40 that defines together with the head body 11 a manifold 100 that communicates with the plurality of pressure generating chambers 12 is fixed to the head body 11 having such a configuration. The case member 40 has substantially the same shape as the communication plate 15 described above in a plan view, is bonded to the protective substrate 30, and is also bonded to the communication plate 15 described above. Specifically, the case member 40 has, on the protective substrate 30 side, a recess 41 having a depth in which the flow path forming substrate 10 and the protective substrate 30 are accommodated. The recess 41 has a larger opening area than the surface of the protective substrate 30 joined to the flow path forming substrate 10. The opening surface of the recess 41 on the nozzle plate 20 side is sealed by the communication plate 15 in a state where the flow path forming substrate 10 and the like are accommodated in the recess 41. Accordingly, the case member 40 and the head body 11 define a third manifold portion 42 on the outer peripheral portion of the flow path forming substrate 10. Then, the manifold 100 of the present embodiment includes the first manifold portion 17 and the second manifold portion 18 provided on the communication plate 15, and the third manifold portion 42 defined by the case member 40 and the head body 11. It is configured.

The case member 40 may be made of resin or metal, for example. Incidentally, the case member 40 can be mass-produced at low cost by molding a resin material.

A compliance substrate 45 is provided on the surface of the communication plate 15 where the first manifold portion 17 and the second manifold portion 18 open. The compliance substrate 45 seals the openings of the first manifold section 17 and the second manifold section 18 on the liquid ejection surface 20a side.

That is, the compliance substrate 45 that constitutes the protection member of the present embodiment is directly fixed to the communication plate 15. Therefore, the position of the surface of the spacer 25 to which the nozzle plate 20 is attached and the position of the surface on the nozzle plate 20 side of the communication plate 15 to which the compliance substrate 45, which is a protection member, is different from each other in the third direction Z. Has become.

Incidentally, in the flow path member, the position where the nozzle plate 20 is attached and the position where the protective member (in this embodiment, the compliance substrate 45 that constitutes the protective member) are attached are the same position in the third direction Z. It means that they are attached on the same plane of the communication plate 15, for example. The flat surface of the communication plate 15 naturally includes height variations due to processing errors when the surface of the communication plate 15 is processed into a flat surface. That is, in the present embodiment, the nozzle plate 20 and the protective member are not fixed to the same surface of the communication plate 15 processed on a plane, but the spacer 25 is fixed to the position where the nozzle plate 20 of the communication plate 15 is fixed. By providing the nozzle plate 20, the nozzle plate 20 is mounted on the surface of the spacer 25, and the mounting positions of the nozzle plate 20 and the protective member in the third direction Z are different.

In this embodiment, such a compliance substrate 45 includes a sealing film 46 and a fixed substrate 47. The sealing film 46 is made of a flexible thin film (for example, a thin film formed of polyphenylene sulfide (PPS) or stainless steel (SUS) and has a thickness of 20 μm or less), and the fixed substrate 47 is made of stainless steel ( It is formed of a hard material such as metal such as SUS). Since the region of the fixed substrate 47 facing the manifold 100 is the opening 48 that is completely removed in the thickness direction, one surface of the manifold 100 is sealed with only the flexible sealing film 46. It is a compliance part 49 which is a flexible part.

The case member 40 is provided with an introduction path 44 that communicates with the manifold 100 and supplies ink to each manifold 100. Further, the case member 40 is provided with a connection port 43 that is in communication with the through hole 32 of the protective substrate 30 and into which the wiring substrate 121 is inserted.

A cover head 130, which is the protective plate of the present embodiment, is provided on the liquid ejecting surface 20a side of the head body 11. The cover head 130 is joined to the surface of the compliance substrate 45 opposite to the communication plate 15, and seals the space on the opposite side of the compliance portion 49 from the flow path (manifold 100). The cover head 130 is provided with an exposure opening 131 that exposes the nozzle opening 21. In this embodiment, the exposure opening 131 has a size that exposes the nozzle plate 20, that is, the same opening as the compliance substrate 45.

Further, in the present embodiment, the cover head 130 is provided with its end portion bent from the liquid ejecting surface 20a side so as to cover the side surface of the head body 11 (the surface that intersects with the liquid ejecting surface 20a).

In the ink jet recording head II having such a configuration, when ejecting ink, the ink is taken in from the ink cartridge 2 through the introduction passage 44, and the inside of the passage from the manifold 100 to the nozzle opening 21 is filled with the ink. After that, according to a signal from the drive circuit 120, a voltage is applied to each piezoelectric actuator 300 corresponding to the pressure generating chamber 12, so that the diaphragm 50 is flexibly deformed together with the piezoelectric actuator 300. As a result, the pressure inside the pressure generating chamber 12 increases and ink droplets are ejected from the predetermined nozzle openings 21. In the inkjet recording head II of this embodiment, the area from the connection port 43 to the nozzle opening 21 is referred to as a liquid flow path. That is, the liquid flow path includes the connection port 43, the manifold 100, the supply communication passage 19, the pressure generating chamber 12, the first nozzle communication passage 16, the second nozzle communication passage 26, and the nozzle opening 21.

The ink jet recording head II having such a configuration has a plurality of liquid flow paths (pressure generation chambers 12) extending in the plane direction (Y direction) having the vibrating plate 50 and a plurality of vertical directions (Z direction) connected to the liquid flow paths. Liquid passages (the supply communication passage 19, the second nozzle communication passage 26, the first nozzle communication passage 16). Since the inkjet recording head II has a longer liquid flow path and a larger volume of the liquid flow path than the conventional inkjet recording head, it is possible to reduce the drying of the ink in the vicinity of the nozzle. As a result, it is possible to mitigate the increase in the viscosity of the ink in the nozzles that are not ejecting the ink, so that the ejection stability of the ink becomes good.

On the other hand, when the ink jet recording head II filled with the ink containing the self-dispersion pigment is placed in a low temperature environment, the ink in the liquid flow path starts to gradually freeze from the +Z direction side, and It was found that the ink of No. 2 was gradually blocked from the +Z direction to the −Z direction, so that there was no escape path for the ink, and as a result, the diaphragm and the piezoelectric element were damaged. Such a problem occurs when an ink containing a self-dispersion pigment is filled, but the detailed mechanism has not been clarified. To solve such a problem, the present invention devises the composition of the ink containing the self-dispersion pigment when the ink jet recording head II having the above-described structure is filled with the ink containing the self-dispersion pigment. As a result, it has succeeded in avoiding cracks in the vibration plate and the piezoelectric element that occur when the ink freezes.

The ink jet recording head II of this embodiment constitutes a part of an ink jet recording head unit having an ink flow path communicating with an ink cartridge or the like, and is installed in an ink jet recording apparatus. FIG. 5 is a schematic view showing an example of the ink jet recording apparatus.

In the ink jet recording apparatus I shown in FIG. 5, an ink jet recording head unit 1 (hereinafter, also referred to as head unit 1) having a plurality of ink jet recording heads II is provided such that a cartridge 2 constituting an ink supply unit is detachably attached. The carriage 3 on which the head unit 1 is mounted is provided on a carriage shaft 5 attached to the apparatus body 4 so as to be movable in the axial direction. The recording head unit 1 is configured to eject, for example, a black ink composition and a color ink composition, respectively.

Then, the driving force of the drive motor 6 is transmitted to the carriage 3 via a plurality of gears (not shown) and the timing belt 7, so that the carriage 3 on which the head unit 1 is mounted is moved along the carriage shaft 5. On the other hand, a platen 8 is provided on the apparatus main body 4 along the carriage shaft 5, and a recording sheet S, which is a recording medium such as paper fed by a feeding roller (not shown), is wound around the platen 8. It is designed to be transported.

In the above-described inkjet recording apparatus I, the inkjet recording head II (head unit 1) mounted on the carriage 3 and moved in the main scanning direction is illustrated, but the invention is not particularly limited to this and, for example, an inkjet recording apparatus. The present invention can be applied to a so-called line type recording apparatus in which the recording head II is fixed and printing is performed only by moving the recording sheet S such as paper in the sub-scanning direction.

Further, in the above-described example, the ink jet recording apparatus I has a configuration in which the ink cartridge 2 that is a liquid storage unit is mounted on the carriage 3, but the invention is not particularly limited to this, and for example, a liquid storage unit such as an ink tank. May be fixed to the apparatus main body 4, and the storage means and the ink jet recording head II may be connected via a supply pipe such as a tube. Further, the liquid storage means does not have to be mounted on the ink jet recording apparatus.

Further, the present invention is broadly applied to liquid jet heads in general, and for example, for manufacturing recording heads such as various ink jet recording heads used in image recording devices such as printers and color filters for liquid crystal displays. It can also be applied to a coloring material ejecting head used, an organic EL display, an electrode material ejecting head used for forming electrodes such as an FED (field emission display), and a bioorganic substance ejecting head used for biochip manufacturing.

1.2. Aqueous Ink Composition The aqueous ink composition used in this embodiment is an aqueous ink composition for use in the inkjet recording device described above. This water-based ink composition contains at least an oxidation-treated pigment and a self-emulsifying resin having an acid value of 10 to 90 mg/KOH. Hereinafter, each component contained in the water-based ink composition used in this embodiment will be described in detail.

1.2.1. Self-Dispersion Pigment The aqueous ink composition used in this embodiment contains an oxidation-treated pigment. The pigment has a lactone group or a carboxyl group introduced on its surface by this oxidation treatment. In this oxidized pigment, hydrophilic functional groups such as lactone groups and carboxyl groups are oriented toward the water side. It can be dispersed stably. In the present specification, this oxidation-treated pigment is also referred to as "self-dispersion pigment". The term "dispersion" in the present specification refers to a state in which the self-dispersion pigment is stably present in water without a dispersant, not only in a dispersed state but also in a dissolved state. It also includes things.

The water-based ink composition containing the self-dispersion pigment has higher dispersion stability than the ordinary water-based ink composition containing the pigment and the dispersant other than the self-dispersion pigment, and the water-based ink composition has a high dispersion stability. Since the viscosity is appropriate, it is possible to add a larger amount of pigment, and it is possible to form an image such as characters and figures having excellent coloring properties on plain paper. Furthermore, since the water-based ink composition containing the self-dispersion pigment does not cause deterioration in fluidity even when a water-soluble organic solvent (described later) effective for improving print quality is added, Printing quality is also improved by using an organic solvent together.

On the surface of the self-dispersion pigment, the molar ratio of the carboxyl group to the carboxyl group is 0.8 to 1.1 times, preferably 0.85 to 1.05 times, and more preferably 0.9 to 1.0 times. And a lactone group of 500 μmol/g or more, preferably 600 μmol/g or more, more preferably 700 μmol/g or more, and particularly preferably 700 to 900 μmol/g in terms of the number of moles per mass of the pigment.

The carboxyl group on the surface of the self-dispersion pigment is also 700 μmol/g or more, and preferably 700 to 900 μmol/g in terms of the number of moles.

A self-dispersion pigment having a hydrophilic functional group, a carboxyl group or a lactone group, within the above range has a large electrostatic capacitance between the pigments because the hydrophilic functional group is oriented toward the water side. Repulsive force is working, and in combination with the relatively large number of lactone groups, it is difficult to aggregate. Furthermore, the self-dispersion pigment has a strong interaction with water because it has a hydrophilic functional group, and since carboxyl groups and lactone groups are present on the surface of the pigment in an appropriate ratio, it is easy to disperse in water, difficult to settle, and stable. It has become.

Therefore, the self-dispersion pigment can be dispersed in water without a dispersant. A water dispersion having a desired pigment concentration can be prepared by adding water to the self-dispersion pigment and then concentrating it. If desired, any appropriate water-soluble organic solvent and additives such as preservatives may be added to this dispersion liquid.

The dispersion liquid of the self-dispersion pigment is excellent in stability due to temperature change. Even after 5 weeks at 70° C., the average particle size change rate is preferably 15% or less, and more preferably 10% or less. The above-mentioned rate of change is particularly problematic when the average particle size is significantly changed.

In addition, the dispersion liquid of the self-dispersion pigment does not change in viscosity and is excellent in stability. The viscosity change rate is preferably 10% or less even after 5 weeks at 70°C. The above rate of change is particularly problematic when the change in viscosity is significant.

As the pigment capable of forming the self-dispersion type pigment, the same pigments as those in ordinary ink compositions for ink jet recording are used, and examples thereof include azo lake, insoluble azo pigment, condensed azo pigment, chelate azo pigment, phthalocyanine pigment and perylene pigment. , Perinone pigment, quinacridone pigment, thioindigo pigment, isoindolinone pigment, quinofuraron pigment, dioxazine pigment, anthraquinone pigment, nitro pigment, nitroso pigment, aniline black, titanium white, zinc white, lead white, carbon black, red iron oxide, vermilion, cadmium Examples thereof include organic pigments or inorganic pigments such as red, yellow lead, ultramarine blue, cobalt blue, cobalt violet and zinc chromate. Further, any pigment not listed in the color index can be used as long as it can be dispersed in the aqueous phase. Of these, it is particularly preferable to use carbon black.

The carbon black may be carbon black obtained by the furnace method, carbon black obtained by the channel method, or the like. The furnace method introduces fuel (gas or oil) and air into a special combustion furnace lined with bricks that can withstand high temperatures up to about 2000°C, and completely burns it to form a high temperature atmosphere of 1400°C or higher. Liquid raw material oil is continuously sprayed and pyrolyzed, water is sprayed to the high temperature gas containing carbon black generated in the latter part of the furnace to stop the reaction, and then it is separated into carbon black and exhaust gas with a bag filter. This is a bulk powder manufacturing method. According to such a manufacturing method, a small amount of lactone group or carboxyl group is introduced also on the surface of the carbon black bulk powder. This phenomenon is deeply related to the shape and surface structure of the carbon black structure together with the manufacturing method, and this is an important factor for the self-dispersion pigment obtained by subjecting the carbon black bulk powder to an oxidation treatment.

Examples of the pigment oxidation treatment method include an oxidation method by contact with air; a gas-phase oxidation method by reaction with nitrogen oxide and ozone; nitric acid, potassium permanganate, potassium dichromate, chlorous acid, perchloric acid, A liquid phase oxidation method using an oxidizing agent such as hypohalite, hydrogen peroxide, an aqueous bromine solution, an aqueous ozone solution may be used. The surface may be modified by plasma treatment or the like.

A particularly preferable oxidation treatment method is a method in which the pigment is wet-oxidized using hypohalous acid or a salt thereof. Specific examples of the hypohalite include sodium hypochlorite and potassium hypochlorite, and sodium hypochlorite is more preferable from the viewpoint of reactivity.

When oxidizing carbon black, for example, an aqueous solution of hypohalous acid and/or hypohalous acid salt is added to a liquid prepared by suspending carbon black bulk powder prepared by a furnace method in water, and oxidation treatment is performed. There is at least a step of obtaining a self-dispersion pigment, stirring it with a mill medium having a diameter of 0.6 to 3 mm by a disperser, filtering it with a wire mesh of 100 to 500 mesh, and desalting the filtrate with an ultrafiltration membrane. A method of obtaining a dispersion liquid by this is preferable.

The surface of the raw carbon black powder is oxidized by introducing an oxidative treatment using an aqueous solution of hypohalous acid or a salt thereof, preferably sodium hypochlorite, as an oxidant to introduce a lactone group, a carboxyl group or the like. The amount of hypohalous acid or a salt thereof used is appropriately adjusted according to the size of the BET specific surface area of the carbon black bulk powder. The carbon black bulk powder has a surface area of 0.6×10 ^{−4 to} 2.5×10 ⁻⁴ mol/m ² , preferably 0.6×10 ^{−4 to} 1.5×10 ⁻⁴ mol/m ^2. By oxidation treatment with hypochlorous acid and/or hypohalous acid salt having the above chlorine amount, a self-dispersing carbon black having good stability can be obtained.

It is preferable that the smaller the BET specific surface area, the smaller the amount of hypohalous acid or its salt, ie, the hypohalous acid, and the larger the BET specific surface area, the larger the amount of hypohalous acid. This is because the smaller the BET specific surface area, the smaller the number of active points that react with hypohalous acids, and the larger the specific surface area, the larger number of active points that react with hypohalous acids. Addition of an amount of hypohalous acid that reacts with the active site does not hinder the reaction, but useless hypohalous acid is used, and an extra desalting operation is required. When the reaction is carried out with an amount of hypohalous acid that is less than the amount that reacts with active sites, the target amounts of lactone groups and carboxyl groups are not reached, and the sedimentation rate increases, resulting in a decrease in long-term storage stability.

When suspending the carbon black bulk powder in water, it is important to mix the carbon black sufficiently with water in order to properly perform the oxidation treatment. You may disperse|distribute using a disperser with a high load, a high speed stirrer, etc. A water-soluble solvent may be preliminarily impregnated into the carbon black. Further, the dispersion treatment may be performed with a mixed system of water and a water-soluble solvent.

In the process of oxidizing/dispersing or crushing carbon black, a ball mill, an attritor, a fluo jet mixer, an impeller mill, a colloidal mill, a sand mill (for example, “super mill”, “agitator mill”, “dyno mill” as a disperser or pulverizer ,” “bead mill” (commercially available products), and the like. At that time, the mill medium is not necessarily used, but it is preferably used. The mill medium preferably has a diameter of 0.6 to 3 mm, and specific examples thereof include glass beads, zirconia beads, magnetic beads, stainless beads and the like. The conditions in the step of dispersing while oxidizing are preferably 10 to 70° C. for 3 to 10 hours and the number of revolutions is 500 rpm or more. Generally, the higher the reaction temperature is, the more easily the oxidation reaction proceeds. However, if the temperature is too high, the hypohalite is decomposed. Therefore, the oxidation reaction is preferably performed at 40 to 60°C.

Filtration with a wire mesh is performed to remove coarse particles and mill media. The pH of the obtained filtrate may be adjusted. Excess acid or water-soluble acidic group produced as a by-product in the obtained filtrate may be neutralized with a basic substance. Examples of such basic substances include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide; ammonia and aqueous ammonia; amine compounds. Examples of amine compounds include water-soluble volatile amines and alkanolamines. Specifically, a volatile amine substituted with an alkyl group having 1 to 3 carbon atoms (for example, methylamine, trimethylamine, diethylamine, propylamine); an alkanolamine substituted with an alkanol group having 1 to 3 carbon atoms (for example, (Ethanolamine, diethanolamine, triethanolamine, triisopropanolamine); and alkylalkanolamines substituted with an alkyl group having 1 to 3 carbon atoms or an alkanol group having 1 to 3 carbon atoms.

The desalting of the liquid obtained above is performed, for example, by an ultrafiltration membrane until the electric conductivity of the liquid reaches a maximum of 1.5 mS/cm. If desalting is stopped outside this range, a large amount of impurities such as NaCl will be contained in the ink, resulting in poor storage stability of the ink. Further, in order to prepare a more stable ink, the desalting method may be a combination of various desalting methods. A desalted pigment dispersion can be obtained by the above method.

The self-dispersion type carbon black obtained from such a desalted dispersion has an electric conductivity of 0.7 mS/cm or less and can be used for preparing an aqueous ink composition having good storage stability. .. After desalting, coarse particles of 1 μm or more may be further removed using a centrifuge or a filter to obtain a dispersion liquid.

The self-dispersion pigment preferably has an average particle size of 1 to 300 nm, more preferably 10 to 200 nm, from the viewpoints of storage stability of the ink and prevention of nozzle clogging. In the present specification, the “average particle size” means the volume average particle size (Mv) measured by a particle size distribution measuring device having a dynamic light scattering method as a measuring principle, unless otherwise specified. As such a particle size distribution measuring device, for example, a dynamic light scattering particle size distribution measuring device “LB-500” manufactured by Horiba Ltd. may be mentioned.

The content of the self-dispersion pigment in the water-based ink composition used in this embodiment is preferably in the range of 0.1 to 30.0 mass% with respect to the total mass (100 mass%) of the water-based ink composition. , And more preferably 0.5 to 15.0% by mass. When the content is in the above range, the dispersion stability is excellent, the viscosity of the water-based ink composition is appropriate, and it is possible to form an image such as characters and figures excellent in color development especially on plain paper. ..

1.2.2. Self-Emulsifying Resin The water-based ink composition according to the present embodiment contains a self-emulsifying resin having an acid value of 10 to 90 mg/KOH, preferably 30 to 80 mg/KOH. The acid value is the amount of mg of KOH required to neutralize 1 g of resin. By including such a self-emulsifying resin, the freezing point of the water-based ink composition does not change, but the properties of the solidified product can be changed. That is, when freezing of the water-based ink composition begins, the self-emulsifying resin enters between the crystal structures of the solidified product, so that a softer solidified product is formed. As a result, it is possible to prevent the above-mentioned cracks in the ejection head during freezing. Further, by containing the self-emulsifying resin, it is possible to improve the abrasion resistance of recorded matter such as images and characters. When a self-emulsifying resin having an acid value of more than 90 mg/KOH is added, the surface-active effect becomes too strong, so that the penetrating into the plain paper tends to reduce the color developability. In addition, since the film becomes brittle, scratch resistance decreases. On the other hand, when a self-emulsifying resin having an acid value of less than 10 mg/KOH is added, the affinity for water becomes low and the solidified product becomes hard, which may cause a failure of the ejection head during freezing. .. Further, since the affinity for water is low, the redispersibility of the ink is lowered, and clogging tends to occur.

Polymer materials that compose self-emulsifying resins include copolymers of monomers with hydrophobic groups and monomers with hydrophilic groups, and monomers with hydrophobic and hydrophilic groups in the molecular structure. The following polymers are listed. Specific examples of the polymer material include polyvinyl alcohols, polyvinylpyrrolidones, polyurethane (urethane resin), polyacrylic acid (acrylic resin), polyester, acrylic acid-acrylonitrile copolymer, potassium acrylate-acrylonitrile copolymer, Acrylic copolymers such as vinyl acetate-acrylic acid ester copolymers and acrylic acid-acrylic acid alkyl ester copolymers; styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene-methacrylic acid-acrylic acid Styrene-acrylic acid copolymers such as alkyl ester copolymers, styrene-α-methylstyrene-acrylic acid copolymers, styrene-α-methylstyrene-acrylic acid-acrylic acid alkyl ester copolymers; styrene-maleic acid Styrene-maleic anhydride; vinylnaphthalene-acrylic acid copolymer; vinylnaphthalene-maleic acid copolymer; vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinylethylene copolymer, vinyl acetate-maleic acid ester Examples thereof include polymers, vinyl acetate-crotonic acid copolymers, vinyl acetate-acrylic acid copolymers and other vinyl acetate-based copolymers, and salts thereof. Among these, polyurethane (urethane resin) is particularly preferable in terms of achieving both suppression of cracks of the ejection head during freezing and improvement of abrasion resistance of recorded matter.

The urethane resin is not particularly limited, and a urethane resin obtained by subjecting an isocyanate compound and a compound having a hydroxyl group to a condensation reaction can be used.

As the isocyanate compound, for example, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, hydrogenated xylylene diisocyanate, 1,4-cyclohexane diisocyanate, alicyclic diisocyanate compounds such as 4,4-dicyclohexylmethane diisocyanate, Xylylene diisocyanate, araliphatic diisocyanate compounds such as tetramethyl xylylene diisocyanate, toluylene diisocyanate, aromatic diisocyanate compounds such as phenylmethane diisocyanate, modified products of these diisocyanates (carbodiimide, uretdione, uretoimine-containing modified products, etc.) and the like. To be

Examples of the compound having a hydroxyl group include diol compounds obtained by (co)polymerizing alkylene oxides such as ethylene oxide and propylene oxide, and heterocyclic ethers such as tetrahydrofuran. Specific examples of such diol compounds include polyether diols such as polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, polyethylene adipate, polybutylene adipate, polyneopentyl adipate, poly-3-methylpentyl. Examples thereof include polyester diols such as adipate, polyethylene/butylene adipate, and polyneopentyl/hexyl adipate, polylactone diols such as polycaprolactone diol, and polycarbonate diols. Among these, at least one of polyether type, polyester type and polycarbonate type is preferable.

In addition to the above, a diol compound having an acidic group such as a carboxylic acid group or a sulfonic acid group can also be used, and specific examples thereof include dimethylol acetic acid, dimethylol propionic acid, and dimethylol butyric acid. Of these, dimethylolpropionic acid is preferred. Two or more kinds of these diol compounds may be used in combination.

When synthesizing the urethane resin, a low molecular weight polyhydroxy compound may be added. Examples of the low molecular weight polyhydroxy compound include glycols, alkylene oxide low molar adducts, trihydric alcohols such as glycerin, trimethylolethane and trimethylolpropane, and alkylene oxide low molar adducts used as raw materials for polyester diols. Can be mentioned. Further, the urethane prepolymer thus obtained can be water-extended or chain-extended with di(tri)amine after or while neutralizing the acid group derived from dimethylolalkanoic acid. Examples of the polyamine used in the chain extension include hexamethylenediamine, isophoronediamine, hydrazine, piperazine and the like, and these may be used in combination of two or more kinds.

As the urethane resin, polyether-based polyurethane, polyester-based polyurethane, polycarbonate-based polyurethane obtained by using a polyether-based, polyester-based, or polycarbonate-based compound having a hydroxyl group is preferable. Further, among the above compounds, a diol having an acidic group such as a carboxyl group or a sulfonic acid group is used, a low molecular weight polyhydroxy compound is added, or an acidic group-introduced polyurethane is preferable, and a carboxyl group is particularly preferable. .. Further, it is desirable to crosslink these functional groups such as a carboxyl group by a crosslinking treatment which will be described later, from the viewpoint of improving gloss and improving abrasion resistance.

The urethane resin may be neutralized. Examples of the base used for neutralization include alkylamines such as butylamine and triethylamine, alkanolamines such as monoethanolamine, diethanolamine and triethanolamine, and inorganic bases such as morpholine, ammonia and sodium hydroxide. The weight average molecular weight of the urethane resin is preferably 2,000 or more and 20,000 or less, more preferably 3,000 or more and 10,000 or less.

The solid content of the self-dispersion resin in the water-based ink composition used in this embodiment is preferably 1.0 to 10.0 mass% with respect to the total mass (100 mass%) of the water-based ink composition. Is more preferable, the range of 2.0-9.0 mass% is more preferable, and the range of 3.0-7.0 mass% is particularly preferable. When the content is in the above range, the dispersion stability is excellent, cracks of the ejection head at the time of freezing can be prevented, and in particular, the abrasion resistance of recorded images such as characters and figures can be improved.

1.2.3. Water-soluble organic solvent A water-soluble organic solvent may be added to the water-based ink composition used in the present embodiment. By adding the water-soluble organic solvent, it is possible to prevent the ink from drying on the front surface of the nozzle and effectively prevent the clogging of the ejection head. Examples of the water-soluble organic solvent include monohydric alcohols, polyhydric alcohols and their derivatives.

Examples of the monohydric alcohol include monohydric alcohols having 1 to 4 carbon atoms, such as methanol, ethanol, n-propanol, i-propanol and n-butanol.

As the polyhydric alcohol and its derivative, it is possible to use a C 2-6 C 2-5 alcohol, and a complete or partial ether of them and a C 1-4 lower alcohol. Here, the polyhydric alcohol derivative is an alcohol derivative in which at least one hydroxyl group is etherified, and does not mean the polyhydric alcohol itself which does not contain an etherified hydroxyl group.

Specific examples of these polyhydric alcohols and their lower alkyl ethers include 1,2-hexanediol, 1,3-hexanediol, 1,2-heptanediol, 1,3-heptanediol and 1,2-octane. Diols, 1,3-octanediol, 1,2-pentanediol and other diols, mono-, di- or tri-ethylene glycol mono- or di-alkyl ethers, mono-, di- or tri-propylene glycol mono- or di-alkyl ethers, Glycerin is mentioned, preferably 1,2-hexanediol, triethylene glycol monobutyl ether, diethylene glycol monobutyl ether, diethylene glycol monopropyl ether, diethylene glycol monopentyl ether, diethylene glycol-2-ethylhexyl ether, propylene glycol monobutyl ether, glycerin and the like. To be

The content of the water-soluble organic solvent in the water-based ink composition used in this embodiment is preferably 5.0 to 30.0% by mass, based on the total mass (100% by mass) of the water-based ink composition. Preferably it is 10.0-25.0 mass %.

1.2.4. Surfactant The aqueous ink composition used in this embodiment may include a surfactant. As the surfactant, any of nonionic surfactants, anionic surfactants, cationic surfactants and amphoteric surfactants can be used, and these may be used in combination.

The nonionic surfactant is preferably at least one selected from the group consisting of acetylene glycol-based surfactants, acetylene alcohol-based surfactants, fluorine-based surfactants, and polysiloxane-based surfactants. .. These nonionic surfactants are excellent in the ability to properly maintain the surface tension and interfacial tension of the water-based ink composition. This makes it possible to appropriately maintain the surface tension and the interfacial tension with the printer member that comes into contact with the ink, such as the head nozzle surface, so that when this is applied to an inkjet recording system, ejection stability can be improved.

The above-mentioned acetylene glycol-based surfactant and acetylene alcohol-based surfactant include, but are not limited to, 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,4,7. ,9-Tetramethyl-5-decyn-4,7-diol alkylene oxide adduct, and 2,4-dimethyl-5-decyn-4-ol and 2,4-dimethyl-5-decyn-4-ol, Selected from 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyne-3-ol, alkylene oxide adduct of 2,4-dimethyl-5-hexyne-3-ol One or more types can be illustrated. Further, commercially available acetylene glycol-based surfactants and acetylene alcohol-based surfactants can be used, and Surfynol 104, 104E, 104H, 104A, 104BC, 104 can be used.
DPM, 104PA, 104PG-50, 104S, 420, 440, 465, 485, SE, SE-F, 504, 61, DF37, CT111, CT121, CT131, CT136, TG, GA (all product names, Air Products and Chemicals. Inc.), Olfine B, Y, P, A, STG, SPC, E1004, E1010, PD-001, PD-002W, PD-003, PD-004, EXP. 4001, EXP. 4036, EXP. 4051, AF-103, AF-104, AK-02, SK-14, AE-3 (all above are trade names, manufactured by Nissin Chemical Industry Co., Ltd.), acetylenol E00, E00P, E40, E100 (all above trade names, Kawaken Fine Chemical Co., Ltd.) and the like.

As the fluorine-based surfactant, a commercially available one may be used, and examples thereof include Megafac F-479 (manufactured by DIC Corporation) and BYK-340 (manufactured by Big Chemie Japan).

As the polysiloxane-based surfactant, commercially available products can be used, and examples thereof include Olfine PD-501, Olfine PD-502, Olfine PD-570 (all manufactured by Nisshin Chemical Industry Co., Ltd.), BYK. -347, BYK-348 (all manufactured by Big Chemie Co., Ltd.) and the like.

Further, as the nonionic surfactant, for example, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, alkyl glucoside, polyoxyalkylene glycol alkyl ether, polyoxyalkylene glycol, polyoxyalkylene glycol alkylphenyl ether, sucrose. Fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene sorbitan fatty acid ester, sorbitan fatty acid ester, polyoxyalkylene acetylene glycol, polyoxyalkylene glycol alkylamine, polyoxyethylene alkylamine, polyoxyethylene alkylamine oxide, fatty acid alkanolamide, You may use alkylol amide, polyoxyethylene polyoxypropylene block polymer, etc.

Further, among the nonionic surfactants, the acetylene glycol-based surfactant is particularly excellent in the ability to appropriately maintain the surface tension and the interfacial tension, and is more preferable because it has the property of having almost no foaming property. Can be used. That is, since the air bubble property is small, for example, when the water-based ink composition is applied to an inkjet recording device, it is desirable that air bubbles are hard to be fixed to the step portion of the ink flow path.

Examples of the anionic surfactant include higher fatty acid salt, soap, α-sulfofatty acid methyl ester salt, linear alkylbenzene sulfonate, alkyl sulfate ester salt, alkyl ether sulfate ester salt, monoalkyl phosphate ester salt, α -Olefin sulfonate, alkylbenzene sulfonate, alkylnaphthalene sulfonate, naphthalene sulfonate, alkane sulfonate, polyoxyethylene alkyl ether sulfate, sulfosuccinate, polyoxyalkylene glycol alkyl ether phosphate ester salt, etc. Are listed.

Examples of the cationic surfactant include alkyl trimethyl ammonium salt, dialkyl dimethyl ammonium salt and alkyl dimethyl benzyl ammonium salt as the quaternary ammonium type, and N-methylbishydroxyethylamine fatty acid ester hydrochloride as the amine salt type.

Examples of the amphoteric surfactant include an alkylamino fatty acid salt as an amino acid type, an alkylcarboxyl betaine as a betaine type, and an alkylamine oxide as an amine oxide type. The amphoteric surfactant is not limited to these.

The content of the surfactant in the water-based ink composition used in this embodiment is preferably 0.1 to 2.0% by mass, more preferably 100% by mass with respect to the total mass (100% by mass) of the water-based ink composition. Is 0.2 to 1.0% by mass.

1.2.5. Water The water-based ink composition used in this embodiment contains water. As water, deionized water, ultrafiltered water, reverse osmosis water, distilled water, or other pure water, or ultrapure water can be used. The content of water in the water-based ink composition according to this embodiment is preferably 30 mass% or more, more preferably 50 mass% or more and 95 mass% with respect to the total mass (100 mass%) of the water-based ink composition. Hereafter, it is particularly preferably 60% by mass or more and 90% by mass or less. Here, the content of water is not limited to the amount to which water is added, and when other additives are added, the water content in the additives is also included.

In the present specification, the “water-based” ink composition refers to an ink composition containing 30% by mass or more of water based on the total mass (100% by mass) of the ink composition.

1.2.6. Other components In addition to the above components, the water-based ink composition used in the present embodiment contains a pH adjusting agent, a chelating agent, a preservative, a viscosity adjusting agent, a dissolution aid, an antioxidant, a fungicide, etc. You may.

1.2.7. Content Ratio In the water-based ink composition used in the present embodiment, the content ratio of the self-dispersion pigment (oxidation-treated pigment) and the self-emulsifying resin (self-dispersion pigment/self-emulsifying resin) is preferable. Is 0.5 or more and 6.0 or less, more preferably 0.8 or more and 4.0 or less, and particularly preferably 1.0 or more and 3.0 or less. When the content ratio of the self-dispersion pigment and the self-emulsifying resin is within the above range, the self-emulsifying resin enters an appropriate amount between the crystal structures of the solidified product generated by freezing of the aqueous ink composition, resulting in a softer solidification. An object is formed. As a result, it is possible to effectively prevent the above-mentioned cracks in the ejection head during freezing.

1.2.8. Physical Properties Since the water-based ink composition used in the present embodiment is used in the above-mentioned inkjet recording device, the viscosity (viscosity at 25° C.) is preferably 2 mPa·s or more and 20 mPa·s by adjusting the composition and the composition, for example. s or less, more preferably 3 mPa·s or more and 15 mPa·s or less. Thereby, the ejection stability of the water-based ink composition (stability of ejection amount, flight characteristics of droplets, etc.), ejection response (response speed, high frequency response (frequency characteristics), etc.) should be improved. You can The viscosity of the inkjet ink can be determined by measurement according to JIS Z8809 using a vibrating viscometer.

1.3. As described above, the ejection head of the ink jet recording apparatus according to the present embodiment has the liquid flow path extending in the plane direction having the vibrating plate and the plurality of vertical liquid flow paths connected to the liquid flow path. Have When an ink containing an acid-treated self-dispersion pigment is filled in a cartridge using an inkjet recording apparatus having such an ejection head, the ink is ejected from the nozzle plate side when the inkjet recording apparatus is placed in a low temperature environment. There was a problem that the liquid flow path of the ink began to freeze and the ink flow path was gradually blocked from the nozzle plate side, so that there was no escape path for the volume expansion green of the ink, and the diaphragm or the piezoelectric element was damaged.

According to the inkjet recording apparatus of the present embodiment, it is possible to prevent the above-mentioned cracks of the ejection head when frozen. This mechanism is speculated as follows. By adding a self-emulsifying resin having an acid value of 10 to 90 mg/KOH to the ink containing the acid-treated self-dispersion pigment, the properties of the coagulated substance of the water-based ink composition can be changed. That is, when freezing of the water-based ink composition begins, the self-emulsifying resin enters between the crystal structures of the solidified product to form a softer solidified product. It is considered that this makes it possible to prevent the above-described cracks in the ejection head during freezing.

Further, according to the water-based ink composition according to the present embodiment, not only it is possible to prevent cracks in the ejection head at the time of freezing in the inkjet recording apparatus, but also to contain a self-dispersion pigment and a self-emulsifying resin. This makes it possible to form an image having excellent storage stability and excellent color development and abrasion resistance.

2. EXAMPLES Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples. In addition, "part" and "%" in Examples and Comparative Examples are based on mass unless otherwise specified.

2.1. Preparation of water-based ink composition 2.1.1. Preparation of self-dispersion carbon black dispersion <dispersion A>
Carbon black bulk powder 500 g (primary particle diameter=18 nm, BET specific surface area=180 m ² /g, DBP oil absorption=186 mL/100 g) prepared by the furnace method was added to 3750 g of ion-exchanged water and stirred with a dissolver to give 50 The temperature was raised to °C. Then, while pulverizing with a sand mill using zirconia beads having a diameter of 0.8 mm, 5300 g of an aqueous solution of sodium hypochlorite (effective chlorine concentration=12%) was added dropwise at 50-60° C. over 3.5 hours. did. Then, the mixture was continuously ground for 30 minutes by a sand mill to obtain a reaction liquid containing self-dispersion type carbon black. The reaction solution was filtered through a 400-mesh wire net to separate the reaction solution from the zirconia beads and unreacted carbon black. A 5% aqueous solution of potassium hydroxide was added to the reaction solution obtained by fractionation to adjust the pH to 7.5. Desalination and purification were performed with an ultrafiltration membrane until the electric conductivity of the liquid reached 1.5 mS/cm. Further desalting and purification were performed using an electrodialyzer until the electric conductivity of the liquid reached 1.0 mS/cm. The liquid was concentrated until the concentration of self-dispersion carbon black was 17% by weight. The concentrated liquid was centrifuged to remove coarse particles, and filtered through a 0.6 μm filter. Ion-exchanged water was added to the obtained filtrate to dilute and disperse the self-dispersion carbon black until the concentration of the self-dispersion carbon black became 15% by weight, to obtain a dispersion A of self-dispersion carbon black.

<Dispersion B>
500 g of carbon black bulk powder (primary particle size=16 nm, BET specific surface area=215 m ² /g, DBP oil absorption=210 mL/100 g) prepared by the furnace method was added to 3750 g of ion-exchanged water, and while stirring with a dissolver, 50 The temperature was raised to °C. Then, while pulverizing with a sand mill using zirconia beads having a diameter of 0.8 mm, 7000 g of an aqueous solution of sodium hypochlorite (effective chlorine concentration=12%) was added dropwise at 50-60° C. over 3.5 hours. did. Then, the mixture was continuously ground for 30 minutes by a sand mill to obtain a reaction liquid containing self-dispersion type carbon black. The reaction solution was filtered through a 400-mesh wire net to separate the reaction solution from the zirconia beads and unreacted carbon black. A 5% aqueous solution of sodium hydroxide was added to the reaction solution obtained by fractionation to adjust the pH to 7.5. Desalination and purification were performed with an ultrafiltration membrane until the electric conductivity of the liquid reached 1.5 mS/cm. Further desalting and purification were performed using an electrodialyzer until the electric conductivity of the liquid reached 1.0 mS/cm. The liquid was concentrated until the concentration of self-dispersion carbon black was 17% by weight. The concentrated liquid was centrifuged to remove coarse particles, and filtered through a 0.6 μm filter. Ion-exchanged water was added to the obtained filtrate to dilute and disperse the self-dispersion carbon black until the concentration of the self-dispersion carbon black became 15% by weight, to obtain a dispersion liquid B of self-dispersion carbon black.

<Dispersion C>
Carbon black bulk powder 500 g (primary particle size=17 nm, BET specific surface area=200 m ² /g, DBP oil absorption=185 mL/100 g) prepared by the furnace method was added to 3750 g of ion-exchanged water, and while stirring with a dissolver, 50 The temperature was raised to °C. Then, 5400 g of an aqueous solution of sodium hypochlorite (effective chlorine concentration 12%) was added dropwise at 50 to 60° C. over 3.5 hours. Immediately after the dropwise addition, glass beads having a diameter of 3 mm were added and stirred at 50° C. for 30 minutes to obtain a reaction liquid containing self-dispersion type carbon black. The reaction solution was filtered through a 400-mesh wire net to separate the glass beads and unreacted carbon black from the reaction solution. A 5% aqueous solution of sodium hydroxide was added to the reaction solution obtained by fractionation to adjust the pH to 7.5. Desalination and purification were performed with an ultrafiltration membrane until the conductivity of the liquid reached 1.5 mS/cm. Using an electrodialyzer, desalting and purification were performed until the electric conductivity of the liquid reached 1.0 mS/cm. The liquid was concentrated until the concentration of self-dispersion carbon black was 17% by weight. The concentrated liquid was centrifuged to remove coarse particles, and filtered through a 0.6 μm filter. Ion-exchanged water was added to the obtained filtrate to dilute and disperse the self-dispersion carbon black until the concentration of the self-dispersion carbon black became 15% by weight, to obtain a dispersion C of self-dispersion carbon black.

<Dispersion D>
500 g of carbon black bulk powder (primary particle size=20 nm, BET specific surface area=124 m ² /g, DBP oil absorption=165 mL/100 g) was added to 3750 g of ion-exchanged water, and the temperature was raised to 50° C. while stirring with a dissolver. .. Then, while pulverizing with a sand mill using zirconia beads having a diameter of 0.8 mm, 2250 g of an aqueous solution of sodium hypochlorite (effective chlorine concentration=12%) was added dropwise at 50-60° C. over 3.5 hours. did. Then, the mixture was continuously ground for 30 minutes by a sand mill to obtain a reaction liquid containing self-dispersion type carbon black. The reaction solution was filtered through a 400-mesh wire net to separate the reaction solution from the zirconia beads and unreacted carbon black. A 5% aqueous solution of sodium hydroxide was added to the reaction solution obtained by fractionation to adjust the pH to 7.5. Desalination and purification were performed with an ultrafiltration membrane until the electric conductivity of the liquid reached 1.5 mS/cm. The liquid was concentrated until the concentration of self-dispersion carbon black was 17% by weight. The concentrated liquid was centrifuged to remove coarse particles, and filtered through a 0.6 μm filter. Ion-exchanged water was added to the obtained filtrate to dilute and disperse the self-dispersion carbon black until the concentration of the self-dispersion carbon black became 15% by weight, to obtain a dispersion D of self-dispersion carbon black.

<Dispersion E>
500 g of carbon black bulk powder (primary particle size=40 nm, BET specific surface area=56 m ² /g, DBP oil absorption=122 mL/100 g) was added to 3750 g of ion-exchanged water, and the temperature was raised to 50° C. while stirring with a dissolver. .. Then, while pulverizing with a sand mill using zirconia beads having a diameter of 0.8 mm, 1700 g of an aqueous solution of sodium hypochlorite (effective chlorine concentration=12%) was added dropwise at 50-60° C. over 3.5 hours. did. Then, the mixture was continuously ground for 30 minutes by a sand mill to obtain a reaction liquid containing self-dispersion type carbon black. The reaction solution was filtered through a 400-mesh wire net to separate the reaction solution from the zirconia beads and unreacted carbon black. A 5% aqueous solution of sodium hydroxide was added to the reaction solution obtained by fractionation to adjust the pH to 7.5. Desalination and purification were performed with an ultrafiltration membrane until the electric conductivity of the liquid reached 1.5 mS/cm. The liquid was concentrated until the concentration of self-dispersion carbon black was 17% by weight. The concentrated liquid was centrifuged to remove coarse particles, and filtered through a 0.6 μm filter. Ion-exchanged water was added to the obtained filtrate, and the self-dispersion carbon black was diluted to a concentration of 15% by weight and dispersed to obtain a dispersion E of self-dispersion carbon black.

<Dispersion liquid F>
500 g of carbon black bulk powder (primary particle size=19 nm, BET specific surface area=145 m ² /g, DBP oil absorption=125 mL/100 g) was added to 3750 g of ion-exchanged water, and the temperature was raised to 50° C. while stirring with a dissolver. .. Then, while pulverizing with a sand mill using zirconia beads having a diameter of 0.8 mm, 4500 g of an aqueous solution of sodium hypochlorite (effective chlorine concentration=12%) was added dropwise at 50-60° C. over 3.5 hours. did. Then, the mixture was continuously ground for 30 minutes by a sand mill to obtain a reaction liquid containing self-dispersion type carbon black. This reaction liquid was filtered through a 400-mesh wire net to separate the reaction liquid from the zirconia beads and unreacted carbon black. A 5% aqueous solution of sodium hydroxide was added to the reaction solution obtained by fractionation to adjust the pH to 7.5, and then desalting and purification were performed using an ultrafiltration membrane until the electric conductivity became 1.5 mS/cm. The liquid was concentrated until the concentration of self-dispersion carbon black was 17% by weight. The concentrated liquid was centrifuged to remove coarse particles, and filtered with a 0.6 μm filter. Ion-exchanged water was added to the obtained filtrate to dilute and disperse the self-dispersion carbon black until the concentration of the self-dispersion carbon black became 15% by weight, to obtain a dispersion F of self-dispersion carbon black.

<Dispersion G>
500 g of carbon black bulk powder (primary particle size=19 nm, BET specific surface area=153 m ² /g, DBP oil absorption=130 mL/100 g) was added to 3750 g of ion-exchanged water, and the temperature was raised to 50° C. while stirring with a dissolver. .. Then, while pulverizing with a sand mill using zirconia beads having a diameter of 0.8 mm, 5500 g of an aqueous solution of sodium hypochlorite (effective chlorine concentration=12%) was added dropwise at 50-60° C. over 3.5 hours. did. Then, the mixture was continuously ground for 30 minutes by a sand mill to obtain a reaction liquid containing self-dispersion type carbon black. This reaction liquid was filtered through a 400-mesh wire net to separate the reaction liquid from the zirconia beads and unreacted carbon black. A 5% aqueous sodium hydroxide solution was added to the reaction solution obtained by fractionation to adjust the pH to 7.5, and then desalting and purification were carried out with an ultrafiltration membrane until the electric conductivity became 1.5 mS/cm. The liquid was concentrated until the concentration of self-dispersion carbon black was 17% by weight. The concentrated liquid was centrifuged to remove coarse particles, and filtered with a 0.6 μm filter. Ion-exchanged water was added to the obtained filtrate to dilute and disperse the self-dispersion carbon black until the concentration of the self-dispersion carbon black became 15% by weight, to obtain a dispersion liquid G of self-dispersion carbon black.

2.1.2. Evaluation of Physical Properties of Self-Dispersion Carbon Black The physical properties of the self-dispersion carbon black dispersions A to G obtained above were evaluated as follows.

<Measurement of lactone group and carboxyl group abundance of self-dispersing carbon black>
The self-dispersion carbon black obtained above is dried at 60° C. for 15 hours, and the carbon black is used at 358° C. using a pyrolysis gas chromatography device (manufactured by Hewlett-Packard Co., device name “HP5890A”). CO ₂ generated by decomposition of the lactone group and the carboxyl group at 650° C. was measured. From the measured values, the amounts of lactone groups and carboxyl groups present in carbon black were converted. The measurement conditions are as follows.
Gel permeation chromatography/GPC: Tosoh HLC-8020
・Column: Tosoh GMH-XL (two in series)
・Detector: differential refractometer (RI)
The polystyrene-reduced weight average molecular weight (Mw) of each polymer was determined based on monodisperse polystyrene.

<Method of measuring the electric conductivity of self-dispersion type carbon black>
47.5 g of ion-exchanged water was added to 2.5 g of the self-dispersion type carbon black obtained by drying by the above method, and ultrasonic waves were irradiated for 5 minutes. Then, the mixture was stirred for 5 minutes and the electric conductivity was measured. The conductivity used was COND METER ES-51 (made by HORIBA).

<Measurement of average particle size of self-dispersion type carbon black>
The average particle size of the aqueous solution adjusted to a modified carbon black concentration of 0.065 wt% was measured using a particle size analyzer (manufactured by Nikkiso Co., Ltd., device name "Microtrac 9340-UPA").

The evaluation results are shown in Table 1.

2.1.3. Preparation of Aqueous Ink Composition A resin, glycerin, triethylene glycol monobutyl ether, olphin E1010, and triethanolamine were added to the carbon black dispersion so as to have the compositions shown in Tables 2 and 3. Then, the mixture was stirred at room temperature for 1 hour, filtered through a membrane filter having a pore size of 5 μm, and then degassed by using a vacuum pump to obtain each water-based ink composition used in Examples and Comparative Examples. The numerical values in Tables 2 and 3 represent the content (% by mass) in the water-based ink composition, and the abbreviations of the components shown in Tables 2 and 3 are as follows.

<Pigment>
Resin-dispersed pigment 10 parts by mass of styrene-acrylic acid copolymer ammonium salt (weight average molecular weight 10,000, polymer component 15%) as a dispersant and 80 parts by mass of ion-exchanged water with respect to 10 parts by mass of carbon black as a pigment. After parts were added and mixed well, this mixture was dispersed in a sand mill (Yasukawa Seisakusho Co., Ltd.) with glass beads (diameter 1.7 mm, 1.5 times the amount of the mixture) for 2 hours. After the dispersion, the glass beads were removed to obtain resin-dispersed pigments shown in Table 3.
-Dispersions A to G (dispersions prepared above)
<Resin>
-Urethane resin [acid value 6]: Product name "Akrit WBR-2000U", manufactured by Taisei Fine Chemicals Co., Ltd., self-emulsifying resin-Urethane resin [acid value 11.6]: Product name "SANCURE 2260", GCI Creos Co., Ltd. Made, self-emulsifying resin/urethane resin [acid value 31.5]: trade name "Sancure 1511", manufactured by GCI Creos Co., Ltd., self-emulsifying resin/urethane resin [acid value 75]: obtained in Synthesis Example 1 below. Resin.
Urethane resin [acid value 110]: Resin obtained in Synthesis Example 2 below.
-Acrylic resin [acid value 53]: trade name "John Krill 611", manufactured by BASF Corporation, self-emulsifying resin/polyester [acid value 13]: trade name "KA-5971S", manufactured by Unitika Ltd., self Emulsifying resin/water-soluble acrylic resin: Product name “HPD-96”, BASF Corporation urethane resin emulsion: Product name “Evaphanol AP-6”, Nika Chemical Co., Ltd. acrylic resin emulsion: Product name “Movinyl 790", manufactured by Nichigo Movinyl Co., Ltd. <Surfactant>
・Olfin E1010 (trade name, Nisshin Chemical Industry Co., Ltd., acetylene glycol surfactant)

(Synthesis example 1)
A four-necked flask equipped with a thermometer, a stirrer, a nitrogen introducing tube, and a cooling tube was charged with 592 g of methyl ethyl ketone, 147 g of dimethylolpropionic acid and 444 g of isophorone diisocyanate, and reacted at 70° C. for 2 hours under a nitrogen gas atmosphere to react. Product A was obtained. The reaction product A had an isocyanato group quantitative value of 6.53 and a reaction index of 0.977.
Then, in a four-necked flask equipped with a thermometer, a stirrer, a nitrogen introducing tube, and a cooling tube, 268 g of the reaction product A obtained above, 45 g of polypropylene glycol (OH group equivalent 281) of Mn400, and ethylene glycol were added. 7.2 g, 0.001 g of dibutyltin dilaurate and 320 g of methyl ethyl ketone were charged and reacted for 16 hours at 80° C. under a nitrogen gas atmosphere, then 5 g of methanol was added to stop the reaction, and a carboxy group having an acid value of 75 and Mw of 30,000 was added. A polyurethane containing was obtained. The obtained resin solution was neutralized with the same molar amount of sodium hydroxide as the charged amount of dimethylolpropionic acid, phase inversion emulsified by adding water, and after removing methyl ethyl ketone by desolvation under reduced pressure, water was added to the mass. An aqueous solution having a reduced solid content of 20% was used. The aqueous solution was colorless and transparent, and the particle size was less than 50 nm.

(Synthesis example 2)
In a four-necked flask equipped with a thermometer, a stirrer, a nitrogen introducing tube, and a cooling tube, 206.1 g of the reaction product A obtained in Synthesis Example 1, 10 g of polypropylene glycol (OH group equivalent 281) of Mn400, and dibutyl were added. After charging 0.001 g of tin dilaurate and 320 g of methyl ethyl ketone and reacting at 80° C. for 16 hours in a nitrogen gas atmosphere, 5 g of methanol was added to stop the reaction to obtain a carboxy group-containing polyurethane having an acid value of 110 and Mw of 30,000. .. The obtained resin solution was neutralized with the same molar amount of sodium hydroxide as the charged amount of dimethylolpropionic acid, phase inversion emulsified by adding water, and after removing methyl ethyl ketone by desolvation under reduced pressure, water was added to the mass. An aqueous solution having a reduced solid content of 20% was used. The aqueous solution was colorless and transparent, and the particle size was less than 50 nm.

(Preparation of acrylic dispersion and polyester dispersion)
3.00 parts by mass of a water-insoluble resin (John Cryl 611 or KA-5971S) was dissolved in 7.00 parts by mass of N-methyl-2-pyrrolidone to obtain an organic solvent solution of the resin. This organic solvent solution was neutralized with 0.15 parts by mass of dimethylethanolamine, 0.30 parts by mass of Newcol 3240 (manufactured by Nippon Emulsifier Co., Ltd.) and 39.55 parts by mass of ion-exchanged water were mixed and emulsified and dispersed to obtain an aqueous resin. A dispersion was obtained.

(Method of measuring acid value)
The acid value was measured by a method according to JIS K0070. In the present invention, the following solvents were used as the measuring solvent. 10 g of the resin obtained by drying and solidifying the above resin aqueous solution is weighed in a 300 ml Erlenmeyer flask, and about 50 ml of a mixed solvent of ethanol:benzene=1:2 is added to dissolve the resin. Then, using a phenolphthalein indicator, it was titrated with a previously standardized 0.1 mol/L potassium hydroxide ethanol solution, and the acid value (according to the calculation formula (1) was calculated from the amount of the potassium hydroxide ethanol solution used for the titration ( mgKOH/g) is calculated.
A (mgKOH/g)=numerator/denominator (1)
Molecule: 0.1 (mol/L) x B/1000 (L) x 56.11 (g/mol) x 10
Denominator: S
In the formula, A is the acid value of the resin (mgKOH/g), B is the amount of the 0.1 mol/L potassium hydroxide ethanol solution used for titration (mL), S is the mass of the resin (g), and 56.11 is , The formula weight of potassium hydroxide.
For some resins that do not dissolve in about 50 ml of a mixed solvent of ethanol:benzene=1:2, select either 50 ml of ethanol or about 50 ml of a mixed solvent of ethanol/pure water=1:1. Then, the other steps are the same.

(Quantification of acid value)
1.0 g of the sample solution was diluted with 10 g of methyl ethyl ketone, dissolved in 40 ml of a mixed solvent of toluene and methanol (toluene:methanol=7:3), and then dissolved with 0.1N potassium hydroxide in methanol. It was quantified by performing a neutralization titration using phenolphthalein as an indicator.

2.2. Preparation of Inkjet Recording Device An inkjet recording device including the ejection head described above with reference to FIGS. 1 to 4 was prepared. In Table 2, the ejection head of this inkjet recording apparatus is referred to as “head A”.

On the other hand, an inkjet recording apparatus was prepared in which the structure of the ejection head of the inkjet recording apparatus corresponding to FIG. In Table 2, the ejection head of this inkjet recording apparatus is referred to as "head B". As shown in FIG. 6, the liquid flow path of the head B has a structure including a liquid flow path extending in the plane direction having the vibrating plate 50 and one vertical liquid flow path connected to the liquid flow path. Therefore, as compared with the above-mentioned head A, the flow path volume on the upstream side of the nozzle is smaller.

2.3. Evaluation method 2.3.1. Evaluation of Intermittent Printing The water-based ink composition prepared above was filled in the head of either the head A or the head B of the inkjet printer. Ink was ejected from all nozzles onto a photo paper (gloss) (manufactured by Seiko Epson Corporation). After that, the carriage was idle for 12 seconds, and then all the nozzles of ink were ejected onto the above-mentioned photographic paper (gloss). Intermittent characteristics were evaluated by the deviation of the landing positions of dots before and after free running. The evaluation criteria are as follows.
(Evaluation criteria)
1: Landing deviation is 0 μm or more and less than 100 μm.
2: The landing deviation is 100 μm or more and less than 200 μm.
3: The landing deviation is 200 μm or more and less than 300 μm.
4: The landing deviation is 300 μm or more.

2.3.2. Evaluation of Coloring Property The water-based ink composition prepared above was filled in the head of either the head A or the head B of the inkjet printer. After the filling, solid printing was performed on a photomat paper/pigment-only (manufactured by Seiko Epson Corporation) at 1440×720 dpi and an ink weight of 24 ng. After the printed matter was dried, the reflection density value (OD value) was measured with Spectrolino (trade name, manufactured by GretagMacbeth). The evaluation criteria are as follows.
(Evaluation criteria)
1: OD value is 2.1 or more.
2: OD value is 2.0 or more and less than 2.1.
3: OD value is 1.9 or more and less than 2.0.

2.3.3. Abrasion resistance The water-based ink composition prepared above was filled in the head of either an inkjet printer, head A or head B. After the filling, solid printing was performed on a photomat paper/pigment-only (manufactured by Seiko Epson Corporation) at 1440×720 dpi and an ink weight of 24 ng. With respect to the obtained printed matter, a gold width was placed on the printed surface of the printed matter that had passed 1 hour after printing, and a weight of 50 g was placed thereon. The gold width under the weight was pulled out, the degree of transfer to the drawn gold width was visually observed, and the abrasion resistance was evaluated according to the following criteria.
(Evaluation criteria)
1: No transcription is observed.
2: Transfer is slightly recognized.
3: Transcription is clearly recognized.

2.3.4. Freezing Stability of Head The water-based ink composition prepared above was filled in the head of an inkjet printer, either head A or head B. The entire ink jet recording apparatus with the cap attached was allowed to stand in a freezer compartment whose temperature was set to -20°C. After the lapse of 5 days, the ink jet recording apparatus was taken out of the freezer and returned to room temperature. This operation was performed for five inkjet printers, and the presence or absence of breakage of the piezoelectric actuator was observed with a microscope, and the failure rate of the piezoelectric actuator was calculated and evaluated. The evaluation criteria are as follows.
(Evaluation criteria)
1: The failure rate is 0% (no failure).
2: The failure rate was 20% (1 unit failed).
3: The failure rate is 40% or more (two or more failed).

2.3.5. Ink Redispersibility One drop of the water-based ink composition was dropped on the SUS substrate and dried at 80° C. for 1 hour. Then, one drop of the same type of water-based ink composition was dripped on the dried product. After leaving for a predetermined time, the ink was absorbed with a tissue paper to confirm the presence or absence of a dried product. The time required for the dried product to redissolve and disappear was evaluated. The evaluation criteria are as follows.
(Evaluation criteria)
1:1 less than a minute.
2: 1 minute or more and less than 5 minutes.
3: 5 minutes or more.

2.3.6. Storage stability of ink The water-based ink composition prepared above was placed in a screw tube of 50 g and left at 70°C for 6 days. Regarding the viscosity before and after standing, the viscosity was measured using an E-type viscometer RE550L (device name, manufactured by Toki Sangyo Co., Ltd.), and the storage stability of the ink was evaluated based on the rate of change in viscosity before and after standing. The evaluation criteria are as follows.
Viscosity change rate (%)=|(η2-η1)/η1|×100 (2)
η1: Viscosity of ink before standing, η2: Viscosity of ink after standing (evaluation standard)
1: The change rate of viscosity is less than 5%.
2: The rate of change in viscosity is 5% or more and less than 10%.
3: Change rate of viscosity is 10% or more.

2.4. Evaluation Results The compositions and evaluation results of the water-based ink compositions of Examples and Comparative Examples are shown in Tables 2 and 3 below.

As is clear from the results of Tables 2 and 3, the water-based ink composition according to the present invention, even when filled in the ink cartridge of the ink jet recording apparatus including the head A, causes the failure of the head A during freezing. It was clarified that an image which can be prevented, is excellent in storage stability, and is excellent in color developability and abrasion resistance can be formed.

The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the invention includes configurations substantially the same as the configurations described in the embodiments (for example, configurations having the same function, method and result, or configurations having the same object and effect). Further, the invention includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. Further, the invention includes a configuration that achieves the same effects as the configurations described in the embodiments or a configuration that can achieve the same object. Further, the invention includes configurations in which known techniques are added to the configurations described in the embodiments.

I... Inkjet recording apparatus (liquid ejecting apparatus), II... Inkjet recording head (liquid ejecting head), III... Head B, 1... Inkjet recording head unit (liquid ejecting head unit), 2... Cartridge, 3... Carriage 4... Device body, 5... Carriage shaft, 6... Drive motor, 7... Timing belt, 8... Platen, 10... Flow path forming substrate, 11... Head body, 15... Communication plate, 20... Nozzle plate, 20a... Liquid Jetting surface, 21... Nozzle opening, 25... Spacer, 30... Protective substrate, 40... Case member, 45... Compliance substrate, 50... Vibrating plate, 60... First electrode, 70... Piezoelectric layer, 80... Second electrode, 100... Manifold, 120... Drive circuit, 130... Cover head (protection plate)

Claims (10)

A supply communication path formed by the first substrate,
A liquid flow path extending in a plane direction having a vibrating plate, which is connected to the supply communication path ,
A first nozzle communication path formed by the first substrate and connected to the liquid flow path;
A water-based ink composition for use in an ink jet recording apparatus, comprising an ejection head having a second nozzle communication path formed by a second substrate and connected to the first nozzle communication path ,
Comprising a pigment that has been oxidized, and tree fat acid value 10~90mg / KOH, and
The surface of the oxidation-treated pigment has a carboxyl group and a lactone group having a molar ratio of 0.9 to 1.1 times that of the carboxyl group and a molar number per pigment mass of 500 μmol/g or more. Has,
The resin is a copolymer of a monomer having a hydrophobic group and a monomer having a hydrophilic group or a polymer composed of a monomer having a hydrophobic group and a hydrophilic group in the molecular structure,
An aqueous ink composition, wherein the pigment is carbon black obtained by a furnace method . The water-based ink composition according to claim 1, wherein the number of moles of lactone groups per mass of the pigment on the surface of the oxidation-treated pigment is 700 μmol/g or more. The content ratio of the oxidized pigment before Bark fat (pigment / tree fat which is oxidized) is 0.5 to 6.0, the water-based ink according to claim 1 or claim 2 Composition. Before Bark butter is a urethane resin, water-based ink composition according to any one of claims 1 to 3. The water-based ink composition according to any one of claims 1 to 4, wherein the number of moles of carboxyl groups per mass of the pigment on the surface of the oxidation-treated pigment is 700 µmol/g or more. Before solids content of Bark fat, based on the total mass of the aqueous ink composition is more than 2.0 mass% to 9.0 mass%, in any one of claims 1 to 5 The water-based ink composition described. An inkjet recording apparatus comprising: an aqueous ink composition; and an ejection head that ejects the aqueous ink composition,
The discharge head includes a supply communication passage formed by a first substrate,
A flow path extending in a plane direction having a vibrating plate, which is connected to the supply communication path ,
A first nozzle communication path formed by the first substrate and connected to the flow path;
A second nozzle communication path formed by a second substrate and connected to the first nozzle communication path ,
The aqueous ink composition comprises a pigment which has been oxidized, and tree fat acid value 10~90mg / KOH, and
The surface of the oxidation-treated pigment has a carboxyl group and a lactone group having a molar ratio of 0.9 to 1.1 times that of the carboxyl group and a molar number per pigment mass of 500 μmol/g or more. Has,
The resin is a copolymer of a monomer having a hydrophobic group and a monomer having a hydrophilic group or a polymer composed of a monomer having a hydrophobic group and a hydrophilic group in the molecular structure,
An inkjet recording apparatus, wherein the pigment is carbon black obtained by a furnace method . The inkjet recording device according to claim 7, wherein the number of moles of lactone groups per mass of the pigment on the surface of the pigment that has been subjected to the oxidation treatment is 700 μmol/g or more. The content ratio of the oxidized pigment before Bark fat (pigment / tree fat which is oxidized) is 0.5 to 6.0, the ink-jet recording according to claim 7 or claim 8 apparatus. Before Bark butter is a urethane resin, an ink jet recording apparatus according to any one of claims 7 to 9.

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