JP7182973B2 - Ink tank and inkjet recording device - Google Patents

Description

The present invention relates to an ink tank and an inkjet recording apparatus.

2. Description of the Related Art As an ink tank used in an inkjet recording apparatus, there is an ink tank equipped with an ink containing bag made of resin because it can contain a large amount of ink. One of the problems with ink tanks having ink storage bags is the ability to use up the ink. When ink is supplied to the recording head of the inkjet recording apparatus through the ink supply port of the ink tank, the ink containing bag shrinks and collapses irregularly as the ink is supplied (flowed out). The force that shrinks and crushes the ink containing bag is usually only the force that causes the ink to flow out.

When recording an image using an inkjet recording apparatus, an amount of ink corresponding to the amount used for recording is supplied from the ink containing bag to the recording head. Even if a large amount of images are recorded at once, the amount of ink supplied to the recording head is considerably less than the total amount of ink that can be stored in the ink storage bag, so the force that causes the ink to flow out of the ink storage bag is extremely small. weak. Then, the ink containing bag with a small remaining amount of ink shrinks and is crushed and partially closed. As a result, the ink in the ink containing bag cannot be discharged with only a very weak force for causing the ink to flow out, and it becomes difficult to use up the ink, resulting in a problem that the efficiency of using up the ink is lowered.

In order to solve such problems, for example, an ink storage bag has been proposed in which a mechanism such as a spring or an elastic member that applies external pressure is provided to push out the ink (Patent Document 1). This ink containing bag is formed by adhering the edges of two sheets of film, and is processed so as to be crushed in a direction parallel to the adhering surfaces. In addition, an ink containing bag in which the crushing direction is controlled has been proposed (Patent Document 2). The ink containing bag is pre-creased so that it can be crushed in a specific direction.

Japanese Patent Application Laid-Open No. 2003-226023 JP 2009-226809 A

However, providing a mechanism for adjusting the internal pressure of the ink containing bag and performing shape processing for controlling the way the ink containing bag is crushed and folded are cumbersome in terms of ease of manufacture, installation space, and structure. It can also be said that it is disadvantageous in terms of cost and cost. For example, the structure of the ink tank can be simplified by not providing a mechanism for adjusting the pressure inside the ink containing bag. In addition, if the ink containing bag is manufactured by blow molding or the like without creasing or bonding, it is advantageous in terms of ease of manufacture and cost. However, if a mechanism for adjusting the pressure inside the ink containing bag or a mechanism for controlling the shrinkage of the ink containing bag is not provided, as described above, the ink containing bag will become irregular as the ink flows out. It is difficult to fully use up the ink. In addition, assuming that the inkjet recording apparatus will be used in various regions, it is required that it can be used in a wide range of temperatures without change. Therefore, in designing an inkjet recording apparatus, various performances are evaluated while changing the temperature. As a result of studies by the present inventors, it has been found that the ability to use up the ink may be further reduced depending on the temperature environment in which the ink tank is placed.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an ink tank which has a simple structure and is excellent in the ability to use up the ink. Another object of the present invention is to provide an ink jet recording apparatus using this ink tank.

That is, according to the present invention, the ink containing bag which contains the ink therein does not have a mechanism for contracting the side wall portion into a predetermined shape, and the side wall portion contracts as the ink flows out. 1. An ink tank for use in an inkjet recording apparatus having no mechanism for adjusting the pressure inside said ink containing bag, wherein said ink containing bag is made of a resin, and said ink containing bag has a cylindrical shape. wherein the ink containing bag is a blow-molded product, the ink is a water-based ink containing a coloring material and a water-soluble organic solvent, and the average SP value of the water-soluble organic solvent and the ink containing bag is 2.0 (cal/cm ³ ) ^1/2 or more from the SP value of the resin constituting the ink tank.

According to the present invention, it is possible to provide an ink tank that has a simple structure and is excellent in the ability to use up the ink. Further, according to the present invention, it is possible to provide an inkjet recording apparatus using this ink tank.

1 is a schematic diagram showing an embodiment of an ink tank of the present invention; FIG. 1 is a schematic diagram showing an example of an ink tank; FIG. FIG. 5 is a schematic diagram showing another example of an ink tank; FIG. 5 is a schematic diagram showing another example of an ink tank; FIG. 5 is a schematic diagram showing another example of an ink tank; FIG. 4 is a schematic diagram showing a process of manufacturing an ink containing bag by blow molding. FIG. 4 is a schematic diagram showing a process of manufacturing an ink containing bag by blow molding. FIG. 4 is a schematic diagram showing a process of manufacturing an ink containing bag by blow molding. 1 is a perspective view schematically showing an embodiment of an inkjet recording apparatus of the present invention; FIG.

The present invention will be further described in detail below with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is dissociated into ions in the ink, but for convenience, it is expressed as "containing the salt." In addition, water-based ink for inkjet is sometimes simply referred to as "ink". Unless otherwise specified, physical property values are values at normal temperature (25° C.) and normal pressure (1 atm).

The present inventors filled ink into an ink storage bag of an ink tank which has an ink storage bag made of resin and does not have a mechanism for adjusting the internal pressure of the ink storage bag. Assuming the usage environment and transportation environment of the ink jet recording apparatus, various studies were conducted by storing the ink tank in various temperature environments. As a result, assuming an environment such as a cold region, it was confirmed that using ink that has been frozen and then melted would cause problems such as partial clogging of the ink storage bag and the inability to use up the ink. was done.

If the water-based ink is placed in an environment below 0°C, it may freeze. At this time, since hydrogen bonding occurs between water molecules, the water freezes in a state in which components other than water, such as water-soluble organic solvents, are excluded from the water crystals. As a result, the water-soluble organic solvent is concentrated in the unfrozen portion. When the ink is dissolved in such a state, the concentrated water-soluble organic solvent does not mix with water quickly, and the portion where the water-soluble organic solvent is concentrated comes into contact with the ink containing bag. A part of the ink containing bag in contact with the concentrated water-soluble organic solvent swells and softens. As a result, when the ink containing bag shrinks due to the outflow (supply) of the ink, the softened portions on the inner surface of the ink containing bag tend to stick together, partially clogging the ink containing bag, and reducing the ability to use up the ink.

In particular, ink tanks using ink containing a colorant are more likely to be used up more easily. When the frozen ink melts, the water, which has the highest dielectric constant among the liquid components in the water-based ink, freezes, and the water-soluble organic solvent, which has a dielectric constant lower than that of water, is concentrated. Become. As a result, the dielectric constant of the liquid component in the ink after freezing and dissolving is significantly lower than before freezing. As a result, the pigment present in the vicinity of the concentrated water-soluble organic solvent aggregates due to the reduction in the electrostatic repulsion force, increasing the viscosity of the ink. In addition, since the dye present in the vicinity of the concentrated water-soluble organic solvent aggregates due to the decrease in solubility, the viscosity of the ink increases. As a result, it is considered that the outflow of the ink from the ink containing bag becomes difficult, and the efficiency of using up the ink further deteriorates.

In general, the SP value is used as an indicator of the compatibility of a two-component solution, and the smaller the difference in SP value between the components, the greater the mutual solubility. As a result of investigation, the present inventors found that the difference between the average SP value of the water-soluble organic solvent and the SP value of the resin forming the ink containing bag should be 2.0 (cal/cm ³ ) ^1/2 or more. found that swelling of the ink containing bag can be suppressed even when the ink is frozen and dissolved. The reason for this is presumed as follows. When this relationship is satisfied, even if the concentrated water-soluble organic solvent in the process of dissolving the once-frozen ink comes into contact with the resin constituting the ink containing bag, the SP value of the resin and the average of the water-soluble organic solvent The difference from the SP value is large, and it is difficult to increase the compatibility between the resin and the water-soluble organic solvent. For this reason, swelling of the ink containing bag is suppressed, and it is considered that the ink can be used up more easily. Most of the water is frozen under the condition that the concentrated water-soluble organic solvent swells the ink containing bag. Therefore, most of the components in liquid contact with the inner surface of the ink containing bag are water-soluble organic solvents. Therefore, the SP value of water does not need to be taken into consideration because the effect of water is small.

<Ink tank>
The ink tank of the present invention is an ink tank for use in an inkjet recording apparatus, which includes an ink containing bag for containing ink therein. The ink containing bag does not have a mechanism for shrinking the side walls into a predetermined shape such as crease processing. Also, the ink tank of the present invention does not have a mechanism for adjusting the pressure inside the ink containing bag. That is, the ink containing bag that constitutes the ink tank of the present invention is a bag-like member whose side walls can contract irregularly as ink flows out. The ink containing bag is made of resin, and the ink is water-based ink containing a coloring material and a water-soluble organic solvent. The difference between the average SP value of the water-soluble organic solvent and the SP value of the resin forming the ink containing bag is 2.0 (cal/cm ³ ) ^1/2 or more. The details of the ink tank of the present invention will be described below.

(Ink storage bag)
FIG. 1 is a schematic diagram showing one embodiment of the ink tank of the present invention. The ink tank 50 of the embodiment shown in FIG. 1A includes a housing 10 and an ink containing bag 1 housed in the housing 10 and containing ink 2 therein. The ink 2 contained in the ink containing bag 1 flows out of the ink 2 through the ink supply port 3 and is supplied to the recording head of the ink jet recording apparatus communicating with the ink supply port 3 . The ink tank 50 of this embodiment does not have a mechanism for adjusting the pressure inside the ink containing bag 1 . Further, the ink containing bag 1 that constitutes the ink tank 50 does not have a mechanism for contracting the side walls into a predetermined shape. Therefore, as shown in FIGS. 1(b) and 1(c), when the ink 2 in the ink containing bag 1 flows out through the ink supply port 3, the ink containing bag 1 is The sidewalls of the shrink and irregularly collapse. The side wall portion of the ink containing bag 1 refers to the “side portion” when the ink supply port 3 is oriented upward in the direction of gravity. When the side wall portion of the ink containing bag 1 shrinks and is irregularly crushed, the opposing inner surfaces of the side wall portion of the ink containing bag 1 approach each other. However, since the ink 2 contains a water-soluble organic solvent that satisfies a specific relationship, adhesion between adjacent inner surfaces of the ink containing bag 1 is suppressed. As a result, the ink 2 in the ink containing bag 1 can be used up without waste (Fig. 1(c)). Alternatively, even if a closed portion 4 occurs in a part of the ink containing bag 1, the amount of the remaining ink 5 can be reduced to a very small amount (FIG. 1(b)), and the efficiency of using up the ink can be improved. can be done. In addition, as described above, the present invention suppresses deterioration of the single-use property due to adhesion of the inner surface, so the problem of deterioration of the single-use property due to adhesion does not occur. "Bottom" shall not be included in "Sidewall".

On the other hand, as shown in FIG. 2A, by applying pressure (positive pressure) to the ink containing bag 1 in the direction in which the side wall of the ink containing bag 1 shrinks, the pressure inside the ink containing bag 1 is reduced. Assume that the ink tank 60 has a mechanism for adjusting the In the case of this ink tank 60, even when the remaining amount of the ink 2 is low, the side wall portion of the ink containing bag 1 shrinks and collapses (FIG. 2(b)). Therefore, the ink 2 can be used up. Further, by applying pressure (negative pressure) to the ink containing bag 1 in the direction in which the ink containing bag 1 expands, as shown in FIG. 3A, the pressure inside the ink containing bag is adjusted. A case is assumed in which the spring 6 as a mechanism is an ink tank 70 arranged in the ink containing bag 1 . In the case of this ink tank 70, the negative pressure applied by the spring 6 does not cause blockage, so that the ink containing bag 1 does not have a blocked portion. Therefore, as shown in FIG. 3B, the ink can be used up without waste.

Further, as shown in FIG. 4, the case of an ink tank 80 having an ink containing bag 11 provided with a joint portion 12, which is a mechanism for contracting a side wall portion into a predetermined shape, is assumed. 4(a-1) is a front view of the surface provided with the joint 12, and FIG. 4(a-2) is a lateral view of the surface provided with the joint 12. FIG. In the case of this ink tank 80, when the ink 2 flows out of the ink containing bag 11, the side wall portion of the ink containing bag 11 contracts, and the side wall portion contracts into a predetermined shape (FIG. 4B). Therefore, the ink can be used up without waste.

Further, as shown in FIG. 5, assume the case of an ink tank 90 having an ink containing bag 13 provided with folds 14, which is a mechanism for contracting the side wall portion into a predetermined shape. FIGS. 5(a-1) and (a-2) are views viewed from the same direction as FIGS. 4(a-1) and (a-2). In the case of this ink tank 90, when the ink 2 flows out of the ink containing bag 13, the ink containing bag 13 is deformed along the crease 14, and the side wall portion shrinks into a predetermined shape (FIG. 5(b)). Therefore, the ink can be used up without waste.

The ink containing bag that constitutes the ink tank of the present invention is made of resin, which is a material that easily shrinks as ink flows out and that can sufficiently suppress ink leakage. Specific examples of resins include thermoplastic resins such as polyolefins (polyethylene, polypropylene, etc.) and polystyrene; mixtures and modified products of these thermoplastic resins. Among them, it is preferable to use polyolefins and mixtures containing polyolefins. In particular, it is preferable to use polyethylene resin. Further, the resin composition forming the ink containing bag may contain a filler such as glass, pigment, or mineral.

The difference between the average SP value of the water-soluble organic solvent in the ink and the SP value of the resin constituting the ink containing bag is 2.0 (cal/cm ³ ) ^1/2 or more, preferably 4.5 ( cal/cm ³ ) ^1/2 or more. The above SP value difference is preferably 10.0 (cal/cm ³ ) ^1/2 or less. The SP value of the resin forming the ink containing bag is preferably 5.0 (cal/cm ³ ) ^1/2 or more and 10.0 (cal/cm ³ ) ^1/2 or less. For example, the SP value of polyethylene is 8.6 (cal/cm ³ ) ^1/2 and the SP value of polypropylene is 8.0 (cal/cm ³ ) ^1/2 .

The SP value (δ) in the present invention is a value calculated by the Fedors method based on the following formula (1). The ΔE _vap and V of the resin are determined, for example, according to Coating Bulletin No. 193 (1992), etc., can be referred to.

（前記式（１）中、ΔＥ_vapは化合物のモル蒸発熱（ｃａｌ／ｍｏｌ）を表し、Ｖは２５℃における化合物のモル体積（ｃｃ／ｍｏｌ）を表す）

(In the above formula (1), ΔE _vap represents the molar heat of vaporization (cal/mol) of the compound, and V represents the molar volume (cc/mol) of the compound at 25°C.)

The properties of the resin forming the ink containing bag can be verified according to the method shown below. A measurement sample is obtained by cutting the ink containing bag into an appropriate size and analyzed by pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). This makes it possible to confirm the type of resin unit that constitutes the ink containing bag. In addition, the composition ratio of the units can be obtained from the types of the confirmed units and the chemical shift of nuclear magnetic resonance (NMR). Then, the SP value of the resin can be obtained by the Fedors method from the obtained units of the resin and its composition ratio.

The elastic modulus of the ink containing bag is preferably 500 N/mm ² or less. An ink containing bag having a modulus of elasticity of 500 N/mm ² or less is considerably softer than an ink containing bag used for a general inkjet ink tank. By using a soft ink containing bag, the side walls naturally contract without using a mechanism for contracting the ink containing bag in the process of using the ink in the ink tank, and the ink can flow out. The elastic modulus of the ink containing bag is preferably 50 N/mm ² or more. In order to achieve the above elastic modulus, it is preferable to configure the ink containing bag with a single layer of resin.

The elastic modulus of the ink containing bag is measured according to JIS-K-7127 and JIS-K-7161. Elastic modulus is measured using a tensile tester, test mode: tension, displacement rate: 5 mm/min (displace until the yield point of the sample is observed), sample size: length 150 mm, width 25 mm, thickness 1 mm or less. , and the distance between chucks: 100 mm. Under these conditions, the elastic modulus is obtained from the XY slope in the region where the XY relationship is linear when the test force is X and the sample displacement is Y, that is, the region before the yield point appears.

Conventional general ink tanks have used an ink storage bag that has a multi-layer structure in which multiple films are pasted together, or an ink storage bag that has a metal such as aluminum vapor-deposited on a resin film, with an emphasis on barrier properties. rice field. Such an ink containing bag has a modulus of elasticity much higher than 500 N/mm ² and has good barrier properties, but is not soft, so some measures must be taken to prevent the ink from flowing out. For example, in the case of the ink tanks described in Patent Documents 1 and 2, even if the material is made of a hard material, in order to allow the ink to flow out without delay, processing such as adhesion of creases and edges is performed, and the internal pressure is adjusted. We are adopting a mechanism.

The shape of the ink containing bag is preferably cylindrical. The present inventors examined the ink expendability of cylindrical and rectangular ink storage bags. As a result, it was found that the cylindrical ink containing bag is superior in the ability to use up the ink. Since the thickness of the side wall portion of the cylindrical ink containing bag tends to be uniform during molding, the ink containing bag tends to be isotropically crushed as the ink flows out. On the other hand, square-shaped ink storage bags are less likely to have uniform side wall thicknesses than cylindrical ones during molding, so they collapse unevenly as ink flows out, creating a closed space. Ink collects easily. As a result, the ink can be used up less.

The amount of ink contained in the ink containing bag can be appropriately set according to the size of the ink jet recording apparatus, how often the ink tank should be replaced after the ink tank is used up, and the like. The amount of ink contained in the ink containing bag is preferably 100 mL or more and 1,000 mL or less, and more preferably 200 mL or more and 800 mL or less. The size of the ink containing bag can be appropriately set according to the size of the inkjet recording apparatus, the amount of ink contained, and the like. The bottom area of the ink containing bag, excluding the ink supply port, is preferably 10 cm ² or more and 100 cm ² or less, and the height is preferably 10 cm or more and 30 cm or less.

In terms of ease of manufacture and cost, the ink containing bag is preferably manufactured by a molding method such as blow molding. 6A, 6B, and 6C are schematic diagrams showing steps of manufacturing an ink containing bag by blow molding. As shown in FIG. 6A, first, molten resin, which is the raw material of the ink containing bag, is extruded into a mold 300 to form a pipe-shaped parison 301 (FIG. 6A(a-1)). Next, gas is sent into the parison 301 from the direction of arrow A, and the swollen parison 301 is pressed against the inner wall of the mold 300 in the direction of the arrow (FIG. 6A(a-2)). The parison 301 is cooled to manufacture a hollow ink containing bag 21 having a shape that mirrors the shape inside the mold 300 (FIG. 6A(a-3)).

FIG. 6B shows a process for manufacturing the cylindrical ink containing bag 31 . Similar to the process shown in FIG. 6A, first, molten resin is extruded into a mold 310 to form a parison 302 (FIG. 6B(b-1)). Next, gas is sent into the parison 302, and the inflated parison 302 is pressed against the inner wall of the mold 310 (FIG. 6B(b-2)). The parison 302 is cooled to manufacture a cylindrical ink containing bag 31 having a shape that mirrors the shape inside the mold 310 (FIG. 6B(b-3)).

FIG. 6C shows a process for manufacturing the rectangular ink containing bag 41 . Similar to the process shown in FIG. 6A, first, molten resin is extruded into a mold 320 to form a parison 303 (FIG. 6C (c-1)). Next, gas is sent into the parison 303, and the inflated parison 303 is pressed against the inner wall of the mold 320 (FIG. 6C (c-2)). The parison 303 is cooled to manufacture a rectangular ink containing bag 41 having a shape that mirrors the shape inside the mold 320 (FIG. 6C(c-3)). As shown in FIG. 6C, when the rectangular ink containing bag 41 is manufactured by the blow molding method, the corners 305 are formed thicker than the other portions (FIG. 6C (c-2)), and the thickness of the sidewalls is uniform. hard to become For this reason, as described above, the shape of the ink containing bag is preferably cylindrical.

The ink containing bag is housed, for example, in a housing having moderate rigidity. Examples of materials for the housing include thermoplastic resins such as polyester, polycarbonate, polyolefin (polyethylene, polypropylene, etc.), polyphenylene ether; mixtures and modified materials of these thermoplastic resins. The shape of the housing is preferably similar to that of the ink containing bag. In addition, it is preferable to provide an air communication port in the housing in order to maintain the pressure inside the housing at the same level as the atmospheric pressure by taking in air from the outside in conjunction with the contraction of the ink containing bag arranged inside the housing.

(ink)
The ink stored in the ink storage bag of the ink tank of the present invention is a water-based inkjet ink containing a coloring material and a water-soluble organic solvent. The difference between the average SP value of the water-soluble organic solvent and the SP value of the resin forming the ink containing bag is 2.0 (cal/cm ³ ) ^1/2 or more. The ink does not need to be a so-called "curable ink". Therefore, the ink need not contain compounds such as polymerizable monomers that can be polymerized by the addition of external energy. Each component constituting the ink and physical properties of the ink will be described in detail below.

[Color material]
A pigment or a dye can be used as the coloring material. Among them, it is preferable to use a pigment. The content (% by mass) of the coloring material in the ink is preferably 0.50% by mass or more and 15.00% by mass or less, and 1.00% by mass or more and 10.00% by mass, based on the total mass of the ink. More preferably:

Specific examples of pigments include inorganic pigments such as carbon black and titanium oxide; and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole and dioxazine.

Examples of the method of dispersing the pigment include a resin-dispersed pigment using a resin as a dispersant, and a self-dispersing pigment in which a hydrophilic group is bonded to the particle surface of the pigment. Moreover, a resin-bonded pigment in which an organic group containing a resin is chemically bonded to the particle surface of the pigment, or a microcapsule pigment in which the surface of the pigment particle is coated or encapsulated with a resin or the like can be used. However, when pigments are used as colorants, self-dispersed pigments, resin-dispersed pigments dispersed by a resin dispersant physically adsorbed on the pigment particle surface (that is, resins that are not resin-bonded pigments or microcapsule pigments) dispersed pigments) are preferred.

As the resin dispersant for dispersing the pigment in the aqueous medium, it is preferable to use one that can disperse the pigment in the aqueous medium by the action of an anionic group. As the resin dispersant, a resin as described later, especially a water-soluble resin can be used. The content (% by mass) of the pigment in the ink is preferably 0.3 times or more and 10.0 times or less as a mass ratio with respect to the content (% by mass) of the resin dispersant.

As the self-dispersing pigment, those in which an anionic group such as a carboxylic acid group, a sulfonic acid group, or a phosphonic acid group is bonded directly to the particle surface of the pigment or through another atomic group (-R-) is used. be able to. The anionic group may be in either an acid form or a salt form, and in the case of a salt form, it may be in a partially dissociated state or in a completely dissociated state. When the anionic group is in the salt form, cations that serve as counter ions include alkali metal cations, ammonium and organic ammonium. Specific examples of other atomic groups (-R-) include linear or branched alkylene groups having 1 to 12 carbon atoms; arylene groups such as phenylene groups and naphthylene groups; carbonyl groups; imino groups; amide groups; groups; ester groups; ether groups, and the like. Moreover, the group which combined these groups may be sufficient.

As the dye, it is preferable to use one having an anionic group. Specific examples of dyes include dyes such as azo, triphenylmethane, (aza)phthalocyanine, xanthene, and anthrapyridone.

[Water-soluble organic solvent]
The ink is a water-based ink containing a water-soluble organic solvent. The difference between the average SP value of the water-soluble organic solvent and the SP value of the resin forming the ink containing bag is 2.0 (cal/cm ³ ) ^1/2 or more. As the water-soluble organic solvent, alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing compounds, sulfur-containing compounds, and the like, which can be used for inkjet inks, can be used. The content (% by mass) of the water-soluble organic solvent in the water-based ink is preferably 3.00% by mass or more and 50.00% by mass or less, and 10.00% by mass or more and 50.00% by mass or less, based on the total mass of the ink. 00% by mass or less is more preferable. Generally, the "water-soluble organic solvent" is liquid, but in the present invention, for the sake of convenience, those that are solid at 25°C (normal temperature) are also included in the water-soluble organic solvent. Specific examples of water-soluble organic solvents that are solid at 25° C. and are commonly used for water-based inks will be described later.

By stably maintaining the existing state of the coloring material in the process of dissolving the once-frozen ink, it is possible to further improve the use-up of the ink. In order to stably maintain the existing state of the coloring material in the process of dissolving the ink, it is preferable that the above relationship of the SP value is satisfied and the water-soluble organic solvent is present at a certain ratio with respect to the coloring material. Therefore, the content (% by mass) of the water-soluble organic solvent in the ink is preferably 1.0 times or more in terms of mass ratio to the content (% by mass) of the coloring material. When the mass ratio is 1.0 times or more, the amount of the water-soluble organic solvent having a molecule larger than that of water to the coloring material is to some extent relative to the components excluded from the water crystals when the ink freezes. exist. Therefore, aggregation of the coloring material is suppressed by solvation, and it becomes easy to suppress deterioration of ink usability. Further, the mass ratio is preferably 200.0 times or less, more preferably 20.0 times or less, and particularly preferably 10.0 times or less. By setting the above mass ratio to 200.0 times or less, the water-soluble organic solvent does not become too much relative to the coloring material, so excessive aggregation of the coloring material is suppressed, and deterioration of the ink's usability is suppressed. easier.

[SP value]
A water-based ink for inkjet generally contains a plurality of types of water-soluble organic solvents. Therefore, it is suitable to grasp the SP value of the water-soluble organic solvent in the ink used in the ink tank of the present invention with the concept of "average SP value". The average SP value is the value obtained by multiplying the SP value specific to the water-soluble organic solvent by the ratio (% by mass) of the water-soluble organic solvent in the total amount of the water-soluble organic solvent in the ink. Means the value calculated and integrated for the solvent. When the ink contains only one type of water-soluble organic solvent, the SP value of this water-soluble organic solvent is the "average SP value".

For example, in the case of "Ink 1" prepared in "Example" described later, the composition of the water-soluble organic solvent (25.0 parts by mass in total) is as follows. Numerical values in parentheses are SP values (units omitted) of each water-soluble organic solvent.
・Glycerin (16.4): 11.0 parts by mass ・Triethylene glycol (13.6): 5.0 parts by mass ・2-Pyrrolidone (12.6): 5.0 parts by mass ・1,2-Hexanediol (11.8): 2.0 parts by mass Polyethylene glycol having a number average molecular weight of 1,000 (10.1): 2.0 parts by mass

The average SP value of the water-soluble organic solvent in this "ink 1" can be calculated as follows.
Average SP value=16.4×11.0/25.0+13.6×5.0/25.0+12.6×5.0/25.0+11.8×2.0/25.0+10.1×2. 0/25.0=14.2

The average SP value of the water-soluble organic solvent in the ink is preferably 4.5 (cal/cm ³ ) ^1/2 or more and 20.0 (cal/cm ³ ) ^1/2 or less, and preferably 10.5 (cal /cm ³ ) ^1/2 or more and 16.0 (cal/cm ³ ) ^1/2 or less is more preferable. Moreover, it is particularly preferable to be 13.0 (cal/cm ³ ) ^1/2 or more and 16.0 (cal/cm ³ ) ^1/2 or less.

The SP values of general-purpose water-soluble organic solvents for water-based inkjet inks according to the Fedors method are shown below with the unit (cal/cm ³ ) ^1/2 omitted. glycerin (16.4), 1,3-propanediol (16.1), trimethylolpropane (15.9), 1,4-butanediol (15.0), diethylene glycol (15.0), ethylene glycol ( 14.8), 1,3-butanediol (14.8), 2-methyl-1,3-propanediol (14.8), 1,2,6-hexanetriol (14.5), urea (14 .4), ethylene urea (14.2), 1,5-pentanediol (14.2), methanol (13.8), triethylene glycol (13.6), 1,6-hexanediol (13.5 ), 3-methyl-1,5-pentanediol (13.4), tetraethylene glycol (12.8), 2-pyrrolidone (12.6), ethanol (12.6), 1,2-pentanediol ( 12.2), ethylene glycol monomethyl ether (12.0), n-propanol (11.8), 1,2-hexanediol (11.8), isopropanol (11.6), N-methyl-2-pyrrolidone (11.5), ethylene glycol monoethyl ether (12.0), 1,3-dimethyl-2-imidazolidinone (11.4), n-butanol (11.3), diethylene glycol monomethyl ether (11.2) ), 2-butanol (11.1), isobutanol (11.1), diethylene glycol monoethyl ether (10.9), tert-butanol (10.9), triethylene glycol monoethyl ether (10.6), Polyethylene glycol having a number average molecular weight of 600 (10.5), diethylene glycol monobutyl ether (10.5), triethylene glycol monobutyl ether (10.3), tetraethylene glycol monobutyl ether (10.2), number average molecular weight of 1,000 polyethylene glycol (10.1), acetone (9.1), methyl ethyl ketone (9.0), tetraethylene glycol dimethyl ether (8.5), triethylene glycol butyl methyl ether (8.4), ethylene glycol dimethyl ether (7 .6). The SP value of the water-soluble organic solvent contained in the ink is preferably 5.0 (cal/cm ³ ) ^1/2 or more and 20.0 (cal/cm ³ ) ^1/2 or less.

[Relative permittivity]
As described above, in the case of an ink tank using ink containing a coloring material, the ink tends to be used up less. When the water-soluble organic solvent is concentrated in the process of dissolving the frozen ink, the pigment present in the vicinity of the concentrated water-soluble organic solvent aggregates due to a decrease in electrostatic repulsion, increasing the viscosity of the ink. . In addition, since the highly polar water is no longer present, the polarity of the dye present near the concentrated water-soluble organic solvent is relatively lowered, and the decrease in solubility causes the dye to aggregate and increase the viscosity of the ink. As a result, it becomes difficult to discharge the ink from the ink containing bag, and the ability to use up the ink tends to deteriorate. Therefore, considering the interaction with the coloring material in the ink, in order to suppress the increase in the viscosity of the ink and further improve the usability of the ink, it is necessary to use a water-soluble organic solvent with a high relative dielectric constant to reduce the static electricity of the pigment. It is preferable to maintain repulsion and dye solubility. Specifically, the average dielectric constant of the water-soluble organic solvent is preferably 20.0 or more. For the same reason as in the case of the SP value, the influence of water is small, so it is not necessary to consider the influence of water on the dielectric constant as well.

The dielectric constant of a water-soluble organic solvent or water can be measured at a frequency of 10 kHz using a dielectric constant meter (eg, trade name “BI-870” (manufactured by BROOKHAVEN INSTRUMENTS CORPORATION)). The relative dielectric constant of the solid water-soluble organic solvent at a temperature of 25° C. is a value calculated from the following formula (A) after measuring the relative dielectric constant of a 50% by mass aqueous solution. Normally, the term "water-soluble organic solvent" means a liquid, but in the present invention, a water-soluble organic solvent that is solid at 25°C (normal temperature) is also included in the water-soluble organic solvent.

ε _sol = 2ε _50% - ε _water (A)
ε _sol : Relative permittivity of water-soluble organic solvent solid at 25°C ε _50% : Relative permittivity of 50 mass% aqueous solution of water-soluble organic solvent solid at 25°C ε _water : Relative permittivity of water

Specific examples of water-soluble organic solvents that are solid at 25° C. and are commonly used for aqueous inks include 1,6-hexanediol, trimethylolpropane, ethylene urea, urea, and polyethylene glycol having a number average molecular weight of 1,000. can.

The reason for calculating the dielectric constant of the water-soluble organic solvent that is solid at 25° C. from the dielectric constant of the 50 mass % aqueous solution is as follows. Among the water-soluble organic solvents that are solid at 25° C., some of which can be used as constituents of water-based inks are difficult to prepare as highly concentrated aqueous solutions exceeding 50% by mass. On the other hand, in a low-concentration aqueous solution of 10 mass % or less, the dielectric constant of water becomes dominant, and it is difficult to obtain a probable (effective) dielectric constant value of the water-soluble organic solvent. Therefore, when the present inventors conducted a study, it was found that most of the water-soluble organic solvents that are solid at 25 ° C. used for ink can prepare an aqueous solution to be measured, and the calculated dielectric constant is also It was found to be consistent with the effects of the invention. For the above reasons, in the present invention, the dielectric constant of a water-soluble organic solvent that is solid at 25° C. is calculated from the dielectric constant of a 50% by mass aqueous solution and used. For water-soluble organic solvents that are solid at 25°C but have low solubility in water and cannot be prepared into a 50% by weight aqueous solution, an aqueous solution with a saturated concentration is used, and the above ε _sol is calculated according to the calculation method. For convenience, the value of the relative permittivity calculated by

The average dielectric constant is the value obtained by multiplying the specific dielectric constant of the water-soluble organic solvent by the ratio (% by mass) of the water-soluble organic solvent to the total amount of the water-soluble organic solvent in the ink. It means the value calculated and integrated for the organic solvent. When the ink contains only one water-soluble organic solvent, the relative dielectric constant of this water-soluble organic solvent is the "average relative dielectric constant."

For example, in the case of "Ink 1" prepared in "Example" described later, the composition of the water-soluble organic solvent (25.0 parts by mass in total) is as follows. Numerical values in parentheses are relative permittivity of each water-soluble organic solvent.
・Glycerin (42.3): 11.0 parts by mass ・Triethylene glycol (22.7): 5.0 parts by mass ・2-pyrrolidone (28.0): 5.0 parts by mass ・1,2-Hexanediol (14.8): 2.0 parts by mass Polyethylene glycol having a number average molecular weight of 1,000 (4.6): 2.0 parts by mass

The average dielectric constant of the water-soluble organic solvent in this "ink 1" can be calculated as follows.
Average dielectric constant = 42.3 x 11.0/25.0 + 22.7 x 5.0/25.0 + 28.0 x 5.0/25.0 + 14.8 x 2.0/25.0 + 4.6 x 2 .0/25.0=30.3

The average dielectric constant of the water-soluble organic solvent in the ink is preferably 20.0 or more and 50.0 or less, more preferably 30.0 or more and 40.0 or less.

The dielectric constants of general-purpose water-soluble organic solvents for water-based inks for inkjet are shown below. Urea (110.3), ethyl isopropyl sulfone (59.0), ethylene urea (49.7), dimethyl sulfoxide (48.9), glycerin (42.3), γ-butyrolactone (41.9), ethylene glycol (40.4), 1-(2-hydroxyethyl)-2-pyrrolidone (37.6), trimethylolpropane (33.7), methanol (33.1), N-methyl-2-pyrrolidone (32. 0), triethanolamine (31.9), diethylene glycol (31.7), 1,4-butanediol (31.1), 1,3-butanediol (30.0), 3-methylsulfolane (29. 0), 1,2-propanediol (28.8), 1,2,6-hexanetriol (28.5), 2-methyl-1,3-propanediol (28.3), 2-pyrrolidone (28 .0), 1,5-pentanediol (27.0), 3-methyl-1,3-butanediol (24.0), 3-methyl-1,5-pentanediol (23.9), ethanol ( 23.8), 1-(hydroxymethyl)-5,5-dimethylhydantoin (23.7), triethylene glycol (22.7), tetraethylene glycol (20.8), polyethylene glycol with a number average molecular weight of 200 ( 18.9), 2-ethyl-1,3-hexanediol (18.5), isopropanol (18.3), 1,2-hexanediol (14.8), n-propanol (12.0), number Polyethylene glycol with an average molecular weight of 600 (11.4), triethylene glycol monobutyl ether (9.8), tetraethylene glycol monobutyl ether (9.4), tripropylene glycol monomethyl ether (8.5), 1,6-hexane Diol (7.1), polyethylene glycol of 1,000 number average molecular weight (4.6). The dielectric constant of each water-soluble organic solvent contained in the ink is preferably 3.0 or more and 120.0 or less. The vapor pressure at 25°C of the water-soluble organic solvent contained in the ink is preferably lower than the vapor pressure of water at 25°C.

〔Method of verification〕
The properties of the water-soluble organic solvent can be verified according to the method shown below. By diluting an appropriate amount of ink with methanol and performing qualitative analysis by gas chromatography/mass spectrometry (GC/MS), the type of water-soluble organic solvent can be confirmed. Furthermore, the content of the water-soluble organic solvent can be confirmed by the absolute calibration curve method using the standard solution of the component to be analyzed. Then, from the confirmed type and content of the water-soluble organic solvent, the average SP value and average dielectric constant of the water-soluble organic solvent in the ink can be obtained.

[resin]
The ink can contain a resin. The resin content (% by mass) in the ink is preferably 0.10% by mass or more and 20.00% by mass or less, and 0.50% by mass or more and 15.00% by mass or less, based on the total mass of the ink. is more preferable.

The resin can be added to the ink to (i) stabilize the dispersed state of the pigment, that is, as a resin dispersant or as an adjunct thereto. In addition, (ii) it can be added to the ink in order to improve various characteristics of the recorded image. Forms of the resin include block copolymers, random copolymers, graft copolymers, combinations thereof, and the like. Moreover, the resin may be a water-soluble resin that is soluble in an aqueous medium, or resin particles that are dispersed in an aqueous medium. Resin particles do not need to contain a coloring material. Moreover, it is preferable that the resin particles can be dispersed without using a resin dispersant, that is, they are self-dispersible.

As used herein, the phrase "the resin is water-soluble" means that when the resin is neutralized with an alkali equivalent to its acid value, it is water-soluble in a state in which particles whose particle size can be measured by a dynamic light scattering method are not formed. means present in the medium. Whether or not the resin is water-soluble can be determined according to the method described below. First, a liquid (resin solid content: 10% by mass) containing a resin neutralized with an acid value equivalent alkali (sodium hydroxide, potassium hydroxide, etc.) is prepared. Next, the prepared liquid is diluted 10-fold (by volume) with pure water to prepare a sample solution. Then, when the particle size of the resin in the sample solution is measured by the dynamic light scattering method, if particles having the particle size are not measured, it can be determined that the resin is water-soluble. The measurement conditions at this time can be, for example, as follows.

[Measurement condition]
SetZero: 30 seconds Number of measurements: 3 Measurement time: 180 seconds

As the particle size distribution analyzer, a particle size analyzer using dynamic light scattering (for example, trade name “UPA-EX150” manufactured by Nikkiso Co., Ltd.) can be used. Of course, the particle size distribution measuring device and measurement conditions to be used are not limited to those described above.

The acid value of the water-soluble resin is preferably 100 mgKOH/g or more and 250 mgKOH/g or less. The acid value of the resin constituting the resin particles is preferably 5 mgKOH/g or more and 200 mgKOH/g or less. The weight average molecular weight of the water-soluble resin is preferably 3,000 or more and 15,000 or less. The weight average molecular weight of the resin constituting the resin particles is preferably 1,000 or more and 2,000,000 or less, more preferably 250,000 or more and 550,000 or less. The average particle size (volume-based cumulative 50% particle size (D ₅₀ )) of the resin particles measured by a dynamic light scattering method is preferably 100 nm or more and 500 nm or less.

Examples of resins include acrylic resins, urethane resins, and olefin resins. Among them, acrylic resins and urethane resins are preferable, and acrylic resins are more preferable.

As the acrylic resin, one having a hydrophilic unit and a hydrophobic unit as structural units is preferable. Among them, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one of a monomer having an aromatic ring and a (meth)acrylic acid ester-based monomer is preferable. In particular, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one monomer of styrene and α-methylstyrene is preferred. Since these resins easily interact with pigments, they can be suitably used as resin dispersants for dispersing pigments.

A hydrophilic unit is a unit having a hydrophilic group such as an anionic group. A hydrophilic unit can be formed, for example, by polymerizing a hydrophilic monomer having a hydrophilic group. Specific examples of hydrophilic monomers having hydrophilic groups include acidic monomers having carboxylic acid groups such as (meth)acrylic acid, itaconic acid, maleic acid and fumaric acid, and anions such as anhydrides and salts of these acidic monomers. organic monomers, and the like. Examples of cations constituting salts of acidic monomers include ions such as lithium, sodium, potassium, ammonium and organic ammonium. A hydrophobic unit is a unit that does not have a hydrophilic group such as an anionic group. A hydrophobic unit can be formed, for example, by polymerizing a hydrophobic monomer that does not have a hydrophilic group such as an anionic group. Specific examples of hydrophobic monomers include monomers having an aromatic ring such as styrene, α-methylstyrene, and benzyl (meth)acrylate; methyl (meth)acrylate, butyl (meth)acrylate, (meth)acrylic acid 2 - (Meth)acrylic acid ester monomers such as ethylhexyl.

A urethane-based resin can be obtained, for example, by reacting a polyisocyanate with a polyol. Moreover, what made the chain extension agent further react may be used. Examples of olefinic resins include polyethylene and polypropylene.

[Aqueous medium]
The ink used in the ink tank of the present invention is an aqueous ink containing at least water as an aqueous medium. The ink contains an aqueous medium which is a mixed solvent of water and a water-soluble organic solvent. As water, it is preferable to use deionized water or ion-exchanged water. The water content (% by mass) in the water-based ink is preferably 50.00% by mass or more and 95.00% by mass or less based on the total mass of the ink.

[Surfactant]
The ink preferably contains a surfactant. As with water-soluble organic solvents, surfactants also exist in a state excluded from water crystals when frozen. Oriented toward the media side and into the ink containing bag. Therefore, when the ink contains a surfactant, the ink containing bag contracts as the ink flows out, and even when the inner surfaces of the ink containing bag come close to each other, the ink containing bag is likely to be prevented from being clogged. Ease of use can be further improved. The content (% by mass) of the surfactant in the ink is preferably 0.05% by mass or more and 10.00% by mass or less based on the total mass of the ink.

Examples of surfactants include ionic surfactants such as anionic, cationic, and amphoteric surfactants; and nonionic surfactants. Among them, nonionic surfactants are preferred. Since the nonionic surfactant has no electric charge, the interaction with the ink containing bag, which has no electric charge, due to the Van der Waals force becomes stronger, and it tends to be oriented to the ink containing bag. Surfactants can be classified into hydrocarbon-based surfactants, fluorine-based surfactants, silicone-based surfactants, and the like. Among these, fluorine-based surfactants and silicone-based surfactants are preferred. In particular, nonionic fluorine-based surfactants and silicone-based surfactants can effectively lower the surface energy of the oriented ink containing bag. Materials with low surface energies are difficult to adhere to other materials. Therefore, by including a fluorine-based surfactant or a silicone-based surfactant in the ink, it is possible to make it more difficult for the inner surfaces of the ink containing bag to adhere to each other, and to further improve the ink usage efficiency.

[Other additives]
In addition to the above ingredients, the ink may contain various additives such as antifoaming agents, pH modifiers, viscosity modifiers, rust inhibitors, preservatives, anti-mold agents, antioxidants, and anti-reduction agents. may be included. In general, these additives, including surfactants, are contained in ink in a considerably small amount and have a low "direct" effect on the swelling of the ink containing bag. Therefore, in the present invention, these additives are not included in the "water-soluble organic solvent" and are not included in the calculation of the SP value and dielectric constant.

<Inkjet recording device>
An inkjet recording apparatus of the present invention includes the ink tank described above and a recording head that ejects ink supplied from the ink tank by an inkjet method. The inkjet recording apparatus of the present invention will be described below with reference to the drawings.

FIG. 7 is a perspective view schematically showing one embodiment of the inkjet recording apparatus of the present invention. The inkjet printing apparatus 200 of the embodiment shown in FIG. 7 is a so-called serial type inkjet printing apparatus that performs a printing operation by reciprocally scanning the printing head in the X direction (main scanning direction). The print medium 101 is intermittently transported in the Y direction (sub-scanning direction) by transport rollers 107 . The carriage 103 is movably supported along a guide rail 105 arranged along the X direction and fixed to an endless belt 106 that moves parallel to the guide rail 105 . The endless belt 106 reciprocates by the driving force of a motor. The reciprocating motion of the endless belt 106 causes the carriage 103 to reciprocate in the X direction.

The recording unit 102 mounted on the carriage 103 is similarly reciprocated in the X direction (main scanning direction). A printing operation is performed by conveying the printing medium 101 in the Y direction and reciprocating scanning of the printing unit 102 in the X direction. Ink is supplied from the ink tank 100 to the recording unit 102 through the ink supply tube 104 . After that, ink is ejected from the ejection openings of the print head provided in the print unit 102 . The inkjet recording apparatus of the present invention can also be applied to various systems such as a full line system and a serial scan system.

EXAMPLES The present invention will be described in more detail below with reference to examples, comparative examples, and reference examples, but the present invention is not limited by the following examples as long as it does not exceed the scope of the invention. "Parts" and "%" regarding component amounts are based on mass unless otherwise specified.

<Manufacture of ink tank body>
An ink containing bag (bottom area: 20 cm ² , height: 16 cm, capacity: 320 mL) prepared by blow molding was housed in a polyethylene housing, and ink tank bodies 1 to 10 having the configurations shown in Table 1 were manufactured. Various physical properties were measured using a sample obtained by cutting the produced ink containing bag into a suitable size. The SP value of the resin was calculated by analyzing the composition and using the Fedors method. The elastic modulus of the ink containing bag was measured for a sample obtained by cutting the ink containing bag into a strip of 150 mm×25 mm. The modulus of elasticity is measured using a tensile tester (trade name "desktop precision universal testing machine AGS-X" manufactured by Shimadzu Corporation) under the following conditions: test type: tension, distance between chucks: 100 mm, displacement speed: 5 mm/min. measured in

<Preparation of pigment dispersion>
(Pigment dispersion liquid 1)
A mixture of 10.0 parts of a pigment, 15.0 parts of an aqueous resin solution, and 75.0 parts of pure water is placed in a batch-type vertical sand mill (manufactured by Imex) filled with 200 parts of zirconia beads with a diameter of 0.3 mm. The mixture was dispersed for 5 hours while cooling with water. As the pigment, trade name "Chromophthal Jet Magenta 2BC" (manufactured by Ciba Specialty Chemicals) was used. As the aqueous solution of the resin, a styrene-ethyl acrylate-acrylic acid copolymer having an acid value of 150 mgKOH/g and a weight average molecular weight of 8,000 was dissolved in water containing potassium hydroxide in an equimolar amount to the acid value. An aqueous solution with a resin (solid content) content of 20.0% was used. A pigment dispersion liquid 1 was obtained by pressure filtration through a cellulose acetate filter (manufactured by Advantech) having a pore size of 3.0 μm. The pigment content in pigment dispersion 1 was 10.0%, and the resin content was 3.0%.

(Pigment dispersion liquid 2)
As an aqueous solution of the resin, an aqueous solution of a styrene-N,N-dimethylaminoethyl methacrylate-ethyl acrylate copolymer (composition (mass) ratio = 50:40:10) having a weight average molecular weight of 20,000 content 20.0%) was used. Pigment Dispersion Liquid 2 was obtained in the same manner as Pigment Dispersion Liquid 1 described above, except that an aqueous solution of this resin was used. The pigment content in the pigment dispersion 2 was 10.0%, and the resin content was 3.0%.

<Ink preparation>
Each component (unit: %) shown in Tables 2-1 and 2-2 was mixed, thoroughly stirred, and filtered under pressure through a membrane filter with a pore size of 1.2 μm (trade name “HDCII filter”, manufactured by Pall). to prepare each ink. The number given to polyethylene glycol is the number average molecular weight of the polyethylene glycol. "Acetylenol E100" is a trade name of a nonionic hydrocarbon-based surfactant manufactured by Kawaken Fine Chemicals. "Zonyl FS3100" is a trade name of a nonionic fluorosurfactant manufactured by DuPont. "BYK348" is a trade name of a nonionic silicone surfactant manufactured by BYK-Chemie.

<Evaluation>
The combination of the ink tank main body and the ink shown on the left side of Table 3 was prepared, and the ink tank was prepared by filling the ink tank main body with the ink. The amount of ink filled was 95% of the maximum amount of ink contained in the ink tank body. The prepared ink tank was stored in an environment of -10°C for 3 days. Further, the ink tank was left at 25° C. for 24 hours. After that, it was set in an inkjet recording apparatus having the main part shown in FIG. 7, and the ink was continuously discharged under the temperature condition of 25° C. until the ink was no longer supplied. The remaining amount of ink when the ink supply was stopped was measured, and the "ink consumption rate (%)" was calculated based on the following formula (2), and the ink expendability was evaluated according to the evaluation criteria shown below. Table 3 shows the results.
Ink consumption rate (%)={(XY)/X}×100 (2)
X: Amount of ink filled in the ink tank body (g)
Y: Remaining amount of ink (g) when ink supply is stopped

[Evaluation criteria]
A: The ink consumption rate was 90% or more.
B: The ink consumption rate was 80% or more and less than 90%.
C: The ink consumption rate was 70% or more and less than 80%.
D: The ink consumption rate was less than 70%.

In the ink tank of Comparative Example 1, the ink containing bag was clogged at multiple locations at the end of printing, and a sufficient amount of ink could not be supplied. Since the ink tanks of Reference Examples 1 and 2 had a pressure adjusting mechanism, the ink could be used up. Further, since the ink tanks of Reference Examples 3 and 4 had a shrinkage control mechanism, the ink could be used up.

Claims (18)

An ink containing bag that contains ink therein and does not have a mechanism for contracting a side wall portion into a predetermined shape, and the side wall portion contracts with the outflow of the ink. An ink tank for use in an inkjet recording apparatus that does not have a mechanism for adjusting pressure,
the ink containing bag is made of resin,
The shape of the ink containing bag is cylindrical,
The ink containing bag is a blow-molded product,
the ink is a water-based ink containing a coloring material and a water-soluble organic solvent;
The ink tank, wherein the difference between the average SP value of the water-soluble organic solvent and the SP value of the resin forming the ink containing bag is 2.0 (cal/cm ³ ) ^1/2 or more. . 2. The ink according to claim 1, wherein the difference between the average SP value of the water-soluble organic solvent and the SP value of the resin forming the ink containing bag is 4.5 (cal/cm ³ ) ^1/2 or more. tank. 3. The ink according to claim 2, wherein the difference between the average SP value of the water-soluble organic solvent and the SP value of the resin constituting the ink containing bag is 10.0 (cal/cm ³ ) ^1/2 or less. tank. 4. The ink tank according to claim 1, wherein the water-soluble organic solvent has an average dielectric constant of 20.0 or higher. 5. An ink tank according to claim 4, wherein said water-soluble organic solvent has an average dielectric constant of 50.0 or less. 6. The content (% by mass) of the water-soluble organic solvent in the ink is at least 1.0 times the content (% by mass) of the coloring material. Ink tank described in . 7. The ink tank according to claim 6, wherein the content (% by mass) of said water-soluble organic solvent in said ink is 200.0 times or less as a mass ratio with respect to the content (% by mass) of said coloring material. 8. An ink tank according to any one of claims 1 to 7, wherein said ink further contains a surfactant. The ink tank according to any one of claims 1 to 8, wherein the ink containing bag has a modulus of elasticity of 500 N/ ^mm2 or less. 10. The ink tank according to claim 9, wherein the elastic modulus of the ink containing bag is 50 N/mm ^<2> or more. 11. An ink tank according to any one of claims 1 to 10, wherein the side walls of the ink containing bag contract irregularly as the ink flows out. 12. An ink tank according to any one of claims 1 to 11 , wherein the ink containing bag is isotropically crushed as ink flows out. 13. The ink tank according to any one of claims 1 to 12 , wherein the resin forming the ink containing bag contains polyolefin. 13. The ink tank according to any one of claims 1 to 12 , wherein the resin forming the ink containing bag contains polyethylene resin. 15. The ink tank according to any one of claims 1 to 14 , wherein the resin forming the ink containing bag contains a filler. 16. The ink tank according to any one of claims 1 to 15 , wherein the ink containing bag is composed of a single layer of the resin. 17. The ink tank according to any one of claims 1 to 16 , wherein the ink storage capacity of the ink storage bag is 100 mL or more and 1,000 mL or less. an ink tank according to any one of claims 1 to 17 ;
and a recording head that ejects ink supplied from the ink tank by an inkjet method.

Images