JP2019073006A - Ink tank and inkjet recording device - Google Patents

Abstract

To provide an ink tank excellent in ink using-up property with a simple configuration, and an inkjet recording device using the ink tank.SOLUTION: An ink storage bag 1 stores ink 2 inside, has no mechanism such that a side wall part contracts to a predetermined shape, and the side wall part contracts along outflow of the ink 2. An ink tank 50 has no mechanism of adjusting an internal pressure of the ink storage bag 1, and is used for an inkjet recording device. The ink storage bag 1 is formed of a resin, the ink 2 is aqueous ink containing a coloring material and a water-soluble organic solvent, and a difference between an average SP value of the water-soluble organic solvent and a SP value of a resin forming the ink storage bag is 2.0 (cal/cm)or more. An inkjet recording device includes the ink tank and a recording head which discharges the ink supplied from the ink tank by an inkjet method.SELECTED DRAWING: Figure 1

Description

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

  As an ink tank used for an ink jet recording apparatus, there is an ink tank provided with an ink storage bag made of a resin, from the viewpoint of being able to store a large amount of ink. As the problem of the ink tank having the ink containing bag, the ink use-up property can be mentioned. When the ink is supplied to the recording head of the ink jet recording apparatus through the ink supply port of the ink tank, the ink containing bag contracts and irregularly collapses with the supply (outflow) of the ink. The force for shrinking and squeezing the ink containing bag is usually only the force for discharging the ink.

  When an image is recorded using an inkjet recording apparatus, an amount of ink equivalent to that used for recording is supplied from the ink containing bag to the recording head. Even if a large amount of images are recorded at one time, the amount of ink supplied to the recording head is considerably smaller than the total amount of ink that can be stored in the ink storage bag, so the force for discharging the ink from the ink storage bag is extremely high. weak. Then, the ink storage bag with a reduced amount of ink shrinks and collapses and partially closes. For this reason, it is not possible to discharge the ink in the ink storage bag only by the extremely weak force that causes the ink to flow out, it becomes difficult to use up the ink, and a problem arises that the ink use-up performance is reduced.

  In order to solve such a problem, for example, an ink storage bag is proposed in which a mechanism such as a spring or an elastic member for applying an external pressure is provided to push out the ink (Patent Document 1). The ink containing bag is formed by bonding the edges of two films, and is processed so as to collapse in a direction parallel to the bonding surface. In addition, an ink storage bag in which the direction of collapse is controlled has been proposed (Japanese Patent Application Laid-Open No. 2000-147118). The ink containing bag is pre-folded so as to collapse in a specific direction.

JP 2003-226023 A JP, 2009-226809, A

  However, providing a mechanism for adjusting the pressure inside the ink storage bag, and performing a shape process for controlling how the ink storage bag collapses and folds are easiness of manufacture, installation space, and complicated structure. And cost disadvantages. For example, without providing a mechanism for adjusting the pressure inside the ink containing bag, the structure of the ink tank can be simplified. In addition, if the ink storage bag is manufactured by blow molding or the like without fold processing or adhesion processing, it is advantageous in terms of ease of manufacture and cost. However, if there is no mechanism for adjusting the pressure inside the ink containing bag or no mechanism for controlling the contraction of the ink containing bag, as described above, the ink containing bag is irregular as the ink flows out. It will be difficult to fully use the ink because it will collapse. In addition, since it is required that the ink jet recording apparatus can be used unchanged over a wide range of temperatures in anticipation of use in various regions, it is preferable to have a design in which the use at an extreme temperature is also assumed. 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 ink exhaustion performance may be further reduced depending on the temperature environment in which the ink tank is placed.

  Therefore, an object of the present invention is to provide an ink tank having a simple configuration and excellent in ink use-out performance. 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, there is provided an ink containing bag in which the side wall portion shrinks in accordance with the outflow of the ink without containing the ink and having a mechanism in which the side wall portion shrinks in a predetermined shape. An ink tank for use in an ink jet recording apparatus, which does not have a mechanism for adjusting the pressure inside the ink containing bag, wherein the ink containing bag is made of resin, and the ink contains a coloring material and water solubility. It is an aqueous ink containing an organic solvent, and the difference between the average SP value of the water-soluble organic solvent and the SP value of the resin constituting the ink storage bag is 2.0 (cal / cm ³ ) ^1/2 An ink tank characterized by the above is provided.

  According to the present invention, it is possible to provide an ink tank that is excellent in ink use-out performance despite its simple configuration. Further, according to the present invention, it is possible to provide an ink jet recording apparatus using this ink tank.

It is a schematic diagram which shows one Embodiment of the ink tank of this invention. It is a schematic diagram which shows an example of an ink tank. It is a schematic diagram which shows the other example of an ink tank. It is a schematic diagram which shows the other example of an ink tank. It is a schematic diagram which shows the other example of an ink tank. It is a schematic diagram which shows the process of manufacturing an ink storage bag by the blow molding method. It is a schematic diagram which shows the process of manufacturing an ink storage bag by the blow molding method. It is a schematic diagram which shows the process of manufacturing an ink storage bag by the blow molding method. FIG. 1 is a perspective view schematically showing an embodiment of an ink jet recording apparatus of the present invention.

  Hereinafter, the present invention will be described in more detail by way of 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 a salt”. Moreover, the thing of the water-based ink for inkjets may only be described as "ink." Physical property values are values at normal temperature (25 ° C.) and normal pressure (1 atm) unless otherwise specified.

  The inventors of the present invention filled an ink storage bag of an ink tank that is provided with an ink storage bag made of resin and that does not have a mechanism for adjusting the pressure inside the ink storage bag. Then, assuming the use environment of the ink jet recording apparatus and the environment at the time of transportation, the ink tank was stored in various temperature environments to conduct various studies. As a result, assuming an environment such as a cold area, if using frozen ink after freezing once, it is confirmed that the problem that the inside of the ink containing bag is partially blocked and ink can not be used out easily occurs It was done.

  The aqueous ink may freeze if placed in an environment of 0 ° C. or lower. At this time, since hydrogen bonds are generated between water molecules, components such as water-soluble organic solvents other than water are frozen in a state of being excluded from water crystals. As a result, in the portion which is not frozen, the water-soluble organic solvent is in a concentrated state. When the ink is dissolved from such a state, the concentrated water-soluble organic solvent does not mix with water promptly, and the thick portion of the water-soluble organic solvent contacts the ink containing bag. A portion 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 contracts due to the outflow (supply) of the ink, the softened portion on the inner surface of the ink containing bag is likely to stick, and it is considered that the ink is partially blocked and the ink useability is reduced.

  Among them, with regard to an ink tank using an ink containing a coloring material, the ink use-out property is more likely to be degraded. When the frozen ink is dissolved, water belonging to the class having the highest relative dielectric constant among the liquid components in the aqueous ink is frozen, and the water-soluble organic solvent having a relative dielectric constant lower than water is concentrated Become. As a result, the relative dielectric constant of the liquid component in the ink after freezing and melting is significantly reduced as compared to that before freezing. For this reason, since the pigment present in the vicinity of the concentrated water-soluble organic solvent is coagulated due to the decrease in electrostatic repulsion, the viscosity of the ink is increased. In addition, since the dye present in the vicinity of the concentrated water-soluble organic solvent is aggregated due to the decrease in solubility, the viscosity of the ink is increased. As a result, the outflow of the ink from the inside of the ink containing bag becomes difficult, and it is considered that the ink useability is further reduced.

Generally, the SP value is used as an indicator of the compatibility of the two-component solution, and the components having smaller differences in SP value have greater mutual solubility. The inventors of the present invention set the difference between the average SP value of the water-soluble organic solvent and the SP value of the resin that constitutes the ink storage bag to 2.0 (cal / cm ³ ) ^1/2 or more as a result of examination. It has been found that swelling of the ink containing bag can be suppressed even when freezing and melting of the ink are performed. The reason is presumed as follows. When this relationship is satisfied, even if the water-soluble organic solvent concentrated in the process of dissolving the frozen ink once contacts the resin constituting the ink storage bag, the SP value of the resin and the average of the water-soluble organic solvent The difference with the SP value is large, and the compatibility between the resin and the water-soluble organic solvent is difficult to increase. For this reason, it is considered that the swelling of the ink containing bag is suppressed and the ink useability is improved. Under the situation where the concentrated water-soluble organic solvent swells the ink storage bag, most of the water is frozen. Therefore, most of the components in liquid contact with the inner surface of the ink containing bag are water-soluble organic solvents. Because of this, the effect of water is small, so there is no need to consider the SP value of water.

<Ink tank>
The ink tank of the present invention is an ink tank for use in an ink jet recording apparatus, provided with an ink storage bag for storing ink therein. The ink containing bag does not have a mechanism in which the side wall portion shrinks into a predetermined shape such as crease processing. In addition, 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 constituting the ink tank of the present invention is a bag-like member whose side wall portion can shrink irregularly as the ink flows out. The ink containing bag is made of resin, and the ink is an aqueous 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 storage bag is 2.0 (cal / cm ³ ) ^1/2 or more. Hereinafter, the details of the ink tank of the present invention will be described.

(Ink storage bag)
FIG. 1 is a schematic view showing an 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 storage bag 1 housed in the housing 10 and in which the ink 2 is stored. The ink 2 stored in the ink storage 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 in communication with the ink supply port 3. The ink tank 50 of the present embodiment does not have a mechanism for adjusting the pressure inside the ink containing bag 1. Furthermore, the ink containing bag 1 constituting the ink tank 50 does not have a mechanism for the side wall portion to contract in 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 discharged with the ink 2 flowing out. The side wall of the wall shrinks and collapses irregularly. The side wall portion of the ink containing bag 1 refers to the “side portion” when the ink supply port 3 is directed upward in the direction of gravity. When the side wall portion of the ink containing bag 1 is contracted and irregularly crushed, the opposing inner surfaces of the side wall part 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 the inner surfaces of the ink containing bag 1 adjacent to each other is suppressed. Thus, the ink 2 in the ink containing bag 1 can be used up without waste (FIG. 1 (c)). Alternatively, even if the blocked portion 4 is formed in part of the ink storage bag 1, the amount of the remaining ink 5 can be reduced to a very small amount (FIG. 1 (b)) to improve the ink use-out property. Can. Note that, as described above, the present invention is to suppress the deterioration of the single-use property due to the adhesion of the inner surface, so the problem of the deterioration of the single-use property due to the adhesion does not occur. The “bottom” is not included in the “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 portion of the ink containing bag 1 contracts, the pressure inside the ink containing bag is obtained. In the case of an ink tank 60 having a mechanism for adjusting In the case of the ink tank 60, the side wall portion of the ink containing bag 1 contracts and collapses even if the remaining amount of the ink 2 decreases (FIG. 2B). Therefore, the ink 2 can be used up. Further, as shown in FIG. 3A, the pressure inside the ink containing bag is adjusted by applying pressure (negative pressure) to the ink containing bag 1 in the direction in which the ink containing bag 1 is expanded. The case of the ink tank 70 in which the spring 6 which is a mechanism is disposed in the ink containing bag 1 is assumed. In the case of the ink tank 70, since the blockage does not occur under the influence of the negative pressure applied by the spring 6, the block portion is not formed in the ink containing bag 1. For this reason, as shown in FIG. 3B, the ink can be used up without waste.

  Further, it is assumed that the ink tank 80 is provided with the ink containing bag 11 provided with the joint 12 which is a mechanism in which the side wall shrinks in a predetermined shape as shown in FIG. Fig.4 (a-1) is the figure which looked at the surface provided with the junction part 12 from the front, FIG. 4 (a-2) is the figure which looked at the surface provided with the junction part 12 from the horizontal direction. In the case of the ink tank 80, when the ink 2 flows out from the ink containing bag 11, the side wall part of the ink containing bag 11 contracts and the side wall part contracts in a predetermined shape (FIG. 4B). Therefore, the ink can be used up without waste.

  Further, it is assumed that the ink tank 90 is provided with the ink storage bag 13 provided with the fold line 14 which is a mechanism in which the side wall shrinks in a predetermined shape as shown in FIG. FIGS. 5 (a-1) and 5 (a-2) are views as viewed from the same direction as FIGS. 4 (a-1) and 4 (a-2). In the case of this ink tank 90, when the ink 2 flows out from the ink containing bag 13, the ink containing bag 13 is deformed along the fold line 14, and the side wall part contracts in a predetermined shape (FIG. 5B). Therefore, the ink can be used up without waste.

  The ink storage bag constituting the ink tank of the present invention is made of a resin which is easily shrunk with the outflow of the ink and which can sufficiently suppress the ink leakage. Specific examples of the resin include thermoplastic resins such as polyolefin (polyethylene, polypropylene and the like) and polystyrene; mixtures and modified products of these thermoplastic resins. Among them, it is preferable to use a polyolefin and a mixture containing a polyolefin. In particular, it is preferable to use a polyethylene resin. In addition, the composition of the resin constituting 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 forming the ink storage bag is 2.0 (cal / cm ³ ) ^1/2 or more, preferably 4.5 (cal). cal / cm ³ ) ^1/2 or more. It is preferable that the difference of the above-mentioned SP value is 10.0 (cal / cm ³ ) ^1/2 or less. Further, it is preferable that the SP value of the resin constituting the ink containing bag is 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). For example, ΔE _vap and V of the resin are as described in Coating No. No. 193 (1992) etc. can be referred to for reference.

（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 characteristics of the resin constituting the ink containing bag can be verified according to the method described below. The ink storage bag is cut into an appropriate size and used as a measurement sample 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. Also, the composition ratio of the unit can be determined from the type of unit confirmed and the chemical shift of nuclear magnetic resonance (NMR). And SP value of resin can be calculated | required by the Fedors method from the unit of resin calculated | required, 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 an elastic modulus of 500 N / mm ² or less is considerably softer than an ink containing bag used for a general ink jet ink tank. By using the soft ink containing bag, in the process of using the ink in the ink tank, the side wall portion naturally shrinks without using the mechanism for shrinking the ink containing bag, and the ink can flow out. The elastic modulus of the ink containing bag is preferably 50 N / mm ² or more. Further, in order to achieve the above-described elastic modulus, it is preferable to configure the ink storage bag with a single-layer resin.

  The elastic modulus of the ink containing bag is measured in accordance with JIS-K-7127 and JIS-K-7161. The modulus of elasticity is measured using a tensile tester, test mode: tension, displacement speed: 5 mm / min (displaced until sample yield point is observed), sample size: 150 mm long, 25 mm wide, 1 mm thick or less And distance between chucks: 100 mm. Under this condition, the elastic modulus is determined from the slope of XY in a region where the relationship of XY when the test force is X and the sample displacement is Y is linear, that is, the region before the yield point appears.

Conventional ink tanks use an ink storage bag in which a plurality of films are laminated to form a multilayer structure with emphasis on barrier properties, and an ink storage bag in which a metal such as aluminum is deposited on a resin film. The Such an ink containing bag has an elastic modulus far exceeding 500 N / mm ² and has a good barrier property, but is not soft. Therefore, it is necessary to take some measures to allow the ink to flow out. For example, in the case of the ink tanks described in Patent Documents 1 and 2, processing such as adhesion of a fold or an end portion is performed or internal pressure is adjusted in order to allow the ink to flow out without interruption even if it is a hard material. It has adopted a mechanism.

  The shape of the ink containing bag is preferably cylindrical. The present inventors examined the ink useability of the cylindrical and rectangular ink storage bags. As a result, it was found that the cylindrical ink storage bag is more excellent in ink exhaustion. In the cylindrical ink storage bag, the thickness of the side wall portion is likely to be uniform at the time of molding, so the ink storage bag is likely to be collapsed isotropically as the ink flows out. On the other hand, since the thickness of the side wall portion of the rectangular ink storage bag is difficult to be uniform compared to that of the cylindrical shape during molding, the ink is squeezed unevenly and clogged with the outflow of the ink. Ink is easy to collect. As a result, the ink useability may be reduced.

The ink storage amount of the ink storage bag can be appropriately set in accordance with the size of the ink jet recording apparatus and how often the replacement frequency of the ink tank after use is set. The ink storage capacity of the ink storage 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 storage bag can be appropriately set in accordance with the size of the ink jet recording apparatus, the ink storage capacity, and the like. The bottom area of the ink storage 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.

  From the viewpoint of ease of production and cost, the ink containing bag is preferably produced by a molding method such as a blow molding method. 6A, 6B, and 6C are schematic views showing the steps of manufacturing the ink storage bag by the blow molding method. As shown in FIG. 6A, first, a molten resin as a raw material for the ink storage bag is extruded into the mold 300 to form a pipe-like parison 301 (FIG. 6A (a-1)). Next, a gas is fed into the parison 301 from the direction of the arrow A, and the expanded parison 301 is pressed against the arrow direction, that is, the inner wall of the mold 300 (FIG. 6A (a-2)). The parison 301 is cooled to manufacture a hollow ink storage bag 21 having a shape in which the internal shape of the mold 300 is copied (FIG. 6A (a-3)).

  In FIG. 6B, a process of manufacturing the cylindrical ink storage bag 31 is shown. Similarly to the process shown in FIG. 6A, first, the molten resin is extruded into the mold 310 to form the parison 302 (FIG. 6B (b-1)). Next, a gas is fed into the interior of the parison 302, and the expanded 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 storage bag 31 having a shape in which the internal shape of the mold 310 is copied (FIG. 6B (b-3)).

  FIG. 6C shows a process of manufacturing the square ink storage bag 41. As in the process shown in FIG. 6A, first, the molten resin is extruded into a mold 320 to form a parison 303 (FIG. 6C (c-1)). Next, a gas is fed into the parison 303, and the expanded 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 storage bag 41 having a shape in which the internal shape of the mold 320 is copied (FIG. 6C (c-3)). As shown in FIG. 6C, when the rectangular ink storage bag 41 is manufactured by the blow molding method, the corner 305 thicker than the other portions is formed (FIG. 6C (c-2)), and the thickness of the side wall is uniform. It is difficult to become. Therefore, 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 appropriate rigidity. Examples of the material of the housing include thermoplastic resins such as polyester, polycarbonate, polyolefin (polyethylene, polypropylene and the like) and polyphenylene ether; and mixtures and modified products of these thermoplastic resins. The shape of the housing is preferably the same as that of the ink containing bag. Further, it is preferable to provide an air communication port in the housing in order to maintain the pressure inside the housing equal to the atmospheric pressure by taking in air from the outside in conjunction with the contraction of the ink containing bag disposed inside the housing.

(ink)
The ink stored in the ink storage bag of the ink tank of the present invention is an aqueous ink for inkjet 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 storage bag is 2.0 (cal / cm ³ ) ^1/2 or more. The ink does not have to be a so-called "curable ink". Thus, the ink may not contain compounds such as polymerizable monomers that can be polymerized by the addition of external energy. Hereinafter, the components constituting the ink and the physical properties of the ink will be described in detail.

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

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

  Examples of the dispersion method of the pigment include resin dispersion pigments using a resin as a dispersant, and self-dispersion pigments in which a hydrophilic group is bonded to the particle surface of the pigment. Further, 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 covered or encapsulated with a resin or the like can be used. However, when a pigment is used as a coloring material, a resin-dispersed pigment dispersed by a self-dispersing pigment or a resin dispersant physically adsorbed on the particle surface of the pigment (that is, a resin other than a resin-bound pigment or microcapsule pigment) Dispersed pigments are preferred.

  As a resin dispersant for dispersing the pigment in the aqueous medium, it is preferable to use one capable of dispersing the pigment in the aqueous medium by the action of the anionic group. As the resin dispersant, a resin as described later, in particular, 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 by mass ratio to the content (% by mass) of the resin dispersant.

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

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

[Water-soluble organic solvent]
The ink is an aqueous 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 storage bag is 2.0 (cal / cm ³ ) ^1/2 or more. As the water-soluble organic solvent, any of the alcohols, (poly) alkylene glycols, glycol ethers, nitrogen-containing compounds, sulfur-containing compounds and the like that can be used for ink jet inks can be used. The content (% by mass) of the water-soluble organic solvent in the aqueous ink is preferably 3.00% by mass or more and 50.00% by mass or less based on the total mass of the ink, and is 10.00% by mass or more and 50. More preferably, it is at most 00% by mass. Usually, the “water-soluble organic solvent” is a liquid, but in the present invention, one that is solid at 25 ° C. (ordinary temperature) is also included in the water-soluble organic solvent for convenience. Specific examples of the water-soluble organic solvent solid at 25 ° C., which is commonly used for aqueous inks, will be described later.

  By maintaining the existing state of the coloring material in the process of dissolving the ink once frozen, it is possible to further improve the single-use performance 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 to satisfy the relationship of the SP value described above and to have a water-soluble organic solvent in a certain ratio to the coloring material. For this reason, the content (% by mass) of the water-soluble organic solvent in the ink is preferably 1.0 or more by mass ratio with respect to the content (% by mass) of the color material. When the mass ratio is 1.0 times or more, the water-soluble organic solvent having a molecule larger than water with respect to the component excluded to the outside of the crystal of water when the ink is frozen to some extent with respect to the coloring material Exists. Therefore, the aggregation of the coloring material is suppressed by solvation, and it is easy to suppress the decrease in the ink use-up performance. The above 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 amount of the water-soluble organic solvent is not too large relative to that of the coloring material, so excessive aggregation of the coloring material is suppressed, and the deterioration of the ink use-up performance is suppressed. It will be easier.

[SP value]
Aqueous inks for inkjet generally contain a plurality of water-soluble organic solvents. For this reason, it is suitable to catch the SP value of the water-soluble organic solvent in the ink used for the ink tank of the present invention by the concept of “average SP value”. The average SP value is a value obtained by multiplying the SP value specific to the water-soluble organic solvent by the ratio (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 for the solvent and integrated. When the water-soluble organic solvent contained in the ink is only one kind, the SP value of the 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 (total 25.0 parts by mass) is as follows. The numerical value in parentheses is the SP value (unit is 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 the “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 10.5 (cal / cm ³ ) or less. / cm ^{3) 1/2} or more 16.0 (cal / cm ³⁾ and still more preferably ^1/2 or less. In addition, 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 value by the Fedors method of the water-soluble organic solvent generally used for the aqueous ink for inkjet is shown below, omitting a unit (cal / cm ³ ) ^1/2 . Glycerin (16.4), 1,3-propanediol (16.1), trimethylolpropane (15.9), 1,4-butanediol (15.0), diethylene glycol (15.0), ethylene glycol (15.0) 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-pentane (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 Butyl ether (10.5), triethylene glycol monobutyl ether (10.3), tetraethylene glycol monobutyl ether (10.2), polyethylene glycol with a number average molecular weight of 1,000 (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 to be 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.

[Dielectric constant]
As described above, in the case of the ink tank using the ink containing the coloring material, the ink exhaustion tends to be deteriorated. Once the water-soluble organic solvent is concentrated in the process of melting the frozen ink, the pigment present in the vicinity of the concentrated water-soluble organic solvent is coagulated due to a decrease in electrostatic repulsion, and the viscosity of the ink increases. . Further, the dye present in the vicinity of the concentrated water-soluble organic solvent is relatively lowered in polarity due to the absence of highly polar water, and is aggregated due to the decrease in solubility to increase the viscosity of the ink. As a result of the above, it becomes difficult to discharge the ink in the ink containing bag, and it becomes easy to reduce the ink use-out performance. Therefore, in consideration of the interaction with the coloring material in the ink, in order to suppress the increase in viscosity of the ink and further improve the ink use-out property, the electrostatic charge of the pigment using a water-soluble organic solvent having a high relative dielectric constant It is preferable to maintain the repulsive force and the solubility of the dye. Specifically, the average relative 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 also on the relative dielectric constant.

  The relative dielectric constant of the water-soluble organic solvent or water can be measured under the condition of a frequency of 10 kHz using a dielectric constant meter (for example, trade name “BI-870” (manufactured by BROOKHAVEN INSTRUMENTS CORPORATION) or the like). The relative dielectric constant of the water-soluble organic solvent which is solid at a temperature of 25 ° C. is the value calculated from the following formula (A) by measuring the relative dielectric constant of the 50 mass% aqueous solution. Usually, "water-soluble organic solvent" means a liquid, but in the present invention, those which are solid at 25 ° C. (ordinary temperature) are 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% by} 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. that are generally used for aqueous inks include 1,6-hexanediol, trimethylolpropane, ethylene urea, urea, polyethylene glycol having a number average molecular weight of 1,000, etc. it can.

The reason for calculating the relative dielectric constant of the water-soluble organic solvent which is solid at 25 ° C. from the relative dielectric constant of the 50% by mass aqueous solution is as follows. Among water-soluble organic solvents that are solid at 25 ° C., those that can be constituents of aqueous inks include those in which preparation of a high concentration aqueous solution exceeding 50% by mass is difficult. On the other hand, in a low concentration aqueous solution of 10% by mass or less, the relative dielectric constant of water becomes dominant, and it is difficult to obtain a probable (effective) relative dielectric constant value of the water-soluble organic solvent. Then, when the present inventors examined, most of the water-soluble organic solvents which are solid at 25 ° C. used for the ink can prepare an aqueous solution to be measured, and the calculated relative 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 relative dielectric constant of the water-soluble organic solvent which is solid at 25 ° C. is calculated from the relative dielectric constant of the 50% by mass aqueous solution and used. Even for water-soluble organic solvents that are solid at 25 ° C, their solubility in water is low, and for those that can not prepare a 50% by mass aqueous solution, use an aqueous solution with a saturated concentration to calculate the above ε _sol The value of the relative dielectric constant calculated is used for convenience.

  The average relative dielectric constant is a value obtained by multiplying the ratio (mass%) of the water-soluble organic solvent to the total amount of the water-soluble organic solvent in the ink by the specific dielectric constant specific to the water-soluble organic solvent. It means the value calculated and integrated for the organic solvent. When only one type of water-soluble organic solvent is contained in the ink, the relative dielectric constant of the 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 (total 25.0 parts by mass) is as follows. The numerical values in parentheses are the relative dielectric constants of the respective water-soluble organic solvents.
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 relative dielectric constant of the water-soluble organic solvent in the “ink 1” can be calculated as follows.
Average dielectric constant = 42.3 × 11.0 / 25.0 + 22.7 × 5.0 / 25.0 + 28.0 × 5.0 / 25.0 + 14.8 × 2.0 / 25.0 + 4.6 × 2 .0 / 25.0 = 30.3

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

  The dielectric constants of water-soluble organic solvents generally used in 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 (32.3). 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. ), 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), number Polyethylene glycol having an 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), polyethylene glycol having a number 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-hexanediol (7.1), polyethylene glycol having a number average molecular weight of 1,000 (4.6). The relative dielectric constant of each water-soluble organic solvent to be 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 to be 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 described below. The type of water-soluble organic solvent can be confirmed by diluting an appropriate amount of ink with methanol and qualitatively analyzing it by gas chromatography / mass spectrometry (GC / MS). Furthermore, the content of the water-soluble organic solvent can be confirmed by an absolute calibration curve method using a standard solution of the component to be analyzed. Then, the average SP value and the average relative dielectric constant of the water-soluble organic solvent in the ink can be determined from the type and the content of the water-soluble organic solvent confirmed.

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

  The resin can be added to the ink (i) in order to stabilize the dispersed state of the pigment, that is, as a resin dispersant or its aid. In addition, (ii) it can be added to the ink to improve various characteristics of the image to be recorded. As a form of resin, a block copolymer, a random copolymer, a graft copolymer, and these combination etc. can be mentioned. The resin may be a water-soluble resin that can be dissolved in an aqueous medium, or may be resin particles dispersed in an aqueous medium. The resin particles do not need to contain a coloring material. Further, it is preferable that the resin particles can be dispersed without using a resin dispersant, that is, they are self-dispersible.

  In the present specification, "the resin is water-soluble" means that when the resin is neutralized with an alkali equivalent to the acid value, the resin is aqueous without forming particles whose particle size can be measured by the dynamic light scattering method. 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 (solid content of resin: 10% by mass) containing a resin neutralized with an alkali equivalent to an acid value (sodium hydroxide, potassium hydroxide or the like) is prepared. Next, the prepared liquid is diluted 10 times (volume basis) with pure water to prepare a sample solution. And when the particle diameter of resin in a sample solution is measured by a dynamic light scattering method, when the particle | grains which have a particle diameter are not measured, it can be judged that the resin is water solubility. 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 a particle size distribution measuring apparatus, a particle size analyzer (for example, trade name “UPA-EX150” manufactured by Nikkiso Co., Ltd.) by a dynamic light scattering method can be used. Of course, the particle size distribution measuring apparatus to be used and the measuring conditions are not limited to the above.

The acid value of the water-soluble resin is preferably 100 mg KOH / g or more and 250 mg KOH / g or less. The acid value of the resin constituting the resin particles is preferably 5 mg KOH / g or more and 200 mg KOH / 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, and 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 the dynamic light scattering method is preferably 100 nm or more and 500 nm or less.

  As resin, acrylic resin, urethane resin, olefin resin etc. can be mentioned. Among them, acrylic resins and urethane resins are preferable, and acrylic resins are more preferable.

  As an acrylic resin, what has a hydrophilic unit and a hydrophobic unit as a structural unit 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 preferable. These resins are likely to interact with the pigment, and can be suitably used as a resin dispersant for dispersing the pigment.

  The hydrophilic unit is a unit having a hydrophilic group such as an anionic group. The hydrophilic unit can be formed, for example, by polymerizing a hydrophilic monomer having a hydrophilic group. Specific examples of the hydrophilic monomer having a hydrophilic group include acid monomers having a carboxylic acid group such as (meth) acrylic acid, itaconic acid, maleic acid and fumaric acid, and anions such as anhydrides and salts of these acidic monomers And the like. As a cation which comprises the salt of an acidic monomer, ions, such as lithium, sodium, potassium, ammonium, organic ammonium, can be mentioned. The hydrophobic unit is a unit having no hydrophilic group such as an anionic group. The hydrophobic unit can be formed, for example, by polymerizing a hydrophobic monomer having no hydrophilic group such as an anionic group. Specific examples of the hydrophobic monomer include monomers having an aromatic ring such as styrene, α-methylstyrene and benzyl (meth) acrylate; methyl (meth) acrylate, butyl (meth) acrylate and (meth) acrylic acid 2 -(Meth) acrylic acid ester type monomers, such as ethylhexyl, etc. can be mentioned.

  The urethane resin can be obtained, for example, by reacting a polyisocyanate and a polyol. Further, it may be one further reacted with a chain extender. As an olefin resin, polyethylene, a polypropylene, etc. can be mentioned, for example.

[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 exchange water. The content (% by mass) of water in the aqueous 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. Similar to the water-soluble organic solvent, the surfactant also exists in the state of being excluded from the crystal of water at the time of freezing, the hydrophobic portion thereof faces the ink containing bag side, and the hydrophilic portion constitutes the ink. It is directed to the medium side and oriented to an ink containing bag. For this reason, when the surfactant is contained in the ink, the ink containing bag shrinks with the outflow of the ink, and the blockage of the ink containing bag is easily suppressed even when the inner surfaces of the ink containing bag approach each other. Useability 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 the surfactant include ionic surfactants such as anionic, cationic and amphoteric surfactants; and nonionic surfactants. Among them, nonionic surfactants are preferable. Since the nonionic surfactant has no charge, the interaction due to the van der Waals force with the ink containing bag similarly having no charge becomes stronger, and it is easy to be oriented to the ink containing bag. If surfactant is classified by constituent material, hydrocarbon type, fluorine type, silicone type, etc. can be mentioned. Among these, fluorine surfactants and silicone surfactants are preferable. In particular, nonionic fluorine-based surfactants and silicone-based surfactants can reduce the surface energy of the oriented ink storage bag particularly efficiently. Materials with low surface energy do not adhere well to other materials. Therefore, by containing a fluorine-based surfactant or a silicone-based surfactant in the ink, the inner surfaces of the ink containing bag can be made more difficult to adhere to each other, and the ink use-up performance can be further improved.

[Other additives]
In the ink, in addition to the above components, various additives such as an antifoamer, a pH adjuster, a viscosity adjuster, an antirust agent, an antiseptic agent, an antifungal agent, an antioxidant, a reduction inhibitor and the like as needed You may make it contain. Generally, these additives, including surfactants, are also considerably less in the ink and have less direct impact 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 targets for calculating the SP value and the relative dielectric constant.

<Ink jet recording apparatus>
An ink jet recording apparatus according to the present invention includes the above-described ink tank, and a recording head which discharges the ink supplied from the ink tank by an ink jet method. Hereinafter, the ink jet recording apparatus of the present invention will be described with reference to the drawings.

  FIG. 7 is a perspective view schematically showing an embodiment of the ink jet recording apparatus of the present invention. The inkjet recording apparatus 200 of the embodiment shown in FIG. 7 is a so-called serial type inkjet recording apparatus which performs recording operation by reciprocally scanning the recording head in the X direction (main scanning direction). The recording medium 101 is intermittently conveyed by the conveyance roller 107 in the Y direction (sub scanning direction). The carriage 103 is movably supported along a guide rail 105 disposed along the X direction, and is fixed to an endless belt 106 moving parallel to the guide rail 105. The endless belt 106 reciprocates by the driving force of the motor. The carriage 103 is reciprocally scanned in the X direction by the reciprocating motion of the endless belt 106.

  Similarly, the recording unit 102 mounted on the carriage 103 is reciprocally scanned in the X direction (main scanning direction). Then, the recording operation is performed by conveyance of the recording medium 101 in the Y direction and reciprocating scanning of the recording 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. Thereafter, the ink is discharged from the discharge port of the recording head provided in the recording unit 102. The ink jet recording apparatus of the present invention is also applicable to various methods such as a full line method and a serial scan method.

  EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, comparative examples, and reference examples, but the present invention is not limited at all by the following examples as long as the gist thereof is not exceeded. Those described as "parts" and "%" in terms of component amounts are on a mass basis unless otherwise specified.

<Manufacturing of Ink Tank Body>
The ink storage bag (bottom area 20 cm ² , height 16 cm, volume 320 mL) prepared by blow molding was stored in a polyethylene case to manufacture ink tank bodies 1 to 10 having the configuration shown in Table 1. Various physical properties were measured using a sample obtained by cutting out the manufactured ink storage bag into an appropriate size. The SP value of the resin was analyzed by the composition and calculated by the Fedors method. The elastic modulus of the ink containing bag was measured on 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 “table-type precision universal testing machine AGS-X” manufactured by Shimadzu Corporation), under the conditions of test type: tensile, distance between chucks: 100 mm, displacement speed: 5 mm / min. It measured by.

<Preparation of pigment dispersion>
(Pigment dispersion 1)
A mixture of 10.0 parts of pigment, 15.0 parts of an aqueous solution of resin, and 75.0 parts of pure water is placed in a batch-type vertical sand mill (manufactured by Imex) packed with 200 parts of 0.3 mm diameter zirconia beads. Dispersed for 5 hours with water cooling. As a pigment, a trade name "Chromoftar jet magenta 2BC" (manufactured by Ciba Specialty Chemicals) was used. As an aqueous solution of the resin, a styrene-ethyl acrylate-acrylic acid copolymer having an acid value of 150 mg KOH / g and a weight average molecular weight of 8,000 was dissolved in water containing potassium hydroxide equivalent to the acid value, The aqueous solution in which the content of the resin (solid content) was 20.0% was used. The mixture was pressure-filtered with a cellulose acetate filter (manufactured by Advantec) having a pore size of 3.0 μm to obtain a pigment dispersion 1. The content of the pigment in the pigment dispersion 1 was 10.0%, and the content of the resin was 3.0%.

(Pigment dispersion 2)
The aqueous solution (resin (solid content)) 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 as an aqueous solution of a resin The content was 20.0%). A pigment dispersion 2 was obtained in the same manner as the pigment dispersion 1 described above, except that an aqueous solution of this resin was used. The content of the pigment in the pigment dispersion 2 was 10.0%, and the content of the resin was 3.0%.

Preparation of Ink
Each component (unit:%) shown in Tables 2-1 and 2-2 is mixed, and after sufficiently stirring, pressure filtration is performed using a membrane filter (trade name "HDCII filter", manufactured by Pall) having a pore size of 1.2 μm. Each ink was prepared. The numerical value attached to polyethylene glycol is the number average molecular weight of polyethylene glycol. “Acetylenol E100” is a trade name of nonionic hydrocarbon surfactant manufactured by Kawaken Fine Chemicals Co., Ltd. “Zonil FS3100” is a trade name of a nonionic fluorosurfactant manufactured by DuPont. "BYK 348" is a trade name of nonionic silicone surfactant made by Bick Chemie.

<Evaluation>
The combination of the ink tank body and the ink shown on the left side of Table 3 was filled with the ink tank body to prepare an ink tank. The filling amount of the ink was 95% of the maximum storage amount of ink 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. Thereafter, the ink jet recording apparatus having the main part shown in FIG. 7 was set, and the ink was continuously discharged under the temperature condition of 25 ° C. until the ink was not supplied. The ink remaining amount at the time when the ink supply was stopped was measured, and the "ink consumption rate (%)" was calculated based on the following formula (2), and the ink use-out property was evaluated according to the evaluation criteria shown below. The results are shown in Table 3.
Ink consumption rate (%) = {(X−Y) / X} × 100 (2)
X: Amount of ink filled in the ink tank body (g)
Y: Remaining ink amount when ink supply is stopped (g)

[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, clogging occurred at a plurality of locations of the ink containing bag at the end of recording, and a sufficient amount of ink could not be supplied. The ink tanks of Reference Examples 1 and 2 had the pressure adjustment mechanism, so the ink could be used up. In addition, since the ink tanks of Reference Examples 3 and 4 have the shrinkage control mechanism, the ink can be used up.

Claims (8)

The inside of the ink containing bag is provided with an ink containing bag which does not have a mechanism for shrinking the side wall to a predetermined shape for containing ink therein, but which shrinks along with the outflow of the ink. An ink tank used in an ink jet recording apparatus, which does not have a mechanism for adjusting pressure,
The ink containing bag is made of resin,
The ink is an aqueous ink containing a coloring material and a water-soluble organic solvent,
A difference between an average SP value of the water-soluble organic solvent and an SP value of the resin constituting the ink containing bag is 2.0 (cal / cm ³ ) ^1/2 or more. . The ink according to claim 1, wherein a difference between an average SP value of the water-soluble organic solvent and an SP value of the resin constituting the ink containing bag is 4.5 (cal / cm ³ ) ^1/2 or more. tank.   The ink tank according to claim 1, wherein an average relative dielectric constant of the water-soluble organic solvent is 20.0 or more.   The content (% by mass) of the water-soluble organic solvent in the ink is 1.0 or more by mass ratio with respect to the content (% by mass) of the color material. The ink tank described in.   The ink tank according to any one of claims 1 to 4, wherein the ink further contains a surfactant. The ink bag of the elastic modulus, the ink tank according to any one of claims 1 to 5 is 500 N / mm ² or less.   The ink tank according to any one of claims 1 to 6, wherein the ink containing bag has a cylindrical shape. An ink tank according to any one of claims 1 to 7;
An ink jet recording apparatus, comprising: a recording head which ejects the ink supplied from the ink tank by an ink jet method.

Images