JP7182974B2 - 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. 2. An ink tank for use in an inkjet recording apparatus that does not have a mechanism for adjusting the internal pressure of the ink containing bag, wherein the ink containing bag is made of polyolefin resin, and the elastic modulus of the ink containing bag is 500 N/mm ² or less, the ink is an aqueous ink containing a coloring material and a resin, and the glass transition temperature of the resin contained in the ink is higher than that of the polyolefin resin constituting the ink containing bag. It is higher than the glass transition temperature, and the difference between the average SP value of the resin contained in the ink and the SP value of the polyolefin resin constituting the ink containing bag is 2.0 (cal/cm 3 ⁾ 1 ^{. /2} or more is provided.

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 inventors of the present invention have studied the ability to use up the ink of an ink tank provided with an ink containing bag containing ink containing a resin. As a result, it was found that when this ink tank is left in both high and low temperature environments, the problem of deterioration in ink usage efficiency (ink cannot be used up) is more likely to occur. For example, when transporting ink tanks by train or truck using a container that has no temperature control facility, the ink tanks are placed in a high temperature environment of about 50°C or a low temperature environment of about -20°C. state. The performance of ink tanks and ink must be designed to withstand such severe temperature changes.

For the ink tank, an ink storage bag made of polyolefin resin may be used from the viewpoint of flexibility and strength. When an ink tank having such an ink containing bag is placed in a high-temperature environment, thermal motion of the molecular chains forming the polyolefin resin increases. Polyolefin resins contain many portions where the molecular chains are close to each other and crystallized. By containing such a crystallized portion, the ink containing bag made of polyolefin resin exhibits a certain strength. Generally, the crystallinity of polyethylene is about 60% to 90%, and the crystallinity of polypropylene is about 40% to 70%.

When the thermal motion of the molecular chains constituting the polyolefin resin increases, the adjacent molecular chains are separated from each other, the degree of crystallinity of the polyolefin resin decreases, and the resin softens. A portion of the liquid component in the ink that is in contact with the ink containing bag made of the softened polyolefin resin penetrates into the inside from the inner surface of the softened polyolefin resin. When the ink tank is placed in a low-temperature environment after a high-temperature environment, the thermal motion of the molecular chains constituting the polyolefin resin decreases and the molecular chains come closer to each other, causing the polyolefin resin to shrink. At this time, most of the liquid component that has entered the interior of the polyolefin resin is pushed back into the ink, but part of the liquid component remains inside the polyolefin resin. As a result, the ink containing bag placed in an environment with large temperature changes is in a slightly softened state compared to the ink containing bag before being placed in an environment with large temperature changes.

In particular, the inventors of the present invention have found that when an ink tank having a polyolefin resin ink containing bag containing resin-containing ink is placed in an environment with large temperature changes, the ink containing bag is more likely to soften. I found out. A case is assumed in which an ink tank having a polyolefin resin ink containing bag containing resin-containing ink is stored in a high-temperature environment. In this case, not only the liquid component in the ink, but also the resin penetrates into the interior of the polyolefin resin forming the ink containing bag. When the ink tank is placed in a low temperature environment after a high temperature environment, most of the liquid component is pushed back into the ink due to the shrinkage of the polyolefin resin. Easy to stay. As a result, the crystallization of the polyolefin resin is inhibited by the resin derived from the ink that is incorporated into the molecular chains of the polyolefin resin that makes up the ink storage bag, and the degree of crystallinity decreases, making it easier for the ink storage bag to soften. be done. The side walls of the softened ink containing bag are likely to stick to each other in the process of being irregularly shrunk and crushed along with the supply of ink, and are partially clogged. As a result, the number of closed portions in the ink containing bag increases, and it is thought that the ability to use up the ink decreases.

Under such circumstances, the present inventors focused on the properties of the resin contained in the ink, and conducted further studies to improve the ink's usability. As a result, the inventors have found that the ink can be used up more efficiently by containing a resin having a glass transition temperature higher than that of the polyolefin resin forming the ink containing bag. A resin having a glass transition temperature higher than that of the polyolefin resin constituting the ink containing bag is less likely to inhibit the crystallization of the polyolefin resin even if it stays inside the polyolefin resin, so it is thought that softening of the ink containing bag is suppressed. .

<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 polyolefin resin, and the ink is water-based ink containing colorant and resin. The glass transition temperature of the resin contained in the ink is higher than the glass transition temperature of the polyolefin resin forming the ink containing bag. 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 resin having a relatively high glass transition temperature, 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 polyolefin resin such as polyethylene or polypropylene. The polyolefin resin may be a mixture of multiple types of polyolefins, and modified polyolefins may also be used. Among them, it is preferable to use a polyethylene resin. The polyolefin resin composition forming the ink containing bag may contain a filler such as glass, pigment, or mineral.

The glass transition temperature of the resin contained in the ink is higher than the glass transition temperature of the polyolefin resin forming the ink containing bag, preferably by 5° C. or more. The difference between the glass transition temperature of the resin contained in the ink and the glass transition temperature of the polyolefin resin forming the ink containing bag is preferably 300° C. or less, more preferably 200° C. or less. The glass transition temperature of the polyolefin resin is preferably -150°C or higher and 50°C or lower.

The difference between the average SP value of the resin contained in the ink and the SP value of the polyolefin resin forming the ink containing bag is preferably 2.0 (cal/cm ³ ) ^1/2 or more. The difference between the average SP value of the resin contained in the ink and the SP value of the polyolefin resin constituting the ink containing bag is preferably 10.0 (cal/cm ³ ) ^1/2 or less, and preferably 5.0. (cal/cm ³ ) ^1/2 or less is more preferable. The SP value of the polyolefin resin is preferably 5.0 (cal/cm ³ ) ^1/2 or more and 10.0 (cal/cm ³ ) ^{1/2 or} less.

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 polyolefin 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). Thereby, it is possible to confirm whether the resin constituting the ink containing bag is polyethylene, polypropylene, polyolefin composed of a plurality of units, or the like (type of unit). 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). The glass transition temperature of the polyolefin resin forming the ink containing bag can be measured by analyzing the same measurement sample as above using a differential scanning calorimeter (DSC). The SP value of the polyolefin resin composing the ink containing bag can be obtained by the Fedors method based on the above formula (1) from the resin unit and its composition ratio obtained as described above.

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 polyolefin 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 polyolefin 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 resin. The glass transition temperature of the resin contained in the ink is higher than the glass transition temperature of the polyolefin resin forming the ink containing bag. 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. 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, methods other than resin-bonded pigments and microcapsule pigments) (resin-dispersed pigment) is 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.

[resin]
The ink contains resin. The glass transition temperature of this resin is higher than the glass transition temperature of the polyolefin resin forming the ink containing bag. The ink may contain a plurality of resins, and in this case, at least one resin should have a higher glass transition temperature than the polyolefin resin forming the ink containing bag. 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. Among them, the resin contained in the ink is preferably at least one of (1) a water-soluble resin having a weight average molecular weight of 5,000 or more and (2) resin particles. A water-soluble resin having a relatively large weight-average molecular weight is preferable because it hardly penetrates into the polyolefin resin that constitutes the ink containing bag. Also, resin particles are preferable to water-soluble resin because they are less likely to penetrate into the polyolefin resin that constitutes the ink containing bag. 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.

The glass transition temperature of the resin contained in the ink is preferably 0° C. or higher and 100° C. or lower. Moreover, the difference between the glass transition temperature of the resin contained in the ink and the glass transition temperature of the polyolefin resin forming the ink containing bag is preferably 5° C. or more. If the difference in glass transition temperature is less than 5° C., the effect of suppressing the softening of the polyolefin resin due to the decrease in crystallinity may be reduced, and the effect of improving the ink use-up may be somewhat reduced. The difference in glass transition temperature is preferably 300° C. or less, more preferably 200° C. or less.

The difference between the average SP value of the resin contained in the ink and the SP value of the polyolefin resin forming the ink containing bag is preferably 2.0 (cal/cm ³ ) ^1/2 or more. If there is a moderate difference in SP value, the interaction between the resin contained in the ink and the polyolefin resin forming the ink containing bag is weakened. As a result, it is possible to more effectively prevent the resin in the ink from entering the polyolefin resin forming the ink containing bag, and it is possible to further improve the ability to use up the ink. The SP value difference is preferably 10.0 (cal/cm ³ ) ^1/2 or less, more preferably 5.0 (cal/cm ³ ) ^1/2 or less. The SP value of the resin contained in the ink is preferably 9.0 (cal/cm ³ ) ^1/2 or more and 12.0 (cal/cm ³ ) ^1/2 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.

The properties of the resin contained in the ink can be verified according to the following method. A measurement sample was obtained by adding an excess amount of acid to the ink and drying the precipitated resin. You can check the unit type. In addition, the type of unit can be confirmed from the nuclear magnetic resonance (NMR) chemical shift measured for a sample prepared by dissolving the measurement sample in deuterated dimethyl sulfoxide, and the composition ratio of the unit from the ratio of the integrated values can be asked for. Then, the SP value of the resin can be determined using the SP value (SP value according to the Fedors method) of the unit derived from the monomer from the obtained resin unit and its composition (mass) ratio. When the colorant contained in the ink is a pigment, the supernatant obtained by centrifuging the ink may be analyzed in the same manner. The glass transition temperature of the resin can be measured by analyzing the same measurement sample as above using a differential scanning calorimeter (DSC). The weight-average molecular weight of the resin can be measured by polystyrene-equivalent gel permeation chromatography (GPC) using a sample prepared by dissolving the same measurement sample as above in tetrahydrofuran.

Table 1 shows the physical properties of various common monomers. "Homopolymer glass transition temperature Tg (°C)" in Table 1 is the glass transition temperature of a monomer homopolymer measured using a differential scanning calorimeter (DSC) in accordance with JIS K 6240:2011. is. The glass transition temperature of the resin can be obtained from the glass transition temperature of the homopolymer of the monomers shown in Table 1 and the composition (mass) ratio based on the FOX formula. "SP value (cal/cm ³ ) ^1/2 of unit derived from monomer" in Table 1 is a value determined by the Fedors method. The SP value of the resin can be obtained from the SP value of the unit derived from the monomer shown in Table 1 and the composition (mass) ratio.

[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 can contain water or an aqueous medium that 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. Also, 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 based on the total mass of the ink. 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.

[Other additives]
In addition to the above ingredients, various other agents such as surfactants, antifoaming agents, pH adjusters, viscosity adjusters, rust inhibitors, antiseptics, anti-mold agents, antioxidants, and anti-reduction agents may be added to the ink. may contain additives.

<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 15 having the configurations shown in Table 2 were manufactured. Various physical properties were measured using a sample obtained by cutting the produced ink containing bag into a suitable size. The glass transition temperature of the resin was measured using a differential scanning calorimeter (trade name “DSC Q1000”, manufactured by TA Instruments). 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

<Synthesis of Resin>
(Resin 1-13)
After adding 100.0 parts of ethylene glycol monobutyl ether to a four-necked flask equipped with a stirrer, a reflux condenser, and a nitrogen gas introduction tube, nitrogen gas was introduced into the reaction system and stirred, and the temperature was raised to 110°C. warmed up. A mixture of the monomers shown in Table 3 (abbreviations are as shown in Table 1) and an ethylene glycol monobutyl ether solution containing 1.3 parts of t-butyl peroxide (polymerization initiator) were added dropwise to the flask over 3 hours. After aging for 2 hours, the ethylene glycol monobutyl ether was removed under reduced pressure to give a solid resin. The obtained resin is dissolved at 80 ° C. by adding potassium hydroxide equimolar to the acid value and an appropriate amount of ion-exchanged water, and resins 1 to 1 having a resin (solid content) content of 20.0% An aqueous solution of 13 was obtained. Resins 1 to 13 were all water-soluble resins.

(Resin particle 1)
A four-necked flask equipped with a stirrer, a reflux condenser, and a nitrogen gas inlet tube was prepared. In this flask, 0.3 parts of sodium lauryl sulfate (emulsifier), 65.6 parts of benzyl methacrylate, 28.0 parts of methyl methacrylate, 6.4 parts of acrylic acid, and 100.0 parts of ion-exchanged water are added, and the contents are emulsify the material. Into this flask, 10.0 parts of a 5% potassium persulfate aqueous solution was added dropwise over 3 hours. After aging for 2 hours, an appropriate amount of deionized water was added to obtain an aqueous dispersion of resin particles 1 having a resin (solid content) content of 20.0%. Resin Particle 1 had a glass transition temperature of 70° C., a weight average molecular weight of 400,000, and an SP value of 10.7 (cal/cm ³ ) ^1/2 .

<Ink preparation>
Each component (unit: %) shown in Tables 4-1 and 4-2 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. "Acetylenol E100" is a trade name of a surfactant manufactured by Kawaken Fine Chemicals.

<Evaluation>
The combination of the ink tank body and the ink shown on the left side of Table 5 was prepared, and the ink tank was prepared by filling the ink tank 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 for 10 cycles, one cycle being "70° C. for 3 hours, -30° C. for 3 hours". After leaving the ink tank at 25° C. for one day, it was set in an ink jet recording apparatus having the main part shown in FIG. 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 5 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 tanks of Comparative Examples 1 and 2, clogging occurred at a plurality of locations in the ink storage bag 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 (16)

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 polyolefin resin,
The elastic modulus of the ink containing bag is 500 N/mm ² or less,
the ink is a water-based ink containing a coloring material and a resin;
The glass transition temperature of the resin contained in the ink is higher than the glass transition temperature of the polyolefin resin constituting the ink containing bag,
A difference between an average SP value of the resin contained in the ink and an SP value of the polyolefin resin constituting the ink containing bag is 2.0 (cal/cm 3 ) ^1/2 or ^more . ink tank. 2. An ink tank according to claim 1, wherein the difference between the glass transition temperature of said resin contained in said ink and the glass transition temperature of said polyolefin resin constituting said ink containing bag is 5[deg.] C. or more. 3. An ink tank according to claim 2, wherein the difference between the glass transition temperature of said resin contained in said ink and the glass transition temperature of said polyolefin resin constituting said ink containing bag is 300[deg.] C. or less. 2. The difference between the average SP value of the resin contained in the ink and the SP value of the polyolefin resin forming the ink containing bag is 10.0 (cal/cm ³ ) ^1/2 or less . 4. The ink tank according to any one of items 1 to 3 . 5. The ink tank according to claim 1, wherein the resin contained in the ink is at least one of a water-soluble resin having a weight average molecular weight of 5,000 or more and resin particles. The ink tank according to any one of claims 1 to 5 , wherein the resin contained in the ink contains an acrylic resin. The ink tank according to any one of claims 1 to 6 , wherein the ink containing bag has an elastic modulus of 50 N/mm2 or ^more . 8. An ink tank according to any one of claims 1 to 7 , wherein the side walls of the ink containing bag contract irregularly as the ink flows out. 9. An ink tank according to any one of claims 1 to 8 , wherein said ink containing bag has a cylindrical shape. 10. An ink tank according to claim 9 , wherein said ink containing bag is isotropically crushed as ink flows out. The ink tank according to any one of claims 1 to 10 , wherein the polyolefin resin forming the ink containing bag contains polyethylene resin. 12. The ink tank according to any one of claims 1 to 11 , wherein the polyolefin resin forming the ink containing bag contains a filler. 13. The ink tank according to any one of claims 1 to 12 , wherein the ink containing bag is composed of a single layer of the polyolefin resin. 14. The ink tank according to any one of claims 1 to 13 , wherein the ink storage capacity of the ink storage bag is 100 mL or more and 1,000 mL or less. 15. The ink tank according to any one of claims 1 to 14 , wherein the ink containing bag is a blow-molded product. an ink tank according to any one of claims 1 to 15 ;
and a recording head that ejects ink supplied from the ink tank by an inkjet method.

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