Inkjet ink composition, inkjet recording method, and inkjet recording apparatus

Abstract

Provided are an ink jet ink composition, an ink jet recording method, and an ink jet recording apparatus which are capable of suppressing transfer of an obtained recorded matter and have excellent discharge reliability and miscibility. An inkjet ink composition includes: a pigment; an acetylene glycol-based surfactant, wherein the HLB value of the acetylene glycol-based surfactant is less than or equal to 5; a lactam compound having a lactam ring that is a 6-to 8-membered ring; a solvent component; the inkjet ink composition includes a solvent component, and a water-soluble resin dissolved in the solvent component, in which the content of the water-soluble resin is 0.3% by mass or more with respect to the total mass of the inkjet ink composition, and the solvent component includes water and is an aqueous ink.

Description

Technical Field

[0001] The present invention relates to an inkjet ink composition, an inkjet recording method and an inkjet recording device. Background Art

[0002] Inkjet recording methods, capable of recording high-definition images using relatively simple equipment, have seen rapid development in various fields. Among these, various studies have focused on issues such as the ejection reliability of ink compositions used for recording. For example, Patent Document 1 discloses an ink composition comprising a self-dispersible pigment, a resin, and an organic solvent, with the goal of providing an ink composition capable of suppressing the formation of aggregates within an ink container. The ink composition is intended for use in an ink container having a predetermined ink chamber and a predetermined ink inlet.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-061896.

[0006] However, when the aqueous ink composition is transported, ejected, or stacked within a recording device before it has fully dried, ink transfer is likely to occur. On the other hand, preventing such ink transfer can reduce ink ejection reliability or worsen compatibility with other ink components. Summary of the Invention

[0007] The inkjet ink composition of the present invention comprises: a pigment; an acetylene glycol surfactant having an HLB value of 5 or less; a lactam compound having a 6- to 8-membered lactam ring; a solvent component; and a water-soluble resin dissolved in the solvent component, wherein the content of the water-soluble resin is 0.3% by mass or more relative to the total mass of the inkjet ink composition, the solvent component contains water, and the inkjet ink composition is a water-based ink.

[0008] The recording method of the present invention includes a discharge step of discharging the above-mentioned inkjet ink composition from an inkjet head and causing it to adhere to a recording medium.

[0009] The recording apparatus of the present invention comprises: the inkjet ink composition described above; and an inkjet head for ejecting the inkjet ink composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 Table 1 shows the components of the ink compositions used in Examples and the evaluation results thereof.

[0011] Figure 2Table 2 shows the components of the ink compositions used in Examples and the evaluation results thereof.

[0012] Figure 3 Table 3 shows the components of the ink compositions used in Examples and the evaluation results thereof.

[0013] Figure 4 Table 4 shows the components of the ink compositions used in Examples and the evaluation results thereof.

[0014] Figure 5 This is a diagram showing an example of an inkjet recording apparatus used in the inkjet recording method of this embodiment.

[0015] Figure 6 This is a diagram showing an example of a continuous supply type ink container as an ink container.

[0016] Figure 7 This is a diagram showing an example of an ink cartridge as an ink container.

[0017] Figure 8 This is a diagram showing an example of an ink bottle as an ink container.

[0018] Explanation of symbols

[0019] 10. Recording device; 11. Conveying path; 12. Feeding section; 14. Conveying section; 16. Belt conveying section; 18. Recording section; 20. Fd discharge section; 22. Fd loading section; 24. Reversing path section; 26. Fu discharge section; 28. Fu loading section; 30. Feed tray; 32. Feed roller; 34. Conveying drive roller; 36. Conveying driven roller; 38. First roller; 40. Second roller; 42. Endless belt; 42a. Upper section of the endless belt; 44. Support body; 46. Head holder; 48. Inkjet head; 50. First branch section; 52. Reversing path; 54. Second branch section; 56. Discharge Roller pair; 64, discharge drive roller; 68, drive shaft; 76, loading surface; 78, convex portion; 80, first force-applying member; 82, second force-applying member; 84, 86, support shaft; P, recording medium; E, gas-liquid interface; I, ink; 601, continuous supply type ink container; 602, ink supply port; 603, atmosphere supply port; 604, ink receiving chamber; 605, ink flow path; 606, sub-tank; 607, inkjet head; 701, ink cartridge; 702, ink supply port; 703, atmosphere communication port; 704, receiving chamber; 801, ink bottle; 802, container body; 803, ink replenishing port. DETAILED DESCRIPTION

[0020] Below, as needed, refer to the attached Figure 1While an embodiment of the present invention (hereinafter referred to as the "present embodiment") will be described in detail, the present invention is not limited thereto and various modifications are possible without departing from the spirit and scope of the present invention. In the drawings, identical elements are denoted by the same reference numerals, and duplicate descriptions are omitted. Furthermore, positional relationships, such as up and down, left and right, are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to those shown.

[0021] 1. Inkjet ink composition

[0022] The inkjet ink composition according to the present embodiment (hereinafter referred to as the "ink composition") includes: a pigment; an acetylene glycol surfactant having an HLB value of 5 or less; a lactam compound having a 6- to 8-membered lactam ring; a solvent component; and a water-soluble resin dissolved in the solvent component, wherein the content of the water-soluble resin is 0.3% by mass or greater relative to the total mass of the inkjet ink composition, the solvent component contains water, and the inkjet ink composition is a water-based ink.

[0023] When recording using a water-based ink composition, if the ink composition adheres to the recording medium and is immediately conveyed and discharged via a conveyor roller, there is a problem of transfer due to the undried ink composition adhering to the conveyor roller or adhering to the contact surface of the previous or next recorded material being discharged. One reason for this transfer is believed to be insufficient penetration of the ink composition into the recording medium. Therefore, as a method to suppress transfer, it is desirable to improve the permeability of the ink. By rapidly penetrating the recording medium, the ink is thoroughly infiltrated into the recording medium before the recording medium contacts the conveyor roller or another recording medium, thereby suppressing transfer.

[0024] Furthermore, it is believed that even if the ink composition is fully penetrated and absorbed by the recording medium, the ink may still transfer to the roller within the recording device or another recording medium before drying. Regarding this, it is believed that by adding resin particles as a fixing resin to the ink composition, the ink's fixability can be improved, thereby inhibiting the transfer of the ink. However, when stored in the ink container, this resin tends to aggregate at the gas-liquid interface and easily form foreign matter, thus creating new technical issues with ejection reliability. Therefore, as a method for inhibiting transfer without compromising ejection reliability, it is desirable to use an alternative component to this resin.

[0025] Furthermore, transfer occurs early after the ink adheres to the recording medium and occurs before the ink is fully dried. Therefore, it is believed that by forming a film on the surface of the recording medium with the ink adhered, even before the adhered ink is fully dried, transfer can be effectively suppressed when the ink adheres to the recording medium and before the ink has fully dried.

[0026] In this embodiment, an acetylene glycol surfactant having an HLB value of 5 or less is used as a component to enhance the permeability of the ink. Furthermore, by using a water-soluble resin that is less likely to form foreign matter at the gas-liquid interface, a film can be formed on the surface of the recording medium at an early stage without reducing ejection reliability, thereby suppressing transfer.

[0027] Furthermore, acetylene glycol surfactants with an HLB value of 5 or less, which improve ink permeability, tend to phase separate easily in the ink composition, reducing ejection stability. Therefore, a lactam compound having a 6- to 8-membered lactam ring is used in combination. This suppresses phase separation and improves ejection reliability. This makes it possible to provide an ink composition with excellent ejection reliability, transfer resistance, and compatibility.

[0028] The ink composition of the present invention is believed to have excellent ejection reliability, transfer resistance, and compatibility as a synergistic effect achieved by combining the above-mentioned components. However, the reason for this is not limited to the above.

[0029] The inkjet ink composition of this embodiment is an ink ejected and used by an inkjet recording device. In such an inkjet recording device, the ink tank supplied with the ink composition, or the ink container supplying the ink composition to the inkjet recording device, preferably has a structure that generates a gas-liquid interface between the ink composition and a gas, i.e., an ink liquid surface. As described above, the presence of a gas-liquid interface is particularly prone to technical problems related to ejection reliability. Therefore, the effects of the present invention are more effective when using such an ink tank or ink container.

[0030] The ink tank is not particularly limited, but examples thereof include a tank equipped in a recording apparatus such as a continuous supply type ink container or a sub-tank to which an inkjet ink composition is supplied.

[0031] Here, in Figure 6 An example of the structure of the continuous supply type ink container and the sub-tank is shown in FIG. Figure 6 In the figure, the structure of the continuous supply type ink container and the sub-tank is shown together, but the recording device only needs to have at least one of the sub-tank and the continuous supply type ink container. The continuous supply type ink container is a type of ink tank, namely, a continuous supply type ink tank.

[0032] like Figure 6As shown, a continuous supply type ink container 601 includes an ink containing chamber 604 having an ink supply port 602 and an atmospheric air supply port 603. Air supplied from the atmospheric air supply port 603 is supplied from the lower portion of the ink containing chamber 604 as air G, moves upward within the ink containing chamber 604, and is supplied to an air layer K located above the layer of ink I within the ink containing chamber 604, thereby becoming part of the air layer.

[0033] The continuous supply ink container 601 has a structure that enables continuous printing by injecting (replenishing) an ink composition. When the continuous supply ink container is filled with ink, an ink liquid surface (gas-liquid interface) E is generated in the container.

[0034] The ink level is the interface between the ink layer (ink layer) in the ink tank or ink container and the air layer above the ink layer. The ink level is a horizontal surface and has a predetermined area.

[0035] If the recording device includes a continuous-supply ink container, supplying ink from the ink supply port 602 to the continuous-supply ink container prevents the ink in the continuous-supply ink container from decreasing below a predetermined level, enabling continuous printing. Ink supply from the ink supply port 602 can be supplied from, for example, an ink bottle, as described later. If the recording device includes a continuous-supply ink container, the recording device does not need to include a sub-tank; ink can be supplied directly to the inkjet head from the ink flow path 605.

[0036] In addition, if Figure 6 As shown, the sub-tank 606 is a relay tank for the ink composition provided in the recording apparatus and can be connected to the continuous supply type ink container 601 via the ink flow path 605 .

[0037] When the recording device has a sub-tank, even if the ink supply to the sub-tank is temporarily interrupted, printing can be temporarily performed using the ink in the sub-tank. Figure 6 As shown, the recording device can be operated from a continuous-supply ink container or from an ink cartridge (described later). In the case of using an ink cartridge, the recording device includes an ink supply mechanism (cartridge mounting mechanism) (not shown). The ink cartridge is mounted on the ink supply mechanism, and ink is supplied from the ink cartridge to the sub-tank via the ink supply mechanism and ink flow path. In this case, the recording device does not include a continuous-supply ink container.

[0038] In addition, the ink pressure for supplying the ink composition to the inkjet head 607 may be generated according to the height of the sub-tank 606. The direction in which the ink is supplied to the inkjet head is IK.

[0039] The sub-tank is more flexible in placement than a continuous supply type ink container and can be easily placed at a position where the ink composition can be easily supplied to the inkjet head 607 , and is therefore preferable.

[0040] In this auxiliary tank 606, as Figure 6 As shown, similarly, an ink liquid surface (gas-liquid interface) is generated at the boundary between the ink layer I in the sub-tank and the air layer above it.

[0041] The supply of ink from the ink tank to the inkjet head can be achieved, for example, by generating ink pressure based on the relationship between the ink level in the inkjet head and the ink tank, or by generating ink pressure using an ink pump (not shown). The same applies to the supply of ink from the continuous supply ink container to the sub-tank when the recording device includes a sub-tank and a continuous supply ink container.

[0042] The ink container is not particularly limited, but examples thereof include containers such as ink cartridges and ink bottles that supply an inkjet ink composition to a structure included in a recording apparatus.

[0043] exist Figure 7 An example of the structure of the ink cartridge is shown in FIG. Figure 7 As shown, ink cartridge 701 is used in an ink supply mechanism (not shown) mounted on a recording device. The ink cartridge includes a storage chamber 704 having an ink supply port 702 and an air communication port 703. As the ink composition is used and the amount of ink I in storage chamber 704 decreases, air is supplied from air communication port 703, creating an air layer and an ink liquid surface (air-liquid interface) within storage chamber 704. The ink cartridge is preferably a foam-free type, and a non-encapsulated type is also preferred.

[0044] exist Figure 8 An example of the structure of the ink bottle is shown in FIG. Figure 8 As shown, an ink bottle 801 includes a container body 802 capable of containing an ink composition, and an ink refill port 803 attached to the top end of the container body 802. Although not particularly limited, for example, the ink refill port 803 of the ink bottle 801 can be inserted into the ink supply port 602 of a continuous supply ink container to supply the ink composition contained in the ink bottle 801 to the continuous supply ink container.

[0045] In the ink bottle, an ink liquid surface is generated at the boundary between an ink layer (not shown) and an air layer above the ink layer.

[0046] As described above, when the ink tank or ink container has an ink liquid surface, the maximum area of the ink liquid surface is preferably 400 mm. 2 More than, more preferably 500mm 2 More than 600mm, more preferably 2Above, especially preferably 700mm 2 In addition, the upper limit of the maximum area of the ink liquid surface also varies depending on the size of the recording device, etc., and is not particularly limited, but can be, for example, 1000 mm 2 The maximum area of the ink liquid surface is within the above range, which makes the effect of the present invention more effective. In addition, the maximum area of the ink liquid surface refers to the largest cross-sectional area in the horizontal cross section of the ink tank or ink container, etc., which contains the ink.

[0047] Hereinafter, the components constituting the ink composition of this embodiment will be described in detail.

[0048] Pigments

[0049] The ink composition contains a pigment. Examples of the pigment include self-dispersible pigments, which are obtained by introducing hydrophilic functional groups onto the pigment surface through a chemical reaction on the surface of the pigment particles, thereby imparting dispersion stability to the pigment and dispersing it. Examples of the hydrophilic functional groups include phosphorus-containing groups such as carboxyl groups and phosphonic acid groups, and sulfonic groups.

[0050] In addition, resin-dispersed pigments can be used, which use a dispersant resin as a resin. This dispersant resin adheres to and adsorbs on the pigment surface, thereby imparting dispersion stability to the pigment and dispersing it. From the perspective of improving ejection reliability, transfer resistance, and compatibility, self-dispersing pigments are preferably included.

[0051] Self-dispersible pigments do not require a dispersant such as a dispersant resin for dispersing the pigment. Even when the ink contains a large amount of pigment, the viscosity of the ink can be made relatively low, and the ejection stability and color development properties are excellent, which makes them preferable.

[0052] The pigments may be used alone or in combination of two or more.

[0053] Examples of self-dispersible pigments include azo pigments (e.g., azo lakes, insoluble azo pigments, condensed azo pigments, and chelated azo pigments), polycyclic pigments (e.g., phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, and quinolinonephthalein pigments), organic pigments such as nitro pigments, nitroso pigments, and aniline black; inorganic pigments such as carbon black (e.g., furnace black, heat lamp black, acetylene black, and channel black); metal oxides, metal sulfides, and metal chlorides; and extender pigments such as silica, calcium carbonate, and talc. Among these, carbon black is preferably used as the pigment from the perspective of more effectively and reliably achieving the effects of the present invention.

[0054] The pigment content is preferably 1.0% to 15% by mass, 3.0% to 10% by mass, or 5.0% to 8.0% by mass, relative to the total amount of the ink composition. By maintaining the pigment content within these ranges, the effects of the present invention tend to be more effectively and reliably achieved.

[0055] 1.2. Alkyne diol surfactants

[0056] The ink composition contains an acetylene glycol-based surfactant with an HLB value of 5 or less. The inclusion of an acetylene glycol-based surfactant with an HLB value of 5 or less (hereinafter referred to as "acetylene glycol-based surfactant," with HLB values being assumed to be 5 or less unless otherwise specified) improves the ink's permeability and provides excellent transfer resistance. Furthermore, the ink's ejection characteristics are improved, with enhanced ejection reliability and stability. However, acetylene glycol-based surfactants have low water solubility, tending to cause phase separation in the ink composition and reducing compatibility.

[0057] From the same viewpoint, the HLB value of the acetylene glycol surfactant contained in the ink composition is preferably 4 or less. The lower limit is 0 or more, and although there is no particular limitation, it is preferably 1 or more, and more preferably 2 or more.

[0058] Furthermore, as the acetylene glycol-based surfactant, one species may be used alone, or two or more species may be used in combination.

[0059] Furthermore, the acetylene glycol surfactant contained in the ink composition preferably contains a surfactant having an HLB value of 5 or less and a surfactant having an HLB value greater than 5, more preferably contains a surfactant having an HLB value of 5 or less and a surfactant having an HLB value of 7 or greater, and even more preferably contains a surfactant having an HLB value of 5 or less and a surfactant having an HLB value of 10 or greater. The upper limit of the HLB value is 20 or less, preferably 15 or less.

[0060] Among acetylene glycol surfactants, those with an HLB value of 5 or less tend to improve ink permeability more than those with an HLB value greater than 5. However, they also tend to more easily cause phase separation in the ink composition. Therefore, when including both a surfactant with an HLB value of 5 or less and a surfactant with an HLB value greater than 5 as an acetylene glycol surfactant, the content of the acetylene glycol surfactant in the ink can be increased, further improving the ink's ejection characteristics, permeability, and suppression of phase separation, which is preferable.

[0061] In this specification, the “HLB value (hydrophilic lipophilic balance)” refers to a value calculated by the Griffin method. Specifically, the HLB value of a surfactant can be calculated according to the following formula (H).

[0062]

[0063] Examples of commercially available acetylene glycol surfactants include Surfynol 104 (HLB = 4), Surfynol 420 (HLB = 4), Surfynol 82 (HLB = 4), Surfynol DF110D (HLB = 3), Surfynol 104S (HLB = 4), Surfynol 104PG50 (HLB = 4), Surfynol 420 (HLB = 4), Surfynol 82 (HLB = 4), and Surfynol MD-20 (HLB = 4) (all trade names, manufactured by Nissin Chemical Industry Co., Ltd.). From the perspective of more effectively and reliably achieving the effects of the present invention, the ink composition preferably contains Surfynol 104PG50 or Surfynol 420.

[0064] Specific examples of the acetylene glycol surfactant include 2,5,8,11-tetramethyl-6-dodecyl-5,8-diol or an alkylene oxide adduct thereof, 5,8-dimethyl-6-dodecyl-5,8-diol or an alkylene oxide adduct thereof, 2,4,7,9-tetramethyl-5-decyl-4,7-diol or an alkylene oxide adduct thereof, and 4,7-dimethyl-5-decyl-4,7-diol or an alkylene oxide adduct thereof.

[0065] The content of the acetylene glycol surfactant is preferably 0.01% to 3.0% by mass, 0.05% to 1.0% by mass, or 0.1% to 0.8% by mass, relative to the total amount of the ink composition. By adjusting the content of the acetylene glycol surfactant within this range, transfer resistance, ejection reliability, and ejection stability tend to be further improved.

[0066] The content of the acetylene glycol surfactant having an HLB value of 5 or less may also be set in the above range, which is preferred from the above viewpoint, more preferably from 0.1% by mass to 0.5% by mass, more preferably from 0.1% by mass to 0.4% by mass, and even more preferably from 0.1% by mass to 0.3% by mass.

[0067] The ink composition of this embodiment may contain other surfactants in addition to the acetylene glycol surfactant. Examples of such surfactants include fluorosurfactants and silicone surfactants. Examples of fluorosurfactants include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphates, and perfluoroalkyl ethylene oxide adducts. Furthermore, examples of silicone surfactants include polysiloxane compounds and polyether-modified organosiloxanes.

[0068] The content of other surfactants is not particularly limited as long as it does not inhibit the effects of the present invention, but is, for example, 0% by mass to 3% by mass, 0% by mass to 1% by mass, or 0% by mass to 0.1% by mass relative to the total amount of the ink composition.

[0069] 1.3. Lactam compounds

[0070] The ink composition contains a lactam compound having a 6- to 8-membered ring. The lactam compound has a structure in which a ring is formed by a dehydration condensation reaction between a carboxyl group and an amino group in the molecule. By including a lactam compound having a 6- to 8-membered ring in the ink composition, transfer resistance, ejection reliability, or ejection stability is improved. From the same viewpoint, a lactam compound having a 6- or 7-membered ring is preferred, and a lactam compound having a 7-membered ring is more preferred. In addition, in the lactam compound, an n-membered ring means that the number of atoms constituting the ring is n. As the lactam compound, one species may be used alone, or two or more species may be used in combination.

[0071] Specific examples of 6- to 8-membered ring lactam compounds include ε-caprolactam, δ-valerolactam, ω-heptylamide, and 5-(methylamino)valerolactam. ε-caprolactam is preferably included. The inclusion of ε-caprolactam in the ink composition tends to further improve transfer resistance, ejection reliability, and ejection stability.

[0072] In the ink composition, the mass ratio (A / B) of the content A of the acetylene glycol surfactant having an HLB value of 5 or less to the content B of the lactam compound is preferably 0.01 to 0.7, 0.02 to 0.6, or 0.03 to 0.5. It is more preferably 0.05 to 0.4, and even more preferably 0.1 to 0.3.

[0073] When the mass ratio (A / B) is within the above range, the transfer resistance, discharge reliability, and discharge stability tend to be further improved.

[0074] The content of the 6- to 8-membered ring lactam compound is preferably 0.1% to 15% by mass, 0.5% to 10% by mass, or 1.0% to 8.0% by mass, relative to the total amount of the ink composition. It is more preferably 2.0 to 5.0% by mass, and even more preferably 2.0 to 3.0% by mass.

[0075] When the content of the 6- to 8-membered ring lactam compound is within the above range, there is a tendency for transfer resistance, discharge reliability, and discharge stability to be further improved.

[0076] 1.4. Water-soluble resin

[0077] The ink composition includes a water-soluble resin dissolved in a solvent component. The inclusion of the water-soluble resin improves transfer resistance, ejection reliability, and ejection stability. Examples of the water-soluble resin include urethane resins, acrylic resins, polyalkylene oxide resins, polyvinyl alcohol resins, and carboxymethylcellulose resins. Of these, from the perspective of further improving transfer resistance, ejection reliability, and ejection stability, it is preferred to include a urethane resin or an acrylic resin as the water-soluble resin, and more preferably, a urethane resin. Furthermore, the water-soluble resin may be used singly or in combination of two or more.

[0078] The water-soluble resin used in this embodiment is a water-soluble resin that dissolves in the ink solvent components including water in the ink, and is not a resin that adheres to or adsorbs to the pigment. In addition, it is not a dispersant resin for dispersing ink components such as the pigment.

[0079] The water-soluble resin is a resin such that, when 1% by mass of the resin is mixed with water at room temperature of 25° C. and stirred, no dissolved residue is observed or the entire mixed solution becomes white and turbid.

[0080] The urethane resin is not limited as long as it is a water-soluble resin having a urethane bond in the molecule, and examples thereof include resins having repeating units derived from polyisocyanate and polyol.

[0081] Examples of the polyisocyanate include tetramethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and aliphatic polyisocyanates such as isophorone diisocyanate, dicyclohexylmethane-4,4-diisocyanate (hydrogenated MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate (hydrogenated TDI), bis(2-isocyanate), and methylcyclohexylene diisocyanate. alicyclic polyisocyanates such as 2,5- or 2,6-norbornane diisocyanate; aromatic polyisocyanates such as toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,5-naphthalene diisocyanate, xylene diisocyanate, and 1,3-phenylene diisocyanate.

[0082] Examples of the polyol include polyether polyols such as polyethylene glycol and polypropylene glycol, polyester polyols, and polycarbonate polyols that do not have an acid group, and polyols having a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, and the like as an acid group.

[0083] As acrylic resin, there is no limitation as long as it is a water-soluble resin obtained by polymerizing acrylic monomers such as (meth) acrylic acid and (meth) acrylic ester as a component. In addition, (meth) acrylic acid represents a concept including both "methacrylic acid" and "acrylic acid". As (meth) acrylic resin, there is no limitation, but for example, polymers of (meth) acrylic monomers such as (meth) acrylic acid and (meth) acrylic ester or copolymers of (meth) acrylic monomers and other monomers can be listed. From the viewpoint of making the effect of the present invention more effective and reliable, it is preferred to use styrene-acrylic resin as the water-soluble resin.

[0084] As the urethane resin and acrylic resin of this embodiment, it is preferable to use resins obtained by the method described in the Examples below. According to this method, the effects of the present invention can be achieved more effectively and reliably.

[0085] The acid value of the water-soluble resin is preferably 40-100 mgKOH / g, 40-90 mgKOH / g, 45-80 mgKOH / g, or 50-70 mgKOH / g. When the acid value of the urethane resin is within this range, transfer resistance, discharge reliability, and discharge stability tend to be further improved. The acid value can be determined by potentiometric titration.

[0086] The weight-average molecular weight of the water-soluble resin is preferably 5,000 to 150,000, 10,000 to 100,000, 15,000 to 50,000, or 20,000 to 30,000. By adjusting the weight-average molecular weight of the water-soluble resin within this range, transfer resistance, ejection reliability, and ejection stability tend to be further improved. The weight-average molecular weight can be determined by GPC.

[0087] The content of the water-soluble resin is 0.3% or more by mass, preferably 0.3% to 3.0% by mass, 0.3% to 2.0% by mass, or 0.3% to 0.8% by mass, relative to the total amount of the ink composition. When the content of the water-soluble resin is within this range, transfer resistance, ejection reliability, and ejection stability tend to be further improved.

[0088] 1.5. Resin particles

[0089] The ink composition preferably does not contain resin particles. The resin particles are resin emulsions, etc. The resin particles are resin particles in which a water-insoluble resin is dispersed in the ink.

[0090] The resin particles are not particularly limited as long as they are not water-soluble resins. Examples thereof include resin particles composed of urethane resins, acrylic resins, fluorene resins, polyolefin resins, rosin-modified resins, terpene resins, polyester resins, polyamide resins, epoxy resins, vinyl chloride resins, or ethylene vinyl acetate resins.

[0091] The ink composition preferably does not contain more than 0.1% by mass of resin particles relative to the total amount of the ink composition, more preferably does not contain more than 0.05% by mass, and even more preferably 0.00% by mass. By controlling the content of the resin particles within this range, the effects of the present invention can be achieved more effectively and reliably.

[0092] 1.6. Solvent composition

[0093] The ink composition is a water-based ink and contains water as a solvent component and may further contain an organic solvent.

[0094] 1.6.1. Water

[0095] As the water, water from which ionic impurities have been removed as much as possible is preferred. Such water is not particularly limited, and examples thereof include pure water and ultrapure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water.

[0096] The water content is preferably 55 to 99% by mass, more preferably 60 to 90% by mass, and even more preferably 65 to 80% by mass relative to the total amount of the ink composition.

[0097] 1.6.2. Water-soluble organic solvents

[0098] The ink composition preferably contains a water-soluble organic solvent as a solvent component. The inclusion of a water-soluble organic solvent improves transfer resistance and discharge stability of the ink composition and tends to suppress water evaporation during storage. Examples of water-soluble organic solvents include polyhydric alcohols, glycol ethers, nitrogen-containing solvents, ethers, and cyclic esters. Among these, polyhydric alcohols are preferably included as the water-soluble organic solvent.

[0099] The polyhydric alcohols have two or more hydroxyl groups in the molecule, and examples thereof include polyols and alkanediols.

[0100] Specific examples of the polyol compounds include ethylene glycol, propylene glycol, 1,2-propylene glycol, 1,2-butylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, trimethylolpropane, and glycerin.

[0101] Examples thereof include compounds having three or more hydroxyl groups in the molecule, compounds having an ether group (an intermolecular condensate of an alkanediol) in the skeleton, and alkanediols having 4 or less carbon atoms.

[0102] Among these, glycerin or triethylene glycol is preferably used from the viewpoint of achieving the effects of the present invention more effectively and reliably.

[0103] The ink composition preferably contains an alkanediol compound having 5 or more carbon atoms as a water-soluble organic solvent. The inclusion of an alkanediol compound having 5 or more carbon atoms tends to further improve transfer resistance, ejection reliability, and ejection stability. The upper limit of the carbon number is not particularly limited, but is, for example, 15 or less, 12 or less, or 10 or less. 1,2-alkanediol is preferred.

[0104] Specific examples of alkanediol compounds include 1,2-hexanediol, 1,2-pentanediol, 1,2-octanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,3-butanediol, 2-ethyl-1,3-hexanediol, 3-methyl-1,5-pentanediol, and 2-methylpentane-2,4-diol. Among these, 1,2-hexanediol is preferably included from the viewpoint of further improving transfer resistance, discharge reliability, and discharge stability.

[0105] Among these, the ink composition preferably contains a polyol with a normal boiling point of 280°C or higher, such as glycerin, as a water-soluble organic solvent. The inclusion of a polyol with a normal boiling point of 280°C or higher tends to further improve transfer resistance, ejection reliability, and ejection stability. The content of the polyol with a normal boiling point of 280°C or higher in the ink is preferably 0.5-10% by mass, more preferably 1.0-7.0% by mass, even more preferably 2.0-6.0% by mass, and particularly preferably 3.0-6.0% by mass.

[0106] The content of polyhydric alcohols including polyhydric alcohols having a normal boiling point of 280° C. or higher in the ink may be within the above-mentioned range.

[0107] The content of the water-soluble organic solvent is preferably 5.0% to 40% by mass, 10% to 30% by mass, 11% to 25% by mass, or 12% to 20% by mass, relative to the total amount of the ink composition. By adjusting the content of the water-soluble organic solvent within the above ranges, the effects of the present invention tend to be more effectively and reliably achieved.

[0108] The polyol content is preferably 5.0% to 30% by mass, 10% to 20% by mass, or 12% to 15% by mass, relative to the total amount of the ink composition. Within these ranges, the effects of the present invention tend to be more effectively and reliably achieved.

[0109] The content of the alkanediol is preferably 1.0% to 15% by mass, 2.0% to 10% by mass, or 3.0% to 7.0% by mass, relative to the total amount of the ink composition. Within these ranges, the effects of the present invention tend to be more effectively and reliably achieved.

[0110] 1.7. Inorganic oxide particles

[0111] The ink composition may contain inorganic oxide particles. Inorganic oxide particles refer to fine particles of an inorganic oxide dispersed in a dispersion medium. The inclusion of inorganic oxide particles generally tends to suppress curling of the recording medium. The inorganic oxide particles may be used singly or in combination of two or more.

[0112] The inorganic oxide particles are not particularly limited, but examples thereof include metal oxides such as silicon dioxide, aluminum oxide, titanium dioxide, zirconium oxide, antimony oxide, tin oxide, tantalum oxide, zinc oxide, cerium oxide, lead oxide, and indium oxide; metal nitrides such as silicon nitride, titanium nitride, and aluminum nitride; metal carbides such as silicon carbide and titanium carbide; metal sulfides such as zinc sulfide; metal carbonates such as calcium carbonate and magnesium carbonate; metal sulfates such as calcium sulfate and magnesium sulfate; metal silicates such as calcium silicate and magnesium silicate; metal phosphates such as calcium phosphate; metal borates such as aluminum borate and magnesium borate, or complexes thereof. From the perspective of more effectively and reliably achieving the effects of the present invention, silicon dioxide is preferred. Furthermore, the inorganic oxide particles may be in the form of salts.

[0113] Preferably, the content of the inorganic oxide particles is not more than 0.1% by mass, more preferably not more than 0.05% by mass, and even more preferably not more than 0.00% by mass, relative to the total amount of the ink composition. By keeping the content of the inorganic oxide particles within this range, the effects of the present invention tend to be more effectively and reliably achieved. The inorganic oxide particles may not be included.

[0114] 1.8. Betaine

[0115] Betaine refers to a compound having positive and negative charges at non-adjacent positions within the same molecule, with the positively charged atom not bonded to a dissociable hydrogen atom, forming an intramolecular salt, and the molecule as a whole having no charge. The betaine of this embodiment preferably has a quaternary ammonium cation as the positively charged site.

[0116] When the ink composition contains betaine, it is possible to prevent the ink composition from drying in the nozzles of the inkjet head and causing the ink composition to bend and fly or not be discharged, and the discharge stability tends to be excellent.

[0117] The number of carbon atoms in the betaine compound is preferably 4 to 12, more preferably 4 to 7, and even more preferably 4 to 6. When the number of carbon atoms in the betaine compound is within the above range, the discharge stability tends to be further improved.

[0118] Betaine is not particularly limited, but examples thereof include trimethylglycine, γ-trimethylaminobutyric acid, hominisine, trigonelline, carnitine, homoserine betaine, valine betaine, lysine betaine, ornithine betaine, alanine betaine, stachydrine, and glutamic acid betaine. Among these, trimethylglycine is preferred. This tends to further improve discharge stability. Betaines may be used alone or in combination of two or more.

[0119] The betaine content is preferably 0.0% to 15% by mass, 1.0% to 10% by mass, or 3.0% to 8.0% by mass, relative to the total amount of the ink composition. By adjusting the betaine content within these ranges, the effects of the present invention tend to be more effectively and reliably achieved.

[0120] 1.9. Other ingredients

[0121] The ink composition of this embodiment may contain components other than those described above as needed. Examples of such components include a pH adjuster, a wetting agent, and a chelating agent.

[0122] Examples of pH adjusters include inorganic acids (e.g., sulfuric acid, hydrochloric acid, nitric acid, etc.), inorganic bases (e.g., lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, etc.), organic bases (e.g., triethanolamine, diethanolamine, monoethanolamine, tripropanolamine), and organic acids (e.g., adipic acid, citric acid, succinic acid, etc.). From the viewpoint of more effectively and reliably achieving the effects of the present invention, triethanolamine is preferred.

[0123] The content of the pH adjuster is preferably 0.01 to 1.5 mass%, 0.05 to 1.0 mass%, 0.1 to 0.8 mass%, or 0.3 to 0.7 mass% relative to the total mass of the ink composition. When the content of the pH adjuster is within the above range, the effects of the present invention tend to be more effectively and reliably achieved.

[0124] 2. Recording medium

[0125] The recording medium used for recording with the ink composition of this embodiment is not particularly limited, and examples thereof include absorptive recording media, low-absorptive recording media, and non-absorptive recording media. Among these, absorptive recording media are preferred.

[0126] Absorbent recording media are not particularly limited, but examples include plain paper such as electrophotographic paper, which has high ink permeability, inkjet paper, and fabric. Examples of inkjet paper include specialized inkjet paper that includes an ink-absorbing layer composed of silica particles or alumina particles, or an ink-absorbing layer composed of a hydrophilic polymer such as polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP).

[0127] Low-absorption recording media are not particularly limited, but examples thereof include coated paper, coated paper, and cast-coated paper commonly used for offset printing, which have relatively low ink permeability. Non-absorption recording media are not particularly limited, but examples thereof include films or plates of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, and polyurethane; plates of metals such as iron, silver, copper, and aluminum; or metal plates or plastic films produced by vapor deposition of these metals, or plates of alloys such as stainless steel and brass; and recording media formed by bonding (coating) a film of a plastic such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, or polyurethane to a paper substrate.

[0128] 3. Inkjet recording method

[0129] The inkjet recording method of this embodiment includes a discharge step of discharging the ink composition from an inkjet head and depositing it on a recording medium, and may include other steps as needed, such as a transport step of transporting the recording medium.

[0130] In the ejection process, the ink composition is ejected from the inkjet head and deposited onto the recording medium. More specifically, a pressure generating unit within the inkjet head is driven to eject the ink composition from the nozzles within the pressure generating chamber of the inkjet head. This ejection method is also known as the inkjet method.

[0131] Examples of inkjet heads used in the ejection process include line heads that record in a line format and serial heads that record in a serial format. Line heads are preferred. Using a line head allows for faster recording speeds, shortening the time between ink adhering to the recording medium and contact with the transport roller or other recording medium, further enhancing the effects of the present invention.

[0132] In a line-type recording system using a line head, for example, an inkjet head having a width greater than the recording width of the recording medium is fixed to the recording device. The recording medium is then moved in a scanning direction (the direction in which the recording medium is transported), and ink droplets are ejected from the inkjet head nozzles in conjunction with this movement, thereby recording an image on the recording medium. Recording an image on one side of a recording medium is performed by performing a single scan, ejecting ink droplets from the nozzles while the recording medium is moved in the scanning direction.

[0133] In a serial-type printer using a serial head, for example, an inkjet head is mounted on a carriage that can move across the width of a recording medium. The carriage then moves in the main scanning direction (across the width of the recording medium), and ink droplets are ejected from the nozzles of the inkjet head in conjunction with this movement, thereby recording an image on the recording medium.

[0134] During the transport process, the recording medium is conveyed in a predetermined direction within the recording device. More specifically, a conveyor roller or belt installed within the recording device is used to transport the recording medium from the paper feed section to the paper discharge section. During this transport process, ink ejected from the inkjet head adheres to the recording medium, forming a recorded object. Transport can be continuous or intermittent.

[0135] 4. Inkjet recording device

[0136] The inkjet recording device of this embodiment includes the aforementioned ink composition and an inkjet head for ejecting the ink composition. The inkjet head comprises a pressure chamber for supplying ink and a nozzle for ejecting the ink. The inkjet recording device may further include a transport unit for transporting the recording medium. The transport unit comprises a transport roller or a transport belt disposed within the recording device.

[0137] The inkjet recording device may have a Figure 6 Any of the continuous supply type ink container or sub-tank as shown can also be constructed to be able to install the following Figure 7 The ink cartridge shown in FIG. 1 may also be configured to be capable of being Figure 8 In this case, the generation of foreign matter on the ink liquid surface can be suppressed, making the effect of the present invention more effective.

[0138] Below, refer to Figure 5 The inkjet recording device according to this embodiment is described. Figure 5 In the XYZ coordinate system shown in , the X direction represents the longitudinal direction of the recording medium, the Y direction represents the width direction of the recording medium in the conveyance path in the recording apparatus, and the Z direction represents the apparatus height direction.

[0139] The recording device 10 is, for example, a line inkjet printer capable of high-speed and high-density printing. It includes a feed unit 12 that stores recording media P, such as paper; a conveyor unit 14; a belt conveyor unit 16; a recording unit 18; an Fd (face down) discharge unit 20 (discharge unit); an Fd (face down) placement unit 22 (placement unit); a reversing path 24 (reversing conveying mechanism); a Fu (face up) discharge unit 26; and a Fu (face up) placement unit 28.

[0140] The feed unit 12 is disposed at the lower portion of the recording apparatus 10 . The feed unit 12 includes a feed tray 30 that stores recording media P and a feed roller 32 that feeds the recording media P stored in the feed tray 30 toward the transport path 11 .

[0141] Recording medium P stored in the feed tray 30 is fed along the conveyance path 11 to the conveyor unit 14 by the feed roller 32. The conveyor unit 14 includes a conveyance drive roller 34 and a conveyance driven roller 36. The conveyance drive roller 34 is driven to rotate by a drive source (not shown). In the conveyance unit 14, the recording medium P is nipped (engaged) between the conveyance drive roller 34 and the conveyance driven roller 36 and conveyed to the belt conveyor unit 16 located downstream of the conveyance path 11.

[0142] The belt conveying section 16 includes: a first roller 38, which is located on the upstream side of the conveying path 11; a second roller 40, which is located on the downstream side; an endless belt 42, which is rotatably mounted on the first roller 38 and the second roller 40; and a support body 44, which supports the upper section 42a of the endless belt 42 between the first roller 38 and the second roller 40.

[0143] The endless belt 42 is driven by the first roller 38 or the second roller 40 driven by a driving source (not shown) so as to move from the +X direction to the -X direction in the upper section 42a. Therefore, the recording medium P conveyed from the conveying section 14 is further conveyed on the belt conveying section 16 toward the downstream side of the conveying path 11.

[0144] The recording unit 18 includes a line-type inkjet head 48 and a head holder 46 that holds the inkjet head 48. Alternatively, the recording unit 18 may be a serial-type unit, in which the inkjet head 48 is mounted on a carriage that reciprocates along the Y-axis. The inkjet head 48 is positioned opposite the upper section 42a of the endless belt 42, which is supported by the support body 44. While the recording medium P is being conveyed along the upper section 42a of the endless belt 42, the inkjet head 48 ejects ink onto the recording medium P, performing recording. While recording is being performed, the recording medium P is conveyed downstream of the conveyance path 11 by the belt conveyor 16.

[0145] Furthermore, a "line-type inkjet head" refers to a head whose nozzle area, formed in a direction intersecting the conveyance direction of the recording medium P, covers the entire intersecting direction of the recording medium P. This head is used in an inkjet recording device that forms an image by fixing one of the head or the recording medium P and moving the other. Furthermore, the nozzle area of a line-type head in the intersecting direction may not cover the entire intersecting direction of all recording media P used by the inkjet recording device.

[0146] A first branching portion 50 is provided downstream of the conveyance path 11 of the belt conveyor 16. The first branching portion 50 is configured to switch between the conveyance path 11, which conveys the recording medium P to the Fd discharge unit 20 or the Fu discharge unit 26, and the reversing path 52 of the reversing path portion 24, which reverses the recording surface of the recording medium P and conveys the recording medium P again to the recording unit 18. Furthermore, the recording medium P, which is conveyed by switching to the reversing path 52 by the first branching portion 50, reverses its recording surface during conveyance along the reversing path 52 and is then conveyed again to the recording unit 18 with the surface opposite to the original recording surface facing the inkjet head 48.

[0147] A second branching portion 54 is further provided downstream of the first branching portion 50 along the conveying path 11 . The second branching portion 54 is configured to switch the conveying direction of the recording medium P to either the Fd discharge portion 20 or the Fu discharge portion 26 .

[0148] The recording medium P conveyed to the Fd discharge section 20 by the second branch section 54 is discharged from the Fd discharge section 20 and placed on the Fd placement section 22. At this time, the recording surface of the recording medium P is placed so that it faces the Fd placement section 22. Furthermore, the recording medium P conveyed to the Fu discharge section 26 by the second branch section 54 is discharged from the Fu discharge section 26 and placed on the Fu placement section 28. At this time, the recording surface of the recording medium P is placed so that it faces the side opposite to the Fu placement section 28.

[0149] While the above description uses an example of a line-type inkjet head, the inkjet recording device according to this embodiment may also be a printer using a serial-type inkjet head (serial printer). In a serial printer, printing is performed by moving the inkjet head in a direction intersecting the direction of transport while the recording medium is transported.

[0150] Example

[0151] Hereinafter, the present invention will be described in more detail using Examples and Comparative Examples. However, the present invention is not limited to the following Examples.

[0152] 1. Preparation of ink composition

[0153] exist Figures 1 to 4 In the table, Tables 1 to 4 showing the components of the ink composition are described.

[0154] The components listed in Tables 1 to 4 were added to a mixing tank, mixed and stirred, and then filtered through a membrane filter to produce the respective inkjet ink compositions. Unless otherwise specified, the numerical values for each component in each example in the tables represent mass %. Furthermore, the numerical values for pigment, inorganic oxide particles, and resin in the tables represent the mass % of the solids content of the pigment, inorganic oxide particles, and resin, respectively.

[0155] The details of the abbreviations or product components used in Tables 1 to 4 are as follows. The numbers written to the right of the solvent abbreviations represent the SP values of the solvents.

[0156] Pigment particles: self-dispersible pigments

[0157] CAB-O-JET300 (trade name, solid content 15%, manufactured by Cabot Corporation)

[0158] resin

[0159] Water-soluble urethane resin 1: prepared by the following method.

[0160] First, a four-necked flask equipped with a stirrer, thermometer, nitrogen inlet, and reflux tube was prepared. 41.7 parts by weight of isophorone diisocyanate, 40.1 parts by weight of polypropylene glycol (number-average molecular weight 2000), 13.2 parts by weight of dimethylolpropionic acid, and 200.0 parts by weight of methyl ethyl ketone were added to the flask and reacted at 80°C for 6 hours under a nitrogen atmosphere (primary reaction). Next, 0.6 parts by weight of ethylenediamine, 2.0 parts by weight of methanol, 2.4 parts by weight of dimethylolpropionic acid, and 100.0 parts by weight of methyl ethyl ketone were added. The residual isocyanate group ratio was confirmed by FT-IR, and the reaction was continued at 80°C until the desired residual ratio was reached (secondary reaction), yielding a reaction solution. After cooling the resulting reaction solution to 40°C, ion-exchanged water was added, and potassium hydroxide aqueous solution was added while stirring at high speed with a homomixer. The resulting solution was heated and decompressed to distill off the methyl ethyl ketone, yielding a solution containing water-soluble urethane resin 1.

[0161] The resulting water-soluble urethane resin 1 was prepared by adding hydrochloric acid to a liquid containing the water-soluble urethane resin 1 to precipitate the water-soluble urethane resin. The solution was then vacuum-dried at 40°C overnight. The resulting resin was dissolved in tetrahydrofuran to prepare a sample. The acid value of the water-soluble urethane resin 1 was measured by potentiometric titration using a potassium hydroxide-methanol solution. The acid value was 65 mgKOH / g. The polystyrene-equivalent weight-average molecular weight of the resulting water-soluble urethane resin 1, as measured by gel permeation chromatography (GPC), was approximately 21,000.

[0162] Water-soluble urethane resin 2: prepared by the following method.

[0163] Water-soluble urethane resin 2 was prepared by the same preparation method as water-soluble urethane resin 1, except that the amount of polypropylene glycol added was reduced and the amount of dimethylolpropionic acid added in the primary and secondary reactions was increased. Furthermore, the acid value and weight-average molecular weight were measured by the same methods as for water-soluble urethane resin 1. The acid value and weight-average molecular weight of water-soluble urethane resin 2 were found to be 75 mgKOH / g and approximately 21,000, respectively.

[0164] Water-soluble acrylic resin: prepared by the following method.

[0165] 20.0 parts of a styrene-acrylic acid copolymer with an acid value of 65 mgKOH / g and a weight-average molecular weight of 8000 was dissolved in ion-exchanged water using an amount of sodium hydroxide equivalent to the acid value to prepare an aqueous solution. The resulting aqueous solution was pressure-filtered using a Millipore filter (manufactured by Fujifilm) with a pore size of 3.0 μm. An appropriate amount of water was added to prepare an aqueous resin solution. The resin content in the aqueous solution was 20.0%.

[0166] Emulsion resin 1: X436 (trade name, styrene acrylic resin emulsion, Tg 33°C, acid value 33 mgKOH / g, manufactured by Starlight PMC)

[0167] Emulsion Resin 2: A styrene acrylic resin emulsion was prepared using styrene and acrylic acid monomers. It had a Tg of 10°C and an acid value of 33 mgKOH / g.

[0168] lactam compounds

[0169] HEP (N-hydroxyethylpyrrolidone)

[0170] 2-Pyrrolidone

[0171] ·ε-caprolactam

[0172] Inorganic oxide particles

[0173] Silica SI-30 (trade name, manufactured by JGC Catalysts & Chemicals Co., Ltd.)

[0174] Betaines

[0175] Trimethylglycine (anhydrous betaine, manufactured by Tokyo Chemical Industry Co., Ltd.)

[0176] Alkyne diol surfactants

[0177] Olfin E1010 (trade name, HLB value: 13-14, manufactured by Air Products)

[0178] Surfynol 104PG50 (trade name, HLB value: 4, manufactured by Nissin Chemical Industry Co., Ltd.)

[0179] Surfynol 420 (trade name, HLB value: 4, manufactured by Nissin Chemical Industry Co., Ltd.)

[0180] Other surfactants

[0181] BYK348 (trade name, silicone surfactant, manufactured by BYK Japan Co., Ltd.)

[0182] pH adjusters

[0183] Triethanolamine

[0184] Solvent composition

[0185] ·glycerin

[0186] Triethylene glycol

[0187] 1,2-Hexanediol

[0188] 2. Evaluation Method

[0189] A modified LX-10050 (product name, manufactured by Seiko Epson Corporation), a line inkjet printer with a line head, was prepared as a recording device. In the modified LX-10050, a stainless steel sub-tank was provided between the ink cartridge and the head. Figure 6 The continuous supply type ink container is removed, and a method of supplying ink from an ink cartridge through an ink supply mechanism and an ink flow path to the head is adopted.

[0190] The area of the ink liquid surface (gas-liquid interface) where the ink composition filled in the sub-tank contacts the air inside is 800 mm. 2 When printing, A4-sized copy paper, namely "Xerox P paper" (manufactured by Fuji Xerox Co., Ltd., weight per unit area: 64 g / m2) was used as the recording medium. 2 , paper thickness: 88μm).

[0191] 2.1. Reliability of ejection of foreign matter at the gas-liquid interface

[0192] In the above-mentioned device, after confirming that there were no non-discharging nozzles, the sub-tank was filled with 40cc of the ink composition and allowed to stand at 40°C for one week. Subsequently, printing was performed continuously using one of the line heads (600 nozzles) until 40cc of the ink composition was used. During this time, fresh, unused ink was supplied to the sub-tank to prevent it from running out. After printing, 0.5cc of ink was aspirated from the nozzles, and the nozzle surface was wiped (cleaned) with a rubber wiper. The number of cleanings required to eliminate non-discharging nozzles was evaluated as follows. After the evaluation, an inspection of the recording devices in which non-discharging nozzles were observed revealed foreign matter within the inkjet head and also in the sub-tank.

[0193] Evaluation Benchmarks

[0194] A: After cleaning three times or less, the nozzles that did not spray out disappear.

[0195] B: After cleaning more than four times and less than ten times, the nozzles that do not spray disappear

[0196] C: Nozzles that do not spray even after cleaning ten times

[0197] 2.2. Transfer resistance

[0198] Under the environment of temperature 25℃ and relative humidity 50%, the printing duty cycle is 100% and the ink adhesion amount is 4.5mg / inch. 2 Printing speed: 30 sheets / minute. Within the printable area, print a solid 1 x 1 cm pattern side by side at 1 cm intervals, placing the papers face down. Continue printing until the stacked paper reaches a thickness of 1 cm. Use the original, unused ink. Evaluation was performed using the following method based on ink transfer marks (ink smears) on the sides of the stacked paper.

[0199] Evaluation Benchmarks

[0200] A: When observed from a distance of 30 cm from the stacked paper, a transfer mark is slightly or not visually observed

[0201] B: Transfer marks were visually observed when observed at a distance of 30 cm from the stacked paper, but no transfer marks were visually observed when observed at a distance of 80 cm from the stacked paper

[0202] C: Transfer marks were visually observed when observed from a distance of 80 cm from the stacked paper.

[0203] Miscibility

[0204] The ink composition obtained above was placed in a 100 mL bottle, sealed, and left in a thermostatic chamber at 60° C. for 24 hours. The ink composition was then evaluated based on the following criteria based on the occurrence of phase separation or white turbidity.

[0205] Evaluation Benchmarks

[0206] A: No separation or turbidity of the oil and water layers was observed visually

[0207] B: No separation of the oil layer and the water layer was observed visually, but a slight turbidity was found

[0208] C: Visual observation of the separation of oil and water layers

[0209] 2.4. Ejection stability

[0210] After confirming that the nozzles were ejecting normally in the recording apparatus, the ink composition obtained above was filled and printed. A fresh, unused initial ink was used. The same test pattern as used for the transfer resistance test was printed. Thirty sheets were printed continuously.

[0211] After printing, a nozzle check pattern was recorded to check for any patterns with unfired nozzles. If there were no unfired nozzle patterns, landing position deviation was determined to exist if the nozzle check pattern's landing position deviation was at least 0.5 times the distance between adjacent nozzles. Discharge stability was evaluated according to the following criteria. This evaluation was performed on a single head consisting of 600 nozzles.

[0212] Evaluation Benchmarks

[0213] A: There is no deviation between the nozzle that does not spray and the landing position

[0214] B: The deviation between the nozzles that did not eject and the nozzles that landed was confirmed to be 5 or less.

[0215] C: The deviation between the non-discharging nozzles and the landing position is confirmed to be more than 6 nozzles

[0216] 3. Evaluation results

[0217] Tables 1 to 4 show the composition of the inks used in each example and the evaluation results. These results demonstrate that the following inkjet ink composition exhibits excellent ejection reliability, transfer resistance, compatibility, and / or ejection stability: the inkjet ink composition comprises: a pigment; an acetylene glycol surfactant having an HLB value of 5 or less; a lactam compound having a 6- to 8-membered lactam ring; a solvent component; and a water-soluble resin dissolved in the solvent component, wherein the content of the water-soluble resin is 0.3% by mass or greater relative to the total mass of the inkjet ink composition, and the solvent component is a water-based ink-miscible composition containing water.

[0218] Although not listed in the table, the aforementioned recording device was modified to supply ink to the inkjet head from an ink bag without a sub-tank. Evaluation was conducted in the same manner as in Comparative Example 4. In this case, the ejection reliability at the air-liquid interface was rated A. The ink bag did not generate an ink surface (air-liquid interface) and did not generate foreign matter. However, printing had to be interrupted immediately when the ink bag ran out of ink.

[0219] In Example 1, the same procedure was followed except that the sub-tank had an ink liquid area of 1000 mm. In this case, the gas-liquid interface foreign matter evaluation was B. However, the maximum capacity of the sub-tank was increased, and the number of sheets that could be recorded with the sub-tank's ink increased.

Claims

1. An inkjet ink composition, characterized in that The invention comprises: a pigment; an acetylene glycol surfactant having an HLB value of 5 or less; a lactam compound having a lactam ring as a 6- to 8-membered ring; a solvent component; and a water-soluble resin, wherein the water-soluble resin is dissolved in the solvent component. The content of the water-soluble resin is 0.3% by mass or more relative to the total mass of the inkjet ink composition. The solvent component includes water, and the inkjet ink composition is an aqueous ink.

2. The inkjet ink composition according to claim 1, wherein The inkjet ink composition is an ink ejected by an inkjet recording device. The ink tank supplied with the inkjet ink composition in the inkjet recording apparatus or the ink container supplying the inkjet ink composition to the inkjet recording apparatus has a structure that generates a gas-liquid interface between the inkjet ink composition and gas, that is, an ink liquid surface.

3. The inkjet ink composition according to claim 2, wherein The maximum area of the ink liquid surface is 500mm 2 above.

4. The inkjet ink composition according to claim 1, wherein In the inkjet ink composition, a mass ratio A / B of the content A of the acetylene glycol surfactant to the content B of the lactam compound is 0.01 or more and 0.7 or less.

5. The inkjet ink composition according to claim 1, wherein The water-soluble resin includes a urethane resin.

6. The inkjet ink composition according to claim 1, wherein The inkjet ink composition does not contain 0.1% by mass or more of resin particles based on the total amount of the inkjet ink composition.

7. The inkjet ink composition according to claim 1, wherein The inkjet ink composition does not contain 0.1% by mass or more of inorganic oxide particles based on the total amount of the inkjet ink composition.

8. The inkjet ink composition according to claim 1, wherein The pigment comprises a self-dispersible pigment.

9. The inkjet ink composition according to claim 1, wherein The lactam compound includes ε-caprolactam.

10. The inkjet ink composition according to claim 1, wherein The solvent component contains an alkanediol compound having 5 or more carbon atoms as a water-soluble organic solvent.

11. The inkjet ink composition according to claim 1, wherein The solvent component contains a polyol having a normal boiling point of 280° C. or higher as a water-soluble organic solvent.

12. The inkjet ink composition according to claim 1, wherein The inkjet ink composition is used for recording on an absorptive recording medium.

13. An inkjet recording method, characterized in that: have: The discharge step is to discharge the inkjet ink composition according to any one of claims 1 to 12 from an inkjet head and allow the inkjet ink composition to adhere to a recording medium.

14. The inkjet recording method according to claim 13, wherein The inkjet head is a line head.

15. An inkjet recording device, characterized in that: have: The inkjet ink composition according to any one of claims 1 to 12; and an inkjet head for ejecting the inkjet ink composition.

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