JP2019108452A - Aqueous ink, ink cartridge, and inkjet recording method - Google Patents

Abstract

To provide an aqueous ink which can quickly express whiteness of an image and is excellent in quick drying of the image.SOLUTION: An aqueous ink contains resin particles having a hollow structure, inorganic particles, an ionic surfactant, and a nonionic surfactant. The average particle diameter of the inorganic particles is smaller than the average particle diameter of the resin particles. The nonionic surfactant has a segment configured with an ethylene oxide structure. The molecular mass of the segment is greater than the molecular mass of the ionic surfactant.SELECTED DRAWING: None

Description

  The present invention relates to an aqueous ink, an ink cartridge, and an inkjet recording method.

  2. Description of the Related Art In recent years, ink jet recording apparatuses have come to be used when producing advertisements and exhibits using recording media such as paper and resin films. In particular, when an image is recorded on a transparent recording medium using color ink, it is difficult to obtain clearness of the image because the image is likely to be seen through. Therefore, it is considered to record an image using not only color ink but also white ink. Specifically, there has been proposed an ink jet recording method for recording an image by applying white ink to a transparent recording medium in advance and then applying color ink so that at least a part thereof overlaps with the area to which the white ink is applied. (See Patent Document 1).

  As pigments for white ink, white pigments such as titanium oxide are widely used from the viewpoint of cost and stability of materials. However, since the white pigment has a large specific gravity as compared with the organic pigment, when the ink is left to stand, the pigment tends to settle, and maintenance such as periodical ink agitation is required.

  Then, the resin particle which has a hollow structure is proposed as a white pigment which is hard to precipitate (refer patent document 2 and 3). In addition, as a white pigment, an active energy ray-curable ink containing resin particles having a hollow structure and titanium oxide has been proposed (see Patent Documents 4 and 5). Furthermore, an ink containing resin particles having a hollow structure and titanium oxide is proposed as a white pigment (see Patent Document 6).

JP, 2012-41380, A Japanese Patent Application Laid-Open No. 63-254176 JP 2000-103995 A JP, 2012-140491, A JP 2003-183551 A JP, 2012-17383, A

  The inventors recorded an image using a resin particle having a hollow structure and an ink containing titanium oxide, and found that the whiteness of the image can not be rapidly developed. In this case, the finish of the recorded image can not be confirmed promptly, which may be a factor of decreasing the productivity. Furthermore, it was also found that the fast drying of the image may not be obtained.

  Therefore, an object of the present invention is to provide an aqueous ink which can rapidly develop the whiteness of an image and is excellent in the fast drying of the image. Another object of the present invention is to provide an ink cartridge and an ink jet recording method using the ink.

  The present invention is an aqueous ink containing a resin particle having a hollow structure, an inorganic particle, an ionic surfactant, and a nonionic surfactant, wherein the average particle diameter of the inorganic particle is the average particle of the resin particle. The present invention relates to an aqueous ink, which is smaller than the diameter, and the nonionic surfactant has a segment composed of an ethylene oxide structure, and the molecular weight of the segment is larger than the molecular weight of the ionic surfactant.

  The present invention also relates to an ink cartridge comprising an ink and an ink storage portion for storing the ink, wherein the ink is the aqueous ink of the above configuration.

  Further, the present invention is an ink jet recording method for recording an image on a recording medium by discharging the ink from a recording head of an ink jet system, wherein the ink is the aqueous ink of the above configuration. On the way.

  According to the present invention, it is possible to provide an aqueous ink capable of rapidly expressing the whiteness of an image and excellent in quick drying of the image, an ink cartridge using the aqueous ink, and an inkjet recording method.

FIG. 2 is a cross-sectional view schematically showing an embodiment of the ink cartridge of the present invention. It is a figure which shows typically an example of the inkjet recording device used for the inkjet recording method of this invention, (a) is a perspective view of the principal part of an inkjet recording device, (b) is a perspective view of a head cartridge. It is sectional drawing which shows roughly the resin particle which has a hollow structure.

  Hereinafter, embodiments of the present invention will be described in detail. In the present invention, the water-based ink may be hereinafter referred to as "ink". The salt type ionic group may be dissociated into ions in the ink, but in the present invention, it is expressed as "acid", "anionic group" or "cationic group" for convenience. Various physical property values are values at a temperature of 25 ° C. unless otherwise specified.

  As a result of studies by the present inventors, it was found that when resin particles having a hollow structure were used, the whiteness of the image to be recorded could not be rapidly expressed, and furthermore, the quick drying of the image could not be obtained. The reason is as follows.

  Reflection of light is a phenomenon that occurs at the interface between materials having different refractive indices, and is more likely to occur as the difference in refractive index is larger. In the resin particle having a hollow structure, as the difference in refractive index between the hollow portion A and the portion B of the resin therearound is larger, light incident on the resin particle is more easily reflected. When the hollow part is filled with air, the difference in refractive index between the hollow part A and the surrounding resin part B is larger than when the hollow part is filled with the liquid component. Because, a lot of light is reflected. Thereby, the whiteness of the image can be expressed.

  The resin component in the ink may be in a state in which the liquid component is present in the hollow portion by the liquid component in the ink entering the hollow portion. When the ink adheres to the recording medium and the liquid component in the ink penetrates into the recording medium or the liquid component in the ink evaporates, the liquid component present in the hollow part also flows out and is gradually replaced by air. . When the hollow portion is filled with air, the whiteness of the image can be developed. However, if it takes time for the hollow part to be filled with air, the whiteness of the image can not be expressed quickly. Furthermore, in the ink, since the liquid component is easily stored in the hollow portion of the resin particle, even if the ink adheres to the recording medium, the liquid component is difficult to remove from the ink, and quick drying of the image can not be obtained.

Therefore, the present inventors consider that it is necessary to quickly replace the liquid component present in the hollow portion of the resin particle in the ink after the ink adheres to the recording medium, and a method of controlling the flow of the liquid component We focused on the capillary force and the osmotic pressure difference. The ink of the present invention contains resin particles having a hollow structure, inorganic particles, and an ionic surfactant. The average particle size of the inorganic particles is smaller than the average particle size of the resin particles. Here, the average particle size means the cumulative 50% particle size (D ₅₀ ) of the resin particles and the inorganic particles on a volume basis. The average particle diameter of the inorganic particles and the resin particles is determined by measuring the particle diameter of about 100 randomly selected particles with a scanning electron microscope and taking the average value.

  When the ink contains inorganic particles, inorganic particles are likely to be present around resin particles after the ink adheres to the recording medium. Furthermore, by the presence of inorganic particles having a smaller average particle size than resin particles around the resin particles, the gap between the inorganic particles and the inorganic particles becomes a pseudo capillary, and the liquid component is absorbed from the hollow part by capillary force. Is possible. Thereby, fast drying of the image is obtained. However, it was found that the whiteness of the image was not easily expressed quickly, and there is room for further improvement.

  Therefore, it was decided to make the ink contain an ionic surfactant. The hydrophobic part which an ionic surfactant has is easy to adsorb | suck to the surface of inorganic particle by hydrophobic interaction. Furthermore, since the inorganic particles having a smaller average particle size than the resin particles have a large surface area, the ionic surfactant is more likely to be adsorbed. The presence of the inorganic particles with the ionic surfactant adsorbed around the resin particles results in an increase in ionic strength around the resin particles. The liquid component of the hollow part has a smaller ion concentration because the ionic surfactant is less in the liquid component of the hollow part of the resin particle and the ion concentration is lower than that around the resin particle. It flows around the resin particles. As a result, it was possible to suck up the liquid component from the hollow part, and it was thought that the whiteness of the image could be rapidly developed.

  However, when the present inventors further study, it is difficult to absorb the liquid component from the hollow part by the detachment of the ionic surfactant from the surface of the inorganic particles, and it is difficult to rapidly develop the whiteness of the image. I understand. The reason is as follows.

  Since the ionic surfactant exists in the state of being dissociated into ions, it is considered that the affinity with liquid components such as water is high, and adsorption and desorption on the surface of the inorganic particles are repeated. When the ink adheres to the recording medium, the ionic surfactant is separated from the surface of the inorganic particles by the flow of the liquid component around the resin particles, and an osmotic pressure difference is hardly formed around the resin particles. As a result, it was not possible to suck up the liquid component from the hollow portion, and it was difficult to rapidly develop the whiteness of the image.

  Therefore, in order to suppress the detachment of the ionic surfactant from the surface of the inorganic particles, the ink further contains a nonionic surfactant. The nonionic surfactant has a segment composed of an ethylene oxide structure, and the molecular weight of the segment is larger than the molecular weight of the ionic surfactant.

  The hydrophobic part which nonionic surfactant has is a part other than the segment comprised by ethylene oxide structure, and is adsorbed on the surface of inorganic particles by hydrophobic interaction. The hydrophilic part of the nonionic surfactant is a segment composed of an ethylene oxide structure, and it is difficult to dissociate into ions, so the affinity with liquid components such as water is low, and detachment from the surface of the inorganic particles occurs. Hateful. By making the molecular weight of the segment composed of the ethylene oxide structure larger than the molecular weight of the ionic surfactant, it is possible for the segment to cover the ionic group possessed by the ionic surfactant. As a result, the ionic surfactant becomes difficult to conform to the liquid component such as water, and it becomes difficult to detach from the surface of the inorganic particles. The presence of the inorganic particles to which the ionic surfactant is adsorbed around the resin particles makes it possible to suck up the liquid component from the hollow part, and the whiteness of the image can be rapidly developed. The rapid drying of the image is improved by the formation of an osmotic pressure difference not only by the capillary force of the inorganic particles but also by the ionic surfactant and the nonionic surfactant.

<Ink>
The ink of the present invention is an aqueous ink containing resin particles having a hollow structure, inorganic particles, an ionic surfactant, and a nonionic surfactant. Hereinafter, components that can be used for the ink of the present invention will be described.

(Resin particles)
The resin particles have a hollow structure. In the present invention, “resin particles” means resins which exist in a state of having a particle diameter when neutralized with a base equivalent to the acid value. The particle size is measured by dynamic light scattering. In the present invention, the resin particles are in the form of a so-called resin emulsion in a state of being dispersed in the ink.

  Examples of the resin constituting the resin particles include vinyl resins, ester resins, amide resins and urethane resins. Among them, the resin is preferably a vinyl-based resin because the characteristics of the resin can be easily controlled by the composition of the unit constituting the resin.

  The average particle size (nm) of the resin particles is preferably 300 nm or more and 800 nm or less. When the average particle size is less than 300 nm, the resin particles have a hollow structure, so that it is difficult to reflect light and the whiteness of the image may not be exhibited. If the average particle size exceeds 800 nm, it tends to settle in the ink, and therefore, the storage stability of the ink may not be obtained sufficiently. The porosity of the resin particles is preferably 20% by volume or more and 60% by volume or less based on the total volume of the resin particles. The porosity of the resin particles is calculated as volume% from image analysis by a transmission electron microscope.

  The content (% by mass) of the resin particles is preferably 5.00% by mass or more and 20.00% by mass or less based on the total mass of the ink. When the content is less than 5.00% by mass, the amount of light reflected is reduced, and thus the whiteness of the image may not be exhibited. When the content exceeds 20.00% by mass, the viscosity of the ink may be high, and the ejection stability of the ink may not be sufficiently obtained.

[Method of producing resin particles]
As a method for producing resin particles having a hollow structure, for example, a method of performing multi-step polymerization so that voids are formed during polymerization, a resin is made to contain components that volatilize or foam, and the voids are formed by post treatment. And the like. Among them, the method for producing resin particles is preferably a method of performing multi-step polymerization from the viewpoint that resin particles with uniform particle diameter can be obtained.

(Inorganic particles)
The inorganic particles are preferably metal oxides. Examples of the metal oxide include silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, cesium oxide, yttrium oxide and the like. Among them, the metal oxide is preferably at least one selected from the group consisting of silicon oxide and titanium oxide. The content (% by mass) of the inorganic particles is preferably 1.00% by mass or more and 15.00% by mass or less based on the total mass of the ink.

  The average particle size (nm) of the inorganic particles is preferably 10 nm or more and 100 nm or less. The average particle size of the inorganic particles is smaller than the average particle size of the resin particles. Among them, the average particle size of the resin particles is preferably 9.1 times or more as a ratio (fold) to the average particle size of the inorganic particles. When the ratio is less than 9.1 times, it may be difficult for the inorganic particles to form a capillary around the resin particles, and the fast drying of the image may not be sufficiently obtained. Further, the ratio is preferably 40.0 times or less.

The total surface area of the inorganic particles ^{(m 2)} is the ratio of the total surface area of the resin particles ^{(m 2)} (times), it is preferably not more than 4.00 times 0.50 times or more. If the ratio is less than 0.50 times, the total surface area of the inorganic particles is smaller than that of the resin particles, so the gap is likely to spread between the inorganic particles and the inorganic particles, and pseudo capillaries are hardly formed. Therefore, it is difficult for capillary force to be generated, and it is difficult for the liquid portion to be sucked up from the hollow portion, so that it may be difficult to rapidly develop the whiteness of the image. If the ratio exceeds 4.00 times, the total surface area of the inorganic particles is too large relative to the resin particles, and the liquid component is likely to be contained in the artificial capillary. Therefore, there is a case where quick drying of the image can not be obtained sufficiently.

The average particle diameter of the resin particles and the inorganic particles is determined by measuring the particle diameter of about 100 randomly selected particles by a scanning electron microscope and taking the average value. Further, the total surface area (m ² ) of the resin particles and the inorganic particles can be obtained from the formula of specific surface area (m ² / g) × content in ink (g) calculated from the values of average particle diameter and specific gravity.

(Ionic surfactant)
Examples of the ionic surfactant include anionic surfactants, cationic surfactants, and amphoteric surfactants. The content (% by mass) of the ionic surfactant is preferably 0.02% by mass or more and 0.40% by mass or less based on the total mass of the ink.

  As anionic surfactants, carboxylates having a carboxy group such as laurate, myristate, palmitate, stearate and oleate; dodecylbenzene sulfonate, alkyl naphthalene sulfonate, dioctyl Sulfonic acid salts having a sulfo group such as sulfosuccinic acid ester; sulfuric acid ester salts having a sulfuric acid group such as dodecyl sulfate; phosphoric acid ester salts having a phosphoric acid group such as lauryl phosphate.

  Examples of cationic surfactants include aliphatic quaternary ammonium salts such as didecyldimethyl ammonium chloride, dimethyl dioctadecyl ammonium chloride and hexadecyl trimethyl ammonium bromide; pyridinium salts such as cetyl pyridinium chloride; imidazolinium salts and the like .

  Amphoteric surfactants include carboxybetaines such as lauryl dimethylaminoacetic acid betaine and 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine.

Among them, the ionic surfactant is preferably an anionic surfactant. Furthermore, it is preferable that the anionic group which an anionic surfactant has is at least 1 sort (s) selected from the group which consists of a sulfo group, a sulfuric acid group, and a phosphoric acid group. Here, the sulfo group, the sulfate group and the phosphate group are respectively a SO ₃ M group, an OSO ₃ M group and an OPO ₃ M group. M is a hydrogen atom, an alkali metal ion, an ammonium ion or an organic ammonium ion. Usually, the pH of the aqueous ink is alkaline. Therefore, sulfo group, sulfonic acid group and phosphonic acid group whose pKa is lower than the pH of the ink tend to be stably present as ions in the ink.

(Nonionic surfactant)
As a nonionic surfactant, it has a segment comprised by ethylene oxide structure. The content (% by mass) of the nonionic surfactant is preferably 0.20% by mass or more and 1.50% by mass or less based on the total mass of the ink.

  Examples of nonionic surfactants include polyoxyethylene alkyl (alkenyl) ethers such as polyoxyethylene lauryl ether, polyoxyethylene myristyl ether, polyoxyethylene cetyl ether and polyoxyethylene oleyl ether; polyoxyethylene nonyl phenyl ether and the like Polyoxyethylene alkyl phenyl ethers; polyoxyethylene-polyoxypropylene block copolymers and the like. Among them, nonionic surfactants are preferably polyoxyethylene alkyl ethers.

  Furthermore, the molecular weight of the segment possessed by the nonionic surfactant is larger than the molecular weight of the ionic surfactant. The ethylene oxide adduct of acetylene glycol which is a nonionic surfactant has a plurality of segments, and the molecular weight of the segment is smaller than the molecular weight of the ionic surfactant. The molecular weight of the ionic surfactant is preferably 200 or more and 600 or less, and the molecular weight of the segment possessed by the nonionic surfactant is preferably 300 or more and 900 or less. Furthermore, the molecular weight of the nonionic surfactant is preferably 500 or more and 1,200 or less.

  The content (mmol / g) of the nonionic surfactant is 0.80 times or more and 8.00 times or less in molar ratio (fold) to the content (mmol / g) of the ionic surfactant preferable. When the ratio is less than 0.80 times, the ionic surfactant is likely to be detached from the surface of the inorganic particles because the amount of the nonionic surfactant is smaller than that of the ionic surfactant, and the whiteness of the image is quickly obtained. It may not be expressed. When the ratio exceeds 8.00 times, the ionic surfactant is difficult to be adsorbed on the surface of the inorganic particles because the amount of the nonionic surfactant is larger than that of the ionic surfactant, and the whiteness of the image is quickly obtained. It may not be expressed.

  In addition, when using surfactant in order to disperse | distribute resin particle and inorganic particle, it is included in the value of content of surfactant in ink.

(Aqueous medium)
The ink is an aqueous ink containing water as an aqueous medium. The aqueous medium can further contain a water-soluble organic solvent. It is preferable to use deionized water (ion-exchanged water) as water. The water-soluble organic solvent is not particularly limited, and those usable for ink-jet inks such as alcohols, glycols, alkylene glycols, polyethylene glycols, nitrogen-containing compounds, and sulfur-containing compounds may be used. Either can be used. In addition, one or more of these water-soluble organic solvents can be contained in the ink.

  The content (% by mass) of water in the ink is preferably 50.00% by mass or more and 95.00% by mass or less based on the total mass of the ink. In addition, the content (% by mass) of the water-soluble organic solvent in the ink is preferably 3.00% by mass or more and 50.00% by mass or less, based on the total mass of the ink, and is 3.00% by mass or more It is preferable that it is .00 mass% or less. When the content of the water-soluble organic solvent is less than 3.00% by mass, reliability such as sticking resistance may not be obtained when the ink is used in an ink jet recording apparatus. In addition, when the content of the water-soluble organic solvent is more than 50.00% by mass, supply failure of the ink may occur.

(Other ingredients)
The ink may contain, in addition to the components described above, water-soluble organic compounds that are solid at normal temperature (temperature 25 ° C.) such as urea and derivatives thereof, trimethylolpropane and trimethylolethane. Further, the ink of the present invention may contain, if necessary, various additives such as pH adjusters, antifoaming agents, rust inhibitors, preservatives, fungicides, antioxidants, reduction inhibitors, and chelating agents. May be contained.

(Physical properties of ink)
The viscosity (mPa · s) at a temperature of 25 ° C. of the ink is preferably 1 mPa · s or more and 5 mPa · s or less. The surface tension (mN / m) at a temperature of 25 ° C. of the ink is preferably 10 mN / m to 60 mN / m, and more preferably 20 mN / m to 60 mN / m. The surface tension of the ink can be adjusted by appropriately determining the type and content of surfactant in the ink. The pH of the ink is preferably 7 or more and 10 or less.

(Method of manufacturing ink)
The method for producing the ink comprises charging an aqueous medium, an additive, and a surfactant into a container and sufficiently stirring, confirming that the solution is a uniform solution, and dispersing resin hollow dispersed in water while stirring A solution of particles and inorganic particles is added, and if necessary, it may be filtered.

<Ink cartridge>
The ink cartridge of the present invention comprises an ink and an ink storage portion for storing the ink. The ink stored in the ink storage unit is the ink of the present invention described above. FIG. 1 is a cross-sectional view schematically showing an embodiment of the ink cartridge of the present invention. As shown in FIG. 1, an ink supply port 12 for supplying ink to the recording head is provided on the bottom surface of the ink cartridge. The inside of the ink cartridge is an ink storage portion for storing ink. The ink storage portion is composed of an ink storage chamber 14 and an absorber storage chamber 16, which are in communication via the communication port 18. In addition, the absorber storage chamber 16 is in communication with the ink supply port 12. The ink storage chamber 14 stores liquid ink 20, and the absorber storage chamber 16 stores absorbers 22 and 24 that hold the ink in an impregnated state. The ink storage portion may not have an ink storage chamber for storing liquid ink, and may be configured to hold the entire amount of ink stored by an absorber. In addition, the ink storage portion may be configured to store the entire amount of ink in a liquid state without having an absorber. Furthermore, the ink cartridge may be configured to have an ink storage portion and a recording head.

<Ink jet recording method>
The ink jet recording method of the present invention is a method of discharging an ink of the present invention described above from an ink jet recording head to record an image on a recording medium. Examples of the method of ejecting the ink include a method of applying mechanical energy to the ink and a method of applying thermal energy to the ink. In the present invention, it is particularly preferable to adopt a method of applying thermal energy to the ink to eject the ink. Except for using the ink of the present invention, the steps of the inkjet recording method may be known.

  FIG. 2 is a view schematically showing an example of an ink jet recording apparatus used in the ink jet recording method of the present invention, wherein (a) is a perspective view of the main part of the ink jet recording apparatus, and (b) is a perspective view of a head cartridge. It is. The inkjet recording apparatus is provided with conveyance means (not shown) for conveying the recording medium 32, and a carriage shaft 34. A head cartridge 36 can be mounted on the carriage shaft 34. The head cartridge 36 includes recording heads 38 and 40, and is configured to set the ink cartridge 42. While the head cartridge 36 is conveyed along the carriage shaft 34 in the main scanning direction, ink (not shown) is ejected from the recording heads 38 and 40 toward the recording medium 32. Then, the recording medium 32 is conveyed in the sub scanning direction by the conveyance means (not shown), whereby the image is recorded on the recording medium 32.

  Hereinafter, the present invention will be described in more detail by way of examples and comparative examples, but the present invention is not limited at all by the following examples as long as the gist thereof is not exceeded. In addition, what is described as "part" and "%" regarding component amount is a mass reference | standard unless otherwise indicated.

<Preparation of Dispersion of Resin Particles>
The resin particles were produced by multistage polymerization via seed polymerization.

(Dispersion liquid of resin particles 1 to 5)
Into a reactor equipped with a cooling tower, 290.0 parts of pure water containing 0.4 parts of sodium benzenesulfonate, and then 93.0 parts of styrene, 6.0 parts of acrylic acid, and as a chain transfer agent 1.0 part of dodecyl mercaptan was added. Stir to disperse and warm to a temperature of 80.degree. Next, after the inside of the reactor was replaced with nitrogen, 10.0 parts of pure water containing 0.8 part of sodium persulfate was dropped into the solution in the reactor over 2 hours to advance the polymerization reaction. After completion of the dropwise addition, heating was continued for further 2 hours to obtain a dispersion of resin particles to be a seed polymerization seed.

A cooling tower is provided with 80.0 parts of a dispersion of resin particles (containing 20.0% of resin particles to be a seed polymerization seed) and 210.0 parts of pure water containing 0.4 parts of sodium benzenesulfonate. Into another reactor. Thereafter, 10.0 parts of styrene, 50.0 parts of methyl methacrylate, 6.0 parts of acrylic acid, 4.0 parts of α-methylstyrene and 30.0 parts of divinylbenzene were further charged into the reactor. By gently stirring at a temperature of 50 ° C. for 1 hour, these monomers were absorbed into resin particles to be seeds for seed polymerization. Next, after the inside of the reactor was replaced with nitrogen, 10.0 parts of pure water containing 0.4 part of sodium persulfate was added dropwise to the solution in the reactor and heated to a temperature of 80 ° C. while stirring. . In this state, the polymerization reaction was continued for 4 hours to obtain a dispersion of resin particles. Furthermore, coarse particles were removed using a centrifuge. The average particle size of the resin particles was adjusted by changing the processing time of the centrifuge. Thus, a dispersion of resin particles 1 to 5 was obtained. Content (%) of resin particles in dispersion, average particle diameter (nm) of resin particles, specific gravity (g / cm ³ ) of resin particles, specific surface area (m ² / g) of resin particles, and resin particles The porosity (volume%) is described in Table 1.

(Dispersion liquid of resin particles 6)
Dispersion liquid of resin particles 1 to 5 except that polyoxyethylene cetyl ether (NIKKOL BC-20, segment molecular weight 881, manufactured by Nikko Chemicals) which is a nonionic surfactant is used instead of sodium benzenesulfonate It was prepared in the same manner. Content (%) of resin particles in dispersion, average particle diameter (nm) of resin particles, specific gravity (g / cm ³ ) of resin particles, specific surface area (m ² / g) of resin particles, and resin particles The porosity (volume%) is described in Table 1.

[Method of measuring average particle size of resin particles]
The dispersion of each resin particle was thinly applied to a polyethylene terephthalate film and sufficiently dried, and observed by a scanning electron microscope. The particle diameter of about 100 randomly selected particles was measured by a scanning electron microscope, and the average value was calculated to be the average particle diameter of the resin particles. The value of the average particle size calculated by such a method is not different from the value of the average particle size of the resin particles in the ink.

[Method of measuring porosity of resin particles]
The dispersion of each resin particle was thinly coated on a polyethylene terephthalate film, sufficiently dried, and observed with a transmission electron microscope to calculate the porosity of the resin particle.

Preparation of Dispersion of Inorganic Particles
A dispersion of inorganic particles 1 to 8 described in Table 2 was prepared. The method of measuring the average particle size of the inorganic particles is the same as the method of measuring the average particle size of the resin particles. The content (%) of the inorganic particles in the dispersion, the average particle diameter (nm) of the inorganic particles, the specific gravity (g / cm ³ ) of the inorganic particles, and the specific surface area (m ² / g) of the inorganic particles are shown in Table 2 Described in.

Preparation of Ink
Each component described in Tables 4 to 6 was mixed and prepared. At that time, the surfactant described in Table 3 was used. After sufficient stirring, pressure filtration was performed with a filter with a pore size of 1.2 μm to obtain an ink. Acetylenol E100 is a nonionic surfactant manufactured by Kawaken Fine Chemicals. Acetylenol E100 has two segments, and the molecular weight of the segment is 220 for convenience.

<Evaluation>
Each of the inks obtained above was filled in an ink cartridge, and was set in an ink jet recording apparatus (PIXUS MP480, manufactured by Canon Inc.) which ejects the ink from the recording head by the action of thermal energy. In the present embodiment, an image recorded under the condition of applying one drop of 25 ng ± 10% to a unit area of 1/600 inch × 1/600 inch is defined as having a recording duty of 100%. In the present invention, A or B was an acceptable level and C was an unacceptable level according to the following evaluation criteria. Table 7 describes the evaluation results.

(Expression of whiteness of image)
A solid image (2 cm × 2 cm / 1 line) having a recording duty of 200% was recorded on a transparent recording medium (OHP film for inkjet printer, manufactured by A-one) using the above-mentioned ink jet recording apparatus. A calibration standard in which this image is superimposed on a calibration standard black plate (optical density = 1.83) used for calibration of optical density, and a solid image is overlaid using a reflection densitometer (Macbeth RD-918, manufactured by Macbeth) The optical density of the black plate was measured. Here, it was measured with the passage of time how much the solid image concealed the optical density of the black plate and was able to reduce the value of the optical density. When the hollow portion of the resin particles is a value of optical density _ep optical density of 24 hours after regarded as filled with air, by measuring the time to reach an optical density = optical density _ep +0.02, whiteness We evaluated the speed of expression of
A: The time for the optical density to reach the desired value was within 60 minutes C: The time for the optical density to reach the desired value exceeded 60 minutes.

(Quick-drying of the image)
A solid image (2 cm × 2 cm / 1 line) having a recording duty of 100% was recorded on a transparent recording medium (OHP film for inkjet printer, manufactured by A-one) using the above-mentioned ink jet recording apparatus. The solid image was left to dry at a temperature of 25 ° C. for 60 minutes, and then the recording medium was placed on a flat plate, a silbon paper was placed next to the solid image, and a weight 200 g having a base area of 4 cm ² was placed on the silbon paper. . The fast drying was evaluated by moving the silbon paper with the weight in the direction of the solid image and rubbing the solid image.
A: The ink was not transferred to the silbon paper B: The ink was slightly transferred to the silbon paper C: The ink was transferred to the silbon paper, and the solid image was largely disturbed.

(Ink storage stability)
The storage stability of the ink was evaluated by measuring the absorbance of the ink and confirming the ease of settling of the color material. First, the absorbance A ₀ of each ink was measured. 10 mL of the ink was placed in a 10 mL measuring cylinder, wrapped and allowed to stand at a temperature of 60 ° C. for 30 days. After that, a 2 mL portion of 10 mL of the scale was taken from 8 mL of the scale of the measuring cylinder and transferred to another container. Absorbance A ₁ of the transferred ink was measured to calculate A ₁ / A ₀ . As the value of A ₁ / A ₀ is smaller, it means that the coloring material is settling. The measurement of the absorbance was performed using a spectrophotometer (U-3300, manufactured by Hitachi, Ltd.). The conditions of measurement are shown below.
Measurement cell: 1 cm Quartz cell Sampling interval: 0.1 nm
Scanning speed: 30 nm / min. Number of measurements: 5 measurements Average A: 0.8 or more and 1.0 or less B: 0.6 or more and less than 0.8 C: less than 0.6

Claims (8)

An aqueous ink comprising a resin particle having a hollow structure, an inorganic particle, an ionic surfactant, and a nonionic surfactant,
The average particle size of the inorganic particles is smaller than the average particle size of the resin particles,
The nonionic surfactant has a segment composed of an ethylene oxide structure,
An aqueous ink, wherein the molecular weight of the segment is larger than the molecular weight of the ionic surfactant.   The aqueous ink according to claim 1, wherein an average particle diameter of the resin particles is 9.1 times or more as a ratio (fold) to an average particle diameter of the inorganic particles. The ionic surfactant is an anionic surfactant,
The aqueous ink according to claim 1 or 2, wherein the anionic group contained in the anionic surfactant is at least one selected from the group consisting of a sulfo group, a sulfate group, and a phosphate group.   The aqueous ink according to any one of claims 1 to 3, wherein the nonionic surfactant is a polyoxyethylene alkyl ether.   The content (mmol / g) of the nonionic surfactant is 0.80 times or more and 8.00 times or less the molar ratio (fold) to the content (mmol / g) of the ionic surfactant The aqueous ink according to any one of claims 1 to 4. The total surface area of the inorganic particles ^{(m 2)} is the a ratio to total surface area ^{(m 2)} of the resin particles (times), any one of claims 1 to 5 or less 4.00 times 0.50 times 1 The aqueous ink as described in a term. An ink cartridge comprising an ink and an ink storage portion for storing the ink, the ink cartridge comprising:
An ink cartridge, wherein the ink is the aqueous ink according to any one of claims 1 to 6. An ink jet recording method of discharging an ink from a recording head of an ink jet method to record an image on a recording medium, comprising:
An ink jet recording method, wherein the ink is the aqueous ink according to any one of claims 1 to 6.