JP2017014337A - Ink, ink cartridge, liquid discharge device, and recorded matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide ink which has a small height difference in dots, has high image density, and is excellent in fixability.SOLUTION: There is provided ink which contains a first resin coating pigment having a pigment and a resin on the pigment surface, a second resin coating pigment having a pigment and a resin on the pigment surface, and water, where a content (mass%) of the first resin with respect to the total amount of the pigment in the first resin coating pigment is more than a content (mass%) of the second resin with respect to the total amount of the pigment in the second resin coating pigment by 10 mass% or more.SELECTED DRAWING: None

Description

  The present invention relates to ink, an ink cartridge, a liquid ejection device, and a recorded matter.

  The ink contains pigment, resin, water, and the like. When the ink is applied onto the recording medium, the ink penetrates into the recording medium and evaporates into the air at the same time. To be established.

  At this time, convection of the components in the ink occurs in the ink dots due to the permeation and evaporation of the ink on the recording medium, and the deviation of the components such as pigment and resin is noticeably generated at the edge of the dot having a large surface area. Eventually, a so-called “coffee stain phenomenon” in which the dot edge rises occurs. The coffee stain phenomenon means that the permeation amount penetrating into the recording medium and the evaporation amount evaporating into the atmosphere at the peripheral portion of the ink dots spread on the recording medium are larger than those in other portions in the dot. Therefore, convection occurs in the dot toward the peripheral edge. As a result, it means a phenomenon in which a film having a raised peripheral edge after ink fixing is formed. When the coffee stain phenomenon occurs, there is a difference in height within the dots, which causes problems such as a decrease in image density and a deterioration in ink fixability.

  In view of this, an ink using a resin-coated pigment obtained by coating a pigment with a resin has been proposed (for example, see Patent Documents 1 to 3).

  However, these inventions cause differences in height within the dots, and it has not been possible to achieve high image density and improved ink fixability.

  An object of the present invention is to provide an ink having a small height difference in dots, a high image density, and excellent fixability.

  The ink of the present invention as a means for solving the above-described problems includes a pigment, a first resin-coated pigment having a first resin on the pigment surface, and a second having a pigment and a second resin on the pigment surface. The resin-containing pigment and water are contained, and the content (% by mass) of the first resin with respect to the total amount of pigment in the first resin-coated pigment is equal to the total amount of pigment in the second resin-coated pigment. More than 10 mass% more than content (mass%) of 2nd resin.

  According to the present invention, it is possible to provide an ink having a small height difference in dots, a high image density, and excellent fixability.

FIG. 1 is a schematic diagram (side explanatory view) showing an example of a liquid ejection device used in the present invention. FIG. 2 is a schematic block diagram of the control unit in FIG. FIG. 3 is a schematic diagram showing an example of a head arrangement in the head unit of the liquid ejection apparatus used in the present invention. FIG. 4 is a schematic diagram showing the heads arranged in the head unit of FIG. FIG. 5 is a view showing an example of an ink cartridge used in the liquid ejection apparatus used in the present invention. FIG. 6 is a diagram including a case (exterior) of the ink cartridge of FIG.

(ink)
The ink of the present invention contains a first resin-coated pigment, a second resin-coated pigment, and water, and preferably contains a surfactant, other resin, and wax, and further contains other components as necessary. Comprising.

<First resin-coated pigment>
The first resin-coated pigment has a pigment and a first resin on the surface of the pigment, and further contains other components as necessary.
The first resin-coated pigment is a pigment having a first resin on the pigment surface. The first resin-coated pigment includes not only a pigment having the first resin on the entire surface of the pigment but also a pigment having the first resin on at least a part of the surface of the pigment.

-90% cumulative volume particle size ( _D90 ) of the first resin-coated pigment-
The 90% cumulative volume particle diameter (D ₉₀ ) of the first resin-coated pigment is preferably 100 nm to 200 nm, and more preferably 130 nm to 160 nm. As the 90% cumulative volume particle size (D ₉₀ ), a particle size distribution measuring device (device name: Microtrac UPA-150, manufactured by Nikkiso Co., Ltd.) is used, and the solid content concentration (mass concentration) in the measurement sample is It can be measured by diluting with pure water to 0.01% by mass.

-Electrical conductivity of the first resin-coated pigment-
The electric conductivity of the first resin-coated pigment is preferably from 1,500 μS / cm to 3,000 μS / cm, more preferably from 1,800 μS / cm to 2,700 μS / cm. The electrical conductivity can be measured using an electrical conductivity meter (device name: CM-30R, manufactured by Toa DKK Corporation).

<< Pigment >>
There is no restriction | limiting in particular as said pigment, According to the objective, it can select suitably, For example, an inorganic pigment, an organic pigment, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the inorganic pigment include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, bitumen, cadmium red, chrome yellow, metal powder, and carbon black. These may be used individually by 1 type and may use 2 or more types together. Among these, carbon black is preferable.

  As said carbon black, what was manufactured by well-known methods, such as a contact method, a furnace method, a thermal method, etc. are mentioned, for example.

  Examples of the organic pigment include black organic pigments, color organic pigments, and the like, such as azo pigments, azomethine pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Can be mentioned. These may be used individually by 1 type and may use 2 or more types together. Among these, azo pigments and polycyclic pigments are preferable.

Examples of the azo pigments include azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments. These may be used individually by 1 type and may use 2 or more types together.
Examples of the polycyclic pigment include a phthalocyanine pigment, a perylene pigment, a perinone pigment, an anthraquinone pigment, a quinacridone pigment, a dioxazine pigment, an indigo pigment, a thioindigo pigment, an isoindolinone pigment, a quinofullerone pigment, and a rhodamine β lake pigment. . These may be used individually by 1 type and may use 2 or more types together.
Examples of the dye chelate include basic dye chelate and acid dye chelate. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the organic pigment for black include carbon black (CI pigment black 7) compounds such as furnace black, lamp black, acetylene black, and channel black; copper, iron (CI pigment black 11), Examples thereof include metal compounds such as titanium oxide and aniline black (CI pigment black 1). These may be used individually by 1 type and may use 2 or more types together.

Examples of the carbon black that is the organic pigment for black include those produced by a furnace method and a channel method.
The carbon black, which is the organic pigment for black, preferably has a volume average primary particle size of 15 nm to 40 nm, preferably has a specific surface area by the BET method of 50 m ² / g to 300 m ² / g, and DBP oil absorption 40 mL / 100 g or more and 150 mL / 100 g or less is preferable, the volatile content is preferably 0.5% or more and 10% or less, and the pH is preferably 2 or more and 9 or less.

  As the carbon black which is the organic pigment for black, a commercially available product can be used. Examples of the commercially available product include trade name: MA7, trade name: MA8, trade name: MA100, etc. Chemical Co., Ltd.), Raven 1080, Raven 1100, etc. (above, Colombian Carbon Japan Co., Ltd.), trade name: Mogul, trade name: Monarch 700, trade name: Monarch 800 (above, produced by Cabot Corporation), and the like.

  Examples of the organic pigment for color include a pigment that can be used for yellow ink, a pigment that can be used for magenta ink, and a pigment that can be used for cyan ink. These may be used individually by 1 type and may use 2 or more types together.

  The pigment that can be used in the yellow ink is not particularly limited and may be appropriately selected depending on the intended purpose. I. Pigment yellow 1, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 74, C.I. I. And CI Pigment Yellow 96. These may be used individually by 1 type and may use 2 or more types together. Among these, from the point of color tone and light resistance, C.I. I. Pigment Yellow 74 is preferable.

  The pigment that can be used in the magenta ink is not particularly limited and may be appropriately selected depending on the intended purpose. I. Pigment red 5, C.I. I. Pigment red 7, C.I. I. Pigment red 12, pigment bio red 19, C.I. I. Pigment red 122, C.I. I. And CI Pigment Bio Red 19. These may be used individually by 1 type and may use 2 or more types together. Among these, from the point of color tone and light resistance, C.I. I. Pigment red 122, C.I. I. Pigment Bio Red 19 is preferable.

  The pigment that can be used in the cyan ink is not particularly limited and may be appropriately selected depending on the intended purpose. I. Pigment blue 1, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4. These may be used individually by 1 type and may use 2 or more types together. Among these, from the viewpoint of color tone and light resistance, Pigment Blue 15: 3 is preferable.

  Moreover, as a pigment contained in each ink used in the present invention, a suitably synthesized pigment or a commercially available product may be used.

  The content of the pigment in the first resin-coated pigment is preferably 1% by mass or more and 20% by mass or less, and more preferably 2% by mass or more and 15% by mass or less with respect to the total amount of the ink.

<< first resin >>
Examples of the first resin include an anionic group-containing organic polymer compound.
The anionic group-containing organic polymer compound can be used without particular limitation as long as it can impart water self-dispersibility and solubility by neutralizing the anionic group.

  Examples of the anionic group include a carboxyl group, a sulfonic acid group, and a phosphonic acid group. Among these, a carboxyl group is preferable because it exhibits excellent self-dispersibility and solubility when neutralized with a basic compound.

  The acid value of the anionic group-containing organic polymer compound is preferably from 30 mgKOH / g to 150 mgKOH / g, and more preferably from 50 mgKOH / g to 150 mgKOH / g. When the acid value is 30 mgKOH / g or more, redispersibility in water after acid precipitation and neutralization is good, and the dispersion stability of the pigment can be improved, and is 150 mgKOH / g or less. And it can prevent that hydrophilicity becomes high too much and can improve the water resistance of printed matter.

  There is no restriction | limiting in particular as said anionic group containing organic polymer compound, According to the objective, it can select suitably, For example, polyvinyl resin, polyester resin, amino resin, acrylic resin, methacrylic resin, epoxy Resin, urethane resin, polyether resin, polyamide resin, unsaturated polyester resin, phenol resin, silicone resin, fluorine polymer compound and the like. These may be used individually by 1 type and may use 2 or more types together. Among these, an acrylic resin and a urethane resin are preferable, an acrylic resin is more preferable, (meth) acrylic acid as the acrylic monomer, the alkyl ester of the (meth) acrylic acid, and the hydroxyalkyl ester of the (meth) acrylic acid An acrylic resin containing at least one of the above, further containing styrene as required, and having a content of the acrylic monomer and styrene of 80% by mass or more is particularly preferable. The (meth) acrylic acid means methacrylic acid or acrylic acid, and the acrylic resin means that an acrylic resin having an acrylic structure at least partially in the structure thereof, and the urethane The resin is meant to include a urethane-based resin having a urethane structure at least partially in the structure.

  The acrylic resin can be obtained, for example, by adding an anionic group-containing acrylic monomer and, if necessary, another monomer that can be copolymerized with the anionic group-containing acrylic monomer and polymerizing it in a solvent.

Examples of the anionic group-containing acrylic monomer include an acrylic monomer having at least one anionic group selected from an acrylic monomer having a carboxyl group, an acrylic monomer having a sulfonic acid group, and an acrylic monomer having a phosphonic acid group. Can be mentioned. Among these, an acrylic monomer having a carboxyl group is preferable. Moreover, in order to improve the solvent resistance and durability of the capsule layer and to improve the friction resistance of the printed material, a monomer having a crosslinkable functional group can be used.
Examples of the acrylic monomer having a carboxyl group include acrylic acid, methacrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, and fumaric acid.
Examples of the acrylic monomer having a sulfonic acid group include sulfoethyl methacrylate and butylacrylamide sulfonic acid.
Examples of the acrylic monomer having a phosphonic acid group include phosphoethyl methacrylate.

  Examples of the anionic group-containing organic polymer compound include a carboxyl group-containing styrene-acrylic copolymer.

  The content of the first resin is preferably 50% by mass or more and 80% by mass or less, and more preferably 50% by mass or more and 70% by mass or less based on the total amount of the pigment in the first resin-coated pigment.

-Coating method-
The method of coating the pigment in the first resin-coated pigment with the first resin is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include acid precipitation, phase inversion, interface weight. Examples thereof include a combination method, an in-situ polymerization method, a submerged cured coating method, a coacervation (phase separation) method, a submerged drying method, a melt dispersion cooling method, an air suspension coating method, and a spray drying method. Among these, the acid precipitation method is preferable.

  There is no restriction | limiting in particular as said acid precipitation method, According to the objective, it can select suitably, For example, the 1st containing the anionic group which neutralized a part or all of the anionic group with the basic compound is used. Obtained by kneading the resin and the pigment in an aqueous medium, and depositing the first resin containing an anionic group by neutralizing or acidifying the pH with an acidic compound and fixing the pigment to the pigment. For example, a method may be used in which a pigment is coated with a first resin by neutralizing part or all of an anionic group of a hydrous cake with a basic compound.

-Coverage-
The coverage of the pigment in the first resin is preferably from 50% to 80%, and more preferably from 60% to 70%. The coverage can be measured by observation with an electron microscope. By observing with the electron microscope, an area of 26 μm × 20 μm is photographed at a magnification of 50,000 times, the image is taken in, the number of pixels occupied by the resin in the image is obtained, and it can be obtained by dividing by the total number of pixels.

<Second resin-coated pigment>
The second resin-coated pigment has a pigment and a second resin on the surface of the pigment, and further contains other components as necessary.
The second resin-coated pigment is a pigment having a second resin on the surface of the pigment. Note that the second resin-coated pigment includes not only a pigment having the second resin on the entire surface of the pigment but also a pigment having the second resin on at least a part of the surface of the pigment.

-90% cumulative volume particle size ( _D90 ) of the second resin-coated pigment-
The 90% cumulative volume particle diameter (D ₉₀ ) of the second resin-coated pigment is preferably 90 nm or more and 180 nm or less, and more preferably 100 nm or more and 160 nm or less. As the 90% cumulative volume particle size (D ₉₀ ), a particle size distribution measuring device (device name: Microtrac UPA-150, manufactured by Nikkiso Co., Ltd.) is used, and the solid content concentration (mass concentration) in the measurement sample is It can be measured by diluting with pure water to 0.01% by mass.

-Electric conductivity of the second resin-coated pigment-
The electric conductivity of the second resin-coated pigment is preferably from 1,200 μS / cm to 2,500 μS / cm, and more preferably from 1,350 μS / cm to 2,200 μS / cm. The electrical conductivity can be measured using an electrical conductivity meter (device name: CM-30R, manufactured by Toa DKK Corporation).

<< Pigment >>
As the pigment, the same pigments that can be used for the first resin-coated pigment can be used.

  The content of the pigment is preferably 1% by mass or more and 20% by mass or less, and more preferably 2% by mass or more and 15% by mass or less with respect to the total amount of the ink.

<< second resin >>
As the second resin, the same resin as the first resin can be used.

  The content of the second resin is preferably 20% by mass or more and 50% by mass or less, and more preferably 30% by mass or more and 50% by mass or less with respect to the total amount of the pigment in the second resin-coated pigment.

-Coating method-
The same coating method as that for the first resin-coated pigment can be used.

-Coverage-
The coverage is preferably 20% to 50%, and more preferably 30% to 50%. The coverage can be measured by observation with an electron microscope. By observing with the electron microscope, an area of 26 μm × 20 μm is photographed at a magnification of 50,000 times, the image is taken in, the number of pixels occupied by the resin in the image is obtained, and it can be obtained by dividing by the total number of pixels.

<Water>
There is no restriction | limiting in particular as said water, According to the objective, it can select suitably, For example, pure water, such as ion-exchange water, ultrafiltration water, reverse osmosis water, distilled water, ultrapure water, etc. are mentioned. . These may be used individually by 1 type and may use 2 or more types together.

  The water content is preferably 60% by mass or less, more preferably 20% by mass or more and 60% by mass or less, based on the total amount of ink. When the content is 60% by mass or less, it is possible to prevent an increase in viscosity, gelation, and precipitation of insoluble matter in the ink when water is evaporated.

-1st resin and 2nd resin-
It is preferable to use different types of resins as the first resin and the second resin. Specifically, when the first resin is an acrylic resin, the second resin is preferably a urethane resin, and when the first resin is a urethane resin, the second resin The resin is preferably an acrylic resin.

When different resins are used for the first resin and the second resin, the first resin-coated pigment and the second resin-coated pigment may be measured in the ink using a freeze-cleaving replica method. it can.
As the measurement method, a frozen sample is prepared with a frozen cleaved replica preparation device (device name: JFDII (EM-19500), manufactured by JEOL Ltd.), and the obtained frozen sample is subjected to, for example, a scanning electron microscope ( Device name: Thermal F-SEM, manufactured by Zeiss, ULTRA55), transmission electron microscope (device name: JEM-2100F, manufactured by JEOL Ltd.) and the like can be measured by observing the fine structure.

-Content of the first resin relative to the total amount of pigment in the first resin-coated pigment with respect to the total amount of the second resin relative to the total amount of pigment in the second resin-coated pigment-
As content (mass%) of the said 1st resin with respect to the pigment whole quantity in a said 1st resin coating pigment, from content (mass%) of the said 2nd resin with respect to the pigment whole quantity in the said 2nd resin coating pigment. The amount is preferably 10% by mass or more and more preferably 20% by mass or more and 50% by mass or less. When the content is more than 10% by mass, the first resin-coated pigment and the second resin-coated pigment are closely oriented due to penetration of the ink into the recording medium and evaporation into the air. Since the ink convection in the dots can be suppressed, the coffee stain phenomenon can be reduced. As a result, the height difference in the dots can be reduced, and the fixability and color development of the ink can be improved.
The content can be adjusted by the content of the first resin with respect to the total amount of pigment in the first resin-coated pigment and the content of the second resin with respect to the total amount of pigment in the second resin-coated pigment.

-Height difference in dots-
The height difference in the dots is preferably 0.4 μm or more and 0.8 μm or less, and more preferably 0.5 μm or more and 0.7 μm or less. When the height difference is 0.4 μm or more, it is possible to suppress a decrease in image density due to excessive penetration into the recording medium while maintaining ink fixability. When the height difference is 0.8 μm or less, the image density is maintained. However, it is possible to improve the fixing property of the ink. In addition, as the dot, the ink is discharged using a liquid discharge device (device name: IPSIO GXe5500, manufactured by Ricoh Co., Ltd.) at a temperature of 23 ° C. and a relative humidity of 50%, and the discharge amount is 0,600 dpi × 600 dpi. After discharging to plain paper (trade name: My Paper, manufactured by Ricoh Co., Ltd.) under the condition of 962 mg / cm ² (600 mg / A4), warm air and a drum heater (device name: high-frequency heating heat roll GTR, Using Hydec Co., Ltd.), the dots can be obtained by drying at 90 ° C. for 2 minutes. About the obtained 10 dots, the height of the bulging part (the point where the convex part is the highest) in the dot peripheral part in the dot surface in the laser microscope (device name: VK8510, manufactured by Keyence Corporation) and the dot center part ( The height of the concave portion is the lowest), the height difference is obtained, and the average value can be obtained as the height difference in the dots.

- first 90% cumulative volume particle diameter of the resin-coated pigment to 90% cumulative volume diameter of the second resin-coated pigment _{(D 90) (D 90)} -
As the first 90% cumulative volume particle diameter of the resin-coated pigment _{(D 90),} against 90% cumulative volume diameter of the second resin-coated pigment _{(D 90),} 55nm or less greater than 7.5nm Is preferably 10 nm or more and 50 nm or less, more preferably 10 nm or more and 30 nm or less. When the 90% cumulative volume particle size (D ₉₀ ) is 7.5 nm or more, the first resin-coated pigment and the second resin-coated pigment are closely oriented, so that the fixability of the ink can be improved. If it is below, the discharge stability can be maintained while improving the fixing property of the ink.

-Electrical conductivity of the first resin-coated pigment relative to the electrical conductivity of the second resin-coated pigment-
The electric conductivity of the first resin-coated pigment is preferably higher by 150 μS / cm or more and 1,000 μS / cm or less than the electric conductivity of the second resin-coated pigment, and is 200 μS / cm or more and 500 μS / cm. It is more preferable that it is below. When the electric conductivity is 150 μS / cm or higher, the ink fixing property can be improved. When the electric conductivity is 1,000 μS / cm or lower, the ink fixing property is improved and the ejection stability can be maintained.

-Total content of first resin and second resin with respect to the total amount of pigment-
The total content of the first resin and the second resin is preferably 20% by mass to 70% by mass and more preferably 30% by mass to 70% by mass with respect to the total amount of the pigment. When the total content is 20% by mass or more, the ink fixability can be improved while maintaining the dispersibility of the pigment. When the total content is 70% by mass or less, the color fixability is maintained and the ink fixability is improved. It can be improved. The total amount of the pigment is the total content including the content of other pigments when other pigments are included in addition to the pigments in the first resin-coated pigment and the second resin-coated pigment. Means.

-Content of the second resin-coated pigment with respect to the total amount of the first resin-coated pigment-
The content of the second resin-coated pigment is preferably 60% by mass or more and 500% by mass or less, and more preferably 100% by mass or more and 500% by mass or less with respect to the total amount of the first resin-coated pigment. When the content is 60% by mass or more and 500% by mass or less, excessive penetration into the recording medium can be suppressed, and image density and color developability can be improved.

-Total content of first resin and second resin with respect to the total amount of ink-
The total content of the first resin and the second resin is preferably 1% by mass or more and 5% by mass or less, and more preferably 1% by mass or more and 3% by mass or less with respect to the total amount of the ink. When the total content is 1% by mass or more, the ink fixing property can be improved, and when the total content is 5% by mass or less, the ink ejection stability and the image density can be improved.

<Surfactant>
The surfactant is not particularly limited, and may be appropriately selected from surfactants that do not impair dispersion stability depending on the purpose, depending on the type of colorant, a water-soluble organic solvent, a penetrant, and the like. it can. Examples of the surfactant include a fluorine surfactant, a silicone surfactant, and a higher alcohol surfactant from the viewpoint of low surface tension and high leveling properties, particularly when recording on a recording medium. These may be used individually by 1 type and may use 2 or more types together. Among these, a fluorine surfactant is preferable.

<< Fluorosurfactant >>
Examples of the fluorosurfactant include perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphoric acid ester compounds, perfluoroalkyl ethylene oxide adducts, and And polyoxyalkylene ether polymer compounds having a fluoroalkyl ether group in the side chain. These may be used individually by 1 type and may use 2 or more types together. In addition, a fluorosurfactant is the meaning containing the fluorine-type surfactant which has a fluorine in at least one part of the structure.

  Examples of the perfluoroalkyl sulfonic acid compound include perfluoroalkyl sulfonic acid and perfluoroalkyl sulfonate. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the perfluoroalkyl carboxylic acid compound include perfluoroalkyl carboxylic acid and perfluoroalkyl carboxylate. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the perfluoroalkyl phosphate compounds include perfluoroalkyl phosphate esters and perfluoroalkyl phosphate ester salts. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain include, for example, a sulfate ester salt of a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in the side chain, and a perfluoroalkyl ether group in the side chain. And salts of polyoxyalkylene ether polymers possessed by These may be used individually by 1 type and may use 2 or more types together.

Examples of the counter ion of the salt in the fluorine surfactant include Li, Na, K, NH ₄ , NH ₃ CH ₂ CH ₂ OH, NH ₂ (CH ₂ CH ₂ OH) ₂ , and NH (CH ₂ CH ₂ OH). ) Ions such as ₃ .

  As said fluorosurfactant, what was synthesize | combined suitably may be used or a commercial item may be used. As said commercial item, Asahi Glass Co., Ltd. Surflon series (S-111, S-112, S-113, S-121, S-131, S-132, S-141, S-145); Full Lard Series (FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431) manufactured by 3M Japan Co., Ltd .; Megafuck manufactured by DIC Corporation Series (F-470, F-1405, F-474); Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR manufactured by Dupont; FT manufactured by Neos Corporation -110, FT-250, FT-252, FT-400S, FT-150, FT-400SW; OM-nova PF-151N, etc. And the like. These may be used individually by 1 type and may use 2 or more types together. Among these, the fluorine-type surfactant represented by following formula (i) is preferable.

  The fluorine surfactant of the formula (i) does not contain perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), and is excellent from the viewpoint of global environmental pollution.

<< Silicone surfactant >>
The silicone surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include those that do not decompose even at high pH. Specifically, side chain-modified polydimethylsiloxane, both ends Modified polydimethylsiloxane, one-end-modified polydimethylsiloxane, and side-chain both-end-modified polydimethylsiloxane are preferred, and as a modified surfactant, polyoxyethylene group and polyoxyethylene polyoxypropylene are used as the modified group. Those having a group are more preferred. The silicone surfactant is meant to include a silicone surfactant having a main skeleton with a siloxane bond in at least a part of its structure.

  Examples of the silicone surfactant include polyether-modified silicone surfactants. Among these, the compound which introduce | transduced the polyalkylene oxide structure into the Si part side chain of dimethylsiloxane is preferable.

As said silicone surfactant, what was synthesize | combined suitably may be used, or a commercial item may be used.
Examples of the commercially available products include those manufactured by BYK Japan, Inc., manufactured by Shin-Etsu Chemical Co., Ltd., manufactured by Toray Dow Corning Silicone Co., Ltd., and the polyether-modified silicone compounds include, for example, Shin-Etsu Chemical Co., Ltd. Examples thereof include KF-618, KF-642, and KF-643 manufactured by the company. These may be used individually by 1 type and may use 2 or more types together.

<< Higher alcohol surfactant >>
As the higher alcohol surfactant, an appropriately synthesized product or a commercially available product may be used. Examples of the commercially available products include Kao Corporation, Nippon Emulsifier Co., Ltd., NOF Corporation, and Toho Chemical Industry Co., Ltd. The higher alcohol surfactant is meant to include a higher alcohol surfactant having a higher alcohol in at least a part of its structure.

<< Other surfactants >>
Examples of other surfactants other than the fluorine surfactant, the silicone surfactant, and the higher alcohol surfactant include anionic surfactants, nonionic surfactants, and amphoteric surfactants. These may be used individually by 1 type and may use 2 or more types together.
Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, succinate sulfonate, laurate, polyoxyethylene alkyl ether sulfate, and the like. These may be used individually by 1 type and may use 2 or more types together.
Examples of the nonionic surfactant include acetylene glycol surfactants, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, and the like. These may be used individually by 1 type and may use 2 or more types together.
Examples of the acetylene glycol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, , 5-dimethyl-1-hexyn-3-ol and the like. These may be used individually by 1 type and may use 2 or more types together.
Commercially available products may be used as the acetylene glycol surfactants. Examples of the commercially available products include Surfynol series (104, 82, 465, 485, TG) manufactured by Air Products Co., Ltd. It is done. These may be used individually by 1 type and may use 2 or more types together.
Examples of the amphoteric surfactant include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, lauryl dihydroxyethyl betaine, lauryl dimethyl amine oxide, myristyl dimethyl amine oxide, stearyl dimethyl amine oxide, dihydroethyl lauryl amine oxide, Polyoxyethylene coconut oil alkyl dimethylamine oxide, dimethyl alkyl (coconut) betaine, dimethyl lauryl betaine, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together.
As the amphoteric surfactant, commercially available products may be used. Examples of the commercially available products include Nikko Chemicals Co., Ltd., Nippon Emulsion Co., Ltd., Nippon Shokubai Co., Ltd., Toho Chemical Co., Ltd., Kao Corporation. Examples include those manufactured by ADEKA Corporation, Lion Corporation, Aoki Yushi Kogyo Co., Ltd., and Sanyo Kasei Kogyo Co., Ltd. These may be used individually by 1 type and may use 2 or more types together.

  As the surfactant, one kind may be used alone, or two or more kinds may be used in combination. Even if one kind alone does not easily dissolve in the ink, two or more kinds are mixed. May be solubilized and exist stably.

  The content of the surfactant is preferably 0.01% by mass or more and 4% by mass or less, and more preferably 0.1% by mass or more and 1% by mass or less with respect to the total amount of the ink. When the content is 0.01% by mass or more, the effect of adding the surfactant can be sufficiently exerted, and when the content is 4% by mass or less, the permeability to the recording medium is appropriately maintained. , It is possible to eliminate problems such as a show-through caused by penetration more than necessary.

<Other resins>
The ink of the present invention preferably contains other resins in addition to the first resin and the second resin from the viewpoint of image glossiness and ink fixability. As said other resin, it is preferable to contain at least any one of an acrylic resin and a urethane resin, for example. These may be used individually by 1 type and may use 2 or more types together. In the case of using at least one of an acrylic resin and a urethane resin in combination, it is preferable to contain two or more kinds having different volume average particle diameters. The acrylic resin is meant to include an acrylic resin having an acrylic structure at least partially in its structure, and the urethane resin is a urethane resin having a urethane structure at least partially in the structure. It means to include.

  When using other resins in combination or in combination, it is preferable to contain two or more types having different volume average particle diameters. Specifically, it is preferable to contain at least one type each larger and smaller than the volume average particle diameter of the colorant. When a resin smaller than the particle diameter of the colorant is used, the resin can enter even a small gap between the colorants, and the fixability of the ink can be improved. In addition, when a resin larger than the particle diameter of the colorant contained in the ink is used, the binding property between the resin and the recording medium is physically improved, and as a result, the entire resin may be removed. It becomes difficult to occur. By adopting such a configuration, not only the ink fixing property is improved, but also the image gloss can be improved by increasing the smoothness of the resin surface.

  The volume average particle diameter of the other resin is preferably 10 nm or more and 300 nm or less. If the volume average particle diameter is 10 nm or more, the viscosity of the resin does not become too high, and discharge with a print head becomes possible. Further, if the volume average particle diameter is 300 nm or less, nozzle clogging of the image forming apparatus due to particles is also suppressed. The volume average particle size can be measured using a particle size distribution measuring device (device name: Microtrac UPA, manufactured by Nikkiso Co., Ltd.).

  The acid value of the other resin is preferably 10 mgKOH / g or more and 100 mgKOH / g or less, and more preferably 25 mgKOH / g or more and 80 mgKOH / g or less. When the acid value is 10 mgKOH / g or more, a uniform film can be formed without causing rapid aggregation, and when the acid value is 100 mgKOH / g or less, excessive entrapment of water can be suppressed. In addition, a uniform film can be formed and ink fixability can be improved. The acid value is the number of mg of potassium hydroxide required to neutralize free fatty acids and other acidic substances contained in 1 g of fats and oils such as fats and waxes. As the acid value, a fat and oil sample having a weight corresponding to the acid value of the fat and oil is measured, dissolved in a neutral benzene alcohol solution, etc., and titrated with an alcoholic potassium hydroxide solution using phenolphthalein as an indicator. Can be calculated.

  The glass transition temperature of the other resin is preferably −50 ° C. or higher and 150 ° C. or lower, and more preferably −10 ° C. or higher and 30 ° C. or lower. When the glass transition temperature is 150 ° C. or lower, sufficient ink fixability is obtained, and when it is −50 ° C. or higher, the film is not too soft and the ink fixability is not lowered. Note that. The glass transition temperature can be measured by DSC (differential scanning calorimeter) or TMA (thermomechanical analysis).

  The minimum film-forming temperature (MFT) of the other resin is preferably 25 ° C. or lower. As a result, film formation can be performed at 25 ° C. or lower, and the binding to the recording medium fibers automatically proceeds without heating or drying the image-formed recording medium. The minimum film-forming temperature refers to a continuous film that is transparent when an aqueous emulsion particle obtained by dispersing resin particles in water is thinly cast on a metal plate such as aluminum and the temperature is raised. It means the lowest temperature formed.

  The acrylic resin is preferably an acrylic silicone resin from the viewpoint of strength and gloss when ink is applied to the image forming portion.

  As the acrylic silicone resin, commercially available products can be used. Examples of the commercially available products include trade name: KP-543, trade name: KP-545, trade name: KP-549 (and above, Shin-Etsu Chemical Co., Ltd.). Product name: AQ-914, product name: AQ-ASi-91, product name: AQ-4790 (above, manufactured by Daicel Finechem Co., Ltd.) and the like.

  The urethane resin is preferably an anionic self-emulsifying type urethane resin from the viewpoint of dispersion stability. From the viewpoint of film formability, strength, and bendability when the ink is applied to the image forming portion, anionic self An emulsified ether-based urethane resin is preferred.

  As the ether-based urethane resin, a commercially available product can be used. Examples of the commercially available product include trade name: Permarin Series (manufactured by Sanyo Chemical Industries, Ltd.); trade name: W5661, trade name: XW-75. -W932 (above, made by Mitsui Chemicals); trade name: SF460S (made by NUC Co., Ltd.) and the like. Moreover, you may use what grafted water-based urethane resin and acrylic resin like brand name: WEM-3000 (made by Taisei Fine Chemical Co., Ltd.).

  The content of the other resin is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less based on the total amount of the ink.

<Wax>
The ink of the present invention preferably contains a wax for imparting slipperiness to the image area.

  Examples of the wax include polyethylene wax, paraffin wax, carnauba wax and the like from the viewpoints of film forming properties and slipperiness. These may be used individually by 1 type and may use 2 or more types together. The polyethylene wax means that a polyethylene wax having a polyethylene structure is included in at least a part of the structure, and the paraffin wax means a paraffin wax having a paraffin structure in at least a part of the structure. It is.

  The melting point of the wax is preferably 80 ° C. or higher and 140 ° C. or lower, and more preferably 100 ° C. or higher and 140 ° C. or lower. When the melting point is 80 ° C. or higher, the wax is less likely to be excessively melted or solidified even in a room temperature environment, and the storage stability of the ink can be maintained. It can melt sufficiently and improve the slipping property of the ink.

  The wax has a volume average particle size of preferably 0.01 μm or more, more preferably 0.01 μm or more and 0.1 μm or less. When the volume average particle size is 0.01 μm or more, the wax particles are easily oriented on the surface of the resin-coated pigment, and slipperiness can be imparted to the ink. The volume average particle size can be measured using a particle size distribution measuring device (device name: Microtrac UPA, manufactured by Nikkiso Co., Ltd.).

A commercially available product can be used as the polyethylene wax, and examples of the commercially available product include the Hitech series (manufactured by Toho Chemical Co., Ltd.) and the AQUACER series (manufactured by Big Chemie Japan Co., Ltd.). These may be used individually by 1 type and may use 2 or more types together.
Examples of the paraffin wax include AQUACER series (manufactured by Big Chemie Japan Co., Ltd.).
As the carnauba wax, a commercially available product can be used, and examples of the commercially available product include trade name: Cellozol 524, trade name: Torasol CN (manufactured by Chukyo Yushi Co., Ltd.), and the like. These may be used individually by 1 type and may use 2 or more types together.

  The content of the wax is preferably 0.1% by mass or more and 5% by mass or less, and more preferably 0.1% by mass or more and 2% by mass or less with respect to the total amount of the ink.

<Other ingredients>
The other components are not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include water-soluble organic solvents, sugar compounds and derivatives thereof, penetrants, polymer particles, pH adjusters, foam suppressors, Examples include antiseptic and antifungal agents, rust preventives and the like.

<< Water-soluble organic solvent >>
The water-soluble organic solvent is preferably contained from the viewpoints of prevention of ink drying and dispersion stability.

  Examples of the water-soluble organic solvent include polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, sulfur-containing compounds, propylene carbonate, and carbonic acid. Examples include ethylene.

Examples of the polyhydric alcohols include glycerin, 1,3-butanediol, 3-methyl-1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, Ethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, hexylene glycol, trimethylolethane, trimethylolpropane, glycerol, 1,2,3-butanetriol, 1,2 , 4-butanetriol, 1,2,6-hexanetriol, petriol and the like. These may be used individually by 1 type and may use 2 or more types together.
Examples of the polyhydric alcohol alkyl ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether. It is done. These may be used individually by 1 type and may use 2 or more types together.
Examples of the polyhydric alcohol aryl ethers include ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether. These may be used individually by 1 type and may use 2 or more types together.
Examples of the nitrogen-containing heterocyclic compounds include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, γ-ptyrolactone, and the like. Is mentioned. These may be used individually by 1 type and may use 2 or more types together.
Examples of the amides include acetamide, dimethylformamide, diethylacetamide and the like. These may be used individually by 1 type and may use 2 or more types together.
Examples of the amines include monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, and triethylamine.
Examples of the sulfur-containing compounds include dimethyl sulfoxide, sulfolane, thiodiethanol, and the like. These may be used individually by 1 type and may use 2 or more types together.

  Among these water-soluble organic solvents, glycerin, diethylene glycol, 1,3-butanediol, and 3-methyl-1,3-butanediol are preferable from the viewpoint of prevention of poor jetting characteristics, storage stability, and ejection stability. .

  The content ratio of the pigment and the water-soluble organic solvent has a great influence on the ejection stability of the ink. By appropriately setting the content of the water-soluble organic solvent with respect to the total pigment solid content concentration, it is possible to prevent water evaporation near the nozzle and improve ejection stability.

  The content of the water-soluble organic solvent is preferably 20% by mass or more and 40% by mass or less, and more preferably 30% by mass or more and 40% by mass or less with respect to the total amount of the ink. When the content is 20% by mass or more, the fluidity of the ink can be secured even when the water in the ink evaporates, and when the content is 40% by mass or less, it is necessary for ejection by the print head. The viscosity can be adjusted.

<< Sugar compound and its derivative >>
The sugar compound is preferably contained in order to improve drought resistance, such as monosaccharide compounds, disaccharide compounds, oligosaccharide compounds (including trisaccharide compounds and tetrasaccharide compounds), polysaccharide compounds, and These derivatives are exemplified. Specific examples include glucose, mannose, fructose, ribose, xylose, trehalose, and manntotriose. These may be used individually by 1 type and may use 2 or more types together. In addition, a polysaccharide compound means the saccharide | sugar in a broad sense and means the thing containing the substance which exists widely in nature, such as (alpha) -cyclodextrin and a cellulose.

  Examples of the derivative of the sugar compound include a reducing sugar of the sugar compound and an oxidized sugar of the sugar compound. These may be used individually by 1 type and may use 2 or more types together. Among these, sugar alcohol is preferable, and maltitol and sorbit are more preferable.

  The content of the sugar compound and its derivative is preferably 0.1% by mass or more and 40% by mass or less, and more preferably 0.5% by mass or more and 30% by mass or less with respect to the total amount of the ink.

<< Penetration agent >>
The penetrant is preferably contained in order to increase the penetration speed into the recording medium and prevent bleeding.
Examples of the penetrant include polyol compounds having 8 to 11 carbon atoms, glycol ether compounds, polyhydric alcohol alkyl ether compounds, polyhydric alcohol aryl ether compounds, and the like. These may be used individually by 1 type and may use 2 or more types together.

Examples of the polyol compound having 8 to 11 carbon atoms include 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,2-octanediol, and the like. It is done. These may be used individually by 1 type and may use 2 or more types together.
Examples of the glycol ether compound include polyhydric alcohol alkyl ether compounds and polyhydric alcohol aryl ether compounds. These may be used individually by 1 type and may use 2 or more types together.
Examples of the polyhydric alcohol alkyl ether compound include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether and the like. It is done. These may be used individually by 1 type and may use 2 or more types together.
Examples of the polyhydric alcohol aryl ether compound include ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether. These may be used individually by 1 type and may use 2 or more types together.

  The content of the penetrant is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.5% by mass or more and 5% by mass or less with respect to the total amount of the ink.

<< Polymer particles >>
The polymer particles are preferably contained in order to improve the film forming property. The film-forming property means a property that a resin film is formed when water in the aqueous emulsion is evaporated when polymer particles are dispersed in water to form an aqueous emulsion.
When the polymer particles are contained, the polymer particles form a film when the volatile components in the ink are evaporated, and the role of firmly fixing the colorant in the ink to the recording medium can be imposed. Thereby, it is possible to realize an image excellent in scratch resistance and water resistance.

  The minimum film-forming temperature of the polymer particles is preferably 30 ° C. or lower, more preferably 10 ° C. or lower, from the viewpoint of forming a film at room temperature. The minimum film-forming temperature means that a polymer emulsion obtained by dispersing polymer particles in water is thinly cast on a metal plate such as aluminum, and when the temperature is raised, it is transparent and continuous. It means the lowest temperature at which a film is formed. Examples of the polymer particles include Randy PL series manufactured by Miyoshi Oil & Fat Co., Ltd.

  The volume average particle diameter of the polymer particles is preferably 5 nm to 200 nm, more preferably 10 nm to 100 nm. The volume average particle size can be measured using a particle size distribution measuring device (device name: Microtrac UPA, manufactured by Nikkiso Co., Ltd.).

  Examples of the structure of the polymer particles include single particles. For example, when an alkoxysilyl group is contained in the emulsion particles, it comes into contact with water remaining due to fusion of the emulsions due to water evaporation during the coating film formation process, and hydrolyzes to form silanol groups. Moreover, when a silanol group remains, an alkoxysilyl group or silanols react with each other to form a strong crosslinked structure by a siloxane bond. When reactive functional groups are allowed to coexist in the polymer fine particles, a network structure can be formed by reacting these functional groups during film formation without adding a curing agent.

  Moreover, the polymer particle which has a core shell structure which consists of a core part and the shell part surrounding the said core part can also be used. The core-shell structure refers to a form in which two or more kinds of polymers having different compositions are present in phase separation in the particles. The polymer particles having the core-shell structure may be not only a form in which the shell part completely covers the core part but also a part of the core part. Further, a part of the polymer of the shell part may form a domain or the like in the core particle. Further, it may have a multilayer structure of three or more layers including one or more layers having different compositions between the core portion and the shell portion.

  The polymer particles can be obtained by a known method such as emulsion polymerization of an unsaturated vinyl monomer (unsaturated vinyl polymer) in water in the presence of a polymerization catalyst and an emulsifier.

  The content of the polymer particles is preferably 0.5% by mass or more and 20% by mass or less, and more preferably 1% by mass or more and 5% by mass or less based on the total amount of the ink.

<< pH adjuster >>
Colorant particles (composite pigment particles) obtained by coating the inorganic particles with the colorant have a strong tendency to show acidity when kneaded and dispersed in water together with an anionic dispersant. The surface of the composite pigment dispersed in a medium such as water is negatively charged because it is wrapped in an anionic dispersant, but the inside of the ink is positively charged because the entire ink is acidic. Thus, the negative charge on the particle surface is easily neutralized. In the above state, the dispersed particles aggregate to cause ejection failure. Therefore, it is preferable to stabilize the dispersion state by adding a pH adjuster to the ink to keep it alkaline, thereby stabilizing ejection.

The pH of the ink is preferably 7 or more and 11 or less. When the pH is 7 or more and 11 or less, corrosion of members such as an ink application unit can be prevented.
The pH adjuster is preferably added to the kneaded dispersion together with additives such as a wetting agent and a penetrating agent, rather than being added when the pigment is kneaded and dispersed in water together with the dispersant. This is because dispersion may be destroyed by addition depending on the pH adjusting agent.

Examples of the pH adjuster include alcohol amine compounds, alkali metal hydroxides, ammonium hydroxides, phosphonium hydroxides, and alkali metal carbonates. These may be used individually by 1 type and may use 2 or more types together.
Examples of the alcohol amine compound include diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol, and the like. These may be used individually by 1 type and may use 2 or more types together.
Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide and the like. These may be used individually by 1 type and may use 2 or more types together.
Examples of the ammonium hydroxide include ammonium hydroxide and quaternary ammonium hydroxide. These may be used individually by 1 type and may use 2 or more types together.
Examples of the phosphonium hydroxide include quaternary phosphonium hydroxide.
Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, and potassium carbonate. These may be used individually by 1 type and may use 2 or more types together.

<< foam suppressant >>
The antifoaming agent is preferably contained in order to suppress the generation of bubbles.
The surface active ability of the surfactant containing the compound of the formula (i) is very high, and even if a commonly used silicone type antifoaming agent is added, once bubbles are generated. There is a problem that the bubbles remain without disappearing, causing a problem. With respect to the above problem, by containing a foam suppressor, it is possible to suppress the occurrence of ejection failure or the like when ejected by the ejection head.

  Examples of the antifoaming agent include N-octyl-2-pyrrolidone, 2,4,7,9-tetramethyldecane-4,7-diol, 2,5,8,11-tetramethyldodecane-5,8. -Diol etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together. By using at least one of the above-mentioned foam suppressors and a surfactant such as formula (i) in combination, the generation of bubbles can be suppressed, and problems caused by bubbles can be eliminated.

  As the content of the foam suppressor, the total amount of the surfactant content (mass%) and the foam suppressor content (mass%) is preferably 40% by mass or less based on the total amount of the ink. The mass% or less is more preferable. When the content is 40% by mass or less, ink bubbling can be suppressed.

<< antiseptic and antifungal agent >>
Examples of the antiseptic / antifungal agent include benzotriazole, sodium dehydroacetate, sodium sorbate, 2-pyridinethiol-1-oxide sodium, sodium benzoate, and sodium pentachlorophenol. These may be used individually by 1 type and may use 2 or more types together.

<< rust preventive agent >>
Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite. These may be used individually by 1 type and may use 2 or more types together.

(ink cartridge)
The ink cartridge contains the ink of the present invention in a container, and further includes other members appropriately selected as necessary.

  The container is not particularly limited, and its shape, structure, size, material and the like can be appropriately selected according to the purpose. For example, an ink bag formed of a plastic container, an aluminum laminate film, etc. And the like.

  Next, the ink cartridge will be described with reference to FIGS. Here, FIG. 5 is a view showing an example of the ink cartridge of the present invention, and FIG. 6 is a view including a case (exterior) of the ink cartridge of FIG.

  As shown in FIG. 5, the ink is filled into the ink bag 241 from the ink inlet 242 and exhausted, and then the ink inlet 242 is closed by fusion. In use, ink is supplied to the apparatus by inserting a needle of the apparatus main body into the ink discharge port 243 made of a rubber member. The ink bag 241 is formed of a packaging member such as a non-permeable aluminum laminate film. As shown in FIG. 6, the ink bag 241 is usually housed in a cartridge case 244 made of plastic, and is used as an ink cartridge 240 that is detachably attached to a liquid ejection device.

(Liquid ejection method and liquid ejection device)
The liquid discharge method includes an ink discharge step of recording an image by applying a stimulus and discharging the ink of the present invention.
The liquid ejecting apparatus includes at least ink ejecting means for recording an image by applying a stimulus and ejecting the ink of the present invention.

<Ink ejection process and ink ejection means>
The ink ejection step is a step of recording an image by applying a stimulus to the ink of the present invention and ejecting the ink.
The ink ejection unit is a unit that records an image by applying a stimulus to the ink of the present invention and ejecting the ink.

  There is no restriction | limiting in particular as said irritation | stimulation, According to the objective, it can select suitably, For example, heat | fever (temperature), a pressure, a vibration, light, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together. Among these, heat and pressure are preferable.

  As an aspect of the ink ejection, for example, a piezoelectric element is used as a pressure generating means for pressurizing the ink in the ink flow path, and the diaphragm that forms the wall surface of the ink flow path is deformed to increase the ink flow path volume. A so-called piezo method (for example, see Japanese Patent Publication No. 2-51734) in which ink droplets are ejected by changing; a so-called thermal method in which bubbles are generated by heating ink in an ink flow path using a heating resistor ( For example, see Japanese Examined Patent Publication No. 61-59911); a diaphragm that forms a wall surface of an ink flow path and an electrode are arranged to face each other, and the diaphragm is deformed by an electrostatic force generated between the diaphragm and the electrode. By doing so, an electrostatic system (for example, refer to Japanese Patent Laid-Open No. 6-71882) that discharges ink droplets by changing the volume in the ink flow path can be used.

  The ink droplets preferably have a size of, for example, 3 pL or more and 40 pL or less, the discharge ejection speed is preferably 5 m / s or more and 20 m / s or less, and the drive frequency is 1 kHz or more. The resolution is preferably 300 dpi or more.

  The liquid ejection apparatus includes an image forming unit that records an image by ejecting ink onto the surface of a recording medium, and includes other units such as a stimulus generation unit and a control unit as necessary.

FIG. 1 shows a schematic diagram (side view) of an example of a liquid ejection apparatus according to the present invention.
The liquid ejection apparatus 101 includes head units 110K, 110C, 110M, and 110Y that integrate ink ejection heads, and a head unit 151 that ejects post-treatment liquid, and maintenance that performs head maintenance corresponding to each head unit. Units 111K, 111C, 111M, 111Y, a maintenance unit (not shown), ink cartridges 107K, 107C, 107M, 107Y for supplying ink, post-treatment liquid cartridges (not shown), a part of ink from the cartridges are stored, Sub-ink tanks 108K, 108C, 108M, and 108Y for supplying ink with pressure and a sub-tank for post-processing liquid (not shown) are provided.

Further, a conveyance belt 113 that sucks and conveys the recording medium 114 by the suction fan 120, conveyance rollers 119 and 121 that support the conveyance belt 113, a tension roller 115 that controls the conveyance belt 113 to maintain an appropriate tension, and a conveyance belt 113 are provided. A platen 124 and a platen roller 118 for maintaining appropriate flatness, a charging roller 116 for applying electrostatic charge for attracting the recording medium 114, a discharge roller 117 for pressing the recording medium 114, and a discharged recording medium 114 are stocked. A paper discharge mechanism comprising a paper discharge tray 104, a paper feed tray 103 for stocking the recording medium 114 to be printed, separation pads 112 and 122 for feeding the recording medium 114 one by one from the paper feed tray, and the recording sent A counter roller that securely adsorbs the medium 114 to the charging belt. La 123 has a sheet feeding mechanism comprising a manual feed tray 105 to be used when the paper feed by manual feed.
Furthermore, a waste liquid tank 109 for collecting waste liquid discharged after maintenance and an operation panel 106 capable of operating the apparatus and displaying the apparatus state are also provided.

  The nozzle rows of each head unit are arranged so as to be orthogonal to the conveyance direction of the recording medium 114, and form a nozzle row that is longer than the recording area. The recording medium 114 is separated from the sheet feeding tray into one sheet by a separation roller, and is fixed on the conveyance belt by being in close contact with the conveyance belt by a pressure roller, and liquid is applied to the recording medium when passing under the head unit. By ejecting the droplets, patterning can be performed on the recording medium with the droplets at high speed, separated from the conveying belt by the separation claw, and supported by the ejection rollers and the ejection rollers, the recorded matter is placed on the ejection tray. Discharged.

  Further, by heating the recording medium to which the ink is adhered by the hot air blowing fan 150, it is possible to improve the scratch resistance of the image by promoting drying. Although the drying process is performed on the recording medium after recording with a hot air fan, the drying process may be performed on the recording medium before recording or before and after recording, and the method is not limited to the hot air fan. These means such as a heating roller and those means may be used in combination.

FIG. 3 is a schematic diagram illustrating an example of a head arrangement in the head unit of the liquid ejection apparatus.
In the head unit, the heads 154A to 154L are fixed to the head outer peripheral member 160, and the heads are alternately arranged so that a part of the nozzles overlap.
FIG. 4 is a schematic diagram showing the heads arranged in the head unit of FIG. 3. In each head, a nozzle plate 201 is provided with a nozzle 200, and a filler is provided between the head and the head outer peripheral member. It is sealed at 202 and a gap from the nozzle surface side is eliminated.

  Next, an overview of the control unit of the liquid ejection apparatus shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a schematic block diagram of the control unit in FIG.

  The control unit 300 includes a CPU 301 that controls the entire apparatus, a program executed by the CPU 301, a nozzle surface contamination degree value and nozzle surface contamination allowable threshold for predetermined ink ejection used in the present invention, drive waveform data, and other fixed data. ROM 302 for storing image data, RAM 303 for temporarily storing image data and the like, non-volatile memory (NVRAM) 304 for holding data even while the apparatus is powered off, various signal processing and rearrangement for image data And an ASIC 305 for processing input / output signals for controlling the entire apparatus.

  The control unit 300 includes a host I / F 306 for transmitting and receiving data and signals to and from the host side, and a head drive control unit 307 that generates a drive waveform for driving and controlling the pressure generating means of the recording head 154. A recording medium conveyance motor drive control unit 308 for driving the recording medium conveyance motor 309, a maintenance unit movement motor drive control unit 312 for driving the head unit (carriage) movement motor 311, and an electromagnetic valve 315 for the ink path. An ink path valve control unit 314 for controlling the opening and closing of the ink, a liquid feeding suction motor drive control unit 316 for controlling the driving of the cap suction motor 317 and the ink supply motor 318, and detection according to the moving amount and moving speed of the conveyor belt 113 An encoder that outputs a signal and a sensor that detects environmental temperature and environmental humidity (whichever is acceptable) Detection signals from 323, the ink amount detection signal of the sub ink tank, and a like I / O322 for inputting detection signals from various sensors (not shown). An operation panel 106 for inputting and displaying information necessary for the apparatus is connected to the control unit 300.

  The control unit 300 receives print data from the host side of an information processing device such as a personal computer, an image reading device such as an image scanner, an imaging device such as a digital camera, etc. via the cable or the network at the host I / F 306. .

  The CPU 301 reads and analyzes the print data in the reception buffer included in the host I / F 306, performs necessary image processing and data rearrangement in the ASIC 305, and reduces the print head 154 to one page of the head width. Corresponding image data (dot pattern data) is sent to the head drive controller 307 in synchronization with the clock signal. The generation of dot pattern data for image output may be performed, for example, by storing font data in the ROM 302, or the image data is developed into bitmap data by a host-side printer driver and transferred to this apparatus. You may make it do.

  The head drive control unit 307 selectively applies to the pressure generating means of the recording head 154 based on image data (dot pattern data) corresponding to one page of the recording head 154 input in page units. Drive.

(Recorded material)
The recorded matter of the present invention has an image recorded with the ink of the present invention on a recording medium.
The recording medium is not particularly limited and may be appropriately selected according to the purpose. Examples thereof include plain paper, glossy paper, special paper, general-purpose printing paper, cloth, film, and OHP sheet. These may be used individually by 1 type and may use 2 or more types together.

Examples of the present invention and comparative examples will be described below, but the present invention is not limited to these examples.
The acid value, weight average molecular weight, glass transition temperature, 50% cumulative volume particle size (D ₅₀ ), 90% cumulative volume particle size (D ₉₀ ), and electrical conductivity were determined as follows.

-Acid value-
The acid value was measured using the method described in JIS K 0070-1992.

-Weight average molecular weight-
The weight average molecular weight was measured using a molecular weight distribution measurement system (device name: D5280 LCS M-PDA, manufactured by Shimadzu Corporation).

-Glass transition temperature-
The glass transition temperature was measured using a differential thermothermal gravimetric simultaneous measurement device (device name: STA7200, manufactured by Hitachi High-Tech Science Co., Ltd.).

-50% cumulative volume diameter _{(D 50),} and 90% cumulative volume diameter _{(D 90)} -
The 50% cumulative volume particle size (D ₅₀ ) and 90% cumulative volume particle size (D ₉₀ ) of the colorant were measured using a particle size distribution measuring device (device name: Microtrac UPA-150, manufactured by Nikkiso Co., Ltd.). The sample was diluted with pure water and measured so that the solid content concentration (mass concentration) in the sample was 0.01% by mass.

-Electrical conductivity-
The electric conductivity was measured using an electric conductivity meter (device name: CM-30R, manufactured by Toa DKK Corporation).

(Synthesis of copolymer)
<Synthesis of anionic group-containing styrene-acrylic resin copolymer>
550 g of methyl ethyl ketone was charged into a reaction vessel of an automatic polymerization reaction device (polymerization tester DSL-2AS type, manufactured by Sakai Sangyo Co., Ltd.) having a reaction vessel equipped with a stirring device, a dropping device, a temperature sensor, and a reflux device having a nitrogen introduction device at the top. While stirring, the inside of the reaction vessel was purged with nitrogen. After heating the inside of the reaction vessel at 80 ° C. while maintaining a nitrogen atmosphere, 75.0 g of 2-hydroxyethyl methacrylate, 77.0 g of methacrylic acid, 80.0 g of styrene, 150.0 g of butyl methacrylate, acrylic A mixed solution of 98.0 g of butyl acid, 20.0 g of methyl methacrylate, and 40.0 g of tert-butyl-2-ethylperoxyhexanoate (trade name: Perbutyl O, manufactured by NOF Corporation) was dropped over 4 hours. did. After completion of the dropwise addition, the reaction was further continued at the same temperature for 15 hours to obtain an anionic group-containing styrene-acrylic copolymer having an acid value of 100 mgKOH / g, a weight average molecular weight of 21,000, and a glass transition temperature of 31 ° C. A methyl ethyl ketone solution was obtained. After completion of the reaction, part of methyl ethyl ketone was distilled off under reduced pressure to obtain a solution of an anionic group-containing styrene-acrylic copolymer having a nonvolatile content of 50% by mass.

<Synthesis of anionic group-containing styrene-urethane resin copolymer>
In the synthesis of the anionic group-containing styrene-acrylic resin copolymer, except that butyl acrylate was changed to a urethane prepolymer, the same as the synthesis of the anionic group-containing styrene-acrylic resin copolymer, A methyl ethyl ketone solution of an anionic group-containing styrene-urethane copolymer was obtained. After completion of the reaction, part of methyl ethyl ketone was distilled off under reduced pressure to obtain a solution of an anionic group-containing styrene-urethane copolymer having a nonvolatile content of 50% by mass.

(Preparation of first resin-coated pigment)
<Preparation of first resin-coated pigment 1>
Carbon black (trade name: Raven 1080, manufactured by Colombian Carbon Co., 50% cumulative volume particle size (D ₅₀ ): 120 nm) in a mixing tank equipped with a cooling jacket, and the anionic group-containing styrene-acrylic system A copolymer solution was obtained by adding 800 g of a copolymer solution, 143 g of a 10% by mass aqueous sodium hydroxide solution, 100 g of methyl ethyl ketone, and 1,957 g of water, and stirring and mixing them. By passing the obtained mixed liquid through a dispersion apparatus (apparatus name: SC Mill SC100, manufactured by Nippon Coke Kogyo Co., Ltd.) filled with zirconia beads having a diameter of 0.3 mm, the dispersion liquid discharged from the dispersion apparatus is returned to the mixing tank. Dispersed for 6 hours by a certain circulation system. The number of revolutions of the dispersing device was 2,700 rpm, and the temperature of the dispersion liquid was kept at 40 ° C. or less through the cooling jacket through cold water. After completion of the dispersion, the dispersion stock solution was extracted from the mixing tank, and then the mixing tank and the dispersion device flow path were washed with 10,000 g of water, and the diluted dispersion liquid was obtained together with the dispersion stock solution. The diluted dispersion was put into a glass distillation apparatus, and the whole amount of methyl ethyl ketone and a part of water were distilled off. After cooling to room temperature, 10% by mass hydrochloric acid was added dropwise with stirring to adjust the pH to 4.5, and the solid content was filtered with a Nutsche filter and washed with water to obtain a cake. The obtained cake is put in a container, and after adding 200 g of a 20% by mass aqueous potassium hydroxide solution, the mixture is dispersed in a multiaxial dispersion kneading device (device name: TK Homo Disper, manufactured by Primix Co., Ltd.), and water is further added. First, the non-volatile content was adjusted, and carbon black having a non-volatile content of 20% by mass was dispersed in an aqueous medium as composite particles coated with a carboxyl group-containing styrene-acrylic copolymer neutralized with potassium hydroxide. A dispersion of resin-coated pigment 1 was obtained. The solid content concentration of carbon black in the dispersion of the first resin-coated pigment 1 was 8% by mass.

<Preparation of first resin-coated pigments 2 to 30>
In the production of the first resin-coated pigment 1, the carbon black and the anionic group-containing styrene-acrylic copolymer solution were used as the carbon black and the anionic group-containing styrene-acrylic listed in Tables 1 to 6. The first resin is the same as the production of the first resin-coated pigment 1 except that the composition and the content of the copolymer solution or the anionic group-containing styrene-urethane copolymer solution are changed. A dispersion of coated pigment 2-30 was obtained.

<Production of second resin-coated pigments 1 to 30>
In the production of the first resin-coated pigment 1, carbon black and an anionic group-containing styrene-acrylic copolymer solution are used as the carbon black and the anionic group-containing styrene-acrylic system shown in Tables 1 to 6. The second resin coating is the same as the production of the first resin-coated pigment 1 except that the composition of the copolymer solution or the anionic group-containing styrene-urethane copolymer solution and the content thereof are changed. Dispersions of pigments 1-30 were obtained.

Example 1
Glycerin (manufactured by NOF Corporation) 10.0% by mass, 1,3-butylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd.) 20.0% by mass, and ion-exchanged water 58.0% by mass are stirred uniformly for 1 hour. Mixed. Next, 2.4% by mass of the dispersion of the first acrylic resin-coated pigment 1 (1.6% by mass of carbon black and 0.8% by mass of an anionic group-containing styrene-acrylic copolymer solution), The dispersion of the second acrylic resin-coated pigment 1 7.7% by mass (carbon black 6.4% by mass and anionic group-containing styrene-acrylic copolymer solution 1.3% by mass) was added, The mixture was further stirred for 1 hour and mixed uniformly. This was subjected to pressure filtration with a polyvinylidene fluoride membrane filter having an average pore diameter of 0.8 μm to remove coarse particles and dust, and ink 1 was obtained.

(Examples 2 to 25 and Comparative Examples 1 to 5)
In Example 1, except having changed into the composition of Table 1-Table 6, and content, it is the same as that of Example 1, and the inks 2-30 of Examples 2-5 and Comparative Examples 1-5 are used. Obtained. The compositions of Examples 2 to 25 and Comparative Examples 1 to 5 are shown in Tables 1 to 6.

  With respect to the obtained inks 1 to 30 of Examples 1 to 25 and Comparative Examples 1 to 5, “the height difference in dots”, “image density”, and “fixability” were evaluated as follows. The results are shown in Tables 1-6.

(Elevation difference in dots)
Inks 1 to 30 of Examples 1 to 25 and Comparative Examples 1 to 5 were used in a liquid ejection device (device name: IPSIO GXe5500, manufactured by Ricoh Co., Ltd.) under a temperature of 23 ° C. and a relative humidity of 50%. The paper was discharged onto plain paper (trade name: My Paper, manufactured by Ricoh Co., Ltd.) under the conditions of a resolution of 600 dpi × 600 dpi and a discharge amount of 0.962 mg / cm ² (600 mg / A4). After discharging the ink, 10 dots were formed by drying at 90 ° C. for 2 minutes using warm air and a drum heater (device name: high-frequency heating heat roll GTR, manufactured by Hydec Co., Ltd.).
About the obtained 10 dots, the height of the bulging part (the point where the convex part is the highest) in the dot peripheral part in the dot surface in the laser microscope (device name: VK8510, manufactured by Keyence Corporation) and the dot center part ( The height of the concave portion is the lowest), the height difference is obtained, and the average value is defined as the height difference in the dots. The smaller the height difference value in the dot, the more the occurrence of the coffee stain phenomenon can be prevented, and the fixability of the obtained image is better.

(Image density)
A solid image of 3 cm × 3 cm was obtained in the same manner as the evaluation of the height difference in the dots. The solid portion of the obtained solid image was measured with a spectroscopic color densitometer (device name: 939, manufactured by X-Rite). The larger the numerical value, the better the image density.

(Fixability)
A solid image of 3 cm × 3 cm was obtained in the same manner as the evaluation of the height difference in the dots. The solid portion of the obtained solid image is affixed to a friction tester (device name: clock meter, manufactured by Toyo Seiki Seisakusho Co., Ltd.) with a cloth (trade name: M238CT, manufactured by SDLATLAS Co., Ltd.) and rubbed onto the cloth after rubbing. The transfer density of the ink was measured with a spectroscopic color densitometer (device name: 939, manufactured by X-Rite). The smaller the transfer density, the better the image fixability.

Moreover, in Tables 1 to 6, the manufacturer name and the product name are as follows.
・ Fluorine-based surfactant: Daikin Industries, Ltd., trade name: Unidyne DSN-403N
Carbinol-modified silicone oil: manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KF-6001
・ Polyoxyalkylene alkyl ether: Kao Corporation, trade name: Emulgen LS-106
-Antifoaming agent: Nissin Chemical Industry Co., Ltd., trade name: Envirogem AD01
-Polyethylene wax emulsion: manufactured by Big Chemie Japan, Inc., trade name: AQUACER-515, solid content concentration: 35% by mass
Paraffin wax emulsion: manufactured by Big Chemie Japan Co., Ltd., trade name: AQUACER-537, solid content concentration: 30% by mass
-Carnauba wax: manufactured by Chukyo Yushi Co., Ltd., trade name: Cellosol 524
Acrylic resin: manufactured by Daicel FineChem, Inc., trade name: AQ914, solid content concentration: 24% by mass
-Urethane resin: manufactured by Chuo Rika Kogyo Co., Ltd., trade name: SU-100N, solid content concentration: 35% by mass
Surfactant-treated dispersion: A dispersion in which a pigment is dispersed with a formalin condensate of naphthalenesulfonic acid as a pigment dispersant as described in Japanese Patent No. 5593969. Self-dispersing carbon black: self-dispersing Type dispersion, manufactured by Tokai Carbon Co., Ltd., trade name: Aqua-Black 162

As an aspect of this invention, it is as follows, for example.
<1> a first resin-coated pigment having a pigment and a resin on the pigment surface;
A second resin-coated pigment having a pigment and a resin on the pigment surface;
Containing water,
The content (% by mass) of the first resin with respect to the total amount of pigment in the first resin-coated pigment is 10 than the content (% by mass) of the second resin with respect to the total amount of pigment in the second resin-coated pigment. The ink is characterized by having a mass% or more.
<2> In a dot formed by ejecting ink on a recording medium at a temperature of 23 ° C. and a relative humidity of 50% and having a resolution of 600 dpi × 600 dpi and an ejection amount of 0.962 mg / cm ² ,
The ink according to claim 1, wherein the height difference in the dots is 0.4 μm or more and 0.8 μm or less.
<3> From <1> to <2>, the 90% cumulative volume particle size of the first resin-coated pigment is 7.5 nm or more and 55 nm or less larger than the 90% cumulative volume particle size of the second resin-coated pigment. The ink according to any one of the above.
<4> The electrical conductivity of the first resin-coated pigment is higher than the electrical conductivity of the second resin-coated pigment by 150 μS / cm or more and 1,000 μS / cm or less, any one of <1> to <3> It is the ink described in the above.
<5> The first resin is at least one of an acrylic resin and a urethane resin,
The ink according to any one of <1> to <4>, wherein the second resin is at least one of an acrylic resin and a urethane resin.
<6> Any one of <1> to <5>, wherein the first resin is an acrylic resin and the second resin is a urethane resin, or the first resin is a urethane resin and the second resin is an acrylic resin. Ink.
<7> The ink according to any one of <1> to <6>, wherein the total content of the first resin and the second resin is 20% by mass to 70% by mass with respect to the total amount of the pigment. is there.
<8> The ink according to any one of <1> to <7>, wherein the content of the first resin is 50% by mass or more and 80% by mass or less with respect to the total amount of the pigment in the first resin-coated pigment. It is.
<9> The ink according to any one of <1> to <8>, wherein the content of the second resin is 20% by mass to 50% by mass with respect to the total amount of pigment in the second resin-coated pigment. It is.
<10> The ink according to any one of <1> to <7>, wherein the content of the second resin-coated pigment is 60% by mass to 500% by mass with respect to the total amount of the first resin-coated pigment. It is.
<11> A surfactant that is at least one selected from a fluorosurfactant, a silicone surfactant, and a higher alcohol surfactant,
Any one of <1> to <10>, further including a resin that is at least one of an acrylic resin and a urethane resin, and a wax that is at least one selected from polyethylene wax, paraffin wax, and carnauba wax The ink described.
<12> The content (mass%) of the first resin with respect to the total amount of pigment in the first resin-coated pigment is the content (mass%) of the second resin with respect to the total amount of pigment in the second resin-coated pigment. The ink according to any one of <1> to <11>, wherein the amount is 20 mass% or more and 50 mass% or less.
<13> Any one of <1> to <12>, wherein the 90% cumulative volume particle size of the first resin-coated pigment is 10 nm or more and 50 nm or less larger than the 90% cumulative volume particle size of the second resin-coated pigment. It is the ink described in the above.
<14> The ink according to any one of <1> to <13>, wherein the content of the second resin-coated pigment is 100% by mass or more and 500% by mass or less with respect to the total amount of the first resin-coated pigment. It is.
<15> The ink according to any one of <1> to <14>, wherein the content of the first resin is 50% by mass or more and 70% by mass with respect to the total amount of the pigment in the first resin-coated pigment. is there.
<16> The ink according to any one of <1> to <15>, wherein the content of the second resin is 30% by mass to 50% by mass with respect to the total amount of the pigment in the second resin-coated pigment. It is.
<17> The ink according to any one of <1> to <16>, wherein the total content of the first resin and the second resin is 1% by mass or more and 5% by mass or less based on the total amount of the ink. It is.
<18> An ink cartridge comprising the container according to any one of <1> to <17>.
<19> A liquid ejecting apparatus comprising at least ink ejecting means for recording an image by applying a stimulus to the ink according to any one of <1> to <17> and ejecting the ink. .
<20> A liquid ejection method comprising at least an ink flying step of recording an image by applying a stimulus to the ink according to any one of <1> to <17> and causing the ink to fly. .
<21> A recorded matter comprising an image recorded with the ink according to any one of <1> to <17> on a recording medium.

  The ink according to any one of <1> to <17>, the liquid ejection device according to <19>, the liquid ejection method according to <20>, and the recorded matter according to <21> It is an object to solve the above problems and achieve the following object. That is, the ink, the liquid ejection apparatus, the liquid ejection recording method, and the recorded matter are inks having a small height difference in dots, a high image density, and excellent fixability, a liquid ejection apparatus, a liquid ejection recording method, And to provide recorded materials.

  It is an object of the ink cartridge according to <18> to solve the conventional problems and achieve the following object. That is, an object of the ink cartridge is to provide an ink cartridge in which a difference in height between dots is small, an image density is high, and ink having excellent fixability can be accommodated in a container.

Japanese Patent Laying-Open No. 2015-097517 Japanese Patent No. 553969 JP 2012-180398 A

101: Liquid ejection device 107K, 107C, 107M, 107Y, 240: Ink cartridge

Claims (15)

A first resin-coated pigment having a pigment and a first resin on the pigment surface;
A pigment and a second resin-coated pigment having a second resin on the pigment surface;
Containing water,
The content (% by mass) of the first resin with respect to the total amount of pigment in the first resin-coated pigment is 10 than the content (% by mass) of the second resin with respect to the total amount of pigment in the second resin-coated pigment. An ink characterized by having a mass% or more. In a dot formed by ejecting ink on a recording medium at a temperature of 23 ° C. and a relative humidity of 50% and having a resolution of 600 dpi × 600 dpi and an ejection amount of 0.962 mg / cm ² ,
The ink according to claim 1, wherein a height difference in the dots is 0.4 μm or more and 0.8 μm or less.   The 90% cumulative volume particle size of the first resin-coated pigment is 7.5 nm or more and 55 nm or less larger than the 90% cumulative volume particle size of the second resin-coated pigment. ink.   The ink according to any one of claims 1 to 3, wherein the electric conductivity of the first resin-coated pigment is higher by 150 µS / cm or more and 1,000 µS / cm or less than the electric conductivity of the second resin-coated pigment. The first resin is at least one of an acrylic resin and a urethane resin;
The ink according to any one of claims 1 to 4, wherein the second resin is at least one of an acrylic resin and a urethane resin.   The ink according to claim 1, wherein the first resin is an acrylic resin and the second resin is a urethane resin, or the first resin is a urethane resin and the second resin is an acrylic resin.   The ink according to any one of claims 1 to 6, wherein the total content of the first resin and the second resin is 20% by mass or more and 70% by mass or less based on the total amount of the pigment.   The ink according to any one of claims 1 to 7, wherein the content of the first resin is 50% by mass or more and 80% by mass or less based on the total amount of the pigment in the first resin-coated pigment.   The ink according to any one of claims 1 to 8, wherein the content of the second resin is 20% by mass or more and 50% by mass or less based on the total amount of the pigment in the second resin-coated pigment.   The ink according to any one of claims 1 to 9, wherein the content of the second resin-coated pigment is 60% by mass or more and 500% by mass or less based on the total amount of the first resin-coated pigment.   The ink according to any one of claims 1 to 10, wherein a total content of the first resin and the second resin is 1% by mass or more and 5% by mass or less based on the total amount of the ink. A surfactant that is at least one selected from a fluorosurfactant, a silicone surfactant, and a higher alcohol surfactant,
The ink according to any one of claims 1 to 11, further comprising a resin that is at least one of an acrylic resin and a urethane resin, and a wax that is at least one selected from polyethylene wax, paraffin wax, and carnauba wax. .   An ink cartridge comprising the ink according to claim 1 contained in a container.   13. A liquid ejecting apparatus comprising at least ink ejecting means for recording an image by applying a stimulus to the ink according to claim 1 and ejecting the ink. A recorded matter comprising an image recorded with the ink according to any one of claims 1 to 12 on a recording medium.