JP6631666B2 - Ink jet apparatus, ink jet recording method and ink - Google Patents

Description

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

2. Description of the Related Art Inkjet printers have advantages such as low noise, low running cost, and easy color printing, and have been rapidly spread in recent years as digital signal output devices.
Dye-based inks in which various water-soluble dyes are dissolved in water or a mixture of water and an organic solvent are used, but the dye-based inks are said to have excellent color tone clarity but poor light fastness. An ink using a pigment which has a disadvantage and is superior to a dye in terms of water resistance and weather resistance is used.
However, unlike the dye ink, the pigment ink contains many pigment particles whose dispersion state is unstable in the ink.As a result, aggregates of the pigment particles are generated, nozzles are clogged, and normal ejection is hindered. There was a problem that was. To solve such a problem, it has been proposed to provide a filter between the ink supply unit and the ink ejection unit.

However, in the field of ink jet printers in recent years, there has been a remarkable demand for higher image quality and higher speed, and in order to achieve this, the diameter of nozzles serving as ink flying means tends to be reduced.
For this reason, the diameter of the filter has become considerably smaller than the conventional filter diameter.
As a result, the filter is liable to be clogged, the pressure loss when the ink reaches the nozzle is increased, and the problem that the ejection becomes unstable remains.

On the other hand, various proposals have been made regarding filters in order to ensure long-term reliability.
For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 9-187555) discloses a method of using a sintered nonwoven fabric made of metal fibers, and Patent Document 2 (Japanese Patent Application Laid-Open No. 9-109411) discloses that a metal fiber is twilled and woven. Patent Document 3 (Japanese Patent Application Laid-Open No. 2005-324444) proposes a method using a filter formed by passing a large number of fine holes through a flat metal plate. .
On the other hand, as a device on the ink side, for example, Patent Document 4 (Japanese Patent Application Laid-Open No. 2006-070105) discloses that adding aminopropanediol to the ink improves the dispersion stability of the pigment. Japanese Patent Application Laid-Open No. 2009-173829 discloses that a preservative having a specific structure is added to prevent the generation of foreign matter in the ink. An ink that does not cause clogging of a filter by specifying the type of an organic solvent and the content of a water-soluble resin is disclosed.
However, there is still a problem that the filter is clogged over time due to long-term use, and the problem of increased pressure loss remains unresolved.

Further, Patent Document 7 (Japanese Patent Application Laid-Open No. 2001-302951) discloses a pigment type in an ink for the purpose of obtaining an ink capable of obtaining high quality image without clogging a filter for a long term. There is disclosed an ink jet recording ink in which the surface tension of the ink, the contact angle with plain paper, and the number of coarse particles are specified.
However, in the ink disclosed in Patent Document 7, only the filter resistance increasing mechanism in which coarse particles in the ink are deposited on the filter is considered. For this reason, Patent Literature 7 does not sufficiently study what characteristic values of the ink and the filter should be suppressed to contribute to long-term ink passage performance. Not what you get.
That is, since sufficient studies have not been made on the physical properties of the ink and the wettability of the filter, an ink jet recording apparatus capable of performing stable ejection without causing clogging over a long period of time while securing image quality can be obtained. The problem of not being implemented has not been resolved.

  The present invention has been made in view of the above-described problems in the related art, and has as its object to provide an ink jet apparatus capable of performing stable ejection without clogging a filter even in long-term use.

An ink jet apparatus according to the present invention for solving the above-mentioned problems is an ink jet apparatus including an ink, and a filter provided in an ink supply path for supplying the ink, wherein the ink includes a pigment, water, Wherein the dynamic surface tension at a lifetime of 15 ms is 30 mN / m or more, and the amount of dissolved oxygen in the ink is less than 3 mg / L, and the water-soluble organic solvent in the ink is The filter contains any one of 1,3-butanediol, diethylene glycol and glycerin, and the filter has an advancing contact angle with water of 100 ° or less.

  ADVANTAGE OF THE INVENTION According to this invention, even if it uses for a long time, a stable discharge can be performed without clogging a filter.

  An ink jet apparatus according to the present invention is an ink jet apparatus including an ink, and a filter provided in an ink supply path for supplying the ink, wherein the ink includes a pigment, water, and a water-soluble organic solvent. The dynamic surface tension at a lifetime of 15 ms is 30 mN / m or more, the amount of dissolved oxygen in the ink is less than 3 mg / L, and the filter has an advancing contact angle to water of 100 ° or less. Features.

Next, prior to describing the inkjet apparatus, the ink supply unit, and the inkjet recording method according to the present invention, a description will be given below of the process by which the present inventors complete the present invention.
Hereinafter, the inkjet apparatus will be described as an inkjet recording apparatus.

As a result of intensive studies, the present inventors have found out that the reason why stable ejection over a long period of time is not possible, that is, the cause of an increase in filter resistance during long-term use is due to the wettability of the filter.
If the ink cannot sufficiently wet the filter in the initial stage, the ink tends to pass through an easily passable area, so that the effective area where the filter functions as it is is lower than expected.
In addition, the water-based ink contains a certain amount of air even if it has been subjected to a degassing process in advance.
If the filter does not have sufficient wettability, the air in the ink gradually accumulates in the filter and reduces the effective area.

Due to these two mechanisms, the area of the filter through which the ink passes is smaller than expected by the designer, and a large amount of ink continues to flow through the filter having a small area.
As a result, the present inventors have found that there is a problem that the resistance of the filter tends to increase with time.

A solution to such a problem of filter wettability is to reduce the dynamic surface tension of the ink.However, if the dynamic surface tension of the ink is reduced without limit, the ink to be ejected will be exposed to the nozzle surface. And it becomes impossible to discharge properly. For this reason, the solution of lowering the dynamic surface tension of the ink is not realistic because it has a fatal defect as the ink for ink jet.
Further, from the viewpoint of controlling the behavior on the paper surface for maintaining the image quality, in addition to the ejection stability of the ink, the dynamic surface tension of the ink needs to be 30 mN / m or more with a life time of 15 ms.
Therefore, it is necessary to lower the surface energy on the filter side in order to ensure long-term filter liquid permeability while maintaining these, and good filter liquid permeability when the advancing contact angle with water is 100 ° or less. The present inventors have found that this can be ensured, and have completed the present invention.

Next, the inkjet apparatus, the ink supply unit, and the inkjet recording method according to the present invention will be described in more detail.
Although the embodiments described below are preferred embodiments of the present invention, they are provided with various technically preferable limitations. However, the scope of the present invention limits the present invention in the following description. Are not limited to these embodiments unless otherwise described.

<Ink>
The ink supplied (discharged) by the ink jet apparatus according to the present invention contains a pigment, water and a water-soluble organic solvent, and further includes a surfactant, a penetrant, an antifoaming agent, a pH adjuster, and an antiseptic / antifungal agent as required. And other components such as a rust preventive.

<Pigment>
The pigment contained in the ink is for coloring the ink and improving the image density.
The content of the pigment in the ink is preferably 0.1 wt% or more and 50.0 wt% or less, more preferably 0.1 wt% or more and 20.0 wt% or less, and still more preferably 3.0 wt% or more and 15.0 wt% or less. preferable.
The 50% average particle size (D50) of the pigment is preferably from 10 to ₅₀₀ nm, more preferably from 50 to 200 nm. Here, the 50% average particle diameter of the pigment, 23 ° C., in an environment of 55% RH, indicating the value of D ₅₀ as measured by dynamic light scattering at Nikkiso Co., Ltd. Microtrac UPA.

The pigment used is not particularly limited and can be appropriately selected depending on the purpose.
For example, any of an inorganic pigment and an organic pigment may be used. These may be used alone or in combination of two or more. The pigment may be either a black pigment or a color pigment, and can be appropriately selected according to the purpose.

Examples of the inorganic pigment include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, dark blue, cadmium red, chrome yellow, metal powder, and carbon black. Among them, carbon black and the like are preferable. Examples of the carbon black include those manufactured by a known method such as a contact method, a furnace method, and a thermal method.
Examples of the organic pigment include an azo pigment, an azomethine pigment, a polycyclic pigment, a dye chelate, a nitro pigment, a nitroso pigment, and aniline black. Among these, azo pigments and polycyclic pigments are more preferred.

Examples of the azo pigment include an azo lake, an insoluble azo pigment, a condensed azo pigment, and a chelate azo pigment.
Examples of the polycyclic pigments include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinofuralone pigments, rhodamine B lake pigments, and the like. Can be
Examples of the dye chelates include basic dye chelates and acid dye chelates.

Examples of black pigments include carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black, and channel black, copper, iron (CI pigment black 11), and titanium oxide. And organic pigments such as aniline black (CI Pigment Black 1).
As the carbon black, a furnace method, a carbon black produced by the channel method, primary particle diameter of, 15Nm～40nm, specific surface area by BET ^{method, 50m 2 / g~300m 2 / g} , DBP oil absorption amount 40ml / 100g-150ml / 100g, those having a volatile content of 0.5% -10%, and a pH value of 2-9 are preferred.
As the carbon black, a commercially available product can be used. 2300, no. 900, MCF-88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, No. 2200B (all manufactured by Mitsubishi Chemical Corporation); Raven700, 5750, 5250, 5000, 3500, and 1255 (all manufactured by Columbia); Regal400R, 330R, 660R, Mogul L, Monarch700, 800, 880, 900, 1000, 1100, 1300, Monarch 1400 (all manufactured by Cabot); color black FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Printex 35, U, V, 140U, 140V, Special Black 6, 5, 5, 4A, and 4 (all manufactured by Degussa).

  As the pigment for the color, the pigment that can be used for the yellow ink is not particularly limited and can be appropriately selected depending on the purpose. I. Pigment Yellow 1, C.I. I. Pigment Yellow 2, C.I. I. Pigment Yellow 3, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 16, C.I. I. Pigment Yellow 17, C.I. I. Pigment yellow 73, C.I. I. Pigment yellow 74, C.I. I. Pigment Yellow 75, C.I. I. Pigment yellow 83, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 95, C.I. I. Pigment Yellow 97, C.I. I. Pigment Yellow 98, C.I. I. Pigment yellow 114, C.I. I. Pigment yellow 120, C.I. I. Pigment Yellow 128, C.I. I. Pigment yellow 129, C.I. I. Pigment yellow 138, C.I. I. Pigment Yellow 150, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 154, C.I. I. Pigment yellow 155, C.I. I. Pigment Yellow 174, C.I. I. Pigment Yellow 180, and the like.

  The pigment that can be used for the magenta ink is not particularly limited and can be appropriately selected depending on the purpose. I. Pigment Red 5, C.I. I. Pigment Red 7, C.I. I. Pigment Red 12, C.I. I. Pigment Red 48 (Ca), C.I. I. Pigment Red 48 (Mn), C.I. I. Pigment Red 57 (Ca), C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 112, C.I. I. Pigment Red 122, C.I. I. Pigment Red 123, C.I. I. Pigment Red 146, C.I. I. Pigment Red 168, C.I. I. Pigment Red 176, C.I. I. Pigment Red 184, C.I. I. Pigment Red 185, C.I. I. Pigment Red 202, Pigment Violet 19, and the like.

  The pigment that can be used in the cyan ink is not particularly limited and can be appropriately selected depending on the purpose. I. Pigment Blue 1, C.I. I. Pigment Blue 2, C.I. I. Pigment Blue 3, C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 15: 4, C.I. I. Pigment blue 15:34, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 22, C.I. I. Pigment Blue 60, C.I. I. Pigment Blue 63, C.I. I. Pigment Blue 66; I. Bat Blue 4, C.I. I. Bat Blue 60, and the like.

The pigment is added to the ink as a pigment dispersion in which the pigment is dispersed in an aqueous medium.
In order to stably disperse the pigment in an aqueous medium, at least one type of hydrophilic group is directly bonded to the pigment surface and stably dispersed in the absence of a dispersant, a so-called self-dispersion type pigment dispersion, Any kind of pigment such as a dispersant-dispersed pigment using a pigment dispersant can be used. However, it is preferable to use a self-dispersion pigment or a dispersant-dispersion pigment.
Therefore, the pigment dispersion contains at least a pigment and water, and also contains a dispersant as an essential component depending on the dispersion form of the pigment. The pigment dispersion may further contain other components such as a water-soluble resin and a preservative, if necessary.

<Dispersant>
The dispersant contained in the ink is to stably disperse the pigment in an aqueous medium (a medium containing water).
The content of the dispersant in the ink is preferably 5.0 to 40.0 wt%, and more preferably 10.0 to 30.0 wt%, based on the pigment, from the viewpoint of stable dispersion. If the content is less than 5.0 wt%, the dispersion stability of the pigment is inferior, and the pigment is easily aggregated. If the content is more than 40.0 wt%, clogging due to air bubbles is liable to occur because the ink easily foams.

  The dispersant can be used without any particular limitation, and anionic surfactants, nonionic surfactants having an HLB value of 10 to 20 or water-soluble resins are suitable, and these can be used alone. Or two or more of them may be used in combination.

Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, alkylbenzene sulfonate (eg, NH ₄ , Na, Ca, etc.), alkyl diphenyl ether disulfonate (eg, NH ₄ , Na, Ca, etc.), Na salt of dialkyl succinate sulfonic acid, Na salt of naphthalene sulfonic acid formalin condensate, polyoxyethylene polycyclic phenyl ether sulfate (eg, NH ₄ , Na, etc.), laurate, polyoxyethylene alkyl ether sulfate, oleic acid And the like.
Among these, dioctyl sulfosuccinate Na salt and polyoxyethylene styrene phenyl ether sulfonate NH ₄ salt are particularly preferable.

Examples of the nonionic surfactant having an HLB value of 10 to 20 include polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, polyoxyethylene polycyclic phenyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, and polyoxyethylene sorbitan. Examples include ethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethylene alkylamide, and acetylene glycol.
Among these, polyoxyethylene lauryl ether, polyoxyethylene-β-naphthyl ether, polyoxyethylene sorbitan monooleate, and polyoxyethylene styrene phenyl ether are particularly preferred.

Examples of the water-soluble resin include polyacrylic acid, polymethacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic ester copolymer, acrylic acid-alkyl acrylate copolymer, styrene-acrylic acid Copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid-alkyl acrylate copolymer, styrene-methacrylic acid-alkyl acrylate copolymer, styrene-α-methylstyrene-acrylic acid copolymer Styrene-maleic acid copolymer, vinylnaphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-croton Acid copolymer, vinyl acetate-acrylic acid copolymer And the like.
Among these, those having a carboxyl group on the surface are particularly preferred.

<Surfactant>
The surfactant contained in the ink lowers the surface tension of the ink and facilitates penetration into paper.
The content of the surfactant in the ink is preferably 0.1 wt% to 5 wt% as an active ingredient. If the content is less than 0.1 wt%, the permeability to paper becomes insufficient, so that the image quality is degraded. If the content exceeds 5 wt%, non-discharge occurs due to easy foaming.

  Further, in the present invention, in order to satisfy the stable ejection of the ink, it is essential that the dynamic surface tension at a life time of 15 ms (millisecond) is 30 mN / m or more. Must be designed with this in mind (to satisfy the constraints).

The dynamic surface tension can be measured by using a well-known and commonly used method, but in the present invention, it is preferably measured by the maximum bubble pressure method.
The maximum bubble pressure method is a method in which bubbles are released from a tip portion of a probe immersed in a liquid to be measured, and the surface tension is determined from a maximum pressure required for releasing bubbles.
When the radius of the bubble becomes equal to the radius of the tip of the probe, it indicates the maximum pressure, and the dynamic surface tension σ of the ink at this time is expressed by the following equation.

σ = (ΔP · r) / 2

(Where r is the radius of the probe tip and ΔP is the difference between the maximum pressure and the minimum value on the bubble)

In the maximum bubble pressure method, the term "surface life" refers to the time from when a bubble separates from a probe and a new surface is formed until the next maximum bubble pressure.
An instrument for measuring the dynamic surface tension by the maximum normal pressure method is commercially available, and examples thereof include DynoTester (manufactured by SITA).

As long as the above-mentioned restrictions are satisfied, the surfactant used can be used without any particular limitation.
Any of amphoteric surfactants, nonionic surfactants, and anionic surfactants can be used, but polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ester, and the like are used in view of the relationship between pigment dispersion stability and image quality. Nonionic surfactants such as polyoxyethylene alkylamine, polyoxyethylene alkylamide, polyoxyethylene propylene block polymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, and ethylene oxide adduct of acetylene alcohol are preferably used. . In addition, depending on the prescription, a fluorine-based surfactant or a silicone-based surfactant can be used in combination (or used alone).

<Water-soluble organic solvent>
The water-soluble organic solvent contained in the ink contributes to improving the ejection stability by imparting a moisturizing effect to the ink.
The content of the water-soluble organic solvent in the ink is preferably 5 to 50 wt% in total, and more preferably 10 to 40 wt% or less. If the content is less than 25% by weight, the moisture retention of the ink cannot be sufficiently ensured, and the ejection stability will be reduced regardless of the kind of the organic solvent to be contained and the solvent ratio. On the other hand, if the content exceeds 50 wt%, the viscosity of the inkjet ink becomes extremely high, making it difficult to discharge the ink with a general ink discharge device, or inferior in dryness on paper, and further, on plain paper. The character quality may be degraded.

Examples of the water-soluble organic solvent include the following, but are not limited thereto.
For example, ethylene glycol, diethylene glycol, 1,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,5-pentanediol, 1,6-hexanediol, glycerin , 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, 2-ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, polyhydric alcohols such as petriol , Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, Polyhydric alcohol alkyl ethers such as pyrene glycol monoethyl ether; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl Nitrogen-containing heterocyclic compounds such as -2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam and γ-butyrolactone; amides such as formamide, N-methylformamide and N, N-dimethylformamide; monoethanolamine And amines such as diethanolamine and triethylamine, sulfur-containing compounds such as dimethyl sulfoxide, sulfolane and thiodiethanol, propylene carbonate, ethylene carbonate and the like. These water-soluble organic solvents can be used alone or in combination of two or more.
Among them, the inclusion of 1,3-butanediol, diethylene glycol, triethylene glycol and / or glycerin provides an excellent effect in preventing ejection failure due to moisture evaporation.

<Filter>
An ink supply unit and an inkjet recording apparatus according to the present invention include at least one filter in an ink supply path for supplying ink. The filter has an advancing contact angle with water of 100 ° or less.

  The filter is preferably made of stainless steel from the viewpoint of corrosion resistance because the filter is always in contact with the ink, and among them, austenitic stainless steel, particularly SUS304, SUS316 or SUS316L because of its excellent corrosion resistance. It is desirable that The filter preferably includes any one selected from SUS304, SUS316 and SUS316L, and more preferably includes any one of these.

The advancing contact angle in the present invention refers to the advancing contact angle in the Wilhelmy method, and the smaller the value, the higher the hydrophilicity of the filter surface.
In the present invention, the advancing contact angle can be measured by the following procedure.

-Wilhelmy method A filter to be measured is cut into a width of 5 mm and a length of 1 cm, and set on Sigma700 manufactured by KSV. Next, the sample was immersed in a petri dish containing pure water at 5 mm / min, and the advancing contact angle was calculated from the force acting on the sample by the following equation.
F = L · σ · cos θ
(Where F is the force acting when the sample is advanced, L is the perimeter of the sample, σ is the surface tension of water, and θ is the contact angle)

Means for obtaining a filter having an advancing contact angle to water of 100 ° or less is not particularly limited, but the manufactured filter is subjected to acid cleaning using sulfuric acid, hydrofluoric acid, or the like, or alkali cleaning using hydroxide or the like. It is preferable to perform a combination of processes such as organic solvent cleaning, ultrasonic cleaning, passivation, and electrolytic polishing as needed.
In particular, in the case of a metallic filter, rust generated on the surface or oil stain derived from a person or the like may make the filter extremely hydrophobic, and the value of the advancing contact angle increases.
In addition to the above-described cleaning in this case, it is possible to reduce the contact angle with water by treating the surface with a coating agent.

Also, in the case of the advancing contact angle of the filter, unlike the case of measuring a simple plate, not only the hydrophilicity of the surface but also the factor of easy penetration into the inside of the filter influences the influence of the porosity of the filter. receive.
The porosity of the filter represents the amount of porosity with respect to the density of 100% in terms of weight, and is expressed in%.
The porosity of the filter used in the present invention is desirably 70% or more from the viewpoint of easy penetration of the liquid into the inside.

  In addition, the shape of the filter used in the present invention is not particularly limited, and any known filter that satisfies the conditions can be used. Among them, using a sintered filter made by laminating stainless fibers in a felt shape and sintering, or a tatami woven filter formed by tatami weaving of stainless fibers, inkjet recording with longer-term ejection reliability This is desirable because an apparatus and an ink supply unit can be obtained.

<Dissolved oxygen content>
In the present invention, the amount of dissolved oxygen in the ink is less than 3 mg / L.
The amount of dissolved oxygen can be measured by a known and commonly used method, but in the present invention, it is preferably measured by a diaphragm electrode method. The diaphragm electrode method is a method in which oxygen that has passed through a gas permeable membrane is reduced on an electrode, and the amount of dissolved oxygen is calculated from the amount of current.
A dissolved oxygen amount measuring instrument using this method is commercially available, and examples thereof include TOX-999i (manufactured by Toko Chemical Research Laboratories).

  The ink supply unit includes a plurality of pressurized liquid chambers, a nozzle having a hole diameter of 35 μm or less communicating with the pressurized liquid chamber, an ink supply path, and an electric pressure conversion unit or an electrothermal conversion unit for discharging ink. An ink supply unit including an ink tank that generates a negative pressure in the ink discharge unit, and a filter provided between the ink discharge unit and the ink supply unit (in other words, in an ink supply path). .

  The hole diameter (= nozzle diameter) communicating with the pressurized liquid chamber is 35 μm or less, more preferably 30 μm or less, and still more preferably 25 μm or less.

  The upper limit of the pore size of the filter to be used needs to be not more than half of the nozzle diameter in order to remove foreign substances clogging the nozzle, and is preferably 4 μm or more and 10 μm or less. If it is less than 4 μm, pigment particles that do not need to be removed will be trapped, which may shorten the filter life. If it exceeds 10 μm, there is a possibility that a foreign matter which may not be able to cope with a small-diameter nozzle and clog the nozzle may flow out.

[Inkjet recording apparatus, inkjet recording method, ink recorded matter]
An ink jet recording apparatus according to the present invention is provided with the above-described ink supply unit, and other known configurations can be used.
Further, an inkjet recording method according to the present invention is characterized in that an ink droplet is continuously ejected using the inkjet recording apparatus to form an image on a recording medium.
Further, the ink recorded matter according to the present invention is characterized by having an image formed by the ink jet recording method.

  Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples.

<Method of adjusting pigment dispersion>
Each of the pigment dispersions was prepared as described below.
(1) Black dispersion A
90 g of carbon black having a CTAB specific surface area of 150 m ² / g and a DBP oil absorption of 100 ml / 100 g were added to 3000 ml of a 2.5N (normal) sodium sulfate solution, stirred at a temperature of 60 ° C. and a speed of 300 rpm, and reacted for 10 hours. An oxidation treatment was performed. The reaction solution was filtered, the filtered carbon black was neutralized with a sodium hydroxide solution, and ultrafiltration was performed. The obtained carbon black was washed with water, dried, and dispersed in pure water so that the pigment concentration became 20% by mass. Thus, a black pigment dispersion A was obtained.

(2) Cyan dispersion A
A cyan pigment dispersion A was obtained in the same manner as in (1) except that the pigment used in (1) was changed from carbon black to Pigment Blue 15: 3.

(3) Magenta dispersion A
Pigment: 200 parts by mass of Pigment Red 122 Dispersant: 50 parts by mass of polyoxyethylene (n = 40) β-naphthyl ether Water: 750 parts by mass of highly pure water After premixing the above mixture, a bead mill dispersing machine (manufactured by Kotobuki Kogyo Co., Ltd.) Using UAM-015), the particles were dispersed with zirconia beads having a diameter of 0.03 mm at a peripheral speed of 10 m / s at a liquid temperature of 30 ° C. for 15 minutes, and then coarse particles were separated with a centrifuge (Model: Kuboyama Shoji Co., Ltd., Model-3600). After centrifugation, a magenta pigment dispersion A was obtained.

(4) Yellow dispersion A
A yellow dispersion A was obtained in the same manner as in (3), except that the pigment used in (3) was changed from Pigment Red 122 to Pigment Yellow 74.

(5) Black dispersion B
(Preparation of polymer solution)
1,000 parts of methyl ethyl ketone was charged into a three-liter four-neck flask equipped with a dropping device, a thermometer, a nitrogen gas inlet tube, a stirrer, and a reflux condenser, and the liquid temperature was raised to 78 ° C. A mixture of 700 parts of n-butyl methacrylate, 42 parts of n-butyl acrylate, 150 parts of 2-hydroxyethyl methacrylate, 108 parts of methacrylic acid and 80 parts of tert-butyl peroxy-2-ethylhexanoate was applied for 4 hours. And dropped. Further, the reaction was continued at the same temperature for 8 hours.
After allowing the reaction mixture to cool to room temperature, methyl ethyl ketone was added to dilute it so that the nonvolatile content became 50%, to obtain a polymer solution.

(Preparation of polymer fine particle dispersion containing carbon black pigment)
28 g of the polymer solution, 26 g of carbon black pigment, 13.6 g of a 1 mol / L potassium hydroxide solution, 20 g of methyl ethyl ketone, and 30 g of ion-exchanged water were sufficiently stirred and kneaded using a three-roll mill. The obtained paste was poured into 200 g of ion-exchanged water, and after sufficiently stirring, methyl ethyl ketone and water were distilled off using an evaporator, and the mixture was filtered through a 5 μm filter (acetyl cellulose membrane) to remove coarse particles. Thus, a black pigment dispersion B was obtained.

<Ink manufacturing method>
-Pigment dispersion 25 parts by mass-Glycerin 20 parts by mass-Diethylene glycol 10 parts by mass-1,2-pentanediol 5 parts by mass-Surfactant 1 part by mass-Highly pure water 39 parts by mass

Ink Preparation Examples 1 to 7 were mixed at the ratios shown in Table 1 above, stirred for 1 hour 30 minutes, and then filtered through a membrane filter having a pore size of 0.8 μm to obtain Inks 1 to 7.
In addition, two kinds of surfactants were used for adjustment of the ink, and the surfactants used in each preparation example are as shown in Table 1, and the surfactant A and the surfactant B are respectively as follows. Here's what.

Surfactant A: Pionein D-1007 (manufactured by Takemoto Yushi, polyoxyethylene octyl ether)
Surfactant B: Softanol EP-5035 (secondary higher alcohol ethoxylate, manufactured by Nippon Shokubai Co., Ltd.)

In Table 1, × in the deaeration treatment indicates whether or not the deaeration treatment was performed before the evaluation, and the deaeration treatment was performed under reduced pressure using an aspirator.
The dissolved oxygen amount in Table 1 is a value measured immediately before the evaluation using TOX-999i (manufactured by Toko Chemical Laboratory).

<About filter types>
Six filters were used for the evaluation, and the material, shape, porosity, and advancing contact angle with water of each filter are as shown in Table 2 below.

Here, the details of the processing method of the filters A to F are as follows.
The filter A was used after being subjected to a passivation treatment beforehand. Specifically, the filter A was impregnated with concentrated nitric acid at room temperature for 20 minutes, and then sufficiently rinsed with high-purity water before use.
The filter B was used after the electropolishing treatment was performed. An electrode was connected to the filter, and an electric current was passed through the electropolishing liquid to remove particles adhering to the surface.
The filter C was used after acid cleaning, and the filter was immersed in hydrofluoric acid for 5 minutes to sufficiently remove the acid before use.
The filter D is used after performing the coating treatment. Specifically, the filter is immersed in a solution obtained by diluting Wall Guard # 5000 (manufactured by Nippon Building Giken Co., Ltd.) with high-purity water, and ultrasonic waves are applied for 10 minutes. After that, they were rinsed several times with high-purity water.
-Filters E and F were used without special treatment, soaked in high-purity water to easily remove dirt, and then dried.

The method of measuring the advancing contact angle with water is as follows.
(1) Each filter was cut into a width of 5 mm and a length of 1 cm, ultrasonically washed with methanol for 10 minutes, sufficiently rinsed with high-purity water, and dried at 80 ° C. under reduced pressure.
(2) The filter was set on Sigma700 manufactured by KSV, and immersed in a petri dish containing high-purity water at 5 mm / min, and the force applied to the sample when immersing between 3 mm and 8 mm from the end face of the filter. The advancing contact angle was determined from the average value.
(3) For the measurement, four sample pieces were prepared for each filter, and the average value of N = 4 was used as the measured value.

  Using the ink and the filter obtained as described above, evaluation of filter liquid permeability and evaluation of discharge characteristics were performed. The evaluation results and combinations of inks and filters used in the evaluation are shown in Tables 3 and 4 below. In addition, the method and reference | standard of filter liquid permeability evaluation and discharge characteristic evaluation are mentioned later.

<Evaluation of filter permeability>
Two metal bats were connected by a filter unit, and ink was poured so that the head difference was 150 mm.
In an environment of 25 ° C., the ink was allowed to flow while maintaining the water head pressure at 150 mmaq, and the outflow time per ink weight (g) was measured to calculate the fluid resistance.
The rate of change of the fluid resistance from the initial stage (0 g of ink passing amount) to the time of 4000 g of ink passing was calculated.
A change rate of less than 20% is an allowable range.
It should be noted that those which caused remarkable clogging and could not pass 4000 g of liquid were evaluated as x.

<Ejection characteristics evaluation>
An ink-jet printer (IPSiO GX5000 manufactured by Ricoh) was filled with the prepared ink, and 20P / J one-pass solid printing was repeatedly performed on Type 6200 paper (manufactured by NBS Ricoh) three times under an environment of 25 ° C. and 50% RH. Thereafter, a nozzle check pattern was printed and evaluated according to the following criteria. Up to ○ is the allowable range.

[Evaluation criteria]
：: No nozzle missing occurred.
×: Nozzle missing has occurred.

From the above evaluation results, it can be seen that Examples 1 to 4 ensure excellent liquid permeation performance as compared with the other examples.
In Example 5, the pigment contained in the ink used was a resin-coated pigment, and the resin component released from the pigment resulted in slightly lower liquid permeability than Examples 1 to 4, but sufficient liquid permeability was obtained. Was found. In Example 6, the porosity of the filter used was less than 70%, and the density of the filter was high, so that the resistance was likely to increase. However, as in Example 5, sufficient permeable property was exhibited. Do you get it. Further, in Example 7, the filter used was made of iron, and was inferior in rust resistance as compared with the filter made of austenitic stainless steel. It was found to show a range of liquid permeability. Further, in Example 8, although the filter used was a plain tatami weave, it was found that sufficient liquid permeability could be secured.

  On the other hand, Comparative Example 1 is an example in which the dynamic surface tension at the life time of 15 ms of the ink used is too low than the range of the present invention. Therefore, it was found that it did not make sense as an inkjet ink. Comparative Examples 2 and 3 are examples in which the amount of dissolved oxygen contained in the ink used is too high than the range of the present invention, and the air contained in the ink precipitates when passing through the filter, and substantially coarse particles are formed. This has the same adverse effect as having clogged, so that the liquid-passing performance was found to be significantly inferior. Further, Comparative Examples 4 and 5 are examples in which the advancing contact angle of the used ink to water exceeds the range of the present invention, and the wettability of the filter surface is too poor, regardless of the material or shape of the filter. It was found that the liquid permeability was poor. Further, Comparative Examples 6 and 7 are examples in which both the ink and the filter used are out of the range of the present invention, and it was found that the filter liquid permeability was extremely poor.

JP-A-9-187555 JP-A-9-109411 JP 2005-324444 A JP 2006-070105 A JP-A-2004-204075 JP 2009-173829 A JP 2001-302951 A

Claims (7)

Ink, and an inkjet apparatus comprising a filter provided in an ink supply path for supplying the ink,
The ink contains a pigment, water, and a water-soluble organic solvent, has a dynamic surface tension of 30 mN / m or more at a life time of 15 ms, and has a dissolved oxygen amount of less than 3 mg / L in the ink. Wherein the water-soluble organic solvent contains any of 1,3-butanediol, diethylene glycol or glycerin,
An ink jet apparatus, wherein the filter has an advancing contact angle with water of 100 ° or less. Ink, and an inkjet apparatus comprising a filter through which the ink passes,
The ink contains a pigment, water, and a water-soluble organic solvent, has a dynamic surface tension of 30 mN / m or more at a life time of 15 ms, and has a dissolved oxygen amount of less than 3 mg / L in the ink. Wherein the water-soluble organic solvent contains any of 1,3-butanediol, diethylene glycol or glycerin,
An ink jet apparatus, wherein the filter has an advancing contact angle with water of 100 ° or less.   The inkjet device according to claim 1, wherein the dynamic surface tension is 37 mN / m or less.   The inkjet device according to claim 1, wherein the ink contains a surfactant.   The ink jet apparatus according to claim 1, further comprising a filling unit that fills the ink.   The ink-jet apparatus according to claim 1, wherein the dissolved oxygen amount of the ink is 0.9 mg / L or more and 2.2 mg / L or less. An ink jet recording method, comprising: forming an image on a recording medium by continuously ejecting ink droplets by using the ink jet apparatus according to claim 1 .