JP7005899B2 - Liquid ejection device, image forming set, ink and image forming method - Google Patents

Description

The present invention relates to a liquid ejection device, an image forming set, an ink and an image forming method.

It has been conventionally practiced to spray small droplets of ink onto a medium by inkjet or spray to form an ink image on the surface of the medium or to apply ink coating.

In particular, the inkjet recording method has rapidly become widespread in recent years because it can easily record a color image and the running cost is low. As the ink for inkjet recording, a water-based dye ink in which a dye is dissolved in an aqueous medium and a solvent-based ink in which an oil-soluble dye is dissolved in an organic solvent are used. Generally, from the viewpoint of environment and safety, water-soluble dyes dissolved in water or water and a water-soluble organic solvent are used in offices and homes.
However, the recorded image formed by the ink containing such a water-soluble dye has a problem of being inferior in water resistance and light resistance.

On the other hand, water-based pigment inks in which pigments are made into fine particles and dispersed in water are attracting attention. Inkjet recording inks using water-dispersible pigments are known to have excellent water resistance and light resistance.
However, when a pigment is used as a colorant in the ink for inkjet recording, when a normal hydrocarbon-based surfactant is used, the same level as that of the dye ink is achieved in the uniformity of the solid image portion and the color development property of the color image. Is difficult. Therefore, it is already known that by using a fluorine-based surfactant, the surface tension of the ink can be lowered, the uniformity of the solid image portion can be improved, and the color development property can be improved (Patent Document 1).

It is also known that by adding a pigment aqueous dispersion containing a colorant in a dispersed polymer to the ink, strike-through can be suppressed and the image density can be improved (Patent Document 2).
However, in the method of improving the image density in this way, in the ink in which the solids such as pigments and resin particles are dispersed, the ink becomes non-uniform due to the sedimentation of the solids, causing uneven density, or the ink is precipitated and aggregated. The solid content may lead to ejection instability and deterioration of maintainability due to clogging of the nozzle.

It is known that such a problem of maintainability is improved by containing a high boiling point solvent (Patent Document 3).
However, the inclusion of a high boiling point solvent causes problems such as a decrease in image density and a decrease in image dryness.

Further, in the prior art, mainly when cleaning the nozzle surface in the liquid ejection device, the ink left on the nozzle surface adheres to the nozzle hole, and the ink covers the nozzle hole, leading to non-ejection. There is. Further, during cleaning, the ink wiped off is deposited on the end of the nozzle, and the ink deposit extends from the nozzle, which may adhere to the non-image portion during printing and cause an image abnormality as a stain.

An object of the present invention is to provide a liquid ejection device that achieves both high image density and image dryness and excellent maintainability.

In order to solve the above problems, the present invention is a liquid ejection device provided with a liquid ejection unit having a nozzle for ejecting ink containing a coloring material, an organic solvent and water.
The liquid ejection unit has a liquid chamber communicating with the nozzle, and a first supply port and a second supply port for allowing the ink to flow in or out of the liquid chamber.
The liquid ejection device has a circulation means for flowing the ink flowing out from one of the first supply port or the second supply port into the other supply port via a circulation path.
The organic solvent contains a diol compound having a boiling point of 230 ° C. or lower and does not contain an organic solvent having a boiling point higher than 230 ° C., and the organic solvent is 30% by mass or more and 35% by mass or less with respect to the ink. 57.1% by mass or more of the diol compound having a boiling point of 200 ° C. or lower with respect to the total mass of the organic solvent is 10% by mass or more and 15% by mass of the diol compound having a boiling point of 203 ° C. or more and 230 ° C. or less with respect to the ink. Including% or less
The coloring material is characterized by being a self-dispersing colorant having a functional group.

According to the present invention, it is possible to provide a liquid discharge device that achieves both high image density and image dryness and excellent maintainability.

It is a schematic explanatory drawing which shows an example of the liquid discharge apparatus of this invention. It is a perspective schematic explanatory drawing which shows the other example of the liquid discharge apparatus of this invention. It is a side schematic explanatory view which shows the other example of the liquid discharge apparatus of this invention.

Hereinafter, the liquid ejection device, the image forming set, the ink, and the image forming method according to the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited to the embodiments shown below, and can be modified within the range conceivable by those skilled in the art, such as other embodiments, additions, modifications, and deletions. However, as long as the action and effect of the present invention are exhibited, it is included in the scope of the present invention.

The present invention is a liquid ejection device including a liquid ejection unit having a nozzle for ejecting ink containing a coloring material, an organic solvent and water, wherein the liquid ejection portion includes a liquid chamber communicating with the nozzle and the liquid chamber. The liquid ejection device has one of the first supply port and the second supply port, and has a first supply port and a second supply port for flowing ink into and out of the liquid chamber. The organic solvent has a circulation means for flowing the ink flowing out of the ink into the other supply port via a circulation path, and the organic solvent contains a diol compound having a boiling point of 230 ° C. or lower and having a boiling point higher than 230 ° C. It is characterized by containing no solvent.

Further, the present invention is an image forming set including a liquid ejection device having a liquid ejection portion having a nozzle for ejecting ink containing a coloring material, an organic solvent and water, and a recording medium to which the ink is adhered. The liquid ejection unit has a liquid chamber that communicates with the nozzle, and a first supply port and a second supply port for allowing the ink to flow in or out of the liquid chamber. The organic solvent has a circulation means for flowing the ink flowing out from one of the first supply port or the second supply port into the other supply port via a circulation path, and the organic solvent has a boiling point of 230 ° C. or lower. The recording medium is plain paper or low-liquid-absorbent printing with a stechhito sizing degree of 10 seconds or more at ² o'clock with a basis weight of 50 g / m. It is characterized by being paper.

Further, the present invention is ink ejected from a nozzle provided in a liquid ejection portion of a liquid ejection device having a circulating means, wherein the liquid ejection portion has a liquid chamber communicating with the nozzle and the ink. It has a first supply port and a second supply port for flowing in or out of the liquid chamber, and the liquid discharge device flows out from either the first supply port or the second supply port. The ink has a circulation means for flowing the ink into the other supply port via a circulation path, the ink contains a coloring material, an organic solvent and water, and the organic solvent is a diol compound having a boiling point of 230 ° C. or lower. It is characterized in that it does not contain an organic solvent having a boiling point higher than 230 ° C.

Further, the present invention is an image forming method including a ejection step of ejecting ink from a nozzle provided in a liquid ejection portion of a liquid ejection device and a circulation step of circulating the ink in the liquid ejection device. The circulation step is carried out by the liquid ejection portion having a liquid chamber communicating with the nozzle and a first supply port and a second supply port for inflowing or discharging the ink into the liquid chamber. The ink is circulated by flowing out from one of the first supply port or the second supply port and flowing into the other supply port through the circulation path, and the ink contains a coloring material, an organic solvent and water. The organic solvent is characterized by containing a diol compound having a boiling point of 230 ° C. or lower and not containing an organic solvent having a boiling point higher than 230 ° C.
Hereinafter, the details of this embodiment will be described.

(ink)
First, the ink of the present invention will be described. The ink of the present invention contains a coloring material, an organic solvent and water, and may contain other components if necessary. Further, the organic solvent contains a diol compound having a boiling point of 230 ° C. or lower and does not contain an organic solvent having a boiling point higher than 230 ° C.

In the present invention, by using such an organic solvent, it is possible to achieve both high image density and image dryness. This is because the organic solvent in the ink does not contain an organic solvent having a boiling point higher than 230 ° C., so that the drying speed of the solvent in the ink containing water becomes faster after landing on plain paper or the like at the time of printing. Therefore, the ink droplets after landing cause abrupt aggregation of the pigment, the penetration between the plain paper fibers is suppressed, and more pigment remains on the surface of the recording medium such as plain paper. This makes it possible to achieve high image density.

Further, even when printing on a low-absorbency medium, the drying speed of the solvent in the ink becomes high, so that it is possible to suppress the transfer and spreading of the ink due to scratching after printing. Further, by containing a diol compound having a boiling point of 230 ° C. or lower, it is possible to guarantee discharge stability and storage stability.

However, if the ink does not contain the above-mentioned organic solvent having a high boiling point and the ink has a high drying property, the maintenance reliability may be insufficient. Specifically, on the nozzle surface in contact with the outside air and the cleaning mechanism, the ink discharged for empty ejection and cleaning accelerates drying and thickening, so that the ink sticks to and accumulates on the nozzle surface and the cleaning mechanism. Such sticking / deposition on the nozzle surface and the cleaning mechanism may cause problems such as non-ejection and contact with the media during the printing operation to cause stains.

In the present invention, by circulating the highly dry ink through the liquid chamber communicating with the nozzle, it is possible to suppress the drying caused by the contact with the outside air and prevent the above-mentioned problems.
In this way, by equipping the liquid ejection device with a circulation mechanism in combination with ink that has high drying properties and satisfies good image quality, it is possible to suppress the drying of the ink in the liquid ejection device, and it is compatible with excellent maintainability. Is possible.

<Organic solvent>
The ink in the present invention contains a diol compound having a boiling point of 230 ° C. or lower and does not contain an organic solvent having a boiling point higher than 230 ° C., so that both high image density and image dryness can be achieved at the same time. Even if the ink contains an organic solvent having a boiling point higher than 230 ° C., the effect of the present invention can be obtained when the total content is 3% by mass or less. Therefore, in this case, the ink is included in the present invention. be.

Further, all the organic solvents in the present invention are preferably diol compounds having a boiling point of 230 ° C. or lower, and in this case, higher ejection stability and storage stability can be ensured.

Further, the organic solvent in the present invention is preferably a diol compound having a boiling point of 200 ° C. or lower in an amount of 50% by mass or more based on the total mass of the organic solvent. In this case, the drying speed is increased, and a higher image density can be realized by increasing the drying speed.

A diol compound is a kind of alcohol (polycol), and is a compound having a structure in which one hydroxy group is substituted for each of two carbon atoms of a chain-type aliphatic hydrocarbon or a cyclic-type aliphatic hydrocarbon, and glycol. Also called. Specific examples of the diol compound at 230 ° C. or lower include 1,2-ethanediol, ethylene glycol, 2,5-toluenediol, 1,2-butanediol, 1,3-butanediol, and 1,4-butanediol. , 3-Butoxy-1,2-propanediol, 1,2-propanediol, 1,3-propanediol, 1,3-propanedithiol, 1,6-hexanediol, 2,5-hexanediol, 2-methyl -2,3-Butanediol, 3-Methyl-1,3-Butanediol, 2-Methylene-1,3-Propanediol, 3-methoxy-1,2-Propanediol, Propylene Glycol, 1,2-Pentanediol And so on.

The diol compound can be measured by the following method.
-GC-MS measurement method for diol compounds-
After diluting the primer in a 100-fold THF solution and centrifuging, the measurement is carried out by the following method using a 2 micron supernatant solution. Quantification is possible from the peak having a diol compound at a thermal decomposition temperature of 600 ° C.

[Device]
GC analyzer (7890B manufactured by Agilent)
MS analyzer (JEOL Q1500)
Thermal analyzer (Py-3030D manufactured by Frontier Lab)

[Measurement condition]
Heating temperature: 180 ° C
Pyrolysis temperature: 600 ° C
IF temperature of filerizer and GC: 280 ℃
Column: UltraALLOY + 5 L = 30.0m LD = 0.25mm Film = 0.25μm
GC inlet temperature: 280 ° C
Column temperature rise: 50 ° C (holding 2 minutes) to 20 ° C / min to 280 ° C (holding 11.5 minutes)
Carrier gas temperature: 49.38 kpa constant Column flow rate: 1.00 ml / min
Ionization method: EI method (70eV)
Mass range: m / z 20-800
Data analysis software (manufactured by NIST)

The other organic solvent is not particularly limited except for an organic solvent having a boiling point higher than 230 ° C., and a water-soluble organic solvent or the like can also be used.
Examples of other organic solvents include ethers such as polyhydric alcohols, polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines and sulfur-containing compounds. Be done.
Specific examples of the water-soluble organic solvent include, for example, ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, and 1,4-butane. Diol, 2,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol , 2,4-Pentanediol, 1,5-Pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl-1, Multihydric alcohols such as 3-pentanediol and 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, propylene glycol monoethyl ether, etc. Polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, γ-butyrolactone and the like. Nitrogen heterocyclic compounds, formamides, N-methylformamides, N, N-dimethylformamides, 3-methoxy-N, N-dimethylpropionamides, 3-butoxy-N, N-dimethylpropionamides and other amides, monoethanolamines , Amines such as diethanolamine and triethylamine, sulfur-containing compounds such as dimethylsulfoxide, sulfolane and thiodiethanol, propylene carbonate, ethylene carbonate and the like.

In addition, the following can also be mentioned. Polyol compounds having 8 or more carbon atoms and glycol ether compounds are also preferably used. Specific examples of the polyol compound having 8 or more carbon atoms include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.
Specific examples of the glycol ether compound include polyhydric alcohol alkyls such as 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. Ethers; Examples thereof include polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.

A polyol compound having 8 or more carbon atoms and a glycol ether compound can improve the permeability of ink when paper is used as a recording medium.

Further, the detection of an organic solvent having a boiling point of 230 ° C. or higher can be measured by the following method.
-Detection method for organic solvents with boiling point of 230 ° C or higher-
When the weight change due to TG-DTA is measured for 10 mg of ink under the following measurement conditions, it can be confirmed that the solvent of 230 ° C. or higher is not contained by the following formula.

Remaining weight <(solid content mass% in ink + 3 mass%)

[Device]
TG-DTA thermal analyzer (Thermo plus EVO manufactured by Rigaku)

[Measurement condition]
Heat up to 250 ° C at a temperature rise rate of 10 ° C / min Hold at 250 ° C for 30 minutes

The content of the organic solvent in the ink is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 10% by mass or more and 60% by mass or less from the viewpoint of ink drying property and ejection reliability. It is more preferably 20% by mass or more and 60% by mass or less, and further preferably 30% by mass or more and 50% by mass or less.

Further, it is preferable that the total SP value of water and the organic solvent contained in the ink is 12 or less. As a result, the contact angle of the paper surface with respect to the plain paper is reduced, and the dot diameter after landing is increased, so that a higher image density can be obtained.

<Water>
The content of water in the ink is not particularly limited and may be appropriately selected depending on the intended purpose, but from the viewpoint of ink drying property and ejection reliability, it is preferably 10% by mass or more and 90% by mass or less, and 20% by mass. % To 60% by mass is more preferable.

<Color material>
The coloring material is not particularly limited, and pigments and dyes can be used.
As the pigment, an inorganic pigment or an organic pigment can be used. These may be used alone or in combination of two or more. Further, a mixed crystal may be used.
As the pigment, for example, a black pigment, a yellow pigment, a magenta pigment, a cyan pigment, a white pigment, a green pigment, an orange pigment, a glossy color pigment such as gold or silver, a metallic pigment, or the like can be used.
As inorganic pigments, carbon black produced by known methods such as contact method, furnace method, thermal method, in addition to titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, and chrome yellow. Can be used.
Examples of organic pigments include azo pigments and polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinofuralone pigments, etc.). , Dye chelate (for example, basic dye type chelate, acid dye type chelate, etc.), nitro pigment, nitroso pigment, aniline black and the like can be used. Among these pigments, those having a good affinity with a solvent are preferably used. In addition, resin hollow particles and inorganic hollow particles can also be used.
As a specific example of the pigment, for black, carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black, channel black, or copper, iron (CI pigment black 11) , Metals such as titanium oxide, and organic pigments such as aniline black (CI pigment black 1).
Further, for color, C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104 , 108, 109, 110, 117, 120, 138, 150, 153, 155, 180, 185, 213, C.I. I. Pigment Orange 5, 13, 16, 17, 36, 43, 51, C.I. I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48: 2, 48: 2 (Permanent Red 2B (Ca)), 48: 3, 48: 4, 49: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmin 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81, 83, 88, 101 (Mengara), 104, 105, 106, 108 ( Cadmium Red), 112, 114, 122 (Quinacridone Magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 184, 185, 190, 193, 202, 207, 208, 209, 213, 219, 224, 254, 264, C.I. I. Pigment Violet 1 (Rhodamine Lake), 3, 5: 1, 16, 19, 23, 38, C.I. I. Pigment Blue 1, 2, 15 (phthalocyanine blue), 15: 1, 15: 2, 15: 3, 15: 4 (phthalocyanine blue), 16, 17: 1, 56, 60, 63, C.I. I. Pigment Greens 1, 4, 7, 8, 10, 17, 18, 36, etc.
The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used, and one type may be used alone or two or more types may be used in combination.
As the dye, for example, C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142, C.I. I. Acid Red 52,80,82,249,254,289, C.I. I. Acid Blue 9,45,249, C.I. I. Acid Black 1,2,24,94, C.I. I. Food Black 1, 2, C.I. I. Direct Yellow 1,12,24,33,50,55,58,86,132,142,144,173, C.I. I. Direct Red 1,4,9,80,81,225,227, C.I. I. Direct Blue 1,2,15,71,86,87,98,165,199,202, C.I. I. Dylekdo Black 19,38,51,71,154,168,171,195, C.I. I. Reactive Red 14, 32, 55, 79, 249, C.I. I. Reactive Black 3, 4, 35 can be mentioned.

The content of the coloring material in the ink is preferably 0.1% by mass or more and 15% by mass or less, more preferably 1% by mass or more and 10% by mass, from the viewpoint of improving the image density, good fixing property and ejection stability. It is as follows.

To disperse the pigment in the ink, a method of introducing a hydrophilic functional group into the pigment to obtain a self-dispersing pigment, a method of coating the surface of the pigment with a resin and dispersing it, a method of dispersing using a dispersant, And so on.
As a method of introducing a hydrophilic functional group into a pigment to obtain a self-dispersing pigment, for example, a self-dispersing pigment in which a functional group such as a sulfone group or a carboxyl group is added to a pigment (for example, carbon) so that it can be dispersed in water, etc. Can be used.
As a method of coating the surface of the pigment with a resin and dispersing it, a method in which the pigment is encapsulated in microcapsules and can be dispersed in water can be used. This can be rephrased as a resin-coated pigment. In this case, it is not necessary that all the pigments blended in the ink are coated with the resin, and the uncoated pigments and the partially coated pigments are dispersed in the ink as long as the effect of the present invention is not impaired. May be.
Examples of the method of dispersing using a dispersant include a method of dispersing using a known low-molecular-weight dispersant and high-molecular-weight dispersant represented by a surfactant.
As the dispersant, for example, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant and the like can be used depending on the pigment.
RT-100 (nonionic surfactant) manufactured by Takemoto Oil & Fat Co., Ltd. and a naphthalene sulfonic acid Na formalin condensate can also be suitably used as a dispersant.
The dispersant may be used alone or in combination of two or more.

<Pigment dispersion>
It is possible to obtain an ink by mixing a material such as water or an organic solvent with a pigment. It is also possible to produce an ink by mixing a material such as water or an organic solvent with a pigment dispersion obtained by mixing a pigment and other water or a dispersant.
The pigment dispersion is obtained by dispersing water, a pigment, a pigment dispersant, and other components as necessary, and adjusting the particle size. It is good to use a disperser for dispersion.
The particle size of the pigment in the pigment dispersion is not particularly limited, but the maximum frequency is 20 nm or more in terms of the maximum number because the dispersion stability of the pigment is good and the image quality such as ejection stability and image density is also high. It is preferably 500 nm or less, and more preferably 20 nm or more and 150 nm or less. The particle size of the pigment can be measured using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).
The content of the pigment in the pigment dispersion is not particularly limited and may be appropriately selected depending on the intended purpose. However, good ejection stability can be obtained and the image density is increased by 0.1 mass. % Or more and 50% by mass or less are preferable, and 0.1% by mass or more and 30% by mass or less are more preferable.
It is preferable that the pigment dispersion is degassed by filtering coarse particles with a filter, a centrifuge, or the like, if necessary.

The coloring material contained in the ink of the present invention is preferably a self-dispersing colorant having a functional group from the viewpoint of image density on plain paper and maintainability. Since it is a self-dispersing colorant, the image density on plain paper is improved, and since it has a high redispersity, the viscosity is lowered by coming into contact with fresh ink during cleaning, and high maintainability can be realized. ..

<Resin>
The type of resin contained in the ink is not particularly limited and may be appropriately selected depending on the intended purpose. For example, urethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene resin, etc. Examples thereof include resins, styrene-butadiene resins, vinyl chloride resins, acrylic styrene resins, and acrylic silicone resins.
Resin particles made of these resins may be used. It is possible to obtain ink by mixing resin particles with a material such as a coloring material or an organic solvent in the state of a resin emulsion in which water is used as a dispersion medium. As the resin particles, those synthesized as appropriate may be used, or commercially available products may be used. Further, these may be used alone or in combination of two or more kinds of resin particles.

The volume average particle size of the resin particles is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of obtaining good fixability and high image hardness, 10 nm or more and 1,000 nm or less are preferable. More than 200 nm is more preferable, and 10 nm or more and 100 nm or less is particularly preferable.
The volume average particle size can be measured using, for example, a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).

The content of the resin is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of fixability and storage stability of the ink, 1% by mass or more and 30% by mass or less with respect to the total amount of the ink. Is preferable, and 5% by mass or more and 20% by mass or less is more preferable.

The particle size of the solid content in the ink is not particularly limited and can be appropriately selected according to the purpose, but from the viewpoint of improving image quality such as ejection stability and image density, the maximum frequency in terms of the maximum number of inks. Is preferably 20 nm or more and 1000 nm or less, and more preferably 20 nm or more and 150 nm or less. The solid content includes resin particles, pigment particles, and the like. The particle size can be measured using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).

<Additives>
If necessary, a penetrant, a surfactant, a defoaming agent, an antiseptic / antifungal agent, a rust preventive agent, a pH adjuster and the like may be added to the ink.

<Penetrating agent>
As the penetrant, it is preferable to contain at least one non-wetting agent-type polyol compound or glycol ether compound having 8 to 11 carbon atoms.
Here, the non-wetting agent property means having a solubility of 0.2 to 5.0% by mass in water at 25 ° C. Among these penetrants, the 1,3-diol compound represented by the following general formula (I) is preferable, 2-ethyl-1,3-hexanediol [solubility: 4.2% (25 ° C.)], 2 , 2,4-trimethyl-1,3-pentanediol [solubility: 2.0% (25 ° C.)] is particularly preferable.

[In the formula, R ₇ is a methyl group or an ethyl group, R ₈ is a hydrogen or a methyl group, and R ₉ is an ethyl group or a propyl group. ]

As other non-wetting agent-type polyol compounds, examples of aliphatic diols include 2-ethyl-2-methyl-1,3-propanediol, 3,3-dimethyl-1,2-butanediol, and 2,2-. Diol-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2,4-dimethyl-2,4-pentanediol, 2,5-dimethyl-2,5-hexanediol, Examples thereof include 5-hexene-1,2-diol.
The range of the penetrant contained in the entire ink is preferably in the range of 0.5 to 5% by mass, more preferably in the range of 1 to 3% by mass. If the content is as small as less than 0.5% by mass, the penetrability effect of the ink cannot be obtained, and the image quality may not be effective. If it exceeds 5% by mass, problems such as separation without being dissolved in the ink and an increase in the initial viscosity of the ink may occur.

<Surfactant>
As the surfactant, any of a silicone-based surfactant, a fluorine-based surfactant, an amphoteric surfactant, a nonionic surfactant, and an anionic surfactant can be used.
The silicone-based surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. Among them, those that do not decompose even at high pH are preferable, and examples thereof include side chain modified polydimethylsiloxane, double-ended modified polydimethylsiloxane, single-ended modified polydimethylsiloxane, side chain double-ended modified polydimethylsiloxane, and the like. Those having an oxyethylene group and a polyoxyethylene polyoxypropylene group are particularly preferable because they exhibit good properties as an aqueous surfactant. Further, as the silicone-based surfactant, a polyether-modified silicone-based surfactant can also be used, and examples thereof include compounds in which a polyalkylene oxide structure is introduced into the Si portion side chain of dimethylsiloxane.
Examples of the fluorine-based surfactant include a perfluoroalkyl sulfonic acid compound, a perfluoroalkyl carboxylic acid compound, a perfluoroalkyl phosphate ester compound, a perfluoroalkyl ethylene oxide adduct, and a perfluoroalkyl ether group in the side chain. Polyoxyalkylene ether polymer compounds are particularly preferred because they have low foaming properties. Examples of the perfluoroalkyl sulfonic acid compound include perfluoroalkyl sulfonic acid and perfluoroalkyl sulfonic acid salt. Examples of the perfluoroalkylcarboxylic acid compound include perfluoroalkylcarboxylic acid and perfluoroalkylcarboxylic acid salt. The polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain includes 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. Examples thereof include salts of polyoxyalkylene ether polymers. The counter ions of the salts in these fluorine-based surfactants 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). ₃ etc. can be mentioned.
Examples of the amphoteric tenside include laurylaminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.
Examples of the nonionic surfactant include polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkyl amine, polyoxyethylene alkyl amide, polyoxyethylene propylene block polymer, sorbitan fatty acid ester, and polyoxyethylene sorbitan. Examples thereof include a fatty acid ester and an ethylene oxide adduct of acetylene alcohol.
Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, lauryl salt, polyoxyethylene alkyl ether sulfate salt and the like.
These may be used alone or in combination of two or more.

The silicone-based surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. For example, side chain-modified polydimethylsiloxane, double-ended modified polydimethylsiloxane, one-ended modified polydimethylsiloxane, side. Examples thereof include polydimethylsiloxane modified at both ends of the chain, and a polyether-modified silicone-based surfactant having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modifying group exhibits good properties as an aqueous surfactant, and is particularly effective. preferable.
As such a surfactant, an appropriately synthesized one may be used, or a commercially available product may be used. As commercially available products, for example, they can be obtained from Big Chemie Co., Ltd., Shin-Etsu Chemical Co., Ltd., Toray Dow Corning Silicone Co., Ltd., Nippon Emulsion Co., Ltd., Kyoeisha Chemical Co., Ltd., and the like.
The above-mentioned polyether-modified silicone-based surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a polyalkylene oxide structure represented by the general formula (S-1) may be dimethylpoly. Examples thereof include those introduced into the Si part side chain of siloxane.

(However, in the general formula (S-1), m, n, a, and b represent integers. R and R'represent an alkyl group and an alkylene group.)
Commercially available products can be used as the above-mentioned polyether-modified silicone-based surfactant, for example, KF-618, KF-642, KF-643 (Shinetsu Chemical Industry Co., Ltd.), EMALEX-SS-5602, SS- 1906EX (Nippon Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (Toray Dow Corning Silicone Co., Ltd.), BYK-33, BYK-387 (Big Chemie Co., Ltd.), TSF4440, TSF4452, TSF4453 (Toshiba Silicon Co., Ltd.) and the like can be mentioned.

As the fluorine-based surfactant, a compound having 2 to 16 carbon atoms substituted with fluorine is preferable, and a compound having 4 to 16 carbon atoms substituted with fluorine is more preferable.
Examples of the fluorine-based surfactant include a perfluoroalkyl phosphate ester compound, a perfluoroalkylethylene oxide adduct, and a polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain. Among these, the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain is preferable because it has less foaming property, and is particularly a fluorine-based compound represented by the general formula (F-1) and the general formula (F-2). Surfactants are preferred.

In the compound represented by the general formula (F-1), m is preferably an integer of 0 to 10 and n is preferably an integer of 0 to 40 in order to impart water solubility.
C _n F _{2n + 1-} CH ₂ CH (OH) CH ₂ -O- (CH ₂ CH ₂ O) _a -Y General formula (F-2)
In the compound represented by the above general formula (F-2), Y is H or CnF _{2n + 1} and n is an integer of 1 to 6, or CH ₂ CH (OH) CH ₂ -CnF _{2n + 1} and n is 4 to 6. It is an integer, or CpH _{2p + 1} and p is an integer of 1 to 19. a is an integer of 4 to 14.
Commercially available products may be used as the above-mentioned fluorine-based surfactant. Examples of this commercially available product include Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (all manufactured by Asahi Glass Co., Ltd.); Full Lard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431 (all manufactured by Sumitomo 3M Co., Ltd.); Megafuck F-470, F -1405, F-474 (all manufactured by Dainippon Ink and Chemicals Co., Ltd.); Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR (all) FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW (all manufactured by Neos Co., Ltd.), Polyfox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (manufactured by Omniova), Unidyne DSN-403N (manufactured by Daikin Industries, Ltd.), etc. Among these, good print quality, especially color development and permeability to paper. FS-300 manufactured by Du Pont, FT-110, FT-250, FT-251, FT-400S, FT-150, FT- of Neos Co., Ltd. from the viewpoint of remarkably improving wettability and leveling property. 400SW, Polyfox PF-151N manufactured by Omniova, and Unidyne DSN-403N manufactured by Daikin Industries, Ltd. are particularly preferable.

The content of the surfactant in the ink is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of excellent wettability and ejection stability and improvement in image quality, 0.001 mass is used. % Or more and 5% by mass or less are preferable, and 0.05% by mass or more and 5% by mass or less are more preferable.

<Defoamer>
The defoaming agent is not particularly limited, and examples thereof include a silicone-based defoaming agent, a polyether-based defoaming agent, and a fatty acid ester-based defoaming agent. These may be used alone or in combination of two or more. Among these, a silicone-based defoaming agent is preferable because it has an excellent defoaming effect.

<Preservatives and fungicides>
The antiseptic and antifungal agent is not particularly limited, and examples thereof include 1,2-benzisothiazolin-3-one and the like.

<Rust inhibitor>
The rust preventive is not particularly limited, and examples thereof include acidic sulfites and sodium thiosulfate.

<pH adjuster>
The pH adjusting agent is not particularly limited as long as the pH can be adjusted to 7 or more, and examples thereof include amines such as diethanolamine and triethanolamine.

The physical characteristics of the ink are not particularly limited and may be appropriately selected depending on the intended purpose. For example, the viscosity, surface tension, pH and the like are preferably in the following ranges.
The viscosity of the ink at 25 ° C. is preferably 5 mPa · s or more and 30 mPa · s or less, preferably 5 mPa · s or more and 25 mPa · s or less, from the viewpoint of improving the print density and character quality and obtaining good ejection properties. More preferred. Here, for the viscosity, for example, a rotary viscometer (RE-80L manufactured by Toki Sangyo Co., Ltd.) can be used. As the measurement conditions, it is possible to measure at 25 ° C. with a standard cone rotor (1 ° 34'× R24), a sample liquid volume of 1.2 mL, a rotation speed of 50 rpm, and 3 minutes.
The surface tension of the ink is preferably 35 mN / m or less, and more preferably 32 mN / m or less at 25 ° C. from the viewpoint that the ink is preferably leveled on the recording medium and the drying time of the ink is shortened.
The pH of the ink is preferably 7 to 12, and more preferably 8 to 11 from the viewpoint of preventing corrosion of the metal member that comes into contact with the liquid.

<Pretreatment liquid>
The pretreatment liquid contains a flocculant, an organic solvent, and water, and may contain a surfactant, an antifoaming agent, a pH adjuster, an antiseptic / antifungal agent, an anticorrosive agent, and the like, if necessary.
As the organic solvent, surfactant, defoaming agent, pH adjuster, antiseptic and antifungal agent, and rust preventive, the same materials as those used for ink can be used, and other materials used for known treatment liquids can be used. ..
The type of flocculant is not particularly limited, and examples thereof include water-soluble cationic polymers, acids, and polyvalent metal salts.

<Post-treatment liquid>
The post-treatment liquid is not particularly limited as long as it is possible to form a transparent layer. The post-treatment liquid is obtained by selecting and mixing organic solvents, water, resins, surfactants, defoamers, pH adjusters, antiseptic and antifungal agents, rust preventives and the like, if necessary. Further, the post-treatment liquid may be applied to the entire recording area formed on the recording medium, or may be applied only to the area where the ink image is formed.

<Recording medium to which ink is attached>
An object of the present invention is to provide an ink capable of achieving a good image on plain paper, special paper, and low liquid absorption printing paper.
The ink according to the present invention is an ink that can be printed on low liquid absorption printing paper with high image quality.
The low liquid absorption printing paper may be selected from the group of tracing paper, parchment paper, sulfate paper, glassin paper, paraffin paper, or waxed paper.

In the present invention, the "plain paper" is a wide range of commercially available papers, especially papers used for electrostatic copying, which are manufactured with the intention of having a structure, composition, or characteristics optimized for the application of the inkjet recording method. Means unfinished paper. Examples of such recording media include high-quality paper, medium-quality paper, and PPC paper.

In the present invention, the "dedicated paper" means a paper manufactured with the intention of having a structure, composition, or characteristics optimized for the use of the inkjet recording method.

In the present invention, the "low liquid absorption printing paper" means a paper having a low liquid absorption property and a high size as compared with "plain paper" and "special paper", so that ink penetration is extremely difficult. Specifically, it means a paper having a nice human size degree (JIS-P-8122 "paper nice human size degree test method") at a basis weight of 50 g / cm at ² o'clock for 10 seconds or more.

Examples of such a recording medium include second original drawing paper (for example, tracing paper), parchment paper (parchment paper), sulfate paper, glassin paper, paraffin paper, waxed paper and the like.

<Recorded material>
The ink recording material of the present invention comprises an image formed by using the ink of the present invention on a recording medium.
It can be recorded by an inkjet recording device and an inkjet recording method to obtain a recorded material.

(Liquid discharge device)
The liquid ejection device of the present invention includes a liquid ejection unit having a nozzle for ejecting the ink, and the liquid ejection unit is for flowing in or out of a liquid chamber communicating with the nozzle and the ink. It has a first supply port and a second supply port. The liquid ejection device has a circulation means for causing the ink flowing out from one of the first supply port or the second supply port to flow into the other supply port via the circulation path.

FIG. 1 is a schematic diagram for explaining a configuration in an example of the liquid discharge device of the present invention. Examples of the liquid ejection device include, but are not limited to, an inkjet device.

In FIG. 1, a nozzle 3 and a head 2 (having a liquid chamber communicating with the nozzle 3 and a first supply port 5 and a second supply port 6) and four paths (first ink supply path 100, first 2 ink supply path 110, circulation path 120, cleaning liquid supply path 130), 2 liquid supply sections (1st liquid supply section 20, 2nd liquid supply section 40), 4 valves (valves A to D), In addition, the degassing device 121, the liquid circulation means (pump) 122, and the like are shown in the figure.

This will be described in detail as follows. The liquid ejection device 1 is for supplying a nozzle 3 for ejecting droplets of ink or the like, a head (liquid ejection unit) 2 having an ejection mechanism, and a liquid (first liquid, second liquid) to the head 2. It has a first ink supply path (first path) 100.

Further, the head 2 has a second ink supply path (second path) 110 for supplying a liquid (first liquid, second liquid). Further, it has a first liquid supply unit 20 provided with an ink tank (first liquid storage unit) 21 for supplying ink (first liquid) 22 to the head 2 via the first ink supply path 100. ing.

Further, the first ink supply path 100 and the second ink supply path 110 are connected to each other via the valve A (first switching valve 101) and the valve B (second switching valve 111), respectively. It has a circulation path (third path) 120 that bypasses the head 2. It also has a degassing device 121 (degassing means 121a + vacuum generator (pump) 121b) and a liquid circulation means (pump) 122 arranged on the circulation path 120.

Further, it has a cleaning liquid supply path (fourth path) 130 connected to the first ink supply path 100 or the second ink supply path 110 via a valve C (third switching valve 102). The second liquid supply unit 40 is provided with a cleaning liquid tank 41 for supplying the cleaning liquid (second liquid) 42 to the head via the cleaning liquid supply path (fourth path) 130.

Further, a valve D installed on the first ink supply path 100 or the second ink supply path 110 for flowing the liquid in the first ink supply path 100 or the second ink supply path 110 to the head. (Route opening / closing means 112) is provided.
Further details will be described below.

The head (liquid ejection unit) 2 includes a plurality of fine nozzles 3 for ejecting ink (first liquid) 22 on the tip surface thereof, and inside the head (liquid ejection unit) 2 is a liquid chamber (not shown) that communicates with the nozzles and holds ink. It has. Further, at different portions of the head 2, a first supply port 5 and a second supply port 6 for inflowing or flowing out ink or cleaning liquid into the liquid chamber are arranged, respectively. The first supply port 5 is in communication with one end of the first ink supply path 100, and the second supply port 6 is in communication with one end of the second ink supply path 110.

Examples of the method of ejecting ink as droplets from the nozzle 3 (liquid ejection mechanism) include a method of heating and extruding ink, and a method of extruding ink by applying a voltage to a piezo element arranged inside the head to deform it. Be done. As a result, printing can be performed by ejecting ink to the printing target. Examples of the printing target include sheets such as paper.

One end of the first ink supply path (first path) 100 is connected to the first supply port 5 of the head, and the other end is connected to the ink 22 in the ink tank 21, and the three flow paths r1 and r2 are connected. , R3.

The cleaning liquid supply path (fourth path) 130 is composed of a flow path r4 having one end connected to the valve C and the other end leading to the cleaning liquid 42 in the cleaning liquid tank 41.

Valve A (first switching valve 101), valve B (second switching valve 111), and valve C (third switching valve 102) are connected to each of the three paths and are connected to each of the three paths. It has a function of conducting (communication) any two of them at the same time.

That is, the bulb A is arranged in the middle of the first ink supply path 100 and is connected to one end of the circulation path 120. The valve B is arranged in the middle of the second ink supply path 110 and is connected to the other end of the circulation path 120. The valve C is arranged in the middle of the first ink supply path 100 closer to the ink tank 21 than the valve A, and is connected to one end (downstream side end) of the cleaning liquid supply path 130.

The valve D (path opening / closing means 112) is arranged in the middle of the second ink supply path 110 closer to the waste liquid tank 50 than the valve B, and opens and closes the second ink supply path 110 to communicate with the atmosphere. Has a function to connect / disconnect (block, connect).

Examples of the method for switching the connection pattern (opening / closing pattern) between the paths by the valve A, the valve B, the valve C, and the valve D include a manual type, a pneumatic type, and an electromagnetic type. However, when these are controlled by a control circuit, an electromagnetic type is desirable.

Next, the ink tank 21 and its peripheral portion (first liquid supply unit 20) will be described.
The ink tank 21 is a container for storing ink discharged from the nozzle of the head 2.
The first pressurizing device (first pressurizing means) 23 and the depressurizing device (depressurizing means) 24 communicate with the gas phase at the upper part in the ink tank.

Further, one end (opening) of the first ink supply path 100 enters the ink tank and reaches the lower portion thereof, and is arranged so as to communicate with the ink 22 inside the ink tank.
The first ink supply path 100 is connected from the inside of the ink tank 21 to the first supply port 5 through the valve C and the valve A.

The first pressurizing device 23 is a pneumatic pressurizing device that sends out compressed air, and is arbitrarily controlled to be driven and stopped by receiving a control signal from a control circuit. As an example, the first pressurizing device 23 may include a configuration in which a compressor and a solenoid valve that opens and closes a path for sending out compressed air generated by the compressor are combined. When the first pressurizing device 23 is driven, the gas phase in the sealed ink tank is pressurized, and the ink is pushed out in the direction of the first ink supply path 100.

The decompression device 24 is a device that decompresses air, and is driven, stopped, and the magnitude of the decompression amount is controlled by a control circuit. The decompression device 24 generates a pressure difference between the first liquid supply unit 20 and the second ink supply path 110, and collects ink (first liquid) from the head to the first liquid supply unit 20. It constitutes the first liquid recovery mechanism.

As the decompression device 24, a configuration in which a vacuum pump and an adjustment device for adjusting the magnitude of the decompression amount by limiting the flow rate of air flowing through the path connected to the vacuum pump can be considered. When the pressure reducing device 24 is driven to reduce the gas phase in the ink tank 21, the ink in the first ink supply path 100 is pulled back to the ink tank 21 side.

In the liquid ejection device 1, when the ink pressure in the head 2 is higher than the atmospheric pressure, ink may unintentionally leak from the nozzle 3. In order to prevent this, it is effective to drive the decompression device 24. The ink in the ink tank is depressurized by depressurizing the gas phase in the sealed ink tank. As a result, negative pressure is supplied to the liquid chamber of the head through the first ink supply path 100, and the ink in the head can be depressurized. Therefore, the pressure of the ink in the head can be maintained at an appropriate negative pressure. Further, by increasing the amount of decompression generated by the decompression device, the ink in the head can be collected in the ink tank through the first ink supply path 100.

Next, the configuration of the cleaning liquid tank 41 and its peripheral portion (second liquid supply unit 40) will be described.
The cleaning liquid tank 41 is a closed container for storing the cleaning liquid 42 for cleaning the head 2 and its peripheral paths (first ink supply path 100, second ink supply path 110). The second pressurizing device (second pressurizing means) 43 communicates with the gas phase at the upper part in the cleaning liquid tank 41.

Further, the end portion (opening) of the cleaning liquid supply path 130 enters the cleaning liquid tank and extends to the lower portion thereof, and is arranged so as to communicate with the cleaning liquid inside the cleaning liquid tank. The cleaning liquid supply path 130 is connected to the valve C from the cleaning liquid tank 41.
The internal configuration of the second pressurizing device 43 is the same as that of the first pressurizing device 23. When the second pressurizing device 43 is driven, the gas phase in the cleaning liquid tank is pressurized, and the cleaning liquid is pushed out in the direction of the cleaning liquid supply path 130.

Next, the configuration of the waste liquid tank 50 and its surroundings will be described.
The waste liquid tank 50 is a container for discharging a part of the cleaning liquid 42 that has washed the liquid chamber of the head. The structure is such that the liquid discharged from the head to the second ink supply path 110 is received by the waste liquid tank 50.

The waste liquid in the waste liquid tank is not in contact with the end of the second ink supply path 110, and the end of the second ink supply path 110 on the waste liquid tank 50 side is in contact with the atmosphere. As a result, when the decompression device 24 on the ink tank 21 side is driven, the atmosphere can be sucked into the head 2 from the second ink supply path 110.
The waste liquid tank 50 is used for cleaning the path around the head in the cleaning step described later.

Next, the circulation path 120 for circulating the liquid through the path avoiding the head will be described.
One end of the circulation path 120 is connected to the valve A, and the other end is connected to the valve B. A degassing device 121a, a pump 122, and a filter 123 are arranged on the circulation flow path.
The degassing device 121a is a device for removing the dissolved gas in the ink. The inside of the degassing device has a structure divided into an ink chamber 121a-1 and a gas chamber 121a-2. The ink chamber and the gas chamber are partitioned by a member 121a-3 that does not allow the liquid to pass through but allows the gas to pass through. When the ink is poured into the ink chamber 121a-1 and the pressure in the gas chamber 121a-2 is reduced, the gas dissolved in the ink in the ink chamber moves to the gas chamber via the member 121a-3 through which the gas is transmitted, and the inside of the ink is filled with the ink. You can degas. A hollow fiber membrane is mentioned as a member that allows gas to pass through without passing liquid.

As the degassing device, a hollow fiber bundle made of a material having the property of allowing ink to pass through, for example, a Teflon (registered trademark) tube or a silicon tube, is placed in the degassing chamber, and the surrounding area is degassed by a vacuum pump. It is also possible to use a substance that separates and removes the gas dissolved in the ink by processing. Further, as the ink degassing method in the degassing device, various other methods such as an ultrasonic vibration method and a centrifugal separation method can be adopted.

The filter 123 allows the ink flowing through the circulation path 120 to pass through, and can remove dust, foreign matter, solid matter, and the like mixed in the ink. Examples of the filter material include fibrous materials such as glass fiber.

The pump 122 is a means for circulating the ink in the circulation path 120 and the head 2 at a constant flow rate. The drive and stop of the pump can be arbitrarily controlled using the control circuit.

The gas chamber 121a-2 of the degassing device is communicated with and connected to the vacuum generator 121b via the tube 121c. Degassing from the ink can be performed by driving the vacuum generator 121b to reduce the pressure in the gas chamber 121a-2 in the degassing device 121a.
Examples of the vacuum generator 121b include a vacuum pump and the like. The vacuum generator can be arbitrarily controlled to be driven and stopped by a control circuit. Thereby, the degassing and stopping by the degassing device can be arbitrarily controlled.
The order in which the pump 122, the deaerator 121a, and the filter 123 are arranged in the middle of the circulation path may be in any order.

Next, a procedure for filling the circulation path 120 with ink will be described.
First, the valve A is operated and set so that the flow paths (r1, r2, r8) from the ink tank 21 to the degassing device 121a can pass through. On the other hand, the valve A shuts off the flow path r3, and the valve C also shuts off the flow path r4. Further, the valve B is operated and set so that the pump 122 in the circulation path and the waste liquid tank 50 (atmosphere) can communicate with each other. The pump 122 is driven to move the ink from the ink tank 21 toward the waste liquid tank 50. That is, the flow path r5 is blocked by the valve B to allow the flow path r11 (flow path r10, r9, r8) to communicate with the flow path r6, and the valve D is opened to allow the flow path r6 and r7 to communicate with each other. The pump is driven until the circulation path 120 (r8, r9, r10, r11) from the valve A to the degassing device 121a, the pump 122, and the valve B is filled with ink. The pump is stopped when the circulation path 120 is filled with ink.
As a result, the circulation path of the valve A, the degassing device 121, the pump 122, the filter 123, and the valve B is filled with ink.

Next, a method of filling the head 2 with ink will be described.
The valves A and C are operated to set the flow paths (r1, r2, r3) from the ink tank 21 to the first supply port 5 in a communicating state. Operate the valve A to open the flow path r8. Further, the valve C is operated to shut off the flow path r4. Further, the valve B is operated to allow the flow paths r5, r6, and r11 to communicate with each other, and the flow path is set so as to communicate with the waste liquid tank 50 from the second supply port 6. At this time, the valve D is operated to open the flow path r7.
As a result, the flow paths r1, r2, r3, the liquid chamber in the head, and the flow paths r5, r6, and r7 are in communication with each other. The circulation path 120 is also in a state of communicating with the first ink supply path 100 and the valve B.

Next, the inside of the ink tank 21 is pressurized by using the first pressurizing device 23, and the ink 22 is moved into the head 2 through the first ink supply path 100. When the first ink supply path 100, the liquid chamber in the head, and the flow paths r1 to r3, r5, and r6 from the second supply port 6 to the valve D are filled with ink, the ink tank 21 is pressurized. Stop. Next, the valve D is closed.
As a result, the circulation path of the ink tank 21 to the degassing device 121a to the pump 122 to the filter 123 to the valve B and the head are filled with ink. By driving the head 2 in this state, it becomes possible to eject ink droplets from the nozzle 3.

Further, by driving the vacuum generator 121b while circulating the ink in the circulation path by the pump 122, it is possible to carry out degassing from the ink using the degassing device 121a.

Since the ink is circulated and degassed in the circulation path by using the pump in this way, the ink can be degassed. According to the present embodiment, by circulating the ink in the circulation path, it is possible to suppress the drying caused by the contact with the outside air and prevent the ink from drying in the liquid ejection device. Further, by degassing, the drying caused by contact with the outside air can be further suppressed, and the drying of the ink can be further suppressed.
Further, as will be described later, the inside of the head 2 can be cleaned by pressurizing the cleaning liquid 42 with pneumatic pressure and pushing it out from the nozzle 3, which can prevent the ejection stability due to the clogging of the nozzle and improve maintainability. Can be improved.

Next, a method of ejecting ink (droplets) from the nozzle of the head will be described.
The valve A and the valve C are operated so that the first ink supply path 100 from the ink tank 21 to the first supply port 5 can be set. Operate the valve B to communicate the flow paths r5 and r6, set the flow path so that the flow path can communicate from the second supply port 6 to the waste liquid tank (atmosphere), and operate the valve D so that the flow path r7 opens. set.
At this time, the liquid chamber in the head 2 is filled with ink, and the first ink supply path 100 from the ink tank 21 to the head 2 is open.

Next, the head is driven by using the head drive circuit, and ink is ejected from the nozzle. When the ink is ejected and the ink in the liquid chamber in the head is consumed, the ink is supplied from the ink tank to the head by the osmotic pressure. Further, by driving the decompression device 24 to adjust the decompression amount in the ink tank, the ink pressure in the head is maintained at an appropriate negative pressure through the gas phase in the ink tank and the first ink supply path 100. ..

Here, the amount of negative pressure for properly maintaining the ink pressure in the head 2 will be described. When the ink tank 21 is installed at a position relatively higher than the head 2 and the head is filled with ink, pressure is applied to the ink in the head 2 according to Bernoulli's theorem.

Here, let P1 be the pressure of the gas phase in the ink tank. Further, the ink pressure of the nozzle portion in the head is P2. Further, the height of the bottom surface of the ink tank as seen from the nozzle portion is set to h0.
At this time, the ink pressure P2 of the nozzle portion is given by the following equation.
P2 = P1 + ρ * h0 * g (Equation 1)
Here, ρ is the ink density and g is the gravitational acceleration.

If the pressure P1 of the gas phase in the ink tank is equal to the atmospheric pressure, the ink pressure P2 of the nozzle portion becomes a pressure higher than the atmospheric pressure according to the equation 1. At this time, since the pressure of the air outside the nozzle is atmospheric pressure, the pressure P2 inside the nozzle portion becomes higher than the air outside the nozzle portion, and a phenomenon occurs in which ink drips from the nozzle portion to the outside. In order to prevent the ink from dripping from the nozzle portion to the outside, the ink pressure P2 of the nozzle portion needs to be about the same as the atmospheric pressure. Further, in order to prevent the ink from dripping from the nozzle portion to the outside, it is effective to make the pressure P1 of the gas phase in the ink tank smaller than the atmospheric pressure from the relation of the formula 1.

Assuming that the pressure of the gas in the gas phase in the ink tank is P1'when the ink pressure P2 of the nozzle portion is equal to the atmospheric pressure, P1'is given by the following formula from the formula 1.
P1'= P0-ρ * h0 * g (Equation 2)
Here, P0 is atmospheric pressure.

When the ink is ejected from the head, the decompression device is driven so that the pressure of the gas phase of the ink tank becomes about the same as P1'given by the formula 2. Printing can be performed by moving the print target and the head relative to each other while ejecting ink from the head.

Next, a method of circulating and degassing the ink in the circulation path 120 (circulation and degassing timing, ink flow direction and flow path) will be described.
As an example, in the liquid ejection device 1, a degassing method for degassing while circulating ink (first liquid) in a circulation path (third path) 120 is provided.

In this degassing method of degassing while circulating, the valve A (first switching valve 101), the circulation path 120, the valve B (second switching valve 111), and the head 2 (liquid discharge portion) are closed. In the state where the ink is filled in the path (flow path r3, r8, r9, r10, r11, r5, head), the ink is circulated by the pump 122 (liquid circulation means) and the degassing device 121a (degassing). Means) is used to degas the ink.
That is, in this example, circulation and deaeration are performed in a state where the valves A to the first supply port 5 to the head 2 to the second supply port 6 to the valve B and the circulation path 120 are filled with ink. ..

First, the ink in the closed path of the valve A, the deaerator 121a, the pump 122, the filter 123, the valve B, the second supply port 6, the head 2, the first supply port 5, and the valve A is circulated by the pump. do.
At this time, the valve A is set so that the flow paths r3 and r8 leading from the first supply port 5 to the degassing device 121a communicate with each other (the flow path r2 is cut off). The valve B is set so that the flow paths r10, r11, and r5 from the pump 122 to the second supply port 6 communicate with each other (the flow path r6 is shut off).

Next, while the pump 122 is driven to circulate the ink in the path, the degassing device 121a is used to degas the ink. That is, the vacuum generator 121b is driven to reduce the pressure in the gas chamber 121a-2 inside the degassing device. As a result, the dissolved air in the ink flowing inside the ink chamber 121a-1 of the degassing device 121a is sucked to the vacuum generator side through the degassing device 121a to degas the ink.
At this time, since the ink passes through the filter 123 in the circulation path, fine particles such as dust mixed in the ink can be removed.

Ink circulation and degassing are carried out for a predetermined time. After a predetermined time has elapsed from the start of circulation and degassing, the vacuum generator 121b is stopped to stop the degassing operation. Next, the pump is stopped to stop the ink circulation.
The direction in which the ink is circulated in the closed path by the pump 122 can be circulated and degassed by either clockwise or counterclockwise in FIG.

<Embodiment of Liquid Discharge Device of the Present Invention>
Next, as an embodiment of the liquid ejection device according to the present invention, for example, an image forming apparatus such as an inkjet printer (inkjet recording apparatus) can be mentioned. An example thereof will be described with reference to FIGS. 2 and 3. FIG. 2 is a schematic perspective view of the inkjet recording device, and FIG. 3 is a schematic side view of the recording device.

The inkjet recording apparatus shown in FIGS. 2 and 3 supplies ink to a recording head and a recording head including a carriage movable in the main scanning direction inside the recording apparatus main body 201 and an inkjet head mounted on the carriage and carrying out the present invention. A printing mechanism unit 202 or the like composed of an ink cartridge or the like is stored. A paper cassette (or a paper tray) 204 capable of loading a large number of sheets P can be freely inserted and removed from the front side to the lower portion of the apparatus main body 201.

Further, the manual feed tray 205 for manually feeding the paper P can be opened and closed, the paper P supplied from the paper feed cassette 204 or the manual feed tray 205 is taken in, and the required image is printed by the printing mechanism unit 202. After recording, the paper is discharged to the paper ejection tray 206 mounted on the rear surface side.

The printing mechanism unit 202 slidably holds the carriage 209 in the main scanning direction by the main guide rod 207 and the slave guide rod 208, which are guide members laid horizontally on the left and right side plates. The carriage 209 is provided with a head 210 composed of an inkjet head according to the present invention, which ejects ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk), into a plurality of ink ejection ports (nozzles). The holes) are arranged in a direction intersecting the main scanning direction, and the ink droplets are mounted with the ink droplet ejection direction facing downward. Further, each ink cartridge 211 for supplying ink of each color to the head 210 is replaceably mounted on the carriage 209.

The ink cartridge 211 has an atmosphere port that communicates with the atmosphere above, a supply port that supplies ink to the inkjet head below, and a porous body filled with ink inside, and the capillary force of the porous body. Keeps the ink supplied to the inkjet head at a slight negative pressure. Further, although the head 210 of each color is used as the recording head here, one head having a nozzle hole for ejecting ink droplets of each color may be used.

Here, the carriage 209 is slidably fitted on the main guide rod 207 on the rear side (downstream side in the paper transport direction) and slidably mounted on the slave guide rod 208 on the front side (upstream side in the paper transport direction). is doing. In order to move and scan the carriage 209 in the main scanning direction, a timing belt 215 is attached between the drive pulley 213 rotationally driven by the main scanning motor 212 and the driven pulley 214. The timing belt 215 is fixed to the carriage 209, and the carriage 209 is reciprocated by the forward and reverse rotation of the main scanning motor 212.

On the other hand, in order to convey the paper P set in the paper cassette 204 to the lower side of the head 210, the paper P is guided to the paper feed roller 216 and the friction pad 217 that separate and supply the paper P from the paper feed cassette 204. The guide member 218, the transport roller 219 that inverts and conveys the fed paper P, and the tip that defines the feed angle of the paper P from the transport roller 220 and the transport roller 219 that are pressed against the peripheral surface of the transport roller 219. A roller 221 is provided. The transfer roller 219 is rotationally driven by the sub-scanning motor 222 via the gear train.

A printing receiving member 223, which is a paper guide member for guiding the paper P sent out from the transport roller 219 on the lower side of the recording head 210 corresponding to the moving range of the carriage 209 in the main scanning direction, is provided. On the downstream side of the imprint receiving member 223 in the paper transport direction, a transport roller 224 and a spur 225 that are rotationally driven to feed the paper P in the paper discharge direction are provided, and further, the paper is discharged to the paper discharge tray 206. A roller 226 and a spur 227, and a guide member 228 and 229 forming a paper ejection path are arranged.

At the time of recording, by driving the head 210 in response to an image signal while moving the carriage 209, ink is ejected to the stopped paper P to record one line, and after the predetermined amount of paper P is conveyed, the next Record the line. When the recording end signal or the signal that the rear end of the paper P reaches the recording area is received, the recording operation is ended and the paper P is ejected.

Further, a recovery device 230 for recovering the ejection failure of the head 210 is arranged at a position outside the recording area on the right end side in the moving direction of the carriage 209. The recovery device 230 has a cap means, a suction means, and a cleaning means. The carriage 209 is moved to the recovery device 230 side during printing standby, and the head 210 is capped by the capping means, and the ejection port portion is kept in a wet state to prevent ejection defects due to ink drying. In addition, by ejecting ink that is not related to recording during recording, the ink viscosities of all the ejection ports are kept constant, and stable ejection performance is maintained.

When a ejection failure occurs, the ejection port (nozzle hole) of the head 210 is sealed by a capping means, and air bubbles and the like are sucked out from the ejection port by a suction means through a tube, and ink and dust adhering to the ejection port surface. Etc. are removed by cleaning means and the ejection failure is recovered. Further, the sucked ink is discharged to a waste ink reservoir installed in the lower part of the main body, and is absorbed and held by an ink absorber inside the waste ink reservoir.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples. In addition, Examples 2, 4 to 12 are Reference Examples 2, 4 to 12, which are not included in the present invention.

(Preparation Example 1)
<Preparation of Bk self-dispersion pigment dispersion>
100 g of Black Pearls (registered trademark) 1000 (carbon black having a BET surface area of 343 m ² / g and DBPA 105 mL / 100 g) manufactured by Cabot Corporation, 100 mmol of sulfanilic acid and 1 L of ion-exchanged high pure water were mixed with a Silverson mixer (6000 rpm) in a room temperature environment. If the pH of the resulting slurry is higher than 4, 100 mmol nitric acid is added. After 30 minutes, sodium nitrite (100 mmol) dissolved in a small amount of ion-exchanged high pure water was slowly added to the mixture. Further, the mixture was heated to 60 ° C. with stirring and reacted for 1 hour. A modified pigment in which sulfanilic acid was added to carbon black could be produced. Then, the pH was adjusted to 9 with a 10% tetrabutylammonium hydroxide solution (methanol solution) to obtain a modified pigment dispersion after 30 minutes. Ultrafiltration using a dialysis membrane using a dispersion containing at least one sulfanyl acid group or a pigment bonded to a tetrabutylammonium sulfate sulfate and ion-exchanged high-pure water is performed, and further ultrasonic dispersion is performed to carry out the pigment. A modified pigment dispersion having a solid content concentrated to 20% was obtained. The surface treatment level was 0.75 mmol / g, and the particle size (D50) measured by a particle size distribution measuring device (Nanotrack UPA-EX150 manufactured by Nikkiso Co., Ltd.) was 120 nm.

(Preparation Example 2)
<Preparation of Bk resin-coated pigment dispersion>
-Preparation of polymer solution A-
After sufficient nitrogen gas replacement in a 1 L flask equipped with a mechanical stirrer, a thermometer, a nitrogen gas introduction tube, a reflux tube, and a dropping funnel, 11.2 g of styrene, 2.8 g of acrylic acid, and 12.0 g of lauryl methacrylate. , 4.0 g of polyethylene glycol methacrylate, 4.0 g of styrene macromer, and 0.4 g of mercaptoethanol were mixed and heated to 65 ° C. Next, 100.8 g of styrene, 25.2 g of acrylic acid, 108.0 g of lauryl methacrylate, 36.0 g of polyethylene glycol methacrylate, 60.0 g of hydroxylethyl methacrylate, 36.0 g of styrene macromer, 3.6 g of mercaptoethanol, and azobismethylvalero. A mixed solution of 2.4 g of nitrile and 18 g of methyl ethyl ketone was added dropwise into the flask over 2.5 hours. After the dropping, a mixed solution of 0.8 g of azobismethylvaleronitrile and 18 g of methyl ethyl ketone was dropped into the flask over 0.5 hours. After aging at 65 ° C. for 1 hour, 0.8 g of azobismethylvaleronitrile was added, and the mixture was further aged for 1 hour. After completion of the reaction, 364 g of methyl ethyl ketone was added into the flask to obtain 800 g of the polymer solution A having a concentration of 50% by mass.

-Preparation of carbon black pigment-containing polymer fine particle dispersion-
28 g of polymer solution A and C.I. I. After sufficiently stirring 42 g of carbon black (FW100 manufactured by Degussa), 13.6 g of a 1 mol / L potassium hydroxide aqueous solution, 20 g of methyl ethyl ketone, and 13.6 g of ion-exchanged water, the mixture was kneaded using a roll mill. The obtained paste was put into 200 g of pure water, stirred sufficiently, and then methyl ethyl ketone and water were distilled off using an evaporator, and this dispersion was used with a polyvinylidene fluoride having an average pore size of 5.0 μm in order to remove coarse particles. Pressurization was performed with a membrane filter to obtain a carbon black pigment-containing polymer fine particle dispersion having a pigment solid content of 15% by mass and a solid content concentration of 20% by mass. The particle size (D50) of the polymer fine particles in the carbon black pigment-containing polymer fine particle dispersion was measured by a particle size distribution measuring device (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.) and found to be 104 nm.

(Preparation Example 3)
<Preparation of Bk Surfactant Dispersion Pigment Dispersion>
Carbon black 175 parts by mass (NIPEX160, manufactured by Degussa, BET specific surface area 150 m ² / g,
Average primary particle size 20 nm, pH 4.0, DBP oil absorption 620 g / 100 g)
175 parts by mass of sodium formalin condensate of sodium naphthalene sulfonate (Pionin A-45-PN manufactured by Takemoto Oil & Fat Co., Ltd., dimer of naphthalene sulfonic acid,
Total content of trimers and tetramers = 50% by mass)
Distilled water 650 parts by mass

The above mixture was premixed to prepare a mixed slurry (a). This was circulated and dispersed for 3 minutes at a peripheral speed of 10 m / s and a liquid temperature of 10 ° C. using a disk-type media mill (DMR type manufactured by Ashizawa Finetech Co., Ltd.) using 0.05 mm zirconia beads and a filling rate of 55%. The coarse particles were centrifuged with a centrifuge (Model-7700, manufactured by Kubota Shoji Co., Ltd.) to obtain a surfactant-dispersed pigment dispersion having a pigment concentration of 13% by mass.

(Preparation Example 4)
<Preparation of resin water dispersion 1>
In a simple pressurized reaction device equipped with a stirrer and a heater, Mn2,000 crystalline polycarbonate diol [Duranol T6002, manufactured by Asahi Kasei Chemicals Co., Ltd.] 287.9 parts, 1,4 butanediol 3.6 parts, DMPA ( 8.9 parts of dimethylol propionic acid, 98.3 parts of hydrogenated MDI (diphenylmethane diisocyanate) and 326.2 parts of acetone were charged while introducing nitrogen. After that, it was heated to 90 ° C. and subjected to a urethanization reaction over 8 hours to produce a prepolymer.
After cooling the reaction mixture to 40 ° C., 7.9 parts of triethylamine was added and mixed, and 568.8 parts of water was further added and emulsified with a rotor-stator type mechanical emulsifier to obtain an aqueous dispersion. .. To the obtained aqueous dispersion, 28.1 parts of a 10% aqueous ethylenediamine solution was added under stirring, and the mixture was stirred at 50 ° C. for 5 hours to carry out a chain extension reaction.
Then, acetone was removed at 65 ° C. under reduced pressure, and the water content was adjusted to obtain a resin aqueous dispersion 1 of a polyurethane resin having a solid content of 40% by mass. The particle size (D50) of the resin water dispersion 1 of the polyurethane resin was measured by a particle size distribution measuring device (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.) and found to be 34 nm.

(Preparation Example 5)
<Preparation of resin water dispersion 2>
After sufficiently substituting nitrogen gas in a 1 L flask equipped with a mechanical stirrer, a thermometer, a nitrogen gas introduction tube, a reflux tube, and a dropping funnel, 17.5 g of Latemul S-180 and 350 g of ion-exchanged water are added and mixed. Then, the temperature was raised to 65 ° C.
After raising the temperature, 3.0 g of the reaction initiator t-butylperoxobenzoate and 1.0 g of sodium isoascorbate are added, and after 5 minutes, 45 g of methyl methacrylate, 160 g of -2-ethylhexyl methacrylate, 5 g of acrylic acid, and methacrylic acid are added. Butyl acid (45 g), cyclohexyl methacrylate (30 g), vinyltriethoxysilane (15 g), Latemul S-180 (8.0 g), and ion-exchanged water (340 g) were mixed and added dropwise over 3 hours. Then, after heating and aging at 80 ° C. for 2 hours, the mixture was cooled to room temperature and the pH was adjusted to 7 to 8 with sodium hydroxide. Ethanol was distilled off using an evaporator, and the water content was adjusted to prepare 730 g of a resin aqueous dispersion 2 solution of an acrylic silicone resin having a solid content of 40% by mass. The particle size (D50) of the resin aqueous dispersion 2 of the acrylic silicone resin was measured by a particle size distribution measuring device (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.) and found to be 43 nm.

(Making ink)
Next, the production of ink will be described. The content of the resin particles shown below is limited to the solid content only.

<Ink 1>
20 parts by mass of propylene glycol, 10 parts by mass of 1,3-butanediol, 5 parts by mass of 3-methyl-1,3-butanediol, and 2-ethyl-1,3- as a penetrant in a container equipped with a stirrer. Add 2 parts of hexanediol and 0.5 part by mass of CapstoneFS-300 (manufactured by DuPont) as a surfactant, and stir for about 30 minutes to make it uniform. Next, 6 parts by mass of the self-dispersion type pigment dispersion obtained in Preparation Example 1 and high pure water are added in terms of solid content, and the mixture is stirred for about 60 minutes to make it uniform. Further, 3 parts by mass of the resin water dispersion 1 obtained in Preparation Example 4 is added, and the mixture is stirred for 30 minutes to make the ink uniform. This ink was pressure-filtered with a polyvinylidene fluoride membrane filter having an average pore diameter of 1.2 μm to remove coarse particles and dust to prepare the ink of Example 1. High pure water was added so that the total amount was 100 parts by mass.

<Ink 2 to 15>
Similar to Ink 1, the water-soluble organic solvent and surfactant shown in Table 1 below are mixed and stirred, a water-dispersible colorant (pigment dispersion) and high pure water are added and mixed and stirred, and further, a water-dispersible resin. Mix and stir to make the ink uniform. This ink was pressure-filtered with a polyvinylidene fluoride membrane filter having an average pore diameter of 1.2 μm to remove coarse particles and dust to prepare inks 2 to 15.

(evaluation)
<Ink evaluation>
The obtained ink was evaluated as follows. The evaluation results are shown in Table 2.

<< Ink viscosity measurement >>
The viscosity of the ink was measured at 25 ° C. using a viscometer (RE-550L, manufactured by Toki Sangyo Co., Ltd.).

<< Ink pH measurement >>
The pH of the ink was measured at 25 ° C. using a pH meter (HM-30R type, manufactured by TOA-DKK Corporation).

<< Particle diameter (D50) >>
Using a particle size distribution measuring device (Nanotrack UPA-EX150 manufactured by Nikkiso Co., Ltd.), the pigment particle size (D50) was measured by diluting with pure water so that the solid content concentration became 0.01% by mass.

<< Ink storage stability >>
Each ink was placed in a polyethylene container, sealed, stored at 70 ° C. for 2 weeks, and then the pigment particle size (D50) and viscosity were measured and evaluated as follows based on the rate of change from the initial physical properties.

〔Evaluation criteria〕
A: Both change rate of pigment particle size and viscosity is within 5% B: Change rate of both pigment particle size and viscosity is less than 10% C: Change rate of both pigment particle size and viscosity is 10% or more

<< Fluidity during water evaporation >>
The inks of Examples and Comparative Examples were weighed in a glass petri dish having a diameter of 33 mm with a precision precision precision electronic balance capable of measuring up to four decimal places. Then, it was stored at normal pressure in an ESPEC constant temperature and humidity chamber (ModelPL-3KP) having a temperature of 32 ± 0.5 ° C. and a humidity of 30 ± 5%, and after 24 hours, individual samples were taken out and weighed. Next, the ink in the petri dish was scratched with a spatula so that the bottom of the petri dish could be seen, and the fluidity of the ink was confirmed.

〔Evaluation criteria〕
A: Within 5 seconds after scratching, the bottom of the petri dish is filled with ink and disappears.
B: Within 60 seconds after scratching, the bottom of the petri dish is filled with ink and becomes invisible.
C: The bottom of the petri dish is still visible 2 minutes or more after scratching.

<Evaluation of image formation process>
Next, the following image forming step was performed, and the following evaluation was performed. The results are shown in Table 3.

<< Printing device settings >>
Under environmental conditions adjusted to 23 ± 0.5 ° C and 50 ± 5% RH, the following printing device 1 (inkjet recording device equipped with the circulating head shown in FIG. 1) and printing device 2 (mounted with the circulating head) Inkjet recording device) was used to change the drive voltage of the piezo element so that the amount of ink ejected was even, and the recording media was set to have the same amount of ink attached. Next, the print mode of the inkjet recording device was set to "plain paper fast" and "glossy paper fast" to form an image. Table 3 shows the evaluation results of the combination of the ink and the recording device and the image forming process.

Printing device 1: Inkjet recording device equipped with the circulation type head shown in FIG. 1 (IPSiO GXe-5500 modified machine manufactured by Ricoh Corporation)
Printing device 2: Inkjet recording device without a circulating head (IPSiO GXe-5500 modified machine manufactured by Ricoh Co., Ltd.)

<< Image density measurement >>
In the chart below, the black density was measured with a reflection spectrophotometer (Model: 939 manufactured by Xrite Co., Ltd.).

[Printing conditions]
Evaluation paper: My Paper (manufactured by Ricoh Co., Ltd.) (plain paper)
Chart: Black single color solid patch print mode: Clean mode

〔Evaluation criteria〕
A: 1.3 or more B: 1.1 or more C: less than 1.1

<< Tracing Paper Dryness >>
In the chart below, one minute after printing, the solid black image part is rubbed with the same evaluation paper under a load of 500 g, and the density of the transferred stains is measured with a reflection spectroscopic densitometer (Model: 939 manufactured by Xrite Co., Ltd.). Was measured.

[Printing conditions]
Evaluation paper: RJT (manufactured by Ricoh Corporation) (tracing paper)
Chart: Black single color solid patch print mode: Clean mode

〔Evaluation criteria〕
A: less than 0.1 B: less than 0.3 C: 0.3 or more

<< Discharge stability >>
Printing and ejection stability were evaluated under the following conditions.

[Printing conditions]
200 charts continuously filled with a solid image of 5% of the area of A4 size paper per color created by Microsoft Word2000 were printed on My Paper (manufactured by Ricoh Co., Ltd.), and evaluated from the ejection disturbance of each nozzle after printing. For the print mode, the driver attached to the printer used a mode in which the "plain paper-standard fast" mode was modified to "no color correction" from the user settings for plain paper.

〔Evaluation criteria〕
A: No discharge turbulence B: Slight discharge turbulence C: Discharge turbulence or part that does not discharge

<< Maintenance 1-Nozzle surface dirt->>
The maintainability 1 was evaluated under the following conditions, and after the evaluation, the nozzle check pattern was printed and the number of nozzle omissions was counted.

[Evaluation conditions]
Environment: 32 ° C 30% RH
Maintenance: Head cleaning once every 30 minutes Cycle time: 200 hours

〔Evaluation criteria〕
A: No or some ink adheres to the nozzle surface B: Nozzle surface has ink adhesion but nozzle omission is 20ch or less C: Nozzle surface has ink adhesion and nozzle omission is 20ch or more

<< Maintenance 2-Ink accumulation->>
The maintainability 2 was evaluated under the following conditions, and after the evaluation, a nozzle check pattern was printed and evaluated whether the image portion was blurred.

[Evaluation conditions]
Environment: 32 ° C 30% RH
Maintenance: Head cleaning once every 30 minutes Cycle time: 200 hours

〔Evaluation criteria〕
A: Nozzle cover ink deposits are 0.5 mm or less and there is no blur on the image part B: Nozzle cover ink deposits are 0.5 mm or more and less than 1 mm and there is no blur on the image part C: Nozzle cover ink Adhesion is 1 mm or more, or blurring occurs in the image part

1 Liquid discharge device 2 Head (liquid discharge part)
3 Nozzle 5 1st supply port 6 2nd supply port 20 1st liquid supply section 21 Ink tank (1st liquid storage section)
22 Ink (first liquid)
23 First pressurizing device (pressurizing means)
24 Decompression device (decompression means)
40 Second liquid supply unit 41 Cleaning liquid tank 42 Cleaning liquid (second liquid)
43 Second pressurizing device (pressurizing means)
50 Waste liquid tank 100 First ink supply path (first path)
101 First switching valve 102 Third switching valve 110 Second ink supply path (second path)
111 Second switching valve 112 Path opening / closing means 120 Circulation path (third path)
121 Degassing means 121a Degassing device 121a-1 Ink chamber 121a-2 Gas chamber 121a-3 Member 121b Vacuum generator 121c Tube 122 Liquid circulation means (pump)
123 Filter 130 Cleaning liquid supply route (fourth route)
201 Recording device Main unit 202 Printing mechanism 204 Paper cassette 205 Tray 206 Paper discharge tray 207 Main guide rod 208 Sub guide rod 209 Carriage 210 Head 211 Ink cartridge 212 Main scanning motor 213 Drive pulley 214 Drive pulley 215 Timing belt 216 Paper feed roller 217 Friction pad 218 Guide member 219 Conveying roller 220 Conveying roller 221 Tip roller 222 Sub-scanning motor 223 Imprint receiving member 224 Conveying roller 225 Ink roller 226 Paper ejection roller 227 Accumulator 228 229 Guide member 230 Recovery device

Japanese Patent Application Laid-Open No. 2003-335987 Japanese Unexamined Patent Publication No. 2006-199888 Japanese Unexamined Patent Publication No. 2016-56287

Claims (6)

A liquid ejection device provided with a liquid ejection unit having a nozzle for ejecting ink containing a coloring material, an organic solvent, and water.
The liquid ejection unit has a liquid chamber communicating with the nozzle, and a first supply port and a second supply port for allowing the ink to flow in or out of the liquid chamber.
The liquid ejection device has a circulation means for flowing the ink flowing out from one of the first supply port or the second supply port into the other supply port via a circulation path.
The organic solvent contains a diol compound having a boiling point of 230 ° C. or lower and does not contain an organic solvent having a boiling point higher than 230 ° C., and the organic solvent is 30% by mass or more and 35% by mass or less with respect to the ink. 57.1% by mass or more of the diol compound having a boiling point of 200 ° C. or lower with respect to the total mass of the organic solvent is 10% by mass or more and 15% by mass of the diol compound having a boiling point of 203 ° C. or more and 230 ° C. or less with respect to the ink. Including% or less
The liquid ejection device, wherein the coloring material is a self-dispersing colorant having a functional group. The liquid discharge device according to claim 1, wherein all of the organic solvents are diol compounds having a boiling point of 230 ° C. or lower. The liquid ejection according to claim 1 or 2, wherein the ink is used for plain paper or low liquid-absorbent printing paper having a stakehito size degree of 10 seconds or more at a basis weight of 50 g / m at ² o'clock. Device. An image forming set having a liquid ejection device having a liquid ejection unit having a nozzle for ejecting ink containing a coloring material, an organic solvent, and water, and a recording medium to which the ink is attached.
The liquid ejection unit has a liquid chamber communicating with the nozzle, and a first supply port and a second supply port for allowing the ink to flow in or out of the liquid chamber.
The liquid ejection device has a circulation means for causing the ink flowing out from one of the first supply port or the second supply port to flow into the other supply port via a circulation path.
The organic solvent contains a diol compound having a boiling point of 230 ° C. or lower and does not contain an organic solvent having a boiling point of more than 230 ° C., and the organic solvent is 30% by mass or more and 35% by mass or less with respect to the ink. 57.1% by mass or more of the diol compound having a boiling point of 200 ° C. or lower with respect to the total mass of the organic solvent is 10% by mass or more and 15% by mass of the diol compound having a boiling point of 203 ° C. or more and 230 ° C. or less with respect to the ink. Including the following
The coloring material is a self-dispersing colorant having a functional group.
An image forming set, characterized in that the recording medium is plain paper or low liquid-absorbent printing paper having a stakehito size degree of 10 seconds or more at a basis weight of 50 g / m at ² o'clock. Ink discharged from a nozzle provided in the liquid discharge section of a liquid discharge device having a circulating means.
The liquid ejection unit has a liquid chamber communicating with the nozzle, and a first supply port and a second supply port for allowing the ink to flow in or out of the liquid chamber.
The liquid ejection device has a circulation means for flowing the ink flowing out from one of the first supply port or the second supply port into the other supply port via a circulation path.
The ink contains a coloring material, an organic solvent and water, and contains
The organic solvent contains a diol compound having a boiling point of 230 ° C. or lower and does not contain an organic solvent having a boiling point higher than 230 ° C., and the organic solvent is 30% by mass or more and 35% by mass or less with respect to the ink. 57.1% by mass or more of the diol compound having a boiling point of 200 ° C. or lower with respect to the total mass of the organic solvent is 10% by mass or more and 15% by mass of the diol compound having a boiling point of 203 ° C. or more and 230 ° C. or less with respect to the ink. Including% or less
The coloring material is an ink characterized by being a self-dispersing colorant having a functional group. The ejection process of ejecting ink from the nozzle provided in the liquid ejection part of the liquid ejection device,
An image forming method comprising a circulation step of circulating the ink in the liquid ejection device.
The circulation step is carried out by the liquid ejection portion having a liquid chamber communicating with the nozzle and a first supply port and a second supply port for flowing the ink into or out of the liquid chamber. Is circulated to flow out from one of the first supply port or the second supply port and flow into the other supply port through the circulation path.
The ink contains a coloring material, an organic solvent and water, the organic solvent contains a diol compound having a boiling point of 230 ° C. or lower and does not contain an organic solvent having a boiling point higher than 230 ° C., and the organic solvent is the ink. 30% by mass or more and 35% by mass or less, 57.1% by mass or more of the total mass of the organic solvent is a diol compound having a boiling point of 200 ° C. or less, and a boiling point of 203 ° C. or more and 230 ° C. or less. The compound is contained in an amount of 10% by mass or more and 15% by mass or less based on the ink.
An image forming method, wherein the coloring material is a self-dispersing colorant having a functional group.

Images