JP2023112508A - Ink and inkjet recording device - Google Patents

Abstract

To provide an ink having excellent fixability and discharge stability.SOLUTION: An ink comprises an organic solvent and a colorant. With a longitudinal axis being a viscosity (mPa s) of the ink at 25°C and a horizontal axis being a reciprocal of an absolute temperature T(K) of the ink, a graph has a gradient (a) of 1.00×104 or more and 2.10×104 or less.SELECTED DRAWING: None

Description

The present invention relates to ink and an inkjet recording apparatus.

Inkjet printers have advantages such as low noise, low running costs, and easy color printing, and are widely used as digital signal output devices. As inks used in such inkjet printers, for example, solvent-based inks using an organic solvent as a solvent, ultraviolet curing inks containing a polymerizable monomer as a main component, and the like are widely used.
However, the solvent-based ink is concerned about the environmental impact due to the evaporation of the organic solvent, and the UV-curable ink has a problem that the choice of the polymerizable monomer to be used is limited from the viewpoint of safety.
Therefore, an ink set containing water-based ink, which has less environmental impact, has been proposed (see, for example, Patent Document 1).

On the other hand, when printing images with high resolution and high productivity in an inkjet recording apparatus, it is necessary to increase the number of droplets ejected per printing time. Need to be more frequent. However, as the ejection frequency increases, the ink inside the head vibrates and heats up, causing a drop in ink viscosity. A decrease in viscosity destabilizes the meniscus formed inside the inkjet head, leading to problems such as non-ejection of ink droplets and variations in the velocity of ejected droplets. In addition, when the head surface is heated due to drying of the medium during printing, the viscosity of the ink in the head may decrease, resulting in unstable ejection. Therefore, there is a problem that the upper limit of the drying temperature of the medium is restricted, and the printable medium width is narrowed. On the other hand, if the composition amount of the high-viscosity solvent is increased in order to keep the ink at a high viscosity in consideration of the aforementioned decrease in viscosity, the drying property of the ink is lowered and the fixability to the media is weakened.

An object of the present invention is to provide an ink having excellent fixability and ejection stability.

The ink of the present invention is an ink containing an organic solvent,
When the vertical axis is the viscosity (mPa·s) of the ink and the horizontal axis is the reciprocal of the absolute temperature T (K) of the ink, the slope a of the graph is 1.00×10 ⁴ or more and 2.10×10. ⁴ or less.

According to the present invention, it is possible to provide an ink excellent in fixability and ejection stability.

FIG. 1 is a schematic diagram illustrating an example of a printing apparatus using the ink of the present invention. FIG. 2 is a perspective explanatory view showing an example of a main tank of a printing apparatus using the ink of the present invention.

(ink)
The ink of the present invention contains an organic solvent, and preferably contains water, a coloring material, and a resin, and may further contain other components such as additives as necessary.
The ink of the present invention has a slope a of 1.00 when the vertical axis is the viscosity (mPa·s) of the ink at 25° C. and the horizontal axis is the reciprocal of the absolute temperature T (K) of the ink. ×10 ⁴ or more and 2.10×10 ⁴ or less.

As a result of extensive studies by the present inventors, the slope a of the graph when the vertical axis is the viscosity (mPa s) of the ink and the horizontal axis is the reciprocal of the absolute temperature T (K) of the ink is When it is 1.00×10 ⁴ or more and 2.10×10 ⁴ or less, the change in viscosity accompanying the temperature rise of the ink during inkjet printing becomes small, suppressing the separation of ejected ink droplets and stabilizing the ink liquid meniscus inside the inkjet head. The inventors have found that the ink is excellent in fixability and ejection stability because of the high density.

The ink of the present invention has a gradient a of 1.00×10 ⁴ when the viscosity (mPa·s) of the ink is plotted on the vertical axis and the reciprocal of the absolute temperature T (K) of the ink is plotted on the horizontal axis. 2.10×10 ⁴ or more, and more preferably 1.00×10 ⁴ or more and 2.05×10 ⁴ or less. When the slope a is 1.00×10 ⁴ or more, the fixability of the ink is stabilized, and when the slope a is 2.10×10 ⁴ or less, the change in viscosity accompanying the temperature rise of the ink during inkjet printing becomes small.

The method for measuring the viscosity of the ink is not particularly limited and can be appropriately selected according to the purpose. can.
The viscosity can be measured under conditions of 25° C., standard cone rotor (1°34′×R24), sample liquid volume of 1.2 mL, number of revolutions of 50 rpm, and 3 minutes.

<Organic solvent>
The organic solvent is not particularly limited and can be appropriately selected according to the purpose. However, a low-viscosity organic solvent having a viscosity at 25°C of less than 150 mPa s and a viscosity at 25°C of 150 mPa s or more are used. It is preferable to contain a highly viscous organic solvent. As a result, the gradient a of the ink is 1.00×10 when the viscosity (mPa·s) of the ink is plotted on the vertical axis and the reciprocal of the absolute temperature T (K) of the ink is plotted on the horizontal axis. It can be ⁴ or more and 2.10×10 ⁴ or less.

－Low Viscosity Organic Solvent－
The low-viscosity organic solvent is an organic solvent having a viscosity of less than 150 mPa·s at 25°C.
The low-viscosity organic solvent is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include propylene glycol (viscosity: 41 mPa·s).

－High Viscosity Organic Solvent－
The high-viscosity organic solvent is an organic solvent having a viscosity of 150 mPa·s or more at 25°C.
The high-viscosity organic solvent is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include glycerin (viscosity: 1,500 mPa·s).

The method for measuring the viscosity of the organic solvent is not particularly limited and can be appropriately selected according to the purpose. can be done.
The viscosity can be measured under conditions of 25° C., standard cone rotor (1°34′×R24), sample liquid volume of 1.2 mL, number of revolutions of 50 rpm, and 3 minutes.

<Water>
The content of water in the ink is not particularly limited and can be appropriately selected according to the purpose. % to 60% by mass is more preferable.

<Color material>
The coloring material is not particularly limited, and pigments and dyes can be used.
An inorganic pigment or an organic pigment can be used as the pigment. These may be used individually by 1 type, and may use 2 or more types together. Mixed crystals may also be used.
Examples of pigments that can be used include black pigments, yellow pigments, magenta pigments, cyan pigments, white pigments, green pigments, orange pigments, glossy color pigments such as gold and silver, and metallic pigments.
As inorganic pigments, in addition to titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, and chrome yellow, carbon black produced by known methods such as contact method, furnace method, thermal method, etc. can be used.
Organic pigments include azo pigments, polycyclic pigments (e.g., phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.). , dye chelates (eg, basic dye chelates, acid dye chelates, etc.), nitro pigments, nitroso pigments, aniline black, and the like. Among these pigments, those having good affinity with the solvent are preferably used. In addition, resin hollow particles and inorganic hollow particles can also be used.
Specific examples of pigments for black include carbon blacks (C.I. Pigment Black 7) such as furnace black, lamp black, acetylene black and channel black, or copper and iron (C.I. Pigment Black 11). , metals such as titanium oxide, and organic pigments such as aniline black (C.I. 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 carmine 6B), 60:1, 63:1, 63:2, 64:1, 81, 83, 88, 101 (red red), 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 Green 1, 4, 7, 8, 10, 17, 18, 36, etc.
Dyes are not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used, and may be used singly or in combination of two or more.
Examples of the dye include 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. Directed Black 19, 38, 51, 71, 154, 168, 171, 195, C.I. I. Reactive Red 14, 32, 55, 79, 249, C.I. I. and Reactive Black 3,4,35.

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 viewpoints of improving image density, good fixability, and ejection stability. It is below.

In order to disperse the pigment and obtain an ink, there are a method of introducing a hydrophilic functional group into the pigment to make it a self-dispersing pigment, a method of coating the surface of the pigment with a resin for dispersion, and a method of dispersing using a dispersant. method, etc.
As a method of making a self-dispersing pigment by introducing a hydrophilic functional group into a pigment, for example, a method of adding a functional group such as a sulfone group or a carboxyl group to a pigment (for example, carbon) to make it dispersible in water. is mentioned.
As a method of coating the surface of a pigment with a resin and dispersing it, there is a method of encapsulating the pigment in microcapsules to make it dispersible in water. This can be rephrased as a resin-coated pigment. In this case, all the pigments mixed in the ink need not be coated with a resin, and uncoated pigments or partially coated pigments may be dispersed in the ink as long as the effects of the present invention are 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 typified by surfactants.
As the dispersant, it is possible to use, for example, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc. depending on the pigment.
RT-100 (nonionic surfactant) manufactured by Takemoto Yushi Co., Ltd. and sodium naphthalenesulfonate formalin condensate can also be suitably used as a dispersant.
A dispersing agent may be used individually by 1 type, or may use 2 or more types together.

<Pigment dispersion>
Inks can be obtained by mixing materials such as water and organic solvents with pigments. Ink can also be produced by mixing a pigment with water, a dispersant, and the like to form a pigment dispersion, and then mixing materials such as water and an organic solvent.
The pigment dispersion is obtained by mixing and dispersing water, a pigment, a pigment dispersant, and optionally other components, and adjusting the particle size. Dispersion should be carried out using a disperser.
The particle diameter of the pigment in the pigment dispersion is not particularly limited, but the dispersion stability of the pigment is improved, and the image quality such as ejection stability and image density is improved. 500 nm or less is preferable, and 20 nm or more and 150 nm or less is more preferable. The particle size of the pigment can be measured using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd.).
The content of the pigment in the pigment dispersion is not particularly limited and can be appropriately selected according to the purpose. % or more and 50 mass % or less is preferable, and 0.1 mass % or more and 30 mass % or less is more preferable.
The pigment dispersion is preferably degassed by filtering coarse particles with a filter, a centrifugal separator, or the like, if necessary.

<Resin>
The resin is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include polyether-based urethane resin, polyester-based urethane resin, and polycarbonate-based urethane resin. Among these, polyester-based urethane resins are preferred. These may be used individually by 1 type, and may use 2 or more types together.

The volume-average particle diameter of the resin particles is not particularly limited and can be appropriately selected according to the intended purpose. 200 nm or less is more preferable, and 10 nm or more and 100 nm or less is particularly preferable.
The volume average particle diameter can be measured, for example, using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd.).

The content of the resin is not particularly limited and can be appropriately selected according to the purpose. However, from the viewpoint of fixability and storage stability of the ink, the content is 1% by mass or more and 30% by mass or less based on the total amount of the ink. is preferable, and 9% by mass or more and 11% 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. is preferably 20 nm or more and 1000 nm or less, 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 Microtrack Bell Co., Ltd.).

<Additive>
Surfactants, antifoaming agents, antiseptic antifungal agents, anticorrosive agents, pH adjusters, etc. may be added to the ink as necessary.

<Surfactant>
Any of silicone surfactants, fluorine surfactants, amphoteric surfactants, nonionic surfactants, and anionic surfactants can be used as surfactants.
The silicone-based surfactant is not particularly limited and can be appropriately selected depending on the purpose. Among them, those that do not decompose even at high pH are preferable. Those having an oxyethylene group or a polyoxyethylene polyoxypropylene group are particularly preferred because they exhibit good properties as water-based surfactants. 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 side chain of the Si portion of dimethylsiloxane.
Examples of fluorine-based surfactants include perfluoroalkylsulfonic acid compounds, perfluoroalkylcarboxylic acid compounds, perfluoroalkylphosphoric acid ester compounds, perfluoroalkylethylene oxide adducts, and perfluoroalkyl ether groups in side chains. Polyoxyalkylene ether polymer compounds are particularly preferred due to their low foaming properties. Examples of the perfluoroalkylsulfonic acid compound include perfluoroalkylsulfonic acid and perfluoroalkylsulfonate. Examples of the perfluoroalkylcarboxylic acid compounds include perfluoroalkylcarboxylic acids and perfluoroalkylcarboxylic acid salts. As the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in a side chain, a sulfate ester salt of a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in a side chain, and a perfluoroalkyl ether group in a side chain Examples thereof include salts of polyoxyalkylene ether polymers. Counter ions _of salts _in these fluorosurfactants include Li, Na, _K , _NH4 , _NH3CH2CH2OH , _NH2 ( _CH2CH2OH ) _{2 ,} and NH( _CH2CH2OH ). ₃ and the like.
Examples of amphoteric surfactants include laurylaminopropionate, lauryldimethylbetaine, stearyldimethylbetaine, lauryldihydroxyethylbetaine and the like.
Nonionic surfactants include, for example, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan Examples include fatty acid esters and ethylene oxide adducts of acetylene alcohol.
Examples of anionic surfactants include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, laurate, polyoxyethylene alkyl ether sulfate, and the like. These may be used individually by 1 type, or may use 2 or more types together.

As the fluorosurfactant, a fluorine-substituted compound having 2 to 16 carbon atoms is preferable, and a fluorine-substituted compound having 4 to 16 carbon atoms is more preferable.
Examples of fluorine-based surfactants include perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in side chains. Among these, polyoxyalkylene ether polymer compounds having a perfluoroalkyl ether group in the side chain are preferable because of their low foamability, and in particular, fluorine-based compounds represented by general formulas (F-1) and (F-2) Surfactants are preferred.
General formula (F-1)
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.
General formula (F-2)
_{CnF2n +1- CH2CH} (OH)CH2 _- O-( _CH2CH2O ) _{a -} Y
In the compound represented by the above general formula (F-2), Y is H, or CmF _2m+1 and m is an integer of 1 to 6, or CH ₂ CH(OH)CH ₂ -CmF _2m+1 and m is 4 to 6 Integer, or CpH _2p+1 where p is an integer from 1-19. n is an integer of 1-6. a is an integer from 4 to 14;
Commercially available products may be used as the fluorosurfactant. Examples of commercially available products 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.); Fleurard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431 (both manufactured by Sumitomo 3M); Megafac F-470, F -1405, F-474 (both manufactured by Dainippon Ink and Chemicals); Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR, Capstone FS-30, FS-31, FS-3100, FS-34, FS-35 (all manufactured by Chemours); 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 Omnova), Unidyne DSN-403N (manufactured by Daikin Industries, Ltd.) Among these, good print quality, especially color development, penetrability to paper, wettability, and level dyeing properties are remarkably improved,

The content of the surfactant in the ink is not particularly limited and can be appropriately selected according to the purpose. % or more and 5 mass % or less is preferable, and 0.05 mass % or more and 5 mass % or less is more preferable.

<Antifoaming agent>
The antifoaming agent is not particularly limited, and examples thereof include silicone antifoaming agents, polyether antifoaming agents, and fatty acid ester antifoaming agents. These may be used individually by 1 type, or may use 2 or more types together. Among these, silicone-based antifoaming agents are preferred because of their excellent foam breaking effect.

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

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

<pH adjuster>
The pH adjuster is not particularly limited as long as it can adjust the pH to 7 or higher, and examples thereof include amines such as diethanolamine and triethanolamine.

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

<Pretreatment liquid>
The pretreatment liquid contains a flocculant, an organic solvent, and water, and may optionally contain a surfactant, an antifoaming agent, a pH adjuster, an antiseptic agent, an antirust agent, and the like.
Organic solvents, surfactants, antifoaming agents, pH adjusters, antiseptic antifungal agents, and antirust agents can be the same materials as used for inks, 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, polyvalent metal salts, and the like.

<Post-treatment liquid>
The post-treatment liquid is not particularly limited as long as it can form a transparent layer. The post-treatment liquid is obtained by selecting and mixing organic solvents, water, resins, surfactants, antifoaming agents, pH adjusters, antiseptic antifungal agents, anticorrosive agents, etc., as 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>
The recording medium is not limited to those used as general recording media, and wallpaper, floor materials, building materials such as tiles, cloth for clothing such as T-shirts, textiles, leather, and the like can be used as appropriate. Ceramics, glass, metal, etc. can also be used by adjusting the configuration of the path for conveying the recording medium.

<Records>
The ink recorded matter of the present invention has an image formed on a recording medium using the ink of the present invention.
A recorded matter can be obtained by recording with an inkjet recording apparatus and an inkjet recording method.

<Recording device, recording method>
The ink of the present invention can be suitably used for various inkjet recording apparatuses, such as printers, facsimile machines, copiers, printer/facsimile/copier complex machines, stereolithography machines, and the like. In the present invention, a recording apparatus and a recording method refer to an apparatus capable of ejecting ink, various treatment liquids, and the like onto a recording medium, and a method of performing recording using the apparatus. A recording medium means a medium to which ink or various processing liquids can adhere even temporarily.
This recording apparatus can include not only a head portion for ejecting ink, but also means for feeding, conveying, and discharging a recording medium, and other devices called pre-processing devices and post-processing devices. . The recording apparatus and recording method may have heating means used in the heating process and drying means used in the drying process. The heating means and drying means include, for example, means for heating and drying the printing surface and the back surface of the recording medium. The heating means and drying means are not particularly limited, but for example, hot air heaters and infrared heaters can be used. Heating and drying can be performed before, during, or after printing.
Also, the recording apparatus and recording method are not limited to those that visualize significant images such as characters and graphics with ink. For example, it includes those that form patterns such as geometric patterns, and those that form three-dimensional images. In addition, unless otherwise specified, the recording apparatus includes both a serial type apparatus in which the ejection head is moved and a line type apparatus in which the ejection head is not moved.
Furthermore, this recording device can be used not only as a desktop type, but also as a wide recording device that can print on A0 size recording media, and for example, can use continuous paper wound into a roll as a recording medium. A continuous feed printer is also included.
An example of a recording apparatus will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 is a perspective explanatory view of the device. FIG. 2 is a perspective explanatory view of the main tank. An image forming apparatus 400 as an example of a recording apparatus is a serial image forming apparatus. A mechanical unit 420 is provided inside the exterior 401 of the image forming apparatus 400 . Each ink container 411 of the main tank 410 (410k, 410c, 410m, 410y) for each color of black (K), cyan (C), magenta (M), and yellow (Y) is packed with, for example, an aluminum laminated film. It is made up of members. The ink containing portion 411 is contained, for example, in a container case 414 made of plastic. Thus, the main tank 410 is used as an ink cartridge for each color.
On the other hand, a cartridge holder 404 is provided on the far side of the opening when the cover 401c of the apparatus main body is opened. A main tank 410 is detachably attached to the cartridge holder 404 . As a result, each ink discharge port 413 of the main tank 410 communicates with the ejection head 434 for each color via the supply tube 436 for each color, and ink can be ejected from the ejection head 434 onto the printing medium.

This recording apparatus can include not only a portion that ejects ink, but also devices called pre-processing devices and post-processing devices.
As an aspect of the pre-treatment device and the post-treatment device, it has a pre-treatment liquid and a post-treatment liquid in the same manner as in the case of inks such as black (K), cyan (C), magenta (M), and yellow (Y). There is a mode in which a liquid container and a liquid ejection head are added, and the pretreatment liquid and the posttreatment liquid are ejected by an inkjet recording method.
As another aspect of the pre-treatment device and the post-treatment device, there is an aspect in which a pre-treatment device and a post-treatment device using a method other than the inkjet recording method, such as a blade coating method, a roll coating method, and a spray coating method, are provided.

In addition, the method of using the ink is not limited to the ink jet recording method, and can be widely used. In addition to the inkjet recording method, for example, a blade coating method, a gravure coating method, a bar coating method, a roll coating method, a dip coating method, a curtain coating method, a slide coating method, a die coating method and a spray coating method can be used.

The use of the ink of the present invention is not particularly limited and can be appropriately selected according to the intended purpose. Furthermore, it can be used not only as an ink to form two-dimensional characters and images, but also as a three-dimensional modeling material for forming a three-dimensional image (three-dimensional object).
A known three-dimensional modeling apparatus for forming three-dimensional objects can be used, and is not particularly limited. be able to. The three-dimensional object includes a three-dimensional object obtained by applying ink repeatedly. It also includes a molded product obtained by processing a structure obtained by applying ink onto a base material such as a recording medium. The molded product is, for example, a sheet-shaped or film-shaped recorded matter or structure that has been subjected to molding such as heat stretching or punching.・Suitably used for applications where molding is performed after the surface is decorated, such as electronic equipment, meters for cameras, and operation panels.

In the present invention, the terms image formation, recording, printing, and printing are all synonymous.

The terms recording medium, medium, and printed material are all synonymous.

Examples of the present invention will be described below, but the present invention is not limited to these examples.

<Preparation Example of Black Pigment Dispersion>
After premixing the following [materials for black pigment dispersion], a disk-type bead mill (KDL type, media: zirconia balls with a diameter of 0.3 mm, manufactured by Shinmaru Enterprises Co., Ltd.) was used to circulate and disperse for 7 hours. A pigment dispersion was obtained.
[Material for Black Pigment Dispersion]
・C. I. Pigment Black 7: 15% by mass
・ Anionic surfactant (trade name: Pionin A-51-B, manufactured by Takemoto Oil Co., Ltd.): 2% by mass
・Ion-exchanged water: 83% by mass

<Preparation Example 1 of Urethane Resin Emulsion>
In a nitrogen-purged reaction vessel equipped with a stirrer, reflux condenser, and thermometer, 1,500 g of Polylite OD-X-2420 (polyester polyol, manufactured by DIC Corporation) and 2,2-dimethylolpropionic acid were added. (DMPA) 220 g and N-methylpyrrolidone (NMP) 1,347 g were mixed and heated at 60° C. to dissolve DMPA.
Next, 1,445 g of 4,4′-dicyclohexylmethane diisocyanate and 2.6 g of dibutyltin dilaurate as a catalyst are added and heated to 90° C. for urethanization reaction over 5 hours to produce an isocyanate-terminated urethane prepolymer. Obtained.
After cooling the obtained isocyanate-terminated urethane polymer to 80° C., 149 g of triethylamine was added and mixed, and 4,340 g was taken out and added to a mixed solution of 5,400 g of water and 15 g of triethylamine while stirring. .
Next, 1,500 g of ice and 626 g of a 35% by mass 2-methyl-1,5-pentanediamine aqueous solution were added to carry out a chain extension reaction, and the solvent was distilled off so that the solid content concentration was 30% by mass. A resin emulsion was obtained.
The obtained resin emulsion was dispersed with a paint conditioner (speed adjustable in the range of 50 to 1,425 rpm, manufactured by Red Devil) to obtain a urethane resin emulsion A having a solid content concentration of 34.0% by mass.

<Preparation Example 2 of Urethane Resin Emulsion>
200.4 g of polyester polyol (trade name: Polylite OD-X-2251, manufactured by DIC Corporation, average molecular weight: 2,000) was placed in a nitrogen-purged reactor equipped with a stirrer, a nitrogen gas inlet tube, and a thermometer. , 15.7 g of 2,2-dimethylolpropionic acid, 48.0 g of isophorone diisocyanate, 77.1 g of methyl ethyl ketone as an organic solvent, and 0.06 g of DMTDL (dibutyltin dilaurate) as a catalyst were mixed for 4 hours. reacted. After that, 30.7 g of methyl ethyl ketone as a diluent solvent is added, and when the average molecular weight reaches the range of 20,000 to 60,000, 1.4 g of methanol is added to terminate the reaction, and the organic solvent of the urethane resin is added. A solvent solution was obtained.
13.4 g of a 48% by mass potassium hydroxide aqueous solution and 715.3 g of water were added to the obtained organic solvent solution of the urethane resin, and the mixture was sufficiently stirred. A 20.0% by mass urethane resin emulsion B was obtained.

(Example 1)
18.7% by mass of the black pigment dispersion, 0.3% by mass of 2-amino-2-ethyl-1,3-propanediol, 1.2% by mass of glycerin, and 14.0% by mass of isoprene glycol as ink materials , 2-ethyl-1,3-hexanediol 14.0% by mass, fluorine-based surfactant (trade name: FS-300, manufactured by DuPont) 0.8% by mass, antifoaming agent (trade name: Surfynol AD01 , manufactured by Nissin Chemical Industry Co., Ltd.) and 13.1% by mass of high-purity water were mixed to obtain a mixed liquid.
The viscosity of Ink 1 obtained at 25° C. was measured by the method shown below. When the reciprocal of (K) was used, the slope a of the graph was calculated to be 2.01×10 ⁴ .

<Measurement of ink viscosity>
The viscosity of Ink 1 at 25° C. was measured using a rotary viscometer (RE-80L manufactured by Toki Sangyo Co., Ltd.).
The viscosity was measured under conditions of 25° C., standard cone rotor (1°34′×R24), sample volume of 1.2 mL, rotation speed of 50 rpm, and 3 minutes.

(Example 2 and Comparative Examples 1 to 4)
Inks 2 to 6 were obtained in the same manner as in Example 1, except that the ink materials in Example 1 were changed to the materials shown in Table 1 below. Further, the viscosity of each ink at 25° C. was measured in the same manner as in Example 1. The viscosity (mPa s) of ink 1 at 25° C. was plotted on the vertical axis, and the viscosity of ink 1 on the horizontal axis. was calculated as the reciprocal of the absolute temperature T (K) of the graph. The measurement results are shown in Table 1 below.

The obtained inks 1 to 6 were evaluated for "fixability", "ligament length" and "continuous ejection stability". Table 2 shows the evaluation results.

<Fixability>
Using EV2500 (manufactured by Ricoh Co., Ltd.), each ink was printed on a substrate (trade name: Canon Photo Paper Glossy Gold, manufactured by Canon) under conditions of 600×600 dpi to form an image. After leaving for one hour after forming the image, the image is subjected to a load of 200 gf and rubbed 25 times using a Gakushin tester (apparatus name: color fastness tester to rubbing, manufactured by Intec). The gold cloth was rubbed with The image density (OD) of the image transferred to the metal cloth was measured using xRite (manufactured by PANTONE), and the fixability was evaluated based on the following evaluation criteria. In the evaluation criteria, △ or more is practical.
[Evaluation criteria]
○: less than 0.15 △: 0.15 or more and less than 0.28 ×: 0.28 or more

<Ligament length>
Each ink is ejected using EV2500 (manufactured by Ricoh Co., Ltd.), and the time from the passage of the main droplet to the trailing edge of the satellite droplet at the point where the main droplet falls 2 mm from the nozzle surface of the EV2500 The time was measured, and the ligament length was evaluated based on the following evaluation criteria. In the evaluation criteria, △ or more is practical.
[Evaluation criteria]
○: No satellite droplet △: Satellite droplet present, elapsed time less than 20 μs ×: Satellite droplet present, elapsed time 20 μs or more

<Continuous discharge stability>
EV2500 (manufactured by Ricoh Co., Ltd.) was used to measure the ratio of nozzle holes that continue to eject droplets after one hour of droplet ejection, and the continuous ejection stability was evaluated based on the following evaluation criteria. evaluated. In the evaluation criteria, △ or more is practical.
[Evaluation criteria]
○: 100% of the nozzle holes continue to discharge
Δ: Percentage of nozzle holes continuing to discharge is 90% or more and less than 100% ×: Percentage of nozzle holes continuing to discharge is less than 90%

Embodiments of the present invention are, for example, as follows.
<1> An ink containing an organic solvent and a coloring material,
2. The gradient a of the graph is 1.00×10 ⁴ or more when the vertical axis is the viscosity (mPa·s) of the ink at 25° C. and the horizontal axis is the reciprocal of the absolute temperature T (K) of the ink. The ink is characterized by having a density of 10×10 ⁴ or less.
<2> The organic solvent contains a low-viscosity organic solvent having a viscosity of less than 150 mPa·s at 25°C and a high-viscosity organic solvent having a viscosity of 150 mPa·s or more at 25°C,
In the above <1>, the ratio (A/B) of the content (% by mass) A of the low-viscosity organic solvent and the content (% by mass) B of the high-viscosity organic solvent is 1 or more and 2 or less. Ink as described.
<3> The ink according to any one of <1> and <2>, wherein the number of hydroxyl groups of the high-viscosity organic solvent is 2 or more and 3 or less.
<4> the ink contains a resin,
The ink according to any one of <1> to <3>, wherein the content of the resin is 9% by mass or more and 11% by mass or less with respect to the ink.
<5> The ink according to any one of <1> to <4>, wherein the high-viscosity organic solvent has a boiling point of 240° C. or higher and 260° C. or lower.
<6> The ink according to any one of <1> to <5>, wherein the low-viscosity organic solvent has a boiling point of 200° C. or higher and 240° C. or lower.
<7> an ink containing portion containing the ink according to any one of <1> to <6>;
an ejection head for ejecting the ink onto an object to be printed;
and heating means for heating the printed material.

The ink described in any one of <1> to <6> and the inkjet recording apparatus described in <7> can solve the conventional problems and achieve the object of the present invention.

400 Image forming apparatus 401 Exterior of image forming apparatus 401c Cover of apparatus main body 404 Cartridge holder 410 Main tank 410k, 410c, 410m, 410y For black (K), cyan (C), magenta (M), and yellow (Y) main tank 411 ink storage unit 413 ink discharge port 414 storage container case 420 mechanism unit 434 ejection head 436 supply tube

Japanese Patent No. 6464664

Claims (7)

An ink containing an organic solvent and a coloring material,
2. The gradient a of the graph is 1.00×10 ⁴ or more when the vertical axis is the viscosity (mPa·s) of the ink at 25° C. and the horizontal axis is the reciprocal of the absolute temperature T (K) of the ink. An ink characterized by being 10×10 ⁴ or less. The organic solvent contains a low-viscosity organic solvent having a viscosity of less than 150 mPa s at 25°C and a high-viscosity organic solvent having a viscosity of 150 mPa s or more at 25°C,
2. The ratio (A/B) of the content (% by mass) A of the low-viscosity organic solvent and the content (% by mass) B of the high-viscosity organic solvent is 1 or more and 2 or less. ink. 3. The ink according to claim 1, wherein the high-viscosity organic solvent has 2 or more and 3 or less hydroxyl groups. the ink contains a resin,
The ink according to any one of claims 1 to 3, wherein the content of the resin is 9% by mass or more and 11% by mass or less with respect to the ink. The ink according to any one of claims 1 to 4, wherein the high-viscosity organic solvent has a boiling point of 240°C or higher and 260°C or lower. The ink according to any one of claims 1 to 5, wherein the low-viscosity organic solvent has a boiling point of 200°C or higher and 240°C or lower. an ink container containing the ink according to any one of claims 1 to 6;
an ejection head for ejecting the ink onto an object to be printed;
and heating means for heating the printed material.