JP7077695B2 - Image forming method and image forming apparatus - Google Patents

Description

The present invention relates to an image forming method and an image forming apparatus.

The inkjet recording method is a recording method in which ink droplets are directly ejected from a very fine nozzle onto a recording medium and adhered to obtain characters or images.
In recent years, an image forming method using an inkjet recording method has become widespread in industrial applications. In particular, improvements in inkjet technology have made high-speed printing possible. Therefore, in order to support inkjet recording for high-speed printing, an image forming method using an ink having excellent dryness and fixability is desired.

An image forming apparatus including a drying apparatus having a roller in contact with the solvent-applied surface of the recording medium has been proposed (see, for example, Patent Document 1).

An object of the present invention is to provide an image forming method which is excellent in blocking resistance and can suppress image peeling due to white spots.

The image forming method of the present invention as a means for solving the above-mentioned problems includes an ink applying step of applying an ink containing a coloring material and an organic solvent to a recording medium, and an ink-applied surface of the recording medium. Includes a contact step of contacting a contact member heated to 25 ° C. or higher, and is included per unit area of the ink-applied recording medium after the ink-applying step and before the contacting step. The amount (A) of the organic solvent is 100 μg / cm ² or less, and in the contact step, 0.020 kg / cm ² or more and 0.030 kg / cm with respect to the surface of the recording medium to which the ink is applied. A pressure of ² or less is applied.

According to the present invention, it is possible to provide an image forming method which is excellent in blocking resistance and can suppress image peeling due to white spots.

FIG. 1 is a schematic diagram showing an example of an image forming apparatus using continuous paper. FIG. 2 is a schematic view showing an angle between a roller as a contact member and a recording medium. FIG. 3 is a schematic diagram showing an example of the arrangement of rollers when the recording medium is provided with a roller in contact with an inked surface and a roller in contact with a surface opposite to the inked surface. be. FIG. 4 is a perspective view showing an example of continuous paper (roll paper) having an image. FIG. 5 is a side view of a continuous paper (roll paper) having the image of FIG. FIG. 6 is a photograph showing an example of a case where white spots occur in the recording medium. FIG. 7 is a diagram showing a force curve obtained in the measurement of the tack force on the image surface. FIG. 8 is a photograph showing an example of a cantilever provided with a spherical probe in an atomic force microscope.

As a result of diligent studies, the present inventors have found the following.
When the resin emulsion is contained in the ink, the fixability, which is a conventional problem, can be improved, but the resin capable of improving the fixability has high elasticity, and the organic remaining in the image portion on the recording medium. The solvent plasticizes the resin and enhances its adhesive strength. As a result, there is a problem that sticking (blocking) occurs at the timing when pressure is applied to the image part, such as when the image part is fixed by using a roller after image formation or when the image part is wound after printing on roll paper. be. Further, there is a problem that the image is transferred to a roller or another recording medium, the image is peeled off, and the image becomes white.

Specifically, as shown in FIG. 1, an image having a paper feed unit 1, a recording medium 2 which is continuous paper, a roller 3 which is a contact member, an ink ejection unit 4, a heating unit 5, and a winding unit 6. When the forming apparatus is used, the image on the recording medium 2 is subjected to pressure in the horizontal and vertical directions of the image surface when passing through or winding the roller heated by the heating unit 5, and is applied to the image surface. There is a problem that the image is transferred to an overlapping recording medium or a roller in contact with the image, causing image peeling or scratches.

Therefore, the present inventors suppress the plasticization of the resin by setting the amount of the organic solvent contained in the applied ink on the recording medium to 100 μg / cm ² or less, and fix the image on the recording medium. It has been found that the image transfer to the heated contact member can be suppressed and the image peeling can be suppressed because the image can be maintained.
Further, the present inventors can improve the fixing property of the image, the abrasion resistance, and the drying property of the ink by setting the pressure on the surface to which the ink is applied to 0.020 kg / cm ² or more. Further, it has been found that when the image is uniformly contacted with the contact member heated by the pressure, the organic solvent remaining in the image portion on the recording medium is volatilized and the image peeling can be suppressed. ..
Further, the present inventors set the pressure on the surface to which the ink is applied to 0.030 kg / cm ² or less, so that the contact between the image unit and the heated contact member is appropriate, and therefore, on the recording medium. It has been found that the organic solvent remaining in the image portion of the above can be transferred to the heated contact member to suppress the occurrence of image peeling.

(Image forming method and image forming device)
In the image forming method of the present invention, an ink applying step of applying an ink containing a coloring material and an organic solvent to a recording medium and a surface of the recording medium to which the ink is applied are heated to 25 ° C. or higher. The amount (A) of the organic solvent contained in a unit area of the recording medium to which the ink is applied includes the contact step of contacting with the contact member, and after the ink application step and before the contact process. It is 100 μg / cm ² or less, and in the contact step, a pressure of 0.020 kg / cm ² or more and 0.030 kg / cm ² or less is applied to the surface of the recording medium to which the ink is applied, and the drying step is performed. It is preferable to include it.
The image forming apparatus of the present invention provides an ink applying means for applying an ink containing a coloring material and an organic solvent to a recording medium, and a contact member in contact with the surface of the recording medium to which the ink is applied. When the contact member is heated to 25 ° C. or higher and the amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied is 100 μg / cm ² or less. It is preferable to apply a pressure of 0.020 kg / cm ² or more and 0.030 kg / cm ² or less to the surface to which the ink is applied, and include a drying means.
The image forming method of the present invention can be suitably carried out by the image forming apparatus of the present invention.

[Amount of organic solvent on recording medium]
The amount of the organic solvent contained in the applied ink on the recording medium is 100 μg / cm ² or less, preferably 75 μg / cm ² or less, more preferably 40 μg / cm ² or less, and 5 μg / cm ² or more and 40 μg. / Cm ² or less is particularly preferable. When the amount of the organic solvent is 100 μg / cm ² or less, the plasticization of the resin can be suppressed and the fixability of the image on the recording medium can be maintained, so that the image transfer to the heated contact member can be suppressed. It is possible to suppress the occurrence of image peeling.

The amount of the organic solvent contained in the applied ink on the recording medium is particularly affected by the type of resin and solvent in the ink.
The type and content of the resin as an example in which the amount of the organic solvent on the recording medium can be realized will be described in detail below.

[Pressure from heated contact member]
Pressure is applied to the surface (image portion) to which the ink is applied on the recording medium. In the present invention, the pressure means the mass (kg) applied per unit area (1 cm ² ).
The pressure on the surface of the recording medium to which the ink is applied is 0.020 kg / cm ² or more and 0.030 kg / cm ² or less, preferably 0.023 kg / cm ² or more and 0.027 kg / cm ² or less.
When the pressure is 0.020 kg / cm ² or more, the fixing property of the image, the abrasion resistance, and the drying property of the ink can be improved. Further, when the image is uniformly contacted with the contact member heated by the pressure, the organic solvent remaining in the image portion on the recording medium can be volatilized, and the occurrence of image peeling can be suppressed. .. When the pressure is 0.030 kg / cm ² or less, the contact between the image portion and the heated contact member is appropriate, so that the contact member in which the organic solvent remaining in the image portion on the recording medium is heated. It is possible to suppress the occurrence of image peeling by transferring to.

<Ink applying process and ink applying means>
The ink applying step is a step of applying ink to a recording medium to form an image.
The ink applying means is a means for applying ink to a recording medium to form an image.
The ink applying step can be preferably carried out by the ink applying means.

The amount of ink applied to the recording medium is preferably 4.8 × 10 ^-4 mL / cm ² or more and 1.1 × 10 ^-3 mL / cm ² or less, and 8.0 × 10 ^-4 mL / cm ² or more 1 .0 × 10 ^-3 mL / cm ² or less is more preferable.

<< Ink >>
The ink in the ink applying step and the ink applying means contains a coloring material and an organic solvent, preferably contains a pigment dispersion, a resin, a lubricant, and water, and further contains other components as necessary. ..

-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, quinophthalone 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 Calcium 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81, 83, 88, 101 (Bengara), 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. Hood 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.

In order to disperse the pigment to obtain an 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, and a method of dispersing using a dispersant are used. The method, etc. can be mentioned.
As a method of introducing a hydrophilic functional group into a pigment to obtain a self-dispersing 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) so that the pigment can be dispersed in water. Can be mentioned.
Examples of the method of coating the surface of the pigment with a resin and dispersing the pigment include a method of encapsulating the pigment in microcapsules so that the pigment can be dispersed in water. 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 mixing and 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.

-Organic solvent-
The organic solvent used in the present invention is not particularly limited, and a water-soluble organic solvent can be used. Examples thereof 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.
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, Glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl- Polyhydric alcohols such as 1,3-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 Polyhydric alcohol alkyl ethers such as ethers, polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone. , 1,3-Dimethyl-2-imidazolidinone, ε-caprolactam, γ-butyrolactone and other nitrogen-containing heterocyclic compounds, formamide, N-methylformamide, N, N-dimethylformamide, 3-methoxy-N, N- Amidos such as dimethylpropionamide, 3-butoxy-N, N-dimethylpropionamide, amines such as monoethanolamine, diethanolamine and triethylamine, sulfur-containing compounds such as dimethylsulfoxide, sulfolane and thiodiethanol, propylene carbonate and ethylene carbonate. And so on.
It is preferable to use an organic solvent having a boiling point of 250 ° C. or lower because it not only functions as a wetting agent but also has good drying properties.

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.

When a resin is used, it preferably contains an amide solvent, 3-ethyl-3-hydroxymethyloxetane, and propylene glycol monomethyl ether.
Examples of the amide solvent include 3-methoxy-N, N-dimethylpropionamide, 3-ethoxy-N, N-dimethylpropionamide, 3-butoxy-N, N-dimethylpropionamide and the like.
These may be used alone or in combination of two or more. Among these, amide solvents such as 3-methoxy-N, N-dimethylpropionamide, 3-butoxy-N, and N-dimethylpropionamide are used from the viewpoint of promoting the film-forming property of the resin and improving the abrasion resistance. More preferred.

The boiling point of the organic solvent is preferably 180 ° C. or higher and 300 ° C. or lower. When the boiling point of the organic solvent is 180 ° C. or higher, the evaporation rate during drying can be appropriately adjusted. Further, since the unevenness on the surface of the image is reduced by sufficient leveling property, the glossiness can be improved. When the boiling point of the organic solvent is 300 ° C. or lower, the drying property of the ink can be improved.

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. More preferably, it is 20% by mass or more and 60% by mass or less.

The content of the amide solvent is preferably 0.05% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 5% by mass or less, based on the total amount of the ink.

It is preferable to contain diethylene glycol and triethylene glycol from the viewpoint of improving the ejection stability when continuously forming an image and obtaining high vapor pressure and good drying property even at a high temperature.
The content of diethylene glycol and triethylene glycol is preferably 1% by mass or more and 10% by mass or less, and more preferably 3% by mass or more and 6% by mass or less, based on the total amount of ink. When the content is 1% by mass or less, the discharge stability can be improved. When the content is 10% by mass or less, the amount of the organic solvent remaining in the image portion on the recording medium is small, so that the plasticization of the resin can be suppressed and the fixability can be maintained. Image transfer to can be suppressed.

-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.

--Urethane resin particles ---
Among the resin particles, urethane resin particles have a large tack force and lower the blocking resistance, so that they are preferably used in combination with other resin particles.
However, the strength of the tack force of the urethane resin particles can firmly form an image and improve the fixability. Further, the urethane resin particles having a glass transition temperature (Tg) of −20 ° C. or higher and 70 ° C. or lower have a particularly large tack force when an image is formed by ink, and can further improve the fixability.

Examples of the urethane resin particles include polycarbonate urethane resin particles, polyester urethane resin particles, and polyether urethane resin particles. These may be used alone or in combination of two or more. Among these, polycarbonate urethane resin particles are preferable from the viewpoint of abrasion resistance.
The polycarbonate urethane resin particles need only have a polycarbonate structure in the structure, and means that the polycarbonate urethane resin particles are also included.

The glass transition temperature (Tg) of the urethane resin particles is preferably −20 ° C. or higher and 70 ° C. or lower. When the glass transition temperature (Tg) of the urethane resin particles is −20 ° C. or higher and 70 ° C. or lower, the tack force is high and the film forming property is good, so that good scratch resistance is exhibited.

－－Acrylic resin particles －－
Among the resin particles, acrylic resin particles are widely used because they have excellent ejection stability and are inexpensive in terms of cost.
However, since it is inferior in abrasion resistance, it is preferable to use it by mixing it with elastic urethane resin particles.

Examples of the acrylic resin particles include acrylic silicone resin particles and styrene acrylic resin particles. These may be used alone or in combination of two or more. Among these, acrylic silicone resin particles are preferable from the viewpoint of abrasion resistance.

The styrene acrylic resin particles can be produced, for example, by emulsion polymerization, dispersion polymerization, suspension polymerization, pulverization or solution / bulk polymerization, and subsequent post-emulsification.
Commercially available products may be used as appropriate for the styrene acrylic resin particles.
Commercially available products of styrene acrylic resin particles include, for example, trade names: J-352, J-390, J-450, J-511, J-734, J-741, J-775, J-840, J-7100. , J-7600, HPD-71, HRC-1645, JDX-5050, PDX-6102B (above, manufactured by BASF), trade name: UC-3900 (manufactured by Toagosei Co., Ltd.) and the like.

The mass ratio (urethane resin particles / acrylic resin particles) between the content (mass%) of the urethane resin particles and the content (mass%) of the acrylic resin particles is preferably 0.03 or more and 0.7 or less, and is 0. It is more preferably .23 or more and 0.46 or less.

An ink adhesion film formed of an ink having a mass ratio (urethane resin particles / acrylic resin particles) of 0.03 or more and 0.7 or less may be referred to as a Fourier converted infrared absorption spectrum method (hereinafter, also referred to as “FTIR”). ) Connects the region from spectrum 692 cm ^-1 to 707 cm ^-1 with the minimum point between spectra 710 cm ^-1 and above 740 cm ^-1 and the minimum point between spectra 660 cm ^-1 and above 690 cm ^-1 . The area A of the peak region surrounded by the tangent line, and the minimum point between the spectrum 1,731 cm ^-1 to 1,750 cm ^-1 and the spectrum 1,660 cm ^-1 or more and 1,690 cm ^-1 or less. The area ratio (B / A) of the area B of the peak region surrounded by the tangent line connecting the minimum points between the spectra of 1,760 cm ^-1 or more and 1,790 cm ^-1 or less is 0.3 or more and 1.0 or less. It is preferable, 0.51 or more and 1.0 or less is more preferable, and 0.6 or more and 1.0 or less is particularly preferable. When the area ratio (B / A) is 0.3 or more and 1.0 or less, both the effect of improving the abrasion resistance by the urethane resin particles and the effect of improving the blocking resistance by the acrylic resin particles can be achieved. ..

For the measurement of the ink adhesion film by the Fourier transform infrared absorption spectrum method, for example, the ATR (Attented Total Reflection) method of the Fourier transform infrared spectrophotometer can be used.
Specifically, the surface of the image formed on paper (trade name: Lumi Art Gloss 130 gsm, manufactured by Stora Enso) with an ink adhesion amount of 1.12 mg / cm ² (700 mg / A4) is used as a device name: It can be determined from the spectrum measured by the ATR method using a diamond indenter using Spectrum One (manufactured by PerkinElmer).

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.

-Glidant-
The ink preferably contains a lubricant. When the ink contains a lubricant, the abrasion resistance can be improved. Further, by using the lubricant and the resin in combination, the glossiness can be improved.
The lubricant is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include wax.
Examples of the wax include polyethylene wax.

As the polyethylene wax, a commercially available product may be used as appropriate.
The commercially available polyethylene wax is not particularly limited and may be appropriately selected depending on the purpose. For example, polyethylene wax (trade name: Aqua Petro DP2502C, manufactured by Toyo Adre Co., Ltd.), polyethylene wax (trade name: Aqua). Petro DP2401, manufactured by Toyo Adre Co., Ltd.) and the like. These may be used alone or in combination of two or more.

The content of the lubricant is preferably 0.05% by mass or more and 2% by mass or less, more preferably 0.05% by mass or more and 0.5% by mass or less, and 0.05% by mass or more and 0. It is more preferably 45% by mass or less, and particularly preferably 0.15% by mass or more and 0.45% by mass or less. When the content is 0.05% by mass or more and 2% by mass or less, the abrasion resistance and the glossiness can be improved. When the content is 0.05% by mass or more and 0.45% by mass or less, the storage stability and ejection stability of the ink can be improved.

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.).

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

The water is not particularly limited and may be appropriately selected depending on the intended purpose. For example, purified water, ion-exchanged water, ultrafiltered water, back-penetration water, pure water such as distilled water, ultrapure water and the like can be selected. Can be mentioned. These may be used alone or in combination of two or more.

-Additive-
If necessary, a surfactant, an antifoaming agent, an antiseptic / antifungal agent, a rust preventive agent, a pH adjuster and the like may be added to the ink.

--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, lauryldimethylbetaine, stearyldimethylbetaine, and lauryldihydroxyethylbetaine.
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.

（但し、一般式（Ｓ－１）式中、ｍ、ｎ、ａ、及びｂは、それぞれ独立に、整数を表わし、Ｒは、アルキレン基を表し、Ｒ’は、アルキル基を表す。）
上記のポリエーテル変性シリコーン系界面活性剤としては、市販品を用いることができ、例えば、ＫＦ－６１８、ＫＦ－６４２、ＫＦ－６４３（信越化学工業株式会社）、ＥＭＡＬＥＸ－ＳＳ－５６０２、ＳＳ－１９０６ＥＸ（日本エマルジョン株式会社）、ＦＺ－２１０５、ＦＺ－２１１８、ＦＺ－２１５４、ＦＺ－２１６１、ＦＺ－２１６２、ＦＺ－２１６３、ＦＺ－２１６４（東レ・ダウコーニング・シリコーン株式会社）、ＢＹＫ－３３、ＢＹＫ－３８７（ビックケミー株式会社）、ＴＳＦ４４４０、ＴＳＦ４４５２、ＴＳＦ４４５３（東芝シリコン株式会社）などが挙げられる。 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.
[General formula (S-1)]

(However, in the general formula (S-1), m, n, a, and b each independently represent an integer, R represents an alkylene group, and R'represents an alkyl 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.

上記一般式（Ｆ－１）で表される化合物において、水溶性を付与するためにｍは０～１０の整数が好ましく、ｎは０～４０の整数が好ましい。
［一般式（Ｆ－２）］
Ｃ_ｎＦ_{２ｎ＋１－}ＣＨ_２ＣＨ（ＯＨ）ＣＨ_２－Ｏ－（ＣＨ_２ＣＨ_２Ｏ）_ａ－Ｙ
上記一般式（Ｆ－２）で表される化合物において、ＹはＨ、又はＣｍＦ_２ｍ＋１でｍは１～６の整数、又はＣＨ_２ＣＨ（ＯＨ）ＣＨ_２－ＣｍＦ_２ｍ＋１でｍは４～６の整数、又はＣｐＨ_２ｐ＋１でｐは１～１９の整数である。ｎは１～６の整数である。ａは４～１４の整数である。
上記のフッ素系界面活性剤としては市販品を使用してもよい。この市販品としては、例えば、サーフロンＳ－１１１、Ｓ－１１２、Ｓ－１１３、Ｓ－１２１、Ｓ－１３１、Ｓ－１３２、Ｓ－１４１、Ｓ－１４５（いずれも、旭硝子株式会社製）；フルラードＦＣ－９３、ＦＣ－９５、ＦＣ－９８、ＦＣ－１２９、ＦＣ－１３５、ＦＣ－１７０Ｃ、ＦＣ－４３０、ＦＣ－４３１（いずれも、住友スリーエム株式会社製）；メガファックＦ－４７０、Ｆ－１４０５、Ｆ－４７４（いずれも、大日本インキ化学工業株式会社製）；ゾニール（Ｚｏｎｙｌ）ＴＢＳ、ＦＳＰ、ＦＳＡ、ＦＳＮ－１００、ＦＳＮ、ＦＳＯ－１００、ＦＳＯ、ＦＳ－３００、ＵＲ、キャプストーンＦＳ－３０、ＦＳ－３１、ＦＳ－３１００、ＦＳ－３４、ＦＳ－３５（いずれも、Ｃｈｅｍｏｕｒｓ社製）；ＦＴ－１１０、ＦＴ－２５０、ＦＴ－２５１、ＦＴ－４００Ｓ、ＦＴ－１５０、ＦＴ－４００ＳＷ（いずれも、株式会社ネオス社製）、ポリフォックスＰＦ－１３６Ａ，ＰＦ－１５６Ａ、ＰＦ－１５１Ｎ、ＰＦ－１５４、ＰＦ－１５９（オムノバ社製）、ユニダインＤＳＮ-４０３Ｎ（ダイキン工業株式会社製）などが挙げられ、これらの中でも、良好な印字品質、特に発色性、紙に対する浸透性、濡れ性、均染性が著しく向上する点から、Ｃｈｅｍｏｕｒｓ社製のＦＳ－３１００、ＦＳ－３４、ＦＳ－３００、株式会社ネオス製のＦＴ－１１０、ＦＴ－２５０、ＦＴ－２５１、ＦＴ－４００Ｓ、ＦＴ－１５０、ＦＴ－４００ＳＷ、オムノバ社製のポリフォックスＰＦ－１５１Ｎ及びダイキン工業株式会社製のユニダインＤＳＮ-４０３Ｎが特に好ましい。 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.
[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)]
C _n F _{2n + 1-} CH ₂ CH (OH) CH ₂ -O- (CH ₂ CH ₂ O) _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. It is an integer, or CpH _{2p + 1} and p is an integer of 1 to 19. n is an integer of 1 to 6. 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, Capstone FS-30, FS-31, FS-3100, FS-34, FS-35 (all manufactured by The Chemours Company); 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 Co., Ltd.) Among these, FS-3100, FS-34, FS- of The Chemours Co., Ltd. from the viewpoint of remarkably improving good print quality, particularly color development, permeability to paper, wettability, and leveling property. 300, FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW manufactured by Neos Co., Ltd., Polyfox PF-151N manufactured by Omninova, and Unidyne DSN-manufactured by Daikin Industries Co., Ltd. 403N is 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, it has excellent wettability and ejection stability, and the image quality is improved by 0.001 mass. % 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.

－－Antifoaming agent －－
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.

--anti-rust--
The rust preventive is not particularly limited, and examples thereof include acidic sulfite and sodium thiosulfate.

--PH regulator ---
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.

<< Recording medium >>
The recording medium is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include plain paper, glossy paper, special paper, cloth, film, transparency sheet, and general-purpose printing paper.

The transport speed for transporting the recording medium is not particularly limited and may be appropriately selected depending on the intended purpose, but it is preferably changed according to the amount of the organic solvent remaining on the recording medium. Further, it is preferable to control the amount of the organic solvent on the recording medium by controlling the transport speed of the recording medium.
Specifically, when the amount of the organic solvent on the recording medium is small, it is preferable to increase the transport speed of the recording medium. When the amount of the organic solvent on the recording medium is small, the productivity can be improved by increasing the transport speed of the recording medium.
Further, when the amount of the organic solvent on the recording medium is large, it is preferable to slow down the transport speed of the recording medium. By slowing down the transport speed of the recording medium when the amount of the organic solvent on the recording medium is large, the time for the image portion on the recording medium to come into contact with the warm air in the dry portion or the heated contact member becomes longer. Therefore, the amount of the organic solvent remaining on the image surface can be reduced, and image peeling can be suppressed.

The amount of the organic solvent remaining in the image portion on the recording medium can be reduced by various drying methods.
The method for drying the recording medium is not particularly limited and may be appropriately selected depending on the intended purpose. For example, an image forming portion in the recording medium, an image non-forming portion in the recording medium (the back surface of the image forming portion, etc.) and the like. Examples include heat transfer drying in which the contact member heated to the image is directly contacted, warm air drying in which warm air is applied to the image portion, and drying by far infrared rays.
Among these, heat transfer drying in which a heated contact member is directly brought into contact with the image forming portion of the recording medium is preferable because it has high heat transfer efficiency and is excellent in drying efficiency.

Usually, a large amount of organic solvent remains in the image portion immediately after the ink application step. Therefore, first, heat transfer drying in which the image unit does not come into contact with the recording medium and the contact member heated to the non-image forming portion in the recording medium is directly contacted, hot air drying in which warm air is applied to the image unit, and far infrared rays. It is preferable to perform heat transfer drying in which the heated contact member is in direct contact with the image forming portion of the recording medium after the drying or the like is performed. Thereby, the amount of the remaining organic solvent can be further reduced.

The amount of the organic solvent remaining in the image portion on the recording medium can be measured as follows using, for example, a gas chromatograph mass spectrometer (GC-MS).
First, measure the tetrahydrofuran in a vial. Next, a cloth wiper for wiping the image surface is cut into a size that fits in the vial. Next, a solid image before being brought into contact with the heating roller is cut out. Next, the cut cloth wiper is impregnated with a small amount of tetrahydrofuran in the vial, and the cut out solid image is wiped off. Place the wiped cloth wiper in the vial, cover it, and leave it to stand. Then, by measuring the concentration of the organic solvent contained in tetrahydrofuran with a gas chromatograph mass spectrometer, the amount of the organic solvent contained in the applied ink on the recording medium can be determined.
Examples of the gas chromatograph mass spectrometer (GC-MS) include device names: GSMS-TQ8050 and GC-2010plusAF / AOC (all manufactured by Shimadzu Corporation).

As the recording medium, for example, a recording medium having a support and a coating layer provided on at least one surface side of the support, and further having another layer as needed, may be used. Can be mentioned.

The recording medium having the support and the coating layer is generally called coated paper, and is known as a medium having low ink permeability. It is difficult to firmly fix the coloring material to a medium with low permeability such as coated paper, and the scratch resistance is often deteriorated. However, if the tack force of the image is 80 nN or more and 110 nN or less, image formation is performed. Even if a pressure of 3.5 kg / cm ² or more and 8.0 kg / cm ² or less is applied later, blocking does not occur and an image with higher gloss can be obtained, which is particularly preferable.

In the recording medium having the support and the coating layer, the amount of pure water transferred to the recording medium at a contact time of 100 ms measured by a dynamic scanning liquid absorbent meter is 2 mL / m ² or more and 35 mL / m ² or less. Is preferable, and 2 mL / m ² or more and 10 mL / m ² or less is more preferable.
If the transfer amount of the ink and pure water at the contact time of 100 ms is too small, beading may easily occur, and if it is too large, the ink dot diameter after recording becomes too small than the desired diameter. There is.
The amount of pure water transferred to the recording medium at a contact time of 400 ms measured by a dynamic scanning liquid absorbent is preferably 3 mL / m ² or more and 40 mL / m ² or less, and 3 mL / m ² or more and 10 mL / m ² or less. More preferred.
If the amount of transfer at the contact time of 400 ms is small, the drying property is insufficient, so that spur marks may easily occur, and if it is too large, the gloss of the image portion after drying tends to be low. be. The amount of pure water transferred to the recording medium at the contact times of 100 ms and 400 ms can be measured on the surface of the recording medium on the side having the coating layer.

Here, the dynamic scanning absorber (DSA, Paper Technology Cooperative Magazine, Vol. 48, May 1994, pp. 88-92, Shigenori Kukan) absorbs liquid in an extremely short time. It is a device that can measure the amount accurately. The dynamic scanning liquid absorption meter directly reads the speed of liquid absorption from the movement of the meniscus in the capillary, makes the sample disk-shaped, and scans the liquid-absorbing head spirally on the sample, and scans the speed according to a preset pattern. Is automatically changed, and the measurement is performed by the method of measuring the required number of points with one sample.
The liquid supply head to the paper sample is connected to the capillary via a Teflon® tube, and the position of the meniscus in the capillary is automatically read by an optical sensor. Specifically, a dynamic scanning liquid absorption meter (K350 series D type, manufactured by Kyowa Seiko Co., Ltd.) can be used to measure the transfer amount of pure water or ink.
The transfer amount at the contact time of 100 ms and the contact time of 400 ms can be obtained by interpolation from the measured values of the transfer amounts at the contact times in the vicinity of each contact time.

-Support-
The support is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include paper mainly composed of wood fibers, sheet-like substances such as non-woven fabric mainly composed of wood fibers and synthetic fibers, and the like. ..

The paper is not particularly limited and may be appropriately selected from known ones according to the purpose. For example, wood pulp, used paper pulp and the like are used.
Examples of the wood pulp include hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), NBSP, LBSP, GP, TMP and the like.

The raw materials for the recycled paper pulp are fine white, ruled white, cream white, card, special white, medium white, imitation, fair white, Kent, and white, which are shown in the recycled paper standard quality standard table of the Recycled Paper Recycling Promotion Center. Examples include art, special cuts, special cuts, newspapers, and magazines.
Specifically, information-related paper such as non-coated computer paper, heat-sensitive paper, pressure-sensitive paper, and other printer paper; OA waste paper such as PPC paper; art paper, coated paper, finely coated paper, matte paper, and the like. Paper; high-quality paper, high-quality color, notebook, notepaper, wrapping paper, fancy paper, medium-quality paper, newspaper paper, stencil paper, super hanging paper, imitation paper, pure white roll paper, uncoated paper such as milk carton, etc. Used paper and paperboard, such as chemical pulp paper and high-yield pulp-containing paper.
These may be used alone or in combination of two or more.

The recycled paper pulp can generally be produced from a combination of the following four steps.
(1) To dissociate, the used paper is treated with a pulper with mechanical force and chemicals to loosen it into fibers, and the printing ink is peeled from the fibers.
(2) For dust removal, foreign matter (plastic, etc.) and dust contained in used paper are removed with a screen, cleaner, or the like.
(3) For deinking, the printing ink peeled off from the fiber using a surfactant is removed from the system by a flotation method or a cleaning method.
(4) Bleaching enhances the whiteness of fibers by using an oxidizing action or a reducing action.
When the used paper pulp is mixed, the mixing ratio of the used paper pulp in the total pulp is preferably 40% or less from the viewpoint of curling measures after recording.

As the internal filler used for the support, for example, a conventionally known pigment as a white pigment is used.
Examples of the white pigment include light calcium carbonate, heavy calcium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, and silica clay. White inorganic pigments such as calcium silicate, magnesium silicate, synthetic silica, aluminum hydroxide, alumina, lithopone, zeolite, magnesium carbonate, magnesium hydroxide, etc .; styrene plastic pigments, acrylic plastic pigments, polyethylene, microcapsules, urea resins , Organic pigments such as melamine resin, and the like. These may be used alone or in combination of two or more.

Examples of the internal sizing agent used when making the support include a neutral rosin-based sizing agent used for neutral papermaking, alkenyl succinic anhydride (ASA), alkyl ketene dimer (AKD), and petroleum resin. Examples include system size agents. Of these, neutral rosin sizing agents or alkenyl succinic anhydride are particularly suitable. The alkyl ketene dimer can be added in a small amount because of its high size effect, but it is not preferable from the viewpoint of transportability during inkjet recording because the friction coefficient on the surface of the recording paper (recording medium) is lowered and it becomes slippery. In some cases.

-Coating layer-
The coating layer contains a pigment and a binder (binder), and further contains a surfactant and other components, if necessary. In the present invention, the coating layer may contain a pigment and a binder (binder) as described above, and it does not matter whether the coating layer is actually coated or not. Means things.

As the pigment, an inorganic pigment or a combination of an inorganic pigment and an organic pigment can be used.
Examples of the inorganic pigment include kaolin, talc, heavy calcium carbonate, light calcium carbonate, calcium sulfite, amorphous silica, titanium white, magnesium carbonate, titanium dioxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, and the like. Examples include zinc hydroxide and chlorite. Among these, kaolin is particularly preferable because it has excellent glossiness and can have a texture similar to that of paper for offset printing.

The kaolin includes delaminated kaolin, calcined kaolin, engineered kaolin by surface modification, etc., but in consideration of gloss development, a particle size distribution with a particle size of 2 μm or less is 80% by mass or more. It is preferable that the kaolin contained in the kaolin accounts for 50% by mass or more of the total kaolin.

The content of the kaolin is preferably 50 parts by mass or more with respect to 100 parts by mass of the binder. When the content is 50 parts by mass or more, the glossiness can be improved. The upper limit of the content is not particularly limited, but in consideration of the fluidity of kaolin, particularly the thickening under a high shearing force, 90 parts by mass or less is preferable from the viewpoint of coating suitability.

Examples of the organic pigment include water-soluble dispersions such as styrene-acrylic copolymer particles, styrene-butadiene copolymer particles, polystyrene particles, and polyethylene particles. Two or more of these organic pigments may be mixed.
The amount of the organic pigment added is preferably 2 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the total pigment in the coating layer. Since the organic pigment is excellent in gloss development and its specific gravity is smaller than that of the inorganic pigment, it is possible to obtain a coating layer having a bulky, high gloss and good surface coating property. When the content is 2 parts by mass or more, the effect can be improved, and when it is 20 parts by mass or less, the fluidity of the coating liquid is excellent, the coating operability can be improved, and it is economical in terms of cost. be.

The organic pigment includes a dense type, a hollow type, a donut type and the like in its form, but in consideration of the balance between gloss development, surface coating property and fluidity of the coating liquid, the average particle size of the organic pigment is used. Is preferably 0.2 μm or more and 3.0 μm or less, and more preferably a hollow type having a void ratio of 40% or more.

As the binder, it is preferable to use an aqueous resin.
As the water-based resin, at least one of a water-soluble resin and a water-dispersible resin is preferably used.
The water-soluble resin is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a modified product of a polyvinyl alcohol such as a polyvinyl alcohol, an anion-modified polyvinyl alcohol, a cation-modified polyvinyl alcohol, or an acetal-modified polyvinyl alcohol; Polyurethane; Polyvinylpyrrolidone and a copolymer of polyvinylpyrrolidone and vinyl acetate, a copolymer of vinylpyrrolidone and dimethylaminoethyl / methacrylic acid, a quaternized polymer of vinylpyrrolidone and dimethylaminoethyl / methacrylic acid, and vinylpyrrolidone. Modified products of polyvinylpyrrolidone such as a copolymer of methacrylamide propyl trimethylammonium chloride; cellulose such as carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose; modified products of cellulose such as cationized hydroxyethyl cellulose; polyester, polyacrylic acid (ester), Melamine resin or synthetic resins such as modified products thereof, polymers of polyester and polyurethane; poly (meth) acrylic acid, poly (meth) acrylamide, oxidized starch, phosphoric acid esterified starch, self-modified starch, cationized starch, Alternatively, various modified starches, polyethylene oxide, sodium polyacrylic acid, sodium alginate, and the like can be mentioned. These may be used alone or in combination of two or more.
Among these, polyvinyl alcohol, cation-modified polyvinyl alcohol, acetal-modified polyvinyl alcohol, polyester, polyurethane, a copolymer of polyester and polyurethane, and the like are preferable from the viewpoint of ink absorbency.

The water-dispersible resin is not particularly limited and may be appropriately selected depending on the intended purpose. For example, polyvinyl acetate, ethylene-vinyl acetate copolymer, polystyrene, styrene- (meth) acrylic acid ester copolymer weight. Combined, (meth) acrylic acid ester-based polymer, vinyl acetate- (meth) acrylic acid (ester) copolymer, styrene-butadiene copolymer, ethylene-propylene copolymer, polyvinyl ether, silicone-acrylic acid-based copolymer Coalescence, etc. Further, a cross-linking agent such as methylolated melamine, methylolated urea, methylolated hydroxypropylene urea, or isocyanate may be contained, or a copolymer containing a unit such as N-methylol acrylamide having self-crosslinking property may be used. It is also possible to use a plurality of these aqueous resins at the same time.
The content of the aqueous resin is preferably 2 parts by mass or more and 100 parts by mass or less, and more preferably 3 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the pigment. The content is determined so that the liquid absorption characteristics of the recording medium fall within a desired range.

When a water-dispersible colorant is used as the colorant, the cationic organic compound does not necessarily have to be blended, but there is no particular limitation, and the colorant can be appropriately selected and used depending on the intended purpose. For example, primary to tertiary amines and quaternary ammonium salt monomers and oligomers that react with direct dyes in water-soluble inks and sulfonic acid groups, carboxyl groups, amino groups, etc. in acidic dyes to form insoluble salts. Examples thereof include polymers, and among these, oligomers or polymers are preferable.

Examples of the cationic organic compound include dimethylamine / epichlorohydrin polycondensate, dimethylamine / ammonium / epichlorohydrin condensate, poly (trimethylaminoethyl methacrylate / methyl sulfate), diallylamine hydrochloride / acrylamide copolymer, and poly. (Diallylamine hydrochloride / sulfur dioxide), polyallylamine hydrochloride, poly (allylamine hydrochloride / diallylamine hydrochloride), acrylamide / diallylamine copolymer, polyvinylamine copolymer, dicyandiamide, dicyandiamide / ammonium chloride / urea / formaldehyde condensate , Polyalkylene polyamine / dicyandiamidammonium salt condensate, dimethyldiallylammonium chloride, polydialylmethylamine hydrochloride, poly (diallyldimethylammonium chloride), poly (diallyldimethylammonium chloride / sulfur dioxide), poly (diallyldimethylammonium chloride / diallylamine) Hydrochloride derivatives), acrylamide / diallyldimethylammonium chloride copolymers, acrylicate / acrylamide / diallylamine hydrochloride copolymers, ethyleneimine derivatives such as polyethyleneimine and acrylicamine polymers, polyethyleneimine alkylene oxide modified products, etc. Be done. These may be used alone or in combination of two or more.
Among these, low molecular weight cationic organic compounds such as dimethylamine / epichlorohydrin polycondensate and polyallylamine hydrochloride and other relatively high molecular weight cationic organic compounds such as poly (diallyldimethylammonium chloride) are used. It is preferable to use them in combination. When used in combination, the image density is improved and feathering is further reduced as compared with the case of single use.

The cationic equivalent of the cationic organic compound by the colloid titration method (using potassium polyvinyl sulfate and toluidine blue) is preferably 3 meq / g or more and 8 meq / g or less. If the cation equivalent is in this range, good results can be obtained in the range of the dry adhesion amount.
Here, in the measurement of the cation equivalent by the colloid titration method, the cationic organic compound is diluted with distilled water so as to have a solid content of 0.1% by mass, and the pH is not adjusted.

The dry adhesion amount of the cationic organic compound is preferably 0.3 g / m ² or more and 2.0 g / m ² or less. When the dry adhesion amount of the cationic organic compound is 0.3 g / m ² or more, the image density can be sufficiently improved and the effect of reducing feathering can be improved.

The surfactant is not particularly limited and may be appropriately selected depending on the intended purpose, but any of anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants should be used. Can be done. Of these, nonionic surfactants are particularly preferred. By adding the surfactant, the water resistance of the image is improved, the image density is increased, and the bleeding is improved.

Examples of the nonionic surfactant include higher alcohol ethylene oxide adduct, alkylphenol ethylene oxide adduct, fatty acid ethylene oxide adduct, polyhydric alcohol fatty acid ester ethylene oxide adduct, higher aliphatic amine ethylene oxide adduct, and fatty acid. Amidethylene oxide adduct, ethylene oxide adduct of fats and oils, polypropylene glycol ethylene oxide adduct, fatty acid ester of glycerol, fatty acid ester of pentaerythritol, fatty acid ester of sorbitol and sorbitan, fatty acid ester of sucrose, alkyl ether of polyhydric alcohol. , Fatty acid amides of alkanolamines and the like. These may be used alone or in combination of two or more.

The polyhydric alcohol is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include glycerol, trimethylolpropane, pentaerythritol, sorbitol and sucrose.
As for the ethylene oxide adduct, it is also effective to replace a part of ethylene oxide with an alkylene oxide such as propylene oxide or butylene oxide as long as the water solubility can be maintained. The substitution rate is preferably 50% or less.
The HLB (hydrophilic / lipophilic ratio) of the nonionic surfactant is preferably 4 or more and 15 or less, and more preferably 7 or more and 13 or less.

The content of the surfactant is preferably 0 parts by mass or more and 10 parts by mass or less, and more preferably 0.1 parts by mass or more and 1.0 part by mass or less with respect to 100 parts by mass of the cationic organic compound.

Other components can be added to the coating layer as needed, as long as the object and effect of the present invention are not impaired. Examples of the other components include additives such as alumina powder, pH adjusters, preservatives, and antioxidants.

The method for forming the coating layer is not particularly limited and may be appropriately selected depending on the intended purpose, and can be carried out by impregnating or coating the coating layer liquid on the support. The impregnation or coating method of the coating layer liquid is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a conventional size press, a gate roll size press, a film transfer size press, a blade coater, and a rod coater. , Air knife coater, curtain coater, etc. can be applied with various coating machines, but from the viewpoint of cost, the conventional size press, gate roll size press, film transfer size press, etc. installed in the paper machine can be used. It may be impregnated or adhered and finished on-machine.
The amount of the coating layer liquid adhered is not particularly limited and can be appropriately selected depending on the intended purpose. The solid content is preferably 0.5 g / m ² or more and 20 g / m ² or less, and 1 g / m ² or more. More preferably, it is 15 g / m ² or less.
After the impregnation or coating, it may be dried if necessary, and the drying temperature in this case is not particularly limited and may be appropriately selected depending on the intended purpose, but is about 100 ° C. or higher and 250 ° C. or lower. Is preferable.

The recording medium may further form a back layer on the back surface of the support, another layer between the support and the coating layer, and between the support and the back layer, and a protective layer may be formed on the coating layer. It can also be provided. Each of these layers may be a single layer or a plurality of layers.

<Contact process and contact means>
The contact step is a step in which the surface of the recording medium to which the ink is applied comes into contact with the contact member heated to a temperature higher than normal temperature.
The contact means is a means in which the surface of the recording medium to which the ink is applied comes into contact with the contact member heated to a temperature higher than normal temperature.
The contact step can be preferably carried out by the contact means.

<< Heated contact member >>
The heated contact member means a contact member heated to a temperature of 25 ° C. or higher.
Examples of the contact member include rollers and the like.
The roller is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a heating roller, a transport roller and a small diameter roller.
As the heating, the contact member itself may be provided with a mechanism for heating, or the contact member may be heated by convection heat from other drying means. Further, the drying device may be provided with a contact member.

The temperature of the heated contact member is 25 ° C. or higher, preferably 40 ° C. or higher at the set temperature of the heated contact member, and 80 ° C. or higher and 150 ° C. or lower is more preferable from the viewpoint of image dryness. preferable. When the temperature of the heated contact member is 80 ° C. or higher, blocking by the organic solvent remaining in the image portion on the recording medium can be suppressed. When the temperature of the heated contact member is 150 ° C. or lower, the plasticization of the resin by the organic solvent remaining in the image portion on the recording medium is suppressed, so that the image transfer to the heated contact member is suppressed. be able to.

The type of the heated contact member is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include metals such as stainless steel. By using metal as the type of the contact member to be heated, the temperature of the contact member to be heated can be controlled to a desired temperature because the heat responsiveness is excellent.

As for the number of heated contact members, the larger the number, the more the amount of the organic solvent remaining in the image portion on the recording medium can be reduced. However, if the number of heated contact members is excessively increased, not only the transfer of the image to the contact members and other recording media is induced, but also the size of the heated portion is increased. It is preferable to appropriately select the number of heated contact members.

The heated contact member may come into contact with the surface of the recording medium to which the ink has been applied, or may come into contact with the surface of the recording medium opposite to the surface of the recording medium to which the ink has been applied. Further, both a contact member that comes into contact with the ink-applied surface of the recording medium and a contact member that contacts the surface opposite to the ink-applied surface of the recording medium may be provided. As a result, the image forming apparatus including the contact member to be heated can be miniaturized.

When both the contact members in contact with the inked surface of the recording medium and the contact members in contact with the surface opposite to the inked surface of the recording medium are provided, these contact members are arranged alternately. Is preferable. This point will be described with reference to FIGS. 2 and 3. FIG. 2 is a schematic view showing an angle between a roller as a contact member and a recording medium. FIG. 3 includes both a roller in contact with the inked surface of the recording medium and a roller in contact with the surface opposite to the inked surface, and in FIG. 2, from the center of the roller onto the recording medium. It is a schematic diagram which shows an example of the arrangement of a roller when the angle θ formed by the radius which makes tension T a tangential direction is 180 °.
In FIG. 3, after passing through the roller 31, an image is formed on the inner surface of the roller 31 in the ink ejection unit 4. After that, the formed image passes through the outside of the rollers 32, 34, 36 and is conveyed through the inside of the rollers 33, 35. That is, the rollers 32, 34, and 36 come into contact with the surface of the recording medium opposite to the inked surface, and the rollers 33, 35 come into contact with the inked surface of the recording medium.

In the case of a generally known image recording method, when the non-image forming surface of the recording medium is heated to dry the image, and then the image forming surface is heated again to dry the image, the image is warmed. There is a problem that the image is transferred to the heated contact member.
On the other hand, in the present invention, the ink-applied surface of the recording medium comes into contact with the contact members 33 and 35, but the amount of the organic solvent contained in the inked ink on the recording medium is 100 μg / cm ² or less. By setting the pressure on the surface to which the ink is applied to 0.020 kg / cm ² or more and 0.030 kg / cm ² or less, the image is transferred to a contact member or another recording medium, and image peeling occurs. Can be suppressed.

The contact time between the heated contact member and the image unit is appropriately selected according to the angle θ between the contact member and the recording medium, the transport speed of the recording medium, the number of heated contact members, and the like. However, from the viewpoint of blocking resistance, 1.0 second or more and 6.0 seconds or less are preferable.

Pressure is applied to the surface (image portion) to which the ink is applied on the recording medium. The pressure on the surface of the recording medium to which the ink is applied may be any pressure applied to the recording medium, and the method may be active or passive. For example, the pressure from the heated contact member, the pressure due to being pushed by one or more pressing rollers, the pressure generated by rolling the continuous paper into a roll, and the like can be mentioned. Among these, the pressure applied by the heated contact member is preferable, and the pressure applied by the contact of the heated contact member with the image non-forming surface of the recording medium, which first comes into contact with the recording medium, is more preferable.

When the recording medium is continuous paper, the pressure generated by winding the continuous paper after applying ink into a roll is, for example, in the winding step of winding the continuous paper into a roll using a winding device. It is preferable that pressure is applied to the image on the continuous paper due to the tension that the winder winds up the continuous paper. In the winding step of winding continuous paper, the effect of the present invention can be obtained if there is pressure on the image due to the tension applied to the continuous paper.

The pressure applied to the roll-shaped continuous paper can be calculated, for example, from photographs and information of the roll-shaped continuous paper with reference to the diameter, height, and mass of the roll-shaped continuous paper.
Since continuous paper having a wider paper width and a larger basis weight needs to be tensioned, the image portion is strongly pressed against the heated roller that comes into contact with the paper, and the image tends to be easily transferred.

The pressure measuring method is not particularly limited, and a known device can be appropriately selected according to the purpose. For example, a force / pressure distribution measuring device (device name: surface pressure distribution measuring system I-SCAN, Nitta). I-SCAN # 5027 (manufactured by Nitta Corporation) can be used as the sensor sheet (manufactured by Nitta Corporation).

The method for measuring the pressure applied to the roll-shaped continuous paper can be obtained, for example, as follows (FIGS. 4 and 5).
First, the continuous paper 12 is wound in a roll shape, and the sensor sheet 13 for measuring the pressure is installed at a position 20 cm from the outside of the paper tube 11 having the cavity 10. Next, the sensor sheet 13 is installed at three points whose positions are changed in the width direction of the continuous paper 12, and three measurement points are provided. After that, the continuous winding of the continuous paper 13 was continued, the pressure at the stage where the 10 cm papers were overlapped when viewed from the three measurement points was measured, and the average value of the pressures at the three points was taken as the pressure applied to the image. can do.

The pressure may be applied in multiple steps or in only one step. Further, the pressure may be applied to at least a part of the recording medium, and it is preferable that the pressure is applied to the entire recording medium.

[Image peeling]
When the recording medium has a layer containing calcium carbonate (for example, a coat layer) on the cellulose layer and the image is transferred to the heated contact member, the diameter: 100 μm as shown in FIG. Some degree of white spots may be observed. When white spots occur, the depth of white spots becomes about 3 μm to 20 μm, and the coat layer is broken. Therefore, the more white spots there are in the image, the easier it is to visually determine that the image is peeled off.

[Whiteout area ratio]
The whiteout area ratio of the image can be obtained, for example, as follows.
First, the image is scanned using a scanner. Next, the scanned image file is binarized into white spots and non-white spots by image processing software and analyzed, so that the "white spot area ratio" with respect to the image surface can be calculated.
As the scanner, for example, an apparatus name: ES-G11000 (manufactured by Seiko Epson Corporation) or the like can be used. Further, as the image processing software, for example, ImageJ (Fiji) or the like can be used.
As the measurement conditions of the scan, for example, the measurement can be performed under the following conditions.
-Measurement condition-
Mode: Professional mode Image type: 24-bit color Recording resolution: 800 dpi x 800 dpi
File format: TIFF
Proof left setting (color): No color correction

[Tack power]
The tack force of the image formed by using the ink at 25 ° C. is preferably 80 nN or more and 110 nN or less, and more preferably 85 nN or more and 100 nN or less. When the tack force is 80 nN or more, the image binding force can be improved and the film strength is increased, so that the fixability can be improved. When the tack force is 110 nN or less, the force acting between the pressure applied to the image portion and the contact surface can adjust the film strength for maintaining the image, and the image can be prevented from being destroyed. Image peeling can be suppressed.

The tack force of the image can be determined as follows by using, for example, an atomic force microscope (hereinafter, also referred to as “AFM”).
As the image, an image output on a recording medium by various inkjet printers can be used. The probe of the AFM is brought into contact with the image, pushed in by 100 nm, and then the probe is pulled up to monitor the bending of the cantilever as it leaves the image, and a force curve as shown in FIG. 7 is obtained. The tack force can be a value (F = kx) obtained by multiplying the displacement amount x by the spring constant k of the cantilever 20 as shown in FIG. As the cantilever 20, a cantilever 20 having a spherical silicone oxide as a probe 21 can be used.
As the atomic force microscope, for example, an apparatus name: SPM-9500J3 (manufactured by Shimadzu Corporation) or the like can be used.
The measurement conditions can be, for example, a measurement temperature: 23 ° C., a relative humidity: 35%, a probe diameter: 3.5 μm, a measurement mode: force curve measurement, and a measurement frequency: 1 Hz.

<Drying process and drying means>
In the image forming method, it is preferable to include a drying step between the ink applying step and the contacting step. The drying step is a step of drying the organic solvent on the recording medium.
It is preferable to have a drying means in the image forming apparatus. The drying means is a means for drying the organic solvent on the recording medium.
The drying step can be preferably carried out by the drying means.
As the specific drying means, the above-mentioned drying means and the like can be used, and for example, warm air drying, infrared irradiation, ultraviolet irradiation, high frequency dielectric heating, natural drying at room temperature and the like can be used.

Further, in the terms of the present invention, image formation, recording, printing, printing, etc. are all synonymous. Recording media, media, and printed matter are all synonymous.

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

(Example of Fabrication of Pigment Dispersion)
<Preparation of cyan pigment dispersion>
Pigment Blue 15: 3 (Chromofine Blue, manufactured by Dainichiseika Kogyo Co., Ltd.), 20 mmol of the compound of the following structural formula (1), and 200 mL of ion-exchanged water under a room temperature (25 ° C.) environment, a slurryson mixer (6, Mixing at 000 rpm) gave a slurry. When the pH of the obtained slurry was higher than 4, 20 mmol of nitric acid was added. After 30 minutes, sodium nitrite (20 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 was produced by adding the compound of the following structural formula (1) to Pigment Blue. Then, the pH was adjusted to 10 with an aqueous NaOH solution to obtain a modified pigment dispersion after 30 minutes. Ultrafiltration using a dialysis membrane was performed using a dispersion containing a pigment bound to at least one geminalbisphosphonic acid group or a geminalbisphosphonic acid sodium salt and ion-exchanged high pure water, and further ultrasonic dispersion was performed to generate cyanide. A pigment dispersion (pigment solid content: 15% by mass) was prepared.

(Preparation Example 1 of Polyurethane Resin Emulsion)
<Preparation of polyurethane resin emulsion 1>
1,6-Hexanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediic acid, and titanium (IV) tetraisopropoxide in a reaction vessel equipped with a cooling tube, a stirrer, and a nitrogen introduction tube. Add 1,000 ppm (1% by mass with respect to the resin component), the molar ratio of alcohol to carboxylic acid (alcohol / carboxylic acid) = 1.5, and the alcohol component in 1,6-hexanediol: 10 mol%. , And the alcohol component in 1,4-cyclohexanedimethanol: 90 mol%. Then, the temperature was raised to 200 ° C. over 4 hours. Next, the temperature was raised to 230 ° C. over 2 hours, and the reaction was carried out until the runoff water disappeared. Then, the reaction was carried out under reduced pressure of 1,334 Pa or more and 2,000 Pa or less (10 mmHg or more and 15 mmHg or less) for 5 hours to obtain an intermediate polyester.
Next, the intermediate polyester and the isophorone diisocyanate are placed in another cooling tube, a stirrer, and the like so that the molar ratio of the intermediate polyester to the isophorone diisocyanate (the intermediate polyester / isophorone diisocyanate) is 2.0. It was placed in a reaction vessel with a nitrogen introduction tube. Then, ethyl acetate was added to dilute the intermediate polyester so that the concentration of the intermediate polyester was 48% by mass, and then the reaction was carried out at 100 ° C. for 5 hours. Then, a large amount of water was added to stop the reaction to obtain a polyurethane resin emulsion 1 (solid content concentration: 10% by mass) which is a dispersion liquid of the polyurethane resin particles 1.
The glass transition temperature (Tg) of the obtained polyurethane resin particles 1 was measured using a differential scanning calorimeter (device name: Thermo plus EVO2 / DSC, manufactured by Rigaku Co., Ltd.) and found to be -16 ° C.

(Preparation Example 2 of Polyurethane Resin Emulsion)
<Preparation of polyurethane resin emulsion 2>
In Preparation Example 1 of the polyurethane resin emulsion, 1,6-hexanediol and 1,4-cyclohexanedimethanol were used, and the alcohol component in 1,6-hexanediol: 50 mol% and the alcohol component in 1,4-cyclohexanedimethanol. Polyurethane resin emulsion 2 (solid content concentration: 10% by mass), which is a dispersion of polyurethane resin particles 2, was obtained in the same manner as in Preparation Example 1 of the polyurethane resin emulsion except that the content was changed to 50 mol%.
The glass transition temperature (Tg) of the obtained polyurethane resin particles 2 was measured using a differential scanning calorimeter (device name: Thermo plus EVO2 / DSC, manufactured by Rigaku Co., Ltd.) and found to be −49 ° C.

(Preparation Example 3 of Polyurethane Resin Emulsion)
<Preparation of polyurethane resin emulsion 3>
In Preparation Example 1 of the polyurethane resin emulsion, 1,6-hexanediol and 1,4-cyclohexanedimethanol were used, and the alcohol component in 1,6-hexanediol: 30 mol% and the alcohol component in 1,4-cyclohexanedimethanol. Polyurethane resin emulsion 3 (solid content concentration: 10% by mass), which is a dispersion of polyurethane resin particles 3, was obtained in the same manner as in Preparation Example 1 of the polyurethane resin emulsion except that the content was changed to 70 mol%.
The glass transition temperature (Tg) of the obtained polyurethane resin particles 3 was measured using a differential scanning calorimeter (device name: Thermo plus EVO2 / DSC, manufactured by Rigaku Co., Ltd.) and found to be −32 ° C.

(Ink Preparation Example 1)
<Preparation of ink 1>
Cyan pigment dispersion 18.0% by mass, dipropylene glycol dimethyl ether (trade name: Polyethylene, manufactured by Dow Chemical Company) 5.0% by mass, dipropylene glycol monopropyl ether (trade name: dowanol DPnP, Dow Chemical) (Company) 7.0% by mass, 1,2-propanediol 25.0% by mass, polyurethane resin emulsion 1 4.0% by mass, styrene acrylic resin emulsion (trade name: JDX-5050, manufactured by BASF) 1 0.0% by mass, as a surfactant, polyether-modified siloxane copolymer (trade name: TEGO WET270, manufactured by Ebonic) 1.0% by mass, as a lubricant, polyethylene wax (trade name: Aqua Petro DP2502C, manufactured by Toyo Adre Co., Ltd.) ) 0.3% by mass, and after adding the remaining amount of purified water so that the total becomes 100% by mass, mixing and stirring, a polypropylene filter (trade name: Profile Star, manufactured by Nippon Pole Co., Ltd., average pore size: 1. Ink 1 was prepared by filtering with 5 μm).

(Ink 2 to 24)
<Preparation of inks 2 to 24>
Ink 2 to 24 were produced in the same manner as in Ink Preparation Example 1 except that the composition was changed as shown in Tables 1 to 4 below in Ink Preparation Example 1. The content of each resin emulsion in Tables 1 to 4 below is the amount as an emulsion.

In Tables 1 to 4, the product names of the ingredients and the names of the manufacturing companies are as follows.

<Organic solvent>
-Dipropylene glycol dimethyl ether (trade name: Propylene DMM, manufactured by Dow Chemical Company, boiling point: 175 ° C)
-Dipropylene glycol monopropyl ether (trade name: dowanol DPnP, manufactured by Dow Chemical Company, boiling point: 213 ° C)
・ 1,2-Propanediol (manufactured by Tokyo Chemical Industry Co., Ltd., boiling point: 188 ° C)
・ 1,3-Propanediol (manufactured by Tokyo Chemical Industry Co., Ltd., boiling point: 214 ° C)
1,2-Butanediol (manufactured by Tokyo Chemical Industry Co., Ltd., boiling point: 194 ° C)
・ 1,3-Butanediol (manufactured by Tokyo Chemical Industry Co., Ltd., boiling point: 207 ° C)
-3-Methyl-1,3-butanediol (manufactured by Kuraray Co., Ltd., boiling point: 203 ° C)
・ Glycerin (manufactured by Sakamoto Yakuhin Kogyo Co., Ltd., boiling point: 290 ° C)

<Resin>
-Styrene acrylic resin emulsion (trade name: JDX-5050, manufactured by BASF)

<Glidant>
-Polyethylene wax emulsion (trade name: Aqua Petro DP2502C, manufactured by Toyo Adre Co., Ltd.)

<Surfactant>
-Polyether-modified siloxane copolymer (trade name: TEGO WET270, manufactured by Evonik)

(Examples 1 to 19 and Comparative Examples 1 to 5)
[Image formation]
Inkjet printing system (device name: RICOH Pro VC60000, manufactured by Ricoh Co., Ltd.) is set with roll paper (trade name: Lumi Art Gloss, manufactured by Stora Enso, basis weight: 130 g / m ² , paper width: 521 mm) as a recording medium. Then, inks 1 to 24 obtained with a recording resolution of 1,200 dpi × 1,200 dpi and an application amount shown in Table 5 were applied to form a solid image. Next, the solid image of the roll paper is dried with warm air, the contact of the heating roller (diameter: 40 mm) with the image-non-forming surface of the recording medium, and the heating roller of the recording medium with the image-forming surface. Contact (diameter: 40 mm) was sequentially performed to dry the solid image. Further, the roll paper was wound up using a winding device (device name: Rewinding module RW6, manufactured by Hunkeller).
The set temperature for hot air drying, the set temperature for the heating rollers, the number of rollers, the contact angle with the recording medium, and the contact time with the recording medium are as shown in Table 5.

[Pressure from heated rollers]
The pressure applied to the solid image by the heating roller is a force / pressure distribution measuring device (device name) as the pressure applied to the solid image due to the contact of the heating roller with the image non-forming surface of the recording medium, which first comes into contact with the recording medium. : The surface pressure distribution measurement system I-SCAN (manufactured by Nitta Co., Ltd.) was used, and I-SCAN # 5027 (manufactured by Nitta Co., Ltd.) was used as the sensor sheet for measurement. As shown in FIGS. 4 and 5, the continuous paper 12 was wound in a roll shape, and the sensor sheet 13 for measuring the pressure was installed at a position 20 cm from the outside of the paper tube 11 having the cavity 10. By installing the sensor sheet 13 at three points whose positions are changed in the width direction of the continuous paper 12, three measurement points are provided. After that, the continuous winding of the continuous paper 13 was continued, the pressure at the stage where the 10 cm papers were overlapped when viewed from the three measurement points was measured, and the average value of the pressures at the three points was taken as the pressure applied to the image. did.

[Amount of organic solvent on recording medium]
Tetrahydrofuran (manufactured by Tokyo Chemical Industry Co., Ltd., reagent special grade) 2.000 g (measurement error: within ± 0.050 g) was weighed in a 9 mL volume vial. Next, a cloth wiper (Bencot (registered trademark), trade name: BEMCOT S-2, manufactured by Asahi Kasei Corporation) for wiping the image surface was cut into a size that fits in a 9 mL volume vial. Next, a solid image before being brought into contact with the heating roller was cut out in a 4 cm square. Next, a small amount of tetrahydrofuran in a 9 mL capacity vial was impregnated into the cut cloth wiper, and the solid image cut out in a 4 cm square was wiped off. The wiped cloth wiper was placed in a 9 mL volume vial, covered, and left for 1 hour. Then, the concentration of the organic solvent contained in tetrahydrofuran was measured by a gas chromatograph mass spectrometer (GC-MS, apparatus name: GC-2010plusAF / AOC, manufactured by Shimadzu Corporation).

Next, "blocking resistance and no white spots", "image peeling", "white spot area ratio", and "tack force" were evaluated as follows. The results are shown in Tables 1 to 4 below.

<Blocking resistance and no white spots>
Two solid images were prepared, each was pasted with the solid image inside, and placed in an environment of temperature: 40 ° C. and relative humidity: 50% for 24 hours. After that, the presence or absence of sticking between solid images and transfer between solid images was visually determined, and "blocking resistance and no white spots" were evaluated based on the following evaluation criteria. An evaluation of "3" or higher is a feasible level. Further, a rating of "2" or lower is a level at which the quality is significantly deteriorated.
-Evaluation criteria-
6: Solid images do not stick to each other, there is no transfer between solid images, and the solid images are visually uniform. 5: Solid images do not stick to each other, there is no transfer between solid images, but 10 μm to the solid image. There are small white spots less than 4: Solid images do not stick to each other and there is no transfer between solid images, but solid images have minute white spots of 10 μm or more and less than 20 μm 3: Solid images do not stick to each other , There is no transfer between solid images, but there is a minute white spot of 20 μm or more in the solid image 2: Solid images stick to each other and solid images are significantly missing 1: Solid images stick to each other and solid images are significantly missing , Paper is also significantly damaged 0: Solid images stick to each other and do not peel off

<Image peeling>
The obtained solid image was visually inspected to determine the presence or absence of image peeling due to white spots, and "image peeling due to white spots" was evaluated based on the following evaluation criteria.
-Evaluation criteria-
◯: Solid image is white out and image peeling occurs ×: Solid image is not white and image peeling does not occur

<Whiteout area ratio>
The obtained solid image was scanned using a scanner (device name: ES-G11000, manufactured by Seiko Epson Corporation) under the following measurement conditions. Next, the scanned image file is binarized into white spots and non-white spots by the image processing software ImageJ (Fiji) and analyzed, and the "white spot area ratio" for the image surface is calculated and evaluated as follows. The "whiteout area ratio" was evaluated based on the criteria. It should be noted that the evaluation "△" or higher is the feasible level.
-Measurement condition-
Mode: Professional mode Image type: 24-bit color Recording resolution: 800 dpi x 800 dpi
File format: TIFF
Proof left setting (color): No color correction-evaluation criteria-
⊚: White spot area ratio is 0.000% ○: White spot area ratio is more than 0.000% and 0.002 or less Δ: White spot area ratio is more than 0.002% 0. 004 or less ×: Whiteout area ratio exceeds 0.004

<Tack power>
The tack force of the solid image was measured using an atomic force microscope (AFM, device name: SPM-9500J3, manufactured by Shimadzu Corporation). At this time, a cantilever provided with spherical silicone oxide as a probe (spring constant of the cantilever: 0.29 N / m) was used.

Examples of aspects of the present invention are as follows.
<1> An ink applying step of applying an ink containing a coloring material and an organic solvent to a recording medium,
The recording medium comprises a contact step in which the surface to which the ink is applied comes into contact with a contact member heated to 25 ° C. or higher.
The amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied is 100 μg / cm ² or less after the ink application step and before the contact step.
In the contacting step, the image forming method is characterized in that a pressure of 0.020 kg / cm ² or more and 0.030 kg / cm ² or less is applied to the surface of the recording medium to which the ink is applied.
<2> The image forming method according to <1>, wherein the amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied is 75 μg / cm ² or less.
<3> The image forming method according to <2>, wherein the amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied is 40 μg / cm ² or less.
<4> The image forming method according to <3>, wherein the amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied is 5 μg / cm ² or more and 40 μg / cm ² or less. Is.
<5> The image forming method according to any one of <1> to <4>, wherein the pressure is 0.023 kg / cm ² or more and 0.027 kg / cm ² or less.
<6> The image forming method according to any one of <1> to <5>, wherein the temperature of the heated contact member is 40 ° C. or higher.
<7> The image forming method according to <6>, wherein the temperature of the heated contact member is 80 ° C. or higher and 150 ° C. or lower.
<8> The image forming method according to any one of <1> to <7>, which comprises a drying step between the ink applying step and the contact step.
<9> The image according to any one of <1> to <7>, wherein the transport speed for transporting the recording medium is changed according to the amount (A) of the organic solvent contained in the unit area of the recording medium. It is a forming method.
<10> When the amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied is small, the transport speed of the recording medium is increased.
The image forming method according to <9>, wherein when the amount (A) of the organic solvent contained in a unit area of the recording medium to which the ink is applied is large, the transport speed of the recording medium is slowed down.
<11> Any of the above <1> to <10> that controls the amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied by controlling the transport speed of the recording medium. This is the image forming method described in the above.
<12> In the contact step, the recording medium comes into contact with a plurality of contact members heated to 25 ° C. or higher, and the recording medium is in contact with a plurality of contact members.
The contact step is a step of contacting a contact member whose ink-applied surface of the recording medium is heated to 25 ° C. or higher, and 25 of the back surface of the ink-applied surface of the recording medium. The image forming method according to any one of <1> to <11>, which comprises a step of contacting contact members heated to ° C. or higher.
<13> In the ink applying step, the ink is applied to the recording medium in an amount of 4.8 × 10 ^-4 mL / cm ² or more and 1.1 × 10 ^-3 mL / cm ² or less.
In the contact step, the ink-applied surface of the recording medium has a time of 1.0 seconds or more and 6.0 seconds or less with the contact member heated to a set temperature of 80 ° C. or higher and 150 ° C. or lower. The image forming method according to any one of <1> to <12>, wherein the tack force of the image portions formed by contact at 25 ° C. is 80 nN or more and 110 nN or less.
<14> An ink applying step of applying an ink containing a coloring material and an organic solvent to a recording medium,
The recording medium comprises a contact step in which the surface to which the ink is applied comes into contact with a contact member heated to 25 ° C. or higher.
After the ink applying step and before the contacting step, the transport speed for transporting the recording medium is set according to the amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied. Change,
In the contacting step, the image forming method is characterized in that a pressure of 0.020 kg / cm ² or more and 0.030 kg / cm ² or less is applied to the surface of the recording medium to which the ink is applied.
<15> When the amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied is small, the transport speed of the recording medium is increased.
The image forming method according to <14>, wherein when the amount (A) of the organic solvent contained in a unit area of the recording medium to which the ink is applied is large, the transport speed of the recording medium is reduced.
<16> The winding process for winding continuous recording media and
An ink applying step of applying an ink containing a coloring material and an organic solvent to the recording medium,
The step of contacting the ink-applied surface of the recording medium with a contact member heated to 25 ° C. or higher, and the back surface of the ink-applied surface of the recording medium to 25 ° C. or higher. Including a contacting step comprising contacting with a heated contact member and a contacting step comprising.
The amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied is 100 μg / cm ² or less after the ink application step and before the contact step.
In the contacting step, the image forming method is characterized in that a pressure of 0.020 kg / cm ² or more and 0.030 kg / cm ² or less is applied to the surface of the recording medium to which the ink is applied.
<17> An ink applying means for applying an ink containing a coloring material and an organic solvent to a recording medium,
The recording medium has a contact member that comes into contact with the surface to which the ink is applied.
The contact member is heated to 25 ° C. or higher.
When the amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied is 100 μg / cm ² or less.
It is an image forming apparatus characterized by applying a pressure of 0.020 kg / cm ² or more and 0.030 kg / cm ² or less to the surface to which the ink is applied.

According to the image forming method according to any one of <1> to <16> and the image forming apparatus according to <17>, the conventional problems are solved and the object of the present invention is achieved. Can be done.

Japanese Unexamined Patent Publication No. 2009-214399

Claims (12)

An ink applying step of applying an ink containing a coloring material and an organic solvent to a recording medium,
The recording medium comprises a contact step in which the surface to which the ink is applied comes into contact with a contact member heated to 25 ° C. or higher.
The amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied is 100 μg / cm ² or less after the ink application step and before the contact step.
An image forming method, characterized in that, in the contacting step, a pressure of 0.020 kg / cm ² or more and 0.030 kg / cm ² or less is applied to a surface of the recording medium to which the ink is applied. The image forming method according to claim 1, wherein the amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied is 75 μg / cm ² or less. The image forming method according to claim 2, wherein the amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied is 40 μg / cm ² or less. The image forming method according to claim 3, wherein the amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied is 5 μg / cm ² or more and 40 μg / cm ² or less. The image forming method according to any one of claims 1 to 4, which comprises a drying step between the ink applying step and the contact step. The image forming method according to any one of claims 1 to 4, wherein the transport speed for transporting the recording medium is changed according to the amount (A) of the organic solvent contained in the unit area of the recording medium. When the amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied is small, the transport speed of the recording medium is increased.
The image forming method according to claim 6, wherein when the amount (A) of the organic solvent contained in a unit area of the recording medium to which the ink is applied is large, the transport speed of the recording medium is slowed down. The image formation according to any one of claims 1 to 7, wherein the amount (A) of the organic solvent contained in a unit area of the recording medium to which the ink is applied is controlled by controlling the transport speed of the recording medium. Method. In the contact step, the recording medium comes into contact with a plurality of contact members heated to 25 ° C. or higher, and the recording medium is brought into contact with a plurality of contact members.
The contact step is a step of contacting a contact member whose ink-applied surface of the recording medium is heated to 25 ° C. or higher, and 25 of the back surface of the ink-applied surface of the recording medium. The image forming method according to any one of claims 1 to 8, further comprising a step of contacting contact members heated to ° C. or higher. In the ink applying step, the ink is applied to the recording medium in an amount of 4.8 × 10 ^-4 mL / cm ² or more and 1.1 × 10 ^-3 mL / cm ² or less.
In the contact step, the ink-applied surface of the recording medium has a time of 0.1 seconds or more and 0.6 seconds or less with the contact member heated to a set temperature of 80 ° C. or higher and 150 ° C. or lower. The image forming method according to any one of claims 1 to 9, wherein the tack force of the contacted and formed image portions at 25 ° C. is 80 nN or more and 110 nN or less. The winding process for winding continuous recording media and
An ink applying step of applying an ink containing a coloring material and an organic solvent to the recording medium,
The step of contacting the ink-applied surface of the recording medium with a contact member heated to 25 ° C. or higher, and the back surface of the ink-applied surface of the recording medium to 25 ° C. or higher. Including a contacting step of contacting with a heated contact member and having a contacting step.
The amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied is 100 μg / cm after the ink application step and before the contact step. ² Is below
In the contact step, 0.020 kg / cm with respect to the surface of the recording medium to which the ink was applied. ² More than 0.030kg / cm ² An image forming method characterized in that the following pressure is applied. An ink applying means for applying an ink containing a coloring material and an organic solvent to a recording medium,
The recording medium has a contact member that comes into contact with the surface to which the ink is applied.
The contact member is heated to 25 ° C. or higher.
The amount (A) of the organic solvent contained in the unit area of the recording medium to which the ink is applied is 100 μg / cm. ² If:
0.020 kg / cm on the surface to which the ink is applied ² More than 0.030kg / cm ² An image forming apparatus characterized by applying the following pressures.

Images