JP7230364B2 - Image forming method - Google Patents

Description

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

2. Description of the Related Art Inkjet printers have rapidly spread in recent years as digital signal output devices because they have advantages such as low noise, low running costs, and easy color printing.

As the inkjet ink, a water-based inkjet ink is widely used because of its high safety to the living body and the environment. Water-based ink forms an image by heating and drying the ink after printing to volatilize the water content and organic solvent in the ink. In order to improve productivity, the shorter the time for heat drying, the better.

However, when a liquid is applied to a sheet such as paper, the portion to which the liquid is applied swells, and the portion to which the liquid is not applied does not swell. occur.

2. Description of the Related Art Conventionally, for example, there is known a drying apparatus that promotes drying of a liquid while suppressing cockling by conveying continuous paper in contact with the contact surface of a contact member having a contact surface with a predetermined curvature ( Patent document 1).

There is also known a method for correcting curl by sandwiching a sheet between two endless belts and winding the sheet around a plurality of rollers (Patent Document 2).

By the way, when drying a sheet to which a liquid has been applied by a drying device, it is possible to correct deformation such as cockling by heating the sheet with a large amount of heat for a long time, but the drying time becomes long, which lowers production efficiency. There is a problem of lowering

Further, in the inventions described in Patent Documents 1 and 2, for example, in order to enhance the effect of correcting cockling and curling, it is necessary to apply tension when bending and deforming the recording medium. In order to apply tension, it is essential to have a structure that clamps the belt or the like. Further, although the correction effect is enhanced by heating the recording medium, there is a problem that the image which is held and heated by the belt is transferred to the belt, resulting in image defects.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an image forming apparatus capable of efficiently correcting deformation of a sheet during image formation and suppressing transfer of an image nipped by the belt when correcting the deformation of the sheet. be.

The above problem is solved by the following configuration 1).
1) An image forming method using ink, an ink applying means for applying the ink to a sheet, and a sheet correcting device,
The sheet straightening device
a belt pair that sandwiches and conveys the sheet;
a pressing member that bends and deforms a part of the belt pair in a region where the belt pair sandwiches the sheet;
and heating means for heating the sheet,
The ink has a storage modulus at 20° C. of 1.0×10 ⁷ Pa or more as determined by dynamic viscoelasticity measurement when 80% dried, and a loss tangent of 0.60 or less when the ink is 80% dried. and
An image forming method , wherein the sheet is corrected by the sheet correcting device after the ink is applied to the sheet by the ink applying means .

According to the present invention, there is provided an image forming apparatus capable of efficiently correcting deformation of a sheet during image formation and suppressing transfer of an image nipped by the belt when correcting the deformation of the sheet.

1 is a schematic explanatory diagram of a printing apparatus according to a first embodiment provided with a sheet straightening device used in the present invention; FIG. 1 is an explanatory side view of a sheet straightening device according to a first embodiment of the present invention; FIG. It is similarly explanatory drawing of a pressing roller part. It is a perspective explanatory view of a pressing roller portion. FIG. 5 is a side explanatory view of a sheet straightening device according to a second embodiment of the present invention; It is explanatory drawing of a pressing member part. FIG. 11 is an explanatory diagram of a pressing member portion of a sheet straightening device according to a third embodiment of the present invention; It is a side explanatory view of a sheet straightening device according to a fourth embodiment of the present invention. FIG. 5 is a perspective explanatory view of a pressing member portion of a belt pair for explaining a different example of the belt pair in each embodiment; FIG. 3 is a perspective explanatory view for explaining steering control of a belt pair; FIG. 10 is an explanatory diagram of the vicinity of the pressing member for explaining unitization of the opposed rollers;

Embodiments of the present invention will be further described below, but the present invention is not limited to the following embodiments.
First, an embodiment of a sheet straightening device used in the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic explanatory diagram of a printing apparatus according to a first embodiment, which includes a sheet straightening device used in the present invention.

The printing apparatus 1 includes a loading section 100 , a printing section 200 , a drying section 300 , a sheet straightening section 600 configured by the sheet straightening apparatus according to the present invention, and an unloading section 400 . In the printing apparatus 1, the printing unit 200 applies liquid (ink) to the sheet P carried in from the carrying-in unit 100 to perform the required printing, and the drying unit 300 dries the liquid attached to the sheet P. , the sheet correcting section 600 corrects wavy deformation such as cockling occurring in the sheet P, and discharges the sheet P to the carry-out section 400 .

The carry-in unit 100 includes a carry-in tray 110 on which a plurality of sheets P are stacked, a feeding device 120 that separates and feeds the sheets P one by one from the carry-in tray 110, and a registration roller pair that feeds the sheets P to the printing unit 200. 130.

As the feeding device 120, any feeding device can be used, such as a device using rollers or rollers, or a device using air suction. After the leading edge of the sheet P delivered from the carry-in tray 110 by the feeding device 120 reaches the registration roller pair 130 , the registration roller pair 130 is driven at a predetermined timing to deliver the sheet P to the printing section 200 .

The printing unit 200 includes a carrier drum 210 that carries and conveys the sheet P on its outer peripheral surface, and a liquid ejection unit 220 that is means for applying liquid by ejecting liquid toward the sheet P carried by the carrier drum 210 . I have. The printing unit 200 also includes a transfer drum 201 that receives the fed sheet P and transfers it to the carrier drum 210 and a transfer drum 202 that transfers the sheet P conveyed by the carrier drum 210 to the drying unit 300 .

The sheet P conveyed from the carry-in section 100 to the printing section 200 is gripped at the leading edge by a sheet gripper provided on the surface of the transfer cylinder 201 and conveyed as the transfer cylinder 201 rotates. The sheet P conveyed by the transfer drum 201 is transferred to the carrier drum 210 at a position facing the carrier drum 210 .

A sheet gripper is also provided on the surface of the carrying drum 210, and the leading edge of the sheet P is gripped by the sheet gripper. A plurality of suction holes are dispersedly formed on the surface of the carrier drum 210 , and a suction device 211 generates a suction airflow toward the inside of the carrier drum 210 in each of the suction holes.

The leading edge of the sheet P transferred from the transfer drum 201 to the carrier drum 210 is gripped by the sheet gripper, the sheet P is attracted to the surface of the carrier drum 210 by the suction air current, and is conveyed as the carrier drum 210 rotates. be.

The liquid ejection unit 220 ejects four colors of liquid (ink) of C (cyan), M (magenta), Y (yellow), and K (black) to print an image. It has liquid ejection heads 220C, 220M, 220Y, and 220K, which are means for applying individual liquids. If necessary, liquid ejection heads for ejecting special liquids such as white, gold, and silver liquids, and liquid ejection heads for ejecting treatment liquids such as surface coating liquids may be provided.

The ejection operations of the liquid ejection heads 220C, 220M, 220Y, and 220K of the liquid ejection section 220 are controlled by drive signals corresponding to print information. When the sheet P carried by the carrier drum 210 passes through the area facing the liquid ejection section 220, liquids of respective colors are ejected from the liquid ejection heads 220C, 220M, 220Y, and 220K, and an image corresponding to the print information is produced. printed.

The drying unit 300 is a drying device, and includes a suction conveying belt 301 that attracts and conveys the sheet P conveyed from the printing unit 200, and a liquid that dries the sheet P conveyed by the suction conveying belt 301. and a hot air blowing means 302 for blowing warm air. The suction conveying belt 301 is looped around, for example, between a driving roller 303 and a driven roller 304 , and is rotated by driving the driving roller 303 .

The sheet P conveyed from the printing unit 200 is received by the suction conveying belt 301, is conveyed so as to pass through the hot air blowing means 302, is handed over to the sheet correction unit 600, and is carried out from the sheet correction unit 600. It is passed to unit 400 .

The liquid on the sheet P is dried when passing through the hot air blowing means 302 . As a result, liquid components such as moisture in the liquid evaporate, and the colorant contained in the liquid is fixed on the sheet P. As shown in FIG.

By passing the dried sheet P through the sheet correction unit 600, deformation of the sheet P such as cockling is corrected.

The carry-out section 400 includes a discharge tray 410 on which a plurality of sheets P are stacked. The sheets P conveyed from the sheet correcting section 600 are sequentially stacked and held on the discharge tray 410 .

Note that, in the printing apparatus 1, for example, a pre-processing unit that performs pre-processing on the sheet P is arranged on the upstream side of the printing unit 200, or a post-processing unit that performs post-processing on the sheet P on which liquid is adhered. can be arranged between the sheet correcting section 600 and the carry-out section 400 .

As the pretreatment unit, for example, one that performs a pre-coating treatment of applying a treatment liquid to the sheet P for suppressing bleeding by reacting with the liquid is exemplified. Also, as a post-processing unit, for example, a sheet reverse conveyance process for reversing a sheet printed by the printing unit 200 and sending it to the printing unit 200 again for printing on both sides of the sheet P, and binding a plurality of sheets. Those that perform processing and the like can be mentioned.

In addition, the "printing device" in the present application is not limited to an inkjet recording device, but includes a liquid ejection head that ejects liquid toward a sheet, and makes significant images such as characters and figures visible by the ejected liquid. It is not limited, and includes, for example, those that form patterns that have no meaning per se.

In addition, the "liquid" has a viscosity and surface tension that can be discharged from the head, and as described below, in the present invention, the storage elastic modulus at 20 ° C. is 1.0×10 ⁷ Pa or more, and the loss tangent when the ink is 80% dried is 0.60 or less.

Further, the “printing device” includes a serial type device that moves the liquid ejection head, a line type device that does not move the liquid ejection head, and the like.

A "liquid ejection head" is a functional component that ejects and ejects liquid from ejection holes (nozzles). Piezoelectric actuators (laminated piezoelectric elements or thin film piezoelectric elements), thermal actuators using electrothermal conversion elements such as heating resistors, and electrostatic actuators consisting of a vibration plate and a counter electrode are used as energy sources for liquid ejection. Energy generating means can be used, but the ejection energy generating means to be used is not limited.

Next, a sheet correction device according to the present invention, which constitutes the sheet correction section in the first embodiment of the present invention, will be described with reference to FIGS. 2 and 3. FIG. FIG. 2 is an explanatory side view of the sheet straightening device, and FIG. 3 is an explanatory view of the pressing roller portion.

The sheet correction device 601 includes a belt pair 602 composed of an endless upper belt 611 and an endless lower belt 612 for conveying the sheet P therebetween.

The upper belt 611 is looped around a conveying roller 621A, a steering control roller 622A, driven rollers 624A and 625A, and is tensioned by a tension roller 623A.

The lower belt 612 is looped around a conveying roller 621B, a steering control roller 622B, driven rollers 624B and 625B, and is tensioned by a tension roller 623B.

The upper belt 611 and the lower belt 612 circulate in the direction of the arrow when the conveying rollers 621A and 621B are rotationally driven, hold the sheet P therebetween, and convey the sheet P in the conveying direction (arrow Y direction, hereinafter referred to as the “conveying direction”). Y”).

Here, the tension rollers 623A and 623B apply tension acting in a direction in which the belt surfaces of the belt pair 602 sandwiching the sheet P are pulled toward the upstream side and the downstream side in the conveying direction Y. 612, respectively.

Then, in a region where the belt surfaces of the upper belt 611 and the lower belt 612 face each other, a plurality of (here, three) pressing forces are applied to deform (bend) a part of the belt pair 602 into a curved shape. A pressing roller 603 (603A, 603B) is arranged as a curved surface member.

The pressing roller 603 incorporates a heater 604 as a heat generating means, and also serves as a heating means for heating the area of the sheet P which is pressed against the pressing roller 603 via the belt pair 602 and is curved and deformed. A heating roller.

Note that "pressing" may be any of a configuration in which the belt pair 602 side is pressed against the pressing roller 603, a configuration in which the pressing roller 603 is pressed against the belt pair 602, and a configuration in which both the belt pair 602 and the pressing roller 603 are pressed. There may be.

Here, the pressing rollers 603A and the pressing rollers 603B are alternately arranged in a region where the belt surfaces of the upper belt 611 and the lower belt 612 face each other.

A peripheral surface 603a (see FIG. 3) of the pressing roller 603A is pressed against the lower belt 612 side of the belt pair 602, thereby bending and deforming the belt pair 602 in an upward convex shape. The pressing roller 603B bends and deforms the belt pair 602 in a downward convex shape by pressing the peripheral surface 603a of the belt pair 602 toward the upper belt 611 side.

That is, in the conveying direction of the sheet P, there are the pressing roller 603A that bends and deforms one side of the sheet P in a convex shape, and the pressing roller 603B that bends and deforms the other side of the sheet P in a convex shape. are arranged alternately. Note that the pressing roller 603A and the pressing roller 603B may be alternately arranged with the pressing roller 603B on the most upstream side.

Also, the plurality of pressing rollers 603 are arranged at intervals such that the belt pair 602 does not bend between the adjacent pressing rollers 603 , 603 . As a result, the stress of the once curved belt pair 602 can be released, and the adhesion to the pressing roller 603 of the next stage can be improved.

Opposing rollers 606 and 607 are arranged as opposed members to oppose the pressing roller 603 with the belt pair 602 interposed therebetween. The opposing roller 606 determines a pressing start position (winding start position) where the belt pair 602 starts contacting the peripheral surface 603 a of the pressing roller 603 . The opposing roller 607 determines a pressing end position (winding end position) where the belt pair 602 is separated from the peripheral surface 603 a of the pressing roller 603 .

These opposed rollers 606 and 607 are arranged so as to be able to advance and retreat (movable) with respect to the peripheral surface of the pressing roller 603 . Thus, the winding angle θ of the belt pair 602 around the pressing roller 603 can be changed according to the thickness (kind) of the sheet P, the amount of liquid applied, and the like.

Next, the operation of this embodiment will be described with reference to FIG. 4 as well. FIG. 4 is a perspective explanatory view of the pressing roller portion, showing the belt pair in a see-through state.

As shown in FIG. 4, when the cockling (wavy) C remains on the sheet P, if the sheet P is wound around a curved surface such as the peripheral surface 603a of the pressing roller 603 while applying tension, , the wavy disappears. This is because the length of the portion of the sheet P to which the liquid is applied and swollen and the portion to which the liquid is not applied can be forced to be the same.

However, simply winding the tape while applying tension to the curved surface does not correct the waviness when the tension is removed.

Therefore, by heating the sheet P with a heating means and squeezing it while blowing off the moisture in the sheet P, the length of the portion to which the liquid is applied and the portion to which the liquid is not applied can be made the same, and the cockling of the sheet P can be achieved. It is possible to correct waviness deformation such as.

That is, as shown in FIG. 3, the sheet P is sandwiched between two upper belts 611 and lower belts 612, and in this state, the belt pair 602 is pressed against the peripheral surface 603a of the pressing roller 603, which is a heating roller. As a result, the belt pair 602 is curved while holding the sheet P therebetween.

At this time, the tension rollers 623A and 623B apply tension to the upper belt 611 and the lower belt 612 in the direction of pressing against the peripheral surface 603a of the pressing roller 603, which is a heating roller (the direction of arrow B in FIG. 3). is given.

Then, the sheet P sandwiched between the upper belt 611 and the lower belt 612 is tensioned in the direction of the arrow B by the frictional force between the upper belt 611 and the lower belt 612 and the sheet P, and is heated by the heating roller. It is pressed against the peripheral surface 603 a (curved surface) of a pressing roller 603 .

As a result, the sheet P is heated by the pressing roller 603, and follows the peripheral surface 603a of the pressing roller 603, so that the length of the portion to which the liquid is applied and the length of the portion to which the liquid is not applied are the same, and the sheet is formed. Wavy deformation such as P cockling is corrected.

In this manner, while the sheet P is heated, it is pressed against a pressing member (a pressing roller in this embodiment) while applying tension to the sheet P so as to be curved and deformed, thereby efficiently correcting the deformation of the sheet. be able to.

In this embodiment, as shown in FIG. 2, a plurality of pressing rollers 603 (603A, 603B), which are heating rollers, are arranged in the area where the upper belt 611 and the lower belt 612 face each other.

That is, as described above, by heating the sheet P with the heating means and squeezing the sheet P while blowing off moisture, the length of the portion to which the liquid is applied and the portion to which the liquid is not applied can be the same. Waving deformation such as cockling of the sheet P can be corrected.

In this case, the correction effect is greater by winding multiple times on a plurality of curved surface members (pressing rollers) at small winding angles than by winding on the circumferential surface of one curved surface member (pressing roller) at a large winding angle.

For example, the deformation of the sheet P is better when the sheet P is wound three times at a winding angle θ of 30 degrees than when the sheet P is wound once at a winding angle θ of 90 degrees around a roller of φ80. Corrective effect increases.

In the present embodiment, pressing rollers 603A that curve the belt pair 602 in an upward convex shape and pressing rollers 603B that curve the belt pair 602 in a downward convex shape are alternately arranged. are doing.

As a result, both sides of the sheet P are pressed against the pressing roller 603 so as to alternately form convex shapes in the vertical direction, so that deformation of the sheet can be more reliably corrected while suppressing curling.

Next, a sheet straightening device according to a second embodiment of the present invention will be described with reference to FIGS. 5 and 6. FIG. FIG. 5 is an explanatory side view of the sheet straightening device, and FIG. 6 is an explanatory view of the pressing member portion.

In this embodiment, curved surface members 633 (633A, 633B) having curved surfaces 633a are arranged as pressing members. The curved surface member 633 has a heater portion 634 as a heat generating means, and also serves as a heating means for heating the sheet P. As shown in FIG.

Also in this embodiment, the curved surface members 633A and the curved surface members 633B are alternately arranged in the region where the belt surfaces of the upper belt 611 and the lower belt 612 face each other.

When the curved surface 633a of the curved surface member 633A is pressed against the lower belt 612 side of the belt pair 602, the curved surface member 633A curves and deforms the belt pair 602 in an upward convex shape. The curved surface 633a of the curved surface member 633B is pressed against the upper belt 611 side of the belt pair 602, thereby curving and deforming the belt pair 602 in a downward convex shape.

That is, in the conveying direction of the sheet P, the curved surface member 633A that bends and deforms one side of the sheet P in a convex shape and the curved surface member 633B that bends and deforms the other side of the sheet P in a direction that makes the other side of the sheet P alternately. are placed. The curved surface member 633A and the curved surface member 633B may be alternately arranged with the curved surface member 633B on the most upstream side.

Further, the plurality of curved surface members 633 are arranged at intervals such that the belt pair 602 does not bend between the adjacent curved surface members 633 , 633 . Thereby, the stress of the once curved belt pair 602 can be released, and the adhesion to the curved surface member 633 of the next stage can be improved.

Also, opposing rollers 606 and 607 similar to those in the first embodiment are arranged so as to be movable so as to face the curved surface member 633 .

Also in the configuration of this embodiment, as shown in FIG. It is pressed against the curved surface 633a of the curved surface member 633 which also serves as the heating means while being tensioned in the direction.

As a result, the sheet P is heated by the curved surface member 633, and follows the curved surface 633a of the curved surface member 633, so that the length of the liquid-applied portion and the non-liquid-applied portion are the same. Wavy deformation such as cockling is corrected.

Next, a sheet correction device according to a third embodiment of the invention will be described with reference to FIG. FIG. 7 is an explanatory diagram of a pressing member portion of the sheet straightening device.

In this embodiment, the pressing member 643 is composed of a plurality of contact members 646 arranged side by side in the sheet P conveying direction.

A plurality of contact members 646 are held on a base 645 . As for the height from the base 645 of the plurality of contact members 646, the tip end portion 646a of the contact member 646 on the center side protrudes from the tip end portions 646a of the contact members 646 on both sides in the transport direction Y.

Here, since five contact members 646 are arranged, starting from the contact member 646 at the central position in the conveying direction Y, the height of the contact member 646 decreases toward the upstream side, and toward the downstream side. The height of the contact member 646 is made low.

Further, the pressing member 643 has a heater as a heat generating means 644 on the base 645 side, for example, or has a built-in heater in the contact member 646 and also serves as a heating means for heating the sheet P. FIG.

Also in this embodiment, as shown in FIG. 7, the sheet P sandwiched between the upper belt 611 and the lower belt 612 is moved in the direction of the arrow B by the frictional force between the upper belt 611 and the lower belt 612 and the sheet P. In a state where tension is applied, the pressing member 643, which also serves as heating means, is pressed against a plurality of contact members 646 forming a curved shape as a whole.

As a result, the sheet P is heated by the pressing member 643 and conforms to the curved shape formed by the plurality of contact members 646, so that the length of the portion to which the liquid is applied and the portion to which the liquid is not applied are the same. As a result, wavy deformation such as cockling of the sheet P is corrected.

By arranging a plurality of the pressing members 643 along the conveying direction Y as in the first and second embodiments, the correction effect can be further enhanced.

For example, a rotating member can be rotatably provided at the tip portion 646 a of the contact member 646 , thereby reducing the frictional resistance between each contact member 646 and the belt pair 602 and bending the belt pair 602 . can move smoothly.

Next, a sheet straightening device according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 8 is an explanatory side view of the sheet straightening device.

In the present embodiment, instead of the driven rollers 624A and 624B of the first embodiment, heating rollers 654A and 654B are arranged, and the heating rollers 654A and 654B are arranged on the upstream side in the conveying direction of the portion where the sheet P is sandwiched between the upper belt 611 and the lower belt 612. The sheet P is heated.

As pressing members, pressing rollers 653 (653A, 653B) having no heating means are arranged.

With this configuration, the upper belt 611 and the lower belt 612 are heated by the heating rollers 654A and 654B, respectively, and the sheet P is sandwiched between the upper belt 611 and the lower belt 612 while being heated. As a result, the sheet P is heated by the upper belt 611 and the lower belt 612 and pressed against the pressing roller 603 via the belt pair 602 .

That is, when the sheet P is pressed against the pressing roller 653 to be straightened, if the sheet P is maintained at a high temperature, it is not necessary to directly heat the portion where the belt pair 602 is bent and deformed by the pressing roller 653 . do not have. Therefore, in the present embodiment, the belt pair 602 is heated on the upstream side in the conveying direction of the portion where the sheet P is sandwiched between the upper belt 611 and the lower belt 612, and the sheet P is heated by the heated belt pair 602. .

As a result, even if the number of pressing members (correction portions) is increased, the correction function can be enhanced without increasing the number of heating means. In addition, it is not necessary to move the cable of the heating means (for example, heater) together when handling thick paper.

Next, different examples of belt pairs in each embodiment will be described with reference to FIG. FIG. 9 is a perspective explanatory view of the pressing member portion of the belt pair.

An upper belt 611 and a lower belt 612 that constitute the belt pair 602 shown in FIG. An upper belt 611 and a lower belt 612 forming a belt pair 602 shown in FIG. 9B are mesh belts. An upper belt 611 and a lower belt 612 forming a belt pair 602 shown in FIG. 9C are divided belts divided into a plurality of parts in a direction perpendicular to the conveying direction.

As the upper belt 611 and the lower belt 612 constituting the belt pair 602, any of the belts shown in FIGS. 9A to 9C may be used. The full belt shown in FIG. 9(a) is preferred for winding around curved portions.

Next, steering control of belt pair 602 will be described with reference to FIG. FIG. 10 is a perspective view for explaining the same.

Steering control roller 622 is rotatably held by bracket 628 . The bracket 628 rotatably holds the steering control roller 622 at its center portion (or end portion) in the axial direction with a rotary shaft 629 .

By detecting the position of the belt pair 602 and changing the angle of the steering control roller 622, the conveying direction of the belt pair 602 is changed.

Next, unitization of the opposed rollers in each embodiment will be described with reference to FIG. 11 . FIG. 11 is an explanatory diagram of the vicinity of the pressing member.

Opposing rollers 606 and 607 facing the pressing roller 603 (or curved surface member 633), which is a pressing member, are rotatably held by a holder member 608 to form an opposing roller unit 609, for example.

By unitizing a plurality of opposing members in this manner, the structure of the advancing/retreating mechanism can be simplified when the opposing rollers 606 and 607 can be advanced and retracted with respect to the pressing roller 603 (or the curved surface member 633).

In each of the above-described embodiments, the sheet straightening device conveys the sheet in the horizontal direction (horizontal direction). can also

<Ink>
Organic solvents, water, coloring materials, resins, additives, and the like used in the ink are described below.

<Organic solvent>
The organic solvent used in the present invention is not particularly limited, and any water-soluble organic solvent can be used. Examples thereof include polyhydric alcohols, ethers such as polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds.
Specific examples of polyhydric alcohols include 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- 1,3-pentanediol, petriol and the like.
Examples of polyhydric alcohol alkyl ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether and the like.
Examples of polyhydric alcohol aryl ethers include ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.
Nitrogen-containing heterocyclic compounds include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, γ-butyrolactone and the like. mentioned.
Amides include formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide and the like.
Amines include monoethanolamine, diethanolamine, triethylamine, and the like.
Examples of sulfur-containing compounds include dimethylsulfoxide, sulfolane, thiodiethanol and the like.
Other organic solvents include propylene carbonate and ethylene carbonate.
It is preferable to use an organic solvent having a boiling point of 250° C. or less because it not only functions as a wetting agent but also provides good drying properties.

As the organic solvent, polyol compounds having 8 or more carbon atoms and glycol ether compounds are also preferably used. Specific examples of polyol compounds having 8 or more carbon atoms include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.
Specific examples of glycol ether compounds 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; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, and the like.

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

The content of the organic solvent in the ink is not particularly limited and can be appropriately selected according to the purpose. 20% by mass or more and 60% by mass or less is more preferable.

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

<Color material>
As pigments, carbon black, yellow pigments, magenta pigments, and cyan pigments can be used.
Carbon black produced by known methods such as the contact method, the furnace method, and the thermal method can be used.
Specific examples of pigments include yellow pigments such as 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, and magenta pigments such as C.I. I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48:2, 48:2 (Permanent Red 2B (Ca)), 48:3, 48:4, 49:1, 52: 2, 53:1, 57:1 (brilliant carmine 6B), 60:1, 63:1, 63:2, 64:1, 81, 83, 88, 101 (red red), 104, 105, 106, 108 ( cadmium red), 112, 114, 122 (quinacridone magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 184, 185, 190, 193, 202, 207, 208, 209, 213, 219, 224, 254, 264, C.I. I. pigment violet 1 (rhodamine lake), 3, 5:1, 16, 19, 23, 38; I. Pigment Blue 1, 2, 15 (phthalocyanine blue), 15:1, 15:2, 15:3, 15:4 (phthalocyanine blue), 16, 17:1, 56, 60, 63, and the like.

Among them, as a yellow pigment, C.I. I. Pigment Yellow 74, C.I. I. Pigment Yellow 138, C.I. I. Pigment Yellow 155, C.I. I. Pigment Yellow 185 is preferred, and C.I. I. Pigment Red 122, C.I. I. Pigment Red 202, C.I. I. Pigment Violet 19 is preferred, and C.I. I. Pigment Blue 15:2, C.I. I. Pigment Blue 15:3, C.I. I. Pigment Blue 15:4 is preferred.

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

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 or less, from the viewpoint of improving image density and good ejection stability. .

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

<Resin>
The type of resin contained in the ink is not particularly limited and can be appropriately selected according to the purpose. resins, styrene-butadiene-based resins, vinyl chloride-based resins, acrylic-styrene-based resins, acrylic-silicone-based resins, and the like.
Resin particles made of these resins may also be used. Ink can be obtained by mixing resin particles in a state of a resin emulsion in which water is dispersed as a dispersion medium with a material such as a coloring material or an organic solvent. As the resin particles, appropriately synthesized ones may be used, or commercially available products may be used. Moreover, these may be used individually by 1 type, or may be used in combination of 2 or more types of resin particles.

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

The content of the resin is not particularly limited and can be appropriately selected according to the purpose. However, from the viewpoint of fixability and storage stability of the ink, the content is 1% by mass or more and 30% by mass or less based on the total amount of the ink. is preferable, 1% by mass or more and 20% by mass or less is more preferable, and 2% by mass or more and 10% by mass or less is even more preferable.

In the present invention, a urethane resin or an acrylic resin is preferable from the viewpoint of further enhancing the effect of suppressing image transfer.

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

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

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

The silicone-based surfactant is not particularly limited and can be appropriately selected depending on the intended purpose. Examples include polydimethylsiloxane modified at both ends, and polyether-modified silicone surfactants having polyoxyethylene groups or polyoxyethylene polyoxypropylene groups as modifying groups are particularly preferred because they exhibit good properties as water-based surfactants. .
As such a surfactant, an appropriately synthesized one may be used, or a commercially available product may be used. Commercially available products are available from, for example, BYK Chemie Co., Ltd., Shin-Etsu Chemical Co., Ltd., Dow Corning Toray Silicone Co., Ltd., Nihon Emulsion Co., Ltd., Kyoeisha Chemical Co., Ltd., and the like.
The above polyether-modified silicone-based surfactant is not particularly limited and can be appropriately selected according to the purpose. Examples include those introduced into the side chain of the Si portion of siloxane.

(However, in 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 polyether-modified silicone-based surfactants. 1906EX (Japan Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (Dow Corning Toray Silicone Co., Ltd.), BYK-33, BYK-387 (BYK-Chemie Corporation), TSF4440, TSF4452, TSF4453 (Momentive Performance Materials Japan) and the like.

As the fluorosurfactant, a fluorine-substituted compound having 2 to 16 carbon atoms is preferable, and a fluorine-substituted compound having 4 to 16 carbon atoms is more preferable.
Examples of fluorine-based surfactants include perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in side chains. Among these, a polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in a side chain is preferable because of its low foamability, and in particular, fluorine-based compounds represented by general formulas (F-1) and (F-2) Surfactants are preferred.

In the compound represented by the general formula (F-1), m is preferably an integer of 0 to 10 and n is preferably an integer of 0 to 40 in order to impart water solubility.

In the compound represented by the general formula (F-2), Y is H, or CmF _2m+1 and m is an integer of 1 to 6, or CH ₂ CH(OH)CH ₂ -CmF _2m+1 and m is 4 to 6 Integer, or CpH _2p+1 where p is an integer from 1-19. n is an integer of 1-6. a is an integer from 4 to 14;
Commercially available products may be used as the fluorosurfactant. Examples of commercially available products include Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (all manufactured by Asahi Glass Co., Ltd.); Fleurard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431 (both manufactured by Sumitomo 3M); Megafac F-470, F -1405, F-474 (both manufactured by Dainippon Ink and Chemicals); Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR, Capstone FS-30, FS-31, FS-3100, FS-34, FS-35 (all manufactured by Chemours); FT-110, FT-250, FT-251, FT-400S, FT-150, FT- 400SW (all manufactured by Neos Co., Ltd.), Polyfox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (manufactured by Omnova), Unidyne DSN-403N (manufactured by Daikin Industries, Ltd.) Among these, Chemours FS-3100, FS-34, FS- 300, FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW manufactured by Neos Co., Ltd., Polyfox PF-151N manufactured by Omnova Co., Ltd., and Unidyne DSN- manufactured by Daikin Industries, Ltd. 403N is particularly preferred.

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

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

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

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

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

The ink used in the present invention has a storage elastic modulus at 20° C. of 1.0×10 ⁷ Pa or more in dynamic viscoelasticity measurement when the ink is 80% dried, and when the ink is 80% dried has a loss tangent of 0.60 or less.
In order to achieve such a condition, for example, means such as making the fixing resin less likely to be plasticized can be taken, and this can be controlled by the type of resin and the combination of the resin and the solvent used for the ink.

Here, "when the ink is 80% dry" means the ink at the time when the ink reaches 80% of its initial mass when dried in a constant temperature bath at 120°C.

Storage modulus, loss modulus and loss tangent can be measured under the following measurement conditions.
〔Measurement condition〕
・ Apparatus: AR2000 (manufactured by TA Instruments Co., Ltd.)
・Geometry: 40mm 1° cone plate ・Geometry gap: 300μm
・Measurement frequency: 1Hz
・Distortion: 0.1
・Measurement temperature: 20°C
・ Analysis software: TA DATA ANALYSIS (manufactured by TA Instruments Co., Ltd.)

The loss tangent is calculated as follows using the storage modulus and the loss modulus.
Loss modulus (Pa) / Storage modulus (Pa)

The storage elastic modulus at 20° C. measured by dynamic viscoelasticity measurement when 80% dry of the ink used in the present invention is 1.0×10 ⁷ Pa or more, and the loss tangent is 0.60 or less. Since the tackiness of the ink coating film can be suppressed, the deformation of the sheet during image formation can be efficiently corrected, and the transfer of the image nipped by the belt during the correction of the sheet deformation can be suppressed. It is possible to obtain the effect of the present invention.

The storage elastic modulus is preferably 5.0×10 ⁷ Pa or more, more preferably 1.0×10 ⁸ Pa to 1.0×10 ¹⁰ Pa.
The loss tangent is preferably 0.50 or less, more preferably 0.10 to 0.40.

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

<Recording medium>
The recording medium used for recording is not particularly limited, but includes plain paper, glossy paper, special paper, cloth, film, OHP sheet, general-purpose printing paper, and the like.

In the present invention, the terms image formation, recording, printing, and printing are all synonymous.
The terms recording medium, medium, and printed material are all synonymous.

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples. In addition, "parts" in the examples represent "parts by mass", and "%" represents "% by mass" unless otherwise specified.

(Preparation of urethane resin emulsion)
<Preparation of urethane resin emulsion A>
In a reaction vessel fitted with a stirrer, reflux condenser, and thermometer, 1,500 g of Polylite OD-X-2420 (DIC, polyester polyol), 220 g of 2,2-dimethylolpropionic acid (DMPA), and N -Methylpyrrolidone (NMP) 1,347 g was charged under a nitrogen atmosphere and heated to 60° C. to dissolve DMPA.
Next, 1,445 g of 4,4′-dicyclohexylmethane diisocyanate and 2.6 g of dibutyltin dilaurate (catalyst) were added and heated to 90° C. for urethanization reaction over 5 hours to produce an isocyanate-terminated urethane prepolymer. Obtained. This reaction mixture was cooled to 80° C., and 4,340 g of the mixture containing 149 g of triethylamine was taken out and added to a mixed solution of 5,400 g of water and 15 g of triethylamine under strong stirring.
Next, 1,500 g of ice was added, 626 g of a 35% by mass 2-methyl-1,5-pentanediamine aqueous solution was added to carry out a chain extension reaction, and the solvent was distilled off so that the solid content concentration was 30% by mass. Then, the resulting resin emulsion is dispersed with a paint conditioner (manufactured by Red Devil Co., the speed can be adjusted in the range of 50 to 1,425 rpm) to obtain a polyester urethane resin emulsion with a solid content concentration of 40.0% by mass and a Tg of 10 ° C. got an A.
In addition, Tg was measured by DSC (Thermo plus EVO2/DSC manufactured by Rigaku Corporation).

<Preparation of urethane resin emulsion B>
In the preparation of urethane resin emulsion A, the solid content A polyether-based urethane resin emulsion B having a concentration of 30% by mass and a Tg of 75° C. was obtained.

<Adjustment of urethane resin emulsion C>
287.9 parts of Mn 2,000 crystalline polycarbonate diol (Duranol T6002, manufactured by Asahi Kasei Chemicals), 3.6 parts of 1,4-butanediol, and 8.9 parts of DMPA were placed in a simple pressurized reactor equipped with a stirrer and a heater. , 98.3 parts of hydrogenated MDI (diphenylmethane diisocyanate) and 326.2 parts of acetone were charged while introducing nitrogen. After that, the mixture was heated to 90° C. and a urethanization reaction was carried out over 8 hours to produce a prepolymer. After cooling the reaction mixture to 40° C., 6.8 parts of triethylamine was added and mixed, and 568.8 parts of water was added and emulsified with a rotor-stator type mechanical emulsifier to obtain an aqueous dispersion. . 28.1 parts of a 10% aqueous ethylenediamine solution was added to the obtained aqueous dispersion with stirring, and the mixture was stirred at 50°C for 5 hours to carry out a chain elongation reaction. After that, acetone was removed at 65°C under reduced pressure, and the water content was adjusted to obtain a polycarbonate-based urethane resin emulsion C with a Tg of -20°C and a solid content concentration of 40% by mass.

(Preparation of acrylic resin particle emulsion)
<Preparation of Acrylic Resin Emulsion D>
As the acrylic resin emulsion D, Boncoat CF-6140 (manufactured by DIC, Tg 12° C.) was used.

<Preparation of acrylic resin emulsion E>
As the acrylic resin emulsion E, Vinyblan 2682 (manufactured by Nissin Chemical Industry Co., Ltd., Tg-30°C) was used.

<Preparation of acrylic resin emulsion F>
As the acrylic resin emulsion F, JE-1056 (manufactured by Seiko PMC, Tg 82° C.) was used.

<Preparation of Ethylene Vinyl Acetate Resin Emulsion G>
As the ethylene-vinyl acetate resin emulsion G, S-400HQ (manufactured by Sumika Chemtex, Tg 0° C.) was used.

(Ink preparation)
<Preparation of pigment dispersion>
<<Preparation of Black Pigment Dispersion>>
Carbon black manufactured by Tokai Carbon Co., Ltd.: Seast SP (SRF-LS) 100 g is added to 3000 mL of 2.5 N (regulation) sodium hypochlorite solution, stirred at a temperature of 60 ° C. and a speed of 300 rpm, and reacted for 10 hours. A pigment having carboxylic acid groups on the surface of the carbon black was obtained. This reaction solution was filtered, and the filtered carbon black was neutralized with a sodium hydroxide solution and subjected to ultrafiltration.
Next, the pigment dispersion and ion-exchanged water are subjected to ultrafiltration with a dialysis membrane, followed by ultrasonic dispersion to concentrate the solid content of the pigment to 20%. got

<<Preparation of Cyan Pigment Dispersion>>
In the preparation of the black pigment dispersion, a black pigment dispersion having a volume average particle diameter of 75 nm was prepared in the same manner except that the coloring material used was replaced with a copper phthalocyanine pigment manufactured by Toyo Ink Co., Ltd. (CI Pigment Blue 15:4, trade name: LX4033). A cyan pigment dispersion was obtained.

<<Preparation of Magenta Pigment Dispersion>>
A magenta pigment dispersion having a volume average particle diameter of 73 nm was obtained in the same manner as in the preparation of the black pigment dispersion, except that Pigment Red 122 manufactured by Sun Chemical Co. was used as the coloring material.

<<Preparation of Yellow Pigment Dispersion>>
A yellow pigment having a volume average particle diameter of 82 nm in the same manner as in the preparation of a black pigment dispersion, except that the coloring material used was replaced with a yellow pigment manufactured by Dainichiseika Kogyo Co., Ltd. (Pigment Yellow 74, trade name: Yellow No. 46) A dispersion was obtained.

<Ink preparation method>
Inks 1 to 7 were prepared by mixing and stirring each component according to the formulation (mass %) as shown in Table 1 and filtering through a 0.2 μm polypropylene filter. The surfactant used was FS-300 (fluorinated surfactant manufactured by DuPont).

In Table 1, the content of pigment dispersion and the content of emulsions A to G represent the solid content.

Table 2 shows the storage modulus and loss tangent at 20° C. in dynamic viscoelasticity measurement when the ink is 80% dry.

(Example 1)
Ink 1 was evaluated as follows.
Cockling of a 5 cm x 5 cm solid image portion in a printed matter formed on MC glossy paper (manufactured by EPSON) by ejecting ink at 300 dpi x 300 dpi and 4.0 pL per pixel using the printing apparatus shown in FIG. was visually confirmed, and the state of transfer of the pigment to the belt of the sheet correction device was visually observed and evaluated according to the following criteria. The heating temperature in the sheet straightening device was 60°C, 70°C, 100°C or 120°C.

<cock ring>
"Evaluation criteria"
A: No cockling occurred.
B: Slight cockling is observed, but when the paper is separated from the eye by 1 m, the unevenness of the paper cannot be recognized.
C: Significant cockling is observed, and unevenness of the paper can be recognized even if the paper is separated from the eye by 1 m.

<Image transfer>
"Evaluation criteria"
A: No image transfer is observed.
B: Slight image transfer is recognized, but the image transfer cannot be recognized when the belt is separated from the eye by 1 m.
C: Large image transfer is observed, and the image transfer can be recognized even when the belt is separated from the eye by 1 m.

(Examples 2-5)
Evaluation was performed in the same manner as in Example 1, except that the ink and heating temperature were changed as shown in Table 3. Table 3 shows the results.

(Comparative Examples 1 and 2)
Evaluation was performed in the same manner as in Example 1, except that the ink and heating temperature were changed as shown in Table 4. Table 4 shows the results.

Examples 1 and 2 are particularly preferred examples of the present invention. In these examples, both cockling and image transfer were evaluated as A in all cases.

Examples 3-5 are preferred examples of the invention. In these examples, either cockling or image transfer is evaluated as B, but it can be said that there is no problem in use.

In Comparative Examples 1 and 2, the storage elastic modulus at 20° C. measured by dynamic viscoelasticity measurement when the ink is 80% dried is 1.0×10 ⁷ Pa or more, and the loss tangent is 0.60 or less. This is an example of a case that does not satisfy
In these examples, when the printing apparatus 1 has a straightening device that straightens the sheet by applying tension and heat to the paper, there arises a problem that significant image transfer occurs.

Reference Signs List 1 printing device 100 carry-in section 110 carry-in tray 120 feeding device 130 registration roller pair 200 printing section 201 transfer cylinder 202 transfer cylinder 210 carrier drum 211 suction device 220 liquid discharge section 220C, 220M, 220Y, 220K liquid discharge head 300 drying section 301 Suction Conveying Belt 302 Hot Air Blowing Means 303 Driving Roller 304 Driven Roller 400 Carrying Out Section 410 Discharge Tray 600 Sheet Correcting Section P Sheet 601 Sheet Correcting Device 602 Belt Pair 603, 603A, 603B Pressing Roller 603a Peripheral Surface 604 Heater 606, 607 Opposed Roller (opposing member)
608 holder member 609 opposing roller unit 611 upper belt 612 lower belt 621A, 621B transport rollers 622A, 622B steering control rollers 623A, 623B tension rollers 624A, 625A, 624B, 625B driven roller 628 bracket 629 rotating shaft 633, 633A, 633B curved surface member 633a curved surface 634 heater section 643 pressing member 644 heating means 645 base 646 contacting member 646a tip 653A, 653B pressing roller 654A, 654B heating roller

JP 2016-107519 A JP 2008-265987 A

Claims (6)

An image forming method using ink, ink applying means for applying the ink to a sheet, and a sheet straightening device,
The sheet straightening device
a belt pair that sandwiches and conveys the sheet;
a pressing member that bends and deforms a part of the belt pair in a region where the belt pair sandwiches the sheet;
and heating means for heating the sheet,
The ink has a storage modulus at 20° C. of 1.0×10 ⁷ Pa or more as determined by dynamic viscoelasticity measurement when 80% dried, and a loss tangent of 0.60 or less when the ink is 80% dried. and
An image forming method, wherein the sheet is corrected by the sheet correcting device after the ink is applied to the sheet by the ink applying means. 2. The image forming method according to claim 1, wherein the temperature of the heating portion of the heating means for heating the sheet is 80[deg.] C. or higher. The ink has a storage modulus at 20° C. of 5.0×10 ⁷ Pa or more in a dynamic viscoelasticity measurement method when the ink is 80% dried, and a loss tangent when the ink is 80% dried is 0.50 or less. 3. The image forming method according to claim 1, wherein: The pressing member includes a first pressing member that bends and deforms a part of the belt pair in one direction, and a first pressing member that bends and deforms the belt pair in a direction opposite to the direction in which the first pressing member bends and deforms the belt pair. 4. The image forming method according to claim 1, further comprising a second pressing member that bends and deforms a part of the belt pair. 5. The image forming method according to claim 1, wherein the ink contains an acrylic or urethane resin emulsion. 6. The image forming method according to claim 5, wherein the ink contains an acrylic or urethane resin emulsion in an amount of 2% by mass or more and 10% by mass or less as a resin solid content.

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