JP2007056217A - Ink set for inkjet recording, as well as inkjet recording method and inkjet recording apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink set for inkjet recording capable of reducing the difference with time of jetting stability of an ink and a processing liquid to be ejected from a recording head, to inhibit the occurrence of defects in image quality such as unevenness of image density. <P>SOLUTION: The ink set for inkjet recording comprises an ink containing a pigment, fine particles and a processing liquid for coagulating or thickening the ink, and is used for inkjet recording for forming images using the ink and the processing liquid, in which the volume average particle size of the fine particles is within a range of from 5 to 2,000% of the volume average particle size of the pigment. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink set for ink jet recording comprising an ink used for ink jet recording and a treatment liquid, and an ink jet recording method and an ink jet recording apparatus using the ink set.

  A so-called inkjet recording apparatus that discharges liquid or molten solid ink from a nozzle, slit, porous film, etc., and records on paper, cloth, film, etc. has various advantages such as small size, low cost, and quietness, In recent years, not only black single-color printers that provide good print quality on so-called plain paper such as report paper and copy paper, but also many products that can perform full-color recording are on the market, which seems to occupy a large position in the field of recording equipment Became. Above all, the so-called piezo ink-jet method using a piezoelectric element, or the so-called thermal ink-jet method in which droplets are formed by applying thermal energy to perform recording, has many advantages such as high-speed printing and high resolution. Have.

The ink used in the ink jet recording apparatus is mainly composed of a solvent, a color material, and an additive. For such inks, it is possible to obtain a uniform image with high resolution and high density without blurring on paper, fast drying of ink on paper, good image fastness, and long-term storage stability. There are required characteristics such as good things. In addition, office inkjet printers that have been launched in recent years are required not only to have high image quality but also to be capable of high-speed printing.
In order to obtain a high-resolution, high-density, blur-free image, a technique using ink that suppresses penetration into the paper and spread on the paper is effective. However, on the other hand, when used with an inkjet printer that performs high-speed printing because the drying speed is slow, when the paper overlaps on the tray after printing, it is likely to cause a problem that offsets the paper with the undried ink overlaid. . In addition, when performing double-sided printing, undried ink may contaminate the inside of the printer such as a transport roller.

As a technique for achieving both high image quality and quick drying, a so-called 2 that uses a liquid that does not contain a colorant mainly for the purpose of further improving the image quality (hereinafter may be referred to as “treatment liquid”) in addition to ink. A liquid printing method is mentioned.
In general, a component that promotes agglomeration of a coloring material in ink is added to the treatment liquid used in such a two-liquid printing method.
For example, a two-component printing method using an agglutination reaction by contact between an ink containing an anionic substance, a silicone compound and a treatment liquid containing a cationic substance (see Patent Document 1), a cationic substance and a nonionic polymer substance A method of combining a liquid composition (treatment liquid) containing an ink containing an anionic compound (see Patent Documents 2 to 4, etc.) and a method of aggregating color materials by bringing a plurality of inks having different pHs into contact ( Patent Document 5), a method of aggregating color materials by applying a treatment liquid containing a polyvalent metal salt (see Patent Document 6), and the like.

Such a two-liquid printing method generally provides an image with high resolution, high image density and little bleeding, as compared to a printing method using only conventional ink, and is also quick to dry after printing. Has characteristics.
In the above-described two-component printing method, water-soluble and soluble materials are used for the ink and the processing liquid except for pigments that are not originally soluble. On the other hand, a method using fine particles having essentially no solubility like a pigment has been proposed. This method is a method using fine particles as a component for aggregating the ink in the treatment liquid in addition to the pigment, or as a component for promoting / assisting aggregation (see Patent Documents 7 to 9).
In addition, as another two-component printing method in which fine particles are added to the processing liquid, the processing quality is improved by applying the processing liquid to the surface of plain paper before applying ink, thereby improving the surface condition of the plain paper. A method for improving it has also been proposed (see Patent Document 10).
JP-A-8-142500 JP-A-8-193175 JP-A-8-197840 JP-A-9-286940 JP 2001-199150 A JP-A-9-28694 JP 2001-199149 A JP 2002-332432 A JP 2001-315425 A Japanese Patent Laid-Open No. 6-92010

However, in the conventional two-liquid printing method, it is difficult to obtain the temporal ejection stability of the processing liquid ejected from the recording head, compared to the temporal ejection stability of the ink ejected from the recording head. In some cases, the mixing ratio of the ink applied to the same area on the medium surface and the treatment liquid varies, resulting in density unevenness, resulting in deterioration of image quality.
An object of the present invention is to solve the above problems. That is, the present invention can reduce the difference in ejection stability over time between the ink ejected from the recording head and the processing liquid, thereby suppressing the occurrence of image quality defects such as density unevenness, as well as drying and fixing. It is an object of the present invention to provide an ink set for ink jet recording excellent in performance, an ink jet recording method and an ink jet recording apparatus using the ink set.

  In order to solve the above-described problems, the present inventors have found that, in the conventional two-liquid printing method, the ejection stability of ink ejected from the recording head over time and the treatment liquid ejected from the recording head over time. In order to investigate the cause of the difference in the stable ejection stability, the speed of the droplet with respect to the number of ejections (time) of the droplet ejected from the recording head was investigated. As a result, it was confirmed that when the pigment was used as the coloring material, the treatment liquid tended to have larger variations in droplet velocity and droplet amount with respect to time than the ink.

Therefore, the present inventors have further intensively studied the reason why the jetting stability with time is different between the ink and the treatment liquid.
First, as a factor that influences the jet stability over time, it is generally considered that the viscosity and the surface tension are different between the ink and the treatment liquid. However, since the viscosity and surface tension are generally adjusted to be approximately the same between the ink and the processing liquid, these factors are the main causes of the difference in the jetting stability between the ink and the processing liquid. It is difficult to think.

On the other hand, an ink always contains a pigment having a particle size of about submicron, which is a solid component that does not dissolve in an aqueous medium that is a solvent. The present inventors have the effect of breaking the continuity of liquid (liquid phase continuity blocking effect) because the presence of such a fine solid forms a liquid-solid interface in an aqueous medium such as ink. It was estimated that the presence / absence of the liquid phase continuity blocking effect and the difference in the degree caused the difference in ejection stability between the ink and the treatment liquid.
Therefore, the present inventor considers that it is important to add a solid content (fine particles) that does not dissolve in the aqueous medium so that the liquid phase continuity blocking effect is comparable to that of the ink, and the following The present invention has been found.

That is, the present invention
<1>
An ink jet comprising: an ink containing at least a pigment, a water-soluble organic solvent, and water; and a treatment liquid containing fine particles and a water-soluble compound that aggregates or thickens the ink, and forms an image using the ink and the treatment liquid. In an inkjet recording ink set used for recording,
An ink set for inkjet recording, wherein the fine particles have a nonionic property or the same polarity as the pigment.

<2>
The ink set for ink jet recording according to <1>, wherein the volume average particle diameter of the fine particles is in the range of 5 to 1000% of the volume average particle diameter of the pigment.

<3>
<1> or <2>, wherein the content of the fine particles contained in the treatment liquid is in the range of 0.2 to 120% of the content of the pigment contained in the ink. It is an ink set for inkjet recording as described.

<4>
<1> to <3>, wherein the polarity of the pigment is anionic, the polarity of the water-soluble compound is cationic, and the polarity of the fine particles is nonionic or anionic It is an ink set for inkjet recording as described in one.

<5>
<1> to <4>, wherein the pigment is a resin-dispersed pigment, the treatment liquid includes a polymer dispersant that disperses the fine particles, and the polymer dispersant has a weight average molecular weight of 1000 or more. The ink set for inkjet recording as described in any one of these.

<6>
The number of coarse particles having a particle size of 5 μm or more contained in 2 μl of the treatment liquid after leaving the treatment liquid at 70 ° C. for 200 hours is 100 or less, and
Any one of <1> to <5>, wherein the number of coarse particles having a particle diameter of 5 μm or more contained in 2 μl of the ink after leaving the ink at 70 ° C. for 200 hours is 100 or less An ink set for inkjet recording according to any one of the above.

<7>
In an ink jet recording method for forming an image on a recording medium surface by using an ink set for ink jet recording containing an ink and a processing liquid, and applying the ink and the processing liquid to the recording medium surface so as to contact each other.
The ink jet recording ink set according to any one of <1> to <6>, wherein the ink set for ink jet recording is the ink set for ink jet recording.

<8>
The image is formed while conveying the recording medium in one direction, and disposed opposite to the surface of the recording medium that is conveyed in one direction, and a recording head that discharges the ink and the treatment liquid to the surface of the recording medium. Use
The width of the recording head in the direction parallel to the recording medium plane and orthogonal to the recording medium conveyance direction is substantially equal to the width of the recording medium in the direction parallel to the recording medium plane and orthogonal to the recording medium conveyance direction, <1> to <6> for ink-jet recording, wherein the recording head is fixed in a direction parallel to the recording medium plane and perpendicular to the recording medium conveyance direction An ink jet recording method comprising an ink set.

<9>
The image is formed while conveying the recording medium in one direction, and disposed opposite to the surface of the recording medium that is conveyed in one direction, and a recording head that discharges the ink and the treatment liquid to the surface of the recording medium. Use
The inkjet recording method according to <7> or <8>, wherein a width of the recording head in a direction parallel to the recording medium plane and perpendicular to the recording medium conveyance direction is 210 mm or more.

<10>
An ink set for ink jet recording including an ink and a treatment liquid is used, and a recording head for discharging the ink and the treatment liquid onto the surface of the recording medium is provided, and the ink and the treatment liquid are brought into contact with each other on the surface of the recording medium. In an ink jet recording apparatus for forming an image by discharging from the recording head,
An inkjet recording apparatus, wherein the inkjet recording ink set is the inkjet recording ink set according to any one of <1> to <6>.

<11>
The image formation is performed while conveying the recording medium in one direction, and the recording head is disposed to face the recording medium surface conveyed in one direction,
The width of the recording head in the direction parallel to the recording medium plane and orthogonal to the recording medium conveyance direction is substantially equal to the width of the recording medium in the direction parallel to the recording medium plane and orthogonal to the recording medium conveyance direction, The inkjet recording apparatus according to <10>, wherein the recording head is fixed in a direction parallel to the recording medium plane and perpendicular to the recording medium conveyance direction.

<12>
The image formation is performed while conveying the recording medium in one direction, and the recording head is disposed to face the recording medium surface conveyed in one direction,
<10> or <11>, wherein the width of the recording head in a direction parallel to the recording medium plane and perpendicular to the recording medium conveyance direction is 210 mm or more.

  As described above, according to the present invention, it is possible to reduce the difference in ejection stability over time between the ink ejected from the recording head and the processing liquid, and to suppress the occurrence of image quality defects such as density unevenness. In addition, it is possible to provide an ink set for ink jet recording excellent in drying property and fixability, and an ink jet recording method and an ink jet recording apparatus using the ink set.

<Ink set for inkjet recording>
The ink set for ink jet recording of the present invention (hereinafter sometimes abbreviated as “ink set”) includes an ink containing at least a pigment, a water-soluble organic solvent, and water, fine particles, and a water-soluble substance that aggregates or thickens the ink. In the ink set for ink jet recording, which comprises a treatment liquid containing a compound and is used for ink jet recording for forming an image using the ink and the treatment liquid, the polarity of the fine particles is nonionic or the same polarity as the polarity of the pigment It is characterized by being.
Therefore, when ink jet recording is performed using the ink set of the present invention, it is possible to reduce the difference in ejection stability over time between the ink ejected from the recording head and the processing liquid, and thus image quality defects such as density unevenness can be reduced. Occurrence can be suppressed. This is presumed to be because the treatment liquid used in the present invention contains fine particles, and these fine particles function in a manner similar to the pigment contained in the ink in terms of ejection characteristics.

In addition, the pigment contained in the ink has either a cationic or anionic polarity, whereas the fine particles contained in the treatment liquid are nonionic or have the same polarity as the pigment in the ink. It has no action of aggregating the pigment. If the fine particles have an action of aggregating the pigment instead of the water-soluble compound for aggregating the pigment (that is, if the fine particles have a polarity opposite to that of the pigment), in the treatment liquid to ensure sufficient aggregation This is because a larger amount of fine particles must be added to the liquid, the solid content of the treatment liquid increases, and jetting stability and storage stability deteriorate.
As the pigment, a self-dispersing pigment described later and a pigment used together with a pigment dispersant can be used. In the latter case, the polarity of the pigment can be controlled by selecting the polarity of the pigment dispersant.

On the other hand, the volume average particle diameter of the fine particles is preferably in the range of 5 to 1000% of the volume average particle diameter of the pigment.
When the volume average particle size of the fine particles is less than 5% of the volume average particle size of the pigment, the jetting stability with time of the treatment liquid deteriorates to the same extent as when the fine particles are not used. In some cases, the occurrence of image quality defects cannot be suppressed. On the other hand, if it exceeds 1000%, the size of the fine particles is too large, and thus ejection failure such as clogging may occur when the treatment liquid is ejected from the nozzles of the recording head.
Therefore, the volume average particle diameter of the fine particles is more preferably in the range of 10 to 500% of the volume average particle diameter of the pigment, and still more preferably in the range of 30 to 300%.

  In the present invention, “fine particles” contained in the treatment liquid mean a solid content that does not dissolve in the aqueous medium contained in the treatment liquid, like the pigment contained in the ink. It is particularly preferable that the fine particles can maintain a stable dispersion state in the treatment liquid. The fine particles do not have a function of aggregating the pigment contained in the ink.

In the present invention, the volume average particle size was measured using a Microtrac UPA particle size analyzer 9340 (manufactured by Lees & Northrup).
Measurement is performed under the condition of 3 mW output using 4 ml of ink or treatment liquid (hereinafter, the former two may be collectively referred to as “printing liquid”) in a measurement cell, using a laser with a wavelength of 780 nm as a light source. did.
In the measurement, the viscosity of the printing liquid and the density and refractive index of the material constituting the dispersed particles (pigments or fine particles) in the printing liquid were input as parameters to be input to the apparatus. This apparatus measures the particle diameter by utilizing the Brownian motion of the dispersoid, and measures the particle diameter by irradiating the solution with laser light and detecting the scattered light.

Further, the content of the fine particles contained in the treatment liquid is preferably in the range of 0.2 to 120%, and preferably in the range of 2 to 100% of the content of the pigment contained in the ink. More preferably, it is still more preferably in the range of 5 to 80%.
If it is less than 0.2%, the ejection stability of the processing liquid over time deteriorates to the same extent as when fine particles are not used, and therefore it is not possible to suppress the occurrence of image quality defects such as density unevenness. There is. On the other hand, if it exceeds 200%, the content of the fine particles is too large, and thus ejection failure such as clogging may occur when the treatment liquid is ejected from the nozzle of the recording head.

In addition, in the case of a liquid in which many fine solids are dispersed, such as ink or the treatment liquid used in the present invention, it is difficult to avoid the dispersion state changing with the passage of time. In addition, the ink set set in the inkjet recording apparatus is rarely used up within a few days, and the same ink set is generally used over several months.
From such a viewpoint, it is preferable that the dispersion stability with time of the fine particles contained in the treatment liquid is comparable to the dispersion stability with time of the pigment contained in the ink. If the difference in dispersion stability over time is large, even if the difference in ejection stability over time between the ink ejected from the recording head and the treatment liquid is small in the initial stage of using the ink set, the time As time passes, the difference may increase. In such a case, image quality deterioration such as image unevenness may be caused.

  Such dispersion stability over time can be evaluated by an accelerated test by leaving the printing liquid in a high temperature environment. Therefore, after the treatment liquid is left at 70 ° C. for 200 hours, the number of coarse particles having a particle size of 5 μm or more contained in 2 μl of the treatment liquid is 100 or less, and the ink is left at 70 ° C. for 200 hours. After that, it is preferable that the number of coarse particles having a particle diameter of 5 μm or more contained in 2 μl of ink is 100 or less. If the number of coarse particles in any one of the printing liquids exceeds 100, image quality deterioration such as image unevenness may occur after a long period of time has passed since the ink set was used. The number of coarse particles evaluated under the above-described conditions is preferably 90 or less, more preferably 80 or less for both printing liquids.

Note that the number of particles having a particle size of 5 μm or more was measured using an Accusizer TM770 Optical Particle Sizer (manufactured by Particle Sizing Systems). The measurement was performed by weighing 2 μl of the printing liquid and placing it in a measurement cell.
In the measurement, the density of the material constituting the dispersed particles (pigments or fine particles) in the printing liquid was input as a parameter input to the apparatus. This apparatus detects particles passing through a measurement unit using an optical technique.

As described above, in the ink set of the present invention, it is important that various characteristics related to the solid content (pigments and fine particles) contained in the printing liquid are similar between the ink and the treatment liquid. .
On the other hand, various characteristics (for example, viscosity, surface tension, etc.) mainly determined by the liquid components contained in the printing liquid are generally adjusted to the same level between the ink and the processing liquid. For this reason, it is considered that the ejection stability over time of the ink and the treatment liquid does not significantly affect the printing liquid within the general range. For this reason, the characteristics mainly determined by the liquid component may be within a general range.

For example, the viscosity of the ink and the treatment liquid can be adjusted within a range of 1.5 to 15 mPa · s, the surface tension can be adjusted within a range of 20 to 40 mN / m, and the zeta potential is absolutely The value can be adjusted within a range of 0 to 70 mV.
The viscosity can be measured using Rheomat 115 (manufactured by Contraves). The measurement can be performed by putting 10 ml of printing liquid into a measuring container, the temperature is 23 ° C., and the shear rate is 1400 s ⁻¹ .
The surface tension can be measured using an automatic surface tension meter CBVP-Z type (manufactured by FACE). For the measurement, 15 ml of printing liquid was put in a petri dish and measured at 23 ° C.
Further, the zeta potential can be measured using ESA-8000i Matec Applied Science). The measurement was performed in a state where the measurement cell was filled with 400 ml of the printing liquid and the measuring probe was immersed in a specified amount.

-Ink and treatment liquid-
Next, details of the ink and the treatment liquid used in the present invention will be described. The ink used in the present invention contains at least a pigment, a water-soluble organic solvent, and water. In addition to this, a water-soluble polymer, a surfactant / pigment dispersant, and other various additives are added as necessary. It may be included.
In addition to the fine particles, the treatment liquid needs to contain a water-soluble compound (flocculating agent) that aggregates or thickens the ink, and the fine particles may also function as the flocculant. In addition to this, a water-soluble organic solvent, a water-soluble organic solvent, a water-soluble polymer, a surfactant and other various additives may be contained. Details of each component will be described below.

-Pigment-
In the present invention, a pigment is used as a coloring material. Although it does not specifically limit as the volume average particle diameter, It is preferable to exist in the range of 0.01-1.5 micrometers, and it is more preferable to exist in the range of 0.05-1.0 micrometer.
Examples of usable pigments include known organic pigments and inorganic pigments.

  Specific examples of the black color include carbon black pigments such as furnace black, lamp black, acetylene black, channel black, and the like. Raven1190ULTRAII, Raven1170, Raven1255, Raven1080, Raven1060 (manufactured by Columbian Carbon), Regal400R, Regal330R, Regal660R, Mogu L, Black Pearls L, Monarch 800, Monarch 700, Monarch 700 rch 1100, Monarch 880, Monarch 900, Monoarch 1300, Monarch 1400 (manufactured by Cabot), Color Black FW1, Color Black FW2, Color Black FW2V, Color Black 18, Color Black 218, Color Black FW , Printex35, PrintexU, PrintexV, Printex140U, Printex140V, Special Black6, Special Black 5, Special Black 4A, Special Black4 (manufactured by Degussa). 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. 2300, MCF-88, MA600, MA7, MA8, MA100 (manufactured by Mitsubishi Chemical Corporation) and the like can be used, but are not limited thereto.

  In cyan, C.I. I. Pigment Blue-1, C.I. I. Pigment Blue-2, C.I. I. Pigment Blue-3, C.I. I. Pigment Blue-15, C.I. I. Pigment Blue-15: 1, C.I. I. Pigment Blue-15: 3, C.I. I. Pigment Blue-15: 4, C.I. I. Pigment Blue-16, C.I. I. Pigment Blue-22, C.I. I. Pigment Blue-60 and the like, but are not limited thereto.

  For magenta, C.I. I. Pigment Red-5, C.I. I. Pigment Red-7, C.I. I. Pigment Red-12, C.I. I. Pigment Red-48, C.I. I. Pigment Red-48: 1, C.I. I. Pigment Red-57, C.I. I. Pigment Red-112, C.I. I. Pigment Red-122, C.I. I. Pigment Red-123, C.I. I. Pigment Red-146, C.I. I. Pigment Red-168, C.I. I. Pigment Red-184, C.I. I. Pigment Red-202 and the like, but are not limited thereto.

  In yellow, C.I. I. Pigment Yellow-1, C.I. I. Pigment Yellow-2, C.I. I. Pigment Yellow-3, C.I. I. Pigment Yellow-12, C.I. I. Pigment Yellow-13, C.I. I. Pigment Yellow-14, C.I. I. Pigment Yellow-16, C.I. I. Pigment Yellow-17, C.I. I. Pigment Yellow-73, C.I. I. Pigment Yellow-74, C.I. I. Pigment Yellow-75, C.I. I. Pigment Yellow-83, C.I. I. Pigment Yellow-93, C.I. I. Pigment Yellow-95, C.I. I. Pigment Yellow-97, C.I. I. Pigment Yellow-98, C.I. I. Pigment Yellow-114, C.I. I. Pigment Yellow-128, C.I. I. Pigment Yellow-129, C.I. I. Pigment Yellow-138, C.I. I. Pigment Yellow-151, C.I. I. Pigment Yellow-154 and the like, but are not limited thereto.

  These pigments may be used alone or as a mixture of plural kinds. In the present invention, the pigment used in the ink is preferably in the range of 0.5 to 20% by weight, more preferably 2 to 10% by weight, based on the total weight of the ink.

-Pigment dispersant-
When a pigment is used as the color material, it is desirable to use a pigment dispersant together. Examples of the pigment dispersant that can be used include a polymer dispersant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant.
As the polymer dispersant, any polymer having a hydrophilic structure portion and a hydrophobic structure portion can be used effectively. As the polymer having a hydrophilic structure portion and a hydrophobic structure portion, a condensation polymer and an addition polymer can be used. Examples of the condensation polymer include known polyester dispersants.

  Examples of the addition polymer include addition polymers of monomers having an α, β-ethylenically unsaturated group. The desired polymer dispersant is obtained by copolymerizing a monomer having an α, β-ethylenically unsaturated group having a hydrophilic group and a monomer having an α, β-ethylenically unsaturated group having a hydrophobic group as appropriate. It is done. In addition, a homopolymer of a monomer having an α, β-ethylenically unsaturated group having a hydrophilic group can also be used.

  As the monomer having an α, β-ethylenically unsaturated group having a hydrophilic group, a monomer having a carboxyl group, a sulfonic acid group, a hydroxyl group, a phosphoric acid group, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, Itaconic acid monoester, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, vinyl sulfonic acid, styrene sulfonic acid, sulfonated vinyl naphthalene, vinyl alcohol, acrylamide, methacryloxyethyl phosphate, bismethacryloxyethyl phosphate, Examples include methacryloxyethyl phenyl acid phosphate, ethylene glycol dimethacrylate, and diethylene glycol dimethacrylate.

  Examples of monomers having an α, β-ethylenically unsaturated group having a hydrophobic group include styrene derivatives such as styrene, α-methylstyrene, vinyltoluene, vinylcyclohexane, vinylnaphthalene, vinylnaphthalene derivatives, alkyl acrylates, and methacrylic acid. Examples include alkyl esters, methacrylic acid phenyl esters, methacrylic acid cycloalkyl esters, crotonic acid alkyl esters, itaconic acid dialkyl esters, and maleic acid dialkyl esters.

  Examples of preferred copolymers include styrene-styrene sulfonic acid copolymers, styrene-maleic acid copolymers, styrene-methacrylic acid copolymers, styrene-acrylic acid copolymers, vinyl naphthalene-maleic acid copolymers. , Vinyl naphthalene-methacrylic acid copolymer, vinyl naphthalene-acrylic acid copolymer, alkyl acrylate ester-acrylic acid copolymer, methacrylic acid alkyl ester-methacrylic acid copolymer, styrene-methacrylic acid alkyl ester-methacrylic acid Examples thereof include a copolymer, a styrene-alkyl acrylate ester-acrylic acid copolymer, a styrene-methacrylic acid phenyl ester-methacrylic acid copolymer, and a styrene-methacrylic acid cyclohexyl ester-methacrylic acid copolymer. Moreover, you may copolymerize suitably the monomer which has a polyoxyethylene group and a hydroxyl group with these polymers.

  These pigment dispersants may be used alone or in combination of two or more. The amount of pigment dispersant added varies greatly depending on the pigment, so it cannot be said unconditionally, but generally 0.1 to 100% by weight, preferably 1 to 70% by weight, more preferably 3 to 50% by weight based on the pigment. % Is added.

-Self-dispersing pigment-
As the pigment used in the present invention, a self-dispersing pigment can be used. Specifically, Cab-o-jet-200, Cab-o-jet-300 manufactured by Cabot, IJX-253, IJX-266, IJX-273, IJX-444, IJX-55, manufactured by Orient Chemical Co., Ltd. Commercially available self-dispersing pigments such as Microjet Black CW-1 and CW-2 can be used, but are not limited thereto.
As the pigment used in the present invention, a so-called encapsulated pigment in which pigment particles are coated with a polymer can also be used.

-Fine particles-
The fine particles added to the treatment liquid are not particularly limited as long as they are made of a material dispersible in water and are nonionic or have the same polarity as the pigment. Specifically, resin fine particles and / or inorganic fine particles are used. Is available.
Examples of the resin fine particles include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, styrene resins, crosslinked acrylic resins, crosslinked styrene resins, and co-polymers. Examples thereof include a polymerized polyester resin, an ethylene / acrylic acid resin, a polyethylene resin, a copolymerized nylon resin, a polyethylene resin, a benzoguanamine resin, a phenol resin, a silicone resin, and an epoxy resin.

  Examples of the inorganic fine particles include silicic acid, calcium silicate, aluminum silicate, alumina, alumina white, aluminum hydroxide, titanium oxide, titanium white, titania, mica titanium, aluminum oxide, zinc oxide, barium oxide, copper oxide, and oxidation. Examples thereof include yttrium, cesium oxide, kaolin, talc, mica, and sericite.

In addition, when the surface of the fine particles is hydrophobic, dispersion stability in the treatment liquid may be lacking. Therefore, hydrophilicity can be obtained by adding a hydrophilic group to the surface of the fine particles by graft polymerization or the like, and treating with plasma. Hydrophilization treatment can be performed using a known surface treatment method such as imparting properties.
In addition, when the pigment contained in the ink is a self-dispersing pigment, the fine particles are also preferably self-dispersing from the viewpoint of bringing the jetting characteristics closer to the ink, and the pigment contained in the ink is preferably dispersed in the pigment. In the case of a resin-dispersed pigment dispersed by an agent, the fine particles are also preferably resin-dispersed fine particles dispersed by a polymer dispersant.
As the polymer dispersant, those having a weight average molecular weight of preferably 1000 or more, more preferably 2000 or more and having at least a hydrophilic group can be used. Further, it is more preferable to use a pigment dispersant having the same or similar molecular structure as described above.

Specific examples of the polymer dispersant include a copolymer of monomers having an α, β-ethylenically unsaturated group.
Examples of monomers having an α, β-ethylenically unsaturated group include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, Vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, allyl phosphonic acid, vinyl phosphonic acid, sulfonated vinyl naphthalene, vinyl alcohol, acrylamide, methacryloxyethyl phosphate, bismethacryloxyethyl phosphate, methacryloxyethyl phenyl acid phosphate, ethylene glycol Dimethacrylate, diethylene glycol dimethacrylate, styrene derivatives such as styrene, α-methylstyrene, vinyltoluene, vinylcyclohexane, vinylnaphthalene, vinylnaphthalene derivatives Body, alkyl acrylate, phenyl acrylate, methacrylic acid alkyl esters, methacrylic acid phenyl ester, methacrylic acid cycloalkyl ester, crotonic acid alkyl ester, itaconic acid dialkyl esters, maleic acid dialkyl ester and the like.

  Specific examples of the polymer dispersant comprising a copolymer obtained by copolymerizing a single monomer or a plurality of monomers having an α, β-ethylenically unsaturated group include polyacrylic acid, polymethacrylic acid, and styrene. -Styrene sulfonic acid copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl naphthalene-methacrylic acid copolymer, Vinyl naphthalene-acrylic acid copolymer, acrylic acid alkyl ester-acrylic acid copolymer, methacrylic acid alkyl ester-methacrylic acid, acrylic acid-acrylonitrile copolymer, styrene-methacrylic acid alkyl ester-methacrylic acid copolymer, styrene -Acrylic acid alkyl ester-Acrylic acid copolymer, Examples include tylene-methacrylic acid phenyl ester-methacrylic acid copolymer, styrene-methacrylic acid cyclohexyl ester-methacrylic acid copolymer, and the like.

-Flocculant-
Further, the processing liquid contains a water-soluble compound (flocculating agent) having an action of aggregating the pigment contained in the ink.
For example, when the ink contains a pigment having an anionic group on the surface, the treatment liquid preferably contains an electrolyte and / or a cationic compound. Examples of the electrolyte that can be effectively used in the present invention include alkali metal ions such as lithium ions, sodium ions, and potassium ions, and aluminum ions, barium ions, calcium ions, copper ions, iron ions, magnesium ions, manganese ions, nickel ions, Multivalent metal ions such as tin ion, titanium ion, zinc ion, hydrochloric acid, odorous acid, hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid, thiocyanic acid, and acetic acid, oxalic acid, lactic acid, fumaric acid, fumaric acid, citric acid Examples thereof include organic carboxylic acids such as acids, salicylic acid and benzoic acid, and salts of organic sulfonic acids.

  Specific examples include lithium chloride, sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, potassium iodide, sodium sulfate, potassium nitrate, sodium acetate, potassium oxalate, sodium citrate, potassium benzoate and the like. Alkali metal salts and aluminum chloride, aluminum bromide, aluminum sulfate, aluminum nitrate, sodium aluminum sulfate, potassium aluminum sulfate, aluminum acetate, barium chloride, barium bromide, barium iodide, barium oxide, barium nitrate, thioan Barium acid, calcium chloride, calcium bromide, calcium iodide, calcium nitrite, calcium nitrate, calcium dihydrogen phosphate, calcium thiocyanate, calcium benzoate, calcium acetate, salicylic acid Lucium, calcium tartrate, calcium lactate, calcium fumarate, calcium citrate, copper chloride, copper bromide, copper sulfate, copper nitrate, copper acetate, iron chloride, iron bromide, iron iodide, iron sulfate, iron nitrate, oxalic acid Iron, iron lactate, iron fumarate, iron citrate, magnesium chloride, magnesium bromide, magnesium iodide, magnesium sulfate, magnesium nitrate, magnesium acetate, magnesium lactate, manganese chloride, manganese sulfate, manganese nitrate, manganese dihydrogen phosphate , Manganese acetate, manganese salicylate, manganese benzoate, manganese lactate, nickel chloride, nickel bromide, nickel sulfate, nickel nitrate, nickel acetate, tin sulfate, titanium chloride, zinc chloride, zinc bromide, zinc sulfate, zinc nitrate, thiocyanate Examples thereof include salts of polyvalent metals such as zinc acid and zinc acetate.

  On the other hand, examples of the cationic compound include primary, secondary, tertiary and quaternary amines and salts thereof. Specific examples include tetraalkylammonium salts, alkylamine salts, benzalkonium salts, alkylpyridium salts, imidazolium salts, polyamines, etc., for example, isopropylamine, isobutylamine, t-butylamine, 2-ethylhexylamine. , Nonylamine, dipropylamine, diethylamine, trimethylamine, triethylamine, dimethylpropylamine, ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, tetraethylenepentamine, diethanolamine, diethylethanolamine, triethanolamine, tetramethylammonium chloride, tetraethylammonium Bromide, dihydroxyethyl stearylamine, 2-heptadecenyl-hydroxyethyl Imidazoline, lauryl dimethyl benzyl ammonium chloride, cetyl pyridinium chloride, stearamide methyl pyridinium chloride, diallyldimethylammonium chloride polymers, diallylamine polymers include monoallylamine polymer and the like.

  Preferred electrolytes include aluminum sulfate, calcium chloride, calcium nitrate, calcium acetate, magnesium chloride, magnesium nitrate, magnesium sulfate, magnesium acetate, tin sulfate, zinc chloride, zinc nitrate, zinc sulfate, zinc acetate, aluminum nitrate, monoallylamine heavy Examples thereof include a polymer, a diallylamine polymer, and a diallyldimethylammonium chloride polymer.

On the other hand, when the ink contains a pigment having a cationic group on its surface, the treatment liquid preferably contains an anionic compound or the like.
Examples of the anionic compound that can be effectively used in the present invention include organic carboxylic acids or organic sulfonic acids, and salts thereof. Specifically, examples of the organic carboxylic acid include acetic acid, succinic acid, lactic acid, fumaric acid, citric acid, salicylic acid, benzoic acid, and the like, and an oligomer or polymer having a plurality of these basic structures may be used. Examples of the organic sulfonic acid include compounds such as benzenesulfonic acid and toluenesulfonic acid, and an oligomer or polymer having a plurality of these basic structures may be used.

  The above-mentioned flocculants added to the treatment liquid may be used alone or in combination of two or more. The content of the flocculant added to the treatment liquid is 0.1 to 15% by weight, preferably 0.5 to 10% by weight.

  The flocculant contained in the treatment liquid is appropriately determined according to the composition and pH of the ink. For example, when the ink contains a nonionic polymer dispersant or a nonionic surfactant and the pH is in the range of 7.5 to 11.5, the treatment liquid contains pyrrolidonecarboxylic acid, pyronecarboxylic acid, pyrrole. Carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, or derivatives of these compounds, more preferably pyrrolidone carboxylic acid, pyrone carboxylic acid, furan carboxylic acid, coumaric acid, or these Compound derivatives or salts thereof can be added to adjust the pH to 2.0 to 7.0.

-Surfactant-
In the present invention, the ink or the treatment liquid is used to adjust the surface tension and wettability of the ink or the treatment liquid, or to solubilize organic impurities and improve the reliability of ejection from the nozzles of the recording head. For this reason, a cationic surfactant, a nonionic surfactant, and / or an anionic surfactant can be added. These surfactants may be used alone or as a mixture of a plurality of types.
Examples of the anionic surfactant include alkylbenzene sulfonate, alkylphenyl sulfonate, alkylnaphthalene sulfonate, higher fatty acid salt, sulfate of higher fatty acid ester, sulfonate of higher fatty acid ester, sulfuric acid of higher alcohol ether. Examples include ester salts and sulfonates, higher alkyl sulfosuccinates, higher alkyl phosphate esters, phosphate esters of higher alcohol ethylene oxide adducts, such as dodecyl benzene sulfonate and ketyl benzene sulfonate. , Isopropyl naphthalene sulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenylsulfonate, monobutylbiphenylsulfonate, dibutylphenylphenol disulfonate, etc. That.

  Nonionic surfactants include, for example, polypropylene glycol ethylene oxide adduct, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, Examples include sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, fatty acid alkylolamide, acetylene glycol, oxyethylene adduct of acetylene glycol, aliphatic alkanolamide, glycerin ester, sorbitan ester and the like.

Examples of the cationic surfactant include tetraalkylammonium salts, alkylamine salts, benzalkonium salts, alkylpyridium salts, imidazolium salts, and the like, such as dihydroxyethyl stearylamine, 2-heptadecenyl-hydroxyethylimidazoline, Examples include lauryl dimethyl benzyl ammonium chloride, cetyl pyridinium chloride, stearamide methyl pyridium chloride, and the like.
In addition, silicone surfactants such as polysiloxane oxyethylene adducts, fluorine surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers, spicrispolic acid and rhamnolipids Biosurfactants such as lysolecithin can also be used.
The amount of the surfactant added to the ink is preferably 5% by weight or less, more preferably 0.01 to 3% by weight based on the total weight of the ink.

-Water-soluble organic solvent-
Examples of the water-soluble organic solvent used in the present invention include polyhydric alcohols, polyhydric alcohol derivatives, nitrogen-containing solvents, alcohols, and sulfur-containing solvents. The viscosity of the ink and the processing liquid can be adjusted by selecting the type and amount of the water-soluble organic solvent.
Specific examples of water-soluble organic solvents include polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, and glycerin. Can be mentioned. Examples of polyhydric alcohol derivatives include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, and diglycerin. Examples include ethylene oxide adducts. Examples of nitrogen-containing solvents include pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, and triethanolamine. Examples of alcohols include alcohols such as ethanol, isopropyl alcohol, butyl alcohol, and benzyl alcohol. Thiodiethanol, thiodiglycerol, sulfolane, dimethyl sulfoxide and the like. In addition, propylene carbonate, ethylene carbonate, or the like can also be used.

These water-soluble organic solvents may be used alone or in combination of two or more.
Although there is no restriction | limiting in particular about content of the said water-soluble organic solvent in ink, It is preferable that it is 1 to 60 weight% of the total weight of ink, More preferably, it is 5 to 40 weight% of the total weight of ink.

-Other additives-
In the present invention, in addition to the above-mentioned components, the ink and the treatment liquid include cellulose derivatives such as polyethyleneimine, polyvinylpyrrolidone, polyethylene glycol, ethylcellulose, carboxymethylcellulose, and other water-soluble polymers for controlling the properties of the ink and the treatment liquid. Polymer emulsions such as acrylic polymer emulsions and polyurethane emulsions; cyclodextrins, macrocyclic amines, dendrimers, crown ethers, urea and derivatives thereof, acetamide and the like can be added.

  Further, in the present invention, the ink and the treatment liquid include alkali metal compounds such as potassium hydroxide, sodium hydroxide and lithium hydroxide; alkaline earth metals such as calcium hydroxide in order to adjust conductivity and pH. Metal compounds; acids such as sulfuric acid, hydrochloric acid, and nitric acid; strong acid and weak alkali salts such as ammonium sulfate can be used.

  In addition, pH buffering agents, antioxidants, antifungal agents, viscosity modifiers, conductive agents, ultraviolet absorbers, and chelating agents can be added as necessary, and water-soluble dyes, disperse dyes, oil-soluble dyes, and the like can also be added.

<Inkjet recording method, inkjet recording apparatus, and ink tank for inkjet recording>
The ink jet recording method of the present invention is a method of forming an image on the surface of a recording medium by using the ink set of the present invention and applying the ink and the treatment liquid to the surface of the recording medium so as to contact each other.
The ink jet recording apparatus of the present invention includes a recording head that uses the ink set of the present invention and ejects ink and a processing liquid onto the surface of the recording medium, and the ink and the processing liquid are in contact with each other on the surface of the recording medium. The apparatus forms an image by discharging from a recording head.
In the ink jet recording method / recording apparatus of the present invention, the image is usually formed while the recording medium is conveyed in one direction, and is disposed opposite to the surface of the recording medium conveyed in one direction, and the ink and the treatment liquid are used. This is performed using a recording head that discharges to the surface of the recording medium. Here, the recording head is a PWA (Partial Width Array) type that can be scanned in a direction parallel to the recording medium plane and orthogonal to the recording medium conveyance direction (hereinafter sometimes referred to as “width direction”), or recording. The width of the head in the direction parallel to the recording medium plane and orthogonal to the recording medium conveyance direction is substantially equal to the width of the recording medium in the direction parallel to the recording medium plane and orthogonal to the recording medium conveyance direction. Any of FWA (Full Width Array) type in which the head is fixed in a direction parallel to the recording medium plane and perpendicular to the recording medium conveyance direction may be used.

  On the other hand, since the FWA type recording head is fixed and the width is longer than that of the PWA type recording head, the uneven ejection of the ink and the processing liquid in the width direction is more noticeable than the PWA type recording head. If the set is used, such discharge unevenness can be suppressed. From such a viewpoint, the ink set of the present invention is preferably used in combination with an FWA type recording head. Further, the essence of the problem as described above is not caused by the difference between the FWA type and the PWA type, but is caused by the width of the recording head. Therefore, the ink set of the present invention is preferably used in combination with a recording head having a width of 210 mm or more.

The ink jet recording apparatus of the present invention can supply ink and processing liquid to the recording head and can be attached to and detached from the ink jet recording apparatus main body (hereinafter referred to as “ink tank”). May be provided). In this case, the ink set of the present invention may be stored in the ink tank for ink jet recording.
In addition, the ink jet recording apparatus of the present invention can use an ordinary ink jet recording apparatus of a two-liquid printing system that can use the ink set of the present invention. In addition, the ink drying is controlled as necessary. Equipped with a mechanism for transferring to a recording medium such as paper after ejecting (printing) ink and processing liquid onto the intermediate body. Good.
Furthermore, although the ink jet recording apparatus of the present invention can be used for industrial purposes, it is usually preferable to use a so-called ink jet recording apparatus used in offices and homes.

As the recording head, individual recording heads corresponding to each color ink and processing liquid may be integrated, and each recording head corresponding to each color ink and processing liquid is separated and independent. It may be a configuration.
The ink tank for ink jet recording is detachable from the ink jet recording apparatus provided with the recording head, and has a configuration capable of supplying ink and processing liquid to the recording head in a state of being mounted on the ink jet recording apparatus. For example, a conventionally known ink tank can be used. Here, the ink set of the present invention is stored in the ink tank.

In the ink jet recording method (apparatus) of the present invention, the ratio (ink application amount: treatment liquid application amount) between the application amount of the ink per unit area applied to the surface of the recording medium and the application amount of the treatment liquid is as follows: The weight ratio is preferably in the range of 1.2: 1 to 20: 1.
The smaller the ratio of the applied liquid to the ink applied amount from the ratio of 20: 1, the less likely the problem of curl and cockle occurs. However, when the ratio is too small, the effect of the processed liquid becomes insufficient, and the image density and Image resolution may be reduced. On the other hand, if the ratio is out of 1.2: 1 and the amount of treatment liquid applied is large, the image density and the image resolution are good, but curl and cockle are likely to occur. A more preferable range of the ratio is 1: 0.75 to 1: 0.1, and more preferably 1: 0.7 to 1: 0.15.

In the ink jet recording method (apparatus) of the present invention, the weight of the liquid per drop is preferably 500 pg or less for both the ink and the treatment liquid. More preferably, it is 0.1 pg or more and 300 pg or less, More preferably, it is 0.5 pg or more and 100 pg or less. If the liquid weight per drop exceeds 500 pg, bleeding may be worsened. This is because the contact angles of the ink and the treatment liquid with respect to the recording medium change depending on the drop amount, and it is considered that the drop tends to spread in the paper surface direction as the drop amount increases.
However, in an ink jet apparatus capable of ejecting a plurality of drops from a single nozzle, the drop amount refers to the minimum drop amount that can be printed.

  Further, the ink and the treatment liquid are applied on the recording medium so as to be in contact with each other. However, as long as they are in contact with each other, they may be applied so as to be adjacent to each other or to be covered. .

  The order of application to the recording medium is not particularly limited, and any of them may be applied first or substantially simultaneously, but it is preferable to apply ink after applying the treatment liquid. This is because the colorant in the ink can be effectively aggregated by applying the treatment liquid first. As long as the treatment liquid is applied, the ink may be applied at any time. Preferably, it is 1 second or less, more preferably 0.5 seconds or less after the treatment liquid is applied.

The ink jet recording method (apparatus) of the present invention preferably adopts a thermal ink jet recording method or a piezo ink jet recording method from the viewpoint of the effect of improving bleeding and intercolor bleeding.
The cause of this is not clear, but in the case of the thermal ink jet recording method, the ink is heated at the time of ejection and has a low viscosity, but since the temperature of the ink is lowered on the recording medium, the viscosity rapidly increases. Become. For this reason, it is considered that bleeding and intercolor bleeding have an improving effect.
On the other hand, in the case of the piezo ink jet method, it is possible to discharge a high-viscosity liquid, and the high-viscosity liquid can suppress spreading in the paper surface direction on the recording medium. It is estimated that there is an improvement effect on intercolor bleeding.

  In the ink jet recording method (apparatus) of the present invention, replenishment (supply) of ink and processing liquid to the recording head is performed from an ink tank (including a processing liquid tank) filled with each liquid of ink and processing liquid. Is good. The ink tank is preferably a cartridge system that can be attached to and detached from the apparatus main body, and ink and processing liquid can be easily replenished by replacing the ink tank of this cartridge system.

  Hereinafter, preferred embodiments of the ink jet recording apparatus of the present invention will be described in detail with reference to the drawings. In the drawings, members having substantially the same functions are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a perspective view showing an external configuration of a preferred embodiment of an ink jet recording apparatus of the present invention. FIG. 2 is a perspective view showing an internal basic configuration of the ink jet recording apparatus (hereinafter referred to as an image forming apparatus) of FIG.

  The image forming apparatus 100 of this embodiment has a configuration that operates based on the above-described inkjet recording method of the present invention to form an image. That is, as shown in FIGS. 1 and 2, an image forming apparatus 100 mainly includes an external cover 6, a tray 7 on which a predetermined amount of recording medium 1 such as plain paper can be placed, and the recording medium 1 as an image forming apparatus. An image forming unit 8 (image forming unit) for forming an image by ejecting ink and processing liquid onto the surface of the recording medium 1; The main ink tank 4 is configured to supply ink and processing liquid to the sub ink tanks 5 of the forming unit 8.

  The conveyance roller 2 is a paper feed mechanism constituted by a pair of rollers rotatably disposed in the image forming apparatus 100, sandwiches the recording medium 1 set on the tray 7, and has a predetermined amount of recording medium 1. Are conveyed into the apparatus 100 one by one at a predetermined timing.

  The image forming unit 8 forms an image with ink on the surface of the recording medium 1. The image forming unit 8 mainly includes a recording head 3, a sub ink tank 5, a power supply signal cable 9, a carriage 10, a guide rod 11, a timing belt 12, a driving pulley 13, and a maintenance unit 14. ing.

  The sub ink tank 5 has sub ink tanks 51, 52, 53, 54, and 55 in which different colors of ink and processing liquid are stored so as to be ejected from the recording head. These include, for example, black ink (K), yellow ink (Y), magenta ink (M), and cyan ink (C) as the first liquid, and processing liquid from the main ink tank 4 as the second liquid. Replenished and paid.

  The sub ink tank 5 is provided with an exhaust hole 56 and a supply hole 57, respectively. When the recording head 3 moves to the standby position (or replenishment position), the exhaust pin 151 and the replenishment pin 152 of the replenishing device 15 are inserted into the exhaust hole 56 and the replenishment hole 57, respectively. 5 and the replenishing device 15 can be connected. The replenishing device 15 is connected to the main ink tank 4 via the replenishing pipe 16, and the replenishing device 15 replenishes ink or processing liquid from the main ink tank 4 to the sub ink tank 5 through the replenishing hole 57.

  Here, the main ink tank 4 also has main ink tanks 41, 42, 43, 44, 45 in which different colors of ink and processing liquid are stored. These are filled with, for example, black ink (K), yellow ink (Y), magenta ink (M), and cyan ink (C) as the first liquid, and the processing liquid as the second liquid, Each is stored in the image forming apparatus 100 in a detachable manner.

  Furthermore, the power supply signal cable 9 and the sub ink tank 5 are connected to the recording head 3, and when external image recording information is input from the power supply signal cable 9 to the recording head 3, the recording head 3 detects the image recording information. Based on the above, a predetermined amount of ink is sucked from each sub ink tank 5 and discharged onto the surface of the recording medium. The power supply signal cable 9 also has a role of supplying power necessary for driving the recording head 3 to the recording head 3 in addition to the image recording information.

  The recording head 3 is arranged and held on a carriage 10, and the carriage 10 is connected to a guide rod 11 and a timing belt 12 connected to a driving pulley 13. With such a configuration, the recording head 3 extends along the guide rod 11 and is parallel to the surface of the recording medium 1 and perpendicular to the conveyance direction X (sub-scanning direction) of the recording medium 1 (main scanning direction). It can also be moved in the scanning direction.

  The image forming apparatus 100 includes control means (not shown) that adjusts the drive timing of the recording head 3 and the drive timing of the carriage 10 based on the image recording information. Thereby, an image based on the image recording information can be continuously formed in a predetermined region of the surface of the recording medium 1 that is transported at a predetermined speed along the transport direction X.

  The maintenance unit 14 is connected to a decompression device (not shown) via a tube. Further, the maintenance unit 14 is connected to the nozzle portion of the recording head 3 and has a function of sucking ink from the nozzles of the recording head 3 by reducing the pressure in the nozzles of the recording head 3. By providing the maintenance unit 14, if necessary, excess ink adhering to the nozzles during operation of the image forming apparatus 100 is removed, or evaporation of ink from the nozzles is suppressed when the operation is stopped. be able to.

  FIG. 3 is a perspective view showing an external configuration of another preferred embodiment of the ink jet recording apparatus of the present invention. FIG. 4 is a perspective view showing an internal basic configuration of the ink jet recording apparatus (hereinafter referred to as an image forming apparatus) of FIG. The image forming apparatus 101 of the present embodiment has a configuration that operates based on the above-described inkjet recording method of the present invention to form an image.

  In the image forming apparatus 101 shown in FIGS. 3 and 4, the width of the recording head 3 is the same as or larger than the width of the recording medium 1, does not have a carriage mechanism, and is in the sub-scanning direction (conveying direction of the recording medium 1: arrow X). Direction) paper feed mechanism (the transport roller 2 is shown in the present embodiment, but it may be a belt-type paper feed mechanism, for example).

  Although not shown, the nozzle group for discharging each color (including the treatment liquid) is also provided in the same manner as the sub ink tanks 51 to 55 are sequentially arranged in the sub scanning direction (conveyance direction of the recording medium 1: arrow X direction). They are arranged in the sub-scanning direction. Other configurations are the same as those of the image forming apparatus 100 shown in FIGS. In the drawing, since the recording head 3 does not move, the sub ink tank 5 is always connected to the replenishing device 15. However, the sub ink tank 5 may be connected to the replenishing device 15 at the time of ink replenishment.

  In the image forming apparatus 101 shown in FIGS. 3 and 4, since the printing in the width direction (main scanning direction) of the recording medium 1 is collectively performed by the recording head 3, the configuration of the apparatus is simpler than the system having the carriage mechanism. Yes, printing speed will be faster.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

-Preparation of ink and treatment liquid-
In accordance with the following ink composition and treatment liquid composition, the compounds were mixed and stirred, followed by filtration using a membrane filter having an opening of 5 μm.

<Ink A>
Cabojet-300 (manufactured by Cabot) (self-dispersing pigment, volume average particle size = 100 nm): 4% by weight
Styrene-acrylic acid copolymer (NaOH partial neutralization): 0.5% by weight
・ Diethylene glycol: 10% by weight
・ Glycerin: 5% by weight
2-pyrrolidone: 5 mass Acetylene glycol ethylene oxide adduct: 1% by weight
-Ion exchange water: remainder The zeta potential of this ink was -21 mV, the viscosity was 3.3 mPa · s, the surface tension was 31 mN / m, and the volume average particle size was 98 nm.

<Ink B>
・ C. I. Pigment Blue-15: 3: 5% by weight
Styrene-acrylic acid-sodium acrylate copolymer (weight average molecular weight 4000): 0.6% by weight
・ Diethylene glycol: 20% by weight
・ Glycerin: 5% by weight
Polyoxyethylene 2-ethylhexyl ether: 0.75% by weight
-Ion-exchanged water: remainder The viscosity of this ink was 3.1 mPa.s, the surface tension was 30 mN / m, and the volume average particle diameter was 92 nm.

<Processing liquid A>
Calcium carbonate (volume average particle size = 0.20 μm): 1.0% by weight
Β-naphthalenesulfonic acid formalin weight average molecular weight 2300: 0.04% by weight
・ Diethylene glycol: 12% by weight
・ Calcium nitrate tetrahydrate: 6% by weight
-Acetylene glycol ethylene oxide adduct: 0.9% by weight
The treatment liquid had a viscosity of 3.2 mPa · s and a surface tension of 29.8 mN / m.

<Processing liquid B>
Calcium carbonate (volume average particle size = 0.20 μm): 3.0% by weight
Β-naphthalenesulfonic acid formalin (weight average molecular weight 2300): 0.12% by weight
・ Diethylene glycol: 12% by weight
・ Calcium nitrate tetrahydrate: 6% by weight
Acetylene glycol ethylene oxide adduct: 1.0% by weight
This treatment liquid had a viscosity of 3.3 mPa · s and a surface tension of 30.0 mN / m.

<Processing liquid C>
Calcium carbonate (volume average particle size = 0.20 μm): 7.0% by weight
Β-naphthalenesulfonic acid formalin (weight average molecular weight 2300): 0.28% by weight
・ Diethylene glycol: 13% by weight
・ Calcium nitrate tetrahydrate: 6% by weight
Acetylene glycol ethylene oxide adduct: 1% by weight
This treatment liquid had a viscosity of 3.1 mPa · s and a surface tension of 30.0 mN / m.

<Processing liquid D>
Hydrophilic silica (volume average particle size = 0.08 μm): 0.01% by weight
・ Glycerin: 15% by weight
Water-soluble polyamine (weight average molecular weight 6000): 3% by weight
Acetylene glycol ethylene oxide adduct: 1% by weight
The treatment liquid had a viscosity of 3.0 mPa · s, a surface tension of 30.1 mN / m, and a pH of 4.1.

<Processing liquid E>
Hydrophilic silica (volume average particle size = 0.08 μm): 1% by weight
Water-soluble polyamine (weight average molecular weight 6000): 3% by weight
・ Glycerin: 15% by weight
Acetylene glycol ethylene oxide adduct: 1% by weight
This treatment liquid had a viscosity of 3.1 mPa · s, a surface tension of 31.0 mN / m, and a pH of 3.9.

<Processing liquid F>
Alumina (volume average particle size = 0.5 μm): 4% by weight
Polyvinyl alcohol (weight average molecular weight 2200): 0.2% by weight
2-pyrrolidone-5-carboxylic acid: 5% by weight
-Sodium hydroxide: 1.5% by weight
・ Glycerin: 10% by weight
2-pyrrolidone: 5% by weight
Acetylene glycol ethylene oxide adduct: 1% by weight
The treatment liquid had a viscosity of 3.0 mPa · s, a surface tension of 31.2 mN / m, and a pH of 4.2.

<Processing liquid G>
Alumina (volume average particle size = 1.0 μm): 3% by weight
Polyvinyl alcohol Weight average molecular weight 2200: 0.15% by weight
2-pyrrolidone-5-carboxylic acid: 5% by weight
-Sodium hydroxide: 1.5% by weight
・ Glycerin: 10% by weight
2-pyrrolidone: 5% by weight
Acetylene glycol ethylene oxide adduct: 1% by weight
The treatment liquid had a viscosity of 3.0 mPa · s, a surface tension of 31.0 mN / m, and a pH of 4.0.

<Treatment liquid H>
・ Diethylene glycol: 30% by weight
Calcium nitrate tetrahydrate: 6 parts by weight Acetylene glycol ethylene oxide adduct: 1% by weight
-Ion exchange water: remainder The pH of this liquid was 6.1, the surface tension was 30 mN / m, and the viscosity was 2.7 mPa · s.

<Treatment liquid I>
・ Diethylene glycol: 30% by weight
2-furancarboxylic acid: 4% by weight
Sodium hydroxide: 0.75% by weight
Acetylene glycol ethylene oxide adduct: 1% by weight
-Ion exchange water: remainder The pH of this liquid was 4.2, the surface tension was 31 mN / m, and the viscosity was 2.8 mPa · s.

-Evaluation of droplet discharge speed with respect to the number of ejections
Next, using the adjusted (initial) processing liquid and the processing liquid after being left in a 70 ° C. environment for 200 hours, a piezo-type prototype recording head having a nozzle density of 1200 dpi × 600 dpi is used. The droplet discharge speed with respect to the number of ejections of each ink and treatment liquid was evaluated. In the evaluation, for both the ink and the processing liquid, the waveform of the voltage applied to the piezo element of the recording head is set to the same condition, the drop amount is set to 10 pl, and the average value of the droplet discharge speeds when continuously ejected 1000 times, Maximum and minimum values were measured. The results are shown in Table 1.
The droplet discharge speed was obtained by measuring the time from when the ink droplet was discharged until the laser beam irradiated to the position of 0.3 mm from the nozzle surface was blocked, and calculating it based on this. .
The results are shown in Table 1.

-Print evaluation, etc.-
Further, various evaluations were performed by combining the ink and the treatment liquid as shown in Table 2. For the evaluation, an ink jet recording apparatus equipped with an FWA type recording head (recording head width: 50 cm) shown in FIG. 4 was used. In the evaluation, the waveform of the voltage applied to the piezo element of the recording head was set to the same condition for both the ink and the treatment liquid, and the drop amount was set to 10 pl.
The printing test was performed by forming a solid image corresponding to the width of the recording head on the entire surface of the paper (C2 paper manufactured by Fuji Xerox Office Supply Co.) and printing 50 sheets continuously to evaluate image unevenness.

In addition, the printing condition is that the treatment liquid is applied and then the ink is applied for printing, and the recording head applies a drop amount of 10 pl for both the ink and the treatment liquid to the piezo element in the same manner as the evaluation of the droplet discharge speed. By adjusting the number of ejections per unit time under the same voltage waveform, the amount of ink and treatment liquid applied per unit area was set to treatment liquid: ink = 1: 4 in weight ratio.
The evaluation was performed on the density unevenness, the drying property, and the fixing property of the adjusted (initial) ink and processing liquid. The results are shown in Table 3.

In addition, the evaluation method and evaluation criteria of each evaluation item in Table 3 are as follows.
-Image unevenness-
Image unevenness was evaluated visually. The evaluation criteria are as follows.
A: No image unevenness is seen at all in 50 sheets.
○: Some of the 50 images showed slight image unevenness, but the level was not noticeable.
Δ: Among 50 sheets, 5 or more and 10 sheets or less of paper with remarkable image unevenness were observed.
X: 11 or more sheets in which remarkable image unevenness occurred in 50 sheets were observed.
The slight image unevenness is a range of about 1 to 3% in terms of the non-ejection nozzle rate, and the remarkable image unevenness is a range of about 3% or more.

-Dryness-
Drying is performed by placing a plain white paper (Fuji Xerox Co., Ltd., C2 paper) on the printing surface 10 seconds after printing, and further placing a weight of 5 kg and a bottom area of 10 cm ² on it for 3 seconds. The weight was removed and the degree of transfer to blank paper was evaluated. The evaluation criteria are as follows.
◎: The print shift is not apparent. ○: There is a print shift, but I'm almost not interested. △: The print shift is a little anxious. ×: The print shift is worrisome.

-Fixability-
For fixing, white plain paper (C2 paper, manufactured by Fuji Xerox Co., Ltd.) is printed on the printing section, and a weight of 5 kg and a bottom area of 10 cm ² is moved thereon, and the blank paper is moved toward the non-printing section. The degree to which the blank paper and weight were removed and moved to the non-printing part was evaluated. The evaluation criteria are as follows.
◎: The print shift is not apparent. ○: There is a print shift, but I'm almost not interested. △: The print shift is a little anxious. ×: The print shift is worrisome.

As for image unevenness, the PWA type piezo-type recording head shown in FIG. 2 (recording head width: 25. 4 cm) was also evaluated.
As a result, the combination of the ink and the treatment liquid shown in the example gave almost the same result as that evaluated by the ink jet recording apparatus equipped with the FWA type recording head shown in FIG. On the other hand, in the combination of the ink and the treatment liquid shown in the comparative example, the image quality unevenness tends to be improved when the ink jet recording apparatus equipped with the PWA type piezo recording head is used.

1 is a perspective view showing an external configuration of a preferred embodiment of an ink jet recording apparatus of the present invention. FIG. 2 is a perspective view showing an internal basic configuration of the ink jet recording apparatus of FIG. 1. It is a perspective view which shows the external appearance structure of another suitable one Embodiment of the inkjet recording device of this invention. FIG. 4 is a perspective view showing an internal basic configuration of the ink jet recording apparatus of FIG. 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100, 101 Image forming apparatus 1 Recording medium 2 Conveying roller 3 Recording head 4 Main ink tank 5 Sub ink tank 6 External cover 7 Tray 8 Image forming part 9 Power supply signal cable 10 Carriage 11 Guide rod 12 Timing belt 13 Drive pulley 14 Maintenance unit 15 Replenisher

Claims (11)

An ink jet comprising: an ink containing at least a pigment, a water-soluble organic solvent, and water; and a treatment liquid containing fine particles and a water-soluble compound that aggregates or thickens the ink, and forms an image using the ink and the treatment liquid. In an inkjet recording ink set used for recording,
An ink set for ink jet recording, wherein the polarity of the fine particles is nonionic or the same polarity as the polarity of the pigment.   2. The ink set for ink jet recording according to claim 1, wherein the volume average particle diameter of the fine particles is within a range of 5 to 1000% of the volume average particle diameter of the pigment.   The content of the fine particles contained in the treatment liquid is within a range of 0.2 to 120% of the content of the pigment contained in the ink. Ink set for inkjet recording.   The polarity of the pigment is anionic, the polarity of the water-soluble compound is cationic, and the polarity of the fine particles is nonionic or anionic. The ink set for inkjet recording as described in 2.   5. The pigment according to claim 1, wherein the pigment is a resin-dispersed pigment, the treatment liquid contains a polymer dispersant that disperses the fine particles, and the polymer dispersant has a weight average molecular weight of 1000 or more. The ink set for inkjet recording as described in any one. In an ink jet recording method for forming an image on a recording medium surface by using an ink set for ink jet recording containing an ink and a processing liquid, and applying the ink and the processing liquid to the recording medium surface so as to contact each other.
An ink jet recording method, wherein the ink set for ink jet recording is the ink set for ink jet recording according to any one of claims 1 to 5. The image is formed while conveying the recording medium in one direction, and disposed opposite to the surface of the recording medium that is conveyed in one direction, and a recording head that discharges the ink and the treatment liquid to the surface of the recording medium. Use
The width of the recording head in the direction parallel to the recording medium plane and orthogonal to the recording medium conveyance direction is substantially equal to the width of the recording medium in the direction parallel to the recording medium plane and orthogonal to the recording medium conveyance direction, The ink set for inkjet recording according to any one of claims 1 to 5, wherein the recording head is fixed in a direction parallel to the recording medium plane and perpendicular to the recording medium conveyance direction. An ink jet recording method, wherein: The image is formed while conveying the recording medium in one direction, and disposed opposite to the surface of the recording medium that is conveyed in one direction, and a recording head that discharges the ink and the treatment liquid to the surface of the recording medium. Use
8. The ink jet recording method according to claim 6, wherein a width of the recording head in a direction parallel to the recording medium plane and perpendicular to the recording medium conveyance direction is 210 mm or more. An ink set for ink jet recording including an ink and a treatment liquid is used, and a recording head for discharging the ink and the treatment liquid onto the surface of the recording medium is provided, and the ink and the treatment liquid are brought into contact with each other on the surface of the recording medium. In an ink jet recording apparatus for forming an image by discharging from the recording head,
An ink jet recording apparatus, wherein the ink set for ink jet recording is the ink set for ink jet recording according to any one of claims 1 to 5. The image formation is performed while conveying the recording medium in one direction, and the recording head is disposed to face the recording medium surface conveyed in one direction,
The width of the recording head in the direction parallel to the recording medium plane and orthogonal to the recording medium conveyance direction is substantially equal to the width of the recording medium in the direction parallel to the recording medium plane and orthogonal to the recording medium conveyance direction, The inkjet recording apparatus according to claim 9, wherein the recording head is fixed in a direction parallel to the recording medium plane and perpendicular to the recording medium conveyance direction. The image formation is performed while conveying the recording medium in one direction, and the recording head is disposed to face the recording medium surface conveyed in one direction,
11. The inkjet recording apparatus according to claim 9, wherein a width of the recording head in a direction parallel to the recording medium plane and perpendicular to the recording medium conveyance direction is 210 mm or more.

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