JP4501613B2 - Inkjet ink set, image forming method, and image forming apparatus - Google Patents

Description

  The present invention relates to an inkjet ink set, and an image forming method and an image forming apparatus using the same.

  A so-called inkjet recording apparatus that discharges liquid or molten solid ink from nozzles, slits, porous films, etc., and records on paper, cloth, film, etc. has various advantages such as small size, low cost, quietness, There are many products that can perform full color recording as well as black single color printers that can obtain good printing quality on so-called plain paper such as report paper and copy paper, and occupy a large position in the field of recording devices. 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 high-speed, high-quality inkjet printers for offices that have recently been put on the market, the double-sided printing function is emphasized. It has been.

As a means for increasing the density of an image, a method of not only simply increasing the color material concentration in ink but also inhibiting the process of the color material penetrating into the paper and allowing the color material to remain on the paper surface is considered. As this means, in addition to the method of suppressing the permeation by increasing the dispersed particle diameter of the color material, there is a method of retaining the color material on the surface of the paper using a reaction treatment liquid. For example, a method using an aggregation promoting effect of a coloring material by an anion-cation reaction (for example, see Patent Document 1) and a method using an aggregation reaction by a difference in pH between inks (for example, see Patent Document 2). Can be mentioned.
These methods have an effect of improving image quality such as feathering and inter-color bleeding (ICB), and are very effective methods for realizing not only high density but also high resolution.

However, in the method using these reaction processing liquids, the spread of ink on the surface of the paper is suppressed by the inter-liquid reaction, the dots are reduced, and the image is poorly filled. Therefore, it is necessary to print the ink at a high density. As a result, the ejection amount is increased, and not only the recording medium curls and creases but also the drying property is impaired. When the curl or curl occurs, the recording medium is deformed, so that not only the landing position of the ink droplet is shifted and the image quality is deteriorated, but also a paper jam is caused at the time of paper conveyance.
In addition, there is a problem that the deformed paper contacts the print head and damages the nozzle surface. In particular, when performing double-sided printing, the paper is transported inside the recording apparatus after printing on one side. Therefore, when a curl or a curl occurs, a paper jam or a landing position shift is likely to occur. Further, the slow drying causes contamination of the inner wall of the apparatus and the conveyance roller during conveyance inside the recording apparatus, which causes stains and offset of the printed matter.
JP 2002-79740 A JP 2001-199150 A

  An object of the present invention is to provide an ink jet ink set that exhibits a high image density with a smaller amount of ink shot, has excellent drying properties, and does not generate curl and curl, and an image forming method and an image forming apparatus using the same. is there.

That is, the present invention
<1> An inkjet ink set comprising an ink containing at least water, a coloring material and a water-soluble organic solvent, and a treatment liquid containing at least water, a water-soluble organic solvent and a surfactant, wherein the surfactant Is an inkjet ink set which is a polycyclic aromatic compound having an HLB value of 18 to 42 represented by the following general formula (1).

R ₁ —Ar—X ₁ M ₁ Formula (1)

(In the general formula (1), Ar represents a fused ring, R ₁ is a compound represented by an alkyl group having 2 to 10 carbon atoms. One general formula (1) is an anionic surfactant, X ₁ represents —CO ₂ ⁻ , —SO ₄ ^— or —PO ₄ ²⁻ , and M ₁ represents H ⁺ , Na ⁺ , K ⁺ , NH ⁴⁺ or organic amines.

  <2> The ink jet ink set according to <1>, wherein the treatment liquid further contains a surfactant represented by the following general formula (2).

_{R 2 - [Ar 1 (-X} 2 M 2) -Y] n -Ar 2 -X 3 M 3 formula (2)

(In General Formula (2), R ₂ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, Ar ₁ and Ar ₂ each independently represents an aromatic group, and Y represents —CH ₂ — or an oxygen atom. N represents an integer of 1 to 5. X ₂ M ₂ and X ₃ M ₃ each independently represent a hydrophilic group, and when the compound represented by the general formula (2) is a nonionic surfactant , X ₂ M ₂ and X ₃ M ₃ each independently represent a polyethylene oxide group or a polypropylene oxide group, and when the compound represented by the general formula (2) is an anionic surfactant, X ₂ and X ₃ are Each independently represents —CO ₂ ⁻ , —SO ₄ ^— or —PO ₄ ²⁻ , and M ₂ and M ₃ each independently represent H ⁺ , Na ⁺ , K ⁺ , NH ⁴⁺ or organic amines.)

  <3> The inkjet ink set according to <1>, wherein at least one of the surfactants is a nonionic surfactant having an HLB value of 6.5 to 10.

  <5> The inkjet ink set according to <1>, wherein the dot diameter formed with the same liquid amount satisfies (dot diameter of the treatment liquid)> (dot diameter of the ink).

<6> When the surface tension of the ink is γ ₁ and the surface tension of the treatment liquid is γ ₂ , γ ₁ ≦ 39 mN / m, γ ₂ ≦ 39 mN / m, and γ ₁ > γ ₂ It is an inkjet ink set as described in <1> which satisfy | fills that.

<7> The inkjet ink set according to <1>, wherein γ ₁ ≦ 35 mN / m, γ ₂ ≦ 30 mN / m, and γ ₁ > γ ₂ is satisfied.

<8> The inkjet ink set according to <1>, which satisfies 7 ≦ (γ ₂ ) / η ≦ 12 when the viscosity of the treatment liquid is η (cP).

  <9> The ink jet ink set according to <1>, wherein the treatment liquid further contains a flocculant having an action of aggregating at least one of the components contained in the ink.

  <10> The ink jet ink set according to <9>, wherein the flocculant is a polyvalent cation.

  <11> The ink jet ink set according to <9>, wherein the flocculant is an acidic substance or an alkaline substance.

  <12> The flocculant is the inkjet ink set according to <9>, which is an organic electrolyte.

  <13> The inkjet ink set according to <9>, wherein the flocculant is a polyamine.

<14> water, a coloring material and a water-soluble organic solvent contains at least further have other ink that does not cause aggregation by the aggregating agent, the surface tension of the other inks is taken as gamma _n, gamma _n The inkjet ink set according to <9>, satisfying that> γ ₂ .

  <15> The ink jet ink set according to <1>, wherein the treatment liquid further contains an anti-curl agent.

  <16> The anti-curl agent comprises trimethylolpropane, glycine, N, N-bis (hydroxyalkyl) glycine derivative, N, N-bis (hydroxyalkyl) -2-aminoethanesulfonic acid derivative and acetylethanolamine. The inkjet ink set according to <15>, which is at least one selected from the group.

  <17> The ink-jet ink set according to <1>, wherein the color material is a pigment.

  <18> The treatment liquid is the inkjet ink set according to <1>, further including a coloring material.

<19> an ink containing at least water, a coloring material and a water-soluble organic solvent, and a treatment liquid containing at least water, a water-soluble organic solvent and a surfactant, and at least one of the surfactants is Using an inkjet ink set that is a polycyclic aromatic compound having an HLB value of 18 to 42 represented by the following general formula (1), the ink and the treatment liquid are applied onto a recording medium so as to contact each other. An image forming method in which an image is formed, and a ratio of the treatment liquid discharge amount per unit area to the ink discharge amount is 1:20 to 1: 1.2.

R ₁ —Ar—X ₁ M ₁ Formula (1)

(In the general formula (1), Ar represents a fused ring, R ₁ is a compound represented by an alkyl group having 2 to 10 carbon atoms. One general formula (1) is an anionic surfactant, X ₁ represents —CO ₂ ⁻ , —SO ₄ ^— or —PO ₄ ²⁻ , and M ₁ represents H ⁺ , Na ⁺ , K ⁺ , NH ⁴⁺ or organic amines.

  According to the present invention, it is possible to provide an inkjet ink set excellent in image density, image resolution, and curl / curl, and an image forming method and an image forming apparatus using the ink jet ink set.

Hereinafter, the inkjet ink set, the image forming method, and the image forming apparatus of the present invention will be described in detail.
<Inkjet ink set>
The inkjet ink set of the present invention is an inkjet ink set having an ink containing at least water, a coloring material and a water-soluble organic solvent, and a treatment liquid containing at least water, a water-soluble organic solvent and a surfactant. At least one of the surfactants uses a polycyclic aromatic compound represented by the following general formula (1).

R ₁ —Ar—X ₁ M ₁ Formula (1)

(In General Formula (1), Ar represents a condensed ring, R ₁ represents an alkyl group having 2 to 10 carbon atoms, and X ₁ M ₁ represents a hydrophilic group. The compound represented by General Formula (1) is In the case of a nonionic surfactant, X ₁ M ₁ represents a polyethylene oxide group or a polypropylene oxide group. When the compound represented by the general formula (1) is an anionic surfactant, X ₁ is —CO ₂ ⁻ , -SO ₄ ^- or -PO ₄ ^2- represents, and M ₁ represents H ⁺ , Na ⁺ , K ⁺ , NH ^{4 +} or an organic amine.
In the present invention, a condensed ring refers to a ring in which two or more rings are united in a form sharing two (sometimes more) atoms.

  At least one of the surfactants contained in the treatment liquid according to the present invention is a polycyclic aromatic compound represented by the general formula (1). In general, since the additive added to the surface of plain paper is an inorganic material, it is desirable that the surfactant contained in the treatment liquid has a hydrophobic property. Increasing the number of carbons in the hydrophobic chain to increase the hydrophobicity of the surfactant and increasing the linearity of the surfactant results in a decrease in mobility in the solution, resulting in a lack of surface activity and a decrease in effectiveness. There is. Further, when a branched chain is added to the hydrophobic chain to increase the hydrophobicity, the mobility is not lost, but the permeability to the pores is increased by the branched structure. Accordingly, the penetration into the inside of the recording medium becomes larger than the spread of the treatment liquid on the recording medium, and the contribution to the spreading may be reduced.

  Introduction of a polycyclic structure is a technique that can change the molecular length and increase the number of carbon atoms in the hydrophobic portion. Although the behavior of molecules in the solvent has not been clarified, because of the polycyclic structure, the shape of the molecule is compact and excellent in mobility, and because it is highly hydrophobic, it is ejected as a droplet from the nozzle. In this case, it can be presumed that the liquid crystal can be quickly oriented at the gas-liquid interface of the droplets, and the spread of the treatment liquid immediately after landing on the recording medium is increased. Further, the presence of the ring structure provides an effect of suppressing excessive permeation into the recording medium, which is considered to be effective for curling and curling.

  In the general formula (1), specific examples of Ar include, for example, condensed hydrocarbons such as naphthalene structure, anthracene structure, pentalene structure, indene structure, and azulene structure, condensed heterocyclic rings such as indole structure, quinoline structure, and benzofuran structure. Is mentioned.

In the general formula (1), R ₁ represents an alkyl group having 2 to 10 carbon atoms, and X ₁ M ₁ represents a hydrophilic group. When the compound represented by the general formula (1) is a nonionic surfactant, X ₁ M ₁ represents a polyethylene oxide group or a polypropylene oxide group, and the compound represented by the general formula (1) is an anionic surfactant. In this case, X ₁ represents —CO ₂ ⁻ , —SO ₄ ^— or —PO ₄ ²⁻ , and M ₁ represents H ⁺ , Na ⁺ , K ⁺ , NH ⁴⁺ or organic amines.
The organic amine may be any of primary, secondary, tertiary and quaternary amines and salts thereof. Specific examples include tetraalkylammonium, alkylamine, benzalkonium, alkylpyridium, imidazolium, polyamine, and derivatives or salts thereof. Specifically, amylamine, butylamine, propanolamine, propylamine, ethanolamine, ethylethanolamine, 2-ethylhexylamine, ethylmethylamine, ethylbenzylamine, ethylenediamine, octylamine, oleylamine, cyclooctylamine, cyclobutylamine, cyclohexane Propylamine, cyclohexylamine, diisopropanolamine, diethanolamine, diethylamine, di-2-ethylhexylamine, diethylenetriamine, diphenylamine, dibutylamine, dipropylamine, dihexylamine, dipentylamine, 3- (dimethylamino) propylamine, dimethylethylamine, dimethyl Ethylenediamine, dimethyloctylamine, 1,3-dimethylbutylamine, dimethyl 1,3-propanediamine, dimethylhexylamine, amino-butanol, amino-propanol, amino-propanediol, N-acetylaminoethanol, 2- (2-aminoethylamino) -ethanol, 2-amino-2- Ethyl-1,3-propanediol, 2- (2-aminoethoxy) ethanol, 2- (3,4-dimethoxyphenyl) ethylamine, cetylamine, triisopropanolamine, triisopentylamine, triethanolamine, trioctylamine, Tritylamine, bis (2-aminoethyl) 1,3-propanediamine, bis (3-aminopropyl) ethylenediamine, bis (3-aminopropyl) 1,3-propanediamine, bis (3-aminopropyl) methylamine, Bis (2-ethylhexyl ) Amine, bis (trimethylsilyl) amine, butylamine, butylisopropylamine, propanediamine, propyldiamine, hexylamine, pentylamine, 2-methyl-cyclohexylamine, methyl-propylamine, methylbenzylamine, monoethanolamine, laurylamine, Nonylamine, trimethylamine, triethylamine, dimethylpropylamine, propylenediamine, hexamethylesidiamine, tetraethylenepentamine, diethylethanolamine, tetramethylammonium chloride, tetraethylammonium bromide, dihydroxyethyl stearylamine, 2-heptadecenyl-hydroxyethylimidazoline, lauryl Dimethylbenzylammonium chloride, cetylpyridinium mouth Ride, stearamide methylbiridium chloride, diallyldimethylammonium chloride polymer, diallylamine polymer, monoallylamine polymer and the like can be mentioned.
More preferably, triethanolamine, triisopropanolamine, 2-amino-2-ethyl-1,3-propanediol, ethanolamine, propanediamine, propylamine and the like are used.

  Among the polycyclic structures, naphthalene structure exhibits an excellent action. This is thought to be due to the large contribution of molecular shape. In other words, as the number of rings increases, the hydrophobicity increases but the mobility decreases, and as the number of carbon atoms constituting the ring increases, the hydrophobicity increases, but the polycyclic structure is distorted and the orientation at the interface is reduced. descend. As a result of the combination of these factors, it is assumed that the naphthalene structure is most effective.

The functional group added to the condensed ring includes a hydrophobic group (R ₁ ) and a hydrophilic group (X ₁ M ₁ ), and the hydrophobic group (R ₁ ) is preferably an alkyl group having 3 to 6 carbon atoms. . The longer the alkyl group, the higher the hydrophobicity and, conversely, the lower the mobility, so that the number of carbon atoms is an appropriate length.
In the case of a nonionic surfactant, the hydrophilic group (X ₁ M ₁ ) is a polyethylene oxide group or a polypropylene oxide group, and in the case of an anionic surfactant, it may be a carbonate, sulfate, or phosphate. Although desirable, it is more desirable to use an anionic surfactant in order to make the molecular shape compact and not reduce mobility. In view of hydrophilicity and safety, it is more preferable to use carbonate or sulfate.

Further, it is desirable that these hydrophobic group (R ₁ ) and hydrophilic group (X ₁ M ₁ ) are added to different rings. When a hydrophilic group or a hydrophobic group is added to the same ring, another ring exists in a direction away from the axial direction of the main chain with the hydrophilic group-hydrophobic group as an axis. It is because it becomes a factor which reduces mobility.

  Examples of the surfactant represented by the general formula (1) include 2-butyl naphthalene sulfonate Na, 2-butyl naphthalene carboxylate Na, 2-butyl naphthalene ethylene oxide adduct, 2-ethyl naphthalene sulfonate Na, Examples include 2-ethylnaphthalenecarboxylic acid Na, 2-ethylnaphthalene ethylene oxide adduct, 2-hexylnaphthalenesulfonic acid Na, 2-hexylnaphthalenecarboxylic acid Na, 2-hexylnaphthaleneethylene oxide adduct, and the like.

  The treatment liquid preferably further contains a surfactant represented by the following general formula (2).

_{R 2 - [Ar 1 (-X} 2 M 2) -Y] n -Ar 2 -X 3 M 3 formula (2)

In the general formula (2), R ₂ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, Ar ₁ and Ar ₂ each independently represent an aromatic group, and Y represents —CH ₂ — or an oxygen atom. , N represents an integer of 1-5. X ₂ M ₂ and X ₃ M ₃ each independently represent a hydrophilic group, and when the compound represented by the general formula (2) is a nonionic surfactant, X ₂ M ₂ and X ₃ M ₃ are respectively When independently representing a polyethylene oxide group or a polypropylene oxide group and the compound represented by the general formula (2) is an anionic surfactant, X ₂ and X ₃ are each independently —CO ₂ ⁻ , —SO ₄ ^—. Alternatively, -PO ₄ ^2- represents M ₂ and M ₃ each independently represents H ⁺ , Na ⁺ , K ⁺ , NH ^{4 +} or an organic amine.
The organic amine may be any of primary, secondary, tertiary and quaternary amines and salts thereof. Specific examples include tetraalkylammonium, alkylamine, benzalkonium, alkylpyridium, imidazolium, polyamine, and derivatives or salts thereof. Specifically, amylamine, butylamine, propanolamine, propylamine, ethanolamine, ethylethanolamine, 2-ethylhexylamine, ethylmethylamine, ethylbenzylamine, ethylenediamine, octylamine, oleylamine, cyclooctylamine, cyclobutylamine, cyclohexane Propylamine, cyclohexylamine, diisopropanolamine, diethanolamine, diethylamine, di-2-ethylhexylamine, diethylenetriamine, diphenylamine, dibutylamine, dipropylamine, dihexylamine, dipentylamine, 3- (dimethylamino) propylamine, dimethylethylamine, dimethyl Ethylenediamine, dimethyloctylamine, 1,3-dimethylbutylamine, dimethyl 1,3-propanediamine, dimethylhexylamine, amino-butanol, amino-propanol, amino-propanediol, N-acetylaminoethanol, 2- (2-aminoethylamino) -ethanol, 2-amino-2- Ethyl-1,3-propanediol, 2- (2-aminoethoxy) ethanol, 2- (3,4-dimethoxyphenyl) ethylamine, cetylamine, triisopropanolamine, triisopentylamine, triethanolamine, trioctylamine, Tritylamine, bis (2-aminoethyl) 1,3-propanediamine, bis (3-aminopropyl) ethylenediamine, bis (3-aminopropyl) 1,3-propanediamine, bis (3-aminopropyl) methylamine, Bis (2-ethylhexyl ) Amine, bis (trimethylsilyl) amine, butylamine, butylisopropylamine, propanediamine, propyldiamine, hexylamine, pentylamine, 2-methyl-cyclohexylamine, methyl-propylamine, methylbenzylamine, monoethanolamine, laurylamine, Nonylamine, trimethylamine, triethylamine, dimethylpropylamine, propylenediamine, hexamethylesidiamine, tetraethylenepentamine, diethylethanolamine, tetramethylammonium chloride, tetraethylammonium bromide, dihydroxyethyl stearylamine, 2-heptadecenyl-hydroxyethylimidazoline, lauryl Dimethylbenzylammonium chloride, cetylpyridinium mouth Ride, stearamide methylbiridium chloride, diallyldimethylammonium chloride polymer, diallylamine polymer, monoallylamine polymer and the like can be mentioned.
More preferably, triethanolamine, triisopropanolamine, 2-amino-2-ethyl-1,3-propanediol, ethanolamine, propanediamine, propylamine and the like are used.

In the compound of the general formula (2), the main chain having a structure in which aromatic groups are linked is easily oriented at the gas-liquid interface and has high wettability. In addition, since at least one of the aromatic groups has a polycyclic structure, the hydrophobicity of the molecule is increased and the dot diameter is increased, and it is particularly desirable to have a naphthalene structure. R ₂ has the effect of increasing the hydrophobicity of the hydrophobic part, but as the molecule becomes longer, the mobility is lowered and the effect as a surfactant is lowered. Therefore, a hydrogen atom or an alkyl chain having 1 to 5 carbon atoms is preferable. More preferably a hydrogen atom or an alkyl chain having 1 to 2 carbon atoms. The hydrophilic group is more preferably an anionic surfactant in order to make the molecular shape compact and not reduce mobility, and in view of hydrophilicity and safety, it is more preferable to use carbonates and sulfates. desirable.

  Examples of the compound of the general formula (2) include β-naphthalenesulfonic acid Na formalin condensate, butyl diphenyl ether disulfonic acid Na and the like.

  At least one of the surfactants is preferably a nonionic surfactant having an HLB (hydrophilic group / hydrophobic group balance) value of 6.5 to 10. Here, the value obtained by the Davis calculation method is used as the value of “HLB” in this specification. The method of calculating Davis is detailed in, for example, [“Introduction to New Surfactants” by Takehiko Fujimoto, published by Sanyo Chemical Industries, Ltd.]. More preferably, the HLB value is 6.5-8. In order to increase the spread of the treatment liquid on the recording medium, not only the wettability with cellulose but also the affinity with the additive on the recording medium is required. In general, since the additive added to the surface of plain paper is an inorganic material, it is desirable that the surfactant added to the treatment liquid has a hydrophobic property. Therefore, the surfactant in the above range is suitable.

At least one of the surfactants is preferably an anionic surfactant having an HLB value of 18 to 42. More preferably, it is 21-40. An anionic surfactant is also required to have an affinity for an inorganic material as in the case of a nonionic surfactant, and a surfactant having an HLB value in the above range is suitable.
In the present invention, the amount of surfactant added to the treatment liquid is preferably less than 10% by mass, more preferably 0.01% by mass to 5% by mass, and still more preferably 0.01% by mass to 3% by mass. % Is used in the range below.

  In the inkjet ink set of the present invention, it is preferable that the dot diameter formed with the same liquid amount satisfies (dot diameter of the treatment liquid)> (dot diameter of the ink). By using an ink set having such a configuration, the image area that can be formed per unit volume is larger for the processing liquid, and the amount of ink and processing liquid required for printing the processing liquid unit area is (the amount of processing liquid applied). ) <(Ink placement amount). Therefore, compared with the case where the dot diameter of the ink and the dot diameter of the treatment liquid are equal, the discharge amount necessary for printing of the unit area is reduced, and curling / curling of the recording medium can be suppressed.

Examples of a method for reducing the amount of treatment liquid to be applied include a thinning printing method and a drop modulation method, and these methods can be used in combination.
Normally, the processing liquid is printed at the same location as the ink printing unit, whereas in the thinning printing method, the processing liquid is printed on a part of the image forming unit that is thinned. Since the processing liquid spreads more than the ink, the image forming part can be filled even if thinning is performed, and even if the amount of driving is reduced, the original effects of the processing liquid such as high image density and high resolution are not lowered. Improved. The thinning used here can be changed according to image processing such as calculation using image coverage, brightness / saturation, character / photo edge processing, etc., in addition to a method using a staggered pattern or a filter of a certain pattern. .
Further, the drop modulation method is a method for reducing the amount of processing liquid applied to a portion where ink is ejected. Since the treatment liquid dot diameter is larger than the ink dot diameter, the image forming portion can be filled even if the discharge amount is reduced, and high image quality can be maintained and curling and curling can be suppressed.

  The measurement of the dot diameter of the treatment liquid and ink in the present invention was performed by the following method. Printing was performed by using a print head of a commercially available inkjet recording apparatus Work Center B900 (manufactured by Fuji Xerox Co., Ltd.) with an ejection device capable of arbitrarily changing the voltage and frequency applied to the head. The recording medium was C2 paper (Fuji Xerox Office Supply Co., Ltd.). The printed dots were observed with an optical microscope, and the dot diameter was measured. The ejection amount during printing was 13 picoliters.

  The Work Center B900 is a thermal ink jet recording apparatus, but the present invention is not limited to the recording system, and a piezo ink jet recording apparatus may be used.

In order for the ink and the treatment liquid to form an appropriate dot diameter on the recording medium, the surface tension γ _{1 of} the ink is γ ₁ ≦ 39 mN / m, and the surface tension γ _{2 of the} treatment liquid is γ ₂ ≦ It is preferably 39 mN / m and γ ₁ > γ ₂ . Furthermore, it is more preferable that γ ₁ ≦ 35 mN / m, γ ₂ ≦ 30 mN / m, γ ₁ ≦ 32 mN / m, and γ ₂ ≦ 29 mN / m.
By setting the surface tension of the ink and the treatment liquid within this range, the wettability of the ink and the treatment liquid is good, and the spread on the recording medium and the drying property are good. By setting γ ₁ > γ ₂ , it is possible to suppress the bleeding of ink to the processing liquid side. Further, since the surface tension is different, when the ink lands on the processing liquid printing portion, the contact angle of the ink droplet is increased and the reaction time of the ink-processing liquid is increased, so that the feathering is improved.

The wettability of the liquid on the recording medium is mainly discussed by the surface tension. However, when the wettability on the recording medium is considered by dividing into the penetration into the recording medium and the spreading on the recording medium, the liquid The behavior varies depending on the viscosity. When the viscosity is increased, the penetrating action into the pores is lowered, the penetrating power into the recording medium is lowered, and the spread is further increased. Conversely, at low viscosities, priority is given to penetration and spread is reduced. This phenomenon can be discussed in terms of γ / η, which is a parameter representing penetration. When the viscosity η (cP) increases, γ / η decreases, the penetrating power decreases, and the spread increases. The permeation parameter (γ ₂ / η) of the treatment liquid in the present invention is preferably 7 ≦ (γ ₂ / η) ≦ 12, and more preferably 8 ≦ (γ ₂ / η) ≦ 11.

  The treatment liquid preferably contains a flocculant having an action of aggregating at least one of the components contained in the ink. When the aggregating agent aggregates the components in the ink, excessive penetration of the ink into the recording medium and excessive spread on the surface of the recording medium can be suppressed, and image density and image resolution can be improved. The term “aggregation” as used herein may or may not involve a chemical reaction. The aggregating component may be a dispersion component such as a coloring material or an emulsion, or a water-soluble component such as a water-soluble polymer or a water-soluble polymerizable monomer. For example, although the coloring material and the emulsion are dispersed in a normal ink state, the dispersion state becomes unstable due to addition of an electrolyte, an acid-base reaction, and the like, and each particle can associate and aggregate. In addition, the dissolved substance can be precipitated by an acid-base reaction of a water-soluble polymer or a polymerization reaction of a water-soluble polymerizable monomer, and the precipitated substance itself can be aggregated or a colorant or emulsion can be incorporated and aggregated. it can.

The flocculant contained in the treatment liquid is preferably a polyvalent cation. The dispersed colorant and emulsion are easily aggregated by the addition of an electrolyte. In particular, the polyvalent cation has a large effect and is suitable for addition to the treatment liquid. Preferred polyvalent cations include Mg ²⁺ , Ca ²⁺ , Al ³⁺ , Zn ²⁺ , Cu ²⁺ , Fe ²⁺ , Mn ²⁺ , etc., from the viewpoint of water solubility, safety, cost, etc. Mg ²⁺ , Ca ²⁺ and Al ³⁺ are more preferable.
In addition, since the polyvalent cation has an effect of precipitating and aggregating the water-soluble polymer and can promote the aggregation of the coloring material and the emulsion, it is better to include a water-soluble polymer in the ink as an aggregation aid. . The water-soluble polymer used here preferably contains a monomer having a carboxylic acid group such as acrylic acid and methacrylic acid as one of the polymerization components, and the composition ratio (molar ratio) is 40% to 80%. Is desirable. Examples of water-soluble polymers include the John Cryl series manufactured by Johnson Polymer Co., Ltd., and copolymers of styrene, acrylic acid, methacrylic acid, acrylic esters, and methacrylic esters that can be synthesized at any component ratio.

  The flocculant contained in the treatment liquid may be an acidic substance or an alkaline substance. Many colorants, emulsions, and water-soluble polymers that can serve as coagulation aids in inks are stably dispersed and dissolved in basic solutions. By using a liquid, the above-mentioned components in the ink can be aggregated and deposited, and the image quality can be improved. In addition, when a compound that is stable in an acidic solution is used for the colorant, emulsion, and water-soluble polymer in the ink, a basic substance is added to the treatment liquid to obtain a basic treatment liquid. The above components can be aggregated and precipitated to improve the image quality. As an additive in the case of using such a method, in addition to organic acids such as hydrochloric acid, acetic acid, benzoic acid derivatives, pyrrolidone carboxylic acid derivatives, hydroxide salts such as sodium hydroxide, etc., generally used pH buffer materials are used. be able to.

  The flocculant contained in the treatment liquid may be an organic substance such as an organic electrolyte or polyamine. An aromatic electrolyte typified by a benzoic acid derivative has not only an action of supplying a cation as an electrolyte but also an action of inhibiting the dispersion stability of the pigment dispersion, and can improve the aggregation effect. This is presumably because the dispersion state of the pigment surface is destabilized because the aromatic ring is physically adsorbed on the pigment dispersion. The polyamine derivative not only acts as an electrolyte to agglomerate the dispersion, but also has a greater effect as an aggregating agent because the polyamine crosslinks the dispersion and acts as an agglomeration aid polymer.

The inkjet ink set of the present invention may further include other ink that contains at least water, a coloring material, and a water-soluble organic solvent and does not cause aggregation by the aggregating agent. In this case, it is preferable that γ _n > γ ₂ when the surface tension of the other ink is γ _n . By setting such a surface tension, it is possible to suppress color mixing between inks on the recording medium.

The inkjet ink set of the present invention may have one type of ink as the other ink, or may have two or more types of ink. When two or more kinds of inks are used as the other ink, the surface tension of each of the other inks and the surface tension of the ink preferably satisfy γ _n > γ ₂ , more preferably 50 mN / m> γ. _n > γ ₂

  The treatment liquid preferably further contains an anti-curl agent. When the treatment liquid contains an anti-curl agent, curling and curling can be further suppressed. Examples of the anti-curl agent include trimethylolpropane, glycine, N, N-bis (hydroxyalkyl) glycine derivative, N, N-bis (hydroxyalkyl) -2-aminoethanesulfonic acid derivative, and acetylethanolamine. At least one selected is preferred.

The coloring material used for the ink may be a dye or a pigment, but it is desirable to use a pigment when the coloring material is used as an aggregating component.
The pigment that can be used in the ink may be either an inorganic pigment or an organic pigment.
As the black pigment, carbon black pigments such as furnace black, lamp black, acetylene black and channel black are preferable. Raven 1080 ULTRA, Raven 1060 ULTRA, Raven 790 ULTRA, Raven 780 ULTRA, Raven 760 ULTRA (manufactured by Columbian Carbon), Regal 400R, Regal 330R, Regal 66 R, Mul L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400 (above, manufactured by Cabot Corporation), Color Black FW, Color 2 Black C, W2 , Color Black FW200, Color BlackS150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Printex 140V, Special 6P 4A, Special Black4 (manufactured by Degussa), No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. 2300, MCF88, MA600, MA7, MA8, MA100 (manufactured by Mitsubishi Chemical Corporation) and the like can be used.
As the black pigment, magnetic fine particles such as magnetite and ferrite, titanium black, and the like may be used.

  Examples of cyan pigments include 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.

  Examples of magenta pigments include C.I. I. Pigment Red5, C.I. I. Pigment Red7, C.I. I. Pigment Red 12, C.I. I. PigmentRed48, C.I. I. Pigment Red 48: 1, C.I. I. PigmentRed57, C.I. I. Pigment Red 112, C.I. I. Pigment Red122, C.I. I. Pigment Red 123, C.I. I. Pigment Red 146, C.I. I. Pigment Red168, C.I. I. Pigment Red 184, C.I. I. Pigment Red 202 or the like, but is not limited thereto.

  Examples of yellow pigments include 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-151, C.I. I. Pigment Yellow-154 and the like, but are not limited thereto.

  In addition to black, cyan, magenta and yellow primary color pigments, specific color pigments such as red, green, blue, brown and white, metallic luster pigments such as gold and silver, colorless extender pigments, plastic pigments, etc. May be used. Also, newly synthesized pigments may be used for the present invention.

  These pigments are dispersed in a solvent using a dispersant and used as a pigment dispersion. The dispersion method is a method in which a resin dispersant is physically adsorbed on a pigment, a method in which a resin dispersant and a pigment are bonded by a chemical bond (mainly covalent bond), a so-called polymer graft pigment, Examples of the method include, but are not limited to, a method of coating part or all of the pigment surface with a resin, represented by a microencapsulated pigment.

A self-dispersing pigment can also be used as the pigment. Examples of the self-dispersing pigment used in the present invention include pigments obtained by subjecting general pigments to surface modification treatment. For example, oxidation treatment with oxidizing agents (eg nitric acid, permanganate, dichromate, hypochlorite, ammonium persulfate, hydrogen peroxide, ozone, etc.), treatment with coupling agents such as silane compounds, polymer grafting Treatment, plasma treatment and the like.
Other than surface modification treatment, Cab-o-jet-200, Cab-o-jet-300, IJX-253, IJX-266, IJX-273, IJX-444, IJX-55 manufactured by Cabot Corporation, Orient Chemistry Commercially available self-dispersing pigments such as Microjet Black CW-1 and CW-2 manufactured by the company can also be used.

As the dye, commercially available acid dyes, reactive dyes, direct dyes, food dyes, basic dyes, disperse dyes, vat dyes, soluble vat dyes, reactive disperse dyes, oily dyes and the like can be used without any particular limitation. For example, C.I. I. Direct black-2, -4, -9, -11, -17, -19, -22, -32, -80, -151, -154, -168, -171, -194, -195; I. Direct Blue-1, -2, -6, -8, -22, -34, -70, -71, -76, -78, -86, -112, -142, -165, -199, -200, -201, -202, -203, -207, -218, -236, -287, -307; I. Direct Red-1, -2, -4, -8, -9, -11, -13, -15, -20, -28, 31, -33, -37, -39, -51, -59, -62, -63, -73, -75, -80, -81, -83, -87, -90, -94, -95, -99, -101, -110, -189, -227; I. Direct violet-2, -5, -9, -12, -18, -25, -37, -43, -66, -72, -76, -84, -92, -107; I. Direct Yellow-1, -2, -4, -8, -11, -12, -26, -27, -28, 333, -34, -41, -44, -48, -58, -86, -87, -88, -132, -135, -142, -144, -173; I. Food Black-1, -2; C.I. I. Acid Black-1, -2, -7, -16, -24, -26, -28, -31, -48, -52, -63, -107, -112, -118, -119, -121, -156, -172, -194, -208; I. Acid Blue-1, −7, −9, −15, −22, −23, −27, −29, −40, −43, −55, −59, −62, −78, −80, −81, -83, -90, -102, -104, -111, -185, -249, -254; I. Acid Red-1, -4, -8, -13, -14, -15, -18, -21, -26, -35, -37, -52, -110, -144. -180, -249, -257; I. Acid Yellow-1, -3, -4, -7, -11, -12, -13, -14, -18, -19, -23, -25, 34, -38, 41, -42 Examples include dyes such as −44, −53, −55, −61, −71, −76, −78, −79, and −122, but are not limited thereto.
In addition, the ink coloring material used in the present invention may be used by mixing a plurality of types, or may be used by mixing a dye and a pigment.

The color material contained in the ink is preferably used in a range of 0.1% by mass to 20% by mass, more preferably 1% by mass to 10% by mass. When the content of the color material is less than 0.1% by mass, there is a case where a sufficient optical density cannot be obtained, and when the content is more than 20% by mass, the liquid ejection characteristics are unstable. There was a case.
In addition, you may contain a coloring material in the said processing liquid as needed. In this case, the content of the color material contained in the treatment liquid is preferably 0.1% by mass or more and 20% by mass or less, and more preferably 1% by mass or more and 10% by mass or less. The following effects can be obtained by adding a coloring material to the treatment liquid.
That is, in the treatment liquid containing a color material, similarly to the treatment liquid not containing a color material, the color material in the ink is agglomerated by mixing with ink of other colors on the recording medium, and the optical density and bleeding. The image quality improvement effect such as is obtained. Furthermore, the treatment liquid containing the color material can be used as an ink as it is, and the ink necessary for forming an image and the liquid such as the treatment liquid as compared with the treatment liquid not containing the color material. It becomes possible to reduce the total number. As a result, the number of ink tanks and heads can be reduced, and as a result, the machine size and cost can be reduced.

Examples of the water-soluble organic solvent used in the ink and the treatment liquid in the present invention include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, Polyhydric alcohols such as glycerin, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, triethylene glycol monobutyl ether, propylene glycol Monobutyl ether, dipropylene glycol monobutyl ether, etc. Monohydric alcohol derivatives, nitrogen-containing solvents such as pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, alcohols such as ethanol, isopropyl alcohol, butyl alcohol, benzyl alcohol, or thiodiethanol, thiodiglycerol, sulfolane, dimethyl sulfoxide Sulfur-containing solvents such as propylene carbonate and ethylene carbonate can be used.
These water-soluble organic solvents may be used alone or in combination of two or more.
The content of the water-soluble organic solvent in the ink is not particularly limited, but is preferably 1 to 60% by weight of the total weight of the ink, and more preferably 5 to 40% by weight of the total weight of the ink. . The content of the water-soluble organic solvent in the treatment agent is not particularly limited, but is preferably 1 to 80% by weight of the total weight of the treatment agent, and more preferably 5 to 5% of the total weight of the treatment agent. 50% by weight.

In the present invention, the ink and the treatment liquid include cellulose derivatives such as polyethyleneimine, polyvinylpyrrolidone, polyethylene glycol, ethylcellulose, and carboxymethylcellulose for controlling the characteristics of the ink and the treatment liquid in addition to the above components. Other water-soluble polymers; polymer emulsions such as acrylic polymer emulsions and polyurethane emulsions; cyclodextrins, macrocyclic amines, dendrimers, crown ethers, urea and its derivatives, acetamide and the like can be added.
In addition, a pH buffer, an antioxidant, an antifungal agent, a viscosity modifier, a conductive agent, an ultraviolet absorber, a chelating agent, and the like can be added as necessary.

<Image forming method>
The image forming method of the present invention comprises an ink containing at least water, a coloring material and a water-soluble organic solvent, and a treatment liquid containing at least water, a water-soluble organic solvent and a surfactant, and the surfactant At least one of the above is an inkjet ink set which is a polycyclic aromatic compound represented by the following general formula (1), and is applied to a recording medium so that the ink and the treatment liquid are in contact with each other. The ratio of the treatment liquid discharge amount per unit area to the ink discharge amount is 1:20 to 1: 1.2.

R ₁ —Ar—X ₁ M ₁ Formula (1)

(In General Formula (1), Ar represents a condensed ring, R ₁ represents an alkyl group having 2 to 10 carbon atoms, and X ₁ M ₁ represents a hydrophilic group. The compound represented by General Formula (1) is In the case of a nonionic surfactant, X ₁ M ₁ represents a polyethylene oxide group or a polypropylene oxide group. When the compound represented by the general formula (1) is an anionic surfactant, X ₁ is —CO ₂ ⁻ , -SO ₄ ^- or -PO ₄ ^2- represents, and M ₁ represents H ⁺ , Na ⁺ , K ⁺ , NH ^{4 +} or an organic amine.

  In the treatment liquid according to the present invention, since the diameter of dots formed with the same liquid amount is larger than the dot diameter of ink, the discharge amount of the treatment liquid required for printing of unit area may be smaller than the discharge amount of ink. The smaller the amount of the treatment liquid ejected relative to the ink ejection amount, the more curling / caking is suppressed. However, when the amount is too small, the image is not completely filled with the treatment liquid, and the image density and image resolution are lowered. On the other hand, when the discharge amount of the processing liquid is large, the image density and the image resolution are good, but the curl and the kakuru deteriorate. The treatment liquid per unit area is in a state where both of these contradictory properties can be satisfied, that is, the image density and the image resolution are visually good levels, and the curl and curl of the recording medium is sufficiently suppressed. The ratio between the ejection amount and the ink ejection amount was in the range of 1:20 to 1: 1.2. A more preferred range is from 1:16 to 1: 2, more preferably from 1:10 to 1: 3.

The ink and the treatment liquid are applied on the recording medium so as to come into contact with each other. This is because when the ink and the processing liquid come into contact with each other, the ink aggregates, and the recording method is excellent in optical density, bleeding, intercolor bleeding, and drying time. There is no particular limitation on the mode in which the ink and the treatment liquid are in contact with each other. For example, the ink and the treatment liquid may be applied so as to be adjacent to each other, or may be applied so that one application region covers the other.
In addition, when applying to the recording medium, the order in which the ink and the treatment liquid are sequentially applied is arbitrary, but it is preferable to apply the ink after applying the treatment liquid. This is because the constituent components in the ink can be effectively aggregated by applying the treatment liquid first. Furthermore, since the flocculant contained in the processing liquid adheres to the recording medium, the penetration of the coloring material into the recording medium can be suppressed.
The ink may be applied at any time after the treatment liquid is applied, but the ink is preferably applied at a timing of 0.1 second or less after the treatment liquid is applied.

  As recording media applied to the present invention, in addition to plain paper such as P paper, Multiace, C2 paper (Fuji Xerox Office Supply), reproduction of Green 100, WR (Fuji Xerox Office Supply), etc. Paper is an example. It can also be used for thick paper such as postcards, and ink-jet paper such as coated paper and glossy paper having a coating layer on the surface.

<Image recording device>
The image recording apparatus of the present invention comprises an ink containing at least water, a coloring material and a water-soluble organic solvent, and a treatment liquid containing at least water, a water-soluble organic solvent and a surfactant, and the surfactant At least one of which is provided with a recording head for ejecting the ink and the treatment liquid in an inkjet ink set which is a polycyclic aromatic compound represented by the following general formula (1), The ratio of the treatment liquid discharge amount per area to the ink discharge amount is 1:20 to 1: 1.2.

R ₁ —Ar—X ₁ M ₁ Formula (1)

(In General Formula (1), Ar represents a condensed ring, R ₁ represents an alkyl group having 2 to 10 carbon atoms, and X ₁ M ₁ represents a hydrophilic group. The compound represented by General Formula (1) is In the case of a nonionic surfactant, X ₁ M ₁ represents a polyethylene oxide group or a polypropylene oxide group. When the compound represented by the general formula (1) is an anionic surfactant, X ₁ is —CO ₂ ⁻ , -SO ₄ ^- or -PO ₄ ^2- represents, and M ₁ represents H ⁺ , Na ⁺ , K ⁺ , NH ^{4 +} or an organic amine.

  The ratio of the treatment liquid discharge amount per unit area to the ink discharge amount is preferably 1:16 to 1: 2, and more preferably 1:10 to 1: 3.

Hereinafter, preferred embodiments of the ink jet recording apparatus of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.
FIG. 1 is a perspective view showing an external configuration of a preferred embodiment of an image forming apparatus according to the present invention. FIG. 2 is a perspective view showing the basic internal configuration of the image forming apparatus shown in FIG.
The recording apparatus 100 according to this embodiment has a configuration that operates based on the above-described image forming method (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. 100 includes a conveyance roller (conveying means) 2 for conveying the sheet 100 one by one, and an image forming unit 8 (image forming means) for forming an image by ejecting ink and processing liquid onto the surface of the recording medium 1. is doing.

The conveyance rollers 2 are a pair of rollers rotatably disposed in the image forming apparatus 100, sandwiching the recording medium 1 set on the tray 7 and one sheet of a predetermined amount of recording medium 1 at a predetermined timing. Each time it is transported into the apparatus 100.
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, an 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. Yes.
In this embodiment, the ink tank 5 has a plurality of ink tanks 52, 54, 56, and 58 in which inks corresponding to different colors and processing liquids are stored so as to be ejected.

  Further, as shown in FIG. 2, a power feeding signal cable 9 and an ink tank 5 are connected to the recording head 3, and when external image recording information is input to the recording head 3 from the power feeding signal cable 9, the recording head 3 sucks a predetermined amount of ink from each ink tank based on the image recording information and discharges the ink 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 the decompression device via the tube 15. Further, the maintenance unit 14 is connected to the nozzle portion of the recording head 3, and the nozzles of the recording head 3 are reduced by reducing the pressure in the nozzle of the recording head 3 with a vacuum pump (not shown) provided at the connecting portion. From the ink.
By providing the maintenance unit 14, it is possible to remove excess ink adhering to the nozzles when the recording apparatus 100 is in operation, or to suppress ink evaporation from the nozzles when the operation is stopped. it can. However, since the agglomerate may be generated by mixing the ink and the treatment liquid, the maintenance unit 14 configured to accommodate the ink and the treatment liquid separately is preferable.

  As the recording head, it is preferable to use a thermal ink jet method or a piezo ink jet method.

Hereinafter, the present invention will be described in more detail with reference to examples.
The following components were mixed and stirred, and then each treatment solution was prepared by filtration using a membrane filter having a pore size of 5 μm.

<Processing liquid 1>
Diethylene glycol 20% by mass
1,2-hexanediol 10% by mass
Magnesium nitrate hexahydrate 5% by mass
2-Butylnaphthalenesulfonic acid Na (HLB = 39.1) 1.5% by mass
Olfine E1010 (HLB = 7.5) 0.3% by mass
Pure water remaining

<Processing liquid 2>
Diethylene glycol 30% by mass
1,2-hexanediol 5% by mass
Magnesium nitrate hexahydrate 5% by mass
2-Butylnaphthalenesulfonic acid Na (HLB = 39.1) 1.0 mass%
Butyl diphenyl ether disulfonic acid Na (HLB = 76.8) 0.5 mass%
Pure water remaining

<Processing liquid 3>
Diethylene glycol 25% by mass
Butyl carbitol 3% by mass
Acetic acid 3% by mass
Sodium acetate 3% by mass
2-Butylnaphthalenesulfonic acid Na (HLB = 39.1) 1.5% by mass
Olfine E1010 (HLB = 7.5) 0.3% by mass
Pure water remaining

<Treatment liquid 4>
Diethylene glycol 20% by mass
1,2-hexanediol 10% by mass
Magnesium nitrate hexahydrate 5% by mass
2-Butylnaphthalenecarboxylic acid Na (HLB = 19.5) 1.5 mass%
Olfine E1010 (HLB = 7.5) 0.3% by mass
Pure water remaining

<Treatment liquid 5>
Diethylene glycol 20% by mass
1,2-hexanediol 10% by mass
Magnesium nitrate hexahydrate 5% by mass
2-ethylnaphthalenesulfonic acid Na (HLB = 40) 1.5 mass%
Olfine E1010 (HLB = 7.5) 0.3% by mass
Pure water remaining

<Treatment liquid 6>
Diethylene glycol 20% by mass
1,2-hexanediol 10% by mass
Magnesium nitrate hexahydrate 5% by mass
2- (2-Ethylhexyl) naphthalenesulfonic acid Na (HLB = 37.2)
1.5% by mass
Olfine E1010 (HLB = 7.5) 0.3% by mass
Pure water remaining

<Treatment liquid 7>
Diethylene glycol 30% by mass
Magnesium nitrate hexahydrate 5% by mass
Polyoxyethylene lauryl ether (EO number: 9, HLB = 6.17)
0.1% by mass
Pure water remaining

<Treatment liquid 8>
Diethylene glycol 20% by mass
Butyl carbitol 2% by mass
Magnesium nitrate hexahydrate 5% by mass
Pure water remaining

<Ink>
The following components were mixed, stirred, and then filtered using a membrane filter having a pore size of 5 μm to prepare an ink. The obtained ink had a surface tension of 33 mN / m, a viscosity of 2.3 cP, and a dot diameter of 89 μm.

Cab-O-Jet 300 6% by mass
Diethylene glycol 20% by mass
Olfin E1010 1% by mass
Water remaining

<Measurement of surface tension>
In an environment of 23 ° C. and 55% RH, the surface tension of the obtained ink and treatment liquid was measured using a Wilhelmy type surface tension meter (manufactured by Kyowa Interface Science Co., Ltd.). The obtained results are shown in Table 1.
<Viscosity>
Using Rheomatt 115 (manufactured by Contraves) as a measuring device, the viscosity of the obtained ink and treatment liquid was measured. The measurement was performed by placing the ink or the treatment liquid in a measurement container and mounting the ink or the treatment liquid on the apparatus by a predetermined method, at a measurement temperature of 23 ° C. and a shear rate of 1400 s ⁻¹ . The obtained results are shown in Tables 1 and 2.

<Dot diameter measurement>
Printing was performed using a print head of an ink jet recording apparatus Work Center B900 (manufactured by Fuji Xerox Co., Ltd.) with an ejection device capable of arbitrarily changing the voltage and frequency applied to the head. The recording medium was C2 paper (Fuji Xerox Office Supply Co., Ltd.). The printed dots were observed with an optical microscope, and the dot diameter was measured. The ejection amount during printing was 13 picoliters. In the case of a colorless processing liquid, since it is difficult to measure the dot diameter, C.I. I. Printing was performed after adding 0.1% by weight of Direct Blue 199 and coloring. The obtained results are shown in Tables 1 and 2.

<Print evaluation>
Printing evaluation was performed using Fuji Xerox's inkjet printer WorkCenter B900. The recording medium was C2 paper manufactured by Fuji Xerox Office Supply Co., and after the treatment liquid prepared above was underprinted, the ink prepared above was printed. The discharge amount per unit area of the treatment liquid and ink was 1: 4. The obtained results are shown in Tables 1 and 2.

<Image density>
The density of the obtained solid image part was measured with an optical density measuring device X-Rite MODEL 404 (manufactured by X-Rite) and evaluated according to the following criteria. The obtained results are shown in Tables 1 and 2.
-Evaluation criteria-
A: 1.40 or more.
○: 1.30 or more and less than 1.40.
Δ: 1.20 or more and less than 1.30.
X: Less than 1.20.

<Image resolution>
In a 400 dpi image, five straight lines each having a width of 4 dots were printed at intervals of 4 dots, and bleeding between the straight lines was observed. The obtained results are shown in Tables 1 and 2.
-Evaluation criteria-
A: There is no whisker-like oozing between straight lines, and the lines are drawn as independent straight lines.
○… Bearded exudation is seen between straight lines, but drawn as independent straight lines.
Δ: A whisker-like oozing is seen between the straight lines, and the straight lines are connected by the oozing.
X: Most of the space between the straight lines is filled with bleeding.

<Curl>
After image printing, the curls on both the left and right sides of the paper (C2 paper A4 size, manufactured by Fuji Xerox Office Supply Co.) discharged from the printer (inkjet printer WorkCenter B900 manufactured by Fuji Xerox) were measured. The paper was placed on a horizontal surface in an environment of 23 ° C. and 55% RH, and the lifted height of the paper edge after one day was measured. The evaluation pattern was created using application software PhotoShop (manufactured by Adobe). The image resolution is 400 dpi, out of a total of 4 dots of 2 vertical dots and 2 horizontal dots, with 1 dot being 100% black and the remaining 3 dots being a white background, this basic pattern is about 1100 in the vertical direction. This is an evaluation pattern in which about 830 pieces are arranged in the horizontal direction and printed on the entire surface of the paper. The obtained results are shown in Tables 1 and 2.

-Evaluation criteria-
A: Lifting height is less than 2 mm.
○: Lifting height is 2 mm or more and less than 5 mm.
Δ: Lifting height is 5 mm or more and less than 10 mm.
X: Lifting height is 10 mm or more.

<Kakuru>
After the image was shot, the paper discharged from the printer was visually observed for wrinkles and irregularities. The obtained results are shown in Tables 1 and 2.
-Evaluation criteria-
A: There are no wrinkles and unevenness.
○: Wrinkles and irregularities are seen, but the raised height of the convex part is less than 1 mm.
(Triangle | delta): A wrinkle and an unevenness | corrugation are conspicuous, and the raised height of a convex part is 1 mm or more and less than 2 mm.
X: Wrinkles and irregularities are conspicuous, and the raised height of the convex portions is 2 mm or more.

<Drying>
Coated paper (high grade GCAA0002 manufactured by Fuji Xerox Co., Ltd.) is overlaid on the obtained solid image portion, and a load of 100 g / cm ² is applied from above to measure the time until ink is not transferred to the overlaid paper. Then, the drying property of the ink was evaluated according to the following criteria. The obtained results are shown in Tables 1 and 2.
A: Less than 1 second.
○: 1 second or more and less than 3 seconds.
Δ: 3 seconds or more and less than 10 seconds.
X: 10 seconds or more.

  As is clear from Tables 1 and 2, the ink-jet ink set of the present invention is excellent in drying property and does not generate curl and kakuru. Furthermore, the inkjet ink set of the present invention is excellent in image density and image resolution.

1 is a perspective view showing an external configuration of a preferred embodiment of an ink jet recording apparatus according to the present invention. FIG. 2 is a perspective view showing an internal basic configuration of the ink jet recording apparatus of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Recording medium 2 Conveyance roller 3 Recording head 5 Ink tank 6 External cover 7 Tray 8 Image formation part 9 Power supply signal cable 10 Carriage 11 Guide rod 12 Timing belt 13 Drive pulley 14 Maintenance unit 15 Tube

Claims (18)

An ink containing at least water, a coloring material and a water-soluble organic solvent;
A treatment liquid containing at least water, a water-soluble organic solvent, and a surfactant;
An inkjet ink set, wherein at least one of the surfactants is a polycyclic aromatic compound having an HLB value of 18 to 42 represented by the following general formula (1).
R ₁ —Ar—X ₁ M ₁ Formula (1)
(In the general formula (1), Ar represents a condensed ring, R ₁ represents an alkyl group having 2 to 10 carbon atoms. The compound represented by the general formula (1) is an anionic surfactant, and X ₁ Represents —CO ₂ ⁻ , —SO ₄ ^— or —PO ₄ ²⁻ , and M ₁ represents H ⁺ , Na ⁺ , K ⁺ , NH ⁴⁺ or organic amines. The inkjet ink set according to claim 1, wherein the treatment liquid further contains a surfactant represented by the following general formula (2).
_{R 2 - [Ar 1 (-X} 2 M 2) -Y] n -Ar 2 -X 3 M 3 formula (2)
(In General Formula (2), R ₂ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, Ar ₁ and Ar ₂ each independently represents an aromatic group, and Y represents —CH ₂ — or an oxygen atom. N represents an integer of 1 to 5. X ₂ M ₂ and X ₃ M ₃ each independently represent a hydrophilic group, and when the compound represented by the general formula (2) is a nonionic surfactant , X ₂ M ₂ and X ₃ M ₃ each independently represent a polyethylene oxide group or a polypropylene oxide group, and when the compound represented by the general formula (2) is an anionic surfactant, X ₂ and X ₃ are Each independently represents —CO ₂ ⁻ , —SO ₄ ^— or —PO ₄ ²⁻ , and M ₂ and M ₃ each independently represent H ⁺ , Na ⁺ , K ⁺ , NH ⁴⁺ or organic amines.)   The inkjet ink set according to claim 1, wherein at least one of the surfactants is a nonionic surfactant having an HLB value of 6.5 to 10.   2. The inkjet ink set according to claim 1, wherein dot diameters formed with the same liquid amount satisfy (dot diameter of the treatment liquid)> (dot diameter of the ink). When the surface tension of the ink is γ ₁ and the surface tension of the treatment liquid is γ ₂ , γ ₁ ≦ 39 mN / m, γ ₂ ≦ 39 mN / m, and γ ₁ > γ ₂ The inkjet ink set according to claim 1, wherein The inkjet ink set according to claim 1, wherein γ ₁ ≦ 35 mN / m, γ ₂ ≦ 30 mN / m, and γ ₁ > γ ₂ are satisfied. _2. The inkjet ink set according to claim 1, wherein when the viscosity of the treatment liquid is η (cP), 7 ≦ (γ ₂ ) / η ≦ 12 is satisfied.   The inkjet ink set according to claim 1, wherein the treatment liquid further contains a flocculant having an action of aggregating at least one component contained in the ink.   The inkjet ink set according to claim 8, wherein the flocculant is a polyvalent cation.   The inkjet ink set according to claim 8, wherein the flocculant is an acidic substance or an alkaline substance.   The inkjet ink set according to claim 8, wherein the flocculant is an organic electrolyte.   The inkjet ink set according to claim 8, wherein the flocculant is a polyamine. When the ink further includes other ink that contains at least water, a coloring material, and a water-soluble organic solvent and does not cause aggregation by the flocculant, and γ _n is the surface tension of the other ink, γ _n > γ ₂ The inkjet ink set according to claim 8, satisfying that   The inkjet ink set according to claim 1, wherein the treatment liquid further contains an anti-curl agent.   The anti-curl agent is selected from the group consisting of trimethylolpropane, glycine, N, N-bis (hydroxyalkyl) glycine derivative, N, N-bis (hydroxyalkyl) -2-aminoethanesulfonic acid derivative and acetylethanolamine. The inkjet ink set according to claim 14, which is at least one kind.   The inkjet ink set according to claim 1, wherein the color material is a pigment.   The inkjet ink set according to claim 1, wherein the treatment liquid further contains a color material. An ink containing at least water, a coloring material, and a water-soluble organic solvent; and a treatment liquid containing at least water, a water-soluble organic solvent, and a surfactant. At least one of the surfactants is represented by the following general formula: Using an inkjet ink set that is a polycyclic aromatic compound having an HLB value of 18 to 42 represented by (1), an image is formed on a recording medium so that the ink and the treatment liquid are in contact with each other. An inkjet recording method to be formed,
An image forming method in which a ratio of the treatment liquid discharge amount and the ink discharge amount per unit area is 1:20 to 1: 1.2.
R ₁ —Ar—X ₁ M ₁ Formula (1)
(In the general formula (1), Ar represents a condensed ring, R ₁ represents an alkyl group having 2 to 10 carbon atoms. The compound represented by the general formula (1) is an anionic surfactant, and X ₁ Represents —CO ₂ ⁻ , —SO ₄ ^— or —PO ₄ ²⁻ , and M ₁ represents H ⁺ , Na ⁺ , K ⁺ , NH ⁴⁺ or organic amines.

Images