JP4111104B2 - Reaction liquid, ink set, and ink jet recording method - Google Patents

Description

The present invention relates to a reaction solution used for the purpose of improving image quality in inkjet recording,
The present invention also relates to an ink set and an ink jet recording method using the same.

The ink jet recording method is a printing method in which an image is recorded by ejecting ink droplets from a recording head and attaching the ink to a recording medium such as paper. Ink for ink-jet recording is generally water-based ink in which a dye-based or pigment-based color material is dissolved or dispersed in an aqueous medium, and is roughly classified into dye ink and pigment ink. Up to now, dye inks with excellent color reproducibility of recorded images have been widely used. However, preservability of recorded images is regarded as important due to the expansion of applications such as digital photography services and commercial printing of inkjet recording technology. As a result, pigment inks that are superior in water resistance and light resistance of recorded images compared to dye inks are being used.

In general, pigment inks are inferior in image density (color development) of recorded images as compared to dye inks, and have a problem in abrasion resistance. In other words, image formation with dye ink is performed by the coloring material (dye) in the dye ink applied on the recording medium penetrating into the recording medium, thereby dyeing the recording medium. In the image formation with the pigment ink, the coloring material (pigment) in the pigment ink applied on the recording medium remains on the recording medium (the pigment has a larger particle size than the dye,
Because it is made by the coloring of this pigment itself,
Compared to dye ink images, pigment ink images have insufficient image density and are likely to have a difference in color due to irregular reflection of incident light. The pigment may peel off even by friction. Therefore, in ink jet recording using pigment ink, how to increase image density and abrasion resistance is an important technical issue.

Conventionally, as an ink jet recording method for obtaining a high-quality color image having a high image density and no bleeding, a reaction liquid containing an ink and an aggregating agent that instantaneously aggregates color material components in the ink (improved printability) A method using two liquids is also known. Various kinds of flocculants can be used. For example, polyvalent metal salts such as magnesium salts (see Patent Document 1), cationic polymers such as polyallylamine and polyamine sulfonates (Patent Documents 2 to 9). For example). The method using these two liquids is particularly effective for plain paper (general office paper, offset coated printing paper, etc.) that has not been provided with characteristics suitable for the ink jet recording method. According to this method, A high-quality color image can be obtained with relatively inexpensive plain paper without using expensive and special ink-jet paper.
JP 2001-1627 A JP-A-8-104000 JP-A-8-216388 JP-A-8-281929 JP-A-9-277507 Japanese Patent Laid-Open No. 10-166559 Japanese Patent Laid-Open No. 10-226057 Japanese Patent Laid-Open No. 10-146991 Japanese Patent Laid-Open No. 10-151772

According to the ink jet recording method using the two liquids as described above, it is considered that the disadvantages of the pigment ink described above can be solved and the features can be fully utilized. However, when ink jet recording is performed using a pigment ink and a conventional reaction liquid in combination, although improvement in image density is observed, there is no improvement in abrasion resistance, and the recorded image is rub-resistant with pigment ink. Sex remains a problem. Therefore, in order to improve the abrasion resistance, a method of adding a resin as a fixing agent for the pigment to the recording medium in the ink or the reaction liquid can be considered. However, even when polyallylamine or the like is used as the sticking agent, for example, such sticking agent penetrates into the interior of the recording medium without remaining on the surface of the recording medium, and has almost no effect on improving the abrasion resistance. In consideration of such penetration into the recording medium, if a large amount of fixing agent is contained in the ink or the reaction liquid, various physical properties such as viscosity change greatly, and the storage stability and ejection stability of the ink are improved. There is a risk that inconveniences such as clogging of the discharge port of the recording head and bending of the flight may occur.

Therefore, the object of the present invention is most suitable for ink jet recording using water-based pigment ink, and even if plain paper such as general office paper or coated printing paper is used as a recording medium, the image density is high, there is no bleeding, and the abrasion resistance is high. Another object of the present invention is to provide a reaction liquid capable of providing a high-quality image with excellent properties, an ink set using the same, and an ink jet recording method.

As a result of various investigations on the optimum reaction solution for ink jet recording using an aqueous pigment ink, the present inventor has focused on the viscosity characteristic (thixotropic property) of an aqueous hydroxyalkyl cellulose solution, which improves the abrasion resistance of an image by the aqueous pigment ink. We obtained the knowledge that it is effective.

The present invention has been made on the basis of the above findings, and contains at least a pigment as a colorant and has a surface tension of 25 to 50 mN / m in combination with a water-based ink having a surface tension of 20 to 50 mN / m. an inkjet recording the reaction solution on the at least a polyvalent metal salt, containing (cationized) hydroxyethyl cellulose and water, the surface tension, much larger than the average value of the surface tension of the aqueous ink, the The object is achieved by providing a reaction liquid characterized in that the difference is in the range of 5 to 25 mN / m .

The present invention also provides an ink set for ink jet recording comprising the above reaction liquid and an aqueous ink containing at least a pigment as a colorant and having a surface tension in the range of 20 to 50 mN / m .

The present invention also relates to an ink jet recording method using the above reaction liquid and an aqueous ink containing at least a pigment as a colorant and having a surface tension in the range of 20 to 50 mN / m , or the above ink set, and a recording medium And providing the reaction liquid and the water-based ink on the recording surface so that the reaction liquid and the water-based ink are brought into contact with each other on the recording surface. .

According to the present invention, the ink aggregating ability of the ink aggregating agent such as a polyvalent metal salt contained in the reaction liquid provides a high image density and high image quality without bleeding, and the reaction liquid as a pigment fixing agent. Due to the action of the hydroxyalkyl cellulose contained therein, the abrasion resistance of the recorded image by the pigment ink can be greatly improved. When polyolefin resin particles are further contained in the reaction solution, the rub resistance of the recorded image can be further improved. Further, since the reaction liquid and ink set of the present invention are selected from hydroxyalkyl cellulose that can provide a sufficient effect of improving abrasion resistance with a minimum content as a pigment fixing agent, this type of fixing agent is used. The storage stability and the discharge stability, which are feared by the inclusion, are suppressed, and even if the reaction liquid is discharged from the recording head, there is little possibility of causing inconveniences such as clogging and flight bending.
Further, by making the surface tension of the reaction liquid larger than the average value of the surface tension of the ink used in combination with the reaction liquid, the disadvantages observed in the conventional ink jet recording method using two liquids, for example,
It is possible to effectively prevent a shift in dot formation position, a decrease in dot roundness, and the like, and a high-definition image with no noticeable graininess can be obtained. The present invention is particularly effective when color ink jet recording is performed on plain paper using an aqueous pigment ink. In this case, in combination with the good characteristics of the pigment ink such as water resistance and light resistance. As a result, the image quality is good and the image is hardly deteriorated over a long period of time, and an image excellent in storage stability can be obtained.

Hereinafter, first, the reaction solution of the present invention will be described. The reaction liquid of the present invention contains an ink flocculant, hydroxyalkyl cellulose and water as essential components.

The ink aggregating agent has a function of destroying the dispersed state of the colorant and other components in the ink and aggregating them, and a polyvalent metal salt is preferably used. The polyvalent metal salt is a water-soluble salt composed of a divalent or higher polyvalent metal ion and an anion bonded thereto. Specific examples of polyvalent metal ions include Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ²⁺ , Zn ²⁺ , Ba ²⁺ , F
e ^2+, divalent metal ions such as Zr ²⁺ or the ^{like, Al 3+, Fe 3+, Cr} 3+, Zr 3+, include trivalent or higher metal ions such as Zr ^4+. On the other hand, specific examples of anions include Cl ⁻ , NO ₃ ^−.
, I ⁻ , Br ⁻ , ClO ₃ ⁻ , CH ₃ COO ⁻ , F ⁻ , SO ₄ ²⁻ , SO ₃ ^{2− and the} like. The water-soluble polyvalent metal salt may be an anhydride or a hydrate.

Among them, a metal salt composed of Mg ²⁺ , especially magnesium sulfate (MgSO ₄ )
Gives favorable results from the four viewpoints of the quality of the obtained recorded matter, the influence on the recording head (corrosion), safety (toxicity), and cost.

In addition, a cationic polymer can be used as the ink aggregating agent. As the ink aggregating agent, both the polyvalent metal salt and the cationic polymer may be contained in the reaction solution. Examples of the cationic polymer include polyallylamine, polyamine sulfonate,
Polyallylamine hydrochloride and the like, and Japanese Patent Application Laid-Open No. 10-1209 related to the earlier application of the present applicant.
Those described in [0076] and [0077] of No. 56 are also preferably used in the present invention.

What is necessary is just to adjust suitably content of the said ink flocculent so that a predetermined effect may be acquired, Preferably it is 0.5 to 20 weight% with respect to the said reaction liquid. When the content of the ink aggregating agent is less than 0.5% by weight, the effect of improving image quality such as image density is poor, and when it exceeds 20% by weight, the storage stability and ejection stability are lowered, and the components of the recording head are deteriorated. There is a risk of corrosion.

The hydroxyalkyl cellulose acts mainly as a fixing agent for improving the fixing property of a color material (pigment) on a recording medium, and is an essential component for improving the abrasion resistance of a recorded image. The reaction liquid containing hydroxyalkyl cellulose as a fixing agent has an appropriate thixotropy and the apparent viscosity increases immediately after being applied on the recording medium, so that the fixing agent penetrates into the recording medium. Can be effectively suppressed, and a resin component such as a dispersant in the ink contacted on the recording medium is taken in as a protective colloid, so that excellent abrasion resistance can be exhibited. Further, since this reaction liquid does not need to consider the generation of a sticking agent that penetrates into the recording medium and hardly contributes to the development of abrasion resistance, it is not necessary to add a sticking agent more than necessary, and as an ink jet recording liquid It has the necessary storage stability and ejection stability. By the way, carboxyalkyl cellulose (for example, carboxymethyl cellulose, CMC), which is also a cellulose resin, may react with the polyvalent metal salt (ink flocculant) to gel the reaction solution. It is not preferable to contain it.

Examples of the hydroxyalkyl cellulose include hydroxyethyl cellulose (
HEC), hydroxymethyl cellulose (HMC), cationized products thereof, and the like, and one of these can be used alone or in combination of two or more thereof in the reaction solution. Among these, cationized HEC is preferably used in the present invention.

The hydroxyalkyl cellulose is preferably 0.01 to 10 with respect to the reaction solution.
It is contained in the reaction solution so as to be 0.1% by weight, more preferably 0.1 to 0.8% by weight. If the content of hydroxyalkyl cellulose is less than 0.01% by weight, the effect of improving the abrasion resistance of the recorded image is poor, and if it exceeds 10% by weight, the thixotropy increases due to an increase in viscosity, which may cause ejection failure in the recording head. is there.

In the reaction liquid of the present invention, in addition to the above ink flocculant and hydroxyalkyl cellulose,
Furthermore, it is preferable to contain polyolefin resin particles. Thereby, the abrasion resistance of the recorded image can be further improved. Examples of polyolefin resin particles include:
Examples include wax emulsions such as AQUACER series and CERAFLOUR series manufactured by Big Chemie Japan. Among these, those having a minimum film-forming temperature (MFT) exceeding the drying temperature (paper surface temperature) at the time of forced drying of the recording medium after application of the reaction liquid or ink are preferable. Although it depends, what is in the range of 90-130 degreeC is preferable. Examples of such wax emulsions include AQUACER 531 and AQUA.
Nonionic wax emulsions such as CER513 are exemplified.

The polyolefin resin particles preferably have an average particle diameter of 200 nm or less from the viewpoint of stably discharging the reaction liquid from the recording head.

The polyolefin resin particles are preferably contained in the reaction solution at a ratio of 1 to 10% by weight with respect to the reaction solution. If the content of the polyolefin resin particles is less than 1% by weight, there is no effect in improving the abrasion resistance of the recorded image, and if it exceeds 10% by weight, there is a possibility that a problem occurs in stable ejection from the recording head.

In addition to the ink flocculant, hydroxyalkyl cellulose, polyolefin resin particles and water described above, the reaction liquid of the present invention usually contains a high-boiling organic solvent, a low-boiling organic solvent, an interface for moisturizing and adjusting the penetration. An activator is included.

Examples of the high boiling point organic solvent include ethylene glycol, diethylene glycol,
Polyhydric alcohols such as triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, butylene glycol, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, trimethylolethane, trimethylolpropane; ethylene glycol Alkyl ethers of polyhydric alcohols such as monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether , Urea, 2-pyrrolidone, N-methyl-2-pi Pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and triethanolamine. The high boiling point organic solvent is particularly effective in preventing the reaction liquid from drying and preventing the recording head from being clogged. Although content of a high boiling point organic solvent is not specifically limited, Preferably it is 1 to 50 weight% with respect to the said reaction liquid, More preferably, it is 5 to 30 weight%.

Examples of the low-boiling organic solvent include methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol, sec-butanol, tert-
Examples include butanol, iso-butanol, and n-pentanol. The low boiling point organic solvent has an effect of shortening the drying time of the reaction solution. Although content of a low boiling point organic solvent is not specifically limited, Preferably it is 1 to 50 weight% with respect to the said reaction liquid, More preferably, it is 5 to 30 weight%.

Examples of the surfactant include anionic surfactants such as sodium dodecylbenzenesulfonate, sodium laurate, ammonium salt of polyoxyethylene alkyl ether sulfate; polyoxyethylene alkyl ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan Nonionic surfactants such as fatty acid esters, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl amines, polyoxyethylene alkyl amides; Surfynol 82, 104, 440, 465, 485 (above, Air Products and Chemicals), Olfin STG, Olfin E1
Acetylene glycol surfactants such as 010 (manufactured by Nissin Chemical Co., Ltd.); BYK347,
Silicone surfactants such as 348 (manufactured by Big Chemie Japan); cationic surfactants; amphoteric surfactants and the like. The surfactant is effective for adjusting the wettability (surface tension) of the reaction solution. The content of the surfactant is usually 0.01 to the reaction solution.
About 20% by weight.

In the reaction solution of the present invention, in addition to the above-described components, a viscosity adjuster, a pH adjuster, an antiseptic, an antioxidant, an ultraviolet absorber, a light stabilizer, a quencher, an antifungal agent, and an antiseptic as necessary. Various known additives such as an antifoaming agent and an antifoaming agent can be contained.

In addition to the composition as described above, the reaction liquid of the present invention has a surface tension that is the same as that of the aqueous ink used in combination with the reaction liquid from the viewpoint of obtaining a high-definition image with no noticeable graininess. mean value (if an aqueous ink to be used together is one color measurement surface tension of the aqueous ink) has come larger <br/> than. When ink jet recording is performed using the two liquids of the reaction liquid and the ink, a large amount of liquid is applied on the recording medium in a short time. Therefore, a plain paper having poor ink absorbability is used as the recording medium. When used, a large amount of ink or reaction liquid remains on the recording medium immediately after recording, and these flow, causing the dot formation position to deviate from the original position (droplet landing position) or to be true. There is a possibility that the dot shape, which should be circular, may be disturbed, or the adjacent dots may stick together and spread. As described above, the surface tension of the reaction liquid is more than the surface tension of the ink used in combination with this. It is possible to avoid such a problem.

From the viewpoint of more surely achieving the above effect, the difference between the surface tension of the reaction solution and the average value is preferably in the range of 5 to 25 mN / m.

In addition, the surface tension itself of the reaction solution is within a range of 25 to 50 mN / m from the viewpoint of ensuring ejection stability and enhancing the permeability to the inside of the recording medium to improve the drying property of the recording medium immediately after recording. Preferably there is. The surface tension can be adjusted by appropriately adjusting the type and content of the surfactant.

Next, the ink used in combination with the reaction liquid in the present invention will be described. The ink according to the present invention is a water-based ink (water-based pigment ink) containing at least a pigment as a coloring material.
The content of the pigment is usually about 0.5 to 30% by weight with respect to the aqueous ink. Examples of the pigment include inorganic pigments such as carbon black produced by a known method such as titanium oxide and iron oxide, a contact method, a furnace method, and a thermal method; an azo pigment (azo lake,
Insoluble azo pigments, condensed azo pigments, chelate azo pigments, etc.), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments) Etc.), dye chelates (for example, basic dye chelates, acidic dye chelates, etc.), organic pigments such as nitro pigments, nitroso pigments, and aniline black. As the organic pigment, conventionally known organic pigments having a chromatic color tone such as cyan, magenta, yellow, red, green, and blue can be used without any distinction. These chromatic organic pigments may be used in combination.

The pigment may be a so-called self-dispersing pigment (also called a surface-modified pigment) that can be dispersed and / or dissolved in an aqueous medium to which a dispersant such as a water-soluble resin is not added or added in a very small amount. Non-type pigments (resin dispersed pigments) may be used. The self-dispersing pigment preferably has an anionic group bonded to the pigment particle surface. As this anionic group, for example, —COOM, —SO ₃ M, —PO ₃ HM, —PO ₃ M ₂ (wherein, M represents a hydrogen atom, an alkali metal, ammonium, or organic ammonium), etc. Can be mentioned.

When using a resin-dispersed pigment, together with the resin-dispersed pigment, as a dispersant, an anionic surfactant such as a higher fatty acid salt or higher alcohol sulfate, or an anionic polymer such as polyacrylate It is preferable to use an anionic group-containing substance in combination. When a dispersant having no anionic group is used, an anionic compound is preferably contained in the ink. Of course, an anionic group-containing substance may be used as a dispersant, and an anionic compound other than this may be further contained.

By contacting the aqueous pigment ink containing such an anionic compound and the reaction liquid of the present invention on a recording medium, cations derived from the ink flocculant contained in the reaction liquid,
The self-dispersing pigment or the anionic group of the dispersant instantaneously forms an aggregate by ionic interaction, thereby realizing a high image density.

As the dispersant contained in the water-based ink, any water-soluble resin can be used, but the weight average molecular weight is preferably in the range of 1,000 to 30,000,
More preferably, it is in the range of 3,000 to 15,000. Specifically, hydrophobic monomers such as styrene, styrene derivatives, vinyl naphthalene, vinyl naphthalene derivatives, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, or acrylic acid, acrylic acid derivatives, maleic Block copolymer, graft copolymer or random copolymer comprising two or more monomers selected from acids, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, These salts are mentioned. These resins are alkali-soluble resins that are soluble in an aqueous solution in which a base is dissolved. Further, it may be a homopolymer composed of a hydrophilic monomer, or a salt thereof. In addition, water-soluble resins such as polyvinyl alcohol, carboxymethyl cellulose, and naphthalene sulfonic acid formaldehyde condensate can also be used. The dispersant is usually 0 in terms of solid content with respect to the pigment.
. It is contained in the water-based ink at a ratio of 1 to 10% by weight.

The water-based ink according to the present invention includes, as necessary, a high-boiling organic solvent, a low-boiling organic solvent, a surfactant, a viscosity modifier, pH, in addition to the above-described pigment, water for dispersing the same, and a dispersant. Various additives such as a regulator, a preservative, and an antioxidant can be contained. About these, the thing similar to what can be used for the reaction liquid mentioned above can be used.

As the ink set for ink jet recording, an ink set composed of the reaction liquid and the aqueous pigment ink described above can be used. The aqueous pigment ink constituting the ink set is not particularly limited, and may be one color or two or more colors. For example, an ink set composed of a combination of the reaction solution and water-based pigment inks of four colors of cyan, magenta, yellow, and black can be used.

In the ink set, for the reasons described above, the surface tension of the reaction liquid is the average value of the surface tension of the aqueous pigment ink (when the aqueous pigment ink used is one color, the measured value of the surface tension of the aqueous pigment ink). not larger than. A particularly preferable ink set has a surface tension of the reaction liquid of 2 in addition to the surface tension of the reaction liquid being larger than the average surface tension of the aqueous pigment ink.
The surface tension of the aqueous pigment ink is in the range of 5 to 50 mN / m (if the ink set has multiple color aqueous pigment inks, the surface tension of all aqueous pigment inks) itself is 20 to 50 mN / m.
m, and the difference between the surface tension of the reaction solution and the average value is in the range of 5 to 25 mN / m. Such an ink set is excellent in the ejection stability from the recording head, and is less likely to cause clogging, flying bending, etc., and can provide a recorded image with good image quality.

Next, the ink jet recording method of the present invention using the reaction liquid and the aqueous pigment ink or the ink set will be described.

The inkjet recording method of the present invention is to apply the reaction liquid and the aqueous pigment ink onto the recording surface so that the reaction liquid and the aqueous pigment ink are brought into contact with each other on the recording surface of a recording medium. It can be carried out using a known ink jet printer.

As is well known, an ink jet printer is a printing apparatus that ejects ink droplets from a discharge port of a recording head (ink jet head) and attaches the ink droplets to a recording medium to form an image. There are two types of inkjet printers: a continuous type that forms an image by continuously ejecting ink from the nozzles of the recording head at predetermined time intervals and deflecting the ejected ink droplets, and an ink corresponding to the image data. However, in the present invention, an on-demand ink jet printer that can perform fine driving control and has a small amount of waste liquid is preferable. Further, the ink ejection method of the recording head includes an electro-mechanical conversion method using a piezoelectric element such as a piezo element and an electro-thermal conversion method using an electro-thermal conversion element such as a heater. Any inkjet printer equipped with a recording head can be used. In general, when an aqueous pigment ink is used, it is preferable to use an electro-mechanical conversion type recording head from the viewpoint of ejection stability.

As the recording medium, not only known ink jet paper having an ink receiving layer mainly composed of porous particles such as silica, but also plain paper not imparted with characteristics suitable for the ink jet recording method is preferably used in the present invention. Can be used. Examples of plain paper that can be used in the present invention include high-quality paper, recycled paper, copy paper, bond paper, art paper, coated paper, cast coated paper,
Examples include resin-coated paper (resin-coated paper), baryta paper, paperboard, Japanese paper, non-woven fabric, and resin films such as polyethylene, polypropylene, polystyrene, and polyethylene terephthalate.

The reaction liquid may be attached to the entire recording surface of the recording medium with a uniform adhesion amount, or may be selectively adhered only to a portion where ink is adhered. What is necessary is just to adjust suitably the adhesion amount of a reaction liquid in the range with which the predetermined effect is acquired, Preferably it is 0.05-5 g / m < ² > in conversion of solid content.

In the present invention, the reaction liquid and the aqueous pigment ink may be applied so as to contact each other on the recording surface of the recording medium, and the application order is not particularly limited, but the rub resistance of the recorded image is improved. From the viewpoint of further enhancement, it is preferable to apply the aqueous pigment ink and the reaction liquid to the recording medium in this order.

The time from applying one of the two liquids to be contacted to applying the other varies depending on the ejection amount, the type of the recording medium, and the like, but is preferably 5 ms to 60 seconds, and preferably 50 ms. More preferably, it is ˜500 ms (ms means 1/1000 second). If this time lag is shorter than 5 ms, the other droplet may land on one of the droplets before the first applied droplet penetrates into the recording medium. The liquid may overflow on the recording medium and adversely affect image quality and drying properties. On the contrary, if the time lag exceeds 60 seconds, the first applied droplet completely penetrates into the inside of the recording medium and then the other droplet is ejected. Therefore, a predetermined image quality improvement effect is obtained. There is a risk of disappearing.

In addition, since the said reaction liquid and ink permeate | transmit rapidly when provided to a recording medium, the forced drying using a dryer etc. is fundamentally unnecessary, but liquid permeability like a film is low, for example For example, when a recording medium is used, forced drying may be performed as necessary.

  The ink jet recording method of the present invention can be carried out, for example, as follows.

FIG. 1 is a perspective view showing a schematic configuration of an ink jet printer that can be used for carrying out the ink jet recording method of the present invention. The ink jet printer 10 includes a paper feed motor 11.
The recording medium M is conveyed in the direction of the arrow X by the platen roller 12 driven by
3, the recording head 20 mounted on the recording medium M discharges the reaction liquid supplied from the ink tank 30 and the respective color water-based pigment inks onto the recording surface of the recording medium M, and then discharges them from a paper discharge port (not shown). It ’s like that. The carriage 13 is connected to the carriage motor 15 via the carriage belt 14 and slides on the guide rail 16 to perform main scanning in the arrow Y1 or Y2 direction orthogonal to the arrow X direction. Yes.

FIG. 2 is a schematic front view of the discharge port forming surface 20 a of the recording head 20. In FIG. 2, Nz indicates the discharge port of the nozzle, 21 and 26 are discharge port arrays for discharging the reaction liquid,
24 and 25 are yellow (Y), magenta (M), cyan (C), black (
K) is a discharge port array for discharging the aqueous pigment ink.

In the ink jet printer 10 having such a configuration, the recording head 20 includes an arrow Y1.
When scanning in the direction, first, the ejection port arrays 22, 23, 2 are performed on the recording surface of the recording medium M.
The aqueous pigment inks of the respective colors are ejected from 4 and 25, and then the reaction liquid is ejected from the ejection port array 26 to the ink adhesion region. When scanning in the direction of the arrow Y1, the discharge port array 21 is not used. The recording head 20 reaches the end of the recording area in the direction of the arrow Y1, and after the recording medium M is conveyed by a predetermined amount in the direction of the arrow X, the recording head 20 is scanned in the direction of the arrow Y2. When scanning in the direction of the arrow Y2, first, each color aqueous pigment ink is ejected from the ejection port arrays 25, 24, 23, and 22, and then the reaction liquid is ejected from the ejection port array 21 to the ink adhesion region. Discharge. When scanning in the direction of the arrow Y2, the discharge port array 26 is not used.

Based on the input image data, the bidirectional (Y1 and Y2) scanning of the recording head 20 and the conveyance of the recording medium M in the X direction at the end of each scanning are repeated to form a predetermined image. Finally, a recorded matter is obtained.

Hereinafter, the present invention will be described more specifically with reference to examples of the present invention and test examples showing the effects of the present invention. However, the present invention is not limited to the examples. The following actual
Examples 5 to 8 are reference examples.

[Example 1]
The following components were mixed, stirred at room temperature for 30 minutes, and then filtered through a 5 μm membrane filter to prepare a reaction solution, which was used as the sample of Example 1.
(Reaction solution composition)
・ Magnesium sulfate 10% by weight
・ Hydroxyethylcellulose (2% aqueous solution) 4% by weight
・ Glycerin 18% by weight
・ Triethylene glycol monobutyl ether 3% by weight
・ Triethanolamine (pH adjuster) 0.1% by weight
・ Olefin surfactant 0.01% by weight
(Shinfin Chemical, Surfinol 485)
・ Pure water balance
100% by weight

[Example 2]
The following components were mixed, stirred at room temperature for 30 minutes, and then filtered through a 5 μm membrane filter to prepare a reaction solution, which was used as the sample of Example 2.
(Reaction solution composition)
・ Magnesium sulfate 10% by weight
・ Cationized hydroxyethyl cellulose (2% aqueous solution) 4% by weight
・ Glycerin 18% by weight
・ Triethylene glycol monobutyl ether 3% by weight
・ Triethanolamine (pH adjuster) 0.1% by weight
・ Olefin surfactant 0.01% by weight
(Shinfin Chemical, Surfinol 485)
・ Pure water balance
100% by weight

Example 3
The following components were mixed and stirred at room temperature for 30 minutes, and then filtered through a 5 μm membrane filter to prepare a reaction solution, which was used as a sample of Example 3.
(Reaction solution composition)
・ Magnesium sulfate 10% by weight
・ Hydroxyethylcellulose (2% aqueous solution) 4% by weight
・ Polyolefin resin particles 3% by weight
(Made by Big Chemie Japan, AQUACER513, MFT125 ° C)
・ Glycerin 18% by weight
・ Triethylene glycol monobutyl ether 3% by weight
・ Triethanolamine (pH adjuster) 0.1% by weight
・ Olefin surfactant 0.01% by weight
(Shinfin Chemical, Surfinol 485)
・ Pure water balance
100% by weight

Example 4
The following components were mixed and stirred at room temperature for 30 minutes, and then filtered through a 5 μm membrane filter to prepare a reaction solution, which was used as a sample of Example 4.
(Reaction solution composition)
・ Magnesium sulfate 10% by weight
・ Cationized hydroxyethyl cellulose (2% aqueous solution) 3% by weight
・ Polyolefin resin particles 3% by weight
(Made by Big Chemie Japan, AQUACER513, MFT125 ° C)
・ Glycerin 18% by weight
・ Triethylene glycol monobutyl ether 3% by weight
・ Triethanolamine (pH adjuster) 0.1% by weight
・ Olefin surfactant 0.01% by weight
(Shinfin Chemical, Surfinol 485)
・ Pure water balance
100% by weight

Example 5
The following components were mixed, stirred at room temperature for 30 minutes, and then filtered through a 5 μm membrane filter to prepare a reaction solution, which was used as the sample of Example 5.
(Reaction solution composition)
・ Magnesium sulfate 10% by weight
・ Hydroxyethylcellulose (2% aqueous solution) 4% by weight
・ Glycerin 18% by weight
・ Triethylene glycol monobutyl ether 3% by weight
・ Triethanolamine (pH adjuster) 0.1% by weight
・ Fluorosurfactant 0.8% by weight
(Dainippon Ink, MegaFuck F144D)
・ Pure water balance
100% by weight

Example 6
The following components were mixed and stirred at room temperature for 30 minutes, and then filtered through a 5 μm membrane filter to prepare a reaction solution, which was used as the sample of Example 6.
(Reaction solution composition)
・ Magnesium sulfate 10% by weight
・ Cationized hydroxyethyl cellulose (2% aqueous solution) 4% by weight
・ Glycerin 18% by weight
・ Triethylene glycol monobutyl ether 3% by weight
・ Triethanolamine (pH adjuster) 0.1% by weight
・ Fluorosurfactant 0.8% by weight
(Dainippon Ink, MegaFuck F144D)
・ Pure water balance
100% by weight

Example 7
The following components were mixed, stirred at room temperature for 30 minutes, and then filtered through a 5 μm membrane filter to prepare a reaction solution, which was used as a sample of Example 7.
(Reaction solution composition)
・ Magnesium sulfate 10% by weight
・ Hydroxyethylcellulose (2% aqueous solution) 4% by weight
・ Polyolefin resin particles 3% by weight
(Made by Big Chemie Japan, AQUACER513, MFT125 ° C)
・ Glycerin 18% by weight
・ Triethylene glycol monobutyl ether 3% by weight
・ Triethanolamine (pH adjuster) 0.1% by weight
・ Fluorosurfactant 0.8% by weight
(Dainippon Ink, MegaFuck F144D)
・ Pure water balance
100% by weight

Example 8
The following components were mixed, stirred at room temperature for 30 minutes, and then filtered through a 5 μm membrane filter to prepare a reaction solution, which was used as the sample of Example 8.
(Reaction solution composition)
・ Magnesium sulfate 10% by weight
・ Cationized hydroxyethyl cellulose (2% aqueous solution) 3% by weight
・ Polyolefin resin particles 3% by weight
(Made by Big Chemie Japan, AQUACER513, MFT125 ° C)
・ Glycerin 18% by weight
・ Triethylene glycol monobutyl ether 3% by weight
・ Triethanolamine (pH adjuster) 0.1% by weight
・ Fluorosurfactant 0.8% by weight
(Dainippon Ink, MegaFuck F144D)
・ Pure water balance
100% by weight

[Comparative Example 1]
The following components were mixed and stirred at room temperature for 30 minutes, and then filtered through a 5 μm membrane filter to prepare a reaction solution, which was used as a sample of Comparative Example 1.
(Reaction solution composition)
・ Magnesium sulfate 10% by weight
・ Glycerin 18% by weight
・ Triethylene glycol monobutyl ether 3% by weight
・ Triethanolamine (pH adjuster) 0.1% by weight
・ Olefin surfactant 0.01% by weight
(Shinfin Chemical, Surfinol 485)
・ Pure water balance
100% by weight

[Comparative Example 2]
The following components were mixed and stirred at room temperature for 30 minutes, and then filtered through a 5 μm membrane filter to prepare a reaction solution, which was used as a sample of Comparative Example 2.
(Reaction solution composition)
・ Magnesium sulfate 10% by weight
・ Polyallylamine (used as a sticking agent, manufactured by Nittobo) 2% by weight
・ Glycerin 18% by weight
・ Triethylene glycol monobutyl ether 3% by weight
・ Triethanolamine (pH adjuster) 0.1% by weight
・ Olefin surfactant 0.01% by weight
(Shinfin Chemical, Surfinol 485)
・ Pure water balance
100% by weight

Inkjet printer for discharging aqueous pigment ink (manufactured by Seiko Epson, PM400
0PX), a predetermined image was printed on a recording surface of a recording medium (manufactured by Oji Paper Co., Ltd., OK top coat N, basis weight 157 g / m ² ). Next, using an ink jet printer (Seiko Epson, EM930C) in which cyan ink and the above reaction liquid were replaced, the amount of the reaction liquid deposited on these image printed portions was 1 g / m ^{2 in} terms of solid content. It was made to adhere. The time lag between ink application and reaction liquid application was approximately 50 seconds. In this way, recorded matter using each of the above reaction solutions was prepared. The recorded material is YMC for each case.
Printed color patch of OD = 1 for each color (recorded material A), high-definition color digital standard image [(ISO / JIS-SCID), image name “portrait” (sample number 1, image recognition recognition) No. N1)] was printed in MC mat paper printing mode (recommended clean mode) (recorded material B), and two types of images were produced. The average value of the surface tension of each of the aqueous pigment inks of YMCK used here was 28.9 mN / m.

Using a surface tension meter CBVP-A3 manufactured by Kyowa Interface Science, the surface tension of each of the above reaction solutions at a liquid temperature of 25 ° C. was measured, and the storage stability was evaluated by the following method. Further, the image density, bleed, graininess, dot roundness, and abrasion resistance (Sutherland abrasion resistance tester, nail abrasion, eraser abrasion) of each recorded matter were evaluated by the following methods. These results are shown in the following [Table 1].

(Storage stability evaluation method)
100 g of the reaction solution was collected in a sample bottle, and the sample bottle was sealed, at room temperature of 25 ° C.
And left in an environment with a humidity of 25% for 1 week. Then, the reaction liquid after standing for 1 week was filtered through a 5 μm membrane filter, and the degree of generation of aggregated sediment and the ease of filtration were evaluated according to the following evaluation criteria.
Evaluation criteria A: No aggregated sediment was observed, and filtration could be performed smoothly and in a short time, just after the reaction solution was prepared. Good storage stability.
B: Although agglomerated sediment was slightly seen, filtration could be performed smoothly and in a short time.
There is no practical problem.
C: A large amount of aggregated sediment is generated, and it takes a long time for filtration. Not practical.

(Image density evaluation method)
With respect to each color patch of YMCK of the above recorded matter A, a reflection optical density (OD value) was measured using a Spectrolino SPM-50 manufactured by Gretag Macbeth Co. under a condition of a viewing angle of 2 degrees, a light source D50, and no filter. Evaluation was based on the evaluation criteria.
Evaluation criteria A: The sum of the OD values of the four colors of YMCK exceeds 7.5. Good color development.
B: The total of the OD values of the four colors is 7.5 to 6.0. There is no practical problem.
C: The sum of the OD values of the four colors is less than 6.0 (an average OD value of less than 1.5). Not practical.

(Bleed evaluation method)
The portions where the Y and C color patches of the recorded matter A are adjacent to each other (the portion where image quality deterioration is most easily detected) are visually observed, and the degree of non-uniform color mixing at the color boundary is evaluated as follows. It was evaluated by.
Evaluation criteria A: Good image quality without color mixing was obtained.
B: Color mixing slightly occurred. There is no practical problem.
C: Color mixing occurred so that the color boundary was not clear. Not practical.

(Evaluation method for graininess)
The image of the recorded material B was visually observed, and “A” indicates that the graininess is not noticeable, “B” indicates that the graininess is slightly noticeable, and “C” indicates that the graininess is noticeable.

(Dot roundness evaluation method)
For the halftone area of each color patch print portion of YMCK of the recorded matter A, the ink dot diameter (the diameter X in the carriage movement direction and the diameter Y in the paper conveyance direction) is measured using an optical microscope, and the ink dots The distortion rate [{| (X / Y ratio of ink dots) −1.0 | /1.0} × 100%] with respect to the “perfect circle dot with an X / Y ratio of 1.0” was calculated. Is 10% or less (A) (perfect circle or very close to a perfect circle), the strain ratio is over 10% and within 20% is B, and the strain ratio is over 20%.

(Rubbing resistance evaluation method)
After rubbing the printed part of the color patch of the recorded matter A by the following three methods, the state is visually observed, and the printed part is A (good scratch resistance), and the printed part is finely scratched. What was seen was designated as B (no problem in practical use), and a part of the printed part was peeled off and was deficient as C (impractical).
Sutherland abrasion resistance tester: No. manufactured by Toyo Seiki as a tester 468, JIS-
The printed portion of the recorded matter A is rubbed based on K5701.
-Nail rubbing; Gently rub the printed portion of the recorded matter A with the nail.
Eraser rubbing: The recorded matter A is fixed at an inclination angle of 60 degrees with the printed portion facing up, and the printed portion is rubbed back and forth 10 times while applying a load of 1 kg using an eraser with a width of 20 mm.

In the above [Table 1], Examples 5 to 8 are inferior to the other examples in terms of graininess and dot roundness. This is because the surface tension of these reaction liquids is below the average value (28.9 mN / m) of the surface tension of the ink. The ink sets obtained by combining the reaction solutions of Examples 5 to 8 with the YMCK four-color aqueous pigment ink having an average surface tension of 28.9 mN / m are all the ink sets of the present invention. It does not belong to the technical scope.

1 is a perspective view illustrating a schematic configuration of an inkjet printer to which the present invention is applicable. FIG. 2 is a schematic front view of a discharge port forming surface of the recording head shown in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Inkjet printer 11 ... Paper feed motor 12 ... Platen roller 13 ... Carriage 14 ... Carriage belt 15 ... Carriage motor 16 ... Guide roll 20 ... Recording head 20a ... Ejection port formation surfaces 21-26 ... Ejection port array 30 ... Ink tank Nz ... Discharge port M ... Recording medium

Claims (7)

A reaction liquid for ink jet recording having a surface tension in the range of 25 to 50 mN / m in combination with an aqueous ink containing at least a pigment as a colorant and having a surface tension in the range of 20 to 50 mN / m , polyvalent metal salt, containing (cationized) hydroxyethyl cellulose and water, the surface tension, much larger than the average value of the surface tension of the aqueous ink, that the difference is in the range of 5~25mN / m Characteristic reaction solution.   The reaction liquid according to claim 1, further comprising polyolefin resin particles. An ink set for inkjet recording comprising the reaction liquid according to claim 1 and a water-based ink containing at least a pigment as a colorant and having a surface tension in the range of 20 to 50 mN / m .   4. The ink set according to claim 3, wherein the water-based ink is composed of a combination of at least four water-color inks of cyan, magenta, yellow, and black. An ink jet recording method using the reaction liquid according to claim 1 and a water-based ink containing at least a pigment as a coloring material and having a surface tension in the range of 20 to 50 mN / m , and recording on a recording medium An ink jet recording method comprising applying the reaction liquid and the water-based ink onto the recording surface so that the reaction liquid and the water-based ink are brought into contact with each other on the surface.   5. An ink jet recording method using the ink set according to claim 3 or 4, wherein the reaction liquid and the water-based ink are used so that the reaction liquid and the water-based ink are brought into contact with each other on a recording surface of a recording medium. An ink jet recording method comprising applying onto a recording surface.   7. The ink jet recording method according to claim 5, wherein after applying the water-based ink on a recording surface of a recording medium, the reaction liquid is applied to a region where the water-based ink is attached.

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