WO2018116811A1 - Washing liquid and washing method for ink jet recording apparatus - Google Patents

Abstract

The present invention addresses the problem of providing a washing liquid and a washing method with excellent washing performance at a level enabling efficient removal of dirt, such as an ink-derived residue, inside an ink flow path of an ink jet recording apparatus. The present invention pertains to a washing liquid having a pH of 7 to 10 containing water, an organic solvent which is insoluble or sparingly soluble in water, and a surfactant. The washing liquid is characterized in that the organic solvent forms liquid droplets in the water, the liquid droplets have a volume mean diameter of 9 nm or more, and the washing liquid is used for the purpose of washing an ink jet recording apparatus.

Description

Cleaning liquid and method for cleaning ink jet recording apparatus

The present invention relates to a cleaning liquid that can be used for cleaning, for example, an ink discharge head constituting an ink jet recording apparatus.

Water-based pigment ink for inkjet recording can be used for on-demand printing, can be used for the production of printed materials with excellent light resistance, and can reduce risks such as fire and mutagenicity like organic solvent-based inks, etc. Has the advantage of Therefore, water-based pigment inks for inkjet recording are being examined for suitability for printing on various recording media such as plain paper, coated paper, art paper, plastic films such as vinyl chloride and polyester, metals, and fabrics.

In particular, with the dramatic growth of the print-on-demand market in recent years, water resistance comparable to that obtained by the lithographic printing method compared to the printed matter obtained using the aqueous pigment ink for inkjet recording. And printing characteristics such as scratch resistance are required.

As the aqueous pigment ink for inkjet recording capable of forming a printed matter having excellent water resistance and scratch resistance, for example, an aqueous pigment ink containing a binder resin in addition to a pigment and a pigment dispersion resin is known.

However, since the water-based pigment ink tends to increase in viscosity or dry and solidify in the ink discharge head as the content of resin components such as the binder resin and pigment dispersion resin increases, an ink jet recording apparatus is used. In some cases, the ink was not ejected or the ejection direction was abnormal (improper ink ejection).

As a method for preventing the ink ejection failure, there is known a method for removing ink components remaining in the ink flow path by supplying a cleaning liquid to the ink flow path in the ink ejection head provided in the ink jet recording apparatus. Yes.

As the cleaning liquid, for example, an inkjet recording maintenance liquid containing at least water and an organic solvent that is insoluble or hardly soluble in water and is 8 mass% or more based on the total mass is known (for example, Patent Document 1). reference.).

However, in some cases, the maintenance liquid cannot efficiently remove the binder resin solidified product and the thickening component remaining in the ink flow path.

By the way, the inkjet recording method is being studied for application not only to plain paper but also to non-absorbable recording media such as coated paper and resin film that hardly absorb the solvent contained in the ink. Since the ink that has landed on the surface of the non-absorbable recording medium is difficult to dry, for example, the drying speed may be stopped through a heating process or a blowing process using a halogen lamp or the like, and the production efficiency of printed matter may be improved. is there.

However, the heating process and the air blowing process may increase the drying speed of the ink attached to the nozzle surface of the ink discharge head. For this reason, printing on the coated paper or the like tends to cause the solidified material or the like to adhere to the nozzle surface as compared with a printing situation on plain paper, resulting in clogging of the ink discharge nozzles or abnormal ink discharge direction. There were cases where it was easy to cause.

JP 2010-137458 A

The problem to be solved by the present invention is to efficiently remove, for example, dirt in an ink flow path and nozzle face (for example, a residue such as a dried solid matter derived from ink) provided in a printing apparatus such as an ink jet recording apparatus. To provide a cleaning liquid and a cleaning method having a possible level of cleaning performance.

In addition, the problem to be solved by the present invention is that a stain in an ink flow path or a nozzle surface (for example, a binder resin or a dispersion resin contained in the ink) provided in an ink jet recording apparatus for an aqueous pigment ink containing a binder resin. It is to provide a cleaning liquid and a cleaning method having a level of detergency capable of efficiently removing a residue such as a dried solidified product derived from the origin.

The cleaning liquid is required to have a function of removing the ink thickening or solidified product from the ink flow path and the nozzle surface by swelling or dissolving (redispersing) the ink. In particular, an ink containing a resin component such as a binder resin or a pigment-dispersed resin forms a relatively strong film (solidified product) when dried, and thus it is difficult to remove it with a conventional cleaning liquid.

In order to swell or dissolve the solidified ink containing the binder resin so that the ink is easily redispersed in the cleaning liquid, it is required to use an organic solvent having a high dissolving power for the resin component. However, the organic solvent having a high dissolving power may destroy the dispersion stability of the ink when it comes into contact with the ink, and also has a high possibility of adversely affecting the members constituting the ink discharge head. It is not preferable to use a large amount.

On the other hand, in order to avoid adverse effects on the members constituting the ink discharge head, etc., when the cleaning liquid in which the amount of the organic solvent used is excessively reduced cannot sufficiently remove the solidified or thickened ink. There is.

Also, it is effective to use a cleaning liquid containing a surfactant in order to peel the solidified product or thickened product from the ink flow path.

However, the surfactant is dissolved in the cleaning solution containing the organic solvent, and its function may not be fully exhibited.

Therefore, the present inventor has intensively studied the above problems, and if the cleaning liquid is a cleaning liquid in which a specific organic solvent having a high dissolving power of the resin component contained in the ink is dispersed in water with a surfactant, It has been found that ink thickeners and solidified substances resulting from binder resins, pigment dispersion resins, and the like can be easily removed.

That is, the present invention is a cleaning solution having a pH of 7 to 10 containing water, an insoluble or hardly soluble organic solvent, and a surfactant, wherein the organic solvent forms droplets in the water, The liquid droplets have a volume average diameter of 9 nm or more.

If the cleaning liquid and the cleaning method of the present invention are used, it is possible to efficiently remove, for example, dirt in the ink flow path of the ink jet recording apparatus.

The cleaning liquid of the present invention is a cleaning liquid having a pH of 7 to 10 containing water, an organic solvent insoluble or hardly soluble in water, and a surfactant, wherein the organic solvent forms droplets in the water, The liquid droplet has a volume average diameter of 9 nm or more and is used for cleaning a recording apparatus using various inks.

The cleaning liquid of the present invention is preferably used for cleaning an ink jet recording apparatus in the recording apparatus, and is preferably used for cleaning the nozzle surface of the ink ejection head and the ink flow path provided in the ink jet recording apparatus. it can.

As a specific aspect of the cleaning liquid, a part or all of an organic solvent insoluble or hardly soluble in water is encapsulated in a micelle formed by a component containing a surfactant to form droplets, or Examples include so-called O / W emulsions in which droplets are formed in an organic solvent in water.

In the cleaning liquid of the present invention, the organic solvent that is insoluble or hardly soluble in water dissolves or swells the solidified product of the ink, and the surfactant peels the solidified product from the ink flow path or the like, or the solidified product. Since an object or the like can be adsorbed and redispersed in the cleaning liquid, it can be used exclusively for cleaning a head or an ink flow path provided in an ink jet recording apparatus.

Therefore, the cleaning liquid of the present invention can be suitably used for cleaning an inkjet recording apparatus for aqueous ink containing a binder resin that easily causes nozzle clogging or ink ejection failure due to the solidified product or the like. .

In addition, as described above, a part or all of the organic solvent is included in a micelle formed by a component containing a surfactant to form droplets, or the organic solvent forms droplets in water. , Present in the cleaning liquid in a so-called O / W emulsion state. The organic solvent can efficiently swell or dissolve the solidified product and the like. In addition, since the organic solvent is not diluted with water as described above, the solidified product can be efficiently swollen or dissolved even in a small amount, and the dispersion stability of the ink when in contact with the ink is improved. Adverse effects such as destruction or deterioration of the head member can be minimized.

The cleaning liquid of the present invention has a pH in the range of 7-10. The ink may contain a resin having an acid group as a pigment dispersion resin, a binder resin, or the like. Therefore, as the cleaning liquid of the present invention, it is important to use a liquid whose pH is adjusted to be high (neutral to alkaline) in order to further improve the removability of the solidified resin and the like. It is preferable to use those adjusted to.

As the cleaning liquid, it is particularly preferable to use a cleaning liquid having a pH of 8 to 9 in order to achieve both the removability and the suppression of deterioration of the members constituting the ink discharge head.

The droplets contained in the cleaning liquid of the present invention are in a state in which the droplets are included in micelles formed by components containing a surfactant, or so-called O / where the organic solvent has formed droplets in water. It exists in the cleaning liquid in the state of W emulsion. That is, a part or all of the organic solvent is present in the cleaning liquid in a state solubilized or emulsified in water.

The volume average diameter of the droplet greatly varies depending on the amount of the organic solvent contained. The inventor has found that the removal performance of the solidified product or the like can be remarkably enhanced if the cleaning liquid contains droplets having a volume average diameter of 9 nm or more.

The reason why the cleaning liquid containing droplets having a volume average diameter of 9 nm or more can effectively remove the solidified material is not clear, but is presumed as follows.

The droplets having a volume average diameter of 9 nm or more are formed by more organic solvent as described above. It can be said that the surfactant containing more organic solvent has high affinity for the organic solvent. The high-affinity surfactant is considered to have a high affinity for water-insoluble or hardly-soluble ink solidified product and the like, similar to the organic solvent. Therefore, it is presumed that a cleaning liquid containing droplets having a volume average diameter of 9 nm or more easily adsorbs the solidified product or the like.

In the cleaning liquid containing droplets having a volume average diameter of 9 nm or more that is easily adsorbed on the solidified material, a lot of organic solvents contained in the droplets move to the solidified material after the adsorption, and the solidified It is presumed that things or the like are swollen or dissolved.

The volume average diameter of the droplets is preferably 13 nm or more, more preferably 15 nm or more in order to further improve the removal performance of the solidified product, and the upper limit is preferably 100 nm. More preferably, it is 50 nm.

In addition, the volume average diameter of the micelle indicates a value measured by a dynamic light scattering method (DLS method) using NanoTrack® Wave manufactured by Nikkiso Co., Ltd.

In addition, when the cleaning liquid of the present invention is an O / W emulsion and quickly separates into an aqueous phase and other phases, a value obtained by measuring the volume average diameter of droplets present in the aqueous phase by the same method as described above Was defined as the volume average diameter of the droplets referred to in the present invention.

(Organic solvent insoluble or sparingly soluble in water)
The organic solvent insoluble or hardly soluble in water used in the present invention is an organic solvent having a dissolution amount of 10 g or less with respect to 100 g of water at 20 ° C., preferably an organic solvent having a dissolution amount of 7 g or less.

By using an organic solvent that is insoluble or hardly soluble in water, it is possible to obtain a cleaning liquid having excellent removal performance of the solidified product and the like.

The organic solvent may be entirely contained in the micelle, or may be dispersed in water as the O / W emulsion in the form of droplets stabilized by a surfactant.

The content of the organic solvent is preferably 4.5% by mass or more and 30% by mass or less, and preferably 7.0% by mass or more and 15% by mass or less with respect to the total amount of the cleaning liquid of the present invention. The viscosity of the cleaning liquid can be lowered to a level applicable to the cleaning of the width ink flow path, and the removal performance of the solidified matter of the ink can be further improved. This is preferable because the dispersion stability of the ink is hardly destroyed.

As the organic solvent, for example, ethers and alcohols can be used alone or in combination of two or more.

Examples of the ethers include diethyl ether, dibutyl ether, ethyl methyl ether, dihexyl ether, furan, dipropylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, dipropylene glycol t-butyl ether, diethylene glycol monohexyl. Ether, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol mono-2-ethylhexyl ether, propylene glycol methyl ether acetate, dipropylene glycol methyl ether acetate, propylene glycol diacetate, propylene glycol phenyl ether and the like can be used. Examples of the alcohols that can be used include butanol, pentanol, hexanol, and benzyl alcohol.

Among these, as the organic solvent, a monoalkylene glycol alkyl ether or a dialkylene glycol alkyl ether is used in order to reduce the adverse effect on the head member and further improve the cleaning properties of the solidified product and the like. It is preferable to use dipropylene glycol monopropyl ether, propylene glycol monobutyl ether, or dipropylene glycol monobutyl ether.

(Surfactant)
The surfactant is used to form micelles containing an organic solvent that is insoluble or hardly soluble in water, or to form so-called O / W emulsion droplets.

As the surfactant, it is preferable to use a surfactant having a relatively high water solubility, specifically, an HLB of 10 or more. By using a surfactant having an HLB of 10 or more, it is possible to obtain a cleaning liquid in which micelles or so-called O / W emulsion droplets are formed in water.

As the surfactant, it is preferable to use a surfactant having an HLB value of 10 or more and 14 or less in order to obtain a cleaning liquid capable of further improving the removal performance of the solidified product of the ink.

As the surfactant, for example, an anionic surfactant or a nonionic surfactant can be used.

Examples of the anionic surfactants include sodium methyl taurate oleate, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, sodium lauryl sulfate, sodium alkyldiphenyl ether disulfonate, sodium alkyl naphthalene sulfonate, sodium dialkyl sulphosuccinate, stearin. Sodium acid, potassium oleate, sodium dioctyl sulfosuccinate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, sodium dialkylsulfosuccinate, sodium stearate, olein Acid sodium salt, t-octylphenoxyethoxypolyethoxyethyl sulfate Potassium salts and the like.

Examples of the nonionic surfactant include acetylene diol derivatives such as ethylene oxide adducts of acetylene diol, polyoxyethylene lauryl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene oleyl phenyl ether. , Polyoxyethylene nonylphenyl ether, oxyethylene oxypropylene block copolymer, t-octylphenoxyethyl polyethoxyethanol, nonylphenoxyethyl polyethoxyethanol, polyether-biased siloxane copolymer, polyoxyethylene sorbitan monostearate, polyglycerin fatty acid Examples include esters.

Among them, the use of an acetylenic diol surfactant as the surfactant improves the permeability of the cleaning liquid to the ink solidified product and the like, and improves the redispersibility of the solidified product into the cleaning liquid. preferable.

The content of the surfactant is preferably 25% by mass to 110% by mass, and preferably 25% by mass to 100% by mass with respect to the total amount of the organic solvent insoluble or hardly soluble in water. Since the organic solvent can be stably solubilized or emulsified (the state of the O / W emulsion) can be stably maintained, the organic solvent is less likely to directly contact the ink ejection head member of the ink jet recording apparatus, and This is preferable because it can further improve the removal performance of solidified ink and the like, and it is difficult to destroy the dispersion stability of the ink when it comes into contact with the ink.

(water)
As water used by this invention, pure water, such as ion-exchange water, ultrafiltration water, reverse osmosis water, distilled water, or ultrapure water can be used. Water is preferably contained in an amount of 40 to 95% by mass based on the total amount of the cleaning liquid. When the water content is 40% by mass or more, the viscosity of the cleaning liquid can be made relatively low, and the cleaning efficiency is excellent.

(PH adjuster)
As described above, the cleaning liquid of the present invention has a pH in the range of 7 to 10, and more preferably has a pH of 8 to 9. The pH of the cleaning liquid can be adjusted using, for example, a pH adjusting agent. The pH adjusting agent is not particularly limited, but lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, quaternary ammonium hydroxide, ammonia, diethanolamine, trimethylamine. Ethanolamine, tripropanolamine, ammonium hydroxide, quaternary phosphonium, etc. can be used alone or in combination of two or more. Especially, it is preferable to use weak bases, such as diethylaminoethanol and a triethanolamine, for the said pH adjuster, keeping a washing | cleaning liquid weakly alkaline.

As the cleaning liquid of the present invention, those containing conventionally known additives such as antifoaming agents and preservatives can be used as long as the effects of the present invention are not impaired.

(Defoamer)
The antifoaming agent can be used to suppress foaming of the cleaning liquid. As the antifoaming agent, a commonly used antifoaming agent can be used. For example, a silicone-based antifoaming agent, a polyether-based antifoaming agent, or the like can be used alone or in combination of two or more. As said antifoamer, it is preferable to use a silicone type antifoamer which is excellent in an antifoaming effect.

Since the antifoaming agent generally tends to be difficult to dissolve in water, excessive use of the antifoaming agent may cause precipitation of the antifoaming agent. Therefore, it is preferable to use the minimum amount of the antifoaming agent as long as the effect of the cleaning liquid of the present invention is not impaired.

(Cleaning method)
The cleaning liquid of the present invention can be used for cleaning a recording apparatus (printing apparatus) using ink, preferably used for cleaning an inkjet recording apparatus, and more preferably provided in an inkjet recording apparatus. It can be used for cleaning ink flow paths.

The cleaning method is not particularly limited. For example, a cleaning method including a step [1] of bringing the nozzle surface (water repellent surface) constituting the ink discharge head of the ink jet recording apparatus into contact with the cleaning liquid can be mentioned. For the contact, a method of spraying the cleaning liquid onto the nozzle surface, a method of applying the cleaning liquid to the nozzle surface using a roller, or a cap containing the cleaning liquid or a cloth wiper impregnated with the cleaning liquid is used. The method of pressing on a nozzle surface etc. are mentioned.

The contact is preferably performed for several minutes or more (specifically, 15 minutes to 1 hour). At the time of the contact, wiping (wiping) the nozzle surface with a rubber blade, a cloth wiper moistened with the cleaning liquid, or the like is preferable for enhancing the cleaning effect.

Further, examples of the cleaning method include a method of repeating a process of supplying and discharging the cleaning liquid into the ink flow path.

Specifically, as the cleaning method, for example, the step [2] of supplying the cleaning liquid to an ink discharge head provided in an ink jet recording apparatus, the nozzle surface is set after the cleaning liquid is brought into contact with the nozzle surface of the ink discharge head. Examples include a method having a step [3] of wiping and a step [4] of removing the cleaning liquid from the nozzle.

In the step [2], when the cleaning liquid is supplied to the ink flow path such as the ink discharge head, it may be pressurized or sucked. In addition, when supplying the cleaning liquid to the ink flow path, supplying the cleaning liquid after preliminarily cleaning the ink flow path by supplying water to the ink flow path in advance is a cleaning effect. It is preferable to further increase

The step [3] includes, for example, a method of wiping the nozzle surface with a rubber blade or a cloth wiper moistened with a cleaning liquid.

In the step [4], as a method of removing the cleaning liquid, for example, there is a method in which the cleaning liquid is pressurized or sucked and replaced with water.

As the cleaning method, in a state where the cleaning liquid is filled in the ink flow path of the ink discharge head, the cleaning liquid is vibrated in the flow path or ultrasonically vibrated by finely driving the ink discharge head. Or you may.

Further, at the time of the cleaning, the cleaning liquid may be left for several hours to several days in a state where the cleaning liquid is filled in the ink flow path of the ink discharge head or the like.

According to the above cleaning method, for example, the ink flow path provided in the ink jet recording apparatus, in particular, the ink flow path of the ink jet head can be sufficiently cleaned.

The cleaning liquid of the present invention can be suitably used exclusively for cleaning water-based inks for ink-jet recording. In particular, water-based inks for ink-jet recording containing a resin component such as a binder resin and a pigment-dispersed resin, and solid or thickened materials thereof can be cleaned. Can be suitably used.

As the water-based ink for ink jet recording, for example, a binder resin, a pigment, a pigment dispersion resin, which will be described later, and a mixture containing a solvent or the like as required can be used.

Examples of the binder resin include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinyl pyrrolidone, acrylic resin, urethane resin, epoxy ester resin, dextran, dextrin, color ginan (κ, ι, λ, etc.), agar, pullulan, water-soluble One or more kinds of water-soluble polyvinyl butyral, hydroxyethyl cellulose, carboxymethyl cellulose and the like can be used. The cleaning liquid of the present invention is particularly effective for cleaning an aqueous ink containing an acrylic resin, a urethane resin, or an epoxy ester resin used as a binder resin.

The amount of the binder resin contained in the water-based ink for ink jet recording is not particularly limited, but is 2% to 15% by mass (solid content) in order to sufficiently improve properties such as gloss, scratch resistance, and water resistance of the printed matter. ) Often contained. If the content of the binder resin is 2% by mass or more, sufficient properties such as gloss, scratch resistance and water resistance of the printed matter can be obtained. If the content is 15% by mass or less, the viscosity of the ink is not excessively increased. There is little possibility of becoming defective.

With the cleaning liquid of the present invention, it is possible to efficiently clean the ink containing 2 to 15% by mass of the binder resin as described above and its solidified or thickened material.

As the binder resin, it is preferable to use a resin having a high number average molecular weight and a high weight average molecular weight in order to obtain an ink for ink jet recording capable of forming a printed matter excellent in gloss, scratch resistance, water resistance and the like.

A binder resin having a high number average molecular weight or weight average molecular weight is generally difficult to dissolve in an organic solvent. The cleaning liquid of the present invention can be used in an undiluted state with an organic solvent having a relatively high resin solubility, and is therefore suitable for cleaning an inkjet recording apparatus using an ink containing the high molecular weight binder resin. Can be used for Further, emulsion and dispersion type binder resins are dispersed in the ink. Compared with the conventional cleaning liquid, the cleaning liquid of the present invention contains the solvent in the surfactant, and thus it is considered that the decrease in the dispersion stability of the binder particles upon contact with the ink can be suppressed to some extent.

The cleaning liquid of the present invention hardly destroys the pigment dispersion stability of the aqueous ink even when it comes into contact with the aqueous ink.

Since the pigment is stably present in the water-based ink, a means for normally dispersing it in a water-soluble solvent or water is often taken. For example, the pigment may be dispersed in water together with a general-purpose pigment dispersion resin such as a polymer dispersant, a surfactant, or a pigment derivative, or a dispersibility-imparting group (hydrophilic functional group and / or salt thereof) on the pigment surface. Can be directly or indirectly bonded via an alkyl group, alkyl ether group, aryl group, etc., and processed as a self-dispersed pigment that can be dispersed and / or dissolved in a water-soluble solvent and / or water without a general-purpose pigment dispersion resin. Good dispersion stability is maintained by a method of dispersing in a water-soluble solvent and / or water.

However, when the pigment dispersion stability of such ink is destroyed by some kind of stimulation, the pigments tend to aggregate and coarse particles are likely to precipitate, and as a result, there is a tendency to cause ink ejection failure.

Compared with the conventional cleaning liquid, the cleaning liquid of the present invention contains the solvent in the surfactant, so that the deterioration of the pigment dispersion stability when contacting the ink can be suppressed to some extent without deteriorating the cleaning performance. it is conceivable that.

The pigment is not particularly limited, and an organic pigment or an inorganic pigment usually used for water-based ink for ink jet recording can be used. Further, as the pigment, either an untreated pigment or a treated pigment can be used.

Specifically, it can be dispersed in water or a water-soluble organic solvent, and known inorganic pigments and organic pigments can be used.

Examples of inorganic pigments include iron oxide and carbon black. Examples of the carbon black include carbon black produced by a known method such as a contact method, a furnace method, or a thermal method.

Organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), 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 type chelates, acidic dye type chelates), nitro pigments, nitroso pigments, aniline black, and the like can be used.

For example, as a pigment used for black ink, carbon black, No. made by Mitsubishi Chemical Corporation. 2300, no. 2200B, no. 900, no. 960, No. 980, no. 33, no. 40, No, 45, No. 45L, no. 52, HCF88, MA7, MA8, MA100, etc. are Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. made by Columbia, and Regal 400R, Regal 330R, Regal 660R, Mull 660R, Mogul made by Cabot. Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. are Color Black FW1, FW2, FW2V, FW18, FW200, FW200, S170, U, S150, S35, S150, U , V, 1400U, Special lack 6, the 5, 4, 4A, NIPEX150, NIPEX160, NIPEX170, NIPEX180 and the like.

Also, specific examples of pigments used in yellow ink include C.I. I. Pigment Yellow 1, 2, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 120, 128, 129, 138, 150, 151, 154, 155, 174, 180, 185 and the like.

Also, specific examples of pigments used in magenta ink include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 146, 168, 176, 184, 185, 202, 209, 269, 282 Et al., C.I. I. Pigment violet 19 and the like.

Also, specific examples of pigments used for cyan ink include C.I. I. Pigment blue 1, 2, 3, 15, 15: 3, 15: 4, 16, 22, 60, 63, 66, and the like.

Specific examples of pigments used in white inks include silicas such as alkaline earth metal sulfates, carbonates, finely divided silicic acids, synthetic silicates, calcium silicates, alumina, alumina hydrates, Examples thereof include titanium oxide, zinc oxide, talc, and clay. The inorganic white pigment may be surface-treated by various surface treatment methods.

The pigment dispersion resin that can be used for dispersing the pigment is not particularly limited, and known polymer dispersants, surfactants, and pigment derivatives can be used.

As the pigment dispersion resin, it is preferable to use a polymer type pigment dispersion resin. Specifically, acrylic resins such as polyvinyl alcohols, polyvinyl pyrrolidones, acrylic acid-acrylic acid ester copolymers, styrene-acrylic acid, and the like. Copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid ester Examples thereof include styrene-acrylic resins such as copolymers, styrene-maleic acid copolymers, styrene-maleic anhydride copolymers, vinylnaphthalene-acrylic acid copolymers, and the like.

As the pigment dispersion resin, those having a weight average molecular weight of 500 to 50,000 can be used. As the pigment dispersion resin, when a relatively high molecular weight resin of 5000 to 40000 is used, a dispersion stabilizing effect due to steric hindrance or the like is expected. However, as described above, an aqueous ink or a solidified product thereof is an ink jet recording apparatus. In some cases, the ink discharge nozzles are easily clogged. The cleaning liquid of the present invention is highly effective for cleaning water-based inks using the above-described relatively high molecular weight pigment-dispersed resin and solidified products thereof.

Examples of the pigment-dispersed resin include Ajimoto Fine Techno Co., Ltd., Ajisper PB series, Big Chemie Japan Co., Ltd. Disperbyk series, BASF EFKA series, Nippon Lubrizol Corporation SOLPERSE series, Evonik Commercial products such as the TEGO series can be used.

In addition to the above-described pigments, the pigment is produced by subjecting the pigment to a physical treatment or a chemical treatment, and binding (grafting) an active species having a dispersibility-imparting group or a dispersibility-imparting group to the pigment surface. Self-dispersing pigments can also be used.

Examples of the self-dispersing pigment include vacuum plasma treatment, oxidation treatment with hypohalous acid and / or hypohalite, oxidation treatment with ozone, and wet oxidation that oxidizes the pigment surface with an oxidizing agent in water. It is possible to use a product obtained by the method of bonding a carboxyl group via a phenyl group by bonding the p-aminobenzoic acid to the pigment surface.

Commercially available products can also be used as the self-dispersing pigments. Examples of such commercially available products include Microjet CW-1 (trade name; manufactured by Orient Chemical Industry Co., Ltd.), CAB-O-JET200, CAB. -O-JET300 (above, trade name: manufactured by Cabot Corporation).

As the solvent, pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water or water such as ultrapure water, a water-soluble solvent, and a mixed solvent containing water and a water-soluble solvent should be used. It is preferable to use water or the above mixed solvent.

Examples of the water-soluble solvent include ketones such as acetone, methyl ethyl ketone, methyl butyl ketone, and methyl isobutyl ketone; methanol, ethanol, 2-propanol, 2-methyl-1-propanol, 1-butanol, and 2-methoxyethanol. Alcohols such as tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, etc .; dimethylformamide, N-methylpyrrolidone, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, Glycols such as polyethylene glycol and polypropylene glycol; diols such as butanediol, pentanediol, hexanediol, and diols of the same family; laurin Glycol esters such as propylene glycol; glycol ethers such as diethylene glycol monoethyl, diethylene glycol monobutyl, diethylene glycol monohexyl ether, propylene glycol ether, dipropylene glycol ether, and cellosolve containing triethylene glycol ether; methanol, ethanol, isopropyl Alcohols such as alcohol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, butyl alcohol, pentyl alcohol, and alcohols homologous thereto; or sulfolane; lactones such as γ-butyrolactone; N- ( Lactams such as 2-hydroxyethyl) pyrrolidone; glycerin and its derivatives, etc., alone or in combination The above combination can be used.

In addition to the above-described components, the water-based ink for inkjet recording includes a wetting agent (drying inhibitor), a penetrating agent, a surfactant, a preservative, a viscosity adjuster, a pH adjuster, a chelating agent, a plasticizer as necessary. Those containing other additives such as an agent, an antioxidant, and an ultraviolet absorber can be used.

The wetting agent can be used for the purpose of preventing ink drying.

Examples of the wetting agent include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol having a molecular weight of 2000 or less, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol. 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, mesoerythritol, pentaerythritol, etc., among which triethylene glycol, propylene glycol 1,3-butanediol is preferred because it is highly miscible with water and can further improve the clogging prevention effect of the ink ejection head of the ink jet recording apparatus. There.

The wetting agent is preferably used in the range of 3% by mass to 50% by mass with respect to the total amount of the ink.

The penetrant can be used for the purpose of improving the permeability to the recording medium and adjusting the dot diameter on the recording medium.

Examples of the penetrant include lower alcohols such as ethanol and isopropyl alcohol, ethylene oxide adducts of alkyl alcohols such as ethylene glycol hexyl ether and diethylene glycol butyl ether, and propylene oxide adducts of alkyl alcohols such as propylene glycol propyl ether. The penetrant is preferably used in the range of 0.01 to 10% by mass with respect to the total amount of the ink.

The surfactant can be used to adjust ink properties such as surface tension. The surfactant is not particularly limited, and examples thereof include various anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Anionic surfactants, nonions It is preferable to use a surfactant.

Examples of the anionic surfactant include alkylbenzene sulfonate, alkylphenyl sulfonate, alkylnaphthalene sulfonate, higher fatty acid salt, sulfate of higher fatty acid ester, sulfonate of higher fatty acid ester, higher alcohol ether. Sulfate salts and sulfonates of the above, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, etc. Specific examples include dodecylbenzene sulfonate, isopropyl naphthalene sulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenyl sulfonate, dibutylphenylphenol disulfate. Such as phosphate salt can be mentioned.

Nonionic surfactants include, for example, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester , Polyoxyethylene glycerin fatty acid ester, polyglycerin fatty acid ester, sucrose fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene fatty acid amide, fatty acid alkylolamide, alkyl alkanolamide, acetylene glycol, oxyethylene adduct of acetylene glycol, Polyethylene glycol polypropylene glycol block copolymer, etc. Among these, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, Fatty acid alkylolamide, acetylene glycol, oxyethylene adduct of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymer are preferred.

Other surfactants include silicone surfactants such as polysiloxane oxyethylene adducts; fluorine surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers. Biosurfactants such as spicrispolic acid, rhamnolipid, lysolecithin and the like can also be used.

The surfactants described above can be used alone or in combination of two or more. As the surfactant, it is preferable to use a surfactant having an HLB in the range of 4 to 20 in order to achieve both the storage stability of the ink and the good wettability of the ink with respect to the recording medium. The surfactant is preferably used in the range of 0.001% by mass to 2% by mass with respect to the total mass of the ink, and more preferably in the range of 0.001% by mass to 1.5% by mass. The range of 0.01% by mass to 1% by mass is more preferable in terms of achieving both the storage stability of the ink and the good wettability of the ink with respect to the recording medium.

The water-based ink is an ink in which the total mass of the pigment, the pigment-dispersing resin, and the binder with respect to the total amount of the water-based ink is preferably in the range of 5 to 40% by mass, more preferably 5 to 20% by mass. Can be used. With the cleaning liquid of the present invention, excellent cleaning power can be exhibited even in a cleaning scene of a recording apparatus using a water-based ink having a relatively large solid content as described above.

(Recording medium)
The recording medium used as the recording medium of the water-based ink for inkjet recording is not particularly limited, and is an absorptive recording medium, a recording medium having an ink absorption layer, and a non-absorbing ink that does not have ink absorptivity. Recording medium, and a low-absorbing recording medium with low ink water absorption.

Examples of absorbent recording media include, for example, copy paper (PPC paper), plain paper, cloth, cardboard, wood, and the like that are commonly used in copying machines. Further, examples of the recording medium having an absorption layer include inkjet dedicated paper, and specific examples thereof include, for example, Pictrico Pro Photo Paper from Pictorico Co., Ltd.

Examples of the non-water-absorbing recording medium include a plastic film, a paper coated with a plastic, a plastic film adhered, and the like. For example, what is used for the packaging material for foodstuffs etc. can be used, and a well-known plastic film can be used. Specific examples include polyester films such as polyethylene terephthalate and polyethylene naphthalate, polyolefin films such as polyethylene and polypropylene, polyamide films such as nylon, polystyrene films, polyvinyl alcohol films, polyvinyl chloride films, polycarbonate films, polyacrylonitrile films, A polylactic acid film etc. are mentioned. In particular, a polyester film, a polyolefin film, and a polyamide film are preferable, and polyethylene terephthalate, polypropylene, and nylon are more preferable. In addition, the above-mentioned film coated with polyvinylidene chloride or the like for imparting a barrier property may be used, and a vapor deposition layer of a metal oxide such as gold, silver, copper, or aluminum, or a metal oxide such as silica or alumina, if necessary. A laminated film may be used in combination.

The plastic film may be an unstretched film but may be stretched in a uniaxial or biaxial direction. Further, the surface of the film may be untreated, but those subjected to various treatments for improving adhesive properties such as corona discharge treatment, ozone treatment, low temperature plasma treatment, flame treatment, glow discharge treatment and the like are preferable.

The film thickness of the plastic film is appropriately changed according to the application. For example, in the case of a flexible packaging application, the film thickness is 10 μm to 100 μm assuming that it has flexibility, durability, and curl resistance. Preferably there is. More preferably, it is 10 μm to 30 μm. Specific examples thereof include Pyrene (registered trademark) manufactured by Toyobo Co., Ltd.

The low-absorbency recording medium is not particularly limited. For example, a coating layer for receiving ink is provided on the surface of high-quality paper, neutral paper, etc. that are generally not surface-treated, mainly composed of cellulose. Examples include coated paper.

Specifically, the coated paper is a paper whose surface is coated with a paint to enhance aesthetics and smoothness, and is classified as a coated paper for printing according to the Ministry of Economy, Trade and Industry's “Production Dynamic Statistics Classification”. Is mentioned.

The coated paper is not particularly limited. For example, art paper such as printing paper, coated paper, lightweight coated paper, and fine coated paper can be used.

Examples of the low-absorbency recording medium include fine coated paper such as “OK Everlight Coat” manufactured by Oji Paper Co., Ltd. and “Aurora S” manufactured by Nippon Paper Industries Co., Ltd. Lightweight coated paper (A3) such as “OK Coat L” and “Aurora L” manufactured by Nippon Paper Industries Co., Ltd. “OK Top Coat +” manufactured by Oji Paper Co., Ltd. and “Aurora Coat” manufactured by Nippon Paper Industries Co., Ltd. Coated paper (A2, B2), etc., “OK Kanfuji +” manufactured by Oji Paper Co., Ltd., and art paper (A1) such as “Tokuhishi Art” manufactured by Mitsubishi Paper Industries Co., Ltd.

(Example)
Hereinafter, the present invention will be described in more detail by way of examples.

(Method for preparing inkjet recording water-based ink)

(Production Example 1 Synthesis Method of Pigment Dispersion Resin A)
A living anionic polymerization type block copolymer was synthesized using a microreactor having three T-shaped micromixers M1, M2 and M3.

First, butyllithium (BuLi) as a polymerization initiator and styrene (St) as a first monomer are added to the first T-shaped micromixer M1 from the tube reactors P1 and P2 connected to the T-shaped micromixer M1, respectively. The polymer was obtained by introducing and living anionic polymerization.

Next, the obtained polymer is moved to the T-shaped micromixer M2 through the tube reactor R1 connecting the T-shaped micromixer M1 and the T-shaped micromixer M2, and the growth terminal of the polymer is moved to the T-shaped micromixer M2. The sample was trapped by a reaction adjusting agent (α-methylstyrene (α-MeSt)) introduced from a tube reactor P3 connected to the type micromixer M2.

Next, methacrylic acid tert-butyl ester (t-BMA) as a second monomer is introduced into the T-shaped micromixer M3 from the tube reactor P4 connected to the T-shaped micromixer M3, and the T-shaped micromixer M2 and T A continuous living anion polymerization reaction was performed with the polymer moved through the tube reactor R2 connected to the letter-shaped micromixer M3. Thereafter, the reaction was quenched with methanol to produce a block copolymer (PA-1).

The reaction temperature was set to 24 ° C. by immersing the entire microreactor in a constant temperature bath. The monomer and reaction modifier introduced into the microreactor are dissolved in tetrahydrofuran (THF), and BuLi is a commercially available 2.6M hexane solution diluted with hexane. Depending on the dilution concentration and introduction rate, the block copolymer ( The molar ratio of PA-1) was adjusted to BuLi / St / α-MeSt / tBMA = 1/12/20 / 8.1.

The obtained block copolymer (PA-1) is hydrolyzed by treating with a cation exchange resin, the reaction solution is distilled off under reduced pressure, and the resulting solid is pulverized to obtain styrene-methacrylic acid. The pigment dispersion resin A which is a system block copolymer was obtained.

(Production Method 2 Synthesis Method of Pigment Dispersion Resin B)
100 parts by mass of methyl ethyl ketone was charged into a reaction vessel having a stirrer, a dropping device and a reflux device, and the inside of the reaction vessel was purged with nitrogen while stirring. After heating the reaction vessel in a nitrogen atmosphere to bring the methyl ethyl ketone into a reflux state, 74 parts by mass of styrene, 11 parts by mass of acrylic acid, 15 parts by mass of methacrylic acid and a polymerization initiator (Wako Pure Chemical Industries, Ltd.) were added from the dropping device. (Made by Co., Ltd./“V-75 ”) 8 parts by mass of a mixed solution was dropped into the reaction vessel over 2 hours.
Note that the temperature of the reaction system was kept at 80 ° C. during the dropping.

After completion of dropping, the reaction was continued at 80 ° C. for another 25 hours. In the middle of the reaction, a polymerization initiator was appropriately added while confirming the consumption status of the raw materials. After completion of the reaction, methyl ethyl ketone was distilled off under reduced pressure, and the resulting solid was pulverized to obtain pigment dispersion resin B.

(Production Example 3 Production Method of Aqueous Pigment Dispersion (MD-1))
150 g of Pigment Red 122 as a pigment, 30 g of Pigment Dispersion Resin A, 150 g of triethylene glycol as a water-soluble solvent, and 20 g of a 34% by mass aqueous potassium hydroxide solution were charged into a 1.0 L intensive mixer (Nippon Eirich Co., Ltd.) Step 1 of kneading for 25 minutes at a rotor peripheral speed of 2.94 m / s and a pan peripheral speed of 1 m / s was performed.

Subsequently, 450 g of ion-exchanged water was gradually added to the kneaded material in the intensive mixer container while continuing stirring, and then Step 2 in which 185 g of ion-exchanged water was added and mixed was performed. The pigment concentration was 15.0% by mass. An aqueous pigment dispersion (MD-1) was obtained.

(Production Example 4 Production Method of Aqueous Pigment Dispersion (BKD-2))
A commercially available product “CAB-O-JET300” manufactured by Cabot Japan was used as the aqueous pigment dispersion (BKD-2).

(Production Example 5 Production Method of Aqueous Pigment Dispersion (CY-3))
As a pigment, 120 parts by mass of phthalocyanine pigment Fast Gen Blue Pigment (DIC Corporation: CI Pigment 15: 3) and 36 parts by mass of Pigment Dispersion Resin B were added to a 0.2 L atmospheric pressure kneader (manufactured by Advance Co., Ltd.). The mixture was charged and the jacket temperature was mixed at 80 ° C. (number of blade rotations: 40 rpm). Next, 52 parts by mass of diethylene glycol and 20 parts by mass of a 34% by mass potassium hydroxide aqueous solution were added and kneaded for 1 hour.

Next, 360 parts by mass of ion-exchanged water as a dispersion medium (i) is gradually added to the kneaded material in the atmospheric pressure kneader while continuing stirring, and then 68 parts by mass of diethylene glycol as an dispersion medium (ii), ions An aqueous pigment dispersion (CY-3) having a pigment concentration of 15% by mass was obtained by adding and mixing a mixture of 144 parts by mass of exchange water.

(Preparation of water-based ink for inkjet recording)
In order to evaluate the cleaning liquid, water-based inks for inkjet recording were prepared using the water-based pigment dispersions of Production Examples 3 to 5.

(Preparation Example 1)
33.3 g of the aqueous pigment dispersion (MD-1), 20.5 g of Boncoat CM-8430 (manufactured by DIC Corporation, acrylic resin), 15.9 g of distilled water, 6.0 g of 3-methoxy-1-butanol, Propylene glycol 13.0 g, glycerin 10.0 g, ACTICIDE B-20 (preservative manufactured by So Japan Co., Ltd.) 0.1 g, triethanolamine 0.2 g, and SURFYNOL 440 (surfactant manufactured by Air Products) 1 A magenta aqueous ink (X1) was prepared by adding 0.0 g and stirring.

(Preparation Examples 2 to 5)
Aqueous inks (X2) to (X6) were obtained in the same manner as in Preparation Example 1, except that the composition of the aqueous ink was changed to the composition shown in Table 1.

In Table 1, abbreviations are as follows.
PG: Propylene glycol (Asahi Glass Co., Ltd.)
3MB: 3-methoxy-1-butanol (manufactured by Daicel Corporation)
GLY: Glycerin (manufactured by Kao Corporation)
TEG: Triethylene glycol (manufactured by Nippon Shokubai Co., Ltd.)
TEA: Triethanolamine (Mitsui Chemicals)
B-20: ACTICIDE B-20 (preservative manufactured by So Japan Co., Ltd.)
SF440: Surfynol 440 (Surfactant manufactured by Air Products Japan Co., Ltd.)
KL245: TEGO-WET KL245 (surfactant manufactured by Evonik)
CM-8430: Bon coat CM-8430 (acrylic resin manufactured by DIC Corporation)
WLS-213: Hydran WLS-213 (urethane resin manufactured by DIC Corporation)
EFD-5530: Watersol EFD-5530 (epoxy ester resin manufactured by DIC Corporation)
S-725P: Watersol S-725P (acrylic resin manufactured by DIC Corporation)
“Ink solid content” in Table 1 refers to the ratio of the total mass of the pigment, the pigment dispersion resin, and the binder resin to the total amount of the aqueous ink.

(Example: Preparation method of cleaning liquid)
Example 1
Distilled water (84.1 g), dipropylene glycol monobutyl ether (9.3 g), Neugen EA-157 (Daiichi Kogyo Seiyaku Co., Ltd.) (6.5 g) and triethanolamine (0.1 g) were added and stirred, and the washing solution (F01) was added. Prepared.

(Examples 2 to 14)
Cleaning solutions (F02) to (F14) were obtained in the same manner as in Example 1 except that the composition of the cleaning agent was changed as described in Tables 2 and 3.

(Comparative Examples 1 to 9)
Cleaning solutions (H01) to (H10) were obtained in the same manner as in Example 1 except that the composition of the cleaning agent was changed as described in Table 4.

In Tables 2 to 5, abbreviations are as follows.
DPMBE: Dipropylene glycol monobutyl ether PMBE: Propylene glycol monobutyl ether TPMBE: Tripropylene glycol monobutyl ether 2-HEP: 2-heptanol 3MB: 3-methoxybutanol (water-soluble solvent)
DPME: Dipropylene glycol methyl ether (water-soluble solvent)
HEPTAN: heptane NaHCO ₃ : sodium hydrogen carbonate (bicarbonate)
TEA: Triethanolamine EA-157: Neugen EA-157 (Daiichi Kogyo Seiyaku Co., Ltd.)
KL245: TEGO WET KL245 (Evonik Japan Co., Ltd.)
SF465: Surfinol 465 (manufactured by Air Products Japan Co., Ltd.)
O4300: Olphin 4300 (manufactured by Nissin Chemical Industry Co., Ltd.)
E147: Emulgen 147 (manufactured by Kao Corporation)
GLYN: NIKKOL DECAGLYN 1-L (manufactured by Nikko Chemicals Co., Ltd.)
END: Sandet END (manufactured by Sanyo Chemical Industries)
TDS-200: Neugen TDS-200D (Daiichi Kogyo Seiyaku Co., Ltd.)
SLS: Sodium lauryl sulfate (manufactured by Nikko Chemicals)

(Method for measuring pH of cleaning liquid)
The pH of the washings (F01) to (F14) and (H01) to (H10) was measured with a pH meter (MM-60R manufactured by Toa DKK Co., Ltd.).

(Measurement method of volume average diameter of droplets contained in cleaning liquid)
The volume average diameter of the droplets contained in the cleaning liquid was measured using a dynamic light scattering particle size measuring device “NanoTrack Wave” manufactured by Nikkiso Co., Ltd. The washing solution was measured as it was at 25 ° C. without being diluted with water. When the washing liquid was an O / W emulsion and was quickly separated into an aqueous phase and another phase, the aqueous phase portion after separation was fractionated and measured.

(Evaluation method of physical properties necessary for measuring the volume average diameter of droplets contained in cleaning liquid)
The viscosity of the solvent contained in the cleaning liquid is determined by adding an organic solvent identical to the organic solvent contained in the cleaning liquid to the water until it is separated. It refers to the value measured by industrial TV-25). The refractive index of water was used as the refractive index of the solvent.

Also, the refractive index and density of the organic solvent were used as the refractive index and density of the droplets (micelle or emulsion particles containing the organic solvent) contained in the cleaning liquid.

The measurement time of the volume average diameter was 30 seconds. The measurement was performed 3 times, and the average value was shown in the table.

(Evaluation method of cleaning solution)
The characteristics of the cleaning liquids (F01) to (F14) and (H01) to (H10) were evaluated as follows. The results are shown in Tables 6 to 8.

[Cleanability (redispersibility) of solidified ink]
The aqueous ink was dropped on a release paper with a micropipette by 1 microliter and completely dried on a hot plate at 120 ° C. to obtain a solidified ink (1 microliter of ink).

Next, 1 grain of the above-mentioned ink solidified product (for 1 microliter of ink) was simultaneously added to each vial containing 2 g of the cleaning liquids of Examples and Comparative Examples, and was occasionally left with shaking.

Among the cleaning liquids of Examples and Comparative Examples, the cleaning liquid in which the ink solidified product was first dissolved was evaluated as “5”.

When the cleaning liquid evaluated as “5” dissolved the ink solidified product (reference time), the color of the cleaning liquid and the state of the ink solidified product were visually observed, and the following “1” to “4” were evaluated.
4: The cleaning liquid was colored at the reference time, and the solidified ink was finely divided.
3: Although the cleaning liquid was colored at the reference time, the solidified ink remained as particles larger than Evaluation 4.
2: The degree of coloring of the cleaning liquid at the reference time was thinner than that in the evaluation 3, and the solidified ink was almost unchanged from the initial state.
1: The cleaning liquid was not colored at the reference time, and one solidified ink (one microliter of ink) used in this evaluation was present in the cleaning liquid without change.

The above evaluation was carried out with 4 types of water-based inks, and the cleaning properties of each cleaning liquid with respect to the solidified product of each water-based ink were evaluated. The total of the above evaluation points (1 to 5) is shown in the following table.

[Cleanability of ink flow path (cleanability of ink adsorbate)]
On the SUS430 plate simulating the ink flow path, the ink (X2) having the strongest adsorption to the SUS430 is applied to the bar coater No. After coating with No. 2 and drying on a hot plate at 120 ° C. for 5 minutes, the surface was washed with water to obtain a test piece having ink adsorbed on the surface of SU430.

Next, a sample obtained by cutting the test piece into a rectangle having a length of 20 mm and a width of 7 mm was used as a sample, and placed in a vial containing 2 g of a cleaning solution and left for 5 minutes.

After the standing, the sample was taken out from the vial, and the presence or absence of the ink adsorbent on the surface of the SUS430 and the color of the cleaning liquid were visually observed and evaluated according to the following criteria.
3: The ink adsorbate did not remain on the surface of SUS430, SUS430 returned to the original color before the ink was adsorbed, and the cleaning liquid had the ink color.
2: The ink adsorbate remained on the surface of SUS430, but the ink was colored in the cleaning liquid.
1: The ink adsorbate remained on the surface of SUS430, and the cleaning liquid was transparent.

The cleaning liquid having a relatively large droplet diameter was excellent in the ability to redisperse the solidified ink regardless of the pigment dispersion and the binder. Further, even when the organic solvent was not completely solubilized due to the lack of the surfactant and was in an emulsified state (for example, Examples 8 and 12), excellent characteristics were exhibited. Even when a plurality of surfactants were combined (for example, Examples 3, 5, 9, and 10), good detergency was exhibited if the droplet diameter was large.

On the other hand, the cleaning liquid whose pH was not adjusted even though the droplet diameter was large could not re-disperse the solidified ink. Furthermore, the cleaning liquid having a relatively small droplet diameter is inferior in the ability to redisperse the solidified product.

[Ink contact stability]
When the ink discharge head immediately after discharging the water-based ink is washed with water, if the water-based ink remaining in the head comes into contact with the water, the dispersion stability of the pigment, binder, etc. in the water-based ink is reduced and aggregation is caused. This may cause clogging of the ink discharge nozzles. Therefore, the cleaning liquid is required to have characteristics (ink contact stability) that do not lower the dispersion stability of the water-based ink when it comes into contact with the water-based ink. The contact stability of the ink was evaluated by the following method.

First, the volume average diameter (x0) of the water-based ink (X1) and the volume average diameter of the cleaning liquid (F10) or the cleaning liquid (H07) are calculated using a dynamic light scattering particle size measuring device “Microtrack particle size distribution manufactured by Nikkiso Co., Ltd.” Measurement was performed using “UPA-ST150”.

Next, 0.1 g of the water-based ink (X1) diluted 50-fold with water and 1.9 g of the cleaning solution (F10) or the cleaning solution (H07) were each placed in a vial and stored at room temperature for 1 week.

The volume average diameter (x1) of the liquid in each vial after storage was measured with a dynamic light scattering particle size measuring device “Microtrac particle size distribution analyzer UPA-ST150” manufactured by Nikkiso Co., Ltd.

The difference between the volume average diameter (x1) and the volume average diameter (x0) exceeded 10 nm was evaluated as “NG”, and the difference was within 10 nm was evaluated as “OK”.

[Cleanability of ink discharge head (Discharge defect improvement 1)]
The detergency of the ink discharge head was evaluated based on the number of white stripes on the printed matter. White streaks are generated when the ink solidified product or the thickened material adheres to the ink flow path or the nozzle surface and the nozzles of the ink discharge head are clogged.

Two inkjet discharge heads were prepared in which about 17% of the 2556 nozzles were clogged with solidified water-based ink (X1).

Next, each inkjet discharge head is filled with water-based ink (X1), and solid printing of 10 cm × 2 cm is performed on each OK top coat + which is an A2 coated paper made of Oji Paper by a single pass. A printed material was obtained. The number of white streaks in the two printed materials was calculated by a method using image processing software ImageJ, which will be described later.

Next, water was supplied to the nozzle surfaces and the ink flow paths of the two inkjet discharge heads.

Next, the two inkjet discharge heads were each filled with a cleaning solution (F10) or a cleaning solution (H07) filtered through a 0.45 μm syringe filter, and left for 15 minutes.

Next, the nozzle surface of the inkjet discharge head was wiped with a cloth wiper (Nippon Paper Crecia Techno Power Crosslay) sufficiently moistened with the cleaning liquid.

Next, water was supplied to the nozzle surface of the inkjet discharge head and the ink flow path, and the cleaning liquid was thoroughly washed away.

Next, the ink jet discharge head is filled with water-based ink (X1), and a solid print of 10 cm × 2 cm is performed on each OK top coat + which is an A2 coated paper made by Oji Paper Co., Ltd. by a single pass. Got. The number of white stripes in the two printed materials was calculated by a method using image processing software ImageJ described later.

The number of white streaks of the printed matter obtained before the washing was compared with the number of white streaks of the printed matter obtained after the washing.

The number of white streaks in the printed matter was calculated by image processing using image processing software ImageJ. Specifically, the printed material was scanned at 600 dpi to binarize the image, and a luminance profile (PlotProfile) in a straight line (10 cm) in the long side direction of the printed material was obtained. The number of pixels that became white (255) was calculated as the number of white lines.

[Cleaning performance of ink ejection head (improving ejection failure 2)]
An ink jet head having ink stains such as ink remaining on the nozzle surface or dried ink was placed on a cloth wiper sufficiently moistened with the cleaning liquid in a state where the nozzle surface and the wiper were in contact, and left for 15 minutes.

Next, the nozzle surface of the inkjet head was wiped with a cloth wiper moistened with the cleaning liquid.

After that, the nozzle surface was washed away with water, and it was visually confirmed whether the ink stain on the nozzle surface had disappeared.

The cleaning liquid (F10) of the present invention does not cause ink aggregation even when it comes into contact with diluted ink, and can re-disperse the ink solidified product or thickened material on the ink flow path and the nozzle surface, resulting in ink clogging. It was possible to improve the discharge failure. On the other hand, the cleaning liquid (H07) not according to the present invention does not cause aggregation of diluted ink, but has poor ability to re-disperse the solidified product or thickened product, and cannot improve the ejection failure.

Claims (8)

1. A cleaning solution having a pH of 7 to 10 containing water, an insoluble or hardly soluble organic solvent, and a surfactant, wherein the organic solvent forms droplets in the water, and the volume average of the droplets A cleaning liquid having a diameter of 9 nm or more.
2. The cleaning liquid according to claim 1, wherein the organic solvent is a monoalkylene glycol alkyl ether or a dialkylene glycol alkyl ether.
3. The cleaning liquid according to claim 1, wherein the volume average diameter of the droplets is in the range of 12 to 50 nm.
4. The cleaning liquid according to any one of claims 1 to 3, wherein the cleaning liquid is used for cleaning a dry matter of a water-based ink containing a pigment, a pigment dispersion resin, and a binder resin.
5. A method for cleaning an ink jet recording apparatus using the cleaning liquid according to any one of claims 1 to 4.
6. A method for cleaning an ink jet recording apparatus, comprising the step [1] of bringing a nozzle surface constituting an ink discharge head provided in the ink jet recording apparatus into contact with the cleaning liquid according to any one of claims 1 to 4. .
7. The step [2] of supplying the cleaning liquid according to any one of claims 1 to 4 to an ink discharge head provided in the ink jet recording apparatus, and the nozzle surface is wiped after the cleaning liquid is brought into contact with the nozzle surface of the head A method for cleaning an ink jet recording apparatus, comprising a step [3] and a step [4] for removing the cleaning liquid from the nozzle.
8. The cleaning method according to claim 6, wherein the inkjet recording apparatus is an inkjet recording apparatus for aqueous ink containing a pigment, a pigment dispersion resin, and a binder resin.