JP5233421B2 - Inkjet recording method - Google Patents

Description

  The present invention relates to an ink jet recording method, and more particularly to an ink jet recording method for recording on a fabric or a resin material.

  When water-based ink containing a pigment and a fixing resin is recorded on a cloth or a resin material, in the case of the cloth, bleeding along the fiber occurs. In addition, when the recording medium is a resin material, there is no ink absorption layer, so adjacent ink droplets coalesce and bleed and beading occur.

  In addition, pigment inks do not have sufficient binding strength with fibers and resin materials, and the addition of a fixing resin as a binder improves the binding strength, but it is sufficient from the viewpoints of injection characteristics, maintainability, and ink storage stability. The fact is that the required amount cannot be added.

Also known is a method of adding wax to the ink in order to improve the fastness of the paper recording medium (see, for example, Patent Documents 1 and 2). A certain level of effect can be obtained when recording on plain paper or ink jet dedicated paper having an ink absorbing layer, but the recorded matter is insufficient for fabrics and resin materials that require high frictional resistance.
JP 2003-261805 A Japanese Patent Laid-Open No. 5-125313

  The object of the present invention is to simultaneously achieve the prevention of ink mixing by heating when water-based ink is recorded on a recording medium such as a fabric or a resin material, and improvement of friction resistance by adding wax to the water-based ink. It is to provide an ink jet recording method.

  The above object of the present invention can be achieved by the following configuration.

  1. In an inkjet recording method for forming an image on a recording medium by discharging an aqueous ink containing at least a pigment, a fixing resin, and a wax having a melting point of 55 ° C. or higher and lower than 200 ° C., the aqueous ink is discharged while heating the recording medium An ink jet recording method for forming an image on the recording medium, wherein the heating temperature of the recording medium is 20 to 100 ° C. lower than the melting point of the wax.

  2. 2. The ink jet recording method according to 1 above, wherein the glass transition temperature of the fixing resin is lower than the melting point of the wax, and the heating temperature of the recording medium is higher than the glass transition temperature of the fixing resin.

  3. 3. The inkjet recording method according to 1 or 2 above, wherein after forming an image on a recording medium by ejecting water-based ink, the recording medium on which the image has been formed is heated to a melting point or higher of the wax.

  4). 4. The inkjet recording method according to any one of 1 to 3, wherein the average particle size of the wax is smaller than the average particle size of the pigment.

  5. The solid content of the pigment is 4% or more and 8% or less, and the total solid content of the fixing resin and the wax is 1 to 2 times the solid content of the pigment. The inkjet recording method as described.

  6). 6. The inkjet recording method according to any one of 1 to 5, wherein the recording medium is a fabric.

  7). 7. The ink jet recording method according to any one of 1 to 6, wherein the recording medium is a resin material.

  According to the present invention, when recording using water-based ink on a recording medium such as a fabric or a resin material, ink-jet recording simultaneously achieves prevention of ink mixing by heating and improvement of friction resistance by adding wax to the water-based ink. Could provide a way.

  The present invention will be described in more detail. When recording on a recording medium such as a cloth or a resin material using water-based ink, it is effective to cause thickening by drying the water-based ink and to reduce the fluidity of the water-based ink in order to prevent mixing of the water-based ink. In order to prevent coalescence of water-based inks, it is necessary to dry the ink as quickly as possible to cause thickening, and recording while heating the recording medium is an effective method. The speed of thickening is preferably fast.

  The present inventor has simultaneously achieved prevention of mixing of water-based ink by heating when recording water-based ink on a recording medium such as a fabric or a resin material, and improving friction resistance by adding wax to the water-based ink. We have studied earnestly.

  As described above, the heating of the recording medium for preventing water-based ink mixing is preferable as the recording medium is heated to a high temperature. However, the present inventor has discovered that the addition of wax is different and has led to the present invention. is there.

  As a result of this study, it was found that when wax is used, if the recording medium is heated too much at a high temperature, the frictional resistance may not be improved or deteriorated. Furthermore, it has been found that mixing with water-based ink may be worsened. As a result of detailed investigation of the relationship between the heating temperature of the recording medium for each wax used, it was found that heating the recording medium at a temperature of 20 ° C. or less from the melting point of the wax is particularly preferable in terms of friction resistance and water-based ink. did.

  Although this phenomenon has not been clearly clarified, it is estimated as follows. When the heating temperature of the recording medium is close to the melting point of the wax, the wax dissolves near the recording medium surface and covers the recording medium surface. In addition, the wax is usually dispersed by introducing a water-dispersible group on the surface or using a dispersant so that the wax can be stably dispersed in the aqueous ink. When the wax is dissolved in the vicinity of the melting point, the hydrophobic surface of the wax itself appears on the surface, and the slipperiness of the wax is more easily exhibited. On the other hand, the water-based ink is easily repelled, and the permeability of the water-based ink is significantly reduced. This makes it easier for adjacent water-based inks to coalesce, particularly when the amount of water-based ink is large. At the same time, it is considered that the pigment itself tends to be more unevenly distributed near the surface of the recording medium than the normal amount due to the inhibition of water-based ink absorption, resulting in poor frictional resistance.

  A solvent is added to the water-based ink for various purposes. It is estimated that this solvent acts as a plasticizer for the wax, and the dissolution of the wax starts at a temperature lower than the actual melting point of the wax, thereby causing mixing of aqueous ink and a reduction in friction resistance from a temperature lower than the melting point of the wax. . As a result of intensive studies by the present inventors, it has been found that recording is performed by heating the recording medium to a temperature 20 ° C. lower than the melting point of the wax, thereby achieving both prevention of mixing with water-based ink and improvement of friction resistance.

(Pigment)
The pigment used in the present invention is not particularly limited as long as it can be stably dispersed in an aqueous system. A pigment dispersion dispersed with a polymer resin, a capsule pigment coated with a water-insoluble resin, a pigment surface is modified and a dispersion resin is not used. Can also be selected from dispersible self-dispersing pigments and the like. When emphasizing the preservability of the water-based ink, it is preferable to select a capsule pigment coated with a water-insoluble resin.

  When a pigment dispersion dispersed with a polymer resin is used, a water-soluble resin can be used as the polymer-dispersed resin, and styrene-acrylic acid-acrylic acid alkyl ester copolymer is preferably used as the water-soluble resin. Polymer, Styrene-acrylic acid copolymer, Styrene-maleic acid copolymer, Styrene-maleic acid-alkyl acrylate copolymer, Styrene-methacrylic acid copolymer, Styrene-methacrylic acid-alkyl acrylate copolymer Water-soluble resins such as polymers, styrene-maleic acid half ester copolymers, vinyl naphthalene-acrylic acid copolymers, vinyl naphthalene-maleic acid copolymers, and the like.

  In the present invention, even if the water-soluble resin is added as a pigment dispersant at the time of pigment dispersion, the free resin that is not substantially adsorbed to the pigment in the aqueous ink is used as the water-soluble fixing resin component.

  Various methods such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a paint shaker can be used as a method for dispersing the pigment.

  For the purpose of removing the coarse particles of the pigment dispersion of the present invention, it is preferable to use a centrifugal separator or a filter.

  In the case of using a capsule pigment coated with a water-insoluble resin, the water-insoluble resin is a resin that is insoluble in water in a weakly acidic to weakly basic range, and preferably has a solubility in an aqueous solution having a pH of 4 to 10. Is less than 2% resin.

  Examples of such pigment dispersion resins include acrylic, styrene-acrylic, acrylonitrile-acrylic, vinyl acetate, vinyl acetate-acrylic, vinyl acetate-vinyl chloride, polyurethane, silicon-acrylic, acrylic silicon , Polyester-based, and epoxy-based resins.

  Furthermore, a resin containing a hydrophobic monomer and a hydrophilic monomer can be used as the resin.

  Examples of hydrophobic monomers include acrylic acid esters (such as n-butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate), methacrylic acid esters (such as ethyl methacrylate, butyl methacrylate, glycidyl methacrylate), styrene. Etc. are raised.

  Examples of the hydrophilic monomer include acrylic acid, methacrylic acid, acrylamide, and the like, and those having an acidic group such as acrylic acid can preferably be those neutralized with a base after polymerization.

  As the molecular weight of the pigment-dispersed resin, an average molecular weight of 3000 to 500,000 can be used. Preferably, 7,000 to 200,000 can be used.

  The pigment dispersion resin having a Tg of about −30 ° C. to 100 ° C. can be used. Preferably, about -10 degreeC to 80 degreeC can be used.

  As the polymerization method, solution polymerization or emulsion polymerization can be used. The polymerization may be separately synthesized with the pigment in advance, or the monomer may be supplied to the system without dispersing the pigment for polymerization.

  Various known methods can be used as a method for coating the pigment with the resin. Preferably, in addition to the phase-emulsification method and the acid precipitation method, the pigment is dispersed using a polymerizable surfactant. It is preferable to select from a method in which a monomer is fed to the substrate and coating is performed while polymerizing.

  As a more preferred method, the water-insoluble resin is dissolved in an organic solvent such as methyl ethyl ketone, and after partially or completely neutralizing the acidic groups in the resin with a base, the pigment and ion-exchanged water are added and dispersed. Thereafter, a production method in which the organic solvent is removed and the mixture is prepared by adding water as necessary is preferable.

  The mass ratio of the pigment and the pigment dispersion resin can be selected in the range of 100/10 to 100/150 in terms of pigment / resin ratio. In particular, the range of 100/15 to 100/100 has good image durability, injection stability, and aqueous ink storage stability.

  The average particle diameter of the pigment particles coated with the water-insoluble resin is preferably about 80 to 150 nm from the viewpoint of aqueous ink storage stability and color developability.

  Further, as the self-dispersing pigment, commercially available products that have been surface-treated can also be used, and examples thereof include CABO-JET200, CABO-JET300 (manufactured by Cabot Corporation), Bonjet CW1 (manufactured by Orient Chemical Industry Co., Ltd.) and the like. be able to.

  As the pigment that can be used in the present invention, conventionally known organic and inorganic pigments can be used. For example, azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc. Examples include cyclic pigments, dye lakes such as basic dye lakes, and acid dye lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments, and inorganic pigments such as carbon black.

  Specific organic pigments are exemplified below.

  Examples of pigments for magenta or red include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the orange or yellow pigment include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. And CI Pigment Yellow 138.

  Examples of pigments for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  The pigment solid content concentration is preferably 4% or more in order to obtain a sufficiently high concentration. However, if it is higher than 8%, there is an effect that water-based ink ejection properties and aqueous ink storage stability are lowered, and it is preferable to adjust the pigment solid content concentration to 4% -8%.

(Fixing resin)
In the present invention, the fixing resin is different from a so-called pigment dispersion resin that functions as a pigment dispersant and is bonded or adsorbed to the pigment. The fixing resin of the present invention is present in the water-based ink regardless of dissolution or non-dissolution, but is not directly bonded or adsorbed to the pigment, and is separable from the pigment dispersion.

  As the fixing resin according to the present invention, both a water-soluble resin and a water-dispersible resin can be used alone or in combination.

(Water-soluble fixing resin)
Here, the “water-soluble fixing resin” refers to a water-soluble resin having a function of fixing a pigment as a colorant to a recording medium (base material).

  In the present invention, the fixing resin is different from a so-called pigment dispersion resin that functions as a pigment dispersant and is bonded or adsorbed to the pigment. The fixing resin of the present invention is present in the water-based ink regardless of dissolution or non-dissolution, but is not directly bonded or adsorbed to the pigment, and is separable from the pigment dispersion.

  Examples of the water-soluble resin according to the present invention include acrylic resins, styrene-acrylic resins, acrylonitrile-acrylic resins, vinyl acetate-acrylic resins, polyurethane resins, and polyester resins.

  In the present invention, a copolymer resin having a monomer having an acidic group such as acrylic acid, methacrylic acid or itaconic acid as a copolymerizable monomer can be preferably used as the water-soluble resin.

In this case, it is preferable to copolymerize the following three types of monomers.
1) Monomer having acidic group 2) Monomer having Tg> 100 ° C. of homopolymer 3) Monomer having Tg <30 ° C. of homopolymer In order to increase the water solubility of the above copolymer, the acidic group portion is partially Alternatively, it is preferable to completely neutralize with a base component. As the neutralizing base in this case, alkali metal-containing bases such as Na hydroxide, K hydroxide, and amines (ammonia, alkanolamine, alkylamine, etc. can be used) can be used.

  In particular, neutralization with amines having a boiling point of less than 200 ° C. is preferable from the viewpoint of improving image durability. It is particularly preferable to neutralize with ammonia.

  For example, it is preferable to use a resin that contains acrylic acid or methacrylic acid as a copolymerization monomer and is partially or completely neutralized with ammonia.

  In the present invention, in addition to the above resins, urethane and polyester water-soluble resins can also be preferably used.

<Weight average molecular weight of water-soluble fixing resin>
A water-soluble fixing resin having a weight average molecular weight in the range of 5000 to 70000 can be preferably used. Preferably, it is the range of 10000-70000. The weight average molecular weight of the water-soluble fixing resin according to the present invention is measured using gel permeation chromatography (GPC).

  The measurement conditions are as follows.

Solvent: terahydrofuran Column: TSKgel Multipore (Those manufactured by Tosoh Co., Ltd. were used by connecting three)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000 to 500 samples were used. Thirteen samples are used at approximately equal intervals.

<Glass transition temperature of water-soluble fixing resin>
The glass transition temperature of the water-soluble fixing resin according to the present invention is preferably in the range of -20 to 100 ° C.

  If the glass transition temperature is lower than −20 ° C., blocking is not preferable. Further, when the glass transition temperature is higher than 100 ° C., creases are likely to occur depending on the recording medium.

  The glass transition temperature (Tg) according to the present invention is measured using a differential scanning calorimeter “DSC-7” (Perkin Elmer) and a thermal analyzer controller “TAC7 / DX” (Perkin Elmer). Can do.

  As an operation procedure, 4.5 to 5.0 mg of a measurement sample is precisely weighed to two digits after the decimal point, sealed in an aluminum pan (Kit No. 0219-0041), and set in a “DSC-7 sample holder”. The reference used an empty aluminum pan. The measurement conditions were a measurement temperature of 0 to 200 ° C., a temperature increase rate of 10 ° C./min, a temperature decrease rate of 10 ° C./min, and heat-cool-heat temperature control. Analysis was performed based on the data in Heat.

  The glass transition temperature is obtained by drawing an extension of the baseline before the rise of the first endothermic peak and a tangent line indicating the maximum slope between the rise portion of the first peak and the peak apex, and using the intersection as the glass transition point. Show.

  As a method for calculating the glass transition temperature, the following theoretical glass transition temperature may be calculated in the present invention.

  Here, the theoretical glass transition temperature is calculated by multiplying the glass transition temperature when each component constituting the resin forms a homopolymer by the respective composition mass fraction, that is, by weighted averaging.

  That is, the theoretical glass transition temperature Tg (referred to as absolute temperature Tg ′) is calculated from the following formula (1) using the glass transition temperature of the homopolymer of the component constituting the resin.

Formula (1): 1 / Tg ′ = W1 / T1 + W2 / T2 +... + Wn / Tn
(Wherein W1, W2,... Wn are the mass fraction of each polymerizable monomer relative to the total polymerizable monomer (monomer) constituting the resin, and T1, T2... Tn are each polymerizable monomer. (The glass transition temperature (absolute temperature) of the homopolymer formed using the monomer is shown.)
The method for adjusting the glass transition temperature of the water-soluble resin can be performed by selecting a monomer constituting the resin and adjusting the degree of polymerization in the polymerization reaction.

<Acid value of water-soluble fixing resin>
The water-soluble fixing resin according to the present invention preferably has an acidic group, and the acid value of the resin is preferably 70 to 200 mgKOH / g. Especially in this range, the water resistance and the maintenance recovery property are good. The “acid value” refers to the number of milligrams of potassium hydroxide required to neutralize acidic components contained in 1 g of resin.

  The acid value can be measured by a method based on JIS K 0070 (1992).

(Water dispersible fixing resin)
Adding a water-dispersible resin as a fixing resin is preferable because the friction resistance is further improved depending on the recording medium. It is preferable to use it to such an extent that injection property and maintenance recovery property are not hindered. It is also preferable to use the water-soluble fixing resin and the water-dispersible resin in combination.

  In the present invention, it is preferable to use a water-dispersible resin as resin fine particles.

  As the resin fine particles, a dispersion polymerized in an aqueous system may be used as it is or may be treated, or a resin polymerized in a solvent system may be dispersed in an aqueous system, an acrylic system, a urethane system, It can be selected from styrene, vinyl acetate, vinylidene chloride, vinyl chloride, styrene-butadiene, styrene-acrylonitrile, polybutadiene, polyethylene, polyisobutylene, polyester, and the like.

  As the physical properties of the water-based ink, it is preferable that there is no shear dependency on the viscosity. From this viewpoint, the emulsifier such as an activator is made as low as possible as the dispersion form of the resin fine particles, or the soap-free type dispersed resin particles using no emulsifier Is preferred. A preferred aqueous dispersion resin fine particle is a self-dispersion dispersion of a copolymer obtained by polymerizing unsaturated vinyl having a carboxyl group as at least a monomer component. For example, an acrylic monomer such as ethyl acrylate alone or an acrylic Mechanical dispersion is obtained by swelling a dispersion obtained by emulsion polymerization or suspension polymerization of acrylic acid or maleic acid as a carboxylic acid monomer into a composition comprising an ethylenically unsaturated monomer that can be copolymerized with a monomer, and then mechanically shearing. Is an acrylic hydrosol obtained by dividing the particles. Among acrylic hydrosols, it is preferable to contain styrene in the monomer composition from the viewpoint of increasing the refractive index of the resin and obtaining a high gloss feeling.

  The alkali is ammonia, triethylamine, 2-dimethylaminoethanol, 2-di-n-butylaminoethanol, methyldiethanolamine, 2-amino-2-methyl-1-propanol, diethanolamine, triethanolamine, 2-methylaminoethanol, etc. In particular, ammonia, 2-amino-2-methyl-1-propanol, and 2-methylaminoethanol are preferable in terms of dispersion stability of the aqueous dispersion polymer fine particles.

  As the acrylic hydrosol, John Crill (registered trademark) of Johnson Polymer Co., Ltd. is commercially available.

  The glass transition temperature: Tg of the resin fine particles is preferably 20 to 80 ° C. In particular, the temperature is preferably 35 ° C. or higher in order to increase the scratch resistance of the image, and more preferably 49 ° C. or higher. The upper limit of Tg is not particularly limited, but if it is less than about 100 ° C., a flexible water-based ink film can be obtained and image cracking failure due to bending of the printed matter can be prevented. The oxidation of the resin fine particles is preferably 44 or more, more preferably 60 or more, from the viewpoint of obtaining good redispersion / solubility of the water-based ink dry film. The upper limit of oxidation is not particularly limited, but is preferably less than 110 from the viewpoint of easily obtaining a more stable dispersion.

  The average particle diameter of the resin fine particles is preferably 300 nm or less, more preferably 130 nm or less, from the viewpoint that the nozzle of the head is not clogged and a good gloss is obtained. The lower limit of the average particle diameter is preferably 30 nm or more from the viewpoint of the production stability of the fine particles. The average particle diameter of the resin fine particles can be easily measured using a commercially available measuring apparatus using a light scattering method or a laser Doppler method. Alternatively, the dispersion of resin fine particles can be freeze-dried, and the average particle diameter can be converted from the particles observed with a transmission microscope.

  The total amount of the fixing resin in the water-based ink used in the present invention can be used in the range of 1% to 20% as the resin solid content in the water-based ink.

  In particular, it is preferably used in the range of 4% to 16%.

  In addition, the solid content of the pigment and wax is fixed in consideration of the solid content of the pigment and the wax so that the solid content of the pigment is 4% or more and 8% or less and the total solid content of the fixing resin and the wax is 1 to 2 times the solid content of the pigment. It is also preferable to determine the amount of resin.

  The preferable range of the glass transition temperature of the resin added to the water-based ink is as described above, but it is preferable that the melting point of the wax added to the water-based ink is lower.

(wax)
The aqueous ink used in the present invention contains a wax having a melting point of 55 ° C. or higher and lower than 200 ° C. The wax can be selected from animal waxes, plant waxes, petroleum waxes, natural waxes such as mineral waxes, or synthetic waxes.

  The wax may be either water-soluble or sparingly soluble. Slightly soluble waxes are preferable, and it is preferable to use mainly as a wax emulsion. Among these, a product obtained by dispersing a synthetic wax in water can be particularly preferably used.

  At this time, the average particle system of the wax dispersion can preferably be in the range of 30 to 300 nm. Particularly preferred is a range of 30 to 100 nm, which is preferred from the viewpoint of friction resistance, water-based ink mixing, and water-based ink ejection stability.

  In addition, it is particularly preferable to use a wax having an average particle size smaller than the average particle size of the water-based ink as the recording agent from the viewpoint of friction resistance and mixing with the water-based ink.

  When the average particle diameter of the wax is smaller than the average particle diameter of the pigment, the wax does not stay on the surface of the image during printing, so it is estimated that the occurrence of water-based ink mixing due to the repelling of the wax can be prevented. From the viewpoint of its function as a slip agent, it is preferable that the wax remains on the surface. However, according to the study of the present inventors, if the wax is excessively localized on the surface, the image quality is deteriorated due to mixing of water-based ink. . A form in which the wax moves to the surface by a drying process after printing or heating after printing is particularly preferable in terms of achieving both friction resistance and image quality.

  As the synthetic wax, polyethylene wax produced mainly by polymerization of ethylene or thermal decomposition of polyethylene can be preferably used.

  Commercially available polyethylene wax can be used, and for example, AQUACER manufactured by Big Chemie Japan Co., Ltd., JONCRYL WAX26J manufactured by BASF Japan, etc. can be preferably used.

  The amount of the wax added to the water-based ink is preferably 0.1% to 5%, more preferably 0.2% to 2%.

  Further, when the solid content of the pigment is 4% or more and 8% or less and the total solid content of the resin and wax is 1 to 2 times the solid content of the pigment, the friction resistance is further improved. It is preferable to add the wax so that the total solid content of the resin and wax is 1 to 2 times the solid content of the pigment with reference to the solid content of the pigment and the solid content of the resin.

(Average particle diameter of pigment and wax)
The average particle diameter of the pigment and wax can be easily measured using a commercially available measuring apparatus using a light scattering method or a laser Doppler method. Specifically, it is preferable to measure using a Zetasizer 1000 (manufactured by Malvern).

(Heating temperature)
The present invention is a method for forming an image on a recording medium by discharging aqueous ink while heating the recording medium. The heating temperature of the recording medium is 20 ° C. to 100 ° C. lower than the melting point of the wax. Preferably, the heating temperature of the recording medium is 40 ° C. or more lower than the melting point of the wax.

  The heating temperature of the recording medium of the present invention is preferably higher than the glass transition temperature of the resin from the viewpoint of improving the friction resistance. Preferably, the heating temperature of the recording medium is 20 ° C. or more higher than the glass transition temperature of the resin.

  It is preferable to further heat the recording medium after image formation in order to further improve the friction resistance. At this time, it is preferable to heat at a temperature higher than the heating temperature of the recording medium at the time of image formation, and it is more preferable to heat to the melting point of the wax or higher.

(recoding media)
When the recording method of the present invention is used when the recording medium is a fabric, it is preferable because the frictional resistance can be improved greatly and an excellent image quality with little water-based ink mixing can be obtained.

  Usually, the fabric used for the ink jet recording method is one in which a paste component or a cationic substance is previously applied to the fabric as a fabric pretreatment, but the water-based ink of the present invention is also suitable for a fabric not subjected to the fabric pretreatment. In addition, it is particularly preferable that recording is performed not only on the fabric that has been subjected to the fabric pretreatment but also on the fabric that has not been subjected to the fabric pretreatment.

  Examples of the fabric include various fiber materials such as cotton, silk, wool, nylon, polyester, acetate, rayon, polypropylene, vinylon, acrylic fiber, and the like, and those of mixed spinning, woven fabric, non-woven fabric, etc. Also good. Further, the thickness of the yarn constituting the fabric as described above is preferably in the range of 10 to 100d.

  The recording method of the present invention can also be used when the recording medium is a resin material. Heating the recording medium at the time of recording can reduce mixing of water-based ink and is suitable for printing on a non-absorbing medium having no water-based ink absorbing layer. As such a recording medium, various resin materials can be selected and recorded, and can be preferably used for polyvinyl chloride sheets and boards (soft vinyl chloride, hard vinyl chloride, acrylic plates, polyolefins, etc.).

  Examples of the present invention will be described below, but the present invention is not limited thereto.

(Preparation of pigment dispersion)
As a pigment dispersant, a styrene-acrylic acid copolymer (Johncrill 678, molecular weight: 8500, acid value: 215 mgKOH / g) 4.5 parts, dimethylaminoethanol 1.3 parts, ion-exchanged water 80.7 parts at 70 ° C. The mixture was dissolved by stirring.

  Next, C.I. I. After 15 parts of Pigment Blue 15: 3 was added and premixed, the mixture was dispersed using a sand grinder filled with 50% by volume of 0.5 mm zirconia beads, and the cyan pigment content was 15%. Body D1 was prepared.

(Fixing resin)
Monomers were mixed at a molar ratio shown in Table 1, and a water-soluble resin and a water-dispersible resin were polymerized according to a conventional method. Each resin was used by neutralizing acidic groups of an acidic group-containing monomer (such as methacrylic acid) with ammonia.

(Water-based ink preparation)
A pigment dispersion, a water-soluble resin, a solvent, an activator and a water-dispersible resin were added so that the water-based ink concentrations shown in Table 2 were obtained, and the balance was adjusted with ion-exchanged water so that the balance was 100% by mass. After preparation, it was filtered with a 5 μm filter.

  The activator in Table 2 is a silicon activator BYK347 manufactured by Big Chemie Japan.

[Evaluation 1]
The following evaluation was performed using the prepared water-based ink. The evaluation results are also shown in Tables 3 and 4.

  Evaluation was performed using a printing apparatus capable of four-color printing in which four piezo-type heads (720 dpi (dpi represents the number of dots per inch), appropriate amount of 14 pl) were arranged in parallel. In the apparatus, the recording medium can be arbitrarily heated from below by a contact heater. In addition, the head retracting position is equipped with a water-based ink emptying position and a blade wipe type maintenance unit, so that the head can be cleaned at an arbitrary frequency.

(Image quality evaluation)
Each of the water-based inks prepared was introduced into one head of the evaluation apparatus, a single color image was prepared, and the image quality was evaluated. The evaluation conditions are as follows.

Printing resolution: 720 dpi x 720 dpi
Head transport speed: 200 mm / sec (bidirectional printing)
recoding media:
The fabric 1 in Table 3 is a polyester fabric and polyester tropical that have not been pretreated.

  The vinyl chloride in Table 4 is ORAJET 3650G-101 manufactured by ORAFOL.

  Recording medium heating temperature: Table 3 and Table 4 show the print surface temperature.

  As the evaluation image, a wedge image, characters, and white characters were used.

  The evaluation environment was 20 ° C. and relative humidity 55%.

(Evaluation with water-based ink)
The image quality was evaluated by the presence or absence of beading and the occurrence of beading due to the presence of water-based ink and the lowercase drawing ability as follows: 1: Local repellency was observed, beading was severe, and lowercase letters could not be drawn 2: Although there was no repellency ： Beading is conspicuous and lowercase letters cannot be drawn 3: There is no repelling, but beading is slightly seen and lowercase letters can be drawn, but it is slightly unclear 4: Repelling, no beading, lowercase letters can be drawn, but white letters 5: Slightly unclear 5: No repelling, no beading, clear drawing of small letters and white letters.

(Friction resistance evaluation)
A 9N load was applied to cotton cloth (Kanakin No. 3), and the image surface was rubbed to evaluate the coloring of the face cloth.

1: Color can be seen by rubbing 5 times 2: Color can be seen by rubbing 10 times, but coloring is negligible with rubbing 5 times 3: Coloration is seen by rubbing 15 times, but coloring is negligible when rubbing 10 times Yes 4: Color is visible after rubbing 20 times, but color is negligible after rubbing 15 times.

  The above various evaluation results are shown in Tables 3 and 4.

  As is clear from the results shown in Tables 3 and 4, it can be seen that the ink jet recording method of the present invention is superior in performance of mixing with water-based ink and friction resistance.

Claims (7)

In an inkjet recording method for forming an image on a recording medium by discharging an aqueous ink containing at least a pigment, a fixing resin, and a wax having a melting point of 55 ° C. or higher and lower than 200 ° C., the aqueous ink is discharged while heating the recording medium An ink jet recording method for forming an image on the recording medium, wherein the heating temperature of the recording medium is 20 to 100 ° C. lower than the melting point of the wax. 2. The ink jet recording method according to claim 1, wherein the glass transition temperature of the fixing resin is lower than the melting point of the wax, and the heating temperature of the recording medium is higher than the glass transition temperature of the fixing resin. 3. The ink jet recording method according to claim 1, wherein after forming an image on the recording medium by ejecting the water-based ink, the recording medium on which the image has been formed is heated to the melting point of the wax or higher. 4. The ink jet recording method according to claim 1, wherein the average particle size of the wax is smaller than the average particle size of the pigment. The solid content of the pigment is 4% or more and 8% or less, and the total solid content of the fixing resin and the wax is 1 to 2 times the solid content of the pigment. The inkjet recording method according to Item. The ink jet recording method according to claim 1, wherein the recording medium is a fabric. The ink jet recording method according to claim 1, wherein the recording medium is a resin material.