JP2015107604A - Inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording method that can fix an aqueous ink to a non-permeable record medium at a high speed and can prevent solid matter from adhering to a head.SOLUTION: An inkjet recording method includes the steps of: discharging an aqueous ink containing at least a color material and resin particles to a record medium using an ink jet recording head; heating the record medium so that the surface temperature of the record medium at a position facing the ink jet recording head is T1; and heating the record medium so that the surface temperature of the record medium on the downstream side of the position facing the ink jet recording head in the sub-scanning direction is T2. T2 is higher than T1. The glass transition temperature (Tg) of the resin particles is higher than T2. The minimum film forming temperature (Tm) of the resin particles is higher than T1 and not higher than T2.

Description

  The present invention relates to an ink jet recording method.

  Ink jet recording systems are not only used for printing on permeable recording media such as paper, but also for application development such as printing on non-permeable recording media using plastics such as polyvinyl chloride and polyethylene terephthalate. In recent years, water-based inks for non-permeable recording media, which have high environmental safety, have been commercialized.

  As a method of recording on a non-permeable recording medium using water-based ink, in general, a heating process is provided to promote evaporation of a solvent such as water and solvent, and the ink formed on the surface of the recording medium is solidified again. And a method of fixing the color material by performing the above-described process. In order to increase productivity, a recording method that enables high-speed printing, and a recording method that lowers the heating temperature in consideration of heat deformation of the recording medium and low power consumption are being studied.

  In addition, in an ink jet recording apparatus that heats and records a non-permeable recording medium using water-based ink, printing is performed while suppressing water volatilization from the recording head because water, which is the main solvent of water-based ink, is highly volatile. Had to do. Therefore, Patent Document 1 proposes a recording apparatus and a recording method for fixing a color material by keeping the temperature in the vicinity of the recording head low and increasing the heating temperature of the recording medium in the downstream portion.

  On the other hand, Patent Document 2 proposes a recording method in which an ink jet recording apparatus is used for recording on a non-permeable plate-making medium to suppress waviness due to droplet coalescence and to improve the abrasion resistance of printed matter. Has been. The recording method is a method in which an ink containing resin particles is applied to a uniformly heated plate-making medium, and the minimum film forming temperature (MFT) of the resin particles is 40 ° C. or higher, and the MFT is decreased by 5 ° C. or higher. This is a method using an ink containing 20% or more of a water-soluble solvent.

  Patent Document 3 proposes an ink containing 1,2-alkanediol, both-end alkanediol, and further a specific polyorganosiloxane. In this technique, the glossiness of printing paper is improved by using a polyorganosiloxane dissolved with 1,2-alkanediol, and the ejection stability of ink is improved by using both terminal alkanediols.

JP 2011-20318 A International Publication No. 2010-21186 JP 2007-277356 A

  In the recording apparatus and the recording method as in Patent Document 1, it is written that the heating temperature is increased toward the downstream of the recording medium. However, the relationship between the MFT of the resin particles contained in the ink and the heating temperature is not described. Further, the relationship between the Tg of the resin particles and the heating temperature is not described.

  Patent Document 2 describes that the heating temperature of the printing plate material is increased more than the MFT of the resin particles in the ink composition. However, there is no description about the necessity of lowering the printing plate temperature near the head. Further, regarding the fixability, there is no description about the Tg of the resin particles. Furthermore, there is no description of problems in increasing the printing speed.

  Patent Document 3 describes an ink containing 1,2-alkanediol or both-end alkanediol, but does not describe a recording method involving a heating printing process. Moreover, there is neither description nor suggestion about the effect regarding MFT control by combining a resin particle and a water-soluble solvent.

  An object of the present invention is to provide an ink jet recording method capable of fixing water-based ink on an impermeable recording medium at high speed and suppressing the adhesion of solid matter to the head.

The present invention
An inkjet recording method for recording on a non-permeable recording medium,
Discharging a water-based ink containing a coloring material and resin particles from the inkjet recording head to the recording medium;
Heating the recording medium so that the surface temperature of the recording medium at a position facing the inkjet recording head is T1;
Heating the recording medium so that the surface temperature of the recording medium becomes T2 downstream of the position facing the inkjet recording head in the sub-scanning direction;
Have
T2 is higher than T1,
The glass transition temperature (Tg) of the resin particles is higher than the T2,
An ink jet recording method, wherein a minimum film-forming temperature (Tm) of the resin particles is higher than T1 and lower than T2.
It is.

  ADVANTAGE OF THE INVENTION According to this invention, the inkjet recording method which can fix aqueous ink to a non-permeable recording medium at high speed, and can suppress adhesion of the solid substance to a head can be provided.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments.

  The ink jet recording method of this embodiment is an ink jet recording method for recording on a non-permeable recording medium, and includes the following steps.

  A step of discharging an aqueous ink containing a color material and resin particles from an ink jet recording head onto the recording medium.

  Heating the recording medium so that the surface temperature of the recording medium at a position facing the inkjet recording head is T1. Hereinafter, T1 is also referred to as a first surface temperature (T1).

  Heating the recording medium so that the surface temperature of the recording medium becomes T2 downstream of the position facing the inkjet recording head in the sub-scanning direction. Hereinafter, T2 is also referred to as a second surface temperature (T2).

  Here, the second surface temperature (T2) is higher than the first surface temperature (T1). Moreover, the glass transition temperature (Tg) of the resin particles is higher than the second surface temperature (T2). Moreover, the minimum film-forming temperature (Tm) of the resin particles is higher than the first surface temperature (T1) and not more than the second surface temperature (T2).

  When the present inventors analyzed solid matter adhering to an ink jet recording head (hereinafter also referred to as a recording head), resin particles contained in the ink mainly formed a film by drying the ink and could not be dispersed in the ink again. It turned out to be a thing. The reason why the drying progresses on the surface of the recording head is that the recording medium in the vicinity immediately below the recording head facing the recording head is heated to dry the ink droplets landed, and the heat is transmitted to the recording head. This is probably because the surface is also heated. If the vicinity of the head is heated above the minimum film forming temperature (Tm) of the resin particles in the form contained in the ink, the resin particles are formed by drying the ink, and the ink droplets adhering to the head surface are solidified. On the other hand, if the temperature in the vicinity of the head is lower than Tm, that is, if Tm is higher than the temperature in the vicinity of the head, the film formation of the resin particles does not occur even when the ink is dried by heating. Therefore, the deposit on the head surface can be removed by performing at least a recovery process such as wiping the head surface or sucking ink. Therefore, in the inkjet recording method of the present embodiment, Tm is set to be higher than the first surface temperature T1.

  Further, in order to fix the ink landed on the recording medium, the resin particles must be formed, and the surface of the recording medium exceeds the minimum film forming temperature (Tm) of the resin particles in the form contained in the ink. Need to be heated. Therefore, in this embodiment, the recording medium is heated so that the surface temperature of the recording medium becomes T2 on the downstream side in the sub-scanning direction from the position facing the ink jet recording head. The second surface temperature (T2) is higher than the first surface temperature (T1) and is equal to or higher than the minimum film-forming temperature (Tm) (the minimum film-forming temperature (Tm) is equal to or lower than the second surface temperature (T2). Is). Hereinafter, the second surface temperature (T2) may be referred to as a fixing temperature. The first surface temperature (T1) at the position facing the recording head and the second surface temperature (T2) on the downstream side are determined in consideration of controlling the film forming state of the resin particles. If the minimum film forming temperature (Tm) of the resin particles in the ink form satisfies the relationship of T1 <Tm ≦ T2, it is possible to fix the ink while suppressing sticking of the ink to the recording head. Become.

  In addition, the resin particles are solidified as the solvent evaporates after forming the film, but if T2 is equal to or higher than the glass transition temperature (Tg) of the resin particles, the resin particles after the film formation are not solidified and the desired particles are formed. Fixing in time may be difficult. Therefore, satisfying the relationship of T1 <Tm ≦ T2 <Tg is necessary in order to achieve fixing within a certain time at a low temperature while suppressing printing defects due to fixation.

  Hereinafter, the ink jet recording method and the water-based ink used in the recording method according to the present embodiment will be described in detail.

[Inkjet recording method]
In the ink jet recording method of this embodiment, recording is performed on a recording medium by ejecting ink from an ejection port of a recording head by an ink jet method in accordance with a recording signal. In the present embodiment, it is preferable to employ a method in which thermal energy is applied to ink and ink is ejected from the ejection port of the recording head. The diameter of the discharge port is preferably 14 μm or more and 30 μm or less. When the diameter of the discharge port is 14 μm or more, when the resin is fixed due to evaporation of water from the discharge port, it becomes difficult to be affected by printing misalignment, fading, and the like, and the effect of improving discharge stability can be sufficiently obtained. When the diameter of the ejection port is 30 μm or less, the ink droplets that are ejected are prevented from becoming too large, and the contact area with the recording medium per volume can be reduced, so that the mechanical strength of the obtained image is improved and sufficient It is easy to obtain a sufficient image fixing power.

  In the present invention, “recording” means not only giving an image having a meaning such as a character or a figure to a recording medium but also giving an image having no meaning such as a pattern.

  The present embodiment includes a step of heating the recording medium so that the surface temperature of the recording medium at a position facing the inkjet recording head becomes T1. In the heating step, a heating device may be arranged upstream of the position where ink is ejected, that is, the position facing the recording head, and heating is performed near the position facing the recording head including the position facing the recording head. A device may be arranged. For example, before the ink is applied to the recording medium, that is, the recording medium is heated on the upstream side of the recording head, the surface temperature of the recording medium at a position facing the recording head may be set to T1. .

  Naturally, the present invention also includes a mode in which recording is performed (ink is ejected) while the recording medium is heated.

  As a heating method, specifically, for example, the platen is made of an aluminum alloy produced by a die casting method that is not easily deformed by heat, a nickel alloy heater is disposed under the platen, and the recording medium is heated by heating the platen. And a method of recording while doing so. Examples of the heating method on the downstream side of the recording head include a method of heating the surface of the recording medium using a sheathed heater, a halogen heater and a heat reflecting plate in addition to the heating from the lower part of the platen. . These methods can also be applied to heating upstream of the recording head. Further, a heating device may be installed in the vicinity of a position facing the recording head, and a heating device may be provided upstream of the recording head. With this configuration, the surface of the recording medium can be maintained at a desired temperature before coming to the vicinity of the head, and the main purpose of heating at a position facing the head is due to evaporation of ink moisture or water-soluble solvent. Heat deprived by the heat of vaporization will be applied. As a result, it becomes easy to suppress temperature fluctuations near the head during printing. In the case of using a non-permeable recording medium, it is preferable to heat at a temperature not higher than the temperature at which the recording medium is deformed in any heating step.

  If the position facing the recording head is the first position and the position heated on the downstream side of the recording head is the second position, the time from the first position to the second position is the recording time. It is preferable to have at least 20 seconds after printing with the head, and preferably within 200 seconds. The distance between the heating unit of the first heating device arranged near the position facing the recording head or upstream thereof and the heating unit of the second heating device arranged downstream of the recording head is: It is preferably at least 5 cm and preferably within 30 cm.

  In the present invention, T1 <Tm ≦ T2 <Tg may be satisfied, but the difference (T2−T1) between the first surface temperature (T1) and the second surface temperature (T2) is 5 ° C. or more and 40 ° C. The following is preferable. When (T2-T1) is 5 ° C. or higher, it is possible to prevent the temperatures of Tm, T1, and T2 from becoming close to each other, and it is easy to suppress sticking from occurring in a short time. In addition, it is easy to shorten the fixing time for sufficiently forming the resin particles contained in the ink. Moreover, it can prevent that T1 becomes too low or T2 becomes too high as (T2-T1) is 40 degrees C or less. If T1 becomes too low, beading tends to occur between ink droplets that have landed on the recording medium. When beading occurs, the surface area ratio with respect to the ink droplet volume decreases, so the evaporative removal efficiency of the water-soluble solvent decreases, and the fixing time may become longer. Moreover, if T2 becomes too high, the temperature difference from Tg to Tm tends to increase. As a result, since the ink contains a large amount of water-soluble solvent, it may take a long time to evaporate and remove the water-soluble solvent in the film forming process and the subsequent fixing process after landing on the recording medium. Further, the difference between T1 and T2 (T2−T1) is more preferably 5 ° C. or more, and further preferably 10 ° C. or more. The difference between T1 and T2 (T2−T1) is more preferably 20 ° C. or less.

  T1 is preferably 40 ° C. or higher and 60 ° C. or lower. When T1 is 40 ° C. or higher, the occurrence of beading between ink droplets that have landed on the recording medium can be suppressed. When T1 is 60 ° C. or lower, unless T2 is increased, the set width of Tm becomes narrow and sticking may easily occur. Further, when T1 is 60 ° C. or less, T2 can be set low, and it becomes easy to obtain a low-temperature fixing effect such as suppressing deformation of the recording medium and reducing power consumption.

  T2 is preferably 50 ° C. or higher and 80 ° C. or lower. When T2 is 50 ° C. or higher, it is easy to evaporate and remove the solvent from the ink landed on the recording medium, and the fixing time can be easily shortened. When T2 is 80 ° C. or lower, T1 can also be relatively lowered, and it becomes easy to suppress drying of the ink on the head surface. Moreover, by setting T2 to 80 ° C. or less, it becomes easy to obtain the effect of low-temperature fixing. As a result, deformation of the recording medium and increase in power consumption can be easily suppressed.

[Non-permeable recording medium]
The non-penetrable recording medium refers to a recording medium in which water-based ink does not permeate or water-based ink hardly permeates.

A non-permeable recording medium is a non-ink-absorbing recording medium. More quantitatively, the amount of water absorption from the start of contact to 30 msec ^1/2 in the Bristow method is 10 mL / m ² or less. 1 shows a recording medium having a recording surface. This Bristow method is the most popular method for measuring the amount of liquid absorbed in a short time, and is also adopted by the Japan Paper Pulp Technology Association (JAPANTAPPI). For details of the test method, refer to Standard No. of “JAPAN TAPPI Paper Pulp Test Method 2000”. 51 "Paper and paperboard-Liquid absorbency test method-Bristow method".

  Examples of non-permeable recording media include those that are not prepared as recording media for water-based inkjet inks such as glass, plastic, film, cardboard, cloth, and YUPO, and offset printing such as art paper and coated paper. Examples include printing paper. Further, as the non-permeable recording medium, for example, plastic is coated on a substrate such as a plastic film or paper that has not been surface-treated for inkjet printing (that is, an ink absorbing layer is not formed). And the like. Examples of the plastic include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, and polypropylene.

[ink]
Hereafter, each component which comprises the water-based ink used by this embodiment is each demonstrated.

  First, the water-based ink preferably includes at least a color material and resin particles, and includes water and a water-soluble solvent as a solvent. In the aqueous ink used in the present embodiment, the minimum film forming temperature (Tm) of the resin particles and the glass transition temperature (Tg) of the resin particles in the ink form satisfy the relationship of T1 <Tm ≦ T2 <Tg.

[Minimum film forming temperature (Tm) of resin particles in ink form]
First, the minimum film forming temperature (Tm) of the resin particles in the ink form will be described.

  Tm represents the minimum temperature required for the resin particles to form a film by heating. Tm is a point at which a dry film is formed by spreading an ink containing resin particles (for example, containing a coloring material, water, a water-soluble solvent, and resin particles) on a highly thermally conductive metal plate with a temperature gradient. The temperature can be easily measured using a minimum film-forming temperature measuring device. In the present invention, unless otherwise noted, Tm is the minimum film-forming temperature of the resin particles in the ink form. What is the minimum film-forming temperature in an aqueous dispersion that does not contain a coloring material such as a pigment or a water-soluble solvent? Different.

  Tm may be any as long as the relationship of T1 <Tm ≦ T2 <Tg is satisfied, and is preferably 40 ° C. or higher and 80 ° C. or lower. Preferably they are 42 degreeC or more and 64 degrees C or less, More preferably, they are 44 degreeC or more and 60 degrees C or less. If Tm is high, it is easy to make it difficult to fix, and if Tm is low, it is easy to shorten the fixing time. Tm may be any as long as it is higher than T1, but is preferably higher than T1 in the range of 1 ° C. or higher and 19 ° C. or lower. Further, Tm may be any as long as it is T2 or less, but it is preferably lower than T2 in the range of 1 ° C. or more and 19 ° C. or less. If Tm is higher than T1 in the range of 1 ° C or higher and 19 ° C or lower, it becomes easier to fix, and if Tm is lower than T2 in the range of 1 ° C or higher and 19 ° C or lower, fixing time is shortened. Easy to do.

[Resin particles]
In the present invention, “resin particles” mean polymer particles present in a dispersed state in a solvent such as water. By forming the resin particles into a film, the image is fixed on the surface of the non-permeable recording medium. On the other hand, the resin particles formed on the head surface cause sticking.

  The material of the resin particles is not particularly limited as long as Tg is higher than the fixing temperature (T2). Examples of the resin particle material include an acrylic polymer prepared by emulsion polymerization of α, β-unsaturated carboxylic acid and its derivatives (meth) acrylic acid alkyl ester and (meth) acrylic acid alkylamide monomers. Resin particles: Styrene-acrylic resin particles prepared by emulsion polymerization of a styrene monomer with (meth) acrylic acid alkyl ester or (meth) acrylic acid alkylamide; polyethylene resin particles, polypropylene resin particles, polyurethane resin particles, Examples thereof include styrene-butadiene resin particles and fluoroolefin resin particles. Also obtained by emulsion polymerization around the core-shell type resin particles with different polymer compositions in the core and shell parts constituting the resin particles, and acrylic resin particles prepared in advance to control the particle size as seed particles. Particles that can be used may be used. Furthermore, hybrid resin particles in which different resin particles such as acrylic resin particles and polyurethane resin particles are chemically bonded may be used. In view of storage stability in ink and fixability to various recording media, the aforementioned acrylic resin particles are preferable. Any monomer can be used for the acrylic resin particles, but it is more preferable that a monomer having a hydroxyl group is copolymerized. That is, the resin particles are acrylic resin particles, and a monomer (particularly an α, β-unsaturated carboxylic acid having a hydroxyl group and a derivative thereof) having a hydroxyl group in a monomer constituting the acrylic resin particle. It is preferably included. In general, by introducing a hydrophilic hydroxyl group to the hydrophobic resin particle surface, the affinity between the resin particle surface and the water or water-soluble solvent contained in the ink is increased, and a small amount of water-soluble solvent can be added. A desired Tm can be realized. Therefore, since the solvent concentration in the ink can be reduced, the fixing time is shortened. The ratio of the monomer having a hydroxyl group to the whole monomer constituting the resin particle is not particularly limited, but is preferably 3% by mass or more and 10% by mass or less. When the ratio of the monomer having a hydroxyl group is 3% by mass or more, an effect of shortening the fixing time is easily obtained. Moreover, when the ratio of the monomer having a hydroxyl group is 10% by mass or less, it is easy to prevent Tm from being lowered excessively and to make it difficult to fix. Examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate. As the material for the resin particles, one kind may be used alone, or two or more kinds may be used in combination.

  Further, since the resin particles are set to have a Tg higher than T2 (for example, 80 ° C.), the Tg of the resin particles can be controlled by copolymerizing a monomer having a high Tg and a monomer having a low Tg. Examples of the monomer that increases the Tg of the resin particles include styrene, methyl methacrylate, tert-butyl methacrylate, and the like. Examples of the monomer that lowers Tg include 2-ethylhexyl acrylate, n-butyl (meth) acrylate, and ethyl methacrylate.

  In order to improve the dispersion stability of the resin particles in the ink, the resin particles are preferably constituted by copolymerizing a monomer having an anionic functional group. In that case, specific examples of the material of the resin particles include unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid, itaconic acid, fumaric acid, derivatives thereof, and salts thereof. Examples of the salt include alkali metal (lithium, sodium, potassium, etc.) salts, ammonium salts, and organic ammonium salts. Among these, (meth) acrylic acid is preferable as a material for the resin particles. As the salt, sodium salt or potassium salt is preferable.

  Among these monomers, methyl methacrylate, 2-ethylhexyl acrylate, (meth) acrylic acid, and 2-hydroxyethyl methacrylate are preferable as monomers constituting the resin particles having a Tg higher than T2 (for example, 80 ° C.).

  As for the molecular weight of the resin particles, the polystyrene-equivalent number average molecular weight (Mn) obtained by gel permeation chromatography (GPC) is preferably 100,000 or more and 3,000,000 or less, preferably 300,000 or more and 2, More preferably, it is 000,000 or less.

  The average particle diameter (volume average) of the resin particles is not particularly limited as long as the dispersion stability in the ink can be maintained, but is preferably 0.08 μm or more and 0.30 μm or less.

  The glass transition temperature (Tg) of the resin particles is not particularly limited as long as it is higher than T2, but is preferably high in the range of 2 ° C. or higher and 30 ° C. or lower from T2. When the difference from T2 is 2 ° C. or more, a sufficient difference from the fixing temperature can be provided, so that the time required for solidification of the film-formed resin can be shortened, and high-speed fixing can be easily realized. Moreover, when the difference between T2 and Tg is 30 ° C. or lower, it is possible to prevent the minimum film-forming temperature in the aqueous dispersion of resin particles from becoming too high. If the minimum film-forming temperature of the resin particles in the aqueous dispersion is increased, the solvent concentration in the ink is increased to control Tm. As a result, a lot of heating time is required for removing the solvent, and the fixing time is increased. May be longer. The Tg of the resin particles is more preferably higher than T2 in the range of 2 ° C. or higher and 30 ° C. or lower, and more preferably higher in the range of 2 ° C. or higher and 25 ° C. or lower.

  The Tg of the resin particles is preferably 72 ° C. or higher and 95 ° C. or lower. When the Tg of the resin particles is 72 ° C. or higher, the resin has an appropriate hardness, and it becomes easy to obtain a sufficient image fixing force. When the Tg is 95 ° C. or lower, it is possible to prevent the minimum film-forming temperature in the aqueous dispersion of resin particles from becoming too high.

  The content (% by mass) of the resin particles (solid content) is preferably 2.0% by mass or more and 15.0% by mass or less based on the total mass of the ink. When the content of the resin particles is 2.0% by mass or more, a sufficient image fixing force can be easily obtained. When the content of the resin particles is 15.0% by mass or less, Tm can be easily controlled.

<Water-soluble solvent>
The ink preferably contains a water-soluble solvent having water solubility.

  The water-soluble solvent is not particularly limited, but preferably has a function of controlling Tm so as to satisfy the relationship of T1 <Tm ≦ T2 <Tg. The water-soluble solvent is preferably involved in the suppression of ink drying and has a function of reducing sticking on the head surface. These functions (Tm control function, sticking reduction function) may be achieved by one kind of water-soluble solvent, or may be achieved by a plurality of water-soluble solvents.

  The content (total) of the water-soluble solvent is preferably 13% by mass or more and 30% by mass or less based on the total mass of the ink. When the content of the water-soluble solvent is 13% by mass or more, the ink becomes difficult to dry, and the occurrence of sticking can be easily suppressed. When the content of the water-soluble solvent is 30% by mass or less, the time for removing the solvent by heating can be shortened, and the fixing time can be easily shortened.

(Tm control solvent)
Examples of the water-soluble solvent having a function of controlling Tm (Tm control solvent) include 1 such as 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, and 1,2-hexanediol. , 2-alkanediols, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono n-butyl ether, triethylene glycol monomethyl ether, triethylene glycol mono Ethyl ether, triethylene glycol mono n-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene Examples include glycol ethers such as recall mono n-butyl ether, alkylene glycols such as diethylene glycol and triethylene glycol, cyclic amides such as 2-pyrrolidone and N-methyl-2-pyrrolidone, and cyclic esters such as γ-butyrolactone. It is done. Among these, 1,2-alkanediol is preferable as the Tm control solvent. Even if 1,2-alkanediol is contained in the ink at a high concentration, it is difficult to cause an increase in viscosity. Moreover, since 1,2-alkanediol does not have an excessively low Tm reducing effect, it is possible to easily control Tm within an appropriate concentration range in the ink. As the Tm control solvent, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol or the like having a melting point of 30 ° C. or lower (liquid at room temperature) C3-C6 1,2-alkanediol is preferred.

  The content of the Tm control solvent is preferably 3.0% by mass or more and 15.0% by mass or less based on the total mass of the ink. When the content of the Tm control solvent is 3.0% by mass or more, it becomes easy to control the Tm of the resin particles. When content of a Tm control solvent is 15.0 mass% or less, it can prevent that Tm of a resin particle is reduced too much. If the Tm of the resin particles is lowered too much, the resin particles are likely to adhere to the head surface, which may cause image defects. A Tm control solvent may be used individually by 1 type, and may be used in combination of 2 or more type. When using 2 or more types together, content of said Tm control solvent is the sum total of content of Tm control solvent used together.

(Fixing reduction solvent)
Examples of the water-soluble solvent having a function of reducing the occurrence of sticking (sticking reducing solvent) include alkanediols at both ends such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and ethylene. Examples include glycols, alkylene glycols such as polyethylene glycol having an average molecular weight of 200 to 600 or less, urea derivatives such as urea and alkylene urea, and glycerin. Although it is speculated that the effect of reducing sticking is manifested by moisturizing the sticking reducing solvent so that the resin particles do not form a film on the head surface or the like, this guess does not particularly limit the present invention. . The fixing reduction solvent is also required to have a property of being a solvent that evaporates by heating from the viewpoint of high-speed fixing at a low temperature. Therefore, as the fixing reduction solvent, the melting point is 30 ° C. or less (liquid at room temperature), and those having 3 to 5 carbon atoms such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, etc. Both terminal alkanediols are preferred.

  The content of the sticking reduction solvent is preferably 5.0% by mass or more and 20.0% by mass or less based on the total mass of the ink. When the content of the sticking reduction solvent is 5.0% by mass or more, the ink is effectively prevented from drying, and the resin particles are difficult to stick on the head surface. When the content of the fixing reduction solvent is 20.0% by mass or less, the time for removing the solvent from the printed matter can be shortened, and the fixing time can be shortened. The fixing reduction solvent may be used alone or in combination of two or more. When using 2 or more types together, content of said sticking reduction solvent is the sum total of content of the sticking reduction solvent used together.

(Other water-soluble solvents)
The ink may contain a water-soluble solvent (other water-soluble solvent) other than the above-mentioned water-soluble solvent (Tm control solvent, fixing reduction solvent). Specific examples of the water-soluble solvent include alkyl alcohols having 1 to 4 carbon atoms, amides, polyalkylene glycols, glycols, alkylene glycols having 2 to 6 carbon atoms in the alkylene group, Among the monohydric alcohols, polyhydric alcohol alkyl ethers, nitrogen-containing compounds and the like, those which are neither the above-mentioned Tm control solvent nor the fixing reduction solvent can be mentioned. The content of the other water-soluble solvent is preferably smaller than the content of the Tm control solvent or the fixing reduction solvent. More specifically, the content of the other water-soluble solvent is preferably 0% by mass or more and 10.0% by mass or less, and 0.1% by mass or more and 5.0% by mass based on the total mass of the ink. The following is more preferable.

<Water>
The ink preferably contains water. As water, it is preferable to use ion-exchanged water (deionized water) rather than water containing various ions. The water content in the ink is preferably 10.0% by mass or more and 90.0% by mass or less, preferably 30.0% by mass or more and 80.0% by mass or less, based on the total mass of the ink. More preferred.

<Color material>
Examples of the color material include pigments and dyes. A color material may be used individually by 1 type, and may be used in combination of 2 or more type. The pigment and the dye are not particularly limited, and for example, known ones can be used. The content of the color material is preferably 0.3% by mass or more and 20.0% by mass or less, more preferably 0.5% by mass or more and 12.0% by mass or less, based on the total mass of the ink. . In particular, it is preferable to use a pigment as a coloring material from the viewpoint of weather resistance. When a pigment is used as a coloring material, the dispersion method of the pigment is a resin dispersion type pigment using a resin as a dispersing agent (a resin dispersing pigment using a resin dispersing agent, a microcapsule in which the surface of pigment particles is coated with a resin. Examples thereof include a pigment, a polymer-bonded self-dispersing pigment in which an organic group containing a polymer is chemically bonded to the surface of the pigment particle, and a self-dispersing type pigment in which a hydrophilic group is introduced to the surface of the pigment particle (self-dispersing pigment). It is also possible to use pigments with different dispersion methods in combination. As a specific pigment, it is preferable to use carbon black or an organic pigment. A pigment may be used individually by 1 type and may be used in combination of 2 or more type.

  Regarding the color material content, the color material content (% by mass) based on the total mass of the ink is 0.1 times or more the resin particle content (% by mass) based on the total mass of the ink. It is preferable that it is 2.0 times or less. When the content of the color material is 0.1 times or more than the content of the resin particles, it is easy to realize a necessary color reproduction range, or the content of the resin particles in the ink is excessively increased. Prevent and prevent sticking. Further, when the content of the color material is 2.0 times or less than the content of the resin particles, the relative amount of the resin particles with respect to the color material can be a sufficient amount, and the fixing power of the printed matter is sufficient. It becomes easy to obtain.

<Other ingredients>
In addition to the above-described components, the ink of the present embodiment includes a surfactant, a pH adjuster, a rust inhibitor, an antiseptic, an antifungal agent, an antioxidant, an anti-reduction agent, an evaporation accelerator, And various additives such as chelating agents. The content of such additives in the ink is preferably 0.05% by mass or more and 10.0% by mass or less, and 0.2% by mass or more and 5.0% by mass or less, based on the total mass of the ink. It is more preferable that

  The ink preferably contains a fluorine-based or silicone-based surfactant. Since the fluorine-based or silicone-based surfactant can reduce the surface tension of the ink even in a small amount, the wettability of the ink to the recording medium can be improved. As a result, even when recording on a non-permeable recording medium, the phenomenon of ink being repelled on the medium is suppressed, and the image quality can be further improved. Examples of the fluorine-based or silicone-based surfactant include Zonyl FSO, Zonyl FSO100, Zonyl FSN, Zonyl FSN100, Capstone FS-3100 (above, Dupont product), MegaFuck F-410, MegaFuck F-493, Megafuck F-443, Megafuck F-444, Megafuck F-445 (above, product of DIC), Novec FC-4430, Novec FC-4432 (above, product of 3M), Aftergent 100, Aftergent 150, Aftergent 150CH, Aftergent 250, Aftergent 400SW, Aftergent 501 (above, Neos product), KS508, KP360A, KP360A (above, Shin-Etsu Silicone product), FZ-2191, Z-2123,8211ADDITIVE (or more, Toray Dow Corning's products), and the like.

  The pH of the ink is preferably in the range of 7.0 or more and 10.0 or less, and more preferably more than 7.0 and less than 10.0. When the pH of the ink is 7.0 or higher, the anionic group (for example, carboxylate ion group) of the colorant or resin particle that is dissolved or dispersed in the ink is negatively charged. It becomes easy to become. If the pH of the ink is less than 7.0, there will be a large number of functional groups (for example, carboxyl groups) that have received protons and become electrically neutral. For this reason, the solubility of the coloring material and the resin particles and the repulsive force between the particles become small, and the coloring material and the resin particles may become unstable and precipitate in the ink. When the pH of the ink is 10.0 or less, it becomes easy to prevent corrosion of members constituting the ink jet recording apparatus.

  The ink can contain a pH adjuster. Examples of the pH adjusting agent include organic amines such as diethanolamine and triethanolamine; alkali metal hydroxides such as sodium hydroxide, lithium hydroxide and potassium hydroxide; organic acids and inorganic acids. The pH of the ink is a value at 25 ° C., and can be measured using a general pH meter.

[ink cartridge]
An ink cartridge that can be used in the ink jet recording method of the present embodiment includes an ink storage portion that stores ink, and the ink described above is stored in the ink storage portion. As for the structure of the ink cartridge, the ink storage portion includes an ink storage chamber that stores liquid ink and a negative pressure generation member storage chamber that stores a negative pressure generation member that holds the ink therein by a negative pressure. Things. Alternatively, the ink cartridge may be an ink container that does not have an ink storage chamber for storing liquid ink and is configured to hold the entire storage capacity by a negative pressure generating member. Furthermore, an ink cartridge configured to have an ink containing portion and a recording head may be used.

  Hereinafter, the present invention will be described in detail using Examples and Comparative Examples. The present invention is not limited in any way by the following examples as long as the gist thereof is not exceeded. In the description of the following examples, “part” means “part by mass” unless otherwise specified. Abbreviations in the specification and tables are as follows.

12PD: 1,2-propanediol 12BD: 1,2-butanediol 12PenD: 1,2-pentanediol 12HD: 1,2-hexanediol 12OD: 1,2-octanediol 13PD: 1,3-propanediol 14BD: 1,4-butanediol 15PenD: 1,5-pentanediol 16HD: 1,6-hexanediol 2Me13PD: 2-methyl-1,3-propanediol 3Me15PenD: 3-methyl-1,5-pentanediol Py: 2- Pyrrolidone TEGMe: triethylene glycol monomethyl ether DEGBe: diethylene glycol mono n-butyl ether EL: ethyl lactate Gly: glycerin EG: ethylene glycol St: styrene MMA: methyl methacrylate TBMA: tert-butyl Methacrylate EMA: ethyl methacrylate EHA: 2-ethylhexyl acrylate BA: n-butyl acrylate MAA: methacrylic acid AA: acrylic acid HEA: 2-hydroxyethyl acrylate HEMA: 2-hydroxyethyl methacrylate HPMA: 2-hydroxypropyl methacrylate

<Preparation of aqueous dispersion of resin particles>
The resin particle aqueous dispersion Em. 1 to Em. 17 was prepared.

(Preparation of resin particle aqueous dispersion Em.1)
A three-necked flask was connected to a stirring rod, a cooling tube, a dropping syringe, and a nitrogen gas introduction tube, and the three-necked flask was placed in a thermostatic bath maintained at 50 ° C. In the three-necked flask, the following (the raw material to be put into the three-necked flask) was put in an emulsified state by stirring for 15 minutes in advance with a homogenizer (stirring rotation speed: 10,000 rpm).

(Raw material put in a three-necked flask)
-Polymerization initiator: 0.5 parts of potassium persulfate-Emulsifier: Latemul PD-104 (manufactured by Kao Corporation) 3.0 parts-Methyl methacrylate (MMA) 16.4 parts-2-ethylhexyl acrylate (EHA) 0 parts, 0.6 parts of methacrylic acid (MAA), 20.0 parts of ion-exchanged water Further, the following (raw material to be put into the syringe for dropping) in a dropping syringe with a homogenizer in advance (stirring rotation speed: 10,000 rpm) What was emulsified by stirring for 15 minutes was added.

(Raw material put in the syringe for dropping)
-Polymerization initiator: 0.5 parts of potassium persulfate-Emulsifier: Latemul PD-104 (manufactured by Kao Corporation) 3.0 parts-Methyl methacrylate (MMA) 65.6 parts-2-ethylhexyl acrylate (EHA) 12. 0 parts, methacrylic acid (MAA) 2.4 parts, ion-exchanged water 100.0 parts

  And the raw material put into the syringe for dripping was dripped in said 3 necked flask over 1 hour, Then, the temperature of the constant temperature layer was kept at 80 degreeC for 30 minutes, and the resin particle was synthesize | combined. In order to increase the stability of the obtained resin particles, a 10% aqueous potassium hydroxide solution and ion-exchanged water were further added dropwise, the pH was 8.3, and the content of resin particles (solid content) was 45.0% by mass. The resin particle aqueous dispersion Em. 1 was prepared.

  The glass transition temperature (Tg) of the obtained resin particles was determined. The Tg of the resin particles was measured using a differential scanning calorimeter Thermo plus EVOII / DSC8230 (manufactured by Rigaku). The results are shown in Table 1-1.

(Preparation of resin particle aqueous dispersion Em.2-17)
Except that the resin components of (raw material to be put into a three-necked flask) and (raw material to be put into a dropping syringe) were set to the values shown in Table 1, resin particle aqueous dispersion Em. 1 and the resin particle aqueous dispersion Em. 2-17 were obtained. The results are shown in Table 1-1 and Table 1-2. The resin particle aqueous dispersion Em. 2-17, about a polymerization initiator, an emulsifier, and ion-exchange water, resin particle water dispersion Em. The value was the same as 1.

(Resin Particle Water Dispersion Em.18)
Styrene-acrylic resin particles JONCRYL 780 (manufactured by BASF) (resin (solid content) content: 48.0% by mass) were dispersed in resin particle aqueous dispersion Em. 18 (Tg: 92 ° C.).

<Preparation of pigment dispersion>
(Preparation of black pigment dispersion K1)
Self-dispersed pigment Cab-O-Jet300 (manufactured by Cabot) was diluted with water and sufficiently stirred to obtain a black pigment dispersion K1 (pigment content: 10.0% by mass).

(Preparation of cyan pigment dispersion C1)
Self-dispersed pigment Cab-O-Jet250C (manufactured by Cabot) was diluted with water and sufficiently stirred to obtain cyan pigment dispersion C1 (pigment content: 10.0% by mass).

(Preparation of magenta pigment dispersion M1)
Self-dispersed pigment Cab-O-Jet265M (manufactured by Cabot) was diluted with water and sufficiently stirred to obtain a magenta pigment dispersion M1 (pigment content is 10.0% by mass).

(Preparation of yellow pigment dispersion Y1)
Self-dispersed pigment Cab-O-Jet 740Y (manufactured by Cabot) was diluted with water and sufficiently stirred to obtain a yellow pigment dispersion Y1 (pigment content is 10.0% by mass).

(Preparation of black pigment dispersion K2)
The following components were mixed, heated to 70 ° C. in a water bath, and the styrene-acrylic resin resin dispersant (JONCRYL683 (manufactured by BASF)) was completely dissolved under stirring. 10.0 parts of black pigment carbon black (Printex 95 IQ; manufactured by Orion Engineered Carbons) was added to this solution, and premixing was performed for 30 minutes. Thereafter, dispersion processing (beads used: 0.05 mm diameter zirconia beads, bead filling rate: 70% (in terms of bulk specific gravity), rotor rotation speed: 42.1 Hz, dispersion time using bead mill UAM-015 (manufactured by Kotobuki Industries) 2 hours) to obtain a black pigment dispersion K2 (pigment content is 10.0% by mass).
・ Resin dispersant: JONCRYL683 (manufactured by BASF) 4.0 parts ・ 0.5 parts of potassium hydroxide ・ 85.5 parts of ion-exchanged water

<Preparation of ink>
(Preparation of inks 1 to 56)
The pigment dispersion, the resin particle aqueous dispersion and the water-soluble solvent obtained above were mixed in the combinations shown in Table 2, and sufficiently stirred and dispersed to prepare each ink. The content (% by mass) of the water-soluble solvent shown in Table 2 is a value based on the total mass of the ink. The pigment dispersion and the resin particle aqueous dispersion are contained in the ink with the following content (based on the total mass of the ink).

-Pigment dispersion 30.0% by mass (3.0% by mass as solid content)
・ Aqueous dispersion of resin particles 10.0% by mass (4.5% by mass as solid content)

In addition, the inks 1 to 56 include the following components in addition to the pigment dispersion, the resin particle aqueous dispersion, and the water-soluble solvent described in Tables 2-1 to 2-6.
・ Capstone FS-3100 (manufactured by DuPont) 1.0% by mass
-NIKKOL BC-20 (manufactured by Nikko Chemicals) 0.5% by mass
・ Ion exchange water balance

  Moreover, Tm of the produced ink was measured with a minimum film-forming temperature measuring device MINIMUM FILM FORMING TEMPERATURE BAR 90 (manufactured by RHOPOINT INSTRUMENTS LTD). The results are shown in Tables 2-1 to 2-6.

(Preparation of ink 57)
Ink 57 was prepared by mixing the following components so as to have the same composition as ink 1 of Patent Document 2 (International Publication No. 2010-21186).

-Pigment dispersion C1 6.0% by mass
-Resin particle aqueous dispersion Em. 18 5.0 mass% (solid content)
・ 12PD 40.0 mass%
・ Ion exchange water 73.5% by mass

  When Tm of the obtained ink 57 was measured, Tm was 45 ° C.

(Preparation of ink 58)
The following components were mixed to prepare ink 58. The ink 58 corresponds to the ink obtained by replacing the pigment dispersion of the black ink composition 1B of Patent Document 3 (Japanese Patent Laid-Open No. 2007-277356) with the pigment dispersion K2.

-Pigment dispersion K2 3.0 mass% (solid content)
・ Styrene-acrylic acid resin (resin dispersant) 1.2% by mass (solid content)
・ 1,2-Hexanediol 6.0% by mass
・ 1,5-pentanediol 3.0% by mass
・ Polysiloxane surfactant 0.1% by mass
・ Triethanolamine 0.9% by mass
・ Glycerin 12.0% by mass
・ Ion exchange water balance

  As the polysiloxane surfactant, AW13 and X-22-6551 (both manufactured by Shin-Etsu Chemical Co., Ltd.) were used, and the mixing ratio was AW13: X-22-6551 = 9: 1.

  The Tm of the ink 58 was measured but could not be measured because it did not contain resin particles.

(Preparation of ink 59)
Resin particle Em. Each component was mixed with a composition adjusted by adding 4.5% by mass (solid content) of 1 and reducing the amount of ion-exchanged water, thereby preparing ink 59.

  When Tm of ink 59 was measured, Tm was 85 ° C. or higher.

[Example 1]
In Example 1, as shown in Table 3, using ink 1, T1 and T2 were set as follows to produce a printed matter. Moreover, the produced printed matter was evaluated by the following method.

<Evaluation>
In the evaluation criteria of the following evaluation items, A to D are preferable levels, and E is an unacceptable level. The evaluation results are shown in Table 4.

<Fixability of image>
(Evaluation image production method)
Each of the inks obtained above was filled in an ink cartridge and mounted on an inkjet recording apparatus imagePROGRAF iPF9400S (manufactured by Canon). Then, a solid image (an image having a recording duty of 100%) having a width of 1000 mm was printed using LLJET glossy PVC gray paste EX LLSPEX 133 (manufactured by Sakurai), which is an impermeable recording medium, with a print pass of 10 pass. . The print pass is related to the length that the recording medium is fed in the sub-scan direction after the print head scans once in the main scan direction. The feed length is the number of passes in the nozzle row direction of the head. The value divided by. Therefore, usually, a desired image is formed on the recording medium while the head reciprocates several times on the recording medium. In the ink jet recording apparatus, the recording duty is 100% under the condition that four droplets of a volume of 4 pL per droplet are applied to a unit area of 1/600 inch × 1/600 inch with a resolution of 1200 dpi × 1200 dpi. Defined. In the following examples, the platen is made of an aluminum alloy produced by a die-casting method that is not easily deformed by heat, a nickel alloy heater is disposed under the platen, and recording is performed while heating the recording medium by heating the platen. It was. Further, the surface temperature (T1) of the recording medium at a position facing the recording head was measured, and the surface temperature (T1) was kept constant by PID control in order to suppress temperature fluctuation.

  The heating at this time was set so that the surface temperature (T1) of the recording medium at the position facing the recording head would be the value shown in Table 3.

  In addition, a sheathed heater was installed at the upper part on the downstream side where the recording medium is transported from the platen (on the downstream side and facing the recording medium). In addition, the stainless steel plate was curved and installed so as to cover the sheathed heater (facing the sheathed heater so as to face the recording medium) so that the recording medium conveyed to the downstream side could be heated uniformly. The distance from the recording head to the sheathed heater was 20 cm. Further, it takes approximately 63 seconds for the ink ejected by the recording head to reach the heating portion of the sheathed heater.

  Further, the surface temperature (T2) of the heated recording medium was measured, and the surface temperature (T2) was kept constant at the set temperature shown in Table 4 while performing PID control.

  In Comparative Example 7 using ink 57, T1 and T2 were set to the same 60 ° C.

(Fixing power evaluation method)
The solid image of the recorded matter obtained by the above method is rubbed 50 times by a method in accordance with JIS L0849 using a friction white cloth specified in JIS L0805, and the optical density of the solid image before and after that is measured by a reflection densitometer (RD- 19I; manufactured by Gretag Macbeth). Then, the ratio DR ₁ = OD ₅₀ / OD ₀ was calculated, where the optical density of the image before rubbing was OD ₀ , and the optical density of the image after rubbing 50 times was OD ₅₀ . The heating time taken to produce the printed part with DR ₁ exceeding 0.8 was taken as the fixing time. The evaluation criteria for the fixing power are as follows. The evaluation results are shown in Tables 4-1 to 4-2.

A: 1 minute or less B: 1 minute or more and less than 3 minutes C: 3 minutes or more and less than 5 minutes D: 5 minutes or more and less than 10 minutes E: 10 minutes or more

<Print defects due to sticking>
In the evaluation image production method described above, the recorded material produced without performing the recovery operation during printing is observed, and the printing failure due to sticking is recorded until the streaks generated by the flying deviation of the ink droplets are confirmed on the recorded material. The printed area was evaluated. Since the print width is fixed, the evaluation is performed based on the print length in the sub-scanning direction, and the evaluation criteria are as follows. The evaluation results are shown in Table 4.

A: 1200 mm or more B: 600 mm or more and less than 1200 mm C: 300 mm or more and less than 600 mm D: 150 mm or more and less than 300 mm E: It was less than 150 mm

[Examples 2-66 and Comparative Examples 1-9]
Examples 2 to 66 and Comparative Examples 1 to 9 were carried out except that the ink No., surface temperature (T1), and surface temperature (T2) used were set as shown in Table 4-1 or Table 4-2. Recorded materials were prepared and evaluated in the same manner as in Example 1.

Claims (9)

An inkjet recording method for recording on a non-permeable recording medium,
Discharging a water-based ink containing a coloring material and resin particles from the inkjet recording head to the recording medium;
Heating the recording medium so that the surface temperature of the recording medium at a position facing the inkjet recording head is T1;
Heating the recording medium so that the surface temperature of the recording medium becomes T2 downstream of the position facing the inkjet recording head in the sub-scanning direction;
Have
T2 is higher than T1,
The glass transition temperature (Tg) of the resin particles is higher than the T2,
An ink jet recording method, wherein a minimum film-forming temperature (Tm) of the resin particles is higher than T1 and lower than T2.   The inkjet recording method according to claim 1, wherein the color material is a pigment.   The inkjet recording method according to claim 1, wherein the T1 is 40 ° C. or more and 60 ° C. or less, and the T2 is 50 ° C. or more and 80 ° C. or less.   The inkjet recording method according to claim 3, wherein a difference (T2-T1) between T1 and T2 is 5 ° C or more.   The inkjet recording method according to claim 1, wherein the Tg is higher than the T2 in a range of 2 ° C. or more and 30 ° C. or less.   The inkjet recording method according to claim 1, wherein the water-based ink contains a water-soluble solvent.   The inkjet recording method according to claim 6, wherein the water-soluble solvent is 1,2-alkanediol having a melting point of 30 ° C. or lower, or both-end alkanediol having a melting point of 30 ° C. or lower.   The inkjet recording method according to claim 6 or 7, wherein the content of the water-soluble solvent is 13% by mass or more and 30% by mass or less based on the total mass of the ink.   The ink jet recording method according to claim 1, wherein the resin particles are acrylic resin particles, and a monomer having a hydroxyl group is contained in a monomer constituting the acrylic resin particles.