WO2025023197A1 - 画像形成方法 - Google Patents

画像形成方法 Download PDF

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Publication number
WO2025023197A1
WO2025023197A1 PCT/JP2024/026079 JP2024026079W WO2025023197A1 WO 2025023197 A1 WO2025023197 A1 WO 2025023197A1 JP 2024026079 W JP2024026079 W JP 2024026079W WO 2025023197 A1 WO2025023197 A1 WO 2025023197A1
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WO
WIPO (PCT)
Prior art keywords
treatment liquid
ink
droplets
image forming
less
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PCT/JP2024/026079
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English (en)
French (fr)
Japanese (ja)
Inventor
大隆 田郡
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Konica Minolta Inc
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Konica Minolta Inc
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Priority to JP2025535804A priority Critical patent/JPWO2025023197A1/ja
Publication of WO2025023197A1 publication Critical patent/WO2025023197A1/ja
Anticipated expiration legal-status Critical
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/205—Ink jet for printing a discrete number of tones
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/30—Inkjet printing inks
    • C09D11/38—Inkjet printing inks characterised by non-macromolecular additives other than solvents, pigments or dyes
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/54—Inks based on two liquids, one liquid being the ink, the other liquid being a reaction solution, a fixer or a treatment solution for the ink

Definitions

  • the present invention relates to an image forming method.
  • a known image forming method is one in which ink droplets are ejected from an inkjet head onto a recording medium to form an image.
  • the recording medium is a substrate with low ink absorbency (low-absorbency substrate)
  • a phenomenon called liquid concentration in which the deposited ink droplets merge together, or color bleeding, in which different colors bleed, may occur.
  • a two-liquid image forming method is known that uses both ink and a treatment liquid that aggregates the coloring material in the ink.
  • treatment liquid has traditionally been ejected onto all pixels onto which ink is ejected (positions where ink dots are formed). This means that the amount of treatment liquid applied tends to be large, which can lead to unevenness (cockling) on the recording medium surface and, when using multi-color ink, can easily lead to color mixing. For this reason, methods for reducing the amount of treatment liquid applied are being considered.
  • Patent Document 1 discloses a method of controlling the pixels onto which the processing liquid is ejected (the positions at which processing liquid dots are formed) according to the distribution state of the pixels onto which the ink is ejected. Specifically, the processing liquid dots are made larger than the ink dots, and one processing liquid dot is formed across multiple positions where the ink dots are formed.
  • Patent Document 2 also discloses a method of forming an image in which, in low-density print regions, the pixels onto which processing liquid is ejected and the pixels onto which ink is ejected are relatively different, and in high-density print regions, the amount of processing liquid ejected is thinned out. Specifically, in low-density print regions, the pixels onto which ink is ejected and the pixels onto which processing liquid is ejected are shifted by one pixel, and in high-density print regions, the amount of processing liquid ejected is thinned out.
  • Patent document 3 also discloses a method of increasing the amount of droplets of treatment liquid in areas where the area printed in solid is relatively large, and decreasing the amount of droplets of treatment liquid in areas where the area printed in solid is relatively small, i.e., a method of setting the application ratio of ink to treatment liquid at two or more levels.
  • the amount of treatment liquid applied can be reduced because the treatment liquid can be thinned out to a certain extent.
  • areas where the treatment liquid droplets and the ink droplets come into contact and areas where the treatment liquid droplets and the ink droplets do not come into contact tend to be formed regularly, which can easily result in streaky unevenness.
  • the contact area between the treatment liquid droplets and the ink droplets is large, so the coloring material in the ink is likely to coagulate excessively due to the treatment liquid before the ink has fully wetted and spread, which can easily result in uneven density.
  • the present invention was made in consideration of the above circumstances, and aims to provide an image forming method that can form an image with minimal streaky unevenness and minimal density unevenness, even when applying a small amount of treatment liquid from a position away from the surface of the recording medium, while reducing the amount of treatment liquid applied.
  • An image forming method comprising: a treatment liquid ejecting step of ejecting droplets of a treatment liquid from a first inkjet head onto a recording medium; and an ink ejecting step of ejecting droplets of ink containing a color material that aggregates by the treatment liquid from a second inkjet head, wherein in the treatment liquid ejecting step, some pixels are irregularly selected from an image forming area onto which the ink droplets are ejected, and the treatment liquid droplets are ejected at positions shifted by a range of less than one pixel from the selected pixels, the treatment liquid droplets include two or more types of droplets having different droplet sizes, and a maximum droplet size of the treatment liquid ejected in the treatment liquid ejecting step is smaller than a droplet size of the ink ejected in the ink ejecting step.
  • the present invention provides an image forming method that can form an image with minimal streaky unevenness and minimal density unevenness, even when applying a small amount of treatment liquid from a position away from the surface of the recording medium while reducing the amount of treatment liquid applied.
  • FIG. 1A is a schematic diagram showing the main components of an image forming apparatus applicable to an image forming method according to one embodiment of the present invention
  • FIG. 1B is a schematic diagram showing the application of ink and treatment liquid to a surface of a recording medium by the apparatus of FIG. 1A
  • FIG. 2 is a schematic diagram showing an image formed by an image forming method according to one embodiment of the present invention.
  • 3A to 3E are schematic diagrams showing the procedure for forming the image of FIG.
  • FIG. 4 is a schematic diagram showing an image formed by a conventional image forming method.
  • 5A to 5E are schematic diagrams showing an image forming method according to a modified example.
  • the droplet size of the treatment liquid is larger than that of the ink, as in the past, the contact area between the ink and the treatment liquid on the recording medium becomes large, which can easily cause an excessive reaction between the ink and the treatment liquid. If the reaction becomes excessive, the color material will aggregate before the ink has a chance to wet and spread, which can easily result in uneven density. Furthermore, if the treatment liquid droplets are of only one type with a large droplet size, the reaction between the ink and the treatment liquid is likely to be excessive, whereas if the treatment liquid droplets are of only one type with a small droplet size, the reaction between the ink and the treatment liquid is likely to be insufficient. Therefore, by making the droplet size of the treatment liquid smaller than that of the ink and providing two or more different droplet sizes for the treatment liquid, it is possible to reduce concentration unevenness due to overreaction without causing underreaction.
  • an image forming method includes: 1) a treatment liquid ejection step of ejecting droplets of treatment liquid from a first inkjet head onto a recording medium; and 2) an ink ejection step of ejecting droplets of ink containing a coloring material that aggregates with the treatment liquid from a second inkjet head.
  • the treatment liquid ejection process some pixels are randomly selected from the image formation area onto which the ink droplets are ejected, and droplets of treatment liquid are ejected onto positions shifted from the selected pixels by less than one pixel.
  • the droplet size of the treatment liquid is made smaller than the droplet size of the ink, and two or more types of droplets having different droplet sizes are used as the droplets of the treatment liquid. This makes it possible to sufficiently reduce density unevenness while suppressing streaky unevenness.
  • Fig. 1A is a schematic diagram showing the main parts of an image forming apparatus applicable to an image forming method according to an embodiment of the present invention.
  • Fig. 1B is a schematic diagram showing how ink or treatment liquid is applied to a recording medium surface by the apparatus of Fig. 1A.
  • Fig. 1A shows a total printing area P as a range in which an image can be formed on a recording medium M by scanning the droplet ejection means 2 in the X direction and transporting the recording medium M in the Y direction.
  • the length of the total printing area P in the X direction is the printing area width PW
  • the length in the Y direction is the printing area length PL.
  • the image forming device 1 includes a droplet ejection means 2 and a scanning unit 3.
  • the droplet ejection means 2 includes a first inkjet head 4Pr for the treatment liquid, second inkjet heads 4Y, 4M, 4C, and 4K corresponding to each color ink (hereinafter collectively referred to as the "head unit 4"), and a carriage 5 that holds these inkjet heads.
  • each inkjet head facing the surface of the recording medium M has multiple nozzles arranged in a direction Y perpendicular to the scanning direction X, and droplets of ink or treatment liquid are ejected from the nozzles.
  • the droplet ejection means 2 is supported in a state where the nozzle surface of the head unit 4 is spaced a predetermined distance from the surface of the recording medium M in a direction perpendicular to the surface (height direction).
  • the distance between the nozzle surface (ejection surface) of each inkjet head and the surface of the recording medium M is not particularly limited, and can be, for example, 1.5 mm or more, and preferably 3 mm or more.
  • the upper limit of the above distance is not particularly limited, but can be 20 mm or less.
  • the scanning unit 3 is a mechanism for scanning the droplet ejection means 2 in the scanning direction X.
  • the scanning unit 3 has a rail that extends along the scanning direction X, and supports the carriage 5 so that it can move along the rail.
  • both the inks Y, M, C, and K (hereinafter collectively referred to as "In") and the treatment liquid Pr may be applied in an area of width W in the direction Y perpendicular to the scanning direction X of the head unit 4 for the printing area width PW of the entire printing area P.
  • the operation of simultaneously ejecting the ink In and the treatment liquid Pr by moving the droplet ejection means 2 once in the scanning direction X is regarded as one printing pass, and multiple printing passes are performed to finally form the desired image on the recording medium M (Pattern 1).
  • the droplet ejection means 2 may be moved in the scanning direction X while ejecting only the treatment liquid, and multiple printing passes may be performed for the printing area width PW of the entire printing area P, after which the recording medium M may be returned to the state at the start of printing, and the droplet ejection means 2 may be moved again in the scanning direction X while ejecting only the ink In, and multiple printing passes may be performed for the printing area width PW of the entire printing area P. This may ultimately form the desired image on the recording medium M (Pattern 2).
  • the area to which ink and treatment liquid are applied in one printing pass of the droplet ejection means 2 is an area (hereinafter also referred to as "printing area A") that is the product of the printing area width PW in the scanning direction X and the width W of the head unit 4 in the direction Y perpendicular to the scanning direction X (hereinafter also referred to as "width W of head unit 4").
  • the total printing area P is a collection of these printing areas A.
  • the number of printing areas A that make up the total printing area P is indicated by the value obtained by dividing the printing area length PL by the width W of the head unit 4.
  • the number of printing areas A that make up the total printing area P is six, and the total printing area P is made up of printing areas A1, A2, A3, A4, A5, and A6 arranged in parallel in order from the front to the back of the recording medium M.
  • the control unit determines whether or not to apply treatment liquid or ink and the amount to be applied (discharge amount) for each pixel according to image data. Then, based on this determination, the droplet discharge means 2 discharges droplets of treatment liquid or ink onto the surface of the recording medium M to form an image. Then, each step of the image forming method described below is carried out under the control of the control unit.
  • the type of recording medium M is not particularly limited, but it is preferably a low-absorbency substrate.
  • a low-absorbency substrate is a substrate in which a 0.5 ⁇ L water droplet is dropped onto the recording surface of the substrate, and the contact angle reduction rate (comparing the contact angle 0.5 milliseconds after impact with the contact angle 5 seconds after impact) is 1.0% or more and less than 30%.
  • the contact angle can be measured at 25°C by the droplet method, for example, using a contact angle meter manufactured by Kyowa Interface Science Co., Ltd.
  • the contact angle of the treatment liquid on the recording surface of the low-absorbency substrate at 25°C is, for example, 10° or more and 105° or less, and preferably 20° or more and 90° or less.
  • FIG. 2 is a schematic diagram showing an image 10 formed by the image forming method according to the present embodiment.
  • Figs. 3A to 3E are schematic diagrams showing the procedure for forming the image 10 in Fig. 2. In these diagrams, the smallest unit of a square partitioned into a lattice pattern represents one pixel.
  • the image forming method includes 1) a step of ejecting droplets of a treatment liquid from a first inkjet head (treatment liquid ejection step), and 2) a step of ejecting droplets of ink containing a coloring material from a second inkjet head (ink ejection step).
  • the order of steps 1) and 2) is not particularly limited, and steps 1) and 2) may be performed in the order 1), 2), or steps 2) and 1). In this embodiment, steps 1) and 2) are preferably performed in the order 1).
  • pixels onto which ink droplets are discharged are determined based on the image data to be formed, and an image formation area a is determined (see FIG. 3A).
  • the image formation area a constitutes a part of the image formation area Im (see FIG. 1A).
  • filled pixels are pixels onto which ink droplets are discharged, and become the image formation area a.
  • the method for randomly selecting pixels is not particularly limited, and may be a dither method or an error diffusion method.
  • a droplet 12 of the treatment liquid is ejected from the selected pixel at a position shifted by less than one pixel in the nozzle row direction (Y direction) (see FIG. 3C) (see FIG. 3D).
  • the pixel is shifted in the nozzle row direction (Y direction), but this is not limiting and the pixel may be shifted in a direction perpendicular to the nozzle row (X direction) (see FIG. 5C described later).
  • the method of shifting the position where the droplets of the treatment liquid are ejected from the position where the droplets of the ink are ejected is not particularly limited, and for example, in the image forming device 1, it may be done by shifting the nozzle position of the first inkjet head 4Pr by less than one pixel from the nozzle position of the second inkjet head 4Y, 4M, 4C or 4K, or by changing the feed amount of the recording medium M during multiple passes.
  • the ratio (pixel ratio) of the total number of pixels onto which droplets 12 of the treatment liquid are discharged in the treatment liquid discharge process to the total number of pixels onto which droplets 14 of the ink are discharged in the ink discharge process is preferably 30% or more and 65% or less, and more preferably 30% or more and 50% or less.
  • the pixel ratio is 30% or more, the reaction between the ink and the treatment liquid is more likely to be sufficient, and the image density can be further increased.
  • the pixel ratio is 65% or less, the reaction between the treatment liquid and the ink is less likely to be excessive, and density unevenness can be further suppressed.
  • the size of the droplets 12 of the treatment liquid ejected in the treatment liquid ejection process is smaller than the size of the droplets 14 of the ink ejected in the ink ejection process. This makes it possible to reduce the contact area between the droplets of the treatment liquid and the droplets of the ink on the recording medium M, thereby suppressing overreaction.
  • the droplets 12 of the treatment liquid include two or more types of droplets with different droplet sizes (see Figure 3D).
  • the droplets 12 of the treatment liquid include first droplets 12a with a large droplet size and second droplets 12b with a small droplet size.
  • the maximum droplet size (volume) of the treatment liquid is preferably 20% or more and 90% or less of the droplet size (volume) of the ink. If the droplet size of the treatment liquid is 20% or more, insufficient reaction between the ink and the treatment liquid can be further suppressed, and if it is 90% or less, excessive reaction can be further suppressed.
  • the method of allocating the first droplets 12a and the second droplets 12b is not particularly limited, but may be based on a general halftone, for example.
  • the ratio of the total number of pixels onto which the first droplets 12a are discharged to the total number of pixels onto which the second droplets 12b are discharged in the image forming area a is preferably 1:0.4 to 1:1.6.
  • Increasing the ratio of the first droplets 12a reduces the insufficient reaction between the ink and the treatment liquid, and can further suppress the decrease in image density. Reducing the ratio of the first droplets 12a makes it easier to suppress the excessive reaction between the ink and the treatment liquid, and can further suppress unevenness in density.
  • the total number of pixels onto which the first droplets 12a are discharged is greater than the total number of pixels onto which the second droplets 12b are discharged.
  • the droplet size of the first droplet 12a is preferably 10 pL or more and less than 20 pL, and more preferably 14 pL or more and 18 pL or less.
  • the droplet size of the second droplet 12b is preferably 10 pL or more and more preferably 5 pL or more and 9 pL or less.
  • the difference between the droplet size of the first droplet 12a and the droplet size of the second droplet 12b is preferably 4 pL or more and 10 pL or less.
  • the size of the ink droplets 14 is not particularly limited, but it is preferable that the volume of each droplet is 15 pL or more and 45 pL or less.
  • the droplet volume is large, and it is more preferable that the volume is 20 pL or more and 45 pL or less.
  • the image forming method in the treatment liquid ejection step, some pixels are irregularly selected from the pixels onto which ink droplets are ejected, and droplets of treatment liquid are ejected onto positions shifted by less than one pixel from the selected pixels. Furthermore, the droplet size of the treatment liquid is made smaller than the droplet size of the ink, and two or more types of droplets with different droplet sizes are combined. This makes it possible to suppress excessive reaction between the ink and the treatment liquid while suppressing streak-like unevenness, thereby making it possible to sufficiently reduce density unevenness.
  • the ink contains at least a coloring material.
  • the coloring material is preferably a pigment.
  • the ink preferably contains, for example, a pigment as a coloring material, a polymer dispersant for dispersing the pigment, resin particles, water, and an organic solvent.
  • the coloring material is preferably a pigment.
  • the pigment include an anionic dispersed pigment, such as an anionic self-dispersing pigment, and a pigment dispersed with an anionic polymer dispersant.
  • an anionic dispersed pigment such as an anionic self-dispersing pigment
  • a pigment dispersed with an anionic polymer dispersant it is preferable to use a pigment dispersion liquid in which the pigment is dispersed with an anionic polymer dispersant.
  • Titanium oxide has three crystal forms: anatase, rutile, and brookite. The most commonly used are broadly classified into anatase and rutile. Among them, rutile is preferred because it has a high refractive index and high hiding power. Specific examples include Fuji Titanium Industry Co., Ltd.'s TR series, Teika Corporation's JR series, and Ishihara Sangyo Co., Ltd.'s Typeque.
  • the organic pigments include the following pigments: Examples of pigments for magenta or red include C.I. Pigment Red 2, C.I. Pigment Red 3, C.I. Pigment Red 5, C.I. Pigment Red 6, C.I. Pigment Red 7, C.I. Pigment Red 15, C.I. Pigment Red 16, C.I. Pigment Red 48:1, C.I. Pigment Red 53:1, C.I. Pigment Red 57:1, C.I. Pigment Red 122, C.I. Pigment Red 123, C.I. Pigment Red 139, C.I. Pigment Red 144, C.I. Pigment Red 149, C.I. Pigment Red 166, C.I. Pigment Red 177, C.I.
  • pigments examples include C.I. Pigment Red 178, C.I. Pigment Red 202, C.I. Pigment Red 222, C.I. Pigment Violet 19, and the like.
  • pigments for orange or yellow include C.I. Pigment Orange 31, C.I. Pigment Orange 43, C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, C.I. Pigment Yellow 15, C.I. Pigment Yellow 15:3, C.I. Pigment Yellow 17, C.I. Pigment Yellow 74, C.I. Pigment Yellow 93, C.I. Pigment Yellow 128, C.I. Pigment Yellow 94, C.I. Pigment Yellow 138, C.I. Pigment Yellow 155, etc.
  • C.I. Pigment Yellow 155 is preferred in terms of the balance between color tone and lightfastness.
  • pigments for green or cyan include C.I. Pigment Blue 15, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 16, C.I. Pigment Blue 60, C.I. Pigment Green 7, and the like.
  • black pigments include C.I. Pigment Black 1, C.I. Pigment Black 6, C.I. Pigment Black 7, and the like.
  • the pigment content is not particularly limited, but in the case of titanium oxide, it is preferable that the content be 7% by mass or more and 18% by mass or less relative to the ink.
  • the organic pigment content is preferably 0.5% by mass or more and 7% by mass or less relative to the ink.
  • the polymer dispersant is not particularly limited, but a polymer dispersant having an anionic group is preferred.
  • polymeric dispersants include block copolymers and random copolymers having a structure derived from two or more monomers selected from styrene, styrene derivatives, vinylnaphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, and fumaric acid derivatives, as well as salts thereof, polyoxyalkylenes, and polyoxyalkylene alkyl ethers.
  • the polymer dispersant preferably has an acryloyl group, and is preferably neutralized with a neutralizing agent (neutralizing base) before addition.
  • the neutralizing base is preferably an organic base such as ammonia, monoethanolamine, diethanolamine, N-methylethanolamine, N-methyldiethanolamine, triethanolamine, morpholine, etc.
  • the pigment is titanium oxide
  • it is preferable that the titanium oxide is dispersed with a polymer dispersant having an acryloyl group.
  • Commercially available polymer dispersants may be used.
  • An example of a commercially available polymer dispersant is Joncryl 819 manufactured by BASF.
  • the molecular weight of the polymer dispersant can be, for example, 5,000 or more and 200,000 or less.
  • the molecular weight can be measured as a polystyrene-equivalent value using the GPC method.
  • the amount of polymer dispersant contained is not particularly limited, but is preferably 10% by mass or more and 100% by mass or less, and more preferably 10% by mass or more and 40% by mass or less, relative to the pigment.
  • the average particle size of the pigment in the dispersed state in the ink is preferably 50 nm or more and less than 200 nm. This can further improve the dispersion stability of the pigment and the storage stability of the ink.
  • the particle size of the pigment can be measured by dynamic light scattering.
  • the resin particles are preferably water-insoluble resin particles that have solubility or affinity for the ink.
  • water-insoluble resin microparticles are inherently water-insoluble, but have a form in which the resin disperses in an aqueous medium as microscopic particles. They are water-insoluble resins that are forcibly emulsified and dispersed in water using an emulsifier, etc., or water-insoluble resins that have hydrophilic functional groups introduced into their molecules and can self-emulsify to form a stable aqueous dispersion without the use of emulsifiers or dispersion stabilizers. These resins are usually used in an emulsified and dispersed state in water or a water/alcohol mixed solvent.
  • the resin fine particles are preferably anionic.
  • the resin fine particles preferably contain an acidic group. This makes it possible to disperse the resin fine particles in water even with a small amount of surfactant added, and improves the water resistance of the resulting image.
  • Such resin fine particles are also called self-emulsifying resin fine particles, and can be dispersed and stabilized in water only by molecular ionicity without using a surfactant.
  • the acidic group include a carboxy group (-COOH), a sulfonic acid group (-SO 3 H), etc.
  • At least a portion of the acidic groups are neutralized.
  • Neutralizing the acidic groups can further increase the water dispersibility of the resin.
  • organic amines are preferable, and for example, it is preferable to use organic amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, N-methyldiethanolamine, and triethanolamine.
  • the resin fine particles may be commercially available products. Examples of commercially available resin fine particles are listed below by type of resin. ⁇ Polyester type> Manufactured by Takamatsu Oil Co., Ltd.: PES RESIN A-110F, A-520, A-613D, A-615GE, A-640, A-645GH, A-647GEX; manufactured by Unitika Ltd.: Elitell KA-5034, KA-5071S, KA-1449, KA-0134, KA-3556, KA-6137, KZA-6034, KT-8803, KT-8701, KT-9204, KT-8904, KT-0507, KT-9511, and the like.
  • the amount of resin microparticles contained is not particularly limited, but is preferably 2% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 5% by mass or less, relative to the ink.
  • organic solvent a water-soluble organic solvent can be suitably used, for example, alcohols, polyhydric alcohols, amines, amides, glycol ethers, 1,2-alkanediols having 4 or more carbon atoms, and the like.
  • Alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, t-butanol, 3-methoxy-1-butanol, 3-methoxy-3-methylbutanol, 1-octanol, 2-octanol, n-nonyl alcohol, tridecyl alcohol, n-undecyl alcohol, stearyl alcohol, oleyl alcohol, and benzyl alcohol.
  • polyhydric alcohols examples include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycols having five or more ethylene oxide groups, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycols having four or more propylene oxide groups, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, and thiodiglycol.
  • amines include ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, and tetramethylpropylenediamine.
  • amides examples include formamide, N,N-dimethylformamide, and N,N-dimethylacetamide.
  • glycol ethers examples include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and tripropylene glycol monomethyl ether.
  • 1,2-alkanediols having 4 or more carbon atoms examples include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, and 1,2-heptanediol.
  • polyhydric alcohols are preferred from the viewpoint of effectively suppressing bleeding during high-speed printing, and examples of such preferred alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol.
  • the organic solvent content is preferably, for example, 10% to 60% by mass of the ink.
  • the water content is preferably, for example, 45% by mass or more and 5% by mass or less with respect to the ink.
  • the ink may contain various known additives as necessary for the purpose of improving various performances such as a surfactant, ejection stability, storage stability, image storage stability, etc. Among them, it is preferable that the ink contains a surfactant. This can further increase the ejection stability of the ink from the nozzle, and make it easier to control the spread of the ink droplets that land on the recording medium (increase in dot diameter).
  • the surfactant is not particularly limited, but when the other components of the ink contain anionic compounds, the ionic nature of the surfactant is preferably anionic, nonionic, or betaine type.
  • fluorine-based or silicone-based surfactants that have a high static surface tension reducing ability
  • anionic surfactants such as dioctyl sulfosuccinate that have a high dynamic surface tension reducing ability
  • nonionic surfactants such as relatively low molecular weight polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, acetylene glycols, Pluronic surfactants (Pluronic is a registered trademark), and sorbitan derivatives are preferably used.
  • Pluronic surfactants Pluronic is a registered trademark
  • sorbitan derivatives are preferably used. It is also preferable to use a fluorine-based or silicone-based surfactant in combination with a surfactant that has a high dynamic surface tension reducing ability.
  • a silicone-based or fluorine-based surfactant as the surfactant is advantageous in that it can further suppress ink mixing (beading) on recording media made of various hydrophobic resins, such as polyvinyl chloride sheets, and on recording media with low ink absorption, such as printing paper, and can result in high-quality printed images.
  • Fluorosurfactants refer to surfactants in which some or all of the hydrogen atoms bonded to the carbon of the hydrophobic group of a normal surfactant have been replaced with fluorine. Of these, those that have a perfluoroalkyl group in the molecule are preferred.
  • fluorine-based surfactants are commercially available from Dainippon Ink and Chemicals under the trade name Megafac F, from Asahi Glass under the trade name Surflon, from Minnesota Mining and Manufacturing Company under the trade name Fluorad FC, from Imperial Chemical Industries under the trade name Monflor, from E.I. duPont Nemelas & Co. under the trade name Zonyls, and from mistakewerke Hoechst under the trade name Licowet VPF.
  • the amount of surfactant contained is not particularly limited, but it is preferable that the amount is 0.1% by mass or more and 5.0% by mass or less with respect to the ink.
  • the viscosity of the ink is, for example, preferably 1 mPa ⁇ s or more and 40 mPa ⁇ s or less at 25°C, and more preferably 2 mPa ⁇ s or more and 10 mPa ⁇ s or less.
  • the viscosity of the ink can be measured using a rotational viscometer. Unless otherwise specified, the viscosity in this specification is the viscosity at 25°C.
  • the static surface tension of the ink is preferably 25 mN/m or more and 33 mN/m or less at 25°C, and more preferably 25 mN/m or more and 29 mN/m or less.
  • the static surface tension of the ink can be measured using a surface tensiometer that employs the platinum plate method (Wilhelmy method) or the like. Unless otherwise specified, the static surface tension in this specification is the static surface tension at 25°C.
  • the treatment liquid contains at least a flocculant.
  • the treatment liquid preferably contains, for example, a flocculant, a surfactant, water, and an organic solvent. It is preferable that the treatment liquid does not contain resin particles.
  • the aggregating agent may be any material that generates an aggregate when it is combined with the ink containing the coloring material. This increases the interaction between the treatment liquid and the ink when the treatment liquid is combined, and has the effect of fixing the ink dots and suppressing the increase in dot diameter.
  • the aggregating agent can be selected according to the type of coloring material contained in the ink.
  • the flocculant preferably contains either a cationic polymer, an organic acid, or a polyvalent metal salt, and more preferably contains a cationic polymer or a polyvalent metal salt.
  • Cationic polymers and polyvalent metal salts can aggregate anionic components in the ink (usually colorants or pigments, etc.) by salting out.
  • Organic acids have the ability to aggregate anionic components in the ink by changing the pH.
  • cationic polymers examples include polyallylamine, polyvinylamine, polyethyleneimine, and polydiallyldimethylammonium chloride.
  • Commercially available cationic polymers include, for example, KHE100L and FPA100L manufactured by Senka Corporation, and PAS-92A, PAS-M-1A, and PAS-21CL manufactured by Nittobo Medical Co., Ltd.
  • polyvalent metal salts examples include water-soluble salts such as calcium salts, magnesium salts, aluminum salts, and zinc salts.
  • Compounds that form salts with polyvalent metals include hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid, thiocyanic acid, and organic carboxylic acids such as acetic acid, oxalic acid, lactic acid, fumaric acid, citric acid, salicylic acid, and benzoic acid, and organic sulfonic acids.
  • the organic acid is capable of aggregating pigments that may be contained in the ink, and preferably has a first dissociation constant of 3.5 or less, and more preferably 1.5 or more and 3.5 or less.
  • organic acids include formic acid, acetic acid, propionic acid, isobutyric acid, oxalic acid, fumaric acid, malic acid, citric acid, malonic acid, succinic acid, maleic acid, benzoic acid, 2-pyrrolidone-5-carboxylic acid, lactic acid, acrylic acid and its derivatives, methacrylic acid and its derivatives, or compounds having a carboxy group including acrylamide and its derivatives, sulfonic acid derivatives, or phosphoric acid and its derivatives.
  • the content of the coagulant is not particularly limited, but is preferably 5% by mass or less, and more preferably 1% by mass or more and 4% by mass or less, relative to the treatment liquid. When the content of the coagulant is within the above range, the anionic components in the ink can be more effectively coagulated, and the image density can be further increased.
  • the content of the organic acid may be an amount that adjusts the pH of the treatment liquid to less than the first dissociation constant of the organic acid.
  • the water content is not particularly limited, but is preferably 45% by mass or more and 80% by mass or less based on the treatment liquid.
  • the treatment liquid may further contain an organic solvent in addition to water.
  • the organic solvent the same organic solvents as those exemplified for the ink may be used.
  • the content of the organic solvent is preferably 10% by mass or more and 50% by mass or less with respect to the treatment liquid.
  • the treatment liquid may contain a surfactant.
  • the surfactant may be the same as those exemplified for the ink.
  • the surfactant content is preferably, for example, 0.08% by mass or more and 3% by mass or less with respect to the treatment liquid.
  • the treatment solution may contain other ingredients such as crosslinking agents, antifungal agents, and bactericides as necessary.
  • the viscosity of the treatment liquid is adjusted by adding a solvent or the like so that it can be ejected from the nozzles of the inkjet head.
  • the viscosity of the treatment liquid is preferably 1 mPa ⁇ s or more and 40 mPa ⁇ s or less at 25°C, and more preferably 1 mPa ⁇ s or more and 10 mPa ⁇ s or less.
  • the static surface tension of the treatment liquid at 25°C is preferably 22 mN/m or more and 30 mN/m or less at 25°C, and more preferably 22 mN/m or more and 26 mN/m or less.
  • the dynamic surface tension of the treatment liquid at 25°C and 50 ms is preferably 40 mN/m or less, more preferably 36 mN/m or less, and even more preferably 25 mN/m to 35 mN/m.
  • the dynamic surface tension of the treatment liquid can be determined at 25°C using a Dynamic Surface Tension Meter BP-D4 type manufactured by Kyowa Interface Science Co., Ltd., as the value at a lifetime of 50 ms when bubbles are continuously generated.
  • the dynamic surface tension in this specification is the dynamic surface tension measured at 25°C and 50 ms using the maximum bubble pressure method.
  • treatment liquid and ink ⁇ Preparation of treatment liquid> The following components were mixed to prepare treatment solution a.
  • Polyvalent metal salt calcium acetate 3% by mass
  • Organic solvent propylene glycol 30% by mass
  • Water Remainder
  • Ink A was prepared by mixing the following ingredients: Pigment: Pigment Blue 15:3 5% by weight
  • Organic solvent propylene glycol 30% by mass
  • Surfactant: KF-351A manufactured by Shin-Etsu Chemical Co., Ltd. 0.5% by mass Water: Remainder
  • Image formation test and evaluation ⁇ Example 1> An acrylic rubber substrate was prepared as a recording medium.
  • the contact angle of the treatment liquid measured by the drop method at 25° C. was 60°.
  • an image formation test was carried out using the treatment liquid and ink prepared above.
  • an image forming apparatus having an independently driven inkjet head manufactured by Konica Minolta 360 dpi, droplet volume: small droplets 5 pL to 7 pL, medium droplets 14 pL to 16 pL, large droplets 20 pL to 25 pL) as shown in Figure 1 was prepared.
  • the treatment liquid A and ink A prepared above were set in the apparatus.
  • image formation area a an area consisting of 3000 rows and 3000 columns, a total of 9 million pixels, was designated as image formation area a.
  • the pixels onto which the treatment liquid was to be ejected were selected to have the method and pixel ratio shown in Table 1, and a position shifted by half a pixel in the nozzle row direction from the selected pixel was set as the position onto which the treatment liquid was to be ejected.
  • the shift width W1 of the pixel onto which the treatment liquid was to be ejected from the selected pixel was achieved by shifting the distance between the nozzle position of the inkjet head 4Pr for the treatment liquid and the nozzle position of the inkjet head for the ink by half a pixel (0.5 times the pixel) in the nozzle row direction (Y direction).
  • the head unit 4 was moved in the scanning direction X and the recording medium M was moved in the transport direction Y, and the treatment liquid a was ejected onto the recording medium M at the set pixels in the first pass, and then the ink A was ejected onto all pixels in the second pass to form an image.
  • Each liquid was ejected at 25°C and 50% RH. Each liquid was ejected at 540 dpi in the main scan direction and 720 dpi in the sub scan direction. dpi represents the number of ink droplets (dots) per 2.54 cm. The ejection frequency was 22.4 kHz.
  • the ink droplet size (droplet volume) and treatment liquid droplet size (droplet volume) were the values shown in Table 1.
  • the material was dried in a dryer at 80°C for 15 minutes to obtain an image.
  • Examples 2 to 6 and Comparative Examples 1 to 7 Image formation was carried out in the same manner as in Example 1, except that the image formation conditions were changed as shown in Table 1.
  • Image Edge Disorder The periphery of the image was visually observed to check for the presence or absence of image edge disorder, and was evaluated based on the following criteria. ⁇ : No image edge disturbance is observed. ⁇ : Some image edge disturbance is observed, but no practical problem is observed. ⁇ : Image edge disturbance is observed. XX: Obvious image edge disturbance is observed.
  • the present invention provides an image forming method that can form an image with minimal streaky unevenness and minimal density unevenness, even when applying a small amount of treatment liquid from a position away from the surface of the recording medium while reducing the amount of treatment liquid applied.
  • Image forming apparatus REFERENCE SIGNS LIST 1 Image forming apparatus 2 Droplet ejection means 3 Scanning section 4 Head unit 4Y, 4M, 4C, 4K Ink ink heads 4Pr Ink jet head for treatment liquid 10 Image 12 Treatment liquid droplet 12a First droplet 12b Second droplet 14 Ink droplet a Image forming area

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PCT/JP2024/026079 2023-07-26 2024-07-22 画像形成方法 Pending WO2025023197A1 (ja)

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002079740A (ja) * 2000-06-21 2002-03-19 Canon Inc インクジェットプリント方法
EP1582358A1 (en) * 2004-03-30 2005-10-05 Hewlett-Packard Development Company, L.P. Formation of images
JP2008132669A (ja) * 2006-11-28 2008-06-12 Canon Inc インクジェット記録装置
JP2011245865A (ja) * 2005-03-31 2011-12-08 Fujifilm Corp 画像形成装置及びインクジェット記録装置
JP2012186714A (ja) * 2011-03-07 2012-09-27 Fujifilm Corp 画像処理装置及び方法、並びに画像形成装置
JP2020189439A (ja) * 2019-05-22 2020-11-26 株式会社リコー 前処理液、インクと前処理液のセット、印刷方法及び印刷装置
JP2023011181A (ja) * 2021-07-12 2023-01-24 セイコーエプソン株式会社 インクジェットインク組成物及び記録方法

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002079740A (ja) * 2000-06-21 2002-03-19 Canon Inc インクジェットプリント方法
EP1582358A1 (en) * 2004-03-30 2005-10-05 Hewlett-Packard Development Company, L.P. Formation of images
JP2011245865A (ja) * 2005-03-31 2011-12-08 Fujifilm Corp 画像形成装置及びインクジェット記録装置
JP2008132669A (ja) * 2006-11-28 2008-06-12 Canon Inc インクジェット記録装置
JP2012186714A (ja) * 2011-03-07 2012-09-27 Fujifilm Corp 画像処理装置及び方法、並びに画像形成装置
JP2020189439A (ja) * 2019-05-22 2020-11-26 株式会社リコー 前処理液、インクと前処理液のセット、印刷方法及び印刷装置
JP2023011181A (ja) * 2021-07-12 2023-01-24 セイコーエプソン株式会社 インクジェットインク組成物及び記録方法

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