Inkjet recording method and inkjet recording device

Abstract

To provide an inkjet recording method and an inkjet recording device which achieve both suppression of color unevenness of a recorded matter and continuous discharge properties of ink.SOLUTION: There is provided [1] an inkjet recording method for performing recording on a low liquid-absorptive recording medium R, using an inkjet recording device 100 having a recording head 30 for discharging aqueous ink. The inkjet recording device 100 includes a conveyance mechanism 10 for conveying the recording medium R, a hot air blowing unit 50 for blowing hot air to the recording medium R, and a duct 70 for recovering a part of ink mist and the hot air. The duct 70 is located on a relatively downstream side of the recording head 30, in a conveyance direction C of the recording medium R, and the hot air blowing unit 50 is located on a relatively downstream side of the duct 70, in the conveyance direction C of the recording medium R. There is also provided [2] the inkjet recording device 100 used in [1].SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an inkjet recording method and an inkjet recording apparatus. [Background technology]

[0002] Inkjet recording is a method of directly ejecting ink from fine nozzles in a recording head and depositing it onto a print medium to produce a printed product with characters and images recorded on it. This method offers numerous advantages, including easy and inexpensive full-color printing and non-contact with the print medium. In recent years, this method has been applied not only to consumer printing for general consumers but also to commercial and industrial printing. In the commercial and industrial printing fields, high-speed inkjet printing has been considered in order to increase productivity. This involves providing a linear fixed print head capable of printing across the entire width of the print medium, and using a so-called single-pass method to continuously print rolls or sheets of print medium. Furthermore, in recent years, inkjet printing devices using aqueous inks containing pigments have been considered for this type of printing, from the perspectives of improving the weather resistance and water resistance of printed materials and reducing environmental impact.

[0003] Patent Document 1 discloses a recording device that has the objective of providing a technology that smooths the wind speed of air blown into the gap between a recording head and an ejected medium, thereby enabling good print quality to be maintained, and that includes a recording head that ejects liquid, a transport unit that transports the ejected medium so that it passes through a position opposite the recording head, an air supply unit, and a blowing mechanism that is arranged upstream of the recording head in the relative movement direction between the recording head and the ejected medium and has an outlet for blowing the air supplied from the supply unit toward the gap between the recording head and the ejected medium, wherein the outlet is composed of a plurality of slits that are arranged in a direction that intersects the relative movement direction, and the plurality of slits are arranged in a direction that intersects the relative movement direction so that the long sides of adjacent slits have areas that face each other in a direction perpendicular to the long sides.

[0004] Patent Document 2 discloses a recording method for recording on a recording medium, with the objective of solving problems such as poor ink drying properties, resulting in poor image quality, and a tendency for the impact position to be significantly misaligned when recording using an aqueous ink containing an organic solvent. The recording method includes an ink deposition step of ejecting an aqueous ink composition from an inkjet head and depositing it on the recording medium, a primary drying step including a step of applying air by a blower mechanism to dry the aqueous ink composition deposited on the recording medium, and a secondary drying step of heating the aqueous ink composition deposited on the recording medium using a heating mechanism after the primary drying step, wherein the aqueous ink composition contains a colorant and water and does not contain an organic solvent in an amount exceeding a specific amount relative to the total amount of the aqueous ink composition, and wherein the wind speed in the primary drying step is within a specific range. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-19282 [Patent Document 2] Patent Publication No. 2021-154547 Summary of the Invention [Problem to be solved by the invention]

[0006] When inkjet printing is performed using aqueous inks on low-absorbency recording media, color unevenness tends to occur in the printed matter. In order to suppress the occurrence of color unevenness in the printed matter, it is necessary to quickly dry the aqueous ink ejected onto the low-absorbency recording medium. Therefore, it is desirable to position a drying device for drying the aqueous ink as close as possible to the recording head, downstream of the recording head in the conveyance direction of the recording medium.

[0007] However, for example, if a hot air blower that blows hot air is used as a drying device and placed close to the recording head, the hot air blown from the hot air blower dries the surface of the recording head, causing the nozzles of the recording head to become clogged, resulting in a problem of reduced continuous ink ejection.

[0008] An object of the present invention is to provide an inkjet recording method and an inkjet recording apparatus that can suppress color unevenness in recorded material while also achieving continuous ink ejection properties. [Means for solving the problem]

[0009] The inventors have discovered that an inkjet recording method and an inkjet recording device can be provided that achieve both suppression of color unevenness in the recorded material and continuous ink ejection by positioning a duct for collecting ink mist and a portion of the warm air relatively downstream of the recording head in the transport direction of the recording medium, and by positioning a warm air blowing unit for blowing warm air onto the recording medium relatively downstream of the duct in the transport direction of the recording medium. That is, the present invention provides the following [1] and [2]. [1] An inkjet recording method for recording on a low-liquid-absorbency recording medium using an inkjet recording device equipped with a recording head that ejects water-based ink, wherein the inkjet recording device is equipped with a transport mechanism that transports the recording medium, a hot air blowing unit that blows hot air onto the recording medium, and a duct for recovering ink mist and a portion of the hot air, wherein the duct is located relatively downstream of the recording head in the transport direction of the recording medium, and the hot air blowing unit is located relatively downstream of the duct in the transport direction of the recording medium. [2] An inkjet recording device for recording on a low-liquid-absorbent recording medium, comprising: a transport mechanism for transporting the recording medium; a recording head for ejecting water-based ink onto the recording medium; a hot air blowing unit for blowing hot air onto the recording medium; and a duct for recovering ink mist and a portion of the hot air, wherein the duct is located relatively downstream of the recording head in the transport direction of the recording medium, and the hot air blowing unit is located relatively downstream of the duct in the transport direction of the recording medium. [Effects of the Invention]

[0010] According to the present invention, there are provided an inkjet recording method and an inkjet recording apparatus that can suppress color unevenness in recorded material while also achieving continuous ink ejection properties. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram illustrating an example of the configuration of an inkjet recording apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments for carrying out the present invention will be described below with reference to the drawings. Note that the following embodiments do not limit the inventions according to the claims, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0013] In this specification, "recording" is a concept that includes printing and printing to record characters and images, and "recorded matter" is a concept that includes printed matter and printed matter on which characters and images are recorded. Furthermore, "low liquid absorption" is a concept that includes low liquid absorption and non-liquid absorption, and the water absorption amount of the recording medium when the recording medium is in contact with pure water for 100 ms is 0 g / m. 2 More than 10g / m 2Furthermore, "color unevenness" refers to unevenness (non-uniformity) in print density in a recorded product, and "continuous ejection properties" refers to the ejection properties when ink is continuously ejected from a recording head in cases such as when recording products are continuously produced.

[0014] First, an example of the configuration of an inkjet recording apparatus 100 used in the inkjet recording method according to this embodiment will be described with reference to FIG. 1. Here, FIG. 1 is a schematic diagram for explaining an example of the configuration of the inkjet recording apparatus according to this embodiment. For ease of explanation, the up-down direction is defined based on the normal installation direction of the inkjet recording apparatus 100. Specifically, the down direction is the side of the installation surface (base B) of the transport mechanism 10, i.e., the downward direction on the paper surface of FIG. 1, and the up direction is the upward direction on the paper surface of FIG. 1. Also, for ease of explanation, the thickness of the recording medium R is depicted as being thick in FIG. 1.

[0015] [Inkjet recording apparatus 100] As shown in Figure 1, the inkjet recording device 100 according to this embodiment includes a transport mechanism 10 for transporting a low-liquid-absorbent recording medium R, a recording head 30 for ejecting water-based ink, a hot air blowing unit 50 for blowing hot air onto the recording medium R, and a duct 70 for recovering the ink mist and a portion of the hot air, the duct 70 being located relatively downstream of the recording head 30 in the transport direction C of the recording medium R, and the hot air blowing unit 50 being located relatively downstream of the duct 70 in the transport direction C of the recording medium R.

[0016] As described above, the low-liquid-absorbent recording medium R has a water absorption of 0 g / m when the recording medium is in contact with pure water for 100 ms. 2 More than 10g / m 2The term "film" refers to any of the following, including coated paper, art paper, and transparent synthetic resin film sheets. Examples of coated paper include general-purpose glossy paper and multicolor foam gloss paper. Examples of transparent synthetic resin film sheets include polyester film sheets, vinyl chloride film sheets, polypropylene film sheets, polyethylene film sheets, and nylon film sheets. These film sheets may be biaxially oriented film sheets, uniaxially oriented film sheets, or unoriented film sheets. Among these, the recording medium R may be a polyester film sheet or an oriented polypropylene film sheet, or a polyester film sheet such as a polyethylene terephthalate film sheet that has been subjected to a surface treatment such as corona discharge treatment, or a biaxially oriented polypropylene film sheet. The thickness, width, and depth of the recording medium R can be appropriately changed depending on the intended use of the recorded material.

[0017] Commercially available transparent synthetic resin film sheets can be used, and examples of commercially available products include Lumirror T60 (manufactured by Toray Industries, Inc., polyethylene terephthalate), Taiko FE2001 (manufactured by Futamura Chemical Co., Ltd., corona-treated polyethylene terephthalate), E5100, E5102 (manufactured by Toyobo Co., Ltd., corona-treated polyethylene terephthalate), PVC80B P (manufactured by Lintec Corporation, polyvinyl chloride), KYNAS KEE70CA (manufactured by Lintec Corporation, polyethylene), YUPO SG90 PAT1 (manufactured by Lintec Corporation, polypropylene), FOR, FOR-AQ, FOS, FOS-AQ (manufactured by Futamura Chemical Co., Ltd., corona-treated polypropylene), P2161, P2111, DP053 (manufactured by Toyobo Co., Ltd., corona-treated polypropylene), U1 (manufactured by RM Tocello Co., Ltd., corona-treated polypropylene), and Bonyl RX (manufactured by Kohjin Film & Chemicals Co., Ltd., nylon).

[0018] The transport mechanism 10 is for transporting a low-liquid-absorbent recording medium R. As shown in FIG. 1 , the transport mechanism 10 according to this embodiment has a flat upper surface so that the recording medium R can be placed on the upper surface and transported, although this is not particularly limited. In this embodiment, the recording medium R is placed on the upper surface of the transport mechanism 10, and the transport mechanism 10 carrying the recording medium R moves horizontally on a base B, which serves as an installation base, although this is not particularly limited. In FIG. 1 , the direction in which the transport mechanism 10 transports the recording medium R horizontally from left to right on the page is referred to as the transport direction C, but this direction is not particularly limited. That is, as long as the duct 70 is positioned relatively downstream of the recording head 30 and the warm air blowing unit 50 is positioned relatively downstream of the duct 70, the transport direction C is not particularly limited and does not have to be horizontal.

[0019] The base B is a portion having a flat surface that serves as an installation reference for the transport mechanism 10 and the like. The base B may be a floor or a member having a flat surface as long as it has a flat surface that serves as an installation reference for the transport mechanism 10 and the like. As shown in FIG. 1 , in this embodiment, the transport mechanism 10 is configured to move horizontally on the base B, but this is not limited to this. For example, the base B may be an inclined surface, and the transport mechanism 10 may move by climbing up and down the base B. Note that if the transport mechanism 10 is a cylindrical transport drum, the recording medium R is transported by the rotation of the transport drum. Therefore, although the base B serves as an installation reference for the transport drum of the transport mechanism 10, the transport drum of the transport mechanism 10 does not usually move on the base B.

[0020] The transport speed of the recording medium R by the transport mechanism 10 can be changed as appropriate depending on the size of the inkjet recording apparatus 100, the type and size of the recording medium R, the type of aqueous ink, etc. The transport speed can be, for example, 5 m / min or more and 100 m / min or less. Note that the recording medium R is usually transported by the transport mechanism 10 at a speed at which proper recording can be performed on the recording medium R, so the transport speed of the recording medium R becomes the recording speed of the recording medium R. Therefore, the recording speed of the recording medium R can be changed as appropriate depending on the size of the inkjet recording apparatus 100, the type and size of the recording medium R, the type of aqueous ink, etc., but can be, for example, 5 m / min or more and 100 m / min or less. In other words, the recording speed of the recording medium R can be 5 m / min or more and 100 m / min or less when converted into the transport speed of the recording medium R. From the viewpoint of achieving both improved quality of the resulting recording material and reduced recording time, the recording speed of the recording medium R can be set to 5 m / min or more, 15 m / min or more, 20 m / min or more, and 100 m / min or less, 80 m / min or less, 60 m / min or less, or 50 m / min or less.

[0021] The transport mechanism 10 may be equipped with a recording medium heating device to heat the recording medium R to a desired temperature. The recording medium heating device may be disposed on the upper surface of the transport mechanism 10, and its location is not particularly limited. If the transport mechanism 10 is equipped with an under-heater as the recording medium heating device, for example, the temperature of the under-heater can be changed appropriately depending on the type of recording medium R and water-based ink, and is not particularly limited, but can be 15°C or higher, or 25°C or higher, and from the viewpoint of suppressing deformation of the recording medium R, can be 80°C or lower, or 70°C or lower.

[0022] The recording head 30 (inkjet head) ejects water-based ink toward the recording medium R transported by the transport mechanism 10. The ejection method of the recording head 30 can be selected appropriately, such as a piezoelectric method or a thermal method. The recording head 30 can eject water-based ink from nozzles (not shown).

[0023] A water-based ink is an ink whose main solvent is water, i.e., an ink containing 50% by mass or more of water relative to the total mass of the solvent. The water-based ink (hereinafter simply referred to as ink) can be appropriately selected depending on the purpose of the recorded matter, etc. Examples of water-based inks include cyan ink, magenta ink, yellow ink, red ink, blue ink, orange ink, green ink, violet ink, black ink, and white ink, and are not particularly limited, but may be at least one type including cyan ink, magenta ink, yellow ink, and black ink.

[0024] The surface temperature of the recording medium R when recording by ejecting water-based ink onto the recording medium R can be changed appropriately depending on the type of water-based ink and the recording medium R, and is not particularly limited, but can be set to 35° C. or higher, and can be set to 80° C. or lower, 70° C. or lower, or lower than 65° C. from the viewpoint of suppressing deformation of the recording medium R. The surface temperature of the recording medium R can be adjusted to the above temperatures, for example, by arranging an under-heater or the like in the transport mechanism 10.

[0025] The hot air blowing unit 50 blows hot air onto the recording medium R. More specifically, it uses the hot air to dry the ink ejected onto the recording medium R from the recording head 30. By blowing hot air to dry the ink ejected onto the recording medium R from the recording head 30, it is easier to dry the ink ejected onto the recording medium R compared to blowing non-warm air, such as room temperature air, onto the recording medium R, and as a result, it is possible to suppress the occurrence of color unevenness in the recorded matter.

[0026] As shown in FIG. 1, the hot air blowing unit 50 according to this embodiment is not particularly limited, but is configured so that the tip (lower side) facing the recording medium R has a tapered shape, and hot air is blown onto the recording medium R from a hot air blowing outlet 51 at the tapered tip of the hot air blowing unit 50. This configuration narrows the area through which the hot air reaches, preventing the nozzles (not shown) of the recording head 30 from drying out and, as a result, reducing the continuous ink ejection performance. Note that the hot air blowing unit 50 may have, for example, a slit as the hot air blowing outlet 51 and be able to blow hot air from the slit, or may have a nozzle as the hot air blowing outlet and be able to blow hot air from the nozzle, and the hot air blowing outlet 51 for blowing hot air from the hot air blowing unit 50 to the recording medium R is not particularly limited. A shorter width of the hot air outlet 51 narrows the area through which the hot air reaches, which can more effectively prevent the nozzles (not shown) of the recording head 30 from drying out and, as a result, the continuous ejection of ink from the recording medium R from decreasing. On the other hand, a longer width of the hot air outlet 51 makes it easier to increase the amount of hot air blown, which makes it easier to dry the ink ejected onto the recording medium R, and as a result, makes it possible to prevent color unevenness from occurring in the recorded product.

[0027] The temperature of the hot air at the outlet of the hot air outlet 51 of the hot air blowing unit 50 can be changed appropriately depending on the type of recording medium R and water-based ink, and is not particularly limited. From the viewpoint of suppressing color unevenness in the recorded product, the temperature can be 30°C or higher, 35°C or higher, 40°C or higher, 45°C or higher, or 50°C or higher. From the viewpoint of suppressing drying of the nozzles of the recording head 30, the temperature can be 100°C or lower, 85°C or lower, 70°C or lower, or 65°C or lower. As described above, compared to blowing non-warm air, such as room temperature air, onto the recording medium R, the ink ejected onto the recording medium R is more easily dried, and as a result, color unevenness in the recorded product can be suppressed.

[0028] The speed of the hot air blown from the hot air blowing unit 50 can be changed appropriately depending on the type of water-based ink and recording medium R, and is not particularly limited, but can be set to 3 m / min or more, 5 m / min or more, 8 m / min or more, 10 m / min or more, and 80 m / min or less. By increasing the speed of the hot air, the ink can be dried more easily, and as a result, color unevenness in the recorded matter can be further suppressed.

[0029] 1, the hot air blowing unit 50 is disposed so as to be located relatively downstream of the recording head 30 and a duct 70, which will be described later, in the transport direction C of the recording medium R. With this configuration, it is possible to prevent the hot air blown by the hot air blowing unit 50 from drying out the nozzles (not shown) of the recording head 30, which would result in a decrease in the continuous ejection of ink.

[0030] The duct 70 is for collecting ink mist and a portion of the hot air. More specifically, it is a pipe for collecting and transporting ink mist that is by-produced when ink is ejected from the recording head 30 onto the recording medium R and a portion of the hot air blown from the hot air blowing unit 50. The shape of the duct 70 is not particularly limited, and may be circular, elliptical, square, or rectangular in cross section. As shown in FIG. 1, the duct 70 according to this embodiment is configured to have the same width and height as the hot air blowing unit 50, but this is not limited thereto and can be modified as appropriate.

[0031] The duct 70 is configured to be located relatively downstream of the recording head 30 in the transport direction C of the recording medium R. This configuration prevents the ink mist from adhering to other components of the inkjet recording apparatus 100 or to unintended locations on the recording medium R, causing problems such as stains. Furthermore, the inkjet recording apparatus 100 according to this embodiment is configured such that the warm air blowing unit 50 is located relatively downstream of the duct 70 in the transport direction C of the recording medium R. This configuration prevents the water-based ink in the recording head 30 from drying out due to the warm air blown from the warm air blowing unit 50. As a result, clogging of the nozzles of the recording head 30 can be prevented, and a decrease in the continuous ink ejection performance can be suppressed. Therefore, the inkjet recording apparatus 100 according to this embodiment can achieve both suppression of color unevenness in the recorded product and continuous ink ejection performance.

[0032] The inkjet recording apparatus 100 according to this embodiment can be modified as appropriate depending on the size of the apparatus 100, but the distance between the recording head 30 and the duct 70 located relatively downstream in the conveying direction C of the recording medium R is not particularly limited, and can be set to 10 cm or less, 8 cm or less, or 5 cm or less. Such a configuration makes it easier to collect the ink mist, and can more effectively prevent problems such as the ink mist adhering to other components of the inkjet recording apparatus 100 or to unintended locations on the recording medium R, causing stains, etc.

[0033] Furthermore, the inkjet recording apparatus 100 according to this embodiment can be modified as appropriate depending on the size of the apparatus 100, and the distance between the recording head 30 and the hot air blowing unit 50, which is located relatively downstream of the duct 70 in the transport direction C of the recording medium R, is not particularly limited, but can be set to 25 cm or less, and can be set to 20 cm or less. This configuration makes it easier to collect the hot air blown from the hot air blowing unit 50 and prevents the water-based ink in the recording head 30 from drying out due to the hot air blown from the hot air blowing unit 50. As a result, clogging of the nozzles of the recording head 30 can be prevented and a decrease in the continuous ejection of ink can be suppressed.

[0034] While the preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the scope described in the above embodiments. Various modifications and improvements can be made to the above embodiments. For example, in the above-described embodiment, a sheet is used as the recording medium R, but a long sheet or a rolled sheet can also be used. Furthermore, for example, the inkjet recording device 100 according to the above-described embodiment is configured to include one recording head 30, one duct 70, and one hot air blowing unit 50, but the inkjet recording device 100 may include two or more recording heads 30, two or more ducts 70, and one or more hot air blowing units 50, as long as the duct 70 is positioned relatively downstream of the recording head 30 in the transport direction C of the recording medium R, and the hot air blowing unit 50 is positioned relatively downstream of the duct 70 in the transport direction C of the recording medium R. Furthermore, for example, the transport mechanism 10 may be configured to reciprocate on a base B. In FIG. 1 , the transport mechanism 10 moves on the base in the transport direction C, and the recording medium R passes under the recording head 30, the duct 70, and the hot air blowing unit 50. After the hot air blowing unit 50 has finished blowing hot air, the transport mechanism 10 moves in the opposite direction to the transport direction C and returns to its original position. Then, the transport mechanism 10 moves again on the base in the transport direction C, and the recording medium R passes under the recording head 30, the duct 70, and the hot air blowing unit 50. With this configuration, further recording can be performed on the recording medium R, or recording can be performed on an unrecorded recording medium R.

[0035] Next, the inkjet printing method of the present invention will be described. Components that are the same as or similar to those in the above-described embodiment will be given the same reference numerals, and descriptions thereof may be omitted.

[0036] [Inkjet recording method] The inkjet recording method of the present invention is an inkjet recording method for recording on a low-liquid-absorbent recording medium R using an inkjet recording device 100 equipped with a recording head 30 that ejects water-based ink, and the inkjet recording device 100 is equipped with a transport mechanism 10 that transports the recording medium R, a hot air blowing unit 50 that blows hot air onto the recording medium R, and a duct 70 for recovering a portion of the ink mist and hot air, the duct 70 being located relatively downstream of the recording head 30 in the transport direction C of the recording medium R, and the hot air blowing unit 50 being located relatively downstream of the duct 70 in the transport direction C of the recording medium R.

[0037] As described above, in the inkjet recording method of the present invention, by positioning the duct 70 relatively downstream of the recording head 30 in the transport direction C of the recording medium R, it is possible to prevent problems such as ink mist adhering to components other than the recording medium R in the inkjet recording apparatus 100 and causing stains. Furthermore, by positioning the hot air blowing unit 50 relatively downstream of the duct 70 in the transport direction C of the recording medium R, the duct 70 prevents the water-based ink in the recording head 30 from drying due to the hot air blown from the hot air blowing unit 50. As a result, it is possible to prevent clogging of the nozzles of the recording head 30 and suppress a decrease in the continuous ink ejection performance. Therefore, the inkjet recording method of the present invention can achieve both suppression of color unevenness in the recorded product and continuous ink ejection performance. [Example]

[0038] In the following examples, comparative examples and production examples, "parts" and "%" are "parts by mass" and "% by mass" unless otherwise specified. The methods for measuring each physical property are as follows.

[0039] (1) Water absorption amount of recording medium when the recording medium is in contact with pure water for 100 ms Using an automatic scanning absorbency meter (KM500win, manufactured by Kumagai Riki Kogyo Co., Ltd.), the amount of transferred water was measured at 23°C and a relative humidity of 50% for a contact time of 100 ms with pure water, and the amount of water absorbed in 100 ms was determined. The measurement conditions are as follows: <Measurement conditions> "Spiral Method" Contact Time (sec): 0.010 to 1.0 Pitch(mm):7 Length Per Sampling(degree):86.29 Start Radius(mm):20 End Radius(mm):60 Min Contact Time(ms):10 Max Contact Time(ms):1000 Sampling Pattern(1-50):50 Number of Sampling Points(>0):19 "Square Head" Slit Span(mm):1 Slit Width(mm):5

[0040] (2) Measurement of weight-average molecular weight of water-insoluble polymers The measurement was performed using a gel permeation chromatography method (GPC system manufactured by Tosoh Corporation (HLC-8120GPC), columns manufactured by Tosoh Corporation (TSK-GEL, α-M × 2), flow rate: 1 mL / min) with an eluent of N,N-dimethylformamide dissolved in phosphoric acid and lithium bromide to concentrations of 60 mmol / L and 50 mmol / L, respectively, and monodisperse polystyrene of known molecular weight as a standard substance.

[0041] (3) Measurement of solids concentration of pigment water dispersion 10.0 g of sodium sulfate, brought to a constant weight in a desiccator, was weighed into a 30 mL polypropylene container (φ=40 mm, height=30 mm), and approximately 1.0 g of the sample was added and mixed. The mixture was then accurately weighed and maintained at 105°C for 2 hours to remove volatiles. The mixture was then left in the desiccator for a further 15 minutes, after which the mass was measured. The mass of the sample after devolatilization was taken as the solid content and divided by the mass of the added sample to obtain the solid content concentration.

[0042] (4) Measurement of the average particle size of pigment-containing polymer particles Measurements were performed by cumulant analysis using a laser particle analysis system "ELS-8000" (manufactured by Otsuka Electronics Co., Ltd.). The measurement conditions were a temperature of 25°C, an angle of 90° between the incident light and the detector, and 100 accumulations. The refractive index of water (1.333) was input as the refractive index of the dispersion solvent. The measured concentration was 5 x 10 -3 The results were calculated in mass % (solid concentration).

[0043] (5) Measurement of viscosity of water-based ink The viscosity was measured at 32°C using an E-type viscometer "TV-25" (manufactured by Toki Sangyo Co., Ltd., using a standard cone rotor 1°34' x R24, rotation speed 50 rpm).

[0044] (6) Static surface tension of water-based ink Using a surface tensiometer (manufactured by Kyowa Interface Science Co., Ltd., product name: CBVP-Z), a platinum plate was immersed in a cylindrical polyethylene container (diameter 3.6 cm x depth 1.2 cm) containing 5 g of water-based ink, and the static surface tension of the water-based ink was measured at 20°C.

[0045] (7) Measurement of pH of water-based ink The pH of the water-based ink at 25°C was measured using a tabletop pH meter "F-71" (manufactured by Horiba, Ltd.) equipped with a pH electrode "6337-10D" (manufactured by Horiba, Ltd.).

[0046] <Production of water-based ink> Production Example 1 (Synthesis of water-insoluble polymer) 16 parts of methacrylic acid (reagent manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 44 parts of styrene (reagent manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 30 parts of styrene macromonomer "AS-6S" (manufactured by Toagosei Co., Ltd., number average molecular weight 6,000, solids content 50%), and 25 parts of methoxypolyethylene glycol methacrylate "BLEMMER PME-200" (manufactured by NOF Corporation) were mixed to prepare 115 parts of a monomer mixture. In a reaction vessel, 18 parts of methyl ethyl ketone, 0.03 parts of 2-mercaptoethanol as a chain transfer agent, and 10% (11.5 parts) of the monomer mixture were placed and mixed, and the atmosphere was thoroughly purged with nitrogen gas. Separately, the remaining 90% (103.5 parts) of the monomer mixture was mixed with 0.27 parts of the chain transfer agent, 42 parts of methyl ethyl ketone, and 3 parts of the polymerization initiator 2,2'-azobis(2,4-dimethylvaleronitrile) "V-65" (Fujifilm Wako Pure Chemical Industries, Ltd., reagent), and placed in a dropping funnel. The mixture in the reaction vessel was heated to 75°C under a nitrogen atmosphere while stirring, and the mixture in the dropping funnel was added dropwise over 3 hours. After 2 hours at 75°C from the end of the dropping, a solution of 3 parts of the polymerization initiator in 5 parts of methyl ethyl ketone was added, and the mixture was further aged at 75°C for 2 hours and then at 80°C for 2 hours. 50 parts of methyl ethyl ketone was then added to obtain a solution of a water-insoluble polymer (weight average molecular weight: 50,000). The solids concentration of the water-insoluble polymer solution was 45% by mass.

[0047] Production Example 2 (Production of aqueous dispersion of black pigment-containing polymer particles) 95.2 parts of the water-insoluble polymer solution obtained in Production Example 1 was diluted with 53.9 parts of methyl ethyl ketone, and 15.0 parts of 5N aqueous sodium hydroxide and 0.5 parts of 25% aqueous ammonia were added as neutralizing agents, along with 341.3 parts of deionized water. 100 parts of CI Pigment Black 7 (PB7, manufactured by Cabot Corporation) were then added as a carbon black pigment to obtain a pigment mixture. The degree of neutralization was 78.8 mol%. The resulting pigment mixture was mixed using a disperser blade at 7000 rpm and 20°C for 1 hour. The resulting dispersion was dispersed 15 times using a Microfluidizer "High-Pressure Homogenizer M-140K" (manufactured by Microfluidics) at a pressure of 180 MPa. The resulting pigment-containing polymer particle dispersion was subjected to vacuum decompression at 60°C to remove methyl ethyl ketone, and then a portion of the water was removed. The resulting dispersion was centrifuged. The liquid layer was filtered through a Minisart syringe filter (manufactured by Sartorius, pore size: 5 μm, material: cellulose acetate) to remove coarse particles, yielding an aqueous dispersion of pigment-containing polymer particles. The solids concentration was 25% by mass. To 100 parts of the resulting aqueous dispersion of pigment-containing polymer particles, 0.45 parts of trimethylolpropane polyglycidyl ether (manufactured by Nagase ChemteX Corporation, Denacol EX321L) and 15.23 parts of deionized water were added, and the mixture was heated at 70°C for 3 hours with stirring to perform a crosslinking treatment. After cooling to room temperature, the liquid layer was filtered through a Minisart syringe filter (manufactured by Sartorius, pore size: 5 μm, material: cellulose acetate) to remove coarse particles, yielding an aqueous dispersion of black pigment-containing polymer particles (solids concentration: 22.0% by mass). The average particle size of the black pigment-containing polymer particles was 100 nm. Table 1 shows the measurement results for the water dispersion of the black pigment-containing polymer particles.

[0048] [Table 1]

[0049] Manufacturing Example 3 (Manufacturing Black Ink) A mixture of 46.3 parts (pigment content: 7.0% by weight) of the aqueous dispersion of black pigment-containing polymer particles obtained in Production Example 2 (solid content: 22.0% by weight), 24.0 parts of propylene glycol, 3.0 parts of diethylene glycol monoisobutyl ether, 0.3 parts of a silicone surfactant (Shin-Etsu Chemical Co., Ltd., product name: SAG-005), and 0.3 parts of an acetylene surfactant (Nissin Chemical Industry Co., Ltd., Surfynol 104PG50, active ingredient: 50% by weight) was added, and deionized water was added to bring the total ink volume to 100 parts to obtain a mixed solution. The resulting mixed solution was filtered through a MiniSart syringe filter (acetylcellulose membrane filter: 5 μm opening diameter, Sartorius), to obtain Black Ink 1 as an aqueous ink. The measurement results for Black Ink 1 are shown in Table 2.

[0050] [Table 2]

[0051] Example 1 The recording medium was a corona-treated PET (manufactured by Futamura Chemical Co., Ltd., Taiko FE2001, polyester film, thickness 12 μm, water absorption of the recording medium when the recording medium was in contact with pure water for 100 ms) was 0 g / m 2 ) and the black ink 1 obtained above were used to carry out the various evaluations using a print evaluation device with the following settings.

[0052] <Print evaluation device settings> The print evaluation device used in this example was the same as the inkjet recording device 100 shown in FIG. In an environment with a temperature of 25±1°C and a relative humidity of 30±5%, black ink 1 was loaded into a single-pass printing evaluation device (manufactured by Kao Corporation) equipped with an inkjet head (Kyocera Corporation, "KJ4B1200," piezo-electric type, indicated as "PH" in Table 3), a conveyor table, an underheater (Kawai Electric Manufacturing Co., Ltd.), a duct, and a hot air blower unit. The underheater temperature, the hot air speed from the hot air blower unit, the distance between the inkjet head and the duct, and the distance between the inkjet head and the hot air blower unit were set to the values ​​shown in Table 3. The temperature of the hot air blower unit was set so that hot air of 55°C was blown onto the top surface of the recording medium, and the surface temperature of the recording medium reached 50°C when the underheater temperature was set to 40°C. The recording medium was conveyed at a speed of 30 m / min.

[0053] The printing evaluation device conditions were set using a printing software program to change the piezoelectric element drive voltage waveform of the head, setting the droplet volume to 3 pL and the resolution to 1200 dpi. An A4-sized underheater (manufactured by Kawai Electric Works, Ltd.) was attached above the transport mechanism to heat the recording medium (corona-treated PET). The recording medium was then fixed on the underheater with glue so that its longitudinal direction was aligned with the transport direction. A print command was transferred to the printing evaluation device, and black ink 1 was ejected onto the recording medium. A 10 cm x 10 cm solid image was printed at 100% ink duty, resulting in a recorded product.

[0054] Examples 2 to 8 The distance between the inkjet head and the hot air blowing unit, the speed of the hot air from the hot air blowing unit, and the temperature of the under-heater were changed as shown in Table 3, and black ink 1 was ejected onto the recording medium in the same manner as in Example 1 to obtain a recorded product on which a solid image was printed.

[0055] Comparative Examples 1 to 3 The positional relationship between the hot air blowing unit and the duct, and the presence or absence of the duct and hot air blowing unit were changed as shown in Table 3, and black ink 1 was ejected onto the recording medium in the same manner as in Example 1 to obtain a recorded material with a solid image printed thereon.

[0056] <Evaluation of color unevenness> The resulting printed matter was placed on coated paper (OK Topcoat+ (Oji Paper Co., Ltd.)), and an image of the printed surface was captured using a portable magnifying camera "PIAS-II" (QEA). The solid coverage ratio was then calculated using the image analysis software "Image-J" using the following formula. The higher the calculated value, the more even the color is and the better the result. Solid fill ratio (%) = (number of pixels hidden by backing paper / total number of pixels) x 100 5: The solid fill ratio is 95% or more. 4: The solid fill ratio is 90% or more but less than 95%. 3: The solid fill ratio is between 85% and 90%. 2: The solid fill ratio is between 75% and 85%. 1: The solid fill ratio is less than 75%.

[0057] <Evaluation of continuous ejection> A 10cm x 10cm solid image was continuously printed on 500 sheets of recording medium using 100% ink duty to obtain a recorded image. A print check pattern was then printed to determine whether ejection had occurred from all 2656 nozzles, and the number of missing nozzles was counted to evaluate the continuous ejection performance according to the following evaluation criteria. The hot air blower unit and duct were not stopped during the continuous printing. 5: No missing nozzles 4: Nozzle chipping 1-2 3: Nozzle chipping 3-10 2: Missing nozzles 11-14 1: 15 or more nozzle chips

[0058] The above evaluation results of the recorded materials of the Examples and Comparative Examples are shown in Table 3.

[0059] [Table 3]

[0060] As shown in Table 3, the inkjet recording method of the present invention can achieve both suppression of color unevenness in the recorded material and continuous ink ejection properties. [Explanation of symbols]

[0061] 100: Inkjet recording device, 10: conveying mechanism, 30: recording head, 50: warm air blower unit, 51: warm air blower outlet, 70: Duct, B: Base, C: Transport direction, R: Recording medium

Claims

1. 1. An inkjet recording method for recording on a low-liquid-absorbent recording medium using an inkjet recording apparatus equipped with a recording head that ejects a water-based ink, comprising: The inkjet recording apparatus includes: a conveying mechanism for conveying the recording medium; a warm air blowing unit that blows warm air onto the recording medium; a duct for recovering the ink mist and a portion of the hot air; Equipped with the duct is located relatively downstream of the recording head in a conveying direction of the recording medium, The inkjet recording method, wherein the hot air blowing unit is positioned relatively downstream of the duct in a transport direction of the recording medium.

2. 2. The ink jet recording method according to claim 1, wherein the duct prevents the water-based ink in the recording head from drying out due to the hot air from the hot air blowing unit.

3. 3. The inkjet recording method according to claim 1, wherein the temperature of the hot air at the outlet of the hot air blowing port of the hot air blowing unit is 30[deg.] C. or higher.

4. 3. The inkjet recording method according to claim 1, wherein the hot air has a wind speed of 3 m / min or more and 80 m / min or less.

5. The inkjet recording method according to claim 1 or 2, wherein recording is performed on the recording medium having a surface temperature of 35°C or higher and 80°C or lower.

6. 3. The inkjet recording method according to claim 1, wherein the recording speed of the recording medium is 5 m / min or more and 100 m / min or less in terms of a conveying speed of the recording medium.

7. 3. The inkjet recording method according to claim 1, wherein a distance between the recording head and the duct located relatively downstream in the transport direction of the recording medium is 10 cm or less, and a distance between the recording head and the hot air blowing unit located relatively downstream of the duct in the transport direction of the recording medium is 25 cm or less.

8. 3. The inkjet recording method according to claim 1, wherein the water-based ink is at least one of a cyan ink, a magenta ink, a yellow ink, and a black ink.

9. An inkjet recording apparatus for recording on a low-liquid-absorbent recording medium, a conveying mechanism for conveying the recording medium; a recording head that ejects a water-based ink onto the recording medium; a warm air blowing unit that blows warm air onto the recording medium; a duct for recovering the ink mist and a portion of the hot air; Equipped with the duct is located relatively downstream of the recording head in a conveying direction of the recording medium, The hot air blowing unit is located relatively downstream of the duct in a transport direction of the recording medium.

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