Recording method and recording device

Abstract

To provide a recording method that can provide a recording material in which density unevenness is suppressed and which is excellent in the color development property and scratch resistance, and that can improve the printing speed.SOLUTION: A recording method comprises: a white ink adhesion step of discharging a white ink composition containing a white color material from a white ink jet head to make the white ink composition adhere to a recording medium; a non-white ink adhesion step of discharging a non-white ink composition containing a non-white color material from a non-white ink jet head to make the non-white ink composition adhere to the recording medium; and a primary drying step of heating, by a drying mechanism, the white ink composition and the non-white ink composition adhering to the recording medium. In the white ink adhesion step and the non-white ink adhesion step, plural times of main scans that discharge the ink composition to make the ink composition adhere to the recording medium are performed while the relative position of the ink jet head to the recording medium is being shifted, in addition, the white ink composition and the non-white ink composition are made to adhere to the same scan region of the recording medium by the same main scan to form a layer containing the white ink composition and the non-white ink composition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Inkjet recording methods are capable of recording high-resolution images using relatively simple equipment and have been rapidly developing in various fields. In the process, various studies have been conducted on ejection stability, etc. For example, Patent Document 1 discloses an ink composition containing at least one colorant selected from metal compounds and hollow resin particles, and a sulfonic acid group-containing polymer, with the aim of improving hiding power and abrasion resistance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-83684 Summary of the Invention [Problem to be solved by the invention]

[0004] By recording a base layer using the ink composition described in Patent Document 1 and then recording a color image layer, a recorded product with good color image visibility can be obtained, but on the other hand, this method of laminating a base layer and a color image layer has problems in that the recording speed is slower due to the amount of lamination required and a large head is required. Furthermore, even if a method is intended to eliminate the need for a large head or to achieve excellent recording speed, there is a problem in that excellent image quality cannot be obtained. [Means for solving the problem]

[0005] The present invention is a recording method comprising: a white ink applying step of ejecting a white ink composition containing a white coloring material from a white inkjet head and adhering it to a recording medium; a non-white ink applying step of ejecting a non-white ink composition containing a non-white coloring material from a non-white inkjet head and adhering it to a recording medium; and a primary drying step of heating the white ink composition and the white ink composition adhered to the recording medium by a drying mechanism, wherein in the white ink applying step and the non-white ink applying step, main scanning is performed multiple times to eject the ink composition and adhere it to the recording medium while moving the position of the inkjet head relative to the recording medium, and the white ink composition and the non-white ink composition are adhered to the same scanned region of the recording medium by the same main scanning, thereby forming a layer containing the white ink composition and the non-white ink composition.

[0006] The present invention provides a recording device that performs recording by the above-mentioned recording method, the recording device comprising: a white inkjet head that ejects a white ink composition containing a white coloring material and deposits it onto a recording medium; a non-white inkjet head that ejects a non-white ink composition containing a non-white coloring material and deposits it onto a recording medium; a drying mechanism that dries the white ink composition and non-white ink composition deposited on the recording medium; and a control unit that controls the execution of recording using the white inkjet head and the non-white inkjet head. [Brief explanation of the drawings]

[0007] [Figure 1] 1 shows an example of a recording device used in this embodiment. [Figure 2] 1 shows an example of the configuration of an inkjet head. [Figure 3] 1 shows an example of the configuration of an inkjet head. [Figure 4] 1 shows an example of a recording device used in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is not limited to this, and various modifications are possible without departing from the spirit of the present invention. In the drawings, the same elements are given the same reference numerals, and redundant explanations will be omitted. Furthermore, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

[0009] In this embodiment, when there is no particular distinction between a white inkjet head and a non-white inkjet head, they are simply referred to as "inkjet heads." Similarly, when there is no particular distinction between a white ink composition and a non-white ink composition, they are simply referred to as "ink compositions."

[0010] Furthermore, "main scanning" refers to the operation of ejecting an ink composition from the inkjet head and depositing it on a recording medium while moving the inkjet head relative to the recording medium. The inkjet head can be mounted on a carriage, for example. The inkjet head may be moved by moving the carriage, and in this case, too, it is referred to as movement of the inkjet head.

[0011] Furthermore, the "main scanning direction" refers to the direction of movement of the inkjet head, which is the width direction of the recording medium. Note that "main scanning" refers to movement of the inkjet head relative to the recording medium, and the inkjet head may move relative to the recording medium, or the recording medium may move relative to the inkjet head. The direction of such relative positional movement is the main scanning direction. The movement of the inkjet head relative to the recording medium can also be referred to as the movement of the recording medium relative to the inkjet head. In other words, it is relative movement between the inkjet head and the recording medium.

[0012] On the other hand, "sub-scanning" refers to the operation of moving the relative positions of the inkjet head and the recording medium in the sub-scanning direction, which is a direction that intersects with the main scanning direction. For example, recording can be performed by repeating the process of depositing an ink composition to a certain area of a recording medium in a main scan, moving the recording medium a small distance in a sub-scan, and then performing a next main scan to deposit an ink composition adjacent to or partially overlapping the previously deposited ink composition. Note that "sub-scanning" also refers to movement of the inkjet head relative to the recording medium, and the inkjet head may move relative to the recording medium, or the recording medium may move relative to the inkjet head. The direction of such relative movement is the sub-scanning direction.

[0013] Printing can be performed by performing main scanning and sub-scanning multiple times, for example, by alternately repeating main scanning and sub-scanning.

[0014] 1. Recording method The recording method of this embodiment comprises a white ink applying step of ejecting a white ink composition containing a white coloring material from a white inkjet head and adhering it to a recording medium; a non-white ink applying step of ejecting a non-white ink composition containing a non-white coloring material from a non-white inkjet head and adhering it to a recording medium; and a primary drying step of heating the white ink composition and non-white ink composition adhered to the recording medium by a drying mechanism. In the white ink applying step and the non-white ink applying step, main scanning is performed multiple times while the inkjet head is moved relative to the recording medium, and the white ink composition and the non-white ink composition are adhered to the same scanned area of the recording medium by the same main scanning, thereby forming a layer containing the white ink composition and the non-white ink composition.

[0015] Conventionally, a high-quality image has been recorded by forming a white ink layer and a non-white ink layer in layers, and using the white ink layer as a hiding layer.

[0016] In contrast, in this embodiment, the white ink composition and the non-white ink composition are deposited on the same scanning area of the recording medium by the same relative scanning, which makes it possible to form a single ink layer containing the white ink composition and the non-white ink composition on the recording medium, and it has been found that this makes it possible to form an image with excellent color development without unevenness in density, even without forming a white ink layer and a non-white ink layer by overlapping them as in the conventional method.

[0017] On the other hand, when the deposition of a white ink composition and a non-white ink composition is performed on the same scanning area of a recording medium by the same relative scanning, the amount of ink simultaneously deposited on the same area increases, causing problems such as the droplets of these ink compositions mixing on the recording medium, which is likely to cause unevenness in density and a decrease in color development. This problem is particularly likely to occur with low-absorbency recording media and non-absorbency recording media, as the ink compositions remain on the recording medium.

[0018] In contrast, in the printing method of this embodiment, a primary drying process is performed to quickly dry the ink droplets that have adhered to the printing medium, thereby quickly suppressing the flow of the ink droplets and preventing the deterioration of image quality as described above.

[0019] Furthermore, in this embodiment, there is no need to form a white ink layer and a non-white ink layer in layers, which makes it possible to further improve the printing speed.

[0020] Furthermore, a head configuration can be used in which nozzles for ejecting the white ink composition and nozzles for ejecting the non-white ink compositions are arranged side by side so that the deposition of the white ink composition and the deposition of the non-white ink compositions are performed to the same scanning area of the recording medium by the same relative scanning. Therefore, it is possible to reduce the overall size of the inkjet head compared to a head configuration based on conventional lamination.

[0021] 1.1. White ink application process and non-white ink application process The white ink applying step is a step of ejecting a white ink composition containing a white coloring material from a white inkjet head and applying it to a recording medium, and the non-white ink applying step is a step of applying a non-white ink composition containing a non-white coloring material from a non-white inkjet head to a recording medium. Note that the white ink composition and the non-white ink composition may be ejected from the same inkjet head. In other words, the white inkjet head and the non-white inkjet head may be separate or integrated.

[0022] In the recording method of this embodiment, the deposition of the white ink composition and the deposition of the non-white ink composition are performed by relative scanning of the recording head and the recording medium, and the deposition of the white ink composition and the deposition of the non-white ink composition are performed by the same relative scanning to the same scanning area of the recording medium.

[0023] Here, the same relative scan means, for example, in the case of a serial inkjet printing device, a single scan in which the print head moves relatively in a main scanning direction that intersects with the transport direction of the print medium. The scan may be a relative scan, and may be a scan in which the print head moves relative to the print medium, or a scan in which the print medium moves relative to the print head. The scan is performed while ink is ejected from the print head to the print medium.

[0024] For example, in a serial inkjet recording device, when the recording head makes multiple scans back and forth over the same area of the recording medium in the main scanning direction, one of the forward or backward scans is counted as one scan. Therefore, when the white ink application process and the non-white ink application process are performed in the same relative scan, this means that both processes are performed during one scan of the recording head.

[0025] Furthermore, depositing each ink composition on the same scanning region of the recording medium means depositing the white ink composition and the non-white ink composition in the region that passes through during the scanning, thereby forming a single ink layer containing the white ink composition and the non-white ink composition on the recording medium.

[0026] A white ink recording head and a non-white ink recording head perform scanning simultaneously. During this scanning (the same scanning), the white ink composition and the non-white ink composition are deposited in the same scanning area. The scanning area during a scanning is the area of the recording medium scanned by the recording head during that scanning. In the case of a serial inkjet recording device, this is the part of the recording medium over which the recording head moves relative to the recording medium during that scanning.

[0027] The deposition of white ink and non-white ink in the same scanning area of the recording medium by the same relative scan means that the scanning area by the white ink print head and the scanning area by the white ink print head have the same area (overlapping area) in the same scan. It is sufficient that they have at least a part of the same area.

[0028] In this way, a layer containing the white ink composition and the non-white ink composition can be formed by the same main scanning. By forming the ink layer by the same main scanning, the white ink composition and the non-white ink composition can be uniformly mixed.

[0029] In the recording method of this embodiment, it is preferable to perform main scanning multiple times on the same region of the recording medium. That is, it is preferable to deposit a layer containing a white ink composition and a non-white ink composition on a certain region on the recording medium by one main scanning, and then deposit a layer containing a white ink composition and a non-white ink composition on top of that by another main scanning. In this case, the main scanning to deposit the white ink composition and the non-white ink composition will pass multiple times over the same scanned region. The more scanning times there are, the more ink can be deposited in multiple separate passes (multiple passes) on the desired region, and the image quality of the resulting recorded matter tends to be improved.

[0030] When recording an arbitrary area, the number of times the inkjet head passes over that area is also called a “pass.” For example, if the main scan is performed four times over the same scanning area to deposit the white ink composition and the non-white ink composition, the number of passes is called four passes. 2, if the length of one sub-scan in the sub-scan direction is one-fourth the length of nozzle row N1 in the sub-scan direction, then four scans will be performed on a rectangular scan area that is the length of one sub-scan in the sub-scan direction and extends in the main scanning direction. The number of scans viewed in this way is called the number of scans or the number of passes. The number of scans is 1 or more, preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, and particularly preferably 8 or more. There is no upper limit, but it is preferably 24 or less, and more preferably 12 or less. The greater the number of scans, the more times ink can be applied to the rectangular area, which is preferable as it results in excellent image quality.

[0031] Although a smaller number of passes means that more dots are printed per pass, which can lead to the problem of uneven shading, the printing speed also tends to be faster, making the present invention, which can suppress uneven shading, particularly useful.

[0032] Of the areas of the recording medium where the white ink composition and the non-white ink composition are adhered, in the area where the amount of adhered non-white ink composition is the greatest, the ratio of the amount of adhered white ink composition to 100% by mass of the amount of adhered non-white ink composition is defined as ratio A. The ratio of the amounts of adhered white ink composition / amount of adhered non-white ink composition is expressed as a percentage, and is 100% by mass if the amounts of adhered white ink composition and non-white ink composition are equal.

[0033] The ratio A is preferably 80% by mass or less, more preferably 5 to 75% by mass, even more preferably 10 to 70% by mass, and even more preferably 35 to 65% by mass. When the ratio A is 80% by mass or less, color development tends to be further improved and unevenness in shade tends to be further reduced. Furthermore, when the ratio A is 10% by mass or more, visibility tends to be further improved. Note that the unit region when specifying the amount of adhesion is a region having a predetermined area, and can be, for example, a region of 2 × 2 mm.

[0034] Furthermore, when the amount of non-white ink composition adhered in the area where the amount of non-white ink composition adhered is the greatest among the areas where the white ink composition and the non-white ink composition are adhered is defined as the maximum non-white ink adhesion amount B, it is preferable that the ratio of the adhesion amounts be in the above range across the area where the white ink composition and the non-white ink composition are adhered, from the area where the amount of non-white ink composition adhered is the maximum non-white ink adhesion amount B to the area where the amount of non-white ink composition adhered is 40 mass % of the maximum non-white ink adhesion amount B.

[0035] Of the regions where the white ink composition and non-white ink composition are adhered, regions where the amount of adhered non-white ink composition is less than 40% by mass of the maximum non-white ink adhesion amount B are regions where the color of the non-white ink composition image is relatively light and where the difference in image quality is not particularly noticeable. However, in these regions, the ratio of the adhered amounts may be within the above range, exceeding the above range, or less than the above range. When priority is given to image quality (OD value), the ratio may be within the above range or less than the above range. When priority is given to image quality (visibility), the ratio may be within the above range or more than the above range.

[0036] In the area of the recording medium where the white ink composition and the non-white ink composition are deposited, the maximum amount of the white ink composition deposited is preferably 10 mg / inch. 2 More preferably, it is 7.5 mg / inch or less. 2 More preferably, it is 6.0 mg / inch or less. 2 The following is the result.

[0037] The lower limit of the maximum deposition amount of the white ink composition is preferably 0.50 mg / inch 2 More preferably, it is 1.0 mg / inch or more. 2 More preferably, it is 3.0 mg / inch or more. 2 More preferably, it is 5.0 mg / inch or more. 2 That's all. There are no particular restrictions on the maximum amount of non-white ink composition that can be applied, and it may be determined according to the image to be recorded, but it is preferable that the ratio A is within the above-mentioned preferred range. This prevents the resulting image from becoming too whitish, and tends to further improve visibility and color development.

[0038] 1.2. Ink composition The white ink composition used in this embodiment contains a white colorant, and the non-white ink composition contains a non-white colorant. The white ink composition and the non-white ink composition may each be an aqueous ink composition containing water as the main solvent, or a solvent-based ink composition containing an organic solvent as the main solvent. Below, the components of the ink composition will be illustrated using an aqueous ink composition as an example, but the components constituting the ink composition of this embodiment are not limited to the following.

[0039] The white ink composition and non-white ink composition used in this embodiment may be solvent-based inks or water-based inks, but are preferably water-based inks. Water-based inks have a relatively low organic solvent content compared to solvent-based inks, making them highly environmentally friendly. On the other hand, water-based inks tend to be easily mixed with white and non-white inks, which can lead to reduced color development and uneven shading, and in particular, can result in images that tend to be whitish. For this reason, the present invention is particularly useful. Note that when referring to an "water-based" ink, the term "water-based" refers to inks that contain at least water as the main solvent component. The water content in the ink is 40% by mass or more, preferably 50% by mass or more, and more preferably 60 to 98% by mass.

[0040] The non-aqueous ink contains an organic solvent as a main solvent component. The content of the organic solvent in the non-aqueous ink is preferably 40% by mass or more, more preferably 50 to 98% by mass. The content of water in the non-aqueous ink is preferably 1% by mass or less, more preferably 0.5% by mass or less. The components of the non-aqueous ink other than the solvent component may be the same as the components that may be contained in the aqueous ink described below.

[0041] In the case of aqueous ink compositions, the white ink composition and non-white ink composition may contain, in addition to the above-mentioned coloring materials, water, an organic solvent, a surfactant, resin particles, wax, etc. Below, each component of the ink composition will be described in detail using an aqueous ink as an example.

[0042] 1.2.1.White color material The white colorant is not particularly limited, and examples thereof include white inorganic pigments such as CI Pigment White 6, 18, and 21, silica, alumina, titanium dioxide, zinc oxide, antimony oxide, magnesium oxide, zirconium oxide, zinc sulfide, barium sulfate, and calcium carbonate. In addition to these white inorganic pigments, white organic pigments such as white hollow resin particles and polymer particles can also be used.

[0043] Among the above-listed white coloring materials, it is preferable to use titanium dioxide as the white coloring material from the viewpoint of good whiteness, etc. The white coloring material may be used alone or in combination of two or more kinds.

[0044] The content of the white colorant relative to the total amount of the white ink composition is preferably 5.0% by mass or more, more preferably 8.0% by mass or more, and even more preferably 10% by mass or more. The content of the white colorant relative to the total amount of the white ink composition is preferably 20% by mass or less, more preferably 16% by mass or less, even more preferably 14% by mass or less, and even more preferably 13% by mass or less. When the content of the white coloring material is within the above range, a higher quality image can be obtained.

[0045] It is preferable that the white colorant be stably dispersed in the dispersion medium, and therefore a dispersant may be used for dispersion. Examples of dispersants include resin dispersants, and these are selected from those that can improve the dispersion stability of the white colorant in the white ink composition containing the white colorant. Furthermore, the white colorant may be used as a self-dispersing pigment by modifying the surface of the pigment particles by oxidizing or sulfonating the pigment surface with, for example, ozone, hypochlorous acid, fuming sulfuric acid, or the like.

[0046] 1.2.2. Non-white coloring material The non-white colorant is not particularly limited as long as it is a colorant other than the above-mentioned white colorants, but examples thereof include inorganic pigments such as carbon blacks (CI Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black; and organic pigments such as quinacridone pigments, quinacridonequinone pigments, dioxazine pigments, phthalocyanine pigments, anthrapyrimidine pigments, anthanthrone pigments, indanthrone pigments, flavanthrone pigments, perylene pigments, diketopyrrolopyrrole pigments, perinone pigments, quinophthalone pigments, anthraquinone pigments, thioindigo pigments, benzimidazolone pigments, isoindolinone pigments, azomethine pigments, and azo pigments. The non-white colorants may be used alone or in combination of two or more.

[0047] The content of the non-white colorant relative to the total amount of the non-white ink composition is preferably 0.5 to 10% by mass, more preferably 0.5 to 7.5% by mass, even more preferably 1.0 to 6.0% by mass, and even more preferably 1.5 to 4.0% by mass. When the content of the non-white coloring material is within the above range, color development and visibility are further improved, and higher quality images can be obtained.

[0048] It is preferable that the non-white colorant can be stably dispersed in the dispersion medium, and therefore a dispersant may be used for dispersion. Examples of dispersants include resin dispersants, and dispersants are selected from those that can improve the dispersion stability of the non-white colorant in the non-white ink composition containing the non-white colorant. In addition, the non-white colorant may be used as a self-dispersing pigment by modifying the surface of the pigment particles by oxidizing or sulfonating the pigment surface with, for example, ozone, hypochlorous acid, fuming sulfuric acid, or the like.

[0049] Non-white ink compositions containing non-white coloring materials include, but are not limited to, cyan ink, yellow ink, magenta ink, and black ink.

[0050] 1.2.3.Water The water content is preferably 40 to 98% by mass, more preferably 50 to 85% by mass, even more preferably 55 to 80% by mass, and still more preferably 60 to 75% by mass, relative to the total amount of the ink composition.

[0051] 1.2.4. Organic Solvents The organic solvent is not particularly limited as long as it is a water-soluble organic solvent, and examples thereof include triol or higher polyols such as glycerin; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and propylene glycol monomethyl ether. Examples of the organic solvent include glycol ethers such as glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, triethylene glycol monomethyl ether, and triethylene glycol monobutyl ether; nitrogen-containing solvents such as 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone; and alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, 2-butanol, tert-butanol, isobutanol, n-pentanol, 2-pentanol, 3-pentanol, and tert-pentanol. The organic solvent may be used alone or in combination of two or more.

[0052] Glycols are compounds with two hydroxyl groups in the molecule. Examples of glycols include alkanediols, in which an alkane is substituted with two hydroxyl groups, and condensates in which the hydroxyl groups of two or more molecules of such alkanediol are condensed together. The glycols preferably have 2 to 10 carbon atoms, more preferably 3 to 8 carbon atoms, further preferably 3 to 6 carbon atoms, and particularly preferably 3 to 5 carbon atoms in the molecule.

[0053] Preferred examples of glycols include propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,2-hexanediol, etc. Preferred examples of alkanediols include 1,2-alkanediol and alkanediols terminated at both ends.

[0054] The nitrogen-containing solvent may be an amide solvent, such as acyclic amides or cyclic amides.

[0055] Examples of cyclic amides include lactams, such as pyrrolidones such as 2-pyrrolidone, 1-methyl-2-pyrrolidone, 1-ethyl-2-pyrrolidone, 1-propyl-2-pyrrolidone, and 1-butyl-2-pyrrolidone, N-methyl-ε-caprolactam, N-cyclohexyl-2-pyrrolidone, and β-propiolactam.

[0056] Examples of the acyclic amides include 3-methoxy-N,N-dimethylpropionamide, 3-methoxy-N,N-diethylpropionamide, 3-methoxy-N,N-methylethylpropionamide, 3-ethoxy-N,N-dimethylpropionamide, 3-ethoxy-N,N-diethylpropionamide, 3-ethoxy-N,N-methylethylpropionamide, 3-n-butoxy-N,N-dimethylpropionamide, 3-n-butoxy-N,N-diethylpropionamide, 3-n-butoxy-N,N-methylethylpropionamide, 3-n-propoxy-N,N-dimethylpropionamide, 3-n-propoxy-N,N-diethylpropionamide, 3-n-propoxy-N,N-methylethylpropionamide, 3-iso-propoxy- Examples include alkoxyalkylamides such as N,N-dimethylpropionamide, 3-iso-propoxy-N,N-diethylpropionamide, 3-iso-propoxy-N,N-methylethylpropionamide, 3-tert-butoxy-N,N-dimethylpropionamide, 3-tert-butoxy-N,N-diethylpropionamide, and 3-tert-butoxy-N,N-methylethylpropionamide; N,N-dimethylacetoacetamide, N,N-diethylacetoacetamide, N-methylacetoacetamide, N,N-dimethylisobutyric acid amide, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, and N,N-dimethylpropionamide.

[0057] Triol or higher polyols are compounds having three or more hydroxyl groups in the molecule, and examples thereof include glycerin.

[0058] Glycol ethers are compounds in which one or two of the hydroxyl groups of an alkanediol in which an alkane is substituted with two hydroxyl groups or a condensate in which the hydroxyl groups of two or more molecules of such an alkanediol are intermolecularly condensed together are etherified. The etherification is mono-etherification or di-etherification. The etherification is preferably alkyl-etherification. Glycol ethers are compounds having one or no hydroxyl groups in the molecule. Examples of glycol ethers include those mentioned above.

[0059] Alcohols are compounds in which an alkane is substituted with one hydroxyl group, and have one hydroxyl group per molecule. Examples of alcohols include those listed above.

[0060] By using such an organic solvent, the ejection stability of the ink and the abrasion resistance of the resulting recorded matter tend to be improved, and unevenness in density tends to be reduced.

[0061] The content of the organic solvent relative to the total amount of the ink composition is preferably 40% by mass or less, more preferably 30% by mass or less, more preferably 5.0 to 27.5% by mass, and even more preferably 10 to 25% by mass, still more preferably 15 to 22% by mass, and still more preferably 20 to 33% by mass.

[0062] The content of the glycol organic solvent may be within the above range. The content of the nitrogen-containing solvent is preferably 40% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 2% by mass or less, relative to the total amount of the ink composition. The lower limit is 0% by mass or more.

[0063] When the content of the organic solvent is within the above range, the abrasion resistance of the obtained recorded matter is improved, unevenness in density is reduced, and the recording speed tends to be improved. When the content of the nitrogen-containing solvent is within the above range or less, the image quality and abrasion resistance are more excellent, which is preferable.

[0064] The normal boiling point of the organic solvent is preferably 280° C. or lower, more preferably 150 to 280° C., preferably 160 to 270° C., and preferably 170 to 260° C., still more preferably 180 to 200° C., and even more preferably 190 to less than 200° C. When the normal boiling point of the organic solvent is within the above range, the abrasion resistance is improved and unevenness in shade tends to be reduced.

[0065] Among the organic solvents contained in the white ink composition and the non-white ink composition, the content of organic solvents having a normal boiling point of less than 200°C is, relative to the total amount of organic solvents, 0% by mass or more, preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 55% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. Furthermore, the upper limit of the content of organic solvents having a normal boiling point of less than 200°C is 100% by mass or less, preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 70% by mass or less.

[0066] In particular, it is preferable that the content of organic solvents with a normal boiling point of less than 200°C among the organic solvents contained in the white ink composition be within the above range. When the content of organic solvents with a normal boiling point of less than 200°C is within the above range, abrasion resistance is further improved and unevenness in shading tends to be further reduced.

[0067] Of the organic solvents contained in the white ink composition and non-white ink composition, the content of organic solvents having a normal boiling point of 200°C or higher is 100% by mass or less, preferably 60% by mass or less, more preferably 50% by mass or less, more preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, relative to the total amount of organic solvents. The lower limit of the content of organic solvents having a normal boiling point of less than 200°C is 0% by mass or more, preferably 5% by mass or more, and may even be 10% by mass or more. Keeping the content of organic solvents having a normal boiling point of 200°C or higher within the above range tends to further improve abrasion resistance and reduce unevenness in shading.

[0068] Furthermore, the white ink composition and non-white ink composition preferably contain an organic solvent having a normal boiling point within the above range as the organic solvent which is a glycol.

[0069] Furthermore, the white ink composition and non-white ink composition preferably contain both an organic solvent having a normal boiling point of less than 200° C. and an organic solvent having a normal boiling point of 200° C. or higher. Such a solvent composition tends to further improve abrasion resistance and reduce unevenness in shading. The organic solvent having a normal boiling point of less than 200°C and the organic solvent having a normal boiling point of 200°C or higher are preferably glycols.

[0070] The maximum normal boiling point of the organic solvent contained in the white ink composition or non-white ink composition is preferably 280°C or less, more preferably 250°C or less, more preferably 240°C or less, and even more preferably 230°C or less. The maximum normal boiling point of the organic solvent is preferably 150°C or more, more preferably 160°C or more. It is particularly preferable that the maximum normal boiling point of the organic solvent contained in the white ink composition is within the above range. When the maximum normal boiling point is within the above range, abrasion resistance is further improved and unevenness in shading tends to be further reduced.

[0071] In particular, it is preferable that the white ink composition and the non-white ink composition are each aqueous ink compositions containing no more than 2% by mass of organic solvents that are glycols or polyols of triol or higher having a normal boiling point above 280°C. "No more than 2% by mass" means that the organic solvent may be 0% by mass or may be contained within a range not exceeding the specified percentage by mass. The above range is more preferably no more than 1% by mass, and even more preferably no more than 0.5% by mass. It is also preferable that the content of organic solvents, including but not limited to organic solvents that are glycols or polyols of triol or higher, be within the above range.

[0072] Surfactants The surfactant is not particularly limited, but examples thereof include acetylene glycol surfactants, fluorine-based surfactants, and silicone-based surfactants. Among these, silicone-based surfactants are preferred. This tends to further suppress unevenness in the density of the resulting printed matter.

[0073] The acetylene glycol surfactant is not particularly limited, but is preferably at least one selected from the group consisting of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and alkylene oxide adducts of 2,4-dimethyl-5-decyne-4-ol and alkylene oxide adducts of 2,4-dimethyl-5-decyne-4-ol.

[0074] The fluorine-based surfactant is not particularly limited, but examples thereof include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphates, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl betaines, and perfluoroalkyl amine oxide compounds.

[0075] Examples of silicone surfactants include polysiloxane compounds and polyether-modified organosiloxanes.

[0076] The content of the surfactant is preferably 0.1 to 4.0% by mass, more preferably 0.3 to 3.0% by mass, and even more preferably 0.5 to 2.0% by mass, relative to the total amount of the ink composition, which tends to further suppress unevenness in density in the resulting recorded matter.

[0077] 1.2.6.Resin particles The use of resin particles further improves the abrasion resistance of the resulting image. The resin particles are not particularly limited, but examples thereof include resin particles made of urethane resin, acrylic resin (including styrene-acrylic resin), fluorene resin, polyolefin resin, rosin-modified resin, terpene resin, polyester resin, polyamide resin, epoxy resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, ethylene vinyl acetate resin, etc. The resin particles may be in the form of an emulsion.

[0078] Among these, urethane resins, acrylic resins, and polyolefin resins are preferred. These resin particles are often handled in emulsion form, but may also be in powder form. The resin particles may be used alone or in combination of two or more types.

[0079] Urethane resin is a general term for resins having urethane bonds. In addition to urethane bonds, the urethane resin may be a polyether urethane resin containing ether bonds in the main chain, a polyester urethane resin containing ester bonds in the main chain, or a polycarbonate urethane resin containing carbonate bonds in the main chain.

[0080] Acrylic resin is a general term for polymers obtained by polymerizing at least an acrylic monomer such as (meth)acrylic acid or a (meth)acrylic acid ester as one component. Examples include resins obtained from acrylic monomers and copolymers of acrylic monomers with other monomers. Examples include acrylic-vinyl resins, which are copolymers of acrylic monomers and vinyl monomers. Another example of a vinyl monomer is styrene. Other usable acrylic monomers include acrylamide and acrylonitrile.

[0081] Among these, styrene-acrylic resins are preferred. Examples of styrene-acrylic resins include, but are not limited to, styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene-methacrylic acid-acrylic acid ester copolymers, styrene-α-methylstyrene-acrylic acid copolymers, and styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymers. Use of such resins tends to further improve the image quality and abrasion resistance of the resulting recorded matter.

[0082] The polyolefin resin has an olefin such as ethylene, propylene, or butylene in its structural skeleton, and any known polyolefin resin can be appropriately selected and used.

[0083] The content of the resin particles is preferably 0.5 to 15% by mass, more preferably 1.0 to 10% by mass, and even more preferably 2.5 to 7.5% by mass, relative to the total amount of the ink composition. When the content of the resin particles is within the above range, the abrasion resistance of the resulting recorded matter tends to be further improved.

[0084] Wax The wax is not particularly limited, but examples include plant and animal waxes such as carnauba wax, candelilla wax, beeswax, rice wax, and lanolin; petroleum waxes such as paraffin wax, microcrystalline wax, polyethylene wax, oxidized polyethylene wax, and petrolatum; mineral waxes such as montan wax and ozokerite; synthetic waxes such as carbon wax, Hoechst wax, polyolefin wax, and stearic acid amide; and natural and synthetic wax emulsions and blended waxes such as α-olefin-maleic anhydride copolymers. Waxes may be used alone or in combination of two or more. The wax may also be in the form of an emulsion.

[0085] Among these, it is preferable to use polyolefin wax (particularly polyethylene wax and polypropylene wax) and paraffin wax, as the use of such waxes tends to further improve the abrasion resistance of the resulting recorded matter.

[0086] The wax content is preferably 0.1 to 7.5% by mass, more preferably 0.3 to 5.0% by mass, and even more preferably 0.5 to 2.5% by mass, relative to the total amount of the ink composition. When the wax content is within the above range, the abrasion resistance of the resulting recorded matter tends to be further improved.

[0087] 1.2.8.Other Ingredients The ink composition may further contain components such as preservatives, antifungals, rust inhibitors, chelating agents, viscosity modifiers, antioxidants, and antifungal agents, as required.

[0088] 1.3.Primary drying process The primary drying step is a step in which the white ink composition and the non-white ink composition applied to the recording medium are quickly dried by a drying mechanism. In particular, the primary drying step refers to the early drying of the areas to which the white ink composition and the non-white ink composition are applied in the white ink application step and the non-white ink application step.

[0089] The primary drying step is a step of drying the ink adhered to the recording medium at an early stage. The primary drying step is a step for drying at least a portion of the solvent component of the ink adhered to the recording medium to at least an extent that the ink flow is reduced. In the primary drying step, the ink composition may be applied to a heated recording medium, or drying may be performed at a position of the recording medium facing the inkjet head, or drying may be performed early after application. In the primary drying step, it is preferable that the ink droplets adhered to the recording medium start to dry within 0.5 seconds of the ink droplets being applied.

[0090] The drying mechanism used in the primary drying step is not particularly limited, but examples include a conduction type that uses a platen heater or preheater for heating, a radiation type that uses an IR heater for heating, and a blowing type (air blowing) using a fan or the like. Air blowing promotes evaporation by removing evaporated solvent components from the media, resulting in excellent image quality. The air blowing method is not limited to hot air, and room temperature air can also be used. Room temperature air is also preferred because it does not have a thermal effect on the nozzle.

[0091] The drying mechanism is also referred to as a drying means. The drying means may be one of these, or two or more may be used in combination. In particular, it is preferable to use either a conduction type or a radiation type, and a blowing type, and it is more preferable to use both a conduction type and a blowing type. In this case, heating is performed by either the conduction type or the radiation type, and evaporation can be promoted by the blowing type, resulting in better image quality. In this case, the blowing type may send either warm air or room temperature air, but room temperature air is preferred in terms of better ejection stability.

[0092] The air velocity is preferably 0.5 to 5 m / s, more preferably 0.5 to 4 m / s, and even more preferably 0.5 to 3 m / s. By keeping the air velocity within the above range, the air can remove evaporated solvent components from the media, promoting evaporation, and also tends to reduce the likelihood of deflection of the ink due to the air. The air velocity is the air velocity near the recording medium.

[0093] The temperature of the blown air may be room temperature air or hot air, and is preferably 10 to 50° C., more preferably 15 to 45° C., even more preferably 20 to 40° C., and particularly preferably 25 to 30° C. When the blown air temperature is within the above range, evaporation of the ink can be promoted and ejection stability is also excellent, which is preferable.

[0094] The surface temperature of the recording medium in the primary drying step is preferably 25°C or higher, and preferably 60°C or lower. Furthermore, it is preferably 30 to 50°C, more preferably 35 to 45°C, and even more preferably 40 to 45°C. Alternatively, it is preferably 30 to 40°C, and more preferably 30 to 35°C. The surface temperature of the recording medium in the primary drying step is the maximum temperature during recording.

[0095] By keeping the surface temperature of the recording medium in the primary drying step within the above range, abrasion resistance and visibility are improved, and unevenness in density tends to be suppressed.

[0096] 1.4.Secondary drying process The recording method of this embodiment may include a secondary drying step after the primary drying step, for the purpose of further drying the recorded matter. The secondary drying step refers to drying the recording medium to which the ink composition has been applied sufficiently to enable the recorded matter to be used, and refers to drying performed to complete the recording. The secondary drying may include heating to form a flat film of components such as resin contained in the ink composition. It is preferable that heating is started after all of the ink that should be applied to a certain area of the recording medium has been applied, and more than 0.5 seconds after application is completed.

[0097] The secondary drying step is also called a post-drying step. Heating is preferably used in the secondary drying step. The surface temperature of the recording medium in the secondary drying step is preferably 50 to 120°C, more preferably 50 to 100°C, and even more preferably 60 to 90°C.

[0098] The drying method in the secondary drying method is not particularly limited, but examples thereof include conduction methods such as a platen heater or a preheater, radiation methods such as an IR heater, and air blowing methods such as a blower fan.

[0099] 1.5. Recording Media The recording medium used in this embodiment is not particularly limited, but examples thereof include absorbent recording media such as paper, film, and cloth, low absorbent recording media such as printing paper, and non-absorbent recording media such as metal, glass, and polymers.

[0100] Among these, low-absorbency or non-absorbency recording media are preferred from the viewpoint of ink absorbency. Furthermore, non-white recording media are preferred from the viewpoint of color. Conventionally, such recording media have been used to record high-quality images by forming a white ink layer and a non-white ink layer on top of each other, and using the white ink layer as a concealing layer. Therefore, by using the present invention, the effect of the present invention, that is, to form an image without unevenness in density and excellent color development, can be particularly effectively exhibited.

[0101] In this embodiment, the non-absorbent or low-absorbent recording medium is a recording medium that is "absorbent within 30 msec from the start of contact in the Bristow method." 1 / 2 Water absorption up to 10mL / m 2 This refers to the recording medium described below. The Bristow method is the most widely used method for measuring liquid absorption in a short period of time, and is also adopted by the Japan Pulp and Paper Technical Association (JAPAN TAPPI). Details of the test method are described in Standard No. 51 "Paper and paperboard - Liquid absorbency test method - Bristow method" of the "JAPAN TAPPI Paper and Pulp Test Methods 2000 Edition."

[0102] Non-absorbent recording media include, for example, those in which a plastic is coated on a substrate such as paper, those in which a plastic film is adhered to a substrate such as paper, plastic films that do not have an absorption layer (receiving layer), etc. Examples of plastics include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, polypropylene, etc.

[0103] Further, examples of low-absorbency recording media include recording media having a low-absorbency coating layer on the surface, such as so-called coated paper. For example, recording media having a paper substrate include printing paper such as art paper, coated paper, and matte paper. For example, recording media having a plastic film substrate include those having a polymer or the like coated on the surface of polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, polypropylene, or the like, and those having particles of silica, titanium, or the like coated together with a binder.

[0104] An absorbent recording medium can also be used as the recording medium. The absorbent recording medium is a recording medium that is absorbed within 30 msec from the start of contact in the Bristow method. 1 / 2 Water absorption up to 10mL / m 2 It refers to a "super recording medium."

[0105] Examples of non-white recording media include transparent recording media (transparent recording media). Transparent recording media may be colorless and transparent or colored (colored) and transparent. Transparent also includes translucency. These are recording media that are visually translucent. They are also recording media that are visible light transmissive. In such cases, an image formed on one side of the recording medium by the recording method of this embodiment can be clearly viewed from both sides.

[0106] Furthermore, examples of non-white recording media include non-white colored recording media (non-white colored recording media). Examples include non-white colored opaque recording media and non-white colored transparent recording media. In these cases, the recording method of this embodiment also makes it possible to easily form images with good image quality, such as good visibility, good filling, and reduced image quality differences. The non-white colored recording media may be the transparent recording media described above, or may not be transparent recording media. Recording media that are not transparent are recording media that do not have optical transparency when observed with the naked eye. They are also recording media that are opaque to visible light. Here, non-white colored recording media refers to colors other than white.

[0107] 2. Recording device The recording apparatus of this embodiment includes a white inkjet head that ejects a white ink composition containing a white coloring material to adhere to a recording medium, a non-white inkjet head that ejects a non-white ink composition containing a non-white coloring material to adhere to the recording medium, a drying mechanism that dries the white ink composition and non-white ink composition adhered to the recording medium, and a control unit that controls the execution of recording using the white inkjet head and the non-white inkjet head, and performs recording by the above-mentioned recording method.

[0108] An example of a recording apparatus used in this embodiment will be described below with reference to the drawings, but the recording apparatus used in this embodiment is not limited to the following aspect.

[0109] An example of a recording apparatus used in this embodiment is shown in Figure 1. While Figure 1 illustrates an on-carriage type printer in which ink cartridges are mounted on a carriage, the recording apparatus is not limited to on-carriage type printers and may also be off-carriage type printers in which ink cartridges are fixed externally. In the case of an off-carriage type printer, the ink cartridge 3 is mounted in a location other than the carriage 4, and ink is supplied from the ink cartridge 3 to the recording head 2 via an ink supply pipe.

[0110] The printer used in the following explanation is a serial printer in which a recording inkjet head is mounted on a carriage that moves in a predetermined direction, and the inkjet head moves in conjunction with the movement of the carriage, thereby ejecting droplets onto the recording medium. The serial type may be a type in which main scanning is performed in a direction that intersects with the sub-scanning direction, which is the direction in which the recording medium is fed, or a lateral type in which the inkjet head moves alternately in the main scanning direction and sub-scanning direction relative to a fixed recording medium.

[0111] As shown in FIG. 1, the printer 1 includes a recording head 2, an ink cartridge 3, a carriage 4, a platen 5, a drying mechanism 6, a carriage movement mechanism 7, a medium feed mechanism 8, a guide rod 9, a linear encoder 10, and a control unit CONT.

[0112] The control unit CONT controls the overall operation of the printer 1. The carriage 4 mounts the recording head 2, which will be described later, and detachably mounts ink cartridges 3 that supply each ink composition to the recording head 2. The platen 5 is disposed below the recording head 2, and transports the recording medium M. A drying mechanism 6 heats the recording medium M. A carriage movement mechanism 7 moves the carriage 4 in the medium width direction of the recording medium M. A medium feed mechanism 8 transports the recording medium M in the medium feed direction. Here, the medium width direction is the main scanning direction MS, which is the direction in which the recording head 2 is operated. The medium feed direction is the sub-scanning direction SS, which is the direction perpendicular to the main scanning direction MS and in which the recording medium M moves.

[0113] The recording head 2 is a means for depositing each ink composition onto the recording medium M, and is equipped with a first nozzle for ejecting a white ink composition and a second nozzle for ejecting a non-white ink composition on the surface facing the recording medium M to which each ink composition is deposited. These multiple nozzles are arranged in a row, thereby forming a nozzle face on the surface of the nozzle plate. In Figure 1, the recording head 2 serves as both a white inkjet head and a non-white inkjet head.

[0114] Examples of a method for ejecting the white ink composition or non-white ink composition from a nozzle include a piezoelectric method in which pressure and a recording information signal are simultaneously applied to the white ink composition or non-white ink composition by a piezoelectric element, thereby ejecting and recording droplets of the ink or non-white ink composition. Furthermore, the recording head 2 may be an inkjet head, a dot impact head, a thermal transfer head, or the like.

[0115] 2 shows the nozzle formation surface when an inkjet head is used as the recording head 2. When scanning is performed by ejecting a white ink composition from nozzle row N1 and a non-white ink composition from nozzle row N2, the nozzle rows N1 and N2 have an overlapping portion in the sub-scanning direction SS when projected in the main scanning direction MS. In this case, a single scan of the inkjet head results in the white ink composition and the non-white ink composition being deposited in the same region of the recording medium.

[0116] In the above example, the same area is the part where nozzle row N1 that ejects white ink and nozzle row N2 that ejects non-white ink overlap each other in the sub-scanning direction SS when projected in the main scanning direction MS.

[0117] FIG. 3 shows another embodiment of the inkjet head. The inkjet head shown in FIG. 3 is further divided into blocks B1 and B2 in the sub-scanning direction SS. This inkjet head can change the type of droplets ejected for each block and nozzle row. For example, in FIG. 3, the inkjet head can be configured so that block B1 of nozzle row N1 ejects white ink, and blocks B1-B2 of nozzle row N2 eject non-white ink. In this way, by further dividing the inkjet head into blocks in the sub-scanning direction SS, more flexible ejection modes can be achieved.

[0118] In this case as well, the white ink composition and the non-white ink composition are deposited in the same area of the recording medium facing the block B1 by the same main scanning.

[0119] In FIG. 1, the ink cartridges 3 that supply the white ink composition and the like to the recording head 2 consist of four independent cartridges. For example, three of the four cartridges are filled with different types of non-white ink compositions, and one of the four cartridges is filled with a white ink composition. The ink cartridges 3 are detachably attached to the recording head 2. In the example of FIG. 1, the number of cartridges is four, but this is not limited to four, and any desired number of cartridges can be installed.

[0120] The carriage 4 is attached while being supported by a guide rod 9, which is a support member installed in the main scanning direction, and moves in the main scanning direction along the guide rod 9 by a carriage movement mechanism 7. In the example of Fig. 1, the carriage 4 moves in the main scanning direction, but this is not limiting, and the carriage 4 may move in the sub-scanning direction in addition to the movement in the main scanning direction.

[0121] The installation position of the drying mechanism 6 is not particularly limited as long as it is located in a position where it can heat the recording medium M. In the example of Fig. 1, the drying mechanism 6 is installed on the platen 5 in a position facing the recording head 2. When the drying mechanism 6 is installed in a position facing the recording head 2, it is possible to reliably heat the position on the recording medium M where the ink or non-white ink composition is attached, and it is possible to efficiently dry the white ink composition or non-white ink composition attached to the recording medium M.

[0122] Examples of the drying mechanism 6 include a print heater mechanism that heats the recording medium M by contacting it with a heat source, a mechanism that irradiates infrared rays or microwaves, which are electromagnetic waves with a maximum wavelength of about 2450 MHz, and a dryer mechanism that blows hot air.

[0123] The heating of the recording medium M by the drying mechanism 6 is carried out before, during, or immediately after the droplets ejected from the nozzles of the recording head 2 adhere to the recording medium M. The control unit CONT controls the heating conditions, such as the timing of heating, the heating temperature, and the heating time.

[0124] The linear encoder 10 detects the position of the carriage 4 in the main scanning direction using a signal. The signal detected by the linear encoder 10 is sent to the control unit CONT as position information. The control unit CONT recognizes the scanning position of the recording head 2 based on the position information from the linear encoder 10, and controls the recording operation, i.e., the ejection operation, of the recording head 2. The control unit CONT is configured to be able to variably control the movement speed of the carriage 4.

[0125] Figure 4 is a schematic cross-sectional view of the inkjet head and its periphery in the recording device of Figure 1, as seen from the side. A drying mechanism and other components are also shown in Figure 4. The recording device 100 includes a carriage 2, an inkjet head 3, a platen 4, a platen heater 4a, a preheater 7, an IR heater 8, a blower fan 8a, an afterheater 5, and a cooling fan 5a. Recording is performed on a recording medium 1.

[0126] The drying mechanism used in the primary drying step can be a conduction type using a platen heater 4a or a preheater 7, a radiation type using an IR heater 8, or a blower type using a blower fan 8a. At least one of these can be used to perform the primary drying step. When blowing air using the blower fan 8a, air can be blown to the ink adhering to the recording medium near the position facing the inkjet head 4 in the recording medium transport direction, thereby promoting evaporation. The afterheater 5 is a drying mechanism used in the secondary drying step. [Example]

[0127] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0128] 1. Ink composition Each material was mixed in the composition shown in Table 1 below and thoroughly stirred to obtain each ink composition. Specifically, each material was mixed uniformly and insoluble matter was removed using a filter to prepare the ink composition. In Table 1 below, the units of values are mass %, and the total is 100.0 mass %. Unless otherwise specified, the solid content is shown.

[0129] The colorant was mixed with a dispersant and stirred to prepare a pigment dispersion, which was then used to prepare the ink. A dispersant resin was used as the dispersant, and a commercially available product suitable for each pigment was mixed in a pigment:dispersant ratio of 2:1 by mass.

[0130] [Table 1] *The values in parentheses for organic solvents refer to their standard boiling points. Styrene acrylic resin: BASF, product name JONCRYL 537J Polyethylene wax: BYK, product name AQUACER 539 BYK348: BYK, silicone surfactant

[0131] 2. Evaluation The recording device used was a modified serial inkjet printer (product name SC-S80650). The nozzle density per nozzle row was 360 npi, with 360 nozzles.

[0132] In the "simultaneous" printing method, the inkjet head has nozzle rows aligned horizontally in the main scanning direction as shown in Figure 2. The printing resolution was 720 x 720 dpi.

[0133] The number of ink droplets per pixel and the ink amount of the ink droplets were adjusted so that the deposition amount at the resolution was the value shown in the table. The number of ink droplets per pass was also adjusted.

[0134] Recording tests were then carried out using the recording device to obtain recorded images under the conditions shown in Tables 2 to 4. Specifically, each ink composition was recorded on a recording medium (PET50A (transparent film), manufactured by Lintec) in a predetermined amount of adhesion and number of passes under the conditions of each example, to record a solid image.

[0135] In an example where white ink and non-white ink were applied "simultaneously," the first nozzle row of the horizontally aligned head was filled with white ink and the second nozzle row with color ink, and these were then ejected simultaneously in the same main scan using the number of passes shown in the table.

[0136] In the example where white ink and non-white ink were applied in a "layered" manner, the white inkjet head was positioned upstream of the color inkjet head in the media transport direction, and the white ink was printed first using the number of passes listed in Tables 2 to 4, and then the color inks were printed on top of each other using the number of passes listed in Tables 2 to 4. The amount of ink adhered is the amount of ink adhered in a 2×2 mm area in the recording pattern.

[0137] The recording device was also equipped with a platen heater and blower fan as shown in Figure 4. The wind speed of the blower fan was the wind speed near the paper surface, and the values shown in Tables 2 to 4 were used. The wind temperature was the value shown in the table. The wind temperature was the wind temperature near the surface of the recording medium, and was set and measured in advance without the influence of the platen heater temperature, and recording was performed under those set conditions.

[0138] The heating strength of the platen heater was adjusted so that the surface temperature of the recording medium reached the value shown in the table.

[0139] Furthermore, a secondary drying step was carried out using a downstream secondary heater so that the surface temperature of the recording medium reached 70°C.

[0140] 2.1.Abrasion resistance The recorded material obtained as described above was rubbed 50 times back and forth with a cloth placed on the surface of the coating film under a load of 500 g using a Gakushin-type rub fastness tester (manufactured by TESTER SANGYO CO., LTD.). After rubbing, the surface of the coating film was visually inspected for peeling or scratches, and the rub resistance was evaluated according to the following evaluation criteria. (Evaluation criteria) A: No peeling of the image is observed B: Less than 10% peeling C: Peeling of 10% to less than 40% of the surface area D: Peeling of 40% or more of the surface area

[0141] 2.2.Discharge stability Recording was carried out continuously for two hours under the conditions shown in Tables 2 to 4. However, this was simulated recording in which ink was not ejected from the inkjet head after recording. After this recording, suction cleaning was performed by discharging 1 cc, and a nozzle inspection was carried out to check for the presence of non-ejecting nozzles. If non-ejecting nozzles were found, suction cleaning was carried out again, and the number of cleanings was counted until all nozzles were restored, and the ejection stability was evaluated according to the following evaluation criteria. (Evaluation criteria) A: All nozzles recovered with one cleaning B: All nozzles recovered after 2-3 cleanings C: All nozzles recovered after 4 to 6 cleanings D: Some nozzles do not recover after six cleanings

[0142] 2.3.Image quality (uneven shading) The pattern image of the recorded matter obtained as described above was visually inspected, and the unevenness of the density of the printed matter was evaluated according to the following evaluation criteria. (Evaluation criteria) A: No unevenness in shading can be seen B: Minor variations in shading are slightly visible C: Fine variations in shading are clearly visible. D: Significant unevenness in shading is visible.

[0143] 2.4.Image Quality (Visibility) The recorded matter obtained as described above was placed on black paper, and the visibility of the image was visually observed and evaluated according to the following evaluation criteria. Note that if the amount of white ink attached is small, the hiding power of the image is insufficient, and the black of the black paper underneath is visible, making it difficult to see. (Evaluation criteria) A: It is easy to see. B: Looks a little dark but is easy to see. C: Looks black but is still visible. D: It looks black and is difficult to see. E: It looks black and is very difficult to see.

[0144] 2.5.Image Quality (OD Value) The solid image of the recorded matter obtained as described above was measured for OD value under the following measurement conditions using a colorimeter (i1Pro2, manufactured by X-reite), and the color development was evaluated according to the following evaluation criteria. (Measurement conditions) D50 light source, Status T, Standard observer 2°, Background: White paper (Evaluation criteria) A:OD value is 1.0 or more B: OD value is 0.8 or more and less than 1.0 C: OD value is 0.6 or more and less than 0.8 D: OD value is 0.4 or more and less than 0.6 E:OD value is less than 0.4

[0145] Productivity The productivity was evaluated according to the following evaluation criteria in accordance with the number of passes required for recording on a portion of the recording medium in a recording area whose length in the conveyance direction is the length of one sub-scan. (Evaluation criteria) A: 4 passes or less B: 5-6 passes C: 7-8 passes D: 9 passes or more

[0146] [Table 2]

[0147] [Table 3]

[0148] [Table 4]

[0149] 3. Evaluation Results As described above, by comparing the Examples and Comparative Examples, all Examples in which white ink and non-white ink were simultaneously printed and a primary drying process was performed had excellent image quality (shade unevenness) and also excellent productivity. On the other hand, all of the comparative examples that did not have this feature were inferior in either image quality (unevenness in shading) or productivity. Comparing Examples 1 and 14 to 17, a lower deposition amount ratio (white / non-white) resulted in better image quality (OD value) and image quality (shade unevenness), and a higher deposition amount ratio resulted in better image quality (visibility). A comparison of Examples 1, 3, and 9 showed that inks containing a higher content of organic solvents below 200°C provided better image quality and abrasion resistance, while inks containing a lower content of organic solvents above 200°C provided better ejection stability. Furthermore, inks containing both organic solvents below 200°C and organic solvents above 200°C provided a good balance of excellent image quality, abrasion resistance, and ejection stability. A comparison of Examples 1, 8, and 10 shows that inks with a lower organic solvent content have better image quality, and inks with a higher organic solvent content have better ejection stability.

[0150] In Comparative Examples 1 to 3, the primary drying step was not performed, but the image quality (unevenness in density) was poor, and the image quality (OD value) also tended to decrease. In Comparative Examples 4 to 6, white ink and non-white ink were not simultaneously applied, but rather recording was performed by a layering method. Although image quality problems such as uneven density were unlikely to occur, the recording speed was poor. In contrast, the Examples showed excellent productivity. In Reference Example 7, no white ink was used, but the image quality (visibility) was poor. In Reference Example 8, no non-white ink was used, but the image quality (OD value) was poor. [Explanation of symbols]

[0151] 1...printer, 2...recording head, 3...ink cartridge, 4...carriage, 5...platen, 6...drying mechanism, 7...carriage movement mechanism, 8...medium feeding mechanism, 9...guide rod, 10...linear encoder, M...recording medium, CONT...control unit

Claims

1. a white ink deposition step of ejecting a white ink composition containing a white colorant from a white inkjet head and depositing the ink on a recording medium; a non-white ink deposition step of ejecting a non-white ink composition containing a non-white colorant from a non-white inkjet head and depositing the ink on the recording medium; a primary drying step of heating the white ink composition and the non-white ink composition attached to the recording medium by a drying mechanism, In the white ink applying step and the non-white ink applying step, a main scanning movement is performed a plurality of times to eject ink compositions and apply them to the recording medium while moving the position of the inkjet head relative to the recording medium, and the white ink composition and the non-white ink composition are applied to the same scanning area of the recording medium by the same main scanning movement, thereby forming a layer containing the white ink composition and the non-white ink composition; a ratio A of the amount of the white ink composition to the amount of the non-white ink composition (100% by mass) deposited in an area of the recording medium where the white ink composition and the non-white ink composition are deposited and where the amount of the non-white ink composition deposited is the largest is 80% by mass or less.

2. A white ink deposition step of ejecting a white ink composition containing a white colorant from a white inkjet head and depositing it on a recording medium; a non-white ink deposition step of ejecting a non-white ink composition containing a non-white colorant from a non-white inkjet head and depositing the ink on the recording medium; a primary drying step of heating the white ink composition and the non-white ink composition attached to the recording medium by a drying mechanism, In the white ink applying step and the non-white ink applying step, a main scanning movement is performed a plurality of times to eject ink compositions and apply them to the recording medium while moving the position of the inkjet head relative to the recording medium, and the white ink composition and the non-white ink composition are applied to the same scanning area of the recording medium by the same main scanning movement, thereby forming a layer containing the white ink composition and the non-white ink composition; A recording method, wherein the maximum amount of the white ink composition deposited in the area of the recording medium to which the white ink composition and the non-white ink composition are deposited is 10 mg / inch 2 or less.

3. In the primary drying step, either heating or air blowing is performed.

3. The recording method according to claim 1 or 2.

4. In the primary drying step, air is blown, The wind speed of the air blown is 0.5 to 5 m / s. The recording method according to any one of claims 1 to 3.

5. the surface temperature of the recording medium in the primary drying step is 35 to 60°C; The recording method according to any one of claims 1 to 4.

6. performing the main scanning a plurality of times on the same area of the recording medium; The recording method according to any one of claims 1 to 5.

7. the content of the white colorant is 8% by mass or more relative to the total amount of the white ink composition; The recording method according to any one of claims 1 to 6.

8. the white ink composition contains an organic solvent, the content of organic solvents having a normal boiling point of less than 200°C among the organic solvents is 50 mass% or more based on the total amount of the organic solvents; The recording method according to any one of claims 1 to 7.

9. the white ink composition contains an alkanediol having 3 to 5 carbon atoms at both ends as an organic solvent; The recording method according to any one of claims 1 to 8.

10. the white ink composition contains an organic solvent, The maximum normal boiling point of the organic solvent is 250°C or less. The recording method according to any one of claims 1 to 9.

11. the white ink composition contains an organic solvent, The organic solvent includes an organic solvent having a normal boiling point of less than 200°C and an organic solvent having a normal boiling point of 200°C or higher. The recording method according to any one of claims 1 to 10.

12. the white ink composition and the non-white ink composition are each a water-based ink composition or a solvent-based ink composition; The recording method according to any one of claims 1 to 11.

13. the white ink composition and the non-white ink composition are each the water-based ink composition; the content of an organic solvent in each of the white ink composition and the non-white ink composition is 30% by mass or less; The recording method according to claim 12.

14. The recording medium is a low-absorbency recording medium or a non-absorbency recording medium. The recording method according to any one of claims 1 to 13.

15. The layer containing the white ink composition and the non-white ink composition formed in the same main scanning region by the same main scanning is a layer in which the white ink composition and the non-white ink composition are mixed. The recording method according to any one of claims 1 to 14.

16. a white inkjet head that ejects a white ink composition containing a white colorant onto a recording medium; a non-white inkjet head that ejects a non-white ink composition containing a non-white colorant onto the recording medium; a drying mechanism that dries the white ink composition and the non-white ink composition that have been applied to the recording medium; a control unit that controls recording using the white inkjet head and the non-white inkjet head, A recording apparatus that performs recording using the recording method according to any one of claims 1 to 15.

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