Recording method and recording device

Abstract

To provide a recording method and a recording device capable of suppressing the occurrence of uneven color difference.SOLUTION: There is provided a recording method which comprises a discharge step of discharging a first ink and a second ink from a line head having a length larger than a recording width of a recording medium to adhere the inks to the recording medium, wherein the line head has a plurality of unit heads aligned in the recording width direction of the recording medium and has portions where the distance between the nozzles of the first nozzle for discharging the first ink and the second nozzle for discharging the second ink in the scanning direction is different, the first ink and the second ink contain a color material and inorganic oxide particles and the compositions of the color material are different from each other.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Inkjet recording methods, which enable recording of high-definition images with relatively simple apparatuses, have achieved rapid development in various fields. Various studies have been conducted on image quality and other aspects among these. For example, Patent Document 1 discloses a recording method that uses a predetermined aqueous ink for the purpose of recording an image with inconspicuous bonding streaks and excellent uniformity and color developability when a recording apparatus provided with a line head is used.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] However, it has been found that such conventional methods produce color differences depending on the location when the recorded matter is viewed in the width direction intersecting the scanning direction.

Means for Solving the Problem

[0005] The present invention is a recording method including an ejection step of ejecting a first ink and a second ink from a line head having a length equal to or longer than the recording width of a recording medium to cause the inks to adhere to the recording medium, wherein the line head includes a plurality of unit heads arranged in the direction of the recording width of the recording medium, and has portions where an inter-nozzle distance between a first nozzle that ejects the first ink and a second nozzle that ejects the second ink in the scanning direction is different, the first ink and the second ink each contain a color material and inorganic oxide particles, and compositions of the color materials are different from each other.

[0006] The present invention relates to a recording device comprising a line head having a length greater than or equal to the recording width of a recording medium, a first ink and a second ink, wherein the line head has a plurality of unit heads arranged in the direction of the recording width of the recording medium, and has a portion in which the distance between the nozzles of a first nozzle that ejects the first ink and a second nozzle that ejects the second ink in the scanning direction is different, and the first ink and the second ink contain a colorant and inorganic oxide particles, and the composition of the colorant is different from that of the other. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic cross-sectional view of a recording device that can be used in the recording method of the present invention. [Figure 2A] This figure shows a first example A of the nozzle surface of an inkjet head having portions with different nozzle distances. [Figure 2B] This figure shows a first example B of the nozzle surface of an inkjet head having areas with different nozzle distances. [Figure 2C] This figure shows a first example C of the nozzle surface of an inkjet head having portions with different nozzle distances. [Figure 3A] This figure shows an example of the nozzle surface of an inkjet head that does not have areas with different nozzle distances. [Figure 3B] This figure shows a second example B of the nozzle surface of an inkjet head that does not have areas with different nozzle distances. [Figure 3C] This figure shows a second example C of the nozzle surface of an inkjet head that does not have areas with different nozzle distances. [Modes for carrying out the invention]

[0008] The embodiments of the present invention (hereinafter referred to as "these embodiments") will be described in detail below, with reference to the drawings as necessary. However, the present invention is not limited thereto, and various modifications are possible without departing from its essence. In the drawings, the same elements will be denoted by the same reference numerals, and redundant explanations will be omitted. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings. Moreover, the dimensional ratios in the drawings are not limited to those shown.

[0009] 1. Recording Method The recording method of this embodiment includes an ejection step of ejecting a first ink and a second ink from a line head having a length greater than or equal to the recording width of the recording medium and adhering them to the recording medium, wherein the line head has a plurality of unit heads arranged in the direction of the recording width of the recording medium, and has a portion where the distance between the nozzles of the first nozzle that ejects the first ink and the second nozzle that ejects the second ink in the scanning direction is different, and the first ink and the second ink contain a colorant and inorganic oxide particles, and the composition of the colorant is different from that of the other.

[0010] Since a line head 10 is generally constructed by arranging multiple unit heads 12 in the width direction (see Figure 3A, etc.), joints 13 inevitably occur between the unit heads 12. When the recorded material is viewed in the width direction, it is known that the recording density differs at these joints 13, and this can be observed as streaks. This is because, when arranging multiple unit heads 12, the positions of the unit heads 12 in the width direction do not align precisely, and the distance between nozzles between the unit heads 12 in the width direction is not precise at the joints 13.

[0011] For streaks of varying density at such joints 13, methods are known to reduce density unevenness using image processing techniques.

[0012] The present inventors have now conducted thorough research and found that, in addition to streaks caused by uneven density, color differences may occur at the joint 13. The reason for such color differences is not particularly limited, but it is thought to be due to the fact that when attempting to form a color with multiple inks, there may be areas where the time difference between each ink adhering to the recording medium differs.

[0013] At the joint 13, in the scanning direction, there may be areas where the distance Lmin between unit head 12a and unit head 12b is close, and areas where the distance Lmax between unit head 12a and unit head 12b is far (Figures 2A to 2C). In this way, when there are areas where the distance L between unit head 12a and unit head 12b differs in the scanning direction, there may be areas where the time difference between when the first ink lands on the recording medium and when the second ink lands differs when viewed in the width direction. Consequently, when viewed in the width direction, there may be areas where the second ink lands and forms color after the first ink has penetrated the recording medium, and areas where the second ink lands and forms color before the first ink has penetrated the recording medium, and it is presumed that this is the cause of the color difference. In other words, it is presumed that a similar phenomenon is occurring as when two inks penetrate a recording medium sequentially to form a color, and when they penetrate simultaneously to form a color, resulting in a difference in the resulting color due to the difference in the degree of penetration of the two inks.

[0014] On the other hand, it is also conceivable to arrange the unit heads 12 such that there are areas where the distance Lmin between unit heads 12a and 12b is close, and areas where the distance Lmax between unit heads 12a and 12b is far (Figures 3A to 3C). However, if arranged in this way, there is often a relatively large gap 14 where no unit heads are placed. Therefore, in order to secure a predetermined number of nozzles on the nozzle surface 11 of the line head, the head itself must be designed to be large, which leads to an increase in the size of the recording device.

[0015] In other words, when it is desired to configure the line head as compact as possible, there will be a region where the distance Lmin between the unit head 12a and the unit head 12b is short and a region where the distance Lmax between the unit head 12a and the unit head 12b is long, so the aforementioned difference in color difference may occur. In particular, when it is desired to reduce the size of the line head in the scanning direction, the aforementioned difference in color difference may occur.

[0016] Particularly, in the case of a line printer, since ink adhesion to a recording material is completed in one pass, the aforementioned difference in color difference is particularly noticeable. In the case of a serial printer, even if color difference occurs due to the configuration of the head, ink is applied dispersedly over a plurality of passes, so the color difference caused by the head configuration becomes inconspicuous.

[0017] Since the cause of such color difference lies in the difference in penetration state, it cannot be reduced by image processing techniques or the like unlike density unevenness. Accordingly, in the present embodiment, by using inorganic oxide particles, the ink is caused to contain the inorganic oxide particles, the penetration speed of a plurality of inks is reduced, and the difference in the degree of penetration between the region where the distance Lmin between the unit head 12a and the unit head 12b is short and the region where the distance Lmax between the unit head 12a and the unit head 12b is long is reduced. In other words, in the present embodiment, by using inorganic oxide particles, the penetration speed of a plurality of inks is reduced, and even if there is a difference in the distance L, a state close to that when a plurality of inks penetrate simultaneously can be obtained.

[0018] Thereby, even when the line head is configured as compact as possible, it becomes possible to reduce the difference in the degree of penetration, and the color difference when the recording material is viewed in the width direction can be reduced. Hereinafter, the configuration of the present embodiment will be described in detail.

[0019] 1.1. Ejection step The ejection step is a step of ejecting a first ink and a second ink from a line head having a length equal to or greater than the recording width of a recording medium to cause the inks to adhere to the recording medium. Fig. 1 shows a schematic cross-sectional view of a recording apparatus that can be used in the recording method of the present invention.

[0020] 1.1.1. Line Head The line head 10 has a length greater than or equal to the recording width of the recording medium and is a means for ejecting an ink composition and adhering it to the recording medium M. The inkjet head 10 has a plurality of unit heads 12 arranged in the direction of the recording width of the recording medium on a nozzle surface 11 facing the recording medium M. The unit heads 12 have nozzles for ejecting an ink composition, and the nozzles may be arranged in rows. A group of nozzles arranged in rows is also called a "nozzle row". The recording medium M is supported by a belt B and transported in the transport direction. The belt B is moved in the transport direction D1 by a belt roller 20. The recording device may include a paper feed tray, a paper output tray, etc., which are not shown.

[0021] The unit head 12 only needs to have such a nozzle row, and its structure is not limited to anything other than having a nozzle row. The part of the line head 10 that has one nozzle row is one unit head 12. It can also be said that the nozzle row is the unit head 12.

[0022] In this embodiment, the line head 10 has a portion where the distance between the first nozzle that ejects the first ink and the second nozzle that ejects the second ink in the scanning direction is different. This results in a color difference, which is why the present invention is particularly useful.

[0023] In a line-type system using a line head, for example, an inkjet head with a width greater than the recording width of the recording medium is fixed to the recording device. The recording medium is then moved along the scanning direction (the vertical direction of the recording medium, the transport direction), and an image is recorded on the recording medium by scanning in conjunction with this movement, in which ink droplets are ejected from the nozzles of the inkjet head.

[0024] Alternatively, the recording medium is fixed to the recording device. Then, an inkjet head having a width greater than or equal to the recording width of the recording medium is moved along the scanning direction, and an image is recorded on the recording medium by performing a scan in which ink droplets are ejected from the nozzles of the inkjet head in conjunction with this movement. The scanning direction is the direction of scanning.

[0025] In this type of line-based printing system using a line head, recording can be performed with a single scan of the line head and recording medium, thus improving printing speed.

[0026] Figures 2A to 2C show first A to first C examples of the nozzle surface of an inkjet head having portions with different nozzle distances. In this embodiment, a unit head equipped with a first nozzle for ejecting first ink is referred to as the first unit head 12a, a unit head equipped with a second nozzle for ejecting second ink is referred to as the second unit head 12b, and when neither is distinguished, it is simply referred to as the unit head 12.

[0027] Furthermore, the following examples illustrate a configuration in which the first unit head 12a ejects the first ink and the second unit head 12b ejects the second ink, but this configuration is merely one example. In other words, the present invention may include embodiments in which a single unit head, without distinction between a first unit head and a second unit head, includes a nozzle for ejecting a first ink and a nozzle for ejecting a second ink. More specifically, if the unit head includes multiple nozzle rows, each nozzle row may be capable of ejecting a different ink composition.

[0028] For example, the first unit head 12a and the second unit head 12b may not be separate parts but a single unit. Also, multiple first unit heads 12a and multiple second unit heads 12b arranged in the width direction may not be separate parts but a single unit. Multiple unit heads 12 constituting the line head may not be separate parts but a single unit.

[0029] In this case as well, the part containing one nozzle row that ejects the first ink is the first unit head 12a, and the part containing one nozzle row that ejects the second ink is the second unit head 12b. In other words, the unit head 12 is also the nozzle row.

[0030] Furthermore, in the figure, one first unit head 12a has two nozzle rows in the scanning direction, but the number of nozzle rows may be one or more, and at least one of these nozzle rows must be the nozzle row that ejects the first ink. The same applies to the second unit head 12b.

[0031] In the first example shown in Figure 2A, the first unit head 12a and the second unit head 12b are arranged in a single unit 12' along their longitudinal direction, and these units 12' are arranged with gaps 14 between them so that the longitudinal direction of the unit 12' is parallel to the width direction D2 of the line head. In addition, multiple rows of such units 12' are arranged on the scanning direction side, with the positions of the joints 13 offset so that the positions of the joints 13 in the width direction D2 do not overlap. It is also possible to arrange multiple rows of units 12' on the scanning direction side, with the positions of the gaps 14 offset so that the positions of the gaps 14 in the width direction D2 do not overlap.

[0032] In the first example A shown in Figure 2A, there may be a portion indicated by Lmin where the first unit head 12a and the second unit head 12b are configured to be close together in the scanning direction, and a portion indicated by Lmax where the first unit head 12a and the second unit head 12b are configured to be far apart in the scanning direction. As a result, there may be a portion where the distance between the first nozzle that ejects the first ink and the second nozzle that ejects the second ink in the scanning direction is different.

[0033] The Lmin and Lmax portions inevitably occur in areas that are not at the joint 13.

[0034] A joint 13 is the portion where the nozzle rows of two first unit heads 12a or two second unit heads 12b overlap in the width direction. Two unit heads 12 are arranged in the width direction so that nozzles exist at such joints 13. The number of nozzles per first unit head 12 at one joint 13 is one or more, but is not limited to one, although for example, 1 to 10 is preferred.

[0035] The Lmin and Lmax portions occur in the areas where the nozzle row positions of the two first unit heads 12a do not overlap with each other in the width direction, and where the nozzle row positions of the two second unit heads 12b do not overlap with each other in the width direction.

[0036] The nozzle at the joint 13 can control the discharge by using the nozzle of one of the two unit heads 12, the nozzle of the other unit head 12, or the nozzles of both unit heads 12.

[0037] For example, by using the nozzles of both unit heads 12, the unevenness of concentration at the joint 13 can be reduced. In this case, the joint 13 may have nozzles with different distances between them when viewed on a nozzle-by-nozzle basis.

[0038] Furthermore, it is possible to use only the nozzle of one unit head 12, or only the nozzle of the other unit head 12. In this case, the joint 13 becomes either the Lmin portion or the Lmax portion.

[0039] In the example shown in Figure 2A, compared to the example in Figure 2B, the portion where the positions of the two first unit heads 12a and the portion where the positions of the two first unit heads 12b overlap in the scanning direction, i.e., the widthwise length of the joint 13, is relatively short. This is preferable because it reduces the number of unit heads 12 required to constitute the line head.

[0040] Furthermore, in the first example B shown in Figure 2B, the first unit head 12a and the second unit head 12b are arranged in a single unit 12' in the longitudinal direction, and these units 12' are arranged without gaps so that the longitudinal direction of the unit 12' is parallel to the width direction D2 of the line head. In addition, multiple rows of such units 12' are arranged on the scanning direction side, with the positions of the joints 13 offset so that the positions of the joints 13 in the width direction D2 do not overlap.

[0041] In the first example B shown in Figure 2B, in the scanning direction, there may be a portion indicated by Lmin where the first unit head 12a and the second unit head 12b are close together, and a portion indicated by Lmax where the first unit head 12a and the second unit head 12b are far apart. As a result, at least a portion may be created where the distance between the first nozzle that ejects the first ink and the second nozzle that ejects the second ink is different in the scanning direction.

[0042] In the example shown in Figure 2B, compared to the example in Figure 2A, there are relatively more areas where the positions of the two first unit heads 12a and the positions of the two first unit heads 12b overlap in the scanning direction, and the length of the joint 13 in the width direction is longer. Furthermore, gaps 14 are less likely to occur, resulting in superior strength of the line head, which is preferable.

[0043] In the first example shown in Figure 2C, the first unit head 12a and the second unit head 12b are arranged in the longitudinal direction to form a single unit 12', and these units 12' are arranged in the width direction D2 such that the longitudinal direction of the unit 12' intersects the width direction D2 of the line head at an angle. In Figure 2C, there is a gap between adjacent units 12' that are arranged at an angle, but instead, adjacent units 12' may be arranged adjacent to each other without any gaps.

[0044] It is preferable that the first nozzle group, consisting of multiple first nozzles that eject the first ink, and the second nozzle group, consisting of multiple second nozzles that eject the second ink, are arranged diagonally or parallel to the recording width direction. This results in different apparent nozzle density in the width direction of the entire line head and different numbers of unit heads required to construct a line head with a predetermined width direction distance.

[0045] Comparing the case where the nozzles are arranged diagonally to the width direction D2, as in the example in Figure 2C, with the case where they are arranged parallel to the width direction D2, as in the example in Figure 2A, even when using the same nozzle density for the first unit head 12a and second unit head 12b, the overall nozzle density in the width direction of the line head is higher when the nozzles are arranged diagonally to the width direction D2, as in the example in Figure 2C. In other words, arranging the nozzles diagonally to the width direction D2, as in the example in Figure 2C, improves the nozzle density. This results in higher recording resolution and superior image quality, which is preferable. In this case, the distance between nozzles in the scanning direction is increased, making the present invention particularly useful.

[0046] On the other hand, when the units are arranged parallel to the width direction D2 as in the example in Figure 2A, it is preferable because the number of unit heads required to construct a line head with a predetermined width direction distance is reduced. It is also preferable because the overall length of the line head in the scanning direction can be shortened. Therefore, it becomes possible to further miniaturize the line head.

[0047] In the first example C shown in Figure 2C, a region indicated by Lmax may occur in the scanning direction where the first unit head 12a and the second unit head 12b are far apart. Conversely, a region indicated by Lmin may occur where the first unit head 12a and the second unit head 12b are close together. As a result, at least a region may occur where the distance between the first nozzle that ejects the first ink and the second nozzle that ejects the second ink differs in the scanning direction.

[0048] Furthermore, in contrast to inkjet heads that have areas with varying nozzle distances, we will also describe inkjet heads that do not have areas with varying nozzle distances. Figures 3A to 3C show examples 2A to 2C of the nozzle surface of an inkjet head that does not have areas with varying nozzle distances.

[0049] In the 2A example shown in Figure 3A, at the joint 13 in the width direction D2, two or more first unit heads 12a are arranged alternately so as to overlap in the scanning direction D1. Also, at the joint 13 in the width direction D2, two or more second unit heads 12b are arranged alternately so as to overlap in the scanning direction D1. As a result, the distance L between nozzles remains constant in all sections. Furthermore, at the joint 13 where the first unit heads 12a are arranged alternately so as to overlap in the scanning direction D1, it is sufficient to ensure that ink is ejected from at least one of the first unit heads 12a.

[0050] For example, at seam 13 in the figure, if the nozzle of the first unit head 12a located at the top of the figure is used, then at the same position in the width direction, the nozzle of the second unit head 12b located at the top of the figure is used. Alternatively, at seam 13 in the figure, if the nozzle of the first unit head 12a located at the bottom of the figure is used, then at the same position in the width direction, the nozzle of the second unit head 12b located at the bottom of the figure is used. In this way, the distance L between the nozzles of the first unit head 12a and the second unit head 12b in the scanning direction D1 is equal at any position in the width direction.

[0051] In the examples shown in Figures 3A to 3C, the joint 13 of the first unit head 12a and the joint 13 of the second unit head 12b are aligned in the width direction. In addition, the distance between nozzles is constant in areas other than the joints 13.

[0052] Therefore, the distance L between the nozzles of the first unit head 12a and the second unit head 12b in the scanning direction D1 can be made equal at any position in the width direction.

[0053] In the second example shown in Figure 3B, the first unit head 12a and the second unit head 12b form a single unit 12' aligned in the scanning direction D1. At the joint 13 in the width direction D2, two or more units 12' are arranged alternately so as to overlap in the scanning direction D1. This ensures that the distance L between nozzles remains constant throughout the unit. Furthermore, at the joint 13 where the first unit heads 12a are arranged alternately so as to overlap in the scanning direction D1, ink can be ejected from any of the first unit heads 12a.

[0054] In the second example shown in Figure 3C, the first unit heads 12a are arranged in the width direction D2 such that the longitudinal direction of the first unit heads 12a and the width direction D2 of the line head intersect diagonally. Similarly, the second unit heads 12b are arranged in the width direction D2 such that the longitudinal direction of the second unit heads 12b and the width direction D2 of the line head intersect diagonally. As a result, the distance L between nozzles remains constant in all sections. Furthermore, at the joints 13 where the first unit heads 12a are arranged alternately so as to overlap in the scanning direction D1, ink should be ejected from at least one of the first unit heads 12a.

[0055] However, in the examples 2A to 2C shown in Figures 3A to 3C, it is necessary to provide a gap equivalent to approximately 14 in each example to ensure that there are no parts with different distances between nozzles. As a result, miniaturization of the head cannot be achieved.

[0056] For example, in Figure 3A, the distance between the first nozzle that ejects the first ink and the second nozzle that ejects the second ink will formally differ depending on whether the control is set to eject ink using the first nozzle n1 and the second nozzle n2, or to eject ink using the first nozzle n3 and the second nozzle n4. However, in this embodiment, "the distance between the first nozzle that ejects the first ink and the second nozzle that ejects the second ink is different" does not mean that the distance between the first nozzle that ejects the first ink and the second nozzle that ejects the second ink is different due to such control, or that the distance between the first nozzle that ejects the first ink and the second nozzle that ejects the second ink is the same. In this embodiment, "the distance between the first nozzle that ejects the first ink and the second nozzle that ejects the second ink is different" means a line head configuration in which, as shown in Figures 2A to 2C, it is unavoidable that "the distance between the first nozzle that ejects the first ink and the second nozzle that ejects the second ink is different" regardless of how the ejection is controlled.

[0057] In this embodiment, when focusing on the nozzles that actually eject ink during recording, the device has a first nozzle that ejects the first ink and a second nozzle that ejects the second ink, such that the distance between the nozzles is different.

[0058] Furthermore, in this embodiment, the recording device has a first nozzle for ejecting the first ink and a second nozzle for ejecting the second ink, such that the time difference between the first ink ejected from the first nozzle and the second ink ejected from the second nozzle landing on the recording medium is different.

[0059] In areas where the distance between nozzles differs, the difference in the distance between nozzles (Lmax-Lmin) is preferably 5 mm or more, or preferably 150 mm or less. Furthermore, it is preferably 5 to 100 mm, more preferably 5 to 80 mm, even more preferably 10 to 50 mm, and even more preferably 15 to 50 mm. Moreover, it is preferably 15 to 30 nm, and more preferably 15 to 20 mm.

[0060] The present invention is more useful when the difference in nozzle distance is 5 mm or more, as this is prone to color unevenness. Conversely, when the difference in nozzle distance is less than the above, color unevenness tends to occur less frequently.

[0061] In areas with long or short nozzle distances, the nozzle distances (Lmax, Lmin) are preferably 5 mm or more, or preferably 100 mm or less. More preferably 10 to 50 mm.

[0062] Furthermore, the difference (Imax-Imim) between the time difference (Imax) between the first ink ejected from the first nozzle and the second ink ejected from the second nozzle in the portion where the scanning distance between the first nozzle and the second nozzle is long, and the time difference (Imin) between the time difference (Imin) between the first ink ejected from the first nozzle and the second ink ejected from the second nozzle in the portion where the scanning distance between the first nozzle and the second nozzle is short, is preferably 5 seconds or more, or preferably 100 milliseconds or less. More preferably, it is 10 to 50 milliseconds, more preferably 15 to 40 milliseconds, and particularly preferably 20 to 30 milliseconds.

[0063] Furthermore, the time difference between the first ink ejected from the first nozzle and the second ink ejected from the second nozzle in the portion with a long distance between nozzles (Imax), and the time difference between the first ink ejected from the first nozzle and the second ink ejected from the second nozzle in the portion with a short distance between nozzles (Imim), are preferably 5 seconds or more, or preferably 100 milliseconds or less. More preferably, they are 10 to 50 milliseconds, more preferably 15 to 40 milliseconds, and particularly preferably 20 to 30 milliseconds.

[0064] The scanning speed of the recording medium is preferably 1000 mm / s or less, more preferably 800 mm / s or less, and even more preferably 600 mm / s or less. Furthermore, the scanning speed of the recording medium is preferably 50 mm / s or more, even more preferably 100 mm / s or more, and even more preferably 300 mm / s or more.

[0065] The faster the scanning speed of the recording medium, the shorter the difference in landing time between the first and second inks becomes, and the more the color difference tends to be suppressed. However, other problems such as misalignment of the landing position may occur. Furthermore, the slower the scanning speed of the recording medium, the more likely color difference unevenness is to occur, making the present invention more useful.

[0066] The nozzle density of the nozzle row in the unit head 12 is preferably 50 npi. It is also preferably 1000 npi or less. Furthermore, 100 to 800 npi is preferred, 200 to 600 npi is more preferred, and 300 to 500 npi is even more preferred.

[0067] Furthermore, the nozzle density in the width direction of the recording device may also be the same as the range described above, which is preferable. In the case where the head is positioned diagonally with respect to the width direction D2, as in the example in Figure 2C, the nozzle density in the width direction of the recording device is the apparent nozzle density in the width direction. Also, the nozzle density is the nozzle density of a nozzle row that ejects one ink.

[0068] The recording device 100 of this embodiment is not particularly limited as long as it can eject a first ink and a second ink having different colorant compositions from a single line head, and may have separate independent inkjet heads 10 for each color such as cyan, magenta, yellow, black, and white. Alternatively, one inkjet head 20 may be configured to eject two or more ink compositions.

[0069] Methods for ejecting ink compositions from nozzles include driving a pressure generating means to eject the composition filled in the pressure generating chamber of the inkjet head from the nozzle, and using thermal energy for ejection. Such ejection methods are also called inkjet methods. There are no particular limitations on the method of applying pressure to the ink composition in the nozzle, but examples include the piezo method, which uses a piezoelectric element to eject droplets of the ink composition, and the thermal method, which ejects droplets by heating.

[0070] 1.1.2. Ink The first ink and the second ink contain a colorant and inorganic oxide particles, and are not particularly limited as long as the composition of the colorants are different from each other. They may further contain water, water-soluble organic solvents, lactam compounds, resin emulsions, surfactants, pH adjusters, etc., as needed. "The composition of the colorants is different from each other" means that the colors themselves are different, such as cyan and magenta; that is, the types of colorants they contain are different, and the resulting color of the recorded material obtained when applied to the recording medium is different from each other. Alternatively, even if the color system is the same, such as dark cyan and light cyan, the type and concentration (content) of the colorant are different, and the resulting color density of the recorded material obtained when applied to the recording medium is different from each other. It is one of these. Preferably, the colors themselves are different. The following describes each component, but unless otherwise specified, the components exemplified below can be used in both the first and second inks.

[0071] 1.1.2.1. Colorants The colorants are not particularly limited as long as the compositions of the first ink and the second ink colorants are different from each other, and examples include pigments and dyes. Among these, pigments are preferred. One type of colorant may be used alone, or two or more types may be used in combination.

[0072] It is preferable that one or both of the first and second inks are chromatic inks. The present invention is particularly useful in the case of chromatic inks because color differences are more likely to occur.

[0073] The colorant content is preferably 0.5 to 15% by mass, more preferably 1.0 to 10% by mass, and even more preferably 2.0 to 7.0% by mass, relative to the total amount of the first ink, as solid content. When the colorant content is within the above range, the color development and clogging recovery tend to be further improved.

[0074] The colorant content is preferably 0.5 to 15% by mass, more preferably 1.0 to 10% by mass, and even more preferably 2.0 to 7.0% by mass, relative to the total amount of the second ink, as solid content. When the colorant content is within the above range, the color development and clogging recovery tend to be further improved.

[0075] 1.1.2.1.1. Pigments One or both of the first and second inks may contain a pigment as a colorant. The pigment is not particularly limited, but examples of pigments that can be used include organic pigments such as azo pigments (e.g., azo lake, insoluble azo pigment, condensed azo pigment, chelate azo pigment, etc.), polycyclic pigments (e.g., phthalocyanine pigment, perylene pigment, perinone pigment, anthraquinone pigment, quinacridone pigment, dioxazine pigment, thioindigo pigment, isoindolinone pigment, quinophthalone pigment, etc.), nitro pigments, nitroso pigments, and aniline black; inorganic pigments such as carbon black (e.g., furnace black, thermal lamp black, acetylene black, channel black, etc.), metal oxides, metal sulfides, and metal chlorides; and extender pigments such as calcium carbonate and talc.

[0076] The above-mentioned pigment may be added to the ink as a pigment dispersion obtained by dispersing it in water with a dispersant, or as a pigment dispersion obtained by dispersing a self-dispersing surface-treated pigment (hereinafter also referred to as "self-dispersing pigment") in which hydrophilic groups have been introduced to the surface of the pigment particles using a chemical reaction in water, or as a pigment dispersion obtained by dispersing a polymer-coated pigment (hereinafter also referred to as "resin-dispersed pigment") in water. Among these, it is preferable to include a self-dispersing pigment. Using a self-dispersing pigment tends to further improve the water repellency of the nozzle plate and the intermittent printing stability.

[0077] The pigments and dispersants constituting the above-mentioned pigment dispersion may be used individually or in combination of two or more types.

[0078] 1.1.2.1.2.Dye The dyes are not particularly limited, but examples include acid dyes such as CI Acid Yellow, CI Acid Red, CI Acid Blue, CI Acid Orange, CI Acid Violet, and CI Acid Black; basic dyes such as CI Basic Yellow, CI Basic Red, CI Basic Blue, CI Basic Orange, CI Basic Violet, and CI Basic Black; direct dyes such as CI Direct Yellow, CI Direct Red, CI Direct Blue, CI Direct Orange, CI Direct Violet, and CI Direct Black; reactive dyes such as CI Reactive Yellow, CI Reactive Red, CI Reactive Blue, CI Reactive Orange, CI Reactive Violet, and CI Reactive Black; and disperse dyes such as CI Disperse Yellow, CI Disperse Red, CI Disperse Blue, CI Disperse Orange, CI Disperse Violet, and CI Disperse Black. The above dyes may be used individually or in combination of two or more.

[0079] 1.1.2.2. Inorganic Oxide Particles The inorganic oxide particles are not particularly limited, but examples include silica, alumina, zirconia, titania, ceria, antimony oxide, tin oxide, tantalum oxide, zinc oxide, lead oxide, and indium oxide. Among these, it is preferable to include at least one selected from the group consisting of silica, alumina, zirconia, titania, and ceria. By using such inorganic oxide particles, curling of the resulting recordings is further suppressed and stackability is further improved. The inorganic oxide particles may be used alone or in combination of two or more types. The inorganic oxide particles are only required to contain at least one inorganic oxide within the particle. Preferably, the particles are made of inorganic oxide.

[0080] The inorganic oxide particles may be surface-treated. For example, silica may be surface-treated with alumina. This tends to expand the pH range in which silica can be stably dispersed and further improve dispersion stability.

[0081] As the silica described above, commercially available products can be used, for example, the cataloid series SI-45P, SI-80, SI-30P, and S-40 manufactured by JGC Catalysts & Chemicals Corporation, and Snowtex 20, Snowtex 30P, Snowtex 40, Snowtex O, Snowtex N, and Snowtex C manufactured by Nissan Chemical Industries, Ltd. Among the silicas described above, it is preferable to use SI-45P and / or SI-80 from the viewpoint of achieving the effects of the present invention more effectively and reliably.

[0082] The volume-average particle diameter of the inorganic oxide particles contained in the first ink is preferably 150 nm or less, more preferably 100 nm or less, and even more preferably 60 nm or less. Furthermore, the volume-average particle diameter of the inorganic oxide particles contained in the first ink is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 15 nm or more. When the average particle diameter of the inorganic oxide particles is 150 nm or less, the color development and clogging recovery tend to be further improved. Furthermore, when the average particle diameter of the inorganic oxide particles is 5 nm or more, the color difference unevenness and stacking tend to be further suppressed.

[0083] The volume-average particle diameter of the inorganic oxide particles contained in the second ink is preferably 150 nm or less, more preferably 100 nm or less, and even more preferably 60 nm or less. Furthermore, the volume-average particle diameter of the inorganic oxide particles contained in the second ink is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 15 nm or more. When the average particle diameter of the inorganic oxide particles is 150 nm or less, the color development and clogging recovery tend to be further improved. Furthermore, when the average particle diameter of the inorganic oxide particles is 5 nm or more, the color difference unevenness and stacking tend to be further suppressed.

[0084] The average particle size of inorganic oxide particles can be measured using a particle size distribution analyzer that employs dynamic light scattering as its measurement principle. An example of such a particle size distribution analyzer is the "Zeta Potential, Particle Size, and Molecular Weight Measurement System ELSZ2000ZS" (product name) manufactured by Otsuka Electronics Co., Ltd., which employs a homodyne optical system as its frequency analysis method. In this specification, "average particle size" refers to the average particle size based on the number of particles, unless otherwise specified.

[0085] The inorganic oxide particle content in the first ink is preferably 1.0 to 10% by mass, more preferably 1.5 to 8.0% by mass, and even more preferably 2.0 to 6.0% by mass, relative to the total amount of the first ink, as solid content. When the inorganic oxide particle content is 1.0% by mass or more, color difference uniformity and stackability tend to be further improved. Furthermore, when the inorganic oxide particle content is 10% by mass or less, color development and clogging recovery tend to be further improved.

[0086] The inorganic oxide particle content in the second ink is preferably 1.0 to 10% by mass, more preferably 1.5 to 8.0% by mass, and even more preferably 2.0 to 6.0% by mass, relative to the total amount of the second ink, as solid content. When the inorganic oxide particle content is 1.0% by mass or more, color difference uniformity and stackability tend to be further improved. Furthermore, when the inorganic oxide particle content is 10% by mass or less, color development and clogging recovery tend to be further improved.

[0087] 1.1.2.3.Water Preferably, one or both of the first and second inks are water-based inks. Water-based inks are inks that contain water as the main solvent component. The water content in water-based inks is preferably 40% by mass or more, more preferably 40 to 98% by mass, relative to the total amount of ink. Furthermore, it is preferably 45% by mass or more and 80% by mass or less, more preferably 50% by mass or more and 75% by mass or less, and even more preferably 55% by mass or more and 70% by mass or less. When the water content is 45% by mass or more, the increase in viscosity of the ink is suppressed even when some of the water evaporates, and clogging recovery tends to be further improved. Also, when the water content is 80% by mass or less, stackability tends to be further improved.

[0088] 1.1.2.4. Water-soluble organic solvents Preferably, one or both of the first and second inks contain a water-soluble organic solvent. The inclusion of a water-soluble organic solvent in the ink composition tends to further improve its shelf life.

[0089] The water-soluble organic solvent is not particularly limited, but examples include: polyols of triol or greater types such as glycerin; nitrogen-containing solvents such as 2-pyrrolidone and N-methylpyrrolidone; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, propanediol, butanediol, pentanediol, and 1,2-hexanediol; and glycol monoalkyl ethers such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, and triethylene glycol monomethyl ether. Among these, glycerin is preferred in terms of its moisturizing effect.

[0090] The content of the water-soluble organic solvent is preferably 0.5 to 25% by mass, more preferably 3.0 to 20% by mass, and even more preferably 5.0 to 15% by mass, relative to the total amount of ink. Having the water-soluble organic solvent content within the above range tends to further improve shelf life.

[0091] 1.1.2.5. Lactam compounds At least one or both of the first and second inks may contain a lactam compound. The inclusion of a lactam compound tends to improve the resolubility of inorganic oxide particles even if they aggregate, and to improve clogging recovery.

[0092] Lactam compounds are not particularly limited, but examples include 2-pyrrolidone, N-methyl-2-pyrrolidone, 1-(2-hydroxyethyl)-2-pyrrolidone, 3-methoxy-2-pyrrolidone, 3-acetoxy-2-pyrrolidone, 4-pentanelactam, and ε-caprolactam.

[0093] Lactam compounds are preferably water-soluble. Among lactam compounds, water-soluble compounds that are liquid at room temperature are also the water-soluble organic solvents mentioned above. Lactam compounds have three or more membered rings, preferably 3 to 9 membered rings, and preferably 5 to 8 membered rings.

[0094] The lactam compound content in the first ink is preferably 1.0 to 10% by mass, more preferably 1.5 to 8.0% by mass, and even more preferably 2.0 to 7.0% by mass, relative to the total amount of the first ink. Even more preferably, it is 4.0 to 6.0% by mass. Alternatively, it is preferably 3.0 to 5.0% by mass, and even more preferably 3.0 to 4.0% by mass. When the lactam compound content is within the above range, clogging recovery and color difference reduction tend to be further improved.

[0095] The lactam compound content in the second ink is preferably 1.0 to 10% by mass, more preferably 1.5 to 8.0% by mass, and even more preferably 2.0 to 7.0% by mass, relative to the total amount of the second ink. Even more preferably, it is 4.0 to 6.0% by mass. Alternatively, it is preferably 3.0 to 4.0% by mass, and even more preferably 3.0 to 4.0% by mass. When the lactam compound content is within the above range, clogging recovery and color difference reduction tend to be further improved.

[0096] 1.1.2.6. Resin Emulsion The mixture may further contain a resin emulsion. The resin emulsion is not particularly limited, but examples include (meth)acrylic resin emulsion and urethane resin emulsion. Using such a resin emulsion tends to further suppress image blurring and improve scratch resistance. The resin emulsion may be used alone or in combination of two or more types.

[0097] The acrylic resin emulsion is not particularly limited, but examples include those obtained by polymerizing (meth)acrylic monomers such as (meth)acrylic acid and (meth)acrylic acid esters, or those obtained by copolymerizing (meth)acrylic monomers with other monomers, such as styrene acrylic resin. Among these, anionic acrylic resin fine particles are preferred.

[0098] The urethane resin emulsion is not particularly limited as long as it is a resin emulsion having urethane bonds in its molecule, and examples include polyether-type urethane resins containing ether bonds in the main chain, polyester-type urethane resins containing ester bonds in the main chain, and polycarbonate-type urethane resins containing carbonate bonds in the main chain. Among these, anionic urethane resin fine particles are preferred.

[0099] The resin emulsion 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 3.0% by mass, relative to the total amount of the first ink, as solid content. When the resin emulsion content is 0.1% by mass or more, blurring of the resulting image is suppressed and scratch resistance tends to be further improved. Furthermore, when the resin emulsion content is 7.5% by mass or less, ejection stability tends to be further improved.

[0100] The resin emulsion 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 3.0% by mass, relative to the total amount of the second ink, as solid content. When the resin emulsion content is 0.1% by mass or more, blurring of the resulting image is suppressed and scratch resistance tends to be further improved. Furthermore, when the resin emulsion content is 7.5% by mass or less, ejection stability tends to be further improved.

[0101] 1.1.2.7. Surfactants One or both of the first and second inks may contain a surfactant. The surfactant is not particularly limited, but examples include acetylene glycol-based surfactants, fluorine-based surfactants, and silicone-based surfactants.

[0102] The acetylene glycol-based surfactant is not particularly limited, but for example, one or more selected from 2,4,7,9-tetramethyl-5-decine-4,7-diol and its alkylene oxide adduct, and 2,4-dimethyl-5-decine-4-ol and its alkylene oxide adduct are preferred. The acetylene glycol-based surfactant may be used alone or in combination of two or more.

[0103] Fluorine-based surfactants are not particularly limited, but examples include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphate esters, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl betaines, and perfluoroalkylamine oxide compounds. Note that fluorine-based surfactants may be used individually or in combination of two or more.

[0104] Examples of silicone-based surfactants include polysiloxane compounds and polyether-modified organosiloxanes. Silicone-based surfactants may be used individually or in combination of two or more types.

[0105] The surfactant content in the first ink is preferably 0.1 to 5.0% by mass, more preferably 0.1 to 2.0% by mass, and even more preferably 0.3 to 1.5% by mass, relative to the total mass of the first ink. When the surfactant content is within the above range, the clogging recovery performance tends to be further improved.

[0106] The surfactant content in the second ink is preferably 0.1 to 5.0% by mass, more preferably 0.1 to 2.0% by mass, and even more preferably 0.3 to 1.5% by mass, based on the total mass of the second ink. Furthermore, 0.5 to 1.3% by mass is preferred, and 0.7 to 1.0% by mass is even more preferred. When the surfactant content is within the above range, the clogging recovery performance tends to improve further. Furthermore, the reduction of color difference is excellent and desirable.

[0107] 1.1.2.8. pH adjusters Examples of pH adjusting agents are not particularly limited, but include inorganic acids (e.g., sulfuric acid, hydrochloric acid, nitric acid, etc.), inorganic bases (e.g., lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, etc.), organic bases (e.g., triethanolamine, diethanolamine, monoethanolamine, trippropanolamine), and organic acids (e.g., adipic acid, citric acid, succinic acid, etc.). Among these, organic bases are preferred. pH adjusting agents may be used individually or in combination of two or more.

[0108] The pH adjusting agent content in the first ink is preferably 0.1 to 2.0% by mass, more preferably 0.1 to 1.5% by mass, and even more preferably 0.1 to 1.0% by mass, relative to the total mass of the first ink. When the pH adjusting agent content is within the above range, the clogging recovery performance tends to be further improved.

[0109] The pH adjusting agent content in the second ink is preferably 0.1 to 2.0% by mass, more preferably 0.1 to 1.5% by mass, and even more preferably 0.1 to 1.0% by mass, relative to the total mass of the second ink. When the pH adjusting agent content is within the above range, the clogging recovery performance tends to be further improved.

[0110] 1.1.3. Recording media The recording medium is not particularly limited, but examples include absorbent recording media, low-absorbent recording media, and non-absorbent recording media. Among these, absorbent recording media and low-absorbent recording media are preferred, and absorbent recording media are more preferred. The present invention is particularly useful because the higher the absorbency, the more likely it is that differences in penetration will occur due to differences in the distance between nozzles.

[0111] Here, "low-absorption recording medium" or "non-absorbent recording medium" refers to a recording medium in which the amount of water absorbed from the start of contact to 30 msec in the Bristow method is 10 mL / m². 2 The following refers to the recording medium. The Bristow method is the most widely used method for measuring liquid absorption in a short time and is also adopted by the Japan Paper & Pulp Technology Association (JAPAN TAPPI). Details of the test method are described in standard No. 51 "Paper and cardboard - Liquid absorbency test method - Bristow method" of the "JAPAN TAPPI Paper & Pulp Test Methods 2000 Edition".

[0112] Furthermore, the low-absorption recording medium has a water absorption capacity of 5 mL / m². 2 More than 10mL / m 2 The following refers to recording media. On the other hand, the absorbent recording media has a water absorption capacity of 10 mL / m³. 2 It refers to a recording medium that is extremely high in quality.

[0113] Absorbent recording media are not particularly limited, but examples include ordinary paper such as electrophotographic paper with high ink permeability, inkjet paper (inkjet-specific paper equipped with an ink-absorbing layer composed of silica particles or alumina particles, or an ink-absorbing layer composed of a hydrophilic polymer such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP)), and cloth.

[0114] Low absorption recording media are not particularly limited, but examples include coated paper having a coating layer on its surface for receiving oil-based ink. Coated paper is not particularly limited, but examples include printing paper such as art paper, coated paper, and matte paper.

[0115] Examples of non-absorbent recording media include, but are not limited to, films and plates of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, and polyurethane; plates of metals such as iron, silver, copper, and aluminum; metal plates or plastic films made by vapor deposition of these metals; plates of alloys such as stainless steel and brass; and recording media in which films of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, and polyurethane are bonded (coated) to a paper substrate.

[0116] 2.2. Conveying Process The recording method of this embodiment may further include a transport step. In the transport step, the recording medium is transported in a predetermined direction within the recording device. More specifically, the recording medium is transported from the paper feed section to the paper discharge section of the recording device using transport rollers or a transport belt provided within the recording device. During this transport process, ink ejected from the inkjet head adheres to the recording medium, forming a recorded material. The transport may be performed continuously or intermittently.

[0117] 2. Recording device The recording device of this embodiment comprises a line head having a length greater than or equal to the recording width of the recording medium, a first ink and a second ink, wherein the line head has a plurality of unit heads arranged in the direction of the recording width of the recording medium, and has a portion where the distance between the nozzles of the first nozzle that ejects the first ink and the second nozzle that ejects the second ink in the scanning direction is different, and the first ink and the second ink contain a colorant and inorganic oxide particles, and the composition of the colorant is different from that of the other.

[0118] The recording device of this embodiment may further include a transport means for transporting the recording medium. The transport means may consist of, for example, transport rollers or a transport belt provided inside the recording device. [Examples]

[0119] The present invention will be described more specifically below using examples and comparative examples. The present invention is not limited in any way by the following examples.

[0120] 1. Ink preparation Each example of inkjet ink was obtained by placing the components into a mixing tank to achieve the composition shown in Table 1, mixing and stirring, and then filtering through a 5 μm membrane filter. Unless otherwise specified, the numerical values ​​for each component in the table represent mass percent. Furthermore, in the table, the numerical values ​​for inorganic oxide colloids and pigment dispersions represent mass percent of the solid content.

[0121] [Table 1]

[0122] [Table 2]

[0123] The abbreviations and product ingredients used in Table 1 are as follows:

[0124] [Pigment dispersion] Cyan pigment (CAB-O-JET450C (manufactured by Cabot Corporation)) Yellow pigment (CAB-O-JET470Y (manufactured by Cabot)) [Inorganic oxide particles] Colloidal silica (Cataloid SI-30 (D50=11nm), manufactured by JGC Catalysts & Chemicals Co., Ltd.) Colloidal silica (Cataloid SI-45 (D50=45nm), manufactured by JGC Catalysts & Chemicals Co., Ltd.) [Water-soluble organic solvents] Glycerin Triethylene glycol Triethylene glycol monobutyl ether Triethylene glycol monomethyl ether 1,2-Hexanediol [Lactam compounds] 2-Pyrrolidone 1-(2-hydroxyethyl)-2-pyrrolidone ε-caprolactam [Resin emulsion] Styrene-acrylic resin emulsion (manufactured by Seikoh PMC, X-436, Tg: 33℃, acid value 33 mg KOH / g) [Surfactants] Olphine E1010 (product name manufactured by Air Products, acetylene glycol-based surfactant) Surfinol 104 (product name manufactured by Nisshin Chemical Industry Co., Ltd., acetylene glycol-based surfactant) Olphine EXP4300 (product name manufactured by Air Products, acetylene glycol-based surfactant) [pH adjuster] Triethanolamine

[0125] 2. Evaluation 2.1. Uneven color difference A Seiko Epson LX-10050MF was modified to create a line printer equipped with the line heads H1 to H4 listed in Table 1, and the two inks listed in Table 1 were filled to enable ejection. Cyan ink was filled into the nozzle (first nozzle) of one nozzle row of the first unit head, and yellow ink was filled into the nozzle (second nozzle) of one nozzle row of the second unit head. Then, the two inks were layered and recorded onto plain paper (Xerox P paper). Each ink was used to ensure a dot was attached to each pixel, with an ink deposition rate of 6 ng / dot and a recording resolution of 600 x 2400 dpi. The recording medium transport speed was set to 600 mm / s.

[0126] However, due to the low nozzle density in the width direction of the H3 head, the recording resolution was limited to 300 x 2400 dpi. Furthermore, in Example 11, the transport speed of the recording medium was set to 300 mm / s, resulting in differences in the inter-color distance and other parameters compared to Example 1.

[0127] The configuration of line heads H1 to H4 is as follows: Line head H1: A line head having the nozzle surface 11 shown in Figure 2C. Apparent nozzle density in the width direction is 600 npi. Line head H2: A line head having the nozzle surface 11 shown in Figure 3C. Apparent nozzle density in the width direction is 600 npi. Line head H3: A line head having the nozzle surface 11 shown in Figure 2A. Nozzle density in the width direction is 300 npi. Line head H4: A line head that has a greater tilt relative to the width direction of the head than line head H1, and a larger difference in the distance between the first nozzle and the second nozzle.

[0128] Each line head has two rows of nozzles in the scanning direction, as shown in the figure, but only the upper nozzle row was used. The nozzle density in the width direction of the nozzle row was 300 npi, and the number of nozzles in the nozzle row was 300. In addition, the number of nozzles in one joint 13 was set to 5 per nozzle row of one unit head. Furthermore, at the joint 13, when recording dots in the scanning direction with nozzles whose positions overlap in the width direction, the nozzles of one unit head 12a and the nozzles of the other unit head 12a were used alternately. This reduced density unevenness.

[0129] Furthermore, when the first nozzle of the first unit head 12a at the lower part of the diagram is used at the joint 13 of the line head H2, the second nozzle at the same position in the width direction of the diagram uses the second nozzle of the second unit head 12b at the lower part of the diagram. When the first nozzle of the first unit head 12a at the upper part of the diagram is used, the second nozzle at the same position in the width direction of the diagram uses the second nozzle of the second unit head 12b at the upper part of the diagram. In this way, there is no difference in the distance between nozzles at the joint 13.

[0130] In Table 3, the difference in inter-color distance is the difference in nozzle distance (Lmax-Lmin). The difference in inter-color time difference is the difference in impact time (Imax-Imim).

[0131] In the green portion of the recorded material, which is composed of cyan and yellow as described above, the color was measured at both the long and short nozzle distances, and the color difference ΔE was calculated. Head H2 does not have long and short nozzle distances, so the color was measured at appropriate positions. (Evaluation Criteria) A: ΔE is less than 2 B: ΔE is 2 or greater and less than 4 C:ΔE is 4 or greater and less than 6 D:ΔE is 6 or greater

[0132] 2.2. Color development In the green portion of the recorded material obtained as described above, composed of cyan and yellow, the area with the highest density in the width direction D2 was measured using a colorimeter (Xrite i1, manufactured by Xrite Corporation), and the OD value of that area was obtained. Based on the obtained OD value, the color development was evaluated according to the following evaluation criteria. (Evaluation Criteria) A: OD value exceeds 1.0 B:OD value greater than 0.95 and less than or equal to 1.0 C:OD value greater than 0.90 and less than or equal to 0.95 D:OD value is 0.9 or less

[0133] 2.3. Clogging recovery In the ink cartridges of the inkjet recording device used for evaluating color difference unevenness, ink was filled and it was confirmed that ink could be ejected from all nozzles. Subsequently, the inkjet head was misaligned from the position of the cap on the printer, and the head was left uncapped for 7 days in a 40°C environment.

[0134] After a period of inactivity, the inkjet head was cleaned by performing an ink suction operation to remove ink from the nozzles. The number of nozzles unable to eject ink was counted after each operation, and the cleaning process was repeated until all nozzles recovered. The clogging recovery performance was then evaluated based on the number of cleaning cycles required to recover all nozzles, according to the following evaluation criteria. The results are shown in Table 1.

[0135] (Evaluation Criteria) AA: Fully restored in one cleaning. A: Fully restored in 2-3 cleanings. B: Fully restored after 4-5 cleanings. C: Fully restored after 6 or more cleanings.

[0136] 2.4. Stackability Using the inkjet recording device used for evaluating color difference uniformity, 20 sheets were printed continuously, and the stackability when the sheets were ejected in stacks on the output tray was evaluated according to the following evaluation criteria. (Evaluation Criteria) A: They are neatly arranged so that you can staple them together (they fit together and the edges of the paper are neatly aligned). B: 20 ​​sheets can be stacked, but they don't line up (they fit inside, but the edges of the paper don't align). C: Cannot stack 20 discs (they will fall out of the tray)

[0137] [Table 3]

[0138] 3. Evaluation Results From the reference example, it was found that when using line head H2, which does not have a section where the distance between the first nozzle that ejects the first ink and the second nozzle that ejects the second ink is different, the problem of uneven color difference does not occur. On the other hand, it was also found that the line head H2 used in the reference example has many gaps, making miniaturization difficult.

[0139] Furthermore, a comparison of the examples and comparative examples revealed that even when using a head with different distances between the first nozzle that ejects the first ink and the second nozzle that ejects the second ink, color unevenness can be suppressed by using an ink composition containing inorganic oxide particles. [Explanation of Symbols]

[0140] 10...Line head, 11...Nozzle surface, 12...Unit head, 12'...Unit, 12a...First unit head, 12b...Second unit head, 13...Joint, 14...Gap, 100...Recording device, D1...Scanning direction, D2...Width direction, L...Distance, Lmax...Distance, Lmin...Distance, M...Recording medium

Claims

1. The system includes an ejection process in which a first ink and a second ink are ejected from a line head having a length greater than the recording width of the recording medium and deposited onto the recording medium. The line head has a plurality of unit heads arranged in the direction of the recording width of the recording medium, The unit head is positioned such that its longitudinal direction intersects the width direction of the line head at an angle, The first nozzle for ejecting the first ink and the second nozzle for ejecting the second ink are located in positions that overlap each other in the direction of the recording width, and have portions where the distance between the first nozzle and the second nozzle in the scanning direction is different. The first nozzle and the second nozzle, whose positions in the recording width direction overlap each other, are included in separate unit heads. The group of first nozzles that eject the first ink of the unit head to which the first nozzle belongs, and the group of second nozzles that eject the second ink of the unit head to which the second nozzle belongs, are positioned so that their positions in the direction of the recording width overlap with each other, and their positions in the direction of the recording width are partially different. The first ink and the second ink each contain a colorant and inorganic oxide particles, and the composition of the colorant is different from that of the first ink. In the line head, the pairs of the first nozzle and the second nozzle, whose positions in the recording width direction overlap with each other, are all in the same order in the scanning direction. Recording method.

2. The portion where the nozzle distance differs is the portion where the nozzle distance between the first nozzle and the second nozzle, which are located in positions that overlap each other in the direction of the recording width, is long and the nozzle distance between the first nozzle and the second nozzle is short in the scanning direction, and the nozzle distance differs in that portion. The recording method according to claim 1.

3. The amount of inorganic oxide particles contained in the first ink is 1.0 to 10% by mass relative to the total amount of the first ink. The amount of inorganic oxide particles contained in the second ink is 1.0 to 10% by mass relative to the total amount of the second ink. The recording method according to claim 1 or 2.

4. The volume-average particle diameter of the inorganic oxide particles contained in the first ink is 100 nm or less. The volume-average particle diameter of the inorganic oxide particles contained in the second ink is 100 nm or less. The recording method according to any one of claims 1 to 3.

5. The first ink comprises a lactam compound, The second ink contains a lactam compound, The recording method according to any one of claims 1 to 4.

6. The amount of the lactam compound contained in the first ink is 1.0 to 10% by mass relative to the total amount of the first ink. The amount of the lactam compound contained in the second ink is 1.0 to 10% by mass relative to the total amount of the second ink. The recording method according to claim 5.

7. The first ink contains a surfactant, The second ink contains a surfactant, The amount of the surfactant contained in the first ink is 0.1 to 2.0% by mass relative to the total amount of the first ink. The amount of the surfactant contained in the second ink is 0.1 to 2.0% by mass relative to the total amount of the second ink. The recording method according to any one of claims 1 to 6.

8. In the portion where the distance between nozzles differs, the difference in the distance between nozzles is 5 to 80 mm. The recording method according to any one of claims 1 to 7.

9. The scanning speed of the recording medium is 600 mm / s or less. The recording method according to any one of claims 1 to 8.

10. The inorganic oxide particles contained in the first ink and the second ink include at least one selected from the group consisting of silica, alumina, zirconia, titania, and ceria. The recording method according to any one of claims 1 to 9.

11. The first ink and the second ink are water-based inks. The recording method according to any one of claims 1 to 10.

12. The first ink and the second ink are chromatic inks. The recording method according to any one of claims 1 to 11.

13. The recording medium is an absorbent recording medium. A recording method according to any one of claims 1 to 12.

14. A recording device that performs recording using the recording method described in any one of claims 1 to 12, The line head having a length greater than or equal to the recording width of the recording medium, The invention comprises the first ink and the second ink, Recording device.

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