JP2010188702A - Image forming method, image forming apparatus, quality improving method for image, and black ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method by which the images of a high grade wherein bleeding or white mist, and in addition, color unevenness are suppressed can be formed even in a high-speed recording method such as single pass reciprocating recording. <P>SOLUTION: This image forming method has a process in which an image is formed by imparting a pigment black ink 1100 containing a pigment 1101 and a dye black ink 1300 in random order in such a manner that at least certain parts of them may be overlapped on a recording medium 1000. In this case, the dye black ink 1300 contains a reactive content 1202 which makes the dispersed state of the pigment 1101 unstable, and a dye 1301, and also, has a lower surface tension than that of the pigment black ink. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image recording method, an image recording apparatus, an image quality improving method, and a black ink used in these methods.

  Conventionally, inks for writing instruments (fountain pens, sign pens, water-based ballpoint pens, etc.) and inks used for ink jet recording methods can provide recorded products with high image density and excellent fastness. (Pigment ink) is used. Especially in recent years, in order to record well on various plain papers such as copy papers commonly used in offices, report papers, notebooks, notepaper, bond papers, continuous slip papers, etc. Many studies have been conducted. Regarding pigments, for example, there are proposals relating to pigment inks containing carbon black and a dispersant, and pigment inks containing self-dispersing carbon black that can disperse the pigment without using a dispersant (Patent Documents 1 to 3). reference).

  In an ink jet recording method aiming to achieve both character quality and full-color image quality, the pigment ink as described above is used as black ink and is used in combination with other color inks to form an image. Specific examples of the color ink include at least one selected from magenta ink, cyan ink, yellow ink, red ink, green ink, and blue ink.

  The following are known as problems that occur when a full-color image is formed. For example, there may be a phenomenon (bleeding) in which bleeding occurs at the boundary between an image formed with black ink and an image formed with color ink. In addition, uneven white unevenness (white haze) may occur in an image formed with black ink. Further, image quality may be deteriorated due to bleeding or white haze. For this reason, as a typical technique for suppressing such bleeding and white haze, a color ink having reactivity with the components in the black ink is applied to the area where the image is formed with the black ink. A recording method is disclosed (see Patent Documents 4 and 5).

  However, when the color ink having reactivity as described above and the black ink containing the pigment are applied to the recording medium in an overlapping manner, the color tone of the obtained image may depend on the order in which these inks are applied to the recording medium. May occur, that is, color unevenness may occur. In order to suppress this color unevenness, an ink set having a black ink containing a pigment and a salt, and a color ink containing a component destabilizing the dispersion state of the pigment, and image recording using such an ink set There are proposals regarding the method (see Patent Documents 6 and 7).

  In an image forming method or an image forming apparatus that performs recording using a plurality of inks, a plurality of inks having different surface tensions may be used. For example, in order to obtain sharp character quality, black ink is required to give an image having a higher image density than other color inks. For this reason, it is a common practice to design inks so that the surface tension is higher than other color inks (see Patent Document 8).

JP 63-152681 A JP-A 64-6074 JP-A-8-3498 Japanese Patent Laid-Open No. 11-343441 JP 2004-115549 A JP 2001-150793 A JP 2001-152059 A JP 2003-96371 A

  The present inventors have disclosed a recording method in which a color ink having reactivity with components in the black ink is applied to a region to be recorded with a black ink containing a pigment as described in Patent Documents 4 and 5 We examined about again. As a result, it was confirmed that according to the recording method, an effect of suppressing bleeding and an effect of suppressing white haze in an image formed with the black ink were obtained. However, on the other hand, it has been confirmed that an image formed by using the recording method has a problem that color unevenness occurs.

  Further, the present inventors have disclosed a black ink containing a pigment and a salt as described in Patent Documents 6 and 7, and a color ink containing a component that destabilizes the dispersion state of the pigment in the black ink. And an image recording method using the ink set. As a result, it was confirmed that according to the ink set and the image recording method, an effect of suppressing color unevenness in the recorded image can be obtained.

  In recent years, one-pass reciprocal recording has been studied as an inkjet recording method in order to shorten the recording time. This recording method includes a method of recording in both the forward and backward directions of the main scanning of the recording head (reciprocal recording), and a method of recording an image having the same width as the length of the recording head in one main scanning (1 (Pass recording). By using this one-pass reciprocal recording, the recording time can be greatly shortened.

  However, as a result of studying the application of the techniques described in Patent Documents 6 and 7 to 1-pass reciprocal recording, the present inventors may not sufficiently suppress the color unevenness as described above. I found out. Specifically, in the one-pass reciprocal recording, the next ink is applied before the previously applied ink penetrates the recording medium and the ink components are evaporated. For this reason, ink droplets contact each other in a liquid state on the recording medium, and it has been newly found that color unevenness may not be sufficiently suppressed even when the above technique is used.

  In other words, in the techniques described in Patent Documents 6 and 7, when black ink containing a pigment and color ink that reacts with the ink are recorded in an overlapping manner, depending on the recording conditions, color unevenness may be sufficient. In some cases, the suppression effect may not be obtained. In particular, when the surface tension of black ink is greater than the surface tension of color ink, color unevenness may not be sufficiently suppressed if each ink is applied to the recording medium in the order of color ink and then black ink. . Specifically, when recording is performed in this way, the area recorded with black ink is affected by the hue of the color ink, and color unevenness may be particularly noticeable.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming method, an image forming apparatus, an image quality improving method, and a black ink used in these for forming an image excellent in bleeding and white haze. Another object of the present invention is to provide an image forming method, an image forming apparatus, an image quality improving method, and an image forming method for forming an image with suppressed color unevenness even in a high-speed recording method such as one-pass reciprocal recording. Another object of the present invention is to provide a black ink to be used in the above. Furthermore, another object of the present invention is to provide an image forming method, an image forming apparatus, an image quality improving method, and a black ink used in the image forming method for forming an image satisfying these objects and satisfying the coloring property. There is to do.

  The above object is achieved by the present invention described below. That is, the present invention includes a pigment black ink containing a pigment, a dye black ink containing a reactive component and a dye that destabilizes the dispersion state of the pigment, and having a surface tension lower than that of the pigment black ink, The image forming method is characterized in that the image forming method includes a step of forming images on the recording medium in a random order so that at least a part thereof is overlapped.

  Another embodiment of the present invention includes a recording head for ejecting a pigment black ink containing a pigment, a reactive component and a dye that destabilize the dispersion state of the pigment, and the pigment black A recording head for ejecting a dye black ink having a surface tension lower than that of the ink, and a method for forming an image by applying the pigment black ink and the dye black ink to a recording medium so as to overlap at least partially in any order. And an image forming apparatus.

  Another embodiment of the present invention includes a pigment black ink containing a pigment, a reactive component and a dye that destabilizes the dispersion state of the pigment, and a pigment black ink on the recording medium. In this method, the dye black ink having a low surface tension is applied in random order so that at least a part thereof overlaps on the recording medium, thereby improving the image quality of the part where the inks overlap.

  Another embodiment of the present invention is used in an inkjet recording apparatus that forms a black image by applying a pigment black ink containing a pigment in each of reciprocating scans in which a recording head is moved relative to a recording medium. A black ink that is applied in each of reciprocating scans when forming the black image so that at least a part of the pigment black ink overlaps the recording medium, and the dispersion state of the pigment contained in the black ink is A black ink comprising a destabilizing reactive component and a black dye and having a surface tension lower than that of the black ink.

  According to the present invention, it is possible to provide an image forming method, an image forming apparatus, an image quality improving method, and a black ink used for these, which form an image with excellent bleeding and white haze. In addition, according to the present invention, an image forming method, an image forming apparatus, an image quality improving method, and an image forming method for forming an image with suppressed color unevenness, even in a high-speed recording method such as one-pass reciprocal recording Black ink can be provided. According to the present invention, it is possible to provide an image forming method, an image forming apparatus, an image quality improving method, and a black ink used in these, which satisfy these requirements and satisfy the coloring property.

FIG. 4 is a conceptual diagram when ink is applied to a recording medium in the order of pigment black ink and reactive color ink. FIG. 4 is a conceptual diagram when ink is applied to a recording medium in the order of reactive color ink and pigment black ink. FIG. 3 is a conceptual diagram when ink is applied to a recording medium in the order of pigment black ink and reactive black ink. FIG. 3 is a conceptual diagram when ink is applied to a recording medium in the order of reactive black ink and pigment black ink. It is the schematic which shows an example of an inkjet recording device. FIG. 3 is a schematic diagram illustrating an example of a recording head cartridge.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments of the present invention. The surface tension is a value measured at room temperature (25 ° C.), and the unit is mN / m.
Here, the reason why the present inventors have found a means for solving the above-mentioned problems is as follows. As a result of intensive studies by the present inventors, it has been found that when an image is formed by overlaying black ink and color ink, the difference in surface tension between black ink and color ink makes color unevenness remarkable. . First, as described above, generally, a black ink is required to have a higher image density than other color inks, so that the surface tension is designed to be higher than that of other color inks. This is to make the best use of the required performance, which differs depending on the color, such that black has the highest priority on image density and other colors have the highest priority on bleeding suppression between different colors.

  However, the present inventors have found that the following phenomenon occurs in such a case. That is, when inks having different surface tensions are brought into contact with each other, it has been confirmed that a phenomenon occurs in which ink having a relatively low surface tension pulls ink having a relatively high surface tension. That is, when black ink is recorded first and color ink is recorded later, before the black ink is fixed on the recording medium, the black ink having a relatively high surface tension is replaced with the color ink having a relatively low surface tension. Be pulled into. Then, the color ink quickly and uniformly spreads and spreads on the black ink. As a result, the color ink and the black ink in a uniformly mixed state are fixed on the recording medium, and visually, a black image with only the black ink that is hardly affected by the color ink is visually observed. Remains.

  On the other hand, when the color ink is recorded first and the black ink is recorded later, the black ink having a relatively high surface tension is pulled into the color ink having a relatively low surface tension, and the black ink is not on the color ink. It does not spread so much and does not spread. For this reason, the color ink and the black ink in a non-uniformly mixed state are fixed on the recording medium, and visually, a black image having the color ink color remains. In other words, when an image is formed by applying black ink and color ink with different surface tensions in random order, a black image with a color of only black ink and a black image with a color of color ink are mixed. As a result, color unevenness occurs.

  Further, as a result of investigations by the present inventors, the phenomenon as described above can be seen even when black ink and a reactive color ink that reacts with components in the black ink are used depending on conditions. I understood. In this case, by using a reactive color ink containing a component that destabilizes the dispersion state of the colorant in the black ink, the black ink expresses a higher image density when recorded over the black ink. Therefore, uneven color tends to be reduced. However, even in this case, it is insufficient from the recent requirement level. Also, in recent years, due to a demand for an improvement in recording speed, the next ink is applied before the previously applied ink reaches the paper and permeates or evaporates, such as 1-pass reciprocal recording. In other words, a higher-speed recording method in which ink droplets come into contact with each other at the liquid-liquid interface has been studied. And when using for such a recording method, it turned out that it is difficult to suppress color nonuniformity only by the above-mentioned prior art.

  In order to meet these particularly demanding requirements, the present inventors have continued to further study. As a result, when a plurality of inks having different surface tensions are overlaid, it has been found that the same color ink can be overlaid to reduce a change in color and suppress uneven color. .

  The present invention found by the above-described circumstances is as follows. That is, one aspect of the present invention includes a pigment black ink containing a pigment, a reactive component that destabilizes the dispersion state of the pigment, and a dye on a recording medium, and a surface that is more surface than the pigment black ink. This is a method for improving image quality using a dye black ink having a low tension. Then, these inks are applied in random order so that at least a part of them overlaps, and the quality of the image where the inks overlap is improved.

<Image forming method>
The image forming method of the present invention embodying the above-described image quality improving method of the present invention is as follows. That is, the pigment black ink containing the pigment and the dye black ink containing a reactive component and a dye that destabilizes the dispersion state of the pigment and having a lower surface tension than the pigment black ink are at least partially overlapped in any order. In this way, an image is formed by giving the image. Hereinafter, the image forming method of the present invention will be described in detail.

  Here, in the following description, a pigment black ink containing a pigment is referred to as a “pigment black ink”. A dye black ink containing a reactive component and a dye that destabilizes the dispersion state of the pigment and having a surface tension lower than that of the pigment black ink is referred to as “reactive black ink”. A color ink containing a reactive component that destabilizes the dispersion state of the pigment in the pigment black ink is referred to as “reactive color ink”. A reactive component that destabilizes the dispersion state of the pigment contained in the reactive black ink and the reactive color ink is referred to as a “reactive component”.

  In addition, the reactive component in the present invention refers to a component that causes insolubility of the color material, dispersion breakage, increase in the viscosity of the ink, and the like when the amount of this component contained in the reactive black ink is applied to the pigment black ink. . In addition, the content of the reactive component in the reactive black ink only needs to include an amount that causes insolubility of the coloring material, dispersion breakage, increase in viscosity, and the like when applied to the pigment black ink. Specifically, the content is preferably 0.01% by mass or more and less than 50.0% by mass based on the total mass of the reactive black ink.

  In the present invention, it is preferable that the pigment black ink and the reactive black ink have colors that are determined to be similar when the image formed with each ink is visually confirmed. Specifically, it is preferable that the absolute value of the difference in brightness in the CIELab color space measured for each ink obtained by diluting the pigment black ink and the reactive black ink 2,000 times with pure water is preferably within 20 It is. In particular, the absolute value of the difference in brightness is preferably 0 or more and 20 or less. In addition, although the brightness in CIELab color space can be measured with a general apparatus, in the Example mentioned later, it measured using the ultraviolet visible spectrophotometer L-4200 (made by Hitachi, Ltd.).

  In the present invention, the pigment black ink is preferably a so-called overlay ink having relatively low permeability to a recording medium in order to obtain sharp character quality and high image density. Specifically, the surface tension of the pigment black ink is preferably in the range of 30 mN / m to 50 mN / m. In the present invention, the reactive black ink is preferably a so-called penetrating ink having relatively high permeability to a recording medium in order to suppress bleeding between color inks. Specifically, the surface tension of the reactive black ink is preferably in the range of 20 mN / m to 40 mN / m. Furthermore, in order to obtain the effect of the present invention, the surface tension of the reactive black ink is adjusted to be smaller than the surface tension of the pigment black ink. Specifically, the surface tension of the reactive black ink is preferably adjusted to be smaller than the surface tension of the pigment black ink in the range of 5 mN / m to 10 mN / m.

  In the image forming method of the present invention, the step of applying each ink to the recording medium is specifically performed in any order. First, the reactive black ink is applied to at least a part of the recording medium where the pigment black ink is to be applied, and then the pigment black ink is applied to at least a part of the region to which the reactive black ink is applied. If you want to. Further, there is a case where a pigment black ink is applied to at least a part of the area of the recording medium, and then a reactive black ink is applied to at least a part of the area where the pigment black ink is applied.

  In this case, the amount of each ink applied is preferably 2/100 or more and 50/100 or less based on the mass of the amount of the reactive black ink applied relative to the amount of the pigment black ink applied. That is, when the application amount of the pigment black ink is 100, the application amount of the reactive black ink is preferably 2 or more and 50 or less. The reason why the application amount of each ink is preferably in the above range is as follows. This is because if the amount of reactive black ink applied is less than the above range relative to the amount of pigment black ink applied, the effects of the present invention may not be sufficiently obtained. Further, when the amount of the pigment black ink applied is larger than the above-mentioned range with respect to the amount of the reactive black ink applied, new bleeding may occur and the image quality may be lowered.

  In the present invention, the occurrence of color unevenness can be suppressed even when recording is performed at a high speed, such as 1-pass reciprocal recording, by the image forming method configured as described above. In other words, in order to suppress bleeding, when the pigment black ink and the reactive black ink are applied in an overlapping manner, the color unevenness caused by the difference in the order in which the pigment black ink and the reactive black ink are applied is reduced. Can be made. The reason why such an effect can be obtained is not clearly clear, but as a result of investigations by the present inventors, it is considered that it is due to the mechanism described below.

[Mechanism of image formation in conventional image forming method]
In estimating the reason why the effect of the present invention can be obtained, first, when a reactive black ink is not used, that is, a conventional image formation in which an image is formed by applying only a black pigment ink and a reactive color ink. A method will be described. Here, as an example, the case where the order in which the pigment black ink and the reactive color ink are applied in the one-pass reciprocal recording is different between the forward recording and the backward recording will be considered with reference to FIGS. 1 and 2.

  In the following discussion, each ink is assumed to have a general configuration as shown below. That is, the reactive color ink and the reactive black ink have a relatively lower surface tension than that of the pigment black ink in order to suppress the ink fixability and the occurrence of bleeding between the color inks of the respective colors. It is assumed that the sex will be relatively large. In addition, the pigment black ink assumes that the surface tension is relatively higher than that of the reactive color ink and the reactive black ink and the permeability to the recording medium is relatively reduced in order to improve the character quality. .

(1) A case where ink is applied to a recording medium in the order of pigment black ink and reactive color ink in forward recording.
FIG. 1 is a conceptual diagram when ink is applied to a recording medium in the order of pigment black ink and reactive color ink. First, when the pigment black ink is applied to the recording medium (1000), the pigment black ink (1100) covers the recording medium (1000) as shown in FIG. The pigment black ink has a characteristic that the penetration into the recording medium is relatively slow. Thereafter, the pigment (1101) in the pigment black ink (1100) starts to aggregate on the surface of the recording medium (1000), and the aqueous medium (1102) in the pigment black ink (1100) starts to penetrate into the recording medium. . Here, when the reactive color ink (1200) containing the dye (1201) and the reactive component (1202) is applied over the pigment black ink, the pigment black ink having a relatively high surface tension has a relatively high surface tension. Is pulled into a low reactive color ink. Then, as shown in FIG. 1B, the reactive color ink (1200) spreads and diffuses quickly and uniformly in the pigment black ink layer on the recording medium. At this time, due to the action of the reactive component (1202) in the reactive color ink, the aggregation of the pigment (1101) on the recording medium (1000) proceeds rapidly and uniformly, and as shown in FIG. Are uniformly distributed near the surface of the recording medium (1000). As a result, a uniform image is obtained. In addition, some of the dye (1201) in the reactive color ink (1200) may be present inside the pigment layer fixed near the surface of the recording medium, but the black pigment is uniformly distributed. Therefore, visual contribution to optical density is small.

(2) The case where ink is applied to the recording medium in the order of reactive color ink and pigment black ink in reverse recording.
FIG. 2 is a conceptual diagram when ink is applied to a recording medium in the order of reactive color ink and pigment black ink. First, when the reactive color ink (1200) is applied to the recording medium (1000), as shown in FIG. 2 (d), the reactive color ink having the characteristic of being easily penetrated into the recording medium is the recording medium (1000). It penetrates into the inside (1203). Thereafter, when the pigment black ink (1100) containing the pigment (1101) is applied to the reactive color ink (1200) in an overlapping manner, the pigment black ink having a relatively high surface tension is reactive with a relatively low surface tension. Pulled into color ink. At this time, as shown in FIG. 2 (e), the pigment black ink (1100) does not spread so much and hardly diffuses in the layer of the reactive color ink (1200) previously applied. At the same time, the pigment (1101) in the pigment black ink (1100) starts to agglomerate rapidly due to the action of the reactive component (1202). However, the contact area between the reactive component (1202) and the pigment black ink (1100) is smaller than in the case of (1) above, and the reactive component (1202) is contained in the pigment black ink (1100). The pigment aggregates non-uniformly because it hardly diffuses. As a result, as shown in FIG. 2F, the pigment (1101) is present in a non-uniform distribution on the recording medium (1000). Of the non-uniform distribution of the pigment, the portion where the pigment distribution is particularly small becomes an image that looks whitish. In this portion, a part of the dye in the reactive color ink fixed on the recording medium is visible, so that the visual Therefore, the image becomes uneven.

  As described above, in the conventional image forming method in which an image is formed by applying the pigment black ink and the reactive color ink in an overlapping manner, the recording of the above (1) and (2) is repeated, and a uniform image is obtained. Since nonuniform images are alternately formed for each recording, color unevenness occurs. In the recordings (1) and (2) described above, even if the order of applying the inks to the recording medium is reversed, color unevenness occurs due to the same mechanism. In other words, color unevenness occurs even when an image is formed by applying each ink to the recording medium in the order of reactive color ink and pigment black ink in forward recording, and in the order of pigment black ink and reactive color ink in backward recording. To do.

[Mechanism of image formation in the case of the image forming method of the present invention]
Next, the image forming method of the present invention will be described with examples. Here, as an example, the image forming method of the present invention for forming an image by superimposing pigment black ink and reactive black ink on one-pass reciprocal recording will be described. First, as (3), a case where ink is applied to a recording medium in the order of pigment black ink and reactive black ink in forward recording will be considered with reference to FIG. Further, as (4), a case where ink is applied to a recording medium in the order of reactive black ink and pigment black ink in reverse recording will be considered with reference to FIG.

(3) A case where ink is applied to a recording medium in the order of pigment black ink and reactive black ink in forward recording.
FIG. 3 is a conceptual diagram when ink is applied to a recording medium in the order of pigment black ink and reactive black ink. First, when the pigment black ink is applied to the recording medium (1000), the pigment black ink (1100) covers the recording medium (1000) as shown in FIG. The pigment black ink has a characteristic that the penetration into the recording medium is relatively slow. Thereafter, the pigment (1101) in the pigment black ink (1100) starts to aggregate on the surface of the recording medium (1000), and the aqueous medium (1102) in the pigment black ink (1100) starts to penetrate into the recording medium. . Here, when the reactive black ink (1300) containing the dye (1301) and the reactive component (1202) is applied over the pigment black ink, the pigment black ink having a relatively high surface tension has a relatively high surface tension. Is pulled into the low reactive black ink. Then, as shown in FIG. 3 (h), the reactive black ink (1300) spreads and diffuses quickly and uniformly in the layer of the pigment black ink (1100) on the recording medium. At this time, due to the action of the reactive component (1202) in the reactive black ink, the aggregation of the pigment (1101) on the recording medium (1000) proceeds rapidly and uniformly, and as shown in FIG. Are uniformly distributed near the surface of the recording medium (1000). As a result, a uniform image is obtained. Further, a part of the dye (1301) in the reactive black ink (1300) may be present inside the pigment layer fixed near the surface of the recording medium. However, since the black pigment is uniformly distributed and the pigment black ink and the reactive black ink have the same color, there is little visual contribution to the optical density.

(4) The case where ink is applied to the recording medium in the order of reactive black ink and pigment black ink in reverse recording.
FIG. 4 is a conceptual diagram when ink is applied to a recording medium in the order of reactive black ink and pigment black ink. First, when the reactive black ink (1300) is applied to the recording medium (1000), as shown in FIG. 4 (j), the reactive black ink having a characteristic that is relatively easy to penetrate into the recording medium is the recording medium (1000). It penetrates into (1302). Thereafter, when the pigment black ink (1100) containing the pigment (1101) is applied over the reactive black ink (1300), the pigment black ink having a relatively high surface tension reacts with a relatively low surface tension. It is pulled in the characteristic black ink. At this time, as shown in FIG. 4 (k), the pigment black ink (1100) does not spread so much to the layer of the previously applied reactive black ink (1300) and hardly diffuses. At the same time, the pigment (1101) in the pigment black ink (1100) starts to agglomerate rapidly due to the action of the reactive component (1202). However, the contact area between the reactive component (1202) and the pigment black ink (1100) is smaller than that in the case of the above (3), and the reactive component (1202) is hardly contained in the pigment black ink (1100). Since it does not diffuse, the aggregation of the pigment becomes non-uniform. As a result, as shown in FIG. 4 (1), the pigment (1101) is present in a non-uniform distribution on the recording medium. Of the non-uniform distribution of the pigment, a portion where the pigment distribution is particularly small becomes an image that looks whitish, and in this portion, a part of the dye in the reactive black ink fixed on the recording medium can be seen. However, since the pigment black ink and the reactive black ink have similar colors, a visually uniform image can be obtained.

  As described above, in the image forming method of the present invention in which an image is formed by applying the pigment black ink and the reactive black ink in an overlapping manner, the recording of the above (3) and (4) is repeated. However, since a uniform image is formed, the occurrence of uneven color is suppressed. In the recordings (3) and (4) described above, even if the order of applying each ink to the recording medium is reversed, the occurrence of color unevenness is suppressed by the same mechanism. In other words, even when an image is formed by applying each ink to the recording medium in the order of reactive black ink and pigment black ink in forward recording, and in the order of pigment black ink and reactive black ink in backward recording, color unevenness occurs. Is suppressed.

<Ink>
Hereinafter, with respect to the pigment black ink and reactive black ink used in the image forming method according to the present invention, and the non-reactive color ink that can be used in addition to these, characteristic components constituting each ink and common to each ink It demonstrates in order of the component which can be used.

[Pigment black ink]
(Pigment)
The color material of the pigment black ink needs to be a pigment. The dispersion form of the pigment in the pigment black ink may be any form such as a self-dispersion type or a resin dispersion type using a resin as a dispersant. These pigments may be used alone or in combination of two or more. The pigment content (% by mass) in the pigment black ink is 0.1% by mass or more and 15.0% by mass or less, and further 1.0% by mass or more and 10.0% by mass based on the total mass of the pigment black ink. The following is preferable. In addition to pigments, dyes can also be used for purposes such as toning.

(Self-dispersing pigment)
In the present invention, a self-dispersing pigment in which at least one hydrophilic group (anionic group or cationic group) is bonded to the surface of the pigment particle directly or through another atomic group (—R—) is used. It is preferable. By using such a self-dispersing pigment, it is not necessary to add a dispersant for dispersing the pigment in the ink, or the amount of the dispersant added can be reduced.

Specifically, the hydrophilic group bonded to the surface of the pigment particle is, for example, —COO (M ₁ ), —SO ₃ (M ₁ ), —PO ₃ H (M ₁ ), —PO ₃ (M ₁ ) ₂ ,-(COO (M ₁ )) _{n and the} like. In the formula, “M ₁ ” is a hydrogen atom, an alkali metal, ammonium, or organic ammonium, and n is an integer of 2 or more. These hydrophilic groups may be directly bonded to the surface of the pigment particle. Alternatively, another atomic group (-R-) is interposed between the surface of the pigment particle and the hydrophilic group, and the hydrophilic group as described above is indirectly bonded to the surface of the pigment particle. Also good. Examples of the other atomic group (—R—) include an alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, and a substituted or unsubstituted naphthylene group. Of course, the present invention is not limited to this. In addition, the form of the hydrophilic group in the ink may be any form in which a part thereof is dissociated or completely dissociated.

In the present invention, in particular, a pigment obtained by a diazo coupling method and having a compound having a —R— (COOM ₁ ) _n group in part as a surface can be suitably used. Examples of the method for producing an anionically charged self-dispersing pigment include a method in which the pigment is oxidized with sodium hypochlorite. According to this method, a —COONa group is formed on the surface of the pigment particles. Can be chemically bonded. Of course, the present invention is not limited to this.

Further, in the -R- bonded to the surface of the pigment particles, that -COO (M ₁₎ is a carbon atom adjacent to the carbon atom to which they are attached, are attached to -COO (M ₁₎ preferable. The n is preferably 2, and the R is preferably C ₆ H ₃ . This is because such a configuration can provide excellent effects on image quality and bleeding resistance. Incidentally, in the -R- bonded to the surface of the pigment particles, the -COO (M ₁₎ is a carbon atom adjacent to the carbon atom to which they are attached, it is attached to -COO (M ₁₎ and Means that two or more adjacent carbon atoms in R each have a —COO (M ₁ ) group. Specifically, this is to have a structure represented by the following general formula (1). In the present invention, it is preferable to use a self-dispersing pigment in which a group represented by the following general formula (1) is bonded to the surface of the pigment particle. Of course, the present invention is not limited to this.

In the pigment black ink, it is preferable that the —R— (COOM ₁ ) _n groups are bonded to the surface of the pigment particles at a higher density. Specifically, for example, the hydrophilic group density on the surface of the pigment particles is preferably 2.00 μmol / m ² or more. This is because the solid-liquid separation resulting from the degree of solvation described above is further promoted, and the above-described effect can be obtained more remarkably. In the present invention, the hydrophilic group density in the pigment particles is greatly affected by the specific surface area of the pigment, the structure of the functional groups bonded to the surface of the pigment particles, and the like, and therefore is not limited to this range. Absent.

Furthermore, in the pigment black ink, when M ₁ is ammonium, it is particularly preferable because better water resistance can be obtained. This is because, when such ink is applied to a recording medium, the ammonium is decomposed, the ammonia is evaporated, and the hydrophilic group bonded to the surface of the pigment particles becomes H type (acid type), and the hydrophilicity is lowered. This is thought to be due to Here, the self-dispersing pigment in which M ₁ is ammonium can be obtained by the following method. For example, the self-dispersion pigment M ₁ is an alkali metal, M ₁ is added and a method of replacing the ammonium M ₁ by the ion exchange method, ammonium hydroxide after the H-type by adding acid And the like.

(Resin dispersion type pigment)
In the present invention, a resin-dispersed pigment that disperses pigment particles by using a resin or the like as a dispersant can also be used. Any dispersant can be used as long as it has water solubility. In the present invention, those having a hydrophilic group, particularly an ionic group, and capable of stably dispersing the pigment in an aqueous medium by the action thereof are preferable. As the dispersant, it is preferable to use a resin having a weight average molecular weight of 1,000 to 30,000, more preferably 3,000 to 15,000. The content (% by mass) of the dispersant in the pigment black ink is preferably 0.1% by mass or more and 10.0% by mass or less based on the total mass of the pigment black ink. The ratio (P / B ratio) of the pigment content (P) and the dispersant content (B) in the pigment black ink is preferably 0.02 or more and 150 or less.

Specifically, for example, the following can be used as the dispersant.
Styrene-acrylic acid copolymer, styrene-acrylic acid-alkyl acrylate copolymer. Styrene-maleic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer. Styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, styrene-maleic anhydride-maleic acid half ester copolymer. Or the salt of these copolymers.

〔Carbon black〕
Examples of the pigment used in the pigment black ink include carbon black. For example, furnace black, lamp black, acetylene black, channel black, and the like can be used as the carbon black. Specifically, for example, the following commercially available products can be used. Of course, the present invention is not limited to these.
Ray Van: 7000, 5750, 5250, 5000 ULTRA, 3500, 2000, 1500, 1250, 1200, 1190 ULTRA-II, 1170, 1255 (above Colombia). Black Pearls L, Legal: 400R, 330R, 660R, Mogle: L, Monak: 700, 800, 880, 900, 1000, 1100, 1300, 1400, 2000, Vulcan XC-72R (above, manufactured by Cabot). Color Black: FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Printex: 35, U, V, 140U, 140V, Special Black: 6, 5, 4A, 4 (above, manufactured by Degussa). No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. 2300, MCF-88, MA600, MA7, MA8, MA100 (above, manufactured by Mitsubishi Chemical).
Carbon black newly prepared for the present invention can also be used. Further, the material is not limited to carbon black, and magnetic fine particles such as magnetite and ferrite, titanium black, and the like may be used.

(salt)
The pigment black ink preferably further contains a salt. As a result, the aggregation of the pigment on the recording medium is promoted, so that the effects of the present invention can be stably obtained regardless of the type of the recording medium. In addition, the form of the salt in the pigment black ink may be in any form of a partly dissociated state or a completely dissociated state.

Specific examples of the salt that can be used in the pigment black ink include, for example, (M ₂ ) NO ₃ , CH ₃ COO (M ₂ ), C ₆ H ₅ COO (M ₂ ), C ₂ H ₄ (COO (M ₂ )) ₂ , C ₆ H ₄ (COO (M ₂ )) ₂ , (M ₂ ) ₂ SO _{4 and the} like. In the formula, “M ₂ ” is an alkali metal, ammonium, or organic ammonium. Of course, the present invention is not limited to these.

  The salt content in the pigment black ink may be within a range in which the effects of the present invention are sufficiently obtained. Specifically, the salt content (% by mass) in the pigment black ink is preferably 0.05% by mass or more and 10.0% by mass or less based on the total mass of the pigment black ink. When the content is less than 0.05% by mass, the effects of the present invention may not be obtained. When the content exceeds 10.0% by mass, the storage stability of the ink may not be obtained.

[Reactive black ink]
(Reactive component)
The reactive black ink contains a reactive component that destabilizes the dispersion state of the pigment in the pigment black ink. In the present invention, destabilizing the dispersion state of the pigment in the pigment black ink is defined as satisfying the following aspect (1) or (2). First, a reactive black ink and a pigment black ink are mixed in an equal volume to prepare a mixed ink. At this time, (1) a mode in which pigment precipitates and aggregates are generated in the mixed ink, (2) the viscosity A of the reactive black ink, the viscosity B of the pigment black ink, and the viscosity C of the mixed ink are C> (( A mode that satisfies the relationship of A + B) / 2) × 1.2, and the like. The viscosity is a value measured at room temperature (25 ° C.), and the unit is mPa · s. Specifically, the above-described aspect (1) or (2) can be, for example, the following aspects (A), (B), (C), or (D).

(A) A mode in which the pigment or dispersant in the pigment black ink has an anionic group, and the reactive black ink contains a cationic component as a reactive component.
In this case, when the pigment black ink and the reactive black ink are mixed, the cationic component in the reactive black ink reacts with the anionic group of the pigment or the dispersant in the pigment black ink, resulting in an unsatisfactory dispersion state of the pigment. Stabilize. As a result, pigment aggregation and precipitation occur, and the mixed ink thickens.

As the cationic component, for example, a polyvalent metal can be used. A specific means for the ink to contain a polyvalent metal is, for example, that the ink contains a polyvalent metal salt. The polyvalent metal salt exists in the ink by dissociating into a polyvalent metal ion and an anion. In this case, the ink is expressed as containing a polyvalent metal. Specifically, the polyvalent metal ions include, for example, Mg ²⁺ , Ca ²⁺ , Cu ²⁺ , Co ²⁺ , Ni ²⁺ , Fe ²⁺ , La ³⁺ , Nd ³⁺ , Y ³⁺ , And Al ^{3+ and the} like. Further, specifically, the anion is preferably an inorganic acid ion such as NO ₃ ⁻ , SO ₄ ²⁻ or Cl ⁻ or an organic acid ion such as CH ₃ COO ⁻ .

In the present invention, from the viewpoint of storage stability of the reactive black ink and not dissolving a member (such as an ink flow path constituting the ink jet recording apparatus) in contact with the reactive black ink, Of these, Mg ²⁺ is particularly preferred. From the viewpoint of solubility, among the above-mentioned anions, it is preferable to use NO ₃ ⁻ , SO ₄ ²⁻ , Cl ⁻ , CH ₃ COO ⁻ , and since the solubility in water is excellent, NO ₃ ⁻ , It is particularly preferable to use SO ₄ ²⁻ or CH ₃ COO ⁻ .

  The content (% by mass) of the polyvalent metal in the reactive black ink is preferably 0.01% by mass or more and 10.0% by mass or less based on the total mass of the reactive black ink. In the polyvalent metal salt form, the content (% by mass) of the polyvalent metal salt in the reactive black ink is 0.1% by mass or more and 15.0% by mass based on the total mass of the reactive black ink. Hereinafter, it is further preferably 0.2% by mass or more and 10.0% by mass or less.

(B) A mode in which the pigment or dispersant in the pigment black ink has a cationic group, and the reactive black ink contains an anionic component as a reactive component.
In this case, when the pigment black ink and the reactive black ink are mixed, the anionic component in the reactive black ink reacts with the cationic group of the pigment or the dispersant, and the dispersion state of the pigment becomes unstable. Aggregation and precipitation occur, and the mixed ink thickens.

(C) A mode in which the pigment in the pigment black ink is stably dispersed at pH 3 to 7, and the pH of the reactive black ink is 8 to 11.
In this case, when the pigment black ink and the reactive black ink are mixed, the pH of the pigment black ink is increased, the dispersion state of the pigment becomes unstable, the aggregation and precipitation of the pigment occurs, and the mixed ink is thickened. To do.

(D) An embodiment in which the pigment in the pigment black ink is stably dispersed at pH 7 to 11, and the pH of the reactive black ink is 3 to 6.
In this case, when the pigment black ink and the reactive black ink are mixed, the pH of the pigment black ink is lowered, the dispersion state of the pigment becomes unstable, the aggregation and precipitation of the pigment occurs, and the mixed ink is increased in viscosity. To do.

(dye)
The coloring material of the reactive black ink needs to be a dye. The dye used for the reactive black ink may be a known one or a newly synthesized one, and can be appropriately selected and used. The content (% by mass) of the dye in the reactive black ink is preferably 0.05% by mass or more and 15.0% by mass or less based on the total mass of the reactive black ink.

[Black dye]
Listed below are black dyes that can be used in reactive black ink. Of course, the present invention is not limited to these.
C. I. Direct black: 17, 19, 22, 31, 32, 51, 62, 71, 74, 112, 113, 154, 168, 195, etc. C. I. Acid Black: 2, 48, 51, 52, 110, 115, 156, etc. C. I. Food black: 1, 2, etc. In addition, a compound represented by the following general formula (2) or a salt thereof, a compound represented by the following general formula (3) or a salt thereof.

（一般式（２）中、Ｒ₁及びＲ₂はそれぞれ独立に、水素原子；ヒドロキシル基；アミノ基；カルボキシル基；スルホン酸基；炭素数１乃至４のアルキル基；又は炭素数１乃至４のアルコキシ基である。Ｒ₃及びＲ₄はそれぞれ独立に、水素原子；炭素数１乃至４のアルキル基；炭素数１乃至４のアルコキシ基；ヒドロキシル基。又は、ヒドロキシル基若しくは炭素数１乃至４のアルコキシ基で置換されていてもよい炭素数１乃至４のアルキル基；ヒドロキシル基、炭素数１乃至４のアルコキシ基、スルホン酸基若しくはカルボキシル基で置換されていてもよい炭素数１乃至４のアルコキシ基。又は、アルキル基若しくはアシル基によって置換されているアミノ基である。ｎは０又は１である。）なお、一般式（２）におけるｎ＝０とは、ＳＯ₃Ｈの位置がＨであることを示す。

(In General Formula (2), R ₁ and R ₂ are each independently a hydrogen atom; a hydroxyl group; an amino group; a carboxyl group; a sulfonic acid group; an alkyl group having 1 to 4 carbon atoms; or an alkyl group having 1 to 4 carbon atoms. R ₃ and R ₄ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a hydroxyl group or 1 to 4 carbon atoms. An alkyl group having 1 to 4 carbon atoms which may be substituted with an alkoxy group; an alkoxy group having 1 to 4 carbon atoms which may be substituted with a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms, a sulfonic acid group or a carboxyl group Or an amino group substituted by an alkyl group or an acyl group. N is 0 or 1. Note that n = 0 in the general formula (2) is SO _3. Indicates that the position of H is H.

（一般式（３）中、Ｒ₁、Ｒ₂、Ｒ₃、及びＲ₄はそれぞれ独立に、水素原子；ニトロ基；ヒドロキシル基；アミノ基；カルボキシル基；スルホン酸基；炭素数１乃至４のアルキル基。又は、炭素数１乃至４のアルコキシ基；ヒドロキシル基、炭素数１乃至４のアルコキシ基、スルホン酸基若しくはカルボキシル基で置換されているアルコキシ基；カルボキシル基若しくはスルホン酸基でさらに置換されてもよい炭素数１乃至４のアルコキシ基。又は、フェニル基、アルキル基若しくはアシル基によって置換されているアミノ基である。ｎは０又は１である。）なお、一般式（３）におけるｎ＝０とは、ＳＯ₃Ｈの位置がＨであることを示す。

(In the general formula (3), R ₁ , R ₂ , R ₃ and R ₄ are each independently a hydrogen atom; a nitro group; a hydroxyl group; an amino group; a carboxyl group; a sulfonic acid group; An alkyl group, or an alkoxy group having 1 to 4 carbon atoms; an alkoxy group substituted with a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms, a sulfonic acid group, or a carboxyl group; And may be an alkoxy group having 1 to 4 carbon atoms, or an amino group substituted by a phenyl group, an alkyl group or an acyl group.n is 0 or 1.) Note that n in the general formula (3) = 0 indicates that the position of SO ₃ H is H.

  Hereinafter, exemplary compounds Bk1 to Bk3 as specific examples of the compound represented by the general formula (2) or a salt thereof, and exemplified compounds Bk4 to Bk6 as specific examples of the compound represented by the general formula (3) or a salt thereof. Indicates. In addition, exemplary compound Bk1-Bk6 is shown in the form of a free acid. In the present invention, the compound represented by the general formula (2) or a salt thereof is particularly preferably the exemplified compound Bk1, and the compound represented by the general formula (3) or a salt thereof is the exemplified compound Bk4. It is particularly preferred. Two or more dyes may be used at the same time, and in the present invention, it is particularly preferable to use the exemplified compound Bk1 and the exemplified compound Bk4 in combination.

  The reactive black ink used in the present invention is not limited to the black dyes listed above, and may be any ink having a black color tone. For example, a so-called toned black ink in which at least one dye such as yellow, magenta, cyan, red, green, and blue is mixed can be used. In such a case, the total content (% by mass) of the dye in the reactive black ink is preferably 0.05% by mass or more and 15.0% by mass or less based on the total mass of the reactive black ink. . Below, the specific example of the dye which can be used by this invention is given for every color tone. Of course, the present invention is not limited to these.

[Yellow dye]
C. I. Direct yellow: 8, 11, 12, 27, 28, 33, 39, 44, 50, 58, 85, 86, 87, 88, 89, 98, 100, 110, 132, 173, etc. C. I. Acid Yellow: 1, 3, 7, 11, 17, 23, 25, 29, 36, 38, 40, 42, 44, 76, 98, 99, etc. C. I. Food yellow: 3 etc. A compound represented by the following general formula (4).

（一般式（４）中、Ｍはそれぞれ独立に、水素原子、アルカリ金属、アルカリ土類金属、有機アミンのカチオン、又はアンモニウムイオンであり、ｎはそれぞれ独立に１又は２である。）

(In General Formula (4), M is each independently a hydrogen atom, an alkali metal, an alkaline earth metal, a cation of an organic amine, or an ammonium ion, and n is independently 1 or 2.)

  Specific examples of the compound represented by the general formula (4) include exemplified compounds Y1 to Y4 having the structure shown in Table 1 below. Of course, the present invention is not limited to this. In Table 1, for convenience, the substitution positions of the sulfonic acid groups are shown as A ring and B ring as shown in the following general formula (5). The substitution position of the sulfonic acid group is as defined in the following general formula (5).

（一般式（５）中、Ｍはそれぞれ独立に、水素原子、アルカリ金属、アルカリ土類金属、有機アミンのカチオン、又はアンモニウムイオンであり、ｎはそれぞれ独立に１又は２である。）

(In General Formula (5), M is each independently a hydrogen atom, an alkali metal, an alkaline earth metal, a cation of an organic amine, or an ammonium ion, and n is independently 1 or 2.)

  Preferable specific examples of the compound represented by the general formula (4) include the following exemplified compound Y1. Of course, the present invention is not limited to this.

[Magenta dye]
C. I. Direct Red: 2, 4, 9, 11, 20, 23, 24, 31, 39, 46, 62, 75, 79, 80, 83, 89, 95, 197, 201, 218, 220, 224, 225, 226 227, 228, 229, 230, etc. C. I. Acid Red: 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 42, 51, 52, 80, 83, 87, 89, 92, 106, 114, 115, 133, 134, 145 158, 198, 249, 265, 289, etc. C. I. Food Red: 87, 92, 94, etc. C. I. Direct violet: 107 etc. A compound represented by the following general formula (6) or a salt thereof.

（一般式（６）中、Ｒ₁は、水素原子、アルキル基、ヒドロキシアルキル基、シクロヘキシル基、モノ若しくはジアルキルアミノアルキル基、又はシアノアルキル基である。Ｒ₂、Ｒ₃、Ｒ₄、Ｒ₅、及びＲ₆はそれぞれ独立に、水素原子、炭素数１乃至８のアルキル基、又はカルボキシル基（ただし、Ｒ₂、Ｒ₃、Ｒ₄、Ｒ₅及びＲ₆すべてが水素原子である場合を除く。）である。）

(In General Formula (6), R ₁ is a hydrogen atom, an alkyl group, a hydroxyalkyl group, a cyclohexyl group, a mono- or dialkylaminoalkyl group, or a cyanoalkyl group. R ₂ , R ₃ , R ₄ , R ₅ , And R ₆ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a carboxyl group (except when all of R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are hydrogen atoms). .).)

  The following exemplary compounds M1 to M7 are preferred exemplary compounds of the compound represented by the general formula (6) or a salt thereof. Of course, the present invention is not limited to these. In the exemplified compounds M1 to M7 below, the solubilizing groups are all described in the H form, but may form a salt. In the present invention, it is preferable to use the exemplified compound M1 among these exemplified compounds.

[Cyan dye]
C. I. Direct blue: 1, 15, 22, 25, 41, 76, 77, 80, 86, 90, 98, 106, 108, 120, 158, 163, 168, 199, 226, 307, etc. C. I. Acid Blue: 1, 7, 9, 15, 22, 23, 25, 29, 40, 43, 59, 62, 74, 78, 80, 90, 100, 102, 104, 112, 117, 127, 138, 158 161, 203, 204, 221, 244, etc. A compound represented by the following general formula (7).

（一般式（７）中、Ｍはアルカリ金属又はアンモニウムである。Ｒ₁及びＲ₂はそれぞれ独立に、水素原子、スルホン酸基、カルボキシル基（ただし、Ｒ₁及びＲ₂が同時に水素原子となる場合を除く。）である。Ｙは塩素原子、ヒドロキシル基、アミノ基、アルキルアミノ基、ジアルキルアミノ基、ヒドロキシアルキルアミノ基、カルボキシアルキルアミノ基又はスルホニルアルキルアミノ基である。ｌ、ｍ、ｎはそれぞれ、ｌ＝０乃至２、ｍ＝１乃至３、ｎ＝１乃至３（ただし、ｌ＋ｍ＋ｎ＝３乃至４）であり、置換基の置換位置は４位又は４’位である。）

(In General Formula (7), M is an alkali metal or ammonium. R ₁ and R ₂ are each independently a hydrogen atom, a sulfonic acid group, or a carboxyl group (provided that R ₁ and R ₂ are simultaneously hydrogen atoms). Y is a chlorine atom, a hydroxyl group, an amino group, an alkylamino group, a dialkylamino group, a hydroxyalkylamino group, a carboxyalkylamino group, or a sulfonylalkylamino group. 1 = 0 to 2, m = 1 to 3, n = 1 to 3 (where l + m + n = 3 to 4), and the substitution position of the substituent is the 4-position or the 4′-position.

As the colorant, an unsubstituted sulfamoyl group (—SO ₂ NH ₂ ) or a substituted sulfamoyl group (a group represented by the following general formula (8)) is selected only at the 4-position or the 4′-position in the general formula (7). Introduced phthalocyanine derivatives. The compound represented by the general formula (7) is synthesized by reacting a 4-sulfophthalic acid derivative, or a 4-sulfophthalic acid derivative and an (anhydrous) phthalic acid derivative in the presence of a metal compound. The phthalocyanine compound obtained is used as a raw material. Further, it is obtained by converting a sulfonic acid group in the phthalocyanine compound to a chlorosulfonic acid group and then reacting with an aminating agent in the presence of an organic amine.

  Preferred specific examples of the group represented by the general formula (8) (substituted sulfamoyl group) are shown below. Of course, the present invention is not limited to these. The substituted sulfamoyl group represented by the general formula (8) is shown in the form of a free acid.

  Preferable specific examples of the compound represented by the general formula (7) include a compound substituted by the exemplified substituent 1, that is, the exemplified compound C1 shown below. Of course, the present invention is not limited to this. In the following structural formula, M is an alkali metal or ammonium.

(Red dye)
C. I. Acid orange: 7, 8, 10, 12, 24, 33, 56, 67, 74, 88, 94, 116, 142, etc. C. I. Acid Red: 111, 114, 266, 374, etc. C. I. Direct orange: 26, 29, 34, 39, 57, 102, 118, etc. C. I. Food orange: 3 etc. C. I. Reactive orange: 1, 4, 5, 7, 12, 13, 14, 15, 16, 20, 29, 30, 84, 107, etc. C. I. Disperse orange: 1, 3, 11, 13, 20, 25, 29, 30, 31, 32, 47, 55, 56, etc.

(Green dye)
C. I. Acid Green: 1, 3, 5, 6, 9, 12, 15, 16, 19, 21, 25, 28, 81, 84, etc. C. I. Direct green: 26, 59, 67, etc. C. I. Food green: 3 etc. C. I. Reactive green: 5, 6, 12, 19, 21, etc. C. I. Disperse Green: 6, 9 etc.

(Blue dye)
C. I. Acid Blue: 62, 80, 83, 90, 104, 112, 113, 142, 203, 204, 221, 244, etc. C. I. Reactive blue: 49 etc. C. I. Acid violet: 17, 19, 48, 49, 54, 129, etc. C. I. Direct violet: 9, 35, 47, 51, 66, 93, 95, 99, etc. C. I. Reactive violet: 1, 2, 4, 5, 6, 8, 9, 22, 34, 36, etc. C. I. Disperse violet: 1, 4, 8, 23, 26, 28, 31, 33, 35, 38, 48, 56, etc.

[Non-reactive color ink]
In the present invention, in addition to the above-described pigment black ink and reactive black ink, other inks can be used in combination. The other ink in the present invention includes, for example, an ink (non-reactive color ink) that does not contain a polyvalent metal or the like, that is, does not react with the pigment black ink. The dye of the non-reactive color ink may be a known one or a newly synthesized one, and can be appropriately selected and used. Specifically, those listed as dyes that can be used in the above-described reactive black ink can be used. Of course, the present invention is not limited to these. The content (% by mass) of the dye in the non-reactive color ink is preferably 0.05% by mass or more and 15.0% by mass or less based on the total mass of the non-reactive color ink.

Hereinafter, components that can be commonly used in the pigment black ink, the reactive black ink, and the non-reactive color ink will be described.
[Aqueous medium for each ink]
For the above-described pigment black ink, reactive black ink, and non-reactive color ink, it is preferable to use water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. It is preferable to use deionized water instead of general water containing various ions. Specifically, for example, the following water-soluble organic solvents can be used. The following water-soluble organic solvents can be used alone or as a mixture.

  Alkyl alcohols having 1 to 6 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol and tert-butyl alcohol; Amides such as dimethylformamide and dimethylacetamide. Ketones or ketoalcohols such as acetone and diacetone alcohol. Ethers such as tetrahydrofuran and dioxane. Polyalkylene glycols such as polyethylene glycol and polypropylene glycol. Alkylene glycols having 2 to 6 carbon atoms in the alkylene group, such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, and diethylene glycol. Alkyl ether acetates such as polyethylene glycol monomethyl ether acetate. Glycerin. Alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether. N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like.

  The content (% by mass) of the water-soluble organic solvent in each ink is 1.0% by mass or more and 50.0% by mass or less, and further 3.0% by mass or more and 40.0% by mass based on the total mass of the ink. The following is preferable. The water content (% by mass) in each ink is preferably 30.0% by mass or more and 95.0% by mass or less based on the total mass of the ink.

[Other ingredients]
In addition to the above-described components, a moisturizing compound such as urea, a urea derivative, trimethylolpropane, or trimethylolethane may be used for each ink in order to maintain the moisturizing property. The content (% by mass) of the moisturizing compound in the ink is from 0.1% by mass to 20.0% by mass, and more preferably from 3.0% by mass to 10.0% by mass, based on the total mass of the ink. It is preferable that

  Further, each ink may contain various compounds as necessary in addition to the above components in order to obtain an ink having a desired physical property value. Specifically, for example, various additions such as surfactants, pH adjusters, rust inhibitors, antiseptics, fungicides, antioxidants, anti-reduction agents, evaporation accelerators, chelating agents, water-soluble polymers, etc. An agent may be contained.

  For example, one or more surfactants such as the following anionic surfactants or nonionic surfactants can be appropriately selected and used. Examples of the anionic surfactant include fatty acid salts, higher alcohol sulfate esters, fatty oil sulfate esters, and alkyl allyl sulfonates. Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan alkyl esters, acetylene alcohol, and acetylene glycol. Among these, acetylene alcohols and acetylene glycols are particularly preferable because they exhibit an effect of excellent permeability to plain paper.

  Also, the pigment black ink is preferably a so-called overlay ink that has relatively low permeability to a recording medium in order to obtain sharp character quality and high image density. Specifically, the surface tension of the pigment black ink is preferably 30 mN / m or more and 50 mN / m or less. In order to suppress bleeding, the reactive black ink is preferably a so-called penetrating ink having relatively high permeability to a recording medium. Specifically, the surface tension of the reactive black ink is preferably 20 mN / m or more and 40 mN / m or less. Furthermore, in order to obtain the effect of the present invention, the surface tension of the reactive black ink is adjusted to be smaller than the surface tension of the pigment black ink. Specifically, the surface tension of the reactive black ink is preferably smaller than the surface tension of the pigment black ink in the range of 5 mN / m to 10 mN / m. The surface tension of each ink is preferably adjusted as appropriate depending on the type and content of the water-soluble organic solvent or surfactant.

  In the present invention, the reactive black ink is applied to an inkjet recording apparatus that forms a black image by applying a pigment black ink containing a pigment in each of reciprocating scans in which the recording head is moved relative to the recording medium. It is preferable to be used. The reactive black ink is preferably applied in each of the reciprocating scans in forming the black image so as to at least partially overlap the pigment black ink.

<Image forming apparatus>
An image forming apparatus according to the present invention has the following configuration. That is, it has a recording head for discharging a pigment black ink containing a pigment. A recording head for discharging a dye black ink containing a reactive component and a dye that destabilizes the dispersion state of the pigment and having a surface tension lower than that of the pigment black ink; Further, the image forming apparatus includes means for forming the image by applying the pigment black ink and the dye black ink in any order so as to overlap at least partially. In the image forming apparatus of the present invention, the absolute value of the difference in brightness in the CIELab color space measured for each ink obtained by diluting the pigment black ink and the dye black ink 2,000 times with pure water is 20 or less. It is preferable that The dye black ink is the reactive black ink described above.

  As an image forming apparatus suitable for recording using the reactive black ink and pigment black ink described above, an ink jet recording apparatus capable of reciprocal recording will be described with reference to FIGS.

  FIG. 5 is a schematic explanatory view showing an example of an ink jet recording apparatus. The chassis 10 is composed of a plurality of plate-like metal members having a predetermined rigidity, and forms a skeleton of the ink jet recording apparatus. The chassis 10 includes a feeding unit 11 that feeds a recording medium, a transport unit 13 that guides the recording medium to a predetermined recording position and guides the recording medium to a discharge unit 12, a recording unit that performs predetermined recording on the recording medium, and recovery of the recording unit A head recovery unit 14 that performs the operation is incorporated. The recording unit includes a carriage 16 that is supported so as to be able to scan along the carriage shaft 15, a recording head cartridge that is detachably mounted on the carriage 16 via a head set lever 17, and a carriage cover that positions the recording head cartridge at a predetermined position. 20 One end of a contact flexible printed cable (hereinafter abbreviated as a contact FPC) 22 is connected to another engaging portion of the carriage 16 with respect to the recording head cartridge. The contact portion formed at the end of the contact FPC 22 and the contact portion 301 which is an external signal input terminal provided in the recording head cartridge are in electrical contact with each other to exchange various information and to supply power to the recording head cartridge. It is designed to supply.

  FIG. 6 is a schematic explanatory view showing an example of a recording head cartridge. Here, a case where non-reactive cyan ink, non-reactive yellow ink, non-reactive magenta ink, reactive black ink, and pigment black ink are used as an example of the ink set will be described. In FIG. 6, reference numerals 101, 102, 103, 104, and 105 denote a reactive black ink, a non-reactive cyan ink, a non-reactive magenta ink, a non-reactive yellow ink, and a pigment black ink, respectively. Recording head. In FIG. 6, reference numerals 201 and 205 denote an ejection port array for reactive black ink and an ejection port array for pigment black ink, respectively. In the recording head shown in FIG. 6, an electrical signal such as a recording signal is exchanged through the electrical contact 301. The recording head that discharges the dye ink is preferably configured to have a mass per ink drop of 5 ng or less, more preferably 4 ng or less, and particularly 2 ng or less. The recording head that discharges the pigment ink is preferably configured so that the mass per ink drop is 50 ng or less, and further 30 ng or less.

  Here, as an embodiment of the recording head, a bubble jet (registration) that performs recording using an electrothermal transducer (recording element) that generates thermal energy for causing film boiling to the ink in response to an electrical signal. A trademark type recording head has been described with an example. About this typical structure and principle, for example, what is performed using the basic principle disclosed in US Pat. Nos. 4,723,129 and 4,740,796 is preferable. . This method is applicable to both so-called on-demand type and continuous type. In the case of the on-demand type, thermal energy is generated by applying to the electrothermal transducer at least one drive signal that gives a rapid temperature rise exceeding nucleate boiling corresponding to the recorded information. As a result, film boiling occurs on the heat acting surface of the recording head, and as a result, bubbles in the liquid (ink) corresponding to the drive signal on a one-to-one basis can be formed. By the growth and contraction of the bubbles, ink is ejected through the ejection port to form ink droplets. It is more preferable that the drive signal has a pulse shape, since bubbles are grown and contracted immediately and appropriately, and ink ejection with particularly excellent responsiveness can be achieved.

  In addition, the ink jet recording apparatus using the second mechanical energy includes a nozzle forming substrate having a plurality of nozzles, a pressure generating element made of a piezoelectric material and a conductive material disposed opposite to the nozzles, and this pressure. Ink filling the periphery of the generating element. In this embodiment, the pressure generating element is displaced by the applied voltage, and ink is ejected.

  Further, the ink jet recording apparatus can be used even if the recording head and the ink cartridge are separated, or they are integrated so as not to be separated. In addition, the ink cartridge is integrated with the recording head so as to be separable or non-separable and mounted on the carriage, or is provided at a fixed portion of the ink jet recording apparatus, and the recording head is connected via an ink supply member such as a tube The ink may be supplied to the ink. Further, when the ink cartridge is provided with a configuration for applying a preferable negative pressure to the recording head, the following configuration can be adopted. That is, a mode in which an absorber is disposed in an ink storage portion of an ink cartridge, or a mode in which a flexible ink storage bag and a spring portion that applies a biasing force in the direction of expanding the inner volume of the flexible ink storage bag are provided. Can be adopted. The ink jet recording apparatus preferably employs a serial recording method as described above, but may take the form of a line printer in which recording elements are aligned over a range corresponding to the entire width of the recording medium.

  Hereinafter, although it demonstrates more concretely using an Example and a comparative example, this invention is not limited to these, unless the summary is exceeded. In the following description, “%” is based on mass unless otherwise specified.

<Preparation of pigment dispersion>
To a solution obtained by dissolving 5 g of concentrated hydrochloric acid in 5.5 g of water, 1.5 g of 4-amino-1,2-benzenedicarboxylic acid was added while being cooled to 5 ° C. Next, the container containing the solution was placed in an ice bath and the solution was stirred to keep the solution constantly at 10 ° C. or lower, and 1.8 g of sodium nitrite was dissolved in 9 g of water at 5 ° C. The solution was added. After stirring this solution for another 15 minutes, 6 g of carbon black having a specific surface area of 220 m ² / g and a DBP oil absorption of 105 mL / 100 g was added with stirring. Thereafter, the mixture was further stirred for 15 minutes. The obtained slurry was filtered with a filter paper (trade name: Standard filter paper No. 2; manufactured by Advantech), and then the particles were sufficiently washed with water and dried in an oven at 110 ° C. to prepare self-dispersing carbon black. About the obtained self-dispersion type carbon black, sodium ions were replaced with ammonium ions by an ion exchange method. Further, water was added to the obtained self-dispersing carbon black and dispersed so that the pigment concentration became 10% to prepare a dispersion. By the above method, a pigment dispersion was obtained in a state where self-dispersing carbon black having —C ₆ H ₃ — (COONH ₄ ) ₂ groups introduced on the surface of carbon black particles was dispersed in water.

When the ionic group density of the self-dispersing carbon black prepared above was measured, it was 3.1 μmol / m ² . The ionic group density used here was measured by measuring the sodium ion concentration of the self-dispersing carbon black (sodium salt type) prepared above using an ion meter (manufactured by Toa DKK). It was converted into the ionic group density of the dispersed carbon black.

<Synthesis of dyes>
(Synthesis of Black Dye 1)
The following compound A was dissolved in water to which sodium carbonate was added, and diazotization was carried out by further adding hydrochloric acid and sodium nitrite. To this diazo turbid solution, an aqueous solution of 6-phenylamino-1-hydroxynaphthalene-3-sulfonic acid was added and dissolved in the presence of sodium carbonate to obtain a solution B. Next, 2-aminosulfonic acid was dissolved in the presence of sodium hydroxide, and diazotization was performed by adding hydrochloric acid and sodium nitrite. Next, 6-amino-1-hydroxynaphthalene-3-sulfonic acid was dissolved in the presence of sodium hydroxide, and acetic anhydride was added to carry out acetylation. The diazo turbid solution obtained above was added dropwise in the presence of sodium carbonate to perform a coupling reaction, whereby a reaction solution C was obtained. To this reaction solution C, sodium hydroxide and then sodium chloride were added for salting out to obtain a compound. This compound was dissolved in water in the presence of sodium hydroxide, and diazotization was performed by adding hydrochloric acid and sodium nitrite. Solution B was added dropwise to the diazo turbid solution in the presence of sodium carbonate to complete the coupling reaction to obtain a reaction solution. The reaction solution was salted out with sodium chloride and then filtered to obtain Compound D. 2-Nitro-4-cresol, toluene, and potassium hydroxide were added to N, N-dimethylformamide, water was distilled off by azeotropy with toluene, and propane sultone was added dropwise. Then, after adding sodium hydroxide and concentrating this, palladium carbon was added in the autoclave, hydrogen gas was enclosed, and the solution was obtained. This was diazotized by adding hydrochloric acid and sodium nitrite, and the reaction solution C obtained above was added dropwise to complete the coupling reaction in the presence of sodium hydroxide to obtain a reaction solution. It was. Diazotization was carried out by adding hydrochloric acid and sodium nitrite to the reaction solution, and this diazo turbid solution was added to an aqueous solution in which the compound D was dissolved to complete the coupling reaction. This was salted out with sodium chloride, followed by filtration and washing to obtain black dye 1 (a sodium salt of exemplary compound Bk1).

(Synthesis of Black Dye 2)
The following compound E was dissolved in water to which sodium hydroxide was added, and a sodium nitrite aqueous solution was further added to carry out diazotization. This diazo turbid solution was dropped into an alkaline aqueous solution of 6-amino-1-hydroxynaphthalene-3,5-disulfonic acid to carry out a coupling reaction, salted out with sodium chloride, filtered and washed to obtain compound F. Got. Next, Compound F was dissolved by adding water to which sodium hydroxide was added, and diazotization was performed by adding hydrochloric acid and sodium nitrite. To this diazo turbid liquid, 8-amino-1-hydroxynaphthalene-3,6-disulfonic acid and sodium carbonate were added and stirred overnight to obtain a reaction liquid G. Next, 1-amino-2-benzenesulfonic acid was added and dissolved in water to which sodium hydroxide was added, and a sodium nitrite aqueous solution was further added to perform diazotization. This diazo turbid solution is dropped into an alkaline aqueous solution of 6-amino-1-hydroxynaphthalene-3-sulfonic acid to perform a coupling reaction, and after salting out with sodium chloride, filtration and washing are performed to obtain Compound H. It was. Next, Compound H was dissolved in water to which sodium hydroxide was added, and diazotization was performed by adding hydrochloric acid and sodium nitrite. This diazo turbid solution is added to the reaction solution G to perform a coupling reaction, salted out with sodium chloride, filtered and washed to obtain the following black dye 2 (sodium salt of exemplary compound Bk4). Obtained.

<Preparation of ink>
Each component shown in the upper part of Table 2 and Table 3 below is mixed and dissolved or dispersed with sufficient stirring. After that, the pigment black ink has a pore size of 0.3 μm, and the other inks have a pore size of 0.2 μm. Ink was prepared by pressure filtration with Fujifilm. In Table 2 and Table 3 below, acetylenol E100 is an ethylene oxide adduct of acetylene glycol (surfactant; manufactured by Kawaken Fine Chemicals).

  Moreover, after each ink was diluted 2,000 times (mass times) with pure water, the brightness in the CIELab color space was measured using an ultraviolet-visible spectrophotometer L-4200 (manufactured by Hitachi, Ltd.). Then, the absolute value of the difference in brightness between the pigment black ink (PigBk ink) and each of the inks 1 to 9 was obtained. The obtained results are also shown in the lower part of Table 3. Furthermore, about each ink, the surface tension in 25 degreeC was measured using Kyowa CBVP type surface tension meter A-1 type (made by Kyowa Kagaku). The obtained results are shown together in the lower part of Tables 2 and 3.

<Evaluation>
(Uneven color and white haze)
A solid black image was formed by an image forming method in which other inks were applied in an overlapping manner on the region to which the pigment black ink was applied using a combination of the pre-printed ink and the post-printed ink shown on the left side of Table 4 below. As the image forming apparatus, a modified BJF850 (manufactured by Canon) capable of reciprocal recording was used. As the recording medium, high color plain paper super white paper SW101 (manufactured by Canon) was used. The respective inks were applied to the recording medium in the order of first ink and second ink shown in Table 4 below. The image was formed by one-pass reciprocal recording. The amount of ink applied was about 28 ng of pigment black ink and about 2 ng of other inks per 1/600 inch square.

Regarding the image obtained above, the image formed by forward recording and the image formed by backward recording were visually confirmed, and these images were compared to evaluate color unevenness. The evaluation criteria for color unevenness are as follows. The evaluation results are shown in Table 4.
○: Color unevenness was hardly noticeable.
X: Color unevenness was conspicuous.

Moreover, about the image obtained above, the state of white haze was confirmed visually and white haze was evaluated. The evaluation criteria for white haze are as follows. The evaluation results are shown in Table 4.
○: White haze was hardly noticeable.
X: White haze was conspicuous.

(Bleeding resistance)
An image in which a solid image formed with color ink was adjacent to a black solid image similar to the above was formed. At this time, ink 10 which is yellow non-reactive color ink was used as the color ink. As the image forming apparatus, a modified BJF850 (manufactured by Canon) capable of reciprocal recording was used. As the recording medium, high color plain paper super white paper SW101 (manufactured by Canon) was used. The image was formed by one-pass reciprocal recording. The amount of ink applied when forming a solid color image was about 14 ng per 1/600 inch square.

About the image obtained above, the bleeding resistance was evaluated by visually confirming the degree of blurring at the boundary between the black solid image and the color solid image. The evaluation criteria for bleeding resistance are as follows. The evaluation results are shown in Table 4.
○: Bleeding was hardly noticeable.
X: Bleeding was conspicuous.

10: Chassis 11: Feeding unit 12: Discharging unit 13: Conveying unit 14: Head recovery unit 15: Carriage shaft 16: Carriage 17: Headset lever 20: Carriage cover 22: Contact flexible print cable (contact FPC)
101: Reactive black ink recording head 102: Cyan ink recording head 103: Magenta ink recording head 104: Yellow ink recording head 105: Pigment black ink recording head 201: Reactive black ink ejection port array 205: Pigment black ink ejection port array 301: Electrical contact 1000: Recording medium 1100: Pigment black ink 1101: Pigment in pigment black ink 1102: Aqueous medium in pigment black ink penetrating into the recording medium 1200: Reactive color ink 1201 : Reactive component 1203: Reactive component 1203: Reactive color ink 1300 that has penetrated into the recording medium 1300: Reactive black ink 1301: Dye 130 in the reactive black ink: Reactive black ink that has penetrated into the recording medium

Claims (6)

  A pigment black ink containing a pigment and a dye black ink containing a reactive component and a dye that destabilize the dispersion state of the pigment and having a surface tension lower than that of the pigment black ink are at least partially in any order. An image forming method comprising a step of forming an image by applying the image to a recording medium so as to overlap each other.   2. The image formation according to claim 1, wherein the absolute value of the difference in brightness in the CIELab color space measured for each of the pigment black ink and the dye black ink diluted 2,000 times with pure water is 20 or less. Method.   A recording head for ejecting a pigment black ink containing a pigment, a reactive component that destabilizes the dispersion state of the pigment, and a dye, and a dye black ink having a lower surface tension than the pigment black ink An image comprising: a recording head for discharging; and means for forming an image by applying the pigment black ink and the dye black ink to a recording medium so as to overlap at least partially in any order. Forming equipment.   The image formation according to claim 3, wherein the absolute value of the difference in brightness in the CIELab color space measured for each ink obtained by diluting the pigment black ink and the dye black ink 2,000 times with pure water is 4 or less. apparatus.   A pigment black ink containing a pigment and a dye black ink containing a reactive component and a dye destabilizing the dispersion state of the pigment and having a lower surface tension than the pigment black ink are arranged in any order on the recording medium. In the image quality improving method, the image quality is improved by applying the ink so that at least a part thereof overlaps on the recording medium. Used in an inkjet recording apparatus for forming a black image by applying a pigment black ink containing a pigment in each of reciprocating scans in which a recording head is moved relative to a recording medium, and at least the pigment black ink and the recording medium A black ink that is applied in each of the reciprocating scans in forming the black image so that a part thereof overlaps,
A black ink comprising a reactive component destabilizing a dispersion state of a pigment contained in the pigment black ink and a black dye, and having a surface tension lower than that of the pigment black ink.

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