JP2001150793A - Image recording method, quality improving method for multi-color image, image recording device, ink set, and recording unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink set, printing a clear and highly fresh multi-color image while restraining the variability of color due to the inversion of order of giving black ink and color ink. SOLUTION: A method of recording a multi-color image, including the images different in the alternately superposing order of black ink and color ink, is characterized in that the black ink contains a pigment dispersed into a water base medium by the effect of salt base or water base medium and an ionic base while the color ink contains a dye.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image recording method, a method for improving the quality of a multicolor image, an image recording apparatus, an ink set, and a recording unit.

[0002]

2. Description of the Related Art An ink jet recording method is a low-noise, non-impact recording method for recording an image by directly discharging ink onto a recording material. In addition, since this method does not require a complicated device for implementation, low running costs, miniaturization of the device, colorization, and the like are easy. Therefore, recording apparatuses such as printers, copiers, facsimile machines, word processors and the like to which the ink jet recording method has been applied have been practically used.

[0003] Further, using such an ink jet recording technique, black ink and color ink (for example, at least one color ink selected from yellow ink, cyan ink, magenta ink, red ink, green ink and blue ink) are used. A color ink jet recording apparatus for forming a multi-color image has also been put to practical use.

In such a color ink jet recording apparatus, in particular, black ink is frequently used for printing characters and the like, so that it is required to achieve sharpness, sharpness and high print density of printing. As a means, there is known a technique of reducing the permeability of black ink into a recording material and suppressing the penetration of a coloring material in the black ink into the recording material.

On the other hand, with respect to color inks, when two types of inks of different colors are applied adjacently to a recording material,
In order to prevent a phenomenon (bleeding) in which the inks are mixed with each other at the boundary between them and the quality of the color image is reduced (bleeding), the permeability to the recording material is increased, and the color inks are mixed on the surface of the recording material. There is also known a technique for preventing such a phenomenon (for example, Japanese Patent Application Laid-Open No. 55-65269).

By the way, in ink jet recording,
As a method of shortening the printing time, the forward direction of main scanning,
A method of printing in both directions in the backward direction (hereinafter referred to as “reciprocal printing”) and a method of low-pass printing in which an image having the same width as the length of the recording head is completed in one main scan are being attempted. By a method such as reciprocal printing, all carriage scanning returning to the home position without performing any recording is omitted, so that the recording time per page can be substantially reduced by half. Further, in the method of forming an image by one main scan, it is not necessary to scan the same portion on the recording paper many times, and the printing time can be greatly reduced. There is also known a method of shortening the printing time by moving the carriage at a high speed.

In order to realize high quality images,
A method such as multi-pass printing, in which an image having the same width as the length of the recording head is completed by main scanning at a degree or more, has also been attempted. With such a method, it is possible to alleviate variations inherent in each head.

In this case, in order to complete the image by dividing it into a plurality of times, printing is performed using a set of masks as shown in FIGS. 19A and 19B, for example. In the figure, the hatched portion represents a print region, and the non-hatched portion represents a non-print region. In this case, the logical product of the print area of the mask and the actual image area is calculated to determine the print area.

By using different masks for different ink types, or using masks offset for each ink type, unevenness inherent to the mask is reduced, and a higher quality image can be obtained. It is known to be obtained.

Further, there is a printing method in which low-pass printing can provide the same effect as multi-pass printing by providing two or more heads having the same type of ink. FIG. 20 shows an example in which heads 84 having black ink are arranged at both ends of heads 81 to 83 of color ink. Also in this case, the heads at both ends for ejecting two identical types of ink use a mask as shown in FIG.
The two heads are complementary.

[0011]

SUMMARY OF THE INVENTION The present inventors have developed a color ink jet recording method using a black ink having low permeability to a recording material and a color ink having high permeability to the recording material. In, the reciprocating printing and multi-pass printing as described above, using a printing method with multiple heads,
Various studies were made to shorten the printing time and achieve high-quality printing. As a result, the following technical problem was newly found.

That is, in color ink jet recording, black ink and color ink are sometimes superimposed and printed in order to smooth the gradation. When such a printing method is performed in the above-described ink jet recording apparatus capable of reciprocating printing, in a multi-pass printing using different masks for color and black head, and when a head having the same kind of ink is used, It has been found that when there are two or more colors, the reproduced color tone may be different depending on the application order of the color ink and the black ink.

That is, the color tone may differ between the case where an image which should have the same color tone is printed when the print head is scanned in the forward direction and the case where the image is printed when the image is scanned in the backward direction. (This phenomenon is hereinafter referred to as “reciprocal unevenness”). In particular, such a phenomenon is remarkably detected in a region where a large amount of color ink and black ink are applied to the paper surface.

In multi-pass printing, when different masks are used for color and black heads, and when there are two or more heads having the same type of ink, black and color inks are applied in different application orders. There are places, which may cause non-uniform unevenness.

Such a phenomenon (unevenness caused by a difference in the application order of the color ink and the black ink) may significantly deteriorate the image in which the color and the black are mixed, and may cause a higher quality image. We have come to the conclusion that this is a technical problem that must be solved when developing an inkjet recording device capable of recording multicolor images at high speed.

An object of the present invention is to provide an image recording method capable of recording a higher quality multicolor image in a shorter time.

Another object of the present invention is to provide a method for improving the image quality of a multicolor image using an ink jet recording apparatus.

Another object of the present invention is to provide an image recording apparatus capable of recording a higher quality multicolor image at a high speed.

Another object of the present invention is to provide an ink set and a recording unit suitably used in an ink jet recording apparatus capable of recording a higher quality multicolor image at a high speed.

[0020]

An image recording method according to an embodiment of the present invention, which can achieve the above object, is a method for recording a multicolor image including an image in which the order of alternately superimposing black ink and color ink is different. A recording method, wherein the black ink contains a salt, an aqueous medium and a pigment dispersed in the aqueous medium by the action of an ionic group, and the color ink contains a dye.

A method for improving the quality of a multicolor image according to an embodiment of the present invention, which can achieve the above object, uses an ink jet recording head individually provided with black ink and color ink. A method for improving the quality of a multicolor image including an image in which the order in which the black ink and the color ink are alternately superimposed, wherein the black ink is dispersed in the aqueous medium by the action of a salt, an aqueous medium and an ionic group. Black ink containing a pigment and color ink containing a dye are used.

The image recording apparatus according to one embodiment of the present invention, which can achieve the above object, comprises: (i) an ink jet recording head which individually discharges black ink and color ink onto a recording material; And (ii) in the image recording apparatus provided with means for conveying the recording material to a recording position by the recording head, wherein the black ink is dispersed in the aqueous medium by the action of a salt, an aqueous medium, and an ionic group. The color ink contains a pigment, and the color ink contains a dye.

An ink set according to an embodiment of the present invention that can achieve the above object is an ink set including a combination of a black ink and a color ink, wherein the black ink is a salt, an aqueous medium, and an ionic ink. A pigment dispersed in the aqueous medium by the action of an ionic group, wherein the color ink comprises a dye which, when mixed with the black ink, destabilizes the dispersion stability of the pigment in the black ink; Or containing an additive that, when mixed with the black ink, destabilizes the dispersion stability of the pigment in the black ink, or contains the dye and the additive. .

Further, the recording unit according to an embodiment of the present invention which can achieve the above object has a black ink containing section containing black ink, an ink jet head for discharging the black ink, and a color ink. A recording unit including a color ink container and an inkjet head for discharging the color ink, wherein the black ink includes a salt, an aqueous medium, and a pigment dispersed in the aqueous medium by the action of an ionic group. The color ink contains a dye that destabilizes the dispersion stability of a coloring material in the black ink when mixed with the black ink, or contains a color in the black ink when mixed with the black ink. Including an additive that destabilizes the dispersion stability of the material, or including the dye and the additive It is characterized in that there.

By employing the various configurations described above, for example, when a multi-color image is printed at a high speed by performing printing in both the forward scan and the backward scan of the print head. It can significantly improve the reciprocating unevenness that has been observed, and has the effect of obtaining a good image with a small optical density difference due to the difference in the scanning direction in low-pass reciprocal printing. It is. Furthermore, a good image can be obtained by suppressing poor uniformity on the image caused by the presence of a printing portion in the image in which the application order of the color ink and the black ink is different, which occurs in the multi-pass printing or the like. be able to.

In a more preferred embodiment of the present invention,
As the color ink, a color ink containing a dye that destabilizes the dispersion stability of the pigment in the black ink when mixed with the black ink is used, or when mixed with the black ink, the black ink is used. Use a color ink containing an additive that destabilizes the dispersion stability of the pigment in the ink, or a dye that destabilizes the dispersion stability of the pigment in the black ink when mixed with the black ink. And color inks containing both additives. By adopting such a mode, it is possible to more effectively improve the uniformity on the image generated in the reciprocating unevenness and the multi-pass printing.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to various embodiments.

In the first embodiment of the present invention, when an image is formed by alternately overlaying black ink and color ink on a recording material, the black ink and the color ink are applied to the recording material. In the recording method in which the order of application to the image forming site is changed, a black ink containing a salt, an aqueous medium and a pigment dispersed in an aqueous medium by the action of an ionic group is used as the black ink, and the black ink is used as the color ink. A color ink containing a dye as a coloring material is used.

According to this embodiment, as described above,
The influence of the order of applying the black ink and the color ink on the image unevenness can be reduced. Although it is not clear why such an effect can be obtained, the present inventors have repeatedly studied the above technical problem and purpose, and as a result, the above image unevenness is caused by a difference in permeability between black ink and color ink. Supposed to be

That is, for example, in the case of reciprocating printing, when the order of application of ink at the time of scanning in the forward direction of the head is black ink and then the order of color ink, the application of ink at the time of scanning in the backward direction of the head is performed. The order is color ink followed by black ink, but it is considered that the reciprocating unevenness occurs as a result of different degrees of penetration of the coloring material into the recording material in each case.

Using FIG. 11, FIG. 22, and FIG. 23, an ink set (hereinafter, referred to as “control ink”) consisting of a black ink containing no pigment and containing a pigment as a color material and a color ink containing a dye as a color material, using FIGS. This is referred to as “set”.

First, the optical density and the amount of the pigment coloring material present on the paper will be described. When ordinary black ink is applied on the paper surface, on the paper surface and near the surface in the paper surface
(Hereinafter referred to as “above the paper”) shows the dominant contribution of the reflection optical density. The relationship between the pigment fixed above the paper surface and the optical density usually shows a saturation curve as shown in FIG.

As an example, the state of the color material on the paper at the time of recording using the reference ink set will be described.

When the black ink of the control ink set is discharged alone, the fixing amount of the color material and the optical density above the paper surface are determined by the point 23 in the curve shown in FIG.
Suppose you hit 01. Since black ink generally has low permeability, a large amount of pigment is fixed relatively above the paper surface.

Next, the case where the color ink of the control ink set is applied to the paper surface prior to the black ink will be described. In this case, as shown in FIG.
Since the black ink 1101 is applied to the surface of the easily wettable (easily penetrated) recording medium 1103 to which the color ink 1105 has already been applied, FIG.
As described above, the coloring material of the black ink easily permeates into the recording paper. For this reason, the optical density decreases. Also,
In this printing order, since the black ink penetrates after the color ink penetrates uniformly, there is no problem in uniformity.

Next, a case where black ink is applied to the paper surface prior to color ink will be described. In this case, FIG.
As shown in FIG. 1A, the black ink 1101 having low permeability covers the recording medium 1103. In this state, the black ink 1101 permeates the recording medium 1103 at a low speed because of low permeability. Then, a highly permeable color ink 1105 is applied thereafter, and as shown in FIGS. 11B and 11C, the surface of the recording medium is black ink.
Since it is covered with 1101, the permeability of the black ink does not change much.

In such a situation, the black ink penetrates into the recording medium very slowly, so that the coloring material of the black ink tends to remain on the surface of the recording medium, and as a result, the printed matter has a high optical density. become. In addition, when the applied amount of the color ink is large, since the color ink and the black ink do not mix uniformly on the recording medium, the image may not be uniform.
(Furthermore, the optical density may decrease due to the non-uniformity.) Further, since the color ink has a high permeability, the color ink passes through the gap of the pigment aggregate on the paper surface, and as shown in FIG. It is thought that it will penetrate as shown in d) as 1105.

Using the optical density-pigment color material amount curve described above, the mechanism by which the difference in optical density occurs due to the reversal of the application order will be described.

As described above, the point 2301 in FIG. 23 (a) is the amount of the pigment coloring material present above the paper surface when the black ink of the control ink set is applied alone to the paper surface, and the realized optical density. It is a thing showing the relationship. In this case, as described above, the amount of the pigment coloring material fixed above the paper surface is relatively large.

Next, point 2302 is the relationship between the amount of black ink fixed above the paper surface and the optical density when the color ink is applied onto the paper surface before the black ink. In this case, as shown in FIGS. 11 (e) to 11 (g), since the black ink permeates the paper surface, the amount of the pigment existing above the paper surface decreases, and the optical density is low. Further, the dye contained in the color ink has a high permeability of the color ink and penetrates into the paper, so that the dye does not contribute much to the optical density.

Next, point 2303 is the relationship between the amount of pigment coloring material and the optical density when the color ink is applied after the black ink is applied. In this case, as shown in FIGS. 11A to 11D, the permeation speed of the pigment color material on the paper surface is low because of the low permeation speed of the black ink 1101. as a result,
The amount of the pigment fixed on the upper side of the paper is almost the same as that in the case of printing with the black ink alone.

Color ink on pigment fixed above paper
Strictly speaking, the dye in 1105 shows a slightly higher optical density than the black ink alone, but the colorant density in the inkjet ink is not so high, so 2303 and 2301 There is no significant difference in optical density between the two. But 2302 and
There is a large difference in optical density between 2303 and 2303, and a difference occurs in the density of the obtained image depending on the application order of black ink and color ink.

Further, this phenomenon also depends on the application amounts of the color ink and the black ink to the paper surface. FIG.
3 (b) shows the difference between the optical densities when the black ink ejection amount and the color ink ejection amount are small. In this case, since the color ink has a small ejection amount, the high permeability of the color ink has little effect on the permeability of the black ink to the recording material.

Therefore, when the color ink is applied on the paper surface prior to the black ink, the amount of the black ink fixed above the paper surface (point 2312) is substantially the same as the fixed amount of the black ink alone (point 2311). It is.
In addition, even when the black ink is applied prior to the color ink, the influence on the amount of the black ink fixed above the paper surface is small, and the amount of the dye on the pigment fixed above the recording material is also small, It has little effect on improving optical density (point 2313).

That is, the density difference 2314 between the points 2312 and 2313 is not so large. Further, since the color ink and the black ink are present in small amounts, the uniformity is not deteriorated.

Next, there is a case where the application amounts of the black ink and the color ink to the paper surface are large. In this case, as shown in FIG. 23 (c), there is a large difference 2324 in the optical density due to the difference in the printing order. This is because the amount of black ink fixed above the paper surface is greatly reduced when the color is applied on the paper surface first.

○ With non-reactive salt In contrast to the phenomenon observed with the above control ink set,
Let us look at the case where the ink set according to the first embodiment of the present invention is used.

First, a description will be given of the difference in the state of penetration of the black ink containing salt and the black ink containing no salt onto the recording material when applied to the recording material.

FIGS. 9 (a) to 9 (c) and 10 (a) to 10 (c) respectively show a black ink containing a salt and a black ink containing no salt discharged from an orifice by an ink jet recording method. FIG. 4 is an explanatory diagram schematically and conceptually showing a state of solid-liquid separation that occurs when applied to a recording medium having high performance.

That is, immediately after the ink has landed, the pigment ink 901 or 1001 is applied to the paper (90) regardless of the addition of the salt as shown in FIGS. 9 (a) and 10 (a).
3 or 1003) on the surface.

After the lapse of the time T1, the pigment ink to which the salt has been added, as shown in FIG. 9 (b), rapidly undergoes solid-liquid separation, and the area where most of the solid components in the ink are abundantly contained.
05 and the solvent in the ink are separated, and the permeation tip 907 of the separated solvent proceeds into the paper 903. On the other hand, as shown in FIG. 10 (b), the pigment ink to which no salt is added does not undergo solid-liquid separation as quickly as the ink to which salt has been added. Infiltrate into.

After a lapse of time T2, as shown in FIG. 9 (c), the pigment ink to which the salt has been added further penetrates into the inside of the paper at the solvent permeation tip 907, but the area 905 includes the surface of the paper and its surface. Maintained in the vicinity. On the other hand, in the pigment ink to which no salt is added, as shown in FIG. 10 (c), solid-liquid separation starts gradually at this point, and the solid-liquid separation tip 1007 and the solvent However, the solid content-containing region 1005 in the ink reaches a deep portion of the recording medium.

The times T1 and T2 in the above description
Is a reference time for conceptually understanding the difference in solid-liquid separation due to the presence or absence of salt.

As is clear from the above description, the addition of a salt causes solid-liquid separation to occur quickly,
It is presumed that the above-described effect is produced because the liquid permeates into the paper together with the solid-liquid separation at a relatively fast stage. That is, it is considered that the image quality is hardly influenced by the degree of permeability of the recording medium by adding the salt. Among the above-mentioned salts, sulfates (for example, potassium sulfate, etc.) and benzoates (for example, ammonium benzoate) have good compatibility with self-dispersion type carbon black, and specifically, solid-liquid separation when applied to a recording medium. Because of the particularly excellent effect, it is possible to form an ink jet recorded image of particularly excellent quality on various recording media.

For the reasons described above, when the black ink according to the present embodiment is applied alone on paper, the black ink has low permeability and the solid-liquid separation speed is high due to the effect of salt. The concentration of the pigment fixed above the paper is very high. Therefore, it shows a higher optical density than the black ink of the control ink set.

Next, the case where the color ink and the black ink constituting the ink set according to this embodiment are applied to the recording medium in the order of color and black is shown in FIGS.
Shown in Since the black ink 1201 is applied to the recording medium 1203 whose permeability is increased by the color ink 1205, the penetration of the black ink becomes faster. However, due to the effect of the salt coexisting in the black ink, solid-liquid separation of the black ink occurs quickly with respect to penetration of the coloring material in the black ink into the recording medium, and the solidifying of the coloring material is performed quickly. As shown in FIG. 12 (g), the penetration of the color material in the black ink into the recording medium is suppressed. The resulting print has a high optical density. Reference numeral 1207 denotes a leading end of the aqueous medium in the ink.

Conversely, the case where black ink and color ink are applied in this order is shown in FIGS. First, FIG.
As shown in (a), low permeability black ink 1201
Covers the recording medium 1203. In this state, the black ink 1201 permeates the recording medium 1203 at a low speed because of its low permeability. In addition, the pigment in the black ink causes rapid aggregation on the surface of the recording material due to the action of the salt. Then, even after the highly permeable color ink 1205 is applied as shown in FIG. 12 (b), the surface of the recording medium is covered with the black ink 1201 in which the aggregation of the pigment is rapidly progressing. The permeability of the pigment in it does not change much.

As a result, as shown in FIG. 12C, the pigment in the black ink tends to remain on the surface of the recording medium 1203, and as a result, the printed matter has a high optical density. Even when the amount of the color ink applied is large, a sufficient solid content remains above the paper surface due to the solid-liquid separation of the black ink, so that the state of uniformity is good. In addition, although a part of the dye in the color ink is on the pigment fixed above the recording medium, the dye concentration in the inkjet ink is usually not so high. Is less. In this regard, in this regard, when the dye concentration in the color ink is 10% by mass or less of the total mass of the color ink, the contribution of the dye on the fixed pigment to the optical density is substantially negligible. It will be.

The reason why the deviation of the optical density due to the order of applying the black ink and the color ink when the black ink has a salt is suppressed is as described above.

Here, the point 2331 in FIG.
The graph shows the amount of the pigment coloring material present above the paper surface and the achieved optical density when the black ink according to the present embodiment is applied alone to the recording material. In this case, a high optical density is exhibited due to the presence of the salt.

Next, when the color ink is applied prior to the black ink, as shown at point 2332, the fixing amount of the black ink is slightly reduced by increasing the permeability of the color ink. However, since the black ink rapidly causes solid-liquid separation, the penetration of the pigment in the black ink into the paper is suppressed, and the amount of the pigment fixed above the paper is large.

When the black ink is applied prior to the color ink, the black ink hardly increases in permeability, so that it is sufficiently fixed above the paper surface.
(Point 2333).

In either order, most of the dye penetrates into the paper because the dye has high permeability to the color ink, and the influence on the optical density is small. By using such a mechanism, regardless of the order in which the black ink and the color ink are applied, high optical density is exhibited in both cases, whereby density unevenness (2334) due to the application order can be effectively suppressed.

Second Embodiment Reaction System Compared with the first embodiment, the unevenness of the image density caused by the order of applying the color ink and the black ink can be further improved, and an image of excellent quality can be obtained. A second embodiment suitable for obtaining is described.

The visual optical density of an image formed on a recording material is generally determined by the amount of coloring material on the surface of the recording material and within a range of about 15 to 30 μm from the surface. It is considered that in order to obtain a high density image,
It is necessary to make the coloring material exist at a high density within the above range. And in this embodiment, an aqueous medium, a black ink containing a pigment dispersed in the aqueous medium by a salt and an ionic group, and a dye as a coloring material, and the dispersion stability of the pigment in the black ink By using a color ink containing a component that destabilizes
The occupation density of the coloring material in the above range of the recording material can be further improved, and the unevenness can be eliminated very effectively.

Second Embodiment (1) First, the case where the component that destabilizes the dispersion stability of the pigment in the black ink is the dye itself in the color ink will be described. That is, an embodiment in which the dye in the color ink directly reacts with the pigment will be described.

FIGS. 13 (d) to 13 (d) show the behavior of the ink on the paper when the color ink and black ink constituting such an ink set are applied to the recording medium in this order.
(f) schematically and schematically shows.

In this case, the black ink 1305 is placed on the recording medium 1303 whose permeability has been increased by the color ink 1305.
Since 301 is added, the penetration of the black ink becomes faster. However, due to the effect of the salt coexisting in the black ink, solid-liquid separation of the black ink occurs quickly with respect to penetration of the coloring material in the black ink into the recording medium, and the solidifying of the coloring material is performed quickly. As shown in FIG. 13F, the penetration of the color material in the black ink into the recording medium is suppressed.

Further, the dye coloring material present in the color ink and the black ink react on the surface of the paper surface to form aggregates 1309, whereby the penetration into the recording material is more effectively suppressed. In the case of the above-described control ink set, the dye in the color ink hardly contributes to the formation of agglomerates because it penetrates deep into the recording material, but in this embodiment, the dye reacts with the pigment. The dye thus dyed is fixed above the paper surface and contributes to the formation of aggregates.

Further, the pigment which has not contributed to the reaction also rides on the aggregate as shown in FIG. 13 (f) due to the formation of the aggregate. This effectively suppresses a decrease in the optical density due to the penetration of the pigment into the paper surface due to the permeability of the color ink, and maintains a high optical density. Reference numeral 1307 denotes a leading end of the aqueous medium in the ink.

Conversely, the case where black ink and then color ink are applied in this order will be described with reference to FIGS. 13 (a) to 13 (c).

As shown in FIG. 13A, the black ink 1301 having low permeability covers the recording medium 1303. In this state, the black ink 1301 permeates the recording medium 1303 at a low speed because of its low permeability. In addition, the salt causes rapid aggregation on the pigment in the black ink and on the surface of the recording medium.

Then, as shown in FIG. 13B, even if the color ink 1305 having high permeability is applied, the surface of the recording medium is covered with the black ink 1301, so that the permeability of the pigment in the black ink is reduced. Not much. In such a situation, the permeation of the black ink 1301 and the color ink 1305 into the recording medium 1303 is slow.
As shown in FIG. 3 (c), the color material of the black ink is 1303
Easy to remain on the surface.

Further, since the color ink is mixed with the black ink in a state where the black ink is sufficiently left on the paper surface, the dye and the pigment sufficiently react with each other, and the dye and the pigment are mixed on the paper surface. A large amount of mixed agglomerate 1309 remains on the paper. Therefore, a high optical density is exhibited.

Here, although the dye in the color ink rides on the surface of the dye-pigment aggregate on the recording material, the dye concentration in the inkjet ink is not so high.
Between the color ink described in FIGS. 13D to 13F and then the image formed by applying the black ink in this order,
There is no visually discernable difference in optical density.

In the present embodiment, the reason why the deviation of the optical density depending on the application order of the color ink and the black ink is suppressed is as described above.

A point 2341 in FIG. 23 (e) indicates the amount of the pigment coloring material present above the paper surface when the black ink of the ink set according to the present embodiment is applied alone to the recording material, and the optical density realized thereby. It is shown. In this case, a high optical density is exhibited due to the presence of the salt.

Next, when the color ink is applied prior to the black ink, as shown at point 2342, the decrease in the fixed amount of the black ink due to the increased permeability of the color ink is caused by the black ink and the color ink. Very low due to reaction and rapid solid-liquid separation by the salt in the black ink. Further, as described above, the dye that has contributed to the reaction participates in the formation of aggregates and is fixed on the paper. Therefore, strictly speaking, the relationship between the density of the image and the fixing amount of the color material due to the superposition of the black ink and the color ink is not plotted on the curve of the pigment alone.
The curve on which point 2341 is riding and points 2342 and 234
The difference (2345) between the curve on which 3 is riding represents the difference. However, the concentration of the dye in the inkjet ink is not so high. For example, if the dye concentration of the color ink is about 10% by mass or less of the mass of the color ink, this difference is not a difference that can be visually recognized.

When the black ink is applied prior to the color ink, the solid-liquid separation of the black ink proceeds rapidly, and the dye is sufficiently mixed with the pigment on the paper surface. Are sufficiently fixed above the recording material, thereby exhibiting a high optical density.

With such a mechanism, regardless of the application order of the black ink and the color ink, both exhibit a high optical density, and the penetration of the black ink is effectively suppressed, especially when the color is applied prior to the application. It is possible to more effectively suppress unevenness due to the order of applying ink.

The content of the dye in the color ink is preferably 10% by mass or less based on the total mass of the color ink. That is, if the concentration is at this level,
When the black ink is applied prior to the color ink, the contribution of the dye on the agglomerates to the optical density becomes too large, and the difference between the black ink and the image when the color ink is applied prior to the black ink. It is possible to extremely effectively prevent the occurrence of unevenness due to the difference in the order of ink application without increasing the deviation, and to achieve a level at which little or no difference occurs in optical density by visual observation. it can.

Second Embodiment (2) Reaction System Finally, as another form of the second embodiment, a component for destabilizing the dispersion stability of the pigment in the black ink is added to the color ink. The following is an explanation of an embodiment that is an additive.

FIG. 2 shows a case where the color ink and the black ink according to this embodiment are applied to a recording medium in this order.
4 (e) to (g). In this case, since the black ink 2401 is applied to the recording medium 2403 whose permeability is increased by the color ink 2405, the penetration of the black ink becomes faster.

However, due to the effect of the salt coexisting in the black ink, solid-liquid separation of the black ink occurs quickly with respect to the penetration of the color material in the black ink into the recording medium, and the solidification of the color material proceeds quickly. Furthermore, the color ink and the black ink react on the surface of the paper surface due to the additives present in the color ink. This allows
The dispersion stability of the pigment in the black ink becomes unstable, and pigment aggregates 2410 precipitate.

As a result, the penetration of the pigment into the recording medium is suppressed, and as shown in FIG. 24 (f), the aggregate 2410 of the pigment coloring material is present above the recording medium, resulting in a high optical density. The concentration is maintained. In this embodiment, the dye of the color ink does not participate in the reaction with the black ink,
Further, since the color ink has high permeability, the color ink rapidly penetrates into the paper surface, so that the optical density hardly increases due to the dye in the color ink. Reference numeral 2412 denotes a leading end of the ink penetrating the aqueous medium.

Conversely, when black and color inks are applied in this order, the black ink 2401 having low permeability covers the recording medium 2403 as shown in FIG. In this state,
The black ink 2401 permeates the recording medium 2403 at a low speed because of its low permeability. In addition, the pigment in the black ink undergoes rapid solid-liquid separation on the surface of the recording medium due to the action of the salt, and accordingly causes rapid aggregation.

Then, as shown in FIG. 24B, even if the color ink 2405 having a high permeability is applied, the surface of the recording medium is covered with the black ink 2401, so that the permeability does not change much. In such a situation, the recording medium 2403 of black ink 2401 and color ink 2405
24C, the black ink coloring material tends to remain on the surface of the recording medium 2403 as shown in FIG.

Further, since the color ink is mixed with the black ink in a state where the black ink is sufficiently left on the paper surface, the color ink and the pigment react sufficiently,
The pigment remains on the paper in large quantities as aggregates 2410 on the paper. Therefore, a high optical density is exhibited. Here, although the dye in the color ink is on the pigment aggregates 2410, the concentration of the dye in the inkjet ink is usually not so high, and the color ink and the black ink described in FIGS. It does not cause a difference in optical density that can be visually discerned from an image formed by sequentially giving the images. Further, in this regard, the content of the dye in the color ink is 1 to the total mass of the color ink for the same reason as described above.
The content is preferably set to 0% by mass or less. Further, it is considered that some dyes in the color ink penetrate into the recording medium through pigment aggregates.

In this embodiment, the reason why the deviation of the optical density depending on the order of applying the color ink and the black ink is suppressed is as described above.

According to this embodiment, as shown in FIG. 23 (f), the optical density point 2351 for black alone, the point (2352) for color first-stroke black post-strike, and the black first-stroke color post-strike point. Point 2353 is almost the same point. That is, the improvement of the density unevenness caused by the order of application of the ink can be improved to a level that does not cause any problem by the first embodiment (1), but according to the second embodiment, a more ideal state is achieved. Becomes

Further, as a variation of the second embodiment, a combination of (1) and (2) of the second embodiment is also included in the scope of the present invention. That is, as a color ink, a dye that destabilizes the dispersion stability of the pigment in the black ink when mixed with the black ink, and a dispersion stability of the pigment in the black ink when mixed with the black ink A color ink containing an additive that destabilizes the color ink may be used.

Next, the structure, recording method, recording apparatus and the like of the ink used in the first embodiment will be described.

The ink jet recording method according to the first embodiment includes an image recording method in which the black ink and the color ink are alternately overlapped by using an ink jet recording head individually provided with the black ink and the color ink. A method for recording a multicolor image, wherein the black ink has one feature in that it includes a salt, an aqueous medium, and a pigment coloring material dispersed in the aqueous medium by the action of an ionic group. The color ink is at least one selected from color materials for cyan, magenta, yellow, red, green and blue, for example.
It has two color materials.

[Regarding Black Ink] (Regarding Carbon Black) As a coloring material in the black ink, for example, carbon black is preferably used. The form of dispersion of carbon black in the ink may be a self-dispersion type or a form of dispersion with a dispersant.

(Self-dispersion type carbon black) As the self-dispersion type carbon black, for example, at least one hydrophilic group (anionic group or cationic group) is used as an ionic group directly on the surface of the carbon black or another atom. And carbon black bonded through groups.
By using this, it is not necessary to add a dispersant to disperse the carbon black.

In the case of carbon black having an anionic group bonded to the surface directly or via another atomic group, examples of the hydrophilic group bonded to the surface include, for example, -COO (M2), -SO ₃ (M2), -PO ₃ H (M2), -PO
₃ (M2) _{2 and the} like. In the above formula, "M2" represents a hydrogen atom, an alkali metal, ammonium or organic ammonium.

Among these, particularly, -COO (M2), -SO
_The self-dispersible carbon black in which ₃ (M2) is anionically charged by bonding to the carbon black surface is particularly suitable for use in this embodiment because of its good dispersibility in the ink.

By the way, among the hydrophilic groups represented by "M2", specific examples of the alkali metal include:
Examples thereof include Li, Na, K, Rb, and Cs. Specific examples of the organic ammonium include, for example, methylammonium, dimethylammonium, trimethylammonium, ethylammonium, diethylammonium, triethylammonium, methanolammonium, dimethanolammonium, and triammonium. Methanol ammonium and the like.

The ink of the present embodiment containing self-dispersible carbon black in which M2 is ammonium or organic ammonium can further improve the water resistance of a recorded image, and is particularly suitable in this respect. It is. This is considered to be due to the effect that when the ink is applied on the recording medium, ammonium is decomposed and ammonia is evaporated.

Here, the self-dispersion type carbon black in which M2 is ammonium (in the production method) may be, for example, a method in which self-dispersion type carbon black in which M2 is an alkali metal is replaced with ammonium by ion exchange method or an acid. Was added to form H-form, and then ammonium hydroxide was added to form M2.
To ammonium.

As a method for producing self-dispersible carbon black charged anionic, for example, a method of oxidizing carbon black with sodium hypochlorite may be mentioned.
Na groups can be chemically bonded.

In the case of cationically charged carbon black, those in which a hydrophilic group bonded directly or via another atomic group is bonded to at least one selected from the following quaternary ammonium groups, for example, are exemplified. Can be

[0103]

[0104]

Embedded image In the above formula, R represents a linear or branched alkyl group having 1 to 12 carbon atoms, a phenyl group which may have a substituent or a naphthyl group which may have a substituent.

[0105] Note that the above cationic such as NO as a counter ion based ₃ ^- and CH ₃ COO ^- is present.

As a method for producing a cationically charged self-dispersible carbon black having a hydrophilic group bonded thereto as described above, for example, a method for bonding an N-ethylpyridyl group having the following structure is exemplified. To illustrate with an example:

[0107]

Embedded image A method of treating carbon black with 3-amino-N-ethylpyridinium bromide. Carbon black charged anionic or cationic by the introduction of a hydrophilic group to the surface of the carbon black in this manner has excellent water dispersibility due to repulsion of ions, so even when contained in an aqueous ink, A stable dispersion state is maintained without adding a dispersant or the like.

Incidentally, various hydrophilic groups as described above are
It may be directly bonded to the surface of carbon black. Alternatively, another atomic group may be interposed between the carbon black surface and the hydrophilic group, and the hydrophilic group may be indirectly bonded to the carbon black surface.

Here, specific examples of the other atomic groups include a linear or branched alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, and a substituted or unsubstituted naphthylene group. Can be Here, examples of the substituent of the phenylene group and the naphthylene group include a linear or branched alkyl group having 1 to 6 carbon atoms.

Specific examples of the combination of another atomic group and a hydrophilic group include, for example, -C ₂ H ₄ COOM, -Ph-SO ₃ M,-
Ph-COOM and the like (where Ph represents a phenyl group).

Incidentally, in the present embodiment, two or more of the above-mentioned self-dispersion type carbon blacks may be used as a coloring material of an ink appropriately selected. The amount of the self-dispersible carbon black in the ink is 0.1 to 15% by mass, especially 1 to 15% by mass based on the total mass of the ink.
It is preferable to be in the range of 10% by mass. Within this range, the self-dispersion type carbon black can maintain a sufficiently dispersed state in the ink. Further, a dye may be added as a coloring material in addition to the self-dispersion type carbon black for the purpose of adjusting the color tone of the ink.

(Normal Carbon Black) As a coloring material for black ink, ordinary carbon black, which is not a self-dispersion type, can also be used.

Examples of such carbon black include carbon black pigments such as furnace black, lamp black, acetylene black, channel black and the like.
50, Ray-Van 5250, Ray-Van 5000ULTRA-, Ray-Van 3500, Ray-Van 2000, Ray-Van 1500, Ray-Van 1250, Ray-Van 1200, Ray-Van 1190 ULTR
A-II, Ray-Van 1170, Ray-Van 1255 (all manufactured by Columbia), Black Pearls (Black Pearls) L, Regal (Regal) 400R, Regal 330R, Legal 660R,
Mogul L, Monarch 700, Monak 80
0, Monak 880, Monak 900, Monak 1000, Monak 1100,
Monak 1300, Monak 1400, Valcan XC-72
R (Cabot Corporation), Color Black (Color Bla
ck) FW1, color black FW2, color black F
W2V, color black FW18, color black FW20
0, color black S150, color black S160, color black S170, PRINTEX 35, PRINTEX U, PRINTEX V, PRINTEX 140
U, Printtex 140V, Special Black (Speci
al Black) 6, Special Black 5, Special Black 4A, Special Black 4 (from Degussa),
No. 25, No. 33, No. 40, No. 47, No. 52, No. 900,
No.2300, MCF-88, MA600, MA7, MA8, MA
100 (Mitsubishi Chemical Corporation) etc. can be used,
The carbon black is not limited to these, and conventionally known carbon black can be used.

Further, magnetic fine particles such as magnetite and ferrite and titanium black may be used as a black pigment.

When such a normal carbon black is used as a coloring material of a black ink, it is preferable to add a dispersant to the ink in order to stably disperse the carbon black in an aqueous medium.

As the dispersant, for example, having an ionic group,
What can stably disperse carbon black in an aqueous medium by its action is suitably used, and as such a dispersant, for example, specifically, as a dispersant,
Styrene-acrylic acid copolymer, styrene-acrylic acid-
Acrylic acid alkyl ester copolymer, styrene-maleic acid copolymer, styrene-maleic acid-alkyl acrylate copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-alkyl acrylate copolymer, Styrene-maleic acid half-ester copolymer, vinylnaphthalene-acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer, styrene-maleic anhydride-maleic acid half-ester copolymer, or
These salts are exemplified. In this, the mass average molecular weight is
It is preferably in the range of 1000 to 30,000, more preferably in the range of 3000 to 15,000.

(Regarding the Salt of the Black Ink) The salt of the black ink according to the present embodiment includes (M1)
₂ SO ₄ , CH ₃ COO (M1), Ph-COO (M1), (M
1) NO ₃ , (M1) Cl, (M1) Br, (M1) I, (M1) ₂ S
It is preferable to use at least one selected from O ₃ and (M1) ₂ CO ₃ . Here, M1 represents an alkali metal, ammonium or organic ammonium, and Ph represents a phenyl group.

Specific examples of the alkali metal include Li, Na, K, Rb, and Cs. Specific examples of the organic ammonium include methyl ammonium and
Examples include dimethylammonium, trimethylammonium, ethylammonium, diethylammonium, triethylammonium, trimethanolammonium, dimethanolammonium, trimethanolammonium, ethanolammonium, diethanolammonium and triethanolammonium.

As described above, by coexisting the above-described salt in the ink containing the self-dispersible carbon black, it is possible to stably produce high-quality images without greatly changing the image quality depending on the type of recording medium. An ink that can be formed can be obtained.

The detailed mechanism by which the ink according to this embodiment exhibits the above-described characteristics is not clear at present. However, with respect to the Ka value obtained by the Bristow method, which is known as a measure of the permeability of the ink into the recording medium, the ink of the present embodiment is compared with an ink having the same composition except that no salt is added. The present inventors have found that they show a large Ka value.

An increase in the Ka value indicates that the permeability of the ink to the recording medium has been improved, and it is common knowledge of those skilled in the art that the improvement in the permeability of the ink means a decrease in the image density. Was something. That is, it has been recognized by those skilled in the art that the image density is reduced as a result of the permeation of the coloring material into the recording medium along with the permeation of the ink.

Comprehensively judging from such various findings on the ink of the present embodiment, the salt in the ink of the present embodiment is separated from the solvent and the solid content of the ink after application onto the paper surface (solid content). (Liquid separation) very quickly. In other words, if the solid-liquid separation is slow when the ink is applied to the recording medium, the ink is isotropically diffused into the paper together with the color material on the ink having a large value of Ka or on the paper having a large ink permeability, As a result, it is expected that the sharpness (character quality) of the character is impaired, and at the same time, the color density penetrates deep into the paper, so that the image density is also reduced.

However, since such a phenomenon is not observed in the ink of the present embodiment, solid-liquid separation occurs quickly when applied to a recording medium, and as a result, despite the increase in the Ka value of the ink, a high level is achieved. It is presumed to give a different image. In addition, even if the paper has relatively high permeability, in the case of the ink of the present embodiment, it is considered that the reason why it is difficult to cause a phenomenon such as a decrease in character quality and a decrease in image density is the same.
Hereinafter, this point will be further described with reference to FIGS.

FIGS. 9 (a) to 9 (c) and FIGS. 10 (a) to 10 (c) show that the ink containing salt and the ink not containing salt are respectively discharged from the orifice by the ink jet recording method. FIG. 4 is an explanatory diagram schematically and conceptually showing a state of solid-liquid separation that occurs when applied to a high recording medium.

That is, immediately after the ink has landed, as shown in FIGS. 9A and 10A, the pigment ink 901 or 1001 is applied to the paper irrespective of the presence or absence of the salt, as shown in FIGS.
(903 or 1003).

After the lapse of time T1, the pigment ink to which the salt has been added, as shown in FIG. 9 (b), rapidly undergoes solid-liquid separation, and has a region where most of the solid components in the ink are abundantly contained.
05 and the solvent in the ink are separated, and the permeation tip 907 of the separated solvent proceeds into the solvent paper 903. On the other hand, the pigment ink to which no salt is added, as shown in FIG.
Since solid-liquid separation does not occur as quickly as ink with salt added, it permeates into the paper 1003 in a state 1005 where solid-liquid separation is not performed.

After a lapse of time T2: As shown in FIG. 9C, the pigment ink to which the salt is added further penetrates into the inside of the paper at the solvent permeation tip 907, but the area 905 includes the surface of the paper and its surface. Maintained in the vicinity. On the other hand, in the pigment ink to which no salt is added, as shown in FIG. However, the solid content-containing region 1005 in the ink reaches a deep portion of the recording medium.

The times T1 and T2 in the above description
Is a reference time for conceptually understanding the difference in solid-liquid separation due to the presence or absence of salt.

As is clear from the above description, the addition of a salt causes solid-liquid separation to occur quickly,
It is presumed that the above-described effect is produced because the liquid permeates into the paper together with the solid-liquid separation at a relatively fast stage. That is, it is considered that the image quality is hardly influenced by the degree of permeability of the recording medium by adding the salt.

Among the above salts, sulfates (eg, potassium sulfate) and benzoates (eg, ammonium benzoate) have good compatibility with self-dispersible carbon black.
Specifically, it is possible to form an ink jet recorded image of particularly excellent quality on various recording media, probably because the solid-liquid separation effect when applied to the recording medium is particularly excellent.

The content of the self-dispersion type carbon black in the ink is 0.1 to 15 with respect to the total mass of the ink.
% By mass, and particularly preferably in the range of 1 to 10% by mass. The content of the salt is preferably in the range of 0.05 to 10% by mass, particularly 0.1 to 5% by mass with respect to the total mass of the ink. By setting the content of the self-dispersible carbon black and the salt in the ink within the above ranges, more excellent effects can be enjoyed.

(Aqueous Medium in Black Ink) Examples of the aqueous medium used in the black ink according to the present embodiment include, for example, water or a mixed solvent of water and a water-soluble organic solvent. As the water-soluble organic solvent, those having an effect of preventing drying of the ink are particularly preferable.

Specifically, for example, alkyl alcohols having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol; Amides such as formamide and dimethylacetamide; ketones or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol, propylene glycol and butylene glycol , Triethylene glycol,
Alkylene glycols having an alkylene group containing 2 to 6 carbon atoms, such as 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol; lower alkyl ether acetates such as polyethylene glycol monomethyl ether acetate; Glycerin; lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, and triethylene glycol monomethyl (or ethyl) ether;
Polyhydric alcohols such as trimethylolpropane and trimethylolethane; and N-methyl-2-pyrrolidone, 2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone. The water-soluble organic solvents as described above can be used alone or as a mixture. It is desirable to use deionized water as the water.

The content of the water-soluble organic solvent contained in the ink according to this embodiment is not particularly limited, but is preferably in the range of 3 to 50% by mass based on the total mass of the ink. The content of water contained in the ink is preferably in the range of 50 to 95% by mass based on the total mass of the ink.

(Ink characteristics; inkjet discharge characteristics,
Regarding permeability to recording medium) The black ink according to this embodiment can be used for writing implement ink and ink jet recording ink. Examples of the inkjet recording method include a recording method in which mechanical energy is applied to ink to eject droplets, and a recording method in which thermal energy is applied to ink to eject droplets by foaming the ink.
The ink of the present invention is particularly suitable for those recording methods.

When the ink according to each of the above embodiments is used for ink jet recording, it is preferable that the ink has a characteristic that can be ejected from an ink jet head. From the viewpoint of dischargeability from the ink jet head, the properties of the liquid include, for example, a viscosity of 1 to 15 mPa · s and a surface tension of 25 mN / m or more, particularly a viscosity of 1 to 5 mPa · s and a surface tension of 25 mN / m. It is preferably set to 〜50 mN / m.

As a measure of the penetrability of the ink into the recording medium, there is a Ka value obtained by the Bristow method. That is, when the ink permeability is represented by the ink amount V per m ² , the ink penetration amount V (mL / mL) into the recording medium after a predetermined time t has elapsed since the ink droplet was ejected.
m ² = μm) is shown by Bristow's equation shown below.

V = Vr + Ka (t-tw) ^1/2 Here, immediately after the ink droplets adhere to the surface of the recording medium, the ink is absorbed in the irregularities on the surface of the recording medium (the surface roughness of the recording medium). In most cases, it hardly penetrates into the recording medium. The time during that time is the contact time (tw), and the amount of ink absorbed by the concave and convex portions of the recording medium during the contact time is Vr.

If the contact time is exceeded after the ink has been applied, the amount of permeation into the recording medium increases by the time exceeding the contact time, that is, by an amount proportional to the half power of (t-tw). . Ka is a proportional coefficient of this increase, and shows a value corresponding to the permeation rate. The Ka value is determined by the Bristow's method for testing the dynamic permeability of a liquid (for example, trade name:
Dynamic permeability tester S (manufactured by Toyo Seiki Seisakusho) or the like can be used.

In the ink according to each of the embodiments of the present invention, it is preferable that the Ka value is less than 1.5 in order to further improve the quality of a recorded image, and more preferably, it is 0.2 or more and 1.2 or less. It is less than 5. That is, when the Ka value is less than 1.5, solid-liquid separation occurs at an early stage of the process of penetrating the ink into the recording medium, and it is considered that a high-quality image with very little feathering can be formed.

The K according to the Bristow method in the present invention
The a value is based on plain paper (for example, PB paper or electrophotographic method used for a copier or page printer (laser beam printer) using an electrophotographic method or a printer using an ink jet recording method, manufactured by Canon Inc.). This is a value measured using PPC paper, which is used for copying machines, as a recording medium. The measurement environment is assumed to be a normal office environment, for example, a temperature of 20 to 25 ° C. and a humidity of 40 to 60%.

Examples of the preferred composition of the aqueous medium in which the ink according to each of the above embodiments can carry the above-mentioned properties include, for example, glycerin, trimethylolpropane, thiodiglycol, ethylene glycol, diethylene glycol, isopropyl alcohol, and acetylene. It is preferable to include alcohol.

(Regarding Color Ink) As a coloring material that can be used in the color ink, known dyes and pigments can be used. As the dye, for example, an acid dye, a direct dye, or the like can be used. For example, as the anionic dye, any existing dye or newly synthesized dye can be used as long as it has an appropriate color tone and density. It is also possible to use a mixture of any of these.

Specific examples of the anionic dye are shown below.

(Coloring Material for Yellow) CI Direct Yellow 8, 11, 12, 27, 28, 33, 3
9, 44, 50, 58, 85, 86, 87, 88, 89, 98, 100, 110, 1
32 CI Acid Yellow 1, 3, 7, 11, 17, 23, 2
5, 29, 36, 38, 40, 42, 44, 76, 98, 99 C.I. Reactive Yellow 2, 3, 17, 25, 37, 4
2 CI Food Yellow 3 (coloring material for red) CI Direct Red 2, 4, 9, 11, 20, 23, 2
4, 31, 39, 46, 62, 75, 79, 80, 83, 89, 95, 197, 20
1, 218, 220, 224, 225, 226, 227, 228, 229, 230 CI Acid Red 6, 8, 9, 13, 14, 18, 26, 2
7, 32, 35, 42, 51, 52, 80, 83, 87, 89, 92, 106, 11
4, 115, 133, 134, 145, 158, 198, 249, 265, 289 C.I. Reactive Red 7, 12, 13, 15, 17, 2
0, 23, 24, 31, 42, 45, 46, 59 CI Food Red 87, 92, 94 (color material for blue) CI Direct Blue 1, 15, 22, 25, 41, 76 , 7
7, 80, 86, 90, 98, 106, 108, 120, 158, 163, 168, 1
99,226 CI Acid Blue 1,7,9,15,22,23,25,2
9, 40, 43, 59, 62, 74, 78, 80, 90, 100, 102, 104,
117, 127, 138, 158, 161 CI Reactive Blue 4, 5, 7, 13, 14, 1
5, 18, 19, 21, 26, 27, 29, 32, 38, 40, 44, 100 (black colorant) C.I.Direct Black 17, 19, 22, 31, 32, 51, 6
2, 71, 74, 112, 113, 154, 168, 195 CI Acid Black 2, 48, 51, 52, 110, 115, 1
56 CI Food Black 1, 2 (Solvent) Examples of the ink solvent or dispersion medium containing the coloring material for the color ink as described above include water, or water and a water-soluble organic solvent. Examples of the water-soluble organic solvent include the same ones as described in the black ink. When the color ink is applied to a recording medium by an ink jet method (for example, a bubble jet (registered trademark) method), the ink has a desired viscosity and surface tension so as to have excellent ink jet discharge characteristics as described above. It is preferable to prepare as follows.

(Content of Coloring Material) The content of the coloring material in the color ink to be written here is, for example, when the ink is used for ink jet recording, the ink has excellent ink jetting characteristics and the desired color tone and density can be adjusted. It may be appropriately selected so as to have the ink.
The range is preferably from 50 to 50% by mass. The amount of water contained in the ink is preferably in the range of 50 to 95% by mass based on the total mass of the ink. Further, in consideration of unevenness in image density due to the order of ink application, the concentration of the dye in the color ink is preferably 10% by mass or less of the total mass of the color ink containing the dye.

(Permeability of Color Ink) With respect to the above-described color ink, it is preferable to use an ink having a Ka value of, for example, 5 or more, since a high-quality color image can be formed on a recording medium. That is, since the ink having such a Ka value has a high permeability to the recording medium, even when images of at least two colors selected from, for example, yellow, magenta and cyan are to be recorded adjacently, the distance between the adjacent images is low. Color bleeding can be suppressed, and even if these inks are overprinted to form a secondary color image, the permeability of each ink is high. Can effectively suppress bleeding.

As a method for adjusting the Ka value of the color ink to such a value, a conventionally known method such as addition of a surfactant or addition of a permeable solvent such as glycol ether can be applied. Of course, the amount of addition may be selected as appropriate.

(Recording Apparatus Using Ink Set, Recording Method) Next, a recording apparatus according to the present invention will be described. In the present invention, it is preferable to use a method in which a recording signal is applied to the recording ink of the recording head and droplets are ejected by the generated thermal energy. FIGS. 1, 2, and 3 show the configuration of a recording head, which is a main part of the apparatus.

The head 13 includes a heating head 15 (a head is shown in the figure, but is not limited to this) having a glass, ceramic or plastic or the like having an ink flow path 14 and a heating resistor used for thermal recording. Are obtained by bonding. The heating head 15 includes a protective film 16 made of silicon oxide or the like, and aluminum electrodes 17-1 and 17-1.
7-2, a heating resistor layer 18 made of nichrome or the like, a heat storage layer 19, and a substrate 20 having good heat dissipation such as alumina.

The recording ink 21 reaches the discharge orifice 22 and forms a meniscus 23 by the pressure P.

Here, when an electric signal is applied to the electrodes 17-1 and 17-2, the area of the heating head 15 indicated by n rapidly generates heat, and bubbles are generated in the ink 21 in contact with the area. The meniscus is ejected by the pressure, becomes a recording liquid droplet 24 from the orifice 22, and flies toward the recording material 25.

FIG. 3 is a schematic view of a recording head in which a number of nozzles shown in FIG. 1 are arranged. The recording head is formed by closely contacting a glass plate 27 having a number of flow paths and a heating head 28 similar to the head described with reference to FIG.

FIG. 1 shows a head 1 along an ink flow path.
3 is a sectional view, and FIG. 2 is a sectional view taken along line AB in FIG.

FIG. 4 shows an example of an ink jet recording apparatus incorporating this head. Here, the blade 61 is a wiping member, one end of which is held by a blade holding member to become a fixed end, and has a form of a cantilever lever.

The blade is arranged at a position adjacent to the recording area of the recording head, moves in a direction perpendicular to the direction of movement of the recording head, comes into contact with the discharge port surface, and performs capping.

Reference numeral 63 denotes an ink absorber provided adjacent to the blade, which is held in a form protruding into the movement path of the recording head, similarly to the blade. The blade 61, the cap 62, and the absorber 63 constitute an ejection recovery unit 64, and the blade 61 and the absorber 63 remove moisture, dust, and the like from the ink ejection port surface.

Reference numeral 65 denotes a recording head having ejection energy generating means for performing recording by discharging ink on a recording material facing a discharge port surface provided with discharge ports, and 66 denotes a recording head on which the recording head 65 is mounted. This is a carriage for moving the head. The carriage is slidably engaged with a guide shaft 67, and a part of the carriage is connected to a belt 69 driven by a motor 68 (not shown). As a result, the carriage can move along the guide axis, and the recording head can move in the recording area and the adjacent area.

On the other hand, 51 is a recording material supply section for inserting a recording material, and 52 is a feed roller driven by a motor (not shown). With these configurations, the recording material is conveyed to a position facing the ejection port surface of the recording head, that is, a recording position, and is discharged to a discharge unit provided with rollers 53 as recording proceeds.

In the image recording apparatus according to this embodiment, the recording head is reciprocated in a direction perpendicular to the conveying direction of the recording material, and both in the forward scanning and the backward scanning. The head is configured to apply at least one of black ink and color ink to a recording material. Note that a conventionally known technique related to bidirectional printing can be used as a method of processing print data in bidirectional printing.

In the above configuration, when the recording head returns to the home position at the end of recording or the like, the cap 62 of the head recovery unit 64 is retracted from the moving path of the recording head.
The blade protrudes into the movement path. As a result, the ejection port surface of the recording head is wiped. When capping is performed by contacting the cap with the discharge port surface of the recording head, the cap moves so as to protrude into the moving path of the recording head.

When the recording head moves from the home position to the recording start position, the cap and the blade are at the same position as the position at the time of wiping. As a result, even in this movement, the ejection port surface of the recording head is wiped.

The movement of the print head to the home position is not only at the end of printing or at the time of ejection recovery, but also at a predetermined interval while the printing head moves through the printing area for printing. Position, and the wiping is performed with this movement.

FIG. 5 shows an example of an ink cartridge containing ink supplied to the head via an ink supply member, for example, a tube. Here, reference numeral 40 denotes an ink storage portion that stores the supply ink, for example, an ink bag, and a rubber stopper 42 is provided at the tip thereof. Needle in this stopper
(Not shown), the ink in the ink bag 40 can be supplied to the head. Reference numeral 44 denotes an absorber for receiving the waste ink.

[0165] As the ink containing portion, it is preferable that the contact surface with the ink is formed of polyolefin, particularly polyethylene. Further, as another aspect of the cartridge according to the present invention, the cartridge has two accommodating portions accommodating the black ink and the color ink, respectively, and a head for ejecting the black ink and the color ink is provided. An example of the cartridge is a detachable cartridge that is configured so that each ink can be supplied to the recording head.

FIG. 14 shows an example of such a cartridge 1401. Reference numeral 1403 denotes a black ink storage portion containing black ink, and reference numeral 1405 denotes a color ink storage portion containing color ink. As shown in FIG. 15, the liquid composition and the ink are provided so as to be detachable from a recording head 1501 for discharging each of the black ink and the color ink, and the cartridge 1401 is mounted on the recording head 1501. Is supplied to the recording head 1501.

The ink jet recording apparatus used in the present invention is not limited to the one in which the head and the ink cartridge are separated as described above, and a recording unit in which they are integrated as shown in FIG. 6 is also suitable. Used.

In FIG. 6, reference numeral 70 denotes a recording unit, in which an ink storage section for storing ink, for example, an ink absorber is stored, and the ink in such an ink absorber has a plurality of orifices. The head unit 71 is configured to be ejected as ink droplets. As a material of the ink absorber, for example, polyurethane can be used.

Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the recording unit with the atmosphere. This recording unit is used in place of the recording head shown in FIG. 4, and is detachable from the carriage 66.

Further, as another embodiment of the recording unit according to the present invention, the black ink and the color ink (for example, at least one color ink selected from yellow, magenta, cyan, red, green and blue)
And a recording unit integrally containing a recording head for discharging each of the inks in each of the ink storage units in one ink tank, for example, FIG.
, The black ink is stored in the storage section 1601Bk, the yellow, cyan, and magenta color inks are stored in the color ink storage sections 1601Y, 1601C, and 1601M, respectively, and the respective inks can be individually discharged. Head 1603 with separate ink channels
The recording unit 1601 is provided with such a unit.

In the recording apparatus used in the present invention, an ink jet recording apparatus which ejects ink by applying thermal energy to ink is described as an example. However, in the present invention, for example, mechanical energy is applied to ink to apply ink to the ink. The present invention can be similarly applied to a recording apparatus that discharges ink, for example, a piezo-type inkjet recording apparatus that uses a piezoelectric element.

FIG. 17 shows a configuration example of a recording head which is a main part of the recording apparatus. The head includes an ink flow path 1701 communicating with an ink chamber (not shown), an orifice plate 1703 for discharging ink droplets of a desired volume, a vibration plate 1705 for directly applying pressure to ink, and a vibration plate 1705.
Piezoelectric element that is bonded to
And an orifice plate 1703, and a substrate 1709 for pointing and fixing a diaphragm and the like.

In FIG. 17, an ink flow path 1701 is formed of a photosensitive resin or the like, and an orifice plate 1703 is
A discharge port 1711 is formed by drilling a metal such as stainless steel or nickel by electroforming or press working.
5 is formed of a metal film such as stainless steel, nickel, titanium and the like and a high elastic resin film, and the piezoelectric element 83 is
It is formed of a dielectric material such as barium titanate or PZT.

In the recording head having the above-described structure, a pulse voltage is applied to the piezoelectric element 1707 to generate a strain stress, and the energy thereof deforms the diaphragm joined to the piezoelectric element 1707, and the ink flow path 80 The ink in the orifice plate is pressurized vertically and an ink droplet (not shown) is
It operates so as to perform recording by discharging more. Such a recording head is used by being incorporated in a recording apparatus similar to that shown in FIG. The detailed operation of the recording apparatus may be performed in the same manner as described above.

(Resolution of unevenness due to different application order) When the recording method according to the present embodiment is performed, for example, a recording method in which four recording heads shown in FIG. 3 are arranged on a carriage is used. Use the device. FIG. 7 shows an example. Reference numerals 81, 82, 83, and 84 denote recording heads for ejecting recording inks of yellow, magenta, cyan, and black, respectively. These heads are arranged in the above-described printing apparatus, and discharge recording ink of each color according to a printing signal. Further, by adopting a configuration in which the color inks are arranged vertically as shown in FIG. 8, it is also possible to eliminate color unevenness due to a difference in the application order in reciprocal printing between the color inks.

That is, in a printing method such as reciprocating printing in which printing is performed in both the left and right directions which are the main scanning directions in the drawing with the head as shown in FIGS. 7 and 8, the black ink and the color ink are placed at the same location on the recording paper. In some cases. At this time, when the conventional black ink having low permeability to the recording material and the color ink having high permeability are used, printing is performed in the order of color ink and black ink, and black ink and color ink are used. The density may change significantly when printed in the order described above, and this is particularly noticeable in a method such as low-pass printing in which an image having the same width as the length of the recording head is completed in one main scan, As described above, the quality of a multicolor image may be reduced, and this is a technical problem to be solved in forming a high-quality image in which black and color coexist in a short time, as described above.

Further, in a head such as that shown in FIGS. 7 and 8, even when performing multi-pass printing, if different masks are used for different colors, the black ink is first applied to the recording material at the image location. And a portion where the color ink is first applied to the recording material, which causes uneven density unevenness.

Also, in a case where a black image is realized by two heads using a head configuration as shown in FIG. 20, a portion where the black ink is applied to the recording material first, and a portion where the color ink is applied first. Occurs on the recording material, which causes uneven density unevenness.

In order to solve such a problem, according to the present embodiment,
(When the black ink is applied to the recording medium surface,
It is considered that the salt in the black ink plays a role in promoting the separation (solid-liquid separation) between the coloring material in the black ink and the aqueous medium. Therefore, even if the black ink is applied after the color ink having a high permeability through the recording medium is applied, solid-liquid separation occurs due to the action of the salt, and the color material remains on the surface of the recording medium and penetrates into the recording medium. It is thought that it is effectively prevented from doing.

As a result, even in one-pass reciprocal printing in which an image is formed by one main scan, density unevenness can be effectively suppressed in reciprocating printing, and a high-quality inkjet multicolor image can be formed in a short time. It can be formed.
Further, even in the case of multi-pass printing, density unevenness can be effectively suppressed, and an image with a very good uniformity can be realized.

(Second Embodiment) In a second embodiment according to the present invention, the color ink and the black ink used in the first embodiment are used when the color ink and the black ink are mixed. Another feature is that each composition is prepared so that the dispersion stability of the coloring material in the black ink becomes unstable.

(Reactivity of Black and Color Inks) The composition of the black ink and the color ink in this embodiment is as follows.
It is preferable that each of the black ink and the color ink is prepared so as to cause a viscosity increase or agglomeration by reacting when mixed, thereby destabilizing the dispersion stability of the coloring material in the black ink. Examples of such combinations of the black ink and the color ink include the following.

(1) A mode in which the dye in the color ink is used as a component for destabilizing the dispersion stability of the pigment in the black ink; (2) The dispersion stability of the pigment in the black ink in the color ink is A mode in which an additive for destabilization is contained.

More specifically, the mode (1) is as follows.
For example, there are the following two.

I) An example is given in which the coloring material in the black ink has an anionic group and the coloring material of the color ink has a cationic group.

In this example, when the color ink and the black ink are mixed, the cationic group of the color material of the color ink reacts with the anionic group of the color material of the black ink, and the color material of the black ink is mixed. Causes dispersion destruction, agglomerates the coloring material, and thickens the ink. Here, the amount of the coloring material dye contained in the color ink is preferably, for example, about 0.1 to 10% by mass based on the total mass of the color ink.

Ii) An example in which the coloring material in the black ink has a cationic group and the coloring material in the color ink has an anionic group.

In this example, when the color ink and the black ink are mixed, the anionic group of the color material in the color ink reacts with the cationic group of the color material in the black ink, and as a result, Of the coloring material causes dispersion destruction, the coloring material agglomerates, and the ink thickens. Here, the amount of the coloring material dye contained in the color ink is preferably, for example, about 0.1 to 10% by mass based on the total mass of the color ink.

More specifically, the above-mentioned embodiment (2) includes the following three embodiments.

I) The color material in the black ink has an anionic group, and the color ink is a polyvalent metal salt composed of a polyvalent metal cation, for example, Mg ²⁺ , Ca ²⁺ , Cu ²⁺ , Co ²⁺ , Ni ²⁺ , F
An example is given in which the composition is prepared so as to have at least one polyvalent metal salt composed of a polyvalent metal cation selected from e ²⁺ , La ³⁺ , Nd ³⁺ , Y ³⁺ , and Al ³⁺ .

In this example, when the color ink and the rack ink are mixed, the polyvalent metal cation of the polyvalent metal salt in the color ink reacts with the anionic group of the coloring material in the black ink, and As a result, the coloring material in the black ink undergoes dispersion destruction, aggregating the coloring material, and increasing the viscosity of the ink. Here, the polyvalent metal salt contained in the color ink is, for example, about 0.1 with respect to the total mass of the color ink.
It is preferable to contain を 15% by mass.

Ii) The color material of the black ink has a pH of 3 to
7 is an example in which the color ink has the property of being stably dispersed and is prepared so that the color ink has a pH of 8 to 11.

In this example, when the color ink and the black ink are mixed, the pH of the black ink rises, thereby destroying the dispersion stability of the color material, causing the color material to aggregate and increase the viscosity of the ink. .

Iii) The color material of the black ink has a pH of 7
Examples in which the color inks have a characteristic of being stably dispersed in Nos. 1 to 11, and are prepared so that the color ink has a pH of 3 to 6.

In this example, when the color ink and the black ink are mixed, the pH of the black ink is lowered, so that the dispersion stability of the color material is destroyed, and the color material is aggregated to thicken the ink. .

(Resolution of unevenness caused by the difference in the application order) A printing method such as reciprocating printing in which printing is performed in the head in both the left and right directions as shown in FIGS. , A multi-pass printing method using a different mask for each of black and color, and an application order of black and color ink as in printing using a plurality of heads having the same colored ink as shown in FIG. In the case where a different portion exists on the recording material, by using the ink set in the present embodiment, the density unevenness in the reciprocation and black and color are further increased in order of black and color than those shown in the first embodiment. An ink set that can improve the sense of uniformity when printed, and that provides clear and high-quality images. It is possible to provide a recording method and inkjet equipment.

The reason and mechanism are as described above.

Here, the black ink and the color ink used in the second embodiment can be easily prepared by appropriately combining the compositions of the inks used in the first embodiment based on the above examples.

By using a black ink using a salt and a set of color inks characterized by reacting with the black ink by the effects described above,
An image having very high optical density without density unevenness and unevenness of uniformity can be realized.

[0200]

The present invention will be described in more detail with reference to the following examples and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist of the present invention. In the following description, parts and percentages are by mass unless otherwise specified.

Experimental Example I- (1) (Adjustment and Evaluation of Ink Set According to First and Second Embodiments) First, pigment dispersion 1 was adjusted.

Pigment Dispersion 1 The specific surface area is 230 m ² / g and the DBP oil absorption is 70 mL / 10
0 g of carbon black 10 g and p-amino-N-benzoic acid
After 3.41 g was well mixed with 72 g of water, 1.62 g of nitric acid was added dropwise thereto, followed by stirring at 70 ° C. Here after another few minutes, 5g
A solution prepared by dissolving 1.07 g of sodium nitrite in water was added, and the mixture was further stirred for 1 hour. The obtained slurry was filtered through filter paper (trade name: Toyo Filter Paper No. 2; manufactured by Advantis).
The collected pigment particles were sufficiently washed with water, dried in an oven at 90 ° C., and further added with water to prepare a pigment aqueous solution having a pigment concentration of 10% by mass. By the above method, a group represented by the following chemical formula was introduced into the surface of carbon black.

[0203]

Embedded image Next, using each of the pigment dispersions described above, Black Ink 1 and Black Ink 2 as Comparative Example were prepared by the following method.

[0204] The color ink was prepared by mixing the following components, sufficiently stirring and dissolving, and then performing pressure filtration with a micro filter having a pore size of 3.0 μm (manufactured by Fuji Film Co., Ltd.).

[0205] Example 1 An ink set was prepared by combining the above-prepared inks as follows. Black ink 1 Yellow ink 1 Magenta ink 1 Cyan ink 1 Comparative example 1 An ink set was prepared by combining the inks prepared above as follows. Black Ink 2 Yellow Ink 1 Magenta Ink 1 Cyan Ink 1 Further, the following color ink was prepared by adding a divalent metal salt, which is a precipitating material of a black pigment, to the color ink used in Example 1.

[0206] Example 2 An ink set was prepared by combining the inks prepared above in the following manner. Black Ink 1 Yellow Ink 2 Magenta Ink 2 Cyan Ink 2 Table 1 below shows the main constitutions of the ink sets of Examples 1 and 2 and Comparative Example 1.

[0207]

[Table 1] [Experiment 1] Regarding reciprocal printing unevenness Using the inks of Example 1, Example 2, and Comparative Example 1, recording was performed on commercially available copy paper. The inkjet recording apparatus used is an inkjet recording apparatus having an on-demand type multi-recording head that ejects ink by applying thermal energy according to a recording signal to the ink (trade name: BJF-800; Canon Inc.) Was used.

As a print pattern, one-pass bidirectional printing was performed at the same position with three different ejection amounts of yellow, magenta, cyan, and black inks (100).
The amount of driving of% duty is in the area of 1 / 600inch square,
The amount of ink is 20 ng for the color ink and 30 ng for the black ink.)

Each of the shot amounts shown in this embodiment is an example of the shot amount existing in the gray area existing in the color gamut between black solid and white. The following table shows the state of color unevenness and uniformity during reciprocation in Comparative Example 1, Example 1 and Example 2.

[0210] (Reciprocal unevenness) For commercially available copy paper,
Printing was carried out at the amount of ejection shown in Table 2, and the density unevenness and the sense of uniformity of the image in the case of printing in black and color order and in the case of printing in color and black order were visually observed and evaluated according to the following evaluation criteria.

Regarding density unevenness: A: Almost no unevenness is observed. B: No unevenness is observed in a very small area. C: Remarkable density unevenness is observed.

Regarding uniformity: A: There is no problem in uniformity. B: Although the uniformity is slightly disturbed when closely observed, it is at a level that does not cause any problem in practical use. C: Uniform feeling is bad.

[0213]

[Table 2] In addition, each evaluation was performed after printing on a commercially available copy paper and then left for 1 hour.

[Experiment 2] Regarding uniformity in two-pass printing Using the ink sets of Examples 1, 2 and Comparative Example 1, recording was performed on commercial copy paper.

As the ink jet recording apparatus used, an ink jet recording apparatus having an on-demand type multi-recording head for discharging ink by applying thermal energy according to a recording signal to the ink (product name: BJ
F-800; manufactured by Canon Inc.).

As a print pattern, yellow, magenta, cyan, and black inks were printed at the same position with one kind of ejection amount (a 100% duty ejection amount was a 1/600 inch square area of the color ink). Is 20n
g, black ink is the ejection amount when 30 ng of ink is applied).

Each of the ejection amounts shown in this embodiment is an example of the ejection amount existing in the gray area existing in the color gamut between black solid and white. The following table shows the state of color unevenness and uniformity during reciprocation in Comparative Example 1, Example 1 and Example 2.

Further, as masks used in two-pass printing in which the same portion is formed by two scans, the masks shown in FIGS. 21A to 21D for yellow, magenta, cyan, and black inks, respectively. Using.

In the following table, using the ink sets of Comparative Example 1, Example 1 and Example 2, the state of uniformity of the images obtained by the method of Experiment 2 was visually observed, and the following criteria were used. evaluated.

Regarding uniformity: A: There is no problem in uniformity. B: Although the uniformity is slightly disturbed when closely observed, it is at a level that does not cause any problem in practical use. C: Uniform feeling is bad.

[0221]

[Table 3] [Experiment 3] Regarding uniformity in a printing method having two heads having black ink Recording was performed on commercially available copy paper using the ink sets of Example 1, Example 2, and Comparative Example 1 described above. . The inkjet recording apparatus used is an inkjet recording apparatus having an on-demand type multi-recording head that ejects ink by applying thermal energy according to a recording signal to the ink (trade name: BJF-800; Canon Inc.) Was used.

As a print pattern, one-pass bidirectional printing was performed at the same position using yellow, magenta, cyan, and black inks with one type of ejection amount. (100% dut
The ejection amount of y is an ejection amount when 20 ng of color ink and 30 ng of black ink are applied to a 1/600 inch square area. Each of the ejection amounts shown in this embodiment is an example of the ejection amount existing in the gray area existing in the color gamut between black solid and white.

In the following table, using the ink sets prepared in Comparative Example 1, Example 1 and Example 2, the state of uniformity of the image obtained by the method of Experiment 3 was visually observed, and the following criteria were used. evaluated.

It should be noted that two heads containing black ink are provided, and as shown in FIG. 20, a mask shown in FIG. Was used. In the table below, using the ink sets of Comparative Example 1, Example 1 and Example 2, the state of uniformity of images obtained by the method of Experiment 3 was visually observed and evaluated according to the following criteria.

Regarding uniformity: A: There is no problem in uniformity. B: Although the uniformity is slightly disturbed when closely observed, it is at a level that does not cause any problem in practical use. C: Uniform feeling is bad.

[0226]

[Table 4]

[0227]

As described above, according to each of the embodiments of the present invention, even if the printing order of black and color is reversed, such as reciprocating printing, the optical density and
It is possible to extremely effectively suppress or almost eliminate the occurrence of color unevenness due to different uniformity. as a result,
A high-quality multicolor image can be formed in a short time.

By using black ink, printing with excellent character quality (sharpness, optical density, etc.) can be performed, and bleeding between color images can be extremely suppressed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a head section of an ink jet recording apparatus.

FIG. 2 is a cross-sectional view of the head portion of the inkjet recording apparatus taken along line AB.

FIG. 3 is an external perspective view of a head unit of the inkjet recording apparatus.

FIG. 4 is a perspective view illustrating an example of an ink jet recording apparatus.

FIG. 5 is a vertical sectional view of the ink cartridge.

FIG. 6 is a perspective view of a recording unit.

FIG. 7 is a perspective view showing a recording unit in which a plurality of recording heads used in an embodiment of the present invention are arranged.

FIG. 8 is a perspective view of another recording head used in the present invention.

FIG. 9 is a schematic diagram showing a solid-liquid separation process when a pigment ink containing a salt is applied to a recording medium.

FIG. 10 is a schematic diagram showing a process of solid-liquid separation when a pigment ink containing no salt is applied to a recording medium.

FIG. 11 is a schematic diagram illustrating a state of a color material on a recording medium when a pigment ink and a color ink containing no salt are applied to the recording medium.

FIG. 12 is a schematic diagram illustrating a state of a color material on a recording medium when a pigment ink including a salt and a color ink are applied to the recording medium.

FIG. 13 is a schematic diagram showing a state of a color material on a recording medium when a pigment ink containing a salt and a color ink reactive with the pigment ink are applied to the recording medium.

FIG. 14 is a schematic plan view of an ink cartridge according to an embodiment of the present invention.

FIG. 15 is a schematic plan view showing a state where the cartridge of FIG. 14 is mounted on a recording head.

FIG. 16 is a schematic perspective view of a recording unit according to an embodiment of the present invention.

FIG. 17 is an enlarged view of an orifice portion of one embodiment of a recording head portion of the ink jet printer.

FIG. 18 is a graph showing the relationship between the presence / absence of a salt in the ink, the pigment concentration in the ink, and the image density.

19A is a mask used for a first scan in multi-pass printing, and FIG. 19B is a mask used for a second scan.

FIG. 20 is a perspective view showing a recording unit in which a head having black ink is disposed at both ends of a head of color ink.

FIGS. 21A to 21D are masks used for applying black ink, yellow ink, magenta ink, and cyan ink used in Experiment 3, respectively.

FIG. 22 is a schematic diagram showing the relationship between the amount of pigment fixed above a recording medium and the optical density of an image formed by the pigment.

FIG. 23 is a graph comparing the density of an image formed with black ink alone, an image formed by superimposing color ink after applying black ink, and an image formed by superimposing black ink after applying color ink. (a) For the control ink set. (b) In the control ink set, the amount of black ink and the amount of color ink applied are small. (c) When the amount of the black ink and the color ink applied to the paper surface is large in the control ink. (d) In the case of the ink set according to the first embodiment of the present invention. (e) In the case of the ink set according to (1) of the second embodiment of the present invention. (f) In the case of the ink set according to (2) of the second embodiment of the present invention.

FIG. 24 shows the behavior of the ink and color material on a recording medium when an image is formed by superimposing black ink and color ink using the ink set according to (2) of the second embodiment of the present invention. It is the figure which showed the outline.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 13 Head 14 Ink flow path and groove 15 Heating head 16 Protective film 17-1 Aluminum electrode 17-2 Same as above 18 Heating resistor 19 Heat storage layer 20 Substrate 21 Ink 22 Orifice 23 Meniscus 24 Recording droplet 25 Recording material 26 Multi-groove 27 Glass Plate 28 Heating head 40 Ink bag 42 Plug 44 Ink absorber 45 Ink cartridge 51 Recording material 52 Paper feed roller 53 Discharge roller 61 Wiping member 62 Cap 62 'Same as above 63 Ink absorber 64 Discharge recovery section 65 Recording head 65' Same as 66 Carriage 67 guide shaft 68 motor 69 belt 70 recording unit 71 head unit 72 atmosphere communication port 81 recording head for yellow ink 82 recording head for magenta ink 83 recording head for cyan ink 84 black ink 901, 1301 (pigment) black ink 1201, 2401 Salt-containing (pigment) black ink 1001, 1101 Salt-free (pigment) black ink 905, 1005 Rich in solid components in ink Area 903, 1003, 1103, 1203, 2403 Recording medium 1105, 1205, 1305, 2405 Color ink 1007 Solid penetration tip 907, 1009, 1207, 1307, 2412 Solvent penetration tip 1309, 2410 Aggregate 1401 Cartridge 1403 Black ink 1405 Color ink storage 1501 and 1603 Recording head 1601 Recording unit 1601Bk Black ink storage 1601Y Color ink (yellow) storage 1601C Color ink (cyan) storage 1601M Color ink (magenta) storage 1701 Ink flow path 1703 Orifice plate 1705 Vibration plate 1707 Piezoelectric element 1709 Substrate 1711 Discharge port 2301-2230, 2311-2313, 2331-2333, 2341-2343, 23
51 to 2353 Points on the curve showing the fixing amount and optical density of the coloring material above the paper surface 2304, 2314, 2324, 2334, 2344, 2345 Difference in optical density

Claims (88)

[Claims] 1. A method for recording a multicolor image including images in which the order of alternately superimposing black ink and color ink is different, wherein the black ink is applied to the aqueous medium by the action of a salt, an aqueous medium and an ionic group. Including pigments that are dispersed,
A method for recording a multicolor image, wherein the color ink contains a dye. 2. The black ink is an ink having a Ka value in a Bristow method of less than 1.5 mL · m ⁻² · msec ^−1/2 , and the color ink has a Ka value in a Bristow method of 5 mL ·
2. The method according to claim 1, wherein the ink is at least m ^- 2.msec- ^{1 / 2} . 3. The method according to claim 2, wherein the black ink is an ink having a Ka value in the Bristow method of not less than 0.2 and less than 1.5 mL · m ⁻² .msec ^−1/2 . 4. The salt comprises (M1) ₂ SO ₄ , CH ₃ COO (M
1), Ph-COO (M1), (M1) NO ₃ , (M1) Cl, (M
1) Br, (M1) I , The method according to any one of claims 1 to 3 are those selected from (M1) ₂ SO ₃ and (M1) ₂ CO _3. 5. The pigment of the black ink is carbon black, and the carbon black has at least one kind of hydrophilic group on its surface as the ionic group directly or with another atomic group on the surface of the carbon black. 5. The method according to any one of claims 1 to 4, wherein the method is linked via an amino acid. 6. The method according to claim 1, wherein the black ink contains carbon black as a pigment colorant, and further contains the dispersant having the ionic group. 7. The concentration of the carbon black in the black ink is necessary for obtaining a printed matter having a predetermined optical density when the black ink is applied alone to a recording material by an inkjet method. And a density at which a printed matter having the predetermined optical density cannot be obtained when the black ink contains no salt.
The method according to any one of the above. 8. The method according to claim 1, wherein the dye of the color ink is an acid dye or a direct dye. 9. The color ink contains the dye as a component that destabilizes the dispersion stability of a pigment in the black ink when mixed with the black ink, or is mixed with the black ink. 2. The composition of claim 1, further comprising an additive for destabilizing the dispersion stability of the pigment in the black ink, or comprising the dye and the additive.
The method according to any one of claims 1 to 8, wherein 10. The method according to claim 9, wherein the black ink is a black ink containing an anionic group as the ionic group, and the color ink is a color ink containing a polyvalent metal salt as the additive. . 11. The method according to claim 11, wherein the polyvalent metal salt is Mg.²⁺, Ca²⁺, C
u²⁺, Co²⁺, Ni²⁺, Fe ²⁺, La³⁺, Nd³⁺, Y³⁺and
Al³⁺At least one polyvalent metal cation selected from
11. The method according to claim 10, comprising a polyvalent metal salt consisting of: 12. The method according to claim 10, wherein the color ink contains 0.1 to 15% by mass of the polyvalent metal salt based on the total mass of the color ink. 13. The black ink contains an anionic group as the ionic group, and the color ink contains a dye having a cationic group as the additive.
Or the method of 10. 14. The color ink, wherein the dye having a cationic group is contained in an amount of 0.1 to 1 with respect to the total mass of the color ink.
14. The method according to claim 13, comprising 0% by mass. 15. The black ink contains a cationic group as the ionic group, and the color ink contains a dye having an anionic group as the dye.
The method described in. 16. The color ink, wherein the dye having an anionic group is contained in an amount of 0.1 to 1 with respect to the total mass of the color ink.
The method according to claim 15, comprising 0% by mass. 17. The pigment in the black ink has a pH of
Is stable at 3 to 7 and the color ink is pH
Is from 8 to 11. 18. The pigment in the black ink has a pH of
Is stable at 7 to 11, and the color ink is p
The method according to claim 9, wherein H is 3-6. 19. A method for improving the quality of a multi-color image including an image in which the order of alternately superimposing the black ink and the color ink is different by using an ink jet recording head separately provided with the black ink and the color ink. Wherein a black ink containing a pigment and a color ink containing a dye dispersed in the aqueous medium by the action of a salt, an aqueous medium and an ionic group are used as the black ink, wherein a multicolor image quality is provided. How to improve the quality of the. 20. The black ink is an ink having a Ka value in a Bristow method of less than 1.5 mL · m ⁻² · msec ^-1/2 , and the color ink has a Ka value in a Bristow method of 5 mL ·
^20. The method according to claim 19, wherein the ink is at least m ^- 2.msec- ^{1 / 2} . 21. The method according to claim 20, wherein the black ink is an ink having a Ka value in the Bristow method of 0.2 or more and less than 1.5 mL · m ⁻² .msec ^−1/2 . 22. The salt comprises (M1) ₂ SO ₄ , CH ₃ COO
(M1), Ph-COO (M1), (M1) NO ₃ , (M1) Cl,
(M1) Br, (M1) I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃
The method according to any one of claims 19 to 21, which is selected from the group consisting of: 23. The color material of the black ink is carbon black, and the carbon black has at least one hydrophilic group on its surface as the ionic group directly on the surface of the carbon black or another atomic group. 22. The method according to any one of claims 19 to 21, wherein the method is linked via a link. 24. The concentration of the carbon black in the black ink is necessary for obtaining a printed matter having a predetermined optical density when the black ink is applied alone to a recording material by an ink jet method. 20. Further, when the black ink contains no salt, the density is such that a printed matter having the predetermined optical density cannot be obtained.
The described method. 25. The method according to claim 19, wherein the dye in the color ink is an acid dye or a direct dye. 26. The color ink contains the dye as a component that destabilizes the dispersion stability of a pigment in the black ink when mixed with the black ink, or when mixed with the black ink. 2. The composition according to claim 1, further comprising an additive for destabilizing the dispersion stability of the pigment in the black ink, or comprising the dye and the additive.
The method according to any one of 9 to 25. 27. The method according to claim 26, wherein the black ink is a black ink containing an anionic group as the ionic group, and the color ink is a color ink containing a polyvalent metal salt as the component. 28. The method according to claim 28, wherein the polyvalent metal salt is Mg.²⁺, Ca²⁺, C
u²⁺, Co²⁺, Ni²⁺, Fe ²⁺, La³⁺, Nd³⁺, Y³⁺and
Al³⁺At least one polyvalent metal cation selected from
28. The method of claim 27, comprising a polyvalent metal salt consisting of: 29. The method according to claim 27, wherein the color ink contains 0.1 to 15% by mass of the polyvalent metal salt based on the total mass of the color ink. 30. The black ink contains an anionic group as the ionic group, and the color ink contains a dye having a cationic group as the dye.
The method described in. 31. The color ink, wherein the dye having a cationic group is contained in an amount of 0.1 to 1 with respect to the total mass of the color ink.
31. The method according to claim 30, comprising 0% by weight. 32. The black ink contains a cationic group as the ionic group, and the color ink contains a dye having an anionic group as the dye.
7. The method according to 7. 33. The color ink, wherein the dye having an anionic group is contained in an amount of 0.1 to 1 with respect to the total mass of the color ink.
33. The method of claim 32 comprising 0% by weight. 34. The pigment in the black ink has a pH of
Is stable at 3 to 7 and the color ink is pH
28 is the method of claim 26. 35. The pigment in the black ink has a pH of
Is stable at 7 to 11, and the color ink is p
27. The method according to claim 26, wherein H is 3-6. 36. (i) an ink jet recording head which individually discharges black ink and color ink onto a recording material; and (ii) means for conveying the recording material to a recording position by the recording head. An image recording apparatus comprising: a black ink containing a salt, an aqueous medium, and a pigment dispersed in the aqueous medium by the action of an ionic group; and the color ink containing a dye. . 37. The image recording apparatus according to claim 36, wherein said means (ii) includes a paper feed roller driven by a motor. 38. The image forming apparatus further comprises means for moving the head in a direction perpendicular to the direction in which the recording material is transported, the means including a carriage, a guide shaft, and a belt driven by a motor, and the carriage comprising: The image recording apparatus according to claim 37, wherein the image recording apparatus is slidably engaged with the guide shaft, and a part of the carriage is connected to the belt. 39. The black ink is an ink having a Ka value in a Bristow method of less than 1.5 mL · m ⁻² · msec ^−1/2 , and the color ink having a Ka value in a Bristow method of 5 mL ·
39. An ink of m ^- 2.msec- ^{1 / 2} or more.
The image recording device according to any one of the above. 40. The image according to any one of claims 36 to 39, wherein the black ink is an ink having a Ka value in the Bristow method of 0.2 or more and less than 1.5 mL · m− ² · msec− ^{1 / 2.} Recording device. 41. The salt comprises (M1) ₂ SO ₄ , CH ₃ COO
(M1), Ph-COO (M1), (M1) NO ₃ , (M1) Cl,
(M1) Br, (M1) I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃
The image recording apparatus according to any one of claims 36 to 40, wherein the image recording apparatus is selected from the group consisting of: 42. The coloring material of the black ink is carbon black, and the carbon black has at least one hydrophilic group on its surface as the ionic group directly on the surface of the carbon black or another atomic group. The image recording apparatus according to any one of claims 36 to 41, wherein the image recording apparatus is connected via a link. 43. The concentration of the carbon black in the black ink is necessary for obtaining a printed matter having a predetermined optical density when the black ink is applied alone to a recording material by an inkjet method. 43. When the black ink contains no salt, the density is such that a printed matter having the predetermined optical density cannot be obtained.
The image recording apparatus according to claim 1. 44. The image recording apparatus according to claim 36, wherein the color material of the color ink is an acid dye or a direct dye. 45. The color ink contains the dye as a component that destabilizes the dispersion stability of a pigment in the black ink when mixed with the black ink, or is mixed with the black ink. 4. The composition of claim 3, further comprising an additive for destabilizing the dispersion stability of the pigment in the black ink, or containing the dye and the additive.
The image recording apparatus according to any one of claims 6 to 44. 46. The image according to claim 45, wherein the black ink is a black ink containing an anionic group as the ionic group, and the color ink is a color ink containing a polyvalent metal salt as the additive. Recording device. 47. The method according to claim 47, wherein the polyvalent metal salt is Mg.²⁺, Ca²⁺, C
u²⁺, Co²⁺, Ni²⁺, Fe ²⁺, La³⁺, Nd³⁺, Y³⁺and
Al³⁺At least one polyvalent metal cation selected from
47. The image recording according to claim 46, comprising a polyvalent metal salt comprising
apparatus. 48. The image recording apparatus according to claim 46, wherein the color ink contains the polyvalent metal salt in an amount of 0.1 to 15% by mass based on the total mass of the color ink. 49. The black ink contains an anionic group as the ionic group, and the color ink contains a dye having a cationic group as the dye.
The image recording apparatus according to claim 1. 50. The color ink, wherein the dye having a cationic group is contained in an amount of 0.1 to 1 with respect to the total mass of the color ink.
50. The method of claim 49 comprising 0% by weight. 51. The black ink contains a cationic group as the ionic group, and the color ink contains a dye having an anionic group as the dye.
6. The image recording device according to 5. 52. The color ink, wherein the dye having an anionic group is contained in an amount of 0.1 to 1 based on the total mass of the color ink.
52. The image recording apparatus according to claim 51, comprising 0% by mass. 53. The pigment in the black ink has a pH of
Is stable at 3 to 7 and the color ink is pH
46. The image recording apparatus according to claim 45, wherein n is 8 to 11. 54. The pigment in the black ink has a pH of
Is stable at 7 to 11, and the color ink is p
The image recording apparatus according to claim 45, wherein H is 3 to 6. 55. An ink set comprising a combination of a black ink and a color ink, wherein the black ink comprises a salt, an aqueous medium and a pigment dispersed in the aqueous medium by the action of an ionic group, Contains a dye that destabilizes the dispersion stability of the pigment in the black ink when mixed with the black ink, or the dispersion stability of the pigment in the black ink when mixed with the black ink. An ink set comprising an additive for destabilizing the dye, or comprising the dye and the additive. 56. The Ka value of the black ink in the Bristow method is less than 1.5 mL · m ⁻² · msec ^−1/2 , and the Ka value of the color ink in the Bristow method is 5 mL ·
56. The ink set according to claim 55, wherein the value is not less than m ^-2 · msec ^-1/2 . 57. The ink set according to claim 55, wherein the Ka value of the black ink in the Bristow method is 0.2 or more and less than 1.5 mL · m ⁻² .msec ^−1/2 . 58. The salt comprises (M1) ₂ SO ₄ , CH ₃ COO
(M1), Ph-COO (M1), (M1) NO ₃ , (M1) Cl,
(M1) Br, (M1) I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃
The ink set according to any one of claims 55 to 57, wherein the ink set is selected from the group consisting of: 59. The pigment of the black ink is carbon black, and the carbon black has at least one kind of hydrophilic group on its surface as the ionic group, directly or with another atomic group on the surface of the carbon black. The ink set according to any one of claims 55 to 58, wherein the ink set is connected via a link. 60. The concentration of the carbon black in the black ink is necessary for obtaining a printed matter having a predetermined optical density when the black ink is applied alone to a recording material by an inkjet method. 60. When the black ink contains no salt, the density is such that a printed matter having the predetermined optical density cannot be obtained.
The ink set described in the above. 61. The ink set according to claim 55, wherein the dye in the color ink is an acid dye or a direct dye. 62. The color ink according to claim 55, wherein the black ink is a black ink containing an anionic group as the ionic group, and the color ink is a color ink containing a polyvalent metal salt as the additive. An ink set according to Crab. 63. The polyvalent metal salt comprising Mg²⁺, Ca²⁺, C
u²⁺, Co²⁺, Ni²⁺, Fe ²⁺, La³⁺, Nd³⁺, Y³⁺and
Al³⁺At least one polyvalent metal cation selected from
63. The ink cartridge according to claim 62, comprising a polyvalent metal salt consisting of
To 64. The ink set according to claim 62, wherein the color ink contains the polyvalent metal salt in an amount of 0.1 to 15% by mass based on the total mass of the color ink. 65. The black ink contains an anionic group as the ionic group, and the color ink contains a dye having a cationic group as the dye.
65. The ink set according to any one of to 64. 66. The color ink, wherein the dye having a cationic group is contained in an amount of 0.1 to 1 with respect to the total mass of the color ink.
The ink set according to claim 65, which contains 0% by mass. 67. The black ink contains a cationic group as the ionic group, and the color ink contains a dye having an anionic group as the dye.
63. The ink set according to any one of items 5 to 62. 68. The color ink, wherein the dye having an anionic group is contained in an amount of 0.1 to 1 with respect to the total mass of the color ink.
The ink set according to claim 67, wherein the ink set contains 0% by mass. 69. The pigment of the black ink has a pH of
Is stable at 3 to 7 and the color ink is pH
The ink set according to any one of claims 55 to 61, wherein is 8 to 11. 70. The pigment in the black ink has a pH of
Is stable at 7 to 11, and the color ink is p
63. The ink set according to claim 55, wherein H is 3-6. 71. A recording unit comprising a black ink containing section containing black ink, an ink jet head for ejecting the black ink, a color ink containing section containing color ink, and an ink jet head for ejecting the color ink. Wherein the black ink comprises a salt, an aqueous medium and a pigment dispersed in the aqueous medium by the action of an ionic group, wherein the color ink, when mixed with the black ink, forms a pigment in the black ink. It contains a dye that destabilizes dispersion stability, or contains an additive that, when mixed with the black ink, destabilizes the dispersion stability of a coloring material in the black ink, or contains the dye and the additive. And a recording unit comprising: 72. The Ka value of the black ink in the Bristow method is less than 1.5 mL · m ⁻² · msec ^-1/2 , and the Ka value of the color ink in the Bristow method is 5 mL ·
^73. The recording unit according to claim 71, wherein the recording unit is at least m- ² · msec- ^{1 / 2} . 73. The recording unit according to claim 71, wherein the Ka value of the black ink in the Bristow method is 0.2 or more and less than 1.5 mL · m ⁻² .msec ^−1/2 . 74. The salt is (M1) ₂ SO ₄ , CH ₃ COO
(M1), Ph-COO (M1), (M1) NO ₃ , (M1) Cl,
(M1) Br, (M1) I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃
The recording unit according to any one of claims 71 to 73, wherein the recording unit is selected from the group consisting of: 75. The pigment of the black ink is carbon black, and the carbon black has at least one kind of hydrophilic group on its surface as the ionic group directly or with another atomic group on the surface of the carbon black. 75. The recording unit according to any one of claims 71 to 74, wherein the recording unit is connected via a recording medium. 76. The concentration of the carbon black in the black ink is necessary for obtaining a printed matter having a predetermined optical density when the black ink is applied alone to a recording material by an inkjet method. 75. A density at which a printed matter having the predetermined optical density cannot be obtained when no salt is contained in the black ink.
A recording unit according to item 1. 77. The recording unit according to claim 71, wherein the color material of the color ink is an acid dye or a direct dye. 78. The black ink according to claim 71, wherein the black ink is a black ink containing an anionic group as the ionic group, and the color ink is a color ink containing a polyvalent metal salt as the additive. A recording unit according to Crab. 79. The polyvalent metal salt comprising Mg²⁺, Ca²⁺, C
u²⁺, Co²⁺, Ni²⁺, Fe ²⁺, La³⁺, Nd³⁺, Y³⁺and
Al³⁺At least one polyvalent metal cation selected from
79. The recording unit according to claim 78, comprising a polyvalent metal salt consisting of
To 80. The recording unit according to claim 78, wherein the color ink contains 0.1 to 15% by mass of the polyvalent metal salt based on the total mass of the color ink. 81. The recording unit according to claim 71, wherein said black ink contains an anionic group as said ionic group, and said color ink contains a dye having a cationic group. 82. The color ink, wherein the dye having a cationic group is contained in an amount of 0.1 to 1 with respect to the total mass of the color ink.
The recording unit according to claim 81, wherein the recording unit contains 0% by mass. 83. The recording unit according to claim 71, wherein the black ink contains a cationic group as the ionic group, and the color ink contains a dye having an anionic group. 84. The color ink contains the dye having an anionic group in an amount of 0.1 to 1 based on the total mass of the color ink.
The recording unit according to claim 83, wherein the recording unit contains 0% by mass. 85. The pigment in the black ink has a pH of
Is stable at 3 to 7 and the color ink is pH
The recording unit according to any one of claims 71 to 77, wherein n is 8 to 11. 86. The pigment in the black ink has a pH of
Is stable at 7 to 11, and the color ink is p
The recording unit according to any one of claims 71 to 76, wherein H is 3 to 6. 87. The ink jet head is a head for applying thermal energy to ink to discharge the ink.
90. The recording unit according to any one of to 86. 88. The recording unit according to claim 71, wherein said ink jet head is a head which applies mechanical energy to ink to eject the ink.