JPH10219162A - Ink composition, ink set and method and apparatus for recording image therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink composition having good fixability and character quality, having sufficient image density and high solid uniformity and can give a recorded image having improved water resistance and light resistance. SOLUTION: This composition is one essentially consisting of a colorant and a liquid medium, wherein the colorant is a mixture of a plurality of water- soluble anionic dyes each of which has a molecular structure having an anionic hydrophilic group essentially consisting of a sulfonic group or a carboxylic group and a conjugated part having any one selected among an aromatic ring, a phthalocyanine ring, an azo group or a vinylene group and has, in the stereostructural aspect, at least one planarity. The wavelength showing the peak of an absorbance in the visible region of an aqueous solution of the dye shifts by 5nm in the pH region of 3-7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for obtaining a water-resistant image by reducing bleeding generated in the formation of a color image, and more particularly to an image forming method using an ink jet recording system and an ink composition used therefor. And an ink set.

[0002]

2. Description of the Related Art In an ink jet recording method, recording is performed by flying small ink droplets and attaching them to a recording medium such as paper. In particular, Japanese Patent Publication No. 61-59912,
According to the method disclosed in Japanese Patent Publication No. 61-59914, which uses an electrothermal converter as a discharge energy supply means and applies thermal energy to ink to generate bubbles, thereby discharging droplets, the height of the recording head is reduced. The density multi-orifice can be easily realized, and high-resolution and high-quality images can be recorded at high speed.

However, inks used in conventional ink jet recording generally contain a colorant and water as main components, and further contain a water-soluble high-boiling solvent such as glycol for the purpose of preventing drying and clogging. When recording is performed on plain paper using such an ink, sufficient fixability cannot be obtained, or due to uneven distribution of filler and sizing agent on the recording paper surface. An estimated non-uniform image occurred. Also, especially when obtaining a color image, since the inks of a plurality of colors are successively superimposed before being fixed on the paper, the colors may bleed or mix unevenly at the boundary portions of the images of different colors. (Below,
This phenomenon is called bleeding.) A satisfactory image was not obtained.

As means for improving the fixing property, Japanese Patent Laid-Open No.
JP-A-65269 discloses adding a compound such as a surfactant that enhances permeability to the ink.
Japanese Patent Application Laid-Open No. 55-66976 discloses the use of an ink mainly containing a volatile solvent. However, in the former method, although the penetrability of the ink into the recording paper is increased, the fixability and the bleeding are improved to some extent, but the color material also penetrates deep into the recording paper along with the ink. In addition to inconveniences such as a decrease in saturation and the like, the ink also spreads in the horizontal direction, and as a result, problems such as reduced edge sharpness and reduced resolution also occurred. On the other hand, in the latter case, in addition to the former disadvantage,
Clogging was likely to occur due to evaporation of the solvent in the nozzle portion of the recording head.

Further, in order to solve the above-mentioned problems, there has been proposed a method of applying a specific liquid for improving an image on a recording medium prior to the ejection of recording ink. For example, JP-A-63-29971 discloses an ink containing an anionic dye after a liquid containing an organic compound having two or more cationic groups per molecule is attached to a recording medium. A method of recording using the information is disclosed. JP-A-64-9279 discloses a method in which an acidic liquid containing succinic acid or the like is attached to a recording medium, and recording is performed using an ink containing a water-soluble anionic dye. Have been. Further, JP-A-64-6
No. 3185 discloses a method in which a liquid for insolubilizing a dye is applied prior to recording of ink.

However, any of the above methods is intended to improve the bleeding of an image and the water resistance by precipitating the dye itself, and the effect of suppressing the bleeding which occurs between the respective color inks described above is insufficient. In addition, since the deposited dye tends to be non-uniformly distributed on the recording paper, the coating properties of the recording paper on the pulp fiber are poor, and the uniformity of the image is deteriorated. Furthermore, the present applicant, as a method for improving the above-mentioned problem, includes a step of first applying a liquid composition containing a cationic substance to a recording medium and a step of applying an ink containing a water-soluble anionic dye. In the image forming method,
As the cationic substance, it has been proposed to use two kinds of substances belonging to a low molecular weight region having a weight average molecular weight of 1,000 or less and those belonging to a high molecular region having a molecular weight of 1,500 or more. (See Japanese Patent Application Laid-Open No. Hei 8-224595).

That is, the above-mentioned liquid composition and ink are
When mixed on the recording paper or where it permeated the recording paper,
The cationic substance and the anionic group of the dye contained in the ink are electrostatically bonded to cause instantaneous aggregation, whereby the dye component and the solvent component in the ink are separated (this phenomenon is called solid-liquid separation). Since only the solvent component permeates the recording paper, the dye component, which is a coloring material, does not bleed. The solid-liquid separation occurs more efficiently when the liquid composition contains, as the cationic substance, a component having a molecular weight of 1,000 or less and a component having a molecular weight of 1,500 or more. Here, the molecular weight means a weight average molecular weight, which is defined by GPC.
(Gel permeation chromatography).

The mechanism by which the above-mentioned solid-liquid separation occurs more effectively when two kinds of cationic substances having different molecular weights are present in the liquid composition is unknown, but is generally not as follows. It has been explained as.

First, as a first stage of the reaction, a low molecular weight component of the cationic substance contained in the liquid composition and a water-soluble dye having an anionic group used in the ink are used. An association is caused by ionic interaction, and instantaneous separation from the solution phase is caused. Next, as the second stage of the reaction, the above-mentioned aggregate of the dye and the low molecular weight cationic substance is adsorbed by the high molecular weight component contained in the liquid composition, so that the aggregate of the dye formed by the association is formed. Is further increased, and it is difficult to enter the gaps between the fibers of the recording paper, and as a result, only the liquid portion separated into solid and liquid penetrates into the recording paper, thereby achieving both print quality and fixability. .

At the same time, the aggregate formed by the low molecular weight component of the cationic substance, the water-soluble anionic dye, and the high molecular weight component of the cationic substance produced by the mechanism described above has a viscosity. Since it becomes large and does not move with the movement of the liquid medium, the sharpness of the edges of characters or images is not lost even if the fixing property is increased as in the prior art, so that good print quality can be obtained. Also, the agglomerates are essentially water-insoluble, and the water resistance of the formed image is perfect.

[0011]

However, in order to realize sufficient water resistance and print quality when a recorded image is formed by the above-described method, the cationic composition to be imparted to the liquid composition containing a cationic substance must be used. The amount of the substance must be more than a certain amount, and if so, the amount of the liquid composition applied on the recording medium increases, not only takes time to fix and dry the image, but also increases the water solubility on the recording medium. In some cases, the progress of aggregation of the anionic dye was uneven, causing color unevenness. Further, in the above-mentioned image recording method, a cationic substance is brought into contact with a water-soluble anionic dye. When the cationic substance has an amino group in particular, there is a fear that this may promote photobleaching of the dye.

Accordingly, an object of the present invention is to provide an ink composition, an ink set, an image recording method, a recording apparatus and the like which can satisfy all of the following requirements. (1) Good character quality while having good fixing properties (2) Sufficient image density is obtained and solid uniformity is high (3) Complete water resistance of recorded images (4) ) To improve the light fastness of recorded images

[0013]

The above object is achieved by the present invention described below. That is, the present invention provides an ink composition having at least a coloring material and a liquid medium, wherein the coloring material is
A mixture of a plurality of water-soluble anionic dyes, wherein the molecular structure of the dye is an anionic hydrophilic group containing at least one of a sulfone group and a carboxyl group, and an aromatic ring, a phthalocyanine ring, an azo group, or vinylene. And a conjugated moiety having any one selected from the group, and is a molecule having one planarity in terms of steric structure, and further, the peak of the absorbance in the visible region of the aqueous solution of the dye. An ink composition, an ink set using the ink composition, an image forming method, and an ink jet recording apparatus, wherein the wavelength shown shifts by 5 nm or more in a pH range of pH 3 to pH 7 of the aqueous solution. In particular, an ink composition containing a water-soluble anionic dye having the above-mentioned structure is preferably used as a liquid composition containing a cationic substance having a molecular weight of 1,500 or less, more preferably 700 to 1,500. , Simply referred to as "liquid composition")
In addition, excellent effects can be obtained when used for image formation.

[0014]

Next, the present invention will be described in more detail with reference to preferred embodiments. Hereinafter, the operation of the present invention will be described, and further, various materials constituting the ink composition of the present invention will be described. First, the mechanism of aggregation between a liquid composition containing a cationic substance and a water-soluble anionic dye will be briefly described with reference to FIG. The water-soluble anionic dye has a structure having an anionic group at a terminal as schematically shown in FIG. On the other hand, a liquid composition containing a cationic substance is schematically represented by a structure having a cationic group at a terminal. Then, as described above, the cation portion of the liquid composition and the anion portion of the water-soluble anionic dye are associated by ionic interaction, and the size of the aggregate of the dye generated by the association is further increased (FIG. 1 ~)). As a result, the dye aggregates are less likely to enter the gaps between the fibers of the recording paper, and only the liquid portion that has been solid-liquid separated penetrates into the recording paper, thereby achieving both print quality and fixability.

At the same time, as a result of the dye forming a dye aggregate in this way, the viscosity of the coloring material in the ink increases, so that it does not move with the movement of the liquid medium. The sharpness of the edge is not lost, and good print quality can be obtained. Also, since the dye aggregates are essentially water-insoluble, the water resistance of the formed image is perfect.

However, in the above-mentioned conventional technology,
When an anionic dye molecule in the ink forms an image on a recording medium, the degree of aggregation with the cationic substance in the liquid composition varies depending on time and place, and as shown in FIG. They also differ in the size and form of objects. For this reason, some dye agglomerates penetrate the recording medium quickly, while others do not penetrate and cover the surface, which causes print quality due to color unevenness, color material bleeding, pixel shape distortion, etc. It is thought that the decrease in the concentration is a noticeable cause.

In order to solve this problem, the present inventors have set the structure of the anionic dye to be used so that the molecules of the dye are oriented to some extent on the recording medium and are easily associated with each other. It is further considered that if a plurality of such dyes are mixed and used, the problem of the above-described conventional technique can be solved, and various studies are made on the dyes.
The present invention has been reached. That is, if the above-mentioned dye is used, these dye molecules are in a state of association to some extent in advance, and as shown in FIG. Therefore, when the dye in such a state comes into contact with the cationic substance and reacts with the cationic substance by ionic interaction, as shown in FIG. 2 (2), the dye aggregate becomes bulky as a whole. That is, the aggregates cover the surface of the recording medium. As a result, unlike the conventional method, the low-volume dye agglomerate does not permeate randomly into the paper or other recording medium formed of uneven fibers or sizing agents, and the color A uniform image without unevenness or bleeding can be formed. Further, when the dye itself is in an associated state, the photodegradable portions such as the azo group constituting the dye molecule are less likely to be exposed to the surrounding ultraviolet light or active oxygen which causes photobleaching. The performance is also improved.

In general, water-soluble anionic dyes tend to aggregate and precipitate dye molecules in an acidic region to form an associated state. In an acidic region, it is difficult to dissolve the dye molecule. It has the property that the property is improved. Then, depending on the type of the dye, the pH at which the association can be broken differs. In addition, since the color tone of the aqueous dye solution varies depending on the association state, the peak wavelength shifts when the absorbance of the aqueous dye solution is measured by changing the pH. On the other hand, what is used as a recording medium is mainly plain paper, coated paper, a film with an ink receiving layer, etc., and their surface pH is generally weakly acidic to near neutral or slightly alkaline. It is. The liquid composition containing a cationic substance used for image formation in the present invention is also not preferably a strong acid or strong alkali because of the problem of liquid contact with the head member of the recording apparatus.
It is preferable to use a weakly acidic to near neutral or weakly alkaline one.

When the above effects are achieved, first, when forming an image on a recording medium, in order to bring the water-soluble anionic dye molecules in the ink into a certain degree of association state, the dye is used. Since the association state of the molecules exists in a weakly acidic to near neutral or weakly alkaline environment, at least a weakly acidic to neutral environment in which the dye molecules are in an associated state under these conditions, that is, in a pH of 3 to 7, It can be seen that a water-soluble anionic dye capable of forming an association state may be selected. In other words, when the absorbance of an aqueous solution of a water-soluble anionic dye is measured, the pH of the aqueous solution changes from pH 3 to pH 7, and the color tone changes such that the peak wavelength of the absorbance shifts. It is only necessary to select a sex dye. More preferably, if the association state of the dye is generated in an environment where the pH is weakly acidic or less, as described above, the dye is hardly dissolved in the acidic region, so that the water resistance of the dye itself is improved. The amount of the cationic substance to be used can be reduced, and the time for fixing and drying the recorded image can be shortened.

The present inventors have conducted intensive studies on anionic dyes that can satisfy the above requirements, and as a result, as a coloring material for ink, the molecular structure of the dye always contains either a sulfone group or a carboxyl group. An anionic hydrophilic group,
A molecule having an aromatic ring, a phthalocyanine ring, an azo group, or a conjugated moiety having any one selected from a vinylene group, and a molecule having one planarity in terms of a steric structure; Use a solution in which the wavelength showing the absorbance peak in the visible region of the aqueous solution shifts by 5 nm or more in the pH region of the aqueous solution from pH 3 to pH 7, and use a mixture of a plurality of different types of dyes having such a structure. It has been found that the above-mentioned excellent effects can be obtained in such cases.

That is, as shown in FIG. 1, an anionic hydrophilic group containing at least one of a sulfone group and a carboxyl group of the dye constitutes a terminal portion of the dye molecule, and forms a cationic substance and an ionic group. Interact. In addition, since the conjugated portions of the dyes sandwiched by the hydrophilic groups can be oriented to each other, the presence of the conjugated portions causes the molecules of the different types of dyes to associate to some extent, as shown in FIG. As described above, the dye itself becomes bulky. Further, the dye used in the present invention is composed of molecules having one planarity in terms of three-dimensional structure, and has a structure in which the dyes are more easily associated with each other. When a plurality of dyes having a high degree of association are used by mixing a plurality of dyes having a wavelength at which the absorbance peak in the visible region of the aqueous dye solution shifts by 5 nm or more in the pH region from pH 3 to pH 7, these dyes are used. As a result of association of the dyes to form bulky dyes, the excellent effects of the present invention can be obtained.

Hereinafter, the ink composition of the present invention, which has the coloring material having the above structure, will be described. The ink composition of the present invention has at least the coloring material and the liquid medium, but as other components, for example,
It may have a viscosity adjuster, a pH adjuster, a preservative, a surfactant, an antioxidant and the like.

First, the water-soluble anionic dye material constituting the coloring material used in the ink composition of the present invention will be described. The water-soluble anionic dye has a chemical structure and a steric structure as described above, and has a wavelength at which the absorbance peak in the visible region of the aqueous solution is pH 3 to pH 7.
Any of the acidic dyes, direct dyes, and reactive dyes described in the color index may be used as long as the color shifts by 5 nm or more in the H region. Any of them can be used. The coloring material used in the ink composition of the present invention is composed of a mixture of a plurality of such dyes.

Examples of the water-soluble anionic dye material usable in the ink composition of the present invention include those described in Color Index, for example, C.I.
I. Acid Black 3, 7, 21, 24, 27, 3
2, 36, 129, 232, C.I. I. Acid Green 34, C.I. I. Acid Brown 14, C.I. I. Acid blue 19, 249, C.I. I. Acid Yellow 7
4, 86, 98, C.I. I. Acid Red 51, 87,
92, 93, 94, 95, C.I. I. Direct Black 51, 195, C.I. I. Direct Blue 55, 86,
87, 93, 109, 116, 129, 132, 14
9, 158, 164, 167, 185, 199, 22
6, C.I. I. Direct Green 11, 21, 34, 4
2, 60, C.I. I. Direct orange 1,2,5,
6, 7, 8, 15, 29, 31, 33, 63, 85, 9
0, 96, 102, 104, C.I. I. Direct Brown 2, 58, 59, 60, 73, 112, 167, 16
8, 179, 185, C.I. I. Direct Red 1, 1
4, 18, 29, 33, 52, 59, 88, 99, 14
1, 144, 155, 156, 174, 180, 18
1, 185, 186, 218, C.I. I. Direct Yellow 1, 11, 15, 20, 24, 26, 33, 41,
42, 44, 49, 66, 69, 70, 72, 73, 7
4, 86, 132, 142, C.I. I. Reactive Blue 3, 7, 14, 15, 18, 21, 25, 38, 4
1, C.I. I. Reactive Green 5, C.I. I. Reactive Orange 14, Projet Fast Yellow 2, Projet Fast Cyan 2, Projet Fast Magenta 2 manufactured by Zenca, and the like.

In the present invention, even those not described in the color index, having the above-mentioned chemical structure and steric structure, and having a peak wavelength of the absorbance in the visible region in the pH range of pH 3 to pH 7 of the aqueous solution. Is 5 nm
There is no particular limitation as long as it has the property of shifting. In the present invention, the coloring material in the ink composition is composed of a mixture of the water-soluble anionic dyes as described above, so that the dyes that can be used are limited by structural reasons. By appropriately determining the mixing ratio of each water-soluble anionic dye, an ink composition having a desired color tone can be easily obtained.

Next, a liquid medium constituting the ink composition of the present invention together with the above-described coloring material will be described. As the liquid medium used in the present invention, it is preferable to use water or a mixture of water and a water-soluble organic solvent. Examples of the water-soluble organic solvent that can be used here include amides such as dimethylformamide and dimethylacetamide,
Ketones such as acetone, ethers such as tetrahydrofuran and dioxane, polyalkylene glycols such as polyethylene glycol and polypropylene glycol, ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodi Alkylene glycols such as glycol, hexylene glycol and diethylene glycol; lower alkyl ethers of polyhydric alcohols such as ethylene glycol methyl ether, diethylene glycol monomethyl ether and triethylene glycol monomethyl ether; ethanol, isopropyl alcohol, n
Other than monohydric alcohols such as -butyl alcohol and isobutyl alcohol, glycerin, N-methyl-2-pyrrolidone, 1,3-dimethyl-imidazolidinone, triethanolamine, sulfolane, dimethyl sulfoxide and the like can be mentioned.

The content of the water-soluble organic solvent in the ink composition is not particularly limited, but is preferably 1 to 60% by weight, more preferably 5 to 30% by weight, based on the total amount of the ink composition. Is a preferable range. In addition, the physical properties of the ink composition of the present invention comprising the above-mentioned components include a pH of about 3 to 12, a surface tension of about 10 to 60 dyn / cm, and a viscosity of about 1 to 30 cp at around 25 ° C.
It is preferably within the range of s. However, regarding the surface tension, it may be more effective to perform image formation if the surface tension of the ink composition is adjusted to be higher than the surface tension of a liquid composition described later. It is considered that the reason for this is that, in such a configuration, when the liquid composition is mixed with the ink on the recording medium in the printing process, the liquid composition has an effect of making the wettability of the ink uniform. But the details are not clear.

In order to further enhance the effects of the present invention, an anionic surfactant or an anionic polymer may be added to the ink composition in addition to the components described above. . Alternatively, the amphoteric surfactant may be used after being adjusted to a pH above its isoelectric point. As the anionic surfactant, for example, a general one such as a carboxylate type, a sulfate type, a sulfonate type and a phosphate type can be used without any problem. Examples of the anionic polymer include, for example, an alkali-soluble resin, specifically, sodium polyacrylate, or a polymer obtained by copolymerizing acrylic acid with a part of the polymer. Of course,
It is not limited to these.

Next, a liquid composition containing a cationic substance, which constitutes the ink set of the present invention in combination with the above-described ink composition of the present invention, will be described. As a function of the cationic substance contained as an essential component in the liquid composition used in the present invention, as described above with reference to FIGS. 1 and 2, the cationic part of the cationic substance corresponds to the ink described above. An object of the present invention is to form a dye aggregate by bonding with an anionic portion of a water-soluble anionic dye constituting the composition by ionic interaction.

The liquid composition that can be preferably used in the present invention is preferably a cationic substance having a molecular weight of 1,500 or less, more preferably a cationic substance having a molecular weight of 700 to 1,500. And the like. That is, as described above, in the ink composition of the present invention, as shown in FIG. 2A, the dye molecules can be originally associated with each other. When the molecular weight of the dye exceeds 1,500, the molecular weight of the dye aggregates becomes excessively large, and the color development of an image is reduced. However, with only a cationic substance having a molecular weight of less than 700, the molecular weight of the dye aggregate is too low, and the intended object of the present invention is hardly achieved.

Hereinafter, the molecular weight of 1,5 which can be used in the present invention will be described.
Specific examples of the cationic substance of 00 or less are listed. For example, primary, secondary or tertiary amine salt type compounds, laurylamine, cocoamine, stearylamine,
Hydrochloride salts such as rosinamine, acetate salts, etc .; quaternary ammonium salt type compounds, such as lauryl trimethyl ammonium chloride, lauryl dimethyl benzyl ammonium chloride, benzyl tributyl ammonium chloride, benzalkonium chloride, etc .; pyridinium salt type compounds, Specific examples thereof include cetylpyridinium chloride and cetylpyridinium bromide; imidazoline-type cationic compounds such as 2-heptadecenyl-hydroxyethylimidazoline; and dihydroxyethylstearylamine which is an ethylene oxide adduct of a higher alkylamine.

Further, in the present invention, an amphoteric surfactant having a cationic property in a certain pH range can also be used. Specifically, for example, amino acid type amphoteric surfactant,
_{R-NH-CH 2 -CH 2} -COOH type compounds, betaine compounds, for example, stearyl dimethyl betaine, other carboxylic acid salt type amphoteric surfactants such as lauryl betaine, sulfuric ester type, Examples include amphoteric surfactants such as sulfonic acid type and phosphoric acid ester type. Of course, when these amphoteric surfactants are used, the liquid composition is adjusted to have a pH below their isoelectric point, or when mixed with ink on a recording medium, the isoelectric point is adjusted. It is necessary to adjust to the following pH or to take any one of the methods. As described above, the molecular weight is 1,500
The following examples of the cationic substance are given, but it goes without saying that the cationic substance that can be used in the present invention is not necessarily limited to these.

In the present invention, as described above, among the cationic substances having a molecular weight of 1,500 or less, particularly,
A cationic substance having a relatively high molecular weight and a molecular weight of 700 or more and 1,500 or less is suitably used. As described above, the action and effect are formed by coordinating the anionic dyes by combining the liquid composition containing such a cationic substance with the ink composition of the present invention. By appropriately increasing the size of the aggregate or the aggregate of the dye formed by the association of the anionic dye and the cationic substance, the gap between the fibers of the recording paper is
Another object of the present invention is to further improve print quality and fixability by making it more difficult for a coloring material to penetrate and allowing only the liquid portion of the ink separated into solid and liquid to penetrate into the recording paper. Molecular weight 70
Examples of the cationic substance of 0 or more and 1,500 or less include polyallylamine hydrochloride, polyaminesulfone hydrochloride, polyvinylamine hydrochloride, chitosan acetate, and the like, but are not limited thereto.
Further, it is not limited to the hydrochloride type and the acetate type.

Another specific example of the cationic substance having a molecular weight of 700 or more and 1,500 or less is a compound obtained by partially cationizing a nonionic polymer substance. Specifically, for example, a copolymer of vinylpyrrolidone and a quaternary salt of aminoalkyl alkylate, a copolymer of acrylamide and a quaternary salt of aminomethylacrylamide, and the like, of course, include these compounds. Needless to say, it is not limited. Further, the above-mentioned cationic substance is satisfactory if it is water-soluble, but may be a dispersion such as a latex or an emulsion.

Further, in the present invention, the molecular weight is 700
Above 1,500 cationic substances, when this is combined with the ink composition of the present invention to form an image,
It is preferable from the viewpoint that the coloring property of the dye is not reduced.

The molecular weight of the cationic substance described above is, for example, a molecular weight in terms of polystyrene obtained by an analytical method such as GPC (gel permeation chromatography). In addition, the molecular weight distribution of the cationic substance used in the present invention may be measured by GPC alone in advance, or after measuring the molecular weight distribution of the liquid composition itself, a dye having at least an anionic group is contained. A sufficient amount of the ink composition and the liquid composition are mixed and stirred in a beaker, and a GPC measurement is performed again after removing the precipitate, and a GPC measurement result before mixing the ink composition,
The results may be obtained from the molecular weight distribution of the components removed from the system precipitated by the dye in the ink by comparing the results of the GPC measurement after removing the precipitate by mixing the ink.

The amount of the cationic substance contained in the liquid composition is preferably in the range of 0.005 to 20% by weight on the basis of weight, but the optimal amount depends on the combination of the substances used. The range needs to be determined.

Next, other components constituting the liquid composition of the present invention will be specifically described. The liquid composition usually comprises water, a water-soluble organic solvent and other additives in addition to the above-mentioned cationic substance. As the water-soluble organic solvent, those similar to those used in the ink composition described above are used, for example, dimethylformamide, amides such as dimethylacetamide, ketones such as acetone, tetrahydrofuran, ethers such as dioxane,
Polyalkylene glycols such as polyethylene glycol and polypropylene glycol, ethylene glycol,
Alkylene glycols such as propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol and diethylene glycol, ethylene glycol methyl ether, diethylene glycol monomethyl ether, and triethylene glycol monomethyl ether; Lower alkyl ethers of polyhydric alcohols, monohydric alcohols such as ethanol, isopropyl alcohol, n-butyl alcohol and isobutyl alcohol,
Glycerin, N-methyl-2-pyrrolidone, 1,3-dimethyl-imidazolidinone, triethanolamine, sulfolane, dimethylsulfoxide and the like. The content of the water-soluble organic solvent in the liquid composition is not particularly limited, but is preferably 1 to 60% by weight, more preferably 5 to 30% by weight based on the total amount of the liquid composition.
Is a preferable range. In addition, if necessary, additives such as a viscosity adjuster, a pH adjuster, a preservative, a surfactant, an antioxidant, and an evaporation promoter may be blended. The choice of surfactant is particularly important in adjusting the permeability of the liquid.

The liquid composition according to the present invention does not contain a coloring material, and has a color tone that is colorless or does not change the color tone of an ink containing a recording coloring material. The physical properties of this liquid composition include pH around 25 ° C.
It is preferable in the present invention that the surface tension is in the range of 3 to 12, the surface tension is in the range of 10 to 60 dyn / cm, and the viscosity is in the range of 1 to 30 cps. However, as for the surface tension, adjusting the surface tension of the liquid composition to be lower than the surface tension of the ink composition described above may be effective in performing image formation in some cases.

The image forming method of the present invention comprises a step of applying a liquid composition containing a cationic substance to a recording medium and a step of applying an ink containing a water-soluble anionic dye to the recording medium. A feature of the present invention is to use an ink set of the present invention in which the above-described liquid composition and the ink composition of the present invention are combined. The recording medium used at this time is not particularly limited, and so-called plain paper such as copy paper and bond paper which have been conventionally used can be suitably used. Of course, coated paper and OHP transparent film specially prepared for ink jet recording can be suitably used, and can also be suitably used for general high quality paper and glossy paper.

In the image recording method of the present invention, there is provided a step of applying a liquid composition containing a cationic substance to a recording medium and a step of applying an ink containing a water-soluble anionic dye to the recording medium. Any of the liquid composition and the ink may be applied to the recording medium first, or may be applied almost simultaneously. That is, the step of applying the liquid composition to the recording medium may be performed prior to the step of applying the ink to the recording medium, or the step of applying the liquid composition to the recording medium may be performed by recording the ink on the recording medium. It may be performed after the step of applying to the medium. In particular, in a preferred embodiment of the present invention, the liquid composition is applied to the image forming area of the recording medium or the image forming area and its vicinity before the ink, and then the ink composition is applied. Here, the image forming area is an area where ink dots are attached, and the vicinity of the image forming area is an area about 5 dots apart from 1 outside the area where the ink dots are attached. Point.

As a method of attaching the liquid composition to the recording medium, for example, a spray, a roller, or the like is used.
There is a method of attaching to the entire surface of the recording medium,
It is preferable to apply the liquid composition on the recording medium by an ink jet method that can selectively and uniformly apply the ink composition only to the image forming area to which the ink composition adheres and the vicinity of the image forming area. It should be noted that there is no particular limitation on the time difference between the time when the liquid composition and the ink adhere to the recording medium.

As a method for attaching the liquid composition and the ink composition to a recording medium, various ink jet recording methods can be used. Particularly preferred is a method in which droplets are formed by using bubbles generated by thermal energy. This is a method of discharging. Hereinafter, an example of an ink jet recording apparatus suitable for forming an image using the ink set of the present invention will be described.

FIGS. 3, 4 and 5 show examples of the structure of a head which is a main part of the apparatus. The head 13 includes a glass, ceramic or plastic plate or the like having a groove 14 through which ink passes, and a heating head 15 (a thin film head is shown in the figure, but is not limited to this) used for thermal recording. Are obtained by bonding. The heating head 15 has a good heat dissipation property such as a protective film 16 formed of silicon oxide or the like, aluminum electrodes 17-1 and 17-2, a heating resistor layer 18 formed of nichrome or the like, a heat storage layer 19, and alumina. It consists of a substrate 20.

The ink 21 has a discharge orifice (fine hole) 2
2, and a meniscus 23 is formed by a pressure (not shown). Now, aluminum electrodes 17-1 and 17
When electric signal information is added to -2, the area indicated by n of the heating head 15 generates heat rapidly, bubbles are generated in the ink 21 in contact with the area, and the meniscus 23 protrudes due to the pressure, and the ink 21 is ejected. The ink orifices 22 fly toward the recording material 25 from the ejection orifices 22.

FIG. 5 is an external view of a multi-head in which many heads shown in FIG. 3 are arranged. The multi-head is manufactured by closely contacting a glass plate 27 having a multi-groove 26 and a heating head 28 similar to that described with reference to FIG. FIG. 3 is a cross-sectional view of the head 13 along the ink flow path.
FIG. 4 is a sectional view taken along line AB in FIG.

FIG. 6 shows an example of an ink jet recording apparatus incorporating the above head. In FIG. 6, reference numeral 61 denotes a blade as a wiping member, one end of which is held by a blade holding member to become a fixed end, and forms a cantilever. The blade 61 is arranged at a position adjacent to a recording area of the recording head 65, and in the present example, is held in a form protruding into the movement path of the recording head 65. Reference numeral 62 denotes a cap on the ejection port surface of the recording head 65, which is disposed at a home position adjacent to the blade 61, moves in a direction perpendicular to the moving direction of the recording head 65, and comes into contact with the ink ejection port surface to perform capping. It has a configuration to perform. Further, reference numeral 63 denotes an ink absorber provided adjacent to the blade 61, which is held in a form protruding into the movement path of the recording head 65, similarly to the blade 61.

The blade 61, the cap 62, and the ink absorber 63 constitute an ejection recovery section 64, and the blade 61 and the ink absorber 63 remove water, dust, and the like from the ink ejection port surface. A recording head 65 having ejection energy generating means for ejecting ink to a recording material facing an ejection port surface provided with ejection ports to perform recording;
Reference numeral 6 denotes a carriage on which the recording head 65 is mounted and moved. The carriage 66 is slidably engaged with the guide shaft 67, and a part of the carriage 66 is connected to a belt 69 driven by a motor 68 (not shown).
As a result, the carriage 66 can move along the guide shaft 67, and the recording head 65 can move the recording area and the adjacent area.

Reference numeral 51 denotes a paper feed unit for inserting a recording material,
Reference numeral 2 denotes a paper feed roller driven by a motor (not shown). With such a configuration, the recording material is fed to a position facing the discharge port surface of the recording head 65, and is discharged to a discharge section provided with a discharge roller 53 as recording proceeds.

In the above configuration, when the recording head 65 returns to the home position at the end of recording or the like, the cap 62 of the ejection recovery section 64 is retracted from the moving path of the recording head 65, but the blade 61 projects into the moving path. I have. As a result, the ejection port surface of the recording head 65 is wiped.
When capping is performed by contacting the cap 62 with the ejection port surface of the recording head 65, the cap 62 moves so as to protrude into the moving path of the recording head.

When the recording head 65 moves from the home position to the recording start position, the cap 62 and the blade 61 are at the same position as the position at the time of wiping described above. As a result, the ejection port surface of the recording head 65 is also wiped during this movement. The movement of the print head 65 to the home position is performed not only at the end of printing or at the time of ejection recovery, but also at the home position adjacent to the printing area at a predetermined interval while the printing head 65 moves through the printing area for printing. And the wiping is performed with this movement.

FIG. 7 is a diagram showing 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 unit that stores the supply ink, for example, an ink bag, and a rubber stopper 42 is provided at the end thereof. By inserting a needle (not shown) into this stopper 42,
The ink in the ink bag 40 can be supplied to the head. An ink absorber 44 receives the waste ink. It is preferable for the present invention that the ink absorbing portion has a liquid contact surface with the ink formed of polyolefin, particularly polyethylene.

The ink-jet recording apparatus used in the present invention is not limited to the above-described apparatus in which the head and the ink cartridge are separated from each other, but also preferably the apparatus in which they are integrated as shown in FIG. Used. In FIG. 8, reference numeral 70 denotes a recording unit, in which an ink storage unit storing ink, for example, an ink absorber is stored, and a head unit having a plurality of orifices in which the ink in the ink absorber is stored. It is configured to be ejected from 71 as ink droplets.

As the material of the ink absorber, it is preferable for the present invention to use polyurethane, cellulose or polyvinyl acetal. Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the recording unit with the atmosphere. The recording unit 70 is used in place of the recording head shown in FIG. 6, and is detachable from the carriage 66.

As a configuration of a head that can be suitably used in the image forming method of the present invention, when a method of discharging a liquid composition by an ink jet recording head is used, the head for discharging ink is moved in the moving direction of the carriage. That is, they may be arranged in parallel at right angles to the scanning direction of the recording medium, or may be arranged in tandem. In the case of arranging in a column, the nozzles of one head may be divided into an upper half and a lower half, and the flow paths of the ink composition and the liquid composition may be separately supplied.

[0056]

The present invention will be described more specifically with reference to the following examples and comparative examples. Examples 1 to 10 and Comparative Examples 1 to 10 <Preparation of Liquid Composition> After the following components were mixed and dissolved,
Further, pressure filtration was performed using a membrane filter having a pore size of 0.22 μm (trade name: Fluoropore Filter, manufactured by Sumitomo Electric Industries, Ltd.) to obtain liquid compositions M-1 and M-2. (M-1) Cationic compound: BTBAC (benzyltributylammonium chloride, manufactured by Tokyo Chemical Industry, molecular weight = 312) 1 part Cationic compound: PAA-HCL-L (polyallylamine hydrochloride, molecular weight = 1,000) , Nitto Boseki) 1.5 parts ・ Solvent: 10 parts diethylene glycol ・ Water 97.5 parts

(M-2) Cationic compound: G-50 (benzalkonium chloride, manufactured by Sanyo Chemical Industries, molecular weight = 340) 1 part Cationic compound: PAA-HCL-L (polyallylamine hydrochloride, molecular weight = 1,000 parts, manufactured by Nitto Boseki) 3 parts ・ Solvent: 10 parts diethylene glycol ・ 96 parts water

<Preparation of Ink> The following components were mixed and filtered under pressure through a membrane filter having a pore size of 0.22 μm (trade name: Fluoropore Filter, manufactured by Sumitomo Electric Industries, Ltd.). 10 was obtained. Ink I-
For each dye used in 1 to I-10, the dye concentration was 20
ppm, an aqueous solution of pH 3 and an aqueous solution of pH 7 were prepared,
The absorbance was measured for each solution. Table 1 shows the peak wavelength of the absorbance and the number of wavelength shifts.

(Ink I-1) C.I. I. Direct Black 195 1 part-Projet Fast Cyan 2 (Zeneca) 3 parts-Projet Fast Yellow 2 (Zeneca) 0.5 parts-Diethylene glycol 15 parts-Water 80.5 parts

(Ink I-2) C.I. I. Direct Black 195 1.5 parts I. Reactive Blue 15 1 part ・ Projet Fast Yellow 2 (Zeneca) 0.5 part ・ Diethylene glycol 15 parts ・ Water 82 parts

(Ink I-3) 1 part of the dye represented by the following structural formula (1) I. Direct Blue 199 1 part ・ Projet Fast Magenta 2 (Zeneca) 2 parts ・ Diethylene glycol 15 parts ・ Water 81 parts

[0062] (In the formula (1), M represents an alkali metal ion, an ammonium ion, or an organic amine.)

(Ink I-4) C.I. I. Direct Black 195 1.5 parts I. Direct Blue 199 2 parts ・ C. I. Direct Yellow 86 0.5 parts ・ Diethylene glycol 15 parts ・ Water 81 parts

(Ink I-5) C.I. I. Direct Black 195 1.5 parts ・ Dye of the following structural formula (1) 1 part ・ C. I. Direct Blue 199 1 part ・ Diethylene glycol 15 parts ・ Water 81.5 parts

[0065] (In the formula (1), M represents an alkali metal ion, an ammonium ion, or an organic amine.)

(Ink I-6) 1 part of the dye of the following structural formula (2) 1 part of Pro jet Fast Cyan 2 (manufactured by Zeneca) 3 parts 0.5 part of Projet Fast Yellow 2 (manufactured by Zeneca) 15 parts of diethylene glycol 80.5 parts of water

[0067] (In the formula (1), M represents an alkali metal ion, an ammonium ion, or an organic amine.)

(Ink I-7) C.I. I. Food Black 1 1.5 parts I. Reactive Blue 9 1 part ・ Projet Fast Yellow 2 (Zeneca) 0.5 part ・ Diethylene glycol 15 parts ・ Water 82 parts

(Ink I-8) C.I. I. Food Black 2 3.5 parts I. Direct Blue 199 0.5 parts ・ Diethylene glycol 15 parts ・ Water 81 parts

(Ink I-9) 1.5 parts of dye represented by the following structural formula (1) I. Acid Blue 9 2 parts ・ C. I. Direct Yellow 86 0.5 parts ・ Diethylene glycol 15 parts ・ Water 81 parts

[0071]

Embedded image (In the formula (1), M represents an alkali metal ion, an ammonium ion, or an organic amine.)

(Ink I-10) C.I. I. Food Black 2 3.8 parts ・ C. I. Acid Blue 9 0.2 parts ・ Diethylene glycol 15 parts ・ Water 81 parts

Table 1 Peak wavelength of absorbance of aqueous dye solution and number of wavelength shifts

<Recording> The ink compositions of Examples 1 to 10 and Comparative Examples 1 to 10 were prepared by using the liquid composition and the ink composition obtained as described above in combinations shown in Table 2. did. Using this ink set, recording was performed on commercially available copy paper. As the ink jet recording apparatus used, the same ink jet recording apparatus as that shown in FIG. 6 was used, and the heads were arranged in parallel with the ink discharging head and the liquid composition discharging head in the carriage movement direction. The configuration is such that it is applied to the recording medium later. The recording head used here had a recording density of 360 dpi, and the driving conditions were a driving frequency of 5 kHz. The ejection volume per dot was 55 picoliter. These recording conditions are constant throughout the examples and comparative examples of the present invention. The environmental conditions for the print test were 25 ° C / 55%
It is unified to RH.

<Evaluation> The evaluation of the recorded image was performed by the following method. (1) Image density A solid image was formed with the liquid composition and each black ink, and the reflection after standing for 12 hours was measured with a reflection densitometer Macbeth RD915 (manufactured by Macbeth). The evaluation criteria are as follows. The evaluation results are summarized in Table 2. ：: The reflection density is 1.20 or more Δ: The reflection density is 1.10 or more and 1.19 or less ×: The reflection density is 1.09 or less

(2) Solid Uniformity Using the liquid composition and the ink composition, a black solid image was formed, and the obtained image was visually observed. The evaluation criteria are as follows. Table 2 shows the evaluation results.
Are shown together. ：: The solid image is uniform without unevenness. X: Unevenness is observed in the solid image.

(3) Fixability A black solid image was formed using the liquid composition and the ink composition. After the image was formed, the time during which the image flow did not occur even when the printed portion was rubbed with a finger was measured. The evaluation criteria are as follows. The evaluation results are summarized in Table 2. ：: Fixing property is within 30 seconds △: Fixing property is from 31 seconds to 50 seconds △: Fixing property is 51 seconds or more

(4) Character Quality Using the liquid composition and the ink composition, black alphanumeric characters were printed and evaluated visually. When the feathering was inconspicuous, it was marked as “○”, and when it was at other levels, it was marked as “x”. The evaluation results are summarized in Table 2.

(5) Water resistance (1) The image obtained in the evaluation of image density was left for 30 minutes, then immersed in tap water at a water temperature of 20 ° C. for 3 seconds, and the remaining state of the image was visually evaluated. did. An image having no flow of the image was indicated by ○, and an image having other levels was indicated by ×. The evaluation results are summarized in Table 2.

(6) Light fastness (1) The image obtained in the evaluation of the image density was exposed for 100 hours with a fade meter (Atlas C; -35).
The residual state of the image was evaluated by the residual ratio of OD. O
D: 95% or more of the residual ratio was evaluated as ○, 85 or more and less than 95% as Δ, and less than 85% as ×. The evaluation results are summarized in Table 2.

Table 2 shows the combinations of the liquid compositions used in Examples and Comparative Examples, and the results of evaluations (1) to (6) of Examples 1 to 10 and Comparative Examples 1 to 10. Throughout the examples and comparative examples, the area where the liquid composition adheres to the recording medium was the same as the image forming area of the ink composition, and the printing duty was 50% for both the liquid composition and the ink composition. . Further, the printing direction was unidirectional, and the liquid composition was always driven before the ink composition.

Table 2 Evaluation results

However, the ink compositions I-6, I-7, I-
8, I-9, and I-10, the ejection ratio of the liquid composition was 100% with respect to the ink composition.
When the amount was increased, the evaluation (2) solid uniformity, the evaluation (3) print quality, and the evaluation (4) water resistance were at the ○ level.

Further, the order of applying the ink and the liquid composition to the recording material was reversed, and the liquid composition was applied prior to the application of the ink, and the same test was performed. The result was obtained.

[0085]

As described above, according to the present invention, the character quality is good, the color tone is good, the image density is high, the solidity is high, and the water resistance of the recorded image is good. An image recorded matter having excellent properties and light fastness of a recorded image can be obtained. In particular, according to the present invention, the above effects can be stably obtained by inkjet recording.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the aggregation mechanism of a cationic substance and an anionic dye.

FIG. 2 is a schematic diagram showing an aggregation mechanism of a cationic substance and a water-soluble anionic dye in the present invention.

FIG. 3 is a longitudinal sectional view of a head of the ink jet recording apparatus.

FIG. 4 is a cross-sectional view of a head of the inkjet recording apparatus.

FIG. 5 is an external perspective view of a head obtained by multiplying the head shown in FIG. 1;

FIG. 6 is a perspective view illustrating an example of an inkjet recording apparatus.

FIG. 7 is a longitudinal sectional view of the ink cartridge.

FIG. 8 is a perspective view illustrating an example of a recording unit.

[Explanation of symbols]

 13: Head 14: Ink groove 15: Heating head 16: Protective film 17-1, 17-2: Aluminum electrode 18: Heating resistor layer 19: Heat storage layer 20: Substrate 21: Ink 22: Discharge orifice (fine hole) 23 : Meniscus 24: Ink 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: Paper feed unit 52: Paper feed roller 53: paper discharge roller 61: blade 62: cap 63: ink absorber 64: ejection recovery unit 65: recording head 66: carriage 67: guide shaft 68: motor 69: belt 70: recording unit 71: head unit 72: atmosphere communication mouth

Claims (11)

[Claims] 1. An ink composition having at least a coloring material and a liquid medium, wherein the coloring material is a mixture of a plurality of water-soluble anionic dyes, and the dye has a molecular structure of either a sulfone group or a carboxyl group. One having an anionic hydrophilic group and a conjugated moiety having any one selected from an aromatic ring, a phthalocyanine ring, an azo group, and a vinylene group, and having one planarity in terms of steric structure. An ink characterized in that the wavelength of the aqueous solution of the dye has a peak of absorbance in the visible region that shifts by 5 nm or more in the pH range of pH 3 to pH 7 of the aqueous solution. Composition. 2. An ink set comprising a liquid composition containing a cationic substance and an ink containing a water-soluble anionic dye, wherein the ink is the ink composition according to claim 1. . 3. The ink set according to claim 2, wherein the liquid composition contains a cationic substance having a molecular weight of 1,500 or less. 4. The liquid composition has a molecular weight of 700 or more and 1,5.
3. The ink set according to claim 2, wherein the ink set contains no more than 00 cationic substances. 5. An image forming method comprising the steps of: applying a liquid composition containing a cationic substance to a recording medium; and applying an ink containing a water-soluble anionic dye to the recording medium. An image forming method using the ink set according to any one of claims 1 to 4. 6. The step of applying ink to a recording medium,
The image forming method according to claim 5, wherein the ink is ejected by an ink jet recording method. 7. The image forming method according to claim 6, wherein the ejection of the ink is performed by applying thermal energy to the ink. 8. The image forming method according to claim 5, wherein the step of applying the liquid composition to the recording medium ejects the liquid composition by an ink jet recording method. 9. The method according to claim 5, wherein the step of applying the liquid composition containing the cationic substance to the recording medium is performed prior to the step of applying the ink containing the water-soluble anionic dye to the recording medium. The image forming method according to any one of the above. 10. The method according to claim 5, wherein the step of applying the liquid composition containing the cationic substance to the recording medium is performed after the step of applying the ink containing the water-soluble anionic dye to the recording medium. The image forming method according to any one of the above. 11. An ink jet recording apparatus for ejecting ink from an ejection orifice as droplets onto a recording medium in accordance with a recording signal, wherein the ink is the ink composition according to claim 1. .