JPH08174997A - Liquid composition, ink set and method and apparatus for forming image using the composition - Google Patents

Abstract

PURPOSE: To provide ink set which has high image density, excellent fixing properties and character quality level on a sheet, and excellent water resistance and in which bleeding is suppressed to obtain an excellent image. CONSTITUTION: A liquid composition comprises at least cationic substance in which at least one of the peaks of a molecular weight distribution measured by using GPC exists in two ranges of different molecular weights, and ink set of at least one of yellow, magenta, cyan, black, red, blue and green. A method and an apparatus for forming an image applied by it are provided.

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 that occurs when a color image is formed by an ink, and more particularly to an image forming method and an apparatus using the ink jet system, and further,
The present invention relates to a liquid composition and an ink set applied to these.

[0002]

2. Description of the Related Art An ink jet recording method is one in which a small ink droplet is ejected and adhered to a recording medium such as paper for recording. In particular, Japanese Patent Publication No. 61-59911, Japanese Patent Publication No. 61-59912, and Japanese Patent Publication No. 61-59914.
According to the method disclosed in Japanese Patent Laid-Open Publication No. 2003-242242, in which an electrothermal converter is used as a discharge energy supply means, heat energy is applied to ink to generate bubbles to discharge droplets, it is easy to realize a high density multi-orifice of a recording head. It can realize high resolution and high quality images can be recorded at high speed.

However, conventional inks used for ink jet recording generally contain water as a main component, and a water-soluble high-boiling point 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 may not be obtained, or a non-uniform image that is estimated to be due to the non-uniform distribution of the filler or sizing agent on the surface of the recording paper may occur. It was In particular, when trying to obtain a color image, the inks of multiple colors are superimposed one on top of the other before they are fixed on the paper, so the colors may bleed at the boundary of different color images, or may be mixed unevenly. (Hereinafter, this phenomenon will be referred to as breeding) A satisfactory image could not be obtained.

As a means for improving the fixing property, JP-A-55-6
Japanese Patent No. 5269 discloses that a compound such as a surfactant which enhances permeability is added to the ink. Further, JP-A-55-66976 discloses the use of an ink containing a volatile solvent as a main component.

However, in the former method, the permeability of the ink into the recording paper is increased, and although the fixing property and the bleeding are improved to some extent, the coloring material penetrates deeply into the recording paper together with the ink, so that the image density is increased. In addition, inconveniences such as a decrease in saturation occur, and ink spreads in the horizontal direction, resulting in problems such as a decrease in edge sharpness and a decrease in resolution. On the other hand, in the latter case, in addition to the inconvenience of the former case, clogging due to evaporation of the solvent in the nozzle portion of the recording head is likely to occur, which is not preferable.

Further, in order to improve the above-mentioned problems, there has been proposed a method of adhering a liquid for improving an image on a recording medium prior to ejection of recording ink.

For example, JP-A-63-60783 discloses a method of recording an ink containing an anionic dye after depositing a liquid having a basic polymer, and JP-A-63-22681. The publication discloses a recording method in which a first liquid containing a reactive chemical species and a liquid containing a compound that reacts with the reactive chemical species are mixed on a recording medium. Japanese Patent No. 299971 discloses a method of recording an ink containing an anionic dye after depositing a liquid containing an organic compound having two or more cationic groups per molecule. Further, JP-A-64-9279 discloses a method of recording an ink containing an anionic dye after depositing an acidic liquid containing succinic acid or the like.

Further, Japanese Patent Application Laid-Open No. 64-63185 discloses a method of applying a liquid insolubilizing a dye prior to recording of ink.

However, all of the above methods are intended to suppress image bleeding and improve water resistance by precipitating the dye itself, and the effect of suppressing bleeding between the color inks described above is also insufficient, and the precipitation is also caused. Since the dye is likely to be unevenly distributed on the recording paper, the coverage of the recording paper on the pulp fibers is poor, and the uniformity of the image is deteriorated.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the following five problems in view of the above circumstances. That is, when performing inkjet recording on plain paper, (1) good character and good character quality are obtained, (2) sufficient image density is obtained, and solid image uniformity is high; , (3) Preventing bleeding, especially when forming a color image on plain paper, (4) good color reproducibility and high-definition image, (5) complete waterproofness of recorded image What to do,
Is.

[0011]

[Means and Actions for Solving the Problems]
The following is achieved by the present invention.

That is, the present invention provides a liquid composition containing at least a cationic substance, wherein the cationic substance has at least one peak of the molecular weight distribution measured by GPC in two regions having different molecular weights. It is a liquid composition characterized by having.

The present invention is also an ink set characterized by combining the above liquid composition with at least one ink of yellow, magenta, cyan, black, red, blue and green, and preferably the above ink composition. Liquid composition and three color inks of yellow, magenta and cyan, and the above liquid composition and four color inks of yellow, magenta, cyan and black, wherein the ink contains an anionic compound. An ink set in which the anionic compound is a polymer having a molecular weight of 1000 or more, or the anionic compound is a surfactant.

Further, in the present invention, the step (A) of adhering the above liquid composition to at least an image forming area of a recording medium.
And an step (B) of applying an ink containing at least an anionic compound to the recording medium by an inkjet method.

Furthermore, an image forming apparatus having the above-mentioned ink set and an ink jet means, a first recording unit having a storage portion and an ejection means for the liquid composition, and at least an anionic compound. An image forming apparatus comprising: a second recording unit having an ink containing portion containing ink and a discharging unit.

Next, the operation of the present invention will be described.

In the present invention, as a result of mixing the above-mentioned liquid composition with the ink on the recording paper or at the position where the ink has penetrated, the low molecular weight cationic substance contained in the liquid composition as the first step of the reaction. The water-soluble dye having an anionic group used in the ink or the anionic compound used in the pigment ink causes association due to ionic interaction and instantaneously separates from the solution phase. As a result, dispersion destruction occurs in the pigment ink, and pigment aggregates are formed.

Next, in the second step of the reaction, the above-mentioned dye-low molecular weight cationic substance aggregate or pigment agglomerate is adsorbed by the high molecular weight component of the cationic substance contained in the liquid composition. In dye ink, the aggregate of dyes formed by association, or in pigment ink, the size of the aggregate of pigment becomes larger, and it becomes difficult to enter into the gaps between the fibers of the recording paper, resulting in solid-liquid separation. Only the liquid portion soaked into the recording paper makes it possible to achieve both print quality and fixability.

In particular, when a pigment is used as the coloring material, the pigment in the ink is aggregated on the surface of the recording paper, so that the hiding power is increased, and the coloring property and the image density are remarkably improved.

At the same time, a low molecular weight cationic substance and an anionic dye produced by the mechanism as described above, or
Aggregates formed from the anionic compound in the pigment ink and the high molecular component of the pigment and the cationic substance have high viscosity and do not move with the movement of the liquid medium. Even if adjacent dots are formed of different color inks, they do not mix with each other, and bleeding does not occur.
Also, the above-mentioned aggregates are essentially water-insoluble, and the water resistance of the formed image is perfect.

In carrying out the present invention, it is not necessary to use a cationic polymer substance having a large molecular weight as in the prior art. Therefore, since the viscosity of the liquid composition containing the cationic substance does not increase, it was attempted to adhere the liquid composition to a recording medium using an inkjet recording head, particularly an on-demand type thermal inkjet recording head. In this case, it is advantageous for ejection characteristics such as frequency response, stable ejection volume, and stable ejection speed, and since there is no need to use a polyvalent metal salt, the problem of kogation does not occur. The advantage of is also mentioned as another effect of the present invention.

[0022]

Preferred Embodiments Next, preferred embodiments of the present invention will be described to explain the present invention in more detail.

First, the liquid composition will be described.

The essential components contained in the liquid composition described in the present invention are (1) a low molecular weight cationic substance and (2)
It is a cationic polymer substance.

Further, the ink according to the embodiment of the present invention is (3)
A water-soluble dye having at least an anionic group,
The ink according to another embodiment of the present invention contains at least (4) a pigment and an anionic compound.

The effects of the above substances in the present invention are as described above, and the water-soluble dye or pigment ink having the low molecular weight cationic substance of (1) and at least the anionic group of (3) contained in the ink. The anionic compound therein forms an aggregate by ionic interaction. This association formation reaction rate needs to be extremely high.

The low molecular weight cationic substance (1) is preferably one having at least one peak in the molecular weight distribution measured by GPC in the region of molecular weight: 1000 or less.

Preferred specific examples of the low molecular weight cationic substance (1) are listed below. In the present invention, the low molecular weight cationic substance can be used in the molecular weight distribution in many cases that are close to monodisperse.For compounds without a molecular weight distribution, the molecular weight obtained from the usual chemical formula is the peak position of the molecular weight distribution. think of.

Primary to secondary to tertiary amine salt type compounds, specifically, laurylamine, coconut amine, stearylamine, rosinamine and other hydrochlorides, acetates, etc., as well as quaternary ammonium salt type compounds, Specific examples include lauryltrimethylammonium chloride, lauryldimethylbenzylammonium chloride, benzyltributylammonium chloride, benzalkonium chloride, cetyltrimethylammonium chloride, and the like, and further pyridinium salt-type compounds, specifically cetylpyridinium chloride and cetylpyridinium bromide. And more,
There are imidazoline type cationic compounds, specifically 2-heptadecenyl-hydroxyethyl imidazoline,
Furthermore, ethylene oxide adduct of secondary alkyl amine,
Specifically, preferred examples include dihydroxyethylstearylamine and the like.

Further, in the present invention, an amphoteric surfactant which exhibits a cationic property in a certain pH range can be used.

More specifically, there are amino acid type amphoteric surfactants and RNHCH2-CH2COOH type compounds, and betaine type compounds such as stearyl dimethyl betaine and lauryl dihydroxyethyl betaine. Of course, when these amphoteric surfactants are used, the liquid composition is adjusted so as to have a pH below their isoelectric point, or when mixed with ink on a recording medium, the pH below the isoelectric point. It is necessary to take either method of adjusting to become.

Although examples of low molecular weight cationic compounds have been given above, it goes without saying that the compounds usable in the present invention are not necessarily limited to these.

As the cationic polymer substance (2),
The peak of the molecular weight distribution measured using GPC is in the region of molecular weight: 1500 or more (more preferably, molecular weight: 1
It is preferable that there is at least one in the region of 500 to 10,000).

As to the action and effect of the cationic polymer substance of (2) in the present invention, as described above, as the second step of the reaction between the liquid composition and the ink, the anion in the dye or pigment ink described above is used. The solid-liquid separation is achieved by adsorbing the aggregate of the reactive compound and the low molecular weight cationic substance into the molecule, and further increasing the size of the aggregate of the dye generated by the association to prevent the dye aggregate from entering the gaps between the fibers of the recording paper. It is to achieve both print quality and fixability by making only the liquid part soaked in the recording paper.

Specific examples of the cationic polymer substance (2) include polyallylamine, polyamine sulfone, polyvinylamine, chitosan and their neutralized or partially neutralized products with acids such as hydrochloric acid and acetic acid. I can, but
Needless to say, it is limited to these. The position of the peak of the molecular weight distribution of these polymer substances is 1500 or more 1
If at least one is present in 0000 or less, the effect is sufficient when carrying out the present invention.

Unless otherwise specified, the molecular weight of the polymer substance in the present invention refers to the average molecular weight obtained by using GPC (gel permeation chromatography), which is the weight average molecular weight in terms of polyethylene oxide. Say that.

As another specific example of the cationic polymer substance (2), a compound obtained by cationizing a part of the nonionic polymer substance may be used.

Specific examples thereof include a copolymer of vinylpyrrolidone and a quaternary salt of aminoalkyl alkylate and a copolymer of a quaternary salt of acrylic amide and aminomethyl acrylic amide. It goes without saying that the compound is not limited.

Further, the above-mentioned cationic polymer substance is satisfactory as long as it is water-soluble, but it may be a dispersion such as latex or emulsion.

The amount of these components contained in the liquid composition is preferably 0.05 to 20% by weight, more preferably 0.5 to 5% by weight, based on the weight. However, it is necessary to determine the optimum range depending on the combination of substances used. The mixing ratio of the low molecular weight cationic substance (1) and the polymer substance (2) in the liquid composition is 10: 1 to 1:10, preferably 5: 1 by weight.
Is in the range of to 1: 5. If this ratio exceeds 10: 1, the water resistance of the printed matter is likely to decrease, and conversely, if it is 1:10 or less, bleeding is insufficiently suppressed and the edge sharpness of the image is likely to decrease.

Next, other components constituting the liquid composition will be specifically described.

The liquid composition has the above-mentioned (1) and (2).
In addition to the above components, it usually comprises water, a water-soluble organic solvent and other additives. Examples of the water-soluble organic solvent 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 and butylene. Glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol,
Alkylene glycols such as diethylene glycol, lower alkyl ethers of polyhydric alcohols such as ethylene glycol methyl ether, diethylene glycol monomethyl ether and triethylene glycol monomethyl ether, monohydric alcohols such as ethanol, isopropyl alcohol, n-butyl alcohol and isobutyl alcohol. , Glycerin, N-methyl-2-pyrrolidone,
1,3-Dimethylimidazolidinone, triethanolamine, sulfolane, dimethylsulfoxide, etc. are used.

The content of the water-soluble organic solvent is not particularly limited, but it is preferably 5 to 60% by weight, more preferably 5 to 40% by weight based on the total weight of the liquid.

In addition, if necessary, a viscosity modifier, pH
You may mix | blend additives, such as a regulator, a preservative, a surface-active agent, an antioxidant, and an evaporation promoter. The choice of surfactant is especially important in adjusting the permeability of the liquid.

The liquid composition described in the present invention has a color tone within a range that does not change the color tone of the recording ink. The preferred range for the physical properties of this liquid composition is around 25 ° C.,
pH is 3-12, preferably 3-8, more preferably 3
The surface tension is 10 to 60 dyn / cm, preferably 10 to 40 dyn / cm, and the viscosity is 1 to 30.
cps.

Next, the recording ink (3) used in the present invention
Will be described.

The recording ink (3) used in the present invention comprises the above-mentioned water-soluble dye having an anionic group, water, a water-soluble organic solvent and other components such as a viscosity adjusting agent, a pH adjusting agent, a preservative and an interface. If necessary, an activator, an antioxidant and the like are included.

The water-soluble dye having an anionic group used in the present invention includes a color index (COLOUR).
There is no particular limitation as long as it is a water-soluble acid dye, direct dye or reactive dye described in INDEX). In addition, even if not described in the color index, an anionic group,
For example, there is no particular limitation as long as it has a sulfone group, a carboxyl group or the like. Among the water-soluble dyes mentioned here,
Those that have pH dependence of solubility are also included.

As the water-soluble organic solvent used in the ink, the water-soluble organic solvent used in the liquid composition can be similarly used. The same applies to the preferable range of the content of the water-soluble organic solvent. Also, the preferable physical property range of the ink is exactly the same as that of the liquid composition.

In order to more effectively carry out the effect of the present invention, in addition to the components described above for the ink, an anionic surfactant or an anionic (preferably molecular weight: 1000 or more) high ink is used. A molecular substance may be added. Alternatively, the amphoteric surfactant may be adjusted to a pH above its isoelectric point before use. As examples of the anionic surfactant, those commonly used such as carboxylate type, sulfate type, sulfonate type and phosphate type can be used. Examples of the anionic polymer include alkali-soluble resins, specifically, sodium polyacrylate, and those obtained by copolymerizing a part of the polymer with acrylic acid. Of course, it is not limited to these.

Next, a recording ink (4) which is another embodiment of the ink used in the present invention will be described.

The recording ink (4) contains, in addition to the pigment and the anionic compound, water, a water-soluble organic solvent and other components such as a viscosity adjusting agent, a pH adjusting agent, a preservative, a surfactant and an antioxidant. Include as needed. Here, the anionic compound may be a dispersant for the pigment, or when the dispersant for the pigment is not an anionic compound, an anionic compound different from the dispersant may be added. Of course, even when the dispersant is an anionic compound, another anionic compound may be added.

The pigment that can be used in the present invention is not particularly limited, but specifically, the pigments described below are preferably used.

First, the carbon black used in the black pigment ink is carbon black produced by the furnace method or the channel method, the primary particle diameter is 15 to 40 mm, and the specific surface area by the BET method is 50 to 50 mm. 300 square meters / g, DBP oil absorption is 40 to 150 ml / 100g, volatile content is 0.5 to 10%, p
H value has 2 to 9 and, for example, No. 2300, N
o. 900, MCF88, No. 40, No. 52, M
A7, MA8, No. 2200B (Made by Mitsubishi Kasei)
RAVEN1255 (made in Colombia), REGAL40
0R, REGAL660R, MOGUL L (made by Cabot), Color Black FW1, Color
Black FW18, Color Black S
170, Color Black S150, Prin
Commercial products such as tex 35 and Printex U (Degussa) can be used. In addition, a new prototype may be used for the present invention. Examples of pigments used in yellow ink include C.I. I. Pigment Yell
ow 1, C.I. I. Pigment Yellow2,
C. I. Pigment Yellow 3, C.I. I.
Pigment Yellow 13, C.I. I. Pig
ment Yellow 16, C.I. I. Pigmen
t Yellow 83, pigments used as magenta ink include C.I. I. Pigment Red
5, C.I. I. Pigment Red 7, C.I. I. Pi
gment Red 12, C.I. I. Pigment
Red48 (Ca), C.I. I. Pigment Red
48 (Mn), C.I. I. Pigment Red 5
7 (Ca), C.I. I. Pigment Red 11
2, C.I. I. Pigment Red 122, a pigment used as a cyan ink includes C.I. I. Pig
ment Blue 1, C.I. I. Pigment B
lue 2, C.I. I. Pigment Blue 3,
C. I. Pigment Blue 15: 3, C.I.
I. Pigment Blue 16, C.I. I. Pig
ment Blue 22, C.I. I. Vat Blue
4, C.I. I. Vat Blue 6 and the like can be mentioned, but those newly manufactured for the present invention can also be used. The above-mentioned pigment is 1 to 20 relative to the total amount of ink.
It is preferable to use it in the range of% by weight, preferably 2 to 12% by weight.

As the dispersant for the pigment in the ink used in the present invention, any water-soluble resin can be used, but the weight average molecular weight is preferably in the range of 1,000 to 30,000. Further, it is preferably in the range of 3000 to 15000. Specifically, hydrophobic monomers such as styrene, styrene derivatives, vinylnaphthalene, vinylnaphthalene derivatives, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, or acrylic acid, acrylic acid derivatives, maleic acid. Acid, maleic acid derivative, itaconic acid, itaconic acid derivative, fumaric acid, a block copolymer consisting of two or more monomers selected from fumaric acid derivatives, a graft copolymer, or a random copolymer, or
These salts etc. are mentioned. These resins are alkali-soluble type resins that are soluble in an aqueous solution in which a base is dissolved. Further, a homopolymer composed of a hydrophilic monomer or a salt thereof may be used. It is also possible to use water-soluble resins such as polyvinyl alcohol, carboxymethyl cellulose, and naphthalene sulfonic acid formaldehyde condensate. However, the use of an alkali-soluble type resin has the advantages that the viscosity of the dispersion liquid can be reduced and the dispersion is easy. The water-soluble resin is preferably used in the range of 0.1 to 5% by weight with respect to the total amount of the ink.

Further, in the ink of the present invention, it is preferable that the whole ink is adjusted to be neutral or alkaline so that the solubility of the water-soluble resin is improved and the long-term storage stability is further improved. It is desirable because it can be More preferably, the pH is in the range of 7 to 10.

Examples of the pH adjuster include various organic amines such as diethanolamine and triethanolamine, inorganic alkali agents such as alkali metal hydroxides such as sodium hydroxide, lithium hydroxide and potassium hydroxide,
Examples include organic acids and mineral acids.

As described above, the pigment and the water-soluble resin are dispersed or dissolved in the water-soluble medium.

A suitable aqueous medium in the ink (4) of the present invention is a mixed solvent of water and a water-soluble organic solvent, and the water is not ordinary water containing various ions but ion-exchanged water (deionized water). Water) is preferably used.

Other examples of the water-soluble organic solvent used by mixing with water include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol. Butyl alcohol and other carbon atoms 1
-4 alkyl alcohols; dimethylformamide,
Amides such as 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, butylene glycol, tri Alkylene glycols such as ethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, and diethylene glycol having 2-6 carbon atoms; glycerin, ethylene glycol monomethyl (or ethyl) ether, Lower polyhydric alcohols such as diethylene glycol methyl (or ethyl) ether and triethylene glycol monomethyl (or ethyl) ether Ruki ethers; N-methyl-2-
Pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-
Examples include imidazolidinone. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are preferable.

Further, in order to obtain ejection stability, it is effective to add ethanol or isopropyl alcohol in an amount of 1% or more. This is probably because the addition of these solvents makes it possible to more stably foam the recording liquid on the thin film resistor. However, if these solvents are added excessively, there is a drawback that the print quality of the printed matter is impaired.
It was found to be -10% by weight. Furthermore, as an effect of these solvents, by adding these solvents to the dispersion liquid, it is possible to suppress the generation of bubbles during dispersion and perform efficient dispersion.

The content of the water-soluble organic solvent in the ink of the present invention is generally in the range of 3-50% by weight, preferably 3-40% by weight, based on the total weight of the ink.
The water used is in the range of 10-90% by weight, preferably 30-80% by weight, based on the total weight of the ink.

When the dispersant is not an anionic polymer, it is necessary to add an anionic compound to the ink containing the above pigment. Examples of the anionic compound preferably used in the present invention include high molecular substances such as alkali-soluble resins described in the section of the pigment dispersant, and low molecular anionic surfactants.

Specific examples of the low molecular weight anionic surfactant include lauryl disodium sulfosuccinate, disodium polyoxyethylene lauroyl ethanolamide sulfosuccinate, disodium polyoxyethylene alkyl sulfosuccinate, and carboxylated polyoxyethylene. Sodium lauryl ether salt, carboxylated polyoxyethylene lauryl ether sodium salt, carboxylated polyoxyethylene tridecyl ether sodium salt, sodium polyoxyethylene lauryl ether sulfate, polyoxyethylene lauryl ether sulfate triethanolamine, polyoxyethylene alkyl ether sulfate Sodium, sodium polyoxyethylene alkyl ether sulfate, sodium alkyl sulfate, alkyl sulfate Although ethanolamine and the like but is not limited thereto.

The preferable amount of the above-mentioned anionic substance used is in the range of 0.05 to 10% by weight, more preferably 0.05 to 5% by weight, based on the total amount of the ink. .

In addition to the above-mentioned components, the ink of the present invention may contain a surfactant, a defoaming agent, an antiseptic agent, etc. in order to obtain an ink having desired physical properties, if necessary. Further, a commercially available water-soluble dye or the like can be added.

Examples of the surfactant include anionic surfactants such as fatty acid salts, higher alcohol sulfate ester salts, liquid fatty oil sulfate ester salts, and alkylallyl sulfonates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters. , Polyoxyethylene sorbitan alkyl esters, acetylene alcohol, acetylene glycol, and other nonionic surfactants, and one or more of these can be appropriately selected and used. The amount used varies depending on the dispersant, but is preferably 0.01 to 5% by weight with respect to the total amount of the ink. At this time, it is preferable to determine the amount of the activator to be added so that the surface tension of the ink is 30 dyne / cm or more. This is because, if the surface tension of the ink is smaller than the above value, in a recording method such as the present invention, an unfavorable situation such as printing deviation (deviation of ink droplet landing point) due to wetting of the nozzle tip may occur. Is.

As a method for producing the ink (4) of the present invention, first, a pigment is added to an aqueous solution containing at least a dispersion resin and water, the mixture is stirred, and then dispersed using a dispersing means described later, if necessary. According to the centrifugal separation treatment, a desired dispersion liquid is obtained. Next, the components listed above are added to this dispersion, and the mixture is stirred to form an ink.

When an alkali-soluble resin is used,
It is necessary to add a base to dissolve the resin. It is necessary to add the amount of amine or base that dissolves the resin in an amount of at least 1 times the amount of amine or base calculated from the acid value of the resin. The amount of this amine or base is calculated by the following formula.

Amount of amine or base (g) = (acid value of resin * molecular weight of amine or base * resin amount (g)) /
5600

Further, if the premixing is performed for 30 minutes or more before the dispersion treatment of the aqueous solution containing the pigment, the dispersion efficiency is good. This premixing operation improves the wettability of the pigment surface and promotes the adsorption of the dispersant on the pigment surface.

As the bases added to the dispersion when the alkali-soluble resin is used, organic amines such as monoethanolamine, diethanolamine, triethanolamine, amine methyl propanol and ammonia, potassium hydroxide and water. Inorganic bases such as sodium oxide are preferred.

On the other hand, the disperser used in the present invention may be any disperser generally used, and examples thereof include a ball mill and a sand mill.

Among them, a high speed type sand mill is preferable, and examples thereof include a super mill, a sand grinder, a bead mill, an agitator mill, a grain mill, a dynol mill, a pearl mill, and a cobol mill (all are trade names).

The recording medium used in carrying out the present invention is not particularly limited, and so-called plain paper such as conventionally used copy paper and bond paper is preferably used. Of course, a coated paper specially prepared for ink jet recording and a transparent film for OHP are also preferably used, and can also be suitably used for general high-quality paper and glossy paper.

The image forming method of the present invention may be any method as long as the liquid composition and the ink can coexist on the recording medium, and it does not matter which of the liquid composition and the ink is applied to the recording medium first. Absent.

The image forming area referred to in the present invention is an area where ink dots are attached, and the vicinity of the image forming area is separated by 1 to 5 dots outside the area where ink dots are attached. It refers to the area.

As a method for adhering the liquid composition to the recording medium, a method of adhering it to the entire surface of the recording medium with a spray, a roller or the like can be considered, but only in the image forming area to which the ink adheres and in the vicinity of the image forming area. It is preferable to carry out by an ink jet method capable of selectively and uniformly adhering.

The time from the application of the liquid composition to the recording medium to the application of the ink is not particularly limited, but in order to more effectively carry out the present invention, within a few seconds, Particularly preferably, it is within 1 second. This is also the case when the ink is first applied to the recording medium and then the liquid composition is applied.

As a method for attaching the colorless or light-colored liquid composition to the recording medium, various ink jet methods can be used, but it is particularly preferable to discharge the droplets by using bubbles generated by thermal energy. The so-called on-demand type thermal inkjet system.

The molecular weight distribution of the cationic compound used in the present invention may be measured by GPC individually in advance, or after measuring the molecular weight distribution of the liquid composition itself, at least a dye having an anionic group is contained. A sufficient amount of the ink and the liquid composition are mixed and stirred in a beaker, the precipitate is removed, and the GPC measurement is performed again.
It may be obtained by comparing the measurement results of GPC before mixing the ink and after mixing the ink and removing the precipitate, and from the molecular weight distribution of the component precipitated by the dye in the ink and removed from the system.

Next, the recording apparatus used in the present invention will be described. In the present invention, a so-called on-demand type thermal inkjet system, in which a recording signal is applied to the recording ink of the recording head and droplets are ejected by the generated thermal energy, is preferable. The structure of the recording head, which is the main part of the apparatus, is shown in FIGS.

The head 13 is a heating head 15 having a heating resistor used for heat-sensitive recording such as glass, ceramics, or plastic in which ink is formed as a flow path (a head is shown in the drawing, but is not limited to this. Not a thing)
It is obtained by bonding and. The heating head 15 includes a protective film 16 made of silicon oxide or the like, an aluminum electrode 17-
1, 17-2, heating resistor layer 1 formed of nichrome, etc.
8, a heat storage layer 19, and a substrate 20 having a good heat dissipation property such as alumina.

The recording ink 21 reaches the ejection orifice 22 and forms a meniscus 2-3 by the pressure P.

Here, when an electric signal is applied to the electrodes 17-1 and 17-2, the area indicated by n of the heating head 15 rapidly generates heat, and bubbles are generated in the ink 21 in contact therewith, 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 shows a schematic view of a recording head in which a large number of nozzles shown in FIG. 1 are arranged. The recording head is made by closely adhering a glass plate or the like 27 having a large number of flow paths to a heating head 28 similar to that described in FIG.

Incidentally, FIG. 1 shows the head 13 along the ink flow path.
2 is a sectional view taken along line AB in FIG. 1.

FIG. 4 shows an example of an ink jet recording apparatus incorporating the head.

In FIG. 4, 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, which is in the form of a wrench lever. The blade 61 is arranged at a position adjacent to the recording area of the recording head, and is configured to move in a direction perpendicular to the moving direction of the recording head to come into contact with the ejection port surface to perform capping. Further, 63 is an ink absorber provided adjacent to the blade 61, and like the blade 61, is held in a form protruding in the moving path of the recording head. 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 water, dust, and the like from the ink ejection port surface.

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

Reference numeral 51 denotes a feeding section for inserting a recording material,
52 is a feed roller driven by a motor (not shown). With these configurations, the recording material is fed to a position facing the ejection opening surface of the recording head, and is ejected to the ejection portion provided with the ejection roller 53 as the recording progresses.

In the above structure, when the recording head 65 returns to the home position after recording is completed, the cap 62 of the head recovery section 64 is retracted from the movement path of the recording head 65, but the blade 61 is projected in the movement path. There is. As a result, the ejection port surface of the recording head 65 is wiped. When the cap 62 comes into contact with the ejection port surface of the recording head 65 to perform capping, the cap 62 moves so as to eject in 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 in the same position as the above wiping position. As a result, the ejection opening surface of the recording head 65 is wiped even during this movement.

The above-mentioned movement of the recording head to the home position is not limited to the completion of recording and the recovery of ejection, but also to the home adjacent to the recording area at a predetermined interval while the recording head moves in the recording area for recording. The wiper is moved to the position, and the wiping is performed along with the move.

FIG. 5 is a diagram showing an example of an ink cartridge in which the ink is supplied to the head through an ink supply member, for example, a tube. Here, 40 is an ink containing portion containing the supply ink, for example, an ink bag, and a rubber stopper 42 is provided at the tip thereof. By inserting a needle (not shown) into this stopper 42, the ink in the ink bag 40 can be supplied to the head. Four
Reference numeral 4 is an absorber that receives waste ink.

As the ink containing portion, it is preferable that the liquid contact surface with the ink is formed of polyolefin, especially polyethylene.

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 the one in which they are integrated as shown in FIG. 6 is also preferably used. .

In FIG. 6, reference numeral 70 denotes a recording unit in which an ink containing portion for containing ink, for example, an ink absorber is contained, and the ink in the ink absorber has a plurality of orifices. It is configured to be ejected as an ink droplet from the portion 71. As a material for the ink absorber, for example, polyurethane can be used. The recording unit 70, which is an atmosphere communication port for communicating the inside of the recording unit with the atmosphere, is used in place of the recording head shown in FIG. 4, and is detachable from the carriage 66. Incidentally, in the recording apparatus used in the present invention, the ink jet recording apparatus in which thermal energy is applied to the ink to eject the ink droplets has been described above as an example, but the same may be applied to a piezo type ink jet recording apparatus using a piezoelectric element. Available for

When carrying out the image forming method of the present invention, for example, a recording apparatus in which five recording heads shown in FIG. 3 are arranged on a carriage is used. FIG. 7 shows an example thereof. Recording heads 81, 82, 83, and 84 respectively eject yellow, magenta, cyan, and black recording inks. Reference numeral 85 is a head for ejecting the liquid composition. The head is arranged in the above-described recording device and ejects recording ink of each color according to a recording signal. Further, prior to that, the liquid composition is preliminarily attached to a portion where the recording ink of each color is attached to the recording paper. Although FIG. 7 shows an example in which five recording heads are used, the present invention is not limited to this, and as shown in FIG. 8, one recording head can be used for yellow ink, magenta ink, cyan ink, black ink, and liquid. It is also preferable when the composition is divided into liquid channels.

Of course, the heads may be arranged so that the recording order of the liquid composition and the ink is the reverse of the above order.

[0100]

EXAMPLES The present invention will be described more specifically by showing Examples and Comparative Examples below.

(Preparation of Liquid Composition) The following components were mixed and dissolved, and then pressure-filtered with a membrane filter (trade name: Fluoropore filter, manufactured by Sumitomo Electric Industries) having a pore size of 0.22 micron to obtain a liquid composition. Products A to G were obtained.

(Composition of liquid composition A) Stearyl trimethyl ammonium chloride (trade name; Electrostriper QE, Kao Corporation / Mw
= 340) 2 parts Polyamine sulfone hydrochloride (trade name; PAS-A-1 /
Nitto Boseki Co., Ltd./Molecular weight distribution peak position 20
00) 10 parts Thiodiglycol 10 parts Deionized water 85 parts

(Composition of Liquid Composition B) Stearyl trimethyl ammonium chloride (trade name: Electrostriper QE, manufactured by Kao Corporation / Mw
= 340) 2 parts Polyamine sulfone hydrochloride (trade name; PAS-A-5 /
Nitto Boseki Co., Ltd./Molecular weight distribution peak position 350
0) 6 parts Thiodiglycol 10 parts Ion-exchanged water 82 parts

(Composition of Liquid Composition C) Stearyl trimethyl ammonium chloride (trade name: Electrostriper QE, manufactured by Kao Corporation / Mw)
= 340) 2 parts polyallylamine hydrochloride (trade name; PAS-92 / Nitto Boseki Co., Ltd./peak position of molecular weight distribution 5000)
4 parts Thiodiglycol 10 parts Ion-exchanged water 84 parts

(Composition of liquid composition D) Stearyl trimethyl ammonium chloride (trade name: Electrostriper QE, Kao Corporation / Mw
= 340) 2 parts Polyallylamine hydrochloride (in-house synthesis) / position of peak of molecular weight distribution 8500 3 parts Thiodiglycol 10 parts Ion-exchanged water 85 parts (*) Polyallylamine is a functional material, Vol. 5,2
9 (1986). The same applies to the other examples below.

(Composition of Liquid Composition E) Polyallylamine (in-house synthesized) Peak position of molecular weight distribution 800 3 parts Polyamine sulfone hydrochloride (trade name; PAS-A-1 /
Nitto Boseki Co., Ltd./Molecular weight distribution peak position 200
0) 10 parts Thiodiglycol 10 parts Ion-exchanged water 77 parts (*) Allylamine oligomer is also a functional material, Vol.
5,29 (1986). The same applies to the other examples below.

(Composition of Liquid Composition F) Polyallylamine (in-house synthesized) / position of peak of molecular weight distribution 650 5 parts Polyallylamine hydrochloride (in-house synthesized) / position of peak of molecular weight distribution 8500 3 parts Thioglycol 10 parts Ion-exchanged water 72 parts

(Composition of Liquid Composition G) Benzyltri-n-butylammonium chloride (Reagent grade manufactured by Tokyo Kasei Kogyo / Mw = 311) 3 parts Polyallylamine hydrochloride (in-house synthesis) / position of peak of molecular weight distribution 8500 3 parts Thiodiglycol 10 parts Ion-exchanged water 84 parts

(Preparation of Recording Ink) (Preparation of Recording Ink 1) The following components were mixed and pressure-filtered with a membrane filter (trade name: Fluoropore Filter, manufactured by Sumitomo Electric Industries) having a pore size of 0.22 micron. As recording ink 1, yellow ink, cyan ink, magenta ink, and black ink were obtained.

(Yellow ink of recording ink 1 / Y1) C.I. I. Direct Yellow 142 2 parts Thiodiglycol 10 parts Acetylenol EH (acetylene glycol EO adduct from Kawaken Fine Chemicals) 0.05 parts Ion-exchanged water 87.95 parts

(Cyan ink of recording ink 1 / C1) C.I. I. Direct Yellow 86 is C.I. I. Direct Blue 199 2.5
Parts, and the same composition as Y1 except that the ion-exchanged water was changed to 87.45 parts.

(Magenta ink of recording ink 1 / M1)
C. in the cyan ink C1. I. Direct Blue 199 is C.I. I. Acid 92 had the same composition as C1 except that 2.5 parts were used.

(Black ink of recording ink 1 / Bk
1) C.I. in the magenta ink M1 I. Acid 92 2.5 parts C.I. I. Food Black 2 4.
The composition was the same as that of M1 except that the amount was changed to 0 part and the ion-exchanged water was changed to 85.95 parts.

(Preparation of Recording Ink 2) For each color of Recording Ink 1, a styrene-acrylic copolymer manufactured by Johnson Co. (trade name; John Cryl 61J; Mw = 10000) is used.
The amount of ion exchanged water is 10 parts by adding 0.5 parts of
Y of recording ink 1 was used except that it was prepared so as to be 0 part.
Recording ink 2 in the same manner as 1, M1, C1, Bk1
Yellow Y2, cyan C2, magenta M2, and black Bk2.

(Preparation of Recording Ink 3) For each color of Recording Ink 1, an anionic surfactant (trade name; Beaulite ESS; polyoxyethylene alkyl (C12-C16) disodium sulfosuccinate) manufactured by Sanyo Kasei Co., Ltd. was used. (2E.O.)) was added to adjust the amount of ion-exchanged water so that the total amount of the recording liquid was 100 parts.
In the same manner as Y1, M1, C1, and Bk1 of the recording ink 1, the yellow Y3, the cyan C3, the magenta M3, and the black Bk3 of the recording ink 3 were prepared.

(Preparation of Recording Ink 4) (Yellow / Y4 of Recording Ink 4) The following yellow dispersion was carried out using an alkali-soluble resin (styrene-acrylic acid-ethyl acrylate; acid value 160; weight average molecular weight 8000) as a dispersant. Created the body.
Monoethanolamine was used as the neutralizing agent for the alkali-soluble resin. Alkali-soluble resin aqueous solution P1 (solid content 20% by weight) 35 parts C.I. I. Pigment Yellow 83 24 parts Triethylene glycol 10 parts Diethylene glycol 10 parts Ethylene glycol monobutyl ether 1.0 part Isopropyl alcohol 0.5 parts Ion-exchanged water 135 parts The above ingredients are charged into a batch type vertical sand mill (made by AIMEX) and 1 mm diameter Glass beads of No. 1 were filled as a medium, and the dispersion treatment was performed for 3 hours while cooling with water. This dispersion was centrifuged to remove coarse particles to obtain a dispersion having an average particle size of 100 millimicrons.

100 parts of ion-exchanged water was added to the above dispersion, and the mixture was thoroughly stirred to obtain a yellow ink Y4 having a pH of 9.5.
I got

(Cyan / C4 of recording ink 4) Using the same alkali-soluble resin water-soluble P1 as that used to prepare Y4, the following components were mixed and then dispersed under the same conditions as those used to prepare Y4. .

Alkali-soluble resin aqueous solution P1 (solid content 2
0% by weight) 30 parts C.I. I. Pigment Blue 15: 3 24 parts Triethylene glycol 10 parts Diethylene glycol 10 parts Ethylene glycol monobutyl ether 1.0 part Isopropyl alcohol 3 parts Ion-exchanged water 135 parts The resulting dispersion had an average particle diameter of 120 millimicrons.

100 parts of water was added to the above dispersion, and the mixture was sufficiently stirred to obtain a cyan ink C4 having a pH of 9.2.

(Magenta / M4 of Recording Ink 4) Using the same aqueous alkali-soluble resin solution P1 used to prepare Y4, the following components were mixed and then dispersed under the same conditions as used to prepare Y4.

Alkali-soluble resin aqueous solution P1 (solid content 2
0 parts by weight) 20 parts C.I. I. Pigment Red 122 24 parts Glycerin 15 parts Isopropyl alcohol 3 parts Deionized water 135 parts The resulting dispersion had an average particle size of 115 microns.

100 parts of water was added to the above dispersion, and the mixture was sufficiently stirred to obtain magenta ink M4 having a pH of 9.4.

(Black ink of recording ink 4 / Bk4
Preparation) The following components are mixed and heated to 70 ° C. in a water bath to completely dissolve the resin component.

Styrene-acrylic acid-ethyl acrylate copolymer (acid value 160; weight average molecular weight 8000)
1.5 parts Monoethanolamine 1.2 parts Deionized water 81.5 parts Carbon black MCF88 (manufactured by Mitsubishi Kasei) in this solution
After adding 10 parts and 1 part of isopropyl alcohol and performing premixing for 30 minutes, dispersion treatment was performed under the following conditions.

Disperser Sand grinder (manufactured by Igarashi Kikai) Grinding media Zirconium beads Packing ratio of grinding media 50% (volume) Grinding time 3 hours Centrifugation treatment (12000 rpm, 20 minutes) is performed to disperse coarse particles for dispersion. It was a liquid.

Next, the following components were mixed to obtain a black ink Bk4 of a recording ink 4 having a pH of 9.5.

Dispersion 30 parts Glycerin 10 parts Ethylene glycol 5 parts N-Methylpyrrolidone 5 parts Isopropyl alcohol 2 parts Ion-exchanged water 48 parts

(Preparation of Recording Ink 5) The same amount of the dispersant in Recording Ink 4 was used as polyvinylpyrrolidone PVP K-.
Yellow, magenta, cyan, and black inks were prepared in exactly the same manner, except that the ink was replaced with 15 (manufactured by International Specialty Chemicals / Mw = 7000).

Next, the ink obtained above was mixed with an anionic surfactant (trade name; Beaulite ESS; polyoxyethylene alkyl (C12 to C1) manufactured by Sanyo Kasei Co., Ltd.
6) 1.0 part of the disodium sulfosuccinate (2E.O.)) was added to 100 parts of the ink of each color, and the mixture was thoroughly stirred to prepare recording ink 5, yellow Y5, cyan C5, and magenta M5. , Black Bk5 were obtained.

Next, recording was carried out on a Canon PPC paper using the liquid composition and ink obtained as described above. As the inkjet recording apparatus used, the same recording apparatus as shown in FIG.
A color image was formed using one recording head. The recording head used here had a recording density of 360 dpi and a driving frequency of 5 KHz. The ejection volume per dot is 40 pl / do for yellow ink, magenta ink, cyan ink and liquid composition.
t head is used, black ink is 80 p for ink when dye is used as a recording agent.
A 60 pl / dot head was used for inks that used a 1 / dot head and pigmented as the recording agent.

Printing was performed by changing the combination of the liquid composition and the recording ink shown in Table 1 on the next page and the printing order of both, respectively.

[0133]

[Table 1]

[0134]

[Table 2]

The evaluation of the recorded image was performed by the following method.

1. Image density A solid image is formed with a liquid composition and black ink, and
Reflection density after leaving for 2 hours Macbeth RD91 reflection densitometer
5 (manufactured by Macbeth). The evaluation criteria are as follows. ⊚: Reflection density of 1.30 or more ○: Reflection density of 1.25 or more and less than 1.30 Δ: Reflection density of 1.15 or more and less than 1.25 ×: Reflection density of less than 1.15

2. Fixability After forming a red solid image using the liquid composition and yellow and magenta inks, another white paper is superposed on the recorded image by its own weight, and the transfer of the image recorded on the back side of the paper disappears. The time until the occurrence of scumming was measured by setting the time at the end of recording as zero, and was used as a measure of fixing property. The evaluation criteria are as follows. ⊚: Fixability is less than 20 seconds ◯: Fixability is 20 seconds or more and less than 30 seconds Δ: Fixability is 30 seconds or more and less than 40 seconds x: Fixability is 40 seconds or more

3. Character quality Black alphanumeric characters were printed using the liquid composition and black ink and evaluated visually. When the feathering was almost inconspicuous, it was marked with ⊚, when the feathering was slightly conspicuous, but there was no problem in practical use, it was marked with ◯, and when it was lower than that, it was marked with x.

4. Bleeding Canon Color Bubble Jet Printer BJC-8
In the same printing mode as the printing mode E (1Pass, one-way printing) of 20J (trade name), the liquid composition and the solid portions of each color of yellow, magenta, cyan, and black are printed adjacent to each other, and at the boundary of each color. The degree of bleeding was visually observed. The case where bleeding hardly occurs was marked with ⊚, the one where bleeding occurred a little but was a level where there was practically no problem was marked with ○, and other levels were marked with ×.

5. Water resistance After printing solid images and alphanumeric characters of each color of yellow, magenta, cyan and black and leaving it for 1 hour, water temperature 20
It was immersed in tap water at 0 ° C for 10 seconds. Then, it was taken out from water, air-dried as it was, and visually evaluated for water resistance. Among yellow, magenta, cyan, and black, the ink having the lowest water resistance was evaluated as the water resistance. The water resistance evaluation criteria are as follows. ⊚: The recording material did not flow into the margins, and scumming was hardly observed. Almost no bleeding of alphanumeric characters has occurred. ◯: The recording material started to flow into the margins slightly, and alphanumeric characters were slightly blurred, but there was no problem in actual use. X: The recording material started to flow to the margins and the background stain was remarkable. Also, the blurring of alphanumeric characters is terrible.

Throughout Example 1 and Comparative Example 1 of the present invention, the area where the liquid composition adheres to the recording medium is the same area as the ink image forming area, and the printing duty is that of the liquid composition and the ink. Both are 100%.

The print evaluation results are summarized in Table 2.

Comparative Example Using the recording inks 1 to 5, the same printing test and evaluation as in Example were carried out except that the liquid composition was not used. The results are shown in Table 3.

[0144]

[Table 3]

[0145]

[Table 4]

[0146]

[Table 5]

[0147]

As described above, by carrying out the present invention when performing color ink jet recording on plain paper, it is possible to obtain an image satisfying high-speed fixing, high print quality, bleedlessness, and complete water resistance. It has become possible.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a head portion of an inkjet recording apparatus.

FIG. 2 is a cross-sectional view of a head portion of an inkjet recording device.

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

FIG. 4 is a perspective view showing an example of an inkjet recording apparatus.

FIG. 5 is a vertical sectional view of an 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.

[Explanation of symbols]

 13 heads 15 and 28 heat generating head 21 ink 25 recording medium 40 ink bag 44 ink absorber 45 ink cartridge 61 wiping member 65 recording head 66 carriage 70 recording unit 71 head portion 72 atmosphere communicating hole

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B41J 2/21 // C09D 11/00 PSZ 11/02 PTG B41J 3/04 101 Z (72) Invention Person Keiichi Murai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (22)

[Claims] 1. A liquid composition containing at least a cationic substance, wherein the cationic substance has at least one peak of molecular weight distribution measured by GPC in two regions having different molecular weights. A characteristic liquid composition. 2. The liquid composition according to claim 1, wherein one of the regions has a molecular weight of 1000 or less and the other region has a molecular weight of 1500 or more. 3. The liquid composition according to claim 1, which contains the cationic substance in a range of 0.05 to 20% by weight. 4. The liquid composition according to claim 1, wherein the cationic substance is composed of at least two kinds of compounds. 5. The liquid composition according to claim 1, wherein at least one of the cationic substances is a surfactant. 6. An ink set comprising a combination of the liquid composition according to claim 1 and at least one ink of yellow, magenta, cyan, black, red, blue and green. . 7. An ink set comprising a combination of the liquid composition according to claim 1 and three color inks of yellow, magenta and cyan. 8. The liquid composition according to claim 1, and 4 of yellow, magenta, cyan and black.
An ink set featuring a combination of color inks. 9. The ink set according to claim 6, wherein the ink contains an anionic compound. 10. The ink set according to claim 6, wherein the ink contains a water-soluble dye having an anionic group. 11. The ink set according to claim 6, wherein the ink contains a pigment and an anionic compound. 12. The ink set according to claim 9, wherein the anionic compound is a polymer substance having a molecular weight of 1000 or more. 13. The ink set according to claim 9, wherein the anionic compound is a surfactant. 14. A step (A) of adhering the liquid composition according to claim 1 to at least an image forming region of a recording medium, and an ink containing at least an anionic compound is recorded by an inkjet method. An image forming method comprising the step (B) of applying to a medium. 15. The image forming method according to claim 14, wherein the inkjet system is an on-demand inkjet system. 16. The image forming method according to claim 14, wherein the liquid composition is attached to a recording medium by an inkjet method. 17. The image forming method according to claim 14, wherein the inkjet system is an inkjet system in which thermal energy is applied to the ink. 18. The image forming method according to claim 14, wherein step (A) is performed prior to step (B). 19. The image forming method according to claim 14, wherein step (A) is performed after step (B). 20. An image forming apparatus comprising the ink set according to claim 6 and an ink jet means. 21. A first recording unit having a storage portion and a discharging means of the liquid composition according to claim 1, and a storage portion and a discharging means of an ink containing at least an anionic compound. An image forming apparatus comprising a second recording unit. 22. The image forming apparatus according to claim 21, wherein the ejection unit is an inkjet unit.