JP2011025469A - Set of pigment ink and reaction liquid, inkjet recording method, and inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a set of pigment ink and reaction liquid that can impart high-grade scratch resistance and marker resistance to an image without impairing high image density and ink storage stability. <P>SOLUTION: The set of the pigment ink containing at least a pigment and resin, and the reaction liquid containing a reactive material that makes the dispersed state of the pigment unstable is provided. The pigment ink contains a graft polymer including a nonionic unit represented by a general formula (I), a unit having a polysiloxane structure, and a unit having a carboxy group. In the general formula (I), R<SB>1</SB>and R<SB>2</SB>are respectively independent hydrogen atoms or methyl groups, R<SB>3</SB>is an ester bond or an ether bond, and x is an integer of 1 or 2, wherein when R<SB>2</SB>is the methyl group, R<SB>3</SB>is not the ether bond. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a set of pigment ink and reaction liquid, an ink jet recording method, and an ink jet recording method.

  Studies are underway on inks containing pigments (pigment inks) as colorants for inks used in ink jet recording methods. However, when recording is performed on a recording medium such as plain paper by the ink jet recording method, a sufficient image density may not be obtained because the liquid ink permeates the recording medium.

  In response to the above-mentioned problems, after a liquid containing a cationic compound was applied to the recording medium, the pigment or dispersion resin in which the anionic group was chemically modified was adsorbed and dispersed in an anionic state. There is a method of recording using an ink containing a pigment (see Patent Document 1). In this method, the cationic compound in the reaction liquid and the anionic pigment in the ink come into contact with each other in the recording medium, so that the dispersion state of the pigment is destabilized, the aggregation of the pigment is promoted, and the image density is improved. Is achieved.

  The present invention also relates to an ink that imparts high scratch resistance and marker resistance to an image by adding a resin to the pigment ink and protecting the pigment by causing the resin to act as a binder when the ink is fixed to a recording medium. There is a proposal (see Patent Document 2).

Japanese Patent Laid-Open No. 11-203037 JP-A-9-188732

  The inventors of the present invention have made various studies on a conventional pigment ink and reaction liquid set. As a result, when the pigment ink contains a resin for improving scratch resistance and marker resistance and the content thereof is increased, the reactivity with the reaction liquid gradually decreases, and a sufficient image density is obtained. It was found that there was no problem. When the present inventors have sought the cause of such a problem, when a resin is added to the pigment ink in order to provide the above-described performance, the resin has an effect of stably maintaining the dispersion state of the pigment. It was found that the reactivity between the pigment ink and the reaction liquid was lowered. As a result, the generated aggregates become small, so that the penetration into the recording medium is not suppressed, and it is considered that the image density cannot be sufficiently obtained. Therefore, it was possible to confirm the effect that the above problems can be reduced by adding a resin that can rapidly aggregate to the pigment ink, but the storage stability of the pigment ink is reduced due to the aggregation property of the resin. There was a tendency to. In other words, the methods as described so far have not been able to provide images with high scratch resistance and marker resistance without impairing high image density and ink storage stability.

  Therefore, an object of the present invention is to provide a set of a pigment ink and a reaction liquid that can impart high scratch resistance and marker resistance to an image without impairing high image density and storage stability of the ink. is there. Another object of the present invention is to provide an ink jet recording method and an ink jet recording apparatus using such a set.

  The above object is achieved by the present invention described below. That is, the present invention is a set of a pigment ink containing at least a pigment and a resin and a reaction liquid containing a reactive substance that destabilizes the dispersion state of the pigment, and the pigment ink is represented by the following general formula: A set of an ink and a reaction liquid containing a graft polymer including a nonionic unit represented by (I), a unit having a polysiloxane structure, and a unit having a carboxyl group.

(In General Formula (I), R ₁ and R ₂ are each independently a hydrogen atom or a methyl group, R ₃ is an ester bond or an ether bond, and x is an integer of 1 or 2. However, R ₂ When R is a methyl group, R ₃ is not an ether bond.)

  According to the present invention, it is possible to provide a set of a pigment ink and a reaction liquid that can impart high scratch resistance and marker resistance to an image without impairing high image density and storage stability of the ink. Moreover, according to another embodiment of the present invention, an ink jet recording method and an ink jet recording apparatus using such a set can be provided.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.

  A feature of the present invention is that the pigment ink constituting the set of the pigment ink and the reaction liquid (hereinafter sometimes simply referred to as “set” or “ink”) contains a graft polymer having a specific structure. It is in that. The graft polymer is a graft polymer containing a nonionic unit represented by the following general formula (I), a unit having a polysiloxane structure, and a unit having a carboxyl group (hereinafter sometimes simply referred to as “graft polymer”). It is. And, according to the set having such a configuration, a high degree of scratch resistance can be applied to the image without impairing the high image density and the storage stability of the ink by the action of the graft polymer in which each structural unit is clearly functionally separated. And marker resistance can be imparted.

(In General Formula (I), R ₁ and R ₂ are each independently a hydrogen atom or a methyl group, R ₃ is an ester bond or an ether bond, and x is an integer of 1 or 2. However, R ₂ When R is a methyl group, R ₃ is not an ether bond.)
The function of each unit constituting the graft polymer used in the present invention is as follows. First, a unit having a polysiloxane structure is quickly oriented on the image surface and imparts high scratch resistance and marker resistance to the image. Moreover, the unit which has a carboxyl group improves the solubility of the graft polymer to the aqueous medium which comprises ink. Furthermore, the nonionic unit represented by the general formula (I) suppresses insolubilization of the graft polymer due to interaction (aggregation reaction) with the reactive substance. As described above, even if these units are present as resins separately, it is not possible to satisfy all the effects of the present invention at the same time, and it is particularly important to form a graft polymer having both these units. is there.

<Set of pigment ink and reaction liquid>
Hereinafter, the set of the ink and the reaction liquid of the present invention will be described in detail.

[Pigment ink]
Hereinafter, the pigment ink constituting the set of the ink and the reaction liquid of the present invention (hereinafter sometimes abbreviated as “ink”) will be described in detail for each component constituting the ink.

(Graft polymer)
The graft polymer used in the ink used in the present invention has at least a nonionic unit represented by the general formula (I), a unit having a polysiloxane structure, and a unit having a carboxyl group. In the present invention, when “unit” is described, it includes both cases where one or a plurality of repeating units constitute the unit.

  The graft polymer in the present invention is “a polymer having a structure in which a branch polymer (side chain) is bonded to one trunk polymer (main chain)”. And as a method of discriminating whether the structure of a certain polymer is a graft polymer, the following methods are mentioned, for example. That is, it is possible to determine that the structure of a certain polymer is a graft polymer by measuring the absolute molecular weight and the molecular size in combination with gel permeation chromatography and a multi-angle light scattering detector. Specifically, the greater the difference between the absolute molecular weight and molecular size measured by these methods, the higher the degree of branching of the polymer, and in the form of a graft polymer. Judgment can be made.

  The graft polymer used in the present invention preferably has a structure in which the functions of each unit are clearly separated in the molecule so that the functions of each unit can be efficiently exhibited. Specifically, in order to further clarify the functional separation of these units, the graft polymer includes a unit having a carboxyl group in the main chain, and a unit having the nonionic unit and a polysiloxane structure in the side chain. It is preferable that the structure contains. Further, as the nonionic unit, it is preferable to use a low molecular weight unit instead of a high molecular weight unit. Specifically, the molecular weight of the nonionic unit is preferably in the range of 70 to 190 in terms of weight average molecular weight. In this case, the nonionic units can be arranged evenly in the main chain, that is, the nonionic units branched from the main chain can be delocalized, which is particularly effective for obtaining the effects of the present invention. is there.

  In the present invention, the content (% by mass) of the graft polymer in the ink is 0.1% by mass or more and 10.0% by mass or less, and further 0.1% by mass or more and 5.0% by mass based on the total mass of the ink. It is preferable that it is below mass%.

  Further, according to the study by the present inventors, an appropriate amount of ink is applied to the recording medium, and the graft polymer is oriented on the surface of the image in order to improve the scratch resistance and marker resistance of the image. I found it important. In the present invention, the weight average molecular weight of the graft polymer is preferably in the range of 5,000 or more and 50,000 or less so that an appropriate amount of ink is applied to the recording medium. If the weight average molecular weight is more than 50,000, the viscosity of the ink increases, so that sufficient ejection stability cannot be obtained, and an appropriate amount of ink cannot be applied to the recording medium, resulting in image abrasion resistance. And marker resistance may not be sufficiently obtained. In addition, when the weight average molecular weight is larger than 50,000, the fluidity of the ink is lowered, the orientation of the graft polymer on the image surface is difficult to occur, and the image scratch resistance and marker resistance cannot be sufficiently obtained. There is. On the other hand, when the weight average molecular weight is less than 5,000, the above graft polymer penetrates into the inside of the recording medium together with the aqueous medium constituting the ink, and does not act as a binder. Marker resistance may not be sufficiently obtained.

  In the present invention, the acid value of the graft polymer is preferably 80 mgKOH / g or more and 150 mgKOH / g or less. According to the study by the present inventors, if the acid value is larger than 150 mgKOH / g, the following problems may occur. That is, since the viscosity of the ink is increased, sufficient ejection stability cannot be obtained, and an appropriate amount of ink cannot be applied to the recording medium, so that sufficient image scratch resistance and marker resistance can be obtained. It may not be possible. On the other hand, when the acid value is less than 80 mgKOH / g, the water solubility of the graft polymer is lowered, and the storage stability of the ink may not be sufficiently obtained. Furthermore, it may be difficult to maintain ejection stability when an ink containing the above graft polymer having an acid value of less than 80 mg KOH / g is ejected by an ink jet recording method using thermal energy.

  Furthermore, in the present invention, the pigment content (% by mass) in the ink is 0.2 to 2.0 times in terms of the mass ratio with respect to the graft polymer content (% by mass). preferable. That is, (content of pigment / content of graft polymer) = 0.2 times or more and 2.0 times or less is preferable. In the present invention, the content of the pigment and the graft polymer is the content of each component in the total mass of the ink. When the above-mentioned mass ratio is less than 0.2 times, the scratch resistance and marker resistance of the image may not be sufficiently obtained. The reason is considered as follows. When the mass ratio is less than 0.2 times, the amount of the graft polymer is increased with respect to the pigment. Therefore, the graft polymer is not only on the image surface but also inside the pigment layer constituting the image. May become present. In this case, the graft polymer is also present between the pigment particles forming the image, and the aggregates of the pigments become slippery. As a result, the image has sufficient scratch resistance and marker resistance. It may not be obtained. On the other hand, if the mass ratio exceeds 2.0 times, the amount of the graft polymer that is oriented on the image surface decreases, so that the image scratch resistance and marker resistance may not be sufficiently obtained.

  Hereinafter, each unit constituting the graft polymer used in the present invention will be described in more detail.

[Nonionic unit]
In the present invention, the nonionic unit constituting the graft polymer used in the ink has a structure represented by the following general formula (I). In the nonionic unit having this structure, the number of repeating units of the ethylene oxide group is 1 or 2, and a monomer of the following general formula (I ′) having a polymerizable functional group at one end is copolymerized. Is. Furthermore, in the graft polymer used in the present invention, the vinyl group or vinylidene group of the monomer represented by the following general formula (I ′) becomes a part of the main chain of the graft polymer, and the portion from the ester bond to R ₁ is branched. Thus, the structure is preferably a side chain.

(In General Formula (I), R ₁ and R ₂ are each independently a hydrogen atom or a methyl group, R ₃ is an ester bond or an ether bond, and x is an integer of 1 or 2. However, R ₂ When R is a methyl group, R ₃ is not an ether bond.)

(In general formula (I ′), R ₁ and R ₂ are each independently a hydrogen atom or a methyl group, R ₃ is an ester bond or an ether bond, and x is an integer of 1 or 2. _{When 2} is a methyl group, R ₃ is not an ether bond.)
In the present invention, the number of repeating units of the ethylene oxide group in the nonionic unit represented by the general formula (I) is 1 or 2, that is, x in the general formula (I) is 1 or 2. It is necessary to use something. When x in the general formula (I) is 3 or more, when the nonionic unit is included in the main chain, the tendency of the nonionic property to be localized is increased, and the graft polymer as a whole Since the hydrophilicity of the image becomes high, the marker resistance of the image cannot be obtained. Further, as described above, when the hydrophilicity of the graft polymer as a whole becomes high, the graft polymer has an action like a surfactant in the ink. In this case, the penetrability of the ink into the recording medium of the graft polymer is increased, an image density is not obtained, and the amount of the graft polymer that is oriented on the outermost surface of the image is reduced, so that a sufficient image can be obtained. The scratch resistance cannot be obtained.

  In addition, when the graft polymer further includes a unit having an ethylene oxide group having a structure different from that of the nonionic unit represented by the general formula (I), the number of repeating units of the ethylene oxide group in the unit is determined. 1 or 2 is preferable. This is because, as in the case of the nonionic unit represented by the general formula (I) described above, the image scratch resistance, marker resistance, and image density may be insufficient.

  Further, according to the study by the present inventors, if the graft polymer having an anionic unit and a unit having a polysiloxane structure is contained in the ink without having the nonionic unit, the image density may be lowered. all right. The present inventors presume this reason as follows. When an ink containing a graft polymer having an anionic unit and a unit having a polysiloxane structure without having the nonionic unit is applied to a recording medium, the following phenomenon occurs. That is, the graft polymer is insolubilized rapidly due to the interaction (aggregation reaction) with the reactive substance in the reaction solution applied to the recording medium. As a result, the alignment action on the image surface by the unit having a polysiloxane structure is impaired, and as a result, the graft polymer is taken in between the plurality of pigments, the aggregation of the pigments is inhibited, and the pigments penetrate into the recording medium. It is considered that the image density cannot be obtained.

  Specific examples of the nonionic unit represented by the general formula (I) include those obtained by copolymerization of (meth) acrylate monomers. Moreover, in the graft polymer used in the present invention, the nonionic unit may be composed of one kind or a combination of two or more kinds.

  Examples of (meth) acrylate monomers include 2-hydroxyethyl methacrylate, diethylene glycol monomethacrylate, 2-hydroxyethyl acrylate, diethylene glycol monoacrylate, methoxydiethylene glycol-monomethacrylate, methoxydiethylene glycol-monoacrylate, and the like. In the present invention, among these monomers, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and methoxydiethylene glycol-monomethacrylate are preferably used. Examples of such (meth) acrylate monomers include commercially available products such as BLEMMER: PE-90, AE-90, PME-100 (above, NOF Corporation), BHEA, HEMA (above, Nippon Shokubai Co., Ltd.). Can be used.

  Examples of vinyl ether monomers include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, and the like. As such a vinyl ether monomer, for example, commercially available products such as HEVE and DEGV (manufactured by Maruzen Petrochemical Co., Ltd.) can be used.

  In the present invention, among these monomers, those having a structure in which the number of ethylene oxide repeats is 2, that is, diethylene glycol monomethacrylate and methoxydiethylene glycol-monomethacrylate are preferred.

  In the present invention, the proportion of the nonionic unit represented by the general formula (I) based on the total mass of the graft polymer is 5.0% by mass or more and 45.0% by mass or less. preferable. When this ratio is less than 5.0% by mass, the graft polymer is insolubilized rapidly after the ink and the reaction liquid are in contact, and the image density may not be sufficiently obtained for the same reason as described above. On the other hand, if this ratio is larger than 45.0% by mass, the scratch resistance, marker resistance and image density of the image may not be sufficiently obtained. This is because when the ratio is greater than 45.0% by mass, the hydrophilicity of the graft polymer is increased, and the graft polymer is stably present in the ink. As a result, the graft polymer is likely to penetrate into the recording medium, and the amount of the graft polymer oriented on the image surface may be reduced.

[Units having a polysiloxane structure]
In the present invention, the unit having a polysiloxane structure constituting the graft polymer used in the ink may be any unit having a polysiloxane structure. In the present invention, it is particularly preferable to use a unit represented by the following general formula (V) among the units having a polysiloxane structure. The unit represented by the general formula (V) is obtained by copolymerization of a monomer represented by the following general formula (V ′). Moreover, in the graft polymer used in the present invention, the unit having a polysiloxane structure may be constituted by one kind or a combination of two or more kinds.

(In General Formula (V), R ₈ is a hydrogen atom or a methyl group, R ₉ is an alkylene group having 1 to 6 carbon atoms, R ₁₀ is independently a methyl group or a phenyl group, and R ₁₁ is (It is a C1-C6 alkyl group or a phenyl group, and m is an integer of 1-150.)

(In general formula (V ′), R ₈ is a hydrogen atom or a methyl group, R ₉ is an alkylene group having 1 to 6 carbon atoms, R ₁₀ is independently a methyl group or a phenyl group, and R ₁₁ Is an alkyl group having 1 to 6 carbon atoms or a phenyl group, and m is an integer of 1 to 150.)

  In the present invention, as the monomer represented by the general formula (V ′), for example, commercially available products such as Silaplane FM-0711, FM-0721, FM-0725 (manufactured by Chisso) and the like may be used. it can.

  In the present invention, the proportion of the unit having the polysiloxane structure based on the total mass of the graft polymer is preferably 10.0% by mass or more and 40.0% by mass or less. When the ratio is less than 10.0% by mass, the amount of the graft polymer that is oriented on the image surface is decreased regardless of the content of the graft polymer in the ink, and the image is scratch resistant and marker resistant. There are cases where sufficient sex cannot be obtained. When the above ratio is larger than 40.0% by mass, the scratch resistance and marker resistance of the image may not be sufficiently obtained. Contrary to the above, since the amount of the graft polymer in the ink increases, the graft polymer may exist not only on the image surface but also inside the pigment layer constituting the image. Because there is. That is, the graft polymer is also present between the pigment particles, and the aggregates of the pigment may become slippery.

[Unit having carboxyl group]
In the present invention, the unit having a carboxyl group constituting the graft polymer used in the ink may be any unit having a carboxyl group. Specific examples include those obtained by copolymerization of monomers having a carboxyl group such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid. In the present invention, among units having a carboxyl group, it is particularly preferable to use a unit obtained by copolymerizing acrylic acid and methacrylic acid. Moreover, in the graft polymer used in the present invention, the units having a carboxyl group may be constituted by one kind or a combination of two or more kinds. In addition, the acid value of the graft polymer demonstrated above can be adjusted by setting suitably the ratio for which the unit which has a carboxyl group contained in a graft polymer is occupied. Specifically, the proportion of units having a carboxyl group may be set so that the acid value of the graft polymer is 80 mgKOH / g or more and 150 mgKOH / g or less.

[Other units]
In the present invention, the graft polymer used in the ink needs to have at least the above-described nonionic unit represented by the following general formula (I), a unit having a polysiloxane structure, and a unit having a carboxyl group. . The graft polymer used for the ink may further include other units in addition to these units. In the present invention, it is particularly preferable that the main chain of the graft polymer has a structure in which other units are included, that is, other units are not included in the side chain.

  Examples of the other units include units obtained by copolymerizing monomers such as ester compounds of monomers having a carboxyl group, unsaturated acid monomers such as sulfonic acid and phosphoric acid, and derivatives thereof (anhydrides, salts, ester compounds). It is done. Specifically, for example, acrylic acid esters such as methyl acrylate, ethyl acrylate, and butyl acrylate, methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate, styrene sulfonic acid, maleic anhydride, 2 -Unsaturated acid monomers such as acrylamido-2-methylpropanesulfonic acid and vinylphosphonic acid and their derivatives (anhydrides, salts, ester compounds), more specifically, 3-sulfopropyl (meth) acrylic acid ester, bis -(3-sulfopropyl) -itaconate, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyl Roxye Ruhosufeto, dioctyl-2- (meth) acryloyloxyethyl phosphate. Among these, methyl acrylate, butyl acrylate, methyl methacrylate, and butyl methacrylate are preferable. In many cases, a pigment frequently used as a coloring material for ink jet ink is dispersed with an anionic polymer dispersant. In consideration of the stability of the ink containing such a pigment, it is preferable that the unit constituting the graft polymer does not include a unit derived from a cationic monomer that can react with the polymer.

(Other polymers)
The ink of the present invention may contain one or more polymers different from the graft polymer. Such a polymer is contained in the ink as a dispersant for dispersing the pigment in the ink or for other purposes as required, and any polymer having water solubility can be used. Even things can be used.

  Specifically, co-polymerization in the form of block, random, graft, etc. synthesized from at least two monomers selected from the following monomers and their derivatives (of which at least one is a hydrophilic monomer) Examples include coalescence and salts thereof. Examples of the monomer include styrene, styrene derivatives, vinyl naphthalene, vinyl naphthalene derivatives, and aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids. Acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, vinyl acetate, vinylpyrrolidone, acrylamide and the like. Natural resins such as rosin, shellac and starch can be preferably used. The resin for dispersing the pigment in the ink is preferably an alkali-soluble resin.

  The resin (dispersant) preferably has a weight average molecular weight of 1,000 to 30,000, more preferably 3,000 to 15,000. The content (% by mass) of the resin (dispersant) in the ink is preferably 0.1% by mass or more and 10.0% by mass or less based on the total mass of the ink.

(Water-soluble organic compounds)
In addition to the graft polymer described above, the ink used in the present invention further comprises compounds represented by the following general formula (II), the following general formula (III), and the following general formula (IV). It is preferable to contain at least one water-soluble organic compound selected from the group. In the following description, a water-soluble organic compound of the group consisting of compounds represented by the following general formula (II), the following general formula (III), and the following general formula (IV) is referred to as “specific water-soluble”. It may be abbreviated as “organic compound”.

(In the general formula (II), R ₄ is an alkylene group having 2 to 5 carbon atoms which may have a substituent, and each R ₅ is independently a hydrogen atom or an optionally substituted carbon. In general formula (III), R ₆ is an alkylene group having 2 to 5 carbon atoms which may have a substituent, and R ₇ is a hydrogen atom or a substituent. (In general formula (IV), n is a number of 1 to 3.)
Here, the reason why it is preferable to further contain the specific water-soluble organic compound in the ink in addition to the above-described graft polymer essential in the present invention will be described. First, in order to obtain the effect of the present invention, as described above, it is important that an appropriate amount of ink is applied to a recording medium and the graft polymer is oriented in a large amount on the image surface. Further, the nonionic unit and the unit having a carboxyl group constituting the graft polymer used in the ink have high hydrophilicity, and the unit having a polysiloxane structure has high lipophilicity. For this reason, in the ink, it is considered that a plurality of the graft polymer molecules form an aggregate. In order to improve the effect of the present invention particularly remarkably when an ink containing the graft polymer in such a state is applied to a recording medium, the amount of the graft polymer oriented on the image surface is set to It is preferable to increase more.

  Therefore, as a result of investigations by the present inventors, the effect of the present invention can be particularly remarkably improved by using an ink having a configuration containing the graft polymer and the specific water-soluble organic compound. all right. In the ink having such a configuration, the aggregate of the graft polymer molecules is unwound. Here, the compounds represented by the general formula (II) or the general formula (III), which are nitrogen-containing heterocyclic compounds, have high affinity for the graft polymer having a hydrophilic unit and a lipophilic unit. And has the effect of unwinding the aggregate of the graft polymer molecules. In addition, the compound represented by the general formula (IV) which is 1,2-alkanediol has a molecular structure in which a hydrophilic part and a lipophilic part are clearly separated, and thus acts like a surfactant. And unwinds the aggregate of the graft polymer molecules in the ink. In other words, by such a mechanism, when the ink of this configuration is applied to the recording medium, the graft polymer molecules that do not form an aggregate are efficiently and uniformly oriented on the image surface. It is considered that the effect of the present invention is particularly remarkably improved.

  It can be confirmed by measuring the dynamic surface tension of the ink that the aggregate of the graft polymer molecules is unwound in the ink. For example, the dynamic surface tension at a certain lifetime is measured for each of the ink containing the specific water-soluble organic compound and the ink not containing the specific water-soluble organic compound together with the graft polymer. At this time, since the specific water-soluble organic compound is contained, the ink that does not form an association of the graft polymer molecules is compared with the ink that does not contain the specific water-soluble organic compound. The value of the dynamic surface tension at the lifetime is lowered. This is because, in the ink in which the aggregate of the graft polymer molecules is unwound, the graft polymer molecules are relatively oriented to the interface, so that the dynamic surface tension of the ink is lowered. That is, when the dynamic surface tension value of the ink containing the specific water-soluble organic compound is low by comparing the dynamic surface tension values of these inks, the aggregate of the graft polymer molecules in the ink Can be said to be in an unwound state. As an apparatus for measuring the dynamic surface tension, for example, Bubble Pressure Tensiometer BP2 (manufactured by KRUSS) or the like can be used.

  The compound represented by the general formula (II) and the compound represented by the general formula (III) are nitrogen-containing heterocyclic compounds. Specifically, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3 -Dimethyl-2-imidazolidinone, ethyleneurea and the like. Further, the compound represented by the general formula (IV) is 1,2-alkanediol, specifically, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1, 2-hexanediol is mentioned. Among these compounds, it is particularly preferable to use at least one selected from 2-pyrrolidone, N-methyl-2-pyrrolidone, ethylene urea, and 1,2-hexanediol.

  In the present invention, the total content (mass%) of the compounds represented by the general formula (II), the general formula (III), and the general formula (IV) in the ink is the content of the graft polymer. The mass ratio with respect to the amount (mass%) is preferably 2.0 times or more. That is, (total content of the specific water-soluble organic compound / content of the graft polymer) = 2.0 times or more is preferable. The specific water-soluble organic compound and the content of the graft polymer are the content of each component in the total mass of the ink. On the other hand, when the mass ratio is less than 2.0 times, the content of the specific water-soluble organic compound is reduced in the ink, and the aggregate of the graft polymer molecules cannot be sufficiently unwound. In some cases, the effects of the invention cannot be significantly improved. Moreover, it is preferable that the upper limit of said mass ratio is 8.0 times or less. If the upper limit of the mass ratio is larger than 8.0 times, the viscosity of the ink is increased, so that sufficient ejection stability cannot be obtained, and therefore an appropriate amount of ink may not be applied to the recording medium. In some cases, the effects of the present invention cannot be significantly improved.

  In the present invention, the total content (mass%) of the compounds represented by the general formula (II), the general formula (III), and the general formula (IV) in the ink represents the total mass of the ink. As a reference, it is preferably 2.0% by mass or more. When the content is less than 2.0% by mass, the content of the specific water-soluble organic compound in the ink is reduced, and the aggregate of the graft polymer molecules cannot be sufficiently unwound. In some cases, the effect cannot be improved significantly. Moreover, it is preferable that the upper limit of content of the said specific water-soluble organic compound is 20.0 mass% or less. If the upper limit of the content is greater than 20.0% by mass, the viscosity of the ink increases, so that sufficient ejection stability cannot be obtained, and therefore an appropriate amount of ink may not be applied to the recording medium. In some cases, the effects of the present invention cannot be significantly improved.

(Pigment)
The ink used in the present invention includes a resin dispersion type pigment (resin dispersion type pigment) in which a pigment is dispersed using a dispersant, and a self dispersion type pigment (self dispersion) in which a hydrophilic group is introduced on the surface of pigment particles. Type pigments). Also, pigments (resin-bonded self-dispersing pigments) in which organic groups containing a polymer are chemically bonded to the surface of pigment particles, microcapsules that can be dispersed without using a dispersant by increasing the dispersibility of the pigment Type pigments can also be used. Of course, these pigments having different dispersion methods may be used in combination. The pigment content (% by mass) in the ink is 0.1% by mass or more and 15.0% by mass or less, and further 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the ink. Is preferred.

  The pigment that can be used in the ink of the present invention is not particularly limited, and any conventionally known inorganic pigment or organic pigment can be used, but in the present invention, it is particularly preferable to use an organic pigment.

(Aqueous medium)
In the ink used in the present invention, an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent can be used. The content (% by mass) of the water-soluble organic solvent in the ink is preferably 3.0% by mass or more and 50.0% by mass or less based on the total mass of the ink. In addition, content of this water-soluble organic solvent is content containing the specific water-soluble organic compound demonstrated above. The water-soluble organic solvent is not particularly limited as long as it is water-soluble, and any known solvent that is generally used for ink-jet inks can be used. One or more water-soluble organic solvents can be used. It is preferable to use deionized water (ion exchange water) as the water. The content (% by mass) of water in the ink is preferably 50.0% by mass or more and 95.0% by mass or less based on the total mass of the ink.

<Other ingredients>
The ink used in the present invention may contain a moisturizing solid content such as urea, a urea derivative, trimethylolpropane, and trimethylolethane in addition to the above components. The content (% by mass) of the moisturizing solid content in the ink is 0.1% by mass or more and 20.0% by mass or less, and further 3.0% by mass or more and 10.0% by mass or less based on the total mass of the ink. It is preferable that

  Furthermore, the ink of the present invention includes various pH adjusters, rust inhibitors, antiseptics, antifungal agents, antioxidants, anti-reduction agents, and the like in order to obtain inks having desired physical properties as required. These additives may be included.

[Reaction solution]
Hereinafter, with respect to the reaction liquid constituting the set of the ink and the reaction liquid of the present invention, each component constituting the reaction liquid will be described in detail.

(Reactive substance)
The reaction liquid has a function of destabilizing the dispersion state of the pigment in the ink and aggregating the pigment. Specifically, the reaction liquid is preferably a reactive substance, preferably a cation such as a polyvalent metal salt or a cationic polymer. A chemical compound. In the present invention, the content (% by mass) of the reactive substance in the reaction solution is preferably 5.0% by mass or more and 20.0% by mass or less based on the total mass of the reaction solution. When the content is less than 5.0% by mass, the reactivity may be insufficient, and a sufficient image density may not be obtained. When the content exceeds 20.0% by mass, the storage stability and ejection stability of the reaction liquid may be obtained. May not be cooked enough. In the reaction solution, depending on the type of reactive component, at least a part thereof may be dissociated into ions, but in the present invention, it is expressed as containing a salt for convenience.

The polyvalent metal salt is preferably composed of a divalent or higher polyvalent metal ion and an anion bonded thereto, and is soluble in water. Specific examples of the polyvalent metal ions include divalent metal ions such as Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ²⁺ , Zn ²⁺ , Ba ²⁺ , Fe ²⁺ , Zr ²⁺ , Al ³⁺ , Fe ³⁺ , Cr ³⁺ , Zr Trivalent or higher metal ions such as ³⁺ and Zr ⁴⁺ can be used. Examples of the anion include Cl ⁻ , NO ₃ ⁻ , I ⁻ , Br ⁻ , ClO ₃ ⁻ , CH ₃ COO ⁻ , F ⁻ , SO ₄ ²⁻ , SO ₃ ^{2− and the} like. Examples of the cationic polymer include polyallylamine, polyamine sulfonate, polyallylamine hydrochloride and the like. Moreover, in the reaction liquid used for this invention, you may contain the reactive component 1 type or in combination of 2 or more types.

(Other components of the reaction solution)
Components other than the reactive substances described above that constitute the reaction liquid used in the present invention are the same as the aqueous medium (water and water-soluble organic solvent) and additives described as those that can be contained in the pigment ink. Can be used. The content (% by mass) of water in the reaction solution is preferably 50.0% by mass or more and 95.0% by mass or less based on the total mass of the reaction solution. The content (% by mass) of the water-soluble organic solvent in the reaction solution is preferably 3.0% by mass or more and 50.0% by mass or less based on the total mass of the ink.

<Inkjet recording method, inkjet recording apparatus>
The ink jet recording method of the present invention is an ink jet recording method in which recording is performed on a recording medium by discharging the ink and the reaction liquid constituting the set of the present invention described above by an ink jet method. In the present invention, it is preferable to perform recording by applying a pigment ink to a recording medium after applying the reaction liquid to the recording medium. In particular, the reaction liquid is preferably applied to the recording medium so as to include at least the area of the recording medium to which the pigment ink is applied. The ink jet recording apparatus of the present invention includes a plurality of liquid storage portions that respectively store the ink and the reaction liquid that constitute the set of the present invention described above, and an ink jet recording head that discharges the pigment ink and the reaction liquid. An ink jet recording apparatus is provided. The recording method and the recording apparatus of the present invention can apply any of the conventionally known configurations except that the set of the present invention described above is applied. In particular, the recording method and the recording apparatus are adapted to a recording system that discharges liquid by the action of thermal energy. It is preferable to apply.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited in any way by the following examples as long as the gist thereof is not exceeded. “Part” or “%” is based on mass unless otherwise specified.

<Synthesis of graft polymer>
According to the following procedures, graft polymers 1 to 23 were respectively synthesized. A known polymerization method can be used as the synthesis method. In this example, graft polymers 1 to 13 were synthesized using the following polymerization methods. First, in a flask equipped with a stirrer, a thermometer, and a nitrogen introduction tube, each monomer having the composition (unit: part) shown in the upper part of Tables 1 and 2 below, 4.0 parts of azobisisobutyronitrile, and a solvent 500 parts of 1-methoxy-2-propanol was charged. Then, a polymerization reaction was performed at a temperature of 110 ° C. for 4 hours under reflux of nitrogen gas. The solution containing the copolymer thus obtained was dried under reduced pressure to obtain a copolymer. After adding 25 parts of methyl ethyl ketone as a solvent to the obtained copolymer and dissolving it, 2 parts of 30% potassium hydroxide aqueous solution was added to neutralize a part of the salt-forming group of the copolymer, 300 parts of exchange water was added and stirred. Thereafter, the solvent was removed under reduced pressure at a temperature of 60 ° C., and further concentrated by removing a part of water to obtain an aqueous solution of graft polymer having a solid content concentration of 20.0%. With respect to the graft polymers 1 to 23 thus obtained, the absolute molecular weight and the molecular size were measured by combining gel permeation chromatography (manufactured by Shimadzu Corporation) and a multi-angle light scattering detector (manufactured by Shoko Tsusho). . As a result, it was confirmed that the measured values of the absolute molecular weight and the molecular size were greatly different and had a graft polymer structure.

In Tables 1 and 2 below, (* 1) to (* 5) represent the following monomers, respectively.
(* 1): Silaplane FM-0711 (manufactured by Chisso; monomer having polysiloxane structure represented by the general formula (V ′), number average molecular weight of about 1,000)
(* 2): BHEA (product name: manufactured by Nippon Shokubai; nonionic monomer in which R ₁ and R ₂ in the general formula (I ′) are a hydrogen atom, R ₃ is an ester bond, and x is 1)
(* 3): HEMA (product name: manufactured by Nippon Shokubai; nonionic monomer in which R ₁ in the general formula (I ′) is a hydrogen atom, R ₂ is a methyl group, R ₃ is an ester bond, and x is 1)
(* 4): Blemmer PME-100 (Product name: NOF Corporation; R ₁ and R ₂ in the general formula (I ′) are methyl groups, R ₃ is an ester bond, and x is 2)
(* 5): Blemmer PME-200 (Product name: NOF Corporation; R ₁ and R ₂ in the general formula (I ′) are methyl groups, R ₃ is an ester bond, and x is about 4)

<Preparation of pigment dispersion>
10 parts of carbon black, 6 parts of glycerin, 10 parts of resin (dispersant), and 74 parts of water were charged into a sand mill (manufactured by Kanada Rika Kogyo Co., Ltd.) with a filling rate of 0.6 mm diameter zirconia beads being 70%. Dispersion was carried out at 500 rpm for 5 hours. The carbon black used had a specific surface area of 220 m ² / g and a DBP oil absorption of 130 ml / 100 g. The resin is a random copolymer having a copolymerization ratio (mass ratio) of styrene, methyl acrylate and acrylic acid of 58:25:17, a weight average molecular weight of 4,000, and an acid value of 130 mgKOH / g. Using. In addition, the said resin used previously what added the potassium hydroxide and water equivalent to said acid value, and stirred at the temperature of 80 degreeC, and was used as the aqueous solution. Thereafter, the mixture is centrifuged at 5,000 rpm for 10 minutes to remove the agglomerated components, and the concentration is further increased with water so that the pigment content is 2.5% and the resin content is 2.5%. To obtain a pigment dispersion.

<Preparation of ink>
After mixing each component with the composition shown in Tables 3 and 4 and stirring sufficiently, pressure filtration was performed with a polypropylene filter (manufactured by Pall) having a pore size of 1.2 μm, and the inks of Examples and Comparative Examples were used. Each was prepared. In Tables 3 and 4 below, the graft polymer is shown as a content value as a solid content. In Tables 3 and 4 below, (* 1) represents a surfactant (manufactured by Kawaken Fine Chemicals), and (* 2) represents polyethylene glycol having an average molecular weight of 600. The “specific water-soluble organic compound” refers to a water-soluble organic compound in the group consisting of the compounds represented by the general formula (II), the general formula (III), and the general formula (IV). Indicates. In Tables 3 and 4 below, “specific graft polymer” refers to a graft polymer used in the present invention, and in the present example, refers to graft polymers 1 to 10.

<Preparation of reaction solution>
After mixing each component with the composition shown below and stirring sufficiently, pressure filtration was performed with a polypropylene filter (manufactured by Pall) having a pore size of 1.2 μm to prepare reaction solution 1.
Calcium nitrate tetrahydrate: 4.0 parts Glycerin: 15.0 parts Polyethylene glycol (average molecular weight 600): 5.0 parts Acetylenol E100 (surfactant; manufactured by Kawaken Fine Chemicals): 0.5 Parts / pure water: 75.5 parts <Evaluation>
(Evaluation of ink storage stability)
100 g of each ink was put in a 180 cc Teflon (registered trademark) container, and the average particle diameter d ₅₀ and ink viscosity of the particles before and after being left in a 60 ° C. oven in a sealed state for 1 month were measured. The average particle size was set using a dynamic light scattering particle size distribution analyzer (UPA-150EX; manufactured by Nikkiso), set zero: 60 s, measurement time: 120 s, measurement frequency: 3 times, pigment refractive index: 1.8 Measured under conditions. The viscosity was measured using an E-type viscometer (RE80L; manufactured by Toyo Seiki Co., Ltd.) under the conditions of a rotation speed: 20 rpm, a measurement temperature: 25 ° C., and a measurement frequency: 3 times. And the average particle diameter before and behind preservation | save and the change rate of a viscosity were calculated | required and storage stability was evaluated. The evaluation criteria for the storage stability of the ink are as follows. The results are shown in Table 5.
AA: The rate of change is less than 10% in both items.
A: The rate of change in both items is less than 15%.
B: Either d ₅₀ or viscosity is 15% or more.
C: The rate of change is 15% or more for both items.

(Creation of recorded material used for image evaluation)
Each ink and reaction liquid obtained above was filled in an ink cartridge and set in an ink jet recording apparatus BJF900 (manufactured by Canon Inc.). Then, a solid image was formed by one-pass one-way recording so that the reaction liquid was applied first and the ink was applied later to a recording medium (PPC paper office planner; manufactured by Canon) to create a recorded matter. In this case, application amount of the reaction solution 5.0 g / ^{m 2,} the application amount of the ink was 9.5 g / ^{m 2.}

(Evaluation of image density)
The image obtained above was allowed to stand at room temperature for 1 day, and then the image density of the solid image was measured using a reflection type color densitometer (RD915: manufactured by Macbeth) to evaluate the image density. The image density evaluation criteria are as follows. The results are shown in Table 5.
AA: The image density is 1.45 or more.
A: The image density is 1.35 or more and less than 1.45.
B: The image density is 1.25 or more and less than 1.35.
C: The image density is less than 1.25.

(Evaluation of image scratch resistance)
The image obtained above was allowed to stand at room temperature for 10 minutes, and then the solid image was rubbed with a finger, and the degree of ink transfer to the non-recorded portion was visually confirmed to evaluate the scratch resistance of the image. The evaluation criteria for scratch resistance are as follows. The results are shown in Table 5.
AA: There is no ink transfer.
A: There is almost no ink transfer.
B: There is some ink transfer.
C: Ink transfer is bad.

(Evaluation of marker resistance of images)
The image obtained above is allowed to stand at room temperature for 10 minutes, and then a line is drawn on the solid image with a marker pen (product name: OPTEX; manufactured by Zebra) to visually check the degree of ink transfer to the non-recording area. The marker resistance of the images was evaluated. The evaluation criteria for marker resistance are the same as the evaluation criteria for scratch resistance. The results are shown in Table 5.

Claims (10)

A set of a pigment ink containing at least a pigment and a resin, and a reaction liquid containing a reactive substance that destabilizes the dispersion state of the pigment,
The pigment ink contains a graft polymer containing a nonionic unit represented by the following general formula (I), a unit having a polysiloxane structure, and a unit having a carboxyl group, and a set of an ink and a reaction liquid .

(In General Formula (I), R ₁ and R ₂ are each independently a hydrogen atom or a methyl group, R ₃ is an ester bond or an ether bond, and x is an integer of 1 or 2. However, R ₂ When R is a methyl group, R ₃ is not an ether bond.)   The set according to claim 1, wherein the graft polymer has a weight average molecular weight of 5,000 or more and 50,000 or less.   The set according to claim 1 or 2, wherein a proportion of the unit having the polysiloxane structure based on the total mass of the graft polymer is 10.0% by mass or more and 40.0% by mass or less.   The proportion of the nonionic unit represented by the general formula (I) based on the total mass of the graft polymer is 5.0% by mass or more and 45.0% by mass or less. The set according to item 1.   The set according to any one of claims 1 to 4, wherein an acid value of the graft polymer is 80 mgKOH / g or more and 150 mgKOH / g or less. The pigment ink further contains at least one water-soluble organic compound selected from the group consisting of compounds represented by the following general formula (II), the following general formula (III), and the following general formula (IV). Item 6. The set according to any one of Items 1 to 5.

(In the general formula (II), R ₄ is an alkylene group having 2 to 5 carbon atoms which may have a substituent, and each R ₅ is independently a hydrogen atom or an optionally substituted carbon. In general formula (III), R ₆ is an alkylene group having 2 to 5 carbon atoms which may have a substituent, and R ₇ is a hydrogen atom or a substituent. (In general formula (IV), n is a number of 1 to 3.)   The set according to any one of claims 1 to 6, wherein the reactive substance is a cationic compound. An ink jet recording method for recording on a recording medium by discharging a pigment ink and a reaction liquid by an ink jet method,
An ink jet recording method using the pigment ink and the reaction liquid constituting the set according to any one of claims 1 to 7 as the pigment ink and the reaction liquid.   9. The ink jet recording method according to claim 8, wherein after the reaction liquid is applied to a recording medium, recording is performed by applying the pigment ink to the recording medium. An ink jet recording apparatus comprising a plurality of liquid storage portions that respectively store pigment ink and reaction liquid, and an ink jet recording head that discharges pigment ink and reaction liquid,
The pigment ink and the reaction liquid respectively stored in the plurality of liquid storage portions are the pigment ink and the reaction liquid constituting the set according to any one of claims 1 to 7. Inkjet recording device.