JP4891024B2 - Dispersing resin, dispersion, and ink-jet pigment ink - Google Patents

Description

  The present invention relates to a dispersion resin for enabling preparation of a fine particle dispersion having high storage stability, and an inkjet pigment ink excellent in ejection stability and storage stability from an inkjet nozzle using the dispersion resin.

  A dispersant is used in order to maintain particles that are not dissolved in a solution (simply referred to as particles) in a stable dispersion state in the solution to form a dispersion (also referred to as a dispersion). The dispersant has a function of physically adsorbing on the particle surface and reducing the interfacial tension between the solution and the particle, thereby stabilizing the dispersion state of the dispersion. When water or a water-soluble solvent is used as the dispersion medium, the dispersant includes various surfactants containing a hydrophobic functional group and a hydrophilic functional group in the molecule, and hydrophobic monomers and hydrophilic monomers. A dispersion resin obtained by copolymerization has been used. In particular, a dispersion resin obtained by copolymerizing various monomers can be suitably used as a dispersant for various particles because various properties can be imparted depending on the monomer used as a raw material for forming the copolymer. Yes. Conventional dispersion resins have always been linear polymers having both ends, and polymers having ends even if they have a branched structure.

  One of the uses of particles dispersed by a dispersing resin is an ink used for inkjet recording containing a pigment. Conventionally, water-based inks that use water as the main component and dyes that dissolve in water as color materials have been common, but in recent years, pigments have been used as color materials in order to improve the weather resistance and water resistance of recorded materials. The development of water-based pigment inks has been progressing (see Patent Document 1). Among them, in order to improve the image quality of the image formed using the pigment ink, the pigment fine particles dispersed in the ink are dispersed with a particle diameter of about 100 nm or less. .

JP 2001-81369 A

  In such fine particles, the ratio of the surface area to the volume of the particles becomes large, so that the interface between the fine particles and the solution is very activated, and the dispersion state of the fine particles becomes unstable. In particular, the method for recording by ejecting ink from an inkjet head using thermal energy has the following problems. That is, when ink is ejected, very large heat energy is instantaneously generated in the vicinity of the electrothermal transducer, so that the physical properties of the ink change rapidly and the dispersion state of the pigment fine particles tends to become very unstable. . As a result, aggregates precipitate, block the vicinity of the nozzle, or deposit on the electrothermal transducer to form a kogation, so that the ejection stability of the ink from the inkjet head tends to be impaired. Accordingly, an object of the present invention is to provide a dispersion resin that is suitable as a dispersant for fine particles having a fine particle diameter and can form a fine particle dispersion having extremely high storage stability. Another object of the present invention is to provide an ink jet recording pigment ink that can form a high-quality image and is excellent in ejection stability.

The above object is achieved by the present invention described below. That is, the present invention is a dispersion resin having a cyclic structure segment which is a polymer forming a cyclic structure in the structure, and the dispersion resin has a number average molecular weight of 300 to 30,000. And each of the plurality of cyclic structure segments is obtained by polymerizing a monomer having at least a hydrophobic functional group, and the acid value of the dispersion resin is 50 mgKOH / g or more and 300 mgKOH / g. The monomer having a hydrophobic functional group is at least one selected from the group consisting of a vinyl compound having an aromatic functional group, an alkyl (meth) acrylate, and a (meth) acrylate having an alicyclic skeleton. It is a dispersion resin characterized by being a vinyl compound. By using such a dispersion resin, it is possible to maintain a very stable dispersion state even when fine particles having a particle diameter of 100 nm or less are used.

Furthermore, another embodiment of the present invention is a dispersion comprising particles and a dispersion resin in which the particles are dispersed, wherein the particles are pigment particles, and the dispersion resin is the dispersion resin described above. Dispersion characterized. Another embodiment of the present invention is an inkjet pigment ink comprising a pigment, a dispersion resin, water and a water-soluble organic solvent, wherein the dispersion resin is the dispersion resin described above. It is.

  According to the present invention, it is possible to provide a dispersion resin that can improve the dispersion stability even in a fine particle having a small particle diameter and can improve the storage stability of the fine particle dispersion. Further, by using such a dispersion resin as a dispersant for pigment particles, an inkjet pigment ink having extremely high discharge stability and storage stability is provided.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. First, the reason why the dispersion resin of the present invention can exhibit a high dispersion function with respect to fine particles will be described. As described above, when particles are made fine, the particle surface is activated and the dispersion state becomes unstable. For this reason, for example, the dispersion state of the pigment particles becomes unstable with respect to an abrupt change in ink physical properties during ejection from the inkjet head. Therefore, in particular, the fine particle dispersant is required to be capable of imparting very large dispersion stability to the fine particles. In order to reduce the activation of the particle surface and stably disperse in the solvent (solution), the following is required. That is, since the particle surface is generally hydrophobic, the hydrophobic functional group in the dispersed resin is physically adsorbed on the particle surface, while the solvophilic functional group is oriented in the solvent to It is required to increase the affinity of the solvent interface. Therefore, a copolymer of a monomer having a hydrophobic functional group and a monomer having a hydrophilic functional group is usually used for such a dispersant.

  On the other hand, the repulsive force between particles is performed by electrostatic repulsive force or steric hindrance repulsive force applied to the particles by the solvophilic functional group of the dispersion resin. For example, when the solvent is aqueous, the particle surface is generally hydrophobic as described above. Therefore, the dispersion resin usually includes a monomer having a hydrophobic functional group and a monomer having a hydrophilic functional group. It is formed by a copolymer obtained by copolymerization as a raw material. Here, when the proportion of any one of the monomers is increased, the other is decreased. In this case, a dispersion resin that can impart sufficient dispersion stability to the particles cannot be formed.

  As a result of intensive studies on the structure of the above-described conventional dispersion resin and its dispersion function, the present inventors have found the following and arrived at the present invention. That is, in order to exhibit a higher dispersion function, the structure of the dispersion resin is obtained by polymerizing a monomer having a cyclic structure segment and at least a hydrophobic functional group. Found that is effective. That is, the resin having such a structure has the following characteristics. First, the hydrophobic functional group in the cyclic structure segment constituting the resin allows the resin to be adsorbed to the surface of the hydrophobic particles with a very strong adhesive force. Can be reduced. As a result, the ink containing the resin can reduce the desorption of the resin from the particle surface even when an abrupt change in ink physical properties occurs during ink jet ejection. As a result, if the dispersion resin of the present invention is used, a dispersion state can be stably maintained even for fine particles having a particle diameter of 100 nm or less, which could not be made into a dispersion having sufficient dispersion stability. Is possible.

  Next, the dispersion resin of the present invention having the above-described excellent function will be described. The dispersion resin of the present invention is characterized by having a cyclic structure segment, and the polymer forming the segment has a structure obtained by polymerizing at least a monomer having a hydrophobic functional group. In the present invention, “polymerization” includes copolymerization.

  In the present invention, the cyclic structure segment (that is, the polymer segment forming the cyclic structure) is a cyclic structure in which at least one polymer terminal of the segment is bonded to a part of the polymer by a covalent bond or an ionic bond. It is what forms. The cyclic structural segment characterizing the present invention is a segment having no end. That is, in the structure, cyclic structures such as aromatic compounds such as benzene ring, naphthalene ring, anthracene ring and derivatives thereof, alicyclic compounds such as cyclohexane and derivatives thereof, and heterocyclic compounds such as pyridine and thiophene. It is completely different from the copolymer including those having. The cyclic structure segment characterizing the present invention can be produced by, for example, the method reported in Macromolecules, 2003, 36, 9264 and the like. Hereinafter, the monomer raw material used when producing the dispersion resin of the present invention will be described.

Examples of the monomer having a hydrophobic functional group used in the present invention include the following vinyl compounds having a hydrophobic functional group. For example, those having an aromatic functional group such as styrene, methylstyrene, vinylnaphthalene, divinylbenzene, benzyl (meth) acrylate;
Methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate,
n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate,
Alkyl (meth) acrylates such as 2-ethyl-hexyl (meth) acrylate and lauryl (meth) acrylate;
(Meth) acrylates of alicyclic compounds such as cyclohexyl (meth) acrylate, isobornyl acrylate, tricyclodecane dimethanol di (meth) acrylate and the like can be used. The monomer having a hydrophobic functional group is preferably selected appropriately according to the chemical properties of the fine particle surface. However, for many organic pigments, monomers having an aromatic functional group such as styrene and benzyl (meth) acrylate are preferred.

  Moreover, in this invention, the monomer which has these hydrophobic functional groups should just be contained in the cyclic structure segment at least. In particular, among the monomers constituting the polymer forming the cyclic structure segment, it is preferable that the monomer having a hydrophobic functional group is 50% by mass or more. That is, if the proportion of the monomer having a hydrophobic functional group is configured to occupy 50% by mass or more of the cyclic structure segment, the physical adsorption force to the particle surface can be improved, and the concentration of the dispersed resin can be increased. Even if it crosses, cross-linking with respect to a plurality of fine particles is suppressed due to the cyclic structure. These effects make it possible to achieve further dispersion stability.

The polymer forming the cyclic structure segment may contain any monomer as long as it is a monomer copolymerizable with the above-described monomer having a hydrophobic functional group. Examples of the monomer copolymerizable with the monomer having a hydrophobic functional group include those listed below. For example, it has an acidic functional group such as (meth) acrylic acid, (meth) acrylic acid derivative, maleic acid, maleic acid derivative, itaconic acid, itaconic acid derivative, fumaric acid, fumaric acid derivative, vinylsulfonic acid, vinylphosphonic acid, etc. Vinyl compounds;
Monomers having a heterocyclic ring such as vinylpyridine, N-vinylcarbazole, morpholyacrylamide, etc .;
(Meth) acrylamide and its derivatives;
Hydroxyl group-terminated polyalkylene glycol (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and polyethylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate;
NK ester M90-G (product name: Shin-Nakamura Chemical);
Alkoxypolyalkylene glycol (meth) acrylic acid esters such as BLEMMER 50POEP800B (product name: manufactured by NOF Corporation);
Examples thereof include (meth) acrylate added with ethylene oxide and propylene oxide such as 2-phenoxyethylene glycol (meth) acrylate.

  The dispersion resin of the present invention having a cyclic structure segment, which is a polymer having a hydrophobic functional group, may be composed of only the cyclic structure segment described above, or at least one cyclic structure segment in the resin. It may be in the form of having. For example, at least one cyclic structure segment may be a side chain branched from a chain polymer. That is, if the resin has a cyclic structure segment as described above, a sufficient steric hindrance repulsive force can be imparted to the fine particles, and dispersion stabilization can be achieved. According to the study by the present inventors, the above-described effect can be obtained as long as at least one cyclic structure segment is included in the resin. In that case, it is more preferable that the plurality of annular structure segments have the following relationship.

  When the resin has a plurality of cyclic structure segments, any of the monomers used for the formation of the cyclic structure segments may be common among the plurality of cyclic structure segments, or may be different from each other. May be. When it is formed of a common monomer, it is advantageous to physically adsorb the dispersed resin uniformly on the dispersed particles, and the dispersion stability can be further improved. On the other hand, in the case of being formed with different monomers, in addition to the dispersion stability, for example, it is free to add various characteristics whose effects are determined by a chemical structure such as curing reactivity. There is an advantage that the design increases and the design is easy.

  Further, in a plurality of cyclic structure segments, regardless of whether the composition of the monomers constituting the segments is the same or different, the degree of polymerization of the monomers is not particularly limited and is the same Or different. In this case, when the degree of polymerization of the monomers is the same, it is possible to increase the uniformity of the physical properties of the dispersion resin, to further increase the dispersion stability of the dispersed particles, or to lower the viscosity of the dispersion. Etc. are possible. Further, when the polymerization degrees of the monomers are different, different physical properties can be added between the dispersed particles. If different physical properties are added between the dispersed particles, the physical and chemical environment around the dispersed particles becomes non-uniform. For example, it is possible to impart weak structural viscosity, etc. Low dispersion particles can be made. On the other hand, when the composition of the monomer constituting the cyclic structure segment is different, the molecular weight of the plurality of cyclic structure segments may be the same by setting the polymerization degree to be different. By doing so, it is possible to improve the dispersion stability of the dispersed particles.

  The molecular weights of the plurality of cyclic structure segments included in the dispersion resin may be the same or different. That is, when the molecular weights of these cyclic structure segments are the same, it is possible to increase the uniformity of the physical properties of the dispersed resin, and to further increase the dispersion stability of the dispersed particles and to lower the viscosity of the dispersion. Etc. are possible. On the other hand, when the molecular weights of the plurality of cyclic structure segments are different from each other, different physical properties can be added between the dispersed particles. In this case, since the physical and chemical environment around the dispersed particles becomes non-uniform, for example, it is possible to impart a weak structural viscosity or the like, and it is possible to produce dispersed particles with low sedimentation properties. It becomes possible.

  In the present invention, the degree of polymerization of the monomer forming the cyclic structure segment is preferably 4 or more in order to stabilize the cyclic structure. Moreover, it is preferable that the molecular weight of a cyclic structure segment is 300-30,000 by a number average molecular weight. More preferably, those having a number average molecular weight of 400 to 20,000 are used. If the molecular weight of the cyclic structure segment is too smaller than the above range, it is difficult to form a cyclic structure. On the other hand, if it is larger than the above range, the molecular weight of the dispersion resin is increased, so that the viscosity of the dispersion is increased.

  The molecular weight of the entire dispersion resin including the cyclic structure segment is preferably in the range of weight average molecular weight of 1,000 to 30,000, more preferably in the range of 3,000 to 15,000. It is. Moreover, it is preferable that the dispersion resin containing the cyclic structure segment of the present invention includes a monomer having an acidic functional group. When the constituent ratio of the monomer having an acidic functional group in the dispersion resin is represented by an acid value, it is preferably in the range of 50 to 300 mgKOH / g. More preferably, a dispersion resin having an acid value of 80 to 200 mgKOH / g is preferable. If the acid value is lower than this range, the dispersion stability of the dispersion or the pigment ink for inkjet may be lowered. In the case of inkjet ink, the ejection stability may be deteriorated. On the other hand, if the acid value is higher than this range, the adhesion of the dispersion resin to the particle surface is lowered, and the storage stability of the dispersion or the pigment ink for inkjet may be lowered.

  When the resin having an acidic functional group is contained in the resin, the dispersion stability of the particles can be further improved by ionizing the acidic functional group. For this purpose, it is preferable to adjust the whole of the dispersion obtained by using the dispersion resin of the present invention and the inkjet pigment ink to be neutral or alkaline. However, in this case, since it may cause corrosion of various members used in the ink jet recording apparatus, it is desirable that the pH range is 7 to 10. As the pH adjuster used at this time, the following can be used. Examples thereof 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, organic acids and mineral acids. The dispersion resin as described above is dispersed or dissolved in the dispersion medium.

  Specifically, the dispersion resin of the present invention preferably has the following structure. For example, a block copolymer or graft copolymer having a hydrophilic segment composed mainly of a monomer having a hydrophilic functional group and a hydrophobic cyclic segment composed mainly of a monomer having a hydrophobic functional group. A polymer is mentioned. The hydrophilic segment in such a block copolymer or graft copolymer is not particularly limited, and may be a cyclic structure or a linear structure. The block copolymer referred to in the present invention refers to a copolymer in which at least one cyclic structure segment and at least one linear (co) polymer segment, or a plurality of cyclic structure segments are bonded, Each segment deserves a block. A graft copolymer is one in which at least one cyclic structure segment and / or at least one linear (co) polymer chain is branched and bonded from one linear (co) polymer chain. Alternatively, it refers to a structure in which at least one cyclic structure segment and / or at least one linear (co) polymer chain is branched from one cyclic structure segment.

  The hydrophilic segment in the above may contain at least a monomer having a hydrophilic functional group. However, in order for the hydrophilic segment constituting the dispersion resin to exhibit interparticle repulsion sufficient for dispersion stability, at least 50% by mass or more of the monomers constituting the hydrophilic segment. Is preferably a monomer having a hydrophilic functional group.

Examples of the monomer having a hydrophilic functional group that can be used in this case include the following. For example, it has an acidic functional group such as (meth) acrylic acid, (meth) acrylic acid derivative, maleic acid, maleic acid derivative, itaconic acid, itaconic acid derivative, fumaric acid, fumaric acid derivative, vinylsulfonic acid, vinylphosphonic acid, etc. Vinyl compounds;
(Meth) acrylamide and its derivatives;
Hydroxyl group-terminated polyalkylene glycol (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and polyethylene glycol (meth) acrylate; methoxyethylene glycol (meth) acrylate;
NK ester M90-G (product name: Shin-Nakamura Chemical);
Alkoxypolyalkylene glycol (meth) acrylic acid esters such as BLEMMER 50POEP800B (product name: manufactured by NOF Corporation);
Ethylene oxide such as 2-phenoxyethylene glycol (meth) acrylate, (meth) acrylate added with propylene oxide, and the like can be used.

  The hydrophobic segment refers to a monomer having at least 50% by mass of a monomer having a hydrophobic functional group among monomers copolymerized to constitute the segment. As the monomer having a functional group, the monomer having the hydrophobic functional group described above is used.

  As described above, the resin having a cyclic structure segment described above has a high dispersion function, but it can be suitably used as an ink forming component as well as a pigment dispersant in ink. be able to. Next, the ink-jet pigment ink of the present invention (hereinafter also referred to as ink) containing the dispersion resin of the present invention will be described. Although the case where the dispersion resin of the present invention is used as a component for dispersing the pigment will be mainly described, as described above, the present invention is not limited to this.

  The resin having a cyclic structure segment is preferably contained in a range of 0.1% by mass to 15% by mass with respect to the total mass of the ink. In particular, when used as a dispersion resin for dispersing a pigment, it is preferably contained in a range of 0.1% by mass or more and 8% by mass or less with respect to the total mass of the ink. If necessary, natural resins such as rosin, shellac, and starch, and synthetic resins that are not resins having the cyclic structure can be preferably used. These resins can be contained in such an amount that does not exceed the amount of the resin having the cyclic structure segment described above.

  The ink of the present invention comprises at least a pigment, a water-soluble organic solvent, and water in addition to the resin described above. Hereinafter, these components will be described. The ink of the present invention contains a pigment in a mass ratio of 1% by mass to 20% by mass, more preferably 2% by mass to 12% by mass with respect to the total mass of the ink. Is preferred. In the present invention, the following pigments can be used.

First, carbon black is mentioned as a black pigment which can be used in the present invention. Specifically, for example, a furnace method, a carbon black produced by channel technique, following a primary particle diameter of 11~40mμm (nm), BET specific surface area is 50m ² / g~400m ² / g, Those having characteristics such as a volatile content of 0.5 to 10% by mass and a pH value of 2 to 10 can be preferably used. Examples of commercially available products having such characteristics include those listed below, and any of these can be preferably used. For example, no. 33, 40, 45, 52, 900, 2200B, 2300, MA7, MA8, MCF88 (above, manufactured by Mitsubishi Chemical);
RAVEN 1255 (made in Colombia);
REGAL 330R, 400R, 660R, MOGUL L (above, manufactured by Cabot);
There are Nipex 160IQ, Nipex170IQ, Nipex180IQ, Nipex75, Printex 95, Printex 90, Printex 35, Printex U (manufactured by Degussa).

Examples of the color pigments that can be used in the ink of the present invention include the following. Examples of yellow pigments include C.I. I. Pigment Yellow 1, 2, 3, 13, 16, 74, 83, 109, 128, 155 and the like. Examples of magenta pigments include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 202;
Quinacridone solid solution, C.I. I. Pigment Violet 19 etc. are mentioned. Examples of cyan pigments include C.I. I. Pigment Blue 1, 2, 3, 15: 3, 15: 4, 16, 22, C.I. I. Vat Blue 4, 6 etc. are mentioned. Furthermore, pigments of colors other than those described above can also be used, but in that case, any pigment may be used alone in each color ink, or two or more pigments may be mixed. Of course, the present invention is not limited to these. In addition to the above, newly manufactured pigments such as self-dispersing pigments can also be used.

  The aqueous medium forming the ink of the present invention is a mixed solvent of water and a water-soluble organic solvent. As water, it is preferable to use ion-exchanged water (deionized water) instead of general water containing various ions.

Specific examples of the water-soluble organic solvent used by mixing with water include those listed below, but are not limited thereto. For example, alkyl alcohols having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol;
Amides such as dimethylformamide and dimethylacetamide;
Ketones or ketoalcohols such as acetone and diacetone alcohol;
Ethers such as tetrahydrofuran and dioxane;
Polyalkylene glycols such as polyethylene glycol and polypropylene glycol;
Ethylene glycol, 1,2-propanediol, 1,3-propanediol, triethylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, 1,2-hexane Alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms, such as diol and diethylene glycol;
Glycerin;
Lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether;
N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like can be mentioned. Among the 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.

  The content of the water-soluble organic solvent in the ink as described above is generally in the range of 3% by mass to 50% by mass, and more preferably 3% by mass to 40% by mass of the total mass of the ink. Range. The water content is in the range of 10% to 90% by weight, more preferably 30% to 80% by weight, based on the total weight of the ink.

  In addition to the above-described components, the ink of the present invention may be appropriately added with additives such as surfactants, antifoaming agents, preservatives, etc. in order to obtain inks having desired physical properties as required. be able to. As an example of the addition amount, 0.05 mass% or more and 10 mass% or less, preferably 0.2 mass% or more and 5 mass% or less is suitable with respect to the total mass of the ink.

  The ink of the present invention comprises the components as described above. Hereinafter, an example in which a resin having a cyclic structure segment is used as a dispersant will be described as a method for producing the ink. First, a pigment is added to an aqueous medium in which at least a resin having a cyclic structure segment and water are mixed, mixed and stirred, and then subjected to a dispersion treatment using a dispersion means described later. After the dispersion treatment, a desired pigment dispersion is obtained by performing a centrifugal separation treatment as necessary. Next, if necessary, the above-mentioned water-soluble organic solvent or additive components appropriately selected as necessary are added to this pigment dispersion and stirred to obtain the ink of the present invention. In order to dissolve the dispersion resin used at this time, it is preferable to add a base when preparing the pigment dispersion as described above. In this way, the dispersion stability of the obtained ink can be further improved. Examples of bases that can be preferably used in this case include the following. For example, organic amines such as monoethanolamine, diethanolamine, triethanolamine, amine methylpropanol, and ammonia can be preferably used. Or inorganic bases, such as potassium hydroxide, sodium hydroxide, lithium hydroxide, can be used preferably.

  In the method for producing an ink containing a pigment, as described above, generally, a pigment dispersion obtained by performing a dispersion treatment in advance is used. More preferably, it is effective to perform premixing by adding a pigment to an aqueous medium in which a dispersant and water are mixed at least before the dispersion treatment performed when preparing the pigment dispersion. That is, by performing such a premixing operation, the wettability of the pigment surface can be improved and the adsorption of the dispersant to the pigment surface can be promoted.

  In the above, any disperser that is generally used can be used as the disperser used in the pigment dispersion treatment. Examples thereof include a ball mill, a roll mill, a sand mill, a bead mill, and a nanomizer. Among these, a bead mill is preferably used. Examples of such include a super mill, a sand grinder, an agitator mill, a glen mill, a dyno mill, a pearl mill, and a cobol mill (all are trade names).

  In order to enable the ink containing the pigment produced as described above to be suitably used in the ink jet recording method, the pigment has an optimal particle size distribution from the demand for clogging resistance and the like. It is preferable to use what has. As a method for obtaining a pigment having a desired particle size distribution, the following conventionally known methods can be applied. Reduce the size of the grinding media of the disperser as mentioned above, increase the filling rate of the grinding media, increase the processing time, classify with a filter or centrifuge after grinding, etc. A method such as a combination of these methods may be mentioned.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In the following description, “parts” and “%” are based on mass unless otherwise specified.

[Example 1]
In this example, a segment having a cyclic structure formed by copolymerization of a monomer having a hydrophobic functional group (hereinafter referred to as a cyclic structure segment) is a graft copolymer branched from the hydrophobic segment of the main chain. An example of the constituted dispersion resin will be described.

<Preparation of dispersion resin A1>
(Synthesis of cyclic structure segment B1)
Cyclic structural segment B1 was synthesized by copolymerizing styrene, which is a monomer having a hydrophobic functional group, and Karenz MOI-BM (trade name: Showa Denko) having the following structure. Karenz MOI-BM is a compound having a structure that is deblocked by heat treatment to regenerate active isocyanate groups as shown below. Synthesis of cyclic structure segment B1 is described in J. Org. Polym. Sci. 1999, 37, 2027. The copolymerization ratio of styrene and Karenz MOI-BM was 20: 1 in terms of mol charge ratio. The cyclic structure segment obtained by copolymerizing styrene and Karenz MOI-BM has a number average molecular weight of 2,310, and the copolymer has a degree of polymerization of 21.

(Synthesis of main chain copolymer C1)
As a monomer having a hydrophilic functional group, 30 parts of acrylic acid, 10 parts of 2-hydroxyethyl methacrylate, and 1 part of azobisisobutyronitrile as a radical polymerization initiator were used. A mixture of these monomers and a polymerization initiator was dropped into 1-methoxy-2-propanol to perform radical polymerization. At this time, the polymerization temperature was 110 ° C., and the dropping time was 3 hours under N ₂ reflux. After completion of the dropwise addition, the polymerization reaction was carried out at 110 ° C. for 3 hours. Then, it cooled to room temperature, developed the reaction material in 1,000 parts of hexane, removed the unreacted material by precipitation refinement | purification, and dried under reduced pressure, and obtained the main chain copolymer C1. The number average molecular weight of the obtained main chain copolymer C1 was 4,200.

(Synthesis of dispersion resin A1)
60 parts of the cyclic structure segment B1 synthesized above, 40 parts of the main chain copolymer C1 having a hydrophilic functional group and 800 parts of dioxane are dissolved in 800 parts of dioxane and heated to 150 ° C. to block the cyclic structure segment B1 The isocyanate group was deblocked and covalently bonded to the hydroxyl group of the main chain copolymer C1. Thereafter, the reaction product was developed in 1,000 parts of hexane, the unreacted product was removed by precipitation purification, and dried under reduced pressure to obtain dispersion resin A1. The number average molecular weight of the dispersion resin A1 synthesized in this manner was 10,000. The acid value was 180 mgKOH / g.

<Usage example of dispersion resin A1>
(Preparation of titanium oxide dispersion t1)
・ Dispersion resin A1 15 parts ・ Potassium hydroxide 3 parts ・ Methanol 10 parts ・ Ion-exchanged water 57 parts

  The above components including the dispersion resin A1 synthesized above are mixed and heated to 70 ° C. in a water bath to completely dissolve the resin component. 15 parts of titanium oxide particles (MT-100SA, manufactured by Teica) were added to this solution, and premixing was performed for 30 minutes. Thereafter, a dispersion treatment was performed under the following conditions to obtain a titanium oxide dispersion t1. It was 50 nm when the average particle diameter of the obtained titanium oxide dispersion liquid t1 was measured with the particle size distribution measuring apparatus (FPAR-1000 made from Otsuka Electronics).

・ Disperser: Bead mill UAM-015 (product name) (manufactured by Kotobuki Industries)
・ Crushing media: zirconia beads, 0.05 mm diameter (made by Nikkato)
・ Filling rate of grinding media: 70% (volume ratio)
・ Crushing time: 1 hour

(Storage stability test)
[Measurement of average particle size before and after storage at 80 degrees]
The storage stability of the titanium oxide dispersion t1 was evaluated by the following method and criteria. The titanium oxide dispersion t1 obtained above was put in a sealed container and left in a constant temperature bath at 80 ° C. for 24 hours. The average particle size before and after this test was measured by a particle size distribution measuring device (FPAR-1000 manufactured by Otsuka Electronics Co., Ltd.). Then, the average particle diameter PD ₁ (pre-test) of the respective measurement values, the ratio of the PD ₂ (after test), obtains the RPD = PD ₂ / PD _1, the following criteria by using the obtained RPD evaluated. The evaluation results are shown in Table 1.

〔Evaluation criteria〕
A: 0.9 <RPD ≦ 1.2
○: 0.8 <RPD ≦ 0.9, 1.2 <RPD ≦ 1.4
Δ: 0.7 <RPD ≦ 0.8, 1.4 <RPD ≦ 1.8
×: RPD ≦ 0.7, 1.8 <RPD

上記したように、平均粒子径が５０ｎｍと微粒子でありながら、保存安定性に極めて優れた酸化チタン粒子の分散液が作製できることが確認された。

As described above, it was confirmed that a dispersion of titanium oxide particles having an excellent average particle size of 50 nm and excellent storage stability can be produced.

[ Reference Example 1 ]
In this reference example, an example of a dispersion resin composed only of a cyclic structure segment will be described.

<Preparation of dispersion resin A2>
A dispersion resin A2 having a cyclic structure was synthesized according to the method for producing a cyclic structure polymer described in Macromolecules, 2003, 36, 926. As raw materials, 10 mmol of methyl acrylate and 20 mmol of styrene were used. The obtained segment was formed with a cyclic structure consisting of a copolymer of methyl acrylate and styrene. By hydrolyzing the methyl residue with an aqueous KOH solution, the copolymer of acrylic acid and styrene A cyclic structure segment A2 made of a coalescence was obtained. The number average molecular weight was 21,680, the polymerization degree of acrylic acid was 70, and the polymerization degree of styrene was 160. The mass ratio of styrene in the dispersion resin A2 is 76% by mass. Further, the acid value of the dispersion resin A2 is 203 mgKOH / g.

<Usage example of dispersion resin A2>
(Production and evaluation results of titanium oxide dispersion t2)
The dispersion resin A1 in Example 1 was replaced with the dispersion resin A2 obtained above, and a titanium oxide dispersion liquid t2 was produced according to the method of Example 1. The average particle diameter was 80 nm. The titanium oxide dispersion t2 was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 2 below.

上記したように、平均粒子径が８０ｎｍの微粒子でありながら、保存安定性に優れた酸化チタンの分散液が得られることが確認された。

As described above, it was confirmed that a dispersion of titanium oxide having excellent storage stability was obtained while being fine particles having an average particle diameter of 80 nm.

[Example 3]
<Preparation of dispersion resin A3>
In this example, an example of a dispersion resin composed of a graft copolymer in which a cyclic structure segment is branched from a hydrophilic segment of the main chain will be described.

(Synthesis of cyclic structure segment B3)
A cyclic structure segment B3 was synthesized using the same method as the method of synthesizing the dispersion resin A2 of Reference Example 1 , using 15 mmol of methyl acrylate and 20 mmol of styrene as raw materials. The obtained segment was formed with a cyclic structure consisting of a copolymer of methyl acrylate and styrene. By hydrolyzing the methyl residue with an aqueous KOH solution, the copolymer of acrylic acid and styrene A cyclic structure segment B3 made of a coalescence was obtained. The number average molecular weight of the cyclic structure segment B3 was 5,000, the polymerization degree of acrylic acid was 25, and the polymerization degree of styrene was 30. Therefore, the degree of polymerization of the cyclic structure segment B7 is 55. The mass ratio of styrene in the cyclic structure segment B3 was 63% by mass.

(Synthesis of main chain copolymer C3)
As a monomer having a hydrophobic functional group, 70 parts of methyl acrylate, 10 parts of n-butyl methacrylate, and 5 parts of glycidyl methacrylate were used. As a radical polymerization initiator, 4 parts of azobisisobutyronitrile was used. The mixture of the monomer raw material and the polymerization initiator was dropped into 1-methoxy-2-propanol to perform radical polymerization. The polymerization conditions at this time were a polymerization temperature of 110 ° C. and a dropping time of 3 hours under N ₂ reflux. After completion of the dropping, the polymerization reaction was carried out at 110 ° C. for 3 hours. Thereafter, the mixture was cooled to room temperature, the reaction product was developed in 1,000 parts of hexane, unreacted products were removed by precipitation purification, and dried under reduced pressure to obtain a main chain copolymer C3. The number average molecular weight of the obtained main chain copolymer C3 was 5,800.

(Synthesis of Dispersing Resin A3)
Using 50 parts of the cyclic structure segment B3 synthesized as described above and 50 parts of the main chain copolymer C3, a dispersion resin A3 was synthesized as follows. These copolymers are dissolved in 800 parts of dioxane, a small amount of N, N, N-triethylamine is added, heated to 70 ° C., and the carboxyl group of the cyclic structure segment B3 and the glycidyl group in the main chain copolymer C3 The bond was made between. Thereafter, the methyl residue of methyl acrylate in the main chain copolymer was hydrolyzed in an aqueous KOH solution to form a hydrophilic segment containing the acrylic acid in the main chain copolymer. Thereafter, the reaction product was developed in 1,000 parts of hexane, the unreacted product was removed by precipitation purification, and dried under reduced pressure to obtain dispersion resin A3. The synthesized dispersion resin A3 has a structure in which a copolymer having a plurality of cyclic structure segments B3 is branched from the main chain copolymer C3, and has a number average molecular weight of 20,000. The acid value of the dispersion resin A3 is 220 mgKOH / g.

<Usage example of dispersion resin A3>
(Production and evaluation results of titanium oxide dispersion t3)
The dispersion resin A1 in Example 1 was replaced with the dispersion resin A3 obtained above, and a titanium oxide dispersion liquid t3 was produced according to the method of Example 1. The average particle diameter was 80 nm. The titanium oxide dispersion t3 was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 3 below.

上記したように、平均粒子径が８０ｎｍの微粒子でありながら、保存安定性に優れた酸化チタンの分散液が得られることが確認された。

As described above, it was confirmed that a dispersion of titanium oxide having excellent storage stability was obtained while being fine particles having an average particle diameter of 80 nm.

[Example 4]
In this example, an example of a dispersion resin composed of a graft copolymer in which two types of cyclic structure segments having different monomer compositions are branched from the hydrophobic segment of the main chain will be described.

<Preparation of dispersion resin A4>
(Synthesis of cyclic structure segment B4)
A cyclic structure segment B4 was synthesized using a method similar to the method of synthesizing the dispersion resin A2 of Reference Example 1 , using 18 mmol of methyl acrylate and 15 mmol of n-butyl acrylate as raw materials. The obtained segment has a cyclic structure formed of a copolymer of methyl acrylate and n-butyl acrylate. By hydrolyzing the methyl residue with an aqueous KOH solution, acrylic acid and n A cyclic structure segment B4 made of a copolymer of -butyl acrylate was obtained. The number average molecular weight was 3,300, the polymerization degree of acrylic acid was 20, and the polymerization degree of n-butyl acrylate was 15. The mass ratio of n-butyl acrylate in the cyclic structure segment B3 is 57% by mass.

(Synthesis of dispersion resin A4)
Using the cyclic structure segment B4 obtained above, the cyclic structure segment B3 used in Example 3 and the main chain copolymer C3, the dispersion resin A3 was synthesized in the same manner as the method of synthesizing the dispersion resin A3 of Example 3. A4 was synthesized. At that time, 25 parts of cyclic structure segment B3, 25 parts of cyclic structure segment B4, and 50 parts of main chain copolymer C3 were used. The cyclic structure segments B4 and B3 have different monomer compositions. The synthesized dispersion resin A4 was a structure in which copolymer segments B3 and B4 having two kinds of cyclic structures were branched from the main chain copolymer C3, and the number average molecular weight was 18,000. The acid value of this dispersion resin A4 was 210 mgKOH / g.

<Usage example of dispersion resin A4>
(Production and evaluation results of titanium oxide dispersion t4)
The dispersion resin A1 in Example 1 was replaced with the dispersion resin A4 obtained above, and a titanium oxide dispersion liquid t4 was produced according to the method of Example 1. The average particle diameter was 80 nm. The titanium oxide dispersion t4 was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 4 below.

上記したように、平均粒子径が８０ｎｍの微粒子でありながら、保存安定性の優れた酸化チタンの分散液が得られることが確認された。

As described above, it was confirmed that a dispersion of titanium oxide having excellent storage stability was obtained while being fine particles having an average particle diameter of 80 nm.

[Example 5]
In this example, an example of a dispersion resin in which two types of cyclic structure segments having the same monomer composition but different degrees of polymerization are each composed of a graft copolymer branched from a hydrophobic segment of the main chain. Is described.

<Preparation of dispersion resin A5>
(Synthesis of cyclic structure segment B5)
A method similar to the method of synthesizing the dispersion resin A2 of Reference Example 1 was used, and 36 mmol of methyl acrylate and 30 mmol of n-butyl acrylate were used as raw materials. The obtained segment has a cyclic structure formed of a copolymer of methyl acrylate and n-butyl acrylate. By hydrolyzing the methyl residue with an aqueous KOH solution, acrylic acid and n A cyclic structure segment B5 made of a copolymer of -butyl acrylate was obtained. The number average molecular weight was 6,600, the polymerization degree of acrylic acid was 40, and the polymerization degree of n-butyl acrylate was 30. The mass ratio of n-butyl acrylate in the cyclic structure segment B5 is 57% by mass.

(Synthesis of Dispersing Resin A5)
Similar to the method of synthesizing the dispersion resin A3 of Example 3 using the cyclic structure segment B5 obtained above, the cyclic structure segment B4 used in Example 4, and the main chain copolymer C3 used in Example 3. Dispersion resin A5 was synthesized using the above method. The cyclic structure segment B4 and the cyclic structure segment B5 are cyclic structure segments having the same composition but different degrees of polymerization. For the synthesis of dispersion resin A5, 25 parts of cyclic structure segment B5, 25 parts of cyclic structure segment B4, and 50 parts of main chain copolymer C3 were used. The synthesized dispersion resin A5 is a structure in which copolymers having two types of cyclic structures having the same composition and different degrees of polymerization are branched from the main chain copolymer C3, and the number average molecular weight is 21,000. there were. The acid value of Dispersing Resin A5 was 210 mgKOH / g.

<Usage example of dispersion resin A5>
(Production and evaluation results of titanium oxide dispersion t5)
In place of the dispersion resin A1 obtained in Example 1 and the dispersion resin A5 obtained above, a titanium oxide dispersion liquid t5 was produced according to the method of Example 1. The average particle diameter was 80 nm. The titanium oxide dispersion t5 was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 5 below.

上記したように、平均粒子径が８０ｎｍの微粒子でありながら、保存安定性の優れた酸化チタンの分散液が得られることが確認された。

As described above, it was confirmed that a dispersion of titanium oxide having excellent storage stability was obtained while being fine particles having an average particle diameter of 80 nm.

[Example 6]
In this example, an example of a dispersion resin composed of two types of annular structure segments will be described. The two types of segments are composed of copolymers having different monomer compositions and the same molecular weight.

<Preparation of dispersion resin A6>
(Synthesis of cyclic structure segment B6)
A method similar to the synthesis of dispersion resin A2 in Reference Example 1 was used, and 18 mmol of methyl acrylate and 20 mmol of n-butyl acrylate were used as raw materials. The obtained segment has a cyclic structure formed of a copolymer of methyl acrylate and n-butyl acrylate. By hydrolyzing the methyl residue with an aqueous KOH solution, acrylic acid and n A cyclic structure segment B6 made of a copolymer of -butyl acrylate was obtained. The number average molecular weight was 5,000, the polymerization degree of acrylic acid was 20, and the polymerization degree of n-butyl acrylate was 28. The mass ratio of n-butyl acrylate in the cyclic structure segment B6 is 72% by mass.

(Synthesis of Dispersing Resin A6)
As the cyclic structure segments having different molecular weights, the cyclic structure segment B3 used in Example 3 and the cyclic structure segment B6 synthesized above were used. The cyclic structure segment B3 and the cyclic structure segment B6 are composed of copolymers having different monomer compositions but the same molecular weight of the segments. For the synthesis of the dispersion resin A6, 10 parts of the cyclic structure segment B3, 10 parts of the cyclic structure segment B6, 3 parts of hexamethylenediamine, 1 part of N, N, N-triethylamine, and 2-chloropyridium iodide One part was used. And what melt | dissolved these in 1,000 parts of dichloromethanes was synthesize | combined by stirring for 10 hours. The synthesized dispersion resin A6 is different in composition but has a number average molecular weight of 5,000 and the same two kinds of cyclic structure segment B3 and cyclic structure segment B6 bonded by hexamethylenediamine, and the number average thereof The molecular weight was 12,000. The acid value of the dispersion resin A6 is 180 mgKOH / g.

<Usage example of dispersion resin A6>
(Production and evaluation results of titanium oxide dispersion t6)
The dispersion resin A1 in Example 1 was replaced with the dispersion resin A6 obtained above, and a titanium oxide dispersion liquid t6 was produced according to the method of Example 1. The average particle diameter was 85 nm. The titanium oxide dispersion t6 was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 6 below.

上記したように、平均粒子径が８５ｎｍの微粒子でありながら、保存安定性の優れた酸化チタンの分散液が得られることが確認された。

As described above, it was confirmed that a dispersion of titanium oxide having excellent storage stability was obtained while being fine particles having an average particle diameter of 85 nm.

[Example 7]
In this example, an example of a dispersion resin composed of two types of annular structure segments will be described. The two types of segments are composed of copolymers having different monomer compositions and the same degree of polymerization.

<Preparation of dispersion resin A7>
(Synthesis of cyclic structure segment B7)
A method similar to the synthesis of dispersion resin A2 in Reference Example 1 was used, and 15 mmol of methyl acrylate and 20 mmol of n-butyl acrylate were used as raw materials. The obtained segment has a cyclic structure formed of a copolymer of methyl acrylate and n-butyl acrylate. By hydrolyzing the methyl residue with an aqueous KOH solution, acrylic acid and n A cyclic structure segment B7 made of a copolymer of -butyl acrylate was obtained. The number average molecular weight was 5,400, the polymerization degree of acrylic acid was 30, and the polymerization degree of n-butyl acrylate was 25. Therefore, the polymerization degree of the cyclic structure segment B7 is 55, which is the same as the polymerization degree of the cyclic structure segment B3. The mass ratio of n-butyl acrylate in the cyclic structure segment B7 is 72% by mass.

(Synthesis of Dispersing Resin A7)
As the cyclic structure segments having different molecular weights, the cyclic structure segment B3 used in Example 3 and the cyclic structure segment B7 synthesized above were used. The cyclic structure segment B3 and the cyclic structure segment B7 are composed of copolymers having different monomer compositions but the same degree of polymerization of the segments. For the synthesis of the dispersion resin A7, 10 parts of the cyclic structure segment B3, 10 parts of the cyclic structure segment B7, 3 parts of hexamethylenediamine, 1 part of N, N, N-triethylamine, and 2-chloropyridium iodide One part was used. And what melt | dissolved these in 1,000 parts of dichloromethanes was synthesize | combined by stirring for 10 hours. The synthesized dispersion resin A7 has a different composition, but has a polymerization degree of 55 and the same two types of cyclic structure segment B3 and cyclic structure segment B7 bonded by hexamethylenediamine, and its number average molecular weight is 12,000. The acid value of the dispersion resin A7 is 180 mgKOH / g.

<Usage example of dispersion resin A7>
(Production and evaluation results of titanium oxide dispersion t7)
In place of the dispersion resin A1 in Example 1 instead of the dispersion resin A7 obtained above, a titanium oxide dispersion liquid t7 was produced according to the method of Example 1. The average particle diameter was 85 nm. The titanium oxide dispersion t7 was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 7 below.

上記したように、平均粒子径が８５ｎｍの微粒子でありながら、保存安定性の優れた酸化チタンの分散液が得られることが確認された。

As described above, it was confirmed that a dispersion of titanium oxide having excellent storage stability was obtained while being fine particles having an average particle diameter of 85 nm.

[Example 8]
In this example, an example in which the dispersion resin A1 having a cyclic structure segment is used as a dispersion resin for dispersing carbon black will be described.

<Production and Evaluation Results of Pigment Dispersion Liquid k1>
In the preparation of the titanium oxide dispersion t1 of Example 1 using the dispersion resin A1 in Example 1, the pigment dispersion k1 was prepared according to the same method except that the titanium oxide was replaced with carbon black MCF88 (manufactured by Mitsubishi Chemical). Produced. The average particle diameter was 65 nm. The carbon black dispersion k1 was evaluated in the same manner as in Example 1, and the results obtained are shown in Table 8 below.

上記したように、平均粒子径が６５ｎｍの微粒子でありながら、保存安定性の非常に優れたカーボンブラックの分散液が得られることが確認された。

As described above, it was confirmed that a dispersion of carbon black having very excellent storage stability was obtained while being fine particles having an average particle diameter of 65 nm.

[ Reference Example 2 ]
This reference example, although described examples of dispersion resin comprising only one cyclic structure segments in the same manner as in Reference Example 1, and the reference example 1, the different degrees of polymerization of the monomers constituting the cyclic structure segment.

<Preparation of dispersion resin A8>
A method similar to the synthesis of the cyclic structure segment B2 in Reference Example 1 was used, and 10 mmol of methyl acrylate and 30 mmol of styrene were used as raw materials. The obtained segment was formed with a cyclic structure consisting of a copolymer of methyl acrylate and styrene. By hydrolyzing the methyl residue with an aqueous KOH solution, the copolymer of acrylic acid and styrene Dispersion resin A8 made of coalescence was obtained. The synthesized dispersion resin A8 is a copolymer having a cyclic structure, and is obtained by copolymerizing acrylic acid and styrene. The number average molecular weight was 22,000, the polymerization degree of acrylic acid was 60, and the polymerization degree of styrene was 170. The mass ratio of styrene in the dispersion resin A8 was 80% by mass, and the acid value of the dispersion resin A8 was 100 mgKOH / g.

<Usage example of dispersion resin A8>
(Production and evaluation results of titanium oxide dispersion t8)
The dispersion resin A1 in Example 1 was replaced with the dispersion resin A8 obtained above, and a titanium oxide dispersion liquid t8 was produced according to the method of Example 1. The average particle diameter was 85 nm. The titanium oxide dispersion t8 was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 9 below.

上記したように、平均粒子径が８５ｎｍの微粒子でありながら、保存安定性の優れた酸化チタンの分散液が得られることが確認された。

As described above, it was confirmed that a dispersion of titanium oxide having excellent storage stability was obtained while being fine particles having an average particle diameter of 85 nm.

[Example 10]
This example describes an example of an ink-jet pigment ink containing a resin having a cyclic structure segment. In this example, a resin having an annular structure segment is used as one of the ink components without using the dispersant as a dispersant.
<Preparation of pigment dispersion k2>
・ Johncrill 678 (manufactured by Johnson Polymer) 5 parts ・ Potassium hydroxide 1 part ・ Isopropyl alcohol 10 parts ・ Ion-exchanged water 69 parts First, the above ingredients are mixed and heated to 70 ° C. in a water bath to completely remove the resin. Dissolve in. To this, 15 parts of carbon black (MCF88, manufactured by Mitsubishi Chemical) was added, and then a pigment dispersion k2 in which carbon black was dispersed in the same manner as in the method of preparing the titanium oxide dispersion t1 described in Example 1. Produced.

<Preparation of black ink K2>
Using the pigment dispersion k2 prepared above, components having the following composition ratio including the dispersion resin A1 used in Example 1 were mixed to prepare a black ink K2. The obtained black ink K2 contains the dispersion resin A1, but the black ink K2 is not particularly subjected to the dispersion treatment in a state where the dispersion resin A1 is contained. Therefore, the dispersion resin A1 does not necessarily function as a carbon black dispersant.

・ Pigment dispersion k2 (5 parts as pigment concentration) 33 parts ・ Dispersion resin A1 3 parts ・ Glycerin 10 parts ・ Ethylene glycol 5 parts ・ N-methylpyrrolidone 5 parts ・ Acetylenol EH (manufactured by Kawaken Fine Chemicals) 1 part ・ Ion exchange 43 parts of water

[Evaluation]
<Evaluation of ejection stability>
[Test A. Discharge stability test]
The ejection stability of the black ink K2 was evaluated by the following method and criteria. Using black ink K2, an image was formed on PR-101 (Canon), which is an inkjet photographic paper, with an inkjet printer PIXUS850i (Canon). In image formation, 2,000 sheets were continuously recorded. Then, the 2,000th sample of the test was taken out of the printed matter created by the continuous recording, and the optical density measurement was performed on the sample using a reflection densitometer RD-19I (manufactured by GretagMacbeth). . The optical density obtained by measuring the 2,000th sample is defined as OD _3, and the optical density measured by the same method as described above is defined as OD ₁ using the printed matter formed before the discharge durability test as a sample. From these values, ROD _{2 represented} by the following formula was determined. Then, using the value of ROD ₂ obtained was evaluated according to the following criteria. The evaluation results are shown in Table 10.
ROD ₂ = OD ₃ / OD ₁

(Evaluation criteria)
A: ROD ₂ > 0.9
○: 0.8 <ROD ₂ ≦ 0.9
Δ: 0.6 <ROD ₂ ≦ 0.8
×: ROD ₂ ≦ 0.6

<Test B. Storage stability test>
[Measurement of average particle size before and after storage test at 80 ° C.]
The storage stability of the ink was evaluated by the following method and criteria. Black ink K2 was placed in a sealed container and left in a constant temperature bath at 80 ° C. for 24 hours. The average particle diameter before and after this test was measured with a particle size distribution measuring device (FPAR-1000, manufactured by Otsuka Electronics). The average particle diameter PD ₁ (pre-test) obtained, the ratio of the PD ₂ (after test), obtains the RPD = PD ₂ / PD _1, using the obtained value was evaluated according to the following criteria. The evaluation results are shown in Table 10.

(Evaluation criteria)
A: 0.9 <RPD ≦ 1.2
○: 0.8 <RPD ≦ 0.9, 1.2 <RPD ≦ 1.4
Δ: 0.7 <RPD ≦ 0.8, 1.4 <RPD ≦ 1.8
×: RPD ≦ 0.7, 1.8 <RPD

上記のように、ブラックインクＫ２は、吐出安定性及び保存安定性に優れたインクであることが確認された。

As described above, it was confirmed that the black ink K2 is an ink excellent in ejection stability and storage stability.

[Example 11]
In this example, an example of an ink-jet pigment ink obtained by dispersing a pigment with the dispersion resin A1 used in Example 1 will be described.

(ink)
<Preparation of pigment dispersion k3>
・ Dispersion resin A1 15 parts ・ Potassium hydroxide 3 parts ・ Isopropyl alcohol 10 parts ・ Ion-exchanged water 57 parts

  First, the above components are mixed and heated to 70 ° C. in a water bath to completely dissolve the resin component. Next, 15 parts of carbon black (MCF88, manufactured by Mitsubishi Chemical) was added to this solution and premixed for 30 minutes. Thereafter, a dispersion treatment was performed under the same conditions as in the production method of the titanium oxide dispersion t1 described in Example 1 to obtain a pigment dispersion k3 in which carbon black was dispersed with the dispersion resin A1.

<Preparation of black ink K3>
Using the pigment dispersion k3 obtained above, components having the following composition ratios were mixed to obtain a black ink K3.
・ Pigment dispersion k3 (5 parts as pigment concentration) 33 parts ・ Glycerin 10 parts ・ Diethylene glycol monoethyl ether 5 parts ・ N-methylpyrrolidone 5 parts ・ Acetyleneol EH (manufactured by Kawaken Fine Chemicals) 1 part ・ Ion-exchanged water 46 parts

[Evaluation]
The black ink K3 was evaluated by the same method and standard as used in Reference Example 2 . The obtained results are shown in Table 11 below.

上記のように、ブラックインクＫ３は、吐出安定性及び保存安定性に非常に優れたインクであることが確認された。

As described above, it was confirmed that the black ink K3 is an ink excellent in ejection stability and storage stability.

[Comparative Example 1]
In this comparative example, a dispersion obtained by using a conventional dispersion resin having no annular structure segment will be described.

<Preparation of titanium oxide dispersion t7>
Titanium oxide dispersion t7 was prepared with the following composition according to Example 1 using John Krill 678 (manufactured by Johnson Polymer) as the dispersion resin.
・ Jonkrill 678 5 parts ・ Potassium hydroxide 1 part ・ Isopropyl alcohol 10 parts ・ Ion-exchanged water 69 parts ・ Titanium oxide particles (MT-100SA, manufactured by Teica) 15 parts

  The produced titanium oxide dispersion had an average particle size of 70 nm. This titanium oxide dispersion was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 12 below.

上記した通り、従来の分散樹脂で平均粒子径７０ｎｍの酸化チタンを分散させた比較例１の分散液は、保存安定性が不十分であった。本比較例と、実施例との比較から、本発明の分散樹脂は、従来の分散樹脂では得ることができなかった極めて高い保存安定性を有する微粒子分散体の提供を可能とすることが確認された。

As described above, the dispersion liquid of Comparative Example 1 in which titanium oxide having an average particle diameter of 70 nm was dispersed with a conventional dispersion resin had insufficient storage stability. From a comparison between this comparative example and the examples, it was confirmed that the dispersion resin of the present invention can provide a fine particle dispersion having extremely high storage stability that could not be obtained by a conventional dispersion resin. It was.

Claims (7)

A dispersion resin having a cyclic structure segment, which is a polymer that forms a cyclic structure in the structure,
The dispersion resin has a plurality of the cyclic structure segments whose number average molecular weight is 300 or more and 30000 or less , and each of the plurality of cyclic structure segments is a polymerized monomer having at least a hydrophobic functional group. Is obtained by
The acid value of the dispersion resin is 50 mgKOH / g or more and 300 mgKOH / g or less,
The monomer having a hydrophobic functional group is at least one vinyl compound selected from the group consisting of a vinyl compound having an aromatic functional group, an alkyl (meth) acrylate, and a (meth) acrylate having an alicyclic skeleton. Dispersing resin characterized by that.   The monomer having the hydrophobic functional group is styrene, methylstyrene, vinylnaphthalene, divinylbenzene, benzyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (Meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethyl-hexyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, iso The dispersion resin according to claim 1, which is at least one compound selected from the group consisting of bornyl acrylate and tricyclodecane dimethanol di (meth) acrylate. The dispersion resin according to claim 1 or 2 , wherein each of the plurality of cyclic structure segments is obtained by polymerizing a common monomer. The dispersion resin according to claim 1 or 2 , wherein the plurality of cyclic structure segments are obtained by polymerizing monomers different from each other. The dispersion resin according to any one of claims 1 to 4 , wherein the monomer having the hydrophobic functional group is 50% by mass or more of the monomer for constituting the cyclic structure segment. A dispersion comprising particles and a dispersion resin for dispersing the particles,
The particles are pigment particles;
A dispersion characterized in that the dispersion resin is the dispersion resin according to any one of claims 1 to 5 . An inkjet pigment ink comprising a pigment, a dispersion resin, water, and a water-soluble organic solvent, wherein the dispersion resin is the dispersion resin according to any one of claims 1 to 5. .