JP6323844B2 - Aqueous ink composition, image forming method, and print using the same - Google Patents

Description

  The present invention relates to a water-based ink composition, an image forming method, and a print using the same.

  The image recording method by the ink jet method is an image recording method in which an ink composition (ink) is ejected from a droplet ejection head based on an image data signal, and an image is directly formed on a recording medium such as paper. The ink jet system does not require a printing plate, and has an advantage that ink can be used efficiently and running cost is low because ink is ejected only to the required image area. Furthermore, an inkjet image recording apparatus is relatively inexpensive, can be miniaturized, and has low noise. As described above, the ink jet method is excellent in various respects as an image recording method.

Among the ink compositions used for image recording by the ink jet method, the water-based ink composition has low odor and is excellent in safety, so that it is widely used not only for industrial use but also for home use. In recent years, with the advancement of inkjet technology, it has become possible to easily create high-definition, high-color, high-quality images. For this reason, it is possible to easily duplicate a printed matter, and it is desired to develop a genuine appraisal means in order to prevent unauthorized duplication. In addition, with the automation of product management and delivery, the development of means for entering information on products and cargo packaging without deteriorating the appearance of the printed object is also underway. As an ink composition suitable for such an application, a colorless ink composition containing an invisible fluorescent dye can be given. In this method, information can be written without damaging the appearance by irradiating light of a specific wavelength and reading a light emission pattern, so authenticity information, product information, transportation information, etc. are printed invisible and read. It is possible.
For example, Patent Document 1 discloses an aqueous ink using a fluorescent dye such as rhodamine B. This water-based ink satisfies various characteristics as ink for inkjet printers, and information recorded on recording paper cannot be identified with the naked eye, and emits blue fluorescence when irradiated with black light. Further, this ink hardly causes nozzle clogging.
Patent Document 2 discloses an aqueous ink composition containing a fluorescent colorant, water, a water-soluble organic solvent, and polymer fine particles having a film-forming ability. Furthermore, it is described that the fluorescent colorant may be chemically bonded to the polymer fine particles. According to this invention, it is described that sufficient fluorescence intensity and abrasion resistance can be obtained even when an image is recorded on a penetrating substrate.

JP 58-49765 A JP 2000-303008 A

However, in the water-based ink described in Patent Document 1, since the fluorescent dye is a low molecule, if the binder is not used in combination, the image may be peeled off or the dye may penetrate into the recording medium and the ink may bleed. There was a problem with the stability of the image. The ink composition described in Patent Document 2 is a polymer fine particle having a film-forming ability, and finally forms a film. Therefore, the glass transition temperature needs to be lowered to 30 ° C. or lower, and a process for coating is necessary. It was. In addition, the water-based inks described in the above two patent documents have improved abrasion resistance in the permeation base, but when printing on a non-penetration base, the ink composition does not fix to the recording medium, There was a problem that it was inferior in abrasion resistance. Furthermore, when printing is performed on a substrate such as inkjet paper where bleeding is difficult to suppress, there is a problem that blurring occurs and a clear image cannot be obtained.
Furthermore, when the processing time for drying and fixing ink is shortened as the speed of the apparatus increases, the next recording medium is overlaid on the recording medium on which the recorded image is not dried. As a result, the previous recorded image is transferred to the back surface of the next recording medium, or a phenomenon called stacker blocking occurs in which the recording media stick to each other. Resistance to such a phenomenon is called blocking resistance. In order to prevent this, ink that dries and fixes quickly is required.

  The present invention has been made in view of the above circumstances, and is a water-based ink composition that has a fluorescence emission property, provides a clear image with little blur when recording an image, and is non-permeable. An object of the present invention is to provide a water-based ink composition that is excellent in image abrasion resistance even when printed on a base material, and excellent in image fastness and blocking resistance under high humidity conditions. Another object of the present invention is to provide an image forming method using the water-based ink composition of the present invention, a water-based ink composition of the present invention, and a print obtained by the image forming method.

  When the present inventors use an ink composition in which a conventional fluorescent colorant (fluorescent dye) or pigment is dispersed in a solvent or an ink composition in which polymer fine particles are incorporated as an emulsion or latex, these ink compositions are used. The phenomenon on the substrate of the object was examined in detail. As a result, the present invention is based on the knowledge that an ink composition is excellent in various properties by incorporating a polymer in which a fluorescent dye is chemically bonded to the composition, that is, a polymer fluorescent dye in a dissolved state. It came.

The above problem has been solved by the following means.
<1> contains an ink-soluble polymer fluorescent dye having a fluorescent site in a repeating unit, an organic solvent, and water , and does not substantially absorb visible light ; and
The water-based ink composition in which the polymeric fluorescent dye has a repeating unit represented by the following general formula (1) .

In general formula (1), R ¹ represents a hydrogen atom or a methyl group, X represents a phenylene group, —COO— or —CONR ² —, and R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. . Y represents a single bond or a linear or branched alkylene group having 1 to 8 carbon atoms. In the alkylene group, —O—, —OC (═O) —, —CH (OH) —, —NH—, -NHC (= O)-may be included. Z represents a fluorescent dye residue.
<2> The water-based ink composition according to <1>, wherein the glass transition temperature of the polymeric fluorescent dye is 40 ° C. or higher.
<3> The aqueous ink composition according to <1> or <2>, wherein the content of the polymeric fluorescent dye is 0.5% by mass or more and 5.0% by mass or less with respect to the total mass of the aqueous ink composition. .
<4 > The content of the repeating unit represented by the general formula (1) in the polymer fluorescent dye is 5% by mass or more and 30% by mass or less with respect to all the repeating units constituting the polymer fluorescent dye < The water-based ink composition according to any one of 1> to <3> .
< 5 > The water-based ink composition according to any one of <1> to < 4 >, which is for inkjet.
< 6 > An ink application step of applying the aqueous ink composition according to any one of <1> to < 5 > onto a recording medium;
And a step of drying the aqueous ink composition applied on the recording medium .

In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
In the present specification, “(meth) acrylate” represents both and / or one of acrylate and methacrylate, and “(meth) acryl” represents both and / or one of acrylic and methacrylic.
In this specification, the term “process” is not limited to an independent process, and is included in the term if the intended action of the process is achieved even when it cannot be clearly distinguished from other processes. .

According to the present invention, it is possible to provide an aqueous ink composition in which image bleeding is suppressed, excellent in abrasion resistance, and further, anti-blocking property and image fastness when stored under high humidity conditions. it can.
Further, according to the present invention, it is possible to form an image in which bleeding of an image to be recorded is suppressed, excellent in abrasion resistance, blocking resistance, and image fastness when stored under high humidity conditions. It is possible to provide an image forming method and a printed matter in which bleeding is suppressed, excellent in abrasion resistance, excellent in blocking resistance, fastness and gloss.

<< Water-based ink composition >>
The water-based ink composition of the present invention (hereinafter also simply referred to as “ink composition” or “ink”) has an ink-soluble polymer fluorescent dye (hereinafter referred to as “polymer fluorescent dye”) having a fluorescent site in a repeating unit. A water-based ink composition that contains an organic solvent and water and does not substantially absorb visible light.

In the present invention, the “ink-soluble polymer” is not present in the water-based ink composition in the form of particles or fine particles, but is dissolved in the mixed medium of the organic solvent and water in the water-based ink composition. The polymer is not formed, and the particle size is not observed when the ink composition is measured with a particle size measuring device such as a dynamic light scattering device. In the present invention, a dense particle size analyzer FPAR-1000 manufactured by Otsuka Electronics Co., Ltd. was used. As the numerical values of the viscosity and the refractive index used for the measurement, the numerical values of the refractive index and the viscosity of the liquid component in the ink composition were used.
That is, the ink-soluble polymer is not dispersed in the form of fine particles dispersed in a surfactant and present in the form of fine particles dispersed in the composition, but is a latex or emulsified dispersion in which water-insoluble fine particles are dispersed in the composition. It is different from the embodiment including the object.

  Further, “substantially does not absorb visible light” means that it does not substantially absorb light in the visible light wavelength region. In the present invention, an ultraviolet-visible spectrophotometer is used, and it is 2000 times as large as the ink composition. When the absorbance in the visible light wavelength region (380 to 780 nm) of the diluted product is measured, it means that the absorbance value is less than 0.2. In this invention, the value measured in the range of 380 nm-780 nm using Shimadzu Corp. make and ultraviolet visible spectrophotometer UV-2550 is used. When printing is performed using such an ink composition, it is possible to obtain a printed material in which the printed portion and the non-printed portion cannot be distinguished under the condition where the excitation light is not irradiated. In this specification, the fact that such a printed part cannot be distinguished from a non-printed part may be described as “invisible”.

  As a result, when printing is performed using the ink composition of the present invention, since the polymeric fluorescent dye is contained in the ink composition, the printed portion is invisible when the printed material is observed with visible light. However, when the printed matter is irradiated with excitation light such as ultraviolet light, the fluorescent portion in the polymer fluorescent dye emits fluorescence, and necessary character information and image information can be read out.

In the present invention, by using an ink-soluble polymer fluorescent dye, the mechanism of action that cannot be obtained with a fine particle dispersion of the polymer fluorescent dye is not clear, but is presumed as follows.
In ink-jet printing, in order to obtain a high-definition image without bleeding, it is necessary to prevent liquid diffusion in the in-plane direction of the base material in a permeable base material such as paper. When low-molecular fluorescent dyes or particulate fluorescent dyes are used for low-viscosity inks, it is estimated that bleeding occurs because the ink droplets maintain low viscosity after landing on the substrate. Is done.
On the other hand, when the ink-soluble polymer fluorescent dye of the present invention is used, when the ink droplets land on the substrate, the viscosity rapidly increases with the progress of penetration and drying. It is presumed that the penetration of the ink is suppressed and the bleeding can be reduced. Further, even when a non-permeable base material such as vinyl chloride is used, bleeding can be suppressed due to the property that the viscosity rapidly increases. Furthermore, when printed on a non-permeable substrate, the polymer fluorescent dye is a polymer compound, so that it has film-forming properties and is excellent in adhesion to printed matter and abrasion resistance. In addition, when water-soluble polymer compounds are dried, relatively low hydrophilic sites in the polymer chain tend to gather at the air interface, and since they are polymers, the viscosity of the material is high and the diffusibility is reduced. Therefore, it is considered that bleeding under high humidity conditions is also suppressed.

<Ink-soluble polymer fluorescent dye having a fluorescent site in the repeating unit>
The ink composition of the present invention contains at least an ink-soluble polymer fluorescent dye having a fluorescent site in a repeating unit.
The polymeric fluorescent dye of the present invention is a polymeric compound that has a fluorescent site in its repeating unit and dissolves in the ink composition. By dissolving in the ink composition, the viscosity increases in the drying step, and bleeding can be suppressed. The polymer compound in the present invention refers to a compound in which three or more monomer units are bonded by a covalent bond and does not have a single molecular weight.

The polymer compound of the present invention has a site emitting fluorescence in a repeating unit. A known fluorescent dye that does not substantially absorb visible light can be arbitrarily selected as the site that emits fluorescence, and is not particularly limited. By dissolving in a water-based ink a polymer fluorescent dye obtained by introducing a fluorescent dye into a polymer compound, unevenness caused by precipitation in the ink or crystallization during drying can be effectively suppressed. As the fluorescent dye to be introduced into the polymer compound, an organic fluorescent dye is preferable, and among them, an acridone dye, a fluorescein dye, a rhodamine dye, a 9-hydroxyphenanthrene dye, an acridine dye, a coumarin dye, a benzofurazan dye, a resorufin dye, and a dansyl dye. Benzofuran dye, cyanine dye, merocyanine dye, rhodacyanine dye, oxonol dye, styryl dye, pyromethene dye, and the like.
Among these, an acridone dye, a fluorescein dye, a rhodamine dye, a 9-hydroxyphenanthrene dye, a coumarin dye, a benzofuran dye, a merocyanine dye, a styryl dye, and an acridine dye are preferable, and an acridone dye, a coumarin dye, and a fluorescein dye are more preferable.

  The polymeric fluorescent dye in the present invention is preferably a polymeric compound having a repeating unit represented by the following general formula (1).

In General Formula (1), R ¹ represents a hydrogen atom or a methyl group, and X represents a phenylene group, —COO—, or —CONR ² —. Here, R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Y represents a single bond or a linear or branched alkylene group having 1 to 8 carbon atoms, and in the alkylene group, —O—, —OC (═O) —, —CH (OH) —, —NH— or -NHC (= O)-may be included. Z represents a fluorescent dye residue.

  The polymeric fluorescent dye in the present invention is prepared by synthesizing a monomer having an ethylenically unsaturated group (for example, a vinyl group, acryloyl or methacryloyl group) having a fluorescent dye portion that gives the repeating unit represented by the general formula (1). Depending on the case, it is preferably produced by copolymerization with other vinyl monomers.

R ¹ is preferably a hydrogen atom.

X represents a phenylene group, —COO—, or —CONR ² —. Here, R ² represents a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms, preferably a hydrogen atom. X is preferably a phenylene group or —COO— from the viewpoint of polymerizability.

  Y represents a single bond, a linear or branched alkylene group having 1 to 8 carbon atoms, and in the alkylene group, —O—, —OC (═O) —, —CH (OH) —, —NH—, — NHC (= O)-may be contained. 1-6 are more preferable and, as for carbon number of Y, 1-4 are the most preferable.

The repeating unit represented by the general formula (1) in the present invention is a polymerization of a monomer having an ethylenically unsaturated group (for example, a vinyl group, acryloyl or methacryloyl group) that gives the repeating unit represented by the general formula (1). Or it can synthesize | combine by reaction with the polymer which has the reactive functional group (beta) which reacts with this specific functional group (alpha) in the side chain, and the compound which has a fluorescent dye part and specific functional group (alpha).
In the former case, a monomer having an ethylenically unsaturated group and a fluorescent dye portion is synthesized in advance. This monomer includes, for example, a fluorescent dye having a reactive functional group γ, a monomer having a reactive functional group δ and an ethylenically unsaturated group that react with the reactive functional group γ by an addition reaction, a substitution reaction, or a condensation reaction. Can be synthesized.
On the other hand, in the latter case, a polymer is synthesized in advance with a monomer unit having a reactive functional group β, and a fluorescent dye having a specific functional group α that reacts with the reactive functional group β by an addition reaction, a substitution reaction or a condensation reaction; By this reaction, a fluorescent dye site is introduced into the polymer.
That is, Y is a partial structure formed by the reaction of a reactive functional group site in the monomer or polymer and a reactive site in the fluorescent dye or a structure containing this.

Preferable specific examples of Y include a single bond, a linear or branched alkyl group having 1 to 8 carbon atoms, —CH ₂ CH ₂ O—, —CH ₂ CH ₂ OCH ₂ —, —CH ₂ CH (OH) CH. ₂ O—, —CH ₂ CH (OH) CH ₂ NH—, —CH ₂ CH (OH) CH ₂ OCH ₂ —, —CH ₂ OCH ₂ CH (OH) CH ₂ O—, —CH ₂ CH ₂ OCH _{2 CH (OH) CH 2 O -} , - CH 2 CH 2 C (= O) OCH 2 CH (OH) CH 2 O -, - CH 2 CH 2 OC (= O) CH 2 CH 2 C (= O) OCH ₂ CH (OH) CH ₂ O—, —CH ₂ CH ₂ NHC (═O) OCH ₂ —, —CH ₂ CH ₂ NHC (═O) OCH ₂ CH ₂ —, —CH ₂ CH ₂ NHC (═O) NH—, —CH ₂ CH ₂ NHC (═O) NHCH ₂ — Etc.

Z represents a fluorescent dye residue. Examples of the fluorescent dye residue include groups obtained by removing one hydrogen atom from the fluorescent dyes mentioned above.
Specifically, an acridone dye, fluorescein dye, rhodamine dye, 9-hydroxyphenanthrene dye, acridine dye, coumarin dye, benzofurazan dye, resorufin dye, dansyl dye, benzofuran dye, cyanine dye, merocyanine dye, rhodacyanine dye, oxonol dye, A group obtained by removing one hydrogen atom from a known fluorescent dye such as a styryl dye and a pyromethene dye is preferable. Among these, an acridone dye, a fluorescein dye, a rhodamine dye, a 9-hydroxyphenanthrene dye, a coumarin dye, a benzofuran dye, and a merocyanine dye A group obtained by removing one hydrogen atom from a styryl dye or acridine dye is more preferred, and a group obtained by removing one hydrogen atom from an acridone dye, coumarin dye or fluorescein dye is more preferred.

  Z is preferably a group represented by the following general formulas (a-1) to (a-5).

In general formulas (a-1) to (a-5), Ra to Rc each independently represents an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom. m1 and m2 each independently represents an integer of 0 to 4. m3 represents an integer of 0-2. L ¹ represents a single bond or a phenylene group. The ring to which L ¹ is bonded may be any of Cy ^{1 to} Cy ³ . A ¹ is = O or ^{= N + (Rd1) (Rd2} ) X α - represents, the X _alpha represents a halogen atom. A ² represents —OH or —N (Rd 1) (Rd 2). Here, Rd1 and Rd2 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. B1 represents a carbon atom or a nitrogen atom.

  Specific examples of the repeating unit of the general formula (1) in the present invention include the following structures, but the present invention is not limited thereto.

  The content of the repeating unit of the general formula (1) that can be used in the polymer fluorescent dye used in the present invention is 5% by mass to 30% by mass with respect to all the repeating units constituting the polymer fluorescent dye. The range is preferable, and the range of 5% by mass to 20% by mass is more preferable.

  The polymeric fluorescent dye of the present invention preferably further has a repeating unit derived from a hydrophilic monomer in order to impart solubility to the aqueous ink composition.

(Repeating unit derived from hydrophilic monomer)
The polymeric fluorescent dye used in the present invention preferably contains a repeating unit derived from a hydrophilic monomer in addition to the repeating unit represented by the general formula (1).
The hydrophilic monomer is a monomer containing a hydrophilic group and is not particularly limited as long as the monomer itself is a monomer that dissolves in water. In the present invention, it is preferable that at least one type of repeating unit derived from a hydrophilic monomer is included, but two or more types may be included.
There is no restriction | limiting in particular as a hydrophilic group which a hydrophilic monomer has, A dissociative group or a nonionic hydrophilic group (For example, group containing a hydroxyl group or an ether bond) may be sufficient.
From the viewpoint of the solubility of the polymeric fluorescent dye in the ink composition, at least one of the hydrophilic groups of the hydrophilic monomer in the present invention is preferably a dissociable hydrophilic group, and more preferably an anionic dissociative group. preferable.
Examples of the anionic dissociable group include a carboxy group, a phosphate group, a sulfo group, or a salt thereof. Among them, a carboxy group, a sulfo group, or a salt thereof is preferable, and a carboxy group or a salt thereof is further included. preferable.

  These salts are preferably lithium salts, potassium salts, and sodium salts, more preferably potassium salts and sodium salts, and even more preferably sodium salts.

From the viewpoint of self-dispersibility, the hydrophilic monomer in the present invention is preferably a monomer containing a dissociable hydrophilic group, and is preferably a dissociable group-containing monomer having a dissociable group and an ethylenically unsaturated bond.
Examples of the dissociable group-containing monomer include an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer, and an unsaturated phosphoric acid monomer.

Among such monomers, as the unsaturated carboxylic acid monomer having a carboxy group as a hydrophilic group, specifically, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid 2-methacryloyloxymethyl succinic acid or a salt thereof.
Specific examples of the monomer having a sulfonic acid group as a hydrophilic group include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, and bis (3-sulfopropyl). ) Itaconic acid esters or salts thereof.
Specific examples of monomers having a phosphate group as a hydrophilic group include vinyl phosphonic acid, vinyl phosphate, bis (methacryloyloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl -2-acryloyloxyethyl phosphate or a salt thereof.
Among these dissociable group-containing monomers, a monomer having a carboxy group or a salt thereof is preferable from the viewpoint of the stability of the obtained ink composition and ejection stability, and acrylic acid or a salt thereof and methacrylic acid or a salt thereof. Monomers selected from salts are more preferred, and methacrylic acid or salts thereof are particularly preferred.

Examples of the monomer having a non-dissociable nonionic hydrophilic group that can be contained in the polymer fluorescent dye include 2-methoxyethyl acrylate, 2- (2-methoxyethoxy) ethyl acrylate, 2- (2-methoxy). Ethoxy) ethyl methacrylate, ethoxytriethylene glycol methacrylate, methoxypolyethylene glycol (molecular weight 200-1000) monomethacrylate, polyethylene glycol (molecular weight 200-1000) monomethacrylate and other (poly) ethyleneoxy groups or ethylene containing polypropyleneoxy groups Unsaturated monomers, hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate Rate, hydroxypentyl (meth) acrylate, ethylenically unsaturated monomer having a hydroxyl group such as hydroxymethyl (meth) acrylate.
As the monomer having a nonionic hydrophilic group that can be contained in the polymer fluorescent dye, an ethylenically unsaturated monomer having a terminal alkyl ether is preferable to an ethylenically unsaturated monomer having a terminal hydroxyl group.

As a repeating unit derived from a hydrophilic monomer in the present invention, an embodiment containing only a repeating unit derived from a hydrophilic monomer having an anionic dissociable group, and a repeating derived from a hydrophilic monomer having an anionic dissociative group It is preferable that it is either of the aspects containing both a unit and the repeating unit derived from the hydrophilic monomer which has a nonionic hydrophilic group.
Also, an embodiment containing two or more repeating units derived from a hydrophilic monomer having an anionic dissociable group, a repeating unit derived from a hydrophilic monomer having an anionic dissociative group, and a nonionic hydrophilic group It is also preferable that two or more repeating units derived from hydrophilic monomers are used in combination.

The content of the repeating unit derived from the hydrophilic monomer that can be contained in the polymer fluorescent dye is preferably in the range of 5% by mass to 50% by mass with respect to all the repeating units constituting the polymer fluorescent dye, A range of 5% by mass to 20% by mass is more preferable.
When the content of the repeating unit derived from the hydrophilic monomer is less than 5% by mass, the solubility of the polymeric fluorescent dye in the ink composition tends to decrease, and the range is from 5% by mass to 50% by mass. There is a tendency to obtain an ink composition having a viscosity exhibiting good ejection properties.
In the present invention, it is particularly preferable to use a monomer having a carboxy group as a hydrophilic group and a monomer having a carboxy group salt.
Therefore, among the repeating units derived from the above hydrophilic monomer, the molar ratio of the monomer having a carboxy group and the monomer having a carboxy group salt (mol of monomer having carboxy group: mol of monomer having salt of carboxy group) Is preferably 60:40 to 0: 100, and more preferably 50:50 to 5:95.

(Other repeat units)
The polymeric fluorescent dye in the present invention preferably contains a repeating unit derived from a monomer having no hydrophilic group in addition to the repeating unit derived from the hydrophilic monomer.
The repeating unit derived from a monomer having no hydrophilic group (hereinafter, appropriately referred to as “other repeating unit”) is not particularly limited as long as it is a repeating unit derived from a monomer having no hydrophilic group in the molecule. . The other repeating unit may contain only 1 type and may contain 2 or more types. As a monomer which does not have a hydrophilic group, the monomer which contains at least 1 of a chain aliphatic group, a cyclic aliphatic group, and an aromatic group in a molecule | numerator, and does not contain a hydrophilic group is mentioned, for example. In addition, since the polymeric fluorescent dye used in the present invention does not have a cross-linked structure, it is necessary that other repeating units do not contain a cross-linkable group.

As such a monomer, a monomer having an ethylenically unsaturated group is preferable, and the total carbon number of the monomer is preferably 4 to 12, more preferably 4 to 10, and still more preferably 4 to 8.
As such a monomer group, a styrene compound, alkyl (meth) acrylate, aryl (meth) acrylate, (meth) acrylamide and the like are preferable.

  Specific examples include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, and t-butyl. Alkyl (meth) acrylates such as (meth) acrylate, hexyl (meth) acrylate, and ethylhexyl (meth) acrylate; aromatic ring-containing (meth) acrylates such as benzyl (meth) acrylate and phenoxyethyl (meth) acrylate; styrene, α- Styrenes such as methylstyrene and chlorostyrene; Dialkylaminoalkyl (meth) acrylates such as dimethylaminoethyl (meth) acrylate; N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) N-hydroxyalkyl (meth) acrylamides such as chloramide and N-hydroxybutyl (meth) acrylamide; N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N- (n-, iso) butoxymethyl ( (Meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide, N-alkoxyalkyl (meth) acrylamide such as N- (n-, iso) butoxyethyl (meth) acrylamide, etc. ) Acrylamide and the like.

The polymeric fluorescent dye in the present invention is a copolymer of a monomer having an ethylenically unsaturated group (for example, an acrylic group, a methacryl group, or a vinyl group of styrene, etc.) due to the dischargeability and production suitability of the ink composition. preferable.
The polymeric fluorescent dye in the present invention can be obtained, for example, by a known polymerization method such as a radical polymerization method using a monomer having a hydrophilic group and a monomer having no hydrophilic group. The polymeric fluorescent dye in the present invention can also be obtained by neutralizing a part of the dissociable hydrophilic group among the hydrophilic groups with an alkali metal hydroxide or the like as necessary. A known radical polymerization method can be used for the polymeric fluorescent dye of the present invention without limitation.

  The polymeric fluorescent dye preferably has a weight average molecular weight of 3,000 to 100,000, more preferably a weight average molecular weight of 5,000 to 80,000, and 5,000 to 50,000. It is particularly preferred. When adjusted to this range, it tends to be excellent in abrasion resistance and ejection properties and to suppress bleeding.

  The weight average molecular weight is measured by gel permeation chromatography (GPC). For GPC measurement, for example, HLC-8020GPC (manufactured by Tosoh Corporation) is used, TSKgel SuperHZM-H, TSKgel SuperHZ4000, TSKgel SuperHZ200 (4.6 mm IDφ15 cm, manufactured by Tosoh Corporation) are used as columns and THF (tetrahydrofuran) as an eluent. ) Can be used.

The glass transition temperature (Tg) of the polymeric fluorescent dye of the present invention is preferably 40 ° C or higher, more preferably 50 ° C or higher, further preferably 60 ° C or higher, and particularly preferably 60 ° C to 130 ° C. When the glass transition temperature is within the above range, the blocking resistance and rubbing resistance of the image are improved, and the image preservability tends to be excellent.
The glass transition temperature can be measured as follows.
The glass transition temperature of the polymer compound in the present invention indicates a numerical value measured by a differential scanning calorimeter DSC (Differential scanning calorimetry). In the present invention, by using DSC-6220 manufactured by Seiko Instruments Inc., a measurement sample of 5.0 mg is obtained by measuring at a temperature rising rate of 10 ° C./min in a temperature range of −100 ° C. to 150 ° C. The obtained value (glass transition temperature) was used.

  The polymeric fluorescent dye in the invention is preferably contained in the range of 0.05% by mass to 20% by mass, more preferably 1% by mass to 15% by mass, and more preferably 1% by mass to 10% by mass with respect to the total amount of the ink composition. Mass% is most preferred. Within this range, both color developability and dischargeability can be achieved. The ink composition of the present invention needs to be substantially invisible when the print is not irradiated with excitation light. However, the polymer fluorescent dye that absorbs visible light is low so as to be substantially invisible. It can also be used by using in concentration.

<Organic solvent>
The ink composition of the present invention contains an organic solvent together with water described later as a main solvent.
The organic solvent in the present invention is preferably a water-soluble organic solvent that is miscible with water, and refers to an organic solvent that is miscible with water at 25 ° C. Preferred examples of the water-soluble organic solvent used in the present invention include alcohol solvents, ketone solvents, ether solvents and amide solvents.

Examples of the alcohol solvent suitably used in the present invention include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, isobutanol, sec-butanol, tert-butanol, pentanol, hexanol, cyclohexanol, Examples thereof include benzyl alcohol, glycols, glycol monoalkyl ethers, and preferably include isopropyl alcohol, n-butanol, tert-butanol, glycols, glycol monoalkyl ethers and the like.
As glycols, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butylene glycol, dibutylene glycol, and 2-methylpropanediol are preferable. As glycol monoethers, the above glycols Of these, monomethyl ether, monoethyl ether, monopropyl ether and monobutyl ether are preferred.
Examples of the ether solvent include dibutyl ether and dioxane.
Examples of amide solvents include dimethylformamide, dimethylacetamide, 2-pyrrolidone, N-methylpyrrolidone, N-ethylpyrrolidone and the like.
Of these, 2-pyrrolidone is particularly preferable from the viewpoint of increasing the solubility of the polymer dye, and glycols such as 2-methylpropanediol and glycol monoalkyl ethers are preferable from the viewpoint of increasing the dischargeability.

The water-soluble organic solvent contained in the ink composition of the present invention may be only one type or a combination of two or more types, but when they are combined, it is preferable to select those having good compatibility with each other. .
The content of the water-soluble organic solvent in the ink composition of the present invention needs to be in the range of 5% by mass to 40% by mass with respect to the total amount of the ink composition, and is in the range of 5% by mass to 35% by mass. It is preferable that it is in the range of 10% by mass to 30% by mass.

<Water>
The ink composition of the present invention contains water.
As water, it is preferable to use ion-exchanged water, distilled water or the like that does not contain impurities.
The content of water in the ink composition of the present invention is appropriately selected according to the content of other components, but is generally 20% by mass to 80% by mass with respect to the total mass of the ink composition. It is preferable that it is 30 mass%-80 mass%, and it is more preferable that it is 40 mass%-70 mass%.

<Other ingredients>
In addition to the above-described components, the ink composition of the present invention includes ejection stability, compatibility with print heads and ink cartridges, storage stability, and image storage stability, as long as the effects of the present invention are not impaired. Depending on the purpose of improving various other performances, various known additives such as viscosity modifiers, surface tension modifiers, specific resistance modifiers, film forming agents, dispersants, surfactants, ultraviolet absorbers, oxidation agents An inhibitor, a discoloration inhibitor, a fungicide, a rust inhibitor, a solid wetting agent, silica fine particles, a pH adjuster and the like can be appropriately selected and used.

(Thickener)
A thickener may be used in the ink composition of the present invention for the purpose of adjusting the viscosity. The thickener that can be used in the present invention is preferably a compound containing a basic group or an acidic group.
As a basic group which a thickener has, the amino group which may have a substituent, a quaternary ammonium group etc. can be mentioned, for example. Among these, from the viewpoint of ink dispersion stability, a thickener having an amino group is preferable.
Moreover, as an acidic group which a thickener has, a carboxy group, a phosphoric acid group, a phosphonic acid group, a sulfonic acid group, a sulfonamide group etc. can be mentioned, for example. Among these, from the viewpoint of ink dispersion stability, a thickener having a carboxy group or a sulfonic acid group is preferable.

The thickener having a basic group that can be used in the present invention only needs to have at least one basic functional group. Among them, the amine value is preferably 10 mgKOH / g or more, more preferably 20 mgKOH / g or more, and further preferably 40 mgKOH / g or more.
Moreover, the thickener which has an acidic group should just have at least 1 sort (s) of acidic functional group. Especially, it is preferable that an acid value is 10 mgKOH / g or more, It is more preferable that it is 20 mgKOH / g or more, It is still more preferable that it is 40 mgKOH / g or more.
Here, the amine value indicates the total amount of 1, 2, and tertiary amines as basic groups, and the number of mg of KOH equivalent to hydrochloric acid required to neutralize all basic groups in 1 g of a sample. It is represented by. The acid value is the number of mg of KOH required to neutralize all the acidic groups contained in 1 g of the sample.

When the thickener that can be used in the present invention contains a basic group, from the viewpoint of ink dispersion stability, the pH of the ink composition is preferably 7.5 or more, and is 8.0 to 9.0. More preferably.
When the thickener that can be used in the present invention contains an acidic group, the pH of the ink composition is preferably 6.5 or less from the viewpoint of ink dispersion stability, and is preferably 5.0 to 6.0. It is more preferable that

Thickeners that can be used in the present invention may be used alone or in combination of two or more.
The content of the thickener in the ink composition can be appropriately selected according to the type of the thickener. The addition rate of the thickener in the ink composition can be, for example, 0.01% by mass to 20% by mass. Among these, from the viewpoint of ejection stability, it is preferably 0.01% by mass to 5% by mass, more preferably 0.1% by mass to 3% by mass, and 0.1% by mass to 2% by mass. More preferably.

(Nonionic surfactant)
The aqueous ink composition of the present invention preferably contains at least one nonionic surfactant. The surface tension of the ink composition can be adjusted by adding a nonionic surfactant.
The addition amount of the nonionic surfactant is preferably an amount for adjusting the surface tension of the ink composition of the present invention to 20 mN / m to 60 mN / m in order to drop the ink composition well by the ink jet method. The amount is preferably an amount that can be adjusted to 20 mN / m to 45 mN / m, and more preferably an amount that can be adjusted to 25 mN / m to 40 mN / m.

Specific examples of the nonionic surfactant that can be used in the present invention include, for example, polyoxyethylene lauryl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene oleyl phenyl ether, polyoxyethylene nonyl phenyl ether, oxyethylene oxypropylene Block copolymer, t-octylphenoxyethyl polyethoxyethanol, nonylphenoxyethyl polyethoxyethanol, acetylene-based polyoxyethylene oxide surfactant SURFYNOLS (Air Products & Chemicals), and acetylene glycol-based surfactant Olphine E1010 (Nisshin Chemical Industries ( Etc.).
Only one type of nonionic surfactant may be used, or two or more types may be selected and used in combination. A preferred nonionic surfactant is an acetylene-based polyoxyethylene oxide surfactant.
The addition rate of the nonionic surfactant to be added to the ink composition in the invention is not particularly limited as long as it is an amount suitable for the adjustment of the surface tension, but when added, from the viewpoint of the effect. It is preferable that it is 1 mass% or more, More preferably, it is 1 mass%-10 mass%, More preferably, it is 1 mass%-3 mass%.

In the ink composition of the present invention, a fluorine-based surfactant having a fluorinated alkyl group may be preferably used for the purpose of improving dischargeability. Inclusion of a fluorosurfactant can be expected to improve ejection properties and adhesion to a recording medium. Examples of the fluorosurfactant include surfactants described in JP-A-2002-277862, and the following commercially available surfactants can be used as they are.
Examples of commercially available surfactants that can be used include ZONYL FSN (manufactured by fluorinated surfactant Aldrich), MegaFuck F171, F173, F176, F189, R08 (manufactured by Dainippon Ink & Chemicals, Inc.), Surflon S- Fluorine-based surfactants such as 382, SC101, 102, 103, 104, 105, 106 (Asahi Glass Co., Ltd.) can be used.

<Method for Preparing Ink Composition>
The ink composition according to the present invention is not particularly limited, and each component is used in a container drive medium mill such as a ball mill, a centrifugal mill, and a planetary ball mill, a high-speed rotation mill such as a sand mill, and a medium agitation mill such as a stirring tank mill. The mixture can be prepared by stirring, mixing, and if necessary, stirring, mixing, and dispersing with a simple disperser such as a disper. About the addition order of each component, it is arbitrary. Preferably, the azo pigment, the polymer dispersant and the organic solvent are premixed and then subjected to a dispersion treatment, and the obtained dispersion is mixed with the resin and the organic solvent. In this case, at the time of addition or after addition, the mixture is uniformly mixed with a simple stirrer such as a three-one motor, a magnetic stirrer, a disper, or a homogenizer. You may mix using mixers, such as a line mixer. Further, in order to make the dispersed particles finer, they may be mixed using a dispersing machine such as a bead mill or a high-pressure jet mill. Depending on the type of pigment or polymer dispersant, a resin may be added during premixing before pigment dispersion.
In addition, after the ink composition is prepared, it is preferable to remove coarse particles or the like that may reduce the dischargeability by filtering.

  As described above, the ink composition of the present invention preferably has a surface tension at 25 ° C. of 20 mN / m to 60 mN / m, more preferably 20 mN / m to 45 mN / m, still more preferably 25 mN / m to 40 mN / m. The surface tension is measured under the condition of 25 ° C. using an Automatic Surface Tensiometer CBVP-Z [manufactured by Kyowa Interface Science Co., Ltd.]. Moreover, 1-40 mPa * s is preferable and, as for a viscosity, 3-30 mPa * s is more preferable. The viscosity of the ink composition is measured using a VISCOMETER TV-22 (manufactured by TOKI SANGYOCO. LTD) at 25 ° C.

<Image forming method>
The image forming method of the present invention includes an ink application step of applying an aqueous ink composition onto a recording medium, and a step of drying the aqueous ink composition (a drying step of reducing water in the applied ink composition). Including.
By performing these steps, an image of the ink composition fixed on the recording medium is formed.
It is preferable to perform a drying process in the temperature range of 30 to 70 degreeC.
The ink composition of the present invention can form an image excellent in gloss and fixability to a recording medium even when dried at a low temperature. Usually, drying is performed at a heating temperature of about 30 ° C. to 110 ° C. When drying at a low temperature of 70 ° C. or lower, for example, a resin sheet or a paper laminated with a resin is used as a recording medium described later. In addition, the influence on the recording medium due to heating can be reduced.

(Ink application process)
Hereinafter, the ink application process in the image forming method of the present invention will be described. The ink application process in the present invention is not limited as long as it is a process of applying an ink composition onto a recording medium.
In the image forming method of the present invention, it is preferable to eject the ink composition using an ink jet recording apparatus, and the ink jet recording apparatus that can be used is not particularly limited, and is a known ink jet recording capable of achieving a target resolution. An apparatus can be arbitrarily selected and used. That is, any known inkjet recording apparatus including a commercially available product can discharge the ink composition onto the recording medium in the image forming method of the present invention.

Examples of the ink jet recording apparatus that can be used in the image forming method of the present invention include an apparatus including an ink supply system, a temperature sensor, and a heating unit.
The ink supply system includes, for example, an original tank containing the ink composition of the present invention, a supply pipe, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head. The piezo-type inkjet head preferably has a multi-size dot of 1 to 100 pl, more preferably 8 to 30 pl, preferably 320 × 320 to 4,000 × 4,000 dpi, more preferably 400 × 400 to 1,600 ×. It can be driven so that it can discharge at a resolution of 1,600 dpi, more preferably 720 × 720 dpi. The dpi (dot per inch) referred to in the present invention is 2.54 cm (1 inch).
This represents the number of dots per hit.

In the ink composition of the present invention, in the image forming method using the ink jet recording apparatus, it is desirable that the ink composition to be ejected is kept at a constant temperature. It is preferable to provide. The parts to be kept at a constant temperature are all the piping systems and members from the ink tank (intermediate tank if there is an intermediate tank) to the nozzle ejection surface. That is, heat insulation and heating can be performed from the ink supply tank to the inkjet head portion.
The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors in each piping portion and perform heating control according to the flow rate of the ink composition and the environmental temperature. The temperature sensor can be provided near the ink supply tank and the nozzle of the inkjet head. Moreover, it is preferable that the head unit to be heated is thermally shielded or insulated so that the apparatus main body is not affected by the temperature from the outside air. In order to shorten the printer start-up time required for heating or to reduce the loss of heat energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

  For discharging the ink composition using the above-described ink jet recording apparatus, the ink composition is preferably heated to 25 to 80 ° C., more preferably 25 to 50 ° C., and the viscosity of the ink composition is preferably 3 to 15 mPa · s, more preferably after the pressure is lowered to 3 to 13 mPa · s. In particular, it is preferable to use an ink composition having a viscosity of 50 mPa · s or less at 25 ° C. as the ink composition of the present invention, since it can be discharged satisfactorily. By using this method, high ejection stability can be realized.

  The temperature of the ink composition during ejection is preferably constant, and the control range of the temperature of the ink composition is more preferably ± 5 ° C. of the set temperature, more preferably ± 2 ° C. of the set temperature, and most preferably set. A temperature of ± 1 ° C. is appropriate.

  In the present invention, the recording medium is not particularly limited, and a known recording medium can be used as a support or a recording material. Examples of the recording medium include paper, paper laminated with plastic (eg, polyethylene, polypropylene, polystyrene, etc.), metal plate (eg, aluminum, zinc, copper, etc.), plastic film (eg, polyvinyl chloride resin, two Cellulose acetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, etc.) A plastic film etc. are mentioned. Especially, since the ink composition of the present invention is excellent in adhesion, it can be suitably used as a recording medium for a non-absorbing (non-penetrating) recording medium. As the non-absorbable recording medium, a plastic base material such as polyvinyl chloride, polyethylene terephthalate, or polyethylene is preferable, a polyvinyl chloride resin base material is more preferable, and a polyvinyl chloride resin sheet or film is further preferable.

(Drying process)
The drying step is a step of reducing water in the applied ink composition. In this step, the water-soluble organic solvent in the ink composition is reduced together with water, and the ink image is fixed on the recording medium.
The heating means is not particularly limited as long as the amount of water and water-soluble organic solvent contained in the ejected ink composition can be reduced. For example, a heat drum, hot air, an infrared lamp, a heat oven, a heat Known heating means such as plate heating can be appropriately used.
The heating temperature may be in a temperature range of 30 ° C. to 110 ° C., but depending on the recording medium, a temperature range of 30 ° C. to 70 ° C. is preferable, and a temperature range of 40 ° C. to 70 ° C. is more preferable. The drying and heating time can be appropriately set in consideration of the composition and printing speed of the ink composition to be used.
The ink composition of the present invention forms an image with excellent gloss even when dried at low temperature. Therefore, even when the drying process is performed at a temperature at which there is no possibility of affecting the recording medium, the ink composition can be applied to the recording medium. An image having excellent adhesion and gloss is formed.

<Printed matter>
The printed matter of the present invention has an image formed with the aqueous ink composition of the present invention on a recording medium or an image of the aqueous ink composition recorded by the image forming method of the present invention. Therefore, the printed matter of the present invention has an ink image with excellent glossiness, which suppresses bleeding at the time of droplet ejection.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “%” is based on mass.

  The raw materials of the ink composition used in Examples and Comparative Examples are shown below.

<Preparation of polymeric fluorescent dye>
(Synthesis of monomer A-1 having fluorescent dye moiety)
Monomer A-1 was synthesized as follows.

  9 (10H) acridone [manufactured by Wako Pure Chemical Industries, Ltd.] 15 g and sodium hydroxide [manufactured by Wako Pure Chemical Industries, Ltd.] 3.4 g were added to 84 g of dimethyl sulfoxide [manufactured by Wako Pure Chemical Industries, Ltd.] Dissolved and heated to 45 ° C. To this solution, 17.6 g of CMS-P [chloromethylstyrene, manufactured by AGC Seimi Chemical Co., Ltd.] was added dropwise, and the mixture was further heated and stirred at 50 ° C. for 5 hours. This reaction solution was poured into a mixed solution of 30 g of distilled water and 30 g of methanol [manufactured by Wako Pure Chemical Industries, Ltd.] with stirring. The precipitate in the mixed solution was filtered off and washed with 300 g of a solution in which distilled water and methanol were mixed in the same mass. This precipitate was monomer A-1, and the yield was 17.5 g.

(Synthesis Example 1: Synthesis of polymeric fluorescent dye P-1)
Polymer fluorescent dye P-1 was synthesized as follows.

  In a 300 ml three-necked flask equipped with a stirrer and a condenser, 63 g (0.63 mol) of methyl methacrylate, 9.0 g (0.029 mol) of monomer A-1 and 18.0 g (0.21) of methacrylic acid were added. Mol) and 126 g of methyl ethyl ketone were added and heated to 75 ° C. under a nitrogen atmosphere. To this reaction solution, 1.20 g of dimethyl 2,2'-azobisisobutyrate dissolved in 8 g of methyl ethyl ketone was added and reacted for 2 hours. Subsequently, 0.50 g of dimethyl 2,2'-azobisisobutyrate dissolved in 0.6 g of methyl ethyl ketone was added, and the mixture was further reacted for 2 hours. Further, 0.50 g of dimethyl 2,2′-azobisisobutyrate dissolved in 0.6 g of methyl ethyl ketone was added, the temperature was raised to 80 ° C., and the mixture was heated and stirred for 4 hours to react all unreacted monomers. After completion of the reaction, the polymer was reprecipitated in a large amount of hexane to obtain a polymeric fluorescent dye P-1 (polymer P-1). 45 g of the obtained polymer P-1 was added to an aqueous solution consisting of 2.93 g (0.0732 mol) of sodium hydroxide and 402.1 g of water, and dissolved by stirring at 60 ° C. A polymer fluorescent dye aqueous solution (P-1) containing 10% by mass was obtained.

The composition of the obtained polymer was confirmed by ¹ H-NMR. The weight average molecular weight (Mw) obtained from GPC was 30,000. The weight average molecular weight (Mw) is detected by a differential refractometer using a TPCgel GMHxL, TSKgel G4000HxL, and TSKgel G2000HxL (all trade names manufactured by Tosoh Corporation) in series with a GPC analyzer using THF as a solvent. Then, it was calculated by mass conversion using polystyrene as a standard substance.
Moreover, the glass transition temperature of the obtained polymer was 130 degreeC as a result of measuring by Seiko Instruments Co., Ltd. DSC-6220.

(Synthesis Example 2: Synthesis of polymeric fluorescent dye P-2)
Polymer fluorescent dye P-2 was synthesized as follows.

A polymeric fluorescent dye P-2 (polymer P-2) was synthesized in the same manner as in Synthesis Example 1 except that methyl methacrylate was changed to an equal mass of butyl methacrylate.
Moreover, it carried out similarly to the synthesis example 1, and obtained the polymeric fluorescent dye aqueous solution (P-2) containing 10 mass% of polymers P-2.
The composition of the obtained polymer was confirmed by ¹ H-NMR, the weight average molecular weight (Mw) obtained in the same manner as in Synthesis Example 1 was 36,000, and the glass transition obtained by the same method as in Synthesis Example 1 The temperature was 60 ° C.

(Synthesis Example 3: Synthesis of polymeric fluorescent dye P-3)
Polymer fluorescent dye P-3 was synthesized as follows.

The polymer fluorescent dye P-3 was used in the same manner as in Synthesis Example 1 except that instead of methyl methacrylate, monomers were used so as to be an alkyl methacrylate having the above structure, and the amounts of these monomers were changed to the above mass ratio. (Polymer P-3) was synthesized.
Moreover, it carried out similarly to the synthesis example 1, and obtained the polymeric fluorescent dye aqueous solution (P-3) containing 10 mass% of polymers P-3.
The composition of the obtained polymer was confirmed by ¹ H-NMR, the weight average molecular weight (Mw) obtained in the same manner as in Synthesis Example 1 was 42,000, and the glass transition obtained by the same method as in Synthesis Example 1 The temperature was 35 ° C.

(Synthesis Example 4: Synthesis of Comparative Fluorescent Dye B-1)
Comparative fluorescent dye B-1 was synthesized as follows.

  9-Oxoacridine-10 (9H) -acetic acid [manufactured by Tokyo Chemical Industry Co., Ltd.] was neutralized with 1 equivalent of sodium hydroxide and purified to obtain fluorescent dye B-1.

(Synthesis Example 5: Synthesis of Polymeric Fluorescent Dye Dispersion B-2)
Polymer fluorescent dye dispersion B-2 was synthesized as follows.

  In addition to methyl methacrylate, a monomer that becomes an alkyl methacrylate having the above structure was used, and the amount of these monomers was changed so as to be the above mass ratio. Obtained in minutes. 45 g of the obtained polymer B-2 was added to an aqueous solution composed of 1.46 g (0.0366 mol) of sodium hydroxide, 203.3 g of water, and 200.0 g of 2-pyrrolidone, and stirred and mixed at 60 ° C. Thus, a polymeric fluorescent dye dispersion B-2 (volume average particle size of 80 nm) containing 10% by mass of polymer B-2 was obtained.

  The volume average particle size was measured by a dynamic light scattering method using a nanotrack particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.).

<Preparation of ink composition>
Examples 1-9, Comparative Examples 1-4
Using a mixer (trade name “L4R”, manufactured by Silverson Co., Ltd.) so that the polymer fluorescent dye or the comparative fluorescent dye, the solvent, the surfactant, and water have the ratios shown in Table 1 below, The ink compositions of Examples and Comparative Examples were obtained by mixing and stirring for minutes. Each was packed in a disposable syringe made of plastic and filtered with a polyvinylidene fluoride (PVDF) pore size 5 μm filter (trade name “Millex-SV”, diameter 25 mm, manufactured by Millipore). Each ink composition of Examples 1-4 was obtained.

In Table 1, DPG represents dipropylene glycol [manufactured by Wako Pure Chemical Industries, Ltd.], and PG represents propylene glycol [manufactured by Wako Pure Chemical Industries, Ltd.]. 2-Pyrrolidone manufactured by Wako Pure Chemical Industries, Ltd. was used. In addition, Olphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd .; HLB value is 13) is used as the surfactant, and is indicated as E1010 in the table.
The viscosity of the ink composition was in the range of 3 to 8 mPa · s at room temperature (25 ° C.).

(Measurement of viscosity of ink composition)
The viscosity of the ink composition was measured as follows.
The viscosity of the ink was measured at 25 ° C. using an E-type viscometer [manufactured by Toki Sangyo Co., Ltd., RE-80L, rotor number 1].

(Measurement of absorbance of ink composition)
10 mg of the ink composition was weighed, and 15 g of PG, 4 g of DPG and 78.9 g of water were mixed therewith, and 20 ml was weighed from the obtained mixed solution, and the absorbance of the ink composition was measured.
The absorbance in the visible light region of each of the mixed liquids prepared using each ink composition was less than 0.2. Absorbance was measured using Shimadzu Corporation UV-2550.

(Measurement of volume average particle diameter of polymeric fluorescent dye in ink composition)
With respect to the polymers P-1 to P-3 of each ink composition of Examples 1 to 9, an attempt was made to observe the particle size of the polymer with a dynamic light scattering measurement device [FPAR-1000, manufactured by Otsuka Electronics Co., Ltd.]. However, the polymer fluorescent dye was not present as fine particles, and the particle size of the polymer was not observed.

<Evaluation of ink composition>
Each of the obtained ink compositions was printed on 8 cm square plain paper (manufactured by Nippon Paper Industries Co., Ltd., trade name: Shirai, paper thickness 149 μm) using a hand coater (bar No. 2) manufactured by RK PRINTCOAT INSTRUMENTS. , And a vinyl chloride sheet (Avery Dennison, trade name: Avery 400 Gloss White PERMANENT, paper thickness 90 μm) were applied to each with a thickness of 12 μm to form a solid image (1/1 density image). Then, the water | moisture content was dried for 3 minutes at 60 degreeC.
Each ink composition was diluted 10 times with water to prepare a sample having a concentration of 1/10. Next, a solid image (1/10 density image) was formed using the sample by the same method as the formation of the solid image. Of the following evaluations, the evaluations other than the concentration were performed without diluting each ink composition.

<Concentration>
The obtained 1/1 density image and 1/10 density image were irradiated with a low-pressure mercury lamp, and the emission intensity was visually evaluated according to the following criteria.

Evaluation Criteria A: Sufficient blue light emission is observed in both the 1/1 density image and the 1/10 density image B: The blue light emission is sufficiently observed in the 1/1 density image, but 1/10 Density image shows little blue light emission. C: Even blue light emission is slight in 1/1 density image.

<Bleeding evaluation>
As an ink jet recording apparatus, a commercially available ink jet printer (manufactured by FUJIFILM Dimatics, trade name: DMP-2831) was prepared. Each ink composition thus obtained was loaded into this ink jet printer and heated at 40 ° C., plain paper (manufactured by Nippon Paper Industries Co., Ltd., trade name: Shirai, paper thickness 149 μm) and a substrate made of polyvinyl chloride (Avery -Two thin wires having a width of 1 mm and a length of 5 cm were recorded in parallel at intervals of 0.5 mm on a product manufactured by Denison, product name: AVERY 400 GLOSS WHITE PERMANENT, paper thickness 90 μm. After the discharge was stopped, the obtained fine lines were visually evaluated according to the following criteria by visual observation while irradiating with a low-pressure mercury lamp.

Evaluation criteria A: A state in which there is almost no blur and the fine line is a straight line. B: A slight blur is present, but the fine line is almost a straight line and there is no problem in practical use. C: A part of the fine line becomes thick due to the blur. Combined and practically problematic

<Abrasion resistance>
The center of the fine line image obtained in the bleedability evaluation test was evaluated by the following criteria by visually observing the image and the swab while irradiating a low-pressure mercury lamp, with the image of rubbing the fine line in the minor axis direction with a cotton swab 5 times. did.

Evaluation criteria A: Image is not damaged and the cotton swab does not move B: Image is not damaged and the cotton swab is transferred C: The image is damaged and the cotton swab is transferred

<Glossy evaluation>
The glossiness of the image was evaluated by measuring the glossiness under the following conditions.
The prepared solid image and support were measured at a measurement angle of 60 ° using a gloss meter manufactured by Sheen Instruments based on JIS Z8741. Evaluation was made according to the following criteria. The evaluation B or higher is a practically acceptable level.

Evaluation criteria A: The difference in glossiness between the support and the printed part is -5 or more and 5 or less B: The difference in glossiness between the support and the printed part is -10 or more and less than -5, or more than 5 and 10 or less It is.
C: The difference in glossiness between the support and the printed part is less than −10 or more than 10.

<Blocking resistance evaluation>
The obtained two printed materials were overlapped so that the printed screens matched each other, and further pressurized at 30 ° C. for 1 hour at a pressure of 1 kg / cm ² . Thereafter, the two printed materials were peeled off, and the state of the image was observed while irradiating with a low-pressure mercury lamp. The following criteria were used for visual evaluation.

Evaluation criteria A: No peeling of image (white spots) and no peeling sound when peeling printed matter B: No white spots and no image transfer, but no peeling noise when peeling printed matter Occurs C: There are no white spots, but some image transfer is observed. D: White spots occur.

<High humidity resistance>
The fine line image obtained in the bleedability evaluation test was allowed to stand in an environment of 30 ° C. and 80% humidity for 1 hour, and then the fine line image was visually evaluated according to the following criteria under the same conditions as the bleedability evaluation.

Evaluation criteria A: A state in which there is almost no blur and the fine line is a straight line. B: A slight blur is present, but the fine line is almost a straight line and there is no problem in practical use. C: A part of the fine line becomes thick due to the blur. Combined and practically problematic

  The results are summarized in Table 1.

As is clear from Table 1, the water-based ink composition of the present invention had all the evaluation items as B or better as compared with the comparative example. In addition, Example 1 in which an image was recorded on plain paper having a penetrating support had a good evaluation of bleeding as in Example 9 in which an image was recorded on vinyl chloride having a non-permeable support.
Further, as can be seen from Examples 1 to 5, it is understood that the higher the content of the polymeric fluorescent dye within the specified range, the better the evaluation result of the bleeding property and the evaluation result of the concentration.
On the other hand, Comparative Example 1 and Comparative Example 3 using a fluorescent dye that is not a polymer were inferior in evaluation of bleeding and high humidity resistance.

Claims (6)

Contains an ink-soluble polymer fluorescent dye having a fluorescent site in the repeating unit, an organic solvent, and water , and does not substantially absorb visible light , and
The water-based ink composition in which the polymeric fluorescent dye has a repeating unit represented by the following general formula (1) .
In general formula (1), R ¹ represents a hydrogen atom or a methyl group, X represents a phenylene group, —COO— or —CONR ² —, and R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. . Y represents a single bond or a linear or branched alkylene group having 1 to 8 carbon atoms, and in the alkylene group, —O—, —OC (═O) —, —CH (OH) —, —NH— , —NHC (═O) — may be contained. Z represents a fluorescent dye residue.   The water-based ink composition according to claim 1, wherein the polymer fluorescent dye has a glass transition temperature of 40 ° C. or higher.   3. The aqueous ink composition according to claim 1, wherein the content of the polymeric fluorescent dye is 0.5% by mass or more and 5.0% by mass or less based on the total mass of the aqueous ink composition. Claim The content of the repeating unit represented by the above general formula in the polymer fluorescent dye (1) is not more than 5% by weight to 30% by weight of the total repeating units constituting the polymer fluorescent dye The water-based ink composition according to any one of 1 to 3 . The water-based ink composition according to any one of claims 1 to 4 , which is used for inkjet. An ink application step of applying the aqueous ink composition according to any one of claims 1 to 5 onto a recording medium;
Drying the water-based ink composition applied on the recording medium .