JP2005097567A - Inkjet recording fluorescent water-based ink, and cartridge containing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording fluorescent water-based ink which ensures clear coloring and excellent water resistance, and provides sufficient OD value and fluorescence intensity. <P>SOLUTION: The inkjet recording fluorescent water-based ink for use in an inkjet printer comprises water, a fluorescent dye represented by formula (1), a pigment, and a compound having a primary or secondary amide group. In formula (1), R<SP>1</SP>is independently OH or N(R<SP>3</SP>)R<SP>4</SP>, and R<SP>2</SP>is independently hydrogen or a halogen, wherein R<SP>3</SP>is hydrogen or a 1-5C alkyl group and R<SP>4</SP>is hydrogen or a 1-5C alkyl group. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fluorescent water-based ink for ink-jet recording which can obtain a sufficient optical density value (OD value) and fluorescence value while ensuring vivid color development and excellent water resistance.

  Examples of the ink jet recording method include an electrostatic suction method, a method of applying mechanical vibration or displacement to the ink using a piezoelectric element, a method of generating bubbles by heating the ink, and utilizing a pressure generated at this time. With this ink ejection method, ink droplets are formed, and a part or all of the ink droplets are attached to a recording medium such as paper to perform recording. Ink jet recording methods have not been widely used in recent years because there are no processes such as development and fixing, and colorization is easy. Recently, high-definition and high-speed printing of ink jet printers has rapidly progressed, and color printers that can print on plain paper have become mainstream.

  Under such circumstances, the performance required for the ink jet ink used in the ink jet recording method is also high, for example, providing a vividly colored recording image; excellent water resistance after image formation; Fast drying when forming an image and good rub resistance; stable ejection without clogging in the head discharge section and ink flow path of an ink jet printer; Performances such as no discoloration and excellent light resistance and gas resistance are required. Among these, providing a brightly colored recorded image and water resistance after image formation is one of the very important performances in order to achieve clear and blur-free image quality. is there.

  As an ink having vivid color development and excellent water resistance, for example, Patent Document 1 contains a fluorescent dye such as an acid dye, a direct dye, or a basic dye and a pigment as an ink coloring material, and the pigment is dispersed. Therefore, an ink for a postage meter to which a resin dispersant is added is disclosed. However, in such inks, acid dyes, direct dyes, basic dyes, etc. used as fluorescent dyes are easily dissolved in water because the dyes themselves are salts, and even when used in combination with pigments The water resistance after formation was not sufficient.

  In contrast, an ink using a fluorescent dye having excellent water resistance such as a fluorescent dye having a xanthene skeleton has been studied. If such a fluorescent dye is used, a fluorescent ink having extremely high water resistance can be obtained. However, when a fluorescent water-based ink for ink-jet recording is prepared using such a fluorescent dye, there is a problem that a sufficient OD value cannot be obtained because the water solubility of the fluorescent dye itself is poor.

US Pat. No. 6,176,908

  The present invention has been made to solve the above-described problems, and provides a fluorescent water-based ink for ink-jet recording capable of obtaining a sufficient OD value and fluorescence value while ensuring vivid color development and excellent water resistance. The purpose is to do.

  According to the present invention, there is provided a fluorescent aqueous ink for ink-jet recording, which comprises water, a fluorescent dye represented by the following formula (1), a pigment, and a compound having a primary or secondary amide group. A fluorescent aqueous ink is provided.

In formula (1), R ¹ is independently OH or N (R ³ ) R ⁴ , and R ² is independently a hydrogen atom or a halogen atom. R ³ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R ⁴ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.

  According to the present inventors, when a fluorescent dye having a water resistance and a pigment are used in combination, the fluorescence intensity of the fluorescent ink is lower than when the fluorescent dye is used alone, and a sufficient OD value is obtained. It has been found that when the pigment is added to the extent, the vivid color developed by the fluorescent dye cannot be obtained. This is considered to be due to the fact that the fluorescence emitted from the fluorescent dye is blocked and absorbed by the pigment present in the ink as a solid content. The present inventors have succeeded in providing a novel ink having a sufficient OD value while ensuring vivid color development and excellent water resistance. Such an excellent effect is considered to be mainly based on the interaction between a fluorescent dye described later and a compound having a primary or secondary amide group.

  In the present invention, an ink cartridge containing the ink of the present invention is also provided. The ink cartridge includes a container having an arbitrary shape for containing ink. The ink cartridge may be mounted on the ink jet head or may be attached in the main body case of the ink jet recording apparatus. In the latter case, ink is supplied from the ink cartridge to the inkjet head via a flexible tube or the like.

  According to the present invention, a novel ink having a sufficient OD value and fluorescence value while ensuring vivid color development and excellent water resistance is provided.

The fluorescent water-based ink for ink jet recording of the present invention contains a fluorescent dye represented by the above formula (1). Since the fluorescent dye represented by the above formula (1) has a xanthene skeleton, it has low water solubility and excellent water resistance after image formation. In formula (1), R ¹ is independently OH or N (R ³ ) R ⁴ . R ² is independently a hydrogen atom or a halogen atom. For example, all R ² may be hydrogen or halogen, or at least one R ² may be hydrogen and the remaining R ² may be halogen. R ³ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, preferably 1 to 2 carbon atoms, and R ⁴ is a hydrogen atom or 1 to 5 carbon atoms, preferably 1 to 2 carbon atoms. It is an alkyl group having.

  The fluorescent dye represented by the above formula (1) is not particularly limited. For example, color indexes (hereinafter referred to as CI) Solvent Red 43 and 48 represented by the following formulas (2) to (6), respectively. 49, 72 or 73. These fluorescent dyes may be used alone or in combination of two or more.

The content of the fluorescent dye represented by the above formula (1) is preferably 0.1 to 2.0% by weight based on the total amount of the fluorescent aqueous ink for inkjet recording. If the amount is less than 0.1% by weight, sufficient fluorescence cannot be emitted. If the amount exceeds 2.0% by weight, the excited molecules consume energy and quench each other's fluorescence, The fluorescence value may decrease. More preferably, it is 0.3 to 1.0% by weight.

  The fluorescent aqueous ink for inkjet recording of the present invention contains a pigment. The pigment has a role as an auxiliary color material for increasing the OD value of the fluorescent aqueous ink for inkjet recording.

  The pigment is preferably a self-dispersing pigment that has been surface-modified and can be stably dispersed without a dispersant. For pigments that require a dispersant, the surface tension of the ink decreases depending on the dispersant used, and the ink is not ejected normally, and the ink permeability is imbalanced and the print quality deteriorates. It may end up. In addition, when the ink is evaporated, the dispersant may adversely affect the dispersion state of the fluorescent dye or pigment, and aggregation or precipitation may occur. The surface modification is performed by bonding a hydrophilic functional group such as a carboxyl group, a carbonyl group, or a hydroxyl group or a salt thereof directly or via an alkyl group, an alkyl ether group, an aryl group, or the like to the pigment surface. . Specifically, for example, a method of introducing a hydrophilic functional group by chemical treatment in which the pigment surface is oxidized with an oxidizing agent in water, a hydrophilic functional group or an active species containing a hydrophilic functional group is grafted to the pigment surface. The method etc. can be given.

  The self-dispersing pigment is not particularly limited as long as it is dispersible in an aqueous phase. Examples of commercially available pigments include CAB-O-JET260 (manufactured by Cabot Corporation).

  The content of the pigment is preferably 0.5 to 3.0% by weight as a solid content with respect to the total amount of the fluorescent aqueous ink for inkjet recording. If the amount is less than 0.5% by weight, a sufficient OD value cannot be obtained. If the amount exceeds 3.0% by weight, the amount of solids dispersed in the ink becomes large, thereby stabilizing the dispersion of the ink. The ink cannot be secured, and agglomeration is likely to occur during evaporation of water, which may adversely affect ink ejection stability. More preferably, it is 1.0 to 3.0% by weight.

  The fluorescent water-based ink for ink-jet recording of the present invention contains a compound having a primary or secondary amide group. As a result of intensive studies, the inventors of the present invention can increase the fluorescence of fluorescent dyes by adding a compound having a primary or secondary amide group to a fluorescent water-based ink for inkjet recording. It has been found that it is possible to prevent a decrease in the fluorescence value due to the presence of the pigment, and the present invention has been completed.

  The compound having the primary or secondary amide group is not particularly limited, and examples thereof include acetamido, urea, ε-caprolactam, hydantoin, dimethylhydantoin, succinimide, and 2-pyrrolidone. These may be used alone or in combination of two or more.

  The compound having a primary or secondary amide group preferably has a polarity value of 3.5 or more. This is because the above-mentioned compound having a primary or secondary amide group has a greater effect of increasing the fluorescence value as the polarity increases, and if it is less than 3.5, the fluorescence value cannot be sufficiently increased. Table 1 shows the polar values of the compounds having the primary or secondary amide group. The polarity value is calculated by molecular orbital calculation software WinMOPAC (calculation conditions: Hamiltonian AM1, manufactured by Fujitsu Limited).

The content of the compound having a primary or secondary amide group is preferably 3.0 to 10.0% by weight with respect to the total amount of the fluorescent aqueous ink for inkjet recording. If the amount is less than 3.0% by weight, a sufficient effect cannot be exerted to increase the fluorescence value. If the amount exceeds 10.0% by weight, the ink has a high viscosity. May cause adverse effects. More preferably, it is 5.0 to 8.0% by weight.

The reason why the compound having the primary or secondary amide group has the effect of increasing the fluorescence value of the fluorescent aqueous ink for ink jet recording is considered as follows. The oxygen atom or nitrogen atom of the functional group (R ¹ ) bonded to the xanthene skeleton of the fluorescent dye represented by the formula (1) and the hydrogen atom of the compound having the primary or secondary amide group By hydrogen bonding, the oxygen atom and nitrogen atom of the fluorescent dye are charged. As a result, a difference in charge occurs in the molecule of the fluorescent dye, and the flow of electrons occurs, thereby amplifying the fluorescence. Therefore, the greater the polarity of the compound having the primary or secondary amide group, the easier it is to generate hydrogen bonds and the difference in charge within the molecule of the fluorescent dye, thus increasing the fluorescence value. From the inventor's hypothesis that fluorescence is amplified by the hydrogen bond between the fluorescent dye and the compound having an amide group as described above, there is a certain amount of the compound having an amide group with respect to the fluorescent dye. According to the experimental results described later, it was found that the molar ratio of the compound having an amide group to the fluorescent dye in the ink is preferably 30 or more, and particularly preferably 50 or more.

  The fluorescent water-based ink for ink-jet recording of the present invention contains water. The water is not general water, but highly purified water such as ion exchange water or distilled water is preferably used. The water content is 10 with respect to the total amount of the fluorescent water-based ink for ink jet recording, although it depends on the desired characteristics of the ink and the type and composition of the fluorescent dye represented by the above formula (1) and the pigment. It is preferable that it is 0.0-95.0 weight%. If the amount is less than 10.0% by weight, the ratio of components other than water inevitably increases, so when ink is printed on the paper, the ink becomes blurred or the viscosity becomes high, so it is difficult to introduce the ink into the nozzle. There is. If it exceeds 95.0% by weight, the ink viscosity after the volatile component has evaporated may become too high, resulting in non-ejection. More preferably, it is 30.0 to 90.0% by weight.

  The basic configuration of the fluorescent water-based ink for ink-jet recording of the present invention is as described above. For the purpose of improving ejection stability, compatibility with head and ink cartridge materials, storage stability, image storage stability, and other various performances. In response to the above, further various conventionally known wetting agents, penetrants, surfactants, viscosity modifiers, surface tension regulators, pH regulators, metal rust inhibitors, specific resistance regulators, film formers, ultraviolet absorbers, You may contain antioxidant, discoloration prevention agent, antiseptic | preservative antifungal agent, etc. In the case where the fluorescent aqueous ink for ink jet recording of the present invention is applied to an ink jet system in which it is ejected by the action of thermal energy, thermal physical properties such as specific heat, thermal expansion coefficient, and thermal conductivity may be adjusted.

  In particular, the fluorescent aqueous ink for inkjet recording of the present invention may contain glycerin as a wetting agent.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited only to these examples.

<Examples 1-4>
C. as a fluorescent dye I. Solvent Red 43, 49 or 72, self-dispersing pigment or CAB-O-JET260 (manufactured by Cabot) as a pigment, urea, ε-caprolactam, acetamide or succinimide as a compound having a primary or secondary amide group The ink material having the composition shown in Table 2 was stirred and then filtered through a 2.5 μm membrane filter to prepare an ink. The concentration of each component in Table 2 indicates wt%. The self-dispersing pigment was prepared according to the following procedure.
(1) 20 g of quinacridone pigment and 500 g of quinoline were mixed and dispersed for 3 hours using a bead mill. (2) Water was removed as much as possible from the mixture obtained in (1) above under reduced pressure.
(3) The temperature was raised to 160 ° C., 20 g of a sulfonated pyridine complex was added, and the mixture was stirred for 4 hours.
(4) The slurry obtained in (3) above was washed with quinoline, poured into water, further washed with water and dried, then adjusted to a pigment concentration of 15% by weight with water, and the surface-treated quinacridone pigment 15 A weight percent dispersion was obtained. Table 2 shows the molar ratio of the fluorescent dye used and the compound having an amide group.

<Comparative Examples 1-7>
C. as a fluorescent dye I. Solvent Red 43, 49 or 72, self-dispersing pigment as a pigment or CAB-O-JET260 (manufactured by Cabot), urea, primary or secondary amide group as a compound having a primary or secondary amide group N-methylcaprolactam, N, N-dimethylacetamide or N-methylsuccinimide was used as a compound not to be stirred, and the ink material having the composition shown in Table 3 was stirred, followed by filtration with a 2.5 μm membrane filter to remove the ink. It was adjusted. The concentration of each component in Table 3 indicates wt%. Table 3 also shows the molar ratio between the fluorescent dye and the compound having an amide group.

<Evaluation>
The inks prepared in Examples 1 to 4 and Comparative Examples 1 to 7 were evaluated by the following methods. For the evaluation, a recording sample recorded on plain paper (XEROX 4200) using an inkjet recording apparatus MFC-5100J (manufactured by Brother Industries, Ltd.) was used, and the recording sample used a portion with a coverage of 100%. .
(1) OD value measurement The OD value of the recording sample using the ink prepared in Examples 1 to 4 and Comparative Examples 1 to 7 was measured using an optical densitometer (X-Rite 400, manufactured by X-Rite). Measurement was performed at 620 nm and evaluation was performed according to the following criteria.
◎: OD value is 0.8 or more ○: OD value is 0.7 or more and less than 0.8 Δ: OD value is 0.5 or more and less than 0.7 ×: OD value is less than 0.5 The fluorescence values of the recording samples using the inks prepared in Examples 1 to 4 and Comparative Examples 1 to 7 were measured using a fluorescence spectrophotometer (F-4500, manufactured by Hitachi). The wavelength of the excitation light source at the time of fluorescence value measurement was 254 nm, and the fluorescence measurement wavelength was 600 nm. Evaluation was performed according to the following criteria.
A: Fluorescence value of 270 or more ◯: Fluorescence value of 200 or more and less than 270 Δ: Fluorescence value of 150 or more and less than 200 ×: Fluorescence value of less than 150 The measured fluorescence values are shown in Table 2 and Table 3.

As is apparent from Table 4, the inks prepared in the examples had good OD values and fluorescence values. On the other hand, in the ink prepared in the comparative example, either the OD value or the fluorescence value was not a sufficient value.
<Examples 5-9>
C. of Example 1 I. The composition of the ink containing Solven Red 43 was changed to various values as shown in Table 5, and changes in fluorescence values were observed. Examples 5 and 6 are C.I. I. The concentration of sorben red 43 was changed. In Examples 7 and 8, the concentration of the pigment was changed in the composition of Example 1, respectively. In Example 9, the urea concentration in the composition of Example 1 was changed. In the table, C.I. I. The concentrations of sorben red 43 and urea are expressed in molar concentration, and the molar ratio (ratio of the compound having a dye and an amide group) is also shown in Table 5. The OD value and fluorescence value were measured in the same manner as in Example 1, and the evaluation results and fluorescence values are shown in Table 5. The fluorescence value of Example 5 is relatively low. I. This is probably because the concentration of sorben red 43 is absolutely low. Further, the fluorescence value of Example 6 is relatively low. I. This is probably because the concentration of sorben red 43 is high and self-quenching occurs.

Furthermore, in order to investigate the relationship between the molar ratio of the compound having an amide group to the dye and the fluorescence value (fluorescence intensity), C.I. I. Example 1, Comparative Example 1 and Example 9 using Solven Red 43; I. In Examples 3 to 4 and Comparative Example 4 using Solven Red 72, C.I. I. The graph shown in FIG. 1 was created using the results of Example 2 and Comparative Example 2 using Solven Red 49. From the results in FIG. 1, it can be seen that the fluorescence value increases as the molar ratio of the compound having an amide group to the dye increases. In particular, the molar ratio of the compound having an amide group to the dye is 30 or more to obtain a good fluorescence value (evaluation ◯), and the compound having an amide group to the dye is required to obtain the best fluorescence value (evaluation ◎). It can be seen that the molar ratio is desirably 50 or more.

  The fluorescent water-based ink for ink-jet recording of the present invention sufficiently solves the problems of the prior art, and has excellent water resistance and vividness by containing the fluorescent dye and pigment represented by the above formula (1). It is possible to realize a fluorescent water-based ink for ink-jet recording having a good color. Further, by containing a compound having a primary or secondary amide group, even when a fluorescent dye and a pigment are used in combination, a decrease in fluorescence value due to the presence of the pigment can be prevented, A sufficient fluorescence value can be obtained. Furthermore, when a self-dispersing pigment is used as the pigment, stable discharge can be achieved without causing a decrease in surface tension or occurrence of precipitation.

  The present invention can provide a water-based ink for inkjet recording and an ink cartridge including the same, which can obtain a sufficient OD value and fluorescence value while ensuring vivid color development and excellent water resistance.

It is a graph which shows the relationship between the molar ratio of the compound which has an amide group with respect to dye, and fluorescence intensity.

Claims (8)

A fluorescent water-based ink for inkjet recording,
A fluorescent aqueous ink for ink-jet recording comprising water, a fluorescent dye represented by the following formula (1), a pigment, and a compound having a primary or secondary amide group.

In formula (1), R ¹ is independently OH or N (R ³ ) R ⁴ , and R ² is independently a hydrogen atom or a halogen atom. R ³ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R ⁴ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. The fluorescent water-based ink for ink-jet recording according to claim 1, wherein the molar ratio of the compound having a primary or secondary amide group to the fluorescent dye is 30 or more. The fluorescent water-based ink for ink-jet recording according to claim 1 or 2, wherein the pigment is a self-dispersing pigment. The fluorescent water-based ink for ink-jet recording according to any one of claims 1 to 3, wherein the fluorescent dye is a kind selected from the group consisting of Color Index Solvent Red 43, 48, 49, 72 and 73. Furthermore, the fluorescent aqueous ink for inkjet recording as described in any one of Claims 1-4 containing glycerol. The fluorescent water-based ink for ink jet recording according to any one of claims 1 to 5, wherein the compound having a primary or secondary amide group has a polarity value of 3.5 or more. The inkjet recording fluorescence according to any one of claims 1 to 6, wherein the compound having a primary or secondary amide group is one selected from the group consisting of acetamide, urea, ε-caprolactam, and succinimide. Water based ink. An ink cartridge comprising the fluorescent aqueous ink for ink jet recording according to any one of claims 1 to 7.

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