JP3931896B2 - Fluorescent aqueous ink for inkjet recording - Google Patents

Description

The present invention relates to a fluorescent aqueous ink for inkjet recording having high fluorescence intensity.

In the ink jet recording system, ink is ejected from nozzles, slits, porous films, and the like, and recording is performed on paper, cloth, films, and the like. As a method for ejecting ink, for example, an electrostatic attraction method for ejecting using electrostatic attraction force, a drop-on-demand method for applying mechanical vibration or displacement to ink using a piezoelectric element, and heating the ink There is a thermal ink jet system that generates bubbles by using the pressure generated at this time. Recording is performed by forming ink droplets by various ink ejection methods and attaching some or all of these to a recording material.

The development of inks that can be applied in various fields using such an ink jet recording system is progressing. Among them, the fluorescent ink has a property of absorbing light (excitation light) having a specific wavelength and emitting light (fluorescence) having a wavelength longer than that of the excitation light. In addition, it has been attempted to apply to applications in which information can be read by emitting fluorescence by irradiating ultraviolet rays as excitation light. Fluorescent inks include not only transparent inks that do not absorb in the visible region, but also colored inks that absorb in the visible region. The colored fluorescent ink having absorption in the visible region can be recognized visually, and the reading means can be selected according to the contents of the information, so that the versatility of the ink is expected to be widened.

However, in general, it is known that a fluorescence quenching phenomenon occurs in the fluorescent ink, when the concentration of the fluorescent dye in the ink exceeds a certain amount, the fluorescence intensity decreases. This is because the fluorescent dye transitions from an excited state to a more stable state without emitting absorbed energy as light due to the interaction of the excited fluorescent dye (non-radiation process). Therefore, no matter how much the fluorescent dye concentration is adjusted, there is a problem that a fluorescent ink having a fluorescence intensity above a certain level cannot be obtained.

On the other hand, various attempts have been made to increase fluorescence within a concentration range where concentration quenching does not occur. For example, Patent Document 1 discloses a fluorescent ink using a combination of two types of fluorescent dyes having a common absorption wavelength region in the ultraviolet region and a common fluorescence emission wavelength region in the visible region. By combining these two types of fluorescent dyes, the fluorescent intensity of the second fluorescent dye is added to the fluorescent intensity of the first fluorescent dye, and an ink having a high fluorescent intensity is obtained. However, in practice, the fluorescence intensity of this fluorescent ink was smaller than the sum of the fluorescence intensity when each of the two types of fluorescent dyes was used alone. This is because the first fluorescent dye and the second fluorescent dye have an absorption wavelength region common to the ultraviolet region, so that the first fluorescent dye and the second fluorescent dye share the excitation energy, and the respective fluorescent dyes. This is probably because the dye cannot emit sufficient fluorescence.

JP 2003-192962 A

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fluorescent aqueous ink for ink jet recording having high fluorescence intensity.

According to the present invention, at least water; a first fluorescent dye having a first ultraviolet absorption wavelength region in the absorption spectrum and a first fluorescence emission wavelength region in the fluorescence spectrum; a first different from the first ultraviolet absorption wavelength region in the absorption spectrum A first ultraviolet absorption, wherein the first fluorescent dye overlaps at least a part of the second fluorescent emission wavelength region, and a second fluorescent dye having a second fluorescent emission wavelength region in the fluorescence spectrum. It further has an absorption wavelength region different from the wavelength region (provided that the first fluorescent dye is CI Acid Red 52 and the second fluorescent dye is CI Acid Yellow 73; and 1 fluorescent dye is C.I. acid Red 52, and, except where the second fluorescent dye is C.I. solvent Green 7) the inkjet recording Fluorescence aqueous ink is provided.

In the fluorescent water-based ink for ink jet recording of the present invention, since the first ultraviolet absorption wavelength region of the first fluorescent dye and the second ultraviolet absorption wavelength region of the second fluorescent dye are different, the light energy in the ultraviolet region is changed to the first fluorescent dye and The second fluorescent dye can be used effectively without sharing. Furthermore, since the first fluorescent dye has an absorption wavelength region that overlaps at least a part of the second fluorescent emission wavelength region of the second fluorescent dye, the first fluorescent dye emits the fluorescence emitted by the second fluorescent dye. Can be absorbed as. As a result, the total light energy for exciting the first fluorescent dye is increased, so that the fluorescence intensity from the first fluorescent dye is amplified. The fact that the first fluorescent dye absorbs the fluorescence emitted by the second fluorescent dye as excitation energy means that the peak intensity in the second fluorescent emission wavelength region when the fluorescence spectrum of the ink is measured is the fluorescence spectrum of the second fluorescent dye alone. This is confirmed from the fact that it is lower than the peak intensity in the second fluorescence emission wavelength region when measuring.

In the fluorescent aqueous ink for ink-jet recording of the present invention, the absorption wavelength region overlapping at least a part of the second fluorescence emission wavelength region of the first fluorescent dye may be present in the visible region. The peak wavelength in the first ultraviolet absorption wavelength region may be 10 nm or more, particularly 15 nm or more away from the peak wavelength in the second ultraviolet absorption wavelength region. Further, the first fluorescence emission wavelength region may exist in the visible region. As the first fluorescent dye, C.I. I. Acid Red 52, C.I. I. Acid Yellow 73 or C.I. I. Solvent Red 49 can be used, and a compound represented by the following chemical formula (1) can be used as the second fluorescent dye.

ADVANTAGE OF THE INVENTION According to this invention, the fluorescent aqueous ink for inkjet recording which has high fluorescence intensity can be provided.

The fluorescent water-based ink for inkjet recording of the present invention contains at least water, a first fluorescent dye, and a second fluorescent dye. The first fluorescent dye absorbs light having a wavelength in the ultraviolet region (first ultraviolet absorption wavelength region) and fluorescence having a wavelength in a predetermined region (second fluorescent emission wavelength region) emitted from the second fluorescent dye. Fluoresce in the wavelength range. Thus, not only light having a wavelength in the ultraviolet region but also light having a fluorescence wavelength emitted from the second fluorescent dye is used as excitation light, whereby an ink with extremely high fluorescence intensity can be obtained. In the present specification, light in the ultraviolet region means light having a wavelength of 200 to 380 nm.

The fluorescence emitted by the first fluorescent dye may be fluorescence having a wavelength in the visible region or fluorescence having a wavelength outside the visible region. When the first fluorescent dye emits fluorescence having a wavelength in the visible region, the emitted fluorescence can be read by visual observation, and various images and characters that can be visualized can be recorded using this fluorescence. it can. On the other hand, when the first fluorescent dye emits fluorescence having a wavelength outside the visible region, it is possible to record information that can be read by the human eye only when a special reading device is used. Can be suitably used for recording necessary information.

The first fluorescent dye may be a colored fluorescent dye having an absorption wavelength region in the visible region, or a colorless fluorescent dye having no absorption wavelength region in the visible region. In the case where the first fluorescent dye is a colored fluorescent dye having an absorption wavelength region in the visible region, information can be recognized visually and can be used for color recording, so that the versatility of the ink is expanded. On the other hand, when the first fluorescent dye is a colorless fluorescent dye that does not have an absorption wavelength region in the visible region, information cannot be visually recognized, which is suitable for recording information that requires security, for example. Can be used. Thus, by selecting the fluorescent emission wavelength and absorption wavelength region of the first fluorescent dye, the fluorescent aqueous ink for ink jet recording of the present invention can be suitably used for a wide range of applications.

The first fluorescent dye is not particularly limited, and examples thereof include C.I. I. Acid Red 51, 52, 87, 92 and 94; I. Acid Yellow 73; I. Direct yellow 11, 24, 26, 87, 100, 132 and 147; I. Direct orange 26, 29, 29: 1 and 46; I. Direct red 1, 13, 17, 239, 240, 242 and 254; I. B. Basic Red 1, 2, 9, 12, 13, 14, and 17; I. B. Basic violet 1, 3, 7, 10, 11: 1 and 14; I. Solvent Yellow 82 and 116; C.I. I. Solvent Red 43, 44, 45, 48, 49, 60, 72 and 73; I. Fluorescent 86, 87, 90, 113, 119, 166, 219, 220, 264 and 271 may be mentioned. For example, C.I. I. Acid Red 52 absorbs light of 240 to 260 nm and 540 to 580 nm and emits fluorescence of 590 to 650 nm. I. Solvent Red 49 absorbs light of 250 to 270 nm and 520 to 570 nm and emits fluorescence of 580 to 640 nm. I. Acid Yellow 73 absorbs light of 230 to 240 nm and 470 to 500 nm and emits fluorescence of 400 to 450 nm and 500 to 600 nm.

The blending amount of the first fluorescent dye in the fluorescent aqueous ink for ink jet recording of the present invention is preferably 0.1 to 2.0% by weight. If the amount is less than 0.1% by weight, sufficient fluorescence intensity may not be obtained. If the amount exceeds 2.0% by weight, a concentration quenching phenomenon may occur and the fluorescence intensity may decrease. More preferably, it is 0.2 to 1.0% by weight.

In the ultraviolet region, the second fluorescent dye absorbs light having a wavelength in the ultraviolet region (second ultraviolet absorption wavelength region) different from the wavelength of light absorbed by the first fluorescent dye, thereby predetermining a predetermined region (second fluorescent emission wavelength region). ) Is a fluorescent dye that emits fluorescence having a wavelength of. Since the absorption wavelength region in the ultraviolet region is different between the first fluorescent dye and the second fluorescent dye, the light in the given ultraviolet region can be effectively used as the excitation energy without overlapping each fluorescent dye. Note that “the first fluorescent dye and the second fluorescent dye have different absorption wavelength regions in the ultraviolet region” means that the peak wavelength in the ultraviolet absorption wavelength region of the first fluorescent dye and the peak in the ultraviolet absorption wavelength region of the second fluorescent dye. It means that the wavelengths are separated from each other by 10 nm or more.

For the second fluorescent dye, an optimum combination is selected in consideration of absorption wavelengths in the ultraviolet region and other regions of the first fluorescent dye. That is, for example, C.I. I. When Acid Red 52 is used, the absorption wavelength in the ultraviolet region of the second fluorescent dye is in a region different from 240 to 260 nm which is the ultraviolet absorption wavelength region of the first fluorescent dye, and excitation light in the ultraviolet region is used. Is selected such that the wavelength of the fluorescence emitted by absorbing the light is in the range of 540 to 580 nm which is the absorption wavelength region of the first fluorescent dye. Examples of such second fluorescent dye include C.I. I. Acid Green 5, C.I. I. Solvent Yellow 82 and 116 , C.I. I. Solvent blue 5, a fluorescent dye having a basic structure represented by the following chemical formula (1), and the like can be mentioned.

Other combinations include, for example, C.I. I. Solven Red 49 absorbs light of 250 to 270 nm and 520 to 570 nm and emits fluorescence of 580 to 640 nm. On the other hand, C.I. I. Acid Yellow 73 absorbs light of 230 to 240 nm and 470 to 500 nm and emits fluorescence of 400 to 450 nm and 500 to 600 nm. Therefore, C.I. I. Solven Red 49 is a first fluorescent dye, C.I. I. When Acid Yellow 73 is used in combination as the second fluorescent dye, each dye absorbs excitation light and emits fluorescence without overlapping in the ultraviolet region. I. The fluorescence of 500 to 600 nm emitted from Acid Yellow 73 is further reduced by C.I. I. Used as excitation light for sorben red 49. As a result, C.I. I. Fluorescence with an extremely high fluorescence intensity of 580 to 640 nm due to sorben red 49 is observed.

It is preferable that the compounding quantity of the 2nd fluorescent dye in the fluorescent aqueous ink for inkjet recording of this invention is 0.1 to 5.0 weight%. If the amount is less than 0.1% by weight, the fluorescence intensity amplification effect by the second fluorescent dye cannot be obtained, and sufficient fluorescence intensity may not be obtained. If the amount exceeds 5.0% by weight, solids in the ink may be obtained. This can increase the amount of ink and adversely affect ink stability. More preferably, it is 0.2 to 3.0% by weight.
Further, as described above, if the fluorescence of the second fluorescent dye is a function of amplifying the fluorescence of the first fluorescent dye, the second fluorescent dye has a molar ratio of 0.5 to 4 with respect to the first fluorescent dye. It is desirable to be.

The fluorescent water-based ink for ink-jet recording of the present invention contains water. The said water is not general water, but highly purified things, such as ion-exchange water and distilled water, are used suitably. The water content in the fluorescent water-based ink for ink jet recording of the present invention is 10.0 to 95.0 weights, although it depends on the desired ink characteristics and the types and compositions of the first fluorescent dye and the second fluorescent dye. % Is preferred. If it is less than 10.0% by weight, the ratio of components other than water will inevitably increase, so that ink will bleed or increase in viscosity when printed on paper, making it difficult to introduce ink into the nozzle. May be. 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 accordance with the above, 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.
When applied to an inkjet system in which the fluorescent aqueous ink for inkjet recording of the present invention is ejected by the action of thermal energy, thermal properties such as specific heat, thermal expansion coefficient, and thermal conductivity may be adjusted.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
<Examples 1-5>
The materials having the respective compositions shown in Table 1 were stirred and then filtered through a 0.8 μm membrane filter to prepare a fluorescent aqueous ink.

<Comparative Examples 1-9>
The materials having the respective compositions shown in Table 2 were stirred and then filtered through a 0.8 μm membrane filter to prepare a fluorescent aqueous ink. In addition, the fluorescent dye of the chemical formula (2) in the table represents the following chemical formula (2).

<Absorption spectrum measurement>
The absorption spectrum of each fluorescent dye added to the inks of Examples 1 to 5 and Comparative Examples 1 to 9 was measured using an ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation, UV-3100PC). As an example of the absorption spectrum, FIGS. I. The absorption spectrum of sorben red 49 in the ultraviolet region and visible region is shown. 3 and FIG. I. The absorption spectrum of Acid Yellow 73 in the ultraviolet region and the visible region is shown. As can be seen from the ultraviolet absorption spectrum of Solven Red 49 in FIG. 1, the wavelength at which absorption is maximum in the ultraviolet region (near 258 nm indicated by the arrow in the figure) is C.I. I. It is an ultraviolet absorption peak wavelength of Solven Red 49. Further, in FIG. I. As can be seen from the ultraviolet absorption spectrum of Acid Yellow 73, the wavelength at which absorption is maximum in the ultraviolet region (near 238 nm indicated by the arrow in the figure) is C.I. I. It is the ultraviolet absorption peak wavelength of Acid Yellow 73. In the ultraviolet region, there are a plurality of wavelengths at which the absorption is maximized. Of the wavelengths at which the plurality of absorptions are maximized, the wavelength having the highest absorbance is defined as the peak wavelength. From these spectra, C.I. I. Solven Red 49 and C.I. I. It can be seen that the ultraviolet absorption peak positions of Acid Yellow 73 are separated from each other by 10 nm or more, particularly 15 nm or more. For the other fluorescent dyes used in Examples 2 to 4 and Comparative Examples 1 to 9, the peak positions were determined from the absorption spectra.
<Fluorescence spectrum measurement>
The inks prepared in Examples 1 to 5 and Comparative Examples 1 to 9 were recorded on plain paper (XEROX 4200, manufactured by Fuji Xerox Co., Ltd.) using an inkjet printer (manufactured by Brother Industries, Ltd., MFC-5100J). Using the 100% coverage portion as a recording sample, the fluorescence intensity of the recording sample was observed using a spectrofluorometer (manufactured by Hitachi High-Technologies Corporation, F-4500). The fluorescence spectrum was obtained by measuring the fluorescence intensity between the fluorescence wavelengths of 400 and 650 nm while changing the wavelength of the excitation light source between 200 and 380 nm.

A three-dimensional fluorescence spectrum of the ink of Example 1 is shown in FIG. In the three-dimensional fluorescence spectrum of FIG. 5, the vertical axis indicates the wavelength (nm) of excitation light, the horizontal axis indicates the wavelength (nm) of fluorescence, and the fluorescence intensity is represented by contour lines. In the figure, a single square pattern in which both fluorescence and excitation light move to the long wavelength side is caused by excitation light and its secondary light. Ink of Example 1 is C.I. I. Solven Red 49 and C.I. I. Acid yellow 73 is included in the ink. In order to investigate the influence of these fluorescent dyes on the fluorescence intensity, C.I. I. An ink containing only Solven Red 49 and C.I. I. An ink containing only Acid Yellow 73 was prepared in the same manner as described above, recorded under the same conditions as described above, and then measured for a three-dimensional fluorescence spectrum. Note that C.I. I. In an ink containing only Solven Red 49, C.I. I. The weight percent of sorben red 49, glycerin, and butyl triglycol is the same as the weight percent of each component of the ink of Example 1. In addition, C.I. I. In ink containing only Acid Yellow 73, C.I. I. The weight percent of Acid Yellow 73, glycerin and butyl triglycol is the same as the weight percent of each component of the ink of Example 1. C. I. An ink containing only Solven Red 49 and C.I. I. The three-dimensional fluorescence spectra of ink containing only Acid Yellow 73 are shown in FIGS. 6 and 7, respectively. 5 to 7 are compared with each other as shown in FIG. I. In the case of Acid Yellow 73 alone, the fluorescent band appearing at 500 to 600 nm is C.I. I. Solven Red 49 and C.I. I. By including both Acid Yellow 73 (Example 1), it turns out that it has disappeared. In addition, C.I. I. In the case of Solben Red 49 alone, the intensity of the fluorescent band appearing at 580 to 640 nm is C.I. I. Solven Red 49 and C.I. I. It can be seen that by including both Acid Yellow 73 (Example 1), it appears stronger.

In order to make the results of FIGS. 5 to 7 easier to understand, the wavelength of the excitation light source is 254 nm, and the three-dimensional fluorescence spectrum of FIGS. The (vertical axis) represents the two-dimensional fluorescence spectrum of FIGS. C. appearing in FIG. I. The characteristic 500-600 nm fluorescent band of Acid Yellow 73 is C.I. I. Solven Red 49 and C.I. I. It can be seen that the fluorescence spectrum of FIG. 8 of the ink containing Acid Yellow 73 (Example 1) completely disappears. Further, the intensity of the characteristic fluorescent band appearing at 580 to 640 nm in the fluorescence spectrum of FIG. I. It is increased as compared with the intensity of the fluorescent band of 580 to 640 nm in the case of only Solven Red 49. From this, C.I. I. Acid Yellow 73 emits light having a wavelength of 500 to 600 nm, which is absorbed by Solven Red 49 having absorption characteristics as shown in FIG. I. It is considered that Solven Red 49 was able to generate stronger fluorescence.
<Evaluation>
For the inks of Examples 1 to 5 and Comparative Examples 1 to 9, the peak intensity was obtained from the fluorescence spectra measured as described above, and the fluorescence intensity was determined from the obtained peak intensity according to the following criteria. The peak intensity is the peak intensity of fluorescence when the wavelength of the excitation light is 254 nm. Here, in the following criteria, a fluorescence intensity of 250 or higher is sufficient when visually recognized, and a fluorescent intensity of 300 or higher is extremely excellent when visually recognized.
A: Fluorescence intensity is 300 or more ◯: Fluorescence intensity is 250 or more and less than 300 Δ: Fluorescence intensity is 200 or more and less than 250 ×: Fluorescence intensity is less than 200 The results are shown in Tables 1 and 2. As can be seen from Tables 1 and 2, the ink using the fluorescent dye combination according to the present invention is excellent in fluorescence intensity. In particular, it can be seen that when the fluorescent dye of the chemical formula (1) is used, the fluorescence intensity is remarkably increased.

C. I. The absorption spectrum of sorben red 49 in the ultraviolet region is shown. C. I. The absorption spectrum of the sorben red 49 in the visible region is shown. C. I. The absorption spectrum of Acid Yellow 73 in the ultraviolet region is shown. C. I. The absorption spectrum in the visible region of Acid Yellow 73 is shown. The three-dimensional fluorescence spectrum of the ink of Example 1 is shown. C. I. The three-dimensional fluorescence spectrum of the ink containing only Solven Red 49 is shown. C. I. The three-dimensional fluorescence spectrum of the ink containing only Acid Yellow 73 is shown. The fluorescence spectrum of the ink of Example 1 in excitation wavelength 254nm is shown. C.I. at an excitation wavelength of 254 nm. I. The fluorescence spectrum of the ink containing only Solven Red 49 is shown. C.I. at an excitation wavelength of 254 nm. I. The fluorescence spectrum of the ink containing only Acid Yellow 73 is shown.

Claims (10)

at least,
water;
A first fluorescent dye having a first ultraviolet absorption wavelength region in the absorption spectrum and a first fluorescence emission wavelength region in the fluorescence spectrum;
A second fluorescent dye having a second ultraviolet absorption wavelength region different from the first ultraviolet absorption wavelength region in the absorption spectrum and a second fluorescence emission wavelength region in the fluorescence spectrum, wherein the first fluorescent dye has a second fluorescence emission. It further has an absorption wavelength region that overlaps at least a part of the wavelength region and is different from the first ultraviolet absorption wavelength region (provided that the first fluorescent dye is CI Acid Red 52 and the second fluorescent dye is CI Acid Yellow 73, and the case where the first fluorescent dye is CI Acid Red 52 and the second fluorescent dye is CI Solvent Green 7) . A fluorescent aqueous ink for ink-jet recording. When the fluorescence spectrum of the fluorescent aqueous ink containing the first fluorescent dye and the second fluorescent dye having a predetermined concentration is measured, the peak intensity in the second fluorescent emission wavelength region does not include the first fluorescent dye, and the first intensity of the predetermined concentration. 2. The fluorescent water-based ink for ink-jet recording according to claim 1, wherein the fluorescent water-based ink for ink jet recording is lower than the peak intensity in the second fluorescence emission wavelength region when the fluorescence spectrum of the fluorescent water-based ink containing two fluorescent dyes alone is measured. 3. The fluorescent aqueous ink for ink jet recording according to claim 1, wherein the first fluorescent dye emits fluorescence by absorbing fluorescence emitted from the second fluorescent dye. 4. The ink jet recording according to claim 1, wherein the absorption wavelength region overlapping at least part of the second fluorescence emission wavelength region of the first fluorescent dye is present in a visible region. Fluorescent aqueous ink. The fluorescent aqueous ink for ink jet recording according to any one of claims 1 to 4, wherein the peak wavelength in the first ultraviolet absorption wavelength region is 10 nm or more away from the peak wavelength in the second ultraviolet absorption wavelength region. The fluorescent aqueous ink for ink jet recording according to any one of claims 1 to 5, wherein the first fluorescence emission wavelength region exists in a visible region. The first fluorescent dye is C.I. I. Acid Red 52, C.I. I. Acid Yellow 73 and C.I. I. The fluorescent water-based ink for ink-jet recording according to any one of claims 1 to 6, wherein the fluorescent water-based ink for ink-jet recording is one kind selected from the group consisting of Solvent Red 49. The fluorescent aqueous ink for ink jet recording according to any one of claims 1 to 7, wherein the second fluorescent dye is a compound represented by the following chemical formula (1).

9. The fluorescent water-based ink for ink-jet recording according to claim 1, wherein the blending amount of the first fluorescent dye is 0.1 to 2.0% by weight in the water-based fluorescent ink for ink-jet recording. . 10. The fluorescent water-based ink for ink-jet recording according to claim 1, wherein the blending amount of the second fluorescent dye is 0.1 to 5.0% by weight in the water-based fluorescent ink for ink-jet recording. .

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