JP3311963B2 - Inkjet recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording method. More specifically, the present invention relates to an ink jet recording method in which a photosensitive water-soluble dye contained in ink is insolubilized by exposing an ink dot on a recording material on which ink jet recording has been performed to fix the ink.

[0002]

2. Description of the Related Art In an ink jet recording method, printing or image recording is performed by ejecting minute droplets of ink from a nozzle and attaching the droplets to a surface of a recording material such as paper.
Various ink jet recording methods have been proposed, and a method called a continuous method is described in, for example, US Pat.
SP 3,298,030 and USP 3,596,27
5 is disclosed. In the drop-on-demand method, for example, US Pat. No. 3,946,398 discloses a technique in which deformation of a piezo element is applied to a driving force of ink ejection. An ink jet recording method for ejecting ink droplets using thermal energy is described in, for example, US Pat. No. 4,251,824.
Is disclosed. Each of these patent publications proposes a method for ejecting ink droplets.

In any of the ink jet recording methods, ink is ejected at a high speed as fine droplets from orifices of fine nozzles, so that the ejection stability of the ink droplets is greatly affected by the viscosity and surface tension of the ink. That is, it is preferable that the viscosity of the ink is as small as possible, and in practice, the viscosity is preferably 2 to 10 mPa · s. The surface tension of the ink is preferably as large as possible, and is actually 40 dyn /
cm or more is desirable. If the ink viscosity is high, it becomes difficult to supply ink stably to the recording head following high frequency driving in the ink chamber. In addition, when the surface tension of the ink is small, the wetting of the ink droplet to the nozzle opening becomes large, and it is difficult to fly the ink droplet in an accurate direction. Cause things to happen.

[0004] For the above reasons, aqueous inks containing water as a main solvent are generally used as ink jet recording inks. Also, a water-soluble dye as a coloring material,
For example, acid dyes, direct dyes, basic dyes and the like are used. However, the printed matter recorded with the aqueous ink containing such a water-soluble dye has a problem that the water resistance of the coloring material is extremely low. Further, the storage stability of the printed matter was not sufficient due to poor light resistance.

[0005] To cope with this problem, many proposals have been made to use aqueous inks in which a pigment is dispersed (for example, Japanese Patent Application Laid-Open No. 56-147859). According to this method, although the robustness of the recorded matter can be satisfied to some extent, when it is used as an ink jet ink, a problem of nozzle clogging occurs.

[0006] In order to avoid the above-mentioned inconvenience, after ink jet recording using an aqueous ink containing a water-soluble dye,
A method of insolubilizing an ink dye on a recording material has been proposed (for example, Japanese Patent Publication No. Hei 7-29477).

[0007] The sulfuric acid ester sodium salt of the vulcanizate liuco compound has photosensitivity, and it has been conventionally known that when light energy is applied, the original insoluble dye is photochemically regenerated. For example, British Patent BP354,
No. 575 and BP431, 072 propose a method for obtaining a wet color photograph utilizing this property. Japanese Patent Application Laid-Open No. 50-123991 proposes a method of printing a photographic pattern on a textile by utilizing the photosensitivity of the dye.

[0008] The vulcanized dye liuco compound and its sodium sulfate ester salt have absorption in the ultraviolet and visible light regions having a wavelength of 200 nm to 600 nm. Therefore, when irradiated with high energy ultraviolet rays, the molecules are excited, and the insoluble dye is regenerated through the process shown in Chemical formula 1. In Chemical Formula 1, the color index number C.I. I. 73360 (CI Vat
Red 1), corresponding to 4,4′-dimethyl-6.
6'-dichlorothioindigo is used as an example of the sodium salt of the sulfated lithium compound.

[0009]

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A quinone type organic pigment having two or more carbonyl groups in a conjugated double bond system of a dye compound molecule and a vat dye are reduced with an alkaline reducing agent such as caustic soda and hydrosulfite to form a water-soluble dye. Rico compounds. The light absorption of the Rico compound shifts to a shorter wavelength side than that of the original quinone type dye, so that the compound has absorption in an ultraviolet wavelength region. Rico compounds are light sensitive and oxidize immediately upon exposure to regenerate the original insoluble dye.
The process of reduction and oxidation of this quinone dye is described in C.I.
I. Vat Red 1 (CI. 73360) 4,
4'-Dimethyl-6,6'-dichlorothioindigo is shown in Chemical Formula 2 as an example.

[0011]

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Rico compounds of quinone type dyes are easily oxidized by oxygen in the air and easily return to the original insoluble dyes, so that they are generally unstable in the air and inconvenient to handle. Therefore, those obtained by stabilizing the rico compounds by esterification with sulfuric acid are used for dyeing fibers.
In dyeing, the dye is insolubilized by thermal energy.

However, when the quinone-type dye-based rico compound is irradiated with ultraviolet rays to be insolubilized, the rate of insolubilization is extremely slow, so that a high-output light source is required. For example, in the embodiment of Japanese Patent Application Laid-Open No. 50-123991, a fade meter is used as a light source. The fade meter is a light fast acceleration tester for testing the photo-fading property of a dye, and is equipped with a powerful light source (carbon arc lamp) having a lamp output of 2 to 3 KW. Such a large-output lamp has a large amount of heat radiation and requires a large-scale power supply stabilizing device and cooling device, so that it cannot be applied to the ink jet recording method. Inkjet printers as office machines are limited in volume and size, and can only use small UV lamps with low power and low power consumption. However, a small-sized UV lamp with a low output has a small total energy amount of ultraviolet rays, so that long-time exposure is required, and the ink dye cannot be insolubilized at the same printing speed as an ink jet printer. For example, Examples 6 to 1 of Japanese Patent Publication No.
0, small UV with wavelength of 365 nm
The lamp required an exposure time of about 10 minutes or more.

[0014]

The current ink jet printer uses one sheet of recording paper (JIS standard A4 size:
(Length 297 mm x width 210 mm) is printed in 30 to 60 seconds. If a small UV lamp capable of insolubilizing a photosensitive water-soluble dye by exposing an ink dot recorded with an ink jet for 30 to 60 seconds is obtained, it can be mounted on an ink jet printer. The durability (water resistance, light resistance, and heat resistance) of the printed matter by the ink jet recording method is superior to that of a laser printer, and it can be expected that the use of the ink jet printer will be significantly expanded.

Therefore, a low-power UV lamp (lamp output of about 200 W) as a line light source which can be used with a power stabilizer of an electronic mechanism such as that used for a fluorescent lamp for indoor lighting is shown in FIG. There has been a demand for a method which can be mounted on a printer to insolubilize a photosensitive water-soluble dye contained in an aqueous ink in a short time.

[0016]

In an ink jet recording method for insolubilizing a photosensitive ink dye by using light energy, a minute amount of an ink dot attached to the surface of a recording material is irradiated with ultraviolet rays. One drop of ink is about 5
The volume is 50 pico-ml and the total amount of UV energy required to insolubilize the photosensitive water-soluble dye contained therein is small. Therefore, it is important to have a method for efficiently absorbing ultraviolet light by the photosensitive dye.

The inventor of the present invention has been able to remarkably rapidly insolubilize the quinone-type liquorium compound sulfate of a photosensitive dye contained in an aqueous ink by performing exposure using a low-pressure mercury lamp (germicidal lamp) and a metal halide lamp in combination. Was found. Ultraviolet fluorescent lamps may be used instead of metal halide lamps. As a result, about 200
The ink can be fixed within 60 seconds even with a low output UV lamp of about W (watt).

Here, the characteristics of a UV lamp, particularly a mercury lamp, will be briefly described. The principle of any light source that emits ultraviolet light is the same, and a substance (metal such as mercury) having an atomic structure that easily emits electromagnetic waves in the ultraviolet region is heated to a vapor state in a discharge tube (quartz glass tube). It emits light when large energy is injected from the outside. Examples of means for applying energy from the outside include a discharge lamp method (arc lamp), a flash lamp method, a laser method, and an electrodeless lamp method. Of these, the most practical one is the discharge lamp system, in which mercury is sealed in a discharge tube (arc tube), called a mercury discharge lamp (mercury lamp), and in which mercury and metal chloride are sealed. Is called a metal halide lamp. FIG. 2 shows the structure of a mercury discharge lamp. The emission spectrum of a mercury lamp varies greatly depending on the mercury vapor pressure in the arc tube. In a low-pressure mercury lamp (P = 10 ⁻² mmHg), the lamp power cannot be increased to about 1 to 5 W / cm or more because the mercury vapor pressure is low, and only a low-power lamp can be obtained. Therefore, although it has not been used as a light source for a photochemical reaction, ultraviolet rays having a wavelength of 254 nm are efficiently emitted. Low-pressure mercury lamps are used as germicidal lamps. Low-pressure mercury lamps are characterized by high UV efficiency, although the total radiant energy is small. As the mercury vapor pressure in the arc tube increases, the ultraviolet light of 254 nm decreases, and instead, the wavelength of 365, 405, 436 nm
And more light.

A high-pressure mercury lamp (P = 1 atm) has a large amount of ultraviolet light having a wavelength of about 365 nm, and is widely used as a light source for a photochemical reaction because a high-output lamp can be obtained. When the mercury vapor pressure is further increased, the ultrahigh-pressure mercury lamp (P = 30 atm) has a continuous spectrum, and the main wavelength is in the visible light region to the near infrared region, and is no longer suitable as a UV lamp. Table 1 shows that the mercury vapor pressure in the discharge tube was 1 × 10
The emission spectra of each mercury lamp at ⁻² mmHg (low pressure), 1 atm (high pressure), and 30 atm (ultra high pressure) are shown.

[0020]

[Table 1]

The structure of the metal halide lamp is exactly the same as that of the mercury lamp, and the electric characteristics are almost the same. Iron chloride is sealed in the arc tube together with mercury. The emission spectrum of the metal halide lamp is 250-600
This is different from a mercury lamp in this point. The extinction of the quinone dye Rico compound is 200 wavelengths.
It can be seen that the continuous emission spectrum of the metal halide lamp is efficiently absorbed because it covers the ultraviolet to visible light range of up to 600 nm. Table 2 shows the difference between the emission spectra of the metal halide lamp and the mercury lamp.

[0022]

[Table 2]

A fluorescent lamp is a mercury lamp in which a fluorescent substance is applied to the inner wall of an arc tube, and is excited by ultraviolet rays emitted by mercury vapor to emit light having a longer wavelength. An ultraviolet fluorescent lamp that emits light in a wavelength range of 300 to 400 nm by selecting a fluorescent substance is also called a chemical lamp,
It is used for pre-curing of ink.

Since a low-pressure mercury lamp can obtain only a low-output lamp, it has been conventionally used only as a germicidal lamp.
However, low-pressure mercury lamps have a high energy wavelength of 254.
It has been found that the compound is suitable for radiating nm efficiently and insolubilizing the sodium sulfate salt of a quinone-type dye-riuco compound. The low-pressure mercury lamp used in the present invention can be adjusted to have a mercury vapor pressure in the range of 0.01 to 1 mmHg.

Soluble vat dyes are dyes originally made for dyeing fibers, and hydrolysis and oxidative coloring are performed by steam heating to regenerate insoluble dyes on the fibers. Commercially available dyes contain only about 25 to 40% (by weight) of the main component of the vulcanized dye, the sodium salt of the sulfuric acid ester of the ryuko compound. The remaining minor components are sodium chloride, sodium sulfate, sodium dimethylaniline sulfonate, and the like. In the case of dyeing, the dyes are colored (insolubilized) by thermal energy (steam heating), so that these subcomponents are harmless.

However, when the dye is insolubilized by light energy, the dye cannot be efficiently insolubilized because sodium dimethylaniline sulfonate as a sub-component absorbs ultraviolet rays. Therefore, it is preferable to use a sulfuric acid ester of a vat dye, a main component of the vat dye, instead of a commercially available dye for the ink jet recording ink of the present method.

Since the solubility of sodium dimethylaniline sulfonate in a solvent is similar to that of a water-soluble dye, it is very difficult to purify a commercially available soluble vat dye to extract only a photosensitive water-soluble dye as a main component. is there. Therefore, it is more economical to directly synthesize a photosensitive water-soluble dye (a vulcanized dye, a ureco compound sulfate Na salt) from a vat dye as a precursor, and a high-purity product can be easily obtained.

A general method for synthesizing a sulfate salt of a quinone-type dye, a liuco compound, is as follows. Commercially available vat dyes and quinone type organic pigments can be used as starting materials.
After washing and removing impurities such as a dispersant with a methanol mixture, the mixture is dried. On the other hand, a chlorosulfonic acid / pyridine adduct is prepared over about 2 hours while slowly adding 100 parts of chlorosulfonic acid to 500 parts of dried pyridine at 15 to 20 ° C under cooling so that the liquid temperature does not exceed 20 ° C.
100 parts of the dried vat dye (or quinone type organic pigment) is added thereto, and 40 parts of pure iron powder is added thereto all at once with stirring.
Reach 0-60 ° C. Stirring is continued as it is, and the esterification reaction is completed in about 6 hours. Thereafter, the reaction mixture is poured into ice water containing about 6 times the amount of 5% caustic soda and stirred. Several drops of an antifoaming agent are added, and pyridine at 30 to 35 ° C. is recovered by distillation under reduced pressure. After collecting the pyridine, the total amount is made up to about 3000 parts by adding water and the mixture is heated to 80 ° C. and filtered after 2 hours. The residue is iron, iron oxide, etc., which is discarded. After the filtrate is concentrated by distillation under reduced pressure, a sulfuric acid ester salt of the vulcanized dye liuco compound is obtained by a salting out method.

There are several other methods besides the above method.
For example, British Patent No. BP186,057, BP25
1,491, BP258,626, BP461,4
No. 30, BP630, 459 and US patent US
P1, 954, 702 and the like can be referred to.
The same photosensitive water-soluble dye can be obtained by either method. All of the water-soluble dyes listed in the following Chemical Formula 3 can be prepared from the insoluble precursor dyes by the above-mentioned method.
All of these photosensitive water-soluble dyes can be insolubilized by exposure.

[0030]

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Of these photosensitive dyes, anthraquinone dyes have a high oxidation (insolubilization) rate by light energy, and yellow anthraquinone dyes in particular exhibit photocatalytic properties. When an anthraquinone dye is mixed with a dye of another species, it also has a function of accelerating the insolubilization rate of the other dye. This unique property of the anthraquinone dye is very advantageous when making black ink. In the case of black ink, the dye concentration becomes high, and a longer exposure time is required. However, for example, with a black ink made by blending a yellow anthraquinone dye and a black indolethionaphthene dye, a dark black which is insolubilized by short-time exposure can be obtained.

It is a remarkable advantage that the indigoid dye and the anthraquinone dye among the photosensitive water-soluble dyes mentioned in the above chemical formula 3 can be used for the ink for a thermal ink jet printer. In a thermal ink jet printer, a heating element is installed in an ink chamber of a recording head, and ink is ejected from a nozzle by the pressure of bubbles generated by high temperature. At this time, since the dye component of the ink deposits an insoluble substance on the surface of the heating element and hinders the thermal conductivity, a trouble that the normal ink ejection from the nozzle cannot be maintained easily occurs. The photosensitive water-soluble dye described in Chemical formula 3 decomposes at a temperature of 200 ° C. or more, and generates an insolubilized dye on the surface of the heating element. However, since the indigoid dye and the anthraquinone dye have small molecular weights, they sublime at a temperature of 200 ° C. or more. Therefore, there is an advantage that the dye does not deposit on the surface of the heating element and the insolubilized dye is dispersed and discharged in the ink in the form of ultrafine particles, so that no problem occurs.

Further, although not a quinone type dye, only cobalt phthalocyanine among phthalocyanine dyes is different from other metal phthalocyanines and can be solubilized by an alkaline reducing agent as if it were a quinone type vat dye. Particularly, a partially sulfonated cobalt phthalocyanine is used in the color index for C.I.
I. It is classified as Vat Blue 29 (C.I. 74140), and those made water-soluble in the form of sodium salt can be insolubilized by UV exposure similarly to the water-soluble dyes described in Chemical formula 3. Cobalt phthalocyanine exhibits a clear yellowish blue color and is useful as a coloring material for cyan ink.

As described above, the water fastness and light fastness of the recorded images and prints obtained by the ink jet recording method of the present invention are the same as those of conventional aqueous inks containing water-soluble dyes (direct dyes, acid dyes, basic dyes). The durability of the printed matter is equal to or higher than that of the laser printer. The ink jet recording method of the present invention can be applied not only to paper as a recording material, but also to textiles such as cotton, silk, wool, and nylon, leather, synthetic leather, and nonwoven fabric. Next, the present invention will be described more specifically with reference examples and examples. All parts or percentages in Reference Examples and Examples are based on weight.

[0035]

[0036]

Reference Example 1 150 g of chlorosulfonic acid was gradually added to 750 g of pyridine at 15 to 20 ° C. over 2 hours to prepare a pyridine-chlorosulfonic acid adduct. At a temperature of 20 to 25 ° C., 1- [paraphenylbenzoylimino] -anthraquinone (color index number C.I.
I. 60530) 150 g was added and stirring continued for a while. Thereafter, 60 g of electrolytic iron powder was added at a time, and stirring was further continued. The temperature of the reaction mixture rose to 55 ° C., which was heated to 60 ° C. and stirred at this temperature for 3 hours to complete the esterification reaction. The reaction mixture was poured into a 4% aqueous sodium hydroxide solution 51 for neutralization. The released pyridine was recovered by distillation at reduced pressure at 28-35 ° C. The residue was filtered to remove residues such as iron oxide. The filtrate was evaporated under reduced pressure and concentrated, and then salted out with 15 to 20% sodium chloride. The resulting dark yellow-brown precipitate was a photosensitive water-soluble dye represented by the following chemical formula, and showed a clear greenish yellow upon exposure.

[0037]

Embodiment 1 Color index structure number I. 73
The following photosensitive color materials (G), (H) and (I) were obtained in the same manner as in the synthesis method of Reference Example 1 using 905, 67910 and 67915 as starting materials, respectively.

[0038]

[0039]

Example 2 The photosensitive color material (G) obtained in Example 1 was used ,
Using (H) or (I) , an aqueous ink for an ink jet printer was prepared based on the following ink formulation. The ink containing the photosensitive color material (G) was designated as ink (G) . Similarly, the ink containing the photosensitive color material (H) is
Ink (H) and ink containing the photosensitive color material (I).
Ink (I) was used . The aqueous inks (G), (H) and (I) prepared as described above are filled in each ink bottle,
A commercially available ink jet printer having a piezo-type recording head was loaded and solid printing was performed on plain paper. After the ink jet recording, each solid-printed recording paper was irradiated by the next hybrid UV lamp (exposure time was 30 seconds and 60 seconds). The distance between the UV lamp and the recording paper is about 1
cm. Hybrid UV lamp 1): 45W low pressure mercury lamp (15W germicidal lamp x 3) 100W metal halide lamp Hybrid UV lamp 2): 45W low pressure mercury lamp (15W germicidal lamp x 3) 90W ultraviolet fluorescent lamp (30W chemical lamp x 3) Evaluation method of insolubilizing speed of ink color material by exposure: Solid printing paper with each of the above inks was exposed outdoors under direct sunlight for 5 hours under direct sunlight on a sunny day in summer, and the color density of recording paper was 100%. The standard densities were used, and the color densities of the respective inks obtained by exposure to the above-mentioned hybrid UV lamp were compared with a colorimeter to provide a measure of the insolubilizing speed (color developing speed). Explanation of symbols: 〇: Color density of 91 to 100% △: Color density of 60 to 90% ×: Color density of 59% or less

[0040]

Example 3 Test of light resistance, water resistance and heat resistance: Recording paper (standard color density) on which the photosensitive aqueous inks (G), (H) and (I) obtained in Example 2 were respectively solid printed. Were used to test light resistance, water resistance and heat resistance. As a comparative example, solid printed matter (standard color density) by a laser printer was tested and compared under the same conditions. Light fastness test: After irradiating with a fade ometer (carbon arc lamp) for 10 hours, the fading was judged and evaluated. (Evaluation method): ・ ・ ・: Almost no fading occurs. X: markedly faded. Water resistance test: The test piece was immersed in hot water (60 ° C.) (for 1 minute) to visually determine whether or not the coloring material eluted. (Evaluation method): ・ ・ ・: The coloring material does not dissolve. ×: The coloring material began to melt. Heat resistance test: Lay white paper on solid recording paper. An iron at 130 ° C. was placed thereon, and after 30 seconds, it was visually determined whether or not the color had transferred to a blank sheet. (Evaluation method): ・ ・ ・: No color transfer. X: Color transfer occurred.

[0041]

According to the ink jet recording method of the present invention, the water resistance and light resistance of a printed matter are remarkably superior to conventional water-based inks, and have the same durability as laser printer inks. Further, the heat resistance of the printing ink is remarkably superior to the toner of the laser printer, and the durability of the printing ink obtained by the ink jet recording method of the present invention is the same as that of the printing ink. Therefore, the ink jet recording method of the present invention can be used for preparing a public document or a business document in which long-term storage is important. Therefore, the application of the ink jet printer to on-demand digital printing, short run printing, electronic publishing, and the like is dramatically expanded.

[0042]

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an entire ink jet printer equipped with a UV lamp for embodying the ink jet recording method of the present invention.

FIG. 2 is an explanatory view showing a structure of a mercury discharge lamp.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Inkjet printer main body 2 ... Recording head and ink bottle 3 ... Hybrid UV lamp 4 ... Recording head guide rail 5 ... Platen 6 ... Recording paper carry-in tray 7.・ Recording paper discharge tray 8 ・ ・ ・ Printer cover 9 ・ ・ ・ Mercury discharge lamp 10 ・ ・ ・ Discharge tube (quartz glass sealed body) 11 ・ ・ ・ Argon gas and mercury 12 ・ ・ ・ Electrode 13 ・ ・ ・ Sealing Part 14 ・ ・ ・ Base 15 ・ ・ ・ Arc length

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/00 B41J 2/01 B41J 29/00 C09D 11/00

Claims (1)

(57) [Claims] An ink jet recording is carried out using an aqueous ink containing any of the water-soluble dyes represented by the following chemical structural formulas, and then the ink on the recording material is irradiated with ultraviolet rays to convert the water-soluble dye. Ink jet recording method characterized by insolubilizing and fixing: (However, M in the formula represents sodium, potassium or lithium)