JPS6210551B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel recording liquid, and particularly to a recording liquid suitable for an inkjet recording method in which droplets are ejected from fine ejection orifices provided in a recording head and used for recording. BACKGROUND ART Writing instruments (fountain pens, felt-tip pens, etc.) for recording on recording materials such as paper have conventionally used inks prepared by dissolving various dyes in water or other organic solvents. Furthermore, in the so-called inkjet recording method, in which recording is performed by ejecting liquid in the recording head from an ejection orifice using vibrations by a piezo vibrator or electrostatic attraction caused by high voltage application, various dyes are dissolved in water or organic solvents. It is known that compositions are used. However, compared to ink for stationery such as general fountain pens and felt pens, recording liquid for ink jets requires more stringent conditions in terms of many characteristics. The inkjet recording method generates little noise and allows high-speed recording or color recording on plain paper without special fixing treatment, and various types are being actively researched. In such an inkjet recording method, recording is performed by causing droplets of a recording liquid called ink to fly and adhere to a recording material. The basic components of such a recording liquid include a recording agent (dye or pigment is used) and a liquid medium for dissolving or dispersing it (water or various organic solvents or a mixture thereof is used), and if necessary, Various additives are added. There are various types of such recording methods depending on the method of generating droplets and the method of controlling the flight direction of the droplets. An example is shown in FIG. That is, the apparatus shown in FIG. 1 applies a recording signal to a recording head section having a piezo vibrator, and performs recording by generating droplets of recording liquid in response to the signal.
In FIG. 1, reference numeral 1 denotes a recording head, which has a piezo vibrator 2a, a diaphragm 2b, an inlet 3 for recording liquid, a liquid chamber 4 in the head, and an ejection port (ejection orifice) 5. A recording liquid 7 stored in a storage tank 6 is introduced into the liquid chamber 4 through a supply pipe 8 . Incidentally, an intermediate treatment means 9 such as a pump or a filter may be provided in the middle of the supply pipe 8 depending on the case. And in the piezo vibrator 2a,
A signal converted from the recording signal S into a pulse by the signal processing means (for example, a pulse converter) 10 is applied, and a pressure change occurs in the recording liquid in the liquid chamber 4 in accordance with the signal. As a result, the recording liquid 7 is ejected from the ejection orifice 5 as droplets 11, and the recording material 12 is
Recording is done on the surface of the In addition to the above devices, various types of devices are known. For example, as shown in FIG.
As a modification of the figure, there is a device in which the liquid chamber 4 is shaped like a nozzle and a cylindrical piezoelectric vibrator is installed around the outer periphery (the mechanism of droplet generation in this device is essentially the same as in FIG. 1). (same as the equipment shown). In addition, there is a device that continuously generates charged droplets and uses a part of the droplets for recording, or a device that applies thermal energy corresponding to the recording signal to the recording liquid in the chamber of the recording head, and uses the energy to generate the liquid. Devices that generate droplets are also known. An example thereof is shown in Fig. 3-a, Fig. 3-b, and Fig. 4. The head 13 is made of glass, ceramic, plastic plate, etc., having grooves 14 through which ink passes, and a heat-generating head 15 used for thermal recording (a thin film head is shown in the figure, but is not limited to this). Obtained by gluing. Heat generating head 15
consists of a protective film 16 made of silicon oxide or the like, aluminum electrodes 17-1, 17-2, a heating resistor layer 18 made of nichrome or the like, a heat storage layer 19, and a substrate 20 with good heat dissipation properties such as alumina. There is. The ink 21 has reached the discharge orifice 22 and forms a meniscus 23 due to the pressure P. Now, when an electric signal is applied to the electrodes 17-1 and 17-2, the part of the heating head 15 indicated by n suddenly generates heat, bubbles are generated in the ink 21 in contact with this part, and the pressure causes meniscus formation. 23 is projected and the ink 21 is ejected from the orifice 22 to form a recording droplet 2.
4 and flies toward the recording material 25. Fourth
The figure shows an external view of a multi-head in which a large number of heads shown in Figure 3-a are arranged. The multi-head is constructed by mounting a glass plate 27 having multi-grooves 26 and a heating head 28 similar to that described in FIG. 3-a. As described above, even if it is said to be a device that performs recording by flying droplets, the method of generating droplets and the method of controlling the flying direction of droplets are quite different. Therefore, in order to perform good recording, biological values such as viscosity, surface tension, and specific resistance values must be determined for the recording liquid used, depending on the method of generating droplets or the method of controlling the flying direction of droplets. is required. In either method, the recording liquid must not contain any solid content due to vaporization of the liquid medium components or chemical changes in the constituent components during long-term storage or cessation of recording. Generally, the ejection orifice of this type of recording device is a minute hole (generally about several tens of microns in diameter), so the generation of solid content may cause clogging, resulting in no droplets being ejected at all. Furthermore, even if ejection does not stop, the generation of solid content has an adverse effect on the generation of uniform droplets or the stable flight of droplets, resulting in poor recording performance, ejection stability, etc.
Ejection responsiveness or continuous recording performance may deteriorate. Alternatively, if the constituent components of the recording liquid undergo chemical changes, the physical properties of the recording liquid, which were adjusted to desired values at the time of preparation, may change, and the recording performance, ejection stability, and ejection response may also deteriorate. Therefore, there is a need for a solvent component that does not easily vaporize, a chemically stable recording agent, or a combination of a liquid medium and recording agent that does not cause the above-mentioned drawbacks. Furthermore, it is also required that the recorded image has sufficiently high contrast and clarity. In general, with conventional recording liquids, when attempting to increase the contrast of a recorded image by increasing the content of the recording agent, the ejection orifice tends to become clogged. Therefore, there is a need for a recording agent with high solubility in a liquid medium and a bright color tone. Furthermore, in addition to the above characteristics, recording can be performed without limiting the type of recording material, the fixing speed is high, and images with excellent water resistance, light resistance, abrasion resistance, and resolution can be provided. Properties such as no odor are also required. From this point of view, many proposals regarding recording liquids have been made, but hardly any practical recording liquids that satisfy all of the above conditions have been obtained. An object of the present invention is to provide a recording liquid that satisfies all of the above-mentioned drawbacks. That is, the main object of the present invention is to obtain a recording liquid that is excellent in ejection stability, ejection response, and continuous recording performance. Another object of the present invention is to obtain a recording liquid that can easily have appropriate physical properties. Another object of the present invention is to obtain a recording liquid that is less likely to generate solid content during a storage period or during a recording suspension period. Another object of the present invention is to obtain a recording liquid which can have a wide degree of freedom in selecting constituent components and is excellent in versatility and practicality. The recording liquid of the present invention that achieves the above object includes a recording agent which is a component for forming a recorded image, and a liquid medium for dissolving or dispersing this recording agent, and has the following general formula: (However, in the above general formula, R is hydrogen or has 1 to 1 carbon atoms.
4 alkyl group, X is an ethoxy group and/or isopropoxy group, and n is 0 or an integer from 1 to 30); . In this way, the compound represented by the above general formula (imidazoline derivative ethylene oxide and/or
(or propylene oxide adduct) not only improves recording liquid storage stability, versatility, and device maintainability over a wide temperature range from low to high temperatures, but also improves ejection stability and ejection response. sex,
Good results can also be obtained in long-term continuous recording. In particular, it exhibits an outstanding effect on the initial ejection characteristics after being left in a non-operating state. Conventionally, systems have been known in which only polyhydric alcohols such as ethylene glycol, diethylene glycol, and glycerin are added to prevent clogging due to solvent evaporation in orifices. However, when polyhydric alcohols are added to a sufficient extent to have a sufficient clogging prevention effect, the viscosity increases markedly or the temperature dependence of viscosity becomes large, making it difficult to generate droplets faithfully to the recording signal and perform recording. becomes impossible. Furthermore, it is known that the viscosity of liquid media containing glycols and water as main components and recording liquids containing water-soluble dyes as a recording material component changes after being left for a long period of time. That is, it is thought that this is because hydrogen bonds occur between these molecules and the viscosity increases. For this reason, conventionally known recording liquids having such a composition often cause problems in ejection after being left for a long period of time. It has been known that urea or thiourea is effective as an additive for preventing such a phenomenon. However, urea and thiourea
Since the recording liquid itself is a solid and has low solubility in glycols, after the water in the recording liquid composition evaporates at the tip of the fine orifice, it crystallizes and causes clogging. The compound represented by the above general formula of the present invention has a low freezing point, remains liquid even at considerably low temperatures, and exhibits excellent solubility in water, glycols, or a wide range of other organic solvents. Also, since it has an ethylene oxide or propylene oxide unit of appropriate length in the molecule, it has the effect of interfering with hydrogen bonding between molecules. Furthermore, it has the advantage of having strong dissolving power for various dyes. Therefore, even if some of the components constituting the recording liquid evaporate, there is no risk of clogging. In order for the compound represented by the above general formula of the present invention to exhibit the above effects, the optimum number of moles of ethylene oxide and/or propylene oxide added per mole of the corresponding imidazoline derivative is 1 to 30 moles. . This compound can be synthesized by a known synthesis method, for example, by subjecting an imidazoline derivative to an addition reaction with ethylene oxide or propylene oxide in the presence of a suitable solvent and catalyst. Here, specific examples of the compounds represented by the above general formula are illustrated below. The preferred amount of the compound represented by the above general formula in the recording liquid of the present invention is % by weight based on the total weight of the recording liquid.
is in the range of 0.5% to 30%, more preferably 1
It ranges from % to 20%. The recording liquid of the present invention is composed of a liquid medium as a carrier of the recording liquid, a recording agent for forming a recorded image, and additives added as necessary to obtain desired characteristics. The compound represented by the above general formula, which is formed by adding and/or propylene oxide, is an essential component.
In the present invention, in addition to using the above compound as a liquid medium component,
Water or the following non-aqueous liquids, which have been conventionally commonly used in the recording field related to the present invention, can be used in combination. For example, methyl alcohol, ethyl alcohol,
n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, Sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol,
Alkyl alcohols having 1 to 10 carbon atoms such as nonyl alcohol, decyl alcohol, benzyl alcohol, etc.; For example, cyclopentane, hexane, cyclohexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetralin, decalin, benzene, toluene , aliphatic or aromatic hydrocarbon solvents such as xylene; halogenated hydrocarbon solvents such as carbon tetrachloride, trichloroethylene, tetrachloroethane, and dichlorobenzene; such as ethyl ether, butyl ether, ethylene glycol diethyl ether, and ethylene. Ether solvents such as glycol monoethyl ether; ketone solvents such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl amyl ketone, cyclohexanone; ethyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, phenyl acetate, ethylene Ester solvents such as glycol monoethyl ether acetate and lactate ethyl propylene carbonate; polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, and glycerin; and other amine, amide, and N-methyl alcohols such as triethanolamine and dimethylformamide. Various solvents include nitrogen-containing heterocyclic systems such as pyrrolidone and 1,3 dimethylimidazolidinone, and intramolecular esters of oxycarboxylic acids such as valerolactone and caprolactone. These listed liquid media are appropriately selected and used so as to satisfy the compatibility with the recording agent and additives used and the above-mentioned properties as a recording liquid. Two or more types may be mixed as appropriate within the range in which a recording liquid having characteristics can be prepared. As a recording agent, the relationship with the liquid medium composition and additives should be adjusted to prevent sedimentation and agglomeration in rooms and recording liquid tanks due to long-term storage, and furthermore, to prevent clogging of supply pipes and discharge orifices. be selected and used. The recording agent that can be used in the present invention is appropriately selected depending on the characteristics of the recording material to suit its recording conditions, and many conventionally known dyes and pigments can be used. is valid. The dye that can be effectively used in the present invention is one that can satisfy the above-mentioned properties of the prepared recording liquid, and generally includes, for example, monoazo, polyazo, metal complex azo, pyrazolone azo, and stilbene. Azo, thiazole, azo-based azo dyes, anthrone, anthraquinone dyes consisting of anthraquinone derivatives, indigo, indigoid dyes consisting of thioindico derivatives, phthalocyanine dyes, diphenylmethane, triphenylmethane, xanthene, acridine carbonium dyes, azine,
Dyes such as oxazine and thiazine-based quinone imine dyes, polymethine and azomethine-based methine dyes, benzoquinone and naphthoquinone dyes, naphthalimide dyes, and perinone dyes can be mentioned. These dyes are appropriately selected as desired and used after being dissolved in the liquid medium used. Pigments that can be effectively used in the present invention include many inorganic and organic pigments. The quantitative relationship of these recording agents is 0.5% to 50%, preferably 0.5% to 40%, and more preferably 1% to 50% by weight, based on the total weight of the recording liquid.
It is best to set it in the range of 30%. As the recording agent, it is preferable to use a recording agent that is soluble in the liquid medium, but even if it is a recording agent that is dispersible or poorly soluble in the liquid medium, such as a pigment, it can be soluble in the liquid medium using an appropriate dispersant. It may be used as long as the particle size of the recording agent during dispersion is made sufficiently small. In this case, the particle size of the recording agent is usually 0.01μ to 3μ, preferably
It is in the range of 0.01μ to 2μ, more preferably 0.01μ to 1μ. Furthermore, it is preferable that the particle size distribution of the dispersed recording agent be as narrow as possible. In this way, the recording liquid of the present invention not only has excellent ejection stability, ejection response, droplet uniformity, and continuous recording performance, but also has excellent image quality, long-term storage stability, maintainability of the device, and selection of constituent components. It also shows excellent properties in terms of the degree of freedom. The recording liquid of the present invention, which has the above-mentioned components as its basic constituents, has excellent properties in itself, but various additives may be added in order to provide even more remarkable recording properties. Examples of such additives include viscosity modifiers, surface tension modifiers, resistivity modifiers, and the like. The present invention will be specifically explained with reference to the following examples. Example 1 Water Black P-200 (CI35255) [Orient Chemical Industry] 5% by weight Diethylene glycol 20 1,3 dimethyl-2-imidazolidinone 10 Ion exchange water 60 Compound No. 1 in the specification 5 The above components were thoroughly mixed and dissolved in a container, filtered under pressure through a Teflon (trade name) filter with a pore size of 1 μm, and then degassed using a vacuum pump to obtain a recording liquid. Using the recording liquid, a recording device having an on-demand type recording head (discharge orifice diameter 50μ, piezoelectric vibrator drive voltage 60V, frequency 4KHz) that discharges the recording liquid by a piezoelectric vibrator is used to perform T ₁ to _T5 . When we investigated the following, we obtained good results in all cases. (T ₁ ) Long-term storage stability of recording liquid: Even after recording liquid was sealed in a glass container and stored at -30℃ and 60℃ for 2 years, no precipitation of insoluble matter was observed, and the physical properties and color tone of the liquid did not change. There was no change. (T ₂ ) Ejection stability: Continuous ejection was performed for 48 hours in an atmosphere of room temperature, 5° C., and 40° C. Under all conditions, stable high-quality recording was possible from beginning to end. (T ₃ ) Ejection response: Intermittent ejection every 2 seconds and ejection after being left for 3 months were investigated, and in both cases, stable and uniform recording was achieved without clogging at the orifice tip. (T ₄ ) Quality of recorded images: The images recorded on the recording materials listed in the first table had high density and were clear. The rate of decrease in concentration after 3 months of exposure to indoor light is 1
% or less, and when immersed in water for 1 minute, there was very little blurring of the image. (T ₅ ) Fixability on various recording materials; After 15 seconds of printing on the following recording materials, the printed area was rubbed with a finger to determine the presence or absence of image shift and bleeding. All of them exhibited excellent fixing properties with no image shift or blurring.

[Table] Example 2 A recording liquid having the composition shown in the table below was prepared in the same manner as in Example 1, and T ₁ to T ₅ were examined in the same manner as in Example 1 (in Table 2, ) The numbers in parentheses indicate the composition ratio). All of these had excellent recording performance. We also have an on-demand type multi-head (discharge orifice diameter 35μ,
Heat generating resistor resistance value 150Ω, drive voltage 30V, frequency
The same study as in Example 1 was conducted using the recording device shown in FIG. 4 having a frequency of 2KHz) and excellent results were obtained.

【table】

【table】

【table】

[Table] Example 3 A recording liquid composition having the composition shown in Table 3 below was prepared in the same manner as in Example 1. Separately, the following composition was similarly prepared as a comparative example. Each of these compositions was filled into a felt pen, the cap was removed, and the writability was examined after the pen was left for one week. Table 4 shows the results. The recording liquid of the present invention had particularly excellent writability after standing.

【table】

【table】 [Brief explanation of the drawing]

1 and 2 are schematic diagrams of an inkjet recording apparatus, respectively. Figures 3-a and 3-b are a vertical sectional view and a horizontal sectional view of a main part of another recording device. FIG. 4 is an external perspective view of a multi-head head shown in FIGS. 3-a and 3-b. However, in the figure, 1...recording head, 2a...
...Piezo vibrator, 2b...Vibration plate, 3...Inflow port, 4...Liquid chamber, 5...Discharge orifice, 6...
Storage tank, 7... Recording liquid, 8... Supply pipe, 9...
...Intermediate processing means, 10...Signal processing means, 11...
...Droplet, 12, 25... Recording material, S... Recording signal, 14... Liquid chamber, 15... Heat generating head, 16...
... protective layer, 17 ... electrode, 18 ... heating resistor layer, 19 ... heat storage layer, 20 ... substrate, 26 ... groove.

Claims (1)

[Claims] 1. In a recording liquid mainly composed of a recording agent and a liquid medium for dissolving or dispersing the recording agent, the general formula: (However, in the above general formula, R is hydrogen or has 1 to 1 carbon atoms.
4, X is an ethoxy group and/or isopropoxy group, and n is 0 or an integer from 1 to 30.