JPS6045669B2 - recording liquid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel recording liquid, particularly a recording liquid suitable for inkjet recording methods.

BACKGROUND ART Inks used for writing instruments (felt pens, fountain pens, etc.) have been known in the past, in which various dyes and pigments are dissolved or dispersed in a liquid medium consisting of water or other organic solvents.

The above-mentioned recording liquid is also used in the so-called inkjet recording method, in which recording is performed by ejecting the liquid in the recording head from the ejection orifice using vibration by a piezo vibrator, electrostatic attraction by applying high voltage, thermal energy, etc. It is known.

Writing instruments such as felt-tip fountain pens and inkjet recording liquids have many properties in common, such as the absence of clogging due to ink drying at the tip and good water resistance and light resistance of recorded images. Compared to physical writing instruments, inkjet recording liquids require conditions that are not present in writing instruments, such as ejection responsiveness and ejection stability when droplets are generated from minute orifices.

Conventionally, as a recording liquid for stationery or inkjet recording, for example, Japanese Patent Application Laid-Open No. 50-91427 and Japanese Patent Application Laid-Open No. 51-90
624, Special Publication No. 51-40484, Special Publication No. 52-1
No. 3126, Japanese Patent Publication No. 13127, 1983, Japanese Patent Publication No. 1983-
As shown in publications such as No. 95008, there are known dyes and pigments in which various dye pigments are dissolved or dispersed in aqueous or non-aqueous solvents.

Preferable conditions common to recording liquids for inkjet recording for stationery are (1) no clogging due to drying at the pen tip or orifice tip;

(2) Fast fixation on recording materials (paper, cloth, film, etc.) with little bleeding.

(3) The color tone of the recorded image is clear and the density is high.

(4) The recorded image has excellent water resistance and light resistance. (
5) Do not damage surrounding materials (containers, filters, etc.) of the recording liquid.

(6) It must have excellent stability in terms of odor, toxicity, flammability, etc.

etc.

Furthermore, inkjet recording liquids must have liquid physical properties (viscosity, surface tension, electrical conductivity, etc.) that match the ejection conditions (driving voltage, driving frequency, ejection orifice shape and material, orifice diameter, etc.). Therefore, it is required to have long-term discharge stability. That is, it has good ejection responsiveness to form droplets in response to the driving frequency, a wide stable ejection margin against fluctuations in driving voltage and driving frequency, and when recording while the ejection orifice moves left and right as in a printer. The ejection orifice is required to have properties such as holding the recording liquid so that the recording liquid is not ejected during non-recording. Also cyan, magenta, yellow, and black. In the case of color recording, it is required that the recording liquid permeates the recording material quickly and without bleeding, and that the color of the recording liquid does not change even during long-term storage so that the intended color balance does not change. It is necessary to satisfy the above characteristics at the same time. - It is extremely difficult, and the previously known techniques described above are unsatisfactory in this respect.

The dye pigments used in this type of recording liquid are, for example,
Direct dye Dyes such as , acid dyes, and basic dyes have problems with the water resistance and light resistance of recorded images, and pigments have the problem of poor dispersion stability and are prone to clogging.Furthermore, dyes have the disadvantage of molecular association in the liquid medium. The problem is that the color tone changes due to the pigment settling, and the concentration of the dispersed pigment decreases due to sedimentation, which disrupts the color balance. A highly practical recording liquid that satisfies stability, fixation, image density, sharpness, water resistance, and light resistance, and is also highly safe and odorless, non-toxic, and non-flammable. Particularly suitable for color recording. The aim is to provide a recording liquid with a bright red color.

) In other words, the present invention provides a recording liquid composed of a recording agent for forming a recorded image and a liquid medium for dissolving and/or dispersing this recording agent, in which the recording agent contains a water-soluble red dye and a red pigment. and a molecular weight of 10 in the liquid medium.
00 to 100,000 and water. That is, the present invention provides a red recording liquid useful for color recording, which has both the excellent water resistance and light resistance of pigments and the vivid color tone of dyes, and has excellent dispersion stability for long-term storage.

Although the reason is not clear, the composition of the present invention produces a synergistic effect in that the water resistance of the dye is significantly improved compared to when the dye is used alone, and the dispersion stability of the pigment is significantly improved compared to when no dye is present. Further, the recording liquid of the present invention includes dyes,
It has the extremely favorable properties of reduced thixotropy and no color change over time compared to when each pigment is used alone. Preferred dyes in the present invention that exhibit such a remarkable synergistic effect are C.I. I. Direct dyes shown by Tirectrect 2, 20, 31, 46, 75, 80, 83, C soil acid red 52, 92, 94, 106
, 133, 154, 155, 249, 265, 274; I. Basic Cred 1, 2,
Examples include basic dyes represented by 12, 13, and 14.

Similarly, the pigment preferably used in the present invention is C.I. I. Pigment Red 5, 11, 48, 49, 57, 60, 139
, 144, 165, 166, C.I. I
．． Pigment Red 122,209, a quinacridone pigment, C.I. I. Pigment Red 123, a perylene pigment, C.I. I. Anthraquinone pigment represented by Pat Red 10, C.I. I. Pat Red 1, 2
A thioindigo pigment represented by C. I. Examples include lake pigments represented by Pigment Red 81 and 90.

The dyes and pigments are C.I. I. Color value (JISZ-8701
), preferably the dominant wavelength is 490 nanometers or more, the stimulus purity is 51 to 61 percent, and the brightness is 15 to 25 per cent. In the recording liquid of the present invention, the preferred ratio of dye to pigment is in the range of 10:1 to 1:10.

The dispersant preferably used in the present invention has a molecular weight of 1000.
There are 0 to 100,000 polymer dispersants. Examples of preferred polymeric dispersants include polyvinyl alcohol, polyvinylpyrrolidone, polyvinylpyridine, polyacrylate, polymethacrylate, condensed naphthalene sulfonate, and styrene-maleic acid copolymer, all of which have the above molecular weight range. , diisobutylene-maleic acid copolymer, polyethylene glycol, polypropylene glycol, polyoxyethylene-oxypropylene block polymer,
Styrene-(meth)acrylic acid, (meth)acrylic acid ester-(meth)acrylate copolymer, styrene-itaconate copolymer, itaconate-itaconate copolymer, vinylnaphthalene-maleate copolymer Polymers, vinylnaphthalene-(meth)acrylic acid copolymers, vinylnaphthalene-itaconate copolymers, etc., and derivatives thereof. The above polymers may further be copolymerized with monomers such as acrylonitrile, vinyl acetate (meth)acrylamide, N-methylol (meth)acrylamide, vinyl chloride, vinylidene chloride, and ethylene. Some are commercially available or can be easily synthesized by known polymerization methods. The amount of the dispersant added is preferably 1 to 300% by weight, more preferably 5 to 200% by weight based on the pigment content. As the liquid medium of the recording liquid of the present invention, water or a mixed system of water and a water-miscible organic solvent is used.

Examples of water-miscible organic solvents that are preferably used include methyl alcohol, ethyl alcohol, propyl alcohol, diacetone alcohol, furfuryl alcohol, ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, dipropylene glycol, and triethylene. Glycol, tetraethylene glycol, 1,2,6, hexanetriol, thiodiglycol, glycerin, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl carbitol, ethyl carbitol, butyl carbitol, triethylene glycol monomethyl ether, Triethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, methyl carbitol acetate, ethyl carbitol acetate, diethanolamine, triethanolamine, formamide,
Dimethylformamide, dimethylacetoa. morpholine, dimethylacetamide, N-methyl-2-pyrrolidone, 1,3 dimethyl-2-imidazolidinone, and the like. The preferred content of these water-miscible organic solvents is 5 to 8 weight percent in the liquid medium, more preferably 10 to 8 weight percent.
(4) Weight percent.

In addition, to the recording liquid of the present invention, conventionally known viscosity modifiers, surface tension modifiers, PH modifiers, conductivity modifiers, binders (polymer vehicles), antifungal sterilizers, etc. may be added. I can do it. The recording liquid of the present invention is composed mainly of the above-mentioned components, and various methods can be employed for its preparation.

For example, a method is employed in which the above-mentioned components are blended and mixed and ground using a ball mill, roll mill, speed line mill, homomixer, sand grinder, or the like. still,
The pigment dispersion process is carried out in a state where the pigment is as highly concentrated as possible, and after the dispersion treatment, this is diluted with an aqueous liquid.
The viscosity of the ink is finally adjusted to about 1-20 CpS1, preferably about 3-10 CpS.

In the recording liquid prepared in this manner, pigment particles do not aggregate or settle even when stored for a long period of time in a low viscosity range.

This recording liquid can be used under (1) a wide range of recording liquid ejection conditions (driving voltage of the piezoelectric element,
Liquid physical properties (viscosity, surface tension,
electrical conductivity, etc.).

(2) Stable for long-term storage and does not cause clogging of inkjet devices.

(3) Fixing to recording materials (paper, film, etc.) is fast and reliable, and the periphery of dots is smooth and does not bleed.

(4) The color tone of the formed image is clear and the density is high.

(5) The formed image has excellent water resistance and light resistance.
(6) Do not damage materials surrounding the recording liquid (container, connecting tube, sealing material, etc.).

(7) It has various characteristics such as low odor, toxicity, non-flammability, and excellent safety.

Here, the present invention will be explained in further detail by showing examples. Note that the numbers in the examples are parts by weight.

Example 1 C. I. Pigment Red 575 parts C. I. Direct Red 3 parts polyacrylic acid (MW.2OOO) 3 parts diethylene glycol + ion exchange water
Marked part The above ingredients were placed in a ball mill and rotated for an hour to mix and grind.

The obtained dispersion liquid was subjected to an ultracentrifuge to remove coarse particles, and a red recording liquid was obtained. C. of recording liquid. I. E. The color values were a dominant wavelength of 500 nanometers, an excitation purity of 57%, and a brightness of 21%. Using the recording liquid, T1 to T5 were examined using a recording apparatus having an on-demand recording head (discharge orifice diameter 50μ, piezoelectric vibrator drive voltage 60V, frequency 4KHz) that discharges the recording liquid using a piezoelectric vibrator. All experiments yielded good results.

Long-term storage stability of T1 recording liquid: Even after the above recording liquid was sealed in a glass container and stored at -30°C and 60°C for 6 months, no precipitation of insoluble matter was observed, and there were no changes in the physical properties or color tone of the liquid. Nakatsuta.

T2 ejection stability: Continuous ejection was performed for 24 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.

T3 ejection response: Intermittent ejection every 2 seconds and ejection after 2 months of standing were investigated, and in both cases stable and uniform recording was achieved without clogging at the orifice tip.

Quality of T4 recorded images: The images recorded on the recording materials shown in Table 1 had high density and were clear.

After three months of exposure to outdoor light, the density reduction rate was less than 1%, and when immersed in water for 1 minute, there was no image smearing. T5 Fixability on various recording materials: After one printing with the following recording materials, the printed area was rubbed with a finger to determine whether the image was blurred or not and whether there was any bleeding.

All of them exhibited excellent fixing properties with no image fading or blurring. Example 2 A recording liquid having the composition shown in the table below was prepared in the same manner as in Example 1, and T1 to T4 were examined in the same manner as in Example 1.

(In Table 2, the numbers in parentheses indicate the composition ratio)
. Also, an on-demand type multi-head that performs recording by applying thermal energy to the recording liquid in the recording head to generate droplets (discharge orifice diameter 35μ, heating resistor resistance value 150Ω, drive voltage 30μ, frequency 2KHz). The same study as in Example 1 was conducted using a recording device having the following.

In all cases, the recorded images obtained had excellent light fastness and water resistance, clear color tone and high density, smooth dot periphery without bleeding or blurring, and good fixing properties.

Claims (1)

[Scope of Claims] 1. A recording liquid composed of a recording agent for forming a recorded image and a liquid medium for dissolving and/or dispersing the recording agent, wherein the recording agent contains a water-soluble blue dye and a blue pigment. A recording liquid comprising: a polymer dispersant having a molecular weight of 1,000 to 100,000 and water in the liquid medium. 2 C. of the dyes and pigments. I. Both E color values are
The recording liquid according to item 1, having a dominant wavelength of 490 nanometers or more, a chemical purity of 56±5%, and a brightness of 20±5%. 3 The ratio of the dye to the pigment is 10:1 to 1:1 by weight.
The recording liquid according to claim 1, which is in the range of 0. 4. The recording liquid according to claim 1, wherein the contents of the dye and the pigment are both in the range of 1 to 20 weight percent based on the total weight of the recording liquid. 5 The dye is C.I. I. Direct Red 2, 20, 3
1,46,75,80,83,C. I. Acid Red 52, 92, 94, 106, 133, 154, 155,
249, 265, 274, C. I. Basic Cred 1
, 2, 12, 13, and 14. 6 The pigment is C.I. I. Pigment Red 5, 11, 4
8, 49, 57, 60, 81, 90, 122, 123,
139, 144, 165, 166, 209, C. I. The recording liquid according to claim 1, which is a pigment selected from Bat Red 1, 2, and 10.