JPH04309573A - Recording liquid - Google Patents

Abstract

PURPOSE:To provide an ink jet recording liq. which enables a high-quality printing without causing blurring on plain paper. CONSTITUTION:A recording liq. which comprises a liq. medium contg. an org. solvent, a recording agent consisting of a pigment, and a surfactant having a surface activity in an org. solvent. The surfactant reduces the surface tension and the speed of penetration of the liq. into paper, thus retarding the spreading of the liq. to give a high-quality printing without causing blurring.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording liquid, and more particularly to a recording liquid for inkjet recording.

0002

2. Description of the Related Art Inkjet recording is a recording method that enables high-speed printing with low noise, and is a recording method that is rapidly becoming popular in recent years. In this type of inkjet recording, recording is performed by ejecting a recording liquid as small droplets by heating or pressurizing the recording liquid and making the droplets adhere to a recording member such as paper.

The recording liquid used is usually prepared by adding a dye or pigment as a recording agent to a liquid medium consisting of water or an organic solvent.

0004

[Problems to be Solved by the Invention] When an organic solvent is used as the liquid medium of the recording liquid, it is possible to use various recording agents having excellent water resistance and light resistance. but,
The organic solvent very easily wets the fibers of paper, which is a recording member, and as a result, a so-called bleeding phenomenon occurs on plain paper. Therefore, the use of such a recording liquid is limited to printing on special paper whose surface is coated with inorganic fine particles or the like.

When considering the phenomenon of liquid permeation into paper, the Lucas-Washburn equation shown below is a commonly used theoretical equation.

h=(rγcosθt/2η)1/2

[0007] This formula shows that the depth (h) that the liquid penetrates is:
It is shown that it is proportional to the square root of the cosine of the capillary radius (r), the surface tension of the liquid (γ), and the contact angle between the liquid and the capillary (θ), and is inversely proportional to the square root of the liquid viscosity (η). Generally, the print quality tends to improve as the penetration depth h per unit time is smaller, that is, the penetration speed is slower. When the liquid is an organic solvent, the contact angle θ with paper is approximately 0° and cos θ is 1, which is the maximum. Therefore, in order to reduce the penetration depth h, the viscosity η of the liquid must be increased or the surface tension γ must be decreased.

Attempts have been made to increase the viscosity of the recording liquid in order to suppress bleeding of the organic solvent, but when used for inkjet recording, the viscosity of the recording liquid is usually 10 cp or less, and at most 50 cp or less, due to the structure of the inkjet head. must be adjusted.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a recording liquid that can produce high-quality prints without bleeding on plain paper.

0010

[Means for Solving the Problems] The recording liquid of the present invention is characterized in that it is composed of a liquid medium containing an organic solvent, a pigment as a recording agent, and a surfactant having a surfactant effect in the liquid medium. That is. Moreover, as the surfactant, a fluorine-based surfactant is preferable.

[0011]

[Function] The recording liquid of the present invention has a surfactant that has a surfactant effect even in organic solvents, which lowers the surface tension of the recording liquid, thereby reducing the rate of penetration into paper and increasing the This is to achieve printing quality.

The recording liquid of the present invention mainly contains a liquid medium containing an organic solvent, a pigment as a recording agent, and a surfactant, and further contains a dispersant, a viscosity modifier, inorganic fine particles, other additives, etc. may be added.

[0013] In the present invention, the liquid medium is basically not limited, and conventionally used organic solvents can be used. For example, low molecular weight monohydric alcohols such as ethanol, n-propyl alcohol, and isopropyl alcohol, low molecular weight ketones such as acetone, methyl ethyl ketone, and diethyl ketone, cyclic ethers such as tetrahydrofuran and dioxane, methyl acetate, ethyl acetate, isopropyl acetate, etc. esters, aromatic solvents such as benzene and toluene, glycols such as triethylene glycol and dipropylene glycol, glycol derivatives such as tripropylene glycol monomethyl ether and cellosolve acetate, glycerin, amine-based and amide-based nitrogen-containing compounds, etc. can be mentioned. Alternatively, it may be a mixture of these organic solvents, or a mixture with water as long as it is a water-soluble organic solvent.

Examples of pigments include azo, phthalocyanine, quinacridone, anthraquinone, dioxazine, indigo, thioindigo, perylene, perinone, isoindolinone, quinophthalone, titanium oxide, cadmium, Examples include iron oxide type and carbon black.

[0015] As the surfactant, a surfactant having a surfactant effect in an organic solvent can be used, and is appropriately selected depending on the liquid medium used in preparing the recording liquid. As the surfactant, fluorinated surfactants are preferred, and among organic solvents, fluorinated alkyl esters are examples of those having particularly high surfactant effects.

The dispersant is appropriately selected depending on the liquid medium used and the pigment to be dispersed, and examples thereof include rosin derivatives, maleic acid resins, fumaric acid resins, phenol resins, xylene resins, urea resins, melamine resins, ketone resins, and alkyd resins. Resin, polyamide resin, acrylic resin, polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, butyral resin, styrene resin, epoxy resin, polyurethane,
Examples include polymeric materials such as cellulose derivatives, various nonionic surfactants, and ionic surfactants.

Furthermore, the following additives may be added to the recording liquid to be prepared as necessary. As a viscosity modifier, a polymer material, a surfactant, etc. are used similarly to a dispersant. Examples of inorganic fine particles include SiO2
, Al2O3, FeO, Fe2O3, CaO
, MgO, zeolite, etc. Other examples include antioxidants, ultraviolet absorbers, and stabilizers.

[0018]

EXAMPLES Next, the present invention will be explained in more detail by way of examples. (Example 1) <Composition> N-methylpyrrolidone
89% by weight ethylcellulose
5% by weight carbon black
5% by weight nonionic fluorosurfactant 1
Weight% (Florado FC-171; manufactured by Sumitomo 3M)

0
The recording liquid prepared based on the above composition was stable and had a surface tension of 19 dyne/cm at 25°C. When this recording liquid was mounted on a piezoelectric inkjet head and printed on several types of plain paper, the recording liquid flew well.
Clear black print without bleeding was obtained. Further, even when the printed matter was immersed in water, it did not smear at all. Further, even after 50 hours of exposure to a fade meter, there was no color change at all in the printed matter.

(Example 2) <Composition> Triethylene glycol mono-n-butyl ether 86% by weight Polyvinyl butyral

5% by weight carbon black

5% by weight nonionic fluorine surfactant
1% by weight (Florado FC-431; manufactured by Sumitomo 3M) SiO2

3% by weight

The recording liquid prepared based on the above composition is stable and has a surface tension of 20 dyne at 25°C.
/cm. When this recording liquid was mounted on a piezoelectric inkjet head and printed on several types of plain paper, the recording liquid flew well and a clear black print without bleeding was obtained. Further, even when the printed matter was immersed in water, it did not smear at all. Further, even after 50 hours of exposure to a fade meter, there was no color change at all in the printed matter.

(Example 3) <Composition> Tripropylene glycol mono-n-butyl ether 86.5% by weight Polyvinylpyrrolidone
5% by weight carbon black
5% by weight
Nonionic fluorine surfactant
0.5% by weight
(Florado FC-430; manufactured by Sumitomo 3M) S
iO2

3% by weight

The recording liquid prepared based on the above composition is stable and has a surface tension of 19 dyne at 25°C.
/cm. When this recording liquid was mounted on a piezoelectric inkjet head and printed on several types of plain paper, the recording liquid flew well and a clear black print without bleeding was obtained. Further, even when the printed matter was immersed in water, it did not smear at all. Further, even after 50 hours of exposure to a fade meter, there was no color change at all in the printed matter.

(Comparative Example 1) A recording liquid having the composition of Example 1 was prepared without using a fluorine-based surfactant. The recording liquid was stable, but the surface tension was 30 dyn at 25°C.
e/cm. When this recording liquid was mounted on a piezoelectric inkjet head and printed on several types of plain paper, the recording liquid flew well, but the printing was about 1.
It expanded three times and became blurry.

(Comparative Example 2) A recording liquid having the composition of Example 2 was prepared without using a fluorine-based surfactant. The recording liquid was stable, but the surface tension was 31 dyn at 25°C.
e/cm. When this recording liquid was mounted on a piezoelectric inkjet head and printed on several types of plain paper, the recording liquid flew well, but the printing was about 1.
It expanded five times and became blurry.

[0026]

As described above, in the present invention, by using a surfactant having a surfactant effect in an organic solvent to lower the surface tension of the recording liquid, it is possible to achieve high quality printing without bleeding on plain paper. It is possible to obtain Furthermore, the recording liquid of the present invention has good ejection properties from an inkjet head, and furthermore, since a pigment is used, it also has excellent light resistance and water resistance.

Claims (2)

[Claims] 1. A recording liquid comprising a liquid medium containing an organic solvent, a pigment as a recording agent, and a surfactant having a surfactant effect in the liquid medium. 2. The recording liquid according to claim 1, wherein the surfactant is a fluorosurfactant.