JPS6274973A - recording ink - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a recording ink, and more particularly to an inkjet recording ink suitable for an inkjet system in which recording is performed by ejecting droplets from an orifice of a recording head.

(Prior art) Inks for writing instruments (signature pens, water-based ballpoint pens, etc.) that record on recording materials such as paper have traditionally been made by dissolving or dispersing various dyes and pigments in water or other organic solvents. is used. In addition, various dyes are used as ink in the so-called ink shared recording method, in which ink in the head is ejected from minute nozzles using the pressure generated by the vibration and heat of a pressure vibrator or the electrostatic attraction caused by the application of high voltage. , pigments dissolved or dispersed in water or other organic solvents are used. However, compared to stationery inks such as general felt-tip pens and water-based ballpoint pens, inkjet recording inks have many characteristics because the inkjet recording method generates ink droplets from extremely fine nozzles. More stringent conditions are required. Namely.

1. The material must have appropriate physical properties depending on the droplet generation method and droplet flight direction control method.

2. It must be stable for long-term storage, and no solid matter should adhere to the vicinity of the nozzle.

3. The printed image must have sufficiently high contrast and clarity.

4. The printed image has deteriorated in water resistance and light resistance.

5. Dry quickly after printing.

It is required to satisfy the following conditions.

In the inkjet recording method, the viscosity and surface tension of the ink have a large influence on the printing characteristics, and the viscosity and surface tension of the ink are determined by the device and the word value of the electrical drive pulse in the appropriate viscosity region and appropriate surface tension region. If it comes off, problems will occur in the ink jetting process and return process, making it impossible to obtain satisfactory printing performance. For example, if the viscosity is higher than the appropriate range, the return process of returning the ink meniscus to its initial state by capillary force takes a long time, resulting in poor ejection response and reduced printing speed.

Also, if the surface tension is lower than the appropriate range, the capillary force will be small when returning the ink meniscus that has fallen after ink jetting to its initial state, which will lengthen the return time and worsen the jetting response.

This reduces the printing speed, makes it difficult to keep the shape of the ink droplets constant, and increases blurring between the two image openings, making the printed image unclear. The appropriate viscosity range that does not cause the above-mentioned phenomenon is 3 cps or less, and the appropriate surface tension range is 4 Q dyne/c1n or more. Many studies have been conducted to satisfy conditions 1 to 5 and physical property values related to condition 1 described above.

For example, Japanese Patent Publication No. 52-13126, Japanese Patent Publication No. 49-89
No. 554, JP-A-50-95008, JP-A-53-7
Publications such as No. 7706 and Japanese Unexamined Patent Publication No. 51-90624 include
Dye-based inks and/or pigment-based inks used for color recording using the three primary colors of cyan and magenta yellow and plaques are disclosed.

(Problems to be Solved by the Invention) However, although dye-based inks have excellent long-term storage stability and ejection stability, the recorded images are not water resistant or
It is insufficient in terms of light resistance.

Various additives have been proposed to improve the aqueous and light resistance of No. 1, but none have been satisfactory.

On the other hand, although pigment-based inks have excellent water resistance and light resistance, they require a good dispersant for pigment particles, and in the case of inkjet recording inks in particular, pigment particles are
Not only must it be stably distributed, but it must also be stable against rapid changes in the environment. Nine different types of surfactants have been known to be used as good dispersants, but in order to disperse pigments at the concentration necessary to produce sufficient contrast in printed images, it is necessary to use the equivalent surfactants. It is necessary to use a certain amount of surfactant, and as a result, there is a problem that the surface tension decreases, causing blurring in the image and making the printed image unclear. Father, due to evaporation of the solvent in the ink. Two types of high boiling point solvents are used to prevent clogging due to precipitation and adhesion of solids near the nozzle.

For example, ethylene glycol, diethylene glycol,
A composition in which only a polyhydric alcohol such as propylene glycol is added is known.

If a high boiling point solvent is added to a sufficient extent to prevent clogging 9, there is a problem that the viscosity increases significantly and stable discharge becomes impossible.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present inventors focused on dispersants and high-boiling point solvents and completed the present invention as a result of intensive research.

That is, 9 the present invention combines a pigment, a polymer as a dispersant, and 6 to 1
5% by weight of urea and 5-35% by weight of glycerin/and 01-
The gist of the invention is a recording ink comprising at least 6% by weight of butyl cellosolve.

(Function) Since the inkjet recording ink of the present invention uses a polymer compound as a dispersant, 9 there is little decrease in surface tension, and by using urea in combination, a 1oop layer of a polymer adsorption layer on the surface of the pigment particle is formed. Since the steric stability of the thick pigment particles is increased, the two-dispersion stability is significantly improved. As for urea.

It suppresses evaporation of water by forming hydrogen bonds with water molecules, which is effective in preventing clogging near the nozzle. Since butyl cellosolve and glycerin are high boiling point solvents, they are effective in preventing clogging near the nozzle. The reason why the inkjet recording ink of the present invention has a low viscosity despite using the high boiling point solvent is not clear, but it contains 5 to 35% by weight of glycerin and 111 to 3% by weight.
It is thought that some kind of synergistic effect works in the direction of lowering the viscosity in the combination of butyl cellosolve.

(Structure of the Invention) The pigment is used as a coloring material, and various known pigments can be used. Specific examples include azo pigments, condensed polyazo pigments, phthalonanine pigments, quinacridone pigments, and anthraquinone pigments. ,) Organic pigments such as oxazine pigments, indigo pigments, thioindigo pigments, perinone/perylene pigments, titanium oxide, and iron oxide.

Examples include inorganic pigments such as carbon blank, fluorescent pigments, and the like.

Polymer compounds used as dispersants work to improve dispersion stability through effects such as reducing interfacial free energy through adsorption onto the pigment surface, and steric hindrance protection through the formation of adsorption and solvation layers on the polymer itself. Proteins such as gelatin, albumin, and casein, natural gums such as gum arabic and gum tragacanth, glucosides such as saponin, lignin sulfonate, and various proteins such as hexalac. Synthesis of various natural polymers and anionic polymers such as polyacrylates, styrene-maleate copolymers, styrene-acrylate copolymers, formalin condensates of aromatic sulfonates, etc. Polymers can be used as appropriate.

The purpose of urea is to improve pigment dispersion stability and prevent clogging near the nozzle, and the amount used is:

It is preferably 3 to 15% by weight based on the total amount of ink.

If it is less than 5% by weight, the effect on preventing clogging near the nozzle and dispersion stability of the pigment will be poor.

If the amount is more than 15% by weight, urea tends to precipitate as crystals, making clogging in the vicinity of the nozzle more likely. Glycerin and butyl cellosolve.

For the purpose of preventing clogging in the vicinity of the nozzle, the amounts used are preferably 5 to 35% by weight of glycerin and 01 to 5% by weight of butyl cellosolve based on the total amount of the ink. When the amount of glycerin is less than 5M%, the effect of preventing clogging near the nozzle is poor.

If glycerin is 35% by weight or more or butylcellosolve is 0.1% by weight or less, the viscosity will exceed the appropriate range, and if butylcellosolve is 3% by weight or more, the surface tension will be below the appropriate range.

In addition to the above ingredients, in order to prevent mold growth and ink flow inhibition due to ink spoilage, indium omazine, thiapenguzole, sodium dehydroacetate, 1,2-benzisothiazolin-5-one, etc. may be added as necessary. Preservatives and antifungal agents such as the following may be added as appropriate. Further, when the ink comes into contact with a metal part, a corrosion-preventing agent such as benzotriazole or ethylenediaminetetraacetate may be added as necessary to prevent corrosion of the metal. Although the ink of the present invention having the above-mentioned components as its basic constituents has excellent properties in itself, various additives may be added in order to provide even more outstanding recording characteristics.

Various methods can be employed for producing the inkjet recording ink of the present invention.

-911 is obtained by blending the above-mentioned components and mixing and grinding the mixture using a conventionally known dispersing machine such as a ball mill, homomixer, sand grinder, speed line mill, or roll mill.

(Example) The present invention will be described in more detail based on the following examples, where "parts" in the examples indicate "parts by weight."

Example 1 Carbon plastic (CI pigment plaque #10) 1
2.0 parts styrene-amine salt of acrylic acid (dispersant) 4. S part glycerin & 55 parts butyl cellosolve ethylene glycol motubutyl ether)
α77 part urea
6.0 parts Broxel XL-2 (preservative, anti-mold agent.

1.2-benzisothiazolin-3-one1. C, 1, Japan ■) Q, 2 parts ion-exchanged water 6 parts 1 part Disperse each of the above ingredients in a ball mill, centrifuge the resulting dispersion, and remove coarse particles with a filter. A black inkjet recording ink was obtained. The viscosity of the ink is 19ep9
, the surface tension was 48 dyne/me.

Comparative Example 1 A black inkjet recording ink was obtained in the same manner as in Example 1 except that the glycerin and butyl cellosolve in Example 1 were removed and water was added in the same amount. The viscosity of the ink is 1
．． 8 c p s + surface tension is 54 dyne/C
It was tn.

Comparative Example 2 A black inkjet recording ink was obtained in the same manner as in Example 1 except that the urea used in Example 1 was removed and water was added in the same amount.

The viscosity of the ink is i, 9 cps + surface tension is 47 dyne/Ca.

Example 2 Watching Red (C, I, Pigment Red #4
8:2) 1 [15 parts styrene-amine salt of maleic acid (dispersant) 4
．． O part Glycerin 7.5 parts Butyl cellosolve (ethylene glycol motupyl ether) 1.0 part Urea
ao part Broxel XL-213 parts ion-exchanged water 6 parts 7 parts The above components were used in the same manner as in Example 1 to obtain a red inkjet recording ink. The viscosity of the ink is 2.1 cps
The surface tension was 45 dyne/cm.

Comparative Example 3 A red inkjet recording ink was obtained in the same manner as in Example 1 except that the glycerin in Example 2 was changed to 40 parts and the increased water content was removed. The viscosity of the ink is 5.3 cps,
The surface tension was 44 dyne/mouth.

Comparative Example 4 A red inkjet recording ink was obtained in the same manner as in Example 1, except that the urea of Example 2 was changed to 1.0 part and water was added in the same amount. The ink had a viscosity of 2.3 cps and a surface tension of 44 dyne/cWL.

Example 3 Phthalone Anine Blue (CI Pigment Blue 〇15)
9.0 parts styrene-amine salt of maleic acid 4. O! Glycerin 15.0 parts Butyl cellosolve
1.5 parts urea
9 o parts Broxel XL-20, 5 parts ion-exchanged water 61.0 parts or more ingredients were used in the same manner as in Example 1 to obtain a blue inkjet recording ink. The ink had a viscosity of 2.2 cps and a surface tension of 47 dyne/C'n'L.

Comparative Example 5 A blue inkjet recording ink was obtained in the same manner as in Example 1, except that 10 parts of butyl cellosolve from Example 6 was added and the water was reduced by the same amount. The viscosity of the ink is 2.3
cps, and the surface tension was 55 dyne/α.

Example 4 Hansa Yellow 100 (CI Pigment Yellow #5)
20 parts styrene-amine salt of acrylic acid 4.
5 parts glycerin 85 parts butyl cellosolve 0.7 parts urea
6.5 parts Broxel XL-2α 2 parts ion-exchanged water 7d 6 parts or more components were used in the same manner as in Example 1 to obtain a yellow inkjet recording ink. The viscosity of the ink is 2.4 cps
+Surface tension was 42 dyne/cm.

Comparative Example 6 A yellow inkjet recording ink was obtained in the same manner as in Example 1 except that the urea of Example 4 was changed to 20 parts and the water was reduced by that amount. The ink had a viscosity of 2.6 cps and a surface tension of 41 dyne/ci.

Comparative Example 7 Water Blue #9 (CI Ac1d Blue
e #9゜Orient Chemical ■) 50 parts glycerin 7.0 parts butyl cellosolve 1.5 parts urea
10.0 parts Broxel XL-2a 2 parts Ion-exchanged water 766 parts The above components were mixed and stirred to obtain a blue inkjet recording ink. The ink has a viscosity of 2.3 cps and a surface tension of 41 d.
It was yne/cm.

(Effects of the Invention) As described above, using the inks of Examples 1 to 4 and Comparative Examples 1 to 7, T1 was studied, and an on-demand recording head (discharge orifice diameter: 5 μm) that discharges ink by vibration of a piezoelectric vibrator ), T2 to T were investigated using a recording device having the following.

(T,) Storage stability of ink: The ink was sealed in a glass container and stored at -5°C and 50°C for one year, and changes were examined.

○: Precipitation of insoluble matter, ink physical properties/color tone No change was observed.

×: Precipitation of insoluble matter, ink physical properties/color tone There was a change.

(T2) Ejection stability: Continuous ejection was performed in an atmosphere at a room temperature of 5° C. and 140° C. to examine recording stability.

○: Stable discharge continued.

×: Disturbance occurred in discharge.

(T,) Color tone and density of recorded images: Test pieces were printed on inkjet paper (ST-704A, manufactured by Jujo Paper Co., Ltd.) and visually evaluated.

(T4) Water resistance of recorded images: After the test piece used for color tone evaluation was immersed in water for 1 hour.

It was air-dried indoors and evaluated visually.

(T,) Light resistance of recorded images: The test piece used for color tone evaluation was irradiated for 5 hours with a fade meter, and the color difference from before irradiation was determined by f and il.

○: ΔE = less than 5 NBS ΔE = 5 NBS or more The inks obtained in Examples 1 to 4 showed no sedimentation of pigment particles or changes in ink physical properties or color tone even after long-term storage. Stable ejection was achieved during actual printing, and there was no clogging caused by solid matter adhering to the vicinity of the nozzle. Furthermore, the recorded images have excellent water resistance and light resistance, and each color tone is vivid.

Similar studies were conducted on the inks obtained in Comparative Examples 1 to 7. The inks of Comparative Examples 1 to 6 are inferior to the inks of Examples in terms of long-term storage stability and nozzle drying resistance, while the ink of Comparative Example 7 has poor water resistance and light resistance. It was inferior to sex.

As described above, the ink of the present invention has excellent ejection stability.

This inkjet not only has excellent ejection response and storage stability, but also records images with excellent water resistance and light resistance.

It is ideal as a recording ink.

Claims (1)

[Scope of Claims] 1) A recording ink comprising at least a pigment, a polymer compound as a dispersant, 3 to 15% by weight of urea, 5 to 35% by weight of glycerin, and 0.1 to 3% by weight of butyl cellosolve. . 2) The recording ink according to claim 1, wherein the composition ink has a viscosity of 3 cps or less and a surface tension of 40 dyne/cm or more.