JPH03255178A - Ink for ink jet recording - Google Patents

Abstract

PURPOSE:To obtain the title ink used for a specified recording system, which is excellent in foaming response to thermal energy and can realize recording free from blotting even on plain paper with excellent penetration, by using at least a water-soluble dye, water, and a specified compound as the constituents. CONSTITUTION:The title ink used for a recording system wherein thermal energy corresponding to a recording signal is given to an ink in a recording head chamber and liquid droplets are splashed upon a recording medium by the energy to effect recording, which contains at least 0.1-10wt.% water-soluble dye (e.g. C.I. Direct Yellow 86), 70-95wt.% water, and 5-16wt.% 5C straight-chain alkylene glycol (e.g. HOCH2CH2CH2CH2CH2OH).

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to inkjet inks, and more specifically to coated papers specially prepared for inkjet use, as well as other papers generally used in offices and homes. copy paper and report paper.

Non-coated paper such as notebooks, stationery, bond paper, continuous slip paper, etc.
The present invention relates to an inkjet ink suitable for a method that utilizes thermal energy, which enables high-definition and high-quality recording even on so-called plain paper.

(Prior Art) Conventionally, inkjet inks with a wide variety of compositions have been reported. In particular, in recent years, detailed ink composition and physical properties have been developed to enable good recording even on plain paper such as copy paper, report paper, notebooks, and stationery, which are commonly used in offices. A lot of research and development is being carried out.

In addition, various methods have been proposed for inkjet recording, including a method in which charged droplets are continuously generated and a portion of the droplets are used for recording, and a method in which a signal is sent to a recording head having a piezoelectric element. Give.

A method in which recording is performed by generating ink droplets in response to the signal, or a method in which thermal energy corresponding to the recording signal is applied to the ink in the chamber of the recording head, and the energy is used to generate droplets to perform recording. There is.

In particular, a type that ejects ink through a bubbling phenomenon of ink due to thermal energy, such as that described in Japanese Patent Application Laid-Open No. 54-59936, has attracted particular attention recently because it is easy to increase the integration and density of nozzles. This is the method by which they are collected. However, since it utilizes a phenomenon called foaming that is not found in other methods, more stringent conditions are required for the ink used.

Preferred conditions for the ink used in this method are listed below. (2) Even if the ink is left without a cap during a recording pause, stable ejection can be obtained immediately after resuming recording; that is, the ink near the ejection ports is difficult to dry, causing clogging. There isn't.

(3) A high-quality image without irregular shapes or irregular bleeding can be obtained, especially on plain paper; (4) The fixing property (print drying property) is fast on plain paper, and the printed matter can be easily rubbed. (5) It has good storage stability and retains its ink performance over a long period of time; and (6) It has excellent safety in terms of toxicity and flammability.

In response to these demands, conventional ink formulations include:
The ejection method is not particularly limited to one type using thermal energy, but for example, ink generally contains a high boiling point organic solvent such as glycol for the purpose of preventing drying and clogging. When recording on plain paper with a high degree of size, it is difficult for the ink to penetrate into the inside of the paper, and the drying of the recorded area is poor, so if you touch the recorded material with your hands, the ink may stick to your hands. There were problems with fixation, such as characters being scratched or scratched.

On the other hand, in order to improve the permeability of the ink into the inside of the paper, Japanese Patent Application Laid-Open No. 55-29546 proposes a method of adding a large amount of surfactant to the ink. but,
In this case, depending on the type of paper, a lot of bleeding may occur, or when ink is filled into an inkjet head, depending on the structural conditions of the head, the ink may retreat from the orifice surface and no ejection may occur. On the other hand, problems such as the entire orifice surface becoming wet and ink not being ejected were observed.

Furthermore, in Japanese Patent Application Laid-open No. 56-57862, the ink p
A method of making H strongly alkaline has been proposed, but in this case it is dangerous if the ink is touched, and it is not suitable for papers using certain sizing agents, such as neutral paper. has drawbacks such as bleeding and drying properties which may not be good.

Further, JP-A-62-16'11175 proposes a pigment ink using a diol having 4 to 6 carbon atoms as a dispersion stabilizer for a water-insoluble pigment.

However, compared to dyes, pigments still have insufficient dispersion stability in inks, and therefore there is a problem in the long-term storage stability of inks. Furthermore, inkjet systems that use thermal energy have problems in that foaming response is poor, ejection tends to become unstable, and image quality deteriorates significantly.

As mentioned above, although various improvements have been attempted in addition to the above, even if there is no limitation to using only one type of heat energy, problems such as the aforementioned bleeding, drying properties, and even eye resistance can be overcome. The current situation is that no ink has been known to date that satisfactorily solves all problems such as clogging and storage stability, and in addition, it responds well to the phenomenon of foaming, which is unique to thermal energy systems. Designing an ink with even higher performance is important, but it can be said to be an extremely difficult task.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide a foaming material that has good responsiveness to thermal energy and that can be used for uncoated copy paper, report paper, notebooks, stationery, etc. commonly used in offices, etc. An object of the present invention is to provide an inkjet ink that solves the problems of ink bleeding and slow drying of recorded matter when recorded on engineered paper, so-called plain paper.

Another object of the present invention is to provide an inkjet ink that is highly safe for use in offices and homes.

Still another object of the present invention is to provide an inkjet ink that is less likely to cause clogging in the nozzles of an inkjet head and has excellent reliability.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention provides an inkjet ink used in a recording method in which thermal energy corresponding to a recording signal is applied to ink inside a recording head chamber, and droplets caught in the energy are ejected onto a recording material to perform recording. At least 0.
This is an inkjet ink characterized by containing 1 to 10% by weight of a water-soluble dye, 70 to 95% by weight of water, and 5 to 16% by weight of a linear alkylene glycol having 5 carbon atoms.

(Function) The present inventors have developed a method suitable for a recording method in which ink is ejected by a bubbling phenomenon caused by thermal energy, and which improves the bleeding, drying and permeability of ink on paper, and furthermore improves the appearance of ink in the nozzle of an inkjet head. As a result of intensive research into a highly reliable ink composition that is less likely to cause clogging, we found that an ink containing 70 to 95% water and 5 to 16% by weight of a linear alkylene glycol with a carbon number of 5 has the ability to reduce bleeding and permeability. The present inventors have discovered that the present invention is well-balanced in that respect, and has particularly good anti-clogging properties.

That is, according to the research conducted by the present inventors, addition polymers of ethylene oxide, glycerin, etc. have been conventionally used as ink clogging prevention agents, and glycerin in particular can prevent clogging with the addition of a relatively small amount. It is a particularly preferred anti-clogging agent because of its ability to prevent clogging, and because it is less likely to cause ink to bleed on plain paper. However, this glycerin has a drawback in that it has poor wettability with the sizing agent present in paper, and depending on the type of paper, the drying properties and permeability of ink on the paper surface are significantly poor.

On the other hand, addition polymers of ethylene oxide have a clogging prevention effect, but the problem of ink bleeding is considerably inferior to that of glycerin, and although the permeability is slightly better than glycerin, it has not reached a sufficient level. There wasn't.

On the other hand, the linear alkylene glycol having 5 carbon atoms used in the present invention has the same clogging prevention effect as glycerin, and has a very good balance between ink bleeding and permeability. The reason for this is thought to be that the compound has a low vapor pressure and has two hydroxyl groups, so it has excellent dissolution or dispersibility of the five dyes, and as a result, a good anti-clogging effect can be obtained. Furthermore, since it is a linear glycol, hydrophilic and hydrophobic parts are conveniently distributed within the molecule. Therefore, it is considered that the wettability with respect to the sizing agent is good, and as a result, the permeability of the ink on the paper surface is significantly improved.

On the other hand, the responsiveness to foaming is determined when the alkylene glycol content in the ink is 5 to 16% by weight and water is also 7% by weight.
It becomes particularly good when it is contained in an amount of 0 to 95% by weight. This is considered to be because the physical properties of the ink mixed at the above ratio and its wettability with respect to each member inside the nozzle are particularly suitable for a recording method in which the ink is ejected by the bubbling phenomenon of the ink due to natural energy.

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

The compounds used in the present invention and mainly characterizing the present invention are:
These are linear alkylene glycols having 5 carbon atoms, and all of them can be obtained by conventionally known methods. Preferred specific examples of the above compounds are as follows, but the present invention is not limited to these specific examples.

Compound Example 1: )10-C)1. -CIl□-CH
,-CHI2-CI(,-OH compound example 2: No
-CHI-C)1. -CH, -CH-C)l.

8 Compound Example 3: HO-CHz-C1h-CH-CHi
-CHs[ H Compound example 4: HO-CH2-CH-CH, -CH
I-CHIH 0)1 0H 0)108 Even if the number of carbon atoms is 5, if a branched alkylene glycol is used, the balance between clogging resistance, permeability, and bleeding of the ink will be lower than the above-mentioned direct balance. This is not preferable because it is inferior to the case where a chain alkylene glycol is used, and the foaming response to thermal energy is also inferior.

The above-mentioned linear alkylene glycols having 5 carbon atoms can be used alone or as a mixture, and the amount added to the ink will vary depending on the pigment used and other liquid medium components used together. The proportion thereof is approximately 5 to 16% by weight, preferably 6 to 15% by weight.

The amount of the linear alkylene glycol having 5 carbon atoms added is 5.
If it is less than 16% by weight, there is no effect on foaming response and ink permeability, while if it exceeds 16% by weight, the surface tension of the ink decreases, making it easier to bleed depending on the paper and reducing print quality. do.

The pigments constituting the ink of the present invention include direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, disperse dyes,
Vat dyes, soluble architectural dyes, reactive disperse dyes, oil dyes,
Various pigments may be used, but water-soluble dyes are particularly preferred from the viewpoint of ink performance.

The content of these pigments is determined depending on the type of liquid medium component, the properties required of the ink, etc.; 0.
The proportion is 5 to 8%, more preferably 1 to 5%.

Further, the proportion of water, which is an essential component of the ink of the present invention, in the ink is 70 to 95% by weight, preferably 75 to 95% by weight.
It accounts for 78 to 95% by weight, more preferably 78 to 95% by weight. When the amount of water is less than 70% by weight, the proportion of organic solvent is high, causing the paper to curl and the quality of printing on plain paper to be significantly degraded. On the other hand, if the amount of water exceeds 95% by weight, the stability of ink ejection from the nozzle orifice will deteriorate significantly.

The essential components constituting the ink of the present invention are as described above, but by using a monohydric alcohol in combination, irregular bleeding of the ink can be suppressed while further improving permeability and responsiveness to thermal energy. I can do it. Specific examples of the monohydric alcohol that can be used include aliphatic monohydric alcohols, preferably aliphatic monohydric alcohols having 2 to 5 carbon atoms.

The amount of the monohydric alcohol added to the ink varies depending on its type, but is 0.1 to 10% by weight, more preferably 0.5 to 5% by weight of the ink. If the amount of monohydric alcohol added is less than 0.1% by weight, there will be little effect on response to thermal energy and ink permeability, while if it exceeds 10% by weight, irregular bleeding may occur depending on the paper. occurs, and the image quality deteriorates significantly.

In addition, other general organic solvents that have been used in conventionally known inks can also be used in combination if necessary. For example, amides such as dimethylformamide and dimethylacetamide; ketones such as acetone and diacetone alcohol; Keto alcohols; ethers such as tetrahydrofuran and dioxane; oxyethylene or oxypropylene addition polymers such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, and polypropylene glycol; ethylene glycol, propylene Alkylene glycols other than essential components in the present invention, such as glycol, trimethylene glycol, butylene glycol, 1,2.6-hexanetriol, hexylene glycol, etc., in which the alkylene group contains 2 to 6 carbon atoms; thiodiglycol; Glycerin;
Lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether; triethylene glycol dimethyl (or ethyl) ether, tetra Lower dialkyl ethers of polyhydric alcohols such as ethylene glycol dimethyl (or ethyl) ether; sulfolane, N-methyl-2-pyrrolidone, 1
．． Examples include 3-dimethyl-2-imidazolidinone.

The content of the water-soluble organic solvent is in the range of 1 to 20% by weight, preferably 2 to 15% by weight based on the total weight of the ink for boat fishing.

When organic solvents such as those mentioned above are used together, they can be used alone or as a mixture, but the most preferable liquid medium composition is that the medium is at least one water-soluble high-boiling organic solvent, such as diethylene glycol, triethylene glycol, glycerin. It contains polyhydric alcohols such as.

In addition, various other dispersants, surfactants, viscosity modifiers, surface tension modifiers, fluorescent brighteners, etc. can also be added as necessary within a range that does not hinder the achievement of the objects of the present invention.

For example, viscosity modifiers such as polyvinyl alcohol, celluloses, and water-soluble resins; cationic, anionic, or nonionic surfactants; surface tension modifiers such as jetanolamine and triethanolamine; pH modifiers using buffers; Antifungal agents and the like can be mentioned.

Furthermore, the ink of the present invention better solves the problems of ink bleeding when recording on plain paper, dryness, and permeability of recorded materials, and at the same time improves matching with inkjet heads. As the physical property of 2
Surface tension at 5°C is 30-68 dyne/ca
+, it is desirable that the viscosity be adjusted to 1OcP or less, preferably 5cP or less, more preferably 3cP or less.

The composition and physical properties of the ink of the present invention have been explained above, but the most preferred form of use is disclosed in Japanese Patent Application Laid-Open No. 54-59936.
It is used in a method similar to the thermal energy one-way method described in the publication, and the frequency in this case is 0.2 to 2.
The advantages of the ink of the present invention become even clearer when used in the range of 0 KHz, preferably 1 to 10 KH2, more preferably 3 to 9 KHz.

(Example) Next, the present invention will be explained in more detail by giving examples and comparative examples. In the text, parts and percentages are based on weight unless otherwise specified.

After mixing the ingredients shown in Table 1 below and stirring for 5 hours, the pH was adjusted to 7.5 with 0.1% aqueous solution of sodium hydroxide, and the pore size was 0.22 μm. Pressure filtration was performed using a membrane filter (trade name: Fluorobor Filter, manufactured by Sumitomo Electric Industries, Ltd.) to obtain inks A to F of the present invention.

Next, using the obtained inks A-F, an inkjet printer BJ-130 using a heating element as an ink ejection energy source was used as an inkjet recording device.
(Product name: manufactured by Canon ■) to record on commercially available copy paper and bond paper.
The rate of occurrence of bleeding, the clogging property during reprinting after stopping printing, the clogging recovery property during printing after a long printing stop, and the frequency response were evaluated. The result is the third
Shown in the table. Note that the evaluation was normally performed under conditions of 25° C. and 60% RH.

(The following is a blank space) KI [''-j Mugi 1 ≦ L1 Mugi Ink G-N of Comparative Examples 1 to 8 was obtained in the same manner as Examples 1 to 6 using each of the ingredients in Table 2 below. , Various evaluations were performed in the same manner as in the examples. The results are shown in Table 3.

Part 3 - *Disperse dye Dyanix Black BGFS bulk 2
Add 50% of the dispersant represented by the following formula to the dye and ion-exchanged water to make a total volume of 200 cc, then add 200 cc of glass beads (diameter 1 mm), and disperse with a sand grinder for 30 hours. liquid obtained by

h (margins below) $1 Fixability evaluation 10 and 30 seconds after printing on commercially available copy paper and bond paper, rub the printed area with filter paper (product name No. 2, manufactured by 5C1 Toyo Roshi ■) and perform the following procedures. It was evaluated as follows.

0...Cast in io seconds None○...Cast in 10 seconds Small △...Cast in 30 seconds Small After printing 300 discontinuous dots on copy paper or bond paper, leave it for more than an hour, then use a microscope to count the number of dots that have smudged, and display the percentage of the total number of dots as a percentage. It was evaluated as follows.

○...10% or less △...11-30% ×...31% or more Okay, what happens when you fill the printer with the specified ink, print alphanumeric characters continuously for 10 minutes, stop printing, leave it for 10 minutes without a cap, and then print alphanumeric characters again? Evaluation was made based on the presence or absence of defective parts such as missing or missing characters.

O...-No defective parts from the first letter △...-Some part of the letter is missing or missing X...-
Characters cannot be printed at all $4 Long-term clogging recovery ability Long-term clogging recovery ability refers to the ability to recover from clogging when reprinting after a long-term printing stop, and continues for 10 minutes after filling the printer with the specified ink. After printing alphanumeric characters, stop printing, leave it for 7 days without a cap, etc., perform an operation to recover from clogging of the nozzle, and perform an operation to recover from clogging of the nozzle. It was determined whether normal printing without defective parts was possible.

○... Normal printing is possible after 1 to 5 recovery operations △... Normal printing is possible after 6 to 10 recovery operations ×... Normal printing is possible after 11 or more recovery operations $5 Frequency Responsiveness The printed condition of the obtained printed matter, that is, the condition of shadows and white spots, and the condition of landing point defects such as splash and wobbling were observed and evaluated with the naked eye.

0: The ink follows the frequency well, and there are no spots, white spots, or poor landing points in solid character printing.

○: The tracking state of the ink to the frequency is almost good, and there are no shadows, white spots, or poor landing points in character printing, but there is a slight shadow in solid printing.

△: There are no spots or white spots in character printing, but there are some poor impact points. In addition, in solid printing, smearing and white spots are observed in about 1/3 of the entire solid printing.

×: There are many spots and white spots in solid printing, and there are many spots and poor landing points in character printing.

Umbrella 6 Storage stability 100ml of each ink in a heat-resistant glass bottle Pour CC one by one, seal tightly and heat to 60℃. After being stored in the tank for 3 months, it is recorded in the recording device. Installed and printed on 100 sheets of continuous slip paper and evaluated based on the following criteria.

○...No abnormality Even on plain paper such as copy paper, report paper, notebook, letter paper, etc. that is generally used in offices, it is possible to record with no bleeding, excellent quality, and good permeability.

Furthermore, according to the present invention, it is possible to obtain ink that is highly safe even when used in offices and homes.

Further, according to the ink of the present invention, highly reliable recording can be performed without clogging of the nozzles of the inkjet head.

Claims (2)

[Claims] (1) In an inkjet ink used in a recording method in which thermal energy corresponding to a recording signal is applied to ink in a chamber of a recording head, and the energy is used to fly droplets onto a recording material to perform recording, at least 0.1 ~10% by weight water soluble dye, 70-95% by weight water and 5-16% by weight
An inkjet ink characterized by containing % by weight of a linear alkylene glycol having 5 carbon atoms. (2) The inkjet ink according to claim 1, further comprising 0.1 to 10% by weight of monohydric alcohol.