JPH03255176A - Ink - Google Patents

Abstract

PURPOSE:To obtain an ink consisting of a coloring matter and a liquid medium which can realize recording free from blotting even on plain paper with excellent penetration and has high safety by using a liquid medium containing water and a specified compound each in a specified amount. CONSTITUTION:An ink consisting of a coloring matter (e.g. C.I. Direct Yellow 86) and a liquid medium, wherein the liquid medium at least contains 50-95wt.% water and 0.001-4wt.% 9C or higher aliphatic monohydric alcohol [e.g. CH3(CH2)8 OH].

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to ink, and more specifically to coated paper specially prepared for inkjet use, as well as other types of copying paper commonly used in offices and homes. The present invention relates to an inkjet ink that has extremely good fixing properties even on non-coated paper such as paper, report paper, notebooks, stationery, bond paper, and continuous slip paper, so-called plain paper, and is capable of high-definition and high-quality recording.

(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.

For example, ink generally contains high boiling point organic solvents such as glycol to prevent drying and clogging, but when such ink is used to record on plain paper with a high degree of size. Ink is difficult to penetrate inside the paper,
In addition, since the drying properties of the recorded area were poor, there were problems with fixation, such as ink getting on the hands when touching the recorded matter and characters being rubbed and smudged.

On the other hand, in order to improve the permeability of the ink into the inside of the paper, Japanese Patent 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 paper using certain sizing agents, such as neutral paper. has drawbacks such as bleeding and drying properties which may not be good.

Furthermore, JP-A-55-145774 describes an ink containing an aliphatic monohydric alcohol to prevent freezing by lowering the freezing point of the ink; is limited to 5-20% by weight.

According to studies conducted by the present inventors, the use of alcohol as a penetrant itself is an extremely effective means for suppressing bleeding and promoting fixation. However, if the amount added exceeds 5% by weight, irregular bleeding generally tends to occur, and this cannot be said to be at a level that can be used satisfactorily for the purpose of printing quality as intended by the present invention. This tendency can be alleviated considerably if a lower alcohol with a carbon number of 3 or less is used, but in this case, the vapor pressure of the alcohol is high, so the alcohol evaporates from the head orifice, etc., making it easier to change the ink composition. . This phenomenon is particularly serious and a serious problem when the ink is used in an inkjet head of a type having an atmosphere communication hole. Furthermore, in systems where the alcohol content exceeds 5% by weight, in the case of an aqueous medium,
The dissolution or dispersion of the dye becomes unstable, and the storage stability and clogging resistance of the ink deteriorate.

Although various improvements have been attempted in addition to the above, to date, no ink has been known that satisfactorily solves all of the aforementioned problems such as bleeding, drying properties, clogging resistance, and storage stability. The current situation is that there is no such thing.

(Problems to be Solved by the Invention) Therefore, the purpose of the present invention is to reduce ink when recording on uncoated paper, so-called plain paper, such as copy paper, report paper, notebook, stationery, etc., commonly used in offices, etc. An object of the present invention is to provide an ink that solves the problems of bleeding and slow drying of recorded materials.

Another object of the present invention is to provide an inkjet ink that is highly safe for use in offices and homes, and is resistant to changes in composition due to reeding even when left for a long period of time.

Another object of the present invention is to provide an ink that is less likely to cause clogging in the nozzles of an inkjet head and has excellent reliability such as storage stability.

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

That is, the present invention provides an ink composed of a pigment and a liquid medium, in which at least 50 to 95% by weight is contained in the liquid medium.
The ink is characterized by containing water and 0.001 to 4% by weight of aliphatic monohydric alcohol having 9 or more carbon atoms.

(Function) In order to improve the bleeding, drying properties, and permeability of ink on paper, the inventors of the present invention have conducted extensive studies on various ink compositions, and found that 50 to 95% by weight of water and 0.001
The ink containing ~4% by weight of aliphatic monohydric alcohol with a carbon number of 9 or more is well-balanced in terms of bleeding and permeability, and has no adverse effect on clogging prevention, making it a highly reliable material. This discovery led to the present invention.

In other words, according to the research conducted by the present inventors, when using a surfactant used in ordinary ink, the bleeding and permeability of ink on paper may be good in some cases or not depending on the type of paper. are mixed, making it difficult to obtain stable records. On the other hand, when the liquid medium system used in the present invention is used, extremely good results can be obtained in that stable recording can be obtained with little difference in quality depending on the type of paper.

The reason for this is that the bleeding and permeability of ink are largely controlled by the phenomenon of wetting at the interface between ink droplets and paper, but when a surfactant is used, the ink that adheres to the paper Whereas good results cannot be obtained because the wetting properties differ between the surface and internal parts of the droplet, this is unlikely to occur with the ink of the present invention, and furthermore, the ink of the present invention It is thought that this is because the affinity between the sizing agent added to the surface or inside of the paper and the ink is an exquisitely balanced relationship that allows the inkjet ink to be used on plain paper.

(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:
It is an aliphatic monohydric alcohol having 9 or more carbon atoms, and can be obtained by any conventionally known method. Preferred specific examples of the above compounds are as follows, but the present invention is not limited to these specific examples.

Compound Example 1: C)1. (CH,),OH compound example 2
: CHs(CHz)6CH(OH)CHs Compound Example 3: Ctls (CL) fic)I (OHI
Cll2CH.

Compound Example 4: CH-(C)It)4C)I(081
(CH2)zcHs Compound Example 5: [CI(, (CH
I),]2C)+01(Compound Example 6: [(Ctl-
)2CHCHHz]□C) IOH compound example 7: (CI
(s)sccH2C(CH-) (CH□), OH compound example 8: (CH3)aCCH,fJcH3), CH
ffiOH Compound Example 9: C) I-(CH2). OH
Compound Example 10: CH3(CH2), Ctl(OH)
C8° Compound Example 11: CH, (CH218CH(O
H)CH2C)I.

Compound Example 12: CHs (CI(□1acH(OH
) (CHz)tcHs Compound Example 13: CH, (C
112) 4CH(OH) (CH2), CHs Compound Example 14: CH, (C)1. ), 00H Compound Example 1
5: CH3(CH2), OH The above specific examples were selected as particularly preferable by the inventors as a result of intensive study, and among them, those having 9 to 10 carbon atoms are more preferable.

The above-mentioned aliphatic monohydric alcohols having 9 or more carbon atoms can be used alone or as a mixture, and the amount added to the ink depends on the amount of the pigment used and other substances used in combination. 11i Although it differs depending on the medium components etc., it is about 0.001 to 4% by weight in the ink, preferably 0.005 to 3% by weight, and more preferably 0.001 to 4% by weight.
It accounts for 0.01 to 2% by weight.

The amount of the aliphatic monohydric alcohol having 9 or more carbon atoms added is 0.
．． When the amount is less than 0.01% by weight, there is no effect on the ink permeability, while when it exceeds 4% by weight, the surface tension of the ink decreases, so that it tends to bleed depending on the paper and the print quality deteriorates.

Further, the proportion of water in the ink, which is an essential component of the ink of the present invention, is 50 to 95% by weight, preferably 5% by weight.
The proportion is 5 to 95% by weight, more preferably 60 to 95% by weight. When the amount of water is less than 50 M%, the proportion of organic solvent is high, and the paper may curl or the quality of printing on plain paper or the like may be significantly degraded. On the other hand, if the amount of water exceeds 95% by weight, the stability of ink ejection from the nozzle office and the clogging resistance after stopping during printing will be significantly deteriorated.

The ink of the present invention is characterized by containing 50 to 95% by weight of water and 0.001 to 4% by weight of aliphatic monohydric alcohol having 9 or more carbon atoms together with the pigment, and other known Common organic solvents used in ink can also be used. However, formamide, dimethylformamide,
Like amides such as dimethylacetamide, the carbon number is 9.
There are some substances that cannot be used due to poor compatibility with the above aliphatic monohydric alcohols, such as ketones or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; diethylene glycol and triethylene Oxyethylene or oxypropylene addition polymers such as glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, polypropylene glycol; ethylene glycol, propylene glycol,
trimethylene glycol, butylene glycol, 1,2
．． Alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms such as 6-hexane alkylene glycol and hexylene glycol; Thiodiglycol: Glycerin; Ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, Lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether; triethylene glycol dimethyl (or ethyl)
Lower dialkyl ethers of polyhydric alcohols such as ether and tetraethylene glycol dimethyl (or ethyl) ether; sulfolane, N-methyl-2-pyrrolidone,
Examples include 1,3-dimethyl-2-imidazolidinone.

The content of the water-soluble organic solvent is generally 1% to 49% by weight, preferably 2% to 3% by weight based on the total weight of the ink.
The range is 0%.

Although the above-mentioned media can be used alone or in mixtures, the most preferred liquid medium composition is at least one water-soluble high-boiling organic solvent, such as diethylene glycol,
It contains polyhydric alcohols such as triethylene glycol and glycerin.

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 media components, the properties required of the ink, etc.

The proportion of the shells is about 0.2 to 20% by weight, preferably 0.5 to 10%, and more preferably 1 to 5% by weight in the total amount of the ink.

The main components of the ink of the present invention are as described above, but various other dispersants, surfactants, viscosity modifiers, surface tension modifiers, fluorescent brighteners, etc. may be added within the range that does not impede the achievement of the purpose of the present invention. It can be added as needed.

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

In addition, in order to prepare ink used in inkjet recording methods that charge the ink, lithium chloride,
A resistivity adjuster such as inorganic salts such as ammonium chloride and sodium chloride is added.

The ink of the present invention is particularly suitable when applied to an inkjet recording method in which ink is ejected by a bubbling phenomenon of the ink caused by thermal energy, and the ink is said to be extremely stable in ejection and free from the generation of satellite dots. It has characteristics.

However, in this case, thermal properties (eg, specific heat, coefficient of thermal expansion, thermal conductivity, etc.) may be adjusted.

Furthermore, the ink of the present invention solves the problems of ink bleeding when recorded on plain paper, dryness, and permeability of recorded materials, and at the same time improves the physical properties of the ink itself in order to improve matching with inkjet heads. It is desirable that the surface tension at 25° C. is adjusted to 30 to 68 dyne/cm and the viscosity is adjusted to 15 cP or less, preferably 1 ocP or less, more preferably 5 cP or less.

(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 a 0.1% aqueous solution of sodium hydroxide. Membrane filter (product name: Fluorobore filter, Sumitomo Electric etc.)
The inks A-E of the present invention were obtained by pressure filtration using a commercially available company, Ltd.).

Next, using the obtained inks A-E, an inkjet printer BJ-130, which uses a heating element as an ink ejection energy source, was used as an inkjet recording device.
(trade name, manufactured by Cano Y ■) was used to record on commercially available copy paper and bond paper.
The incidence of bleeding was evaluated. At the same time, the clogging properties during reprinting after a printing stop, clogging recovery during printing after a long printing stop, frequency response, and ink storage stability were also evaluated. The results are shown in Table 3. Note that the evaluation was normally performed under conditions of 25° C. and 60% RH.

(Margin below) Inks F to L of Comparative Examples 1 to 7 were obtained in the same manner as Examples 1 to 5 using the components in Table 2 below, and various evaluations were performed in the same manner as in the Examples. . The results are shown in Table 3.

Negami" - J Mugi B Mugi - 1 Σ - 2i $1 Fixability Evaluation 10 and 30 seconds after printing on commercially available copy paper and bond paper, the printed area was coated with filter paper (Product name: No. 5C1 Toyo Roshi) (manufactured by) and evaluated as follows.

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

O...10% or less △...11-30% ×...31% or more Temporary clogging property refers to the clogging property when reprinting after stopping printing. 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 cast and missing characters.

○...-No defective parts from the first letter △...-Some part of the first letter is cast or missing ×...-
Book 4 in which characters cannot be printed at all Long-term clogging recovery property Long-term clogging recovery property refers to clogging recovery performance when reprinting after a long-term printing stop.The printer is filled with the specified ink and continues for 10 minutes. After printing alphanumeric characters, stop printing, leave it without a cap etc. for 7 days, perform an operation to recover from clogging of the nozzle, and how many times do you have to operate it to remove casts, missing characters, etc. 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 cast 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 tracking state of the ink with respect to the frequency was good, and no cast, white spots, or poor landing points were observed in solid character printing.

Good: The tracking state of the ink relative to the frequency is almost good, and no cast, white spots, or poor landing points are observed in character printing, but a slight cast is observed in solid printing.

△...No cast or white spots are observed in character printing, but some impact point defects are observed. Furthermore, in solid printing, fading and white spots are observed in about 1/3 of the entire solid printing.

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

Book 6: Storage Stability Pour 100 cc of each ink into a heat-resistant glass bottle, seal it tightly, and store it in a high-temperature tank at 60°C for 3 months, then load it into the recording device and print on 00 sheets of continuous slip paper. , evaluated based on the following criteria.

○...No abnormalities ×...Failure to eject, irregular printing, or discoloration occurs (Effects) As explained above, according to the ink of the present invention, copy paper commonly used in offices, etc. 6. Excellent quality with no bleeding on plain paper such as report paper, notebooks, and stationery.
In addition, recording with good permeability is possible.

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, it is possible to perform highly reliable recording without clogging of the nozzle of an inkjet head, especially in a type of recording in which ink is ejected by a bubbling phenomenon of ink caused by thermal energy. Frequency response becomes much better.

Claims (1)

[Claims] (1) In an ink composed of a pigment and a liquid medium,
At least 50-95% by weight of water in the liquid medium and 0
．． An ink characterized by containing 0.001 to 4% by weight of an aliphatic monohydric alcohol having 9 or more carbon atoms.