JPH0418468A - Ink and method for ink jet recording with the same - Google Patents

Abstract

PURPOSE:To provide an ink not solidifying at the tip of an ink jet head even when allowed to stand for a long period, giving printed products having excellent fastness and high concentration and stably jetted by adding a pigment, a water-soluble resin and a specific compound to an aqueous medium. CONSTITUTION:A pigment, a water-soluble resin and a compound of the formula (m, n are integers of >=0 satisfied with an equation: 1<=l+m+n<=25) preferably in an amount of 0.5-30wt.% are added to an aqueous medium [preferably comprising water and a water-soluble organic solvent containing a polyhydric alcohol (alkyl ether) and an aliphatic monohydric alcohol] to provide the objective ink.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ink particularly suitable for inkjet printers, and furthermore, the present invention relates to ink suitable for inkjet printers, and furthermore, the present invention relates to ink that is ejected from an orifice of a recording head by the action of thermal energy to print on uncoated paper,
The present invention relates to an inkjet recording method for recording on so-called plain paper.

[Conventional technology]

The inkjet recording method has the advantage that it generates little noise during recording and can obtain high-resolution recorded images at high speed by using a highly integrated head.

In such an inkjet recording method, ink prepared by dissolving various water-soluble dyes in water or a mixture of water and an organic solvent is used.

However, when water-soluble dyes are used, the light resistance of recorded images often becomes a problem because these water-soluble dyes inherently have poor light resistance.

Furthermore, since the ink is water-soluble, water resistance of recorded images often becomes a problem. That is, if a recorded image is exposed to rain, sweat, or drinking water, the recorded image may smudge or disappear.

On the other hand, similar problems exist in stationery using dyes such as ballpoint pens, and various water-based pigment inks for stationery have been proposed to solve the problems of light resistance and water resistance. In order to put water-based pigment ink into practical use, examples of studies investigating dispersion stability, prevention of ink solidification at the pen tip, and prevention of wear on the ball of a ballpoint pen include JP-A-58-80368 and JP-A-61-200182. Publication, JP-A-61-24
7774, JP 61-272278, JP 61-568, JP 62-101671.
Publication No. 101672, JP 1-249869.1-3
Publication No. 01760 and the like can be mentioned. Recently, ballpoint pens and markers using water-based pigment inks have become commercially available on the market.

[Problem that the invention seeks to solve]

However, when conventional water-based pigment ink for stationery is used in an inkjet recording device that performs recording by ejecting the recording liquid from the orifice of the recording head by the action of thermal energy, it causes a significant problem in ejection stability.
There was a drawback that printing defects occurred. In particular, when conventional pigment ink is used for recording by ejecting droplets by applying thermal energy, when a pulse is applied to the ink, the heat causes deposits to form on the thin film resistor, causing the ink to eject. Foaming may be incomplete and droplet ejection may not respond to the applied pulse, resulting in non-ejection. In other words, in order to stably eject ink from the nozzle tip, the ink must have the ability to foam on the thin film resistor to a desired volume, and also to be able to repeat foaming and defoaming in a desired amount of time. However, conventional inks for stationery do not satisfy these performance requirements, and therefore, when an inkjet recording device is filled with the ink and used for recording, various inconveniences as described above occur.

Furthermore, when using a dispersion system called pigment ink for inkjet recording, preventing solidification at the tip of the head due to long-term storage is an important technical issue, and the composition of the ink is important in designing a reliable pigment ink. This is a great point.

Furthermore, although some conventional water-based pigment inks have excellent ejection properties in a relatively short period of time, ejection becomes unstable when the driving conditions of the print head are changed or continuous ejection is performed for a long period of time. Eventually, the problem arises that it stops being discharged.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art described above and to provide an ink that eliminates the solidification of pigment ink at the tip of a head due to long-term storage.

Another object of the present invention is to provide an ink that can be constantly and stably ejected even when driving conditions change or when used for a long time.

A further object of the present invention is to provide an inkjet recording method that enables stable high-speed recording at all times and provides recorded images with excellent robustness such as water resistance and light resistance when printed on uncoated paper. It is in.

c. Means and operation for solving the problems] The above objects are achieved by the present invention as described below.

That is, the present invention is an ink characterized by containing a pigment, a water-soluble resin, and a compound represented by the following general formula (I) in an aqueous medium, and the ink is heated according to a recording signal. This is an inkjet recording method in which recording is performed by ejecting ink as droplets from minute holes by applying energy.

HO÷CH2CH2OjiCH2 (1.m and n represent O or a positive integer that satisfies the following relationship: 1≦1! 10m10n≦25) The present invention will be described in detail below.

In order to prevent the ink from solidifying at the tip of the recording head and causing various problems with water-based pigment ink, the inventors of the present invention have conducted intensive studies on ways to increase the resolubility of solidified ink, and found the following. It has been discovered that when a compound represented by the structural formula is contained, the ink that has solidified upon drying can be redissolved with the ink itself, thereby solving various problems at the tip of the head, leading to the present invention.

Water-based pigment inks generally aggregate when dried and, unlike inks using dye inks, cannot be easily redissolved. In order to redissolve it,
Do not re-disperse the ink in a highly alkaline solution using ultrasonic waves, etc. On the other hand, the solidification of ink at the tip of the head will increase the airtightness of the cap, and should be cleaned regularly with a wiper etc. on the face of the head. , it is possible to improve it to some extent.

However, providing a device with a high alkali cleaning means increases costs, and is not a desirable solution for printer users because high alkali is dangerous if they touch it.

Therefore, the present inventors investigated ways to increase the resolubility of solidified ink by improving the constituent elements of the ink, and found that by incorporating the above-mentioned compounds into the ink, the resolubility of the ink could be improved. was found to be significantly improved.

The water and low boiling point solvent contained in the ink adhering to the face of the head quickly evaporate, leaving behind the pigment dispersion and the high boiling point solvent. Depending on the ink composition, some of the ink solidified products formed at this time form a film, while others do not form a film, and it has been found that this is related to the hygroscopicity of the remaining solvent. In other words, ink using highly hygroscopic solvents does not form a film when drying, and this solidified material can be redissolved by the ink itself relatively easily. A film is formed in the ink containing the compound, making it difficult to re-dissolve it.It is not clear why the compound having the above general formula used in the present invention has excellent hygroscopicity, but it is difficult to dissolve it again. It is thought that these compounds have a strong ability to take in water because of the large amount of ethylene oxide they contain.Furthermore, these compounds have lower viscosity by introducing ethylene oxide chains, so they have particularly favorable performance as solvents for inkjet inks. It is equipped with

Preferred specific examples of the compound represented by the above general formula are listed below.

Among these compounds, NQI to Nα7 are particularly preferred for the present invention in terms of preventing the pigment ink from sticking.

The above compound is prepared by placing a predetermined amount of polyhydric alcohol and NaOH as a catalyst in a pressure-resistant glass container.

Alternatively, put KOH and replace the inside with nitrogen through the supply tube. Next, while stirring the reaction solution, the temperature was increased from 110°C to 1°C.
The temperature was raised to 30°C, and the amount of ethylene oxide gas planned for reaction was gradually introduced. Stir at that temperature for several hours. After the reaction is completed, the reaction solution is passed under pressure through a filter paper laminated with diatomaceous earth in order to remove remaining NaOH% or KOH in the unreacted solution to obtain the desired product. (If the viscosity is high, it is made into an aqueous solution and filtered under heat and pressure.) The content of such a compound in the ink is suitably in the range of 0.5 to 30% by weight, preferably 5 to 20% by weight. When this amount is less than 0.5% by weight, there is no effect in preventing solidification of the ink at the tip of the head, and when this amount exceeds 30% by weight, the viscosity of the ink becomes too high.

The amount of pigment used in the present invention is 3 to 20% by weight,
Preferably, it is used in a range of 3 to 12% by weight.

Any pigment can be used in the present invention as long as it satisfies the above performance, but for example, black pigments include NQ 2300, Nα900, MCF8
8, N(133, N(L40.Na2S, N052, M
A7, MA8, #2200B (manufactured by Mitsubishi Chemical), R
AVEN1255 (made in Colombia), REGAL440
R, REGAL330R.

REGAL660R, MOGUL L (Cabot)
, Co1or B l a c k F W 1, C0
LORBlack FWI8, Co1orBlack
5170, Co1or Black 5150,
Carbon blacks such as Pr1ntex 35 and Pr1ntex U (manufactured by Degutsusa), and even carbon blacks newly manufactured for this purpose can be used.

In the present invention, the water-soluble resin contained as a pigment dispersant is preferably one that is soluble in an aqueous solution containing an amine and has a weight average molecular weight in the range of 3,000 to 30,000. Furthermore, preferably anything in the range of 5,000 to 15,000 can be used;
Acrylic acid copolymer, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid copolymer, styrene- Examples include methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinylnaphthalene-acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer, or salts thereof. The amount of the water-soluble resin is 0.1 to 5% by weight, preferably 0.3 to 2% by weight based on the total amount of the recording liquid.
It is preferable that the content be within the range of .

Further, in the ink of the present invention, preferably the entire ink is adjusted to be neutral or alkaline, so that the solubility of the water-soluble resin is improved, and - the recording liquid has excellent long-term storage stability of the layer. It is desirable because it allows However, in this case, it may cause corrosion of various members used in the inkjet recording device, so preferably 7-10.
It is desirable that the pH is within the range of .

Examples of pH adjusting agents include various organic amines such as diethanolamine and triethanolamine, inorganic alkali agents such as alkali metal hydroxides such as sodium hydroxide, lithium hydroxide, and potassium hydroxide, organic acids, and minerals. Acid can be given. As described above, the carbon black and the water-soluble resin are dispersed or dissolved in the water-soluble medium.

A suitable aqueous medium for the ink of the present invention is a mixed solvent of water and a water-soluble organic solvent, and as water, ion-exchanged water (deionized water) is used instead of ordinary water containing various ions. is preferred.

In addition, other water-soluble solvent components that can be used in combination with any water include, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, inpropyl alcohol, n-butyl alcohol, 5ec-butyl alcohol. C1-4 alkyl alcohols such as tert-butyl alcohol and isobutyl alcohol; amides such as dimethylformamide and dimethylacetamide; ketone or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; Polyalkylene glycols such as polyethylene glycol and polypropylene glycol, ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1.2. When an alkylene group such as 6-hexandriol, thione glycol, hexylene glycol, or diethylene glycol is 2-
Alkylene glycols containing 6 carbon atoms; glycerin: ethylene glycol monomethyl (or ethyl)
Lower alkyl ethers of polyhydric alcohols such as ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether; N-methyl-2-pyrrolidone, l, 3-
Examples include dimethyl-2-imidazolidinone. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are preferred.

Among these many water-soluble organic solvents, organic amine water is contained as an essential component in the ink of the present invention, preferably in an amount of 0.001 to 10% by weight based on the total ink.

Furthermore, it has been found that it is effective to add 3% to 15% by weight of aliphatic monohydric alcohol, such as ethanol or isopropyl alcohol, in order to obtain stability in ejection. This is thought to be because the addition of these solvents allows the ink to foam on the thin film resistor more stably. However, if an excessive amount of these solvents is added, the print quality of the printed matter will be impaired, so a more suitable concentration of these solvents is in the range of 3 to 10% by weight. Further, as an effect of these solvents, by adding these solvents to the dispersion liquid, generation of bubbles can be suppressed during dispersion, and efficient dispersion can be performed.

The content of the water-soluble organic solvent in the ink of the present invention is in the range of 3 to 50% by weight, preferably 3 to 40% by weight of the total weight of the ink, and the water used is in the range of 10 to 90% by weight of the total weight of the ink.
% by weight, preferably in the range 30-80% by weight.

In addition to the above-mentioned components, the ink of the present invention may contain surfactants, antifoaming agents, preservatives, etc., if necessary, in order to obtain a recording liquid with desired physical properties. It is also possible to add commercially available water-soluble dyes.

Examples of surfactants include fatty acid salts, higher alcohol sulfate ester salts, liquid fatty oil sulfate ester salts, anionic surfactants such as alkylaryl sulfonates, polyquinoethylene alkyl ethers, polyoxyethylene alkyl esters, polyoxy There are nonionic surfactants such as ethylene solhytan alkyl esters, and one or more of these can be appropriately selected and used.

The amount used varies depending on the dispersant, but it is preferably from 0 to 5% by weight based on the total amount of the ink. At this time, it is preferable to determine the amount of the activator added so that the surface tension of the ink is 30 dyne/cm or more. This is because if the surface tension of the ink exhibits a value smaller than this, in a recording method such as the present invention, undesirable situations such as print distortion (deviation of the landing point of ink droplets) due to wetting of the nozzle tip will occur. It is. On the other hand, in order to obtain an ink with desired physical properties, a water-soluble organic solvent, a pH adjuster, an antifoaming agent, a preservative, etc. can be added. Furthermore, it is also possible to add commercially available water-soluble dyes.

In general, the performance required for inkjet inks includes physical properties such as ink viscosity, surface tension, and pH, but in dispersion systems such as aqueous pigment inks, even if these physical properties are satisfied, ink foaming may occur. is often unstable.

Therefore, the present inventors conducted extensive research on the performance of water-based pigment inks that are thermally stable and capable of optimal foaming. It has been found that by setting the amount to 2% or less, preferably 1% or less, the ink foams accurately on the resistor under various driving conditions, and furthermore, no deposits are generated on the thin film resistor even over a long period of time. In other words, if there is a large amount of excess water-soluble resin in the ink relative to the pigment, the ink may not foam even if a certain amount of thermal energy is applied on the thin film resistor, or the excess water may be absorbed by the heat during pulse application. The water-soluble resin becomes an insoluble substance and accumulates on the thin film resistor, causing non-discharge and irregular printing.

The dissolved water-soluble resin refers to a resin that is not adsorbed to the pigment in the ink but is dissolved in the liquid medium.

One way to reduce the amount of dissolved water-soluble resin is to adjust the ratio of pigment to water-soluble resin to a weight ratio of 3:1 to 10.1, preferably 10 to 10:I, during ink preparation. It is to be.

Furthermore, the total amount of pigment and water-soluble resin in the dispersion was 10%.
It is preferable that it is above. The reason for this is that unless the pigment and water-soluble resin are present in the dispersion liquid at a certain concentration or higher, dispersion cannot be carried out efficiently and an optimum dispersion state cannot be obtained.

The method for preparing the recording liquid of the present invention involves first adding a pigment to an aqueous solution containing at least a dispersion resin, an amine, and water, stirring, dispersing using the dispersion means described later, and centrifuging if necessary. Separation treatment is performed to obtain the desired dispersion. Next, the components listed above are added to this dispersion liquid and stirred to obtain a recording liquid.

In particular, in order to reduce the amount of unadsorbed resin to 2% or less, in the preparation method, an aqueous solution containing resin, amine, and water must be
It is necessary to completely dissolve the resin in advance by stirring at a temperature of at least 30 minutes.

Further, it is necessary to add the amount of amine that dissolves the resin at least 1.2 times the amount of amine calculated from the acid value of the resin. The amount of this amine is determined by the following formula.

Furthermore, it is also necessary to perform premixing for 30 minutes or more before dispersing the aqueous solution containing the pigment.

This premixing operation improves the wettability of the pigment surface and promotes adsorption of the resin onto the pigment surface.

The amines added to the dispersion include monoethanolamine, jetanolamine, triethanolamine,
Organic amines such as aminomethylpropertool and ammonia are preferred.

On the other hand, the dispersing machine used in the present invention may be any commonly used dispersing machine, and examples thereof include a ball mill, a roll mill, and a sand mill.

Among these, high-speed sand mills are preferred, and examples include super mills, sand grinders, Heath mills, agitator mills, grain mills, Dyno mills, pearl mills, and Kobol mills (all trade names).

In the present invention, methods for obtaining a pigment having a desired particle size distribution include reducing the size of the grinding media of the dispersion machine, increasing the filling rate of the grinding media, lengthening the processing time, and slowing down the discharge speed. After crushing, methods such as classification using a filter or centrifugal separation are used. or a combination of these methods.

The method of measuring the amount of unadsorbed resin according to the present invention is to precipitate the pigment bones and the resin adsorbed to the pigment using an ultracentrifuge or the like, and then calculate the amount of residual resin contained in the supernatant liquid. TOC (Total Organic Carbon,
A total organic carbon meter) and a gravimetric method (a method in which the supernatant is evaporated to dryness and the amount of resin is measured) are preferably used.

The recording liquid of the present invention is particularly suitable for use in an inkjet recording system in which recording is performed by ejecting droplets under the action of thermal energy, but it goes without saying that it can also be used for general writing instruments.

A suitable recording device for recording using the ink of the present invention includes a device that applies thermal energy corresponding to a recording signal to a recording liquid in a chamber of a recording head and generates droplets using the energy.

An example of the configuration of the head, which is the main part, is shown in FIG. 1(a).

(b), shown in FIG.

The head 13 includes a glass, ceramic, or plastic plate having grooves 14 through which ink passes, and a heat generating head 15 used for thermal recording (a thin film head is shown in the figure, but is not limited to this). Obtained by gluing. The heat generating head 15 includes a protective film 16 formed of silicon oxide or the like, aluminum electrodes 17-1. 17-2, a heating resistor layer 18 made of nichrome or the like, a heat storage layer 19, and a substrate 20 with good heat dissipation properties such as alumina.

The ink 2 has come to a discharge orifice (microhole) 22, and a meniscus 23 is formed by the pressure P.

Now, when an electric signal is applied to the electrodes 17-1 and 17-2, the area indicated by n of the heating head 15 suddenly generates heat, bubbles are generated in the ink 21 in contact with this area, and the pressure causes the meniscus 23 to protrudes, the ink 21 is ejected, becomes a recording droplet 24 from the orifice 22, and flies toward the recording medium 25. FIG. 2 shows an external view of a multi-head in which a large number of heads shown in FIG. 1(a) are arranged. The multi-head is assembled by bonding a glass plate 27 having multi-grooves 26 and a heating head 28 similar to that described in FIG. 1(a).

Note that FIG. 1(a) shows the head 13 along the ink flow path.
FIG. 1(b) is a sectional view taken along A-B in FIG. 1(a).
This is a cut plane along a line.

An example of an ink jet recording apparatus incorporating the head according to FIG. 3 is shown.

In FIG. 3, 61 is a blade as a wiping member, one end of which is held by a blade holding member and becomes a fixed end in the form of a cantilever. The blade 61 is disposed adjacent to the recording area of the recording head, and in this example, is held in a protruding form in the movement path of the recording head. A cap 62 is disposed at a home position adjacent to the plate 61, and is configured to move in a direction perpendicular to the direction of movement of the recording head and come into contact with the ejection port surface for capping. Furthermore, 63 is an ink absorber provided adjacent to the blade 61;
Like the blade 61, it is held in a protruding form in the movement path of the recording head. The blade 61 and cap 62
The absorber 63 constitutes an ejection recovery section 64, and the blade 61 and the absorber 63 remove moisture, dust, etc. from the ink ejection orifice surface.

Reference numeral 65 is a recording head that has an ejection energy generating means and performs recording by ejecting ink onto a recording material facing the ejection orifice surface on which ejection ports are arranged, and 66 is a recording head that mounts the print head 65 and moves the print head 65. It is a carriage for carrying out. The carriage 66 is slidably engaged with a guide shaft 67, and a portion of the carriage 66 is connected to a belt 69 (not shown) driven by a motor 68. This allows the carriage 66 to move along the guide shaft 67, allowing the recording head 65 to move the recording area and its adjacent area.

Reference numeral 51 indicates a paper feed section for inserting recording material, and 52 indicates a paper feed row driven by a motor (not shown). With these configurations, the recording material is fed to a position facing the ejection opening surface of the recording head, and as recording progresses, the recording material is discharged to a paper discharge section provided with a paper discharge roller 53.

In the above configuration, when the recording head 65 returns to the home position after recording ends, etc., the cap 6 of the head recovery section 64
2 is retracted from the moving path of the recording head 65, but the blade 61 protrudes into the moving path. As a result, the ejection port surface of the recording head 65 is wiped. Note that when the cap 62 contacts the ejection surface of the recording head 65 to perform capping, the cap 62 moves so as to protrude into the movement path of the recording head.

When the recording head 65 moves from the home position to the recording start position, the cap 62 and the blade 61 are in the same position as the wiping position described above. As a result, even during this movement, the ejection orifice surface of the recording head 65 is wiped.

The above-mentioned movement of the print head to the home position is not limited to the end of printing or recovery of ejection, but also the movement of the print head to the home position adjacent to the print area at predetermined intervals while moving the print area for printing. However, along with this movement, the above-mentioned wiping is performed.

FIG. 4 is a diagram showing an example of an ink cartridge containing ink supplied to the head via an ink supply tube. Here, 40 is an ink bag containing supply ink, and a rubber stopper 42 is provided at the tip of the ink bag. By inserting a needle (not shown) into this plug 42,
The ink in the ink bag 40 can be supplied to the head. 44 is an ink absorber that receives waste ink.

The inkjet recording device used in the present invention includes:
Not only the above-mentioned one in which the head and ink cartridge are separate bodies, but also one in which they are integrated as shown in FIG. 5 can be suitably used.

In FIG. 5, 70 is an inkjet cartridge, which houses an ink absorber impregnated with ink. It is configured to be discharged as

Reference numeral 72 denotes an atmospheric air passage port for communicating the inside of the cartridge with the atmosphere.

This inkjet cartridge 7o is used in place of the recording head 65 shown in FIG. 3, and is detachable from the carriage 66.

Next, the present invention will be specifically explained with reference to Examples.

〔Example〕

Example 1 (Preparation of pigment dispersion) Styrene-acrylic acid-butyl acrylate copolymer
2 parts (acid value 116, weight average molecular weight 3700 mmonoethanolamine 1 part ion exchange water
73 parts diethylene glycol
Mix 5 parts of the above ingredients and water bath for 7
Heat to 0'C to completely dissolve the resin. A newly prototyped carbon black (MCF88) was added to this solution.
After adding 14 parts (manufactured by Mitsubishi Kasei) and 5 parts of isopropyl alcohol and performing premixing for 30 minutes, dispersion treatment was performed under the following conditions.

Dispersion machine Sand grinder (manufactured by Igarashi Kikai) Grinding media Filling rate of grinding media after 1 mm of zirconium beads 50% (volume) Grinding time 3 hours Further centrifugation treatment (12000 RPM, 20 minutes) is performed to remove coarse particles and form a dispersion liquid And so.

(Preparation of ink) Above dispersion 30 parts Specification Exemplary Compound (1) lo part N-methyl 2-
Pyrrolidone 5 parts Isopropyl alcohol
5 parts ion exchange water
50 parts of the above components were mixed, and the pH was adjusted from 8 to 10 with monoethanolamine to prepare ink (A).

Example 2 (Preparation of pigment dispersion) Styrene-acrylic acid-butyl acrylate copolymer
5 parts (acid value 12Q, weight average molecular weight 6100) triethanolamine 2 parts ion exchange water
66 parts diethylene glycol
Mix 5 parts of the above ingredients and 7 parts in a water bath.
Heat to 0'C to completely dissolve the resin. To this solution, 15 parts of newly produced MOGUL L (manufactured by Cabot) and 7 parts of ethanol were added, premixing was performed for 30 minutes, and then dispersion treatment was performed under the following conditions.

Disperser Pearl Mill (Pearl Mill) Grinding Media Glass Peas Filling rate of 1mm diameter grinding media 50% (volume) Discharge speed 100mI!
/min.

Further centrifugation treatment (12000 RPM, 20 minutes)
to remove coarse particles and prepare a dispersion.

(Preparation of ink) Above dispersion 30 parts ethanol 5 parts ion exchange water
45 parts of the above components were mixed, and the pH was adjusted from 8 to 10 with triethanolamine to prepare an ink (B).

Example 3 (Preparation of pigment dispersion) Styrene-acrylic acid-ethyl acrylate copolymer
4 parts (acid value 138, weight average molecular weight 5600) aminomethyl propatool 2 parts ion exchange water
69 parts diethylene glycol
Mix 5 parts of the above ingredients and water bath for 70 minutes.
Heat to ℃ to completely dissolve the resin. To this solution, 15 parts of carbon black (MCF88, manufactured by Mitsubishi Kasei) and 5 parts of ethanol were added, premixing was performed for 30 minutes, and then dispersion treatment was performed under the following conditions.

Dispersing machine Pearl mill (Pearl mill) Grinding media Glass beads 1mm diameter grinding media Filling rate 50% (volume) Discharge speed 100 mjl
! / min.

Further, centrifugation treatment (1200 ORPM, 20 minutes) was performed to remove coarse particles and obtain a dispersion.

(Preparation of ink) Above dispersion 50 parts Specification Exemplified Compound (3) 15 parts Ethylene glycol 5 parts Ethanol
5 parts ion exchange water
Mix 25 parts of the above ingredients, adjust the pI (pI) from 8 to 10 with aminomethyl propatool, and add the ink (C
) was obtained.

Example 4 An ink was prepared using Compound (4) exemplified in the specification instead of Compound (1) exemplified in the specification in the ink of Example 1, and designated as Ink (D).

Example 5 An ink was prepared using Compound (5) exemplified in the specification instead of Compound (2) exemplified in the specification in the ink of Example 2, and designated as Ink (E).

Example 6 An ink was prepared using Compound (6) exemplified in the specification instead of Compound (3) exemplified in the specification in the ink of Example 3, and designated as Ink (F).

Comparative Example 1 An ink was prepared in the same manner as in Example 1 except that compound (1) was changed to diethylene glycol monobutyl ether, and it was designated as ink (G).

Comparative Example 2 An ink was prepared using the same formulation except that compound (2) contained in the dispersion of Comparative Example 2 was replaced with ethylene glycol monobutyl ether to obtain Ink (H).

Using each of the above inks, the following tests were conducted using an inkjet recording apparatus having an on-demand type multi-recording head that ejects ink by applying thermal energy according to a recording signal. The results are shown in Table 1.

T1: Driving conditions and ejection stability The driving voltage is set to 25V, and the frequency is 2KH at each voltage.
Printing is performed at room temperature under two conditions: z and 4KHz.
The ejection stability was evaluated by observing the presence or absence of irregularities in printing, chipping, and non-ejection.

A: Clean ejection from the first character, no ejection failure, chipping, or irregular printing at all during continuous printing.

The B1 character area was ejected cleanly, but there were several areas of solid printing where ejection failure occurred.

C: Even in the character part, non-ejection occurs when several characters are printed, and the printing becomes disordered to the extent that the characters are impossible to read.

T2 Niblint - Clogging when reprinting after time stopPrint - Reprinting after time stop Regarding clog,
After filling the printer with the specified ink and printing alphanumeric characters continuously for 10 minutes, stop printing and leave it at room temperature for 30 minutes with no cap etc., then print alphanumeric characters again and print the characters. Judgment was made based on the presence or absence of defects such as scratches and chips.

8 - No defects starting from the 8th letter.

B - Some of the letters are faded or blurred.

The C knee character cannot be printed at all.

T3 Print clogging recovery when reprinting after a long-term stop After printing alphanumeric characters continuously for 10 minutes using the specified ink on the printer, stop the printer and leave it at 60°C for 10 days without caps etc. After that, we performed an operation to recover from the nozzle clogging, and determined how many times it took to print normally without blurring or missing characters.

A: Normal printing is possible with normal operation after 1 or 5 recovery operations.

B: Normal printing is possible after 6 to 10 recovery operations.

C: Normal printing is possible after 11 or more recovery operations.

TO: Amount of dissolved water-soluble resin The obtained ink is centrifuged at 5500 rpm for 5 hours using an ultra-high-speed refrigerated centrifuge (manufactured by Beckman) to sediment the pigment and the resin adsorbed on the pigment. A certain amount of the supernatant liquid is collected and dried and solidified in a vacuum dryer (60° C., 24 hours). The percentage of this resin amount to the charged ink is calculated and determined as the residual resin concentration.

Table 1 Evaluation results [Effects] As explained above, when the ink of the present invention is applied to an ink jet printer, the ink does not solidify at the tip of the head even if left for a long time, and the solidity of printed matter is improved. Not only does it have excellent print density, it also has the advantage of being able to always perform stable ejection even when driving conditions fluctuate or when used for long periods of time, and is also highly reliable.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are a vertical cross-sectional view and a cross-sectional view of a head portion of an inkjet bell recording device. FIG. 2 is an external perspective view of a multi-head head shown in FIG. 1. FIG. 3 is a perspective view showing an example of an inkjet recording apparatus. FIG. 4 is a longitudinal sectional view of the ink cartridge. FIG. 5 is a perspective view of the ink cartridge. 61... Wiping member 62... Cap 63... Ink absorber 64... Ejection recovery section 65... Recording head 66... Calibration error 10CO) b Part ■ Flash (b) error? Mouth 4El Eye

Claims (11)

[Claims] (1) An ink characterized by containing a pigment, a water-soluble resin, and a compound represented by the following general formula (I) in an aqueous medium. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (However, l, m, and n represent 0 or a positive integer that satisfies the relationship 1≦l+m+n≦25.) (2) The amount of water-soluble resin dissolved in the ink is
The ink according to claim 1, wherein the content is 2% by weight or less. (3) The ink according to (1), wherein the aqueous medium contains water and a water-soluble organic solvent. (4) The ink according to (3), wherein the water-soluble organic solvent contains a polyhydric alcohol and/or an alkyl ether thereof and an aliphatic monohydric alcohol. (5) The ink according to claim (1), wherein the content of the compound represented by the general formula (I) is in the range of 0.5 to 30% by weight based on the total weight of the ink. (6) In an inkjet recording method in which recording is performed by ejecting ink as droplets from micropores by applying thermal energy to the ink according to a recording signal, the ink is mixed with a pigment and a water-soluble material in an aqueous medium. 1. An inkjet recording method, comprising: a synthetic resin; and a compound represented by the following general formula (I). ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (However, l, m, and n represent 0 or a positive integer that satisfies the relationship 1≦l+m+n≦25.) (7) The inkjet recording method according to (6), wherein the recording method is an on-demand type recording method. (8) The amount of water-soluble resin dissolved in the ink is
The inkjet recording method according to claim 6, wherein the content is 2% by weight or less. (9) The inkjet recording method according to (6), wherein the aqueous medium of the ink contains water and a water-soluble organic solvent. (10) The water-soluble organic solvent is a polyhydric alcohol and/or
or an alkyl ether thereof and an aliphatic monohydric alcohol. (11) The inkjet recording method according to claim (6), wherein the amount of the compound represented by formula (I) contained in the ink is in the range of 0.5 to 30% by weight based on the total weight of the ink.