JPH09272829A - Ink for ink jet - Google Patents

Abstract

(57) Abstract: The present invention can significantly reduce the generation of bubbles due to electrolysis even if the AC frequency of the voltage applied to the electrodes is 5 MHz or less, and the current flows smoothly between the electrodes. Is stable and discharge can always be performed in a normal state, and discharge stability and discharge response are remarkably excellent, continuous recording property can be dramatically improved, and further generation of dissolution reaction of the electrode can be significantly suppressed. An inkjet ink that can prevent abrasion of the electrode and can significantly improve the durability of the electrode. An inkjet ink of the present invention contains a color former, an additive, and a solvent that dissolves the color former and the additive, and has a specific resistance of 8 to 50 at 25 ° C.
Ω · cm, and the decomposition temperature of at least one of the color formers is less than 130 ° C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet ink used in a recording apparatus of an inkjet recording system which prints or prints by ejecting ink droplets.

[0002]

2. Description of the Related Art In recent years, there have been increasing demands for printers for higher speed printing, color printing, and noise reduction. Since the inkjet printer is a non-impact recording system, quietness during recording can be achieved, and since ink droplets are ejected to form an image on the paper, high-speed recording is possible and there is no special fixing process. Since it can be recorded on plain paper, it has been used in a wide range of fields. Further, since it is easy to colorize by separately ejecting the inks of the three primary colors, it has come to be widely used as an output printer for a home or office computer.

The printing mechanism of an ink jet printer is roughly classified into a continuous system and an on-demand system in which ink is ejected according to a recording signal, and the on-demand system is currently the mainstream.

[0004] The on-demand system is described in, for example, US Pat.
As disclosed in Japanese Patent No. 4747120, an electric recording signal is added to a piezoelectric element attached to a recording head, and this is converted into mechanical vibration of the piezoelectric element, and this mechanical vibration causes ink to be ejected from a nozzle hole. This is a method of recording by ejecting small droplets and adhering them to recording paper. In other words, since ink is ejected according to the recording signal, it is not necessary to collect the droplets that were not required to record an image among the droplets ejected and ejected as in the continuous method, so a simple structure is possible. Is. However, it is difficult to process the recording head and it is extremely difficult to miniaturize the piezo vibrating element, and it is difficult to make multiple nozzles.Because of the mechanical energy of mechanical vibration of the piezo element, small droplets fly, which is not suitable for high-speed recording. It has drawbacks.

As another example of the on-demand system, there is a bubble jet system in which ink is heated to generate bubbles in the ink and the volume of the ink changes to fly the ink. The scheme disclosed in US Pat. No. 3,179,042 describes using thermal energy. Compared with the method that uses mechanical vibration energy, the energy conversion efficiency is high and it is easy to make multiple nozzles.

Generally, in the ink discharge method using such heat, since the temperature of the ink changes depending on the environmental temperature and the history of printing, an attempt is made to keep the temperature of the ink constant. Most commonly, a heater for preheating ink is provided somewhere in the ink flow path, and the ink temperature is controlled to be constant while detecting the ink temperature.

Next, the principle of the ejection will be described. FIG.
FIG. 3 is a schematic sectional view of the ink ejection device. In FIG. 1, 1 is an ink chamber, 2 is a conductive inkjet ink filled in the ink chamber, 3 is an ink tank containing the inkjet ink 2, and 4 and 5 are liquids of the inkjet ink 2 in the ink chamber 1. A pair of electrodes arranged below the surface, 6 is a power source, 7 is a switch of the power source 6, 8 is a nozzle for ejecting the inkjet ink 2, 9 is a recording paper, and 10 is an ink droplet ejected from the nozzle 8.

The operation of the ink discharge device having the above structure will be described below. When a voltage is applied to the pair of electrodes 4 and 5, a current flows through the inkjet ink 2, and the Joule heat causes a part of the inkjet ink 2 between the tips of the electrodes 4 and 5 to vaporize. Further, the vaporized vapor of the inkjet ink 2 expands until a sufficient pressure is generated to eject the ink droplet 10 from the nozzle 8 onto the recording paper 9. By applying a voltage with the switch 7, it is possible to select a nozzle hole for ejecting the inkjet ink 2 and form a desired character on the recording paper 10.

Inkjet Ink 2, as described in US Pat. No. 4,536,776, is an ink for a selective ink jet printer which comprises an aqueous mixture of dyes, the mixture having a specific resistance of 15 to 50 Ω per cm ^2. An ink characterized in that it comprises a hydrolyzed salt in such an amount as to
No. 70, an ink composition for ink jet recording characterized by containing a quaternary ammonium salt as an essential component, and an aqueous ink for ink jet recording further containing water and a colorant in JP-A-5-179182. Disclosed is an ink containing a salt consisting of an alkanolamine or an ethylene oxide adduct or a propylene oxide adduct and a hydrogen halide in a composition.

[0010]

However, in the conventional ink jet ink described above, when the AC frequency of the voltage applied to the electrodes is lower than 5 MHz, the ink jet ink is electrolyzed instead of bubbles that shrink like boiling bubbles. By the chemical reaction of, hydrogen, bubbles such as oxygen that do not shrink and disappear, are retained between the electrodes and in the nozzle holes, the current does not flow to the inkjet ink, it will be impossible to continue boiling, Alternatively, there is a problem in that even if an electric current flows into the inkjet ink and the ink is boiled, bubbles due to electrolysis stay in the nozzle holes and ejection is not performed normally. Further, at the same time, a dissolution reaction of the electrodes occurs, which makes it difficult for an electric current to flow in the inkjet ink, making it impossible to boil the ink. Furthermore, this problem is solved by increasing the AC frequency of the voltage applied to the electrodes to 5 MHz or more, but if the AC frequency applied to the electrodes is increased to 5 MHz or more, unnecessary radiant noise generated from the drive circuit increases. However, there is a problem that the price of the driving driver becomes very high.

The present invention solves the above-mentioned conventional problems. Even when the AC frequency of the voltage applied to the electrodes is 5 MHz or less, the generation of bubbles due to electrolysis can be significantly reduced, and the current flowing between the electrodes can be smooth. The flow bubbles are stable and the discharge can always be performed in a normal state, and the discharge stability and discharge response are remarkably excellent, continuous recording performance can be dramatically improved, and the generation of the dissolution reaction of the electrode is significantly An object of the present invention is to provide an inkjet ink that can suppress the abrasion of the electrodes and can significantly improve the durability of the electrodes.

[0012]

In order to solve this problem, the ink-jet ink of the present invention contains a color former, an additive, and a solvent that dissolves the color former and the additive, and The specific resistance is 8 to 50 Ω · cm at 25 ° C, and the decomposition temperature of at least one of the color formers is less than 130 ° C.

With this configuration, the coloring agent adheres to the surface of the electrode, so that the AC frequency of the voltage applied to the electrode is 5 MHz.
Even if it is lower than z, bubbles due to electrolysis that do not shrink and disappear due to chemical reactions such as electrolysis of ink jet inks are less likely to occur, and the bubbles do not stay between the electrodes and in the nozzle holes. In addition, since the current smoothly flows in the inkjet ink, the boiling is stable, and the ejection is normally performed, the ejection stability, the ejection response, and the continuous recording property can be improved. At the same time, the dissolution reaction on the electrode surface is suppressed, a current flows through the ink, and boiling is stabilized. Further, there is no need to increase the AC frequency of the voltage applied to the electrodes to 5 MHz or higher, unnecessary radiant noise generated from the drive circuit can be reduced, and the cost of the drive driver can be kept low. Have.

Further, it is more preferable that the compound has the action of adjusting the specific resistance by incorporating the compound represented by the following general formula (Formula 1).

R ₁ R ₂ R ₃ N ⁺ —X ⁻ (Chemical formula 1) (wherein R ₁ , R ₂ and R ₃ are H, CH ₂ OH, C ₂ H ₄ O
It is a group selected from H, an alkyl group having 1 to 3 carbon atoms, an aryl group and alkylene having 1 to 3 carbon atoms, and R ₁ , R ₂ and R ₃ may be the same or different. X
Are halogen, ClO ₄ , BF ₄ , PF ₆ , NO ₃ ,
It is a group selected from SO ₄ , BO ₄ , and HCOOCH ₃ COO. R _{1 to} R ₃ may combine with each other to form a ring. ) In the inkjet recording type head, a recording liquid is heated by a heat generating source such as a resistance heater and is made to boil, and the recording liquid is discharged from a direction control mechanism such as a nozzle by the expansion force of the boiling bubbles to print on a paper surface. A method in which a high voltage is applied to the recording liquid and the electrostatic liquid is used to discharge the recording liquid from a direction control mechanism such as a nozzle to print on the paper surface, or the pressure is applied to the recording liquid by the mechanical movement of the piezoelectric element, and the recording liquid is applied to the nozzle, etc. A method of ejecting from the direction control mechanism to print on the paper surface, a method of adding a magnetic material to the recording liquid to give kinetic energy to the recording liquid by an external magnetic field and ejecting the recording liquid from the direction control mechanism such as a nozzle to print on the paper surface, Electrical energy is added to the recording liquid by adding a conductive material, and the recording liquid is ejected from a direction control mechanism such as a nozzle by the expansion force of boiling bubbles generated by self-heating of the recording liquid. Method of printing on the surface (electric heating method)
Many operating principles have been proposed and put into practical use. Various methods, structures, and construction methods have been proposed for the structure of the active element device for realizing these operating principles. Since higher resolution printing patterns are required as printing quality improves, most of the active element devices are formed by thin film technology. The ink of the present invention can be used in any system of the above-mentioned principle, but it is particularly preferable to use it in an electric heating system.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The ink-jet ink according to claim 1 of the present invention contains a color former, an additive, and a solvent for dissolving the color former and the additive, and at 25 ° C. The specific resistance is 8 to 50 Ω · cm, and the decomposition temperature of at least one of the color formers is less than 130 ° C. With this configuration, the color former having a decomposition temperature of 130 ° C. or lower is decomposed by heating during energization heating and adheres to the electrode surface, and even if the AC frequency of the voltage applied to the electrode is lower than 5 MHz, the electrical conductivity of the inkjet ink is reduced. Bubbles due to electrolysis that do not shrink and disappear due to hydrogen, oxygen, etc. due to chemical reactions such as decomposition become less likely to occur, and the bubbles will not stay between the electrodes and in the nozzle holes, causing a current to flow smoothly through the inkjet ink and boiling Is stable and the ejection is normally performed, it is possible to improve the ejection stability, the ejection response, and the continuous recording property. At the same time, the dissolution reaction on the electrode surface is suppressed, a current flows through the ink, and boiling is stabilized. Further, there is no need to increase the AC frequency of the voltage applied to the electrodes to 5 MHz or higher, unnecessary radiant noise generated from the drive circuit can be reduced, and the cost of the drive driver can be kept low. Have.

Water-soluble ink for ink jet,
Either oil-soluble is acceptable. Considering odor and safety, water-soluble is preferred. Inkjet ink, a coloring agent, as an additive, alcohol as a wetting agent, a surfactant, a water-soluble organic solvent such as glycols, water, or bleeding to add a mixture thereof, a drying speed, It is preferable because the boiling state can be adjusted, the electrode life, and the nozzle clogging can be prevented. Further, it is preferable to add a preservative in order to enhance durability.

Next, a specific example of the structure that can be used in the present invention will be described. As the coloring agent, a coloring agent, dye or pigment is used. As the color former, methylene green and fast garnet GB are particularly used as those having a decomposition temperature of less than 130 ° C.
C or the like is used.

As the dye, an azo dye, an acid dye, a basic dye, a direct dye or the like is used. Pigments include carbon black, azo lake pigments, insoluble azo pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, berylene pigments, verinone pigments, atraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, bases. Use is made of functional dye type lakes, acid dye type lakes, nitro pigments, aniline black, fluorescent pigments, titanium oxide, iron oxide and the like. As the anti-drying agent, glycerin, urea, sorbitan, sorbitol, inositol, a chelating agent and the like are used. As the dispersant, proteins, natural rubbers, cellulose dielectrics, natural polymers, ionic polymers, anionic surfactants, nonionic surfactants and the like are used. Isopropyl alcohol and polyhydric alcohol are used as the foaming agent. As the antioxidant, vitamin C, sodium sulfite, hydroquinone, pyrazolidone, hydrazine and the like are used.

It is particularly preferable to use a conductive ink in the present invention. US Pat. No. 4 for conductive ink
536776, "In an ink for an selective ink jet printer comprising an aqueous mixture of dyes, the mixture comprising a hydrolyzed salt in an amount such that the ink has a resistivity of 15 to 50 ohms / cm ^2. Ink characterized by ". Japanese Patent Laid-Open No. 5-179
No. 182, "Aqueous ink composition for ink jet recording containing water and a colorant, containing an alkanolamine or ethylene oxide adduct and / or propylene oxide adduct, and a salt consisting of hydrogen halide" is disclosed. There is. Japanese Patent Publication No. 2-5785 specifically describes inorganic salts. The conductivity-imparting agent used in the present invention may be an alkali metal compound salt such as lithium (Li), an inorganic salt such as ammonium sulfate, lithium chloride, sodium chloride or potassium chloride, or an organic salt, but a quaternary organic ammonium salt. The above dielectrics can be preferably used. Specific examples of the compound include monoethanolamine sulfate, diethanolamine sulfate, triethanolamine sulfate, monoethanolamine nitrate, diethanolamine nitrate, triethanolamine nitrate, monoethanolamine phosphate, diethanolamine phosphate, Triethanolamine phosphate, dimethanolamine sulfate, trimethanolamine sulfate, diethylamine sulfate, triethylamine sulfate, dimethylamine sulfate, trimethylamine sulfate, monopropylamine sulfate, dipropylamine sulfate, tripropyl Amine sulfate, phenylamine sulfate, diphenylamine sulfate, dimethyleneamine sulfate, trimethyleneamine sulfate, diethyleneamine sulfate, triethyleneamine sulfate, dipropyleneamine Salt, tripropylene amine sulfate, pyridine sulfate, can be mentioned pyrrole sulfate.

The wetting material has a boiling point higher than that of water,
Used to prevent drying of the nozzle tip. Specific examples of the wetting agent include polyethylene glycol, polypropylene glycol, butylene glycol, hexylene glycol, and other alkylene glycols having an alkylene group containing 2 to 6 carbon atoms, such as ethylene glycol ethyl ether, diethylene glycol methyl ether, and diethylene glycol. Examples include lower alkyl ethers of diethylene glycol such as ethyl ether and glycerin. The polyhydric alcohol is contained in an amount of 0.1 to 10% by weight, preferably 0.5 to 3.0% by weight. As the polyhydric alcohol becomes less than 0.5% by weight, the nozzle tip tends to be clogged due to the drying of the ink, and as the polyhydric alcohol exceeds 3.0% by weight, the ink specific resistance tends to increase. And it was found that each was not preferable.

Examples of the solvent include water and organic solvents which can be mixed with water. Examples of the organic solvent include alkyl alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol and isopropyl alcohol, ketones such as acetone and diacetone alcohol or keto alcohols, amides such as dimethylformamide and dimethylacetamide, tetrahydrofuran and dioxane. Examples thereof include ethers, ether alcohols such as ethylene glycol monomethyl ether and rembricol monoethyl ether, and water-soluble polymer compounds. Water used as a solvent is 30 to 80% by weight, preferably 50
７０70% by weight. As the amount of water becomes less than 50% by weight, the tendency for the paper to permeate is improved.
As the amount exceeds 0% by weight, the penetrability into paper tends to decrease, which is not preferable.

In the case of adding a surfactant, a pH adjusting agent, a viscosity adjusting agent, a drying inhibitor, a dispersant, a coloring agent, an antioxidant, etc., to the ink jet ink in order to adjust the liquid physical properties. There is.

The surface tension adjusting agent is added to improve the quick-drying property of the inkjet ink and at the same time prevents evaporation of the inkjet ink. As the adjusting agent, a water-soluble organic solvent or a surfactant is preferably used. The water-soluble organic solvent may be selected from the above solvents. Specific examples of the surfactant include fatty acid salts, higher alcohol sulfate ester salts, liquid fatty oil sulfate ester salts, fatty alcohol phosphate ester salts, dibasic fatty acid ester sulfone salts, fatty acid amide sulfonates, and alkylallyl sulfones. Acid salts, formalin-bonded naphthalene sulfonates, alkylpyridinium salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxy ylene alkyl esters, sorbitan alkyl esters, polyoxy ylene sorbitan alkyl esters Can be mentioned.

The pH adjusting agent may be any one as long as it can be adjusted to a desired pH value without adversely affecting the ink jet ink to be prepared, and specific examples thereof include lower alkanolamine and alkali metal hydroxide. And monovalent hydroxides, ammonium hydroxide and the like.

The viscosity modifier adjusts the viscosity of the ink jet ink, and specifically, polyvinyl alcohol, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, water-soluble acrylic resin, polyvinyl pyrrolidone, glycerin, An example is gum arabic starch.

As the anti-drying agent, glycerin, urea,
Examples thereof include sorbitan, sorbitol, inositol, chelating agents and the like.

Furthermore, in order to reinforce the strength of the ink film when it adheres to printing paper, alkyd resin, acrylic resin, acrylamide resin, polyvinyl alcohol,
A resin polymer such as polovinylpyrrolidone may be added. In addition, it is advantageous to add a preservative such as alcohol, formalin, and omasin sodium in terms of ensuring reliability during long-term storage.

The viscosity is adjusted to 10 cp or less, preferably 5 cp or less. It was found that as the viscosity exceeds 5 cp, there is a tendency that inconvenience occurs in the ejection of ink droplets from the nozzle holes, which is not preferable. The surface tension is 2
8 to 55 dyne / cm, preferably 30 to 45 dyn
e / cm. As the surface tension becomes less than 30 dyne / cm, it is recognized that the fine line bleeding of the print tends to worsen and the print density tends to decrease.
It has been found that the color bleeding property of the color overprinting tends to decrease as the value exceeds yne / cm, which is not preferable. pH is 6-10, preferably 7
~ 9. It was observed that the solubility stability of the dye tends to decrease as the pH becomes less than 6, and that the fading of the dye tends to occur as the pH exceeds 10, which is not preferable. all right.

An ink jet ink according to a second aspect of the present invention has the structure according to the first aspect, wherein the color former is methylene green. With this configuration, methylene green is rapidly decomposed at the ink heating temperature when the electrode is applied and covers the surface of the electrode, so that the electrolysis reaction by the electrode can be suppressed.

The ink-jet ink according to claim 3 of the present invention has a constitution in which the coloring agent is fast garnet GBC. With this configuration, the fast garnet GBC is rapidly decomposed at the ink heating temperature when the electrode is applied and covers the surface of the electrode, so that the electrolytic reaction by the electrode can be suppressed.

The ink-jet ink according to claim 4 of the present invention has a constitution containing a compound represented by the following general formula (Formula 1). This configuration reduces the specific resistance to 2
It has an effect that it can be adjusted to 8 to 50 Ω · cm at 5 ° C. and that clogging of ink can be prevented.

R ₁ R ₂ R ₃ N ⁺ —X ⁻ (Chemical formula 1) (wherein R ₁ , R ₂ and R ₃ are H, CH ₂ OH, C ₂ H ₄ O
It is a group selected from H, an alkyl group having 1 to 3 carbon atoms, an aryl group and alkylene having 1 to 3 carbon atoms, and R ₁ , R ₂ and R ₃ may be the same or different. X
Are halogen, ClO ₄ , BF ₄ , PF ₆ , NO ₃ ,
It is a group selected from SO ₄ , BO ₄ , and HCOOCH ₃ COO. R _{1 to} R ₃ may combine with each other to form a ring. ) Specific compounds for adjusting the specific resistance include monoethanolamine sulfate, diethanolamine sulfate, triethanolamine sulfate, monoethanolamine nitrate, diethanolamine nitrate, triethanolamine nitrate, monoethanolamine phosphate, diethanolamine phosphate. , Triethanolamine phosphate, dimethanolamine sulfate, trimethanolamine sulfate, diethylamine sulfate, triethylamine sulfate, dimethylamine sulfate, trimethylamine sulfate, monopropylamine sulfate, dipropylamine sulfate, tri Propylamine sulfate, phenylamine sulfate, diphenylamine sulfate, dimethyleneamine sulfate, trimethyleneamine sulfate, diethyleneamine sulfate, triethyleneamine sulfate, dipropylene Amine sulfate, tripropylene amine sulfate, pyridine sulfate, pyrrole sulfate, etc. are used. The resistivity adjusting agent is 8 to 50 Ω · c at 25 ° C.
m, preferably 15 to 25 Ω · cm. The specific resistance is 8
As the content of the conductivity-imparting agent in the inkjet ink increases as the resistance becomes less than Ω · cm, the dissolution stability of the dye decreases and the nozzle clogging tends to deteriorate, and the specific resistance is 50 Ω · cm. As the content of the conductive compound decreases as the temperature exceeds the above value, lowering the AC frequency of the voltage applied to the electrode makes it impossible to prevent the chemical reaction on the substrate, and the electrode is dissolved or the ejection stability deteriorates. However, it is not preferable in each case.

(Embodiment 1) Kayaset Black 008 (N) Pure (Kayaset Bl)
ack 008 (N) pure, Nippon Kayaku dyestuff 3
%, Methylene green (manufactured by Wako Pure Chemical Industries, Ltd.), 0.01% by weight, 1% by weight of glycerin which is a wetting agent, 16% by weight of monoethanolamine sulfate, and 4% by weight of isopropyl alcohol, and a solvent. Ion-exchanged water is added to prepare a total amount of 100% by weight, and these raw materials are stirred until they are sufficiently homogeneous, and then 0.45 μm
m under pressure filtration with a Fluoropore filter (manufactured by Sumitomo Electric Industries, Ltd.) to obtain the inkjet ink of the first embodiment.

Then, the specific resistance, viscosity, surface tension and pH of the ink jet ink of the first embodiment were measured.

The specific resistance was measured in a constant temperature bath adjusted to 25 ° C. using a conductivity meter (trade name ES-12) manufactured by Horiba Ltd. Viscosity is a viscous viscometer manufactured by Yamaichi Denki (trade name VIS
(COMATE VM-1A-L). The surface tension was measured by a Wilhelmy method (suspension plate type) using a platinum plate, using a fully automatic parallel type electro surface tensiometer (trade name ESB-V) manufactured by Kyowa Kagaku. The pH was measured using a pH meter (trade name HM-20E) manufactured by Toa Denpa Kogyo. The measurement result shows that at 25 ° C., the specific resistance is 20 Ω · cm, the viscosity is 2.0 cp, and the surface tension is 5.
It was 0 dyne / cm and pH was 6.8.

An insulating film such as an organic polymer or ceramics is formed on the electrode not exposed in the ink chamber and the substrate by coating or vapor deposition or sputtering. A resin sheet having nozzle holes formed by an excimer laser beam machine and a nozzle sheet formed by an excimer laser beam machine are bonded to the substrate on which the insulating film and the electrodes are laminated so that the centers of the nozzle holes coincide with the centers of the two electrodes.
Examples of the organic polymer used for the insulating film include polyimide, polyamide-imide, urea resin, phenol resin, epoxy resin, fluororesin, acrylic resin, and silicone resin, and heat-resistant polymers such as polyimide are particularly preferable. Moreover, you may use the metal alkoxide used for a sol-gel method.

Further and / or SiO ₂ , Al ₂ O ₃ ,
A metal oxide such as TiO _{2 is} formed by a vapor deposition method or a sputtering method. As the resin sheet, heat-resistant engineering plastics such as polyimide, polyamide-imide, polyether sulfone, polyphenylene sulfide, and polyether ether ketone can be used, but polyimide and polyether sulfone are preferable in view of ink resistance and laser processability. A thermosetting resin such as an epoxy resin, a polyimide resin, a triazine resin, an acrylic resin, a polyurethane resin, a silicone resin, or a urea resin can be used as the adhesive. It is also possible to add a thermoplastic resin such as nitrile rubber, silicon rubber, nylon, polyester resin, or the like in order to impart flexibility. In addition, SiO ₂ , Al ₂ O ₃ ,
Fine powder of a metal oxide such as TiO ₂ may be added as a filler, and an appropriate amount of a coupling agent may be added to improve adhesiveness. Considering ink resistance and heat resistance, epoxy resin and polyimide resin are preferable. The adhesive is diluted with an organic solvent to a concentration to obtain a predetermined film thickness, applied on the resin sheet in advance, and then the solvent is volatilized by heating to form an adhesive layer.

An excimer laser is incident from the adhesive surface side,
Nozzle holes are formed in the resin sheet. When a heat-resistant plastic film such as polyimide is attached as a protective sheet to the surface of the adhesive during excimer laser processing and processed, high-temperature processing waste does not come into direct contact with the adhesive, so the adhesiveness does not decrease. The resin sheet having the nozzle holes and the substrate are bonded by a rubber pressing method or the like. The bonding temperature is appropriately set according to the curing temperature of the adhesive. Apply pressure with an optimum load that does not cause the adhesive to float or bleed.

The ink cartridge used in the present invention is an integral type in which the recording head for ejecting ink and the ink tank for storing the ink to be supplied to the recording head are integrated, but the recording head and the ink tank are It may be a detachable type that is detachably configured. It is desirable to provide a filter between the ink flow path from the ink tank to the recording head in order to trap foreign matters and bubbles in the ink that adversely affect the ejection.

It is advantageous in terms of reliability that the filter is three-dimensionally knitted with a metal such as stainless steel so as to have a filtration particle size of about 10 microns.

As a condition for improving the print quality,
It has been known for some time that it is important to apply a static negative pressure to the ink ejection port. By applying a negative pressure, the liquid surface of the ink ejection port becomes a negative meniscus, and it is possible to prevent the ink from being drawn in, improving the landing accuracy, and reducing the extra droplets (extra dots). In order to generate a negative pressure at the ink ejection port, it is desirable to provide a negative pressure generating means such as filling the ink tank with a sponge made of polyurethane foam or providing a spring member inside and outside the ink tank.

In the recording apparatus in which the present invention is used, one or a plurality of recording heads are mounted on a carriage, and ink is ejected by the recording heads while reciprocating in the main scanning direction on the front surface of the recording material to record the recording material. Even in a so-called serial type recording apparatus that performs recording by feeding a predetermined amount of material in the sub-scanning direction, the recording head is provided over the entire width of the recording material in the main scanning direction, and the recording material has a predetermined width in the sub-scanning direction. A so-called line-type recording device that performs recording by feeding only the amount may be used.

Also, so-called plotter type recording in which one or a plurality of recording heads are mounted on a carriage and ink is ejected from the recording heads while moving over the entire surface of the recording material in the main scanning direction and the sub-scanning direction. It may be a device.

FIG. 5 is a timing chart of the signal generator for controlling the pulse voltage applying means. The timing operation of the pulse signals i to j will be described according to this timing chart. Now, when the print data g is high, that is, when the printing is instructed, the output h becomes a signal for selecting the on-time setting signal e at the time of printing by the AND circuit 12 and the OR circuit 16. Similarly, when the print data g is low, that is, when printing is not instructed, the output h becomes a signal that selects the on-time setting signal f for non-printing by the NOT circuit 11, the AND circuit 13, and the OR circuit 16. Further, by inputting the enable signal h and the basic pulse signals c and d into the AND circuits 14 and 15, pulse signals i and j are obtained. In other words, during printing, during the t1 period, during non-printing (dummy printing) during the t2 period, the transistor Q has the frequency and phase of the basic pulse c.
1 and Q2 are switched, and the transistors Q3 and Q4 are switched at the frequency and phase of the basic pulse d.

FIG. 6 is a diagram showing the relationship between ink temperature and ink resistivity characteristic. As can be seen from this graph, the ink specific resistance decreases as the ink temperature decreases. That is, it is understood that the current easily flows through the ink.

FIG. 7 is an explanatory diagram of a change in ink temperature of the electrode portion due to printing. Now, suppose that the ink temperature is 20 at time 0.
C., preheat to ink temperature 70.degree. When continuous printing starts at time 5T, print power / dot = P1 The ink temperature is always kept at 70 ° C. by designing with.

However, in the case of intermittent printing, 5 as shown in the graph
If there is no printing from T to 9T, the ink temperature will gradually drop without inputting energy, and it will be difficult for the ink to boil and the current will not flow easily in the ink, and printing will not be possible at 10T.

In the present invention, dummy printing is carried out during the non-printing period. Ink heat retention energy / dot = P1 * t2 = E2 = energy lost / T period Next, a performance test of the ink jet ink of the first embodiment was conducted.

The ink jet ink of the first embodiment is formed by using the ink jet of the electric heating type shown in FIG.
Printing was performed under the conditions shown in (Table 1).

[0051]

[Table 1]

As a test for examining the ejection stability, the state of the electrode when the ink for ink jetting according to the first embodiment was continuously applied with a voltage of 10 KHz for 10 hours, continuous recording property for 10 hours (ejection state of ink droplets). Observe,

[0053]

[Table 2]

As the image evaluation, the disturbance around the dots when adhered to the printer paper was observed, and the results are shown in (Table 2).

As is clear from (Table 2), the ink-jet ink according to the present embodiment has almost no deterioration in the electrode state and the recording property over time, and no disturbance is observed around the dots. Thus, it was found that an excellent effect was obtained as compared with the comparative example described later.

As described above, according to the present embodiment, since methylene green is contained, even if the AC frequency of the voltage applied to the electrode is lowered, the electrode state hardly deteriorates with time, and the ejection stability is improved. It was found that deterioration with time was not observed at all.

(Embodiment 1) FIG. 9 is a diagram showing the relationship between the methylene green content and the boiling characteristics. The limit of the content of methylene green is 0.08% by weight, and when it exceeds the limit, the amount of dye decomposition products attached to the electrode surface increases and the boiling characteristics deteriorate. It was also found that the effect of addition was not observed when the methylene green content was less than 0.005% by weight.

(Comparative Examples 1 and 2) As a first comparative example, an ink jet ink similar to that of the first embodiment was manufactured without adding methylene green. As a second comparative example,
An inkjet ink was manufactured in the same manner as in Embodiment 1 except that 0.1% by weight of methylene green was contained.

Performance tests were conducted on the ink jet inks of the first and second comparative examples in the same manner as in Embodiment 1, and the results are shown in (Table 2).

As is clear from this (Table 2), the ink-jet ink according to the first comparative example does not show the improvement in the boiling characteristics as compared with the first embodiment, and the electrode tends to dissolve. Was observed, and it was found that the recording property became unstable in 7 to 8 hours. The inkjet ink according to the first comparative example had good recording property and image stability when the electrode driving condition was set to 5 MHz 3 OV. It was found that the inkjet ink according to the second comparative example had a problem in that the boiling property was deteriorated due to an increase in the amount of the dye decomposition product attached, and the recording property was unstable in the ejection property after 2 to 3 hours.

(Second Embodiment) Kayaset Black 008 (N) Pure (Kayaset Bl)
ack 008 (N) pure, Nippon Kayaku dyestuff 3
% By weight, 0.01% by weight of Fast Garnet GBC (manufactured by SIGMA), 1% by weight of glycerin which is a wetting agent,
16% by weight of monoethanolamine sulfate and 4% by weight of isopropyl alcohol were mixed, and ion-exchanged water as a solvent was added to prepare 100% by weight, and Fast Garnet GBC was used instead of methylene green. Ink was manufactured and a performance test was conducted in the same manner as in Embodiment 1 except that a sulfate was used, and the results are shown in (Table 2).

As is clear from this (Table 2), the ink jet ink according to the present embodiment is the same as that of the first embodiment.
Similarly, it was found that an excellent effect can be obtained in that there is almost no deterioration in the electrode state and the recording property over time, and that there is no disturbance around the dots.

Fast Garnet GB of the Second Embodiment
Fast garnet GBC ・ B instead of C ・ SO ₄ salt
The same results as in the second embodiment were obtained using the F ₄ salt.

As described above, according to the present embodiment, since the fast garnet GBC is contained, even if the AC frequency of the voltage applied to the electrode is lowered, there is almost no deterioration of the electrode state over time, and the ejection stability is stable. No deterioration of the properties with time is observed at all.

(Embodiments 3 to 8) In the same manner as in Embodiment 1 except that the following compounds are used as color formers instead of Kayaset Black 008 (N) Pure which is the color former of Embodiment 1. An inkjet ink was manufactured.

As a third embodiment, BAYSCRIP
T BLACK BS (Dye manufactured by Bayer), as a fourth embodiment, Duasyn D.M. Black HEFS
FVP332 (Hoechst dye), as the fifth embodiment, Aizen Direct Black 3000
S (Hosho ■ Tani Kagaku dye), as the sixth embodiment, K
ayase Yellow J-005 (Dye manufactured by Nippon Kayaku), as a seventh embodiment, Kayaset Re
d J-011 (Nippon Kayaku dye), and as the eighth embodiment, Kayaset Cyan J-301 (Nippon Kayaku dye) was used.

Performance tests were conducted on the third to eighth embodiments in the same manner as the first embodiment, and the results are shown in (Table 3) to (Table 4).

[0068]

[Table 3]

[0069]

[Table 4]

As is clear from (Table 3) to (Table 4), the ink-jet ink according to the present embodiment shows almost no deterioration in the electrode state and the recording property over time, and there is no disturbance in the dot peripheral area. It was found that an excellent effect can be obtained in that it does not exist.

[0071]

As described above, according to the present invention, when at least one of the color formers has a decomposition temperature of less than 130 ° C., the color former adheres to the surface of the electrode and is applied to the electrode. Even if the AC frequency of the applied voltage is lower than 5 MHz, bubbles due to electrolysis that does not shrink and disappear due to chemical reactions such as electrolysis of the inkjet ink are less likely to occur. The electric current smoothly flows through the ink jet ink without staying in the holes, the boiling is stabilized, and the ejection is normally performed, whereby the ejection stability, the ejection response, and the continuous recording property can be improved. At the same time, the dissolution reaction on the electrode surface is suppressed, a current flows through the ink, and boiling is stabilized. Furthermore, the AC frequency of the voltage applied to the electrodes is 5 MHz.
It is not necessary to raise it higher than this, unnecessary radiant noise generated from the drive circuit can be reduced, and the cost of the drive driver can be kept low.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an ink ejection device.

FIG. 2 is a sectional view of a main part of a conventional inkjet head.

3 is a sectional view taken along the line AA ′ of FIG.

FIG. 4 is a diagram showing a head drive circuit.

FIG. 5 is a timing chart of a signal generator.

FIG. 6 is a diagram showing the relationship between ink temperature and ink resistivity characteristic.

FIG. 7 is an explanatory diagram of a change in ink temperature of an electrode portion due to printing.

FIG. 8 is an explanatory diagram of gradation control of dot diameter.

FIG. 9 is a relationship diagram between the methylene green content and the boiling characteristics.

[Explanation of symbols]

 1 Ink Chamber 2 Conductive Ink 3 Ink Tank 5 Electrode 6 Power Supply 7 Power Switch 8 Nozzle 9 Recording Paper 10 Ink Drop 22 Nozzle 23 Nozzle Plate 24 Substrate 26 Insulation Member 27 Pressure Chamber 28 Signal Generation Section 30 Ink Flow Path

Claims (4)

[Claims] 1. A color developing agent, an additive, and a solvent that dissolves the color developing agent and the additive, and the specific resistance at 25 ° C. is 8 to 50 Ω · cm. An inkjet ink, wherein the decomposition temperature of at least one of the color formers is less than 130 ° C. 2. The color developing agent is methylene green.
3. The ink for inkjet according to item 1. 3. The ink jet ink according to claim 1, wherein the color former is Fast Garnet GBC. 4. A compound represented by the following general formula (Chemical formula 1) is contained, wherein any one of claims 1 to 3 is contained.
3. The ink for inkjet according to item 1. R ₁ R ₂ R ₃ N ⁺ —X ⁻ (Chemical formula 1) (wherein R ₁ , R ₂ and R ₃ are H, CH ₂ OH, C ₂ H ₄ O
It is a group selected from H, an alkyl group having 1 to 3 carbon atoms, an aryl group and alkylene having 1 to 3 carbon atoms, and R ₁ , R ₂ and R ₃ may be the same or different. X
Are halogen, ClO ₄ , BF ₄ , PF ₆ , NO ₃ ,
It is a group selected from SO ₄ , BO ₄ , and HCOOCH ₃ COO. R _{1 to} R ₃ may combine with each other to form a ring. )