JPH0462865B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an inkjet recording method that performs recording by ejecting ink from an orifice using thermal energy. Non-impact recording methods have recently attracted attention because the noise generated during recording is so small that it can be ignored. Among these non-impact recording methods, the so-called inkjet recording method (liquid jet recording method), which enables high-speed recording and can record on plain paper without the need for special processing, is an extremely useful recording method. Until now, various methods have been proposed and devices have been devised to implement them, some have been improved and commercialized, and efforts are still being made to put them into practical use. There are some. Among them, for example, the liquid jet recording method described in Japanese Patent Application Laid-Open No. 54-51837 and German Opening Publication (DOLS) No. 2843064 applies thermal energy, which is the energy for forming ink droplets, to the ink. It has a different feature from other liquid jet recording methods in that it obtains the motive force for ejecting droplets. That is, in the recording method disclosed in the above-mentioned publication, the ink subjected to the action of thermal energy undergoes a state change accompanied by a sharp increase in volume, and the acting force based on this state change causes the recording head portion to Ink droplets are ejected from the orifice at the tip, fly, and adhere to the recording member to perform recording. In order to record high-resolution, high-quality images at higher speeds and for longer periods of time using such a recording method, or to dramatically improve the usable life of the implementing device, it is necessary to increase the repeated use life (durability) of the recording head. need to be improved. The factors that determine the service life of the recording head applied to the above recording method include the life of the electric/thermal converter included, as well as the deposition of solid matter on the surface of the converter. . That is, the recording head applied to the above recording method has a structure as shown in FIG. 1, for example. In the figure, the electrical/thermal converter 102 comes into contact with the liquid introduced from arrow A through the heat action surface 109 as the energy action surface in the heat action section 107 which is the droplet formation energy action section. are doing. Such a configuration is adopted for the purpose of causing the generated thermal energy as droplet formation energy to act effectively and efficiently on the liquid in the heat acting section 107. For this reason, although it depends on the ink used, when using an ink that uses ordinary water as a liquid medium, it is necessary to prevent electrical leakage between the electrodes 113 and 114 through the ink, and Heat generating resistance layer 11
1 from the ink or thermal oxidation, an upper layer 112 is formed on the heat generating resistor layer 111 at the heat generating portion 108 during head fabrication. The principle of ink droplet formation in the recording method using such a recording head is that, as mentioned above, when electricity is turned on to the electricity-to-thermal converter, the droplets are formed by the droplet formation energy, which is thermal energy. Action part 107
The ink in the heat effecting part 107 undergoes a state change accompanied by a rapid increase, that is, the ink in the heat effecting part 107 reaches a vaporized state within a very instant of about μsec or less, and in the heat effecting part 107, Generation and growth of bubbles occur, and the heat acting part 107 and orifice 1
05 is ejected as droplets. As the ink receives high heat during the repeated generation and disappearance of bubbles, thermally unstable ink tends to undergo chemical changes, resulting in the formation and deposition of insoluble matter on the surface of the heat-acting part. As a result, the head may become unable to eject. Therefore, in order to perform high-speed, long-term recording using such an apparatus, the thermal stability of the ink is extremely important. By the way, as an example of the general basic composition of inkjet recording ink, there is an ink that has three main components: a water-soluble dye, water as a solvent for the dye, and glycols as an anti-drying agent. . As water-soluble dyes, direct dyes, acid dyes, and basic dyes are preferably used because they are excellent in fastness and color tone when recording. However, these dyes often contain m-phenylenediamine, which is one of the raw materials for dye synthesis, and chloride, which is a by-product during dye synthesis or is added as a salting-out agent, diluent, or leveling agent. It is contaminated with inorganic salts such as sodium and sodium sulfate. Conventionally, when inks were prepared using dyes containing such impurities, the following problems often occurred. That is, many of the above-mentioned impurities lower the dye dissolution stability in the ink, causing aggregation and precipitation of the dye, and causing clogging of the fine orifices of the ink jet device. Furthermore, according to the knowledge of the present inventors, inorganic salts and
- Phenylene diamine lowers the thermal stability of the ink (that is, the dissolution stability at high temperatures). Therefore, with conventional ink, especially in the inkjet recording method that uses thermal energy to generate ink droplets as described above, the ink is heated, so the ink is not deposited on the surface of the heat-acting part in the inkjet head. In many cases, insoluble matter was deposited from within, impairing the ink ejection function of the head. The present invention has been made in view of the above, and includes:
Significantly extends the service life of the recording head you use,
However, it is an object of the present invention to provide an inkjet recording method that can significantly improve reliability and significantly lower the failure rate. Furthermore, another object of the present invention is to provide an inkjet recording method that guarantees high-quality recording over a long period of time using an ink that has excellent thermal dissolution stability over a long or short period of time. do. The present invention, which achieves such objects, is an inkjet recording method in which thermal energy is applied to ink to form ink droplets, and recording is performed using these ink droplets, the ink being an aqueous liquid composition containing a water-soluble dye. a) mixing the liquid composition with an adsorbent or ion exchange resin, stirring and then filtering; or b) passing the liquid composition through a column filled with an adsorbent or ion exchange resin. It is characterized by using a liquid composition prepared through any of the following purification processes. The recording liquid used in the present invention, that is, the ink, is prepared by adding appropriate solvents such as water and organic solvents, as well as additives such as surface tension modifiers and viscosity modifiers as necessary, in addition to dyes. It is obtained by removing free inorganic salts, m-phenylenediamine, etc. through a purification process. By the way, the content of water-soluble dyes (for example, direct dyes, acid dyes, basic dyes) used in the ink of the present invention is usually in the range of approximately 1 to 10% by weight based on the total weight of the ink. Ru. Furthermore, although the ink of the present invention has water as a main liquid medium component, not only water alone but also a mixture of water and various water-soluble organic solvents are preferably used. Examples of water-soluble organic solvents include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, etc.
4 Alkyl alcohols: Amides such as dimethylformamide and dimethylacetamide: Ketones or keto alcohols such as acetone and diacetone alcohol: Ethers such as tetrahydrofuran and dioxane: Polyalkylene glycols such as polyethylene glycol and polypropylene glycol : Alkylene glycols in which the alkylene group has 2 to 6 carbon atoms, such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6 hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol: Glycerin : Examples include lower alkyl ethers of polyhydric alcohols such as ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether, and triethylene glycol monomethyl (or ethyl) ether. 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. The content of the water-soluble organic solvent in the ink is generally in the range of 10 to 70% by weight based on the total weight of the ink. The water content at this time depends on the type of solvent component mentioned above,
Although it is determined within a wide range depending on the composition and desired properties of the ink, it is generally within a range of 20 to 70% by weight based on the total weight of the ink. In addition to the above components, various conventionally known additives may also be added. Examples include viscosity modifiers such as polyvinyl alcohol, cellulose, and water-soluble resins; various cationic, anionic, or nonionic surfactants; surface tension modifiers such as diethanolamine and triethanolamine; and PH modifiers using buffer solutions. be able to. In the present invention, the ink composition prepared from such components is further purified by various methods described below to reduce the concentration of inorganic salts and m-phenylenediamine in the ink to an extremely low range. suppress. In this purification process, in the present invention, the concentration of inorganic salts in the ink is approximately 0.2% by weight or less, and m-
The concentration of phenylenediamine is approximately 1000 ppM or less. The ink purification method adopted in the present invention includes: a. Mixing an adsorbent (activated carbon, zeolite, diatomaceous earth, etc.) with a liquid composition (which may be ink) containing a dye, stirring, and then adding the adsorbent to the dye. (b) A method of passing at least a dye (which may be an ink) through a column filled with an adsorbent. (Among the above adsorbents, activated carbon is particularly preferred. 〉 c A method of passing a liquid composition (which may be an ink) containing a dye through an ion exchange resin (cation exchange resin, anion exchange resin), d A method of passing an ion exchange resin containing at least a dye (an ink). ) and then stirring, and then separating the ion exchange resin. (For methods c and d, it is more effective to use a cation exchange resin and an anion exchange resin together.) It is. 〉 etc. Ink prepared in this way has excellent recording properties (signal response, droplet formation stability, ejection stability, long-term continuous recording performance, long-term continuous recording performance, and (Discharge stability) Storage stability, fixing property to recording material, light resistance, weather resistance, water resistance of recorded images, etc. are all well-balanced and excellent. EXAMPLES Hereinafter, the present invention will be specifically explained and its effects will be illustrated with reference to Examples. Example 1 _Two SiO layers (lower layer) were formed on an alumina substrate to a thickness of 5 μm by sputtering, then HfB ₂ was laminated to a thickness of 1000 Å as a heating resistance layer, and aluminum was laminated to a thickness of 3000 Å as an electrode, and then selective etching was performed. A heating resistor pattern of 50 μm x 200 μm was then formed. Next, _two layers of SiO are added by sputtering.
After forming an electrical/thermal converter on the substrate by laminating it as a protective layer (upper layer) to a thickness of 1 μm,
A glass plate with a 50 μm groove cut thereon was bonded so that the groove and the heating resistor matched. Subsequently, the end face of the orifice was polished so that the distance between the tip of the heating resistor and the orifice was 250 μm to prepare a recording head. Using this recording head, ink having the liquid composition shown below was ejected. All numerical values shown in the liquid composition below are parts by weight unless otherwise specified.

【table】

【table】

[Table] All of the above inks were used after passing through a membrane filter with a bore size of 1 μm. In this case, when the recording head was driven for 10 μsec by inputting a 40 V rectangular voltage pulse signal at a cycle of 200 μsec, inks A-2, B-2, C-
When inks No. 2, D-2, and E-2 were used, all had a lifespan sufficient to withstand continuous ink ejection for 160 hours or more. On the other hand, for comparison, among the above inks, A-1,
When B-1, C-1, D-1, and E-1 were used, ink stopped being ejected before 10 hours had passed in all cases. Furthermore, inks A-2, B-2, C-2, D-
2. Regarding E-2, the following items were checked and all the results were good. Long-term storage; ink is sealed in a glass container, -
Even after storage at 30°C and 60°C for 6 months, no precipitation of insoluble matter was observed, and there was no change in the physical properties or color tone of the ink. Ejection stability: Continuous ejection was performed for 24 hours in an atmosphere of room temperature, 5° C., and 40° C. Under all conditions, stable high-quality recording was possible from beginning to end. Ejection response: Intermittent ejection every 2 seconds and ejection after being left for 2 months were investigated, and in both cases stable and uniform recording was achieved without clogging at the orifice tip. Quality of ink dots: The ink dots placed on the paper had a high density and were clear. 3 for indoor light
After being exposed for a month, the rate of decrease in density was less than 1%, and when immersed in water for 1 minute, there was very little blurring of the image. Comparative example Ink A-1, B-1, C-1, D-1, E-
1 was used to examine the same items as above, but in both cases, insoluble matter precipitated within one month while the ink was being stored, and the recording head often became clogged during ejection and during storage. I woke up. Comparative Experiment The following ink was also prepared as a comparative ink.

【table】

It was used after filtration with the membrane filter shown in [Table]. )
Drive the recording head using the above ink.
A rectangular voltage pulse signal of 10 μsec and 40 V was input at a cycle of 200 μsec to evaluate the continuous ejection performance of the ink. As a result, A-3, B-3, C- of the above ink
No matter which one was used, ink stopped being ejected before 10 hours had elapsed.

[Brief explanation of the drawing]

FIG. 1a is a partial front view of an example of a liquid jet recording head for carrying out the present invention, viewed from the orifice side, and FIG. FIG. 3 is a partial cross-sectional view. In the figure, 105 is an orifice, and 107 is a heat acting part.

Claims (1)

[Scope of Claims] 1. An inkjet recording method in which thermal energy is applied to ink to form ink droplets and recording is performed using the ink droplets, the ink comprising an aqueous liquid composition containing a water-soluble dye; Either a. The liquid composition and the adsorbent or ion exchange resin are mixed, stirred, and then filtered, or b. The liquid composition is passed through a column filled with the adsorbent or ion exchange resin. An inkjet recording method characterized by using a liquid composition prepared through the above purification process.