JPH0341507B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording liquid suitable for use in an inkjet system in which recording is performed by ejecting droplets from an orifice of a writing instrument or a recording head, particularly an inkjet system that utilizes thermal energy. BACKGROUND ART Writing instruments (fountain pens, felt pens, etc.) for recording on recording materials such as paper have traditionally used inks prepared by dissolving various dyes in water or other organic solvents. Furthermore, in the so-called inkjet method, in which recording is performed by discharging the liquid in the recording head using vibrations caused by a piezo vibrator or electrostatic attraction caused by the application of high voltage, various dyes are dissolved in water or organic solvents. It is known to use ink. However, compared to ink for general stationery, ink for ink jets is required to meet more stringent conditions in many characteristics. The inkjet recording method generates little noise and can perform high-speed recording or color recording on plain paper without requiring any special fixing treatment, and various types of inkjet recording methods are being actively researched. In this type of recording method, the ink used must have physical properties such as viscosity and surface tension within appropriate ranges, and must have high dissolution stability and not clog the fine orifice. , it is required to provide a recorded image with a sufficiently high density, and that physical property values do not change or solid content does not precipitate during storage. In addition to the above characteristics, it also has the ability to record without being restricted by the type of recording material, has a high fixing speed, and has excellent water resistance, solvent resistance (especially alcohol resistance, light resistance, and abrasion resistance). In addition, properties such as providing images with excellent resolution are also required. Among the inkjet recording methods, for example,
The method disclosed in No. 54-51837 differs greatly from other methods in that thermal energy is applied to obtain the motive force for ejecting droplets. That is, in this method, thermal energy is generated in the recording head section in response to a supplied recording signal, and bubbles are instantaneously generated, grown, and disappeared in the recording liquid that is affected by the thermal energy. Recording is performed by ejecting droplets from an orifice at the tip of the recording head due to changes in the pressure energy of the recording liquid. This recording method is not only extremely effective for so-called on-demand recording, but also has a high-density multi-orifice structure in the recording head and can easily realize full-line recording operations, making it possible to produce high-resolution images. It has the advantage that it can be obtained at high speed. However, in this recording method, thermal energy is directly applied to the recording liquid, and the temperature instantaneously reaches over 250°C, especially in the bubble generating area. Therefore, in order to satisfy continuous recording performance over a long period of time or ejection stability after a long period of cessation of recording, the characteristics of the recording liquid must include the characteristics of ink for general ink jets, especially those with thermal dissolution stability. Other properties are also required, such as high performance, no clogging of orifices, and no change in ink color due to heat. but,
A recording liquid that satisfies all of these characteristics has not been known so far. An object of the present invention is to provide a recording liquid for writing instruments such as felt pens and for inkjet recording. Another object of the present invention is to provide a recording liquid for inkjet recording that uses thermal energy, which extends the life of a recording head and has high recording stability over a long period of time, and to provide an inkjet recording method using the recording liquid. It is about providing. The above and other objects are achieved by the following invention. That is, the present invention provides the following general formula This is a recording liquid characterized by containing a compound represented by: However, in the formula, Q represents a 1,4-naphthylene group substituted with any substituent or not, and naphthalene rings A and B may be substituted with any substituent, but at least one of them is an OH group,
SO ₃ represents a naphthalene ring substituted with at least one substituent of M group, COOM group and NRR' group, where M represents a base selected from alkali metals, ammonium and amines, R and
R' each independently represents hydrogen, an optionally substituted alkyl group, or a phenyl group. Further, the inkjet recording method of the present invention is an inkjet recording method in which recording is performed by applying thermal energy to a recording liquid and ejecting it as droplets from an orifice, in which the recording liquid contains a compound represented by the above general formula. It is characterized by containing. Among the compounds represented by the above general formula, preferred compounds have at least one OH group in the molecule,
It has SO ₃ M group, COOM group or NH ₂ group. In addition, Q is a halogen atom, OH
group, _SO3M group, COOM group, _NH2 group, _NO2 group, substituted or unsubstituted with an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, 1,4- Naphthylene group is preferred. Preferred substituents for naphthalene rings A and B include halogen atom, OH group, SO ₃ M group, COOM
group, NRR' group, NO ₂ group, alkyl group having 1 to 4 carbon atoms, and alkoxy group having 1 to 4 carbon atoms. Furthermore, R and R' are each independently preferably hydrogen, an alkyl group having 1 to 4 carbon atoms, or a phenyl or benzyl group which may have a substituent. More preferred compounds are those in which naphthalene rings A and B both have an OH group at the 2-position and/or an SO ₃ M group or an NRR' group at an unrestricted position. The compound (dye) of the general formula contained in the recording liquid of the present invention generally has a solubility of 10% by weight or more in the recording liquid medium, and has a low temperature (approximately -30°C).
It also has high dissolution stability. Furthermore, since this compound has an azo bond (-N=N-) in its molecule, the recording liquid instantly reaches 250
Even if the compound decomposes when exposed to high temperatures exceeding .degree. C., it is presumed that cleavage occurs mainly at the azo bond. Even if decomposition occurs, the decomposition products themselves from the compound are relatively stable, and many of them have highly hydrophilic groups such as SO ₃ M groups or OH groups. It still has high solubility in recording liquid. Therefore, stable recording is possible even during long-term continuous recording without forming deposits inside the recording head. Of course, other properties required of dyes for writing instruments or inkjet inks, such as weather resistance, ozone resistance, water resistance of printed matter, alcohol resistance, and even toxicity, are also sufficient. Specific examples of the compound of the general formula contained in the recording liquid of the present invention include dyes having the following chemical structures. More specifically, the bases that combine with the sulfonic acid groups of these compounds to form sulfonic acid groups include:
Alkali metal cations such as Na ⁺ , K ⁺ , Li ⁺ , Ca ^{+ ,} quaternary ammonium cations such as NH ₄ ⁺ , NH(C ₂ H ₄ OH) ₃ ⁺ and amines such as N(C ₂ H ₅ ) ₃ There are many types. In the recording liquid of the present invention, these dyes are usually 0.5 to 20% by weight, preferably 0.5% by weight, based on the recording liquid.
It is used at a concentration of ~15% by weight, more preferably 1-10% by weight. Of course, these dyes can be used alone or in combination of two or more, or in combination with various dyes such as other direct dyes and acid dyes, using the dye as an essential component. As a liquid medium component for composing the recording liquid of the present invention, water or a mixture of water and an aqueous solution of various organic solvents is used. Examples of water-soluble organic solvents include alkyl alcohols having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, and isobutyl alcohol. Alcohols; Amides such as dimethylformamide and dimethylacetamide; Ketones or ketone alcohols such as acetone and diacetone alcohol; Ethers such as tetrahydrofuran and dioxane; N-
Methyl-2-pyrrolidone, 1,3-dimethyl-2
-Nitrogen-containing heterocyclic ketones such as imidazolidinone; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,
Alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms, such as 2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol; glycerin; ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol; Examples include lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl (or ethyl) ether. Among these many water-soluble organic solvents, diethylene glycol of polyhydric alcohol, triethylene glycol monomethyl (or ethyl) ether of lower alkyl ether of polyhydric alcohol, etc.
This is preferable. The content of the water-soluble organic solvent in the recording liquid is generally 5% by weight based on the total weight of the recording liquid.
~95%, preferably 10-80%, more preferably 20
It is considered to be within the range of ~50%. The recording liquid of the present invention prepared from such components can be used as a recording liquid for writing instruments or a recording liquid for so-called inkjet recording, and has excellent recording properties (signal response, droplet formation stability, ejection stability, etc.). long-term continuous recording performance, ejection stability after long-term recording cessation) storage stability, dissolution stability of the recording agent, fixation to the recording material, or light resistance, weather resistance, water resistance, and resistance of the recorded image. The alcohol content is well-balanced and excellent. In order to further improve such properties, various conventionally known additives may be further added and contained. Such additives include, for example, viscosity modifiers such as polyvinyl alcohol, celluloses, and water-soluble resins; various cationic, anionic, or nonionic surfactants; surface tension modifiers such as diethanolamine and triethanolamine; and buffers. Examples include PH adjusting agents using agents. In order to prepare a recording liquid used in a type of recording method in which the recording liquid is charged, a resistivity adjuster such as inorganic salts such as lithium chloride, ammonium chloride, and sodium chloride is used. Further, urea and thiourea are preferably used as water retention improvers at the tip of the discharge orifice. Note that in the case of a type that discharges recording liquid by the action of thermal energy, thermal physical property values (for example, specific heat, coefficient of thermal expansion, thermal conductivity, etc.) may be adjusted. When the recording liquid of the present invention is used as a so-called recording liquid for writing instruments, it is necessary to adjust the physical property values in consideration of viscosity, compatibility with recording members made of various materials, etc. The invention will be explained in more detail in the following examples. Example 1 A recording head for ink jet recording in which ink is ejected by the action of thermal energy was prepared as follows. First, a SiO ₂ layer (lower layer) was formed on an alumina substrate to a thickness of 5 μm by sputtering, and then HfB ₂ was formed as a heating resistance layer to a thickness of 1000 Å.
Furthermore, after laminating aluminum as an electrode to a thickness of 3000 Å, selective etching was performed to form a layer of 50 μm x 200 μm.
A heating resistor pattern was formed. Next, _two layers of SiO were laminated as a protective layer (upper layer) to a thickness of 3500 Å by sputtering to form an electric/thermal converter on the substrate, and then a glass plate with grooves of 50 μm width x 50 μm depth was cut into the grooves. They were joined so that the heating resistors 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. On the other hand, a recording liquid was prepared using the dye having the aforementioned chemical structural formula No. 1 according to the following formulation. Dye with structural formula No. 1 3 parts by weight diethylene glycol 25 〃 N-methyl-2-pyrrolidone 20 〃 Water 52 〃 The above ingredients were thoroughly mixed and dissolved in a container, and filtered under pressure using a Teflon filter with a pore size of 1μ. After that, it was degassed using a vacuum pump to obtain a recording liquid. This recording liquid was supplied to the recording head described above, and a continuous printing test was conducted. To the recording head: 10μsec,
A rectangular voltage pulse printing signal of 40 V was continuously applied at a period of 500 μsec. As a result, the recording liquid was sufficiently durable for continuous recording for 150 hours. Example 2 ~ A recording liquid was prepared in the same manner as in Example 1, except that the type of dye and the amount of dye blended were changed. A 150-hour continuous printing test similar to that in Example 1 was conducted using these recording liquids. However, the print signal
It was added at a period of 350μsec. Table 1 shows the durability times in these tests. The durability time was defined as the time when the ink flight became unstable and recording in accordance with the pulse signal began to become impossible. 【table】

Claims (1)

[Claims] 1. The following general formula A recording liquid characterized by containing a compound represented by: However, in the formula, Q represents a 1,4-naphthylene group substituted with any substituent or not, and naphthalene rings A and B may be substituted with any substituent, but at least one of them is an OH group,
SO ₃ represents a naphthalene ring substituted with at least one substituent of M group, COOM group and NRR' group, where M represents a base selected from alkali metals, ammonium and amines, R and
R' each independently represents hydrogen, an optionally substituted alkyl group, or a phenyl group. 2. An inkjet recording method in which recording is performed by applying thermal energy to a recording liquid and ejecting it as droplets from an orifice, wherein the recording liquid contains a compound represented by the following general formula. Method. However, in the formula, Q represents a 1,4-naphthylene group substituted with any substituent or not, and naphthalene rings A and B may be substituted with any substituent, but at least one of them is an OH group,
SO ₃ represents a naphthalene ring substituted with at least one substituent of M group, COOM group and NRR' group, where M represents a base selected from alkali metals, ammonium and amines, R and
R' each independently represents hydrogen, an optionally substituted alkyl group, or a phenyl group.