JPH04218574A - Ink-jet recording method - Google Patents

Abstract

PURPOSE:To prolong the working life of a recording head and ensure the high- quality recording over a long period in an ink-jet recording process for recording with ink droplets ejected by the application of thermal energy. CONSTITUTION:Recording is performed with ink droplets formed by the application of thermal energy to an ink. The ink to be used in the above ink-jet recording method contains an aqueous liquid composition containing a water-soluble dye and purified to get an inorganic salt concentration of <=0.2wt.% and a m-phenylenediamine concentration of <=1,000ppm in the composition either by (a) mixing the liquid composition with an adsorbent or an ion exchange resin and filtering the mixture or (b) passing the liquid composition through a column packed with an adsorbent or an ion exchange resin.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording method for recording by ejecting ink from an orifice using thermal energy.

0002

2. Description of the Related Art 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 is capable of high-speed recording and can perform recording without the need for special processing of fixing on so-called plain paper, is extremely popular. It is considered to be a useful recording method, and various methods have been proposed and devices to realize it have been devised, some have been improved and commercialized, and efforts are still being made to put it into practical use. Some are still continuing.

Among them, for example, Japanese Patent Application Laid-Open No. 54-51837
The liquid jet recording method described in DOLS No. 2843064 is based on the fact that the driving force for ejecting ink droplets is obtained by applying thermal energy, which is the energy for forming ink droplets, to the ink. However, it has different characteristics from other liquid jet recording methods.

That is, in the recording method disclosed in the above-mentioned publication, the ink undergoes a state change accompanied by a sharp increase in volume under the action of thermal energy, and the acting force based on the state change causes the recording head to Ink droplets are ejected from the orifice at the tip of the section, fly, and adhere to the recording member to perform recording.

[0006] In order to record high-resolution, high-quality images at higher speed and for a longer period 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. It is necessary to improve

Factors that determine the service life of a recording head applied to the above-mentioned recording method include the life of the electric/thermal converter included, as well as the accumulation of solid matter on the surface of the converter. can be given. That is, the recording head applied to the above recording method has a structure as shown in FIGS. 1 and 2, for example. In the figure, an electric/thermal converter 102 is connected to a liquid introduced from an arrow A through a heat action surface 109 as a thermal energy action surface in a heat action section 107 that is a droplet formation energy action section. are in contact. 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.

[0008] Therefore, depending 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 to prevent the heating resistor layer 111 from being exposed to the ink or thermal radiation. In order to protect the head from oxidation, an upper layer 112 is formed on the heat generating resistor layer 111 in the heat generating section 108 during head fabrication.

[0009] The principle of ink droplet formation in the recording method using such a recording head is that, as described above, when electricity is turned on to the electric/thermal converter, the ink droplet is subjected to the action of thermal energy, which is the energy for forming the droplet. In addition, the state of the ink in the heat acting section 107 changes with a rapid increase in volume, that is, the ink in the heat acting section 10
The ink at 7 reaches a vaporized state within a very instant of about μsec or less, and bubbles are generated and grow instantaneously in the heat acting part 107, causing the heat acting part 107 and the orifice 105 to become vaporized. The ink existing between the two is ejected as droplets.

[0010] As the ink is exposed to high heat during the repeated generation and disappearance of bubbles, chemical changes are likely to occur in thermally unstable ink, resulting in the formation and formation of insoluble matter on the surface of the heat-acting part. Deposition may occur, and 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.

[0011] By the way, as an example of the general basic composition of an inkjet recording ink, there is one in which the main components are a water-soluble dye, water as a solvent for the dye, and glycols as an anti-drying agent. be able to. 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 have
Contains m-phenylenediamine, which is one of the raw materials for dye synthesis, and inorganic salts such as sodium chloride and sodium sulfate, which are by-products during dye synthesis or are added as salting out agents, diluents, or leveling agents. It is.

Conventionally, when inks were prepared using dyes containing such impurities, the following problems often occurred.

That is, many of the above-mentioned impurities reduce the dye dissolution stability in the ink, causing aggregation and precipitation of the dye, and causing clogging of the fine orifice of an inkjet device.

Furthermore, according to the findings of the present inventors, inorganic salts and m-phenylenediamine reduce the thermal stability (that is, the dissolution stability at high temperatures) of the ink.

Therefore, in the conventional inkjet recording method, especially in the method of generating ink droplets using thermal energy as described above, the ink is heated, so the heat acting part in the inkjet recording head is heated. Insoluble matters from the ink were deposited on the surface, often impairing the ink ejection function of the head.

[0017]

[Problems to be Solved by the Invention] The present invention has been made in view of the above, and it is possible to significantly extend the service life of the recording head used, significantly improve reliability, and significantly reduce failure rate. The purpose of this invention is to provide an inkjet recording method that can reduce the amount of water used.

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 long-term or short-term thermal dissolution stability. The purpose of

[0019]

[Means for Solving the Problems] The present invention, which achieves the above objects, provides an inkjet recording method in which thermal energy is applied to ink to form ink droplets, and recording is performed using these ink droplets. includes an aqueous liquid composition containing a water-soluble dye, and the inorganic salt concentration in the composition is 0.
．． 2% by weight or less, the concentration of m-phenylenediamine is 10
00ppm or less, a. Mixing the liquid composition and an adsorbent or ion exchange resin, stirring, and then filtering; or b. This is an inkjet recording method characterized by using a liquid composition prepared through a purification process in which the composition is passed through a column filled with an adsorbent or an ion exchange resin.

The recording liquid used in the present invention, that is, the ink, contains, in addition to the dye, a suitable solvent such as water and an organic solvent, and if necessary, additives such as a surface tension modifier and a viscosity modifier. It is obtained by preparing it and removing free inorganic salts, m-phenylenediamine, etc. through a purification process.

By the way, the content of the water-soluble dye (for example, direct dye, acid dye, basic dye) used in the ink of the present invention is usually about 1 to 1% by weight based on the total weight of the ink.
It is said to be in the range of 10%.

The ink of the present invention has water as a main liquid medium component, but not only water alone but also preferably a mixture of water and various water-soluble 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. Amides such as dimethylformamide and dimethylacetamide: Ketones or ketone alcohols such as acetone and diacetone alcohol: Ethers such as tetrahydrofuran and dioxane: Polyalkylene glycols such as polyethylene glycol and polypropylene glycol: Ethylene glycol, Alkylene glycols in which the alkylene group has 2 to 6 carbon atoms, such as propylene glycol, butylene glycol, triethylene glycol, 1, 2, 6 hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol: Glycerin: Ethylene glycol methyl Ether, diethylene glycol methyl (
or lower alkyl ethers of polyhydric alcohols such as 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 10 to 70% by weight based on the total weight of the ink.
The range of

The water content at this time is determined within a wide range depending on the type of solvent component, its composition, and the desired properties of the ink, but it is generally expressed as a percentage by weight based on the total weight of the ink. It is said to be within the range of 20 to 70%.

In addition to the above components, various conventionally known additives may also be added.

For example, 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; pH adjustment using buffer solutions; Agents, etc. can be mentioned.

[0028] In the present invention, the ink composition prepared from such components is further purified by various methods described below, so that the concentration of inorganic salts and m-phenylenediamine in the ink is extremely low. Keep it within range.

In this purification process, in the present invention, the inorganic salt concentration in the ink is approximately 0.2% by weight or less, and m-
The concentration of phenylenediamine is approximately 1000 ppm or less.

[0030] The ink purification method employed in the present invention includes: a. Mixing an adsorbent (activated carbon, zeolite, diatomaceous earth, etc.) with a liquid composition (which may be an ink) containing a dye, and then stirring; , a method of filtering out the adsorbent, b. a method of passing a liquid composition (which may be an ink) containing a dye through a column filled with an adsorbent; This is particularly suitable. 〉 c. A method of passing a dye-containing liquid composition (or ink) through an ion exchange resin (cation exchange resin, anion exchange resin); d. A method of passing an ion exchange resin into a dye-containing liquid composition. A method in which the ion exchange resin is separated by filtration after mixing with the composition (which may also be an ink) and stirring. It is more effective to use them together. 〉 etc.

The ink prepared in this manner has not only thermal stability but also recording properties (signal response, liquid formation stability, ejection stability, long-term continuous recording, long-term Ejection stability after stopping recording) The storage stability, fixing property to the recording material, and the light resistance, weather resistance, and water resistance of the recorded image are all well-balanced and excellent.

[0032] Hereinafter, the present invention will be specifically explained and its effects will be illustrated based on Examples.

[0033]

[Example] Example 1 A SiO2 layer (lower layer) was formed on an alumina substrate by sputtering to a thickness of 5 μm, and then Hf was formed as a heating resistance layer.
B2 with a thickness of 1000 Å and aluminum as an electrode with a thickness of 30
After laminating to a thickness of 00 Å, selective etching is performed to form a layer of 50 μm.
A heating resistor pattern of x200 μm was formed. Next, S
After laminating an iO2 layer as a protective layer (upper layer) to a thickness of 1 μm by sputtering to form an electrical/thermal converter on the substrate, a glass plate with a groove of 50 μm wide x 50 μm deep was placed between the groove and the heating resistor. They were joined so that they 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, thereby producing a recording head. Using this recording head, ink having the liquid composition shown below was ejected.

[0034] All numerical values shown in the liquid composition below are parts by weight unless otherwise specified.

[0035]

[Table 1]

[0036]

[Table 2]

[0037] All of the above inks have a pore size of 1.
It was used after filtration with a μm membrane filter.

In this case, the recording head is driven for 10 μsec.
c. When a 40 V rectangular voltage pulse signal was input at a cycle of 200 μsec, inks A-2, B-2,
When C-2, D-, 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, B-1, C-1, D-1, and E-1, ink stopped being ejected before 10 hours had passed in all cases.

Furthermore, inks A-2, B-2, C-2, D
- After checking the following items regarding E-2,
The results were good in all cases.

Long-term storage: Even after the ink was sealed in a glass container and stored 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 2 months of standing were investigated, and in both cases, stable and uniform recording was achieved without clogging at the tip of the orifice.

Quality of ink dots: The ink dots printed on the paper had a high density and were clear. After 3 months of exposure to room light, the density reduction rate was less than 1%, and when immersed in water for 1 minute, there was very little blurring of the image.

Comparative Example Inks A-1, B-1, C-1, D-1, and E-1 were used to study the same items as above, but in each case, the ink was stored during storage. Insoluble matter precipitates within one month,
In addition, the recording head often became clogged during ejection and during storage.

[Brief explanation of the drawing]

[Fig. 1] A partial front view of an example of a liquid jet recording head for carrying out the present invention from the orifice side.

[Figure 2] A cutaway partial view when cutting along the dashed-dotted line XY in Figure 1(a)

[Explanation of symbols]

105 Orifice 107 Heat action part

Claims (1)

[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; a. Mixing the liquid composition and an adsorbent or ion exchange resin, stirring, and then filtering; or b. An inkjet recording method characterized by using a liquid composition prepared through a purification process in which the composition is passed through a column filled with an adsorbent or an ion exchange resin.