JPS6218352B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a non-impact recording method, and more particularly to a so-called inkjet recording method suitable for use in devices such as copying machines, facsimile machines, word processors, printers, and plotters that perform recording by jetting a recording liquid. Non-impact recording methods have recently attracted attention because the noise generated during recording is so small that it can be ignored. Among these, the so-called inkjet recording method is an extremely powerful recording method that enables high-speed recording and can record on so-called plain paper without the need for special fixing treatment, and various methods have been devised so far. Some have been improved and commercialized, while others are still being worked on to put them into practical use. This type of recording method performs recording by ejecting so-called ink from a fine-diameter ejection orifice provided in a recording head.
Such recording liquids are usually formulated with a "recording agent" consisting of various dyes and pigments and a "liquid medium" for dissolving or dispersing them, and various additives are added and contained as necessary. has been done. Alternatively, if a recording member such as paper is specially subjected to a coloring process, a recording liquid consisting only of a liquid medium may be used. There are several types of methods for ejecting recording liquid from an ejection orifice. For example, an electric field is created between the recording liquid and an electrode placed in front of the ejection orifice, and recording is performed electrostatically from the ejection orifice. There is a so-called electric field control method that generates liquid droplets. Another method is to apply continuous vibration to the recording liquid to generate droplets, control the charging of the droplets according to an external signal, and make them fly between deflection electrodes where an electric field is uniformly applied to record. There is a charge amount control method that performs this. Another method is the so-called atomization control method, in which the atomization state of droplets is controlled by modulating the electric field intensity applied between the liquid chamber and the charging electrode in accordance with the recording signal. Furthermore, there is also a so-called on-demand piezo vibration method in which droplets are generated by applying mechanical vibration of a piezo vibration element to the recording liquid in accordance with an external signal. The applicant of the present invention has published a completely new method and device for generating recording liquid droplets, which is fundamentally different from the conventional methods, in Japanese Patent Application Laid-Open No. 52-118798 (Japanese Patent Application Laid-Open No. 54-59936).
and Japanese Patent Application No. 53-101189 (Japanese Patent Application No. 55-27282)
Posted at. In this method, thermal energy is applied to the recording liquid present in the liquid chamber of the recording head, and the thermal energy causes a thermal state change in the recording liquid (volume expansion, generation of bubbles, etc.), resulting in a pressure change. The recording liquid is ejected from an ejection orifice using the ejection orifice, and is caused to fly as droplets. The present inventors have conducted research and development with the aim of further improving the ejection response, ejection efficiency, ejection stability, and image quality of recorded images of the method of ejecting recording liquid by the action of thermal energy. The present invention was developed during this period. That is, FIG. 1 is a schematic diagram of an example of a recording head used in the above-mentioned recording method.
A pressure P is applied to the extent that the recording liquid 2 cannot be ejected as droplets if only this is done. Now, when the signal S is processed by the signal processing means 3 (for example, a pulse converter) and applied to the electrothermal converter 6 through the electrodes 4 and 5, the converter 6 generates heat in a pulsed manner. The resulting thermal energy is applied to the recording liquid 2. The recording liquid 2 subjected to the action of thermal energy undergoes a rapid thermal state change (volume expansion, generation of bubbles, etc.)
This causes a pressure change, and part of the recording liquid is ejected from the ejection orifice 8, forming a droplet 9.
and fly away. The electrothermal converter 6 and the electrodes 4 and 5 are usually coated with a layer of 1 μm in order to prevent oxidation, protect against mechanical shock, or prevent current leakage, considering high durability.
A protective layer 7 with a thickness of about m to 2 μm is provided, but the ejection response, ejection efficiency, and
In order to improve ejection stability, it is desirable to make the thickness of the protective layer 7 as small as possible. However, if the thickness of the protective layer 7 is made smaller than the above value, not only may oxidation occur on the surfaces of electrothermal converters, electrodes, etc., but in some cases, the current may penetrate through the fine pores of the protective layer 7. Leakage may also occur from cracks, etc. Recording liquids conventionally used in the inkjet recording field have electrical conductivity values of 10 ^- because the liquid medium is mainly water-based, or substances are added to adjust the physical properties of the liquid. Most of them are larger than ⁹ cm. Therefore, the thickness of the protective layer is 1μ.
If continuous recording is performed at a temperature below m, an electrolysis reaction will occur due to the current leak as described above, and decomposition products and bubbles generated by electrolysis will adhere to the liquid chamber or the vicinity of the discharge orifice, resulting in a decrease in discharge response. ,
This may lead to a decrease in discharge efficiency, discharge stability, etc.
This resulted in a decrease in image density and a change in color tone. The present invention has been made in view of the above points, and provides a recording method capable of high-speed recording. The main objects of the present invention are discharge response, discharge efficiency,
The object of the present invention is to provide a recording method in which characteristics such as ejection stability are significantly improved. Another object of the present invention is to provide a recording method that does not cause deterioration or decomposition of the recording liquid even during long-term recording and has excellent image density and color tone. The present invention, which achieves these objects, supplies a recording liquid having an electrical conductivity of less than 10 ^-12 /cm to a liquid chamber of a recording head, and a recording liquid having an electrical conductivity of 1 μm provided in the liquid chamber.
A part of the recording liquid is ejected from an ejection orifice communicating with the liquid chamber by applying a signal to an electrothermal converter having a protective layer with a thickness of less than m or without a protective layer to generate heat. , which is characterized by recording by flying droplets. In this way, when used in a recording method in which recording is performed by ejecting a recording liquid containing a liquid medium with an electrical conductivity of less than 10 ^-12 /cm from an ejection orifice and flying it as droplets, , an electrothermal converter can be provided to improve ejection response, ejection efficiency, and ejection stability during high-speed recording,
Also, even if continuous recording is performed, the components of the recording liquid may change or
Decomposition is less likely to occur and good images can be obtained. Examples of the recording agent components of the recording liquid used in the present invention include Eisenspiron Yellow 3RH, Eisenspiron Black BH, Orient Oil Yellow 3G, and Orient Oil Scarlet.
No. 308, Orient Oil Blue BO, Orient Oil Brown GR, Orient Oil Black HBB, Variable Asto Black No. 3804, Silado Oil Red 5BN, Arsol Fast Green B, Neoposan Yellow GG, Neoposan Red GE, Neoposan Blue FLE, A dye that is soluble in organic solvents, such as Neoposan Black RE, is preferable. Further, other fine materials such as inorganic pigments and organic pigments may also be used as appropriate. On the other hand, the liquid medium component may preferably have an electrical conductivity of 10 ^-12 /cm (25°C) or less, such as aliphatic hydrocarbons such as n-hexane, n-heptane, etc. , petroleum hydrocarbons such as petroleum ether and ligroin, aromatic hydrocarbons such as toluene, halogenated hydrocarbons such as carbon tetrachloride, ethyl ether, methyl phenyl ether, 1. Examples include ethers such as 4-dioxane. These materials may be mixed as necessary. Furthermore, it is desirable that the substance used for the liquid medium component be one that does not easily vaporize during recording pauses and clog the discharge orifice. The content of the above recording agent in the recording liquid is usually 0.5% to 30%, preferably 0.5% to 30% by weight.
It is preferably in the range of 20%, more preferably 1% to 15%. Furthermore, various additives such as viscosity modifiers, anti-drying agents, fixing agents, etc. may be added to the main components as required. When a recording liquid constructed in this way is used for recording in a device that generates droplets by the action of thermal energy, it is possible to realize the inherent characteristics of this type of device, that is, it is extremely simple in structure. Since microfabrication can be easily performed, the recording head itself can be made much smaller than before, and its simple structure and ease of processing make it extremely easy to create multi-orifices, which are essential for high-speed recording. What can be achieved,
Additionally, in multi-orifice configuration, the recording head has an array of ejection orifices.
Advantages such as the fact that the structure can be designed arbitrarily as desired and the recording head can be formed into a bar shape very easily are effectively utilized. In addition,
In particular, even if the thickness of the protective layer formed on the electrothermal converter, electrode, etc. is 1 μm or less, or even 0.5 μm or less, electrode oxidation is unlikely to occur, and electric current leakage No decomposition products are generated, and not only the ejection response, ejection efficiency, ejection stability, etc. during high-speed recording are improved, but also the density, color tone, etc. of the recorded image is difficult to change even during continuous recording. This allows good recording. EXAMPLE A multi-orifice recording head as shown in FIG. 2 was prepared and recording was performed. That is, as shown in FIG. 2, a grooved plate 10 is formed with a large number of grooves 11 forming liquid chambers.
(Made of glass plate, thickness 1.3mm, depth of groove 11 0.05mm, width
0.08mm, groove pitch 0.125mm). In addition, a SiO ₂ heat storage layer 14 (thickness 4 μm) is placed on the alumina substrate 13.
m), ZrB ₂ heating resistance layer 15, (width 0.09 mm, length
0.2mm, thickness 1000Å) aluminum electrode layer 16
(thickness 800 Å) and protective layer 17 of SiO ₂ (thickness 0.5 μ
m) are sequentially laminated and photo-etched to form an electrothermal transducer in a predetermined pattern, and the heating element substrate 1 is formed.
It was set as 2. Furthermore, the supply block 18, pipe 19, etc. are prepared, and the grooved plate 10 and the heating element substrate 12 are
It was integrated with the recording head to form a recording head. Next, the recording liquid shown in Table 2 was prepared based on the liquid medium exhibiting the electrical conductivity shown in Table 1, and the recording liquid was applied to the head at 10 KHZ, an applied pulse width of 10 μsec, and an applied voltage of 3.5 V.
Recording was performed under the following recording conditions. The electrical conductivity of recording liquids No. 1 to 10 are all
The value was smaller than 10 ^-12 /cm.

【table】

【table】 The experimental results of discharge are shown in Table 3.

【table】

[Table] As described above, the recording liquid containing a liquid medium having an electrical conductivity of 10 ⁻¹² ·cm ⁻¹ or less showed good results in the ejection experiment.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a recording head according to the present invention, and FIG. 2 is a diagram of one experimental embodiment of the recording head used in the recording method of the present invention. In the figure, 1...liquid chamber, 2...recording liquid, 3...
... Signal processing means, 4, 5 ... Electrode, 6 ... Electrothermal converter, 7, 17 ... Protective layer, 8 ... Discharge orifice, 9 ... Droplet, 10 ... Grooved plate, 1
1...Groove, 12...Heating element substrate, 13...Substrate,
14... Heat storage layer, 15... Heat generating resistor layer, 16...
...electrode layer, 18...supply block, 19...pipe.

Claims (1)

[Claims] 1. A recording liquid having an electrical conductivity of less than 10 ^-12 /cm is supplied to the liquid chamber of the recording head, and a protective layer is disposed in the liquid chamber and has a thickness of 1 μm or less, or there is no protective layer. A recording method characterized in that a part of the recording liquid is ejected from an ejection orifice communicating with the liquid chamber by applying a signal to an electrothermal transducer to generate heat, and the recording liquid is caused to fly as droplets to perform recording.