JPS5811167A - Liquid-injection recording method - Google Patents

Abstract

PURPOSE:To improve the performance of discharge, and enable stable recording for a prolonged term by making unnecessary bubbles generated contain into liquid drops, discharging them and removing them from a flow path in the titled recording system which ejects a recording liquid as the liquid drops by utilizing thermal energy. CONSTITUTION:Pulse voltage is applied between electrodes 113, 114, a resistance layer 111 positioned between the electrodes is heat-generated and the recording liquid of a thermal operating section 107 on a thermal operating surface 109 is evaporated, the liquid drops of the recording liquid are injected from an orifice 105 by a pressure change generated at that time, and desired characters and symbols are recorded. Bubbles generated per unit pulse are all made contain into the liquid drops and discharged from the orifice 105 together with the liquid drops by making pulse frequency fb approximately (fr)<2>/680 (where fr is the response frequency of the orifice) and the pulse voltage approximately 1.02- 1.3Vth (where Vth is the minimum voltage capable of discharging the liquid drops) in the conditions of discharge and drive in said system.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a so-called liquid jet recording method in which liquid droplets are ejected and jetted, which is suitable for use in devices such as the above. Recently, it has been attracting attention because of its extremely small size. Among these, the so-called ink shot recording method, which allows high-speed recording and can record on plain paper without the need for special fixing processing, is an extremely powerful recording method, and various methods have been used up until now. Some have been devised and improved, and some have been commercialized, while others are still being worked on to put them into practical use. There is a so-called electric field control method in which droplets of recording liquid are electrostatically generated from an ejection orifice by applying an electric field. Another method is to generate droplets by applying continuous imaging to the recording liquid, control the charging of the droplets according to external signals, and record by flying between deflection electrodes where an electric field is uniformly applied. There is a charge amount control method. Another method is a new control method that controls the atomization state of droplets by modulating the electric field strength applied between the nozzle and the charging electrode according to the recording signal.Furthermore, according to an external signal, There is also a so-called on-demand piezo vibration method in which mechanical vibrations of a piezo vibration element are applied to the recording liquid to generate droplets.The present invention has been developed to create a completely new recording liquid that is fundamentally different from conventional methods. A method and apparatus for generating droplets were published in Japanese Patent Application Laid-Open No. 1983
-59936.

To briefly describe this method, energy generated by a thermal energy generating means (for example, a heating resistor) is applied to the recording liquid existing in the liquid chamber of the recording head, and the thermal energy causes the recording liquid to change its state (change in volume). The resulting pressure change is used to eject the recording liquid from the orifice, causing it to fly as droplets. It is simple and can be easily miniaturized by microfabrication, and its structural simplicity makes it extremely easy to add additional nozzles.Additionally, in the case of multi-orifice configuration, the ejection of the recording head array of orifices
) The structure can be arbitrarily designed as desired, and therefore, the recording head can be made into a bar shape very easily. These various types of recording heads are capable of high speed recording. Alternatively, when continuous recording is performed for a long time, the ejection response, ejection efficiency, ejection stability, etc. of the recording liquid may deteriorate. The cause of this is that the recording liquid generates bubbles in the liquid chamber of the recording head, and the bubbles obstruct the flow of the recording liquid near the fine ejection orifice, or that droplets are ejected by an ejection energy generating means such as a heating resistor. The motive force is absorbed by the bubbles, causing problems such as a decrease in responsiveness and an inability to stably eject droplets in response to a signal. The reason why bubbles are generated, which has such an adverse effect, is that since the recording liquid is ejected by the action of thermal energy, the driving force for ejecting droplets is essentially to change the shape of the recording liquid (in particular, the formation of bubbles due to thermal energy). This is because we are seeking for Therefore, unnecessary air bubbles are likely to be generated, and this tends to have a large influence on ejection response, ejection efficiency, ejection stability, and the like.

Once unnecessary air bubbles are generated using the mechanism described above,
In addition, dissolved gas in the recording liquid may promote the generation of bubbles that are necessary for cineration.

Conventionally, various methods have been adopted to remove unnecessary air bubbles generated in the recording liquid.Methods to reduce the amount of dissolved gas include, for example, the method of using an airtight storage tank, and the method of using an oxygen absorbent in the recording liquid. Addition method: A method is to provide a flow path for removing air bubbles that communicates with the liquid chamber above the liquid chamber of the recording head, and to naturally collect the air bubbles in the upper flow path due to the buoyancy of the air bubbles. For example, even if the recording liquid is stored in a storage tank made of airtight material, after a certain period of time, the airtightness may not be achieved. These include the fact that gas (air) permeates through the material and reaches almost the dissolved saturation level, and adding an oxygen absorber to the recording liquid may have an adverse effect on the physical properties of the liquid.In addition, the effect of thermal energy In the case of a recording head that ejects a recording liquid by a method, it is advantageous to cause a rapid state change in order to improve responsiveness, ejection efficiency, etc., and to actively dissolve gas. The method of eliminating dissolved gas is not necessarily the best method.O Or, with the method of providing a flow path for collecting air bubbles above the liquid chamber of the recording head, the air bubbles move only by the buoyancy of the air bubbles, and the air bubbles are not captured. Since the collection channel is quite narrow, bubbles may not be removed smoothly. The present invention was developed in view of the above points, and is unnecessary for the formation of flying droplets. The liquid jet recording method of the present invention aims to improve the ejection stability, ejection responsiveness, and ejection efficiency by removing air bubbles in the recording liquid from the liquid flow path at the same time as the liquid is ejected. , has an orifice provided for discharging liquid to form flying droplets, and a heat-acting section that communicates with the orifice and is a part on which thermal energy for discharging the liquid acts on the liquid. In a liquid jet recording method using a recording head equipped with a liquid ejecting section and an electrothermal converter as a means for generating thermal energy, a certain amount of air bubbles from the orifice is secured to contain unnecessary air bubbles. By repeating the formation of flying droplets by ejecting different liquids, unnecessary air bubbles are removed from the inside of the liquid ejecting part.

FIG. 1(a) is a partial front view of a liquid jet recording head to which the present invention is applied, seen from the orifice side, and FIG. 1(b) is a portion indicated by a dashed line XY in FIG. 1(a). FIG. 3 is a partial cross-sectional view when cut.

The recording head 1 shown in the figure has a predetermined number of grooves of a predetermined width and depth at a predetermined linear density on the surface of a substrate 3 on which an electrothermal transducer 2 is provided. It has a structure in which an orifice 5 and a liquid discharge part 6 are formed by joining so as to be covered with an attached plate 4. Although the recording head shown in the figure is shown as having a plurality of orifices 5, the present invention is of course limited to this. The liquid discharge section 6 has an orifice 5 at its end for discharging droplets, and thermal energy generated by the electrothermal converter 2 acts on the liquid to generate bubbles, which expand and contract in volume. It has a heat acting part 7 that causes a rapid state change.

The heat acting part 7 is located above the heat generating part 8 of the electrothermal converter 2, and has a heat acting surface 9 that contacts the liquid of the heat generating part 8 as its bottom surface.

The heat generating section 8 includes a lower layer 10 provided on the substrate 3 , a heat generating resistive layer 11 provided on the lower layer 10 , and an upper layer 12 provided on the heat generating resistive layer 11 . The heating resistor layer 11 is provided with electrodes 13 and 14 on its surface for supplying electricity to the layer 11 in order to generate heat. The electrode 13 is an electrode common to the heat generating section of each liquid discharging section, and the electrode 14 is a selection electrode for selectively generating heat in the heat generating section of each liquid discharging section. In the flow path? It is provided with a.

The upper layer 12 isolates the heating resistance layer 11 from the liquid in the liquid discharge part 6 in order to chemically and physically protect the heating resistance layer 11 from the liquid used, and also connects the electrode 1 through the liquid.
The heating resistor j-11 has a protective function of preventing a short circuit between 3 and 14.

The upper layer 12 has the above-mentioned functions, but
The heat generating resistive layer 11 may be designed as an electrothermal transducer having high liquid resistance and having a structure in which the electrodes 13 and 14 are in electrical contact with each other through the liquid.

The lower layer 10 mainly has a heat flow control function.

That is, when discharging droplets, even though the heat generated in the heat generating resistor layer 11 is conducted toward the substrate 3 side, the proportion of heat generated toward the heat acting section 7 side is increased as much as possible. After the liquid droplets are ejected and the power to the clogging heat generating resistor layer 11 is turned off, the heat in the heat acting part 7 and the heat generating part 8 is quickly released to the substrate 3 side and the liquid in the heat acting part 7 is turned off. and is provided for rapidly cooling the generated air bubbles.

In order to record the droplet ejection as described above, by inputting an electric signal to the electrothermal converter 2 in an ON-OFF operation, the liquid is vaporized on the heat action surface 9 and effective bubbles are formed. When this occurs, at the same time unnecessary bubbles are generated due to dissolved gas in the liquid, and these unnecessary fine bubbles are diffused into the liquid flow path of the liquid discharge section. These fine bubbles accumulate in the liquid flow path, causing instability in liquid discharge. Furthermore, if forced to do so, the discharge will stop.

Here, vb is the volume of the liquid in which minute bubbles that are generated per unit pulse of the signal input to the electrothermal converter 2 diffuse.
Then, as shown in FIG. 2, when the volume Vd of the liquid discharged from the orifice 5 is larger than vb, unnecessary bubbles will not accumulate in the liquid flow path upstream of the orifice 5. Therefore, if the drive conditions and head shape are sufficient to ensure this amount of ejection, stable and continuous ejection will be possible, and the print quality will be maintained even when continuous recording is performed for a long time. become.

The present invention will be specifically described below according to Example 12.

EXAMPLE A layer (lower layer) of Sin was formed on a silicon substrate to a thickness of 3 μm by snootering, and then 1 layer was formed as a heating resistor layer.
After laminating 1,000 layers of 1,000 layers of 1,000 layers of 1,000 layers of 1,000 layers of 1,000 layers of aluminum as electrodes, a heating resistor pattern was formed by five-selection etching. Next, the protective layer (top 7
After forming an electrothermal transducer on the substrate by laminating them as (m), a glass plate with a groove of 80 μm width x 80 μm depth 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 300 μm to create a record.

While supplying ink containing black dye and ethanol as main components to the heat acting section with a back pressure of 0.01 atm, a rectangular voltage pulse print signal is applied to the electrothermal transducer to record and evaluate an image. At this time, the driving conditions (voltage) that determine the ejection amount.

Figure 3 shows the relationship between the discharge amount and unnecessary bubbles when changing the frequency. FIG. 3(a) shows the relationship between voltage change and ejected liquid amount, and FIG. 3(b) shows the relationship between frequency change and ejected liquid amount.

Here, the discharged liquid amount is 0.21μjJ/ regardless of the driving conditions.
When the temperature was lower than pu I se (-wb), unnecessary air bubbles accumulated in the liquid flow path, making the liquid discharge unstable. The voltage Vs at this time is 1.0% of the voltage Vth at which liquid discharge can begin.
By applying a voltage of 0.5 times or more, sufficient ejection power can be obtained, and unnecessary bubbles do not accumulate in the liquid flow path, and liquid ejection can be performed stably for a long time. Also, the upper limit frequency fmax tends to correlate with the response frequency fr of the orifice s fb=f
``At r/6so or more, the ink supply could not be kept in time, unnecessary bubbles were formed in the liquid flow path, and the liquid ejection became unstable. (However, fr > IKH2) At lr or less, the amount of ejected liquid was constant. When the applied voltage was appropriate as described above, no bubbles were accumulated in the liquid flow path, stable liquid ejection was always obtained, and the best image quality was obtained.

Regarding the voltage, if the stain pressure is increased by the voltage value to obtain u+b, the amount of discharged liquid will be 4. The voltage increases until it reaches a voltage value of 1.2 times vth. After that, the increase in the amount of ejected liquid stopped, and the liquid ejected state and printing quality were both very good at this voltage value Vs, which reached the saturation value.

Here, it has the dimensions shown in Table 1, and has the dimensions shown in Fig. 1(a),
Various recording heads shown in (b) were created, and the presence or absence of unnecessary air bubbles in the liquid flow path and evaluation of recorded images were performed. Table 2.3
．． I got a result like this.

Therefore, regardless of the shape of the head, the ejection drive conditions are such that the frequency is f2r/680 or less, and the applied voltage is 1.07 to 1 of Vth.
．． By driving the head at 2x, unnecessary air bubbles in the liquid flow path are discharged to the outside of the flow path.Table 1 Table 2 Table 3

[Brief explanation of the drawing]

FIGS. 1(a) and 1(bl) are for explaining the structure of the recording head according to the present invention, FIG. 1(a) is a partial front view, and FIG. (→Dot-dash line XY
FIG. 2 is an explanatory diagram for explaining the present invention, and FIG. 3 fa) and FIG. 3(b) are explanatory diagrams for explaining the present invention, respectively. . DESCRIPTION OF SYMBOLS 1... Recording head, 2... Electrothermal transducer, 3... Substrate, 4... Grooved plate, 5... Orifice, 6. ...Liquid discharge part, 7--Heat action part, 9...Heat action surface procedural amendment (voluntary) May 25, 1980 1, Incident indication 1981 Patent application No. 108726 2,
Name of the invention: Liquid injection recording method 3; Relationship with the case of the person making the amendment Patent applicant: 3-30-2 Shimomaruko, Ota-ku, Tokyo Name (IOQ): Canon Co., Ltd. Representative: Ryu Kaku Sanbe 4; Agent: Residence Te146 Canon Co., Ltd. 3-30-2 Shimomaruko, Ota-ku, Tokyo (Telephone 75B-2111) 5, "Detailed Description of the Invention" column 6 of the specification to be amended, Contents of the amendment (1) of the specification. The entire text of page 16 has been amended as shown in the attached sheet. (2) Same page 14, line 9 71.07 - 1.2 times j to 71
．． 02 to 1.6 times." 7. A document containing the entire text of page 16 of the catalog specification of the attached documents - Here, the amount of liquid discharged is 0.21 μg/pu regardless of the driving conditions.
When the temperature drops below lsd(,-,Wb), unnecessary air bubbles accumulate in the liquid flow path, making the liquid discharge unstable. At this time, by applying a voltage Vs that is 1.02 times or more of the voltage vth that can start discharging the liquid, sufficient ejection power can be obtained, and unnecessary bubbles will not accumulate in the liquid flow path and the liquid will not be ejected. It was achieved stably for a long time. Furthermore, if the drive is performed at a frequency higher than fb shown in Fig. 5, the ink supply will not be in time;
Unnecessary bubbles accumulated in the liquid flow path, making the liquid discharge unstable. From our many experimental results, f r (Hz) > 1
000 (Hz), the distance between fb and fr is fl)'' (fr)/680 (1, however, in this formula, fb and fr have no dimensions, and the numerical value when expressed in H2 units is It has been found as an experimental fact that the following relationship holds true: When fb is less than fr, the amount of liquid discharged is constant, and if the applied voltage is appropriate as described above, all (air bubbles) are removed in the liquid flow path. It was irresistible, stable liquid ejection was always obtained, and the image quality was the best.

Claims (1)

[Claims] A liquid having an orifice provided for ejecting liquid to form flying droplets, and a heat-acting part that communicates with the orifice and is a part where thermal energy acts on the liquid in order to eject the liquid. In a liquid jet recording method using a recording head equipped with a discharge part and an electrothermal converter as a means for generating thermal energy, a certain amount of air bubbles such as the above-mentioned Oriswiss is secured to contain the necessary air bubbles. A liquid jet recording method characterized by repeatedly forming flying droplets by ejecting different amounts of liquid, removing necessary air bubbles from within a liquid ejecting part, and recording with the droplets.