JPH021315A - Liquid jet recording head - Google Patents

Abstract

PURPOSE:To prevent clogging of an orifice by a method wherein a ratio of a surface area coming in contact with liquid of a member composing a liquid jet recording head to a liquid volume is taken as 0.50, and an elution amount of organic matter from the member into recording liquid is taken as 1.0 or under in absorbance. CONSTITUTION:Materials of an organic material member used for a babble jet head and recording liquid are so determined that an elution amount of this organic material member into the recording liquid meets the following conditions. That is, a liquid of which pH is made equal to that of the recording liquid by regulating pH of a liquid obtained by removing a dye component from the recording liquid is taken as the liquid to be checked. Further, a ratio of a surface area (cm<2>) coming in contact with the liquid of this member to a liquid volume (ml) is taken as 0.50, and the member is immersed into the liquid at 20 deg.C for 2,000h. An amount of eluted organic matter in the liquid after this immersion is taken as 1.0 or under in the maximum absorbance in a wavelength area of 190 to 700nm, and suitably as 0.5 or under. Consequently, clogging of an orifice in a bubble jet type ink jet recording head can be prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid ejecting recording head, more specifically, to a bubble jet type inkjet recording head, and is suitable for dissolving the recording liquid from the members constituting the recording head into the recording liquid. related to relationships.

Conventional non-impact recording methods have recently attracted attention because the noise generated during recording is so small that it can be ignored. Among them, high-speed recording is possible,
However, the so-called inkjet recording method, which allows recording on plain paper without the need for special fixing treatment, is an extremely powerful recording method, and various methods have been proposed, improved, and commercialized. Some have been developed, and efforts are still being made to put them into practical use.

In this type of inkjet recording method, recording is performed by causing droplets of a recording liquid called ink to fly and adhere to a recording member. There are several types of methods depending on the control method used to control the flight direction of the generated recording liquid droplets.

First, the first method is the one disclosed in USP 3060429 (Tele type method), in which droplets of recording liquid are generated by electrostatic attraction, and the generated droplets of recording liquid are used as a recording signal. Recording is performed by controlling the electric field in accordance with the temperature and selectively depositing recording liquid droplets on the recording member.

To explain this in more detail, an electric field is applied between the nozzle and the accelerating electrode to eject a negatively charged recording liquid droplet from the nozzle, and the ejected recording liquid droplet is converted into a recording signal. Accordingly, the droplets are flown between x and y deflection electrodes configured to be electrically controllable, and the droplets are selectively deposited on the recording member by changing the intensity of the electric field, thereby performing three-step recording.

The second method is 1 e.g. US P 3596275, U
The method disclosed in SI' 3298030 etc. (Sw
eat method) and 4r by continuous vibration generation method;
By generating droplets of recording liquid with a controlled amount of rTi and flying the generated droplets with a controlled charging area between deflection electrodes to which a --like electric field is applied, a recording member - Records are to be made every two days.

Specifically, the orifice (discharge port) of a nozzle, which is a part of the recording head to which the piezo vibrating element is attached.
'4'F configured so that the recording signal is applied before
Electrical electrodes are placed a predetermined distance apart, and an electric signal of a constant frequency is applied to the piezoelectric vibrating element to mechanically vibrate the piezoelectric vibrating element, thereby ejecting small droplets of recording liquid from the ejection opening. At this time, a charge is electrostatically induced in the recording liquid droplet discharged by the charging electrode, and the droplet is IF-electrified with an amount of charge corresponding to the recording signal. When a droplet of recording liquid with a controlled amount of charge flies between deflection electrodes to which a constant electric field is uniformly applied, it is deflected according to the amount of charge added, and the droplet carries the recording signal. Only the recording member 2 can be attached to the recording member 2.

The third method is, for example, the method disclosed in U.S. Pat. No. 3,416,153 (Llertz method), in which an electric field is applied between a nozzle and a link-shaped charged electrode, and small droplets of recording liquid are generated by a continuous vibration generation method. This is a method of converting and recording. That is, in this method, the atomization state of droplets is controlled by modulating the electric field intensity applied between the nozzle and the charging electrode in accordance with the recording signal, and the gradation of the recorded image is produced.

The fourth method is, for example, the method disclosed in US Pat. No. 3,747,120 (Stemme method), and this method is fundamentally different in principle from the above three methods.

That is, in all three methods, the droplets of recording liquid ejected from the nozzle are electrically controlled while they are in flight, and the droplets carrying the recording signal are selectively attached to the recording member. In contrast, this Stemme method
Recording is performed by ejecting a small amount of recording liquid from an ejection port in response to a recording signal.

In other words, the Stemme method applies an electrical recording signal to a piezo vibrating element attached to a recording head that has an ejection port for discharging recording liquid, and converts this electrical recording signal into mechanical vibration of the piezo vibrating element. In this method, recording is performed by ejecting small droplets of recording liquid from the ejection opening according to the mechanical vibrations and adhering them to the recording member.

These four conventional methods each have their own advantages, but there are also points that can be solved in the other method.

That is, in the first to third methods, the direct energy for generating the droplets of the recording liquid is electrical energy, and the deflection control of the droplets is also electric field control.

Therefore, although the first method is simple in structure, it requires a high voltage to generate droplets, and it is difficult to use a multi-nozzle recording head, making it unsuitable for high-speed recording.

The second method allows the recording head to have multiple nozzles and is suitable for high-speed recording, but it has a complicated structure, and the electrical control of the recording liquid droplets is sophisticated and difficult. - There are problems such as the tendency to generate dots.6 The third method has the advantage of being able to record images with excellent gradation by atomizing recording liquid droplets, but on the other hand, It is difficult to control, fog occurs in the recorded image, and it is difficult to use a multi-nozzle recording head.
There are various problems such as being unsuitable for high-speed recording.

The fourth method has relatively many advantages compared to the first to third methods. In other words, the configuration is simple, and since recording is performed by ejecting the recording liquid from the ejection opening of the nozzle on-demand, it is possible to reduce the number of small droplets that fly as in the first to third methods. Second, it is not necessary to collect droplets that are not needed to record an image, and unlike the first and second methods, there is no need to use a conductive recording liquid, and the material of the recording liquid is It has great advantages such as a high degree of freedom. On the other hand, it is difficult to make the recording head multi-nozzle because there are problems in processing the recording head, and it is extremely difficult to miniaturize the piezoelectric vibrating element having the desired resonance number. This method has drawbacks such as that it is not suitable for high-speed recording because the recording liquid droplets are ejected and ejected in flight using the mechanical energy of the mechanical vibration of the piezoelectric vibrating element.

Furthermore, Japanese Patent Application Laid-Open No. 48-9622 (the above USP:
1747120) discloses, as a modification, the use of thermal energy instead of the mechanical vibration energy produced by means such as the piezo vibrating element.

In other words, in Publication No. 1, a heating coil that directly heats the liquid is piezo-oscillated to generate steam that increases the pressure by 1! I! It is described that it is used as a pressure increasing means in place of the lJ element.

However, the above publication describes that the liquid ink in the bag-shaped ink chamber (liquid chamber), which has only one opening through which liquid ink can enter and exit, is directly heated by energizing a heating coil as a means for increasing the pressure by 1. It is only described that the liquid is vaporized, and there is no suggestion as to how to heat the liquid when continuously and repeatedly discharging the liquid. In addition, the heating coil is located at the deepest part of the bag-shaped liquid chamber far from the liquid ink supply path, which makes the head structure complicated and requires high-speed printing. It is not suitable for continuous repeated use.

Moreover, with the technical content described in the above-mentioned publication, it is not possible to quickly prepare for the next liquid discharge after discharging the liquid using the generated heat, which is important in practice.

In this way, the conventional method has a configuration that requires high-speed recording, multi-nozzle recording spatula, and satellite 1 to 1.
These methods have advantages and disadvantages in terms of the occurrence of blemishes and fogging of recorded images, and there is a restriction that they can only be applied to applications that take advantage of these advantages.

In addition, Japanese Patent Publication No. 59-43315 discloses that in bubble jet type inkjet 1 to recording devices, the amount of weight reduction of the part of the electrical/thermal converter in contact with the liquid (ink) in the heat acting part is 1/10 or less than that of aluminum. , it is disclosed that the life of the electric/thermal converter is extended.

FIG. 6 is a diagram for explaining an example of the liquid droplet jet recording head disclosed in the above-mentioned Japanese Patent Publication No. 59-43315, and FIG. 6(a) is a diagram as seen from the orifice side of the liquid jet recording head. The front partial view, Fig. 6(b), is the same as Fig. 6(a).
FIG. 2 is a partial cross-sectional view taken along a section indicated by a dashed line XX.

The recording head 1 shown in the figure has a predetermined number of grooves with a predetermined linear density and a predetermined depth 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 the grooved plate 4 so as to cover it. In the case of the recording head 1 shown in the figure, a plurality of orifices 5 (51, 5□, 5.
), but application to a single orifice recording head is also possible.

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 portion 7 is located at the second portion of the heat generating portion 8 of the electricity/thermal converter 2, and has a heat acting surface 9, which is a portion of the heat generating portion 8 that comes into contact with the liquid, as its bottom surface.

The heat generating section 8 is composed of a lower layer 10 provided on the substrate 3, a heat generating resistor layer 11 provided on the lower layer 10, and a two-part layer 12 provided on the heat generating resistor layer 17. has been done.

The heating resistance layer 11 is provided with 'IIi poles 13 and 14 on its surface for supplying current to the core layer 11 to generate heat. The electrode 13 has a t common to the heat generating section of each liquid discharge section.
The electrode 14 is a selective electrode for selectively generating heat in the heat generating section of each liquid discharge section, and is provided along the flow path of the liquid discharge section.

10) The f'J 12 is separated from the liquid in the liquid discharge part 6 and the heating resistance layer 11 in order to chemically and physically protect the heating resistance layer 11 from the liquid used, and also connects the electrode 13 and the liquid through the liquid. Heat generating resistor layer 1 that prevents short circuit between 14 and 14.
It has 1 protective function.

The lower layer 1o mainly has a heat flow-jt control function.

That is, when discharging a droplet, the proportion of heat generated by the heat generating resistor H1J11 being conducted to the heat acting part 7 side is as high as possible, rather than being conducted to the substrate 3 side, and after discharging the droplet. ,
In other words, after the power to the heating resistor layer 11 is turned off,
This is provided so that 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 and the generated bubbles are rapidly cooled.

The liquid jet recording head 1 described above is characterized in that the heat action surface 9, which is the part of the wall surface of the heat action section 7 that comes into contact with the liquid, is made of an aluminum plate with a purity of 99.9% as a test standard. The weight reduction amount ΔW (AQ) per unit area of the test surface in the heavy electricity reduction test is 1 mg/a
(When the weight decrease ΔW per unit area at the elapsed time t from the start of the test becomes ΔW (1/1 of A(1)
0 or less, which extends the service life and makes it possible to significantly increase the frequency of droplet formation for high-speed recording. Even if the level value becomes high, stable droplet discharge can be performed continuously for a long time.

On the other hand, the invention described in Japanese Patent Publication No. 59-43315 (1) discusses the amount of weight reduction from the viewpoint of the life of the electrothermal converter, but in reality, before destruction occurs,
An abnormality occurs in the ink, and satisfactory ejection performance cannot be obtained. Satisfactory discharge performance refers to discharge without clogging of the orifice and without bending in the jet direction.

In addition, in Japanese Patent Publication No. 59-43315 mentioned in -, the amount of weight reduction of the heat acting part is specified based on the weight reduction of aluminum, but in Bubble Dien 1-type inkjet 1-type recording devices, aluminum Structures in which aluminum comes into direct contact with ink are not normally used (because aluminum is quickly corroded by ink), and using such materials as a standard ignores reality. Although it is meaningful to discuss the amount of weight loss based on the materials actually used,
In Publication No. 15, the reason for selecting the material aluminum is ambiguous, and it must be said that its technical basis is weak.

Purpose The present invention was made in view of the above-mentioned circumstances.
In particular, this was done for the purpose of preventing clogging of the bubble diene 1-type liquid jet recording head.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention contains a recording liquid to be introduced, generates bubbles in the recording liquid by heat, and generates an action force as the volume of the bubbles increases. an orifice connected to the flow path for discharging the recording liquid as MM by the acting force;
In a liquid jet recording head that includes a liquid chamber for introducing the recording liquid into the flow path and a means for introducing the recording liquid into the liquid chamber, the liquid jet recording head includes a liquid jet recording head that includes a liquid jet recording head that includes a liquid jet recording head that includes a liquid chamber for introducing the recording liquid into the flow path, and a means for introducing the recording liquid into the liquid chamber. The material of the member and the recording liquid are determined so that the amount of organic matter eluted into the recording liquid used in the head satisfies the following conditions (a) to (d). .

(b) The liquid to be checked is a liquid whose pH is adjusted to the same pH as the recording liquid by removing the dye component from the recording liquid.

(b) Surface area of member in contact with liquid (d)/liquid volume (
ml)=0.50 (c) Immerse the member in the liquid for 2000 hours at 20°C.

(d)” - eluted organic matter b in the liquid after immersion under the conditions described.
t is 190-700 by measuring the absorbance with a spectrophotometer.
The maximum absorbance in the nm wavelength range is 1.0 or less.

Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a perspective view of a main part for explaining one embodiment of the present invention (a diagram showing an electrode protective resin layer (shaded area) formed on a heating element substrate), and FIG. 2 is a perspective view of an embodiment of the present invention. A diagram for explaining the operation of a bubble jet head as an example of an applied inkjet head, FIG. 3 is a perspective view showing an example of a bubble jet head, and FIG. 4 is a configuration of the head shown in FIG. 3. The lid substrate (Fig. 4(a)) and the heating element substrate (
Figure 4(b)) is a perspective view when disassembled, and Figure 5 is a perspective view of the
This is a perspective view of the lid substrate shown in FIG. A region for forming a liquid chamber, 27 is an individual (independent) electrode, 28 is a common electrode, 29 is a heating element (heater), 30 is ink, 31
is a bubble, and 32 is a flying ink droplet, and the present invention is applicable to such a bubble jet type liquid jet recording head.

First, ink ejection by bubble jet will be explained with reference to FIG.

(,) is a steady state, in which the surface tension of the ink 30 and the external pressure are in equilibrium on the orifice surface.

In (b), the heater 29 is heated until the surface temperature of the heater 29 rises rapidly and IIIS rise development occurs in the adjacent ink layer, and microbubbles 31 are scattered.

(c) shows a state in which the adjacent ink layer that is rapidly heated on the entire surface of the heater 29 is instantaneously vaporized to form a boiling film, and the bubbles 31 grow. At this time, the pressure inside the nozzle increases by the amount of bubble growth, and the balance with the external pressure on the orifice surface is lost, causing an ink column to begin to grow from the orifice.

(d) shows a state in which the bubble has grown to its maximum, and ink 30 corresponding to the volume of the bubble is pushed out from the orifice surface. At this time, no current is flowing through the heater 29, and the surface temperature of the heater 29 is decreasing. The maximum value of the volume of the bubble 31 is slightly delayed from the timing of electric pulse application.

(e) shows a state in which the bubbles 31 are cooled by ink or the like and begin to contract. At the tip of the ink column, it moves forward while maintaining the extruded speed, and at the rear end, the ink flows backward from the orifice surface into the nozzle due to the decrease in nozzle internal pressure as the bubbles contract, creating a constriction in the ink column. .

In (f), the air bubbles 31 are further contracted, the ink comes into contact with the heater surface, and the heater surface is cooled even more rapidly. At the orifice surface, the external pressure is higher than the nozzle internal pressure, so the meniscus is largely moving into the nozzle. The tip of the ink column becomes a droplet and drops 5 to 1 droplets toward the recording paper.
It is flying at a speed of 0m/sec.

In (g), the air bubbles have completely disappeared in the process of refilling the orifice with ink by capillary action and returning to the state of (a).

The present invention was developed by analyzing the problems that occur when the head member, particularly the organic material, comes into contact with the recording liquid (ink) in the recording head for the bubble jet type inkjet 1 as described above.

In a bubble jet type inkjet recording head, for example, the lid substrate may be made of plastic molding, or the channels, orifices, etc. may be made of dry film photoresist. When dry film photoresist is used, the ceiling substrate and the like are bonded using an adhesive such as epoxy. FIG. 1 is an enlarged view of the heating element substrate, and a resin coating 33 such as resin is formed in the shaded area of the figure to protect the electrodes from the recording liquid. As mentioned above, in the bubble jet head, most of the parts that come into contact with the recording liquid are organic materials. Therefore, matching the organic material and the recording liquid is an extremely important issue. Now, considering the various problems that may occur if the matching is not carried out properly, the recording liquid and the adhesive may undergo a chemical reaction, causing the recording liquid to leak from the bonded portion or peeling off. Alternatively, the shape of the flow path from the dry film photoresist 1 to the resist 1 may be distorted, or the dry film photoresist may be peeled off from the heating element substrate. Furthermore, the resin layer for protecting the electrodes may peel or fall off, causing the recording liquid to corrode the electrode patterns. These conditions are terminal conditions, and there are important problems before they reach that stage. In other words, these organic substances elute into the recording liquid and cause a chemical reaction with the recording liquid.
This creates undesirable deposits and clogs the orifice. Orifice clogging has been a problem unique to inkjet recording, and various solutions have been proposed. However, in the Bubble Jet 1 technology, since there is a heat cycle of the recording liquid in the thermal energy acting part, it is not possible to use a conventional drop-on-mand method using PZT or a continuous flow jet/jet method that does not have a large thermal effect. They are exposed to different and more degrading conditions than those in which they are not exposed. Since chemical reactions are accelerated by the P1 cycle, things that would not have been a problem with the conventional Infusiera 1 technology become important problems with the Bubble Diene 1 technology.

The present invention has been made in view of the points mentioned above, and the permissible value was determined through repeated experiments to determine the permissible extent to which the organic material used in the bubble jet head is allowed to elute into the recording liquid. is precisely determined, and the matching of the components and recording liquid is optimized. According to the inventor's experiments, the organic material that can be used must be determined so as to satisfy the following conditions. In other words, when a member is immersed in the following liquid, the elution amount must be below a certain value.

(a) The liquid to be checked is a liquid that has been pH-adjusted by removing the dye component from the recording liquid to have the same pH as the recording liquid.

(b) Surface area of member in contact with liquid (d)/liquid volume (
+nQ)-=0.50 (c) Immerse the member in the liquid at 20°C for 2000 hours.

(d) - 1 of the eluted organic matter in the liquid after immersion under the conditions described above.
．． f is 190 to 70 when absorbance is measured with a spectrophotometer.
The maximum absorbance in the 0 nm wavelength region is 1.0 or less.

Here, the reason why the liquid used in the test is not a recording liquid (ink) is that dye is detected when determining the absorbance at 21ill with a spectrophotometer. Therefore, a liquid (vehicle) obtained by removing the dye component from the recording liquid is used. Also, since the vehicle has a lower P H than the ink, in order to adjust the p I-I, for example, No2G O
3 to bring the pH to the same as that of the ink.

It should be noted that the parts used in the test are not necessarily the same as the surface area (d)/liquid volume (mI2) that comes into contact with the liquid of one member during the test.
There is no need to satisfy 0.50, just convert it later. For example, if the above ratio is 0.2 and the absorbance determined by d1g at that time is 0.6, the converted absorbance is as follows, and this value of 1.5 is adopted.

According to the inventor's experiments, this absorbance (converted absorbance when the ratio of the member surface area to the liquid surface area is not 0.50) is preferably 1.0 or less, and optimally 0.5 or less. At times, good injection performance was obtained with no clogging of the orifice or debris near the orifice.

Table 1 shows an example of the results. In addition, the injection results are based on the elution amount (
The results were obtained after filling a spatula with a vehicle whose absorbance was known and continuously ejecting for 10 minutes (f = 1.5 kllz).

Table 1 This must be resolved regardless of the refurbishment size, etc.
In reality, we aim for higher resolution printing quality.

That is, the higher the orifice array density, the more stringently it must be controlled.

From the results in Table 1, in a head with an arrangement density of about 16 lines/m, if the amount of organic matter eluted is 1.0 or less in terms of absorbance, no clogging will occur and satisfactory results can be obtained. I understand.

Next, in order to achieve higher-definition printing quality, a head with an arrangement density of 16 lines/m or more was prototyped and a similar test was conducted. Table 2 shows the results.

The head used here has an orifice array density of 16 lines/+nm, aiming for medium to high resolution printing quality.6 The reliability problem of clogging of the ink jet was
The elution of organic matter from the orifice arrangement density or the absorbance is preferably 1.0 or less, and in order to achieve higher definition printing quality, it needs to be 0.5 or less. I understand that.

Effects As is clear from the above explanation, according to the present invention, there is no clogging of the orifice or unnecessary deposits near the orifice, stable ejection performance (jetting performance), and high print quality. is obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of essential parts for explaining an embodiment of the present invention, and FIG. 2 is a perspective view for explaining the operation of a bubble jet head as an example of the Infusiera 1-head to which the present invention is applied. 3 is a perspective view showing an example of a bubble jet head, FIG. 4 is an exploded perspective view, FIG. 5 is a view of the lid substrate seen from the back side, and FIG. 6 is a conventional bubble jet head.
- It is a diagram for explaining an example of a recording head. 21... Lid! , 1. Plate, 22...Heating element board, 27
．． 28...electrode, 29...heating element, 33...resin film] To ward T Muro diagram (d) (e) 2 to C = 0-2nd 3rd blade r'o)

Claims (1)

[Claims] 1. A flow path that accommodates the recording liquid introduced and is provided with a thermal energy acting section that generates bubbles in the recording liquid by heat and generates an acting force as the volume of the bubbles increases. an orifice that communicates with the flow path and causes the recording liquid to be ejected as droplets by the acting force; and a liquid chamber that communicates with the flow path and introduces the recording liquid into the flow path. , in a liquid jet recording head comprising means for introducing the recording liquid into the liquid chamber, the amount of organic matter eluted from the members constituting the liquid jet recording head into the recording liquid used in the liquid jet recording head is as follows: A liquid jet recording head characterized in that the material of the member and the recording liquid are determined so as to satisfy conditions (a) to (d). (a) The liquid to be checked is a liquid obtained by removing the dye component from the recording liquid and adjusting its pH to the same pH as the recording liquid. (b) Surface area of the member in contact with the liquid (cm^2)/liquid volume (ml) = 0.50 (c) The member is immersed in the liquid for 2000 hours at 20°C. (d) The amount of eluted organic matter in the liquid after immersion under the above conditions was determined by measuring the absorbance with a spectrophotometer and measuring the absorbance at 190 to 700 nm.
The maximum absorbance in the wavelength range of 1.0 or less.