JPH021314A - Liquid jet recording head - Google Patents

Abstract

PURPOSE:To stabilize performance of discharge by eliminating clogging of an orifice by a method wherein an amount of Si or Ti among elements which are eluted from a structure member of a head into recording liquid is taken as 15ppm or under. CONSTITUTION:When a member composing a liquid jet recording head is brought into contact with recording liquid under conditions of 1,000h and 50 deg.C, an elution amount of Si and Ta contained in this member, especially in a protective layer 34 into the recording liquid is taken as 15ppm or under, an in an optimum manner as 10ppm or under. Consequently, clogging of an orifice for discharging the recording liquid as a liquid drop by operation force of a thermal energy operating part in a bubble jet type liquid jet recording head can be prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a liquid jet recording head, and more particularly to a suitable relationship between the recording liquid of a bubble jet type ink jet recording head and elution from the members of the recording head into the recording liquid.

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,
The so-called Infusiera 1-recording method, which allows recording on so-called plain paper without the need for special fixing treatment, is an extremely powerful recording method, and various methods have been proposed and improvements have been made. Some have been commercialized, and efforts are still being made to put them into practical use.

Such an inkjet recording method involves jetting droplets of a recording liquid called ink.

Recording is performed by attaching the recording liquid to a recording member, and it is roughly divided into several methods depending on the method of generating recording liquid droplets and the control method for controlling the flight direction of the generated recording liquid droplets. Ru.

First, the first method is the one disclosed in USP 3060429 (Tels type method), in which droplets of recording liquid are generated by electrostatic attraction and the generated recording liquid droplets are used as a recording signal. The electric field is controlled according to the recording member] and recording liquid droplets are selectively attached to the recording member. It is something to do.

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 droplet is caused to fly 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 to perform recording.

The second method is described, for example, in US P3596275, US
The method disclosed in P 3298030 etc. (Swee
t method), in which droplets of recording liquid with a controlled amount of charge are generated by a continuous vibration generation method, and the generated droplets with a controlled amount of charge are subjected to a -like world. Recording is performed on a recording member by flying it between deflection electrodes.

Specifically, the orifice (discharge port) of a nozzle, which is a part of the recording head to which the piezo vibrating element is attached.
A charged electrode configured to have a recording signal applied thereto is arranged at a predetermined distance in front of the piezo vibrating element, and electricity No. 78 of a constant frequency is applied to the piezo vibrating element to mechanically vibrate the piezo vibrating element. , a small droplet of recording liquid is ejected from the ejection port. The said charge at this time? ! ! A charge is electrostatically induced in the recording liquid droplet ejected by the pole, and the droplet is charged 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, an applied band 'f'! ! The droplets are deflected according to the amount so that only the droplets carrying the recording signal can be deposited on the recording member.

The third method is, for example, the method disclosed in U.S.P. 3416153 (Hertz method), in which an electric field is applied between a nozzle and a ring-shaped charged electrode, and small droplets of recording liquid are generated by a continuous vibration generation method. This method records by atomizing it. That is, in this method, the atomization state of the droplets is controlled by modulating the electric field strength applied between the nozzle and the charged electrode according to the recording signal, and the gradation of the recorded image is produced.6 The fourth method is For example, there is a method (Stamme method) disclosed in US Pat. No. 3,747,120, which is fundamentally different in principle from the above three methods.

That is, in all three methods, the droplets of the recording liquid ejected from the nozzle are electrically controlled while they are in flight, and the droplets carrying the recording signal are selectively sent to the recording section 1. As opposed to recording by attaching it.

The Stemme method performs recording by ejecting small droplets of recording liquid from an ejection port in response to a recording signal.

In other words, the StemOIe method applies an electrical recording signal to a piezoelectric vibrating element attached to a recording head that has an ejection port for ejecting recording liquid, and converts this electrical recording signal into mechanical vibration of the piezoelectric 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 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 form dots.

The third method has the advantage that an image with excellent M'r tonality can be recorded by atomizing the recording liquid weight; blue, but on the other hand, it is difficult to control the atomization state, and both recorded images There are various problems such as fogging, difficulty in making the recording head multi-nozzle, and unsuitability for high-speed recording.

The fourth method has relatively many advantages compared to the first to third methods. In other words, the structure is simple, and since recording is performed by ejecting 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 small particles that are not needed for image recording, 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 large degree of freedom. On the one hand, it is difficult to make a recording head with multiple nozzles due to problems in the processing of the recording head and the extremely difficult miniaturization of a piezoelectric vibrating element with a desired resonance number. This method has disadvantages such as that it is not suitable for high-speed recording because the recording liquid droplets are ejected into 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-mentioned US P3
No. 747120) discloses, as a modification, the use of thermal energy instead of the mechanical vibration energy provided by means such as the piezo vibration element.

That is, the above-mentioned publication describes the use of a heating coil that directly heats a liquid as a pressure increasing means in place of the piezo vibrating element in order to generate steam that causes a pressure increase.

However, in the above publication, the liquid ink in the bag-shaped ink chamber (liquid chamber), which has only one opening through which liquid ink can go in and out, is directly heated and vaporized by energizing the heating coil as a pressure increasing means. However, there is no information on how to heat the liquid when discharging the liquid repeatedly.
There is nothing to suggest. 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 continuous high-speed printing. For repeated use,
It is not suitable.

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.

As described above, conventional methods have advantages and disadvantages in terms of structure, high-speed recording, multi-nozzle recording heads, generation of satellite dots, and fogging of recorded images. There was a restriction that it could only be applied.

Furthermore, in Japanese Patent Publication No. 59-43315, in a Bubble Jet 1 type inkjet recording device, the amount of weight loss of the part of the electrical/thermal converter in contact with the liquid (ink) in the heat acting part is set to be 1/10 or less of that of aluminum. , has been disclosed to extend the life of the electric/thermal converter.

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 of a predetermined width and depth at a predetermined linear density on the surface of a substrate 3 on which an electric/thermal converter 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 1 shown in the figure is shown as having a plurality of orifices 5 (5, 5□, 53), it is also possible to apply the present invention to a recording head with a single orifice.

The liquid discharge part 6 has an orifice 5 at its end for discharging liquid droplets, and thermal energy generated from the upper air heat converter 2 acts on the liquid to generate bubbles, causing expansion and contraction of its volume. It has a heat acting part 7 which is a place where rapid changes in state are caused due to.

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

The heat generating section 8 is a lower layer 10 provided on the substrate 3. The heating resistor layer 11 provided on the lower layer 10, the heating resistor J
f'J l and an upper layer 12 provided on top of the top layer 12 . The heat generating resistor layer 11 includes the J-1 in order to generate heat.
Electrodes 13 and 14 for energizing 1 are provided on its surface. The electrode 13 is a common electrode for 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. It is located along the road.

” Part J+112 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 the electrodes 13 and 14 are connected through the liquid. Heat generating resistance layer 11 that prevents short circuits
It has a protective function.

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

That is, when discharging a droplet, the proportion of heat generated by the heat generating resistor M11 being conducted toward the heat acting section 7 side is as high as possible, rather than toward the substrate 3 side, and after discharging the droplet. , that is, after the power to the heating resistor RI111 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 acting portion 9, which is the wall surface portion of the heat acting portion 7 that comes into contact with the liquid, is pure! Using a 99.9% aluminum plate as the test standard, the unit at the elapsed time t from the start of the test when the weight loss ΔW (AI2) per unit area of the test surface in the heavy equipment reduction test becomes 1■/d. It is composed of a material whose weight loss per area ΔW is less than 1/10 of ΔW (AM), which not only extends its service life but also significantly increases the frequency of droplet formation for high-speed recording. Furthermore, even if the level value of the pulse signal input to the electrothermal transducer becomes high, stable droplet ejection can be performed continuously for a long time.

The invention described in Japanese Patent Publication No. 59-43315 discusses the amount of weight loss from the perspective of the life of the electrothermal converter, but in reality, the ink may undergo abnormal changes before destruction occurs. occurs, making it impossible to obtain satisfactory ejection performance.

What is satisfactory discharge performance?

Refers to discharge without clogging of the orifice and without bending in the jet direction.

Furthermore, in Japanese Patent Publication No. 59-43315, the amount of weight reduction of the heat acting part is specified based on the weight reduction of aluminum. Structures that come into direct contact with aluminum 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 material actually used, the reason for selecting the material aluminum in the above-mentioned Japanese Patent Publication No. 59-43315 is ambiguous, and the technical basis for this is low. I have to say that.

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 Bubble Geno 1-type liquid jet recording heads.

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 acting force as the volume of the bubbles increases. a flow path provided with a thermal energy acting portion; an orifice connected to the flow path for causing the recording liquid to be ejected as droplets by the acting force;
In a liquid jet recording head comprising a liquid chamber for introducing the recording liquid into the flow path, and a means for introducing the recording liquid in [1j] into the liquid chamber, the liquid is Among the elements eluted into the recording liquid used in the jet recording head, Si is
When it comes into contact with the recording liquid at a constant temperature, it is 15 ppm or less, and further, in the liquid jet recording head, the element to be eluted is Ta. Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a sectional view of a main part (a view of a thermal energy acting part) for explaining an embodiment of the present invention, and FIG. 2 is a bubble jet head as an example of an inkjet head to which the present invention is applied. Figure 3 is a diagram for explaining the operation of
A perspective view showing an example of a bubble jet head, FIG.
The lid substrate that constitutes the head shown in Fig. 3 (Fig. 4 (a)
) and the heating element board (Fig. 4(b)).

This is a perspective view of the lid substrate shown in FIG. 4(a) from the back side.
In the figure, 21 is a lid substrate, 22 is a heating element substrate, 23 is a recording liquid inlet, 24 is an orifice, 25 is a flow path, 26 is 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 a bubble jet will be described with reference to FIG. 2. (a) is a steady state, in which the surface tension of the ink 30 and the external pressure are in equilibrium on the orifice surface.

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

(c) shows a state in which the adjacent ink WJ 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 made by analyzing the problems that occur when the members of the bubble jet liquid jet recording head actually used come into contact with the recording liquid (ink) in the bubble jet type ink jet recording head as described above. be.

FIG. 1 shows the cross-sectional area of the thermal energy acting part in the bubble jet type inkjet recording head.
Of these, those that come into contact with the recording liquid (ink) are
34 and electrode protection N35 (generally an organic material is used).

Now, as the protective layer 34, SiO□, Si, N4, Ta, or the like is generally used. These materials generate heat W
This is to protect the J 29 (heating resistor) from the recording liquid 30, and it must not happen that the protection #34 is destroyed and the recording liquid 30 reaches the heating layer 29. This is the role of the protective layer 34 when viewed from the recording head side, but on the other hand, when viewed from the recording liquid side,
More stringent conditions are required. That is, there is a problem in that, before the protective layer 34 is destroyed, the metal element of the protective layer material causes a chemical reaction with the recording liquid, causing the recording liquid to change in quality. The most important problem caused by degraded recording fluid is orifice clogging. Orifice clogging is a problem specific to inkjet recording.
This has been a problem for some time, and various solutions have been proposed. However, in bubble jet technology, because there is a heat cycle of the recording liquid in the part where thermal energy is applied, 5 there is a drop-on-demand method using ordinary PZT, or continuous flow inkjet, which is not subject to much heat action. It is exposed to different and more severe conditions than other methods. Since chemical reactions are accelerated by heat cycles, things that would not have been a problem with the conventional Infusiera 1 technology become important problems with the bubble jet technology.

In view of this point, the present invention conducts repeated experiments to determine to what extent the metal elements of the protective layer are allowed to elute into the recording liquid, and the permissible value is strictly determined. According to the inventor's experiments, Si and Ta contained in the members constituting the recording head, especially the protective layer,
The amount of elution when brought into contact with a recording liquid at 50° C. for 000 hours is desirably 15 ρρm or less, and optimally needs to be lop ρm or less. Table 1 shows an example of the results.

Note that the elution amount was measured by plasma emission spectrometry. The jetting performance was measured by filling the recording head with a recording liquid whose elution amount of metal elements was known, and continuously jetting it for 10 minutes.
This is the result after (using a ball at f: 1.5). Note that recording liquids with different elution amounts can be used depending on the area of the protective layer or the vacuum deposition method (protective layer Sio, Si, Si, etc. used in the present invention).
The samples were prepared by immersing samples under different conditions (N4 or Ta is preferably formed by a vacuum deposition method) into a recording liquid at 50° C. for 1000 hours.

The head used here has an orifice arrangement density of 16/1111 aiming at medium to high resolution printing quality. The reliability problem of inkjet clogging must be solved regardless of the orifice array density or orifice size, but in reality, the higher the orifice array density is aimed at, the higher the orifice array density. Must be more strictly controlled.

From the results in Table 1, it can be seen that in a head with an arrangement density of about 16 lines/m, if the element capacity is 15 ppm or less, no clogging occurs and a completely satisfactory result can be obtained.

Next, aiming at higher-definition printing quality, a head with an arrangement density of 16 lines/m or more was prototyped and similar tests were conducted.Table 2 shows the results.

From the above, it is desirable that the elution amount is 15 ppm or less, and in order to aim for higher definition printing quality.

It can be seen that it needs to be less than or equal to topρm.

As is clear from the explanation in E-H, according to the present invention, stable discharge performance can be obtained without clogging the orifice or causing localized vegetation.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part for explaining an embodiment of the present invention, and FIG. 2 is a diagram for explaining the operation of a Bubble Geno 1 head as an example of an inkjet head to which the present invention is applied. , FIG. 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 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 J, (plate, 22...Heating element substrate, 27.
28... Electrode, 29... Heating element, 33... Heat storage layer, 34... Protective layer, 35... Electrode protective layer. Kazuhakushi, right 3, Figure No. (b)

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, among the elements that elute from the members constituting the liquid jet recording head into the recording liquid used in the liquid jet recording head, Si or A liquid jet recording head characterized in that Ta is 15 ppm or less when the member is in contact with the recording liquid at a constant temperature for a constant time. Here, the constant time is 1000 hours and the constant temperature is 50°C. 2. The liquid jet recording head according to claim 1, wherein the element to be eluted is Ta.