JPS62169657A - Liquid jet recording head - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a liquid that performs recording by ejecting and flying a recording liquid as droplets from a liquid ejection port, and making the droplets land on a recording medium such as paper. The present invention relates to a liquid jet recording head, particularly an on-demand type liquid jet recording head that performs discharge when a print signal is applied, and particularly to a liquid jet recording head that has high-speed response and excellent discharge stability.

[Prior Art] A liquid jet recording method (inkjet recording method) in which recording is performed by ejecting and flying a recording liquid has been known.

This method has excellent features such as high-speed printing, low noise, high recording quality, easy color image recording, and the ability to record on plain paper.

An inkjet recording device used in such an inkjet recording method generally includes a liquid ejection opening (orifice) for ejecting the recording liquid as flying droplets, a liquid flow path (nozzle) communicating with the orifice, and the nozzle. The inkjet recording head is provided in a part of the nozzle and has an ejection energy generating means for applying ejection energy to the recording liquid in the nozzle to form flying droplets.

Recording is performed by driving the ejection energy generating means to supply ejection energy to the recording liquid in the nozzle, ejecting the recording liquid as flying droplets from the orifice, and causing the droplets to land on the recording medium.

The recording liquid used when recording with such an inkjet recording device generally consists of a recording agent such as a pigment or dye, and mainly water, or water and a water-soluble organic solvent or a water-soluble organic solvent for dissolving or dispersing it. It is formed from a solvent component such as a non-aqueous solvent.In an inkjet recording device, the orifice provided at the tip of the nozzle from which the recording liquid is ejected is constantly exposed to the outside air outside the device, regardless of whether the device is being driven or not. Therefore, if recording is not performed for a long period of time, some of the solvent may evaporate from the orifice into the outside air, causing recording material components and solvent components that are difficult to volatilize to evaporate. remains in the recording liquid, the composition of the recording liquid staying in this area changes and the viscosity increases, resulting in an increase in viscous resistance at the nozzle area.Therefore, immediately after restarting recording after printing has stopped. In this method, there is a problem in that droplet ejection failure is likely to occur in which droplets are not ejected even though an ejection signal is applied, and defects occur in the initial printed portion of the recorded image.

Furthermore, in order to repeatedly eject droplets with an inkjet recording apparatus, the amount of liquid lost during ejection must be replenished before the next ejection. For that purpose
A typical method uses the surface tension of the liquid to guide the liquid to an orifice by capillary action. In this case, the time t2 required to guide the liquid to the orifice is determined by t2''d/u, where d is the distance that the liquid remaining in the nozzle retreated from its original position after the droplet was cut, and U is the moving speed of the liquid due to capillary action.The above time t2 is usually much larger than the time 1 required for the formation of a droplet, and the repeated driving is determined by f=17(t,+t,). The possible frequency f is effectively limited by 1°, and no matter how far the droplet forms,
There was a problem in that the repeat drive frequency could not be increased.

One effective way to solve these problems is to shorten the length of the nozzle. Reducing the length of the nozzle is equivalent to reducing the resistance of the nozzle wall to the flow, which leads to a reduction in t2. However, shortening the nozzle causes a decrease in the velocity of flying droplets and an increase in velocity instability, causing the problem that stable recording cannot be performed.

Apart from this, the rear of the discharge energy generating means (
It has been proposed that a fluid resistance element be provided on the orifice (on the side opposite to the installation side) to reduce energy loss during droplet ejection, improve droplet velocity, and stabilize ejection. However, even in this case, the recording liquid cannot always be supplied sufficiently by the fluid resistor, which essentially causes an increase in the above-mentioned t2. Therefore, there is a natural limit to the improvement of the driving frequency, and There was a problem that requests could not always be satisfied.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned problems of the prior art. The purpose of the present invention is to provide a new inkjet recording head capable of recording.

[Means for Solving the Problems] The above objects of the present invention are achieved by the present invention below.

An inkjet recording head comprising an orifice for ejecting a recording liquid and an ejection energy generation means for supplying ejection energy to the recording liquid, the inkjet recording head having a heating means separate from the ejection energy generation means on the opposite side of the orifice. An inkjet recording head characterized in that a fluid resistor having an opening is installed between the ejection energy generating means and the heating means.

That is, in the present invention, an opening is provided in the fluid resistance body for effectively utilizing the ejection energy applied to the recording liquid by the ejection energy generating means to prevent an increase in t2, and the opening is provided separately from the ejection energy generating means. By using a heating means to eliminate energy loss caused by the provision of the opening, it is possible to achieve high-speed responsiveness and stable ejection of droplets during recording, as well as to enable recording when resuming recording after being left unused for a long time. This also solves the problem of liquid ejection failure.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings as necessary.

1 and 2 are diagrams for explaining the schematic configuration of a preferred embodiment of the inkjet recording head of the present invention, and FIG. 1 is a perspective view of the head, and FIG. A partial plan view of the head is shown in each of the figures.

In these figures, 102 is an orifice for ejecting the recording liquid as flying droplets, and 103 is a nozzle communicating with the orifice 102.

107 is a liquid chamber for supplying recording liquid to the nozzle 103, and 108 is a liquid supply port provided as necessary to supply recording liquid to the liquid chamber 107 from outside the recording head. 10] is an ejection energy generation means for supplying ejection energy to the recording liquid in the nozzle 103, 104 is a fluid resistor having an opening 106, and 105 is a heating means provided separately from the ejection energy generation means 101. .

In the present invention, the discharge, energy generation means 101, opening 1
06 and the heating means 105 from the orifice 102 side.
1. Although it is necessary to provide the fluid resistor 104 and the heating means 105 in this order, there are no particular limitations on the member structure or formation method of the recording head other than providing such a fluid resistor and heating means. It may be the same desired configuration as in conventional inkjet recording heads. Of course, it goes without saying that the number of nozzles, orifice shape, etc. may be set as desired.

The ejection energy generating means 101 in the present invention may be of any type as long as it can eject droplets in the same manner as in conventional inkjet recording heads, and specifically, for example, it may use various heating resistors. Typical examples include thermal energy generating means and pressure energy generating means using various piezoelectric bodies. Incidentally, in FIGS. 1 and 2, a heating resistor is illustrated as an example of the ejection energy generating means 101.

The fluid resistor 104 prevents the ejection energy applied to the recording liquid by the ejection energy generating means 101 from flowing backward and effectively utilizes the ejection energy.
For example, in order to effectively supply recording liquid to a plurality of nozzles 103 as in this example, the liquid chamber 1
07 is provided, the fluid resistance body 10
4 may be provided in the nozzle 103 or may be provided in the liquid chamber 107 at the rear of the nozzle 103. Of course, if the liquid chamber 107 is not particularly provided, it goes without saying that it may be arranged inside the nozzle 103. The fluid resistor 104 may have any shape and material as long as it can prevent the energy loss as described above. Also,
The opening 106 may be disposed in the fluid resistance body 104 so as not to obstruct the inflow of the recording liquid, and its shape and numerical aperture are not particularly limited.

Separately from the discharge energy generating means 101 as described above, the heating means 105 is configured to heat the fluid resistor 10 by installing the opening as described above.
Although it is provided at the rear of the fluid resistor to compensate for the energy loss during discharge that occurs in step 4, there are no particular limitations on its material or shape. This is a typical example of what you can get.

Incidentally, in order to make the present invention effective, the heating means 10
5 is preferably provided close to the fluid resistor 104.

Hereinafter, the discharge energy generating means 101 and the heating means 1
The present invention will be further explained by showing an example of operation during recording when 05 is used as a heating resistor.

FIGS. 3(a) to 3(d) show the discharge energy generating means 10.
1 and a heating means 105, the heating means 105 is a schematic partial view of the X-Y cross section of FIG. 2 shown over time.

FIG. 3(a) shows the recording head in a printable state in which the ejection energy generating means 101 and the heating means 105 are inactive and the recording liquid is supplied from the liquid chamber 107 to the re-nozzle 103.

From such a non-operating state (a), first the heating means 105
Send a recording signal to the unit to make it operational. After the heating means 105 starts operating, the discharge energy generating means 101 starts operating. Thermal energy is supplied to the recording liquid by the operation of the heating means 105 and the ejection energy generating means 101, and this thermal energy causes a bubbling phenomenon in the recording liquid.
Steam bubbles 205 and 20 as shown in FIG.
1 is generated.

FIG. 3(b) shows the state of the recording head immediately after the ejection energy generating means 101 is operated after the heating means 105 is operated. FIG. 3(C) shows the state of the vapor bubbles 201 when the volume is at its maximum due to the discharge energy generating means 101 (heating resistor).
In order to make the present invention effective, it is desirable that the time be immediately before or immediately after the self-contraction of the vapor bubbles 205 starts. Specifically, such a state can be easily achieved, for example, by applying a pulse signal with a width of about 10 μsec to the heating means 105 several μsec before applying a recording signal to the ejection energy generating means 101.

In the states (b) to (C), the vapor bubbles 205 formed by the heating means 105 do not discharge droplets. This is because the orifice direction component of the acting force due to the growth of the vapor bubbles 205 has a large resistance loss against the flow generated in the recording liquid by the nozzle constituent wall. Further, the purpose of forming the vapor bubbles 205 by the heating means 105 is not to perform discharge, but to eliminate energy loss during droplet discharge caused by providing an opening in the fluid resistor 104, and effectively utilize the discharge energy. Since the purpose is to function as a fluid diode for the purpose of discharging, there is no problem even if the contribution to discharge is zero.

The droplets 203 are formed in the process of the vapor bubbles 201 growing and self-contracting by the ejection energy generating means 101 (see FIG. 2(d)). In the acting force when the vapor bubble 201 foams and grows, there is a component in the liquid chamber direction opposite to the droplet flying direction, which causes energy loss in droplet ejection. At this time, by increasing the resistance to the flow in that direction and reducing the acting force in the liquid chamber direction that does not contribute to droplet ejection, it is possible to increase the contribution rate of the total acting force to ejection. . One way to improve this contribution rate is to provide a fluid resistor, but simply providing a fluid resistor will lengthen the recording liquid supply time t2 after ejection.

In the present invention, since the fluid resistor 104 is provided with an opening, the supply of recording liquid is not hindered, and the above-mentioned t2 is shortened, making it possible to record at a high green return drive frequency. Moreover, the fluid resistance body 104 and the heating means 1
Combined with the steam bubbles 205 caused by 05, the nozzle 103
By increasing the resistance in the direction of the liquid chamber, the contribution of the acting force to ejection is increased, and the flying speed of the droplet is increased and stabilized. Furthermore, even for highly viscous recording liquid that may cause ejection failure after being left for a long period of time, the ejection energy can be used effectively by the action of the fluid resistance element and heating means, so that the liquid can overcome the viscous resistance. This makes it possible to eject droplets, and the frequency of occurrence of ejection failure immediately after resuming recording is reduced.

The present invention will be further explained below by showing an example of a detailed structure of a substrate on which ejection energy generating means and heating means for performing such an operation are mounted, and an example of a method of manufacturing a recording head.

FIGS. 4(a) and 4(b) are a partial plan view and an AA sectional view of an example of a substrate used in the inkjet recording head of the present invention, respectively.

This substrate 1 includes a heating resistor 2 as a means for generating ejection energy, and a heating resistor 3 as a heating means for increasing the resistance to the flow toward the rear of the nozzle and preventing the recording liquid from retreating during droplet ejection as described above. A common electrode 14 and individual electrodes 15 and 17 are installed for applying a desired electrical signal according to the ejection pattern to each of these heating resistors.

As shown in FIG. 4(b), these are formed on a substrate 1 made of a desired material such as glass, ceramics, Si, etc., with a common electrode 14, an insulating protective layer 18, and each heating resistor layer 2.
．． 3. It has a laminated structure in which each individual electrode 15, 17 and an insulating protective layer 19 are laminated in order.

Such a substrate is produced, for example, as follows.

First, the common electrode 14 is formed on the substrate 1 using Au, aluminum or the like. In this example, Au was deposited by ion beam evaporation to a thickness of 0.5 μm on a Si substrate 1 having a thermal oxidation layer 2 to 5 scales thick on its surface. Next, the insulating protective layer 18 is created, and examples of materials constituting the protective layer 18 include titanium oxide, vanadium oxide, niobium oxide, molybdenum oxide, tantalum oxide, tungsten oxide, chromium oxide, zirconium oxide, and hafnium oxide. , transition metal compounds such as lanthanum oxide, yttrium oxide, manganese oxide, metal oxides such as aluminum oxide, calcium oxide, strontium oxide, barium oxide, silicon oxide, and complexes thereof, silicon nitride, aluminum nitride, boron nitride, High-resistance nitrides such as tantalum nitride, complexes of these oxides and nitrides, and semiconductors such as amorphous silicon and amorphous selenium, even if they have low resistance in bulk, can be processed using sputtering, CVD, vapor deposition, and gas phase reaction methods. , thin film materials that can be made high in resistance during manufacturing processes such as liquid coating methods, and the layer thickness is generally 0.
．． 1. -5 scales, preferably 0.2p - 3p. In this example, a 5i02 layer with a thickness of 2#LfI was created by sputtering.

Next, a heating resistor layer 2.3 is created. As the material constituting the heating resistor layer, almost any material can be used as long as it generates desired heat when energized.

Specific examples of such materials include tantalum nitride, nichrome, silver-palladium alloy, silicon semiconductor,
Or hafnium, lanthanum, zirconium, titanium,
Preferred examples include borides of metals such as tantalum, tungsten, molybdenum, niobium, chromium, and vanadium.

Among these materials constituting the heating resistor layer, metal borides are particularly excellent, and among these, hafnium boride has the best properties, followed by zirconium boride, The order is lanthanum boride, tantalum boride, vanadium boride, and niobium boride.

The heating resistor layer can be formed using the above-mentioned materials using methods such as electron beam evaporation and sputtering.

After that, using well-known buttering techniques such as photolithography and etching, unnecessary parts of each of these layers are removed, and layers that will become electrodes 14, 15, and 17 are created, and unnecessary parts are removed using the same buttering technique as described above. A portion is removed to create an electrode layer with a desired pattern. Furthermore,
If necessary, an insulating protective layer 19 is created. In this example, the insulation protective layer 19 is made of 5i02 by sputtering.
Two scales were formed.

Furthermore, in order to improve the durability performance against the mechanical impact force generated when vapor bubbles disappear, Am Ta, Ti,
Zr%Hf%V%Nb, Mg, St, Mo, W
The protective layer may be formed using metals such as , Y, La, alloys thereof, or oxides, carbides, nitrides, borides, etc. of these metals and alloys.

Although not particularly shown in the figure, each electrode is provided with an exposed portion for connection to the outside by a method such as bonding. Further, the heat generating resistors may be of any desired shape and size as long as they can achieve the purpose, and may have different shapes and sizes. However, in this embodiment, in order to avoid complicating the drive circuit, they are all the same size and shape, with a width of 30μ and a length of 150μ.

The inkjet recording head of the present invention as illustrated in FIG. Complete. FIG. 5 shows another example of such an ink jet recording head of the present invention, and FIG. 5 shows a partial perspective view of the head.

The nozzle 7 may be formed using a photosensitive material such as a photosensitive resin film or photosensitive glass, or may be formed by forming a groove on a suitable flat plate such as glass by a mechanical method, etching, etc. It can also be manufactured by a method such as pasting it on the inkjet recording head substrate. Further, at this time, the liquid chamber, the liquid supply port, etc. may be manufactured in one piece. In this embodiment, a photosensitive resin film 5 is used to create a nozzle wall and a liquid chamber wall by a photolithography process and an etching process, and a glass plate 21 (not shown) with a liquid supply date is bonded thereon. An inkjet recording head was constructed.

As mentioned above, the shorter the length of the nozzle 7, the shorter the above-mentioned t2, but this causes a decrease in the ejection speed and stability.

In the present invention, this problem is solved by the fluid resistor 8 having the opening 9 and the heating means 3, so the nozzle can be made as short as necessary, and the recording head can be made more compact. However, it is necessary to provide an opening 9 in the fluid resistor 8. In this example, the nozzle length is 500ul.
Two barriers as fluid resistors 8 were arranged on the left and right behind the nozzle so that an opening 9 of 50)u+X50μ was provided in the direction perpendicular to the nozzle 7. Of course, the fluid resistance body may be formed of an integral member having an opening, or, as in this example, two or more barrier members having no opening may be used to form the opening. It is something. The fluid resistor of this example was made from the same photosensitive resin film as the nozzle at the time of nozzle formation.

The pulse signals shown in FIGS. 6(a) and 6(b) are applied to the inkjet recording head shown in FIG. 5 created by the above method, and heat generation is performed as heating means and ejection energy generating means according to the present invention, respectively. Resistors 3 and 2 were operated sequentially. In this embodiment, since the two heating resistors have exactly the same shape and the same resistance value, they can be driven with the same voltage waveform.

The voltage waveform is a pulsed rectangular wave, and the pulse width is 10μ.
sec was used. The shorter the pulse width, the better from the viewpoint of the speed of the flying droplets and the repetition stability. However, if the pulse width is shortened, it becomes necessary to apply a larger voltage to the heating resistor, which may shorten the durability performance of the heating resistor. Become. Also,
If the pulse width is made longer than necessary, unnecessary bubbles will be generated during droplet ejection, which is not preferable. Therefore, the selection of the pulse width is determined by a balanced design that takes into account the above points. The pulse width is preferably in the range of 50 μsec or less, preferably 20 μsec or less, and optimally IO
It is within μsec.

The operation is performed as follows. First, the heating resistor 3 is
It is operated at the timing shown in Figure (a) to generate steam bubbles. FIG. 7 is a growth curve of such a vapor bubble. As is clear from the figure, the vapor bubble caused by the heat generating resistor 3 does not change sharply before and after its maximum volume, and functions sufficiently as a liquid diode in ejecting droplets. When the vapor bubbles of the heating resistor 3 are in this state, an electric signal is applied to the heating resistor 2 so that the vapor bubbles generated by the heating resistor 2 as a discharge energy generating means are maximized (Fig. 6). (See (b)).In this embodiment, the ejection speed of droplets generated by operating the ejection energy generating means at the timing shown in FIG. I was able to speed it up by about 50%.

The supply of recording liquid to the nozzle is started in the process of disappearance of the vapor bubbles by the heating resistor 3 and the ejection energy generating means 2, but the presence of the opening shortens the supply time of the recording liquid and increases the repetition frequency of up to 10 KHz. I was able to get it.

In addition, since the energy involved in ejection increases due to the vapor bubbles and fluid resistor caused by the heating resistor 3, it is possible to prevent ejection failure due to an increase in the viscosity of the recording liquid after leaving it for a long time, and even after leaving it for a long time. It is now possible to record stably.

FIG. 8 shows an inkjet printer as an example of an inkjet recording apparatus using such an inkjet recording head of the present invention.

The printer shown in FIG. 8 uses the recording head illustrated in FIG.

This printer ejects recording liquid while moving a recording head 20 mounted on a carriage 21 left and right on rails 22 and 23, and prints characters on a recording medium using a tod matrix of the recording liquid. Reference numeral 24 indicates paper as a recording medium, and 24 a platen that supports the recording medium. When printing was performed using this printer, no ejection failure occurred even after being left for a long time, and recorded images with excellent print quality could be obtained.

[Function] In the present invention, by providing a fluid resistor having an opening and a heating means separate from the ejection energy generating means behind the resistor, the flying speed of the droplet can be increased. became more stable, the error in the landing position on the recording medium became smaller, and the recording quality improved. Furthermore, since ejection energy can now be effectively applied to the recording liquid, stable ejection can be performed even after being left for a long time, and the reliability of the inkjet recording head can be improved.

[Effects of the Invention] As described above, the present invention makes it possible to provide a novel inkjet recording head that is excellent in high-speed droplet ejection response and ejection stability.

[Brief explanation of drawings]

1 and 2 are diagrams illustrating a schematic configuration of an example of an inkjet recording head of the present invention, respectively, in which FIG. 1 is a perspective view of the head, FIG. 2 is a partial plan view of the head, and FIG. 3(a) to 3(d) are partial schematic views of the X-Y cross section of FIG. 2 shown over time to explain an example of the operation of the discharge energy generating means and the heating means, and FIG. 4(a) and (b) are respectively a partial plan view and a sectional view taken along line A-A of the substrate used in the inkjet recording head of the present invention, and FIG. 5 is a schematic explanatory diagram of another example of the inkjet recording head of the present invention. 6(a) and (b) are diagrams showing an example of the pulse signal pattern applied to the inkjet recording head of the present invention, FIG. 7 is a diagram showing an example of the growth curve of vapor bubbles by the heating means, and FIG. FIG. 1 is a diagram illustrating an example of an inkjet printer using an inkjet recording head of the present invention. 1; Substrate 101: Discharge energy generating means 102; Orifice 103; Nozzle 104; Fluid resistor 105; Heating means 106; Opening
1o7; Liquid chamber 108; Liquid supply port

Claims (1)

[Claims] (1) In a liquid jet recording head comprising a liquid ejection port for ejecting a recording liquid and an ejection energy generation means for supplying ejection energy to the recording liquid, the ejection energy generation means is provided on the opposite side of the liquid ejection port. 1. A liquid jet recording head comprising a heating means separate from the ejection energy generating means and a fluid resistor having an opening provided between the ejection energy generating means and the heating means.