JP2716722B2 - Liquid jet recording head - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid jet recording head, and more particularly, to a bubble jet type ink jet recording head.

2. Description of the Related Art Non-impact recording methods have recently attracted attention in that the generation of noise during recording is extremely small to a negligible level. Among them, the so-called ink jet recording method, which can perform high-speed recording and can perform recording on so-called plain paper without requiring a special fixing process, is an extremely powerful recording method. Some have been proposed and commercialized with improvements, while others are still being put to practical use.

In such an ink jet recording method, recording is performed by flying droplets of a recording liquid called so-called ink and attaching the droplets to a recording member. The control method for controlling the flying direction of the generated recording liquid droplet is roughly classified into several types.

First, the first system is, for example, a system disclosed in US Pat. No. 3,060,429 (Tele type system), in which droplets of a recording liquid are generated by electrostatic attraction, and the generated droplets of the recording liquid are converted according to a recording signal. The electric field is controlled, and recording is performed by selectively adhering the recording liquid droplets onto the recording member.

More specifically, in more detail, an electric field is applied between the nozzle and the accelerating electrode to discharge a uniformly charged droplet of the recording liquid from the nozzle, and the discharged droplet of the recording liquid is converted into a recording signal. In accordance with this, recording is performed by causing the droplets to fly between the xy deflection electrodes configured so as to be electrically controllable and selectively adhering small droplets onto the recording member by a change in the intensity of the electric field.

The second method is a method (Sweet method) disclosed in, for example, US Pat. No. 3,596,275, US Pat. No. 3,298,030, in which a droplet of a recording liquid whose charge amount is controlled by a continuous vibration generation method is generated, and the generated charging is performed. The recording is performed on the recording member by causing the controlled amount of the droplet to fly between the deflection electrodes to which a uniform electric field is applied.

More specifically, a charging electrode configured so that a recording signal is applied in front of an orifice (ejection port) of a nozzle, which is a part of a recording head provided with a piezoelectric vibrating element, is separated by a predetermined distance. The piezoelectric vibrating element is mechanically vibrated by applying an electric signal of a constant frequency to the piezoelectric vibrating element, and the liquid droplet is discharged from the discharge port. At this time, a charge is electrostatically induced in the recording liquid droplet discharged by the charging electrode, and the droplet is charged with a charge amount according to the recording signal. When the droplet of the recording liquid whose charge amount is controlled flies between the deflection electrodes to which a constant electric field is uniformly applied, the droplet is deflected according to the added charge amount and carries a recording signal. Only the recording material can be deposited on the recording member.

The third method is, for example, a method (Hertz method) disclosed in U.S. Pat. No. 3,341,152, in which an electric field is applied between a nozzle and a ring-shaped charging electrode to generate and atomize small droplets of a recording liquid by a continuous vibration generation method. This is the method of recording. That is, in this method, the atomization state of the small droplet is controlled by modulating the electric field intensity applied between the nozzle and the charging electrode in accordance with the recording signal, and the image is recorded with the gradation of the recorded image.

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

That is, in each of the three methods, the droplet of the recording liquid discharged from the nozzle is electrically controlled during the flight, and the droplet carrying the recording signal is selectively attached to the recording member. On the other hand, according to the Stemme method, recording is performed by ejecting a small droplet of recording liquid from an ejection port in accordance with a recording signal.

In other words, in the Stemme method, an electric recording signal is applied to a piezoelectric vibrating element attached to a recording head having a discharge port for discharging a recording liquid, and this electric recording signal is applied to mechanical vibration of the piezoelectric vibrating element. Alternatively, the recording is performed by ejecting and ejecting a small droplet of the recording liquid from the ejection port in accordance with the mechanical vibration and attaching the droplet to the recording member.

Each of these four conventional methods has its own features, but on the other hand, there are points that can be solved.

That is, in the first to third methods, the direct energy of the generation of the droplet of the recording liquid is electric energy,
Droplet deflection control is also electric field control. Therefore, the first method is simple in structure, but requires a high voltage to generate small droplets, and is not suitable for high-speed printing because it is difficult to use a multi-nozzle recording head.

The second method enables multi-nozzle recording heads and is suitable for high-speed recording. However, the method is complicated in structure, and the electrical control of small droplets of recording liquid is difficult and difficult. Are liable to occur.

The third method has a feature that an image having excellent gradation can be recorded by atomizing a recording liquid droplet, but on the other hand, it is difficult to control the atomization state, and fogging occurs in the recorded image. In addition, there are problems such as the fact that it is difficult to form a multi-nozzle recording dot, and it is not suitable for high-speed recording.

The fourth scheme has relatively many advantages over the first to third schemes. That is, in order to perform recording by discharging the recording liquid from the discharge port of the nozzle on demand (on-demand), it is simple in terms of the configuration. It is not necessary to collect small droplets that are not required for recording an image, and there is no need to use a conductive recording liquid as in the first and second methods, and the recording liquid material Has a great advantage such as a large degree of freedom. However, on the other hand, it is difficult to form a multi-nozzle recording head because there are problems in processing the recording head and it is extremely difficult to reduce the size of the piezoelectric vibrating element having a desired resonance number. However, since the recording liquid droplets are ejected and fly by the mechanical energy of mechanical vibration of the piezo-vibration element, it is not suitable for high-speed recording.

Furthermore, JP-A-48-6922 (corresponding to US Pat. No. 3,747,120) describes, as a modification, the use of thermal energy instead of the use of mechanical vibration energy by means such as the above-described piezo vibrating element. Have been.

That is, the above-mentioned publication describes that a heating coil that directly heats a liquid in order to generate a vapor that causes a pressure increase is used as a pressure increasing means instead of the piezoelectric vibrating element.

However, the above publication discloses that a heating coil serving as a pressure increasing means is energized to directly evaporate the liquid ink in a bag-shaped ink chamber (liquid chamber) having only one opening through which the liquid ink can enter and exit. It is only described that when performing continuous repetitive liquid discharge, how to heat should be
There is no suggestion. In addition, since the position where the heating coil is provided is provided at the deepest part of the bag-shaped liquid chamber far from the supply path of the liquid ink, in addition to being complicated in terms of the head structure, continuous For repeated use,
It is not suitable.

Moreover, according to the technical contents described in the above-mentioned publication, it is not possible to quickly form a preparation state for the next liquid discharge after performing the liquid discharge with the generated heat which is practically important.

As described above, the conventional method has advantages and disadvantages in terms of configuration, high-speed recording, multi-nozzle recording head, generation of satellite dots and occurrence of fogging of a recorded image, etc. There was a restriction that only the application was possible.

Japanese Patent Application Laid-Open No. 55-132259 discloses that a steep state change is caused in a liquid by the action force of thermal energy, and the liquid is caused to fly as droplets by an action force based on the change in state, and is applied to a recording surface. In a liquid jet recording apparatus for performing recording by adhering, a discharge orifice for ejecting liquid in a predetermined direction is communicated with the vomiting orifice at a flow path having a discharge orifice at the end thereof, and the acting force generated there is directed to the discharge orifice direction. The heat acting portion arranged so as to be effectively transmitted is constituted by at least two independently-inputable electric-to-heat converters, and each of these electric-to-heat converters includes It describes that gradation recording is performed by appropriately shifting the input timing. Thus, the above-mentioned JP-A-55-13
In the invention described in Japanese Patent No. 2259, two (or more) signals are input twice (or more) even if the timing is shifted, so that two (or more) bubbles are generated with a time lag. The time required for the ink column to grow from the orifice to discharge to recover the mechanical varnish (ink replenishment from the supply side) becomes longer due to the occurrence, growth, and contraction, resulting in a decrease in printing speed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and particularly, it is possible to perform gradation recording in a bubble jet type ink jet recording apparatus,
It is an object of the present invention to provide a new liquid knitting recording head capable of performing gradation recording without slowing down unlike the apparatus described in 132259.

Configuration In order to achieve the above object, the present invention provides a thermal energy operating section that accommodates a recording liquid to be introduced, generates bubbles in the recording liquid by heat, and generates an action force accompanying an increase in the volume of the bubbles. And an orifice communicating with the flow path to discharge the recording liquid as droplets by the action force, and an orifice communicating with the flow path to introduce the recording liquid into the flow path. A liquid chamber and a means for introducing the recording liquid into the liquid chamber, wherein the thermal energy action section comprises two heating elements which can be driven independently, and the two heating elements correspond to the flow elements. In the direction of the road, the orifices are arranged in a distance relationship with each other, and the heating element farther from the orifice receives one pulse of electric energy corresponding to the recording information to form one recording droplet. One or more pulses of electric energy having a pulse width smaller than the pulse width of the electric energy applied to the distant heating element are applied to the heating element closer to the heat source, and a recording droplet formed by the distant heating element. One or more smaller recording droplets are formed, and two or more of the plurality of recording droplets are formed.
It is characterized in that pixels are formed at approximately the same position on the surface to be recorded or coalesced during the flight of more than one recording droplet, and the size of the pixel changes according to the number of recording droplets.
Hereinafter, a description will be given based on examples of the present invention.

FIG. 3 is a view for explaining the operation of a bubble jet head as an example of an ink jet head to which the present invention is applied, FIG. 4 is a perspective view showing an example of a bubble jet head, and FIG. FIG. 4 is a perspective view when disassembled into a lid substrate (FIG. 5 (a)) and a heating element substrate (FIG. 5 (b)) which constitute the head shown in FIG. 4, and FIG. FIG. 2 is a perspective view of the lid substrate shown from the back side, in which 1 is a lid substrate;
Is a heating element substrate, 3 is a recording liquid inlet, 4 is an orifice,
5 is a flow path, 6 is a region for forming a liquid chamber, 7 is an individual (independent) electrode, 8 is a common electric conduction, 9 is a heating element (heater),
10 is a recording liquid (ink), 11 is a bubble, and 12 is a flying ink droplet. The present invention is applied to such a bubble jet type liquid jet recording head.

First, ink ejection by bubble jet will be described with reference to FIG. 3. (a) is a steady state, and the surface tension of the ink 10 and the external pressure are in an equilibrium state at the orifice surface.

6B shows a state in which the heater 9 is heated until the surface temperature of the heater 9 rises rapidly and a boiling phenomenon occurs in the adjacent ink layer, and minute bubbles 11 are scattered.

FIG. 3C shows a state in which the adjacent ink layer rapidly heated on the entire surface of the heater 9 is instantaneously vaporized to form a boiling film, and the bubbles 11 grow. At this time, the pressure in the nozzle rises by an amount corresponding to the growth of the bubble, the balance with the external pressure on the orifice surface is lost, and the ink column starts to grow from the orifice.

(D) is a state in which the bubbles have grown to the maximum, and the ink 10 corresponding to the volume of the bubbles is pushed out from the orifice surface. At this time, no current is flowing through the heater 9, and the surface temperature of the heater 9 is decreasing. The maximum value of the volume of the bubble 11 is slightly delayed from the timing of applying the electric pulse.

(E) shows a state in which the bubble 11 is cooled by ink or the like and starts to contract. At the front end of the ink column, the ink moves forward while maintaining the pushed speed, and at the rear end, the ink flows backward from the orifice surface into the nozzle due to a decrease in the nozzle internal pressure due to the contraction of the bubble, and the ink column is constricted. .

(F) is a state in which the bubble 11 is further contracted, the ink comes into contact with the heater surface, and the heater surface is more rapidly cooled. At the orifice surface, the external pressure is higher than the internal pressure of the nozzle, so that the meniscus largely enters the nozzle. The tip of the ink column becomes a droplet and moves in the direction of the recording paper.
Flying at a speed of 10m / sec.

(G) is a process in which the ink is supplied (refilled) to the orifice again by capillary action and returns to the state of (a).
The bubbles have completely disappeared.

The present invention is applied to a bubble jet type ink jet recording apparatus that operates as described above. FIG. 1 is a configuration diagram of a main part (a heating element and an electrode portion) of a bubble jet type ink jet head according to the present invention. FIG. 2 shows the state of ink droplets and pixels formed by the present invention.

In FIG. 1, (a) is a plan view of an orifice portion showing an example of a heating element and an electrode pattern used in the present invention, and (b) is a sectional view of the orifice portion (however, electrodes and protective layers are omitted. In the figure, 9a is a heating element near the orifice, 9b is a heating element far from the orifice, 7a is a control electrode of the heating element 9a, 7b is a control electrode of the heating element 9b, and 8 is a common electrode. , There are two heating elements for one orifice, which can be driven independently.

FIG. 2 is a diagram for explaining the operation principle of the present invention.
In the present invention, the heating element 9b far from the orifice 4 operates as described in FIG. In other words, as shown in FIG. 2A, the heating element 9b is driven by the pulse 14, but the pixel formed by the heating element 9b is a large pixel, and almost always the same if the applied energy is the same. It is size. On the other hand, in the present invention, there is further a heating element 9a close to the orifice, and as shown in FIG. 2 (b), one or more pulse energies are applied in small intervals, and one or more Of small ink drops (12 ₁ to 1
₂₄ ) is formed. In this case, the applied pulse energy is smaller than in the case of FIG. 2 (a), and therefore the formed ink droplet is also smaller. In addition, since this small pulse energy is applied with one or more pulses at a high frequency (several to several tens KHz), as shown in FIG. 2 (b), fine ink droplets are continuously ejected and fly to the paper. Attach to form pixels. Since these minute ink droplets adhere to paper in a short time, one pixel is formed by a plurality of ink droplets. In addition, during flight, they may unite and adhere to paper. That is, the pixel size is changed according to the number of ink droplets, and gradation recording is performed. According to the present invention, a heating element far from the orifice is driven in accordance with image information to perform recording with a large pixel (FIG. 2A), or a heating element near the orifice is driven to perform fine gradation recording. (FIG. 2 (b)).

Effects As is apparent from the above description, according to the present invention, a heating element farther from the orifice is used to obtain a substantially constant dot diameter, binary recording is used, and a heating element closer to the orifice is used. Thus, a plurality of ink droplets are overprinted on the same location to perform multi-value recording (gradation recording), so that binary recording and gradation recording can be performed efficiently (of course,
Although binary recording can be performed using this multi-value recording,
A plurality of droplets must be ejected for one dot, and the recording speed is slow and inefficient).

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part for explaining an embodiment of the present invention, FIG. 2 is a diagram for explaining an operation of the present invention, and FIG.
FIG. 4 is a diagram for explaining the operation of a bubble jet head as an example of an ink jet head to which the present invention is applied, FIG. 4 is a perspective view showing an example of a bubble jet head, and FIG. FIG. 6 is a view of the lid substrate viewed from the back side. 7, 7a, 7b ... control electrode, 8 ... common electrode, 9, 9a, 9b ... heating resistor, 10 ... ink, 11 ... bubble, 12 ... flying ink droplet, 13 ... pixel, 14 ...... Driving pulse.

Claims (1)

(57) [Claims] 1. A storage device for accommodating a recording liquid to be introduced,
A flow path provided with a thermal energy action portion for generating bubbles in the recording liquid by heat and generating an action force in accordance with an increase in the volume of the bubbles; and connecting the recording liquid by the action force to communicate with the flow path. A liquid jet recording head comprising: an orifice for discharging droplets; a liquid chamber for communicating with the flow path to introduce the recording liquid into the flow path; and a means for introducing the recording liquid into the liquid chamber. , The heat energy action section is composed of two heating elements that can be independently driven,
The two heating elements are arranged in a perspective relationship with the orifice in the direction of the flow path, and the heating element farther from the orifice is applied with one pulse of electric energy corresponding to recording information to form one recording droplet. The heating element closer to the orifice has an electric energy having a pulse width smaller than the pulse width of the electric energy applied to the heating element farther away.
A plurality of pulses are applied to form one to a plurality of recording droplets smaller than a recording droplet formed by a distant heating element, and two or more recording droplets among the plurality of recording droplets are flying A liquid ejecting recording head, wherein pixels are formed at substantially the same position on the recording surface, and the size of the pixel changes according to the number of recording droplets.