JP3061188B2 - Liquid jet recording device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid jet recording apparatus, and more particularly, to a liquid jet recording apparatus.
The present invention relates to a configuration of a recording head of a bubble jet printer.

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 method is disclosed in, for example, US Pat. No. 3,060,429 (Tele type method),
Recording liquid droplets are generated by electrostatic attraction, and the generated recording liquid droplets are subjected to electric field control according to a recording signal, and recording is performed by selectively adhering the recording liquid droplets onto a recording member. It is.

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 described, for example, in US Pat. No. 3,596,275,
The method disclosed in US Pat. No. 3,298,030 and the like (S
Weet method) in which droplets of the recording liquid with a controlled charge amount are generated by a continuous vibration generation method, and the generated droplets with a controlled charge amount are subjected to a uniform electric field. The recording is performed on the recording member by flying between the deflection electrodes.

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 a droplet of the recording liquid 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 a method (Hertz method) disclosed in, for example, US Pat. No. 3,416,153, in which an electric field is applied between a nozzle and a ring-shaped charging electrode, and a continuous vibration generation method is used. This is a method in which small droplets are generated and atomized for 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 system is, for example, a system (Stemme system) disclosed in US Pat. No. 3,747,120, and this system is fundamentally different from the above three systems 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 discharging small droplets of a recording liquid by an ejection port in accordance with a recording signal.

That is, in the Stemme method, the piezoelectric vibrating element attached to the recording head having the ejection port for ejecting the recording liquid includes:
Applying an electrical recording signal, converting the electrical recording signal into mechanical vibration of a piezo-vibrating element, and ejecting a droplet of the recording liquid from the ejection port in accordance with the mechanical vibration to cause the droplet to fly and adhere to the recording member. Is to record.

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 configuration,
Since a high voltage is required to generate small droplets, and it is difficult to form a multi-nozzle recording head, it is not suitable for high-speed recording.

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 use a multi-nozzle recording head, and it is not suitable for high-speed recording.

The fourth method has relatively many advantages compared to the first to third methods. That is, in order to perform recording by discharging the recording liquid from the discharge port of the nozzle on demand (on-demand), the droplets ejected and flying in the first to third manners include: There is no need to collect small droplets that did not require image recording, and there is no need to use a conductive recording liquid, as in the first and second methods, and there is no need to use a recording liquid material. It has great advantages such as a large degree. 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.

Further, Japanese Patent Application Laid-Open No. 48-9622 (the aforementioned U.S. Pat.
No. 120) describes, as a modification, the use of thermal energy instead of the mechanical vibration energy by means such as the piezo-vibration element.

That is, the above-mentioned publication describes a so-called bubble jet liquid jet recording apparatus which uses a heating coil for directly heating a liquid as a pressure increasing means instead of a piezo vibrating element in order to generate vapor which causes a pressure increase. I have.

However, according to the above publication, a heating coil serving as a pressure increasing unit is energized to directly heat the liquid ink in a bag-shaped ink chamber (liquid) having only one port through which the liquid ink can enter and exit, to vaporize the liquid ink. However, there is no suggestion as to how to perform heating in the case of performing continuous and repeated liquid ejection. 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, it is continuously repeated at high speed. Unsuitable for use.

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.

In Japanese Patent Application Laid-Open No. 57-87958, the size of droplets discharged from each orifice is made uniform by changing the distance from the orifice to the thermal energy action surface, but it is not necessarily stable by changing the distance. However, it is not always possible to obtain a droplet discharge state, and there is a disadvantage that the discharged droplets become mist-like or the flying speed is significantly reduced depending on the distance.

In Japanese Patent Application Laid-Open No. 57-87960, the size of droplets discharged from individual orifices is made uniform by changing the area of the heat energy acting surface. Similarly, a stable liquid ejection state is not always obtained.

In the above-mentioned JP-A-57-87958 and JP-A-57-87960,
As described in the specification, all of them aim at solving the problems that can occur when the discharge orifice pitch is 125 μm, that is, about 8 lines / mm. Applicable. However, there is no specific description when the arrangement of the ejection orifices is arranged at 16 lines / mm or more in order to aim at higher definition image quality, and it is not necessarily a satisfactory condition when aiming at a copier or the like. .

In the case of a multi-nozzle arrayed in an array of 16 nozzles / mm or more, since the adjacent nozzles are very close, the ink droplets or ink columns ejected from multiple adjacent nozzles should be ejected almost simultaneously. In such cases, merging can often occur. This is because the size of the ejected ink droplets is generally larger than the orifice diameter. Another reason is that the conditions for ejecting the ink droplets are not always favorable (unstable ejection conditions,
For example, it occurs in the case of splash or asymmetric ejection of ink droplets (pillars). Asymmetrical ejection of ink droplets (pillars) may be caused by processing problems such as minute chips in the nozzle portion, but also occurs when the ejection conditions are unstable.

Therefore, in a multi-inkjet device having a discharge orifice pitch of about 125 μm, which is not so high, there are many problems to be solved in order to achieve a high density even if it is not a problem.

In addition, higher speed conditions (for example, a maximum response frequency of 4 kHz
In the case of driving in (above), there is no specific description of what to do.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and proposes optimal conditions for stable ejection of ink droplets. It is an object of the present invention to provide a liquid jet recording apparatus for improving the frequency (continuously ejecting ink droplets) and obtaining high-speed recording and high image quality.

Another object of the present invention is to improve the ejection performance by proposing optimal conditions for stable ejection of ink droplets of a multi-nozzle head capable of performing extremely high-definition printing with a heating element width of 19 μm or less. It is to plan.

Still another object of the present invention is to operate at higher speed (for example,
An object of the present invention is to improve the ejection performance by proposing optimum conditions for stable ejection of ink droplets of a multi-nozzle type head (above 4 kHz).

Configuration In order to achieve the above object, the present invention provides a thermal energy acting section that accommodates a recording liquid to be introduced, generates bubbles in the recording liquid by heat, and generates an action force associated with 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. In the liquid jet recording apparatus including the liquid chamber and the means for introducing the recording liquid into the liquid chamber, the energy action section has an area S of 39.
In the range of 7.5 to 1387 μm ^2, the energy acting surface has a length in the width direction of 19 μm or less with respect to the flow direction, and
When the array density is 16 lines / mm or more, and the distance from the orifice side tip of the thermal energy action surface to the orifice is D, And the maximum response frequency of recording droplet ejection is 4k
It is characterized in that the speed of the droplets is set to be higher than 3 Hz and the speed of the droplets is set to 3 to 10 m / s.

First, the principle of ink ejection by a bubble jet will be described with reference to FIG. 4. (a) is a steady state, in which the surface tension of the ink 30 and the external pressure are in an equilibrium state at the orifice surface.

3B shows a state in which the heater 29 is heated until the surface temperature of the heater 29 sharply rises and the adjacent ink layer is heated until a boiling phenomenon occurs, and minute bubbles 31 are scattered.

(C) shows a state in which the adjacent ink layer, which 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 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 bubble has grown to the maximum, and the 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 applying the electric pulse.

(E) shows a state where the bubble 31 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 31 further contracts, the ink comes into contact with the heater surface, and the heater surface is cooled more rapidly. 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. 32 is a flying ink droplet.

FIG. 5 is a perspective view of a bubble jet recording head, and FIG.
The figure is an exploded configuration diagram of the recording head, (a) is a lid substrate,
(B) is a view showing a heating element substrate, and FIG. 7 is FIG. 6 (a).
FIG. 4 is a rear view of the lid substrate shown in FIG. 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, and 29 is a heating element (heater).

FIG. 8 is a partial view of a bubble jet liquid jet recording head, (a) is a front partial view as viewed from the orifice side,
(B) is a partial cutaway view of the dashed line XX in (a).

In the recording head 41 shown in these figures, a predetermined number of grooves having a predetermined linear density and a predetermined width and depth are provided on a substrate 43 provided with an electrothermal transducer 42 on the surface thereof. Grooved plate
By joining the substrate 44 so as to cover the substrate 43, a liquid ejection portion 46 including an orifice 45 for flying a liquid is formed.

The liquid discharge unit 46 includes a heat acting unit 47 in which thermal energy generated by the orifice 45 and the electrothermal converter 42 acts on the liquid to generate bubbles, and causes a sudden state change due to expansion and contraction of the volume. And

The heat acting portion 47 is located above the heat generating portion 48 of the electrothermal converter 42, and has a heat acting surface 49 serving as a surface of the heat generating portion 48 that comes into contact with the liquid, as its bottom surface. The heat generating section 48 includes a lower layer 50 provided on the base 43, a heating resistor layer 51 provided on the lower layer 50, and an upper layer 52 provided on the heating resistor layer 51.

On the surface of the heating resistance layer 51, electrodes 53 and 54 for supplying electricity to the layer 51 to generate heat are provided on the surface thereof.
A heat generating portion 48 is formed by a heat generating resistance layer between these electrodes.

The electrode 53 is an electrode common to the heat generating unit of each liquid discharging unit, and the electrode 54 is a selection electrode for selecting the heat generating unit of each liquid discharging unit to generate heat. It is provided along the flow path.

The upper layer 52 includes a heating resistor layer 51 and a liquid discharging portion 46 for chemically and physically protecting the heating resistor layer 51 from a liquid used.
And separate the electrodes 53,5 through the liquid.
It has a protective function of the heating resistor layer 51 for preventing short circuit between the four.

The upper layer 52 has the function as described above,
The heating resistance layer 51 is liquid-resistant, and the electrode 5
In the case where there is no need to electrically short-circuit the wires 3 and 54 at all, it is not always necessary to provide them, and the heat generating resistor 51 may be designed as an electrothermal converter having a structure in which the liquid immediately contacts the surface.

The lower layer 50 has a heat flow control function next, that is, at the time of discharging the droplets, the heat generated in the heat generating resistance layer 51 is closer to the heat acting portion 47 than to the substrate 43. The rate of conduction to the heater becomes as high as possible,
After the power to the power supply 51 is turned off, the heat in the heat application unit 47 and the heat generation unit 48 is quickly released to the substrate 43 side, and the liquid and the generated bubbles in the heat application unit 47 are rapidly cooled. Is provided.

 The above is described based on the embodiment of the present invention.

FIG. 1 is a diagram for explaining an embodiment of a recording head according to the present invention, and is a diagram showing a relationship between a thermal energy working surface and a distance D from the tip of the orifice side to the orifice. 45 _{1-45 3} orifice 49 _{1-49 4} thermal energy application surface 53 is a common electrode, 54 ₁ to 54 ₃ illustrates a selection electrode. The hatched portions in the figure indicate portions of the photosensitive dry film for forming the walls of the flow path. A represents the length in the width direction of the heat energy action surface with respect to the flow direction, and B represents the length of the heat energy action surface in the flow direction. In practice, a protective layer is often provided on the thermal energy working surface 49 and the electrodes 53 and 54 in order to prevent corrosion by the ink.

In the bubble jet technology, flying ink droplets are required to have no satellite droplets and to be discharged without flying in the form of mist. The present inventors have repeated the experiment and found that the optimum ejection can be obtained when the following conditions are satisfied in order to solve the above-mentioned problems.

In order to find such conditions, heads were prototyped by changing the lengths A and B of the heat energy action surface and the distance D to the orifice 45 in FIG. And observed.

The present invention determines the relationship between the area of the heat energy acting surface and the distance to the orifice as one of the factors that most influence the optimum condition as a factor for determining the optimum discharge condition. By driving the head, stable ejection of ink droplets can be obtained.

FIG. 2 is a view for explaining the structure of a means for generating bubbles using a heating resistor. In the drawing, reference numeral 61 denotes a heating resistor, 62 denotes an electrode, 63 denotes a protective layer, and 64 denotes a power supply device. as the material constituting the resistance 61, the useful, for example, a mixture of Tantaru SiO _2, tantalum nitride, nichrome, silver - palladium alloy, silicon semiconductor or hafnium,
Examples include borides of metals such as lanthanum, zirconium, titanium, tantalum, tungsten, molybdenum, niobium, chromium, and vanadium.

Among these materials constituting the heating resistor 61, metal borides can be mentioned as being particularly excellent, and among them, hafnium boride has the most excellent characteristics.
Next are zirconium boride, lanthanum boride, tantalum boride, vanadium boride, and niobium boride.

The heating resistor 61 can be formed using the above-mentioned materials by using a technique such as electron beam evaporation or sputtering. The film thickness of the heating resistor 61 is determined according to its area, material, shape and size of the heat acting portion, and furthermore, power consumption in an actual plane, so that the amount of heat generated per unit time is as desired. , But usually 0.001-5μ
m, preferably 0.01 to 1 μm.

As the material forming the electrode 62, many commonly used electrode materials are effectively used, and specifically,
For example, Al, Ag, Au, Pt, Cu and the like can be mentioned, and these are used to be provided at a predetermined position in a predetermined size, shape and thickness by a method such as vapor deposition.

The characteristics required for the protective layer 63, without preventing the heat generated by the heating resistor 61 from being effectively transmitted to the recording liquid,
This means that the heating resistor 61 is protected from the recording liquid. Useful materials for forming the protective layer 63 include, for example, silicon oxide, silicon nitride, magnesium oxide, aluminum oxide, tantalum oxide, zirconium oxide, and the like. Can be formed. Protective layer
The film thickness of 63 is usually 0.01 to 10 μm, preferably 0.1 to 5 μm.
m, optimally 0.1 to 3 μm.

FIG. 3 is a configuration diagram of a heat acting portion of the recording head according to the present invention.

101 is a Si substrate, 102 is a lower layer, 103 is a heating resistance layer, 104 is an electrode, 105 is a first protective layer, 106 is a second protective layer, 107 is a resin layer, and 108 is a heat acting surface.

After sputtering SiO ₂ as a lower layer 102 to a thickness of 5 μm on a Si substrate 101, using photolithography, etching, sputtering, etc., a heating resistance layer 103 of Ta ・ SiO ₂ of 400 mm and an electrode 104 Al as 5000
The desired shape was obtained with a thickness of Å.

Next, as the first protective layer 105, SiO ₂ was sputtered to a thickness of 5000 ° C.
i ₃ N ₄ was sputtered to a thickness of 5000 °, and a resin (resin) layer was patterned only where Al was laminated to form a heater board.

A photosensitive dry film is laminated on the heater board to form desired ink chamber and flow path walls. Next, it joins with a glass top plate via an adhesive layer. Discharge ports are formed by cutting the substrate with a slicer.

By such a method, a discharge element capable of performing very high-definition recording with a heating element width of 19 μm or less was manufactured, and the discharge state of the flying ink droplet when the repetition frequency was driven at 4.1 kHz was evaluated. . The results are shown in Table 1.

From the above results, it can be seen that, in the present invention, stable ejection of ink droplets can be easily obtained if the area of the heat energy acting surface and the distance to the orifice are selected under optimum conditions.

Note that the stable ejection of the ink droplets here means the speed of the ejected ink droplets, which is 3 to 10 m / s, and the adjacent ink droplets (or ink columns) do not coalesce, and the satellite (main ink liquid) This means that there is no unnecessary microdroplet attached to the drop and the mist is not ejected.

Effects As is clear from the above description, according to the present invention, in the liquid jet recording apparatus, by selecting the heat-acting surface of the liquid jet recording head under the above-mentioned optimum condition, stable ejection of ink droplets can be obtained, and the repetition frequency Improved characteristics, high-speed recording,
High image quality can be realized.

It should be noted that the above relational expression can be applied to a multi-inkjet having a medium printing density (about 180 dpi) like a conventional printer that prints with a 24 × 24 dot matrix, It is suitable to be applied to copiers that require high density and high-definition quality (for example, arrangement of 16 lines / mm or more).

Also, in order to form high-definition image quality like a copier, the pixel diameter is small, so the number of dots to be printed on the paper surface is inevitably large, and it takes time to form a single image from a simple viewpoint. It takes a lot. Therefore, it is preferable to drive the head at a high driving frequency, and in that sense, the above-described relational expression of the present invention should be applied to a head driven at a high frequency (for example, higher than 4 kHz).

[Brief description of the drawings]

FIG. 1 is a view for explaining an embodiment of a recording head according to the present invention, and is a view showing a relationship between a thermal energy working surface and a distance D from the tip of the orifice side to the orifice.
FIG. 3 is a configuration diagram of a bubble generating means using a heating resistor of a recording head portion, FIG. 3 is a configuration diagram of a heat acting portion of a head unit portion, and FIG. FIG. 5 is a perspective view of the recording head, FIG. 6 is an exploded view of the recording head, (a) shows a lid substrate, (b) shows a heating element substrate, and FIG. Fig. 8 is a rear view of the cover substrate of the recording head, Fig. 8 is a partial view of the recording head, (a) is a front partial view from the orifice side of the head, and (b) is an XX line of (a). It is a fragmentary view. 24 ... orifice, 25 ... flow path, 26 ... liquid chamber, 45 ... orifice, 47 ... thermal energy acting section, 49 ... thermal energy acting surface, 53 ... common electrode, 54 ... selection electrode.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Kimura 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-55-132275 (JP, A) JP-A Sho 56-46769 (JP, A)

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 air bubbles in the recording liquid by heat and generating an operation force accompanying an increase in the volume of the air bubbles; and A liquid jet recording apparatus comprising: an orifice for discharging droplets; a liquid chamber for communicating with the flow path and introducing the recording liquid into the flow path; and a unit for introducing the recording liquid into the liquid chamber. The heat energy action section has an area S in the range of 397.5 to 1387 μm ² , the heat energy action surface has a length in the width direction of 19 μm or less with respect to the flow direction, and has an array density of 16 lines / mm or more, and the distance from the orifice side tip of the heat energy action surface to the orifice is D, And the maximum response frequency of recording droplet ejection is 4k
A liquid jet recording apparatus wherein the speed of the liquid droplets is higher than 3 Hz and the speed of the liquid droplets is 3 to 10 m / s.