JP2698413B2 - Liquid jet recording method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid jet recording method, more specifically, a conventionally known drop-on-demand type ink jet using an electromechanical transducer such as a bubble jet ink jet or PZT, The present invention relates to a driving condition for forming an optimum ink droplet and a configuration for obtaining the most stable image quality when the formed ink droplet adheres to the paper surface to form an image.

2. Description of the Related Art Non-impact recording methods have recently attracted attention in that noise generation 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, for example, a method disclosed in US Pat. No. 3,060,429 (Tele type method), 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, an electric field is applied between the nozzle and the accelerating electrode to discharge a uniformly charged recording liquid from the droplet nozzle, and the discharged droplet of the recording liquid according to the recording signal. In this case, the recording is performed by causing the droplets to fly between the xy deflection electrodes configured to be electrically controllable and selectively attaching 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 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 deflecting 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 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.

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 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 is suitable for high-speed recording because the recording head can be multi-nozzle, but it is complicated in structure, and it is difficult and difficult to electrically control the recording liquid droplets. There is a problem that it is likely to occur.

The third method has a feature that an image excellent in gradation is 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 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, Japanese Patent Application Laid-Open No. 48-9622 (corresponding to the above-mentioned US Pat. No. 3,747,120) describes, as a modification, the use of thermal energy instead of the mechanical vibration energy by means such as the piezo-vibration 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. However, there is no suggestion as to how to heat the liquid when the liquid is continuously and repeatedly discharged. 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 It is not suitable for repeated 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.

Further, JP-A-61-274949 discloses that the recording liquid is discharged from an orifice provided in the recording head by means for pressurizing the recording liquid in the recording head according to a recording signal.
When dots are formed on a recording medium by using the discharged recording liquid and recording is performed, the recording liquid discharged from the opening forms droplets from the opening and records the leading end of the liquid column. The recording head forms dots on the recording medium by reaching the recording medium, and a part of the liquid column of the recording liquid being ejected from the opening, which is not used for forming the dots, is separated from the opening. Although a recording method in which the paper and the head are moved relative to each other has been proposed, the invention disclosed in Japanese Patent Application Laid-Open No.
If the liquid droplets are adhered to the paper so as not to be properly separated into droplets, a "tailing" phenomenon occurs on the paper surface, and there is a disadvantage that the image quality is significantly deteriorated.

Object of the Invention The present invention has been made in view of the above-mentioned circumstances, and has been made with the object of obtaining stable ink droplet ejection and high-quality printing quality.

In order to achieve the above object, the present invention provides a liquid jet recording method in which a liquid chamber and a multi-orifice are provided on a substrate, and a recording liquid is ejected from the multi-orifice as droplets, flies, and adheres to a recording surface. The recording surface is a liquid ejection recording method in which the recording liquid is moved relative to a multi-orifice surface, and the recording liquid is ejected from the multi-orifice to form a liquid column, and the liquid column forms the multi-orifice surface. The length of the liquid column at the time of cutting is 1 (mm), the driving frequency at the time of continuous ejection is f (kHz), and the velocity of the droplet formed at that time at the position of the recording surface is V ( m /
s), when the driving frequency is in the range of 0.5 kHz to 15 kHz, And the distance L (mm) from the multi-orifice to the recording surface satisfies 2l ≦ L ≦ 20l. Hereinafter, a description will be given based on an example of the present invention.

FIG. 1 is a diagram showing a configuration of a main part for describing an embodiment of the present invention, and FIG. 2 is a diagram showing a state in which ink droplets are continuously ejected. Liquid column) is the length (unit mm) when cutting from the discharge port surface, and this length l is
It can be changed depending on ink physical properties (viscosity, surface tension), ink temperature, applied energy (for example, pulse voltage, pulse width, pulse waveform) and the like.

The distance l ₀ between ink droplets is expressed as V / f, where Vm / s is the ink droplet speed (this is the speed at the paper surface position) when ejecting continuously at a frequency f (k Hz). .
The present inventor obtains uniform and stable ink droplets through experiments of forming uniform ink droplets of a bubble jet type ink jet and a normal drop-on-demand type ink jet (in this case, the ink droplets are scattered in a mist form or are accompanied by satellite droplets). Do not insert such ink drops.) It was found that it was necessary to satisfy a certain relationship. If this condition is not satisfied, in addition to the above-described defects such as mist or satellite, when continuous high-speed ejection is performed, the ink droplets are merged, or they are not completely separated. However, by satisfying the above inequality, uniform ink droplets can be formed. Next, high-quality recording on paper will be described.

When ink droplets are repeatedly ejected, at first glance, it appears that all the ink droplets are ejected and fly with the same kinetic energy. However, due to changes in environmental conditions, or changes in the state of wetting of the discharge ports, or, in particular, for bubble jets, changes in the discharge conditions due to changes in the ink temperature cause each ink droplet to necessarily have the same movement. I don't have energy. This is markedly different when multi-orifices are used. However, the distance L between the paper surface and the head is
(Mm) is constant, so a fast ink drop arrives quickly on the paper and a slow ink drop arrives slowly. However, in ink-jet printing, since the paper and the head are moving relative to each other, variations in the time for the ink droplets to reach the paper surface mean that pixels are not immediately formed at desired positions on the paper surface.

FIG. 1 is a diagram showing a positional relationship between recording paper and a head in the case of a bubble jet type recording head.
The recording liquid 3 introduced into the inside instantaneously changes its state in accordance with the energized heat generation of the electric / thermal converter 4 attached to the liquid chamber 2. The conversion element 4, the electrodes 51 _to which is connected thereto
By ON-OFF of energization through 5 ₂ is intended to generate pulse thermally.

Due to the change in the state of the recording liquid 3, an acting force is applied to the liquid 3 on the orifice 6 side.
Is ejected from the orifice 6 as a droplet 7 and flies, and adheres to a recording member 10 such as paper to perform recording.

The electric heat exchanger 4 is provided on the substrate 8, a voltage based on the power supply 9 is applied according to the recording signal, heat is generated according to the input signal, and the recording corresponding to the input signal flies and adheres to the recording member 10. Done.

In order to satisfy the above-mentioned relational expression (1) and satisfy the allowable limit capable of maintaining good image quality through experiments, L in the figure is expressed as follows: 2l ≦ L ≦ 20l ... ……… (2) was found to be necessary.

If this is not satisfied, for example, when L <2l, ink tailing may occur on the paper. Also, 20l
In the case of <L, as described above, the influence of the speed variation of the ink droplets becomes large due to the conditions (temperature, etc.) and the variations for each orifice, and it is impossible to maintain a highly accurate pixel position.

Table 1 below shows an example of the result of experimentally examining the relationship between the frequency f KHz, the distance 1 between ink droplets, and the ink discharge performance when the ink droplet speed is continuously discharged at the ink droplet speed Vm / s. Show.

Than this, It is understood that it is necessary to satisfy the following condition in order to maintain good ink ejection performance.

Next, Table 2 shows one example of the result of substantially examining the relationship between the distance L to the paper surface, the distance 1 between ink droplets, and the image quality. At this time, an experiment was performed at f = 3 KHz, and V was 5.6 m
/ s (actual value).

This shows that it is necessary to satisfy 2l ≦ L ≦ 20l in order to obtain high image quality.

In the above, a bubble jet type inkjet printer has been described as an example. However, the present invention is not limited to a bubble type inkjet printer, and is applicable to a normal drop-on-demand type inkjet printer. is there.

Effects As is clear from the above description, according to the present invention, stable ejection performance can be obtained, a highly accurate pixel position can be obtained on the paper surface, and high image quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between recording paper and a head for explaining one embodiment of the present invention, and FIG. 2 is a diagram showing a state in which ink droplets are continuously ejected. 1 ...... inlet tube, 2 ...... liquid chamber, 3 ...... recording liquid, 4 ...... electrothermal exchanger, 5 _1, 5 ₂ ...... electrode, 6 ...... orifice, 7 ...
... droplets, 8 ... substrates, 9 ... power supplies, 10 ... recording paper.

Claims (1)

(57) [Claims] 1. A liquid jet recording method in which a liquid chamber and a multi-orifice are provided on a substrate, and a recording liquid is ejected from the multi-orifice as droplets, flies, and adheres to a recording surface. Is a liquid jet recording method that makes a relative motion with a multi-orifice surface, wherein the recording liquid is ejected from the multi-orifice to form a liquid column, and the liquid column when the liquid column is cut from the multi-orifice surface. When the length of the liquid droplet is 1 (mm), the driving frequency during continuous ejection is f (kHz), and the velocity of the droplet formed at the position of the recording surface is V (m / s), The drive frequency is driven in a range from 0.5 kHz to 15 kHz, A liquid ejecting recording method, wherein the following relationship is satisfied, and a distance L (mm) from the multi-orifice to the recording surface satisfies 2l ≦ L ≦ 20l.