JPS62225388A - Image recording method and image recording apparatus - Google Patents

Abstract

PURPOSE:To make the high speed recording possible, by a method wherein liquid coloring agent is arranged, electric energy and thermal energy being applied thereto and the liquid coloring agent existing in the area to which both energies are applied, is flown. CONSTITUTION:If the voltage from a power source 22 is applied to between an electric field forming electrode 19 and an counter electrode 21, an uniform electric field is applied to the liquid coloring agent 13 near a discharge part 14. Current is selectively supplied to a heating resistor 16 under this state. Thereby, ink 13 is flown toward a recording component 12 only near the heating resistor 16 to which current is supplied and a round dot is recorded on that recording surface. Thus, ink is flown at a temperature to a extent of not generating extreme thermal deterioration in the ink, thermal resistor, etc. and by the electric field to an extent of not generating the leak or the like between the electrodes and the recording of a high speed and a high density can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to an image recording method and an image recording apparatus for recording an image on a recording member by jetting a liquid colorant such as ink.

"Prior Art" The so-called non-impact recording method is attracting attention as a method for converting image information converted into electrical signals into hard copies because it generates little noise during recording.

Among these, the inkjet method, which can use plain paper and can perform recording without special processing such as fixing, is considered to be an extremely useful recording method.

Conventionally, in the inkjet method that has been put into practical use, ink is stored in a sealed container, pressure pulses are applied to the container, and the ink is ejected from an ejection opening (orifice) of the container for recording. This method does not allow the ink ejection device to be miniaturized due to its operating mechanism, so it is necessary to mechanically scan the ink ejection device in order to print at the required image density. Therefore, this resulted in a decrease in recording speed.

On the other hand, several techniques have been proposed as methods for improving the drawbacks of the above-mentioned inkjet method and enabling high-speed recording.

One such method is a magnetic inkjet method, in which magnetic ink is placed near a magnetic electrode array, the ink is swelled by a magnetic field, and an ink discharge state corresponding to a pixel is formed, and the magnetic ink is ejected using an electrostatic field. This method allows high-speed recording because electronic scanning is possible, but it has the drawback that it is not easy to select the ink and it is difficult to print in color, which is an inherent characteristic of inkjet printing.

Separately, ink is placed in a slit-shaped ink reservoir parallel to the electrode array, and the ink is ejected through the recording paper according to the electric field pattern formed between the opposing electrodes and the electrode array. A method called planar inkjet method is also well known. This method eliminates the need for fine orifices to store ink and can improve ink clogging, but since the voltage applied to fly the ink is high, in order to prevent voltage leaks between adjacent and nearby electrodes, It is necessary to time-divisionally drive the electrode array, which has the disadvantage that high speed cannot be achieved.

A so-called thermal bubble jet method has also been proposed in which ink is ejected from an ejection port using thermal energy.

In this method, the ink is rapidly heated to cause film surface boiling, and the pressure increases due to the rapid formation of bubbles within the orifice, and the ink is ejected from the orifice.

However, since the temperature at which film surface boiling occurs is as high as 5 to 600°C, it has practical drawbacks such as thermal deterioration of the ink and thermal deterioration of the heating resistor protective layer provided as a heating means. had.

``Problems to be Solved by the Invention'' As mentioned above, the inkjet methods that have been developed so far have the difficulty of increasing the recording speed sufficiently, the use of special inks, and the problems with the drive. However, there are problems such as requiring a certain amount of ingenuity or causing thermal deterioration of the ink and heating means, and each method still has problems that must be solved in terms of practical use.

The present invention has been made in view of the above points, and it is an object of the present invention to provide an image recording method and an image recording apparatus that enable easy selection of ink and high-speed recording.

"Means for Solving the Problem" The image recording method of the present invention involves disposing a liquid coloring agent, applying electrical energy and thermal energy to the liquid coloring agent, and disposing the liquid colorant in an area where both of the above-mentioned energies are applied. It is characterized by making the colorant fly.

This involves applying the electrical energy by applying a uniform electric field to the liquid colorant, and further applying the thermal energy locally to the liquid colorant so that both energies are applied together. The liquid coloring agent is sprayed onto the area.

Alternatively, the thermal energy is applied by uniformly heating the liquid colorant, and the electrical energy is locally applied to the liquid colorant, so that both energies are applied together. The liquid coloring agent is sprayed onto the area.

Further, the image recording apparatus of the present invention includes a storage means for accommodating a liquid colorant, a thermal energy application means for heating the liquid colorant, an electric energy application means for applying an electric field to the liquid colorant, and an electric energy application means for applying an electric field to the liquid colorant. an applying means and a control means for driving the electric energy applying means to apply both the thermal energy and the electric energy to the liquid colorant; and applying the thermal energy and the electric energy together. and a recording member disposed in the flight path of the liquid colorant that flies as a result of the liquid coloring.

Here, for example, the thermal energy application means includes a plurality of heating elements, and the control means drives the electric energy application means to apply a uniform electric field to the liquid colorant, while the plurality of heating elements selectively driving the heating elements of the
The liquid colorant is locally heated and controlled so that the liquid colorant in the area where both of the energies are applied is caused to fly.

Alternatively, the electric energy applying means includes a plurality of electric field forming elements, and the control means drives the thermal energy applying means to uniformly heat the liquid colorant, while forming the plurality of electric fields. The element is selectively driven to locally apply an electric field to the liquid colorant, and the liquid colorant in the area where both of the energies are applied is controlled to fly.

"Operation" The image recording method of the present invention applies electric energy and thermal energy to a liquid colorant, and causes the liquid colorant in an area where both are applied to fly.

This method is realized, for example, in the following manner.

First, a uniform electric field is applied to the liquid colorant.

This alone does not cause the liquid colorant to fly. Here, thermal energy is locally applied to the liquid colorant. As a result, the liquid colorant in the area to which this thermal energy has been applied flies.

The same thing happens even if the liquid colorant is uniformly heated to a temperature that does not cause it to fly, and then an electric field is applied locally.

The following aspects can be cited as an apparatus for carrying out such a method.

For example, a plurality of heating elements are arranged in an array. Then, these heating elements are kept in contact with the liquid colorant. Then, a heating element located at a position corresponding to a recording pixel is selectively caused to generate heat, and a uniform electric field is applied. In this way, the liquid colorant is ejected toward the recording member. One pixel can be recorded in one flight.

By repeating this process, recording pixel rows in a line, and then scanning the recording member, an image can be recorded.

Similar recording can be performed even if the liquid colorant is heated to a uniform temperature and a plurality of electric field generating elements are installed to locally apply an electric field.

"Example" (Operating principle) The recording operation principle of the present invention will be explained with reference to FIG.

First, as shown in FIG. 1a, a liquid colorant 1 is placed between the base electrode 2 and the counter electrode 3. Liquid colorant 1 includes:
For example, an ink that is liquid at room temperature and whose formulation is adjusted to provide an appropriate electrical resistance is used. Below, liquid colorant l
The explanation will be continued by expressing simply as ink l. Base electrode 2
and the counter electrode 3 are both electrically conductive plates.

A predetermined voltage is applied between these electrodes 2.3 by a DC power supply 4. At this time, a certain electrostatic field is applied to the ink 1, and due to the electrostatic conduction effect, a Coulomb force given by the product of the induced charge generated here and the electrostatic field acts on the free surface of the ink.

This force causes the ink 1 to fly in the direction of arrow 5.

On the other hand, the surface tension of the ink, the interfacial tension, and the viscous resistance to the flying ink act as drag forces here. FIG. 1a shows a state in which this drag force is greater than the Coulomb force and the ink liquid level is kept horizontal.

Here, this ink 1 is locally heated. That is,
In the figure, the temperature TI of the region S1 is made higher than the temperature TO of the other regions (FIG. 1b). As a result, the ink liquid level rises in the region S1, as shown in FIG. That is, in this region Sl, the above-mentioned drag force decreases due to an increase in the temperature of the ink, and the action of Coulomb force locally increases. The electric field concentrates on the raised ink 1', and a strong Coulomb force acts on it. In this way, finally, as shown in FIG. 1C, a portion of the ink 1' in the region Sl grows into a columnar shape, breaks off, and flies toward the counter electrode 3.

This phenomenon can be caused even if the ink is not heated so rapidly as to bring about a phase change such as film boiling.

That is, electrical energy is applied to the ink by the electric field, and thermal energy is further applied by heating. The amounts of electrical energy and thermal energy to be applied are selected so that ink will fly only in the area where both energies are applied.

This enables practical control of the ink flying location and flying timing.

This principle could be demonstrated through the following experiment.

First, as shown in FIG. 1a, ink 1 is applied to the base electrode 2.
The voltage of the power supply 4 is gradually increased while keeping the temperature constant. When this voltage exceeds a certain voltage, ink columns 1' as shown in FIG. 1C grow randomly from the ink liquid surface toward the counter electrode 3.

This phenomenon has been described, for example, by J. R. Melcher (USA M.
, published by I, T, PRESS) rFIELD-COUP
LED 5URFACEWAVESJ (P61~
This can be interpreted as a growth phenomenon of unstable electrohydrodynamic waves, as described in P. 66).

In other words, when the Coulomb force acting upward and the drag force acting downward perpendicular to the ink liquid surface maintain a certain balance, certain perturbations (such as deformation of the liquid surface or local electric field) that may occur naturally occur. Coulomb force is concentrated locally due to non-uniformity). Therefore, the Coulomb force overcomes the drag force and the ink column grows.

In the present invention, for example, the electric field is selected to have an intensity insufficient for the growth of the disordered ink columns, and is applied to the ink. When the ink is heated in this state, the surface tension, viscosity, etc. of the ink in the heated area are reduced.

As a result, even in the electric field as described above, unstable surface waves are generated, and ink columns grow in that region.

If the ink thus ejected is guided to the surface of a recording member such as recording paper, one dot can be recorded. Furthermore, if these dots are arranged regularly, an image can be recorded.

(Embodiment of Recording Head) FIG. 2 is a longitudinal sectional view showing an embodiment of the recording head and its peripheral portion of an image recording apparatus embodying the present invention.

Here, a pair of wall members 1O111 are arranged with one edge thereof facing toward the recording member 12.

The recording member 12 is plain paper used for recording in general copying machines and the like.

The pair of wall members l0111 are arranged at a predetermined interval, and the liquid colorant 13 is accommodated between them. The wall member 10111 has a slit having a constant width in the direction perpendicular to the paper surface on one edge facing the recording member 12. In the present invention, this portion is referred to as the discharge section 14. The liquid colorant 13 forms a convex curved surface 13' in the discharge portion 14 due to its surface tension.

On the inner surface of one wall member 11, a large number of heating resistors 16 are arranged in an array in a direction perpendicular to the plane of the paper, and each of these has a common electrode 17 at one end and a lead electrode 18 at the other end. is connected.

Further, on the inner surface of the other wall member IO, an electric field forming electrode 19 is formed over almost the entire surface thereof.

Figure 3 shows a perspective view of its main parts.

The heating resistors 16 arranged in an array have, for example, a structure similar to that of a conventional thermal head commonly used for thermal recording.

In this embodiment, a so-called edge-type thermal head is used, and it is possible to perform recording at a recording density of 8 dots/mm on thermal recording paper with a coloring temperature of about 90°C.

When recording on this thermal paper, each heating resistor receives 0.5W/
Dot power is applied for 1 m5ec.

Furthermore, the distance between the pair of wall members 1O111 is 100 μm.
was selected.

Returning to FIG. 2 again, the distance l between the ejection section 14 and the recording member 12 was selected to be 200 μm. Further, a counter electrode 21 was provided on the back surface of the recording member 12, and a power source 22 for applying a predetermined voltage was connected between the counter electrode 21 and the electric field forming electrode 19. In this example, the electric field forming electrode 19 was grounded, and a voltage of +1500 V was applied to the counter electrode 21. These constitute an electric energy applying means.

Furthermore, on the electrodes 17.18 at both ends of the heating resistor 16,
The power supply 23 was connected. These constitute a thermal energy applying means.

A control means 24 is connected to the power supply #i 22 and 23 so that the application of energy is turned on and off according to the image signal of the image to be recorded. This control means 24 is constituted by a circuit including a shift register driver and the like for driving a known thermal head.

In this example, the liquid colorant 13 includes approximately 15ffi of carbon black pigment in liquid paraffin. A percent dispersed ink was used. Its volume resistivity at 20°C was 1.0XlO1l Ω·cm, viscosity was 300 cp, and surface tension was 7Qdyne/cm.

In the recording head having the above configuration, the electric field forming electrode 19
When a voltage is applied by the power source 22 between the electrode 21 and the counter electrode 21, a uniform electric field is applied to the liquid colorant 13 in the vicinity of the discharge portion 14.

In this state, current is selectively supplied to the heating resistor 16. In this example, 1m5ec at 25V and 25mA
energized.

As a result, the ink 13 flies toward the recording member 12 only in the vicinity of the heating resistor 16 to which the current is supplied.
A circular dot with a diameter of about 150 μm was recorded on the recording surface. Even if this energization time is shortened to 200μsec,
A similar record could be made.

Note that when the above operation was performed without applying a voltage between the electric field forming electrode 19 and the counter electrode 210, the ink did not fly.

Conversely, without energizing the heating resistor 16,
As the voltage applied between the electric field forming electrode 19 and the counter electrode 21 is increased, when this voltage exceeds 3000V, the ink 13 is randomly distributed throughout the ejection section 14.
was seen flying.

(Ink flying conditions) Since the present invention applies electrical energy and thermal energy to the liquid colorant to make it fly, it is important to control the conditions for ink flying and stable control of ink flying. It is necessary to clarify the limit value (threshold value) that can be achieved.

FIG. 4 is a graph showing the results of an experiment conducted to find this threshold value.

According to the data shown in FIG. 4a, it can be seen that as the temperature of the ink increases, the value of the threshold electric field decreases.

Furthermore, according to FIG. 4, the viscosity of the ink, although drawing a curve, decreases as the temperature of the ink increases, similar to the threshold electric field described above. Similar trends are observed for surface tension (C in the same figure) and volume resistivity (D in the same figure).

Therefore, it is clear that these factors are greatly involved in the value of the threshold electric field.

That is, it is considered that the value of the threshold electric field decreases as the temperature rises due to the combined effects of changes in physical property values such as the viscosity, surface tension, and electrical conductivity of the ink.

Therefore, if an electric field is applied to a level that does not cause ink to fly at room temperature, and the ink is locally heated, the ink will fly due to the cooperation between the heat and the electrostatic field, allowing pixel-like recording. It is.

"Modification" (Modification of Electric Energy Applying Means) FIG. 5 shows a modification of the main part of the recording head for the image recording apparatus of the present invention.

In the figure, a large number of electric field forming electrodes 33 are arranged in an array on the inner surface of one of the pair of wall members 30, 31. Ink (not shown) is accommodated between these wall members 30, 31, and is uniformly heated by thermal energy applying means (not shown).

Further, a counter electrode 21 is provided on the back surface of the recording member 12, and a power source 34 for applying a voltage is connected between this and the electric field forming electrode 33. This voltage source 34 selectively applies a predetermined voltage to a large number of electric field forming electrodes 33 in accordance with the image signal.

As a result, an electric field strong enough to cause ink to fly is formed between the electric field forming electrode 33 to which a voltage is applied and the counter electrode 21. In this way, recording can be performed on the recording member 12 according to the image signal. In this way, even if the position at which electrical energy is applied is controlled, similar recording can be performed. In this case, since the ink is heated, there is an advantage that the ink can be caused to fly with a relatively low voltage.

(Modification of thermal energy application means) FIG. 6 shows still another embodiment of the main part of the recording head of the image recording apparatus of the present invention.

In this embodiment, heating resistors 16 having the same configuration as that shown in FIG. 2 are arranged in an array on a horizontally arranged substrate 40. The ink 13 is applied to the layered members 41 provided on the left and right sides of the ink 13.
．． 42 above the heating resistor 16.

A recording member 12 is placed above the ink 13 with its recording surface facing downward. Further, an electric energy applying means (not shown) forms an electric field in a direction perpendicular to the substrate 40.

In such a recording head, when a current is supplied to the heating resistor 16 to generate heat, the ink 13 is ejected in the vertical direction based on the same principle as described above, and recording can be performed on the recording member 12. The present invention can also be implemented with such a configuration.

(Others) The image recording method and image recording apparatus of the present invention are not limited to the above embodiments.

For example, a laser oscillator can also be used as the thermal energy applying means. In this case, the laser light is modulated according to the image information to be recorded, and the ink is irradiated with the laser light to selectively generate heat in the ink.

In addition, either the electrical energy application means or the thermal energy application means can be used at any time! Although an example has been shown in which the ink is driven simultaneously, it is also possible to drive both locally and simultaneously for a short period of time to make the ink fly.

"Effects of the Invention" According to the image recording method and image recording apparatus of the present invention described above, the temperature is low enough to prevent significant thermal deterioration of the ink, heating resistor, etc., and high enough to prevent leakage between electrodes. The electric field causes ink to fly, making it possible to perform high-speed, high-density recording.

Moreover, the means for holding the ink may have a relatively simple structure and does not require a complicated and precise mechanism.

In addition, relatively small amounts of electrical energy and thermal energy are required to be applied, and it is possible to downsize the drive circuit and the like.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating the principle of the image recording method of the present invention, FIG. 2 is a vertical sectional view of an embodiment of a recording head used in the image recording apparatus of the present invention, and FIG. 3 is a perspective view of the main parts thereof. , FIG. 4 is a graph showing the temperature dependence of the electric field threshold value and the characteristics of ink, FIG. 5 is a perspective view of a modified example of a recording head suitable for carrying out the present invention, and FIG. 6 is a longitudinal sectional view of another example. It is. 13...Liquid colorant, 16.17.18.23...Thermal energy application means, 19.21.22...Electrical energy application means. Applicant: Fuji Xerox Co., Ltd. Agent

Claims (1)

[Claims] 1. A liquid coloring agent is arranged, electrical energy and thermal energy are applied thereto, and the liquid coloring agent in an area where both of the energies are applied is made to fly. Image recording method. 2. Applying the electrical energy by applying a uniform electric field to the liquid colorant, and further applying the thermal energy locally to the liquid colorant, so that both energies are applied together. 2. The image recording method according to claim 1, wherein the liquid colorant in the area is caused to fly. 3. Applying the thermal energy by uniformly heating the liquid colorant, and further applying the electrical energy locally to the liquid colorant, to an area where both energies are applied together. 2. The image recording method according to claim 1, wherein the liquid colorant is caused to fly. 4. A storage means for accommodating a liquid colorant, a thermal energy application means for heating the liquid colorant, an electric energy application means for applying an electric field to the liquid colorant, the thermal energy application means and the electric energy application means a control means for controlling the liquid colorant to apply both the thermal energy and the electric energy to the liquid colorant, and the liquid colorant to fly as a result of applying both the thermal energy and the electric energy. and a recording member disposed in the flight path of the image recording apparatus. 5. The thermal energy application means comprises a plurality of heating elements, and the control means drives the electric energy application means to apply a uniform electric field to the liquid colorant;
The method is characterized in that the plurality of heating elements are selectively driven to locally heat the liquid colorant, and the liquid colorant in the area where both of the energies are applied is controlled to fly. An image recording device according to claim 4. 6. The electric energy applying means includes a plurality of electric field forming elements, and the control means drives the thermal energy applying means to uniformly heat the liquid colorant while controlling the plurality of electric field forming elements. The liquid colorant is selectively driven to locally apply an electric field to the liquid colorant, and is controlled to fly the liquid colorant in a region where both of the energies are applied together. The image recording device according to item 4.