Patent Grant
11351806
The present application is based on, and claims priority from JP Application Serial Number 2019-121931, filed Jun. 28, 2019, the disclosure of which is here by incorporated by reference here in its entirety.
The present disclosure relates to an electromagnetic wave generator, an ink dryer, and an ink jet printer.
Various types of inkjet recording devices have been developed. For example, a technology for printing on a medium to which ink is unlikely to permeate, such as a film or a metal sheet, has been developed. When the ink is fixed on a medium that does not easily absorb the ink, the ink droplets are allowed to flow on the medium for a while after the ink is attached to the medium, and color mixing between dots or image bleeding is likely to occur. As one of the measures to suppress such a phenomenon, it is conceivable to dry the ink in as short a time as possible after the ink is attached to the medium.
As a method of drying the ink, for example, it is conceivable to apply a heated transport roller to the back surface of a medium to dry a film of ink droplets attached to the surface by heat conduction. However, the energy consumed is very large, and it takes time for the heat to be conducted, which is not always the best method. Further, as another method, in a drying device described in JP-A-2017-165000, an attempt has been made to dry ink by applying an AC electric field to the medium and dielectrically heating the attached ink.
However, in the device described in JP-A-2017-165000, a grounded conductor rod and conductor rods for applying a high-frequency voltage to both ends thereof are arranged in parallel at a predetermined interval, so that a high-frequency radiation device such as a loop antenna is provided. Such a radiation device radiates an electromagnetic wave in a relatively wide range due to the characteristics of the antenna. Therefore, it is considered that large power is radiated in addition to the power supplied to the ink film to be heated by the radiating device, and that the energy efficiency is low and the radiated electromagnetic wave needs to be shielded. Further, since an electromagnetic wave is uniformly radiated to a printing pattern, in which an area where ink does not exist and an area where ink exists, present intricately, energy efficiency deteriorates.
An electromagnetic wave generator according to an aspect of the present disclosure includes: an electromagnetic wave generation section generating an electromagnetic wave; a high-frequency voltage generation section generating a voltage applied to the electromagnetic wave generation section; and a transmission line electrically coupling the electromagnetic wave generation section and the high-frequency voltage generation section to each other, in which the electromagnetic wave generation section includes a first electrode, a second electrode, a first conductor that electrically couples the first electrode and the transmission line to each other, and a second conductor that electrically couples the second electrode and the transmission line to each other, one of the first electrode or the second electrode is a reference potential electrode to which a reference potential is applied and the other is a high-frequency electrode to which a high-frequency voltage is applied, a minimum separation distance between the first electrode and the second electrode is 1/10 or less of a wavelength of an output electromagnetic wave, a minimum separation distance between the first conductor and the second conductor is 1/10 or less of a wavelength of an output electromagnetic wave, and the first conductor further includes a coil, and the coil is closer to the first electrode than the transmission line.
The electromagnetic wave generator according to the aspect may have a structure in which one of the first electrode and the second electrode is disposed so as to surround the other of the first electrode and the second electrode in plan view.
In the electromagnetic wave generator according to the aspect, the reference potential electrode may continuously surround a periphery of the high-frequency electrode, the high-frequency electrode may be coupled to an inner conductor of a coaxial cable, and the electromagnetic wave generator may have a structure in which the reference potential electrode and an outer conductor of the coaxial cable are coupled via a continuous planar conductor.
An ink dryer according to another aspect of the present disclosure includes the electromagnetic wave generator according to any of the above aspects that heats a thin ink film, in which the first electrode and the second electrode have a flat plate shape and are disposed in parallel to the thin ink film.
An ink dryer according to another aspect of the present disclosure in which the electromagnetic wave generator according to any of the above aspects heats a thin ink film, in which the first electrode and the second electrode extend with respect to the normal line direction of the thin ink film.
The ink dryer according to any of the aspects may further include a conductor plate, in which the conductor plate may be disposed in parallel to the thin ink film at a side opposite to the first electrode and the second electrode.
An ink jet printer according to another aspect of the present disclosure includes: the ink dryer according to any of the above aspects; a carriage reciprocating in a width direction of a recording medium; and an ink jet head discharging ink, in which the ink dryer and the ink jet head are mounted on the carriage.
An embodiment of the present disclosure will be described below. The embodiment described below describes an example of the present disclosure. The present disclosure is not limited to the following embodiment at all, and includes various modifications implemented without departing from the spirit of the present disclosure. Note that not all of the configurations described below are essential configurations of the present disclosure.
The electromagnetic wave generator of the present embodiment includes an electromagnetic wave generation section that generates an electromagnetic wave, a high-frequency voltage generation section that generates a voltage applied to the electromagnetic wave generation section, and a transmission line for electrically coupling the electromagnetic wave generation section and the high-frequency voltage generation section to each other. The electromagnetic wave generation section includes a first electrode, a second electrode, a first conductor for electrically coupling the first electrode and the transmission line to each other, and a second conductor for electrically coupling the second electrode and the transmission line to each other. Further, the first conductor includes a coil, and the coil is provided at a position closer to the first electrode than the transmission line.
Therefore, the electromagnetic wave generator of the present embodiment includes at least a first electrode, a second electrode, and a coil.
The heating energy efficiency of the ink film differs greatly depending on the position where the coil is inserted in series, even when the coil has the same inductance. Therefore, it is desirable to install the coil as close to the electrode as possible. Regarding the coil 3, the coil 3 may be omitted by giving the electrode itself an inductance by, for example, forming the first electrode or the second electrode in a meander shape.
1.1. Electrode
The electromagnetic wave generator 10 includes a first electrode 1 and a second electrode 2. The first electrode 1 and the second electrode 2 have conductivity. A reference potential is applied to one of the first electrode 1 and the second electrode 2. A high-frequency voltage is applied to the other of the first electrode 1 and the second electrode 2. The method of selecting the first electrode 1 and the second electrode 2 can be any methods. The reference potential is applied to one of the two electrodes, and a high-frequency voltage is applied to the other. In this specification, an electrode to which a reference potential is applied may be referred to as a “reference potential electrode”, and an electrode to which a high-frequency voltage is applied may be referred to as a “high-frequency electrode”.
The reference potential is a constant potential serving as a reference for a high-frequency voltage, and may be, for example, a ground potential. Further, when the high-frequency voltage generation circuit that generates a high-frequency voltage to be input to the electromagnetic wave generator 10 is a differential circuit, there is no distinction between the first electrode 1 and the second electrode 2. When the frequency of the high-frequency is 1 MHz or more, there is a heating effect. Further, the dielectric loss tangent becomes maximum near the frequency of 20 GHz, and the heating efficiency also becomes maximum. In particular, when heating water such as ink, the bandwidth is desirably 2.0 GHz or more and 3.0 GHz or less, and from a legal viewpoint, a 2.4 GHz bandwidth, which is one of the ISM bandwidth, is desirable, for example, 2.44 GHz or more and 2.45 GHz or less. Further, the higher the high-frequency voltage, the greater the amount of heat supplied to the ink. However, since a high-frequency voltage is transmitted to the electromagnetic wave generator through a transmission line of 50Q normally, the high-frequency voltage applied to the electromagnetic wave generator 10 is represented as “high-frequency power=V{circumflex over ( )}2/R=V{circumflex over ( )}2/50”. Furthermore, to suppress the amount of heat generated by the internal resistance of the electromagnetic wave generator 10, the power per electromagnetic wave generator 10 is set to about 10 W, and it is desirable to use a plurality of electromagnetic wave generators 10 to ensure the power required for drying the ink. Further, the ink is heated by dielectric heating due to an electric field generated between the first electrode 1 and the second electrode 2. The electric field at this time has a value of about 1×10{circumflex over ( )}6 V/m. Further, the ink is heated by dielectric heating due to an electric field generated between the first electrode 1 and the second electrode 2. At this time, the electric field between the first electrode and the second electrode has a value of about 1×10{circumflex over ( )}6 V/m by the effect of the coil 3 or the distance between the electrodes.
The application of the high-frequency voltage means that the central portion of a surface of the first electrode 1 or the second electrode 2 opposite to a surface facing the ink is set to a feeding point, and the power of the above described high-frequency voltage is supplied to this feeding point. Incidentally, as shown in
In the illustrated example, the first electrode 1 and the second electrode 2 have a flat plate shape. The plane shape of the first electrode 1 and the second electrode 2 can be any shapes, and may be, for example, a square, a rectangle, a circle, or a combination of these shapes. In the illustrated example, the first electrode 1 and the second electrode 2 have a substantially square shape in plan view. The plane size of the first electrode 1 and the second electrode 2 is 0.01 cm2 or more and 100.0 cm2 or less, desirably 0.1 cm2 or more and 10.0 cm2 or less, more desirably 0.5 cm2 or more and 2.0 cm2 or less, and further desirably 0.5 cm2 or more and 1.0 cm2 or less on one electrode, as an area in plan view. The areas of the first electrode 1 and the second electrode 2 in plan view may be the same or different. The plan view refers to a state viewed from the z direction in
It is desirable that the first electrode 1 and the second electrode 2 are disposed so as not to overlap with each other in plan view. In the illustrated example, the first electrode 1 and the second electrode are disposed in parallel on the same plane. With such a disposition, a predetermined electromagnetic wave can be generated efficiently. The shapes and dispositions of the first electrode 1 and the second electrode 2 will be further described later. The details of the generated electromagnetic waves will be described later.
The first electrode 1 and the second electrode 2 are formed of a conductor. Examples of the conductor include metals, alloys, and conductive oxides. The first electrode 1 and the second electrode 2 may be the same material or different materials. The first electrode 1 and the second electrode 2 may be appropriately formed by selecting the thickness or strength so that the first electrode 1 and the second electrode 2 can be self-supporting, or can be formed on a surface of a substrate or the like made of a material (not shown) having a low dielectric loss tangent that transmits electromagnetic waves when it is difficult to maintain the strength of the first electrode 1 and the second electrode 2.
Each of the first electrode 1 and the second electrode 2 are electrically coupled to a coaxial cable 4 coupled to the high-frequency source via an inner conductor 4a and an outer conductor 4b, as schematically shown in
1.2. Electrode Interval
The minimum separation distance d between the first electrode 1 and the second electrode 2 is 1/10 or less of the wavelength of the electromagnetic wave output from the electromagnetic wave generator 10. For example, when the frequency of the electromagnetic wave output from the electromagnetic wave generator 10 is 2.45 GHz, the wavelength of the high-frequency is substantially 12.2 cm, and in this case, the minimum separation distance between the first electrode 1 and the second electrode 2 is substantially 1.22 cm or less. In the example in
By setting the minimum separation distance d between the first electrode 1 and the second electrode 2 to be 1/10 or less of the wavelength of the output electromagnetic wave, most of the electromagnetic waves can be attenuated near the first electrode 1 and the second electrode 2. Thereby, the intensity of the electromagnetic wave reaching the distant place from the first electrode 1 and the second electrode 2 can be reduced.
That is, the electromagnetic wave radiated from the electromagnetic wave generator 10 is very strong near the first electrode 1 and the second electrode 2 and very weak far from the first electrode 1 and the second electrode 2. In this specification, an electromagnetic field generated by the electromagnetic wave generator 10 near the first electrode 1 and the second electrode 2 may be referred to as a “near electromagnetic field”. Further, in this specification, an electromagnetic field generated by a general antenna (antenna) for transmitting electromagnetic waves to a distant place may be referred to as a “distant electromagnetic field”. Note that the boundary between the near and far distances is a position separated from the electromagnetic wave generator 10 by substantially ⅙ of the wavelength of the generated electromagnetic wave.
The electromagnetic wave generator 10 is used for applications such as televisions and mobile phones, and is not an electromagnetic wave generator that transmits electromagnetic waves at intervals of m units. Instead, the electromagnetic wave generator 10 is an electromagnetic wave generator in which during the transmission of the distance of ⅙ of the wavelength of the generated electromagnetic wave, the electric field density of the electromagnetic wave is attenuated to 30% or less of the electric field density between the first electrode 1 and the second electrode 2. That is, the electromagnetic wave generator 10 is not suitable for a communication. Furthermore, since the electromagnetic wave generated by the electromagnetic wave generator 10 has a high attenuation rate, the range of the electric field is suppressed. Therefore, unnecessary radiation hardly occurs in an area farther from the device than the distance of substantially the wavelength of the generated electromagnetic wave. Therefore, it is unnecessary or easy to comply with regulations by the Radio Law and the like, and even when compliance is required, it is possible to reduce the scattering of electromagnetic waves around the electromagnetic wave generator by a simple electromagnetic wave shield or the like. Such properties of the electromagnetic wave generator 10 are caused by the small size of the electrodes, the short distance between the electrodes, the difficulty of resonance, and the like.
In other words, the electromagnetic wave generator 10 of the present embodiment is not a device for generating a distant electromagnetic field such as a dipole antenna, but is equivalent to a slot antenna where the negative/positive is inverted with respect to the dipole antenna and the slot width is made sufficiently small with respect to the wavelength to make it difficult to generate distant electromagnetic fields. The present structure only generates an electric field like a capacitor, and this electric field does not generate a magnetic field as a secondary matter. Therefore, a so-called distant electromagnetic field in which an electric field and a magnetic field are generated in a chain and an electromagnetic wave is transmitted to a distant place is not generated.
1.3. Coil
The electromagnetic wave generator 10 includes a coil 3, and the coil 3 is coupled to the first electrode 1 or the second electrode 2 in series. The first electrode 1 or the second electrode 2 is coupled to a path to which a high-frequency voltage is applied via the coil 3.
The coil 3 is installed for three purposes: matching, increasing an electric field generated between electrodes, and enhancing by adding an electric field generated by a coil to an electric field generated between electrodes.
Role of Coil (1): Matching
Generally, a voltage applied to an antenna is transmitted to the antenna via a coaxial cable (for example, a characteristic impedance of 50Ω). It is desirable that the impedance of the antenna matches the impedance of the high-frequency voltage generation circuit or the impedance of the coaxial cable transmitted from the circuit to the antenna. By matching or approaching the impedance of the antenna to the impedance of a cable or the like, the energy transmission efficiency is improved. Conversely, when a high-frequency voltage of a sine wave is input to the antenna and the impedance of the high-frequency voltage generation circuit does not match the impedance of the antenna, signal reflection occurs at a discontinuous place of impedance, and it is difficult to input a signal to the antenna. Therefore, at the coupling place between the antenna and the coaxial cable where impedance discontinuity is likely to occur, a matching circuit constituted by a coil and a capacitor is inserted, the impedance of the antenna is adjusted, and the energy transmission efficiency improvement is performed between the inner conductor of the coaxial cable and the electrode of the antenna, or between the outer conductor and the electrode of the antenna. The coaxial cable is normally 50Ω, and the matching circuit is adjusted so that the antenna also has 50Ω. If the coaxial cable has an imaginary impedance, the antenna is adjusted to an imaginary impedance conjugate to the imaginary impedance. Such a coil is called a so-called matching coil.
Role of Coil (2): Increasing Electric Field Density Between Electrodes
As described above, since the electromagnetic wave generating circuit A includes the capacitor C, a specific resonance frequency can be obtained by coupling the coil L so as to be in series with the capacitor C. Further, when the inductance of the coil L is increased and the capacitance of the capacitor C is reduced as much as possible, the transmission efficiency is improved. The inductance of the coil L and the capacity of the capacitor C are appropriately designed.
The radiation resistance is smaller (for example, substantially 7Ω) than the impedance of the coaxial cable 4 (for example, 50Ω), and the capacity of the capacitor C apparently formed by the first electrode 1 and the second electrode 2 is, for example, substantially 0.5 pF.
In the electromagnetic wave generator 10 including a first electrode 1 and a second electrode 2 each having a plane shape of 5 mm×5 mm square and a minimum separation distance of 5 mm, and a 10 nH coil L coupled to the second electrode 2 in series, when a voltage of 1 V is generated from the high-frequency voltage generation circuit B as shown in
Role of Coil (3): Adding an Electric Field Generated by a Coil to an Electric Field Generated Between Electrodes to Enhance the Electric Field
The coil 3 is typically configured as a winding of a long electric wire of metal such as copper, which has an internal resistance as well as an inductance component. For example, when the inductance component is substantially 30 nH, the internal resistance is normally substantially 3Ω. Due to the inductance and the internal resistance, a potential difference is generated at both ends of the coil, and an electric field is generated at a place where the potential difference exists.
1.4. Variation of Disposition and Structure of Electrode
The electromagnetic wave generator may have a structure in which one of the first electrode 1 and the second electrode 2 is disposed so as to surround the other, as the electromagnetic wave generator 12 shown in
The first electrode 1 of the electromagnetic wave generator 12 has a square shape in plan view. In the electromagnetic wave generator 12, the second electrode 2 is disposed in a hollow square shape so that the second electrode 2 surrounds the first electrode 1 in plan view. Although not shown, the first electrode 1 may have a circular shape in plan view, the second electrode 2 may have an annular shape in plan view, or a hexagonal outer periphery. The plane or spatial disposition of the first electrode 1 and the second electrode 2, and the coil 3 are the same as those of the above-described electromagnetic wave generator 10, and thus the description will be simplified.
In the electromagnetic wave generator 12, a high-frequency potential and a reference potential are fed to the rectangular first electrode 1 disposed at the center in plan view and a hollow rectangular shape (frame shape) second electrode 2 surrounding the first electrode 1, respectively. The coil 3 is inserted between the first electrode 1 and the inner conductor 4a of the coaxial cable 4, and it is important that the coil 3 is positioned as close to the first electrode 1 as possible.
In the electromagnetic wave generator 12, when the second electrode 2 is a hollow rectangular shape in plan view, the length of one side of the outer periphery is, for example, 0.1 cm or more and 10.0 cm or less, desirably 0.3 cm or more and 5.0 cm or less, and more desirably 0.4 cm or more and 1.0 cm or less. Further, in this case, the width of the second electrode 2 in plan view is 1.0 mm or more and 2.0 mm or less, desirably 1.4 mm or more and 1.6 mm or less, and more desirably substantially 1.5 mm.
In the electromagnetic wave generator 12, the minimum separation distance d between the first electrode 1 and the second electrode 2 is 1/10 or less of the wavelength of the electromagnetic wave output from the electromagnetic wave generator 12.
As the electromagnetic wave generator 14 shown in
The plane shape and disposition of the first electrode 1 and the second electrode 2 of the electromagnetic wave generator 14 are the same as those of the electromagnetic wave generator 12.
In the electromagnetic wave generator 14, the minimum separation distance d between the first electrode 1 and the second electrode 2 is 1/10 or less of the wavelength of the electromagnetic wave output from the electromagnetic wave generator 12.
Although not shown, in the electromagnetic wave generator 14, the conductor 30 may be integral with the second electrode 2. In this case, the conductor 30 becomes the second electrode 2. Similarly, the first electrode 1 of the electromagnetic wave generator 14 may be integrated with the columnar conductor 32. In this case, the conductor 32 becomes the first electrode 1. Further, the coupling may be made without the inner conductor 4a of the coaxial cable 4 and the conductor 32. In this case, the inner conductor 4a becomes the first electrode 1.
In the electromagnetic wave generator 14, when it is a structure that the second electrode 2 is set as a reference potential electrode, the first electrode 1 is set as a high-frequency electrode, the high-frequency electrode is coupled to the inner conductor 4a of the coaxial cable 4, and the reference potential electrode and the outer conductor 4b of the coaxial cable 4 are coupled via a continuous conductor, the electromagnetic wave generator 14 becomes a structure similar to a coaxial cable. Therefore, the manufacturing becomes easier. Further, in the electromagnetic wave generator 14, the heating efficiency of the thin ink film described later is improved.
Furthermore, in the electromagnetic wave generator 14, when it is a structure that the second electrode 2 is set as a reference potential electrode, the first electrode 1 is set as a high-frequency electrode, the high-frequency electrode is coupled to the inner conductor 4a of the coaxial cable 4, and the reference potential electrode and the outer conductor 4b of the coaxial cable 4 are coupled via a continuous conductor, a shield effect by the reference potential electrode is obtained and the electromagnetic wave is less likely to leak outside the reference potential electrode. With such a structure, a transmission mode is formed near the electrode, so that a target object (for example, a thin ink film described later) can be sufficiently irradiated with the electromagnetic wave even when an interval from the target object to be irradiated with the electromagnetic wave is large. That is, with such a structure, it is possible to make the electromagnetic waves generated from the device have directivity and to extend a reaching distance of the nearby electromagnetic field.
In the electromagnetic wave generator 14, it has been found that the width w of the second electrode 2 in plan view affects the heating efficiency of the thin ink film described later. The width w of the second electrode 2 in plan view is 1.0 mm or more and 2.0 mm or less, desirably 1.4 mm or more and 1.6 mm or less, and more desirably substantially 1.5 mm from the viewpoint of increasing the heating efficiency. Further, it has been found that the plane shape of the first electrode 1 also affects the heating efficiency. A rectangular shape (not shown) increases the heating efficiency as compared with a square shape as shown in the figure, for example, when the rectangular shape is 0.5 mm×5.0 mm, the heating efficiency is further improved.
In each of the electromagnetic wave generators 12 and 14, the minimum separation distance d between the first electrode 1 and the second electrode 2 is 1/10 or less of the wavelength of the output electromagnetic wave, and since the coil 3 is coupled to the second electrode 2 in series, an electromagnetic field can be efficiently generated near the device.
1.5. High-Frequency Source
The electromagnetic wave generator according to the present embodiment includes a high-frequency source. The high-frequency source includes the high-frequency voltage generation circuit B described above. The high-frequency source generates a high-frequency voltage applied to the first electrode 1 and the second electrode 2. The high-frequency source includes, for example, a quartz crystal oscillator, a phase locked loop (PLL) circuit, and a power amplifier. The high-frequency power generated by the high-frequency source is supplied to the first electrode 1 and the second electrode 2 via, for example, a coaxial cable.
The basic peripheral circuit configuration of the electromagnetic wave generator of the present embodiment is such that a high-frequency signal generated by a PLL is amplified by a power amplifier and fed to the first electrode 1 and the second electrode 2. When a large number of sets of the first electrode 1 and the second electrode 2 is used, for example, one power amplifier may be used for one set of the first electrode 1 and the second electrode 2, and electromagnetic waves may be individually generated by dividing the output of the PLL and transmitting the output to the power amplifier. Further, a plurality of power amplifiers may be used, and in such a case, the amplification factor of each power amplifier can be individually controlled more easily.
The electromagnetic wave generator of the above embodiment can be used as an ink dryer. The ink dryer is the above-described electromagnetic wave generator, in which the first electrode and the second electrode 2 are disposed in parallel with respect to the thin ink film, and by applying a high-frequency voltage, the thin ink film can be heated very efficiently.
2.1. Thin Ink Film
The thin ink film dried by the ink dryer 10 may be a thin film obtained by attaching ink to a sheet such as paper or a film, a thin film obtained by attaching ink to a surface of a molded body having a three-dimensional shape or the like. The method for attaching the ink is not particularly limited, but may be an ink jet method, a spray method, a coating method using a brush, or the like. In the illustrated example, a thin ink film T formed by attaching ink on one side of a recording medium M using the ink jet method is illustrated.
The thickness of the thin ink film T is, for example, 0.01 μm or more and 100.0 μm or less, desirably 1.0 μm or more and 10.0 μm or less. Various components may be contained in the ink, and examples of components to be dried by the ink dryer 10 include water and an organic solvent. When the frequency of the electromagnetic wave radiated by the ink dryer 10 is from substantially 1 MHz to 30 GHz, since water can be efficiently heated and dried, the ink desirably contains water. As a frequency actually used, 2.45 GHz used in a microwave oven has a clear legal standard and is easy to use.
When the thin ink film T is irradiated with an electromagnetic wave, the water in the ink is heated. The main principle of the heating is frictional heat due to the vibration of water molecules due to dielectric heating and/or Joule heat due to eddy current generated in the water. When the ink is an ink having a high ion concentration, such as dye ink, conductivity is generated, so that the effect of heating by Joule heat increases. In the ink dryer 10 of the present embodiment, since a vibration electric field is easily applied in parallel to the thin ink film T, when the ink is water-based, both heating principles can be used.
2.2. Heating Mechanism
It is known that when electromagnetic waves (3 GHz) are incident on the surface of the water, although it depends on the temperature, the depth reached by the electromagnetic wave is substantially 1.2 cm at 20° C. This depth is called the skin depth. As described above, the thickness of the thin ink film is extremely thin as compared with the penetration depth of the electromagnetic wave. Therefore, it can be assumed that when the thin ink film is irradiated with the electromagnetic wave perpendicularly, almost all electromagnetic waves penetrate, and water in the thin ink film can hardly be heated, or even when it can be heated, the efficiency becomes very poor.
According to a preliminary experiment conducted by the inventor, it has been found that even when a heating operation is performed with a sheet having the ink attached thereto in a microwave oven (microwave oven), the ink can hardly be heated. It is considered that the reason is that, the power, among the power of the electromagnetic waves with which the thin ink film is irradiated, that turns into heat inside the ink is very low by the electromagnetic wave penetrating the ink thin film.
As described above, the electromagnetic wave generator of the present embodiment generates a near electromagnetic field. That is, by disposing the thin ink film to the ink dryer at an appropriate distance, it is possible to irradiate in a narrow range around the thin ink film with the electromagnetic waves with concentration. Since the electromagnetic wave generated from the ink dryer of the present embodiment presents only in a nearby narrow space and has a very weak distant electromagnetic field, energy is less dissipated, and by appropriately disposing the thin ink film in the area where electromagnetic waves present, the thin ink film can be heated very efficiently.
The mechanism of heating the thin ink film T by the ink dryer 10 will be described below.
As shown in
When the electric field is applied in parallel to the thin ink film T, the heating efficiency of the thin ink film T is improved. Therefore, it is desirable that the direction of the electric field is as parallel as possible to the thin ink film T, and in the ink dryer 10 of the present embodiment, the first electrode 1 and the second electrode 2 having a structure capable of applying such an electric field are adopted. Further, as the electric field of the electromagnetic wave with which the thin ink film T is irradiated increases, the amount of heat generated by the thin ink film T increases. Since the electric field increases as the potential difference between the electrodes increases, the amount of heat generated can be increased by increasing the potential difference by the coil 3 as described above. The coil 3 has an effect of impedance matching in addition to the effect of increasing the potential difference. Further, since the coil 3 itself generates an electric field, the coil 3 is disposed near the first electrode 1 or the second electrode 2, and the electric field generated by the coil 3 is added to the electric field generated between the electrodes to enhance the electric field and improve the heating efficiency.
2.3. Disposition of Electrode
The first electrode 1 and the second electrode 2 may be disposed perpendicular to the thin ink film T. For example, in the above-described electromagnetic wave generator 14, when the conductor 32 and the first electrode 1 are integrally formed and the conductor 30 and the second electrode 2 are integrally formed, the first electrode 1 becomes a columnar electrode, the second electrode 2 becomes a cylindrical electrode, and the extending direction becomes a direction of a normal line of the thin ink film T. In this case, when the electromagnetic wave generator 14 is installed so as to face the thin ink film T, the first electrode 1 and the second electrode 2 are disposed with respect to the thin ink film T in a posture in which the extending direction extends in a direction perpendicular to the surface where the thin ink film T spreads. Even with such a disposition, the thin ink film T can be efficiently heated.
2.4. Conductor Plate
The ink dryer of the present embodiment may include a conductor plate.
The conductor plate 5 has conductivity. The conductor plate 5 is disposed to face the first electrode 1 and the second electrode 2 via the thin ink film T, and thus it is possible to suppress a change in impedance of the ink dryer 16 due to the thin ink film T. The above-described ink dryer 10 having no conductor plate 5 transmits energy to the thin ink film T very efficiently, and this may cause the thin ink film T to be electrically coupled to such an extent that it can be considered as a part of the ink dryer 10. In such a case, the impedance of the ink dryer 10 changes depending on the thickness, volume, conductivity, and the like of the thin ink film T.
The ink dryer 16 can suppress such a change in impedance by disposing the conductor plate 5. Further, by disposing the conductor plate 5, the energy may be transmitted to the thin ink film T more efficiently.
Regarding the conductor plate 5, for example, when the ink dryer 16 is provided in an ink jet printer, the platen can be formed of a conductive material and set as the conductor plate 5.
2.5. Operation Effect
According to the ink dryer of the present embodiment, the heating efficiency, that is, the ratio of the power, among the high-frequency power input to the antenna, used for increasing the temperature of the ink can be increased to 80% or more. According to the ink dryer of the present embodiment, the generated electromagnetic waves can be present only in a very limited area around the thin ink film. Thereby, the heating efficiency of the thin ink film is very good.
Since the ink dryer of the present embodiment uses a small electromagnetic wave generator having a minimum separation distance of 1/10 or less of the wavelength of the electromagnetic wave, the ink dryer can be used with saving the power and a simple shield can be used even when it becomes necessary to suppress the scattering of electromagnetic waves. Further, since the power is saved, a circuit for generating a high-frequency voltage can be downsized.
Since the ink dryer of the present embodiment utilizes the near electromagnetic field, it is possible to suppress the propagation of the energy to an object such as a sheet on which the thin ink film is attached. Therefore, for example, even when the sheet is made of a material that is affected by the temperature, the sheet is not easily heated, so that the deterioration of the sheet can be suppressed.
The ink jet printer of the present embodiment includes the above-described ink dryer, a carriage that reciprocates a recording medium in the width direction, and an ink jet head that discharges ink, and the ink dryer and the ink jet head are mounted on the carriage.
The ink jet printer 200 includes an ink jet head 60 on the carriage 50 and a plurality of ink dryers 10. A first electrode 1, a second electrode 2, and a coaxial cable 4 of the ink dryer 10 are mounted on the carriage 50. Although not shown, the ink jet printer 200 includes a high-frequency source for driving each of the ink dryers 10. Further, although not shown, the plurality of ink dryers 10 are arranged so as to cover an area equal to or longer than the length of a nozzle row of the ink jet head 60 in a moving direction SS of the recording medium M. The ink jet printer 200 is a serial type printer, and has a mechanism for moving the recording medium M and a mechanism for performing a reciprocation operation on the carriage 50.
The ink jet printer 200 forms a predetermined image on the recording medium M by repeating moving and disposing the recording medium M at a predetermined position and a plurality of times, and discharging ink from the ink jet head 60 while scanning the carriage 50 in a direction intersecting the moving direction SS of the recording medium M and attaching the ink to a predetermined position on the recording medium M with a predetermined amount, a plurality of times.
The ink dryer 10 is arranged in the carriage 50 on one side or both sides of the ink jet head 60 in the scanning direction MS of the carriage 50. In the illustrated example, a plurality of ink dryers 10 are arranged on both sides of the ink jet head 60 in the scanning direction MS. With this arrangement, the ink discharged from the ink jet head 60 and attached to the recording medium M to forma thin ink film can be dried quickly in a short time after a lapse of time in accordance with a moving speed of the carriage 50 and a distance from the nozzle of the ink jet head 60 to the ink dryer 10 in the scanning direction MS.
In
In
The ink jet printer 200 of the present embodiment is particularly effective when the recording medium M is made of a material such as a film to which the ink does not soak or hardly soaks. However, even with a recording medium M that absorbs ink such as paper, a sufficient drying effect can be obtained.
Although the serial type ink jet printer 200 has been described as an example, the ink dryer can be applied to a line type ink jet printer. In the case of a line type ink jet printer, an ink dryer is disposed downstream of the line type ink jet head in a direction in which the recording medium flows.
Hereinafter, the present disclosure will be further described with reference to experimental examples, but the present disclosure is not limited to the following examples.
A simulation of the heating state of the thin ink film by the ink dryer having a structure of the electromagnetic wave generator 14 described above is performed.
In the electromagnetic field simulation, a second electrode, which has a cubic outer shape with a side of 5 mm, and a hollow and open lower surface, is used, and the thickness of the side surface of the second electrode is set to 0.1 mm. The first electrode is disposed at the center of the second electrode, and has a rectangular (1 mm×1 mm) plate shape in plan view. The thin ink film has a sufficiently large area and a thickness is set to 5 μm. The distance between the upper surface of the thin ink film and the lower surface of the electrode is set to 2 mm. Furthermore, a conductor plate having a sufficiently large area is disposed on the lower surface side of the thin ink film.
A coil having an inductance of 25 nH is coupled in series with the high-frequency electrode (first electrode 1) in the ink dryer. The frequency of the high-frequency voltage is set to 2.45 GHz. The feeding power is set to 1 W.
The present disclosure is not limited to the embodiments described above, and various modifications are possible. For example, the present disclosure includes substantially the same configurations, for example, configurations having the same functions, methods, and results, or configurations having the same objects and effects, as the configurations described in the embodiments. Further, the present disclosure includes a configuration obtained by replacing non-essential portions in the configurations described in the embodiments. Further, the present disclosure includes a configuration that exhibits the same operational effects as those of the configurations described in the embodiments or a configuration capable of achieving the same objects. The present disclosure includes a configuration obtained by adding the configurations described in the embodiments to known techniques.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2019-121931 | Jun 2019 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20140239294 | Yamazaki | Aug 2014 | A1 |
| 20170266986 | Yamada | Sep 2017 | A1 |
| 20200406607 | Aizawa | Dec 2020 | A1 |
| Number | Date | Country |
|---|---|---|
| 2017-165000 | Sep 2017 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20200406659 A1 | Dec 2020 | US |
