JPH0624868B2 - Thermal electrostatic ink jet recording head - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal static ink jet recording apparatus used for a thermal electrostatic ink jet recording apparatus which forms an image by selectively flying an ink material by the cooperative action of thermal energy and an electrostatic field. The present invention relates to an electric inkjet recording head.

Conventional technology Since the non-impact recording method produces less noise during recording, there is a method for making hard copy of electronic image information.
I am interested.

Among them, the inkjet method, which can record on plain paper and can perform recording without a special process called fixing, is regarded as an extremely useful recording method.

However, the ink jet method that has been put into practical use is a method in which a pressure pulse is applied to a member that seals ink and ink is ejected from an ejection port (orifice) for recording. However, since it is necessary to mechanically scan the ink ejection device in order to perform printing with a required image density, the speed has been reduced.

On the other hand, some techniques have been proposed as methods for improving the above-mentioned drawbacks of the inkjet and enabling high-speed inkjet. The magnetic ink jet method, in which magnetic ink is provided in the vicinity of the magnetic electrode array, the ink ejection state corresponding to the image density is formed by utilizing the ink rise due to the magnetic field, and the magnetic ink is ejected by the electrostatic field, is capable of electronic scanning Therefore, high-speed recording is possible, but there is a drawback that it is difficult to colorize, which is an original feature of inkjet. On the other hand, the ink is arranged in a slit-shaped ink reservoir parallel to the electrode array, and the ink is caused to fly according to the electric field pattern formed between the electrode and the electrode array that face each other via the recording paper.
The so-called flat ink jet method does not require a fine orifice and can improve ink clogging, but since the voltage applied for ink flight is high, the electrode array is often used to prevent voltage leakage between adjacent and neighboring electrodes. It is necessary to drive separately, and the speed cannot be increased so much.

Further, a so-called thermal bubble jet has also been proposed in which ink is ejected from an ejection port by thermal energy. In this method, the ink is rapidly heated to cause film surface boiling,
Bubbles are rapidly formed in the orifice to eject ink with a rise in pressure, but it is necessary to rapidly heat and heat the heating element to cause boiling of the film surface. It has a practical defect that alteration or thermal deterioration of the heating resistor protective layer provided as a heating means is likely to occur.

The present inventors apply a heat signal to ink as a novel high-speed inkjet method that improves the low-speed property that is a drawback of the conventional inkjet method and does not have the drawbacks of the high-speed inkjet method proposed as described above. Then, a so-called thermal electrostatic ink jet method has been previously proposed in which an electrostatic field is applied simultaneously or sequentially and only ink in a heated region is ejected by electrostatic force.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The thermal electrostatic ink jet recording head used in this thermal electrostatic ink jet method has a heating element (heating element) for applying a thermal signal to the ink and an electrostatic force applied to the ink. And an electrostatic induction electrode electrically connected to the ink, and means for supplying and holding the ink up to the ink ejection port in order to facilitate the flight of the ink by the electrostatic force. Structurally, a slit-shaped space is formed by a first plate member made of an insulating substrate such as alumina and a second plate member facing the first plate member at a predetermined distance. A heating resistor array in which heating resistors are arranged at equal intervals is provided on the wall surface of one plate member forming the slit.

According to the subsequent research conducted by the present inventors, the distance between the tip of the heating resistor array provided on the wall surface of the slit and the end of the recording head on the ink material flying side causes the ink flying in the thermal electrostatic inkjet recording method. It was found that the ease and energy efficiency of the heating resistor used for heat generation have a great influence.

The present invention has been made in view of the above points, and an object of the present invention is to provide a thermal electrostatic ink jet recording head suitable for stable high speed flight and low energy flight of an ink material in a thermal electrostatic ink jet recording method. That is.

Means for Solving the Problems To achieve the above-mentioned object, the present invention defines a slit suitable for holding an ink material by an insulating substrate, and selectively forms the ink material on the slit wall of the slit. In a thermal electrostatic ink jet recording head provided with means for heating the ink material and electrostatic field induction means for inducing and applying an electrostatic field to the ink material, the tip of the means for selectively heating the ink material is composed of an insulating substrate. Provided is a thermal electrostatic ink jet recording head, which is provided at a distance of 300 μm or less from the ink material flying side end of the recording head.

According to a preferred embodiment of the present invention, the means for selectively heating the ink material is composed of a heating resistor group (array) arranged at equal intervals in the slit direction.

Operation While supplying and holding the ink material in the slit and selectively heating the ink material according to the image information, at the same time or sequentially, the electrostatic field induction means induces and applies an electrostatic field to the ink material to heat the ink. By selectively flying only the ink material of (1) to the recording medium, an image is formed on the recording medium.

According to the present invention, since the tip of the heating means is provided within a distance of 300 μm from the end of the recording head on the ink material flying side, the heating effect of the ink material by the heating means is enhanced, and the ink flying can be performed at high speed. And it becomes possible to achieve it stably.

EXAMPLES The present invention will be described below in detail based on examples shown in the drawings. FIG. 1 is a configuration diagram schematically showing an arrangement of a heating resistor array according to an embodiment of the present invention, and FIG. 2 is a vertical sectional view of a recording head having the heating resistor array shown in FIG. A first plate member 10 and a second plate member 12 made of an insulating substrate such as alumina are provided at a distance of, for example, about 100 μm, and a slit is formed between them. Specifically, for example, the first plate member 10 and the second plate member 12 are separated by a spacer, and the spacer and both plate members 10 and 12 are bonded by an adhesive to form a slit. On the slit wall 14 of the first plate member 10, tantalum nitride (Ta ₂ N) having a pitch of 125 μm and a width of 110 μm.
The heat generating resistors 16 are vapor-deposited at equal intervals by, for example, a high frequency sputtering method to form a heat generating resistor array 18. A control electrode 22 and a return electrode 24 as energizing electrodes are connected to each heating resistor 16.

Explaining an example of a method of forming the heating resistor array 18, the heating resistor 16 is formed by depositing tantalum nitride (Ta ₂ N) on a ceramic substrate on which a glass layer having a thickness of about 60 μm is mounted by a high frequency sputtering method by about 300 angstroms. Then, a pattern was formed by photolithography and further etched to form an array as shown in FIG. The current-carrying electrodes 22 and 24 were formed as shown in FIG. 1 by photolithography by continuously and uniformly depositing Ni—Cr 500 angstrom and Au 1 μm.

Further, SiO ₂ was deposited on the electrodes 22 and 24 by a high frequency sputtering method to a thickness of about 1 μm to ₂ μm to form a protective layer for ink resistance. The SiO ₂ film also serves as electrical insulation between the electrostatic induction electrode 28 deposited on the SiO ₂ film and the energization electrodes 22 and 24 provided under the SiO ₂ . The electrically conductive layer 28 for electrostatic induction laminated on the insulating layer 26 made of SiO ₂ includes Cr—Cu—Cr.
To 500 Å, 1000 Å and 500 Å, respectively, by continuous vapor deposition. The first Cr layer was formed for the purpose of enhancing the adhesion between SiO ₂ and Cu, and the last Cr layer was formed for the purpose of an antioxidation layer of Cu.

The distance A between the tip of the heating resistor 16 and the ink material flying side end 20 of the insulating substrates 10 and 12 was 100 μm in this embodiment. Further, the electric resistance value of the heating resistor 16 is set to be 120Ω to 200Ω by controlling the film thickness and size of the heating resistor layer.

Referring to FIG. 2, this figure shows a schematic vertical cross-sectional view of the thermal electrostatic ink jet recording head of the present embodiment. As described above, on the respective electrodes 22 and 24, for example, SiO 2 is formed.
_{The second} insulating film 26 is laminated, and C is formed on the insulating film 26.
An electrically conductive layer 28 made of r-Cu-Cr is laminated. Reference numeral 30 denotes an ink material, which is supplied and held in a slit formed by the plate members 10 and 12 by an ink supply unit (not shown). The electroconductive layer 28 acts as an electrode, and by applying a high voltage between the counter electrode 32 and the electroconductive layer 28, an electrostatic field is induced and applied to the ink material 30. The electrically conductive layer 28 is continuously formed in the slit direction of the plate member 10 as shown in FIG. However, the electrically conductive layer 28 may be divided into a plurality of parts in the slit direction. Reference numeral 34 is a recording medium such as paper.

The electrically conductive layer 28 for electrostatic induction is provided at a position lower than the tip portion of the heating resistor 16 by several tens of μm in order to prevent gas discharge between the electrically conductive layer 28 and the counter electrode 32 provided via the recording medium 34. ing. Furthermore, the distance between the tip 20 of the plate members 10 and 12 and the counter electrode 32 is 200 to 300 μm.
The range of m is desirable.

The operation of the thermal electrostatic ink jet recording head configured as described above will be described below. The heating resistor 16 at the location corresponding to the image information has
Pulsed electrical energy of 2.0 W is applied. As a result, the heating resistor 16 is caused to generate heat, and the temperature of the ink material 30 at the location corresponding to the image information is instantaneously raised to about 200 ° C., and the physical properties such as viscosity, surface tension, and electrical conductivity are suddenly changed. To bring. At the same time, by applying a high voltage of 1.0 to 3.0 KV between the electric conductive layer 28 and the counter electrode 32, the ink material at the location heated to about 200 ° C. flies to the recording medium 34. We were able to.

However, the heat generation of the heating resistor 16 and the application of the electrostatic field between the electric conductive layer 28 and the counter electrode 32 do not necessarily have to be performed at the same time, and may be performed at a certain timing. Further, an electrostatic field may be constantly applied to generate heat in the heating resistor 16 at a location corresponding to image information.

In the above-described embodiment, the distance A between the front end of the heat generating resistor 16 and the slit edge, that is, the ink flying side end 20 of the plate members 10 and 12 is 100 μm, but this distance A is 300 μm and 600 μm. A thermal electrostatic ink jet recording head was prepared and a comparative experiment was conducted.

In the recording head with the distance A of 100 μm, 0.4
The ink material started flying with W and an applied energy of 0.7 msec, and the image dot size was 50 to 60 μm. On the other hand, in the recording head with the distance A of 300 μm and the recording head with the distance of 600 μm, the applied pulse width of 1.4 msec was required under the same power condition. The obtained image dot sizes are about 100 μm and 3 respectively.
It was 00 μm. The applied pulse width is 0.5 msec.
The distance A was 300μ when the applied voltage was changed by fixing to
Ink jetting started only when a voltage of 1.2 W was applied to the m recording head and a voltage of 2.5 W was applied to the recording head having a distance A of 600 μm. Image dot size is 70μm,
It was about 100 μm.

According to this experiment, by setting the distance between the tip of the heating resistor 16 and the slit edge, that is, the tip 20 of the plate members 10 and 12 to 300 μm or less, preferably 100 μm or less, thermal diffusion can be sufficiently suppressed and flight It has been found that the ink can be raised to temperature at high speed.

The difference in image dot size is a prominent manifestation of thermal diffusion,
If a high voltage is applied to the heating resistor to prevent this, the heating resistor is burdened and its life is shortened. In order to prevent this, as in the present invention, the distance between the tip of the heating resistor and the slit edge is 300 μm, preferably 100 μm.
By providing the heating resistor 16 so that it is within the range,
It is possible to reduce the energy required for heat generation.

Further, in the present invention, the control electrode 22 and the return electrode 24, which form the energizing electrode, are drawn out from the ink supply side, so that the distance between the tip of the heating resistor 16 and the slit edge is made extremely small. It is possible to achieve a distance of 300 μm or less, preferably 100 μm or less.

Although the heating resistor array is provided only on one plate member in the above-described embodiments, the heating resistor array may be provided on both plate members.

EFFECTS OF THE INVENTION As described in detail above, according to the present invention, the tip of the means for selectively heating the ink material is provided within a distance of 300 μm from the ink material flying side end of the recording head composed of an insulating substrate. As a result, thermal diffusion can be sufficiently suppressed, and the ink can be heated to the flight temperature at high speed.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a heating resistor array of the recording head of the present invention, and FIG. 2 is a longitudinal sectional view of a recording head having the heating resistor array of FIG. 10, 12 ... Plate member (insulating substrate), 14 ... Slit wall, 16 ... Heating resistor, 18 ... Heating resistor array, 22 ... Control electrode, 24 ... Return electrode, 26 ... Insulation Layer, 28 ... Electrically conductive layer, 30 ... Ink material, 32 ... Counter electrode, 34 ... Recording medium.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiko Fujimura 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.Ebina Business Office (72) Inventor Keishi Fujimaga 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.Ebina Business In-house (72) Inventor Kiyoshi Horie 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd. Ebina Works (56) References JP-A-59-12858 (JP, A) JP-A-56-46769 (JP, A) JP 62-151348 (JP, A)

Claims (1)

[Claims] 1. A means for selectively heating the ink material on a slit wall of the slit, and an electrostatic field induction for inducing and applying an electrostatic field to the ink material, wherein a slit suitable for holding the ink material is defined by a substrate. And a means for selectively heating the ink material, wherein the means for selectively heating the ink material comprises a heating resistor group arranged at equal intervals in the slit direction of the slit, and the heating resistor group. Is provided on the slit wall so that the tip portion thereof is within a distance of 300 μm from the ink material flying side end portion of the recording head composed of the substrate, and the electrostatic field induction means is provided with an insulating layer on the heating resistor group. A thermal electrostatic ink jet recording head characterized in that it is provided through.