JP2658020B2 - Ink jet recording device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ink jet recording apparatus,
The present invention relates to an improvement in an ink jet recording apparatus that flies ink using thermal energy and electrostatic energy.

[Prior Art] As a conventional ink jet recording apparatus, a large number of ink discharge devices that seal ink are provided with discharge ports (orifices) corresponding to pixel densities, and pressure pulses are appropriately applied to the ink discharge devices. 2. Description of the Related Art There has been known an apparatus in which ink is ejected from an ejection port.

In this type, a large volume ratio between the ejection port and the ink ejection device must be ensured in order to maintain the ink ejection operation from the ejection port. Therefore, it is difficult to reduce the size of the ink ejection device. Minutes, the arrangement pitch between the ejection ports must be increased to some extent, not only can the image recording density not be set high, but also the ink is ejected by mechanical scanning of applying a pressure pulse. Therefore, there is a problem that the recording speed is inevitably reduced.

As means for solving such a problem, a magnetic ink is arranged near a magnetic electrode array, an ink ejection state corresponding to an image density is formed by using a swelling of the ink by a magnetic field, and the magnetic ink is applied to a recording sheet by an electrostatic field. A method using a so-called magnetic ink jet method in which ink is caused to fly to the side (Japanese Patent Application Laid-Open No. 55-69469), or a method in which ink is filled in a slit-shaped ink reservoir parallel to an electrode array and is opposed via a recording sheet A so-called flat-scanning ink jet method in which ink flies toward a recording sheet according to an electric field pattern formed between an electrode and an electrode array is applied (Japanese Patent Application Laid-Open No. 56-1981).
No. 37163) Alternatively, by applying thermal energy to the ink, the ink is rapidly heated to cause film surface boiling, and the pressure rise due to the rapid growth of bubbles in the discharge port (orifice). An application of a so-called thermal bubble jet method in which ink is ejected from a discharge port (Japanese Patent Application Laid-Open No. 55-161664) is provided.
In each of the conventional inkjet recording methods described above,
In any case, not only can the density of the recorded image be increased, but also high-speed recording can be performed as much as electronic scanning becomes possible.

[Problems to be Solved by the Invention] However, in the case of applying the above-mentioned magnetic ink jet method, it is necessary to use ink mixed with magnetic powder, so that the ink is necessarily black. This makes it difficult to obtain a color image by overprinting ink. Further, in the application of the above-described flat-scanning inkjet method, clogging of the ink can be improved by eliminating the need for a fine orifice, but a high voltage must be applied to fly the ink. Therefore, in order to prevent voltage leakage between adjacent and neighboring electrodes, it is necessary to drive the electrode array in a time-division manner, which is not preferable for high-speed recording. Further, in the case of applying the above-described thermal bubble jet method, it is necessary to rapidly heat and raise the temperature of the heating element in order to cause the film surface to boil. There is a problem in that the heating resistor protection layer provided as a means tends to be thermally deteriorated.

In order to solve such a problem, the present inventors have:
A so-called thermal electrostatic ink jet recording apparatus has already been proposed in which a heat signal according to image information is applied to recording ink and an ink portion heated based on a predetermined electrostatic field is caused to fly to a recording sheet side. I have.

According to this type, it is not necessary to use magnetic ink by a so-called magnetic ink jet method, and accordingly, colorization based on overprinting of ink can be easily realized, and static ink such as a so-called flat ink jet method can be realized. It is not necessary to fly the ink only by the electric field, and it is not necessary to extremely increase the strength of the electrostatic field, so that voltage leakage between the vicinity of the ink can be effectively prevented. Since it is not necessary to fly the ink only with energy, the amount of heat energy can be suppressed to some extent, and thermal deterioration of the ink can be effectively prevented. Therefore, high-speed, high-density recording can be performed while effectively preventing the drawbacks of the conventional systems.

By the way, in such a thermal electrostatic ink jet recording apparatus, as a means for applying a heat signal to the ink, a heating array in which a plurality of heating resistors are arranged in accordance with the pixel density is usually used. The ink in the ink container is indirectly heated by being disposed at the edge of the main body near the opening of the ink container. At this time, when arranging the heat generating array on the edge portion near the opening surface of the ink containing portion, for example, a photolithography process or the like is performed on an insulating substrate constituting one wall of the ink containing portion. Since it is difficult to dispose the heat generating array near the end of the insulating substrate while maintaining it, usually, the heat generating array is disposed at a position some distance from the end of the insulating substrate, and the end of the insulating substrate is To set the relative position of the heat generating array near the end of the insulating substrate. In order to maintain good recorded image quality, it is necessary to stabilize the ink flying operation. One of the means is to form a stable ink meniscus. As described above, since the end of the head main body is cut, the end face is inevitably rough, and it is necessary to grind the end face to reduce the surface roughness. For this reason, there is a problem that the manufacturing process of the head body becomes complicated.

Further, since the heat generating array is mounted on the insulating substrate, heat from the heat generating resistor inevitably escapes to the insulating substrate side, and the heat transfer efficiency to the ink deteriorates accordingly. There are also problems.

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned problems, and improves the manufacturability while utilizing the advantages of the so-called thermal electrostatic inkjet method, and improves the ink quality. An object of the present invention is to provide an ink jet recording apparatus which improves heat transfer efficiency to heat.

That is, the present invention provides a head body having an ink chamber, and a heat signal applying unit that appropriately applies a heat signal corresponding to image information to each ink unit area according to a pixel density.
An electrostatic field forming means for forming a predetermined electrostatic field between the ink surface and the recording sheet at least at the time of ink flying, and forming the ink unit area to which a heat signal has been applied by the heat signal applying means into the electrostatic field formation. An ink jet recording apparatus configured to fly toward the recording sheet along the electrostatic field formed by the means, wherein an ink chamber partition wall located on the recording sheet side of the head body is formed of an organic resistive film, An opening for ink flying is opened in this organic resistance film,
As the heat signal applying means, a current-carrying electrode is disposed at a unit opening edge on both sides of the partition wall of the organic resistive film corresponding to the ink unit area in the ink flying opening, and each unit opening edge is provided according to image information. The unit is heated by energizing to heat the ink unit area.

In such a technical means, the head body may be appropriately changed in design as long as it has at least an ink chamber for accommodating ink, but the ink chamber partition wall located on the recording sheet side of the head body has It is necessary to provide an organic resistive film having an opening for flying ink. In this case, the opening may be a through hole according to the pixel density or a slit having an appropriately set width. At this time, the above-described through hole is desirable to accurately partition the ink unit area corresponding to the pixel, but a slit is desirable as an opening from the viewpoint of preventing ink clogging.

As the heat signal applying means, an organic resistor capable of generating heat by energization is used, and a unit opening edge of both surfaces of the partition wall of the organic resistive film corresponding to the ink unit area in the ink flying opening of the organic resistor. It is necessary to apply a signal corresponding to the image information to the current-carrying electrodes provided in the respective sections, and to design the corresponding portion to function as a heating section. In this case, in order to maintain good heat transfer efficiency to the ink, it is desirable to insulate between the current-carrying electrode and the organic resistance film that are exposed other than at the opening edge for the ink flight.

Further, the electrostatic field forming means may be appropriately changed in design as long as it forms an electrostatic field enough to cause the heated ink to fly toward the recording sheet between the ink surface and the recording sheet.

Furthermore, the ink to be used may be appropriately selected as long as it can fly when a predetermined heat signal is applied. In this case, the specific conditions for the ink to fly are that the viscosity and surface tension of the ink are reduced and the conductivity of the ink is improved to such an extent that the ink can fly due to the electrostatic field acting on the ink. is necessary.

Further, the organic resistive film constituting the recording sheet side of the head body is made of a suitable resin material in which a suitable conductive powder is dispersed and contained in an amount of several tens%, and has a volume resistivity of approximately 0.01 to 10 ⁴ Ωc.
m is used. In this case, aromatic polyamide, polyimide, polysulfone, polyphenylene oxide, polycarbonate, polyester, various fluorinated polymers are used as the resin material, and fine metal particles such as Ni, Cu, and Ag are used as the conductive powder. Powder or SnO ₂ , ZnO, F
Metal oxides such as e ₂ O ₃ and carbon are used.

[Operation] According to the technical means described above, when a signal corresponding to image information is applied to the energizing electrode, the unit opening edge of the organic resistance film is directly energized and heated, and the unit opening edge is heated. Is heated. Then, the viscosity and the surface tension of the heated ink unit area are reduced and the conductivity is improved, and the heated ink unit area is in a state where it is easy to fly, and the above-mentioned heating is caused by the attractive force of the electrostatic field acting on the ink surface. The ink unit area thus flies to the recording sheet side, and the end of the raised ink column is contact-transferred to the recording sheet surface to form an ink dot.

Hereinafter, the present invention will be described in detail based on an embodiment shown in the accompanying drawings.

1 to 3, an ink jet recording apparatus includes a head body 1 having an ink chamber 2 and an ink chamber 2
A thermal signal applying means 4 for applying a thermal signal to the ink 3 contained in the ink sheet 3 and an electrostatic field forming means 6 for forming a predetermined electrostatic field between the surface of the ink 3 and the recording sheet 5 are provided.

In this embodiment, the head main body 1 is made of an insulating material such as alumina ceramics and has a base member 11 having one end open to define a box-shaped ink chamber 2.
And an organic resistive film 12 for closing the opening of the base member 11.
It is composed of As the organic resistance film 12, for example, 30 μm of a polyimide containing 48% by weight of carbon is used.
A conductive polyimide film with a thickness of about m is used,
The volume resistivity is set to about 1 Ωcm. The organic resistive film 12 is provided with through holes 13 for ink flying according to the pixel density (for example, 6 / mm, hole diameter 100 μm).

Ink 3 is supplied to the ink chamber 2 at an appropriate pressure by an ink supply means (not shown).
Is filled in the through hole 13 by capillary action. In this embodiment, as the ink 3 contained in the ink chamber 2, for example, a conductive ink having a volume resistance of 10 ⁷ Ωcm or less is used, and its viscosity characteristic is approximately at room temperature (20 ° C.). The viscosity is set to about 20 to 300 cps, and the viscosity is reduced by one digit or more during heating (for example, 200 ° C.).

Further, the heat signal applying means 4 includes the organic resistance film 12.
And a pair of current-carrying electrodes 14 (14a, 14b) disposed at both ends of each through-hole 13 of the organic resistive film 12, and image information interposed between each pair of current-carrying electrodes 14. And a power supply 16 for energization connected in series with each switching element 15. In this embodiment, the current-carrying electrode 14 is composed of a ring-shaped portion 17 having an outer diameter of 150 μm disposed around the through-hole 13 and a linear portion 18 extending from one end of the ring-shaped portion 17. Yes,
Each opposed ring-shaped portion 17 is provided directly on the surface of the organic resistive film 12, while each opposed linear portion 18 is formed of an insulating layer such as SiO _2.
It is provided on the organic resistance film 12 via 19. And
On the outer surface side of the organic resistance film 12, an insulating film 20 of, for example, SiO ₂ is provided with a thickness of about 10 μm. More specifically, the manufacturing process of the current-carrying electrode 14 and the insulating film 20 will be described.
For example, after the insulating layer 19 is formed by sputtering on portions of both surfaces of the organic resistance film 12 except for the opening portion of the through-hole 13, Cr, Cu, Al, and the like are formed on the organic resistance film 12 and the insulation layer 19.
A metal layer such as Au is deposited, and the energizing electrode 14 of the pattern is formed by a photolithographic process, and thereafter, the insulating film 20 is formed by sputtering,
At this stage, a method is adopted in which the through holes 13 are opened by means such as laser, micro drill, and plasma processing.

Further, the electrostatic field forming means 6 includes a conductive layer 21 using the one energizing electrode 14b and a roll which is disposed at a predetermined distance from the surface of the ink 3 and also functions as a support surface of the recording sheet 5. -Shaped electrostatic induction electrode 22 and an electrostatic induction power supply interposed between the conductive layer 21 and the electrostatic induction electrode 22 to form an electrostatic field from the ink surface to the electrostatic induction electrode 22 side It consists of 23. In this embodiment, the electrostatic control pulse applied by the electrostatic induction power supply 23 to the electrostatic induction electrode 22 is output at a timing synchronized with the drive pulse of the heat signal application unit 4. .

Therefore, according to the ink jet recording apparatus according to this embodiment, the switching element is switched according to the image information to be recorded.
When the switch 15 is turned on, a current a flows through the corresponding through-hole 13 via the current-carrying electrode 14, as shown in FIG. 2, and the through-hole 13 is directly heated. The heat signal Q is applied to the ink unit area M facing the corresponding through-hole 13 to be heated. Then, in the heated ink unit area M, the viscosity and the surface tension of the ink 3 are reduced, the conductivity is improved, and the ink 3 changes to a state in which the ink 3 can fly. On the other hand, when the electrostatic control pulse is applied to the electrostatic induction electrode 22 of the electrostatic field forming means 6 in synchronization with the drive timing of the heat signal applying means 4, the ink 3 facing the conductive layer 21 and the dielectric induction An electrostatic field S is formed between the recording sheet 5 and the electrode 22, and the ink unit area M heated based on the electrostatic field S passes through the front side of the electrostatic induction electrode 22.
It will fly toward. At this time, as shown by the phantom line in FIG. 2, when the end of the ink column 3a protruding due to the flying operation comes into contact with the recording sheet 5, the ink 3 is attached and dislocated to the recording sheet 5, and the recording sheet 5 is displaced. An ink dot D is formed on the upper surface.

In the recording operation process of this embodiment, first,
Since the 13 edge portions are directly energized and heated, the ink unit areas M facing the through holes 13 are directly heated. Secondly, since the substrate supporting the heating array is not attached to the organic resistance film 12 as the heating element, the situation that the heat generated in the organic resistance film 12 escapes to the substrate side does not occur. Since the edge of the hole 13 is secured as a cylindrical peripheral surface, the heat generation area can be enlarged as compared with the case where the heating resistor is arranged on the flat surface. From these points, the efficiency of heat transfer to the ink unit area M is improved as compared with the conventional type using the heat generating array.

In order to demonstrate such a recording operation process, the present inventors have applied a driving pulse corresponding to image information of 7v, 0.5 ms,
When 1000V / 300μm and 0.5ms were applied synchronously as an electrostatic control pulse, a stable recording operation was performed at a repetition frequency of 500Hz, and the thermal signal power was confirmed to be about 0.1W / dot. .

Further, in this embodiment, when manufacturing the head main body unit U of the ink jet recording apparatus, a hole 13 for ink flying is opened in the organic resistive film 12,
A current-carrying electrode 14 is provided at the edge of the through-hole 13, and an insulating film 20 is further provided on the outer surface of the organic resistance film 12, while the organic resistance film 12 manufactured in this manner and a box-shaped base member 11 What is necessary is just to adhere and fix. In the head body unit U manufactured in this manner, the through holes of the organic resistive film 12 are formed.
13 As the edge is designed to function as a heating part,
As before, the step of cutting the substrate in disposing the heating resistor at the edge of the substrate can be omitted, and the surface roughness of the organic resistive film 12 is reduced to an extremely small value in manufacturing. Organic resistance film 12
The surface roughness of the insulating film 20 disposed thereon can be suppressed to an extremely small value correspondingly, and the step of polishing the end surface of the head main body 1 can be omitted. Therefore, a part of the work process when manufacturing the head main body unit U is reduced as compared with the related art, and the manufacturing workability can be improved accordingly. Further, since the surface roughness of the end surface of the head main body 1 can be suppressed to a very small value, the ink meniscus of the ink unit area M facing the through hole 13 can be held in a stable state. Become.

Further, in this embodiment, since the organic resistance film 12 is formed of a polyimide film having a moderate elasticity, if the organic resistance film 12 is expanded by heating,
Even if it is deformed by an impact load, a certain amount of deformation allowance is absorbed as elastic deformation. For this reason,
A rigid base member that is one of the constituent members of the head body 1
When the organic resistance film 12 is bonded to the organic resistance film 12, the sealed state and the bonded state between the two are kept good.

Furthermore, an insulating coating is formed on the outer surface of the organic resistance film 12.
Since the electrode 20 is provided, the discharge phenomenon between the current-carrying electrode 14 and the electrostatic induction electrode 22 is effectively prevented, and the ink meniscus in the through-hole 13 is reduced by the thickness of the insulating film 20. Since it is arranged close to the electrostatic induction electrode 22 side, the strength of the electrostatic field S acting on the ink meniscus is correspondingly increased, so that the electric charge can be easily induced to the ink meniscus.

In the above-described embodiment, the through holes 13 are used as the openings for flying ink. However, the present invention is not limited to this. For example, as shown in FIG. A slit 25 is formed in the organic resistive film 12, and a pair of energizing electrodes 26 (specifically, 26a, 26b), 27 (27a, 27b) may be provided, and the edge of each of the unit openings 25a may be energized and heated through the energizing electrodes 26, 27. According to this type, since there is no orifice portion that directly partitions the ink unit region M, clogging of the ink 3 can be effectively prevented as compared with the embodiment.

Further, in the above-described embodiment, the organic resistive film 12 is shown using a conductive polyimide film having a predetermined electrical conductivity and volume resistivity.However, the present invention is not limited to this. A resin film with a thickness of about 20 μm containing 40% by weight of carbon and having a volume resistivity of 30 Ωcm or polyester
Even if a resin film having a thickness of about 50 μm containing 20% by weight of SnO ₂ powder and having a volume resistivity of 3 × 10 ³ Ωcm is used, it is confirmed that the same effect as in the example is exerted. .

Further, as another modified example of the above embodiment, a through hole
The arrangement of the 13 groups may be staggered or oblique instead of a straight line, or one of the conducting electrodes 14 may be uniform, and one conducting electrode 14a may be used as the conductive layer 21 of the electrostatic field forming means 6.
And the like can be provided separately without using the same.

[Effects of the Invention] As described above, according to the ink jet recording apparatus of the present invention, the following effects can be obtained while taking advantage of the so-called thermal electrostatic ink jet method.

First, an opening for ink flying was opened in the organic resistive film constituting a part of the head main body, and the edge of the opening was appropriately heated by heating to directly heat the ink unit area. Compared to the type in which the heat generating array is provided on the upper side, the heat transfer path is direct, and the heat transfer efficiency to the ink can be improved because the heat loss to the substrate or the like is eliminated.

Secondly, when manufacturing the head body unit, the opening edge of the organic resistive film, which is a constituent member of the head body, can be easily configured as a heat generating portion, and the end surface of the head body is not subjected to a polishing step. Since the heat generating array can be formed smoothly, the number of manufacturing steps can be reduced and the manufacturing workability of the head body unit can be improved as compared with the type in which the heat generating array is provided on the substrate.

[Brief description of the drawings]

FIG. 1 is a perspective explanatory view showing one embodiment of an ink jet recording apparatus according to the present invention, and FIGS. 2 and 3 are II in FIG.
FIG. 4 is a perspective view showing a modified example of the ink jet recording apparatus according to the present invention. [Explanation of Symbols] (1) Head body (2) Ink chamber (3) Ink (4) Heat signal applying means (5) Recording sheet (6) Electrostatic field forming means (12) ... Organic resistive film (13) ... Through-hole (opening) (14) ... Conducting electrode (25) ... Slit (opening) (26, 27) ... Conducting electrode

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naho Inoue 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd. In-house (56) References JP-A-61-102254 (JP, A) JP-A-61-70039 (JP, U)

Claims (4)

(57) [Claims] 1. A head body having an ink chamber, a heat signal applying means for appropriately applying a heat signal corresponding to image information to each ink unit area corresponding to a pixel density, and at least an ink surface at the time of ink flying. An electrostatic field forming means for forming a predetermined electrostatic field between the recording sheet and the recording sheet, wherein the ink unit area to which the thermal signal is applied by the thermal signal applying means is formed by the electrostatic field forming means. An ink jet recording apparatus which is configured to fly to a recording sheet side along an ink jet head, wherein an ink chamber partition wall located on the recording sheet side of the head body is formed of an organic resistive film, and ink jetting is performed on the organic resistive film. And an energizing electrode at the edge of the unit opening on both sides of the partition wall of the organic resistive film corresponding to the ink unit area, as the heat signal applying means. The ink jet recording apparatus being characterized in that so as to heat the ink unit region by energizing heating each unit opening edge portion in accordance with image information. 2. An ink jet recording apparatus according to claim 1, wherein said organic resistance film is made of a conductive polyimide film. 3. An ink jet recording apparatus according to claim 1, wherein said opening is formed by a through hole according to a pixel density. 4. An ink jet recording apparatus according to claim 1, wherein said opening is constituted by a slit.