JPH0284344A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To prevent the widening of the distribution of the line of electric force of the electric field formed from the electrode on an ink side to the counter electrode in a sub-scanning direction to a necessary extent or more by setting the width of the counter electrode in the sub-scanning direction to the specific magnification or less of the slit width of an ink emitting part. CONSTITUTION:A plurality of dot corresponding heating units 11 arranged in a slit S like emitting part corresponding to printing dots, the electrode 14 on an ink side in contact with the conductive ink I allowed to fill the ink emitting part and the counter electrode 21 arranged in opposed relation to the ink emitting part so as to interpose recording paper 8 are provided and the dot corresponding heating unit 11 corresponding to the position of a printing dot based on image data is allowed to generate heat in such a state that predetermined potential difference is held between the electrode 14 on the ink side and the counter electrode 21 and the conductive ink I in the vicinity of the dot corresponding heating unit 14 concerned is allowed to jet from the ink emitting part toward the recording paper 18. In the ink recording apparatus thus constituted, the width (h) of the counter electrode 21 in the sub-scanning direction is set to 10 times or less of the width of the slit S of the ink emitting part.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to the so-called thermoelectrostatic slit jet type (
For details regarding TSJ>'s inkjet recording device, please see
A plurality of dot-compatible heating elements arranged in a slit-shaped ink ejection section corresponding to the printed dots, an ink-side electrode that comes into contact with the conductive ink filled in the ink ejection section, and an ink-side electrode that faces the ink ejection section with the recording paper in between. The ink-side electrode and the facing electrode are arranged at a predetermined potential difference between the ink-side electrode and the facing electrode, and a dot heating element corresponding to the position of the printed dot is heated based on the image information to generate the dot. The present invention relates to an inkjet recording device in which conductive ink near a corresponding heating element is ejected from an ink ejection unit toward recording paper.

[Prior Art] The basic mechanism of this type of inkjet recording apparatus is as shown in FIG.
(See Publication No. 67301). This is a so-called thermostatic slit jet type (TSJ) recording device, and in its print head section, an ink ejection section 10 is formed in the shape of a slit S, and the inner wall of this slit S section corresponds to the print dot. A heating resistor 11 (dot-compatible heating element) is provided. A current-carrying electrode 12 is bonded to each heat-generating resistor 11, and an insulating layer 13 and a conductive layer 14 are laminated on top of the heat-generating resistor 11 and current-carrying electrode 12 in this bonded state. It has become. The inside of the slit S is filled with conductive ink, and in this state, a voltage is applied to each heating resistor 11 via the current-carrying electrode 12, and the conductive ink I is applied to the conductive layer 14. The ink side electrode is formed by being filled with the ink. A facing electrode 20, which also serves as a feeding roller for the recording paper 18, is disposed facing the print head portion having such a structure, and the recording paper 18 is wound around the facing electrode 20.

In this thermostatic slit jet type recording device, a heating resistor 1 corresponding to a printing dot position based on image information is used.
A predetermined voltage is applied between the conductive layer 14 and the facing electrode 20 at the same time as the current is applied to the electrode 1 . Then, the conductive ink in the vicinity whose viscosity and surface tension have decreased due to the heat generated by the heating resistor 11 is exposed to an electric field formed between the conductive ink (2) and the facing electrode 20 due to the voltage applied between the electrodes 14 and 20. The electrostatic force from the discharge unit 10 causes the recording paper 18 to fly toward the recording paper 18 . In this way, by applying a voltage between the conductive layer 14 and the facing electrode 20 at the same time as the heating resistor 11 is switched on based on the image information, and by sequentially moving the recording paper 18 (nl scanning), Recording paper 18
A dot image corresponding to the image information is drawn on top.

[Problems to be Solved by the Invention] Incidentally, in the conventional inkjet recording device as described above, the variation in the dot printing position in the sub-scanning direction on the paper is relatively large, and fine images may appear around the dot print image. The above noise is likely to occur.

This is because in this type of recording device, when a voltage is applied between the ink side electrode and the facing electrode, the conductive ink I filling the ink side electrode itself can be considered as a kind of electrode, but the electrode and the facing electrode 2 This is because the lines of electric force f formed between the two extend in the sub-scanning direction, as shown in FIG. 6, for example. In addition, after being deviated and flying along the spread lines of electric force f, when the voltage applied to the heating resistor 11 is cut off, the remaining string-like conductive ink (
The thread) does not return to the slit as it is, but falls around the ejection port, and its tip becomes contaminated by the conductive e.In this state, the prescribed voltage is again applied to each electrode 14 and 20, and the When the resistive heating element 11 is energized, the spread lines of electric force f that are formed fly away to the ink attached around the ejection opening, causing noise on the image.

Therefore, an object of the present invention is to prevent the distribution of the lines of electric force of the electric field formed from the ink-side electrode side to the facing electrode side from expanding more than necessary in the sub-scanning direction.

[i! [Technical means for solving two problems] The present invention includes a plurality of dot-compatible heating elements (11) arranged in a slit S-shaped ink ejection portion corresponding to the depths of printed dots, and a conductive heating element filled in the ink ejection portion. The ink side electrode (14) has an ink side electrode (14) that comes into contact with the sexual ink ■, and a facing electrode (21, 28) that is arranged to face the ink ejection part with the recording TFI (18) in between. and facing electrodes (21, 28)
A dot-compatible heating element (11) corresponding to the printing dot position based on the image information is
) to generate heat, the heating element corresponding to the dot (1
4) This assumes an inkjet recording device in which nearby conductive ink I is ejected from an ink ejection unit toward the recording paper (18), and technical means for solving the above problems in the inkjet recording device. teeth,
The subscanning of the facing electrodes (21, 28) in the sub-scanning direction is set to 10 times or less the width of the slit S of the ink ejection section.

The facing electrodes (21, 28) are embedded and fixed in a paper support that supports the back surface of the recording paper (18), and a wear-resistant layer is formed on the surface of the paper support that comes into sliding contact with the recording paper (18). This is to prevent damage to the recording paper 4 due to the relatively narrow facing electrodes (21, 28), and also to prevent damage to the recording paper 4 due to wear of the sliding surface of the paper support with the recording paper (18).
8) is preferable in that it prevents the situation from being exposed.

The abrasion resistant layer of the paper support is formed of the discharge suppressing member, which means that the ink side electrode (14) and the facing electrode (21, 28)
) is preferable in terms of preventing unnecessary discharge between the two.

Further, the discharge suppressing member is made of a high resistance material or a dielectric material.

Furthermore, it is preferable to arrange a charge suppressing material in sliding contact with the back surface of the recording paper (18) in order to prevent the recording paper from being charged by being exposed to an electrostatic field.

[Function] The dot-compatible heating element (11) corresponding to the dot printing position based on the image information is made to generate heat, and the ink side electrode (11) is made to generate heat.
4) and the facing electrodes (21, 28) to a predetermined potential difference. Then, the spread of the lines of electric force of the electric field formed between the conductive ink I in the ink extrusion section and the facing electrodes (21, 28) becomes relatively small.

Then, the conductive ink I, whose viscosity and surface tension have been reduced by the heat generated by the dot-compatible heating element (11), flows from the ink discharge section 1 along the lines of electric force f narrowed to a relatively narrow range as described above. Fly.

[Example] Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a diagram showing an example of the basic configuration of an inkjet recording apparatus according to the present invention.

In the same figure, 19 is a print head main body, and the structure of this print head main body 19 is almost the same as that of the conventional one shown in FIG. An ink ejection section is formed. Then, conductive ink is supplied into the ink chamber 15 through the ink supply pipe 16 by the action of a pump or the like (the illustrated path), and the conductive ink I is constantly kept inside the ink chamber 15 up to the opening end of the slit. It is in a filled state.

A heating resistor 11 is disposed on the bottom plate of the ink chamber 15 at a density corresponding to the printing pixel density (e.g., 8 dots/tuttr) over a width equivalent to the assumed width of the paper (in the direction perpendicular to the plane of the paper). A current-carrying electrode and a current-carrying electrode 12 are connected to the heating resistor 11 .

Further, an insulating layer 13 and a second conductive layer 14 are laminated on top of the heating resistor 11 and current-carrying electrode 12 in this bonded state, and this conductive layer 14 is electrically connected to the heating resistor 11 and current-carrying electrode 12. The electrodes on the ink side are insulated from each other.

On the other hand, regarding the facing electrode body 30, which is arranged at a predetermined distance from the print head main body 19 having the above-described structure and also serves as a supporting function on the back side of the recording paper 18, the above-mentioned print head main body A metal plate with a thickness thinner than the slit S width of 19 (for example, stainless steel, nickel, gold,
The facing electrode 21 is made of epoxy, copper, chromium, etc.
It has a structure in which it is sandwiched between insulating blocks 22 made of polycarbonate, fluororesin, ceramic such as alumina, or the like.

Further, a wear-resistant layer 23 is formed on the surface of the facing electrode body 30 that comes into sliding contact with the recording paper 18 . This wear-resistant layer 23 prevents wear of the facing electrode body 30 itself due to sliding contact with the recording paper 18, and furthermore, by selecting a material with excellent dielectric strength, the layer 23 is formed between the ink side electrode 14 and the facing electrode 21. The effect of reliably suppressing the discharge of in particular,
Carbon, 5102, ZnO, etc. to urethane, epoxy,
It is formed by appropriately dispersing it in a binder such as polyester and applying it to the recording paper sliding contact surface of the facing electrode body 30, or by applying S+02-Ta, Zr-T to the sliding contact surface.
a, 5i02-8iO1S i N-Ta, S i
It is formed by depositing a film of 02-Cu, Ta205, etc. When considering discharge suppression in this way, the wear-resistant layer 2
It is preferable that the volume resistivity value of the material forming 3 is 1014 Ω·m or more.

With respect to the print head main body 19 and the facing electrode body 30,
A high voltage power supply 25 applies voltage (for example, 2.0 KV, positive on the conductive layer 14 side) between the conductive layer 14 serving as the ink side electrode and the facing electrode 21, and each heating resistor 11 is energized. A driving power source 26 and a synchronization control circuit 27 that synchronizes voltage application by the high voltage power source 25 and energization by the driving power source 26 are provided.

In the inkjet recording apparatus as described above, for example, the conductor 1114 on the print head main body 19 side is
In the process of applying a voltage between the electrode 23 and the facing electrode 23, if a pulse current is applied to the heating resistor 11 corresponding to the dot based on the image information in synchronization with the voltage application, the heating resistor 11 that generates heat due to the energization can be The viscosity and surface tension of the ink I around the electrodes 11 are reduced, and the ink I is applied to each of the electrodes 14.
The electric field generated by applying a voltage to the recording paper 21 causes the recording paper 18 to fly toward the recording paper 18 . At this time, the electric lines of force f of the electric field formed between the ink surface at the tip of the slit S and the facing electrode 21 are set so that the plate thickness of the facing electrode 21 is thinner than the width of the slit S of the print head main body 19. Therefore, for example, as shown in FIG. 2, the ink becomes constricted from one surface toward the facing electrode 21. Therefore, there is little variation on the recording paper 18 of the ink droplets flying along the lines of electric force f narrowed toward the facing electrode 21. Further, since the ink adhered to the outside of the slit opening tip of the print head main body 19 also flies along the electric force lines f, noise on the image is also reduced.

FIG. 3 shows a facing electrode body 30 facing the print head main body 19.
It is a figure which shows the other structural example of.

In this example, a tungsten wire 28 constitutes a facing electrode, and the diameter of this tungsten wire 28 is set smaller than the slit width of the print head main body 19. The tungsten wire 28 serving as the facing electrode is held in the form of being partially buried in the tip of the insulating block 22, and furthermore, a wear-resistant layer 23 similar to that described above is formed on the surface of the tungsten wire 28. The recording paper 18 is supported on the front surface.

In each of the above embodiments, the slit width S of the print head main body 19 is
is 50 μm, whereas the thickness of the plate-shaped facing electrode 21 is 100 μm.
In addition, the diameter of the wire-shaped facing electrode 28 is set to be about 120 μm, and density unevenness in the sub-scanning direction occurs in solid images, 50% halftone images, and 25% halftone images, respectively. Good printing results were obtained with no blemishes.

Some of the printed image states when the width of the facing electrodes is changed in the apparatus configuration shown in FIG. 1 are shown below. In this case, the slit width S is 50 μm, the heating pulse for the heating resistor 17 is 0.25 W, 2 m5 EC, 13 the electric layer 14 and the facing electrode 2.
Electrostatic pulse applied during 1 hour is 2.0KV, 0.4m5E
Set t'L T to C respectively.

As mentioned above, when the width of the facing electrode was 600 μm, density unevenness was observed in the sub-scanning direction in each image, solid image and 50% halftone image.
0. In the case of 100 μm, good printing results with no density unevenness in the sub-scanning direction were obtained for all solid images, 50% halftone images, and 25% halftone images. from this result,
The facing electrode width is 10 times or less than the slit width (in this case, 50
0 μm or less), the spread of electric lines of force formed between the open end of the slit and the facing electrode will not have a negative effect on the image, and the image will be good without density unevenness in the sub-scanning direction. Print results are obtained.

FIG. 4 shows yet another structural example of the facing electrode body 30.

This example is basically the same as that shown in FIG. 1, in which a plate-shaped facing ffi pole 21 is sandwiched between insulating blocks 22, and a wear-resistant layer 23 is formed on the sliding surface of the recording paper 18.

Further, a conductive layer 29 grounded on the upper and lower surfaces of the insulating block 22 is formed so as to be in sliding contact with the recording paper 18 at its leading end.

This grounded conductive layer 29 functions as an antistatic material,
The potential of the recording paper 18 is always maintained at the ground level to prevent it from being charged. This makes the state of the electrostatic field more stable and the printing state more stable.

[Effects of the Invention] As described above, according to the invention described in claim 1, since the width of the facing electrode in the sub-scanning direction is set to 10 times or less the slit width of the ink ejection part, the conductive ink tip and The electric field line distribution of the electric field formed between the facing electrodes is narrowed down to some extent.

As a result, variations in dot printing positions on the recording paper in the sub-scanning direction are reduced, and noise around the dot print image is also reduced. Therefore, recording can be performed with better image quality.

According to the second aspect of the invention, since the facing electrode is embedded in the paper support and the abrasion resistant layer is formed on the surface of the paper support that comes into sliding contact with the recording paper, recording using the relatively narrow facing electrode is possible. In addition to preventing damage to the paper, it is possible to prevent the facing electrode from being exposed from the paper support due to abrasion due to sliding contact with the recording paper.

According to the invention described in any one of claims 3 to 5, since the wear-resistant layer is formed of a discharge inhibiting material, it is possible to reliably prevent discharge between the ink side electrode and the facing electrode, and the above-mentioned Combined with the fact that the facing electrodes are buried within the paper support without being exposed, the safety of the device is further enhanced.

According to the invention described in claim 6, since the charge suppressing material is arranged in sliding contact with the back surface of the recording paper, it is possible to suppress the charge on the recording paper before and after printing, and the printing state becomes more stable.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the basic configuration of an inkjet recording apparatus according to the present invention, FIG. 2 is a diagram showing the state of electric lines of force formed by the electrode configuration shown in FIG. 1, and FIGS. The figure shows another example of the structure of the facing electrode body, and FIGS. 5 and 6 show a conventional inkjet recording apparatus. [Explanation of symbols] 11... Heat generating resistor 12... Current-carrying electrode 13... Insulating layer 14... Conductive layer 18... Recording paper 19... Print head body 21... Facing electrode 22... Insulating block 23... Wear-resistant layer 25... High voltage power source 26... Drive power source 27... Synchronous control circuit 30... Facing electrode body

Claims (6)

[Claims] (1) A plurality of dot-corresponding heating elements (11) arranged in a slit (S)-shaped ink ejection part corresponding to the printed dots;
An ink side electrode (14) that comes into contact with the conductive ink (I) filled in the ink ejection part, and facing electrodes (21, 2) that are arranged opposite to the ink ejection part with the recording paper (18) in between.
8), and the ink side electrode (14) and the facing electrode (
21, 28) while maintaining a predetermined potential difference between
By heating the dot-corresponding heating element (11) corresponding to the printing dot position based on the image information, the conductive ink (I) near the dot-corresponding heating element (11) is transferred from the ink ejection unit to the recording paper (18). In the inkjet recording device, the width (h) of the facing electrodes (21, 28) in the sub-scanning direction is set to 10 times or less the width of the slit (S) of the ink ejection part. Inkjet recording device. (2) In the inkjet recording device according to claim 1, the facing electrodes (21, 28) are embedded in a paper support that supports the back surface of the recording paper (18), and the surface of the paper support that comes into sliding contact with the recording paper An inkjet recording device characterized by having a wear-resistant layer formed on the side. (3) The inkjet recording apparatus according to claim 2, wherein the wear-resistant layer of the paper support is formed of a discharge suppressing member. (4) The inkjet recording apparatus according to claim 3, wherein the discharge suppressing member is a high-resistance material. (5) The inkjet recording apparatus according to claim 3, wherein the discharge suppressing member is a dielectric. (6) An inkjet recording apparatus according to any one of claims 1 to 5, characterized in that a charge suppressing material is disposed in sliding contact with the back surface of the recording paper.