JPH1120170A - Ink jet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability of ejection of ink drops and to raise a density of nozzles to be formed on a recording head. SOLUTION: A recording head is so constituted that plate-like insulation substrates each having a conductive layer on the surface are laminated with an inner spacer 20 therebetween. A liquid ink 1 is supplied to the face provided with the conductive layer and a voltage is applied to the conductive layer. As a result, supplying of the ink to a tip of a nozzle 14 can be assured and sticking of a coloring agent in the ink to the nozzle can be prevented. Nozzle arrangement with high resolution can be achieved and the head having sufficient strength can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and more particularly to an ink jet recording apparatus using a liquid ink in which a coloring agent is dispersed in a solvent, and at least a coloring agent component contained in the ink as ink droplets on a recording medium. The present invention relates to an ink jet recording apparatus that records information including characters and images by flying.

[0002]

2. Description of the Related Art Recording dots (pixels) are formed by flying liquid ink as fine droplets called ink droplets onto a recording medium.
A recording apparatus that records an image by forming an image has been put to practical use as an inkjet printer. This ink-jet printer has the advantage that it has less noise than a mechanical recording device such as a wire dot printer, and does not require processing such as development and fixing as compared with an electrophotographic recording device such as the Carlson method. It has attracted attention as a plain paper recording technology.

Various types of ink-jet printers have been proposed so far. Typical methods include (a) discharging and flying ink droplets by the pressure of steam generated by the heat of a heating element. A piezoelectric method in which ink droplets are ejected by a mechanical pressure pulse generated by a piezoelectric element (for example, see Japanese Patent Publication No. 56-9429 and Japanese Patent Publication No. 61-59911). (Special Publication 53-1
No. 2138).

A recording head (hereinafter, referred to as an ink-jet head) used in an ink-jet printer is mounted on a carriage and is orthogonal to a conveying direction of a recording sheet (hereinafter, referred to as a sub-scanning direction) (hereinafter, main scanning). A serial scanning head that performs recording while moving in the direction has been put to practical use. Since the serial scanning head cannot perform recording unless it is always moved by a predetermined amount in the main scanning direction, it is difficult to increase the recording speed. Therefore, a line scanning type printer in which the recording speed is increased by using a long head in which the length of the recording head is set substantially equal to the width of the recording paper has been considered. Realization is not easy for the following reasons.

[0005] In the ink jet recording system, a large number of individual fine nozzles corresponding to the resolution are provided. However, evaporation or volatilization of a solvent is liable to cause local concentration of ink, which is a cause of clogging of the nozzles. Cause. Further, in the method of using the pressure of steam for forming an ink jet, the adhesion of unnecessary substances formed by reacting with the ink thermally or chemically induces nozzle clogging, and the pressure by a piezoelectric element is used. In the system, a complicated structure such as an ink flow path makes it easier to induce nozzle clogging. Even a serial scanning head using several tens to hundreds of tens of nozzles can cause nozzle clogging, but a line scanning head using many thousands of nozzles In
Further, it has been proved stochastically that the nozzles are clogged with a higher frequency of occurrence, and there is a problem that practical reliability is lacking.

Further, in the method using the pressure of steam, it is difficult to generate ink droplets having a diameter of 20 μm or less corresponding to recording dots having a diameter of about 50 μm on a recording paper. Is difficult to manufacture. Further, in the method using the pressure by the piezoelectric element, the structure of the recording head is complicated, so that it is also difficult to manufacture a high-resolution head due to a problem in processing technology. For this reason, in the conventional ink jet recording apparatus, there is a problem that it is difficult to improve the resolution in any method.

In order to solve these problems, a voltage is applied to an electrode array formed by arranging a plurality of individual electrodes formed of thin films on a substrate, and ink or ink is discharged from the ink liquid surface using electrostatic force. There has been proposed an ink jet recording method in which a colorant component in the ink composition is made to fly as an ink droplet.

More specifically, a method of flying ink droplets using electrostatic attraction (Japanese Patent Application Laid-Open Nos. 49-62024 and 56-62024)
Japanese Patent Application Laid-Open No. 7-502218) and a method in which the concentration of a coloring material is increased by using an ink containing a charged coloring material component to fly ink droplets (see Japanese Patent Application Laid-Open No. 7-502218). In these systems, the recording head has a slit-shaped nozzle structure that does not require a nozzle for each individual dot,
Alternatively, because of the nozzleless structure that does not require a partition of the ink flow path for each individual dot, it is effective for preventing and recovering from clogging of ink, which has been a major obstacle in realizing a line scanning recording head. is there. In the latter method of increasing the colorant concentration, ink droplets having a very small particle diameter can be stably generated and fly, so that the method is suitable for high resolution.

[0009]

However, in the above-described method of increasing the concentration of the colorant using the ink containing the charged colorant component and causing the ink droplets to fly, the charge polarity of the colorant and the voltage applied to it are usually used. Set the same polarity as the voltage.
This is for applying a force in the direction away from the electrode to the color material, and is natural for the purpose of discharging the color material component. However, the direction of movement of the colorant when a voltage is applied is not necessarily the direction of ejection of the ink droplet, and the colorant may escape from the electrode in the horizontal direction depending on the head structure. In such a case, the ink droplet is not ejected but only spreads laterally from the electrode. This is because the pressure on the ink due to the electrostatic force is considerably lower than the pressure due to the generation of bubbles or the piezoelectric material, and the ink cannot overcome the surface tension of the ink. For this reason, it is necessary to have a structure in which the surface tension of the ink at the voltage application point can be made as small as possible and the electric field force can be sufficiently exerted, and that the colorant does not easily escape.

In order to realize this, the structure of the ink droplet ejection position is formed in the shape of a weight, or the ink is reliably supplied and held to a predetermined position by utilizing the capillary force of the ink. Also, various improvements have been proposed, such as a configuration for preventing unnecessary movement of the colorant by an electric method. Among these improvements, the configuration in which the ink ejection structure is formed in the shape of a weight is disadvantageous in narrowing the pitch of ink ejection locations (that is, increasing the density of nozzles). In other words, arranging the weights at a high density involves manufacturing difficulties, and there is a limit in securing the contrast of the ink shapes. In order to maintain the reliability of ejection, it is necessary to form a thin film of ink on the electrode from the viewpoint of securing the electric field strength. This causes a phenomenon such as the adhesion of the coloring material to the electrode due to the fixing component, which causes a problem that it becomes difficult to discharge the ink after the operation is stopped for a certain period.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and it is possible to form a higher-density nozzle array while eliminating the problem of ink drying while securing the advantages of the ink jet recording system. An object is to provide a highly reliable ink jet recording apparatus.

[0012]

In order to achieve the above object, an ink jet recording apparatus according to claim 1 applies a voltage to a liquid ink in which a coloring material is dispersed in a solvent,
In an ink jet recording apparatus for recording information by flying ink droplets to form image points on a recording medium, a conductive layer was formed on a surface facing each other via a spacer while being laminated via a spacer. A recording head including a flat insulating substrate, an ink supply unit for supplying the liquid ink including the colorant between the insulating substrates of the recording head, and an ink droplet formed from the liquid ink between the insulating substrates. A voltage supply unit configured to apply a voltage to the conductive layer of the recording head so as to fly from the recording head to the recording medium.

According to a second aspect of the present invention, in the ink jet recording apparatus according to the first aspect, the insulating substrate constituting the recording head has a protruding portion protruding toward the recording medium, and the protruding portion. Is characterized in that it tapers toward the tip.

According to a third aspect of the present invention, there is provided an ink jet recording apparatus according to the first aspect, wherein the recording head is provided between the insulating substrates on which the spacers are interposed, and a leading end of the recording head is provided. An ink ejection substrate that projects toward the recording medium from the tip of the insulating substrate and that causes the ink droplets to fly is provided.

Further, the ink jet recording apparatus according to claim 4 is the ink jet recording apparatus according to claim 3, wherein the ink discharge substrate has a front end surface having a flat front end portion, and the front end surface is flat. It is characterized in that it protrudes from the tip of the insulating substrate in the direction of the recording medium.

Further, according to a fifth aspect of the present invention, in the ink jet recording apparatus according to the third aspect, the ink discharging substrate has a slit at a tip end thereof,
The present invention is characterized in that there are inclined surfaces inclined down both shoulders between both inner walls of the slit and both outer walls of the substrate.

Furthermore, an ink jet recording apparatus according to claim 6 is the ink jet recording apparatus according to claim 4 or 5, wherein the ink discharging substrate is provided with a conductive layer at least on an outer peripheral side thereof.

According to a seventh aspect of the present invention, in the ink jet recording apparatus according to the first aspect, the ink supply means is provided in the ink reservoir between the insulating substrates stacked so as to face each other via the spacer. An ink supply path for supplying liquid ink, and an ink recovery path for recovering from the ink reservoir the liquid ink having a reduced ink density by flying toward the recording medium.

According to an eighth aspect of the present invention, in the ink jet recording apparatus according to the seventh aspect, the ink supply path and the ink recovery path are provided in a plurality of sets, respectively, and the bypass flow path is provided in each set. The ink supply path and the ink recovery path are formed in different positions, and are provided for each set.

According to a ninth aspect of the present invention, in the ink jet recording apparatus according to the first aspect, the voltage supply means supplies the same voltage to the conductive layers formed on the opposing surfaces of the insulating substrate. Then, an image point is formed at a desired position on the recording medium corresponding to a substantially middle point of the separation distance of the insulating substrate.

Further, in the ink jet recording apparatus according to a tenth aspect, in the ink jet recording apparatus according to the ninth aspect, the voltage supply means supplies a different voltage to a conductive layer formed on an opposing surface of the insulating substrate. Thus, an image point is formed at a desired position of the recording medium which is displaced from a middle point of the separation distance of the insulating substrate.

According to an eleventh aspect of the present invention, in the ink jet recording apparatus according to the first aspect, a plurality of the recording heads are provided in a laminating direction of the insulating substrate and also in a direction orthogonal to the laminating direction. A plurality of rows are provided in a matrix so that ink droplets can fly based on print information in a predetermined area of the print medium corresponding to a fixed two-dimensional range.

According to a twelfth aspect of the present invention, a voltage is applied to a liquid ink in which a colorant is dispersed in a solvent, and an ink droplet is caused to fly to form a dot on a recording medium. In an ink jet recording apparatus for recording information, another insulating substrate laminated via a spacer, provided between the insulating substrates, and having a leading end protruding toward the recording medium from the leading end of the insulating substrate. A recording head including an ink discharge substrate, an ink supply means for supplying the liquid ink containing the colorant between the insulating substrates of the recording head, and ink droplets formed from the liquid ink between the insulating substrates And a voltage supply unit for applying a voltage to the ink discharge substrate that constitutes the recording head in order to fly the recording medium from the recording head to the recording medium. It is characterized by a door.

According to a thirteenth aspect of the present invention, in the ink jet recording apparatus according to the twelfth aspect, the ink discharge substrate has a slit at a tip end thereof, and both inner walls of the slit and both ends of the substrate. It is characterized in that it has an inclined surface falling down from both shoulders with the outer wall.

In the above configuration, a conductive layer is formed on the surface of an ink jet recording apparatus in which a voltage is applied to a liquid ink in which a coloring agent is dispersed in a solvent to form an image spot by causing ink droplets to fly. A flat insulating substrate (hereinafter, referred to as an ink holding substrate) is stacked with a spacer interposed therebetween, and a liquid ink is supplied between the ink holding substrates and a voltage is applied to the conductive layer to cause the ink droplets to fly. Cause. The ink holding substrate particularly has a tapered tip.

The ink moves in a narrow space (hereinafter, referred to as an individual ink flow path) formed between the ink holding substrates by capillary force, reaches the tip of the ink holding substrate without fail, and is held between the ink holding substrates. You. The ink droplets are ejected from the leading ends of the two ink-holding substrates. Since the present recording head is formed only by laminating the insulating substrates, the pitch of the nozzles with one unit between the ink holding substrates depends only on the thickness of the insulating substrate and the spacer.

Regarding the signal voltages applied to the conductive layers of the two ink holding substrates forming the nozzles, the same voltage may be set or voltages having different amplitudes may be applied. In the former case, ink droplets are ejected around the center of the nozzle, and in the latter case, the ink droplets are ejected with the position biased toward the lower voltage amplitude.

Further, an ink holding substrate having a conductive layer formed on the surface and a substrate made of an insulator having a projection at the tip (hereinafter, referred to as an ink discharge substrate) are sequentially laminated via a spacer to form a conductive layer. A similar effect can be obtained by applying a voltage to. The tip of the ink holding substrate may be tapered or not. In this case, while the ink is held between the ink holding substrates, the ink droplets are ejected from the protrusions of the ink ejection substrate inserted therebetween, and the ink ejection operation is performed only by the shape of the ink ejection substrate. Greatly depends on Further, the pitch of the nozzles depends on the thickness of each of the ink holding substrate, the spacer, and the ink discharging substrate. The same effect can be obtained by configuring the ink discharging substrate only with an insulator, and configuring the ink holding substrate with an insulating substrate having a conductive layer or the conductive substrate itself, and applying a voltage to the conductive layer.

The above construction is not limited to the case where a single nozzle is laminated, but the ink holding substrate or the ink discharging substrate may have a plurality of tapered portions or projections in a direction perpendicular to the laminating direction. It is possible. In this case, it is possible to arrange the nozzles two-dimensionally.

The ink control mechanism includes an ink supply section above or below the recording head and an ink recovery section on the other side. The ink flowing out of the ink supply unit flows along the periphery of the spacer and flows into the ink recovery unit.

Alternatively, the ink supply unit and the recovery unit are provided on the side of the recording head, and a common ink flow path is provided inside the ink holding substrate and the spacer in a direction perpendicular to the laminating direction of the ink holding substrate and the spacer. Is done. The ink common flow path includes at least two paths of an ink supply flow path and an ink recovery flow path, and each spacer has a bypass formed between the ink common flow path and the individual ink flow path. The ink that has flowed out of the ink supply unit is supplied to each individual ink channel through a common channel, reaches the opposite side of the head along the periphery of the spacer, and then flows into the ink recovery unit via another common channel. .

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the ink jet recording apparatus according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a configuration of a main part of an inkjet recording apparatus according to a first embodiment of the present invention.

In FIG. 1, the ink jet recording apparatus includes a plurality of nozzles 14 arranged in the main scanning direction of the recording medium 50 so that the ink droplets 2 fly toward the recording medium 50.
And an ink supply unit 30 provided commonly to these nozzles 14, an ink collection unit 31, an ink supply tank 32, and an ink collection tank 33.

For one unit of nozzle 14, two ink holding substrates 12 each composed of an insulating substrate 11 having a conductive layer 10 on one surface as shown in FIG. 2 are prepared, and as shown in FIG.
It is configured such that the conductive layer 10 is attached to the inside with the internal spacer 20 interposed therebetween. The individual ink flow paths 13 are formed in the nozzles 14, and the nozzles 14 are further laminated via an external spacer 21. As the insulating substrate 11, a material such as polyimide, glass epoxy resin, or polyethersulfone is used. The conductive layer 10 on the surface can be formed by depositing copper or gold. The spacers 20, 21 are made of a normal insulating material. The ink holding substrate 12 has a tapered tip for the purpose of increasing the electric field strength at the tip and making the shape of the ink droplet approximate to a cone shape or a teardrop shape to facilitate the ejection of the ink droplet. I have.

Behind the recording head 1, an internal spacer 20 is provided.
The ink supply unit 30 and the ink recovery unit 3
In addition, an ink holding material such as a sponge, which can hold ink, is inserted into the inside thereof in order to reduce the influence of disturbance such as vibration or to form a stable flow of ink. Ink supply unit 30 and ink recovery unit 3
1 can be installed either above or below. An ink supply tank 32 and an ink recovery tank 33 are connected to the ink supply unit 30 and the ink recovery unit 31, respectively.

An individual signal voltage source 41 and a common bias voltage source 42 are connected to the pair of ink holding substrates 12 constituting each nozzle 14. In front of the recording head,
A conductive drum 51 around which a recording medium 50 is wound is provided with a gap of about 0.5 mm on the surface, and the drum 51 is electrically grounded. The ink 1 to be used is one in which a positively-chargeable colorant component is colloidally dispersed and suspended in an insulating solvent together with a charge control agent, a binder, and the like.

Next, the operation of the recording head having the above configuration will be described. After the ink 1 supplied from the ink supply tank 32 fills the ink holding material of the ink supply unit 30, the ink 1
4 flows to the tip. Since the pair of ink holding substrates 12 form a very narrow flow path, a strong capillary force acts on the ink 1. As a result, the ink 1
4 can be reached. After that, it flows so as to travel around the inner spacer 20 (arrow in FIG. 1), flows into the ink recovery unit 31, and is recovered in the ink recovery tank 33.

Although a part of the ink 1 in the nozzle 14 is exposed to the open surface, since the strong surface tension is applied, the ink does not drip from the nozzle. As described above, since the ink droplet 2 contains the colorant at a higher ratio than the normal ink concentration, the amount of the colorant at the tip of the nozzle 14 may usually be insufficient. Therefore, nozzle 1
In order to maintain the ink density at the tip of No. 4 at a constant value, a flow is actively formed in the ink as described above. Therefore, the density of the ink flowing from the tip of the nozzle 14 to the ink recovery unit 31 is reduced.

The overall flow of the ink is as shown by the arrow in FIG. 1. The upper side forms an ink supply channel 13a and the lower side forms an ink recovery channel 13b via the internal spacer 20. When the inkjet recording apparatus starts a recording operation, a bias voltage of, for example, 1.4 kV is applied to the conductive layer 10 of each nozzle 14. At this time, nozzle 1
At the four tips, the colorant particles in the ink 1 become concentrated and distributed near the ink surface due to the electric field formed inside the ink, and a thin layer of the ink 1 is formed at the tip of the nozzle 14 (FIG. 3 (a)).

Next, for example, 400 V from the signal voltage source 41
Is superimposed, a meniscus having the ends of the two ink holding substrates 12 forming the nozzle 14 as skirts is formed, and the ink droplet 2 is formed from the tip of the meniscus.
Is discharged (FIG. 3B). The ejected ink droplet 2 flies by the electric field formed between the recording head and the drum 51, reaches the recording medium 50, and forms an image point.

As described above, in the present invention, the capillary force acting on the ink 1 can be used to the maximum by supplying the ink 1 through the narrow flow path formed between the two ink holding substrates 12. In addition, it is possible to increase the reliability of the ink supply and to reduce the influence of disturbance such as vibration of the apparatus as much as possible. Further, since the ejection position of the ink droplet 2 is at the center position between the two ink holding substrates 12,
The ink 1 in this portion is always held at a fixed position away from the ink holding substrate 12, and there are problems such as adhesion of the colorant particles to the ink holding substrate 12 or drying of the ink due to a mirror image or a contained fixing component. Can be removed. That is, it is possible to minimize the problem that re-discharge becomes difficult when the discharge operation of the ink droplet 2 is stopped for a certain period.

Since the pitch of the nozzles 14 depends on the thicknesses of the ink holding substrate 12, the internal spacers 20, and the external spacers 21, it is possible to realize a higher density nozzle arrangement by adjusting those values. Becomes The present invention is a structure that is advantageous in strength in order to take a laminated structure,
Even when a recording paper jam or the like occurs, damage to the recording head can be reduced, and a highly reliable apparatus can be provided. Further, it is configured such that signal lines can be drawn from three places, that is, the upper side, the lower side, and the rear side of the recording head. That is, since the signal lines can be distributed to a maximum of three places, there is also an advantage that even if the nozzle arrangement becomes high density, a wiring structure adapted to the arrangement can be obtained.

In the ink jet recording apparatus according to the first embodiment, the recording head is shown to be positioned laterally with respect to the drum 51, but the recording head faces the center of the drum. As long as it is, it can be positioned at any angle with respect to the drum. This is exactly the same for all embodiments herein.

In the ink jet recording apparatus according to the first embodiment, the ink holding substrate 1 constituting the nozzle
The tip of the nozzle 2 has a pointed shape, but if this is provided with a flat portion 14a at the tip as in the modification shown in FIG. 4, the ink 1 can reach the tip of the nozzle 14 more reliably. it can. If the angle of the tip is sharp, the amount of ink that can be present at the tip decreases and the surface tension also increases,
This is in consideration of the difficulty in supplying the ink 1 in the tip direction. Thereby, the reliability of ejection can be improved.

In the first embodiment, the ink supply unit 30 and the ink recovery unit 31 serve as an ink supply mechanism.
Are separated from each other, but it is also possible to adopt a configuration in which both are common and only the ink supply tank 32 is connected (FIG. 5). In this case, the ink 1 is supplied to the tip of the nozzle 14 from both the upper and lower sides via the internal spacer 20, and the flow of the ink is not artificially generated. In the first embodiment, a positive ink flow is formed to keep the ink density at the tip of the nozzle 14 constant. However, when the electric field inside the ink fluctuates due to the discharge of the colorant, The colorant is automatically supplied to compensate for the variation.

That is, the colorant is supplied to some extent even if there is no global ink flow. If the balance between the consumption of the colorant and the spontaneous supply capacity is maintained depending on the recording frequency or the ink concentration used, it is not necessary to form an aggressive ink flow. Can respond. In this case, since the color material shortage occurs eventually, when the color material runs short, replenish the ink with a high density from the ink supply tank 32 or change the color material density filled in the head. Low ink is once swept out of the head and the ink supply tank 32
The problem can be solved by replenishing the ink having the desired density from the above. Observation of the colorant density can be realized by providing a sensor for detecting the colorant amount at any position in the head such as in the nozzle or the ink supply unit. Note that this is not limited to the first embodiment, and the same can be said for the other embodiments described in this specification.

Next, an ink jet recording apparatus according to a second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a view of the tip of the recording head of the ink jet recording apparatus according to the second embodiment as viewed from directly above. The structure of the recording head itself is exactly the same as in the first embodiment. However,
In the first embodiment, the same signal voltage is applied to the two ink holding substrates 12 constituting the nozzle 14, whereas in the second embodiment, a pulse voltage is applied from different signal voltage sources. Are different.

The principle of operation will be described. A certain nozzle 1
4 when an image signal is input, one of the conductive layers 1
Assuming that a signal applied to 0 is Vs1 and a signal applied to the other conductive layer 10 is Vs2, a relationship of Vs1 <Vs2 or Vs1> Vs2 is always established between the two. The former case will be described with reference to FIG.
Since there is a potential difference of “Vs2−Vs1” between them, the colorant in the ink moves to the left in the figure. Therefore, the meniscus formed by the ink surface is inclined to the left, and the ink droplet 2
Is discharged (FIG. 7A). When the relationship is reversed, the ink droplets 2 are ejected in the same manner from the vicinity of the tip of the ink holding substrate 12 on the right side (FIG. 7B). This is an example in which ink droplets are ejected from the lower signal voltage,
By changing the conditions such as the volume resistivity of the ink, the viscosity, and the size of the colorant particles to be contained, the ink droplets 2 are arranged in descending order of the signal voltage as shown by broken lines in FIGS. Can be ejected.

In the second embodiment, by inverting the relationship between Vs1 and Vs2 at regular intervals as described above,
Ink droplets can be ejected from two places in one nozzle. In other words, image spots can be formed at a density twice the nozzle array density, and high-resolution image spots can be formed. Further, by adjusting the ratio between Vs1 and Vs2s, it is also possible to form a pixel from an arbitrary position between the two ink holding substrates 12, and it is possible to further improve the resolution of the pixel formation. .

Next, a third embodiment will be described. FIG. 8 is an enlarged perspective view of a nozzle portion of the ink jet recording apparatus according to the third embodiment. The configuration other than the nozzle is exactly the same as that of the ink jet recording apparatus according to the first embodiment. As shown in FIG. 8, the recording head is formed by laminating an insulating ink holding substrate 12 having a conductive layer 10 on the surface and an insulating substrate (ink discharging substrate 15) having a protrusion at the tip with a spacer interposed therebetween. It is configured. The supply of ink between the two ink holding substrates 12 is the same as that of the first embodiment, but when the ink discharging substrate 15 is inserted between the ink holding substrates 12, the ink discharging substrate tip 15
Also reaches the ink 1. In this state, the ink holding substrate 1
When a bias voltage is applied to the conductive layer 10 on the surface of the second substrate 2, the colorant in the ink is moved by the electric field formed from the conductive layer 10 toward the front end of the ink discharge substrate 15. (FIG. 9A), and when the pulse voltage from the signal voltage source 41 is superimposed thereon, the ink droplet 2 is ejected in a state containing a large amount of colorant (FIG. 9A).
(B)).

In the ink jet recording apparatus according to the third embodiment, the electric field strength at the discharge point is high to cause discharge from the projection shape, the reliability of discharge is improved, and the recording gap can be secured. In addition, there is a specific merit in that the ejection position of the ink droplet can be stabilized.

By providing the ink discharge substrate 15 separately from the ink holding substrate 12 as in the third embodiment, the discharge conditions of the ink droplets are greatly affected by the shape of the ink discharge substrate 15. become. Therefore, the tip shape of the ink holding substrate 12 does not necessarily need to be tapered, and may be flat, so that a structure that is easy to manufacture can be adopted. However, the tapered shape is advantageous from the viewpoint of electric field strength or ink supply.

Next, a modification of the ink jet recording apparatus according to the third embodiment will be described. The third embodiment has the same basic configuration as that of the first embodiment. Therefore, in addition to the first embodiment, a thickness corresponding to each one of the ink ejection substrate 15 and the internal spacer 20 is added. The pitch of the minute nozzle becomes wider. Therefore, the ink holding substrate 12 having the conductive layers 10 formed on both surfaces as in the modification shown in FIG.
When the nozzle is constituted by the ink ejection substrate 15 and the internal spacer 20, the pitch of the nozzle can be narrowed. Further, even if the ink holding substrate 12 is made of metal, the same effect can be obtained, and the structure is advantageous in manufacturing. However, since the one ink holding substrate 12 becomes a constituent element of two nozzles when made of metal, the simultaneous driving is at least three.
This is performed every other nozzle.

The tip shape of the ink discharging substrate 15 is shown in FIG.
(A) can also be used. This is one in which a slit 16 is formed at the tip of the substrate 15, and the ink held between the ink holding substrates 12 advances inside the slit 16 by capillary force to supply ink to the tip of the ink discharge substrate 15. It has the effect of ensuring. The ink discharge substrate 15 shown in FIG. 11A is made of an insulator, but as shown in FIG.
5 may be composed of a conductor or an insulator having a conductor layer formed on the surface. The driving voltage for causing the ink droplets to fly is supplied from the signal voltage source 41 to the conductive layer 10 of the ink holding substrate 12, but is sandwiched between the conductive layers 10 and is closer to the recording medium than the tip of the ink holding substrate 12. By configuring the protruding ink discharge substrate 15 also to have a conductive layer, the ink discharge substrate 15 is immediately charged when a signal voltage is applied, and the time during which an electric field acts on the ink droplets is shortened. This has a unique effect that the responsiveness of droplet flight can be greatly improved.

Next, an ink jet recording apparatus according to a fourth embodiment will be described. FIG. 12 shows a structure similar to that of the third embodiment, except that the ink holding substrate 12 is made of only an insulator, that the ink discharging substrate 15 has a conductive layer, that a bias voltage is superimposed thereon. The difference is that a signal voltage is applied to the ink ejection substrate 15. Note that the ink ejection substrate 15 may be composed of only a conductive material. The operation principle is almost the same as that of the third embodiment, but the direction of the electric field formed inside the ink is directed outward from the ink ejection substrate 15, so that the colorant in the ink escapes from the ink ejection substrate. is there. Therefore, the fourth embodiment has a structure in which the ink discharge substrate 15 has the slit 16 at the tip. In this structure, even when the voltage is applied, the ink 1 is held by the strong capillary force between the slits, so that the colorant does not escape and a stable ejection operation can be obtained.

When a voltage is directly applied to the ink ejection substrate 15 as in the fourth embodiment, the electric field strength can be increased, and the distance between the ink surface at the flight point and the conductive layer is reduced, so that the ink is discharged. The effect of the electrical time constant of the has become less, it is possible to follow a higher recording frequency,
It has such advantages. The former is effective from the viewpoint of securing the recording gap, and the latter is effective from the viewpoint of high-speed recording. The shape of the ink holding substrate 12 is the same as that of the third embodiment, and is omitted here.

Next, a fifth embodiment will be described. FIG. 13 shows a main part of an ink jet recording apparatus according to a fifth embodiment, in which an ink holding substrate 12 has a plurality of protrusions in a vertical and horizontal matrix, A plurality of nozzles 14 are formed as a set. Further, by stacking a plurality of nozzles 14 in the row direction and the column direction in the same manner as in the first embodiment, a recording head having a nozzle structure having a two-dimensional spread is realized. As in the first to third embodiments, when a conductive layer is provided on the ink holding substrate and a voltage is applied to the conductive layer, the conductive layer is formed as shown in FIG. It has to be formed individually corresponding to the part. In the fifth embodiment, the ink supply flow path 1
Since it is difficult to provide the ink recovery flow path 13b and the ink recovery flow path 13b separately, as described in the first embodiment, the ink 1
Is used because the system is supplied from both above and below the internal spacer 20. The operation is the same as in the first embodiment.

According to the fifth embodiment, since the nozzle 14 can be developed in a plane, the following effects can be obtained. First, when the position of the nozzle 14 coincides with the lamination direction of the ink holding substrate, one row is recorded by a plurality of nozzles. Let f be the driving frequency of f and n can correspond to a recording frequency substantially equivalent to "fxn". That is, the recording speed can be improved by the number of layers.

The nozzle 1 is arranged in the vertical direction of the head.
By slightly shifting the position between the four, a staggered head structure as shown in FIG. 14 can also be realized. As a result, even when the nozzle pitch in the same ink holding substrate 12 cannot be reduced, the amount of displacement in the horizontal direction of the head can be freely adjusted, so that the substantial nozzle pitch can be reduced as much as possible. It is possible to realize a head capable of resolution recording. Further, the fifth embodiment is not limited to the application of only the first embodiment,
The same applies to the second to fourth embodiments.

Next, a sixth embodiment will be described. FIG. 15 shows a recording head of an ink jet recording apparatus according to the sixth embodiment. The basic configuration is the same as that of the first embodiment. However, in the sixth embodiment, common ink flow paths 34 and 35 are provided in the laminating direction of the ink holding substrate 12 and the spacers 20 and 21. As shown in FIG. 16, the ink common flow paths 34 and 35 and the individual flow paths 13
A bypass 36 is formed between the two, and ink 1 flows in and out through the bypass 36. The head has at least two ink common flow paths, an ink supply common flow path 34 and an ink recovery common flow path 35, which are connected to the ink supply unit 30 and the ink recovery unit 31, respectively. The operation principle is the same as in the first embodiment.

In the sixth embodiment, since ink can be supplied and collected from the side of the recording head, the positions of the ink supply unit 30 and the ink collection unit 31 connected to the ink can be freely set. it can. For this reason,
This is particularly advantageous in designing a head suitable for downsizing.

Next, a seventh embodiment will be described. FIG. 17 shows a recording head of an ink jet recording apparatus according to the seventh embodiment. The basic structure is the same as that of the recording head of the sixth embodiment.
a to 34c, 35a to 35c and an ink supply unit 30a
30C and the ink collecting units 31a to 31c are different from the sixth embodiment. Ink supply unit 30
Reference numerals a to 30c hold inks of three colors of cyan, magenta, and yellow, respectively, and the respective inks are supplied to the individual nozzles 14 via ink common flow paths 34a to 34c. FIG. 18 is a cross-sectional view showing a cross section of the nozzle 14, and the bypass flow path 36 is provided only between the ink common flow path of the corresponding color so that only one color is supplied to each nozzle.
Are formed. As described above, the recording head according to the seventh embodiment shown in FIGS. 17 and 18 holds ink of the same color every three nozzles, and adjacent nozzles 14 perform recording with inks of different colors. ing. The above configuration is exactly the same for the ink recovery flow channel.

As described above, by providing a plurality of ink common flow paths in the recording head, it becomes possible to supply different color inks to the nozzles 14 forming the same line. Normally, when performing color printing, it is necessary to form a nozzle row of a separate line for each color. At this time, misalignment between lines is likely to occur, which tends to adversely affect image quality. As described above, when color printing is performed on the same line, according to the seventh embodiment shown in FIG. 17, although the printing resolution is reduced to about 1/3, there is no misregistration for each color. A highly reliable recording head can be realized. The color arrangement is not limited to the seventh embodiment shown in FIG.
By changing the position of No. 6, there is flexibility that the arrangement can be variously changed.

[0064]

As described above, according to the present invention, the following effects can be obtained. The recording head can make maximum use of the capillary force acting on the ink by supplying the ink through a narrow flow path, increase the reliability of the ink supply, and minimize the effect of disturbances such as vibration of the device. It is possible to reduce.

Further, since the discharge position of the ink droplet is located at the center position between the two ink holding substrates, the ink in this portion is always held at a fixed position away from the ink holding substrate, and the ink is discharged onto the substrate. Problems such as adhesion or drying of the ink can be eliminated. In other words, it is possible to minimize the problem that re-discharge becomes difficult when the ink droplet discharge operation is suspended for a certain period.

Since the pitch of the nozzles depends on the thickness of the ink holding substrate and the spacer, by adjusting those values, a higher-density nozzle arrangement can be realized. In addition, the stacked structure is advantageous in terms of strength, and can reduce damage to the recording head even when a recording paper jam or the like occurs, thereby providing a highly reliable apparatus.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration of an inkjet recording apparatus according to a first embodiment of the present invention.

FIG. 2 is a partially enlarged view of an ink holding substrate according to the first embodiment.

FIG. 3 is an explanatory diagram illustrating an operation of the inkjet recording apparatus according to the first embodiment.

FIG. 4 is a perspective view showing a modification of the first embodiment.

FIG. 5 is a side view showing another modified example of the first embodiment.

FIG. 6 is a plan view illustrating a main part of an inkjet recording apparatus according to a second embodiment of the present invention.

FIG. 7 is a plan view for explaining the operation of the inkjet recording apparatus according to the second embodiment.

FIG. 8 is a partially enlarged perspective view showing a main part of an ink jet recording apparatus according to a third embodiment of the present invention.

FIG. 9 is a plan view illustrating an operation of the inkjet recording apparatus according to the third embodiment.

FIG. 10 is a plan view showing a modification of the third embodiment.

FIG. 11 is a perspective view showing another modification of the third embodiment including a recording head having (a) an insulating ink discharge substrate and (b) a conductive ink discharge substrate.

FIG. 12 is a partially enlarged perspective view illustrating an inkjet recording apparatus according to a fourth embodiment of the present invention.

FIG. 13 is a partially enlarged perspective view showing an inkjet recording apparatus according to a fifth embodiment of the present invention.

FIG. 14 is a side view for explaining a nozzle arrangement in a fifth embodiment.

FIG. 15 is a plan view illustrating a main part of an inkjet recording apparatus according to a sixth embodiment of the present invention.

FIG. 16 is a side view for explaining the flow of ink in a sixth embodiment.

FIG. 17 is a plan view illustrating a main part of an inkjet recording apparatus according to a seventh embodiment of the present invention.

FIG. 18 is a side view for explaining the flow of ink in a seventh embodiment.

DESCRIPTION OF SYMBOLS 1 Ink 2 Ink droplet 10 Conductive layer 12 Ink holding substrate 13 Individual flow path 14 Nozzle 15 Ink ejection substrate 16 Slit 20 Internal spacer 21 External spacer 34 Ink supply common flow path 35 Ink recovery common flow path 36 bypass 41 signal voltage source 42 bias voltage source

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuo Hosaka 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba R & D Center (72) Inventor Kazushi Nagato, Sachi-ku, Kawasaki-shi, Kanagawa Komukai Toshiba-cho 1 Toshiba R & D Center (72) The inventor Hideyuki Nakao 1 Komukai Toshiba-cho 1 Saiyuki-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba R & D Center (72) Inventor Yuko Nomura 1 Toshiba R & D Center, Komukai Toshiba-cho, Kawasaki-shi, Kanagawa

Claims (13)

[Claims] An ink jet recording apparatus for recording information by applying a voltage to a liquid ink in which a colorant is dispersed in a solvent and causing ink droplets to fly to form dots on a recording medium. In the above, a recording head including a flat insulating substrate having a conductive layer formed on a surface opposing via the spacer and facing through the spacer, including the colorant between the insulating substrates of the recording head An ink supply unit configured to supply the liquid ink, and a voltage applied to the conductive layer of the recording head in order to cause ink droplets formed from the liquid ink between the insulating substrates to fly from the recording head to the recording medium. An ink jet recording apparatus comprising: 2. The recording head according to claim 1, wherein the insulating substrate has a protruding portion protruding toward the recording medium, and the protruding portion tapers toward the leading end. Item 2. An ink jet recording apparatus according to item 1. 3. The recording head is provided between the insulating substrates on which the spacers are interposed, and a tip of the recording head projects toward a recording medium from a tip of the insulating substrate. 2. The ink jet recording apparatus according to claim 1, further comprising an ink ejection substrate to be made to fly. 4. The ink discharge substrate according to claim 1, wherein the ink discharge substrate has a flat front end surface, and the front end surface protrudes from the front end of the insulating substrate toward the recording medium. The inkjet recording apparatus according to claim 3, wherein 5. The ink discharge substrate according to claim 1, wherein the substrate has a slit at a tip end thereof, and has a slope inclined downward from both shoulders between both inner walls of the slit and both outer walls of the substrate. Item 4. An ink jet recording apparatus according to item 3. 6. The ink jet recording apparatus according to claim 4, wherein the ink discharge substrate has a conductive layer at least on an outer peripheral side thereof. 7. The ink supply means is constituted by a through hole formed in a direction orthogonal to the laminating direction of the insulating substrates, and the ink reservoir between the insulating substrates stacked facing each other via the spacer. An ink supply path for supplying the liquid ink to the substrate, and a through-hole formed in a direction perpendicular to the laminating direction of the insulating substrate. The ink jet recording apparatus according to claim 1, further comprising: an ink recovery path for recovering the ink from the pool, and a bypass flow path for connecting the ink pool and the ink recovery path. 8. The ink supply path and the ink recovery path,
8. The apparatus according to claim 7, wherein a plurality of sets of the bypass flow paths are provided, and the bypass flow paths are provided for each of the sets such that the formation positions of the bypass flow paths are different for each set of the ink supply path and the ink recovery path. Inkjet recording device. 9. The recording medium according to claim 1, wherein said voltage supply means supplies the same voltage to a conductive layer formed on an opposing surface of the insulating substrate, and corresponds to a substantially middle point of a separation distance of said insulating substrate. 2. The ink jet recording apparatus according to claim 1, wherein an image point is formed at a desired position. 10. The voltage supply means supplies a different voltage to a conductive layer formed on an opposing surface of an insulating substrate, and applies a different voltage to the recording medium which is displaced from a midpoint of a separation distance of the insulating substrate. 10. The ink jet recording apparatus according to claim 9, wherein an image point is formed at a desired position. 11. A plurality of recording heads are provided in a laminating direction of the insulating substrate, and a plurality of recording heads are arranged in a matrix in a direction perpendicular to the laminating direction, and the recording heads correspond to a fixed two-dimensional range. 2. The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is configured to enable the ink droplet to fly on a predetermined area of the medium based on the recording information. 12. An ink jet recording apparatus for recording information by applying a voltage to a liquid ink in which a coloring agent is dispersed in a solvent and causing ink droplets to fly to form image points on a recording medium. , Includes an insulating substrate laminated via a spacer, and a conductive ink discharging substrate provided between the insulating substrates and having a leading end protruding toward the recording medium from a leading end of the insulating substrate. A recording head,
An ink supply unit that supplies the liquid ink containing the colorant between the insulating substrates of the recording head, and an ink droplet formed from the liquid ink between the insulating substrates flying from the recording head to the recording medium And a voltage supply means for applying a voltage to the ink discharge substrate constituting the recording head. 13. The ink discharge substrate according to claim 1, wherein the substrate has a slit at a tip end thereof, and has an inclined surface falling down from both shoulders between both inner walls of the slit and both outer walls of the substrate. Item 13. An ink jet recording apparatus according to Item 12.