JP3367840B2 - Ink jet recording device - Google Patents

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 in particular, a liquid ink in which a colorant is dispersed is used, and at least the colorant component in the liquid ink is ejected as an ink droplet onto a recording medium. The present invention relates to an inkjet recording device that records images such as characters and figures.

[0002]

2. Description of the Related Art A recording apparatus for recording an image by forming recording dots by ejecting liquid ink as minute droplets called ink droplets on a recording medium has been put into practical use as an inkjet printer. This inkjet printer has less noise than mechanical recording devices such as wire dot printers, and does not require processing such as development and fixing compared to electrophotographic recording devices such as the Carlson method. It has attracted attention as a plain paper recording technology.

Various types of ink jet printers have been proposed up to the present, and a typical method thereof is: (a) Ink droplets are ejected by the pressure of vapor generated by the heat of a heating element. Electricity / heat conversion method to fly (see, for example, Japanese Patent Publication No. 56-9429, Japanese Patent Publication No. 61-59911, etc.), or (b) Fly ink droplets by mechanical pressure pulse generated by piezoelectric element Piezoelectric method (Japanese Patent Publication 53-1
2138), etc.

A recording head (hereinafter, referred to as an inkjet head) used in an inkjet printer is mounted on a carriage and is orthogonal to a conveyance direction (hereinafter, referred to as a sub-scanning direction) of a recording paper (hereinafter, referred to as a main scanning direction). A serial scanning type head that performs recording while moving in the scanning direction) has been put to practical use. This serial scanning type head cannot perform recording unless it moves by a predetermined amount in the main scanning direction, so it is difficult to increase the recording speed. Therefore, a line scanning printer in which the recording speed is dramatically increased by using a long head in which the length of the recording head is set to be substantially the same as the width of the recording paper is also considered. Practical application of the scanning head is not easy due to the following reasons.

In the ink jet recording system, a large number of individual fine nozzles corresponding to the resolution are provided, but in essence, local evaporation of the solvent tends to cause local ink concentration, which causes clogging of the nozzles. It is the cause. Further, in the method using the pressure of steam for forming an inkjet, adhesion of an insoluble substance formed by thermally or chemically reacting with the ink induces clogging of the nozzle, and 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. Probably much higher in line scan heads that use thousands of nozzles, which is more than serial scan heads that use tens to hundreds of nozzles. Since the nozzles are clogged depending on the frequency of occurrence, there is a problem in terms of practical reliability.

Further, in the method using the pressure of steam, it is difficult to generate ink particles having a diameter of 20 μm or less, which is equivalent to a recording dot having a diameter of about 50 μm, on a recording paper, so that a head having high resolution is obtained. Is difficult to manufacture. Further, in the method using the pressure by the piezoelectric element, it is difficult to manufacture a head having a high resolution due to a problem in processing technology because the structure of the recording head is complicated. Therefore, the conventional ink jet recording apparatus has a problem that it is difficult to improve the resolution regardless of which method is used.

In order to solve these problems, a voltage is applied to an electrode array formed by arranging a plurality of individual electrodes formed of a thin film on a substrate, and electrostatic force is used to eject ink from the ink surface. An inkjet recording method has been proposed in which the colorant component therein is ejected as ink droplets.

Specifically, a method of ejecting ink droplets by using electrostatic attraction (Japanese Patent Laid-Open Nos. 49-62024 and 56-56).
No. 4467 method), and a method of increasing the concentration of the colorant by using an ink containing a charged colorant component to eject ink droplets (see Japanese Patent Publication No. 7-502218).
In these methods, the recording head has a slit-shaped nozzle structure that does not require a nozzle for each individual dot, or a nozzleless structure that does not require a partition of an ink flow path for each individual dot. This is effective in preventing and recovering from clogging, which was a major obstacle in realizing a line scan recording head. Further, in the latter method of increasing the colorant concentration, ink droplets having a very small particle diameter can be stably generated and ejected, which also contributes to the improvement of resolution.

[0009]

However, in the ink jet recording apparatus of the type in which the colorant component is ejected as ink droplets by the above-mentioned electrostatic force, the recording head is nozzleless, so that it is effective for preventing clogging. On the other hand, there is a problem that the ink droplet ejection position becomes unstable because the ink can freely move in the main scanning direction on the substrate of the recording head.

Further, since the ink droplets are ejected by the voltage having the same polarity as the colorant of the colorant to be ejected onto the recording medium, the colorant component repels and escapes from the electrode position on the recording head. There is also a problem that the colorant component cannot be stably supplied to the ink droplet ejection position. Therefore, there is a problem that it is difficult to stably eject a sufficient amount of ink droplets from a predetermined ejection position, and it is not possible to form a good image point.

According to the present invention, the colorant component contained in the ink can be stably supplied to the tip of the individual electrode, which is the ejection position of the ink droplet, without clogging, whereby the stable ejection of the ink droplet can be achieved. It is an object of the present invention to provide an inkjet recording device that can realize flight.

[0012]

In order to achieve the above object, an ink jet recording apparatus according to the present invention is provided with at least a coloring agent by applying an electrostatic force to a coloring agent component in an ink in which a coloring agent is dispersed in a solvent. In an inkjet recording apparatus for recording by ejecting ink droplets containing a component toward a recording medium, a plurality of individual nozzles for applying an electrostatic force to the colorant component in the ink are provided on an insulating substrate. An array of head substrates and an ink supply unit for supplying the ink onto the head substrate are provided, and the individual nozzles have a quadrangular pyramid shape with a V-shaped groove formed on one side surface . , A part or all of which is made of a conductive layer.

As described above, in the ink jet recording apparatus according to the present invention, the surface tension due to the capillarity strongly acts on the ink supplied on the head substrate by the ink supply means in the V-shaped groove of each individual nozzle. Therefore, the ink reachable distance is long and the ink can be reliably supplied to the ink droplet flying position. In addition, the supplied ink is V
Since it is held by the strong surface tension acting on the ink at the bottom of the groove, even if the pulsation of the ink flow or the vibration of the recording device occurs, the influence on the ink shape of the individual nozzle tip is suppressed. be able to.

The V-shaped groove, which is the ink supply channel, is
Since the ink is formed for each individual nozzle, the ink does not move in the lateral direction, and adjacent individual nozzles do not affect each other. In the ink jet recording apparatus according to the present invention, since minute ink droplets can be ejected from the electrode having a large opening, it is not necessary to reduce the nozzle diameter as in the conventional ink jet recording apparatus using individual nozzles. The individual nozzle has a V-shaped groove formed on one surface side and is in an open state, so that ink clogging in the nozzle does not occur. Furthermore, since the tip of each individual nozzle has a tapered shape, the flying position of the ink droplet is stable.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of an ink jet recording apparatus according to the present invention will be described in detail below with reference to the drawings. FIG. 1 shows the configuration of an ink jet recording apparatus using a line scanning head according to the first embodiment of the present invention, and FIG. 2 shows the main part thereof.

In FIG. 1, the recording head is an insulating substrate 10.
The head substrate 100 is provided with the individual nozzles 20 arranged in an array thereon, and the ink recovery substrate 30 is provided thereon. The insulating substrate 10 is made of resin having excellent workability such as peak (PEEK-Poly EtherEther Ketone) or ceramics whose surface is insulation-coated. Grooves 11 for holding the individual nozzles 20 are formed on the upper surface of the insulating substrate 10, and grooves 12 for collecting residual ink are formed on the end surface and the back surface of the insulating substrate 10. The residual ink collecting groove 12 is formed in a rectangular shape as an example, but the present invention is not limited to such a shape, and may be any shape as long as it forms a depression, such as a V shape. It doesn't matter.

As shown in FIG. 3, the residual ink collecting mechanism includes a plurality of grooves 12 formed in parallel from the end surface of the insulating substrate 10 to the back surface thereof, and a residual ink storage tank 41 attached to the back surface of the substrate 10. Is equipped with.

The individual nozzle 20 is made of a metal material and is shown in FIG.
As shown in the longitudinal direction to have a V-shaped groove and the tip are What Do the projecting portions Tsu Do a tapered shape. Specifically this
As shown in Fig. 4, the tip of the protrusion has one side surface (upper surface) .
Has a substantially quadrangular pyramid shape which lacks a V shape, V-shaped grooves are formed to substantially the center position of the individual nozzles 20. The insulating material is processed into the same shape, it is possible to form a separate nozzle 20 by forming a conductive layer by plating or vapor deposition or the like to the inner wall of the V-shaped groove. Figures 1 In those illustrated in Figure 3, the tip of the individual nozzles 20 are formed in sharp shapes such as paulownia, or by forming a slit or with a small rounded tip of the individual nozzles Is also good. Therefore, the tip of the protrusion is
Strict quadrangular pyramid shape due to V-shaped groove and minute shape of tip
However, it does not have to be a substantially pyramidal shape. Also protruding
The part has a quadrangular pyramid shape as a whole,
As shown in FIGS. 1 to 3, at least the inclined surface
The two surfaces on both sides form a tapered inclined plane on the tip side.
ing. Furthermore, a V-shaped groove is formed on the upper surface and opens upward.
Although it is released, the lower surface is similar to the two surfaces on both sides,
It is a slanted flat surface.

The ink collecting substrate 30 is made of the same material as that of the insulating substrate 10, and the groove corresponding to the individual nozzle 20 is formed in the inclined portion. This groove serves as an ink recovery channel 31. Further, when the head substrate 100 and the ink recovery substrate 30 are joined, a space corresponding to the depth of the V-shaped groove of the head substrate 100 is formed, and the ink supply channel 20 is formed. The groove for collecting ink has a rectangular cross section, but the shape is not limited as long as it has a depression. This means that the residual ink collecting groove 12 is
Is the same as.

An ink recirculation mechanism 40 including a pump and an ink flow path is connected to the recording head, and the ink 50
The flow of is being optimized. The ink 50, the positive chargeability of the coloring material component together with a charge control agent and a binder and the like, 10 ⁸ Omega
It is dispersed and suspended in a colloidal state in an insulating solvent having a resistivity of not less than cm. An opposing drum 61 holding the recording medium 60 on the surface is installed in front of the recording head and also serves as a platen.

Next, the operation of the ink jet recording apparatus according to this embodiment will be described. Ink circulation mechanism 40
The ink 50 thus supplied passes through the ink supply path 21 and reaches the tip of the head. Since the ink supply path 21 is formed by the V-shaped groove, the surface tension based on the capillary action acts on the ink 50 at the groove bottom, so that the ink 50 is surely at the tip of the individual nozzle 22 at the ink flying position. Is supplied to. When the amount of the supplied ink reaches such a level as to fill the V-shaped groove, the excess ink 50 flows into the recovery passageway 31 through the groove formed in the ink recovery substrate 30. In the head substrate 100, like the insulating substrate 10, the groove of the ink recovery substrate 30 exerts a strong surface tension on the ink due to the capillary phenomenon, so that the ink can be reliably recovered. In this way, by constantly circulating the excess ink, the ink amount at the tip of the individual nozzle 20 can be always optimized.

When the ink jet recording apparatus starts a recording operation, a bias voltage source 70 constantly applies a bias voltage of, for example, DC 1.5 kV to the individual nozzles 20,
As a signal voltage corresponding to the image signal from the signal voltage source 71, for example, a pulse voltage of 500 V is superimposed on the signal voltage when it is turned on. On the other hand, the counter electrode 61 provided on the back surface of the recording medium 60 is set to the ground potential 0V as shown in FIG.
Now, if any one of the individual nozzles 20 is turned on (a state where 500 V is applied) and a total voltage of 2 kV in which a pulse voltage of 500 V is superimposed on the bias DC of 1.5 kV is applied, it is turned on. The ink droplet 51 containing the colorant component jumps out from the ink droplet flying position 22 at the tip of the individual nozzle 20 which has become, is pulled by the counter electrode 61, and flies toward the recording medium 60 to form an image point. . Further, the ink that did not fly as an ink drop from the ink drop flying position 22 and did not contribute to recording, that is, the ink in which the concentration of the coloring material component was thin and the solvent component was large, was formed on the end surface and the back surface of the head substrate 100. It is collected and stored in the residual ink storage tank 41 through the residual ink recovery channel 12.

As described above, in this embodiment, since the individual nozzle 20 has the V-shaped groove and at least the inside of the groove is made of a metal having high wettability, it is based on the capillary phenomenon inside the groove. A strong acting force works to ensure the supply of the ink 50. Moreover, since the ink 50 linearly follows the bottom of the V-shaped groove corresponding to the central portion of the individual nozzle 20, it reliably reaches the tip 22 of the individual nozzle, which is the ink flying position. As a result, it is possible to reliably eject ink droplets.

Further, since the surface tension acts on the bottom of the V-shaped groove, it is difficult for the ink 50 to flow out in the lateral direction, and there is almost no influence on the adjacent portion. Further, there is an advantage that even if the pulsation of ink supply or the vibration of the apparatus occurs, the influence on the state of the ink 50 at the tip of the head is small. Furthermore, since the tip of the individual nozzle 20 has a tapered shape, the ejection position of the ink droplet 51 is stabilized and the electric field strength formed is increased, so that the gap with the recording medium 60 can be widened. Since the individual nozzle 20 can be formed with a certain thickness, it is not damaged by the contact of the recording medium 60 and the like, and the life of the head can be kept long.

FIG. 5 shows a modification of the tip shape of the individual nozzle 20. In FIG. 5A, the tip of the individual nozzle 23 viewed from the recording medium side has a shape corresponding to a triangular pyramid lacking one side surface. Since the area occupied by the individual nozzles 20 is narrower in the same space as compared with the shape shown in FIG. 4, the electric field strength at the tip can be improved. As a result, it is possible to operate at a lower driving voltage. At this time, the individual nozzles 20 formed on the head substrate 10
The groove 11 for holding is V-shaped. Figure 5
In (b), the individual nozzle 26 seen from the recording medium side has a thin V shape (left in the figure), and the shape seen from the side surface of the head has a tapered tip (right in the figure). ). With such a structure, the individual nozzles 26 are further thinned, so that a higher electric field can be applied to the ink 50. Therefore, driving with a low voltage can be enabled.

FIG. 6 shows a modification of the head substrate 100. A mountain-shaped partition 13 is provided between the adjacent individual nozzles 20. As described above, the ink head 50 is unlikely to flow out in the lateral direction because the flow path of this recording head is individualized. However, the re-ink amount is abnormal due to a malfunction of the supply system or the like. If you do, you may not be able to deal with it. Therefore, the partition 1 as shown in FIG.
Even in such a case, the ink 50
Can be prevented from flowing out in the lateral direction.

Next, an ink jet recording apparatus according to the second embodiment of the present invention will be described. FIG. 7 shows the main part of the recording apparatus according to the second embodiment. In FIG. 7, the end surface positions of the insulating substrate 10 and the ink collecting substrate 30 that form the head substrate 100 are substantially aligned with each other, and the individual nozzles 20 projecting therefrom are surely provided with a long gap in the nozzle extension direction. It is in a separated state. The configuration of the other parts is similar to that of the recording apparatus according to the first embodiment. In this way, when the individual nozzles 20 are completely separated, even if the ink is excessively supplied and the ink 50 overflows from the V-shaped groove, the ink 50
Circulates to the back side of the individual nozzle 20 and flows to the residual ink recovery flow path 12. Therefore, it is possible to completely prevent the problem that the ink 50 flows out to the adjacent individual nozzle 20. Further, as compared with a configuration in which resin or the like is filled between the adjacent individual nozzles 20,
Since the dielectric constant is lowered, the electric field contrast formed by the individual nozzle 20 is improved, and as a result, the electric field strength can be increased. Therefore, operation at a lower drive voltage can be expected.

Next, a third embodiment of the present invention will be described. FIG. 8 shows the tip of the individual nozzle 20 in the inkjet recording apparatus according to the third embodiment. FIG. 8 is a plan view of the head substrate 100, and the slit 24 is formed at the tip of the individual nozzle 20. This slit 24
Can be re-formed by a wire cut electric discharge machine using a wire having a small diameter. The other parts are the same as those in the first embodiment. When the curvature R of the V-shaped groove formed in the individual nozzle 20 is large, the tip of the individual nozzle 20 is in a state close to a flat plate, and the ink supply capability is reduced. In addition, as shown in FIG.
In the case where the slanted portion is obliquely cut at the tip of the individual nozzle 20 to leave a large thickness, as shown in FIG.
As shown in (b), the top 22 of the tip and the bottom 25 of the V-shaped groove
If and do not match, it becomes difficult to supply ink to the tip of the individual nozzle 20. Ink 50 is individual nozzle 20
If it does not reach the tip 22 of the head, there is a problem that the accuracy of ink ejection is lowered and the reliability of the head is greatly impaired. Therefore, if the slit 24 is formed at the tip 22 of the individual nozzle 20, if the ink 50 can be supplied to only a part of the slit 24, the ink 50 will reach the end of the individual nozzle 20 due to the capillary phenomenon in the slit 24. Can be reached.

As a result, even if the tip of the individual nozzle 20 is not formed into a desired shape due to a manufacturing defect, the ink 50 can be reliably supplied to the tip of the individual nozzle 20 and a stable operation is achieved. Can be secured. Furthermore, since high manufacturing precision is not required, the yield of head manufacturing can be improved. Further, instead of forming the slit at the tip as described in the present embodiment, it is possible to improve the ink supply capability by providing a minute groove only at the tip.

[0030]

As described above, the present invention has the following effects. Since the individual nozzle that ejects the ink droplet has a V-shaped groove, the ink supplied inside the groove can be reliably supplied to the tip of the individual nozzle, and the ink droplet ejection operation can be performed. It is possible to carry out surely.

Even if a disturbance such as a fluctuation of ink supply or a vibration of the apparatus occurs because the strong surface tension due to the capillary phenomenon acts on the ink inside the V-shaped groove, the tip of the individual electrode does The influence on the ink can be suppressed to a low level, and highly reliable operation can be expected.

In addition, since the flow paths are separated, the ink does not flow out to the adjacent individual nozzles, and the upper surface of the nozzle is open despite the nozzle is formed. In addition, there is also an effect that ink adhesion and sticking hardly occur.

Further, by forming a slit at the tip of each individual nozzle, it is possible to ensure stable operation even when a manufacturing defect occurs, and it is possible to improve the product yield.

[0034]

[Brief description of drawings]

FIG. 1 is a diagram showing an entire inkjet recording apparatus according to the present invention.

FIG. 2 is a diagram showing a main part of the inkjet recording apparatus according to the first embodiment.

FIG. 3 is a perspective view showing a back surface of the ink jet recording apparatus of FIG.

FIG. 4 is an explanatory diagram showing a nozzle tip shape of the recording head according to the first embodiment.

FIG. 5 is a diagram showing a modified example of the recording head according to the first embodiment.

FIG. 6 is a diagram showing another modified example of the recording head according to the first embodiment.

FIG. 7 is a diagram showing a main part of an ink jet recording apparatus according to a second embodiment.

FIG. 8 is a diagram showing a tip of a recording head according to a third embodiment.

FIG. 9 is a diagram showing an example of manufacturing defects of the inkjet recording head according to the present invention.

[Explanation of symbols]

10 Insulating substrate 12 Residual ink recovery channel 13 partitions 20, 23, 26 Individual nozzle 21 ink supply channel 22 Cutting edge of individual nozzles (ink drop ejection position) 24 slits 30 Ink recovery substrate 31 ink recovery channel 40 Ink recirculation mechanism 41 Residual ink storage tank 50 ink 100 head substrate

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Teruo Murakami Inventor Komukai-shi Toshiba-cho, Kawasaki-shi, Kanagawa 1 Komatsu Toshiba R & D Center Co., Ltd. (72) Inventor Yasushi Hosaka Ko-sachi-ku, Kawasaki-shi, Kanagawa Muko Toshiba Town 1 Co., Ltd. Toshiba Research and Development Center (72) Inventor Hideyuki Nakao 1 Komukai Toshiba Town 1, Komukai Toshiba Town, Kawasaki City, Kanagawa Prefecture (56) Reference JP-A-58-124662 ( JP, A) Special table 7-502218 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41J 2/06 B41J 2/385

Claims (7)

(57) [Claims] 1. Ink jet recording for recording by causing an electrostatic force to act on a colorant component in an ink in which a colorant is dispersed in a solvent to fly an ink droplet containing at least the colorant component toward a recording medium. in the apparatus, a plurality of individual nozzles for applying an electrostatic force to the coloring material component in the ink, and the head substrate formed by arranging on the insulating substrate, for supplying the ink to the head substrate
And a ink supply means, the individual nozzle is square V-shaped grooves are formed on one side
An ink jet recording apparatus having a conical shape , a part or all of which is formed of a conductive layer. 2. The ink jet recording apparatus according to claim 1, wherein a part of an upper surface of the individual nozzle is in an open state. The method according to claim 3, wherein the individual nozzle arrangement side surface of the head substrate, an inclined surface on the end face side, and parallel grooves communicating from the V-shaped grooves of the individual nozzles in each array location of the individual nozzles The ink jet recording apparatus according to claim 1, further comprising an ink collecting substrate for collecting ink through the parallel groove. 4. The head substrate is positioned so as to project toward the recording medium side from the end face of the ink recovery substrate so that the end face of the insulating substrate supports the individual nozzles provided in parallel. The inkjet recording device according to claim 3, wherein 5. The ink jet recording apparatus according to claim 4, wherein the head substrate is provided with a partition for partitioning the adjacent individual nozzles. 6. The ink jet recording apparatus according to claim 3, wherein the head substrate is positioned so that the end surface of the insulating substrate is flush with the end surface of the ink recovery substrate. 7. The V nozzle is provided at the tip of each of the individual nozzles.
The inkjet recording apparatus according to claim 1, further comprising a slit formed along the forming direction of the groove.