JP6200676B2 - Inkjet recording device - Google Patents

Description

The present invention relates to an ink jet recording apparatus, and more particularly to a continuous discharge ink jet apparatus.

  In general, an ink jet recording apparatus is used for forming and recording characters and images by patterning colored ink. The continuous discharge ink jet apparatus to which the present invention relates is a highly stable droplet discharge apparatus having high reliability and high maintainability compared to an on-demand ink jet apparatus generally used in a printer for home and office use. It is. Therefore, such an apparatus can be applied to a manufacturing apparatus such as an electronic apparatus that requires functional ink coating and patterning using a liquid that requires high reliability, high maintenance, and high stability.

  Various ink jet recording apparatuses are already known. In particular, the basic operation principle of a continuous discharge ink jet apparatus to which the present invention relates will be described below with reference to FIG. FIG. 7 is a schematic configuration diagram of such an ink jet apparatus. The ink supply path 21 is connected to an ink container 1 that stores ink, and a supply pump 22 that pumps ink is provided in the middle of the ink supply path 21 to supply ink to the nozzle 6. The nozzle 6 is provided with a piezoelectric element, and ink droplets are ejected from the nozzle 6 by supplying an AC voltage. A charging electrode 7 is provided at the tip of the nozzle 6 so as to be parallel to the droplet flying direction. A recording signal source is connected to the charging electrode 7. By applying a recording signal voltage to the charging electrode 7, the ink droplets 8 ejected regularly from the nozzle 6 are charged. Further, deflection electrodes 9 and 10 are provided at the tip of the charging electrode 7. Since a high voltage line (not shown) is connected to the upper deflection electrode 9 and the lower deflection electrode 10 is installed, an electrostatic field is formed between the upper deflection electrode 9 and the lower deflection electrode 10. The charged droplets 8 are changed according to the amount of charge and adhere to a recording medium (not shown) to form an image. Droplets that are not used for printing are collected by the gutter 11 that collects the droplets. A collection circuit 23 and a pump 24 are connected to the gutter 11, and the ink can be reused by returning the droplets to the ink container 1. The ink container 1 is provided with a concentration measuring device (not shown) for measuring the concentration of the liquid in the ink container 1, and the solvent in the solvent container 2 is removed from the solvent circuit by an ink concentration control device (not shown). By supplying the ink container 1 through 25, the density in the ink container 1 is controlled to a desired density.

  In the above-described continuous discharge type ink jet device, since the amount of charge to the liquid (ink) after discharge is controlled and used for deflection of the liquid, it is not necessary to perform droplet discharge control for each droplet. The configuration of the apparatus becomes simple, and since the liquid droplets are continuously discharged, nozzle clogging hardly occurs, so that high reliability can be ensured. For these reasons, the above-described continuous discharge ink jet apparatus is suitable as an industrial marking apparatus that requires a long life and high reliability, and is widely used.

  However, even in such an ink jet apparatus, since the ink is always ejected while the apparatus is in operation, the ink hardly clogs the nozzle. However, when the apparatus is stopped, the ink is not contained in the nozzle. In this case, there is a problem that the ink flying direction is bent due to the presence of the sticking object, and printing cannot be performed at a target place, or the image quality at the time of printing is deteriorated. Therefore, in order to prevent ink from sticking to the inside of the nozzle, the nozzle 6 is usually cleaned at the end of the operation. There are mainly two methods for cleaning. In the first cleaning method, at the end of the operation, the solvent is supplied from the solvent container 2 to the nozzle 6 through the cleaning circuit 26, and the ink inside the nozzle is dissolved in the solvent and pushed out from the nozzle. The extruded ink and the solvent in which the ink is dissolved are collected by the gutter 11. As a result, the ink density inside the nozzle 6 decreases, and the ink inside the nozzle hardly sticks. The second cleaning method is a method in which a solvent is injected from the outside of the nozzle 6 into a nozzle opening for ejecting ink. In this case, the ink in the nozzle 6 is sucked by a suction pump (not shown) and collected in the ink container 1 through a suction circuit (not shown). However, in any of the cleaning methods, the ink in the nozzle is not completely cleaned. In the first cleaning method, a small amount of ink component remains in the solvent. In the second cleaning method, the gas inside the nozzle or the circuit expands due to the temperature rise, and this serves as a driving force, and the solvent containing the ink component remaining without being sucked moves to the nozzle opening 64. To do. Usually, the solvent is volatile and evaporates over time. Therefore, in any of the cleaning methods, the concentration of ink in the solvent increases, and the ink may eventually stick inside the nozzle. Here, taking as an example the case of cleaning by the first cleaning method, the process of ink fixing inside the nozzle will be described with reference to FIGS. 8, 9, and 10. FIG. FIG. 8 is a partially enlarged view of the nozzle 6 around the nozzle opening 64. The nozzle 6 is formed with a columnar convex portion 61, and a nozzle opening 64, which is a cylindrical opening, is formed on the nozzle end surface 62. The nozzle opening 64 is formed by, for example, pressing, and has a nozzle inner wall 63. In the first cleaning method, the solvent 81 containing the pumped ink component is ejected in a direction indicated by S in the figure (hereinafter, ink ejection direction). At this time, the solvent 81 containing the ink component spreads on the nozzle end face 62 and a liquid film 82 is formed. FIG. 9 is a partially enlarged view around the nozzle opening 64 at the time when the cleaning by the first cleaning method is completed. The solvent 81 containing the ink component is separated into a liquid film 83 adhering to the nozzle end surface 62 and a residual solvent 84 existing in the nozzle opening 64. The residual solvent 84 forms a meniscus inside the nozzle opening 64. Over time, the liquid film 83 and the residual solvent 84 evaporate, and the residue 85 is fixed as shown in FIG. When the fixed object 85 is formed on the inner wall 63 of the nozzle, there is a problem that the ink flying direction is bent due to the presence of the fixed object, and printing cannot be performed at a target place or image quality at the time of printing is deteriorated. To do.

On the other hand, in Patent Document 1, for example, a recess is provided on the nozzle forming surface, and liquid (ink) near the nozzle is wiped by a wiping means, and moved to the recess to be captured.

Japanese Patent Laid-Open No. 2004-148606

  However, in the method described in Patent Document 1, the ink is removed mainly by the wiping on the nozzle forming surface, and the ink tends to remain inside the nozzle. There has been a problem that ink sticking is difficult to prevent. In general, the formation of a fixed object on the inner wall of the nozzle has a greater influence on the ink flying direction than the nozzle end face, and therefore, it has been required to prevent the formation of a fixed object on the inner wall of the nozzle. Further, in the method described in Patent Document 1, it is necessary to provide a wiping means, and there is a problem that the apparatus is complicated and the cost is increased.

Accordingly, an object of the present invention is to solve the above-described problems in an ink jet device and provide an ink jet device having a stable ink flying direction.

In the present invention, in order to achieve the above object, a nozzle having a nozzle opening for ejecting ink, a nozzle end face on which the nozzle opening is formed, means for generating a recording signal corresponding to recording information, In an ink jet recording apparatus, comprising: a means for charging ink droplets based on a recording signal; and a means for deflecting the flying direction of the charged ink droplets, and recording characters or the like on a recording object. There is provided an ink jet recording apparatus having a plate-like cover member opposed to the nozzle member and having a gap for holding a liquid between the nozzle end face and the cover member.

According to the present invention, there is an effect that a residue such as ink is hardly fixed inside the nozzle. For this reason, it is possible to prevent the printing at the target location or the deterioration of the image quality when printing. That is, there is an effect that it is possible to provide a highly reliable ink jet recording apparatus, in particular, a continuous discharge type ink jet recording apparatus having a stable ink flying direction.

In the ink jet recording apparatus according to the first embodiment of the present invention, there are a view and a cross-sectional view of the vicinity of a nozzle opening as seen from a particle ejection direction. In the ink jet recording apparatus according to the second embodiment of the present invention, a view and a cross-sectional view of the vicinity of a nozzle opening as seen from a particle ejection direction. In the ink jet recording apparatus of the 3rd Example of this invention, the figure and sectional drawing which looked at the nozzle opening part vicinity from the particle ejection direction. In the inkjet recording apparatus of the 4th Example of this invention, it is the figure and sectional drawing which looked at the nozzle opening part vicinity from the particle ejection direction. In the inkjet recording apparatus of the 5th Example of this invention, it is the figure and sectional drawing which looked at the nozzle opening part vicinity from the particle ejection direction. In the ink jet recording apparatus according to the sixth embodiment of the present invention, a view and a cross-sectional view of the vicinity of a nozzle opening as seen from a particle ejection direction. It is the schematic which shows the whole structure of the continuous discharge type inkjet recording device in a prior art. In prior art, it is sectional drawing of the nozzle opening part vicinity of a 1st washing process. It is the elements on larger scale around the nozzle opening at the time of the completion | finish of the washing | cleaning by the 1st washing | cleaning method in a prior art. It is the elements on larger scale around the nozzle opening part of the state which the residue adhered in the prior art. It is a schematic diagram which shows the interface vicinity of the liquid in the inside of a microgroove.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram (a diagram viewed from the gutter 11) of the nozzle 6 viewed from the particle ejection direction and a cross section taken along the line A-A 'in the first embodiment according to the present invention. In the embodiment shown in FIG. 1, the nozzle cover 100 is installed on the convex portion 61 of the nozzle 6. A nozzle cover surface 102 is formed so as to face the nozzle end surface 62, and a minute gap 101 is formed between the nozzle end surface 62 and the nozzle cover surface 102. The nozzle cover 100 has a nozzle cover opening 104 downstream of the nozzle opening 64 in the ink ejection direction. A nozzle cover opening inner wall 103 is formed in the nozzle cover opening 104. In the first cleaning process inside the nozzle described above, for example, as shown in FIG. 8, the solvent 81 containing the ink component spreads wet on the nozzle end surface 62. In the embodiment shown in FIG. 1, at this time, the solvent 81 containing the ink component is captured by the capillary effect in the minute gap 101 formed between the nozzle end surface 62 and the nozzle cover surface 102.

  The principle of being trapped in the minute gap 101 by the capillary effect is as follows. In general, a pressure difference ΔP occurs at the interface between two types of fluids. This pressure difference is called Laplace pressure and is expressed by [Equation 1].

Here, ΔP is the pressure difference, γ is the surface tension, and R and R ′ are the principal curvature radii of the interface. In the case of this embodiment, the interface is formed by the solvent 81 containing the ink component and air. When the solvent 81 containing the ink component easily gets wet with the nozzle end surface 62 and the nozzle cover surface 102, a concave meniscus is formed inside the minute gap 110 as shown in FIG. FIG. 11 is a schematic diagram in the vicinity of the interface of the solvent 81 containing the ink component inside the minute groove 110. However, in FIG. 11, the main curvature radius R ′ is omitted. In this case, the solvent 81 containing the ink component is depressurized only by the Laplace pressure. With this reduced pressure as the driving force, the solvent 81 containing the ink component spreads and is held inside the minute gap 101 as indicated by an arrow in FIG. The width of the minute gap 101 is desirably smaller than the diameter of the nozzle opening 64. As a result, the solvent 81 containing the ink component is firmly held in the minute gap 101 by the capillary effect, and the solvent 81 containing the ink component evaporates even when the solvent 81 containing the ink component evaporates over time. It does not remain inside, but remains inside the minute gap 101. Therefore, no fixed matter is formed on the nozzle inner wall 63, and instead, a fixed matter is formed on the nozzle end surface 62 or the nozzle cover surface 102. As a result, no fixed matter is formed inside the nozzle opening 64, and the ink flying direction can be prevented from being bent.

  Here, it is desirable that the nozzle cover 100 be made of a material that can easily wet the solvent 81 containing the ink component, but the present invention does not limit the material of the nozzle cover 100. As long as it can be fixed to the convex portion 61 and can hold the solvent 81 containing the ink component, either metal or resin can be used. Further, since the solvent 81 containing the ink component is firmly held in the minute gap 101, the nozzle end face 62 and the surface of the nozzle cover 100 may be subjected to lyophilic treatment. In particular, it is desirable that the nozzle end surface 62, the nozzle cover surface 102, and the inner wall 103 of the nozzle cover opening be easily wetted. Furthermore, the solvent 81 containing the ink component is reliably held in the minute gap 101 and the nozzle cover opening 104. Therefore, it is desirable that the nozzle end surface 62, the nozzle cover surface 102, and the nozzle cover opening inner wall 103 are more easily wetted than the nozzle inner wall 63. Further, the nozzle cover 100 may be always attached to the nozzle 6 while the ink jet apparatus is operated, or may be attached at the end of the operation. When the nozzle cover opening 104 is always mounted during operation, the nozzle cover opening 104 preferably has a larger diameter than the nozzle opening 64 so as not to prevent ink ejection. In order to firmly hold the solvent 81 containing the ink component, it is desirable that the diameter be small as long as ink ejection is not affected. Further, the present invention does not limit the method for fixing the nozzle cover 100 to the convex portion 61. For example, the convex portion 61 may be fixed to the nozzle cover 100 by press fitting. Further, it may be fixed with an adhesive or may be fixed with a screw or the like. Further, the convex portion 61 and the nozzle cover 100 itself are threaded, and the nozzle cover 100 may be fixed to the convex portion 61 by screwing. Further, in the embodiment of FIG. 1, the shape having the convex portion 61 is used, but the shape having the convex portion 61 is not necessarily required. In this case, the nozzle cover 100 is fixed to the nozzle end surface 62 with screws, an adhesive, or the like.

Further, this embodiment is effective not only for the first cleaning method but also for the second cleaning method. This is because even if the inside of the nozzle 6 is cleaned by the second cleaning method, the solvent 81 containing the ink component is driven from the nozzle 6 or the circuit by using, for example, the expansion force of the air due to temperature (air temperature) rise as a driving force. This is because the nozzle end face 62 is wet and spread through the nozzle opening 64. Also in this case, as described above, the solvent 81 containing the ink component is captured by the capillary effect in the minute gap 101 formed between the nozzle end surface 62 and the nozzle cover surface 102 or the nozzle cover opening 104. As a result, no fixed matter is formed inside the nozzle opening 64, and the ink flying direction can be prevented from being bent.

FIG. 2 is a view of the nozzle 6 as viewed from the particle ejection direction (a view seen from the gutter 11), its BB 'section, and its CC' section, in the second embodiment of the present invention. . In the present embodiment, the convex portion 61 is fixed to the support portion 105 of the nozzle cover 100 by press-fitting. However, the support portion 105 is not provided over the entire circumference of the convex portion 61, and is not partially formed as seen in the CC ′ cross-sectional view. Is formed. As a result, when the solvent 81 containing the ink component enters the minute gap 101, the air originally present in the minute gap 101 is discharged through the vent 106 as indicated by arrows T and U in the figure. Therefore, it is possible to efficiently hold the solvent 81 containing a larger amount of ink component in the minute gap 101. As a modification of the present embodiment, the nozzle cover opening 104 may not be formed, and the nozzle opening may be closed. In this case, the nozzle cover 100 is attached to the convex portion 64 after the operation of the ink jet apparatus is completed. Also in this case, as described above, for example, the solvent 81 containing the ink component passes through the nozzle opening 64 from the nozzle 6 or the circuit by using the expansion force of air due to temperature (air temperature) rise as a driving force. When the nozzle end face 62 is wetted and spread, the solvent 81 containing the ink component is trapped in the minute gap 101. As a result, no fixed matter is formed inside the nozzle opening 64, and the ink flying direction can be prevented from being bent. Further, the present invention does not limit the size or number of the vent holes 106. The size and number of the vent holes 106 are determined by the ink holding capacity, the manufacturing cost, the ease of mounting the nozzle cover 100, the strength, and the like.

FIG. 3 is a view of the nozzle 6 as viewed from the particle ejection direction (viewed from the gutter 11), its DD ′ section, and its EE ′ section, in the third embodiment of the present invention. . In the present embodiment, the surface of the nozzle cover 100 facing the nozzle end surface 62 has a minute groove 110 (110a, 110b, 110c, 110d). Since the solvent 81 containing the ink component is captured by the minute groove 110, no fixed matter is formed on the inner wall 63 of the nozzle opening, and instead, it is formed inside the minute groove 110. This can prevent the ink flying direction from being bent. Here, in the present embodiment, the number of the minute grooves 110 is four, but the present invention does not limit the number of grooves, and may be smaller or larger than this. The width of the minute groove 110 is preferably equal to or smaller than the diameter of the nozzle opening 64 in order to hold the solvent 81 containing the ink component more strongly. It is not intended to limit. In addition, it is desirable that the number of minute grooves 110 is large. The width and number of the minute grooves 110 are determined by the manufacturing cost, the amount of the solvent 81 containing the ink component to be retained, the diameter of the nozzle opening 64, and the like.

FIG. 4 is a view (a view seen from the gutter 11) of the nozzle 6 viewed from the particle ejection direction and a FF ′ cross section of the nozzle 6 according to the fourth embodiment of the present invention. In the present embodiment, the nozzle cover 100 is formed with a plurality of fine holes 120. Since the solvent 81 containing the ink component is trapped in the minute gap 101 and the minute hole 120, no fixed matter is formed on the inner wall 63 of the nozzle opening. Instead, the nozzle end surface 62, the nozzle cover surface 102, and the minute hole are formed. 120 is formed inside. This can prevent the ink flying direction from being bent. Here, the plurality of micro holes 120 need not have the same diameter. Further, in order to firmly capture the solvent 81 containing the ink component by the capillary effect, it is desirable that the diameter of the fine hole 120 is smaller than the diameter of the nozzle opening 64, but the nozzle cover 100 can be removed even during operation of the ink jet apparatus. When mounting, the diameter of the fine hole 120 facing the nozzle opening 64 may be larger than the diameter of the nozzle opening 64 so as not to affect the flying of the ink.

  FIG. 5 is a view (a view seen from the gutter 11) of the nozzle 6 seen from the particle ejection direction and a G-G ′ cross section of the fifth embodiment of the present invention. In this embodiment, the nozzle cover 110 is provided with nozzle cover openings 134, and grooves 130 are formed radially from the nozzle cover openings 134. Further, the groove 130 is provided with a tapered portion 130a so that the groove depth becomes shallower as the distance from the nozzle opening 64 increases. As a result, the solvent 81 containing the ink component is pulled radially in the direction away from the nozzle opening 64 and held in the groove 130 by the capillary effect. Even when the solvent 81 containing the ink component evaporates over time, the solvent 81 containing the ink component does not remain in the nozzle opening 64 but remains in the groove 130. Therefore, no fixed object is formed on the nozzle inner wall 63, and instead, a fixed object is formed on the tapered portion 130a. As a result, no fixed matter is formed inside the nozzle opening 64, and the ink flying direction can be prevented from being bent.

  The effect of the taper portion 130a is mainly that it becomes easy to clean the fixed matter inside the groove 130. The nozzle is removed from the ink jet apparatus regularly or when a fixed object is formed, and is cleaned by ultrasonic waves or the like. When a groove is formed in the nozzle cover, there is a possibility that a fixed object is formed at a corner portion inside the groove. Although the fixed matter inside the groove 130 has little influence on the ink flying, it is desirable that the inside of the groove 130 is also cleaned. In the present embodiment, since the groove is shallower toward the tip of the groove 130 by providing the tapered portion 130a, it can be easily cleaned by ultrasonic waves or the like, and a fixed object is formed inside the groove 130. Can be easily removed.

  In this embodiment, the nozzle cover 100 is installed. However, a groove may be formed directly on the nozzle 6 without using the nozzle cover. In this case, the groove is formed by etching, pressing, electric discharge machining, or the like. Further, in order to hold the solvent 81 containing the ink component more firmly, the width of the groove 130 is desirably a shape that becomes narrower as it goes away from the nozzle opening 64 in the radial direction, but the present invention defines the change in the width of the groove 130. However, the width of the groove 130 may be constant, or may be a shape that becomes wider as the nozzle opening 64 moves away in the radial direction. However, it is desirable that it is equal to or smaller than the diameter of the nozzle opening 64.

Further, the present invention does not limit the number of grooves 130. Although it is desirable to have more grooves 130, the actual number is determined by the manufacturing cost, the amount of the solvent 81 containing the ink component to be retained, and the like.

FIG. 6 is a view (a view seen from the gutter 11) of the nozzle 6 as viewed from the particle ejection direction and a HH ′ cross section of the sixth embodiment of the present invention. In the present embodiment, radial grooves 140 are provided outside the nozzle opening in the radial direction. Also in this embodiment, as in the fifth embodiment, the solvent 81 containing the ink component is pulled radially in the direction away from the nozzle opening 64 and held in the groove 140. In particular, as described above, when a driving force such as an air expansion force due to a rise in temperature (air temperature) is acting in the ink ejection direction from the nozzle 6 or the circuit, the solvent 81 containing the ink component is , More strongly pulled radially away from the nozzle opening 64. Therefore, even when the solvent 81 containing the ink component evaporates over time, the solvent 81 containing the ink component does not remain in the nozzle opening 64 but remains in the groove 140. Therefore, no fixed matter is formed on the inner wall 63 of the nozzle, but is formed inside the groove 140 instead. As a result, no fixed matter is formed inside the nozzle opening 64, and the ink flying direction can be prevented from being bent. Here, in order to hold the solvent 81 containing the ink component more firmly, it is desirable that the nozzle end surface 62 and the inside of the groove 140 are more easily wetted than the nozzle inner wall 63. Further, as in the fifth embodiment, the width of the groove 140 is preferably a shape that becomes narrower as the diameter of the nozzle opening 64 increases. However, the present invention does not regulate the change in the width of the groove 140, and The width may be constant, or may be a shape that becomes wider as the nozzle opening 64 moves away in the radial direction. However, it is desirable that it is equal to or smaller than the diameter of the nozzle opening 64. Further, the present invention does not limit the number of grooves 130. Although it is desirable to have more grooves 130, the actual number is determined by the manufacturing cost, the amount of the solvent 81 containing the ink component to be retained, and the like.

    DESCRIPTION OF SYMBOLS 1 ... Ink container, 2 ... Solvent container, 6 ... Nozzle, 7 charging electrode, 8 ... Ink droplet, 9 ... Upper deflection electrode, 10 ... Lower deflection electrode, 11 ... Gutter, 21 ... Ink supply path, 22 ... Supply pump , 23 ... Recovery circuit, 24 ... Pump, 25 ... Solvent circuit, 26 ... Cleaning circuit, 61 ... Projection, 62 ... Nozzle end face, 63 ... Nozzle inner wall, 64 ... Nozzle opening, 81 ... Solvent containing ink component, 83 DESCRIPTION OF SYMBOLS ... Liquid film, 84 ... Residual solvent, 85 ... Solid matter, 100 ... Nozzle cover, 101 ... Fine gap, 102 ... Nozzle cover surface, 103 ... Nozzle cover opening inner wall, 104 ... Nozzle cover opening, 105 ... Supporting part, 106 ... vent hole, 110 ... minute groove, 120 ... minute hole, 130 ... groove, 134 ... nozzle cover opening, 140 ... groove

Claims (3)

A nozzle having a nozzle opening for ejecting ink; a nozzle end face on which the nozzle opening is formed; means for generating a recording signal according to recording information; and means for charging ink droplets based on the recording signal And an ink jet recording apparatus for recording characters on a recording object that moves in a direction substantially perpendicular to the deflection direction.
The nozzle has a plate-like cover member facing the nozzle end surface, and has a gap for holding the liquid by forming an interface between the nozzle end surface and the cover member by liquid and air ,
An ink jet recording apparatus comprising an inner peripheral portion close to the nozzle and an outer peripheral portion farther from the nozzle than the inner peripheral portion, which is open to the gas, and having a gas-liquid interface . 2. The ink jet recording apparatus according to claim 1, wherein the cover member is more lyophilic than at least one of the inside of the nozzle and the nozzle opening. 3. The ink jet recording apparatus according to claim 1, wherein the cover member has one or more through holes, and one end of at least one of the through holes is connected to the gap. An ink jet recording apparatus.