JP4631171B2 - Inkjet recording method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a droplet deflection type inkjet recording apparatus that performs recording by applying some force to ejected droplets to deflect the flight direction.
[0002]
[Prior art]
As disclosed in, for example, U.S. Pat. No. 3,596,275, a conventional apparatus has ink droplet ejection nozzle holes arranged facing a media surface, and ink droplets continuously ejected from the nozzle holes. The continuous ink jet method is used in which the landing on the media surface is selectively deflected according to the recording signal and landed at the target location. An embodiment of an ink jet recording head in which the nozzles are arranged in a row for high speed and high definition is also disclosed.
[0003]
[Problems to be solved by the invention]
Attempts have also been made to deflect droplets on an on-demand ejection head that obtains droplet ejection force by piezoelectric elements or bubbles generated in the liquid based on a print signal. In these systems, the droplets discharged for landing at one location start to fly as a plurality of masses such as a shape that is split into two or more or constricted. When a deflection force is applied, the amount of deflection differs for each lump of droplets, and there is a problem that the recording quality is lowered due to landing on different places.
[0004]
An object of the present invention is to prevent a deterioration in recording quality due to landing of a plurality of deflected droplets at different locations in an on-demand type ink jet recording apparatus.
[0005]
[Means for Solving the Problems]
The main feature of the present invention is that r1 and r2 are the radii of two adjacent droplets ejected with a speed difference, and r and the deflection angle difference between the two lumps is θ [rad]. In this case, the distance L1 from the place where the deflection force is applied most greatly to the point where the two droplet masses merge is made to satisfy the relationship L1 ≦ (r1 + r2) / θ.
[0006]
In addition, the position of the mechanism that gives the ejection force or the deflection force is set so as to satisfy this relationship.
[0007]
As a result, when the rear droplet catches up with the previous droplet, both droplets come into contact with each other, and thereafter land on the recording medium together.
[0008]
Further, in the case where the rear droplet cannot catch up with the preceding droplet, when the distance from the place where the deflection force is applied to the recording medium is L2, the relationship of L2 ≦ (r1 + r2) / θ is satisfied. Configure.
[0009]
As a result, although the two droplets do not merge with each other, they land on one place of the storage medium.
[0010]
Other features according to the invention are illustrated by the following examples.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic view of a droplet deflection type inkjet recording apparatus according to an embodiment of the present invention and an enlarged view of a portion where two deflected droplet masses are combined. Due to the pressure generated in the liquid chamber 3 of the head 2 by the pressure generator 1, the liquid droplets discharged from the nozzle 4 are split into two liquid droplets 5 and 6 having different sizes, for example, and fly toward the recording medium 7. To do. These droplets are charged by the electric field created by the charging electrode 8, but are charged to different sizes, depending on their surface area. For this reason, it is deflected when crossing the electric field generated between the deflection electrodes 9, and the droplet 5 flies along a flight trajectory 10 and the droplet 6 flies along a flight trajectory 11, and the trajectory has a deflection angle. The difference 12 or θ [rad] is generated. Here, the flight trajectories 10 and 11 after deflection can be approximated to a straight line extending from the point 13 having the greatest deflection force. The radius of the droplet 5 is r1, the radius of the droplet 6 is r2, the distance from the center of the droplet 5 flying ahead to the flight trajectory 11 of the droplet 6 flying behind is d, and the deflection force is the most. If the distance from the large point 13 to the place where the droplets coalesce is L1, the length of the fan-shaped arc having the radius L1 and the central angle θ [rad] is L1 × θ, so the difference θ in the deflection angle is small. When the arc is approximated to a straight line, L1 × θ≈d. If d> r1 + r2, even if the droplet 6 that flew later catches up with the droplet 5 that flew forward, the two droplets pass each other, they do not merge, and land at different positions on the medium 7 Deteriorate print quality. However, if the interval d between the droplets is d ≦ r1 + r2, when the droplet 6 that flies later catches up, the two 5 and 6 come into contact with each other without passing each other. For this reason, the two divided liquid droplets come together and land on the same point on the medium 7, and the print quality is improved.
[0012]
In this embodiment, the on-demand discharge type ink nozzle 4 that obtains the discharge force of the droplets 5 and 6 by the piezoelectric element 1 or the like based on the print signal and the ink droplets 5 and 6 to be landed at one place. On the other hand, in the droplet deflection type ink jet recording apparatus that controls the bending of the flight direction by applying a physical force such as electrostatic force or magnetic force by the charging electrode 8 and the deflection electrode 9, the ink to be landed at one place When the two droplets 5 and 6 are split or constricted to start flying, the masses of these droplet masses are r1 and r2, respectively, and the difference between the deflection angles of two adjacent masses is θ [rad]. When the distance from the place 13 where the deflection force is most applied to the point where two adjacent droplet clusters are combined is L1, the relationship L1 ≦ (r1 + r2) / θ is satisfied. Here, there are two types of positions where the two droplets are combined, that is, a region up to the end 14 of the deflection electrode (deflection means) 9 or between the end 14 and the medium 7.
[0013]
On the other hand, in order to improve the print quality when the subsequent droplet 6 cannot catch up, the two droplets 5 and 6 may be landed on the same point on the medium 7 one after the other. That is, it can be said that two droplets land at the same place if the interval d between the droplets satisfies d ≦ r1 + r2 until reaching the medium 7. Therefore, when the distance to the medium 7 is L2, if the condition of L2 ≦ (r1 + r2) / θ is satisfied, the print quality can be improved without landing a plurality of droplets at different locations.
[0014]
In this embodiment, when an ink droplet to be landed at one location starts to fly as two droplets 5 and 6, the radius of these droplet masses is set to r1 and r2, respectively. When the difference in deflection angle is θ [rad] and the distance from the place 13 where the deflection force is applied most to the recording medium 7 is L2, the relationship of L2 ≦ (r1 + r2) / θ is satisfied.
[0015]
Even if the discharged droplets 5 and 6 are constricted as shown in FIG. 2, the same can be said if the radii of the respective masses are r1 and r2.
[0016]
FIG. 3 is a diagram for explaining the droplet flight speed and the position of the deflection electrode. The previous droplet 15 and the subsequent droplet 16 immediately after being discharged from the nozzle 4 are shown. At the moment when the rear droplet 16 is completely discharged, the distance between the previous droplet 15 and the rear droplet 16 discharged earlier is L3, and the velocity of the previous droplet 15 is V1. The speed is V2, and the distance from the nozzle 4 to the point 13 where the deflection force is the largest is L4. Since the time until the two droplets merge is L3 / (V2−V1), the distance L1 + L4 from the nozzle 4 at the position where the two droplets merge is L1 + L4 = L3 × V2 / (V2−V1). Substituting this into L1 ≦ (r1 + r2) / θ,
L3 × V2 / (V2−V1) ≦ (r1 + r2) / θ + L4 (1)
If two conditions are satisfied, two droplets can be combined and landed on the same point on the medium 7. Therefore, in order to satisfy this, it can be seen from Equation 1 that the following method can be adopted.
(1) The speed V1 of the previous droplet is decreased by adjusting the ejection force or the like (the ink viscosity can be adjusted). In an ink jet recording apparatus, a constriction or splitting into two or more lumps occurs at the time of ejection. At this time, it is possible to control the velocity relationship between the two divided liquid droplets by adjusting the waveform of the electric signal applied to the pressure generating device 1 composed of a piezoelectric element or the like.
[0017]
A piezo-on-demand ink jet recording apparatus will be described as an example. A position where the amplitude of the electric signal waveform applied to the piezoelectric element is 32 V, the velocity V1 of the previous droplet is 7.5 [m / s], and the front droplet and the rear droplet are shifted by 32 [μm] in the deflection direction. Landed on the surface and formed an elliptical dot. When the amplitude of the electric signal waveform was changed from 32 V to 28 V and the velocity V1 of the previous droplet was decreased from 7.5 [m / s] to 5.7 [m / s], We landed at the same position and were able to improve to a perfect circle dot.
(2) The speed V2 of the trailing droplet is increased by adjusting the drive waveform, adjusting the ink viscosity, or the like. When the electric signal waveform applied to the piezoelectric element is a rectangular wave, the velocity V1 of the preceding droplet is 5.5 [m / s], and the velocity V2 of the following droplet is 5 [m / s]. The front droplet and the rear droplet landed at a position shifted by 25 [μm] in the deflection direction to form an elliptical dot. By changing the electric signal waveform applied to the piezoelectric element from the rectangular wave to the trapezoidal wave as described above, the previous droplet velocity V1 remains 5.5 [m / s]. When the velocity V2 of the rear droplet is increased from 5 [m / s] to 6 [m / s], the front droplet and the rear droplet are landed at the same position on the medium 7 and are almost circular. Print quality can be improved with dots.
(3) The distance L4 from the nozzle 4 to the point 13 where the deflection force is the largest is increased by separating the position of the mechanism that applies the deflection force from the nozzle 4. Thus, if V1 <V2, in the vicinity of the deflection electrode 9 to which the deflection force is applied, the two split liquid droplets have already joined or approached just before the joining, and do not become discrete after deflection. Specifically, when the droplet velocity is about 5 [m / s], the distance between the nozzle and the deflecting electrode can be about 300 [μm], so that the discreteness of the droplet can be eliminated, but 5.5 [m / s]. When the droplet velocity is about [600 μm], the discreteness of the droplets can be eliminated by setting the distance between the nozzle and the deflection electrode to about [600 μm].
(4) The droplet weight is increased to increase r1 and r2. As a specific example, the distance L5 from the nozzle 4 to the tip of the deflection electrode 9 is 0.6 [mm], the preceding droplet velocity V1 is 5.4 [m / s], and the following droplet velocity. In the printer of 6 [m / s], when the weight of the droplet discharged from the nozzle 4 is 12 [ng], the deflection force is kept the same so that the deflection amount is the same 25 [ng] In this case, the front droplet and the rear droplet do not merge but land at a position shifted by 12 [μm] in the deflection direction and form an elliptical dot. The print quality was improved to almost a perfect circle.
(5) Decrease θ by decreasing the deflection force, increasing the speed of all of the droplet mass, or increasing the droplet weight. Specifically, when the deflection amount of the front droplet is 53 [ μm ], the deflection voltage 480 [V] is changed to the position that is shifted by 38 [μm] with the deflection voltage 480 [V]. When changed to 360 [V], it was possible to land at the same position on the media 7. In addition, when the droplet velocities V1 and V2 are 4.2 [m / s] and the landing is shifted by 11 [μm], the droplet velocities V1 and V2 are increased to 5.2 [m / s]. I was able to land at the same position. Further, the weight of the droplet was changed from 9 [ng] to 13.8 [ng], and it was possible to land at the same position instead of landing at a position shifted by 12 [μm].
[0018]
FIG. 4 shows the results of measuring the distance between the nozzle 4 and the point at which the droplets merge together when L1 ≦ (r1 + r2) / θ is satisfied. The heads A and B have different boundary lines due to the influence of different ratios of the sizes of the ejected droplets. Further, when the flight distance of the liquid droplet is long, the distance L1 + L4 from the nozzle 4 to the position where the liquid droplet is combined, and the end 14 of the deflection electrode from the nozzle 4 due to the effect that the liquid droplet is decelerated and the deflection angle becomes large. Is not proportional to the distance L5. However, in general, it can be said that the liquid droplets are combined if the distance is equal to or less than the boundary line (distance L5 from the nozzle 4 to the end of the deflection electrode) = (distance L1 + L4 from the nozzle 4 to the position where the liquid droplets merge). By combining the liquid droplets before passing through the end portion 14 of the mechanism for applying force, it is possible to provide a deflection type ink jet recording apparatus in which a plurality of liquid droplets do not land at different locations even if deflection is performed.
[0019]
When droplets fly as three or more lumps, deflection is performed by satisfying the relationship of L1 ≦ (r1 + r2) / θ between the droplets of two adjacent lumps. In addition, it is possible to provide a deflection type ink jet recording apparatus in which a plurality of droplets do not land at different locations.
[0020]
In addition, the multi-nozzle head in which a plurality of nozzles are arranged can be set according to the present invention for each nozzle set. According to the present embodiment, for example, by using a common electrode for a plurality of nozzles, even when the position of the electrode cannot be individually set for each nozzle set, the droplet velocity is individually set for all the nozzles. In addition, it is possible to provide a deflection type ink jet recording apparatus in which a plurality of droplets do not land at different locations.
[0021]
The electrode is not limited to a flat plate shape. For example, if the electrode is cylindrical, the terminal end 14 of the electrode is at the position shown in FIG.
[0022]
【The invention's effect】
According to the present invention, a droplet to be landed at one location is deflected with respect to a droplet that starts to fly as a plurality of masses such as a shape in which the droplet is split into two or more or constricted. It is possible to land a plurality of droplets on one place, and the print quality is not impaired.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a droplet deflection type ink jet recording apparatus according to an embodiment of the present invention and an enlarged view of a portion where two deflected droplets are combined.
FIG. 2 is a diagram showing a shape when a constriction occurs in a discharged droplet.
FIG. 3 is a schematic view of a droplet deflection type ink jet recording apparatus showing elements of respective distances for explaining an embodiment of the present invention.
FIG. 4 is a result of measuring a distance from a nozzle to a position where droplets merge when L1 ≦ (r1 + r2) / θ is satisfied.
FIG. 5 is a schematic view showing an electrode terminal position when a deflection electrode according to another embodiment of the present invention is cylindrical.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Pressure generator (piezoelectric element), 2 ... Head, 3 ... Liquid chamber, 4 ... Nozzle, 5, 15 ... One of droplets of different sizes, 6, 16 ... Other of droplets of different sizes 1, 7 ... recording medium, 8 ... charged electrode, 9 ... deflection electrode, 10 ... flight trajectory of droplet 5, 11 ... flight trajectory of droplet 6, 12 ... difference difference [theta] [rad of two droplets , 13 ... the point where the deflection force is the largest, 14 ... the end of the mechanism (deflection electrode) that gives the deflection force, L1 ... the distance from the point 13 to the union point, L2 ... the distance from the point 13 to the medium 7, L3 ... the distance between the previous droplet 15 and the rear droplet 16 at the moment when the rear droplet 16 is ejected; L4: the distance from the nozzle 4 to the point 13 where the deflection force is greatest; L5: the deflection from the nozzle 4 Distance to the end 14 of the electrode 9.

Claims (6)

On-demand ejection type ink nozzles that obtain droplet ejection force with piezoelectric elements etc. based on the drive waveform generated by the print signal, and electrostatic force, magnetic force or In a recording method of an ink jet recording apparatus provided with a droplet deflecting device that controls to deflect a flight direction by exerting a physical force such as wind force,
When the ink to be landed at one place splits into two droplets or starts to fly and starts to fly, the radius of the front droplet and the rear droplet lump are set to r1 and r2, respectively. When the difference between the deflection angles of two masses is θ [rad] and the distance from the place where the deflection force is most applied to the point where two adjacent liquid masses merge is L1, L1 ≦ (r1 + r2) / θ In order to satisfy the relationship, at least one of the driving waveform, the ink viscosity, and the weight of the ejected ink droplet is adjusted, and the relative droplet velocity of the front droplet and the rear droplet is adjusted. An ink jet recording method characterized by reducing the difference between the two . On-demand ejection type ink nozzles that obtain droplet ejection force with piezoelectric elements etc. based on the drive waveform generated by the print signal, and electrostatic force, magnetic force or In a recording method of an ink jet recording apparatus provided with a droplet deflecting device that controls to deflect a flight direction by exerting a physical force such as wind force,
When the ink to be landed at one place splits into two droplets or starts to fly and starts to fly, the radius of the front droplet and the rear droplet lump are set to r1 and r2, respectively. When the difference between the deflection angles of two masses is θ [rad] and the distance from the place where the deflection force is most applied to the point where two adjacent liquid masses merge is L1, L1 ≦ (r1 + r2) / θ In order to satisfy the relationship, at least one of the position of the mechanism that applies the deflection force or the deflection force applied to the ink droplet is adjusted, and the relative droplet between the front droplet and the rear droplet An ink jet recording method characterized in that a difference in speed is reduced . The inkjet recording method according to claim 1 or 2,
An ink jet recording method characterized in that the relationship of the L1 ≦ (r1 + r2) / θ, and to fill in the area to the end portion of the mechanism that gives biasing force. The inkjet recording method according to claim 1 or 2,
Wherein L1 ≦ (r1 + r2) / the relationship theta, ink jet recording method is characterized in that to meet in the region to the recording medium from the end portion of the mechanism that gives biasing force. An on-demand ejection type ink nozzle that obtains a droplet ejection force by a piezoelectric element or the like based on a drive waveform generated by a print signal, and a droplet deflection device that controls the flight direction of the ejected ink droplet In the recording method of the inkjet recording apparatus provided ,
When an ink droplet to be landed at one place starts to fly as two droplets, the radius of the front droplet and the rear droplet mass is set to r1 and r2, respectively, and the difference between the deflection angles of these masses Θ [rad], where L2 is the distance from the place where the deflection force is most applied to the recording medium , the drive waveform, ink viscosity, or ejection is performed so as to satisfy the relationship of L2 ≦ (r1 + r2) / θ. An ink jet recording method, wherein at least one of the weights of ink droplets is adjusted to reduce a difference in relative droplet velocity between a front droplet and a rear droplet . An on-demand ejection type ink nozzle that obtains a droplet ejection force by a piezoelectric element or the like based on a drive waveform generated by a print signal, and a droplet deflection device that controls the flight direction of the ejected ink droplet In the recording method of the inkjet recording apparatus provided ,
When an ink droplet to be landed at one place starts to fly as two droplets, the radius of the front droplet and the rear droplet mass is set to r1 and r2, respectively, and the difference between the deflection angles of these masses Θ [rad], where L2 is the distance from the place where the deflection force is most applied to the recording medium , the position of the mechanism or ink that gives the deflection force so as to satisfy the relationship L2 ≦ (r1 + r2) / θ An inkjet recording method characterized by adjusting at least one of the deflection forces applied to the droplets to reduce the difference in relative droplet velocity between the front droplet and the rear droplet .

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