JPH07178897A - Thermal ink jet printer - Google Patents

Abstract

PURPOSE:To achieve high definition printing without reducing printing speed without cross talks. CONSTITUTION:With a print head 1 placed in the position A, nozzles 3 and 5 are driven with a printing pulse applied. Nozzles 4 and 6 are driven in the position B with a printing pulse applied later than the point of the stop of cross talks. The nozzles are constructed so that ink drop jetting courses for the nozzles 3 and 5 are deflected toward the front side of moving direction of the print head 1 while the ink drop jetting courses for the nozzles 4 and 6 are deflected toward the rear side of moving direction of the print head 1. The amount of movement from the position A to the position B, namely a time lag in drivings of the nozzles 3, 5 and the nozzles 4, 6, is made to agree with the degree of deflection between the nozzles 3, 5 and the nozzles 4, 6, and thereby printing dots 7, 9 and printing dots 8, 10 are formed on the same line as shown in the attached figure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal ink jet printer, and more particularly to a thermal ink jet printer configured as a high density multi-nozzle head.

[0002]

2. Description of the Related Art An ink jet printer is a printer that ejects ink, which is a recording liquid, by various methods and attaches it to a recording medium for recording. As a method of ejecting ink, minute droplets are continuously ejected by a pump,
There are also known a continuous method of deflecting by an electric field or the like, and an on-demand method of generating a pressure change in a flow channel by using a pressure element or the like and generating minute droplets by the pressure.

Among such ink jet printers, a printer using a thermal ink jet print head for ejecting ink by giving energy to a heating element provided in the flow path to generate heat and film-boiling the ink on the heating element. Is simpler than other types of printers, can easily be multi-nozzle, and can be made longer and two-dimensional, and can be miniaturized by making full use of semiconductor technology. Since it has the advantage that it is easy and nozzles can be arranged at high density, it has a major feature that high resolution printing can be performed.

However, as the density is increased and the number of nozzles is increased, when the liquid droplets are ejected from the adjacent nozzles almost at the same time, the mutual pressures influence each other through the common reservoir. However, there is a drawback in that unnecessary meniscus vibration occurs and print quality is degraded.

As a means for solving this drawback, Japanese Unexamined Patent Publication No. Sho.
Japanese Laid-Open Patent Publication No. 6-77158 proposes a method in which an ink supply path from a common ink chamber to a liquid chamber in a piezoelectric element is multilayered and bent at right angles many times to prevent crosstalk with an adjacent nozzle. However, this method has the drawback that the flow path resistance increases and the frequency characteristics deteriorate significantly. Further, Japanese Patent Application Laid-Open No. 62-116154 proposes a method of changing the drive pulse according to the drive status of other nozzles. However, this method requires complicated control logic because it takes into account the driving status of a plurality of other nozzles, and it also compensates for changes in the physical properties of the ink due to temperature and changes in the pressure propagation state. Is very difficult.

Japanese Unexamined Patent Publication (Kokai) No. 55-109672 proposes a method of providing a phase difference for driving adjacent nozzles. However, if the phase difference is small, there is no effect, and if a phase difference is provided to eliminate crosstalk, there is a problem that the dot formation position on the recording medium shifts.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and in a thermal ink jet printer, there is no reduction in printing speed, no complicated logic is used, and crosstalk is eliminated. The purpose of this is to achieve high quality printing.

[0008]

According to the present invention, there are provided a plurality of ink flow paths provided with heating elements for generating thermal energy for ejecting liquid drops, and an ink reservoir for supplying ink to the ink flow paths. In a thermal inkjet printer including a print head in which a plurality of nozzles for ejecting the liquid droplets are aligned with respect to the ink flow path, the nozzles are adjacent to each other in the relative movement direction of the recording medium and the print head. Have different injection directions,
Each of the heating elements is applied with a pulse whose timing is shifted between adjacent heating elements.

[0009]

According to the present invention, in the thermal ink jet print head, a method of shifting the pulse timing between adjacent heating elements is used in order to prevent deterioration of the printing quality due to crosstalk, and the resulting dot formation position on the recording medium. The deviation can be corrected by nozzles having different jetting directions, and dots can be formed on the same straight line. Therefore, particularly in a high density multi-nozzle thermal inkjet printer, high quality printing is possible.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an illustration of an embodiment of the thermal ink jet print head of the present invention. In the figure, 1 is a print head, 2 is a recording medium, 3 to 6 are nozzles, and 7 to 1
0 is a print dot. In the figure, only four nozzles 3 to 6 are shown in the print head 1 for the sake of clarity. The print dots 7 are formed by ink drops ejected from the nozzles 3, the print dots 8 are dots formed by the nozzles 4, the print dots 9 are dots formed by the nozzles 5, and the print dots 10 are dots formed by the nozzles 6. ing. The arrow indicates that the print head 1
It means that the position moves from the position B to the position B.

In this embodiment, the nozzles 3 and 5 are nozzles whose ejection direction is biased forward in the moving direction of the recording medium 2 or the print head 1, and the nozzles 4 and 6 are provided.
Is a nozzle whose ejection direction is biased rearward in the moving direction of the recording medium 2 or the print head 1.

The printing operation will be described. First, a print pulse is applied to the nozzles 3 and 5 to drive them, and then the nozzles 4 and 6 are driven to receive a print pulse delayed from the print pulse by a time longer than the time when the crosstalk converges. The print head 1 moves from the position A to the position B between the driving of the nozzles 3 and 5 and the driving of the nozzles 4 and 6. The amount of movement from A to B, that is, the drive timing deviation between the nozzles 3, 5 and the nozzles 4, 6 and the nozzles 3, 5
As shown in the figure, the print dots 7 and 9 and the print dots 8 and 10 can be formed on the same straight line by making the deviations between the nozzles 4 and 6 coincide with each other.

FIG. 2 is a time chart of drive pulses. In the figure, T is the print pulse, Tp is the print pulse width, and Tc
Is the time when the crosstalk converges, and ΔT is the print pulse interval. The nozzles 3 and 5 are driven by the print pulse having the print pulse width Tp, and then the time Tc at which the crosstalk converges.
The printing pulse delayed as described above is applied to the nozzles 4 and 6.
In this case, the print pulse interval ΔT needs to be ΔT> (Tp + Tc), which can prevent deterioration of the print quality due to crosstalk.

Next, regarding the timing of the pulse for forming the print dots on the same straight line on the recording medium,
This will be described with reference to FIGS.

In FIG. 3, the print head 1 moves at a moving speed V.
Indicates that printing is performed while moving from the position A to the position B in the direction of the arrow. L is print head 1
The distance between the nozzle surface and the recording medium 2 is shown. Further, θ ₁ represents a forward deviation angle of the nozzles 3 and 5 in the ejection direction, and θ ₂ represents a backward deviation angle of the nozzles 4 and 6 in the ejection direction. The conditions for forming a line perpendicular to the moving direction of the print head 1 on the recording medium 2 by these nozzles 3 to 6 are as follows.
As shown in FIG. 3, the position of the print dot printed by the print head 1 at the position A and the position of the print dot printed at the position B after ΔT are the same when viewed from the side. It is understood that it is sufficient to satisfy the relationship of = (tan θ ₁ + tan θ ₂ ) × L / V. As described above, this ΔT is the time Tc at which the crosstalk converges.
It goes without saying that it is necessary to set it to be longer.

It should be noted that θ ₁ and θ ₂ may be measured by measuring the jetting direction of the print head while the print head is not moving, but in practice, printing is performed while the print head is moving. It is more accurate to determine the ejection direction from the ejection position in the moving state and the position of the print dot on the recording medium. Although the moving speed of the print head has been described as V, the recording medium may move. Therefore, the moving speed of the print head means the relative moving speed of the print head and the recording medium. .

In the above-described embodiment, the nozzles of the print head are divided into two groups so as to have two kinds of ejection directionality. However, the nozzles are divided into n groups and have n kinds of ejection directionality. You may make it equip with the nozzle to have. Even for a print head in which nozzles are divided into n groups, the print pulse interval of the print pulses applied to the nozzles having different ejection directions for each group is ΔTn,
After the nozzles of one group are driven, when the time when the crosstalk affecting the next group converges is Tc, ΔTn> (Tp + Tc) may be satisfied. Also, the print pulse cycle T
Needs to be T> n × ΔTn.

FIG. 4 is a principle view of an embodiment of a nozzle having a deviation angle in the jetting direction. In the figure, 11 is a hydrophilic treatment film, 12 is a hydrophobic treatment film, 13 is a nozzle ejection port, 14 is an ink meniscus surface, and 15 is ink. In this embodiment, by providing the hydrophilic treatment film 11 on the inner surface of the nozzle, it is hydrophilic to the ink. Further, the lower portion of the inner surface of the nozzle is hydrophobic with respect to the ink due to the provision of the hydrophobic treatment film 12. After the ink is ejected, the hydrophobic inner surface is not refilled with the ink, and thus the ink meniscus surface 14 is formed to be inclined as shown in the figure. A print signal is applied to a heating element (not shown), and ink is ejected from the nozzle ejection port 13 by the action of bubbles generated by film boiling of the ink on the heating element, but the ink meniscus surface 14 is formed inclined. Therefore, on the hydrophilic treatment film 11 side, the ink ejection progresses quickly, and on the hydrophobic treatment film 12 side, the ink ejection progresses slowly, so that the ink bends upward and the ink is ejected. Is ejected.

The angle of the ink ejection direction depends on the hydrophilic treatment film,
It can be selected according to the degree of hydrophilicity and hydrophobicity of the hydrophobic treatment film, length, area and the like. Of course, it is not always necessary to provide both the hydrophilic treatment film and the hydrophobic treatment film, and only one treatment film may be provided.

FIGS. 5 and 6 are for explaining a first specific example of the print head in which the embodiment described in FIG. 4 is applied to actual nozzles, and FIG. 5 is a cross section in the ink flow path direction. 6 and 6 are front views seen from the nozzle surface side. In the figure,
Reference numeral 11 is a hydrophilic treatment film, 12 is a hydrophobic treatment film, 16 is a channel substrate, 17 and 18 are thick film resin layers, 19 is a heater substrate, 20 is a heater, and 21 is an ink reservoir. In this print head, a heater substrate 19 provided with thick film resin layers 17 and 18 and a heater 20 and a channel substrate 16 in which an ink flow path is formed by anisotropic etching are joined and then diced. It is formed separately on the head chip. An electrode for supplying a driving current is connected to the heater 20, a heat storage layer for efficiently transmitting the generated heat to the ink is provided under the heater, and cavitation due to insulation of the ink and contraction of bubbles is provided on the heater surface. Although a protective layer for protecting from damage is provided, these are not shown.

The ink reservoir 21 supplies ink to a plurality of ink channels in common, and the generated pressure of bubbles is propagated to the adjacent channels via the ink reservoir 21.

1 is provided on the inner surface of the nozzle on the side of the channel substrate 16.
The hydrophilic treatment film 11 and the hydrophobic treatment film 1 are alternately arranged every nozzle.
2 has been given. The inner surface of the nozzle on the heater substrate 19 side is provided with a hydrophobic or hydrophilic treatment film that is opposite to the hydrophilic or hydrophobic treatment film on the corresponding channel substrate 16 side. The hydrophilic treatment film 11 is formed by vapor-depositing a metal thin film, spray-coating a silane coupling agent, or the like. In addition, the hydrophobic treatment film 1
2 is formed by spray coating or sputtering after masking with a silicone resin, a fluororesin, a silazane compound or the like so that unnecessary portions are not treated. The hydrophilic treatment and the hydrophobic treatment are easily performed in the manufacturing process before joining the channel substrate 16 and the heater substrate 19 in terms of manufacturing.

7 and 8 are for explaining a second specific example of the print head in which the embodiment described in FIG. 4 is applied to an actual nozzle, and FIG. 7 is a cross section in the ink flow path direction. 8 and 9 are front views seen from the nozzle surface side. In the figure,
The same parts as those in FIGS. 5 and 6 are designated by the same reference numerals and the description thereof will be omitted. The hydrophilic treatment or the hydrophobic treatment need not necessarily be performed on both sides of the heater substrate side and the channel substrate side. It suffices that only the meniscus surface be formed to be inclined. In this specific example, only the inner surface on the heater substrate 19 side, the nozzle rows alternate, the hydrophilic treatment films 11 or
The hydrophobic treatment film 12 was applied. In this specific example as well, the ejection directionality can be changed between the adjacent nozzles.

FIGS. 9 and 10 are for explaining a third specific example of the print head in which the embodiment described in FIG. 4 is applied to actual nozzles, and FIG. 9 is a cross section in the ink flow path direction. FIG. 10 and FIG. 10 are front views seen from the nozzle surface side. In the figure, the same parts as those in FIGS. 5 and 6 are designated by the same reference numerals, and the description thereof will be omitted. In this specific example, only the channel substrate 16 side was subjected to hydrophilic treatment or hydrophobic treatment. Similar to the first or second specific example, the ejection directionality between adjacent nozzles can be changed.

In the above-mentioned specific example, all the nozzles are subjected to hydrophilic treatment or hydrophobic treatment. However, since the inclination of the meniscus surface can be made different between the untreated nozzle and the nozzle that has been subjected to the hydrophilic treatment or the hydrophobic treatment, it is not necessary to treat all the nozzles, and the treatment is performed every other nozzle. The nozzles that have been subjected to the treatment and the nozzles that are not to be processed may be arranged alternately.

FIG. 11 is a principle view of another embodiment of the nozzle having a deviation angle in the jetting direction. In the figure, 13 is a nozzle ejection port, 15 is ink, 15 'is ejected ink, 22
Is a protrusion. In this embodiment, a protrusion 22 that changes the ink movement direction is formed near the nozzle discharge port 13. By providing the protrusions 22, it is possible to impart a lateral momentum to the ink at the nozzle ejection ports 13 and bend the ejection direction. In this embodiment, the action of the bubbles generated on the heating element gives momentum to the ink 15, and when the ink is ejected from the nozzle ejection port 13, the protrusion 22 is projected on the upper part of the inner surface of the nozzle, The flow velocity of the ink on the side of the protrusion 22 indicated by the short arrow is low, and the flow velocity of the ink on the side away from the protrusion 22 indicated by the long arrow is high. Due to the difference in the flow velocities, the ejected ink 15 ′ is given a downward momentum, and is ejected while curving downward.

12 to 14 are explanatory views of an example of a method of manufacturing the nozzle of the embodiment described in FIG. In the figure,
The same parts as those in FIG. 5 are designated by the same reference numerals and the description thereof will be omitted. 22 is a protrusion, 23 is a long channel, and 24 is a short channel.

FIG. 12 is a plan view of the channel substrate 16. Channels are formed by anisotropic etching using a silicon substrate. In adjacent channels, a long channel 23 and a short channel 24 are formed so that the positions of the end portions on the ink ejection port side are different. Form. The short channel 24 in which the protrusion is formed is preferably thicker than the long channel 23 in which the protrusion is not formed. If the long channel 23 and the short channel 24 are formed to have the same thickness, the nozzle having the protrusion 22 has a smaller ink ejection port and a larger flow path resistance than the nozzle having no protrusion. This is because the channel resistance can be made the same by making the short channel 24 in which the projection 22 is formed thicker than the channel 23 in which the projection is not formed.

The protrusions 22 can be formed by adjusting the dicing position of the channel substrate 16 described with reference to FIG. As shown in FIG. 13, after bonding the channel substrate 16 to a heater substrate (not shown), dicing is performed at a dicing position indicated by a broken line AA. Due to the oblique etching shape of the anisotropic etching, the projection 22 remains in the nozzle opening in the short channel 24 and the projection does not remain in the nozzle opening in the long channel 23. FIG. 14 is a sectional view of the short channel 2 shown by a solid line.
4, the protrusion 22 remains due to the dicing position AA,
No protrusions remain in the long channel 23 shown by the dotted line. In this way, it is possible to form the nozzles with and without the projections 22 that change the ejection direction on every other nozzle.

In the above description, the nozzle having two kinds of jetting direction is arranged every other nozzle, but the nozzle having n kinds of jetting direction is arranged every n nozzles. Good. A head having n nozzles with uneven jetting directionality is capable of changing the area of hydrophilic treatment or hydrophobic treatment stepwise, or changing the size of the protrusions near the nozzle outlet stepwise. Can be created by an appropriate method such as a combination of these methods.

An experimental example will be described. In the experimental example, a silicone resin (Toray
Dow Corning Co., Ltd .: Product name SR2411) 1
% Toluene solution was subjected to dipping treatment to form a hydrophobic film. Next, this hydrophobic film was heated at 120 ° C. for 1 hour to be hardened and sintered. After the dicing, this hydrophobic treatment film is 8 μm, 1 μm
It was manufactured in three sizes reaching the positions of 5 μm and 37 μm. This substrate was bonded to a channel substrate and diced to produce a nozzle of the type described in the specific examples of FIGS. Every other nozzle not subjected to the hydrophobic treatment is not treated at all. The nozzle density is 300 spi.

When printing was carried out with this head, there was a bias in the jetting directionality shown in FIG. From these results, assuming that the distance from the print head to the recording medium is 1.5 mm, the driving frequency is 4.5 kHz, the head moving speed is 0.38 m / s, and the crosstalk convergence time is 20 μs, tan θ ₁ + tan θ ₂ > 5.0 × 10 ^-3 was calculated to be good. Therefore, using a head having a processed film formed up to 37 μm, ΔT = 39 μs was obtained from θ ₁ = 10 mrad and θ ₂ = 0, and printing was performed at 4.5 kHz and printing pulse interval (ΔT).
Was printed for 39 μs, it was possible to print without crosstalk and without deviation of the dot formation position.

[0033]

As is clear from the above description, according to the present invention, in the thermal ink jet printer,
Even if a pulse delayed by more than the time when the crosstalk converges is applied, it is possible to obtain a print head with no deviation of print dots, prevent the print quality from deteriorating, and achieve high-quality printing. is there.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of a thermal inkjet printhead of the present invention.

FIG. 2 is a time chart of drive pulses.

FIG. 3 is an explanatory diagram of a print state of a print head.

FIG. 4 is a principle diagram of an embodiment of a nozzle having a deviation angle in a jet direction.

5 is a cross-sectional view of the first specific example of the embodiment described in FIG. 4 in the ink flow path direction.

FIG. 6 is a front view of the first specific example of the embodiment described with reference to FIG. 4, as seen from the nozzle surface side.

7 is a cross-sectional view of the second specific example of the embodiment described in FIG. 4 in the ink flow path direction.

FIG. 8 is a front view of the second specific example of the embodiment described in FIG. 4, as seen from the nozzle surface side.

9 is a cross-sectional view in the ink flow path direction of a third specific example of the embodiment described in FIG.

FIG. 10 is a front view of the third specific example of the embodiment described in FIG. 4, as seen from the nozzle surface side.

FIG. 11 is a principle view of another embodiment of the nozzle having a deviation angle in the ejection direction.

12 is an explanatory diagram of an example of a channel substrate in the nozzle of the embodiment described in FIG.

13 is an explanatory diagram of a dicing position of the channel substrate of FIG.

14 is a cross-sectional view of the channel substrate of FIG.

FIG. 15 is an explanatory diagram of experimental results.

[Explanation of symbols]

1 ... Print head, 2 ... Recording medium, 3-6 ... Nozzle,
7 to 10 ... Print dots, 11 ... Hydrophilic treatment film, 12 ... Hydrophobic treatment film, 13 ... Nozzle ejection port, 14 ... Ink meniscus surface, 15 ... Ink, 16 ... Channel substrate, 17, 1
8 ... Thick film resin layer, 19 ... Heater substrate, 20 ... Heater, 21 ... Ink reservoir, 22 ... Protrusion, 23 ... Long channel, 24 ... Short channel.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B41J 3/04 103 B

Claims (1)

[Claims] 1. A plurality of ink flow paths provided with a heating element for generating thermal energy for ejecting droplets, an ink reservoir for supplying ink to the ink flow paths, and the ink flow path for the ink flow paths. In a thermal inkjet printer including a print head in which a plurality of nozzles for ejecting liquid droplets are arranged, each of the nozzles has a different ejection direction with respect to a relative movement direction of a recording medium and a print head with respect to adjacent nozzles. The thermal ink jet printer is characterized in that each heating element is applied with a pulse whose timing is shifted between adjacent heating elements.