JP2002355973A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet head exhibiting excellent thermal efficiency in which an ink drop can be ejected well and stably toward a recording sheet while suppressing power consumption. SOLUTION: A head substrate arranged linearly with a large number of heating resistors 3 and a nozzle member 6 having a large number of ink ejection holes 7 arranged on the heating resistors 3 in one and one correspondence therewith are arranged on the upper surface of a base plate to form a specified gap between and the gap is filled with ink. Recording operation is performed while circulating the ink to flow on the large number of heating resistors 3 in the sub-scanning direction. In such an ink jet head, centroid of the ink ejection hole 7 is shifted from that of the heating resistor 3 to the downstream side of ink flow.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head for recording an image by depositing ink droplets on recording paper in a predetermined pattern.

[0002]

2. Description of the Related Art Conventionally, an ink jet head has been used as a recording device for recording an image on recording paper.

[0003] Ink-jet head recording methods include those that use thermal energy generated by a heating resistor to discharge ink droplets toward recording paper, those that use deformation of a piezoelectric element, and those that use electromagnetic waves. Some of them use the heat generated by them. Among them, the thermal jet type that uses the heat energy of the heating resistor is easy to pattern the heating resistor and has a small area. However, since it can generate a relatively large amount of heat energy, it has been attracting attention as being suitable for high-density recording.

As a thermal jet type ink jet head, for example, as shown in FIG. 3, a base plate 12 made of alumina ceramics or the like is used.
A head substrate 11 having a large number of heating resistors 13 linearly attached and arranged on the upper surface of the head, and a nozzle member 16 having a large number of ink ejection holes 17 corresponding to the heating resistors 13 in a one-to-one correspondence.
Are arranged so as to form a predetermined gap therebetween, and the gap is filled with ink 18. The recording paper is conveyed along the outer surface of the nozzle member 16. Meanwhile, a large number of heating resistors 13 are individually and selectively heated based on image data from the outside, and bubbles A are generated in the ink 18 by the heat energy, and the pressure generated by the bubbles A is generated. A predetermined image is recorded by ejecting the ink 18 in the ink ejection hole 17 to the outside through the ink ejection hole 17 and attaching these ink droplets i to the recording paper.

[0005] The nozzle member 16 of the above-described conventional ink-jet head is arranged such that the center of the ink ejection hole 17 coincides with the center of the corresponding heating resistor 13 as shown in FIG. It was positioned at a predetermined location on the head substrate 11.

[0006]

The above-mentioned conventional ink jet head uses the thermal energy generated by the heating resistor 13 to discharge the ink 18 to the outside. A part of the heat generated by the head 13 is accumulated in the head substrate 11 and causes the temperature of the head substrate 11 to rise excessively, or the heat generated by the heating resistor 13 causes the moisture of the ink 18 near the ink ejection hole 17 to become wet. The oil is evaporated and the ink ejection holes 17
May cause clogging.

In order to solve the above-mentioned problem, at the time of recording operation, the ink 18 is circulated so that the ink 18 flows between the head substrate 11 and the nozzle member 16 in the sub-scanning direction. By absorbing heat in the head substrate 11 by the
Is cooled, and at the same time, the ink 18 in the ink ejection hole 17 is replenished with moisture and oil by constantly flowing the ink 18 sufficiently containing water and oil near the ink ejection hole 17, and the clogging of the ink ejection hole 17 is prevented. Prevention is being considered.

However, when the ink 18 flows between the head substrate 11 and the nozzle member 16 as described above, the ink 18 flows while absorbing heat from the head substrate 11. During the contact with the ink 18, the temperature of the ink 18 continues to increase gradually, and the temperature of the head substrate 11 cooled by such ink 18 tends to be higher on the downstream side than on the upstream side in the flowing direction of the ink 18. There is. Therefore, the surface temperature of the heating resistor 13 becomes the highest at a position shifted to the downstream side in the flow direction of the ink 18 from the centroid of the heating resistor 13 (see FIG. 5). The generated pressure from the bubble A does not efficiently transmit to the ink 18 in the ink discharge hole 17, and as a result, it has a disadvantage that it is impossible to discharge the ink droplet i better than the ink discharge hole 17. Was.

Further, in order to eliminate such a drawback,
It is conceivable that the pressure from the bubble A is sufficiently transmitted to the ink 18 in the ink ejection hole 17 by increasing the power applied to the heating resistor 13 to generate a large bubble A in the ink 18.

However, when the power applied to the heating resistor 13 is increased, the power consumption increases, the thermal efficiency of the ink jet head decreases, and the heating resistor 13
When the arrangement pitch of the heating resistors 13 and the ink ejection holes 17 becomes extremely narrow, for example, when the arrangement pitch of the heating resistors 13 and the ink ejection holes 17 is extremely narrow, for example, when , And may affect the ejection of the ink droplet i from the adjacent ink ejection hole 17. As a result, a disadvantage that the ejection amount of the ink droplet i becomes unstable is induced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and has as its object to enable good and stable ejection of ink droplets onto recording paper, and to reduce power consumption. An object of the present invention is to provide an ink jet head having excellent thermal efficiency.

[0012]

An ink jet head according to the present invention has a head substrate in which a large number of heating resistors are linearly arranged on an upper surface of a base plate, and one-to-one correspondence with the heating resistors on the heating resistors. And a nozzle member having a large number of ink ejection holes to form a predetermined gap between the nozzle members and filling the gap with ink. An ink jet head that performs a recording operation while circulating ink so as to flow in a direction, wherein the centroid of the ink ejection hole is shifted to the downstream side in the ink flow direction with respect to the centroid of the heating resistor. It is characterized by being located.

In the ink jet head of the present invention, the peak position where the surface temperature of the heating resistor becomes the highest when the heating resistor is heated is located downstream of the centroid of the heating resistor in the ink flow direction. Is characterized in that it is shifted from

Further, in the ink jet head according to the present invention, the centroid of the ink supply hole is located right above the peak position.

According to the ink jet head of the present invention,
A head substrate having a large number of heating resistors linearly arranged on an upper surface of a base plate, and a nozzle member having a large number of ink ejection holes corresponding to the heating resistors on the heating resistor on a one-to-one basis. An ink-jet printer is provided so as to form a gap, and the gap is filled with ink, and the recording operation is performed while circulating the ink so that the ink flows on a large number of heating resistors in the sub-scanning direction. In the head, since the centroid of the ink ejection hole is shifted to the downstream side in the ink flowing direction with respect to the centroid of the heating resistor, the surface temperature of the heating resistor during printing operation is reduced. At the downstream side in the flow direction (peak position) where
The pressure from the bubble generated from the starting point can be efficiently transmitted to the ink in the corresponding ink ejection hole,
It is possible to discharge ink droplets better from the ink discharge holes.

Further, according to the ink jet head of the present invention, it is possible to apply the pressure required for discharging the ink droplets to the ink in the ink discharge holes without increasing the power applied to the heating resistor. The power consumption can be kept low and the thermal efficiency of the inkjet head can be kept high,
Further, since bubbles generated by such a small amount of power have an appropriate size, even if the heating resistors and the ink ejection holes are arranged at a high density of 600 dpi or more, the pressure from the bubbles is high. Has almost no adverse effect on the ejection of ink droplets from adjacent ink ejection holes, and can stabilize the ejection amount of ink droplets.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of an inkjet head according to an embodiment of the present invention, and FIG. 2 is a plan view showing a positional relationship between a heating resistor and ink ejection holes in the inkjet head of FIG. Is generally composed of a head substrate 1 and a nozzle member 6, and a gap formed therebetween is filled with ink 8.

The head substrate 1 has a structure in which a large number of heating resistors 3, electrodes 4, and the like are adhered in a predetermined pattern on the upper surface of a base plate 2 formed in a rectangular shape.

The base plate 2 is made of an electrically insulating material such as alumina ceramics, a semiconductor material such as single crystal silicon, a metal material such as aluminum, and the like, and has an upper surface for supporting the heating resistor 3 and the electrodes 4 and the like. Functions as a supporting base material.

When such a base plate 2 is made of alumina ceramics, an appropriate organic solvent or the like is added to and mixed with a ceramic raw material powder of alumina, silica, magnesia or the like to form a slurry. A ceramic green sheet is obtained by employing a blade method, a calendar roll method, or the like, and thereafter, the ceramic green sheet is punched into a predetermined shape, and then fired at a high temperature. still,
When the base plate 2 is formed of a semiconductor material or a metal material, a substrate whose surface is covered with an insulating film such as silicon oxide or aluminum oxide is used.

A large number of heating resistors 3 provided on the upper surface of the base plate 2 are linearly adhered and arranged in the longitudinal direction of the base plate 2 at a density of, for example, 600 dpi, each of which is made of TaN, TaSiO, TaSiN.
A rectangular shape (for example, 55 μm × 55 μm) made of an electric resistance material such as O, TiSiO, TiSiCO,
m), and electrodes 4 are electrically connected to both ends of each heating element in the sub-scanning direction.

Since these heat generating resistors 3 are made of an electric resistance material such as TaN, when power is applied through the electrodes 4 and the like, Joule heat is generated and bubbles A are generated in the ink 8. Required temperature, for example, 20
The temperature is between 0C and 320C.

The electrodes 4 connected to both ends of the heating resistor 3 function as a power supply wiring for supplying a predetermined electric power necessary for causing the heating resistor 3 to generate Joule heat, such as aluminum. Is formed so as to form a predetermined pattern.

The heating resistor 3 and the electrode 4 are formed by sequentially applying the above-described electric resistance material and metal material on the upper surface of the base plate 2 by a conventionally known thin film forming technique such as a sputtering method. It is formed by employing a lithography technique, an etching technique, or the like, and processing it into a predetermined pattern.

On the other hand, the nozzle member 6 has a predetermined gap (for example, 25 μm to 20 μm) between the nozzle member 6 and the head substrate 1 described above.
0 μm) is formed on the head substrate 1.

The nozzle member 6 has a large number of circular ink ejection holes 7 corresponding one-to-one with the large number of heating resistors 3 described above. Part of the ink 8 filled in the gap is also filled in the inside of these ink ejection holes 7. Therefore, when a bubble A is generated in the ink 8 due to the heat generated by the heating resistor 3 during the recording operation of the ink jet head, the ink 8 in the ink ejection hole 7 becomes an ink droplet i due to the pressure at the time of the bubble generation. It is discharged toward the outside.

Such a nozzle member 6 is made of polyimide resin, molybdenum, alumina ceramics or the like. For example, when the nozzle member 6 is formed of molybdenum,
First, a molybdenum ingot is formed into a plate having a predetermined thickness by employing a conventionally known metal working method, and ink ejection holes having a diameter of 10 μm to 50 μm are formed on the surface of the plate by a conventionally known laser processing method. The nozzle member 6 is manufactured by piercing the nozzle substrate 7, and the obtained nozzle member 6 is mounted and fixed on the head substrate 1 via a spacer (not shown) or the like, thereby being integrally attached to the head substrate 1 described above. You.

The ink 8 to be filled in the gap between the head substrate 1 and the nozzle member 6 is, for example, a pigment type oil-based ink or a water-based dye ink, and has a viscosity of, for example, 0.3 mPa · s to 3 mPa.s. 0.0mPa · s (25 ° C)
It is adjusted to.

The ink 8 is supplied from an ink tank (not shown) between the head substrate 1 and the nozzle member 6.
It circulates between the ink tanks so as to flow in the sub-scanning direction (a direction orthogonal to the arrangement of the heating resistors 3) at a flow rate of ec to 2000 μm / sec. A predetermined pump or the like is used to circulate the ink 8 described above, and the ink 8 that has passed over the head substrate 1 is discharged outside through an ink discharge hole provided near the end of the head substrate.

Thus, the head substrate 1-nozzle member 6
By circulating the ink 8 so that the ink 8 flows in the sub-scanning direction, the circulating ink 8 can favorably absorb the heat in the head substrate 1 and cool the head substrate 1. Thereby, it is possible to effectively prevent the temperature of the head substrate 1 from becoming excessively high.

In this case, since the ink 8 containing a sufficient amount of water and oil always flows immediately below the ink discharge holes 7, the ink 8 in the ink discharge holes 7 is removed from these inks 8.
Is supplied with water and oil, and the clogging of the ink ejection holes 7 can be effectively prevented.

When the ink 8 is made to flow as described above, the temperature of the ink 8 is set while the ink 8 is in contact with the head substrate 1.
Since the temperature of the head substrate 1 cooled by the ink 8 is increased gradually on the downstream side as compared with the upstream side in the flowing direction of the ink 8, the surface temperature of the heating resistor 3 becomes such an ink temperature. , The temperature becomes highest at a position shifted downstream of the centroid of the heating resistor 3 in the flow direction of the ink 8. For example, the flow rate of the ink 8 is 1 mm / sec.
Is set, the position (peak position) where the surface temperature of the heating resistor 3 becomes the highest is shifted by 1 μm to 4 μm downstream of the centroid of the heating resistor 3 in the flow direction of the ink 8. Become.

The most important point in this embodiment is that the nozzle member 6 is connected to the center of each ink ejection hole 7 by
It is arranged so as to be shifted by a predetermined width on the downstream side in the flow direction of the ink 8 with respect to the centroid of the corresponding heating resistor 3.

In the present embodiment, the centroid of the ink ejection hole 7 is located immediately above the peak position described above, and the pressure from the bubble A generated from the peak position corresponds to the ink ejection hole 7. The ink is efficiently transmitted to the ink 8 inside. Accordingly, it is possible to discharge the ink 8 in the ink discharge holes 7 to the outside extremely well, and it is possible to record an accurate image corresponding to the image data on the recording paper.

Moreover, in this case, the pressure required for discharging the ink droplet i can be applied to the ink 8 in the ink discharge hole 7 without increasing the power applied to the heating resistor 3. The thermal efficiency of the ink-jet head can be maintained high by suppressing the power consumption thereof, and the bubble A generated by such a small amount of power has an appropriate size. Even when the holes 7 are arranged at a high density of 600 dpi or more, the pressure from the bubble A has almost no adverse effect on the ejection of the ink droplet i from the adjacent ink ejection hole 7, and the ink droplet i Can be stabilized.

Thus, in the above-described ink jet head, while the recording paper is being conveyed along the outer surface of the nozzle member 6, a large number of the heating resistors 3 are individually selectively heated in accordance with image data from the outside. This thermal energy causes bubbles A to be generated in the ink 8 on the heating resistor 3, and the ink 8 in the ink discharge holes 7 is discharged to the outside by the pressure of the generated bubbles A, and adheres to the recording paper. By doing so, a predetermined image is recorded on the recording paper.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be made without departing from the gist of the present invention.

For example, in the above embodiment, the heating resistor 3
Is formed in a rectangular shape. Alternatively, the heating resistor 3 may be formed in a circular shape. In this case, since the shape of the heating resistor and the ink discharge holes 7 in plan view are substantially similar to each other, the shape of the bubbles generated in the ink 8 is also substantially similar to the ink discharge holes 7 and, therefore, the outer periphery of the bubbles. Since the distance between the ink and the inner periphery of the ink ejection hole 7 is substantially constant, the pressure from the bubbles can be transmitted to the entire ink in the ink ejection hole 7 with substantially the same strength, and the ink droplet Discharge can be performed more favorably than the discharge holes 7.

In the above-described embodiment, the heating resistor 3 and the electrodes 4 provided on the head substrate 1 are covered with a protective film made of silicon nitride, glass, or the like. Needless to say, a driver IC for controlling heat generation may be mounted.

[0040]

According to the ink jet head of the present invention, a head substrate having a large number of heating resistors linearly arranged on an upper surface of a base plate, and a plurality of heating resistors corresponding to the heating resistors on the heating resistor in a one-to-one correspondence. And a nozzle member having an ink ejection hole is arranged so as to form a predetermined gap therebetween, and the gap is filled with ink, and this ink flows in a sub-scanning direction over a large number of heating resistors. An ink jet head that performs a recording operation while circulating ink so as to flow, wherein the centroid of the ink ejection hole is shifted to the downstream side in the ink flow direction with respect to the centroid of the heating resistor. Therefore, during the printing operation, the pressure from the bubble generated from the downstream position (peak position) in the flow direction where the surface temperature of the heat generating resistor becomes the highest during the recording operation is changed to the ink in the corresponding ink ejection hole. Efficiently we can tell, the ink droplet becomes possible to discharge better than the ink discharge hole against.

Further, according to the ink jet head of the present invention, it is possible to apply the pressure required for discharging the ink droplets to the ink in the ink discharge holes without increasing the power applied to the heating resistor. The power consumption can be kept low and the thermal efficiency of the inkjet head can be kept high,
Further, since bubbles generated by such a small amount of power have an appropriate size, even if the heating resistors and the ink ejection holes are arranged at a high density of 600 dpi or more, the pressure from the bubbles is high. Has almost no adverse effect on the ejection of ink droplets from adjacent ink ejection holes, and can stabilize the ejection amount of ink droplets.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an inkjet head according to one embodiment of the present invention.

FIG. 2 is a plan view showing a positional relationship between a heating resistor and ink ejection holes in the ink jet head of FIG.

FIG. 3 is a cross-sectional view of a conventional inkjet head.

FIG. 4 is a plan view showing a positional relationship between a heating resistor and ink ejection holes in the ink jet head of FIG.

FIG. 5 is a schematic diagram showing a surface temperature distribution of a heating resistor.

[Explanation of symbols]

1 ... head substrate, 2 ... base plate, 3 ...
· Heating resistor, 4 ··· electrode, 6 ··· nozzle member, 7
... Ink ejection holes, 8 ... Ink, A ... Bubble,
i: ink drop

Claims (3)

[Claims] A head substrate having a plurality of heating resistors linearly arranged on an upper surface of a base plate; and a nozzle member having a plurality of ink ejection holes corresponding to the heating resistors on the heating resistor on a one-to-one basis. Are disposed so as to form a predetermined gap therebetween, and the gap is filled with ink.
An ink jet head that performs a recording operation while circulating the ink so that the ink flows in a sub-scanning direction over a large number of heating resistors, wherein a centroid of the ink ejection hole is aligned with a centroid of the heating resistor. On the other hand, the ink jet head is shifted to the downstream side in the flow direction of the ink. 2. A peak position where the surface temperature of the heating resistor becomes the highest when the heating resistor is heated, is shifted from the centroid of the heating resistor to the downstream side in the ink flow direction. The ink jet head according to claim 1, wherein: 3. The ink jet head according to claim 2, wherein the centroid of the ink supply hole is located immediately above the peak position.