JP4562248B2 - Inkjet head - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet head that forms an image by adhering ink droplets to a recording paper in a predetermined pattern.
[0002]
[Prior art]
Conventionally, an ink jet head has been used as a recording device for forming an image on recording paper.
[0003]
The inkjet head recording system uses thermal energy generated by the heating resistor to eject and fly ink droplets toward the recording paper, uses the deformation of the piezoelectric element, and is accompanied by irradiation with electromagnetic waves. Among these, the thermal jet type using the heat energy of the heating resistor is easy to form the heating resistor pattern, and the area of the heating resistor Since a relatively large thermal energy can be generated even when the size is small, it is attracting attention as being suitable for high-density recording.
[0004]
As such a thermal jet type ink jet head, for example, a substrate having a large number of heating resistors arranged in a straight line and a plurality of ink discharge holes corresponding to the heating resistors in a one-to-one correspondence. And a board having a structure in which a gap is provided between the substrate and the top board and ink is filled in the recording paper along the top surface of the top board. While transporting, a large number of heating resistors are selectively heated individually based on the image data, and bubbles are generated in the ink by this thermal energy, and a part of the ink is evacuated by the pressure of the generated bubbles. A predetermined image is recorded by ejecting the ink from the ink ejection holes of the plate and attaching it to the recording paper.
[0005]
In addition, after the ink is ejected to the outside through the ink ejection holes, the same amount of ink as the ejected ink flows between the substrate and the top plate and is replenished. The operation can be repeated continuously.
[0006]
[Problems to be solved by the invention]
By the way, in the conventional ink jet head described above, after ink droplets are ejected by the heat energy of the heating resistor, most of the bubbles between the substrate and the top plate disappear by replenishment of the ink described above, but they are fine. Bubbles may remain. Since the ink between the substrate and the top plate containing residual bubbles is in the same place until the recording operation of the next line is started, the heating resistor is reheated to generate new bubbles. If this happens, the ink will be ejected outside with small residual bubbles, or the newly generated bubbles and residual bubbles will merge to form large bubbles, resulting in variations in the amount of ink discharged. And has the disadvantage that uneven density is formed.
[0007]
In addition, the ink filled between the substrate and the top plate of the conventional ink jet head described above hardly flows except when bubbles are generated or when ink is replenished, and heat tends to be trapped in the ink and the substrate. It has become. Therefore, if the ink jet head is used for a long time, the temperature of the substrate or the like becomes excessively high, which also causes variations in the ink discharge amount, resulting in uneven density, or unnecessary ink is discharged to the outside. It had the fault which produces malfunctions, such as being.
[0008]
Therefore, in order to eliminate the above disadvantages, the ink filled between the substrate and the top plate is made to flow to remove residual bubbles from between the ink discharge holes and the heating resistor, and at the same time, the ink that flows between the substrate and the top plate. It has been studied to cool the substrate by absorbing the heat in the substrate.
[0009]
However, in the ink jet head described above, since the ink is filled in a narrow gap between the substrate and the top plate, when such ink is flowed at a high speed, in the ink, in the vicinity of the heating resistor and the ink ejection hole. There is a disadvantage that a spiral flow is generated and the flow of ink stops due to the generation of the spiral. In this case, it takes a long time to remove the residual bubbles, and the ink flow rate required for cooling the substrate in a short time cannot be obtained, so that it cannot be used for high-speed recording. Was.
[0010]
[Means for Solving the Problems]
The present invention has been devised in view of the above drawbacks, and an ink jet head according to the present invention includes a substrate having a large number of linearly arranged heating resistors, and a large number of inks corresponding to the heating resistors in a one-to-one relationship. a top plate in which the discharge holes are formed, causes disposed at predetermined intervals between the ink discharge hole so as to be positioned above the heat generating resistor, the substrate and the top plates It becomes the ink is filled into the gap formed by the ink ejecting ink droplets from the ink ejecting holes by thermal energy generated by the said heating resistor in flowing in the direction orthogonal to the arrangement of the heating resistors image an inkjet head that forms, said the lower surface of the top plate, and the region between adjacent said ink discharge hole, along with the partition wall along the flow direction of the ink is formed, prior to Substrate and are cross-sectional mountain shape of the glaze layer is interposed between the heating resistor, and is characterized in that the partition wall over the intermediate region of the glaze layer is disposed.
[0011]
The ink jet head according to the present invention is characterized in that the partition wall is formed integrally with the top plate.
[0013]
Further the ink jet head of the present invention also is characterized in that the partition wall is kept non-contact with respect to the substrate or the glaze layer.
[0014]
Furthermore ink jet head of the present invention, the flow rate of the ink is characterized in that controlled by the region 50μm / sec~2000μm / sec between at least the heat-generating resistor and the ink discharge hole.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
1 is a perspective view of an inkjet head according to an embodiment of the present invention, FIG. 2 is a sectional view of the inkjet head of FIG. 1 in the sub-scanning direction, and FIG. 3 is a sectional view of the inkjet head of FIG. 1 is a substrate, 2 is a glaze layer, 3 is a heating resistor, 7 is a top plate, 8 is an ink ejection hole, 9 is ink, and 10 is a partition.
[0016]
The substrate 1 is formed in a rectangular shape by an electrically insulating material such as alumina ceramics, and functions as a support base material for supporting the glaze layer 2 and a large number of heating resistors 3 on the upper surface thereof.
[0017]
When the substrate 1 is made of, for example, alumina ceramics, an appropriate organic solvent and solvent are added to and mixed with ceramic raw material powders such as alumina, silica, and magnesia to form a slurry, and this is formed into a conventionally known doctor blade. A ceramic green sheet is obtained by adopting a method, a calender roll method or the like, and thereafter, the ceramic green sheet is punched into a predetermined shape and then fired at a high temperature so as to form a rectangular shape.
[0018]
Further, on the upper surface of the substrate 1, a glaze layer 2 having a mountain-like cross section is formed in a strip shape along one long side, and a number of heating resistors 3 are linearly deposited and arranged on the top. .
[0019]
The glaze layer 2 is formed of glass or the like so as to have a mountain-shaped cross section, and since the surface thereof is extremely smooth, a large number of heating resistors 3 are formed on the glaze layer 2 by a conventionally known photolithography or the like. When the pattern is formed, fine processing of the heating resistor 3 can be performed relatively easily.
[0020]
When the glaze layer 2 is made of glass, a predetermined glass paste obtained by adding and mixing an appropriate organic solvent, organic binder, etc. to the glass powder is applied to the upper surface of the substrate 1 by a conventionally known screen printing. It is formed so as to have a cross-sectional mountain shape by printing and applying in a strip shape by, for example, and baking at high temperature.
[0021]
A number of heating resistors 3 provided on the glaze layer 2 are linearly arranged in the main scanning direction at a dot density of, for example, 600 dpi, and are TaN, TaSiO, TaSiNO, TiSiO, TiSiCO. When the power supply power is supplied to the heating resistor 3 through the electrode layers 4 and 4 that are electrically connected to both ends of each heating resistor 3. Joule heat is generated, and the heat energy necessary for forming bubbles A in the ink 9 is generated.
[0022]
The heating resistor 3 employs a conventionally well-known thin film technique, specifically, sputtering, photolithography technique, etching technique, etc., and the above-described electric resistance material is applied to the upper surface of the glaze layer 2 in a predetermined thickness and pattern. It is formed by depositing.
[0023]
Further, a protective film 5 made of silicon nitride or the like is deposited on the upper surface of the heating resistor 3 or the like with a substantially constant thickness, and the heating resistor 3 and the electrodes 4 and 4 are covered with the protective film 5.
[0024]
The protective film 5 is for protecting the heat generating resistor 3 and the electrode layers 4 and 4 from corrosion due to contact with the ink 10 and is, for example, 2.0 μm on the upper surface of the heat generating resistor 3 or the like by well-known sputtering or the like. Deposited to a thickness of ˜20.0 μm.
[0025]
A top plate 7 having a large number of ink discharge holes 8 corresponding to the heating resistors 3 on a one-to-one basis is disposed on the substrate 1 described above in a substantially parallel manner to the upper surface of the substrate with a predetermined interval therebetween. Is done.
[0026]
The top plate 7 is aligned so that the ink discharge holes 8 are positioned above the corresponding heat generating resistors 3, and the lower surface of the top plate 7 is located in the region between the adjacent ink discharge holes 8, 8. A partition wall 10 extending along a direction (sub-scanning direction) orthogonal to the arrangement is formed integrally with the top plate 7.
[0027]
The ink ejection holes 8 of the top plate 7 are for ejecting ink droplets i toward the recording paper during the recording operation of the ink jet head, and generate heat in a one-to-one correspondence with the heating resistors 3. They are arranged in a straight line in the main scanning direction at a density substantially equal to that of the resistors 3, for example, a dot density of 600 dpi.
[0028]
Further, the partition wall 10 provided on the lower surface of the top plate 7 is disposed over the intervening region of the glaze layer 2 interposed between the substrate 1 and the heating resistor 3, and the lower end thereof is the substrate 1 or above. The glaze layer 2, the protective film 5, and the like provided in the non-contact state are maintained in a non-contact state, and the width is set to, for example, 5 μm to 60 μm.
[0029]
Here, keeping the partition 10 in non-contact with the substrate 1 or the like effectively prevents the lower end of the partition 10 from coming into contact with the substrate 1 or the like and damaging the contact portion when the ink jet head is assembled. Because.
[0030]
The top plate 7 is made of a metal material such as molybdenum. For example, when the top plate 7 is made of molybdenum, an ingot of molybdenum is formed into a predetermined shape by a conventionally well-known metal processing method. This is manufactured by drilling a plurality of ink ejection holes 8 having a diameter of 50 μm to 110 μm by laser processing or the like.
[0031]
Further, a spacer (not shown) is interposed between the top plate 7 and the substrate 1 along the outer periphery of the top plate 7, and the gap between the substrate 1 and the top plate 7 is made substantially constant by the spacer. Retained.
[0032]
Further, ink 9 is filled in the gap formed between the top plate 7 and the substrate 1 described above.
[0033]
As the ink 9, for example, pigment type oil-based ink or water-based dye ink is used. The ink 9 is supplied from an ink tank (not shown) between the substrate 1 and the top plate 7, and the heat energy of the heating resistor 3 described above. As a result, when bubbles A are generated in the ink 9, a part of the ink 9 becomes ink droplets i by the pressure of the bubbles A and is ejected to the outside from the ink ejection holes 9.
[0034]
The ink 9 is circulated between the heating tank 3 and the ink ejection holes 8 by a circulation pump (not shown) that flows in a direction (sub-scanning direction) orthogonal to the arrangement of the ink ejection holes 8. In this region, for example, it is controlled to flow at a flow rate of 50 μm / sec to 2000 μm / sec. Regardless of the driving state of the heating resistor 3, the flow of the ink 9 is always maintained at substantially the same flow rate when the heating resistor 3 is generating heat and when it is not generating heat.
[0035]
Therefore, even if some fine bubbles a remain between the substrate 1 and the top plate 7 after the ink droplets are ejected from the ink ejection holes 8 by the thermal energy generated by the heating resistor 3, these residual bubbles a Moves in the direction orthogonal to the arrangement of the ink discharge holes 8 together with the ink 9 flowing between the substrate 1 and the top plate 8, and before the recording operation of the next line is started, the heating resistor 3 and the ink discharge It is quickly eliminated from the area between the holes 8. Accordingly, when the heating resistor 3 is reheated in association with the recording operation of the next line to generate new bubbles, fine residual bubbles a are included in the ink droplets i ejected from the ink ejection holes 8. The newly generated bubbles A and the residual bubbles a are rarely combined to form a large bubble, thereby forming a good image with little variation in density with the discharge amount of the ink 9 being substantially constant. It becomes possible.
[0036]
When the flow direction of the ink 9 is set to a direction other than the sub-scanning direction, for example, a main scanning direction parallel to the arrangement of the ink discharge holes 8, there are other directions in which the residual bubble a moves along with the flow of the ink 9. In order to eliminate all residual bubbles a from the region between the heating resistor 3 and the ink discharge holes 8, the recording operation of the next line is started. During this time, it is necessary to cause the ink 9 to flow in the main scanning direction. In this case, it takes a very long time to start the recording operation for the next line, and the high-speed recording is not performed. Therefore, in order to quickly remove the residual bubbles a immediately below the ink discharge holes 8, it is important to match the flow direction of the ink 9 with the sub-scanning direction.
[0037]
Further, since the ink 9 flows while being in contact with the heating resistor 3 and the protective film 5 covering the substrate 1, the heating resistor is used even when the ink jet head is used for a long time. The heat accumulated inside the body 3, the substrate 1, the glaze layer 2, etc. is absorbed well by the ink 9 through the protective film 5, and the temperature of the substrate 1, the glaze layer 2, etc. does not become excessively high. . Therefore, even if a sufficient cooling time is not provided between the recording operations of the respective lines, the temperature of the heating resistor 3 is maintained at a temperature suitable for the recording operation, and the ejection amount of the ink 9 from the ink ejection holes 8 is reduced. It can always be substantially constant, and a clear image with little density unevenness can be recorded at high speed.
[0038]
Moreover, in this embodiment, the partition wall 10 is formed along the flow direction of the ink 9 on the lower surface of the top plate 7 and in the region 8-8 between the adjacent ink ejection holes, and the ink 9 forms the partition wall 10. The flow is good and stable along the direction, that is, the sub-scanning direction. For this reason, even if the ink 9 is made to flow at a relatively high flow rate (50 μm / sec to 2000 μm / sec), a spiral flow hardly occurs in the ink 9 and the flow of the ink 9 stops locally. Such inconveniences can be effectively prevented. Accordingly, the residual bubbles a in the ink 9 are removed well in a shorter time than between the heating resistor 3 and the ink discharge holes 8, and a predetermined flow velocity required to quickly cool the substrate 1 with the flowing ink 9 is obtained. Therefore, it is possible to cope with high-speed recording.
[0039]
The ink 9 passes between the substrate 1 and the top plate 7 and then returns to the ink tank and is supplied between the substrate 1 and the top plate 7 again. Thus, the ink 9 is repeatedly circulated between the region between the substrate 1 and the top plate 7 and the ink tank.
[0040]
Further, the heat absorbed by the ink 9 flowing between the substrate 1 and the top plate 7 is dissipated to the outside in the process of flowing through the circulation path as described above, and is again supplied to the space between the substrate 1 and the top plate 7. It is cooled to a sufficiently low temperature.
[0041]
Thus, the ink jet head described above individually transfers a number of heating resistors 3 on the basis of image data from the outside while transporting the recording paper along the top surface of the top plate 7 in a direction orthogonal to the arrangement direction of the ink discharge holes 8. Heat is selectively generated, and bubbles A are generated on the heating resistor 3 by the generated thermal energy, and a part of the ink 9 is discharged to the outside from the ink discharge holes 8 of the top plate 7 by the pressure of the bubbles A. A predetermined image is recorded by adhering the ejected ink droplets i to the recording paper.
[0042]
In addition, this invention is not limited to the above-mentioned form, A various change, improvement, etc. are possible in the range which does not deviate from the summary of this invention.
[0043]
For example, in the above-described embodiment, a polyimide resin film may be further adhered to the upper surface of the top plate 8 made of a metal material. In this case, an ink discharge hole that is slightly smaller than the discharge hole 9 is formed at a position where the ink discharge hole 9 is formed in the film, and the ink droplet i is discharged to the outside from the ink discharge hole provided in the film. It will be.
[0044]
Further, in the above-described embodiment, if the ink 9 between the substrate 1 and the top plate 7 always flows in the region immediately below all the ink ejection holes 8, the heat in the ink 9 is generated by the heat generated by the heating resistor 3. Even if a large amount of water or oil is evaporated from the ink discharge holes 8 and the viscosity of the ink 9 in the ink discharge holes 8 is going to increase, the water or oil from the ink 9 flowing directly under the ink discharge holes 8 is in this portion. By sequentially replenishing, the ink 9 does not harden in the vicinity of the ink ejection holes 8, and clogging of the ink ejection holes 8 can be effectively prevented. In this case, there is an advantage that an accurate image corresponding to the image data can be formed, and the reliability of the inkjet head can be improved.
[0045]
【The invention's effect】
According to the ink jet head of the present invention, since ink between the substrate and the top plate is made to flow in a direction orthogonal to the arrangement of the ink discharge holes, ink droplets are discharged by the heat energy of the heating resistor. After that, even if some fine bubbles remain between the substrate and the top plate, these bubbles move with the ink flowing between the substrate and the top plate in the direction perpendicular to the arrangement of the ink ejection holes, and the next line. Until the recording operation is started, it is promptly removed from the region between the heating resistor and the ink ejection holes. Therefore, when the heating resistor is reheated during the next line recording operation to generate new bubbles, fine residual bubbles may be included in the ink droplets discharged from the ink discharge holes or newly generated. The combined bubbles and residual bubbles rarely form a large bubble, which makes it possible to form a good image with a small density unevenness with a constant ink discharge amount.
[0046]
Further, according to the ink jet head of the present invention, since the ink filled between the substrate and the top plate is made to flow, even when the ink jet head is used for a long time, a heating resistor, a substrate, etc. The heat accumulated inside is well absorbed by the ink, and the temperature of the substrate does not become excessively high. Therefore, even if a sufficient cooling time is not provided between the recording operations of each line, the temperature of the heating resistor is maintained at a temperature suitable for the recording operation, and the amount of ink discharged from the ink discharge holes is substantially constant. As a result, a clear image with little density unevenness can be recorded at high speed.
[0047]
Furthermore, in the ink jet head of the present invention, since the partition wall is formed along the flow direction of the ink on the lower surface of the top plate and in the region between the adjacent ink ejection holes, the ink between the substrate and the top plate is used. Can be stably flowed in a predetermined direction at a relatively high flow rate, and it is possible to effectively prevent a spiral flow from occurring in the ink. Therefore, it is possible to remove residual bubbles in the ink satisfactorily in a shorter time than between the heating resistor and the ink discharge hole, and to obtain a predetermined flow velocity necessary for quickly cooling the substrate, and to cope with high-speed recording. Is possible.
[Brief description of the drawings]
FIG. 1 is a perspective view of an ink jet head according to an embodiment of the present invention.
2 is a cross-sectional view of the inkjet head of FIG. 1 in the sub-scanning direction.
3 is a cross-sectional view of the inkjet head of FIG. 1 in the main scanning direction.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Glaze layer, 3 ... Heat generating resistor, 7 ... Top plate, 8 ... Ink ejection hole, 9 ... Ink, 10 ... Partition

Claims (4)

A substrate having a large number of heating resistors arranged in a straight line, and a top plate in which a large number of ink discharge holes corresponding to the heating resistors are formed, and the ink discharge holes are the heating resistors. together is arranged at a predetermined interval between so as to be positioned on top of the body, it makes the ink is filled into the gap formed on the substrate and the top plates, the array of heating resistors of the ink An ink jet head that forms an image by ejecting ink droplets from the ink ejection holes by heat energy generated by the heating resistor while flowing in a direction orthogonal to
In the lower surface of the top plate, and the region between adjacent said ink discharge hole, along with the partition wall along the flow direction of the ink is formed, cross-sectional mountain shape between the heating resistors and the substrate An ink jet head, characterized in that a glaze layer is interposed and the partition wall is disposed over an intervening region of the glaze layer .   The inkjet head according to claim 1, wherein the partition wall is formed integrally with the top plate. The inkjet head according to claim 1 or 2, characterized in that the partition wall is kept non-contact with respect to the substrate or the glaze layer. Flow rate of the ink, at least the heat-generating resistor and the ink-jet head according to claim 1, wherein the region to be controlled to 50μm / sec~2000μm / sec between the ink discharge hole.

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