JP3638293B2 - Inkjet head - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an ink jet head used in an ink jet printer.
[0002]
Inkjet printers are characterized by high efficiency, small size, high resolution, and quiet printing. In recent years, there has been remarkable spread, but recently there has been a demand for small printers typified by portable printers. Therefore, there is an urgent need for further miniaturization and higher efficiency.
[0003]
In order to meet these demands, not only the so-called edge chute type in which the nozzle is provided on the end face of the thin plate-like head but also the so-called side chute type in which the nozzle is provided on the plane of the thin plate is considered. Of these, in particular, a pressure generator was installed almost directly under the nozzle to reduce the size and increase the efficiency (hereinafter referred to as the direct type).
[0004]
[Prior art]
An example of a conventional direct ink jet head using this method18(A) thru | or figure18Shown in (D). These configurations are as follows. Figure18(A) uses a piezoelectric element as a pressure generation source, and pressure chambers 1 as pressure generation units are arranged in a substantially arc shape in communication with the nozzles 2 on both sides of the nozzles 2 in two rows, On the diaphragm in contact with each pressure chamber 1, a piezoelectric element 3 facing each pressure chamber 1 is attached. The arrow A direction is the ink ejection direction from the nozzle 2, and the arrow B direction is the head scanning direction.
[0005]
Figure18(B) shows the pressure chambers connected in parallel to the nozzles arranged obliquely intersecting the scanning direction, and the piezoelectric elements 3 are respectively arranged on the diaphragms in contact with the pressure chambers. It is attached. Figure18(C) shows a configuration in which the nozzles are diagonally arranged in two rows and the pressure chambers are arranged facing each other in two rows.
[0006]
Also figure18(D) is a bubble jet type using an electrothermal conversion element 4 as a pressure generation source, and the electrothermal conversion element 4 is disposed on the bottom surface of the pressure chamber 6 almost directly below the nozzle 5. .
[0007]
[Problems to be solved by the invention]
However, the conventional structure has the following drawbacks. That is, figure18In the case of (A), since the useless space that does not contribute to the performance of the head becomes wider as it goes to the outside of the nozzle, the head becomes relatively large and the shape of the pressure chamber becomes complicated, and immediately after printing. Considerable ingenuity is required for the medium feeding mechanism for solving the problem peculiar to the ink jet printer that the medium is soiled when pressed.
[0008]
Also figure18In the case of (B), if the number of nozzles is increased in order to increase the resolution, the width of the head increases, and the risk of soiling or tearing the medium increases due to contact with the medium during head scanning. Drive timing control must be performed every time, and the control method becomes complicated, making it difficult to maintain print quality.
[0009]
Also figure18In the case of (C), the above-mentioned drawbacks are improved by facing the pressure chambers in two rows, but the disadvantage that the control method becomes complicated and it becomes difficult to maintain the print quality still remains.
[0010]
Also figure18In the case of (D), since the energy density of the drive source is high, a relatively small pressure chamber can be used.18(A) to Figure18A considerably smaller head than (C) can be realized, and there are few defects. However, with this shape as it is, the resolution is limited to about 300 dpi, and it is difficult to achieve higher resolution.
[0011]
SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet head that makes it possible to produce a high-resolution, small-sized ink jet head at low cost.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, in the ink jet head in which 2n nozzle rows each including at least one nozzle are formed (where n ≧ 2 is an integer), the nozzle that prints the uppermost dot is the first nozzle. When numbers are assigned to the nozzles that print the lowest dot in the following order as the first nozzle, the nozzle row to which an arbitrary mth nozzle belongs and the nozzle row to which the (m + n) th nozzle belongs are simulated. The intervals a are arranged so as to be an integral multiple of p / 2 with respect to the dot pitch p so that they can be handled as one row, and the (m + 1) th nozzle row to which the mth nozzle belongs. ) The nozzle row to which the No. 1 nozzle belongs is arranged relatively far from the closely arranged interval, and pressure chambers corresponding to the 2n nozzle rows are formed in a common member.In addition, the planar shape of the pressure chamber is a square shape, and the nozzle position and the ink supply port in each pressure chamber are arranged at diagonal positions of the square corner.In addition, a configuration (first configuration) is provided in which means for driving the two nozzle rows arranged close to each other in synchronism with each other is driven in a pseudo manner.
[0013]
Further, in the ink jet head having the first configuration, the entire circumference of the ink supply path may be such that two pressure chamber rows corresponding to two nozzle rows arranged close to each other with the nozzles facing each other form one pressure chamber group. It is set as the structure (2nd structure) characterized by being surrounded.
[0014]
Further, in the ink jet head having the second configuration, there are a plurality of pressure chamber groups, and the ink supply passages surrounding them are separated for each pressure chamber group, and the separated ink supply passages have different color inks. A configuration (third configuration) is characterized by receiving supply.
[0015]
[Action]
In the case of the first configuration, the pressure chamber can be arranged without difficulty without taking up a useless area. Further, since the nozzle rows are close to each other so that the interval a is an integral multiple of p / 2 with respect to the dot pitch p so that the nozzle rows can be handled as one row in a pseudo manner, the head drive control is performed. When performing, it becomes possible to handle the printing timing of the two nozzle rows synchronously as one row, that is, the control becomes very easy.
In addition, the pressure chamber has a square shape, and the nozzle position and the ink supply port in each pressure chamber are arranged at diagonal positions with respect to the square corner. Air bubbles do not remain, and the reliability of the head is further improved.
Further, the area of the portion that does not contribute to ink ejection is eliminated, and as a result, the head can be further downsized.
[0016]
In the case of the second configuration, by forming the ink supply path in such a shape, ink can be supplied from above and below to each pressure chamber, and the substantial ink supply capability is increased. As a result, ink ejection is more stable and high-speed printing is possible.
[0017]
In the case of the third configuration, a plurality of colors can be printed by supplying different colors of ink to the separated ink supply paths, so that color printing is performed by minute line feeds corresponding to the number of colors. be able to.
[0018]
In summary, according to the present invention, a high-resolution and small-sized inkjet head can be obtained at low cost.
[0019]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
[0020]
The present invention realizes a structure in which the pressure chambers can be arranged in a minimum area without difficulty, and the defects listed in the prior art can be minimized. For this purpose, the longitudinal direction of the pressure chambers, including the partition walls, needs to be divided so that the maximum width is 2n times the resolution pitch of the head (where 2n is the number of nozzle rows described above). The scanning direction of the inkjet head is determined so as to have the minimum necessary width according to the performance of the drive source.Ru.
[0021]
1 to 4ActuallyAn example is shown.
[0022]
FIG. 1 is an explanatory view of the structure of the ink jet head of this embodiment, and FIG. 1 (A) shows a standard arrangement of each pressure chamber and nozzle. In the ink jet head 11 of FIG. 1A, 2n nozzle rows (where n ≧ 2) are formed by arranging a plurality of nozzles 12 in the vertical direction, and each nozzle 12 is connected to a pressure chamber 13. doing. In the figure, the case of n = 2 is shown.
[0023]
Each nozzle row uses the nozzle that prints the highest dot (the top nozzle in the leftmost nozzle row) as the first nozzle, and the nozzle that prints the lowest dot in the following order (the rightmost nozzle) Nozzle row to which any <m> -th nozzle belongs, when numbers are assigned to the nozzles at the bottom of the row (in the figure, the number with <> in the pressure chamber 13 is the nozzle number). And the nozzle row to which the (m + n) th nozzle belongs are arranged close to each other, and the row to which the mth nozzle belongs and the nozzle row to which the (m + 1) th nozzle belongs are arranged apart from each other. .
[0024]
Specifically, these arrangements will be described. For example, the nozzle row to which the ninth nozzle 12 belongs (leftmost row) and the nozzle row to which the eleventh nozzle 12 of (9 + 2) belongs (second from the left) The nozzle row to which the ninth nozzle 12 belongs and the nozzle row to which the (9 + 1) th tenth nozzle 12 belongs (the third row from the left) are separated.
[0025]
When such a nozzle and a pressure chamber are arranged, the pressure chamber can be arranged without difficulty without taking up a useless area. Further, although there are four nozzle rows, the two rows are close to each other with an interval a, so that it is possible to handle them as two rows in a pseudo manner when performing head drive control. This is very easy to control as compared to the case where four-row control is performed.
[0026]
Note that the distance a in FIG. 1A (for example, the inter-column distance between the nozzle row with the ninth nozzle and the nozzle row with the 9 + 2 nozzle) will be described. For example, when the resolution is 360 dpi, the dot pitch p is 70.5 μm (= 360 / 25.4 × 1000 μm), and if a is set to an integral multiple of p, the print timings of the two nozzle arrays can be synchronized. Therefore, the number of timing signals is only one, and the control becomes simple.
[0027]
However, in general, in a serial dot printer, in order to make the connection of diagonal lines beautiful, dots are printed at positions corresponding to an apparently double resolution in the horizontal direction. When this is also taken into consideration, a may be set to an integer multiple of p / 2.
[0028]
Further, the contents and effects of the dimension b in FIG. 1A (for example, the distance between the nozzle array having the ninth nozzle and the nozzle array having the (9 + 1) th nozzle) are substantially the same as described above. is there.
[0029]
In addition, the inkjet head 21 in FIG. 1B is set such that the distance between the nozzle rows in FIG. 1A and the vertical interval (depending on the resolution) of the nozzles 22 are a constant ratio. Thus, the upper and lower partition walls of the pressure chambers 23 corresponding to each nozzle row form a straight line as shown by dotted lines over the 2n pressure chamber rows in the lateral direction. For this reason, each pressure chamber 23 has a shape as shown in the figure.
[0030]
In this case, the area of the pressure chamber may be smaller than in the case of FIG. 1A depending on how the partition wall is determined. However, the dimensional inspection is facilitated and a piezoelectric element or the like is used as a drive source as will be described later. Can be used, the drive source can be integrally formed and then separated, and the manufacturability is greatly improved.
[0031]
In addition, the inkjet head 31 in FIG. 1C has a parallelogram shape with the straight lines formed by the upper and lower partition walls in parallel in order to maximize the area of the pressure chamber in FIG. Is. In the figure, 32 is a nozzle and 33 is a pressure chamber.
[0032]
In this case, since the width of the partition wall is constant everywhere, the area of the portion that does not contribute to the ink ejection is eliminated, and as a result, the head can be made smaller than that in FIG.
[0033]
FIG. 2 is an explanatory view of the structure of the ink supply path of the inkjet head 11 in FIG. 1A. As shown in FIG. 2A, each pressure chamber 13 in the first row from the left is connected to the ink supply path 41a. The pressure chambers 13 in the second and third rows are connected to the ink supply path 41b passing between the two rows, and the pressure chambers 13 in the fourth row are connected to the ink supply passage 41c.
[0034]
By the way, the frictional resistance of the pipe is inversely proportional to the fourth power of the cross-sectional area, as is known as the Darcy-Weissbach equation. Therefore, as compared with the conventional method as shown in FIG. 2B, the width in the horizontal direction required for the ink supply path can be reduced by sharing the ink supply path. This is also an effective means for reducing the size of the head.
[0035]
Another example of the ink supply path is shown in FIG.
In a serial dot printer, it is rare that all nozzles are driven simultaneously except in the case of full printing. Accordingly, the ink supply path 42 is shaped as shown in FIG. 3A (the ink supply path so that two pressure chamber rows corresponding to two nozzle rows in which the nozzles are close to each other constitute one pressure chamber group. 42), the ink can be supplied from above and below the common ink supply path 42 to each pressure chamber 13, and the substantial ink supply capability is increased. As a result, ink ejection is further stabilized and high-speed printing is possible.
[0036]
FIG. 3B shows a yellow ink supply path 43a, a cyan ink supply path 43b, a magenta ink supply path 43c, and a black ink supply that communicate the ink supply paths with the respective pressure chamber rows. A separated road 43d is shown. With this head, four colors can be printed in one pass, and characters can be printed with four minute line feeds. Of course, black can be printed by mixing three colors. In that case, the pressure chamber group may be divided into three rows. In this way, a small and single color head can be realized.
[0037]
As described above, when ink is supplied from the ink supply path to each pressure chamber, it is important to appropriately set the positions of the ink supply path and the nozzle in order to eliminate the retention of bubbles. It shows the point. This will be described in detail below with reference to FIGS. 4 (A) to 4 (E).
[0038]
As shown in FIG. 4B, when the nozzle 51 is not at the corner of the pressure chamber 52, the bubbles 54 are likely to remain in the pressure chamber 52 at the time of initial ink injection from the ink supply path 53, and there is a certain timing. Thus, even when bubbles are sucked from the nozzle 51, the bubbles 54 are easily caught at the same position. Even when the ink discharging operation is performed, these bubbles are not easily discharged because they are at the stagnation point of the ink flow.
[0039]
If bubbles exist in the pressure chamber, the pressure wave from the driving source is greatly attenuated, and ink ejection stops. On the other hand, when the nozzle 51 is arranged near the corner of the pressure chamber 52 as shown in FIG. 4A, even if bubbles are present, the ink flow indicated by the arrow during the discharge operation is performed. Since it rides, it can be easily discharged and the reliability of the head is improved.
[0040]
Even when the nozzles are provided at the corners of the ink chamber as described above, when the ink supply path 53 is connected to the center of the pressure chamber 52, as shown in FIG. Air bubbles tend to remain in the right corner inside. This place is also a stagnation point of the ink flow during the ink discharging operation, and bubbles are not easily discharged. Therefore, if the ink supply path 53 is arranged diagonally to the nozzle 51 as shown in FIG. 4D, the ink flow becomes as indicated by the arrow in the figure, and there is no stagnation point, and bubbles remain when ink is injected. The reliability of the head is further improved.
[0041]
Furthermore, as shown in FIG. 4E, when the structure shown in FIG. 4D is arranged symmetrically, each pressure chamber 52 can have the same shape from the ink supply path 53 to the nozzle 51. . This makes it easy to ensure head characteristics.
[0042]
About main composition and effect of the inkjet head of the present inventionAs above,nextthisThe operation and manufacturing method of the head will be described.
[0043]
Figure5Is an operation explanatory diagram of an ink jet head using a piezoelectric element as a drive source.5(A) shows the non-operating state,5(B) shows the time of operation. In the figure, 71 is a nozzle plate provided with a nozzle 71a, 72 is a pressure chamber 72a and a flow path plate provided with an ink supply path (not shown) connected to the pressure chamber 72a, 73 is a vibration plate, and these three plates Are laminated by bonding or the like. 74 is a piezoelectric element. The pressure chamber 72a communicates with the nozzle 71a, and the piezoelectric element 74 is fixed to the surface of the diaphragm 73 by adhesion or the like and faces the pressure chamber 72a.
[0044]
Figure5(A) is a state in which no voltage is applied to the piezoelectric element 74, and the diaphragm 73 is not bent. Figure5(B) shows a state in which a voltage is applied to the piezoelectric element 74. The diaphragm 73 is deflected by the displacement force of the piezoelectric element 74, and ink particles 75 are ejected from the nozzle 71a.
[0045]
Figure6Is an explanatory diagram of the operation of an inkjet head using electrostatic force.6(A) shows the non-operating state,6(B) shows the time of operation. In the figure, 81 is a nozzle plate having a nozzle 81a, 82 is a pressure plate 82a and a flow path plate having an ink supply path (not shown), 83 is a vibration plate, 84 is an insulating layer having an air gap 84a, and 85 is a substrate. It is.
[0046]
Figure6(A) is a state in which no voltage is applied, and the diaphragm 83 is not bent. Figure6(B) shows a state in which a voltage is applied as shown in the figure. The diaphragm 83 is deflected by an electrostatic force, and ink particles 86 are ejected from the nozzle 81a.
[0047]
Figure7Is an operation explanatory diagram of an inkjet head using an electrothermal conversion element.7(A) shows the non-operating state,7(B) shows the time of operation. In the figure, 91 is a nozzle plate having a nozzle 91a, 92 is a pressure chamber 92a and a channel plate having an ink supply path (not shown), 93 is a substrate, and 94 is an electric circuit disposed on the substrate 93 in the pressure chamber 92a. It is a thermal conversion element.
[0048]
Figure7(A) is a state in which the electrothermal transducer 94 is not energized. Figure7(B) is a state in which the electrothermal conversion element 94 is energized, and a part of the ink boils instantaneously due to the generated thermal energy to form bubbles 96. As the bubbles grow, ink particles 95 are ejected from the nozzle 91a.
[0049]
Figure8These are explanatory drawings of a piezoelectric element forming method. Usually, the piezoelectric element is5As shown in the figure, the plate is joined on the diaphragm at a position corresponding to each pressure chamber.8In this case, after joining the piezoelectric elements 101 having a size covering a plurality of pressure chambers, the piezoelectric elements 101 are cut at positions directly above the partition walls that partition the pressure chambers to form pressure chambers corresponding to the respective pressure chambers. .
[0050]
As a cutting machine, it is effective to use a precision slicer used for separating semiconductors and the like. In this case, since the width of the cutting groove can be made very thin, about 50 μm, the portion to be removed can be reduced and the head can be prevented from becoming unnecessarily large, and the cutting position accuracy can be kept within an error of about ± 5 μm. The variation in size of the individual piezoelectric elements can be made extremely small.
[0051]
Figure9Is an explanatory diagram of another method for forming a piezoelectric element, which is illustrated after bonding a piezoelectric element 100 larger than covering all the pressure chambers.8The pressure chamber corresponding to each pressure chamber is formed by cutting in the same manner as described above. Thereby, an inferior part (shaded part in the figure) remains on the outer periphery of the piezoelectric element group. In general, when a piezoelectric element is bonded to a vibration plate, the adhesive may protrude to the surface of the element and be cured depending on the amount of adhesive applied.
[0052]
When this protruding adhesive covers the electrode on the surface of the element, conduction failure occurs. The problem is the figure9This can be solved by providing an unnecessary portion on the outer periphery of the piezoelectric element group. In addition, when the piezoelectric element is soldered to the diaphragm, the element itself is generally thin, so that the solder becomes a bridge between the upper and lower electrodes on the outer periphery of the piezoelectric element, which may cause insulation failure. When the insulation defect is severe, it leads to destruction of the device itself, which is a serious problem.
[0053]
Even in such a case, if an unnecessary part is provided on the outer periphery of the element, even if a solder bridge is generated, since the part actually used is ensured to be insulated, there is no problem in use. . Furthermore, when cutting a piezoelectric element, chipping (minute chipping) is likely to occur at the beginning and end of cutting, but if an unnecessary portion is provided on the outer periphery, it is actually used even when chipping occurs. Because there is no damage to the part, it will not be defective. Therefore, the yield of the head is improved and the reliability is improved.
[0054]
Figure10Is an explanatory view of the positioning means of the piezoelectric element and the pressure chamber, 103₁, 103₂Is a cross-shaped fiducial mark provided on the bonding surface of the piezoelectric element 101 outside the bonding range. In the case of cutting after bonding the piezoelectric element to the vibration plate, the displacement between the cutting position and the pressure chamber becomes a serious problem. When the displacement increases, the displacement of the piezoelectric element is not effectively transmitted to the diaphragm. At the same time, when a piezoelectric element corresponding to a certain pressure chamber is driven, a part of the element is applied to another adjacent pressure chamber. This causes a problem that mechanical interference occurs.
[0055]
Therefore, it is important how to reduce the positional shift. However, since the piezoelectric element is opaque, it is impossible to align with the pressure chamber through the element. This problem can be solved with accurate and easy cutting positioning by simultaneously forming the reference mark 103 as a reference for the cutting position of the pressure chamber when forming the flow path plate.
[0056]
Figure11FIG. 4 is an assembly process diagram of the head. The head includes a nozzle plate 111 having a nozzle 111a, a flow channel plate 112 (not shown) having a pressure chamber 112a and an ink supply path (not shown) communicating with the pressure chamber 112a.5And the piezoelectric element 113 are laminated. The assembly process is as follows.
[0057]
First, figure11A nozzle plate 111 and a flow path plate 112 shown in FIG. The nozzle plate 111 is manufactured by etching photosensitive glass (product name: PEG3, manufactured by Hoya Co., Ltd.). The nozzle diameter was 50 μm and the plate thickness was 200 μm. Moreover, as a manufacturing method of the nozzle, an electroforming method or the like may be used regardless of this method. The flow path plate 112 was manufactured by etching photosensitive glass. The plate thickness was 150 μm and the etching depth was 50 μm. As a material, silicon or stainless steel may be used, and the flow path may be formed by etching. Further, the flow path plate can also be formed by processing unevenness on a single plate by pressing.
[0058]
Next, these two sheets11Join as shown in (B). For joining, (1) parts are not dropped off during use, and at the same time, they are joined firmly without leakage at the very thin partition wall so that crosstalk with the adjacent pressure chamber does not occur. (2) Make sure that the bonding adhesive and binder do not overflow into the pressure chamber, block the nozzle, make it easy for air bubbles to collect, and prevent ink flow. Need to be satisfied.
[0059]
Therefore, when various joining experiments were conducted, it was confirmed that the following three kinds of joining methods were effective. That is, a method using an epoxy adhesive, a method using an ultraviolet curable anaerobic adhesive, and a brazing method are effective. Next, each case will be described in detail.
[0060]
When using an epoxy-based adhesive, it is desirable to use a two-component mixed type with a relatively high viscosity, and the application is carried out using a rubber roller or bar coater so that a small amount of adhesive is applied thinly and evenly to the flow path plate. To. Then, it is combined with the nozzle plate and heated and cured while applying pressure. As an epoxy adhesive, AW106, made by HV953U Ciba Geigy (cured at 80 ° C. for 3 hours) is used.
[0061]
In the case of using an ultraviolet curable anaerobic adhesive (LI210, Loctite), the application method is the same as that of the epoxy-based adhesive, but in the case of curing, ultraviolet rays are irradiated while applying pressure. If either the nozzle plate or the flow channel plate is transparent, the adhesive can be directly irradiated with ultraviolet rays, but even if both are opaque, the adhesive exposed at the end is cured by the ultraviolet rays, and the internal adhesive The agent is shielded from the air, and thereafter the curing gradually proceeds to the inside due to anaerobic properties.
[0062]
The advantage of using adhesives is that the material of the flow path plate and nozzle plate can be selected quite freely, and the work can be done at a relatively low temperature of 100 ° C or less. Metamorphosis is difficult to occur.
[0063]
In the case of brazing, both the flow path plate and the nozzle plate must be made of metal. In the soldering procedure, solder plating, nickel plating or the like is applied to the surface of the flow path plate as a binder, and the pressure is applied together with the nozzle plate, and heating is performed above the melting point of the binder agent to perform bonding. The characteristic of brazing is that the strength is very high, leakage and overflow hardly occur, and even if a strong solvent is mixed in the ink, the bonded portion is not damaged.
[0064]
Next, figure11As shown in (C), a silver paste (Sylvest, PS707, manufactured by Tokuri Chemical Laboratory) is applied to the surface of the flow path plate 112 where the flow path is not formed, and baked at 160 ° C. for 1 hour. Form. If a stainless steel plate is used as the flow path plate, this electrode formation is unnecessary.
[0065]
Next, figure11As shown in (D), a Tokin piezoelectric element 113 is joined onto the flow path plate 112. About this joining, (1) the piezoelectric element displacement energy is efficiently transmitted to the vibration plate (the portion of the flow path plate 112 in contact with the pressure chamber 112a), and at the same time, the piezoelectric element is firmly joined to withstand repeated loads; (2) Since the piezoelectric element does not operate unless electrical conduction is established between the lower electrode of the piezoelectric element and the electrode 114, the bonding layer is conductive or the bonding layer is very thin (about 10 μm or less). It is necessary to satisfy the following two points: a part of the lower electrode of the piezoelectric element is in contact with the electrode 114.
[0066]
Therefore, when various joining experiments were performed, it was confirmed that the following various joining methods were effective. That is, a method using an epoxy adhesive, a method using an ultraviolet curable adhesive, a method using a conductive adhesive, and a soldering method are effective.
[0067]
When an epoxy adhesive is used, the adhesive used and the coating method are the same as in the above case (joining of the nozzle plate and the flow path plate), so detailed explanations are omitted, but there are few bubbles remaining and the adhesive state is good. is there. In addition, if a defoaming process is performed in a vacuum chamber after adhesive application, a better result is obtained.
[0068]
When an ultraviolet curable anaerobic adhesive is used, adhesion is performed in the same manner as described above. However, since the operation can be performed at a relatively low temperature of 100 ° C. or less, the piezoelectric element is hardly deteriorated.
[0069]
On the other hand, in the case of soldering, the flow path plate needs to be a metal. In the soldering procedure, the surface of the flow path plate is subjected to solder plating, and is heated to a melting point of the solder or higher while being strongly pressed together with the piezoelectric element. As a feature of soldering, since the strength is very high and there is electrical conductivity, no conduction failure occurs, and since the solder is plated on the vibration plate, the joining layer becomes very thin. When soldering is performed, the piezoelectric element is exposed to a high temperature, and therefore it is desirable to take a repolarization measure for the element.
[0070]
Then figure11As shown in (E), after cutting with a dicing saw (DAD25P / 6T, Disco Inc.)11As shown in (F), a joint 115 is attached to the supply port and connected to an ink cartridge (not shown). And figure11As shown in (G), the flexible cable 116 connected to the piezoelectric element drive source is routed to just before the piezoelectric element and connected to each piezoelectric element by wire bonding.
[0071]
Detail of connection part by wire bonding12Shown in (A). As is apparent from this drawing, the exposed surface of the conductor 116a of the flexible cable 116 and the piezoelectric element are connected by wire bonding. Reference numerals 116b and 116c denote a base film and a cover film of the flexible cable 116, respectively. The feature in this case is the versatility of the equipment and the low cost. However, since the piezoelectric element vibrates, it is necessary to reinforce the bonding strength (silicon coating or the like) that also serves as a moisture-proof effect.
[0072]
Next, a connection method other than the wire bonding will be described.
[0073]
Figure12(B) is a thermocompression bonding method in which a solder 117 having a thickness of several μm to several tens of μm is surface-treated on the conductor exposed surface of the flexible cable 116 and the surface of the piezoelectric element 113 and soldered by heat pressing with a heater 118. It is. Its features are low cost and high reliability of connection strength. However, in order to avoid short-circuiting between adjacent electrodes, it is necessary to carefully manage the pitch and the thickness of the solder surface treatment.
[0074]
Figure12(C) and (D) are bump bonders.12As shown in (C), a solder bump (solder ball) 119 having an outer diameter of about several μm to several tens of μm is provided on the piezoelectric element 113, and this is thermally pressed by a heater 118.12Soldering is performed as shown in (D). The feature of this method is that it is possible to reduce the possibility of a short circuit between adjacent ones as compared with the thermocompression bonding method.
[0075]
Figure12(E) is an anisotropic conductive rubber system.12As shown in (E), an anisotropic conductive rubber 120 is inserted between the piezoelectric element 113 and the flexible cable 116, and this is inserted into the pressure plate 122 via an elastic material 121 provided with a convex portion 121a only on the exposed portion of the conductor. Conductivity is obtained by pressurizing with. The feature of this method is that it is not necessary to heat the piezoelectric element, so that repolarization processing is not necessary. However, it is necessary to appropriately set the hardness and pressure of the elastic material so as not to hinder the vibration of the piezoelectric element.
[0076]
Figure12(F) is an anisotropic conductive film system, which is an improvement of the anisotropic conductive rubber system. In this case, the anisotropic conductive film 123 is inserted between the piezoelectric element 113 and the flexible cable 116, and the conductor exposed portion is thermally pressed by the heater 118 to establish conduction. Anisotropic conductive film (trade name: Anisolum, etc.) is made by kneading a conductive powder in a thermosetting resin, and its feature is that the thermosetting resin hardens after hot pressing, so that it is like an anisotropic conductive rubber. There is no need to pressurize normally, and the heating temperature can be kept lower than the temperature required for soldering.
[0077]
Figure11The following is a detailed supplementary explanation of the various manufacturing methods of the nozzle plate and flow path plate described in connection with the above.
[0078]
The nozzle plate is manufactured by electroforming, photosensitive glass etching, silicon etching, micro press, or the like. For the electroforming method,13As shown in FIG. 5A, after a pattern 132 is formed on a substrate 131, Ni 133 having a shape shown in the figure is attached and grown to form a nozzle plate 134. Reference numeral 134a denotes a nozzle. The electroformed product is peeled from the substrate 131 to obtain a product. The feature of this method is that it is inexpensive and excellent in mass productivity.
[0079]
In case of photosensitive glass etching method,13As shown in (B), a mask pattern 136 is overlaid on the photosensitive glass 135, and exposure and etching are performed to obtain a nozzle plate 137 having nozzles 137a. The feature of this method is that it is possible to increase the length of the nozzle, to increase the accuracy of the flying direction of the ink particles, and to easily ensure the stability of ejection. Moreover, since it is transparent, it is possible to inspect from the outside even after the head is assembled.
[0080]
For the silicon etching method,13As shown in (C), a resist 139 is applied on a silicon plate 138, a mask pattern 141 is overlaid, and exposure, development, and etching are performed to obtain a nozzle plate 141 provided with a nozzle 141a. The feature of this method is that the processing accuracy is high because the etching rate is low and dimensional control is easy.
[0081]
For the micro press method,13As shown in (D), the substrate is embossed, stamped, and lapped to obtain a nozzle plate 142 having a nozzle 142a. The feature of this method is that the nozzle length can be increased and the processing accuracy is high.
[0082]
The flow path plate is manufactured by stainless steel etching or glass etching, silicon etching, photosensitive glass etching, plastic mold or the like. For stainless steel etching or glass etching method,14As shown in (A), a resist 144 is applied on a stainless steel or glass substrate 143, a mask pattern 145 is overlaid, the resist is removed by exposure and etching with an etching solution, and a flow path provided with a flow path 146a. A plate 146 is obtained. The feature of this method is that the material cost is low and the processing is easy.
[0083]
For the silicon etching method,14As shown in (B), a resist 148 such as SiO2 is applied on a 4-inch-thick Si (100) substrate 147, exposed to light, developed and etched (50 ° C. using an aqueous KOH (10%) solution). 40 minutes) to obtain a flow path plate 149 having a flow path 149a. The feature of this method is that the processing accuracy is high because the etching rate is low and dimensional control is easy.
[0084]
For the photosensitive glass etching method,14As shown in (C), a mask pattern 151 is overlaid on the photosensitive glass 150, and exposure and etching are performed to obtain a flow path plate 152 having a nozzle 152a. The feature of this method is that the processing accuracy is relatively high and the inspection is possible from the outside because it is transparent.
[0085]
For the plastic mold method,14As shown to (D), a type | mold is manufactured in the process shown on the left side. First, a photoresist 154 is applied to the glass substrate 153 in a predetermined pattern, Ni155 is formed on the surface by sputtering, and Ni156 is further applied by electroforming. Next, a substrate 157 is attached to the surface and peeled from the glass substrate 153 to obtain a mold 158. At the time of product molding, as shown on the right side, this mold is set on a flat lower mold 159, and a 2P material is cast and then irradiated with UV, whereby a flow path plate 160 having a flow path 160a is obtained. . The feature of this method is that it is excellent in mass productivity.
[0086]
Figure above11In the following description, the integrated flow path plate was described.11An example of the flow path plate 112 is shown in FIG.15As shown in Fig. 4, the feature is that the number of parts and the number of processing steps are small. The flow path plate may be not only an integral type but also a pasted type, an example of which is shown in the figure.16Shown in
[0087]
This pasted type flow path plate is obtained by forming a photosensitive resin 162 on the vibration plate 161 by laminating, exposing the pattern through a photomask, and removing unnecessary portions with a solvent. Reference numeral 163 denotes a pressure chamber, and 164 denotes an ink supply path. The feature of this method is that materials optimal for the performance required for the diaphragm and the partition wall can be selected, and the accuracy control of the height of the partition wall can be easily performed.
[0088]
Figure shows the alignment method when joining each plate constituting the head17Shown in This figure is a figure11In this case, two guide pins are used. In general, it is said that the alignment accuracy in the pin guide method is about ± 10 μm, and when trying to determine the position between the nozzles with the pin guide, there is a problem in the printing accuracy in a head with high resolution.
[0089]
However, in the case of the shape like the head in this figure, the positional accuracy between the nozzles is ensured by the nozzle plate itself, and a deviation of about ± 10 μm between the relative position of the flow path and the nozzle does not cause a problem in characteristics. In that case, the pin guide system is a simple and effective assembly means. The assembly procedure for this figure is as follows.
[0090]
Reference numeral 165 denotes an alignment jig provided with two guide pins 166. Each member of the nozzle plate 111, the flow path plate 112, the piezoelectric element 113, and the flexible cable 116 is provided with guide holes corresponding to the two guide pins 166, and these guide holes are fitted into the guide pins 166. By joining, each member is positioned.
[0091]
In the head structure as described above, it is easy to discriminate similar heads by engraving data such as the head resolution and part number at a position that can be seen from outside the bonding area of the piezoelectric element bonding surface of the flow path plate. It is possible to eliminate mistakes in parts. Moreover, there is no cost increase for that purpose.
[0092]
【The invention's effect】
As described above, according to the present invention, a high-resolution and small-sized inkjet head can be mass-produced at low cost.
[Brief description of the drawings]
FIG. 1 shows the present invention.The fruitFIG. 1 (A) shows the standard arrangement of each pressure chamber and nozzle, and FIG. 1 (B) and FIG. 1 (C) show the arrangement of partition walls, respectively. Yes.
FIG. 2 shows the present invention.The fruitFIG. 2A shows the structure of the ink supply path of the embodiment, FIG. 2A shows the present invention, and FIG. 2B shows the conventional one.
FIG. 3 shows the present invention.The fruitFIG. 3A illustrates the case of a common ink supply path, and FIG. 3B illustrates the case of an ink supply path separation type.
FIG. 4 shows the present invention.The fruitFIG. 4A to FIG. 4C show the case where the ink supply path is connected to the center of the pressure chamber, and FIG. 4D and FIG. Indicates a case where the ink supply path is connected to a position diagonal to the nozzle.
[Figure 5]FIG. 5A shows a non-operating state, and FIG. 5B shows an operating state of an inkjet head using a piezoelectric element.
[Fig. 6]FIG. 6A shows a non-operating state and FIG. 6B shows an operating state of the electrostatic force-based inkjet head.
[Fig. 7]FIG. 7A shows a non-operating state and FIG. 7B shows an operating state of the ink jet head using an electrothermal conversion element.
[Fig. 8]It is explanatory drawing of the formation method of a piezoelectric element.
FIG. 9It is explanatory drawing of the other formation method of a piezoelectric element.
FIG. 10It is explanatory drawing of the alignment means of a piezoelectric element and a pressure chamber.
FIG. 11FIG. 11A to FIG. 11G show the respective steps in order in the assembly process diagram of the head.
FIG.FIG. 12A illustrates a wire bonding method, FIG. 12B illustrates a thermocompression bonding method, and FIG. ), (D) shows a bump bonder, FIG. 12 (E) shows an anisotropic conductive rubber system, and FIG. 12 (F) shows an anisotropic conductive film system.
FIG. 13FIG. 13A shows the case of the electroforming method, FIG. 13B shows the case of the photosensitive glass etching method, and FIG. 13C shows the silicon etching method. FIG. 13D shows the case of the micro press method.
FIG. 14FIG. 14 (A) shows a stainless steel or glass etching method, FIG. 14 (B) shows a silicon etching method, and FIG. 14 (C) shows a photosensitive glass etching method. FIG. 14D shows a plastic mold method.
FIG. 15It is a perspective view which shows the actual shape of the flow-path board of FIG.
FIG. 16It is a perspective view showing the shape of a pasting type channel board.
FIG. 17It is a perspective view which shows the joining system of each board.
FIG. 18FIGS. 18A to 18D are perspective views showing an outline of the structure of various conventional direct ink jet heads, and FIGS. 18A to 18D show various arrangements of pressure generation sources and pressure chambers, respectively.
[Explanation of symbols]
11, 21, 31 Inkjet head
12, 22,51, 71a, 81a, 91a, 111a, 134a, 137a, 141a, 142a Nozzle
13, 23,52, 72a, 82a,
92a, 112a, 163 Pressure chamber
41a-41c, 42,53,164            Ink supply path
71, 81, 91, 111, 134, 137,
141, 142 Nozzle plate
72, 82, 92, 112, 146, 149,
160 Channel plate
73, 83, 104, 161 Diaphragm
74, 101, 102, 113 Piezoelectric element
94 electrothermal transducer

Claims (3)

In an inkjet head in which 2n nozzle rows each including at least one nozzle are formed (n is an integer of 2 or more),
When the nozzle that prints the highest dot is numbered first and the nozzles that print the lowest dot are numbered in order, the nozzle row to which an arbitrary mth nozzle belongs and the (m + n) th nozzle The m-th nozzle is arranged so that the interval a is an integral multiple of p / 2 with respect to the dot pitch p so that the nozzle row to which the nozzle belongs can be treated as one row in a pseudo manner. And the nozzle row to which the (m + 1) th nozzle belongs are disposed relatively apart from the adjacently arranged interval, and pressure chambers corresponding to the 2n nozzle rows are provided. The pressure chamber is formed in a common shape, and the planar shape of the pressure chamber is a quadrangle, and the nozzle position and the ink supply port in each pressure chamber are arranged at diagonal positions with respect to the square corner, and are adjacent to each other. The Ink jet head, characterized in that a means for driving the print timing of the two nozzle rows that location as synchronization with pseudo first column. The inkjet head according to claim 1,
An ink jet characterized in that two pressure chamber rows corresponding to two nozzle rows arranged close to each other with the nozzles facing each other are surrounded by an ink supply path so as to form one pressure chamber group head. The inkjet head according to claim 2, wherein
An ink jet head, comprising: a plurality of pressure chamber groups, wherein ink supply paths surrounding the pressure chamber groups are separated for each pressure chamber group, and each separated ink supply path is supplied with ink of a different color.

Images