Patent Publication Number: US-8534796-B2

Title: Liquid-discharging recording head

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 12/482,321 filed Jun. 10, 2009, which claims priority from Japanese Patent Application No. 2008-155355 filed Jun. 13, 2008, which are hereby incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to liquid-discharging recording heads for performing printing by discharging liquid, and more particularly, to an inkjet recording head for performing recording by discharging ink. 
     2. Description of the Related Art 
     In recording heads mounted in inkjet recording heads, electrothermal transducers (heaters) and driving circuits and lines therefor are typically formed on a substrate using a semiconductor process technique, as disclosed in Japanese Patent Laid-Open No. 2005-138428. 
     In recent years, inkjet recording apparatuses have been required to have a higher image quality and a higher recording speed. For that purpose, in substrates for inkjet recording heads, there are demands to increase the mount density of heaters and logic sections, to increase the number of arrays of nozzles in response to the increase in number of ink colors, and to increase the length of the nozzle arrays in response to the increase in number of heaters themselves. 
     The length of the recording head can be increased by a method disclosed in Japanese Patent Laid-Open No. 7-276643 in which a long recording head is formed by arranging a plurality of substrates in a predetermined direction. 
     The size of droplets to be discharged has recently been reduced further. For example, heaters and nozzles for discharging small droplets of 3 pl or less are sometimes arranged on a substrate at a high density (e.g., 600 dpi or more). When the length of the recording head becomes more than or equal to 1 inch (e.g., 2 inches), a flow-path forming member (orifice plate) tends to be easily peeled off the substrate by the influence of stress therebetween. Further, since the substrate and a support member supporting the substrate generally have different coefficients of linear expansion, the above-described peeling easily occurs through a heating process during mounting. 
     When two substrates each having a length of about one inch are arranged to be used as a recording head having a length of two inches, the influence of stress is reduced compared to an integrated substrate having a length of two inches. Therefore, the risk of peeling is reduced, and the production yield is improved. As a result, it is possible to enhance reliability of the head, to reduce the cost, and to enhance reliability as the product. 
     However, in the above-described head in which a plurality of substrates are arranged, the support member and a TAB (Tape Automated Bonding) serving as mounted components become relatively large, and this increases the cost. 
     Therefore, to reduce the cost of a long recording head in which a plurality of substrates are arranged, it is important to minimize the size of mounted components. 
     SUMMARY OF THE INVENTION 
     The present invention provides a long recording head in which a plurality of substrates are arranged on a support member and which can be reduced in size and cost by reducing the size of mounted components such as the support member and a TAB. 
     A liquid-discharging recording head according to an embodiment of the present invention includes two substrates each including an energy generating element configured to generate energy used to discharge liquid and a supply port configured to supply the liquid to the energy generating element; and a support member on which the substrates are arranged to extend along each other in a longitudinal direction. The substrates include a first substrate provided on one side of the support member in the longitudinal direction, and a second substrate provided on an other side of the support member opposite the one side in the longitudinal direction. A region of the first substrate on the other side overlaps with a region of the second substrate on the one side in a direction intersecting the longitudinal direction. A distance between an end of the supply port in the first substrate on the one side in the longitudinal direction and an end of the first substrate on the one side is smaller than a distance between an end of the supply port in the first substrate on the other side in the longitudinal direction and an end of the first substrate on the other side. A distance between an end of the supply port in the second substrate on the other side in the longitudinal direction and an end of the second substrate on the other side is smaller than a distance between an end of the supply port in the second substrate on the one side in the longitudinal direction and an end of the second substrate on the one side. A region between the end of the supply port in the first substrate on the other side in the longitudinal direction and the end of the first substrate on the other side and a region between the end of the supply port in the second substrate on the one side in the longitudinal direction and the end of the second substrate on the one side each includes a driving circuit configured to drive the energy generating element. 
     According to the embodiment of the present invention, it is possible to reduce the sizes of mounted components, and to thereby reduce the size and cost of the recording head. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an overall view of a recording head according to a first embodiment of the present invention. 
         FIG. 2  is an exploded perspective view of the recording head of the first embodiment. 
         FIGS. 3A and 3B  are schematic views of the recording head of the first embodiment, as viewed from a discharge port side. 
         FIG. 4  is a schematic view of a recording head of the related art, as viewed from a discharging port side. 
         FIGS. 5A and 5B  are schematic views showing the layout in a substrate in the first embodiment. 
         FIG. 6  is a block diagram of a circuit in the substrate in the first embodiment. 
         FIG. 7  shows the order of DATA signals in the first embodiment. 
         FIG. 8  is a table of decoder truth values in the first embodiment. 
         FIG. 9  is a table of BE and INV truth values in the first embodiment. 
         FIG. 10  is a table of inversed BE truth values in the first embodiment. 
         FIG. 11  is a general view of a recording apparatus according to an embodiment of the present invention. 
         FIG. 12  is a block diagram showing a control configuration of the recording apparatus in the embodiment. 
         FIG. 13  is a schematic view of a recording head according to a second embodiment of the present invention, as viewed from a discharging port side. 
         FIG. 14  is a schematic view of a recording head according to a third embodiment of the present invention, as viewed from a discharging port side. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     In this specification, the term “recording” is not limited to formation of significant information such as characters and graphics. In short, the term “recording” broadly includes formation of images, figures, patterns, and the like on a recording medium, or processing of the medium, regardless of whether they are significant or insignificant and whether they are visualized such as to be visually perceivable by humans. Also, the term “recording medium” not only includes paper used in common recording apparatuses, but also broadly includes materials capable of receiving ink, such as cloth, a plastic film, a metal plate, glass, ceramics, wood, and leather. 
     Further, the term “ink” (sometimes referred to as “liquid”) should be broadly interpreted similarly to the definition of the above-described term “recording.” That is, “ink” includes a liquid which, when applied onto a recording medium, can form images, figures, patterns, and the like, can process the recording medium, or can process ink (e.g., can solidify or insolubilize a coloring agent contained in ink applied to the recording medium). 
       FIG. 1  is a perspective view of a liquid-discharging recording head according to a first embodiment of the present invention, that is, an inkjet recording head  400 . In the first embodiment, the inkjet recording head  400  is a monochromatic head that achieves a printable area length of 1.7 inches with two substrates  100  and  200  each having a printable area length of 0.85 inch. 
     The recording head substrates  100  and  200  are chiefly formed of silicon. The substrates  100  and  200  are bonded to a support member  301  formed of alumina, and are attached to a sub-tank  403 . Signal lines and power lines for the substrates  100  and  200  are connected to a printed circuit board  402  via a TAB  401 . The printed circuit board  402  includes a plurality of contact pads, which are electrically connected to a connector of a carriage provided in an inkjet recording apparatus that will be described below. 
       FIG. 2  illustrates bonding portions between the substrates  100  and  200  and the support member  301  in detail.  FIG. 5A  shows the layout in the substrate  100 . Mounting of the substrates will be described below with reference to  FIGS. 2 and 5A . 
     A second support member  302  is bonded to the support member  301 . The support member  301  has ink supply openings  303  shaped like through holes, and bottom sides of the substrates  100  and  200  communicate with the sub-tank  403  so that ink is supplied from the sub-tank  403 . 
     Since the substrates  100  and  200  are provided in openings of the second support member  302 , the surface height of the substrates  100  and  200  is substantially equal to the surface height of the second support member  302 . This allows inner leads of the TAB  401  to be easily connected to pads  104   a  and  104   b  of the substrates  100  and  200 . 
     To produce the recording head  400 , first, the support member  301  provided with the second support member  302  is prepared, and the substrates  100  and  200  are die-bonded into the openings of the second support member  302 . Then, the TAB  401  is bonded onto the second support member  302 , and the inner leads of the TAB  401  are connected to the pads  104   a  and  104   b  of the substrates  100  and  200 . Subsequently, the support member  301  is joined to the sub-tank  403 , the TAB  401  and the printed circuit board  402  are connected, and the printed circuit board  402  is attached to the sub-tank  403  by caulking, so that the recording head  400  is completed. 
     The layout in the substrate  100  will now be described with reference to  FIG. 5A . 
     While an ink supply port  101  is, in general, provided in the center of the substrate  100 , that is, at a vertically and horizontally symmetrical position, an opening of the ink supply port  101  is provided at a position offset toward one longitudinal side of the substrate  100  in the first embodiment. An area  102  in which an array of energy generating elements (heaters) for generating energy used to discharge liquid and drivers for driving the heaters are arranged is provided on each side of the supply port  101 . On outer sides of the areas  102 , selection circuits  103  are provided to select the energy generating elements. The substrate  100  also includes driving circuits serving as main circuit components, for example, a shift register (S/R)  105 , a latch circuit (LT)  106 , and a decoder  107 . These driving circuits are provided on the upper side in  FIG. 5A , that is, on a side where a region between the longitudinal end of the ink supply port  101  and the longitudinal end of the substrate  100  is larger. 
       FIG. 6  is a block diagram of a circuit for driving heaters arranged on one lateral side of the ink supply port. In the first embodiment, 256 heaters are arranged on one side of the ink supply port, and are driven in 16 time divisions. Here, 20 bits of data shown in  FIG. 7  are input to the S/R  105  via DATA_EV or DATA_OD. The first 16 bits of the input data are DATA signals DATA 0  to DATA 15  for selecting any of adjacent units of 16 segments. The last four bits of the input data are BE signals BE 0  to BE 3  for generating block selection signals BLE that select any of 16 blocks by which driving is performed. The four bits of data BE 0  to BE 3  are decoded into 16 time division signals BLE 0  to BLE 15 , as shown in  FIG. 8 . 
       FIG. 10  is an equivalent circuit diagram of driver sections in the adjacent 16 segments. As a DATA signal, any of DATA 0  to DATA 15  described above is input. The signals BLE 0  to BLE 15  are sequentially connected to the adjacent 16 segments. In a segment in which the DATA signal and the BLE signal simultaneously become high, the levels of signals are increased by a level converter  503 , so that a driver transistor  502  is driven and current flows through a heater  501 . 
     Referring again to  FIG. 6 , an INV terminal is a signal terminal for logically inverting the BE signal, and XORs the BE signal. The INV terminal is normally low because it is pulled down. In a state in which nothing is connected to the INV terminal, the BE signal enters the decoder without changing the logic, as shown in  FIG. 9 . When the INV terminal is made high by being connected to VDD, the BE signals is logically inverted and then enters the decoder, as show in  FIG. 9 . 
       FIG. 3A  is a schematic view of the liquid-discharging recording head in which two substrates (first substrate  100  and second substrate  200 ) are provided on the support member  301 . The substrates  100  and  200  are arranged in the longitudinal direction thereof so that regions at the ends of the substrates overlap in a direction orthogonal to the longitudinal direction. In sealing regions  304 , the pads  104   b  shown in  FIG. 5A  and lines to be connected to the pads  104   b  are sealed by a sealant. 
     The substrate  100  is oriented in the same direction as that of the substrate  100  shown in  FIG. 5A , and the substrate  200  is turned  180  degrees from the substrate  100 . In other words, in the substrate  100  shown in  FIG. 3A , the supply port  101  is offset toward the lower side (toward one side of the support member  301 ) in the longitudinal direction of the substrate  100 . Further, a shift register (S/R)  105 , a latch circuit (LT)  106 , etc. are provided in a side where a region between the end of the supply port  101  and the end of the substrate  101  is wider (on the upper side in  FIG. 3A ; at the other side opposite the one side). In contrast, in the substrate  200 , a supply port  201  is offset toward the upper side (toward the other side) in  FIG. 3A , and a shift register (S/R)  105 , a latch (LT) circuit  106 , etc. are provided on the lower side (on the one side) of the supply port  201 . 
     From another viewpoint, the distance between an end of the supply port  101  in the substrate  100  (first substrate) on the one side and an end of the substrate  100  on the one side is shorter than the distance between an end of the supply port  101  on the other side and an end of the substrate  100  on the other side. Further, the distance between an end of the supply port  201  in the substrate  200  (second substrate) on the other side and an end of the substrate  200  on the other side is shorter than the distance between an end of the supply port  201  on the one side and an end of the substrate  200  on the one side. 
     A structure shown in  FIG. 4  will now be described as a comparative example. In the structure shown in  FIG. 4 , two substrates each having an ink supply port in the center thereof are arranged on a support member, unlike the structure adopted in the first embodiment of the present invention. Compared with the first embodiment shown in  FIG. 3A , the printable area length L is substantially equal in both the structures, but the overall longitudinal substrate length A in the first embodiment is smaller than the overall longitudinal substrate length B in the comparative example. As described above, in the first embodiment, the supply port is offset in the longitudinal direction of the substrate, and the side where the region between the end of the supply port and the end of the substrate is wider is close to the center of the support member. In other words, when a plurality of substrates are arranged on the support member, in the substrates provided at both ends in the arrangement direction, the side where the region between the end of the supply port and the end of the substrate is narrower is close to the end of the support member. Since this can reduce the sizes of the support member  301  and the TAB  401  serving as mounted components, the size of the head itself can be reduced, and cost reduction is achieved. 
     In the substrate  200 , the BE signal is inverted by connecting the INV terminal  110  to VDD. Referring to  FIG. 8 , when a signal input to DECODER is inverted, the order is reversed, that is, BLE 15  becomes high at a position where BLE 0  is high, and BLE 14  becomes high at a position where BLE 1  is high. 
     Since the substrate  200  is turned  180  degrees, as a result, the order of time division driving becomes the same as that of the substrate  100 . Hence, the apparatus can control printing without any attention to a gap in the time division timing due to inversion of the substrate. This allows the landing positions of dots printed by the substrate  100  to be easily aligned with the landing positions of dots printed by the substrate  200  in so-called multi-pass printing in which pixels are formed by a plurality of scanning operations. As a result, a good print result can be obtained. 
     A second embodiment will now be described with reference to  FIG. 13 . Components substantially identical to those adopted in the above-described first embodiment are denoted by the same reference numerals, and descriptions thereof are omitted. 
     In the second embodiment, a substrate  100  and a substrate  200  include five ink supply ports  101  and five ink support ports  201 , respectively. Each of the ink supply ports is offset toward one longitudinal side of the substrate. The advantages of the present invention can also be obtained in such a case in which each substrate includes a plurality of supply ports. In other words, when a plurality of substrates are arranged on a support member, in the substrates provided at both ends in the arrangement direction, a side where a region between the end of the supply port and the end of the substrate is narrower is close to the end of the support member. Since the sizes of a support member  301  and a TAB  401  serving as mounted components can be thereby reduced, the size of the head itself is reduced, and this can achieve size reduction. 
     A third embodiment will now be described with reference to  FIG. 14 . Components substantially identical to those adopted in the above-described embodiments are denoted by the same reference numerals, and descriptions thereof are omitted. 
     In a recording head according to the third embodiment, three substrates (a first substrate  100  having a supply port  101 , a second substrate  200  having a supply port  201 , a third substrate  210  having a supply port  211 ) are arranged on a support member  301  in the longitudinal direction of the substrates. In the third embodiment, an ink supply port in each of the substrates is offset toward one longitudinal side of the substrate. 
     Similarly to the above-described embodiments, of a plurality of substrates arranged on the support member  301 , the substrates  100  and  200  at both ends of the arrangement are each arranged so that a side where a region between the end of the supply port and the end of the substrate is narrower is close to the end of the substrate. For this reason, similarly to the above-described embodiment, the total substrate length A can be decreased without reducing the printable area. Thus, it is possible to limit the total size of the recording head and to reduce the cost. 
     In the present invention, when a plurality of substrates are arranged on the support member, the substrates provided at both ends in the arrangement direction are provided so that the side where the region between the end of the supply port and the end of the substrate is narrower is close to the end of the support member. In contrast, in a substrate or substrates other than the substrates at both ends (e.g., the third substrate  210  in the third embodiment), the supply port does not always need to be offset in the substrate. That is, similar advantages can be obtained even when the supply port is provided at almost the longitudinal center of the substrate, as in the related art. 
     The present invention is not limited to the third embodiment, and also includes a case in which four or more substrates are provided on the support member  301 . In this case, in substrates other than the substrates at both ends, a supply port may be provided offset in the longitudinal direction of the substrate or may be provided in the center of the substrate. 
     When the supply port is provided in the center of the substrate, particularly when a plurality of, for example, eight substrates are provided, it is possible to share substrates other than substrates provided at both ends, and this is preferable in terms of production cost. 
     When recording is performed by discharging ink from the recording head, the temperature of the center region of the support member generally tends to become higher than the temperature of the end regions. For this reason, in the substrates other than the substrates at both ends, of a plurality of substrates, it is preferable that a wider region between the supply port and the end of the substrate be close to the longitudinal end of the support member. This can reduce the above-described increase in temperature in the center region of the support member. 
     In any of the embodiments, there is no dimensional restrictions on the mounted components even when the wider region (length) at the end of the substrate is further enlarged. Therefore, it is preferable that the circuit sections, which need a relatively large area in the substrate, concentrate in the wider end region. To reduce the size of the recording head, it is preferable that not only the shift register and the decoder described in the above embodiments, but also a LVDS circuit for high-speed signal transfer, a fuse ROM in which driving parameters are written, and a constant-current driving circuit concentrate in the wider end region. 
     In any of the embodiments, a head shown in  FIG. 3B  can be configured using substrates in which only pads  104   a  are provided in a wider end region of the substrate, as shown in  FIG. 5B . Since the region for the pads  104   b  in  FIG. 5A  is not provided, the total substrate length A′ can be shortened further. 
     While all the shift register  105 , the latch circuit  106 , and the decoder  107  are provided in the wider region between the end of the supply port and the end of the substrate in the above-described embodiments, the present invention is not limited thereto. That is, the present invention is also applicable to a case in which any of the shift register  105 , the latch circuit  106 , and the decoder  107  is provided in the narrower region between the end of the supply port and the end of the substrate. 
     Recording Apparatus 
     A brief description will be given below of an inkjet recording apparatus IJRA in which the inkjet recording head  400  of the present invention can be mounted. Referring to  FIG. 11 , a lead screw  5004  rotates via driving-force transmission gears  5011  and  5009  in association with forward and reverse rotations of a driving motor  5013 . A carriage HC has a pin (not shown) engaged with a spiral groove  5005  of the lead screw  5004 , and is caused by the rotation of the lead screw  5004  to reciprocate along a guide rail  5003  in the directions of arrows a and b. An inkjet recording head  400  is mounted on the carriage HC. An ink tank IT is connected to the inkjet recording head  400 . 
     A paper presser plate  5002  presses paper P against a platen  5000  through the moving direction of the carriage HC. Photosensors  5007  and  5008  serve as home-position detecting members for checking the presence of a lever  5006  of the carriage HC in this region and for switching the rotating direction of the motor  5013 . A support member  5016  supports a cap member  5022  that puts on a cap on the front face of the recording head  400 . A suction member  5015  sucks from the cap so as to conduct suction recovery on the recording head  400  via an in-cap opening  5023 . A moving member  5019  moves a cleaning blade  5017  in the front-rear direction, and the moving member  5019  and the cleaning blade  5017  are supported on a main-body support plate  5018 . A known cleaning blade can be applied to the cleaning blade  5017  in the third embodiment. A lever  5021  is used to start suction in suction recovery. The lever  5021  moves with the movement of a cam  5020  engaged with the carriage HC, and the driving force of the driving motor  5013  is controlled by a known transmission method, such as switching of a clutch circuit, via a gear  5010 . 
     These capping, cleaning, and suction recovery operations are desirably performed at corresponding positions by the action of the lead screw  5004  when the carriage HC reaches a region near the home position. However, in any of the embodiments, the operations can be desirably performed at a known timing. 
     A control configuration for controlling recording of the above-described inkjet recording apparatus will now be described with reference to  FIG. 12  serving as a block diagram of a control circuit. The control circuit shown in  FIG. 12  includes an interface  1700  to which a recording signal is input, a MPU  1701 , a program ROM  1702  that stores a control program to be executed by the MPU  1701 , a dynamic RAM  1703  (hereinafter referred to as a DRAM) that stores various data (the recording signal and recording data to be supplied to the head), and a gate array  1704  that controls the supply of recording data to a recording head  1708 . Signals for driving the recording head  1708  are supplied via the gate array  1704 . The gate array  1704  also controls data transfer among the interface  1700 , the MPU  1701 , and the DRAM  1703 . 
     A carrier motor  1710  carries the recording head  1708 , and a conveying motor  1709  conveys a recording sheet. An inkjet recording head substrate  1705  is provided in the recording head  1708 , and includes heaters for ink discharging and driving circuits therefor. Motor drivers  1706  and  1707  drive the conveying motor  1709  and the carrier motor  1710 , respectively. 
     In the above-described control configuration, when a recording signal is input to the interface  1700 , it is converted into recording data for printing between the gate array  1704  and the MPU  1701 . Then, the motor drivers  1706  and  1707  are driven, and the ink discharging heaters are driven according to the recording data supplied to the inkjet recording head substrate  1705  in the recording head  1708 , so that printing is performed. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications and equivalent structures and functions.