Abstract:
There is provided an inkjet print head including: an ink discharging unit including a plurality of actuators; a connection substrate disposed on the ink discharging unit and having a first circuit pattern electrically connected to the plurality of actuators; and a switching board having a second circuit pattern connected to the first circuit pattern and including a plurality of driving integrated chips (ICs) controlling the plurality of actuators.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Korean Patent Application No. 10-2012-0014567 filed on Feb. 14, 2012, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an inkjet print head, and more particularly, to an inkjet print head capable of being miniaturized and performing high resolution printing. 
     2. Description of the Related Art 
     An inkjet print head may include a plurality of nozzles in order to achieve high quality printing. For example, the inkjet print head may have a 512 structure (for reference, a 512 structure is an inkjet print head structure in which 512 nozzles are formed in a length direction). 
     In a 512 structure, since a plurality of nozzles are disposed densely in the length direction of the inkjet print head, relatively high quality printing may be achieved. 
     Meanwhile, in the 512 structure, an interval between the nozzles (or an interval between actuators) is 280 μm, larger than 200 μm, corresponding to a minimum wiring interval of a flexible substrate. Therefore, in the inkjet print head having the 512 structure, a plurality of actuators and driving integrated chips (ICs) may be easily connected to each other using the flexible substrate. 
     However, as high resolution printing quality has gradually become necessary, the development of an inkjet print head having a 1024 structure has been required. However, since the 1024 structure is a structure in which 1024 nozzles are densely disposed in a length direction of the inkjet print head, an interval between nozzles is less than that of the 512 structure. Therefore, in an inkjet print head having the 1024 structure, respective actuators and driving ICs may not be connected to each other using the flexible substrate. 
     As the related art, there are provided Patent Documents 1 and 2. Patent Document 1 discloses a configuration in which a piezoelectric element  300  and a driving IC  130  are connected to each other using a driving wiring  140 . However, in order to utilize the configuration disclosed in Patent Document 1 in the inkjet print head having the 1024 structure, the driving IC should be customized. In addition, in the case of Patent Document 1, since a distance between the driving IC  130  and the piezoelectric element  300  is relatively small, the driving IC  130  may malfunction due to heat generated from the piezoelectric element  300 . 
     In contrast, Patent Document 2 discloses a configuration in which a piezoelectric element  300  and a driving circuit  200  are connected to each other using a chip on film (COF) substrate  410 . However, in the configuration disclosed in Patent Document 2, since a size of the COF substrate may be increased to match that of the driving circuit  200 , it is difficult to miniaturize the inkjet print head. In addition, in Patent Document 2, since the piezoelectric element  300  and the driving circuit  200  are connected to each other by the COF substrate  410 , it is difficult to utilize the configuration disclosed in Patent Document 2 in a structure in which an interval between nozzles is small. 
     RELATED ART DOCUMENT 
     
         
         (Patent Document 1) JP2004-001366 A 
         (Patent Document 2) JP2011-025483 A 
       
    
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides an inkjet print head appropriate for a 1024 structure. 
     According to an aspect of the present invention, there is provided an inkjet print head including: an ink discharging unit including a plurality of actuators; a connection substrate disposed on the ink discharging unit and having a first circuit pattern electrically connected to the plurality of actuators; and a switching board having a second circuit pattern connected to the first circuit pattern and including a plurality of driving integrated chips (ICs) controlling the plurality of actuators. 
     The plurality of actuators may be connected to the first circuit pattern by wires. 
     The connection substrate may include a plurality of through-holes into which a plurality of wires connecting the plurality of actuators and the first circuit pattern to each other are inserted, respectively. 
     The connection substrate may have a disposition space in which the plurality of actuators are disposed. 
     The plurality of driving ICs may be obliquely disposed with respect to a length direction of the switching board. 
     The first circuit pattern may include a plurality of first connection pads and a plurality of second connection pads. 
     The second connection pads adjacent to each other may be alternately disposed. 
     The switching board may include third connection pads connected to the second connection pads. 
     The inkjet print head may further include a cooling unit formed in the connection substrate and cooling the switching board. 
     According to another aspect of the present invention, there is provided an inkjet print head including: an ink discharging unit including a plurality of actuators arranged in two rows; a connection substrate disposed on the ink discharging unit and having a first circuit pattern electrically connected to the plurality of actuators; an ink supplying unit disposed at a center of the connection substrate; and a pair of switching boards having a second circuit pattern connected to the first circuit pattern, including a plurality of driving ICs controlling the plurality of actuators, and disposed to be symmetrical to each other, based on the ink supplying unit. 
     The plurality of actuators may be connected to the first circuit pattern by wires. 
     The connection substrate may include a plurality of through-holes into which a plurality of wires connecting the plurality of actuators and the first circuit pattern to each other are inserted, respectively. 
     The connection substrate may have a disposition space in which the plurality of actuators are disposed. 
     The plurality of driving ICs may be obliquely disposed with respect to a length direction of the switching board. 
     The first circuit pattern may include a plurality of first connection pads and a plurality of second connection pads. 
     The second connection pads adjacent to each other may be alternately disposed. 
     The switching board may include third connection pads connected to the second connection pads. 
     The inkjet print head may further include a cooling unit formed in the connection substrate and cooling the switching board. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a cross-sectional view of an inkjet print head according to an embodiment of the present invention; 
         FIG. 2  is an enlarged cross-sectional view of an ink discharging unit shown in  FIG. 1 ; 
         FIG. 3  is a plan view showing an upper surface of a connection substrate contacting a switching board; 
         FIG. 4  is a bottom view showing a lower surface of the switching board contacting the connection substrate; 
         FIG. 5  is a plan view of the switching board in a state in which a driving integrated chip (IC) is removed therefrom; 
         FIG. 6  is an enlarged view of part A of  FIG. 5 ; 
         FIG. 7  is a plan view of the switching board in a state in which the driving IC is disposed; 
         FIG. 8  is a plan view of the switching board in another state in which the driving IC is disposed; and 
         FIG. 9  is a cross-sectional view of an inkjet print head according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Terms used in the present specification will be first defined as follows. 
     In the present specification, a 512 structure indicates an inkjet print head having 512 nozzles disposed in a length direction thereof, while a 1024 structure indicates an inkjet print head having 1024 nozzles disposed in a length direction thereof. 
     As high resolution printing quality has become necessary, an interval between nozzles in an ink head has gradually decreased. 
     Inkjet print heads have recently been changed from the 512 structure into the 1024 structure. 
     However, the following limitations in manufacturing the inkjet print head having the 1024 structure may exist. 
     First, it may be difficult to connect an actuator and a driving integrated chip (IC) to each other. 
     In an inkjet print head having the 512 structure, an interval between actuators is 280 μm or more, larger than 200 μm, corresponding to a minimum wiring interval of a flexible substrate. Therefore, in the inkjet print head having the 512 structure, it is easy to connect the actuator and the driving IC to each other using the flexible substrate. 
     However, in an inkjet print head having the 1024 structure, since an interval between actuators is 200 μm or less, smaller than a minimum wiring interval of the flexible substrate, it is not easy to connect a plurality of actuators and driving ICs that are disposed densely with regard to each other. 
     Second, manufacturing costs may be high. 
     The above-mentioned limitations may be solved by changing a circuit pattern in a silicon substrate having actuators formed thereon or manufacturing a customized driving IC appropriate for the 1024 structure. 
     However, in the former case, since an expensive silicon substrate is manufactured to be relatively large, inkjet print head manufacturing costs increase. Further, in the latter case, since a driving IC is separately manufactured according to a kind of inkjet print head, manufacturing costs also increase. 
     Third, it is difficult to normally operate a driving IC. 
     In the inkjet print head having the 1024 structure, since a plurality of actuators are densely integrated, a significant larger amount of heat may be generated as compared to that generated in an inkjet print head having the 512 structure during an ink discharging process. However, when the plurality of actuators and driving ICs are directly connected to each other, the heat generated from the actuator is transferred to the driving IC as it is, such that the driving IC may malfunction in a printing process for a long period of time. 
     In the present invention, the purpose of which is to solve the above-mentioned problem, a connection structure between an actuator and a driving IC appropriate for a 1024 structure has been developed. More specifically, according to the present invention, the connection structure between the actuator and the driving IC may be improved by disposing a connection substrate between an ink discharging unit and a switching board. 
     According to the present invention configured as described above, since the actuator and the driving IC are connected to each other by the connection substrate, it is not necessary to increase a size of the ink discharging unit formed of a relatively expensive material. 
     In addition, according to the present invention, since the actuator and the connection substrate may be connected to each other by a wire, the actuators may be densely disposed. 
     Further, according to the present invention, since the connection substrate may block heat generated from the ink discharging unit, a phenomenon in which the driving IC malfunctions due to high heat may be significantly reduced. 
     In addition, according to the present invention, since a space in which the driving IC may be disposed may be secured by the connection substrate, a lifespan of the driving IC may be ensured. Therefore, according to the present invention, a manufacturing cost of the inkjet print head may be reduced. 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     In describing the present invention below, terms indicating components of the present invention are named in consideration of functions thereof. Therefore, the terms should not be understood as limiting technical components of the present invention. 
       FIG. 1  is a cross-sectional view of an inkjet print head according to an embodiment of the present invention.  FIG. 2  is an enlarged cross-sectional view of an ink discharging unit shown in  FIG. 1 .  FIG. 3  is a plan view showing an upper surface of a connection substrate contacting a switching board.  FIG. 4  is a bottom view showing a lower surface of the switching board contacting the connection substrate.  FIG. 5  is a plan view of the switching board in a state in which a driving integrated chip (IC) is removed therefrom.  FIG. 6  is an enlarged view of part A of  FIG. 5 .  FIG. 7  is a plan view of the switching board in a state in which the driving IC is disposed.  FIG. 8  is a plan view of the switching board in another state in which the driving IC is disposed.  FIG. 9  is a cross-sectional view of an inkjet print head according to another embodiment of the present invention. 
     An inkjet print head according to an embodiment of the present invention will be described with reference to  FIGS. 1 to 3 . 
     An inkjet print head  1000  according to the embodiment of the present invention may include an ink discharging unit  100 , a connection substrate  300 , and a switching board  500 . 
     The ink discharging unit  100  may include a component for discharging ink. To this end, the ink discharging unit  100  may include nozzles  210  discharging ink, pressure chambers  220  temporarily storing the ink therein, and actuators  140  applying pressure to the ink stored in the pressure chambers  220 . 
     The ink discharging unit  100  may further include an oxide layer. More specifically, the oxide layer may be formed on a surface of the ink discharging unit  100 . The oxide layer formed as described above may block an electric connection between the ink discharging unit  100  and another member. 
     The ink discharging unit  100  may include a plurality of substrates. For example, the ink discharging unit  100  may include a first substrate  110 , a second substrate  120 , and a third substrate  130 . Here, the first substrate  110 , the second substrate  120 , and the third substrate  130  may be sequentially stacked and be formed of single crystalline silicon. 
     The first substrate  110  may form a lower layer of the ink discharging unit  100 . The first substrate  110  may be formed of a single crystalline silicon substrate or a silicon on insulator (SOI) substrate as needed. Alternatively, the first substrate  110  may be a laminated substrate in which a silicon substrate and a plurality of insulating members are laminated. 
     The first substrate  110  may include a plurality of the nozzles  210 . Each of the nozzles  210  may be formed to extend in a thickness direction (a Z axis direction based on  FIG. 1 ) of the first substrate  110 . 
     The nozzles  210  may be formed at predetermined intervals in a length direction (a Y axis direction based on  FIG. 1 ) of the first substrate  110  and formed in multiple rows in a width direction (an X axis direction based on  FIG. 1 ) of the first substrate  110 . 
     Each nozzle  210  may have a cross-sectional area varied in the thickness direction of the first substrate  110 . For example, the nozzle  210  may have a cross-sectional area gradually reduced toward a-Z axis, as shown in  FIG. 1 . However, the shape of the nozzle  210  is only an example and is not limited thereto. That is, the nozzle  210  may have a hole shape in which it has the same cross-sectional size. 
     The second substrate  120  may form an intermediate layer of the ink discharging unit  100 . That is, the second substrate  120  may be stacked on the first substrate  110 . 
     The second substrate  120  may be formed of a single crystalline silicon substrate or an SOI substrate as needed. Alternatively, the second substrate  120  may be a laminated substrate in which a silicon substrate and a plurality of insulating members are laminated. 
     The second substrate  120  may include the pressure chambers  220  and a manifold  240 , and selectively further include restrictors  230 . 
     The pressure chambers  220  may be disposed in the second substrate  120 . More specifically, the pressure chambers  220  may be formed to extend in a thickness direction (the Z axis direction) of the second substrate  120 . 
     The pressure chambers  220  may be connected to the nozzles  210  of the first substrate  110 . That is, the pressure chambers  220  may be in communication with the nozzles  210  in a state in which the first and second substrates  110  and  120  are coupled to each other. 
     Each pressure chamber  220  may have a predetermined volume. For example, the pressure chamber  220  may have volume the same as or larger than a single ink discharge amount. Here, the former may be advantageous for fixed quantity discharging of ink, and the latter may be advantageous for continuous discharging of ink. 
     The pressure chambers  220  formed as described above may be formed at predetermined intervals in a horizontal direction (the X axis direction) and a vertical direction (the Y direction) of the second substrate  120 , similar to the nozzles  210 . 
     The manifold  240  may be formed in the second substrate  120 . More specifically, the manifold  240  may be formed to be spaced apart from the pressure chambers  220  in the X direction as shown in  FIG. 2 . 
     The manifold  240  may be connected to a plurality of the pressure chambers  220 . For example, a single manifold  240  may be connected to the plurality of pressure chambers  220  through the restrictors  230  formed to extend in the X axis direction. To this end, the manifold  240  may be formed to extend in a length direction (the Y axis direction) of the second substrate  120 . 
     Unlike this, the manifold  240  may be provided in plural and a plurality of manifolds  240  may be connected to the plurality of pressure chambers  220  in a one-to-one manner. For example, the plurality of manifold  240  may be formed at the same intervals as those of the plurality of pressure chambers  220  in the length direction of the second substrate  120 . 
     In this structure, since the ink is separately supplied to each pressure chamber  220  through the manifold  240 , the ink may be stably supplied. Therefore, this structure may be advantageous in achieving high resolution printing quality. Further, in this structure, since an adjacent pressure chamber is not affected by a pressure change (for example, a reverse ink flow phenomenon) generated in any pressure chamber, a cross-talk phenomenon which is a problem of the inkjet print head may be reduced. 
     The third substrate  130  may form an upper layer of the ink discharging unit  100 . That is, among three substrates, the third substrate  130  may be disposed in an uppermost position. 
     The third substrate  130  may be formed of a single crystalline silicon substrate or a silicon on insulator (SOI) substrate as needed. Alternatively, the third substrate  130  may be a laminated substrate in which a silicon substrate and a plurality of insulating members are laminated. 
     The third substrate  130  may be formed of at least two substrates. For example, the third substrate  130  may be formed of a substrate in which the restrictors  230  are formed and a substrate vibrated by the actuators  140 . However, the third substrate  130  is not necessarily formed of a plurality of substrates. 
     The restrictors  230  may be formed in the third substrate  130 . More specifically, the restrictors  230  may be formed at the same intervals as those of the pressure chambers  220  in a length direction (the Y axis direction) of the third substrate  130 . 
     The restrictors  230  may connect the pressure chambers  220  and the manifold  240  to each other in a state in which the second and third substrates  120  and  130  are coupled to each other and control a flow rate of the ink supplied from the manifold  240  to the pressure chambers  220 . 
     Although the embodiment illustrates that the restrictors  230  are formed in the third substrate  130 , the restrictors  230  may be formed in the second substrate  120  as needed. 
     The actuators  140  may be formed on an upper surface of the third substrate  130 . More specifically, the actuators  140  may be formed at positions of the third substrate  130 , corresponding to the pressure chambers  220 . 
     Each actuator  140  may include a piezoelectric element and upper and lower electrode members. More specifically, the actuator  140  may be a laminate in which the piezoelectric element is disposed between the upper and lower electrode members. 
     The lower electrode member may be formed on the upper surface of the third substrate  130 . The lower electrode member may be formed of a single conductive metal material or a plurality of conductive metal materials. For example, the lower electrode member may be formed of two metal members made of titanium (Ti) and platinum (Pt). 
     The piezoelectric element may be formed on the lower electrode member. More specifically, the piezoelectric element may be thinly formed on a surface of the lower electrode member by screen printing, sputtering, or the like. The piezoelectric element may be formed of a piezoelectric material. For example, the piezoelectric element may be formed of a ceramic (for example, lead zirconate titanate (PZT)) material. 
     The upper electrode member may be formed on an upper surface of the piezoelectric element. The upper electrode member may be formed of any one selected from the group consisting of Pt, Au, Ag, Ni, Ti, Cu, and the like. 
     The actuator  140  configured as described above may provide driving force for discharging the ink in the pressure chamber  220  while extending and contracting according to an electrical signal. 
     The ink discharging unit  100  may further include an electrode pattern  150 . 
     The electrode pattern  150  may be formed on the third substrate  130  and may be connected to the electrode members of the actuators  140 . 
     The electrode pattern  150  may be formed to extend in a width direction (an X axis direction based on  FIG. 2 ) of the third substrate  130 . More specifically, the electrode pattern  150  may have a length greater than that of the actuator  140 . 
     The electrode pattern  150  formed as described above may be connected to the first circuit pattern  310  of the connection substrate  300  by a wire. 
     The connection substrate  300  may be formed on the ink discharging unit  100 . More specifically, the connection substrate  300  may be stacked on the ink discharging unit  100 . 
     The connection substrate  300  may include a disposition space  302  and a through-hole  304 . 
     The disposition space  302  may be formed in a lower portion of the connection substrate  100 . More specifically, the disposition space  302  may be formed to face the actuators  140  in a state in which the ink discharging unit  100  and the connection substrate  300  are coupled to each other. 
     The disposition space  302  may have a size capable of receiving the actuators  140  therein. For example, the disposition space  302  may be formed to extend in the length direction (the Y axis direction based on  FIG. 1 ) of the inkjet print head so as to receive a plurality of the actuators  140  disposed in a row therein. 
     The through-hole  304  may be formed to extend in a thickness direction (a Z axis direction based on  FIG. 2 ) of the connection substrate  300 . The through-hole  304  may be formed to be spaced apart from the disposition space  302  and may be used as a space into which a wire or a connecting wiring is inserted. 
     The connection substrate  300  may include the first circuit pattern  310  as shown in  FIG. 3 . 
     The first circuit pattern  310  may be formed on the connection substrate  300  and include first and second connection pads  320  and  330 . 
     The first connection pads  320  may be formed at predetermined intervals in a length direction (a Y axis direction based on  FIG. 3 ) of the connection substrate  300 . More specifically, the first connection pads  320  may be formed on the connection substrate  300  at the same intervals as those of actuators  140  formed in the ink discharging unit  100 . Each first connection pad  320  formed as described above may be connected to each actuator  140  by a wire  400  (See  FIG. 1 ) and the electrode pattern  150 . 
     The second connection pads  330  may be arbitrarily formed in a width direction (an X axis direction based on  FIG. 3 ) of the connection substrate  300 . Here, an arrangement interval of the second connection pads  330  may be larger than that of the first connection pads  320 . The second connection pads  330  adjacent to each other may have a wide interval therebetween, to thereby be easily connected to other connection pads. For example, the second connection pads  330  may be connected to third connection pads  530  (See  FIG. 4 ) of the switching board  500 . 
     The switching board  500  may be formed on the connection substrate  300 . More specifically, the switching board  500  may be disposed so as to contact the second connection pads  330  of the connection substrate  300 . 
     The switching board  500  may fixed to the connection substrate  300 . For example, the switching board  500  may be adhered to the connection substrate  300  by an anisotropic conductive film (ACF). 
     The switching board  500  may include a second circuit pattern  510 , driving ICs  520  and the third connection pads  530 . 
     The second circuit pattern  510  may be formed on the switching board  500  as shown in  FIGS. 5 and 6 . The second circuit pattern  510  may connect the actuators  140  and the driving ICs  520  to each other. In addition, the second circuit pattern  510  may connect the driving ICs  520  and an external terminal  550  to each other. 
     The driving ICs  520  may be mounted on the switching board  500  as shown in  FIG. 7 . More specifically, the driving ICs  520  may be mounted at predetermined intervals so as to control a preset group of actuators  140 . 
     Meanwhile, although the driving ICs  520  are disposed in parallel with a length direction (a Y direction based on  FIG. 7 ) of the switching board  500  in  FIG. 7 , the driving ICs  520  may be obliquely disposed with respect to the length direction as shown in  FIG. 8  as needed. For reference, the latter may be advantageous in reducing lengths of the switching board  500  and the inkjet print head  1000 . 
     The third connection pads  530  may be formed on a lower surface of the switching board  500 . More specifically, the respective third connection pads  530  may be formed at positions corresponding to those of the second connection pads  330  in a state in which the connection substrate  300  and the switching board  500  are bonded to each other. 
     The third connection pads  530  may include via electrodes  540 . The via electrodes  540  may be formed to extend in the thickness direction (the Z direction based on  FIG. 1 ) of the switching board  500  and connect the third connection pads  530  and the second circuit pattern  510  to each other. 
     In the inkjet print head  1000  configured as described above, the actuator  140  having a relatively dense electrode pattern and the driving IC  520  having a relatively wide electrode pattern may be easily connected to each other. 
     In addition, in the inkjet print head  1000  according to the embodiment of the present invention, since the connection substrate  300  may block the heat generated from the ink discharging unit  100 , an overheating phenomenon in the switching board  500  may be efficiently prevented. 
     Further, in the inkjet print head  1000  according to the embodiment of the present invention, since a size of the switching board  500  is not limited, the driving ICs  520  may be easily disposed, and cooling units for cooling the driving ICs  520  may also be disposed. Therefore, the inkjet print head  1000  may be advantageously used for high resolution printing work and high speed printing work. 
     Meanwhile, in the inkjet print head  1000 , the connection substrate  300  and the switching board  500  may be disposed to be symmetrical to each other, based on a bisecting line (L-L) of the ink discharging unit  100  as shown in  FIG. 9 . 
     In addition, the inkjet print head  1000  may further include an ink supplying unit  600  formed at the center of the ink discharging unit  100 . In this case, the connection substrate  300  may be further provided with a channel connecting the ink supplying unit  600  and the manifold of the ink discharging unit  100 . 
     In the inkjet print head  1000  configured as described above, the ink supplying unit  600  is disposed at an empty space formed between one switching board  500  and the other switching board  500 , which is advantageous in miniaturizing the inkjet print head  1000 . 
     As set forth above, according to the embodiments of the present invention, a small-sized inkjet print head capable of achieving high resolution printing quality may be provided. 
     While the present invention has been shown and described in connection with the embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.