Patent Publication Number: US-7896476-B2

Title: Inkjet printhead board and inkjet printhead using same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an inkjet printhead board and to an inkjet printhead using same. 
     2. Description of the Related Art 
     The inkjet printer is of so-called a non-impact print scheme, having features of capable of printing at high speed, capable of printing on various recording media, and less causing noise upon printing. From those, the inkjet printer is broadly employed on an apparatus acting for a print mechanism, e.g. a printer, a copier, a facsimile machine or a word processor. 
     As for the inkjet printhead, there are known various schemes in respect of forming an ink droplet to eject. Among those, the inkjet printhead utilizing heat as ink-ejection energy realizes comparatively easily a multi-nozzle structure with high density, thus allowing for printing with high resolution and image quality at high speed. 
     There are cases that a ROM (read only memory) is mounted on a printhead in order to readably store information unique to the printhead, including printhead ID (identity) code and ink ejection mechanism drive characteristics. This function is very effective means in acquiring information unique to the printhead during printing and effecting drive optimally where a removable inkjet printhead is used on the inkjet printer body. For example, Japanese Patent Laid-Open No. H3-126560 discloses that an EEPROM (electrically erasable programmable ROM) is mounted on the printhead. However, in the printhead of Japanese Patent Laid-Open No. H3-126560, the EEPROM is mounted not on the printhead board but separately from the printhead. This makes structure complicate and productivity not well, thus hindering the size and weight reduction of the apparatus. Furthermore, such a ROM is useful in storing a great capacity of information but is not favor in respect of cost where information to store is not great in capacity. 
     Meanwhile, U.S. Pat. No. 5,363,134 and U.S. Pat. No. 5,504,507 disclose that a ROM having a fuse array is formed together with an ink ejection mechanism layer film on its base plate, i.e. a printhead board. In this case, when forming a layer film having an ink ejection mechanism, etc. on the base plate in the manufacture process of a printhead board, a fuse array to turn into a ROM can be formed at the same time. For example, in case a logic circuit is formed simultaneously with the fuse array and the fuses are selectively blown by controlling the logic circuit after completing a printhead, 2 values information can be held on the fuses in accordance with a presence/absence of meltdown. The printhead having a ROM on its printhead board does not require the preparation of a ROM chip separately from the printhead board, thus being not complicated in structure, well in productivity and realized in reduced size and weight. 
       FIGS. 10A and 10B  are sectional views showing a printhead of an existing inkjet recorder having a ROM on its printhead board.  FIG. 10A  illustrates the usual state of the printhead while  FIG. 10B  the state that cracks are caused in an interlayer insulation film  804  and protection film  806 . 
     In the usual inkjet printer, its printhead has a surface formed as an ink holder in the greater part thereof. As can be seen from  FIG. 10A , the interlayer insulation film  804  and the protection film  806  exist between a fuse element  803  and an ink liquid  808 . Although the fuse element  803  is shown only one in  FIG. 10A , a plurality of fuse elements are practically provided on the printhead board. By selectively blowing the fuse elements, data can be held thereon in an amount of square of the number of the fuse elements. 
     However, heat is involved in blowing the fuse elements wherein, as the fuse elements increase in the number, a greater amount of heat inevitably occurs correspondingly. And there are possibilities that cracks possibly occur in the interlayer insulation film  804  and protection film  806 , as shown in  FIG. 10B . Where cracks are caused in this manner, ink  808  possibly permeates through the crack and reaches the fuse element  803 . It can be considered that, by the permeated ink  808 , the blown fuse element  803  is short circuited or a fuse electrode is eroded. Particularly, where a logic circuit for controlling to blow the fuse elements or to read data is arranged close to the fuse element, the ink intruding through the crack reaches the logic circuit resulting in a possibility to pollute the logic circuit and raise a malfunction. 
     In order to avoid this, Japanese Patent Laid-Open No. 2000-127403 describes a structure that an ink holder, a fuse array and a logic circuit are arranged separate to prevent ink from intruding. 
     However, the printhead in the recent has a plurality of ink supply openings and a plurality of heaters densely arranged corresponding to the ink supply openings, on one base plate constituting a printhead, in order to meet the demands for higher resolution, image quality and operation speed. Consequently, the base plate for use in a printhead is occupied in greater part thereon by a heater power line, a logic circuit, drive elements, etc., thus making it difficult to arrange an especial fuse element in a position distant from the ink holder. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to provide an inkjet printhead board having a storage element which is capable of storing information without damages to an interlayer insulation film and protection film thereby holding information with high reliability and being free from the restriction in arrangement position. Another object is to provide an inkjet printhead having the same inkjet printhead board. 
     According to a first aspect of the invention, there is provided an inkjet printhead board having an element for generating ink-ejection energy, the inkjet printhead board characterized by comprising: a resistor provided as an information storage element and having a resistance value corresponding to a temperature of thermal process and formed to be supplied with a current in a manner the resistance value can be read out. 
     According to a second aspect of the invention, there is provided an inkjet printhead comprising: an inkjet printhead board; and an ejection opening through which ink is to be ejected commensurately with a heat generation at the resistor constituting an element for generating the energy. 
     The invention uses, as information storage element, a resistor having a resistance value to be changed by conducting a thermal process. The resistance value, obtained by supplying a current, can be read out as information. This makes it possible to store information without causing damages to a high-temperature interlayer insulation film and protection film and to hold information thereon with high reliability because significant heat generation is not caused as occurring upon blowing fuses. Meanwhile, where an energy generating element for ink ejection is provided by a resistor that generates thermal energy by being supplied with a current, the relevant resistor and the resistor constituting the information storage element are to be formed common in material and process. Therefore, the restriction to be arranged can be reduced. 
     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 a figure showing a printing device board according to a first embodiment; 
         FIG. 2  is a graph showing a change of a resistance value of an information storage element with a change of the number of pulses; 
         FIG. 3  is a figure showing an equivalent circuit to a circuit for holding information with using the information storage element; 
         FIG. 4  is a block diagram showing a relationship between an A/D converter and a printing device board; 
         FIG. 5  is a figure showing a printing device board according to a second embodiment; 
         FIG. 6  is a figure showing an equivalent circuit to a circuit for holding information with using the information storage element; 
         FIG. 7  is a plan view showing an inkjet printer according to the first embodiment; 
         FIGS. 8A and 8B  are views showing an ink cartridge wherein  FIG. 8A  is a perspective view as seen from below while  FIG. 8B  is a perspective view as seen from above; 
         FIG. 9  is a perspective view, shown by partially broken away, of the printing device board of the printhead according to the first embodiment; and 
         FIG. 10A  shows a usual state of the printhead substrate while  FIG. 10B  a state that cracks are caused in an interlayer insulation film and protection film. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     First Embodiment 
     With reference to the drawings, explanation will be now made in detail on a first embodiment according to the present invention. 
       FIG. 7  is a plan view showing an inkjet printer capable of mounting a printhead according to the present embodiment. In  FIG. 7 , an auto sheet feeder (ASF)  505  is stacked with printing media  508  that are to be supplied into the inkjet printer  500  by the drive of a paper feeding motor  510 . Then, the printing medium  508  is conveyed to a printing site by a conveying roller  506  rotated by the drive of the conveying motor  502 . The printing media  508 , in the printing site, is held to form a flat printing surface by the platen, not shown. 
     By driving a carriage motor  504 , a carriage  502  is reciprocated in a main scanning direction (in a direction of arrow α) over a guide shaft  503  through a motor pulley  507  and a timing bet  511 . The carriage  502  mounts an ink cartridge  509  incorporating a printhead and an ink tank therein. Printing is to be carried out by ejecting ink from the printhead while repeating to feed the printing media  508  and to move the carriage  502  alternately. 
       FIGS. 8A and 8B  are views showing the ink cartridge  509  according to the embodiment, wherein  FIG. 8A  is a perspective view as seen from below while  FIG. 8B  is a perspective view as seen from above. An ink tank  602  has therein an absorber, not shown, that impregnates ink and generates a negative pressure therein, being structured to supply a proper amount of ink to the printhead  601 . The printhead  601  is provided on the bottom of the ink tank  602 . By receiving print data at the printhead  601 , the ink supplied from the ink tank  602  to the printhead  601  is ejected through an ejection opening, not shown, provided in the printhead  601 . 
       FIG. 9  is a perspective view, shown partially broken away, of the printhead  601  according to the present embodiment. A printing device board  700 , i.e. printhead board, is made by an Si substrate having a thickness of from 0.5 to 1 mm and formed with an ink supply opening  701 , an ink passage  704  and the like. The ink supply opening  701 , i.e. a through-hole in the form of an elongate groove, is formed by anisotropic etching or sandblast utilizing the crystal orientation of Si. On both sides of the ink supply opening  701  ink is to be supplied, there are arranged electro-thermal converter elements  702  that are a plurality of energy generating elements. Ejection openings  703  are provided above the electro-thermal converter elements  702 , in positions corresponding to the electro-thermal converter elements  702 . The ink, supplied from the ink supply opening  701 , is delivered to the ejection openings  703  through the ink passage  704 . By actuating the electro-thermal converter elements  702 , ink is to be ejected as droplets through the ejection openings  703 . 
     In this embodiment, unique information is to be printed by use of an information storage device as a storage device to print the unique information about the printhead, in place of a fuse element conventionally used. Here, explanation is made in detail on the information storage device to be used in the present embodiment. 
       FIG. 1  is a figure showing an inkjet printhead board (printing device board)  700  according to a first embodiment, which is typically shown as is known from the circuit arrangement internally provided. An information storage element  101  is a resistor formed common in material and process to the electro-thermal converter elements  110  for use in ejecting an ink droplet, which can be formed without the necessity of an especial material or process. The information storage elements  101  and electro-thermal converter elements  110 , in the embodiment, are formed by using a reactive sputtering process to be carried out in a nitrogen atmosphere using an alloy target based on Cr and Si. The CrSiN thin film formed by the process is generally an amorphous thin film. It is generally known that an amorphous alloy has an electric resistance comparatively greater in value as compared to that of the alloy in a crystalline state. The CrSiN thin film formed in the embodiment is unexceptionally high in electric resistance value. It is known that, by thermally processing the high-resistant CrSiN thin film at from 400 to 700° C., CrSi micro-crystals are formed to constitute a structure low in resistance and stable in crystallinity. It is also known that, by heating the high-resistant CrSiN thin film at a temperature (equal to or higher than 200° C. and lower than 400° C.) lower than the above thermal process, a resistance value is provided in accordance with the temperature of heating. 
     Therefore, in the present embodiment, electro-thermal converter elements  110  and information storage elements  101  are formed by utilization of the relevant phenomenon. Namely, the embodiment uses, for electro-thermal converter elements  110 , a CrSiN thin film that is stabilized in crystallinity and reduced in resistance by conducting a process with heating at a temperature of from 400 to 700° C. Meanwhile, for information storage elements  101 , processing is conducted at a temperature of equal to or higher than 200° C. and lower than 400° C. to thereby provide unique resistance values respectively to the information storage elements  101 . 
     In the embodiment, when forming elements (electro-thermal converter elements  110  and information storage elements  101 ) by heating the CrSiN thin film, the self-heating of the CrSiN thin film is used that is caused by applying a pulse voltage to the CrSiN thin film. Namely, by changing the number of application pulses, heat-generation temperature is changed to obtain a desired state. 
       FIG. 2  is a graph representing a change of resistance value of the information storage element  101  against the number of pulses. In the state no pulse voltage is applied, resistance value is high. As the number of pulses increases, resistance value gradually decreases. It can be seen that the change of resistance value is smaller in the neighborhood a predetermined number of pulses is exceeded. 
     By utilizing the change of resistance value, two or more resistance values can be exhibited correspondingly to the information to store. For example, at least three values of information can be stored by using a state of high resistance value, a state of low resistance value and a state of desired resistance value intermediate between those. The information to store is, for example, a difference of drive characteristic unique to the printhead resulting from the variation caused in the manufacture of the printhead. By classifying it into several ranks (e.g. three), processing can be made such that the information storage element  101  exhibits a resistance value correspondingly to the rank. The processing can be carried out together with a test process after the manufacture of a board or a printhead. Due to this, when the printhead is used by being mounted on a printer, the printer is allowed to read the resistance value (rank information) thereby effecting drive under conditions suited for the printhead. 
     Referring again to  FIG. 1 , the printing device board  700  is formed with drive elements for controlling the current supply to electro-thermal converter elements  110  and information storage elements  101 , together with required wiring, on an Si substrate by use of a semiconductor manufacturing process. 
     The information storage elements  101  are arranged side by side on an extension of the array of the electro-thermal converter elements  110 , thus being designed to use equal voltage to the voltage for driving the electro-thermal converter elements  110 . Consequently, a voltage pulse can be applied to the information storage elements  101  without newly increasing a power source separately from the power source for supplying voltage to the electro-thermal converter elements  110 . Driving the information storage elements  101  on the equal voltage to the electro-thermal converter elements  110  requires a second drive element  102 , used for driving the information storage element  101 , to withstand the equal voltage to a first drive element  103  for driving the electro-thermal converter elements  110 . Therefore, by forming second drive elements  102  in the common structure and process to the first drive elements  103  for driving the electro-thermal converter elements  110 , the second drive elements  102  having required breakdown characteristics can be formed without adding any other process in the manufacture. 
     Incidentally, because the operation voltage (logic voltage) of a logic circuit  104  for selectively supplying a drive signal to the second drive element  102  is generally lower than the voltage for driving the second drive element  102 , the second drive element  102  cannot be driven unless making any change. For this reason, a booster circuit  106  is provided in front of the second drive element  102  so that the second drive element  102  can be driven on the signal selected at the logic circuit  104 . Here, this is true for the first drive element  103  for driving the electro-thermal converter element  110 , wherein a booster circuit (not shown) having the same configuration is used. The booster circuit uses a power voltage based on a power source (not shown) provided in the same printing device board  700 . 
     The select signal for selecting the second drive element  102  and the select signal for selecting the first drive element  103  are both on the same signal system. A logic circuit  104  for selecting the second drive element  102  is connected parallel with the logic circuit for selecting the first drive element  103 . Namely, the first and second drive elements share a signal line for sending a select signal to the first drive element  103 , a time sharing drive signal decoder, a latch circuit (LT), a shift register (S/R) and external signal input pads (not shown). Therefore, the second drive element  102  can be selected to drive the information storage element  101  without adding new signal lines, wiring areas, circuits and the like. 
     As shown from  FIG. 1 , in this embodiment, the second drive elements  102  for selectively activating the information storage element  101  lies on an extension of the array of the first drive elements  103 , one of which is arranged adjacent to the outermost first drive element  103 . 
     The above structure provides an arrangement covering from the logic circuit  104  to the information storage element  101  equally to an arrangement covering from the logic circuit  104  to the electro-thermal converter element  110 . Accordingly, the printing device board  700  can be manufactured easily without having an effect upon the arrangement of an in-board aperture of the ink supply opening  111  and signal lines, to suppress the size increase of the printing device board  700 . Furthermore, by arranging similar circuits on both sides of the ink supply opening  111 , space can be effectively utilized over the printing device board  700 , which makes it possible to arrange the information storage elements with high density. 
     In the printing device board  700  of this structure, when storing information in the information storage element  101 , the second drive element  102  is selectively driven corresponding to the information storage element  101  thereby applying a 24V pulse voltage separately to the information storage element  101 . Specifically, the information storage elements  101  are changed to desired resistance values by applying a pulse voltage of from 0.1 μsec to 100 μsec (self-heating of the information storage element  101  corresponding to a temperature equal to or higher than 200° C. and lower than 400° C.) to a terminal  112   a . Information can be stored by linking the changed resistance value of the information storage element  101  to the information unique to the printhead. Meanwhile, a 24V pulse voltage, capable of causing a self-heating at 400 to 700° C., is applied to those for use as electro-thermal conversion elements  110 , to form electro-thermal conversion elements  110  stable in crystallinity and low in resistance. 
     The present inventors have confirmed that no damages nor cracks occur in the interlayer insulation film and protection film existing above the electro-thermal converter elements  110  even at a self-heating temperature of 700° C. for use in forming the electro-thermal converter elements  110 . It is therefore natural that the interlayer insulation film and the protection film are not damaged upon forming electro-thermal converter elements  110  at a temperature lower than 700° C. Meanwhile, when storing information to the information storage element  101 , no damages are naturally caused in the interlayer insulation film and protection film because information storage is at a temperature lower than that. 
       FIG. 3  is a figure showing an equivalent circuit to an information hold circuit using an information storage element  101 .  FIG. 4  is a block diagram showing a relationship between an A/D converter that converts an analog output into a digital value and a printing device board  700 . 
     When reading stored information, a read voltage, for example, of 3.3 V is applied to the terminal  112   a , followed by driving the second drive element  102  corresponding to the information storage element  101  to read. As a result, by obtaining voltage-drop information corresponding to the resistance value possessed by the information storage element  101  through the count terminal  112   b , it is possible to obtain resistance information about the information storage element  101 , i.e. information unique to the printhead. This may be given correspondingly to the 2 values, i.e. high resistance state (may be in a state not thermally processed) and low resistance state, or to three values or more of information with using one or more desired states intermediate of those. The resistance information obtained here is converted into a digital signal by the A/D converter  113 . For example, three values can be set to the A/D converter such that resistance information obtained is Hi when greater than a certain resistance value R 1 , Mid when equal to or greater than a resistance value R 2  and smaller than the resistance value R 1  (&gt;R 2 ) or Low when smaller than the resistance value R 2 . The A/D-converter-included circuit, used in reading information in this manner, may be provided on the printing device board  700  or on the side of the inkjet printer  500 . Meanwhile, by arranging the information storage elements side by side as shown in  FIG. 1 , it is possible to store information greater in the number or greater in types. 
     In this manner, the present embodiment uses information storage elements  101  formed, on printing device board  700 , common in material and process to electro-thermal converter elements  110  so that information can be stored by changing the resistance value thereof through thermal process and be read out of the information storage element  101 . This enables printing without causing a damage to the interlayer insulation film and protection film when storing information, thus realizing an inkjet print board and inkjet printhead having reliable storage elements free from positional restrictions in arrangement. 
     Second Embodiment 
     Now a second embodiment is explained. 
       FIG. 5  is a figure showing a printing device board  900  according to a second embodiment, which is shown to know a circuit configuration internally provided. Meanwhile,  FIG. 6  is a diagram showing an equivalent circuit to the circuit that holds information with use of information storage elements  901 . This embodiment is similar to the first embodiment but different in the configurational connection form of the resistors constituting the information storage element. Namely, the first embodiment juxtaposed with information storage elements  101  each configured by a single resistor, as shown in  FIG. 1 . On the contrary, the present embodiment has information storage element sets  901  each of which is in a form that a plurality of information storage elements are arranged in series. 
     In this embodiment, the information storage element set  901 , provided in series on an extension of the array of electro-thermal converter elements  910 , is designed to use a voltage equal to the voltage for driving the electro-thermal converter element  910 . The other structure than the information storage element set  901 , i.e. the structure of the electro-thermal converter element  910 , first drive element  903 , second drive element  902 , logic circuit  904  and booster circuit  906  (see  FIG. 6 ), is similar to the first embodiment. 
     Where resistors are arranged in series as in the present embodiment, the procedure of writing and reading data to and from the information storage element  901  is different from that of the first embodiment, which is hence explained. In this case, explanation is on the case to store 2 values information to the information storage element. 
     Here, six points a 1 , a 2 , b 1 , b 2 , c 1  and c 2  are taken at which resistance value increases (i.e. temperature/the number of application pulses decreases) in order on a change curve of a resistance against a temperature (the number of application pulses) ( FIG. 2 ). The point a 1  or a 2  is assumed set to the information storage element  901   a , the point b 1  or b 2  is to the information storage element  901   b , and the point c 1  or c 2  is to the information storage element  901   c , respectively. 
     In storing data on the information storage element  901   a  of the present embodiment, the second drive element  902   a  is first driven to change the resistance of the information storage element  901   a  at a predetermined pulse voltage to a desired value (a 1  or a 2 ). For the information up to 2 values, the second drive element  902   a  is driven to supply energy to the information storage element  901   a  and change the resistance value thereof. 
     After storing the information up to 2 values, the second drive element  902   b  is driven to supply energy to the information storage elements  901   a ,  901   b  thereby changing the resistance of the information storage element  901   b  to a desired value (a 1  or a 2 ). However, in this case, the number of application pulses is reduced than that upon energy supply to the information storage element  901   a  through driving the second drive element  902   a . By doing so, the resistance value of the information storage element  901   b  can be changed without changing the resistance value of the information storage element  901   a . For the information greater than two values and up to four values, the second drive element  902   b  is driven to supply energy to the information storage element  901   b  and change the resistance value thereof. 
     After storing the information up to four values, the second drive element  902   c  is then driven to supply energy to the information storage elements  901   a ,  901   b ,  901   c  thereby changing the resistance of the information storage element  901   c  to a desired value (c 1  or c 2 ). However, in this case, the number of application pulses is reduced than that upon energy supply to the information storage elements  901   a ,  901   b  through driving the second drive element  902   b . By doing so, the resistance value of the information storage element  901   c  can be changed without changing the resistance values of the information storage elements  901   a ,  901   b . Because the respective resistance values of the information storage elements  901   a ,  901   b  are known, resistance value can be read on the information storage element  901   c.    
     In reading the recorded data, data is first read out of the information storage element  901   a . In this case, after applying a read voltage, for example, of 3.3 V to the terminal  912   a , the second drive element  902   a  is driven corresponding to the information storage element  901   a  to read. As a result, voltage drop information is obtained corresponding to the resistance value of the information storage element  901   a  through a count terminal  912   b , thereby obtaining resistance information about the information storage element  901   a.    
     In reading the resistance value from the information storage element  901   b , a read voltage of 3.3 V is similarly applied to the terminal  912   a , to drive the second drive element  902   b  corresponding to the information storage element  901   b . The information, obtained from the count terminal  912   b  on this occasion, is given as voltage drop information commensurate with the resultant resistance of the resistance value the information storage element  901   a  possesses and the resistance value the information storage element  901   b  possesses. Accordingly, in obtaining a resistance from the information storage element  901   b , calculation is by subtracting the resistance value of the information storage element  901   a  from the resultant resistance obtained. In obtaining the recorded data from the information storage element  901   c , calculation is similarly from the resultant resistance of the information storage elements  901   a ,  901   b ,  901   c.    
     Incidentally, information storage operation is not limited to the foregoing. For example, the procedure may be as in the following. At first, the second drive element  902   c  only is selected to set the information storage elements  901   a - 901   c  all at c 1  or c 2 . Then, the second drive element  902   b  only is selected to set the information storage elements  901   a ,  901   b  at b 1  or b 2 . 
     Finally, the second drive element  902   a  only is selected to set the information storage element  901   a  at a 1  or a 2 . 
     By thus storing information to the information storage element and separately reading information therefrom, information can be handled in a degree up to 2 values×3=6 values. In addition, the information stored can be combined properly, thus being handled in a degree up to maximally (2 values) 3 =8 values. 
     The information to be stored in the information storage elements is not limited to two values but may be three values or more. For example, four-valued information can be stored on each element similarly to the above. In such a case, information can be handled in a degree of from 4 values×3=12 value to (4 values) 3 =64 values. Furthermore, the number of information storage elements is naturally not limited to the foregoing example. 
     As described above, the present embodiment is arranged with information storage elements  901  formed, on printing device board  900 , common in material and process to electro-thermal converter elements  910  so that information can be stored by changing the resistance value thereof and be read out of the information storage element  901 . This enables printing and reading information without causing a damage to the interlayer insulation film and protection film when data, thus realizing an inkjet print board and inkjet printhead having reliable storage elements free from positional restrictions in arrangement. 
     Other Embodiments 
     The information storage elements illustrated in the embodiments are not limited in the number but can be provided in plurality as long as space is available over the printing device board. 
     The embodiment utilized self-heating of the information storage element itself caused upon applying a pulse voltage, as a method to heat up the information storage element. However, this is not limitative. Namely, heating may be in a temperature-controlled bath or the like provided that temperature control is available with accuracy. 
     The inkjet printhead board in the invention satisfactorily has elements that generate energy for ejecting ink, having a resistance value corresponding to the temperature of thermal process and a resistor, as an information storage element, for reading the resistance value thereof. 
     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 such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2006-343000, filed Dec. 20, 2006, which is hereby incorporated by reference herein in its entirety.